System and method for monitoring wear of braking frictional pad of motor vehicle

Patent metadata

Field	Value
Publication number	US-12196282-B2
Application number	US-202217746137-A
Country	US
Kind code	B2
Filing date	May 17, 2022
Priority date	May 18, 2021
Publication date	Jan 14, 2025
Grant date	Jan 14, 2025

Abstract

A method and a system for monitoring wear of a braking frictional pad of a motor vehicle, includes stopping the motor vehicle stably on a horizontal or substantially horizontal plane; determining a current fluid level in a brake fluid reservoir; determining a volume difference (ΔV L ) of the brake fluid in the brake fluid reservoir by comparing the determined current fluid level with a predetermined reference fluid level; when a thickness loss of a braking frictional pad equipped for a front vehicle wheel or a rear vehicle wheel is known, determining a thickness loss of a braking frictional pad assigned for the other front vehicle wheel or the other rear vehicle wheel based on the volume difference of the brake fluid in the brake fluid reservoir and a diameter of a brake piston of the respective brake device.

First claim

What is claimed is:

1. A method for monitoring wear of a braking frictional pad of a motor vehicle, the motor vehicle comprising vehicle wheels, a brake device acting on each vehicle wheel, the brake device including a braking frictional pad configured to be non-rotatable relative to the vehicle wheel and be linearly movable parallel to a rotational axis of the vehicle wheel, the motor vehicle also comprising a hydraulic brake drive and a brake fluid reservoir in fluid communication with the hydraulic brake drive, the hydraulic brake drive including a linearly movable brake piston configured to act on the braking frictional pad to brake the vehicle wheel, the method comprising:
stopping the motor vehicle stably on a horizontal or substantially horizontal plane;
determining a current fluid level in the brake fluid reservoir;
determining a volume difference (ΔVL) of the brake fluid in the brake fluid reservoir by comparing the determined current fluid level with a reference fluid level; and
when a thickness loss of a braking frictional pad equipped for a front vehicle wheel or a rear vehicle wheel is predetermined, determining a thickness loss of a braking frictional pad equipped for the other front vehicle wheel or the other rear vehicle wheel based on the volume difference of the brake fluid in the brake fluid reservoir and a diameter of the brake piston of the respective brake device,
wherein the thickness loss of the braking frictional pad equipped for the other front vehicle wheel or the other rear vehicle wheel is determined using the following equation:
Δ LX =(Δ VL− π D 0 2 ·ΔL 0−γ)/( π DX 2 ),

wherein ΔL X is the thickness loss of the braking frictional pad to be determined, D0 is a diameter of the brake piston associated with the braking frictional pad having the predetermined thickness loss, D X is a diameter of a brake piston associated with the braking frictional pad with the thickness loss to be determined, ΔVL is the volume difference of the brake fluid in the brake fluid reservoir, γ is an empirical constant.

2. The method according to claim 1 , wherein the reference fluid level is a fluid level in the brake fluid reservoir measured when the motor vehicle stays stably in a horizontal or substantially horizontal plane and when the motor vehicle is installed with brand new braking frictional pads or braking frictional pads having known thickness for all vehicle wheels.

3. The method according to claim 2 , wherein after the reference fluid level has been measured and before any subsequent determination of fluid level in the brake fluid reservoir, no additional brake fluid is added into the brake fluid reservoir.

4. The method according to claim 3 , wherein an electric parking brake or an electric mechanical brake is equipped for the braking frictional pad having the known thickness loss.

5. The method according to claim 4 , wherein the electric parking brake or the electric mechanical brake comprises a drive motor, and a piston driving part driven by the drive motor to be linearly movable; when the motor vehicle is braked, the brake piston is driven by the piston driving part to contact and move the braking frictional pad.

6. The method according to claim 5 , further comprising:
operating, after the motor vehicle has been parked, the drive motor to move the piston driving part to a preset reference position;
continuing to operate the drive motor to move the piston driving part from the reference position to a stop position where the piston driving part drives the brake piston to contact the braking frictional pad, wherein the stop position corresponds to a parking braking position of the brake piston;
determining a distance between the reference position and the stop position; and
calculating a difference between the determined distance and a predetermined reference distance to determine a thickness loss of the associated braking frictional pad as the known thickness loss.

7. The method according to claim 6 , wherein the reference distance is a travel distance of the piston driving part from the reference position to the stop position, when the thickness of the associated braking frictional pad is known or the associated braking frictional pad is brand new, and when the motor vehicle is in parking braking.

8. The method according to claim 7 , wherein the known thickness loss is absolute value of the difference between the determined distance and the reference distance.

9. The method according to claim 8 , further comprising alerting a driver of the motor vehicle to replace the braking frictional pad with a new one when the thickness loss of the braking frictional pads exceeds a threshold.

10. The method according to claim 9 , wherein the electric parking brake or the electric mechanical brake further comprises a reducer mechanism connected to an output shaft of the drive motor, and a linear movement mechanism driven by the reducer mechanism, the reducer mechanism is configured to provide a lock function in braking to prevent the piston driving part from moving freely, and the piston driving part is configured to be driven by the linear movement mechanism to linearly move.

11. The method according to claim 10 , wherein the linear movement mechanism is a thread-screw mechanism that includes a core shaft connected to the output shaft of the drive motor, the core shaft comprising external threads on its outer surface, and the piston driving part is a threaded part having internal threads that engage the external threads of the core shaft and is configured to be non-rotatable relative to the core shaft, and be axially movable back and forth along the core shaft.

12. The method according to claim 11 , wherein the distance between the reference position and the stop position is at least dependent on a rotation speed of the output shaft of the drive motor, a transmission ratio of the reducer mechanism, a pitch of thread of the thread-screw mechanism, and a time duration during which the drive motor is turned on.

13. The method according to claim 7 , wherein before the known thickness loss is determined, parking braking of a vehicle wheel that is not equipped with the electric parking brake is carried out by the hydraulic brake drive.

14. The method according to claim 13 , wherein a direction along which the piston driving part moves to the reference position is opposite to a direction along which the piston driving part moves from the reference position to the stop position.

15. The method according to claim 3 , wherein the known thickness loss of the braking frictional pad is determined by a resistance sensor disposed within the braking frictional pad.

16. A system for monitoring wear of a braking frictional pad of a motor vehicle, the motor vehicle comprising vehicle wheels and a brake device acting on each of the vehicle wheels, the brake device including a braking frictional pad configured to be non-rotatable relative to the vehicle wheel and be linearly movable parallel to a rotational axis of the vehicle wheel, the motor vehicle also comprising a hydraulic brake drive and a brake fluid reservoir in fluid communication with the hydraulic brake drive, the hydraulic brake drive including a linearly movable brake piston which is configured to act on the braking frictional pad to brake the vehicle wheel, the system comprising:
a fluid level sensor provided in the brake fluid reservoir; and
an electronic control unit connected to the fluid level sensor to receive fluid level data, comprising:
a first module configured to provide instructions for stopping the motor vehicle stably o

Assignees

• Volvo Car Corp

Inventors

• Jin Yongxing
• Yuan Ming
• Yu Yi

Classifications

• F16D2125/40

  Screw-and-nut · CPC title

• F16D2125/06

  Pistons · CPC title

• F16D2121/24

  using motors · CPC title

• F16D2121/04

  acting on a piston-type actuator, e.g. for liquid pressure · CPC title

• F16D2066/003

  Position, angle or speed · CPC title