Power unit, with the help of which the front wheels of the car are synchronously turned in the direction in which the driver turns the steering wheel. Knowing the device of the steering rack, as well as the principle of its operation, is useful for every car owner, since the safety of passengers and pedestrians depends on this device.

Principle of operation

Gear-rack mechanism

Let's consider the principle of operation of the steering rack. When the driver turns the steering wheel, the force is transferred from it to the gear, which forces the rack to move. It moves left or right, and with it the steering rods move, which turn the hubs or steering knuckles. Accordingly, the wheels themselves are fixed on the hubs. As a result, when the driver turns the steering wheel, the front wheels of the car turn synchronously.

The rack and pinion steering mechanism is often equipped with a power amplifier, which significantly reduces the effort when the driver turns the steering wheel.

Device and main components

Steering rack diagram

Consider how the steering rack works. Will be described as a whole. So, its main components:

• steering wheel (or steering wheel) - a device for controlling the movement of a car in a given direction;
• steering shaft - a metal rod that has slots (grooves) for securing the steering wheel on one side, and on the other, slots for attaching the steering shaft itself to;
• steering rack - a power unit, which consists of a rack and pinion. It is she who sets the rail in motion. This unit is assembled into a light alloy body and fixed to the car body;
• steering rods - metal rods. Each rod on one side has a thread, and on the opposite side - a hinged ball device, which also has a thread;
• steering tip - a part for screwing in the rod. Has a ball joint and an internal thread.

Note that sometimes the steering gear has another component - the steering rack damper. This element is installed between the rods and the steering rack housing. The damper is a double-acting shock absorber. The main function of the damper is to reduce vibration on the steering wheel. The steering rack damper is often pre-installed on various SUVs, since this type of car is most often used to drive on bad roads.

Types of steering racks

There are three main types of steering racks:

• Mechanical steering rack. It is the simplest version of the steering mechanism. Here, the rotation of the front wheels is carried out only due to the physical efforts of the driver. Often, to facilitate his work, a steering rack is installed, which has a variable gear ratio. In it, the pitch of the teeth changes from the center to the edges. For the first time in the history of a domestic car, such a rail was used on a VAZ-2110 car.
• Hydraulic steering rack. The main difference from the mechanical one is the presence (abbreviated as power steering), which greatly facilitates the rotation of the steering wheel. At the same time, the driver not only gets less tired while driving, but also gets more safety while driving. Rail c is widespread in modern cars.
• Electric steering rack. Here the steering wheel is powered by an electric motor. Separately, it is worth noting the placement of the electric motor: it can be built into the steering column, be located on the steering shaft, or be combined with the rack. The steering rack has the highest efficiency, is more economical and more reliable. You can read more about the electric power steering at.

Advantages and disadvantages

First, about the advantages of the rack and pinion steering gear:

• simplicity and small dimensions of the structure;
• light weight;
• frequent maintenance is not required;
• good control precision;
• small price.

Now about the cons:

• transmits impacts from irregularities in the roadway to the steering wheel;
• frequent malfunctions in the form of backlashes and knocks in the rail;
• This mechanical device is limited in most cases to light vehicles with independent steering wheel suspension.

Despite its reliability, the service life of this power unit depends on the build quality of the car, conditions of use, driving style, storage conditions. If the machine is damp for a long time, the mechanism may simply rust. Extreme driving over bumps and holes and other irregularities will also reduce the life of the mechanical steering rack.

On passenger cars, the rack and pinion steering mechanism remains the most common. This is facilitated, first of all, by the simplicity of the design, the low cost of the mechanism, as well as its small dimensions.

Almost all models of modern passenger cars are presented in the form of a steering rack. It is a mechanical unit designed to convert steering wheel deflection into horizontal deflection of the front wheels. Initially, the steering rack device was not particularly complicated. In its simplest form, this is a mechanism consisting of a gear located on the steering shaft, a rack mated to it, and steering rods.

Types and versions

Currently, there are three types of rack and pinion mechanisms. The difference between them lies in the principle of action.

Mechanical steering rack

The simplest steering option. The turning of the wheels is carried out exclusively by the physical strength of the driver. In order to facilitate the driver's work and improve driving comfort, many vehicles use a variable steering rack. In other words, the pitch of the rack teeth changes from the middle to the edges. Such a device at small steering angles, which is typical for driving at high speeds, provides a large gear ratio, heavy and sharp steering wheel. At the same time, when maneuvering in a parking lot, when the steering wheel has to be turned "from edge to edge", it is easy to do this due to the lower gear ratio. The first domestic car where such a design was applied was the VAZ-2110.

Hydraulic steering rack

It differs from the mechanical one in that the mechanical effect that the driver has on the steering wheel is amplified by the hydraulic booster. This allows for both sharpness and ease of steering. Such a device is most often used in modern cars.


The power steering also contributes to increased driving safety, since the unevenness of the road is not transmitted to the steering wheel so much, and if the car gets into a hole with the front wheel at high speed, the impact will be repeatedly extinguished by the power steering, and the steering wheel will not be pulled out of the hands, as will happen on a car with mechanical rail. However, there is a downside to this coin, because worse feedback leads to a decrease in the "feeling of the car". Automakers are trying to compensate for this shortcoming by changing the design of the suspension, as well as by using an electric motor to drive the power steering (electric hydraulic booster).

Electric steering rack

The principle of operation is similar to the hydraulic one, only the amplification is performed by an electric motor, which is either built into the steering column (the cheapest and more dangerous option), or is located on the steering shaft, or integrated with the rack (the safest option, used on high-class cars).


The option of placing an electric motor in the steering column is dangerous in that if it fails, the car becomes practically uncontrollable, since it is impossible to turn the steering wheel. Unfortunately, this sometimes sinned the Lada Priora cars of the first years of production - the EURs on them were not highly reliable.

Such a device has many advantages:

• higher efficiency in comparison with the hydraulic booster;
• efficiency (the electric motor turns on only when the steering wheel is turned, while the oil in the power steering constantly circulates, which takes away some of the engine power;
• independence from ambient temperature;
• no need to regularly service the device, because no need to change and top up the working fluid;
• higher overall reliability due to the absence of hoses, gaskets and seals that could leak.

Structure

The design of a mechanical steering rack is as follows. Inside the crankcase, which has a sectional view of a hollow cylinder, there is a protective corrugated cover. On bearings in the crankcase there is a drive gear, against which the steering rack is pressed by a spring. The spring is required to eliminate the gap in the gear-rack pair. The travel of the rack is limited on one side by a restrictive ring, and on the other - by the steering rod joint bushing. This steering rack layout is extremely simple and reliable.

Malfunction symptoms

The correctness of the steering is the key to safe driving, so you need to monitor its condition. This does not mean that you need to carry out a thorough check before each trip, because the breakdown does not happen all of a sudden. There are signs of malfunction of the steering rack, by which you can judge the need for repair.

1. Knock, manifested when driving on small irregularities, decreases when the steering wheel is turned to extreme positions.
2. Lack of effort when turning the steering wheel.
3. The steering effort disappears in the center position.
4. Spontaneous rotation of the steering wheel.
5. The steering wheel does not return or returns poorly to center when the vehicle exits a corner.
6. Increased sensitivity of the car (it is thrown to the side with a slight turn of the steering wheel, the angle of rotation of the wheels does not correspond to the angle of rotation of the steering wheel).
7. A constant drop in the level of fluid in the power steering reservoir, as well as its appearance in the anthers of the steering rods.

Hello dear motorists! The principle of rack and pinion power transmission is not the first time used in the automotive industry in the form of a steering rack. A cremalier (French crémaillère) is one of the many types of mechanical transmission that converts translational movements into rotational ones.

Remember the old, foldable cameras that used rack and pinion to focus. But, we have a conversation about the steering rack of a car.

The steering rack of a car has long been an integral part of the steering system. I. practically on all modern passenger cars, a steering rack is used. That does not exclude the use of such types of steering mechanisms as: worm gear or screw-ball nut.

Car steering rack device

So, we already understood that the steering rack of a car is a mechanical device that converts the driver's effort when acting on the steering wheel, which is required to control the car (turning the wheels).

According to the principle of operation, steering racks are divided into three main types:

• Mechanical steering rack - has the simplest device. The gear mechanism, located at the end of the steering column, interacts with the gear rack, which, in turn, is connected to the steering gear (trapezoid from).
• Hydraulic Steering Rack - Mounted on most modern passenger cars. Carries out the most convenient and easy control of the car by connecting the power steering (power steering), which increases the force applied by the driver.
• An electric steering rack differs from a hydraulic one in that there is no hydraulics in it, and the driver's efforts when controlling the steering wheel are increased by an electric motor.

The principle of the steering rack device differs only in the design features of the car brand.

The location of the steering rack can also be different depending on the car brand:

• Top Location - The steering rack is attached to the body and located behind the engine.
• Bottom Location - The steering rack attaches to the subframe, body or beam from the bottom.

The design of the steering rack (for example, a gear-rack)

• Carter. It is usually made of aluminum alloy. Has a cavity inside, which is protected by a corrugated cover.
• Drive gear mounted in the crankcase on bearings.
• The rack is pressed against the pinion by a spring in order to ensure backlash-free adhesion of the pinion and rack teeth.
• The stop ring on one side and the tie rod bushing on the other, limit the rack travel to the required range.

This design of the steering rack has a small gear ratio and allows you to quickly steer the wheel in the desired direction.

By the way, the designers of the BMW concern have improved the steering rack by connecting it to the planetary gear. This steering rack layout allows you to change the gear ratio depending on the vehicle speed.

The principle of operation of the power steering rack

So, let's find out in more detail why the steering wheel with power steering turns so easily. An integral amplifier is when the power steering actuator is connected to the steering rack.

The power steering pump is driven by the engine using gears: belt or gear. It supplies high pressure hydraulic fluid to the spool valve. The directional spool valve is integrated in the steering rack housing (housing).

The main task of the spool valve is to control the effort on the steering wheel and the dosage of hydraulic fluid for turning the steering rack. The dosing device, as a rule, is a torsion bar, which is built into the section of the steering rack shaft.

There is no effort on the steering rack when parked or driving in a forward direction. This means that the metering channels of the spool valve are closed, and the oil is in the reservoir.

When you turn the steering wheel, wheel resistance begins. In this case, the torsion bar begins to twist: the more effort on the steering wheel, the stronger. At this time, the spool valve opens the channels and supplies hydraulic fluid to the actuator - the steering rack. Here the oil is distributed in the right direction and pushes the rail.

Taking into account the fact that the steering rack is in constant intensive use, it is advisable for you, as a driver, to systematically monitor the health of its elements: anthers, oil seals, tubes.

It is not necessary to constantly climb under the car for this. Do not be lazy to check for oil leaks under the machine by visual inspection.

The steering rack is the power unit of the steering system that makes it easier for the vehicle driver to turn the steering wheel.

Steering rack diagram:

• rice. 1 - without power steering (mechanical);
• rice. 2 - with hydraulic booster (with power steering);
• rice. 3 - with an electric amplifier (with EUR).

Steering rack device without power steering

The service life of the steering rack is influenced by:

• the degree of wear of other elements of the steering system (anthers, power steering reservoir), brake pads, car suspension, etc .;
• condition and type of road surface (presence of potholes, driving through rails, on paving stones, etc.);
• driving style (hard braking, improper gear shifting);
• the quality of the working fluid in the power steering system.

The principle of operation of the mechanical type steering rack. When the driver turns the steering wheel in either direction, the rack moves at the same time. The steering wheels of the car are turned through the steering rods attached to the rack and pinion mechanism on both sides.

The mechanical rail has found wide application in passenger cars due to such characteristics as:

• simple device;
• low weight and cost;
• high efficiency;
• a small number of rods and joints;
• high response during sharp maneuvers.

It is also important that the rack and pinion steering mechanism is located perpendicular to the car, which saves space in the engine compartment for comfortable placement of the internal combustion engine and other vehicle components.

Although the principle of operation of the steering rack is simple, it has its drawbacks:

• hypersensitivity when driving through holes and protruding elements of the roadway with the transmission of vibration to the steering wheel;
• installation on passenger cars only with independent steering wheel suspension.

Power steering rack operation

The hydraulic booster is designed to relieve the driver's efforts when turning the steering wheel. It consists of a pump, a reservoir for storing hydraulic fluid and an ATF pressure regulator in the system.

Steering rack device with power steering

The principle of operation of the power steering rack. When the vehicle is stationary or driving in a straight line, the steering rack is not engaged. At this time, the ATF oil rests in the power steering reservoir, and not in its dosing systems. If the driver turns the steering wheel, the driven wheels offer resistance, during which the torsion bar is twisted, the distributor channels open, the working fluid is supplied to the steering rack and sets it in motion.

The principle of operation of the hydraulic steering rack also has a drawback: with strong acceleration, the car's steering turns out to be uninformative, which can provoke on-board rocking of the vehicle even at small amplitudes of steering wheel rotation. In short, the risk of road accidents increases.

Steering rack with EUR

The first electric power steering was installed back in 1986, but the electric power steering system has not yet become dominant due to its maintenance features.

Over the past three decades, the design of the EUR has become less cumbersome and now it is installed directly on the steering rack.

Steering rack device with EUR

The principle of operation of a rack with an electric power steering is similar to the principle of operation of a steering rack with a power steering, only the strengthening of control is carried out by an electric motor.

The advantages of the steering gear with EUR:

• Lack of hydraulic oil in the system. Due to the absence of hoses, pipes and other power steering elements, the unit is more compact and meets European eco-standards. The noise level has decreased.
• High information content. This is facilitated by the active wheel and steering wheel return function, the smooth response of the amplifier to the driver's commands.
• Reduced driver effort. In the process of parking, the steering wheel is twisted strongly, and the speed of movement is almost zero. As a result, the power steering ECU transmits a signal for increased steering assistance. This property of the EUR helps to increase the life of spare parts and reduces the cost of driver's efforts.
• Support vehicle stability on the open highway. If during the movement of the car along a straight path a side wind blows or resistance arises from the slope of the road section, the EUR provides a stabilizing effect of the vehicle, freeing the driver from additional efforts.

The device of the three types of steering mechanisms has a lot in common.

In terms of quality indicators, endurance and maintenance, the steering rack with power steering takes precedence. Its advantages over the mechanics are the reduction of the effort applied to the rotation of the steering wheel, as well as damping the shock coming to the steering wheel when the car is moving on a bumpy road. In comparison with the rail with the EUR, the hydraulic one is more accessible for maintenance.

Regardless of the type of steering mechanism, it is necessary to monitor its serviceability, undergo maintenance in a timely manner and replace worn out components.

You can purchase it on our website. For professional advice, you can use the chat in the lower right corner and call our company.

If you are an experienced motorist, then you probably know what a steering rack is and why it should be constantly in working order. But if you are a beginner, knowledge about the steering rack will probably come in handy. In the article, we will consider what types of this mechanism are, how to determine a breakdown and what you will have to face in this matter.

Rack and pinion steering is the correct name for the part of the car that we are considering. Although the common expression of the steering rack has stuck for a long time and everyone understands what is at stake. This mechanism converts the rotation of the rudder shaft into left-right movement of the rods. And they, in turn, transfer power to the steering knuckles of the front wheels. In other words, the steering rack is a transitional link between the driver who turns the steering wheel and the wheels that turn. Now you yourself understand how important the performance of this device is.

On the other hand, the rack is a piston rod, the body of which is the power steering cylinder. The body contains a spool that distributes the fluid flows into the first or second cylinder cavity. Depending on which direction the driver turns the steering wheel, the side with the fluid, which is under pressure there, will also change.

The steering rack device also depends on the type of mechanism. The mechanical type is the simplest and most common. It can be installed on both front-wheel drive vehicles and rear-wheel drive vehicles.

In this case, the wheels turn directly due to the efforts made by the driver. And in order to reduce them as much as possible, a rail containing a variable subordinate number can be used.

The size of the steering clearance is very important for the good and correct operation of the car, and this indicator directly depends on the condition of the steering rack.

Therefore, we will consider the device of the mechanical section. In such a mechanical mechanism, the teeth of the rack change their pitch from the center to the edges. Therefore, when driving at high speed, the steering wheel becomes a little heavier and its maneuverability decreases. And on the road at low speed, for example, when parking, the steering wheel turns a little easier (since there is a smaller subordinate ratio).

The first domestic car with such a device is the VAZ-2110. The drivers considered it a big plus that when turning, due to the mechanical rack, the steering wheel automatically became in the initially level position. It was not necessary to exert effort in order to return the steering wheel to its original position after turning, it was enough just to release it.

Hydraulic rack device

How is the hydraulic steering rack structured? This question can be asked by the drivers of new cars in which the hydraulic booster has been introduced. The most basic difference from the mechanical type is that power steering is present here and it gives ease of control and its sharpness.

If we consider the structure of a hydraulic mechanism with a rack, then it consists of:

1. Entrance.
2. Spool bushings.
3. Dust cap.
4. Retaining ring.
5. Spool oil seal.
6. Spool.
7. Bearing.
8. Rod oil seal.
9. The back.
10. Rail stock.
11. Retaining ring.
12. Back seal.
13. Piston rod.
14. Stem bushings.
15. Clamp nuts.
16. Spool nuts.
17. Spool plugs.
18. Spool worm.
19. Bypass tubes.
20. Exit.

Whatever version of the steering rack is on the car, it is important to listen to its work and identify errors that are present. It can be knocking, creaking, whistling in the steering gear. And every driver should be alerted by these sounds. Even if they pass only one time, something is broken in the work - contact a specialist or look at the problem yourself.

Very often, to eliminate unpleasant sounds of a car, it is enough to lubricate all parts with oil or add liquid to a mechanical device. This will keep the machine working for many more years without the use of major repairs. It is better to fix small problems right away than they turn into big problems. Take care of your car and it will serve you well and for a long time!

Video " How to replace the steering rack "

The entry shows step-by-step instructions for replacing the steering rack. Watch this video and you can easily repeat all the steps on your car.