Bi-directional Wear Adjuster for Disc Brake Clearance Control
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Solution Overview
Problem
Existing disc brake wear adjusters often lead to rapid wear on vehicle wheel ends and high temperatures due to over-adjustment, which is not effectively addressed by current technologies.
Innovation Solution
A bi-directional wear adjuster with a rotatable stem, ratchet arrangement, and lost motion connection that allows for controlled brake pad clearance adjustment, reducing the risk of over-adjustment and maintaining original clearance without increasing brake chamber stroke, featuring a pin and slot arrangement with spring bias for overload protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a typical wear adjuster is used to compensate for brake pad wear, then the brake pad clearance is maintained, but over-adjustment occurs leading to rapid wheel end wear and high temperatures
Solution Approach 1:
The ratchet arrangement provides automatic feedback control by allowing the adjusting spindle to rotate freely when brake pad clearance is within acceptable limits (ratchet teeth disengaged) and automatically preventing further adjustment when the clearance reaches the limit (ratchet teeth engaged). This eliminates over-adjustment by providing mechanical feedback that stops the adjustment process at the appropriate point.
Solution Approach 2:
The adjuster mechanism changes the adjustment parameter from continuous rotation to discrete incremental adjustments. The ratchet arrangement allows the adjusting spindle to rotate in small discrete steps (one tooth at a time) rather than continuous rotation, enabling precise control of brake pad clearance and preventing excessive adjustment that leads to wheel end wear and high temperatures.
2Ease of operation
If brake pad clearance is increased for inspection and replacement access, then maintenance accessibility is improved, but the brake chamber stroke must be increased
Solution Approach 1:
The adjuster mechanism segments the brake system into independent adjustment and actuation functions. The wear adjuster with ratchet arrangement handles clearance adjustment independently, allowing the brake chamber stroke to remain fixed while providing adjustable pad clearance. This segmentation enables maintenance accessibility improvement without requiring changes to the brake chamber stroke length.
Solution Approach 2:
The adjuster mechanism introduces dynamic adjustability to the brake pad clearance system. The ratchet arrangement allows the adjusting spindle to be rotated manually to any position within the ratchet tooth engagement range, enabling dynamic adjustment of pad clearance for optimal maintenance accessibility without changing the fixed brake chamber stroke length.
3Device complexity
If a unidirectional adjuster is used, then the structure is simpler, but the adjuster cannot return pads to original clearances
Solution Approach 1:
The ratchet arrangement uses asymmetric tooth geometry that allows rotation in one direction (adjustment) while preventing rotation in the opposite direction (over-adjustment prevention). This asymmetric design enables the adjusting spindle to be rotated forward to increase clearance or backward to return to original clearance, providing bidirectional adjustment capability within a simple structural framework.
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 provides a low-cost, bi-directional adjuster that increases brake pad-to-rotor clearance by 30-40% without increasing brake chamber stroke, reducing brake wear and susceptibility to over-adjustment issues, while maintaining effective brake torque and immunity to vibrations.
Implementation Method 1
A torsion spring opposes relative movement of the pin and the slot upon disc brake actuation
Implementation Method 2
Teeth of the opposing bushings are spring biased into engagement with teeth on opposite sides of the middle bushing. The teeth in facing teeth sets are preferably configured to permit one way indexing.
Data Source
Figure 1
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AI summary
A wear adjuster (20), securable to disc brake caliper structure includes, a stem (36) extending along an axis (37) about which the stem (36) is rotatable in opposite directions, a spindle driver (22) securable to an axial end of the stem (36) to transmit rotational motion of the stem (36) to an adjusting spindle, and an input element (32) receiving input force supplied to the wear adjuster (20) to produce rotation of the stem (36). A running clearance element (44) is rotatable together with the input element (32) to a limited extent, and a ratchet arrangement (40), located between the input element 832) and the running clearance element (44), initiates any necessary adjustment for wear after rotation of the input element (32) beyond the limited extent, and completes such adjustment during return rotation of the input element (32). To avoid transmitting an excessive amount of the input force received by the input element (32), a lost motion connection (33, 80) is defined between the ratchet arrangement (40) and the input element (32).