Motor Temperature Detection Circuit Isolation and Current Correction

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Solution Overview

Problem

The existing temperature detection systems in motor-driven devices suffer from errors due to the overlap between the current path for detecting thermistor voltage and the current path for the motor, leading to inaccurate battery temperature readings, which can result in unnecessary reduction or suspension of the conducting current, affecting device usability.

Innovation Solution

A device body with a current detector and correction unit is implemented to correct temperature information based on the conducting current, reducing the influence of the motor's current on the temperature detection, thereby improving the accuracy of battery temperature detection and abnormality determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the current path for detecting thermistor voltage overlaps with the current path for motor conducting current, then the device structure is simplified, but the temperature detection accuracy deteriorates due to voltage drop interference

Engineering Contradiction:
Improvecurrent path structureVSAvoidtemperature detection accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent extracts the temperature detection function from the motor current path by introducing a separate detection current path. The detection current is supplied through a dedicated terminal (S1, S2) that is electrically isolated from the motor current path, allowing temperature measurement without interference from motor operating currents. This separation eliminates the voltage drop interference while maintaining structural simplicity.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary detection current path that mediates between the thermistor and the measurement system. By using a separate current supply terminal and detection terminal, the system creates an intermediary measurement pathway that does not share the high-current motor path, thus eliminating direct interference while still achieving temperature monitoring.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Device complexity

If temperature detection is performed using the existing current path, then the device complexity is reduced, but erroneous temperature readings occur leading to unnecessary current reduction

Engineering Contradiction:
Improvedetection system structureVSAvoidtemperature reading accuracy
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent segments the electrical system into distinct functional pathways: a motor current path for power delivery and a separate detection current path for temperature measurement. By providing separate terminals (S1, S2) for detection current supply and detection, the system divides the measurement function from the power function, eliminating interference and ensuring reliable temperature readings without increasing overall system complexity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent implements feedback by continuously monitoring the temperature through the separate detection path and using this information to control motor current. The detection terminal provides accurate feedback on battery temperature, enabling the control unit to make informed decisions about current limiting, thus preventing erroneous temperature-based current reduction while maintaining battery protection.

Inventive Principle:
Principle #23Feedback

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 effectively reduces detection errors and unnecessary corrections, enhancing the usability of motor-driven devices by providing more accurate temperature readings and preventing erroneous determination of battery temperature abnormalities.

Implementation Method 1

a temperature detector configured to vary a resistance value of the temperature detector in accordance with temperature of the battery

Methodology Applied
Scientific EffectThermistor effect: Thermistor

Implementation Method 2

a correction unit configured to correct the temperature information based on the current value so as to reduce influence given to the temperature information by the conducting current

Methodology Applied
Scientific EffectVoltage drop compensation: Ohm's Law

Data Source

PatentEP3107180B1Device body, motor-driven device, and temperature detection method
Publication Date: 2020.03.25 MAKITA CORP
  • EP3107180B1 patent drawingFigure 1
  • EP3107180B1 patent drawingFigure 2
  • EP3107180B1 patent drawingFigure 3

AI summary

A device body (5, 105) in one aspect of the present disclosure comprises a motor (20), a current path (43), a positive terminal (41), a negative terminal (42), a device-side signal terminal (45), a temperature information detector (64), a current detector (68, 64), and a correction unit (64). The correction unit (64) is configured to correct temperature information based on a current value of a conducting current, so as to reduce an influence given to the temperature information by the conducting current.