Twisted Brake Cable Layout for Quieter Electric Parking Brakes
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Solution Overview
Problem
The existing electric parking brake device generates a slapping sound and increased wear due to the clearance between the projection portion and groove in the rotation restricting means, leading to high sliding resistance and operating noise during switching between parking brake states.
Innovation Solution
The device incorporates a brake cable formed by twisting wires, with the twisting force acting in the same direction as the nut's rotational direction, and features rotation restricting projection portions on the screw shaft and grooves in the actuator case to reduce contact and sliding resistance, thereby minimizing operating noise and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotation restricting means with clearance between projection portion and groove is used, then rotational motion of screw shaft is restricted, but slapping sound and operating noise occur during switching between parking brake states
Solution Approach 1:
A resin layer is applied to the groove surface in the rotation restricting means, serving as an intermediary between the projection portion and groove. This resin layer fills the clearance and reduces direct metal-to-metal contact, thereby suppressing slapping sounds and operating noise while maintaining rotation restriction functionality.
2Reliability
If projection portion is pressed strongly against groove side surface during axial movement, then rotational motion is restricted, but sliding resistance increases and wear occurs
Solution Approach 1:
The physical and chemical parameters of the groove surface are changed by applying a resin coating. This resin layer reduces the coefficient of friction between the projection portion and groove, thereby reducing sliding resistance during axial movement and minimizing wear of both the projection portion and actuator case while maintaining effective rotation restriction.
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
This design effectively suppresses slapping sounds and reduces wear by aligning the twisting force with the nut's rotation, decreasing sliding resistance and operating noise, while maintaining effective torque control for the electric motor.
Implementation Method 1
the brake cable is formed by twisting a plurality of wires so as to generate a twisting force in a fixed direction when the brake cable is pulled
Data Source
AI summary
In an electric parking brake device configured in such a way that a parking brake state resulting from pulling of a brake cable is released by loosening the brake cable, the brake cable is formed by twisting together a plurality of wires and the direction of twisting is rotational direction of the nut when the brake cable is pulled. This makes it possible to reduce an operating sound and to reduce wear of members constituting a rotation restricting device.