Method for actively changing the frictional value of a hybrid disconnect clutch installed in a power train of a vehicle

Abstract

A method actively changes the frictional value of a hybrid disconnect clutch installed in a powertrain of a vehicle in which a first electric motor (18) is connected to a clutch input (21) and an internal combustion engine (17), and a second electric motor (19) is connected to a clutch output (22) and a vehicle output (23). The frictional value of the hybrid disconnect clutch is actively changed, in order to roughen a surface of the friction linings on the hybrid disconnect clutch (20). A slip situation is established at the hybrid disconnect clutch (20), and during this slip situation energy is introduced into the hybrid disconnect clutch (20) in a controlled manner.

Claims

1. A method for actively changing a frictional value of a hybrid disconnect clutch installed in a powertrain of a vehicle, the method comprising: providing a first electric motor connected to a clutch input and an internal combustion engine, providing a second electric motor connected to a clutch output and a vehicle output, and roughening a surface of the friction linings on the hybrid disconnect clutch by establishing a controlled slip at the hybrid disconnect clutch, wherein during the controlled slip, more energy is introduced into the hybrid disconnect clutch to increase the frictional value of the friction linings, and wherein the controlled slip on the hybrid disconnect clutch for controlled energy input into the hybrid disconnect clutch ends in response to a predetermined energy input threshold value being reached.

2. The method according to claim 1, wherein the hybrid disconnect clutch is opened completely without interruption before the controlled slip is established, and then the hybrid disconnect clutch is closed to a predetermined torque capacity to roughen a surface of friction linings of the hybrid disconnect clutch.

3. The method according to claim 2, wherein the hybrid disconnect clutch is opened without interruption in a single step.

4. The method according to claim 1, wherein the controlled slip and the controlled input of energy take place in response to a maximum clutch torque capacity of the hybrid disconnect clutch being less than a maximum torque of the internal combustion engine.

5. The method according to claim 4, further comprising determining that the maximum torque of the internal combustion engine exceeds the maximum clutch torque capacity of the hybrid disconnect clutch by monitoring a difference between speeds of the first and second electric motors, wherein the controlled slip is set with the controlled energy input when the difference is greater than a slip speed threshold.

6. The method according to claim 1, wherein a slip speed control is activated with the first and the second electric motor.

7. The method according to claim 6, wherein a speed of the second electric motor determines a target speed for the first electric motor for the slip speed control.

8. The method according to claim 6, wherein the target speed is determined by subtracting an offset from the speed of the second electric motor.

9. A method for actively changing the frictional value of a hybrid disconnect clutch, the method comprising: in response to measured torque capacity being less than a maximum engine torque, initiating a controlled slip by setting a speed of a first motor based on a speed of a second motor, the first motor being driveably connected to vehicle wheels and the second motor being drivably connected to an engine; during the controlled slip, introducing a predetermined amount of energy into the hybrid disconnect clutch to roughen a surface of a friction lining to increase the frictional value of the friction lining, wherein the controlled slip and the controlled input of energy take place in response to a maximum clutch torque capacity of the hybrid disconnect clutch being less than a maximum torque of the internal combustion engine, and determining that the maximum torque of the internal combustion engine exceeds the maximum clutch torque capacity of the hybrid disconnect clutch by monitoring a difference between speeds of the first and second electric motors, wherein the controlled slip is set with the controlled energy input when the difference is greater than a slip speed threshold.

10. The method of claim 1 wherein the hybrid disconnect clutch is actuated via a pump in a common hydraulic circuit containing at least one further consumer.

11. The method of claim 9 wherein the hybrid disconnect clutch is actuated via a pump in a common hydraulic circuit containing at least one further consumer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment will be explained in detail with reference to the figures shown in the drawing.

(2) In the figures:

(3) FIG. 1 shows a schematic diagram of a hydraulic device for carrying out the method,

(4) FIG. 2 shows a schematic diagram of a hybrid drive for interaction with the hydraulic device according to FIG. 1,

(5) FIG. 3 shows an exemplary embodiment of the method,

(6) FIG. 4 shows a schematic diagram of the change in the frictional value setting according to the method.

DETAILED DESCRIPTION

(7) FIG. 1 shows a schematic diagram of a hydraulic device for carrying out the method. The hydraulic device 1 comprises a pump 2 which is connected to a coolant line 3 on one side. The coolant line 3 feeds a hydraulic medium 7, for example oil, to a first consumer 4 in the form of a heat exchanger. The hydraulic medium 7 is fed to this first consumer 4 for the purpose of cooling or lubrication.

(8) On the other side, the pump 2 is connected to an actuation line 5. The actuation line 5 is provided to feed the hydraulic medium 7 to a second consumer 6, which is designed as a clutch slave cylinder 21, which is in an operative connection with a hybrid disconnect clutch 20 of a hybrid drive system 16 (FIG. 2). Basically, the same hydraulic medium is contained in both lines, such as the coolant line 3 and the actuation line 5. A parking lock actuator 8, which acts on a parking lock 9, is connected to the actuation line 5 as a further consumer. A switching valve 10 is integrated into the coolant line 3 and/or the actuation line 5 in such a way that the hydraulic medium 7 can be fed to the parking lock actuator 8 in a targeted manner.

(9) The pump 2 is designed as an electrically driven reversing pump, which enables a first conveying direction in order to supply the hydraulic medium 7 as required to the cooling/lubricating task, the pump 2 supplying the hydraulic medium 7 in a second conveying direction to one or more actuation functions, which in this example correspond to the clutch and/or parking lock function. The pump 2 is driven by an electric motor 11 which is activated by a control unit 12. The pump 2, the electric motor 11 and the control unit 12 form an electric pump actuator. A type of transmission sump is used as the hydraulic fluid source 13 for all consumers 4, 6, 8. In the actuation line 5, a pressure sensor 14 is arranged, which is connected to the control unit 12 of the pump and via this to power electronics that control the entire drive unit.

(10) FIG. 2 shows a schematic diagram of a hybrid drive system 16 which comprises an internal combustion engine 17 and two electric motors 18, 19. The two electric motors 18, 19 can be coupled via the hybrid disconnect clutch 20. On the input side of the hybrid disconnect clutch 20, the internal combustion engine 17 is rigidly connected to the first electric motor 18, which works as a generator and, if necessary, provides energy for the second electric motor 19, which drives a vehicle with the hybrid drive system 16 during the electric journey. The second electric motor 19 is positioned on the output side of the hybrid disconnect clutch 20 and is coupled to the output 23 of the hybrid vehicle. Such a hybrid disconnect clutch 20 can be closed step by step due to the pump actuation, but can only be opened completely in one step. In this constellation, the hybrid disconnect clutch 20 does not have to compensate for any differences in speed, since only a power flow from the internal combustion engine 17 to the output 23 has to be established. Since the normal use of the hybrid disconnect clutch 20 does not provide for higher frictional power, which would roughen the lining again, this has to be done artificially using a special software function.

(11) FIG. 3 shows an exemplary embodiment of the method. FIG. 3a shows the clutch torque M over time t, while FIG. 3b shows the difference n between the speed of the second electric motor 19 and the internal combustion engine 17/first electric motor 18 over time t. The maximum transferable clutch torque M of the hybrid disconnect clutch 20 is continuously monitored. If this maximum transferable clutch torque M of the hybrid disconnect clutch 20 falls below the maximum torque of the internal combustion engine 17, a slip situation is activated.

(12) Before this slip situation is set, the hybrid disconnect clutch 20 is completely opened without interruption at time t.sub.1. At time t.sub.2, the hybrid disconnect clutch 20 is closed to a clutch torque M below a maximum electric motor torque M.sub.Emax. As a result of this setting of the hybrid disconnect clutch 20, as shown in FIG. 3b, a slip speed n.sub.S between clutch input 21 and clutch output 22, i.e., the electric motors 1 and 2, is set and regulated at time t.sub.3. During this slip speed n.sub.S, a predetermined amount of energy is introduced into the friction linings of the hybrid disconnect clutch 20, as a result of which they are roughened. If an energy input threshold value E.sub.S is reached by the energy input E.sub.Sch in the friction linings, the slip speed n.sub.S is reduced (time t.sub.4). This is shown in FIG. 3b, where the curve A shows the speed n.sub.V of the internal combustion engine 17, while the curve B shows the speed n.sub.E2 of the second electric motor 19.

(13) As can be seen from FIG. 4, where FIG. 4a shows the energy input E.sub.Sch over time t and FIG. 4b shows the frictional value of the clutch linings of the hybrid disconnect clutch 20 over time t, the frictional value for the clutch linings also increases with the energy input E.sub.Sch during the slip situation in the hybrid disconnect clutch 20. The maximum clutch torque M of the hybrid disconnect clutch 20 can be achieved again after the increase in the frictional value if a predetermined amount E.sub.S of energy is introduced into the linings of the hybrid disconnect clutch 20. As a result, the maximum torque of the internal combustion engine 17 can be transmitted again.

LIST OF REFERENCE SYMBOLS

(14) 1 Hydraulic device 2 Pump 3 Coolant line 4 Consumer 5 Actuation line 6 Consumer 7 Hydraulic medium 8 Parking lock actuator 9 Parking lock 10 Switching valve 11 Electric motor 12 Control unit 13 Hydraulic fluid source 14 Pressure Sensor 15 Power electronics 16 Hybrid powertrain system 17 Internal combustion engine 18 Electric motor 19 Electric motor 20 Hybrid disconnect clutch 21 Clutch input 22 Clutch output 23 Output M Clutch torque M.sub.V Torque of the internal combustion engine M.sub.Emax=Maximum torque of an electric motor n Speed difference n.sub.S Slip speed E.sub.Sch Energy input E.sub.S Energy input threshold Frictional value t Time