Lawn Mower Height Adjustment via Torque Limiter Sensor

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Solution Overview

Problem

Existing work machines with torque limiters face accuracy issues in adjusting the working height due to interrupted motor force transmission, which impairs the correlation between motor rotation and unit position, leading to deteriorated height adjustment accuracy.

Innovation Solution

A work machine with a torque limiter that includes a displaceable transmission member biased by an elastic member and a sensor to detect the transmission state, allowing accurate detection of upper and lower limit positions, enabling precise height adjustment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a torque limiter is used to prevent overload at upper/lower limit positions, then the motor and lifting mechanism are protected from damage, but the correlation between motor rotation amount and work unit position is impaired, deteriorating height adjustment accuracy

Engineering Contradiction:

Improveprotection of motor and lifting mechanismVSAvoidposition detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

A sensor is introduced as an intermediary device to detect the transmission member's position, which indirectly indicates the work unit's position. This mediator bypasses the correlation breakage caused by the torque limiter, allowing accurate position detection without requiring direct motor rotation measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical correlation-based position detection (relying on motor rotation amount) with a sensor-based detection system. The sensor detects the transmission member's position directly, substituting the mechanical measurement approach with an sensing approach that works independently of the torque limiter's interruption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the transmission member is made displaceable to enable torque limiting, then overload protection is achieved, but the structural complexity of the lifting mechanism increases

Engineering Contradiction:

Improveoverload protection capabilityVSAvoidlifting mechanism structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The torque limiter function is merged with the existing lifting mechanism structure by integrating the transmission member into the lifting mechanism's transmission path. The transmission member serves dual purposes: it is part of the lifting mechanism's power transmission and simultaneously functions as the torque limiter's movable element. This merging avoids adding a completely separate torque limiter assembly.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The transmission member is designed with multi-functionality: it acts as both a power transmission component and a torque limiter element. By making the transmission member displaceable between transmission and non-transmission positions, it provides both lifting function and overload protection function, reducing the need for additional dedicated components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution improves the accuracy of height adjustment by detecting the torque limiter state, reducing the need for multiple sensors and allowing adjustment without a rotation amount sensor, enhancing the precision and cost-effectiveness of the process.

Implementation Method 1

an elastic member configured to bias the transmission member to the transmission position

Methodology Applied

Scientific EffectElastic force: Elasticity

Data Source

PatentUS12102036B2Lawn mower cutter height adjustment

Publication Date: 2024.10.01 HONDA MOTOR CO LTD

AI summary

A work machine includes a work unit, and an adjustment unit configured to adjust a working height of the work unit. The adjustment unit includes a lifting mechanism configured to lift and lower the work unit; a torque limiter configured to interrupt transmission of a driving force of a motor to the lifting mechanism when the work unit reaches an upper and lower limit positions; and a sensor. The torque limiter includes a transmission member provided to be displaceable between a transmission position at which the driving force is transmitted to the lifting mechanism and a non-transmission position at which the driving force is not transmitted to the lifting mechanism, and an elastic member configured to bias the transmission member to the transmission position. The sensor detects displacement of the transmission member.