# US 5,343,990 A · Control system for lock-up torque converter for automatic transmissions

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- Number: US 5,343,990 A
- Document ID: US5343990A
- Status: Granted
- Kind: A
- Application number: 08/008,142
- Filed: 1993-01-25
- Granted: 1994-09-06
- Earliest claimed: 1992-01-28
- Assignees: JATCO Ltd
- Inventors: Naonori Iizuka
- Web page: https://patentgrep.com/patent/US5343990A

## CPC

- F16H 61/143: {using electric control means}
- F16H 2059/6807: {Status of gear-change operation, e.g. clutch fully engaged}
- F16H: GEARING

## Abstract

A control system for a lock-up clutch employed in a lock-up torque converter for an automotive automatic transmission includes a lock-up control valve for controlling a lock-up of the lock-up clutch, a duty-ratio controlled lock-up solenoid, and a control unit for quickly releasing the lock-up clutch at a higher speed based on a controlled duty ratio, when the change-speed operation is performed simultaneously with the lock-up clutch releasing operation.

## Claims

### Claim 1

A control system in combination with a lock-up clutch employed in an automatic transmission of an automotive vehicle having a lock-up clutch releasing means for gradually releasing said lock-up clutch so as to reduce an engaging force of said lock-up clutch, a transient state in which said lock-up clutch is shifted from a lock-up clutch engaged state to a lock-up clutch released said control system comprising:
a change-speed determination means for judging whether a change-speed operation of the vehicle should be performed depending on a running condition of the vehicle and for generating a change-speed instruction when said change-speed determination means determines that the change speed should be performed;
a lock-up judgment means for judging whether said lock-up clutch should be conditioned in either one of an engaged state and a disengaged state, depending on the vehicle running condition; and
a quick releasing means, responsive to said change-speed instruction generated at a same time as when said lock-up judgment means determines that said lock-up clutch should be conditioned in a disengaged state, for reducing the engaging force of said lock-up clutch at a higher lock-up clutch releasing speed than during non-change-speed operation.

### Claim 2 (depends on 1)

The control means as set forth in claim 1, wherein said quick releasing means reduces the engaging force of said lock-up clutch at a higher lock-up clutch releasing speed than during up-shift, when a down-shift operation is performed simultaneously with the lock-up clutch releasing operation.

### Claim 3

A control system in combination with a lock-up clutch employed in an automatic transmission of an automotive vehicle, comprising:
a lock-up control spool valve connected to first and second pressure chambers defined at both sides of a lock-up piston of said lock-up clutch, for engaging and releasing said lock-up clutch; said spool valve being operable between a first position wherein a fluid pressure in said first pressure chamber is kept at a higher level than that in said second pressure chamber and said lock-up clutch is biased in a lock-up clutch releasing direction, and a second position wherein the fluid pressure in said first pressure chamber is kept at a lower level than that in said second pressure chamber and said lock-up clutch is biased in a lock-up clutch engaging direction;
a lock-up solenoid connected to said spool valve, for controlling the position of said spool valve; said lock-up solenoid being operable at a controlled duty cycle, so as to provide a controlled duty ratio equivalent to a designated engaging and releasing speed for said lock-up clutch;
a change speed determination means for judging whether a change-speed operation of the vehicle should be performed depending on a running condition of the vehicle and for generating a change-speed instruction when said change-speed determination means determines that the change speed should be performed;
a lock-up judgment means for judging whether said lock-up clutch should be conditioned in either one of an engaged state and a disengaged state, depending on the vehicle running condition; and
a quick releasing means, responsive to said change-speed instruction generated at a same time as when said lock-up judgment means determines that said lock-up clutch should be conditioned in a disengaged state, for varying the duty ratio of said lock-up solenoid to reduce an engaging force of said lock-up clutch at a higher lock-up clutch releasing speed than during non-change-speed operation.

### Claim 4 (depends on 3)

The control system as set forth in claim 3, wherein said quick releasing means reduces the engaging force of said lock-up clutch at a higher lock-up clutch releasing speed than during up-shift, when a down-shift operation is performed simultaneously with the lock-up clutch releasing operation.

### Claim 5 (depends on 3)

The control system as set forth in claim 3, wherein said lock-up solenoid is a duty-ratio controlled electromagnetic solenoid, and the fluid pressure in said first pressure chamber is regulated in inverse proportion to the duty ratio of said lock-up solenoid.

### Claim 6 (depends on 5)

The control system as set forth in claim 5, wherein said lock-up clutch is kept in a clutch released state when the duty ratio is equal to 0, while said lock-up clutch is kept in a clutch engaged state when the duty ratio is equal to 100%.