# US 11,077,838 B2 · Technique for determining a wear valve, which indicates wear of a friction lining of a vehicle brake > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,077,838 B2 - Document ID: US11077838B2 - Status: Granted - Kind: B2 - Application number: 16/437,786 - Filed: 2019-06-11 - Published: 2019-12-19 - Granted: 2021-08-03 - Earliest claimed: 2018-06-19 - Assignees: ZF Active Safety GmbH - Applicants: ZF Active Safety GmbH - Inventors: Erwin Michels; Benedikt Ohlig; Michael Bast; Matthias Fuchs - Web page: https://patentgrep.com/patent/US11077838B2 ## CPC - B60T 17/221: {Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems (hydraulic pressure systems in general F15B19/00, F15B21/04; testing structures or apparatus G01M)} - B60T 1/065: {employing disc (B60T1/062 takes precedence)} - B60T 13/662: {characterised by specified functions of the control system components} - F16D 55/226: in which the common actuating member is moved axially {, e.g. floating caliper disc brakes} - F16D 65/183: {with force-transmitting members arranged side by side acting on a spot type force-applying member} - F16D 66/021: {using electrical detection or indication means} - F16D 66/022: {indicating that a lining is worn to minimum allowable thickness} - F16D 2066/006: {without direct measurement of the quantity monitored, e.g. wear or temperature calculated form force and duration of braking} - F16D 2121/04: acting on a piston-type actuator, e.g. for liquid pressure - F16D 2121/24: using motors - B60T: VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL (electrodynamic brake systems for vehicle, in general B60L; brakes per se, i.e. devices where braking effect occurs, including ultimate brake actuators, F16D); ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES ## Abstract The present disclosure relates to a method for operating a vehicle brake system which includes the following steps: (1) determining a first wear value, which indicates wear of the friction lining of the vehicle brake, by taking into account at least one of the relevant parameters related to the operational history of the vehicle; (2) In dependence upon whether the first wear value meets a predetermined criterion, measuring the wear of the friction lining by moving the parking brake unit and by recording the curve of operating parameters of the parking brake unit while moving; (3) determining, based on the measurement, a second wear value, which indicates wear of the friction lining of the vehicle brake. The present disclosure also relates to a vehicle braking system, as well as a computer program and a control unit for implementing the method. ## Claims ### Claim 1 A method for operating a vehicle brake system of a vehicle, wherein the vehicle brake system comprises at least one vehicle brake, wherein the vehicle brake includes a service brake having an actuating piston which, in order to generate a braking force by the action of a hydraulic pressure, is movable into an operating position, in which the actuating piston presses a friction lining against a rotating brake disc, and wherein the vehicle brake further comprises a parking brake unit, that is designed to apply a braking force acting on the brake disc, characterized in that it is supported against the actuating piston to press the friction lining against the brake disc, wherein the method comprises the following steps: to determine a first wear value that indicates wear of the friction lining of the vehicle brake, by taking into account at least one parameter of the operational history of the vehicle, in dependence upon whether the first wear value meets a predetermined criterion, to perform a measurement of wear of the friction lining by moving the parking brake unit and recording the curve of an operating parameter of the parking brake unit while moving, and to determine, based on the measurement, a second wear value, which indicates wear of the friction lining of the vehicle brake. ### Claim 2 (depends on 1) The method according to claim 1, wherein the predetermined criterion of the first wear value includes an assessment as to whether the first wear value is above a predetermined threshold. ### Claim 3 (depends on 1) The method according to claim 1, further comprising the steps of: determining a third wear value indicating wear of the friction lining of the vehicle brake by identifying an overall elasticity of the vehicle brake, and in dependence upon whether the third wear value meets a predetermined criterion, performing the measurement of wear. ### Claim 4 (depends on 3) The method according to claim 3, wherein the predetermined criterion of the third wear value includes an assessment as to whether the third wear value is above a predetermined threshold. ### Claim 5 (depends on 4) The method according to claim 4, wherein the step of determining the third wear value is carried out after the step of determining the first wear value, in dependence upon whether the first wear value meets its predetermined criterion. ### Claim 6 (depends on 1) The method according to claim 1, further comprising the step of determining at least one fourth wear value of a further vehicle brake of the vehicle brake system based on the second wear value of the vehicle brake. ### Claim 7 (depends on 6) The method according to claim 6, wherein the further vehicle brake is a vehicle brake without a parking brake unit. ### Claim 8 (depends on 1) The method according to claim 1, wherein performing the wear measurement comprises determining a position of a support point (AS) of the parking brake unit by detecting a change in the operating parameter. ### Claim 9 (depends on 1) The method according to claim 1 wherein the parking brake unit comprises an electric motor drive unit and an actuator unit interacting with the actuating piston, wherein the electric motor drive unit is designed to move the actuator unit in order to press the friction lining against the brake disc, and wherein the operating parameter of the parking brake unit comprises a motor current of the electric motor drive unit and/or a rotational speed of the electric motor drive unit. ### Claim 10 (depends on 1) The method according to claim 1 wherein the step of determining the first wear value comprises a calculation based on a mathematical model and the at least one parameter relating to the vehicle's operational history is taken into account in the mathematical model. ### Claim 11 (depends on 1) The method according to claim 1, wherein the parameter relating to the vehicle's operational history comprises at least one of the following parameters: Total sum of the distance traveled by the vehicle; The sum of the distance traveled by the vehicle since the last change of the friction lining; Time elapsed since the initial operation of the vehicle braking system; Time elapsed since the last change of the friction lining; Vehicle operating period since the initial operation of the vehicle; Vehicle operating period since the last change of the friction lining; Number of previous braking operations; Number of braking operations since the last change of the friction lining; Applied force of past braking operations; and Environmental conditions of the vehicle. ### Claim 12 (depends on 11) The method according to claim 11 wherein the environmental conditions of the vehicle includes at least the outside temperature. ### Claim 13 (depends on 1) The method according to claim 1, further comprising the step of providing notice to the driver of the vehicle, who will be advised that changing a brake lining is required which is dependent upon whether the second wear value meets a predetermined criterion. ### Claim 14 (depends on 1) The method according to claim 1 wherein the at least one parameter of the operational history of the vehicle is stored in a memory of a control unit of the vehicle brake system.