Alternator Rectifier Disk Hollow Structure Reduces Pellet Stress

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Solution Overview

Problem

Conventional alternators face challenges in reducing stress on semiconductor pellets in rectifiers due to hardness differences between heat sinks and disks, leading to increased heat generation and difficulty in downsizing the rectifier while maintaining effective cooling performance.

Innovation Solution

The alternator design features a heat sink with holes that allow disks to be positioned between its surfaces, reducing stress on semiconductor pellets by limiting contact to a specific surface area and using a disk structure with a solid portion and hollow portion to distribute force, thereby stabilizing the attachment and reducing thermal stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the disk is thickened to place the semiconductor pellet further away from the heat sink surface, then stress on the semiconductor pellet is reduced, but the rectifier cannot be downsized

Engineering Contradiction:

Improvestress on semiconductor pelletVSAvoidrectifier size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The invention transitions from a conventional thick disk design to a thin disk design by utilizing the hollow portion structure. This dimensional change allows the semiconductor pellet to be positioned away from the heat sink surface not through increased thickness but through the creation of a hollow space, thereby reducing stress on the pellet while maintaining compact rectifier dimensions.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The disk is segmented into a solid portion and a hollow portion. The hollow portion creates space to position the semiconductor pellet away from the heat sink surface without increasing the overall disk thickness. This segmentation allows the disk to maintain structural integrity while providing the necessary spacing to reduce stress on the semiconductor pellet.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If holes in the heat sink are formed by deformation processing, then manufacturing is simplified, but the size of each hole cannot be precisely set and hardness at portions surrounding the holes is heightened

Engineering Contradiction:

Improveheat sink manufacturingVSAvoidhole size precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention changes the parameter of disk thickness to be smaller than the heat sink thickness, which compensates for the imprecision in hole sizing caused by deformation processing. By making the disk thin and utilizing the hollow portion, the design becomes less sensitive to variations in hole dimensions, allowing the use of simpler deformation processing while maintaining acceptable assembly quality.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If the alternator is disposed near the engine to accommodate limited space, then vehicle layout requirements are met, but heat received in the alternator from the engine is increased

Engineering Contradiction:

Improvealternator sizeVSAvoidheat received from engine

Core Design Contradiction:

Volume of moving objectVSTemperature

Solution Approach 1:

The invention converts the harmful thermal stress that would normally result from close proximity to the engine into a benefit by designing a disk structure with a hollow portion. This structure reduces stress on the semiconductor pellet, making the rectifier more tolerant of thermal environments. The reduced stress allows the alternator to withstand higher temperatures without compromising the reliability of the semiconductor components.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design effectively reduces stress on semiconductor pellets, allowing for stable attachment and improved cooling performance without enlarging the rectifier, even when the heat sink and disk hardness vary, and enables downsizing of the rectifier while maintaining efficient heat dissipation.

Implementation Method 1

To dissipate heat generated in the semiconductor pellets to the atmosphere, the disks of the rectifier are attached to a heat sink

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a heat dissipating area of the heat sink becomes large, so that a cooling performance of the rectifier can be improved

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS7876006B2Alternator for vehicle

Publication Date: 2011.01.25 DENSO CORP

AI summary

An alternator has a rectifier converting an alternating current to a direct current. The rectifier has a heat sink and rectifying elements. The sink has front and rear surfaces opposite to each other along a depth direction. The sink has holes each extending along the depth direction. Each element has a disk disposed in one hole and a semiconductor pellet attached to the disk. Each disk has upper and bottom surfaces opposite to each other along the depth direction. Each pellet is disposed on the upper surface. A contact surface of each disk is in contact with the sink. A position of the upper surface of each disk is placed between the first and second surfaces of the heat sink. A range of the contact surface of each disk is within a range between the upper and bottom surfaces of the disk.