Disc Brake Adjuster Wrap Spring for Low-Torque De-Adjustment
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Solution Overview
Problem
The existing adjuster units for vehicle disc brakes face challenges in the de-adjustment procedure, requiring significant torque to move the adjustment spindle away from the disc due to the clamping action of the wrap spring, which is detrimental.
Innovation Solution
Positioning the wrap spring on the adjustment spindle to engage a stop, allowing its diameter to increase when rotated in the second direction, thereby minimizing the necessary torque for de-adjustment, and incorporating a torque-transmitting interface for easier operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the wrap spring clamps on the adjustment spindle during de-adjustment, then the adjustment spindle can be rotated in the second direction, but significant torque has to be applied which is detrimental
Solution Approach 1:
The wrap spring is designed to dynamically change its diameter during rotation. When the adjustment spindle rotates in the second direction (de-adjustment), the wrap spring expands in diameter, transitioning from a clamped state to an expanded state. This dynamic transformation allows the spring to release its clamping force progressively, reducing the torque required to rotate the spindle away from the disc.
Solution Approach 2:
The invention changes the physical parameter of the wrap spring's diameter during operation. By positioning the spring to engage a stop upon rotation in the second direction, the diameter of the wrap spring increases. This parameter change transforms the spring from a high-force clamping configuration to a lower-force expanded configuration, directly addressing the torque problem during de-adjustment.
2Productivity
If the actuator ring assembly is used for adjustment, then the brake pad moves towards the disc efficiently, but it cannot be employed for de-adjustment as it only couples non-rotatably in the first direction
Solution Approach 1:
The adjustment spindle is designed as a universal component that can perform both adjustment (first direction) and de-adjustment (second direction) functions. By equipping the spindle with a torque-transmitting interface and designing the wrap spring to expand rather than clamp during reverse rotation, the system achieves bidirectional functionality. The same mechanical assembly handles both tightening and loosening operations, eliminating the need for separate mechanisms.
Solution Approach 2:
The invention inverts the traditional approach by designing the wrap spring to expand during reverse rotation rather than clamp. This inversion allows the de-adjustment operation to work in the opposite direction of the adjustment operation, enabling the actuator ring assembly and adjustment spindle to function bidirectionally. The spring's expansion mechanism during second-direction rotation creates the necessary clearance for reverse operation.
3Force
If the wrap spring is positioned to engage a stop and expand in diameter, then the torque for de-adjustment is minimized, but the structure becomes more complex
Solution Approach 1:
The adjustment spindle is segmented into functional zones: a first end portion for coupling to the brake pad, a second end portion with a torque-transmitting interface, and a middle section where the wrap spring engages. The stop feature is segmented as a separate element that the wrap spring engages during expansion. This segmentation allows each component to perform its specific function while maintaining overall system simplicity.
Solution Approach 2:
The stop acts as an intermediary element between the wrap spring and the adjustment spindle housing. By introducing this intermediate feature, the wrap spring can engage and expand in a controlled manner during de-adjustment without requiring complex mechanical structures. The stop provides a simple geometric feature that enables the spring's diameter increase while maintaining structural simplicity.
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
Significantly reduces the torque required for de-adjustment, improving the efficiency and precision of the adjuster unit's functionality during both adjustment and de-adjustment processes.
Implementation Method 1
positioning the wrap spring, being part of the adjuster unit, on the adjuster unit, in particular on the adjustment spindle, to engage a stop upon rotation of the adjustment spindle in the second direction, causing the diameter of the wrap spring to increase
Data Source
AI summary
An adjuster unit (100) for a vehicle disc brake (1), in particular an air disc brake (1) of a commercial vehicle, includes an adjustment spindle (101) adapted to be operatively coupled with one of the brake pads (9) such that by rotation in a first direction, the adjustment spindle (101) moves the brake pad (9) towards the disc (11). By rotation in a second direction opposite of the first direction, the adjustment spindle (101) moves the brake pad away from the disc (11). An actuator ring assembly (107) is rotatable about the adjustment spindle (101); and a wrap spring (109) is helically wound around the adjustment spindle (101). The wrap spring (109), being part of the adjuster unit, is positioned on the adjuster unit, in particular on the adjustment spindle, to engage a stop (117) upon rotation of the adjustment spindle (101) in the second direction, causing the diameter of the wrap spring (109) to increase.