Barrel-Cam Gear Shift Actuator for Blocked Dog Clutch Engagement
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Solution Overview
Problem
Gear shift actuators face challenges when the teeth or dog wheels of a dog clutch are in a relative angular position that prevents shifting to the gear engaged position until they are aligned, leading to temporary blockages.
Innovation Solution
A gear shift actuator design with a rotary member and driven component that includes a hollow cylindrical sleeve with inward cam followers and barrel cams, allowing for asymmetric actuation characteristics to handle blocked shift forks by storing and releasing actuation force through a compression mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional linear drive assembly with lead screw and nut is used, then the actuator can shift gears under normal conditions, but it cannot handle situations where the shift fork is temporarily blocked due to misaligned dog wheels
Solution Approach 1:
The patent introduces a compression spring between the nut and the lead screw that acts as a cushioning element. When the shift fork is blocked, the spring can be compressed to absorb the actuation force, preventing damage to the mechanical components. This beforehand cushioning allows the system to handle blocked conditions reliably without requiring complex sensor-based control systems.
Solution Approach 2:
The compression spring serves as an intermediary element between the rigid lead screw-nut mechanism and the potentially blocked shift fork. It mediates the force transmission, allowing the system to transition from a rigid connection to a compliant one when blocking occurs, thereby protecting the overall mechanism while maintaining structural simplicity.
2Reliability
If the actuation force is transmitted directly without compliance, then the response is immediate and efficient, but the blocked shift fork causes incomplete movement or mechanical damage
Solution Approach 1:
The compression spring is pre-installed in the force transmission path to provide compliance before blocking occurs. This allows the system to maintain smooth force transmission during normal operation while being prepared to absorb shocks when blocking happens, ensuring complete movement to the engaged position without damage.
Solution Approach 2:
The system changes the mechanical parameter of force transmission from rigid to compliant through the compression spring. This parameter change allows the actuation force to be transmitted smoothly during normal operation while providing the necessary compliance to handle blocked conditions, ensuring reliable complete movement.
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 actuator reliably and efficiently shifts gears by absorbing force when blocked, ensuring complete movement to the engaged position once the blockage is released, with compliant and direct force transmission in different directions.
Implementation Method 1
A compression spring extends in the axial direction from the first barrel cam along the central rod in the direction towards the second end stop on the central rod remote from the first barrel cam
Data Source
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AI summary
The present invention is directed to a gear shift actuator comprising a linear drive assembly having a rotary member which is supported in a housing to be rotatable, but unmovable in an axial direction defined by its rotary axis, an electric motor for rotating the rotary member, and a driven component engaged by the rotary member to transmit rotary movement into a linear axial movement of the driven component to drive a shift fork from a neutral position to a first gear engaged position and back to neutral, when the rotary member is rotated in a first sense of rotation and in a second, opposite sense of rotation, respectively, characterized in that the rotary member comprises a hollow cylindrical sleeve (4) having a first cam follower (6) on its inner wall, the driven component comprises a first barrel cam (10) having a helical cam groove (12) in its outer wall configured to receive the first cam follower (6) and being supported in the sleeve (4) by a central rod (30) to be slidably moveable in axial direction but to be locked against rotational movements with respect to the central rod (30), the central rod (30) is supported in the housing to be moveable in axial direction but to be locked against rotational movements, and carries a second end stop (34) coupled thereto at a distance to the first barrel cam (10), the central rod (30) being configured to be linked to a shift fork, a compression mechanism (40) is configured to extend the central rod (30) from the first barrel cam (10) by biasing the second end stop (34) away from the first barrel cam (10), wherein the biased movement is limited by a first end stop (32) on the central rod (30), and the helical cam groove is configured such that rotation of the sleeve (4) in the first sense of rotation moves the first barrel cam (10) axially in a first direction, which movement is transmitted via the compression mechanism (40) to the central rod (30) to drive a coupled shift fork (50) from the neutral position towards the first gear engaged position, and such that rotation of the sleeve (4) in the second sense of rotation moves the first barrel cam in an opposite second direction, which movement is transmitted to the central rod (30) to drive a coupled shift fork (50) from the first gear engaged position to the neutral position.