Gearshift Fork and Rod Interface for Reliable Gear Engagement

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Solution Overview

Problem

Existing gearshift arrangements in vehicle transmissions, particularly in heavy-duty vehicles, face issues with reliability and robustness due to unwanted forces acting on shift forks, leading to potential misalignment and mechanical failures.

Innovation Solution

A gearshift arrangement featuring a first shift fork and shift rod with a contacting interface designed to direct forces parallel to the movement direction, utilizing a curved surface and groove configuration, along with a biasing element and nested piston-sleeve mechanism to ensure reliable and robust movement, preventing unwanted gear positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional shift fork design is used, then the gearshift arrangement can be simple in structure, but unwanted forces act on the shift fork causing misalignment and mechanical failures

Engineering Contradiction:

ImprovereliabilityVSAvoidcomplexity of contacting interface

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The shift fork includes a curved surface and the shift rod includes a groove with a curved bottom, forming a contacting interface where the normal is continuously directed parallel to the shift rod axis. This curved geometry ensures that forces act along the intended movement direction, preventing misalignment and mechanical failures while maintaining structural simplicity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If the shift fork is moved without rotational freedom, then the structure is simpler, but the shift fork cannot properly engage with the clutch for gearwheel

Engineering Contradiction:

Improveengagement reliabilityVSAvoidcomplexity of shift fork movement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The shift fork is designed to be rotatable about a pivot located between its first end (contacting the shift rod) and its second end (engaging the clutch). This rotational freedom allows the shift fork to adapt its orientation during movement, ensuring proper engagement with the clutch while maintaining a relatively simple structure.

Inventive Principle:

Principle #15Dynamics

3Reliability

If forces are not directed parallel to the shift rod axis, then the contacting interface can be simpler, but unwanted forces cause misalignment and mechanical failures

Engineering Contradiction:

ImproverobustnessVSAvoidcomplexity of force direction control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The curved surface of the shift fork and the groove with curved bottom in the shift rod are specifically designed so that the normal to these surfaces at the contacting interface is continuously directed parallel to the shift rod axis. This geometric design naturally directs forces along the intended movement direction, preventing misalignment and mechanical failures without requiring additional complex force control mechanisms.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentEP4682403A1A gearshift arrangement and a vehicle

Publication Date: 2026.01.21 VOLVO TRUCK CORP

Figure 1
Figure 2a~2b
Figure 2c~2d

AI summary

The disclosure relates to a gearshift arrangement (1) comprising a first shift fork (5) and a first shift rod (51), wherein the first shift rod (51) is movable along a first shift rod axis (A) and is configured to move the first shift fork (5) between at least two positions.