Page is loading ...
6
4241262-Rev B 6-1
Chapter 6
Hydraulics
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Test Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Repair Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
Hydraulic Hose, Tube, and Fitting General Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
O-Ring Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
Hydraulic Hose Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
Hydraulic Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
Portable In-Line Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
Digital Hydraulic Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6
Hydraulic Flow Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6
Digital Pressure Gauge Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Hydraulic Hose Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Hydraulic Test Fitting Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7
Blocking Disk Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Component Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8
Hydraulic Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10
Theory of Operation and Diagnostic Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16
Steering Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16
Steering Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17
Raise Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18
Raise Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-19
Lower Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20
Lower Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
Mow Circuit (On) Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22
Mow Circuit (On) Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23
Backlap Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24
Backlap Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-25
Field Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26
Preliminary Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26
Lift Cylinder Leakage Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26
Steering Leakage Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27
Reel Motor Case Drain Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-28
6-2 4241262-Rev B
HYDRAULICS
6
Instrument Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29
Instrument Test Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29
Front Cutting Units Circuit Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-30
Front Cutting Units Pump Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-32
Front Reel Valve Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-33
Front Reel Motors Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-35
Rear Cutting Units Circuit Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-38
Rear Cutting Units Pump Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-41
Rear Reel Valve Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-42
Rear Reel Motors Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-44
Lift/Steering Relief Valve Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46
Lift/Steering Relief Valve Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-48
Lower Relief Valve Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-49
Lift/Steer Pump Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-50
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52
Hydraulic Oil Tank—Drain Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52
Gear Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52
Lift Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-57
Rear Reel Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-60
Front Reel Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-63
Hydraulic Oil Return Filter Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-65
Hydraulic Oil Charge Filter Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-66
Rear Lift Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-67
Center Lift Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-68
Left and Right Front Lift Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-71
Hydraulic Oil Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-74
Hydraulic Oil Cooler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-76
HYDRAULICS
4241262-Rev B 6-3
6
Specifications
Test Specifications
Specifications
Front Cutting Units Pump Flow gpm (lpm) 6.8 (25.7) at 3150 rpm
Rear Cutting Units Pump Flow
gpm (lpm) 6.8 (25.7) at 3150 rpm
Lift/Steer Pump Flow
gpm (lpm) 6.8 (25.7) at 3150 rpm
Hydraulic Leakage Percentage Ranges 0–10% = Good
11–20% = Marginal
21% and Beyond = Bad
Lift/Steering Relief Valve Pressure Setting
psi (bar) 1450 ± 10% (100 ± 10%)
Lower Relief Valve Pressure Setting
psi (bar) 450 ± 10% (31 ± 10%)
Reel Motor Forward Relief Valve Pressure Setting
psi (bar) 1167 ± 10% (81 ± 10%)
Reel Motor Reverse Relief Valve Pressure Setting
psi (bar) 1167 ± 10% (81 ± 10%)
Reel Motor Case Drain Rate Less than 1 pint (0.47 L) per minute
6-4 4241262-Rev B
HYDRAULICS
6
Repair Specifications
Specifications
Gear Pump—Rear Cover-to-Pump Body Bolt Torque lb-ft (N·m) 33 (45)
Gear Pump—Test Fitting Torque
lb-ft (N·m) 32.9 (44.6)
Gear Pump—Tee Fitting Torque
lb-ft (N·m) 55 (74.6)
Gear Pump—Outlet Port Fitting Torque
lb-ft (N·m) 55 (74.6)
Gear Pump—Inlet Port Fitting Torque
lb-ft (N·m) 32.9 (44.6)
Lift Valve—Coil Nut Torque
lb-ft (N·m) 10 (13.5)
Lift Valve—Relief Valve Torque
lb-ft (N·m) 24–26 (32.5–35.3)
Lift Valve—Check Valve Torque
lb-ft (N·m) 19–21 (25.8–28.5)
Lift Valve—Port “P” and Front Side Port “T” Fitting
Torque
lb-ft (N·m) 60 (81.4)
Lift Valve—Port “G” Fitting Torque
lb-ft (N·m) 17 (23)
Lift Valve—Ports “1,” “2,” “3,” “8,” “9,” and “10” Fitting
Torque
lb-ft (N·m) 17 (23)
Lift Valve—Ports “4” and “6” Fitting and One-Way
Restrictor Torque
lb-ft (N·m) 17 (23)
Lift Valve—Rear Side Port “T” Fitting Torque
lb-ft (N·m) 60 (81.4)
Reel Valve—Coil Nut Torque
lb-ft (N·m) 10 (13.5)
Reel Valve—Flow Control Torque
lb-ft (N·m) 24–26 (32.5–35.3)
Reel Valve—Ports “A” and “B” Fitting Torque
lb-ft (N·m) 60 (81.4)
Reel Valve—Port “G” Fitting Torque
lb-ft (N·m) 17 (23)
Reel Valve—Port “P” Elbow Fitting Torque
lb-ft (N·m) 80 (108.5)
Reel Valve—Port “T” Fitting Torque
lb-ft (N·m) 60 (81.4)
Hydraulic Oil Tank Capacity
gal (L) 14 (53)
Center and Rear Lift Cylinder Rod Nut Torque
lb-ft (N·m) 50 (67.8)
Left and Right Front Cylinder Rod Nut Torque
lb-ft (N·m) 50 (67.8)
HYDRAULICS
4241262-Rev B 6-5
6
Hydraulic Hose, Tube, and
Fitting General Instructions
O-Ring Installation
• Always install new O-rings.
• On hoses with O-ring fittings, make sure O-rings are
properly seated before tightening.
• O-rings should be lubricated with the fluid to be used
in the system prior to assembly.
Boss Fitting O-Ring Installation
O-Ring Seal Kits
• SAE Boss O-Ring Kit Jacobsen PN 5002452
• O-Ring Face Seal (ORS) O-Ring Kit PN 5002454
• Common O-Ring Sizes Kit PN 5002453
Replacement O-Rings for ORS (Face Seal)
Fittings
Replacement O-Rings for O-Ring Boss
Fittings
Hydraulic Hose Installation
Hold the fixed portion of the hose coupling with one
wrench; use a second wrench to tighten or loosen the
hose nut. This will avoid damaging the fitting seal. When
tightening a hose, do not permit the hose to twist; hold
the hose in a normal straight position.
When installing hoses, place fittings at angles to avoid
contact with fixed parts when turning. Make sure hoses
are assembled to proper “A” and “B” ports on
components.
Hydraulic Hose and Tube Torque Values
1 Tubing O.D. or Hose I.D. 2 O-Ring 3 Thread Size
ORS (Face Seal)
Tube Size
ORS (Face Seal)
O-Ring Size
Jacobsen
Part
Number
4 11 339908
6 12 339909
8 14 339910
10 16 339911
12 18 339912
16 21 339913
20 25 339914
24 29 339915
TN4075
1
2
3
TN4097
Tubing O.D.
or Hose I.D.
Thread
Size
Jacobsen Part
Number
1/8 5/16-24 459290
3/16 3/8-24 459291
1/4 7/16-20 339896
5/16 1/2-20 459293
3/8 9/16-18 339897
1/2 3/4-16 339898
5/8 7/8-14 339899
3/4 1-1/16-12 339900
7/8 1-3/16-12 459296
1 1-5/16-12 339901
1-1/4 1-5/8-12 339902
1-1/2 1-7/8-12 339903
2 2-1/2-12 459300
Size lb-ft N·m
Dash Fractional Min Max Min Max
-4 1/4 10121416
-6 3/8 18202427
-8 1/2 32404354
-10 5/8 46 56 60 75
-12 3/4 65 80 90 110
-16 1 92 105 125 240
-20 1-1/4 125 140 170 190
-24 1-1/2 150 180 200 246
6-6 4241262-Rev B
HYDRAULICS
6
Hydraulic Service Tools
NOTE
The hydraulic service tools listed here can be obtained
from K-Line Industries at http://klineind.com.
Portable In-Line Filter
Part Number JAC5097
When hydraulic components fail internally, debris from
the failed component can spread throughout the
hydraulic system and cause additional damage.
This situation can be magnified when dealing with a
closed-loop traction system, where oil is not filtered. In
the event of a traction system component failure, it is
recommended that all traction system components be
disassembled and cleaned, or filtered using a portable
in-line filter available through your Jacobsen Dealer. The
portable in-line filter should also be used when testing
hydraulic systems or after replacing a failed component.
IMPORTANT
Always install the in-line filter so oil flows through
the filter before entering a component. Once filtering
has begun, never reverse the flow of oil, or debris
will re-enter the system.
Digital Hydraulic Tester
Part Number AT40031
Features
• Flow up to 100 gpm (379 lpm)
• Pressure up to 6000 psi (414 bar)
• Temperature up to 250° F (120° C)
• Digital display for flow and temperature
• Analog display for pressure
• Flow accuracy 1% of full scale
Hydraulic Flow Meter
Part Number AT40002
Features
• Glycerin filled pressure gauge
• Precision needle-type load valve
• 4–40 gpm (15–15 lpm) flow range
• Pressure up to 5000 psi (345 bar)
• -12 port size
TN4286
TN4288
TN4287
HYDRAULICS
4241262-Rev B 6-7
6
Digital Pressure Gauge Kit
Part Number JAC5106
Features
• Quick disconnect fittings
• Pressure up to 5000 psi (345 bar)
• Includes one 5 ft (152 cm) hose
Hydraulic Hose Kit
Part Number JAC5001H
NOTE
This hydraulic hose kit is intended to be used with the
JAC5001A Hydraulic Test Fitting Kit.
Contents
• Two 8 ft (244 cm) 12 ORFS (F) x 10 ORFS (F) hoses
• Four 8 ft (244 cm) 10 ORFS (F) x 10 ORFS (F) hoses
• Two 8 ft (244 cm) 8 ORFS (F) x 10 ORFS (F) hoses
Hydraulic Test Fitting Kit
Part Number JAC5001A
NOTE
For detailed component descriptions and sizes, please
see the K-Line Industries website at http://klineind.com.
Contents
• Twenty ORFS tee fittings in five sizes
• Eight ORFS 90° elbow fittings in four sizes
• Forty ORFS caps in five sizes
• Forty ORFS plugs in five sizes
• Six ORS reducer adapters in three sizes
• Sixteen ORS adapters in four sizes
• Eight blocking disks in four sizes
• Three JIC tee fittings in three sizes
• Three 4 in. (102 mm) jumper hoses in three sizes
• One ORS/male NPTF adapter
• One vented bushing
• One copper tube assembly
Blocking Disk Set
Part Number JAC5001-1
NOTE
This blocking disk set is part of the JAC5001A Hydraulic
Test Fitting Kit.
Contents
• Two -6 blocking disks
• Two -8 blocking disks
• Two -10 blocking disks
• Two -12 blocking disks
• Two -16 blocking disks
TN4290
TN4289
6-8 4241262-Rev B
HYDRAULICS
6
Component Location
See Figure 6-1.
Figure 6-1: Component Location—Left Side
1 Gear Pump 4 Return Filter Assembly 7 Front Reel Valve 10 Center Lift Cylinder
2 Radiator/Hydraulic Oil Cooler 5 Hydraulic Oil Tank 8 Lift Valve 11 Right Lift Cylinder
3 Charge Pressure Filter 6 Rear Lift Cylinder 9 Left Lift Cylinder 12 Rear Reel Valve
1
2
4
3
TN3586, TN3628, TN3590, TN3649
9
11
10
8
7
5
6
12
HYDRAULICS
4241262-Rev B 6-9
6
Page Intentionally Blank
6-10 4241262-Rev B
HYDRAULICS
6
Hydraulic Schematic
See Figures 6-2 through 6-6.
Figure 6-2
10 Micron
Filter
Traction Pump
Suction
Screen
100 Mesh
25 psi
Switch
Hydraulic Tank
25 psi Crack Bypass
10 Micron
Filter
0.50 ci
Forward
Relief Valve
(See Note)
Charge
Filter
Check
Valve
Check
Valve
A
B
123
3150 ±50 rpm
Return
Filter
Oil
Cooler
25 psi
Crack
Bypass
Gear
Pump
TN2805
Reverse
Relief Valve
3625 psi
Tow
Valve
0.50 ci 0.50 ci
2.81 ci
Screen
40 Mesh
Charge
Pressure
Relief Valve
315 psi
25 psi
Crack
Bypass
REV
Test
Port
FOW
Test
Port
Control Sleeve
STRG
Test
Port
M2
M3
M1L1
EDC
L2
M4
M5
1
2
3
4
5
6
8
7
9
10 Micron
Filter
Tank Fill Cap
Assembly
0.031 in.
0.031 in.
Note:
Forward relief valve pressure is 3625 psi for machines with serial numbers ending 1651 through 2499.
Forward relief valve pressure is 4350 psi for machines with serial numbers ending 2500 and up.
HYDRAULICS
4241262-Rev B 6-11
6
Hydraulic Schematic,
Continued
Figure 6-3
4WD
Valve
RF
Relief Valve
400 psi
Brake Release
Valve
RF
Left Front
Wheel Motor
TN2806
Reverse
Forward
Brake
Solenoid
Valve
RRF
Check
Valve
Hot Oil
Shuttle
Relief Valve
350 psi
Right Front
Wheel Motor
(See Note)
REV LF
LF
Relief
Valve 400
DRN
0.052
in.
LRF
Check
Valve
RRR LRR
RRF LRF
Right Rear
Wheel Motor
Left Rear
Wheel Motor
11.90 ci 11.90 ci
DRN
BR
ST
Check
Valve
CHG
1
2
3
4
5
6
8
7
9
1
7
8
6
5
4
10
Brake
Cylinder
Brake
Cylinder
Note:
Front wheel motor displacement is 19.23 ci for machines with serial numbers ending 1651 through 2499.
Front wheel motor displacement is 17.09 ci for machines with serial numbers ending 2500 and up.
(See Note)
6-12 4241262-Rev B
HYDRAULICS
6
Hydraulic Schematic,
Continued
Figure 6-4
Steering Cylinder
Relief Valve
1450 psi
Steering Unit
R
Steering Valve
Check
Valve
TN2807
3.90
ci
TEP
L
1
7
8
6
4
10
5
6
4
5
8
7
11
12
HYDRAULICS
4241262-Rev B 6-13
6
Hydraulic Schematic,
Continued
Figure 6-5
Lift Valve
Solenoid Valve
T
0.040
in.
Left Front
Cylinder
Center
Cylinder
Left Rear
Cylinder
Right Rear
Cylinder
10
One-Way Restrictor
TN2808
Lift/Lower
Test Port
T
G
P
Lower
Relief Valve
450 psi
98 6 3 2 4 1
Right Front
Cylinder
0.055 in.
0.040 in.
0.026
in.
Check
Valve
Check
Valve
Check
Valve
0.040
in.
0.040
in.
0.040
in.
0.040
in.
0.040
in.
0.040 in.
6
4
5
8
7
11
12
7
8
6
4
5
6-14 4241262-Rev B
HYDRAULICS
6
Hydraulic Schematic,
Continued
Figure 6-6
RF Reel Motor
Rear Reel Valve
P
A
B
Solenoid
Valve
T
Backlap
Valve
Reverse
Relief Valve
1167 psi
TN2809
C Reel Motor LF Reel Motor
• Reel Motor Displacement
LF 550 0.72 ci
LF 570 1.01 ci
• Reel Motor Displacement
LF 550 0.72 ci
LF 570 1.01 ci
RR Reel Motor LR Reel Motor
Rear Reel
Test Port
G
Check
Valve
Check
Valve
Front Reel
Test Port
Forward
Relief Valve
1167 psi
7
8
6
4
5
Reverse
Relief Valve
1167 psi
Check
Valve
Check
Valve
Forward
Relief Valve
1167 psi
Reverse
Relief Valve
1167 psi
Check
Valve
Check
Valve
Forward
Relief Valve
1167 psi
Reverse
Relief Valve
1167 psi
Check
Valve
Check
Valve
Forward
Relief Valve
1167 psi
Reverse
Relief Valve
1167 psi
Check
Valve
Check
Valve
Forward
Relief Valve
1167 psi
Front Reel Valve
P
A
B
Solenoid
Valve
T
Backlap
Valve
G
HYDRAULICS
4241262-Rev B 6-15
6
Page Intentionally Blank
6-16 4241262-Rev B
HYDRAULICS
6
Theory of Operation and
Diagnostic Information
Steering Circuit Schematic and
Theory of Operation
System Conditions:
• Engine running
• Steering wheel turned to the right or left (left turn
shown)
Oil Supply to Steering Unit
Hydraulic oil is drawn from the hydraulic oil tank by
section 1 of the gear pump assembly. Before entering the
gear pump assembly, the inlet oil is filtered by a
100-mesh screen to remove any debris. Operating
pressure oil from section 1 of the three-section gear
pump is routed to port “P” of the steering unit.
Steering Circuit
Operating pressure oil enters the steering unit at port “P,”
and is routed to the pilot line of the 1450 psi (100 bar)
relief valve, against the relief valve and check valve, and
to the steering valve.
With the steering wheel in the neutral (straight ahead)
position, the steering valve routes all of the operating
pressure oil out of the steering unit through port “E,”
supplying operating pressure oil to the lift valve.
With the steering wheel turned to the left, the steering
valve is moved, allowing oil to flow through the valve to
the gerotor metering section. Oil is then routed through
port “L” of the steering unit to the piston side of the
steering cylinder, extending the rod, and moving the rear
wheels in the desired direction.
Oil from the rod end of the steering cylinder flows back
into the steering unit through port “R,” through the
steering valve, and through port “T.” Oil exiting the
steering unit is routed through the lift valve and then
returns to the hydraulic tank.
Oil from the rod end of the steering cylinder is also routed
to port “ST” of the park brake release valve. When the
park brake release valve (lever) is in the normal position,
oil is blocked.
Circuit Relief
The steering system is protected by the 1450 psi (100
bar) relief valve. If the pressure on the pilot line of the
relief valve reaches 1450 psi (100 bar), the valve will
open, dumping operating pressure oil through port “T” of
the lift valve to the hydraulic tank.
HYDRAULICS
4241262-Rev B 6-17
6
Steering Circuit Schematic
See Figure 6-7.
Figure 6-7
1 Operating Pressure Oil from Gear Pump (Section 1) 3 Return Oil to Lift Valve (Port T)
2 Operating Pressure Oil to Lift Valve (Port P) 4 Return Oil to Park Brake Release Valve (Port ST)
TN2862
Steering Cylinder
Relief Valve
1450 psi
Steering Unit
R
Steering Valve
Check
Valve
3.90
ci
TEP
L
1
2
3
4
Operating Pressure Oil
Return Oil
Metered Oil
6-18 4241262-Rev B
HYDRAULICS
6
Raise Circuit Schematic and Theory
of Operation
System Conditions:
• Engine running at fast idle
• Mower raise/lower switch in the raise position
NOTE
The cutting unit motors will automatically shut off as the
cutting units are raised.
Oil Supply to the Lift Valve
Hydraulic oil is drawn from the hydraulic oil tank by
section 1 of the gear pump assembly. Before entering the
gear pump assembly, the inlet oil is filtered by a
100-mesh screen to remove any debris. Operating
pressure oil from section 1 of the gear pump is routed
through the steering unit. The steering unit will supply oil
flow to the lift valve via port “E.”
Raise Circuit
Operating pressure oil supplied by section 1 of the gear
pump enters the lift valve at port “P.” The oil flows
through the solenoid valve, check valves, and 0.040 in. (1
mm) orifices to the rod side of the front and center lift
cylinders. Oil also flows unrestricted through the 0.026 in.
(0.66 mm) one-way restrictor to the rod side of the rear lift
cylinders. Oil flow to the rod side of the lift cylinders
raises the cutting units.
Oil from the piston end of the front and center lift
cylinders flows through the 0.040 in. (1 mm) orifices and
back to the return filter, oil cooler, then hydraulic tank. Oil
from the piston end of the rear lift cylinders flows through
the 0.055 in. (1.4 mm) orifice and back to the hydraulic
tank. The orifice restricts the flow of oil, dampening the
reaction of the cylinder retraction.
Circuit Relief
The lift system is protected by the 1450 psi (100 bar)
relief valve in the steering unit. If the pressure on the pilot
line of the relief valve reaches 1450 psi (100 bar), the
valve will open, dumping operating pressure oil through
port “T” of the lift valve to the return filter, oil cooler, and
then the hydraulic tank.
HYDRAULICS
4241262-Rev B 6-19
6
Raise Circuit Schematic
See Figure 6-8.
Figure 6-8
1 Operating Pressure Oil from Steering Unit (Port E) 3 Return Oil to Hydraulic Tank
2 Return Oil from Steering Unit (Port T)
TN2863
Lift Valve
Solenoid Valve
T
0.040
in.
Left Front
Cylinder
Center
Cylinder
Left Rear
Cylinder
Right Rear
Cylinder
10
One-Way Restrictor
Lift/Lower
Test Port
T
G
P
Lower
Relief Valve
450 psi
98 6 3 2 4 1
Right Front
Cylinder
0.055 in.
0.040 in.
0.026
in.
Check
Valve
Check
Valve
Check
Valve
0.040
in.
0.040
in.
0.040
in.
0.040
in.
0.040
in.
0.040 in.
1
2
3
Operating Pressure Oil
Return Oil
Metered Oil
6-20 4241262-Rev B
HYDRAULICS
6
Lower Circuit Schematic and Theory
of Operation
System Conditions:
• Engine running
• Mower raise/lower switch in the lower position
Oil Supply to Lift Valve
Hydraulic oil is drawn from the hydraulic oil tank by
section 1 of the gear pump assembly. Before entering the
gear pump assembly, the inlet oil is filtered by a
100-mesh screen to remove any debris. Operating
pressure oil from section 1 of the gear pump is routed
through the steering unit. The steering unit will supply oil
flow to the lift valve via port “E.”
Lower Circuit
Operating pressure oil supplied by section 1 of the gear
pump enters the lift valve at port “P.” The oil flows
through the solenoid valve to the pilot lines of the check
valves, the 450 psi (31 bar) relief valve, and through the
0.040 in. (1 mm) orifices to the piston side of the front
and center lift cylinders. Oil also flows through the 0.055
in. (1.4 mm) orifice to the piston side of the rear lift
cylinders. The 450 psi (31 bar) relief valve allows
sufficient pressure to build up to unseat the check valves.
Once that pressure is satisfied, the relief valve will shift,
dumping excess oil to the return filter, oil cooler, and then
the hydraulic tank.
With operating pressure oil at the pilot lines of the check
valves, the check valves open. Gravity allows the cutting
units to lower, pulling against the lift cylinders. Oil from
the rod end of the front and center lift cylinders flows
through the 0.040 in. (1 mm) orifices, which dampen the
lowering of the reels to prevent damage to the cutting
units, and then flows through the check valves, and back
to the hydraulic tank. Oil from the rod end of the rear lift
cylinders flows through the 0.026 in. (0.66 mm) one-way
restrictor, which lowers the rear cutting units at a slightly
slower rate than the front cutting units, then flows through
the check valve, and back to the hydraulic tank.
Circuit Relief
The lower system is protected by the 450 psi (31 bar)
relief valve. If the pressure on the pilot line of the relief
valve reaches 450 psi (31 bar), the valve will open,
dumping operating pressure oil through port “T” of the lift
valve to the hydraulic tank.
/
