Brush Motor Life Estimation Without a Current Sensor

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Solution Overview

Problem

Conventional life determining devices for brush motors require a current sensor to estimate motor current, which is not always feasible or necessary.

Innovation Solution

A life determining device that estimates the current of a brush motor using fluid temperature and pressure, eliminating the need for a current sensor by employing a current estimating unit, operation time measuring unit, and life determining unit, with a stored map to derive current values based on temperature and pressure parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a current sensor is provided to measure motor current for life determination, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvemotor current measurementVSAvoidsensor quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses fluid temperature and fluid pressure as intermediary parameters to indirectly estimate motor current. Instead of directly measuring current with a sensor, the system measures temperature and pressure of the fluid passed through the motor, then uses these readings to calculate the current via a map or formula, eliminating the need for a current sensor while maintaining measurement capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the electrical measurement system (current sensor) with a thermal-hydraulic measurement system. By measuring fluid temperature and pressure changes caused by motor operation, the system substitutes direct electrical current measurement with indirect thermal and pressure-based estimation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If fluid temperature and pressure are used to estimate motor current, then device complexity is reduced, but measurement precision may deteriorate

Engineering Contradiction:

Improvesensor quantityVSAvoidcurrent estimation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent transforms the current measurement problem into a different parameter space by using temperature and pressure parameters instead of direct current parameters. A map or calculation formula is established that correlates fluid temperature and pressure with motor current, allowing accurate current estimation through parameter transformation rather than direct measurement

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system continuously monitors fluid temperature and pressure and uses this feedback to dynamically estimate motor current. The estimation is updated based on real-time temperature and pressure readings, creating a closed-loop system that adapts to changing operating conditions and maintains accuracy

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20240231354A1Life determining device and life determining method

Publication Date: 2024.07.11 TOYOTA JIDOSHA KK

AI summary

ECU is configured to determine a life of a brush motor that is a power source of the oil pump. ECU estimates the motor current of the brush motor based on the oil temperature and the hydraulic pressure. ECU measures the operation time of the brush motor at the estimated motor current. ECU determines the life of the brush motor based on the estimated motor current and the measured operation times.