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The weight of wire harnesses increases with the growing number of systems used in the vehicle in recent years. For the purpose of reducing the weight of wire harnesses, aluminum instead of the conventional copper is getting popular as a wire conductor. The conventional Al wire, however, is not able to be used for small gauge wires such as the sizes of 0.35mm2 and 0.5mm2 and wires used in the engine compartment due to its insufficient conductor strength. For this reason, we tried to develop a stronger aluminum alloy that has conductor strength equivalent to or stronger than that of copper. For the first time in the industry, we have successfully developed a high-strength aluminum alloy wire. Starting with the application of 0.35mm2 wire for engine wire harnesses, we began mass production in April 2015. This paper reports the development of high-strength aluminum alloy that can be used for small gauge wires and wires used in the engine compartment.

From the viewpoint of reducing the environmental impacts by automobile emission, improving fuel efficiency is essential. That is why automobiles need to be lightened. However, more and more electrical systems have been necessary in an automobile to ensure safety and comfort. With the increase in the number of electrical systems, the weight of Electrical Distribution System (EDS) also has become increased. In order to reduce the weight of EDS, it was decided to evaluate a change of material from copper to aluminum. In fact, aluminum wires have been used for high-voltage wires, but they have almost never been used for low-voltage wires. SUMITOMO ELECTRIC GROUP developed an aluminum wire that is available for low-voltage wire harnesses and started mass production of the wire from October 2010. In this paper, I'm reporting mainly on our development of a new aluminum alloy that can be used for aluminum wires.

With the rapid advances in electronic control within automobiles, the junction block (J/B), primarily used for electrical transmission and electrical wiring, has begun to house electronic control units. It is evolving into an active component with smart functions that also controls vehicle devices, at the core of the wiring harness. We have developed a method using CAE to predict the fatigue failure life of J/B brackets for use as a design-assist tool in the early stage of J/B development. Failure of J/B brackets starts with the repetitive stress generated in the brackets during resonance. This stress is maximum at primary natural vibration which is the lowest frequency during resonance. By accurately estimating the above-mentioned stresses using CAE, we established a method to determine the number of vibrations at which fatigue failure of the J/B bracket would occur (fatigue failure life) from the fatigue failure life characteristics of the material.

Using tin-plated terminals generally used for vehicle connectors, we studied the variation in thickness of the oxide film on the terminal surface, progress of copper diffusion to the tin-plated layer, and terminal stress remaining rate against the ambient conditions of temperature, humidity, and oxygen concentration. As well, we collected terminals from aged vehicles for actual field data, and tested them in the same way. We analyzed the obtained data using the regression analysis technique and obtained an expression for the relationship between the environmental factors and the transition of the terminal state as time elapses. This paper describes the accelerated test method that produces the same results as actual products used for ten years, by making calculations with the said expression.

Electric connectors for automobile have a housing locking structure to prevent the electric contacts from being disconnected by vibration. As the environment in the automobile becomes more severe, the connector housing tends to deteriorate more quickly. However, we must make sure the locking structure does not break when disconnecting the connector for maintenance. We estimated the lifetime of the locking structure, focusing on heat deterioration properties by using CAE and Miner's rule. In addition, we determined the design standards and the accelerated test conditions to guarantee market reliability.

We developed a remote control unit (Hereinafter referred to as the controller) employing mainly an eight-directional joystick with push-button function. And it has good operational feeling. As previous joysticks generated operator feeling via springs, so the click sensation could not be felt. We thought that a good click feeling can be obtained by applying rubber contacts to the switch element of the joystick. Additionally, in order to include the push-button functions, we supported the operant unit with biaxial bearing and employed a sliding-knob structure penetrating this operant unit. Also in order to obtain a uniform operator feeling for all eight directions, we applied eight rubber contacts and gave the switches eight contacts. In order to restrain the rise in IC costs with the increase to eight contacts, we introduced an eight-contact four- output switch matrix and a one-contact three-electrode pattern.

This paper describes a display unit for automotive navigation systems. The distinguishing feature of this display unit is the fact that it employs a 5.6 inch TFT-LCD (Thin Film Transistor Liquid Crystal Display) for on-vehicle use. Compared with a 6-inch CRT, the unit has an expanded effective display area (screen) for improved readability, as well as greater compactness (for savingspace), lighter weight, and lower power consumption. In terms of reliability, the display unit outperforms conventional LCDs due to its wider working temperature range and outstanding resistance to thermal shock. In terms of operation, the system employs a combination of infrared touch switches, hard-key switches and a joy stick to ensure safety and ease of operation. The 1994 Model MAZDA “SENTIA” is equipped with this newly developed display unit for an automobile navigation system.

We have developed an optical link which is suitable for the on-vehicle environment and can be used in navigation systems and other applications. The distinctive features of this link are its fiber structure, terminal processing, shielding and protective mechanism for fiber ends. In terms of the fiber structure, a high tension of 100N has been realized without using tension member in the fiber, and a heat resistance temperature of 105 deg C has also been achieved. Terminal processing is done with only crimping and heat treatment, and shielding of the receiver IC is achieved with a molded component composed of electrically conductive plastic. To keep the ends of fibers from being damaged or soiled, the link is equipped with a mechanism wherein a protective hood rotates at engagement and disengagement.

We have developed a power window switch unit for use in multiplex wiring systems for automobile doors. As the systems are multiplexed, signal switches mounted on PC boards prove to be more advantageous than conventional switches having a metal spring and metal contact. We chose to use a rubber contact in one of the signal switches, and combined a good operational feeling into the rubber contact, thereby succeeding in designing a switch structure that requires less parts. We expressed the operational feeling of the switch by four values, and designed the switch with the help of CAE to meet each of the values. We could therefore develop a rubber contact with an operational feeling as high as we had aimed without the need to make any prototypes.