Hydraulic control system for automatic transmission

Claim 2

In an automatic transmission: fluid operated friction units, including a first clutch, a second clutch and a brake, which are selectively made operative and inoperative to produce first, second, third and fourth speed ratios, the first clutch having a first chamber and being engaged when the first chamber is pressurized, the second clutch having a second chamber and being engaged when the second chamber is pressurized, the brake having a servo apply chamber and a servo release chamber, said brake being released when said servo release chamber is pressurized and being applied when said servo release chamber is discharged with said servo apply chamber being pressurized; means for generating an actuating fluid pressure; a 2-3 shift valve communicating with said actuating fluid pressure generating means and the first chamber, said 2-3 shift valve having an upshift position wherein it supplies the actuating fluid pressure to the first chamber; a 3-4 shift valve communicating with said actuating fluid pressure generating means and the first, second and servo release chambers, said 3-4 shift valve having a downshift position wherein it supplies the actuating fluid pressure to the second chamber and provides communication between the first and servo release chambers, said 3-4 shift valve having an upshift position wherein it discharges the second servo release chambers; and means for defining a drain passage which allows the fluid discharged from said servo release chamber to pass therethrough when the 3-4 shift valve is moved to the upshift position thereof, wherein said drain passage defining means includes an orifice and a 3-4 timing valve means for providing a passage portion bypassing said orifice.

Claim 3

An automatic transmission as claimed in claim 1, wherein said drain passage defining means includes a second orifice and a 2-4 timing valve means responsive to the fluid pressure in said first chamber for providing a passage portion bypassing said second orifice.

Claim 4

In an automatic transmission: fluid operated friction units, including a first clutch, a second clutch and a brake, which are selectively made operative and inoperative to produce first, second, third and fourth speed ratios, the first clutch having a first chamber and being engaged when the first chamber is pressurized, the second clutch having a second chamber and being engaged when the second chamber is pressurized, the brake having a servo apply chamber and a servo release chamber, said brake being released when said servo release chamber is pressurized and being applied when said servo release chamber is discharged with said servo apply chamber being pressurized; means for generating an actuating fluid pressure; a 2-3 shift valve communicating with said actuating fluid pressure generating means and the first chamber, said 2-3 shift valve having an upshift position wherein it supplies the actuating fluid pressure to the first chamber; a 3-4 shift valve communicating with said actuating fluid pressure generating means and the first, second and servo release chambers, said 3-4 shift valve having a downshift position wherein it supplies the actuating fluid pressure to the second chamber and provides communication between the first and servo release chambers; said 3-4 shift valve having an upshift position wherein it discharges the second servo release chambers; and means for defining a drain passage which allows the fluid discharged from said second and servo release chambers to pass therethrough; wherein said drain passage defining means includes an orifice and a 2-4 timing valve means responsive to the fluid pressure in said first chamber for providing a passage portion bypassing said orifice.

Claim 5

In an automatic transmission: fluid operated friction units, including a first clutch, a second clutch and a brake, which are selectively made operative and inoperative to produce first, second, third and fourth speed ratios, the first clutch having a first chamber and being engaged when the first chamber is pressurized, the second clutch having a second chamber and being engaged when the second chamber is pressurized, the brake having a servo apply chamber and a servo release chamber, said brake being released when said servo release chamber is pressurized and being applied when said servo release chamber is discharged with said servo apply chamber being pressurized; means for generating an actuating fluid pressure; a 2-3 shift valve communicating with said actuating fluid pressure generating means and the first chamber, said 2-3 shift valve having an upshift position wherein it supplies the actuating fluid pressure to the first chamber; a 3-4 shift valve communicating with said actuating fluid pressure generating means and the first, second and servo release chambers, said 3-4 shift valve having a downshift position wherein it supplies the actuating fluid pressure to the second chamber and provides communication between the first and servo release chambers; said 3-4 shift valve having an upshift position wherein it discharges the second servo release chambers; and means for defining a drain passage which allows the fluid discharged from said second and servo release chambers to pass therethrough; wherein said drain passage defining means includes an orifice and a 2-4 timing valve means responsive to the fluid pressure in said first chamber for providing a passage portion bypassing said orifice.