9.1. Features of a design
The Chevrolet/Daewoo Lanos cars are equipped with two independent brake systems: working and parking. The first, equipped with the hydraulic drive, provides braking at the movement of the car, the second slows down the car on the parking. Working system double-circuit, with diagonal connection of brake mechanisms of forward and back wheels. One contour of a hydraulic actuator ensures functioning right forward and left back brake mechanisms, another — left forward and right back.
At refusal of one of contours of the working brake system other contour providing a car stop with sufficient efficiency is used.
The hydraulic drive switched on the vacuum amplifier and regulators of pressure in hydraulic actuators of back brakes.
The parking brake system has the hummock drive on brake mechanisms of back wheels.
|Fig. 9.1. Brake mechanism of a forward wheel: 1 – brake shoes; 2 – support of the brake mechanism; 3 – guide of blocks; 4 – brake disk; 5 – the directing support finger; 6 – valve of production of air; 7 – brake hose
The brake mechanism of forward wheels disk, with automatic adjustment of a gap between blocks of 1 (fig. 9.1)
and a disk 4, with a floating bracket. The mobile bracket is formed by a support 2 with the one-piston working cylinder. The guide of 3 blocks is attached by bolts to a rotary fist. The mobile bracket is attached by bolts to the directing fingers 5 established in openings of a guide of blocks. The directing fingers are greased with jellied lubricant and protected by rubber covers. In a cavity of the wheel cylinder the piston with a sealing ring is installed. Due to elasticity of this ring the optimum gap between blocks and the ventilated disk which surface is protected by a brake board is supported. When braking the piston under the influence of pressure of liquid presses an internal block to a disk, as a result of reaction force the support moves on fingers and the external block nestles on a disk too, at the same time force of pressing of blocks is identical. At a disinhibition the piston due to elasticity of a sealing ring is taken away from a block, between blocks and a disk the small gap is formed.
Main brake cylinder
|Fig. 9.2. The main brake cylinder with pressure regulators in hydraulic actuators of brake mechanisms of back wheels and a tank: 1 – main brake cylinder; 2 – tank of the main brake cylinder; 3 – a tank stopper with the sensor of level of brake fluid; 4 – connecting plugs; 5 – pressure regulators in hydraulic actuators of brake mechanisms of back wheels
1 (fig. 9.2)
of the tandem type of the hydraulic drive of brakes consists of two separate cameras connected to independent hydraulic contours. The first camera is connected with right forward and left back brake mechanisms, the second — with left forward and right back.
The tank 2 is installed on the main cylinder via rubber connecting plugs 4, the internal cavity of which is divided by partitions into three compartments. Each compartment feeds one of cameras of the main brake cylinder and the main cylinder of the drive of switching off of coupling.
By pressing a brake pedal pistons of the main brake cylinder begin to move, working edges of cuffs block compensation openings, cameras and a tank are separated and replacement of brake fluid begins.
In a stopper 3 tanks the sensor of level of brake fluid is installed. When falling level of liquid is lower admissible in a combination of devices the alarm lamp of failure condition of the brake system lights up.
The vacuum amplifier (fig. 9.3)
established between the mechanism of a pedal and the main brake cylinder when braking due to depression in an inlet pipe of the engine through a rod and the piston of the first camera of the main cylinder creates the additional effort proportional to effort from a pedal.
In the hose connecting the vacuum amplifier to an inlet pipe the backpressure valve is installed. It holds in the amplifier depression at its falling in an inlet pipe and interferes with hit of fuel-air mix in the vacuum amplifier.
Regulators of pressure
5 (see fig. 9.2
), established on the main brake cylinder, correct when braking pressure of brake fluid in back brake mechanisms, excepting a possibility of the advancing blocking of back wheels. It is reached by proportional reduction of pressure in a hydraulic actuator of brake mechanisms of back wheels in relation to pressure in a hydraulic actuator of brake mechanisms of forward wheels. The ratio of values of pressure in forward and back working cylinders at various values of effort to pedals is given in tab. 9.1.
The table 9.1 Ratio of Values of Pressure in contours of a hydraulic actuator of brakes, supported by pressure regulators
The brake mechanism of back wheels
drum, with automatic adjustment of a gap between blocks and a drum. Brake shoes 1 and 11 (fig. 9.4)
are put in action by one hydraulic working cylinder 8 with two pistons. The optimum gap between a drum and blocks is supported by the mechanical regulator 6 installed on an expansion level 9.
|Fig. 9.4. Brake mechanism of a back wheel: 1 – front brake shoe; 2 – board of the brake mechanism; 3 – spring of the lever of the regulator of gaps; 4 – basic racks; 5 – lever of the regulator of gaps; 6 – regulator of gaps; 7 – top coupling spring; 8 – working cylinder; 9 – expansion level; 10 – razzhimny lever of the drive of the parking brake; 11 – back brake shoe; 12 – cable of the drive of the parking brake; 13 – lower coupling spring
The parking brake
put in action mechanically consists of the lever installed on the basis of a body between front seats, a forward cable with the adjusting device and the equalizer to which two back cables, and also the razzhimny levers 10 (see fig. 9.4
) installed in brake mechanisms of back wheels are attached.
The parking brake does not demand special leaving. At maintenance check degree of wear of teeths of the sector and a doggie. Replace excessively worn-out details.
At detection of break of covers or delays of cables it is necessary to replace them new.
The working course of a pedal of a brake at the working engine has to be about 60-65 mm. Too low working speed demonstrates the wrong initial installation of a pedal of a brake, violation of adjustment of the vacuum amplifier of brakes or jamming of the working cylinder, causes the increased fuel consumption and the accelerated wear of brake shoes. Too big working course — a sign of excess gaps in the mechanism of a pedal or violation of tightness of a hydraulic actuator of the brake system. If the working course decreases by numerous pressing a pedal, i.e. it becomes "more rigid", in system air. If the full speed of a pedal begins to increase, the system is untight.
If when braking the brake pedal always begins to vibrate, most likely, brake disks are jarred on. Unfortunately, in their such situation it is only necessary to change, and at once both.
If when braking begins to pull the car aside, check working cylinders: perhaps, their replacement will be required.
If in a forward suspension bracket there was a knock vanishing when braking check an inhaling of bolts of fastening of a support.
After replacement of brake shoes prior to the movement surely several times press a brake pedal — pistons in working cylinders have to rise into place.