WO2005028819A1

WO2005028819A1 - Method of manufacturing suction port of internal combustion engine and suction port of internal combustion engine

Info

Publication number: WO2005028819A1
Application number: PCT/JP2004/013814
Authority: WO
Inventors: Fumio Takamiya; Takeshi Okumura
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2003-09-22
Filing date: 2004-09-22
Publication date: 2005-03-31
Also published as: JP2007046457A

Abstract

A suction port (1) of an internal combustion engine, wherein the centerline (C1) of the suction port (1) is tilted relative to the centerline (C2) of a combustion chamber (2), and an annular seat ring (5) is disposed in the area of the suction port (1) facing the combustion chamber (2). Inner peripheral surfaces (valve seat faces) (6a) and (6b) formed symmetrically with respect to the axis (C3) of a suction valve (4) to close suction flow by the contact of the suction valve (4) thereon and diverging toward the combustion chamber (2) are formed on the combustion chamber (2) side inner peripheral surface of the seat ring (5). Suction port side inner peripheral surfaces (6c) and (6d) formed symmetrically with respect to an axis tilted by a specified angle from the axis (C3) of the suction valve (4) to the centerline (C1) side of the suction port (1) are formed on the suction port (1) side inner peripheral surface of the seat ring (5). The inner peripheral surface (6b) of the seat ring (5) is joined to the suction port side inner peripheral surface (6c) at an obtuse angle.

Description

Specification

TECHNICAL FIELD The present invention relates to a method of manufacturing an intake port of an internal combustion engine and an intake port of the internal combustion engine.

The present invention relates to a method of manufacturing an intake port of an internal combustion engine and an intake port of the internal combustion engine manufactured by the method, and more particularly, to an intake port of an internal combustion engine capable of achieving both a high tumble ratio and a high flow coefficient. The present invention relates to a method of manufacturing the same and an intake port of an internal combustion engine.

Background art

[0002] Conventionally, in order to improve the combustion of an internal combustion engine, various means have been provided for increasing the turbulence of the air flow in a combustion chamber by utilizing an intake air flow. FIG. 8 is a cross-sectional view schematically showing an example of a conventional intake port.

[0003] As shown in FIG. 8, the intake port 101 has a cylinder head (not shown) at a predetermined inclination angle に such that its center line C1 is inclined with respect to the center line C3 of the intake valve (not shown). ). The inlet of the combustion chamber of the intake port 101 is bent in a direction substantially perpendicular to the ceiling of the combustion chamber (not shown).

[0004] At the edge of the intake port 101 facing the combustion chamber, an annular seat ring 5 on which the intake valve is detached and seated is press-fitted. Such a shape of the intake port 101 is set with the inclination angle Θ, the bending range h, the representative inner diameter D of the intake port 101 and the edge portion 101c as main design factors.

[0005] Further, such an intake port 101 is cut as follows. That is, as shown in FIGS. 9 and 10, the center axis of the throat cutter 105, which is a cutting tool, is aligned with the center axis C3 of the intake valve provided in the cylinder head 3 and cut into the intake port 101. As a result, both the inner peripheral surface 6 of the seat ring 5 and the throat portion 101a are calorie at once.

[0006] At this time, the intake port 101 has a step-shaped non-smooth portion 101b and an edge portion 101c. Here, FIG. 9 is a cross-sectional view showing the seat ring and the throat part before cutting, and FIG. 10 is a cross-sectional view showing the seat ring and the throat part after cutting. It is.

Next, another conventional technique disclosed in Patent Document 1 will be described with reference to FIG. FIG. 11 is a sectional view showing a conventional intake port disclosed in Japanese Patent Application Laid-Open No. 2001-173513. As shown in FIG. 11, an annular seat ring 5 on which the intake valve 4 is detached and seated is press-fitted into the inlet of the intake port 101 to the combustion chamber 2. In the following description, of the inner peripheral surface 6 of the seat ring 5, a region near the center of the combustion chamber 2 is referred to as an inner peripheral surface 6a, and a region near the outer peripheral portion of the combustion chamber 2 is referred to as an inner peripheral surface. 6b.

[0008] The central axis of the inner peripheral surface 6 of the seat ring 5 is inclined along the flow path of the intake port 101 with respect to the central axis of the outer peripheral surface 106. The inner peripheral surface 6a of the seat ring 5 is formed so as to be smoothly connected to the upper inner wall surface of the intake port 101, and is formed so as to be substantially linear toward the combustion chamber 2.

[0009] The inner peripheral surface 6b of the seat ring 5 has an edge formed on the combustion chamber 2 side at an acute angle. The opening area of the seat ring 5 is formed so as to be substantially uniform in the thickness direction of the seat ring 5. In the drawings, reference numeral 7 denotes a cylinder, 8 denotes a piston, and an exhaust port, an exhaust valve, and a spark plug are not shown.

[0010] As described above, the inner peripheral surface 6a of the seat ring 5 is formed so as to be smoothly connected to the upper inner wall surface of the intake port 101, and has a substantially linear shape facing the combustion chamber 2. When the intake valve 4 is opened, the intake air introduced into the combustion chamber 2 from the intake port 101 via the seat ring 5 mainly flows through the inner peripheral surface 6a of the seat ring 5. Flows smoothly into the combustion chamber 2 along the. As a result, the directivity of the intake air flow is increased, and the intake air flow velocity is maintained at a high level, so that the tumble flow T is strengthened and the combustion efficiency is improved.

Next, another conventional technique disclosed in Patent Document 2 will be described with reference to FIG. FIG. 12 is a cross-sectional view showing a conventional intake port disclosed in Japanese Patent Application Laid-Open No. 8-27746. As shown in FIG. 12, the intake port 101 is configured such that the intersection P between the center line C1 and the center axis C3 of the intake valve 4 is located near or downstream of the seating surface 5a of the seat ring 5. .

The intake port 101 is formed so as to be substantially linear with respect to the combustion chamber 2. In addition, the inner peripheral surface 6a of the seat ring 5 is also joined with the upper inner wall surface 101A of the intake port 101. The combustion chamber 2 is formed so as to be substantially linear with respect to the force. This allows the intake port 1

The flow resistance of the intake air flowing through 01 is suppressed to a small value, so that the decrease in the flow coefficient is suppressed, and the activation of the tumble flow is promoted.

An inner peripheral surface 6 b of the seat ring 5 is formed so as to expand toward the combustion chamber 2. The angle Θ4 formed by the inner peripheral surface 6b with the lower inner wall surface 101B of the intake port 101 is formed substantially at a right angle.

Patent Document 1: JP 2001-173513 A

Patent Document 2: JP-A-8-277746

Disclosure of the invention

Problems to be solved by the invention

[0015] In order to enhance the tumble flow, while reducing the inner diameter D of the intake port 101 and reducing the edge portion 101c in the first prior art shown in FIG. The design will be in the direction to give a strong force, and as a result, the tumble flow will be strengthened by reducing the flow cross section and increasing the flow velocity. For this reason, there is a problem that an angle is generated at the intake port 101, and the intake angle of the intake air is also bent, so that the flow coefficient is reduced, the forward tumble flow is weakened, and the engine performance is reduced. Was.

As shown in FIG. 9 and FIG. 10, the intake port 101 is formed by the throat cutter 105 so that both the inner peripheral surface 6 of the seat ring 5 and the throat portion 101a are formed at one predetermined angle. Is processed at once, so that a non-smooth portion 101b, which is a step, is formed in the throat portion 101a, and an edge portion 101c is generated, which disturbs the intake air flow and causes energy loss. was there.

On the other hand, in the second prior art disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2001-173513, as shown in FIG. 11, the inner peripheral surface 6 of the seat ring 5 It is formed almost linearly along the road and opens toward the combustion chamber 2 so that the tumble ratio is improved, but the edge of the inner peripheral surface 6b on the combustion chamber 2 side is an edge. However, there has been a problem that energy loss occurs due to separation 107 occurring in the intake air flow, and there is a risk that the intake air flow is reduced and the engine performance is reduced. Further, since the opening area of the seat ring 5 is formed almost uniformly in the thickness direction of the seat ring 5, it is difficult to increase the intake air flow rate! There was also a title.

Further, in the third conventional technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-277746, as shown in FIG. Since it is formed so as to be substantially linear with the wall surface 101A toward the combustion chamber 2, the tumble ratio is improved. Also, the inner peripheral surface 6b of the seat ring 5 is formed so as to expand toward the combustion chamber 2! /, So that the intake flow rate can be increased more easily than in the case of the second prior art.

However, since the angle Θ4 formed between the inner peripheral surface 6b of the seat ring 5 and the lower inner wall surface 101B of the intake port 101 is formed substantially at a right angle, the inner peripheral surface 6b of the inner peripheral surface 6b on the combustion chamber 2 side is formed. There was a problem that the edge became an edge, and a decrease in the intake air flow rate due to separation was inevitable.

[0020] As described above, in the design of the intake port, there is a conflicting problem that the flow coefficient decreases when the tumble ratio is increased, and the tumble ratio decreases when the flow coefficient is increased, and various studies have been made so far. However, it was difficult to provide an intake port that can achieve both a high tumble ratio and a high flow coefficient. That is, in the engine with a high tumble ratio, although the combustion is improved, there is a problem that the maximum output depending on the absolute flow rate is reduced.

The present invention has been made in view of the above, and an object of the present invention is to provide a method of manufacturing an intake port of an internal combustion engine that can achieve both a high tumble ratio and a high flow coefficient.

[0022] Another object of the present invention is to provide an intake port of an internal combustion engine that can achieve both a high tumble ratio and a high flow coefficient.

Means for solving the problem

[0023] In order to solve the above-described problems and achieve the object, a method of manufacturing an intake port of an internal combustion engine according to claim 1 of the present invention provides a method of manufacturing a combustion engine, wherein the center line of the intake port is inclined with respect to the center line of the combustion chamber. A method for manufacturing an intake port of an internal combustion engine, wherein an annular seat ring is disposed in a region facing the combustion chamber of the intake port, the inner peripheral surface of the seat ring on the combustion chamber side. Further, a valve seat surface for closing the intake flow by contact of the intake valve is formed so as to be symmetrical with respect to the axis of the intake valve, and to expand toward the combustion chamber. A first step of forming an axial force of the intake valve on an inner peripheral surface of the seat ring on the intake port side so as to be symmetric with respect to an axis inclined at a predetermined angle to the center line side of the intake port. Form the inner peripheral surface on the intake port side, One, the Bal And a second step of forming the inner surface of the seat ring and the inner peripheral surface of the intake port side so as to form an obtuse angle on the outer peripheral side of the combustion chamber of the seat ring. Things.

[0024] Further, in the intake port of the internal combustion engine according to claim 2 of the present invention, the center line of the intake port is inclined with respect to the center line of the combustion chamber, and the intake port is located in a region facing the combustion chamber. An annular seat ring is arranged, and the inner circumferential surface of the seat ring on the combustion chamber side is symmetrical with respect to the axis of the intake valve in order to close the intake flow by contact of the intake valve. And a valve seat surface that expands toward the combustion chamber is formed. An inner peripheral surface of the seat ring on the intake port side is located on a center line side of the intake valve from the axis of the intake valve. An inner peripheral surface of the intake port side is formed symmetrically with respect to an axis inclined at a predetermined angle, and the valve seat surface of the seat ring and the inner peripheral surface of the intake port side correspond to the combustion of the seat ring. Room Peripheral side Nio, connected at an obtuse angle Te is characterized in that the Ru.

[0025] Further, in the intake port of the internal combustion engine according to claim 3 of the present invention, in the invention according to claim 2, the two intake ports are connected to one combustion chamber. Each intake port is characterized by being arranged eccentrically by a predetermined amount so that each center line approaches the center line of the combustion chamber.

The invention's effect

[0026] According to the method for manufacturing an intake port of an internal combustion engine according to the present invention (claim 1), after the first step is completed, another cutting tool is inclined at a predetermined angle to perform cutting. Step 2 can be easily performed, and the inner wall surface of the intake port and the inner peripheral surface of the seat ring can be continuously and smoothly slid.

[0027] Further, according to the intake port of the internal combustion engine according to the present invention (Claim 2), it is possible to enhance the positive tumble flow without narrowing the flow line of the intake flow, and achieve both a high tumble ratio and a high flow rate. can do.

[0028] Further, according to the intake port of the internal combustion engine according to the present invention (claim 3), the center flow velocity between the two intake valves is increased, and can be introduced into the combustion chamber without deceleration. You. Therefore, the forward tumble flow can be further enhanced, and the engine performance can be further improved. It is possible to achieve a riddling.

Brief Description of Drawings

FIG. 1 is a sectional view showing an intake port according to Embodiment 1 of the present invention.

FIG. 2 is a graph showing a relationship between a tumble ratio and a flow coefficient.

FIG. 3 is a cross-sectional view showing a state before machining an intake port.

FIG. 4 is a cross-sectional view showing a process of processing a seat ring by a first throat cutter.

FIG. 5 is a cross-sectional view showing a state before tilting a second throat cutter.

FIG. 6 is a cross-sectional view showing a state in which a second throat cutter is cut and inclined.

FIG. 7 is an external perspective view showing an intake port according to Embodiment 2 of the present invention.

FIG. 8 is a cross-sectional view schematically showing one example of a conventional intake port.

FIG. 9 is a cross-sectional view showing a seat ring and a throat portion before cutting.

FIG. 10 is a cross-sectional view showing a seat ring and a throat portion after cutting.

FIG. 11 is a cross-sectional view showing a conventional intake port.

FIG. 12 is a cross-sectional view showing a conventional intake port.

Explanation of symbols

[0030] 1 intake port

la throat part

lb inner wall

1A Upper inner wall

1B Lower inner wall

2 Combustion chamber

3 Cylinder head

4 Intake valve

5 Seat ring

6, inner surface

6a, 6b, inner peripheral surface (Vanoreb seat surface) 6c, 6d Inner peripheral surface on intake port side

7 cylinder

8 piston

9a The first throat cutlet

9b Second throat cutlet

10 Exhaust port hole

C1, C2, C3 center line

L axis

r radius of curvature

D Typical inner diameter of intake port

T positive tumble flow

0 1, 0 2, Θ 3 Angle

S Eccentricity

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of an intake port of an internal combustion engine and a method of manufacturing the same according to the present invention will be described in detail with reference to the drawings. The present invention is not limited by the embodiments.

Example 1

FIG. 1 is a sectional view showing an intake port of an internal combustion engine according to Embodiment 1 of the present invention. In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

As shown in FIG. 1, the intake port 1 is provided in the cylinder head 3 such that the center line C 1 is inclined with respect to the center line C 2 of the combustion chamber 2. Reference numeral 1A denotes an upper inner wall surface of the intake port 1, and reference numeral 1B denotes a lower inner wall surface of the intake port 1. An annular seat ring 5 on which an intake valve 4 is detachably seated is press-fitted into an end portion of the intake port 1 facing the combustion chamber 2.

[0034] The seat rings 5 have inner peripheral surfaces 6a and 6b as valve seat surfaces for closing the intake air flow by contacting the intake valve 4, and are formed symmetrically with respect to the center line C3 of the intake valve 4. Is The combustion chamber 2 is formed so as to be inclined along the flow path of the intake port 1 and expand toward the combustion chamber 2. That is, as shown in FIG. 6, which will be described later, the throat portion la of the intake port 1 and the inner peripheral surface 6a of the seat 5 are smoothly connected, and the energy loss of the intake air flow is minimized. , Positive tumble flow T is weakened, is configured as! RU

[0035] Also, from the lower inner wall surface 1B of the intake port 1 to the inner peripheral surface 6b of the seat ring 5, the inner wall surface lb, which will be described later, and the intake port side inner peripheral surface 6c are almost smoothly connected. The inner peripheral surface 6b is expanded toward the combustion chamber 2 with a predetermined radius of curvature r so as to reduce separation of the intake flow at the inner peripheral surface 6b and minimize energy loss. .

[0036] The radius of curvature r is preferably set, for example, in the range of DZlO or more and DZ2 or less, where D is the representative inner diameter of the intake port 1. The radius of curvature r of the inner peripheral surface 6b of the seat ring 5 is formed as an approximate curved surface by a plurality of taperings.

As shown in FIG. 6, which will be described later, the intake port side inner peripheral surfaces 6c and 6d formed on the intake port 1 side of the seat ring 5 and the end region of the lower inner wall surface IB on the combustion chamber 2 side. Is formed symmetrically with respect to an axis L inclined at a predetermined angle θ1 from the center line (axis line) C3 of the intake valve 4 to the center line C1 side of the intake port 1 from the center line (axis line) of the intake valve 4. It is cut and formed simultaneously by the throat cutter 9b. An angle 02 formed between the inner peripheral surface 6b and the intake port side inner peripheral surface 6c is formed to be an obtuse angle. As a result, it is possible to significantly suppress a decrease in the intake air flow rate, which is likely to cause separation of the intake air flow. Also, the angle Θ3 between the inner wall surface 1B and the inner wall surface lb is formed at an obtuse angle near 180 °, so that separation of the intake air flow hardly occurs.

Next, a method for manufacturing the intake port 1 will be described with reference to FIGS. Here, FIG. 3 is a cross-sectional view showing a state before processing the intake port, FIG. 4 is a cross-sectional view showing a processing step of the seat ring using the first throat cutter, and FIG. 5 is an inclination of the second throat cutter. FIG. 6 is a cross-sectional view showing a state before cutting, and FIG. 6 is a cross-sectional view showing a state in which the second throat cutter is inclined to perform cutting.

It is assumed that the unprocessed seat ring 5 is press-fitted into a predetermined position of the intake port 1 in advance, as shown in FIG. First, in the first step, as shown in FIGS. 3 and 4, the first throat cutter 9a is advanced by a predetermined amount along the center line C3 of the intake valve 4, and the inner peripheral surface 6 of the seat ring 5 and the intake port 1 throat part la That is, the first throat cutlet According to the outer shape of 9a, cutting is performed so as to expand toward the combustion chamber 2 on the inner peripheral surfaces 6a and 6b.

In the next second step, as shown in FIG. 5, the central axis of the second throat cutter 9 b is made to enter the intake port 1 by a predetermined amount while being aligned with the center line C 3 of the intake valve 4. Then, as shown in FIG. 6, the center axis of the second throat cutter 9b is inclined by a predetermined angle θ1 toward the center line C1 of the suction port 1 with respect to the center line C3 to advance the seat by a predetermined amount. Simultaneously apply the inner peripheral surfaces 6c and 6d of the ring 5 on the intake port side, the throat la and the inner wall surface lb of the intake port 1.

[0041] The throat cutters 9a and 9b have an outer shape with a predetermined curvature so that the inner peripheral surface 6a of the seat ring 5 and the boundary portion of the throat la are smoothly continuous. Thus, the first step is completed, and the second step is performed by inclining the second throat cutter 9b at the predetermined angle θ1 to perform the second step, thereby forming the upper inner wall surface 1A of the intake port 1 and the inner peripheral surface 6a of the seat ring 5. Can be continuously and smoothly added. Also, the inner peripheral surface 6c and the inner wall surface lb on the intake port side can be continuously and smoothly machined. It should be noted that the throat cutters 9a and 9b may have a shape corresponding to a desired processing shape, and are not limited to the shapes in the illustrated example.

Next, the operation of the intake port 1 manufactured as described above will be described with reference to FIG. 1 and FIG. When the intake valve 4 opens, the intake air passes through the intake port 1 and is introduced into the combustion chamber 2 through the seat ring 5 due to the negative pressure generated in the cylinder 7 by the stroke of the piston 8.

At this time, since the throat portion la of the intake port 1 is smoothly connected to the inner peripheral surfaces 6d and 6a of the seat ring 5, the loss of the flow of the positive tumble flow at the throat portion la is reduced, It is guided into the combustion chamber 2 while maintaining a strong flow. Further, the inner peripheral surface 6b of the seat ring 5 forms a predetermined obtuse angle と 2 with the inner peripheral surface 6c on the intake port side, and expands toward the combustion chamber 2. Is suppressed. In addition, since the angle 03 formed between the inner wall surface 1B and the inner wall surface lb is also formed at an obtuse angle close to 180 degrees, the separation of the flow at this portion is suppressed.

Next, the performance of the intake port 1 manufactured as described above will be described with reference to FIG. Here, FIG. 2 is a graph showing the relationship between the tumble ratio and the flow coefficient. As you can see from Figure 2 In the case of the present invention, since the energy loss of the positive tumble component is smaller than in the case of the related art, it is possible to achieve both a high tumble flow and a high flow rate. Further, in the case of the present invention, the rate of decrease in the flow coefficient decreases as the tumble ratio increases, as compared with the case of the related art.

As described above, according to the intake port of the internal combustion engine according to the first embodiment, since the throat portion la of the intake port 1 and the inner peripheral surfaces 6d and 6a of the seat ring 5 are smoothly connected, The loss of the flow of the positive tumble flow at the throat la is reduced, and the flow is guided into the combustion chamber 2 while maintaining a strong flow. Therefore, the positive tumble flow T without narrowing the flow line of the intake flow can be strengthened, and both a high tumble ratio and a high flow can be achieved. In particular, since the inner peripheral surface 6b of the seat ring 5 forms a predetermined obtuse angle と 2 with the inner peripheral surface 6c on the intake port side and expands toward the combustion chamber 2, the flow of the flow in this portion is reduced. Separation can be suppressed, and a decrease in the intake air flow rate can be significantly suppressed.

[0046] Further, by increasing the positive tumble flow T in the combustion chamber 2, the turbulence of the flow in the combustion chamber 2 is increased, and the combustion of the air-fuel mixture is promoted, so that the combustion efficiency can be increased. In addition, the generation of the strong positive tumble flow T makes it possible to promote fuel leaning and high EGR siding, thereby improving fuel efficiency. Furthermore, high-speed performance (output performance) is improved by improving combustion and increasing the amount of air.

Further, in the above manufacturing method, in the second step, the second throat cutter 9b may be cut by inclining at a predetermined angle 傾斜 1, so that the intake port 1 and the intake port 1 can be continuously and efficiently provided. The seat ring 5 can be formed into a desired shape.

[0048] The first embodiment can be applied not only to a bifurcated intake port of a four-valve engine but also to a non-branched intake port of a two-valve engine. It can also be applied to direct injection gasoline engines.

[0049] In the method of manufacturing the intake port 1, it is possible to reverse the order of the first step and the second step to perform processing, and similar effects can be expected.

Example 2

FIG. 7 is an external perspective view showing an intake port of an internal combustion engine according to Embodiment 2 of the present invention. As shown in Fig. 7, the fast intake flow is moved toward the central axis of the combustion chamber 2 to strengthen the positive tumble flow. In this case, the intake ports 1 and 1 configured in the first embodiment are eccentrically arranged so as to approach the center axis direction of the combustion chamber 2.

That is, the center line C 4 of the intake port 101 that is not eccentric, which is illustrated for comparison, is moved closer to the center axis direction of the combustion chamber 2 (formed below the cylinder head 3 in the figure). By eccentrically moving the center line C1 by a predetermined eccentric amount S, the intake ports 1 and 1 are configured. Reference numeral 10 in the drawing is an exhaust port hole.

As described above, according to the intake port of the internal combustion engine according to the second embodiment, the intake ports 1 and 1 configured in the first embodiment are eccentric so as to approach the center axis direction of the combustion chamber 2. Because of the arrangement, the central flow velocity between the intake valves 4 and the intake valves 4 increases, and this can be introduced into the combustion chamber 2 without deceleration. Therefore, the forward tumble flow can be further strengthened, and the engine performance can be further improved. Industrial applicability

As described above, the method of manufacturing an intake port of an internal combustion engine according to the present invention and the intake port of the internal combustion engine manufactured by the method are useful for an intake device of an internal combustion engine. Suitable for intake system of internal combustion engine that can achieve both ratio and high flow coefficient

Claims

The scope of the claims

[1] Manufacture of an intake port for an internal combustion engine in which a center line of an intake port is inclined with respect to a center line of a combustion chamber, and an annular seat ring is arranged in a region of the intake port facing the combustion chamber. The method

On the inner peripheral surface of the seat ring on the combustion chamber side, a valve seat surface for closing an intake flow by contact of an intake valve is formed so as to be symmetric with respect to the axis of the intake valve, and A first step of forming so as to expand toward the combustion chamber, and a predetermined angle on the inner peripheral surface of the seat ring on the intake port side from the axis of the intake valve to the center line side of the intake port. The intake port side inner peripheral surface is formed so as to be symmetrical with respect to the inclined axis, and the valve seat surface and the intake port side inner peripheral surface are obtuse at the outer peripheral side of the combustion chamber of the seat ring. A second step of forming so as to connect

A method for manufacturing an intake port of an internal combustion engine, comprising:

[2] The center line of the intake port is inclined with respect to the center line of the combustion chamber, and an annular seat ring is arranged in a region of the intake port facing the combustion chamber,

An inner peripheral surface of the seat ring on the combustion chamber side is formed symmetrically with respect to an axis of the intake valve so as to close an intake flow by contact of the intake valve, and is directed toward the combustion chamber. A valve seat surface that expands with force is formed,

An inner peripheral surface of the seat ring on the intake port side has an intake port side inner peripheral surface formed symmetrically with respect to an axis inclined at a predetermined angle from the axis of the intake valve to the center line side of the intake port. Formed,

The intake port of an internal combustion engine, wherein the valve seat surface of the seat ring and the inner peripheral surface on the intake port side are connected at an obtuse angle on the outer peripheral side of the combustion chamber of the seat ring.

[3] Two of the intake ports are connected to one of the combustion chambers, and each of the intake ports is eccentric by a predetermined amount so that a center line of each of the intake ports approaches a center line of the combustion chamber. 3. The intake port for an internal combustion engine according to claim 2, wherein the intake port is arranged at a right angle.