Abstract: A cooling structure of an internal combustion engine includes a cylinder block, an inner-block coolant passage, a cylinder head, and an inner-head coolant passage. In the cylinder block, cylinders are provided in a row in a cylinder row direction. The inner-head coolant passage is provided in the cylinder head and includes a main coolant passage, an upper exhaust side coolant passage, and a lower exhaust side coolant passage. The main coolant passage is provided above combustion chambers and extends in the cylinder row direction so that a coolant flows into the main coolant passage from the inner-block coolant passage at a first end side of the cylinder head in the cylinder row direction and so that the coolant flows out from the main coolant passage at a second end side of the cylinder head opposite to the first end side in the cylinder row direction.

Abstract: A cooling structure of an internal combustion engine includes a cylinder block, an inner-block coolant passage, a cylinder head, and an inner-head coolant passage. In the cylinder block, cylinders are provided in a row in a cylinder row direction. The inner-head coolant passage is provided in the cylinder head and includes a main coolant passage, an upper exhaust side coolant passage, and a lower exhaust side coolant passage. The main coolant passage is provided above combustion chambers and extends in the cylinder row direction so that a coolant flows into the main coolant passage from the inner-block coolant passage at a first end side of the cylinder head in the cylinder row direction and so that the coolant flows out from the main coolant passage at a second end side of the cylinder head opposite to the first end side in the cylinder row direction.

Abstract: A holding structure of an oil control valve includes an oil control valve, a cam holder, and a head cover. A valve portion is provided on a second end side of the oil control valve opposite to a first end side in a longitudinal direction. The valve portion is configured to switch oil passages by driving a solenoid portion and has a drain hole at a shaft end portion of the valve portion. The cam holder is attached to a cylinder head of an internal combustion engine and rotatably supports a camshaft of the internal combustion engine. A valve portion side of the oil control valve is embedded in the cam holder and supported by the cam holder. An axis of the oil control valve in the longitudinal direction is oriented towards the camshaft. The head cover is provided on an upper portion of the cylinder head.

Abstract: A holding structure of an oil control valve includes an oil control valve, a cam holder, and a head cover. A valve portion is provided on a second end side of the oil control valve opposite to a first end side in a longitudinal direction. The valve portion is configured to switch oil passages by driving a solenoid portion and has a drain hole at a shaft end portion of the valve portion. The cam holder is attached to a cylinder head of an internal combustion engine and rotatably supports a camshaft of the internal combustion engine. A valve portion side of the oil control valve is embedded in the cam holder and supported by the cam holder. An axis of the oil control valve in the longitudinal direction is oriented towards the camshaft. The head cover is provided on an upper portion of the cylinder head.

Abstract: A water-jacket structure, for a water-cooled internal combustion engine, forms a cylinder block water jacket in a cylinder block so as to surround cylinder bores formed in the cylinder block to make cooling water flow through the cylinder block water jacket into a cylinder head water jacket formed in a cylinder head joined to the cylinder block. An upper connecting opening is formed in an upper part of the cylinder block water jacket so as to open into the cylinder head water jacket. In the cylinder block is formed a lower connecting passage opening into a lower part of the cylinder block water jacket, extending upward, and connecting to the cylinder head water jacket.

Abstract: A water-jacket structure, for a water-cooled internal combustion engine, forms a cylinder block water jacket in a cylinder block so as to surround cylinder bores formed in the cylinder block to make cooling water flow through the cylinder block water jacket into a cylinder head water jacket formed in a cylinder head joined to the cylinder block. An upper connecting opening is formed in an upper part of the cylinder block water jacket so as to open into the cylinder head water jacket. In the cylinder block is formed a lower connecting passage opening into a lower part of the cylinder block water jacket, extending upward, and connecting to the cylinder head water jacket.