STEERING SYSTEM
Structure and Function
Steering System
P
5 3
PF
4 T2 T1
L
R To lift cylinder
T
P
1 2
6
210104
Main Components
1 Hydraulic tank 4 Steering valve
2 Hydraulic pump (Gear pump) 5 Steering wheel
3 Inlet section of hydraulic control valve 6 Steering cylinder
(Including flow priority valve)
The steering system of this lift truck is full hydraulic. The oil delivered from the Gerotor is directed to the left
The oil drawn by hydraulic pump 2 from hydraulic tank or right chamber of steering cylinder through the L or R
1 enters the inlet section of the hydraulic control valve port, applying a pressure to the cylinder rod.
3 through the P port. There is built-in flow priority Simultaneously, the spool-and-sleeve valve in the
valve in the inlet section. The function of the flow steering valve 4 opens the return oil passage from the
priority valve is to deliver pressure oil preferentially to chamber of the steering cylinder to the hydraulic tank
steering valve 4. From the PF port, the oil flows to the 1. (The return oil goes through the steering valve’s T
P port of the steering valve. port and then the hydraulic control valve 3 to the
When the steering wheel is not turned (in the straight- hydraulic tank 1.)
ahead position), the oil flows through the steering Two actions of the steering cylinder piston, each of
valve’s T port to the T2 port in the hydraulic control which supplies and returns pressure oil, respectively,
valve’s inlet section and then returns to hydraulic tank extend the cylinder rod to the right or left. These
1. actions turn the knuckle via the tie rod, steering rear
When the steering wheel is turned, the oil from the PF wheels.
port enters the “Gerotor” passing through the P port For the priority valve and the steering cylinder, refer to
and spool-and-sleeve valve in the steering valve 4. “GROUP 11 HYDRULIC SYSTEM” and “GROUP 8
(The Gerotor is a small trochoid pump capable of REAR AXLE,” respectively.
delivering oil at a rate proportional to the number of
turns in which the steering wheel is turned.)
10-1
STEERING SYSTEM
Steering Gear
a, b, c: Metering pump inlets
d, e, f: Metering pump oulets
208745A
1 Spool 7 Drive shaft A: Contol section
2 Sleeve 8 Centering spring B: Metering section
3 Outlet port (port T) 9 Pin
4 Inlet port (port P) 10 Left turn port (port L)
5 Rotor 11 Right turn port (port R)
6 Rotor ring 12 Housing
The steering valve consists of two sections: control When the operator turns the steering wheel clockwise,
section A and metering section B. the passage in the steering valve opens, allowing
Control section A includes spool 1, sleeve 2, and pressure oil to flow through inlet port 4 into areas a, b,
housing 12, constituting a rotary type directional and c.
control valve. Spool 1 is spline-coupled to the steering As rotor 5 turns together with the steering wheel, the oil
shaft. When spool 1 is turned, sleeve 2 rotates, opening in areas d, e, and f is forced into the steering cylinder
the following passages to form a hydraulic circuit: through right turn port 11. When the steering wheel is
(1) A passage that allows oil to flow from inlet port 4 turned counterclockwise, oil flows in the direction
to metering section B reverse to the above, entering the steering cylinder
through left turn port 10.
(2) A passage that allows oil to flow from metering
section B to port L or R Since the pressure oil from port 4 applies rotating force
to rotor 5, operator’s effort on the steering wheel is
(3) A passage that allows the return oil from the reduced.
steering cylinder to port T
Check valve 13 is normally pushed to the left direction
Metering section B is a trochoid-gear type, small by pressure oil in the inlet port, blocking the bypass
hydraulic pump called “Gerotor” consisting of rotor passage. When oil supply from the PF port of the
ring 6 and rotor 5. Spool 1 and rotor 5 are connected to hydraulic valve stops for any reason, the bypass
each other with drive shaft 7. The rotor, therefore, passage opens, allowing oil from the hydraulic tank to
turns in the same direction and at the same speed as the flow to the metering section B. When the operator
steering wheel. turns the steering wheel, the metering section acts as a
When the operator does not turn the steering wheel, the complete manually-operated pump, causing oil to flow
oil flows from the P port to T port and finally returns to to the steering cylinder.
the hydraulic tank. The oil does not flow to the
metering section B as it is blocked by the spool 1 and
sleeve 2.
10-2
STEERING SYSTEM
Steering Column
Column position when steering column
is tilted fully forward
Column position when lock is released Column neutral tilt position
13° (inclination of 30 degrees to vertical line)
5° Column position when steering column is
7° tilted fully rearward
Combination switch
mounting plate
Steering column
mounting plate A
1
2
Tilt angle
setting plate B
2
Bolt
Fix 3
Loosen
5 Nut
Lock release
4
When the tilt lever 3 is turned counterclockwise, the
plates A and B are fixed between the bolt and nut. 209705
Main components
1 Steering column 4 Column lock lever
2 Bracket (secured to truck body) 5 Lock pin
3 Tilt lock lever
The steering column is tilt adjustable in the range of 5
degrees forward and 7 degrees rearward as shown in the
illustration.
For adjustment, lock the column lock lever 4 and then,
loosen the tilt lock lever 3 by turning it clockwise. Then,
tilt the steering column 1 to an adequate angle and turn the
tilt lock lever counterclockwise (pulling up) to lock.
The role of the column lock lever is to tilt the entire column
forward by a large amount for the convenience of getting
on and off, and of maintenance work. Push down the lock
lever to disengage the lock lever 4 from the lock pin 6 and
to tilt the steering column forward.
10-3
STEERING SYSTEM
Disassembly and Reassembly
Disassembly and Reassembly of Piping
1
A
7
6
5
2 7
4
6
4
View A
210105
Main parts or devices
1 Steering valve 5 Hose and pipe (steering valve T port → T2
2 Hydraulic control valve (The illustration shows port)
MC valve.) 6 Hose (steering valve L port ↔ steering
3 Steering cylinder cylinder)
4 Hose (PF port → steering valve P port) 7 Hose (steering valve R port ↔ steering
cylinder)
Suggestions for disassembly and reassembly
(1) The important point in maintenance of the (4) When removing or installing hoses, use a double
hydraulic system is to perform work in a clean spanner as needed to prevent excessive force from
place and never allow abrasive foreign substance to being applied to the matching fittings.
enter the system. (5) Bleed air after reassembly. Air bleeding method is
(2) O-rings must be replaced, once disturbed. as follows.
(3) Hoses (especially high-pressure section) of the (a) Raise the rear tires by placing blocks under the
steering system are safety related parts. Replace truck body.
them with new ones after a lapse of a (b) While changing the engine revolution by
predetermined time interval regardless of the depressing the accelerator pedal, turn the
presence or absence of damage. For a replacement steering wheel lock-to-lock and relieve
interval, follow the “Operation & Maintenance pressure to bleed air.
Manual”.
10-4
STEERING SYSTEM
Removal and Installation of Steering Wheel and Steering Valve
Disassembly sequence
2 Tightening torque:
52.6 to 65.3 N·m 1 Steering wheel
(5.36 to 6.48 kgf·m) 2 Nut
[38.8 to 46.8 lbf·ft]
3
3 Spring washer
4 Cover
5 Steering valve mounting bolt
6 Steering valve
4 1 7 Steering column assembly
mounting bolt
8 Steering column assembly
Tightening torque: 8
27 to 35 N·m
(2.8 to 3.6 kgf·m)
[19.9 to 25.8 lbf·ft]
7
4
5 Tightening torque:
21 to 29 N·m
(2.1 to 3.0 kgf·m)
Apply grease. [15.5 to 21.4 lbf·ft]
6 210106
1. Steering wheel
M12 bolt
Removal M8 bolt
(1) Remove the horn button.
(2) Remove the steering wheel nut 2 and then, remove the 91268 - 10600
steering wheel 1 using a wheel puller. Wheel puller
Special tool needed
Steering wheel
Wheel puller 91268 - 10600
209708
CAUTION Wheel puller setting
When removing the steering wheel, do not tap
the top end of the steering shaft.
10-5
STEERING SYSTEM
Steering wheel
Horn switch contact
Installation
Install in the following sequence. Front
(1) Place the projection (a) on the steering sensor of the
combination switch at the front as shown in the
illustration. (a)
(2) Apply a light coating of grease to a sliding area of the Projections form an
horn contact under the steering wheel boss. isosceles triangle.
(3) Reassemble the steering wheel in a straight-ahead Front
position. (The projections of the combination switch fit Combination switch
into the pits on the steering wheel.) Completely fit the
projections into the pits by turning the steering wheel
in the right and left directions several times. Forward
(4) Before tightening the steering wheel nut, check that
automatic return of the combination switch functions.
(5) If automatic return does not function, repeat the
sequence (3) and (4) above.
(6) Tighten the steering wheel nut to the specified torque.
209709
Inspection after Installation
Steering effort
(1) Pull the hand brake lever.
(2) Run the engine to warm the hydraulic oil to an
operation temperature of 40 to 60 °C (104 to 140 °F)
(3) Attach a spring scale to the rim (or a spoke) of the
steering wheel, and measure the steering effort required
to turn the steering wheel clockwise or
counterclockwise from the straight-ahead position.
Steering effort
13 N (1.3 kgf) [2.87 lbf]
(tangential force)
209710
10-6
STEERING SYSTEM
2. Steering valve
Removal
(1) Remove the cover 4 around the steering column. Face the elbow right
(2) Disconnect four hoses connected to the steering valve. downward to install.
Tightening torque of nut:
(3) Remove the bolt 5 and then, remove the steering valve 34 to 39 N·m
6. (3.5 to 4.0 kgf·m)
[25.0 to 28.8 lbf·ft]
Installation
Follow the sequence of disassembly in reverse, paying
attention to the following points. 209711
(1) Apply grease to the serration area on the lower part of
the steering shaft.
(2) Tighten the mounting bolt to the specified torque.
(3) Be careful about the orientation when installing the
elbow on the steering valve. Tighten it to the specified
torque.
3. Tilt lock lever
Top face of
Disassembly lever
1. Put match marks on the tilt lock lever and the nut B for
convenience of reassembly.
2. Remove the bolt A and then, remove the tilt lock cover.
★
Reassembly
When match marks put at the time of disassembly
Tilt lock lever
disappear or when the lever is replaced with a new one,
install the lever in the following sequence. (The illustration
on the right shows the layout of related parts when the tilt Lever mounting bolt
position is neutral and the column lock lever is locked.)
1. Tighten the nut B to the tightening torque of 11 to 15
N·m (1.1 to 1.5 kgf·m) [8.1 to 11.1 lbf·ft]. (This Nut B
represents a lever-locked condition.)
2. Select the optimal position for the tilt lock lever in a
locked condition and fit the tilt lock lever into the
Tilt lock lever
serration of the nut B.
The optimal position is in an area where the “★” notch Bolt A
209712
on the bracket and the top face of the lever cross each
other.
3. Tighten the bolt A.
4. Loosen the tilt lock lever and check that the bracket
slides in the entire tilting area without interfering with
other parts.
10-7
STEERING SYSTEM
Steering Valve
Disassembly
209713
Sequence
1 End cap, Bolts, O-ring, Spacers 7 Control sleeve
2 “Gerotor” set, O-ring 8 Control spool
3 Drive shaft, Spacer plate, O-ring 9 Pin
4 Retaining ring 10 Centering springs
5 Seal gland bushing, O-ring, Oil seal, Dust seal 11 Long housing
6 Thrust needle, Race bearing
10-8
STEERING SYSTEM
Suggestions for Disassembly
(1) Retaining ring removal
Remove the ring from the housing by prying its end out of
the groove. Do not damage the machined surface.
200665
(2) Seal gland bushing removal
Position the control spool and control sleeve assembly so
that the pin is even with the center of the assembly.
Remove the gland bushing.
200666
(3) Control spool and sleeve removal
Remove the control spool and sleeve assembly from the
housing by pulling it toward the end of the housing
opposite to the flange. Remove the pin from the
assembly.
CAUTION
To prevent damage to the housing, slowly pull out
the assembly while twisting.
200667
(4) Control spool and sleeve disassembly
CAUTION
Before removing the spool from the sleeve, put a
mark across the spool and sleeve so that the
spool can be installed in the same position.
Pull the control spool from the sleeve enough to permit
removal of the centering springs. Remove the centering
springs. Remove the spool from the sleeve by pulling it 200668
toward the rear end of the sleeve while turning slowly.
10-9
STEERING SYSTEM
Inspection after disassembly
(1) Check sliding areas between the sleeve and the housing
and between the sleeve and the spool.
(a) Check for sliding movement in sub-assembly
condition.
(b) If any defective movement is found, check sliding
surfaces.
If any defect such as abnormal wear, scratch, burr
or rust is found, replace the entire unit with a new
one.
Reassembly
8
6
11
3 4 2 5 1
10
209714
Sequence
1 Long housing 7 Seal gland bushing, Oil seal, Dust seal, O-ring
2 Control sleeve 8 Retaining ring
3 Control spool 9 Drive shaft, Spacer plate, O-ring
4 Centering springs 10 “Gerotor” set, O-ring
5 Pin 11 End cap, O-ring, Spacer, Bolts
6 Thrust needle, Race bearings
10-10
STEERING SYSTEM
CAUTION
Perform the following preparatory work before
reassembly.
(1) For damaged parts, prepare new parts for
replacement.
(2) Clean all metal parts, blow off foreign
substances with compressed air and dry them.
(3) Prepare new parts for an O-ring seal and lip
seal included in a seal kit.
CAUTION
Precautions during reassembly
(1) Reassemble each part while applying a light
coating of oil to them.
(2) Apply grease to O-rings.
(3) Do not wear cloth gloves when reassembling.
Lint may enter the valve.
Suggestions for Reassembly
(1) Reassembly of control spool and sleeve
Spring groove
Check the direction in which the spring groove of the
sleeve is aligned with that of the spool and then, slide the Spring groove
spool into the sleeve while twisting the spool.
If there are any match marks put at the time of disassembly
or marks put by a manufacturer, check such marks.
Match marks
CAUTION
200670
Check that the control spool rotates smoothly in
the control sleeve.
(2) Installation of centering springs
Align the spring grooves of the spool-and-sleeve and stand
the spool-and-sleeve on a flat bench. Use the spring
inserting tool to install springs. Place each set of three
springs back to back and pinch six springs in the tool with
notches on both sides facing downward. See the
illustration on the right.
As shown in the illustration, push one end of the springs
with fingers and push the springs into the spool-and-sleeve
groove. In case there is no inserting tool, assemble the
springs by inserting them one by one and right and left 200671
alternately.
Spring inserting tool 97157 - 00100
10-11
STEERING SYSTEM
(3) Insertion of the control spool-and-sleeve assembly into
the housing
Insert the pin into the hole of the control spool-and-sleeve
assembly and align both ends of the pin with the outside
diameter of the sleeve. Insert the spool-and-sleeve
assembly into the housing from the rear (in the direction as
shown in the illustration).
Insert the spool-and-sleeve assembly while slowly twisting 200672
it with the pin kept at a horizontal position. Insert the
spool-and-sleeve assembly until its rear edge face becomes
flush with the edge face of the housing. Do not insert any
further.
(4) Installation of thrust bearing
(5) Installation of seal gland bushing and seals
(a) Install the dust seal on the seal gland bushing to
place the flat side facing the bushing. Then install
the oil seal in the bushing. 200673
(b) After installing the O-ring, fit the seal gland
bushing into the spool while turning the seal gland
Dust seal Retaining ring
bushing. Drive the bushing into the specified
Seal gland
position by a plastic hammer. Check that the bushing
bushing contacts the top face of the thrust bearing
race evenly. O-ring
Securely fit the retaining ring into the housing
groove.
Oil seal 209715
(6) Reassembling the spacer plate
(a) Clamp the housing in a vise, equipped with soft
jaws or softened with rag. Clamp lightly over the
flats of the flange. Do not overtighten the vise
jaws.
NOTE
Check that the spool and sleeve are flush with or
slightly below the surface of the housing.
208240
(b) Install the O-ring in the housing. Place the spacer
plate on the housing and align the bolt holes with
the tapped holes in the housing.
208241
10-12
STEERING SYSTEM
(7) Reassembling the drive shaft
Turn the control spool-and-sleeve assembly to make the
Port surface
port surface of the housing parallel with the pin. Insert the
drive shaft to engage the pin in the yoke of the drive shaft. Drive shaft
To insure positioning in the following work process, draw a
line such as line B in the illustration right below on the end
Pin parallel with
face of the drive shaft spline with a felt-tip pen. port surface
Pin
200675
(8) Reassembling the gerotor set
Root of “Gerotor”
Face the O-ring side of the rotor set toward the spacer plate set star
side and fit the rotor set into the drive shaft by aligning the
root (line A) of the rotor set with line B of the drive shaft. Spacer plate
Check that lines A, B, C, and D are in parallel with each
Drive shaft
other. (with marked line)
Align bolt holes of the “Gerotor” set with the drive shaft
and star kept engaged.
This procedure is important in determining the valve timing 200676
of this unit.
(9) Reassembling the end cap
Install the drive spacer in the gerotor set. Install the O-ring
in the end cap. Install the end cap in the gerotor set and
align the holes.
208244
Apply oil to bolt threads and tighten bolts evenly in the
sequence as shown in the illustration on the right. The
tightening torque is shown in the table below.
Install the steering shaft in the spool and check that the
spool turns smoothly.
28.4 N·m
Tightening torque of end cap
(2.9 kgf·m)
mounting bolt
[2.1 lbf·ft] 200677
10-13
STEERING SYSTEM
Troubleshooting
No steering flow
(1) Foreign materials clogged in spool — Disassemble and clean.
pit
(2) Fatigued or damaged spring in the — Replace spring.
spool
Defect in flow Malfunction of relief valve
priority valve
(1) Low relief pressure — Adjust relief pressure.
(2) Damaged valve seating surface — Replace valve assembly.
(3) Fatigued or damaged spring — Replace springs and
adjust relief pressure.
Oil leak from relief valve
(1) Damaged O-rings on the valve — Replace O-rings.
body circumference
Clogging in “Gerotor” — Disassemble and clean.
Stiff steering Malfunction by spool seizure — Replace.
Defect in due to foreign material
wheel operation steering valve
Damaged bearing — Replace.
Excessive tightening of end cap bolt — Reassemble.
Defect in Bent piston rod — Repair or replace.
steering cylinder Faulty piston seal — Replace.
Misalignment Faulty installation of steering valve to — Readjust.
tilt column
Other defects Flattened pipe — Replace.
Defect in Seizure of spool or sleeve — Replace.
steering valve Breakage of centering spring — Replace.
Unstable steering
operation
Trapped air — Bleed.
Other defects Flattened pipe — Replace.
Faulty piston seal of steering cylinder — Replace.
10-14
STEERING SYSTEM
Service Data
A: Standard value
Truck Models
1 ton class 2 ton class 3 ton class
Items
Steering effort (at steering wheel rim) 13 (1.3) [2.9] 13 (1.3) [2.9] 13 (1.3) [2.9]
A
N (kgf) [lbf] or less or less or less
52.6 to 63.5 52.6 to 63.5 52.6 to 63.5
Tightening torque of steering wheel nuts A (5.4 to 6.5) (5.4 to 6.5) (5.4 to 6.5)
N·m (kgf·m) [lbf·ft] [38.8 to 46.8] [38.8 to 46.8] [38.8 to 46.8]
27 to 35 27 to 35 27 to 35
Tightening torque of steering bracket bolts A (2.8 to 3.6) (2.8 to 3.6) (2.8 to 3.6)
N·m (kgf·m) [lbf·ft] [20.0 to 25.8] [20.0 to 25.8] [20.0 to 25.8]
Displacement
A 69 (4.2) 96 (4.2) 120 (7.3)
cc (cu in.)/rev.
Rotating torque in normal poeration
Steering valve A 1.5 (0.2) [1.1] 1.5 (0.2) [1.1] 1.5 (0.2) [1.1]
N·m (kgf·m) [lbf·ft]
Tightening torque of cap bolt 1
A 28.4 (2.9) [20.9] 28.4 (2.9) [20.9] 28.4 (2.9) [20.9]
N·m (kgf·m) [lbf·ft]
+0.5 +0.5 +0.5
8.8 0 10.3 0 10.3 0
Steering system relief valve set pressure A (90 +5.1
0 ) (105 +5.1
0 ) (105 +5.1
0 )
MPa (kgf/cm2) [psi] [1276.5 +72.5
0 ] [1494.1 +72.5
0 ] [1494.1 +72.5
0 ]
209716
10-15
