Shibaura ST318, Руководство по ремонту

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138
(2) Forward
By depressing the HST pedal to the forward side, the variable displacement pump starts the pumping operation and
discharges the oil.
The discharged oil is supplied to the fixed displacement motor and output shaft is rotated.
The high pressure side check valve is closed under the pressure of the oil and the low pressure relief valve is opened
under the charge pressure.
The check valve is opened at the neutral position but the high pressure side valve port is gradually closed with the
increase of the circuit pressure action as a cushion at the time of acceleration enduring smooth acceleration.
When the pedal is returned to the neutral position, the valve returns to the neutral condition quickly by the change pump
pressure.
The high pressure relief valve is closed usually. But when excessive load acts on the motor output and the pressure in
the HST circuit exceeds 27.4 MPa (280 kgf/cm
2
) the relief valve is actuated to prevent damage of various parts. The oil
flows into the low pressure side circuit after passing through the relief valve.
T517
Oil flow – Forward position
1. Charge pump 8. High pressure relief valve
2. Input shaft 9. Fixed displacement motor
3. Oil cooler 10. Output shaft
4. Filter 11. Variable displacement pump
5. Low pressure relief valve 12. Hydraulic filter
6. Safety valve 13. Oil tank (Transmission)
7. Check valve