Yanmar ViO12-2A, Service Manual

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6. HYDRAULIC SYSTEM
6
-10
-2
2. Theory of Operation
1) Motor
When the travel section spool of the control valve is switched for travel, the pressure oil which has flown in through
the hydraulic valve flows to the valve plate
5 . Then, the pressure oil flows from the valve plate 5 into the cylinder
ports, which correspond to the port A, in the cylinder barrel 4 and presses the pistons 6 . This pressing force is
applied to the sliding surface of the swash plate 7 , and the shoes installed to the pistons slide on the sliding surface
of the swash plate toward the circumference of the plate. That motion of more than one piston on the high pressure
side is converted into the rotational motion of the cylinder barrel
4 .
The rotational motion is transmitted to the shaft 3 splined to the cylinder barrel 4 .
When those pistons move to the low pressure side, the oil in the cylinder ports is pushed out by the pistons. The dis-
charged oil flows through the port B of the valve plate
5 to the tank passage.
When the travel section spool of the control valve is switched to the opposite side, the pressure in the port B
becomes high and the pressure in the port A becomes low, so that the rotation of the shaft
3 is reversed.
Shaft 3
Swash plate 7
Piston 6
Cylinder barrel 4
Valve plate 5
Port A
Port B