Process and device for adjusting the braking effect in a vehicle

• US 6,381,531 B1
• Filed: 12/01/1998
• Issued: 04/30/2002
• Est. Priority Date: 12/02/1996
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Schmidt, Günther
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Tran, Dalena
• Application Number:
  US09/117,591
• Time in Patent Office: 1,246 Days
• Field of Search: 701/71, 701/73, 701/75, 701/78, 701/80, 701/83, 701/89, 303/150, 303/171, 303/174, 303/159, 303/DIG.5, 303/DIG.4, 303/147, 303/169, 303/149, 303/148, 188/181.A
• US Class Current: 701/73
• CPC Class Codes: B60T 8/00 Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force by changing number of effective brake cylinders in power brake systems B60T17/10
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: B60T 8/1764 Regulation during travel on surface with different coefficients of friction, e.g. between left and right sides, mu-split or between front and rear
• CPC Class Codes: B60T 8/32 responsive to a speed condition, e.g. acceleration or deceleration using electrical circuitry or regulation means B60T8/17 ; B60T8/28 takes precedence; electric devices on electrically propelled vehicles indicating the wheel slip B60L3/10; measuring linear or angular speed per se G01P3/00
• CPC Class Codes: B60T 8/4208 Debooster systems
• CPC Class Codes: B60T 8/48 connecting the brake actuator to an alternative or additional source of fluid pressure , e.g. traction control systems
• CPC Class Codes: B60T 8/58 responsive to speed and another condition or to plural speed conditions

Abstract

The braking effect in a vehicle is set in the sense of preventing a tendency to lock-up with at least two wheels which are arranged on at least one axle on the right and left and whose motion characteristics are detected. The braking effect on the two wheels is set jointly, with at least two operating modes (select low, select high) being provided; they can be selected depending on the coefficients of friction prevailing on the wheels and/or depending on the vehicle speed. An operating mode is selected according to the value of the prevailing coefficients of friction when there are coefficient of friction differences of a preselectable lower value. As an alternative or in addition, an operating mode is selected according to the detected vehicle speed when there are coefficient of friction differences of a preselectable greater value.

Claims

1. A method for controlling a braking effect in a vehicle to prevent a wheel lock-up tendency, the vehicle including at least one axle and wheels rolling on a road surface, at least one right wheel of the wheels being arranged on a right end of the at least one axle and at least one left wheel of the wheels being arranged on a left end of the at least one axle, the at least one right wheel having a first friction coefficient and the at least one left wheel having a second friction coefficient, the first friction coefficient being different from the second friction coefficient, the method comprising the steps of:

detecting first and second motion characteristics of the wheels;

comparing the first friction coefficient to the second friction coefficient to determine a higher coefficient, a lower coefficient and a difference value between the first friction coefficient and the second friction coefficient;

setting the braking effect on the wheels with a joint setting device using a first operating mode and a second operating mode, wherein, in the first operating mode, the braking effect is set as a function of the first motion characteristics of a first wheel of the wheels which has the lower coefficient, and wherein, in the second operating mode, the braking effect is set as a function of the second motion characteristics of a second wheel of the wheels which has the higher coefficient; and

selecting one of the first and second operating modes as a function of;

one of the first and second friction coefficients when the difference value is smaller than a predetermined value, and

a speed of the vehicle when the difference value is greater than the predetermined value.

2. The method according to claim 1, wherein a magnitude of the difference value relative to the predetermined value is determined by:

determining a rotational motion of the wheels,

determining the higher coefficient at least as a function of defined characteristics of the first and second motion characteristics, and

comparing the difference value to [preselected threshold values] the predetermined value.

3. The method according to claim 2, wherein the defined characteristics are indicative of a maximum wheel deceleration determined from the rotational motion.

4. The method according to claim 1, further comprising the step of:

selecting the second operating mode for a front axle of the at least one axle and a rear axle of the at least one axle.

5. The method according to claim 4, wherein the second operating mode is selected for a front axle of the at least one axle and a rear axle of the at least one axle when the difference value is equal to a high predetermined value.

6. The method according to claim 1, further comprising the step of:

selecting one of the first and second operating modes with hystereses.

7. A method for controlling a braking effect in a vehicle to prevent a wheel lock-up tendency, the vehicle including at least one axle and wheels rolling on a road surface, at least one right wheel of the wheels being arranged on a right end of the at least one axle and at least one left wheel of the wheels being arranged on a left end of the at least one axle, the at least one right wheel having a first friction coefficient and the at least one left wheel having a second friction coefficient, the first friction coefficient being different from the second friction coefficient, the method comprising the steps of:

detecting first and second motion characteristics of the wheels;

comparing the first friction coefficient to the second friction coefficient to determine a higher coefficient, a lower coefficient and a difference value between the first friction coefficient and the second friction coefficient;

setting the braking effect on the wheels with a joint setting device using a first operating mode and a second operating mode, wherein, in the first operating mode, the braking effect is set as a function of the first motion characteristics of a first wheel of the wheels which has the lower coefficient, and wherein, in the second operating mode, the braking effect is set as a function of the second motion characteristics of a second wheel of the wheels which has the higher coefficient;

selecting one of the first and second operating modes as a function of at least one of;

one of the first and second friction coefficients when the difference value is smaller than a predetermined value, and

a speed of the vehicle when the difference value is greater than the predetermined value;

selecting the second operating mode when the difference value is smaller than the predetermined value; and

selecting the first operating mode when the difference value is greater than the predetermined value.

8. The method according to claim 7, wherein the first and second operating modes are selected for a front axle of the at least one axle.

9. A method for controlling a braking effect in a vehicle to prevent a wheel lock-up tendency, the vehicle including at least one axle and wheels rolling on a road surface, at least one right wheel of the wheels being arranged on a right end of the at least one axle and at least one left wheel of the wheels being arranged on a left end of the at least one axle, the at least one right wheel having a first friction coefficient and the at least one left wheel having a second friction coefficient, the first friction coefficient being different from the second friction coefficient, the method comprising the steps of:

detecting first and second motion characteristics of the wheels;

comparing the first friction coefficient to the second friction coefficient to determine a higher coefficient, a lower coefficient and a difference value between the first friction coefficient and the second friction coefficient;

setting the braking effect on the wheels with a joint setting device using a first operating mode and a second operating mode, wherein, in the first operating mode, the braking effect is set as a function of the first motion characteristics of a first wheel of the wheels which has the lower coefficient, and wherein, in the second operating mode, the braking effect is set as a function of the second motion characteristics of a second wheel of the wheels which has the higher coefficient;

selecting one of the first and second operating modes as a function of at least one of;

one of the first and second friction coefficients when the difference value is smaller than a predetermined value, and

a speed of the vehicle when the difference value is greater than the predetermined value;

selecting the second operating mode when the speed is smaller than a predetermined speed value and the difference value is greater than the predetermined value; and

selecting the first operating mode when the speed is greater than the predetermined speed value and the difference value is greater than the predetermined value.

10. The method according to claim 9, wherein the first and second operating modes are selected for a front axle of the at least one axle.

11. A device for controlling a braking effect in a motor vehicle, the motor vehicle including at least one axle and wheels, at least one right wheel of the wheels being arranged on a right end of the at least one axle and at least one left wheel of the wheels being arranged on a left end of the at least one axle, the at least one right wheel having a first friction coefficient and the at least one left wheel having a second friction coefficient, the first friction coefficient being different from the second friction coefficient, the device comprising:

a first arrangement detecting motion characteristics of the wheels;

a second arrangement jointly setting the braking effect on the wheels; and

a control arrangement generating control signals for controlling the second arrangement using at least two operating modes, the control arrangement determining a higher coefficient, a lower coefficient and a difference value between the first friction coefficient and the second friction coefficient by comparing the first friction coefficient to the second friction coefficient, the control arrangement selecting one of the at least two operating modes as a function of;

one of the first and second friction coefficients when the difference value is smaller than a predetermined value, and

a speed of the motor vehicle when the difference value is greater than the predetermined value,

wherein, in a first operating mode of the at least two operating modes, the second arrangement jointly sets the braking effect as a function of the motion characteristics of a first wheel of the wheels which has the lower coefficient, and

wherein, in a second operating mode of the at least two operating modes, the second arrangement jointly sets the braking effect as a function of the motion characteristics of a second wheel of the wheels which has the higher coefficient.

12. The device according to claim 11, wherein the difference value is determined by:

a third arrangement detecting a rotational motion of each of the wheels,

a fourth arrangement determining the higher coefficient at least as a function of the motion characteristics, and

a fifth arrangement comparing the difference value to predetermined threshold values.

13. The device according to claim 12, wherein the motion characteristics are indicative of a function of a maximum wheel deceleration determined from the rotational motion.

14. A device for controlling a braking effect in a motor vehicle, the motor vehicle including at least one axle and wheels, at least one right wheel of the wheels being arranged on a right end of the at least one axle and at least one left wheel of the wheels being arranged on a left end of the at least one axle, the at least one right wheel having a first friction coefficient and the at least one left wheel having a second friction coefficient, the first friction coefficient being different from the second friction coefficient, the device comprising:

a first arrangement detecting motion characteristics of the wheels;

a second arrangement jointly setting the braking effect on the wheels; and

a control arrangement generating control signals for controlling the second arrangement using at least two operating modes, the control arrangement determining a higher coefficient, a lower coefficient and a difference value between the first friction coefficient and the second friction coefficient by comparing the first friction coefficient to the second friction coefficient, the control arrangement selecting one of the at least two operating modes as a function of at least one of;

one of the first and second friction coefficients when the difference value is smaller than a predetermined value, and

a speed of the motor vehicle when the difference value is greater than the predetermined value,

wherein, in a first operating mode of the at least two operating modes, the second arrangement jointly sets the braking effect as a function of the motion characteristics of a first wheel of the wheels which has the lower coefficient,

wherein, in a second operating mode of the at least two operating modes, the second arrangement jointly sets the braking effect as a function of the motion characteristics of a second wheel of the wheels which has the higher coefficient, and

wherein the control arrangement selects the second operating mode for the lower coefficient when the difference value is smaller than the predetermined value, and wherein the control arrangement selects the first operating mode for higher coefficient when the difference value is smaller than the predetermined value.

15. The device according to claim 14, wherein the control arrangement selects the first and second operating modes for a front axle of the at least one axle.

16. A device for controlling a braking effect in a motor vehicle, the motor vehicle including at least one axle and wheels, at least one right wheel of the wheels being arranged on a right end of the at least one axle and at least one left wheel of the wheels being arranged on a left end of the at least one axle, the at least one right wheel having a first friction coefficient and the at least one left wheel having a second friction coefficient, the first friction coefficient being different from the second friction coefficient, the device comprising:

a first arrangement detecting motion characteristics of the wheels;

a second arrangement jointly setting the braking effect on the wheels; and

a control arrangement generating control signals for controlling the second arrangement using at least two operating modes, the control arrangement determining a higher coefficient, a lower coefficient and a difference value between the first friction coefficient and the second friction coefficient by comparing the first friction coefficient to the second friction coefficient, the control arrangement selecting one of the at least two operating modes as a function of at least one of;

one of the first and second friction coefficients when the difference value is smaller than a predetermined value, and

a speed of the motor vehicle when the difference value is greater than the predetermined value,

wherein, in a first operating mode of the at least two operating modes, the second arrangement jointly sets the braking effect as a function of the motion characteristics of a first wheel of the wheels which has the lower coefficient,

wherein, in a second operating mode of the at least two operating modes, the second arrangement jointly sets the braking effect as a function of the motion characteristics of a second wheel of the wheels which has the higher coefficient, and

wherein the control arrangement selects the second operating mode when the speed is smaller than a predetermined speed value and when the difference value is greater than the predetermined value, and wherein the control arrangement selects the first operating mode when the speed is greater than the predetermined speed value and when the difference value is greater than the predetermined value.

17. The device according to claim 16, wherein the control arrangement selects the first and second operating modes for a front axle of the at least one axle.