1600378, OPR, HYSTER, Hyster2, SRM

//-->.pos {position:absolute; z-index: 0; left: 0px; top: 0px;}INTRODUCTIONGENERALModels of the N40-50EA and N40-45ER series have a powersteering system. This section describes the disassembly andassembly of the steering system for repairs. There is a descrip-tion for each part of the steering system at the beginning ofeach repair section. The steering system rotates the master driveunit (MDU) to steer the lift truck. The pump for this systemalso supplies oil to operate auxiliary hydraulic functions whenthe lift truck has these functions.THE STEERING CONTROL UNIT, 1600 SRM 54This section has the description, operation, checks and trouble-shooting for the steering control unit. The shaft and columnassembly on the N40-50EA and N40-45ER units is not asshown. Removal and installation of the steering control unit isin this section (STEERING SYSTEM, 1600 SRM 378).NOTE: Many of the procedures need the door open. To openthe door, remove the capscrew at the top of the left-hand postfor the overhead guard to permit the post to move with thedoor. Then, remove the screw that fastens the door and openthe door. Make sure to tighten the capscrew at the top of thepost after closing the door.DESCRIPTION(See Figure 1)The power steering system is a hydraulic system. The controlof the steering is through a hydraulic circuit. An electric motorfor the steering pump is energized when the key switch is inthe “ON” position and the brake switch is closed. When theelectric motor operates the steering pump, hydraulic oil flowsthrough the power steering system. Moving the steering handlerotates the shaft of the steering control unit. The steering con-trol unit controls the flow of oil to the hydraulic motor on theaxle weldment. The hydraulic motor moves a chain to rotatethe MDU and steer the lift truck.The hydraulic oil flows from the gear pump through the steer-ing control unit and returns to the hydraulic tank when theAdditional information for the components of thesteering systemis found in the following sections:THE MASTER DRIVE UNIT, 630 SRM 283This section has the description, repair and adjust-ments for the Master Drive Unit (MDU). The MDUis part of the axle assembly. Removal and installa-tion of the MDU us in this section (STEERINGSTSTEM, 1600 SRM 378).THE DC MOTOR, 620 SRM 145This section has the general description and operation of Di-rect Current (DC) motors. Removal and installation of the trac-tion and steering pump motors is in this section (STEERINGSYSTEM, 1600 SRM 378).D.C. MOTOR MAINTENANCE, 620 SRM 294This section has the general maintenance procedures for DCmotors.HYDRAULIC GEAR PUMPS, 1900 SRM 97This section has the general description and repair for gearpumps. The steering pump and internal parts are not as shown.Use the general repair procedures. Use the correct repair kit(see Parts Manual) when repairing the steering pump. Removaland installation of the steering pump is in this section (STEER-ING SYSTEM, 1600 SRM 378).FIGURE 1. STEERING SYSTEM COMPONENTSSTEERING CONTROL UNIT ASSEMBLYsteering control unit.The steering control unit is a ro-tary valve. When the steering handle is not moved,The steering handle is fastened to the shaft of the this rotary valve has a minimum restriction to oil flow.steering column. This shaft engages the spool of the During the steering operation, the valve controls theoil flow to the hydraulic motor. The unit controls boththe direction of oil flow and theDESCRIPTION(See Figures 2 and 3)FIGURE 2. STEERING SYSTEM, HYDRAULIC SCHEMATIC (1 OF 2)regulation of oil flow to operate the hydraulic mo-tor. If the steering pump does not operate, a checkvalve closes in the steering control unit. The steer-ing control unit can then operate as a hand pump tomake steering possible. The lift truck is difficult tosteer when the power steering is not operating. Theassembly is fastened to the frame weldment of thelift truck by two of the capscrews that also hold theassembly together.steering handle. Carefully pull the steering handlefrom the shaft. Do not let the woodruff key fall. Thekey is between the shaft and the steering handle.C. Remove the two capscrews and lock washers thatfasten the steering control unit to the bracket. Donot let the steering control unit fall.D. Make an identification of the hydraulic hoses atthe steering control unit so that the hydraulic hosesREMOVAL (See Figure 3)can be correctly connected during assembly. Dis-connect the hydraulic hoses and install caps on theA. Pull the Battery Disconnect to disconnect the bat- hoses and the ports of the steering control unit totery. Open the door of the motor compartment. keep dirt out.NOTE: See the section THE STEERING CON-B. Remove the cap over the hub of the steering han- TROL UNIT, 1600 SRM 54, to repair the steeringdle. Remove the nut and washer that fasten the control unit.FIGURE 2. STEERING SYSTEM, HYDRAULIC SCHEMATIC (2 OF 2)INSTALLATION(See Figure 3)A. Connect the hydraulic hoses to the steering con-trol unit. Make sure each hydraulic hose is connectedto the correct port on the steering control unit as iden-tified during removal.B. Install the two capscrews and lock washers to fas-ten the steering control unit to the bracket of the lifttruck.C. Install the woodruff key in the shaft and carefullyinstall the steering handle on the shaft without mov-ing the woodruff key out of position.D. Install the nut and washer on the shaft to fastenthe steering handle.E. Connect the battery and move the steering handlefor a complete turn in each direction to remove theair from the system. Check for leaks.FIGURE 3. STEERING CONTROLUNIT ASSEMBLYSTEERING PUMP MOTOR AND PUMPDESCRIPTION(See Figure 4)This motor and pump also supply oil for the auxil-iary hydraulic functions. The steering pump motorand pump are fastened to the lift truck frame in avertical mount at the left front corner of the motorcompartment. A strap fastens the motor contactor tothe motor. The steering pump motor and pump op-erate when the key switch is “ON” and the operatorhas the brake pedal pushed. There is no shaft seal atthe pump drive shaft. A passage from the pump per-mits oil to fill the cavity between the pump and mo-tor for lubrication of the shaft drive. The oil seal atREMOVAL AND DISASSEMBLYthe motor keeps oil out of the motor.(See Figures 4 and 5)The outlet (pressure port) of the pump is connectedto the steering control unit or the main control valvewith a hydraulic hose. A relief valve in the outlet ofthe pump controls the pressure of the steering sys-tem on the N40-50EA and later N40-45ER units. Thisrelief valve also controls the pressure of the auxil-iary functions on the N40-45ER units. A relief valvein the main control valve controls the pressure forthe steering system on the early N40-45ER units.There is a test port for system pressure at the bottomof the pump.The steering and auxiliary pump is a small gear pump NOTE: The steering pump motor must he removedthat is fastened to the permanent magnet DC motor. from the mounts on the frame when the brushes mustThe inlet (suction port) of the pump is connected to be replaced.the hydraulic tank with a hydraulic hose.

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