Cooling structure of cylinder block and swash plate type liquid-pressure apparatus including same

Abstract

The present invention provides a cooling structure of a cylinder block, the cooling structure being capable of improving a cooling performance of sliding surfaces. A cylinder block includes a plurality of cylinders, and pistons are respectively inserted into the cylinders through openings. Each of the pistons performs reciprocating sliding on a sliding surface which defines the cylinder. A plurality of cooling depressions are formed on an outer peripheral surface of the cylinder block. Each of the cooling depressions extends from a front end surface of the cylinder block on a dividing wall located between the two adjacent cylinders and is formed by reducing the thickness of the dividing wall so as to reduce a thickness of a portion between the sliding surface and the outer peripheral surface.

1 . A cooling structure of a cylinder block configured such that: a plurality of cylinders each including an opening on a piston insertion end surface of the cylinder block are formed on the cylinder block; and when the cylinder block is rotated, pistons respectively inserted in the cylinders perform reciprocating sliding,
 the cooling structure comprising   a plurality of cooling depressions formed on an outer peripheral surface of the cylinder block, wherein   each of the cooling depressions extends from the piston insertion end surface on a dividing wall located between the two adjacent cylinders and is formed by reducing a thickness of the dividing wall so as to reduce a thickness of a portion between the outer peripheral surface of the cylinder block and a sliding surface on which the piston slides.   
     
     
         2 . The cooling structure according to  claim 1 , wherein:
 each of the pistons performs the reciprocating sliding between a top dead center and a bottom dead center in the cylinder; and   each of the cooling depressions is formed so as to extend from the piston insertion end surface in parallel with the cylinder and is formed such that a tip end of the cooling depression is located on the piston insertion end surface side of a vicinity of an end surface of the piston located at the bottom dead center, the end surface being located in the cylinder.   
     
     
         3 . The cooling structure according to  claim 1 , wherein each of the cooling depressions is formed so as to satisfy 0.02 D≦tmin≦0.3 D, where train denotes a minimum thickness of the portion between the outer peripheral surface of the cylinder block and the sliding surface, and D denotes an inner diameter of the cylinder. 
     
     
         4 . A swash plate type liquid-pressure apparatus configured to be connected to a low-pressure passage through which a low-pressure operating liquid flows and a high-pressure passage through which a high-pressure operating oil flows and further configured such that: the cylinder block is rotated by supplying the operating liquid through the high-pressure passage to the cylinders and discharging the operating liquid from the cylinders to the low-pressure passage; or by rotating the cylinder block, the operating liquid is suctioned through the low-pressure passage to the cylinders, and the operating liquid is then compressed and ejected to the high-pressure passage,
 the swash plate type liquid-pressure apparatus comprising the cooling structure according to  claim 1 .   
     
     
         5 . The swash plate type liquid-pressure apparatus according to  claim 4 , further comprising a casing configured to accommodate the cylinder block, wherein
 the casing is connected to the low-pressure passage through a communication passage, and low-pressure operating oil in the low-pressure passage is introduced to the casing.   
     
     
         6 . A swash plate type liquid-pressure apparatus configured to be connected to a low-pressure passage through which a low-pressure operating liquid flows and a high-pressure passage through which a high-pressure operating oil flows and further configured such that: the cylinder block is rotated by supplying the operating liquid through the high-pressure passage to the cylinders and discharging the operating liquid from the cylinders to the low-pressure passage; or by rotating the cylinder block, the operating liquid is suctioned through the low-pressure passage to the cylinders, and the operating liquid is then compressed and ejected to the high-pressure passage,
 the swash plate type liquid-pressure apparatus comprising the cooling structure according to  claim 2 .   
     
     
         7 . A swash plate type liquid-pressure apparatus configured to be connected to a low-pressure passage through which a low-pressure operating liquid flows and a high-pressure passage through which a high-pressure operating oil flows and further configured such that: the cylinder block is rotated by supplying the operating liquid through the high-pressure passage to the cylinders and discharging the operating liquid from the cylinders to the low-pressure passage; or by rotating the cylinder block, the operating liquid is suctioned through the low-pressure passage to the cylinders, and the operating liquid is then compressed and ejected to the high-pressure passage,
 the swash plate type liquid-pressure apparatus comprising the cooling structure according to  claim 3 .