 | |
| Illustration 1 | g02161472 |
Pressure circuit for swing system (1) Passage (supply oil or return oil) (2) Check valve (3) Relief valve (4) Makeup port (5) Line (makeup oil or return oil) (6) Right swing motor (7) Motor rotary group (8) Check valve (9) Relief valve (10) Passage (supply oil or return oil) (11) Passage (return oil) (12) Check valve (13) Check valve (14) Swing control valve (15) Passage (makeup oil flow from the swing pump) (16) Back pressure valve (swing) (17) Return line (18) Line (swing pump supply oil) (19) Bypass check valve (20) Return line (21) Return line (22) Check valve (23) Back pressure valve (24) Hydraulic tank (25) Swing pump | |
Introduction
The oil makeup operation of the left swing motor is identical to the oil makeup operation of the right swing motor.
When the swing joystick is moved to the NEUTRAL position, the inlet port and the outlet port of swing control valve (14) are blocked. The oil delivery from swing pump (25) cannot flow through the spool in swing control valve (14). The upper structure will attempt to continue to rotate after the swing joystick is returned to the NEUTRAL position and flow to the swing motor is blocked at swing control valve (14). The swing motor is now operating as a pump. As a result, makeup oil must be supplied at passage (1) or passage (10). The passage will depend on the swing direction. In order to prevent this condition, two types of oil makeup operations function at the same time.
- Makeup oil can be delivered from the swing pump. Back pressure valve (16) causes the pressure of bypass oil from line (18) to increase. This oil then flows through passage (15) and check valve (13) to passage (1) .
- Makeup oil can be delivered from the return system. Bypass check valve (19) and back pressure valve (23) causes the oil pressure in line (5) to increase. This oil then flows through check valve (2) to passage (1) .
Oil Makeup Operation (Swing Pump Supply Oil)
 | |
| Illustration 2 | g02161799 |
Oil makeup operation (1) Passage (swing pump supply oil) (7) Motor rotary group (12) Check valve (13) Check valve (14) Swing control valve (15) Bypass passage (16) Back pressure valve (17) Return line (18) Line (swing pump supply oil) (25) Swing pump | |
 | |
| Illustration 3 | g02161692 |
Swing motor compartment (14) Swing control valve (17) Return line (18) Line (swing pump supply oil) | |
Back pressure valve (16) is installed in swing control valve (14) .
When swing control valve (14) is in the NEUTRAL position, the oil delivery from swing pump (25) flows through line (18) and bypass passage (15) in swing control valve (14). The oil then flows through back pressure valve (16) and return line (17) to the hydraulic tank. Back pressure valve (16) restricts the oil in bypass passage (15). The oil pressure of the oil in bypass passage (15) is maintained at 290 kPa (42 psi).
If a vacuum condition begins to occur in the swing motor, the pressure oil in bypass passage (15) flows through check valve (13) and into passage (1) .
If a vacuum condition begins to occur in the swing motor during a left swing operation, oil flows through check valve (12) instead of check valve (13) .
Oil Makeup Operation (Swing Return Oil)
| | |
| Illustration 4 | g02161472 |
Oil makeup operation (1) Passage (supply oil or return oil) (2) Check valve (3) Relief valve (4) Makeup port (5) Line (makeup oil or return oil) (6) Right swing motor (7) Motor rotary group (8) Check valve (9) Relief valve (10) Passage (supply oil or return oil) (11) Passage (return oil) (12) Check valve (13) Check valve (14) Swing control valve (15) Passage (makeup oil flow from the swing pump) (16) Back pressure valve (swing) (17) Return line (18) Line (swing pump supply oil) (19) Bypass check valve (20) Return line (21) Return line (22) Check valve (23) Back pressure valve (24) Hydraulic tank (25) Swing pump | |
 | |
| Illustration 5 | g02161631 |
Main control valve (top view) (19) Bypass check valve (20) Return line (21) Return line (23) Back pressure valve | |
Pressures
-
(19) Bypass check valve ... 800 kPa (116 psi) (23) Back pressure valve ... 400 kPa (58 psi)
 | |
| Illustration 6 | g02161659 |
Back pressure valve (sectional view) (17) Return line (21) Return line (22) Check valve (26) Orifice | |
Bypass check valve (19) is installed between makeup line (5) and hydraulic tank (24). Back pressure valve (23) is installed between return line (17) and hydraulic tank (24). These two valves are identical in construction. The pressure setting of bypass check valve (19) is higher than the pressure setting of back pressure valve (23). The oil pressure in return line (17) is maintained at 400 kPa (58 psi) by the pressure setting of back pressure valve (23). The oil pressure in return line (5) is maintained at 800 kPa (116 psi) by the pressure setting of bypass check valve (19) .
If a vacuum condition begins to occur in the swing motor, the oil in return line (20) flows through makeup line (5). The oil then flows through makeup port (4), passage (11) and check valve (2) to passage (1) .
Oil in return line (21) flows through orifice (26) in check valve (22) of back pressure valve (23). The oil then flows to makeup line (5) .
If a vacuum condition begins to occur in the swing motor during a left swing operation, oil flows through check valve (8) instead of check valve (2) .