Internal combustion engine

Abstract

When viewed from the upper face of a cylinder head in which an intake port communicating with a combustion chamber of an internal combustion engine is formed, a starting point of the port is defined as a point of intersection of the streamline of the intake port and an inlet-side opening plane of the intake port as projected on a horizontal plane, and an end point is defined as a point of intersection of the streamline of the port and the center axis of an intake valve as projected on the horizontal plane. The starting point is located closer to the center of the chamber than a straight line that contains the end point and extends in a direction orthogonal to the axis of the crankshaft on the plane, and the streamline of the port projected on the horizontal plane is curved toward the center of the chamber, with respect to a straight line that contains the starting point and extends in a direction orthogonal to the axis of the crankshaft on the plane.

1 . An internal combustion engine comprising:
 an intake port that communicates with a combustion chamber, and   an intake valve that has an umbrella portion and a stem connected at one end thereof to the umbrella portion, wherein   said intake port having a starting point that is a first point of intersection of a streamline of the intake port and an inlet-side opening plane of the intake port, and an end point that is a second point of intersection of the streamline of the intake port and a center axis of the intake valve, as viewed from an upper face of a cylinder head in which the intake port is formed, said first and second points of intersection being projected on a horizontal plane, wherein   the streamline of the intake port projected on the horizontal plane is curved toward a center of the combustion chamber so as to be at least partially located closer to the center of the combustion chamber than a first straight line that contains the starting point and extends in a direction orthogonal to an axis of a crankshaft on the horizontal plane, and a second straight line that contains the end point and extends in a direction orthogonal to the axis of the crankshaft on the horizontal plane, wherein:   the intake valve comprises a specific intake valve in which the stem is offset such that an inner passage region located closer to the center of the combustion chamber, out of two intake-air passage regions on the opposite sides of a plane that contains a center axis of the stem, becomes larger, and such that the center axis of the stem does not contain a center of a bottom face of the umbrella portion.   
   
   
       2 . The internal combustion engine according to  claim 1 , wherein
 the stem of the specific intake valve is offset to an upstream side with respect to the center of the specific intake valve, in a direction of flow of intake air.   
   
   
       3 . The intake combustion engine according to  claim 1 , wherein
 a portion of the umbrella portion of the specific intake valve, which corresponds to the inner passage region, has a smaller volume than a portion of the umbrella portion which corresponds to the outer passage region.   
   
   
       4 . The internal combustion engine according to  claim 1 , wherein
 the specific intake valve further includes a rotation preventing device that prevents the specific intake valve from rotating about the center axis of the stem of the specific intake valve.   
   
   
       5 . An internal combustion engine comprising:
 an intake port that communicates with a combustion chamber, and   an intake valve that has an umbrella portion and a stem connected at one end thereof to the umbrella portion, wherein   said intake port having a starting point that is a first point of intersection of a streamline of the intake port and an inlet-side opening plane of the intake port, and an end point that is a second point of intersection of the streamline of the intake port and a center axis of the intake valve, as viewed from an upper face of a cylinder head in which the intake port is formed, said first and second points of intersection being projected on a horizontal plane, wherein   the streamline of the intake port projected on the horizontal plane is curved toward a center of the combustion chamber so as to be at least partially located closer to the center of the combustion chamber than a first straight line that contains the starting point and extends in a direction orthogonal to an axis of a crankshaft on the horizontal plane, and a second straight line that contains the end point and extends in a direction orthogonal to the axis of the crankshaft on the horizontal plane, and wherein   the intake valve comprises a specific intake valve in which the stem is inclined, when the intake valve is in a closed state, such that a distal end of the stem is located closer to a plane that contains a center axis of a cylinder and is substantially orthogonal to the axis of the crankshaft, than a center of a bottom face of the umbrella portion, in a direction substantially parallel to the axis of the crankshaft.   
   
   
       6 . The internal combustion engine according to  claim 5 , wherein
 the stem of the specific intake valve is inclined, when the specific intake valve is in a closed state, such that the distal end of the stem is located closer to an exhaust port than the center in a direction of flow of intake air.   
   
   
       7 . The intake combustion engine according to  claim 2 , wherein
 a portion of the umbrella portion of the specific intake valve, which corresponds to the inner passage region, has a smaller volume than a portion of the umbrella portion which corresponds to the outer passage region.   
   
   
       8 . The internal combustion engine according to  claim 2 , wherein the specific intake valve further includes a rotation preventing device that prevents the specific intake valve from rotating about the center axis of the stem of the specific intake valve. 
   
   
       9 . The internal combustion engine according to  claim 3 , wherein the specific intake valve further includes a rotation preventing device that prevents the specific intake valve from rotating about the center axis of the stem of the specific intake valve.