While driving, the driver experiences a constant need to control the car and the road. Very often there is a need to change the driving mode: entering or exiting a parking lot, changing the direction of travel (turning, turning, changing lanes, advancing, overtaking, detouring, driving in reverse etc.), stopping or parking. The implementation of these actions is ensured by the steering of the car, which is one of the most important systems of any vehicle.

General structure and principle of operation

General device steering, despite the large number of components and assemblies, seems quite simple and effective. The logistics and optimality of the design and operation of the system is proven by the fact that over many years of theory and practice in the automotive industry, the steering control has not undergone significant global changes. Initially, it includes three main subsystems:

1. a steering column designed to transmit the rotational movement of the steering wheel;
2. steering mechanism - a device that converts rotational movements of the steering wheel into translational movements of drive parts;
3. steering gear, which aims to bring control functions to the rotary wheels.

In addition to the main subsystems, large-capacity trucks, route vehicles and many modern passenger cars have special device power steering, allowing you to use the generated force to facilitate its movement.

Thus, the steering circuit is quite simple and functional. The steering wheel, as a primary unit, well known to every driver, under the influence of his thoughts and the influence of force, makes rotational movements in the required direction. These movements are transmitted through the steering shaft to a special steering mechanism, where torque is converted into plane movements.
The latter, through the drive, communicate the required rotation angles to the steering wheels. In turn, pneumatic, hydraulic, electric and other amplifiers (if available) facilitate the rotation of the steering wheel, making the process of driving a vehicle more comfortable.

Steering column

The steering circuit necessarily includes a column, which consists of the following parts and assemblies:

• steering wheel (or steering wheel);
• column shaft (or shafts);
• casing (pipe) of the column with bearings intended for rotation of the shaft (shafts);
• fastening elements to ensure immobility and stability of the structure.

The column's operation scheme consists of applying driver force to the steering wheel and then transmitting directional rotational movements of the steering wheel to the entire system if the driver wants to change the vehicle's driving mode.

Steering gear

The steering mechanism of any car is a way of converting the rotation of the column into translational movements of the steering gear. In other words, the functions of the mechanism are reduced to ensuring that turns of the steering wheel turn into the necessary movements of the rods and, ultimately, the wheels.


The steering mechanism design is variable. Currently, it is represented by two main principles - worm and rack, which differ in the methods of converting torque.
The general structure of the worm-type steering mechanism includes:

1. a couple of “worm-roller” parts;
2. crankcase of the specified pair;
3. steering bipod.

Power steering

The steering of modern cars is equipped with a special additional option- amplifier. Power steering is a subsystem consisting of a mechanism that can significantly reduce the driver's effort when turning the steering wheel and steering the car.


The main types of power steering are:

1. pneumatic booster (using the power of compressed air);
2. hydraulic booster (based on changes in the pressure of a special fluid);
3. electric booster (operating on the basis of an electric motor);
4. electric hydraulic booster (using a combined operating principle);
5. mechanical amplifier (special mechanism with an increased gear ratio).

Initially, the reinforcement system was used on large-capacity and large-sized equipment. Here the driver’s muscle strength was clearly not enough to carry out the intended maneuver. In modern passenger cars In mobile phones, it is used as a means of ensuring comfort when taxiing.

Basics of Control System Operation

During the operation of the car, individual components and assemblies included in the steering system gradually become unusable. This is especially aggravated when driving on poor-quality roads. The driver’s insufficient attention paid to the prevention of malfunctions also contributes to the wear and tear of the system, as well as low quality spare parts and components. Not the least important role is played by the low qualifications of the servicemen whom the driver trusts to service his car.

The importance of the vehicle control system is determined by the requirements general security traffic. Thus, the norms of the “Basic provisions for the approval of a vehicle for operation...” and paragraph 2.3.1 of the Traffic Regulations categorically prohibit driving (even to a car service center or parking place) in a vehicle if there are faults in the steering system. Such malfunctions include:

• exceeding the permissible free play (play) of the steering wheel (10 degrees for passenger cars, 25 for trucks, 20 for buses);
• movement of parts and components of the control system not provided by the manufacturer;
• presence of looseness in threaded connections;
• inadequate functioning of the power steering.

However, this list of faults is not exhaustive. In addition to them, there are other “popular” flaws in the system:

1. tight rotation or sticking of the steering wheel;
2. knocking or beating that sounds in the steering wheel;
3. system leakage, etc.

Such malfunctions are considered acceptable during vehicle operation if they do not cause the previously noted system deficiencies.

Summarize. Steering is one of the most important components design of a modern vehicle. It requires constant monitoring of its condition and implementation of timely and high-quality service and Maintenance.

Many will agree that the engine is the basis of the car. And indeed it is. However, it is also difficult to imagine a car without steering. This is an important and necessary element in every car. The purpose of steering is to ensure that the vehicle moves in a given direction. This unit consists of several components. These are the steering wheel, column, drive and steering mechanism. We'll talk about the latter today.

Functions

The steering mechanism has several main tasks:

• Transfer of forces to the drive.
• An increase in the force applied by the driver to the steering wheel.
• Self-return of the steering wheel neutral position when removing the load.

Varieties

This element can be of several types. Today the following types of steering mechanisms are found:

• Rack and pinion.
• Worm.
• Screw.

What is each of them? We will consider all these types of mechanisms separately.

Rack and pinion

On this moment it is one of the most common. Mainly installed on cars and crossovers. The rack-and-pinion steering mechanism requires the following parts:

The first was installed on the steering shaft. The gear is in constant mesh with the rack. This mechanism works quite simply. When the steering wheel is rotated, the rack moves to the right or left. At the same time, the rods that are attached to the drive turn steerable wheels to a given angle.

Among the advantages of such a mechanism, it is worth noting the simplicity of the design, high efficiency and high rigidity. However, such a mechanism is very sensitive to unevenness on the road, which is why it wears out quickly. Often, owners of used cars are faced with the problem of a knocking rack. This is a consequence of wear on the steering mechanism. Therefore, the element is installed only on certain types of cars. Mainly front wheel drive cars with independent front suspension. If we talk about VAZ, then the rack is found on all models, starting with the “eight”. On the “classic”, a slightly different steering mechanism is installed.

Worm

This type is used on domestic Zhiguli cars, as well as on some buses and light trucks. This unit consists of:

• Globoid type worm with variable diameter.
• The steering shaft to which the worm is connected.
• Roller.

A bipod is located outside the steering mechanism. This is a special lever that is connected to the drive rods. The steering mechanism on the GAZ-3302 is designed according to the same scheme.

Among the advantages of such a unit, it is worth noting less sensitivity to shock loads. Therefore, this steering mechanism, installed on the VAZ-2107, is practically eternal. Owners rarely encounter knocking and vibrations on the steering wheel. However, this design scheme has more connections. Therefore, the mechanism periodically needs adjustment.

Screw

This is a more complex unit to construct. Its design includes:

• Screw. Located on the steering wheel shaft.
• Screw. It moves over the previous element.
• Rack.
• Gear selector. It is connected to the rail.
• Steering bipod. Located on the selector shaft.

The key feature of this mechanism is the way the nut and screw are connected. Fastening is carried out using balls. Thus, less wear and friction of the pair is achieved.

The principle of operation of the screw element is similar to the worm element. The steering wheel is turned by rotating the screw, which moves the nut. The latter moves the gear sector with the help of a rack, and with it the steering bipod.

Where is the screw mechanism used? Often, it is used on heavy commercial equipment - trucks and buses. If we talk about passenger cars, these are just models executive class. The mechanism is more complex and expensive, therefore significantly increasing the cost of the car itself.

Amplifier

Nowadays, almost all cars use power steering. It serves to reduce the effort required to turn the front wheels. This element allows for high accuracy and speed of steering. At the moment, there are several types of amplifiers:

• Hydraulic.
• Electric.

The first type is more popular. Installed on both cars and trucks. The amplifier device has a pump that creates a certain pressure in the hydraulic system. Depending on the direction the steering wheel is turned, this fluid presses on the first or second contour of the rack. This reduces the effort required to turn. Among the advantages of the hydraulic system it is worth noting high reliability. The amplifier rarely fails. However, since the pump mechanism is driven by the crankshaft, some of the power is taken from the internal combustion engine. Although on modern engines it's not noticeable at all.

Electric amplifier consists of a separate engine. The torque from it is transmitted to the steering wheel shaft itself. The design is used only on passenger cars, as it is not designed for high forces.

The EUR is equipped with separate electronics, which controls this engine. Sometimes the amplifier is understaffed adaptive systems, which are aimed at increasing safety when driving in the lane.

Among the innovative solutions, it is worth noting the system dynamic control from Audi. Here gear ratio changes depending on the current vehicle speed. Thus, at high speeds the steering is stiff and stiff, but when parking it becomes light. The gear ratio is changed using a dual planetary gearbox, which is added to the shaft. Its body can rotate depending on the speed of the car.

Conclusion

So, we found out what this mechanism is. This is a very important component in the steering. Regardless of the type, it must be checked periodically. After all, loss of control at speed is the most dangerous thing that can happen to a driver.

5.3. Design and operation of steering

The steering serves to turn the front wheels of the car while it is moving and consists of a steering gear and a steering mechanism. In order for the movement of the car's wheels when turning to occur without lateral slipping, the steered wheels must turn at different angles: the inner wheel at a larger angle, and the outer wheel at a smaller angle.

The steering mechanism serves to convert the rotational movement of the steering wheel into linear linear movement, transmitted to wheels. For rectilinear movement, it is necessary to convert the rotational movement of the steering wheel into swinging of the steering bipod or create a reciprocating movement of the steering rack. In addition, the steering mechanism provides a reduction gear ratio, which reduces the effort exerted by the driver to control the wheels. This is especially important when the car is stationary or moving slowly and turning the steering wheel is as difficult as possible.

The relationship between the steering angle and the steering angle is called the steering ratio. Gear ratios can be constant or variable. Steering with a constant gear ratio is called "linear". With linear steering, turning the steering wheel a fixed number of degrees moves the steered wheels by a proportional angle based on the gear ratio at any steering position.

Variable ratio steering is called "proportional" steering. With proportional steering, the gear ratio changes with each turn of the steering wheel. Generally, as the steering wheel angle increases, the rate of change in the wheel angle increases. The gear ratio is the steering angle divided by the steering angle.

Typically, the low-range steering ratio ranges from 14:1 to 22:1. Ratios between 14:1 and 18:1 typically require power steering. To move the wheels between the limit positions, you need to turn the steering wheel 3–4 full revolutions. The steering mechanism must be strong enough to withstand different loads to which he is exposed in different conditions movements. The driver should not feel the shocks accompanying the movement through the steering wheel.

5.3.1. Steering mechanisms

There are several different design options for steering mechanisms, but there are two main types:

Steering mechanisms with rotational motion (Fig. 5.26);

Rice. 5.26. Rotary steering mechanism

Steering mechanisms with sliding movement (Fig. 5.27).

Rice. 5.27. Steering mechanism with sliding motion

Rotary steering mechanisms

Rotary steering mechanisms have different designs:

Ball screw steering mechanism;

Steering mechanism of the “screw-nut” type with slider rings;

Worm-sector steering mechanism;

Worm-roller steering mechanism;

Steering mechanism with worm and roller pin.

In Fig. Figure 5.28 shows a ball screw steering mechanism. It uses multiple balls that circulate in “tracks” formed by grooves found in the steering nut and steering shaft. When the steering shaft rotates, the balls roll along the “paths” and force steering nut move up or down the steering shaft. The steering bipod is rotated by a toothed sector, which meshes with the teeth on the steering nut.

Rice. 5.28. Ball screw steering mechanism

The gear ratio in this steering mechanism is constant. The balls reduce friction between moving elements, so this type of steering mechanism is practically not subject to wear. Increased play in the steering mechanism can usually be eliminated by adjusting the position of the steering shaft.

In Fig. Figure 5.29 shows a steering mechanism with a worm and a roller pin. Its design uses a cylindrical worm with an uneven pitch. As the worm rotates, the conical pin moves axially along the worm. The steering bipod is mounted on a corresponding shaft connected to a pin and can be rotated by 70°. The wear of the working elements of this mechanism is relatively low, the play in the steering shaft and between the pin and the worm is adjustable. The gear ratio of a steering mechanism with a worm and a roller pin changes proportionally due to the uneven pitch of the worm.

Rice. 5.29. Steering mechanism with worm and roller pin

The worm-sector steering mechanism is shown in Fig. 5.30.

Rice. 5.30. Worm-sector steering mechanism

In this type of steering mechanism, a cylindrical worm is provided at the end of the steering shaft, which moves the gear sector. The advantage of the worm gear steering is that high gear ratios of up to 22:1 can be easily achieved. The gear sector is in constant engagement with the worm; any rotation of the steering shaft causes the gear sector to rotate. The steering bipod is mounted on a gear sector and can be rotated by 70°. The wear of this type of steering mechanism is relatively high due to the sliding friction of the working elements. The disadvantage of the worm-and-sector steering mechanism is that the driver needs to apply significant force to the steering wheel.

In Fig. Figure 5.31 shows a screw-nut type steering mechanism with slider rings.

Rice. 5.31. Steering mechanism of the “screw-nut” type with slider rings

According to the principle of operation, this mechanism is similar to a steering mechanism with circulating balls. Slider rings located on the side of the steering nut transmit the movement of the nut to the steering fork. The steering bipod, mounted on the bipod shaft, which is located on the steering fork, rotates 90°. The wear of this type of steering mechanism, caused by friction, is usually high. The gear ratio is constant.

Rice. 5.32 represents a worm-roller steering mechanism.

Rice. 5.32. Worm and roller steering mechanism

This steering mechanism uses a roller instead of a gear sector to transmit movement from the worm. The worm in this steering mechanism is tapered towards the center and takes on a shape resembling an hourglass (globoid). The advantage of this worm shape is that it allows the roller to rotate about its center and this reduces the size of the steering gear. The steering bipod is attached to the roller shaft and can be rotated 90°. The gear ratio remains constant. Increased play can be eliminated by adjusting the position of the steering shaft.

Sliding steering gear

In Fig. Figure 5.33 shows a steering gear with a constant tooth pitch - the most common type of steering gear used in modern cars.

Rice. 5.33. Steering gear with constant tooth pitch

Rack and pinion steering gears use a rotating gear to create linear movement of the rack. The gear teeth are in constant mesh with the rack teeth, and any movement of the steering column shaft causes lateral movement of the steering rack. The movement of the rack is directly transmitted to the steering rods installed at both ends of the rack. Ball joints, located between the rack and the steering rods, provide the possibility of independent vertical movement of the steering rods. The rack is held in mesh with the pinion by a spring-loaded pressure block that adjusts any clearance between the teeth. Sliding friction between the rack and pinion provides a shock-absorbing effect and absorbs shocks that occur during movement.

Among the advantages of the rack and pinion steering mechanism is direct steering. The gear ratio is constant.

In Fig. Figure 5.34 shows a steering rack with variable tooth pitch. For clarity, the steering gear housing and gear are not shown.

Rice. 5.34. Variable pitch steering rack

A variable pitch rack and pinion steering mechanism operates in the same way as the fixed pitch rack and pinion steering mechanism described above. In the center of the rack the tooth pitch is greater than at the edges. Variable pitch allows the steering ratio to increase as the gear rotates. The teeth in the center of the rack provide more movement of the rack with each rotation of the gear, which requires relatively great effort. The teeth on the ends of the rack provide less movement of the rack, requiring relatively little effort from the driver. To eliminate this drawback, power steering is installed on modern cars. In fact, in this system, the more the steering wheel is turned, the less force there is. When driving in a straight line, the steering is heavier than when the steering wheel is turned to the limit position - this makes maneuvering and parking easier.

The variable pitch rack and pinion steering mechanism has a proportionally increasing gear ratio.

In Fig. 5.35 (see also the color insert in Fig. CV 5.35) shows a typical hydraulic power steering system, equipped with a liquid pump, which serves to supply working fluid under pressure into the hydraulic circuit. The pump may have electric drive and be located in the power steering reservoir or be mechanically driven by the engine.

Rice. 5.35. Hydraulic system power steering

Mechanical pumps are usually equipped with a separate reservoir for working fluid. Working fluid under the pressure created by the pump, it enters the spool valve in the steering mechanism. When the steering shaft is in a straight position, the hydraulic fluid passes through the spool valve and returns to the reservoir. When the steering wheel is turned, the spool control valve directs hydraulic fluid to the appropriate side of the piston, which is located in a cylinder at the end of the rack and pinion steering gear. The rod attached to the piston is connected to the rack, and any pressure of the working fluid acting on the piston helps move the rack. Working fluid with reverse side returns to the reservoir through the spool valve. When turning the steering wheel in a different direction, the opposite process occurs. If the power steering fails, the mechanical action steering mechanism, but you will have to apply much more force.

5.3.2. Steering gear

The steering gear serves to transmit the driver's force through the steering wheel to the steering wheels of the vehicle. The steering mechanism converts the rotational motion of the steering wheel into linear motion, which pulls the steering linkages. The converted movement is transferred from the steering mechanism to the steering gear. Ball joints at the ends of the longitudinal and transverse steering rods provide the possibility of any rotary and rotational movements in the drive. The layout and number of tie rods in the steering drive depends on the design of the axle and suspension.

Steering gear drive configuration options

The simplest design of the steering gear is a single-section transverse Tie Rod, moved by the steering bipod (Fig. 5.36). The steering arm pushes or pulls the tie rod to move the arm, which is connected to the pivot joint on the steering knuckle. The tie rod connects both steering joints on the steering knuckles of the vehicle's front wheels. Any movement of one of the steering joints is transmitted through the steering linkage to the joint on the opposite steering knuckle.

Rice. 5.36. Steering gear with single-section tie rod

This type of steering gear is typically used in vehicles with a rigid axle, in which the distance between the steering knuckle arms does not change. Ball joints are used to connect the longitudinal steering rod with the steering knuckle arms.

In Fig. Figure 5.37 shows a modified version of a single-section tie rod - a steering drive with a two-section tie rod moved by a steering bipod. The steering arm pulls or pushes two separate tie rods, which are connected to the steering knuckle arms via ball joints. Moving the tie rods turns the steering joints on the steering knuckles. This type of steering gear is typically used in vehicles with independent suspension, in which the steering joints can move independently of each other.

Rice. 5.37. Steering gear with two-piece tie rod

A steering drive with a three-section steering rod, moved by a steering bipod, is shown in Fig. 5.38. This tie rod has a swing arm that transmits the steering movement to the opposite side of the vehicle. This type of steering gear is used in cars with independent suspension, but this design option has a high cost.

Rice. 5.38. Steering gear with three-section tie rod

The three-piece tie rod provides the highest degree of precision and maximum steering control. When a car moves on an uneven road, shocks are transmitted through the steering gear and steering mechanism to the driver. To soften these shocks, a shock absorber is installed on the steering gear. Steering shock absorbers can be built into any type of steering gear (Fig. 5.39), but they are not often used in cars with rack and pinion steering. A steering damper helps counteract increased steering forces and unintentional steering wheel movement.

Rice. 5.39. Steering shock absorbers

In Fig. Figure 5.40 shows steering actuators with two-section steering rods of a moving rack. A rack and pinion steering system uses two tie rods to transmit steering input to the steering knuckles.

Rice. 5.40. Steering drives with two-piece tie rods

There are also steering racks to connect to the steering knuckles. They use steering gears of a similar design. The linear movement of the steering rack is transmitted through the ball joint to the steering rods.

5.3.3. Diagnostics and maintenance of the front, rear suspension and steering

Malfunctions and ways to eliminate them

The amount of free play of the steering wheel is indicated in the vehicle operating instructions. Increased freewheel detected by rocking the steering wheel. There may be several reasons for its occurrence:

Loosening the tie rod ball joint nuts;

Increased clearance of steering rod ball joints;

Increased clearance of ball joints of front suspension arms;

Play as a result of wear of the front wheel bearings;

Backlash as a result of wear of the steering gear teeth;

Play in the elastic coupling connecting the steering mechanism to the steering wheel shaft;

Play in the bearings of the steering wheel steering shaft.

To eliminate the malfunction, it is necessary to check the tightness of all fasteners and replace worn parts.

Noise (knocking) in the steering can be caused by the following reasons:

Loosening the tie rod ball joint nuts;

Increasing the gap between the rack stop and the nut;

Loosening of the steering mechanism mounting nuts, as well as all of the above malfunctions.

Stiff steering wheel rotation:

Bearing damage top support steering wheel shaft;

Reduced air pressure in the front tires;

Damage to parts of the telescopic strut and wheel suspension;

Malfunction of the power steering pump;

Foreign particles entering the steering hydraulic system;

Increased oil level in the steering pump reservoir;

Worn or damaged steering cuffs and pump;

Worn hydraulic hoses.

To troubleshoot problems, it is necessary to check the tightness of all fasteners and replace worn components and parts, as well as check the power steering fluid level and replace worn and damaged power steering parts.

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Management. What is it for? The main functions are aimed at converting the rotational motion of the steering wheel into reciprocating motion. This task is performed by the steering and mechanism. Installed on cars various systems. Let's look at the design and principle of operation of these units.

Purpose

In order for vehicles to be able to move in the direction chosen by the driver, they must be equipped with steering mechanisms. Its design determines whether driving a car will be safe, as well as at what speed the driver will become tired and fatigued.

Requirements

There are certain requirements for the steering and mechanism. First of all, it ensures high maneuverability. In addition, the mechanism must be designed in such a way that it is easy to drive the vehicle. If possible, only rolling is ensured, without lateral sliding of the tires when turning. The steered wheels should automatically return to straight-ahead motion after the driver releases the steering wheel. Another requirement is the absence of reversibility. That is, the control system should not have even the slightest possibility of transferring shocks from the road to the steering wheel.

It is important that the system has a tracking action. The car should immediately respond to even the most minimal steering turns.

Device

Let's look at the design of the steering mechanism. In general, the system consists of a mechanism, an amplifier, and a drive. As for the types, they distinguish:

• rack and pinion steering;
• worm gear;
• screw.

The general structure is quite simple. The design is logical and optimal. This is proven by the fact that for many years in the automotive industry no significant changes have been made to the control mechanism.

Column

Without exception, all mechanisms are equipped with a steering column. Its device includes several various nodes and details. This is a steering wheel, a steering shaft, and also a casing in the form of a pipe with bearings. In addition, the column consists of various fasteners that ensure the immobility and stability of the entire structure.

This unit functions very simply. The driver of the vehicle operates the steering. The mechanism converts the driver's force, which is transmitted along the shaft.

Rail

This is the most popular and widespread type of steering mechanism. This control is often equipped in passenger cars that have an independent suspension system on a steerable pair of wheels. It is based on a gear and rack. The first is rigidly and permanently attached to the steering shaft through a cardan. It is also in constant engagement with the teeth on the rack. When the driver rotates the steering wheel, the gear moves the rack left or right. Rods and tips are attached to it on each side. These are the parts of the steering gear that act on the steered wheels.

Among the advantages are the simplicity and reliability of the design, high efficiency, and fewer rods compared to other types of steering. The steering mechanism is compact and has a low price.

There are also disadvantages - this is susceptibility and sensitivity to road irregularities. Any shocks from the front steered wheels are immediately transmitted to the steering wheel. In general, the mechanism is very afraid of vibrations. The system is difficult to install on cars with dependent front wheel suspension. This limits the scope of application of this mechanism only to passenger cars and light commercial transport (for example, Fiat Ducato or Citroen Jumper).

It is worth noting that the rack and pinion mechanism loves a neat and measured ride on smooth roads. If you drive carelessly, the part begins to knock and quickly fails. If the teeth on the rack or gear are damaged, the steering wheel may bite. These are the main malfunctions of the unit.

Worm

The worm steering mechanism is now considered obsolete. But it definitely needs to be considered, because old cars (for example, “classics” from AvtoVAZ) are equipped with it, and they are still in use. Also this system can be found on four-wheel drive vehicles for off-road use, on vehicles with a dependent type of suspension of a steerable pair of wheels. In addition, light trucks and buses are equipped with a mechanism of this design. The steering mechanism of the UAZ is designed and works in the same way.

The worm gear is based on a gear screw of variable diameter. It is linked to other elements. This is the roller and steering column shaft. A special lever is installed on this shaft - a bipod. The latter is connected to the steering rods.

It all works as follows. When the driver needs to change the direction of movement, he acts on the steering wheel. It turns and acts on the column shaft. The shaft, in turn, acts on the worm gear. The roller rolls along the steering shaft, causing the bipod to also move. Along with the bipod, the steering rods move, and then a pair of front steered wheels.

This type of mechanism has low sensitivity to shock loads, unlike a rack and pinion mechanism. As for other characteristics, we can highlight greater wheel turn and improved maneuverability. However, the device is more complex, and the production price is higher due to the large number of different connections. For efficient work This type of steering mechanism requires frequent adjustments.

Many motorists have encountered this system on GAZ, VAZ and other cars. But such a gearbox is also found on expensive, comfortable luxury cars with large mass and front independent suspension.

Helical gearbox

There are several elements working together in this mechanism. This is a screw mounted on the steering column shaft, a nut that moves along the screw, a gear rack and a sector connected to the rack. The latter is equipped with a shaft, and fixed on it bipod. These gearboxes are found mainly on trucks - this is how the KamAZ steering mechanism is designed.

The peculiarity of this mechanism is a screw and a nut connected to each other by means of balls. Due to this, it was possible to achieve a reduction in friction and wear of this pair.

As for the principle of operation, this mechanism works in approximately the same way as a worm mechanism. When the steering wheel is turned, the screw rotates, moving the nut. At the same time, the balls circulate. The nut moves the sector through the rack, and the bipod moves with it.

This mechanism is different high efficiency and is able to implement significant efforts. The system is used not only on trucks, but also on light cars (mostly executive class). Similar controls are also found on buses. You can find a similar steering mechanism on the GAZelle. But this only applies to older models, as well as business class versions. The new Nexts already use a rack.

Malfunctions

Malfunctions of steering mechanisms are considered one of the most serious damage car. Since most passenger cars have a rack and pinion mechanism, the number of breakdowns has been significantly reduced.

Typical breakdowns include wear of the rack-and-pinion pair, a leak in the mechanism housing, a worn bearing on the steering shaft, as well as rod joints. The latter is the most common malfunction in rack and pinion mechanisms.

During the active use of the car, the working areas of the bearing roller, bipod shaft, and worm naturally wear out. The adjusting screw is also erased. Due to wear, gaps appear in the steering mechanisms, which can cause knocking noises when driving. Often these gaps can cause vibrations on the steered wheels and loss of vehicle stability. The appearance of gaps can be determined by the increased play on the steering wheel. The gap occurs in the worm-roller pair. Then the axial movement of the worm increases. Gaps can be eliminated by adjustment.

Causes of malfunction

Among the reasons typical faults we can highlight several of the most basic ones, So, the first and main reason The reason why the slats fail is the quality of the roads. Then we can note periodic violations of operating rules, the use of low-quality components, and unqualified repairs of steering mechanisms.

Signs

If, while driving the car, a knocking sound is clearly detected by ear, then this indicates that the articulated joint of the rod end is badly worn. These same symptoms can also indicate an excessively worn ball joint.

If you feel a beating on the steering wheel, then the joint on the rod end may be worn out, or the shaft bearing may be damaged. When free play is clearly felt on the steering wheel, this also indicates a worn rod or a faulty transmission pair.

Adjustment

This process is a complex of operations aimed at reducing steering play, increasing driving accuracy, and the vehicle’s response speed to driver actions. To set up, you need to correctly set the axial and lateral clearances of the sector shaft and worm. The correct settings will provide a slight backlash.

The adjustment process involves unscrewing the locking nut and tightening the adjusting screw. In this case, constantly in the process of tightening the screw you need to check for play. Once removed, the screw is secured in position with a locknut.

This adjustment most often helps eliminate backlash, but if the gap remains, then the worm pair in the mechanism is too worn and requires replacement. To do this, dismantle the gearbox and replace worn elements.

Conclusion

These are all types of steering mechanisms existing today. We learned how they work, briefly became acquainted with their principle of operation, and learned about the signs of malfunctions. This information can help during vehicle repair or routine maintenance. It is important to remember that steering is very important node and you must always keep it in good condition. With its help, the driver can quickly change the direction of movement of the vehicle, which allows him to maneuver the car on any section of the road and quickly react when dangerous situations arise.

Lecture 14. Steering.

Purpose of steering.

The steering provides the required direction of movement of the car. The steering includes a steering mechanism, which transmits force from the driver to the steering gear, and a steering gear, which transmits force from the steering mechanism to the steering wheels. Each steered wheel is mounted on a steering axle (steering knuckle) 13 (Fig. 1) connected to the beam 11 bridge with kingpin 8 . The kingpin is fixedly fixed in the beam, and its upper and lower ends fit into the eyes of the steering axle. When turning the trunnion by the lever 7 it, together with the steered wheel mounted on it, rotates around the kingpin. The pivot pins are connected to each other by levers 9 And 12 and transverse thrust 10 . Therefore, the steered wheels turn simultaneously.

Rice. 1. Steering diagram

The steering wheels turn when the driver rotates the steering wheel 1 . From it, rotation is transmitted through the shaft 2 on a worm 3 , in engagement with the sector 4 . A bipod is attached to the sector shaft 5 , turning through longitudinal thrust 6 and lever 7 pivot pins 13 with steered wheels.

Steering wheel 1 , shaft 2 , worm 3 and sector 4 form a steering mechanism that increases the torque applied by the driver to the steering wheel to turn the steered wheels. Bipod 5 , longitudinal thrust 6 , levers 7 , 9 And 12 stub axles and transverse rod 10 constitute a steering drive that transmits force from the bipod to the steering axles of both steered wheels. Lateral thrust 10 , levers 9 And 12 , beam 11 form a steering trapezoid, providing the necessary ratio between the angles of rotation of the steered wheels.

The steered wheels rotate at a limited angle, usually equal to 28 - 35º. This is done so that the wheels do not touch the frame, fenders and other parts of the car when turning.

Some cars use power steering to make it easier to turn the steering wheels.

Stabilization of steered wheels.

The forces acting on the car tend to deflect the steered wheels from the position corresponding to linear motion. To prevent the wheels from turning under the influence of random forces (shocks from hitting uneven roads, gusts of wind, etc.), the steered wheels must maintain a position corresponding to straight-line motion and return to it from any other position. This ability is called steering wheel stabilization. Wheel stabilization is ensured by tilting the kingpin in the transverse and longitudinal planes

and elastic properties of a pneumatic tire.

Design of steering mechanisms.

Worm and roller steering mechanism, shown in Fig. 2, made in the form of a globoid worm 5 and a three-ridge roller engaged with it 8 . The worm is installed in a cast iron crankcase 4 on two tapered roller bearings 6 . The raceways for the rollers of both bearings are made directly on the worm. The outer ring of the upper bearing is pressed into the crankcase seat. The outer race of the lower bearing, mounted in the crankcase with a sliding fit, rests on the cover 2 , bolted to the crankcase. Gaskets are placed under the cover flanges 3 of varying thicknesses to adjust bearing preload.

The worm has splines with which it is pressed onto the shaft. An oil seal is installed where the shaft exits the crankcase. The upper part of the shaft, which has a flat, fits into the hole in the flange of the universal joint fork 7 , where it is secured with a wedge. Through universal joint The steering pair is connected to the steering wheel.

Shaft 9 the bipod is installed in the crankcase through a window in the side wall and closed with a lid 14 . The shaft is supported by two bushings pressed into the crankcase and cover. Three-ridge roller 8 placed in the groove of the bipod shaft head on the axis using two roller bearings. On both sides of the roller, polished steel washers are placed on its axis. When the bipod shaft moves, the distance between the axes of the roller and the worm changes, which makes it possible to adjust the gap in the engagement.

Rice. 2. Steering mechanism of the KAZ-608 “Kolkhida” car

At the end of the shaft 9 conical splines are cut, on which the steering bipod is secured with a nut 1 . The shaft exit from the crankcase is sealed with an oil seal. At the other end of the steering bipod shaft there is an annular groove into which the thrust washer fits tightly 12 . Between the washer and the end of the cover 14 there are gaskets 13 , used to regulate the engagement of the roller with the worm. A thrust washer with a set of shims is secured to the crankcase cover with a nut 11 . The position of the nut is fixed with a stopper 10 , screwed to the cover with bolts.

The clearance in the steering gear engagement is variable: minimal when the roller is in the middle part of the worm and increasing as the steering wheel is turned in one direction or another.

This nature of the change in the gap in the new steering gear makes it possible to repeatedly restore the required gap in the middle, most wear-prone area of ​​the worm without the danger of jamming at the edges of the worm. Similar steering mechanisms are used on GAZ and VAZ cars with a difference in the mechanism for adjusting the worm gearing 5 with roller 8 .

Rack and pinion steering(Fig. 3, A). When turning the steering wheel 1 gear 2 moves the rack 3 , from which the force is transmitted to the steering rods 5 . Steering rods for swing arms 4 turn the steered wheels. The rack and pinion steering mechanism consists of a helical gear 2 , cut on the shaft 8 (Fig. 3, b) and helical racks 3 . The shaft rotates in the crankcase 6 on thrust bearings 10 And 14 , the tension of which is carried out by the ring 9 And top cover 7 . Emphasis 13 pressed by a spring 12 to the rack, receives radial forces acting on the rack and transfers them to the side cover 11 , which ensures the accuracy of pair engagement.

Rice. 3. Steering with rack and pinion mechanism:

A– steering diagram; b– rack and pinion steering mechanism

Rack and pinion steering mechanism(Fig. 4) has two working pairs: screw 1 with nut 2 on circulating balls 4 and piston-rack 11 , engaged with the gear sector 10 bipod shaft. Gear ratio steering gear 20:1. Screw 1 The steering mechanism has a precision-ground helical groove with an “arched” profile. The same groove is made in the nut 2 . The screw channel formed by the screw and nut is filled with balls. The nut is rigidly fixed inside the piston-rack with a stopper.

Rice. 4. Steering mechanism with built-in hydraulic booster:

A- device; b- scheme of work; 1 – screw; 2 - screw; 3 – gutter; 4 - ball; 5 – steering shaft;

6 – control valve body; 7 – spool; 8 – bipod; 9 – bipod shaft; 10 – gear sector; 11 – piston-rack; 12 – crankcase-cylinder; 13 – crankcase; A And B– cylinder cavity;

IN And G– oil inlet and outlet hoses; D And E– channels.

When the screw rotates 1 from the steering wheel, the balls come out from one side of the nut into the groove 3 and return along it to the screw grooves on the other side of the nut.

The rack and gear sector have teeth of varying thickness, which allows you to adjust the gap in the rack-sector engagement with an adjusting screw screwed into the side cover of the steering mechanism housing. Elastic split cast iron rings are installed on the piston-rack, ensuring its tight fit in the crankcase-cylinder. 12 . The rotation of the steering shaft is converted into translational movement of the piston-rack due to the movement of the nut along the screw. As a result, the piston-rack teeth rotate the sector, and with it the shaft 9 with bipod 8 . In front of the steering gear housing in the housing 6 installed control valve with spool 7 . With hose control valve IN And G The power steering pump is connected.

While the car is moving in a straight line, the spool is in the middle position (as shown in Fig. 4), and oil from the pump is carried through the hose G through the control valve it is pumped back into the tank via a hose IN. When turning the steering wheel to the left, the spool 7 moves forward (to the left in the figure) and allows oil to enter the cavity A via channel D, and from the cavity B oil is flowing into the cavity IN and into the pump. As a result, it is easier to turn the wheel to the left. If the driver stops rotating the steering wheel, the control valve spool will take a middle position, and the angle at which the steering wheels are turned will remain unchanged.

When turning the steering wheel to the right, the screw with the spool 7 moves backward (to the right in the figure) as a result of the interaction of the piston-rack teeth and the sector. Moving backwards, the spool allows oil to enter the cavity B through the channel E. As a result of oil pressure on the piston-rack, the effort required to turn the steering wheel is reduced. In this case, the steering bipod turns counterclockwise.

Steering gear.

Steering linkage(Fig. 5). Depending on the layout capabilities, the steering linkage is placed in front of the front axle (front steering linkage) or behind it (rear steering linkage). At dependent suspension wheels use trapezoids with a solid transverse rod; at independent suspension– only trapezoids with dismembered transverse rods, which is necessary to prevent spontaneous rotation of the steered wheels when the vehicle oscillates on its suspension. For this purpose, the joints of the split transverse link must be located so that vehicle vibrations do not cause them to rotate relative to the king pins. Diagrams of various steering linkages are shown in Fig. 9.

Rice. 5. Schemes of steering trapezoids

With dependent and independent suspensions, they can be used as rear (Fig. 9, A), and the front (Fig. 9, b) trapezoid.

In Fig. 9, V – e rear trapezoids of independent suspensions with different numbers of hinges are shown.

Design of steering gears with dependent suspension. When the wheels turn, the steering gear parts move relative to each other. Such movement also occurs when the wheel hits uneven roads and when the body oscillates relative to the wheels. To create the possibility of relative movement of drive parts in horizontal and vertical planes while reliable transmission connections are made in most cases using ball joints.

Longitudinal thrust 1 (Fig. 6, A) the steering gear is made tubular with thickenings at the edges for mounting parts of two hinges. Each joint consists of a finger 3 , crackers 4 And 7 , covering the ball head of the pin, springs with spherical surfaces 8 and limiter 9 . When tightening the plug 5 the head of the finger is clamped with breadcrumbs, and the spring 8 shrinks. The hinge spring prevents the formation of gaps as a result of wear and softens the shocks transmitted from the wheels to the steering mechanism. The limiter prevents excessive compression of the spring, and if it breaks, it does not allow the pin to leave the connection with the rod. The springs are positioned in the rod relative to the fingers 2 And 3 so that forces are transmitted through the springs, acting on the rod as from a bipod 6 , and from the rotary lever.

Rice. 6. Steering rods of a GAZ car:

A– longitudinal; b– transverse

In the transverse longitudinal rod, the hinges are placed in tips screwed onto the ends of the rod. The threads on the ends of the rod usually have a carved direction. Therefore, by rotating the thrust 10 (Fig. 6, b) with fixed tips 11 you can change its length when adjusting the wheel toe. Fingers 15 rigidly fixed in the steering axle arms. The spherical surface of the finger is pressed by a pre-compressed spring 12 through the heel 13 to the cracker 14 installed inside the rod end. This hinge design allows direct transmission of forces from the finger to the rod and into reverse direction. Spring 12 eliminates the gap in the hinge caused by wear. Thus, the main difference between transverse thrust joints and longitudinal thrust joints is that the former do not have springs through which forces in the steering drive are directly transmitted.

The steering rod joints are lubricated through oil nipples. On some cars in the hinges lubricant is included during assembly and is not required to be replenished during operation.

Features of steering drives with independent suspension of steered wheels ( rice. 7 ) . The steering drive with independent suspension must prevent arbitrary rotation of each wheel individually when it swings on the suspension. This requires the closest possible coincidence of the swing axes of the wheel and the drive rod, which is achieved by using a split transverse rod. This rod consists of articulated parts that move with the wheels independently of one another.

Rice. 7. Steering gear diagram with independent suspension:

1 – stand; 2 – rotary axles; 3 – steering axle lever; 4 And 9 – lateral thrusts;

5 – pendulum lever; 6 – bipod; 7 - steering gear; 8 - average traction.

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