Semiconductor Switch Integration in Electric Power Steering Control

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Solution Overview

Problem

Conventional electric power steering apparatuses face issues with mechanical relays, including large size, limited number of openings due to contact deterioration, and inadequate heat dissipation, leading to potential failures and increased lifespan degradation.

Innovation Solution

The use of semiconductor switch elements in an electric power steering apparatus with a control device integrated-type electric motor, where semiconductor power elements and switch devices are mounted on a board attached to a metallic case, allowing for efficient power management and heat dissipation, reducing the size and improving reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical relay is used as a protective relay, then the electric motor can be protected from abnormal behavior, but the control device requires a comparatively large volume and the contact point deteriorates limiting the number of openings

Engineering Contradiction:

Improveprotection functionVSAvoidcontrol device volume

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent replaces the mechanical relay with a semiconductor switch element that has a failure-proof structure. The semiconductor switch element inherently prevents short-circuiting between the collector and emitter, eliminating the need for a mechanical relay while maintaining the protection function. This substitution reduces the control device volume and removes the limitation on the number of openings.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and eliminates the mechanical relay component from the system by using a semiconductor switch element with built-in failure prevention. The protective function is integrated into the semiconductor switch element itself, removing the separate mechanical relay and its associated volume requirements.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If a mechanical relay is used as a protective relay, then the electric motor can be protected from abnormal behavior, but the contact point deteriorates reducing lifespan

Engineering Contradiction:

Improveprotection functionVSAvoidrelay lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent replaces the mechanical relay with a semiconductor switch element that has no moving parts or contact points subject to wear. The semiconductor switch element provides the same protective function but with indefinite lifespan as there are no contact points to deteriorate.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses a semiconductor switch element with a failure-proof structure that eliminates the need for maintenance or replacement due to contact point deterioration. The inherent design prevents short-circuiting, making the component effectively permanent rather than short-lived.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Temperature

If the contact point of the protective relay is enlarged to suppress heat generation, then heat dissipation is improved, but the control device size increases

Engineering Contradiction:

Improveheat dissipationVSAvoidcontrol device volume

Core Design Contradiction:

TemperatureVSVolume of stationary object

Solution Approach 1:

The patent replaces the mechanical relay with a semiconductor switch element that generates less heat and requires smaller conductive members. The semiconductor material inherently has better electrical conductivity, allowing for smaller component sizes while maintaining effective heat dissipation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the material parameter from mechanical relay contacts to semiconductor material, which has superior electrical and thermal properties. This parameter change allows for smaller component dimensions while achieving better heat dissipation performance.

Inventive Principle:

Principle #35Parameter changes

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

This configuration results in a smaller, more efficient, and reliable electric power steering system that prevents degradation and lifespan issues, while effectively managing heat and reducing mechanical failures.

Implementation Method 1

the power elements and the semiconductor switch element are mounted on a board attached to a metallic case... the heat dissipation performance of the protective relay and the control device is not particularly considered, and dissipation of internally generated of heat is structurally difficult

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS8924081B2Electric power steering apparatus and control device integrated-type electric motor

Publication Date: 2014.12.30 MITSUBISHI ELECTRIC CORP

AI summary

An electric power steering apparatus and control device integrated-type electric motor includes an electric motor driving circuit constituted by a plurality of semiconductor power elements and controlling electric power supplied to an armature winding of an electric motor, a switch device for opening and closing a connection between an input terminal of the electric motor driving circuit and an external power source, and another switch device for opening and closing the armature winding, wherein at least one of both the switch devices is constituted by a semiconductor switch element, and the power elements and the semiconductor switch element are mounted on a board attached to a metallic case.