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Aluminum harness
Product data
Aluminum harness

What is the wiring harness?

Just push a button and you can start engine or see DVD in the back sheet. With advancing car functions, the number of electronic devices mounted on an automobile is increasing. To connect each device and transfer electric power and signals to every corner of a car, a network of electric wiring, or wiring harness, is indispensable. It is an important part and likened to the blood vessels or nerves of the human body.

A wiring harness is made of bundled multiple wires. A car may use total 500 to 1500 wires in a form of wiring harness, with total length of two kilometers and total weight of 20 kilograms. Although it accounts for just 2% of total vehicle weight, with increasing demands for eco-friendly cars in and outside of Japan, improving fuel efficiency by reducing vehicle weight, including wiring harness, becomes one of the requirements today.

Features of Sumitomo Electric aluminum wiring harness

High-strength aluminum alloy wire
High-strength aluminum alloy wire

Usually wiring harness employs copper wires for their excellent conductivity.*1 To reduce vehicle weight, however, the Sumitomo Electric Group developed aluminum alloy wires, which have equivalent conductivity to copper wires at a half weight, and started sales of the aluminum wiring harness in 2010. However, the aluminum alloy wires developed at that time had poor vibration resistance in comparison with conventional copper wires, thus limiting application to the interior and instrument panel*2 wiring.

The development continued and in 2015, by exploiting the technology within the Group, new high-strength aluminum alloy wires, which exceed the strength of conventional copper wires, were successfully developed. The development has expanded the use of aluminum alloy wires to applications involving more severe vibration, such as engine harness.

In addition to the achievement in weight reduction, the development is also expected to contribute to the conservation of precious resources, because aluminum has several times greater reserves than copper.

Sumitomo Electric’s aluminum wiring harness is appreciated by automobile manufacturers in and outside of Japan and adopted in many car models, contributing to the reduction of vehicle weight and manufacturing costs .

Conductivity is an index to show ease of electric flow.
An instrument panel is a control panel placed in front of the driver.
Interview with the engineer in charge
Fumitoshi Imazato
Wires and Cables Laboratory, Wires and Cable Materials Research Department, AutoNetworks Technologies, Ltd.
Fumitoshi Imazato

What response have you had from customers?

An automobile is used in various conditions with different temperatures and humidity, and thus the wires used in a wiring harness need to resist high temperature and vibration. Our recently developed high-strength aluminum alloy wires showed excellent performance in severe and “mean” environmental examinations. As a result, the product is highly appreciated by our customers and adopted in engine harness for the first time in the world.

In the future, to further promote the replacement of conventional copper wires, we will expand the product range of aluminum alloy wires, and thus contributing to the improvement of fuel efficiency and the reduction of CO2 emissions, by reducing overall vehicle weight.

What difficulties did you face in developing the aluminum harness?

As conventional aluminum wires do not meet the requirements of wiring harness, both in strength and electrical conductivity at the same time, we needed to develop a new aluminum alloy. In particular, aluminum alloy used for engine harness requires more strength than that of copper, while maintaining high conductivity, thus demanding us delicate adjustment of alloy ingredients and thermal treatment conditions.

This time, in consideration of vibration resistance, we adopted ultrafine wires with a diameter of 0.155 mm, which provided us more difficulties in production. However, by establishing a unique processing technology, which is not conceivable in conventional wire manufacturing, we have solved this problem.

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