WO2019110391A1

WO2019110391A1 - A controller and method to detect the wear of a vehicle brake pad

Info

Publication number: WO2019110391A1
Application number: PCT/EP2018/082866
Authority: WO
Inventors: Palghat Sitaram AVINASH; Shreyas Kota HANDE
Original assignee: Robert Bosch Gmbh; Bosch Limited
Priority date: 2017-12-08
Filing date: 2018-11-28
Publication date: 2019-06-13

Abstract

The present invention provides a controller (110) and a method for the vehicle (100), to detect or predict the wear in brake pad (128) of the braking system (130). The controller (110) is in electronic communication with a hydraulic unit (122) comprising a pump (124) and at least one valve (126) such as electric valve for example solenoid valve. The controller (110) is adapted to supply brake fluid and increase pressure in the brake circuit to a predetermined test pressure by means of the pump (124). The controller (110) then operates at least one valve (126) to decrease pressure in the brake circuit to a threshold pressure. The controller (110) computes the time taken to reach the threshold pressure, and detects wear of the brake pad (128) based on said computed time.

Description

TITLE: A CONTROLLER AND METHOD TO DETECT THE WEAR OF A VEHICLE

BRAKE PAD

Field of the invention:

[0001] The present invention relates to a controller and method to detect wear in brake pad of a vehicle.

Background of the invention:

[0002] According to a patent literature US2004/0183365, a vehicle braking device is disclosed. The aim is to reliably detect abnormality of a brake device with a simple structure without providing a special detecting means. A pump for generating brake hydraulic pressure of a hydraulic brake device is driven when the ignition switch for starting the vehicle is closed. The rise time of the output of a brake hydraulic pressure detecting means provided in the hydraulic brake device is detected, and it is determined that uneven wear of the pads has occurred if the rise time is longer than a predetermined time. An alarm lamp is turned on to notify abnormality. Thereby it is possible to accurately detect abnormality of the brake device before the driver drives the vehicle without providing a special detecting means.

Brief description of the accompanying drawings:

[0003] An embodiment of the disclosure is described with reference to the following accompanying drawing,

[0004] Fig. 1 illustrates a vehicle fit with a controller to detect wear in brake pad, according to an embodiment of the present invention;

[0005] Fig. 2 illustrates a volume, pressure and time graph of a brake fluid, according to the present invention, and

[0006] Fig. 3 illustrates a method of detecting wear in brake pad of the vehicle, according to the present invention.

Detailed description of the embodiments:

[0007] Fig. 1 illustrates a vehicle fit with a controller to detect wear in brake pads, according to an embodiment of the present invention. A two-wheeler vehicle 100 or a straddle type vehicle 100 is shown. Other vehicles 100 comprising a three-wheeler, four-wheelers, etc are also applicable. The vehicle 100 comprises a front wheel 102 and a rear wheel 104. A braking system 130 is provided for at least one of the wheel 102, 104 of the vehicle 100. The braking system 130 corresponds to electronically controlled brakes of the vehicle 100, such as Anti- lock Braking System (ABS), an Electronic Stability Program (ESP), and the like. The braking system 130 either already exist in the vehicle 100 or is installed/retrofit to the vehicle 100. The braking system 130 comprises at least one brake pad 128 fit to a caliper, which is operated based on the pressing of a brake lever 118. The brake pad 128 is operated through a brake circuit comprising tubes carrying fluid to transfer the braking force to the caliper piston (not shown). The brake pad 128 is pressed against the disc 116 or drum, by the caliper piston to bring the vehicle 100 to a stop.

[0008] In accordance to an embodiment of the present invention, a controller 110 is provided for the vehicle 100, to detect or predict the wear in brake pad 128 of the braking system 130. The controller 110 is in electronic communication with a hydraulic unit 122 comprising a master cylinder 120, a pump 124 and at least one valve 126 such as electric valve for example solenoid valve. The controller 110 is adapted to supply brake fluid and increase pressure to a first threshold in the brake circuit when the brake lever/ pedal 118 is pressed. The controller 110 then operates at least one valve 126 to decrease pressure in the brake circuit to a second threshold. The controller 110 compute time taken to reach the second threshold, and detects wear in the brake pad 128 based on the computed time taken.

[0009] In accordance to one embodiment of the present invention, the controller 110 detects wear before an engine 112 of the vehicle 100 is ignited or started. Before the engine 112 is started, the controller 110 increases the pressure in the brake circuit to the first threshold and then decreases to the second threshold, with an input from a pressure sensor 108. The controller 110 computes the time taken to reach the second threshold. If the time taken to reach the second threshold is beyond a predetermined time, then the controller 110 detects wearing in the brake pad 128. The predetermined time is different for different combinations of the first threshold and the second threshold, which is stored in a memory unit 114 of the controller 110. Thus, before the vehicle 100 is driven, the wear in brake pad 128 is determined, which assists the driver/owner of the vehicle 100 to take necessary precautionary measures. The driver may take the vehicle 100 to a garage for replacement of brake pad 128.

[0010] In the case where the wear in the brake pad 128 is detected before the engine is started, the first threshold is at least one test pressure. The test pressure corresponds to a pressure in the brake circuit when a brakes are activated or the brake pad 128 are pushed to the disc or drum for braking. The first threshold may also be a pressure where the pressure is increased but the brake pad 128 is not yet pushed. The second threshold is lower than the first threshold.

[0011] The vehicle 100 is selected from a two wheeler such as motorcycles, scooters, a three wheeler such as auto-rickshaws, a four wheeler such as car and the like.

[0012] In accordance to another embodiment of the present invention, the controller 110 detects wear in the brake pad 128 during a runtime or braking operation of wheel 102 of the vehicle 100. In case before the vehicle 100 starts, if the controller 110 fails to detect the wear in the brake pad 128, or if a considerable wear in the brake pad 128 has occurred during runtime of the vehicle 100, then also the controller 110 is enabled to detect the wear of the brake pad 128. The controller 110 is adapted to activate the pump 124 to supply brake fluid and increase pressure in the brake circuit to the first threshold. In this case, the first threshold corresponds to the pressure needed for braking the vehicle 100. The controller 110 monitors the speed of the vehicle 100 by the speed sensor 106 and detects wheel lock or slip. The controller 110 then operates at least one valve 126 to decrease pressure in the brake circuit to the second threshold. The second threshold in this case is the pressure until the wheel slip is eliminated/ or the wheel slip is unlocked. The controller 110 then computes time taken to reach the second threshold, and detects wear in the brake pad 128 based on the computed time taken.

[0013] In the case of detecting wear in brake pad 128 during braking operation, the first threshold is the pressure at which the brake are activated and is pressed against the disc or drum of the respective wheel. Further, the first pressure may be the pressure at which the respective wheel is locked after braking.

[0014] If the time taken to reach the second threshold is beyond the predetermined time, then the controller 110 detects wearing in the brake pad 128. The predetermined time is different for different combinations of the first threshold and the second threshold, which is stored in a memory unit 1 14 of the controller 110.

[0015] In accordance to another embodiment of the present invention, the controller 110 is adapted to determine a severity of the wear based on the computed time taken. Further, the controller 110 is adapted to control vehicle 100 either dependent or independent of the severity, such as inhibiting vehicle start, alert the driver through audio, visual or in a communication device of the driver through mobile networks or wireless means.

[0016] Fig. 2 illustrates a volume, pressure and time graph of a brake fluid, according to the present invention. The X-axis 204 represents volume and time, whereas the Y-axis 202 is represented by Pressure. The graph is for representation purpose and is not to the scale. In the brake circuit of the braking system 130, the volume of brake fluid to the caliper piston keeps changing with the wear rate of the brake pad 128. As the brake pad 128 wears, the caliper piston automatically move frontward thereby increasing the dead volume in the brake circuit. During braking, when wheel slip is detected, the controller 110 operates the at least one valve 126 in the brake circuit to reduce the pressure at the caliper to the second threshold. The time taken to reduce the pressure depends on the volume in the circuit, because with increase in volume, time taken for the at least one valve 126 to reduce pressure increases.

[0017] The graph shows a first curve 206 representing first volume, a second curve 208 representing a second volume and a third curve 210 representing a third volume. The volume in the brake circuit keeps increasing as the brake pad 128 wears. Thus, time take to reduce/decrease pressure also increases. The controller 110 monitors or computes the time taken to reduce the pressure to the second threshold and compares with a threshold time, and detects the wear in the brake pad 128.

[0018] Fig. 3 illustrates a method of detecting wear in brake pad of the vehicle, according to the present invention. The method comprises a step 302 comprising activating the pump 124 to supply brake fluid and increasing pressure to the first threshold in the brake circuit. A step 304 comprises operating at least one valve 126 to decrease pressure in the brake circuit to the second threshold. The method enables to detect wear in the brake pad 128 before the vehicle 100 is started or during runtime/ braking operation of the vehicle 100. A next step 306 comprises computing by the controller 110, the time taken, for the pressure in the brake circuit, to reach the second threshold. The controller 110 detects the first and second threshold using the pressure sensor 108. A step 308 comprises detecting the wear in the brake pad 128 based on the computed time taken. The time taken is compared with a threshold time stored in the memory unit 114 of the controller 110. [0019] In the case where the wear in the brake pad 128 is detected before the engine is started, the first threshold is at least one test pressure. The test pressure corresponds to a pressure in the brake circuit when a brakes are activated or the brake pad 128 are pushed to the disc or drum for braking. The first threshold may also be a pressure where the pressure is increased but the brake pad 128 is not yet pushed/pressed.

[0020] In the case of detecting wear in brake pad 128 during braking operation, the first threshold is the pressure at which the brake are activated and is pressed against the disc or drum of the respective wheel. The first threshold also may be the pressure at which the respective wheel is locked. The first threshold is higher than the second threshold.

[0021] During the braking operation, the method comprises operating the at least one valve 126 by detecting a wheel slip/lock by means of the wheel speed sensor 106. The second threshold is the pressure at which the vehicle slip/lock is eliminated.

[0022] If the time taken to reach the second threshold is beyond a predetermined time, then the controller 110 detects wearing in the brake pad 128. The predetermined time is different for different combinations of the first threshold and the second threshold, which is stored in a memory unit 114 of the controller 110.

[0023] The present invention though is explained for a single front wheel 102 of the vehicle 100, but is equally applicable for other wheels such as rear wheels of different types of vehicles, and must not be understood in limiting sense. [0024] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

Claims

We claim:

1. A controller (110) to detect wear in brake pad (128) of a vehicle (100), said controller (110) adapted to

activate a pump (124) to supply brake fluid and increase pressure to a first threshold in a brake circuit;

operate at least one valve (126) to decrease pressure in said brake circuit to a second threshold pressure;

compute time taken to reach said second threshold pressure, and detect wear in said brake pad (128) based on said computed time taken.

2. The controller (110) as claimed in claim 1, detects said wear before starting an engine (112) of said vehicle (100).

3. The controller (110) as claimed in claim 1, wherein said second threshold pressure is a pressure at which wheel slip is eliminated.

4. The controller (110) as claimed in claim 3, detects said wear during braking of a wheel (102, 104) of said vehicle (100).

5. The controller (110) as claimed in claim 4, operates said at least one valve (126) upon detection of a wheel slip by means of wheel speed sensor (106).

6. A method for detecting wear in brake pad (128) of a vehicle (100), said method comprising the steps of:

activating a pump (124) to supply brake fluid and increase pressure to a first threshold in a brake circuit;

operating at least one valve (126) to decrease pressure in said brake circuit to a second threshold;

computing time taken to reach said second threshold, and

detecting wear in said brake pad (128) based on said computed time taken.

7. The method as claimed in claim 6, comprises detecting said wear before starting an engine (112) of said vehicle (100).

8. The method as claimed in claim 6, wherein said second threshold pressure is a pressure at which wheel slip is eliminated.

9. The method as claimed in claim 8, comprises detecting said wear during braking operation of a wheel (102, 104) of said vehicle (100).

10. The method as claimed in claim 9, further comprises operating said at least one valve (126) upon detection of a wheel slip by means of wheel speed sensor (106).