What Is a Cable Harness?

A wiring group (circuit group) provides the overall service equipment for a certain load source group, such as relay lines, switching devices, control systems, and so on. The basic research content of traffic theory is to study the relationship between traffic volume, call loss and harness capacity. Harness is an important basic concept in traffic theory.

Wiring harness

The load source is the service object of the wiring 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, and the number of service devices contained in the harness is called the harness capacity. Figure 1 is a schematic diagram of the harness. The harness has a capacity of V and it serves N load sources. Any load source that makes a call can occupy an idle service device in the harness.

1. In order to facilitate installation and maintenance and ensure that electrical equipment can work in the worst conditions, the wires of different specifications and colors used in the electrical equipment of the entire car are reasonably arranged to be integrated into one, and the wires are bundled with insulating materials Bundle, so that it is complete and reliable.

1) Detection and judgment of burnout failure of wire harness

In the circuit of the power supply system, the wire harness burns wherever it is grounded. The junction of the burned and intact part can be considered as the ground of the wire; if the wire harness burns to the wiring part of an electrical device , It indicates that the electrical equipment is faulty.

2) Detection and judgment of short circuit, open circuit and poor contact between lines

-The wire harness is extruded and impacted externally, causing damage to the wire insulation inside the wire harness, resulting in short circuits between the wires.

The standard of the wiring harness is mainly calculated by its crimping rate. The calculation of the crimping rate requires a special instrument. The standard tester for the wire harness section developed by Suzhou Oka Optical Instrument Factory is the most specialized test used to check whether the crimping of the wire harness is qualified. Effective detector. Mainly through several steps such as cutting, grinding and polishing, corrosion, observation, measurement and calculation.

Automotive wiring harness also has strict requirements on materials:

Including its electrical properties, material emission, temperature resistance, etc., are higher than the general wiring harness requirements, especially the safety requirements are more stringent.

1. The ambient temperature of the engine is high, and there are many corrosive gases and liquids. Therefore, the wires of the engine harness must be resistant to high temperature, oil, vibration and friction.

2. The wires on the automatic transmission are hydraulic oil resistant, high temperature resistant, and temperature stable.

3. The wires of the wiring harness on the luggage compartment cover should maintain their elasticity at low temperatures, so cold elastic wires should be selected to ensure their normal operation.

4. Use shielded wires for weak signal sensors.

5. The ABS wiring harness assembly is resistant to high temperatures of 150-200 ° C, the outer protective insulation layer is hard and wear-resistant, but the core must be greater than 133 stranded wires.

6. Power lines, such as starter alternator output line, battery line, are special wires that can withstand high current insulation and have good heat dissipation performance and reduced voltage. [1]

In modern cars, electronic control systems are closely related to wiring harnesses. Someone once used an image metaphor: a microcomputer is equivalent to the human brain, a sensor is equivalent to a sensory organ, and an actuator is equivalent to a motor tube. Then the wiring harness is the nerve and blood vessels.

There are two types of automotive wiring harnesses: power lines that carry the power of driving actuators (actuators) and signal lines that transmit sensor input commands. Power lines are thick wires that carry large currents, while signal lines are thin wires (optical fiber communications) that do not carry electricity.

The cross-sectional area of wires for motors and actuators is 0.85, 1.25mm2, while the cross-sectional area of wires for power circuits is 2, 3, and 5mm2; and for special circuits (starter, alternator, engine ground wire, etc.), 8, 10, 15, 20mm2 different specifications. In addition to considering the electrical performance, the choice of electrical wires is also subject to the physical properties of the vehicle. For example, the frequently opened / closed doors on taxis and the wires that cross the body should be composed of wires with good flexibility. In recent years, electromagnetic shielding wires used by weak signal circuits have also been increasing.

With the increase of automobile functions and the widespread application of electronic control technology, the number of circuits and power consumption in automobiles has increased significantly, and the wiring harnesses have become thicker and heavier. How to make a large number of wiring harnesses more effective and reasonable in a limited automotive space Arrangement, so that the automotive wiring harness can play a greater role, has become a problem facing the automotive industry.

The first station for wire harness production is the wire-opening process. The accuracy of the line-opening process is directly related to the entire production progress. Once an error occurs, especially the short-line size, it will cause rework at all stations, which will take time and effort to affect production efficiency.

The second station after the opening is the crimping process. The crimping parameters are determined according to the type of terminal required by the drawing, and the crimping operation manual is prepared. For special requirements, it is required to indicate and train operators on the process file.

The next step is the pre-assembly process. First, the pre-assembly process operation manual must be prepared. In order to improve the overall assembly efficiency, a pre-assembly station must be set for a complex wiring harness. If there are too few pre-assembled parts or the wiring path of the assembly is not reasonable, it will increase the workload of the total assembly staff.

The final step is the final assembly process. According to the assembly platen designed by the product development department, design the tooling equipment, material box specifications and affix the numbers of all assembly sheaths and accessories on the material box to improve assembly efficiency.

The electronic technology content and quality of automotive wiring harnesses in cars has gradually become an important indicator for evaluating automotive performance. Car manufacturers should pay particular attention to the selection of wiring harnesses. It is also necessary to understand the process and production of automotive wiring harnesses.

According to the structure, it is divided into full utilization wiring harness, partial utilization wiring harness, and link system; according to different service methods, it is divided into loss-based wiring harness and waiting-system wiring harness (see random service system); according to the number of service load sources Different, it is divided into infinite load source harness and limited load source harness.

In the telecommunication system, the equipment directly used for communication between users is mostly a full utilization link system with an infinite load source loss, and the equipment used to control the connection process of the communication equipment is mostly an infinite load source waiting for a full utilization system. . When the number of load sources is not large relative to the capacity of the wiring harness, a full utilization system or a partial utilization system with a limited load source is generally used.

According to the call behavior of the load source, that is, whether a new call attempt is made after the user fails to call, the wiring harness can be divided into a repeated call system and a non-repeated call system. Actual communication systems have repeated calls. Non-repeated call systems are an approximation of repeated call systems.

1) Full utilization harness. If any service device (trunk or machine key) in the harness can be used by any load source in the load source group it serves, such a harness is called a full utilization harness.

Figure 2 shows the full utilization of the 100 first preselectors (load source groups) of the step-by-step switch, which are connected to the 10 first group selectors (service devices are machine keys). Harness. Any service device (first selector) in the circle can be used by any load source (first preselector) in the load source group (100 first preselectors) it serves.

2) Partial utilization harness. If any load source in the load source group can only use part of the service equipment in the harness, such a harness is called a partial utilization harness. Partial utilization of the wiring harness divides the load source component into several subgroups, which is divided and reconnected between the outgoing lines of the load group. This structure can be described by the example shown in the figure below.

The quality of the wiring harness material directly affects the quality of the wiring harness, and the choice of wiring harness material is related to the quality and service life of the wiring harness. As a reminder to everyone, in the choice of wire harness products, you must not covet cheap, cheap wire harness products may be used inferior wiring harness materials. How to distinguish the quality of the wiring harness? Know the material of the wiring harness. The following is the material selection of wiring harness.

The wiring harness is generally composed of a wire, an insulation sheath, a terminal, and a bandage material. As long as you understand these materials, you can easily distinguish the quality of the wiring harness.

First, the material selection of the terminal

The copper used for the terminal material (copper) is mainly brass and bronze (the hardness of brass is slightly lower than the hardness of bronze), and the proportion of brass is larger. In addition, different plating layers can be selected according to different needs.

Second, the choice of insulation sheath

Sheath material (plastic parts) commonly used materials are PA6, PA66, ABS, PBT, pp, etc. According to the actual situation, flame retardant or reinforcing materials can be added to the plastic to achieve the purpose of strengthening or flame retardant, such as adding glass fiber reinforcement.

Third, the choice of wiring harness

According to the different use environment, choose the corresponding wire material.

Fourth, the choice of dressing materials

Harness banding has the functions of wear resistance, flame retardant, corrosion resistance, interference prevention, noise reduction, and beautification of appearance. Generally, the bandaging material is selected according to the working environment and space size. There are usually tapes, corrugated pipes, PVC pipes, etc. in the choice of bandaging materials.

Investigate the working characteristics of the wiring harness. The key problem is to solve the state probability distribution of the wire harness. The basic mathematical model of a wire harness is a process of augmentation and elimination. It is assumed that: In a very small time t, the wire harness can only transition from the current state to the adjacent state or no state change occurs. For example, the number of calls in a harness can be considered the status of the harness. If there are n calls, the current state is En. Its neighboring states are En-1 or En + 1. The current state of the harness is En, and the conditional transition probability of the same transition to state En + 1 after t is nt + 0 ( t), where n is the call intensity in the En state. 0 ( t) represents the high-order infinitesimal of t. The current state of the wire harness is En, and the conditional transition probability to the state En-1 after t time is n t + 0 (t), where n is the call end intensity in the En state.

Based on the probability distribution of the harness state given in the process of increasing and decreasing, a series of problems related to the load capacity of the harness can be solved.

First, harness utilization

Refers to the number of service devices that can be used by any load source in the load source group. In some utilization harnesses, it is impossible for any load source to use the full capacity of the harness, and only some of the equipment is used. Let K be the harness utilization and V be the harness capacity, then VK. When V = K, the harness is full utilization, the size of the utilization K is restricted by the structure of the wiring device.

Harness utilization

Refers to the use efficiency of the wiring harness. It is numerically equal to the average completed traffic intensity per line. Expressing harness utilization with , there are

n

In the formula, A0 and A are the completed traffic intensity and the incoming traffic intensity of the harness, V is the harness capacity, and E is the loss probability of the harness.

One of the tasks of the telecommunication system designer is to form a network with high utilization rate under a certain quality of service, that is, to constitute the most economical wiring harness structure and application method. Harness utilization and load, capacity, structure, and service quality of harnesses are interrelated and restricted. Take the loss-making harness as an example, under a certain call loss condition, the larger the harness capacity, the higher the harness utilization rate. For a certain capacity harness, the greater the call loss, the higher the harness utilization rate.

Third, the overload of the wiring harness

Refers to the situation where the wiring harness is running at a load greater than the rated load. In actual telecommunication systems, wiring harnesses are sometimes overloaded. Overload will reduce the service quality of the wiring harness. The correct design should be, when

Figure 7 Harness utilization curve

When the overload is in the allowable range, the decline in service quality should be limited to the given range. To meet this requirement, harness utilization cannot be increased indefinitely. Overutilized harnesses are very sensitive to overload.