Internal combustion engine

An internal combustion engine comprising:

• a cylinder head having a through-hole;
• a cylinder pressure sensor including a sensor body and a pressure receiving portion,
• the sensor body including a fixed portion abutting with a head wall surface of the cylinder head on an opposite side to a combustion chamber of the internal combustion engine,
• the sensor body having a bar shape,
• the sensor body being placed inside the through-hole,
• the pressure receiving portion being provided in an end portion of the sensor body on a combustion-chamber-side;
• a sealing member that seals between a hole wall surface as a wall surface of the through-hole and a body-side wall surface as a side wall surface of the sensor body;
• and
• a fixing member configured to fix the fixed portion such that the fixed portion is pressed against the head wall surface, wherein
• the sealing member is placed in a middle of the sensor body in a direction of a central axis of the sensor body, when the sensor body is placed inside the through-hole,
• the sensor body and the through-hole in a reference state are configured such that at least one combination of values that are taken as D1, D2, D3, and D4 satisfies a dimension relationship of D1<D3×(D4/D2),
• D1 is a distance in a direction of a central axis of the through-hole from a reference position of the sealing member to a first given position, the first given position being a position of one of the hole wall surface and the body-side wall surface placed on a side closer to the combustion engine than the sealing member,
• D2 is a distance between the hole wall surface and the body-side wall surface at the first given position where the hole wall surface and the body-side wall surface face each other;
• D3 is a distance in the direction of the central axis of the through-hole from the reference position to a second given position, the second given position being a position of one of the hole wall surface and the body-side wall surface placed on a side farther from the combustion engine than the sealing member;
• D4 is a distance between the hole wall surface and the body-side wall surface at the second given position where the hole wall surface and the body-side wall surface face each other, and
• the reference state is a state where the central axis of the through-hole is aligned with the central axis of the sensor body.