Apparatus for Controlling a Plurality of Actuators

Abstract

The invention relates to an apparatus having a plurality of hydraulic actuators (S.sub.i) and a piston-cylinder unit (K), one working chamber (AK.sub.1) of which is connected, via at least one hydraulic connection line (HL) and supply lines (ZL.sub.i), to working chambers (AS.sub.i) of the hydraulic actuators (S.sub.i), wherein each working chamber (AS.sub.i) of a hydraulic actuator (S.sub.i) is connected to a supply line (ZL.sub.i) and switch valves (EV.sub.i) for selective opening and closing of the hydraulic supply lines (ZL.sub.i) are provided such that, in the opened position of the associated switch valve (EV.sub.i), a pressure change in the working chamber (AS.sub.i) of the actuator (S.sub.i) or an adjustment of the actuator (S.sub.i) can occur, wherein at least one pressure sensor (DS.sub.i) for determining the pressure in a working chamber (AS.sub.i) of an actuator (S.sub.i) or a hydraulic line (HL, ZL.sub.i, AL.sub.i) and a control device (ECU) is provided, characterized in that, for simultaneous pressure change in at least two actuators, (S.sub.i, S.sub.k), the (ECU) permanently opens the switch valve (EV.sub.i) associated with a first actuator (S.sub.i) during the pressure change phase and adjusts or regulates the pressure by adjusting the piston (KK) of the piston-cylinder unit (K), and in that the control device (ECU) adjusts or regulates the pressure in at least one additional actuator (S.sub.k) by means of the switch valve (EV.sub.k), which is clocked during the pressure change phase, and in particular is controlled by pulse width modulation.

Claims

1. Apparatus comprising a plurality of hydraulic actuators (S.sub.i) and a piston-cylinder unit (K), which comprises a working chamber (AK.sub.1) which is connected, via at least one hydraulic connection line (HL) and supply lines (ZL.sub.i), to working chambers (AS.sub.i) of the hydraulic actuators (S.sub.i), wherein each working chamber (AS.sub.i) of a hydraulic actuating unit (S.sub.i) is connected to a supply line (ZL.sub.i), and switch valves (EV.sub.i) are provided for selectively opening and closing the hydraulic supply lines (ZL.sub.i) such that, in the open position of the associated switch valve (EV.sub.i), a pressure change in the working chamber (AS.sub.i) of the actuator (S.sub.i) or a movement of the actuator (S.sub.i) can take place, wherein at least one pressure sensor (DS.sub.i) is provided for determining the pressure in a working chamber (AS.sub.i) of an actuator (S.sub.i) or a hydraulic line (HL, ZL.sub.i, AL.sub.i), and a control device (ECU) is provided, characterized in that, in order to change the pressure in at least two actuators (S.sub.i, S.sub.k) simultaneously, the control device (ECU) continuously opens the switch valve (EV.sub.i) belonging to a first actuator (S.sub.i) during the pressure change phase and sets or adjusts the pressure by way of the movement of the piston (KK) of the piston-cylinder unit (K), and in that the control device (ECU) sets or adjusts the pressure in at least one further actuator (S.sub.k) by means of the switch valve (EV.sub.k), which is clocked during the pressure change phase, and that the apparatus is a 2-speed transmission with torque vectoring.

2. Apparatus according to claim 1, characterized in that the pressure in the first and/or further actuator (S.sub.i, S.sub.k) is set using at least one pressure sensor (DS.sub.i, DS.sub.k), by which the pressure in a hydraulic line (HL, ZL.sub.i, ZL.sub.k, AL.sub.i, AL.sub.k, ABL) and/or in the working chamber (AS.sub.i, AS.sub.k) of the respective actuator (S.sub.i, S.sub.k) can be determined.

3. Apparatus according to claim 1, characterized in that the pressure in the first actuator (S.sub.i) is set using the motor current and/or the rotor position or the rotor angle (α) of the drive (M) of the piston-cylinder unit (K).

4. Apparatus according to claim 1, characterized in that at least one or each actuator (S.sub.i) is assigned an outlet valve (AV.sub.i) which is arranged in a hydraulic drain line (AL.sub.i), via which hydraulic medium can flow out of the working chamber (AS.sub.i) of the actuator (S.sub.i) towards a reservoir (VB).

5. Apparatus according to claim 4, characterized in that a common outlet valve (AVR) designed for pulse width modulation is arranged in a common drain line (ABL) in order to selectively open and close the common drain line (ABL).

6. Apparatus according to claim 5, characterized in that the outlet valves (AV.sub.i) and the power output stages thereof are designed for switching frequencies which are smaller than the switching frequencies of the common outlet valve (AVR), wherein, in order to reduce the pressure in an actuator (S.sub.i), the outlet valve (AV.sub.i) assigned thereto is continuously open during the pressure reduction phase and the controlled or regulated pressure reduction in the actuator (S.sub.i) takes place by way of the clocking of the common outlet valve (AVR).

7. Apparatus according to claim 1, characterized in that the pressure in the hydraulic medium can be determined by means of a pressure sensor (DSA) in the common drain line (ABL) or in a drain line (AL.sub.i) between the outlet valve (AV.sub.i) and the reservoir (VB).

8. Apparatus according to claim 1, characterized in that each actuator (S.sub.i) is assigned a pressure sensor (DS.sub.i), by means of which the pressure in the actuator (S.sub.i) can be determined.

9. Apparatus according to claim 1, characterized in that each actuator (S.sub.i) has a piston-cylinder unit (KS.sub.i) comprising the working chamber (AS.sub.i) and a movable piston (SK.sub.i), wherein either the clutch (K.sub.i), the gear selector or the multi-plate clutch (TV-li, TV-re) thereof can be moved by way of the piston (SK.sub.i).

10. Apparatus according to claim 9, characterized in that at least two actuators (S.sub.i) move clutches (K.sub.i) of a transmission of a vehicle.

11. Apparatus according to claim 9, characterized in that at least one actuator (S.sub.i) is a gear selector.

12. Apparatus according to claim 1, characterized in that at least one actuator (S.sub.i) is a hydraulic parking lock or parking brake, a hydraulically actuated freewheel, or a hydraulically actuated brake.

13. (canceled)

14. Apparatus according to claim 1, characterized in that the piston (KK) of the piston-cylinder unit (K) is a single-stroke piston which delimits only a single working chamber (AK.sub.1).

15. Method for changing the pressure in an apparatus having a plurality of hydraulic actuators (S.sub.i) and a piston-cylinder unit (K), which comprises a working chamber (AK.sub.1) which is connected, via at least one hydraulic connection line (HL) and supply lines (ZL.sub.i), to working chambers (AS.sub.i) of the hydraulic actuators (S.sub.i), characterized in that, in order to change the pressure in a plurality of actuators (S.sub.i, S.sub.k) simultaneously, in a first actuator (S.sub.i) the pressure takes place to a first pressure level (p.sub.1) by way of the movement of the piston (KK) of the piston-cylinder unit (K) while at the same time the associated switch valve (EV.sub.i) is continuously open, and in that in at least one further actuator (S.sub.k) the pressure change takes place to a further pressure level (p.sub.2) by opening and/or clocking the associated outlet valve (AV.sub.k), wherein, by changing the pressure, a gear change is effected in a 2-speed transmission with or without torque vectoring.

16. Method according to claim 15, characterized in that, when building up the pressure in at least two actuators (S.sub.i, S.sub.k, S.sub.m) simultaneously, the first pressure level (p.sub.1) to be set or adjusted in the first actuator (S.sub.i) is greater than the further pressure level(s) (p.sub.2, p.sub.2′) of the at least one further actuator (S.sub.k, S.sub.m).

17. Method according to claim 15, characterized in that a pressure build-up or pressure reduction in at least one actuator (S.sub.i) takes place by means of the piston-cylinder unit (K), wherein a pressure reduction in at least one actuator (S.sub.k) takes place by way of at least one outlet valve (AV.sub.i), wherein the pressure reduction takes place either by clocking the outlet valve(s) (AV.sub.i), or by way of an outlet valve (AV.sub.i) which is continuously open during the pressure reduction phase, wherein the common outlet valve (AVR) is clocked or is operated by means of pulse width modulation.

18. Method for changing the pressure in an apparatus having a plurality of hydraulic actuators (S.sub.i) and a piston-cylinder unit (K), which comprises a working chamber (AK.sub.1) which is connected, via at least one hydraulic connection line (HL) and supply lines (ZL.sub.i), to working chambers (AS.sub.i) of the hydraulic actuators (S.sub.i), wherein a respective switch valve (EV.sub.i) is arranged between the piston-cylinder unit (K) and each hydraulic actuator (S.sub.i), the method comprising the following steps: building up the pressure and/or reducing the pressure in the plurality of hydraulic actuators (S.sub.i) simultaneously, moving the piston while simultaneously opening or PWM-clocking the switch valves (EV.sub.i) in order to build up the pressure, and simultaneously actuating a plurality of hydraulic actuators (S.sub.i) by way of the build-up of pressure, wherein at least one hydraulic actuator (S.sub.i) is a hydraulic parking lock or parking brake, a hydraulically actuated freewheel, a hydraulically actuated brake, or a 2-speed transmission with or without torque vectoring.

19. Method according to claim 18, characterized in that, when building up the pressure in at least two actuators (S.sub.i, S.sub.k, S.sub.m) simultaneously, the first pressure level (p.sub.1) to be set or adjusted in the first actuator (S.sub.i) is greater than the further pressure level(s) (p.sub.2, p.sub.2′) of the at least one further actuator (S.sub.k, S.sub.m).

20. Method according to claim 18, characterized in that a pressure build-up or pressure reduction in at least one actuator (S.sub.i) takes place by means of the piston-cylinder unit (K), wherein a pressure reduction in at least one actuator (S.sub.k) takes place by way of at least one outlet valve (AV.sub.i), wherein the pressure reduction takes place either by clocking the outlet valve(s) (AV.sub.i), or by way of an outlet valve (AV.sub.i) which is continuously open during the pressure reduction phase, wherein the common outlet valve (AVR) is clocked or is operated by means of pulse width modulation.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0014] FIG. 1: shows a first possible embodiment of an apparatus according to the invention in the form of a powershiftable 2-speed transmission;

[0015] FIG. 1a: shows an apparatus for building up or reducing the pressure in three actuators simultaneously;

[0016] FIG. 2: shows an apparatus according to the invention in the form of a powershiftable 2-speed transmission;

[0017] FIG. 2a: shows an apparatus for building up and/or reducing the pressure in three actuators simultaneously, the figure showing the pressure being built up in two actuators simultaneously, the pressure being built up in one actuator by way of the piston movement and in the other actuator by way of the clocking of the switch valve;

[0018] FIG. 2b: shows an apparatus according to FIG. 2a, the figure showing the pressure being reduced in two actuators simultaneously, the pressure being reduced in one actuator by way of the piston movement and in the other actuator by way of the clocking of the outlet valve;

[0019] FIG. 3: shows an apparatus according to the invention with five actuators;

[0020] FIG. 4a: shows another possible embodiment, wherein the apparatus has a common outlet valve arranged in the drain line, said common outlet valve being designed for rapid clocking such that, when the outlet valve of an actuator is continuously open during the pressure reduction phase, the pressure in said actuator can be reduced by way of the clocking of the common outlet valve, each actuator being assigned a pressure sensor;

[0021] FIG. 4b: shows an embodiment with a common pressure sensor which serves to determine the pressure in the common drain line, and with an optional pressure sensor which serves to determine the pressure in the hydraulic line that connects the working chamber of the piston-cylinder system to the actuators;

[0022] FIG. 5: shows an apparatus according to FIG. 4 with three instead of two actuators;

[0023] FIG. 6: shows an apparatus according to FIG. 4 with five instead of two actuators.

DETAILED DESCRIPTION

[0024] FIG. 1 shows an apparatus according to the invention in the form of a powershiftable 2-speed transmission. The 2-speed transmission has a piston-cylinder unit K and two actuators S.sub.1 and S.sub.2. The piston-cylinder unit K has a cylinder Z and a piston KK displaceably mounted therein, which piston is driven by a motor drive M via a spindle SP. Sensors MS.sub.i and/or MS.sub.α may be provided for measuring the motor current and the motor angle. The piston KK and the cylinder Z delimit a working chamber AK.sub.1, which is connected to a hydraulic connection line HL. The hydraulic connection line HL is connected to supply lines ZL.sub.1 and ZL.sub.2. The supply lines ZL.sub.1 and ZL.sub.2 are respectively connected to working chambers AS.sub.1 and AS.sub.2 of the piston-cylinder systems KS.sub.1 and KS.sub.2, wherein a switch valve EV.sub.1 is arranged in the supply line ZL.sub.1 and a switch valve EV.sub.2 is arranged in the supply line ZL.sub.2 in order to selectively open and close the respective supply line. Between the switch valve EV.sub.1 and the working chamber AS.sub.1, the pressure can be determined by means of a first pressure sensor DS.sub.1. Between the switch valve EV.sub.2 and the working chamber AS.sub.2, the pressure can be determined by means of a second pressure sensor DS.sub.2. The pistons SK.sub.1 and SK.sub.2 displaceably mounted in the piston system KS.sub.1 and KS.sub.2 move the clutches TV-LI and TV-RE via a tappet. If there is no pressure or insufficient pressure in the working chambers AS.sub.1 and AS.sub.2, the clutches TV-LI and TV-RE are open. Optionally, the pressure in the hydraulic line HL can be determined using a pressure sensor DS.sub.HL. The control unit ECU, which is connected to the drive M, to the switch valves EV.sub.1 and EV.sub.2 and also to the pressure sensors DS.sub.1 and DS.sub.2 and optionally to the pressure sensor DS.sub.HL via the signal and/or communication lines shown in dashed line, controls the 2-speed transmission. The working chamber AK.sub.1 of the piston-cylinder unit K is connected to a reservoir VB via the hydraulic connection line HL.sub.VB.

[0025] According to the invention, it is possible to change the pressure for example in the working chamber AS.sub.1 of the actuator S.sub.1, in which the associated switch valve EV.sub.1 is continuously open during the pressure change phase, wherein the pressure in the working chamber AS.sub.1 is set by way of the piston movement of the piston KK. For example, the pressure in the supply line ZL.sub.1 may be continuously determined by means of the sensor DS.sub.1 and adjusted by way of the piston movement of the piston KK. The pressure-volume characteristic can also be used or taken into account in the control.

[0026] The switch valves EV.sub.1 and EV.sub.2 are designed such that they can be switched at a sufficiently high switching frequency, for example by means of pulse width modulation PWM. The pressure in the second actuator S.sub.2 can thus be changed simultaneously by clocking the switch valve EV.sub.2. In this case, it is advantageous if a pressure control takes place by measuring the pressure in the supply line ZL.sub.2 by means of the sensor DS.sub.2.

[0027] In the apparatus shown in FIG. 1, the pressure in both working chambers AS.sub.1 and AS.sub.2 can only be simultaneously built up or reduced. With this apparatus, it is not possible to reduce the pressure in one actuator and to build up the pressure in the other actuator simultaneously. Of course, it is also possible that the pressure in the actuators is changed successively, wherein then in each case the associated switch valve EV.sub.i is open and the pressure in the actuator is adjusted by the movement of the piston KK.

[0028] FIG. 1a shows an apparatus for building up or reducing the pressure in three actuators simultaneously. Said apparatus is basically constructed in a manner identical to the apparatus in FIG. 1, but also has an additional supply line ZL.sub.n, via which a further actuator S.sub.n is connected to the hydraulic connection line HL. A switch valve EV.sub.n is also provided in the supply line ZL.sub.n in order to selectively open and close the supply line ZL.sub.n. In principle, any number of further actuators S.sub.n can be provided in a corresponding manner. FIG. 1a shows the simultaneous pressure build-up and subsequent simultaneous pressure reduction in the actuators S.sub.1 and S.sub.2, which starts at the time t.sub.0. By means of the piston-cylinder unit K, by moving the piston KK, which is moved to the right along the piston path S.sub.Kol, there is built up in the hydraulic line HL a pressure p.sub.1 which corresponds to the pressure that is to be built up in the working chamber AS.sub.1 of the actuator S.sub.1. By means of the current i.sub.EV1, a current flows continuously through the switch valve EV.sub.1 during the pressure build-up phase, which lasts from t.sub.0 to t.sub.1, and thus said switch valve is continuously open, so that the pressure acting in the hydraulic line HL acts in the working chamber AS.sub.1. The pressure in the hydraulic line HL is also applied to the input of the switch valve EV.sub.2. By clocked switching of the switch valve EV.sub.2 by means of the current i.sub.EV2, liquid also flows into the working chamber AL.sub.2 of the second actuator S.sub.2, as illustrated by the dashed arrow, so that a pressure p.sub.2, which is lower than the pressure p.sub.1, is also set therein.

[0029] At the time t.sub.1, the required pressure p.sub.1 and respectively p.sub.2 is reached in both actuators S.sub.1 and S.sub.2, and therefore the switch valves EV.sub.1 and EV.sub.2 are closed at the time t.sub.1, as a result of which the pressure in the working chambers AS.sub.1 and AS.sub.2 is maintained and the clutches of the actuators S.sub.1 and S.sub.2 remain in their position. The pressure reduction starts at the time t.sub.2, wherein the switch valve EV.sub.1 is clocked by means of the current i.sub.EV1 and the switch valve EV.sub.2 is continuously open by means of the current I.sub.EV2 until the pressure in the respective working chambers AS.sub.1 and AS.sub.2 has been completely reduced by moving the piston KK to the left. As shown in FIG. 1, the pressure in the actuator S.sub.n is not changed during the pressure build-up and pressure reduction phase in the actuators S.sub.1 and S.sub.2. However, it is also possible that, simultaneously with the pressure change in the actuators S.sub.1 and S.sub.2, a pressure change also takes place in the actuator S.sub.n by switching the switch valve EV.sub.n.

[0030] In principle, in order to change the pressure in a plurality of actuators S.sub.i, S.sub.k simultaneously, in a first actuator S.sub.i the pressure takes place to a first pressure level p.sub.1 by moving the piston KK of the piston-cylinder unit K while at the same time the associated switch valve EV.sub.i is continuously open, and in at least one further actuator S.sub.k the pressure change takes place to a further pressure level p.sub.2, wherein the switch valve EV.sub.k belonging to the actuator S.sub.k is clocked or is operated for example by means of pulse width modulation. The pressure p.sub.1 is greater than the pressure p.sub.2 in the case of a pressure build-up and is lower than the pressure p.sub.2 in the case of a pressure reduction.

[0031] FIG. 2 shows an apparatus according to the invention as a powershiftable 2-speed transmission, wherein, in addition to the switch valves EV.sub.1 and EV.sub.2 arranged in the supply lines ZL.sub.1 and ZL.sub.2, outlet valves AV.sub.1 and AV.sub.2 are also provided, by means of which the drain lines AL.sub.1 and AL.sub.2 can selectively be shut off so that hydraulic fluid can flow via the drain line AL.sub.1 or AL.sub.2, when the outlet valve AV.sub.1 or AV.sub.2 is open, towards the common drain line ABL and towards the reservoir VB. By clocking and simultaneously measuring the pressure in the respective working chamber AS.sub.1 or AS.sub.2 or in the drain line AL.sub.1 or AL.sub.2 by means of the pressure sensors DS.sub.1 or DS.sub.2, the pressure in the respective working chamber AS.sub.1 or AS.sub.2 can be reduced in a controlled manner towards the reservoir VB.

[0032] FIG. 2a shows the apparatus according to FIG. 2 which has been expanded by a further actuator S.sub.n, wherein yet more actuators (not shown) may be provided which can likewise be connected, via a supply line ZL.sub.n, to the hydraulic line HL or directly to the working chamber AK.sub.1. FIG. 2a shows the simultaneous pressure build-up, which takes place in a manner identical to the pressure build-up shown and explained in FIG. 1a, that is to say the pressure p.sub.1 is generated by moving the piston KK of the piston-cylinder unit K, wherein, during the pressure build-up phase between t.sub.0 and t.sub.1, a current continuously flows through the switch valve EV.sub.1 and thus said switch valve is open, and the switch valve is rapidly clocked. The pressure generated by means of the piston-cylinder unit K and the duty cycle between the opening and closing of the switch valve EV.sub.2 determines the rate of pressure change in the working chamber AS.sub.2. At t.sub.1, the required pressure has been set both in the working chamber AS.sub.1 and in the working chamber AS.sub.2. In addition, the actuators S.sub.i also have additional outlet valves AV.sub.i, by way of which the pressure in the respective actuator S.sub.i can be reduced.

[0033] FIG. 2b shows an apparatus according to FIG. 2a, wherein, in the apparatus shown in FIG. 2b, the pressure is reduced in two actuators S.sub.1 and S.sub.2 simultaneously between the times t.sub.1 and t.sub.2, and from the time t.sub.2 the pressure in the actuator S.sub.1 continues to reduce until the time t.sub.3, at which there is zero pressure, and the pressure in the actuator S.sub.2 at the time t.sub.3 has been increased back to the initial pressure p.sub.2 by way of the piston movement s.sub.Kol.

[0034] Either one pressure sensor DS.sub.i or all pressure sensors DS.sub.1-3 can be used to control the drive M and/or the clocked valve(s) EV.sub.i and/or AL.sub.i. However, it is also possible to determine or estimate the pressure in the working chamber AS.sub.i of the piston-cylinder unit K by way of the pressure-volume characteristic, the motor current i and the piston position of the piston-cylinder unit K.

[0035] Here, too, the pressure reduction in the actuator S.sub.2 takes place by way of the piston movement s.sub.Kol while at the same time the switch valve EV.sub.2 is continuously open. The pressure reduction in the actuator S.sub.1 takes place by way of the clocked outlet valve AV.sub.1, wherein the pressure in the working chamber AS.sub.1 is continuously determined by means of the pressure sensor DS.sub.1 and is taken into account in controlling the pressure reduction in the actuator S.sub.1.

[0036] FIG. 3 shows an apparatus according to the invention with five actuators in the form of a 2-speed transmission with torque vectoring. Here, the actuator S.sub.1 is a first clutch K.sub.1, the second actuator S.sub.2 is a second clutch K.sub.2, the actuators S.sub.3 and S.sub.4 are the multi-plate clutches TV-li and TV-re, and the actuator S.sub.5 is a hydraulically actuated parking lock HPS.

[0037] The pressure build-up and pressure reduction in the individual actuators S.sub.1-5 can take place in a manner analogous to the embodiments described above.

[0038] FIG. 4a shows another possible embodiment of the apparatus according to the invention, wherein the apparatus has a common outlet valve AVR arranged in the common drain line ABL, said common outlet valve being designed for rapid clocking. To reduce the pressure in one actuator S.sub.i, the outlet valve AV.sub.i associated with the respective actuator S.sub.i is continuously open during the pressure reduction phase. The actual pressure control takes place by way of the clocking of the common outlet valve AVR. Each actuator may be assigned a pressure sensor DS.sub.1 and DS.sub.2. However, it is also possible that, as shown in FIG. 4b, the pressure in the respective actuator S.sub.i can be determined by way of a common pressure sensor DS.sub.ABL since the outlet valve AV.sub.i is continuously open during the pressure reduction. In addition, a further pressure sensor DS.sub.HL may be provided, the signals of which can likewise be used to control the pressure in the actuators S.sub.i. The pressure sensor DS.sub.HL may be omitted for example if the pressure in the working chamber AK.sub.1 of the piston-cylinder unit K can be precisely calculated by way of a motor current measurement MS.sub.i and/or a rotor angle measurement MS.sub.α. Optionally, the pressure-volume characteristic(s) of the apparatus can also be used for pressure control.

[0039] FIG. 5 shows the apparatus according to FIG. 4 with three instead of two actuators S.sub.1-3, wherein the pressure reduction in the actuator S.sub.2 takes place by way of the clocked common switch valve AVR, wherein the pressure in the common drain line ABL is continuously determined by means of the pressure sensor DS.sub.ABL and is taken into account in controlling the switch valve AVR. Between the times t.sub.1 and t.sub.2, the pressure in the actuator S.sub.1 is reduced from an initial pressure p.sub.1 to zero pressure and the pressure in the actuator S.sub.2 is reduced from an initial pressure p.sub.2 to zero pressure. Both the switch valve EV.sub.1 and the outlet valve AV.sub.2 are continuously open between the times t.sub.1 and t.sub.2. The pressure reduction in the actuator S.sub.1 takes place by way of the piston movement of the piston-cylinder unit K.

[0040] The switch valve AVR must be designed for sufficiently high switching frequencies, wherein the control stage for the switch valve AVR must also be dimensioned for the high switching frequencies. In contrast, the outlet valves AVi can be simple, inexpensive switch valves.

[0041] FIG. 6 shows an apparatus according to FIG. 4 with five instead of two actuators, in the form of a 2-speed gearbox with torque vectoring, wherein the pressure build-up and/or pressure reduction in the individual actuators S.sub.1-5 takes place in a manner analogous to the apparatuses described above.