Vehicle Hose and Its Quality Inspection

Automobile hose plays the role of transporting oil, gas, water and transmitting power in the three major systems of automobile chassis, engine and body. It is an important part of the automobile. Automotive hoses mainly include brake hoses, air conditioner pipes, radiator pipes, fuel pipes, power steering pipes, oil pipes, hydraulic pipes, and special-shaped hoses. The main material is generally nitrile rubber (NBR), chloroprene rubber (CR), chlorinated polyethylene (CPE), chlorosulfonated polyethylene (CSM), binary ethylene propylene rubber (EPDM), epichlorohydrin rubber and hydrogenated nitrile rubber (HNBR) and their combined rubber, skeleton material is generally vinylon, polyester cord, etc. The molding process is mostly hard core method, soft core method and coreless method.

Car Rubber Connection Hose Category and Features

The rubber connection hose on the car can be roughly divided into three categories: low-pressure hose, high-pressure hose and oil-resistant hose. Although the structure of the hose is different, it is roughly composed of three basic parts: the inner rubber layer, the reinforced layer and the outer rubber layer. The inner rubber layer is the working layer of the hose contacting the medium, which plays the role of sealing the medium and protecting the reinforcement layer. The reinforcement layer is the part of the hose that bears the pressure, while giving the entire hose the necessary stiffness and strength. The outer adhesive layer is the protective layer of the hose.

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1. Low pressure hose has radiator connection hose and brake bleed hose. The mechanical properties of low-pressure hoses are not demanding.

2. High pressure hose has brake system and hydraulic system connection hose. The reinforced layer of the high-pressure hose adopts braided hose and winding hose. The high-pressure hose is required to have good pressure resistance, oil resistance, flexibility resistance, no cracks at low temperature, vibration resistance and small expansion. The inner adhesive layer must be uniform, with smooth surface and no air holes; the reinforcement layer must be tightly bound to the inner adhesive layer; the outer adhesive layer must also be tightly attached to the reinforcement layer to prevent damage. The threads of the metal joints at both ends shall be tightly embedded in the rubber surface.

3. Oil-resistant hoses are gasoline, diesel and lubricating oil hoses. The oil-resistant hose has good oil resistance and can be used for a long time under working pressure.

The function and use requirements of the main hose for vehicles

1. Radiator hose

The car radiator hose is a flexible pipeline connecting the car engine and the radiator, and is one of the key parts of the car One of the components. With the rapid development of the automobile industry, especially the development of automobiles in the direction of energy saving and low pollution, the engine compartment temperature has increased by 15~50 ℃ in recent years, and the continuous improvement of vehicle performance has put forward higher technical requirements for rubber hoses used in automobiles. The hose must withstand the high temperature test around the engine and adapt to the use of extremely high temperature and extremely low temperature conditions in the field, and the market demand is also expanding accordingly. Therefore, the original use of sulfur vulcanization system production of radiator hose is gradually replaced by hydrogen peroxide system production products, the main material used for EPDM rubber.

2. Coolant hose

is connected as a flexible pipe. Coolant hose is widely used in automobile pressure accumulators and auxiliary heat exchangers. In order to ensure that the coolant flows smoothly through the manifold and the valve body, the coolant hose adopts a strange tree-shaped multi-branch sub-channel structure. The coolant hose must not only meet the requirements of function, structural size and performance, but also ensure that it is fully adapted to the extremely complex and compact engine room. Leaving aside the influence of the design, the high-temperature radiation of the engine and oil immersion can also gradually age the outside of the coolant hose. But in any case, the most common aging is carried out from the inside out. Therefore, when a tiny needle eye appears on the outside, it indicates that severe corrosion has occurred inside the hose. The loss tank is the result of electrochemical corrosion and is also a natural phenomenon of the micro-battery effect of the cooling system. Oxygen in the air is one of the main factors that cause the chemical reaction to occur, so improving the filling process of the cooling system can effectively avoid such failures.

When the coolant leaks substantially, the fault is naturally clear at a glance. However, the key to the problem is how to diagnose the internal corrosion without disassembling the hose. The following method can quickly and accurately find the coolant hose that is about to be scrapped: knead the hose by hand, especially the hose of the upper part of the radiator, the bypass, the manifold, the valve body and the heater, and its connection end is the most important. If the kneading area has obvious soft or lack of elastic feel (relative to other parts), it indicates that the hose has been severely corroded. If the mileage of the car is low at this time, it is recommended to check the voltage of its cooling system. During the inspection, the negative pole of the voltmeter is connected to the ground electrode of the battery; the positive pole is inserted into the coolant (no metal parts can be touched). If the voltage reading is above 0.3V, a comprehensive and systematic inspection of the grounding electrode of the vehicle is required. At the same time, make sure that no auxiliary grounding electrode is connected to the radiator bracket. For the hose sub-channel, even if only one branch leaks, it is wise to replace the entire coolant hose, otherwise it will only get twice the result with half the effort. Although most hoses can be flexibly installed without kinks, almost all hoses use a form-molded process because form-molded hoses are more suitable for compact installation space requirements. The OEM clamp of

coolant hose usually adopts elastic snap ring structure. The resilient snap ring creates a compression set inside the hose, thereby achieving a more secure connection with a uniform and continuous pressure. However, when the hose connection end is grooved or deformed, the sealing performance of the OEM elastic snap ring is not as good as the high-quality maintenance clamp. The maintenance clamps mainly include plastic shrink snap rings that can continuously adjust the pressing force and turbine sub-clamps with permanent tension rings or leaf springs. Among them, the turbine sub-clamp can generate uniform pressure in the circumferential direction of 360 °, and ensure the reliability of the fastening connection through the compression set generated by the compression. The superior hose clamp can not only prevent the leakage of coolant, but also greatly reduce the amount of air sucked in during the engine cooling process.

3. Automatic transmission coolant hose

Many automatic transmission cooling pipes contain some rubber hoses. Its flow path is quite complex, dazzling and difficult to distinguish. Once they leak, it will inevitably cause the transmission assembly to malfunction, and during this period, the on-board early warning system will not make any prompt, that is, the automatic transmission is not equipped with a coolant leak sensor.

4. Air-conditioning hose

With the application of the new environmentally friendly refrigerant R134a, the structure and material of the air-conditioning hose have changed greatly. The inner rubber layer is made of resin, chlorinated butyl rubber and EPDM rubber. The structure becomes the best combination of air-conditioning hoses. Automobile air conditioning system refrigerant with HFC-134a instead of CFC-12. Due to the decrease in the permeability of sun-134a and the decrease in the permeability of nylon and water, the high acrylonitrile NBR/CR blend in the inner layer of the hose was replaced by IIR.

5. Vacuum tube

Today's emission control technology can monitor and compensate the mixture concentration in real time, and can maintain the normal operation of the emission test system even when the vacuum tube leaks. However, if the vacuum tube is ill for a long time, it will definitely cause the driver to complain about the reduced driving comfort. The vacuum tubes are located between the complex and compact powertrain components, making it difficult to perform otherwise simple visual inspections, not to mention field trips deep into the hinterland. Because the vacuum tube is adjacent to (or resting on) the exhaust manifold and the top of the cylinder, it is potentially dangerous. In addition, the vacuum tube passes near the input signal tube of the exhaust gas recirculation device EGR, and passes under the battery pack along the hood. These areas have sharp thin iron corners and the possibility of battery acid leakage, so the vacuum tube It is extremely easy to damage.

6. Brake hose

Due to the emergence of non-insured cars, the increase in the working environment temperature of brake fluid and the use of high-boiling brake fluid, there is a tendency to use EPDM instead of styrene butadiene rubber in the inner rubber layer of brake hose. In foreign countries, the inner and outer rubber layers of brake hose are mostly EPDM rubber, and the reinforcement layer uses polyester, polyvinyl alcohol or rayon fiber. The inner adhesive layer can use pressure-resistant polyamide, and the outer adhesive layer uses chlorosulfonated polyethylene. At present, the inner and outer materials of the power steering hose are changing from nitrile rubber and chloroprene rubber to hydrogenated nitrile rubber, chlorosulfonated polyethylene, chlorinated polyethylene and acrylic rubber, and the reinforcement layer is mainly nylon 66. The biggest requirement for turbocharger hoses is to have good heat resistance. At present, foreign turbocharger hoses adopt an all-rubber structure, that is, the inner rubber layer is composed of fluorine rubber and silicone rubber with good heat resistance, and the reinforcement layer is made of high-strength aramid. Composed of fiber knitting, the outer rubber layer is made of silicone rubber.

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Material of Automotive Hose

Hose Material According to the requirements of ozone resistance, acid gasoline resistance, low permeability, heat resistance, etc., the material is changed and selected according to the balance principle of cost performance. However, the corresponding high combustion pressure, low permeability, refrigerant, continuously variable transmission (CVT) will become a major technical issue in the future, and its supporting material selection and combination technology is being developed. For example, the inner rubber layer of fuel hoses has been developed to replace nitrile rubber with fluororubber, epichlorohydrin rubber or acrylate rubber to reduce fuel permeability and further improve heat resistance. The original inner layer of the power control hose (PS) is NBR and the outer layer is CR. However, in order to improve the heat resistance, ACM is used on the low-pressure side and HNBR is used on the inner layer on the high-pressure side, which increases its service life by 4 to 5 times. The Kyoto Conference on the Prevention of Global Greenhouse Effect (COP-3) proposed to abolish HFC completely. It is foreseeable that the refrigerant will change in the future, and the rubber material will also change accordingly. At present, the production of automobile hoses in China is still in the initial stage of development, and the scale, quality, variety, energy level and serialization supporting capacity are far from the market demand. In terms of energy level, China has not been able to mass produce medium and high-grade car hoses, but can only be equipped with low-grade hoses. Hoses such as anti-lock braking system, air conditioning system and steering system still need to rely on imports. Specifically, the main varieties of automotive hoses that need to be developed in my country are: new fuel oil-resistant hoses, thin-walled textile hoses, multi-channel special-shaped hoses, power steering hoses, high-performance brake pipes, and new refrigerant-resistant hoses., Ozone-resistant, oil-resistant, and heat-resistant hoses. Reducing the noise of brake pipe, clutch pipe and compressed air hose is also the research focus of hose industry.

Hose Quality Inspection

The inner rubber layer is the working layer of the hose in contact with the medium. It is soaked, corroded and rubbed by the conveying medium for a long time. At the same time, it also plays the role of sealing the medium and protecting the reinforcement layer. In order to meet the needs of the work, the inner rubber layer is required to have a certain thickness, temperature resistance, corrosion resistance, friction resistance, and a certain degree of air tightness, flexibility and strength. The reinforcement layer is the part of the hose that bears the pressure and gives the necessary rigidity and strength to the entire hose. The outer rubber layer of the hose is the protective layer of the hose. Due to contact with the external environment, it is not only required to be wear-resistant and have a certain thickness, but also require a certain degree of corrosion resistance and aging resistance.

Low-pressure hoses commonly used by auto workers include radiator connecting hoses, brake bleed hoses, etc. The requirements for its mechanical properties are not high. In the selection, the main inspection of its appearance size, the appearance should be no delamination, plastic hole, bubble, wrinkle, crack, dent, distortion, uneven wall thickness, etc. If necessary, the heat aging test of the radiator connecting hose can be done.

The connecting hoses used in automobile brake systems and hydraulic systems are accessories related to safe driving and safe operation, especially requiring them to be resistant to high pressure and oil. Therefore, the reinforced layer of the hose adopts braided hose and winding hose. In addition, the hose is also required to have good flex resistance, no cracks at severe cold and low temperature, vibration resistance, and low expansion. It is required that the inner adhesive layer must be uniform, the surface must be smooth, and there must be no pores; the reinforcement layer must be tightly bound to the inner adhesive layer; the outer adhesive layer must also be tightly attached to the reinforcement layer to prevent damage. The metal joint threads at both ends are tightly embedded in the rubber surface. In addition to the need to check the appearance of high-pressure resistant hose size, but also one by one before use pressure test.

All hoses that transport oil must be oil resistant. It can be used continuously under working pressure; the appearance and size should meet the requirements, and the thread of the hose joint should be undamaged to avoid oil leakage after tightening.

automotive hose is the most concerned market in recent years, but also the largest hose market. According to incomplete statistics, there are currently more than 40 manufacturers of automotive hoses in China, of which 15 are foreign-funded enterprises, accounting for about 1/3, accounting for most of the supporting market. Some data show that the demand for rubber hoses for new vehicles in 2006 is about 0.13 billion m, and the total demand for rubber hoses for automobile maintenance is about 0.16 billion m. By 2010, the output of automobiles will reach about 9 million and the number of automobiles will reach more than 50 million. By then, the demand for new car rubber hoses will be about 0.18 billion m, the demand for maintenance rubber hoses will be more than 50 million m, and the total demand for car rubber hoses will reach 0.23 billion m. It is predicted that the "Eleventh Five-Year Plan" period is a period of rapid development of auto parts, and the automotive hose is no exception, and there will be broad prospects for development.