DE102018211493A1 - Adjustment drive for a steering column, motor-adjustable steering column for a motor vehicle, and method for adjusting a bearing arrangement of an adjustment drive - Google Patents

Abstract

The invention relates to an adjustment drive (5, 6) for a motorized steering column (1) for a motor vehicle, comprising a threaded spindle (52, 62) with an axis (G) engaging in a spindle nut (51, 61), a drive unit (55 , 65) and a gear wheel (7) which can be driven by the drive unit (55, 65) to rotate about the axis (G) and which is non-rotatably connected to the spindle nut (51) or the threaded spindle (62) and which is located in a bearing housing (53, 63) in a bearing arrangement between two axially supported on the bearing housing (53, 63) outer bearing rings (93) rotatably about the axis (G), the outer bearing rings (93) on their mutually facing sides each having a coaxial to the axis (G) outer bearing surface which each face a bearing surface (81) formed on the end face of the gear wheel (7). In order to allow for smoother running and less wear, the invention proposes that at least one outer bearing ring (93) is axially resiliently supported on the bearing housing (53, 63) via an elastic pretensioning element (94, 95), which is one of the two outer bearing rings (93) exerts pretensioning force (F) axially bracing against one another.

Description

State of the art

The invention relates to an adjustment drive for a motor-adjustable steering column for a motor vehicle, comprising a threaded spindle engaging in a spindle nut with an axis, a drive unit and a gearwheel that can be driven by the drive unit to rotate about the axis and is connected in a rotationally fixed manner to the spindle nut or the threaded spindle a bearing housing in a bearing arrangement between two axially supported on the bearing housing outer bearing rings is rotatably mounted about the axis, the outer bearing rings on their mutually facing sides each having a coaxial to the axis outer bearing surface, which is opposite a bearing surface formed on the end face of the gear wheel. Furthermore, the invention relates to a motor-adjustable steering column for a motor vehicle with such an adjustment drive and a method for adjusting a bearing arrangement of an adjustment drive.

Steering columns for motor vehicles have a steering shaft with a steering spindle, at the rear end of which, facing the driver and facing the driver, a steering wheel is attached for introducing a steering command by the driver. The steering spindle is rotatably mounted about its longitudinal axis in an actuating unit which is held on the vehicle body by a support unit. Because the actuating unit is accommodated in a jacket unit connected to the carrying unit, also referred to as a guide box or box rocker, so that it can be displaced telescopically in the direction of the longitudinal axis, a longitudinal adjustment can take place. A height adjustment can be realized in that the actuating unit or a jacket unit receiving it is pivotably mounted on the support unit. The adjustment of the adjusting unit in the longitudinal or height direction enables the setting of an ergonomically comfortable steering wheel position relative to the driver position in the operating position, also referred to as the driving or operating position, in which a manual steering intervention can take place.

It is known in the prior art to provide a motorized adjustment drive with a drive unit for adjusting the actuating unit relative to the support unit, which drive unit comprises an electric servomotor, which is connected to a spindle drive, which is screwed into a spindle nut, as a rule via a gear Includes threaded spindle. By means of the drive unit, the threaded spindle and the spindle nut can be rotated relative to one another about an axis, namely the threaded spindle axis, whereby the threaded spindle and the spindle nut can be moved translationally towards or away from one another, depending on the direction of rotation. In one embodiment, the threaded spindle of the drive unit, which is fixedly connected to the actuating unit or the supporting unit, can be driven to rotate about its threaded spindle axis and engages in the spindle nut, which is fixedly attached to the supporting unit or alternatively to the actuating unit with respect to rotation about the threaded spindle axis , In the direction of the threaded spindle axis, the threaded spindle is supported on the supporting unit or the actuating unit, and the spindle nut correspondingly on the adjusting unit or alternatively on the supporting unit, so that a rotary drive of the threaded spindle causes a translational adjustment of the supporting unit and adjusting unit relative to one another in the direction of the threaded spindle axis , This version is therefore also referred to as a rotary spindle drive.

In an alternative embodiment, the threaded spindle is non-rotatably coupled to the support unit or alternatively to the actuating unit with respect to rotation about its threaded spindle axis, and the spindle nut is rotatable but is fixed in the direction of the threaded spindle axis accordingly on the actuating unit or alternatively on the support unit. As in the first embodiment, the threaded spindle is supported on the support unit or on the adjusting unit in the direction of the threaded spindle axis, and the spindle nut is supported on the adjusting unit or on the supporting unit accordingly, so that the threaded spindle can be displaced translationally in the direction of the threaded spindle axis by the spindle nut of the drive unit is driven in rotation. This version is also known as a plunger spindle drive.

As in the first-mentioned embodiment, the rotary drive of the threaded spindle causes a translatory adjustment of the carrying unit and the actuating unit relative to one another in the direction of the threaded spindle axis. In both versions, the spindle drive forms a motor-driven adjusting drive which is effective between the supporting unit and the adjusting unit and by means of which the adjusting unit can be adjusted for adjustment relative to the supporting unit.

To achieve a longitudinal adjustment of the actuating unit in the direction of the longitudinal axis of the steering spindle, the spindle drive of an adjusting drive can be arranged between the actuating unit and a jacket unit, also called a guide box or box rocker, which axially displaceable longitudinally and which is connected to the support unit, and the threaded spindle axis essentially can be aligned parallel to the longitudinal axis. For height adjustment, a spindle drive can be arranged between the support unit and an actuating unit or jacket unit, which is pivotally mounted thereon and in which the actuating unit is accommodated. A motorized longitudinal and height adjustment can be designed individually or in combination.

The spindle drive is driven by the drive unit via a gear wheel which can be driven to rotate about its axis, which is identical to the threaded spindle axis and which, depending on the design of the spindle drive, is connected in a rotationally fixed manner to the spindle nut or to the threaded spindle. The gear wheel has a toothed section in the form of a spur gear with an external toothing or worm toothing.

The gear wheel has on each of its two end faces a bearing surface running coaxially to the axis. In a bearing arrangement, the bearing surfaces are arranged between two corresponding outer bearing surfaces, which are arranged on the opposite sides of the two outer bearing rings, between which the gear wheel is rotatably mounted. The outer bearing rings, as seen from the gearwheel, are supported and fixed on the outside of the bearing housing in the axial direction. As a result, the holding and adjusting forces acting on the gear wheel in both axial directions of the threaded spindle axis on the spindle drive are transmitted via the gear wheel and the outer bearing rings to the bearing housing, and are supported from there on the actuating unit or the carrying unit.

Such an adjustment drive with a rotatably mounted and axially supported gear wheel is for example from the US 4,967,618 known. The bearing surfaces of the gear wheel have raceways for rolling elements, specifically ball raceways of ball bearings. Balls are arranged as rolling elements between these ball raceways and these corresponding ball raceways in the axially or diagonally opposite outer bearing surfaces of the outer bearing rings. This forms a bearing arrangement in which the gear wheel is supported in an axial direction between two axial thrust bearings, each of which is formed from a bearing surface, an outer bearing surface and the balls arranged therebetween. The outer bearing rings are rigidly fixed to the bearing housing.

During assembly, a bearing arrangement is adjusted by axially positioning and fixing the outer bearing rings relative to one another, so that the balls roll between the ball raceways without play. So that there is as little bearing play as possible during operation and to ensure low-noise operation, the outer bearing rings are braced against one another in the bearing housing, so that the bearing and outer bearing surfaces are pressed axially against one another. On the one hand, the axial setting force exerted on the outer bearing rings must be high enough to ensure that the balls run without play even under temperature fluctuations and when worn. On the other hand, the setting force must not be too high, as a result of which an increased torque of the gear wheel and increased wear can occur.

In view of the problems explained above, it is an object of the present invention to provide an improved adjustment drive and a steering column with an improved adjustment drive, which has a higher running smoothness and less wear.

Presentation of the invention

This object is achieved by an adjustment drive with the features of claim 1 and a motor-adjustable steering column for a motor vehicle with the features of claim 9. Claim 10 specifies a method for adjusting a bearing arrangement according to the invention of an adjustment drive for a motor-adjustable steering column for a motor vehicle. Advantageous further developments result from the subclaims.

To achieve the stated object, an adjustment drive for a motor-adjustable steering column for a motor vehicle with the features mentioned in the introduction is proposed, in which according to the invention at least one outer bearing ring is axially resiliently supported on the bearing housing via an elastic prestressing element which axially braces the two outer bearing rings against one another Exerts preload.

According to the invention, the two outer bearing rings are not rigidly supported on the bearing housing as in the prior art, but are clamped elastically in the axial direction. The axis direction corresponds to the direction of the longitudinal axis. The at least one prestressing element is formed by an axially effective spring element which is axially supported on the bearing housing on its side facing away from the bearing arrangement, that is to say from the outer bearing rings, and on its other side acts axially on the corresponding outer bearing ring. In the assembled operating state, the pretensioning element is pretensioned or compressed in the axial direction, i.e. in the direction of the longitudinal axis, to such an extent that it exerts a predetermined pretensioning force on the outer bearing ring, and is fixed in this pretensioning or assembly position relative to the bearing housing. The prestressing element axially tensioned in this way presses the outer bearing ring against the gearwheel with the elastic force, that is to say the spring force, which is thereby also pressed against the other outer bearing ring with the prestressing force. The bearing arrangement is thus elastically biased in the axial direction by the biasing element.

An advantage of the invention is that the preload force, which can be adjusted by compressing the preload element during assembly, even under unfavorable operating conditions, for example thermal stress or wear, over the entire service life of the adjustment drive for a more uniform axial pressure between the bearing surfaces and the Corresponding outer bearing surfaces ensures that undesirable and harmful bearing play is suppressed. In a rolling bearing arrangement, the rolling elements roll off without play, and in an alternative sliding bearing arrangement an optimized sliding contact is ensured. This increases the running smoothness and minimizes wear.

It is possible for the prestressing element to exert the prestressing force on one of the two outer bearing rings, and for the other outer bearing ring to be axially rigidly supported on an abutment on the bearing housing. The preload force is thereby coupled axially in the preload direction into the bearing arrangement which is fixed relative to the bearing housing. Alternatively, it is possible to provide two preloading elements, which act on the outer bearing rings from both sides. As a result, the bearing arrangement is also elastically preloaded, and is also held elastically in both axial directions with respect to the bearing housing. Torque peaks can thus be absorbed and damped elastically.

The biasing element can comprise an annular spring element. The spring element can be elastically compressed axially with the prestressing force and transmits it permanently as a spring force to the bearing arrangement. The annular design coaxial to the axis corresponds to the dimensions of the outer ring against which the spring element bears directly or indirectly in the assembled state. The spring travel in the axial direction can be adapted to the deviations due to wear and temperature fluctuations to be expected during operation, so that these deviations, which occur over the course of the service life, are effectively compensated for thanks to the solution according to the invention. The spring element can comprise, for example, a spring or corrugated ring, a helical, plate or leaf spring or the like, preferably made of spring steel, or alternatively, or in combination, an elastomer, rubber or O-ring, which is also elastically deformable in the axial direction or a cord ring made of elastomer. Different designs of spring elements can be combined for optimized spring and damping properties, for example a spring ring and an O-ring on one or both outer bearing rings.

The biasing element can comprise a securing element. This securing element can be elastically compressed axially with the preload force, and transmits it permanently as a spring force to the bearing arrangement. The securing element also serves as a holding or supporting element which is fixed to the bearing housing in the axial direction, for example via a form, force and / or material connection. The connection can be designed to be detachable, for example by means of a clamp, snap-in or screw connection, or non-detachably, for example by welding.

The biasing element is preferably designed as a one-piece securing element.

The securing element is preferably designed as a one-piece sheet metal part, preferably as a one-piece integral component. The securing element is preferably formed in one piece as a spring element, an intermediate element being arranged as a damping element between the spring element and the outer ring. This intermediate element can be designed, for example, as an elastomer element, such as an O-ring. Alternatively, the intermediate element can be applied to the securing element, for example by a vulcanized-on elastomer element.

In a preferred embodiment it can be provided that the prestressing element is supported on a securing element connected to the bearing housing. The securing element serves as a holding or supporting element which is fixed to the bearing housing in the axial direction, for example via a form, force and / or material connection. The connection can be designed to be detachable, for example by a clamp, screw or snap connection, or non-detachable, for example by welding. A prestressing element according to the invention can be elastically clamped between the securing element and an outer bearing ring. It is also possible for one of the outer bearing rings to be supported on the bearing housing via a securing element without an intermediate preload element, which then forms a rigid abutment.

The biasing element can be adapted in shape and dimensions to an outer bearing ring and a securing element, which can be designed, for example, as an annular or segment-shaped securing ring. It is possible to provide a securing element on one end face of a bearing arrangement, which is supported on its other side against an abutment which is connected to or formed on the bearing housing. It is also possible that the bearing arrangement is fixed on the bearing housing between two securing elements, so that the biasing force generated by the biasing element is introduced into the bearing housing via the securing elements.

In a further development it can be provided that the prestressing element is at least partially formed by the securing element. This can be achieved in that the securing element is elastic in itself in the axial direction. This gives it a double function, namely, on the one hand, the support and mounting on the bearing housing, and, on the other hand, the generation of the elastic pretensioning force. For example, the securing element can be designed as a securing ring, for example made of spring steel, which has fastening means on its circumference, such as, for example, retaining edges or cutting edges which engage in a form-fitting manner. Outside the fastening means, axially active spring elements can be provided on the retaining ring, for example a conical section of a plate spring, a corrugated section of a corrugated spring, resilient tabs or the like. The spring elements can be supported directly or indirectly from the outside on an outer bearing ring.

Rolling elements can be arranged between the gear wheel and the outer bearing rings. The gearwheel, together with an outer bearing ring and the rolling elements arranged between them, each form an angular contact roller bearing. Both an X and an O arrangement of the angular contact bearings can be provided. Alternatively, an axial roller bearing can also be provided. Alternatively, it is conceivable and possible for an outer bearing surface and a corresponding bearing surface to have sliding surfaces sliding on one another to form an inclined sliding bearing.

One of the two outer bearing rings can be axially rigidly supported on the abutment on the bearing housing. As a result, the bearing arrangement, which is elastically loaded by the prestressing element via the other outer bearing ring, is fixedly supported on the bearing housing. The abutment can be fixed to the bearing housing, or can be formed by a securing element fixed to the bearing housing. The abutment can preferably be designed as a shoulder, this shoulder preferably being formed by a reshaping operation, for example by circumferential rolling, a bead formed on the outer lateral surface forming a shoulder on the inner lateral surface. Alternatively, projections distributed over the circumference can also form such a shoulder. These projections can be introduced into the bearing housing from the outside, for example, by local plastic deformations.

An advantageous embodiment of the invention provides that the bearing housing has a hollow cylindrical receiving space in which the outer bearing rings and the gear wheel are arranged coaxially to the axis. The receiving space forms a passage with a circular inner cross section, in which the bearing arrangement formed from the gear wheel and the outer bearing rings is received coaxially. The securing element (s) can preferably also be designed in the form of a ring as securing rings which are arranged and fixed coaxially in the receiving space.

A further development provides that the securing element has fastening means for fixing inside in the receiving space. Characterized in that the securing element is fixed to the inner wall in a force-fitting and / or form-fitting manner, the entire bearing arrangement, including the axial support, can be arranged in the bearing housing, as a result of which a compact and protected structure can be achieved. An advantageous embodiment is that the securing element is designed as a securing ring with an outer cross-section that corresponds to the inner cross-section of the receiving space of the bearing housing. Fastening means for connection to the inner wall of the receiving space can be arranged or formed on the outer circumference of the preferably round securing ring. For example, the fastening means can comprise holding structures on the outer circumference of the locking ring, for example cutting-edge, sharp-edged edges or cutting edges that can be positively inserted or pressed into the inner wall and secure the locking ring against axial movement in order to axially a preload element or an outer bearing ring in the required preload position in the bearing housing to fix.

It can be provided that the fastening means are self-fixing. This can be achieved, for example, by holding structures designed like barbs, which slide along the inner wall of the receiving space when the securing element is inserted axially into the passage of the bearing housing during assembly in the preload direction and is pressed against a preload element with the preload force. In the operating state after assembly, the securing element is axially loaded against the prestressing direction by the prestressing force, as a result of which the barb-like holding structures of the fastening means are spread radially and claw into the inner wall automatically, as a result of which the securing ring is axially fixed relative to the bearing housing. As a self-fixing fastener, for example, a cutting edge inclined relative to the axis can be provided, which is formed or arranged at least in sections on the outer circumference of the securing ring. For assembly, this enables simple axial insertion into the receiving space in the prestressing direction against the prestressing element. After assembly, the cutting edge is plastically buried radially into the inner wall by the prestressing force then acting against the direction of insertion, and is thus positively in axial direction fixed. Such self-fixing holding means with barb-like holding structures can be implemented with little effort, enable simple assembly and a secure hold.

The invention further comprises a motor-adjustable steering column for a motor vehicle, which has an adjusting drive with the features described above, with a support unit which can be attached to a vehicle body and from which an actuating unit is held, in which a steering spindle is rotatably mounted about a longitudinal axis , and with an adjustment drive, which is connected to the support unit and to the actuating unit, and of which the actuation unit is adjustable relative to the support unit, wherein the adjustment drive has a threaded spindle engaging in a spindle nut with an axis, a drive unit and one of the drive unit around that Axially drivable, rotatably connected to the spindle nut or the threaded spindle gear, which is rotatably mounted in a bearing housing in a bearing arrangement between two axially supported on the bearing housing outer bearing rings about the axis, the outer bearing rings on their egg nander facing sides each have a coaxial to the axis outer bearing surface, which is opposite a bearing surface formed on the face of the gear wheel.

This enables the adjustment drive to run more smoothly under all operating conditions of a steering column, which is of particular importance for acceptance by the driver. Furthermore, the wear and thus the maintenance effort are advantageously reduced.

1. A) Aufbringen einer axialen Vorspannkraft auf das Vorspannelement,
2. B) Aufbringen eines Belastungsmoments auf das Getrieberad und Messen des Belastungsmoments,
3. C) Messen einer mit dem Belastungsmoment korrelierten Lagerzustandsgröße (Be-lastungsmoment selbst, oder auch: Verlagerung des Getrieberads),
4. D) Vergleichen der gemessenen Lagerzustandsgröße mit einem vorgegebenen Zu-standszielwert,
5. E) wenn die gemessene Lagerzustandsgröße von dem Zustandszielwert (innerhalb vorgegebener Toleranzbereiche) abweicht: Verändern der axialen Vorspannkraft,
6. F) wenn die gemessene Lagerzustandsgröße den Zustandszielwert (innerhalb vorgegebener Toleranzbereiche) erreicht: Fixieren des Vorspannelements (9) in axialer Vorspannposition am Lagergehäuse und Beenden der Einstellung.

A method according to the invention for adjusting a bearing arrangement of an adjusting drive for a motor-adjustable steering column for a motor vehicle, comprising a threaded spindle with an axis engaging in a spindle nut, and a gearwheel connected non-rotatably to the spindle nut or the threaded spindle, which in a bearing housing in a bearing arrangement between two is axially supported on the bearing housing outer bearing rings rotatably about the axis, an outer bearing ring is axially resiliently supported on the bearing housing via an elastic biasing element,
includes the steps:

1. A) applying an axial prestressing force to the prestressing element,
2. B) applying a load torque to the gear wheel and measuring the load torque,
3. C) measuring a bearing condition variable correlated with the loading torque (loading torque itself, or also: displacement of the gear wheel),
4. D) comparing the measured state of the bearing state with a predetermined state target value,
5. E) if the measured bearing condition variable deviates from the target condition value (within specified tolerance ranges): changing the axial preload force,
6. F) when the measured bearing condition quantity reaches the target condition value (within specified tolerance ranges): fix the preload element ( 9 ) in the axial preload position on the bearing housing and ending the setting.

The method according to the invention enables an optimized setting of a bearing arrangement with the features described above, which has a preload element according to the invention. In doing so, at least one bearing condition quantity that is directly or indirectly dependent on the preload force is brought to a condition target value within specified tolerances, i.e. settled in an optimal state target range. As a result, smooth running, low wear and the highest possible rigidity of the bearing arrangement can be achieved.

The application of an axial prestressing force to the prestressing element can correspond to the application of an axial press-in force which acts on the prestressing element, the acting press-in force being opposite to the prestressing force.

In the first step A), a preassembled bearing arrangement is provided, the outer bearing rings and the at least one prestressing element being held together with a defined, predetermined starting value of the prestressing force. The starting value is chosen so that the pretensioning force is at or below a limit value required for ready-to-use assembly, so that in other words the axial pretensioning force produces a loose preassembly.

In the next step B), a loading torque is exerted on the gear wheel. A loading torque can be, for example, a torque with which the gear wheel must be driven to rotate about its axis in order to carry out a rotation in the bearing arrangement, or also a tilting or displacement torque which acts on the gear wheel transversely to the axis. These two operating cases are explained in more detail below.

In the following, a bearing state variable correlated with the loading torque is measured in step C). The size of the load moment itself can be measured, for example the torque or overturning torque coupled into the gearwheel, and alternatively or additionally also a variable dependent on the loading torque, such as, for example, a displacement of the gearwheel, for example tilting to the axis, which is generated by a coupled loading torque, for example a said tipping moment.

In step D), the measured state of the bearing state is compared with a predetermined state target value. The target state value defines a reference value that corresponds to a bearing state that is to be maintained in the operating state.

Step E) takes place when the measured bearing condition variable deviates from the condition target value within predetermined tolerance ranges. For this purpose, the axial preload force is changed in order to move the actual value of the bearing condition variable in the direction of the target condition value. When the measured bearing condition quantity reaches the condition target value - within specified tolerance ranges - the preload element is fixed in the axial preload position on the bearing housing, i.e. supported so that it permanently exerts the set preload on the bearing assembly. The setting is now complete.

The prestressing force is preferably exerted on a securing element arranged in front of an outer bearing ring. The securing element is moved axially in the direction of the preload force against the outer bearing ring and pressed against it. The further the securing element is moved against the prestressing element, the more it is compressed and the prestressing force is increased accordingly. When the specified value of the preload force is reached during the adjustment, the securing element is fixed to the bearing housing in the preload position that is then set.

An advantage of the method according to the invention is that the preloading of the bearing arrangement can take place in a control process taking into account a bearing state variable which is dependent on the preloading force.

• B1) Aufbringen eines Durchdrehmoments als Belastungsmoment zum rotierendes Antreiben des Getrieberads und dabei Messen des Durchdrehmoments als korrelierende Lagerzustandsgröße,
• C1) Vergleichen des gemessenen Durchdrehmoments mit einem vorgegebenen Drehmomentzielwert als Lagerzustandsgröße,
• E1) wenn das gemessene Durchdrehmoment als Lagerzustandsgröße kleiner ist als der vorgegebene Drehmomentzielwert als Zustandszielwert: Erhöhen der axialen Vorspannkraft,
• F1) wenn das Durchdrehmoment als Lagerzustandsgröße den vorgegebenen Drehmomentzielwert als Zustandszielwert erreicht: Fixieren des Vorspannelements in axialer Vorspannposition am Lagergehäuse und Beenden der Einstellung.

A possible execution of the method comprises the steps:

• B1) applying a torque as a loading torque for rotating driving of the gear wheel and thereby measuring the torque as a correlating bearing state variable,
• C1) comparing the measured torque with a predetermined torque target value as a bearing condition variable,
• E1) if the measured torque as the bearing state variable is smaller than the specified torque target value as the target state value: increasing the axial preload force,
• F1) if the torque as the bearing state variable reaches the specified torque target value as the target state value: fix the preload element in the axial preload position on the bearing housing and end the setting.

Thus, in this embodiment of the method, the torque corresponds to the loading torque, the measured torque to the correlated bearing condition quantity and the torque target value to the condition target value.

To carry out the adjustment, the bearing arrangement comprising the outer bearing rings and the gear wheel, and optionally the rolling elements arranged between them, are arranged in the bearing housing. The gear wheel is driven in rotation. The drive can be carried out by the drive unit of the adjustment drive. Alternatively, in the case of a rotary spindle drive in which the threaded spindle is connected to the gear wheel in a rotationally fixed manner, the gear wheel can be driven by an external adjusting drive which drives the threaded spindle in a rotating manner.

The load torque is the torque, that is the drive torque, which has to be used to turn the gear wheel in the bearing arrangement. This drive torque can be measured by means of suitable sensors, for example via torque sensors, or via a motor current of the drive unit or an external adjustment drive.

During the rotating drive, an axial prestressing force is applied to the prestressing element, for example via a securing element which presses the prestressing element axially against an outer bearing ring. The preload force is preferably measured using suitable force sensors.

The preload is then increased gradually or continuously. As a result, the bearing friction of the bearing arrangement increases, and the measured torque, which is correlated with the preload force, also increases.

The momentarily measured torque, which correlates with an applied pretensioning force, is compared step-by-step or continuously, preferably automatically, with a predetermined torque target value.

If the measured torque is less than the specified torque target value, this means that the bearing play is still too large or the preload is still too low, so that the required rigidity of the bearing arrangement and a play-free run under load conditions during operation are not yet guaranteed. In this case, the preload force is increased and the measured torque is measured again and compared with the target torque value.

The aforementioned steps are repeated until the torque reaches the specified torque target value. In the axial position reached, the preload position, the preload element is fixed relative to the bearing housing, preferably by a securing element. In the preload position, the preload element is axially supported on the bearing housing in such a way that it permanently exerts the set preload force on the outer bearing ring.

As a result, a force- or torque-controlled setting of the torque is realized, the pretensioning force being regulated by the measured torque. An automated, precise adjustment of the torque is made possible. The prestressing element ensures that the set torque of the adjustment drive remains essentially constant over the entire service life of the adjustment drive, regardless of wear and operating conditions.

• B2) Aufbringen eines Kippmoments als Belastungsmoment quer zur Achse auf das Getrieberad und dabei Messen einer Verlagerung des Getrieberads relativ zum Lagergehäuse als korrelierende Lagerzustandsgröße,
• C2) Vergleichen der gemessenen Verlagerung als Lagerzustandgröße mit einem vorgegebenen Steifigkeitsgrenzwert als Zustandszielwert,
• E2) wenn die gemessene Verlagerung als Lagerzustandsgröße größer ist als ein vorgegebener Steifigkeitsgrenzwert als Zustandszielwert: Erhöhen der axialen Vorspannkraft,
• F2) wenn die gemessene Verlagerung als Lagerzustandsgröße den vorgegebenen Steifigkeitsgrenzwert erreicht: Fixieren des Vorspannelements in axialer Vorspannposition am Lagergehäuse und Beenden der Einstellung.

Alternatively, or additionally or together with the last described embodiment, the method according to the invention can provide the following steps:

• B2) applying a tilting moment as a loading moment transverse to the axis to the gear wheel and thereby measuring a displacement of the gear wheel relative to the bearing housing as a correlating bearing state variable,
• C2) comparing the measured displacement as a bearing condition quantity with a predetermined stiffness limit value as the condition target value,
• E2) if the measured displacement as the bearing condition quantity is greater than a predetermined stiffness limit value as the condition target value: increasing the axial preload force,
• F2) if the measured displacement as the bearing condition variable reaches the stiffness limit: fix the preload element in the axial preload position on the bearing housing and end the setting.

Thus, in this embodiment of the method, the tilting moment corresponds to the loading moment, the measured displacement of the gear wheel relative to the bearing housing corresponds to the correlated bearing condition quantity and the stiffness limit value to the condition target value.

By applying a tilting moment, the bearing arrangement is loaded transversely on bending. The lateral deformation that occurs is a measure of the rigidity of the bearing arrangement. The rigidity of the bearing arrangement depends on the preload force, a high preload force being correlated with a high rigidity.

As with the versions described above, a start value of the preload is set first. A tilting moment is exerted on the gear wheel as the load moment. The tilting moment can be coupled in, for example, by a tilting or bending force introduced transversely into the threaded spindle.

The displacement of the gear wheel generated by the tilting moment is measured, for example by a radial deflection of the threaded spindle connected to the gear wheel.

The measured displacement is compared to a stiffness limit. This designates a reference value of the displacement correlated with the required stiffness.

As long as the measured displacement is greater than a predetermined stiffness limit, the required stiffness is not given. In this case, the preload force is increased until the measured displacement is less than or equal to the stiffness limit within predetermined tolerance ranges. This results in a path-controlled setting of the rigidity, the preload being regulated by the measured displacement of the gear wheel.

As described above, the preload force can be set as a function of the torque or tipping moment, or also of the torque and tipping torque. This allows an adjustment of an adjustment drive to take place, which ensures the highest possible rigidity with easy adjustment.

When the preload is applied, the preload can be measured. Errors can be detected by comparison with the other measured variables. For example, a deviatingly high torque with a relatively small preload force can indicate a defect that can lead to a stiff bearing.

The torque and / or the tilting moment can be introduced via the threaded spindle become. The threaded spindle, which is fixedly connected to the gear wheel in particular in the case of a rotary spindle drive, can be driven in rotation with an external adjustment drive in order to drive the gear wheel in rotation. Due to the fact that a tipping force is introduced into the threaded spindle at an axial distance transversely to the axis, a tilting moment can be introduced into the gearwheel both when immersing and when rotating the spindle drive.

• A) Aufbringen einer axialen Vorspannkraft auf das Vorspannelement,
• B) Messen der axialen Vorspannkraft,
• D) Vergleichen der gemessenen Vorspannkraft mit einer vorgegebenen Zielvorspannkraft,
• E) wenn die gemessene Vorspannkraft von der vorgegebenen Zielvorspannkraft abweicht: Verändern der axialen Vorspannkraft,
• F) wenn die gemessene Vorspannkraft die vorgegebene Zielvorspannkraft erreicht: Fixieren des Vorspannelements in axialer Vorspannposition am Lagergehäuse und Beenden der Einstellung.

Furthermore, the invention relates to a further method for adjusting a bearing arrangement of an adjustment drive for a motor-adjustable steering column for a motor vehicle, comprising a threaded spindle with an axis engaging in a spindle nut, and a gearwheel connected non-rotatably to the spindle nut or the threaded spindle, which in a bearing housing in a bearing arrangement between two axially supported on the bearing housing outer bearing rings rotatably about the axis, an outer bearing ring ( 93 ) is axially resiliently supported on the bearing housing via an elastic biasing element,
comprising the steps:

• A) applying an axial prestressing force to the prestressing element,
• B) measuring the axial preload force,
• D) comparing the measured pretensioning force with a predetermined target pretensioning force,
• E) if the measured preload deviates from the specified target preload: changing the axial preload,
• F) when the measured preload reaches the specified target preload: fix the preload element in the axial preload position on the bearing housing and complete the setting.

The target prestressing force can preferably encompass a range. The target biasing force is thus designed as a target biasing area. This area can be determined in tests so that the bearing arrangement in this area fulfills the corresponding requirements with regard to smooth running, rigidity and torque.

The prestressing force can be exerted on a securing element arranged in front of an outer bearing ring. It is advantageous that the securing element can be moved relative to the bearing housing in the direction of the pretensioning force and is designed to be self-fixing against the pretensioning force on the bearing housing. As described above, the outer bearing rings and the gear wheel can be arranged coaxially in a hollow cylindrical receiving space of the bearing housing, and the securing element is formed by a securing ring which has barb-like fastening means. Such a self-fixing circlip can be easily pressed against the bearing arrangement in the preload direction under the effect of the preload force. In the assembled state, the prestressing force now acting through the spring force of the prestressing element acts in the opposite direction on the retaining ring, causing it to claw or dig into the bearing housing in a form-fitting manner with corresponding cutting edges, and thereby automatically fix itself in its prestressing position.

The core element is preferably outside the force flow between the bearing rings. As a result, a force acting on the bearing rings in the direction of the axis is not introduced into the core element. The bearing rings, which are supported against one another, form a support device which supports pressure forces acting axially on the bearing rings outside the core element and thus prevents them from the core element,

Furthermore, to achieve the object, an adjustment drive for a motor-adjustable steering column for a motor vehicle is proposed, comprising a threaded spindle with an axis that engages in a spindle nut, a drive unit and a gear wheel that can be driven by the drive unit to rotate about the axis and that has a toothing section that is axial is arranged between two coaxial to the axis bearing surfaces, the gear wheel is rotatably connected to the spindle nut or the threaded spindle. According to the invention, it is proposed for a generic adjustment drive with the aforementioned features that the gear wheel has a core element to which two bearing rings are connected, each of which has a bearing surface and which are axially supported against one another.

The core element is preferably outside the force flow between the bearing rings. As a result, a force acting on the bearing rings in the direction of the axis is not introduced into the core element. The bearing rings, which are supported against one another, form a support device which supports pressure forces acting axially on the bearing rings outside the core element and thus prevents them from the core element,

In the gearwheel according to the invention, the bearing rings are connected on the end face to a core element, so that an assembly-friendly, one-piece component is provided. The bearing rings are mounted axially on both sides of the toothed section, and each have a bearing surface on their outer sides facing away from the core element, which also form outer sides of the gear wheel. The bearing rings are connected to one another in accordance with the invention in such a way that a force introduced in the axial direction on the bearing surfaces from the one bearing ring to the is transmitted to another bearing ring without the core element being loaded by the force between the bearing rings. In other words, when an axial force is exerted, for example when an axial clamping force is applied to adjust the bearings without play, the core element is held in the axial direction with little load between the bearing rings. The axial flow of force between the bearing rings can be established by the two bearing rings contacting one another and axially supporting one another, or indirectly, a force transmission element being able to be arranged between the two bearing rings, which likewise does not transmit any force in the axial direction to the core element , In any case, the force transmission in the axial direction takes place without interposing the core element via the rigid structure formed by the bearing rings for the transmission or transmission of force independently of the core element. The two bearing rings can also be designed as a one-piece, integral component.

The bearing surfaces are arranged between outer bearing surfaces of a bearing arrangement. An outer bearing surface, which is usually arranged on an outer ring, lies axially opposite a bearing surface, so that the bearing gap is located between the outer bearing surface and the bearing surface. Because the outer bearing surfaces are axially adjusted relative to one another, the distance to the bearing surfaces and thus the bearing play can be adjusted, and an axial force can be applied in order to clamp the bearing surfaces between the outer bearing surfaces without play.

The axial forces acting on the bearing rings are transmitted by the mutual support according to the invention in an axial force flow past the core element, an axially applied load on the bearing surfaces is intercepted by the structure according to the invention between the bearing rings and thereby prevented from the core element. The fact that there is no material of the core element in the axial force flow means that it is not burdened by the forces that arise when the bearing is braced and the forces that occur during operation.

This results in the possibility of independently optimizing the materials of the bearing rings and the core element with regard to the properties required in operation. The bearing rings can preferably consist of a hard, pressure-rigid material, which enables a rigid and resilient axial connection, which is suitable for absorbing the forces acting on the bearing surface, and preferably enables an integrated formation of slide bearing surfaces or rolling element raceways. Steel, for example, can meet these requirements well. The core element, however, can consist of a softer material, for example softer metal alloys, such as brass, or plastic. In particular, plastics can be optimized in terms of their properties to meet the respective requirements, for example with regard to elasticity and sliding properties, in order to implement low-backlash and smooth-running gears and spindle drives. The property of such plastic materials to flow under pressure and to plastically deform is not critical in the design of a gear wheel according to the invention because potentially harmful forces are absorbed by the mutually supporting bearing rings, and thus an undesirable deformation of the axial direction between the Bearing rings arranged core element is practically excluded. This allows greater design freedom than in the prior art with regard to the combination of different materials for the bearing rings and the core element.

The bearing rings can be firmly, preferably non-detachably, connected to the core element, for example by a material connection such as welding or gluing, or embedding or encapsulation. As a result, the gear wheel can be provided as a one-piece, assembly-friendly component.

The bearing rings are preferably attached to both axial end faces of the core element, the bearing surfaces being directed axially outward, as seen from the core element, for example as essentially circular or conical bearing surfaces. In a bearing arrangement, the bearing surfaces are in sliding contact or, via rolling elements, in rolling contact with corresponding outer bearing surfaces arranged axially on both sides of the gear wheel. In this case, tapered bearings can be realized by conical bearing surfaces, which can also be provided with roller raceways lying at an angle to the axis, which at the same time enable optimized radial and axial bearing and support.

The bearing rings can initially be provided as two separate components which are joined together in the gear wheel with the core element, so that they are connected to one another in the axial direction directly or indirectly for the purpose of axial force transmission. The force transmission can take place in direct contact, or via force transmission elements arranged between them, which, however, do not introduce any force in the axial direction into the core element.

It can be provided that the two bearing rings are formed in one piece together. Both bearing rings are formed on a one-piece integral bearing ring element. Such a thing Bearing ring element can be designed, for example, in the form of a sleeve or drum, the bearing surfaces being located in the region of the axial end faces. The bearing surfaces are connected in one piece continuously in the axial direction via the bearing ring element. The force flow with an axial load consequently takes place through the continuous material of the bearing ring element. It is also conceivable and possible to first produce separate bearing rings and to connect them to one another in a further step to form a bearing ring element before the connection to the core element takes place.

The gear wheel can be supported in roller bearings, the bearing surfaces of the bearing rings having roller raceways, preferably ball raceways. The axially opposite outer bearing surfaces assigned to the bearing rings likewise have corresponding ball raceways, and balls are arranged such that they can be rolled off as rolling bodies between the ball raceways. In this embodiment, the bearing rings form inner rings of roller bearings, preferably with bearing surfaces or ball raceways lying at an angle to the axis, so that angular contact ball bearings are formed which enable bearing loads to be absorbed in the axial and radial directions with a compact structure. The bearing surfaces are preferably designed such that the gear wheel is mounted in the housing by means of an X-bearing.

The bearing rings and the outer bearing surfaces can also have sliding surfaces sliding on one another, so that a sliding bearing arrangement is formed.

It is possible for the bearing rings to be formed as sheet metal parts, preferably from sheet steel. Such sheet metal parts can be efficiently manufactured as press-stamped parts with the required properties. Individual bearing rings can be provided as bearing shells, each of which has a bearing surface and which are connected to one another and to the core element according to the invention. Both bearing rings can also be arranged on a single bearing ring element, which is produced by connecting two bearing rings, or can be produced as a one-piece sheet metal part from a single sheet section. The sheet metal part can have integrally molded raceways for rolling elements, preferably ball raceways, which can be made sufficiently hard, for example also by means of continuous or partial hardening or hard coating. The raceways are connected by one-piece continuous sheet metal sections.

Alternatively, it is also conceivable and possible for the bearing rings to be designed as cold extrusion parts or as selective laser melting components.

An advantageous embodiment provides that the toothed section and / or the spindle nut and / or a connecting piece is integrally formed in one piece with the core element. The core element can be made of materials which, due to their material properties, are well suited for use as gear elements. For example, plastics are well suited for providing smooth-running and low-wear gears and screw drives. According to the invention, the toothing for the drive engagement with the drive unit can be molded into the plastic core element, and - in a submersible spindle drive with a spindle nut that can be driven in rotation - the internal thread of the spindle nut can be molded into the plastic core element. In the case of a rotary spindle drive, the core element can also have a toothing integrally molded in the plastic, and a connecting piece for the rotationally fixed connection of the gear wheel to the threaded spindle.

It is advantageous that the core element is designed as a plastic injection molded part. The production in the injection molding process from thermoplastic materials, for example polypropylene (PP), polyoxymethylene (POM) or the like, is efficient and enables flexible shaping, also with regard to the formation of the toothing or the internal thread. If necessary, the plastic can be provided with reinforcement, for example by adding reinforcement fibers, in order to increase the strength.

The production of the core element as a plastic injection molded part enables a particularly advantageous connection to the bearing rings in that the core element is injection molded onto the bearing rings. The bearing rings are arranged in the cavity of an injection molding tool and at least partially enclosed by the molten plastic injected therein, so that after cooling they are integrally connected to the plastic of the core element. A particularly firm connection can be achieved in that the bearing rings have form-fitting elements which are connected to the core element in a material and form-fitting manner. The interlocking elements can, for example, have openings and / or projections and / or a knurling of the bearing ring or rings which are penetrated by the plastic material during injection of the core element and are embedded therein. After cooling, the bearing rings, or a bearing ring element having both bearing rings, are anchored non-detachably firmly in the core element in a form-fitting and material-locking manner via the form-locking elements. As a result, the toothing, the internal thread and / or a connecting piece can be securely and precisely connected to the bearing rings in the long term. The final elements can also serve to produce a positive connection between the core element and one or both bearing rings in a core element that is not manufactured as an injection molded part.

In an adjustment drive according to the invention, the bearing rings can be clamped between corresponding outer bearing rings of a bearing arrangement. The gear wheel is rotatably supported between the outer bearing rings via the bearing surfaces of the bearing rings. To set and minimize the bearing play, the outer bearing rings can be moved in the axial direction against each other, and thus against the corresponding bearing rings, and pressed against them with a preload. The prestressing force can be generated by elastic prestressing elements which are supported in the axial direction on a fixed abutment, for example a bearing housing. Depending on the design of the steering column, the abutment can be firmly attached in the axial direction to the actuating unit, the support unit or a jacket unit connected to the support unit. Such a biasing element can have a spring element, for example a plate or corrugated spring, or also an elastomer element in the form of a rubber ring or the like.

list of figures

• 1 eine schematische perspektivische Ansicht einer erfindungsgemäßen Lenksäule,
• 2 eine weitere perspektivische Ansicht der erfindungsgemäßen Lenksäule gemäß 1 aus einem anderen Betrachtungswinkel,
• 3 einen Längsschnitt entlang der Gewindespindelachse durch eine Verstelleinrichtung einer Lenksäule gemäß 1 und 2 in einer perspektivischen Ansicht,
• 4 einen Längsschnitt wie in 3 in Seitenansicht,
• 5 eine auseinandergezogene Darstellung des Spindeltriebs gemäß 3 und 4,
• 6 einen Längsschnitt durch die Lageranordnung eines Spindeltriebs wie in 4 bei der Einstellung der Lageranordnung,
• 7 eine zweite Ausführung einer Verstelleinrichtung in einer Ansicht wie in 4,
• 8 eine dritte Ausführung einer Verstelleinrichtung in einer Ansicht wie in 4,
• 9 eine vierte Ausführung einer Verstelleinrichtung in einer Ansicht wie in 4,
• 10 eine fünfte Ausführung einer Verstelleinrichtung in einer Ansicht wie in 4,.

Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. Show in detail:

• 1 2 shows a schematic perspective view of a steering column according to the invention,
• 2 another perspective view of the steering column according to the invention 1 from a different angle,
• 3 a longitudinal section along the threaded spindle axis by an adjusting device of a steering column 1 and 2 in a perspective view,
• 4 a longitudinal section as in 3 in side view,
• 5 an exploded view of the spindle drive according to 3 and 4 .
• 6 a longitudinal section through the bearing arrangement of a spindle drive as in 4 when adjusting the bearing arrangement,
• 7 a second embodiment of an adjusting device in a view as in 4 .
• 8th a third embodiment of an adjusting device in a view as in 4 .
• 9 a fourth embodiment of an adjusting device in a view as in 4 .
• 10 a fifth embodiment of an adjusting device in a view as in 4 .

Embodiments of the invention

In the different figures, the same parts are always provided with the same reference numerals and are therefore usually only named or mentioned once.

1 shows a steering column according to the invention 1 in a schematic perspective view from the top right obliquely to the rear end, based on the direction of travel of a vehicle, not shown, where a steering wheel, not shown here, is held in the operating area. 2 shows the steering column 1 in a view from the opposite side, seen from the top right.

The steering column 1 includes a support unit 2 , which is designed as a console, the fasteners 21 has in the form of mounting holes for attachment to a vehicle body, not shown. From the support unit 2 becomes an actuator 3 kept in a jacket unit 4 - Also known as a guide box or box swing arm - is included.

The control unit 3 has a casing tube 31 on in which a steering shaft 32 around a longitudinal axis L is rotatably mounted axially in the longitudinal direction, ie in the direction of the longitudinal axis L , extends. At the rear end is on the steering shaft 32 a mounting section 33 formed on which a steering wheel, not shown, can be attached.

The control unit 3 is for realizing a longitudinal adjustment in the jacket unit 4 in the direction of the longitudinal axis L telescopically slidably added to that with the steering spindle 32 connected steering wheel relative to the support unit 2 to be able to position back and forth in the longitudinal direction, as with the double arrow parallel to the longitudinal axis L indicated.

The jacket unit 4 is about a transverse to the longitudinal axis L horizontal pivot axis S pivotable in a pivot bearing 22 on the support unit 2 stored. In the rear area is the jacket unit 4 via a control lever 41 with the carrying unit 2 connected. By rotating the control lever 41 by means of an actuator shown 6 (please refer 2 ) the jacket unit 4 relative to the support unit 2 around the swivel axis lying horizontally when installed S can be pivoted, thereby adjusting an on the fastening section 33 attached steering wheel in the height direction H can be made, which is indicated by the double arrow.

A first adjustment drive 5 for longitudinal adjustment of the control unit 3 relative to the jacket unit 4 in the direction of the longitudinal axis L has a spindle drive with a spindle nut 51 with one along an axis G extending internal thread 74 in which a threaded spindle 52 engages, that is, with its external thread in the corresponding internal thread 74 the spindle nut 51 is screwed in. The lead screw axis of the lead screw 52 is identical to the axis G and runs essentially parallel to the longitudinal axis L ,

The spindle nut 51 is about the axis G rotatable in a bearing housing 53 stored, which is fixed with the jacket unit 4 connected is. In the direction of the axis G is the spindle nut 51 axially over the bearing housing 53 on the jacket unit 4 supported, as will be explained in more detail below.

The threaded spindle 52 is with a fastener formed at its rear end 54 via a transmission element 34 with the actuator 3 connected, firmly in the direction of the axis G or the longitudinal axis L and fixed with respect to rotation about the axis G , Thanks to the spindle nut that can be driven in rotation 51 and the threaded spindle fixed with respect to rotation 52 a so-called sub-spindle drive is implemented.

That transmission element 34 extends from the actuator 3 through a slot-shaped through opening 42 in the jacket unit 4 , For adjusting the steering column 1 in the longitudinal direction, the transmission element 34 free in the through opening 42 be moved lengthways.

The adjustment drive 5 has an electric servomotor 55 on from which the spindle nut 51 with respect to the axis G relative to the fixed threaded spindle 52 is driven to rotate. This can - depending on the direction of rotation of the servomotor 55 - the threaded spindle 52 in the direction of the axis G translationally relative to the spindle nut 51 be shifted so that the corresponding with the threaded spindle 52 connected actuating device 3 relative to that with the spindle nut 51 connected jacket unit 4 in the direction of the longitudinal axis L is adjusted. The drive of the spindle nut 51 as well as the support of the spindle nut 51 in the direction of the axis G on the jacket unit 4 will be explained in more detail below.

In 2 showing a perspective view of the steering column 1 from the in 1 rear side, can be seen like a second adjustment drive 6 for height adjustment H on the steering column 1 is appropriate. This adjustment drive 6 includes a spindle nut 61 , in their internal thread 74 along an axis G a threaded spindle 62 intervenes. The threaded spindle 62 is in a bearing housing 63 which on the jacket unit 4 is attached, rotatable about the axis G supported and axially, in the direction of the axis G , on the jacket unit 4 supported, and by an electric servomotor 65 optionally in both directions of rotation around the axis G can be driven in rotation. This is explained in more detail below.

The spindle nut 61 is about a rotation about the axis G fixed at one end of the two-armed lever 41 attached to a pivot bearing 23 rotatable on the support unit 22 is stored, and the other arm with the other end with the jacket unit 4 connected is.

By turning the threaded spindle 61 can - depending on the direction of rotation of the servomotor 65 - the spindle nut 61 in the direction of the axis G translationally relative to the threaded spindle 62 be shifted so that the corresponding over the adjusting lever 41 with the spindle nut 41 connected jacket unit 4 together with the actuator included 3 relative to the support unit 2 in the height direction H can be adjusted up or down, as indicated by the double arrow. The drive of the threaded spindle 62 as well as the support of the threaded spindle 62 in the direction of the axis G on the jacket unit 4 is explained in more detail below.

3 and 4 make a longitudinal section through the bearing housing 63 of the adjustment drive 6 along the axis G in different views.

On the threaded spindle 62 is non-rotatable with respect to the axis G a gear wheel designed according to the invention 7 attached. The gear wheel 7 has a core element made of plastic 71 on, which is preferably made of a thermoplastic material such as PP, POM or the like as a plastic injection molded part. The gear wheel has on its outer circumference 7 on the core element 71 one coaxial to the axis G circumferential gearing 72 on, which is formed in the example shown as a worm gear, so that the gear 7 forms a worm wheel. In the gearing 72 grabs one of the servomotor 65 drivable screw 66 on.

The core element 71 is in the area of a central connecting section 73 , which forms a connector, rotatably with the threaded spindle 62 connected. The connection can be made cohesively, for example, by the core element 71 to the threaded spindle 62 injection molded onto the threaded spindle 62 is injected. Additionally or alternatively, a form-fitting and / or other fastening can be provided.

With the core element 71 are bearing rings 8th of the gear wheel 7 firmly connected. Every bearing ring 8th has a ball raceway, coaxial to the axis G annular bearing surface 81 on. The two storage areas 81 run from the core element 71 seen from the outside, conical together at the front. In other words, the ball races are at an angle to the axis G.

The bearing rings 8th point axially in the direction of the axis G opposing support sections 82 on, which in the example shown lie directly against each other, so that the bearing rings 8th in the direction of the axis G are supported directly against each other. In particular, there is no plastic material for the core element 71 between the contacting sections 82 the bearing rings 8th ,

The bearing rings 8th are preferably designed as sheet metal parts, particularly preferably as press-stamped parts made of sheet steel. For connection to the gear wheel 7 are the bearing rings 8th from the plastic of the core element 71 overmoulded, and is so except for the bearing surfaces exposed on the outside 81 material and form-fitting in the core element 71 embedded. Optionally, a fixing element 83 be provided on which the two bearing rings 8th during the encapsulation with plastic positioned and held relative to each other so that they are axially in the direction of the axis G against each other. The fixing element 83 can also be omitted. Alternatively, it is also conceivable for the bearing rings 8th to be connected directly to one another before the encapsulation, for example by spot welding or the like.

The storage areas 81 form the inner rings of a rolling bearing arrangement 9 what balls 91 includes that in a ball cage 92 are rotatably held and in the axial bearing gap between said ball raceways of the bearing surfaces 81 and corresponding ball raceways in outer bearing rings 93 are arranged rollable. The outer bearing rings 93 are from the gear wheel 7 seen from both ends, axially outwards via elastic spring elements 94 , which form prestressing elements, in the example shown elastomer or rubber rings, against axial abutments in the form of retaining rings 95 supported, which in turn in the axial direction of the axis G fixed with the bearing housing 53 are connected, for example by wedging, caulking or jamming. The spring element 94 can also be designed as a corrugated spring or plate spring.

In the in 4 execution shown are on both ends of the gear 7 spring elements designed as prestressing elements 94 arranged, which is over the two circlips 95 axially on the bearing housing 63 support and are axially elastically clamped. The spring force acts as a preload F via the outer bearing rings 93 , the balls 91 on the storage areas 81 so that the gear 7 between the rolling bearing arrangements 9 is axially biased.

The circlips can be used for fixation 95 fasteners on its outer circumference 951 have, for example in sections or completely circumferential, outwardly projecting cutting edges, which form-fit plastically in the inner wall of the bearing housing 63 dig. The cutting edges are preferred against the axis G inclined so that the fasteners 951 are barb-like. This allows the circlips 95 in the bearing housing 63 axially only in the direction against the gear wheel 7 be moved. Due to the pre-tensioning force F, which is in the assembled state, the retaining rings 95 oppositely loaded by the fasteners 951 through their barb-shaped design in the inner wall of the bearing housing 63 cling. In other words, the circlips 95 trained self-fixing.

When assembling the roller bearing assembly 9 is used to avoid bearing play in the direction of the axis G an axial biasing force F is applied. This is from the circlips 95 , the spring elements designed as biasing elements 94 , and the bullets 91 on the storage areas 81 the bearing rings 8th on the bearing rings 8th upset as in 4 marked with the force arrows. The preload F during the entire service life due to the elastic spring elements that serve as pretensioning elements 94 kept upright. This will make the two bearing rings 8th axially pressed against each other, with the bearing surfaces 81 force acting in operation F completely in the flow of force through the bearing rings 8th is transmitted. It is particularly advantageous that the plastic material of the core element 71 not in the flow of force between the bearing rings 8th is located, so it is not subjected to pressure. This relief ensures that the plastic material is not plastically deformed by flowing.

In 5 are the individual parts of the gear wheel 7 and the rolling bearing arrangement 9 in an exploded view in the direction of the axis G shown pulled apart.

6 shows an adjustment drive 6 when setting in an adjustment device, the axially movable plunger 96 and a relatively fixed abutment 97 includes. By means of a power source, not shown, the pressure stamp can 96 are loaded with a biasing force F, which thus serves as a press-in force.

For setting the roller bearing arrangements 9 will be the one in 6 left circlip 95 on the abutment 97 axially supported while by the pressure stamp 96 the other circlip on the right in the drawing 95 with the preload F axially towards the gear wheel 7 is pressed. The circlip 95 by the barb-shaped design of the fastening means described above 951 first up to the spring element 94 postponed. The spring element is in contact 94 by the preload F axially compressed, and the preload F initiated in the rolling bearing assembly.

The amount of preload F with which the gear wheel 7 in the rolling bearing arrangement 9 is biased, depending on a torque M, which must be applied to the gear 7 to turn. For this, the gear wheel 7 driven in rotation, for example by the adjusting motor 66 the drive unit. Alternatively, in the case of a rotary spindle drive, according to 3 . 4 . 6 . 7 or 8th where the lead screw 62 rotatable with the gear wheel 7 is connected, the drive by an external adjusting drive, not shown, the threaded spindle 62 drives rotating.

The spin torque M can be measured using suitable sensors, for example via torque sensors, or via a motor current of the servomotor 65 or an external adjustment drive.

The axial preload force is applied during the rotating drive F through the pressure stamp 96 applied to the bearing arrangement based on a predetermined starting value and increased continuously or stepwise, and preferably measured by means of suitable force sensors. This increases the bearing friction, and that with the preload F correlated, measured torque M also increases.

The measured torque M is preferably automatically compared with a predetermined torque target value.

If the measured torque M is smaller than the specified torque target value, this means that the bearing play is still too large or the preload is still too low, so that the required rigidity of the bearing arrangement and a play-free run under load conditions during operation are not yet guaranteed. In this case the preload F increased, and the measured torque M is measured again and compared with the target torque value.

The aforementioned steps are carried out until the measured torque M as the bearing state variable reaches the predetermined torque target value as the target state value. In the axial position reached, the pretension position, the locking ring 95 and thus the spring element 94 relative to the bearing housing 63 fixed. The axial fixation can take place in such a way that when the pressure ram is relieved or moved back 96 the barbed fasteners 951 through by the spring element 94 exerted preload F form-fitting plastic in the inner wall of the bearing housing 63 dig in and secure it in the pretension position. As an alternative or in addition, fixation can take place by means of a material connection, for example welding or the like, or by means of additionally inserted fastening elements.

Alternatively or additionally, the pretension can be dependent on the bending stiffness of the adjustment drive 6 can be set. For this purpose, the bearing arrangement is caused by a tilting moment K which transversely into the threaded spindle 62 is introduced, loaded on the bend. The one that occurs by means of a path measuring device 99 measured radial deflection x is a measure of the rigidity. This depends on the preload F , with a high preload F is correlated with a small deflection x and correspondingly high rigidity.

The deflection x, which serves as a correlating bearing state variable, corresponds to a displacement of the gear wheel generated by the tilting moment, which serves as the loading moment 7 , for example a tilt in the bearing housing 63 , The measured deflection x is compared with a reference value of a maximum permissible displacement which is assigned to a stiffness limit value which corresponds to the state target value.

As long as the measured deflection x is greater than a predetermined stiffness limit, the required stiffness is not given. In this case the preload F increased until the measured deflection x is less than or equal to the stiffness limit value within predetermined tolerance ranges.

The preload can be adjusted by regulating the torque M , or the overturning moment K take place, or also taking into account both loading moments M and K ,

Alternatively, the pretension can be set by regulating the applied and measured pretensioning force. If it reaches a predetermined limit value, the so-called target pretensioning force, the pretensioning element is fixed and the setting of the pretensioning force is ended.

7 shows a second embodiment, in which instead of a retaining ring 95 the outer bearing ring on the left in the drawing 93 axially against a shaping of the bearing housing designed as a shoulder 63 formed axial abutment 67 is supported. In addition, this version has only one spring element 94 on, which is designed as an O-ring made of rubber-elastic material, and in the drawing on the right between the outer bearing ring 93 and the locking ring 95 is arranged.

8th shows a third embodiment, which is like the embodiment according to 6 two circlips 95 has, but only one spring element 94 which like in 7 is designed as an O-ring or the like elastic element.

The fourth version according to 9 is regarding the storage of the gear wheel 7 basically constructed like that in 4 and 6 shown execution. In contrast to this, however, it is a submersible spindle drive in which the threaded spindle 62 into a thread in the gear wheel 7 connected spindle nut 61 intervenes, ie not rotatably with the gear wheel 7 connected is.

The fifth version according to 10 is characterized in that at least one of the locking rings 95 is axially resilient in itself, or both retaining rings 95 , The pretensioning element according to the invention is, to a certain extent, integrated in at least one securing ring 95 ,

The setting of the in the 7 . 8th . 9 and 10 Executions shown can be as to 6 described.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 4967618 [0009]

Claims (17)

Adjustment drive (5, 6) for a motor-adjustable steering column (1) for a motor vehicle, comprising a threaded spindle (52, 62) engaging in a spindle nut (51, 61) with an axis (G), a drive unit (55, 65) and a gear wheel (7) which can be driven by the drive unit (55, 65) and rotates about the axis (G) and is connected in a rotationally fixed manner to the spindle nut (51) or the threaded spindle (62) and which is located in a bearing housing (53, 63) in a bearing arrangement two axially supported on the bearing housing (53, 63) outer bearing rings (93) is rotatably mounted about the axis (G), the outer bearing rings (93) on their mutually facing sides each having a coaxial to the axis (G) circumferential outer bearing surface, each of which opposite a bearing surface (81) formed on the end face of the gear wheel (7), characterized in that at least one outer bearing ring (93) on the bearing housing (53, 63) is axially resilient via an elastic prestressing element (94, 95) is supported, which exerts a biasing force (F) which axially braces the two outer bearing rings (93). Adjustment drive (5, 6) after Claim 1 , characterized in that the biasing element (94) comprises an annular spring element. Adjustment drive (5, 6) according to one of the preceding claims, characterized in that the biasing element (94) is supported on a securing element (95) connected to the bearing housing (63). Adjusting drive (5, 6) according to one of the preceding claims, characterized in that the biasing element (95) comprises a securing element. Adjustment drive (5, 6) according to one of the preceding claims, characterized in that the biasing element is designed as a one-piece securing element (95). Adjusting drive (5, 6) according to one of the preceding claims, characterized in that rolling elements (91) are arranged between the gear wheel (7) and the outer bearing rings (93). Adjustment drive (5, 6) according to one of the preceding claims, characterized in that an outer bearing ring (93) on the bearing housing (53, 63) is axially rigidly supported on an abutment (97). Adjustment drive (5, 6) according to one of the preceding claims, characterized in that the bearing housing (63) has a hollow cylindrical receiving space in which the outer bearing rings (93) and the gear wheel (7) are arranged coaxially to the axis (G). Adjustment drive (5, 6) after Claim 8 , characterized in that the securing element (95) has fastening means (951) for fixing on the inside in the receiving space. Motor-adjustable steering column (1) for a motor vehicle, with a support unit (2) which can be attached to a vehicle body and from which an actuating unit (3) is held, in which a steering spindle (32) is rotatably mounted about a longitudinal axis (L) and with an adjustment drive (5, 6), which is connected to the carrying unit (2) and to the adjusting unit (3), and from which the adjusting unit (3) is adjustable relative to the carrying unit (2), the adjusting drive ( 5, 6) a threaded spindle (52, 62) engaging in a spindle nut (51) with an axis (G), a drive unit (55, 65) and one which can be driven in rotation by the drive unit (55, 65) about the axis (G) , rotatably connected to the spindle nut (51) or the threaded spindle (62) comprises gear wheel (7) which in a bearing housing (53, 63) in a bearing arrangement between two axially supported on the bearing housing (53, 63) outer bearing rings (93) the axis (G) is rotatably supported, the outer bearing rings (93) on their mutually facing sides each have an outer bearing surface which runs coaxially to the axis (G) and which is opposite each bearing surface (81) formed on the end face of the gear wheel (7), characterized in that the adjustment drive (5, 6) is designed according to at least one of the Claims 1 to 8th , Method for adjusting a bearing arrangement of an adjustment drive (5, 6) for a motor-adjustable steering column (1) for a motor vehicle, comprising a threaded spindle (52, 62) engaging in a spindle nut (51, 61) with an axis (G), and a Gear wheel (7) connected to the spindle nut (51) or the threaded spindle (62) in a rotationally fixed manner, which in a bearing housing (53, 63) in a bearing arrangement between two outer bearing rings (93) axially supported on the bearing housing (53, 63) about the axis (G) is rotatably supported, an outer bearing ring (93) being axially resiliently supported on the bearing housing (53, 63) via an elastic prestressing element (94, 95), comprising the steps: A) applying an axial prestressing force (F) to the Preloading element (94, 95), B) Applying a loading torque (M, K) to the gear wheel (7) and measuring the loading torque (M, K), C) Measuring a bearing condition variable (M, K) correlated with the loading torque (M, K) x) D) comparing the measured bearing condition quantity (M, x) with a predetermined condition target value, E) if the measured bearing condition quantity (M, x) deviates from the condition target value: changing the axial preload force (F), F) if the measured bearing condition quantity (M, x ) reached the target state value: fix the preload element (9) in the axial preload position on the bearing housing (63) and finish the setting. Procedure according to Claim 11 , characterized by the steps: B1) applying a torque (M) as a loading torque for rotating driving of the gear wheel (7) and thereby measuring the torque (M) as a correlating bearing condition variable, C1) comparing the measured torque (M) as a bearing condition variable with a predetermined one Torque target value as the target status value, E1) if the measured torque (M) as the bearing condition variable is smaller than the specified torque target value as the target target value: Increase the axial preload force (F), F1) if the torque (M) as the bearing condition parameter reaches the specified torque target value as the target target value: Fix of the biasing element (9) in the axial biasing position on the bearing housing (63) and ending the setting. Procedure according to Claim 11 or 12 , characterized by the steps: B2) applying a tilting moment (K) as a loading moment transverse to the axis (G) to the gear wheel (7) and thereby measuring a displacement (x) of the gear wheel (7) relative to the bearing housing (63) as a correlating bearing state variable , C2) Comparing the measured displacement (x) as a bearing condition variable with a stiffness limit value as a target state value, E2) if the measured displacement (x) as a bearing state variable is greater than the stiffness limit value as a target target value: increase the axial preload force (F), F2) if the measured displacement (x) as the bearing condition quantity reaches the stiffness limit value specified as the condition target value: fix the preload element (9) in the axial preload position on the bearing housing and finish the adjustment. Procedure according to one of the Claims 11 to 13 , characterized in that when the biasing force (F) is applied, the biasing force (F) is measured. Procedure according to one of the Claims 11 to 14 , characterized in that the pretensioning force (F) is exerted on a securing element (95) arranged in front of an outer bearing ring (93). Procedure according to Claim 15 , characterized in that the securing element (95) can be moved in the direction of the pretensioning force (F) relative to the bearing housing (63) and is designed to be self-fixing against the pretensioning force (F) on the bearing housing (93). Method for adjusting a bearing arrangement of an adjustment drive (5, 6) for a motor-adjustable steering column (1) for a motor vehicle, comprising a threaded spindle (52, 62) engaging in a spindle nut (51, 61) with an axis (G), and a Gear wheel (7) connected to the spindle nut (51) or the threaded spindle (62) in a rotationally fixed manner, which in a bearing housing (53, 63) in a bearing arrangement between two outer bearing rings (93) axially supported on the bearing housing (53, 63) about the axis (G) is rotatably supported, an outer bearing ring (93) being axially resiliently supported on the bearing housing (53, 63) via an elastic prestressing element (94, 95), comprising the steps: A) applying an axial prestressing force (F) to the prestressing element (94, 95), B) measuring the axial preload force (F), D) comparing the measured pretensioning force (F) with a predetermined target pretensioning force, E) if the measured preload (F) deviates from the specified target preload: changing the axial preload (F), F) when the measured preload force (F) reaches the predetermined target preload force: fix the preload element (9) in the axial preload position on the bearing housing (63) and finish the setting.

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