Even vehicles designed to travel on rails have steering devices. What can we say about a car, where the steering mechanism, taking into account the need for almost constant maneuver, the most unexpected and inadequate condition of the road, should be reliable and easily functional.

Appointment

The steering mechanism on a car is a gearbox, with the help of which a small force applied by the driver in the cockpit to the steering wheel, increasing, is transmitted to the steering gear. On heavy-duty vehicles and, more recently, on passenger cars, for greater ease of control, manufacturers install a hydraulic booster.

A properly working system must meet a number of basic requirements:

1. The gear ratio, which determines the ratio between the steering angle and the wheels, must be optimal. It is unacceptable that for making a turn by 900, the steering wheel had to make 2-3 turns.
2. At the end of the maneuver, the steering wheel (steering wheel) must randomly return to the neutral position,
3. A slight backlash is allowed and provided.

Classification

Depending on the class of the car, its size, and on other design solutions of a particular model, today there are three main types:

• worm;
• screw;
• gear.

Let's look at it in order.

Worm

The first scheme is a worm steering gear. One of the most common schemes - "globoid worm - roller" - is used mainly on buses and light trucks, on high-traffic cars and cars with dependent front wheel suspension. It was installed on domestic "Zhiguli" (VAZ 2105, 2107).


The worm gear tolerates shock from road irregularities well and provides a larger than rack and pinion angle of rotation of the wheels. However, this type of device is quite expensive to manufacture and requires mandatory periodic adjustment.

Helical gear

This type is most common on large trucks and heavy buses. They can also be equipped with such expensive cars as Range Rover, Mercedes and others. The most common scheme looks like this:

• screw;
• nut (ball);
• rail;
• toothed sector.
• The helical gearbox can be either with a built-in hydraulic booster, or without it. Having the same advantages as the worm, the screw has a higher efficiency.

Gear or rack

The last type of gearbox is most familiar to the mass Russian car enthusiast. It is better known as a rack and pinion steering mechanism due to the presence of a toothed horizontal rack in the device. This rack, by means of a gear on the steering wheel shaft, receives movement to the right or left and turns the wheels through the rods. The device is most widely used in passenger cars.


The rack-and-pinion steering mechanism is simple in design, light in weight and relatively low in manufacturing cost. The rack and pinion steering mechanism includes a small number of rods and joints and at the same time has a fairly high efficiency. Due to the increased rigidity, the car perfectly obeys the steering wheel. But for the same reason, the car is more sensitive to road bumps.

The rack and pinion steering mechanism can be installed on cars with or without power steering. However, due to its design features, it is difficult to mount it on vehicles with dependent front suspension. Due to this, the scope of its application is limited only to passenger cars with independent suspension of the front steering wheels.

Steering gear care and prevention

A car is a single complex organism. The service life of units and parts in the device of the machine in general and the steering mechanism in particular depends on many factors. These include:

1. the driving style of a particular person;
2. condition of highways;
3. timely passage of MOT.

Whenever driving a car onto an overpass or going down into a viewing hole for any reason, pay attention to the condition of the protective rubber bands, levers and steering nuts. Nothing should be dangling. The play in the drive joints can be easily checked by rocking the wheel and listening to the work of the articulated parts.
Remember, prevention is the best treatment.

Hello dear motorists! It is not in vain that the steering wheel is the most important symbol of the car and everything connected with it. - this is the only possible way to control the direction of movement of the car today.

In the process of auto-evolution from a banal ring with an ebonite finish, the steering wheel has turned into an electronic unit that allows you to control a large number of functions. Of which, nevertheless, the most important is the change in the movement of the car, in the direction set by the driver. Driving a vehicle whose steering is faulty or not adjusted is not allowed. This rule must be strictly followed by all drivers.

In this regard, any person who gets behind the wheel must thoroughly know, have an idea of \u200b\u200bthe symptoms of a malfunction and own methods of eliminating them.

As you know, any steering system consists of two parts:

• steering gear;

Types of steering mechanisms used in cars

The steering gear is one of the most important parts of the steering system. The rotational movements of the steering wheel must somehow be converted into reciprocating movements: levers that turn the wheel hubs in different directions. This is why the steering gear was created. On modern cars, both passenger cars and trucks, two types of steering mechanisms are used: worm and rack.

Worm gear steering - one of the oldest devices, which is used, for example, in all models of the VAZ classics. Being an extension of the steering shaft, the worm in the crankcase transmits rotational movements to the roller, with which it is in constant engagement. The roller is firmly fixed on the steering arm shaft, which transmits the movement to the rods.

The worm gear design of the steering gear has its advantages:

• the ability to turn the wheels at a large angle;
• damping shock and vibration of the suspension;
• the ability to transfer large efforts.

Rack and pinion steering gear quite often began to be used in new models of cars. The gear, which is installed at the end of the steering shaft, snuggles tightly to the toothed rack, which transfers the rotation, converting it into longitudinal motion. The rods attached to the rail transfer the force to the hub knuckles.

The rack and pinion steering mechanism differs from the worm gear:

• a simpler and more reliable device;
• fewer steering rods;
• compactness and low cost.

Steering gear adjustment - basic parameters

There are many settings available for any steering system. consists in establishing close contact of the elements "worm-roller" and "gear-rack".

The force with which the working parts of the elements are pressed should be moderate and ensure close contact, without any gaps. On the other hand, if you strongly press the worm against the roller or gear against the rack, it will be very difficult to rotate the steering wheel, and even impossible with significant effort. This leads to fatigue while driving and quick wear of the steering parts.

The steering gear is adjusted using special adjusting devices. For the worm, a special bolt is provided in the crankcase cover, and the river devices have a pressure spring in the lower part in the projection of the steering gear. Not only comfort depends on this procedure, but also safe car control. In this regard, a specialist with the required qualifications should be involved in making adjustments.

Steering gear repair - basic requirements

As in any other unit, they actively work in the steering mechanism, which means that rubbing parts wear out. According to the operating conditions, the worm with a roller and a pinion with a rack should be found in a lubricating medium, which can significantly increase the life of the parts, but sooner or later the moment comes when the steering mechanism needs to be repaired.

The need to consult a specialist may be indicated by such signs as: an increase in the free wheeling of the steering wheel, the appearance of backlash in different planes, "biting" or the appearance of idle rotations of the steering wheel when the wheels do not react to them. In any of these cases, you should immediately carry out deep diagnostics and repair the steering mechanism. And in order to protect yourself from trouble, you should conduct an inspection and a kind of testing of the steering system every time you leave the garage.

5.3. Steering device and operation

The steering control is used 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 wheels of the car when cornering to occur without side slip, the steered wheels must turn at different angles: the inner wheel at a greater angle, and the outer wheel at a smaller one.

The steering gear is used to convert the rotary motion of the steering wheel into a linear motion that is transmitted to the wheels. For rectilinear movement, you need to convert the rotary movement of the steering wheel into a swing of the steering arm or create a reciprocating movement of the steering rack. In addition, the steering gear provides a reduction ratio, which reduces the amount of effort the driver can apply to steer the wheels. This is especially important when the car is stationary or moving slowly and 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 and variable. Steering with a constant ratio is referred to as "linear". In linear steering, turning the steering wheel a fixed number of degrees moves the steered wheels by a proportional angle, depending on the gear ratio, at any steering position.

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

Typically, the steering reduction ratio is between 14: 1 and 22: 1. With gear ratios between 14: 1 and 18: 1, power steering is usually required. To move the wheels between the limit positions, it is required to turn the steering wheel 3-4 full turns. The steering gear must be strong enough to withstand the various loads it is subjected to in various driving conditions. The driver should not feel any jolts through the steering wheel that accompany movement.

5.3.1. Steering mechanisms

There are several different options for steering gear designs, but there are two main types:

Steering gears with rotary motion (Fig.5.26);

Figure: 5.26. Steering gear with rotary motion

Steering gears with sliding motion (fig. 5.27).

Figure: 5.27. Sliding motion steering gear

Steering gears with rotary motion

Steering gears with rotary motion have various designs:

Ball screw steering gear;

Steering gear of the "screw-nut" type with slider rings;

Worm-sector steering gear;

Worm and roller steering gear;

Steering gear with worm and roller pin.

In fig. 5.28 depicts a ball screw steering gear. It uses several balls that circulate in “grooves” formed by grooves in the steering nut and on the steering shaft. As the steering shaft rotates, the balls roll along the "tracks" and cause the steering nut to move up or down the steering shaft. The steering arm is rotated by a toothed sector that meshes with the teeth on the steering nut.

Figure: 5.28. Ball screw steering gear

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

In fig. 5.29 depicts a steering gear with a worm and a roller pin. Its design uses a cylindrical worm with an uneven pitch. When the worm rotates, the tapered pin moves axially along the worm. The steering arm is secured to a corresponding shaft connected to a pin and can be rotated 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 the worm and roller pin steering gear changes proportionally due to the uneven pitch of the worm.

Figure: 5.29. Steering gear with worm and roller pin

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

Figure: 5.30. Worm-sector steering gear

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

In fig. 5.31 depicts a screw-nut steering gear with slide rings.

Figure: 5.31. Screw-nut steering gear with slide rings

In principle, this mechanism is similar to the ball circulation steering mechanism. Sliding 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 °. Frictional wear on this type of steering gear is generally high. The gear ratio is constant.

Figure: 5.32 represents the worm and roller steering gear.

Figure: 5.32. Worm and roller steering gear

This steering mechanism uses a roller instead of a toothed sector to transmit motion from the worm. The worm in this steering mechanism is tapering towards the center and takes the shape of an hourglass (globoid). The advantage of this worm shape is that it allows the roller to pivot about its center, and this reduces the size of the steering gear. The steering arm is attached to the roller shaft and can be rotated 90 °. The gear ratio remains constant. The increased backlash can be eliminated by adjusting the position of the steering shaft.

Sliding steering gear

In fig. 5.33 depicts a constant pitch steering gear - the most common type of steering gear used in modern cars.

Figure: 5.33. Steering gear with constant tooth pitch

Rack and pinion steering mechanisms use a rotating gear to create linear movement of the rack. The gear teeth are in constant engagement 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 mounted on both ends of the rack. Ball joints located between the rack and the steering rods allow for independent vertical movement of the steering rods. The rack is held in mesh with the pinion by a spring-loaded pressure pad that adjusts any gap between the teeth. The sliding friction between the rack and the pinion provides a shock-absorbing effect and absorbs the shocks that occur during movement.

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

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

Figure: 5.34. Steering rack with variable tooth pitch

The variable pitch rack and pinion steering works in the same way as the constant pitch rack and pinion described above. In the center of the rack, the tooth pitch is greater than at the edges. Variable pitch makes it possible to increase the steering ratio as the gear rotates. The teeth in the center of the rack provide more movement for the rack with each rotation of the gear, which requires a relatively large force. The teeth at the ends of the rack provide less rack movement, which requires relatively little driver effort. To eliminate this drawback, steering amplifiers are installed on modern cars. In fact, in this system, the more the steering wheel is turned, the less effort is made. When driving in a straight line, the steering is heavier than turning the steering wheel to the limit position, which makes it easier to maneuver and park.

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

In fig. 5.35 (see also the color insert in Fig. CV 5.35) shows a typical power steering hydraulic system equipped with a fluid pump that supplies a pressure fluid to the hydraulic circuit. The pump can be electrically driven and located in the power steering reservoir or mechanically driven by the engine.

Figure: 5.35. Power steering hydraulic system

Mechanical pumps are usually equipped with a separate fluid reservoir. The working fluid, under the pressure generated by the pump, enters the directional spool valve in the steering gear. When the steering shaft is in a straight position, the hydraulic fluid flows through the directional spool valve and returns to the reservoir. When the steering wheel is turned, the directional spool valve directs the hydraulic fluid to the corresponding side of the piston, which is located in the cylinder at the end of the rack and pinion steering gear. The rod, connected to the piston, is connected to the rack, and any pressure of the working fluid acting on the piston helps the rod move. The working fluid from the back side returns to the reservoir through the directional spool valve. When the steering wheel is turned in the other direction, the opposite process occurs. If the power steering fails, the mechanical action of the steering mechanism remains, but much more force is required.

5.3.2. Steering drive

The steering gear is used to transfer the driver's effort through the steering wheel to the steering wheels of the vehicle. The steering gear converts the rotary motion of the steering wheel into a straight-line motion that pulls the steering linkage. The converted motion is transmitted from the steering gear 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 arrangement and number of tie rods in the steering gear depends on the axle and suspension design.

Steering drive arrangement options

The simplest design of the steering gear is a single-section tie rod, moved by the steering arm (Fig.5.36). The bipod pushes or pulls the steering link to move a lever that is connected to the pivot on the steering knuckle. A track rod connects both pivot joints on the steering knuckles of the front wheels of the vehicle. Any movement of one of the pivot joints is transmitted via the steering rod to the joint on the opposite steering knuckle.

Figure: 5.36. Steering gear with one-piece tie rod

A steering drive of this type is usually 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 to the steering knuckle levers.

In fig. 5.37 shows a modified version of a single-section steering rod - a steering gear with a two-section steering rod moved by the steering arm. The bipod pulls or pushes two separate tie rods, which are connected to the steering knuckle arms by means of ball joints. Moving the steering rods rotates the steering joints on the steering knuckles. A steering gear of this type is usually used in vehicles with independent suspension, in which the pivot joints can move one independently of the other.

Figure: 5.37. Steering gear with two-piece tie rod

The steering drive with a three-section steering rod moved by the steering arm is shown in Fig. 5.38. This steering rod has a pendulum arm which transmits the steering movement to the opposite side of the vehicle. Steering gear of this type is used in vehicles with independent suspension, but this design option has a high cost.

Figure: 5.38. Steering gear with three-piece tie rod

The three-piece steering linkage provides the highest degree of precision and maximum steering control. When the vehicle is driving on uneven roads, jolts are transmitted through the steering gear and the steering mechanism to the driver. To mitigate these shocks, a shock absorber is installed on the steering gear. Steering dampers 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. The steering damper helps counteract increased steering forces and unintentional steering wheel movement.

Figure: 5.39. Steering dampers

In fig. 5.40 shows steering drives with two-section steering rods of a movable rack. The rack and pinion steering system uses two tie rods to transmit steering action to the steering knuckles.

Figure: 5.40. Steering gears with two-piece steering rods

There are also steering racks for connecting to the steering knuckles. They use steering drives of a similar design. The straight-line movement of the steering rack is transmitted through a ball joint to the steering rods.

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

Malfunctions and remedies

The amount of free play of the steering wheel is specified in the vehicle manual. Increased free play is detected by swinging the steering wheel. There may be several reasons for its occurrence:

Loosening of the nuts securing the ball joints of the steering rods;

Increased clearance of the ball joints of the steering rods;

Increased clearance of the ball joints of the front suspension arms;

Backlash due to wear on the front wheel bearings;

Backlash due to wear on the steering gear teeth;

Backlash in the elastic coupling connecting the steering gear to the steering wheel shaft;

Backlash in the steering shaft bearings of the steering wheel.

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

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

Loosening of the nuts securing the ball joints of the steering rods;

Increasing the gap between the rail stop and the nut;

Looseness of the steering gear mounting nuts, as well as all of the above malfunctions.

Tight steering wheel rotation:

Damage to the bearing of the upper support of the steering wheel shaft;

Lowering the air pressure in the tires of the front wheels;

Damage to parts of the telescopic rack and wheel suspension

Violation of the power steering pump;

Ingress of foreign particles into the steering hydraulic system;

Increased oil level in the steering pump reservoir;

Worn or damaged steering gear and pump cuffs;

Worn hydraulic hoses.

To eliminate faults, 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. This text is an introductory fragment.