DE102023106979A1 - Hydraulic actuation system and method for operating a hydraulic actuation system - Google Patents

Abstract

The invention relates to a hydraulic actuation system (1) for engaging and disengaging a clutch (2), with a double-acting hydraulic cylinder (5) which has a first hydraulic connection (15) on an engagement side, which is subjected to hydraulic pressure when the clutch (2) is engaged, and which has a second hydraulic connection (16) on a disengagement side, which is subjected to hydraulic pressure when the clutch (2) is disengaged.
In order to increase the switching comfort when engaging and disengaging the clutch (2), the hydraulic actuation system (1) on the engagement side of the hydraulic cylinder (5) is equipped with a defined compressibility (20), which provides a desired switching elasticity only when engaging the clutch (2) but not when disengaging the clutch (2).

Description

The invention relates to a hydraulic actuation system for engaging and disengaging a clutch, with a double-acting hydraulic cylinder which has a first hydraulic connection on an engagement side, which is subjected to hydraulic pressure when the clutch is engaged, and a second hydraulic connection on a disengagement side, which is subjected to hydraulic pressure when the clutch is disengaged. The invention further relates to a method for operating such a hydraulic actuation system.

The German disclosure document EN 10 2016 222 761 A1 discloses a drive train for a motor vehicle with a hybrid drive, wherein an electric motor with a stator and a rotor can be coupled to a transmission on the output shaft side and is connected to a crankshaft-fixed component of an internal combustion engine via a separating clutch designed as a claw clutch, wherein the claw clutch is prepared by its geometry and its materials for carrying out an impulse start. The German patent specification EN 10 2021 124 487 B3 discloses a hydraulic system with a reversing pump that can be driven by a pump motor in opposite directions of rotation for providing different volume flows and/or pressure levels in the hydraulic system.

The object of the invention is to increase the shifting comfort when engaging and disengaging a clutch.

The task is solved in a hydraulic actuation system for engaging and disengaging a clutch, with a double-acting hydraulic cylinder, which has a first hydraulic connection on an engagement side, which is subjected to hydraulic pressure when the clutch is engaged, and a second hydraulic connection on a disengagement side, which is subjected to hydraulic pressure when the clutch is disengaged, in that the hydraulic actuation system on the engagement side of the hydraulic cylinder is equipped with a defined compressibility, which only provides a desired switching elasticity when the clutch is engaged, but not when the clutch is disengaged. The clutch is, for example, a hydraulically actuated claw clutch. The clutch is used, for example, to represent a separating clutch in a drive train of a motor vehicle that includes an electric motor drive. The clutch is engaged and disengaged via the double-acting hydraulic cylinder. The clutch can be held in its engaged or disengaged state by a locking device. The defined compressibility can, on the one hand, minimize the switching time when the clutch is actuated. In addition, the shifting comfort when operating the clutch can be increased. In addition, by providing the defined compressibility on the engagement side of the hydraulic cylinder, actuator components and/or transmission components in the drive train of the motor vehicle can be protected from damage. The defined compressibility on the engagement side of the hydraulic cylinder can be particularly advantageous in reducing an undesirable shock load in tooth-on-tooth positions during engagement of the clutch, which is preferably designed as a claw clutch. It is particularly advantageous that the defined compressibility on the engagement side of the hydraulic cylinder has no effect when the clutch is disengaged. This means that the clutch can be disengaged as quickly as desired by applying pressure to the disengagement side of the double-acting hydraulic cylinder.

A preferred embodiment of the hydraulic actuation system is characterized in that the defined compressibility on the insertion side of the hydraulic cylinder comprises a cavity that contains a defined amount of a compressible medium. With the compressible medium, the defined compressibility on the insertion side of the hydraulic cylinder can be provided with relatively simple structural means.

A further preferred embodiment of the hydraulic actuation system is characterized in that the cavity contains air. The air can represent the compressible medium in the cavity, since the air can be considered compressible compared to the hydraulic medium with which the hydraulic actuation system is operated. The hydraulic medium is, for example, hydraulic oil, which is considered incompressible.

A further preferred embodiment of the hydraulic actuation system is characterized in that the cavity is arranged above components of the hydraulic actuation system containing hydraulic medium, relative to a line of action of the earth's gravity. By specifically placing the entire hydraulic arrangement of the hydraulic actuation system at a hydraulic medium level, for example in a transmission equipped with the hydraulic actuation system, a defined amount of air can be enclosed in the cavity without affecting the hydraulic operation. When the hydraulic actuation system is actuated in the direction of engaging the clutch, the air contained in the cavity has an effect. The enclosed air acts like an elasticity that is only effective when the clutch is engaged.

A further preferred embodiment of the hydraulic actuation system is characterized in that the cavity has a cross-section that is significantly smaller than a height of the cavity. The term cross-section refers to a dimension of the cavity transverse to the line of action of the earth's gravity. The term height refers to a dimension of the cavity in the direction of the line of action of the earth's gravity. The claimed design of the cavity provides, among other things, the advantage that the compressed medium enclosed in the cavity, in particular the air enclosed in the cavity, is influenced as little as possible by a fill level of hydraulic medium. The hydraulic medium is, for example, oil. The fill level of the hydraulic medium is then, for example, an oil level in a transmission to which the clutch is assigned that is actuated with the hydraulic actuation system.

A further preferred embodiment of the hydraulic actuation system is characterized in that the defined compressibility is combined with a venting device. With the venting device, which for example comprises a vent, an excessive accumulation of air in the cavity can advantageously be avoided. With the venting device it can be ensured in a simple manner that not too much air accumulates in the cavity, in particular against the background that additional air enters the cavity via the hydraulic medium. The venting device is advantageously designed and positioned in such a way that the air from the cavity is specifically vented to a desired level in order to maintain a stable separation plane between the hydraulic medium and the air.

Three further embodiments are described in general terms below for the sake of completeness. However, in the context of the claimed hydraulic actuation system, the embodiments without a membrane, without elastically deformable material and without a spring are preferred because this allows costs to be saved in design and manufacture.

A further embodiment of the hydraulic actuation system is characterized in that the cavity contains a membrane that separates the compressible medium from a hydraulic medium with which the hydraulic actuation system is operated. The membrane prevents the air contained in the cavity from mixing with the hydraulic medium in an undesirable manner.

A further embodiment of the hydraulic actuation system is characterized in that the defined compressibility on the insertion side of the hydraulic cylinder comprises an elastically deformable material. The elastically deformable material can have the same or a similar effect as the compressible medium in the cavity. The elastically deformable material can also be combined with the compressible medium, such as air, in the cavity.

A further embodiment of the hydraulic actuation system is characterized in that the defined compressibility on the insertion side of the hydraulic cylinder comprises a spring. The spring is advantageously arranged in the cavity. In this way, the desired elasticity on the insertion side can be provided with relatively simple structural means.

A further preferred embodiment of the hydraulic actuation system is characterized in that the clutch is a dog clutch. The dog clutch comprises dogs which are brought into engagement with one another in a known manner in order to form a rotationally fixed connection when the clutch is engaged. The claimed hydraulic actuation system is preferably used exclusively with a dog clutch or in combination with a mechanism which includes a dog clutch. Such a mechanism comprises, for example, a synchronization.

The invention also relates to a defined compressibility for a previously described hydraulic actuation system. The defined compressibility can be handled separately, depending on the design. This is particularly the case when the hydraulic actuation system with the defined compressibility is constructed in a modular manner.

In a method for operating a previously described hydraulic actuation system, the above-mentioned object is alternatively or additionally achieved in that the defined compressibility provides a desired switching elasticity when the clutch is engaged, but not when the clutch is disengaged. The desired switching elasticity is particularly advantageous when the clutch, in particular the claw clutch, assumes an intermediate state when engaged, in which the teeth or claws of the claw clutch come into contact with one another before the teeth or claws engage with one another.

A preferred embodiment of the method is characterized in that information about an oil level, a vehicle position, an ambient pressure and an ambient temperature are used to estimate the compression behavior of the defined compressibility. With the help of this information, the compression behavior can be better calculated. This allows the stressed hydraulic actuation system to be controlled more robustly.

• 1 eine schematische Darstellung eines hydraulischen Betätigungssystems zum Einlegen und Auslegen einer Kupplung mit einer definierten Kompressibilität auf einer Einlegeseite eines doppelt wirkenden Hydraulikzylinders in einem ausgelegten Zustand der Kupplung;
• 2 das hydraulische Betätigungssystem in einem Zwischenzustand der Kupplung;
• 3 das hydraulische Betätigungssystem mit der Kupplung im eingelegten Zustand;
• 4 einen vergrößerten Ausschnitt der definierten Kompressibilität des hydraulischen Betätigungssystems aus den 1 bis 3 mit einer zusätzlichen Membran;
• 5 eine ähnliche Darstellung wie in 4 mit einer zusätzlichen Feder; und
• 6 vier übereinander angeordnete kartesische Koordinatendiagramme, die einen Einlegevorgang der als Klauenkupplung ausgeführten Kupplung mit einem Lufteinschluss als Schaltelastizität veranschaulichen.

Further advantages, features and details of the invention emerge from the following description, in which various embodiments are described in detail with reference to the drawing. They show:

• 1 a schematic representation of a hydraulic actuation system for engaging and disengaging a clutch with a defined compressibility on an engagement side of a double-acting hydraulic cylinder in a disengaged state of the clutch;
• 2 the hydraulic actuation system in an intermediate state of the clutch;
• 3 the hydraulic actuation system with the clutch engaged;
• 4 an enlarged section of the defined compressibility of the hydraulic actuation system from the 1 to 3 with an additional membrane;
• 5 a similar representation as in 4 with an additional spring; and
• 6 Four Cartesian coordinate diagrams arranged one above the other, which illustrate an engagement process of the clutch designed as a claw clutch with an air inclusion as switching elasticity.

In the 1 to 3 a hydraulic actuation system 1 with a clutch 2 is shown schematically in different switching states. The clutch 2 is designed as a claw clutch with claws 3, 4, which can be brought into engagement with one another in order to represent a rotationally fixed connection between two rotating elements in a drive train of a motor vehicle.

In 1 the clutch 2 is in a disengaged state 9. In the disengaged state 9, the claws 3, 4 of the clutch 2 are not in engagement with one another.

In 2 the clutch 2 is in an intermediate state 11. In the intermediate state 11, the claws 3, 4 of the clutch 2 are in contact with each other. Depending on the design of the claws 3, 4, these are also referred to as teeth. Therefore, the intermediate state 11 can also be referred to as a tooth-on-tooth position.

In 3 the clutch 2 is in the engaged state 10. In the engaged state 10, the claws 3, 4 of the clutch 2 engage with each other to enable torque transmission in a rotationally fixed connection.

The hydraulic actuation system 1 comprises a double-acting hydraulic cylinder 5, in which a piston 6 in the 1 to 3 in a horizontal direction, i.e. movable to the left and to the right. The piston 6 is axially fixedly connected to the claws 3 of the claw coupling 2 via a piston rod 7.

By movements of the piston 6, the claws 3 of the claw clutch 2 can be moved back and forth relative to the claws 4 in order to engage or disengage the clutch 2.

The piston rod 7 can be axially fixed by means of a locking device 8 when the clutch 2 assumes its disengaged state 9 or its engaged state 10. The locking device 8 comprises a spring-loaded 1 to 3 upwardly preloaded locking body 12, which engages in one of two locking recesses 13, 14 on the piston rod 7 for axially fixing the piston rod 7.

The double-acting hydraulic cylinder 5 comprises a first hydraulic connection 15 and a second hydraulic connection 16. The first hydraulic connection 15 is in the 1 to 3 arranged on a left side of the hydraulic cylinder 5. The left side of the hydraulic cylinder 5 is also referred to as the insertion side because the clutch 2 is inserted or closed when the hydraulic cylinder 5 is subjected to hydraulic pressure at its first hydraulic connection 15.

The second hydraulic connection 16 is on a 1 to 3 right side of the hydraulic cylinder 5. The right side of the hydraulic cylinder 5 is also referred to as the release side because the clutch 2 is released or opened when the hydraulic cylinder 5 is subjected to hydraulic pressure at its second hydraulic connection 16.

The first hydraulic connection 15 is pressurized with hydraulic pressure via a first hydraulic line 17. The second hydraulic connection 16 is pressurized with hydraulic pressure via a second hydraulic line 18. When the corresponding pressure is applied, the other side of the hydraulic cylinder 5 is relieved of pressure.

Through a in the 1 to 3 The earth's gravity 19 is indicated by a vertically downward arrow. A defined compressibility 20 is arranged, in relation to a line of action of the earth's gravity 19, in a cavity 21 above a hydraulic medium 22, with which the hydraulic actuation system 1 is actuated. In the 1 to 3 A certain amount of a compressible medium 23, such as air, is arranged in the cavity 21 to represent the defined compressibility 20.

When the claw clutch 2 is actuated in the direction of engagement, the air 23 in the cavity 21 acts like an elasticity, which is only effective when the clutch 2 is engaged and plays no role when the clutch 2 is disengaged. Since the air inclusion representing the defined compressibility 20 is only hydraulically connected to the first hydraulic connection 15, the elasticity represented by the defined compressibility 20 advantageously has no influence on the disengagement process. In this way, with the defined compressibility 20 on the engagement side of the double-acting hydraulic cylinder 5, a one-sided elasticity can be easily implemented when the clutch 2 is engaged or closed.

During operation of the hydraulic actuation system 1, in a first phase 31 the first hydraulic connection 15 is supplied with an oil volume flow, the hydraulic medium being referred to as oil for short. In this first phase 31 the air 23 in the cavity 21 is compressed and hydraulic pressure is built up at the first hydraulic connection 15. When the hydraulic pressure at the first hydraulic connection 15 increases to such an extent that the counterforce caused by the locking device 8 is overcome, the piston 6 in the hydraulic cylinder 5 moves into 1 to the right in the direction of engaging clutch 2.

In a 2 In the second phase 32 shown, the piston 6 in the hydraulic cylinder 5 cannot move further to the right due to the previously described tooth-on-tooth position of the claws 3, 4 of the clutch 2. The air inclusion in the cavity 21 is still elastic despite the compression. This advantageously prevents pressure peaks that are damaging to components, for example on the claws 3, 4. The compression in the air inclusion is indicated by the reduced volume of the air 23 in the cavity 21. In 2 In contrast, the hydraulic medium 22 occupies the largest part of the cavity 21.

In a 3 In the third phase 33 shown, it is indicated that the air 23 in the cavity 21 expands again. This enables the claw coupling 2 to be inserted quickly.

To create the air inclusion in the cavity 21, the cross section of the cavity 21 is chosen to be as small as possible, while the height of the cavity 21 is designed to be as large as possible. This ensures that the volume of the air enclosed in the cavity 21 is influenced as little as possible by the oil level in the transmission. Information available within the vehicle, for example about the oil level, vehicle position, ambient pressure and temperature, can be used to calculate the compression behavior of the air 23 in the cavity 21. This allows the hydraulic actuation system 1 to be controlled more robustly.

In the 4 and 5 The defined compressibility 20 is shown enlarged according to two design variants. In 4 the defined compressibility 20 comprises an additional membrane 24 which is arranged in the cavity 21 between the hydraulic medium 22 and the enclosed air 23.

In 5 the defined compressibility 20 further comprises an additional spring 25. The additional spring 25 is formed from an elastically deformable material 26 and is prestressed against the membrane 24 in the cavity 21.

In 6 A total of four Cartesian coordinate diagrams are shown, each with an x-axis 34, 35, 36, 37 and y-axes 54, 55, 56 and 57. In 6 The three phases 31, 32 and 33 mentioned above in the operation of the hydraulic actuation system are indicated by double arrows at the top. The engagement path of the claws 3 of the clutch 2, which is designed as a claw clutch, is plotted on the x-axes 34 to 37 in a suitable path unit.

On the y-axis 54, an air volume enclosed in the cavity 21 is plotted in a suitable volume unit. On the y-axis 55, a piston position of the piston 6 is plotted in a suitable travel unit. On the y-axis 56, a volume flow at the first hydraulic connection 15 is plotted in a suitable volume flow unit. On the y-axis 57, a hydraulic pressure at the first hydraulic connection 15 is plotted in a suitable pressure unit.

44 shows the pressure curve at the first hydraulic connection 15 during the insertion process. 45 shows the volume flow curve at the first hydraulic connection 15 during the insertion process. 46 shows the piston position curve during the insertion process. 47 shows the change in volume in the cavity 21 during the insertion process.

By presenting the 6 illustrates how the switching elasticity or the volume of the cavity 21 can be specifically optimized or designed. In addition, 6 an initial indication is provided as to how large the cavity 21 must be. This allows the required installation space to be estimated during construction.

List of reference symbols

1

hydraulic actuation system

2

coupling

3

To steal

4

To steal

5

double-acting hydraulic cylinder

6

Pistons

7

Piston rod

8

Locking device

9

designed condition

10

inserted state

11

Intermediate state

12

Locking body

13

Locking recess

14

Locking recess

15

first hydraulic connection

16

second hydraulic connection

17

first hydraulic line

18

second hydraulic line

20

defined compressibility

21

cavity

22

Hydraulic medium

23

compressible medium

24

membrane

25

Feather

26

elastically deformable material

31

first phase

32

second phase

33

third phase

34

x-axis

35

x-axis

36

x-axis

37

x-axis

44

Pressure at the first hydraulic connection 15

45

Volume flow at the first hydraulic connection 15

46

Piston position at the first hydraulic connection 15

47

Volume of the compression medium in the cavity 21

54

y-axis

55

y-axis

56

y-axis

57

y-axis

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102016222761 A1 [0002]
• DE 102021124487 B3 [0002]

Claims (10)

Hydraulic actuation system (1) for engaging and disengaging a clutch (2), with a double-acting hydraulic cylinder (5) which has a first hydraulic connection (15) on an engagement side, which is subjected to hydraulic pressure when the clutch (2) is engaged, and which has a second hydraulic connection (16) on a disengagement side, which is subjected to hydraulic pressure when the clutch (2) is disengaged, characterized in that the hydraulic actuation system (1) on the engagement side of the hydraulic cylinder (5) is equipped with a defined compressibility (20) which provides a desired switching elasticity only when the clutch (2) is engaged but not when the clutch (2) is disengaged. Hydraulic actuation system according to Claim 1 , characterized in that the defined compressibility (20) on the insertion side of the hydraulic cylinder (5) comprises a cavity (21) which contains a defined amount of a compressible medium (23). Hydraulic actuation system according to Claim 2 , characterized in that the cavity (21) contains air. Hydraulic actuation system according to Claim 2 or 3 , characterized in that the cavity (21), relative to a line of action of an earth's gravity (19), is arranged above components of the hydraulic actuation system (1) containing hydraulic medium (22). Hydraulic actuation system according to Claim 4 , characterized in that the cavity (21) has a cross-section which is significantly smaller than a height of the cavity. Hydraulic actuation system according to one of the preceding claims, characterized in that the defined compressibility (20) is combined with a venting device. Hydraulic actuation system according to one of the preceding claims, characterized in that the clutch (2) is a claw clutch. Defined compressibility (20) for a hydraulic actuation system (1) according to one of the preceding claims. Method for operating a hydraulic actuation system (1) according to one of the Claims 1 until 7 , characterized in that the defined compressibility (20) provides a desired switching elasticity when engaging the clutch (2), but not when disengaging the clutch (2). Procedure according to Claim 9 , characterized in that information about an oil level, a vehicle position, an ambient pressure and an ambient temperature are used to estimate the compression behavior of the defined compressibility (20).

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