Automobile tires play a very important role in driving safety. This paper mainly introduces the premise of automobile tire maintenance, studies and discusses the means of automobile tire maintenance, and the correct maintenance methods and skills of automobile tires.
Keywords: automobile; Tires; Wear; Air pressure; Maintenance and maintenance
Talking about automobile tire maintenance
I. Introduction Tire is an important part of automobile driving system. According to the air pressure inside, it can be divided into high pressure tires, low pressure tires and ultra-low pressure tires; According to whether they have inner tubes or not, they can be divided into inner tube tires and tubeless tires; According to the carcass ply structure, it can be divided into bias tire and radial tire. Modern cars use pneumatic tires. The tire is installed on the wheel hub and directly contacts the road surface. Its function is to support the quality of the car and bear all kinds of loads from the road. Together with the automobile suspension, it reduces the impact of the automobile when driving, attenuates the vibration caused by it, and ensures the automobile to have good ride comfort and ride comfort; Ensure the good adhesion between the wheels and the road surface, and improve the power, braking and passability of the car. It can be seen that automobile tires play a very important role in driving safety, and it is very necessary to use them reasonably, maintain them correctly, and repair and handle them skillfully.
Second, the basic premise of tire maintenance and maintenance
(1) Load evenly according to the rated load. Friction is directly proportional to the tire load, so overloading increases the tire load, tire wear is also great, and tire mileage is reduced. Overloading will also increase the sidewall deflection, make the shoulder touch the ground, and cause uneven wear of the tread edge; Frequent overloading will cause abnormal tire wear; The positioning angle of the front wheel will change with the degree of overload of the car. Overloading will change the inclination of the wheel, change the camber of the steering wheel, destroy the matching relationship with the toe-in of the steering wheel, make the wheel slip, and thus aggravate the wear of the tire. When the tire load exceeds 20%, the tire mileage will be reduced by 35%; When the tire load exceeds 50%, the tire mileage will be reduced by 59%. In addition, when the load is too large, the tire will produce severe radial deformation, thus reducing the cornering stiffness and increasing the cornering angle. As long as it is subjected to lateral force, the wheel deviation will increase, which will affect the handling stability of the car.
(2) Insisting on driving at medium speed and speeding is not only detrimental to safe driving, but also increases the internal friction of tires and the friction between tires and the road surface due to the increase of tire linear speed and revolutions per unit time, thus increasing the generated heat, tire temperature and air pressure, thus accelerating the wear of inner and outer tires. When a speeding car turns a corner, the centrifugal force increases, which causes the car to slip and aggravates the tire crown wear. The worse the driving conditions, the greater the wear and tear when speeding. Tests show that tire wear is directly proportional to vehicle speed. When the car is driving at 60km/ h, tire wear is normal; When driving at 70km/ h, tire wear began to increase, and tire mileage decreased by 30% compared with 60 km/ h; When the vehicle speed reaches 100 km/ h, the tire mileage will be reduced by 70%. It can be seen that the influence of vehicle speed on tire life is considerable. The test also shows that the fuel consumption at constant speed is the lowest at medium speed. Therefore, in order to be safer, save fuel and prolong the service life of tires, we must adhere to the medium speed driving.
(3) Drive correctly to reduce or avoid abnormal tire wear. Correct driving will affect the service life of tires, and correct driving can reduce or avoid abnormal tire wear. When the car accelerates rapidly, the local tread of the driving wheel will slip, which may lead to flaky wear on the tread shoulder; When the car is in emergency braking, the wheels are locked, and the tires are dragged and slipped on the road surface. The hard road surface grinds off a layer of tire crown rubber like a file, leaving a clear tire footprint on the road surface, which will also cause local flaky wear on the tire surface; When a car turns a corner, the tire will deform laterally. If the vehicle speed is high at this time, the tire will have large tangential deformation, which will aggravate the local deformation of the tread, and even cause the local slip of the tread, which will seriously wear the tread and sidewall.
Third, the means of automobile tire maintenance-inspection means of automobile tire maintenance-inspection-tire inspection mainly checks the degree of tire wear and air pressure.
(1) Inspection of tire wear By observing the tire grounding, you can also judge the hidden dangers of vehicle four-wheel alignment and suspension. This needs careful study. Generally speaking, if you find a problem with one tire, you should carefully observe the other symmetrical coaxial tire, or even the other two eccentric tires. Figure 1 shows tire wear marks caused by various conditions. If this kind of trace is found, we can judge what is wrong with the vehicle according to the different traces. Figure 1 A shows that the tire pressure is often high or the driving conditions are often bad; B, indicating that there is a problem with the suspension or four-wheel alignment; C, indicating that the air pressure is often too low, so that the grounding patterns on both sides are worn when turning; 3 D, indicating that it is probably caused by long-term shimmy or unstable operation; E, said the high-speed operation of the emergency forced action caused by local wear marks of a certain part. Tire tread pattern has a great influence on tire life. The earliest pneumatic tires had smooth treads. With the development of automobile industry, the speed of automobile is getting faster and faster, and there are more and more problems in the safety and performance of automobile driving. 1904 Continental Tire Company introduced the first automobile tire with patterns. Since then, tire tread technology has been developing continuously. Nowadays, unpainted tires are only used for motorcycle sports (racing tires). In developed countries, the law stipulates that tires driving on public roads must have patterns. The most important function of tire tread pattern is to drain water, and to eliminate the accumulated water that affects the contact between tire and road surface in rainy days. When there is water on the road surface and the car runs at high speed, there will be a "water wedge" between the tire and the road surface, and the tire will be lifted and the car will lose control. Even if the tire has a deep enough pattern, the above extremely dangerous situation cannot be ruled out. Even if the vehicle is driving at a low speed, worn tires will increase the possibility of accidents, especially in the case of wet roads. The shallower the tire tread, the longer the braking distance. As far as cars are concerned, when the tread pattern depth of tires is worn to 1.6 mm, the braking distance is almost twice that of new tires (the tread pattern depth of new tires is about 8 mm). The tire must have patterns in the circumferential direction and the whole tread width direction, that is, there can be no complete wear of local patterns. The depth measurement of the pattern must measure the depth of the main drainage ditch. Modern tires have the TWI logo. If the mark is worn, the tire must be replaced. In most western European countries, the law stipulates that the tread depth of tire must be greater than1.6 mm. For the sake of drivers' own safety, traffic experts suggest that the tread depth of tire 4 should not be less than 2 mm in summer. The tread depth of winter tires should not be less than 4 mm; The tread pattern depth of flat tire should not be less than 3 mm. In addition, the four wheels of the car should use the same pattern of tires (winter and summer tires can not be mixed at the same time), at least the same axle should use the same tire. Excessive tire wear and shallow tread are important unsafe factors in driving. Excessive tire wear, in addition to easy puncture, will also make the vehicle handling stability worse. When the car is driving at high speed in the rain, the tire will slip and the car will lose control because it can't drain all the water under the tire. The shallower the pattern, the more serious the tendency of water sliding. Inspection of tire wear degree includes:
1. Inspection of tread pattern depth. According to GB7258- 1997 "Technical Provisions on Motor Vehicle Operation Safety", when the tread on the crown of an automobile tire is worn to a depth less than 1. 6 mm, the tread on the crown turned out by the truck is less than 3. The tread depth of other tires is less than 1. 6 mm, it should stop. The tread wear trace is located at the bottom of the tread groove. When the tread is worn here, the groove is broken, indicating that the tire must be stopped for retreading. According to the regulations of radial tire (GB9743- 88) and bias truck tire (GB5 16- 89), each tire should have at least four equally spaced wear marks in the circumferential direction.
2. Inspection of abnormal tire wear. The common abnormal wear of tire includes middle wear of shoulder or tread, inner or outer wear, toe and toe wear (feathering wear), front and rear wear. Check the abnormal tire wear, you can find the early signs and causes of the failure, so as to eliminate the bad factors that affect the tire life in time and prevent the early tire wear and damage.
(2) Inspection of tire pressure Inspection of tire pressure is also very important for driving. Insufficient tire pressure will lead to overheating and uneven wear of tires, or rapid wear of shoulders and sidewalls due to uneven ground contact area of tires, which will shorten the service life of tires. At the same time, it will increase rolling resistance, increase fuel consumption, affect vehicle handling, and even cause traffic accidents in serious cases. If the tire pressure is too high, the body mass will be concentrated in the center of the tread, which will lead to the rapid wear of the tread center, which will not only shorten the service life of the tire, but also reduce the comfort of the vehicle. Therefore, it is very necessary to check the tire pressure during daily maintenance and maintenance at all levels. Tire pressure can be measured with a barometer. Different vehicles may have different tire pressure values, so please refer to the maintenance manual of the corresponding vehicle when checking. Generally, the tire pressure of Santana 2000 is 0. Front wheel 18 MPa, 0. The rear wheel is 22 MPa, which means that the front wheel is 1. Eight atmospheres, and the rear wheel is two atmospheres. 2 atmospheres.
Fourth, the correct maintenance of tires In the process of using cars, we should adhere to the principle of putting prevention first and doing what we can, find and eliminate faults in time, and prevent abnormal tire wear.
(a) Ensure normal tire pressure.
1. Inflate according to the air pressure standard specified in the automobile manual. Never inflate according to the air pressure value marked on the tire.
2. Check whether the tire pressure meets the actual requirements, especially when driving on highways and mountain roads. When checking the tire pressure, make sure to use the calibrated tire pressure value.
3. The air pressure of radial tires should be strictly controlled, because the settlement of radial tires of the same specification is greater than that of bias tires 1% ~ 3%. If the air pressure is not used properly, it will cause abnormal and sharp tire wear.
(2) Safe operation, scientific inflation and safe operation,
1. When inflating, the crowbar should be inserted into the hole of the hub to hold down the lock ring, especially when driving without air, so as to prevent the lock ring from jumping out and hurting people. In addition, beat about 6 tires while inflating, bring them to the lock ring to restore the original state, and return to the lock position to prevent people from jumping out.
2. Pay attention to the scientific inflation of inner tube tire, because its tightness mainly depends on internal pressure to tension the hub and bead. The tire should be 0 when it is inflated. 2 MPa higher than the standard air pressure, but not too high, otherwise the rim will be damaged. When it expands to zero. When the pressure is 2 MPa higher than the standard pressure, the rim and the bead are tightly attached, and then deflated to the standard pressure. The tubeless tire needs to be replaced with a new O-ring after each installation (it should be soaked in vegetable oil for a period of time before use).
(3) Reasonable tire transposition During the use of tires, due to abnormal air pressure, steering wheel sideslip, abnormal front wheel positioning and other reasons, tire wear will be inconsistent, so tire transposition should be carried out during secondary maintenance.
1, timely transposition can make the tire wear evenly and prolong its service life by about 20%. In areas with large camber or in summer, the tire wear is quite different, so the number of transposition can be increased appropriately.
2. The commonly used tire transposition methods include cross transposition, cyclic transposition and unilateral transposition.
3. After tire transposition, the air pressure should be readjusted according to the requirements of replacing fetal position; And make records, the next transposition should still be carried out according to the transposition method selected last time.
(IV) Rational use of automobile tires: Do a good job in tire maintenance, regularly observe the tire pressure, check whether there are cracks and tread wear on the tire sidewall and tire top, and repair and eliminate them in time; Prevent cars from speeding; Prevent tire pressure from being too high or too low; Prevent tire mechanical damage; Correct selection of tires, we should choose tires produced recently, tires of the same type, specification and rim, tires with the same pattern, structure, grade and speed on the same axle; When the car goes down a long slope, the braking is reduced; Prevent the car from overloading and overloading; Tires worn to the mark should be 7 times new; Prevent the height of tire ply from being inconsistent with the load; Prevent the use of mismatched tires and rims.
Five, the correct maintenance of tires
(1) Tire changing skills without jack. When the car is running, if the tire is damaged, the tire can be replaced by the following methods without a jack:
1. Rear wheel tire replacement. Before disassembling the tire, put a block of wood, stone or brick in front of the inner tube, then start the car to press the inner tube on the pad, and then stop. Then squeeze the front and rear parts of the inner tube with other objects to prevent slipping, and then remove the outer tire and replace it.
2. Replacement of inner tube of front wheel or rear wheel. Drive the car to a hard dirt road, pad the front axle or rear axle with wood blocks or bricks, dig a hole under the tire to be replaced, and then replace the tire.
3. Replace the tire with the wooden column top frame. Support the side of the front or rear end of the frame where the tire is to be changed with wooden posts with appropriate thickness, and then drive the wooden posts to lift the roof. After the wooden pillars are upright and the wheels are blocked with stones in front and back, the tires can be changed.
(2) The skill of tapping the sidewall to check the internal damage of the tire. If the sidewall is tapped, there may be a big gap in the carcass; If there is a "tutu" sound, it may be that there is a small hole in the carcass; If there is a "buzzing" sound, it may be caused by adhesion of the carcass; If there is a creaking sound, it may be caused by the rupture of the tire buffer layer; If there is a "plop" sound, it generally means that the carcass is good and there is no major damage.
(3) Clever elimination of abnormal tire wear
1. Early wear of tire center. The main reason is that the tire pressure is too high, which can be eliminated by measuring 8, adjusting the tire pressure and changing the tire position.
2. Excessive wear on both sides of the tire. The main reason is that the tire pressure is insufficient for a long time or the vehicle is overloaded for a long time, which can be eliminated by measuring the tire pressure and adjusting it to the specified value to prevent the vehicle from overloading.
3. Tread serrated wear. The main reason is that the front wheel is misaligned or the position of the front suspension system is abnormal, and the ball head is loose. It can be eliminated by adjusting the front wheel alignment, checking the front suspension system and adjusting the ball pin or replacing the ball pin.
4. One side of the tire is excessively worn. The main reason is that the camber angle of the steering wheel is not suitable. It can be eliminated by trimming or replacing the parts on the axle and suspension, and adjusting the camber and toe-in of the wheel to match them. 5, individual tire wear is too large. The main reason is that the suspension system of individual wheels is abnormal, the support is bent or the individual wheels are unbalanced. It can be solved by checking the positioning of severely worn wheels, the working conditions of independent suspension springs and shock absorbers, and shortening the tire transposition period.
6. The tire is bald and worn. The reason of serious baldness and wear in some parts of the tire is poor tire balance. If it is found that the vehicle is slightly shaking at a certain speed during the running of the vehicle, the wheels should be balanced to prevent the tire from being bald and worn.
In summary, automobile tires not only affect the power, economy and service life of the whole vehicle, but also directly affect the handling stability and controllability of the automobile driving direction, which is related to people's lives and property safety. Therefore, it is necessary to scientifically control tire pressure according to technical requirements, reduce or avoid abnormal tire wear, and properly maintain and use tires.
Thank you
References:
Zhang Hongwei, Wang Guolin. Automobile Chassis Structure and Maintenance Higher Education Press, June 2004, Xue Hongjian, Zhang Quanliang. Automobile Maintenance and Emergency Skills, Beijing Machinery Industry Press, July 2005, Cui 8, GB7258- 1997, Automobile Fault Diagnosis Technology, People's Communications Press, 2005.