Drum Brake Adjuster With Disc Spring for Parking Force Retention
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Solution Overview
Problem
Conventional electric parking brakes face inefficiencies in maintaining braking force due to elastic deformation and increased size of the motor gear unit, leading to reduced shoe spreading force efficiency.
Innovation Solution
A drum brake device with a parking brake mechanism that incorporates an elastic member in the adjuster, eliminating the need for a compression spring on the motor gear unit, allowing direct application of elastic force to prevent shoe spreading force loosening, and utilizing disc springs for adjustable preload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compression spring is mounted on the motor gear unit side to transmit propulsive force to the output member, then the shoe spreading force loosening can be prevented, but the motor gear unit becomes long in the pulling direction of the parking lever and becomes large in size
Solution Approach 1:
The invention extracts the compression spring from the motor gear unit assembly and relocates it to the adjuster mechanism. This separation allows the motor gear unit to maintain its compact size while the spring provides the necessary elastic force through the adjuster's lever mechanism, resolving the contradiction between reliability and size.
Solution Approach 2:
The invention introduces the adjuster mechanism as an intermediary between the motor gear unit and the brake shoes. The adjuster lever translates the spring's elastic force into effective shoe spreading force, mediating the force transmission and eliminating the need for a long compression spring in the motor gear unit.
2Reliability
If a compression spring is used to transmit propulsive force via the output member, then the shoe spreading force can be maintained, but the elastic force is reduced due to deformation of the output member and the efficiency of preventing loosening is lowered
Solution Approach 1:
The invention extracts the elastic force generation function from the output member and assigns it to the compression spring in the adjuster mechanism. This eliminates the need for the output member to transmit tensile forces, removing the source of elastic force loss through deformation.
Solution Approach 2:
The invention replaces the direct tensile force transmission mechanism (compression spring → output member → brake shoes) with a lever-based mechanical advantage system (spring → adjuster lever → brake shoes). This substitution eliminates force loss through member deformation by using rigid lever arms instead of flexible cable or rod transmission.
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 solution effectively prevents shoe spreading force loosening during parking operations with high efficiency while maintaining a compact motor gear unit size, reducing the loss of braking force and simplifying assembly.
Implementation Method 1
an elastic member which bends along an expansion/opening direction of the pair of brake shoes and biases the pair of brake shoes in the expansion/opening direction
Implementation Method 2
the compression spring is compressed and an elastic restoring force is generated in the compression spring
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
This drum brake device (100) comprises a parking brake mechanism (31) including: first and second brake shoes (17, 19) that are arranged in an expandable manner, each shoe opposing the inner circumferential surface of a brake drum; an adjuster (33) that is interposed between adjacent one ends of the respective brake shoes and that automatically adjusts the distance between the shoes; and an expanding mechanism (43) that is interposed between the first brake shoe (17) and one end of the adjuster (33) and that expands the first and second brake shoes (17, 19) by a thrust of an operation lever (49) to which an external force has been applied. A disc spring (97) that warps along the expanding direction of the pair of brake shoes when parking is effected is arranged on the adjuster (33).