JPH06108951A - Intake port structure of stratified charge combustion type internal combustion engine - Google Patents

Abstract

PURPOSE:To maintain a stable lean combustion state even with the mixture with a small quantity of fuel by forming the intake port of an internal combustion engine into such structure as to accelerate the stratification of tumbling flow of intake air in a cylinder. CONSTITUTION:An internal combustion engine is provided with an intake port 46 with two combustion chamber openings respectively opened/closed by two intake valves 58, 58 and constituted in such a way that intake flow from the intake port 46 becomes tumbling flow in a combustion chamber 30.An ignition means for combustion is disposed at the top center part of the combustion chamber 30, and a fuel injection means 12 is provided at the upstream part of the intake port 46. A partition wall 21 is disposed to divide the inside of the intake port 46 into an ignition means side passage 4 and an anti-ignition means side passage 5, and this partition wall 21 is formed almost along the whole area in the intake port 46 positioned upstram of the stems 57 of the intake valves 58.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake port structure for a stratified combustion internal combustion engine, and more particularly to a stratified combustion internal combustion engine constructed so that an intake air flow from the intake port becomes a stratified tumble flow in a combustion chamber. Of the intake port structure.

[0002]

2. Description of the Related Art In recent years, in order to increase the intake passage area of a combustion chamber of an engine without increasing the size of an intake valve, an internal combustion engine provided with two intake ports in one combustion chamber has come to be used. There is. In such an internal combustion engine, the air-fuel mixture flows into the combustion chamber from each of the two intake ports.

Further, as means for improving combustion in an internal combustion engine, a so-called tumble flow F (F) in a cylinder such as a vertical swirling flow shown in FIGS. 12 and 13 in the intake stroke.
It is effective to generate a, Fm). For example, FIGS. 12 and 13 show the structure of one cylinder of a two-intake-port internal combustion engine that generates such tumble flows Fa and Fm. In the drawings, reference numeral 22 is a cylinder block, 24 is a cylinder bore, and 26 is a cylinder bore. Is a piston, 28 is a cylinder head, and 30 is a combustion chamber. The reference numeral 34 designates a pent roof formed on the upper wall of the combustion chamber 30.
Reference numerals 0'and 42 'denote intake passages provided in two for each cylinder, and an intake valve 58 is installed at each intake port 44' of each intake passage 40 ', 42'.

The pent roof 34 includes the intake passages 40 ',
The intake passages 40 ', 42' are provided with slopes so as to guide the intake air flow from 42 'downward along the inner wall surface of the cylinder bore 24 on the extension axes of the intake passages 40', 42 '.
The intake flow from the air flows in the tumble flow direction as indicated by arrows Fa and Fm, respectively, also assisted by the guidance of the pent roof 34.

Further, in order to promote the tumble flow, the shape of the intake port 44 'is important, and in general, as shown in FIG.
2, the intake port 44 'is formed into a straight straight port as shown in FIG. 13, or the intake port 44' is narrowed as shown in FIG. 16 to devise to rectify the flow. . 12 and 16, reference numerals 40F and 42F indicate normal intake ports that are not straight ports.

The cross-sectional shape of the intake port 44 'is generally formed in a circular shape as shown in FIG. 14, but it is formed in an elliptical shape or an oval shape as shown in FIG. It may be formed in. Also, in this example,
As shown in FIG. 13, the injector 12 is provided only in one intake passage 42 ′, and the spark plug 11 is arranged in the vicinity of the intake valve 58 of the intake passage 42 ′ equipped with this injector 12. Therefore, this spark plug 11
A mixture of the fuel injected from the injector 12 and the intake air flows into the combustion chamber 30 through the intake passage 42 'and the intake port 44' in the vicinity of the above, and a tumble flow Fm of this mixture is formed. . Also, the intake passage 40 '
Only the air flows into the combustion chamber 30 from the intake port 44 ′ of the above, and a tumble flow Fa of this air is formed.

As a result, a stratified tumble flow of the tumble flow Fm of the air-fuel mixture and the tumble flow Fa of air is formed in the combustion chamber 30. The tumble flow generated in this way is effective in increasing the flame propagation speed and combustion stability, and experimental data on the heat generation amount Q, in-cylinder pressure P, and heat generation rate dQ are shown in FIG. 17, for example. Therefore, the cycle variation of the heat generation amount Q, the indicated mean effective pressure P, and the heat generation rate dQ is smaller when the tumble flow is generated compared to the standard (a general case where the tumble flow is not particularly generated). It can be seen that the combustion stability is good.

In the figure, reference numeral 47 is an exhaust port communicating with the exhaust passage 60, and 59 is an exhaust valve.

[0009]

However, as described above, in the case of the intake port 44 'having a circular or elliptical cross section, the intake port 4 is used to strengthen the tumble flow.
If 4'is formed into a straight port, the intake port 4
4'becomes a structure that enters the valve seat 62 at an acute angle, and the flow passage cross-sectional area is inevitably small. Naturally, by narrowing the intake port 44 'as shown in FIG. Becomes smaller and the maximum flow rate is reduced. In other words, there is a contradictory relationship that the maximum flow rate (flow rate coefficient) decreases as the strength of the tumble flow (tumble strength) increases. Such a decrease in the maximum flow rate causes a decrease in the full-open performance of the engine, which is not preferable.

Further, in recent years, an internal combustion engine is operated with a mixture of fuel in an amount smaller than the theoretical air-fuel ratio, and two intake ports are provided in order to reduce vibration and reduce fuel consumption. There is also a proposal for supplying an air-fuel mixture, but in this case, since the spark plug is located between the two intake ports, ignitability may deteriorate when operating with a small amount of fuel. Therefore, there is a problem that it is difficult to operate with a small amount of fuel.

The present invention was devised in view of the above-mentioned problems, and is capable of promoting stratification while strengthening the tumble flow of the intake air in the cylinder, so that a mixture of fuel in an amount smaller than the theoretical air-fuel ratio is promoted. However, it is an object of the present invention to provide an intake port structure of a stratified combustion internal combustion engine that can maintain a stable lean combustion state.

[0012]

Therefore, the intake port structure for a stratified combustion internal combustion engine according to the present invention has an intake port having two combustion chamber openings that are opened and closed by two intake valves, respectively. In a stratified combustion internal combustion engine configured such that the intake flow from each of them can be a stratified tumble flow in the combustion chamber, a combustion ignition means is disposed in the central portion of the top of the combustion chamber, and an upstream portion of the intake port is provided. A fuel injection means is provided in the intake port, and an anti-ignition means for forming an air flow in which the fuel from the fuel injection means is mixed with an ignition means side passage forming a mixed air flow mixed with the fuel from the fuel injection means. A partition wall that divides the side passage into two along the flow direction is provided, and the partition wall extends from the upper surface to the lower surface in the port upstream of the stem of the intake valve in the intake port. Pot is characterized in that it is formed over the entire region.

[0013]

In the structure of the intake port for the stratified combustion internal combustion engine of the present invention described above, the intake flow flowing into the combustion chamber through the combustion chamber opening of the intake port forms a tumble flow smoothly. At the same time, the inside of the intake port is divided into the ignition means side and the anti-ignition means side by a partition wall formed over almost the entire area from the upper surface to the lower surface in the port upstream of the stem of the intake valve in the intake port. Therefore, the intake flow flowing into the intake port is bisected by the partition wall into the ignition means side and the anti-ignition means side, and the fuel injected by the fuel injection means is divided into the intake flow divided to the ignition means side. Mix.

As a result, a stratified tumble flow of the air-fuel mixture containing fuel is formed on the ignition means side in the combustion chamber, and the stratified tumble flow supplies fuel to the ignition means.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the intake port structure for a layered combustion internal combustion engine of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing the structure, and FIG. 2 is a schematic top view showing the structure. 1. It is a figure and the A arrow view in FIG. 1, FIG. 3 is a typical partial sectional view which shows the structure, CC sectional drawing in FIG. 2, FIG. 4 is a typical partial sectional view which shows the structure. FIG. 5 is a cross-sectional view taken along line BB in FIG. 3, FIG. 5 is a schematic diagram showing its configuration, and FIGS. 6 (a) to 6 (c) are all schematic diagrams showing its configuration. 7A to 7D are schematic diagrams showing variations of the fuel injection method, and FIGS. 8 to 11 are graphs for explaining the action and effect.

As shown in FIG. 1, in each cylinder of this internal combustion engine, a combustion chamber 30 is formed by being surrounded by a cylinder bore 24 formed in a cylinder block 22, a piston 26 and a cylinder head 28. Each cylinder of this internal combustion engine is configured as a four-valve internal combustion engine having two intake valves and two exhaust valves, and an intake port 46 is introduced into the combustion chamber 30. The intake port 46 is a Siamese port divided into two intake port parts 46A and 46B by a port partition wall (intake port branch part) 46C on the way, and the combustion chambers of the intake ports 46A and 46B are separated. An intake valve 58 is installed in each opening. Further, the exhaust port 47 is also a siamese port, and two exhaust ports 47 are provided in the combustion chamber 30.
The A and 47B parts are also guided, and exhaust valves (not shown) are installed respectively.

As shown in FIGS. 1, 2 and 5,
Each intake port portion (hereinafter, this intake port portion is also simply referred to as an intake port) 46A, 46B is connected to an intake passage (intake manifold) not shown. Also, in the figure, 1A and 1B are intake ports 46A,
The axis center line of 46B (upper and lower ends and the center lines of the left and right ends) is shown. Further, the exhaust ports 47A and 47B join together on the downstream side, and are also communicatively connected to a common exhaust passage (not shown).

An injector 12 as a fuel injection means, which will be described later, is attached to the intake ports 46A and 46B in the vicinity of the branch portion 46C, and the injector 12 is attached to the injector 12.
As a result, the fuel is injected into the intake ports 46A and 46B. In this embodiment, the axial center lines 1A and 1B of the intake ports 46A and 46B are the same as those shown in FIGS.
And, as shown in FIG. 6 (a), there are two straight lines parallel to each other. Therefore, on the downstream side of the vicinity of the branch portion 46C of the intake ports 46A, 46B, each intake port 46A,
46B are formed in parallel with each other, and the intake air from the intake ports 46A and 46B flows into the combustion chamber 30 in parallel with each other. That is, the intake ports 46A and 46B are formed as straight straight ports that are substantially parallel to each other.

Further, as the intake ports 46A and 46B, those shown in FIGS. 6B and 6C are also conceivable. FIG. 6B is an intake port 46 in which the intake ports 46A and 46B slightly expand from the branch portion 46C of the intake ports 46A and 46B toward the intake valve 58. When the spread of the intake ports 46A, 46B is very small, the intake ports 46A, 46B are substantially parallel to each other, and the intake air flows into the combustion chamber 30 along the intake ports 46A, 46B in a substantially parallel state. To do.

Further, FIG. 6C shows each intake port 46.
A and 46B are parallel to each other, but two intake valves 5
For the straight line L connecting the centers of 8 and 58, the intake port 46
A and 46B are connected to the combustion chamber 30 without being orthogonal to each other. In addition to these, the intake ports are intake ports 46A, 46
For example, curved intake ports in which the intake ports 46A and 46B are bent may be used as long as the intake ports 46A and 46B flow into the combustion chamber 30 in a state of being substantially parallel to each other along B.

Further, the sectional shape of this straight port is, as shown in FIG. 4, the tumble flow side half of the intake ports 46A, 46B (that is, the upper side of the intake ports 46A, 46B through which the main component flow forming the tumble flow flows). Half) 46A
-1, 46B-1 are wider than the other half (that is, the lower half of the intake ports 46A, 46B through which the component flow that blocks the tumble flow) 46A-2, 46B-2 and The intake flow center F1 of the ports 46A and 46B is on the tumble flow side (that is, the upper half 4 of the intake ports 46A and 46B).
6A-1, 46B-1). As a result, the intake air flow from the intake ports 46A and 46B is transferred to the combustion chamber 3
A tumble flow is easily formed within 0. Further, in this first embodiment, the intake ports 46A, 46B
Are formed so as to have a substantially inverted triangular cross section as shown in FIG. The reference numerals 21 and 21 shown in FIG.
The partition wall divides the intake ports 46A and 46B into two parts, which will be described later in detail.

Further, as shown in FIG.
A recess 35 is formed on the top surface of the so as to secure a space between the cylinder head 28 and the piston 26 when the piston 26 reaches the top dead center. And piston 2
The top surface of 6 is also provided with a raised portion 39, which is raised more than the recess 35, close to the recess 35. This ridge 3
9 is a slope 3 formed between the raised portion 39 and the recess 35.
7, it connects gently to the recess 35.

Further, the recess 35 is formed below an exhaust valve (not shown), and the raised portion 39 has the intake valves 58, 5.
It is formed below 8. Therefore, as shown in FIG. 1, the tumble flow side half portion 4 of the intake ports 46A, 46B.
6A-1, 46B-1 intake air flows Fa, Fm
Is designed to reach the ridge 39 from the recess 35 through the slope 37, thereby promoting the formation of the tumble flow.

Further, as shown in FIGS. 1 and 5, a spark plug 11 as an ignition means is arranged in the central portion of the upper part of the upper portion of the combustion chamber 30, and the intake ports 46A, 4 are provided.
It is located on the reference plane 3 between 6B. The reference plane 3 is a virtual plane located at the center of both intake ports 46A and 46B. By the way, as shown in FIGS. 1 to 5, in the intake ports 46A, 46B, a partition wall 2 is formed so as to divide the intake ports 46A, 46B into two parts in the left-right direction.
1 is provided, and each of the intake ports 4 is provided by the partition wall 21.
6A and 46B are divided into a passage 4 on the reference surface 3 side (spark plug side) of the intake air flow and a passage 5 on the outside (anti spark plug side) of the reference surface 3 along the intake air flow direction. ing. That is, the intake ports 46A and 46B are separated into the ignition means side passage (center side passage) 4 and the anti-ignition means side passage (side passage) 5.

As shown in FIG. 2, the partition wall 21 extends along the axial center lines 1A and 1B of the intake ports 46A and 46B.
It is formed substantially vertically and extends from the vicinity of the position where the injector 12 is disposed to the downstream side. Further, since the intake ports 46A and 46B are substantially parallel to each other, the partition walls 21 and 21 are also arranged substantially parallel to each other. Then, as shown in FIG.
It is formed from the upper wall surface 8 of A and 46B to the lower wall surface 7, and on the downstream side of the intake ports 46A and 46B, along the axial center line 2 of the intake valve 58 to the vicinity of the umbrella portion 56 of the intake valve 58. It has been extended. However, the partition wall 21 is formed so as to ensure a proper clearance with the umbrella portion 56 and the stem portion 57 of the intake valve 58 so as not to come into contact therewith, so that the operation of the intake valve 58 is not affected at all. It has become.

Further, the partition wall 21 is provided with an intake port 46.
The intake ports A and 46B are extended from the upstream ends of the intake ports 46A and 46B so as to completely separate the intake flow into the central passage 4 and the lateral passages 5. Therefore, the intake port 46
In A and 46B, the intake air flow branches into the central side passage 4 and the side passage 5 and flows into the combustion chamber 30 while being separated from each other while being rectified by the partition wall 21. . As a result, due to the partition wall 21, when the intake air flows into the combustion chamber 30 as shown in FIG. 5, the air-fuel mixture layer Fm and the air-only layers Fa and Fa are mixed. And three layers (a total of three flows of the central side passage 4 and the side passages 5 on both sides thereof), that is, in a layered state, are formed into a tumble flow. Therefore, the present internal combustion engine is configured as a layered combustion internal combustion engine.

In the intake ports 46A and 46B,
Since the cross-sectional areas of the intake ports 46A and 46B are reduced by the cross-sectional integration of the partition wall 21, it is conceivable that the flow coefficient of the intake ports 46A and 46B is reduced and the engine full-open performance is reduced. Therefore, the intake ports 46A, 46B
As shown by the hatched portion 13 in FIGS. 2 and 4, the upper half portions 46A-1 and 46B-1 of the cross section of the substantially inverted triangle are made sufficiently large to cancel this cross-section integration, and the engine is fully opened. It is designed to secure the flow coefficient at the time.

Further, as described above, it is desirable that the partition wall 21 has its sectional area as small as possible in order to secure the flow coefficient, and therefore, the partition wall 21 is formed so as to be as thin as possible. Therefore, in this embodiment, as shown in FIG. 2, the partition wall 21 has a thickness equal to or slightly smaller than the diameter of the valve stem 57. As a result, the intake resistance of the valve stem 57 can be reduced while ensuring the intake flow rate of the intake port 46, so that the intake air smoothly flows into the combustion chamber 30.

In FIG. 5, a modified example of the partition wall 21 is shown. In this way, the partition wall 21 is formed as thin as possible on the upstream side of the valve stem 57, and gradually approaches the valve stem 57. The valve stem 57 may be formed to have a thickness substantially equal to the diameter of the valve stem 57.
Even in this case, the flow of the intake air flow is not limited to the valve stem 57.
Therefore, it can smoothly flow into the combustion chamber 30 without being disturbed.

Further, in the modification shown in FIG. 5, the partition wall 2
Although the upstream end of 1 is formed in the middle of the intake port 46, this partition wall 21 divides the air-fuel mixture into air into the center side passage 4 and the side passage 5, and the fuel injected from the injector 12 is divided. It suffices if diffusion to the side passages 5 is prevented, and the partition walls 2
As shown in FIG. 5, the upstream end of 1 does not necessarily have to extend to the upstream end of the intake port 46.

By the way, as shown in FIGS. 1 and 5, the injector 12 as the above-mentioned fuel injection means is disposed above the two intake ports 46A, 46B near the branch portion 46C. Further, the injector 12 is a reference plane (center plane) of the intake flow between the two intake ports 46A and 46B.
The intake ports 46A and 46B are arranged along
The fuel is to be injected downstream of and below. Reference numeral 6 in FIGS. 2, 3 and 5 is an injector injection axis line, which indicates the injection direction of the injector 12. That is, the injector 12 is configured to inject fuel from the upper side between the intake ports 46A and 46B toward the lower side on the downstream side.

The fuel injected downward in the intake ports 46A, 46B becomes the intake ports 46A, 46B.
The partition walls 21 and 21 provided in the intake ports 46A and 46B allow the intake air to be taken into the combustion chamber 30 through the central passages 4 in the intake ports 46A and 46B. , Only air flows.

Further, as an injection variation of the injector 12, the branch portion 4 of both intake ports 46A and 46B is used.
The types shown in FIGS. 7A to 7D can be considered according to the shape of 6C. (A) is for injecting fuel toward the branch portion 46C of the Siamese type intake ports 46A and 46B. After positively colliding the fuel with the branch portion 46C,
The diffused fuel is made to flow into the central passage 4 in the intake ports 46A and 46B. This intake port 46
The branch portion 46C of A and 46B has a surface that is substantially orthogonal to the injection direction of the injector 12, and diffuses fuel that has collided with this surface.

Next, (b) is of a type that uses an injector 12 having two fuel injection holes. The two fuel flows injected from each fuel injection hole are respectively the intake ports 46A and 46B. It directly flows into the central passage 4 of the. In this case, the intake port 46A,
The branch portion 46C of 46B is formed in a curved surface shape to reduce the suction resistance of the suction flow.

Further, as shown in (c), the injector 12 having a single fuel injection hole is used to inject the fuel directly into the central passage 4 so that the fuel does not adhere to the partition walls 21 and 21. It is also possible to think of the type. In this case, the branch portions 46C of the intake ports 46A and 46B are formed in an acute angle so that the fuel is smoothly taken in with the intake air.

Contrary to (c) described above, (d) is a type in which fuel is positively injected toward the wide angle up to the partition walls 21 and 21. In this case, the branch portions 46C of the intake ports 46A and 46B are rounded in a curved shape in the same manner as (b) above in order to reduce resistance. Then, in this embodiment, any of the injection variations described above is used.

The above-mentioned (a) to (d) show injection variations of the injector 12, and the disposition position of the injector 12 and the injection axis 6 are the same. Since the intake port structure of the stratified combustion internal combustion engine as one embodiment of the present invention is configured as described above, the intake air is mixed with the fuel injected by the injector 12, and each intake port 46A, Combustion chamber 30 from 46B
After flowing in, being compressed and expanded (explosion) in the combustion chamber 30, it is discharged from each exhaust port 47A, 47B to an exhaust passage (not shown).

In each of the intake ports 46A and 46B, the intake flow component in the tumble flow side half portions 46A-1 and 46B-1 is significantly larger than the intake flow components in the other half portions 46A-2 and 46B-2. It becomes a large amount. Then, the tumble flow side half portions 46A-1, 46 of the intake ports 46A, 46B.
The intake flow component that enters the combustion chamber 30 from B-1 is a flow component that forms a tumble flow, and the intake port 46A,
Combustion chamber 30 from the other half 46A-2, 46B-2 of 46B
Since the intake flow component that enters inside is a component that blocks the tumble flow, the strength of the tumble flow is increased by the above-mentioned flow rate imbalance. In particular, the intake ports 46A, 4
Since the flow passage cross-sectional area of the entire 6B is reduced, the tumble flow can be strengthened while keeping the flow rate (flow velocity) of the intake flow in the entire intake port constant.

At this time, at the time of intake, each intake port 4
6A and 46B, the partition wall 21 divides the intake air flow into two parts, the inner part and the outer part. Since the injector 12 injects the fuel toward the inner central passage 4 partitioned by the partition wall 21 of each intake port 46A, 46B, the fuel is the central passage partitioned by the partition wall 21 of the intake ports 46A, 46B. 4 and the fuel and air are mixed in this passage 4. On the other hand, only air is sent to the outer side passage 5, and as shown in FIG. 1, a fuel-rich mixture layer Fm is formed in the vicinity of the spark plug 11 in the center of the combustion chamber 30, Air layers Fa are formed on both sides.

In particular, since the intake ports 46A, 46B and the partition wall 21 provided therein are arranged substantially parallel to each other, as shown in FIG. 5, the intake ports 46A, 46B are provided.
Even in the combustion chamber 30, the layer Fm of the air-fuel mixture that has flowed into the combustion chamber 30 from the center side passage 4 and the layer Fa of the air that has flowed into the combustion chamber 30 from the outer side passage 5 that is partitioned by the partition wall 21 It is layered while maintaining the separated state.

As a result, the air-fuel mixture containing less fuel is sent to the combustion chamber 30 as a whole, but a sufficient amount of fuel is sent to the vicinity of the spark plug 11 for ignition. In this way, the mixed air-fuel mixture flows near the spark plug 11, so that the engine can be operated with a smaller amount of fuel air-fuel mixture than the theoretical air-fuel ratio without deteriorating the ignitability. is there.

Further, by promoting the stratification of the intake flow in this manner, the formation of the tumble flow in the combustion chamber 30 is also strengthened. That is, the intake air flow is directed to each intake port 46A, 46B.
The center side passage 4 and the side passage 5 are branched, and the branched intake flow is introduced into the combustion chamber 30 while maintaining the parallel state, whereby the intake flow is rectified and a tumble flow is easily formed. It will be.

By the way, it is considered that the partition wall 21 of the intake ports 46A and 46B is also provided on the downstream side of the valve stem 57 so that the intake flow is further completely separated into the air-fuel mixture and the air and flows into the combustion chamber 30. However, it is difficult to provide a partition wall in the narrow space on the downstream side of the valve stem 57, and the manufacturing cost and the number of processing steps increase. In this structure, since the partition wall 21 is provided only on the upstream side of the valve stem 57, the processing of the partition wall 21 in the intake ports 46A and 46B is relatively easy, which can reduce the manufacturing cost. Even if the valve stem 57 of the partition wall 21 is provided only on the upstream side in this way, a significant difference occurs as compared with the case where the partition wall 21 is provided on the downstream side of the valve stem 57 as described above. Without
The intake flow that flows into the combustion chamber 30 can be sufficiently stratified.

Further, as described above, the intake port 46
By providing the partition wall 21 in A and 46B, the intake flow is rectified and the tumble flow can be strengthened. By providing the intake ports 46A and 46B with the partition walls 21 to promote stratification of the air-fuel mixture, the engine can be operated with a leaner air-fuel mixture as shown in the graph of FIG. Here, the horizontal axis of the graph in FIG. 8 indicates the air-fuel ratio (A /
F), and the vertical axis represents the NOx emission amount and the Pi (average indicated effective pressure) fluctuation rate. Lines a and c show the characteristics of the engine in which the partition wall 21 is provided in the intake port, and lines b and d.
Shows the characteristics of an engine having a normal tumble flow intake port without the partition wall 21. Also, line a, line b
Shows the NOx emission, and lines c and d show the Pi fluctuation rate.

First, the lines a and b show the relationship between the A / F and the NOx emission amount. As shown in this figure, in the engine provided with the partition wall 21 (see the line a). The NOx emission amount peaks on the lean (thin) side of the A / F value compared to the engine using the normal tumble flow (see line b). Further, the peak value of the NOx emission amount itself can be reduced. That is, since the stratification of the tumble flow in the combustion chamber 30 is promoted, the A / F at which the NOx emission amount reaches the peak value moves to the lean side as compared with the conventional engine.

Lines c and d show the relationship between A / F and Pi fluctuation rate. Here, the Pi fluctuation rate serves as a guide for determining the combustion stability of the engine. If the Pi fluctuation rate is too high, the combustion of the engine is not stable, and an uncomfortable operating state accompanied by torque fluctuations occurs. . The reference line e in the figure is generally the Pi fluctuation rate of the combustion stability limit at which the engine can be operated without any discomfort.

As shown in this figure, in the engine provided with the partition wall 21 (see the line c), the normal tumble flow is used for the limit value of the Pi fluctuation rate at which the stable combustion state in the cylinder is obtained. A / on the leaner side than the engine (see line d)
The engine can be operated at F, and the NOx emission amount at this time can be significantly reduced. That is, it is shown that a stable combustion state can be obtained even with a leaner A / F, and the A / F at the combustion limit can be improved.

Therefore, with this structure, it is possible to realize an internal combustion engine that has extremely low fuel consumption and emits almost no NOx. Further, as shown in FIGS. 9 and 10, by sufficiently increasing the upper half portions 46A-1 and 46B-1 of the substantially inverted triangular cross section of the intake ports 46A and 46B, the flow coefficient at the time of fully opening the engine is secured. can do.

That is, FIG. 9 shows the relationship between the port cross-sectional area and the average tumble ratio and average flow coefficient. Here, the line a shows the relationship between the port cross-sectional area and the average tumble ratio, and the line b shows the relationship between the port cross-sectional area and the average flow coefficient. Further, in FIG. 9, the mark □ shows the average flow coefficient of the engine provided with the intake port of a normal tumble flow, and the mark ■ shows the upper half portions 46A-1, 46B- of the cross section of the intake ports 46A, 46B. 1 is an average flow coefficient of an engine having an intake port of which 1 is sufficiently large.

Further, ◯ indicates the average tumble ratio of the engine equipped with the intake port of the normal tumble flow,
● indicates the upper half 46A of the intake port 46A, 46B cross section
It shows the average tumble ratio of an engine having an intake port in which -1,46B-1 is sufficiently large. In the intake ports 46A and 46B of the present invention, the upper half portion 46A is
Since -1, 46B-1 is made sufficiently large to secure the port cross-sectional area, as shown in the figure, the average tumble ratio,
Both the average flow coefficient can be improved.

As a result, the relationship between the tumble ratio and the flow coefficient becomes as shown in FIG. Also, in FIG.
In the figure, the triangle mark indicates an engine using a conventional tumble flow, the star mark indicates an engine in which a partition wall 21 is provided but the partition wall 21 reduces the cross-sectional area in the intake ports 46A and 46B, and the star mark indicates this structure. Intake port 46A, 4
The upper half portions 46A-1 and 46B-1 of the cross section of 6B are made sufficiently large.

That is, as shown in FIG. 10, if the partition wall 21 is provided only in the intake ports 46A and 46B, the flow coefficient will decrease even if the stratification of the intake flow is promoted, and the full-open performance may be deteriorated. To be Here, as shown by the asterisk, the upper half portion 46A of the cross section of the intake ports 46A, 46B.
By making -1,46B-1 sufficiently large, the tumble ratio and the flow coefficient can be improved. In this way, the intake port 46 by providing the partition wall 21
The reduction in the cross-sectional area of A and 46B can be compensated for, and the full open performance of the engine can be secured.

FIG. 11 shows the rotational speed, torque and output of the engine. In the figure, lines a and c are graphs showing the characteristics of the engine having this structure, and lines b and d.
[Fig. 4] is a graph showing characteristics of an engine having a conventional intake port structure. First, lines a and b show the relationship between the engine speed and the torque, but there is almost no difference between these two curves, and the engine with this structure operates with a leaner mixture than before. However, it shows that the torque equivalent to that of the conventional engine is realized.

The lines c and d show the relationship between the engine speed and the output. These lines c and d
Similar to the above-mentioned torque characteristics, there is almost no difference in the above, and it is shown that the output can be obtained with the conventional engine even if the air-fuel mixture is operated leaner than the conventional one. Therefore, as shown in FIG. 11, the engine having this structure is configured to increase the tumble ratio and the flow coefficient of the intake ports 46A and 46B so that the partition walls 21 and 21 are provided in the intake ports 46A and 46B. It is possible to realize an internal combustion engine with torque and output characteristics equivalent to those of

Thus, the partition walls 21 and 21 are provided in the intake ports 46A and 46B, and the intake ports 46A and 4B are
Upper half half 46A-1, 46B of the cross section of the substantially inverted triangle 6B
By making -1 sufficiently large, it is possible to maintain a stable combustion state with a leaner air-fuel mixture than the conventional internal combustion engine without lowering both torque and output compared with the conventional internal combustion engine, and reduce NOx. be able to. At the same time, fuel efficiency can be improved.

In the present invention, the intake ports 46A, 46
The present invention can also be applied to a three-valve internal combustion engine having two B and one exhaust port 47 in the same manner as described above.

[0057]

As described in detail above, according to the intake port structure for a stratified combustion internal combustion engine of the present invention, the intake port has two combustion chamber openings which are opened and closed by two intake valves, respectively. In an internal combustion engine configured such that the intake flow from the intake port becomes a tumble flow in the combustion chamber, a combustion ignition means is arranged at the central portion of the top of the combustion chamber, and at the upstream portion of the intake port. Fuel injection means is provided, and inside the intake port,
A partition wall that divides the fuel injection means into two parts along the flow direction is provided in an ignition means side passage that forms a mixed air flow in which fuel is mixed and an anti-ignition means side passage that forms an unmixed air flow. , The partition wall is formed over almost the entire area from the upper surface to the lower surface in the port upstream of the stem of the intake valve in the intake port, while strengthening the tumble flow while inhaling air from each intake port. The intake air flow can be stratified into an air layer and an air-fuel mixture layer. Therefore, a stable combustion state can be obtained even with a lean mixture, and an internal combustion engine with extremely low fuel consumption can be realized. Further, there is an advantage that the NOx emission amount can be reduced.

The above effect can be obtained by providing the partition wall in the intake port only on the upstream side of the stem of the intake valve, and the partition wall on the upstream side can be easily processed. It is possible to minimize the increase in manufacturing cost and the number of processing steps.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an intake port structure of a stratified combustion internal combustion engine as an embodiment of the present invention.

FIG. 2 is a schematic top view showing a configuration of an intake port structure of a layered combustion internal combustion engine as one embodiment of the present invention, and FIG.
FIG.

3 is a schematic partial cross-sectional view showing the structure of the intake port structure of the layered combustion internal combustion engine as one embodiment of the present invention, which is a cross-sectional view taken along line CC of FIG.

FIG. 4 is a schematic partial cross-sectional view showing the configuration of the intake port structure of the layered combustion internal combustion engine as one embodiment of the present invention, which is a cross-sectional view taken along the line BB in FIG.

FIG. 5 is a schematic diagram showing a configuration of an intake port structure of a layered combustion internal combustion engine as one embodiment of the present invention.

FIG. 6 is a schematic diagram showing a configuration of an intake port structure of a stratified combustion internal combustion engine as one embodiment of the present invention, and is a schematic diagram showing an arrangement state of intake ports.

FIG. 7 is a schematic diagram showing a variation of fuel injection method in the intake port structure of the layered combustion internal combustion engine as one embodiment of the present invention.

FIG. 8 is a graph showing an effect of an intake port structure of a stratified combustion internal combustion engine as one embodiment of the present invention.

FIG. 9 is a graph showing the effect of the intake port structure of the layered combustion internal combustion engine as one embodiment of the present invention.

FIG. 10 is a graph showing the effect of the intake port structure of the layered combustion internal combustion engine as one embodiment of the present invention.

FIG. 11 is a graph showing the effect of the intake port structure of the layered combustion internal combustion engine as one embodiment of the present invention.

FIG. 12 is a schematic vertical cross-sectional view showing an intake port structure of a conventional layered-combustion internal combustion engine together with the periphery of a combustion chamber.

FIG. 13 is a schematic perspective view showing an intake port structure of a conventional layered-combustion internal combustion engine together with the periphery of a combustion chamber.

FIG. 14 is a schematic cross-sectional view of a plane orthogonal to the flow direction of intake air in a conventional intake port structure for a stratified combustion internal combustion engine (FIG. 12).
6 is a sectional view taken along line D-D of FIG.

FIG. 15 is a cross-sectional view showing another example of a schematic cross section of a surface of a conventional intake port structure for a layered-combustion internal combustion engine, which is orthogonal to the flow direction of intake air (a view corresponding to a cross section taken along the line DD in FIG. 12). ).

FIG. 16 is a schematic vertical sectional view showing another example of an intake port structure of a conventional stratified combustion internal combustion engine.

FIG. 17 is a graph showing the effect of a tumble flow in a conventional stratified combustion internal combustion engine.

[Explanation of symbols]

 1A, 1B Intake port axial line 2 Intake valve axial line 3 Intake port reference plane 4 Ignition means side passage or central side passage 5 Anti-ignition means side passage or side passage 6 Injector injection axis 7 Intake port lower side wall surface 8 Intake Port upper wall surface 11 Spark plug as ignition means 12 Injector as fuel injection means 13 Intake port oblique line part 21 Partition wall 22 Cylinder block 24 Cylinder bore 25 Cylinder 26 Piston 28 Cylinder head 30 Combustion chamber 34 Pentroof 35 Recess 37 Slope 39 Raised part 40 ', 42' Intake passage 46,44 ', 40F, 42F Intake port 46A, 46B Intake port part 46A-1,46B-1 Upper half part of intake port 46A-2,46B-2 Lower half part of intake port 46C Port partition or port branch 47, 47A, 47 Nagarekokoro L straight exhaust port 56 valve head portion 57 the valve stem 58 intake valve 59 exhaust valve 60 exhaust passage Fa tumble flow in the tumble flow F1 intake port Fm air mixture

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuki Tamura 5-3-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Michihiro Hata 5-33-8, Shiba, Minato-ku, Tokyo Mitsubishi Automotive Industry Co., Ltd.

Claims (1)

[Claims] 1. An intake port having two combustion chamber openings, each of which is opened and closed by two intake valves,
In a stratified combustion internal combustion engine configured such that an intake air flow from the intake port can be a stratified tumble flow in the combustion chamber, a combustion ignition means is disposed at a central portion of the top of the combustion chamber, and the intake port is A fuel injection means is provided in an upstream portion of the fuel injection means, and an air flow not mixed with the ignition means side passage that forms a mixed air flow mixed with the fuel from the fuel injection means is formed in the intake port. A partition wall that divides the flow path along the flow direction is provided in the anti-ignition means side passage, and the partition wall is formed over the entire area from the upper surface to the lower surface in the port upstream of the stem of the intake valve in the intake port. Intake port structure for a stratified combustion internal combustion engine, characterized in that