Water-cooled four-cycle engine

摘要

In a water-cooled four-cycle engine, an engine core including a cylinder block, a cylinder head and a first crankcase half body is formed as a unitary part cast integrally; a water jacket including a cylinder jacket surrounding a cylinder bore and a head jacket surrounding a combustion chamber is formed in the engine core; and a timing-belt chamber being adjacent to the cylinder jacket is provided in a side portion of the engine core. A first opening portion for forming a first semi-peripheral portion of the cylinder jacket on a side opposite from the timing-belt chamber by casting out is provided in a side surface of the cylinder block. A second opening portion for forming a second semi-peripheral portion of the cylinder jacket and the head jacket by casting out is provided in an upper surface of the cylinder head.

主权项

1. A water-cooled four-cycle engine, comprising:
an engine core including a cylinder block, a cylinder head and a first crankcase half body formed as a unitary part cast integrally, the cylinder block including a cylinder bore, the cylinder head including a combustion chamber, an intake port and an exhaust port, the intake port and the exhaust port being opened to the combustion chamber, the first crankcase half body forming a first half portion of a crank chamber; a second crankcase half body forming a second half portion of the crank chamber and connected to the first crankcase half body; a head cover connected to the cylinder head and defining a valve-operation chamber between the head cover and the cylinder head; a crankshaft housed in the crank chamber and supported by the first and second crankcase half bodies; and a camshaft housed in the valve-operation chamber and supported by the cylinder head; wherein a water jacket including a cylinder jacket and a head jacket is formed in the engine core, the cylinder jacket surrounding the cylinder bore, the head jacket communicating with the cylinder jacket and surrounding the combustion chamber; wherein a timing-belt chamber is provided in a side portion of the engine core, the timing-belt chamber being adjacent to the cylinder jacket across a partition wall integrated with the engine core, and the timing-belt chamber housing a timing belt which connects between the crankshaft and the camshaft, wherein a first opening portion is provided in a side surface of the cylinder block, the first opening portion forming a first semi-peripheral portion of the cylinder jacket on a side opposite from the timing-belt chamber, wherein a second opening portion is provided in an upper surface of the cylinder head, the second opening portion forming a second semi-peripheral portion of the cylinder jacket and the head jacket, wherein first and second lid plates for water-tightly closing the first and second opening portions are removably connected to the cylinder block and the cylinder head, respectively, the first and second plates being non-unitary with the cylinder block and cylinder head, respectively, wherein the second lid plate is disposed between the head cover and the cylinder head, and wherein the second opening portion is extended over an area including an axis of the cylinder bore, above the combustion chamber, the axis of the cylinder bore passing through the center of the cylinder bore and being parallel to a cylinder wall, wherein the second opening portion is open in a direction upward of the cylinder head, and is closed by the second lid plate, wherein the first semi-peripheral portion and the second semi-peripheral portion of the cylinder jacket together to form an entire peripheral portion of the cylinder jacket, and wherein the second opening portion is disposed on a side of the cylinder bore where the timing-belt chamber is disposed, opposite a side of the cylinder bore where the first opening portion is disposed.