Electronic brake pad wear indicator unit in disc brake system of vehicle
FIELD OF INVENTION
[001] This invention relates to electronic brake pad wear indicator 5 unit in disc brake system of vehicle. The indicator operates through indirect sensing and is non-destructive type.
BACKGROUND/PRIOR ART
[002] Generally two types of brake, namely disc and drum brake are 10 employed. Drum brake has been suggested in the automobile industry prior to disc brake. Generally, Front wheels are connected with disc brake and rear wheels are connected with disc/drum brake.
[003] Brake systems are employed in various types of vehicles such 15 as automobiles and aircraft to slow and subsequently stop vehicles. A brake system that is used in an automobile typically employs high friction brake pads so as to prevent rotation of the rotors. When a braking force is desired, each pad is moved into engagement with a rotor that is typically in the form of a disc. Specifically, a caliper 20 assembly of the brake system squeezes the rotor between a pair of pads.
[004] The pads are typically made of a composite material and the rotor is typically made of metal. The friction between the non-rotating 25 pads and the rotor provides the braking force. The friction surface of
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each pad and some part of Disc is gradually worn away until the pad is consumed and therefore must be replaced.
[005] Naturally, replacement of pads within a vehicle braking system is a periodic necessity. Failure to replace pads in a timely manner 5 may result in damage to the rotor or other components within the brake system and ineffective braking. Typically, repair expense to correct damage to the rotor or other brake system structure is greater than the cost of timely pad replacement.
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[006] Hence, brake pad wear indicator was introduced in automobile industry so as to give indication in respect of brake pad wear to user.
[007] Some indicators are currently available in the art applicable to four wheelers which can be discussed hereinbelow. 15
[008] Direct sensing type indicator in disc brake system constitutes mechanical indicator, in the form of a lug. Here, one type of disc brake comprises a caliper comprising of housing, carrier and a pair of pads. The pads rest against the carrier and housed inside housing of 20 caliper. A disc is sandwiched between the pads. The disc is connected with wheel of vehicle.
[009] The pad is having wear out surface of friction material in contact with the disc. During periodic loading, the pad wears out 25 leading to contact of the disc with the indicator thereby creating noise and affecting braking action.
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[0010] A lug forms said indicator provided with the pad. The Lug (L) as illustrated in the figure 1 is having an L-section.
[0011] The disadvantages associated with the above can be listed hereinbelow:- 5
- Creation of noise which may be ignored by the driver.
- Indicator needs to be replaced together with pad.
- May damage the disc.
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[0012] Another prior art suggests electronic indicator, in which said lug (L) as described above is substituted by an electronic part. However, the drawbacks of this art are as follows:-
- Indicator is required to be replaced alongwith pad incase of 15 wear out of the pad.
- High maintenance cost.
[0013] Now, reference may be made to the following publications:-
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[0014] A disclosure has been made regarding proximity sensor for detection of wear in a brake disc stack on an aircraft comprising of a wear pin, which moves in a particular direction when the brake disc stack wears and a switch for measuring said movement of the wear pin. When the wear pin moves to a predetermined position, the 25 switch signals that the brake disc stack has worn a predetermined amount.
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[0015] The above technology is particularly meant for aircraft disc brakes consisting of multitude of rotors and stators. It uses extra part for wear indication (wear pin).
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[0016] In the above technology, Wear condition is only checked with pads in pressed condition. Wear pin is in direct contact with disc and using direct measurement.
[0017] Another known technology is directed to brake pad wear 10 sensing system for four wheeler disc brakes comprising of a magnet and a hall effect sensor. There is provision of means for mounting said magnet and sensor at appropriate location, so that the system signals pad wear.
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[0018] The above is dedicated for fixed opposed piston type caliper. The hall effect sensor is placed on the caliper head and magnet on the brake pad. It uses direct sensing for wear indication. (Direct sensing refers to, either of the sensor or actuator in contact with the Pads.) Further, drawback is that wear indicator is replaced every time 20 the pad is replaced as the indicator is mounted on the pad.
[0019] In view of the above, it is required to introduce electronic brake pad wear indicator in disc brake system of vehicle which can obviate prior issues and serve the purpose efficiently. 25
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OBJECTS OF THE INVENTION
[0020] An object of the invention is to propose electronic brake pad wear indicator unit in disc brake system of vehicle which overcomes shortcomings of known art(s). 5
[0021] Another object of the invention is to propose electronic brake pad wear indicator unit in disc brake system of vehicle which is simple in construction and gives clear indication of pad worn out condition to driver. 10
[0022] Still another object of the invention is to propose electronic brake pad wear indicator unit in disc brake system of vehicle which is not required to be replaced with pad and hence can be used multiple times for detection. 15
[0023] Further object of the invention is to propose electronic brake pad wear indicator unit in disc brake system of vehicle which does not create undesirable noise and prevents disc damage.
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SUMMARY OF INVENTION
[0024] According to this invention, there is provided an electronic brake pad wear indicator unit in disc brake system of vehicle wherein 25 caliper assembly of the disc brake system includes a pair of brake pads resting against carrier and housed inside housing of caliper with a disc therebetween, in which the indicator unit comprising a sensor mounted on carrier/housing and an actuator placed on
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housing/carrier of caliper assembly, in which the sensor is actuated upon variation of relative distance between said carrier and housing.
[0025] A reed switch forms the sensor and magnet constitutes the actuator. The reed switch and magnet are mounted on the 5 carrier/housing by means of brackets and/or screws.
[0026] The configuration of the magnet and switch are subjected to change according to the required gap therebetween.
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[0027] The reed switch is actuated by magnetic field of magnet when the change in distance between the switch and magnet is greater than the predetermined value.
[0028] The sensor is connected to a controller, which is provided in 15 connection with an indicator. The indicator includes a telltale/audio signal in the instrument panel.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
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[0029] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of exemplary embodiments of invention and wherein:
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Fig. 1 shows: Mechanical brake pad wear indicator in disc brake system of vehicle according to the prior art.
Fig. 2 shows: Caliper assembly of present invention.
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Fig. 3 shows: Electronic brake pad wear indicator in disc brake system of vehicle in accordance with the present invention.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE 5 TO THE ACCOMPANYING DRAWINGS:
[0030] The invention pertains to electronic brake pad wear indicator in disc brake system of vehicle.
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[0031] The brake system of invention includes a caliper assembly comprising of housing (1), carrier (2) and a pair of brake pads (6,7) as illustrated in fig. 1 and 2. The pads rest against the carrier and are accommodated inside the housing.
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[0032] The pair of brake pads consists of brake pad inboard (6)and brake pad outboard (7) as shown.
[0033] With the wear of the pad, the housing moves inward in width direction of the vehicle. This results in variation of relative distance 20 between said carrier and housing.
[0034] Hence, the present invention proposes an electronic brake pad wear indicator which can indirectly measure wear of the pad relying on the variation in the gap between the carrier and housing. 25
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[0035] According to the present invention, for which reference may be made to fig. 2. The indicator unit includes a reed switch (3) and a magnet (4).
[0036] The reed switch (3) is mounted on carrier and magnet (4) is 5 mounted on housing.
[0037] Alternatively, reed switch is placed on housing and the magnet is placed on the carrier.
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[0038] Said mounting is carried out through a bracket which is secured to the surface of the housing/carrier.
[0039] The magnet emits a magnetic field that permeates space adjacent to the magnet. The sensor detects the portion of magnetic 15 field that is imposed upon the sensor switch. The portion of the magnetic field that is imposed upon the sensor switch is dependent upon the gap between housing and carrier.
[0040] The reed switch is operational by means of magnet, wherein 20 said reed switch constitutes a open/close circuit that closes/opens respectively when affected by a magnetic field.
[0041] A controller of the brake pad wear sensing system is operatively connected to the sensor. In response to the magnetic field, the sensor 25 switch outputs an electric signal to the controller. The controller processes information conveyed via the electric signal and determines whether the associated brake pad is sufficiently worn to merit
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replacement relying on the variation in the gap. Said indicator is operatively connected to the controller. The controller can be a separate controller or part of any existing controller in vehicle.
[0042] Thus, the indicator is triggered by the controller when the 5 predetermined gap between the switch and magnet varies and value of change in gap exceeds a certain predetermined value.
[0043] The configuration of the magnet and switch can be varied according to the required gap therebetween. 10
[0044] Initially, in one embodiment of invention, the magnet is present in proximity to the sensor by maintaining the predetermined gap therebetween. Thus, the connection in the sensor is closed and therefore the indication light in instrument panel is switched off. As 15 the brake pads wear out, the housing moves inward. When the predetermined distance between the carrier and housing changes, the sensor is open by getting detached from the actuator magnetic field. So that, the circuit of the sensor gets disconnected. As a result the indication light glows alarming the driver that the brake pads 20 have worn out.
[0045] Thus the signal from said sensor (reed switch) is indicative of pad wear. The magnet creates a magnetic field, the change of which is sensed by the sensor. Said sensor outputs an electrical signal 25 indicative of the change of the sensed magnetic field. The signal is generated if the change in magnetic field is greater than a predetermined value.
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[0046] As the indicator is not mounted on the brake pads, therefore it needs not to be replaced every time the pads are renewed. Thus, the indicator can be employed multiple times of pad wear, which in turn results in longer life span of the indicator.
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[0047] In addition to the above, the indicator system does not create any undesirable noise upon activation thereof unlike mechanical indicator system.
[0048] Instead light glows in the instrument panel. Thus, it is easily 10 recognizable to the driver and gives rise a premium feeling as well.
[0049] As the indicator is not mounted on the pad, therefore can’t establish contact with the disc. Hence, it does not involve any chance of damage to the disc. 15
[0050] The advantageous features of the invention can be briefly summarized hereinbelow:
- Longer life span of sensor system. 20
- Noise free
- Easily recognizable to the driver regarding wear of brake pad
- Avoids damage to disc.
- No requirement of changing the sensor system with the replacement of the pad. 25
[001] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art.
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Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM:
1. Electronic brake pad wear indicator unit in disc brake system of vehicle wherein caliper assembly of the disc brake system includes a pair of brake pads resting against carrier and housed inside housing of caliper with a disc therebetween, in 5 which the indicator unit comprising a sensor mounted on carrier/housing and an actuator placed on housing/carrier of caliper assembly, in which the sensor is actuated upon variation of relative distance between said carrier and housing.
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2. Electronic brake pad wear indicator unit in disc brake system of vehicle as claimed in claim 1 wherein reed switch forms the sensor and magnet constitutes the actuator.
3. Electronic brake pad wear indicator unit in disc brake system 15 of vehicle as claimed in claim 1 or 2 wherein the reed switch and magnet are mounted on the carrier/housing by means of a respective bracket and/or fasteners.
4. Electronic brake pad wear indicator unit in disc brake system 20 of vehicle as claimed in any of the preceding claims wherein the magnet and switch, configuration of which can be varied according to the required gap therebetween.
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5. Electronic brake pad wear indicator unit in disc brake system of vehicle as claimed in any of the preceding claims wherein the reed switch is actuated by magnetic field of magnet when the change in gap between the switch and magnet is greater than the predetermined value. 5
6. Electronic brake pad wear indicator unit in disc brake system of vehicle as claimed in any of the preceding claims wherein the indicator operates through indirect sensing method, in which sensor and actuator are provided to measure distance travelled 10 by said housing, which indicates pad wear.
7. Electronic brake pad wear indicator unit in disc brake system of vehicle as claimed in any of the preceding claims wherein the sensor is connected to a controller, which is provided in 15 connection with the indicator.
8. Electronic brake pad wear indicator unit in disc brake system of vehicle as claimed in claim 6 wherein the indicator includes a telltale/audio signal in the instrument panel. 20
9. Electronic brake pad wear indicator unit in disc brake system of vehicle as claimed in any of the preceding claims is associated with the advantageous features such as herein described. 25
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10. Electronic brake pad wear indicator unit in disc brake system of vehicle substantially as herein described with reference to the accompanying drawings.