This application is based on and claims the benefit of priority from Japanese Patent Application No. 2021-006330, filed on 19 Jan. 2021, the content of which is incorporated herein by reference.
The present disclosure relates to an internal combustion engine.
Direct injection-type internal combustion engines have been known. An internal combustion engine of this type includes a piston that reciprocates in a cylinder, and an ignition plug and a fuel injection nozzle (injector) that face a combustion chamber provided in the cylinder. In the internal combustion engine, while the cylinder is generally filled with a lean air-fuel mixture, fuel is directly injected into the cylinder from the fuel injection nozzle, so that a stratified air-fuel mixture with good ignitability is generated only in the vicinity of the fuel injection nozzle, thereby enabling stratified charge combustion (see, for example, Patent Document 1).
However, according to the conventional technique, fuel is injected to a position above the center of a vortex of a swirl flow in the vertical direction (hereinafter referred to as the intake tumble flow) in the cylinder. As a result, the fuel is carried away by the intake tumble flow toward a cylinder sleeve end to collide with the vicinity of the cylinder sleeve end. This may cause a large amount of the fuel to adhere to the piston.
The present disclosure has been achieved in view of the above circumstances, and is intended to provide an internal combustion engine that can inhibit fuel from adhering to a piston and can reduce generation of soot.
To achieve the above object, a first aspect of the present disclosure provides an internal combustion engine (e.g., an engine 1 to be described later) including a piston (e.g., a piston 20 to be described later), a cylinder (e.g., a cylinder 30 to be described later) accommodating the piston, and an injector (e.g., an injector 10 to be described later including a nozzle (e.g., a nozzle 12 to be described later) that has a plurality of nozzle holes (e.g., nozzle holes 121 to 126 to be described later) configured to inject fuel into the cylinder from above the cylinder. Among the plurality of nozzle holes, one nozzle hole (e.g., a sixth nozzle hole 126 to be described later) an axial direction of which is most deflected toward the piston has a nozzle hole diameter larger than nozzle hole diameters of other nozzle holes. The nozzle hole diameter of the one nozzle hole corresponds to at least 20% of a total of the nozzle hole diameters of the other nozzle holes.
A second aspect of the present disclosure is an embodiment of the first aspect. In the internal combustion engine of the second aspect, all the other nozzle holes may be arranged such that when viewed in an isometric perspective view, division of a length of a straight line extending from a center of each nozzle hole in the axial direction of the nozzle hole to an opposite side wall surface of the cylinder by the nozzle hole diameter of the nozzle hole gives a quotient of 545 or more. At the same time, all the other nozzle holes may be arranged such that when viewed in a planar view, division of a length of a straight line extending from the center of each nozzle hole in the axial direction of the nozzle hole to the opposite side wall surface of the cylinder by the nozzle hole diameter of the nozzle hole gives a quotient of 393 or more.
In the internal combustion engine of the first or second aspect, the plurality of nozzle holes may include: a first nozzle hole (e.g., a first nozzle hole 121 to be described later) as an uppermost one among the plurality of nozzle hole; a sixth nozzle hole (e.g., a sixth nozzle hole 126 to be described later) as a lowermost one among the plurality of nozzle holes, the sixth nozzle hole having the axial direction that is the most deflected toward the piston; a second nozzle hole (e.g., a second nozzle hole 122 to be described later) and a third nozzle hole (e.g., a third nozzle hole 123 to be described later) that are disposed at positions symmetrical to each other with respect to a center line passing through a center of the first nozzle hole and a center of the sixth nozzle hole and that are adjacent to the first nozzle hole; and a fourth nozzle hole (e.g., a fourth nozzle hole 124 to be described later) and a fifth nozzle hole (e.g., a fifth nozzle hole 125 to be described later) that are disposed at positions symmetrical to each other with respect to the center line and that are adjacent to the sixth nozzle hole. The nozzle hole diameters of the second and third nozzle holes may be smaller than those of the first, fourth, and fifth nozzle holes.
The present disclosure provides an internal combustion engine that can inhibit fuel from adhering to the piston and can reduce generation of soot.
An embodiment of the present disclosure will be described in detail with reference to the drawings.
The engine 1 further includes a cylinder block 2 and a cylinder head 3 provided on top of the cylinder block 2. The cylinder 30 having a cylindrical shape and opening upward is formed in the cylinder block 2.
The cylinder 30 accommodates therein the piston 20 such that the piston 20 can slidingly reciprocate. The piston 20 is coupled to the crankshaft (not illustrated), and slidingly reciprocates in the cylinder 30 according to a crank angle, as the engine 1 operates. The piston 20 has, on its top surface, a cavity (not illustrated) into which fuel is injected.
The cylinder head 3 is placed on the cylinder block 2 to cover the cylinder 30. A combustion chamber 4 is formed between the cylinder head 3 and the top surface of the piston 20. The cylinder head 3 has an intake port and an exhaust port (both not illustrated) that open at the combustion chamber 4, and is provided with an intake valve and an exhaust valve (both not illustrated) that open and close the intake and exhaust ports.
The cylinder head 3 is further provided with an ignition plug 5 and the injector (fuel injection nozzle) 10.
The ignition plug 5 is mounted approximately vertically on the cylinder head 3. The ignition plug 5 faces a vicinity of the center of the combustion chamber 4 from above and emits sparks to ignite an air-fuel mixture. The timing (ignition timing) at which the ignition plug 5 emits sparks is controlled by an ECU (not illustrated) according to an operating state of the engine 1.
The injector 10 includes an injector body 11, a nozzle 12 provided at a leading end of the injector body 11, and a solenoid valve (not illustrated) incorporated in the injector body 11 and having a solenoid, a needle valve, etc. The nozzle 12 has, on its leading end surface, a plurality of nozzle holes that face the combustion chamber.
The injector 10 is supplied with a high-pressure fuel from a fuel pump (not illustrated). When the needle valve opens, streams of spray of the fuel are injected through the plurality of nozzle holes into the cylinder 30 at predetermined different angles. The amount of the fuel to be injected by the injector 10 and the injection timing are controlled by the ECU (not illustrated) according to an operating state of the engine 1.
As illustrated in
Next, the six nozzle holes provided to the injector 10 of the present embodiment will be described in detail with reference to
When viewed in the side view illustrated in
The above-mentioned inclination angles satisfy the size relationship described as α1<α2=α3<α4=α5<α6. That is, among the six nozzle holes, the axial direction of the axis C6 of the sixth nozzle hole 126 is inclined most downward and is most deflected toward the piston 20. The sixth nozzle hole 126, the axis of which is the most deflected toward the piston, is the most distant from an opposite side wall surface 31 of the cylinder 30. The present embodiment has the following feature. Among the plurality of nozzle holes provided to the injector 10, the sixth nozzle hole 126, which is the most distant from the opposite side wall surface 31 of the opposing cylinder 30 because of its axial direction being the most deflected toward the piston 20, has a larger nozzle hole diameter than any of the first to fifth nozzle holes 121 to 125 (hereinafter referred to also as the other nozzle holes). This feature will be described later in detail.
As illustrated in
In
As illustrated in
The second nozzle hole 122 and the third nozzle hole 123 are at positions symmetrical to each other with respect to a center line passing through the center of the first nozzle hole 121 and the center of the sixth nozzle hole 126 (a straight line passing through the origin O and extending in the Y-axis direction in
The fourth nozzle hole 124 and the fifth nozzle hole 125 are at positions symmetrical to each other with respect to the center line passing through the center of the first nozzle hole 121 and the center of the sixth nozzle hole 126 (the straight line passing through the origin O and extending in the Y-axis direction in
Table 1 summarizes, for each of the nozzle holes, the angles with respect to the central axis C (in the lateral direction (X-axis direction) and in the vertical direction (Y-axis direction)), the nozzle hole diameter, and a ratio of the nozzle hole diameter to the total of the diameters of all the six nozzle holes.
As shown in Table 1, among the plurality of nozzle holes provided to the injector 10 of the present embodiment, the sixth nozzle hole 126, the axial direction of which is the most deflected toward the piston 20, is larger in nozzle hole diameter than any of the other nozzle holes. As described above, the sixth nozzle hole 126, the axis of which is the most deflected toward the piston, is the nozzle hole most distant from the opposite side wall surface 31 of the cylinder 30. In addition, the sixth nozzle hole 126, which is the most deflected toward the piston, can point and inject fuel toward the center of a vortex with weak flow in a tumble flow having at least vertical swirl flow. In other words, the present embodiment has the following feature. Among the plurality of nozzle holes provided to the injector 10, the sixth nozzle hole 126, which is the most distant from the opposite side wall surface 31 of the opposing cylinder 30 because of its axial direction being the most deflected toward the piston 20 and which can point and inject fuel toward the center of a vortex with weak flow in an intake tumble flow, has a larger nozzle hole diameter than any of the first to fifth nozzle holes 121 to 125 (hereinafter referred to also as the other nozzle holes).
The above feature is based on the following fact. As a nozzle hole diameter increases, a flow rate of fuel and a droplet diameter of fuel increase, thereby enhancing penetration (spray reach distance). The sixth nozzle hole 126, which is the most distant from the opposite side wall surface 31 of the opposing cylinder 30 because of its axial direction being the most deflected toward the piston 20, can inhibit fuel adhesion to the piston 20 even though the sixth nozzle hole 126 has a large nozzle hole diameter. This will be described later in detail.
Specifically, as shown in Table 1, the present embodiment has the configuration in which the sixth nozzle hole 126 has a nozzle hole diameter corresponding to at least 20%, specifically 24.3%, of the total of the nozzle hole diameters of the other nozzle holes. This configuration makes it possible to further reliably inhibit adhesion of fuel to the piston 20.
The above feature is also based on the fact that the sixth nozzle hole 126, which is the most deflected toward the piston, can point and inject fuel toward the center of a vortex with weak flow in an intake tumble flow, whereby the fuel is caused to stagnate around the center of the vortex and is inhibited from being carried away by the intake tumble flow and adhering to the piston 20. This will also be described in detail later.
As shown in Table 1, it is preferable that the second nozzle hole 122 and the third nozzle hole 123 have the same nozzle hole diameter. Likewise, it is preferable that the first nozzle hole 121, the fourth nozzle hole 124, and the fifth nozzle hole 125 have the same nozzle hole diameter. Furthermore, it is preferable that the nozzle hole diameters of the second and third nozzle holes 122 and 123 are smaller than those of the first, fourth, and fifth nozzle holes 121, 124 and 125. This configuration inhibits interference between the fuel flows injected from the nozzle holes.
The other nozzle holes including the first to fifth nozzle holes 121 to 125 will be described in more detail with reference to
All the first to fifth nozzle holes 121 to 125 of the engine 1 of the present embodiment are preferably arranged such that when viewed in the planar view of
[Formula]
Xd=Ld/D Formula (1)
Likewise, all the first to fifth nozzle holes 121 to 125 of the engine 1 of the present embodiment are preferably arranged such that when viewed in the isometric perspective view illustrated in
[Formula]
Xi=Li/D Formula (2)
Table 2 summarizes the nozzle hole diameter D, the ratio of the nozzle hole diameter, the linear distance Li, the ratio Xi of the linear distance Li to the nozzle hole diameter D, the linear distance Ld, and the ratio Xd of the linear distance Ld to the nozzle hole diameter D of the first to fifth nozzle holes 121 to 125.
In the planar view illustrated in
In the isometric perspective view illustrated in
Table 3 summarizes events that are caused by an increase and a decrease in each of the nozzle hole diameter D, the linear distance Li, the ratio Xi of the linear distance Li to the nozzle hole diameter D, the linear distance Ld, and the ratio Xd of the linear distance Ld to the nozzle hole diameter D.
From Table 3, it can be appreciated that setting the ratio Xi of the linear distance Li to the nozzle hole diameter D and the ratio Xd of the linear distance Ld to the nozzle hole diameter D to large values makes it possible to inhibit adhesion of fuel to the piston 20. On the other hand, as shown in Table 2, for all the first to fifth nozzle holes 121 to 125 of the present embodiment, the ratio Xi of the linear distance Li to the nozzle hole diameter D is set to a value equal to or larger than 393 and the ratio Xd of the linear distance Ld to the nozzle hole diameter D is set to a value equal to or larger than 545. Therefore, it can be appreciated that the present embodiment can inhibit adhesion of fuel to the piston 20 and can reduce generation of soot.
A fuel injection operation of the engine 1 of the present embodiment having the above-described configuration will be described in detail with reference to
As illustrated in
In contrast, as illustrated in
Here, results of a simulation according to computational fluid dynamics (CFD), conducted on the engine 1 of the present embodiment and the conventional engine of
The present embodiment exerts the following effects. According to the present embodiment, among the plurality of nozzle holes of the injector 10, the sixth nozzle hole 126, the axial direction of which is the most deflected toward the piston 20, has a nozzle hole diameter larger than those of the other nozzle holes, and the nozzle hole diameter of the sixth nozzle hole 126 corresponds to at least 20% of the total of the nozzle hole diameters of the other nozzle holes. According to the injector 10 of the present embodiment, the sixth nozzle hole 126, the axial direction of which is the most deflected toward the piston 20, can point and inject fuel toward the center of a vortex having weak flow in an intake air tumble flow having at least vertical swirl flow. In addition, the sixth nozzle hole 126, the axial direction of which is the most deflected toward the piston 20, has a larger nozzle hole than any of the other nozzle holes, whereby the fuel is caused to stagnate around the center of the vortex and is inhibited from adhering to the piston 20. As a result, adhesion of the fuel to the piston 20 can be inhibited, and generation of soot can be reduced.
In the present embodiment, all the other nozzle holes are arranged such that when viewed in an isometric perspective view, division of the length of a straight line extending from the center of each nozzle hole in the axial direction of the nozzle hole to the opposite side wall surface 31 of the cylinder 30 by the nozzle hole diameter of the nozzle hole gives a quotient of 545 or more. At the same time, all the other nozzle holes are arranged such that when viewed in a planar view, division of the length of a straight line extending from the center of each nozzle hole in the axial direction of the nozzle hole to the opposite side wall surface 31 of the cylinder 30 by the nozzle hole diameter of the nozzle hole gives a quotient of 393 or more. This feature makes it possible to further reliably inhibit fuel from adhering to the piston 20 and to further reliably reduce generation of soot.
According to the present embodiment, the second nozzle hole 122 and the third nozzle hole 123 have a smaller nozzle hole diameter than the first nozzle hole 121, the fourth nozzle hole 124, and the fifth nozzle hole 125. This feature exerts, in addition to the above-described effects, an effect of inhibiting interference between the fuel flows injected from the nozzle holes.
It should be noted that the above-described embodiment is not intended to limit the present disclosure, and the scope of the present disclosure encompasses modifications and variations that are made within the range in which the object of the present disclosure is achieved.
Number | Date | Country | Kind |
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2021-006330 | Jan 2021 | JP | national |