COMPONENT OPERATION ／ HST Pump <Idling> The pressure difference between fore-and-aft the orifice (6) is small since the output volume of the charging pump is small, thus the differential piston (5) will be located at the position shown in the figure. Hence, low control pressure due to reduction in section between the charging circuit [C] and the control circuit [B] will be drawn into the control circuit [B].
<High Idle> The pressure difference between fore-and-aft the orifice (6) becomes larger since the output volume of the charging pump is large, thus the differential piston (5) will be pressed up to the position as shown in the figure. Hence, high control pressure will be drawn into the control circuit [B].since the section area of the passage between the charging circuit [C] and the control circuit [B] will becomes large.
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