PURPOSE: To reduce the pressure drop of hydraulic fluid by a method wherein a set bolt which has a fixing function and male threads at the tip is used and inserted into a through-hole of a core so that an oil return passage is formed inside the through-hole in the axial direction of the core.
CONSTITUTION: An oil cooler 101 is attached on an oil cooler mount 105 by a set bolt 113 having only a fixing function. Oil whose temperature rises at a load side is cooled down in a core 21 and led to an oil passage 29 of the oil cooler mount 105 through an oil return passage 117. The set bolt 113 having a male thread part 113A at the tip is inserted into a through-hole 23A of the core 21 so that the oil return passage 117 having a specified annular cross section is formed inside the through-hole 23A in the axial direction of the core 21. Therefore, the cross sectional area of the oil return passage 117 becomes large enough to reduce the pressure drop of hydraulic fluid. In addition, as the male thread part 113A of the set bolt 113 is screwed in a female thread part 119, the passage resistance is small.
TASAKA SHOJI
BEPPU TAKASHI
