COMPONENT OPERATION / HST Pump OUTLINE The HST pump is a two-direction displacement angle swash plate type variable displacement plunger pump. The forward/reverse selection solenoid valve (3), the DE pump solenoid valve (2), the cutoff valve (4), the high pressure relief valves (5,10), the low pressure relief valve (8), and the HST charging pump (7) are provided in the HST pump. The HST pump (6) consists of the shaft, the plunger, the cylinder block, the displacement angle control cylinder, and the swash plate. Engine power is transmitted to the shaft of the HST pump directly. The shaft rotation of the HST pump is also transmitted to the main pump unit through the coupling.
2
3
A
4 5
1
View A
15 16
6 7
17
8 9
14
13
12
10
11
T4FG-03-04-001
1 - Displacement Angle Control Cylinder 2 - DE Pump Solenoid Valve 3 - Forward/Reverse Selection Solenoid Valve 4 - Cutoff Valve 5 - High-Pressure Relief Valve
6 - Port MB
11 - Port S
16 - Port Fa
7 - HST Charging Pump
12 - Port G
17 - Port B (Port A at Opposite Side)
8 - Low-Pressure Relief Valve
13 - Port T2
9 - Port MA 10 - High-Pressure Relief Valve
14 - Port PS (T1) 15 - Port Fe
T3-4-1
