Selector Piston Mounting for Play-Free Transmission Rod Actuation
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Solution Overview
Problem
Existing hydraulic setting devices for actuating selector rods in transmissions face challenges such as axial play, which affects precise stroke detection, gear engagement, and leads to increased wear and energy losses, particularly due to the use of plastics materials and screw connections that require matching tolerances and can result in excessive stress and crushing.
Innovation Solution
A setting device with a selector piston mounted on a selector rod using a securing screw and a washer embedded in the plastics material, providing a play-free connection by distributing clamping forces between metallic components, thus eliminating the risk of damaging plastics materials and allowing for precise gear engagement and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a securing screw with collar section and threaded section is used to connect the selector piston to the selector rod, then the connection strength is improved, but axial play between the selector piston and selector rod increases due to tolerance accumulation
Solution Approach 1:
A play-free connection element is introduced as an intermediary component between the selector piston and selector rod. This element has a first connection portion that engages with the selector piston and a second connection portion that engages with the selector rod, eliminating axial play while distributing mechanical stresses away from the plastics material of the selector piston.
Solution Approach 2:
The connection system is divided into separate functional components: the securing screw provides clamping force, the play-free connection element provides precise positioning and play-free connection, and the washer distributes loads. This segmentation allows each component to optimize its specific function without compromising the others.
2Ease of manufacture
If the selector piston is made from plastics material to reduce weight and corrosion, then the ease of manufacture is improved, but the risk of crushing and excessive stress increases when using screw connections
Solution Approach 1:
The play-free connection element acts as a mediator that transfers mechanical loads between the selector piston and selector rod without concentrating stresses on the plastics material. The load path goes through the metallic connection elements rather than directly through the plastics, preventing crushing while maintaining the benefits of using plastics for the piston body.
Solution Approach 2:
The play-free connection element and washer are designed as replaceable metallic components that can be easily replaced if worn or damaged, while the main selector piston body made from durable plastics remains in place. This approach protects the investment in the molded piston while allowing replacement of wear-prone connection elements.
3Ease of operation
If axial play is allowed for ease of assembly with circlip retention, then the ease of operation is improved, but the measurement precision of selector piston stroke detection deteriorates
Solution Approach 1:
The play-free connection element serves as a precision intermediary that transmits the exact position and stroke of the selector piston to the selector rod without the interference of axial play. This enables accurate stroke detection while still allowing for simple assembly operations.
Data Source
Figure 1
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Figure 5
AI summary
A setting device (10) for actuating a transmission selector rod (12) has a cylinder housing (14) in which a selector piston (16) is displaceably received that has a base body (18) of plastics material. The selector piston is provided with a recess (26) extending along a longitudinal axis (24) for reception of an end (28) of the selector rod and is mounted on the end of the selector rod by a securing screw (30) with a screw head (32). For play-free connection of the selector piston with the selector rod a washer (34) protruding transversely to the longitudinal axis into the recess is embedded in the plastics material of the base body and as seen along the longitudinal axis forms on a front side a first support surface (36) for the screw head and on a rear side a second support surface (38) for the end of the selector rod.