11.1. General information and security measures
The brake system consists of the main brake cylinder, the vacuum amplifier and disk brake mechanisms of forward and back wheels and is divided according to the diagonal scheme into two independent hydraulic contours. At refusal of any of contours (for example as a result of sealing violation) the second continues to function in the normal mode, providing adequate braking of the vehicle. In addition pressure valve regulator providing dynamic correction of effort of braking of back wheels according to change of load of a back axis of the car is built in contours of both back brake mechanisms. Liquid pressure in both contours is created by the main brake cylinder (MBC) having a tandem design. Activation of GTTs happens when squeezing a pedal of a foot brake.
Scheme of the organization of a hydraulic actuator of brake mechanisms
The short description of the principles of functioning of auxiliary electronic systems of anti-blocking of brakes (ABS), strengthenings of emergency brake application (BAS), distribution of brake efforts (EBV), antiprobuksovochny (ASR/4-ETS) and antistrange (ESP) is provided in the Head Governing bodies and methods of safe operation.
Scheme of an arrangement of components of system of strengthening of emergency brake application (BAS)
Scheme of an arrangement of components of the auxiliary electronic ASR/ETS/ESP systems
The tank with brake fluid is under the main brake cylinder, it supplies with liquid all hydraulic system of braking.
The amplifier of a brake accumulates a part of the vacuum created in the soaked-up engine pipeline. As the diesel engine has no necessary vacuum on absorption, cars with the diesel engine have the special vacuum pump. By means of the corresponding valve if necessary the effort to pedals of a brake increases thanks to effect of vacuum.
The parking brake with the pedal drive influences through cables brake mechanisms of back wheels. In addition back brake mechanisms are equipped with drum knots of the parking brake with a pedal trosovym the drive.
Principles of functioning of the auxiliary ABS/4-ETS/ESP/EBV systems
The electrohydraulic scheme of functioning of auxiliary systems is submitted on an illustration to which all references which are found in the text belong.
Scheme of a hydraulic contour of the auxiliary electronic ABS/4-ETS/ESP/EBV systems
Components of systems of the closed contour of dynamic control of the ABS, 4-ETS/ASR and ESP systems are a part of the hydromodulator of auxiliary brake systems (A7/3).
Pressure head and returnable pump (A7/3m1)
The self-filled pressure head and returnable pumps (p1, p2) are built in assembly of the hydromodulator (A7/3) and are switched by pulse signals in phases of forcing and dumping of pressure of system of active management of ETS and ESP, and also during adjustment of a returnable stream at ABS activation.
The self-filled pressure head and returnable pumps (p1, p2) are started if necessary for the purpose of minimization of noise level.
Each brake contour is equipped with the separate damper (10) reducing the level of the noise made by the pump.
Electromagnetic valves of deduction (inlet) and dumping (final) pressure (A7/3y6 - A7/3y13)
One 2/2-hodovy valve is used at management of pressure in contours of each of wheels in phases of forcing/deduction and deduction/dumping of the operating ABS, ETS and ESP modes.
Low pressure accumulator (11)
The low pressure accumulator (11) is filled with brake fluid in a phase of dumping of pressure of ABS, ETS or ESP and provides its transfer to pressure head returnable pump (p1/p2).
The operating multiple-pass electromagnetic valves (A7/3y24 and A7/3y25)
Electromagnetic multiple-pass valves switches (y24 and y25) provide a cut-off of active pressure head diagonal contours from GTTs during functioning of ETS and ESP. Also valves provide dumping of pressure at rise it over 150 atm. The brake fluid passed via valves switches goes back to GTTs.
Electromagnetic valves of preliminary filling (A7/3y26 and A7/3y27)
Valves (y26, y27) open in phases of increase of pressure ETS/ESP.
The principle of functioning of assembly of the sensor of the taking-away moment / cross overloads of ESP
Sensors of the taking-away moment and cross overloads for economy of the place are united in uniform assembly (B24/2). Micromechanical touch assembly will transform cross and vertical projections of angular accelerations to electric signals. Working elements, various on weight, under the influence of arising during not inertial movement of the vehicle (commission of turns and accelerations) of overloads provide various extent of deformation. The special electronic converter converts the received signals and on the tire of CAN transfers them on the module control of antiprobuksovochny and antistrange systems (N47).
The sensitive element of the sensor of the taking-away moment is created from the micromechanical ring (a) equipped with eight spring crossing points (b) providing its movement and electromagnetic action. At rotation in assembly there are additional Coriolis forces proportional to rotation speed fixed in an electromagnetic way and, after transformation in the ACIS module to a form of analog signals, combinations of devices given on the control unit.
Design of the capacitor sensor of the taking-away ESP system moment
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and — the Silicon ring |
with — the Electronic sensor |
The principle of measurement of cross overloads is based on use of a spring and mass element with the capacitor detector. Working tension moves from the module of management of ESP (N47-2).
The cross overloads arising during commission of turns provide the shift of a spring and mass element from balance position at a size proportional to value of the arising reaction force. Any change in the provision of an element leads to change of capacity of the detector. Further, the recorded size of a deviation will be transformed to the alarm tension allowing the module of management of ESP (N47-2) to make quantitative assessment of sizes of the fixed cross overloads.
The electronic module of management watches that the system, in case of mechanical damages of a contour (for example, break of a cable), or at excessive power failure, was automatically disconnected. The situation is displayed on the dashboard by activation of a control lamp of ABS. At the same time there is a shutdown of the ESP and BAS systems that is confirmed by operation of the corresponding indicator (see the Head Governing bodies and methods of safe operation). The main brake system continues keeps at the same time the working capacity, - during braking the car behaves as if the ABS system is absent.
Activation during the movement of a control lamp of ESP demonstrates detection of malfunction of the amplifier of emergency brake application (BAS) or antistrange system (ESP), - the corresponding systems at the same time are also disconnected with preservation of ability of functioning of the main brake system.
At activation during the movement of a red control lamp of the brake system, it is necessary immediately to stop and try to establish to find out a cause of infringement which can be in particular a falling of level of brake fluid, or not up to the end released lever of the parking brake.
Operations procedure at operation of a control lamp of ABS during the movement
Stop the car, switch off the engine and again start it.
Check the level of tension of the rechargeable battery, - if the result of measurement makes less than 10.5 In, make recharge of the battery.
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If the control lamp of ABS lights up in a start of motion and then after a while dies away, then it indicates the low voltage of the rechargeable battery which increases after the beginning of operation of the generator. |
Make sure of reliability of fastening of tips of wires on polar plugs of the battery, in case of need tighten fixture.
The car also establish to Poddomkratta it on props, remove wheels and check a condition of an electrical wiring of wheel sensors.
More detailed diagnostics has to be carried out in conditions HUNDRED with use of the special equipment for reading of the codes of malfunctions (DTC) which are written down in memory of the module of management.
Security measures
- Brake fluid is among highly toxic and chemically aggressive connections and at contact with body panels destroys a paint and varnish covering!
- The brake dust produced in the course of wear of brake shoes may contain unhealthy asbestos of the person, - at all do not inhale it when cleaning brake mechanisms!
- Work with the brake system demands special purity and exact observance of instructions. In the absence of necessary experience it is expedient to address on HUNDRED.
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At movement along wet roads it is necessary to press periodically a brake pedal for removal of moisture from brake disks |
- In the course of rotation of a wheel moisture under the influence of centrifugal force is dumped from brake disks, but there is a silicone film, rubber attrition products, lubricant and other pollution reducing efficiency of braking!
- After installation of new brake shoes the last have to be earned extra, - try to avoid sharp braking the first 200 km of a run after replacement performance!
- The disk brake mechanisms damaged by corrosion when braking create the effect of jolting which is not disappearing over time, - replace disks!
- Burning of dirt to a surface of brake shoes is led to formation of furrows on a surface of brake disks that leads to decrease in efficiency of braking!