Adapt to the needs of high-speed driving of automobiles

From the point of view of maneuverability, stability and safe driving, more advanced technologies and methods are widely used in automobile manufacturing, including variable speed ratio steering gear and high rigidity steering gear. "High speed ratio and high rigidity" is the direction of steering gear structure produced in the world at present. Steering system

Fully consider safety and portability.

With the increase of vehicle speed, the safety of drivers and passengers is very important. At present, many cars at home and abroad are generally equipped with anti-collision safety steering columns, seat belts, airbags and other energy-absorbing devices, which are gradually popularized. From the perspective of ergonomics, adjustable steering column and power steering system have been gradually adopted.

Low cost, low fuel consumption, mass specialized production.

With the deterioration of the international economic situation, the oil crisis led to economic recession, and automobile production paid more and more attention to economy. Therefore, it is necessary to design low-cost and low-fuel consumption cars and low-cost and reasonable production lines to achieve large-scale specialized production as much as possible. The production of parts, especially steering gear, is more prominent.

Computerization of automobile steering gear device

The development of automobile steering gear must take the road of computerization.

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Development trend of modern automobile steering gear

Application trend of modern automobile steering gear.

With the rapid development of automobile industry, the structure of steering device has also changed greatly. There are many kinds of automobile steering gear structures. Judging from the widely used steering gear at present, there are mainly four types: worm shaft type (WP type), worm roller type (WR type), circulating ball type (BS type) and rack and pinion type (RP type). These four types of steering gears have been widely used in automobiles.

It is understood that in the world, automobile circulating ball steering gear accounts for about 45%, rack and pinion steering gear accounts for about 40%, worm steering gear accounts for about 10%, and other types of steering gear account for about 5%. Circulating ball steering gear has been developing steadily. Rack-and-pinion steering gear has made great progress in western European buses. The characteristic of Japanese automobile steering gear is that the proportion of circulating ball steering gear is increasing. In Japan, all kinds of cars with different engines use different types of steering gear, and the circulating ball steering gear used in buses has increased from 62.5% in the 1960s to 65,438+000% now (the worm steering gear has been eliminated in buses). Most large and small trucks use circulating ball steering gear, but rack-and-pinion steering gear has also developed. The circulating ball steering gear for minivans accounts for 65%, and the rack and pinion steering gear accounts for 35%.

Based on the above analysis of the varieties of steering gear, the following conclusions are drawn:

Circulating ball steering gear and rack-and-pinion steering gear have become two main steering gears in the world today. And a worm wheel # 0; Worm steering gear and worm steering gear are gradually being eliminated or kept in a small position.

There are different views on developing steering gear on passenger cars. The United States and Japan focus on developing circulating ball steering gear, with the proportion reaching or exceeding 90%. Western Europe focuses on the development of rack-and-pinion steering gear, with the proportion exceeding 50% and France reaching 95%.

Because of the advantages of rack-and-pinion steering gear, its application in small cars (including passenger cars, minivans or vans) has developed by leaps and bounds; However, the main structure of large vehicles is the circulating ball steering gear.

Characteristics of circulating ball steering gear

The circulating ball steering gear has the characteristics of high efficiency, easy operation and smooth steering force characteristic curve.

Convenient layout. Especially suitable for large and medium-sized vehicles and power steering systems; Easy to transmit the driver's control signal; High reversing efficiency, good reversion, and good cooperation with the action of hydraulic booster.

It can realize the speed change ratio characteristics and meet the portability requirements. The steering force in the middle position is small, which is often used and requires sensitive steering. Therefore, it is hoped that the speed ratio near the middle position will be smaller to improve the sensitivity. The steering resistance of the large-angle steering position is large, but it is used less, so it is hoped that the speed ratio of the large-angle steering position will be larger to reduce the steering force. Because the circulating ball steering gear can realize the speed change ratio, it is widely used.

The steering force is transmitted through the rolling contact of a large number of steel balls, which has greater strength and better wear resistance. Moreover, the steering gear can be designed as an equal strength structure, which is one of the reasons for its wide application.

The transmission ratio structure has high rigidity and is especially suitable for improving the speed of high-speed vehicles. High-speed vehicles need good steering stability when driving at high speed, and the steering gear must be ensured to have high stiffness.

The gap is adjustable. It is one of the advantages of this kind of steering gear that the gap can be readjusted after the rack tooth fan pair is worn, so that it has a suitable steering gear transmission gap, thus improving the service life of the steering gear.

China's steering gear production, in addition to the early production of Jiefang brand car worm # 0; Except for the roller steering gear and worm steering gear used by Dongfeng Motor, most other models have adopted the circulating ball structure, and they all have certain production experience. At present, Jiefang and Dongfeng are also actively developing the circulating ball steering gear, which has been widely used in the second generation of cars. It can be seen that China's steering gear is also developing towards mass production of circulating ball steering gear.

Specialization of steering gear production

The circulating ball steering gear has achieved specialized production abroad, and at the same time, great efforts have been made to carry out experimental research, which has greatly improved the output and quality of products. In Japan, the circulating ball steering gear of "Seiko" (NSK) company gradually occupied the Japanese market with low cost, good quality and large output, and its products were sold all over the world. German ZF company is also a famous large-scale steering gear professional factory. Production of ZF steering gear started from 1948, with an annual output of more than 2 million steering gears. There are also some large steering gear manufacturers, such as Sagino branch of Delphi company in the United States; British Burm # 0；; A company is a well-known professional manufacturer with large output and sales. Specialized production has become a trend. Only by taking this road can we make products with high quality, large output, low cost and competitive market.

Power steering is the development direction.

Power steering system is widely used, not only in heavy-duty cars, but also in high-class cars, and its application in medium-sized cars is gradually popularized. Mainly from reducing driver fatigue and improving maneuverability and stability; The second is to reduce accidents caused by sudden puncture of front wheels at high speed. Although it has brought problems such as high cost and complex structure, it has developed rapidly due to its obvious advantages.

There are three forms of power steering: integral, semi-split and combined valve power steering structure. At present, the three forms have their own characteristics and are developing rapidly. Integral type is mostly used for automobiles with front axle load of 3 ~ 8t, and combined valve type is mostly used for front axle load of 5 # 0. 18t car, semi-split, mostly used for super-heavy trucks with front axle load of 6t or more.

From the development trend, the integrated steering gear developed rapidly abroad, and the reversing valve structure of the integrated steering gear is the current development direction.

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Common faults of steering system

deviation of directivity

The direction deviation is as follows: when driving, I feel that the car automatically leans to one side, and I have to hold the steering wheel hard to keep the straight driving direction. The reasons are: the left and right tire pressures are not equal; Individual brake shoes scratch the brake hub, or one wheel housing bearing is too tight; Individual leaf springs are broken, and the elasticity of steel plates on both sides is uneven; Front axle or frame bending; The front wheel alignment is inaccurate or the wheelbase on both sides is unequal; The clearance between the steering knuckle kingpin and the bushing is different from left to right, or the tightness adjustment of the ball heads on both sides of the tie rod is different; The goods on the truck are unevenly loaded.

Directional swing head

The performance of steering head swing is: when the car is driving, it feels that the two front wheels swing left and right, and the steering wheel is difficult to master. The reasons are as follows: the adjustment of the ball head of the horizontal tie rod is too loose (the spring is broken or the adjustment gap is too large); Excessive free travel of steering wheel; The meshing clearance between steering wheel and worm is too large; The clearance between upper and lower bearings of worm is too large; The gap between the steering knuckle kingpin and the bushing is too large; The front wheel housing bearing is loosely assembled, or the front wheel rim is not round; Front wheel alignment deviation.

Turn heavily when turning.

The heavy steering performance is: turning the steering wheel when making the driving car turn, feeling heavy and hard. The reasons are: the upper and lower shafts of the worm are adjusted too tightly or the bearings are damaged; The worm gear and worm are engaged too tightly, and there is no gap between the steering rocker shaft and the steering gear bushing; The steering shaft is bent or the pipe column is sunken and collides with each other; The steering wheel rubs the pipe string; The thrust bearing on the steering knuckle is short of oil or damaged; The steering knuckle kingpin and bushing are assembled too tightly or lack of lubricating oil; The plug of steering knuckle tie rod (straight tie rod) is screwed too tightly, or the tie rod joint is short of oil; The ball head of the pull rod is adjusted too tightly, or the slider is short of oil; Insufficient tire pressure; The front axle or frame is bent and the front wheels are misaligned.

Understeering when turning.

The understeer when turning is manifested as: the car is understeer when turning. The reasons are: the steering rocker arm is not installed in the right position on the rocker arm shaft; The steering angle limit bolt is adjusted too long; The front axle moves back and forth; Improper assembly of circulating ball or steering gear sector teeth with worm gear box.

Adjustment of maximum deflection angle of front wheel

When a car turns, the maximum deflection angle (steering angle) of the front wheel affects the steering radius (also called the passing radius). The larger the deflection angle, the smaller the steering radius, and the stronger the maneuverability of the car.

The maximum deflection angle of the front wheel is adjusted by the limit screw on the front axle. The method is as follows: jack up the front axle and turn the steering wheel so that the front wheel deviates from the collision object (fender, tie rod, frame, etc.) by 8~ 10mm. ), and turn the limit screw to limit the wheel in this position. At this time, the included angle between the center line of the tire landing track and the center line of the tire landing track when driving in a straight line is the maximum deflection angle. The maximum deflection angle and minimum steering radius of various models are different. Please refer to the user manual before adjustment.

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Steering system maintenance

Power steering system is widely used in modern middle and high-grade cars and heavy-duty cars, which not only greatly improves the portability of vehicle handling, but also improves the driving safety of vehicles. Power steering system is formed by adding a set of steering afterburner based on engine output power on the basis of mechanical steering system. At present, the shift lever power steering mechanism is widely used in automobiles. This kind of steering gear has the advantages of simple structure, high steering sensitivity and light steering. Moreover, because the steering gear is fully enclosed, there is no need to check and adjust it at ordinary times.

Maintenance of power steering system mainly includes:

Regularly check the level of power steering fluid in the reservoir.

When it is hot (about 66℃, it feels hot by hand), its liquid level must be between the hot and cold signs. If it is cold (about 265438 0℃), the liquid level must be between the mark of ADD and CLOD. If the liquid level does not meet the requirements, DEXRON2 power steering fluid (hydraulic transmission oil) must be filled.

Cleaning, oil change and protection of power steering system

The cleaning, oil change and protection of the power steering system should be carried out in the automobile maintenance center equipped with power steering oil change equipment. Special equipment should be used. First, replace the old oil of the power steering system with the powerful cleaning agent of the power steering system, then clean the power steering system with the cleaning agent, and finally replace the power steering cleaning agent with new oil (adding power steering protective agent) until the oil change is over. The cleaning, oil change and protection of the power steering system should usually be carried out every 50,000 kilometers. This can ensure that the power steering system works more safely and reliably, avoid early damage and prolong the service life.