The principle of operation of the power steering rack. Hydraulic steering rack auto - device and principle of operation

The steering rack is the centerpiece of the steering system in virtually any modern vehicle.

In essence, this is a mechanism that converts the rotation of the steering wheel by the driver into turning the wheels of a car in one direction or another.

Of course, modern steering models are equipped with hydraulic or electric boosters, include hydraulic cylinders and other technical refinements, but initially everything was very, very laconic - the steering column had a gear at its end, coupled to the steering rack and steering rods, respectively. That's all.

Types and versions

Now let's figure out what a rack is in the framework of the steering of a modern passenger car, what it consists of, how the steering rack works, what types there are, what is the structure of the steering rack and the principle of operation of the steering rack.

It is usually customary to distinguish 3 main types of steering racks:

Fully mechanical option

This is the simplest and most primitive version of the existing ones, although we must pay tribute to innovative technologies - cars with such mechanisms are becoming less and less every year. Buying a car without electric or hydraulic power steering is already considered almost "mauvais ton", especially among the representatives of the "office class". Of course, the grandfather, who needs his swallow to regularly carry potatoes from the market to the house, or depending on the situation, grandfather's entrepreneurial spirit and weather conditions in the opposite direction, do not need such bells and whistles. But the number of "swallows" perishing in an unequal battle with road troubles is growing from year to year, and grandfathers have, willy-nilly, forced to retrain as "loganovodov".

So the essence of the mechanical steering rack is the complete absence of auxiliary mechanisms and devices and is reduced to the rotation of the steering wheel solely with the help of the driver's physical strength.

Of course, here the designers also managed to introduce several technical tricks, such as a changing gear ratio, that is, changing the pitch between the teeth on the rail closer to the edges, optimizing vehicle control, both for driving at high speeds on the highway, and for maneuvering when parking a car. but, nevertheless, this technology is no longer just the past, but deeply past century.

Hydraulic power steering (GUR)

As the name of this type of steering implies, the driver's effort used to turn the steering wheel, and therefore the wheels themselves, in this version of the version replaces the hydraulic booster, abbreviated as power steering. This system is very widespread today, and there is no reason to believe that it will be replaced by something else in the foreseeable future. For the system, although it was once a rarity and an expensive curiosity, but today it is already well known in almost all services, it is great - they know how to fix it quickly and efficiently, and most importantly, it does not break very often. So it's almost a golden mean. When using power steering, the steering is quite informative and sharp, so we put a big fat plus!

In addition, the power steering makes driving much safer, thanks to less strong feedback between the steering wheel and road surface defects. If on the "mechanics" the steering wheel, when it hits a particularly deep hole, could break out of the driver's hands, then the hydraulics will calmly "swallow" all irregularities and flaws, with its twitching and vibration, however, informing the driver that "we drove something like that there. ...

Electric steering (EUR)

Here, in principle, everything is completely similar to the power steering, with the only difference that the power to the steering rack from the steering wheel is transmitted not by the power steering, but by the electric one, which on modern cars, starting with the golf class and above, has adaptive mechanisms and with the help of the onboard the computer focuses on the speed of movement, increasing or decreasing its effort, making the steering wheel, thus, extremely sensitive and responsive in any ride. At high speed, the steering wheel "becomes heavier", allowing you to avoid unnecessary "bumpiness" on the road, and at low speed, on the contrary, it becomes "lighter", making it easier to maneuver in traffic jams and when parking.
There is, of course, a serious minus in such adaptive systems, if such a mechanism fails, driving will be almost impossible, since the steering wheel will stop turning, but these problems were left behind already 10 years ago, so now we can actually talk about solid pluses:
1. A more economical option compared to hydraulics - the electric motor only turns on when you are turning.
2. Higher degree of sensitivity than power steering - you will feel the steering wheel equally well at any speed mode.
3. Complete absence of dependence on air temperature - there is no fluid in the system that could freeze, as in hydraulic variations
4. Again, due to the lack of process fluids, there is no need to carry out regular service work
5. And of course, a higher level of reliability and safety compared to power steering - again because there are no hoses and joints that can leak or break.

Steering rack malfunctions and repair

Despite the high level of reliability of modern steering systems in general and steering racks in particular, they periodically fail. The cost of repairing the steering rack is a very expensive thing, so it makes sense to immediately contact the service in order to limit yourself to preventive measures if necessary, and not bring the situation to the replacement of the assembly.
What is the main reason for the failure of steering racks in Russia, and what are the first signs of a steering rack failure? And also, why is the steering rack knocking?
You will not be surprised - these are roads, or rather, their extremely low quality. Dust falling on the steering joints under the boot of the steering rack, wheels turned out in severe frost (only for the power steering), driving through severe damage to the road surface at high speed - all this will definitely lead to the fact that the steering rack will be broken.
Any extraneous knocking coming from under the steering wheel, closer to the engine compartment, is most likely emitted by your steering rack. A knock on the steering rack is the first sign that it's time to contact the service.
It may be that a knock appears when the steering wheel is turned only in one direction or both at once, sometimes it can be a creak, but if there is already something crunching, then the matter is definitely a disaster.
In no case should it be brought to this, because if it crunches, it means that soon the wheels and the steering wheel will cease to obey each other.
In addition, it obviously means that you have something wrong with the rail, a suddenly "heavy" steering wheel, especially for electric boosters.
If you have fluid flowing from the power steering, it means that the hose or the steering rack oil seal is leaking, it is very easy to notice, since spots of black oil will remain at the parking place of your car. A leaking steering rack will quickly cause the hydraulic mechanism to stop working and the steering wheel can only be turned with great effort. Therefore, as soon as you notice the spots - immediately go to the service!

The knock of the steering rack can turn into steering vibration, and in general can be heard even with sharp jerks of the steering wheel to the side on a completely muffled car (by the way, this is the answer to the question - how to check the steering rack as part of the initial diagnosis, which can be performed independently).
Incorrect centering of the steering wheel most likely indicates that your tooth has come off and you need to adjust the steering rack - this can happen if you fly a hole at high speed, hitting it with one or two front wheels at once.
And, of course, the complete lack of effort when turning the steering wheel will also indicate that the amplifier is not in order.
If any of the above signs are found, you should urgently contact a car service for an early resolution of the problem, where professionals know how to tighten the steering rack, adjust the EUR or replace the steering rack bushing.
Delay is fraught not only with expensive repairs, but also with the fact that you will just stand firmly somewhere on the road and it’s also good if in the city, where you can call a tow truck. Remember, we said that if the EUR fails, the steering wheel cannot be turned. Repairing the steering rack with your own hands on the track is unlikely to be possible. Do not take risks, do not lead to serious damage!

A steering rack is a mechanical device for transmitting force from the steering wheel to the steering, steering rods of the wheels. Or more simply: a device forcing the front wheels of the car to turn synchronously in the direction in which the steering wheel turns. It is worth considering the principle of the steering rack.

This figure shows how the steering rack works. Based on the numbers, it is also easy to understand how the steering rack works. From the rotary device, which rotates the shaft 27, the rotation is transmitted to the gear 21. That, respectively, rotating left and right moves the gear rack 16, inside the steering rack housing 17. Moving in the horizontal plane, the gear rack moves the steering rods 5 and 7 attached to it , and those, in turn, move the wheel levers 3.

Possible malfunctions of the steering rack

The most heavily loaded steering rack assembly is the clutch between the pinion and the rack. Accordingly, malfunctions occur most often in this pair. It can be simple wear of the teeth, and their mechanical destruction. In case of slight wear, it can be eliminated by adjusting the nut, which controls a special stop. It is designed to maintain optimal spacing between rack and pinion teeth.

Important! It is undesirable to carry out this adjustment yourself. The importance of reliable steering in motion is enormous. And this reliability depends on the accuracy of the adjustment. It is better to entrust the work to professionals.

Well, in case of broken teeth, of course, you will have to change either the rack or the gear. Wear on the tie rod end 1 is also possible. In this case, replace the part. Also the ball tip 38. Basically, such work is carried out during vehicle maintenance.

Power steering

Turning the steering wheel under this load, despite the convenient steering rack, is not so easy. When moving, due to centrifugal forces, it is not difficult. What if the car is not moving? And then devices were developed to facilitate this process. Power steering. They are of two types.

hydraulic;
electrical.

It is worth considering them in more detail.

Power steering rack device

The basic principle of operation of a power steering rack is the transmission of power from a running engine to a gear rack using a hydraulic device. A pump is attached to the engine, which creates pressure in the power steering system. It is driven by a belt drive. Pressurized oil enters the distributor. The figure shows schematically how the power steering rack works. On the steering shaft, special valves are installed that allow oil to pass into the oil lines and release it from there. A double-acting piston is mounted on the toothed shaft. Depending on where the steering wheel turns, the oil presses on one side, and freely goes into the power steering reservoir, on the other.

Such a scheme allows, with the engine running, turning the wheels in any direction with almost no effort. But this complication of the system increases the number of possible malfunctions. It can be:

power steering pump malfunction;
malfunction of the distributor valves;
damage to the piston system of the hydraulic cylinder;
damage to the hydraulic cylinder oil seals;
loose or broken pump drive belt.

Malfunctions are diagnosed and eliminated only by experienced mechanics of service stations. Car owners should not go into the power steering system on their own.

Important! As soon as the driver feels that the load during the rotation of the steering wheel has increased, it is necessary to urgently contact the service.

Electric power steering

The hydraulic booster is excellent for helping the driver to steer the machine. And yet it has one drawback. It can only work with the engine running. But this issue was resolved by the creation of an electric amplifier. They are designed in two types. Imported amplifiers are often located directly on the rail as shown in the photo.

Here, an electric motor rotates a pinion, which directly drives the pinion shaft in the rack housing. Rotation direction sensors are mounted on the steering wheel shaft. They transmit a signal to an electronic control unit located directly on the engine. The reversible motor on this signal moves the rack to the right or left.

Russian version of the electric power steering.

A different principle was applied here. The electric motor is integrated in the steering wheel shaft drive. Also, receiving signals from rotary sensors, it, turning in one direction or another, perfectly suppresses the force applied by the driver to turn the steering wheel. You can practically turn the steering wheel with one finger.

But the complication of the system design, as already mentioned, leads to an increase in the probability and number of malfunctions. Besides the fact that the electric power steering itself has a lot of parts, these parts are also quite delicate. The electric power steering consists of the following parts and devices.

electronic control unit;
reversible worm drive motor;
rotary sensors;
force sensor.

The electronic unit is a mini-computer with a pre-programmed program and tables of behavioral situations. Receiving signals from sensors, it transmits them to an actuator - an electric motor. And already that, rotating, facilitates the driver's work. Here, the main malfunction, first of all, may be a breakdown of the electric motor or wear of the brushes, or a short circuit or breakage of the electric motor armature. Wear of the armature bearing bushings is also possible.

The worm gear may break in the drive device. Worn or broken teeth. The electronic control unit is a fairly reliable device, however, and it can fail or get a program failure.

There is a possibility of failure of rotary encoders, which also leads to failure of the entire system. The difficulty in diagnosing malfunctions of the electric amplifier of the rotary device is that this procedure can only be carried out using special equipment. That is, a diagnostic scanner or connecting a computer diagnostic complex.

Repair of the electric power steering rack is available only in the conditions of a good service station, which has an experienced mechanic for repairing electrical equipment of cars on its staff. The cost of repairing this device is quite high, but it is several times lower than the price of the entire device assembled.

A plus for the driver is the fact that this system has an indicator light on the control panel. Here you can no longer rely on tactile sensations. In the event of any malfunction, the warning lamp will immediately inform you of this. Moreover, there is a set of signals for various faults. The lamp blinks with a certain rhythm or lights up constantly. This is a signal about the need to contact the service station.

The picture shows a flashing warning light on the instrument panel of Russian cars of the Priora and Kalina series. This is a yellow sweetheart with a steering wheel and an exclamation mark! It is she who is the indicator of the EUR malfunction.

In the video below, you can view the repair process, and improvements to the VAZ steering rack device:

Power unit, with the help of which the front wheels of the car are simultaneously 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

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 to the left or to the 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 machine 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 purpose 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 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 location of the electric motor: it can be built into the steering column, located on the steering shaft, or be combined with the rack. The steering rack has the highest efficiency, is 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 shocks 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.

Steering column with steering gear assembly:

1 - right steering rod assembly; 2 - support of the steering mechanism; 3 - steering gear support bracket; 4 - intermediate cardan shaft; 5 - electric amplifier; 6 - steering wheel; 7 - steering column; 8 - steering gear; 9 - left steering rod assembly

The steering gear is a rack and pinion type with a variable gear ratio. It is fixed in the engine compartment on the bulkhead of the body with two brackets through rubber mounts. Mounting bolts - welded, two on each side of the bulkhead. The steering gear housing is cast from an aluminum alloy. On the right side, a pipe with a longitudinal groove is inserted into the crankcase, secured in the crankcase with a nut. A helical drive gear (pinion shaft) is installed in the crankcase, which meshes with the rack. On the rack, bevel teeth with a variable pitch are cut (closer to the ends of the cut part of the rack, the pitch of the teeth decreases). To reduce the loads on the pinion shaft and its bearings under extreme operating conditions, a plastic pinion sleeve with a metal support plate is inserted into the crankcase. The pinion shaft rotates on two bearings: the front (at the end of the shaft) is needle-shaped, the rear (closer to the steering column shaft) is a ball bearing. Since axial loads can be high in helical gearing, a thrust roller bearing is additionally installed on the drive gear shaft, consisting of a plastic cage with rollers, lower (inner) and upper (outer) rings. The lower bearing ring is pressed onto the pinion shaft until it stops in the inner ring of the ball bearing, and the upper one is installed in the crankcase cover. In addition, the crankcase cover presses the outer ring of the ball bearing against the end of the bearing seat.
The drive gear oil seal is installed in the cover, and an O-ring is installed between the cover and the steering gear housing. The cover is closed with a protective cover (boot) fitted on the pinion shaft.
The rack is pressed against the gear teeth by a spring through a stop sealed in the crankcase with a rubber ring. To reduce friction between the stop and the rail, a plastic insert is installed. The spring, in turn, is compressed by an adjusting nut (internal octagon "24"). At the factory, when assembling the steering mechanism, a clearance of 0.1 mm is set in the engagement of the rack with the gear, after which the crankcase thread is punched (crushed) at two points (without damaging the nut). The other end of the rail rests on a plastic sleeve that is inserted into the pipe behind the longitudinal groove. The gap between the gear and the rack is adjusted after disassembling the steering mechanism or when a knock appears during operation.
The gap can be adjusted only on the removed steering gear. We set the rail to the middle position and block it from moving. Having taken out the rubber plug, insert the dial-type indicator leg into the hole of the stop adjusting nut until it touches the rail stop. Turning the pinion shaft (torque 15 N'm), while the pinion pushes the rack and stop, we determine the amount of stop movement by the indicator. If it exceeds 0.05 mm, tighten the adjusting nut to achieve the specified amount of stop movement. After that, unlocking the rack, we check the ease of rotation of the pinion shaft over the entire range of the rack travel. The crankcase tube is covered with a protective corrugated cover. The rods are attached to the rail with bolts passing through the connecting plates and spacers of the rubber-metal hinges, as well as the link support mounted on the rail. Spontaneous loosening of the bolts is prevented by a lock plate, put on the bolt heads.
To lubricate the gears, rack and bearings, FIOL-1 grease is used (approximately 20-30 g for the entire mechanism). The steering shaft is connected to the pinion shaft via an intermediate propeller shaft. The steering shaft rotates in two ball bearings, one of which is installed in the tube of the steering column bracket, and the other in the body of the electric booster. The steering column bracket is fastened with nuts at four points: the front to the pedal bracket, the rear to the bracket on the body.
The steering column bracket and its pipe are pivotally connected by two plates through plastic and metal bushings, tightened with four bolts. Thus, the pipe can move in a vertical plane relative to the bracket, allowing the height of the steering wheel to be adjusted. The movement is limited by the length of the slots in the plates. The steering column adjustment lever serves to fix the pipe relative to the bracket. It is connected with a spline hub to an adjusting sleeve and is fixed on it with a retaining ring. The sleeve is screwed onto a tie bolt through the slots in the pipe and bracket guide plates. A spacer sleeve is installed on the bolt. The bolt head is secured against turning by a special protrusion. When the lever is turned down, the bushing is unscrewed and the tightening force of the plates is weakened, which allows you to manually change the position of the steering column. Springs are installed between the plates and the bracket, which pull the bracket pipe to the upper position when the connection is loosened. After installing the steering column in the required position, the lever is lifted up and the connection is tightened, fixing the column.
The steering gear includes two integral tie rods and swing arms welded to the front suspension shock absorber struts. Each rod, in turn, consists of three parts - an inner tip, an outer tip and an adjusting threaded sleeve. The adjusting sleeve is a tube with a hexagon at the end, with external and internal threads of different directions. The length of the tie rod changes with the rotation of the adjusting sleeve. After completing the adjustment, the outer ends of the tie rods are tightened with bolts. The tie rod is connected to the pivot arm via an external ball joint. To protect against dirt, the hinge is covered with a rubber protective cover (boot). The hinge is formed by the tip of a non-separable structure, therefore, if it fails, the tip should be replaced with subsequent adjustment of the wheel alignment
The electric power steering reduces the effort on the steering wheel, making it easier to drive. The basis of the electric booster is a brushless electric motor with a gearbox located under the steering cover. A worm is installed on the engine shaft, which engages with a plastic gear attached to the steering shaft.

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 of 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 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. There is a spool in the body 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 that 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 amount of 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. Drivers considered a big plus that the moment 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 does a hydraulic steering rack work? This question can be asked by the drivers of new cars in which the hydraulic booster is 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:

Entrance.
Spool bushings.
Dust cap.
Retaining ring.
Spool oil seal.
Spool.
Bearing.
Rod oil seal.
The back.
Rail stock.
Retaining ring.
Back seal.
Piston rod.
Stem bushings.
Clamp nuts.
Spool nuts.
Spool plugs.
Spool worm.
Bypass tubes.
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 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 overhaul. 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 long and well!

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.