Shift Fork Actuator with Nested Spring and Helical Gate
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Solution Overview
Problem
Current transmission systems with displaceable shift members are complex, requiring additional construction space for guiding the shift fork, leading to inaccurate angular positioning of the shift gate and unreliable engagement forces, especially in all-wheel drive vehicle transfer cases.
Innovation Solution
A design where the gate is rotationally fixed to the shift fork, with a shaft passing through a sleeve having a radially projecting finger that engages with a helical groove, establishing a precise association between shaft rotation and shift fork displacement, and utilizing a spring accumulator between the sleeve and shift fork for controlled engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a rotary spring is used to drive the gate roller, then the force accumulator function is achieved, but the device complexity increases and construction space is enlarged
Solution Approach 1:
The patent extracts the force accumulator function from a complex rotary spring mechanism and implements it through a simpler spring element integrated into the shift fork assembly. The spring is directly mounted on the shift fork and acts on the gate roller, eliminating the need for a separate rotary spring mechanism while maintaining the force accumulation capability.
Solution Approach 2:
The patent combines multiple functions into the shift fork assembly: the shift fork itself, the spring accumulator, and the guiding mechanism are integrated into a single unit. The shift fork housing surrounds the sleeve and spring accumulator, and the support surfaces guide the shift fork directly on the rotating shaft, merging what were previously separate components into one compact assembly.
2Force
If a rotary spring mechanism is used, then force accumulation is achieved, but the construction space is enlarged
Solution Approach 1:
The patent implements a nested structure where the spring accumulator is housed within the shift fork housing. The compression spring surrounds the sleeve and is contained within the housing, with the spring accumulator components nested concentrically. This nesting arrangement minimizes the volume occupied by the force accumulation mechanism while maintaining full functionality.
3Manufacturing precision
If the shift fork is guided on a rail, then displacement guidance is achieved, but the construction space is enlarged and guiding becomes defective
Solution Approach 1:
The patent removes the separate guide rail component and integrates the guiding function directly into the shift fork housing. The support surfaces are formed on the housing itself, which guides the shift fork on the rotating shaft. This eliminates the need for an additional guide rail while maintaining accurate displacement guidance through the engineered support surfaces.
4Device complexity
If the angular position of the shift gate is not accurately determined, then the mechanism is simpler, but the engagement reliability is reduced
Solution Approach 1:
The patent implements a feedback mechanism where the gate roller runs in a helical groove on the sleeve, creating a defined mechanical relationship between the angular position of the shaft and the linear position of the shift fork. The spring accumulator provides force feedback to maintain engagement, and the support surfaces provide positional feedback through the guiding contact on the rotating shaft, ensuring accurate and reliable position determination.
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 simplifies and enhances the reliability of the transmission system by ensuring accurate angular positioning and controlled displacement, reducing installation space and maintaining consistent friction values, while allowing for efficient engagement and disengagement of clutch parts.
Implementation Method 1
a spring accumulator which acts on the shift fork in the direction of the displacement
Implementation Method 2
a gate which is to be understood as a substantially helical groove with guide surfaces
Data Source
AI summary
The invention relates to a gearbox comprising a shift fork (4) that is displaced by an actuator using a shaft (2), whereby a rotational displacement of said shaft is translated into a displacement of the shift fork. To achieve an accurate displacement with minimum installation space, the gate (14) is configured on a sleeve (13) that is connected to the shift fork unit (4) in a rotationally fixed manner, said sleeve acting on the shift fork unit (4) in the direction of the displacement by means of a spring (24) and the shaft (2) runs through the sleeve (13), said shaft comprising a finger (11) that protrudes radially and co-operates with the gate. The shift fork unit (4) forms a housing (8) that surrounds the sleeve (13) and the spring accumulator (24) and that comprises bearing surfaces (34), by means of which the shift fork unit (4) is guided on the shaft (2) in the direction of the displacement.