Shift control system of hydraulic continuously variable transmission for vehicle

• US 6,533,702 B1
• Filed: 11/22/2000
• Issued: 03/18/2003
• Est. Priority Date: 11/22/1999
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Inventors: Asyama, Hiroki, Hashimoto, Toru, Kondo, Kaoru, Shouichi, Minoru
• Primary Examiner(s): Marmor, Charles A
• Assistant Examiner(s): PANG, ROGER L
• Application Number:
  US09/717,305
• Time in Patent Office: 846 Days
• Field of Search: 477/37, 477/44, 477/45, 477/46, 477/48, 477/49, 477/50, 477/115
• US Class Current: 477/45
• CPC Class Codes: F16H 2061/6605 Control for completing downshift at hard braking
• CPC Class Codes: F16H 61/20 Preventing gear creeping ; Transmission control during standstill, e.g. hill hold control
• CPC Class Codes: F16H 61/66254 controlling of shifting being influenced by a signal derived from the engine and the main coupling
• CPC Class Codes: F16H 61/6648 controlling of shifting being influenced by a signal derived from the engine and the main coupling

Abstract

A shift control system of a hydraulic CVT for an automotive vehicle with which it is possible to control a speed ratio to a target value with certainty while maintaining a required primary pressure, even when the vehicle is substantially stationary. Normally, a speed feedback control means sets a target speed of a rotating element on the basis of the vehicle speed and the load on the vehicle engine. The speed feedback control means feedback-controls a hydraulic pressure control means of the rotating element so that the actual speed approaches the target speed. When the vehicle becomes substantially stationary, control of the hydraulic pressure control means is switched from the speed feedback control executed by the speed feedback control means to pressure feedback control executed by a pressure feedback control means. That is, the actual hydraulic pressure acting on the rotating element is detected by a hydraulic pressure detecting means. A target hydraulic pressure setting means sets a target hydraulic pressure to act on the rotating element, and the shift control valve is feedback-controlled so that the actual pressure approaches the target pressure.

Claims

1. A shift control system of a hydraulic continuously variable transmission for an automotive vehicle having a hydraulic pressure control means for controlling with a hydraulic pressure the behavior of a rotating element and a speed feedback control means for setting a target speed of the rotating element on the basis of a speed of the vehicle and a load on the engine of the vehicle and feedback-controlling the hydraulic pressure control means so that an actual speed of the rotating element approaches the target speed, comprising:

an actual hydraulic pressure detecting means for detecting an actual value of a hydraulic pressure acting on the rotating element;

a target hydraulic pressure setting means for setting a target value of the hydraulic pressure acting on the rotating element;

a pressure feedback control means for feedback-controlling the hydraulic pressure control means so that the actual hydraulic pressure detected by the actual hydraulic pressure detecting means approaches the target hydraulic pressure set by the target hydraulic pressure setting means;

a stationary state detecting means for detecting whether the vehicle is in a substantially stationary state; and

a control means for controlling the hydraulic pressure control means using speed feedback control executed by the speed feedback control means when it is detected by the stationary state detecting means that the vehicle is not in a substantially stationary state and controlling the hydraulic pressure control means using pressure feedback control executed by the pressure feedback control means when it is detected by the stationary state detecting means that the vehicle is in a substantially stationary state.

2. A shift control system according to claim 1, further comprising:

an open loop control means for open loop to control the hydraulic pressure control means so that a predetermined hydraulic pressure acts on the rotating element; and

pressure feedback control possibility determining means for determining whether a state of the transmission is such that pressure feedback control executed by the pressure feedback control means is possible,

wherein after the presence of a stationary state is detected by the stationary state detecting means, and it is determined by the pressure feedback control possibility determining means that pressure feedback control is not possible, the control means switches control of the hydraulic pressure control means from pressure feedback control executed by the pressure feedback control means to open loop control executed by the open loop control means.

3. A shift control system according to claim 2, further comprising failure detecting means for detecting failure of the actual hydraulic pressure detecting means, wherein, when failure of the actual hydraulic pressure detecting means is detected by the failure detecting means, the pressure feedback control possibility determining means determines that pressure feedback control is not possible.

4. A shift control system according to claim 3, wherein the failure detecting means determines whether a detection value from the actual hydraulic pressure detecting means is within a predetermined range and determines that the actual hydraulic pressure detecting means has failed when the detection value is outside the predetermined range.

5. A shift control system according to claim 2, wherein the pressure feedback control possibility determining means determines that pressure feedback control is not possible when the actual hydraulic pressure acting on the rotating element detected by the actual hydraulic pressure detecting means is below a reference hydraulic pressure.

6. A shift control system of a hydraulic continuously variable transmission for an automotive vehicle having a hydraulic pressure control means for controlling with a hydraulic pressure the behavior of a rotating element and a shift control means for controlling a speed ratio by controlling the hydraulic pressure control means, comprising:

an actual hydraulic pressure detecting means for detecting an actual value of a hydraulic pressure acting on the rotating element;

a target hydraulic pressure setting means for setting a target value of the hydraulic pressure acting on the rotating element;

a pressure feedback control means for feedback-controlling the hydraulic pressure control means so that a detection value from the actual hydraulic pressure detecting means approaches the target value set by the target hydraulic pressure setting means;

an open loop control means for open loop controlling the hydraulic pressure control means so that a predetermined hydraulic pressure acts on the rotating element;

a pressure feedback control possibility determining means for determining whether or not a state of the transmission is such that pressure feedback control executed by the pressure feedback control means is possible; and

a control means for, when the hydraulic pressure control means is being pressure feedback controlled by the pressure feedback control means and it is determined by the pressure feedback control possibility determining means that pressure feedback control is not possible, switching control of the hydraulic pressure control means from pressure feedback control executed by the pressure feedback control means to open loop control executed by the open loop control means,

wherein the pressure feedback control possibility determining means determines at least according to one of a failure situation of the actual hydraulic pressure detecting means and the actual value of a hydraulic pressure acting on the rotating element.

7. A shift control system according to claim 6, further comprising failure detecting means for detecting failure of the actual hydraulic pressure detecting means, wherein, when failure of the actual hydraulic pressure detecting means is detected by the failure detecting means the pressure feedback control possibility determining means determines that pressure feedback control is not possible.

8. A shift control system according to claim 7, wherein the failure detecting means determines whether or not a detection value from the actual hydraulic pressure detecting means is within a predetermined range and determines that the actual hydraulic pressure detecting means has failed when the detection value is outside the predetermined range.

9. A shift control system according to claim 6, wherein the pressure feedback control possibility determining means determines that pressure feedback control is not possible when the actual hydraulic pressure acting on the rotating element detected by the actual hydraulic pressure detecting means is below a reference hydraulic pressure.

10. A shift control system according to claim 6, further comprising:

a vehicle speed detecting means for detecting a vehicle speed;

a speed detecting means for detecting a speed of the rotating element;

a target speed setting means for setting a target speed of the rotating element on the basis of the vehicle running state; and

a speed feedback control means for feedback-controlling the hydraulic pressure control means so that a detection value from the speed detecting means approaches the target value set by the target speed setting means,

wherein, when the detection value from the vehicle speed detecting means rises above a predetermined value, the control means switches control of the hydraulic pressure control means from pressure feedback control executed by the pressure feedback control means or open loop control executed by the open loop control means to speed feedback control executed by the speed feedback control means.

11. A shift control method for controlling a speed ratio of a hydraulic continuously variable transmission for an automotive vehicle wherein the behavior of a rotating element is controlled with a hydraulic pressure, comprising the steps of:

detecting whether the vehicle is in a substantially stationary state; and

when the vehicle is not in a substantially stationary state, performing speed feedback control so that a speed of the rotating element approaches a target speed set on the basis of a speed of a vehicle and a load on the engine of the vehicle, and

when the vehicle is in a substantially stationary state, performing pressure feedback control so that a hydraulic pressure acting on the rotating element approaches a set target hydraulic pressure.

12. A shift control method according to claim 11, further comprising the steps of:

when the vehicle is in a substantially stationary state, determining whether a state of the transmission is such that the pressure feedback control is possible; and

when it is determined that the pressure feedback control is not possible, switching from the pressure feedback control to open loop control wherein a predetermined hydraulic pressure is caused to be applied to the rotating element.

13. A shift control method according to claim 12, further comprising the steps of:

when the vehicle is in a substantially stationary state, determining whether an actual hydraulic pressure detecting means for detecting an actual value of the hydraulic pressure acting on the rotating element has failed; and

when it is determined that the actual hydraulic pressure detecting means has failed, determining that the pressure feedback control is not possible.

14. A shift control method according to claim 12, further comprising the steps of:

when the vehicle is in a substantially stationary state, determining whether the actual hydraulic pressure acting on the rotating element is below a reference hydraulic pressure; and

when it is determined that the actual hydraulic pressure acting on the rotating element is below the reference hydraulic pressure, determining that the pressure feedback control is not possible.

15. A shift control method for a controlling a speed ratio of a hydraulic continuously variable transmission for an automotive vehicle wherein the behavior of a rotating element is controlled with a hydraulic pressure, comprising the steps of:

detecting an actual value of the hydraulic pressure acting on the rotating element;

setting a target value of the hydraulic pressure acting on the rotating element;

performing pressure feedback control so that the actual hydraulic pressure acting on the rotating element approaches the target value;

determining whether a state of the transmission is such that the pressure feedback control is possible, at least according to one of a failure situation of detecting the actual value of the hydraulic pressure and the actual value of a hydraulic pressure acting on the rotating element; and

when it is determined that the pressure feedback control is not possible, switching from the pressure feedback control to open loop control wherein a predetermined hydraulic pressure is caused to be applied to the rotating element.

16. A shift control method according to claim 15, further comprising the steps of:

determining whether actual hydraulic pressure detecting means for detecting the actual value of the hydraulic pressure acting on the rotating element has failed; and

when it is determined that the actual hydraulic pressure detecting means has failed, determining that the pressure feedback control is not possible.

17. A shift control method according to claim 15, further comprising the steps of:

determining whether the actual hydraulic pressure acting on the rotating element is below a reference hydraulic pressure; and

when it is determined that the actual hydraulic pressure acting on the rotating element is below the reference hydraulic pressure, determining that the pressure feedback control is not possible.

18. A shift control method according to claim 15, further comprising the steps of:

detecting a vehicle speed;

detecting a speed of the rotating element;

setting a target value of a speed of the rotating element on the basis of a vehicle running state; and

when the pressure feedback control or the open loop control is being carried out, the vehicle speed rises above a predetermined value, switching from the pressure feedback control or the open loop control to speed feedback control wherein the speed of the rotating element is feedback-controlled to approach the target value.