With the continuous improvement of people's requirements for comfort, economy and safety, the types of electronic products in automobiles are also increasing, and the failure rate of increasingly complex harnesses in automobile harnesses is also increasing accordingly. This needs to improve the reliability and durability of the harness. Many people are interested in the technology and production of automobile harness. Here, we will briefly introduce the technology and production knowledge of automobile harness.

After the two-dimensional product diagram of automobile harness is drawn, it is necessary to arrange the production process of the harness, which serves the production.

Production technology of automobile wire harness:

Line opening process

The line opening is the first stop of harness production, and the accuracy of the line opening process is directly related to the entire production schedule. If there are errors, especially if the opening size is too short, all stations will rework, which will waste time and energy and affect production efficiency. Therefore, when preparing the wire opening process, it is necessary to reasonably determine the wire opening size and stripping size according to the drawing requirements. Make line opening operation instructions and process tracking cards.

Crimping process

At the second production station after the line is opened, the crimping parameters shall be determined according to the terminal type required by the drawing, and the crimping operation instructions shall be prepared. For special requirements, the operators shall indicate on the process documents and be trained. For example, some wires need to pass through the sheath to be crimped. It needs to be pre-installed and then returned from the pre-installation station before crimping; There are also special crimping tools for puncture crimping, with good electrical contact performance.

Pre-assembly process

Prepare the pre-assembly process operation instructions. In order to improve the efficiency of the final assembly, the pre-assembly station should be set for the complex harness. Whether the pre-assembly process is reasonable or not will directly affect the overall assembly efficiency and reflect the technical level of a technician. If fewer pre-assembled parts are assembled or the assembly route is ignored, the workload of the general assembly personnel will be increased and the speed of the assembly line will be reduced. Therefore, the process personnel should always stay at the site and constantly summarize their experience to develop a reasonable production process.

FA Process

According to the assembly platform designed by the Product Development Department, design the size of tooling equipment and material box specifications, and paste the number of all assembly jackets and accessories on the material box to improve the assembly efficiency. Formulate the assembly contents and requirements of each station, balance the entire assembly station, and prevent a little too much work from slowing down the speed of the entire assembly line. In order to achieve station balance, the technologist must be familiar with each operation, measure the working hours on site, and adjust the assembly process at any time. The harness also includes the preparation of material consumption quota schedule, man-hour measurement, worker training, etc.

The car harness is mainly made of terminal wires, and there is not much welding and forming. So the investment is mainly terminal machines. Generally speaking, semi-automatic terminal machines can meet all the requirements, and full-automatic terminal machines are wasted. There are also molding machines, testing machines, tensile machines, peeling machines, wire cutting machines, soldering machines, electronic scales, and punch machines.

Production process and flow of automobile wire harness:

1) Wire cutting cuts various required wires to the required length.

2) Terminal crimping crimps the terminal to the wire.

3) Split and install the connector into small strands.

4) During the final assembly, various small strands are divided on a large tooling plate and wrapped with adhesive tape. Various protective components (bellows, protective support, etc.) have been installed.

5) Check whether each circuit is unblocked, appearance test, waterproof test, etc. on the special test board.

Harness production process: opening - crimping - preassembly - final assembly - inspection - electrical test - packaging - shipping

At present, whether it is a high-end luxury car or an economical ordinary car, the harness is basically the same form, consisting of wires, connectors and wrapping tape.

Automobile wires, also known as low-voltage wires, are different from ordinary household wires. Ordinary household wires are copper single-core wires with certain hardness. The automobile wires are all copper multi-core flexible wires. The limited flexible wires are as thin as hair. Several or even dozens of flexible copper wires are wrapped in plastic insulated pipes, which are soft and not easy to break.

Due to the particularity of automobile industry, the manufacturing process of automobile harness is more special than other ordinary harnesses.

With the increase of automobile functions and the wide application of electronic control technology, there are more and more electrical components, more and more wires, and more and more wire harnesses. Therefore, the advanced automobile has introduced the CAN bus configuration and adopted the multiplex transmission system. Compared with the traditional harness, the multiplexer greatly reduces the number of wires and connectors, making wiring easier.

Common specifications

Common wire specifications in automobile wire harnesses include wires with nominal cross-sectional areas of 0.50, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0 and other square millimeters (the nominal cross-sectional areas commonly used in Japanese cars are 0.5, 0.85, 1.25, 2.0, 2.5, 4.0, 6.0 and other square millimeters), each of which has a allowable load current value and is used for wires of different power electrical equipment. Take the whole vehicle harness as an example, 0.5 specification line is applicable to instrument lamp, indicator lamp, door lamp, ceiling lamp, etc; 0.75 specification line is applicable to license plate lamp, front and rear small lamp, brake lamp, etc. 1.0 Specification line is applicable to turn signal lamp, fog lamp, etc; 1.5 The specification line is applicable to headlights, horns, etc; The main power line, such as generator armature wire and grounding wire, requires 2.5 to 4 mm2 wires. This only refers to ordinary cars. The key point is the larger current value of the load. For example, the ground wire of the battery and the positive power line are special car wires used separately. Their wire diameters are relatively large, at least more than 10 square millimeters, so these "Big Mac" wires will not be incorporated into the main harness.

Wiring harness layout

Before arranging the harness, draw the harness diagram in advance, which is different from the circuit schematic diagram. The circuit schematic diagram is an image that represents the relationship between various electrical components. It does not reflect how the electrical components are connected, nor is it affected by the size and shape of various electrical components and the distance between them. The harness diagram must consider the size and shape of each electrical component and the distance between them, and must also reflect how the electrical components are interconnected.

After the technician of the harness factory has made the harness wiring board according to the harness diagram, the worker will cut off the line according to the regulations of the wiring board. The main harness of the whole vehicle is generally divided into engine (ignition, electronic injection, power generation, starting), instrument, lighting, air conditioning, auxiliary electrical appliances and other parts, including main harness and branch harness. A vehicle main harness has multiple branch harnesses, just like tree poles and branches. The main harness of the whole vehicle often takes the instrument panel as the core component and extends forward and backward. For reasons such as length or convenient assembly, some car harnesses are divided into front harness (including instrument, engine, front light assembly, air conditioner, battery), rear harness (tail light assembly, license plate lamp, luggage compartment lamp), roof harness (door, ceiling lamp, audio speaker), etc. Each end of the harness will be marked with symbols and letters to indicate the connection object of the wire. The operator can see that the sign can be correctly connected to the corresponding wire and electrical equipment, which is particularly useful when repairing or replacing the harness. At the same time, the color of the conductor is divided into single-color conductor and two-color conductor. The purpose of the color is also specified, which is generally the standard specified by the depot. China's industry standards only specify the main color, such as the single black for the ground wire and the red single color for the power wire, which cannot be confused.

The harness is wrapped with braided wire or plastic tape. For the sake of safety, processing and maintenance convenience, the braided wire wrapping is canceled, and now it is wrapped with adhesive plastic tape. For the connection between harness and electrical components, use connectors or wire lugs. The connector is made of plastic and is divided into plug and socket. The harness is connected with the harness through the connector, and the connection between the harness and the electrical components is through the connector or wire lug.

Harness material

The material requirements for automobile wiring harness are also strict:

Including its electrical performance, material emissivity, temperature resistance, etc., are higher than the general harness requirements, especially when it comes to safety: the harness of important components such as direction control system and brake has more stringent requirements.

Car harness function

In modern cars, there are many car harnesses, and the electronic control system is closely related to the harness. Someone once made a vivid analogy: if we compare the functions of microcomputer, sensor and actuator with the human body, we can say that the microcomputer is equivalent to the human brain, the sensor is equivalent to the sensory organ, and the actuator is equivalent to the motor tube, then the harness is nerve and blood vessel.

Car harness is the main body of the network of car circuits. It connects the electrical and electronic components of the car and makes them work. Without harness, there is no car circuit. At present, whether it is a high-end luxury car or an economical ordinary car, the harness is basically the same form, consisting of wires, connectors and wrapping tape. It is necessary to ensure the transmission of electrical signals and the reliability of the connecting circuit, provide the specified current value for the electronic and electrical components, prevent electromagnetic interference to the surrounding circuits and eliminate the electrical short circuit.

From the functional point of view, the car harness can be divided into 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. The power line is a thick wire that carries large current, while the signal line is a thin wire that does not carry power (optical fiber communication); For example, the sectional area of wires for signal circuits is 0.3 and 0.5mm ²。

The sectional area of wires used in motors and actuators is 0.85 and 1.25 mm ²， The cross-sectional area of the wire used in the power circuit is 2, 3, and 5 mm ²。 However, special circuits (starter, alternator, engine ground wire, etc.) have 8, 10, 15 and 20 mm of different specifications ²。 The larger the cross-sectional area of the wire, the greater the current capacity. In addition to considering the electrical performance, the selection of wires is also limited by their physical performance when they are on the vehicle, so the selection range is very wide. For example, the wire between the door of a taxi that is often opened and closed and the crossing body should be composed of wires with good flexibility. Generally, wires with good insulation and heat resistance used at high temperatures are covered with vinyl chloride and polyethylene. In recent years, the number of electromagnetic shielding wires used for weak signal circuits has been increasing.

With the increase of vehicle functions and the wide application of electronic control technology, there are more and more electrical components and wires, and the number of circuits and power consumption on the vehicle are significantly increased, so the harness becomes thicker and heavier. This is a big problem that needs to be solved. How to arrange a large number of wire harnesses more effectively and reasonably in the limited car space to make the car wire harness play a greater role has become a problem facing the automobile manufacturing industry.