Front Loader Boom Angle Sensing That Absorbs Backlash

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Solution Overview

Problem

Existing front loader systems face issues in accurately detecting the relative rotation angle between members due to backlash and tolerance, leading to improper detection when the distance between the detection unit and the portion to be detected exceeds the optimal operation distance.

Innovation Solution

A configuration that includes a fixing member, a rotating member, a detection unit, and an engagement member, where the engagement member is engaged with the rotating member to allow axial movement, and an engagement groove is formed in the radial direction to accommodate for backlash, ensuring the detection unit maintains a consistent distance from the portion to be detected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an angle sensor is provided between two relatively rotating members (such as a boom), then the rotation angle can be detected, but the distance between the portion to be detected and the detection unit may exceed the appropriate operation distance due to backlash and tolerance

Engineering Contradiction:

Improverotation angle detection accuracyVSAvoiddetection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The detection system is segmented into three independent components: a fixing member attached to the first rotating member, a rotating member that rotates relative to the fixing member, and an engagement member that connects to the second rotating member. This segmentation isolates the detection unit from the effects of backlash between the first and second rotating members, maintaining a stable detection distance while enabling accurate rotation angle measurement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The rotating member acts as an intermediary between the fixing member and the engagement member. It transfers the rotational motion from the engagement member to the detection unit while maintaining a constant operational distance between the detection unit and the portion to be detected, thereby eliminating the negative effects of backlash and tolerance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the distance between the portion to be detected and the detection unit is kept at an appropriate operation distance, then accurate detection is possible, but additional components and complex structure are required to maintain this distance against backlash

Engineering Contradiction:

Improvedetection accuracyVSAvoidstructure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The rotating member is designed to rotate freely relative to the fixing member while maintaining a fixed operational distance. This dynamic design allows the system to accommodate backlash and tolerance between the first and second rotating members without requiring complex adjustment mechanisms, thereby maintaining detection accuracy with a relatively simple structure.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The fixing member, rotating member, and engagement member are combined into a integrated detection mechanism that automatically maintains the appropriate operation distance. This merging eliminates the need for separate adjustment mechanisms or additional components that would otherwise be required to compensate for backlash and tolerance.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If backlash between rotating members is accommodated, then detection accuracy is maintained, but the engagement member may disengage from the rotating member

Engineering Contradiction:

Improverelative rotation angle detection accuracyVSAvoidengagement reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The engagement member is designed with an engagement groove that extends in the radial direction, allowing the rotating member to be nested within it. This nested configuration enables the rotating member to move axially within the engagement groove to accommodate backlash, while the protruding engagement member prevents complete disengagement, thereby maintaining both detection accuracy and engagement reliability.

Inventive Principle:

Principle #7Nested doll (Nesting)

4Reliability

If the engagement member is fixed rigidly to the rotating member, then engagement is maintained, but the detection accuracy is affected by backlash and tolerance

Engineering Contradiction:

Improveengagement stabilityVSAvoidrotation angle detection precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The rotating member is designed to rotate relative to the fixing member while the engagement member maintains a stable engagement relationship. This dynamic configuration allows the system to accommodate backlash between the first and second rotating members without compromising engagement stability, thereby achieving both reliable engagement and accurate detection.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20260055572A1Front loader and working vehicle

Publication Date: 2026.02.26 KUBOTA CORP

AI summary

Included are: a fixing member (boom rotating shaft) fixed to the first member (side frame); a rotating member (sensor stay) relatively rotatable with respect to the fixing member, a portion to be detected (magnet) fixed to one (boom rotating shaft) of the fixing member and the rotating member, a detection unit (sensor body) fixed to the other (sensor stay) of the fixing member and the rotating member and configured to detect a relative rotation angle of the portion to be detected, and an engagement member (detection rod) fixed to the second member (boom) and engaged with the rotating member in a state of allowing movement of the rotating member in an axial direction of a rotating shaft.