SEAL 2639442 - Caterpillar

Illustration 6 g00704762
Regulator Operation (Partial View) (5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (47) Top surface (48) Passage (49) Passage (50) Set screw (57) Idler pump delivery pressure (58) Drive pump delivery pressure (60) Power shift pressureAn increased load on the main pump increases idler pump delivery pressure (57) from passage (15) and increases drive pump delivery pressure (58) from passage (5). The force acts on ring grooves of piston (14) .The combined forces of increased power shift pressure (60) through passage (20) acts on top surface (47) of control piston (14) to overcome the total forces of springs (22) and (30). Control piston (14) pushes down on control piston (24) through pin (21). Passage (49) closes and passage (48) opens. Therefore, idler pump delivery pressure (57) from passage (17) goes through passage (25) to the bottom surface of ring (34) .Idler pump delivery pressure (57) acts on the top surface of ring (34). Therefore, oil is supplied to piston chamber (37) through passage (35). Idler pump delivery pressure (57) is common to both top and bottom surfaces of ring (34). The bottom surface area of ring (34) is larger than the top surface area. Therefore, ring (34) pushes up piston (32) against the forces of springs (30) and (28). The mechanical linkage of piston (32) and the cylinder through trunnion (31) cause the cylinder to move in a smaller angular direction. Therefore, the pump stroke decreases.As piston (32) moves up, spring (30) compresses. Spring (30) pushes up on control piston (24). Passage (48) closes and passage (49) partially opens. Therefore, oil flows from passage (25) to spring chamber (26). Because spring chamber (26) is open to tank pressure, the pressure on the bottom surface of ring (34) becomes less than idler pump delivery pressure (57). Piston (32) starts to stop upward movement. When the force of idler pump delivery pressure (57) on the top surface of ring (34) becomes more than the force on the bottom surface, piston (32) starts to move down. Because of the decreased compression force of spring (30), control piston (24) also starts to move down. Passage (49) now closes and passage (48) partially opens. Piston (32) now starts to move up again because of idler pump delivery pressure (57) through passage (25) to the bottom surface of the ring.When the idler pump delivery pressure (57) compresses spring (27), pistons (24) and (32) operate.Idler pump delivery pressure (57) is equal to the combined force of springs (28), (30), and (27). Piston (32) is in a balanced position and the angle of the cylinder is held at this point. Control piston (24) is held at a balanced position by keeping the openings slightly opened at passages (48) and (49) .Turning set screw (50) changes the compression force of spring (22) which changes the pump output flow. Increased compression force of the spring increases the pump output flow.Negative