Apparatus and method for detecting the thickness of a brake lining

• US 5,975,250 A
• Filed: 06/25/1997
• Issued: 11/02/1999
• Est. Priority Date: 06/25/1996
• Status: Expired due to Fees

• Current Assignee: Pacifica Group Technologies Pty Limited
• Original Assignee: Siemens AG
• Inventors: Brandmeier, Thomas, Zittlau, Dirk, Rauner, Hans
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): TORRES WILLIAMS, MELANIE
• Application Number:
  US08/882,166
• Time in Patent Office: 860 Days
• Field of Search: 188/1.11 W, 188/1.11 E, 188/1.11 L, 188/1.11 R, 340/453, 340/454
• US Class Current: 188/1.11W
• CPC Class Codes: B60T 13/746 and mechanical transmission of the braking action
• CPC Class Codes: B60T 7/042 by electrical means, e.g. using travel or force sensors
• CPC Class Codes: B60T 8/321 deceleration B60T8/34, B60T8/52, B60T8/54, B60T8/56, B60T8/58, B60T8/72, B60T8/86, B60T8/88 take precedence
• CPC Class Codes: B60T 8/3255 Systems in which the braking action is dependent on brake pedal data
• CPC Class Codes: F16D 2121/24 using motors
• CPC Class Codes: F16D 2125/10 Plural pistons interacting by fluid pressure, e.g. hydraulic force amplifiers using different sized pistons
• CPC Class Codes: F16D 66/026 indicating different degrees of lining wear
• CPC Class Codes: G01B 21/08 for measuring thickness

Abstract

An apparatus and a method detect the current thickness and thus the wear of a brake lining of a motor-vehicle brake system, which has a wheel-brake actuator at each wheel that actuates the wheel brake and is individually electrically controlled. The wheel-brake actuator contains a hydraulic piston which is moved by an electric motor and is provided with a sensor that detects the brake pressure or brake force as well as with a further sensor that detects the travel of the hydraulic piston. The thickness of the brake lining is determined from signals of the two sensors. To that end, a measurement is made of the travel performed by the hydraulic piston until a predetermined brake pressure is reached.

Claims

1. In a motor vehicle including wheels and a brake system having a wheel brake with a brake lining at each wheel, an apparatus for detecting a thickness of the brake linings, comprising:

individually electrically-controlled wheel-brake actuators each having a hydraulic piston and each associated with a respective one of the wheels for actuating the wheel brake;

electric motors each performing a rotary motion transformed into a linear motion of said hydraulic pistons, each of said electric motors having a sensor determining an angle of rotation of said electric motor, and said hydraulic pistons travelling a distance determined from said angle of rotation sensor and from the transformation of the rotary motion into the linear motion;

first sensors each detecting a brake pressure or brake force at a respective one of said actuators; and

second sensors each detecting travel of said hydraulic piston at a respective one of said actuators;

said sensors supplying signals for determining a thickness of the brake lining, the thickness of the brake lining determined with reference to travel performed by said hydraulic pistons until reaching a predetermined brake pressure.

2. The apparatus according to claim 1, wherein the respectively determined thickness of the brake lining is compared with a predetermined minimum value and a warning signal is delivered if the thickness falls below the minimum value.

3. The apparatus according to claim 1, wherein measured values of the brake-lining thickness are stored for a predetermined period, and an average value of brake-lining wear per unit of time is calculated from the measured values.

4. The apparatus according to claim 3, wherein a remaining brake-lining life is determined from an average value of the brake-lining wear.