STRUCTURE AND FUNCTION HYDRAULIC PUMP Function of the control piston (on non-induction of pilot signal) There are no pressure, so control piston (5) doesn’t move and main pump is on neutral condition. P PA =0 P PB =0 P PA =0 P PB =0 5 5 RKS00230 Function of the control piston (on induction of pilot signal) P PA P PB P PA P PB > > 5 5 SK714-5 SK815-5 - SK815-5 turbo RKS00240 When pressurized oil which has the pressure PPA, PPB (PPA>PPB) is led from pilot line (PPC or AS valve), control piston (5) moves the ( ) direction. Control piston (5) moves the balanced position by spring force and pressure PPA, PPB. If the relation of pressure dimension of PPA, PPB is reversed (i.e. PPA rection.
On SK714-5, AS valve is not installed, so pressurized oil from PPC valve is directly inducted to control piston. On SK815-5 and SK815-5 turbo, AS valve is installed and lower pressure between AS valve output pressure and PPC pressure is selected by shuttle valve and inducted to control piston (see topic “shuttle valve”). 10-24 SK714-5 SK815-5 SK815-5 turbo