Automatic transmission control system

• US 4,779,491 A
• Filed: 03/24/1987
• Issued: 10/25/1988
• Est. Priority Date: 03/25/1986
• Status: Expired due to Term

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Mizobe, Tatsutoshi, Fujiwara, Takuji
• Primary Examiner(s): Wright, Dirk
• Application Number:
  US07/029,724
• Time in Patent Office: 581 Days
• Field of Search: 74/867, 74/868
• US Class Current: 477/146
• CPC Class Codes: F16H 2061/026 On-off solenoid valve
• CPC Class Codes: F16H 61/04 Smoothing ratio shift
• CPC Class Codes: F16H 61/065 using fluid control means
• CPC Class Codes: F16H 61/067 using an accumulator
• CPC Class Codes: F16H 61/068 using an orifice control valve F16H61/067 takes precedence

Abstract

In an automatic transmission, a second brake is engaged when the transmission is in second and is released when the transmission is in third and first. The second brake is controlled by a hydraulic actuator. Application of the hydraulic pressure to the hydraulic actuator of the second brake is limited upon upshift from first to second so that the hydraulic pressure is gently applied to the hydraulic actuator. The limitation of application of the hydraulic pressure is nullified upon downshift from third to second.

Claims

1. An automatic transmission control system for controlling an automatic transmission comprising a torque convertor having an input member connected to the engine output shaft and an output member connected to a multiple stage transmission gear mechanism adapted to provide a plurality of gear speeds, and a shifting means for shifting the gear speed, the shifting means having a plurality of frictional members, a plurality of hydraulic actuators for actuating the frictional members and a plurality of valve means which are controlled according to the vehicle operating condition to control application of hydraulic pressure from a hydraulic pressure source to the hydraulic actuators, said shifting means being adapted to shift the gear speed at least among a low gear speed, an intermediate gear speed and a high gear speed, a predetermined one frictional member out of said plurality of frictional members being released in the low gear speed and the high gear speed and engaged in the intermediate gear speed, and the predetermined one frictional member being engaged and released by a predetermined one hydraulic actuator out of said plurality of hydraulic actuators,

wherein the improvement comprises a first control means which limits application of the hydraulic pressure to said predetermined one hydraulic actuator so that the hydraulic pressure is gently applied to the predetermined one hydraulic actuator upon upshift from the low gear speed to the intermediate gear speed, and a second control means which operates upon downshift from the high gear speed to the intermediate gear speed to nullify the limitation of application of the hydraulic pressure to said predetermined one hydraulic actuator.

2. An automatic transmission control system as defined in claim 1 in which said first control means comprises a constriction provided in an oil passage for supplying the hydraulic pressure to said predetermined one hydraulic actuator, and said second control means comprises a bypass passage provided to bypass the constriction.

3. An automatic transmission control system as defined in claim 2 in which said first control means further comprises an accumulator provided in the oil passage between said constriction and said predetermined one hydraulic actuator.

4. An automatic transmission control system as defined in claim 2 in which said second control means further comprises an on-off valve provided in said bypass passage.

5. An automatic transmission control system as defined in claim 2 in which said predetermined one hydraulic actuator comprises a piston for actuating said predetermined one frictional member, an applying side pressure chamber for driving the piston to engage the predetermined one frictional member and a releasing side pressure chamber for driving the piston to release the same, and said constriction is provided in the oil passage for supplying the hydraulic pressure to the applying side pressure chamber.

6. An automatic transmission control system as defined in claim 5 in which said releasing side pressure chamber is provided with a timing valve to which the hydraulic pressure is supplied together with the hydraulic actuator for another frictional member to be engaged to shift the gear speed to the high gear speed, and which directly drains the hydraulic pressure from the releasing side pressure chamber, and said second control means further comprises an on-off valve which opens and closes said bypass passage in response to operation of the timing valve.

7. An automatic transmission control system as defined in claim 6 in which said on-off valve is formed integrally with the valve spool of the timing valve, and the valve is displaced at a predetermined time upon downshift from the high gear speed to the intermediate gear speed to directly drain the hydraulic pressure from the releasing side pressure chamber and to open the bypass passage.

8. An automatic transmission control system for controlling an automatic transmission comprising a torque convertor having an input member connected to the engine output shaft and an output member connected to a multiple stage transmission gear mechanism adapted to provide a plurality of gear speeds, and a shifting means for shifting the gear speed, the shifting means having a plurality of frictional members, a plurality of hydraulic actuators for actuating the frictional members and a plurality of valve means which are controlled according to the vehicle operating condition to control application of hydraulic pressure from a hydraulic pressure source to the hydraulic actuators, said shifting means being adapted to shift the gear speed at least among a low gear speed, an intermediate gear speed and a high gear speed, a predetermined one frictional member out of said plurality of frictional members being released in the low gear speed and the high gear speed and engaged in the intermediate gear speed, and the predetermined one frictional member being engaged and released by a predetermined one hydraulic actuator out of said plurality of hydraulic actuators, wherein the improvement comprises said predetermined one hydraulic actuator comprising a piston for actuating said predetermined one frictional member, an applying side pressure chamber for driving the piston to engage the predetermined one frictional member and a releasing side pressure chamber for driving the piston to release the same, a constriction in the oil passage for supplying the hydraulic pressure to the applying side pressure chamber, and means actuated upon downshift from the high gear speed to the intermediate gear speed to nullify the effect of the constriction.

9. An automatic transmission control system for controlling an automatic transmission comprising a torque convertor having an input member connected to the engine output shaft and an output member connected to a multiple stage transmission gear mechanism adapted to provide a plurality of gear speeds, and a shifting means for shifting the gear speed, the shifting means having a plurality of frictional members, a plurality of hydraulic actuators for actuating the frictional members and a plurality of valve means which are controlled according to the vehicle operating condition to control application of hydraulic pressure from a hydraulic pressure source to the hydraulic actuators, said shifting means being adapted to shift the gear speed among first, second and third, a second brake out of said plurality of frictional members being released in first and third and engaged in second, and the second brake being engaged and released by a second brake actuator out of said plurality of hydraulic actuators,

wherein the improvement comprises a first control means which limits application of the hydraulic pressure to said second brake actuator so that the hydraulic pressure is gently applied to the second brake actuator upon upshift from first to second, and a second control means which operates upon downshift from third to second to nullify the limitation of application of the hydraulic pressure to said second brake actuator, said second brake actuator comprising a piston for actuating said second brake, an applying side pressure chamber for driving the piston to engage the second brake and a releasing side pressure chamber for driving the piston to release the same, and said second control means comprising a constriction provided in the oil passage for supplying the hydraulic pressure to the applying side pressure chamber, said releasing side pressure chamber is provided with a 3-2 timing valve to which the hydraulic pressure is supplied together with the hydraulic actuator for the front clutch to be engaged to shift the gear speed to first, and which directly drains the hydraulic pressure from the releasing side pressure chamber, and said second control means further comprises an on-off valve which opens and closes said bypass passage in response to operation of the 3-2 timing valve.

10. An automatic transmission control system for controlling an automatic transmission comprising a torque convertor having an input member connected to the engine output shaft and an output member connected to a multiple stage transmission gear mechanism adapted to provide a plurality of gear speeds, and a shifting means for shifting the gear speed, the shifting means having a plurality of frictional members, a plurality of hydraulic actuators for actuating the frictional members and a plurality of valve means which are controlled according to the vehicle operating condition to control application of hydraulic pressure from a hydraulic pressure source to the hydraulic actuators, said shifting means being adapted to shift the gear speed at least among a low gear speed, an intermediate gear speed and a high gear speed, a predetermined one frictional member out of said plurality of frictional members being released in the low gear speed and the high gear speed and engaged in the intermediate gear speed, and the predetermined one frictional member being engaged and released by a predetermined one hydraulic actuator out of said plurality of hydraulic actuators,

wherein the improvement comprises a first control means which limits application of the hydraulic pressure to said predetermined one hydraulic actuator so that the hydraulic pressure is gently applied to the predetermined one hydraulic actuator upon upshift from the low gear speed to the intermediate gear speed, and a second control means which operates upon downshift from the high gear speed to the intermediate gear speed to rapidly supply the hydraulic pressure to said predetermined one hydraulic actuator.