 | |
| Illustration 1 | g01388561 |
Hydraulic schematic for the travel circuit (1) Travel speed solenoid (high speed or low speed) (2) Pilot manifold (3) Pilot control valve (4) Pilot pump (5) Travel control valve (6) Proportional solenoid valves (left) (7) Proportional solenoid valves (right) (8) Travel pump (9) Left travel control valve (10) Right travel control valve (11) Swivel (12) Left travel motor (13) Parking brake (14) Displacement control valve (15) Crossover relief valve (forward) (16) Counterbalance valve (17) Load check valve (18) Resolver valve (19) Brake release valve (20) Pressure reducing valve (brake) (21) Pressure reducing valve (brake) (22) Brake release valve (23) Resolver valve (24) Load check valve (25) Counterbalance valve (26) Crossover relief valve (forward) (27) Displacement control valve (28) Right travel motor (29) Parking brake (30) Hydraulic oil tank (31) Motor rotary group (32) control piston (speed) (33) Crossover relief valve (reverse) (34) Crossover relief valve (reverse) (35) control piston (speed) (36) Motor rotary group | |
Travel Control
Introduction
 | |
| Illustration 2 | g00924670 |
Right travel motor (21) Pressure reducing valve (brake) (24) Load check valve (25) Counterbalance valve (26) Crossover relief valve (forward) (34) Crossover relief valve (reverse) (36) Motor rotary group | |
 | |
| Illustration 3 | g00924672 |
Right side final drive (37) Track (38) Sprocket (39) Final drive | |
The output flows from travel pump (8) to travel control valve (5). The oil flows to left travel control valve (9) and right travel control valve (10) through swivel (11) to left travel motor (12) and right travel motor (28). 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 final drive (39). Final drive (39) increases the torque and the rotational force drives track (37) via sprocket (38).
 | |
| Illustration 4 | g01162220 |
Location of the two speed switch (travel) | |
The travel speed can be adjusted by the slight operation of the travel pedals. The travel speed can also be controlled by the travel speed control switch. This changes the travel speed when the travel pedals are moved to the maximum position. The travel speed control switch can be set at the LOW SPEED position (tortoise) or the HIGH SPEED position (rabbit). 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.
 | |
| Illustration 5 | g00924673 |
Operation of travel (12) Left travel motor (28) Right travel motor (40) Footrest (41) Left travel pedal (42) Right travel pedal (43) Footrest (44) Front idlers (45) Forward travel (46) Cab (47) Reverse travel | |
The direction of travel is relative to the position of the lower structure. For normal travel, idlers (44) are positioned in front of cab (46). Travel motors (12) and (28) are positioned to the rear of the cab. With the machine in the normal position of travel, depress the top of travel pedals (41) and (42). The machine will travel in forward direction (45). When the bottom of travel pedals (41) and (42) are depressed the machine travels in reverse direction (47) .
When cab (46) is rotated by 180 degrees, travel motors (12) and (28) are positioned in front of the cab. The direction of travel and the operation of travel pedals (41) and (42) are reversed from the normal travel direction.
When the machine is in the normal position of travel and when one of the travel pedals (41) or (42) 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 6 | g01067588 |
Travel control valve (5) Travel control valve (6) Proportional solenoid valves (7) Proportional solenoid valves (9) Travel control valve (left) (10) Travel control valve (right) | |
Move the hydraulic lockout to the UNLOCKED position. This allows the pilot system oil to flow to proportional solenoid valves (6) and (7) .
When both of the travel pedals are operated in the FORWARD TRAVEL position, a signal is sent to the IQAN control system. The IQAN control system sends a signal that energizes proportional solenoid valves (6) and (7). The proportional solenoid valves for forward travel are energized. The pilot system oil pressure flows from proportional solenoid valves (6) and (7) to left travel control valve (9) and right travel control valve (10).
The pilot system oil pressure shifts the spools in both of the travel control valves. The travel control valves allow the pump oil from travel pump (8) to flow to swivel (11). The swivel transfers the pump oil from the rotating upper structure to the lines in the lower structure. The pump oil flows to left travel motor (12) and right travel motor (28) .
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 pedal is moved to the FORWARD TRAVEL position, The proportional solenoid valve is energized by the IQAN control system. Pilot system oil flows to left travel control valve (9). The spool in left travel control valve (9) shifts. The pump oil from travel pump (8) flows through the center passage of left travel control valve (9). The pump oil flows out of left travel control valve (9) through a supply line to swivel (11). The pump oil flows from swivel (11) through a supply line to left travel motor (12) .
The pump oil from travel pump (8) enters left travel motor (12). The pump oil flows through a check valve to counterbalance valve (16) and crossover relief valve (15). The pump oil passes through an internal passage to displacement control valve (14) and motor rotary group (31). The pump oil flows through an orifice to the top of counterbalance valve (16).
Counterbalance valve (16) shifts downward allowing return oil from motor rotary group (31) to flow through load check valve (17) to the return line. At the same time, a portion of the pump oil from travel pump (8) flows through a passage to resolver valve (18) .
The oil flows through resolver valve (18) through an internal passage to brake release valve (19). Brake release valve (19) sends oil through pressure reducing valve (20) to parking brake (13). Pressure reducing valve (20) and the orifice in the return line limit the maximum pressure in order to release parking brake (13) .
The parking brake inside the final drive is released. The pump oil from travel pump (8) causes left travel motor (9) to rotate in the forward direction.
Low Speed
 | |
| Illustration 7 | g01388553 |
Travel speed solenoid valve The travel speed solenoid valve is located on the pilot manifold. | |
When the travel speed control switch is set at the LOW SPEED position, the travel speed solenoid is energized. The pilot oil flows to displacement control valve (14). The spool in displacement control valve (14) shifts. A portion of the oil that flows from travel pump (8) flows through internal passages and displacement control valve (14) to control piston (32). As a result, control piston (32) moves the barrel of the travel motor to the maximum displacement position. At the same time, the oil that acts on the other side of control piston (32) flows into the drain line. One rotation of motor rotary group (31) displaces a larger amount of oil flow. The rotational speed of left travel motor (12) decreases. The left track moves at a slower speed. This increases the drawbar pull.
The return oil from motor rotary group (31) flows through an internal passage, counterbalance valve (16), load check valve (17), an external line and swivel (11). The return oil then flows to left travel control valve (9). The return oil flows from left travel control valve (9) to a return line. The return oil passes through an oil cooler to hydraulic oil tank (30) .
Right travel motor (28) receives the oil delivery from travel pump (8). The right travel motor functions in the same manner as the left travel motor, when the travel control switch is in the LOW SPEED position.
Medium Speed
The operator may select medium travel speed with the button on the right hand joystick. Medium travel speed is only available when the travel speed control switch is set at the HIGH SPEED position. IQAN receives electrical signals from the travel pedals and the joysticks. IQAN processes the electrical input signals. IQAN then outputs the signals to the solenoids. The pilot system oil is blocked. The spool in displacement control valve (14) shifts. A portion of the oil from travel pump (8) flows through control valve (14) to control piston (32). Control piston (32) moves the barrel of the travel motor to the minimum displacement position. At the same time, the oil that acts on the other side of control piston (32) flows into the drain line. One rotation of motor rotary group (31) displaces a smaller amount of oil flow. The rotational speed of left travel motor (12) increases.
The return oil from motor rotary group (31) flows through an internal passage, counterbalance valve (16), load check valve (17), an external line and swivel (11). The return oil then flows to left travel control valve (9). The return oil flows from left travel control valve (9) to a return line. The return oil passes through an oil cooler to hydraulic oil tank (30) .
Right travel motor (28) receives the oil from travel pump (8). The right travel motor functions in the same manner as the left travel motor, when the travel control switch is in the HIGH SPEED position.
High Speed
When the travel speed control switch is set at the HIGH SPEED position, the travel speed solenoid is de-energized. The pilot system oil is blocked. The spool in displacement control valve (14) shifts. A portion of the oil from travel pump (8) flows through control valve (14) to control piston (32). Control piston (32) moves the barrel of the travel motor to the minimum displacement position. At the same time, the oil that acts on the other side of control piston (32) flows into the drain line. One rotation of motor rotary group (31) displaces a smaller amount of oil flow. The rotational speed of left travel motor (12) increases.
The return oil from motor rotary group (31) flows through an internal passage, counterbalance valve (16), load check valve (17), an external line and swivel (11). The return oil then flows to left travel control valve (9). The return oil flows from left travel control valve (9) to a return line. The return oil passes through an oil cooler to hydraulic oil tank (30) .
Right travel motor (28) receives the oil from travel pump (8). The right travel motor functions in the same manner as the left travel motor, when the travel control switch is in the HIGH SPEED position.