CN110770460A

CN110770460A - Method for adapting the torque characteristic of a friction clutch

Info

Publication number: CN110770460A
Application number: CN201880038997.6A
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: 2017-04-26
Filing date: 2018-03-27
Publication date: 2020-02-07
Also published as: DE102018109720B4; WO2018196913A1; DE112018002185A5; KR20200003389A; KR102548140B1; DE102018109720A1

Abstract

The invention relates to a method for adapting the characteristic curve of a wet-running friction clutch, which is actuated by an actuator (3) in an automated hydraulic clutch actuation system (1). In a method in which the error caused by a torque drop can be reduced, the torque characteristic curve of a wet-running friction clutch (9) is adapted by a variable torque offset within an error range which is characterized by a torque drop of the friction clutch (9).

Description

Method for adapting the torque characteristic of a friction clutch

Technical Field

The invention relates to a method for adaptively modifying the torque characteristic of a wet-running friction clutch, which is actuated by a hydrostatic actuator in an automated hydraulic clutch actuation system.

Background

DE 102012204940 a1 discloses a method for adapting parameters of a clutch, which includes a hydrostatic clutch actuator having a pressure sensor in the motor vehicle. Here, a pressure system is used in order to form an abscissa offset of the pressure course (so-called test point), which also applies to the torque course. Furthermore, the friction system is adapted to the current situation by a factor (the so-called friction value). In the wet system, there is also a cluster of belt-displacement torque characteristics, which are added to the respective characteristics. The characteristic map cluster is related to the stroke of the clutch actuator, the temperature of the friction clutch, the cooling oil flow and the slip of the clutch. These three adapted variables characterize the friction clutch independently of the operating system.

In the disclosed method, in particular, the detection points are calculated and adapted on the basis of the pressure signal. The clutch control comprises a hydrostatic path and is controlled by means of an adapted algorithm. In particular, the effect of slip (Aufschwimmen) occurs in wet-running friction clutches. In this error range, neither the detection point nor the friction value representing the parameter of the friction clutch can be learned when the torque deviation is below 50 to 80Nm in the wet friction system. This deviation is represented by curve B1 of fig. 6 and is limited to moments below 150 Nm. The detection point cannot be adjusted because of the poor signal-to-noise ratio generated by the pressure system, since the pressure is still too low within the tolerance range, although the pressure system is operating at full force. Even when a deviation is fed back from the torque system, there are two inputs that collide with each other, which more easily results in the detection point remaining. In principle, it may not be possible to adjust the friction values at lower torques, since an error of a few Nm would lead to a very large change in the friction values (see fig. 7). Although the band torque characteristic map, which is important for wet-running friction clutches, is known, it has hitherto been possible to adapt the band torque characteristic map to other conditions independently of the input shaft (for example, during synchronization of a preselected gear of the clutch), and thus errors can be caused there. Learning of the current cluster of the belt-displacement torque characteristic with the error under consideration is therefore to be avoided, so that no errors are caused at other operating points.

Disclosure of Invention

The object of the present invention is to provide a method for adapting parameters of a friction clutch, in which errors in the float range of a wet clutch are reliably avoided.

According to the invention, the object is achieved in that the torque characteristic curve of the wet-running friction clutch is adapted by means of a variable torque offset within a tolerance range which is characterized by a drop in torque of the friction clutch. The advantage is that the detection point or the friction value determination can be dispensed with and the error can be reliably adapted by adjusting the torque characteristic only within a predetermined error range. The starting point here is that during the torque adaptation, the adaptation of the remaining parallel runs to the detection point, pressure, friction value and/or shape is frozen. In the proposed method, the most probable cause of the error, here a torque drop, is known, whereby the error can be corrected.

Advantageously, the torque offset is gradually reset, preferably to zero, when the friction clutch leaves the tolerance range. It is thus ensured that no further influence of the error correction is present in the normal driving range of the friction clutch.

In one embodiment, the moment offset is reset in a ramp. The advantage is that the friction clutch is gradually transferred from the error situation to the normal driving mode, thereby ensuring that the passenger does not perceive this different adaptation process.

In one refinement, the tolerance range of the friction clutch is specified by the input shaft speed being less than a predetermined speed threshold value and/or by a pressure in the hydraulic clutch actuation system being less than a predetermined pressure threshold value. For the offset adaptation, the threshold values are selected such that the respective offset can be easily determined, so that little delay occurs in the particular driving situation caused by the torque sag. Creep, take-off or creep with a restart are all such driving conditions.

In one refinement, when the friction clutch is disengaged, the input shaft speed of the friction clutch is determined and a 0 rpm input shaft deflection characteristic curve cluster is determined, which is fused to the speed threshold input shaft deflection characteristic curve cluster by interpolation. By thus additionally introducing an offset into the friction clutch torque, which is determined by the input shaft speed, a more accurate adaptation of the clutch torque is ensured.

In one embodiment, a 0 rpm input shaft characteristic curve cluster is created from the measured extreme characteristic curve cluster and the speed threshold input shaft deflection characteristic curve cluster by a weighted linear combination. Linear combination is a particularly simple mathematical method here, which can be implemented very quickly. The moment offset can thus be calculated very quickly and still accurately in the event of errors.

In another embodiment, the linear combination is based on a weighting factor that depends on the statistically averaged moment offset within the error range. At the beginning of the offset determination, a new friction clutch is basically used, wherein the weighting factor assumes an initial value of zero. The weighting factor can be set between 0 and 1 when the friction clutch is in operation.

Advantageously, the weighting factor is proportional to a statistically averaged negative torque offset which is determined if the rotational speed of the input shaft is below a rotational speed threshold value.

Drawings

The invention achieves many embodiments. Two of which will be further explained with reference to the views shown in the drawings. In the figure:

FIG. 1 shows a schematic structure of a hydrostatic clutch operating system;

FIG. 2 shows a first embodiment of the method of the present invention;

fig. 3 shows an example of a torque-travel characteristic curve according to a first embodiment of the method according to the invention;

FIG. 4 shows a second embodiment of the method of the present invention;

fig. 5 shows an example of a torque-travel characteristic curve according to a second embodiment of the method according to the invention;

FIG. 6 shows an example of a torque versus stroke characteristic according to the prior art;

fig. 7 shows a friction value adaptation according to the prior art.

Detailed description of the preferred embodiments

Fig. 1 schematically shows the structure of a hydrostatic clutch actuation system 1 with a hydrostatic clutch actuator 3, as it is applied in a vehicle. The hydrostatic clutch operating system 1 comprises a control device 2, which controls a hydrostatic clutch actuator 3. When the position of the clutch actuator 3 changes, the piston 4 of the master cylinder 5 moves to the right along an actuator path L _ act, wherein the volume in the master cylinder 5 is compressed and a pressure p is built up in the master cylinder 5. This pressure p is transmitted via a hydraulic fluid 6 acting as a pressure medium via a hydraulic line 7 to a slave cylinder 8, which directly operates a friction clutch 9. The friction clutch 9 is designed here as a wet clutch. Wet-running friction clutches comprise, for example, a fluid-contacting (e.g. oil) friction disk pack having friction disks which are stacked in alternating layers and are held on the input side and on the output side by a friction disk carrier. The disengagement and engagement of the wet-running friction clutch is effected by axial tightening of the friction plate pack. The proposed method is used in particular when a slip effect occurs, in which oil cannot be squeezed out between the individual friction disks, which leads to a torque drop.

The pressure p is detected in the master cylinder 5 by means of a pressure measuring device 10, which is connected to the control unit 2. The distance L _ act covered by the clutch actuator 3 is determined by a travel sensor 11. The stroke L _ act which the clutch actuator 3 has to travel is also the same as the stroke of the friction clutch 9.

In order to carry out the parameter adaptation while the motor vehicle is running, a conventional observer 12 is inserted into the control unit 2, which observer is connected in parallel with the actual clutch actuation system 1 (fig. 2). The observer 12 includes a regulating module 13, which simulates the real clutch actuation system 1. The clutch actuator 3 is actuated by the same input variable, for example, when the friction clutch 9 is actuatedThe elapsed distance L _ act is supplied to the actual clutch actuation system 1 and the module 13. The actual clutch actuation system 1 transmits the transmitted clutch torque T _ CL _ tr (which is also referred to as drive train torque) of the drive motor and feeds it to a summation point 14, to which the torque value T _ CL _ M calculated by the module 13 is also applied, as a result of which a torque difference Δ T is determined, which represents an input variable of the module correction unit 15. Within the module correction unit 15, a query is made in block 100 as to whether the friction clutch 9 is observable. What can be observed is always the case where the friction clutch 9 is in various states other than the engaged or disengaged state and no other clutch is active. If the friction clutch 9 is not observable, the torque offset moves in a ramp to 0 (block 101). If the friction clutch 9 is observable, a jump is made to block 102, where the query is made for the input shaft speed N_ipsWhether it is less than 1000 rpm and/or whether the pressure p in the actual clutch operating system 1 is less than 20 bar, for example. In this case, an input shaft speed Nips of 1000 rpm represents the speed threshold, while a pressure of 20 bar represents the pressure threshold. The unit "rpm" means revolutions per minute, i.e. turns per minute.

If at least one of the threshold values is undershot, in block 103 an amplification factor adap _ fac is determined, which represents a statistically averaged deviation of the torque characteristic of the friction clutch 9. The offset difference supplied to the module 13, from which the torque T _ CL _ M of the friction clutch 9 to be actuated is determined, is determined.

If it is determined in block 102 that there are no input conditions for the adaptive modification method that exceed the speed threshold and/or the pressure threshold. It is queried in block 104 whether the negative moment difference-at is the same sign as the offset. If this is the case, the moment balance is reduced, and the moment offset must be reduced. It is slowly moved to 0 in block 105. If the result of the sign comparison is confirmed in block 104, the friction value is fed back by K in block 106_FCAdapted to the torque, and then fed as a friction difference Δ FC to the module 13 for further torque observation.

The torque-path characteristic of the friction clutch 9 is given by the following equation:

t _ CL _ M ═ FC × f _ nom (L _ act-TP) + band rows + offset,

wherein the content of the first and second substances,

t _ CL _ M is the module moment

FC is the friction value

L _ act is the actuator stroke

Belt row is belt row moment

The offset is limited, then: t _ CL _ M is greater than or equal to the band row.

Fig. 3 illustrates an exemplary torque adaptation by offset correction. The torque T _ CL is shown here on the stroke L _ act. Curve B shows the nominal torque characteristic of the wet-running friction clutch 9.

The dashed characteristic B1 represents the actual torque characteristic, as it occurs in the case of a slip of the wet friction clutch 9 during the predetermined stroke L _ act. This real clutch characteristic B1 describes the fact that too little torque is provided by the friction clutch 9 in the event of an error. By means of the method according to the invention, the offset is determined with the friction clutch 9 disengaged, while a ramp-down is always carried out with the clutch engaged. In order to know the offset, the travel indicated by the torque request is passed and the torque difference is determined in the described manner and method. Curve C shows the adaptively modified torque characteristic set by means of the method according to the invention. It should be mentioned here that the characteristic curve C is only temporarily present when the offset is not restored.

A second embodiment of the inventive method is shown in fig. 4, in which the offset determination is improved by: consider input shaft speed Nips. In this case, a distinction is made between a belt row Nips of 0 in block 200, which corresponds to a belt row torque at an input shaft speed of 0 rpm, and a belt row Nips of >1000 in block 201, which corresponds to a belt row torque at an input shaft speed of more than 1000 rpm. Both blocks 200 and 201 are supplied with the current stroke of the clutch actuator L _ act. Both the output of block 200 and the output of block 201 lead to block 202, in which block 202 a 0 rpm input shaft offset characteristic curve cluster is generated. Here, in point 204, the weighting factor adap _ fac (block 203), which has the value 0 as the initial value in the new clutch, is multiplied by the bank Nips provided in block 200, 0, and in point 205, added to the value formed by equation 1-adap _ fac in block 206. In point 207, the result obtained in block 206 is multiplied by the bank Nips >1000 provided in block 201 and leads to point 205.

Starting from point 205, the 0 rpm input shaft offset characteristic value determined in block 202 is fused by interpolation with the 1000 rpm input shaft offset characteristic curve cluster 208, for which purpose in block 209 the band rows Nips >1000 provided in block 201 are multiplied by a further weighting factor determined in block 210. If the input shaft speed is >1000 rpm, the further weighting factor is 1. In point 211, the product formed in block 209 is added to another product formed in block 212. The product formed in block 212 is formed by the result of block 205 of the 0 rpm input axis offset profile cluster (block 202) and another weighting factor learned in block 213. This further weighting factor is always 0 when the input shaft speed Nips >1000 rpm.

In the result of which an offset compensation is obtained, as it is shown in fig. 5. Here, too, a nominal torque characteristic B is shown, which corresponds to an input shaft deflection characteristic of 0 rpm. Characteristic B1 corresponds with its deviation to an input shaft deflection characteristic of 1000 rpm. By fusing the 0 rpm input shaft offset characteristic curve cluster with the 1000 rpm input shaft offset characteristic curve, the characteristic curve D determined mathematically is adapted to the characteristic curve B, so that an offset down slope towards 0 can be cancelled.

A downhill slope deviating towards 0 should only be made in the case of slip if the clutch error is also pointing in this direction. Otherwise the offset must be maintained until an adhesion condition occurs or the clutch is not activated.

The proposed solution makes it possible to reduce the error formation of a torque drop by means of a variable torque offset in the starting situation without significant disadvantages occurring for the standard normal driving range of the wet-running friction clutch 9.

List of reference numerals

1 Clutch actuation System

2 control device

3 Clutch actuator

4 piston

5 Master cylinder

6 Hydraulic fluid

7 hydraulic circuit

8 follow-up cylinder

9 Friction clutch

10 pressure measuring device

11 stroke sensor

12 observer

13 adjustment module

14 summing point

15 Module calibration Unit

Claims

1. Method for adapting the characteristic curve of a wet friction clutch, which is actuated by an actuator (3) in an automated hydraulic clutch actuation system (1), characterized in that the torque characteristic curve of the wet friction clutch (9) is adapted by means of a variable torque offset within a tolerance range which is characterized by a drop in torque of the friction clutch (9).

2. Method according to claim 1, characterized in that the torque offset is gradually reset, preferably gradually reset to zero, when the friction clutch (9) leaves the error range.

3. The method of claim 2, wherein the moment offset is reset in a ramp.

4. A method according to claim 1, 2 or 3, characterised in that the error range of the friction clutch (9) is specified by the input shaft speed (Nips) being less than a predetermined speed threshold and/or by the pressure (p) in the hydraulic clutch operating system (1) being less than a predetermined pressure threshold.

5. Method according to at least one of the preceding claims, characterized in that when the friction clutch (9) is disengaged, the input shaft rotational speed (Nips) of the friction clutch (9) is determined and a 0 rpm input shaft deflection characteristic curve cluster is known, which is fused by interpolation with a rotational speed threshold input shaft deflection characteristic curve cluster.

6. The method according to claim 5, characterized in that the 0 rpm input shaft deflection characteristic curve cluster is created from a weighted linear combination of the measured extreme characteristic curve cluster and the rotational speed threshold input shaft deflection characteristic curve cluster.

7. The method according to claim 6, characterized in that the linear combination is based on a weighting factor (adap-fac) that depends on the statistically averaged moment deviation within the error range.

8. A method according to claim 7, characterised in that the weighting factor (adap-fac) is proportional to a statistically averaged negative torque offset which is known in case the input shaft speed (Nips) is below a speed threshold.