DE102015205884A1 - Method for adapting a hydrostatic touch point of a clutch arranged in a hydraulic clutch actuation system - Google Patents

Abstract

The invention relates to a method for adapting a hydrostatic contact point of a clutch arranged in a hydraulic clutch actuating system, in which the clutch (9) is actuated by a hydrostatic clutch actuator (3), wherein a pressure-displacement characteristic of the hydrostatic clutch actuator (3) is determined and from the pressure-displacement curve a clamping force-displacement curve (A) of the coupling (9) is derived, from which the hydrostatic touch point (TPh) is determined. In a method in which the hydrostatic touch point can be adapted directly, an additional touch point (TPz) is determined via a torque determination of the clutch (9) and the hydrostatic touch point (TPh) is adapted via the additional touch point (TPz).

Description

The invention relates to a method for adapting a hydrostatic contact point of a arranged in a hydraulic clutch actuation clutch, in which the clutch is actuated by a hydrostatic clutch actuator, wherein a pressure-displacement characteristic of the hydrostatic clutch actuator is determined and from the pressure-displacement curve a Clutch force-displacement characteristic of the clutch is derived, from which the hydrostatic contact point is determined.

In motor vehicles, it is necessary to improve the ride comfort to make the control of a clutch particularly reliable. Both the clutch characteristic and the contact point of the clutch are important. The clutch characteristic may not only vary from vehicle to vehicle but also over the lifetime and during operation, e.g. because of changing coupling temperatures. For this reason, the clutch characteristic curve must be adapted by means of certain adaptation mechanisms.

From the DE 10 2012 204 940 A1 a clutch actuation system is known in which the clutch is part of a hydraulic clutch actuation system comprising a hydrostatic clutch actuator, the pressure of which is determined. The pressure of the hydrostatic clutch actuator is used for clutch characteristic adaptation. For a clutch characteristic adaptation, the touch point determination is of particular importance. The path-pressure characteristic is adapted by means of the pressure to obtain a path-clamping force relation that correlates directly with the transmitted clutch torque. Under the clamping force of the clutch is to be understood the force at which abut the pressure plates on the clutch disc and transmit a moment. For small Ausrückwegen the clutch actuator, the pressure plates are not yet on the clutch disc and the counter-force of a slave cylinder of the clutch actuation system is determined exclusively by a leaf spring, which keeps the clutch open. In this area, no moment is transmitted through the clutch. In order to transmit a moment to the clutch, first the pressure plates of the clutch must be moved against the leaf spring forces, so that contact with the clutch disc takes place. Only from this point can a clamping force and thus a friction torque between the clutch disc and the pressure plate be constructed. After a certain deviation of the force due to the connection of a lining suspension in the meeting of pressure plates and clutch disc, a so-called hydrostatic touch point can be defined. In the area of the small release travel of the clutch actuator, the leaf spring preload are determined relatively slowly via an offset and an incline.

In the further course after detection of the hydrostatic touch point substantially the lining suspension and then the coupling stiffness S are imprinted. If the adapted leaf spring force is subtracted from a force converted from an average pressure, the clamping force is obtained, which is generally described by a nominal characteristic including form factors F and stiffness S. The hydrostatic changes of this nominal clamping force-displacement curve M _G by heating, cooling and pressure equalization, as in 3 represented, in contrast to stiffness S and form factors F, a very fast displacement V of the characteristic. A measured value M _W lying on the nominal clamping force-displacement characteristic curve M _G is likewise displaced very rapidly and perceived as the measured value M _WK .

Likewise, leaf spring non-linearities can easily be misinterpreted as a deviation, so that a determination of the hydrostatic touch point directly in the pressure path is not possible. In addition, the range of small clamping forces in hydrostatic clutch actuation systems is run through very quickly, so that little statistics is available, which is still noisy due to dynamic effects.

When applying the pressure plates to the clutch disc, the pressure is very difficult or even impossible to detect. The noise / payload ratio in the range of small clamping forces is particularly due to the in 4 shown pressure hysteresis very high. An error with low clamping forces can hardly be adjusted by a +/- 20% change in the form factors. The quality at low clamping forces depends very much on the characteristic stiffness S, which is usually learned at high forces. This means that the noise level is very high. Moreover, it is hardly possible to distinguish a slope difference from a shape factor F ( 3 ), so that at high forces, the representation of the characteristic is not unique. This should be in 4 be clarified by the possible characteristics G _G1 and G _G2 . The hydrostatic touch point is therefore interpreted as an overall characteristic shift and learned at higher pressures.

The invention is thus based on the object of specifying a method for adapting a hydrostatic contact point of a coupling arranged in a hydraulic clutch actuating system, in which the hydrostatic contact point can be reliably determined from the clamping force-displacement characteristic of the hydrostatic clutch actuator.

According to the invention, this object is achieved in that an additional tactile point is determined via a torque determination of the clutch and the hydrostatic touch point is adapted via the additional scanning point. This has the advantage that the torque-based touch point determination takes place independently of the hydrostatic touch point determination and thus the torque-based touch point can be used as an aid for the exact adaptation of the obtained from the clamping force-displacement curve of the coupling hydrostatic touch point.

Advantageously, the adaptation of the hydrostatic touch point, the clamping force-displacement curve is adapted in the range of small paths of the hydrostatic clutch actuator. As a result, the entire pressure-displacement curve can still be moved quickly over the pressure at higher clamping forces. The additional tactile point causes only a change in the characteristic curve in the range of small paths of the clutch actuator, where a precise torque-path relationship of the clutch can be detected. The additional sampling point thus has no negative influences on the existing strategy of adapting the pressure-displacement characteristic over the pressure.

For reasons of continuity, at least one support point located in front of and behind the adapted hydrostatic touch point is adapted to the clamping force-displacement curve. The adaptation takes place on the basis of predetermined boundary conditions and can be designed, for example, as a scaling.

In one embodiment, at least one support point of the clamping force-displacement characteristic line located in front of and behind the adapted hydrostatic touch point is adapted. Thus, not only a point is adapted in the range of small clamping forces, but enables a continuous adaptation, which improves the accuracy of the clamping force-displacement curve in this area. The transmission can take place at the printing level.

In one embodiment, the adaptation of the hydrostatic touch point is checked by the additional sampling point at predetermined intervals. Since the changes in this area due to temperature changes or wear are very slow, the adaptation of the hydrostatic touch point must be made only sporadically.

In one variant, a shift of the pressure-displacement characteristic at higher pressures is continuously adapted as a function of the pressure, with time intervals for adapting the pressure-displacement characteristic being smaller than the time intervals for adapting the hydrostatic contact point. This ensures that the characteristic shift is always reliably adapted at higher pressures.

The torque-based additional tactile point can be adapted in the most diverse drive trains in vehicles and used to correct the hydrostatic touch point of the operated in a hydraulic clutch actuation clutch. Thus, it is possible that the determination of the additional sampling point takes place during a drive of a vehicle with an internal combustion engine, wherein a lower torque range of the internal combustion engine is detected.

When using a dual-clutch transmission in a drive train of a vehicle, the determination of the Zusatztastpunktes while driving the vehicle by an inactive clutch of the dual clutch transmission is applied and closed from a dynamic of the inactive coupling connected inactive transmission input shaft to an applied torque and thus the Zusatztastpunkt becomes.

When using the dual-clutch transmission, there is alternatively another possibility in which the determination of the additional sampling point takes place while the vehicle is traveling. In this case, during a slip operation of the active clutch of the dual-clutch transmission, the inactive clutch is applied and a slip control evaluated.

Even with a hybrid vehicle, a torque-based additional touch point can be determined at any time, wherein the determination of the additional touch point while driving the hybrid vehicle is carried out by a torque change of an electric motor is evaluated in a stationary engine.

By means of the torque-based additional touch point thus determined, it is possible to adapt the hydrostatic touch point of a clutch arranged in a hydraulic clutch actuation system.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

Show it:

1 a schematic structure of a hydraulic clutch actuation system,

2 an embodiment of an adapted clamping force-displacement characteristic,

3 a clamping force-displacement curve according to the prior art at a pressure drop in the hydraulic clutch actuator,

4 a clamping force-displacement characteristic according to the prior art with a high noise-to-signal ratio.

In 1 schematically is the structure of a hydraulic clutch actuation system 1 illustrated by the example of a hydrostatic clutch actuator. This schematic diagram shows a structure for operating a clutch, as it can be used in clutch actuation systems with single clutches but also with dual clutch systems. In dual-clutch systems, an analogue structure is available for the second clutch.

The hydraulic clutch actuation system includes a controller 2 , which is the hydrostatic clutch actuator 3 controls. When the position of the clutch actuator changes 3 becomes a piston 4 a master cylinder 5 along the Aktorweges moved to the right, the volume in the master cylinder 5 changed and a pressure p in the master cylinder 5 is built. This pressure p is via a hydraulic fluid 6 , which serves as a pressure medium, via a hydraulic line 7 to a slave cylinder 8th transferring the clutch 9 via a preload spring 12 actuated. The pressure p of the hydraulic fluid 6 causes it in the slave cylinder 8th a change of direction, resulting in the operation of the clutch 9 reflected.

The pressure p is in the master cylinder 5 by means of a pressure measuring device 10 determined with the control unit 2 connected is. The of the clutch actuator 3 traveled distance s is from a displacement sensor 11 certainly. The one of the clutch actuator 3 The distance traveled is further explained with the path of the clutch 9 equated.

When the clutch actuator 3 moving from a fully open position in the direction of "clutch closed", the piston must 4 of the master cylinder 5 move the liquid. The volume of hydraulic fluid 6 in the clutch actuator 3 changes eg with the temperature of the hydraulic fluid 6 , When the temperature increases, the volume of the hydraulic fluid increases accordingly 6 and thus the clutch actuator 3 built-up pressure p at the same position of the clutch actuator 3 , Since the pressure p of the clutch actuator 3 the clutch changes 9 pressed with a different pressure p. The transferable clutch torque M is consequently different.

To determine a hydrostatic touch point, a path-pressure characteristic is first determined. This can be done when the clutch 9 either opened or closed.

In the area of small paths s of the clutch actuator 3 , which corresponds to small coupling positions where the clutch 9 no moment transmits, nevertheless, an engagement force must be applied. This force results from spring elements - usually leaf springs - for safe separation of clutch disc and pressure plate in the clutch 9 are attached. For a moment at the clutch 9 To transfer, first the pressure plates of the clutch 9 be moved toward each other against these leaf spring forces, so that a contact with the clutch disc takes place. From this so-called hydraulic touch point TP _h , a clamping force and thus a friction torque between the clutch disc and pressure plates can be constructed. A derived from the measured pressure-displacement characteristic clamping force-displacement curve A is in 2 shown. The hydrostatic touch point TP _h is also illustrated on this characteristic curve.

In an independent process, a torque-based touch point TP _z is simultaneously determined. In this determination, the path s of the hydrostatic clutch actuator 3 measured at which the clutch 9 begins to transmit a moment. In 2 this additional touch point TP _{z is} at the same level of force as the hydrostatic touch point TP _h but at another waypoint. Through the control unit 2 a difference is formed between the path s of the additional sample point TP _z and the path s of the hydrostatic sampling point TP _h . Depending on this, the hydrostatic touch point TP _{h is} weighted corrected. This results in the adapted touch point TP _a1 .

To the course of the clamping force-displacement curve of the coupling 9 To design continuously, further support points in front of and behind the adapted touch point TP _{a1 are} adapted in the described manner and the points P _a2 and P _{a3 are} determined therefrom. From the points TP _a1 , P _a2 , and P _a3 results in a curve area B in the lower path range of the clutch actuator 3 , Thus, only the lower part of the nominal clamping force-displacement characteristic curve A is corrected by the torque-determined additional touch point TP _z .

By knowing the torque-based additional touch point TP _z , the hydrostatic touch point TP _{h of} the nominal clamping force-displacement characteristic curve A is displaced relatively on the path axis. The entire characteristic curve AB continues to be displaced rapidly at higher clamping forces via the pressure. The additional sampling point TP _z thus has no negative influence on the pressure-displacement characteristic, which is adapted by means of the pressure.

Due to the prescribed solution and the adaptation, in particular the clamping force-displacement curve in the lower region of the clamping forces, a clear representation of the clamping force-displacement curve in this area and thus a reliable definition of the hydrostatic touch point TP _{h is} possible.

LIST OF REFERENCE NUMBERS

1

 hydraulic clutch actuation system

2

 control unit

3

 Hydrostatic clutch actuator

4

 Piston of the master cylinder

5

 Master cylinder

6

 hydraulic fluid

7

 hydraulic line

8th

 slave cylinder

9

 clutch

10

 Pressure measuring device

11

 displacement measuring system

12

 preload

TP _h

 hydrostatic touch point

TP _z

 Zusatztastpunkt

p

 print

s

 path

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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 assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012204940 A1 [0003]

Claims (10)

Method for adapting a hydrostatic touch point of a clutch arranged in a hydraulic clutch actuation system, in which the clutch ( 9 ) from a hydrostatic clutch actuator ( 3 ), wherein a pressure-displacement characteristic of the hydrostatic clutch actuator ( 3 ) is determined and from the pressure-displacement curve a clamping force-displacement curve (A) of the clutch ( 9 ), from which the hydrostatic touch point (TP _h ) is determined, characterized in that an additional touch point (TP _z ) via a torque determination of the clutch ( 9 ) and the hydrostatic touch point (TP _h ) is adapted via the additional touch point (TP _z ). A method according to claim 1, characterized in that by the adaptation of the hydrostatic touch point (TP _h ), the clamping force-displacement characteristic (A) in the region (B) small ways (s) of the hydrostatic clutch actuator ( 3 ) is adjusted. A method according to claim 2, characterized in that at least one before and after the adapted hydrostatic touch point (TP _h ) lying support point of the clamping force-displacement curve (A) is adjusted. A method according to claim 1, 2 or 3, characterized in that before and after the adapted hydrostatic touch point (TP _h ) lying support point of the clamping force-displacement curve (A) is adapted. Method according to at least one of the preceding claims, characterized in that the adaptation of the hydrostatic touch point (TP _h ) is checked at predetermined time intervals. Method according to at least one of the preceding claims, characterized in that a shift of the pressure-displacement curve at higher pressures (p) is continuously adapted as a function of the pressure (p), wherein time intervals for adaptation of the pressure-displacement characteristic curve are smaller as the time intervals for the adaptation of the hydrostatic touch point (TP _h ). Method according to at least one of the preceding claims, characterized in that the determination of the additional touch point (TP _z ) takes place during a journey of a vehicle with an internal combustion engine, wherein a lower torque range of the internal combustion engine is detected. Method according to at least one of the preceding claims 1 to 6, characterized in that the determination of the additional touch point (TP _z ) takes place during the drive of the vehicle by an inactive clutch of a dual-clutch transmission is applied and from a dynamic of the inactive clutch connected to the inactive transmission input shaft on an applied moment and thus the additional sampling point (TP _z ) is closed. Method according to at least one of the preceding claims 1 to 5, characterized in that the determination of the additional sampling point (TP _z ) takes place while the vehicle is running, during a slip operation of the active clutch of the dual-clutch transmission, the inactive clutch is applied and a slip control is evaluated. Method according to at least one of the preceding claims 1 to 5, characterized in that the determination of the additional sampling point (TP _z ) takes place while a hybrid vehicle is traveling, in which a torque change of an electric motor is evaluated in a stationary internal combustion engine.

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