Spark-ignition internal combustion engine

Abstract

To provide an ignition type internal combustion engine capable of improving the strength of the internal combustion engine, and reducing the weight of the internal combustion engine.SOLUTION: An ignition type internal combustion engine 10 igniting mixture formed in a combustion chamber 19a of a cylinder 19, is equipped with a plasma actuator 30 as an ignition device. The plasma actuator 30 as the ignition device can be used for controlling a flow of the mixture in the cylinder 19. By disposing two plasma actuators so as to cancel generated jet flows each other, changes in a flow of the mixture by igniting operation can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a spark-ignition internal combustion engine. [Background technology]

[0002] As an internal combustion engine mounted on a vehicle or the like, there is known an ignition type internal combustion engine that forms a mixture of fuel and air in a combustion chamber of a cylinder and ignites the mixture to burn the mixture and obtain output. As an ignition device that ignites the mixture, as described in Patent Document 1, an ignition plug that is attached to the cylinder head of the internal combustion engine with its tip exposed inside the combustion chamber is generally used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-20332 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a spark plug is used as an ignition device, a part for attaching the spark plug to the internal combustion engine is also required, which is one of the factors that increase the weight of the internal combustion engine. Also, when a spark plug is used as an ignition device, an insertion hole for attaching the spark plug must be provided in the cylinder head, which may reduce the strength of the cylinder head. In particular, when the pressure in the combustion chamber is increased to efficiently obtain the output of the internal combustion engine, if the strength of the internal combustion engine is ensured with the spark plug insertion hole provided, this may be one of the factors that increase the weight.

[0005] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an ignition type internal combustion engine that can increase the strength of the internal combustion engine and reduce the weight of the internal combustion engine. [Means for solving the problem]

[0006] In order to solve the above problems, according to one aspect of the present invention, there is provided an ignition type internal combustion engine that ignites an air-fuel mixture formed in a combustion chamber of a cylinder, the ignition type internal combustion engine having a plasma actuator as an ignition device.

[0007] In the above internal combustion engine, the plasma actuator serving as an ignition device may further be used to control the flow of the air-fuel mixture in the cylinder.

[0008] In the above internal combustion engine, the plasma actuator serving as an ignition device may further be used to control the flow of exhaust gas within the cylinder.

[0009] In the above internal combustion engine, the plasma actuator may be provided in a ring shape around the entire circumference of the inner circumferential surface of the combustion chamber of the internal combustion engine.

[0010] In the above internal combustion engine, the plasma actuator serving as the ignition device may include two plasma actuators which generate jets in opposite directions to each other. Effect of the Invention

[0011] As described above, according to the present invention, the strength of an internal combustion engine can be increased and the weight of the internal combustion engine can be reduced. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a configuration example of an internal combustion engine according to an embodiment of the present invention. [Diagram 2] 2 is an explanatory diagram showing a configuration example of a plasma actuator according to the embodiment; FIG. [Diagram 3] 13 is a schematic diagram showing an example in which the plasma actuator according to the embodiment is divided into a plurality of parts and arranged. FIG. [Figure 4] 13 is a schematic diagram showing an example in which the plasma actuator according to the embodiment is divided into a plurality of parts and arranged. FIG. [Diagram 5] FIG. 4 is a schematic diagram showing another example of the configuration of the internal combustion engine according to the embodiment. [Figure 6] 4 is an explanatory diagram showing another configuration example of the plasma actuator according to the embodiment. FIG. [Figure 7] FIG. 13 is an explanatory diagram showing how two plasma actuators cancel out each other's jets. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and duplicated explanations will be omitted.

[0014] Fig. 1 is a schematic diagram showing a configuration example of an internal combustion engine 10 according to an embodiment of the present invention. Fig. 1 shows a configuration example of one cylinder 19 among a plurality of cylinders provided in the internal combustion engine 10.

[0015] The internal combustion engine 10 according to this embodiment is configured as a so-called four-stroke spark-ignition gasoline engine. The internal combustion engine 10 is mounted on, for example, an automobile and functions as a power source for the automobile. As long as the internal combustion engine 10 is an ignition type internal combustion engine 10, it may be a so-called two-stroke internal combustion engine or an internal combustion engine that uses a fuel other than gasoline fuel.

[0016] The internal combustion engine 10 includes a cylinder block 11 and a cylinder head 13. A substantially cylindrical cylinder bore 11a is formed in the cylinder block 11. A substantially cylindrical recess 13a is formed in the cylinder head 13 so as to be connected to the cylinder bore 11a. A cylinder 19 is formed by the cylinder bore 11a and the recess 13a.

[0017] The internal combustion engine 10 includes a piston 15, a connecting rod 17, an intake valve 23, and an exhaust valve 27 for each cylinder 19. The piston 15 is housed in the cylinder 19 so as to be able to slide freely. Within the cylinder 19, a space defined by the piston 15 functions as a combustion chamber 5.

[0018] One end of the connecting rod 17 is connected to the piston 15. The other end of the connecting rod 17 is connected to a crankshaft (not shown). In other words, the piston 15 is connected to the crankshaft via the connecting rod 17, and the reciprocating motion of the piston 15 rotates the crankshaft, causing power to be output from the internal combustion engine 10.

[0019] An intake port 21 and an exhaust port 25 that communicate with the combustion chamber 19a are connected to the cylinder 19. An intake valve 23 is provided in the intake port 21, and an exhaust valve 27 is provided in the exhaust port 25. The intake valve 23 is disposed at a position where the intake port 21 opens to the combustion chamber 19a, and is constantly biased in a valve closing direction by a return spring (not shown). The intake valve 23 can be moved in a valve opening direction by an intake cam (not shown). The intake cam rotates together with a camshaft that is connected to the crankshaft via a timing belt or chain. As the intake cam rotates, the intake valve 23 opens and closes the intake port 21 with respect to the combustion chamber 19a.

[0020] Similarly, exhaust valve 27 is disposed at the location where exhaust port 25 opens into combustion chamber 19a, and is constantly biased in the valve closing direction by a return spring (not shown). Exhaust valve 27 can be moved in the valve opening direction by an exhaust cam (not shown). The exhaust cam rotates together with a camshaft connected to the crankshaft via a timing belt or chain. As the exhaust cam rotates, exhaust valve 27 opens and closes exhaust port 25 relative to combustion chamber 19a.

[0021] Each cylinder 19 is provided with a fuel injection valve (not shown) whose tip is disposed so as to face the combustion chamber 19a. The fuel injection valve is fixed, for example, to a wall surface of the cylinder block 11. The fuel injection valve injects fuel into the combustion chamber 19a mainly during the intake stroke. As a result, a mixture of intake air and fuel is formed in the combustion chamber 19a.

[0022] A plasma actuator 30 is provided in the cylinder 19 as an ignition device. The plasma actuator 30 is a fluid control device with a relatively simple configuration that does not have any moving parts. The plasma actuator 30 has a function of generating plasma by electrical drive, and therefore is used as an ignition device that ignites the air-fuel mixture in the internal combustion engine 10 according to this embodiment.

[0023] In this embodiment, the plasma actuator 30 is provided in a ring shape around the entire inner circumferential surface of the recess 13a of the cylinder head 13. However, the location of the plasma actuator 30 is not particularly limited as long as it is inside the combustion chamber 19a on the cylinder head 13 side of the top dead center of the piston 15.

[0024] Fig. 2 is an explanatory diagram showing an example of the configuration of the plasma actuator 30. Fig. 2 shows an enlarged view of an area A indicated by a dashed line in Fig. 1. The plasma actuator 30 shown in Fig. 2 is a dielectric barrier discharge plasma actuator (DBD-PA), and includes an insulating layer 31, a dielectric 33, a front electrode 35, and a rear electrode 37.

[0025] The insulating layer 31 is made of an electrically insulating material and is formed on the inner peripheral surface of the cylinder head 13 to electrically insulate the cylinder head 13 from the dielectric 33, the front electrode 35, and the back electrode 37. The material constituting the insulating layer 31 may be, for example, a resin such as a silicone resin or a fluororesin, or an appropriate insulating material such as glass or ceramic.

[0026] The dielectric 33 is made of an electrically insulating material and is laminated on the insulating layer 31. The material constituting the dielectric 33 may be, for example, a resin such as a silicon resin, a fluororesin, or a polyimide resin, or an appropriate insulating material such as glass or ceramic.

[0027] The front electrode 35 and the back electrode 37 are made of a conductive material such as copper or graphite, and are disposed on both sides of the dielectric 33. The front electrode 35 is exposed to the combustion chamber 19a and configured to be able to discharge within the combustion chamber 19a. The back electrode 37 is grounded and is insulated by the dielectric 33 and the insulating layer 31 so that no discharge occurs on the back electrode 37 side.

[0028] Applying an AC voltage or pulse voltage of a predetermined frequency to the front electrode 35 and the back electrode 37 generates a dielectric barrier discharge, generating plasma near the surface of the front electrode 35, and generating a plasma jet in the direction from the front electrode 35 to the back electrode 37. By driving the plasma actuator 30 with an air-fuel mixture formed in the combustion chamber 19a, the generated plasma ignites the air-fuel mixture, causing it to burn. In the internal combustion engine 10 according to this embodiment, the plasma actuator 30 is disposed around the entire inner circumferential surface of the recess 13a of the cylinder head 13, so that the air-fuel mixture in the combustion chamber 19a can be burned uniformly.

[0029] The plasma actuator 30 is not limited to being disposed around the entire inner circumferential surface of the combustion chamber 19a. The plasma actuator 30 may be disposed on a portion of the inner circumferential surface of the combustion chamber 19a, or may be divided into multiple parts. In this case, it is preferable to determine the position of the plasma actuator 30 in consideration of the state of the flow of the air-fuel mixture formed in the combustion chamber 19a. For example, by arranging the plasma actuator 30 at a position where the density of the air-fuel mixture is high in consideration of the density distribution of the air-fuel mixture formed in the combustion chamber 19a, the combustion efficiency of the air-fuel mixture can be improved.

[0030] Alternatively, the plasma actuator 30 may be divided into a plurality of units and the plasma actuator 30 to be driven as an ignition device may be selected taking into consideration the state of the air-fuel mixture flow formed by the operating state of the internal combustion engine 10.

[0031] The plasma actuator 30 can be attached to any position on the inner circumferential surface of the combustion chamber 19a, and therefore does not require an insertion hole that would reduce the strength of the cylinder block 11 or the cylinder head 13. This increases the strength of the internal combustion engine 10. Furthermore, the plasma actuator 30 has a simple configuration consisting of an insulating layer 31, a dielectric 33, and a layered front electrode 35 and a back electrode 37 arranged on both sides of the dielectric 33, and since there is no increase in the number of parts required to attach the plasma actuator 30, the weight of the internal combustion engine 10 can be reduced compared to when an ignition plug is used.

[0032] Furthermore, by using the plasma actuator 30 as an ignition device, the flow of the air-fuel mixture in the combustion chamber 19a can be controlled by utilizing the plasma jet that is generated when the plasma actuator 30 is driven. Therefore, the plasma actuator 30 can also be used to control the combustion characteristics of the air-fuel mixture in the combustion chamber 19a.

[0033] Furthermore, by driving the plasma actuator 30 at a timing other than the ignition timing of the air-fuel mixture, the flow of the air-fuel mixture or the exhaust gas in the combustion chamber 19a can be controlled by utilizing the generated plasma jet. For example, the plasma actuator 30 may be driven before fuel is injected into the combustion chamber 19a during the intake stroke to control the flow of the intake air, and then the flow of the air-fuel mixture formed by mixing the injected fuel thereafter may be controlled. This makes it possible to control the combustion characteristics of the air-fuel mixture in the combustion chamber 19a. Alternatively, the plasma actuator 30 may be driven during the exhaust stroke so that the exhaust is directed toward the exhaust port 25. This improves the exhaust efficiency and improves the intake air filling efficiency during the following intake stroke.

[0034] 3 and 4 are schematic diagrams showing an example in which the plasma actuator is divided into a plurality of parts and arranged. In the example shown in FIG. 3, plasma actuators 40a, 40b, 40c, and 40d divided into four are arranged on the inner circumferential surface of the region of the cylinder 19 corresponding to the combustion chamber 19a. In this case, for example, at the beginning of the intake stroke, the plasma actuators 40a to 40d are driven so that a plasma jet is generated from the top to the bottom of the cylinder 19. This can improve the intake charging efficiency. Also, at the beginning of the expansion stroke (explosion stroke), the two plasma actuators 40a and 40b arranged on the exhaust port 25 side, which are positioned in the traveling direction of the mixture formed by mixing the intake air introduced into the cylinder 19 from the intake port (not shown) with the injected fuel, are driven as ignition devices. This ignites the mixture. Also, at the exhaust stroke, the plasma actuators 40a to 40d are driven so that a plasma jet is generated from the bottom to the top of the cylinder 19. This allows the exhaust gas after combustion to be efficiently discharged to the exhaust port 25, and can improve the intake charging efficiency in the following intake stroke.

[0035] In the example shown in FIG. 4, two divided plasma actuators 41a and 41b are arranged on the inner surface below the opening of the exhaust port 25 and at the top of the cylinder 19 above the opening of the exhaust port 25. In this case, for example, at the beginning of the intake stroke, the plasma actuators 41a and 41b are driven so that a plasma jet is generated from the top to the bottom of the cylinder 19. This can improve the intake charging efficiency. Also, at the beginning of the expansion stroke (explosion stroke), the two plasma actuators 41a and 41b arranged on the exhaust port 25 side, which are positioned in the traveling direction of the mixture formed by mixing the intake air introduced into the cylinder 19 from the intake port (not shown) and the injected fuel, are driven as ignition devices. This ignites the mixture. Also, at the exhaust stroke, the plasma actuators 41a and 41b are driven so that a plasma jet is generated toward the exhaust port 25. This allows the exhaust gas after combustion to be efficiently discharged to the exhaust port 25, and can improve the intake charging efficiency in the following intake stroke.

[0036] On the other hand, in order to suppress changes in the flow of the mixture caused by the plasma jet generated when the plasma actuator 30 is operated as an ignition device, the internal combustion engine 10 may be provided with two plasma actuators 30 that generate plasma jets (jet flows) in opposite directions.

[0037] FIG. 5 is a schematic diagram showing an example of the configuration of an internal combustion engine 10 equipped with a first plasma actuator 30a and a second plasma actuator 30b that generate plasma jets in opposite directions to each other.

[0038] The first plasma actuator 30a is provided in a ring shape around the entire circumference on the inner circumferential surface of the recess 13a of the cylinder head 13. The second plasma actuator 30b is provided in a ring shape around the entire circumference on the inner circumferential surface of the cylinder bore 11a of the cylinder block 11. However, the positions of the first plasma actuator 30a and the second plasma actuator 30b are not particularly limited as long as they are arranged next to each other inside the combustion chamber 19a on the cylinder head 13 side of the top dead center of the piston 15.

[0039] 6 is an explanatory diagram showing an example of the configuration of the first plasma actuator 30a and the second plasma actuator 30b. FIG 6 shows an enlarged view of the area B indicated by the dashed dotted line in FIG 5.

[0040] The insulating layer 31a, dielectric 33a, surface electrode 35a, and back electrode 37a of the first plasma actuator 30a have a layered structure similar to that of the insulating layer 31, dielectric 33, surface electrode 35, and back electrode 37 of the plasma actuator 30 shown in Fig. 2. The second plasma actuator 30b has a layered structure similar to that of the insulating layer 31, dielectric 33, surface electrode 35, and back electrode 37 of the plasma actuator 30 shown in Fig. 2, except that the positions of the surface electrode 35b and back electrode 37b are reversed. That is, in the first plasma actuator 30a, the surface electrode 35a is disposed on the cylinder head 13 side and the back electrode 37a is disposed on the cylinder block 11 side, while in the second plasma actuator 30b, the surface electrode 35b is disposed on the cylinder block 11 side and the back electrode 37b is disposed on the cylinder head 13 side.

[0041] FIG. 7 is an explanatory diagram showing jets generated from the first plasma actuator 30a and the second plasma actuator 30b. As shown in FIG. 7, the jet generated from the first plasma actuator 30a flows toward the second plasma actuator 30b, while the jet generated from the second plasma actuator 30b flows toward the first plasma actuator 30a. As a result, the jets cancel each other out, and the jets generated by the first plasma actuator 30a and the second plasma actuator 30b as a whole can be suppressed. This makes it possible to suppress changes in the flow of the mixture due to the ignition operation by the first plasma actuator 30a and the second plasma actuator 30b.

[0042] Note that, rather than making the jets generated from the first plasma actuator 30a and the second plasma actuator 30b completely cancel each other out, the design may be such that a portion where the jets generated completely cancel each other out, a portion where the jet generated from the first plasma actuator 30a is left behind, and a portion where the jet generated from the second plasma actuator 30b is left behind are appropriately allocated. This makes it possible to control the state of the mixture flow in the combustion chamber 19a by the plasma jets generated in conjunction with the ignition operations by the first plasma actuator 30a and the second plasma actuator 30b.

[0043] As described above, the internal combustion engine 10 according to this embodiment includes the plasma actuator 30, which has a simple configuration as an ignition device. Therefore, there is no need to provide an ignition plug, and the ignition plug and the parts for attaching the ignition plug can be eliminated, allowing the weight of the internal combustion engine 10 to be reduced. Furthermore, since the plasma actuator 30 can be attached to an appropriate position on the inner circumferential surface of the combustion chamber 19a, there is no need to provide holes, such as an insertion hole for an ignition plug, in the cylinder head 13 or the cylinder block 11, which may reduce the strength. Therefore, the strength of the internal combustion engine 10 can be increased, and an increase in weight due to a structure for reinforcing the reduced strength can be suppressed.

[0044] Furthermore, in the internal combustion engine 10 according to this embodiment, the degree of freedom in the arrangement position of the plasma actuator 30 as an ignition device is increased. This allows for greater freedom in the design of the internal combustion engine 10, such as the shape of the combustion chamber 19a.

[0045] Furthermore, in the internal combustion engine 10 according to this embodiment, the plasma actuator 30 may be used to control the flow of the air-fuel mixture in the combustion chamber 19a. This makes it possible to control the combustion characteristics of the air-fuel mixture, such as homogeneous combustion or stratified combustion, and improve the efficiency or fuel economy of the internal combustion engine 10.

[0046] In the internal combustion engine 10 according to this embodiment, the plasma actuator 30 may be used to control the flow of exhaust gas in the combustion chamber 19a. This can improve the exhaust efficiency and increase the intake air charging efficiency in the subsequent intake stroke.

[0047] In the internal combustion engine 10 according to this embodiment, the plasma actuator 30 is provided in a ring shape around the entire circumference of the inner circumferential surface of the combustion chamber 19a. This expands the ignition position for the air-fuel mixture in the combustion chamber 19a, allowing the air-fuel mixture to be burned uniformly.

[0048] The internal combustion engine 10 according to the present embodiment may also include a first plasma actuator 30a and a second plasma actuator 30b that generate jets in opposite directions. For example, the first plasma actuator 30a and the second plasma actuator 30b may be arranged so that the jets generated by each of them cancel each other out, thereby preventing the flow of the mixture from being changed by the ignition operation. In addition, by allocating a portion where the jets generated by each of them completely cancel each other out, a portion where the jet generated by the first plasma actuator 30a remains, and a portion where the jet generated by the second plasma actuator 30b remains, the flow of the mixture can be controlled by the jet generated by the ignition operation.

[0049] Although the preferred embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is clear that a person having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention.

[0050] For example, the plasma actuator 30 is not limited to a dielectric barrier discharge plasma actuator, but may be another known plasma actuator, such as a sliding discharge (SD) type plasma actuator that has been improved to increase the plasma generation area. [Explanation of symbols]

[0051] 10... internal combustion engine, 11... cylinder block, 11a... cylinder bore, 13... cylinder head, 13a... recess, 15... piston, 19... cylinder, 19a... combustion chamber, 30, 30a, 30b... plasma actuator, 31... insulating layer, 33... dielectric, 35... surface electrode, 37... rear electrode

Claims

1. An internal combustion engine of a spark ignition type that ignites an air-fuel mixture formed in a combustion chamber of a cylinder, A piston that reciprocates within the cylinder; a plurality of plasma actuators disposed on an inner surface of the combustion chamber; at least a portion of the plurality of plasma actuators is driven in an early stage of an intake stroke of the internal combustion engine, and a jet flow directed downward from the top of the cylinder is generated from the plasma actuator to introduce intake air into the cylinder; ignites the air-fuel mixture in the cylinder by driving at least a portion of the plurality of plasma actuators; an ignition type internal combustion engine, wherein at least a portion of the plurality of plasma actuators are driven during an exhaust stroke of the internal combustion engine, and a jet flow is generated from the plasma actuator toward the top of the cylinder, and exhausted from within the cylinder.

2. 2. The spark ignition internal combustion engine according to claim 1, wherein the plurality of plasma actuators are provided in a ring shape around an entire circumference of an inner circumferential surface of the cylinder of the internal combustion engine.

3. the plurality of plasma actuators include two plasma actuators which generate jets in directions opposite to each other, at least a portion of the plurality of plasma actuators is driven in an early stage of an intake stroke of the internal combustion engine, and a jet flow directed downward from the top of the cylinder is generated from the plasma actuator to introduce intake air into the cylinder; ignites the air-fuel mixture in the cylinder by driving the two plasma actuators that generate jets in opposite directions from each other among the plurality of plasma actuators; 3. The spark ignition internal combustion engine according to claim 1, wherein at least a portion of the plurality of plasma actuators are driven during an exhaust stroke of the internal combustion engine, and a jet flow directed from below to above the cylinder is generated from the plasma actuator and exhausted from within the cylinder.

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