Nowadays, many new cars are equipped with built-in heating systems. The switch is embedded in the car body. When the switch is pressed, the seat will be hot for a while.When driving, seat heating can improve the temperature and comfort of the seats in the car, and has the advantages of safety and comfort. The heat is transmitted to the waist and back through the seat surface, reducing the dry heat of the air conditioner and eliminating the fatigue during the journey.
Car seat heating is divided into external and built-in.
External – insert the heating sheet into the bottom and back of the seat cushion, install the purchased seat cushion, and remove it when not in use.
Built-in – professional masters modify the car, the operation is more complicated, and the price is higher, but the built-in heating system has the characteristics of stability, high-grade and convenience.
How does the built-in heating system heat it? What kinds of heating materials are there? The following will introduce to you.
01. Composition of heating system
A car seat heating system consists of the following components:
Car battery—-fuse—-switch (including indicator light)—-(control relay)—-(temperature control unit) —- wiring harness (including connector) —- heating Unit —- Ground (Ground)
The working principle of seat heating is that the seat is covered with resistance heating wires, sewn into the seat cover, and heated by energizing the heating resistance wires, so that the seat gradually warms up in a short time.
By arranging a temperature sensor in the heating pad, the change of the seat temperature can be monitored, the power-on and power-off of the heating wire can be controlled, and the temperature of the seat heating can be maintained within an appropriate range.
The temperature of the heating pad adopts multi-level temperature control, and the maximum surface temperature can reach 60 ℃. On the special fiber braid with flame retardant performance, a high-sensitivity temperature control device is installed, and the power is automatically cut off when the temperature reaches 65 ℃.
The built-in heating material is divided into alloy wire and carbon fiber.
02. Development of carbon fiber and alloy wire
In 1989, Germany launched a car seat heating system based on resistance wire heating materials, and its comfort was quickly recognized by the majority of customers. In just three years, the eight major car series have successively launched more than 20 high-end models with seats. The heating system of the car opened the prelude to the development of seat heating.
In 1993, the advent of carbon fiber changed the seat heating industry. This material quickly replaced resistance wire because of its uniform heating and tailoring.
However, major manufacturers have been under tremendous pressure. It is difficult to match carbon fiber and conductive tape, and the service life of heating pads has not been able to meet the requirements of the automotive industry.
In addition, the conductive tape is generally made of copper wire plated with nickel and silver. The oxidation resistance of nickel and silver is both 3-5 years, which cannot meet the requirements of the automobile industry. As a result, automobile manufacturers have to change the car seat heating system to optional. product.
In 2001, Volkswagen of Germany drafted the enterprise standard for car seat heating, and other manufacturers of the eight major car series followed suit. Under pressure, industry insiders developed a new type of heating material-smart alloy wire, which met the standards of all manufacturers of the eight major car series. , to meet the increasingly mature parts quality requirements of the automotive industry.
So far, major car manufacturers have listed the intelligent alloy car seat heating system as a key project to develop.
In 2006, the new models of the eight major car series all adopted the intelligent alloy car seat heating system.
03. Alloy wire heating
The intelligent alloy heating wire is made into a fibrous structure through heat treatment process, etc., to increase the bending resistance, and finally add Teflon material on the surface for double insulation.
The smart alloy wire is made of 30-90 strands of high-quality insulating material alloy wire (multiple single strands of air compression insulation), with good insulation performance, anti-corrosion of various liquids, anti-leakage, anti-oxidation, and strong folding resistance. It will not be easily short-circuited, open-circuited and aged in harsh environments.
The intelligent alloy car seat heating system is a program wiring technology in series.
The parameters are stable, the heat dissipates evenly, and the tensile strength is extremely strong. The 90-degree folding test times of some durable smart alloy wires can reach more than 300,000 times.
According to the process, it can be divided into wiring process and sewing process. The wiring process is to fix the heating wire between the two layers of substrates by hot melt adhesive, similar to the sandwich structure, mainly used for the design of the flank heating pad.
The sewing process fixes the heated thread to the substrate through the sewing thread.
Smart alloy wire is the mainstream heating technology, with simple structure and high strength, suitable for mass production, and applied to almost all models.
04. Carbon fiber heating
Carbon fiber is a high-strength and high-modulus fiber with a carbon content of more than 90%, and its high temperature resistance ranks first among all chemical fibers. Carbon fiber is made of acrylic fiber and viscose fiber, which is made of high-temperature oxidation and carbonization. It is an excellent material for manufacturing aerospace and other high-tech equipment.
Carbon fiber is a new type of high-performance fiber reinforced material, which has many excellent properties such as high strength, high temperature resistance, wear resistance, corrosion resistance, creep resistance, electrical conductivity and thermal conductivity, and is widely used in dynamic environment heating products.
It reduces the weight of the component, thereby improving the technical performance of the component. Therefore, the use of carbon fiber as an electric heating body has excellent performance unmatched by metal, PTC and other electric heating bodies.
The entire heating area of the heating pad is paralleled and connected in series, covered with many tiny carbon fiber meshes.
If a single carbon fiber is damaged somewhere, there will only be localized heat loss over the damaged area, the rest will still function properly, so the carbon fiber heating pad can be cut or folded to the desired size.
Carbon fiber heating pads have less thermal load than traditional resistance wire heating pads. The seat temperature of the carbon fiber heating system is evenly distributed, the surface is relatively flat, and the comfort is strong. You cannot feel the centralized heating source of carbon fiber, and there will be no cold here and hot there.
05. The difference between carbon fiber and alloy wire
The principle of heating
The carbon fiber heating tube is a kind of exothermic heating tube, and the heating cable is a low-temperature electric heating wire.
The heat energy of carbon fiber is not conducted through the medium, but the far-infrared light waves are radiated into the human body, and the heat energy is directly transmitted to the tissues and organs of the human body.
The biggest characteristics of carbon fiber heating are fast heating, uniform heating, long heat radiation transfer distance, fast heat exchange speed, and the amount of electromagnetic radiation is much smaller than that of metal wires, which is harmless to the human body.
The wire heating method is more traditional, and the amount of electromagnetic radiation is relatively large. In addition, the heat transfer rate of carbon fiber heat is about 60% higher than that of metal wire, so it saves more electricity.
Carbon fiber is corrosion-resistant and not easily oxidized. When heated to 3000 degrees in an oxygen-free state, its mechanical properties do not change, and in the electric heating state, it overcomes the shortcomings of low strength and easy oxidation and burning of metal wires, PTC, and silicon carbide electric heating bodies.
At present, domestic alloy wire heating is mostly used. After continuous technical improvement, the performance of alloy heating wire is also very good. Most domestic seat factories still choose alloy heating wire, which has better durability after testing and can be used for more than 5 years.