JP2007297942A - Ignition device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve combustibility in a device igniting by torch shape flame blowing out of an auxiliary chamber. <P>SOLUTION: This device is provided with the auxiliary chamber 15 projecting toward lower side in a cylinder axis direction from a ceiling surface 14 of a combustion chamber 12 and communicating to the combustion chamber (main combustion chamber) 12 via at least one injection hole 11a, and a spark plug 8 having a center electrode 8a face to the auxiliary chamber 11 and discharging between the center electrode 8a and some section of an inner wall surface of the auxiliary chamber 15. Opening area of a main combustion chamber side opening part 11c of the injection hole 11a is formed greater than an auxiliary combustion chamber side opening part 11b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine including a sub-combustion chamber.

  In order to improve the combustibility of an internal combustion engine, in addition to a combustion chamber (main combustion chamber), a sub-combustion chamber communicating with the main combustion chamber via an injection hole is provided, and an ignition plug is provided in the sub-combustion chamber It has been known.

  For example, in an internal combustion engine with a sub-combustion chamber described in Patent Document 1, an air-fuel mixture in the main combustion chamber is introduced into the sub-combustion chamber and sparks are ignited near the compression top dead center in the compression stroke. When combustion starts, the pressure in the sub-combustion chamber suddenly increases, creating a pressure difference between the main combustion chamber and the sub-combustion chamber, and the combustion gas in the sub-combustion chamber is directed to the main combustion chamber from the nozzle hole. And erupts.

By igniting the air-fuel mixture in the main combustion chamber with this torch-like flame, the flame propagation speed of the main combustion chamber as a whole is increased and the combustibility is improved. In addition, if the torch-like flame reaches near the outer periphery of the combustion chamber, the air-fuel mixture near the outer periphery of the combustion chamber, which may be extinguished due to cooling loss on the cylinder wall surface, can be surely burned. Effects such as knocking prevention can also be obtained.
JP-A-8-284665

  However, in the configuration of the sub-combustion chamber described in Patent Document 1, the nozzle hole communicating the main combustion chamber and the sub-combustion chamber has a flow passage cross section from the main combustion chamber side opening to the sub combustion chamber side opening. It is almost constant. For this reason, in order to further improve the combustibility, the pressure in the auxiliary combustion chamber is increased at the start of combustion by reducing the opening area of the nozzle hole so that the torch-like flame reaches more vigorously and far away. It is necessary to erupt. However, if the opening area of the nozzle hole is made smaller, it becomes difficult for gas to flow from the main combustion chamber to the sub-combustion chamber during the compression stroke. Will be reduced. In addition, since it is difficult for the gas in the main combustion chamber to be scavenged in the exhaust stroke, the gas exchange property is deteriorated, and the burned gas tends to stay in the sub-combustion chamber, which may deteriorate the combustibility in the sub-combustion chamber. is there. On the other hand, when the opening area of the nozzle hole is increased, the burned gas in the auxiliary combustion chamber is easily discharged, but during combustion, the combustion gas is injected into the main combustion chamber before the pressure in the auxiliary combustion chamber is sufficiently increased. The increase in the pressure in the auxiliary combustion chamber is reduced. For this reason, the reach distance of the torch-like flame is shortened, and the effect of improving the combustibility is reduced.

  That is, in the structure of the auxiliary combustion chamber described in Patent Document 1, the effect of improving combustibility is small. Accordingly, an object of the present invention is to further improve the combustibility.

  The ignition device for an internal combustion engine of the present invention projects from the ceiling surface of the main combustion chamber downward in the cylinder axial direction, communicates with the combustion chamber through at least one or more injection holes, and a center electrode includes the center electrode. An ignition plug that faces the sub-combustion chamber and discharges between the central electrode and any part of the inner wall surface of the sub-combustion chamber, and the combustion chamber side opening of the nozzle hole is on the side of the sub-combustion chamber The opening area is formed larger than the opening.

  According to the present invention, since the opening area on the main combustion chamber side is larger than that on the sub-combustion chamber side, gas easily flows from the main combustion chamber to the sub-combustion chamber, and the pressure in the sub-combustion chamber after starting combustion It becomes difficult for the combustion gas to be ejected until the temperature rises. Thereby, the pressure increase margin in the sub-combustion chamber is increased, and the reach distance of the torch-like flame is increased, so that the combustibility can be further improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an internal combustion engine to which the present embodiment is applied. 1 is an engine body (hereinafter simply referred to as “engine”), 2 is an intake passage, 3 is an exhaust passage, 4 is an intake valve, 5 is an exhaust valve, 6 is an intake camshaft, 7 is an exhaust camshaft, and 8 is a spark plug , 9 is a combustion injection valve, 10 is a piston, 11 is a dome portion, 12 is a combustion chamber (main combustion chamber), 13 is a swirl control valve (hereinafter referred to as SCV), and 15 is a sub-portion formed inside the dome portion 11. It is a combustion chamber. The engine 1 is provided with two intake valves 4 and two exhaust valves 5 per cylinder. Therefore, the intake passage 2 and the exhaust passage 3 are branched and merged on the way.

  In the engine 1 configured as described above, for example, combustion is injected from the combustion injection valve 9 toward the intake passage 2 during the exhaust stroke, and this fuel is introduced into the combustion chamber 12 while being mixed with air during the intake stroke. To form an air-fuel mixture. The air-fuel mixture in the combustion chamber 12 is introduced into the sub-combustion chamber 15 inside the dome portion 11 through the nozzle hole 11a during the compression stroke. When the piston 10 reaches the vicinity of the compression top dead center, the spark plug 8 sparks and starts combustion. As the combustion starts, the pressure in the auxiliary combustion chamber 15 increases due to the expansion of the combustion gas, and the combustion gas is ejected as a torch-like flame from the nozzle hole 11a toward the main combustion chamber 12. In the exhaust stroke, the exhaust is discharged into the exhaust passage when the piston 10 rises as in a general engine. At this time, the burned gas inside the dome portion 11 is also discharged through the nozzle hole 11a. Here, the combustion in the sub-combustion chamber 15 in the dome portion 11 is referred to as initial combustion, and the combustion in the main combustion chamber 12 is referred to as main combustion.

  The SCV 13 is provided in any one of the branched intake passages 2 and is configured to be able to adjust the flow path cross-sectional area. The operation is controlled according to operating conditions by a control unit (not shown). For example, an intake passage in which the SCV 13 is not provided by reducing the flow passage cross-sectional area of the intake passage 2 under an operating condition where combustion is not stable as in cold start or an operating condition where the combustion speed is low as in low load operation. 2, and a swirl flow is generated inside the main combustion chamber 12.

  Note that a tumble control valve for generating a tumble flow may be provided instead of the SCV 13.

  Next, the dome part 11 will be described.

  FIG. 2 is an enlarged view of the periphery of the dome portion 11 of FIG. As shown in the figure, the dome portion 11 is formed so as to cover the protruding portion of the spark plug 8 from the combustion chamber ceiling surface 14, and communicates the main combustion chamber 12 with the auxiliary combustion chamber 15 inside the dome portion 11. A plurality of nozzle holes 11a are provided. The dome portion 11 also serves as a ground electrode. The nozzle hole 11a is arranged so that the torch-shaped flame spreads radially into the combustion chamber 12 as indicated by the arrow in the figure, and the distance from the center electrode 8a of the spark plug 8 is substantially equal. . In addition, all the opening areas of each nozzle hole 11a are made substantially equal. The spark plug 8 does not include a so-called side electrode and discharges between the inner wall of the dome portion 11 as will be described later.

  By forming the dome portion 11 so as to cover the spark plug 8 in this way, even when a swirl flow is generated, the vicinity of the center electrode 8a of the spark plug 8 is less affected by the swirl flow. Thereby, it is possible to prevent the flame from being blown off by the swirl flow at the time of ignition, and to stabilize the main combustion. Note that it is not always necessary to provide a plurality of nozzle holes 11a.

  FIG. 3 is a diagram showing another example of the dome portion 11. The configuration is basically the same as that in FIG. 2, but the protrusion 16 is provided on the inner wall of the dome 11 on the axial extension line of the center electrode 8a. Since the protruding portion 16 protrudes from the inner wall of the dome portion 11, it becomes a ground electrode when discharged from the center electrode 8a. Thus, by providing the projection 16 as the ground electrode, it is possible to generate a spark more stably, and further stabilization of the main combustion can be achieved.

  FIG. 4 is a view showing still another example of the dome portion 11. The arrangement of the nozzle holes 11a is the same as that shown in FIGS. 2 and 3, except that some of the plurality of nozzle holes 11a are used as the nozzle holes 11a having different opening areas. For example, the opening area of the nozzle hole 11a arranged on the lower end side of the dome portion 11 is made larger than the opening area of the nozzle hole 11a arranged on the upper side.

  With such a configuration, for example, in the exhaust stroke, when the burned gas flows from the combustion chamber 12 into the dome 11 as the piston 10 moves up, it easily flows from the nozzle hole 11a having a large opening area. When a large amount of gas flows in from the nozzle hole 11a having a large opening area and the pressure inside the dome 11 rises, it becomes difficult to flow into the dome 11 from the nozzle hole 11a having a small opening area. Due to the pressure difference from the gas 12, the gas flows out from the inside of the dome 11 to the combustion chamber 12. Thus, the gas exchange property between the inside of the dome 11 and the combustion chamber 12 is improved by generating a gas flow that flows in from the nozzle hole 11a having a large opening area and flows out from the nozzle hole 11a having a small opening area. Therefore, the amount of burned gas staying in the dome 11 can be suppressed, and a more stable initial flame can be obtained.

  The method of distributing the nozzle holes 11a having different opening areas is not limited to the above.

  FIG. 5 is a diagram showing another example of the dome portion 11. In FIG. 5, the combustion chamber 12 is divided into two parts by a cross section including the ignition plug 8 and extending in the cylinder row direction, and one is an intake valve 6 side and the other is an exhaust valve 7 side. The nozzle hole 11a is provided so that the flame is ejected toward the intake valve 6 side. The temperature in the combustion chamber 12 is relatively lower on the intake valve 6 side than on the exhaust valve 7 side. This is because the exhaust valve 7 is warmed by the high-temperature gas after combustion discharged from the exhaust passage 3, whereas the intake valve 6 is exposed to the high-temperature gas in the expansion stroke and then the intake passage 2 in the intake stroke. This is because the air is cooled by the intake air flowing in from the air. Due to the temperature distribution in the combustion chamber 12, there is a difference in the propagation speed of the flame, and the combustion speed on the intake valve 6 side is relatively slower than that on the exhaust valve 7 side. Therefore, as shown in FIG. 5, the torch-like flame is ejected toward the intake valve 6, thereby increasing the combustion speed on the intake valve 6 side and reducing the gradient of the combustion speed in the combustion chamber 12. Improves stability. Although only one injection hole 11a is shown in FIG. 5, a plurality of injection holes 11a may be provided if a torch-like flame is emitted toward the intake valve 6 side from the spark plug 8. Absent.

  FIG. 6 is a diagram showing another example of the dome portion 11. Here, the nozzle hole 11 a is provided so that the torch-like flame is ejected in the vicinity of the combustion chamber ceiling surface 14 along the inclination of the combustion chamber ceiling surface 14. When the flame is propagated from the central portion of the combustion chamber 12 by general spark ignition, there is a risk that the flame is extinguished during the propagation due to a cooling loss near the ceiling surface 14 of the combustion chamber. Further, the flame may be extinguished on the crown surface of the piston 10 due to the cooling loss. If the flame extinguishes in the middle of propagation in this way, the air-fuel mixture does not burn near the outer periphery of the combustion chamber 12 and causes unburned HC to be discharged. However, as shown in FIG. 6, when the torch-like flame is ejected along the combustion chamber ceiling surface 14, the flame reaches the vicinity of the outer periphery of the combustion chamber 12, so that the discharge of unburned HC can be suppressed. .

  Next, the nozzle hole 11a provided in the dome part 11 mentioned above is demonstrated using figures.

  FIG. 7 is a view showing an example of the nozzle hole 11 a and is a cross-sectional view of the nozzle hole 11 a portion of the dome portion 11. As shown in FIG. 7, the nozzle hole 11 a has a so-called orifice shape in which the flow path cross-sectional area gradually increases from the inner surface to the outer surface of the dome portion 11. That is, the opening 11c on the combustion chamber 12 side is larger than the opening 11b on the sub-combustion chamber 15 side, and both the openings are connected by a conical surface.

  In addition, in this embodiment, although the flow-path cross-sectional shape of the nozzle hole 11a is substantially circular, it is not necessarily restricted to this.

  When the nozzle hole 11a is formed in the above-described orifice shape, when the air-fuel mixture flows from the combustion chamber 12 side toward the auxiliary combustion chamber 15, the loss coefficient when passing through the nozzle hole 11a is reduced. Therefore, the air-fuel mixture quickly flows into the auxiliary combustion chamber 15. And when it flows to the combustion chamber 12 direction from the subcombustion chamber 15 side, it will flow more rapidly. Therefore, the gas exchange property between the combustion chamber 12 and the auxiliary combustion chamber 15 during the compression stroke of the engine 1 is improved.

  Further, since the opening area of the opening 11b on the side of the auxiliary combustion chamber 15 is relatively small, it is difficult for the combustion gas to be ejected from the nozzle hole 11a when the pressure immediately after the start of combustion is not sufficiently high. Accordingly, the pressure inside the combustion chamber 15 is likely to rise, and when the pressure increases, the combustion gas becomes a torch-like flame and is ejected vigorously.

  Thus, the combustion in the auxiliary combustion chamber 15 and the main combustion in the combustion chamber 12 can be stabilized and the combustion speed can be increased. In addition, because the ignition timing can be increased by stabilizing the main combustion, emissions from the afterburning effect such as when the engine is started can be significantly reduced while ensuring the combustion of the engine 1. can do.

  FIG. 8 is a view showing another example of the nozzle hole 11a. As shown in the figure, the opening 11c on the combustion chamber 12 side has a larger opening area than the opening 11b on the sub-combustion chamber 15 side, and the flow passage section is narrowed in the middle than the opening 11b on the combustion chamber side. A diaphragm portion 20 is provided. From the opening portion 11b on the auxiliary combustion chamber 15 side to the end portion on the auxiliary combustion chamber 15 side of the throttle portion 20, and from the opening portion on the combustion chamber 12 side to the end portion on the combustion chamber 12 side of the throttle portion 20, respectively. The flow path is gradually narrowed toward 20.

  With such a shape, a rectifying effect by the throttle portion 20 can be obtained, so that the flame ejected from the nozzle hole 11a can be further stabilized as compared with the shape shown in FIG.

  Fig.9 (a) is a figure which shows another example of the nozzle hole 11a. As shown in the figure, a counterbore hole 21 having a constant flow path cross-sectional area by a predetermined depth is provided from the inner surface to the outer surface of the dome portion 11, and the space between the bottom surface 21 a of the counterbore hole 21 and the outer surface of the dome portion 11 is changed to In the same manner as the above, the cross-sectional area of the flow path gradually increases. In FIG. 9A, the diameter of the counterbore hole 21 and the diameter of the opening on the combustion chamber 12 side are substantially the same, but the present invention is not limited to this.

  If it makes such a shape, as shown in FIG.9 (b), a part of combustion gas immediately after ignition will collide with the bottom face 21a of the counterbore hole 21, and will turn in the center direction of the nozzle hole 11a. The swirl flow blocks the nozzle hole 11a and prevents the combustion gas from being ejected from the nozzle hole 11a. Therefore, compared with the shape shown in FIGS. 7 and 8, the pressure of the auxiliary combustion chamber 15 in the dome portion 11 can be further increased, and the combustion gas is torch-shaped from the nozzle hole 11a in a state where the pressure is increased. Can be ejected as a flame. As a result, it is possible to further stabilize the flame ejected from the nozzle hole 11a and to disperse it far away, so that it is possible to further stabilize the main combustion and increase the combustion speed.

  FIG. 10 is a diagram illustrating another example of the nozzle hole 11a. Basically, it is the same as the injection hole 11a shown in FIG. 9, but the portion from the combustion chamber 12 side to the bottom surface 21a of the counterbore hole 21 is formed in a funnel shape.

  With such a shape, in addition to the same effect as the nozzle hole 11a shown in FIG. 9, when the flame is ejected, the flame smoothly separates from the wall surface of the nozzle hole 11a, and the flame is further distant. Therefore, the main combustion can be further stabilized and the combustion speed can be increased.

  The injection hole 11a shown in FIGS. 7 to 10 may be combined with any of the dome parts 11 shown in FIGS.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a schematic block diagram of the engine to which this embodiment is applied. It is a figure showing an example of a dome part. It is a figure showing an example of a dome part. It is a figure showing an example of a dome part. It is a figure showing an example of a dome part. It is a figure showing an example of a dome part. It is a figure showing an example of a nozzle hole. It is a figure showing an example of a nozzle hole. It is a figure showing an example of a nozzle hole. It is a figure showing an example of a nozzle hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 3 Exhaust passage 4 Intake valve 5 Exhaust valve 6 Intake camshaft 7 Exhaust camshaft 8 Spark plug 9 Fuel injection valve 10 Piston 11 Dome part 12 Combustion chamber 13 Swirl control valve (SCV)
14 Combustion chamber ceiling

Claims (12)

A sub-combustion chamber that projects downward from the ceiling surface of the main combustion chamber in the cylinder axial direction and communicates with the combustion chamber via at least one nozzle hole;
A spark plug that discharges between the center electrode and any part of the inner wall surface of the sub-combustion chamber, with the center electrode facing the sub-combustion chamber;
With
An ignition device for an internal combustion engine, wherein an opening area of a main combustion chamber side opening of the nozzle hole is formed larger than that of an auxiliary combustion chamber side opening.   2. The ignition device for an internal combustion engine according to claim 1, wherein a protrusion is provided on an inner wall surface of the auxiliary combustion chamber.   The ignition device for an internal combustion engine according to claim 2, wherein the protrusion is provided on a wall surface of the auxiliary combustion chamber in the axial direction of the center electrode.   2. A plurality of the nozzle holes are provided, and all the nozzle holes are arranged so that distances between the center electrode and the centroid of the auxiliary combustion chamber side opening are substantially equal. The ignition device for an internal combustion engine according to any one of claims 1 to 3.   5. The internal combustion engine ignition according to claim 1, wherein a plurality of the nozzle holes are provided, and a part of the nozzle holes has an opening area different from that of the other nozzle holes. apparatus.   The ignition device for an internal combustion engine according to any one of claims 1 to 5, wherein the nozzle hole is provided so as to communicate with an intake valve side portion of the main combustion chamber.   The said nozzle hole is opened so that a torch-like flame may be jetted in the vicinity of the main combustion chamber ceiling surface along the inclination of the main combustion chamber ceiling surface. An ignition device for an internal combustion engine according to 1.   The ignition device for an internal combustion engine according to any one of claims 1 to 7, wherein an opening area of the nozzle hole gradually increases from the sub-combustion chamber side to the main combustion chamber side.   The ignition device for an internal combustion engine according to claim 8, wherein the injection hole is formed in a funnel shape from the sub-combustion chamber side toward the main combustion chamber side.   The ignition device for an internal combustion engine according to claim 8 or 9, wherein the injection hole has a throttle portion between the sub-combustion chamber side and the main combustion chamber side.   The ignition device for an internal combustion engine according to claim 10, wherein a flow passage cross-sectional area of the throttle portion is smaller than an opening area on the side of the auxiliary combustion chamber.   The ignition device for an internal combustion engine according to any one of claims 8 to 11, wherein the nozzle hole has a countersink of a predetermined depth around the opening portion on the side of the auxiliary combustion chamber.

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