Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
1998-07-14
2001-05-01
Marmor, Charles A. (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
Reexamination Certificate
active
06224507
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydraulic control systems for automatic transmissions.
One of the conventionally proposed hydraulic control systems for automatic transmissions is known in JP-A 5-248526. This reference describes a low-clutch sequence valve for draining an accumulator back pressure of a low clutch on the release side in taking account of a rise of a working pressure of a band brake on the engagement side and the accumulator back pressure of the low clutch on the release side.
With the known hydraulic control system, however, a drain timing is determined based on the accumulator back pressure of the low clutch on the release side, so that if the accumulator back pressure is varied, its drain timing is shifted. Specifically, the accumulator back pressure on the release side and the working pressure on the engagement side produced from a line pressure or a source pressure are varied together, so that if the accumulator back pressure is reduced due to dispersion or deterioration of a device, a working pressure which serves to drain the accumulator back pressure is also reduced, resulting in lowered switching pressure in a characteristic of the working pressure on the engagement side. This decreases the torque capacity on the release side though a sufficient torque capacity on the engagement side is not secured yet, causing engine racing.
It is, therefore, an object of the present invention to provide hydraulic control systems for automatic transmissions which always ensure achievement of an optimum timing for draining the accumulator back pressure on the release side upon shifting regardless of variations in hydraulic pressure due to dispersion or deterioration of a device on the release side.
SUMMARY OF THE INVENTION
One aspect of the present invention lies in providing a hydraulic control system for an automatic transmission which achieves shifting by releasing a first engaging element as engaged and engaging a second engaging element as released, the system comprising:
a first passage connected to the first engaging element;
a second passage connected to the second engaging element;
a first accumulator arranged with said first passage, said first accumulator including a back-pressure chamber having a first pressure;
a second accumulator arranged with said second passage, said second accumulator including a back-pressure chamber having a second pressure; and
a timing valve connected to said back-pressure chamber of said first accumulator, said timing valve determining a timing for draining said first pressure of said first accumulator in accordance with said second pressure of said second accumulator.
Another aspect of the present invention lies in providing a hydraulic control system for an automatic transmission which achieves shifting by releasing a first engaging element as engaged and engaging a second engaging element as released, the system comprising:
a first passage connected to the first engaging element;
a second passage connected to the second engaging element;
a first accumulator arranged with said first passage, said first accumulator including a back-pressure chamber having a first pressure;
a second accumulator arranged with said second passage, said second accumulator including a back-pressure chamber having a second pressure;
a timing valve connected to said back-pressure chamber of said first accumulator, said timing valve determining a timing for draining said first pressure of said first accumulator in accordance with said second pressure of said second accumulator;
a first device connected to said back-pressure chamber of said first accumulator, said first device controlling said first pressure of said first accumulator; and
a second device connected to said back-pressure chamber of said second accumulator, said second device controlling said second pressure of said second accumulator.
Still another aspect of the present invention lies in providing a hydraulic control system for an automatic transmission which achieves shifting by engaging and releasing first, second, and third engaging elements, the system comprising:
a first passage connected to the first engaging element;
a second passage connected to the second engaging element;
a third passage connected to the third engaging element;
a first accumulator arranged with said first passage, said first accumulator including a back-pressure chamber having a first pressure;
a second accumulator arranged with said second passage, said second accumulator including a back-pressure chamber having a second pressure;
a third accummulator arranged with said third passage, said third accumulator including a back-pressure chamber having a third pressure;
a first device connected to said back-pressure chamber of said first accumulator, said first device controlling said first pressure of said first accumulator; and
a second device connected to said back-pressure chamber of said second accumulator, said second device controlling said second pressure of said second accumulator.
A further aspect of the present invention lies in providing a hydraulic control system for an automatic transmission which achieves four speeds by first, second and third engaging elements operated hydraulically and a one-way clutch operated mechanically upon 2-1 shift, said first engaging element being engaged in the first, second and third gears, said second engaging element being engaged in the second and fourth gears, said third engaging element being engaged in the third and fourth gears, the system comprising:
a first passage connected to the first engaging element;
a second passage connected to the second engaging element;
a third passage connected to the third engaging element;
a first accumulator arranged with said first passage, said first accumulator including a back-pressure chamber having a first pressure;
a second accumulator arranged with said second passage, said second accumulator including a back-pressure chamber having a second pressure;
a third accummulator arranged with said third passage, said third accumulator including a back-pressure chamber having a third pressure;
a first device connected to said back-pressure chambers of said first and third accumulators, said first device controlling said first and third pressures of said first and third accumulators; and
a second device connected to said back-pressure chamber of said second accumulator, said second device controlling said second pressure of said second accumulator.
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patent: 4-81065 (1992-12-01), None
patent: 5-248526 (1993-09-01), None
Shimoyama Akihiro
Takiguchi Masahiro
Tazawa Mitsugi
Foley & Lardner
Ho Ha
Jatco Corporation
Marmor Charles A.
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