Lockup control of torque converter

• US 7,346,442 B2
• Filed: 06/08/2005
• Issued: 03/18/2008
• Est. Priority Date: 06/09/2004
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Higashimata, Akira, Segawa, Satoshi
• Primary Examiner(s): NGUYEN, CUONG H
• Application Number:
  US11/147,440
• Publication Number:
  US 20050278103A1
• Time in Patent Office: 1,014 Days
• Field of Search: 701 67- 58
• US Class Current: 701/67
• CPC Class Codes: F16H 2059/366 Engine or motor speed
• CPC Class Codes: F16H 2061/145 for controlling slip, e.g. approaching target slip value
• CPC Class Codes: F16H 59/36 Inputs being a function of speed
• CPC Class Codes: F16H 61/143 using electric control means

Abstract

A controller (5) controls the engaging force between a pump impeller (1a) connected to an engine (2) and a turbine runner (1b) connected to an automatic transmission (23). The controller (5) first performs feedforward control of the engaging force. The controller (5) determines a reference value and a target rotation speed based on the capacity characteristics of the torque converter (1), and if the rotation speed of the engine (2) becomes less than the reference value, performs feedback control of the engaging force so that the deviation between the target rotation speed and the rotation speed decreases. When a predetermined condition is satisfied, the controller (5) changes over from feedforward control to feedback control, even if the rotation speed of the engine (21) is not less than the reference value. As a result, the control precision of feedback control when performing a slip lock-up, is increased.

Claims

1. A lockup control device of a lockup clutch of a torque converter for a vehicle, the torque converter comprising a pump impeller connected to an engine and a turbine runner connected to an automatic transmission, and transmitting a torque therebetween via a fluid and via the lockup clutch according to an engaging force of the lockup clutch, the device comprising:

a mechanism which adjusts the engaging force; and

a programmable controller programmed to;

perform feedforward control of the mechanism;

calculate a target engine rotation speed based on a running state of the engine;

compute a reference value related to a rotation speed of the engine based on a capacity characteristics of the torque converter;

perform, when the rotation speed of the engine falls to less than the reference value during feedforward control, a change-over from feedforward control of the mechanism to feedback control of the mechanism in which a deviation of the rotation speed of the engine from the target engine rotation speed is reduced; and

perform, when a predetermined condition is satisfied, even if the rotation speed of the engine has not fallen to less than the reference value, perform a change-over from feedforward control of the mechanism to feedback control of the mechanism.

2. The lockup control device as defined in claim 1, wherein

the controller is further programmed to compute a hunting prevention change-over value based on the target engine rotation speed, and when the rotation speed of the engine becomes less than the hunting prevention change-over value, determine that the predetermined condition is satisfied.

3. The lockup control device as defined in claim 2, wherein

the controller is further programmed to compute an engine stall prevention change-over value based on a minimum rotation speed of the engine at which lockup can be performed without stalling the engine, and when the rotation speed of the engine is less than the maximum value among the reference value, the hunting prevention change-over value and the engine stall prevention change-over value, determine that the predetermined condition is satisfied.

4. The lockup control device as defined in claim 3, wherein

the engine comprises a throttle to regulate an output power, and

the engine stall prevention change-over value is set to be small when the throttle opening is large, and set to be large when the throttle opening is small.

5. The lockup control device as defined in claim 2, wherein

the engine comprises a throttle to regulate an output power, and

the hunting prevention change-over value is set to be small when a throttle opening is large, and set to be large when the throttle opening is small.

6. The lockup control device as defined in claim 1, wherein

the controller is further programmed to compute an engine stall prevention change-over value based on a minimum rotation speed of the engine at which lockup can be performed without stalling the engine, and when the rotation speed of the engine is less than the engine stall prevention change-over value, determine that the predetermined condition is satisfied.

7. The lockup control device as defined in claim 1, wherein

the engine comprises a throttle to regulate an output power, and

the reference value is set to be large when a throttle opening is large, and set to be small when the throttle opening is small.

8. The lockup control device as defined in claim 1, wherein

the reference value is computed based on a boundary speed ratio when a speed ratio, which is a ratio of a turbine runner rotation speed to a rotation speed of the engine, changes from a non-linear relation to a linear relation with respect to capacity coefficient of the torque converter.

9. A lockup control device of a lockup clutch of a torque converter for a vehicle, the torque converter comprising a pump impeller connected to an engine and a turbine runner connected to an automatic transmission, and transmitting a torque therebetween via a fluid and the lockup clutch according to an engaging force of the lockup clutch, the device comprising:

means for adjusting the engaging force;

means for performing feedforward control of the adjusting means;

means for calculating a target engine rotation speed based on a running state of the engine;

means for computing a reference value related to a rotation speed of the engine based on a capacity characteristic of the torque converter;

means for performing, when the rotation speed of the engine falls to less than the reference value during feedforward control, a change-over from feedforward control of the adjusting means to feedback control of the adjusting means in which the deviation of the rotation speed of the engine from the target engine rotation speed is reduced; and

means for performing, when a predetermined condition is satisfied, even if the rotation speed of the engine has not fallen to less than the reference value, a change-over from feedforward control of the adjusting means to feedback control of the mechanism.

10. A lockup control method of a lockup clutch of a torque converter for a vehicle, the torque converter comprising a pump impeller connected to an engine and a turbine runner connected to an automatic transmission, and transmitting a torque therebetween via a fluid and the lockup clutch according to an engaging force of the lockup clutch which is adjusted by an engaging force adjusting mechanism, the method comprising:

performing feedforward control of the mechanism;

calculating a target engine rotation speed based on a running state of the engine;

computing a reference value related to a rotation speed of the engine based on a capacity characteristic of the torque converter;

performing, when the rotation speed of the engine falls to less than the reference value during feedforward control, a change-over from feedforward control of the mechanism to feedback control of the mechanism in which the deviation of the rotation speed of the engine from the target engine rotation speed is reduced; and

performing, when a predetermined condition is satisfied, even if the rotation speed of the engine has not fallen to less than the reference value, a change-over from feedforward control of the mechanism to feedback control of the mechanism.