Shift control system for automatic transmission

• US 20030064855A1
• Filed: 09/05/2002
• Published: 04/03/2003
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Jatco Limited (Nissan Motor Co., Ltd.)
• Original Assignee: Jatco Limited (Nissan Motor Co., Ltd.)
• Inventors: Suzuki, Takayuki, Tanaka, Hiroyasu, Shimanaka, Shigeki, Takizawa, Satoshi, Akanuma, Masatoshi
• Granted Patent: US 7,044,887 B2
• Time in Patent Office: Days
• US Class Current: 477/115
• CPC Class Codes: F16H 2061/122 Avoiding failures by using redundant parts
• CPC Class Codes: F16H 2061/1284 the failing part is a sensor
• CPC Class Codes: F16H 59/42 Input shaft speed
• CPC Class Codes: F16H 59/44 dependent on machine speed of the machine, e.g. the vehicle
• CPC Class Codes: F16H 61/12 Detecting malfunction or potential malfunction, e.g. fail safe in control of hydrostatic gearing F16H61/4192; Circumventing or fixing failures
• CPC Class Codes: Y10S 477/906 Means detecting or ameliorating the effects of malfunction or potential malfunction

Abstract

A shift control system for a vehicle automatic transmission includes a vehicle speed sensor for detecting a vehicle speed, and a first control means normally performs a shift control of the transmission so that a target speed ratio of the transmission is achieved, which is determined based at least on a vehicle speed detected by the vehicle speed sensor. The shift control system further includes a second control means that properly performs shift control of the transmission when the vehicle speed sensor is in trouble, by generating a command for holding or changing a current speed ratio based on an input rotation speed of the transmission and/or driver'"'"'s accelerating or decelerating operation of the vehicle.

Claims

1. A shift control system for a vehicle automatic transmission, comprising:

a vehicle speed sensor for detecting a vehicle speed;

a first control means for normally performing a shift control of the transmission so that a target speed ratio of the transmission is achieved, said target speed ratio being determined based at least on a vehicle speed detected by the vehicle speed sensor; and

a second control means for performing a shift control of the transmission when the vehicle speed sensor is in trouble, by generating a command for holding or changing a current speed ratio based at least on an input rotation speed of the transmission.

2. The shift control system according to claim 1, wherein said second control means is operative with a hysteresis region of the input rotation speed of the transmission, such that the current speed ratio is held in said hysteresis region.

3. The shift control system according to claim 1, further comprising a transmission input rotation sensor for detecting the input rotation speed of the transmission, wherein said first and second control means are designed so that, when the vehicle speed sensor and the transmission input rotation sensor are in trouble, the shift control by said second control means is prohibited and the shift control by said first control means is performed with a fixed vehicle speed value instead of the vehicle speed detected by the vehicle speed sensor.

4. The shift control system according to claim 1, wherein said second control means is designed so as to change the current speed ratio at a reduced speed.

5. The shift control system according to claim 1, comprising a step motor that can be operated to achieve a target step number when said vehicle speed sensor is in trouble, said target step number having an upper limit value and a lower limit value.

6. A shift control system for a vehicle automatic transmission, comprising:

a first control means for normally performing a shift control of the transmission so that a target speed ratio of the transmission is achieved, said target speed ratio being determined based at least on a vehicle speed detected by a vehicle speed sensor; and

a second control means for performing a shift control of the transmission when the vehicle speed sensor is in trouble, by generating a command for holding or changing a current speed ratio based at least on a driver'"'"'s accelerating or decelerating operation of the vehicle.

7. The shift control system according to claim 6, further comprising an idle switch and a brake switch, which are operated upon depression of an accelerator pedal and a brake pedal of the vehicle, respectively, wherein said driver'"'"'s accelerating or decelerating operation is detected by said idle switch and/or said brake switch.

8. The shift control system according to claim 7, wherein said second control means is operative when said brake switch is in trouble, based on a judgment that the brake pedal is not operated.

9. The shift control system according to claim 6, further comprising an accelerator pedal sensor for detecting a depression amount of an accelerator pedal of the vehicle, wherein said driver'"'"'s accelerating or decelerating operation is detected by said accelerator pedal sensor.

10. The shift control system according to claim 9, wherein said second control means is operative when a hydraulic oil temperature of the transmission exceeds a predetermined value, based on a judgment that said depression amount of the accelerator pedal is a small amount, for suppressing the rotation speed of the transmission by enhancing an upshift tendency.

11. The shift control system according to claim 6, wherein said second control means is operative with a hysteresis region of the driver'"'"'s accelerating or decelerating operation, such that the current speed ratio is held in said hysteresis region.

12. The shift control system according to claim 6, wherein said second control means is designed so as to change the current speed ratio at a reduced speed.

13. The shift control system according to claim 6, comprising a step motor that can be operated to achieve a target step number when said vehicle speed sensor is in trouble, said target step number having an upper limit value and a lower limit value.

14. A shift control system for a vehicle automatic transmission, comprising:

a vehicle speed sensor for detecting a vehicle speed;

a first control means for normally performing a shift control of the transmission so that a target speed ratio of the transmission is achieved, said target speed ratio being determined based at least on a vehicle speed detected by the vehicle speed sensor; and

a second control means for performing a shift control of the transmission when the vehicle speed sensor is in trouble, by generating a command for holding or changing a current speed ratio based on an input rotation speed of the transmission and a driver'"'"'s accelerating or decelerating operation of the vehicle.

15. The shift control system according to claim 14, wherein said second control means is operative with a hysteresis region of the input rotation speed of the transmission, such that the current speed ratio is held in said hysteresis region.

16. The shift control system according to claim 14, further comprising a transmission input rotation sensor for detecting the input rotation speed of the transmission, wherein said first and second control means are designed so that, when the vehicle speed sensor and the transmission input rotation sensor are in trouble, the shift control by said second control means is prohibited and the shift control by said first control means is performed with a fixed vehicle speed value instead of the vehicle speed detected by the vehicle speed sensor.

17. The shift control system according to claim 14, further comprising an idle switch and a brake switch, which are operated upon depression of an accelerator pedal and a brake pedal of the vehicle, respectively, wherein said driver'"'"'s accelerating or decelerating operation is detected by said idle switch and/or said brake switch.

18. The shift control system according to claim 17, wherein said second control means is operative when said brake switch is in trouble, based on a judgment that the brake pedal is not operated.

19. The shift control system according to claim 14, further comprising an accelerator pedal sensor for detecting a depression amount of an accelerator pedal of the vehicle, wherein said driver'"'"'s accelerating or decelerating operation is detected by said accelerator pedal sensor.

20. The shift control system according to claim 19, wherein said second control means is operative when a hydraulic oil temperature of the transmission exceeds a predetermined value, based on a judgment that said depression amount of the accelerator pedal is a small amount, for suppressing the rotation speed of the transmission by enhancing an upshift tendency.

21. The shift control system according to claim 14, wherein said second control means is operative with a hysteresis region of the driver'"'"'s accelerating or decelerating operation, such that the current speed ratio is held in said hysteresis region.

22. The shift control system according to claim 14, wherein said second control means is designed so as to change the current speed ratio at a reduced speed.

23. The shift control system according to claim 14, comprising a step motor that can be operated by a target step number when said vehicle speed sensor is in trouble, said target step number having an upper limit value and a lower limit value.