Different Types Of Automotive Steering Rack Structures And Their Characteristics

1 Mechanical type steering rack

The mechanical type of steering is a purely mechanical mode, which generally requires only human power to drive the car during steering maneuvers, without the help of external forces. At present, the most common types of mechanical steering gears can be divided into the following three types.

1) Rack and pinion steering gears

The rack-and-pinion type of steering gear has a very simple structure and is the easiest to produce. It consists of the steering gear housing, the adjusting screw, the gear and rack, and the guide block for the rack. Between the rack and the adjusting screw, a spring is placed that allows the screw to rotate, thus giving the rack a force that allows it to move in the direction of the gear, allowing the rack to engage the gear very firmly.
At the same time, the rack guide is very closely related to the movement of the rack of the steering structure. For the steering gear, there are three core components: first, the rack; second, the gears; and third, the steering gear housing. From the shape of the steering housing, it is a T-shape, and the gears of the steering structure and the steering shaft are integrated, while the steering cross-rod is integrated with the rack and pinion.

Advantages and disadvantages of rack and pinion steering gears

The advantages are compactness, lightness, compactness, simplicity of processing, low cost of production, and high transmission efficiency of about 90%. In the process of use, the gears and rack are bound to wear out over time, which can be protected by the steering housing, and the spring and the adjusting screw placed at the back of the steering rack can be used to create pressure, which can eliminate the gap between the gears and the rack, and increase the steering wheel angle to improve the steering effect.

The disadvantage is that its reverse efficiency is relatively high, usually between 60% and 70%. Once the car passes the road in an uneven state, the steering wheel of the car will produce a strong impact with the road, and most of these impacts will produce recoil, which can be transmitted to the steering wheel again, easily causing the driver to have difficulty in accurately controlling the driving direction of the car, and may even cause injuries and car accidents. Therefore, large vehicles will hardly install this type of steering, and small vehicles such as beach cars and civilian cars can use a rack and pinion-type steering.

2) Recirculating ball type steering gears

From the viewpoint of the combined structure, the combined parts of the recirculating ball type car steering consist of a screw, a nut, a steering housing, and a large number of small steel balls, usually called recirculating balls, which are placed in the line between the screw and the nut (the line is closed). Secondly, the steering screw of the recirculating ball type is connected to the steering shaft of the car. This type of steering gear has two levels of rotation, one level of the combination includes the steering screw and the nut, both of which interact with each other. The other level is a combination of a rack and a fan. In the lower plane of the steering nut, there is a well-processed rack, and the fan and the fan shaft are closely combined into one. During the steering process, the small steel ball will keep rolling in the pipeline cyclically.

Advantages and disadvantages of the recirculating ball type steering rack

The advantage is that the transmission efficiency is relatively high, the automatic return effect is quite good, the operation process of the equipment application is light, the wear and tear of the combined parts are relatively small, the service life is long, and in the specific operation application, because of the rolling friction force, it can further improve the transmission efficiency of the car.

The disadvantage is that the combined structure of this kind of steering rack is complicated, and the installation of the steering power device is very inconvenient, also because it has a two-stage transmission sub, so it will cause the steering gear to be weakened by the sense of operation. Secondly, because of the relatively high efficiency of the reverse transmission of this steering gear, it is easy to shake the steering wheel and vibration problems, which is not conducive to the stability of steering in the process of steering, and if the driving road is bumpy, or is changing position up and downhill, it is easy to “hit the hand” problem, and even cause traffic accidents.

3) Worm gear crank finger pin type steering racks

In terms of combination structure, the main combination system of worm gear crank finger pin type steering gear includes five types: First, the steering worm of the car. The second is the side cover of the car. Third, the finger pins of the car. Fourth, is the crank of the steering arm. Fifth is the housing of the steering rack. In this combined system of the steering gear, its housing is fixed, usually firmly placed on top of the safety bracket of the steering gear, and in the interior of the housing, it is equipped with the corresponding transmission subassembly. In the steering drive, the active part of the steering gear is the steering worm of the car, the steering structure system presents a trapezoidal cross-section thread, the steering worm is usually supported on two ball bearings (these two bearings are set on the sides of the steering gear housing), the steering gear finger pin is set on the end of the rocker arm crank, it belongs to a follower. If a car is equipped with such a steering gear, during the driving and steering process, the driver will drive the steering worm through the steering wheel, so that the steering gear will rotate with the car pins it engages, and at the same time, the radius of the car’s rotation must be the crank, and the threaded groove of the car worm will carry out circular motion around the axis of the rocker’s arm, thus driving the car’s crank and allowing the steering rocker arm to The crank of the car is driven so that the steering arm can implement a scientifically controlled oscillation, thus enabling the car to achieve safe steering.

Advantages and disadvantages of worm gear crank finger pin type automotive steering gear

The advantage of the worm crank finger pin type of car steering means that it will work well under the action of complete rolling friction, the operation is very simple and flexible, the transmission efficiency is relatively high because it is the use of segmented steering shaft, so the application of the entire vehicle arrangement work and maintenance is more convenient, but also help to improve the safety of the vehicle driving. It is understood that, and other steering applications, compared with the configuration of this steering vehicle often in the driving of the reversal of the transmission efficiency is lower, therefore, the impact of the road will not be too much to the car steering wheel, there is good stability. In addition, this type of steering gear is simple to manufacture and easy to maintain.

The disadvantages are not negligible, because compared with other steering gears, this type of steering gear is a large device, its size is relatively large, so it will lead to the arrangement of work is not very convenient

2 Power type followed by steering

The two most common types of steering used in power type automotive steering applications are hydraulic type automotive power assist systems and electric type automotive power assist systems.

1) Hydraulic power steering system

The hydraulic type power steering system package consists of six core components: First, the fuel line. Second, is the V-shaped vehicle drive belt. Third, is the vehicle’s hydraulic pump. Fourth, is the vehicle’s oil reservoir. Fifth, is the vehicle pressure fluid control valve. The core power source of the system is the car engine, its steering oil pump is mainly with the help of the engine to achieve the operation work, steering control valve in the process of operation will certainly follow the direction of the flow of control fluid, at the same time, will combine the oil pressure parameters for the car’s driving to provide the corresponding steering assistance, so as to produce a good power effect and reduce the driver’s operating burden.

Hydraulic type power steering system can be divided into two types: the first one, mechanical hydraulic type power steering system; the second one, electronically controlled hydraulic type power steering system. The second type of system is based on the first The second type of system is based on the first type of system, with the addition of the hydraulic flow distribution valve, hydraulic system automatic response device and intelligent electronic control system. In the process of application, the electro-hydraulic type power steering system will combine with the driving speed to scientifically adjust the power on the steering wheel of the car. On the whole, the mechanical hydraulic type power steering system has significant advantages and disadvantages that cannot be ignored. In the operation of the system, if the car is at low and medium speeds, the system produces good power performance and can ensure the stability of the maneuvering, however, the power effect of the system is often in a fixed state, which will lead to over-sensitive steering wheel operation, once the car is driving at high speed, it will reduce the driver’s road sense effect, and will consume more engine energy. The electronically controlled hydraulic type power steering system can overcome some of the shortcomings of the mechanical hydraulic steering system, when the car is at high speed, the system will flexibly adjust the power effect to enhance the driver’s maneuvering force, improve the driver’s road sense, make the car steering more light, flexible, safe, and provide good stability for the car steering at high speed. However, this system combination mechanism is complex and a precision device, so it is expensive and consumes a lot of energy. In this regard, it should be safely configured according to the vehicle type. Small vehicles are generally not suitable for this kind of steering, and in the process of configuration, attention should be paid to reducing costs and implementing the concept of energy saving.

2) Electric power-assisted type automobile steering system

The electric power-assisted type of vehicle steering system combination consists of five main types: first, electric motor; second, speed sensor; third, electronic control unit; fourth, torque sensor; and fifth, reduction mechanism. The core component of this system is the electronic control unit. From the application effect, the advantages of the electric power-assisted type car steering system are that it relies on intelligent and automatic technology, which can effectively reduce the amount of fuel consumption and low cost, and can simultaneously take into account the car steering, making the operation more light, safe and stable, and the combined structure of this system is also very compact and light, with a perfect assembly line, which is also easy to maintain. Its shortcomings are reflected in four aspects: first, the manufacturing process is complicated and the production cost is high. Second, the steering system provides extremely limited assistance. Third, the stability function and reliability effect of the electronic components of this system is not as good as the mechanical components, and if it encounters a continuous rotation area, it is easy to make the booster motor stop running problem because of overheating. Fourth, there is a lack of road sensing information [3]. These deficiencies should be overcome as much as possible by choosing the right steering gear and properly controlling the safety parameters of the steering components according to the size and type of the vehicle.

3. Conclusion

To sum up, automotive steering mainly includes mechanical type steering and power type steering. The former is subdivided into rack and pinion type steering gear, recirculating ball type steering gear, and worm crank finger pin type steering gear; the latter can be divided into hydraulic power steering system and electric power steering system, these steering gears have advantages and shortcomings, therefore, in the specific selection and operation, attention should be paid to give full play to their advantages and make up for the shortcomings, and constantly complete. The latter can be divided into hydraulic power steering systems and electric power steering systems.

References

[1] CAD and CAE simulation analysis of rack and pinion steering gear [J]. Liu Xiangli. Smart City. 2019(17)

[2]The use and maintenance of vehicle mechanical steering system[J]. Miao Zhang, Zhou Weidong,Shao Hongliang. Agriculture and Technology. 2009(02)