The wiring harness provides the totality of service equipment for a certain load source group, such as trunk lines, switching devices, control systems, etc. The basic research content of traffic theory is to study the relationship between traffic volume, call loss and wire harness capacity. Therefore, wire harness is an important basic concept in traffic theory. The load source is the service object of the wire harness, which usually refers to the user equipment; in a broad sense, the upper-level equipment is the load source of the lower-level equipment. In telephone communication, the load source is also called the voice source. The number of service equipment contained in the wire harness is called the capacity of the wire harness. The capacity of the wire harness is V, which provides services for N load sources. Any load source making a call can occupy an idle service device in the harness.
The standard of the wire harness is mainly calculated by its crimping rate. The calculation of the crimping rate needs to pass a special instrument. The wire harness cross-section standard detector developed by the optical instrument factory is the most effective test specially used to detect whether the crimping of the wire harness is qualified. instrument. It is mainly completed through the steps of cutting, grinding and polishing, corrosion, observation, measurement and calculation.
Automotive wiring harness supplies, including their electrical properties, material emission, temperature resistance, etc., are higher than the general wiring harness requirements, especially when it comes to safety requirements.
1. The ambient temperature around the engine is high, and there are many corrosive gases and liquids. Therefore, the wires of the engine wiring harness must use high-temperature, oil-resistant, vibration-resistant and friction-resistant wires.
2. The wire on the automatic transmission uses the wire with good resistance to hydraulic oil, high temperature and temperature stability.
3. The wires of the wiring harness on the trunk lid should maintain their elasticity at low temperatures, so cold elastic wires should be selected to ensure their normal operation.
4. Shielded wires should be used for weak signal sensors.
5. The ABS wire harness assembly uses stranded wires with a high temperature resistance of 150-200 °C, a hard outer protective insulating layer and wear resistance, but the cores should be larger than 133.
6. The wires used in power lines such as starter alternator output wires and battery wires are special wires that can withstand high current and have good heat dissipation performance and reduced voltage.
In modern cars, the electronic control system is closely related to the wiring harness. Someone once made a vivid analogy: the microcomputer is equivalent to the human brain, the sensor is equivalent to the sensory organ, the actuator is equivalent to the motor organ, then the wiring harness is the nerve and blood vessel.
In terms of function, the automobile wiring harness has two types: the power line that carries the power of the driving actuator and the signal line that transmits the input command of the sensor. Power lines are thick wires that carry large currents, while signal lines are thin wires that do not carry power (optical fiber communication).
The cross-sectional area of the wire used in the motor and actuator is 0.85, 1.25mm2, while the cross-sectional area of the wire used in the power circuit is 2, 3, 5mm2; and the special circuit (starter, alternator, engine grounding wire, etc.) has 8, 10, 15, 20mm2 different specifications. In addition to considering the electrical performance, the selection of wires is also restricted by the physical performance of the vehicle. For example, the frequently opened and closed doors on a taxi and the wires that span the body should be constructed of wires with good flex properties. In recent years, electromagnetic shielding wires used in weak signal circuits have also been increasing.
With the increase of car functions and the widespread application of electronic control technology, the number of circuits and power consumption on the car have increased significantly, and the wire harness has become thicker and heavier. How to make a large number of wire harnesses more effective and reasonable in the limited car space layout, so that the car cable can play a greater role, has become a problem faced by the automobile manufacturing industry.