Method of controlling a double clutch in a vehicle transmission, and clutch control system for controlling a double clutch

Abstract

The present invention concerns a method of controlling a double clutch transmission (1) comprising two clutches (2a, 2b) one of which that is transmitting torque being the active clutch while the other one constituting the incoming clutch characterized by combining the incoming clutch preparation and the torque handover from the active clutch by over actuating the incoming clutch and shutting off the active clutch in a non proportional way, based on a feedback signal from the incoming clutch.

Claims

1. A method of transferring torque from an active clutch to an incoming clutch in a double clutch transmission, the method comprising: preparing the incoming clutch so as to be ready for taking over the torque transmission from the active clutch, wherein the preparation is achieved by over actuating the incoming clutch; maintaining the over actuation of the incoming clutch before a touch point for engaging the incoming clutch is reached; receiving a feedback signal which indicates that all of the torque transmission has been transferred to the incoming clutch from the active clutch while the incoming clutch is over actuated; and shutting off the active clutch based, at least in part, on receiving the feedback signal.

2. The method according to claim 1, further comprising determining an amount of the over actuation as a function of one or both of an engine speed and a throttle pedal position.

3. The method according to claim 1, further comprising transferring all the torque transmission from the active clutch to the incoming clutch.

4. The method of claim 1, wherein maintaining the over actuation of the incoming clutch comprises applying a current to a hydraulic valve associated with the incoming clutch, and wherein the current is greater than a steady state current associated with operation of the incoming clutch when the incoming clutch reaches the touch point for engaging the incoming clutch.

5. The method of claim 1, wherein over actuating the incoming clutch comprises applying an amount of clutch actuation to the incoming clutch that is greater than a threshold amount of clutch actuation associated with fully taking over the torque transmission.

6. The method of claim 1, further comprising reducing the over actuation of the incoming clutch to a second over actuation amount prior to transferring the engine torque from the active clutch to the incoming clutch, wherein the second over actuation amount of the incoming clutch is greater than a touch point actuation amount for engaging the incoming clutch, and wherein at least part of the torque transmission is taken over by the incoming clutch while the incoming clutch is actuated at the second over actuation amount.

7. A clutch control system for transferring torque, the system comprising: a first actuation device configured to actuate an active clutch; a second actuation device configured to actuate an incoming clutch; and a transmission control unit (TCU) configured to: over actuate the incoming clutch, via the second actuation device, in preparation for transferring torque from the active clutch to the incoming clutch; maintain the over actuation of the incoming clutch before a touch point for engaging the incoming clutch is reached; and shut off, via the first actuation device, the active clutch based, at least in part, on a feedback signal which indicates that all of the torque transmission has been transferred to the incoming clutch from the active clutch while the incoming clutch is over actuated.

8. The clutch control system of claim 7, wherein the first actuation device comprises a first non-proportional valve, wherein the second actuation device comprises a second non-proportional valve, and wherein the active clutch is shut off in a non-proportional way.

9. The clutch control system of claim 8, wherein the first actuation device further comprises a first proportional actuator, wherein the first proportional actuator controls an amount of actuation of the active clutch when the first non-proportional valve is on, wherein the second actuation device further comprises a second proportional actuator, and wherein the second proportional actuator controls the amount of actuation of the incoming clutch when the second non-proportional valve is on.

10. The clutch control system of claim 7, further comprising a hydraulic valve associated with the incoming clutch, wherein an amount of current greater than an amount of current associated with the incoming clutch reaching the touch point is applied to the hydraulic valve.

11. The clutch control system of claim 10, wherein the amount of current applied to the hydraulic valve is greater than an amount of current associated with transferring all the torque to the incoming clutch.

12. The clutch control system of claim 10, wherein the amount of current applied to the hydraulic valve is selected based on one or both of a speed of the engine and a throttle pedal position.

13. The clutch control system of claim 7, wherein the TCU is further configured to reduce an amount of actuation of the incoming clutch prior to maintaining the over actuation of the incoming clutch.

14. An apparatus for transferring torque from an active clutch to an incoming clutch in a double clutch transmission, the apparatus comprising: means for over actuating the incoming clutch in preparation for transferring torque from the active clutch to the incoming clutch, wherein the over actuation of the incoming clutch is maintained before a touch point for engaging the incoming clutch is reached; and means for shutting of the active clutch based, at least in part, on a feedback signal which indicates that all of the torque transmission has been transferred to the incoming clutch from the active clutch while the incoming clutch is over actuated.

15. The apparatus of claim 14, further comprising means for reducing actuation of the incoming clutch to an over actuation amount prior to transferring the engine torque from the active clutch to the incoming clutch, wherein the over actuation amount of the incoming clutch is greater than a touch point actuation amount.

16. The method according to claim 15, wherein the means for reducing comprises means for reducing an amount of current applied to a hydraulic valve associated with the incoming clutch.

17. The method according to claim 16, wherein the amount of current applied to the hydraulic valve is reduced to a second amount of current that is greater than or equal to an amount of current associated with transferring all of the engine torque to the incoming clutch.

18. The apparatus of claim 14, further comprising means for receiving a feedback signal from the incoming clutch and wherein it is decided, based on the feedback signal, that all of the engine torque has been transferred from the active clutch to the incoming clutch while the incoming clutch is actuated at an over actuation amount.

19. The apparatus according to claim 18, further comprising means for determining the over actuation amount of the incoming clutch as a function of one or both of an engine speed and a throttle pedal position.

20. The apparatus of claim 14, further comprising a hydraulic valve associated with the incoming clutch, wherein an amount of current applied to the hydraulic valve is selected based on one or both of the engine speed and the throttle pedal position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings,

(2) FIG. 1 shows a block diagram of a double clutch transmission installed in a car,

(3) FIG. 2 shows an example of a hydraulic layout for controlling a double clutch,

(4) FIG. 3 shows a graph explaining the touch point of a clutch as used in a double clutch transmission,

(5) FIG. 4 shows a graph of a conventional clutch torque handover from the active to the incoming clutch,

(6) FIG. 5 shows a graph of the behaviour during a conventional clutch preparation phase,

(7) FIG. 6 shows a graph of the clutch preparation phase according to the present invention, and

(8) FIG. 7 shows a graph of the active and incoming clutch pressure feedback signals according to the current invention.

DETAILED DESCRIPTION

(9) The method of the invention will now be described with reference to FIGS. 6 and 7. With the inventive method, a double clutch transmission can combine the preparation of the incoming clutch and the torque handover from the active clutch. As one can see in FIG. 6, this can be achieved by actuating the incoming clutch more than what is needed for the touch point (this can be even more than what is needed to transfer the engine torque). But instead of reducing this over-actuation before the touch point is expected to be reached, this over-actuation is maintained. This will lead to a fast preparation of the clutch and a very crisp torque capacity increase of that clutch. During this over-actuation phase, a feedback signal of the incoming clutch is monitored and used to decide when the incoming clutch is prepared and has fully or partially taken over the torque from the active clutch, at this moment the active clutch is shut off and also the over-actuation of the incoming clutch is stopped. When the over actuation of the incoming clutch is stopped it can be actuated like in conventional power shifts after the torque handover, to complete the shift.

(10) The term over-actuation as used here is in particular to be understood as referring to applying more current to the hydraulic valve controlling the respective clutch, then needed in a certain condition. In the application this means that during the clutch preparation phase, the current applied to the hydraulic valve is more then the steady state current which would be needed for the touch point of the clutch, it is even more then what would be needed to transfer the full engine torque.

(11) The shut-off of the active clutch is performed in a non proportional way being by using an on-off actuator 11 or by controlling a proportional actuator 10 with a step or a combination of these two.

(12) FIG. 7 shows the feedback signals of the active and incoming clutch. At time t.sub.1 the control method recognises the incoming clutch is prepared and takes over at least a part of the engine torque from the active clutch. At this moment the active clutch is shut down, which can be seen in the feedback pressure.

(13) EP 1 717 473 shows the general hydraulic lay-out which can be used for actuating the double clutch. The disclosure of this document is explicitly incorporated by reference.

LIST OF REFERENCE SIGNS

(14) TABLE-US-00001 1 double clutch transmission 2 double clutch 2a, 2b clutches of double clutch 2 3 hollow shaft 4 central output shaft 5 clutch housing 6 crank shaft 7, 8 gear sets 9 Pressure supply 10 Proportional actuator 11 Non-proportional actuator 12 Pressure sensor 13a, 13b Connection to clutches TCU Transmission Control Unit