| CPC B60T 17/221 (2013.01) [B60T 1/065 (2013.01); B60T 13/148 (2013.01); B60T 13/58 (2013.01); B60T 13/686 (2013.01); F16D 55/226 (2013.01); F16D 65/74 (2013.01); F16D 66/027 (2013.01); F16D 66/028 (2013.01); B60T 7/042 (2013.01); B60T 7/12 (2013.01); B60T 2270/406 (2013.01); B60T 2270/82 (2013.01); B60T 2270/88 (2013.01); F16D 2121/04 (2013.01); F16D 2125/08 (2013.01); F16D 2125/10 (2013.01)] | 8 Claims |
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1. A method of detecting a degree of pad wear of a brake pad of a hydraulic brake including the brake pad, a brake rotor, and a caliper housing at least partially enclosing the brake pad and brake rotor for relative longitudinal motion therebetween, the caliper housing defining a caliper cavity in selective fluid communication with a reservoir of brake fluid and with a source of pressurized hydraulic fluid via a caliper passage, the method comprising:
providing a hydraulic brake wear detection apparatus including
a caliper piston located at least partially within the caliper cavity and attached to a first side of the brake pad, the caliper piston including a piston cavity extending from a caliper piston rim into a caliper piston body at a location longitudinally opposite, and spaced from, the brake pad, and
an internal piston located at least partially within the piston cavity and entirely enclosed in an internal space defined cooperatively by the piston cavity and the caliper cavity;
interposing a normally open venting valve in the caliper passage hydraulically between the reservoir and both the source of pressurized hydraulic fluid and the caliper cavity;
moving the caliper piston reciprocally longitudinally with respect to the brake rotor to selectively place a second side of the brake pad, longitudinally opposite the first side of the brake pad, into contact with the brake rotor to provide a braking action thereto during a normal non-failure braking mode of operation;
moving the internal piston reciprocally longitudinally with respect to the internal space via a predetermined volume of pressurized hydraulic fluid responsive to wear of the brake pad;
selectively closing the normally open venting valve to isolate the predetermined volume of pressurized hydraulic fluid from the reservoir of brake fluid and thus provide a closed hydraulic loop between the source of pressurized hydraulic fluid and the caliper cavity to place the hydraulic brake wear detection apparatus into a detection mode of operation at least partially having the brake pad advanced into contact with the brake rotor;
with the hydraulic brake wear detection apparatus in the detection mode of operation, retracting the internal piston longitudinally away from the brake rotor into a detection piston position by providing negatively pressurized hydraulic fluid to the caliper cavity;
with the hydraulic brake wear detection apparatus in the detection mode of operation, rebalancing the negatively pressurized hydraulic fluid within the caliper cavity to a neutral level;
with the hydraulic brake wear detection apparatus in the detection mode of operation, advancing the internal piston longitudinally toward the brake rotor and out of the detection piston position by providing the predetermined volume of pressurized hydraulic fluid to the internal space;
after the predetermined volume of volume of pressurized hydraulic fluid is in the internal space, returning the hydraulic brake wear detection apparatus to a service mode of operation; and
determining, responsive to the predetermined volume of pressurized hydraulic fluid provided to the internal space with the hydraulic brake wear detection apparatus in the detection mode of operation, a pad wear status of the brake pad.
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