Gear Shift Lever Joint Geometry for Low-Friction Rotation Lock

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Solution Overview

Problem

Existing ball and socket gear shift devices for motor vehicles suffer from high friction torque and bulkiness due to the need for oversized components to accommodate sweeping motions, resulting in undesirable bulky assemblies.

Innovation Solution

A gear shift device with a hollow, at least partially spherical retaining housing and a gear shift lever featuring a partially spherical projection with retaining means comprising grooves and protrusions in the shape of two opposite cones, preventing rotation around the longitudinal axis while allowing pivotal movement, thus reducing size and increasing rigidity and strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If protrusions slide on grooves performing a sweeping motion to prevent rotation, then the gear shift lever is retained against rotation, but the surrounding parts must be oversized resulting in bulky assemblies

Engineering Contradiction:

Improveretention against rotationVSAvoidsize of ball and socket joint

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The retaining means are segmented into discrete protrusions and grooves with specific geometric shapes (conical or planar surfaces) that divide the retention function into distinct contact zones. This segmentation allows the lever to be retained against rotation without requiring a large sweeping motion envelope, as each segmented element provides a specific constraint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of allowing free sweeping motion and constraining it with large surrounding parts, the invention inverts the approach by designing the protrusions and grooves with specific orientations (conical or planar surfaces angled relative to the longitudinal axis) that inherently guide and constrain the motion path. This inverted design allows the constraint geometry itself to define the motion envelope rather than requiring external oversized structures.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If oversized components are used to accommodate sweeping motion, then rotation prevention is achieved, but friction torque and wear increase

Engineering Contradiction:

Improverotation preventionVSAvoidfriction torque

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The contact between protrusions and grooves is segmented into discrete point or line contacts rather than continuous surface contact. The conical or planar surfaces create specific contact zones that minimize the area of interaction, thereby reducing friction torque while maintaining effective rotation prevention through the geometric constraint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The geometric parameters of the protrusions and grooves are optimized with specific surface orientations (conical angles or planar inclinations) that reduce the normal force during operation. By changing the angular parameters of the contact surfaces relative to the longitudinal axis, the invention minimizes the frictional component while maintaining the rotational constraint function.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional retaining means are used, then the lever is retained against rotation, but the assembly becomes bulky and less rigid

Engineering Contradiction:

Improveretention functionVSAvoidrigidity of assembly

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The retaining function is segmented into multiple discrete protrusion-groove pairs distributed around the lever. This segmentation allows each element to be compact while collectively providing robust rotation prevention. The distributed segmentation enhances rigidity by creating multiple constraint points rather than relying on a single large retaining structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The lever features a spherical projection that interfaces with the retaining housing, and the protrusions/grooves utilize conical or planar curved surfaces. This spheroidal geometry provides inherent rigidity and strength while maintaining a compact form factor, as the curved surfaces distribute stresses more effectively than flat or angular geometries would in this application.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10927947B2Gear shift device for motor vehicles

Publication Date: 2021.02.23 FICO TRIAD

AI summary

A gear shift device (100) includes a hollow, at least partially spherical retaining housing (110), a gear shift lever (120) having an at least partially spherical projection (130) received within the retaining housing (110), and means (140) for retaining the gear shift lever (120) against rotation around its longitudinal axis (125). The retaining means (140) includes at least one of grooves (150) and protrusions (160) for engaging at least one of corresponding grooves (150′) and protrusions formed in the at least partially spherical projection (130) of the gear shift lever (120), said grooves (150, 150′) and protrusions (160) being formed in the shape of two opposite cones.