Electric Disk Brake Pad Retraction to Reduce Drag Torque
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Solution Overview
Problem
Conventional disk brakes lack an effective return mechanism for the pad, leading to increased drag torque and structural complexity due to pad wear, which complicates the brake mechanism.
Innovation Solution
A disk brake design incorporating an elastic member that biases the pad away from the disk rotor, with a biasing force greater than the sliding resistance of the piston on the cylinder portion, and a mounting member that supports the pad's sliding movement on a non-rotational vehicle portion, with the elastic member's force being greater than the combined sliding resistances of the piston and mounting member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Belleville washer is used to return the piston axially, then the piston can be returned in the axial direction by the biasing force of the Belleville washer, but the structure becomes complicated and the pad drag is not effectively reduced
Solution Approach 1:
The invention extracts the pad return function from the piston return mechanism by introducing a separate elastic member (return spring) that acts directly on the pad. This separates the piston return function (handled by Belleville washer) from the pad return function (handled by elastic member), allowing each to be optimized independently and reducing overall structural complexity.
Solution Approach 2:
The elastic member serves as an intermediary element between the piston and the pad, providing a direct return force to the pad without requiring complex mechanical linkages. This intermediary component simplifies the overall structure by eliminating the need for additional return mechanisms while effectively reducing pad drag.
2Device complexity
If no pad wear following mechanism is included, then the structure is simplified, but the pad drag cannot be effectively reduced
Solution Approach 1:
The elastic member is positioned and configured to automatically follow pad wear by maintaining continuous contact and providing constant return force. As the pad wears and moves axially, the elastic member compresses or extends accordingly, self-adjusting to the new pad position without requiring additional wear compensation mechanisms.
3Reliability
If the biasing force of the elastic member is greater than the sliding resistance of the piston, then the pad can be effectively retracted, but the load on the electric motor increases
Solution Approach 1:
The invention carefully selects and adjusts the elastic member's force characteristics (spring constant and pre-compression) to achieve the optimal balance. The biasing force is set to be greater than the sliding resistance of the piston to ensure reliable pad retraction, but not excessively high to minimize the energy required by the electric motor during pad return.
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 reduces pad drag by allowing the pads to retract smoothly away from the rotor, simplifying the structure, and improving brake responsiveness while reducing the load on the electric motor.
Implementation Method 1
an elastic member configured to bias the pad in an axial direction of the disk rotor and in a direction away from the disk rotor
Implementation Method 2
a frictional engagement force generated between the piston and the wall surface of the cylinder portion
Data Source
AI summary
A disk brake includes a brake mechanism configured to apply a braking force by advancing a piston in a cylinder portion based on driving of an electric motor to thus press inner and outer brake pads against a disk rotor, and an elastic member configured to bias the inner and outer brake pads in an axial direction of the disk rotor and in a direction away from the disk rotor. A biasing force of the elastic member is greater than sliding resistance of the piston on the cylinder portion. Due to this configuration, the disk brake can effectively prevent or reduce the drags of the inner and outer brake pads.