Disk Brake Friction Pad Spring Constant for Noise Suppression
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Solution Overview
Problem
Disk brakes experience braking noise during backward vehicle movement due to friction pad abutment with the torque receiver, which existing systems fail to adequately address.
Innovation Solution
A disk brake design featuring a mounting member with a caliper that slidably presses friction pads against a disk, utilizing an urging spring with a specific spring constant smaller than the eigenfrequency-based spring constant, and a cantilevered configuration to prevent resonance and noise during backward movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an urging spring is arranged between the friction pad and mounting member to urge the friction pad toward the exit side of disk rotational direction, then the friction pad is properly positioned during forward movement, but braking noise occurs during backward movement when the friction pad abuts to the torque receiver
Solution Approach 1:
The spring constant of the urging spring is specifically designed to be smaller than the critical value k=4π²f²m, where f is the eigenfrequency of the caliper and m is the mass of the friction pad. This parameter change ensures that the natural frequency of the friction pad-spring system does not coincide with the caliper's eigenfrequency, preventing resonance and braking noise during backward movement while maintaining proper friction pad positioning during forward movement.
2Stability of the object's composition
If the urging spring has a larger spring constant to firmly position the friction pad, then positioning stability improves, but resonance with the caliper eigenfrequency increases causing braking noise
Solution Approach 1:
The spring constant is precisely controlled to be below the threshold value derived from the caliper's eigenfrequency and the friction pad's mass. This creates a stable friction pad positioning system that operates below the resonance frequency of the caliper, eliminating braking noise while maintaining adequate positioning stability for normal operation.
Solution Approach 2:
The urging spring is designed with appropriate elasticity to provide cushioning during backward movement, preventing direct rigid contact between the friction pad and torque receiver. This elastic cushioning effect absorbs impact energy and prevents the generation of braking noise while maintaining friction pad stability during forward operation.
3Stability of the object's composition
If the urging spring is made stiffer to prevent friction pad vibration, then vibration suppression improves, but the system becomes more prone to resonance with the caliper eigenfrequency
Solution Approach 1:
The spring constant is optimized to balance vibration control and resonance avoidance. By setting the spring constant below the critical value k=4π²f²m, the system achieves adequate vibration control during normal operation while ensuring that the natural frequency of the friction pad-spring system remains below the caliper's eigenfrequency, preventing resonance during backward movement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design effectively suppresses braking noise by shifting the resonance frequency of the friction pad, ensuring quiet operation during both forward and backward vehicle movements.
Implementation Method 1
an urging means including an extending portion urging the friction pad toward a disk rotationally exiting side, the extending portion being arranged between one lateral portion of the pair of lateral portions as a disk rotationally entering side at the time of vehicle forward movement and an opposed surface portion of the mounting member opposed to the one lateral portion, the extending portion also elastically contacting to either the one lateral portion or the opposed surface portion
Implementation Method 2
the urging means has smaller spring constant than spring constant k defined by Formula k=4 pi2×f2×m where f is an eigenfrequency defined upon the caliper vibrating as a rigid body in a condition that the caliper is mounted to the mounting member and m is a mass of the friction pad
Implementation Method 3
a friction pad including a lining made of friction material and a backing plate supported by the mounting member
Data Source
AI summary
A disc brake that suppresses braking noises when a vehicle moves backward include an urging spring urging a friction pad toward a rotationally exiting side of a disc when the vehicle moves forward, the urging spring being arranged between a hook portion of the friction pad and a torque receiving portion of a carrier. The urging spring formed through bend of an elastic plate material has its spring constant that is set to be a small value to avoid resonance frequency causing noise where the base end side thereof is fixed to the hook portion of the backing plate while the top end side thereof elastically abuts to the torque receiving portion of the carrier. The urging spring is located at the position that is outside in the radial direction from the center position of the hook portion in its width direction.