Drum Brake Actuator Venting for Boot Pressure Equalization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric actuators in vehicle drum brakes face issues with boot durability due to pressure changes in a sealingly closed space caused by the reciprocating motion of the screw shaft, which are exacerbated by changes in altitude and temperature, and previous solutions complicate the structure and increase costs.
Innovation Solution
An electric actuator with a vent formed on the actuator case, equipped with a breathable waterproof member and filter, allows communication with the atmosphere while preventing water ingress, and is mounted using a mounting tubular portion to enhance durability and simplify the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ventilation unit is attached to a gear case and a vent is formed through a partition wall to create an air flow path between motor case and gear case, then the inner pressure in the sealingly closed space is adjusted through communication with the atmosphere, but the number of components increases and the structure becomes complicated leading to cost increase
Solution Approach 1:
The vent is integrated directly into the actuator case (which forms the sealingly closed space) rather than being a separate component attached to a gear case. This merging of the vent function into the existing actuator case structure eliminates the need for additional ventilation units and complex air flow paths, thereby reducing component count and structural complexity while still achieving pressure equalization to protect the boot
Solution Approach 2:
The vent function is extracted from the complex ventilation unit system proposed in PTL 2 and simplified to a direct opening in the actuator case. This extraction removes the unnecessary complexity of separate ventilation units, partition walls, and multi-path air flow systems, keeping only the essential function of pressure equalization between the sealingly closed space and the atmosphere
2Ease of operation
If the screw shaft reciprocates linearly in the sealingly closed space, then the motion conversion mechanism converts rotation into reciprocating linear motion, but the volume of the sealingly closed space changes causing pressure difference that dents and expands the boot reducing its durability
Solution Approach 1:
The vent acts as an intermediary that allows pressure equalization between the sealingly closed space and the atmosphere. By providing this pressure relief path, the vent mediates the conflict between the need for a sealingly closed space (for motion conversion function) and the need to prevent boot damage (for reliability), allowing the screw shaft to reciprocate freely while protecting the boot from pressure-induced deformation
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 inhibits pressure changes in the sealingly closed space, improves boot durability, reduces component count, and maintains operational stability without increasing complexity or cost, while protecting the boot from external forces.
Implementation Method 1
a breathable waterproof member provided on the vent and configured to block entry and exit of water while permitting entry and exit of air
Implementation Method 2
a filter that removes particles from air entering through the vent
Implementation Method 3
a motion conversion mechanism that converts a rotation of the electric motor into a reciprocating linear motion of a screw shaft, wherein when a nut of the motion conversion mechanism is rotated forwardly and reversely by the electric motor, the screw shaft, which is threadedly inserted through this nut so as to be able to advance and retreat, linearly reciprocates
Implementation Method 4
the screw shaft, which is threadedly inserted through this nut so as to be able to advance and retreat, linearly reciprocates... the volume of the sealingly closed space in the actuator case changes and a pressure difference is generated therein... the boot dents due to this negative pressure... the boot expands due to this positive pressure
Data Source
AI summary
An electric actuator includes a forwardly and reversely rotatable electric motor, a motion conversion mechanism configured to convert rotation of the electric motor into reciprocating linear motion of a screw shaft, an actuator case containing the electric motor and the motion conversion mechanism, and a boot covering a portion of the screw shaft that extends out of the actuator case. A vent is formed on the actuator case. The vent is configured to ventilate a sealingly closed space in the actuator case and the boot. A breathable waterproof member is provided on the vent and a cover member is also provided on the vent. The breathable waterproof member is configured to block entry and exit of water while permitting entry and exit of air. The cover member is configured to cover the vent so as to allow ventilation with outer air.