9.1. Features of the device

The Ford Fusion car is 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 the second contour providing a car stop with sufficient efficiency is used.
The hydraulic drive switched on the vacuum amplifier. Cars of all complete sets equip with anti-blocking system of brakes (ABS). Depending on a complete set on the car install system of emergency brake application (EVA) and system of course stability (ESP).
The parking brake system has the hummock drive on brake mechanisms of back wheels.
The brake mechanism of a forward wheel disk, with automatic adjustment of a gap between blocks of 2 (fig. 9.1) and a disk 1, with a floating bracket. The mobile bracket is formed by a support 3 with the one-piston working cylinder. The guide of 4 blocks is attached by bolts to a rotary fist. The mobile bracket is attached by the directing fingers screwed in carving openings of a guide of blocks. The directing fingers are greased with jellied lubricant and protected by plastic plugs. In a cavity of the working cylinder the piston with a sealing ring is installed. Due to elasticity of this ring the optimum gap between blocks and the ventilated disk is supported. When braking the piston under the influence of pressure of liquid presses an internal block to a disk, under the influence 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, as a result between blocks and a disk the small gap is formed.

Fig. 9.1. Brake mechanism of a forward wheel: 1 – brake disk; 2 – brake shoes (external is not visible as it is closed by a support); 3 – support of the brake mechanism; 4 – guide of blocks; 5 – valve of production of air; 6 – brake hose

The main brake cylinder 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.

Fig. 9.2. Main brake cylinder: 1 – main brake cylinder; 2 – tank of the main brake cylinder; 3 – tank stopper; 4 – sensor of level of brake fluid

The tank 2 is installed on the main cylinder via rubber connecting plugs, 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 the lower half of the case of a tank the sensor 4 levels 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.

Fig. 9.3. Vacuum amplifier

In the hose connecting the vacuum amplifier to an inlet pipe the backpressure valve is installed. It holds depression in the amplifier at his falling in an inlet pipe and interferes with hit of fuel-air mix in the vacuum amplifier.
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 9 installed on an expansion level 6. Install the disk brake mechanisms of back wheels similar on a design on a part of cars to mechanisms of forward wheels, but the smaller size.

Fig. 9.4. Brake mechanism of a back wheel: 1 – front brake shoe; 2 – cable of the drive of the parking brake; 3 – board of the brake mechanism; 4 – clamping brackets of brake shoes; 5 – basic racks; 6 – expansion level; 7 – top coupling spring; 8 – working cylinder; 9 – regulator of gaps; 10 – lever of the drive of the parking brake; 11 – back brake shoe; 12 – 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 the razzhimny levers 10 (see fig. 9.4) installed in drum brake mechanisms of back wheels are attached. When moving razzhimny levers through an expansion level move a front brake shoe against the stop to the brake drum and then, having received a rigid emphasis, press a back block to a drum, blocking a drum. If on the car disk brake mechanisms of back wheels are installed, the rotary levers installed in a support are provided in them. At turn of the lever the piston of the brake cylinder moves and blocks clamp a disk.
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.
Cover or a wire of cables at detection of their break it is necessary to replace new.
The anti-blocking system of brakes (ABS) consists of sensors of frequency of rotation of wheels, the switch of stoplights, the hydraulic block, a hydroelectronic control unit and alarm lamp. Besides, the anti-blocking system is equipped with system of the self-diagnostics revealing malfunctions of components.
ABS serves for regulation of pressure in brake mechanisms of all wheels when braking in difficult road conditions that prevents blocking of wheels.
The ABS system provides the following advantages:
– a detour of obstacles with higher degree of safety, including at emergency brake application;
– reduction of a brake way at emergency brake application with preservation of course stability and controllability of the car, including in turn.
In case of malfunction of system functions of diagnostics and maintenance of work at system failures are provided.
The hydroelectronic control unit (GEBU) obtains information on the speed of the movement of the car, the direction of the movement and road conditions from sensors of frequency of rotation of wheels. After inclusion of ignition the ABS module gives tension on sensors. In sensors Hall's effect is used, they generate an output signal in the form of rectangular impulses. The signal changes in proportion to the frequency of rotation of a pulse ring of the sensor which is built in consolidation of the bearing of a forward nave and directly a back nave.
On the basis of this information of GEBU defines the optimum mode of braking of wheels.
Distinguish the following operating modes of anti-blocking system:
– mode of normal braking. At normal braking the electromagnetic valve is cut off power, the entrance valve is open, the output valve is closed. When pressing a brake pedal brake fluid under pressure moves in the working cylinder via the electromagnetic valve and puts brake mechanisms of wheels in action. At a brake pedal otpuskaniye brake fluid comes back to the main brake cylinder via entrance and return valves;
– mode of emergency brake application. If at emergency brake application blocking of a wheel begins, GEBU issues the command for reduction of supply of brake fluid on the electromagnetic valve, then tension moves on each electromagnetic valve. The entrance valve is closed, and supply of brake fluid from the main cylinder is blocked; the output valve opens, and brake fluid comes from the working cylinder in main, and then to a tank that causes pressure decrease;
– mode of maintenance of pressure. At the maximum pressure decrease in the GEBU working cylinder issues the command for maintenance of pressure of brake fluid on the electromagnetic valve, tension moves on the entrance valve and does not move on the output valve. At the same time entrance and output valves are closed and brake fluid does not leave the working cylinder;
– mode of increase in pressure. If GEBU defines that the wheel is not blocked, then it cuts off power the electromagnetic valve. Tension on electromagnetic valves does not move, brake fluid via the entrance valve comes to the working cylinder in which pressure increases.
Diagnostics and repair of anti-blocking system of brakes requires the special equipment and the equipment. Therefore in case of its exit out of operation address on specialized service station.
The hydraulic system of brakes is united in a whole by metal tubes and hoses. The system is filled with special brake fluid of a class not below DOT-4 which needs to be replaced periodically. The replacement procedure of brake fluid is described in section 4 "Maintenance" (see. "Replacement of brake fluid in hydraulic actuators of brakes and switching off of coupling").
Check of the brake system is described in section 4 "Maintenance" (see. "First maintenance (TO-1)").

Useful tips
Some drivers, seeking to wear out less cables of the parking brake, try to use it less often. Such "economy" results in the return result: a cable, seldom moving in a cover, gradually loses mobility, gets jammed it, as a result the cable breaks. Therefore use the parking brake in all cases, when necessary.
The free wheeling of a pedal of a brake at the idle engine has to be about 3-8 mm. Too low free wheeling demonstrates the wrong initial installation of a pedal of a brake or jamming of the working cylinder, causes the increased fuel consumption and the accelerated wear of brake shoes. Too big free wheeling — 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 free wheeling 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. Periodically appearing and disappearing vibration of a pedal at sharp braking of the car equipped with anti-blocking system of brakes accompanies work of this system and is not a malfunction sign.
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.