Disk Brake Seal Groove Geometry for Easier Piston Return
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Solution Overview
Problem
Conventional vehicle disk brakes face difficulty in piston return when releasing the brake, due to the curved bottom wall of the piston seal groove causing increased frictional force that hinders piston movement back to the cylinder hole bottom portion side.
Innovation Solution
A disk brake design featuring a seal groove with a rear bottom wall having a larger depth than the piston seal in its uncompressed state, allowing easier piston return by reducing frictional force and enabling smoother movement back to the cylinder hole bottom portion side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bottom wall of the piston seal groove includes a curved portion with gradually increasing depth toward the cylinder hole opening side, then the piston seal can accommodate thermal expansion, but the frictional force increases and hinders piston return movement
Solution Approach 1:
The bottom wall of the piston seal groove is segmented into multiple regions with different depths: a first region with greater depth from the cylinder opening side, and a second region with lesser depth from the cylinder bottom side. This segmentation allows the piston seal to expand thermally in the deeper first region while maintaining easier return movement through the shallower second region, resolving the contradiction between thermal expansion accommodation and piston return ease.
Solution Approach 2:
Different portions of the piston seal groove bottom wall are given different local qualities (depths). The first region has a greater depth to accommodate thermal expansion of the piston seal, while the second region has a lesser depth to reduce frictional resistance during piston return. This local differentiation allows each region to optimize for its specific function, resolving the technical contradiction.
2Reliability
If the piston seal groove bottom wall is compressed between the shallow bottom wall and the piston outer circumferential surface, then the piston seal seals liquid-tightly, but the frictional force increases and may hinder piston movement
Solution Approach 1:
The bottom wall is segmented into a first region with greater depth and a second region with lesser depth. The piston seal can be compressed against the piston outer circumferential surface in the second region to maintain liquid-tight sealing, while the first region provides sufficient depth to accommodate thermal expansion and reduce overall frictional resistance, allowing the piston to move easily without compromising sealing reliability.
Solution Approach 2:
The depth parameter of the piston seal groove bottom wall is varied across different regions. By changing the depth parameter from the first region (greater depth) to the second region (lesser depth), the design optimizes both sealing pressure and frictional resistance, enabling the piston seal to maintain liquid-tight sealing while reducing frictional force that would hinder piston 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
Facilitates easier piston return when releasing the brake, preventing brake pad contact with the rotor and improving fuel efficiency by reducing frictional resistance and enhancing the piston's movement back to its initial position.
Implementation Method 1
the piston seal in the initial state not thermally expanded is provided with a space portion to allow thermal expansion of the piston seal
Implementation Method 2
the frictional force between the piston seal and the piston increases, which may hinder the movement of the piston
Data Source
AI summary
The present disclosure provides a disk brake capable of making it easier for the piston to return than conventional ones when the brake is released from a state where the brake is applied. In the disk brake, the seal groove 5 includes a front wall 51, a rear wall 52 farther from the brake rotor than the front wall 51 in the axial direction Dl, and a bottom wall 53 extending along the axial direction Dl between the rear wall 52 and the front wall 51. The bottom wall 53 includes a front bottom wall 53a adjacent to the front wall 51 and a rear bottom wall 53b adjacent to the rear wall 52. The rear bottom wall 53b has a depth d2 from the inner circumferential surface 42a of the cylinder 42, the depth d2 being larger than a dimension d3 of the uncompressed piston seal 6 in the direction of the depth d2 and being larger than a depth d1 from the inner circumferential surface 42a of the cylinder 42 of the front bottom wall 53a.