COMPONENT OPERATION ／

HST Pump

YUKEN ／ Serial No. 1001 ～ 4499

The HST pump is the swash plate type axial piston pump with automotive control. The cylinder block ⑤ , with nine pistons in total, is connected to the shaft ⑭ using a spline; and the main pump ② and charging pump ① are connected to it through the coupling ③

To the HST pump, the AU controller ⑧ which is the center of the automotive control, and the neutral hold mechanism, and the inching valve ⑮ , which controls the pilot pressure for the automotive control, are all integrated into the HST pump.

COMPONENT OPERATION ／

1-Charging pump

2-Main pump

3-Coupling

4-Port plate (valve plate)

5-Cylinder Block

6-Piston

7-Cradle (Swash plate)

8-AU control section Neutral hold Section

COMPONENT OPERATION ／ HST Pump

・AU controller（YUKEN ／ Serial No. 1001 ～ 4499）

1.The electromagnetic selector valve ① for forward and reverse is equiped to the AU controller. When electric current is sent to solenoid ② , the spool of the selector valve is operated and the pilot pressure generated in the inching valve sends pressurized oil to the right or left pressure chamber of the piston ③ .

2.The pilot pressure controls the stroke of the piston ③ against force of the spring ⑦ which is installed in the piston ③ .

3.When the piston ③ is moved, the cradle is tilted through the spacer ④ and the pin ⑤ . When the cradle is tilted, the pump discharges oil.

4.The amount of oil discharging by the pump is decided by the stroke of the piston ③ . The adjusting screw ⑧ limits the stroke of the piston ③ and decides the maximum amount of oil discharge by the pump.

・Neutral holder（YUKEN ／ Serial No. 1001 ～ 4499）

1.Holding the neutral position is done by force of spring ⑦ which is installed in the piston ③

2.The adjusting screw ⑨ is equipped to adjust the piston ③ to the neutral position.

DO NOT re-adjust neutral position in the field. Because it must be adjusted on test bench.

The AU controller and the neutral holder are not independent of each other, but they are combined system.