JP5765535B2 - Fuel injection engine in the intake passage - Google Patents

Description

  The present invention relates to a technique for suppressing air-blow of an air-fuel mixture during valve overlap in a fuel injection engine in an intake passage.

Some 4-stroke engines are provided with valve overlap immediately before the end of the exhaust stroke or immediately after the start of the intake stroke. Valve overlap is a state in which the intake valve and the exhaust valve are opened, and promotes scavenging of the burned gas remaining in the combustion chamber by intake air, and has an effect of improving the charging efficiency of intake air in the vicinity of full opening.
However, in recent years, in order to improve the intake efficiency and scavenging efficiency of the engine, the number of engines in which the opening area of the intake valve and the exhaust valve is ensured as large as possible and the distance between the intake valve and the exhaust valve is close is increasing. As described above, when the intake valve and the exhaust valve are arranged close to each other, the engine of the type in which fuel is injected into the intake passage, in particular, combustion from the intake passage through the intake valve opening in the vicinity of the intake valve. In a semi-direct fuel injection type engine that injects fuel into the room, when fuel is injected at the time of valve overlap, so-called air-fuel mixture blowout from the intake valve to the exhaust valve occurs. This will cause a reduction in fuel consumption.

  In view of this, a technique has been proposed in which a shroud (weir) is provided around the opening of the intake passage or exhaust passage in order to suppress air-fuel mixture blow-off during valve overlap (Patent Document 1). Specifically, a shroud is provided at the edge of the opening of the intake passage or the exhaust passage to suppress the movement of the intake air from the intake passage to the exhaust passage, thereby suppressing the blow-in of the intake air.

Japanese Patent Laid-Open No. 5-1554

  However, the engine disclosed in Patent Document 1 includes two intake valves and two exhaust valves, and an opening of the exhaust passage is disposed on an extension line of the intake passage toward the intake valve in a top view. The intake passage and the exhaust passage are arranged symmetrically across the center of the combustion chamber. Therefore, it has a structure in which swirl is hardly generated in the intake air in the combustion chamber. Patent Document 1 describes an engine in which a shroud is provided between an opening of an intake passage and an opening of an exhaust passage at the edge of the opening portion of the exhaust passage. Although it is possible to generate a tumble flow, it is difficult to generate a swirl.

  The present invention has been made to solve such a problem, and an object of the present invention is to ensure an swirl in the combustion chamber and suppress an air-fuel mixture blow-off during valve overlap. An internal fuel injection engine is provided.

In order to achieve the above object, the fuel injection engine in an intake passage according to claim 1 includes an intake passage and an exhaust passage extending from a combustion chamber to a side of the cylinder, and an intake passage having a fuel injection means in the intake passage. In the internal fuel injection engine, the opening of the intake passage where the intake valve opens and closes opens toward a position offset radially outward of the cylinder from the center of the combustion chamber, and the opening of the exhaust passage where the exhaust valve opens and closes The portion includes a portion that opens toward a position that is offset radially outward of the cylinder from the center of the combustion chamber, and that is offset from an extension line in the opening direction of the intake passage in the radial direction of the cylinder. together with the exhaust valve is opened together and the exhaust valve and the intake valve, the valve overlap period to encourage the scavenging of burned gas remaining in the combustion chamber by an intake A shroud projecting into the combustion chamber at the edge of the opening of the exhaust passage where the exhaust valve opens and closes, and the shroud is part of the entire circumference of the edge on the extension line side in the opening direction of the intake passage. is disposed, the fuel injection means, the injection direction is set so as to inject fuel toward the opening of the intake passage, at least a portion of the fuel injection period you inject fuel so as to overlap the valve overlap period It is characterized by that.

Further, the fuel injection engine in the intake passage according to claim 2 is characterized in that, in claim 1, the amount of protrusion of the shroud into the combustion chamber exceeds the maximum lift position of the exhaust valve.
A fuel injection engine in an intake passage according to claim 3 is the fuel injection engine according to claim 1 or 2, wherein one cylinder includes two intake valves and at least one exhaust valve, and the fuel injection means includes an intake passage during valve overlap. From the two intake valves, fuel is injected into the combustion chamber through the opening of one of the intake valves, and the shroud passes the fuel injected from the fuel injection means during the valve overlap of the entire periphery of the edge. It is arranged at a part of the extended line side in the opening direction of the intake valve.

According to a fourth aspect of the present invention, there is provided a fuel injection engine in an intake passage according to any one of the first to third aspects, wherein each cylinder is provided with two intake valves and two exhaust valves, and two intake valves are provided at a predetermined high load. Switching between opening and closing a pair of intake and exhaust valves that are arranged diagonally across the center of the cylinder of the two intake and exhaust valves when the valve and exhaust valve are all opened and closed at a predetermined low load The shroud is provided at the edge of the opening of the exhaust valve that opens and closes at a predetermined low load, and the opening direction of the opening of the intake valve that opens and closes at the predetermined low load out of the entire circumference of the edge It is arrange | positioned at a part of extension line side of this.

According to the first aspect of the present invention, since the opening of the intake passage opens toward a position offset from the center of the combustion chamber to the outside in the radial direction of the cylinder, the intake air flowing from the intake passage is swirled in the combustion chamber. Is generated. Also, the opening of the exhaust passage that opens and closes the exhaust valve opens toward the position offset from the center of the combustion chamber to the outside in the radial direction of the cylinder, and the radial direction of the cylinder from the extended line in the opening direction of the intake passage Furthermore, a shroud that protrudes into the combustion chamber is provided at the edge of the opening of the exhaust passage where the exhaust valve opens and closes, so that both the intake valve and the exhaust valve open. Sometimes the linear movement of intake air from the intake passage to the exhaust passage is impeded. Therefore, when the fuel is injected toward the fuel injection mechanism during valve overlap to the opening of the intake passage, the intake (mixture) is less likely blow into the exhaust passage including the fuel, it is possible to reduce fuel consumption.

  Further, since the shroud is disposed on a part of the entire circumference of the edge of the opening of the exhaust passage on the extension line side in the opening direction of the intake passage, the air-fuel mixture from the intake passage to the exhaust passage is sufficiently blown out. It is possible to prevent. Compared with the case where it is provided all around the edge of the opening of the exhaust passage, it is possible to maintain the swirl and improve the scavenging efficiency without hindering the exhaust from the combustion chamber to the exhaust passage after combustion. it can.

According to the second aspect of the present invention, the amount of shroud protruding into the combustion chamber is set so as to exceed the maximum lift position of the exhaust valve. Therefore, when fuel is injected from the fuel injection means during valve overlap. The air-fuel mixture becomes difficult to flow out into the exhaust passage by the shroud.
According to the invention of claim 3 , two intake valves are provided in one cylinder, and when the valve overlaps, fuel is injected toward the opening of one of the intake valves, and the shroud is formed at the edge of the opening. The exhaust valve is arranged by a shroud against the intake air from the opening containing the fuel because it is arranged on a part of the entire circumference of the opening of the intake valve through which fuel passes from the fuel injection means. Can be prevented from being blown into the opening.

Therefore, in an engine having two intake valves and one exhaust valve in one cylinder, it is possible to sufficiently ensure scavenging efficiency while suppressing fuel blow-off during valve overlap.
According to the fourth aspect of the present invention, when a predetermined low load is applied, the pair of intake and exhaust valves arranged diagonally with respect to the center of the cylinder are opened and closed, so that swirl is generated in the intake air in the combustion chamber. be able to. Further, since the two intake valves and the exhaust valve are all opened and closed at a predetermined high load, it is possible to secure a sufficient intake flow rate and obtain a high output.

  The shroud is provided at the edge of the opening of the exhaust valve that opens and closes at a predetermined low load. Of the entire periphery of the edge of the opening of the exhaust valve, the shroud of the opening of the intake valve that opens and closes at a predetermined low load Since it is arranged on a part of the extension line side in the opening direction, the intake passage that flows into the combustion chamber from the opening portion of the intake valve toward the opening direction at a predetermined low load is in the exhaust passage even when the valve overlaps. It becomes difficult to blow through. The shroud is not provided on the entire periphery of the edge of the opening of the exhaust valve, and the two exhaust valves open and close at a predetermined high load, so that sufficient suction efficiency and scavenging efficiency can be secured. it can.

1 is a schematic structural diagram of a fuel injection engine in an intake passage according to a first embodiment of the present invention. 1 is a cross-sectional view showing a schematic configuration of an intake / exhaust system of an engine according to a first embodiment of the present invention. It is explanatory drawing which shows an example of a valve opening period and a fuel injection period. It is a cross-sectional view which shows schematic structure of the intake / exhaust system of the engine of the 2nd Embodiment of this invention. It is a cross-sectional view which shows schematic structure of the intake / exhaust system of the engine of the 3rd Embodiment of this invention. It is a cross-sectional view which shows the flow direction of the intake air in a combustion chamber at the time of the 2 valve opening / closing mode of the engine of the 3rd Embodiment of this invention. It is a map for switching between the 4-valve open / close mode and the 2-valve open / close mode.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic structural diagram of a fuel injection engine in an intake passage (hereinafter referred to as an engine 1) according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic configuration of the intake and exhaust system of the engine 1 according to the first embodiment of the present invention. In FIG. 2, the flow direction of the intake air in the combustion chamber 7 is indicated by a white arrow.

As shown in FIGS. 1 and 2, the engine 1 according to the first embodiment of the present invention is a two-valve engine in which one intake valve 3 and one exhaust valve 4 are provided in one cylindrical cylinder 2. is there.
The cylinder head 5 of the engine 1 is provided with an ignition plug 6 and one intake port 8 (intake passage) and one exhaust port 9 across the center of the combustion chamber 7. The cylinder head 5 is provided with an intake valve 3 that opens and closes an intake port 8 and an exhaust valve 4 that opens and closes an exhaust port 9. These intake valve 3 and exhaust valve 4 are not shown on the cylinder head 5. The valve is driven to open and close in synchronism with the rotation of the crankshaft.

An intake manifold 10 (intake passage) connected to the intake port 8 extends from the side of the cylinder 2 toward the intake valve 3, and an exhaust manifold 11 connected to the exhaust port 9 is on the opposite side of the intake manifold 10. It extends from the side of the cylinder 2 toward the exhaust valve 4.
Further, the engine 1 is provided with a fuel injection valve 12 (fuel injection means) that injects fuel into the intake port 8 in the vicinity of the intake valve 3. The injection direction of the fuel injection valve 12 is set so as to inject fuel toward the opening of the intake valve 3. The fuel injection valve 12 is supplied with fuel from a fuel tank 13 by a feed pump 14.

As shown in FIG. 2, the intake manifold 11 and the intake valve 3, and the exhaust manifold 11 and the exhaust valve 4 are not arranged in a straight line when viewed from the top, and the radial direction of the cylinder 2 across the center of the combustion chamber 7 ( In FIG. 2, they are arranged so as to be offset in the vertical direction).
Specifically, the intake port 8 that opens and closes the intake valve 3 opens toward a position offset from the center of the combustion chamber 7 to the outside in the radial direction of the cylinder 2 (downward in FIG. 2). An exhaust valve 4 is disposed offset from the direction extension line.

  In the present embodiment, a shroud 15 that is an arc-shaped weir body protruding toward the combustion chamber 7 is provided at the edge of the opening of the exhaust port 9. The vertical height dimension of the shroud 15 is not particularly limited as long as the intake air can be prevented from being blown through, but is set slightly higher than the maximum lift position of the exhaust valve 4 as an example. Further, the shroud 15 is disposed on a part of the entire circumference of the edge of the opening of the exhaust port 9 on the extension line side in the opening direction of the intake port 8.

  The ECU 30 is electrically connected to sensors such as a crank angle sensor 31 for detecting a crank angle of the engine 1, an air flow sensor 32 for detecting an intake flow rate, a throttle sensor for detecting a throttle opening, an accelerator position sensor for detecting an accelerator operation amount, and the like. Based on the information from these sensors, the fuel injection amount by the fuel injection valve 12, the fuel injection timing, the ignition timing by the spark plug 6, and the like are controlled.

FIG. 3 is an explanatory diagram illustrating an example of a valve opening period and a fuel injection period.
In this embodiment, the fuel injection amount per unit time injected from the fuel injection valve 12 is substantially constant, and the fuel injection amount is controlled by increasing / decreasing the injection time. For example, the fuel injection time is set short when the load is low, and the fuel injection time is set long when the load is high.
As shown in FIG. 3, the engine 1 of the present embodiment is provided with a valve overlap period in which both the intake valve 3 and the exhaust valve 4 are opened before and after the boundary between the exhaust stroke and the intake stroke. Then, the ECU 30 is set to inject fuel in the first half of the intake stroke at the time of low rotation and low load, and to inject fuel continuously in the second half of the exhaust stroke and the first half of the intake stroke at the time of high rotation and high load. Is set.

  With the above configuration, in the present embodiment, the intake port 8 opens toward a position offset from the center of the combustion chamber 7 to the outside in the radial direction of the cylinder 2. Generates a swirl in the combustion chamber 7. In addition, the intake manifold 10 and the exhaust manifold 11 are not in a straight line when viewed from above, and the exhaust valve 4 is arranged offset from the extension line in the opening direction of the intake port 8. The intake air that has flowed into the exhaust port 9 cannot pass through the combustion chamber 7 linearly. Therefore, it is difficult for the intake air to flow out from the intake port 8 to the exhaust port 9 during valve overlap.

Furthermore, since the shroud 15 protruding toward the combustion chamber 7 is provided at the edge of the opening of the exhaust port 9 where the exhaust valve 4 opens and closes, the outflow of the intake air to the exhaust port 9 becomes more difficult. Yes.
Therefore, for example, when fuel is injected from the fuel injection valve 12 at the time of valve overlap, such as at high rotation and high load, the amount of fuel blown into the exhaust port 9 can be reduced. Therefore, the intake air cooling by the fuel can be performed without deteriorating the exhaust gas, the high compression can be achieved, and the fuel consumption can be reduced.

  In particular, in the present embodiment, the shroud 15 is disposed not on the entire periphery of the edge of the opening of the exhaust port 9 but on a part of the extended line side in the opening direction of the intake port 8. 7 is arranged at an appropriate position to prevent exhaust air flowing into the exhaust port 9 from being discharged into the exhaust port 9. Compared with the case where the exhaust valve 4 is provided all around the edge of the opening, the swirl is maintained without hindering the exhaust gas remaining in the combustion chamber 7 from being discharged to the exhaust port 9. It is possible to improve the scavenging performance, and it is possible to suppress a decrease in output due to the provision of the shroud 15 especially during high rotation.

FIG. 4 is a cross-sectional view showing a schematic configuration of the intake and exhaust system of the engine 40 according to the second embodiment of the present invention.
The fuel injection engine in the intake passage (hereinafter referred to as the engine 40) of the second embodiment of the present invention is different from the engine 1 of the first embodiment in that an intake valve (first intake valve 41, The difference is that two second intake valves 42) are provided.

As two intake valves are provided, the intake manifold 10 includes a first intake port 43 that opens and closes the first intake valve 41 at the downstream end, and a first intake port 43 that opens and closes the second intake valve. 2 intake ports 44.
The exhaust valve 4 is located in the extending direction of the intake manifold 10 from an intermediate position between the first intake valve 41 and the second intake valve 42. As a result, also in the second embodiment, the exhaust valve 4 is arranged offset from the extension line in the opening direction of the first intake port 43, and therefore, the exhaust port 4 extends from the first intake port 43 during valve overlap. 9 is configured such that intake air cannot pass through the combustion chamber 7 linearly.

  The fuel injection valve 12 is disposed so as to inject fuel toward the opening of the first intake valve 41. The shroud 15 is disposed on a part of the extended line side in the opening direction of the first intake port 43 where the first intake valve 41 opens and closes. As a result, the air-fuel mixture that includes the fuel injected from the fuel injection valve 12 and flows into the combustion chamber 7 from the first intake port 43 is placed at an appropriate position to prevent discharge to the exhaust port 9. The fuel can be effectively prevented from being blown through at the time of valve overlap.

FIG. 5 is a cross-sectional view showing a schematic configuration of the intake and exhaust system of the engine 50 according to the third embodiment of the present invention.
The fuel injection engine in the intake passage (hereinafter referred to as the engine 50) of the third embodiment of the present invention has an intake valve (first intake valve 41, 1) in one cylinder compared to the engine 1 of the first embodiment. The difference is that two second intake valves (42) and two exhaust valves (first intake valve 51, second intake valve 52) are provided.

In the engine 50 of the present invention, the first intake valve 41 and the second intake valve 42 are arranged side by side on the intake manifold 10 side, and the first exhaust valve 51 and the second exhaust valve 52 are arranged on the exhaust manifold 11 side. Has been placed.
As the intake valves 41 and 42 are provided, the intake manifold 10 is bifurcated at the front end, and the front end (the intake downstream end) is opened and closed by the first intake valve 41. 1 intake port 43 and a second intake port 44 that opens and closes a second intake valve 42. In addition, as the two exhaust valves 51 and 52 are provided, the exhaust manifold 11 is bifurcated at the tip, and the tip (exhaust upstream end) opens and closes the first exhaust valve 51. The first exhaust port 53 is connected to the second exhaust port 54 where the second exhaust valve 52 is opened and closed.

The fuel injection valve 12 is a first fuel injection valve 12 a that injects fuel toward the opening of the first intake valve 41 and a second fuel that injects fuel toward the opening of the second intake valve 42. It is comprised by the injection valve 12b.
Further, in the present embodiment, the valve mechanism for opening and closing the intake valves 41 and 42 and the exhaust valves 51 and 52 is a four valve that opens and closes the two intake valves 41 and 42 and the two exhaust valves 51 and 52 in one cylinder. A function is provided that can be switched by an actuator (not shown) between an open / close mode and a two-valve open / close mode in which one of the intake valves 41 and 42 and the exhaust valves 51 and 52 is closed and opened and closed one by one.

  In the four-valve open / close mode, as shown in FIG. 5, since the two intake valves 41 and 42 and the two exhaust valves 51 and 52 are opened and closed in one cylinder, the intake valves 41 and 42 and the exhaust valves 51 and 52 are opened. At the time of valve overlap that opens together, the intake air flowing in from the two intake valves 41 and 42 moves substantially linearly toward the exhaust valves 51 and 52 facing each other, and the exhaust gas remaining in the combustion chamber 7 is quickly exhausted. It is discharged from the ports 53 and 54.

FIG. 6 is a top view showing the flow direction of the intake air in the combustion chamber 7 in the two-valve open / close mode. In FIG. 6, the flow direction of the intake air is indicated by white arrows.
In the two-valve open / close mode, as shown in FIG. 6, the first intake valve 41 is opened and closed, and the second exhaust valve 52 diagonally opposite to the first intake valve 41 is opened and closed. The intake valve 42 and the first exhaust valve 51 are closed. In the two-valve open / close mode, the operation of the second fuel injection valve 12b is restricted so that fuel is not injected toward the second intake valve 42 to be closed.

The ECU 30 (switching means) switches between the four-valve open / close mode and the two-valve open / close mode based on the operating state of the engine 50.
FIG. 7 is a map for switching between the 4-valve open / close mode and the 2-valve open / close mode.
The ECU 30 uses the map shown in FIG. 7 to determine either the 4-valve open / close mode or the 2-valve open / close mode based on the rotational speed and load of the engine 50. As shown in FIG. 7, the two-valve opening / closing mode is selected at low load or low rotation, and the four-valve rotation mode is selected at high load or high rotation.

  By configuring and controlling as described above, the first intake valve 41 and the second exhaust valve 52 are opened in the two-valve open / close mode, so that the second exhaust valve 52 to be opened is opened. The first intake valve 41 is arranged so as to be offset from the extension line in the opening direction of the opening of the first intake valve 41, and the intake air linearly flows from the first intake port 43 to the second exhaust port 54 when the valve overlaps. 7 can not pass through.

Further, the shroud 15 is disposed at the edge of the opening of the second exhaust valve 52, and the first intake port 43 that opens and closes the first intake valve 41 out of the entire periphery of the edge of the opening. It is arranged at a part on the extended line side in the opening direction.
Therefore, in the third embodiment, in the two-valve open / close mode, the intake air that contains the fuel injected from the first fuel injection valve 12a and flows into the combustion chamber 7 from the first intake port 43 is detected. The fuel is disposed at an appropriate position to prevent discharge to the second exhaust port 54, and fuel blow-off at the time of valve overlap can be effectively prevented.

On the other hand, in the four-valve open / close mode, the first intake valve 41, the second intake valve 42, the first exhaust valve 51, and the second exhaust valve 52 are opened and closed, so that the intake flow rate can be secured. At the same time, scavenging performance can be secured, and characteristics suitable for high rotation and high load can be obtained.
In addition, this invention is not limited to the above embodiment.

  In the above embodiment, the fuel injection valve 12 is a semi-direct fuel injection engine that injects fuel into the combustion chamber 7, but the present invention can be applied to any engine that injects fuel in the intake passage. Further, it is possible to effectively prevent fuel from being blown from the intake passage to the exhaust passage at the time of valve overlap.

1 Engine 2 Cylinder 3 Intake Valve 4 Exhaust Valve 7 Combustion Chamber 8 Intake Port 12 Fuel Injection Valve 15 Shroud 41 First Intake Valve 52 Second Exhaust Valve

Claims (4)

An intake passage fuel injection engine having an intake passage and an exhaust passage extending from a combustion chamber to a side of a cylinder, and having a fuel injection means in the intake passage;
The opening portion of the intake passage where the intake valve opens and closes opens toward a position offset from the center of the combustion chamber to the outside in the radial direction of the cylinder,
An opening portion of the exhaust passage where the exhaust valve opens and closes opens toward a position offset radially outward of the cylinder from the center of the combustion chamber, and extends from the extension line in the opening direction of the intake passage. It is configured to include what is arranged offset in the radial direction,
The exhaust valve, the exhaust passage is opened together and the exhaust valve and the intake valve has a valve overlap period to encourage the scavenging of burned gas remaining in the combustion chamber by an intake, open and close the exhaust valve A shroud projecting into the combustion chamber at the edge of the opening of
The shroud is arranged on a part of the entire circumference of the edge portion on the extended line side in the opening direction of the intake passage ,
The fuel injection means, wherein the injection direction configured to inject fuel toward the opening of the intake passage, at least a portion of the fuel injection period you inject fuel so as to overlap the valve overlap period A fuel injection engine in an intake passage. 2. The fuel injection engine in the intake passage according to claim 1, wherein an amount of protrusion of the shroud into the combustion chamber is set to exceed a maximum lift position of the exhaust valve. One cylinder includes two intake valves and at least one exhaust valve, and the fuel injection means passes through the opening of one of the two intake valves from the intake passage when the valve overlaps. Injecting fuel toward the combustion chamber;
The shroud is disposed on a part of the entire circumference of the edge on the extended line side in the opening direction of the intake valve through which the fuel injected from the fuel injection means passes when the valve overlaps. The fuel injection engine in the intake passage according to claim 1 or 2 . Each cylinder has two intake valves and two exhaust valves,
At the time of a predetermined high load, all of the two intake valves and the exhaust valve are opened and closed, and at the time of a predetermined low load, of the two intake valves and the exhaust valve, they are arranged diagonally across the center of the cylinder. Switching means for opening and closing the pair of intake valves and exhaust valves;
The shroud is provided at the edge of the opening of the exhaust valve that opens and closes at the predetermined low load, and the opening of the opening of the intake valve that opens and closes at the predetermined low load, out of the entire circumference of the edge The fuel injection engine in an intake passage according to any one of claims 1 to 3 , wherein the fuel injection engine is disposed at a part of a direction extension line side.

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