104-5948 Master Cylinder on Standard Machine
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| Illustration 1 | g00427599 |
Bottom view of the master cylinder | |
The master cylinder is located on the left side of the machine, and under the cab. The master cylinder with boost on standard machines controls the service brakes in the front axle. The steering system supplies oil to the brake boost. The brake boost provides additional power in order to move the pistons in the master cylinder. The brake boost assists the operator in stopping the machine. As the brake pressure increases, the required pedal force increases proportionally to the brake pressure. As the brake pressure decreases, the required pedal force decreases proportionally to the brake pressure. This allows the operator to modulate the brake pedal more effectively.
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| Illustration 2 | g00358395 |
View A-A of the Master Cylinder with Boost on Standard Machines Released Service Brakes (AA) Boost oil (tank pressure). (BB) Brake oil (tank pressure). (1) Connection to the brake pedal linkage. (2) Servo piston. (3) Brake boost. (4) Passage. (5) Power piston. (6) Relief Valve. (7) Chamber. (8) Spring. (9) Plunger. (10) Master cylinder. (11) Passage. (12) Inlet port from the reservoir. (13) Internal reservoir. (14) Air purge screw. (15) Outlet port to service brakes. (16) Chamber. (17) Spring. (18) Passage. (19) High-pressure piston. (20) Spring. (21) Chamber. (22) Reaction piston. (23) Low-pressure piston. (24) Spring. (25) Outlet port to hydraulic oil tank. (26) Passage. (27) Inlet port from steering. | |
When the service brakes are released, springs (17) , (20) , (24) and (8) move high-pressure piston (19) , low-pressure piston (23) , power piston (5) , and servo piston (2) to the left. The servo piston (2) allows the supply oil (AA) from port (27) . The oil flows into passage (26) and behind power piston (5) . The oil also flows through passage (4) , into chamber (7) and to hydraulic oil tank port (25) .
The brake oil (BB) from the reservoir enters master cylinder from port (12) . The brake oil (BB) fills master cylinder reservoir (13) , passage (11) , chamber (21) , passage (18) , and chamber (16) .
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| Illustration 3 | g00358632 |
View A-A of the Master Cylinder with Boost on Standard Machines Applied Service Brakes (AA) Supply oil. (BB) Hydraulic oil (tank pressure). (CC) Brake oil (tank pressure). (DD) Brake oil (high pressure). (1) Connection to the brake pedal linkage. (2) Servo piston. (3) Brake boost. (4) Passage. (5) Power piston. (6) Relief Valve. (7) Chamber. (8) Spring. (9) Plunger. (10) Master cylinder. (11) Passage. (12) Inlet port from the reservoir. (13) Internal reservoir. (14) Air purge screw. (15) Outlet port to service brakes. (16) Chamber. (17) Spring. (18) Passage. (19) High-pressure piston. (20) Spring. (21) Chamber. (22) Reaction piston. (23) Low-pressure piston. (24) Spring. (25) Outlet port to hydraulic oil tank. (26) Passage. (27) Inlet port from steering. | |
When the brake pedal is applied, the connection to the brake pedal linkage moves servo piston (2) to the right. The servo piston (2) restricts the supply oil (AA) from flowing through passage (4) and into chamber (7) .
The pressure increases behind power piston (5) . The power piston (5) moves to the right against plunger (9) . The plunger (9) causes reaction piston (22) and low-pressure piston (23) to move to the right against high-pressure piston (19) . Brake oil (CC) is blocked to passage (18) and to chamber (16) . The low-pressure piston (23) also moves high-pressure piston (19) to the right. This causes the pressure to increase in chamber (16) .
As the pressure increases in chamber (16) , the oil exits port (15) to the brake piston. The brake piston is part of the service brakes. The front axle contains the service brakes. For additional information on the service brake, refer to Systems Operation, Testing and Adjusting, SENR6772, "Service Brake".
As the oil in the brake pistons increases, the pressure increases in chamber (15) and passage (16) . This causes reaction piston (22) to move to the left against plunger (9) . The plunger (9) moves servo piston (2) to the left. The servo piston (2) moves slightly to the left, which allows the operator to feel the application of the service brakes.
The maximum pressure in the brake boost is regulated by the relief valve setting. The relief valve (6) will open if the oil pressure behind power piston (5) increases above 1965 ± 70 kPa (285 ± 10 psi). Relief valve (6) will open if the oil flow rate behind the power piston (5) increases above 37.9 L/min (10.0 US gpm).
The service brakes can still be applied if the engine is stopped or if oil is not flowing to brake boost (3) . The operator must depress the pedal with a greater force.
122-9727 130-5521 143-8386 Master Cylinder on High Speed Machines
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| Illustration 4 | g00360157 |
View A-A of the Master Cylinder with Boost on High Speed Machines Released Service Brakes (AA) Supply oil (tank pressure). (BB) Brake oil (tank pressure). (1) Connection to the brake pedal linkage. (2) Servo piston. (3) Brake boost. (4) Passage. (5) Power piston. (6) Relief valve. (7) Chamber. (8) Spring. (9) Plunger. (10) Master cylinder. (11) Inlet port from the reservoir. (12) Passage. (13) Internal reservoir. (14) Piston (bypass valve). (15) Hydraulic line to the bypass valve. (16) Outlet port to front and rear service brakes. (17) Seat. (18) Passage. (19) Chamber. (20) Spring. (21) High-pressure piston. (22) Retainer. (23) Passage. (24) Spring. (25) Chamber. (26) Low-pressure piston. (27) Reaction piston. (28) Hydraulic oil tank port. (29) Spring. (30) Passage. (31) Inlet port from steering. | |
The master cylinder with boost on high speed machines controls the brakes that are located in the front axle and the rear axle. The steering system supplies oil to brake boost (3) . The brake boost provides additional power in order to move the pistons in master cylinder (10) . The brake boost assists the operator in stopping the machine. As the brake pressure increases, the required pedal force increases proportionally to the brake pressure. As the brake pressure decreases, the required pedal force decreases proportionally to the brake pressure. This allows the operator to modulate the brake pedal more effectively.
When the service brakes are released, springs (20) , (24) , (29) , and (8) move high-pressure piston (21) , low-pressure piston (26) , plunger (9) , power piston (5) , and servo piston (2) to the left. The servo piston (2) allows the supply oil (AA) from the steering to enter brake boost (3) . The supply oil (AA) enters through port (30) . The oil flows through passage (30) and the oil fills the area behind piston (5) . The oil also flows through passage (4) and into chamber (17) . The oil exits through hydraulic oil tank port (19) .
Brake oil (BB) from the reservoir enters the master cylinder through port (11) . The brake oil (BB) fills master cylinder reservoir (13) , passage (12) , chamber (19) , passage (18) , and chamber (25) .
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| Illustration 5 | g00360158 |
View A-A of the Master Cylinder with Boost on High Speed Machines Applied Service Brakes (AA) Supply oil. (BB) Hydraulic oil (tank pressure). (CC) Brake oil (tank pressure). (DD) Brake oil (high pressure). (1) Connection to the brake pedal linkage. (2) Servo piston. (3) Brake boost. (4) Passage. (5) Power piston. (6) Relief valve. (7) Chamber. (8) Spring. (9) Plunger. (10) Master cylinder. (11) Inlet port from the reservoir. (12) Passage. (13) Internal reservoir. (14) Piston (bypass valve). (15) Hydraulic line to the bypass valve. (16) Outlet port to front and rear service brakes. (17) Seat. (18) Passage. (19) Chamber. (20) Spring. (21) High-pressure piston. (22) Retainer. (23) Passage. (24) Spring. (25) Chamber. (26) Low-pressure piston. (27) Reaction piston. (28) Hydraulic oil tank port. (29) Spring. (30) Passage. (31) Inlet port from steering. | |
When the brake pedal is applied, the connection to the brake pedal linkage moves servo piston (2) to the right. The servo piston (2) restricts the oil to passage (4) .
The master cylinder has two stages. This provides easier brake applications when the engine is off. The two stages also allow the master cylinder to displace more oil than a master cylinder with only a single stage. The first stage begins as the pressure increases behind power piston (5) . The pressure increase moves servo piston (2) to the right against plunger (9) . The plunger (9) causes reaction piston (27) and the low-pressure piston (26) to move to the right. Passage (12) is blocked to chamber (19) by low-pressure piston (26) . The movement of low-pressure piston (26) forces the oil to flow out of the master cylinder through hydraulic line (16) in order to apply the service brakes.
If the brakes are applied more, low-pressure piston (26) continues to move to the right. The movement causes the high-pressure piston (21) to contact seat (17) . This begins the second stage as low-pressure piston (26) slides around the high-pressure piston (21) . The pressure on the right side of chamber (19) increases. The pressure opens the bypass valve (14) and oil flows from chamber (19) to master cylinder reservoir (13) . The pressure in chamber (19) decreases. This allows low-pressure piston (26) to move to the right more. High-pressure piston (21) slides inside low-pressure piston (26) . The pressure increases in chamber (25) . The seals that are inside chamber (25) block holes (23) . The pressure also increases in passage (18) and in hydraulic line (16) to the service brakes.
The pressure increases in chamber (25) , when low-pressure piston (26) moves to the right. This is sensed on the right end of reaction piston (27) . This causes reaction piston (27) to move to the left against plunger (9) . The plunger moves servo piston (2) to the left. The servo piston (2) moves slightly to the left, which allows the operator to feel the application of the service brakes.
The maximum pressure in the brake boost is regulated by the relief valve setting. The relief valve (6) will open if the oil pressure behind power piston (5) increases above 1965 ± 70 kPa (285 ± 10 psi). The relief valve (6) will open if the oil flow rate behind piston (5) increases above 37.9 L/min (10.0 US gpm).
Illustration 5 does not show the releasing of the brakes. When the brakes are released, low-pressure piston (26) shifts to the left. The high-pressure piston (21) unseats after retainer (22) is contacted. The high-pressure piston (21) shifts to the left. Oil from chamber (25) flows to chamber (19) through holes (23) . The oil pressure in chamber (19) decreases. This causes bypass valve (14) to close.
The service brakes can still be applied if the engine is stopped or if oil is not flowing to brake boost (3) . The operator must depress the pedal with a greater force.
The brake piston is part of the service brakes. The front axle contains the service brakes. Refer to Systems Operation, Testing and Adjusting, SENR6772, "Service Brake" for more information on the service brakes.
Inching Mode
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| Illustration 6 | g00486672 |
The location of the inching valve on the master cylinder Master Cylinder for (S/N: 7ZM1-1178ZM1-1249WM1-871WN1-94) (1) Inching valve. (2) Lever. (3) Rod. (4) Port to the hydraulic oil tank. (5) Signal oil from the hystat pump. | |
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| Illustration 7 | g00486673 |
The location of the inching valve on the master cylinder Master Cylinder for (S/N: 7ZM118-5998ZM125-4999WM88-12981WN95-898) (1) Inching valve. (2) Lever. (3) Rod. (4) Port to the hydraulic oil tank. (5) Signal oil from the hystat pump. | |
The inching mode is standard on all machines. The inching valve may be located in front of the master cylinder. The inching mode is operational during the first 25 to 50 mm (1.0 to 2.0 inch) of travel of either service brake pedal. The inching mode decreases the speed of the machine, while full engine rpm is maintained.
The rod (3) is pushed to the left when the service brake pedal is applied. Lever (2) rotates counterclockwise. The inching valve (1) opens the signal oil for the hydrostatic system from port (5) to the hydraulic oil tank through port (4) . The flow from the hystat pump to the motor is redirected to the hydraulic oil tank. There is a decrease in the pressure of the hystat pump signal. This signals the pump to gradually destroke and this signals the motor to upstroke. The speed of the machine decreases, while full engine rpm is maintained.
During normal operation, the inching mode could be used to load material. The inching mode could be used to unload material. When the brake pedals are released, the inching mode is removed.