Electric power steering device

Abstract

Provided is an electric power steering device that is capable of estimating coil temperatures more accurately for a polyphase motor including multi-system motor windings, with consideration also givento a heat-transfer phenomenon between a control board and coils in addition to heat-transfer phenomena between respective phases of polyphase coils, and that is also capable of estimating coil temperatures even when there is an abnormality in one of the systems. The electric power steering device comprises: a temperature sensor that detects a board temperature of a control board; and a coil temperature estimation unit that finds, from motor currents of respective phases of a polyphase motor, coil heat-generation amounts of the respective phases and a board heat-generation amount of the control board, and that estimates coil temperatures of the respective phases from the coil heat-generation amounts, the board heat-generation amount, and the board temperature on the basis of heat-transferphenomena between the respective phases caused by temperature differences between coils of the respective phases and a heat-transfer phenomenon between the coils and the control board. In cases wherethere is an abnormality in one of the systems, the coil temperature estimation unit estimates the coil temperatures from the board temperature and values obtained by correcting the coil heat-generation amounts and the board heat-generation amount found in the normal system. The heat-transfer phenomenon is expressed by a differential equation.

Description

Technical field [0001] The present invention relates to an electric power steering device having a function of estimating the coil temperature of a multi-phase motor with multiple motor windings. The present invention particularly relates to an electric power steering device, the electric power steering device Consider the heat transfer phenomenon between the phases due to the temperature difference between the coils of each phase and the heat transfer phenomenon between the coil and the control board to estimate the coil temperature. The coil temperature can be calculated even when any system is abnormal. estimate. Background technique [0002] The electric power steering (EPS) that uses the rotational force of the electric motor to impart the steering assist force (assist torque) to the vehicle's steering system, and applies the driving force of the electric motor to the steering assist force via a gear or belt transmission mechanism via a reduction mechanism. Steering shaft o...

AI Technical Summary

Problems solved by technology

[0011] In such an electric power steering device, depending on the steering situation, a large current may flow through the motor (for example, when the end of the steering wheel is held in a locked state for a long time in a stationary state, etc.), when the motor inside When the coil reaches a high temperature such as 180°C or higher, problems such as coil damage will occur

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