Project 2

1       INTRODUCTION

The automotive wiring harness is referred to as the central nervous system in the vehicle. It mainly consists of an electrical harness and the mechanical harness in the design. The current project is focused on the mechanical wiring harness and its rules and procedure to be followed while routing in the virtual condition. CATIA V5 electrical workbench is used as the CAD tool for routing the wires in the engine and tailgate components.

Some terms need to be understood before designing the wiring harness.

1.1     Basics of the electrical distribution system and wiring harness

Electrical Distribution System (EDS): It deals with physical (location of electronic components placed in the vehicle, front end to back end) and logical (different Electrical Control Units) architecture, schematic development, power distribution (set with fuses to check wiring harness is safe in various failure modes), wiring harness design and wiring harness component design of given electrical system.

E & E Architecture: It is a high-level logical connectivity diagram representing the number of systems, sub-systems, and logical connections between them. It is also extended to show the CAN (control area network) network between different electronic controllers.

Logical schematics: It is detailed design of E&E architecture which is extended to show the logical connectivity between different components and controls of different systems and sub-systems.

Electrical schematics: It is detailed design of logical schematics, which describe the pin-to-pin connectivity, properties, fusion distribution, grounding distribution, wire properties (wire type, colour, gauge), interconnects, circuit properties (circuit numbers, connector designation numbers, control device number), specification of component (rating od diode, resistors) etc., This is the end design of electrical core design of system and used as primary input for harness development.

Wiring harness topology: It is strategy to divide the harness between different pieces to achieve the best manufacturability, serviceability and cost-effective design.

Ex: engine harness, door harness, tail gate harness.

Note: Wiring harness cannot be repaired. It is advised to replace the damaged wiring harness parts.

Wiring harness routing: It is the desired path of wiring harness into given vehicle environment by applying set of design rules and industry best practices.

Wiring harness packaging: deals with the fixing/mounting strategy of wiring harness routing to ensure the safe, reliable and durability of wiring harness by applying set of design rules and industry best practices.

Virtual environment: 3D representation of vehicle components.

Benefits: 1) Huge cost saving, 2) Fuse failure avoiding, 3) Easy to predict i.e., warning in harness

1.2     Wiring Harness Terms

Wiring harness is the assembly of different systems, sub-systems in the vehicle. It won’t have any function; it depends on its system and sub-systems. It used to pass the signals between components.

1. Wires: Wiring harness consists of various wires bundled together, with each individual wire responsible for carrying electric signals and energy used ins tarting the engine, lights, meters, navigation system, Power windows and doors, and other devices in the vehicle. Wires are Cu conductors insulated with PVC insulation. Initiative in the industry to use the Al wire to get the benefits of weight and cost reduction.
2. Connector: An electrical connector, is an electro-mechanical device used to join Electrical termination and create an electric circuit. Electrical connectors consist of Housing, Terminal, Wedge Locks, Seals, Cavity, Mounting Cam etc., Connectors are plastic moulded housing with locking and retention features.
3. Terminals: Terminals are defined as “A device designed to terminate a conductor that is to be affixed to a post, stud, chassis, another tongue, etc., to establish an electrical connection.” Terminals are metal (brass) conductor with plating (tin, silver, gold) constructed in specific shape to secure the joint from environmental conditions and with minimum electrical resistance.
4. Protection device:

• Corrugated flexible tubes also known as Cot Tubes / Convoluted Conduits have a wide range of application in automotive industries.
• Corrugated tubes are made from plastic material and they are flexible.
• Theses tubes are used to protect the harness from thermal and physical damage, sometimes to improve harness appearance.
• Protection covering are flexible, temperature, wear and tear resistant moulded plastic/polymer parts.
• Sealing Grommets are used mainly for three purposes. Sealing, Protection and to absorb vibration/shock.
• Protection Grommets are rubber moulded components used in wiring harness for protections.
• Insulations are adhesive/non-adhesive tapes and sleeves. They are made from PVC or cotton/polymer material. Cotton tape in high temperature area (engine).

5. Clips and clamps: Wide variety of clips and clamps are available to mount the wiring harness.
6. Fuse and relay box: are plastic moulded parts used to package Fuses and relays in systematic manner. It also protects them for any damage (Physical and Environmental).
7. Retention device: are plastic moulded parts to mount connectors and other harness components. (Connector mounts, secondary locks, connector back shell etc). Primary locking is provided by the terminal itself; secondary locks are not mandatory but there are used to ensure that there is no damage. Back shells are the packaging devices which are used at the end of the connectors. It guides the wire to the connector in a constrain packaging area or to provide the better appearance at the end of the connector.
8. Guiding channels: are plastic moulded or metal parts designed to guide harness bundle in given geometric area to secure and protect the harness.
9. Electronic components: Diodes, terminating resistors, Flasher, Timer circuits are sometimes part of harness supply.