JPH11350963A - Intake manifold of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve engine performance by making the cylinder head and surrounding portions compact, while equalizing the swirl between cylinders. SOLUTION: A hanging width W of a manifold passage 3 from a cylinder head end face 1a is made narrower to the extent that, at least, flaking off of the main current of suction air occurs. As a result, the cylinder head and surrounding portions can be made compact. In addition, an air inlet angle adjustment projection 40 that decreases an air inlet angle θ3 of the suction air main current relative to the normal of the surface of a furthermost inlet port 23 is provided near the furthermost suction air outlet 33 so that the swirl ratio of a cylinder 13 corresponding to the furthermost inlet port 23 becomes the same extent as that of another cylinder 11. As a result, the equalization of the swirl ratio between cylinders is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake manifold for an internal combustion engine having a plurality of cylinders, and more particularly to an intake manifold for an internal combustion engine in which a space around a cylinder head is limited due to the layout of the internal combustion engine.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional engine in which a sufficient intake air amount can be ensured in a three-cylinder internal combustion engine by sufficiently increasing a projection width W of a manifold passage 43 from a cylinder head end face 1a. The intake manifold 42 is shown. Each cylinder 11, 12,.
13, the first, second and third intake ports 21,
22 and 23 are formed. Each intake port 21,
The valve ports 21a, 22a, and 2 form counter-clockwise swirls S in the cylinders 11, 12, and 13, respectively.
3a shifts rightward from the center of the cylinder, and the valve port 21
The valve stem 9 is formed so as to spiral around from the right side of the valve stem 9 with respect to a, 22a and 23a. Each intake port 2
The upstream portions of 1, 2, and 23 are opened in a posture substantially perpendicular to the cylinder head end surface 1a.

[0003] An intake manifold 42 is attached to the cylinder head end face 1a, and has an intake port 46 at one end in the cylinder head length direction (crank axis direction). The manifold passage 43 has another end along the cylinder head end face 1a. And has intake outlets 51, 52, 53 corresponding to the respective intake ports 21, 22, 23.

The inflow angles θ1, θ2, θ3 of the main intake air flows F1, F2, F3 to the intake ports 21, 22, 23, ie,
Inclination angle θ with respect to normal H set on the intake port entrance surface
The values of 1, θ2, and θ3 gradually increase as the distance from the intake port 46 increases, due to an increase in intake inertia.

[0005] As the inclination angles θ1, θ2, θ3 increase in order, the main intake air flows f1, f2, f3 in the intake ports 21, 22, 23 are changed so that their positions are clearly indicated by arrows. In the structure in which the swirl S is shifted to the right in the intake ports 21, 22, and 23 in a counterclockwise direction, the swirl S increases as the cylinder moves away from the intake port 46. That is, as the cylinder moves away from the intake port 46, the swirl ratio gradually increases as shown in FIG. 10, and the swirl ratio becomes uneven between the cylinders. The solid line P in FIG. 10 indicates the swirl ratio of the port alone, that is, the swirl ratio when one intake pipe is connected to one intake port without using the intake manifold, and corresponds to the magnitude of the swirl ratio of the first cylinder. doing.

[0006] In contrast to the internal combustion engine of a plurality of cylinders in which the overhang width of the manifold passage is ensured as described above, for example, in an internal combustion engine mounted on an agricultural tractor or a small work vehicle, the layout around the cylinder head is small. In many cases, the width is limited, and in this case, as shown in FIG. 11, the projecting width W of the manifold passage 43 is significantly reduced to achieve compactness.

[0007]

In the case of FIG. 11, as in the case of FIG. 9, the intake ports 21, 22, and 23 distant from the intake port 46 due to the increase of the intake inertia in the manifold passage 43. As we go, the main intake air flow F1, F2, F
Although the inflow angles θ1, θ2, and θ3 of FIG. 3 are increased, the cross-sectional area of the flow is small, the flow velocity in the manifold passage 43 is increased, and the intake inlet The intake angle θ3 of the main intake flow F3 of the intake port far from the intake port 46, particularly the third intake port 23 farthest from the intake port is
It is larger than necessary in comparison with the case of FIG.

As described above, as the inflow angle θ3 increases at the third intake port 23 and the momentum of the main flow F3 increases, a large separation zone Z occurs on the left side wall of the intake port 23 as shown by cross-hatching. Subsequently, reattachment to the left side wall occurs as shown by arrow f3, and the swirl ratio of the third cylinder decreases as shown in FIG. 12 due to peeling and reattachment. When the swirl ratio between the cylinders becomes uneven, the combustion state changes for each cylinder, and the engine performance such as the generation of black smoke and the decrease in fuel efficiency is reduced.

An object of the present invention is to maintain uniformity of a swirl ratio between cylinders and maintain engine performance while maintaining compactness around a cylinder head.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention comprises an intake port, a manifold passage extending along a cylinder head end face, and a plurality of intake outlets opening toward the cylinder head end face. Connecting each intake outlet to each intake port inlet surface of the cylinder head end surface, and extending the manifold passage from the cylinder head end surface at least to such an extent that the main intake flow separates in the intake port farthest from the intake inlet. In the intake manifold of the internal combustion engine, the swirl ratio of the cylinder corresponding to the farthest intake port is substantially equal to the swirl ratio of the other cylinders. An inflow angle adjusting projection for reducing the inflow angle θ of the main intake air flow with respect to the line is provided near the upstream side of the farthest intake outlet.

[0011]

FIG. 1 shows a cylinder head of a three-cylinder internal combustion engine to which the present invention is applied. For ease of explanation, the direction of a crankshaft center O is assumed to be a left-right direction, and an intake manifold is assumed. Assuming that the mounting side is the front side, three cylinders arranged along the direction of the crankshaft center O (left-right direction) are, in order from the left, first, second and third cylinders 11, 12,.
13 and will be described below. The structure of the cylinder head 1 is the same as that of FIG. 9, and the same components or parts are denoted by the same reference numerals.

The intake valve openings 21a, 22a, and 23a opening to the cylinders 11, 12, and 13 are formed at positions deviated from the center of each cylinder to the right side.
2, 23 extend rearward from the front end surface 1a of the cylinder head, and the downstream portion thereof is narrowed in flow cross section and spirally wound counterclockwise from the right side of the intake valve stem 9 to form respective valve port portions 21a, 22a. , 23a. As a result, a leftward (counterclockwise) swirl is generated in the cylinders 11, 12, and 13 as shown by the arrow S.

The intake manifold 2 is fixed to the front end face 1a of the cylinder head, and has a first intake port 21 at the left end.
An intake opening 6 having an upward opening shape is formed at a position substantially corresponding to. The manifold passage 3 extends linearly from the left end to the right end along the cylinder head front end surface 1a,
The intake outlets 31, 32, and 33 connected to the inlet surfaces of the intake ports 21, 22, and 23 are formed in a rearward opening shape.

The projecting width W of the manifold passage 3 from the front end face 1a of the cylinder head is as narrow as that of the conventional example shown in FIG. 11 to make the area around the cylinder head compact. That is, assuming that no treatment is performed in the manifold passage 3, the overhang width W becomes larger than necessary so that the inflow angle θ3 of the main intake flow F3 of the farthest third intake port 23 as shown in FIG. , Large peeling and reattachment occur in the third intake port 23.

In order to prevent the above-mentioned separation and reattachment, the left side (upstream side) of the third intake outlet 33 farthest from the intake inlet 6.
The manifold passage 3 from the front end face 1a of the cylinder head.
A protrusion 40 for adjusting the inflow angle of the intake air that protrudes inward is provided. The convex portion 40 reduces the inflow angle θ3 of the main intake flow F3 with respect to the normal H set on the entrance surface of the third intake port 23, that is, the intake flow so as to approach the side perpendicular to the entrance surface. The direction, the swirl ratio of the third cylinder 13, and the amount of protrusion into the manifold passage 3, the length and the shape in the left-right direction, and the shape are set so that the swirl ratio of the first cylinder 11 is substantially equal to the swirl ratio of the first cylinder 11.

The convex section 40 shown in FIG. 1 has a rectangular horizontal section, and extends between the upper and lower end walls of the manifold passage 3 as shown in FIG.

The operation will be described. In FIG. 1, the intake air (supply air) from an intake pipe (not shown) entering the left intake port 6 is
Part of the gas flows into the manifold passage 3, part of the gas flows into the first suction port 21 in a state substantially perpendicular to the inlet surface as indicated by an arrow F 1, and the rest flows rightward in the manifold passage 3. The gas flows through the manifold passage 3 while the inertial force is being applied, and partly flows into the second intake port 22 at an inflow angle θ2 as shown by an arrow F2, and the rest flows further rightward, as shown by the arrow F2. Is given. Second and third cylinders 1
A counterclockwise swirl S occurs in each of the circles 2 and 13.

At the stage before entering the third intake port 23, the intake air is once gathered to the front side by the convex portion 40, whereby the direction of the intake main flow is adjusted, and the intake air is bent backward and flows in as shown by the arrow F3. It enters the third intake port 23 at an angle θ3. That is, the third intake port 2
The inlet angle θ3 at 3 is adjusted to be smaller than the inlet angle θ3 in the case of FIG. Therefore, there is no separation or reattachment in the third intake port 23, and the third intake port 23 is not biased toward the right side wall of the third intake port 23 as shown by the arrow f3 in FIG. The air flows in a rectifying flow backward in the inside 23, turns leftward, and is supplied from the valve port portion 23 a into the third cylinder 13, and a counterclockwise swirl S having an appropriate momentum is generated in the third cylinder 13.

As described above, the swirl ratio of the third cylinder 13 is adjusted so that the intake air flow passes through the intake port 23 without causing separation and reattachment.
As shown in FIG. 7, the swirl ratio of the first cylinder 11 is increased from the conventional value indicated by the broken line to a value substantially equal to the swirl ratio. That is, the swirl ratio between the cylinders is equalized as a whole engine,
The combustion state can be made uniform, and the engine performance has been improved, such as reducing black smoke and improving fuel efficiency.

[0020]

[Other Embodiments] (1) In FIG. 1, only the adjusting projection 40 for the third cylinder is provided.
If large peeling and re-adhesion occur even within 2,
In addition to the adjustment protrusion 40 for the third cylinder, an adjustment protrusion 41 for the second cylinder may be formed on the upstream side of the second intake outlet 32 as shown by a virtual line. In this case, the projecting height of the second convex portion 41 is smaller than that of the third intake port convex portion 40.

(2) FIGS. 4, 5 and 6 each show a modification of the projection 40. The projection 40 shown in FIG. 4 is formed in a plate shape perpendicular to the manifold passage 3. FIG.
Has a curved inclined surface whose protruding height into the passage 3 increases toward the downstream side (right side) of the manifold passage 3, and the downstream end is perpendicular to the manifold passage 3. It is formed on the end face. Adjusting projection 4 shown in FIG.
0 is formed in a rounded trapezoidal shape (helmet shape), and the downstream edge reaches the left end of the third intake port entrance surface.

(3) The vertical cross-sectional shape of the convex portion 40 is not limited to the shape extending over the upper and lower walls of the intake manifold as shown in FIG. 3, but may be a shape having a gap between the upper and lower walls.

(4) Instead of the intake port for generating the left-hand swirl S as shown in FIG. 1, there are provided intake ports 21, 22, 23 for generating the right-hand swirl S as shown in FIG. The present invention can also be applied to a structure in which the intake manifold 2 having the intake port 6 at the left end is attached similarly to the first intake manifold. That is, the overhang width W of the manifold passage 3 is reduced as in FIG. 1, and the adjusting protrusion 40 is formed upstream of the third intake outlet 33 farthest from the intake inlet 6, so that the third intake air is formed. Port 23
Is prevented from increasing, and separation and re-adhesion in the third intake port 23 are prevented from occurring.

However, in this case, the third intake port 23
By preventing the inflow angle θ3 from increasing, the swirl ratio of the third cylinder, which is too large in the conventional narrow manifold passage as shown by the broken line in FIG. The swirl ratio between the cylinders is equalized by suppressing the swirl ratio up to the level of the swirl ratio.

(5) In addition to the intake manifold in which the intake port 6 is arranged at one end in the left-right direction as shown in FIGS. 1 and 7, a manifold passage having an intake port at the center of the left-right width and branching left and right. The present invention can also be applied to an intake manifold having

(6) The shape of the intake port may be either a helical type or a direct type, and it can be applied to an internal combustion engine having two cylinders or four or more cylinders.

(7) Although FIG. 1 shows a structure in which one cylinder has one intake port, the present invention can also be applied to an internal combustion engine in which one cylinder has two or more intake ports.

(8) The projection 40 can be formed integrally with the cylinder head.

[0029]

As described above, according to the present invention,
At least the cylinder head end face 1 is separated to such an extent that the main intake air is separated in the intake port 23 farthest from the intake inlet 6.
a of the manifold passage 3 from the inlet port 23a, and the swirl ratio of the cylinder 13 corresponding to the farthest intake port 23 becomes substantially equal to the swirl ratio of the other cylinders 11 and 12. An inflow angle adjusting projection 40 for reducing the inflow angle θ3 of the main intake flow F3 with respect to the normal H to the inlet surface.
Is provided near the upstream side of the farthest intake outlet, thereby preventing separation and re-adhesion in the intake port 23 while keeping the area around the cylinder head of the internal combustion engine compact, and reducing the swirl ratio between cylinders. Can be equalized. As a result, the engine performance can be improved, such as preventing the generation of black smoke and improving fuel efficiency, as well as making the engine compact.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view of a cylinder head provided with an intake manifold according to the present invention.

FIG. 2 is a comparison diagram of a swirl ratio of each cylinder corresponding to the structure of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG.

FIG. 4 is a horizontal cross-sectional view showing a modification of the adjustment projection.

FIG. 5 is a horizontal cross-sectional view showing a modification of the adjustment protrusion.

FIG. 6 is a horizontal cross-sectional view illustrating a modification of the adjustment protrusion.

FIG. 7 is a horizontal cross-sectional view in which the intake manifold of the present invention is applied to a cylinder head configured to generate swirl in a direction opposite to that of FIG.

8 is a comparison diagram of a swirl ratio of each cylinder corresponding to the structure of FIG. 7;

FIG. 9 is a horizontal sectional view of a conventional example.

10 is a comparison diagram of a swirl ratio of each cylinder according to the structure of FIG. 9;

FIG. 11 is a horizontal sectional view of another conventional example.

12 is a comparison diagram of the swirl ratio of each cylinder corresponding to the structure of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 1a Cylinder head end face 2 Intake manifold 3 Manifold passage 6 Intake port 11, 12, 13 Cylinder 21, 22, 23 Intake port 31, 32, 33 Intake port 40, 41 Adjusting projection

Claims (1)

[Claims] An intake port, a manifold passage extending along an end face of a cylinder head, and a plurality of intake outlets opening toward the end face of the cylinder head. In the intake manifold of an internal combustion engine connected to a surface of the internal combustion engine, the width of the manifold passage extending from the end face of the cylinder head is narrowed to such an extent that the main intake flow is separated at least in the intake port farthest from the intake port. For adjusting the inflow angle θ of the main intake flow with respect to the normal of the inlet surface of the farthest intake port so that the swirl ratio of the cylinder corresponding to the intake port of the other cylinder is substantially the same as the swirl ratio of the other cylinders. An intake manifold for an internal combustion engine, wherein the projection is provided at a position near an upstream side of a farthest intake outlet.