COOLING DEVICE OF CONSTRUCTION MACHINE

摘要

PROBLEM TO BE SOLVED: To provide a cooling device capable of stabilizing the changeover of positive and reverse inversion of a cooling fan while reducing costs.

SOLUTION: The cooling device of a construction machine includes: a hydraulic pilot type switching valve 21 for controlling the flowing direction of pressure oil from a hydraulic pump 15 to a hydraulic motor 16 for a fan; a solenoid valve 22 for generating a pilot pressure of the switching valve 21 by a part of the pressure oil discharged from the hydraulic pump 15; and a variable relief valve 24 for variably controlling a flow rate of the pressure oil from the hydraulic pump 15 to the hydraulic motor 16 for the fan. In the cooling device of the construction machine, the switching valve 21 includes a pressure receiving part 26 for introducing the pilot pressure from the solenoid valve 22 and making it act on a spool, and a spring 27 disposed inside a spring chamber for energizing the spool in a direction opposite to the acting direction of the pilot pressure, and the energizing force of the spring 27 is preset so as to be smaller than the product of the minimum value of the pilot pressure that varies accompanying the variation of the discharge pressure of the hydraulic pump 15 and a pressure receiving area of the spool.

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