Commercial Vehicle Disc Brake Guide Bushing Anti-Twist Locking
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Solution Overview
Problem
Disc brakes in commercial vehicles face a risk of screw loosening due to reduced friction between guide bushings and brake carriers, especially with friction-reducing coatings, leading to potential brake failure and increased costs from additional securing components.
Innovation Solution
A guide bush made of harder material than the brake carrier, with tangentially guided cutouts or recesses on its peripheral edge, creates a form fit that maintains screw preload and prevents twisting, eliminating the need for separate securing elements like wedge lock washers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a friction-reducing coating (e.g., zinc phosphate) is applied to the brake carrier surface, then the sliding friction between the guide bushing and brake carrier is reduced, but the risk of guide bushing twisting increases, leading to screw preload loss and potential loosening
Solution Approach 1:
The guide bushing's outer circumference is segmented into multiple recesses (at least three, preferably four to six) that are open toward the brake carrier. These recesses create discrete contact zones that allow the brake carrier material to plastically deform and enter the recesses, forming a positive locking mechanism that prevents twisting while maintaining sliding capability.
Solution Approach 2:
The guide bushing has non-uniform local properties: the outer circumferential surface contains recesses that create high local pressure zones for positive locking, while the rest of the surface maintains the friction-reducing coating for smooth sliding. This local differentiation allows simultaneous optimization of both sliding ease and anti-loosening reliability.
2Reliability
If wedge-locking washers are added between the guide bushing and brake carrier to prevent loosening, then the screw connection stability is improved, but the device complexity and manufacturing costs increase due to additional components
Solution Approach 1:
The anti-loosening function previously requiring separate wedge-locking washers is merged directly into the guide bushing structure. The recesses in the guide bushing's outer surface perform the locking function that would otherwise require additional components, simplifying the overall assembly to just the guide bushing, screw, and brake carrier.
Solution Approach 2:
The locking function is extracted from the friction-based system and implemented through a positive locking mechanism via the recesses. This eliminates the need for intermediate locking components and creates a more direct, reliable connection between the guide bushing and brake carrier.
3Reliability
If the guide bushing is made of harder material (preferably hardened steel) than the brake carrier, then the material can be plastically deformed to create positive locking, but the manufacturing complexity increases
Solution Approach 1:
The guide bushing is pre-hardened to a specific hardness range (HRC 25-45) before final assembly. This preliminary heat treatment ensures the material has the right balance of hardness for creating the positive locking effect and ductility for the plastic deformation process, simplifying the overall manufacturing sequence.
Solution Approach 2:
The hardness of the guide bushing material is controlled within a specific range (HRC 25-45) to optimize the plastic deformation behavior. This parameter control allows the material to be sufficiently hard for structural integrity and locking capability while remaining ductile enough for the forming process during assembly.
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 provides effective anti-twist protection through positive locking, ensuring the screw connection remains secure under operational stresses and reducing manufacturing complexity and costs, while allowing for retrofittable solutions without additional processing of existing brake carriers.
Implementation Method 1
the material of the brake carrier in the contact area with the guide bushing is plastically deformed in such a way that this material enters the recesses of the guide bushing
Implementation Method 2
the annular contact surface of the guide bushing adjacent to the flange rests against the outside of the brake carrier, with a high-strength screw being used as the screw, which presses the guide bushing against the brake carrier under preload
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A disc brake for a commercial vehicle, comprising a brake caliper extending over a brake disc, which is slidably held on a stationary brake carrier (1) by two guide arms (2), wherein each guide arm (2) has a guide bushing (3) connected to the brake carrier (1) by means of a screw (4) screwed into a threaded bore (7) of the brake carrier (1), which is held in a rotationally secure manner on the brake carrier (1) and which, with a molded collar (6), sits in a recess (9) of the threaded bore (7), is designed such that the guide bushing (3), which is made of a harder material than the brake carrier (1), preferably of hardened steel, has at least one recess (8) open towards the brake carrier (1) on its outer edge region associated with the collar (6), into which material of the brake carrier (1) is pressed by the contact pressure of the screw (4).