Brake control system for vehicle

• US 5,984,435 A
• Filed: 03/27/1997
• Issued: 11/16/1999
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Tsukamoto, Masahiro, Oshiage, Katsunori, Takahashi, Hiroshi
• Primary Examiner(s): Schwartz, Chris
• Application Number:
  US08/827,176
• Time in Patent Office: 964 Days
• Field of Search: 180/167-169, 180/272, 303/113.4, 303/113.5, 303/155, 303/160, 303/166, 303/167, 303/192, 303/193, 303/196, 364/426.01, 701/25, 701/28, 701/98
• US Class Current: 303/191
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems

Abstract

A brake control system is comprised of a vehicle environment recognition device for obtaining vehicle environment including a road condition, an actuator for applying hydraulic pressure set at a target value to each wheel cylinder, and a controller for calculating the target value on the basis of the vehicle environment. The controller controls the wheel cylinder pressure by driving the actuator so as to adjusting the wheel cylinder pressure at the target value. Therefore, it becomes possible to ensure the same braking distance by the same depression degree of the brake even in various road conditions.

Claims

1. A brake control system for executing a braking of a vehicle, comprising:

means for detecting driver braking intent;

an actuator that applies braking force to each wheel on the basis of the detected driver braking intent;

a road inclination detector that detects an inclination of a road on which the vehicle travels; and

a controller that changes a relationship between the driver braking intent and the braking force of each wheel according to the detected road inclination.

2. A brake control system as claimed in claim 1, further including an obstacle sensor that obtains information indicative of an obstacle located near the vehicle without directly contacting the obstacle.

3. A brake control system as claimed in claim 2, the obstacle information includes information relating to at least one of an obstacle preceding the vehicle and a preceding vehicle.

4. A brake control system as claimed in claim 3, wherein the controller increases the braking force relative to the driver braking intent according to increase in at least one of proximity to a forward obstacle or preceding vehicle and the approaching speed to a forward obstacle or the preceding vehicle.

5. A brake control system as claimed in claim 2, wherein the obstacle sensor includes one of a device for reading and processing picture information indicative of vehicle environment, a device for measuring a distance between an obstacle and the vehicle by emitting light and receiving the reflection of the light from the obstacle, and a device for measuring a distance between an obstacle and the vehicle by emitting radio wave and receiving the reflection of the radio wave from the obstacle.

6. A brake control system as claimed in claim 1, further including a device that estimates vehicle environment information from the operation of the driver.

7. A brake control system as claimed in claim 6, wherein the environment information includes a type of road.

8. A brake control system as claimed in claim 7, wherein said controller treats a relationship between the driver braking intent and the braking force on a suburb road as a reference, increasing the braking force relative to the driver braking intent on an expressway, decreasing the braking force relative to the driver braking intent when the vehicle travels on an urban road and the driver braking intent is small, increasing the braking force relative to the driver braking intent when the vehicle travels on the urban road and the driver braking intent is large, increasing the braking force relative to the driver braking intent when the vehicle travels on a downwardly sloped road, and decreasing the braking force relative to the driver braking intent when the vehicle travels on an upwardly sloped road.

9. A brake control system as claimed in claim 1, further including a device that determines a road curvature, the controller also changing the relationship between the braking force of each wheel according to the road curvature determined.

10. A brake control system as claimed in claim 9, wherein the controller increases the braking force of front wheels and decreases the braking force of rear wheels as the road curvature increases.

11. A brake control system as claimed in claim 9, wherein the controller increases the braking force of outer side wheels relative to the driver braking intent during turning operation.

12. A brake control system as claimed in claim 1, wherein the road inclination detector comprises a navigational system from which a vehicle traveling position is obtained, wherein the road inclination is obtained from a map or change of the vehicle traveling position on the basis of the obtained vehicle traveling position.

13. A brake control system as claimed in claim 12, wherein the road inclination is obtained from the map and the vehicle traveling position is changed forward according to the increase of the vehicle speed.

14. A brake control system as claimed in claim 1, further including means for detecting at least one of snow and rain conditions.

15. A brake control system as claimed in claim 14, wherein the controller decreases the braking force relative to the driver braking intent when a heavy snow or rain condition is detected.

16. A brake control system as claimed in claim 1, wherein the driver braking intent detecting means comprises one of a master cylinder pressure detector, a brake pedal depressing force detector, and a brake pedal depressed stroke detector.

17. A brake control system as claimed in claim 16, wherein the controller increases one of the braking force and the wheel cylinder pressure relative to the driver braking intent when the vehicle travels on a downwardly sloped road.

18. A brake control system as claimed in claim 1, further including means for determining whether the vehicle traveling road is a paved road.

19. A brake control system as claimed in claim 18, wherein the controller decreases the braking force relative to the driver braking intent when the traveling road is an unpaved road.

20. A brake control system as claimed in claim 1, wherein the road inclination detector comprises a navigation system that detects a vehicle position, wherein the road inclination is determined based on environmental information of the vehicle position stored in a map.

21. A braking control system as claimed in claim 1, wherein the controller changes the relationship between the driver braking intent and the braking force to keep a distance corresponding to the driver braking intent constant even if the road inclination is varied.

22. A braking control system as claimed in claim 1, wherein the controller changes the relationship between the driver braking intent and the braking force so that a braking distance based on the braking intent becomes equal regardless of the road inclination.

23. A brake control system of a vehicle, comprising:

a road inclination sensor that measures an inclination of a road;

a pressure generating source that generates a brake pressure corresponding to a brake operating force applied by a driver;

an actuator that controllably changes the brake pressure and applies the changed pressure to each wheel cylinder;

a controller that calculates a target value of the wheel cylinder pressure on the basis of the measured road inclination and controls the wheel cylinder pressure to the target value by driving said actuator.

24. A brake control system as claimed in claim 23, wherein the road inclination sensor comprises a forward monitoring camera that monitors a forward direction of the vehicle, wherein the road inclination is measured by obtaining a change ratio of the road inclination from picture information obtained by the forward monitoring camera and by executing an integral of an initial value relative to the change ratio of the road inclination.

25. A brake control system as claimed in claim 24, wherein the initial value of the road inclination is obtained from a drive force obtained from an output torque of the engine and an acceleration of the vehicle.

26. A brake control system as claimed in claim 24, wherein the initial value of the road inclination is obtained from a drive force obtained from a slip ratio of a torque converter and an acceleration of the vehicle.

27. A brake control system as claimed in claim 24, wherein the inclination change ratio is changed according to the vehicle speed.

28. A brake control system as claimed in claim 23, wherein the target value of the wheel cylinder pressure is determined by changing the pressure of the pressure generating source in proportion to the road inclination.

29. A brake control system as claimed in claim 23, wherein the target value of the wheel cylinder pressure is determined by increasing the pressure of the pressure generating source in proportion to the road inclination when the target value is increased.

30. A brake control system as claimed in claim 23, wherein a proportion constant, which is applied to the calculation of the target value of the wheel cylinder pressure, is set from a standard loaded weight of a vehicle and brake system components.

31. A brake control system as claimed in claim 23, wherein the pressure of the pressure generating source is mechanically transferred to the wheel cylinder when the actuator is not operated.

32. A brake control system as claimed in claim 23, wherein the actuator always controls the wheel cylinder pressure on the basis of a master cylinder pressure to the target value when the brake control is executed and the actuator always controls the wheel cylinder pressure on the basis of the master cylinder pressure to follow the pressure of the pressure generating source when the brake control is not executed.

33. A method of controlling braking of a vehicle, comprising:

determining an inclination of a road on which the vehicle is traveling;

deciding a brake control gain according to the determined road inclination;

detecting braking intent of a driver;

deciding a target value of a braking force by correcting driver braking intent through the brake control gain; and

controlling a brake actuator to generate the braking force corresponding with the target value.

34. A brake control system for a vehicle comprising:

a wheel cylinder that is installed to each wheel of the vehicle and generates a braking force by increasing the pressure applied to the wheel cylinder;

a brake pedal application detecting device that detects a braking intent of a driver;

a vehicle environment recognition device that detects vehicle environment, including a road inclination;

an actuator that applies hydraulic pressure to the wheel cylinder at a target value; and

a controller that determines a target value of the wheel cylinder pressure on the basis of the driver braking intent and at least the road inclination to ensure a predetermined braking distance with respect to the predetermined braking intent of the driver.

35. A braking force control device for a vehicle, comprising:

a wheel braking cylinder associated with each wheel of the vehicle;

an actuation means for generating a main braking pressure corresponding to a force applied thereto;

a brake actuation device that supplies the main braking pressure to the wheel braking cylinder and sets the braking pressure applied to the wheel braking cylinder, wherein the braking pressure applied to the braking cylinders is increased or decreased based on vehicle environmental conditions;

a vehicle environmental recognition means for detecting the environmental conditions; and

a controller that determines a road inclination on the basis of the detected environmental conditions, wherein the controller generates a correction value corresponding to the road inclination and corrects the target braking pressure applied to the braking cylinder.