Drum Brake Spreader with Segmented Cam and Stepping Gear
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Solution Overview
Problem
Existing electromechanical spreader devices for drum brakes face inefficiencies in combining braking and adjusting functions, leading to increased moments and loads, and are not effectively designed to compensate for component tolerances and wear.
Innovation Solution
The design incorporates a cam disk connected to a stepping gear, which is segmented for braking and adjusting functions, using a Geneva drive and worm gear to reduce cam lift and adjust with lower forces, allowing for a compact and efficient spreader device that compensates for wear and thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a cam drive is used for both braking and adjusting functions, then the device complexity is reduced, but the moments and loads on the cam disk increase
Solution Approach 1:
The cam disk is segmented into distinct braking area and adjusting area, with the stepping gear engaged only during adjusting operations. This segmentation allows the cam disk to handle braking loads independently while the stepping gear handles adjusting loads separately, preventing the accumulation of both loads simultaneously.
Solution Approach 2:
The stepping gear acts as an intermediary mechanism that is selectively engaged during adjusting operations. It mediates between the cam disk and the adjusting element, allowing precise adjustment while preventing the cam disk from bearing excessive adjusting loads during normal braking operations.
2Volume of moving object
If the cam lift is reduced for lower moments, then the device size is reduced, but the adjusting precision may be compromised
Solution Approach 1:
The recirculating ball screw mechanism replaces the traditional large-cam-lift mechanical system. This substitution enables precise adjustment through threaded engagement while maintaining a compact cam disk with reduced lift, as the ball screw provides mechanical advantage and precision without requiring large cam dimensions.
3Adaptability or versatility
If the stepping gear is engaged during braking, then the adjusting function is compromised, but if disengaged, then the braking function is compromised
Solution Approach 1:
The cam disk is segmented into distinct braking area and adjusting area along its circumference. The stepping gear is designed to be engaged only when the cam disk rotates into the adjusting area, and disengaged during braking area operation. This spatial segmentation ensures that braking and adjusting functions are performed in separate operational phases, preventing interference between the two functions.
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 enables a compact spreader device that efficiently performs braking, adjusting, and parking brake functions with reduced moments and loads, ensuring secure setting and compensation for component wear and thermal expansion.
Implementation Method 1
the cam disk can be connected to an actuating disk of a stepping gear in a torque-transmitting manner
Implementation Method 2
a spring element 18 arranged between an actuating plunger 14 of this first actuating element 8, which contacts the cam disk 12 in a force-transmitting manner, and an abutment 16 of this first actuating element 8
Implementation Method 3
an actuating plunger 14 of this first actuating element 8, which contacts the cam disk 12 in a force-transmitting manner
Data Source
AI summary
An electromechanical spreader device for a drum brake of a vehicle, comprising an electric motor with an output, a cam disc connected to the output so as to transmit torque and is arranged between two actuating elements for simultaneously actuating the two actuating elements during a braking action. The cam disc is connected to an actuating disc of a stepping gear so as to transmit torque. The stepping gear is connected to a second of the two actuating elements so as to transmit force, such that the second actuating element is adjustable via rotation of the cam disc in an engagement angle of rotation range, in which the actuating disc is in torque-transmitting engagement with a remaining part of the stepping gear, and is adjustable away from the brake shoe in the opposite direction in the engagement angle of rotation range via rotation of the cam disc.