JP2019157638A - Sub-chamber type ignitor and engine having the same - Google Patents

Abstract

To make a liquid film hardly formed at a wall face of a sub-chamber.SOLUTION: This sub-camber type ignitor 101 has a sub-chamber 20 communicating with a main chamber 72 of a combustion chamber of an engine 100 by a plurality of communication holes 13, an injector 30 for injecting liquid fuel into the sub-chamber 20 in a mist shape as a liquid spray F, and an ignition plug 40. In the following, a center axial line of the fuel spray F injected from the injector 30 is set as a spray center line C3. The ignition plug 40 comprises an ignition part 43 in a position separated from the spray center line C2 in the sub-chamber 20, and ignites the liquid fuel at the ignition part 43. In the following, a center axial line of each communication hole 13 is set as a hole center line C1. The sub-chamber type ignitor 101 is constituted so that the hole center lines C1 intersect with each other when the hole center line C1 is extended into the sub-chamber 20, and the spray center line C2 intersects with a cross point P of the hole center lines C1.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sub-chamber igniter used for ignition of a liquid fuel engine.

  The sub chamber ignition device generally has a sub chamber, an injection device, and a spark plug. The sub chamber is a section constituting a part of the combustion chamber of the engine, and communicates with the main chamber of the combustion chamber through a plurality of communication holes. The injection device injects liquid fuel into the sub chamber as a fuel spray in the form of a mist. The spark plug is provided with an ignition part at the tip, and ignites liquid fuel mixed with gas at the ignition part. The ignition unit is provided at a position away from the spray center line so as not to get wet (so-called plug plug) by the fuel spray injected from the injection device.

  According to such a sub-chamber ignition device, the fuel concentration of the air-fuel mixture in the sub-chamber is maintained higher than the fuel concentration of the air-fuel mixture in the main chamber, so that the ignitability in the sub-chamber is improved. Further, since the flame generated by the ignition in the sub chamber is vigorously ejected from the communication hole into the main chamber, it can be reliably ignited even when the fuel concentration of the air-fuel mixture in the main chamber is low.

JP 2017-137820 A

  When the fuel spray is injected from the injection device into the sub chamber, the injected fuel spray may adhere to the wall surface of the sub chamber and become a liquid film (fuel wet) due to the small volume of the sub chamber. The liquid film becomes a generation factor of PM (particulate matter). In addition, the amount of unevaporated liquid fuel may increase due to the liquid film, which may increase the required injection amount. In addition, the liquid fuel constituting the liquid film may accumulate in the lower portion of the sub chamber and deposit as a deposit in the communication hole.

  The present invention has been made in view of the above circumstances, and an object thereof is to make it difficult to form a liquid film on the wall surface of the sub chamber.

  The sub-chamber igniter (101 to 103) of the liquid fuel engine (100) of the present invention is configured to communicate with the main chamber (72) of the combustion chamber of the engine (100) through a plurality of communication holes (13). A sub-chamber (20), an injection device (30) for injecting liquid fuel into the sub-chamber as a fuel spray (F), and a spark plug (40). Hereinafter, the central axis of the fuel spray injected from the injector is referred to as a spray center line (C3). The ignition plug includes an ignition unit (43) at a position spaced apart from the spray center line in the sub chamber, and is configured to ignite liquid fuel at the ignition unit.

  Below, let the center axis line of each said communicating hole be a hole center line (C1). In the sub-chamber igniter, when the hole center lines extend into the sub-chamber, the hole center lines intersect with each other, and the spray center line intersects with an intersection (P) between the hole center lines. It is configured.

  According to the present invention, since the spray center line intersects with the intersection of the hole center lines, the fuel spray ejected from the injection device can be diffused by utilizing the inflow air from the communication hole. Therefore, the homogeneity of the air-fuel mixture can be improved in the sub chamber. Moreover, it can avoid that the fuel spray injected from the injection device collides with the wall surface of a subchamber by the said spreading | diffusion. Therefore, it becomes difficult to form a liquid film on the wall surface of the sub chamber. Therefore, it is possible to suppress the generation of PM due to the liquid film (fuel wet) and the increase in the required injection amount due to the increase in the unevaporated liquid fuel due to the liquid film. Moreover, it can suppress that the liquid fuel which comprised the liquid film accumulates in the lower part of a subchamber, and accumulates as a deposit in a communicating hole.

  Patent Document 1 was found as a document in which the injection center line of the gas fuel intersects with the intersection of the hole center lines of the plurality of communication holes. However, this document is related to the technical field of gas engines used for cogeneration and the like, and is not related to the technical field of liquid fuel engines. Therefore, the technical fields are different in the first place. Further, since the gas does not become atomized, the gas injection center line is not the atomization center line.

  Moreover, in patent document 1, in order to raise the temperature of the ignition part (ignition part) of a spark plug with the high temperature gas which flows into a subchamber, the ignition part is arrange | positioned in the intersection of the hole centerlines of each communicating hole. Yes. Since the gas injection device also injects the gas fuel toward the ignition unit, as a result, the injection center line of the gas fuel intersects with the intersection of the hole center lines.

  However, in the technical field of liquid fuel engines, the injection device cannot inject fuel spray toward the ignition unit. This is because there is a risk that ignition may become impossible (so-called plug may be covered) when the ignition part gets wet by fuel spray. Therefore, the ignition part of the liquid fuel engine is located at a position away from the spray center line.

  Therefore, even if a person skilled in the technical field of the liquid fuel engine looks at Patent Document 1 and tries to combine the technical idea related to the gas engine with the liquid fuel engine, at most, the center lines of the holes intersect at the ignition part. The spray center line cannot intersect with the ignition part.

It is front sectional drawing which shows the engine of 1st Embodiment. It is the front sectional view and plane sectional view showing the sub chamber type ignition device of an engine. It is a graph which shows the gravity center position of the gas in a subchamber. It is front sectional drawing which shows the subchamber ignition device of 2nd Embodiment. It is front sectional drawing which shows the engine of 3rd Embodiment.

  Next, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments, and can be implemented with appropriate modifications without departing from the spirit of the invention.

[First Embodiment]
FIG. 1 is a front sectional view showing an engine 100 of the present embodiment. The engine 100 is a liquid fuel engine such as a gasoline engine that is assumed to be used as an engine of an automobile or the like. The engine 100 includes a cylinder 70 and a cylinder head 60 provided above the cylinder 70.

  In the following, for the sake of convenience, one of the longitudinal directions of the cylinder 70 is referred to as “upper” and the other is referred to as “lower” for convenience. However, the engine 100 can be installed in any direction, such as installing the cylinder 70 in the horizontal direction or in an oblique direction with respect to the vertical direction.

  The inside of the cylinder 70 constitutes a piston chamber 71, and a piston 77 is accommodated in the piston chamber 71 so as to be slidable in the vertical direction. The upper part of the piston chamber 71 above the piston 77 constitutes a main chamber 72 of the combustion chamber. Connected to the piston 77 is a connecting rod 78 for transmitting power to a crankshaft (not shown).

  The cylinder head 60 is provided with an intake port 61, an exhaust port 69, and a sub chamber type ignition device 101. The intake port 61 is provided with an intake valve 63. An exhaust valve 68 is provided in the exhaust port 69. A main chamber injection device 62 for injecting liquid fuel into the intake port 61 is installed in the cylinder head 60. Therefore, an air-fuel mixture composed of air and liquid fuel is formed in the intake port 61. The main chamber injection device 62 is controlled by an ECU (not shown).

  FIG. 2A is a front sectional view showing the sub chamber ignition device 101, and FIG. 2B is a plan view showing a section taken along the line IIb-IIb. The sub chamber ignition device 101 functions as an ignition device for the engine 100. The sub chamber ignition device 101 includes a housing 10, an injection device 30, and a spark plug 40.

  The housing 10 is installed in a support hole 65 provided in the cylinder head 60. A sub chamber 20 is provided inside the housing 10. The sub chamber 20 is mostly a cylindrical space, and a lower end is a substantially hemispherical space. Hereinafter, the central axis of the cylindrical portion and the extension line thereof are referred to as “sub-chamber center line C2”.

  Hereinafter, for the sake of convenience, one of the lengths of the sub chamber center line C2 in the length direction is referred to as “upper” and the other is referred to as “lower”. However, the sub-chamber igniter 101 can be installed in an arbitrary direction, for example, by setting the length direction of the sub-chamber center line C2 in the horizontal direction or in an oblique direction with respect to the vertical direction. Further, the sub chamber center line C <b> 2 can be installed such that the length direction of the sub chamber center line C <b> 2 is inclined with respect to the length direction of the cylinder 70.

  A plurality of communication holes 13 communicating with the sub chamber 20 are provided at a substantially hemispherical lower end portion of the housing 10. In the figure, the number of communication holes 13 is four, but may be three, five, six, etc., for example. The main chamber 72 and the sub chamber 20 communicate with each other through the plurality of communication holes 13. Hereinafter, the center axis of each communication hole 13 is referred to as “hole center line C1”. When each hole center line C1 is extended into the sub chamber 20, the hole center lines C1 intersect on the sub chamber center line C2. Hereinafter, the intersection of the hole center lines C1 is referred to as “intersection P”.

  The injection device 30 is provided on one side (right side in the drawing) of the sub chamber center line C2 in front view. The injection device 30 is a device for injecting liquid fuel into the sub chamber 20 as a fuel spray F in the form of a mist. The injection device 30 injects the fuel spray F from a position separated from the sub chamber center line C2. Hereinafter, the central axis of the fuel spray F injected from the injection device 30 is referred to as “spray center line C3”. When the injection device 30 injects the liquid fuel from one nozzle hole in the form of a mist, the center axis of the nozzle hole becomes the spray center line C3. On the other hand, when liquid fuel is sprayed in a mist form through a plurality of nozzle holes, the center of gravity line of the plurality of nozzle holes becomes the spray center line C3. The spray center line C3 extends obliquely with respect to the sub chamber center line C2, and intersects each hole center line C1 and the sub chamber center line C2 at the intersection P. The injection device 30 is controlled by the ECU.

  The spark plug 40 is provided on the other side (left side in the drawing) of the sub chamber center line C2 in front view. The spark plug 40 includes one electrode 42 and the other electrode 44 at a lower end portion, and a space portion therebetween constitutes an ignition portion 43. The ignition spark generated in the ignition unit 43 ignites the liquid fuel mixed with the gas. The ignition unit 43 is provided at a position separated from the spray center line C3 so as not to get wet by the fuel spray F. The spark plug 40 is controlled by the ECU.

  Next, the operation of engine 100 will be described. In the intake stroke, the piston 77 shown in FIG. 1 is lowered and the intake valve 63 is opened, and the air-fuel mixture is drawn into the main chamber 72 from the intake port 61.

  In the next compression stroke, the piston 77 rises. With this rise, as shown by the arrows in FIG. 2, an airflow that flows from the main chamber 72 through the communication holes 13 into the sub chamber 20 is generated. These incoming airflows collide at the intersection P. Therefore, the turbulence of the airflow due to the intake air flow occurs at the intersection P and its vicinity. Furthermore, an air flow is generated upward from the intersection P.

  Under such circumstances, the injection device 30 injects the fuel spray F toward the intersection P. The injection timing is specifically as follows. That is, the flow velocity at the intersection P becomes maximum after the middle stage in the compression stroke. However, after the middle stage of the compression stroke, the upward air flow generated in the sub chamber 20, that is, the air flow toward the injection device 30 side also becomes strong. Therefore, even if the fuel spray F is injected from the injection device 30 at this timing, most of the fuel spray F does not reach the height of the intersection P. Therefore, the fuel concentration in the lower part of the sub chamber 20 decreases, and the homogeneity of the air-fuel mixture in the sub chamber 20 decreases, so that the engine performance also decreases.

  FIG. 3 shows the position of the center of gravity of the gas with respect to the rotation angle of the engine 100 in the compression stroke. If the fuel spray F is injected so as to reach the intersection P within a period R surrounded by a circle in the drawing, that is, when the center of gravity of the gas is low, most of the fuel spray F reaches the height of the intersection P. However, even if the fuel spray F is injected after the position of the center of gravity becomes high, most of the fuel spray F does not reach the height of the intersection P.

  In this respect, the injection timing in the present embodiment is an injection timing at which the fuel spray F reaches the intersection P when the position of the center of gravity of the gas is low. More specifically, the fuel spray F reaches the intersection P and collides with the inflow airflow from each communication hole 13 at the intersection P before the speed of the airflow at the intersection P reaches the maximum in the compression stroke. This is the timing (hereinafter referred to as “preferred timing”). Therefore, the liquid fuel can be efficiently diffused by utilizing the disturbance generated at the intersection P and its vicinity. Thereby, the homogeneity of the air-fuel mixture can be improved in the lower part of the sub chamber 20. Further, by injecting the fuel spray F into the turbulence, the spray penetration is reduced and the adhesion of the fuel spray F to the wall surface of the sub chamber 20 can be suppressed.

  The injection timing (the rotation angle of the engine at the time of injection) is configured to change according to the rotation speed of the engine 100. This is because the state of the airflow at the intersection P and its surroundings and the strength of the ascending airflow in the sub chamber 20 also change according to the number of revolutions of the engine 100, and the preferred timing also changes due to those changes. Preferably, the injection timing changes so as to be the above-mentioned suitable timing regardless of the rotation speed of engine 100. However, the injection timing may be the above-described suitable timing only when the rotational speed of the engine 100 is within a frequently used desired range.

  As shown in FIG. 2, the intersection P serving as the target of the fuel spray F is on the sub-chamber center line C2 farthest from the inner peripheral surface of the sub chamber 20, so that the fuel spray F is in the inner periphery of the sub chamber 20. It is hard to collide with the surface. And the collision width of the fuel spray F to the wall surface of the sub chamber 20 is avoided by making the spread width of the fuel spray F to be injected smaller than the inner diameter of the sub chamber 20. Preferably, the spread width of the fuel spray F is maximized within a limit that does not exceed the inner diameter of the sub chamber 20. Thereby, the volume in the sub chamber 20 can be utilized to the maximum, and the homogeneity of the air-fuel mixture in the sub chamber 20 can be improved.

  After the liquid fuel is diffused at the intersection P and its periphery and mixed with air, the liquid fuel rides on the rising air current in the sub chamber 20 and spreads to the upper portion of the sub chamber 20. Therefore, the homogeneity in the vertical direction of the air-fuel mixture in the sub chamber 20 is improved.

  Thereafter, liquid fuel (air mixture) mixed with air is ignited by the igniter 43 of the spark plug 40 at the timing when the compression stroke ends or before and after. At this time, since the fuel concentration of the air-fuel mixture in the sub chamber 20 is higher than the fuel concentration of the air-fuel mixture in the main chamber 72, the ignitability is good.

  In the next expansion stroke, a flame is generated in the sub chamber 20 shown in FIG. When the flame is squeezed through the communication hole 13, it becomes a high-speed flame and is released into the main chamber 72. Therefore, even when the fuel concentration of the air-fuel mixture in the main chamber 72 is low, ignition can be ensured. Thereby, the efficiency of ignition is improved and high-speed combustion can be realized.

  In the next exhaust stroke, the piston 77 is raised and the exhaust valve 68 is opened to exhaust the gas in the main chamber 72 to the exhaust port 69.

  According to this embodiment, the homogeneity of the air-fuel mixture in the sub chamber 20 can be improved as described above. Further, as described above, it is difficult to form a liquid film on the wall surface of the sub chamber 20. Therefore, it is possible to suppress the generation of PM due to the liquid film (fuel wet) and the increase in the required injection amount due to the increase in the amount of unevaporated liquid fuel due to the liquid film. Moreover, it can suppress that the liquid fuel which comprised the liquid film accumulates in the lower part of a subchamber, and accumulates as a deposit in the communicating hole 13. FIG.

  Next, second and third embodiments will be described. In these embodiments, only differences from the first embodiment will be described. The members that are the same as or correspond to the members of the first embodiment are denoted by the same reference numerals. However, the sub-chamber igniter is given a different symbol for each embodiment.

[Second Embodiment]
FIG. 4 shows the sub-chamber igniter 102 of the second embodiment. In this embodiment, the timing which the injection device 30 injects the fuel spray F differs from 1st Embodiment. That is, there is a timing at which the airflow at the intersection P can be utilized to the maximum in the intake stroke. Even if the fuel spray F is injected at this timing, it is possible to avoid collision of the fuel spray F with the wall surface of the sub chamber 20 and to improve the homogeneity of the air-fuel mixture in the sub chamber 20.

  Specifically, during the intake stroke, an intake airflow from the communication hole 13 on the intake valve 63 side and an exhaust airflow to the communication hole 13 on the opposite side are generated in the sub chamber 20. An air current is generated at the intersection P by these air currents. Under such circumstances, the injection device 30 injects the fuel spray F toward the intersection P. The injection timing is the timing at which the fuel spray F reaches the intersection P and collides with the inflow airflow from the communication hole 13 at the intersection P when the velocity of the airflow at the intersection P reaches the maximum in the intake stroke ( Hereinafter, it is referred to as “second suitable timing”). This is because the airflow at the intersection P can be utilized to the maximum.

  The injection timing is configured to change according to the rotational speed of engine 100. This is because the time when the velocity of the airflow at the intersection P is maximized changes according to the rotation speed of the engine 100, and the second suitable timing also changes due to the change. Preferably, the injection timing changes so as to be the above-described second suitable timing, regardless of the engine 100 speed. However, the injection timing may be the second suitable timing only when the rotational speed of the engine 100 is within a frequently used desired range. Also according to this embodiment, the homogeneity of the air-fuel mixture in the sub chamber 20 can be improved, and a liquid film can be hardly formed on the wall surface of the sub chamber 20.

[Third Embodiment]
FIG. 5 shows an engine 100 according to the third embodiment. In this embodiment, the first embodiment is replaced with a direct injection engine, and a main chamber injection device 62 is installed so as to inject liquid fuel directly into the main chamber 72. The sub chamber ignition device 103 is the same as that of the first embodiment. The present invention can also be implemented by this embodiment.

[Other Embodiments]
The present embodiment can be implemented with the following modifications. For example, the spark plug 40 shown in FIG. 2 or the like may be disposed at the left end, and the injection device 30 and the spray center line C3 may be disposed on the sub chamber center line C2. Further, for example, the intersection P between the hole center lines C1 and the spray center line C3 may be arranged at a position separated from the sub chamber center line C2.

  Further, for example, in the first embodiment, the injection timing of the fuel spray F may be set to a timing at which the tip of the fuel spray F cannot reach the intersection P due to the rising airflow in the sub chamber 20. Even in this case, the effect that the fuel spray F diffuses due to the turbulence of the airflow before the intersection P can be expected.

  Further, for example, in the second embodiment shown in FIG. 4, the fuel spray F reaches the intersection P before or after the injection timing of the fuel spray F reaches the maximum when the velocity of the airflow at the intersection P becomes maximum. The injection timing may be set as follows.

  Further, for example, in each embodiment, the engine 100 may be a power generation engine or the like. In that case, since the engine speed can be made substantially constant, there is no particular problem even if the injection timing is not changed according to the engine speed.

  DESCRIPTION OF SYMBOLS 13 ... Communication hole, 20 ... Sub chamber, 30 ... Injection device, 40 ... Spark plug, 43 ... Ignition part, 72 ... Main chamber, 100 ... Engine, 101-103 ... Sub chamber ignition device, C1 ... Hole center line, C2 ... sub chamber center line, C3 ... spray center line, F ... fuel spray, P ... intersection.

Claims (6)

A sub chamber (20) configured to communicate with the main chamber (72) of the combustion chamber of the engine (100) through a plurality of communication holes (13), and liquid fuel sprayed in a mist form in the sub chamber (F) ) As an injection device (30), and a spark plug (40),
With the central axis of fuel spray injected from the injector as the spray center line (C3), the spark plug includes an ignition unit (43) at a position spaced apart from the spray center line in the sub chamber. In the engine sub-chamber igniter (101 to 103) configured to ignite liquid fuel at
The center axis of each communication hole is defined as a hole center line (C1), and when each hole center line is extended into the sub chamber, the hole center lines intersect with each other, and the spray center line passes between the hole center lines. A sub-chamber igniter configured to intersect the intersection (P).   The sub-chamber igniter according to claim 1, wherein the sub-chamber has a sub-chamber center line (C2) as a central axis thereof, and the injection device injects fuel spray from a position spaced from the sub-chamber center line. .   The sub-chamber igniter according to claim 2, wherein the intersection is arranged on the sub-chamber center line, and the spray center line obliquely intersects the sub-chamber center line at the intersection. An engine comprising the sub chamber ignition device according to any one of claims 1 to 3,
The injection timing of the fuel spray by the injection device is such that the fuel spray reaches the intersection and flows from the communication hole at the intersection before the time when the velocity of the airflow at the intersection becomes maximum in the compression stroke. The engine that is the timing when it will collide with the airflow. An engine comprising the sub chamber ignition device according to any one of claims 1 to 3,
The fuel spray injection timing by the injection device is such that when the velocity of the airflow at the intersection becomes the maximum in the intake stroke, the fuel spray reaches the intersection and collides with the inflow airflow from the communication hole at the intersection. The engine that is at the right time. An engine comprising the sub-chamber igniter according to any one of claims 1 to 3, or the engine according to claim 4 or 5,
The engine configured to change the injection timing of the fuel spray by the injection device in accordance with the rotational speed of the engine.

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