JPH04140420A - Intake device for engine - Google Patents

Abstract

PURPOSE:To improve the charging efficiency by suppressing the exfoliation of stream at the inlet part of a combustion chamber and increasing the ventilation effective area by forming a throttle which bulges toward the center of the circle on the fundamental sectional surface, on the inside and outside surfaces in a curved part of an intake port on the directly upstream side of an intake valve. CONSTITUTION:As for an intake port 4 formed on a cylinder head 1, the downstream edge is opened into a combustion chamber 3, and the inlet part 5 of the combustion chamber due to the opened port part is opened and closed by an intake valve 6. In this case, a throttle 11 is formed at the throat part as the directly upstream side of the intake valve 6 at the intake port 4. Accordingly, though the fundamental sectional surface of the intake port 4 is circular form, the throttle 11 is formed by forming the parts 11a and 11b which bulge toward the center O of the circle on the fundamental sectional surface, on the curved inside and outside surfaces of the throat part. Further, the inside part 11a is bulged out largely toward the center O of the circle in comparison with the outside part 11b. Further, the min. passage area of the throat part having the throttle 11 is set larger than the curtain area in the max. lift of the intake valve 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for an engine that includes an intake port that is curved in the vicinity of an intake valve.

[Conventional technology]

Conventionally, an engine intake device includes an intake port formed in a cylinder head and having a downstream end opening into a combustion chamber.
The opening at the downstream end of this intake port is opened and closed by an intake valve (see, for example, Japanese Utility Model Publication No. 1-66723). The intake port is generally curved near the intake valve in order to avoid interference with the valve train of the intake valve.

[Problem to be solved by the invention]

In a conventional intake device of this type, as shown in FIG. 4, the diameter Ds of the portion (throat portion) near the intake knob 106 of the intake port 104 is [Ds = 0.9Dv] and has a substantially constant diameter, but with such a shape, the intake air does not spread sufficiently in the direction along the cylinder head surface 101a at the combustion chamber inlet portion 105, and the cylinder head surface Separation occurs in the flow of the suction window (arrow) with respect to 101a. For this reason, there is a problem in that the effective area for one pass becomes small, leading to a decrease in filling efficiency.

Therefore, as shown by the broken line in FIG.
Ds=0.8Dv], it is thought to improve the spread of intake air at the combustion chamber inlet portion 105 and reduce separation.

However, as mentioned above, the intake port 10< generally has a curved shape, so simply providing the throttle 111 uniformly at the throat part tends to cause the airflow passing through the curved part to be directed to the outside of the curved part. Peeling easily remained in the portion corresponding to the inside of the groove portion, and the flow at the roasting chamber entrance portion 105 was not sufficiently improved.

In view of these circumstances, the present invention suppresses flow separation at the inlet portion of the combustion chamber, and in particular sufficiently suppresses separation even inside the curved shape, effectively increasing the effective ventilation area and improving charging efficiency. It is an object of the present invention to provide an engine intake system that can be improved.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention is configured such that an opening to a combustion chamber at the downstream end of an intake boat is opened and closed by an intake valve, and the intake port has a curved shape along the intake flow direction near the intake valve. In an engine intake system in which the basic cross section of the intake port is circular, the inner and outer surfaces of the curved part of the intake port immediately upstream of the intake valve bulge toward the circular center of the basic cross section. A diaphragm is provided, and the diaphragm is formed in such a shape that the inner part of the curved shape bulges out more toward the circular center of the basic cross section than the outer part.

In this configuration, it is preferable that the minimum passage area of the portion where the throttle is provided is set larger than the curtain area area when the intake valve is at its maximum lift.

[Effect]

According to the above configuration, when the intake air passes through the throttle and reaches the combustion chamber inlet part, it spreads in the direction along the cylinder head surface and separation is suppressed, and especially in the part corresponding to the inside of the curved shape, separation is sufficiently suppressed. This provides a flow of intake air that looks like this.

Furthermore, the minimum passage area of the part where the above-mentioned throttle is provided is
If the area of the curtain area is set to be larger than the area of the curtain area when the intake valve is at its maximum lift, the throttle will not act as resistance to the intake air at a flow rate commensurate with the area of the curtain area.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

1 to 3 show one embodiment of the present invention. In FIG. 1 showing an outline of the entire intake system, reference numeral 1 denotes a cylinder head provided on a cylinder block 2, and combustion chambers 3 are formed at a predetermined number of locations on the cylinder head. 4 is an intake port formed in the cylinder head 1, and its downstream end opens into the combustion chamber 3. A combustion chamber inlet portion 5 formed by an opening at the downstream end of the intake port 4 is opened and closed by an intake valve 6, and a valve stem 6a of the intake valve 6 extends above the intake port 4 and is connected to the cylinder head 1.
A valve mechanism such as a camshaft 7 is arranged at the top. The intake port 4 has a curved shape near the intake valve 6 so as not to interfere with the valve mechanism, and the upstream side reaches the side surface of the cylinder head 1, and an intake manifold (not shown) is attached to the upstream end of the intake port 4. Connected. In addition, an exhaust boat 8 is formed in the cylinder head 1, and an exhaust valve 9 and a valve mechanism (not shown) for the exhaust valve 9 are disposed thereon.
(not shown) is attached.

A throttle 11 as described below is provided at the throat portion of the intake port 4, which is a portion immediately upstream of the intake valve 6. That is, as shown in FIGS. 2 and 3, the basic cross section (double-dashed line) of the intake port is circular, but the circular center of the basic cross section is located on the inner and outer surfaces of the curve of the throat portion. By providing the portions 11a and llb that bulge toward 0, the aperture 1 is
1, and the boat has a narrow cross-sectional area. In particular, in this diaphragm 11, the inner part 11a of the boat-curved shape bulges out more toward the circular center O of the basic cross section than the outer part 11b. In other words, the amount of bulge from the basic cross section is the inner part 11a and the outer part 11b.
It is larger than the distance from the circular center ○ to the inner part 11a of the aperture! 1. If the distance to the outer portion 11b is 12, it is formed so as to be [12]. Preferably, the relationship between these distances 1t1.12 and the valve diameter Dv of the intake valve 6 is [11<0.4D
v≦! 2] Tosareru.

Further, the minimum passage area Sa of the throat portion where the throttle 11 is provided is larger than the curtain area area sb at the maximum lift of the intake valve 6, that is, if the maximum lift amount is L, [Sa>Sb-πxDvxL ].

Here, the curtain area refers to the area between the area around the intake valve 6 and the area around the entrance of the combustion chamber 30.

According to the intake device having such a structure, the throttle 11 is provided immediately upstream of the intake valve 6 of the intake boat 4, and the intake port 4
Since the downstream end is shaped to expand from the throttle 11 to the combustion chamber inlet portion 5, the flow of intake air that has passed through the throttle 11 is directed to the cylinder head surface 1a at the combustion chamber inlet portion 5.
(arrow in FIG. 2), and separation between the cylinder head surface 1a and the flow is suppressed. In particular, by having a curved shape in which the inside is narrower than the outside, the tendency that peeling is naturally more likely to occur on the inside is corrected, and the portion corresponding to the outside in the combustion chamber inlet portion 5 is corrected. and each ventilation effective area A1 of the part corresponding to the inner side. A2 becomes the same level, and a reasonable inflow of intake air is performed.

Furthermore, since the minimum area of the throat portion is set larger than the curtain area area when the intake valve is at its maximum lift, the aperture 11 causes an increase in flow resistance against the flow of intake air in an amount commensurate with the curtain area area. There is no.

〔Effect of the invention〕

As described above, the present invention provides an intake system in which the intake boat has a curved shape near the intake valve. Since the throttle is provided that bulges toward the center, separation of flow is suppressed to the same extent on the inside and outside of the combustion chamber inlet portion. Therefore, the effective ventilation area is rationally expanded, and the filling efficiency can be greatly improved.

In addition, in this configuration, if the minimum passage area of the part where the throttle is provided is set larger than the curtain area area at the maximum lift of the intake valve, the amount of intake air commensurate with the curtain area area will not be able to flow. The aperture does not become a resistance, and the above-mentioned effect of improving the filling efficiency by improving the flow can be effectively exerted.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway sectional view of an engine including an intake system according to an embodiment of the present invention, Fig. 2 is an enlarged sectional view of main parts of the intake system, and Fig. 3 is a cross-sectional view of a port in the throttle section of the intake system. FIG. 4 is an enlarged cross-sectional view of a main part of a conventional intake device. 2... Combustion chamber, 4... Intake boat, 6... Intake valve, 11... Throttle.

Claims (1)

[Claims] 1. The opening to the combustion chamber at the downstream end of the intake port is opened and closed by an intake valve, and near the intake valve, the intake port has a curved shape along the intake flow direction. In an engine intake system in which a port has a circular basic cross section, a throttle that bulges toward the circular center of the basic cross section is provided on the inner and outer surfaces of the curved portion of the intake port immediately upstream of the intake valve. , and the throttle is formed in such a shape that the inner part of the curved shape bulges out more toward the circular center of the basic cross section than the outer part. 2. The engine intake system according to claim 1, wherein the minimum passage area of the portion where the throttle is provided is set to be larger than the curtain area area when the intake valve is at its maximum lift.