Clutch Servos - wabco india limited
Contents
1. Inlet Valve 12552 WABCO 4 Vehicle Control Systems Pin amp PISTONOFVALVE WHICH OPEN Working Position Pisto Air amp Oil Pressure available in the port Force in the push rod Clutch is Dis Engaged Driver depresses the clutch pedal volume goes to hydraulic chamber of clutch servo through oil port ee THE VALVE GOES TO THE ASSISTANCE ROOM IN ORDER TO TELP THE MOBIL UNIT AND GIVE HE FORCE AT THE PUSH ROD SEAY Hydraulic chamber OIL INLET lt pe FORCE AT THE t PUSH ROD AIR asi EN Ci SUPPLY 12552 WABCO g 5 Vehicle Control Systems Release Position Air amp Oil Pressure depleted Driver releases the clutch pedal Oil volume goes back to Master cylinder Air vented through Exhaust port Clutch is once again engaged f V EXHAUST OF THE AIR VOLUME FROM THE PNEUMATIC CYLINDER Duct Air from these chambers Vented to atmosphere Uem TO THE MASTER CYLINDER AT THE PEDAL cu UNIT FORCE AT THE PUSH ROD FROM THE CLUTCH SPRING AIR SUPPLY A cic 12552 CD WABCO Vehicle Control Systems Annexure 1 CLUTCH SERVO WEAR INDICATOR INSTALLATIONS INSTRUCTIONS L 7 T E T F i m T DEM LI J L E 1 Vehicle Control Systems Purpose To provide visual valuation of the wear from the clutch Operation The wear indic2. 0 Servicing of Clutch Servo No special maintenance is required for Clutch Servo in the field except for the following points 1 Check during routine vehicle maintenance for any leak in the joints both air and hydraulic 2 Check for tightness of mounting bolts Fork and bleeding screw 3 Clean the wear indicator and exhaust valve in case if it is soiled 4 Overhaul the unit using appropriate repair kit once in 3 years through SCL s Authorised Service Centre 7 0 Repair kit details Recommended Repair kit for 3 inch Clutch Servo to part no 9700514290 9700514300 and 9700514350 contains the parts as shown in the exploded view given below in page 5 Repair Kit BOM Ref No Description Qty 25 Protection plug for bleeder screw 1 no 23 O Ring 1 no 19 U Ring Hydraulic 1 no 20 O Ring 1 no 21 Guide 1 no 43 Retaining washer Wear Indicator 1 no 41 opring Wear Indicator 1 no 44 O Ring Wear Indicator 1 no 45 O Ring Wear Indicator Rod 1 no 4T Filter Air inlet 1 no 3 U Ring Pin 1 no 5 O Ring Piston 1 no U Ring Cartridge Outlet 1 no 8 U Ring Cartridge Inlet 1 no 10 Inlet Valve 1 no 11 U Ring Inlet valve 1 no 12 13 Spring Inlet Valve 1 no each 16 17 Exhaust protector assembly 1 no 29 Spring Piston 1 no 31 U Ring Piston 1 no 32 Hanger Piston 1 no 38 Front plate 1 no 33 O Ring 1 no 35 Retaining Ring
3. CD WABCO T vs Vehicle Control Systems Clutch Servo Service Manual Clutch Servos are used to reduce the force required to operate the clutch pedal and to permit sensitive and accurate actuation of the clutch in the vehicle Refer Fig 1 Two sizes are produced by WABCO 3 inch and 4 inch The size refers to the diameter of the pneumatic section of the clutch servo 1 0 Introduction Fig 1 MASTER CYLINDER ON pu A erm d eae ee a 2 Up LE A zm CE k d L CX 4 hE f a h 1 I e Pedal ratio an NNS 2 2 LIA L 2 2 Z y d EEG Dead stroke eg S2 Ratio V2 V1 absorption eee Absorption Dead stroke SLAVE CYLINDER CLUTCH SERVO a V1 F z Slt obsorption N Ex Clutch fork roti 5 At the clutch Stroke release beorin g 2 0 Design The Clutch servo consists of three parts Hydraulic slave cylinder Control Valve Pneumatic Servo cylinder some of the other optional accessories available with clutch servo are Electrical trigger through a electrical sensor to activate transmission control Mechanical wear indicator Page 1 3 0 Operation The clutch servo has two ports one for oil inlet and other for air inlet Oil inlet port connects with the Ma
4. Push rod 1 no 37 Sealing Ring Front plate 1 no A Grease Sachet 1 no Reference no as shown in exploded view Page 4 Parts that are shown as 5 forms part of Repair Kit 970 051 9702 970 051 4290 370 051 4300 970 051 435 0 Las picos sont dans la pochalte Particolare conlanuto nel comedo AHwnrhen par les darb AEC umquam Acti ng Pie n Test Ahengi E Dl Tc a Bc ge ia e aa Ahan ng er iweonrkoshion peril ed beri Er Ls a Laie ree se 1 oe oa 2 qn JN 010 AM lt 0 Diese Toile sind im Reparatursaiz enihalien Estas piezas estan incluktas on ol conj de reparaci n WARNING These parts aro included in the repair kit Issue no 1 Jan 07 Page 5 ED WABCO Vehicle Control Systems Fig 2 Port Details ELECTRICAL INFORMATION L FORCE OUTPUT ag ma T OIL INLET E AIR SUPPLY Pneumatic section AIR EXHAUST Control Valve 11 Air Inlet port 1 4 Oil Inlet Electrical Sensor Optional Fig 3 AT REST Position Air Pressure only available in the port No Force in the push rod Clutch is Engaged a uo SUPPLY WABCO Vehicle Control Systems Air pressure around
5. and reassembly in the vehicle bleeding should be done properly for proper functioning of clutch servo It is recommended to carry out pressurized bleeding through the bleed screw of the clutch servo since this ensures proper bleeding and saves time In case manual bleeding is done please follow the procedure given below Manual bleeding of Clutch Servo 1 Top off clutch master cylinder reservoir and fill adequate amount of fluid 2 Put a transparent Plastic tube or hose on the clutch servo bleeding nipple and submerge the other end of tube in a jar with some hydraulic fluid 3 Slowly depress the clutch pedal 4 Slightly loosen the nipple 5 While fluid is traveling through the plastic tube tighten the bleeder before the pedal is fully released 6 Release the pedal Repeat the procedure until No bubbles appear in the fluid section The bleeder nipple was opened after the clutch pedal started depressing and was closed before the pedal reached the bottom Mounting Using M8 Screws and nut with lock washer Fork Assembled with Lock nut Hydraulic piping Air pipes Min 6mm Inner diameter Hydraulic pipe Min 5mm Inner diameter for length upto 4m Min 6mm Inner diameter for length exceeding 4m Avoid routing the hydraulic pipes without any high points in between which may result in air trap as shown below c Master cylinder Clutch servo Recommended Hydraulic fluid Brake Fluid to SAE J1703 Page 3 6
6. ator is integrated into the clutch servo body The rod is held by an internal friction system and it rests against the moving piston of the clutch servo The rod will project out more when the clutch is worn The clutch wear can be assessed by measuring the gap between the self locking washer and the plastic body of the indicator Picture 4 Initialization See next explanations When assembling of the clutch servo When exchange of the clutch CL na iit i A L P Vehicle Control Systems Initialization When assembling the clutch servo in the vehicle The clutch servo is delivered with the wear indicator in the fully inserted position Picture 1 The initialization has to be done after completing the fitment of clutch servo on vehicle Housing or Bracket Picture 2 After fitment push the lock washer on the rod alone until it comes in contact with the body of indicator This position is called position 0 Picture 3 CL Noy iil J L P J Vehicle Control Systems When changing the clutch during service When a new clutch is mounted then the piston is in its original position After assembly push back the rod along with washer until it comes in contact with the body Some times the washer of wear indicator is put out when the rod is pushed until the piston in such case a new washer internal star washer to be asse
7. mbled on the rod after pushing CL Noy DELIVERY POSITION Body of wear indicator Washer self locking Rod Picture 1 WABCO Vehicle Control Systems MOUNTING POSITION Rod amp Washer are moved back by the piston when mounting Picture 2 CD TVS INITIALIZED POSITION Washer pushed along the rod until body of wear indicator Position O Picture 3 WABCO Vehicle Control Systems WORN POSITION Wear stroke of clutch Picture 4
8. ster Cylinder operated by clutch pedal The air inlet port takes air from the auxiliary reservoir connected to port no 24 of system protection valve Refer fig 2 for details a At Rest Position Refer Fig 3 During this position air from reservoir enters the air inlet port and will be acting around the inlet valve There is no oil pressure in the oil inlet port of the clutch servo The push rod will not travel and generate any force b Working position Refer fig 4 During working position the driver depresses the clutch pedal The pressurized oil from Master Cylinder enters the hydraulic chamber and applies force on the hydraulic rod which in turn provides force output in the push rod Pneumatic assistance The hydraulic pressure acting inside the chamber will also push the PIN amp PISTON of the control valve closing the exhaust opening and Opening the air passage by pushing down the air inlet valve Air from the inlet port now flows through the cross hole to the pneumatic chamber acts on the piston providing assistance Pneumatic and Hydraulic pressure acting on the push rod together will disengage the clutch The air pressure in the chamber below the piston balances the hydraulic pressure acting on the Pin c Release stroke Refer fig 5 When the driver releases the clutch pedal oil from hydraulic chamber returns back to master cylinder The hydraulic pressure reduces and the pin moves up This will make the inlet valve to ret
9. urn back to the original position by return spring closing the air inlet passage Further movement of the pin to the topside will make the exhaust passage to open Air from the pneumatic chamber is vented through the exhaust retracting the push rod This will cause the clutch to engage The air circulation to chamber A will be through the duct which is connected to atmosphere through the exhaust valve The chamber in B remains proportional to the hydraulic pressure at all times thus giving the driver full control when engaging back the clutch In case if there is no air available in the reservoir or the pressure falls down to lower value it is still possible to operate the clutch only with the hydraulic pressure However this requires a greater force to be applied by the driver 4 0 Wear Indicator All the clutch servos supplied to AL are provided with Wear Indicator as shown in figure 1 The purpose of wear indicator is to show the amount of wear taking place in the clutch Method of adjusting wear indicator is given Annexure 1 Page 2 5 0 Installation Requirements The clutch servo should always be installed in horizontal position with the exhaust facing downwards The bleeding screw should always be positioned in such a way that it should facilitate easier bleeding during installation While assembling the Fork to the push rod of clutch servo ensure the stand out is maintained as per recommendations given by the OEM While servicing
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