Vehicle speed control system

• US 20030105574A1
• Filed: 01/11/2002
• Published: 06/05/2003
• Est. Priority Date: 05/16/2000
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Adachi, Kazutaka, Ino, Junsuke, Sudo, Hideki, Ishizu, Takeshi
• Granted Patent: US 6,732,039 B2
• Time in Patent Office: Days
• US Class Current: 701/93
• CPC Class Codes: B60K 31/0008 including means for detecting potential obstacles in vehicle path
• CPC Class Codes: B60K 31/047 the memory being digital
• CPC Class Codes: B60W 2050/0012 Feedforward or open loop systems
• CPC Class Codes: B60W 2050/0031 Mathematical model of the vehicle
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 2720/106 Longitudinal acceleration
• CPC Class Codes: F16H 61/66 specially adapted for continuously variable gearings control of exclusively fluid gearing F16H61/38

Abstract

A vehicle speed control system is installed to a vehicle equipped with an engine and a continuously variable transmission (CVT). The vehicle control system is comprised of a controller arranged to execute a vehicle speed control, to suspend the vehicle speed control when a throttle opening is increased to be greater than a target throttle opening for the vehicle speed control and to restart the suspended vehicle speed control when the throttle opening becomes smaller than the target throttle opening. Further, the controller is arranged to decrease the throttle opening and to execute a shift down of the CVT when the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed. Therefore, this vehicle speed control system can quickly and smoothly decelerate the vehicle without generating shift shocks when the vehicle speed control is restarted.

Claims

1. A vehicle speed control system for a vehicle, the vehicle equipped with an engine and a continuously variable transmission (CVT), the vehicle control system comprising:

a controller arranged,

to execute a vehicle speed control for bringing a vehicle speed closer to a target vehicle speed;

to suspend the vehicle speed control when a throttle opening is increased to an opening which is greater than a target throttle opening for the vehicle speed control;

to restart the suspended vehicle speed control when the throttle opening becomes smaller than the target throttle opening; and

to decrease the throttle opening and to execute a shift down of the CVT when the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed.

2. The vehicle speed control system as claimed in claim 1, wherein said controller commands the CVT to execute the shift-down the CVT when a deceleration ensured only by decreasing the throttle opening is smaller than a desired deceleration of the vehicle speed control.

3. The vehicle speed control system as claimed in claim 1, wherein said controller decreases the throttle opening at the rate of a predetermined deceleration, said controller executing the shift down of the CVT when the deceleration by decreasing the throttle opening is smaller than the predetermined deceleration.

4. The vehicle speed control system as claimed in claim 1, wherein said controller controls the engine rotation speed within a predetermined limit when the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed.

5. The vehicle speed control system as claimed in claim 4, wherein the predetermined limit for the engine rotation speed is set smaller than a limit employed in the condition except for the condition that the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed.

6. The vehicle speed control system as claimed in claim 1, wherein said controller prohibits a brake system of the vehicle from being operated when the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed.

7. The vehicle speed control system as claimed in claim 6, wherein said controller prohibits the brake system from being operated when the vehicle travels on a down slope.

8. The vehicle speed control system as claimed in claim 2, wherein a CVT controller of the CVT has stored a normal traveling shift map adapted for a normal traveling of the vehicle and a constant speed traveling shift map for the vehicle speed control, said controller commands the CVT controller to switch a shift map from the constant speed traveling shift map to the normal traveling shift map when said controller suspends the vehicle speed control.

9. The vehicle speed control system as claimed in claim 5, wherein

wherein said controller commands the CVT to execute the shift-down the CVT when a time period to the target vehicle speed, which time is achieved by the full closing of the throttle, becomes greater than a predetermined time period.

10. A method for controlling a vehicle speed of a vehicle, the vehicle equipped with an engine and a continuously variable transmission (CVT), the method comprising:

executing a vehicle speed control to bring a vehicle speed at a target vehicle speed;

suspending the vehicle speed control when a throttle opening is increased to an opening which is greater than a target throttle opening for the vehicle speed control;

restarting the vehicle speed control when the throttle opening becomes smaller than the target throttle opening for the vehicle speed control; and

decreasing the throttle opening and shifting down the CVT when the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed.