Contours “left front - right front” and “left rear - right rear” using a standard regulator. Used in conjunction with rear disc brakes on the VAZ 21083.
ATTENTION!
Any interference with the brake system is prohibited! You must remember this! We disclaim any liability in the event of force majeure.
Advantages of the scheme.
1.Equal forces on the left and right wheels of the car.
2. The regulator begins to regulate the force on the rear wheels over a wider range.
Disadvantages of the scheme.
If the “left front – right front” circuit fails, braking efficiency drops sharply. Monitor the condition of the circuit!
Master brake cylinder.
There are 3 tubes extending from the GTZ, 2 forward, one backward.
Tubes extend from the first piston of the GTZ, which is closer to the vacuum booster, to the front wheels. From the far one - under the bottom to the rear. The excess hole can be plugged with a bolt and a copper washer.
Pressure regulator.
Two holes on the regulator are plugged - one at the end, the second next to it - the former "right front - left rear" line. This circuit will no longer exist.
We collect.
The only tube that comes from the GTZ is placed at the only entrance of the sorcerer, at the only way out The sorcerer installs a tee from the classics, after the tee of the tube on the rear wheels. Pump it up and enjoy it. It is advisable to use all brake pads from the same company, preferably from well-known global manufacturers. Combinations may result in the brakes being unable to adjust.
Dual-circuit pneumatic braking system
Currently, the vast majority of modern trucks are equipped with a dual-circuit pneumatic braking system. The use of such a system significantly increases reliability in the event of any failure of one of the circuits. In fact, it is the integration of two braking systems. At first glance, such a design will seem quite difficult to understand, but if the principle of operation of the simplest brake system, then the dual-circuit system will be accepted. Generally speaking, one should imagine that in a two-axle vehicle, one circuit provides braking of the wheels of the front axle, and the second circuit performs braking of the wheels of the second axle. If one of the circuits fails, the other will take over the braking function.
So, air is pumped by a compressor into a “wet” receiver, which is protected from excess pressure by a safety valve. The compressed air then flows from the “wet” receiver to the primary “dry” receiver and then to the secondary “dry” receiver. From this moment on, the dual-circuit braking system is ready for use. Through air lines, compressed air from the primary “dry” receiver is supplied to the foot valve with the brake pedal. The situation is similar with the secondary “dry” receiver, from which air also flows to the foot valve. In this case, the foot valve actually consists of two sections, i.e. is two valves in one. One of the sections serves the primary brake circuit, and the second section serves the secondary brake circuit. When braking is performed, air from the primary reservoir is supplied through the foot valve to the rear brake chambers. At the same time, air from the secondary receiver is supplied through to the front brake chambers. If there is an air leak in the primary circuit, the secondary will remain operational, and vice versa. The primary and secondary circuits are equipped with low pressure alarms located in the cab. In addition, every truck, tractor or bus is equipped with an emergency or parking brake. Its operating principle is based on the use of a powerful spring to apply braking force. The fact is that there is a possibility of air leakage from the brake system. In an emergency brake, air pressure prevents the spring from expanding and braking. If there is an air leak, when the pressure in the system is 20-30 pounds per inch, the spring will release and the brakes will automatically apply, stopping the vehicle. The emergency brake is highly dependent on spring adjustment.
1 - compressor, 2 - governor, 3 - air dryer, 4 - "wet" receiver, 5 - primary receiver, 6 - secondary receiver, 7 - brake pedal with foot valve, 8 - front axle limit valve, 9 - accelerator valve, 10 - rear brake chamber, 11 - front brake chamber,
A somewhat more complex braking system is used in road trains, i.e. in the coupling of a tractor with a semi-trailer. The brake system of a semi-trailer is connected to the tractor system using special flexible lines with connectors that prevent air leakage. Before connecting, you must make sure that the connectors are not dirty. The composition also includes special safety valves, which prevent air leakage in the tractor brakes if the semi-trailer accidentally comes off. In addition, a receiver is installed on the semi-trailer, which provides normal or emergency braking, and some other valves.
Modern commercial vehicles are equipped with integrated electronic systems, which include the anti-lock braking system (ABS - anti-lock brake system). ABS controls the rotation speed of each wheel. If a wheel locks during braking, ABS reduces the braking force on that wheel, thereby preventing the wheel from slipping on wet or slippery roads, or when cornering. Typical ABS consists of sensors and toothed rings, the electronic unit control (ECU - electronic control unit), valves. The ECU is the brain of the system. Sensors installed on each wheel send information about the speed of rotation of the wheel to the ECU and, if necessary, the ECU commands to reduce the braking force on that wheel. As a rule, a special lamp is activated in the driver's cabin, indicating that ABS is operating. The semi-trailer can also be equipped with ABS.
In addition to ABS, the vehicle may also have other safety systems. traffic. For example, an automatic traction control system (ATC - automatic traction control), which, like ABS, monitors the rotation speed of each wheel. In this case, the rotation speeds of the rear driving and front driven wheels are compared. If one wheel spins faster than the others, for example when hitting a slippery section of the road, the ATC brakes it.
Effective technical solution became the exchange rate stability system (ESP - Electronic Stability Program), which prevents skidding or rollover vehicle, as well as “folding” the road train. The system has three sensors that measure yaw angle (yaw angle), lateral acceleration and steering wheel position. The ECU analyzes this data and applies the brakes to one or more wheels if necessary.
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To ensure the possibility of braking in the event of failure of any element of the working brake system, the brake drive is divided into independent circuits, each of which, in the event of failure of the other, automatically performs the function of a reserve brake system. Schemes for the formation of independent circuits may be different.
In the simplest case (Fig. 14.18 a), one circuit serves the brake mechanisms of the front wheels, and the other - the rear wheels. However, the vertical reactions of the front and rear wheels, which determine the maximum possible braking reactions of the car, and therefore the deceleration of the vehicle created by the front or rear wheels, can differ quite significantly. For example, front-wheel drive passenger cars in static conditions have a vertical reaction of the front wheels that is greater than the vertical reaction of the rear wheels. During braking, the unevenness of static vertical reactions is aggravated by their dynamic redistribution. The front brake mechanisms of such cars, designed for a large vertical reaction, create greater braking reactions LT1 than the less effective brake mechanisms of the rear wheels. Therefore, in the event of a front circuit failure, the maximum deceleration of the vehicle will be small, approximately 0.33 of the deceleration of a working vehicle. Approximately the same deceleration, but in the event of a failure of the rear brake circuit, will be experienced by a truck with a classical layout design, in which the approximately twofold excess of the vertical reaction of the rear wheels over the vertical reaction of the front wheels in static conditions cannot be compensated by the dynamic redistribution of reactions during braking.
The circuit separation scheme shown in Fig. has much better properties. 14.186. Each of the front wheel brake mechanisms is driven from both circuits, and the drive efficiency is different. In a hydraulic drive, this is ensured by the difference in diameters of the drive (working) cylinders. Smaller diameter cylinders are included in a circuit common to the rear brake mechanisms, while larger diameter cylinders drive only the front brake mechanisms. The ratio of the cylinder diameters is chosen such that if any circuit fails, the car would maintain 50% braking efficiency. Obviously, on a truck with double tires on the rear wheels, the drive from both circuits must have rear brake mechanisms.
From the point of view of maintaining braking efficiency in the event of failure of one circuit, the same properties are shown in Fig. 14.18 in diagonal pattern. However a big difference in the effectiveness of the front and rear brakes of a car leads to in this case to noticeable negative consequences. In a passenger car, a greater road braking reaction of the front, for example the left, wheel of a serviceable circuit - Rt,l (Fig. 14.18f) compared to a smaller braking reaction of the right rear wheel - /?t2p will lead to a sideways displacement of their resultant Lt1. The presence of a shoulder h between the resultant /?TS and the inertial force pj will lead to the emergence of a torque A/, turning the car to the left.
Rice. 14.18. Schemes of dual-circuit brake drives
From Fig. Figure 14.18f shows that the longitudinal tangential reaction of the steered wheel at a radius approximately equal to the running arm “a” (measured from the middle of the tire imprint to point O, the intersection of the road with the wheel’s turning axis), creates a torque tending to turn the wheel around the turning axis. In the case of braking of a working car, these moments applied to the right and left wheels are closed by the steering gear trapezoid and compensate each other. When a car is braking by one diagonal contour, the moment A/2 = i/?t]n turns the steered wheels to the left due to the gaps in the steering, the elasticity of its links and the elasticity of the driver’s hands. Thus, the negative effects of the turning moments mi and L/2 add up, which leads to very unpleasant consequences. To eliminate this drawback when diagonally dividing the brake drive, a negative running arm “-a” is used (Fig. 14.18g). This measure, with a certain combination of design and operational factors, makes it possible to reduce the total effect of the moments mi and A/2 to zero or, in any case, to radically reduce it.
The best properties has the one shown in Fig. 14.18d diagram of division into circuits, providing for complete preservation of braking qualities in the event of failure of the service braking system. You just need to keep in mind that in this case, significantly more force must be applied to the brake pedal. However, this scheme is complex and is used mainly on large, expensive cars.
Also rarely used is the one shown in Fig. 14.18 g diagram, which can be considered as some combination of the two previous ones.
Modern cars have hydraulic brakes on all four wheels. Brakes come in disc and drum types.
Front brakes play big role with stopping the car than the rear ones, because When braking, weight is transferred to the front wheels.
In many cars, the front wheels are equipped with disc brakes, which are considered more effective, and the rear wheels are equipped with drum brakes.
Braking systems that consist only of discs are found on the most expensive and high-performance cars, while brake systems that consist only of drums are common in older, smaller cars.
Dual-circuit braking system
In a typical dual-circuit braking system, each circuit operates on both front wheels and one of the rear wheels. When you press the brake pedal, fluid from the master cylinder passes through the brake pipes to the slave cylinders located next to the wheels. In this case, the main brake cylinder is replenished from a special reservoir.
Hydraulic brake system
The hydraulic brake circuit includes a master cylinder filled with fluid and several auxiliary cylinders connected to each other by pipes.
Main and auxiliary cylinders
When the brake pedal is depressed, the master cylinder forces fluid into the slave cylinders.
The pedal moves the piston in the master cylinder, and fluid moves through the tube.
Once in the auxiliary cylinders located next to the wheels, the fluid sets the cylinders in motion and triggers the brakes.
Fluid pressure is evenly distributed throughout the system.
However, the total pressure area of the pistons in the auxiliary cylinders is greater than the pressure area of the piston in the master cylinder.
Thus, the piston in the master cylinder needs to travel a distance of several tens of centimeters in order to move the pistons in the auxiliary cylinders the couple of centimeters necessary to apply the brakes.
This design allows you to apply to the brakes enormous power, similar to that which occurs in a lever with a long arm even when pressed lightly.
Modern cars use hydraulic circuits with two cylinders, one of which is a spare.
In some cases, one chain works for the front wheels, and the second for the rear wheels. Sometimes one chain connects wheels in pairs (front and rear). IN separate systems one chain provides brake operation on all wheels.
Often, heavy braking transfers the vehicle's weight to the front wheels. In this case, the rear wheels are blocked, which leads to a skid.
To solve this problem, the rear brakes are deliberately made weaker than the front ones.
Some vehicles also have load-sensing pressure limiters. When brake system pressure rises to a level that locks the rear wheels, the restrictor valve closes and fluid no longer flows to the rear brakes.
More advanced models use a complex anti-lock system that takes into account sudden changes in speed.
These systems quickly apply and disengage the brakes to prevent locking.
Power brakes
Many cars have a brake booster, so the driver doesn't have to put as much effort into braking.
Typically, the source of the boost is the pressure difference between the partial vacuum in the intake manifold and the air flow outside the housing.
The actuator, which is responsible for the reinforcement, is connected to the intake manifold by pipes.
The direct acting actuator is located between the brake pedal and the master cylinder. The pedal can act directly on the cylinder if the mechanism fails or the engine is switched off.
The direct acting actuator is located between the brake pedal and the master cylinder. The brake pedal operates a lever, which in turn fires the master cylinder piston.
In addition, the pedal also operates several air valves, and the master cylinder piston is equipped with a large rubber diaphragm.
When the brakes are off, the diaphragm is exposed to vacuum in the intake manifold on both sides.
When you press the pedal, the valve connecting the rear side of the diaphragm to the manifold closes, opening the valve that admits air from outside.
Under air pressure, the diaphragm moves the piston of the master cylinder, strengthening the brakes.
While holding the pedal air valve no longer leaks air and the brake pressure remains constant.
If the pedal is released, the space behind the diaphragm opens, the pressure drops again, and the diaphragm returns to its original position.
When the engine stops, the vacuum disappears, but the brakes continue to work because... The pedal is connected to the brake master cylinder mechanically. However, braking in the described situation will require much more effort from the driver.
How does a brake booster work?
The brakes do not work, both sides of the diaphragm are in contact with vacuum.
When you press the pedal, air is applied to the back of the diaphragm and it moves towards the cylinder.
Some vehicles have indirect-acting mechanisms built into the hydraulic transmission line between the brakes and the brake master cylinder. Such a mechanism is not tied to the pedal and can be present in any section of the engine compartment.
However, it also operates under vacuum from the manifold. When you press the brake pedal, the brake master cylinder applies hydraulic pressure to the valve, which operates the brake mechanism.
Disc brakes
Basic type of disc brake with one pair of pistons. One or more pistons can be used to act on the pads. The calipers can be swinging or sliding.
A disc brake has a disc that rotates with the wheel. The disc is supported by a caliper that contains small hydraulic pistons controlled by the brake master cylinder.
The pistons push against friction linings, which press against the disc to slow or stop it. These pads are curved and cover most disk.
In dual-circuit brake systems there may be several pistons.
The pistons do not have to travel a long way to brake, so when the brakes are released they do not contact the disc and have no return springs.
When you press the brake pedal, the linings are pressed against the disc under fluid pressure.
Rubber O-rings surrounding the pistons allow them to gradually move forward as the linings wear, so that the distance between the disc and the piston remains constant and the braking system does not need to be adjusted.
In some modern models, the linings are equipped with sensors. When the lining wears out, the sensor contacts are exposed and close, lighting an alarm on the dashboard.
Drum brakes
The drum brake with primary and secondary shoes is equipped with one hydraulic cylinder. Dual primary pad brakes have two cylinders that are mounted on the front wheels.
A drum brake has a hollow drum that rotates with the wheel. The top of the drum is covered with a fixed base plate, on which two curved pads with friction lining are located.
Under fluid pressure, the pistons in the cylinders move apart, and the pad casing is pressed against the drum, slowing or stopping it.
When you press the pedal, the pads are pressed against the drum under the action of the pistons.
Each brake shoe is in contact with a lever and a piston. The primary shoe is in contact with the piston on the working side, determining the direction of rotation of the drum.
When the drum rotates, it pulls the block in the opposite direction, providing a braking effect.
Some drums use dual shoes, each equipped with a hydraulic cylinder. Others use a pair of pads (primary and secondary) with levers at the front.
This design allows the pads to be spaced when there is one cylinder with two pistons.
The primary and secondary pad system is simplified and less powerful than the dual drive pad system, so it is usually installed on the rear wheels.
In any case, after the brakes are turned off, the pads return to their original position thanks to the return springs.
The movement of the pads is limited by the regulator. Older systems use mechanical adjusters that require adjustment as the friction lining wears. IN modern systems The regulators operate automatically due to ratcheting mechanisms.
Drum brakes may fail with frequent use because... they overheat and cannot function effectively until they cool down. Discs have a more open design and are considered more reliable.
Hand brake
Handbrake mechanism
The handbrake acts on the pads by mechanical system, which does not use hydraulic cylinders. This system consists of levers that are located in the brake drum and are manually activated from inside the vehicle.
In addition to the hydraulic braking system, all cars are equipped with a hand brake, which acts on two wheels (usually the rear ones).
The handbrake makes it possible to reduce speed in case of failure hydraulic system, however, it is mainly used in parking lots.
The handbrake lever pulls a cable or pair of cables that are connected to the brakes by a collection of smaller levers, pulleys, and guides. The specific components of this system depend on the car model.
The handbrake levers are held in position by a ratchet mechanism. The mechanism is turned off by a button, freeing the levers.
In drum brakes, the hand brake acts on a brake band that is pressed against the drums.
Disc brakes use the same mechanics, but the calipers are small and difficult to wire, so each wheel has a separate lever.
