A water jacket of an engine is capable of implementing cooling water flows as both a cross flow and a parallel flow. The water jacket includes a head water jacket formed in a cylinder head of an engine; a block water jacket formed in a cylinder block of the engine; and a variable partition wall which is configured to induce a cross flow of cooling water in a space between positions of cylinders in the head water jacket, where the variable partition wall has a shape configured to be varied according to an engine operating condition, and the variable partition wall allows the cooling water to flow in a selected one of the cross flow and a parallel flow according to the shape which is varied in head water jacket.

A cylinder structure includes cylinders arranged inline. A cooling channel facing a first side wall of the cylinder structure includes a first inner channel and a first outer channel. The first inner channel is arranged for a first cooling medium to flow through. The first outer channel is away from the first side wall than the first inner channel is, and arranged for a second cooling medium to flow through. A cooling channel facing a second side wall of the cylinder structure includes a second outer channel and a second inner channel. An upstream part of the second outer channel is connected to a downstream part of the first outer channel. The second inner channel is close to the second side wall than the second outer channel is. Connection channels connecting between the second outer channel and the second inner channel are respectively provided at positions facing the cylinders.

Methods and systems are provided for a coolant jacket insert. In one example, a system may include a coolant jacket arranged in a block comprising an insert with a first internal passage configured to direct coolant from an inlet manifold of the coolant jacket directly to a portion of the coolant jacket arranged in a cylinder head.

An internal combustion engine includes an anisotropic thermal conductivity member (37, 51) provided on a wall surface defining a cylinder or a wall surface of a cooling water passage on a side of the cylinder, a thermal conductivity of the anisotropic thermal conductivity member in an axial direction of the cylinder being higher than a thermal conductivity of the anisotropic thermal conductivity member in a radial direction of the cylinder, and a thermally insulating member (38. 52) provided on an outer surface of the anisotropic thermal conductivity member with respect to the radial direction of the cylinder.

A heat retention material cartridge fixed to a base member of a heat retention tool of a cylinder bore's bore wall for heat retention of the cylinder bore wall, which includes a thermosensitive expansion rubber, a back-side pressing member, a rectangular opening, a front-side abutting plate cooperative with the back-side pressing member for sandwiching an outer edge portion of the thermosensitive expansion rubber, and an elastic member attached member to which an elastic member is attached. A convex portion being convex toward the side of the back-side pressing member is formed in a portion of the front-side abutting plate where the outer end is not sandwiched by bendable portions. And, the outer edge portion of the thermosensitive expansion rubber is formed in such a manner that the outer end of the thermosensitive expansion rubber is positioned inside an apex of the convex portion.

A cylinder block defines a cylinder, in which a piston is reciprocated. The cylinder includes an upper bore, a center bore, and a lower bore arranged in order from proximity to a cylinder head in the axial direction of the cylinder. The inner diameter of the center bore is greater than the inner diameters of the upper bore and the lower bore. The cylinder block defines an upper recess that serves as an upper water jacket surrounding the upper bore and a lower recess that serves as a lower water jacket surrounding the lower bore. The upper recess and the lower recess are spaced apart from each other in the axial direction of the cylinder so as to sandwich a spacer.

An engine cooling structure includes a cylinder block including a block inner peripheral wall that defines a water jacket and a block outer peripheral wall, a spacer housed in the water jacket, and a cooler provided outside the engine body. The spacer includes: a peripheral wall surrounding the block inner peripheral wall; and a dividing wall protruding from the peripheral wall to divide the water jacket into an upper passage and lower passages below the upper passage. A coolant introduced from a coolant inlet into the upper passage passes through an inter-bore part of the block inner peripheral wall. The coolant in the lower passages is introduced into the cooler through a coolant exit.

A combustion engine housing with cylinder cooling includes at least one cylinder. The cylinder cooling channel has a distribution cross-sectional area having a cross-sectional area through which coolant can flow, in a first cross-sectional plane that is perpendicular to the cylinder axis. In a second cross-sectional plane, which is perpendicular to the cylinder axis and which is arranged in relation to the vertical direction between the first cross-sectional plane and the coolant outflow opening, has a throttle cross-sectional area, which is a cross-sectional area through which coolant can flow. The throttle cross-sectional area is smaller than the distribution cross-sectional area.

A structure is mounted in a water jacket for a cylinder block of an engine. The structure includes a body forming a housing mounting portion including a panel formed in an arc shape so as to have inner and outer curved surfaces to be surrounded by a block bore. A pad-housing is formed in a plate shape to have curved surfaces with a curvature equal to the inner and outer curved surfaces of the housing mounting portion. The pad-housing is inserted into a housing mounting hole and is formed in a shape to correspond with the housing mounting hole. A pad is formed in a shape to correspond with a pad mounting hole which is bored through the pad-housing through. The pad has a curved surface and is inserted into the pad mounting hole to achieve water tightness.

A cylinder structure includes cylinders arranged inline. A cooling channel facing a first side wall of the cylinder structure includes a first inner channel and a first outer channel. The first inner channel is arranged for a first cooling medium to flow through. The first outer channel is away from the first side wall than the first inner channel is, and arranged for a second cooling medium to flow through. A cooling channel facing a second side wall of the cylinder structure includes a second outer channel and a second inner channel. An upstream part of the second outer channel is connected to a downstream part of the first outer channel. The second inner channel is close to the second side wall than the second outer channel is. Connection channels connecting between the second outer channel and the second inner channel are respectively provided at positions facing the cylinders.