DE1196926B - Device for automatic switching of speed change transmissions with at least one hydrodynamic torque converter - Google Patents

Description

Device for automatic switching of full speed changes, gearboxes with at least one hydrodynamic torque converter The invention relates to a device for automatic switching of speed change transmissions with at least one hydrodynamic torque converter or a hydrodynamic clutch and at least two downstream gear stages with continuously engaged gears, for example, within one Planetary gears that are shifted with friction engagement devices. The invention loading takes place both on vehicles and on stationary installations such. B. Oil extraction systems.

In hydrodynamic torque converters, the input drive torque increases in square dependence on the input speed. On the other hand, the output torque falls approximately linearly with increasing output speed, if it is assumed that the input torque and input speed are kept constant. It is known to adapt transmissions with hydraulic torque converters to the traction curve of a vehicle or other work machine in that the overall transmission is composed of several torque converters of different characteristics or of torque converters and hydrodynamic clutches, or by having one or more hydrodynamic torque converters a multi-stage gear transmission is connected downstream. In a diagram that shows the dependence of the output torque on the output speed, this adaptation to the traction curve is expressed by a series of approximately straight functions with different gradients, which overall show a tendency for the torque to decrease with increasing output speed. The kinks in this traction curve, which is composed of straight sections, represent the operating states in which the gear stages are changed or, in the case of a given curve, in which the gear stages are to be changed (see, for example, the top curve in FIG. 1). These kinks, i.e. H. the switching points can be determined by the ratio of the input speed to the output speed. It is known to shift the gears of multi-speed converter transmissions as a function of the ratio of the input speed to the output speed. Due to the operating conditions of the hydrodynamic torque converters described at the beginning, the optimal switchover points at different input speeds are on parabolas.

There is also a multi-stage drive transmission with a hydrodynamic torque converter and a downstream multi-stage gear transmission as well as a device for automatic switching of the individual gear steps, in which the speed ratio of the converter pump to the converter turbine remains the same even at low part-load speeds, so that the self-switching device is independent of The absolute level of the primary speed always switches in such a way that the converter is always driven in the most efficient transmission range, even with partial load.

It is also a speed change transmission with no hydrodynamic Converter became known that a plurality of epicyclic gears different has transmission ratio that switched with fluid pressure via brakes will. Part of this transmission is under the influence of a friction engagement device, z. B. brake band, which is dependent on a fluid pressure of the engine speed is controlled to gradually bring the torque of the machine into effect, the engagement device z. B. Brake, gradually tightened as the speed increases, suddenly released when the speed drops but at a given speed.

The known devices have the disadvantage that although the switching points are adapted to the various load conditions, or the clutches or brakes can be gradually engaged, the clutches or brakes are designed for the highest transferable torque. The switching pressure for these engagement devices is too high at part load, i. That is, power surges can easily occur. The purpose of the invention is to avoid this deficiency, i. H. to achieve soft, low-impact switching. As is well known, it is possible with converter transmissions in the same load level at constantly changing - maintain an approximately constant pump torque output speed. This means that when a converter is combined with a diesel engine, for example, the load levels are dependent on the input speed.

The object on which the invention is based is achieved in that the contact pressure of the friction engagement device, e.g. B. the pressure in hydraulic switchable clutches or brakes both when rising and falling Speed always from the square of the pump speed of the hydrodynamic. Converter or the hydrodynamic coupling is controlled as a function, for example in such a way that the fluid pressure from a control piston one with the pump of the hydrodynamic Converter driven controller is controlled.

As such, it would be conceivable to have the pressure supplied by the generator pump controlled directly by the controller in the manner described. On the other hand, however, a device for controlling the switching points of the gear steps can be supplied by the same pump, the pressure of which according to another point of view, e.g. B. is controlled depending on the square of the output speed or on the one hand by the square of the input and on the other hand by the square of the output speed. It is therefore advantageous to use the pressure leaving the regulator for control purposes. Since the amount of liquid flowing out of the controller is not sufficient to actuate the engagement devices (clutches or brakes), the invention is advantageously designed by a control valve for regulating the pressure for the engagement devices, which is influenced on the one hand by a pressure that is the square of the Pump speed of the converter (line) or the hydraulic clutch and on the other hand em * "er other flexible force, for example by the pressure generated by the pressure generator (line) is influenced. This idea should only be protected in connection with the main claim is a quadratic function of the speed, it is beneficial to the purpose of the invention to control the influence of a centrifugal governor, which is dependent on the square of the input speed. However, this is not absolutely necessary , which is a linear Fu Function translated into a curved function, in particular into a quadratic function. Resistors and potentiometers wound according to special functions can be used to electrically influence the control valve. Such function resistors or function potentiometers are also suitable for control when deviations from the quadratic basic function are desired.

If several clutches or brakes are to be shifted, several can be used Friction-Einrückvorrich- i control slide can be provided which each influenced in a different quadratic dependence on the output speed are. In terms of the pressure medium flow, these can either be next to one another or one behind the other be arranged branching.

The aforementioned translation from a linear function to a nonlinear one or a deliberate deviation from a theoretically or practically given quadratic Function can also be mechanical through the use of specially coiled helical springs or specially layered disc springs can be achieved.

For control by flyweights, either known centrifugal governors can be used act on the control body, or it is more expedient to proceed so that the Fluid pressure from a control piston proportional to the square of the speed is controlled, the one by a centrifugal force on the one hand and by the one behind the controller on the other hand is influenced.

In the foregoing, the basic idea of the invention has essentially become developed into a hydraulically switchable transmission. It goes without saying equally applicable to an electrically switchable secondary gear. One device for the automatic switching of transmissions with at least one hydrodynamic torque converter and at least two downstream gear stages with continuously engaged Gears fitted with electrical frictional engagement devices such as electromagnetic Clutches, controlled, can, if desired, the switching energy Hardness can be taken from the electrical power for the friction engagement devices is controlled depending on the square of the input speed. With electromagnetic Couplings can also keep the transferable torque constant to the maximum Remain designed moment and only the increase in switching energy as a function of can be controlled by the input speed or the square of the input speed.

In the F i g. 1 and 2 the invention is explained. It shows F i g. 1 shows a speed-torque diagram of a multi-stage converter transmission, FIG . 2 the diagram of a hydraulically switchable transmission, which consists of a hydrodynamic torque converter and a planetary gear connected downstream.

In the Diagran in Fig . 1 shows the operating behavior of a three-stage converter transmission at different load levels. If a diesel engine or a prime mover with similar behavior is assumed as the drive, the families of curves denote the courses of the secondary torques at 100, 90, 80, 70 and 60 % primary torque or primary speed (drive or pump speed). As a result of the properties of the hydrodynamic torque converter described above, the intersections of the torque lines with the ordinate and the square of the primary speed coincide. So they are 100, 81, 64, 49 and 36% of the full load turbine torque. In contrast, the points of intersection of the torque lines with the abscissa go back in a linear relationship, as can be seen from the dashed line extensions of the torque lines 11 for the first gear. The same applies analogously to the torque lines 12 of the second gear and 13 of the third gear. The intersections of the lines of moments, i.e. In other words, the switching points from first to second gear and from second to third gear are therefore on parabolas 14.15.

With F i g. 2 is an automatic hydraulic circuit of a transmission is shown schematically, which consists of a hydrodynamic converter 35 and a downstream multi-stage reversing and change planetary gear. The planetary gear has the following gears, calculated from the converter: a reverse gear that can be shifted with a brake 36 , a forward gear that can be shifted with a brake 37 , a third gear that can be shifted with a brake 38 , a second gear that can be shifted with a brake 39 and one with a clutch 40 switchable direct first gear.

A centrifugal governor 42, which contains at least one centrifugal weight piston 43, is driven in proportion to the converter drive 41. The flyweight piston is arranged so that it can be thrown outwards by centrifugal force. The outer piston surface, together with the regulator housing, forms a chamber 44 which is connected to a control chamber 46 by a bore 45. The inner piston surface also forms a chamber 47 with the regulator housing, which is connected to the free air or to the oil sump. The control chamber 46 is connected on the one hand via a control edge and a line 48 to a gear pump 49 and on the other hand via a line 50 to a central line 51, the branches of which will be described later.

In proportion to the speed of the output shaft 52 of the planetary gear, a second centrifugal governor 53 is driven, which is also provided with flyweight pistons, with as many pistons of different weights as gear shifts are to be made. The transmission of the embodiment has three speed levels, so two shifts are necessary. Accordingly, one or more larger centrifugal pistons 54 and one or more smaller centrifugal pistons 55 are provided. As has been described in connection with the centrifugal governor 42, these centrifugal pistons also form outer chambers 56, 57 with the housing, which are connected to control chambers 60, 61 by means of bores 58, 59. In addition, there are also inner chambers 62, 63 which each have a connection to the outside. The control chambers 60, 61 are also connected to the gear pump 49 via control edges and a line 64. Of the control chambers 60, 61 each carries a further line 65, 66 to a respective control valve 67, 68th

The control valve 67 contains a control slide which has three control chambers 69, 70, 71 and control pistons 72, 73 at the ends. The control piston 72 is acted upon from the centrifugal governor 53 via the line 65 and the control piston 73 from the centrifugal governor 42 via the lines 50 and 51. Two lines 74, 75 go from the control valve 67 , which merge in line 76 and via line 77 lead to gear pump 49. Furthermore, the control valve 67 is connected to the control valve 68 via line 78 and the subsequent branch lines 79, 80 and finally to the coupling 40 via a coupling line 81.

The control valve 68 is constructed analogously to the control valve 67 . From the line 77 coming from the pump, another line 89 with a continuation 90 leads into a reversing valve 91 which, with the help of the switching piston 92, transfers the pressure medium flow either through a line 93 into the brake 37 for the forward gear or through a line 94 into the brake 36 can direct for reverse gear.

A control valve 96 is connected via a branch line 95 to a line connected to the pressure side of the Zalmrad pump, for example to line 89. The control valve has a control slide 97 which, with the help of a control edge, allows a more or less large amount of pressure medium to flow out of the branch line 95 via a discharge line 98 either into the open air or into a cooling system or into the lubrication circuit. The control slide carries a control piston 99 and 100 at each end, one of which, 99, is directly acted upon by the pressure generated by the gear pump 49 via line 101 and lines 89, 77 , while the piston 100 is acted upon by the centrifugal governor 42 the lines 50, 51, 102 is affected.

All of the lines 50 or 51, 65 and 66 connected to the control rooms 46, 60 and 61 are provided at a suitable point with a preferably adjustable discharge nozzle 103, 104, 105 , which can be omitted if the leaks in the system are to a certain extent of Have nature.

The in F i g. The type of pressure regulation shown in FIG. 2 with the aid of the centrifugal pistons 43, 55, 54 is only one example. It is any other known method for pressure control or pressure reduction is usable controlled under the condition that the pressure in dependence on the centrifugal force or the square of the speed.

The mode of operation is as follows: First, let the system run in first gear at a load level of 100 %. The centrifugal governor 42 is then driven with the full pump speed of the converter and the centrifugal governor 53 with the output speed of the first gear. On the flyweight piston 43, the centrifugal force to the outside, on the one hand, and a pressure in the chamber 44, on the other hand, are then kept in equilibrium. The latter pressure is maintained by the gear pump 49 via the line 48, the control edge of the control chamber 46 and the bore 45. If the force due to the pressure in the chamber 44 is greater than the centrifugal force, the piston 43 moves inward, the control edge of the control chamber 46 closes and pressure medium escapes. via the lines 50, 51 through the nozzle 103, so that the pressure falls and the equilibrium is restored. If the centrifugal force predominates, the control edge opens and the pressure increases. The pressure regulated according to the primary speed is passed through the lines 50, 102 to the control piston 100 of the control slide 97 . The other control piston 99 of the same control slide is acted upon directly by the gear pump via lines 77, 89, 101. Due to the equilibrium of the two piston forces, the pressure on the pressure side of the gear pump is proportional to the centrifugal force of the centrifugal piston 43, i.e. H. thus regulated proportionally to the square of the primary speed.

The changeover piston 92 may be in the position shown, then the gear pump 49 conveys pressure medium through the lines 77, 89, 90, through the changeover valve 91 and through the line 93 into the brake 37 for the forward gear. At the same time, the pump also delivers pressure medium through the lines 77, 76, 75, through the control chamber 69, the clutch line 81 into the clutch 40 for the first gear.

With increasing secondary speed, i. H. Output speed or speed of the governor 43, also increases the centrifugal force on the centrifugal piston 54 and 55. First, the larger 54 of the two pistons is effective, which was as described in analogous manner in relation to the governor 42, the pressure in line 65, d . H. the pressure which acts on the control piston 72 , regulates up. If the system moves within the area 11 ( FIG. 1), the pressure on the control piston 73 regulated by the regulator 42 predominates, so that the control slide of the valve 67 is in its right end position during the first gear. If the secondary speed (njl) has reached the parabola 14 (FIG . 1) , the control slide of the control valve 67 is shifted to the right. The drainage channel 107 is first closed and the branch line 108 is opened immediately afterwards. The additional opening of the branch line 108 causes pressure medium from the lines 50, 51 - supporting the pressure from the line 65 - to settle behind the control piston 73 . This pushes the control slide suddenly into the left end position. Now the tooth ad pump promotes pressure medium through the lines 77, 74, 76, control chamber 70, lines 78, 80, 87 in the brake 39 of the second gear, while the clutch 40 is depressurized through the line 81, control chamber 69 and drainage channel 109 . The system now runs in second gear.

If the input speed n, 1 is increased further and the operating state of the transmission approaches the parabola 15, the centrifugal piston 55 becomes increasingly effective until the pressure it controls is sufficient in the operating state marked by the parabola 15 , the control slide of the control valve 68 to the left. This process is analogous to the switching step described in connection with the control valve 68. The brake 38 for the third gear receives pressure medium from the gear pump 49 via the lines 77, 76, 74, 78, 79, 88 , while the brake 39 for the second gear is depressurized via the line 87, 113. Third gear is engaged. The downshift is done in a corresponding manner.

Is driven with an input speed other than 100 11/9, e.g. B. with a load level of 90 or 8011 / o or another, the centrifugal force on the piston 43 is smaller and thus also the pressure regulated by the control valve 96 and thus the clutch pressure. At the same time, the pressures on the control piston 73 also decrease, so that the counter pressures behind the control piston 72 are regulated by smaller centrifugal forces on the pistons 54 and 55 ; this means that switching takes place at a lower output speed. Since the equilibrium at the control spools of the control valves 67, 68 is in the ratio of the centrifugal forces, i. H. is maintained in the ratio of the squares of the input and output speeds, all switching points for the gear changes are on the parabolas 14 and 15 ( FIG. 1).

For the reverse gear, the switching piston 92 is adjusted so that the lines 90 and 94 are connected.

As already mentioned, FIG. 2 shows only a schematic exemplary embodiment. Various variants can be derived from the scheme. So z. B. for each circuit 77, 76 etc. on the one hand and 50, 51 etc. separate pumps are provided. Instead of the flyweight with the pressure regulating organs, d. H. to combine with the piston 43 in one element, separate elements can also be provided for both, which mutually influence one another. The circuit diagram was also designed in such a way that no mechanical resilient forces, i.e. springs, are provided. That is not a necessity either. It is entirely possible to provide adjustable or non-adjustable springs at different points. The hydraulic system can also be expanded to include one or more additional valves or other control elements which, when actuated, for example , jointly depressurize lines 93, 94 in order to interrupt the drive, for example when braking a vehicle. An interrupting switching element can instead also be provided in the line 77 or a line connected to it.

Claims (2)

Claims: 1. Device for the automatic switching of speed change transmissions with at least one hydrodynamic torque converter or a hydrodynamic clutch and at least two downstream gear stages with continuously engaged gears, for example within a planetary gear, which are switched with friction engagement devices, characterized in that the Contact pressure of the friction engagement device, e.g. As the pressure in hydraulically switchable Ku - pplungen or brakes (36 to 40), both in rising and always of the hydrodynamic converter (35) or the hydrodynamic clutch is regulated as a function also with decreasing speed of the square of the pump speed, for example, such that the Fluid pressure is controlled by a control piston (43) of a controller (42) driven by the pump of the hydrodynamic converter. 2. Apparatus according to claim 1 for the automatic hydraulic switching of the clutches or brakes of a speed change transmission, characterized by a control valve (96) for regulating the pressure for the engagement devices (36 to 40), which is influenced on the one hand by a pressure that is from the square of the Pump speed of the converter (line 50) or the hydraulic clutch and on the other hand another resilient force, for example, the pressure generated by the pressure generator (line 77) is influenced. Considered publications: German Patent Specifications Nos. 974 609, 899 312, 865 712, 478 296; Austrian Patent No. 152453; Swiss patent specification No. 181173.