EP1902227A1

EP1902227A1 - Method and device for triggering a vehicle clutch

Info

Publication number: EP1902227A1
Application number: EP06742399A
Authority: EP
Inventors: Reinhard Stehr; Manfred Homm; Marco Grethel
Original assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG; LuK Lamellen und Kupplungsbau GmbH
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2005-07-01
Filing date: 2006-06-07
Publication date: 2008-03-26
Also published as: WO2007003151A1; US7757831B2; JP2008546972A; DE202006021143U1; DE112006001574A5; US20080190729A1; DE112006001574B4

Abstract

The invention relates to a method and a device in the form of a hydraulic unit for triggering at least one clutch (5, 6) in a hydraulic circuit for an axle transmission of a vehicle. Said method and device make it possible to simply and very quickly make available an adequate amount of working fluid at the required pressure to at least one clutch according to the driving situation in order to close said clutch.

Description

Method and device for driving a vehicle clutch

The present invention relates to a method and a device in the form of a hydraulic unit for controlling a vehicle clutch according to the preamble of claims 1 and 11.

Previously known solutions for actuating a clutch in a transaxle of a vehicle to compensate in certain driving situations, a steering failure, provide a hydraulic unit, which includes a high-pressure accumulator, which must be filled to the maximum clutch pressure to react quickly in these particular driving situations, the clutch or To be able to close couplings. To pre-fill a clutch, however, a low pressure in the accumulator would be sufficient.

In the figure 1, such a hydraulic unit, as used in the prior art, shown schematically.

A pump 1 is driven by an (electric) motor 2 and fills the high-pressure accumulator 3, which is designed as a diaphragm accumulator. A sensor 4 measures the pressure. If two clutches 5 and 6 are provided, they are controlled via a respective solenoid valve 7 and 8 and, if necessary, supplied with the working fluid from the high-pressure accumulator 3. The pump 1 is supplied from a tank 9 with the working fluid.

The solenoid valves 7 and 8 are formed for example as pressure reducing valves. For the pre-filling of the clutches 5 or 6, it would be sufficient to supply the working fluid under a low pressure, for example 5 to 10 bar, in order to fill the clearance of the clutches. To close the clutch 5 or 6, a pressure of about 45 bar would have to be present without a volume flow of working fluid would be necessary.

However, the known hydraulic unit uses a large and expensive high-pressure accumulator to fill the clutches 5 or 6 and close.

If the clutches 5 and 6 are opened, the working fluid flows back into the tank 9 via the magnetic valves 7 and 8. The elements shown the known hydraulic unit are about hydraulic lines or control lines connected to each other, as shown in the figure 1.

By appropriate switching of the solenoid valves 7 and 8, the clutches 5 and 6 are supplied with working fluid from the high-pressure accumulator 3, so that they are closed or it is the working fluid from the clutches 5 and 6 conveyed back into the tank 9, wherein the clutches 5 or 6 by its own weight or a spring open.

It is therefore an object of the present invention to provide a device in the form of a hydraulic unit and a method for operating this device, which allows the filling and closing of the at least one clutch with a simple structure and while maintaining a high dynamic (fast reacting) the use of a high-pressure accumulator should be dispensed with.

Preferably, two multi-plate clutches provided in a rear axle of a vehicle, that is to say in a rear differential, are to be closed hydraulically for redistributing the wheel torques.

This problem is solved by the features of claims 1 and 11.

The inventive method for closing a clutch by means of a device designed as a hydraulic unit is set forth in claims 1 to 10.

Accordingly, the hydraulic unit, which is provided in particular for controlling at least one clutch in a hydraulic circuit for a transaxle of a vehicle comprises a pump that promotes a working fluid, a pressure accumulator that stores the pressurized working fluid and at least one solenoid valve, which in the inlet the at least one clutch is arranged, wherein the pressure accumulator is designed as a low-pressure accumulator and is operatively connected to the pump so that the corresponding requirement of working fluid with the required pressure is available depending on the driving situation of the at least one clutch.

The advantage here is that the expensive high-pressure accumulator, as used in the prior art, saved and saved by a simple, robust and cost-effective derdruckspeicher can be replaced. In addition, the pump can be very small in this embodiment of the invention.

The pump, which is preferably driven by an electric motor, charges the low-pressure accumulator to the pressure required to fill the clutch, for example 10 bar. However, the pump can equally well be driven by an axle shaft of an electric motor, or an internal combustion engine of the vehicle, for this purpose, a pressure limiting valve is preferably installed in the hydraulic circuit, which limits the pressure accordingly. After charging the low-pressure accumulator, the pump can be switched off.

Preferably, a pressure reducing valve is installed in front of each clutch to be actuated, so that the pressure from the low pressure accumulator, as soon as this pressure reducing valve is energized, passed into the clutch and this can be filled. Preferably, the pump is put into operation at the same time, so that immediately after the filling of the clutch (s), the pump pressure operates the pressure reducing valves and closes the clutch accordingly.

Furthermore, a follower valve must be provided between the pump and the low pressure accumulator, which always closes so far that the pump pressure operates the pressure reducing valves, wherein the effluent from the follower valve working fluid, preferably an oil, is used to recharge the low pressure accumulator.

In an advantageous embodiment of the invention, the low-pressure accumulator is designed as a spring store, wherein a mechanical spring is installed instead of the usual gas bubble and thus a particularly cost-effective and robust pressure accumulator can be realized.

In a further advantageous embodiment of the solution according to the invention either a pressure-reducing valve is provided in the inlet for each clutch or for two clutches, a pressure reducing valve and a switching valve are provided.

A further advantage is that the solenoid valve is a pressure relief valve, which dammed up the pumped by the pump working fluid to the required for closing the clutch pressure level. Preferably, a separate pump is provided for each of the two clutches so that the two clutches, for example designed as multi-plate clutches and arranged in a rear differential of a vehicle, can be controlled or closed independently of each other.

A preferred embodiment of the invention provides that the power steering pump of the vehicle is used as a pump. Thus, the existing power steering pump serves as a source of pressurized working fluid. For this purpose, the outlet pressure of the power steering system is used to fill and close the clutch (s). In this embodiment, it must be ensured by suitable measures that the steering function is prioritized before the clutch function.

Alternatively, the pump or the pumps, if a separate pump is provided for each clutch, are operated permanently, so that no more pressure accumulator is provided in the hydraulic unit.

It is advantageous in the inventive solution that the expensive high-pressure accumulator used in the prior art can be saved.

The hydraulic unit according to the invention, which is designed in particular for controlling at least one clutch in a transaxle of a vehicle, may have at least one pump which conveys a working fluid and at least one solenoid valve which is associated with the at least one clutch, the pump both for filling the clutch as well as to close the clutch promotes the working fluid under pressure to the clutch.

The working fluid can be permanently conveyed by the pump and therefore not only for the clutch closing function, but possibly also for a cooling function, such as a rear axle differential used.

With the present invention, the technical complexity for the control of preferably two multi-plate clutches in certain Fahrsituatonen in a rear differential, which are to be closed hydraulically to be minimized. A high dynamic is necessary, with a clearance in the clutch has to be done by filling with the working fluid before the actual closing of the clutch. Closing at least one of Both clutches must be done within a short time (less than 100 ms). For filling, a relatively low pressure of 5 to 10 bar is required, while for the final closing of the clutch, a pressure of about 45 bar must be applied, in which case, however, virtually no volume flow of working fluid is required.

Further advantages and advantageous embodiments are the subject of the following description of the figures.

They show in detail:

Fig. 1 is a schematic representation of a hydraulic unit with a high-pressure accumulator according to the prior art

2 shows a schematic representation of a first preferred embodiment of a hydraulic unit according to the invention with two permanently operated pumps for two clutches;

3 shows a schematic representation of a second preferred embodiment of a hydraulic unit according to the invention with a permanently operated pump for two clutches;

4 shows a schematic illustration of a third preferred embodiment of a hydraulic unit according to the invention with a low-pressure accumulator and a follow-up valve;

Figure 5 is a schematic representation of a fourth preferred embodiment of a hydraulic unit according to the invention, which is connected to a power steering system of a vehicle. and

Fig. 6 shows an embodiment according to Figure 4, in which only one pressure reducing valve. is used.

For all embodiments, the same reference numerals are used for identical or equivalent components. A first preferred embodiment according to the present invention will be described below with reference to FIG.

For two clutches 5 and 6, which are installed, for example, in a transaxle, a Hinterachsdifferential a vehicle for the distribution of Radmomente, two pumps 1 are provided which ensure the supply of the clutches 5 and 6 with working fluid or oil. Each of the clutch 5 and 6 is supplied by a respective pump 1 with oil, which are preferably driven by the axle shafts of the rear axle. Optionally, the two pumps 1 (not shown) via electric motors are driven.

The two clutches 5 and 6 of Figure 2 can be controlled independently, d. H. be closed, with no high-pressure accumulator is required. Instead of two separate pumps 1 can also realize an embodiment with only one vane pump, in which case expediently the two floods of this vane pump takes over the oil supply for each of the clutches 5 and 6.

In each of the clutch 5 or 6 associated hydraulic circuit jammed an electrically operated pressure relief valve 10 or 11 when energized the pump flow of working fluid or hydraulic oil to the required pressure level that the respective clutch can be closed, while at an electroless pressure relief valve 10 and 11 open these valves and divert the working fluid or hydraulic oil into the tank 9.

Optionally, a simple switching valve 12 in an emergency, for example, in case of failure of the pressure relief valves 10 or 11, both clutches 5 and 6 depressurized. This variant is shown in the dashed circle in FIG. Then, the working fluid is discharged from the clutches 5 and 6 via the check valves 13 and the switching valve 12 into the tank 9.

In the case of this described embodiment with a low pressure accumulator, the pump can be turned off when no more filling of the low pressure accumulator required or when the clutch is not close. The pump is operated only when actually a closing operation of the clutch is initiated. The (pre-) filling of the clutch will take place from the low-pressure accumulator, while preferably at the same time the pump starts, in order to achieve the final closing of the clutch by means of the pump pressure. In the second embodiment according to the present invention, which is shown in Figure 3, only one pump 1 is provided which supplies both clutches 5 and 6 via the pressure reducing valves 18 and 19 and a biasing valve 15 with working fluid.

Here, the pump 1, which in turn is driven preferably by an axle shaft or an electric motor (not shown), promotes the working fluid via the preload valve 15 into the tank 9 almost without pressure in a rest position, so that a permanently driven pump 1 can be used.

According to a further, not shown, preferred embodiment, the working fluid, which flows from the biasing valve 15, for cooling, for example, for cooling the rear axle, used.

Upon actuation of at least one of the two pressure reducing valves 18 or 19 by the control signal of an electronic control unit, the adjusting clutch pressure of the clutches 5 or 6 via the feedback with the OR element 17 raises the pressure of the working fluid at the pretensioning valve 15 in accordance with the clutch pressure requirement. In a simultaneous operation, if desired, the two pressure reducing valves 18 and 19, the higher of the two coupling pressures is decisive and determining the system pressure.

If necessary, an emergency lowering device 16, similar to that shown in FIG. 2, may be provided. Then the or-member 17 assumes the function of the two check valves 13 provided in FIG. 2. The emergency lowering device 16 is designed as a 2/2-way switching valve in the present embodiment and can be designed as an opener or closer.

A particularly preferred third embodiment according to the present invention is shown in FIG.

A pump 1, which is driven by an electric motor 2, charges the accumulator 20 designed as a low-pressure accumulator to a pressure which is necessary for pre-filling the couplings 5 and 6. This pressure is in practice, for example, 10 bar. This pressure is limited by the provided on the low-pressure accumulator 20, fixed set pressure relief valve 10. If the low-pressure accumulator 20 is filled or charged, the pump 1, controlled by a pressure sensor 4, can be switched off. The accumulator pressure, ie the pressure of the low-pressure accumulator 20 is applied to the pressure reducing valves 18 and 19 via the check valve 13 and can immediately fill the respective clutch 5 or 6 during an energizing of the pressure reducing valves 18 or 19 by the electronic control, while the control unit Start pump 1 again.

If the clutch pressure after the filling phase has risen above the accumulator pressure, in this embodiment the follower valve 21 always closes so far that the pump pressure can operate the pressure reducing valves 18 and 19 and the working fluid flowing from the follower valve 21 can be utilized by means of the pressure limiting valve 10 to recharge the low pressure accumulator 20.

Since the filling of the clutches 5 or 6 takes place from the low-pressure accumulator 20, the pump 1 can also be very small. Likewise, since the accumulator is designed as a low pressure accumulator 20, this can be simple, robust and inexpensive. For example, a mechanical spring can be used as a storage element instead of the gas bubbles commonly used in membrane reservoirs. The memory is thus independent of temperature and suffers no Vorspannverlust due to gas diffusion through a membrane.

Causes the electronic control unit due to the driving situation - for example, to compensate for a steering failure - the opening of one of the clutches 5 or 6, the pressure reducing valves 18 or 19 are switched accordingly and the working fluid can flow back into the tank 9.

In a previously not graphically illustrated embodiment, however, applies to all previously described embodiments and is also applicable there, the actuation of two clutches 5 and 6 is achieved only by means of a pressure reducing valve 18 and a simple switching valve 12. This can reduce costs by eliminating another expensive pressure reducing valve. With the help of the switching valve 12 is switched between the two clutches 5 and 6 or in an emergency situation can be switched by means of a correspondingly designed switching valve 12 and the tank 9 to open either clutch 5 or 6. However, with this embodiment, not shown, the clutches 5 and 6 are operated sequentially, while in the embodiments described above, the clutches 5 and 6 can work with overlap or are simultaneously actuated. In the figure 5, finally, a further preferred embodiment of the present invention is shown, wherein in this fourth embodiment shown as a volume flow source for the working fluid in the vehicle already existing, constantly driven pump, for example, the power steering pump or power steering pump 22, is used.

A power steering system 23 is designed as a circulation system in which a constant (oil) flow of working fluid is throttled by a steering valve 27 and applied to one of the two sides of a steering cylinder 26. Since it is a differential cylinder, the discharge pressure does not matter for the steering function, but only the accumulated differential pressure.

The typical working pressures of the steering hydraulics are significantly greater than the pressures for operating one of the clutches 5 or 6, so that the tank accumulation of the working fluid according to the solution of Figure 5, the design of the power steering system 23 only slightly influenced.

A driver of the vehicle inputs the steering pulses via a steering wheel 24 and the steering valve 27 accordingly controls the steering cylinder 26 with working fluid so that the connected wheels 25 are steered accordingly.

In addition, there are usually power steering pumps 22 with different nominal pressures - depending on the vehicle engine - available, so that when coupled with a clutch actuator of the rear axle, as proposed here, can be transferred to the next larger power steering pump 22.

If the outflow stream of the power steering system 23 is jammed with a pressure limiting valve 10, as shown in FIG. 3, then the actuation of the clutch 5 and / or 6 can be controlled simultaneously by prioritizing the steering function with the power steering pump 22.

If the same working fluid or oil is used in the power steering system 23 for lubricating and cooling the clutch 5 and 6 as the operation, the clutch 5 and / or 6 can additionally be cooled and lubricated with the drain oil.

In addition, a certain power dependency of the cooling would be given about the engine speed of the internal combustion engine of the vehicle. In order to save costs, FIG. 6 shows a fifth preferred embodiment of the solution according to the invention, which is based on the embodiment according to FIG. In this hydraulic unit for the actuation of the two clutches 5 or 6 also only one pressure reducing valve 18 is used in conjunction with a simple switching valve 12 instead of two pressure reducing valves 18 and 19, whereby the same function is fulfilled. By the switching valve is switched between the two clutches 5 and 6 or in an emergency situation, can be switched by means of a correspondingly formed switching valve 12 and the tank 9 to open the clutches 5 and 6.

The filling of the clearance of the clutches 5 or 6 takes place with working fluid from the low pressure accumulator 20, during which the pump 1 starts and builds on the pressure reducing valve 18, the corresponding pressure for the final closing of the clutch 5 or 6.

If, as already mentioned in FIG. 4, a signal that the clutch 5 or 6 is to be opened via the electronic control is actuated, the switching valve 12 is actuated and the working fluid flows back into the tank 9 via the pressure reducing valve 18.

As in the case of FIG. 4, the dynamics for clutch filling are retained in this embodiment as well, and the clutch 5 or 6 closes in a time of less than 100 ms in order to be able to compensate steering error behavior in the shortest possible time. However, in this embodiment, an overlap of the closing operations of both clutches 5 and 6 is not possible.

In FIG. 6, in contrast to FIG. 4, two pressure reducing valves 18 are not constantly pressurized to reduce the leakage. Thus, the leakage can be halved in standby mode.

The pressure reducing valve 18 used in this solution is, for example, in the cartridge design, so that the standby leakage can also be reduced by this design.

If in an emergency situation, as already described above, the power fail, the pressure reducing valve 18 will immediately reduce the clutch pressure. In a jammed pressure reducing valve 18, the pressure build-up is thereby prevented by the electric motor 2 for the Pump 1 does not start. Due to the leakage at the pressure reducing valve 18, the clutch pressure, if still present, degraded to the level of the low-pressure accumulator 20.

The embodiments described above allow the control of multiple clutches in a rear differential of a vehicle for the redistribution of the wheel torques without the use of an expensive and large diaphragm accumulator as a high-pressure accumulator to provide the high pressures of about 45 bar for operating the clutch (s).

LIST OF REFERENCE NUMBERS

pump

electric motor

High-pressure accumulator

Pressure gauge (pressure sensor)

clutch

magnetic valve

tank

Pressure relief valve

switching valve

check valve

filter

Pre-load valve

Notablassvorrichtung

OR gate

Pressure reducing valve

Accumulator / low pressure accumulator

sequence valve

Power steering pump

Power Steering System

steering wheel

wheel

steering cylinder Ōenkventil

Claims

claims

1. A method for controlling at least one clutch (5, 6) of a vehicle in a hydraulic circuit with a pump (1), a pressure accumulator (20) and at least one in the inlet of the at least one clutch (5, 6) arranged solenoid valve, characterized in that, depending on the driving situation, the corresponding requirement of working fluid with the required pressure can be provided in a short time for closing at least one clutch (5, 6).

2. The method of claim 1 with the following steps: a) filling a pressure accumulator (20) by means of a pump (1); b) switching off the pump (1); c) filling a clutch (5, 6) with working fluid from the pressure accumulator (20), if this at least one clutch (5, 6) to be closed and commissioning of the pump (1); d) closing a coupling (5, 6) after being filled with working fluid, by the working pressure supplied by the pump (1); e) refilling the pressure accumulator (20) after the clutch (5, 6) is closed; f) switching off the pump (1); and g) repeating steps c) to f) for re-closing a clutch (5, 6)

3. A method for controlling at least one clutch (5, 6) of a vehicle in a hydraulic circuit with a pump (1) and at least one in the inlet of the at least one clutch (5, 6) arranged solenoid valve, characterized by the following steps: a) filling the coupling (5, 6) with a working fluid which is conveyed by a pump (1); b) closing the clutch (5, 6) by the working pressure supplied by the pump (1).

4. The method according to claim 3, characterized in that the pump (1) is permanently in operation.

5. The method according to claim 1 and 2, characterized in that the pump (1) for filling the pressure accumulator (20) and for closing the clutch (5, 6) is in operation.

6. The method according to claim 1 and 2, characterized in that in the pressure accumulator (20) the working fluid is stored at a pressure of 5 to 10 bar.

7. The method according to claim 1 and 2, characterized in that the pump (1) is set simultaneously with the filling of the clutch (5, 6) in operation to supply the working fluid under high pressure to close the clutch (5, 6).

8. The method according to claim 1 or 2, characterized in that the pump (1), regardless of the driving situation of the vehicle, the working fluid permanently promotes.

9. The method according to claim 3, characterized in that the outlet pressure of the working fluid of a power steering system (23) for filling and closing the at least one clutch (5, 6) is used.

10. The method according to claim 3, characterized in that the outflow of the working fluid of the power steering system (23) is dammed by means of a pressure limiting valve (10), before it via each a pressure reducing valve (18, 19) of the clutch (5, 6) supplied becomes.

11. An apparatus for performing the method according to claim 1, in particular for controlling at least one clutch (5, 6) of a vehicle in a hydraulic circuit with a pump (1), a pressure accumulator (20), and at least one in the inlet of the at least one clutch (5, 6) arranged for carrying out the method according to claim 1, characterized in that the pressure accumulator (20) is designed as a low-pressure accumulator and with the pump (1) is in operative connection that depending on the driving situation of the at least one clutch (5, 6 ) the corresponding demand for working fluid with the required pressure is available.

12. The device according to claim 11, characterized in that the pump (1) for charging the low-pressure accumulator (20) is provided and by an axle shaft of an electric motor (2), or an internal combustion engine of the vehicle is driven.

13. The apparatus according to claim 11, characterized in that two clutches (5, 6) are driven and in the inlet of each clutch (5, 6), a pressure reducing valve (18, 19) is provided.

14. The apparatus according to claim 11, characterized in that between the pump (1) and the pressure accumulator (20), a sequence valve (21) for charging the Niederduckspeichers (20) is provided.

15. Device according to one of claims 11 to 14, characterized in that the low pressure accumulator (20) is a spring accumulator.

16. The apparatus according to claim 11, characterized in that for each clutch (5, 6) either one pressure reducing valve (18, 19) is provided in the inlet or for two clutches (5, 6) a pressure reducing valve (18) and a switching valve ( 12) are provided.

17. The device according to claim 11, characterized in that the solenoid valve is a pressure relief valve (10, 11) which accumulates the working fluid delivered by the pump (1) to the pressure level required for closing the clutch (5, 6).

18. Device according to one of the preceding claims, characterized in that for each coupling (5, 6) a pump (1) is provided.

19. The apparatus according to claim 11, characterized in that the clutches (5, 6) designed as multi-plate clutches and arranged in a rear differential of a vehicle.

20. Device according to one of claims 11 to 19, characterized in that the pump (1) is the power steering pump (22) of the vehicle

21. The apparatus according to claim 20, characterized in that the steering function of the power steering system (23) relative to the clutch actuation has priority.

22. The apparatus according to claim 11, characterized in that between the pump (1) and the clutch (5, 6), a pressure relief valve (10) is provided, which dammed up the working fluid to the required pressure level for closing the clutch (5, 6) ,