6.1.4. Main brake cylinder
Brake system with the new main brake cylinder and the new amplifier of brakes
Operation of the tandemny cylinder is based on a principle of "plunzher".
Unlike the ordinary main brake cylinder, 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 tandemny main brake cylinder by 25 %. Besides, the number of knots is reduced to 15, thus, the weight considerably is reduced, dimensions and duration of service are reduced.
«Плунжерный» the main brake cylinder of tandemny type of the 2nd generation as almost all brake cylinders, ensures functioning of 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 the 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 tandemny main brake cylinder.
In the system used so far the secondary piston it is put in action by pressure in primary contour of brake system. It leads to increase in a free wheeling because at first pressure should grow to the set. The second spring of compression located behind the secondary piston, is returnable. It should be rather rigid to provide overcoming of a friction of pressurizing plugs, but at the same time rather soft that compression possibility 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 tandemny type and the compensatory tank. It provides pressure and productivity compensation in brake system. When the brake is put in action pistons of cylinders enter into condensing plug after a short free wheeling. Connection with the unpackaged compensatory tank then stops. After rubber elements provided consolidation, the volume of brake liquid starts to move and the brake system appears under pressure. After the brake is released, the returnable spring takes away pistons back before restoration depressurized connection between the tandemny brake main cylinder and the compensatory tank.
In cars equipped with ESP system or regulation of traction effort productivity of brake system in case of intervention of system should be provided with additional giving. As time of an exit for an operating mode of the pump ABS depends on resistance of absorption in system, sections of openings and channels should be as much as possible.
In case of intervention of system of regulation of traction effort the proivzoditelnost of 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 condition. When brakes get into gear in the course of regulation, additional brake liquid which was submitted to brake mechanisms system of regulation of traction effort, comes back back to the compensatory tank under pressure. Extent of increase of pressure on return is defined by instant productivity of brake system and pressure in 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 compensatory opening can open under pressure in the main brake cylinder as a result of need of return of brake liquid in the main cylinder during a pressure decrease phase at work of anti-blocking system of brakes. Pressure of outflow in the compensatory tank depends only on pressure in the main cylinder which the driver operates. The amount of liquid which flows back in the tank at this time, depends, in essence, on productivity of brake system and the current parameters of management.
The combination of loading, modulation and release during work of brakes is possible, as a system condition.
The primary plug of the main brake cylinder of tandemny type remains under the pressure created by superfluous productivity in a brake contour, yet final situation until then will not be reached.
The internal ledge of the primary plug is under pressure both from the outer side and from the piston, for compensation of a total pressure on the plug. It prevents damage of edge of the plug (pressurizing edge) at a piston exit out of the established limits as it happens in the main brake cylinder of tandemny type to a compensatory opening where pressure drop on the plug takes place.
In principle change owing to return filling (productivity fall at constant pressure) is same, as well as change at a pedal otpuskaniye (pressure decline at productivity reduction) as the edge of the plug is in contact to the piston at decline of productivity.
In case of ESP system work, however, brake liquid also should move every time when the main brake cylinder is put in action. In this case the pump of anti-blocking system of brakes submits additional brake liquid from the compensatory tank. Then brake liquid passes through the primary plug, causing folding of a condensing ledge, thus between the piston and an opening the ring gap is created. Brake liquid can get now to the corresponding submitting union.
Shooters – the direction of a current of brake liquid.
The shooter of situation – external edge of the condensing plug will bend inside.
Possible malfunctions, their reasons and ways of elimination
Malfunction of a contour
At refusal of a contour of brake system the free wheeling increases. At refusal of primary contour, the primary piston leans on the secondary piston, and the rod of the amplifier of brakes sets the last in motion at the expense of 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).