Electromechanical Drum Brake Expanding Device with Segmented Body
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Solution Overview
Problem
Existing electromechanically actuated spreading devices for drum brakes lack sufficient stroke to achieve a large adjustment path, making them unsuitable for drum brakes, as they fail to restore the original clearance between brake shoes and the brake drum effectively after wear, leading to incomplete contact with the brake shoes.
Innovation Solution
A rotating body with a transmission system featuring balls on coaxial ball tracks and a spacer body with adjustable threads and springs ensures the transmission body remains in contact with the brake shoes, allowing for full actuation path utilization by maintaining contact through self-locking and non-self-locking threaded connections, and needle bearings for smooth rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional electromechanical spreading device is used, then the device structure is simple, but the stroke is insufficient to achieve a large adjustment path for drum brake clearance adjustment
Solution Approach 1:
The rotating body is divided into two partial bodies (first and second partial bodies) that can move relative to each other in the axial direction. This segmentation allows the spreading device to achieve a larger adjustment path by utilizing the relative movement between the two partial bodies, while each individual partial body maintains a relatively simple structure.
Solution Approach 2:
The two partial bodies are arranged concentrically with one inside the other, forming a nested structure. The first partial body is positioned inside the second partial body, allowing both to rotate about the same axis while maintaining axial separation. This nested configuration maximizes the adjustment path within a compact overall structure.
2Reliability
If the brake shoes are adjusted to restore the original clearance, then the clearance between brake shoes and drum is restored, but the transmission body loses contact with the brake shoes
Solution Approach 1:
A spacer body is introduced as an intermediary element between the two partial bodies. The spacer body includes a self-locking threaded connection that maintains a minimum axial distance between the partial bodies, ensuring that the transmission body remains in contact with the brake shoes even after adjustment. This intermediary mechanism prevents the loss of contact while allowing the necessary adjustment path.
Solution Approach 2:
The axial distance between the two partial bodies is dynamically adjusted through the spacer body's threaded connection. The self-locking thread allows the spacer to maintain a fixed position once set, while the adjusting nut with non-self-locking thread enables controlled adjustment of the minimum distance. This parameter change ensures continuous contact between the transmission body and brake shoes throughout the adjustment range.
3Ease of operation
If the two partial bodies are pressed together to close gaps, then contact is restored, but the adjusting mechanism cannot maintain the new basic position
Solution Approach 1:
The adjusting mechanism replaces simple mechanical pressing with a threaded connection system. The self-locking threaded connection between the spacer body and first partial body, combined with the adjusting nut on the second partial body, provides a controlled mechanical system that can both adjust and maintain the new basic position of the brake shoes without requiring continuous force.
Solution Approach 2:
An expansion spring is positioned between the two partial bodies to provide a pre-compression force. This spring ensures that the partial bodies are constantly pressed toward each other, maintaining contact between the transmission body and brake shoes. The spring's elastic force compensates for any gaps that may develop, ensuring continuous contact while allowing the threaded adjustment mechanism to set and maintain the desired position.
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 solution allows for complete adjustment of the clearance between brake shoes and the drum brake, ensuring effective braking performance even after brake pad wear, by maintaining contact and compensating for gaps through controlled rotation and spring-loaded mechanisms.
Implementation Method 1
The partial bodies are loaded towards a greater distance by an expansion spring arranged between them
Implementation Method 2
the threaded connection between the adjusting nut and the spacer is designed as a non-self-locking running drive
Data Source
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AI summary
An electromechanically actuable expanding device for a drum brake provided with a readjustment device. An expanding device for actuating one of the brake shoes (2, 3) of a drum brake consists of a body of revolution (11) and transmission bodies (16, 17) which are actuated by the body of revolution (11) via ball track ramps. In order to follow the play compensation of the readjustment device (6) of the drum brake, the body of revolution (11) is formed in two parts. A spacer body (24) is located between the two partial bodies (12, 13) of the body of revolution, said spacer body being guided by an adjustment spring (37), as the partial bodies (12, 13) are being moved apart by an expansion spring (23), and keeping the partial bodies (12, 13) at the respectively reached distance. In order to guide the spacer body (24) during an air clearance readjustment, said spacer body is screwed onto a pin (27) on the first partial body. A readjustment nut (34) ensures that, when the two partial bodies (12, 13) are pushed apart, said spacer body rotates on the pin (27) and, in the process, first of all moves away from a supporting surface (30) on a partition (29) of the second partial body (13). Upon renewed actuation of the brakes, the stepwise readjustment nut (34) is guided such that the spacer body (24) comes again to bear against the second partial body (13), but takes up a different position on the pin (27), said position corresponding to the air clearance readjustment that has been carried out.