WO2023001327A1 - Method for determining a bite point of a separating clutch of a hybrid module - Google Patents

Abstract

The invention relates to a method for determining a bite point of a separating clutch (6), which is actuated by means of a hydraulic unit, of a hybrid module (2) arranged between an internal combustion engine (3) and drive wheels (14), wherein a slave cylinder operated with a working pressure actuates the separating clutch (6) counter to the action of a lever spring, which adjusts a frictional engagement of the separating clutch (6), and of a restoring spring transferring a piston of the slave cylinder into a zero position as the separating clutch (6) opens, and the separating clutch (6) is opened by dissipating the working pressure. In order to be able to determine the bite point simply and reliably in this environment, a pressure profile which is dependent on the relaxation of the lever spring and of the restoring spring is detected during an opening process of the separating clutch (6) and a bite point is defined when the lever spring is relaxed.

Description

Method for determining a touch point of a separating clutch

hybrid module

The invention relates to a method for determining a touch point of a separating clutch, actuated by a hydraulic unit, of a hybrid module arranged between an internal combustion engine and drive wheels, with a slave cylinder operated with a working pressure activating the separating clutch against the action of a lever spring setting a frictional engagement of the separating clutch and a slave cylinder piston of the slave cylinder when the separating clutch opens, it is actuated and moves the return spring to a zero position, and the separating clutch opens as a result of the reduction in the working pressure.

Separating clutches are used in drive trains for the controllable transmission of torque, for example between an internal combustion engine and a transmission. In a generic hybrid drive train with a hydraulic module, the separating clutch is used to couple and decouple the internal combustion engine from at least one electric machine. For precise control of such separating clutches, it is necessary to determine a current touch point at which the separating clutch begins to transmit torque. This touch point depends on the operating parameters of the drive train, for example the temperature, the wear on the separating clutch and the like.

From publication WO2014/023304 A1, for example, a method for determining a touch point of a hydrostatically actuated friction clutch is known, in which a position sensor of a master cylinder piston of a master cylinder is used for hydrostatic actuation of a slave cylinder that actuates the friction clutch. linders and a pressure/force sensor for detecting the pressure in the hydrostatic line between the master cylinder and the slave cylinder.

A method for estimating clutch parameters is known from the document DE 102011 101 870 A1, in which a profile of an actuating pressure for closing the friction clutch and a setpoint pressure signal and/or time signal are recorded and stored in parallel, with the profile being divided into at least two different areas , the areas are approximated with different approximation functions and at the kink point a clutch parameter, for example the touch point, is determined.

The object of the invention is the development of a method for determining the touch point of a clutch. In particular, the object of the invention is to propose a simple and robust method for determining the touch point of a clutch.

The object is solved by the subject matter of claim 1. The claims dependent on claim 1 provide advantageous embodiments of the subject-matter of claim 1.

The proposed method is used to determine a touch point of a separating clutch in a hybrid module of a hybrid drive train of a motor vehicle.

The hybrid module is arranged, for example, between an internal combustion engine and a differential with drive shafts and drive wheels. The hybrid module contains a first and a second electric machine and the separating clutch arranged between the electric machines. The first electric machine is used, for example, as a generator and is driven, for example, by the internal combustion engine to generate electrical energy shear, which is stored in a battery and with the second electric machine is operated to drive the motor vehicle. Above a certain speed, for example 50 km/h, the separating clutch can be closed and the motor vehicle can be operated in hybrid mode to increase the efficiency of the drive of the motor vehicle.

The separating clutch is actuated, for example, by means of a hydraulic unit with a hydraulic, electrically driven pump. The electric machines and the hydraulic unit are controlled by one or more control units. The Hy draulic unit contains, for example, a pressure line in which a predetermined working pressure is set by means of the pump. The working pressure is recorded by a pressure sensor.

The separating clutch is actuated by means of a slave cylinder. Here, for example, a slave cylinder piston shifts an actuating component such as a lever spring of the clutch axially by means of an intermediate actuating mechanism against the action of a return spring for restoring the slave cylinder piston when the clutch opens. A travel or position sensor for the slave cylinder piston is not provided. If necessary, the actuating mechanism contains a rotational compensation, for example an actuating bearing. The slave cylinder is controlled by means of a switching valve controlled by a control unit, which is arranged in the pressure line between the slave cylinder and the pump. Under the specified working pressure, the slave cylinder cylinder piston of the slave cylinder is shifted when the switching valve is open and the separating clutch is closed. The working pressure in the pressure line can be maintained by means of a non-return valve so that the pump can be switched off or used for other purposes. For example, the pump can be designed as a bidirectional pump, with the working pressure in the pressure line being adjusted in one direction of rotation of the pump and in the other direction of rotation in a pressure medium line, a fluid flow for cooling and / or lubrication of at least one drive train component is provided. If the separating clutch is to be opened, a switching valve between the slave cylinder and an unpressurized sump is opened and the working pressure is relieved. The working pressure on the slave cylinder or in the pressure line is reduced due to leakage. If the working pressure falls below a specified minimum pressure, the pump starts a pumping process up to a specified maximum pressure.

For example, the hybrid module can contain a parking lock, which is actuated by means of a switching valve arranged in the pressure line with a downstream slave cylinder that actuates the parking lock.

In order to be able to determine the touch point easily and, for example, without a position sensor of the slave cylinder, during an opening process of the separating clutch, i.e., for example immediately after the opening of a switching valve which connects the pressure line with the sump, one of the relaxation of the lever spring and the return spring-dependent pressure profile is recorded and a contact point is defined when the lever spring is relaxed.

The lever spring and the return spring are advantageously arranged in series and designed for different rigidities. As a result, the frictional connection on the separating clutch is canceled by the lever spring with high rigidity. The preloaded return spring remains compressed due to its lower rigidity. As soon as the lever spring is relaxed, no more frictional torque is transmitted via the separating clutch, that is, the contact point is reached even though the slave cylinder piston has not yet fully reached its zero position. The further course of pressure with decreasing pressure occurs due to the resetting of the slave cylinder piston in its zero position using the return spring. Due to the two different rigidities of the lever spring and return spring, this results in two pressure branches, at the inflection point of which the touch point is arranged.

It is therefore possible to differentiate between the gradients of the pressure curve when the lever spring relaxes and, due to the lower rigidity, essentially subsequently relaxes the return spring, and a transition region between the gradients can be defined as a touch point.

For example, the pressure curve recorded during the opening process of the separating clutch can be stored in a control unit before the touch point is determined. The touch point can then be determined, for example when the separating clutch is already closed again or at a different point in time. In order to resolve the smooth transition between the two gradients, the pressure curve can be derived over time. In this case, a derived pressure value of the pressure profile can then be determined as a touch point if this lies within a specified target window. The target window can be, for example, a predetermined pressure range gradient or one continuously adapted to the pressure profile.

The contact point is preferably determined regularly and/or as a function of at least one other parameter of the hybrid module, for example its operating temperature, in particular the temperature of the separating clutch and/or the temperature of the hydraulic unit, during an operating period of the hybrid module.

The touch point determined in this way is used in particular to control the separating clutch in order to detect the beginning of a transfer of torque via the separating clutch. In addition, after an initiated opening process of the separating clutch, when the contact point is reached, an open separating clutch can be can be. If necessary, a detected touch point and/or an open separating clutch known to be open can be checked for plausibility by means of a predetermined speed difference between the input part and the output part.

The invention is explained in more detail with reference to the embodiment shown in Figures 1 to 5 game. These show:

FIG. 1 shows a schematically illustrated flybridge drive train,

FIG. 2 shows a hydraulic unit for operating the separating clutch of the hybrid drive train of FIG. 1,

Figure 3 is a diagram showing the detection of the contact point of the separating clutch of Figures 1 and 2,

FIG. 4 shows a diagram for determining the touch point from the pressure profile of the slave cylinder of the hydraulic unit of FIG. 2 and

FIG. 5 shows a flow chart for determining the contact point of the separating clutch of FIGS. 1 and 2.

FIG. 1 shows the hybrid drive train 1 for a motor vehicle in a schematic representation. The internal combustion engine 3 is non-rotatably connected to the hybrid module 2 with the two electric machines 4, 5 and the separating clutch 6 arranged between them. The crankshaft 7 of the internal combustion engine 3 and the rotor 8 of the first electric machine 4 are connected by means of the input shaft 9 in a rotationally fixed manner to the input part 10 of the separating clutch 6, which is automatically actuated by means of the hydraulic unit 100 of FIG. The output part 11 of the separating clutch 6 is connected to the output shaft 12 with the rotor 13 of the second electric machine 5 .

If the separating clutch 6 is fully closed, ie closed without slipping, the speed of the input shaft 9 corresponds to the speed of the output shaft 12 and transmits the maximum transferrable clutch torque, if necessary via a transmission stage and a differential to the drive wheels 14.

To support the sole drive of the hybrid drive train 1 by means of the electric machine 5, the separating clutch 6 can be closed and thus the electric machine 4 and the internal combustion engine 3 can be switched on. The contact point of the separating clutch 6 is determined during an opening process of the separating clutch 6, in that the pressure profile of the clutch slave cylinder closing the separating clutch is detected and evaluated.

Referring to Figure 1, Figure 2 shows the hydraulic diagram of hydraulic unit 100 for hydraulically actuating separating clutch 6, parking lock 101 and for cooling and/or lubricating components of hybrid drive train 1, for example wet-operated separating clutch 6. Pump 104 of the Hydraulic unit 100 works bidirectionally, so that working pressure p is built up in one direction of rotation of pump 104 in pressure line 108 and pressure medium for lubrication and/or cooling is provided in the other direction of rotation in pressure medium line 107 .

The separating clutch 6 and the parking lock 101 are actuated alternatively by means of the switching valve 102 al. When the switching valve 102 is switched through, the separating clutch 6 is connected by means of the switching valve 103 either to the pump 104 or to the pressureless sump 105 .

The pump 104 driven by the electric motor 106 builds up the specified working pressure p in the pressure line 108 when the switching valve 102 and the switching valve 103 are switched accordingly, which is set by correspondingly controlling the electric motor 106 by means of the control unit 109 and is detected by the pressure sensor 110 . Between the pump 104 and the pressure line 108 is the return Check valve 112 is arranged so that when the working pressure p is reached, the pump 104 can be switched off or operated in the other direction of rotation to supply the pressure medium line 107 . If the working pressure falls below a predetermined value in the event of a leak, the pump 104 switches back to the other direction of rotation and builds up the working pressure p again.

By means of the working pressure p present in the pressure line 108, the slave cylinder 111 of the separating clutch 6 is acted upon, the separating clutch 6 is actuated and transmits a clutch torque that is dependent on the working pressure p. In the case of the completely closed separating clutch 6, this transfers the maximum transferrable clutch torque. As a result of the applied working pressure p, the slave cylinder piston 115 is displaced axially and biases the return spring 113 and the lever spring 114 to close the separating clutch 6 . The lever spring 114 adjusts the friction circuit of the separating clutch 6 by axially prestressing, for example, alternately layered disks of the wet-operated separating clutch 6 on the input side and on the output side.

The displacement path As of the slave cylinder piston 115 from a working pressure p=0 to the maximum working pressure contains a touch point pressure at which the lever spring 114 is completely relaxed at the touch point, as a result of which the separating clutch 6 just no longer transmits any clutch torque. At this touch point, the restoring spring 113 can still be partially prestressed. This leads to a pressure profile of the decreasing working pressure p, which transitions from a belfeder 114 due to the higher stiffness of the steep drop with a large incline into a section with a lower Stei supply, in which the return spring 113 is completely relaxed. A break point of the two sections with different gradients marks the tactile point. Referring to FIGS. 1 and 2, FIG. 3 shows diagram 200 with sub-diagrams I, II. Sub-diagram I shows working pressure p over time t in seconds and sub-diagram II shows the associated pressure gradient p/dt over time t.

At present t1, the separating clutch 6 is closed by the switching valve 103 being closed and the switching valve 102 in the direction of the slave cylinder 111 is switched through. From the pressure profile 201 it can be seen that the maximum working pressure pmax has built up by the time t2 and the slave cylinder piston 115 is displaced along the displacement path As (Figure 2) under the pretension of the lever spring 114 and the return spring 113 and thus the Separating clutch 6 is fully closed all the time.

At time t3, the switching valve 103 is opened to open the separating clutch 6 and the working pressure p is reduced by the slave cylinder piston 115 being released first by the prestressed lever spring 114 with a steep pressure curve along the section 202 and after the reduction of its essential prestress with a less steep pressure curve of section 203 is pushed back to its zero position. At the break point K of the two sections 202, 203, the touch point of the separating clutch 6 is reached. In terms of measurement technology, it is sufficient to determine the contact point if the inflection point K is located within the target window Ap.

The pressure gradient p/dt with its gradient curve 204 makes it possible to determine the associated slope of the pressure curve 201 at any point in time. For example, the tactile point can be determined when the slope mtast is within a predetermined value.

Diagram 300 in FIG. 4, with reference to FIGS. 1 to 3, shows pressure curve 201 in FIG. 3 over time t and the associated determination of the touch point. Flierzu are the individual in a control unit, for example in the The pressure values of the pressure profile 201 stored in the control unit 109 are stored and the approximate straight lines g1, g2 are assigned to its two sections 202, 203. If there is a gradient mtast at the point of intersection S of the straight lines g1, g2 and the point of intersection S is within a predetermined range and the point of intersection S is within the target window Dr, an updated point of contact is detected, saved and used in the future.

With reference to the preceding figures, FIG. 5 shows the flow chart 400 with the routine 411 implemented in the control unit 109, for example, for carrying out the method for determining the contact point of the separating clutch 6. The routine 411 is started in block 401, initialized in block 402, That means, for example, registers are deleted and, if necessary, provided with handover data.

In branch 403 it is queried whether the separating clutch 6 should be opened. As long as the separating clutch 6 remains closed, the routine 411 waits at this branch 403. If the separating clutch 6 is to be opened, for example by a signal bit being transferred from the higher-level control unit 109 to the routine 411, the switching valve 102 is opened in block 404. In block 405, the pressure values of pressure sensor 110 are recorded and stored. In block 406, the stored data values are derived over time. In block 407, a data analysis of blocks 405 and 406 takes place. In branch 408, a check is made as to whether the recorded pressure values are within the target window Dr. If this is the case, a check is made in branch 409 to determine whether the predetermined gradient of the inflection point K of the sections 202, 203 or of the intersection point S of the straight lines g1, g2 approximated to them is within the target window Dr. If this is the case, in block 410 the updated touch point is saved. is If this is not the case, the determination of the touch point is terminated and the return takes place before branch 403.

List of reference symbols hybrid drive train hybrid module internal combustion engine electric machine electric machine separating clutch crankshaft rotor input shaft input part output part output shaft rotor drive wheel hydraulic unit parking lock shift valve shift valve pump sump electric motor pressure medium line pressure line control unit pressure sensor slave cylinder check valve return spring lever spring slave cylinder piston diagram 01 pressure curve 02 section 03 section 04 gradient curve 300 diagram 00 flow diagram 01 block

402 blocks

403 branch

404 blocks

405 blocks

406 blocks

407 blocks

408 branch

409 branch

410 blocks

411 Routine 91 straight line g2 straight line K knee point mtast slope

P working pressure p/dt pressure gradient pmax maximum pressure

S Intersection t time t1 time t2 time t3 time

Dr target window

As a route of displacement

I part diagram

II part diagram

Claims

patent claims 1. Method for determining a contact point of a separating clutch (6) actuated by means of a hydraulic unit (100) of a hybrid module (2) arranged between an internal combustion engine (3) and drive wheels (14), wherein a slave cylinder (111 ) the separating clutch (6) against the action of a lever spring (114) setting a frictional engagement of the separating clutch (6) and a return spring (114) guiding a slave cylinder piston (115) of the slave cylinder (111) into a zero position when the separating clutch (6) opens 113) is actuated and the separating clutch (6) is opened by reducing the working pressure (p), characterized in that during an opening process of the separating clutch (6), a pressure curve depends on the relaxation of the lever spring (114) and the return spring (113). (201) is detected and a contact point is defined when the lever spring (114) is relaxed. 2. The method according to claim 1, characterized in that the lever spring (114) and the return spring (113) are arranged in series and are designed for under different stiffnesses. 3. The method according to claim 2, characterized in that the gradients of the pressure curve (201) are differentiated when the lever spring (114) relaxes and, due to the smaller rigidity, the restoring spring (113) then relaxes, and a break point (K) between the gradients gen is set as the tactile point. 4. The method as claimed in claim 3, characterized in that the pressure profile (201) is stored in a control unit before it is determined and the touch point is then determined. 5. The method according to claim 3 or 4, characterized in that the pressure profile (201) is derived according to the time (t) and a derived pressure value is then determined as a touch point if this is within a predetermined target window (Dr). 6. The method according to claim 5, characterized in that the gradient of each individual pressure value is determined and a touch point is recognized when the gradient of a pressure value is equal to a predetermined value or value range and the pressure value with this gradient is within the target window (Dr). 7. The method according to any one of claims 1 to 6, characterized in that the touch point during an operating period of the hybrid module (2) is determined regularly and / or depending on at least one other parameter of the hybrid module (2) in a targeted manner. 8. The method according to any one of claims 1 to 7, characterized in that an open clutch (6) is recognized when the touch point is reached.