CB54B Vibratory Asphalt Compactor Machine Systems Caterpillar

Illustration 1	g03816013
Vibratory Hydraulic System Off (1) Solenoid "C2" (2) Solenoid "C1" (3) From charge filter outlet (4) To propel pump port "E" (5) Servo piston (6) Vibratory pump (7) Pressure limiter valve (8) To return manifold (9) Front drum bypass valve (10) Rear vibratory solenoid (11) Rear drum bypass valve (12) Front vibratory solenoid (13) Intercircuit relief valve (14) Anticavitation check valve (15) Shift solenoid (16) Manual brake release pump (17) Pressure limiter (18) Makeup valve (19) Main relief valve (20) Charge relief valve (21) Makeup valve (22) Main relief valve (23) Front vibratory motor (24) To return manifold (25) Flushing spool (26) Flushing relief valve (27) Rear vibratory motor (28) To return manifold

The vibratory system consists of a closed-loop hydrostatic-drive circuit with one vibratory pump (6) and two vibratory motors (23) and (27). The pump is controlled by two solenoids: solenoid "C1" (2) and solenoid "C2" (1). Machine ECM number-one controls these solenoids.

The fan system provides charge oil to the vibratory system (and the propel system) when the engine is running. Charge oil from charge filter (3) flows into port "E" of vibratory pump (6). Inside the vibratory pump, charge oil flows to makeup valves (18) and (21), to pump control solenoids (1) and (2), and to charge relief valve (20).

Displacement of the rotating group in the pump is electronically controlled. Neither of pump control solenoids (1) and (2) is energized when the vibratory system is off. In this case, both sides of servo piston (5) are open to the case drain across the pump control solenoids. The swashplate in the rotating group is at zero angle, and vibratory pump (6) does not produce flow.

Charge pressure acts against makeup valves (18) and (21). If the pressure in either side of the loop falls below charge pressure, the corresponding makeup valve opens. In this case, charge oil flows into the loop. If the pressure in the charge system is greater than 3000 ± 300 kPa (435 ± 43 psi), charge relief valve (20) directs oil into the pump case.

Since the pressure in each loop is equal when the vibratory system is not operating, flushing spool (25) in the vibratory and brake control valve is in the center position. In this case, the spool prevents flushing oil from flowing into the case drains of the vibratory motors.

Note: Since flushing spool (25) is located in the vibratory and brake control valve, the flushing spools that would normally have been in the vibratory motors have been removed. A plug has been inserted in each vibratory motor in place of the flushing spool. The above illustration shows the plug.

Illustration 2	g03816015
Vibratory Hydraulic System (1) Solenoid "C2" (2) Solenoid "C1" (3) From charge filter outlet (4) To propel pump port "E" (5) Servo piston (6) Vibratory pump (7) Pressure limiter valve (8) To return manifold (9) Front drum bypass valve (10) Rear vibratory solenoid (11) Rear drum bypass valve (12) Front vibratory solenoid (13) Intercircuit relief valve (14) Anticavitation check valve (15) Shift solenoid (16) Manual brake release pump (17) Pressure limiter (18) Makeup valve (19) Main relief valve (20) Charge relief valve (21) Makeup valve (22) Main relief valve (23) Front vibratory motor (24) To return manifold (25) Flushing spool (26) Flushing relief valve (27) Rear vibratory motor (28) To return manifold

The above illustration shows the vibratory system operating. The following table shows the conditions illustrated on this schematic.

When the vibratory operating parameters are as described above, machine ECM number-one sends an output signal to vibratory solenoid "C1" (2). In this case, solenoid "C1" (2) directs charge oil into servo piston (5). The pressure in the servo piston causes the pump servo to move. This movement changes the angle of the swashplate in the rotating group. The stronger the signal to the solenoid, the greater the swashplate angle, and therefore, the greater the oil flow from vibratory pump (6) .

As a swashplate moves, the feedback linkage tends to move the pump solenoid spool back to neutral through an internal feedback spring. This action prevents the servo piston from tilting the swashplate too far.

Supply oil from the rotating group acts against pressure limiter valve (17), makeup valve (18), and main relief valve (19). This oil flows out port "A" of vibratory pump (6) and is directed to port "B1" of the vibratory and brake control valve. Internal passages in the vibratory and brake control valve direct the supply oil to rear drum bypass valve (11), to flushing spool (25) and out port "B" of the vibratory and brake control valve.

From port "B" of the vibratory and brake control valve, oil is directed to port "B" of rear vibratory motor (27). On the outlet side of the rear vibratory motor, oil follows two paths. The first path leads to port "A" of front vibratory motor (23). The second path leads to port "P" of the vibratory and brake control valve.

Note: Port "B" of front vibratory motor (23) is connected to port "B" of vibratory pump (6) through the vibratory and brake control valve.

Inside the vibratory and brake control valve, oil is distributed to the following locations:

• Anticavitation check valve (14)

• Intercircuit relief valve (13)

• Front vibratory solenoid (12)

• Rear drum bypass valve (11)

• Rear vibratory solenoid (10)

• Front drum bypass valve (9)

When the drum mode is set to both drums, front vibratory solenoid (12) is not energized, and rear vibratory solenoid (10) is not energized. In this case, pressurized oil acting against the spring side of rear drum bypass valve (11) keeps the rear drum bypass valve closed. Likewise, pressurized oil acting against the spring side of front drum bypass valve (9) keeps the front drum bypass valve closed.

When rear drum bypass valve (11) and front drum bypass valve (9) are both closed, oil is forced to flow through front vibratory motor (23). In this case, the pressure on the inlet side of the front vibratory motor quickly increases in an attempt to overcome the inertia of the resting eccentric weights.

Note: Machine ECM number-one ramps the amplitude of the signal to vibratory solenoid "C1" (2) in order to limit the initial pressure surge during start-up.

As vibratory pump (6) produces flow from port "A", the pressure differential between port "A" and port "B" of the pump increases. This increase also creates a pressure differential across front vibratory motor (23).

The pressure differential between the two sides of front vibratory motor (23) causes the motor to turn. This rotation creates a pressure drop across rear vibratory motor (27). Under these conditions, the rear vibratory motor also begins to rotate.

Inside vibratory pump (6), supply oil from the rotating group acts against relief valve (19), makeup valve (18), and pressure limiter valve (17). As long as the supply pressure is greater than charge pressure, the makeup valve remains seated. As long as the supply pressure is less than relief pressure, the pressure limiter and the main relief valve remain closed.

If pressure in the return side of the loop falls below charge pressure, makeup valve (21) opens. In this case, charge oil flows into the low-pressure side of the loop. When pressure in the low-pressure side of the loop rises above charge pressure, the makeup valve closes.

Loop flushing is controlled by components in the vibratory and brake control valve. In the valve, oil in the high-pressure side of the circuit acts against one side of flushing spool (25). Oil in the low-pressure side of the circuit acts against the opposite side of the flushing spool. The higher-pressure oil moves the flushing spool. This movement allows oil from the low-pressure side of the circuit to flow across the spool to flushing relief valve (26).

Any time the pressure in the low-pressure side of the circuit is greater than the setting of flushing relief valve (26), the flushing relief valve opens. In this case, oil from the low-pressure circuit flows to port "T1" of the vibratory and brake control valve. From there, flushing oil is directed into port "T1" of front vibratory motor (23) and into port "T1" of rear vibratory motor (27) .

The pressure setting of flushing relief valve (26) is less than the pressure setting of charge relief valve (20). This fact ensures that oil is sent through the motor case drains under normal operating conditions. The flushing relief valve will stop flushing flow if the charge pressure is less than the setting of the flushing relief valve. This fact ensures that flushing flow does not cause charge pressure to decrease to the point at which charge pressure becomes less than the brake release requirement in the propel hydraulic circuit.

Illustration 3	g03816023
Vibratory Hydraulic System (1) Solenoid "C2" (2) Solenoid "C1" (3) From charge filter outlet (4) To propel pump port "E" (5) Servo piston (6) Vibratory pump (7) Pressure limiter valve (8) To return manifold (9) Front drum bypass valve (10) Rear vibratory solenoid (11) Rear drum bypass valve (12) Front vibratory solenoid (13) Intercircuit relief valve (14) Anticavitation check valve (15) Shift solenoid (16) Manual brake release pump (17) Pressure limiter (18) Makeup valve (19) Main relief valve (20) Charge relief valve (21) Makeup valve (22) Main relief valve (23) Front vibratory motor (24) To return manifold (25) Flushing spool (26) Flushing relief valve (27) Rear vibratory motor (28) To return manifold

The above illustration shows the vibratory system operating. The following table shows the conditions illustrated on this schematic.

When the vibratory operating parameters are as described above, solenoid "C1" (2) and front vibratory solenoid (12) are energized. In this case, supply oil is directed out port "A" of the vibratory pump and into port "B1" of the vibratory and brake control valve. Inside the vibratory and brake control valve, the passage on the spring side of rear drum bypass valve (11) is open to tank across the front vibratory solenoid. However, initially, the rear drum bypass valve remains closed.

Internal passages in the vibratory and brake control valve direct the supply oil out port "B" of the valve. From there, oil is directed to port "B" of rear vibratory motor (27). The outlet side of the rear vibratory motor is connected to two locations. The first connection is to port "A" of front vibratory motor (23). The second connection is to port "P" of the vibratory and brake control valve. Oil in the second connection acts against rear drum bypass valve (11), in opposition to a spring.

When front vibratory solenoid (12) is energized, system pressure causes rear drum bypass valve (11) to shift against the spring force. In this case, port "B1", port "B", and port "P" of the vibratory and brake control valve are connected to port "A" of vibratory pump (6). Under these conditions, the pressure at port "A" and port "B" of the rear vibratory motor is equal, and the motor does not rotate. Since port "B" of front vibratory motor (23) and port "B" of the vibratory pump are connected through the vibratory and brake control valve, the front vibratory motor rotates.

Inside vibratory pump (6), main relief valve (19) and pressure limiter valve (17) in the high-pressure loop limit the maximum system pressure. Makeup valve (21) in the low-pressure side of the system allows charge oil to flow into the low-pressure side of the hydrostatic loop.

Flushing spool (25) and flushing relief valve (26) direct oil from the low-pressure side of the hydrostatic loop into the motor case drains.

Illustration 4	g03816220
Vibratory Hydraulic System (1) Solenoid "C2" (2) Solenoid "C1" (3) From charge filter outlet (4) To propel pump port "E" (5) Servo piston (6) Vibratory pump (7) Pressure limiter valve (8) To return manifold (9) Front drum bypass valve (10) Rear vibratory solenoid (11) Rear drum bypass valve (12) Front vibratory solenoid (13) Intercircuit relief valve (14) Anticavitation check valve (15) Shift solenoid (16) Manual brake release pump (17) Pressure limiter (18) Makeup valve (19) Main relief valve (20) Charge relief valve (21) Makeup valve (22) Main relief valve (23) Front vibratory motor (24) To return manifold (25) Flushing spool (26) Flushing relief valve (27) Rear vibratory motor (28) To return manifold

The above illustration shows the vibratory system operating. The following table shows the conditions illustrated on this schematic.

When the vibratory operating parameters are as described above, solenoid "C2" (1) and rear vibratory solenoid (10) are energized. In this case, supply oil is directed out port "B" of the vibratory pump and into port "A1" of the vibratory and brake control valve. Inside the vibratory and brake control valve, the passage on the spring side of front drum bypass valve (9) is open to tank across the rear vibratory solenoid. However, initially, the front drum bypass valve remains closed.

Internal passages in the vibratory and brake control valve direct the supply oil out port "A" of the valve. From there, oil is directed to port "B" of front vibratory motor (23). The outlet side of the front vibratory motor is connected to two locations. The first connection is to port "A" of rear vibratory motor (27). The second connection is to port "P" of the vibratory and brake control valve. Oil in the second connection acts against front drum bypass valve (9), in opposition to a spring.

When rear vibratory solenoid (10) is energized, system pressure causes front drum bypass valve (9) to shift against the spring force. In this case, port "A1", port "A", and port "P" of the vibratory and brake control valve are connected to port "B" of vibratory pump (6). Under these conditions, the pressure at port "A" and port "B" of the front vibratory motor is equal, and the motor does not rotate. Since port "B" of rear vibratory motor (27) and port "A" of the vibratory pump are connected through the vibratory and brake control valve, the rear vibratory motor rotates.

Inside vibratory pump (6), main relief valve (22) and pressure limiter valve (7) in the high-pressure loop limit the maximum system pressure. Makeup valve (18) in the low-pressure side of the system allows charge oil to flow into the low-pressure side of the hydrostatic loop.

Flushing spool (25) and flushing relief valve (26) direct oil from the low-pressure side of the hydrostatic loop into the motor case drains.

Illustration 5	g03816030
CAAC Hydraulic Schematic (29) Front CAAC cylinder (30) Line relief valve (31) Check valve (32) Check valve (33) Front retract solenoid (34) Port "LS" (35) Port "P" (36) Port "T" (37) Pressure reducing valve (38) Front extend solenoid (39) Rear retract solenoid (40) Rear CAAC cylinder (41) Line relief valve (42) Check valve (43) Check valve (44) Rear extend solenoid

Oil from the steering system is directed into port "P" (35) of the CAAC control valve. This oil flows through pressure reducing valve (37), and is available at the CAAC control solenoids.

When the amplitude of the system is not being adjusted, none of the CAAC solenoids are energized. In this case, the passages to front CAAC cylinder (29) and rear CAAC cylinder (40) are blocked.

Illustration 6	g03816251

Note: The above schematic illustrates a machine without a 360-degree seat or a machine with a 360-degree seat with the seat facing forward.

When the electronic control system is increasing the amplitude of the front drum, front drum retract solenoid (33) is energized. In this case, the solenoid spool directs oil to check valve (32) and out port "FC1" of the CAAC control valve. This oil flows into the rod end of front CAAC cylinder (29). As the cylinder retracts, oil displaced from the head end flows through port "FC2", across the solenoid spool, and out port "T" (35) .

When the electronic control system is decreasing the amplitude of the rear drum, rear drum extend solenoid (44) is energized. In this case, the solenoid spool directs oil to check valve (43) and out port "RC2" of the CAAC control valve. This oil flows into the head end of rear CAAC cylinder (40). As the cylinder extends, oil displaced from the rod end flows through port "RC1", across the solenoid spool, and out port "T" (35) .

Check valves (32) and (43) are load-sensing check valves in the signal resolver network. These valves compare the pressure at port "FC1" and port "RC2" to the pressure requirements of the upstream machine functions. The highest pressure requirement is directed out port "LS" (34) and sent to port "LS1" of the steering valve.

Note: Inside the steering valve, a shuttle valve compares the load-sensing signal from port "LS" (34) to the pressure requirements of the steering system. The highest load requirements are directed to the margin spool in the steering valve. The margin spool regulates the amount of oil that is supplied to the components in the hydraulic system.