Intake port for 4-cycle engine

Abstract

An intake port for a 4-cycle engine includes an intake port base integrally formed with a cylinder head, and an intake port forming member that forms an intake port together with the intake port base. The area of the cross section of the intake port orthogonal to a centerline of the intake port is substantially uniform from an open intake side thereof toward a combustion chamber. The angle made by the centerline of the intake port and an intake valve shaft is larger than 90° from a viewpoint of the intake valve. Thereby, the 4-cycle engine can output high power with the intake port shape, as formed with above mentioned configuration, that reduces intake resistance and that uses simple design molds. More specifically, the engine can reliably prevent condensed fuel from remaining in the intake port to avoid incomplete combustion of gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become clear from the following description with reference to the accompanying drawings, wherein:

FIG. 1 is a cross sectional view illustrating relevant parts of a 4-cycle engine according to one embodiment of the present invention;

FIG. 2A is a perspective view and FIG. 2B is a front view of a heat insulator used in the embodiment of the invention;

FIG. 3 is a cross sectional view illustrating relevant parts of the 4-cycle engine in accordance with the embodiment of the present invention;

FIG. 4 is a cross sectional view taken along the line A-A of FIG. 3; and

FIG. 5 illustrates one example of use of the 4-cycle engine in accordance with the embodiment of the invention.

Claims

1. An intake port for a 4-cycle engine comprising: an intake port base integrally formed with a cylinder head; andan intake port forming member that is partly fitted into the intake port base and forms the intake port together with the intake port base, whereinthe intake port has a shape with an area of a cross section orthogonal to a centerline of the intake port that is substantially uniform from an open intake side to apart connected with a combustion chamber, and with an angle made by the centerline of the intake port and an intake valve shaft that is larger than 90° from a viewpoint of an intake valve.

2. The intake port for the 4-cycle engine according to claim 1, wherein a circumference where a plane orthogonal to the centerline of the intake port intersects the intake port is, partly or entirely, made up of two members which are the intake port base and the intake port forming member.

3. The intake port for the 4-cycle engine according to claim 1, wherein the angle made by the centerline of the intake port and the intake valve shaft from a viewpoint of the intake valve becomes gradually larger toward the intake valve.

4. The intake port for the 4-cycle engine according to claim 1, wherein the intake port forming member is a synthetic resin heat insulator.

5. The intake port for the 4-cycle engine according to claim 1, wherein a joint between the intake port base and the intake port forming member where they together form the intake port is substantially parallel to the centerline of the intake port.

6. The intake port for the 4-cycle engine according to claim 5, wherein a groove is provided in an inner surface of the intake port base that extends from the joint toward the intake valve.