CB44B Vibratory Asphalt Compactor Propel System Caterpillar

Illustration 1	g03409357
Right Side of Machine (1) Main hydraulic pump

Main hydraulic pump (1) is located on the right side of the machine. This pump is driven by the engine. The door on the right side of the machine provides access to this component.

Main hydraulic pump (1) is a piston type pump with variable displacement. The pump housing contains two rotating groups. The rotating groups are face to face. The rotating group on the side of the pump with the input shaft provides flow to the propel system. The rotating group on the end cap side of the pump provides flow to the vibratory system.

Note: Refer to "Vibratory System" for additional information about the components and controls of the vibratory system.

Illustration 2	g03409360
Main Hydraulic Pump (2) Pump adjustment (3) Forward solenoid (4) Port "M3" (5) Port "MB" (6) Port "MC" (7) Pump adjustment (8) Vibratory solenoid "MB" (9) Port "MD" (10) Port "MA" (11) Reverse solenoid (12) Port "M5" (13) Makeup and relief valve for port "B" (14) Charge relief valve (15) Port "M4" (16) Interlock solenoid (17) Vibratory solenoid "MA" (18) Port "L3" (19) Port "M5" (20) Port "C" (21) Port "E" (22) Port "M4" (23) Port "L1" (24) Port "M3" (25) Makeup and relief valve for port "A" (26) Makeup and relief valve for port "D" (27) Makeup and relief valve for port "C" (28) Port "D" (29) Port "A" (30) Port "B"

Each port in the pump housing is identified by a numeric or an alpha-numeric designation which is cast into the housing next to the port. The function of each port is as follows:

• Port "A" (29) - This port is a system port. Port "A" is connected to port "P1" of the front propel motor and port "P1" of the rear propel motor.

• Port "B" (30) - This port is a system port. Port "B" is connected to port "P2" of the front propel motor and port "P2" of the right propel motor.

• Port "C" (20) - This port is a system port. Port "C" is connected to port "B1" of the machine valve.

• Port "D" (28) - This port is a system port. Port "D" is connected to port "A1" of the machine valve.

• Port "E" (21) - This port is the charge inlet port. Filtered charge oil is directed into port "E".

• Port "L1" (23) - This port is a case drain port. Port "L1" is plugged.

• Port "L3" (18) - This port is the main case drain port. Case drain oil from the main hydraulic pump flows to the return manifold through port "L3".

• Port "MA" (10) - This port is a gauge port for the pressure at port "A".

• Port "MB" (5) - This port is a gauge port for the pressure at port "B".

• Port "MC" (6) - This port is a gauge port for the pressure at port "C".

• Port "MD" (9) - This port is a gauge port for the pressure at port "D".

• Port "M3" (4) - This port is a charge pressure port.

• Port "M4" (15) and (22) - Each rotating group in the pump is equipped with a port labeled "M4". These ports are located on opposites sides of the pump housing. Each of these ports is plugged. The pressure on one side of the servo piston can be measured at port "M4". Port "M4" (22) on the shaft end of the pump housing can be used to measure servo pressure for the shaft end rotating group. This port is pressurized when the supply oil is directed out port "A" of the pump. Port "M4" (15) on the end cap end of the pump housing can be used to measure servo pressure for the end cap rotating group. This port is pressurized when the supply oil is directed out port "C" of the pump.

• Port "M5" (12) and (19) - Each rotating group in the pump is equipped with a port labeled "M5". These ports are located on opposites sides of the pump housing. Each of these ports is plugged. The pressure on one side of the servo piston can be measured at port "M5". Port "M5" (12) on the shaft end of the pump housing can be used to measure servo pressure for the shaft end rotating group. This port is pressurized when the supply oil is directed out port "B" of the pump. Port "M5" (19) on the end cap end of the pump housing can be used to measure servo pressure for the end cap rotating group. This port is pressurized when the supply oil is directed out port "D" of the pump.

Each rotating group contains a direction control valve and servo piston. Each direction control valve is equipped with two EDCs. The EDCs are proportional solenoids. The function of each solenoid is as follows:

• Reverse solenoid (11) on the input shaft end - This solenoid controls flow out port "A" of the pump. Reverse solenoid (11) is the reverse propel solenoid for the front propel motor and the rear propel motor.

• Forward solenoid (3) on the input shaft end - This solenoid controls flow out port "B" of the pump. Forward solenoid (3) is the forward propel solenoid for the front propel motor and the rear propel motor.

• Vibratory solenoid "MB" (8) on the end cap end - This solenoid controls flow out port "C" of the pump. This solenoid is a component of the vibratory system.

• Vibratory solenoid "MA" (17) on the end cap end - This solenoid controls flow out port "D" of the pump. This solenoid is a component of the vibratory system.

The pump housing is equipped with charge relief valve (14). This valve is mechanically adjustable. The charge relief valve maintains charge pressure at 3000 ± 300 kPa (435 ± 45 psi).

Each rotating group of the pump housing is equipped with two makeup and relief valves. The relief valves limit the pressure in the circuit to 42500 ± 2000 kPa (6164 ± 290 psi). The makeup valves allow charge oil to flow into the low-pressure circuit in order to replenish the oil lost to flushing and internal leakage.

The location of each makeup and relief valve is as follows:

• Valve for port "A" (25)

• Valve for port "B" (13)

• Valve for port "C" (27)

• Valve for port "D" (26)

Each rotating group is equipped with pump adjustment screw (2) and (7). The pump adjustment screw is used to adjust the hydraulic zero setting of the rotating group. This adjustment aligns the swashplate and the direction control valve. This alignment sets each swashplate to zero degrees when the propel system is not operating.

The interlock valve is located inside the main hydraulic pump. The machine ECM number one controls this solenoid operated valve. When the parking brake is engaged, interlock solenoid (16) is not energized. When the parking brake is released, the solenoid is energized.

When interlock solenoid (16) is energized, charge oil is available at the direction control valve in each rotating group. Charge oil is also sent to the parking brakes. When the solenoid is not energized, charge oil is blocked. In this case, the direction control valves and the parking brakes are open to case drain. Under these conditions, the rotating groups of the main hydraulic pump are at zero angle, and the parking brakes are engaged.

Illustration 3	g03409363
Main Hydraulic Pump (31) Servo springs (32) Swashplate (33) Slipper pad (34) Feedback link (35) EDC (36) Servo piston (37) Servo piston (38) EDC (39) Feedback link (40) Servo springs (41) Swashplate (42) Slipper pad (43) Piston (44) Vibratory rotating group (45) Propel rotating group (46) Piston (47) Input shaft

Engine rotation turns pump input shaft (47), which then rotates propel rotating group (45) and vibratory rotating group (44). The rotating groups contain a piston and barrel assembly. Pistons (46) and (43) in the groups rotate with the barrel assembly. Piston slipper pads (33) and (42) allow the pistons to follow the angle of swashplates (32) and (41). The rotating groups only generate flow when the swashplates are not at zero angle.

When the machine electronic control system sends an output signal to EDC (38) or (35), corresponding servo piston (37) or (36) moves. As the servo piston moves, the action of the control linkage causes the angle of swashplates (41) or (32) to change. The swashplate angle is proportional to the signal from the machine electronic control system.

Slipper pads (33) and (42) in each rotating group (44) and (45) follow the angle of swashplates (32) and (41). This action causes pistons (43) and (46) to move in and out of the barrel assembly as input shaft (47) rotates. As a piston moves out of the barrel assembly, oil in the low-pressure circuit is drawn into the piston chamber. As a piston moves into the barrel assembly, oil is forced out of the piston chamber and into the high-pressure circuit.

Illustration 4	g03409364
Makeup and Relief Valves LOW PRESSURE and HIGH PRESSURE Operation (48) Relief poppet (49) Check valve (50) Relief spring (51) Makeup spring

Oil in the high-pressure side of the closed circuit loops acts to close check valve (49). Oil in the low pressure (return) side of the closed circuit loop acts to open the check valve. Flushing and internal leakage cause pressure in the return side of the closed circuit to decrease. This decrease causes charge pressure to unseat the check valve. When the pressure in the return circuit is low enough, the check valve moves the main relief cartridge against the force of makeup spring (51). The check valve opens a passage for charge oil to flow into the return side of the circuit. Charge oil replenishes the oil that the circuit looses from flushing and internal leakage.

Pressure in the high-pressure circuit acts to open relief poppet (48). The combined force from the oil in the charge circuit and relief spring (50) acts to close the relief poppet. When the pressure in the high-pressure circuit reaches the relief setting, the relief poppet compresses the relief spring. In this case, oil from the high-pressure circuit is directed into the charge circuit.