JP3262380B2 - Intake port structure of stratified combustion internal combustion engine - Google Patents

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 in which an intake flow from an intake port becomes a tumble flow stratified in a combustion chamber. Related to 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 been used. I have. In such an internal combustion engine, the air-fuel mixture flows into the combustion chamber from each of the two intake ports.

[0003] As means for improving the combustion of the internal combustion engine, in the intake stroke, for example, a vertical swirling flow in a cylinder as shown in FIGS.
a, Fm) is effective. For example, FIGS. 12 and 13 show the structure of one cylinder of a two-intake-port internal combustion engine that generates the tumble flows Fa and Fm. In the drawings, reference numeral 22 denotes a cylinder block, reference numeral 24 denotes a cylinder bore, and reference numeral 26 denotes a cylinder bore. Is a piston, 28 is a cylinder head, and 30 is a combustion chamber. Reference numeral 34 denotes a pent roof formed on the upper wall portion of the combustion chamber 30.
Reference numerals 0 'and 42' denote two intake passages provided for each cylinder. Intake ports 44 'of the intake passages 40' and 42 'are provided with intake valves 58, respectively.

[0004] The pent roof 34 has a plurality of intake passages 40 ',
The intake passages 40 ', 42' are provided with slopes so that the intake air flow from the intake passages 40 ', 42' can be guided downward along the inner wall surface of the cylinder bore 24 on the extension axis of each intake passage 40 ', 42'.
Is also assisted by the guidance of the pent roof 34 and proceeds in the tumble flow directions as indicated by arrows Fa and Fm, respectively.

Further, in order to promote the tumble flow, the shape of the intake port 44 'is important.
2, the intake port 44 'is formed as a straight straight port as shown in FIG. 13, or the intake port 44' is throttled as shown in FIG. 16 to rectify the flow. . In FIGS. 12 and 16, reference numerals 40F and 42F indicate normal intake ports other than straight ports.

The cross section of the intake port 44 'is generally formed in a circular shape as shown in FIG. 14, but is formed in an elliptical shape or an oblong shape as shown in FIG. May be formed. Also, in this example,
As shown in FIG. 13, the injector 12 is provided only in one intake passage 42 ′, and the ignition plug 11 is disposed near the intake valve 58 in the intake passage 42 ′ equipped with the 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 ′, and a tumble flow Fm of the mixture is formed. . Also, the intake passage 40 '
From the intake port 44 ', only air flows into the combustion chamber 30 to form a tumble flow Fa of this air.

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

In FIG. 1, reference numeral 47 denotes an exhaust port communicating with the exhaust passage 60, and reference numeral 59 denotes 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 increase the tumble flow.
When the straight port 4 ′ is formed, the intake port 4
4 'enters the valve seat 62 at an acute angle, so that the cross-sectional area of the flow passage is inevitably reduced. As shown in FIG. And the maximum flow rate decreases. That is, when the strength of the tumble flow (tumble strength) is increased, the maximum flow rate (flow rate coefficient) is reduced. Such a decrease in the maximum flow rate undesirably causes a decrease in the full opening performance of the engine.

In recent years, an internal combustion engine is operated with a fuel mixture having a smaller amount than the stoichiometric air-fuel ratio, and two intake ports are provided to reduce vibration and reduce fuel consumption. There is also a proposal for supplying an air-fuel mixture, but in this case, since the ignition plug is located between the two intake ports, if the operation is performed with a small amount of fuel, the ignitability may be deteriorated. Therefore, there is a problem that it is difficult to operate with a smaller amount of fuel.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to promote stratification while enhancing the tumble flow of intake air in a cylinder, and to improve the mixture of fuel in an amount smaller than the stoichiometric air-fuel ratio. However, it is an object of the present invention to provide an intake port structure of a stratified combustion internal combustion engine capable of maintaining a stable lean combustion state.

[0012]

Therefore, an intake port structure of a stratified combustion internal combustion engine according to the present invention comprises an intake port having two combustion chamber openings opened and closed by two intake valves, respectively. In a stratified combustion internal combustion engine configured such that the intake air flows from the combustion chambers can be each formed into a laminar tumble flow in the combustion chamber, a combustion ignition means is disposed at a 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 ignition means side passage for forming a mixed air flow in which the fuel from the fuel injection means is mixed and an anti-ignition means for forming an air flow in which the fuel is not mixed in the intake port. A partition that is bisected along the flow direction with the side passage, and the partition extends from an upper surface to a lower surface in the port upstream of the stem of the intake valve in the intake port. URN Rutotomo is formed over the entire
The upper surface side portion of the downstream end of the partition wall is located on the upstream side of the stem.
And the lower surface side is located near the valve seat .

[0013]

In the above-described intake port structure of the stratified combustion internal combustion engine of the present invention, the intake air flowing into the combustion chamber from the opening of the combustion chamber of the intake port smoothly forms a tumble flow. At the same time, the inside of the intake port is partitioned into an ignition means side and a non-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 air flowing into the intake port is divided into the ignition means side and the non-ignition means side by the partition wall, and the fuel injected by the fuel injection means is supplied to the intake air stream divided to the ignition means side. Mix.

As a result, a stratified tumble flow of the air-fuel mixture containing the fuel is formed on the ignition means side in the combustion chamber, and the fuel is supplied to the ignition means by the stratified tumble flow. Ma
In addition, the upper surface side of the downstream end of the bulkhead is the stem of the intake valve.
Along the upstream side and the lower side is located near the valve seat
So that the above-mentioned laminar tumble flow is reliably formed
Is done.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view showing an embodiment of an intake port structure of a stratified combustion internal combustion engine according to the present invention. FIG. 2 is a schematic top view showing the configuration. FIG. 1 is a view taken in the direction of the arrow A in FIG. 1, FIG. 3 is a schematic partial cross-sectional view showing the configuration, FIG. 2 is a CC cross-sectional view in FIG. 2, and FIG. 3 is a cross-sectional view taken along the line BB in FIG. 3, FIG. 5 is a schematic diagram showing the configuration, and FIGS. 6 (a) to 6 (c) are schematic diagrams showing the configuration. 7 (a) to 7 (d) are schematic diagrams showing variations in the manner of fuel injection, and FIGS. 8 to 11 are graphs for explaining the operation and effect, respectively.

As shown in FIG. 1, a combustion chamber 30 is formed in each cylinder of the internal combustion engine by being surrounded by a cylinder bore 24, a piston 26 and a cylinder head 28 formed in a cylinder block 22. Each cylinder of the 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 led into the combustion chamber 30. The intake port 46 is a siamese port that is divided into two intake port portions 46A and 46B by a port partition (intake port branch portion) 46C on the way, and the combustion chamber of each intake port 46A and 46B. An intake valve 58 is installed in each of the openings. The exhaust port 47 is also a siamese port, and two exhaust ports 47 are provided in the combustion chamber 30.
Parts A and 47B are also guided, and exhaust valves (not shown) are provided.

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 the intake ports 46A,
The axis of 46B (the center line of the upper and lower ends and the left and right ends) is shown. The exhaust ports 47A and 47B merge on the downstream side and are connected to a common exhaust passage (not shown).

In the vicinity of the branch portion 46C of the intake ports 46A and 46B, an injector 12 as a fuel injection means described later is mounted.
Thus, the fuel is injected into the intake ports 46A and 46B. In this embodiment, the axial lines 1A and 1B of the intake ports 46A and 46B are shown in FIGS.
As shown in FIG. 6A, the two straight lines are parallel to each other. Therefore, downstream of the vicinity of the branch portion 46C between the intake ports 46A and 46B, the intake ports 46A and 46B
46B are formed parallel to each other, and the intake air from each intake port 46A, 46B flows into the combustion chamber 30 in a state of being parallel to each other. That is, each of the intake ports 46A and 46B is formed as a linear straight port that is substantially parallel to each other.

The intake ports 46A and 46B may be as shown in FIGS. 6 (b) and 6 (c). FIG. 6B is an intake port 46 in which the intake ports 46A and 46B slightly spread from the branch portion 46C of the intake ports 46A and 46B toward the intake valve 58. When the expansion of the intake ports 46A and 46B is minute, the intake ports 46A and 46B are substantially parallel, and the intake air flows into the combustion chamber 30 in a state of being substantially parallel to each other along the intake ports 46A and 46B. I do.

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

Further, as shown in FIG. 4, the cross-sectional shape of this straight port is the half of the intake ports 46A and 46B on the tumble flow side (ie, above the intake ports 46A and 46B through which the main component flow forming the tumble flow flows). Half) 46A
-1 and 46B-1 are wider than the other half (that is, the lower half of the intake ports 46A and 46B through which the component flows for preventing the tumble flow) 46A-2 and 46B-2. The intake flow center F1 of the ports 46A, 46B is located on the tumble flow side (ie, the upper half 4 of the intake ports 46A, 46B).
6A-1, 46B-1). As a result, the intake air flows from the intake ports 46A and 46B are
It is easy to form a tumble flow within 0. In the first embodiment, the intake ports 46A, 46B
Is formed to have a substantially inverted triangular cross section as shown in FIG. Note that reference numerals 21 and 21 shown in FIG.
A partition partitioning the intake ports 46A and 46B into two parts will be described in detail later.

Further, as shown in FIG.
A concave portion 35 is formed on the top surface of the cylinder so that a space is secured 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 protruding portion 39 protruding from the recess 35 in the vicinity of the recess 35. This bump 3
9 is a slope 3 formed between the raised portion 39 and the recess 35.
7, it is smoothly connected to the recess 35.

The recess 35 is formed below an exhaust valve (not shown).
8 is formed below. Therefore, as shown in FIG. 1, the tumble flow side half 4 of the intake ports 46A, 46B is formed.
Intake air flows Fa and Fm flowing from 6A-1 and 46B-1
From the recess 35 to the raised portion 39 via the slope 37, thereby facilitating the formation of a tumble flow.

As shown in FIGS. 1 and 5, a spark plug 11 as ignition means is provided at the center of the top above the combustion chamber 30, and the intake ports 46A, 4
6B on the reference plane 3. Here, the reference plane 3 is an imaginary plane located at the center of both the intake ports 46A and 46B. Incidentally, as shown in FIGS. 1 to 5, a partition wall 2 is formed in each of the intake ports 46A and 46B so as to bisect the inside of each of the intake ports 46A and 46B in the left-right direction.
1 is provided, and the partition 21 allows each intake port 4
6A and 46B, a passage 4 on the reference surface 3 side (spark plug side) of the intake air flow and a passage 5 on the outside of the reference surface 3 (anti-spark plug side) are divided into two along the flow direction of the intake air. ing. That is, each of the intake ports 46A and 46B is separated into an ignition means side passage (center side passage) 4 and an anti-ignition means side passage (side passage) 5.

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

The partition 21 is provided with an intake port 46.
The intake ports 46A, 46B extend from the upstream ends of the intake ports 46A, 46B so as to completely separate the intake flow in the A, 46B into the center side passage 4 and the side passages 5. Therefore, the intake port 46
In A and 46B, the intake air flow branches into the center 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, and
A tumbler pivoting about a transverse axis perpendicular to the axis of bore 24
Form a flow. As a result, the flow of the intake air is changed by the partition 21 as shown in FIG.
When entering the a layer Fm of the mixture air and fuel are mixed in the middle, a layer Fa only air both sides thereof, the side of the three layers (and on both sides the center side passage 4 between Fa passage 5 And three flows in total), that is, a layered state
Is formed in the tumble flow. Therefore, the present internal combustion engine is configured as a stratified combustion internal combustion engine.

In the intake ports 46A and 46B,
Since the cross-sectional area of the intake ports 46A and 46B is reduced by the cross-sectional integral of the partition 21, the flow coefficient of the intake ports 46A and 46B may be reduced and the fully open engine performance may be 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 substantially inverted triangular cross section are sufficiently large so as to cancel out the cross-sectional integration, and the engine is fully opened. The flow coefficient at the time is secured.

As described above, it is desirable to reduce the cross-sectional area of the partition 21 as much as possible in order to secure a flow coefficient. For this reason, the partition 21 is formed so as to be as thin as possible. Therefore, in the present embodiment, as shown in FIG. 2, the thickness of the partition 21 is equal to or slightly smaller than the diameter of the valve stem 57. Thus, the intake resistance by the valve stem 57 can be reduced while securing the intake flow rate of the intake port 46, and the intake air flows into the combustion chamber 30 smoothly.

FIG. 5 shows a modified example of the partition 21. The thickness of the partition 21 is formed as thin as possible on the upstream side of the valve stem 57, and gradually becomes closer to the valve stem 57. The valve stem 57 may be formed so as 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 restricted by the valve stem 57.
Thus, the gas can smoothly flow into the combustion chamber 30 without being disturbed.

In the modified example shown in FIG.
Although the upstream end of the fuel injection valve 1 is formed in the middle of the intake port 46, the partition wall 21 divides the air-fuel mixture and the air into the central passage 4 and the side passage 5, and the fuel mixture injected from the injector 12 is removed. It suffices if diffusion to the side passage 5 can be prevented.
The upstream end of 1 does not necessarily need to extend to the upstream end of the intake port 46 as shown in FIG.

As shown in FIGS. 1 and 5, the injector 12 as the above-described fuel injection means is disposed above the vicinity of the branch portion 46C of the two intake ports 46A and 46B. The injector 12 serves as a reference plane (center plane) of the intake air flow between the two intake ports 46A and 46B.
3, and the intake ports 46A, 46B
The fuel is injected downward and downstream of the fuel cell. Reference numeral 6 in FIGS. 2, 3, and 5 denotes an injector injection axis, which indicates the injection direction of the injector 12. That is, the injector 12 injects fuel from the upstream upper portion between the intake ports 46A and 46B toward the downstream lower portion.

The fuel injected downward into the intake ports 46A and 46B is supplied to the intake ports 46A and 46B.
Are provided in the combustion chamber 30 through the central passages 4 in the intake ports 46A and 46B, and the side passages 5 on both sides of the ignition plug 11 side are provided. , Only air flows.

Further, as an injection variation of the injector 12, the branch portion 4 of the two intake ports 46A and 46B is provided.
Depending on the shape of 6C, types shown in FIGS. 7A to 7D can be considered. (A) is for injecting fuel toward the branch portion 46C of the siamese type intake ports 46A and 46B. After the fuel is positively collided with the branch portion 46C,
The diffused fuel is caused to flow to the center side passage 4 in the intake ports 46A and 46B. This intake port 46
The branch portion 46C of A, 46B has a surface that is substantially perpendicular to the injection direction of the injector 12, and diffuses fuel that has collided with this surface.

Next, (b) shows a type in which an injector 12 having two fuel injection holes is used. The flow of the two fuels injected from each fuel injection hole is determined by each of the intake ports 46A and 46B. , And flows directly into the central side passage 4. In this case, the intake port 46A,
The branch portion 46C of 46B is formed in a curved surface shape to reduce the intake resistance of the intake flow.

Further, as shown in FIG. 3C, the fuel is directly injected into the center side passage 4 by using the injector 12 having one fuel injection hole so that the fuel does not adhere to the partition walls 21 and 21. Such a type is also conceivable. In this case, the branch portion 46C of the intake ports 46A and 46B is formed at an acute angle so that the fuel is smoothly taken in along with the intake.

(D) is a type in which the fuel is positively injected toward the wide angle over each of the partition walls 21 and 21, contrary to the above (c). In this case, the branch portion 46C of the intake ports 46A and 46B is rounded in a curved shape as in the above (b) in order to reduce the resistance. In this embodiment, any of the above-described injection variations is used.

The above (a) to (d) show the injection variations of the injector 12, and the arrangement position of the injector 12 and the injection axis 6 are all 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 the intake ports 46A, 46A, Combustion chamber 30 from 46B
After being compressed and expanded (exploded) in the combustion chamber 30, it is discharged from each of the exhaust ports 47A and 47B to an exhaust passage (not shown).

In each of the intake ports 46A and 46B, the intake flow components in the tumble flow-side half portions 46A-1 and 46B-1 are much larger than the intake flow components in the other half portions 46A-2 and 46B-2. Become a lot. And the tumble flow side half portions 46A-1, 46 of the intake ports 46A, 46B.
The intake flow component entering the combustion chamber 30 from B-1 is a component of a flow that forms a tumble flow, and the intake port 46A,
The combustion chamber 30 from the other half 46A-2, 46B-2 of 46B.
Since the intake flow component that enters the inside is a component that blocks the tumble flow, the intensity of the tumble flow is increased due to the flow rate imbalance described above. In particular, the intake ports 46A, 4
Since the overall flow path cross-sectional area of 6B is reduced, the tumble flow can be enhanced while the flow rate (flow velocity) of the intake flow in the entire intake port is kept constant.

At this time, at the time of intake, each intake port 4
In 6A and 46B, the partition 21 divides the intake air flow into an inner part and an outer part. The injector 12 injects the fuel toward the inner central passage 4 partitioned by the partition 21 of each of the intake ports 46A, 46B, so that the fuel flows through the central passage partitioned by the partition 21 of the intake ports 46A, 46B. 4, where fuel and air are mixed. 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 ignition plug 11 at the center of the combustion chamber 30. An air layer Fa is formed on both sides.

In particular, since the intake ports 46A and 46B and the partition 21 provided therein are disposed substantially in parallel, as shown in FIG. 5, the intake ports 46A and 46B are provided.
The layer Fm of the air-fuel mixture flowing into the combustion chamber 30 from the central passage 4 and the layer Fa of the air flowing into the combustion chamber 30 from the outer side passage 5 partitioned by the partition 21 are also in the combustion chamber 30. Layering is performed while maintaining the separated state. Toes
From the intake ports in all engine operating ranges.
The intake air flow introduced into the combustion chamber 30 is
Vertical rotation occurring around a horizontal axis orthogonal to the axis of the dowel bore 24
By utilizing the circulating flow, the central rich mixture layer F
m and the swirling flow of the air layer Fa on both sides of the swirling flow.
It can be separated into layers.

As a result, a mixture containing less fuel is sent to the entire combustion chamber 30, but a sufficient amount of fuel for ignition is sent to the vicinity of the ignition plug 11. As described above, the fuel-fuel mixture flows near the ignition plug 11, so that the engine can be operated with a fuel mixture of a smaller amount than the stoichiometric air-fuel ratio without deteriorating the ignitability . It is possible to realize an extremely fuel-efficient internal combustion engine
It is.

Further, by promoting the stratification of the intake air flow, the formation of the tumble flow in the combustion chamber 30 is enhanced. That is, the intake air flow is supplied to each intake port 46A, 46B.
Is branched into a central passage 4 and a side passage 5 and the branched intake air flows into the combustion chamber 30 while maintaining a parallel state, whereby the intake air flow is rectified and a tumble flow is easily formed. It becomes.

By the way, it is conceivable that the partition walls 21 of the intake ports 46A and 46B are also provided downstream of the valve stem 57 so that the intake flow is further completely separated into an air-fuel mixture and air and flows into the combustion chamber 30. However, it is difficult to provide a partition in such a narrow space on the downstream side of the valve stem 57, which increases the manufacturing cost and the number of processing steps. 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, so that the manufacturing cost can be reduced. Further, even if the valve stem 57 of the partition 21 is provided only on the upstream side, a significant difference occurs as compared with the case where the partition 21 is provided to the downstream side of the valve stem 57 as described above. Without
The intake air flowing into the combustion chamber 30 can be sufficiently stratified.

As described above, the intake port 46
By providing the partition wall 21 in A and 46B, the intake air flow is rectified, and the tumble flow can be strengthened. By providing such partition walls 21 at the intake ports 46A and 46B 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 of FIG. 8 is the air-fuel ratio (A /
F), and the vertical axis indicates the NOx emission amount and Pi (illustrated average effective pressure) fluctuation rate. Lines a and c show the characteristics of the engine provided with the partition 21 at the intake port, and lines b and d
Shows the characteristics of an engine having a normal tumble flow intake port without the partition 21. Line a, line b
Represents the NOx emission, and the lines c and d relate to the Pi fluctuation rate.

First, the line a and the line 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 21 (see the line a), The NOx emission peaks on the lean (thinner) side of the A / F value as 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 emission amount of NOx has a peak value moves to the lean side as compared with the conventional engine.

Lines c and d show the relationship between the A / F and the Pi fluctuation rate. Here, the Pi fluctuation rate is a measure for judging the combustion stability of the engine. If the Pi fluctuation rate is too high, combustion of the engine is not stabilized, and an uncomfortable operation state accompanied by torque fluctuation is caused. . In addition, the reference line e in the figure is a Pi fluctuation rate of the combustion stability limit that can be operated without any discomfort.

As shown in this figure, the engine provided with the partition 21 (see the line c) uses a normal tumble flow with respect to the limit value of the Pi fluctuation rate at which a stable combustion state in the cylinder is obtained. A / on the leaner side than the institution (see line d)
The engine can be operated at F, and the emission of NOx at this time can also be significantly reduced. In other words, it shows 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, this structure can realize an internal combustion engine that has extremely low fuel consumption and hardly emits NOx. Also, as shown in FIGS. 9 and 10, the upper half portions 46A-1 and 46B-1 of the substantially inverted triangular cross sections of the intake ports 46A and 46B are sufficiently large to secure a flow coefficient when the engine is fully opened. can do.

FIG. 9 shows the relationship between the port cross-sectional area and the average tumble ratio and the 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. In FIG. 9, the symbols □ indicate the average flow coefficient of an engine provided with a normal tumble flow intake port, and the symbols ■ indicate the upper halves 46A-1, 46B- of the cross sections of the intake ports 46A, 46B. 1 shows the average flow coefficient of an engine provided with a sufficiently large intake port.

○ indicates an average tumble ratio of an engine having an intake port of a normal tumble flow,
● is the upper half 46A of the cross section of the intake ports 46A and 46B
The graph shows the average tumble ratio of an engine having an intake port having a sufficiently large value of -1,46B-1. In the intake ports 46A and 46B of the present invention, the upper half portion 46A
-1 and 46B-1 are made sufficiently large to secure the port cross-sectional area.
Both average flow coefficient can be improved.

As a result, the relationship between the tumble ratio and the flow coefficient is as shown in FIG. FIG.
In the figure, the symbol “△” indicates an engine using a conventional tumble flow, the symbol “☆” indicates an engine in which the partition 21 is provided but the cross-sectional area in the intake ports 46A and 46B is reduced by the partition 21. An engine equipped with intake ports 46A, 4
The upper half portions 46A-1 and 46B-1 of the cross section of FIG. 6B are sufficiently enlarged.

That is, as shown in FIG. 10, simply providing the partition 21 in the intake ports 46A and 46B will reduce the flow coefficient even if the stratification of the intake air flow is promoted, and it is considered that the full opening performance is reduced. Can be Here, as shown by the mark ★, the upper half 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. Thus, the intake port 46 provided by the partition 21 is provided.
It is possible to compensate for the decrease in the cross-sectional area of A, 46B, and to ensure the full opening performance of the engine.

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 the present structure, lines b and d.
Is a graph showing characteristics of an engine having a conventional intake port structure. First, the lines a and b show the relationship between the rotational speed and the torque of the engine. There is almost no difference between the two curves, and the engine equipped with this structure is operated with a leaner mixture than before. This shows that torque equivalent to that of a conventional engine is realized.

Lines c and d show the relationship between the rotational speed and the output of the engine.
As with the torque characteristics described above, there is almost no difference between the two, indicating that the engine and the conventional engine can obtain an output even when operated with a leaner air-fuel mixture. Therefore, as shown in FIG. 11, the engine having the present structure can 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. Thus, an internal combustion engine having the same torque and output characteristics as those of the other engines can be realized.

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

It should be noted that the present invention is not limited to the intake ports 46A, 46A.
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 above in detail, according to the intake port structure of the stratified combustion internal combustion engine of the present invention, the intake port having two combustion chamber openings respectively opened and closed by two intake valves is provided. 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 disposed at a central portion of the combustion chamber at the top, and at an upstream portion of the intake port. Fuel injection means is provided, and inside the above-mentioned intake port,
Partition walls are provided for dividing the fuel from the fuel injection means into an ignition means-side passage for forming a mixed gas flow mixed with the fuel and an anti-ignition means-side passage for forming an unmixed air flow along the flow direction. , the partition wall is formed over substantially the entire region from the upper surface of the upstream ports than the stem of the intake valve in the intake port to the lower surface Rutotomoni, under the partition wall
The upper part of the flow end is along the upstream side of the stem and
With a simple structure in which the surface side is located near the valve seat , the tumble flow is strengthened, and the intake air sucked from each intake port is reliably stratified into an air layer and an air-fuel mixture layer. Can be That is, the air introduced from each intake port into the combustion chamber in the entire operation range of the engine
Is a three longitudinal swirling flow swirling around the horizontal axis perpendicular to the axis of Shirindabo A combustion chamber. And these three
Relatively rich mixing of the central swirl of two longitudinal swirls
And the swirl flow on both sides is a lean mixture.
The vertical swirling flow can be separated into layers as the swirling flow of (or air) . Therefore, a stable combustion state can be obtained even if the overall air-fuel ratio in the combustion chamber is lean, and an extremely low fuel consumption internal combustion engine can be realized. Further, there is an advantage that the NOx emission can be reduced.

The above-mentioned effect can be obtained by providing the partition in the intake port only on the upstream side of the stem of the intake valve, and the partition on the upstream side can be easily processed. Increase in the manufacturing cost and the number of processing steps can be minimized.

[Brief description of the drawings]

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

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

3 is a schematic partial cross-sectional view 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 CC cross-sectional view in FIG. 2;

4 is a schematic partial cross-sectional view 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 BB cross-sectional view in FIG.

FIG. 5 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.

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 a fuel injection method in an intake port structure of a stratified 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 an effect of an intake port structure of a stratified combustion internal combustion engine as one embodiment of the present invention.

FIG. 10 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. 11 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. 12 is a schematic longitudinal cross-sectional view showing an intake port structure of a conventional stratified combustion internal combustion engine together with around a combustion chamber.

FIG. 13 is a schematic perspective view showing the intake port structure of a conventional stratified combustion internal combustion engine together with the vicinity of a combustion chamber.

FIG. 14 is a schematic cross-sectional view of a surface of the conventional stratified combustion internal combustion engine that is perpendicular to the flow direction of intake air in the intake port structure (FIG. 12).
3 is a sectional view taken along the line DD in FIG.

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

FIG. 16 is a schematic longitudinal sectional view showing another example of the intake port structure of the 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 surface 4 Ignition means side passage or center passage 5 Anti-ignition means side passage or side passage 6 Injector injection axis 7 Intake port lower wall surface 8 Intake Port upper wall surface 11 Ignition plug 12 as ignition means 12 Injector 13 as fuel injection means 13 Intake port oblique line portion 21 Partition wall 22 Cylinder block 24 Cylinder bore 25 Cylinder 26 Piston 28 Cylinder head 30 Combustion chamber 34 Pent roof 35 Concave 37 Slope 39 Rise 40 , 42 'Intake passages 46, 44', 40F, 42F Intake ports 46A, 46B Intake port portions 46A-1, 46B-1 Upper half of intake port 46A-2, 46B-2 Lower half of intake port 46C Port bulkhead 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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shogo Omori 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Yuki Tamura 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Michihiro Hatake Inventor 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-60-233314 (JP, A) JP 1984-59628 (JP, A) JP-A 3-49371 (JP, U) JP-A 1-125863 (JP, U) JP-A 61-204922 (JP, U) (58) Fields surveyed (Int) .Cl. ⁷ , DB name) F02M 69/00 360 B F02B 17/00 D F02B 31/00 301 B

Claims (1)

(57) [Claims] An intake port having two combustion chamber openings opened and closed by two intake valves, respectively.
In a stratified combustion internal combustion engine configured such that an intake flow from the intake port can become a stratified tumble flow in the combustion chamber, a combustion ignition means is provided at a central portion of a top of the combustion chamber. A fuel injection means is provided at an upstream portion of the fuel injection means, and forms an air flow in which the fuel is not mixed with an ignition means side passage which forms a mixed gas flow in which the fuel from the fuel injection means is mixed in the intake port. A partition that bisects the anti-ignition means side passage along the flow direction is provided, and the partition is formed over substantially 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. And the upper surface side portion of the downstream end of the partition wall
A valve seat along the upstream side of the stem and on the lower side
An intake port structure for a stratified combustion internal combustion engine, which is located in the vicinity .