325C Excavator Hydraulic System Travel Hydraulic System Caterpillar


Travel Hydraulic System
`
1.1. Travel Control
2.1. Forward Travel
3.1. LOW SPEED
4.1. HIGH SPEED
5.1. Automatic Travel Speed Change

Travel Control




Illustration 1g00820118

(1) Left travel motor

(52) Travel brake valve




Illustration 2g00820120

Final drive

(53) Track

(54) Sprocket

(55) Final drive

The output flow from the right pump flows through the swivel to the right travel motor. The output flow from the left pump flows through the swivel to the left travel motor. The pump delivery flow causes rotation of the travel motors. The torque of the travel motors is transmitted to the final drives. The rotational speed of the travel motors is reduced by gear reduction in the final drive. Final drive (55) increases the torque and the rotational force drives track (53) via sprocket (54).




Illustration 3g00699127

Keypad (right console)

(56) Travel speed control switch

The travel speed can be adjusted by the slight operation of the travel levers/pedals. The travel speed can also be controlled by travel speed control switch (56). This changes the travel speed when the travel levers/pedals are moved to the maximum position. The travel speed control switch can be set at the LOW SPEED position or the HIGH SPEED position. When the travel speed control switch is set at the LOW SPEED position, the tortoise appears on the default message display of the monitor. When the travel speed control switch is set at the HIGH SPEED position, the rabbit appears on the default message display of the monitor. During travel on a flat surface or during gradual downhill travel, the travel speed is set at the HIGH SPEED position in order to realize increased mobility.

When travel speed control switch (56) is set at the HIGH SPEED position, the pressure sensors for pump delivery pressure detect the change in pump load. If the pressure sensors detect a high load, the travel speed is automatically adjusted to LOW SPEED. If the pressure sensors detect a small load, the travel speed is automatically adjusted to HIGH SPEED.




Illustration 4g00699131

Operation of travel

(1) Left travel motor

(15) Right travel motor

(57) Forward travel

(58) Left travel lever/pedal

(59) Idler

(60) Right travel lever/pedal

(61) Cab

(62) Reverse travel

The direction of travel is relative to the position of the lower structure. For normal travel, idler (59) is positioned in front of cab (61) and travel motors (1) and (15) to the rear of the cab. With the machine in the normal position of travel, move the travel levers/pedals (58) and (60) forward. The machine will travel in forward direction (57). This movement is called forward travel. When the travel levers/pedals (58) and (60) are moved toward the operator, the machine travels in reverse direction (62). This direction is called reverse travel.

When cab (61) is rotated by 180 degrees, travel motors (1) and (15) are positioned in front of the cab. The direction of travel and the operation of the travel levers/pedals (58) and (60) are reversed from the normal travel direction.

When the machine is in the normal position of travel and when one of the travel levers/pedals (58) or (60) is moved forward, the respective track travels forward. The machine turns because the stationary track acts as the pivot point. This is called a pivot turn.

This machine will spot turn in order to change the travel direction of the machine in a narrow space. To complete a spot turn operation, move one travel lever/pedal to the rear and move the other travel lever/pedal forward at the same time. One track will travel to the rear and the other track will travel forward. The machine will spot turn around the center axis of the machine.

Forward Travel




Illustration 5g00890478

Hydraulic schematic for FORWARD TRAVEL

(1) Left travel motor

(2) Swashplate

(3) Motor rotary group

(4) Swashplate control piston (HIGH SPEED)

(5) Passage (supply oil)

(6) Brake pilot valve

(7) Passage

(8) Counterbalance valve

(9) Swashplate control piston (LOW SPEED)

(10) Parking brake

(11) Passage (return oil)

(12) Displacement change valve

(13) Passage

(14) Line (pilot system oil pressure)

(15) Right travel motor

(16) Swashplate

(17) Swashplate control piston (LOW SPEED)

(18) Passage (supply oil)

(19) Passage

(20) Displacement change valve

(21) Passage (return oil)

(22) Swashplate control piston (HIGH SPEED)

(23) Passage

(24) Passage

(25) Passage

(26) Passage

(27) Line (pilot system oil pressure)

(28) Line (return oil)

(29) Line (supply oil)

(30) Swivel

(31) Line (supply oil)

(32) Line (return oil)

(33) Line (supply oil)

(34) Line (return oil)

(35) Passage (supply oil)

(36) Passage (return oil)

(37) Return passage

(38) Left travel control valve

(39) Passage

(40) Center bypass passage

(41) Right travel control valve

(42) Pilot line (forward left travel)

(43) Pilot line (forward right travel)

(44) Travel pilot control valve

(45) Return line

(46) Pressure sensor for right pump delivery

(47) Pressure sensor for left pump delivery

(48) Travel speed solenoid valve

(49) Left pump

(50) Right pump

(51) Pilot pump

(63) Pilot line




Illustration 6g00820125

Main control valve

(38) Left travel control valve

(41) Right travel control valve

When both of the travel levers/pedals are operated, pilot system oil pressure flows from travel pilot control valve (44) through pilot lines (42) and (43) to left travel control valve (38) and right travel control valve (41). The pilot system oil pressure shifts the spools in both of the travel control valves in an upward direction. The travel control valves allow the oil delivery from the right pump and the left pump to flow to swivel (30). The swivel transfers the oil delivery from the rotating upper structure to the lines in the lower structure. The oil delivery flows to left travel motor (1) and right travel motor (15) .

Note: The right and left travel controls function in the same manner. The explanation for the left travel control will be used to explain both the right and left travel controls.

When the left travel lever/pedal is moved to the FORWARD TRAVEL position, pilot system oil pressure from travel pilot control valve (44) flows through pilot line (42) to left travel control valve (38). The spool in the left travel control valve shifts in an upward direction. The oil delivery from the left pump in center bypass passage (40) flows through passage (39), left travel control valve (38), passage (35), line (33), swivel (30) and line (29) to left travel motor (1) .

The oil delivery from the left pump enters left travel motor (1) and flows through counterbalance valve (8) and passage (5) to motor rotary group (3). At the same time, a portion of the oil delivery from the left pump flows through passage (7) and brake pilot valve (6) to parking brake (10). The parking brake is released and the oil delivery from the left pump causes the motor to rotate.

LOW SPEED




Illustration 7g00820295

Left travel motor (LOW SPEED)

(1) Left travel motor

(2) Swashplate

(3) Motor rotary group

(4) Swashplate control piston

(5) Passage (supply oil)

(8) Counterbalance valve

(9) Swashplate control piston

(11) Passage (return oil)

(12) Displacement change valve

(13) Passage

(27) Pilot line

(46) Pressure sensor (left pump)

(48) Travel speed solenoid valve

(49) Left pump

(51) Pilot pump

(56) Travel speed control switch

(58) Left travel lever/pedal

(A) Indicator for HIGH SPEED

(B) Indicator for LOW SPEED

(C) Engine and pump controller

When travel speed control switch (56) is set at the LOW SPEED position, an electrical signal is sent to engine and pump controller (C). The engine and pump controller does not energize travel speed solenoid valve (48) and pilot system oil pressure does not flow through pilot line (27) to displacement change valve (12). The spool in the displacement change valve does not shift. A portion of the oil flow from the left pump in passage (5) flows through passage (13) and displacement change valve (12) to swashplate control piston (9). As a result, swashplate control piston (9) moves swashplate (2) to the maximum displacement position. At the same time, the oil that acts on swashplate control piston (4) flows into the case drain of the travel motor. One rotation of motor rotary group (3) displaces a larger amount of oil flow. The rotational speed of the left travel motor decreases. The left track moves slowly and better traction is achieved.

The return oil from motor rotary group (3) flows through passage (11), counterbalance valve (8), line (28) and swivel (30). The return oil then flows through line (34), left travel control valve (38), return passage (37) and return line (45) to the hydraulic tank.

Right travel motor (15) receives the oil delivery from the right pump. The right travel motor functions in the same manner as the left travel motor in the LOW SPEED position.

HIGH SPEED




Illustration 8g00773193



Illustration 9g00820297

Left travel motor (HIGH SPEED)

(1) Left travel motor

(2) Swashplate

(3) Motor rotary group

(4) Swashplate control piston

(5) Passage (supply oil)

(8) Counterbalance valve

(9) Swashplate control piston

(11) Passage (return oil)

(12) Displacement change valve

(13) Passage

(27) Pilot line

(46) Pressure sensor (left pump)

(48) Travel speed solenoid valve

(49) Left pump

(51) Pilot pump

(56) Travel speed control switch

(58) Left travel lever/pedal

(A) Indicator for HIGH SPEED

(B) Indicator for LOW SPEED

(C) Engine and pump controller

When travel speed control switch (56) is set at the HIGH SPEED position, an electrical signal is sent to engine and pump controller (D). Pressure sensors (46) and (47) also send an electrical signal to the engine and pump controller. If the travel load is light and when the pump delivery pressure is below a certain pressure, the engine and pump controller energizes travel speed solenoid valve (48). Pilot system oil pressure flows through travel speed solenoid valve (48) and line (27) to displacement change valve (12). The spool in the displacement change valve shifts. A portion of the oil delivery from the left pump flows through the displacement change valve to swashplate control piston (4). Swashplate control piston (4) moves swashplate (2) to the minimum displacement position. At the same time, the oil that acts on swashplate control piston (9) flows into the case drain of the travel motor. One rotation of motor rotary group (3) displaces a smaller amount of oil flow. The rotational speed of the left travel motor increases. The left track moves at a faster speed.

The return oil from motor rotary group (3) flows through passage (11), counterbalance valve (8), line (28) and swivel (30). The return oil then flows through line (34), left travel control valve (38), return passage (37) and return line (45) to the hydraulic tank.

Right travel motor (15) receives the oil delivery from the right pump. The right travel motor functions in the same manner as the left travel motor in HIGH SPEED position.

Automatic Travel Speed Change




Illustration 10g00820128

Main pump compartment

(46) Pressure sensor for right pump delivery

(47) Pressure sensor for left pump delivery

Pressure sensor (46) monitors the delivery pressure of the right pump. Pressure sensor (47) monitors the delivery pressure of the left pump. The motor displacement is low when the travel speed control switch is set at the HIGH SPEED position and the travel load is light. As the pump load increases, the delivery pressure of the pumps increases. When the delivery pressure of the pumps reaches a certain pressure, the pressure sensor sends an electrical signal to the engine and pump controller. The engine and pump controller de-energizes travel speed solenoid valve (48). Travel speed solenoid valve (48) blocks the flow of pilot system supply oil to displacement change valves (14) and (20). The oil in swashplate control pistons (4) and (22) now flows into the case drain of the travel motors. Swashplates (2) and (16) move to the maximum displacement position. One rotation of the motor rotary groups in the travel motors displaces a larger amount of oil flow. The rotational speed of the travel motors decreases. The travel speed is automatically changed to LOW SPEED.

When the pump load decreases and the travel speed control switch is set at the HIGH SPEED position, pressure sensors (46) and (47) will now cause the engine and pump controller to energize travel speed solenoid valve (48). Displacement change valves (12) and (20) will be shifted by pilot pressure so that the motor rotary groups will change to the minimum displacement position. One rotation of the motor rotary groups displaces a small amount of oil flow. The travel speed will automatically change to HIGH SPEED.

The ability of the machine to automatically change the travel speed allows good performance at high speed and better traction control.

Information System:

345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Engine and Hydraulic Pump Controller
345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Additional Functions
345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Work Mode
345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Power Mode Operation
3500B Engines for 5130B and 5230B Excavators Diagnostic Codes
Horizontal Pin Lock Series PW Quick Coupler Specifications
HDB Series and M1 Series Heavy Duty Brushless Alternators Charging System
325C Excavator Hydraulic System Pilot Hydraulic System
322C Excavator Hydraulic System Main Control Valve
322C Excavator Hydraulic System Negative Flow Control System
312C and 312C L Excavator Engine Oil and Filter - Change
322C Excavator Hydraulic System Pump Control (Main Hydraulic) - Main Pump Regulator
5130B Excavator Hydraulic System Control Valve (Implement)
5130B Excavator Hydraulic System Control Valve (Implement)
308B, 311B, 312B, 315B, 317B, 318B, 320B, 322B, 325B, 330B, M325B and W330B Excavators Engine and Pump Control Operator Monitor
345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Switches
345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Sensors
345B, 345B Series II and W345B Series II Excavators Engine and Pump Control Senders
5130B Excavator Ladders
312C Excavator Machine Systems Blade Cylinder - Remove
Quick Coupler Wedge Lock(Wheel Loader) Model View Illustrations
Horizontal Pin Lock Series PW Quick Coupler Operation
Quick Coupler Wedge Lock(Wheel Loader) Quick Coupler Operation
2001/12/24 The New Steering Control Valve Groups Improve Service Life {5051}