GENERAL
INTRODUCTION
This section has the description and repair procedures for the steering housing and the steering control unit. Additional information on parts of the steering system are in the following sections: STEERING AXLE and HYDRAULIC SYSTEM.
DESCRIPTION
This section covers the steering column assembly used on the “XM” series of lift trucks. This assembly uses a steering control unit with hose connections on the bottom of the unit. See FIGURE 4. The steering housing has the mounts for the steering column and the steering control unit. The steering wheel is installed on the steering column. The housing is adjustable and is held in position by a latch. The position of the housing can be changed for operator comfort. The steering housing is also the mount for some control levers and the instrument cluster.
The steering system is a hydraulic system that does not have a mechanical connection between the steering wheel and the steering axle. The control of the steering is through a hydraulic circuit.
If the hydraulic pump for the steering system does not operate, steering is still possible. A check valve permits the steering control unit to control the steering cylinder The lift truck is difficult to steer when the steering pump is not operating, but the steering control unit can operate the steering cylinder and make steering possible.
OPERATION (See FIGURE 2.)
The steering control unit is a rotary valve operated by the steering wheel. During the steering operation, the steering control unit controls the direction of flow and amount of oil that flows to the steering cylinder. The steering cylinder in the axle actuates the steering linkage to move the steer tires. Hydraulic oil returns from the steering cylinder to the steering control unit and then returns to the hydraulic tank.
Turning the steering wheel actuates three main parts of the steering control unit: (1) The spool for the control section, (2) the sleeve for the control section and (3) the rotor in the metering section. When the steering wheel is not moving, the spool and sleeve are held in the neutral (center) position by springs. During this time, oil flows
freely through the steering control unit. The oil does not flow to the steering cylinder.
As the steering wheel is turned, the spool just begins to rotate. The springs try to move the sleeve to keep the neutral position between the spool and sleeve. However, the force necessary to turn the rotor is greater than the pressure of the springs. The springs begin to bend, letting the spool move a small amount within the sleeve. The spool stops moving when it touches the center pin. In this position, the holes in the sleeve and the spool are aligned. Oil coming into the control unit flows to the metering section.
More rotation of the steering wheel causes the spool to rotate the pin. This action causes the rotation of the sleeve and the rotor in the metering section. The oil then
flows to one side of the steering cylinder. Hydraulic oil from the other side of the steering cylinder returns through the control section of the steering control unit.
When the steering wheel stops moving, the metering action in the metering section also stops. The neutral position springs return the sleeve to the neutral position stopping oil flow to or from the cylinder. The pressure
stays in the steering cylinder to keep the steer tires in position. Oil from the pump flows through the steering control unit to the tank or other parts of the system. To return the steer wheels to the straight position, the steering wheel must be rotated in the opposite direction. The steering control unit will operate as described, but all parts will rotate in the opposite direction.
REPAIRS
STEERING WHEEL AND COLUMN ASSEMBLY
(See FIGURE 3. through FIGURE 5.)
The upper end of the steering shaft has splines for the steering wheel. A large nut holds the steering wheel onto the steering shaft. The horn button is the cover for the center of the steering wheel. The lower end of the steering shaft has splines or a tang to engage the steering con-
trol unit. A push rod from the horn button actuates the horn switch.
The steering column assembly is adjustable and held in position by a latch. The position of the steering column assembly can be changed as needed for different operator requirements. An access cover on the steering column give access to the steering control unit, key switch, horn switch and if installed, the direction switch.
11. CONTROL UNIT MOUNT BRACKET
13.LATCH
14.SPRING
15.PIN
16. DRIVEN GEAR
17. DRIVE GEAR
18.BRACKET
19. OPTICAL
20.TRANSDUCER
21. DIRECTION SWITCH
1. STEERING COLUMN
2. STEERING CONTROL UNIT
3.BRACKET
4. STEERING WHEEL
5. STEERING SHAFT
6. HORN COVER
7. BASE PLATE
8.BEARING
9. PLASTIC TUBE
10. PLASTIC WASHER
11.SPRING
12.LATCH
13. LOCK RING
14. ADJUSTER SPOOL NUT
15. STEERING WHEEL NUT
16. EXTERNAL SNAP RING
17. INTERNAL SNAP RING
18. PUSH ROD
19.PIN
20. HORN SWITCH
21.BRACKET
22.LATCH PIVOT PIN
23. SOCKET HEAD SCREW
Removal Of The Assembly Components
(See FIGURE 3., FIGURE 4. and FIGURE 5.)
NOTE: This procedure is for the removal of all components of the steering column assembly. All components are not often removed for a repair procedure. Do only those steps of the procedure necessary to remove the required component.
CAUTION
Disconnect the negative battery cable on internal combustion trucks. Disconnect the battery connector on electric trucks. Disconnect the battery before removing any covers.
1. Attach a tag on the battery connector or negative cable stating “DO NOT CONNECT BATTERY”. Move the steering column to the most forward position. Remove the access cover from the steering column.
2. Remove the key switch from the housing of the steering column. Make an identification of the electric wires and disconnect them from the key switch.
3. On units with the Direction Control Handle, remove the handle, dust cover and large nut that fastens the direction switch. Remove the direction switch from the housing of the steering column. Make an identification of the electric wires and disconnect them from the direction switch.
4. Remove the capscrew that fastens the bracket for the horn switch to the housing of the steering column. Move the horn switch and bracket away from the steering column.
5. Remove the horn cover, snap ring and base plate (no base plate in Petri steering wheel, see FIGURE 5.). Lift the push rod and adjuster spool from the top of the steering shaft. Remove the large hex nut and remove the steering wheel from the shaft. A puller makes removal of the steering wheel easier, but not all steering wheels have puller holes.
6. Some electric units have On–Demand steering. Remove the optical encoder and activator and the brackets of the On–Demand steering. Make an identification of the electrical wires and disconnect them from the assemblies.
7. Make an identification of the hydraulic hoses at the steering control unit so they can be connected correctly during assembly. Some hydraulic hoses have fittings that will permit disconnection at the steering control
unit. Disconnect the other hydraulic hoses at the base of the cowl, the control valve or the steering pump. Remove all mount clamps so that the hoses will turn freely and not become twisted. Disconnect the hydraulic hoses at the bottom of the steering control unit. Install plugs at all hoses and ports to prevent dirt from entering the steering hydraulic system.
8. If there is a display panel on the steering column housing, disconnect all plugs connected to the display panel.
NOTE: The repair procedures for the instrument cluster for the S/H2.00–3.20XM (S/H40–65XM) and H/S1.50–2.00XMS (H/S30–40XMS) are in the section INSTRUMENT CLUSTER, 2200 SRM 514
NOTE: The repair procedures for the instrument cluster for the E/J2.00–3.20XM (E/J45–65XM), J1.60–2.00XMT (J30–40XMT) and N30XMH are in the section ELECTRICAL SYSTEM, 2200 SRM 560.
9. Remove the capscrews, lock washers and lock plates that fasten the steering column to the pivots on the lift truck. Remove the steering column from the lift truck. Make sure the electric wires and the hydraulic hoses are not damaged as the steering column is removed.
10. Do the following procedure to remove the steering shaft:
a.Move the plastic tube and washer toward the steering control unit and compress the spring for the horn switch. Then remove the pin that goes through the steering shaft and engages the plastic tube.
b.Remove the external snap ring that holds the bearing in the steering column. On units that have On–Demand steering, loosen the set screw in the gear on the shaft. The return spring, washer and tube are removed at the same time as the steering shaft and bearing are removed. Use a small prybar at the bottom of the steering shaft near the steering control unit to remove the steering shaft and bearing (also, return spring, washer and tube) from the steering column.
11. Remove the two capscrews that hold the steering control unit and the bracket to the steering column. Remove the four capscrews or nuts that fasten the steering control unit to the bracket.
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Disassembly Of The Steering Control Unit
Disassemble the steering control unit as shown in FIGURE 7.
Cleaning Of The Steering Control Unit WARNING
Cleaning solvents can be flammable and toxic, and can cause skin irritation. When using cleaning solvents, always follow the solvent manufacturer’s recommended safety precautions.
Clean all the parts in solvent. Dry the parts with compressed air. Do not dry the parts with a cloth. Make sure all surfaces are free of scratches and sharp edges.
Assembly Of The Steering Control Unit
Use new seals, O–rings and neutral position springs during assembly as shown in FIGURE 8. Lubricate all parts with clean hydraulic oil.
Installation Of The Steering Control Unit
Install the steering control unit and column assembly on the bracket as shown in FIGURE 6.
Installation Of The Assembly Components
1. Install the steering column on the cowl mounts. Lubricate the pivots with multi–purpose grease and install the capscrews into the housing.
2. Fasten the two halves of the mount bracket to the steering control unit. Make sure to install bracket for the activator assembly. Install the steering control unit assembly into the steering column. Make sure to install the horn switch and the switch bracket as well as the two wire clamps on the same mount capscrews.
3. If removed, install the wires on the key switch that were identified during removal. Install the key switch.
4. If removed, install the wires on the direction switch that were identified during removal. The correct connections are also shown in FIGURE 4. Install the direction switch in the housing and install the large nut, dust cover and handle.
STEP 1
Install the steering column and steering control unit in the bracket. Install the steering wheel and nut. Tighten the nut to 40 to 54 Nm (30 to 40 lbf ft). Connect the wire at the horn button and install the horn button.
STEP 2.
Install the mount on the cowl. Install the latch on the bracket, using the pin and cotter pin. Install the bracket on the mount with the pivot shaft and spring. Install the plates and capscrews that hold the bracket to the shaft. Install the spring, washer and rod for the latch. Install the knob on the latch. Install
STEP 3.
Install the instrument cluster on the front cover. See the section INSTRUMENT CLUSTER, 2200 SRM 514 to make the necessary wiring connections for the S/H2.00–3.200XM (S/H40–65XM). See the section ELECTRICAL SYSTEM, 2200 SRM 560 to make the necessary wiring connections for the J2.00–3.20XM (J40–65XM), E2.00–3.20XM (E45–65XM), J1.60–2.00XMT (J30–40XMT) and N30XMH. Install the covers on the bracket. Connect the hydraulic lines to the steering control unit.
WARNING
The hydraulic hoses MUST be connected to the correct ports or the steering system will not operate as expected. This operation that is not expected can cause damage or personal injury. Make sure the hoses are identified and connected correctly.
5. Install the bearing on the steering shaft. The seal of the bearing must be toward the steering wheel. Install the snap ring in the groove on the steering shaft.
6. Put the steering shaft through the opening for the bearing in the steering housing. Install the pin that holds the plastic tube and flange for the horn switch. Install the plastic tube, the plastic flange and the spring onto the steering shaft. Push the steering shaft into the splines or align the key way of the steering control unit. Install the snap ring that holds the bearing in the steering housing.
7. Install the steering wheel. Install the large hex nut onto the steering shaft. Install the push rod and adjuster spool into the steering shaft. Install the base plate (not part of Petri steering wheel), the lock ring and the horn cover.
WARNING
The hydraulic hoses MUST be connected to the correct ports and fittings or the steering system will not operate as expected. This operation that is not ex-
pected can cause damage or personal injury. Make sure the hoses are identified and connected correctly.
8. Connect the hydraulic hoses to the steering control unit, the cowl, the control valve or the steering pump as removed during removal. Make sure each hydraulic hose is connected to the correct ports or fittings as identified during removal.
9. Connect the wire connectors at the bottom of the steering column. Install the access cover on the steering column.
WARNING
After making repairs, do not extend the hands or arms through the center of the steering wheel. If the control unit was not assembled correctly or the hoses not connected correctly it can rotate with a strong force and cause serious injury. If this action occurs, disassemble the control unit and correct the problem.
10. Connect the battery and operate the steering system to check for correct operation and leaks.
CONTROL UNIT 1 2 3 4
FIGURE 7. DISASSEMBLY OF THE STEERING CONTROL UNIT (1 of 3)
STEP 3.
Remove the stator, rotor and port plate. Put a mark on the stator so that the same side will be toward the body of the control unit at assembly Remove the O–rings. Remove the center shaft.
STEP 4.
Remove the screw for the check valve assembly Remove the parts for the check valve. For some units the check ball is in the opposite end of the control unit.
STEP 5.
Remove the spool and sleeve assembly. Remove the thrust bearing assembly from the spool. Push the center pin from the sleeve. Carefully remove the spool from the sleeve. Rotate the spool slowly during removal. Remove the ring from the sleeve. Remove the neutral position springs from the spool. Remove the seal from the housing.
STEP 6.
When installed, remove the snap ring, bushing, O–ring and seal ring. Remove the oil seal from the bushing or housing.
Put the spool (3) on the work bench then put the housing (6) onto the spool as shown. Install the guide ring (2) with the O–ring (1) on the end of the spool. Put the thrust washer (4), (see STEP 6) on top of the guide ring and O–ring assembly Use a socket or tube (5) to push on the washer and install the O–ring and guide ring in the housing. Carefully remove the washer, tube and spool from the housing.
5
1.SPOOL 2.SLEEVE 2 1 1.O–RING 2. GUIDE
STEP 4. Assemble the neutral position springs then push them into position in the spool (4). Make sure the flat springs (1) are installed to the outside of the curved springs (2). Install the center pin (3). Install the ring (5) on the sleeve (over the neutral position springs). The ring must turn freely on the sleeve.
STEP 5.
When the control unit has the type of bearing arrangement shown here, use the following procedures:
Install the thrust washers and thrust bearing on the spool. Carefully install the spool and sleeve assembly in the housing. Install the dust seal (9) in the bushing (6). Install the bushing (6), seal (8) and the O–ring (3) in the housing. Use the snap ring (7) to hold the bushing in position. Make sure the sleeve rotates freely in the housing.