VEHICLE CLUTCH LINER WEAR MEASUREMENT AND MONITORING
SYSTEM AND METHOD
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a vehicle monitoring system and more
particularly relates to a clutch liner wear measurement and monitoring system and method.
BACKGROUND OF THE INVENTION
[0002] A clutch is a mechanical device which engages and disengages power transmission especially from a driving shaft to a driven shaft. The clutch includes a clutch liner that is composed of a high friction material and fits between a pressure plate and a flywheel. When the clutch is released, powerful springs in the pressure plate force the clutch linier against the flywheel ensuring a slip free connection between an engine and transmission. Study of the clutch 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 clutch liner products in real field conditions of the vehicle is necessary to develop better clutch liners.
[0003] Various clutch liner wear detection systems are utilized for detecting the clutch liner wear. Such prior art systems involves the clutch liner wear measurement using a sensor that intrude with the liner. For example, the measurement sensors are either placed inside a master and slave cylinder or within clutch housing. Thus, it is imperative that, the clutch assembly has to be either completely or partly dismantled for retro fitment or repair of the clutch linear measurement system mentioned in prior arts. Also, such prior art systems provide binary information regarding the clutch liner wear since the system needs the clutch wear to reach a predetermined limit to give an output. Such system cannot provide information about the degree of wear at any given point of time. Additionally, such approaches do not reliably detect the

comparatively small wear displacement, produce inaccurate results and are not readily adaptable to the wide variety of heavy vehicles. The prior art sensors only provide a warning signal when the particular predetermined wear condition has been achieved.
[0004] Hence, there is a need for an improved clutch liner wear measurement and monitoring system during the operation of the vehicle that does not intrude with the vehicle 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 clutch liner wear measurement and monitoring system for a vehicle which is capable of accurately and continuously monitoring the clutch liner wear and does not intrude with vehicle performance.
[0007] It is another aspect of the present invention to provide an improved
clutch liner wear measurement system having a non - damageable and reusable sensor mounted at a defined location apart from the clutch assembly for easy fitment and repair of the clutch liner wear measurement system.
[0008] It is further aspect of the present invention to provide an improved
method for continuously monitoring the clutch liner wear during operation of the vehicle and indicating the clutch liner condition at different stages of the liner wear so that clutch liner is replaced at appropriate time.

[0009] In one aspect of the present invention, the clutch liner wear
measurement and monitoring system, includes a potentiometer sensor having a stationary part clamped to clutch housing and a rotary part assembled to an adapter which in-turn is mounted on a rocker shaft along its center axis at an externally exposed end. The sensor continuously sense and measure an angular position of the rocker shaft for each engagement and disengagement of a clutch disc. The system further includes an electric circuit electrically connected to the potentiometer sensor to receive the angular position of the rocker shaft. The electric circuit determines a relative difference between the angular position and an initial reference position measured by the potentiometer sensor to determine an amount of wear in a clutch liner.
[0010] The rocker shaft rotates and in turn pushes a throw-out bearing by
means of a fork and causes the clutch liner to displace away from a flywheel during each application of clutch and when a clutch pedal is released, the clutch disc makes contact with the flywheel securely aided by a spring force. The electric circuit further includes a processing unit to derive rotation of the rocker shaft using a voltage reading measured by the potentiometer sensor and a linear fit equation relationship to determine the wear in the clutch liner. A storage unit records the voltage reading of the potentiometer sensor for each engagement and disengagement of the clutch disc for continuous monitoring of the wear in the clutch liner. The voltage reading measured at an initial stage of setting the potentiometer sensor during first clutch disc engagement and disengagement operation is recorded and considered as the initial reference position of the rocker shaft and saved to the storage unit as a preset value.
[0011] The relative difference in the angular position of the rocker shaft
between the preset value and current position at successive clutch disc engagement and disengagement is measured by the potentiometer sensor and multiplied by a calibration factor to determine the clutch liner wear. The potentiometer sensor measures the rocker shaft position for each clutch disc engagement and disengagement throughout the vehicle duty cycle and the wear status of the clutch liner at any point of time is extracted from the voltage reading. A display unit is used

for displaying the wear result in the clutch liner to a driver. An alert unit is placed in the vehicle cabin to alert the driver for replacement of the clutch liner when the clutch liner is consumed and crosses a usable threshold limit.
[0012] In another aspect of the present invention, the angular position of the
rocker shaft for each engagement and disengagement of the clutch disc is determined by the potentiometer sensor mounted to the rocker shaft at the externally exposed end. The relative difference between the angular position of the rocker shaft and the initial reference position measured by the potentiometer sensor is determined to measure the amount of wear in the clutch liner. A voltage reading measured at an initial stage of setting the potentiometer sensor during first clutch engagement and disengagement operation is recorded as the initial reference position and stored as the preset value. The relative difference in the angular position of the rocker shaft between the preset value and current position at successive clutch engagement and disengagement is determined and the relative difference is multiplied the calibration factor to determine the clutch liner wear.
[0013] The rotation of the rocker shaft measured by the potentiometer sensor is
converted using the linear fit equation relationship to determine wear in the clutch liner. The potentiometer reading for each clutch engagement and disengagement operation is stored throughout the vehicle running cycle and change in position of the rocker shaft during subsequent clutch events is assessed to extract the wear status of the clutch liner at any given point of time from the reading. A cumulative liner wear pattern versus a vehicle travel distance is established by determining the continuous liner wear against each clutch engagement and disengagement instance over a time period. The wear result in the clutch liner is displayed and the driver is alerted for replacement of the clutch liner when the clutch liner is consumed and crosses a usable threshold limit at different stages of the liner wear.

[0014] 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.
[0015] FIG. 1 illustrates a perspective view of a clutch assembly and a
potentiometer sensor mounted on a rocker shaft for measuring a clutch liner wear, in accordance with the present invention;
[0016] FIG. 2 illustrates another perspective view of the clutch assembly, in
accordance with the present invention;
[0017] FIG. 3 illustrates a block diagram of an electric circuit used to read,
process and display the signal from the potentiometer sensor, in accordance with the present invention; and
[0018] FIG. 4 illustrates a flowchart of operation depicting a method for
continuously monitoring the clutch liner wear during operation of the vehicle and indicating the clutch liner condition at different stages of the liner wear to replace the clutch liner at appropriate time, in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] 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.
[0020] 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.
[0021] 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.
[0022] The present invention is a clutch liner wear measurement and monitoring system and method which is capable of accurately and efficiently monitoring the clutch liner wear throughout vehicle running duty cycle. The present invention involves the clutch liner wear measurement using a non - damageable and reusable sensor mounted at a defined location for easy retro-fitment or repair of the sensor without disturbing the clutch assembly. The sensor output is continuous and the clutch liner displacement is directly proportional to the rocker shaft rotation, hence by tracking the rocker shaft rotation, displacement of clutch liner can be determined. The clutch liner wear measurement and monitoring system is easily adaptable to wide variety of heavy vehicles and does not directly intrude with any of the clutch assembly parts.
[0023] FIG. 1 illustrates a perspective view of a clutch assembly (10) and a potentiometer sensor (22) mounted on a rocker shaft (24) for measuring wear in a clutch liner (40), in accordance with the present invention. Note that in FIGS. 1-4, identical or similar blocks are indicated by identical reference numerals. In general, the clutch assembly (10) includes a master cylinder (not shown) located adjacent to a clutch pedal (not shown), a slave cylinder (12) located adjacent to a clutch housing

(16). Master and slave cylinders are connected by hydraulic tubes. When the clutch pedal is pressed, the master cylinder drives the slave cylinder (12) which in turn rotates the rocker shaft (24). The rocker shaft (24) then moves a throw out fork (14) which in-turn push a throw-out bearing (20) against a spider spring to disengage a clutch disc (42) from the flywheel (18).
[0024] A pressure plate (46) is attached to the flywheel (18) and the clutch disc (42) is located between the flywheel (18) and the pressure plate (46). The clutch disc (42) is splined to an input shaft (26) extending from a transmission (28) to the flywheel (18). When the clutch disc (42) and the pressure plate (46) are locked together by friction, the input shaft (26) rotates with an engine (44) crankshaft. Power is transferred from the engine (44) to the transmission (28), where it is routed through different gear ratios to obtain the best speed and power to start and keep the vehicle moving. The input shaft (26) transmits power from the flywheel (18) after the clutch disc (42) is engaged through the transmission (28) and to a rear axle.
[0025] The potentiometer sensor (22) includes a stationary part clamped to the clutch housing (16) via a clamp (27) by means of a fixture and is constrained from rotation. A rotary part of the potentiometer sensor (22) is assembled to an adapter (25) which in-turn is mounted on the rocker shaft (24) along its center axis at an externally exposed end by means of a fastener, as shown in FIG. 2. The potentiometer sensor (22) measures an angular position of the rocker shaft (24) for each engagement and disengagement of the clutch disc (42). The potentiometer sensor (22) is selected by considering the range of rocker shaft (24) rotation angle and measurable voltage output requirement. The rocker shaft (24) actuates the throw-out fork (14) which in turn disengages or disengages the clutch disc (42) from the flywheel (18). During each application of the clutch, the rocker shaft (24) rotates, which pushes the throw-out bearing (20) by means of the fork (14) which causes the clutch disc (42) to displace away from the flywheel (18). When the clutch is released, the clutch disc (42) makes contact with the flywheel (18) securely aided by the spring force. The rocker shaft (24) rotation is measured using the potentiometer sensor (22) mounted on the rocker shaft (24).

[0026] FIG. 3 illustrates a block diagram of an electric circuit (50) used to read, process and display the signal from the potentiometer sensor (22), in accordance with the present invention. The output cables (23) from the potentiometer sensor (22) run through a vehicle chassis and connect to the electric circuit (50) placed inside the vehicle cabin. The potentiometer sensor (22) is connected to the electric circuit (50) placed in the vehicle’s cabin. The electric circuit (50) includes a processing unit (34), a display unit (32), an amplification board (36) and a storage unit (38). The processor unit (34) provides excitation to the sensor (22), read the potentiometer sensor (22) output and display the results to the driver seated in the vehicle cabin via the display unit (32). In a preferred embodiment, the processing unit (34) is designed based on the requirements of measurements and the selected sensor (22). The electric circuit (50) electrically connected to the potentiometer sensor (22) continuously receives output from the potentiometer sensor (22) for determining a relative difference between the angular position of the rocker shaft (24) and an initial reference position of the rocker shaft (24) measured by the potentiometer sensor (22) to measure an amount of wear in the clutch liner (40).
[0027] After instrumentation, a zero or starting position of the clutch assembly (10) is determined at the first clutch engagement and disengagement operation and measured using the potentiometer (22). The zero position voltage is then saved to the storage unit (38) as a preset value. When the liner (40) starts to wear progressively, the angular position of the rocker shaft (24) shift from its initial set position by certain degrees to compensate wear in the clutch liner (40). All the successive engagements/disengagement of the clutch disc (42) is recorded and its displacement is compared against the preset value. This relative difference in angular position between the preset value and current position is accurately captured by the potentiometer sensor (22) which in turn gives wear in the clutch liner (40). The potentiometer sensor (22) reading for each engagement/disengagement of the clutch disc (42) is recorded throughout the vehicle duty cycle. Thus, the change of position in the rocker shaft (24) during the subsequent clutch events is assessed and wear status of the clutch liner (40) at any given point of time is extracted from the reading.

[0028] The wear in the clutch liner (40) is mapped against distance to generate cumulative wear versus. distance travelled database. An alert unit (48) is placed in the cabin to alert the driver for replacement of the clutch liner (40) when the clutch liner (40) is consumed and crosses its usable threshold limit. The alert unit (48) is customized in such a way that the driver is alerted at different stages of the liner (40) wear. This will ensure that the vehicle operator is prepared for the clutch liner (40) replacement in advance. The data recorded is stored using the storage unit (38) in the electric circuit (50). The data is post processed to serve as a rich data bank for development of the clutch liners (40).
[0029] FIG. 4 illustrates a flowchart of operation depicting a method (80) for
continuously monitoring the wear in the clutch liner (40) during the operation of the vehicle and indicating condition of the clutch liner (40) at different stages of the liner wear so that replacement of the clutch liner (40) is done at appropriate time., in accordance with the present invention. The rotary part of potentiometer sensor (22) is assembled to the adapter (25) mounted on the rocker shaft (24) along its center axis at externally exposed end to measure angular position of the rocker shaft (24) for each engagement and disengagement of the clutch disc (42), as shown at block (82). The stationary part of the potentiometer sensor (22) is clamped to the clutch housing (16) via the clamp (27), as indicated at block (84). The voltage reading measured at initial stage of setting the potentiometer sensor (22) during first clutch engagement and disengagement operation is recorded as preset value, as indicated at block (86). The rotation of the rocker shaft (24) measured by the potentiometer sensor (22) is converted using linear fit equation relationship, as depicted at block (88).
[0030] The relative difference in angular position of the rocker shaft (24)
between the preset value and current position at successive engagement and disengagement of the clutch disc (42) is determined, as shown at block (90). The relative difference is multiplied by the calibration factor to determine wear in the clutch liner (40), as shown at block (92). The reading of the potentiometer sensor (22) for each engagement and disengagement of the clutch disc (42) is stored throughout

vehicle running cycle, as depicted at block (94). The clutch liner (40) wear result is displayed to the driver, as indicated at block (96). The driver is alerted for replacement of the clutch liner (40) when the clutch liner (40) is consumed and crosses usable threshold limit at different stages of liner wear, as shown at block (98).
[0031] The reading of the potentiometer sensor (22) for each engagement and
disengagement operation of the clutch disc (42) is stored throughout the vehicle running cycle and change in position of the rocker shaft (24) during subsequent clutch events is assessed to extract the wear status of the clutch liner (40) at any given point of time from the reading. The cumulative liner wear pattern versus a vehicle travel distance is established by determining the continuous wear in the clutch liner (40) against each clutch engagement and disengagement instance over a time period. The potentiometer sensor (22) in association with the electric circuit (50) continuously monitors the wear in the clutch liner (40) to determine its end usage life and take on-demand action for replacement of the clutch liner (40). This ensures safety of driver and commuters by eliminating the poor clutch performance scenario arising out of complete wear in the clutch liner (40). The present invention involves measurement of wear in the clutch liner (40) using the sensor (22) that doesn’t intrude with the clutch system assembly (10) or functioning. The output of the sensor (22) is continuous rather than depending on the wear limits of the liner (40) to be reached.
[0032] 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.

WE CLAIM:
1. A clutch liner wear measurement and monitoring system, comprising:
a potentiometer sensor (22) having a stationary part clamped to a clutch housing (16) and a rotary part assembled to an adapter (25) which in-turn is mounted on a rocker shaft (24) along its center axis at an externally exposed end to continuously sense and measure an angular position of the rocker shaft (24) for each engagement and disengagement of a clutch disc (42); and
an electric circuit (50) electrically connected to the potentiometer sensor (22) to receive the angular position of the rocker shaft (24) for determining a relative difference between the angular position and an initial reference position measured by the potentiometer sensor (22) to determine an amount of wear in a clutch liner (40).
2. The system of claim 1, wherein the rocker shaft (24) rotates and in turn pushes a throw-out bearing (20) by means of a fork (14) and causes the clutch liner (40) to displace away from a flywheel (18) during each application of clutch and when a clutch pedal is released, the clutch disc (42) makes contact with the flywheel (18) securely aided by a spring force.
3. The system of claim 1, wherein the electric circuit (50) further comprises:
a processing unit (34) to derive rotation of the rocker shaft (24) using a voltage reading measured by the potentiometer sensor (22) and a linear fit equation relationship to determine the wear in the clutch liner (40); and
a storage unit (38) to record the voltage reading of the potentiometer sensor (22) for each engagement and disengagement of the clutch disc (42) for continuous monitoring of wear in the clutch liner (40).
4. The system of claim 1, wherein the voltage reading measured at an initial stage
of setting the potentiometer sensor (22) during first clutch engagement and
disengagement operation is recorded and considered as the initial reference position of
the rocker shaft (24) and stored as a preset value.

5. The system of claims 1 and 4, wherein the relative difference in the angular position of the rocker shaft (24) between the preset value and current position at successive engagement and disengagement of the clutch disc (42) is measured by the potentiometer sensor (22) and multiplied by a calibration factor to determine the wear in the clutch liner (40).
6. The system of claim 1, wherein the potentiometer sensor (22) measures position the rocker shaft (24) for each engagement and disengagement of the clutch disc (42) throughout the vehicle duty cycle and the wear status of the clutch liner (40) at any point of time is extracted from the voltage reading.
7. The system of claim 1, further comprising a display unit (32) for displaying the wear result in the clutch liner (40) to a driver.
8. The system of claim 1, further comprising an alert unit (48) placed in the vehicle cabin to alert the driver for replacement of the clutch liner (40) when the clutch liner (40) is consumed and crosses a usable threshold limit.
9. A method (80) for measuring and monitoring wear of a clutch liner (40), comprising:
continuously sensing and measuring an angular position of a rocker shaft (24) for each engagement and disengagement of a clutch disc (42) by a potentiometer sensor (22) assembled to an adapter (25) which in-turn is mounted to the rocker shaft (24) at an externally exposed end; and
determining a relative difference between the angular position of the rocker shaft (24) and an initial reference position measured by the potentiometer sensor (22) to measure an amount of wear in the clutch liner (40).
10. The method of claim 9, further comprising:
recording a voltage reading measured at an initial stage of setting the potentiometer sensor (22) during first clutch engagement and disengagement

operation as the initial reference position and storing the reference position as a preset value;
determining the relative difference in the angular position of the rocker shaft (24) between the preset value and current position at successive engagement and disengagement of the clutch disc (42); and
multiplying the relative difference by a calibration factor to determine wear in the clutch liner (40).
11. The method of claim 9, further comprising converting rotation of the rocker shaft (24) measured by the potentiometer sensor (22) using a linear fit equation relationship to determine wear in the clutch liner (40).
12. The method of claim 9, further comprising storing the voltage reading of the potentiometer sensor (22) for each engagement and disengagement of the clutch disc (42) throughout the vehicle running cycle and assessing change in position of the rocker shaft (24) during subsequent clutch events to extract the wear status of the clutch liner (40) at any given point of time from the voltage reading.
13. The method of claim 9, further comprising establishing a cumulative liner wear pattern versus a vehicle travel distance by determining the continuous wear in the clutch liner (40) against each engagement and disengagement of the clutch disc (42) over a time period.
14. The method of claim 9, further comprising displaying wear result of the clutch liner (40) and alerting the driver for replacement of the clutch liner (40) when the clutch liner (40) is consumed and crosses a usable threshold limit at different stages of wear in the clutch liner (40).