System for engaging lock-up clutch at highest speed ratios of different operation ranges

Claim 1

A system for controlling a lock-up clutch of a torque converter followed by an automatic transmission of a vehicle, the automatic transmission being shiftable between a plurality of speed ratios including a n th speed ratio and a n-1 th speed ratio, where: n is an integer, the automatic transmission including a first friction device which is subject to a first hydraulic pressure during operation with the n th speed ratio when a first predetermined operation range is selected, a second friction device which is subject to a second hydraulic pressure during operation with the n-1 th speed ratio when a second predetermined operation range is selected, and a third friction device which is subject to a third hydraulic pressure during operation with each of the n th speed ratio and the n-1 th speed ratio when either one of the first or second predetermined operation range is selected, the system comprising: a shuttle valve having a first inlet port subject to the first hydraulic pressure, a second inlet port subject to the second hydraulic pressure, and an outlet port, said shuttle valve including means for delivering an output hydraulic pressure when at least one of said first and second inlet ports is pressurized; a lock-up control valve including a spool movable between a first position where the lock-up clutch is released, and a second position where the lock-up clutch is engaged, said lock-up control valve including means for biasing said spool toward said first position, said spool having a first pressure acting area, and a second pressure acting area; means for transmitting the third hydraulic pressure to said lock-up control valve to have the third hydraulic pressure to act on said first pressure acting area of said spool in such a direction as to urge said spool against said biasing means; and means for transmitting said output hydraulic pressure to said lock-up control valve to have said output hydraulic pressure to act on said second pressure acting area of said spool in such a direction as to urge said spool against said biasing means, said biasing means being so constructed and arranged as to allow movement of said spool to said second position when the third hydraulic pressure acts on said first pressure acting area and said output hydraulic pressure acts on said second pressure acting area.

Claim 2

A system for controlling a lock-up clutch of a torque converter followed by an automatic transmission of a vehicle, the automatic transmission being shiftable between a plurality of speed ratios including a n th speed ratio and a n-1 th speed ratio, where: n is an integer, the automatic transmission including a first friction device which is subject to a first hydraulic pressure during operation with the n th speed ratio when a first predetermined operation range is selected, a second friction device which is subject to a second hydraulic pressure during operation with the n-1 th speed ratio when a second predetermined operation range is selected, and a third friction device which is subject to a third hydraulic pressure during operation with each of the n th speed ratio and the n-1 th speed ratio when either one of the first or second predetermined operation range is selected, the system comprising: a shuttle valve having a first inlet port subject to the first hydraulic pressure, a second inlet port subject to the second hydraulic pressure, and an outlet port, said shuttle valve including means for delivering an output hydraulic pressure when at least one of said first and second inlet ports is pressurized; a lock-up control valve including a spool movable between a first position where the lock-up clutch is released, and a second position where the lock-up clutch is engaged, said lock-up control valve including means for biasing said spool toward said first position, said spool having a first pressure acting area, and a second pressure acting area; means for transmitting the third hydraulic pressure to said lock-up control valve to have the third hydraulic pressure to act on said first pressure acting area of said spool in such a direction as to urge said spool against said biasing means; and means for transmitting said output hydraulic pressure to said lock-up control valve to have said output hydraulic pressure to act on said second pressure acting area of said spool in such a direction as to urge said spool against said biasing means, said biasing means being so constructed and arranged as to allow movement of said spool to said second position when the third hydraulic pressure acts on said first pressure acting area and said output hydraulic pressure acts on said second pressure acting area.

Claim 6

A system for controlling a lock-up clutch of a torque converter followed by an automatic transmission of a vehicle, the automatic transmission being shiftable between four speed ratios including a fourth speed ratio and a third speed ratio, the automatic transmission including a band brake which is subject to a first hydraulic pressure during operation with the fourth speed ratio when an engine brake operation range is not selected, an overrun clutch which is subject to a second hydraulic pressure during operation with the third speed ratio when the engine brake operation range is selected, and a high clutch which is subject to a third hydraulic pressure during operation with each of the fourth speed ratio and the third speed ratio regardless of whether or not the engine brake operation range is selected, the system comprising: a shuttle valve having a first inlet port subject to the first hydraulic pressure, a second inlet port subject to the second hydraulic pressure, and an outlet port, said shuttle valve including means for delivering an output hydraulic pressure when at least one of said first and second inlet ports is pressurized; a lock-up control valve including a spool movable between a first position where the lock-up clutch is released, and a second position where the lock-up clutch is engaged, said lock-up control valve including means for biasing said spool toward said first position, said spool having a first pressure acting area, and a second pressure acting area; means for transmitting the third hydraulic pressure to said lock-up control valve to have the third hydraulic pressure to act on said first pressure acting area of said spool in such a direction as to urge said spool against said biasing means; and means for transmitting said output hydraulic pressure to said lock-up control valve to have said output hydraulic pressure to act on said second pressure acting area of said spool in such a direction as to urge said spool against said biasing means, said biasing means being so constructed and arranged as to allow movement of said spool to said second position when the third hydraulic pressure acts on said first pressure acting area and said output hydraulic pressure acts on said second pressure acting area.

Claim 7

A system for controlling a lock-up clutch of a torque converter followed by an automatic transmission of a vehicle, the automatic transmission being shiftable between four speed ratios including a fourth speed ratio and a third speed ratio, the automatic transmission including a band brake which is subject to a first hydraulic pressure during operation with the fourth speed ratio when an engine brake operation range is not selected, an overrun clutch which is subject to a second hydraulic pressure during operation with the third speed ratio when the engine brake operation range is selected, and a high clutch which is subject to a third hydraulic pressure during operation with each of the fourth speed ratio and the third speed ratio regardless of whether or not the engine brake operation range is selected, the system comprising: a shuttle valve having a first inlet port subject to the first hydraulic pressure, a second inlet port subject to the second hydraulic pressure, and an outlet port, said shuttle valve including means for delivering an output hydraulic pressure when at least one of said first and second inlet ports is pressurized; a lock-up control valve including a spool movable between a first position where the lock-up clutch is released, and a second position where the lock-up clutch is engaged, said lock-up control valve including means for biasing said spool toward said first position, said spool having a first pressure acting area, and a second pressure acting area; means for transmitting the third hydraulic pressure to said lock-up control valve to have the third hydraulic pressure to act on said first pressure acting area of said spool in such a direction as to urge said spool against said biasing means; and means for transmitting said output hydraulic pressure to said lock-up control valve to have said output hydraulic pressure to act on said second pressure acting area of said spool in such a direction as to urge said spool against said biasing means, said biasing means being so constructed and arranged as to allow movement of said spool to said second position when the third hydraulic pressure acts on said first pressure acting area and said output hydraulic pressure acts on said second pressure acting area.