Ignition device and internal combustion engine

Abstract

The present application relates to an ignition device and an internal combustion engine. The ignition device is mounted to a cylinder head of an internal combustion engine formed with an airflow flowing along a top surface of a combustion chamber from an intake port side toward an exhaust port side. The ignition device has a housing, a center electrode, a ground electrode, and a wall portion. The wall portion becomes a barrier to the airflow flowing in a radial direction of the center electrode from an outer side toward a discharge gap. The ignition device is mounted to the cylinder head with the wall portion located between the intake port and the discharge gap in the radial direction of the center electrode.

Description

Technical Field

[0001] This disclosure relates to ignition devices and internal combustion engines. Background Technology

[0002] Japanese Patent Application Publication No. 2015-175318 discloses a spark-ignition internal combustion engine. To prevent the flame nucleus generated by the spark from the spark plug from contacting the top surface of the combustion chamber, an airflow guiding member is provided to change the direction of the airflow passing through the discharge gap during ignition. This airflow guiding member guides the airflow within the combustion chamber toward the discharge gap between the ground electrode and the center electrode. Summary of the Invention

[0003] The airflow in the combustion chamber flows along the airflow guiding member and is directed toward the discharge gap, thus increasing the airflow velocity through the discharge gap. If the airflow velocity through the discharge gap is too high, the flame nucleus generated by the discharge in the discharge gap will be extinguished by the airflow, which may lead to misfire.

[0004] Based on the above viewpoint, the ignition device of the first aspect of this disclosure is mounted on the cylinder head of an internal combustion engine that forms an airflow flowing along the top surface of the combustion chamber from the intake port side toward the exhaust port side. The ignition device includes: a housing; an insulator held within the housing; a center electrode protruding from the front end of the insulator; a ground electrode facing the center electrode axially across a discharge gap; and a wall portion disposed at the front end of the housing, serving as a barrier against the airflow flowing radially from the center electrode toward the discharge gap. The ignition device is mounted on the cylinder head with the wall portion located radially between the intake port and the discharge gap on the center electrode.

[0005] Based on the above viewpoint, in the internal combustion engine of the second aspect of this disclosure, an intake valve for opening and closing the intake port, an exhaust valve for opening and closing the exhaust port, and an ignition device are mounted on the cylinder head, forming an airflow that flows along the top surface of the combustion chamber from the intake port side toward the exhaust port side. The ignition device is disposed between the air inlet and the exhaust outlet. The ignition device includes: a housing; an insulator held within the housing; a center electrode protruding from the front end of the insulator; and a ground electrode facing the center electrode axially across a discharge gap. The grounding electrode includes an opposing portion that faces the center electrode in the axial direction and a support portion that extends from the front end of the housing and supports the opposing portion. The internal combustion engine has a wall portion between the air intake in the cylinder head and the center electrode, the wall portion serving as a barrier against the airflow flowing toward the discharge gap. When viewed axially from the center electrode, a first straight line passing through the centroid of the wall and the central axis of the center electrode is orthogonal to a second straight line passing through the centroid of the support and the central axis.

[0006] Based on the aforementioned ignition device and internal combustion engine, the risk of misfire caused by the flame core being extinguished by the airflow can be reduced. Attached Figure Description

[0007] The features, advantages, technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals denote the same components:

[0008] Figure 1 This is a cross-sectional view showing the structure of the combustion chamber of an internal combustion engine equipped with the ignition device of the first embodiment; Figure 2 It means Figure 1 A cross-sectional view of the ignition device shown; Figure 3 It means Figure 2 A cross-sectional view of the discharge gap of the ignition device shown; Figure 4 It is along Figure 3 A cross-sectional view of line IV-IV; Figure 5 This is a cross-sectional view showing the internal combustion engine according to the second embodiment; Figure 6 It is along Figure 5 A sectional view along line VI-VI. Detailed Implementation

[0009] First Implementation Method

[0010] The following is for reference Figures 1 to 4 The first embodiment, which is an ignition device, will be described.

[0011] Internal combustion engine 10

[0012] like Figure 1 As shown, the internal combustion engine 10, 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 in a reciprocating manner. A cylinder head 82 is connected to the upper end of the cylinder block 80.

[0013] The internal combustion engine 10 has a combustion chamber 13 consisting of a cylinder 81, a piston 14, and a cylinder head 82. Two tops 11 and 12 are formed on the cylinder head 82. The walls of the tops 11 and 12 function as the top surfaces of the combustion chamber 13. That is, the internal combustion engine 10 has a ridge-shaped combustion chamber 13. The cylinder head 82 has an intake port 41 for introducing intake air into the combustion chamber 13 and an exhaust port 42 for discharging exhaust air from the combustion chamber 13. An intake valve 27 is provided on the intake port 41 to open and close relative to the combustion chamber 13. The intake valve 27 is located on the top 11 side. An exhaust valve 28 is provided on the exhaust port 42 to open and close relative to the combustion chamber 13. The exhaust valve 28 is located on the top 12 side.

[0014] When the intake air flows into the combustion chamber 13 from the intake port 41, such as Figures 1 to 6 As indicated by the middle arrow, an airflow FL is formed that flows along the top surface of the combustion chamber 13 from the intake port 41 side toward the exhaust port 42 side. The airflow FL is, for example, a tumble flow.

[0015] The internal combustion engine 10 is equipped with an ignition device 29. The ignition device 29 is disposed between the intake port 41 and the exhaust port 42 in the cylinder head 82. Specifically, the ignition device 29 is disposed at the top of the combustion chamber 13 where the top 11 and the top 12 intersect.

[0016] The internal combustion engine 10 includes a fuel injection valve 30 that directly injects fuel into the combustion chamber 13. The fuel injection valve 30 is an in-cylinder injection valve. The fuel injection valve 30 is located between the ignition device 29 at the top 11 and the intake port 41. The internal combustion engine 10 may also include an intake port injection valve that injects fuel into the intake port 41 as the fuel injection valve 30.

[0017] The mixture of fuel injected from fuel injection valve 30 and air introduced into combustion chamber 13 from intake port 41 as intake valve 27 opens is ignited and burned by spark discharge from ignition device 29. The mixture after combustion in combustion chamber 13 becomes exhaust gas, which is discharged to exhaust port 42 as exhaust valve 28 opens.

[0018] Ignition device 29

[0019] Figure 2 This is a cross-sectional view of the ignition device 29. Figure 3 yes Figure 2 A cross-sectional view of the periphery of the grounding electrode 54 shown. (See figure) Figure 2 as well as Figure 3 As shown, the ignition device 29 includes a housing 50, an insulator 51, a center electrode 52, a ground electrode 54, and a wall 60. The housing 50 is made of metal. The insulator 51 is made of ceramic. The insulator 51 is assembled into the housing 50 in a manner that penetrates the cylindrical housing 50. The insulator 51 is held within the housing 50.

[0020] The center electrode 52 is made of metal. The center electrode 52 is assembled to the insulator 51. The center electrode 52 protrudes from the front end of the insulator 51. That is, the center electrode 52 protrudes from one end of the insulator 51 and is disposed in the combustion chamber 13.

[0021] The grounding electrode 54 faces the center electrode 52 across the discharge gap G along the axial direction of the central axis CL indicated by the single-dotted line on the center electrode 52. The grounding electrode 54 includes an opposing portion 55 and a support portion 56. The opposing portion 55 faces the center electrode 52 axially. The support portion 56 extends from the front end of the housing 50 and supports the opposing portion 55.

[0022] Fuel injection valve 30 injects fuel from injection port 31. Fuel is injected from injection port 31 in the direction of flow along the airflow FL.

[0023] like Figure 3 As shown, a grounding electrode tip 57 is provided on the surface 58 of the grounding electrode 54 opposite to the center electrode 52. When a high voltage is applied to the center electrode 52, a spark discharge is generated in the discharge gap G between the center electrode 52 and the grounding electrode tip 57. The spark discharge ignites the gas mixture, thereby generating a flame core 70 as shown by the double-dotted line.

[0024] The wall portion 60 is disposed at the front end of the combustion chamber 13 side of the housing 50. The wall portion 60 serves as a barrier against the airflow FL flowing radially from the outside toward the discharge gap G of the central electrode 52.

[0025] like Figure 3 As shown, the height H1 of the wall portion 60 is greater than the height H2 of the surface 58 of the ground electrode 54 facing the center electrode 52. Height H1 is the length from the base end 60A of the wall portion 60 to the end end 60B that rises along the axial direction of the center electrode 52. The base end 60A is located at the front end of the combustion chamber 13 side of the housing 50. Height H2 is the length from the front end of the combustion chamber 13 side of the housing 50 to the surface 58.

[0026] Figure 4 It is along Figure 3 A cross-sectional view along line IV-IV. (See also...) Figure 4 As shown, the ignition device 29 is mounted on the cylinder head 82 radially toward the center electrode 52 with the wall portion 60 positioned between the intake port 41 and the discharge gap G. The housing 50 is designed with screws for mounting the ignition device 29 to the cylinder head 82, for example, at a target angle for the mounting angle of the ignition device 29.

[0027] like Figure 4As shown, when viewed axially from the center electrode 52, if the straight line passing through the centroid 60G of the wall portion 60 and the central axis CL is designated as the first straight line L1, and the straight line passing through the centroid 56G of the support portion 56 and the central axis CL is designated as the second straight line L2, the first straight line L1 and the second straight line L2 are orthogonal. Furthermore, the support portion 56 is positioned where it does not intersect with the first straight line L1.

[0028] The role of the first embodiment

[0029] like Figure 4 As shown, the wall portion 60 located between the air inlet 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 rate of the airflow FL through the discharge gap G is slower compared to when the wall portion 60 is not provided.

[0030] Effects of the first implementation method

[0031] 1-1

[0032] According to the ignition device 29 of the internal combustion engine 10, the risk of misfire caused by the flame core 70 being blown out by the airflow FL can be reduced.

[0033] 1-2

[0034] like Figure 3 As shown, 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 center electrode 52. The wall portion 60 has a height H1 that completely shields the discharge gap G from which spark discharge occurs when viewed from the radially outer side of the center electrode 52. According to the ignition device 29 of the internal combustion engine 10, the airflow FL toward the discharge gap G can be effectively blocked.

[0035] 1-3

[0036] like Figure 3 As shown, the grounding electrode 54 includes an opposing portion 55 and a supporting portion 56. The opposing portion 55 faces the center electrode 52 axially. The supporting portion 56 extends from the front end of the housing 50 and supports the opposing portion 55.

[0037] like Figure 4 As shown, when viewed axially from the center electrode 52, the support portion 56 does not intersect the first straight line L1. The airflow FL bypassing the wall portion 60 passes through the discharge gap G located on the downstream side. The flame core 70 generated by the spark discharge extends along the flow direction of the airflow FL. When the support portion 56 is located at the leading edge of the flame core 70, the flame core 70 may come into contact with the support portion 56. When the flame core 70 comes into contact with the support portion 56, the heat of the flame core 70 may be taken away by the support portion 56, causing it to ignite.

[0038] like Figure 3As shown, the discharge gap G is located on the central axis CL of the central electrode 52. Therefore, the airflow FL that bypasses the wall 60 and passes through the discharge gap G is directed towards the center when viewed axially. Figure 4 The flow direction is shown in the first straight line L1. The flame core 70 generated in the discharge gap G extends in the direction of the airflow FL. That is, the flame core 70 easily extends 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 core 70 extending downstream along the airflow FL is unlikely to come into contact with the support portion 56. According to the ignition device 29 of the internal combustion engine 10, the risk of misfire caused by contact between the support portion 56 of the ground electrode 54 and the flame core 70 can be reduced.

[0039] 1-4

[0040] like Figure 4 As shown, when viewed axially from the center electrode 52, the second straight line L2 of the ignition device 29 is orthogonal to the first straight line L1. The greater the deviation between the direction in which the flame core 70 extends from the center electrode 52 along the airflow FL and the direction from the central axis CL of the center electrode 52 toward the centroid 56G of the support portion 56, the lower the likelihood of the flame core 70 contacting the support portion 56. On the other hand, when the support portion 56 is located on the side closer to the wall portion 60 than the discharge gap G, the airflow FL flowing toward the discharge gap G is blocked not only by the wall portion 60 but also by the support portion 56. In this case, the airflow FL flowing into the discharge gap G is turbulent, which may make it difficult to generate the flame core 70.

[0041] The airflow FL through the discharge gap G flows in the direction along the first straight line L1. Therefore, when the support portion 56 is provided at a position where the first straight line L1 and the second straight line L2 are orthogonal, the airflow FL before flowing into the discharge gap G is not easily blocked by the support portion 56. According to the ignition device 29 where the first straight line L1 and the second straight line L2 are orthogonal, the risk of misfire can be reduced, and the airflow FL flowing into the discharge gap G is less likely to be turbulent.

[0042] Modification of the first embodiment

[0043] The support portion 56 may, for example, be positioned downstream of the discharge gap G and the airflow FL when viewed axially from the center electrode 52. In this case, the first straight line L1 and the second straight line L2 are not orthogonal. That is, the first straight line L1 and the second straight line L2 may not be orthogonal. Even if the first straight line L1 and the second straight line L2 are not orthogonal, if the support portion 56 is positioned so as not to intersect with the first straight line L1, the ignition device 29 will still achieve the effects shown in 1-1 to 1-3.

[0044] The ignition device 29 can also have the ground electrode 54 arranged such that the support portion 56 intersects the first straight line L1 when viewed axially from the center electrode 52. In this case, if a wall portion 60 is provided between the intake valve 27 and the discharge gap G, the ignition device 29 also achieves the effects shown in 1-1 and 1-2.

[0045] To reduce the risk of fire, the optimal height H1 of the wall portion 60 can also be determined experimentally. That is, the height H1 of the wall portion 60 can be appropriately changed. For example, the height H1 of the wall portion 60 can also be less than the height H2.

[0046] Second Implementation Method

[0047] The following is for reference Figure 5 and Figure 6 A second embodiment, which is an implementation of an internal combustion engine, will be described. Regarding the second embodiment, it will be compared with reference to... Figures 1 to 4 The explanation focuses on the differences in the structure of the description.

[0048] like Figure 5 As shown, in the second embodiment of the internal combustion engine 10, a wall portion 61 is provided between the air intake 41 in the cylinder head 82 and the center electrode 52 to act as a barrier against 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. It should be noted that the structure of the internal combustion engine 10 of the second embodiment is the same as that of the cylinder head 82, except that the structure in which the wall portion 60 is provided in the ignition device 29 is replaced by a structure in which the wall portion 61 is provided in the cylinder head 82.

[0049] like Figure 5 As shown, the height H3 of the wall portion 61 is greater than or equal to the height H4 of the surface 58 of the grounding electrode 54 facing the center electrode 52. Height H3 is the length from the base end 61A of the wall portion 61 to the end end 61B that rises along the axial direction of the center electrode 52. The base end 61A is located on the top 11. Height H4 is the length from the base end 61A on the top 11 to the surface 58.

[0050] Figure 6 It is along Figure 5 A cross-sectional view along line VI-VI. (See example...) Figure 6 As shown, when viewed axially from the center electrode 52, the straight line passing through the centroid 61G of the wall portion 61 and the central axis CL is designated as the first straight line L3, and the straight line passing through the centroid 56G of the support portion 56 and the central axis CL is designated as the second straight line L2. In this case, the ignition device 29 is mounted on the internal combustion engine 10 in a manner that the first straight line L3 and the second straight line L2 are orthogonal.

[0051] The function of the second embodiment

[0052] Even when the cylinder head 82 is provided with a wall 61 that suppresses the airflow FL flowing toward the discharge gap G, the flow rate of the airflow FL generated in the discharge gap G and blown toward the flame core 70 is slowed down.

[0053] The gas flow FL through the discharge gap G flows in the direction along the first straight line L3. Therefore, when the wall portion 61 and the support portion 56 are positioned such that the first straight line L3 and the second straight line L2 become orthogonal, the flame core 70, which extends downstream due to the gas flow FL, is unlikely to come into contact with the support portion 56.

[0054] The greater the deviation between the direction in which the flame core 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 lower the likelihood of the flame core 70 contacting the support portion 56. On the other hand, when the support portion 56 is located closer to the wall portion 61 than the discharge gap G, the airflow FL flowing toward the discharge gap G is blocked 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 is turbulent, making it difficult to generate the flame core 70. When the wall portion 61 and the support portion 56 are positioned at a point where the first straight line L3 and the second straight line L2 are orthogonal, the airflow FL flowing into the discharge gap G is less likely to be blocked by the support portion 56. That is, with the internal combustion engine 10 having the first straight line L3 and the second straight line L2 orthogonal, the risk of misfire can be reduced, and the airflow FL flowing into the discharge gap G is less likely to be turbulent.

[0055] Effects of the second implementation method

[0056] According to the structure of the second embodiment, it achieves the same effect as 1-1 to 1-4 of the first embodiment.

[0057] Modification of the second implementation method

[0058] To reduce the risk of fire, the optimal height H3 of the wall portion 61 can also be determined experimentally. That is, the height H3 of the wall portion 61 can be appropriately changed. For example, the height H3 of the wall portion 61 can also be less than the height H4.

Claims

1. An ignition device, mounted on the cylinder head of an internal combustion engine that forms an airflow flowing along the top surface of the combustion chamber from the intake port side to the exhaust port side, comprising: case; The insulator is held within the housing; The center electrode protrudes from the front end of the insulator; The grounding electrode is axially opposed to the center electrode, separated by a discharge gap; as well as A wall portion, located at the front end of the housing, serves as a barrier against the airflow moving radially from the outside toward the discharge gap from the central electrode. The ignition device is mounted on the cylinder head radially from the center electrode, with the wall portion positioned between the air intake and the discharge gap.

2. The ignition device according to claim 1, The height of the wall portion is above the height of the surface of the grounding electrode facing the center electrode.

3. The ignition device according to claim 1, The grounding electrode includes: The opposing portion faces the central electrode along the axial direction of the central electrode; and A support portion extends from the front end of the housing and supports the opposing portion. When viewed axially from the center electrode, the support portion does not intersect the straight line passing through the centroid of the wall portion and the central axis of the center electrode.

4. The ignition device according to claim 3, When the straight line passing through the centroid of the wall and the central axis is defined as the first straight line... When viewed along the axial direction, a second straight line passing through the centroid of the support and the central axis is orthogonal to the first straight line.

5. An internal combustion engine, wherein 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 mounted on a cylinder head to form an airflow flowing along the top surface of a combustion chamber from the intake port side toward the exhaust port side. The ignition device is disposed between the air inlet and the exhaust outlet. The ignition device includes: case; An insulator is held within the housing; a center electrode protrudes from the front end of the insulator. And a grounding electrode, which faces the center electrode axially across a discharge gap. The grounding electrode includes an opposing portion that faces the center electrode in the axial direction and a support portion that extends from the front end of the housing and supports the opposing portion. A wall is provided between the air intake in the cylinder head and the center electrode, the wall serving as a barrier against the airflow moving toward the discharge gap. When viewed axially from the center electrode, a first straight line passing through the centroid of the wall and the central axis of the center electrode is orthogonal to a second straight line passing through the centroid of the support and the central axis.

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