STRUCTURE AND FUNCTION HYDRAULIC PUMP 2. When HST pump discharges from port PA 1) Valve at the piston pump delivery side. When the pressure oil is discharged from port PA of the HST pump (4), port PA becomes the high pressure side. This pressure oil at port PA flow into port D through the groove b . When this happen, sleeve ( 3C ) is pushed to direction, because of the difference in area ( A1 > A2 ). Therefore the pressure oil from charge pump is prevented from flowing into HST pump. 2) Valve at piston pump suction side Port PB is at low pressure because port PB is suction side. And sleeve ( 3C ) is pushed to direction to open body seat portion because of the difference in area ( A1 > A2 ).
In this way, the charge pressure oil at port B flows into port PB through this clearance to charge to the HST circuit.. 3C PB A1 A2 B RKS00080 10-24 SK818-5 SK820-5 turbo 3C b D PA A2 A1 RKS00070 PB 1 PB PA 4 PA RKS00130 A2