6.1.4. Main brake cylinder
The brake system with the new main brake cylinder and the new amplifier of brakes
Operation of the tandem cylinder is based on the principle of "plunger".
Unlike the ordinary main brake cylinder, the condensing plugs are built in the case instead of being established on the piston as before. The opening in the case, thus, directly directs pistons. This design allows to reduce length of the tandem main brake cylinder by 25%. Besides, the number of knots is reduced to 15, thus, weight considerably is lost, dimensions and duration of service are reduced.
The "plunger" main brake cylinder of tandem type of the 2nd generation as almost all brake cylinders, ensures functioning of the double-circuit brake system. Contours of pressure are located consistently. The effort of the driver is transferred as usual, from a rod of the amplifier of brakes to primary pistons. The spring of compression creating preliminary pressure is established on the end of primary piston, and it provides actually simultaneous transfer of effort to the secondary piston (the floating piston). Joint operation of two pistons through one spring provides reduction of a free wheeling and forces a secondary brake chain to react more spontaneously, than it occurs in the ordinary tandem main brake cylinder.
In the system used so far the secondary piston it is put in action by pressure in primary contour of the brake system. It leads to increase in a free wheeling because at first pressure has to grow to set. The second spring of compression located behind the secondary piston is returnable. It has to be rather rigid to provide overcoming friction of the pressurizing plugs, but at the same time rather soft that the possibility of compression under the influence of a spring of the first contour when brakes are put in action was provided.
In a starting position there is a depressurized connection between the main brake cylinder of tandem type and the compensation tank. It provides compensation of pressure and productivity in the brake system. When the brake is put in action pistons of cylinders enter the condensing plug after a short free wheeling. Connection with the unpackaged compensation tank then stops. After rubber elements provided consolidation, the volume of brake fluid begins to move and the brake system appears under pressure. After the brake is released, the returnable spring takes away pistons back before the restoration depressurized connection between the tandem brake main cylinder and the compensation tank.
In the cars equipped with the ESP system or regulation of traction effort productivity of the brake system in case of intervention of system it has to be provided with additional giving. As time of an exit to an operating mode of the pump ABS depends on absorption resistance in system, sections of openings and channels have to be as much as possible.
In case of intervention of system of regulation of traction effort the proivzoditelnost of the brake system is provided with a ring groove which is located opposite to an opening in the piston when the main brake cylinder is in a free state. When brakes get into gear in the course of regulation, additional brake fluid which was given to brake mechanisms system of regulation of traction effort comes back to the compensation tank under pressure. Extent of increase in pressure on return is defined by the instant productivity of the brake system and pressure in the brake system which was created by system of regulation of traction effort.
If, when using brakes, the control system passes from regulation of traction effort to involvement of anti-blocking system of brakes, the compensation opening can open under pressure in the main brake cylinder as a result of need of return of brake fluid to the main cylinder during a pressure decrease phase during the work of anti-blocking system of brakes. Outflow pressure in the compensation tank depends only on pressure in the main cylinder which is operated by the driver. The amount of liquid which flows back in the tank at this time depends, in essence, on productivity of the brake system and the current parameters of management.
The combination of loading, modulation and release during work of brakes is possible as a condition of system.
Primary plug of the main brake cylinder of tandem type remains under pressure created by excess productivity in a brake contour until final situation is reached.
The internal ledge of primary plug is under pressure both from the outer side and from the piston, for compensation of total pressure on the plug. It prevents damage of edge of the plug (the pressurizing edge) at a piston exit out of the set limits as it happens in the main brake cylinder of tandem type to a compensation opening where pressure drop on the plug takes place.
In principle change owing to the return filling (decline in production with a constant pressure) is same, as well as change at a pedal otpuskaniye (pressure decline at reduction of productivity) as the edge of the plug is in contact with the piston at decline in production.
In case of work of the ESP system, however, brake fluid also has to move every time when the main brake cylinder is put in action. In this case the pump of anti-blocking system of brakes gives additional brake fluid from the compensation tank. Then brake fluid passes through primary plug, causing folding of the condensing ledge, at the same time between the piston and an opening the ring gap is created. Brake fluid can get to the corresponding giving union now.
Shooters – the direction of current of brake fluid.
Arrow of situation – the outer edge of the condensing plug is bent inside.
Possible malfunctions, their reasons and ways of elimination
Malfunction of a contour
At refusal of a contour of the brake system the free wheeling increases. At refusal of primary contour, primary piston leans on the secondary piston, and the rod of the amplifier of brakes sets the last in motion due to mechanical communication (I).
At refusal of a secondary contour, the secondary piston rests against the limiter at the end of a cylinder opening, after that pressure in primary contour rises (II).