W345B Series II Material Handler Hydraulic System Travel Hydraulic System Caterpillar


Travel Hydraulic System
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1.1. Hydraulic Schematic for Forward Travel
2.1. Travel Control
3.2. Introduction
4.2. Forward Travel Operation
5.3. Low Speed
6.3. High Speed
7.2. Automatic Travel Speed

Hydraulic Schematic for Forward Travel




Illustration 1g00816923

(1) Left travel motor

(2) Left parking brake

(3) Left motor rotary group

(4) Right parking brake control valve

(5) Right travel motor

(6) Right parking brake

(7) Right motor rotary group

(8) Left parking brake control valve

(9) Left travel brake valve

(10) Left travel pilot valve

(11) Left travel counterbalance valve

(12) Travel speed control valve

(13) Right travel brake valve

(14) Right travel pilot valve

(15) Right travel counterbalance valve

(16) Swivel

(17) Line

(18) Passage

(19) Line

(20) Passage

(21) Passage

(22) Line

(23) Line

(24) Line

(25) Line

(26) Passage

(27) Passage

(28) Return passage

(29) Center bypass passage

(30) Right travel control valve

(31) Left travel control valve

(32) Passage

(33) Pilot control valve (left travel and right travel)

(34) Line

(35) Return line

(36) Line

(37) Travel speed solenoid valve

(38) Upper pump

(39) Line

(40) Pressure sensor

(41) Lower pump

(42) Line

(43) Pilot pump

(44) Shuttle valve

Travel Control

Introduction

The components of the travel hydraulic system are identical for both sides of the machine.




Illustration 2g00816695

Drive system (partial view from top of one side)

(1) Travel motor

(2) Parking brake

(3) Speed reducer

(4) Drive shaft

(5) Drive wheel axle

(6) Sprocket

(7) Chain

(8) Axle (driven wheel)

(9) Axle (driven wheel)

(10) Turntable bearing

The drive system for the W345B Series II Wheeled Material Handler includes the following components: travel motor (1), parking brake (2), speed reducer (3), drive shaft (4), drive wheel axle (5), sprockets (6), chains (7), axles for driven wheels (8) and (9) and turntable bearings (10).

Axles (5), (8), and (9) are supported by turntable bearings (10). Axles (5), (8), and (9) have sprockets (6). Drive shaft (4) transmits torque from speed reducer (3) to drive wheel axle (5). The torque is transmitted to axles (8) and (9) through sprockets (6) and chains (7) .

Note: Refer to Illustration 1 as you read the following descriptions.

Left travel motor (1) and right travel motor (5) are supplied oil through swivel (16) from lower pump (41) and upper pump (38). When left travel motor (1) is operated by lower pump oil, the motor torque is transferred to the left travel drive. The left travel drive reduces the speed of left travel motor (1), and the drive also increases the torque of left travel motor (1). The increased torque turns the drive wheel. The drive wheel is connected to two driven wheels on the same side of the machine through sprockets and chains.




Illustration 3g00644767

(47) Travel speed control switch

Travel speed control switch (47) provides a selection of HIGH or LOW travel speed. During partial movements of the travel control lever, the travel speed varies with the travel distance of the lever. When the switch is placed in the TORTOISE position, the machine travels at the LOW speed mode. When the switch is placed in the RABBIT position, the machine travels at the Automatic Travel Speed mode. Select the RABBIT mode for increased speed when the machine is on a flat surface and the machine is travelling straight.

When travel speed control switch (47) is in the HIGH position, pressure sensor (40) automatically changes the travel speed. For higher torque requirements, the machine travels at LOW speed. For lower torque requirements, the machine travels at HIGH speed.




Illustration 4g00818043

(1) Left travel drive

(5) Location of right travel drive

(33) Pilot control valves (left travel and right travel)

(48) Forward direction

(49) Left travel lever

(50) Right travel lever

(51) Cab

(52) Yellow painted area

(53) Reverse direction

The direction of travel (forward or reverse) is relative to the position of the lower structure. For normal travel, the undercarriage is positioned with the yellow end (52) of the walkway to the rear of the machine. When the machine is in the normal position of travel and the travel levers/pedals are moved forward, the machine will travel in the forward direction. When the travel levers/pedals are moved toward the rear of the cab, the machine will begin reverse travel.

When cab (51) is turned 180°, the yellow painted area (52) of the walkway will be visible from the operator's station. When the operator operates the travel levers/pedals, the direction of travel will be reversed. When the travel levers/pedals are moved forward, the machine will begin reverse travel. When the travel levers/pedals are moved toward the rear of the cab, the machine will travel in the forward direction.

Note: Pivot turns and spot turns can only be performed when the travel speed control switch is in the LOW speed position. When the travel speed control switch is in the HIGH speed position, only small steering corrections can be performed. If the operator makes larger corrections, the motor will automatically downshift by the Automatic Travel Speed control to LOW speed. After the correction has been performed and the machine is travelling straight, the motor will automatically upshift to HIGH speed.

A pivot turn is made when the operator changes the travel direction of the machine. When only one of travel levers/pedals (49) or (50) is moved forward, the respective side travels forward. The opposite side of the machine is stationary. Therefore, the machine turns with the stationary side as the pivot point.

A spot turn is made when the travel direction of the machine is changed in tight quarters. In a spot turn, the machine turns with a minimum radius and the center of the machine is the pivot point. To complete a spot turn, one travel lever is moved to the rear while the other travel lever is moved forward at the same time. The two sides of the machine will travel in opposite directions.

Forward Travel Operation




Illustration 5g00818335

Main control valve compartment (front view)

(31) Left travel control valve

(30) Right travel control valve

When the travel pedals are operated, pilot oil from pilot control valve (33) shifts the stem in travel control valves (31) and (30). The travel control valves allow oil flow from lower pump (41) and upper pump (38) to flow to swivel (16). The swivel transfers oil from the rotating upper structure to the lines in the lower structure. The oil flows to left travel motor (1) and right travel motor (5) .

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.

Pilot oil from control valve (33) flows through line (34) and into left travel control valve (31). The pilot oil shifts the stem of left travel control valve (31). Lower pump oil in passage (29) flows through passage (32) to passage (27). The pilot oil in passage (27) flows through line (25), swivel (16), line (22), and counterbalance valve (11). Pilot oil enters motor rotary group (3) through passage (18) from the counterbalance valve.

Part of the lower pump oil flows through passage (19), brake pilot valve (10), and passage (20) to parking brake assembly (2). Parking brake assembly (2) releases. The left travel motor rotates in the forward direction.

Low Speed

When travel speed control switch (47) is placed in the LOW position, pilot oil flow to the left motor rotary group (3) is blocked. This causes the pistons to move to the maximum displacement position, and more oil is required to turn left motor rotary group (3). This causes the motor to rotate at a slower speed. The left track travels at a lower speed, and the slower speed increases the drawbar pull.

Return oil from motor rotary group (3) flows through passage (20), counterbalance valve (11), and line (22) to swivel (16). Oil flows through line (24), passage (29), and left travel control valve (31) to return passage (28). The oil flows back to the hydraulic tank through return line (35) .

Right motor rotary group (7) is turned by oil from the upper pump.

High Speed




Illustration 6g00818339

Pilot oil manifold compartment

(37) Travel speed solenoid valve

Note: The right and left travel motors function in the same manner. The explanation for the right travel motor will be used to explain forward travel in high speed mode.

When travel speed control switch (47) is placed in the HIGH speed position, travel speed solenoid valve (37) is energized. When the pump delivery pressure does not increase to a certain pressure, automatic travel speed solenoid valve (37) remains open. Oil from pilot pump (43) flows through line (42), travel speed solenoid valve (37), line (23), and swivel (16) to motor rotary group (7). This allows the upper pump oil in right travel motor (5) to flow to motor rotary group (7) .

The pressure oil decreases the angle of displacement in motor rotary group (7). Less oil is required to turn right travel motor (5). Therefore, the motor turns at a faster speed, and the higher speed decreases the drawbar pull.

Automatic Travel Speed




Illustration 7g00818356

Pump compartment

(40) Pressure sensor

Note: The right and left travel motors function in the same manner. The explanation for the right travel motor will be used to explain the automatic travel speed. In the explanation, travel speed control switch (12) is placed in the HIGH SPEED position.

Part of oil from upper pump (38) and lower pump (41) combines at shuttle valve (44). The oil flow of the pump with the greater pressure flows into line (39) to pressure sensor (40). Oil pressure maintains the motor rotary group at the minimum displacement. The displacement increases as the load on the machine increases. The output pressure of the pump also increases as the load on the machine increases.

When the output pressure increases to a high level, a signal from pressure sensor (40) de-energizes travel speed solenoid valve (37) and pilot oil is not supplied to the motor rotary group. The displacement in the travel motor increases to the maximum level, and the machine travels at LOW speed.

When the circuit pressure in line (39) decreases to a certain range because of decreased pump output pressure, automatic travel speed solenoid valve (37) is energized, and the displacement in the motor rotary group decreases to the minimum level. The machine travels at HIGH speed.

Automatic travel speed solenoid valve (37) allows the machine to adjust speeds. The machine will travel at HIGH speed under a small torque requirement. The machine will travel at LOW speed under a large torque requirement. This ensures that the machine has both high speed and a high drawbar pull.

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