EP0275876B1 - Method and apparatus for aligning a work piece - Google Patents

Description

The invention relates to a method and a device according to the preambles of claims 1 and 11.

The fatigue strength of workpieces with circular grooves, for example crankshafts, steering knuckles, stepped shafts or the like, is primarily impaired by the reduced strength due to the shape of the materials in the area of these grooves. It is therefore known to treat such workpieces with a method which is referred to as "deep-rolling" and which consists in that deep-rolling rollers with hydraulic cylinders / piston arrangements are pressed against the throat walls which delimit the grooves, in particular the grooves, (DE-C-30 37 688 ). On the one hand, this increases the strength of the materials in the outer layers, and on the other hand, useful compressive residual stresses are generated in the zones adjacent to the throats, which are noticeable in later use of the workpieces by a considerably increased fatigue strength. However, these residual compressive stresses, which are desired in material to increase the fatigue strength, inevitably lead to distortions in the workpieces, the directions and amounts of the distortions largely depending on the history of the workpieces. In the case of a crankshaft, these faults primarily result in directional errors in the main bearing and crank pins and thus in a warping or "knocking" of the entire crankshaft, since inevitable deviations in the vertical position of the crank webs with respect to the journal axes occur. The resulting deviations from the concentricity of the crankshaft with respect to its theoretical axis of rotation must be eliminated by subsequent straightening of the crankshaft regardless of whether the crankshaft bends in defined tolerance ranges during deep rolling be held or not.

Straightening such workpieces by bending has proven to be unsuitable because the useful residual compressive stresses in the area of the throats are largely reduced during bending, as a result of which the increased fatigue strength obtained during deep rolling is lost again.

For straightening crankshafts that have been subjected to a deep rolling process, it is already known, while avoiding this disadvantage, to act once and with sufficient force on the walls delimiting the throats with a special tool at suitable points (GB-A-1 004 962, DE -C-2 556 971)
The directions in which these forces are to be exerted result from the directional deviations obtained by measuring the crankshaft after deep rolling. Here, the knowledge is exploited that a force of sufficient magnitude that is effective over a limited arc of the throat circumference is suitable for causing permanent changes in direction and thereby reducing the impact of a crankshaft. In contrast to bending, only additional compressive stresses are introduced into the material during this straightening process, which do not reduce the fatigue strength. On the other hand, it is disadvantageous that a special processing station for the straightening process with an additional tool including the hydraulic press is required and large forces of up to 1000 kN have to be exerted on the crankshaft.

The use of lower forces is possible when using known methods and devices according to the genera described at the outset (GB-A-957 805). However, in a first step serving the deep rolling, deep rolling is avoided in the area of the central main bearing journals and the crankshaft is directed into a subsequent, second cold rolling step by specifically applying pressure to the fillet walls of the middle main bearing journals alone. Since this second step is only intended to straighten or remove the eccentricity of the central main journal, the pressure is selected solely as a function of the eccentricity to be eliminated.

It follows that this pressure can also happen to be used to produce a sufficient target fatigue strength in the area of the central main bearing journal and that the crankshaft is only straightened at random, since the removal of the eccentricity of the central main bearing journal is usually not sufficient for this.

From JP-A-59 101 228 a method and a device for straightening a crankshaft are known, wherein the concentricity deviations are measured for each individual main bearing journal and the straightening by cold rolling of the throat walls of the crank pins by means of those which can be inserted into the throats and movable transversely to the theoretical axis Tools. No brackets are assigned to the main bearing journals.

The invention has for its object to design the method and the device of the aforementioned types so that the desired target fatigue strength is obtained in the deep rolling step in the area of all main bearing and crank pins and the straightening process can nevertheless be carried out with low forces and without additional tools .

The method and the device with the features of Claims 1 and 11, respectively.

Further advantageous features emerge from the subclaims.

The invention has the advantage that the cold rolling for straightening can be carried out in several successive steps and the forces exerted in each of these steps of up to approximately 50 kN can be considerably smaller than when using the known device. This makes it possible to use the same devices and tools for straightening, which are also used for deep rolling, without the risk that the deep rolling rollers are overloaded during the straightening process. At the same time, this enables the workpieces to be deep-rolled and straightened in the same processing station, the workpieces being able to remain clamped during the measurement of the radial run-out deviations, for example by these deviations can be determined with measuring devices integrated in the deep rolling device.

• Fig. 1 schematisch ein Schlagdiagramm für eine Kurbelwelle;
• Fig. 2 die Draufsicht auf eine erfindungsgemäße Vorrichtung zum Richten von Werkstücken, insbesondere Kurbelwellen;
• Fig. 3 einen Schnitt längs der Linie III-III der Fig. 2;
• Fig. 4 eine schematische, teilweise Vorderansicht der Vorrichtung nach Fig. 1 in starker Vergrößerung;
• Fig. 5 eine Variante für eine Einzelheit der Fig. 3; und
• Fig. 6 schematisch die Anwendung des erfindungsgemäßen Verfahrens auf einen Hauptlagerzapfen einer Kurbelwelle.

The invention is explained in more detail below in connection with the accompanying drawing using an exemplary embodiment. Show it:

• Fig. 1 shows schematically a beat diagram for a crankshaft;
• 2 shows the top view of a device according to the invention for straightening workpieces, in particular crankshafts;
• Fig. 3 is a section along the line III-III of Fig. 2;
• Fig. 4 is a schematic, partial front view of the device of Figure 1 in a large magnification.
• Fig. 5 shows a variant for a detail of Fig. 3; and
• Fig. 6 shows schematically the application of the method according to the invention to a main bearing journal of a crankshaft.

Fig. 1 shows a workpiece 1 in the form of a crankshaft. This has five main bearing journals 2a to 2e, the axes of which lie on a theoretical axis 3, here the axis of rotation of the crankshaft, four crank journals 4a to 4d arranged between the main bearing journals 2 and a crank web 5 each between these and the main bearing journals 2. At the transition points between the crank cheeks 5 and the main bearing or crank pins 2 or 4, grooves 6a to 6d with circular cross-sections are provided which rotate around the axis 3. Alternatively, the workpieces 1 can consist of steering knuckles, stepped shafts or the like. With fillets corresponding to fillets 6, which are generally arranged at the transitions from one cross-section to another and serve to provide the insufficient fatigue strength in the area to enlarge the cross-sectional transitions.

Above the workpiece 1, an impact diagram is shown in FIG. 1, which indicates an arbitrarily assumed curvature of the crankshaft in the drawing plane on a greatly enlarged scale. The distances 1 of the respective center points of the main bearing journal 2 from the left end of the crankshaft in FIG. 1 are plotted along the abscissa, while the respective deviation S of these center points from the theoretical axis 3 is plotted along the ordinate in large magnification. The deviations S that actually occur are generally very small, amount to only a few tenths or hundredths of a millimeter and can each be both positive and negative. 1 also relates to a selected rotational angle position of the crankshaft. Corresponding beat diagrams can be drawn for other rotational angle positions.

errechnet.From the impact diagram it is easy to see by what measure and in which direction the crankshaft on each main journal 2 must be directed in order to ensure that all axes of the main journal 2 lie essentially in one axis, namely the theoretical axis 3. For the main bearing journal 2b according to FIG. 1, for example, a standard dimension of Δ S2 perpendicular to the abscissa would be required, which is based on the formula

calculated.

Since it is very tedious to align a crankshaft one after the other in all possible directions, the following new alignment strategy is proposed according to the invention:
First, any deviation from the concentricity is broken down into two mutually perpendicular components, one of which lies in a plane called the main plane and the other in a plane called the secondary plane. If all the crank pins 4b to 4c according to FIG. 1 lie in a single plane, which also contains the theoretical axis 3, then this is declared the main plane, while the plane perpendicular thereto is defined as the secondary plane. If, on the other hand, the crank pins 4a to 4d differ from FIG. 1 in at least two different planes, for example by being offset by 90 ° in the circumferential direction of the crankshaft, then for each main bearing pin 2b, 2c and 2d, the one according to FIG lies two adjacent crank pins 4, the plane which explains the main plane and which contains the axis 3 and the bisector between the two planes, each of which passes through the axis of one of the adjacent crank pins and the theoretical axis 3. For example, with reference to FIG. 1, the axis of the crank pin 4b and the axis 3 define a first plane, the axis of the crank pin 4c and the axis 3 define a second plane, and the bisector between these two planes and the axis 3 define a third plane that in FIG this example would be the main plane for the main journal 2c. The plane perpendicular to this is the secondary plane for this main journal 2c. On the other hand, the main plane for the main bearing journals 2a and 2e located at the ends of the crankshaft, each of which only one crankpin 4a or 4d is adjacent, results from the axis 3 and the axes of these crankpins 4a and 4d, while the planes perpendicular thereto the minor levels are.

To this extent, the invention is based on the knowledge that directional operations in the secondary planes also generally result in deformations of the crankshaft in the main planes, while conversely, straightening operations in the main planes cause practically no repercussions or deformations in the secondary planes. The directional strategy according to the invention results from this, first of all eliminating all components of a field located in the secondary planes and only then eliminating all components of the field located in the main planes.

The following flow chart results for practical use. After the workpieces have been deep-rolled, the deviation from the concentricity is measured for each individual main bearing journal. Then the components of the deviations in the main and secondary levels are determined. If these values lie outside the specified tolerance ranges, the standard dimension Δ Sn is then first calculated for each individual main journal, by which straightening must take place in the secondary plane. The crankshaft is now straightened in the secondary planes, with all or more main bearing journals being machined simultaneously or in succession. The straightening operations are preferably carried out in several successive steps, with the remaining deviations being measured after each step and the subsequent step being carried out with corrected straightening parameters. Corrected straightening parameters are understood in particular to mean that the magnitude of the force required to bring about the remaining straightening dimension Δ Sn is changed depending on the history of the crankshaft and, above all, depending on the forces on the main bearing journal in previous steps were exercised. In particular, if a certain straightening force was not sufficient in a first step to bring about the desired straightening dimension, a higher straightening force is selected in a subsequent step. If the straightening parameters used in previous straightening operations are not taken into account, reasonable straightening is hardly possible due to the changing dependence between the straightening dimension and the straightening force. The dependencies of the achievable standard dimensions on the applied directives must be determined empirically.

The values obtained in each case can be collected and stored in a database, which can be used as a table of values for the directional forces to be used in the case of statistical handling. A data processing system is therefore preferably used to calculate the straightening forces, in the memory of which all the data relating to a specific workpiece type are collected.

If all components of the concentricity deviations lying in the secondary levels have been eliminated to such an extent that the remaining deviations lie within the required tolerance ranges, the workpiece is aligned in the main levels by correspondingly calculating and empirically determining the guide dimensions Δ Sh lying in the main level or values retrieved from the database can be determined for the respective straightening forces. These straightening operations in the main plane are also preferably carried out successively in a plurality of successive steps until finally the remaining deviations for all main bearing journals lie within the defined tolerance ranges.

Finally, the invention is based on the knowledge that straightening can be carried out by cold rolling and therefore, for example, with the aid of pressure rollers inserted into the throats of the main bearing journal 2, by exerting sufficient pressure on selected circumferential sections of the walls delimiting the throats. For this purpose, the crankshaft is rotated continuously or with a pendulum movement, or the respective pressure roller is guided around the crankshaft or its theoretical axis in a continuous or reciprocating movement. It is only necessary to vary the forces exerted by the pressure rollers on the crankshaft as a function of the respective angular position of the crankshaft with respect to the pressure roller in such a way that a directional effect is only in the required direction, i.e. is achieved when the pressure rollers run onto the preselected sections, while in all other directions no sufficient forces are exerted by the pressure rollers to achieve a directional effect.

The devices known per se for deep rolling are preferably suitable for the practical execution of straightening by cold rolling of crankshafts (DE-C-30 37 688), provided certain changes are made to them. A device of this type suitable for the purposes of the invention is explained in more detail below with reference to FIGS. 2 to 6 and with reference to a workpiece 1, which consists of a crankshaft with only two crank pins 4a, b and three main bearing pins 2a, b, c.

According to FIGS. 2 to 4, the device contains two master shafts 8a and 8b which are rotatably mounted and arranged one above the other in a frame 7 and which correspond in size and shape to the workpiece 1 to be machined and in the example shown correspondingly many main bearing journals 10a and 10b, crank journals 11a and 11b and crank arms 12a and 12b. Both master shafts 8a, b can be driven synchronously by a motor 13 mounted on the frame 7, on the drive shaft of which a gearwheel 14 is fastened. The gearwheel 14 is connected to a gearwheel 15 fastened on the master shaft 8a, which is connected via a further gearwheel 16 to a gearwheel 17 fastened to the master shaft 8b, so that both master shafts are driven in the same direction when the motor 13 is switched on.

Each main bearing and crank pin 10 or 11 is rotatably supported in a lower jaw 18 or 19 of a pincer-type holder for the workpiece 1. Each jaw 18 or 19 is pivotally connected to an upper jaw 21 or 22 of the holder by means of a pivot pin 20 (FIG. 2). At their front end, the two jaws 18, 21 and 19, 22 each carry a rolling tool. This has in each case two cylindrical support rollers 23 which are rotatably mounted and arranged in parallel in the lower jaw 18 and 19 and a known combination of a profile roller 24 and two pressure or deep-rolling rollers 25 mounted in the upper jaw 21 or 22 (cf. 3 and 4). The axes of rotation of the pressure rollers 25 and the axis 3 of the workpiece 1 or the axes of rotation of the profile rollers 24 parallel thereto generally form an angle of approximately 35 °. In addition, the pressure rollers 25 are supported in circumferential grooves 26, which have a circular cross section and at the front ends of the profile roller 24 are formed. The profile roller 24 is rotatably mounted on a shaft 27 fastened in the frame 7, while the deep-rolling rollers 25 are cantilevered on the profile roller 24.

Each tong-like holder is assigned a control device, only the control device for the holder and the main bearing journal 2c being shown in FIG. 3. Here, however, the rolling tool consisting of parts 23 to 25 for holding the main bearing journal 2c to simplify the drawing is only visible in FIG. 4, but not also in FIG. 3. The control device contains a hydraulic or pneumatic cylinder 28, which is fastened to the rear end of the associated lower jaw 18 and in which a piston 29 is slidably mounted and carries a piston rod 30 articulated on the upper jaw 21, so that the upper jaw 21 can be moved in or out Extending the piston rod 30 can be pivoted about the pivot pin 20. The chambers of the cylinder 28 lying on both sides of the piston 29 can optionally be connected via lines 31, 32 and a directional control valve 33 to a line 35 leading to a tank 34 or a further line 36. Line 36 leads to an output of an actuator 37, e.g. of a further directional valve, which is simultaneously designed as a pressure control valve and has a second, blocked outlet. A line 38 connected to the one input of the actuator 37 is either connected via a limiting valve 39 to the one output or via a further limiting valve 40 to the other output of a further directional valve 41, one input of which is blocked off and the other input of which is connected to the output of one Pump 43 driven by a motor 42 for the hydraulic or pneumatic medium, for example Oil, is connected. The outlet of this pump 43 is also connected to a limiting valve 44 which is connected to the tank 34 via a line 45. Finally, the output of the pump 43 is still connected to the other input of the actuator 37 via a limit valve 46.

The directional control valves 33 and 41 are, for example, with conventional switching magnets 33a and 41a, while the actuator 37 is assigned a control member 37a, which may also consist of a switching magnet. The switching magnets 33a, 41a and the control member 37a are connected to a sequencer 47, and the control member 37a also leads to the output of a power amplifier 48c. In addition, each directional control valve 33 and 41 can assume two positions a and b , the position a being the basic position produced by a compression spring 33b, 41b, while the other position b is produced by the corresponding switching magnet 33a, 41a being correspondingly connected via the sequence control 47 is excited. The actuator 37 can also assume two positions a and b , the position b being produced by supplying a control signal to the control member 37a from the sequence control 47 or from the associated power amplifier 48c, while the other position a is the basic position produced by a compression spring 37b. In addition, actuator 37 can be controlled by an analog signal from associated power amplifier 48c to assume any intermediate position between the two positions a and b , in which the pressure at its only open output assumes a value which depends on the pressure its two inputs and also depends on the proportions with which the passages indicated by arrows are involved in the passage of the printing medium. Instead of the directional control valve shown, all other components can also be used for the actuator 47, by means of which - controlled by electrical signals or the like. - The pressure in the line 36 can be continuously adjusted between a minimum and a maximum value. To measure the impact or the bending of the workpiece 1 to be machined, the control device has a measuring element 49 attached to the frame 7 (FIG. 3). The measuring element 49 consists, for example, of a commercially available displacement sensor with a plunger 50, which is pressed against the main bearing journal 2c by a compression spring 51. Depending on the respective position of this plunger 50, an electrical signal appears at the output of the measuring element 49, which is fed to a measuring amplifier 52c assigned to the main journal 2c. Alternatively, purely inductive, non-contact displacement sensors can be used to measure the deviations of the main bearing journals from the concentricity. In addition, a force meter 53 can be provided for monitoring the forces which are exerted on the associated pressure roller 25 or the workpiece 1 with the upper jaw 21 and which consists, for example, of a strain gauge connected to the jaw 21 and an electrical signal at its output emits, which is also supplied to the measuring amplifier 52c.

The control devices for the other main bearing journals 2a and 2b are designed accordingly and provided with corresponding measuring amplifiers 52a, b or power amplifiers 48a, b (FIG. 3). Further, similarly constructed control devices can be assigned to the holders for the crank pins 4a, b, although only the parts required for deep-rolling, but not also the parts required for straightening, need be provided.

To measure the respective angular position of the master shafts 8a, b, at least one of them is equipped with a display element 54 (FIG. 1), e.g. a rotary encoder, which can consist of a conventional angle encoder and whose output signals are fed to an amplifier 55. The output signals of the measuring amplifier 52 and the amplifier 55 are fed via a line bundle 56 to a data processing system 57 and from there via a further line bundle 58 to the power amplifiers 48a, b, c. Finally, a data memory 59, not shown, can be assigned to the computer 57.

The described device works as follows:
In a first processing step, the workpiece 1, that is to say the crankshaft shown in FIGS. 1 to 4, is to be subjected, for example, to a conventional deep-rolling process. For this purpose, starting from the basic positions a directional control valves 33 and 41 and the actuators 37 according to FIG. 3, the directional control valves 33 are first moved into position b by means of the sequence control 47, which is provided with corresponding switches or can be controlled automatically associated switching magnets are excited accordingly. As a result, the lines 31 are connected to the tank 34 and the lines 32 to the lines 36, which lead to the pump 43 via the actuators 37 and the limit valves 46.

When the motor 42 is switched on, the piston rods 30 are therefore pulled into the cylinders 28 and the tong-like holders are thereby opened.

The crankshaft to be machined is now inserted into the holder by placing its main bearing or crank pin 2 or 4 on the support rollers 23 of the associated lower jaws 18 or 19, which is easy due to the corresponding shape of the master shafts 8a, b is possible (see in particular Fig. 2). Then the directional control valves 33 are returned to the basic position a by de-energizing the associated switching magnets and at the same time the actuators 37 are brought into position b by means of the sequence control 47. As a result, the lines 32 are connected to the tank 43 and the lines 31 are connected to the pump 43 via the limit valves 39. When the motor 42 is switched on, the piston rods 30 are therefore extended and the forceps-like holders are closed with a pressure which is predetermined by the limit valves 39. When the motor 13 is switched on, the two master shafts 8a, b are now rotated and the jaws 19 and 22 seated on their crank pins 11a, b are set in a circular orbital movement which is correspondingly transmitted to the crank pins 4a, b of the crankshaft to be machined . This in turn has the consequence that the pressure rollers 25 roll in the throats of the crank pins 4a, b and the main bearing pins 2a, b, c and bring about the desired deep rolling process. The force with which the pressure rollers 25 act on the throat walls can be adjusted manually or automatically using the limit valves 39.

After the deep rolling process has ended, the motor 13 is switched off and the tong-like holders are opened again by appropriate control. The machined crankshaft can now be removed and measured in any manner and in a manner known per se, in order to determine the deviations existing after the deep rolling process, the guide dimensions Δ Sn and Δ Sh and the required guide forces.

The workpiece 1 is preferably measured when the device described is used by virtue of the fact that it remains clamped in the clamp-like holders and is scanned with the measuring elements 49. So that no large forces are exerted by the pressure rollers 25, the directional control valves 33 and 41 are left in the basic position a , while the actuator 37 is controlled into the position b by means of the sequence control 47. As a result, the line 31 is now connected to the pump 43 via the limiting valve 46, which is set to a lower pressure than the limiting valve 39. After the engine 13 is switched on again, the crankshaft to be machined again performs its characteristic rotary movement. At the same time, the measuring elements 49 are activated, as a result of which the signals they measure are fed via the measuring amplifiers 52 and the line bundle 56 to the data processing system 57, to which the output signals of the display element 54 are also continuously fed. The data processing system 57 now uses a previously entered program and the continuously supplied data from the measuring members 49 and the display member 54 to first determine the respective size and the respective direction of the concentricity deviations for all main bearing journals 2a, 2b and 2c and then calculates the standard dimensions Δ Sn and Δ Sh and the straightening forces to be exerted by the pressure rollers 25 on the main bearing journals 2a, b, c, all values and dependencies relating to similar workpiece types stored in the database 59 being able to be taken into account. Finally, the data processing system 57 converts the determined directional forces into analogue control signals for the control elements 37a of the actuators 37.

Finally, the actual straightening process takes place. For this purpose, the crankshaft to be machined remains in the tong-like holders, while the directional control valves 33 and the actuators 37 are controlled into their basic position a . The directional control valve 41, however, is transferred to position b .

By turning on motors 13 and 42, the crankshaft to be machined is set back into its characteristic orbital motion, while at the same time the lines 31 are initially only connected to the pump 43 via the limit valves 46. Under the control of the display element 54, which constantly rotates with the master shafts 8a, b, the data processing system continuously transmits control signals which are fed to the control elements 37a via the line bundle 58 and the power amplifiers 48a, b, c. As a result, their valve stems are displaced more or less in the direction of the positions b in accordance with the calculated directional forces, with the result that pressure is generated in the lines 36, which may lie between the minimum value of the limiting valve 46 and the maximum value of the limiting valve 40. With the aid of the display element 54 and the data processing system 57, these are also controlled so that initially only straightening operations are carried out on the secondary levels on all main bearing journals. These straightening operations are preferably carried out for a plurality or all of the main bearing journals simultaneously or in succession and in accordance with the above description in several successive steps, between which the crankshaft is measured again, so that the data obtained are stored in the database 59 and then new straightening parameters are calculated for the next step in each case can be. After the straightening operations on the secondary level have been completed and there are no tolerable deviations from the concentricity only in the main level, further straightening operations are carried out in the same way in order to make the deviations from the concentricity present in the main level sufficiently small. The advantage here is that the direction in which a straightening operation is carried out on any main journal can be preselected only by the associated actuators 37 providing sufficiently large pressures in the lines 36 at the right moment, while at all other times the pressure in the lines 36 is reduced to a pressure that cannot effect a straightening operation. Since each individual main journal 2a, b, c also has its own bracket and control device , the various straightening operations can be carried out in a single operation even if different main and secondary levels are assigned to all main bearing journals.

In all possible machining situations, the maximum system pressure is finally displayed on the limiting valve 44 in order to avoid the occurrence of critical overpressures. In addition, with the aid of the force meter 53, it is possible to constantly monitor the forces actually exerted on the pressure rollers 25 and, if necessary, to provide control circuits for the cylinders 28, so that the straightening forces calculated by the data processing system 57 actually actually apply to the workpieces 1 or the main bearing journal 2 be exercised.

If the use of a data processing system is not desired, the pressures supplied to the cylinders 28 during straightening can also be generated by controlling each actuator 37 with a device shown schematically in FIG. 5. Instead of the switching magnet, this device contains a sleeve 60, which is connected to the valve stem of the actuator 37 and in which a plunger 61 is displaceably guided. The sleeve 60 has a vertically protruding arm 62 and the plunger 61 has a vertically protruding arm 63 which projects through a slot in the sleeve wall. An adjusting screw 64 is rotatably but axially immovably mounted in the arm 63, the threaded portion of which projects through a threaded hole in the arm 62. Therefore, the distance of the end 65 of the plunger 61 protruding from the sleeve 60 from the valve stem can be changed by turning the adjusting screw.

The free end of the plunger 61 is pressed by a compression spring 37b acting on the valve stem against the control member in the form of a cam plate 67, which is fastened, for example, to a free end of the master shaft 8a and follows its rotary movements. Depending on which circumferential section of the cam plate 67 acts on the end 65, the same as that described with reference to FIG. 3 Embodiment exerted a greater or lesser force on the pressure roller 25. The cam plate 67 is fastened on the master shaft 8a by means of a fastening screw 68 and then always assumes the same rotational angle position relative to this and thus also to the crankshaft to be straightened. Depending on the required straightening forces, different cams 67 are used for straightening in the secondary and main planes, which are also precisely adjusted by rotating the shaft 8a in accordance with the directions in which the straightening forces are to be made effective. The size of the maximum straightening force can be changed by turning the adjusting screws 64.

For straightening any of the main bearing journals 2 shown schematically in FIG. 6, it would in itself only be necessary to exert the straightening force once along an imaginary line extending parallel to the theoretical axis 3 on the circumference of the main bearing journal 2, this line being an extension of a Arrow v is located, which indicates the direction of the straightening operation. However, the straightening forces to be used would be very large. In contrast, when straightening by cold rolling, it has surprisingly been found that substantially smaller straightening forces of, for example, up to 50 kN are sufficient if these are exerted along a selected section 69, which is indicated schematically in FIG. 6 by a widened line, and if this selected section 69 is rolled several times with the pressure roller 25. The section 69 extends along the circumference of the main bearing journal 2 by approximately equal parts on both sides of the imaginary line over an arc of, for example, 10 ° to 20 ° in total. In order to avoid indentations of the pressure roller 25 in the main bearing journal 2, the pressure acting on the cylinder 28 is expediently gradually increased to a maximum value before the pressure roller 25 hits the selected section 69, then is held at this maximum value along section 69 and finally gradually reduced after leaving section 69. When using the data processing system 57, this increase and decrease in pressure can be predetermined by appropriate programs become. 5, this control takes place in that the circumference thereof is provided with an approximately circular section 70, a rising section 71, a further circular section 72 and a falling section 73, section 72 being that section of the main bearing journal 2 corresponds to, along which the pressure roller 25 exerts the straightening force required for the straightening operation. If it is desired with this type of control to reduce the time required for one revolution of the crankshaft to be machined, only the engine 13 needs to be set to a higher speed level whenever the pressure roller 25 is not on the selected section 69.

Alternatively, the straightening operation can also be carried out by subjecting the master shafts 8a, b and the crankshaft to be straightened to a reciprocating oscillating movement in such a way that the pressure rollers 25 always only overflow the preselected sections 69 and narrow neighboring sections. In this case too, the pressure acting on the pressure rollers 25 in the adjacent areas is expediently gradually increased or decreased. In this embodiment, too, the data processing system 57 or the cam disks 67 can optionally be used. In this case, a reversing motor with a corresponding control is expediently used as the motor 13.

Another important parameter when straightening by cold rolling is the number of rollovers of the selected sections 69. Because during rollover, i.e. when the pressure rollers 25 act on the selected sections 69, flow can be prevented in the direction of the bottoms of the throats 6, which can only be compensated for by repeated rolling over, the pressure rollers are expediently guided at least five, preferably at least ten times over the selected section 69.

Claims (12)

1. A method of hard-rolling and then aligning a crankshaft (1) mounted rotatably about its theoretical axis, the crankshaft comprising a plurality of main bearing journals (2), crank cheeks (5) and crank journals (4a to 4d) lying therebetween and fillets (6a to 6d) running round the main bearing journal axes and crank journal axes at the transitions between the main bearing journals and crank journals and the crank cheeks, wherein both the hard-rolling and the aligning are effected by cold rolling the fillet walls by means of tools (24, 25) which can be fitted into the fillets and are movable transversely to the theoretical axis (3), and the crankshaft is so aligned after measuring its deviation from true running relative to the theoretical axis resulting from the cold rolling in that pressure is exerted by means of the tools on selected sections (69) of the fillet walls, characterized in that the hard rolling is effected before the alignment in all regions of the main bearing and crank journals (2, 4a to 4d), the deviations from true running of the crankshaft (1) are measured for each individual main bearing journal (2) and the alignment is so effected thereat that the residual deviations from true running for all main bearing journals (2) then lie within fixed tolerance ranges.
2. A method according to claim 1, characterized in that the cold rolling is effected with at least one pressure roller (25), while relative rotation about the axis (3) between the workpiece (1) and the pressure roller (25) is effected during the cold rolling, and a force effecting the aligning operation is exerted on the pressure roller (25) at least at all times when this roller runs over the selected section (69) of the fillet wall.
3. A method according to claim 2, characterized in that the workpiece (1) or the pressure roller (25) is subjected to a to and fro oscillating movement.
4. A method according to claim 2, characterized in that the workpiece (1) or the pressure roller (25) is subjected to a continuously circulating rotary movement.
5. A method according to claim 3 or 4, characterized in that the force exerted on the workpiece (1) or the pressure roller (25) is increased gradually each time before it runs on to the selected section, up to a maximum value, is then maintained at this maximum value and finally is gradually reduced before leaving this section (69).
6. A method according to claim 4 and 5, characterized in that the angular speed or the rotary movement is increased during that interval of time in which the pressure roller (25) is outside the selected section (69).
7. A method according to at least one of claims 1 to 6, for aligning crankshafts with a plurality of main bearing and crank journals, wherein the axes of the crank journals all lie in a single plane containing the theoretical axis (3), characterized in that the crankshaft is aligned firstly in its subsidiary plane and only then it its main plane, where the subsidiary plane is perpendicular to the main plane and likewise contains the theoretical axis (3).
8. A method according to at least one of claims 1 to 6, for aligning crankshafts with a plurality of main bearing and crank journals, wherein the axes of the crank journals do not all lie in a single plane containing the theoretical axis (3) and one or two crank journals are adjacent to each main bearing journal, characterized in that the crankshaft is firstly aligned in its subsidiary planes and only then in its main planes, wherein for each main bearing journal (2) there is defined as the main plane that plane which either contains the theoretical axis (3) and the axis of the single adjacent crank journal (4) or contains the theoretical axis (3) and bisects the angle between the two planes which run through the respective adjacent crank journals (4) and the theoretical axis (3), and wherein the subsidiary plane for each main bearing journal (2) extends perpendicular to a main plane.
9. A method according to at least one of claims 1 to 8, characterized in that the aligning is effected by simultaneous cold rolling of the walls of the fillets (6) of a plurality or all the main bearing journals (2).
10. A method according to at least one of claims 1 to 9, characterized in that the aligning is effected in sequential steps, the crankshaft (1) being measured afresh after each step and the following step being carried out with modified alignment parameters corrected in the light of the previous steps.
11. Apparatus for carrying out the method according to any of claims 1 to 10, with pincer-like holders carried by two master shafts (8a, 8b) and each comprising two jaws (18, 21 or 19, 22) pivotally connected to each other for clamping an associated main bearing or crank journal (2, 4) of a crankshaft (1), wherein the one jaw (18, 19) is provided with at least one support roller (23) and the other jaw (21, 22) is provided with a pressure roller (25) for fitting into a fillet (6) and wherein the number of main bearing and crank journals (2,4) of the crankshaft (1) corresponds in use of the apparatus to the number of holders, and with control devices for the holders for controlling the clamping force of the jaws (18, 21 or 19, 22), wherein at least one of holders associated with the main bearing journals (2) has associated therewith a measuring member (49) for determining the deviations from true running in the region of the associated bearing journal (2), and an adjusting member (37), wherein the forces exerted on the associated main bearing journal (2) by the pressure rollers (25) by means of the adjusting member (37) can be adjusted in dependence on values determined from the current rotary angular position and the determined deviations from true running to align the main bearing journal (2), such that the deviations from true running remaining after the aligning lie for this at least one main bearing journal (2) within predetermined tolerance ranges, characterized in that each holder of the main bearing journals (2) has associated therewith such a measuring member (49) and a control device with such an adjusting member (37), whereby the forces exerted by the pressure rollers (25) can be adjusted by means of these adjusting members (37) to such values adapted to align the main bearing journals (2) that the deviations from true running remaining after the alignment lie within predetermined tolerance ranges for all main bearing journals (2).
12. Apparatus according to claim 11, characterized in that it comprises at least one indicator device (54) connected to all control devices to indicate the current rotary angular position of the crankshaft (1).

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