When the difference between main pump pressure PP2 and LS pressure PLS, in other words, LS differential pressure APLS, be- comes smaller (for example, when the area of opening of the control valve becomes larger and pump pressure pp drops), spool
(4) is pushed to the right by the combined force of LS pressure PLS and the force of spring (3).
When spool (4) moves, port b and port c are joined and connected to the TVC valve. When this happens, the TVC valve is connected to the drain port, so circuit c - h becomes drain pressure PT. (The operation of the TVC valve is explained later.)
For this reason, the pressure at the large piston diameter end of servo piston (1) be- comes drain pressure PT, and pump pres- sure pp enters the small diameter end, so servo piston (1) is pushed to the right. There- fore, rod (2) moves to the right and moves the svvash plate in the direction to make the discharge amount larger.
If the output pressure Psig of the LS-EPC valve enters port e, this pressure creates a force to move piston (5) to the left. If piston
(5) is pushed to the left, it acts to make the set pressure of spring (3) vveaker, and the difference between PLS and PP2 changes when ports b and c of spool (4) are con- nected
đang được dịch, vui lòng đợi..
