JPH0623685Y2 - Four-cycle engine valve drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a valve operating system for a four-cycle engine.

[Conventional technology and its problems]

In a four-cycle engine, a cylinder head is provided with a camshaft interlocking with a crankshaft, and the camshaft opens and closes an intake valve and an exhaust valve. The ignition plug is preferably arranged at the center of the combustion chamber of the cylinder head in terms of combustion efficiency. Also, two camshafts dedicated for intake and exhaust are provided for high performance, but the structure is complicated and the cost is high, and the cylinder head is large. For example, the actual exploitation 60-167143
See the official gazette. For this reason, some camshafts open and close both the intake valve and the exhaust valve, but there are disadvantages in terms of rigidity, such as interposing a push rod in the rocker arm or attaching the rocker shaft to the cylinder head. . See, for example, Japanese Patent Application Laid-Open No. 61-123746.

There is also one in which the electrode of the spark plug is exposed to the combustion chamber through a plug insertion cylinder that extends obliquely upward with respect to the center axis of the combustion chamber. In this case, the spark plug is inserted diagonally into the plug cylinder. Therefore, workability is not so preferable. In this case, since the electrodes of the spark plug are positioned obliquely with respect to the central axis, the speed at which combustion spreads after sparks ignite in the mixture and then spreads unevenly, so knocking easily occurs. it is conceivable that. Furthermore, since the tip portion other than the electrode is also obliquely positioned in the combustion chamber, the tip portion becomes an obstacle, and it cannot be said that the fire propagation at the time of ignition is preferable. Therefore, it seems that the thermal efficiency is not good. See, for example, JP-A-63-18115.

[Purpose of device]

It is an object of the present invention to provide a valve operating system for a four-cycle engine, in which a ceiling wall of a combustion chamber can be easily processed and has good thermal efficiency, and an ignition plug can be easily inserted to improve workability.

[Constitution of device]

 Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings.

1 to 3 show an embodiment of the present invention. In the cylinder head 1, a combustion chamber 2 is formed on the lower surface, and a plug cylinder 3 having a hollow portion 3a extending from the center 2a of the combustion chamber 2 upward in the vertical direction is provided integrally with the cylinder head. The spark plug 4 is inserted and the screw portion 4a of the spark plug 4 and the screw hole 1a of the cylinder head 1 are screwed together so that the electrode 4b of the spark plug 4 is located at the center 2a of the combustion chamber 2. The hollow portion 3a communicates with a through hole of a boss described later. The single camshaft 5 rotates in conjunction with the crankshaft, and is rotatably mounted on the upper surface above the cylinder head 1 using the bearing fitting 6. The plug cylinder 3 is projected upward from the upper surface of the cylinder head 1, and a boss 7 having a through hole 7a is provided on the side surface of this protruding portion. The rocker arms 8 are arranged on both sides of the plug cylinder 3 until the end surface 9a, which is the end portion of the rocker arm shaft 9 of the short axis that pivotally mounts the rocker arm 8, contacts the outer surface of the seal cylinder described later. The through hole 7 of the boss 7 that faces the hollow portion 3a of the plug cylinder 3 with the short-axis rocker shaft 9
Push in via a. As a result, the rocker arm shaft 9 is held in the through hole 7a. Camshaft 5
Moves the rocker arm 8 with the cam 10 to move the intake valve 1
1 is opened and closed, and the rocker arm 13 is swung by the cam 12 to open and close the exhaust valve 14. Intake valve 11 and exhaust valve 14
Is a four-valve type with two cylinders each. Plug tube 3
A seal cylinder 15 is inserted into the cylinder to seal the end of the boss 7 with an O-ring 16, and a head cover 17 is attached to the upper surface of the cylinder head 1. FIG. 4 corresponds to FIG. 1 showing another embodiment of the present invention, in which an O-ring 18 is inserted between the upper surface of the plug cylinder 3 and the head cover 17,
Others are the same as those shown in FIGS. 1 to 3.

[Function of device]

According to this invention, the electrode 4b of the spark plug 4 is located in the center 2a of the combustion chamber 2 of the cylinder head 1, and the screw plug 4a which is the tip of the spark plug 4 has a portion 4a 'other than the electrode 4b'. Does not extend obliquely from the ceiling wall 2b of the combustion chamber 2. Further, since the spark plug 4 is inserted into the plug cylinder 3 having the hollow portion 3a extending substantially vertically upward from the center 2a of the combustion chamber 2, the spark plug 4 is inserted straight into the plug cylinder 3 and the ceiling wall. 2b can be processed symmetrically with respect to the central axis of the combustion chamber 2.

Further, since the camshaft 5 and the short-axis rocker arm shaft 9 are attached above the cylinder head 1 and the plug cylinder 3 integrated with the cylinder head 1, respectively, the camshaft 5 and the rocker arm shaft 9 are attached. Is firm.

The through hole 7a for holding the rocker arm shaft 9 in the plug cylinder 3 faces the hollow portion 3a of the plug cylinder 3, and the seal cylinder 15 is attached to the plug cylinder 3 so as to be located at the position where the through hole 7a is formed. Since the rocker arm shaft 9 is inserted into the hollow portion 3a, when the rocker arm shaft 9 is inserted into the through hole 7a, the end surface 9a of the rocker arm shaft 9 abuts on the outer surface of the seal cylinder.

Then, since the rocker arms 8 pivotally attached to the rocker arm shaft 9 are arranged on both sides of the plug cylinder, the rocker arm shaft 9 is divided and arranged, and
It is located directly above the combustion chamber 2. Therefore, the rocking center of the rocker arm 8 is located substantially directly above the combustion chamber 2.

[Effect of device]

As described above, according to the present invention, since the tip portion of the spark plug other than the electrode does not protrude obliquely to the ceiling wall 2b of the combustion chamber, the portion interferes with the spread of fire during ignition. You can keep up.

Further, since the spark plug is inserted into the plug cylinder having the hollow portion that extends substantially vertically upward from the center of the combustion chamber,
The spark plug is inserted straight into the plug tube. Therefore, the workability for attaching the spark plug to the plug cylinder can be improved. Since the ceiling wall 2b can be processed symmetrically with respect to the central axis of the combustion chamber 2,
The workability of the combustion chamber 2 can be improved.

Further, since the cam shaft and the rocker arm shaft are mounted above the cylinder head and in the plug cylinder integrated with the cylinder head, respectively, the cam shaft and the rocker arm shaft can be mounted firmly. Therefore, failures can be reduced.

The through hole for holding the rocker arm shaft in the plug cylinder faces the hollow portion of the plug cylinder, and the seal cylinder is inserted into the hollow portion of the plug cylinder so as to be located at the through hole forming position. When the arm shaft is inserted into the through hole, the end of the rocker arm shaft hits the outer surface of the seal cylinder. Therefore, if the rocker arm shaft is set in advance so that the rocker arm shaft can be sufficiently held by the plug cylinder at the abutting portion, the rocker arm shaft can be positioned in the axial direction simply by inserting the rocker arm shaft into the through hole. Therefore, also in this respect, workability can be improved.

Then, since the rocker arms 8 pivotally attached to the rocker arm shaft 9 are arranged on both sides of the plug cylinder, the rocker arm shaft 9 is divided and arranged, and
It is located directly above the combustion chamber 2. Therefore, the rocking center of the rocker arm 8 is located substantially directly above the combustion chamber 2. Therefore, the cylinder head can be reduced in size in the axial direction and can be reduced in weight.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a vertical sectional view taken along the line AA of FIG. 3, FIG. 2 is a vertical sectional view taken along the line BB of FIG. 3 is a plan view with the head cover removed, 4
The drawing is a longitudinal sectional view corresponding to FIG. 1 showing another embodiment of the present invention. 1 ... Cylinder head, 1a ... Screwing means, 2 ... Combustion chamber,
2a ... Center, 3 ... Plug cylinder, 3a ... Hollow part, 4 ... Spark plug, 4a ... Screwing means, 4b ... Electrode, 5 ... Cam shaft, 7a ... Through hole, 8 ... Rocker arm, 9 ... Rocker arm shaft, 15 ... Seal tube.

Claims (1)

[Scope of utility model registration request] 1. A spark plug is arranged via a screwing means,
The electrode of the spark plug is located at the center of the combustion chamber of the cylinder head, and a plug cylinder having a hollow portion extending substantially vertically upward from the center of the combustion chamber is provided integrally with the cylinder head, and the camshaft is provided above the cylinder head. Is rotatably mounted, and rocker arms driven by the cams of this camshaft are axially attached to a short-axis rocker arm shaft and arranged on both sides of the plug cylinder, and the end of this rocker arm shaft is supported. A valve operating device for a four-cycle engine, in which a through hole is provided in the plug cylinder, and a seal cylinder is inserted into a hollow portion of the plug cylinder so as to be positioned at the through hole forming position.