1600459, OPR, HYSTER, Hyster2, SRM

//-->.pos {position:absolute; z-index: 0; left: 0px; top: 0px;}THE STEERING SYSTEMGENERALThis section describes the steering system. Descriptionand operation information is given for the system, hy-draulic pump, flow control valve, steering control unit,and the steering wheel and column assembly. Repair in-formation for the steering cylinder, the hydraulic pump,and the steering control unit is given in the sectionsTHE STEERING AXLE, 1600 SRM 10and1600SRM 258andTHE HYDRAULIC SYSTEM ANDGEAR PUMP ASSEMBLY, 1900 SRM 130andTHESTEERING CONTROL UNIT, 1600 SRM 257.In-formation for pump drive assembly on the GM enginesis inTHE HYDRAULIC PUMP DRIVE ASSEM-BLY, 1900 SRM 339.1.2.3.4.5.STEERING CONTROL UNITMAIN CONTROL VALVEFILTERBREATHERHYDRAULIC TANKDESCRIPTION(See FIGURE 1. and FIGURE 2.)The power steering system has no mechanical link be-tween the steering column assembly and the steerwheels. The control of the steering is through a hydrau-lic circuit. The hydraulic oil flows from the hydraulicpump through the steering control unit and returns to thehydraulic tank.The steering control unit is a rotary valve operated bythe steering wheel. When the steering wheel is notmoved, this rotary valve has a minimum restriction to oilflow. During the steering operation, the steering controlunit sends and controls the oil flow to the steering cylin-der. Hydraulic oil returns from the opposite end of thesteering cylinder to the steering control unit and then re-turns to the hydraulic tank.6.7.8.9.10.11.12.13.14.15.SCREENDRAIN PLUGTEST PORTSTEERING CYLINDERHYDRAULIC PUMPFLOW CONTROL VALVE ANDRELIEF VALVETO UPRIGHTTO/FROM TILT CYLINDERSTHIS RETURN LINE ON ALL UNITSEXCEPT THOSE UNITS WITH GMENGINETHIS RETURN LINE GOES TOCHAIN DRIVE FOR HYDRAULICPUMP ON UNITS WITH GM ENGINE9602FIGURE 1. STEERING SYSTEM COMPONENTS1126231.2.3.4.5.6.HYDRAULIC TANKFILTERHYDRAULIC PUMPFLOW CONTROL VALVERELIEF VALVESTEERING CONTROL UNIT7.8.9.10.11.STEERING WHEELSTEERING CYLINDERTEST PORTTO MAIN CONTROL VALVERETURN LINE ON ALLUNITS EXCEPT THOSEWITH GM ENGINE12. RETURN LINE*13. LUBE LINE, DRIVE CHAIN*14. JET PUMP*15. HOUSING, CHAIN DRIVE**ON UNITS WITH GM ENGINE ONLY.FIGURE 2. STEERING SYSTEM, HYDRAULIC SCHEMATICIf the hydraulic pump does not operate, a check valvecloses and permits the steering control unit to continuecontrol of the steering system. The lift truck is difficultto steer when the steering pump does not operate,. Thesteering control unit can make the hydraulic pressurenecessary to steer the lift truck.The hydraulic circuit for the steering system has the fol-lowing parts: hydraulic tank, hydraulic pump assembly,steering control unit, steering cylinder, filter andbreather. The steering system, and the lift and tilt systemare separate systems of the hydraulic system. Both sys-tems use the common hydraulic tank and hydraulicpump. A breather lets air into the hydraulic tank and aplug can be removed to drain the tank.Oil from the tank is supplied to the hydraulic pump.When the steering wheel is stationary, the oil flow is di-rected to the main control valve. When the steeringwheel is turned, oil flows to the steering control unit.Four lines connect the steering control unit to the supply(IN) port, return (OUT) port, left (LT) and right (RT)steering cylinder ports.2Hydraulic Pump Assembly (See FIGURE 3.)The hydraulic pump assembly has the hydraulic pump, aflow control valve and a relief valve. The valves are inthe end housing of the assembly. The inlet is in the sideof the pump body. The pump outlet connects directly tothe end housing and the flow control valve. The flowcontrol valve has the outlet for the primary flow and theoutlet for the secondary flow. The primary flow is for thesteering control unit. The end housing has an internalpassage that directs oil flow from the relief valve to theinlet side of the pump gears through a passage in thepump body.The hydraulic pump assembly fastens to the engine atthe timing gear cover. The splines of the pump shaft fitinto a gear on the engine which turns the pump shaftwhen the engine operates. The shafts on each side of thegears have bushings. The bushings have passages for theoil flow to the pump outlet and for lubrication. Seals pre-vent leaks between sections and the outside of the pump.1.2.3.4.5.6.7.8.9.10.11.12.13.14.SNAP RINGOIL SEALHOUSING, FLANGE ENDBACK–UP RING, LEFT (2)BUSHINGBACK–UP RING, RIGHT (2)BUSHING (2)DRIVEN GEARDRIVE GEAR AND PUMP SHAFTHOUSING, VALVE ENDO–RINGSEAL, BUSHINGSEAL, BODYPUMP BODY12642DIESEL SHOWNFIGURE 3. HYDRAULIC PUMP ASSEMBLYFlow Control Valve (See FIGURE 4.)The flow control valve makes sure the steering systemhas a constant supply of oil. The flow control valve has aspring, a plunger with an orifice, and two plugs with O–rings. The spring keeps the plunger in the correct posi-tion. Oil pressure can move the plunger and compressthe spring. The plugs keep the plunger and spring in thebore and they also keep the oil in the correct chamber.O–rings are used to seal the plugs.Relief Valve (See FIGURE 5.)A relief valve in a bore in the end housing of the hydrau-lic pump prevents the oil pressure in the steering systemfrom increasing above specifications. The relief valvehas the following parts: a relief valve housing, a poppet,a spring, an adjuster, a lock nut and O–rings. The posi-tion of the adjuster and the amount of compression of thespring determine the relief valve pressure. When the ad-justment is correct, the lock nut will hold the adjuster inthe correct location and O–ring will seal the adjusteragainst the relief valve housing.OPERATIONSteering System(See FIGURE 1. and FIGURE 2.)The hydraulic pump sends oil flow to the steering sys-tem and the lift and tilt system. The hydraulic pump re-ceives oil from the hydraulic tank through a screen at theoutlet of the tank. The oil from the pump flows directlyto the flow control valve. The flow control valve sup-plies a constant flow of oil to the steering system. Thisoil flow is controlled by the steering control unit to oper-ate the steering cylinder. The relief valve on the hydrau-lic pump assembly limits the pressure in the steeringsystem. On units not using a GM engine, oil from thesteering system is returned to the hydraulic tank. Onunits with a GM engine, the oil flows to the chain driveassembly for the hydraulic pump.3limits the pressure in the system. The test port is at theright turn (RT) connection of the steering control valve.The oil returning from the main control valve flowsthrough a filter in the oil line and then to the tank. Thefilter removes small particles from the oil.Hydraulic Pump (See FIGURE 3.)The engine turns the shaft of the hydraulic pump. Thedrive gear of this shaft turns the driven gear of the pump.The gear teeth of the pump have a close tolerance. Thegears also have a close tolerance to the pump body andthe bushings. The tolerances and seals make tight cham-bers between the gear teeth. When the teeth of each gearmove apart at the inlet port, they make a vacuum. Oilfrom the tank enters the inlet port and is moved by thegear chambers around the circumference. Passages onthe opposite side of the inlet connect the gear chambersfor the outlet oil to the flow control valve. Oil at the inletflows through bores and passages in the bushings to bothsides of each bushing. Oil lubricates the bushings andthe gear surface of each bushing. Other bores and pas-sages in the bushings let the outlet oil go to the sides ofthe bushings away from the gears.Flow Control Valve (See FIGURE 5.)The oil at the outlet of the hydraulic pump enters thevalve chamber near the center of the plunger (20). Theoil flows through the orifice (16) in the plunger to thesteering system port. This oil also flows to the reliefvalve (23). If the oil flow at the pump outlet is more thanthe primary flow (13) for the steering system, theplunger will move. This plunger movement allows thesecondary flow to go to the lift and tilt circuit (12). Theplunger will also move and decrease or stop the flow ofoil to the lift and tilt system if the pump flow decreases.The plunger continues to move to make sure the steeringsystem always has a constant supply of oil.Relief Valve (See FIGURE 5.)The pressure in the steering system is sensed at the reliefvalve (23). If the pressure increases to the relief valvesetting, the poppet (8) in the relief valve will moveagainst the spring (2). When the poppet moves off theseat, oil flows through an internal passage (17) that di-rects the oil flow to the pump inlet to decrease the pres-sure. The decrease in pressure lets the spring return thepoppet back to the seat.126421. PLUG (2)7. POPPET, RELIEF VALVE2. O–RING (2)8. RELIEF SPRING3. HOUSING,9. ADJUSTERVALVE END10. LOCK NUT4. O–RING (1)11. REGULATOR SPRING5. O–RING (2)12. ORIFICE6. HOUSING,RELIEF VALVE 13. REGULATOR PLUNGERFIGURE 4. FLOW CONTROL VALVE ANDRELIEF VALVE PARTSThe secondary flow from the pump goes to the maincontrol valve. A relief valve on the main control valve4123456789171020191892322211.2.3.4.5.6.7.8.9.10.11.12.13.14.15.16.17.18.19.20.21.22.23.161115912651121413ADJUSTERRELIEF SPRINGLOCK NUTBACK–UP RINGO–RINGHOUSING, RELIEF VALVEO–RINGPOPPETFLOW, RELIEF PRESSUREO–RINGCHECK BALLPORT TO LIFT SYSTEMPRIMARY FLOWPORT TO STEERING SYSTEMREGULATOR SPRINGORIFICEINTERNAL PASSAGE FOR RELIEFPRESSURE TO THE PUMP INLETPORT, PUMP OUTLET/VALVE INLETSECONDARY FLOWREGULATOR PLUNGERPUMP HOUSINGFLOW CONTROL VALVE(REGULATOR) SECTIONRELIEF VALVE SECTIONFIGURE 5. OPERATION OF THE FLOW CONTROL VALVE AND RELIEF VALVESTEERING WHEEL AND COLUMNASSEMBLYThe steering wheel attaches to the steering shaft withsplines. See FIGURE 6. and FIGURE 7. A large nutholds the steering wheel onto the steering shaft. Thehorn button is the cover for the center of the steeringwheel. The lower end of the steering shaft is machinedand engages the drive plate inside the steering controlunit. The shaft and steering control are fastened insidethe column assembly.Removal (Serial Code C177 And C187)1. Remove the horn button and switch assembly. Re-move the large hex nut. Use a puller to pull the steeringwheel from the shaft.2. Remove the the two instrument panels from the col-umn housing and disconnect the wires.3. Remove the two capscrews that fasten the columnhousing to the support bracket. Remove the columnhousing.4. Make an identification of the hydraulic hoses at thesteering control unit so that the hydraulic hoses can becorrectly connected during assembly. Disconnect thehydraulic hoses at the bottom of the steering controlunit.5. Remove the lock nuts and flat washers that fasten thesteering control unit to the bracket on the cowl of the lifttruck. Remove the steering control unit and shaft assem-bly from the lift truck.6. Remove other parts as needed for repair.Installation (Serial Code C177 And C187)1. Install any parts of the support bracket that were re-moved (see FIGURE 6.)2. Install the steering control unit and shaft assemblyinto the support bracket.3. Install the four hydraulic lines to the correct port con-nections on the steering control unit.WARNINGIf the hydraulic lines are incorrectly installed, re-verse steering can occur, the steering operation canbe unpredictable, or the steering wheel can turnwithout the operator’s motions.4. Make sure the rubber seal is installed in the top of thecolumn housing. Guide the top end of the shaft through5

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