Subaru Legacy/Outback

1999-2003 of release

Repair and car operation

System of antiblocking of brakes (ABS) - the general information, a functioning principle

The scheme of an arrangement of components ABS and adjacent systems


1 — the management/hydromodulator Block 2 — the pressure Valve-terminator 3 — the Diagnostic socket 4 — Control lamp ABS 5 — Socket DLC for connection SSM 6 — the Module of management АТ (TCM)	7 — Rotors of wheel gauges 8 — Wheel gauges 9 — Wheel cylinders 10 — the Gauge of overloads (G-gauge) 11 — the Gauge-switch of stoplights 12 — ГТЦ

Hydromodulator ABS functioning in a mode of normal braking at passive ABS (on an example of a contour of one wheel)


1 — From ГТЦ 2 — Dempfernaja the chamber 3 — the Entrance port is opened 4 — the Inlet electromagnetic valve 5 — the Control valve 6 — Deaktivirovan 7 — the Pump	8 — the Wheel cylinder 9 — the Final electromagnetic valve 10 — the Electromotor 11 — the Target port is closed 12 — Deaktivirovan 13 — the Tank

Hydromodulator ABS functioning in a pressure decrease mode (on an example of a contour of one wheel)


1 — From ГТЦ 2 — Dempfernaja the chamber 3 — the Entrance port is closed 4 — the Inlet electromagnetic valve 5 — the Control valve 6 — It is activated 7 — the Pump	8 — the Wheel cylinder 9 — the Final electromagnetic valve 10 — the Electromotor 11 — the Target port is opened 12 — It is activated 13 — the Tank

Hydromodulator ABS functioning in a mode of deduction of pressure (on an example of a contour of one wheel)


1 — From ГТЦ 2 — Dempfernaja the chamber 3 — the Entrance port is closed 4 — the Inlet electromagnetic valve 5 — the Control valve 6 — It is activated 7 — the Pump	8 — the Wheel cylinder 9 — the Final electromagnetic valve 10 — the Electromotor 11 — the Target port is closed 12 — Deaktivirovan 13 — the Tank

Hydromodulator ABS functioning in a mode of increase of pressure (on an example of a contour of one wheel)


1 — From ГТЦ 2 — Dempfernaja the chamber 3 — the Entrance port is opened 4 — the Inlet electromagnetic valve 5 — the Control valve 6 — Deaktivirovan 7 — the Pump	8 — the Wheel cylinder 9 — the Final electromagnetic valve 10 — the Electromotor 11 — the Target port is closed 12 — Deaktivirovan 13 — the Tank

Design and principle of functioning of the wheel gauge


1 — the gauge Case 2 — the Sensitive element 3 — the Rotor	4 — Full speed of rotation 5 — the Lowered speed of rotation 6 — the Constant magnet

On equipped with brake system of usual type vehicles, sharp squeezing of a pedal of a foot brake leads to blocking of wheels. Coupling of a protector with a road covering is thus broken, and the car can go юзом, losing controllability. The system of antiblocking of brakes (ABS) prevents premature blocking of wheels, continuously operating speed of their rotation during braking at the expense of modulations of pressure of a hydraulic liquid in each of brake mechanisms.

Exit ABS out of operation leads to emergency operation activation at which normal functioning of usual brake system is provided, - on an instrument guard of the car the corresponding control lamp lights up.

The scheme of an arrangement of components ABS and adjacent systems is presented on an illustration.

The management/hydromodulator block

Into a standard complete set of all models Legacy/Outback enters ABS type 5.3i in which hydromodulator, the block of management ABS, the relay of valves and the electromotor for the purpose of service and weight reduction simplification are united in the uniform assemblage called by assemblage of the module of management/hydromodulator. The block of management ABS traces speed of rotation of each of car wheels, being guided by arriving signals from wheel gauges. When at emergency braking any of wheels it starts to be blocked prematurely, the management module gives out a command on activation of the electromagnetic valve placed in the hydraulic modulator which, working, opens a corresponding site of a brake contour, letting out from it in the tank a part of a hydraulic liquid and, accordingly, reducing working pressure.

In type system 5.3i pressure in each of forward wheels of the car is supervised and regulated individually, blocking of any of back wheels leads to uniform decrease in brake pressure in contours of both back brake mechanisms.

As soon as speeds of rotation of wheels are equalised, the valve is closed again, and pressure continues to rise. The cycle lasts fractions of a second on each of wheels and repeats until braking will not be finished. The system design allows to correct pressure in hydraulic contours of each of four wheels. Actually the scheme of functioning ABS is much more difficult, than it can seem, therefore composers of the present Management do not recommend to owners of cars to make attempt of independent performance of repair of system. In case of occurrence of malfunctions it will be most reasonable to address to experts of car-care centre.

The klapannoe relay plays a role of the power switch of windings of electromagnetic valves and the electromotor relay. Relay operation occurs at the command of the management block.

The electromotor relay provides management of functioning of the hydraulic pump.

Principle of functioning of the hydromodulator

The cycle of functioning of the hydromodulator consists of four operating conditions: one passive, - a mode of normal braking (ABS it is not activated), - and three active modes: a mode of increase of pressure, a mode of deduction of pressure and a pressure decrease mode.

Mode of normal braking (ABS it is not activated)

In a mode normal both braking (inlet and final) electromagnetic valves of the modulator деактивированы, i.e. the entrance port of the inlet valve is opened, target port of the final valve is closed and developed in ГТЦ the pressure of a hydraulic liquid completely is transferred to the wheel cylinder.

Pressure decrease mode (ABS it is activated)

Both (inlet and final) the electromagnetic valve are activated (the entrance port is closed, the day off is opened). In the given condition the wheel cylinder is isolated from ГТЦ, but connected to the tank and the brake liquid can freely flow in last that is accompanied by dump of hydraulic pressure and decrease in brake effort.

The liquid accumulating in the tank is pumped over by the pump back in the main cylinder. On continuation of all cycle of the given phase the pump continues to function.

Mode of deduction of pressure (ABS it is activated)

The inlet electromagnetic valve is activated also its entrance port closed. The final valve деактивирован, - its final port also is closed. All channels connecting the wheel cylinder with ГТЦ and the tank are blocked. As a result pressure is kept in the wheel cylinder.

On continuation of all cycle of the given phase the pump continues to function.

Mode of increase of pressure (ABS it is activated)

Both (inlet and final) the electromagnetic valve деактивированы (the entrance port of the inlet valve is opened, the target port of the final valve is closed). In the given condition forced ГТЦ working pressure moves in the wheel cylinder promotes increase of brake effort.

On continuation of all cycle of the given phase the pump continues to function.

Wheel gauges and their rotors

ABS in the electric way exercises administration of pressure in brake mechanisms of all wheels of the car, preventing premature blocking of the last at sharp braking. Each of wheels is equipped by the individual gauge of turns. The gauge consists of a rotor (a ring with teeth in regular intervals located on its perimetre) and a sensitive element in a kind подмагниченной coils. The sensitive element of the gauge fixes the moments of passage by it teeths of a rotor and will transform the received information to the electric signals continuously transferred to the module of management ABS. By results of processing of arriving signals the management module receives the information on relative speed of rotation of each of wheels. While all four wheels rotate with identical frequency, ABS stays in a passive condition. As soon as any of wheels starts to be blocked, the management block fixes change of an entering signal and develops a command on operation of the modulator instantly dumping pressure of a hydraulic liquid in the brake mechanism of the corresponding wheel.

The gauge-switch of stoplights

On the signals arriving from the gauge-switch of stoplights, the management block defines the moment when the driver squeezes out a pedal of a foot brake, at once activating ABS.

The gauge of overloads (G-gauge)

The G-gauge serves for revealing of the longitudinal accelerations of a vehicle connected with an acceleration/deseleratsiej and gives out on the block of management ABS the information in the form of alarm pressure.

Control lamp ABS

Control lamp ABS warns the driver about malfunctions of antiblocking system. The electric chain of the block of management / the hydromodulator is simultaneously broken off and the brake system continues to work in a normal mode (as in the absence of ABS). At short circuit of plugs of a diagnostic socket the lamp can be used as an output equipment stored in memory of the processor of codes of malfunction.

The module of management АТ (TCM)

On equipped АТ models TCM provides the control of a gear change and on the basis of arriving from the block of management ABS of the information can make activation of a mode of restriction on 3rd transfer (3D) or capacity redistribution between forward and back wheels of the car.