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The damage form and failure analysis of V belt of automobile
- Jul 02, 2018 -

The damage form and failure analysis of V belt of automobile

1 introduction

The v-belt of an automobile includes a v-belt or a multi-wedge belt that drives a motor generator, a water pump, an air compressor and a steering gear.

-- safety: serious damage to V belt or multi-wedge belt of automobile or serious skidding will affect the normal operation of compressor, causing the brake failure of automobile and causing traffic accident.High quality transmission belts for automobiles can reduce vehicle accidents, improve vehicle safety, and ensure personal and property safety.

- efficiency (energy saving) : automotive belt in the car have the effect of transmission power, as the elastic slide in the tape drive (i.e., the skid), belt there is always a certain amount of power loss, but if the "skid" serious, will greatly reduce the transmission efficiency of engine auxiliary machinery, increase the fuel consumption of engine.High quality transmission belt and the belt wheel with small elastic slip, and stable, high transmission efficiency, can play a certain role in energy saving.As car, on the other hand, the requirements of miniaturization, lightweight, engine room is narrow small, change the transmission belt is a very troublesome job, if the driving belt damage will have a big impact in various aspects, is a waste of time, and increase the intensity of labor.The high quality transmission belt can predict its service life and will not be damaged during the normal service life.In this way, it can be replaced in time when the car is overhauled before it is damaged, so as to avoid passive and waste time.

- environmental protection: the modern automobile industry on the belt is very demanding, the conditions of use both to resistance to high temperature and low temperature fatigue, require the rubber has good flexing, flexible heating is small, reducing noise and produces very small amounts of harmful substances.When an automobile starts with a transmission belt, noise is caused by friction between the belt and the wheel and vibration of the belt.High quality transmission belt has uniform body, low vibration during operation, moderate friction coefficient between belt and belt wheel, therefore, low transmission noise.On the other hand, when the vehicle transmission belt is delivering power, flexure generates heat, producing harmful substances and causing harm to the human and environmental safety of automobile drivers and passengers.And the high quality transmission belt, rubber formula that its use does not contain halogen and metal oxide, flexible heating, produce very small amounts of harmful substances, only the person and the environment will not result in injury, conform to the trend of environmental protection.

2. Product structure of automotive transmission belt

(1) at present, automotive friction belt - auto V with two kinds of forms: one is the package BianShi automotive V belt, has been very small quantities used to auto transmission system, the other is a cutting-type automotive V belt, V belt widely used this type of car to car drive system, and the type of V with three types of structure, cross section diagram as shown in figure 1.

Auto v-belt ideal structure should be in the constant or changes have enough under the stress of tensile strength and durability, when stretching has high elastic modulus, bending with body is soft, the lateral stiffness.Compared with the v-belt of the trimming car and the v-belt of the enveloping car, the most important feature of the structure is that there is no wrapping on the side, and the v-belt side is the working face, and the tensile material can be seen.

Figure 1a is the V band of the normal cut edge

FIG. 1b is the v-belt of the bottom adhesive clip cutting edge

FIG. 1c is a v-belt with a toothed cutting edge

The v-belt with a toothed cutting edge is the most widely used v-belt structure at present. The teeth at the bottom of the v-belt mainly play the role of making the v-belt longitudinal soft and convenient for heat dissipation.Cutting-type auto v-belt is generally divided into six parts (as shown in figure 1) 2, 8, respectively for the top and bottom cloth (with tooth trimming v-belt bottomless cloth), 3 as the top rubber, 5 for tensile material, widely used at present is polyester cord material, usually in the form of single layer evenly arranged on the neutral layer, it can make the tensile body remain the state of stretching, to avoid it getting into the compression layer under negative stress and damage, 4 is adhesive rubber, no outsourcing cloth for cutting-type automotive V belt, can only rely on glue will top rubber, tensile and compression layer adhesive, 7 for compression layer glue, anti-bending of should have good wear resistance and fatigue resistance,And less heat.

FIG. 1 section diagram of V belt of edge-cutting automobile

2 - top cloth;3 - top glue;4 - adhesive glue;5 - tensile body;6 - settlement layer glue (bottom glue);7 -- adhesive backing;8 - cloth;Because the anti-bending of cutting-type automotive V belt fatigue performance is good, small hysteresis loss, less heating, heat faster, temperature rise is small, the same section of trimming automotive V belt and bag edge V belt, compared to transfer power is high, especially under the high speed running, this advantage is more obvious (tell due to centrifugal force and the belt is proportional to the weight, when large centrifugal force makes the belt and pulley is pressure decreases, and thus prone to skid), trimming automotive V belt because it is on both sides is bare rubber is much larger than the friction package cloth, can greatly improve the transmission capacity.Because the bottom of the belt is hollow-out, the belt bends with small deformation, slow heat generation and fast heat dissipation.High temperatures can be deadly to belts.

(2) as shown in FIG. 2, it is a cross-section of multi-wedge belt for automobiles.It is a special v-belt with many wedges along the longitudinal direction of a piece of tape and belongs to friction transmission belt.According to the wedge belt can be divided into the section size of PH, PJ, PK, PL and PM model of five types, and cars with wedge zone mainly PK type wedge belt, our country's national standard GB13552-2008 "car wedge type only for PK wedge with provisions of the technical requirements.The multi-wedge belt for automobile is generally divided into four parts (as shown in figure 2), one is the top cloth, two is the core rope, three is the stretch layer glue, and four is the wedge glue.

Wedge take top cloth is used to take back the protection, it can make the belt body to maintain a high level of integrity, to prevent the cracks along the long direction, when need to contact with the guide wheel, its protective effect is particularly obvious;Wedge with the core of the rope for tensile material, widely used at present is polyester cord, high-performance wedge belt has more application of aramid cord, its main effect is to bear more wedge must be some tension in the process of use, this makes the tensile body remain the state of stretching, avoid getting into the rubber wedge it under negative stress and damage;The adhesive layer of multi-wedge belt plays the role of "connecting the top and the bottom".Wedge with the friction between the rubber wedge is with pulleys to transmit power, which requires the wedge glue should have wear-resisting, heat resistance, anti-bending of also should have a higher fatigue, low compression deformation, the larger lateral stiffness and enough hardness etc, not only to ensure the glue on the lateral wedge has enough rigidity, and on the longitudinal has high flexibility.

The thin body of the multi-wedge belt used in automobiles and the contact area between the belt and the wheel is large, which increases the stress area of the belt and reduces the negative pressure under the belt, thus achieving the purpose of restraining deformation.Due to the good flexural performance of multi-wedge belt, the belt wheel with a small diameter can be used to improve the structure of automobile transmission device.

Miniaturization and energy-saving are of great benefit.The use of multi - axis drive transmission mode and use

3. Influencing factors of service life and damage forms of automotive transmission belts

(1) factors influencing the service life of friction transmission belt

-- high ambient temperature, harsh operating conditions and improper tension of the belt are the main factors for cracks in the belt.In general, if the ambient temperature rises, a large number of cracks will appear instead of the belt, reducing the service life of the belt.In addition, the small pulley diameter, large load, and the hard drive of small Angle conditions and design issues, as well as the belt tension is too low to produce skid phenomenon, maintenance deficiency of, will make the belt body crack, have greater influence on service life.

-- low machining precision, harsh operating conditions and improper tension of the belt pulley are the main factors that lead to strip delamination.If the processing precision of the belt wheel is low, the belt will be worn off. If the belt and the belt wheel cannot contact normally, the tension will be concentrated in a certain part, resulting in stress concentration, and the belt will be stripped off.In high load and variable load, on the other hand, large and small Angle under the condition of hard drive, cause the belt body bend deformation, stress concentration phenomenon is formed in part of the core wire, will be due to the bend deformation of belt body produces delaminating phenomenon;The tension of the belt is too great, which also makes the belt warped and even delaminated.It can be said that too harsh operating conditions and too much tension are the common causes of belt damage.