UOOMINGUATSUPUKINOOSONAETAYUATSUKUDOSOCHI

摘要

PURPOSE:To automate the warming-up control by providing a warming-up means which keeps a center-bypass type direction change-over valve in the specified opening position in response to a warming-up instruction. CONSTITUTION:A proportional control solenoid valve 18 is connected via a shuttle valve 19 to the pilot pipe passage of a center-bypass type direction change- over valve 2 and a warming-up control circuit 16 and a temperature detector 15 are connected to the controlling part of the proportional control solenoid valve 18. When the temperature of working oil is reduced below the specified temperature at which warming-up may be needed, the signal from the temperature detector 15 actuates a warming-up control circuit 16 so that the pilot pressure signal of a specified level from the proportional control solenoid valve 18 is sent to the center-bypass type directional change-over valve 2 to keep it in the specified opening position. Accordingly, the warming-up may be controlled not manually but automatically.