Shift Sleeve Coating for Low-Wear Gearwheel Coupling
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Solution Overview
Problem
Existing coupling devices in electric drive trains experience significant wear due to friction between the shift sleeve and shift fork, leading to potential failure, particularly during clutch engagement and disengagement, which is exacerbated by the high number of operating cycles.
Innovation Solution
Applying a friction-reducing coating to the contact surfaces and groove flanks of the shift sleeve and shift fork, comprising a two-layer system with a phosphate base layer and a polytetrafluoromene (PTFE) or graphite-based binder layer and a polytetrafluoroethylene (PTFE) cover layer, which reduces the coefficient of friction and minimizes wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a sliding element made of plastic is attached to the shift fork to reduce friction, then the friction between the shift fork and shift sleeve is reduced, but the installation becomes relatively complex and the sliding element has to be secured to the shift fork with great effort against accidental detachment
Solution Approach 1:
The invention changes the surface properties of the contact surfaces by applying a friction-reducing coating directly to the groove flanks and/or contact surfaces. This modifies the coefficient of friction parameter from 0.2-0.3 to approximately 0.04, achieving the same friction reduction effect as the plastic sliding element but without the complexity of attaching and securing a separate component.
Solution Approach 2:
The invention extracts the friction-reducing function from a separate plastic sliding element and integrates it directly into the metal components through surface coating. This eliminates the need for a separate sliding element and its complex attachment process, while maintaining the beneficial low-friction effect.
2Reliability
If no friction-reducing措施 is applied, then the structure remains simple, but the wear on contact surfaces is significant leading to potential failure of the coupling device
Solution Approach 1:
The invention applies a composite coating system consisting of a phosphate base layer and a PTFE or graphite-based binder layer with PTFE cover layer. This composite structure combines the adhesion benefits of phosphate treatment with the low-friction properties of PTFE/graphite, creating a durable surface treatment that significantly reduces wear and extends service life.
Solution Approach 2:
The friction-reducing coating is applied in advance to the contact surfaces and groove flanks before the coupling device begins operation. This preliminary protective action prevents wear from occurring during the high-number operating cycles, thereby extending the service life of the coupling device without affecting its operational simplicity.
3Duration of action of stationary object
If friction-reducing coating is applied to reduce wear, then the service life is extended, but the manufacturing process becomes more complex
Solution Approach 1:
The invention uses standard industrial coating processes (phosphate treatment followed by PTFE/graphite binder application) that are well-established in manufacturing. While these processes add steps, they use conventional techniques and materials that can be efficiently applied in production, making the increased manufacturing complexity acceptable given the significant extension of service life.
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 friction-reducing coating significantly decreases the coefficient of friction, reducing wear and extending the service life of the coupling device by orders of magnitude, while also mitigating the stick-slip effect and delaying tribocorrosion.
Implementation Method 1
The friction-reducing coating reduces the coefficient of friction in the contact area between the shift sleeve and the shift fork by orders of magnitude
Implementation Method 2
The base layer primarily serves as an adhesive layer for adhesion to the respective substrate
Implementation Method 3
a top layer which is formed from a binder material into which at least one filler material is incorporated, wherein the filler material comprises particles dispersed in the binder material
Data Source
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AI summary
The invention relates to a coupling device (1) for coupling and/or decoupling a gearwheel (16) to or from a shaft (13), in particular in an electric drive train of a vehicle, wherein the coupling device (1) comprises a shift sleeve (14) and a shift fork (7), wherein the shift sleeve (14) comprises an annular body (140) which is provided on its outer circumference (142) with a circumferential annular groove (144), wherein the annular groove (144) has a groove base (145) and groove flanks (146, 147), wherein the shift fork (7) comprises a base body (71) and two legs (72, 73) projecting from the base body (71), wherein the legs (72, 73) engage at least in sections in the annular groove (144) such that the shift sleeve (14) relative to the legs (72,73) is rotatable and the shift sleeve (14) is displaceable in an axial direction (100) by a drive of the shift fork (7),wherein the shift fork (7) comes into contact with at least a first contact surface (75a) on a first groove flank (146) of the annular groove (144) when driven in the axial direction (100), and with a second contact surface (75b) on an opposite second groove flank (147) of the annular groove (146) when driven in the opposite axial direction. It is proposed that at least the first contact surface (75a) and the second contact surface (75b) and/or the first groove flank (146) and the second groove flank (147) be provided with a friction-reducing coating (150).