Hydraulic Pump Operation - jcb JS300 Service Manual

Main Pumps (P1 and P2)
The rotary group consists of the drive shaft 7, cylinder rod
19, piston shoe 4, 5, press plate 11, spherical bush 12,
spacer 13 and cylinder spring 14. The drive shaft is
supported on both sides by the bearings 8, 16. The shoe is
caulked on the piston and forms the spherical coupler, and
because it slides slightly on the shoe plate 6, it has a
pocket to balance the oil pressure.
The subgroup, which is made up of the piston and shoe is
held down on the shoe plate by the cylinder spring through
the press plate and spherical bush. In the same way, the
cylinder block is held down on the valve plate 15 by the
cylinder spring.
The swash plate group consists of the swash plate 10,
shoe plate 6, swash plate support 9 bush 2 pin 3 and servo
piston 1. The swash plate is supported by the swash plate
support at the cylindrical part formed by the side opposite
to the shoe sliding surface. The oil pressure controlled by
the regulator is guided to the hydraulic cavities on both
sides of the servo piston which moves the servo piston to
the left and right, causing the swash plate, through the
spherical portion of the pin, to press on the swash plate
support and changes the angle of the swash plate.
The valve cover group comprises of the valve block 17,
valve plate 13 and valve plate pin 18. The valve plate,
which has two oval shaped ports, is on the valve block and
delivers oil to and recovers oil from the cylinder block. The
oil directed by the valve plate flows through the valve block
and is connected to the outer piping.
When the drive shaft is driven by the engine, the cylinder
block rotates simultaneously with the spline coupling.
When the swash plate is leaning, the piston in the cylinder
block rotates simultaneously with the cylinder block and
causes reciprocal motion relative to the cylinder.
Therefore, during one rotation, the piston moves away
from the valve plate for 180° (enough for oil suction) and
approaches the valve plate for the remaining 180°. When
the swash plate leaning angle is at the minimum 5° the
piston does not stroke and does not deliver oil.
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Hydraulic Pump Operation

TE-029_2
9813/5100-1
Section E - Hydraulics
Hydraulic Pump/Regulator
Hydraulic Pump Operation
6
5
4
3
2
1
Fig 1.
18
17
16
15
14
13
12
11
10
9
8
7
A406500-1
E-58