JPS61229962A - Cylinder head of internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable the integral manufacturing of cylinder head by die-cast process using a metal mold by lessening the included angle between the respective axial lines of both valve stem guides so as to eliminate the build-up parts for reinforcing the valve stem guides of intake and exhaust ports. CONSTITUTION:Each of the intake and exhaust ports 4 and 5 is formed in a cylindrical form of which axis is a straight line, and a cam chamber 9 is made comparatively small because of a narrow included angle alpha between the both valve stem guides. Further, since these ports and chamber are made to a comparatively simple form gradually windened upward, the intake and exhaust ports 4, 5 and the cam chamber 9 can be formed by the cores of metal mold at the time of casting, and after casting these cores can be drawn out sideward or upward respectively. Accordingly, cylinder heads with good working accuracy and less product difference can be manufactured by die casting and further the whole cylinder head can be miniaturized and can be made to be lightweight.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder head for an internal combustion engine, particularly a four-stroke internal combustion engine.

Figure 1 is a sectional view showing the cylinder head of a conventional four-stroke internal combustion engine for motorcycles, where 01 is the cylinder head and 0 is the cylinder head.
2 is an intake port, 03 is an exhaust port, and 04 is a combustion chamber. The openings (valve ports) of the intake and exhaust ports 02.03 to the combustion chamber 04 are opened by intake and exhaust valves 05.06, respectively. The intake and exhaust valves 05 and 0B are attached to valve stem guides 08.09 that are press-fitted through the wall of the cylinder head 01 between the upper cam chamber 07 and the intake and exhaust ports 02 and 03, respectively. It can be fitted freely,
A valve spring 010 constantly biases the valve port in the direction of opening. This intake and exhaust valve 02.03
is driven by a cam 011 rotating in conjunction with the output shaft of the internal combustion engine via rocker arms 012 and 013 to open the valve opening against the force of the valve spring 010.

Internal combustion Ij1rIl, which requires stable valve behavior up to high loads and high rotational speeds, such as those used in motorcycles, requires pulp springs with a high load.1 Normally, as shown in the diagram, one wooden valve has two inner and outer valve springs. is installed. On the other hand, the outer spring portion 013 on the cylinder head 01 side that must receive this spring must have a large compression resistance commensurate with the strength of the spring, so it must be attached to the inner surfaces of the intake and exhaust ports 02. A protrusion 014 is provided so that the spring/outer portion 013 has a sufficient wall thickness. This protrusion 014 was also necessary to reinforce the valve stem guide 08.09.

7. As mentioned above, such a conventional cylinder head has suction,
Since the reinforcing protrusion 014 protrudes into the exhaust port, this disturbs the air flow within the port, resulting in large intake and exhaust resistance.

Furthermore, in the conventional cylinder head, as shown in Fig. 1, the intake and exhaust ports have a curved cross-sectional shape, and the cam chambers are also arranged so as to open upward from each other. It will be larger to accommodate the intake and exhaust valves, so reinforcing walls etc. will be provided to give it rigidity.
It has a complex shape. For this reason, when casting cylinder heads, it is necessary to use a sand casting method in which the intake, exhaust ports, and cam chambers are removed using a sand core.A small, lightweight cylinder head can be manufactured using a die casting method using a mold. It was difficult to obtain.

. The present invention solves the above-mentioned problems and provides a cylinder head that can be manufactured in one piece by die-casting using a mold and has low intake and exhaust resistance. For this reason, the cylinder head of the present invention has cylindrical intake and exhaust ports extending linearly from the connection part near the combustion chamber and opening to the outer circumferential surface, and an upper part above the intake and exhaust ports. It has a cam chamber formed to gradually become wider toward the cam chamber, and suction and exhaust valve stem guides that penetrate through the bottom of the cam chamber and reach the suction and exhaust ports, respectively, and each of the pulp stem guides has a The valve stem guide reinforcement part for reinforcing the valve stem guide of the intake and exhaust ports is eliminated by reducing the angle between the respective axes.

In this cylinder head, the intake and exhaust ports are formed in a cylindrical shape with a straight axis, and the cam chamber is relatively small due to the narrow included angle between both valve stem guides, and gradually widens upward. Since it has a relatively simple shape, the suction and exhaust ports and cam chambers can be formed by cores of a mold during casting, and these cores can be pulled out laterally or upwardly after casting. Therefore, by die casting, it is possible to manufacture a cylinder head with good work precision and little product difference, and the entire cylinder head can be made smaller and lighter.

In addition, the intake and exhaust ports are straight, so the distance from the port inlet to the combustion chamber is shortened, and there are no protrusions inside these ports, and the surfaces are made smooth by molding. This reduces intake and exhaust resistance.

The present invention will now be described with reference to an embodiment shown in FIGS. 2 to 4.

FIG. 1 is a sectional view of a cylinder head 1 according to the invention. A combustion chamber 2 is formed in the center of the lower surface of the cylinder head 1, and an intake port 4 and an exhaust port 5 are connected from intake and exhaust valve ports provided in the combustion chamber 2 through connecting portions 3, respectively. extends and has the same opening on the outer peripheral surface of the cylinder head 1. These intake ports 4 and exhaust ports 5 have a straight cylindrical shape with straight axes. A valve seat 6 is fixed to each valve port,
An intake valve 7 and an exhaust valve 8 are in contact with the valve seat 6 so as to be openable and openable.

A cam chamber 9 is provided in the upper part of the cylinder head 1, and holes are bored through the wall of the cylinder head 1 from the bottom of the cam chamber 9 to the intake port 4 and the exhaust bow 5, respectively. A valve stem guide 10 is press-fitted into the valve stem guide 10, and the valve stems 11 of the intake valve 7 and the exhaust valve 8 are fitted into these valve stem guides 10 in a freely aa-a-a-a-a-a-way manner.

A valve spring 14 is inserted between a spring retainer 12 fixed to the head of the valve stem 11 and a receiving surface 13 formed on the bottom surface of the cam chamber 9, and the intake and exhaust valves 7.8 Each is biased upward, that is, in a direction that closes each valve port. A well-known valve operating mechanism consisting of a rocker arm 15 and a cam 16 is provided in the cam chamber 9, and the intake and exhaust valves 7 and 8 are respectively operated by this valve operating mechanism to open and close their valve ports.

In this embodiment, the valve stem 11 of the intake valve 7
The angle α between the axes of the valve stem 11 of the exhaust valve 8 and the exhaust valve 8 is selected to be 36°. This angle is considerably smaller than the angle formed by the intake and exhaust valves in a typical internal combustion engine. In this way, the angle α is set to a fairly small angle of about 30", and the intake port 4 and the exhaust port 5 are formed in a straight line shape without curvature, so that the cylinder head 1 can be connected from the connecting portion 3 near the combustion chamber 2 to the cylinder head 1. By arranging the valve spring 14 sideways toward the outer peripheral surface, the valve spring 14 is placed between the intake and exhaust ports 4 and 5 and the valve stem guide 10.
A thickened portion 17 of cylinder head material sufficient to support the forces and to stiffen the valve stem guide 10 is obtained, and protrusions such as 014 in FIG. There is no need to provide it.

Furthermore, by reducing the angle α, the spacing between the valve stems 11 in the upper cam chamber 9 becomes smaller, so the cam chamber 9 can also be made smaller, and the cylinder head 1 as a whole becomes smaller. Furthermore, since the cam chamber 9 gradually becomes wider upward, even if the core of the mold is used to form the cam chamber 9 when casting the cylinder head 1, the core can be moved in the direction indicated by the arrow after casting. It can be easily pulled out upwards as shown in . The intake port 4 and the exhaust port 5 are also molded using a cylindrical mold core, and after casting, the core can be pulled out in the directions of arrows B and C, respectively. The same applies to the combustion chamber 2 and the connecting portion 3, which can be molded using integral or divided mold cores. Therefore, this cylinder head can be integrally cast by die casting.

Reference numeral 18 denotes a cover that covers the upper part of the cam chamber 9 formed as described above, and this cover 18 is also manufactured by die casting. Incidentally, since the cam chamber 9 is small, the cover 18 may also be small and simple.

In this embodiment, a wire rod 19 having an oval cross section as shown in FIG. 4 is used as the wire of the valve spring 14, and the small end 19a of the cross section is on the inner diameter side and the large end side 19b is on the outer diameter side. It is wound into a coil shape. A coil spring made of such an oval cross-section wire can obtain a higher spring load than a coil spring made of a normal circular cross-section wire at the same installation length and spring outer diameter. Therefore, the single valve spring 14 of this embodiment can satisfy the same requirements as the conventional valve spring (see Fig. 1), which is composed of two inner and outer coil springs, resulting in a major cost reduction. becomes.

In addition, since there is no inner spring, it is possible to squeeze both ends or one end of the spring as shown in Fig. 3, and the spring retainer 12 can be reduced in size, reducing the equivalent weight and width of the valve system and increasing the height. It becomes possible to design a valve system that can follow rotation. Furthermore, since the surface 13 of the spring bearing on the cylinder head side can be made smaller, this bearing is also effective in preventing the thick part (disaster boss) forming the surface from protruding into the intake and exhaust ports 4.5. .

As is clear from BJN and 1 ri or more, in the cylinder head of the present invention, the intake and exhaust ports are linear and there are no protrusions on the inner surface, so the intake and exhaust resistance is small. Furthermore, since the included angle between the intake and exhaust valves is small, the overall size and weight are reduced, and the lengths of the intake and exhaust ports are also shortened, allowing for higher rotation speeds. Furthermore, die casting using a mold is possible.
A stable product with high precision and no unevenness can be obtained. In addition, in this case, the ports and combustion chamber are also manufactured using molds, so the surfaces can be made smooth, further reducing intake and exhaust resistance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional head cylinder, Fig. 2 is a sectional view of a head cylinder according to the present invention, Fig. 3 is a side view of a valve spring, and Fig. 4 is a sectional view of a wire rod of the same valve spring. . 1... Cylinder head, 2... Combustion chamber, 3... Connection part, 4... Intake port, 5... Exhaust port, 6
... Valve seat, 7... Intake valve, 8... Exhaust valve, 9... Cam chamber, 10... Valve stem guide, 11... Valve stem, 12... Spring retainer length, 13...Receiver is surface, 14...Valve spring, 15...Rocker arm, 16...Cam, 17
... Thick part, 18... Cover, 19... Wire rod.

Claims (1)

[Claims] A cylindrical intake/exhaust port extends linearly from a connecting part near the combustion chamber and opens to the outer peripheral surface, and a cam chamber is formed above the intake/exhaust port so as to gradually widen upward. , each having a suction and exhaust valve stem guide that penetrates the bottom of the cam chamber and reaches the suction and exhaust ports, and the intake and exhaust valve stem guides have a small angle between the axes of the two valve stem guides. A cylinder head for an internal combustion engine, characterized in that the port has no built-up portion for reinforcing the valve stem guide.