VEHICLE BRAKE LINER WEAR MEASUREMENT AND MONITORING
SYSTEM AND METHOD
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a vehicle brake system and more particularly relates to a brake liner wear measurement and monitoring system and method.
BACKGROUND OF THE INVENTION
[0002] Brake linings are consumable surfaces in a brake system, such as, for example, a drum brake or a disc brake used in transport vehicles. When the brake lining is worn out, a backing or rivet will contact a rotor or drum during braking, often causing damage requiring re-machining or replacement of the drum or rotor. Study of the brake liner wear with respect to distance travelled by the vehicle, gives insight that aids in development of better liner and ensuring commuter safety. Comparison of different brake liner products in real field conditions of the vehicle is necessary. Because the liner wear pattern varies with respect to different segment of vehicles, loading conditions, terrain patterns, traffic and environmental conditions. Thus the study of continuous liner wear against each braking instance over a period of time helps to develop better brake liners.
[0003] Various brake liner wear detection systems are utilized for detecting the brake liner wear. Such prior art systems involves the brake liner wear measurement using a sensor that intrude with the liner during braking. The sensor output is logic or piecewise output hence the sensor does not monitor the brake liner wear throughout vehicle running duty cycle. Such approaches do not reliably detect the comparatively small wear displacement, produce inaccurate results and are not readily adaptable to the wide variety of axle configurations found on modern vehicles. Additionally, such

sensors only provide a warning signal when a particular predetermined wear condition has been achieved.
[0004] Hence, there is a need for an improved brake liner wear measurement and monitoring system during the operation of the vehicle that does not intrude with the braking performance, as described in greater detail herein.
SUMMARY OF THE INVENTION
[0005] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiments and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
[0006] It is, therefore, one aspect of the present invention to provide an improved brake liner wear measurement and monitoring system for a vehicle that does not intrude with a braking performance.
[0007] It is another aspect of the present invention to provide an improved brake liner wear measurement system having a non - damageable and reusable sensor mounted at a defined location which is capable of accurately and continuously monitoring the brake liner wear.
[0008] It is further aspect of the present invention to provide an improved method for continuously monitoring the brake lining wear during the operation of the vehicle and indicating the brake liner replacement at different stages of the liner wear.
[0009] In one aspect of the present invention, a brake liner wear measurement and monitoring system includes a potentiometer sensor having a rotary part assembled to an adapter and mounted on a S-cam shaft of a vehicle brake unit along its center

axis at the end of a slack adjuster to measure the S-cam shaft rotation. A stationary part of the potentiometer sensor is clamped to a static part of an axle in such a way that a rotational difference between the stationary part and the rotary part provides S¬cam rotation angle information. An electric circuit is electrically connected to the potentiometer sensor to receive the S-cam rotation angle information for determining a difference between the rotation angle information and an initial reference reading of the potentiometer sensor to measure an amount of wear in a brake liner. The S-cam rotates and in turn causes the brake liner to displace during each application of a brake until the brake liner makes contact with a brake drum and the S-cam rotation is measured using the potentiometer sensor. The S-cam rotation is converted using a linear fit equation to determine the wear in the brake liner.
[0010] A voltage reading measured at an initial stage of setting the potentiometer sensor is recorded and considered as the initial reference reading in a brake engaged condition or a brake disengaged condition. The electric circuit further includes a speed unit to extract a speed and distance information of a vehicle to determine a cumulative liner wear pattern versus a vehicle travel distance and a storage unit to record the potentiometer sensor reading for each braking application for continuous monitoring of the liner wear. A display unit is used for displaying a brake liner wear result to a driver in a vehicle cabin. An alert unit is placed in the vehicle cabin to alert the driver for the brake liner replacement when the brake liner is consumed and crosses a usable threshold limit.
[0011] In another aspect of the present invention, the S-cam rotation angle information is measured by determining a rotational difference between a stationary part and a rotary part of the potentiometer sensor mounted to the S-cam shaft of the vehicle brake unit. A difference between the S cam rotation angle information and the initial reference reading of the potentiometer sensor is determined to measure the amount of wear in the brake liner. The difference between the initial reference reading and change in reading at subsequent braking is calculated by measuring the S cam

rotation angle information. The S-cam rotation is converted using a linear fit equation relationship to determine wear in the brake liner.
[0012] A voltage measured at an initial stage of setting the potentiometer sensor is considered as the initial reference reading during a brake engaged condition and at brake disengaged condition when a brake pedal is released so that the brake liner retracts to its original position. The potentiometer sensor reading for each braking application is recorded throughout the vehicle running cycle. A cumulative liner wear pattern is determined by synchronizing the liner wear, the brake performance, a trip time, a vehicle speed and a distance traveled with respect to time. The brake liner wear result is displayed and the driver is alerted for the brake liner replacement when the brake liner is consumed and crosses a usable threshold limit at different stages of the liner wear.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The disclosed embodiments may be better understood by referring to the figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.
[0014] FIG. 1 illustrates a perspective view of a pneumatic assisted drum brake system for a vehicle, in accordance with the present invention;
[0015] FIG. 2 illustrates a perspective view of a potentiometer sensor mounted in the brake system, in accordance with the present invention;
[0016] FIG. 3 illustrates a block diagram of an electrical circuit used to read, process and display the signal from the potentiometer sensor, in accordance with the present invention; and

[0017] FIG. 4 illustrates a flowchart of operation depicting a method for continuously monitoring the brake lining wear during the operation of the vehicle and indicating the brake liner replacement at different stages of the liner wear, in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.
[0019] In the following, numerous specific details are set forth to provide a thorough description of various embodiments. Certain embodiments may be practiced without these specific details or with some variations in detail. In some instances, certain features are described in less detail so as not to obscure other aspects. The level of detail associated with each of the elements or features should not be construed to qualify the novelty or importance of one feature over the others.
[0020] The claimed subject matter has been provided here with reference to one or more features or embodiments. Those skilled in the art will recognize and appreciate that, despite of the detailed nature of the exemplary embodiments provided here; changes and modifications may be applied to said embodiments without limiting or departing from the generally intended scope. These and various other adaptations and combinations of the embodiments provided here are within the scope of the disclosed subject matter as defined by the claims and their full set of equivalents. Like numbers refer to like elements throughout.
[0021] The present invention is a brake liner wear measurement and monitoring system and method for measuring and monitoring the brake liner wear throughout vehicle running duty cycle. The present invention involves the brake liner wear

measurement using a non - damageable and reusable sensor mounted at a defined location which is capable of accurately and efficiently monitoring the brake liner wear and does not intrude with the brake liner during braking. The sensor output is continuous and the brake liner displacement is directly proportional to an S-cam rotation, hence by tracking the S-cam rotation, displacement of brake liner can be determined.
[0022] FIG. 1 illustrates a perspective view of a pneumatic assisted drum brake system (10) for a vehicle, in accordance with the present invention. Note that in FIGS. 1-4, identical or similar blocks are indicated by identical reference numerals. The commercial vehicle braking system (10) includes a brake shoe (20), a brake liner (22), an S-cam (16) with a shaft (18), a slack adjuster (14), a return spring (24) and a pneumatic assisted brake chamber (12). In general, when a brake pedal is pressed by a driver, a distribution control valve directs air from an air-tank to the brake chamber (12) through a pneumatic circuit. The brake chamber (12) in-turn moves a push rod which is mechanically coupled to the slack adjuster (14).
[0023] The slack adjuster (14) then rotates the S-cam (16) which is connected by means of the shaft (18). The S-cam (16) when rotates, thrusts the brake shoe (20) fitted with the liner (22) to come in normal contact with the brake drum (28). Thus friction is developed between the static brake shoe (20) and the rotating brake drum (28) thereby reducing the speed of vehicle and brings the vehicle to halt eventually. The rotation of the S-cam shaft (18) causes the brake liner (22) to move proportionally and makes contact with the brake drum (28). Due to frictional contact between the liner (22) and brake drum (28) during braking, the liner (22) wears and the wear increases with several brake applications. The automatic slack adjuster (14) ensures and maintains constant gap between the liner (22) and the brake drum (28).
[0024] FIG. 2 illustrates a perspective view of a position of a potentiometer sensor (32) in the brake system (10), in accordance with the present invention. Note that the embodiments discussed herein are suitable for use on all vehicles which have

independent brakes for each wheel, such as vehicles which generally incorporate the air-brake system (10). The potentiometer sensor (32) is mounted on the S-cam shaft (18) to measure the S-cam (16) rotation. A threaded hole is made to mount an adapter (30) that holds a rotary shaft of the potentiometer sensor (32) along a center axis of the S-cam shaft (18) at the slack adjuster end (14). The rotary shaft of the potentiometer sensor (32) is then assembled to the adapter (30) which in-turn is mounted to the S¬cam shaft (18) by means of a fastener (34). A stationary part of the potentiometer sensor (32) is constrained from rotation by clamping it to a static part of an axle (36).
[0025] During each application of brake, the S-cam (16) rotates and in turn causes the brake liner (22) to displace until it makes contact with the brake drum (28). The rotating shaft of the potentiometer sensor (32) mounted to the S-cam shaft (18) rotates and this rotation movement of the potentiometer sensor (32) is used to measure rotation of the S cam (16). The rotational difference between the stationary and rotary of the potentiometer sensor (32) provides the rotation angle information (66). At initial stage of setting instrument and after the brake liner (22) clearance stabilizes, reference voltage of the potentiometer sensor (32) is recorded for a brake engaged or a disengaged condition respectively. The difference between the S cam rotation angle information (66) and initial reference reading of the potentiometer sensor (32) is determined to measure amount of wear in the brake liner (22). Calibration carried out and constant is obtained from a linear fit equation between the brake liner (22) wear and rotation of the S-cam shaft (18). The constant is used to convert readings of the potentiometer sensor (32) to the liner wear in metric unit. Thus the measured S-cam shaft (18) rotation is used to determine wear in the brake liner (22).
[0026] FIG. 3 illustrates a block diagram of an electrical circuit (50) used to read, process and display the signal from the potentiometer sensor (32), in accordance with the present invention. The output cables (52) from the potentiometer sensor (32) run through a vehicle chassis and connect to the electrical circuit (50) placed inside the vehicle cabin. In a preferred embodiment, the potentiometer sensor (32) is fitted to all the wheels of the vehicle, as indicated by arrow (53). All the sensors (32) are then

connected to the electric circuit (50) placed in the vehicle’s cabin. The electric circuit (50) includes a processor unit (56), a speed unit (58), a display unit (54), an amplification board (60) and a storage unit (62). The processor unit (56) provides excitation to the sensor (32), read the potentiometer sensor (32) output and display the results to the driver seated in the vehicle cabin via the display unit (54). In a preferred embodiment, the potentiometer sensor (32) is selected by considering the range of rotation angle of the S-cam shaft (18), measurable voltage output requirement and vibration withstanding capacity of the sensor (32). The processing unit (56) is designed based on the requirements of measurements and the selected sensor (32).
[0027] Upon fitment of the potentiometer sensor (32) and requisite electric circuit (50), the reference brake application is carried out with maximum air pressure in the vehicle brake unit. This reference braking causes the S-cam (16) to rotate which in-turn displaces the brake liner (22) to make contact with the brake drum (28). In the brake engaged condition, the voltage reading measured from the potentiometer sensor (32) is recorded and considered as the initial reference of engaged condition reading for wear assessment of the brake liner (22). Further, in the brake disengaged condition and when the brake pedal is released, the liner (22) retracts to its original position, the voltage reading measured from the potentiometer sensor (32) is recorded and considered as the initial reference reading of disengaged condition.
[0028] The number of brake applications increase with the increased vehicle distance covered. This causes the brake liner (22) to wear progressively. When the brake liner (22) starts to wear, the automatic slack adjuster (14) compensates the wear gap by rotating the S cam shaft (18) by certain degrees. By calculating the difference between the initial reference readings and change in reading at subsequent braking the amount of wear in brake liner (22) is determined in the brake engaged and brake disengaged conditions.
[0029] The speed unit (58) is coupled to the electric circuit (50) so that the wear in the brake liner (22), brake performance, trip time, vehicle speed and distance traveled shall be synchronized with respect to time. The speed unit (58) is used to

measure speed and distance information of the vehicle which is extracted from the GPS sensor or any other speed measuring device which is vehicle inbuilt or externally connected to vehicle. The wear in the brake liner (22) is mapped against distance to generate cumulative wear versus. distance travelled database. The brake performance also acquired during measurement in terms of brake time, deceleration, brake force, brake start speed and end speed. This information also provides the amount of energy consumed during braking. An alert unit (64) is placed in the cabin to alert the driver for replacement of the brake liner (22) when the brake liner (22) is consumed and crosses its usable threshold limit. The alert unit (64) is customized in such a way that the driver is alerted at different stages of the liner (22) wear. This will ensure that the vehicle operator is prepared for the brake liner (22) replacement in advance. The data recorded is stored using the storage unit (62) in the electric circuit (50). The data is post processed to serve as a rich data bank for development of the brake liners (22).
[0030] FIG. 4 illustrates a flowchart of operation depicting a method (70) for continuously monitoring the brake lining wear during the operation of the vehicle and to indicate whether the brake liner (22) require replacement, in accordance with the present invention. The rotary part of the potentiometer sensor (32) is assembled to the adapter (30) mounted on the S-cam shaft (18) of the vehicle brake unit along its center axis at end of the slack adjuster (14) to measure the rotation of the S-cam shaft (18), as shown at block (72). The stationary part of the potentiometer sensor (32) is clamped to the static part of the axle (36) in such a way that rotational difference between the stationary part and the rotary part provides S-cam rotation angle information (66), as indicated at block (74).
[0031] The initial reference readings of the potentiometer sensor (32) is recorded in a brake engaged condition or a brake disengaged condition at initial stage of setting the sensor (32) and after the brake liner (22) clearance stabilizes, as shown at block (76). The rotation of the S-cam (16) is converted using linear fit equation relationship to determine wear in the brake liner (22), as indicated at block (78). The difference between the S cam rotation angle information (66) and the initial reference

reading of potentiometer sensor (32) to measure amount of wear in the brake liner (22) is determined, as indicated at block (80). The potentiometer sensor (32) reading is recorded for each braking application throughout vehicle running cycle, as depicted at block (82).
[0032] The cumulative liner wear pattern is determined by synchronizing the liner wear, brake performance, trip time, vehicle speed and distance traveled with respect to time, as shown at block (84). The brake liner wear result is displayed to the driver, as indicated at block (86). The driver is alerted for the brake liner replacement when the brake liner (22) is consumed and crosses usable threshold limit at different stages of the liner wear, as depicted at block (88). The potentiometer sensor (32) in association with the electric circuit (50) continuously monitors the liner wear to determine its end usage life and take on-demand action for the liner replacement. This ensures safety of driver and commuters by eliminating the poor braking performance scenario arising out of complete liner wear.
[0033] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
[0034] As already mentioned, the foregoing description is illustrative of the invention and not the limitative to its scope, number of sensors for brake liner wear measurement, number of axles over which the sensors are mounted, type of the vehicle, because it will be apparent to persons skilled in the art to devise other alternative embodiments without departing from the broad ambit of the disclosures made herein.

WE CLAIM:
1. A brake liner wear measurement and monitoring system (10), comprising:
a potentiometer sensor (32) having:
a rotary part assembled to an adapter (30) and mounted on a S-cam shaft (18) of a vehicle brake unit along its center axis at the end of a slack adjuster (14) to measure rotation of the S-cam shaft (18);
a stationary part clamped to a static part of an axle (36) in such a way that a rotational difference between the stationary part and the rotary part provides an S-cam rotation angle information (66); and
an electric circuit (50) electrically connected to the potentiometer sensor (32) to receive the S-cam rotation angle information (66) for determining a difference between the rotation angle information (66) and an initial reference reading of the potentiometer sensor (32) to measure an amount of wear in a brake liner (22).
2. The system of claim 1, wherein the S-cam (16) rotates and in turn causes the brake liner (22) to displace during each application of a brake until the brake liner (22) makes contact with a brake drum (28) and the rotation of the S-cam (16) is measured using the potentiometer sensor (32).
3. The system of claim 1, wherein the rotation of the S-cam (16) is converted using a linear fit equation to determine the wear in the brake liner (22) by a processing unit (56).
4. The system of claim 1, wherein a voltage reading measured at an initial stage of setting the potentiometer sensor (32) is recorded and considered as the initial reference reading in a brake engaged condition.
5. The system of claim 1, wherein a voltage reading measured at the initial stage of setting the potentiometer sensor (32) is recorded and considered as the initial

reference reading in a brake disengaged condition when a brake pedal is released so that the brake liner (22) retracts to its original position.
6. The system of claim 1, wherein the electric circuit (50) further comprises:
a speed unit (58) to extract a speed and distance information of a vehicle to determine a cumulative liner wear pattern versus a vehicle travel distance; and
a storage unit (62) to record reading of the potentiometer sensor (32) for each braking application for continuous monitoring of the wear in the brake liner (22).
7. The system of claim 1, further comprising a display unit (54) for displaying the wear result in the brake liner (22) to a driver.
8. The system of claim 1, further comprising an alert unit (64) placed in the vehicle cabin to alert the driver for replacement of the brake liner (22) when the brake liner (22) is consumed and crosses a usable threshold limit.
9. A method (70) for measuring and monitoring wear of a brake liner (22), comprising:
measuring an S-cam rotation angle information (66) by determining a rotational difference between a stationary part and a rotary part of a potentiometer sensor (32) mounted to an S-cam shaft (18) of a vehicle brake unit; and
determining a difference between the S cam rotation angle information (66) and an initial reference reading of the potentiometer sensor (32) to measure an amount of wear in the brake liner (22).
10. The method of claim 9, further comprising:
calculating the difference between the initial reference reading and change in reading at subsequent braking by measuring the S cam rotation angle information (66); and
converting the S-cam rotation angle information (66) using a linear fit equation relationship to determine wear in the brake liner (22).

11. The method of claim 9, further comprising measuring a voltage at an initial stage of setting the potentiometer sensor (32) and considering the voltage as the initial reference reading during a brake engaged condition.
12. The method of claim 9, further comprising measuring a voltage at the initial stage of setting the potentiometer sensor (32) and considering the voltage as the initial reference reading during a brake disengaged condition when a brake pedal is released so that the brake liner (22) retracts to its original position.
13. The method of claim 9, further comprising storing the potentiometer sensor (32) reading for each braking application throughout the vehicle running cycle.
14. The method of claim 9, further comprising determining a cumulative liner wear pattern by synchronizing wear in the brake liner (22), the brake performance, a trip time, a vehicle speed and a distance traveled with respect to time.
15. The method of claim 9, further comprising displaying wear result in the brake liner (22) and alerting the driver for replacement of the brake liner (22) when the brake liner (22) is consumed and crosses a usable threshold limit at different stages of the liner wear.