An object is to provide a type of device capable of properly cooling a bearing of a throttle body even under a condition that the throttle body receives heat of high-temperature intake air or exhaust gas. In the present invention, an engine coolant passage that guides a coolant of an engine is provided integrally with a member fixing a bearing to be adjacent to a circumferential wall of the bearing of the member fixing the bearing, which supports a throttle shaft, and heat transferred from the bearing (or likely to be transferred to the bearing) via the member fixing the bearing is carried away to the outside of a throttle body by the engine coolant.

There is provided a water cooled engine including a cylinder head with minimized thermal strain.

A head water jacket includes an inter-exhaust-port-wall water channel between a first exhaust entrance port wall and a second exhaust entrance port wall. A cylinder head includes a cooling water injection passage provided at a bottom wall of the cylinder head. The cooling water injection passage is positioned on the exhaust end side, and includes a passage entrance provided on the exhaust end side, and a passage exit directed toward the inter-exhaust-port-wall water channel. An exhaust port wall includes a heat dissipation fin extending from a first exhaust entrance port wall toward an exhaust end. The space between the heat dissipation fin and a second exhaust entrance port wall forms a water channel entrance of the inter-exhaust-port-wall water channel.

There is provided a water cooled engine including a cylinder head with minimized thermal strain.

A head water jacket includes an inter-exhaust-port-wall water channel between a first exhaust entrance port wall and a second exhaust entrance port wall. A cylinder head includes a cooling water injection passage provided at a bottom wall of the cylinder head. The cooling water injection passage is positioned on the exhaust end side, and includes a passage entrance provided on the exhaust end side, and a passage exit directed toward the inter-exhaust-port-wall water channel. An exhaust port wall includes a heat dissipation fin extending from a first exhaust entrance port wall toward an exhaust end. The space between the heat dissipation fin and a second exhaust entrance port wall forms a water channel entrance of the inter-exhaust-port-wall water channel.

A first coolant flow passage (31, 32) is provided to extend in a longitudinal direction of a cylinder head (101). In at least one of cross sections perpendicular to the longitudinal direction, the first coolant flow passage (31, 32) is located between a flat plane (S1) including central axes of a plurality of combustion chambers (4) and parallel to the longitudinal direction and a central line plane (S2) including central lines of a plurality of intake ports (2). In at least one of cross sections perpendicular to the longitudinal direction, at least a portion (20c) of a second coolant flow passage is located between a cylinder block mating surface (la) of the cylinder head (101) and the intake port central line plane (S2). A coolant at a temperature lower than that of a coolant flowing in the second coolant flow passage (20c) flows in the first coolant flow passage (31, 32).

A first coolant flow passage (31, 32) is provided to extend in a longitudinal direction of a cylinder head (101). In at least one of cross sections perpendicular to the longitudinal direction, the first coolant flow passage (31, 32) is located between a flat plane (S1) including central axes of a plurality of combustion chambers (4) and parallel to the longitudinal direction and a central line plane (S2) including central lines of a plurality of intake ports (2). In at least one of cross sections perpendicular to the longitudinal direction, at least a portion (20c) of a second coolant flow passage is located between a cylinder block mating surface (la) of the cylinder head (101) and the intake port central line plane (S2). A coolant at a temperature lower than that of a coolant flowing in the second coolant flow passage (20c) flows in the first coolant flow passage (31, 32).

A cooling system for a cylinder head of an internal combustion engine includes a cylindrical seat configured to engage an exhaust valve, a first coolant jacket, and a first conduit. The exhaust valve seat defines an annular cooling passage extending along a circumference of the cylindrical seat. A wall of the cylindrical seat defines a first opening into the annular cooling passage and a second opening into the annular cooling passage, where the first opening is positioned diametrically opposite to the second opening. The first coolant jacket is positioned adjacent to a fire-deck of the internal combustion engine. The first conduit fluidly couples the first coolant jacket to the at least one of the first opening and the second opening to the annular cooling passage in the exhaust valve seat.

An engine cooling structure includes a cylinder block including a block inner peripheral wall and a block outer peripheral wall that define a water jacket, and a spacer housed in the water jacket. The block outer peripheral wall includes a coolant inlet for introducing a coolant into the water jacket at one end in a cylinder row direction. The spacer includes a peripheral wall surrounding the block inner peripheral wall, and a dividing wall and a distribution wall provided on the peripheral wall. The dividing wall is provided along a circumferential direction of the peripheral wall and protrudes outward from the peripheral wall between a lower end and an upper end of the coolant inlet. The distribution wall includes an upper distribution wall extending upward from the dividing wall and a lower distribution wall extending downward from the dividing wall.

An engine cooling structure includes a cylinder block including a block inner peripheral wall and a block outer peripheral wall that define a water jacket, and a spacer housed in the water jacket. The block outer peripheral wall includes a coolant inlet for introducing a coolant into the water jacket at one end in a cylinder row direction. The spacer includes a peripheral wall surrounding the block inner peripheral wall, and a dividing wall and a distribution wall provided on the peripheral wall. The dividing wall is provided along a circumferential direction of the peripheral wall and protrudes outward from the peripheral wall between a lower end and an upper end of the coolant inlet. The distribution wall includes an upper distribution wall extending upward from the dividing wall and a lower distribution wall extending downward from the dividing wall.

An internal combustion engine includes a cylinder case forming a plurality of coolant outlets, and an exhaust log structure disposed on the cylinder case and including inner and outer walls defining a coolant jacket therebetween, a plurality of coolant inlets extending through the outer wall and being fluidly connected to the coolant jacket, and a plurality of transfer housings. Each transfer housing includes an inner housing wall forming a gas passage, an outer housing wall disposed at an offset distance around the inner housing wall such that a cooling passage is defined in a space between the inner and outer housing walls, and a coolant inlet and a coolant outlet in fluid communication with the cooling passage. The plurality of coolant inlets is fluidly connected to the plurality of coolant outlets via the cooling passages in the plurality of transfer housings.

An internal combustion engine includes a cylinder case forming a plurality of coolant outlets, and an exhaust log structure disposed on the cylinder case and including inner and outer walls defining a coolant jacket therebetween, a plurality of coolant inlets extending through the outer wall and being fluidly connected to the coolant jacket, and a plurality of transfer housings. Each transfer housing includes an inner housing wall forming a gas passage, an outer housing wall disposed at an offset distance around the inner housing wall such that a cooling passage is defined in a space between the inner and outer housing walls, and a coolant inlet and a coolant outlet in fluid communication with the cooling passage. The plurality of coolant inlets is fluidly connected to the plurality of coolant outlets via the cooling passages in the plurality of transfer housings.