Along with the increase of electronic devices used in automobiles, the use of wiring harnesses for power and signal systems on board is growing remarkably. In these circumstances, the electromagnetic interference (EMI) generated by the power system should cause troubles on signal systems and other chassis-mounted electronic devices. Wiring harnesses act as the direct transmission lines of EMI, so the shielding has become an essential element of power wiring harness system. Generally, braided shield cables and shielded connectors have been used as the EMI shielding measures on the wiring harnesses. Such measures, however, resulted in the increase in cost and size of wiring harnesses. This paper describes the development of a low-cost shielded construction for high-voltage wiring harnesses applied in Toyota’s hybrid electric vehicle (HEV), new Prius.
Conventional high-voltage harnesses using braided wire
Figure 1 shows the appearances of high-voltage wiring harnesses used to connect the motor and inverter of a Toyota Crown 42V (mild hybrid) and an Estima HEV, as well as the locations of these components on board. Both vehicles use braided shield cables together with shielded connectors, with the end of the braided shield connected electrically to the connector shield and high voltage unit.
The photographs in Fig. 2 show shielded high-voltage connectors used in the Estima HEV. Details of the construction for this connector for use with a shielded terminal construction connected electrically to the braided shield will be discussed later. 1-2 New high voltage wiring harness using a bundle shield construction
Figure 3 shows the high-voltage wiring harness used in the new Toyota Prius.
Figure 4 shows the component parts of this high-voltage wiring harness with bundle shield construction, both prior to and after assembly. The wiring harness assembly comprises electrical wire and a waterproof connector, a bundle shield, and a sheath. With the exception of the bundle shield, the other parts are basically the same as those used in a conventional waterproof wiring harness. In other words, the bundle shield is simply used to add a shield to a conventional wiring harness.

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