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The Nerves and Blood Vessels of a Vehicle

Some say today’s automobiles are giant electronic devices, such is the number of electrical and electronic components built into them. Wiring harnesses convey power and electrical signals to these components. Instructions to turn on the ignition, headlights, and radio, and inflate the airbag are all transmitted via wiring harnesses. Cars today cannot go forward or stop without wiring harnesses, which are often described as the nervous system and blood vessels of a vehicle. The quantity of wiring harnesses required per vehicle increased with the use of electronic components. Although depending on the type and size of vehicle, a typical passenger car today requires over 1,000 electric wires, and the total length of wiring harness is around 1,500m. Simply increasing the quantity of wiring harness makes the vehicle heavier and compromises fuel consumption. Since it has to fit in a limited space, there is a limit to how much wiring a vehicle can have. For this reason, explains Takahiro Kato, general manager of Sumitomo Wiring Systems, Ltd. Electrical & Electronics Network System (EENS) Development Group, “progress with wiring harness development is focused solely on achieving smaller, thinner, and more lightweight components.”

Takahiro Kato, general manager of Sumitomo Wiring Systems

“Making vehicles more lightweight is an eternal development goal. We also want to make the interior as spacious as possible to maximize the comfort of the driver and passengers. We approach the task of making wiring harness lighter and more compact from various angles, such as developing finer wires and coatings, reducing the size of connectors by using narrower pitches, cutting down on the number of system circuits by the use of multiplexed communications wiring, and extending in-car LANs. The main size of electric wire used in wiring harnesses was 0.5mm2 20 years ago. Today, the smallest mass-produced wire is 0.2mm2; i.e., the size has been reduced to less than half. The thickness of the wire coating has also been reduced to about a third in 20 years. As a result of the constant increase in the number of electronic components, some parts of the vehicle require around 100 wires in a single location. For this reason, even size reductions of less than a millimeter can make a significant impact.