CN107366695B

CN107366695B - Method for controlling an automatic double clutch of a hydraulic clutch actuation system

Info

Publication number: CN107366695B
Application number: CN201710329795.4A
Authority: CN
Inventors: 格奥尔格·格佩特
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2016-05-11
Filing date: 2017-05-11
Publication date: 2020-08-07
Anticipated expiration: 2037-05-11
Also published as: CN107366695A; DE102016208129A1

Abstract

The invention relates to a method for controlling an automatic dual clutch of a hydraulic clutch actuation system, wherein two sub-clutches (12, 19) of the dual clutch are actuated by means of hydrostatic clutch actuators (4, 5, 7) in accordance with a clutch characteristic curve, wherein a clutch torque is set via an actuation path of the respective sub-clutch (12, 19), and wherein during a ventilation process of a hydraulic line (7, 9, 11) of the clutch actuation system (1) the contacts of the clutch characteristic curve of the respective ventilated sub-clutch (12) are changed and corrected. In a method for compensating for crosstalk effects and also effects acting on the contacts during a ventilation process, a correction factor is determined for correcting the contacts of the non-operating partial clutch (12), the correction factor being dependent on a pressure which occurs at the operating partial clutch (19) during the ventilation process of the non-operating partial clutch (12) and which interferes with the non-operating partial clutch (12).

Description

Method for controlling an automatic double clutch of a hydraulic clutch actuation system

Technical Field

The invention relates to a method for controlling an automatic dual clutch of a hydraulic clutch actuation system in which two partial clutches of a dual clutch are actuated in each case by means of a hydrostatic clutch actuator as a function of a clutch characteristic curve, wherein a clutch torque is set via an actuation path of the respective partial clutch, wherein during a venting process of a hydraulic line of the clutch actuation system the contact points of the clutch characteristic curve of the respective vented partial clutch are changed and corrected.

Background

In automatic clutch applications, torque accuracy is of central importance for the starting comfort and shifting comfort of the vehicle. The knowledge of the clutch torque is based on the stroke-torque relationship, which is referred to as a clutch characteristic curve, which can be shifted, scaled or curved by a corresponding correction. In a hydrostatically engaged clutch, the hydrostatic line must be adjusted accordingly or taken into account in the clutch characteristic curve.

In a hydrostatically engaged clutch, the particularity is that: the position between the slave cylinder and the clutch actuator is changed extremely strongly in time by the expansion and contraction of the hydraulic fluid which is present in the clutch actuator of the clutch actuation system. This has the following basic consequences: the temperature of the hydraulic fluid cannot be determined due to inhomogeneities in the hydraulic line between the clutch actuator and the slave cylinder. Therefore, the clutch characteristic curve shift must be permanently detected. Furthermore, with large volume expansions, the expansion/contraction of the hydraulic fluid must be compensated for by force, which requires a venting process in the clutch actuator.

A method for controlling an automatic dual clutch is known from DE 102011102906 a1, in which the dual clutch comprises two partial clutches, which are arranged in a drive train of a vehicle between at least one drive machine and a transmission. The two partial clutches of the dual clutch are arranged in a clutch housing, wherein each partial clutch is assigned a hydrostatic clutch actuator. The clutch actuator comprises a master cylinder which has a ventilation opening by means of which the master cylinder can be connected to the compensating reservoir. Via the open vent, a volume compensation of the hydraulic volume of the hydraulic fluid closed in the hydrostatic pressure is carried out when the partial clutches of the double clutch are operated. In this case, the input piston contained in the master cylinder is retracted, so that the vent is released and pressure compensation can take place in the compensation reservoir.

DE 102015210175.4, which is not yet published, discloses a method for controlling an automatically actuated friction clutch, in which a clutch torque is transmitted by a hydrostatic clutch release system as a function of a clutch characteristic curve, wherein the contacts of the clutch characteristic curve, which change as a function of the ventilation process, are continuously corrected by means of compensation values in the ventilation position.

In contrast to dry clutches, in wet clutches, the temperature does not tend to change the air gap strongly. However, in the double clutch, the crosstalk of the sub-clutches observed is transmitted via one sub-clutch

GeneratingLarge changes, which are referred to as crosstalk effects. That is, when one sub-clutch is actuated, the full range of action of the other sub-clutch is shifted. This effect can be attributed to the mechanical guidance of the two partial clutches on the plate carrier and the clutch cover.

Disclosure of Invention

The object on which the invention is based is: a method for controlling an automatic dual clutch of a hydraulic clutch actuation system is provided, wherein a shift of a clutch characteristic curve can also be compensated for by a ventilation process when one sub-clutch is in crosstalk with another sub-clutch.

According to the invention, said object is achieved by: in order to correct the contacts of the non-operating partial clutch, a correction factor is determined, which is dependent on the pressure which occurs at the operating partial clutch during the venting process of the non-operating partial clutch and which interferes with the non-operating partial clutch. Since the clutch characteristic curve of the inactive partial clutch is shifted to a greater value, taking into account the crosstalk of the active partial clutch to the inactive partial clutch, a more precise setting of the contacts of the inactive partial clutch is also ensured after the ventilation process.

Advantageously, after a ventilation process of the inactive partial clutch, the long-term contact is set, which is corrected by means of a correction factor. In this case, long-term contacts are known per se. However, since the long-term contact is not constant due to the ventilation process of the inoperative partial clutch and the crosstalk of the pressure of the active partial clutch into the inoperative partial clutch, it is advantageously corrected by a correction factor. This results in approximately exact contact points of the non-operating partial clutch and an exact clutch torque derived from the contact points of the clutch characteristic curve.

In one embodiment, a stroke offset of the clutch is used as a correction factor, which is determined from the difference between the two stroke movements of the clutch, wherein during a ventilation process of the clutch, a first stroke movement of the clutch is carried out if the pressure of the clutch is changing from a first value to a second value, and a second stroke movement is carried out if the pressure of the clutch is changing from the second value to a third value. In the case of a selected adjustment of the inoperative partial clutch to a higher stroke, the slave cylinder is pressed in the direction of the stop by the reduced force of the disk spring during the venting process.

In one embodiment, the correction factor is stored for different pressures in a characteristic map, which is determined on a test bench. Since in this characteristic map the pressure of the active partial clutch can be associated with each clutch travel point of the inactive partial clutch, the correction factor can be determined simply from the characteristic map if the pressure of the active partial clutch is known.

In one variant, the pressure of the active partial clutch, which is exerted on the active partial clutch during the venting process of the inactive partial clutch and which interferes with the inactive partial clutch, is determined at the optimum operating point of the active partial clutch. Thus ensuring that: the design of the venting process of the inactive partial clutch is always adapted to the most possible pressure exerted on the active partial clutch.

In one refinement, after the correction factor is determined, the adaptation of the shift of the long-term characteristic curve of the inactive partial clutch is prohibited. Thereby avoiding errors in adjusting the contacts.

In another variant, the priority of the ventilation process is reduced after the correction factor is determined. Since the immediate subsequent ventilation process is thus inhibited, the source of the fault is likewise minimized.

In one embodiment, the shift of the clutch characteristic curve of the non-operating partial clutch is learned only at a reduced, preferably halved speed in the event of a strong crosstalk of the pressure prevailing in the operating partial clutch to the non-operating partial clutch. Thus, the feedback variable for the characteristic curve movement is reliably determined.

Advantageously, a wet clutch is used as the sub-clutch. The proposed method can be used in particular in directly actuated wet clutches with a hydrostatic stroke, wherein the method is suitable in particular for hydrostatically engaged clutches.

Drawings

The invention allows a large number of embodiments. One of the embodiments is explained in detail on the basis of the figures shown in the drawings.

It shows that:

figure 1 shows a schematic structure of a hydraulic clutch operating system,

figure 2 shows a principle view of a double clutch,

figure 3 shows a simplified elastic model of a double clutch,

figure 4 shows a schematic diagram of the crosstalk effect acting on an inactive sub-clutch,

figure 5 shows a schematic diagram of the compensation of the crosstalk and the ventilation process for the pressure exerted on the active sub-clutch in the characteristic curve shift of the inactive sub-clutch,

fig. 6 shows an embodiment of the method according to the invention.

Detailed Description

Fig. 1 shows the structure of an automatic clutch actuation system 1 by way of example of a schematically illustrated Hydrostatic Clutch Actuator (HCA), which is used, for example, in a vehicle. The hydrostatic clutch actuation system 1 comprises a control device 3 on the drive side 2, which controls an electric motor 4, which drives a transmission 5 in order to convert a rotary motion of the electric motor 4 into a translational motion of a piston 6, which is mounted axially displaceably within a drive cylinder 7. Here, the electric motor 4, the piston 6 and the master cylinder 7 form a hydrostatic clutch actuator. If the rotary movement of the electric motor 4 causes a change in the position of the piston 6 in the master cylinder 7 to the right along the clutch travel, the volume of the master cylinder 7 is changed, as a result of which a pressure p builds up in the master cylinder 7, which pressure p is transmitted via a pressure medium 8 in the form of hydraulic fluid via a hydraulic line 9 to the output side 10 of the hydraulic clutch actuation system 1. The length and shape of the hydraulic line 9 are adapted to the installation space conditions of the vehicle. On the output side 10, the pressure p of the pressure medium 8 in the slave cylinder causes a stroke change, which is transmitted to the clutch 12 in order to actuate the clutch. The master cylinder 7, the hydraulic line 9 and the slave cylinder 11 form a hydraulic line.

The pressure p in the master cylinder 7 on the master side 2 of the hydraulic clutch actuation system can be determined by means of a sensor 13. The sensor 13 is preferably a pressure sensor. The distance s covered by the clutch actuators 4, 6, 7 is determined by means of a second sensor 14, which is designed as a stroke sensor and measures the stroke covered by the piston 6 in the master cylinder 7. The

sensors

13, 14 are connected to the control device 3.

Furthermore, the master cylinder 7 has a vent 16, which connects the pressure medium 8 to the compensation reservoir 15 in the open state. This is necessary in order to compensate for the volume expansion of the hydraulic medium 8 due to temperature changes or by bubbles. In this process, the pressure medium 8 is again at ambient pressure and is used for the subsequent clutch operation. When the piston 6 of the master cylinder 7 moves to the right again, the subsequent clutch operation is initiated, wherein the ventilation opening 16 is closed by the piston 6 and the ventilation operation is ended.

In this illustration, the hydraulic clutch actuation system 1 is only schematically illustrated for one clutch 12. In the case of a dual clutch system, the second partial clutch is actuated analogously. The actuation takes place here by means of a slave cylinder 11 which acts on the second partial clutch via a disk spring (belleville retainer) 17 which is closed by a pressure tank 18. The first and second

partial clutches

12, 19 are supported on a plate carrier 20 and a clutch cover 21 (fig. 2). This defines, together with the volume expansion of the pressure medium 8, the slope of the pressure characteristic curve.

Furthermore, a direct-actuated wet double clutch is considered, in which the following effects occur: that is, the active partial clutch 19 exerts a pressure on the inactive partial clutch 12 as a result of the mechanical connection via the plate carrier 20 and the clutch cover 21, which causes a shift of the clutch characteristic curve of the inactive partial clutch 12. This effect, referred to as crosstalk effect, is illustrated in connection with fig. 3 and 4. Fig. 3 shows a simplified spring model of the double clutch 12, 19, in which the individual mechanical elements are shown as springs. The

partial clutches

12, 19 are connected to a position 23 of the clutch actuator or master cylinder 7 via a spring 22, wherein the partial clutches are controlled by the slave cylinder 11, wherein the spring describes the volume expansion of the

hydraulic lines

7, 9, 11 and the slave cylinder 11. During the aeration process, the pressure medium 8 expands in volume. Furthermore, there is a stop 24 of the slave cylinder 11. The position of the slave cylinder 11 is also connected here to a spring, which is a pressure tank 18, which is in turn connected to a disk spring 17 and to a friction disk spring (Belagfeder)25, which moves onto a stop 26. The springs of the first and second

partial clutches

12, 19 are connected to the springs 27 of the clutch cover 21 and the plate carrier 20.

In fig. 4, only the inactive partial clutch 12 is observed in two states Z1, Z2. The active partial clutch 19, which moves the inactive partial clutch 12 into its operating point, which is indicated in this view only by the arrow P, is based on: the inactive and active

partial clutches

12, 19 transmit no torque (state Z1). The inoperative partial clutch 12 is influenced by crosstalk effects during the ventilation process. In this case, the restoring force of the slave cylinder 11 is designed to be smaller, which in turn influences the clutch characteristic curve of the inactive partial clutch 12 during the venting process. This has the following consequences: the inactive partial clutch 12 is engaged by a crosstalk pressure (state Z2), which is exerted on the active partial clutch 19 transmitting torque. Thereby, another speed state is achieved, since the elasticity of the respective spring varies non-linearly. The contact points of the clutch characteristic curve of the inactive partial clutch 12, in which the partial clutch 12 starts to transmit torque in the active state, no longer occur after the venting process to the original long-term contact points and therefore must be corrected.

Fig. 5 shows a schematic sketch of the characteristic curve shift of the clutch characteristic curve of an inoperative clutch 12 during crosstalk and ventilation compensation. In this case, the characteristic curve shift of the non-operating partial clutch 12 with respect to the pressure of the operating partial clutch 19 is explained. Here, the straight lines P5, P10, P20, and P40 that linearly extend represent: when only a crosstalk effect occurs, i.e. the pressure of the active sub-clutch 19 disturbs the inactive sub-clutch 12 due to the mechanical connection via the clutch cover 21 and the plate carrier 20, the characteristic curve of the inactive sub-clutch 12 shifts. Here, for example, characteristic curve P20 illustrates: in the case of the crosstalk effect, the characteristic curve of the non-operating partial clutch 12 shifts during the last ventilation operation with a pressure of 20bar applied to the operating partial clutch 19. Correspondingly, the

numbers

5, 10 and 40 indicate the respective pressures, in bar, which are applied to the active partial clutch 19. Curve K, shown by a dashed line, shows the clutch characteristic curve which is generated when, in addition to crosstalk effects, a ventilation process also occurs at the active partial clutch 12. The clutch characteristic curve (curve K) is non-linear and therefore deals with a larger volume of pressure medium 8 in the hydraulic line. As a result, the pressure rises earlier and the long-term contact moves into the negative range.

Fig. 6 shows an example of the determination of the clutch characteristic curve of the non-operating partial clutch 12 during the ventilation process when crosstalk effects are active. In point a, with a pressure of 20bar in the active partial clutch 19, a venting process takes place in the inactive partial clutch 12. Subsequently, in the active partial clutch 19, the pressure is reduced from 20bar to 10bar, wherein the inactive partial clutch 12 moves from point a to point B on the characteristic curve P20. In the case of a pressure of 10bar in the active partial clutch 19, a further venting process is triggered in the inactive partial clutch 12, wherein the inactive partial clutch 12 is lifted onto the clutch characteristic P10 (from point B to point C). Point C is the travel point of the clutch characteristic curve of the inactive partial clutch 12, which occurs when the active partial clutch 19 has a pressure of 10 bar. Subsequently, the pressure of the active partial clutch 19 is increased to 40bar, the inactive partial clutch 12 transitioning from point C to point D. In point D, a further ventilation process takes place at a pressure of 40bar on the inactive partial clutch 12, which pressure of 40bar acts on the active partial clutch 19. The clutch characteristic curve of the inactive sub-clutch 12 moves from point D to point E.

The path difference is formed from the path travel, which results in the clutch offset, by means of which the long-term contact is corrected, the inactive partial clutch 12 passing through the path travel between points B and C and points D and E. The travel difference is used as a correction factor for the long-term contact point, so that the correct contact point, which corresponds to the actual condition of the double clutch, is also known for the clutch characteristic curve of the inactive partial clutch 12 in this condition. The corrected contact is used when the inactive partial clutch is transferred into the active clutch state.

List of reference numerals

1 Clutch actuation System

2 active side

3 control device

4 electric motor

5 Transmission device

6 piston

7 driving cylinder

8 pressure medium

9 Hydraulic line

10 driven side

11 slave cylinder

12 sub-clutch not in operation

13 sensor

14 sensor

15 compensating container

16 air vent

17 disc spring

18 pressure tank

19 sub-clutch being active

20 piece carrier

21 Clutch cover

22 spring

Position 23

24 stop

25 friction plate spring

26 stop

Claims

1. A method for controlling an automatic dual clutch of a hydraulic clutch actuation system, wherein two partial clutches (12, 19) of the dual clutch are actuated in each case by means of hydrostatic clutch actuators (4, 6, 7) according to a clutch characteristic curve, wherein a clutch torque is set via an actuation travel of the respective partial clutch (12, 19), wherein during a ventilation process of a hydraulic line (7, 9, 11) of the clutch actuation system (1) the contacts of the clutch characteristic curve of the respective ventilated partial clutch (12) are changed, which are corrected,

characterized in that, in order to correct the contacts of the partial clutch (12) which is not in operation, a correction factor is determined which is related to the following pressures: the pressure occurring during a ventilation process of the inactive partial clutch (12) at the active partial clutch (19) and crossing the inactive partial clutch (12);

the travel offset of the inoperative partial clutch (12) is used as a correction factor, which is determined from the difference between the two travel movements of the inoperative partial clutch (12), wherein during a ventilation process of the inoperative partial clutch (12), a first travel movement of the inoperative partial clutch (12) is carried out if the pressure of the active partial clutch (19) changes from a first value to a second value, and a second travel movement is carried out if the pressure of the active partial clutch (19) changes from the second value to a third value.

2. Method according to claim 1, characterized in that after a ventilation process of the inactive partial clutch (12), a long-term contact is set, which is corrected by means of the correction factor.

3. Method according to claim 1, characterized in that the correction factors are stored for different pressures in a family of characteristics, which is determined on a test bench.

4. Method according to claim 1, characterized in that the following pressures of the active sub-clutch (19) at the optimal operating point of the active sub-clutch (19) are determined: the pressure is applied to the sub-clutch being operated during a venting process of the sub-clutch (12) not being operated and is a crosstalk of the sub-clutch not being operated.

5. Method according to claim 1, characterized in that after the determination of the correction factor, the adaptation of the shift of the long-term characteristic curve of the inactive sub-clutch (12) is prohibited.

6. The method of claim 1, wherein the ventilation process is prioritized down after determining the correction factor.

7. Method according to one of the preceding claims, characterized in that in the event of a strong crosstalk of the pressure prevailing in the active partial clutch (19) to the inactive partial clutch (12), a shift of the clutch characteristic curve of the inactive partial clutch (12) is learned only at a reduced speed.

8. Method according to claim 7, characterized in that in the event of a strong crosstalk of the pressure prevailing in the active partial clutch (19) to the inactive partial clutch (12), a shift of the clutch characteristic curve of the inactive partial clutch (12) is learned only at halved speed.

9. Method according to any of claims 1-6, 8, characterized in that a wet clutch is used as a sub-clutch (12, 19).

10. Method according to claim 7, characterized in that a wet clutch is used as a sub-clutch (12, 19).