Ignition system and internal combustion engine

Abstract

The present invention provides an ignition device that can reduce the risk of misfire due to the flame kernel being extinguished by airflow. [Solution] The ignition device 29 is mounted on the cylinder head 82 of an internal combustion engine where an airflow FL is formed along the ceiling surface of the combustion chamber, flowing from the intake port side to the exhaust port side. The ignition device 29 comprises a housing 50, a center electrode 52, a ground electrode 54, and a wall portion 60. The wall portion 60 acts as a barrier to the airflow FL flowing from the outside toward the discharge gap G in the radial direction of the center electrode 52. The ignition device 29 is mounted on the cylinder head 82 in such a orientation that the wall portion 60 is positioned between the intake port and the discharge gap G in the radial direction of the center electrode 52.

Description

Technical Field

[0001] The present invention relates to an ignition device and an internal combustion engine.

Background Art

[0002] Patent Document 1 discloses a spark ignition type internal combustion engine provided with an airflow guide member for changing the direction of the airflow passing through a discharge gap at the time of ignition, in order to prevent flame kernels generated from discharge sparks of an ignition plug from coming into contact with the ceiling of a combustion chamber. The above airflow guide member guides the airflow in the combustion chamber toward the discharge gap located between the ground electrode and the center electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Since the airflow in the combustion chamber flows along the airflow guide member and is guided toward the discharge gap, the flow velocity of the airflow passing through the discharge gap increases. If the flow velocity of the airflow passing through the discharge gap becomes excessively high, there is a risk of misfire as the flame kernel generated by the discharge in the discharge gap is blown out by the airflow.

Means for Solving the Problems

[0005] An ignition device for solving the above problems is an ignition device attached to the cylinder head of an internal combustion engine in which an airflow is formed along the ceiling surface of the combustion chamber from the intake port side to the exhaust port side. The ignition device comprises a housing, an insulating insulator held within the housing, a central electrode protruding from the tip of the insulating insulator, a ground electrode facing the central electrode via a discharge gap in the axial direction of the central electrode, and a wall portion provided at the tip of the housing, which acts as a barrier to the airflow flowing from the outside toward the discharge gap in the radial direction of the central electrode. The ignition device is characterized in that it is attached to the cylinder head in a orientation such that the wall portion is located between the intake port and the discharge gap in the radial direction of the central electrode.

[0006] An internal combustion engine for solving the above problems is an internal combustion engine in which an intake valve for opening and closing an intake port, an exhaust valve for opening and closing an exhaust port, and an ignition device are attached to the cylinder head, and an airflow is formed that flows along the ceiling surface of the combustion chamber from the intake port side toward the exhaust port side. The ignition device is disposed between the intake port and the exhaust port and comprises a housing, an insulating insulator held within the housing, a central electrode protruding from the tip of the insulating insulator, and a ground electrode facing the central electrode in the axial direction of the central electrode via a discharge gap. The ground electrode comprises a facing portion facing the central electrode in the axial direction, and a support portion extending from the tip of the housing and supporting the facing portion. The internal combustion engine is characterized in that, in the cylinder head, a wall portion is provided between the intake port and the central electrode, which acts as a barrier to the airflow flowing toward the discharge gap, and in an axial view of the central electrode, a first straight line passing through the centroid of the wall portion and the central axis of the central electrode and a second straight line passing through the centroid of the support portion and the central axis are orthogonal. [Effects of the Invention]

[0007] The above-described ignition device and internal combustion engine reduce the risk of misfire due to the flame kernel being extinguished by the airflow. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing the structure of the combustion chamber of an internal combustion engine equipped with an ignition device according to the first embodiment. [Figure 2] Figure 2 is a cross-sectional view showing the ignition device shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing the discharge gap of the ignition system shown in Figure 2. [Figure 4] Figure 4 is a cross-sectional view along line 4-4 in Figure 3. [Figure 5] Figure 5 is a cross-sectional view showing an internal combustion engine according to the second embodiment. [Figure 6] Figure 6 is a cross-sectional view along line 6-6 in Figure 5. [Modes for carrying out the invention]

[0009] (First Embodiment) The first embodiment of the ignition device will be described below with reference to Figures 1 to 4.

[0010] <Internal Combustion Engine 10> As shown in Figure 1, the internal combustion engine 10, which is equipped with an ignition device 29, has a cylinder block 80. A cylinder 81 is provided in the cylinder block 80. A piston 14 is housed in the cylinder 81 so as to be reciprocating. A cylinder head 82 is connected to the upper end of the cylinder block 80.

[0011] The internal combustion engine 10 is provided with a combustion chamber 13, which consists of a cylinder 81, a piston 14, and a cylinder head 82. The cylinder head 82 has two roofs 11 and 12 formed therein. The walls of the roofs 11 and 12 function as the ceiling of the combustion chamber 13. In other words, the internal combustion engine 10 has a pent-roof type combustion chamber 13. The cylinder head 82 is provided with an intake port 41 for introducing intake air into the combustion chamber 13 and an exhaust port 42 for discharging exhaust gas from the combustion chamber 13. The intake port 41 is provided with an intake valve 27 that opens and closes the intake port 41 to the combustion chamber 13. The intake valve 27 is located on the roof 11 side. The exhaust port 42 is provided with an exhaust valve 28 that opens and closes the exhaust port 42 to the combustion chamber 13. The exhaust valve 28 is located on the roof 12 side.

[0012] When intake air flows into the combustion chamber 13 from the intake port 41, an airflow FL is formed that flows along the ceiling surface of the combustion chamber 13 from the intake port 41 side to the exhaust port 42 side, as shown by the arrows in Figures 1 to 6. The airflow FL is, for example, a tumble flow.

[0013] The internal combustion engine 10 is equipped with an ignition device 29. The ignition device 29 is located between the intake port 41 and the exhaust port 42 in the cylinder head 82. Specifically, the ignition device 29 is located at the top of the combustion chamber 13 where the roof 11 and roof 12 meet.

[0014] The internal combustion engine 10 is equipped with a fuel injector 30 that directly injects fuel into the combustion chamber 13. The fuel injector 30 is an in-cylinder injector. The fuel injector 30 is located between the ignition device 29 in the roof 11 and the intake port 41. The internal combustion engine 10 may also be equipped with a port injector as the fuel injector 30, which injects fuel into the intake port 41.

[0015] An air-fuel mixture including fuel injected from the fuel injection valve 30 and air introduced into the combustion chamber 13 from the intake port 41 as the intake valve 27 opens is ignited by spark discharge of the ignition device 29 and combusts. The air-fuel mixture that has combusted in the combustion chamber 13 becomes exhaust gas, and is discharged to the exhaust port 42 as the exhaust valve 28 opens.

[0016] <ignition device 29> Figure 2 shows a cross-sectional view of the ignition device 29. Figure 3 is a cross-sectional view of the vicinity of the ground electrode 54 shown in Figure 2. As shown in Figure 2 and Figure 3, the ignition device 29 includes a housing 50, an insulator 51, a center electrode 52, a ground electrode 54, and a wall portion 60. The housing 50 is made of metal. The insulator 51 is made of ceramic. The insulator 51 is assembled into the housing 50 so as to penetrate through the cylindrical housing 50. The insulator 51 is held inside the housing 50.

[0017] The center electrode 52 is made of metal. The center electrode 52 is incorporated into the insulator 51. The center electrode 52 protrudes from the tip end of the insulator 51. That is, the center electrode 52 is exposed from one end of the insulator 51 and disposed inside the combustion chamber 13.

[0018] The ground electrode 54 faces the center electrode 52 across a discharge gap G in the axial direction of the center axis CL indicated by the one-dot chain line of the center electrode 52. The ground electrode 54 includes a facing portion 55 and a support portion 56. The facing portion 55 faces the center electrode 52 in the axial direction. The support portion 56 extends from the tip end of the housing 50 to support the facing portion 55.

[0019] The fuel injection valve 30 injects fuel from an injection port 31. The fuel is injected from the injection port 31 in a direction along the flow of the airflow FL. As shown in Figure 3, a ground electrode tip 57 is provided on the surface 58 of the ground electrode 54 that faces the center electrode 52. When a high voltage is applied to the center electrode 52, spark discharge occurs in the discharge gap G between the center electrode 52 and the ground electrode tip 57. The air-fuel mixture is ignited by the spark discharge, whereby a flame kernel 70 indicated by the two-dot chain line is generated.

[0020] The wall portion 60 is provided at the tip of the housing 50 on the combustion chamber 13 side. The wall portion 60 acts as a barrier against the airflow FL flowing from the outside toward the discharge gap G in the radial direction of the center electrode 52.

[0021] As shown in FIG. 3, the height H1 of the wall portion 60 is equal to or greater than the height H2 of the surface 58 of the ground electrode 54 that faces the center electrode 52. The height H1 is the length from the base end 60A of the wall portion 60 to the distal end 60B rising in the axial direction of the center electrode 52. The base end 60A is located at the tip of the housing 50 on the combustion chamber 13 side. The height H2 is the length from the tip of the housing 50 on the combustion chamber 13 side to the surface 58.

[0022] FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3. As shown in FIG. 4, the ignition device 29 is attached to the cylinder head 82 in an orientation where the wall portion 60 is located between the intake port 41 and the discharge gap G in the radial direction of the center electrode 52. For example, the housing 50 is provided with a screw for attaching the ignition device 29 to the cylinder head 82, which is designed so that the attachment angle of the ignition device 29 becomes a target angle.

[0023] As shown in FIG. 4, when a straight line passing through the centroid 60G of the wall portion 60 and the central axis CL is defined as a first straight line L1, and a straight line passing through the centroid 56G of the support portion 56 and the central axis CL is defined as a second straight line L2 in the axial view of the center electrode 52, the first straight line L1 and the second straight line L2 are orthogonal to each other. Further, the support portion 56 is provided at a position that does not intersect the first straight line L1.

[0024] <Operation of First Embodiment> As shown in FIG. 4, the wall portion 60 located between the intake port 41 and the discharge gap G suppresses the airflow FL flowing toward the discharge gap G. Therefore, when the wall portion 60 is provided, the flow velocity of the airflow FL passing through the discharge gap G is lower than when the wall portion 60 is not provided.

[0025] <Effects of First Embodiment> (1-1) The ignition device 29 of the internal combustion engine 10 reduces the risk of misfire due to the flame kernel 70 being extinguished by the airflow FL.

[0026] (1-2) As shown in Figure 3, the height H1 of the wall portion 60 is greater than or equal to the height H2 of the surface 58 of the ground electrode 54 facing the central electrode 52. The wall portion 60 has a height H1 that completely shields the discharge gap G where spark discharge occurs when viewed from the radially outer side of the central electrode 52. The ignition device 29 of the internal combustion engine 10 can effectively block the airflow FL toward the discharge gap G.

[0027] (1-3) As shown in Figure 3, the ground electrode 54 comprises an opposing portion 55 and a support portion 56. The opposing portion 55 faces the central electrode 52 in the axial direction of the central electrode 52. The support portion 56 extends from the tip of the housing 50 and supports the opposing portion 55.

[0028] As shown in Figure 4, in an axial view of the central electrode 52, the support portion 56 does not intersect the first straight line L1. The airflow FL that has wrapped around the wall portion 60 passes through the discharge gap G located downstream. The flame kernel 70 generated by the spark discharge extends in the direction of the airflow FL. If the support portion 56 is located at the end of the extension of the flame kernel 70, there is a risk that the flame kernel 70 will come into contact with the support portion 56. If the flame kernel 70 comes into contact with the support portion 56, there is a risk that the heat of the flame kernel 70 will be absorbed by the support portion 56, causing it to misfire.

[0029] As shown in Figure 3, the discharge gap G is located on the central axis CL of the central electrode 52. Therefore, the airflow FL that wraps around the wall 60 and passes through the discharge gap G flows in the direction of the first straight line L1 shown in Figure 4 when viewed axially. The flame kernel 70 generated in the discharge gap G extends in the direction of the airflow FL. That is, the flame kernel 70 tends to extend along the first straight line L1. The support portion 56 is provided at a position that does not intersect with the first straight line L1. Therefore, in the internal combustion engine 10 equipped with the ignition device 29, the flame kernel 70 extending downstream along the airflow FL is less likely to come into contact with the support portion 56. The ignition device 29 of the internal combustion engine 10 can reduce the risk of misfire due to contact between the support portion 56 of the ground electrode 54 and the flame kernel 70.

[0030] (1-4) As shown in Figure 4, in the ignition device 29, the second straight line L2 and the first straight line L1 are perpendicular in the axial view of the central electrode 52. The greater the deviation between the direction in which the flame kernel 70 extends from the central electrode 52 along the airflow FL and the direction from the central axis CL of the central electrode 52 toward the centroid 56G of the support part 56, the less likely it is that the flame kernel 70 and the support part 56 will come into contact. On the other hand, if the support part 56 is located on the wall part 60 side of the discharge gap G, the airflow FL flowing toward the discharge gap G is obstructed not only by the wall part 60 but also by the support part 56. In this case, the airflow FL flowing into the discharge gap G is disturbed, which may make it difficult to generate the flame kernel 70.

[0031] The airflow FL passing through the discharge gap G flows in a direction along the first straight line L1. Therefore, if the support part 56 is provided at a position where the first straight line L1 and the second straight line L2 are perpendicular, the airflow FL before it flows into the discharge gap G is less likely to be obstructed by the support part 56. With an ignition device 29 where the first straight line L1 and the second straight line L2 are perpendicular, it is possible to reduce the risk of misfire while making it less likely to disturb the airflow FL flowing into the discharge gap G.

[0032] <Example of modification of the first embodiment> The support portion 56 may, for example, be provided downstream of the discharge gap G in the airflow FL when viewed in the axial direction of the central electrode 52. In this case, the first straight line L1 and the second straight line L2 are not perpendicular. That is, the first straight line L1 and the second straight line L2 do not have to be perpendicular. Even if the first straight line L1 and the second straight line L2 are not perpendicular, as long as the support portion 56 is provided in a position that does not intersect with the first straight line L1, the ignition device 29 will produce the effects shown in (1-1) to (1-3).

[0033] The ignition device 29 may have a ground electrode 54 provided such that the support portion 56 intersects the first straight line L1 in an axial view of the central electrode 52. Even in that case, if a wall portion 60 is provided located between the intake valve 27 and the discharge gap G, the ignition device 29 will have the effects shown in (1-1) and (1-2).

[0034] The optimal height H1 of the wall 60 to reduce the risk of fire may be determined experimentally. In other words, the height H1 of the wall 60 can be changed as appropriate. For example, the height H1 of the wall 60 may be less than the height H2.

[0035] (Second Embodiment) The second embodiment, which is an internal combustion engine, will be described below with reference to Figures 5 and 6. The second embodiment will be described primarily in terms of the differences from the configuration described with reference to Figures 1 to 4.

[0036] As shown in Figure 5, the internal combustion engine 10 of the second embodiment is provided with a wall portion 61 in the cylinder head 82 between the intake port 41 and the central electrode 52, which acts as a barrier to the airflow FL flowing toward the discharge gap G. The wall portion 61 has the same function as the wall portion 60 in the ignition device 29 of the first embodiment. The configuration of the internal combustion engine 10 of the second embodiment is the same except that the wall portion 61 is provided in the cylinder head 82 instead of the wall portion 60 provided in the ignition device 29.

[0037] As shown in Figure 5, the height H3 of the wall portion 61 is greater than or equal to the height H4 of the surface 58 facing the central electrode 52 of the ground electrode 54. Height H3 is the length from the base end 61A of the wall portion 61 to the end 61B that rises axially from the central electrode 52. The base end 61A is located on the roof 11. Height H4 is the length from the base end 61A on the roof 11 to the surface 58.

[0038] Figure 6 is a cross-sectional view along the line 6-6 in Figure 5. As shown in Figure 6, in an axial view of the central electrode 52, the line passing through the centroid 61G of the wall portion 61 and the central axis CL is defined as the first line L3, and the line passing through the centroid 56G of the support portion 56 and the central axis CL is defined as the second line L2. In this case, the ignition device 29 is mounted on the internal combustion engine 10 such that the first line L3 and the second line L2 are perpendicular to each other.

[0039] <Operation of the second embodiment> Even if a wall portion 61 is provided on the cylinder head 82 to suppress the airflow FL that flows toward the discharge gap G, the flow velocity of the airflow FL blown toward the flame kernel 70 generated in the discharge gap G will be reduced.

[0040] The airflow FL passing through the discharge gap G flows in a direction along the first straight line L3. Therefore, if the wall 61 and the support 56 are positioned so that the first straight line L3 and the second straight line L2 are perpendicular to each other, the flame kernel 70 extending downstream by the airflow FL is less likely to come into contact with the support 56.

[0041] The greater the deviation between the direction in which the flame kernel 70 extends from the central electrode 52 along the airflow FL and the direction from the central axis CL of the central electrode 52 toward the centroid 56G of the support portion 56, the less likely it is that the flame kernel 70 and the support portion 56 will come into contact. On the other hand, if the support portion 56 is located on the wall portion 61 side of the discharge gap G, the airflow FL flowing toward the discharge gap G will be obstructed not only by the wall portion 61 but also by the support portion 56. In this case, the airflow FL flowing into the discharge gap G may be disturbed, making it difficult to generate the flame kernel 70. If the wall portion 61 and the support portion 56 are positioned so that the first straight line L3 and the second straight line L2 are perpendicular to each other, the airflow FL before it flows into the discharge gap G is less likely to be obstructed by the support portion 56. In other words, with an internal combustion engine 10 where the first straight line L3 and the second straight line L2 are perpendicular to each other, the risk of misfire can be reduced while making it less likely for the airflow FL flowing into the discharge gap G to be disturbed.

[0042] <Effects of the second embodiment> The configuration of the second embodiment provides the same effects as (1-1) to (1-4) of the first embodiment.

[0043] <Example of modification of the second embodiment> The optimal height H3 of the wall 61 to reduce the risk of fire may be determined experimentally. In other words, the height H3 of the wall 61 can be changed as appropriate. For example, the height H3 of the wall 61 may be less than the height H4. [Explanation of symbols]

[0044] 10...Internal combustion engine, 13...Combustion chamber, 27...Intake valve, 28...Exhaust valve, 29...Ignition device, 41...Intake port, 42...Exhaust port, 50...Housing, 51...Insulator, 52...Center electrode, 54...Ground electrode, 55...Opposite part, 56...Support part, 58...Surface, 60, 61...Wall part, 82...Cylinder head, CL...Central axis, FL...Airflow, G...Discharge gap, L1, L3...First straight line, L2...Second straight line, H1, H3...Height of wall part, H2, H4...Height of the surface opposite the center electrode at the ground electrode

Claims

1. An ignition device attached to the cylinder head of an internal combustion engine, which forms an airflow along the ceiling surface of the combustion chamber from the intake port side to the exhaust port side, The device comprises a housing, an insulating insulator held within the housing, a central electrode protruding from the tip of the insulating insulator, a ground electrode facing the central electrode via a discharge gap in the axial direction of the central electrode, and a wall portion provided at the tip of the housing, which acts as a barrier to the airflow flowing from the outside toward the discharge gap in the radial direction of the central electrode. The central electrode is mounted to the cylinder head in such a orientation that the wall portion is located between the intake port and the discharge gap in the radial direction of the central electrode. Ignition device.

2. The height of the wall portion is characterized in that it is greater than or equal to the height of the surface of the ground electrode facing the central electrode. The ignition device according to claim 1.

3. The aforementioned grounding electrode is In the axial direction of the central electrode, there is a facing portion that faces the central electrode, The housing comprises a support portion extending from the tip of the housing and supporting the opposing portion, In an axial view of the central electrode, the support portion is characterized in that it does not intersect with a straight line passing through the centroid of the wall portion and the central axis of the central electrode. The ignition device according to claim 1.

4. When the line passing through the centroid and the central axis of the wall is defined as the first line, In the axial view, the second straight line passing through the centroid of the support portion and the central axis is perpendicular to the first straight line. The ignition device according to claim 3.

5. An internal combustion engine in which an intake valve for opening and closing an intake port, an exhaust valve for opening and closing an exhaust port, and an ignition device are attached to the cylinder head, and an airflow is formed that flows along the ceiling surface of the combustion chamber from the intake port side toward the exhaust port side, The ignition device is, Displaced between the intake port and the exhaust port, The device comprises a housing, an insulating insulator held within the housing, a central electrode protruding from the tip of the insulating insulator, and a ground electrode facing the central electrode via a discharge gap in the axial direction of the central electrode. The ground electrode comprises, in the axial direction, an opposing portion facing the central electrode and a support portion extending from the tip of the housing and supporting the opposing portion. In the cylinder head, a wall portion is provided between the intake port and the central electrode, which acts as a barrier to the airflow flowing toward the discharge gap. In an axial view of the central electrode, a first straight line passing through the centroid of the wall and the central axis of the central electrode and a second straight line passing through the centroid of the support and the central axis are orthogonal to each other. Internal combustion engine.

Images