JPH08232756A - Cylinder head structure of four-cycle engine - Google Patents

Abstract

PURPOSE: To improve engine performance and fuel consumption by a method wherein the total height of an engine is reduced to a low value to relax constraint on a design and reduction of ventilation resistance and formation of an intake air tumble are promoted. CONSTITUTION: Valve seats 4 and 5 formed of a material different from that of a cylinder head are mounted on the peripheral edges of the suction and exhaust ports 2a and 3a of the cylinder head through joining, and the insidemost diameters A and C of the valve seats 4 and 5 are set to a value (A>B and C>D) higher than the inside diameters B and D of the throat parts 2a-2 and 3a-2 of the suction and exhaust passages 2 and 3 of the cylinder head. The suction and exhaust passages 2 and 3 are capable of approaching a combustion chamber S. The height of the cylinder head 1, and in turn the total height of the engine is suppressed to a low value and limitation on a design is relaxed and by promoting reduction of ventilation resistance of suction air and exhaust air in the suction and exhaust passages 2 and 3 and formation of a suction tumble in the combustion chamber S, engine performance and fuel consumption are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head structure for a 4-cycle engine.

[0002]

2. Description of the Related Art In a four-cycle engine, intake / exhaust ports opening in a combustion chamber are opened / closed at appropriate timings by an intake / exhaust valve to perform a required gas exchange. A valve seat, on which the intake / exhaust valve is to be seated intermittently, is generally attached to the peripheral portion by press fitting. For example, as shown in FIG. 7, the intake port 102 of the cylinder head 101
A valve seat 104, on which the intake valve 112 is to be seated intermittently, is attached to the peripheral edge of a by press fitting.

By the way, in recent years, for the purpose of high output, etc.
Since the number of valves in a cycle engine is increasing, and a plurality of intake / exhaust ports are arranged close to each other in each cylinder of a cylinder head, the interval between the ports is becoming narrower.

[0004]

However, if the valve seat is conventionally press-fitted into the periphery of the intake / exhaust port under the above-mentioned circumstances, cracks may occur between the ports of the cylinder head due to insufficient strength. .

Further, when the method of press-fitting the valve seat is adopted, as shown in FIG. 7, a large seat 101a necessary for press-fitting the valve seat 104 is required at the periphery of the intake port 102a of the cylinder head 101, and ,
Since the innermost diameter portion of the valve seat 104 constitutes the throat portion 102b of the intake passage 102, the valve seat 10
The innermost diameter of 4 was the diameter of the throat portion of the intake passage 102. For this reason, the intake passage 102 cannot be brought very close to the combustion chamber, and this is the same on the exhaust side not shown, and the total height of the engine becomes high, which imposes restrictions on the design. In addition to increasing the ventilation resistance of the engine, the formation of intake swirl and intake tumble in the combustion chamber was weak, which could lead to deterioration of engine performance, exhaust gas characteristics, and fuel consumption.

The present invention has been made in view of the above problems, and its object is to reduce the overall height of the engine to alleviate design restrictions, to reduce ventilation resistance, and to reduce intake air swirl in a combustion chamber. It is an object of the present invention to provide a cylinder head structure for a four-cycle engine that can promote the formation of intake tumble to improve engine performance and fuel efficiency.

[0007]

In order to achieve the above object, the invention according to claim 1 is characterized in that a valve seat made of a material different from that of the cylinder head is sucked into the cylinder head.
It is characterized in that the valve seat is attached to the periphery of the exhaust port portion by joining, and the innermost diameter of the valve seat is made larger than the diameter of the throat portion of the intake / exhaust passage of the cylinder head.

According to a second aspect of the present invention, in the first aspect of the invention, the intake / exhaust port throat portion of the cylinder head is formed with a taper surface continuous with the throat portion of the intake / exhaust passage and the face surface of the valve seat. However, the innermost diameter end of the valve seat is positioned on the tapered surface.

[0009]

According to the first aspect of the invention, since the valve seat is joined to the cylinder head, cracks do not occur in the cylinder head even in a multi-valve engine.
In addition, a large seat required for press-fitting the valve seat is not required around the intake / exhaust port of the cylinder head.
Since the innermost diameter of the valve seat is set to be larger than the diameter of the throat of the intake / exhaust passage of the cylinder head, the intake / exhaust passage can be brought closer to the combustion chamber, and the height of the cylinder head, and eventually the intake / exhaust system. The overall height of the engine, including parts, can be kept low to alleviate design restrictions, and the protrusion length of the valve guide into the intake / exhaust passages can be kept small, reducing ventilation resistance in the intake / exhaust passages. It can be suppressed to improve engine performance.

Furthermore, by making the intake / exhaust passage closer to the combustion chamber, the angle formed by the throat portion of the intake / exhaust passage with respect to the cylinder head mating surface is suppressed to be small, which promotes the formation of intake tumble in the combustion chamber. The combustion efficiency of the air-fuel mixture is enhanced, and the fuel efficiency and exhaust gas characteristics of the engine are improved.

Further, in a multi-valve engine having a plurality of intake / exhaust ports, the distance between adjacent ports and the distance between each port and the spark plug hole are narrowed, and the ports are collectively arranged in the center of the combustion chamber dome. As a result, the formation of intake tumble in the combustion chamber is promoted, and it is possible to prevent the valve intake flow from interfering with the cylinder wall and to make the combustion chamber have a nearly ideal spherical shape. The combustion efficiency of the air-fuel mixture is enhanced, and the fuel efficiency and exhaust gas characteristics of the engine are improved. In addition, by expanding the port diameter and using large-diameter intake / exhaust valves, it is possible to improve the flow coefficient and improve engine performance.

According to the second aspect of the invention, it is possible to specifically realize the configuration of the first aspect (the configuration in which the innermost diameter of the valve seat is made larger than the intake / exhaust passage throat diameter of the cylinder head). .

[0013]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a vertical cross-sectional view of a cylinder head having a structure according to the present invention, FIG. 2 is a bottom view of the cylinder head (as viewed from the combustion chamber side), and FIG. 3 is a valve seat portion of the cylinder head. FIG. 4 to FIG. 6 are sectional views showing a procedure for joining valve seats (before joining, after joining, and after working).

The cylinder head 1 according to this embodiment is for a four-cycle four-valve engine, which is integrally cast from an Al alloy. The cylinder head 1 has an intake passage 2 and an exhaust gas as shown in FIG. Two passages 3 are formed (only one is shown in the drawing).

Further, a combustion chamber dome 1b forming a combustion chamber S is formed on a mating surface (a mating surface with a cylinder body (not shown)) of the cylinder head 1 and the intake passage 2 is formed.
The exhaust port 3 and the exhaust passage 3 are respectively the intake port 2a and the exhaust port 3
It is open to the combustion chamber S as a. Then, ring-shaped valve seats 4 and 5 are joined to the periphery of the intake port 2a and the exhaust port 3a by a method described later, and the intake port 2a and the exhaust port 3a slide on the cylindrical valve guides 6 and 7. An intake valve and an exhaust valve (not shown) movably inserted therein are opened and closed at appropriate timings, and the valve seats 4 and 5 intermittently seat the intake valve and the exhaust valve, respectively.

The details of the structure of the intake port 2a and the exhaust port 3a of the cylinder head 1 to which the valve seats 4 and 5 are attached will be described with reference to FIG.

As shown in FIG. 3, in the portion near the intake port 2a of the intake passage 2 and the exhaust port 3a of the exhaust passage 3,
Tapered surfaces 2a-1 and 3a- that expand in diameter toward the combustion chamber S
1 is formed, and the tapered surface 2a-1 is a throat portion of the intake passage 2 (a linear portion close to the combustion chamber S) 2
a-2 and the face surface 4a of the valve seat 4 (the surface on which the intake valve is seated) 4a, and the tapered surface 3a-1 is the throat portion 3a-2 of the exhaust passage 3 and the face surface of the valve seat 5 (the exhaust valve is Seating surface) 5a.

Thus, in this embodiment, the innermost diameters A and C of the valve seats 4 and 5 are the inner diameter B of the throat portion 2a-2 of the intake passage 2 and the throat portion of the exhaust passage 3 as shown in the figure. Larger than inner diameter D of 3a-2 (A> B, C>
D) It is set, and the innermost diameter ends of the valve seats 4 and 5 are the tapered surfaces 2a of the intake passage 2 and the exhaust passage 3, respectively.
It is located on -1, 3a-1.

By the way, as shown in FIG. 2, an ignition plug hole 8 is formed in the center (top) of the combustion chamber dome 1b of the cylinder head 1, and the ignition plug hole 8 is formed in the combustion chamber dome 1b. 2 each so that it is surrounded by
An intake port 2a and an exhaust port 3a are arranged.

As shown in FIG. 1, a water jacket 9 is formed around the valve seats 4, 5 of the cylinder head 1, and the water jacket 9 is formed on the mating surface (bottom surface) of the cylinder head 1. It communicates with a water jacket formed in a cylinder body (not shown) through an open communication passage 10. In FIG. 2, 11 is a head bolt hole.

Next, the valve seats 4 and 5 will be described.

The valve seats 4 and 5 are made of a sintered material obtained by a powder metallurgy method. The sintered material is a combination of a large number of powder particles mainly composed of Fe, and the voids are A metal such as Cu having a high electric conductivity is filled by the infiltration treatment.

Thus, the valve seat 4 is joined to the peripheral edge of the intake port 2a by the procedure shown in FIGS.
Since the other valve seat 5 is also joined to the peripheral edge of the exhaust port 3a by the same procedure, description thereof will be omitted.

Before joining the valve seat 4,
In the peripheral portion of the intake port 2a of the cylinder head 1, as shown in FIG.
As shown in FIG.
1 is formed, and a valve seat 4 made of an Fe-based material having a hardness higher than that of the cylinder head 1 made of Al alloy is formed on the tapered surface 2a-1 as shown in FIG. Are joined metallurgically.

That is, the valve seat 4 is set so that its back surface is in contact with the tapered surface 2a-1 of the intake port 2a, and the tapered surface 2a-1 is pressed with a predetermined force by the electrode of the resistance welding machine. After that, electricity is continuously applied. Then F
Al, which has a lower hardness than the valve seat 4 made of e-based material
When the cylinder head 1 made of alloy is plastically deformed and the valve seat 4 is embedded in the cylinder head 1 as shown in FIG. 5, the two react by solid phase diffusion at the interface (reaction between solids At this time, valve seat 4
And the cylinder head 1 are not in a molten state) and are metallurgically bonded and integrated.

Next, the joint portion of the valve seat 4 is cooled,
When the unnecessary portion is cut by machining, the valve seat 4 is finished into the final shape and joined to the peripheral portion of the intake port 2a of the cylinder head 1 as shown in FIG.

By the way, when the valve seat is press-fitted into the peripheral portion of the intake / exhaust port as in the conventional case, the intake / exhaust passages cannot be brought close to each other for the reason described above, and these are indicated by chain lines in FIG. It was formed in the shape shown.

On the other hand, in this embodiment, since the valve seats 4 and 5 are joined to the peripheral edges of the intake port 2a and the exhaust port 3a, the press-fitting, which is conventionally required, is inserted into the intake passage 2 and the exhaust passage 3. A large seat for the valve seats is not required, and as described above, the innermost diameters A and C of the valve seats 4 and 5 are not required.
Is the throat portions 2a-2, 3a-2 of the intake / exhaust passages 2, 3.
Since the inner diameters are set larger than the inner diameters B and D (A> B, C> D), the intake passage 2 and the exhaust passage 3 are shown by solid lines in FIG. 1 in contrast to the conventional shape shown by dashed lines in FIG. The shape can be made close to the combustion chamber S, and the angles α ₁ , α ₂ formed by the throat portions 2a-2, 3a-2 with respect to the mating surface 1a of the cylinder head 1 with respect to the conventional values. It can be kept small.

Thus, by bringing the intake passage 2 and the exhaust passage 3 close to the combustion chamber S as described above, the height of the cylinder head 1 and thus the overall height of the engine can be kept low, and as a result, the design can be reduced. The above restrictions are relaxed. In particular,
In a motorcycle, the seat height can be kept low by keeping the overall height of the engine low, which improves rider's foot contact and has the advantage of increasing the degree of freedom in handling the frame.

Further, by bringing the intake passage 2 and the exhaust passage 3 close to the combustion chamber S, the projection length of the valve guides 6 and 7 into the intake / exhaust passages 2 and 3 can be suppressed to be small, and the intake passage 2 Since the ventilation resistance of the exhaust gas in the exhaust passage 3 is suppressed to be small, the engine performance can be improved.

Further, the throat portion 2 of the intake / exhaust passages 2 and 3
Since the angles α ₁ and α ₂ formed by the a-2 and 3a-2 with respect to the mating surface 1a of the cylinder head 1 are suppressed to be small, the combustion chamber S
The formation of the intake tumble in the engine is promoted, the combustion efficiency of the air-fuel mixture in the combustion chamber S is enhanced, and the fuel efficiency of the engine is improved.

In addition, the cylinder head 1 for a four-valve engine according to this embodiment has two intake ports 2a each.
Since the exhaust port 3a is formed, the distance between the intake / exhaust ports 2a, 3a is shortened, but the valve seats 4, 5 are joined to the intake / exhaust ports 2a, 3a with a sufficiently small cross-sectional area. Therefore, the cylinder head 1 does not crack due to insufficient strength.

By adopting the method of joining the valve seats 4 and 5 to the cylinder head 1 as in the present embodiment, the wall thickness of the valve seats 4 and 5 can be reduced and the cylinder head 1 Since the wall thickness around the intake port 2a and the exhaust port 3a can be reduced,
Conventionally, the water jacket 9 having the cross-sectional shape shown by the chain line in FIG. 3 is brought close to the valve seats 4 and 5 as shown by the solid line, and the water jacket 9 is placed over the entire circumference of the valve seats 4 and 5. Can be formed. As a result, the cross-sectional area of the water jacket 9 is increased and the valve seats 4, 5 and their surroundings are efficiently cooled, so that the surface temperatures of the valve seats 4, 5 and the intake / exhaust valves are lowered to cause these abnormalities. Wear is prevented, the durability of the valve seats 4, 5 and intake / exhaust valves are improved, and it is possible to replace these materials with inexpensive materials, and further improve the knock resistance of the engine. You can

Further, the deformation of the valve seats 4, 5 and the intake / exhaust valves can be suppressed to a small level, so that the engine performance is improved and the fuel consumption and the exhaust gas characteristics are improved.

Further, as a result of the temperature of the intake / exhaust valves being lowered, the strength of these intake / exhaust valves can be afforded, so that the stems can be made smaller in diameter and the thickness of the umbrella portion can be made thinner. Also reduces the intake / exhaust ventilation resistance and improves engine performance.

On the other hand, in this embodiment, as shown in FIG. 2, the cylinder head 1 is provided with two intake ports 2a and two exhaust ports 3a, and the intervals between the adjacent ports 2a and 3a and the respective ports 2a and 3a. Since the ports 2a and 3a are arranged at the center of the combustion chamber dome 1b with a narrow interval between the spark plug hole 8 and the spark plug hole 8, the formation of intake tumble in the combustion chamber S is promoted, and the valve intake flow from the cylinder wall is increased. Since interference can be prevented and the combustion chamber S can be formed into a nearly ideal spherical shape, the combustion efficiency of the air-fuel mixture in the combustion chamber S is increased and the fuel efficiency and exhaust gas characteristics of the engine are improved.

Since the distance between the adjacent ports 2a and 3a and the distance between the ports 2a and 3a and the spark plug hole 8 are narrowed, the diameters of the ports 2a and 3a are enlarged to use large intake / exhaust valves. Therefore, it is possible to improve the engine performance by increasing the flow coefficient.

Although the above description refers to the cylinder head structure for a four-valve engine, the present invention is of course applicable to other cylinder head structures for a multi-valve engine.

[0040]

As is apparent from the above description, according to the present invention, a valve seat made of a material different from that of the cylinder head is attached to the periphery of the intake / exhaust port of the cylinder head by joining, and Since the innermost diameter of the valve seat is made larger than the diameter of the throat part of the intake / exhaust passage of the cylinder head, the intake / exhaust passage can be brought closer to the combustion chamber, reducing the overall height of the engine and alleviating design restrictions and venting. The effect that the engine performance and the fuel consumption can be improved by reducing the resistance and promoting the formation of the intake tumble in the combustion chamber is obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a cylinder head having a structure according to the present invention.

FIG. 2 is a bottom view (a view seen from the combustion chamber side) of a cylinder head having a structure according to the present invention.

FIG. 3 is an enlarged sectional view around a valve seat portion of a cylinder head having a structure according to the present invention.

FIG. 4 is a cross-sectional view showing a procedure for joining valve seats (before joining).

FIG. 5 is a cross-sectional view showing a procedure for joining valve seats (after joining).

FIG. 6 is a cross-sectional view showing a procedure for joining valve seats (after processing).

FIG. 7 is a cross-sectional view showing a conventional cylinder head structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 1a Cylinder head mating surface 1b Combustion chamber dome 2 Intake passage 3 Exhaust passage 2a Intake port 3a Exhaust port 2a-1 Tapered surface 3a-1 Tapered surface 2a-2 Intake passage throat portion 3a-2 Exhaust passage throat portion 4, 5 Valve seat 8 Spark plug hole A, B Innermost diameter of valve seat C Intake passage throat diameter D Exhaust passage throat diameter S Combustion chamber

Claims (2)

[Claims] 1. A valve seat made of a material different from that of the cylinder head is attached to the periphery of the intake / exhaust port portion of the cylinder head by joining, and the innermost diameter of the valve seat is set to the intake / exhaust passage throat portion of the cylinder head. Cylinder head structure for 4-cycle engine characterized by being larger than the diameter. 2. The intake / exhaust port portion of the cylinder head is provided with a taper surface which is continuous with the intake / exhaust passage throat portion and the face surface of the valve seat, and the innermost diameter end of the valve seat is positioned on the taper surface. The cylinder head structure for a four-cycle engine according to claim 1, wherein