Abstract: A cylinder bore wall thermal insulator is provided to a middle-lower part of a groove-like coolant passage of a cylinder block included in an internal combustion engine that includes a plurality of cylinder bores, and insulates part of a cylinder bore wall, the cylinder bore wall thermal insulator including a rubber member that comes in contact with part of a cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage that covers one cylinder bore, or covers two or more cylinder bores, a metal base member on which the rubber member is secured, and an elastic member that is provided to the metal base member, and biases the metal base member so that the metal base member presses the rubber member against the cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage, one or more elastic members being provided to each bore-covering part of the metal base member.

Abstract: A cylinder bore wall thermal insulator is provided to a middle-lower part of a groove-like coolant passage of a cylinder block included in an internal combustion engine that includes a plurality of cylinder bores, and insulates part of a cylinder bore wall, the cylinder bore wall thermal insulator including a rubber member that comes in contact with part of a cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage that covers one cylinder bore, or covers two or more cylinder bores, a metal base member on which the rubber member is secured, and an elastic member that is provided to the metal base member, and biases the metal base member so that the metal base member presses the rubber member against the cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage, one or more elastic members being provided to each bore-covering part of the metal base member.

Abstract: A cylinder bore wall thermal insulator includes a rubber member that comes in contact with half of a cylinder bore-side wall surface of a middle-lower part of a groove-like coolant passage, and has a contact surface having a shape that conforms to the shape of the cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage, a metal base member on which the rubber member is secured, and an elastic member that is provided to the metal base member, and biases the metal base member so that the metal base member presses the rubber member against the cylinder bore-side wall surface of the middle-lower part of the groove-like coolant passage. An internal combustion engine in which a cylinder bore wall has a uniform temperature can be provided by utilizing the cylinder bore wall thermal insulator.