TECHNICAL FIELD
The present invention relates to an apparatus comprising a plurality of hydraulic actuators and a piston-cylinder unit, a working chamber of which is connected, via at least one hydraulic connection line and supply lines, to working chambers of the hydraulic actuators, wherein each working chamber of a hydraulic actuating unit is connected to a supply line, and switch valves are provided for selectively opening and closing the hydraulic supply lines such that, in the open position of the associated switch valve, a pressure change in the working chamber of the actuator or a movement of the actuator can take place, wherein at least one pressure sensor is provided for determining the pressure in a working chamber of an actuator or a hydraulic line, and a control device is provided.
Apparatuses for moving clutches and gear selectors are known for example from DE 10 2006 038 446 A1, WO 2016/146692 A1 and WO 2018/046145 A1.
In the apparatus known from DE 10 2006 038 446 A1, up to six actuators in the form of two clutches and four gear selectors are moved by means of a piston-cylinder unit having a single-stroke piston. Said apparatus is designed in such a way that simultaneously the pressure in one actuator can be built up and the pressure in another actuator can be reduced.
The apparatuses known from WO 2016/146692 A1 and WO 2018/046145 A1 comprise piston-cylinder units having double-stroke pistons, which in each case sealingly separate two working chambers from each other. In all the aforementioned apparatuses, the pressure in one actuator is built up in that the associated switch valve, which functions as an inlet valve during the pressure build-up phase, is continuously open and the pressure is adjusted by way of the piston movement.
The problem addressed by the present invention is that of further developing the aforementioned systems and of providing a flexible and simple apparatus in which it is possible to change the pressure in at least two actuators to different pressure levels simultaneously.
This problem is solved according to the invention by an apparatus having the features of claim 1. Advantageous further developments of the apparatus according to claim 1 will become apparent from the features of the dependent claims.
The apparatus according to the invention according to claim 1 is characterized in that, in order to change the pressure in at least two actuators simultaneously, the control unit continuously opens the switch valve belonging to a first actuator during the pressure change phase and sets or adjusts the pressure by way of the movement of the piston of the piston-cylinder unit, and in that the control device sets or adjusts the pressure in at least one further actuator by means of the associated switch valve, which is clocked during the pressure change phase and in particular is controlled by means of pulse width modulation. The switch valves must therefore be able to be switched sufficiently rapidly, and the power output stages for the valves must be dimensioned accordingly.
The pressure in the first and/or further actuator can in this case be set using at least one pressure sensor, wherein said at least one sensor determines the pressure in a hydraulic line and/or the working chamber of the respective actuator. It is also possible that the pressure in the first actuator, in which the pressure is changed by way of the piston movement while at the same time the switch valve is continuously open, is set using the motor current and/or the rotor position or the rotor angle of the drive of the piston-cylinder unit and/or the pressure-volume characteristic of the apparatus.
If just one single switch valve is assigned to each actuator, only a joint pressure build-up or pressure reduction in a plurality of actuators can take place. A pressure build-up in one actuator and a simultaneous pressure reduction in another actuator is not possible with such an apparatus. However, if at least one or each actuator is assigned an additional outlet valve, which is arranged in a hydraulic drain line, the hydraulic medium can flow out of the working chamber of the actuator towards a reservoir, and a simultaneous pressure build-up and pressure reduction in two or more actuators is possible. The outlet valves may in this case be clocked, as a result of which a controlled pressure reduction in the respective actuator is possible. To this end, the pressure in the discharge line or in the working chamber of the actuator can be determined by means of a pressure sensor for pressure control and appropriate clocking of the outlet valve.
In another advantageous development, a common outlet valve which can be rapidly clocked and which is designed in particular for pulse width modulation may be provided in a common drain line in order to selectively open and close the common drain line, and also a common pressure transducer may be provided. As a result, it is possible to reduce only the number of required pressure transducers and to keep the individual outlet valves simple and small since these need only be designed for relatively low switching frequencies. Only the common clockable outlet valve and the power output stage thereof must be designed for high switching frequencies. A not inconsiderable cost advantage is achieved as a result.
The actuators of the apparatus according to the invention may in each case have a piston-cylinder unit with a working chamber and a movable piston, wherein either the clutch, the gear selector or the multi-plate clutch thereof can be moved by way of the piston. The apparatus may thus be, for example, a powershiftable 2-speed transmission with or without torque vectoring. The apparatus according to the invention may also advantageously have at least one actuator which is a hydraulic parking lock or parking brake or a hydraulically switchable freewheel, or a hydraulically actuated brake.
In addition, the piston of the piston-cylinder unit may advantageously be a single-stroke piston which delimits only a single working chamber, resulting in a simple and inexpensive design of the piston-cylinder unit.
Several possible embodiments of the invention will be explained below with reference to drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1: shows a first possible embodiment of an apparatus according to the invention in the form of a powershiftable 2-speed transmission;
FIG. 1a: shows an apparatus for building up or reducing the pressure in three actuators simultaneously;
FIG. 2: shows an apparatus according to the invention in the form of a powershiftable 2-speed transmission;
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;
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;
FIG. 3: shows an apparatus according to the invention with five actuators;
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;
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;
FIG. 5: shows an apparatus according to FIG. 4 with three instead of two actuators;
FIG. 6: shows an apparatus according to FIG. 4 with five instead of two actuators.
DETAILED DESCRIPTION
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 S1 and S2. 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 MSi and/or MSα may be provided for measuring the motor current and the motor angle. The piston KK and the cylinder Z delimit a working chamber AK1, which is connected to a hydraulic connection line HL. The hydraulic connection line HL is connected to supply lines ZL1 and ZL2. The supply lines ZL1 and ZL2 are respectively connected to working chambers AS1 and AS2 of the piston-cylinder systems KS1 and KS2, wherein a switch valve EV1 is arranged in the supply line ZL1 and a switch valve EV2 is arranged in the supply line ZL2 in order to selectively open and close the respective supply line. Between the switch valve EV1 and the working chamber AS1, the pressure can be determined by means of a first pressure sensor DS1. Between the switch valve EV2 and the working chamber AS2, the pressure can be determined by means of a second pressure sensor DS2. The pistons SK1 and SK2 displaceably mounted in the piston system KS1 and KS2 move the clutches TV-LI and TV-RE via a tappet. If there is no pressure or insufficient pressure in the working chambers AS1 and AS2, the clutches TV-LI and TV-RE are open. Optionally, the pressure in the hydraulic line HL can be determined using a pressure sensor DSHL. The control unit ECU, which is connected to the drive M, to the switch valves EV1 and EV2 and also to the pressure sensors DS1 and DS2 and optionally to the pressure sensor DSHL via the signal and/or communication lines shown in dashed line, controls the 2-speed transmission. The working chamber AK1 of the piston-cylinder unit K is connected to a reservoir VB via the hydraulic connection line HLVB.
According to the invention, it is possible to change the pressure for example in the working chamber AS1 of the actuator S1, in which the associated switch valve EV1 is continuously open during the pressure change phase, wherein the pressure in the working chamber AS1 is set by way of the piston movement of the piston KK. For example, the pressure in the supply line ZL1 may be continuously determined by means of the sensor DS1 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.
The switch valves EV1 and EV2 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 S2 can thus be changed simultaneously by clocking the switch valve EV2. In this case, it is advantageous if a pressure control takes place by measuring the pressure in the supply line ZL2 by means of the sensor DS2.
In the apparatus shown in FIG. 1, the pressure in both working chambers AS1 and AS2 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 EVi is open and the pressure in the actuator is adjusted by the movement of the piston KK.
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 ZLn, via which a further actuator Sn is connected to the hydraulic connection line HL. A switch valve EVn is also provided in the supply line ZLn in order to selectively open and close the supply line ZLn. In principle, any number of further actuators Sn can be provided in a corresponding manner. FIG. 1a shows the simultaneous pressure build-up and subsequent simultaneous pressure reduction in the actuators S1 and S2, which starts at the time t0. By means of the piston-cylinder unit K, by moving the piston KK, which is moved to the right along the piston path SKol, there is built up in the hydraulic line HL a pressure p1 which corresponds to the pressure that is to be built up in the working chamber AS1 of the actuator S1. By means of the current iEV1, a current flows continuously through the switch valve EV1 during the pressure build-up phase, which lasts from t0 to t1, and thus said switch valve is continuously open, so that the pressure acting in the hydraulic line HL acts in the working chamber AS1. The pressure in the hydraulic line HL is also applied to the input of the switch valve EV2. By clocked switching of the switch valve EV2 by means of the current iEV2, liquid also flows into the working chamber AL2 of the second actuator S2, as illustrated by the dashed arrow, so that a pressure p2, which is lower than the pressure p1, is also set therein.
At the time t1, the required pressure p1 and respectively p2 is reached in both actuators S1 and S2, and therefore the switch valves EV1 and EV2 are closed at the time t1, as a result of which the pressure in the working chambers AS1 and AS2 is maintained and the clutches of the actuators S1 and S2 remain in their position. The pressure reduction starts at the time t2, wherein the switch valve EV1 is clocked by means of the current iEV1 and the switch valve EV2 is continuously open by means of the current IEV2 until the pressure in the respective working chambers AS1 and AS2 has been completely reduced by moving the piston KK to the left. As shown in FIG. 1, the pressure in the actuator Sn is not changed during the pressure build-up and pressure reduction phase in the actuators S1 and S2. However, it is also possible that, simultaneously with the pressure change in the actuators S1 and S2, a pressure change also takes place in the actuator Sn by switching the switch valve EVn.
In principle, in order to change the pressure in a plurality of actuators Si, Sk simultaneously, in a first actuator Si the pressure takes place to a first pressure level p1 by moving the piston KK of the piston-cylinder unit K while at the same time the associated switch valve EVi is continuously open, and in at least one further actuator Sk the pressure change takes place to a further pressure level p2, wherein the switch valve EVk belonging to the actuator Sk is clocked or is operated for example by means of pulse width modulation. The pressure p1 is greater than the pressure p2 in the case of a pressure build-up and is lower than the pressure p2 in the case of a pressure reduction.
FIG. 2 shows an apparatus according to the invention as a powershiftable 2-speed transmission, wherein, in addition to the switch valves EV1 and EV2 arranged in the supply lines ZL1 and ZL2, outlet valves AV1 and AV2 are also provided, by means of which the drain lines AL1 and AL2 can selectively be shut off so that hydraulic fluid can flow via the drain line AL1 or AL2, when the outlet valve AV1 or AV2 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 AS1 or AS2 or in the drain line AL1 or AL2 by means of the pressure sensors DS1 or DS2, the pressure in the respective working chamber AS1 or AS2 can be reduced in a controlled manner towards the reservoir VB.
FIG. 2a shows the apparatus according to FIG. 2 which has been expanded by a further actuator Sn, wherein yet more actuators (not shown) may be provided which can likewise be connected, via a supply line ZLn, to the hydraulic line HL or directly to the working chamber AK1. 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 p1 is generated by moving the piston KK of the piston-cylinder unit K, wherein, during the pressure build-up phase between t0 and t1, a current continuously flows through the switch valve EV1 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 EV2 determines the rate of pressure change in the working chamber AS2. At t1, the required pressure has been set both in the working chamber AS1 and in the working chamber AS2. In addition, the actuators Si also have additional outlet valves AVi, by way of which the pressure in the respective actuator Si can be reduced.
FIG. 2b shows an apparatus according to FIG. 2a, wherein, in the apparatus shown in FIG. 2b, the pressure is reduced in two actuators S1 and S2 simultaneously between the times t1 and t2, and from the time t2 the pressure in the actuator S1 continues to reduce until the time t3, at which there is zero pressure, and the pressure in the actuator S2 at the time t3 has been increased back to the initial pressure p2 by way of the piston movement sKol.
Either one pressure sensor DSi or all pressure sensors DS1-3 can be used to control the drive M and/or the clocked valve(s) EVi and/or ALi. However, it is also possible to determine or estimate the pressure in the working chamber ASi 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.
Here, too, the pressure reduction in the actuator S2 takes place by way of the piston movement sKol while at the same time the switch valve EV2 is continuously open. The pressure reduction in the actuator S1 takes place by way of the clocked outlet valve AV1, wherein the pressure in the working chamber AS1 is continuously determined by means of the pressure sensor DS1 and is taken into account in controlling the pressure reduction in the actuator S1.
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 S1 is a first clutch K1, the second actuator S2 is a second clutch K2, the actuators S3 and S4 are the multi-plate clutches TV-li and TV-re, and the actuator S5 is a hydraulically actuated parking lock HPS.
The pressure build-up and pressure reduction in the individual actuators S1-5 can take place in a manner analogous to the embodiments described above.
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 Si, the outlet valve AVi associated with the respective actuator Si 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 DS1 and DS2. However, it is also possible that, as shown in FIG. 4b, the pressure in the respective actuator Si can be determined by way of a common pressure sensor DSABL since the outlet valve AVi is continuously open during the pressure reduction. In addition, a further pressure sensor DSHL may be provided, the signals of which can likewise be used to control the pressure in the actuators Si. The pressure sensor DSHL may be omitted for example if the pressure in the working chamber AK1 of the piston-cylinder unit K can be precisely calculated by way of a motor current measurement MSi and/or a rotor angle measurement MSα. Optionally, the pressure-volume characteristic(s) of the apparatus can also be used for pressure control.
FIG. 5 shows the apparatus according to FIG. 4 with three instead of two actuators S1-3, wherein the pressure reduction in the actuator S2 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 DSABL and is taken into account in controlling the switch valve AVR. Between the times t1 and t2, the pressure in the actuator S1 is reduced from an initial pressure p1 to zero pressure and the pressure in the actuator S2 is reduced from an initial pressure p2 to zero pressure. Both the switch valve EV1 and the outlet valve AV2 are continuously open between the times t1 and t2. The pressure reduction in the actuator S1 takes place by way of the piston movement of the piston-cylinder unit K.
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.
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 S1-5 takes place in a manner analogous to the apparatuses described above.
Patent Application
20210262535
