WO2019225564A1

WO2019225564A1 - Engine unit

Info

Publication number: WO2019225564A1
Application number: PCT/JP2019/019994
Authority: WO
Inventors: 洸佐々木
Original assignee: ヤマハ発動機株式会社
Priority date: 2018-05-25
Filing date: 2019-05-21
Publication date: 2019-11-28
Also published as: TW202004005A; TWI741300B

Abstract

An engine unit 1 has one air intake 12, one intake valve 22, and one injector 23 with respect to one combustion chamber 11. In a case in which a fuel is injected from the injector 23 into a space where there is only atmosphere, with the injector 23 not mounted on the engine unit, the fuel in a first plane S1 that intersects the directions of injection of a plurality of fuel droplets exists within one circle along the edge of the one circle, at a certain point immediately after the injection. The fuel is injected from a plurality of injection holes, during an intake stroke, such that the concentration of the fuel in a first area A1 that is located along the edge of the circle in the first plane S1 becomes higher than the concentration of the fuel in a second area A2 that is located adjacent to the entire inner edge of the first area A1.

Description

Engine unit

The present invention relates to an engine unit having an injector for injecting fuel into an intake passage portion.

Conventionally, an engine unit having an injector that injects fuel into an intake passage is known (see, for example, Patent Document 1). The intake passage portion is connected to the intake port of the combustion chamber. The intake port is opened and closed by an intake valve.

JP 2012-154209 A

Engine units having injectors that inject fuel into the intake passage are required to improve the degree of freedom in designing the fuel concentration distribution in the combustion chamber. For example, it may be required to make the fuel concentration in the combustion chamber uniform, or it may be required to make the fuel concentration around the spark plug higher than other portions.

An object of the present invention is to propose an engine unit capable of improving the degree of freedom in designing the fuel concentration distribution in the combustion chamber.

(1) The engine unit according to the present invention includes at least one combustion chamber partially formed by an inner surface of a cylinder hole, at least one intake port formed in the at least one combustion chamber, and the at least one A cylinder portion having at least one cylinder intake passage portion connected to one intake port and supplying air flowing into the at least one combustion chamber from the at least one intake port, and the cylinder portion And at least one external intake passage portion that is connected to the at least one cylinder intake passage portion and is supplied to the at least one cylinder intake passage portion, and the at least one intake air. At least one suction port movable between a position to open the mouth and a position to close the at least one inlet. A valve and a plurality of injection holes each capable of injecting fuel in the form of a mist, wherein the plurality of injection holes are located in the cylinder intake passage part or in the external intake passage part. A four-stroke cycle engine unit comprising at least one injector installed in an external intake passage section and a control device for controlling fuel injection of the at least one injector. One intake port, one intake valve, and one injector are provided for each combustion chamber, and constitute a single intake port, a single intake valve, and a single intake port injector, respectively. The at least one cylinder intake passage portion and the at least one external intake passage portion include at least one single intake passage portion. The single intake passage portion is provided for each combustion chamber, and is a region from the place where the single intake port injector is installed to the single intake port, in which the flow of air flows. Configured to pass without separation or merging. The single inlet injector is (a) arranged to inject fuel toward the single inlet, and (b) injects fuel into an atmosphere-only space when not mounted on the engine unit. In this case, at a certain time immediately after injection, (i) the fuel on the first plane crossing the injection direction of the plurality of fuel droplets injected from the single inlet injector is one circle or one The oval is present along at least a part of the edge of the one circle or the one oval, and (ii) is included in the region where the fuel on the first plane exists, The second region where the concentration of the fuel in the first region along the edge of the one circle or at least part of the edge of the one oval is in contact with the entire inner peripheral end of the first region on the first plane. To be higher than the fuel concentration of It made which are controlled by the control device so as to inject fuel when in the single intake valve said single intake open mouth position a time (c) an intake stroke. The fuel supplied to one combustion chamber is fuel that is injected from one injector for the single intake port and passes through the single intake port.

According to this configuration, the engine unit of the present invention is a four-stroke cycle engine unit. The engine unit has a cylinder portion having at least one combustion chamber. A portion of each of the at least one combustion chamber is formed by the inner surface of the cylinder bore. The cylinder part has at least one cylinder intake passage part. The at least one cylinder intake passage portion is connected to at least one external intake passage portion disposed outside the cylinder portion. The air that has flowed into the at least one external intake passage portion is supplied to the at least one combustion chamber through the at least one cylinder intake passage portion and the at least one intake port. The engine unit has a single intake passage portion, a single intake port, a single intake valve, and a single intake port injector provided for each combustion chamber. That is, the engine unit has the same number of single intake passage portions, single intake ports, single intake valves, and single intake port injectors as the number of combustion chambers. At least one cylinder intake passage portion and at least one external intake passage portion include at least one single intake passage portion. The single intake port is formed in the combustion chamber and is connected to the single intake passage portion. The single intake valve opens and closes a single intake port. The single intake port injector is installed in the cylinder intake passage portion or the external intake passage portion. The single intake passage portion includes at least a region from a location where the single intake port injector is installed to the single intake port. The single intake passage portion is an area from the location where the single intake port injector is installed to the single intake port. The single intake passage portion is configured such that air flows pass through without separation or merging. The single inlet injector has a plurality of injection holes for injecting fuel in the form of a mist. The single inlet injector is arranged to inject fuel toward the single inlet. The fuel injection of the single inlet injector is controlled by a control device of the engine unit. The single intake port injector is controlled by the control device so as to inject fuel when the single intake valve is in a position to open the single intake port during the intake stroke.

When the fuel is injected into an air-only space when the single air inlet injector is not attached to the engine unit, the single air inlet injector should satisfy the following two requirements at a certain time immediately after the injection. Consists of. The first requirement is that the fuel on the first plane intersecting the injection direction of the plurality of fuel droplets injected from the single-inlet injector is placed in one circle or one oval. Exist along at least part of the edge of one circle or the one oval. The second requirement is included in the region where the fuel on the first plane is present, and the first region where the outer peripheral end and the inner peripheral end are along at least part of the edge of the one circle or the one oval. The fuel concentration in the second region is higher than the concentration in the second region in contact with the entire inner peripheral edge of the first region on the first plane. That is, the concentration of the outer peripheral portion of the mist-like fuel injected from the single inlet injector is higher than the concentration of the central portion. The region where the fuel on the first plane is present may or may not include the second region. The fuel supplied to one combustion chamber is only the fuel injected from one single intake port injector and passed through one single intake port.

If the engine unit has a plurality of intake ports for one combustion chamber, a plurality of intake passage portions respectively connected to the plurality of intake ports are provided. The engine unit of the present invention has only one intake port for one combustion chamber. Therefore, the diameter of the single intake port of the present invention is larger than that of an engine unit having the same cylinder hole diameter as that of the present invention and having a plurality of intake ports for one combustion chamber. Therefore, the single intake passage portion of the present invention has the same diameter as the cylinder hole of the present invention and a larger diameter than the intake passage portion of the engine unit having a plurality of intake ports for one combustion chamber. Since the diameter of the single intake passage portion is large, the injection angle of the fuel injected from the single intake port injector can be increased. The injection angle is the largest angle among the injection directions of a plurality of fuel droplets injected from a single intake port injector when viewed in a certain direction. Since the injection angle of the fuel injected from the single inlet injector is large, it is possible to reduce the diameter of the injected droplets while suppressing the plurality of injected droplets from contacting each other. Due to the small diameter of the injected droplets, the fuel droplets that have flowed into the combustion chamber are likely to diffuse along the air flow. Thereby, the dispersion | variation in the fuel concentration distribution in a combustion chamber is suppressed. That is, in the engine unit of the present invention, variation in the fuel concentration distribution in the combustion chamber is suppressed as compared with an engine unit having a plurality of intake ports for one combustion chamber.

If the engine unit has two intake ports and one injector for one combustion chamber, two intake passage portions connected to a plurality of intake ports are connected to each other. And an injector is arrange | positioned in the upstream of the flow direction of air rather than the location where two intake passage parts are connected. This injector injects fuel toward two intake ports. On the other hand, the engine unit of the present invention has one intake port and one injector for one combustion chamber. Therefore, the single intake port injector of the present invention can be disposed at a position closer to the intake port than an injector of an engine unit having two intake ports and one injector for one combustion chamber. By disposing the single intake port injector at a position close to the intake port, the injection angle of the fuel injected from the single intake port injector can be further increased. As described above, since the injection angle of the fuel injected from the injector for the single intake port is large, it is possible to reduce the diameter of the injected droplet while suppressing the plurality of injected droplets from contacting each other. can do. Due to the small diameter of the ejected droplets, the fuel droplets that flow into the combustion chamber are likely to diffuse along the air flow. Therefore, in the engine unit of the present invention, variation in the fuel concentration distribution in the combustion chamber is further suppressed as compared with an engine unit having a plurality of intake ports and one injector for one combustion chamber.

If the engine unit has a plurality of intake ports for one combustion chamber, the air flowing into the combustion chamber from the plurality of intake ports collides. On the other hand, since the engine unit of the present invention has only one intake port for one combustion chamber, there is no such air collision. In addition, the intake port can be disposed at a position closer to the central axis of the cylinder hole than an engine unit having a plurality of intake ports for one combustion chamber. Therefore, the air that has flowed into the combustion chamber from the intake port is likely to diffuse uniformly in the circumferential direction of the inner surface of the cylinder hole. Therefore, in the engine unit of the present invention, variation in the fuel concentration distribution in the combustion chamber is further suppressed as compared with an engine unit having a plurality of intake ports for one combustion chamber.

By suppressing the variation in the fuel concentration distribution in the combustion chamber, the concentration at a desired position in the combustion chamber can be increased if the injection direction is adjusted. That is, it is easy to adjust the fuel concentration distribution in the combustion chamber. Therefore, the engine unit of the present invention can improve the degree of freedom in designing the fuel concentration distribution in the combustion chamber.

(2) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
When viewed in the direction of the central axis of the cylinder hole, a straight line passing through the center of the two injection directions forming the largest angle among the injection directions of the plurality of fuel droplets injected from the single inlet injector. The two planes forming the largest angle among the injection directions of the plurality of fuel droplets injected from the single intake port injector when the visible plane is the second plane and viewed in the direction orthogonal to the second plane. If the plane that appears as a straight line passing through the center of the injection direction is the third plane, and the intersection line between the second plane and the third plane is the injection center line, the first plane is one point on the injection center line. Among the plurality of planes passing through the third plane of the region where the fuel on the plane is shortest in the direction parallel to the second plane and where the fuel is on the plane The length in the direction parallel to is the shortest It is a surface.

According to this configuration, the first plane has the smallest variation in the distance from the plurality of injection holes of the single inlet injector to the first region among the plurality of planes passing through one point on the injection center line. It can be.

(3) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The single intake port injector is arranged and configured such that the injection center line passes through the single intake port.

If the fuel is injected so that the injection center line does not pass through the single intake port, even if the fuel is injected so that the first region is annular, the single intake valve and the single intake port The amount of fuel passing through the gap is not uniform in the circumferential direction of the gap. Therefore, the concentration of fuel at a specific position in the combustion chamber tends to increase. On the other hand, the single inlet injector of the present invention injects fuel so that the injection center line passes through the single inlet. Thereby, the dispersion | variation in the fuel which passes through the clearance gap between a single intake valve and a single intake port is suppressed. Therefore, variation in the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(4) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The single inlet injector is arranged and configured such that the injection center line passes through the second region.

(5) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The single intake valve includes an umbrella portion that can block the single intake port, and a stem portion that is connected to the umbrella portion and is partially disposed in the single intake passage portion. When viewed in the direction of the central axis of the cylinder hole, the injector for the single intake port allows the injection center line to pass through the stem portion of the single intake valve at a position where the single intake port is opened. Arranged and configured.

According to this configuration, when viewed in the direction of the center axis of the cylinder hole, the injection center line is likely to pass through the center of the single intake port or the vicinity thereof. Therefore, variation in the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(6) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
When the injector for a single intake port is viewed in a direction orthogonal to the second plane, the stem portion and the umbrella portion of the single intake valve in which the injection center line is in a position to open the single intake port Arranged and configured to pass through.

According to this configuration, when viewed in a direction perpendicular to the second plane, the injection center line passes through the center of the single inlet or the vicinity thereof. Therefore, variation in the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(7) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The single intake port injector is arranged and configured so that the injection center line passes through the stem portion and the umbrella portion of the single intake valve at a position where the single intake port is opened.

¡According to this configuration, the injection center line passes through the center of the single air inlet or the vicinity thereof. Therefore, variation in the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(8) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
One cylinder intake passage portion and one external intake passage portion are provided for each combustion chamber. The engine unit includes at least one throttle valve disposed in the at least one external intake passage portion and upstream of the single intake port injector in the air flow direction in the single intake passage portion.

A volume of one space formed between the throttle valve in the closed position and the intake valve in the closed position is defined as a throttle downstream volume. If the engine unit has a plurality of intake ports and one injector for one combustion chamber, the necessary distance between the injector and the intake port is long as described above. For this reason, the necessary distance between the throttle valve and the intake port is also long. In the engine unit of the present invention, the throttle valve can be disposed at a position closer to the intake port than an engine unit having a plurality of intake ports and one injector for one combustion chamber. Therefore, the throttle downstream volume can be reduced.
If the engine unit has a plurality of intake ports, a plurality of injectors, and a throttle valve for one combustion chamber, the engine unit is positioned downstream of the throttle valve and upstream of the injector. It is necessary to connect a plurality of intake passage portions provided. Therefore, the required distance is long between the throttle valve and the intake port. Therefore, the engine unit of the present invention can arrange the throttle valve closer to the intake port than an engine unit having a plurality of intake ports, a plurality of injectors, and one throttle valve for one combustion chamber. Therefore, the throttle downstream volume of the engine unit of the present invention can be made smaller than the throttle downstream volume of an engine unit having a plurality of intake ports, a plurality of injectors, and a throttle valve for one combustion chamber.
Further, the throttle downstream volume of an engine unit having a plurality of intake ports, at least one injector, and one throttle valve for one combustion chamber is a space formed by connecting a plurality of intake passage portions. On the other hand, the throttle downstream volume of the engine unit of the present invention is a space formed in one intake passage portion. Therefore, the throttle downstream volume of the engine unit of the present invention can be further reduced as compared with the throttle downstream volume of an engine unit having a plurality of intake ports, at least one injector, and one throttle valve for one combustion chamber. .
If the engine unit has one throttle valve for a plurality of combustion chambers, the throttle downstream volume is a space formed by connecting a plurality of intake passage portions provided for each combustion chamber. On the other hand, when the engine unit of the present invention has a plurality of combustion chambers, one throttle valve is provided for each combustion chamber. Therefore, the throttle downstream volume of the engine unit of the present invention is a space formed in one intake passage portion. Therefore, the throttle downstream volume of the engine unit of the present invention can be made smaller than the throttle downstream volume of the engine unit having one throttle valve for a plurality of combustion chambers.
As the throttle downstream volume is smaller, the pressure in the intake passage when the intake port is open is more susceptible to negative pressure in the combustion chamber (pressure lower than atmospheric pressure). That is, the smaller the throttle downstream volume, the lower the pressure in the intake passage during the intake stroke. Thereby, the evaporation of the fuel injected during the intake stroke is promoted. In addition, the air flowing into the combustion chamber from the intake port is likely to diffuse uniformly in the circumferential direction of the inner surface of the cylinder hole. Therefore, variation in the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(9) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
In the single inlet injector, the first region on the first plane is an annular shape along the entire circumference of the edge of the one circle or the one oval, or the one circle or 90 on the first plane which is non-annular along a part of the edge of the one oval, and whose circumferential center of the outer circumferential end has both ends passing through both circumferential ends of the non-circular first region. Configured to be radially outside of the arc of °.

According to this configuration, the first region is annular or non-annular with a long circumferential length. Therefore, it is possible to inject a sufficient amount of fuel from the single inlet injector while reducing the diameter of the ejected droplets so that the plurality of ejected droplets can be prevented from coming into contact with each other.

(10) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The single intake valve includes an umbrella portion that can block the single intake port, and a stem portion that is connected to the umbrella portion and is partially disposed in the single intake passage portion. The single inlet injector is disposed at a position where the shortest distance between the plurality of injection holes and the center of the single inlet is smaller than three times the diameter of the single inlet. Is done.

According to this configuration, the distance from the plurality of injection holes of the single inlet injector to the single inlet is relatively short. Therefore, the injection angle of the fuel injected from the single inlet injector can be reliably increased. As described above, since the injection angle of the fuel injected from the injector for the single intake port is large, it is possible to reduce the diameter of the injected droplet while suppressing the plurality of injected droplets from contacting each other. can do. Due to the small diameter of the ejected droplets, it is possible to further suppress variations in the fuel concentration distribution in the combustion chamber. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(11) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The single inlet injector is disposed at a position where the shortest distance between the plurality of injection holes and the center of the single inlet is smaller than twice the diameter of the single inlet. Is done.

According to this configuration, since the distance from the plurality of injection holes of the single intake port injector to the single intake port is further shorter, the injection angle of the fuel injected from the single intake port injector can be further increased. . For this reason, it is possible to reduce the diameter of the ejected droplets while suppressing the plurality of ejected droplets from contacting each other. Thereby, the dispersion | variation in the concentration distribution of the fuel in a combustion chamber can be suppressed more reliably. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

(12) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.
The cylinder portion has at least one exhaust port formed in the at least one combustion chamber. At least one exhaust port is provided for one combustion chamber. The diameter of the intake port is larger than the diameter of the exhaust port.

According to this configuration, since the diameter of the single intake port is relatively large, the diameter of the single intake passage portion is also relatively large. As described above, since the diameter of the single intake passage portion is large, the injection angle of the fuel injected from the single intake port injector can be increased. Since the injection angle of the fuel injected from the single inlet injector is large, it is possible to reduce the diameter of the injected droplets while suppressing the plurality of injected droplets from contacting each other. Due to the small diameter of the ejected droplets, it is possible to further suppress variations in the fuel concentration distribution in the combustion chamber. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be further improved.

<Definition of terms>
In the present invention, the “intake passage section” means a structure surrounding a space through which air supplied to the combustion chamber passes.

In the present invention, the “single inlet” is not a space but a structure. In the case where the portion that is in contact with the single intake valve and is blocked by the single intake valve is cylindrical, the “single intake port” in the present invention is in contact with the single intake valve and is blocked by the single intake valve. It is an end closer to the combustion chamber among both ends of the cylindrical region in the cylinder axis direction. That is, in the present invention, the “single intake port” is an annular linear portion that comes into contact with the single intake valve and is blocked by the single intake valve. The “exhaust port” in the present invention has the same definition.

A part of each of the at least one combustion chamber of the present invention is formed by the inner surface of the cylinder hole. When the engine unit of the present invention has a plurality of fuel chambers, a cylinder hole is provided for each of the plurality of combustion chambers. That is, the number of cylinder holes and combustion chambers of the engine unit is the same.

In the present invention, one intake port, one intake valve, and one injector are provided for each combustion chamber. That is, the engine unit of the present invention does not have a plurality of intake ports for one combustion chamber. The engine unit of the present invention does not have a plurality of intake valves for one combustion chamber. The engine unit of the present invention does not have a plurality of injectors for one combustion chamber.

In the present invention, “at least one cylinder intake passage portion and at least one external intake passage portion include at least one single intake passage portion” means at least one cylinder intake passage portion and at least one external intake passage. It means that at least one single intake passage part is included in one element consisting of parts. The single intake passage portion may be included only in at least one cylinder intake passage portion. A portion of the single intake passage portion may be included in at least one cylinder intake passage portion, and another portion of the single intake passage portion may be included in at least one external intake passage portion. The number of cylinder intake passage portions may be the same as or different from that of the single intake passage portion. The number of external intake passage portions may be the same as or different from that of the single intake passage portion. The number of cylinder intake passage portions may be the same as or different from that of the external intake passage portions.

The single intake passage portion of the present invention is a region from a place where a single intake port injector is installed to a single intake port. In the present invention, the “region from the place where the single inlet injector is installed to the single inlet” refers to the entire area where the single inlet injector is in contact with the cylinder intake passage portion or the external intake passage portion. May be included. In other words, the “region from the place where the single intake port injector is installed to the single intake port” is the area where the single intake port injector is in contact with the cylinder intake passage portion or the external intake passage portion. A position farthest from the single intake port in the flow direction of the exhaust gas may be included.

In the present invention, to inject fuel in the form of a mist means to inject a plurality of small droplets of fuel.

In the present invention, the “injection direction of a plurality of fuel droplets injected from a single intake port injector” refers to the injection direction of a plurality of droplets injected from a single intake port injector in a single injection. It is. More specifically, it is the ejection direction of the droplets when a plurality of droplets are ejected from the single inlet injector, respectively. In other words, the fuel injection direction can be represented by a linear vector starting from the single inlet injector. Even when the movement direction of the droplet changes due to the influence of the air flow, the ejection direction of the droplet does not change.

In the present invention, the fuel on the first plane may include vaporized fuel or only liquid fuel.
In the present invention, the fact that the fuel on the first plane is present in one circle or one oval means that the fuel on the first plane out of the fuel injected from the single inlet injector by one injection process. It may be that all of the fuel, including the vaporized fuel present in is present in one circle or one oval. In the present invention, the fact that the fuel on the first plane is present in one circle or one oval means that the fuel on the first plane out of the fuel injected from the single inlet injector by one injection process. It may be that all of the liquid fuel present in is present in one circle or one oval.

In the present invention, the region where the fuel on the first plane exists is a region surrounding the fuel on the first plane. The region where the fuel exists on the first plane may include a gap between the droplets.

In the present invention, when the outer peripheral end of the first region is along a part of the edge of one circle, the inner peripheral end of the first region is along a part of the edge of the one circle. In the present invention, when the outer peripheral end of the first region is along the entire circumference of the edge of one circle, the inner peripheral end of the first region is also along the entire circumference of the edge of the one circle.
In the present invention, when the outer peripheral end of the first region is along a part of the edge of one oval, the inner peripheral end of the first region is along a part of the edge of the one oval. In the present invention, when the outer peripheral end of the first region is along the entire circumference of one oval edge, the inner peripheral end of the first region is also along the entire circumference of the one oval edge.

The outer peripheral edge of the first region of the present invention may not coincide with at least part of the edge of the circle or oval as long as it is along at least part of the edge of the circle or oval. The outer peripheral edge of the first region of the present invention may not be parallel to at least part of the edge of the circle or oval as long as it is along at least part of the edge of the circle or oval.
The inner peripheral edge of the first region of the present invention may not be parallel to at least part of the edge of the circle or oval as long as it is along at least part of the edge of the circle or oval.

In the present invention, when the first region is non-annular, the first region is a region surrounded by the outer peripheral end of the first region, the inner peripheral end of the first region, and both ends in the circumferential direction of the first region. is there. Both ends in the circumferential direction of the first region may be linear, for example, or may be curved to bulge out of the first region.

In the present invention, when the first region is non-annular, the second region includes at least a region surrounded by the entire inner peripheral end of the first region and a line segment connecting both circumferential ends of the inner peripheral end of the first region. Including. The second area may be constituted only by this area.

In the present invention, the oval is an annular shape composed of only a curve or a curve and a line segment and having a smooth convex shape. The oval may be an ellipse formed by a set of points such that the sum of distances from two fixed points is constant. The oval may have a shape similar to an ellipse. The oval may be shaped like a chicken egg. The oval may have a shape formed by two semicircles and two line segments, such as an athletics track. When the first region is non-annular, if the outer peripheral end and the inner peripheral end of the first region are shaped along a line that can form an oval, the outer region and the inner peripheral end of the first region It may not be possible to specify the overall shape.

The “concentration of fuel in the first region” in the present invention may be the surface density of the fuel in the first region, that is, the mass of fuel per unit area of the first region. Alternatively, the “concentration of fuel in the first region” may be calculated by extracting a value on the first plane from the distribution of the mass of fuel per unit volume in a space including the first region. Good. That is, the “concentration of fuel in the first region” may be the mass of fuel per unit volume in the first region.
The definition of “concentration of fuel in the second region” in the present invention is the same as the definition of “concentration of fuel in the first region” described above.

In the present invention, the “concentration of the fuel in the first region” and the “concentration of the fuel in the second region” may be the concentration of the fuel containing the vaporized fuel or the concentration of the fuel not containing the vaporized fuel. May be. In the present invention, the “first plane” is preferably set at a position close to the single inlet injector that allows most of the injected fuel to reach without vaporization. In this case, whether or not the “concentration of the fuel in the first region” and the “concentration of the fuel in the second region” include vaporized fuel depends on whether the “concentration of the fuel in the first region” and “the fuel concentration in the inner peripheral region”. There is almost no effect on the magnitude relationship of “density”.

In the present invention, “the concentration of fuel in the first region is higher than the concentration of fuel in the second region” means that the average value of the mass of fuel per unit volume or unit area of the first region is that of the second region. It means larger than the average value of the mass of fuel per unit volume or unit area.

The single intake port injector of the present invention is controlled by the control device so as to inject fuel when the single intake valve is in a position to open the single intake port during the intake stroke. Here, the time of the intake stroke is the time of the intake stroke of the combustion chamber connected to the single intake passage portion provided with the single intake port injector.

In the description of “a plane that looks like a straight line passing through the center of the two injection directions forming the largest angle among the injection directions of the fuel injected from the injector for the single intake port when viewed in the direction of the central axis of the cylinder hole” “When viewed in the direction of the central axis of the cylinder hole” means when viewed in the direction of the central axis of the cylinder hole of the combustion chamber connected to the single intake passage portion provided with this single intake port injector. Means. Similarly, “The injector for the single intake port is arranged so that the injection center line passes through the stem portion of the single intake valve at the position where the single intake port is opened when viewed in the direction of the central axis of the cylinder hole. "When viewed in the direction of the central axis of the cylinder hole" in the description of "configured" means that the cylinder hole of the combustion chamber connected to the single intake passage portion provided with this single intake port injector It means when viewed in the direction of the central axis.

In the present invention, “when viewed in the direction of the central axis of the cylinder hole” means when the engine unit is viewed in the direction of the central axis of the cylinder hole. More specifically, it means a case where it is assumed that some members of the engine unit are seen through.
The definition of “when viewed in a direction perpendicular to the second plane” in the present invention is the same as described above.

In the present invention, “the injection center line passes through a single intake port” means that the injection center line is connected to a single intake passage portion provided with a single intake port injector having the injection center line. Means passing through a single inlet.

In the present invention, “the injection center line passes through the stem portion of a single intake valve” means that the injection center line is connected to a single intake passage portion provided with a single intake port injector having the injection center line. It means passing through a single intake valve that opens and closes a single intake port.
In the present invention, “the injection center line passes through the stem portion of the single intake valve at the position where the single intake port is opened” means any position where the single intake port is opened within the movable range of the single intake valve. This means that the injection center line passes through the stem portion when there is a single intake valve. If there is a single intake valve at any position that opens a single intake port within the movable range of the single intake valve, and the injection center line passes through the stem, the single intake valve within the movable range of the single intake valve The injection center line may not pass through the stem portion at other positions where the intake port is opened.

In the present invention and the present specification, at least one (one) of a plurality of options includes all combinations conceivable from the plurality of options. At least one (one) of the plurality of options may be any one of the plurality of options, or may be all of the plurality of options. For example, at least one of A, B and C may be A alone, B alone, C alone, A and B, A and C It may be B, C, A, B and C.

In the claims, the number of a certain component is not clearly specified, and when it is displayed as a single number when translated into English, the present invention may have a plurality of these components. The present invention may have only one of these components.

In the present invention, including, comprising, having and their derivatives are used with the intention of encompassing additional items in addition to the listed items and their equivalents. ing.
In the present invention, the terms mounted, connected, coupled, and supported are used in a broad sense. Specifically, it includes not only direct attachment, connection, coupling and support, but also indirect attachment, connection, coupling and support. Further, connected and coupled are not limited to physical or mechanical connections / couplings. They also include direct or indirect electrical connections / couplings.

Unless defined otherwise, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed as having a meaning consistent with the meaning in the context of the relevant technology and this disclosure, idealized or overly formal It is not interpreted in a sense.

In this specification, the term “preferred” is non-exclusive. “Preferred” means “preferably but not limited to”. In the present specification, the configuration described as “preferable” has at least the above-described effect obtained by the configuration of claim 1. Further, in this specification, the term “may” is non-exclusive. “May” means “may be, but is not limited to”. In the present specification, a configuration described as “may” at least exhibits the above-described effect obtained by the configuration of claim 1.

In the present invention, it is not limited to combine the configurations according to the other viewpoints described above. Before describing in detail embodiments of the present invention, it is to be understood that the present invention is not limited to the details of the arrangement and arrangement of components set forth in the following description or illustrated in the drawings. The present invention is also possible in embodiments other than those described below. The present invention is also possible in embodiments in which various modifications are made to the embodiments described later. In addition, the present invention can be implemented by appropriately combining the later-described embodiments and modification examples.

According to the engine unit of the present invention, the degree of freedom in designing the fuel concentration distribution in the combustion chamber can be improved.

FIG. 1A is a view of the engine unit of the embodiment as viewed in the direction of the central axis of the cylinder hole. FIG.1 (b) is sectional drawing which cut | disconnected the engine unit of embodiment by plane S1 shown to Fig.1 (a). FIG.1 (c) is a figure which shows the injection state of the fuel of the injector for single intake ports of the engine unit of embodiment. FIG.1 (d) is a figure which shows an example of the fuel on the plane S1 shown in FIG.1 (c). FIG.1 (e) is a figure which shows the other example of the fuel on the plane S1 shown in FIG.1 (c). FIG. 2 is a cross-sectional view of an engine unit as a specific example of the embodiment. 3A is a view of the combustion chamber of the engine unit of the specific example of the embodiment as viewed in the direction of the central axis of the cylinder hole, and FIG. 3B is a line III-III in FIG. It is sectional drawing. FIG. 4A is a diagram showing the fuel injection state of the single inlet injector of the engine unit of the specific example of the embodiment, and FIG. 4B is a plan view on the plane S1 shown in FIG. It is a figure which shows concentration distribution of the fuel. FIG. 5A is a diagram showing a fuel injection state of a conventional single inlet injector, and FIG. 5B is a fuel concentration distribution on a plane S801 shown in FIG. 5A. FIG. FIG. 6 is a graph showing the fuel concentration distribution on the plane S1 shown in FIG. 4A and the fuel concentration distribution on the plane S801 shown in FIG. 5A. 7 (a) to 7 (c) are cross-sectional views showing the behavior of a plurality of droplets of injected fuel in the engine unit of the specific example of the embodiment. FIGS. 7 (d) to 7 (f) FIGS. 7A to 7C are views in the direction of the central axis of the cylinder hole. FIGS. 8 (a) to 8 (c) are diagrams showing the behavior of a plurality of droplets of injected fuel in an engine unit when a conventional single intake port injector is used, and FIGS. FIG. 8 (f) is a view of FIGS. 8 (a) to 8 (c) as viewed in the direction of the central axis of the cylinder hole. FIG. 9A is a view of the combustion chamber of the conventional engine unit as viewed in the direction of the central axis of the cylinder hole, and FIG. 9B is a cross-sectional view taken along line BB of FIG. 9A. FIG. 9C is a cross-sectional view taken along the line CC of FIG. 9A. It is a figure which shows the injection state of the fuel of the injector for single inlets of the example of a change. It is sectional drawing of the engine unit with which the injector for single inlets of the example of a change was mounted | worn. It is a figure which shows the 1st area | region and 2nd area | region on the 1st plane of the injector for single inlets of the example of a change. It is a figure which shows the 1st area | region and 2nd area | region on the 1st plane of the injector for single inlets of the example of a change.

<< Embodiment of the Invention >>
Embodiments of the present invention will be described below with reference to FIGS. 1 (a) to 1 (e). The engine unit 1 of the present embodiment is a four-stroke cycle engine unit. As shown in FIGS. 1 (a) and 1 (b), the engine unit 1 includes a cylinder portion 4, at least one external intake passage portion 3, at least one intake valve 22, and at least one injector 23. And a control device 50. The cylinder portion 4 has at least one combustion chamber 11, at least one intake port 12, and at least one cylinder intake passage portion 21. A part of each of the at least one combustion chamber 11 is formed by the inner surface of the cylinder hole 10. At least one intake port 12 is formed in at least one combustion chamber 11. At least one cylinder intake passage portion 21 is connected to at least one intake port 12. The air that has flowed into the at least one cylinder intake passage portion 21 is supplied from at least one intake port 12 to at least one combustion chamber 11. The at least one external intake passage portion 3 is disposed outside the cylinder portion 4 and is connected to at least one cylinder intake passage portion 21. The air that has flowed into the at least one external intake passage portion 3 is supplied to at least one cylinder intake passage portion 21. The at least one intake valve 22 is configured to be movable between a position where the at least one intake port 12 is opened and a position where the at least one intake port is closed. Each of the at least one injector 23 has a plurality of injection holes capable of injecting fuel in the form of a mist. The at least one injector 23 is installed in the cylinder intake passage portion 21 or the external intake passage portion 3 such that the plurality of injection holes are located in the cylinder intake passage portion 21 or the external intake passage portion 3. The control device 50 controls fuel injection of at least one injector 23.

One intake port 12, one intake valve 22, and one injector 23 are provided for each combustion chamber 11, and constitute a single intake port 12, a single intake valve 22, and a single intake port injector 23, respectively. At least one cylinder intake passage portion 21 and at least one external intake passage portion 3 include at least one single intake passage portion 20. One single intake passage portion 20 is provided for each combustion chamber 11. The single intake passage portion 20 is a region from the location where the single intake port injector 23 is installed to the single intake port 12. The single intake passage portion 20 is configured to pass through the inside without being separated or joined together.

The single intake port injector 23 is arranged to inject fuel toward the single intake port 12. The single intake port injector 23 has the following two requirements at a certain time immediately after injection when fuel is injected into a space only in the atmosphere when the single intake port injector 23 is not attached to the engine unit 1. Configured to meet. As shown in FIG. 1C, one plane that intersects the injection directions of a plurality of fuel droplets injected from the single inlet injector 23 is defined as a first plane S1. The first requirement is that, as shown in FIG. 1 (d) or FIG. 1 (e), the fuel on the first plane S1 is contained in one circle or one oval. Exist along at least part of the edge of the two oval. The second requirement is included in a region where the fuel exists on the first plane S1, and an outer peripheral end and an inner peripheral end of the first plane along at least a part of the edge of the one circle or the one oval. The fuel concentration in the region A1 is higher than the fuel concentration in the second region A2 in contact with the entire inner peripheral end of the first region A1 on the first plane S1. That is, the concentration of the outer peripheral portion of the mist-like fuel F1 injected from the single intake port injector 23 is higher than the concentration of the central portion. The fuel supplied to one combustion chamber 11 is only the fuel injected from one single intake port injector 23 and passed through one single intake port 12.

If the engine unit has a plurality of intake ports for one combustion chamber, a plurality of intake passage portions respectively connected to the plurality of intake ports are provided. The engine unit 1 of this embodiment has only one intake port 12 for one combustion chamber 11. Therefore, the single intake port 12 of the present embodiment has a larger diameter than the intake port of an engine unit having the same cylinder hole diameter as that of the present embodiment and having a plurality of intake ports for one combustion chamber. Therefore, the diameter of the single intake passage portion 20 of this embodiment is the same as that of the engine passage having the same cylinder hole diameter as that of this embodiment and having a plurality of intake ports for one combustion chamber. large. Since the diameter of the single intake passage portion 20 is large, the injection angle of the fuel injected from the single intake port injector 23 can be increased. The injection angle is the largest angle among the injection directions of a plurality of fuel droplets injected from a single intake port injector when viewed in a certain direction. Since the injection angle of the fuel injected from the single inlet injector 23 is large, it is possible to reduce the diameter of the injected droplets while suppressing the plurality of injected droplets from contacting each other. . Due to the small diameter of the injected droplets, the fuel droplets that have flowed into the combustion chamber 11 are likely to diffuse along the air flow. Thereby, the variation in the fuel concentration distribution in the combustion chamber 11 is suppressed. That is, in the engine unit 1 of the present embodiment, variation in the fuel concentration distribution in the combustion chamber 11 is suppressed as compared with the engine unit 1 having a plurality of intake ports 12 for one combustion chamber 11.

If the engine unit has two intake ports and one injector for one combustion chamber, two intake passage portions connected to a plurality of intake ports are connected to each other. And an injector is arrange | positioned in the upstream of the flow direction of air rather than the location where two intake passage parts are connected. This injector injects fuel toward two intake ports. On the other hand, the engine unit 1 of the present embodiment has one intake port 12 and one injector 23 for one combustion chamber 11. Therefore, the single intake port injector 23 of the present embodiment can be disposed at a position closer to the intake port than an injector of an engine unit having two intake ports and one injector for one combustion chamber. By disposing the single intake port injector 23 at a position close to the intake port 12, the injection angle of the fuel injected from the single intake port injector 23 can be further increased. As described above, since the injection angle of the fuel injected from the single inlet injector 23 is large, the diameter of the injected droplets can be reduced while suppressing the plurality of injected droplets from contacting each other. Can be small. Due to the small diameter of the injected droplets, the fuel droplets that flow into the combustion chamber 11 are likely to diffuse along the air flow. Therefore, in the engine unit 1 of the present embodiment, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed as compared with an engine unit having a plurality of intake ports and one injector for one combustion chamber. .

If the engine unit has a plurality of intake ports for one combustion chamber, the air flowing into the combustion chamber from the plurality of intake ports collides. On the other hand, since the engine unit 1 of the present embodiment has only one intake port 12 for one combustion chamber 11, there is no such air collision. In addition, the intake port can be disposed at a position closer to the central axis of the cylinder hole than an engine unit having a plurality of intake ports for one combustion chamber. Therefore, the air that has flowed into the combustion chamber 11 from the intake port 12 tends to diffuse uniformly in the circumferential direction of the inner surface of the cylinder hole 10. Therefore, in the engine unit 1 of the present embodiment, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed as compared with an engine unit having a plurality of intake ports for one combustion chamber.

By suppressing the variation in the fuel concentration distribution in the combustion chamber 11, if the injection direction is adjusted, the concentration at a desired position in the combustion chamber 11 can be increased. That is, it is easy to adjust the fuel concentration distribution in the combustion chamber 11. Therefore, the engine unit 1 of the present embodiment can improve the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11.

<< Specific Examples of Embodiments of the Present Invention >>
Next, a specific example of the engine unit 1A according to the embodiment of the present invention will be described with reference to FIGS. Basically, the engine unit 1A of the specific example of the embodiment of the present invention has all the features of the engine unit 1 of the embodiment of the present invention described above. A description of the same parts as those of the engine unit 1 of the embodiment of the present invention described above will be omitted.

Engine unit 1A is mounted on, for example, a straddle-type vehicle. A saddle riding type vehicle refers to any vehicle that rides in a state where a rider straddles a saddle. The saddle riding type vehicle includes a motorcycle, a tricycle, a four-wheel buggy (ATV: All Terrain Vehicle), a water bike, a snowmobile, and the like. Motorcycles include scooters, motorbikes, and mopeds. The engine unit 1A may be mounted on an automobile. The engine unit 1A may be mounted on a vehicle or a device other than an automobile and a saddle type vehicle.

2, the engine unit 1A includes an engine body 2, one external intake passage portion 3, one external exhaust passage portion (not shown), and a control device 50. The external intake passage portion 3 and the external exhaust passage portion are connected to the engine body 2. The control device 50 controls the operation of the engine unit 1A. The control device 50 is connected to various sensors provided in the saddle riding type vehicle.

The specific example engine body 2 is a single cylinder engine. The engine body 2 is a 4-stroke engine. The 4-stroke engine is an engine that repeats an intake stroke, a compression stroke, a combustion stroke (expansion stroke), and an exhaust stroke. The engine body 2 is a gasoline engine. The cooling method of the engine body 2 is not particularly limited.

The engine body 2 has a cylinder part 4 having one cylinder hole 10 and a crankcase part (not shown). Although illustration is omitted, a crankshaft is accommodated in the crankcase portion. The center axis of the crankshaft is a direction orthogonal to the paper surface of FIG. The cylinder part 4 and the crankcase part are arranged on the central axis Cy 1 of the cylinder hole 10. Hereinafter, the central axis Cy1 of the cylinder hole 10 is referred to as a cylinder axis Cy1.

The cylinder axis Cy1 is not a line segment that exists only in the area where the cylinder hole 10 exists, but is a straight line that extends indefinitely. The cylinder axis Cy1 is parallel to the vertical direction of the paper surface of FIG. The vertical direction of the paper surface may or may not coincide with the vertical direction of the saddle riding type vehicle on which the engine unit 1A is mounted. In the saddle riding type vehicle, the cylinder portion 4 constitutes an upper portion or a front portion of the engine body 2. The cylinder axis Cy1 may be parallel to the vertical direction of the saddle riding type vehicle, or may be inclined at an angle of 45 ° or less with respect to the vertical direction of the saddle riding type vehicle. The cylinder axis Cy1 may be parallel to the front-rear direction of the straddle-type vehicle, or may be inclined at an angle of less than 45 ° with respect to the front-rear direction of the straddle-type vehicle.

The cylinder part 4 has a cylinder body 5, a cylinder head 6, and a head cover 7. The cylinder body 5, the cylinder head 6 and the head cover 7 are connected in this order on the cylinder axis Cy1. The cylinder body 5 is connected to the crankcase part. In FIG. 2, the cylinder body 5, the cylinder head 6 and the head cover 7 are members independent of each other. However, at least two of the cylinder body 5, the cylinder head 6, and the head cover 7 may be integrally formed.

The cylinder hole 10 is formed inside the cylinder body 5. A piston 8 is slidably accommodated in the cylinder hole 10. The piston 8 is connected to the crankshaft via a connecting rod (not shown).

The cylinder part 4 has one combustion chamber 11. The combustion chamber 11 includes a lower surface of the cylinder head 6 in FIG. 2, an inner surface of the cylinder hole 10, and an upper surface of the piston 8 in FIG. 2. That is, a part of the combustion chamber 11 is formed by the inner surface of the cylinder hole 10.

As shown in FIG. 3A, the combustion chamber 11 has one intake port 12 and one exhaust port 13 formed therein. The intake port 12 is an example of a single intake port of the present invention. The intake port 12 and the exhaust port 13 are formed on the lower surface of the cylinder head 6 in FIG. The intake port 12 and the exhaust port 13 are circular. The diameter of the intake port 12 is larger than the diameter of the exhaust port 13. When viewed in the direction of the cylinder axis Cy1, the line segment connecting the center P1 of the intake port 12 and the center P2 of the exhaust port 13 passes through the cylinder axis Cy1 or the vicinity thereof.

As shown in FIG. 3A, the combustion chamber 11 has one spark plug insertion port 14 formed therein. The spark plug insertion port 14 has a circular shape. The diameter of the spark plug insertion port 14 is smaller than the diameters of the intake port 12 and the exhaust port 13. The spark plug insertion port 14 is disposed between the exhaust port 13 and the intake port 12 in the circumferential direction centered on the cylinder axis Cy1.

The engine unit 1A has a spark plug (not shown) inserted into the spark plug insertion port 14. The tip of the spark plug is disposed in the combustion chamber 11. The tip of the spark plug generates a spark discharge. By this spark discharge, the air-fuel mixture in the combustion chamber 11 is ignited. In the present specification, the air-fuel mixture is an air-fuel mixture. The spark plug is connected to an ignition coil (not shown). The ignition coil stores electric power for causing spark discharge of the spark plug. As the air-fuel mixture burns in the combustion chamber 11, the piston 8 moves and a crankshaft (not shown) rotates.

As shown in FIG. 2, one cylinder intake passage portion 21 is formed in the cylinder head 6. The cylinder intake passage portion 21 is connected to the intake port 12 of the combustion chamber 11. The cylinder intake passage portion 21 is connected to the external intake passage portion 3. The external intake passage portion 3 may be composed of a plurality of independent parts. The air flowing into the external intake passage portion 3 passes through the cylinder intake passage portion 21 and is supplied to the combustion chamber 11. The external intake passage portion 3 may be connected to an air cleaner or may include an air cleaner.

As shown in FIG. 2, a cylinder exhaust passage 31 is formed in the cylinder head 6. The cylinder exhaust passage portion 31 is connected to the exhaust port 13 of the combustion chamber 11. Gas (exhaust gas) generated by the combustion of the air-fuel mixture in the combustion chamber 11 is discharged to the cylinder exhaust passage portion 31. The cylinder exhaust passage portion 31 is connected to an external exhaust passage portion (not shown).

As shown in FIG. 2, the engine unit 1 A has one intake valve 22 that opens and closes the intake port 12. The specific intake valve 22 is an example of a single intake valve of the present invention. The intake valve 22 has an umbrella portion 22a and a stem portion 22b. As shown in FIGS. 2, 3A, and 3B, the umbrella portion 22a is formed in a substantially conical shape. The diameter (maximum diameter) of the umbrella portion 22 a is substantially the same as the diameter of the air inlet 12. Umbrella part 22a is constituted so that inlet 12 can be closed. When the intake valve 22 closes the intake port 12, at least a part of the umbrella portion 22 a is disposed in the cylinder intake passage portion 21. As shown in FIG. 2, the end surface of the umbrella portion 22 a facing the combustion chamber 11 is parallel to a plane S 4 that includes the entire circumference of the intake port 12. The plane S4 is not a physically existing plane but a virtual plane.

The stem portion 22b is connected to the umbrella portion 22a. Specifically, the stem portion 22b is connected to the central portion of the umbrella portion 22a. The stem portion 22b is connected to a surface of the umbrella portion 22a facing the cylinder intake passage portion 21. A part of the stem portion 22 b is disposed in the cylinder intake passage portion 21. The stem portion 22b extends linearly. An axis passing through the center of the stem portion 22b is defined as a center axis Cv1. The central axis Cv1 of the stem portion 22b is orthogonal to the plane S4 including the entire circumference of the intake port 12. The central axis Cv1 of the stem portion 22b is not a line segment that exists only in the region where the stem portion 22b exists, but is a straight line extending infinitely. The central axis Cv1 of the stem portion 22b passes through the center P1 of the intake port 12. As shown in FIG. 3A, when viewed in the direction of the cylinder axis Cy1, the central axis Cv1 of the stem portion 22b passes through the cylinder axis Cy1.

The intake valve 22 opens and closes the intake port 12 by reciprocating along the central axis Cv1 of the stem portion 22b. The intake valve 22 indicated by a two-dot chain line in FIG. 2 is in a closed position for closing (closing) the intake port 12. The intake valve 22 shown by a solid line in FIGS. 2, 3A and 3B is in an open position where the intake port 12 is opened (opened). The open position of the intake valve 22 is a position where at least a part of the umbrella portion 22 a is disposed in the combustion chamber 11 and a gap is generated between the umbrella portion 22 a and the intake port 12. The open position of the intake valve 22 is not limited to the position indicated by the solid line. The open position of the intake valve 22 includes all positions other than the closed position in the movable range of the intake valve 22. The intake valve 22 is driven by a valve mechanism (not shown) and a spring (not shown) accommodated in the cylinder part 4. The valve mechanism operates as the crankshaft rotates. The intake valve 22 is moved from the closed position to the open position by the valve operating mechanism, and is moved from the open position to the closed position by the spring.

The intake valve 22 is in the open position for at least part of the intake stroke. The intake stroke is a period in which the piston 8 descends from the exhaust top dead center to the intake bottom dead center and the volume of the combustion chamber 11 increases. The timing at which the position of the intake valve 22 changes from the closed position to the open position may be slightly before the start of the intake stroke, may be the same as the start of the intake stroke, or slightly from the start of the intake stroke. It may be later. The timing at which the intake valve 22 moves from the open position to the closed position may be slightly after the end of the intake stroke, may be the same as the end of the intake stroke, or slightly before the end of the intake stroke. It may be. The intake valve 22 may be in the open position over the entire period of the intake stroke, or may be in the open position over a portion of the intake stroke.

As shown in FIG. 2, the engine unit 1 A has one exhaust valve 32 that opens and closes the exhaust port 13. Similarly to the intake valve 22, the exhaust valve 32 also includes an umbrella portion and a stem portion. The basic shape and configuration of the exhaust valve 32 are the same as those of the intake valve 22. The diameter of the umbrella part of the exhaust valve 32 is smaller than the diameter of the umbrella part 22 a of the intake valve 22. The exhaust valve 32 is in the open position over at least a portion of the exhaust stroke. Similarly to the intake valve 22, the exhaust valve 32 is also driven by a valve operating mechanism (not shown). The valve mechanism may include a variable valve timing device that changes the opening / closing timing of at least one of the intake valve 22 and the exhaust valve 32.

As shown in FIG. 2, the engine unit 1 A has one throttle valve 24. The throttle valve 24 is disposed in the external intake passage portion 3. By changing the opening of the throttle valve 24, the amount of air supplied into the combustion chamber 11 is changed. The throttle valve 24 indicated by a broken line in FIG. 2 is in the closed position. When the throttle valve 24 is in the closed position, a slight air flow is allowed. A bypass passage portion that bypasses the throttle valve 24 may be connected to the external intake passage portion 3. A valve may be disposed in the bypass passage portion. The throttle valve 24 may be connected to a throttle operation unit (not shown) without using the control device 50. In this case, the opening degree of the throttle valve 24 is changed by the driver operating the throttle operation unit. The throttle valve 24 is a valve whose electronic opening can be controlled, and may be controlled by the control device 50. In this case, the control device 50 controls the throttle valve 24 based on a signal from a sensor that detects the operation state of the throttle operation unit.

2, 3 (a), and 3 (b), the flow of air in the combustion chamber 11 during the intake stroke and when the intake valve 22 is in the open position is schematically shown by arrows. . 3B is a cross-sectional view taken along the line III-III in FIG. 3A, the arrow in FIG. 3B also represents the air flow that appears before the cross section. During the intake stroke, the piston 8 is lowered, so that the pressure in the combustion chamber 11 is lowered. The air in the external intake passage portion 3 and the cylinder intake passage portion 21 is drawn into the combustion chamber 11 by the negative pressure of the combustion chamber 11 (pressure lower than atmospheric pressure). The air flows into the combustion chamber 11 through an annular gap between the umbrella portion 22 a of the intake valve 22 and the intake port 12. The air flowing into the combustion chamber 11 first flows along the inner surface of the combustion chamber 11. The air that diffuses along the inner surface of the combustion chamber 11 is diffused substantially uniformly in the circumferential direction of the inner surface of the cylinder hole 10.

2 and 3A, the engine unit 1A has one injector 23. The injector 23 is an example of a single intake port injector according to the present invention. The injector 23 is installed in the external intake passage portion 3. The injector 23 is disposed downstream of the throttle valve 24 in the air flow direction. The injector 23 may be installed in the cylinder intake passage portion 21. Of the external intake passage portion 3 and the cylinder intake passage portion 21, a portion downstream of the installation position of the injector 23 in the air flow direction constitutes a single intake passage portion 20. The single intake passage portion 20 is configured to pass through the inside thereof without being separated or joined together.

The injector 23 is arranged and configured to inject fuel toward the intake port 12. A plurality of injection holes are formed at the tip of the injector 23. The injector 23 injects the mist-like fuel F11 from the plurality of injection holes. The plurality of injection holes are in the cylinder intake passage portion 21. The plurality of injection holes may be in the external intake passage portion 3 or may be at the boundary between the cylinder intake passage portion 21 and the external intake passage portion 3. The injector 23 is arranged so as to inject fuel in the single intake passage portion 20.

The injector 23 injects fuel during the intake stroke and when the intake valve 22 is in the open position. The injection of fuel from the injector 23 is controlled by the control device 50. The engine unit 1A includes a fuel tank (not shown) that stores fuel supplied to the injector 23, and a fuel pump disposed in the fuel tank. The fuel pump is connected to the injector 23 via a fuel hose (not shown). The fuel in the fuel tank is supplied to the injector 23 by driving the fuel pump. The drive of the fuel pump is controlled by the control device 50.

The injector 23 simultaneously injects fuel from a plurality of injection holes. The diameter of the fuel droplets injected from the injector 23 is, for example, 50 to 60 μm. The diameter of the fuel droplets injected from the injector 23 is smaller than the diameter of the fuel droplets injected from a general injector. The diameter of fuel droplets injected from a general injector is, for example, 80 to 90 μm. Since the diameter of the fuel droplet is small, the fuel droplet easily evaporates. Therefore, it is not necessary to inject fuel before the intake stroke in order to ensure the time until evaporation. The diameter of the droplet is affected by the diameter of the injection hole, the pressure of the fuel supplied to the injector 23, the viscosity of the fuel, and the like. The smaller the diameter of the injection hole, the smaller the diameter of the droplet. The diameters of the plurality of injection holes of the injector 23 may all be the same or different. The number and shape of the plurality of injection holes are not particularly limited. The surface on which the plurality of injection holes are formed may be, for example, one flat surface or a convex curved surface. The arrangement of the plurality of injection holes is not particularly limited. For example, the plurality of injection holes may be arranged on one circle or may be arranged on two or more concentric circles. The injector 23 does not inject fuel using a swirl (swirl flow).

The engine unit 1 A has no fuel injection device other than one injector 23 for one combustion chamber 11. The fuel injection device here includes not only one that injects fuel in the cylinder intake passage portion 21 or the external intake passage portion 3 but also one that injects fuel in the combustion chamber 11. The fuel injection device includes not only one having a plurality of injection holes but also one having only one injection hole.

The injector 23 injects the mist-like fuel F11 in a substantially conical shape. As shown in FIG. 3A, when viewed in the direction of the cylinder axis Cy1, it passes through the center of the two injection directions forming the largest angle among the injection directions of the plurality of fuel droplets injected from the injector 23. A plane that looks like a straight line is a plane S2. In other words, the plane S2 looks like a straight line that bisects the injection angle of the injector 23 when viewed in the direction of the cylinder axis Cy1. The plane S2 corresponds to the second plane of the present invention. As shown in FIG. 2, when viewed in a direction perpendicular to the plane S 2, a straight line passing through the center of the two injection directions forming the largest angle among the injection directions of the plurality of fuel droplets injected from the injector 23. Let the visible plane be plane S3. In other words, the plane S3 looks like a straight line that bisects the injection angle of the injector 23 when viewed in a direction orthogonal to the plane S2. The plane S3 corresponds to the third plane of the present invention. An intersection line between the plane S2 and the plane S3 is referred to as an injection center line Ci1. The injection center line Ci1 is an infinite straight line.

As shown in FIG. 2, the injection center line Ci 1 of the injector 23 passes through the intake port 12. As shown in FIG. 3A, when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 coincides with the center axis Cv1 of the stem portion 22b. When viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 passes through the cylinder axis Cy1. For example, as shown in FIG. 3A, when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. As described above, the intake valve 22 moves along the central axis Cv1 of the stem portion 22b. Therefore, when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the closed position. For example, as shown in FIG. 2, when viewed in a direction orthogonal to the plane S2, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. When viewed in a direction orthogonal to the plane S2, the injection center line Ci1 passes through the umbrella portion 22a of the intake valve 22 in the closed position. When viewed in a direction perpendicular to the plane S2, the injection center line Ci1 does not pass through the stem portion 22b of the intake valve 22 in the closed position, but may pass through. From the above, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position, when viewed from any direction. That is, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. The injection center line Ci1 passes through the umbrella portion 22a of the intake valve 22 in the closed position. The injection center line Ci1 does not pass through the stem portion 22b of the intake valve 22 in the closed position, but may pass through.

As shown in FIG. 2, the shortest distance between the plurality of injection holes and the center P1 of the intake port 12 is a distance D1. The distance D1 is smaller than three times the diameter of the inlet 12. The distance D1 is smaller than three times the diameter of the intake valve 22. Therefore, the injector 23 is disposed at a position relatively close to the intake port 12. The distance D1 may be smaller than twice the diameter of the inlet 12. The distance D1 may be smaller than twice the diameter of the intake valve 22.

4A, FIG. 4B, and FIG. 6 are graphs of the example of the present invention, which are results obtained by simulating the movement (flow) of fuel injected from the injector 23. FIG. VECTIS (registered trademark) manufactured by Richard was used for the simulation. The simulation assumed a case where the injector 23 was not attached to the engine unit 1A and was injected into a space of only the atmosphere. In other words, it was injected into a space where there was no object at the injection destination. The temperature of the space where only the fuel is injected is normal temperature. The pressure in the space only in the atmosphere where fuel is injected is atmospheric pressure. The space only in the atmosphere where fuel is injected is in a windless state. In addition, the simulation was performed in consideration of the evaporation of the fuel, assuming that the volatility of the fuel is lower than the volatility of the gasoline. FIG. 4A shows the distribution of the fuel droplets as viewed in the Y direction that intersects the injection direction of the plurality of fuel droplets at a certain time immediately after the fuel is injected from the injector 23. More specifically, the Y direction is a direction orthogonal to the injection center line Ci1. In FIG. 4A, vaporized fuel is not displayed. The vertical axis in FIG. 4A indicates the distance in the direction of the injection center line Ci1 from the injection hole injector 23. The horizontal axis of Fig.4 (a) shows the distance of the X direction orthogonal to a Y direction. In FIG. 4 (a), the size of the diameter of the fuel droplet is represented by color shading. A darker color means a larger diameter.

As shown in FIG. 4A, one plane that is orthogonal to the injection center line Ci1 is defined as a plane S1. FIG. 4B shows the fuel concentration distribution on the plane S1. FIG. 4B shows a fuel concentration distribution that is a combination of vaporized fuel and liquid fuel. FIG. 4B shows the values on the plane S1 extracted from the simulation result of the mass distribution of fuel per unit volume. The horizontal axis in FIG. 4B indicates the distance in the X direction, and the vertical axis in FIG. 4B indicates the distance in the Y direction. FIG. 4B shows a region where the fuel concentration is zero in dark gray, and a region where the fuel concentration is higher than zero in light gray. In the simulation, the amount of fuel vaporized on the plane S1 is very small compared to the amount of liquid fuel. Therefore, although not shown, the concentration distribution of the liquid fuel on the plane S1 is almost the same as that shown in FIG.

As shown in FIG. 4B, the contour of the outer edge of the region where the fuel exists on the plane S1 is substantially circular. That is, at a certain time immediately after injection, the fuel on the plane S1 exists in one circle along the entire circumference of the edge of this circle. In the present embodiment, the region where the fuel exists on the plane S1 is annular. The region where the fuel exists on the plane S1 includes an annular first region A1 whose outer peripheral end and inner peripheral end are along the entire circumference of the edge of the circle. The region where the fuel exists on the plane S1 is configured only by the first region A11. A region in contact with the entire inner peripheral edge of the first region A11 on the plane S1 is defined as a second region A12. The injection center line Ci1 passes through the second region A12. There is no fuel in the second region A12. Therefore, the fuel concentration in the first region A11 is higher than the concentration in the second region A12. The injector 23 injects the fuel so that the concentration of the outer peripheral portion of the atomized fuel F11 is higher than the concentration of the central portion.

Temporarily, when the plane S1 is not orthogonal to the injection center line Ci1, the contour of the outer periphery of the region where the fuel exists on the plane S1 is not a circle but an oval. The plane S1 has the shortest length in the X direction of the region where the fuel exists on the plane among a plurality of planes passing through one point on the injection center line Ci1, and the fuel on the plane exists. This is a plane in which the length in the Y direction of the region to be shortened is the shortest. The plane S1 has the shortest length in the direction parallel to the plane S2 of the region where the fuel exists on the plane among the plurality of planes passing through one point on the injection center line Ci1, and the plane S1 This is the plane where the length in the direction parallel to the plane S3 of the region where the fuel exists is the shortest. Accordingly, the plane S1 is a plane having the smallest variation in the distance from the plurality of injection holes of the injector 23 to the first region A11 among the plurality of planes passing through one point on the injection center line Ci1.

The fuel concentration distribution in the first region A11 is substantially constant in the circumferential direction of the first region A11. The graph of the example of the present invention in FIG. 6 shows the fuel concentration distribution on a straight line passing through the injection center line Ci1 on the plane S1 in FIG. The graph of FIG. 6 shows the concentration distribution of the fuel in which the vaporized fuel and the liquid fuel are combined. The horizontal axis in FIG. 6 indicates the distance in the X direction, and the vertical axis in FIG. 6 indicates the fuel concentration. As shown in FIG. 6, the concentration of fuel in the first region A11 is the highest between the inner peripheral end and the outer peripheral end of the first region A11. Although illustration is omitted, the concentration distribution of the liquid fuel on the straight line passing through the injection center line Ci1 on the plane S1 is substantially the same as that in FIG.

Even if the simulation is performed assuming that the volatility of the fuel is the same as that of gasoline, the amount of fuel vaporized on the plane S1 is very small compared to the amount of liquid fuel. Therefore, although illustration is omitted, even when the simulation is performed assuming that the volatility of the fuel is the same as that of gasoline, the fuel concentration distribution on the plane S1 is almost the same as in FIG. 4B and FIG. It is. That is, even when the simulation is performed assuming that the volatility of the fuel is the same as that of gasoline, the region where the fuel exists on the plane S1 is a substantially circular ring.

According to a simulation assuming that fuel is injected from the injector 23 not attached to the engine unit 1A into a space of only the atmosphere, the concentration of fuel in the second region A12 is zero. However, when the fuel is actually injected from the injector 23 attached to the engine unit 1A, the fuel exists in the second region A12 for the following reason. The injector 23 attached to the engine unit 1A injects fuel during the intake stroke and when the intake valve 22 is in the open position. When the intake valve 22 is in the open position during the intake stroke, the air in the external intake passage portion 3 and the cylinder intake passage portion 21 is sucked into the combustion chamber 11 by the negative pressure in the combustion chamber 11. Due to this air flow, the trajectory of the fuel droplets injected from the injector 23 is changed so as to approach the center of the single intake passage portion 20. Therefore, when fuel is injected from the injector 23 attached to the engine unit 1A, the concentration of the central portion of the mist-like fuel F11 injected from the injector 23 becomes larger than zero. When fuel is injected from the injector 23 attached to the engine unit 1A, a region having a concentration of zero may exist in the central portion of the mist-like fuel F11. Even if the injection angle is large by changing the trajectory of the fuel droplets injected from the injector 23 so as to approach the center of the single intake passage portion 20, the fuel to the inner surface of the single intake passage portion 20 can be obtained. Adhesion is reduced.

In the simulation, fuel is injected into a space that is at atmospheric pressure and is free from wind. However, when fuel is injected from the injector 23 attached to the engine unit 1A during the intake stroke and when the intake valve 22 is in the open position, the inside of the single intake passage portion 20 temporarily becomes negative pressure. Due to the negative pressure in the single intake passage portion 20, evaporation of the injected fuel is promoted. Therefore, at least a part of the fuel injected from the injector 23 may evaporate before reaching the intake port 12.

5 (a), FIG. 5 (b), and the graph of the conventional example in FIG. 6 show the simulation results when the conventional injector 823 is used. The simulation conditions other than the injector structure are the same as those of the injector 23 described above. The amount of fuel injected from the conventional injector 823 is the same as in the simulation of the injector 23 described above. The diameter of the fuel droplet at the time of injection from the conventional injector 823 is substantially the same as the simulation of the injector 23 described above. The vertical and horizontal axes in FIGS. 5A and 5B are the same as those in FIGS. 4A and 4B. As shown in FIG. 5A, the conventional injector 823, like the injector 23, injects fuel in a substantially conical shape. When viewed in the Y direction, the injection angle of the conventional injector 823 is substantially the same as the injection angle of the injector 23. The center of the injection angle seen in the Y direction of the conventional injector 823 is taken as an injection center line Ci80. The injection center line Ci80 is also the center of the injection angle of the injector 823 viewed in the X direction. As shown in FIG. 5A, a plane orthogonal to the injection center line Ci80 is defined as a plane S801. As shown in FIG. 5B, the region where the fuel exists on the plane S801 is not annular. The outline of the region where the fuel exists on the plane S801 is substantially circular. As shown in the graph of the conventional example in FIG. 6, the concentration of the fuel in the region where the fuel exists on the plane S801 is higher as it is closer to the injection center line Ci80. In other words, the concentration of the outer peripheral portion in the region where the fuel on the plane S801 exists is lower than the concentration in the central portion of the region where the fuel on the plane S801 exists. In other words, this conventional injector 823 injects so that the concentration of the central portion of the mist-like fuel is higher than the concentration of the outer peripheral portion. In addition, even if the vertical axis | shaft of FIG. 6 is changed into a flow flux, the relative relationship of two graphs of FIG. 6 is substantially the same. The flow rate flux is a flow rate that passes per unit area.

7 (a) to 7 (f) schematically show the behavior of fuel droplets in the engine unit 1A. FIGS. 8A to 8F schematically show the behavior of fuel droplets when the above-described conventional injector 823 is used instead of the injector 23. FIG. 7 (a) to 7 (f) and FIGS. 8 (a) to 8 (f) display fuel droplets as dots (dots). The size of the dots was the same regardless of the diameter of the droplets. Vaporized fuel is not shown. Also, droplets attached to the single intake passage portion 20, the intake valve 22, and the combustion chamber 11 are not shown. FIGS. 7A to 7C and FIGS. 8A to 8C are views in which a cross section cut along the plane S2 is viewed in a direction perpendicular to the plane S2. FIG. 7 (a) to FIG. 7 (c) show different points in time in the intake stroke. FIGS. 8A to 8C also show different points in the intake stroke. FIGS. 7 (d) to 7 (f) are views in which FIGS. 7 (a) to 7 (c) are viewed in the direction of the cylinder axis Cy1, respectively. FIGS. 8 (d) to 8 (f) FIGS. 8A to 8C are views in the cylinder axis Cy1 direction, respectively.

The injector 23 injects the fuel so that the concentration of the outer peripheral portion of the mist-like fuel is higher than the concentration of the central portion. On the other hand, the conventional injector 823 injects so that the density | concentration of the center part of a mist-like fuel may become higher than the density | concentration of an outer peripheral part. Therefore, as can be seen from a comparison between FIG. 7A and FIG. 7B and FIG. 8A and FIG. 8B, the case where the injector 23 is used is more than the case where the conventional injector 823 is used. However, the amount of fuel adhering to the stem portion 22b on the plane S2 is small. Since the stem portion 22b is only on the plane S2 and in the vicinity thereof, when the injector 23 is used, the amount of fuel adhering to the entire stem portion 22b is smaller than when the conventional injector 823 is used. Further, the air in the single intake passage portion 20 is drawn into the combustion chamber 11 through the gap between the umbrella portion 22 a of the intake valve 22 and the intake port 12. The injector 23 injects the fuel so that the concentration of the outer peripheral portion of the atomized fuel is higher than the concentration of the central portion. Moreover, the injector 23 injects fuel so that the injection center line Ci1 passes through the intake port 12. Therefore, most of the fuel injected from the injector 23 passes through the gap between the umbrella portion 22 a of the intake valve 22 and the intake port 12. Therefore, the amount of fuel adhering to the umbrella portion 22a is smaller than when the conventional injector 823 is used.

The diameter of the fuel droplets injected from the

injectors

23 and 823 is small. Therefore, the fuel droplets flowing into the combustion chamber 11 move along the air flow in the combustion chamber 11 shown in FIG. A part of the fuel injected from the

injectors

23 and 823 evaporates before reaching the combustion chamber 11. Of course, the vaporized fuel also moves along the air flow in the combustion chamber 11. The conventional injector 823 injects so that the density | concentration of the center part of a mist-like fuel may become higher than the density | concentration of an outer peripheral part. Therefore, as shown in FIGS. 8B, 8C, 8E, and 8F, the fuel droplets injected from the conventional injector 823 and flowed into the combustion chamber 11 are It moves along the air flow in a tightly packed state. Although illustration is omitted, the vaporized fuel also moves along the air flow in a dense state in a relatively narrow range. On the other hand, as shown in FIG. 7B, FIG. 7C, FIG. 7E, and FIG. It moves along the air flow in a dispersed state. Although illustration is omitted, the vaporized fuel also moves along the air flow in the combustion chamber 11 while being dispersed in a wide range. Therefore, the fuel (liquid and gaseous fuel) injected from the injector 23 is diffused more rapidly in the combustion chamber 11 than the fuel (liquid and gaseous fuel) injected from the conventional injector 823.

The engine unit 91 shown in FIGS. 9 (a), 9 (b) and 9 (c) is an example of a conventional engine unit. As shown in FIG. 9A, the engine unit 91 has two intake valves 922 and one injector 923 for one combustion chamber 911. In the combustion chamber 911, two intake ports 912, two exhaust ports 913, and one spark plug insertion port 914 are formed. Two intake ports 912 are opened and closed by two intake valves 922. The two exhaust ports 913 are opened and closed by two exhaust valves (not shown). The spark plug insertion port 914 is disposed at a position surrounded by the two intake ports 912 and the two exhaust ports 913. Two intake passage portions 920 are connected to the two intake ports 912, respectively. The two intake passage portions 920 are connected to one upstream intake passage portion 919. The injector 923 is disposed so as to inject fuel in the upstream intake passage portion 919. The injector 923 injects the mist-like fuel F9 toward the two intake ports 912. The injector 923 injects the mist-like fuel F9 toward the two intake ports 912 at the same time. The injector 923 may inject the mist-like fuel F9 toward the two intake ports 912 at different timings.

Since two intake ports 912 are formed in the combustion chamber 911, a necessary distance between the intake port 912 and the central axis Cy9 of the cylinder hole 910 is between the intake port 12 and the central axis Cy1 of the cylinder hole 10. Longer than required. In addition, a spark plug insertion port 914 is formed at a position surrounded by the two intake ports 912 and the two exhaust ports 913 of the combustion chamber 911. Therefore, the necessary distance between the intake port 912 and the cylinder axis Cy9 is further increased.

9 (a), 9 (b) and 9 (c) schematically show the flow of air in the combustion chamber 911 during the intake stroke with arrows. 9C is a cross-sectional view taken along the line CC of FIG. 9A, the arrow in FIG. 9C also represents the flow of air that appears before the cross section. During the intake stroke, the air in the two intake passage portions 920 flows into the combustion chamber 911 from the two intake ports 912. When viewed in the direction of the cylinder axis Cy9, air flowing into the combustion chamber 911 from the two intake ports 912 collides between the two intake valves 922 and a region in the vicinity thereof. In addition, the air inlet 912 through which air flows is relatively far from the cylinder axis Cy9. Further, when viewed in the direction of the cylinder axis Cy9, the directions of the airflows flowing in the vicinity of the intake ports 912 of the two intake passage portions 920 are substantially parallel and not toward the cylinder axis Cy9. From these, the air flowing in from the two air inlets 912 cannot be uniformly diffused in the circumferential direction of the inner surface of the cylinder hole 10, and the air flow is concentrated on a part of the inner surface of the cylinder hole 910 in the circumferential direction. Arise.

On the other hand, since the engine unit 1A has only one intake port 12 for one combustion chamber 11, collision between air flowing into the combustion chamber from a plurality of intake ports does not occur. Further, the air inlet 12 through which air flows is close to the cylinder axis Cy1. Further, when viewed in the direction of the cylinder axis Cy1, the direction of the air flow flowing in the vicinity of the intake port 12 of the single intake passage portion 20 is the direction toward the cylinder axis Cy1 as a whole. Therefore, the air flowing into the combustion chamber 11 from the intake port 12 is uniformly diffused in the circumferential direction of the inner surface of the cylinder hole 10 as compared with the conventional engine unit 91. Thereby, as compared with the conventional engine unit 91, variation in the fuel concentration distribution in the combustion chamber 11 is suppressed.

In the conventional engine unit 91, the air flowing into the combustion chamber 911 from the two intake ports 912 collides. The fuel that flows along the air is atomized by the collision of the air. By atomizing the fuel in the combustion chamber, it is considered that variation in the combustion state is suppressed and unburned fuel in the exhaust gas is reduced.
On the other hand, the engine unit 1 A has only one intake port 12 for one combustion chamber 11. Therefore, fuel atomization due to air collision as described above does not occur. Here, it is assumed that the mist fuel F9 injected from the injector 923 has the same injection angle, droplet diameter, and concentration distribution as the mist fuel F11 injected from the injector 23. In this case, it seems that the engine unit 1A has a larger variation in the combustion state than the engine unit 91, and there is more unburned fuel in the exhaust. However, in the engine unit 1A, compared with the engine unit 91, the air that has flowed into the combustion chamber is more likely to diffuse uniformly in the circumferential direction of the inner surface of the cylinder hole. Therefore, even if the atomization of the fuel in the combustion chamber does not occur, variation in the combustion state is suppressed and an increase in unburned fuel in the exhaust is suppressed.

A volume of one space formed between the throttle valve 24 in the closed position and the intake valve 22 in the closed position is defined as a throttle downstream volume. Since the engine unit 91 has a plurality of intake ports 912 and one injector 923 for one combustion chamber 911, as described in the embodiment of the present invention, it is between the injection hole of the injector 923 and the intake port 912. The distance required is long. Therefore, the required distance between the throttle valve and the intake port 912 is also long. Therefore, the engine unit 1A can arrange the throttle valve 24 at a position closer to the intake port 12 than the engine unit 91 having a plurality of intake ports 912 and one injector 923 for one combustion chamber 911. Therefore, the throttle downstream volume of the engine unit 1A can be reduced.
If the engine unit has a plurality of intake ports and a plurality of injectors for one combustion chamber, a plurality of engine units provided for one combustion chamber at a position downstream from the throttle valve and upstream from the injector. It is necessary to connect the intake passage. Therefore, the required distance is long between the throttle valve and the intake port. Therefore, the engine unit 1A can arrange the throttle valve 24 at a position closer to the intake port 12 than an engine unit having a plurality of intake ports and a plurality of injectors for one combustion chamber. Therefore, the throttle downstream volume of the engine unit 1A can be reduced.
Furthermore, the throttle downstream volume of an engine unit having a plurality of intake ports, at least one injector, and one throttle valve for one combustion chamber is a space formed by connecting a plurality of intake passage portions. On the other hand, the throttle downstream volume of the engine unit 1A is a space formed in one intake passage portion. Therefore, the throttle downstream volume of the engine unit 1A can be further reduced as compared with the throttle downstream volume of the engine unit having a plurality of intake ports, at least one injector, and one throttle valve for one combustion chamber.

The smaller the throttle downstream volume, the more easily the pressure in the single intake passage portion 20 when the intake port 12 is open is affected by the negative pressure in the combustion chamber 11. That is, the smaller the throttle downstream volume, the lower the pressure in the single intake passage portion 20 during the intake stroke. Thereby, the evaporation of the fuel injected during the intake stroke is promoted. In addition, the air that has flowed into the combustion chamber 11 from the intake port 12 tends to uniformly diffuse in the circumferential direction of the inner surface of the cylinder hole 10. Therefore, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved. Further, by promoting the evaporation of the fuel, the adhesion of the fuel to the inner surface of the single intake passage portion 20 and the intake valve 22 is reduced.

The injector 23 is disposed at a position such that the shortest distance D1 between the center P1 of the air inlet 12 and the plurality of injection holes is smaller than three times the diameter of the air inlet 12. Thus, the distance from the plurality of injection holes to the intake port 12 is relatively short. Therefore, the injection angle of the fuel injected from the injector 23 can be reliably increased. As described above, since the injection angle of the fuel injected from the injector 23 is large, the diameter of the injected droplets can be reduced while suppressing the plurality of injected droplets from contacting each other. . Due to the small diameter of the ejected droplets, the variation in the fuel concentration distribution in the combustion chamber 11 can be further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved. When the shortest distance D1 between the plurality of injection holes and the center P1 of the intake port 12 is smaller than twice the diameter of the intake port 12, the degree of freedom in designing the concentration distribution of the fuel in the combustion chamber 11 is further increased. It can be improved.

The injection center line Ci1 of the injector 23 passes through the single air inlet 12. If the fuel is injected so that the injection center line Ci1 does not pass through the intake port 12, even if the fuel is injected so that the first region A11 is annular, the single intake valve 22 and the single intake port 12 The amount of fuel passing through the gap is nonuniform in the circumferential direction of the gap. The concentration of fuel at a specific position in the combustion chamber 11 tends to increase. In this specific example, since the injection center line Ci1 passes through the single intake port 12, variation in fuel passing through the gap between the single intake valve 22 and the single intake port 12 is suppressed. Therefore, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved.

The single inlet injector 23 is disposed so that the injection center line Ci1 passes through the stem portion 22b of the intake valve 22 in the open position when viewed in the direction of the cylinder axis Cy1 (see FIG. 3A). . Therefore, when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 is likely to pass through the center P1 of the intake port 12 or the vicinity thereof. Therefore, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved.

The injector 23 is arranged so that the injection center line Ci1 passes through the stem portion 22b and the umbrella portion of the intake valve 22 when the intake port 12 is open when viewed in a direction orthogonal to the plane S2 (FIG. 2). reference). That is, when viewed in a direction perpendicular to the plane S2, the injection center line Ci1 passes through the center P1 of the inlet 12 or the vicinity thereof. Therefore, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved.

The injector 23 is arranged so that the injection center line Ci1 passes through the stem portion 22b and the umbrella portion of the intake valve 22 when the intake port 12 is open. That is, the injection center line Ci1 passes through the center P1 of the intake port 12 or the vicinity thereof. Therefore, variation in the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved.

The diameter of the intake port 12 is larger than the diameter of the exhaust port 13. Since the diameter of the intake port 12 is relatively large, the diameter of the single intake passage portion 20 is also relatively large. Since the diameter of the single intake passage portion 20 is large, the injection angle of the fuel injected from the injector 23 can be increased. Since the injection angle of the fuel injected from the injector 23 is large, the diameter of the injected droplets can be reduced while suppressing the plurality of injected droplets from contacting each other. Due to the small diameter of the ejected droplets, the variation in the fuel concentration distribution in the combustion chamber 11 can be further suppressed. Therefore, the degree of freedom in designing the fuel concentration distribution in the combustion chamber 11 can be further improved.

Assuming that the two intake ports 912 in the engine unit 91 having two intake ports 912 for one combustion chamber 911 are changed to one intake port as shown in FIG. The amount of air supplied to the two combustion chambers 911 needs to be maintained. That is, the total cross-sectional area of the two intake passage portions 920 needs to be substantially the same as the cross-sectional area of one intake passage portion when the two intake ports 912 are changed to one intake port. Therefore, the total circumference of the two intake passage portions 920 is longer than the circumference of one intake passage portion when the two intake ports 912 are changed to one intake port. The longer the circumference of the intake passage portion, the larger the area of the inner surface of the intake passage portion. If a person skilled in the art changes the two intake ports 912 of the engine unit 91 to one intake port, the increase in the area of the inner surface of the intake passage portion will increase the adhesion of fuel to the inner surface of the intake passage portion. I should think about it. A conventional engine unit 91 having two intake ports 912 for one combustion chamber 911 has a concentration of the outer peripheral portion from the injector 923 in order to reduce fuel adhesion to the intake valve 922 and / or the intake passage portion 920. The fuel is injected so as to be higher than the concentration in the center. Therefore, those skilled in the art should not consider changing the fuel deposition to increase. Actually, as a result of research by the inventors of the present application, as described above, the diameter of the droplet of fuel injected from the injector is larger than that of the engine unit 91 having two intake ports 912 for one combustion chamber 911. It was found that can be reduced. As a result, evaporation of the fuel is promoted, so that it is possible to suppress the fuel from adhering to the intake passage and the intake valve as compared with the conventional engine unit 91 having two intake ports 912 for one combustion chamber 911. I understood.

In addition, as shown in FIG. 9, the injection of fuel toward one intake port 912 in one injector 923 that injects fuel toward two intake ports 912 formed in one combustion chamber 911 is performed as 1 In consideration of adopting an injector in an engine unit having one intake port and one injector for one combustion chamber, it is necessary to maintain the amount of fuel supplied to one combustion chamber during the intake stroke. That is, the amount of fuel injected toward one intake port is approximately twice the amount of fuel injected toward one intake port in an injector 923 that injects fuel toward two intake ports 912. Need to increase. As the amount of fuel increases, fuel droplets are more likely to come into contact with each other. This makes it difficult for the fuel droplets to evaporate. Therefore, those skilled in the art should think that the adhesion of fuel to the intake valve increases. A conventional engine unit 91 having two intake ports 912 for one combustion chamber 911 has a concentration of the outer peripheral portion from the injector 923 in order to reduce fuel adhesion to the intake valve 922 and / or the intake passage portion 920. The fuel is injected so as to be higher than the concentration in the center. Therefore, those skilled in the art should not consider changing the fuel deposition to increase. Actually, as a result of research by the inventors of the present application, as described above, the fuel injected from the injector is larger than the engine unit 91 having two intake ports 912 and one injector 923 for one combustion chamber 911. It was found that the diameter of the liquid droplets can be reduced. As a result, evaporation of the fuel is promoted, so that it is possible to suppress the fuel from adhering to the intake passage and the intake valve as compared with the conventional engine unit 91 having two intake ports 912 for one combustion chamber 911. I understood.

≪Change example≫
The present invention is not limited to the above-described embodiments and specific examples thereof, and various modifications are possible as long as they are described in the claims. Hereinafter, a modified example of the embodiment of the present invention will be described. In addition, about what has the same structure as the structure mentioned above, the description is abbreviate | omitted suitably using the same code | symbol. The above-described embodiments, specific examples of the embodiments, and modifications described below can be implemented in appropriate combination.

<Modification example of injector for single inlet>
When fuel is injected into a space only in the atmosphere without the single inlet injector of the present invention attached to the engine unit, a plurality of fuels injected from the single inlet injector at a certain time immediately after injection The region where the fuel on the first plane intersecting the injection direction of the liquid droplets may have two or more first regions. Alternatively, the region where the fuel exists on the first plane may include a region other than the first region in addition to the one first region. However, the region where the fuel exists on the first plane does not include a region having a higher fuel concentration than the first region.
For example, the region where the fuel exists on the first plane may include a second region in contact with the entire inner peripheral end of the first region. However, the concentration of fuel in the first region is higher than the concentration of fuel in the second region. That is, the average value of the mass of fuel per unit volume or unit area of the first region is larger than the average value of the mass of fuel per unit volume or unit area of the second region.
When the first region is non-annular as will be described later, the region where the fuel on the first plane exists may include a region between both ends in the circumferential direction of the first region. However, the concentration of the fuel in the region between the circumferential ends of the first region is the same as or lower than the concentration of the fuel in the first region.

When there are a plurality of first regions in a region where fuel exists on the first plane, the plurality of first regions may be arranged in the circumferential direction along the edge of one circle or one oval.
That the outer peripheral edge of the first region is along at least part of the edge of one circle or one oval means that only a part of the outer edge of the first region is at least one edge of one circle or one oval. It is not included when it is along the section. Thus, for example, if fuel is present along the entire circumference of the circle edge in two circles that fit within one ellipse, the region where the fuel exists along the entire circumference of the circle edge is It does not correspond to the first region of the invention.

When fuel is injected into a space only in the atmosphere with the single inlet injector of the present invention not attached to the engine unit, a plurality of fuels injected from the single inlet injector at a certain time immediately after injection The fuel on the first plane that intersects the injection direction of the droplets may be present in one circle along a part of the edge of the circle. In this case, the region where the fuel exists on the first plane includes a non-circular first region having an inner peripheral end and an outer peripheral end along a part of the edge of the circle. The concentration of the fuel in the non-annular first region is higher than the concentration of the fuel in the second region in contact with the entire inner peripheral end of the first region on the first plane. In this modification, fuel may or may not be present in the second region. FIGS. 10, 11, and 12 (a) to 12 (c) are diagrams showing three specific examples of this modification.

FIG. 10, FIG. 11 and FIG. 12 (a) are explanatory diagrams of one modified example. FIG. 11 is a view of the engine unit as viewed in a direction orthogonal to the second plane. FIG. 10 and FIG. 12A show the first area A21 and the second area A22 on the first plane S21. 2nd area | region A22 is an area | region enclosed by the whole inner peripheral end of non-annular 1st area | region A21, and the line segment which connects the circumferential direction both ends of the inner peripheral end of 1st area | region A21. The outer peripheral end of the first region A21 is an arc having an angle of 90 ° or more. Therefore, as shown in FIG. 12A, the center in the circumferential direction of the outer peripheral end of the first region A21 is a 90 ° arc CA2 on the first plane S21 having both ends passing through both ends of the first region A21 in the circumferential direction. Located radially outside. An arrow Dx shown in FIG. 10 indicates a direction on the first plane S21 parallel to the second plane, and an arrow Dy indicates a direction on the first plane S21 parallel to the third plane. The injection center line Ci2 passes through the second region A22. The first plane S21 has the shortest length in the Dx direction of the region where the fuel on the plane is present among the plurality of planes passing through one point on the injection center line Ci2, and the fuel on the plane. This is a plane in which the length in the Dy direction of the region where is present is the shortest.

FIG. 12B shows the first region A31 and the second region A32 on the first plane S31. The second region A32 is a region surrounded by the entire inner peripheral end of the first region A31 and a line segment connecting both ends in the circumferential direction of the inner peripheral end of the first region A31. The outer peripheral end of the first region A31 is an arc having an angle of 90 ° or more. Therefore, the center in the circumferential direction of the outer peripheral end of the first region A31 is on the radially outer side of the 90 ° arc CA3 on the first plane S31 having both ends passing through both ends of the first region A31 in the circumferential direction. The injection center line Ci3 passes through the second region A32. The first plane S31 has the shortest length in the direction parallel to the second plane of the region where the fuel exists on the plane among the plurality of planes passing through one point on the injection center line Ci3, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

FIG. 12C shows a first area A41 and a second area A42 on the first plane S41. The second region A42 is a region surrounded by the entire inner peripheral end of the first region A41 and a line segment connecting both ends in the circumferential direction of the inner peripheral end of the first region A41. The outer peripheral end of one area A41 is an arc having an angle of less than 90 °. Therefore, the center in the circumferential direction of the outer peripheral end of the first region A41 is located on the radially inner side of the 90 ° arc CA4 on the first plane S41 having both ends passing through both ends of the first region A41 in the circumferential direction. The injection center line Ci4 passes through the first region A41. The first plane S41 has the shortest length in the direction parallel to the second plane of the region where the fuel exists on the plane among the plurality of planes passing through one point on the injection center line Ci4, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

When fuel is injected into a space only in the atmosphere without the single inlet injector of the present invention attached to the engine unit, a plurality of fuels injected from the single inlet injector at a certain time immediately after injection The fuel on the first plane that intersects the injection direction of the liquid droplets may be present in one oval along the entire circumference of the edge of the oval. In this case, the region where the fuel exists on the first plane includes an annular first region along the entire circumference of the edge of the oval. The concentration of the fuel in the annular first region is higher than the concentration of the fuel in the second region in contact with the entire inner peripheral edge of the first region on the first plane. In this modification, fuel may or may not be present in the second region. FIG. 13A is a diagram showing one specific example of this modification. The shape of the oval is not limited to the shape shown in FIG.

FIG. 13A shows a first area A51 and a second area A52 on the first plane S51. The injection center line Ci5 passes through the second region A52. The first plane S51 has the shortest length in the direction parallel to the second plane of the region where the fuel exists on the plane among the plurality of planes passing through one point on the injection center line Ci5, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

When fuel is injected into a space only in the atmosphere with the single inlet injector of the present invention not attached to the engine unit, a plurality of fuels injected from the single inlet injector at a certain time immediately after injection The fuel on the first plane that intersects the injection direction of the liquid droplets may be present in one oval along a part of the edge of the oval. In this case, the region where the fuel on the first plane is present includes a non-annular first region along a portion of the edge of the oval. The concentration of the fuel in the annular first region is higher than the concentration of the fuel in the second region in contact with the entire inner peripheral edge of the first region on the first plane. In this modification, fuel may or may not be present in the second region. FIG. 13B to FIG. 13E are diagrams showing four specific examples of this modification. The shape of the oval is not limited to the shapes shown in FIGS. 13 (b) to 13 (e).

FIG. 13B shows a first area A61 and a second area A62 on the first plane S61. The second region A62 is a region surrounded by the entire inner peripheral end of the first region A61 and a line segment connecting both circumferential ends of the inner peripheral end of the first region A61. The center in the circumferential direction of the outer peripheral end of the first region A61 is on the radially outer side of the 90 ° arc CA6 on the first plane S61 having both ends passing through both ends of the first region A61 in the circumferential direction. The injection center line Ci6 passes through the second region A62. The first plane S61 has the shortest length in the direction parallel to the second plane of the region where the fuel exists on the plane among the plurality of planes passing through one point on the injection center line Ci6, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

FIG. 13C shows a first area A71 and a second area A72 on the first plane S71. 2nd area | region A72 is an area | region enclosed by the whole inner peripheral end of 1st area | region A71, and the line segment which connects the circumferential direction both ends of the inner peripheral end of 1st area | region A71. The center in the circumferential direction of the outer peripheral end of the first region A71 is radially inward of the 90 ° arc CA7 on the first plane S71 having both ends passing through both ends of the first region A71 in the circumferential direction. The injection center line Ci7 passes through the second region A72. The first plane S71 has the shortest length in the direction parallel to the second plane of the region where the fuel on the plane is present among the plurality of planes passing through one point on the injection center line Ci7, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

FIG. 13D shows the first area A81 and the second area A82 on the first plane S81. The second region A82 is a region surrounded by the entire inner peripheral end of the first region A81 and a line segment connecting both circumferential ends of the inner peripheral end of the first region A81. The center in the circumferential direction of the outer peripheral end of the first region A81 is on the radially outer side of the 90 ° arc CA8 on the first plane S81 having both ends passing through both ends of the first region A81 in the circumferential direction. The injection center line Ci8 passes through the second region A82. The first plane S81 has the shortest length in the direction parallel to the second plane of the region where the fuel on the plane is present among the plurality of planes passing through one point on the injection center line Ci8, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

FIG. 13E shows a first area A91 and a second area A92 on the first plane S91. The second region A92 is a region surrounded by the entire inner peripheral end of the first region A91 and a line segment connecting both ends in the circumferential direction of the inner peripheral end of the first region A91. The center in the circumferential direction of the outer peripheral end of the first region A91 is on the radially outer side of a 90 ° arc CA9 on the first plane S91 having both ends passing through both ends of the first region A91 in the circumferential direction. The injection center line Ci9 passes through the first region A91. The first plane S91 has the shortest length in the direction parallel to the second plane of the region where the fuel on the plane is present among the plurality of planes passing through one point on the injection center line Ci9, and This is the plane where the length in the direction parallel to the third plane of the region where the fuel exists on the plane is the shortest.

As shown in FIG. 12A, FIG. 12B, FIG. 13B, FIG. 13D, and FIG. 13E, the circumferential center of the outer periphery of the first region is the first region. When it is on the radially outer side of a 90 ° arc on the first plane having both ends passing through both ends in the circumferential direction, the circumferential length of the non-annular first region is long. Therefore, it is possible to inject a sufficient amount of fuel from the single inlet injector while reducing the diameter of the ejected droplets so that the plurality of ejected droplets can be prevented from coming into contact with each other.

The direction in which the piston descends during the intake stroke is defined as the piston descending direction. The piston downward direction is a direction parallel to the central axis of the cylinder hole. When the first region of the present invention is non-annular along a part of the edge of one circle or one oval, the center in the circumferential direction of the outer peripheral end of the first region is a piston from both ends in the circumferential direction of the first region. It is preferable that it exists in the position away in the downward direction. FIG. 10, FIG. 11 and FIG. 12 (a) show one specific example of this modification. An arrow PD shown in FIG. 11 indicates the piston downward direction. As shown in FIG. 11, when viewed in the direction (Dy direction) orthogonal to the second plane, the circumferential center Ac of the outer peripheral end of the non-annular first region A21 is the piston from both ends in the circumferential direction of the first region A21. It is in a position away in the downward direction. In this case, when viewed in the direction orthogonal to the second plane (Dy direction), the circumferential center Ac of the outer peripheral end of the non-annular first region A21 is located away from the injection center line Ci2 in the piston descending direction. . According to this configuration, the adhesion of fuel to the stem portion 22b of the single intake valve 22 can be suppressed.
In addition, when the 1st area | region of this invention is a non-circular shape along a part of edge of one circle or one oval, the circumferential direction center of the outer periphery end of 1st area | region is the circumferential direction both ends of 1st area | region It does not have to be at a position away from the piston downward direction.

In the present invention, the injection center line passes through the first region or the second region. When the first region is annular, the injection center line passes through the second region. When the first region is non-annular, the injection center line may pass through the second region or may pass through the first region.

The first plane of the present invention has the shortest length in a direction parallel to the second plane of the region where the fuel exists on the plane among a plurality of planes passing through one point on the injection center line, and It is preferable that the length of the region where the fuel exists on the plane is shortest in the direction parallel to the third plane. The first plane is a plane having the smallest variation in distance from the plurality of injection holes of the single inlet injector to the first region among the plurality of planes passing through one point on the injection center line. can do. When the first plane of the present invention satisfies this condition, the first plane may or may not be orthogonal to the injection center line. The first plane of the present invention may not satisfy this condition. When the first plane of the present invention does not satisfy this condition, the first plane may or may not be orthogonal to the injection center line.

In a specific example of the embodiment, the fuel concentration distribution in the first region A1 is substantially constant in the circumferential direction of the first region A1. However, the concentration distribution of the fuel in the first region in the present invention may not be constant in the circumferential direction of the first region. For example, the fuel concentration distribution in the first region may be asymmetric about the first plane. Further, for example, the fuel concentration distribution in the first region may be asymmetric about the second plane. Further, for example, the fuel concentration distribution in the first region may be asymmetric about the third plane.

The plane that includes the center of the single inlet and the center axis of the cylinder hole is the fourth plane. In the specific example of the embodiment, the fourth plane is the same as the plane S2 (second plane). In the specific example of the embodiment, the fuel concentrations on both sides of the plane S2 in the combustion chamber 11 are substantially the same. However, in the present invention, the concentration of the fuel may be higher in the space on the both sides of the fourth plane in the combustion chamber where the spark plug insertion port is located. In order to realize this concentration distribution, the injector 23 of a specific example of the embodiment may be changed as follows. For example, the injection direction may be changed so that the injection center line Ci1 approaches the spark plug insertion port when viewed in the direction of the center axis of the cylinder hole. Further, for example, the injection amount may be changed so that the concentrations of the fuel injected from the injector 23 on both sides of the second plane (plane S2) are different from each other. The injection amount can be adjusted, for example, by changing the size of the injection holes and the density of the arrangement of the injection holes.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the cylinder axis Cy1 when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the single inlet injector of the present invention does not have to pass through the center axis of the cylinder hole when viewed in the direction of the center axis of the cylinder hole.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment coincides with the center axis Cv1 of the stem portion 22b of the intake valve 22 when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the single inlet injector of the present invention does not have to coincide with the center axis of the stem portion when viewed in the direction of the center axis of the cylinder hole.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the single inlet injector of the present invention does not have to pass through the stem portion of the single intake valve in the open position when viewed in the direction of the center axis of the cylinder hole. Further, the injection center line of the single inlet injector of the present invention does not have to pass through the umbrella portion of the single intake valve in the open position when viewed in the direction of the center axis of the cylinder hole.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the closed position when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the single inlet injector of the present invention does not have to pass through the stem portion of the single intake valve in the closed position when viewed in the direction of the center axis of the cylinder hole.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position when viewed in a direction orthogonal to the plane S2. However, the injection center line of the single inlet injector of the present invention does not have to pass through the stem portion of the single intake valve in the open position when viewed in the direction orthogonal to the second plane. Further, the injection center line of the single intake port injector of the present invention does not have to pass through the umbrella portion of the single intake valve in the open position when viewed in the direction orthogonal to the second plane. The injection center line of the single inlet injector of the present invention does not have to pass through both the umbrella portion and the stem portion of the single intake valve in the open position when viewed in the direction perpendicular to the second plane. Only the umbrella portion of the umbrella portion and the stem portion of the single intake valve in the open position may pass, or only the stem portion of the umbrella portion and the stem portion of the single intake valve in the open position may pass.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the stem portion 22b and the umbrella portion 22a of the single intake valve 22 in the open position. However, the injection center line of the single inlet injector of the present invention may not pass through the stem portion of the single intake valve in the open position. The injection center line of the single inlet injector of the present invention may not pass through the umbrella portion of the single intake valve in the open position. The injection center line of the injector for a single intake port of the present invention may not pass through both the umbrella portion and the stem portion of the single intake valve in the open position, and the umbrella portion of the single intake valve in the open position Only the umbrella part of the stem part may be passed, or only the stem part of the umbrella part and the stem part of the single intake valve in the open position may be passed.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the intake port 12. However, the injection center line of the single inlet injector of the present invention may not pass through the inlet.

In the engine unit of the present invention, the shortest distance between the plurality of injection holes and the center of the single intake port may be at least twice as long as the diameter of the single intake port. The shortest distance between the plurality of injection holes and the center of the single air inlet may be at least three times as long as the diameter of the single air inlet.

<Exhaust port change example>
The engine unit 1 A of the specific example of the embodiment has only one exhaust port 13 for one combustion chamber 11. However, the engine unit of the present invention may have a plurality of exhaust ports for one combustion chamber. For example, one single intake port and two exhaust ports may be formed in one combustion chamber.

<Examples of changing the single inlet and outlet>
In the specific example of the embodiment, the diameter of the intake port 12 is larger than the diameter of the exhaust port 13. However, in the present invention, the diameter of the single intake port may be the same as or smaller than the diameter of the exhaust port.

<Modification example of single intake valve>
In the specific example of the embodiment, the end face of the umbrella portion 22a of the intake valve 22 facing the combustion chamber 11 is parallel to the plane S4 including the entire circumference of the intake port 12 (see FIG. 2). However, in the present invention, the end face of the umbrella portion of the single intake valve facing the combustion chamber may not be parallel to a plane including the entire circumference of the single intake port.

In the specific example of the embodiment, the central axis Cv1 of the stem portion 22b of the intake valve 22 is orthogonal to the plane S4 including the entire circumference of the intake port 12 (see FIG. 2). However, in the present invention, the central axis of the stem portion of the single intake valve may not be orthogonal to the plane including the entire circumference of the single intake port.

In a specific example of the embodiment, the central axis Cv1 of the stem portion 22b of the intake valve 22 passes through the center P1 of the intake port 12 (see FIGS. 2 and 3A). However, in the present invention, the central axis of the stem portion of the single intake valve may not pass through the center of the single intake port.

In a specific example of the embodiment, the central axis Cv1 of the stem portion 22b of the intake valve 22 passes through the cylinder axis Cy1 when viewed in the direction of the cylinder axis Cy1 (see FIG. 3A). However, the central axis of the stem portion of the single intake valve of the present invention does not have to pass through the central axis of the cylinder hole when viewed in the direction of the central axis of the cylinder hole.

<Multi-cylinder engine>
A specific example of the engine unit 1A in the embodiment is a single cylinder engine. However, the engine unit of the present invention may be a multi-cylinder engine. That is, the engine unit of the present invention may have a plurality of combustion chambers. The number of combustion chambers is not particularly limited. In this case, the engine unit has a single intake port, a single intake valve, a single intake port injector, and a single intake passage portion, one for each combustion chamber.

When the engine unit of the present invention has a plurality of combustion chambers, the engine unit has at least one cylinder intake passage portion and at least one external intake passage portion. The engine unit may have a plurality of cylinder intake passage portions. For example, the engine unit may have one cylinder intake passage portion for each combustion chamber. The engine unit may have a plurality of external intake passage portions. For example, the engine unit may have one external intake passage portion for each combustion chamber.
The number of cylinder intake passage portions may be the same as or less than the number of single intake passage portions. When the number of cylinder intake passage portions is smaller than the number of single intake passage portions, the cylinder intake passage portion has a branched shape and has a plurality of inflow ports into which air flows. When the number of cylinder intake passage portions is smaller than the number of single intake passage portions, the number of external intake passage portions is the same as the number of cylinder intake passage portions. When the number of cylinder intake passage portions is the same as the number of single intake passage portions, the number of external intake passage portions may be the same as or less than the number of cylinder intake passage portions. That is, the number of external intake passage portions may be the same as the number of single intake passage portions, or may be smaller than that. When the number of external intake passage portions is smaller than the number of cylinder intake passage portions, the external intake passage portion has a plurality of inflow ports that are branched and into which air flows. In any case, the single intake passage portion is configured to pass through the interior of the single intake passage portion without being separated or joined together.

When the engine unit of the present invention has a plurality of combustion chambers, the engine unit may have a throttle valve for each combustion chamber. In this case, one cylinder intake passage portion and one external intake passage portion are provided for each combustion chamber. Each of the plurality of throttle valves is provided in the external intake passage portion.
When the engine unit of the present invention has a plurality of combustion chambers, the engine unit may have one throttle valve for the plurality of combustion chambers. In this case, the external intake passage portion or the cylinder intake passage portion has a plurality of one inflow ports that are branched and into which air flows. The number of cylinder intake passage portions is smaller than the number of single intake passage portions, or the number of external intake passage portions is smaller than the number of cylinder intake passage portions. A plurality of single intake passage portions are connected at a position downstream of the throttle valve and upstream of the single intake port injector in the air flow direction. The throttle valve is provided in the external intake passage portion.

The volume of one space formed between the throttle valve in the closed position and the intake valve in the closed position is defined as the throttle downstream volume. When the engine unit has one throttle valve for each combustion chamber, the throttle downstream volume is a space formed in one intake passage portion. On the other hand, when the engine unit has one throttle valve for a plurality of combustion chambers, the throttle downstream volume is a space formed by connecting a plurality of intake passage portions provided for each combustion chamber. Therefore, the throttle downstream volume of the engine unit having one throttle valve per combustion chamber can be made smaller than the throttle downstream volume of the engine unit having one throttle valve for a plurality of combustion chambers.

When the engine unit of the present invention has a plurality of combustion chambers, the timings of the intake strokes of the plurality of combustion chambers may be the same. Moreover, the timing of the intake stroke of any two combustion chambers of the plurality of combustion chambers may be different from each other, and the timing of the intake stroke of any two other combustion chambers of the plurality of combustion chambers may be the same. . Further, the timing of the intake stroke of any one of the plurality of combustion chambers may be different from the timing of any intake stroke of the remaining combustion chambers. Here, the same timing of the intake stroke does not include that the intake strokes overlap only partially.

When the engine unit of the present invention has a plurality of combustion chambers, the type of the engine unit may be a multi-cylinder engine in which a plurality of combustion chambers are arranged in a straight line. In this case, the central axes of the plurality of cylinder holes of the engine unit are parallel or substantially parallel. Further, the type of the engine unit may be a V-type engine. The V-type engine has two cylinder holes arranged so that the center axis thereof is V-shaped when viewed in the direction of the center axis of the crankshaft. In the case of a V-type engine having four or more cylinders, the central axis has a plurality of cylinder holes arranged in parallel or substantially in parallel.

The first region of the present invention corresponds to the outer peripheral region of the basic application (Japanese Patent Application No. 2018-10000176) of the present application. The second region of the present invention corresponds to the central peripheral region of the basic application of the present application. The first plane of the present invention is an example of the third plane of the basic application of the present application. The second plane of the present invention corresponds to the first plane of the basic application of the present application. The third plane of the present invention corresponds to the second plane of the basic application of the present application.

DESCRIPTION OF

SYMBOLS

1, 1A Engine unit 3 External intake passage part 4 Cylinder part 10 Cylinder hole 11 Combustion chamber 12 Single intake port 13 Exhaust port 20 Single intake passage part 21 Cylinder intake passage part 22 Single intake valve

22a Umbrella part

22b Stem part

23 , 123 Single inlet injector 24 Throttle valve 50 Control device A1, A11, A21, A31, A41, A51, A61, A71, A81, A91 First region A2, A12, A22, A32, A42, A52, A62, A72, A82, A92 Second region Ci1, Ci2, Ci3, Ci4, Ci5, Ci6, Ci7, Ci8, Ci9 Injection center line Cy1 Center axis of cylinder hole Cv1 Center axis of stem portion P1 Center of inlet S1, S21, S31 , S41, S51, S61, S71, S81, S91 First plane S2 2 plane S3 third plane

Claims

At least one combustion chamber, each part of which is formed by the inner surface of the cylinder hole, at least one intake port formed in the at least one combustion chamber, and the at least one intake port, and flows into the interior A cylinder portion having at least one cylinder intake passage portion through which the air is supplied from the at least one intake port to the at least one combustion chamber;
At least one external intake passage portion disposed outside the cylinder portion, connected to the at least one cylinder intake passage portion, and air flowing into the interior is supplied to the at least one cylinder intake passage portion;
At least one intake valve movable between a position for opening the at least one intake opening and a position for closing the at least one intake opening;
Each of the cylinder intake passage portion or the external intake passage has a plurality of injection holes capable of injecting fuel in the form of a mist, and the plurality of injection holes are located in the cylinder intake passage portion or in the external intake passage portion. At least one injector installed in the section;
A four-stroke cycle engine unit comprising a control device for controlling fuel injection of the at least one injector,
The intake port, the intake valve, and the injector are provided one for each combustion chamber, and constitute a single intake port, a single intake valve, and a single intake port injector,
The at least one cylinder intake passage portion and the at least one external intake passage portion include at least one single intake passage portion;
The single intake passage portion is provided for each combustion chamber, and is a region from the place where the single intake port injector is installed to the single intake port, in which the flow of air flows. Configured to pass without separation or merging,
The single inlet injector is
(A) arranged to inject fuel towards the single inlet;
(B) When fuel is injected into an atmosphere-only space without being mounted on the engine unit, at a certain time immediately after injection, (i) a plurality of fuels injected from the injector for single injection port Fuel on a first plane that intersects the injection direction of the droplets is present in one circle or one oval along at least a portion of the edge of the one circle or the one oval; ii) Concentration of the fuel in the first region that is included in the region where the fuel exists on the first plane, and whose outer and inner peripheral edges are along at least part of the edge of the one circle or the one oval. Is configured to be higher than the concentration of fuel in the second region in contact with the entire inner peripheral edge of the first region on the first plane,
(C) controlled by the control device to inject fuel when the intake stroke is in a position where the single intake valve is in a position to open the single intake port;
The engine unit is characterized in that fuel supplied to one combustion chamber is fuel injected from one injector for the single intake port and passed through the single intake port.
When viewed in the direction of the central axis of the cylinder hole, a straight line passing through the center of the two injection directions forming the largest angle among the injection directions of the plurality of fuel droplets injected from the single inlet injector. Let the visible plane be the second plane,
When viewed in a direction perpendicular to the second plane, the straight line passes through the center of the two injection directions forming the largest angle among the injection directions of the plurality of fuel droplets injected from the single inlet injector. Let the visible plane be the third plane,
When an intersection line between the second plane and the third plane is an injection center line,
Of the plurality of planes through which the first plane passes through one point on the injection center line, the length in the direction parallel to the second plane of the region where the fuel exists on the plane is the shortest, and 2. The engine unit according to claim 1, wherein a length in a direction parallel to the third plane of a region where the fuel exists on the plane is the shortest.
The single inlet injector is
The engine unit according to claim 2, wherein the injection center line is arranged and configured to pass through the single intake port.
The single inlet injector is
The engine unit according to claim 2 or 3, wherein the injection center line is arranged and configured so as to pass through the second region.
The single intake valve has an umbrella portion that can block the single intake port, and a stem portion that is connected to the umbrella portion and is partially disposed in the single intake passage portion.
The single inlet injector is
When viewed in the direction of the center axis of the cylinder hole, the injection center line is arranged and configured to pass through the stem portion of the single intake valve at a position where the single intake port is opened. The engine unit according to any one of claims 2 to 4.
The single inlet injector is
When viewed in a direction perpendicular to the second plane, the injection center line is arranged and configured to pass through the stem portion and the umbrella portion of the single intake valve at a position where the single intake port is opened. The engine unit according to any one of claims 2 to 5, wherein:
The single inlet injector is
The said injection center line is arrange | positioned and comprised so that it may pass through the said stem part and the said umbrella part of the said single intake valve in the position which opens the said single intake port. Engine unit.
The cylinder intake passage portion and the external intake passage portion are provided one for each combustion chamber,
The at least one external intake passage portion is provided with at least one throttle valve disposed upstream of the single intake port injector in an air flow direction in the single intake passage portion. Item 8. The engine unit according to any one of Items 1 to 7.
The single inlet injector is
The first region on the first plane is
An annulus along the entire circumference of the edge of the one circle or the one oval, or
A non-annular shape along a part of an edge of the one circle or the one oval, the circumferential center of the outer circumferential end thereof having both ends passing through both circumferential circumferential ends of the non-circular first region. The engine unit according to any one of claims 1 to 8, wherein the engine unit is configured to lie radially outside a 90 ° arc on one plane.
The single intake valve is
An umbrella capable of closing the single air inlet;
A stem portion connected to the umbrella portion and a part of which is disposed in the single intake passage portion;
The single inlet injector is
The shortest distance between the plurality of injection holes and the center of the single intake port is disposed at a position where the shortest distance is smaller than three times the diameter of the single intake port. The engine unit according to any one of 1 to 9.
The single inlet injector is
The shortest distance between the plurality of injection holes and the center of the single air inlet is disposed at a position where the shortest distance is smaller than twice the diameter of the single air inlet. The engine unit according to 10.
The cylinder portion has at least one exhaust port formed in the at least one combustion chamber,
At least one exhaust port is provided for one combustion chamber,
The engine unit according to any one of claims 1 to 11, wherein a diameter of the intake port is larger than a diameter of the exhaust port.