STRUCTURE, FUNCTION, & MAINTENANCE STANDARD HYDRAULIC PUMP 12 Operation 1) Operation of pump i Cylinder block (7) rotates together with shaft (1), and shoe (5) slides on flat surface A . When this happens, rocker cam (4) moves along cylindrical surface B , so angle α between center line X of rocker cam (4) and the axial direction of cylinder block (7) changes. (Angle α is called the swash plate angle.) ii Center line X of rocker cam (4) maintains swash plate angle α in relation to the axial direction of cylinder block (7), and flat surface A moves as a cam in relation to shoe (5).
In this way, piston (6) slides on the inside of cylin- der block (7), so a difference between volumes E and F is created inside cylinder block (7). The suc- tion and discharge is carried out by this difference F - E . In other words, when cylinder block (7) rotates and the volume of chamber E becomes smaller, the oil is discharged during that stroke. On the other hand, the volume of chamber F becomes larger, and as the volume becomes bigger, the oil is sucked in.
iii If center line X of rocker cam (4) is in line with the axial direction of cylinder block (7) (swash plate angle = 0), the difference between volumes E and F inside cylinder block (7) becomes 0, so the pump does not carry out any suction or discharge of oil. (In actual fact, the swash plate angle never becomes 0.) PC210/240-7K 10-33