JP2015017587A - Internal combustion engine and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine improved in heat efficiency.SOLUTION: A chargeable insulating film 32 is formed on a piston surface 31 of a piston 30 forming a combustion chamber 22. When high positive voltage is applied to an electric field formation electrode 35 disposed on a cylinder head portion 24 from an exhaust stroke to a suction stroke, the insulating film 32 is positively charged. As the flame generated in the combustion chamber 22 in the combustion stroke has a property of positive pole, it is separated from the piston surface 31 by repelling the insulating film 32. Thus combustion heat of the flame released to the external through the piston 30 is reduced. Accordingly, cooling loss in an engine 1 can be reduced.

Description

  The present invention relates to an internal combustion engine and a control method thereof.

  Conventionally, an internal combustion engine that promotes combustion in a combustion chamber by an electric field is known. For example, Patent Document 1 describes an internal combustion engine that forms an electric field between a gasket and a piston of a cylinder during a combustion stroke.

Japanese Patent Laid-Open No. 01-036916

  However, in the internal combustion engine described in Patent Document 1, the flame having the positive electrode property moves in the direction of the gasket serving as the negative electrode. Generally, the combustion heat released outside through the wall forming the combustion chamber with respect to the combustion heat of the flame, so-called cooling loss, is the ratio of the amount of heat released outside via the piston or cylinder head portion. Relatively high. In the internal combustion engine described in Patent Document 1, the effect that the electric field formed only in a limited region connecting the end face of the piston and the gasket prevents the flame from approaching or colliding with the inner wall of the cylinder head or the inner wall of the cylinder liner. It is small and the cooling loss cannot be greatly reduced. For this reason, it is thought that the effect of a thermal efficiency improvement is small.

  An object of the present invention is to provide an internal combustion engine that improves thermal efficiency.

  The present invention is an internal combustion engine comprising a piston, a cylinder that forms a combustion chamber whose volume is variable by reciprocating movement of the piston, and an electric field forming means that is provided in the cylinder and forms an electric field in the combustion chamber. In addition, a chargeable insulating film is formed on an end face forming the combustion chamber.

  In general, it is known that a flame has the properties of a positive electrode and behaves so as to repel the positive electrode and approach the negative electrode in an electric field. In the internal combustion engine of the present invention, the insulating film provided on the piston is charged positively or negatively by the electric field forming means provided in the combustion chamber. Thereby, in the internal combustion engine of the present invention, an electric field is formed on the entire combustion chamber wall surface, and the distance between the combustion chamber flame and the combustion chamber wall surface is controlled in accordance with the polarity of the insulating film. For example, when the insulating film is positively charged, the flame moves away from the wall surface of the combustion chamber where the insulating film is located and is biased toward the center of the combustion chamber. Thereby, the combustion heat released from the combustion chamber wall surface among the combustion heat of the flame is reduced, and the cooling loss can be reduced. Thus, the internal combustion engine of the present invention can control the amount of combustion heat released from the wall surface of the combustion chamber, particularly the piston and cylinder head, and reduce the cooling loss of the internal combustion engine.

1 is a schematic diagram of an internal combustion engine according to a first embodiment of the present invention. It is the II section enlarged view of FIG. It is a time chart explaining the control method of the internal combustion engine by a 1st embodiment of the present invention. It is a schematic diagram explaining the charging method of the insulating film in the internal combustion engine by 1st Embodiment of this invention. It is principal part sectional drawing explaining the position of the flame of the combustion chamber in the internal combustion engine by 1st Embodiment of this invention. It is a principal part enlarged view of the internal combustion engine by 2nd Embodiment of this invention. It is a time chart explaining the control method of the internal combustion engine by 2nd Embodiment of this invention. It is a principal part enlarged view of the internal combustion engine by 3rd Embodiment of this invention.

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

(First embodiment)
An internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS.

  The engine 1 according to the first embodiment is, for example, a direct injection type four-stroke engine that injects light oil directly into the combustion chamber 22. The engine 1 includes an intake system 10, a cylinder 20, a piston 30, an electric field forming electrode 35, an exhaust system 40, a control unit 50, and the like. In FIG. 1, the flow of air introduced into the intake system 10 is indicated by an arrow S1, and the flow of exhaust discharged from the exhaust system 40 to the atmosphere is indicated by an arrow S2.

  The intake system 10 supplies air in the atmosphere to the combustion chamber 22. The intake system 10 includes an intake pipe 12, a throttle valve 14, an intake valve 18, and the like.

  The intake pipe 12 is provided so that an intake passage 121 formed by the intake pipe 12 communicates the atmosphere with the combustion chamber 22 formed in the cylinder 20. The intake pipe 12 includes an air cleaner 13 that removes foreign substances contained in the air.

  The throttle valve 14 is provided on the combustion chamber 22 side as viewed from the air cleaner 13, that is, on the downstream side of the intake pipe 12. The throttle valve 14 adjusts the amount of air flowing through the intake pipe 12 according to the opening degree of an accelerator device (not shown) by the driver.

  The intake valve 18 is provided at a position where the intake pipe 12 and the cylinder 20 are connected. The intake valve 18 opens or closes according to the position of the reciprocating movement of the piston 30 relative to the cylinder 20, and supplies air flowing through the intake passage 121 to the combustion chamber 22 when the valve is opened.

  The exhaust system 40 releases exhaust gas, which is a gas after combustion in the combustion chamber 22, to the atmosphere. The exhaust system 40 includes an exhaust pipe 42, an exhaust temperature sensor 44, an exhaust valve 48, and the like.

  The exhaust pipe 42 is provided such that an exhaust passage 421 formed by the exhaust pipe 42 communicates the combustion chamber 22 and the atmosphere. An exhaust temperature sensor 44 is provided on the outer wall of the exhaust pipe 42. The exhaust temperature sensor 44 detects the temperature of the exhaust flowing through the exhaust passage 421.

  The exhaust valve 48 is provided at a position where the exhaust pipe 42 and the cylinder 20 are connected. The exhaust valve 48 opens or closes according to the position of the reciprocating movement of the piston 30 with respect to the cylinder 20, and causes the exhaust in the combustion chamber 22 to flow through the exhaust pipe 42 when the valve is opened.

  The cylinder 20 includes a cylinder head portion 24, a cylinder liner portion 26, and a crankcase portion 28.

  An intake port 244 that communicates with the intake passage 121 and an exhaust port 245 that communicates with the exhaust passage 421 are formed in the cylinder head portion 24. Further, a fuel injection valve 25 is provided in the approximate center of the cylinder head portion 24.

  The fuel injection valve 25 directly injects fuel into the combustion chamber 22. Fuel stored in a fuel tank (not shown) is supplied to the fuel injection valve 25. The fuel injection valve 25 has a charging unit 251 that charges the fuel positively or negatively. The fuel injection valve 25 injects the fuel charged by the charging unit 251 as “charging means” into the combustion chamber 22. An electric field forming electrode 35 is provided on the combustion chamber 22 side of the fuel injection valve 25. The fuel injection valve 25 corresponds to “fuel supply means” described in the claims.

  As shown in FIG. 2, the electric field forming electrode 35 is provided in the circumferential direction so as to surround the fuel injection valve 25 on the radially outer side of the fuel injection valve 25 on the combustion chamber 22 side. The electric field forming electrode 35 as “electric field forming means” is an electrode capable of forming a corona discharge by applying a high voltage, and can apply either a positive or negative voltage. The electric field forming electrode 35 has a plurality of protrusions 351 formed at the tip. The plurality of protrusions 351 have a length that is approximately equal to the distance between the tip of each of the plurality of protrusions 351 and the surface of the insulating film 32 on the piston surface 31 that forms the combustion chamber 22 of the piston 30 when the piston 30 is at TDC. It is formed to be the same. That is, the length of the plurality of protrusions 351 varies depending on the distance to the insulating film 32 as shown in FIG. Thereby, the electric field forming electrode 35 forms an electric field in the entire combustion chamber 22. In FIG. 2, the number of the protrusions 351 of the electric field forming electrode 35 is eight for convenience of drawing, but the number of the protrusions 351 is not limited to this.

  The cylinder liner portion 26 is formed in a substantially cylindrical shape, and forms the cylinder head portion 24 and the piston 30 and the combustion chamber 22. A channel 265 through which cooling water for cooling the engine 1 flows is formed inside the side wall of the cylinder liner portion 26. The temperature of the cooling water flowing through the flow path 265 is detected by a water temperature sensor 27 provided on the side wall of the cylinder liner portion 26.

  The crankcase portion 28 is provided so as to be connected to an end portion of the cylinder liner portion 26 opposite to the side connected to the cylinder head portion 24. The crankcase part 28 accommodates the crank 281 inside.

  The piston 30 is accommodated so as to be capable of reciprocating in the radial direction of the cylinder liner portion 26. The piston surface 31 of the piston 30 forming the combustion chamber 22 is formed in a toroidal shape as shown in FIG. The piston surface 31 is provided with an insulating film 32 made of, for example, chargeable aluminum oxide. The insulating film 32 has a substantially constant thickness and is formed in an uneven shape so that the surface area of the surface is increased.

  The control unit 50 supplies the electric power of the voltage value and the current value calculated based on various information to the electric field forming electrode 35. The control unit 50 includes a calculation unit 52, a power source 54 including a vehicle-mounted battery, a capacitor, a hybrid high voltage circuit, and the like, a boosting unit 56, and the like.

  The arithmetic unit 52 is a well-known small computer having a CPU, ROM, RAM, I / O, and a bus line connecting them. The calculation unit 52 is electrically connected to the throttle valve 14, the fuel injection valve 25, the water temperature sensor 27, the exhaust temperature sensor 44, and the like. The calculation unit 52 is an electric signal indicating the opening degree of the throttle valve 14 output from the throttle valve 14, an electric signal indicating the fuel injection amount output from the fuel injection valve 16, and cooling water of the cylinder liner unit 26 output from the water temperature sensor 27. , An electrical signal indicating a crank angle output by a crank angle sensor (not shown), an electrical signal indicating an exhaust temperature output by an exhaust temperature sensor 44, and the like. The calculation unit 52 calculates the pressure of the combustion chamber 22 based on an electric signal indicating the opening degree of the throttle valve 14, and based on the electric signal indicating the opening degree of the throttle valve 14 and the electric signal indicating the exhaust temperature. The piston position is calculated based on an electric signal indicating the crank angle. The calculation unit 52 calculates an optimum voltage value and current value for forming an electric field in the combustion chamber 22 based on these calculated values. Further, the calculation unit 52 calculates a voltage value and a current value to be applied to the electric field forming electrode 35 in a combustion stroke of the engine 1 described later based on an electric signal indicating the fuel injection amount. In addition, the calculation unit 52 applies a voltage having a polarity in accordance with the operation state of the engine 1 to the electric field forming electrode 35 based on an electric signal indicating the temperature of the cooling water in the cylinder liner unit 26. The calculation unit 52 outputs the calculated voltage value, current value, and polarity to the boosting unit 56.

  The boosting unit 56 boosts the power supplied from the power source 54 based on the voltage value, current value, and polarity output from the computing unit 52, and applies the boosted power to the electric field forming electrode 35. Thereby, a desired electric field is formed in the combustion chamber 22.

  Next, the operation of the engine 1 will be described based on FIGS. Here, for convenience of explanation, explanation will be made from the time when the combustion stroke in which the air-fuel mixture in the combustion chamber 22 burns is completed. In FIG. 3, the horizontal axis indicates the relative position of the piston 30 with respect to the cylinder 20. FIG. 3A shows the amount of fuel injected by the fuel injection valve 25 into the combustion chamber 22. FIG. 3B shows the pressure in the combustion chamber 22. Further, FIG. 3C shows the magnitude of the voltage applied to the electric field forming electrode 35. In the following description, the case where the insulating film 32 is positively charged will be described unless otherwise specified.

  The piston 30 in which the air-fuel mixture in the combustion chamber 22 burns and moves to the bottom dead center (hereinafter referred to as “BDC”) moves toward the top dead center (hereinafter referred to as “TDC”) (after time t10 in FIG. 3). ). At this time, the exhaust valve 48 is opened, and the exhaust from the combustion chamber 22 is discharged to the exhaust passage 421 by the piston 30 heading for TDC (exhaust stroke). At time t <b> 11 during the exhaust stroke, the voltage V <b> 11 is applied to the electric field forming electrode 35, and corona discharge is generated in the combustion chamber 22.

When the voltage V <b> 11 is applied to the electric field forming electrode 35, the insulating film 32 on the piston surface 31 is charged with the same polarity as the polarity of the electric field forming electrode 35. The charging phenomenon of the insulating film will be described with reference to FIG. FIG. 4 shows a schematic diagram of exchange of positive ions, negative ions, and electrons between the protrusion 351 of the electric field forming electrode 35 and the insulating film 32. In FIG. 4, the moving directions of positive ions, negative ions, and electrons between the protrusions 351 of the electric field forming electrode 35 and the insulating film 32 are indicated by white arrows.
When a relatively high positive voltage V11 is applied to the protrusion 351, negative charges such as electrons are extracted from the insulating film 32 provided at a position facing the protrusion 351. Since the insulating film 32 is originally in a potential of 0, when the negative charges are extracted by the protrusions 351, a lot of positive charges remain in the insulating film 32, so that the entire insulating film 32 is positively charged. Although the case where the positive voltage V11 is applied to the protrusion 351 of the electric field forming electrode 35 has been described here, the phenomenon that the insulating film 32 is negatively charged when a negative voltage is applied to the protrusion 351 of the electric field forming electrode 35. Is the same principle.

  Here, the control unit 50 changes the polarity of the electric field forming electrode 35 in accordance with the operating state of the engine 1. Specifically, immediately after the engine 1 is started, the electric field forming electrode 35 is set to the negative electrode. As a result, the insulating film 32 is negatively charged. Further, the electric field forming electrode 35 is changed to a positive electrode when a certain time has elapsed since the engine 1 was started. Thereby, the insulating film 32 is positively charged.

  Next, when the piston 30 in the cylinder 20 moves from TDC toward BDC, the intake valve 18 is opened, and the intake air flowing through the intake pipe 12 flows into the combustion chamber 22 (intake stroke). The application of voltage to the electric field forming electrode 35 started at time t11 during the exhaust stroke ends at time t12 during the intake stroke. When a positive voltage is applied to the electric field forming electrode 35 from time t11 to time t12, the insulating film 32 is positively charged. In addition, when a negative voltage is applied to the electric field forming electrode 35 as shown by a one-dot chain line L11 in FIG. 3C, the insulating film 32 is negatively charged.

  Next, after the intake stroke is completed, the piston 30 moves from BDC toward TDC, and the intake air in the combustion chamber 22 is compressed (compression stroke). At time t13 during the compression stroke, a positive voltage is applied to the electric field forming electrode 35. At this time, the positive voltage applied to the electric field forming electrode 35 increases as the compression stroke proceeds and the pressure in the combustion chamber 22 increases. When the piston 30 reaches TDC, the positive voltage V12 is larger than the positive voltage V11. Is applied (time t14 in FIG. 3). The positive charge amount of the insulating film 32 is further increased by applying a voltage in the compression process. Further, when a negative voltage is applied to the electric field forming electrode 35 from time t13 to time t14 as shown by a one-dot chain line L12 in FIG. 3C, the negative charge amount of the insulating film 32 further increases.

  Further, in the latter half of the compression stroke, the fuel injection valve 25 performs pilot injection (convex portion J1 on the solid line L13 in FIG. 3A), pre-injection (convex portion J2 on the solid line L13 in FIG. 3A), main injection (FIG. 3 (a), the projecting portion J3 in the solid line L13 is performed, and fuel is supplied to the combustion chamber 22. The fuel supplied to the combustion chamber 22 is positively charged by the charging unit 251 and repels against the positively charged insulating film 32, so that the fuel is burned in a state gathered near the center of the combustion chamber 22. Starts.

  After the combustion of fuel starts and the piston 30 reaches TDC, the piston 30 moves toward the BDC (combustion stroke). In the combustion stroke, the fuel injection valve 25 performs after injection (the convex portion J4 on the solid line L13 in FIG. 3A) and post injection (the convex portion J5 on the solid line L13 in FIG. 3A).

  In general, it is known that a flame has the properties of a positive electrode and behaves so as to repel the positive electrode and approach the negative electrode in an electric field. In the engine 1 according to the first embodiment, the insulating film 32 is charged by the electric field forming electrode 35 before the combustion stroke in accordance with the reciprocation of the piston 30. When the insulating film 32 on the piston surface 31 that forms the combustion chamber 22 is charged, the flame in the combustion chamber 22 moves according to the polarity of the charge. Specifically, when the insulating film 32 is positively charged, the flame in the combustion chamber 22 repels the piston surface 31, and as shown in FIG. 5, the flame in the combustion chamber 22 when the insulating film 32 is not charged. Compared to F0 (two-dot chain line in FIG. 5), it separates from the piston surface 31 as in the flame F1 of the combustion chamber 22 (one-dot chain line in FIG. 5). When the flame in the combustion chamber 22 moves away from the piston surface 31, an air layer is formed between the piston 30 and the flame, and the combustion heat of the flame is hardly transmitted to the piston 30. As a result, the amount of combustion heat of the flame released to the outside of the cylinder 20 is reduced, and the combustion heat released outside through the wall surface forming the combustion chamber with respect to the combustion heat of the flame, that is, the cooling loss. Can be reduced. Therefore, the thermal efficiency of the engine 1 can be improved.

Further, immediately after the engine 1 is started, the control unit 50 makes the electric field forming electrode 35 a negative electrode and charges the insulating film 32 negatively. When the insulating film 32 is negatively charged, a flame having a positive electrode property approaches the piston 30 and the heat of the flame is easily transmitted, and the temperature of the piston 30 and the cylinder 20 rises quickly. When the temperature of the piston 30 or the cylinder 20 rises, the engine coolant and the engine oil quickly rise to the predetermined temperatures. Thereby, the startability of the engine 1 can be improved. Specifically, the amount of CO, HC, and PM in the exhaust gas is reduced, and the fuel consumption immediately after starting can be reduced.
Further, when the combustion heat of the flame is quickly transmitted to the piston 30 and the cylinder 20 and the engine 1 is sufficiently warmed and the operation state of the engine 1 is stabilized, the control unit 50 sets the electric field forming electrode 35 as the positive electrode and the insulating film 32 as the positive electrode. To charge. Thereby, since a flame leaves | separates from the piston 30 and it becomes difficult to transmit the heat of a flame, a cooling loss is made small. Therefore, in the engine 1 according to the first embodiment, the operating state of the engine 1 can be quickly stabilized by changing the polarity of the electric field forming electrode 35.

  Further, the surface of the insulating film 32 is formed in an uneven shape. Thereby, when an electric field is formed by the electric field forming electrode 35, the charge amount of the insulating film 32 can be increased as compared with the insulating film having a flat surface. Accordingly, the repulsive force of the flame against the piston 30 is relatively large, and the flame can be further prevented from approaching the piston surface 31, so that the thermal efficiency of the engine 1 can be further improved.

  As shown in FIG. 3, the controller 50 applies a voltage to the electric field forming electrode 35 from time t11 during the exhaust stroke to time t12 during the intake stroke. Thereby, in the engine 1, it is possible to prevent the electric charge of the insulating film 32 from being discharged to the outside of the combustion chamber 22 together with the water vapor discharged in the exhaust stroke.

Further, as shown in FIG. 3, the control unit 50 applies a voltage to the electric field forming electrode 35 from time t13 to time t14 during the compression stroke. At this time, the magnitude of the applied voltage is increased as the pressure in the combustion chamber 22 increases.
In general, the following relationship is established as Paschen's law for the voltage Vs that can be applied between parallel electrodes, the pressure P of the space formed by the parallel electrodes, and the distance d between the electrodes.
Vs = P × d (1)
When Paschen's law is applied to the relationship between the electric field forming electrode 35 and the insulating film 32 of the engine 1, the voltage Vs that can be applied to the electric field forming electrode 35 is the pressure P in the combustion chamber 22 and the electric field forming electrode 35 and the insulating film 32. Of the distance d. In the compression stroke, the pressure P of the combustion chamber 22 increases due to the movement of the piston 30 to the TDC, so that the voltage Vs that can be applied to the electric field forming electrode 35 can be increased. Thereby, the charge amount of the insulating film 32 is further increased, and a relatively strong electric field can be formed in the combustion chamber 22. Therefore, the thermal efficiency of the engine 1 can be further improved.

  The fuel injection valve 16 can perform so-called “electrostatic spraying” in which charged fuel is directly injected into the combustion chamber 22. The charged fuel changes its position relative to the piston 30 according to the polarity of the electric field forming electrode 35 and the polarity of the insulating film 32. Specifically, the positively charged fuel repels the piston 30 having the positively charged insulating film 32 and leaves the piston 30. Further, the negatively charged fuel approaches the piston 30 having the positively charged insulating film 32. Thus, by charging the fuel, the position with respect to the piston 30 can be controlled, and the position of the flame generated in the combustion stroke can be controlled.

  The particulate matter generated in the combustion stroke has a positive or negative polarity applied to the electric field forming electrode 35. When a voltage is applied to the electric field forming electrode 35 in the exhaust stroke, a certain amount of this particulate matter is trapped on the charged insulating film 32 and confined in the combustion chamber 22. Thereby, the amount of particulate matter contained in the exhaust gas can be reduced.

(Second Embodiment)
Next, an internal combustion engine according to a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment in that a charging film is formed on an insulating film. In addition, the same code | symbol is attached | subjected to the site | part substantially the same as 1st Embodiment, and description is abbreviate | omitted.

  In the engine 2 according to the second embodiment, a charging film 33 is formed on an insulating film 32 provided on the piston surface 31. The charging film 33 is made of a material that is more easily charged than the insulating film 32. The charging film 33 is charged to the same polarity as the polarity of the electric field forming electrode 35 when a voltage is applied to the electric field forming electrode 35.

  Next, the operation of the engine 2 will be described based on FIG. The operation of the engine 2 in the exhaust stroke and the intake stroke is the same as that of the engine 1 according to the first embodiment.

  After the intake stroke is completed, the piston 30 moves from BDC toward TDC, and the intake air in the combustion chamber 22 is compressed (compression stroke). A positive voltage is applied to the electric field forming electrode 35 at time t23 during the compression stroke. The positive voltage applied to the electric field forming electrode 35 increases as the compression stroke proceeds and the pressure in the combustion chamber 22 increases. In the engine 2, after the piston 30 reaches TDC and shifts to the combustion stroke, the positive voltage applied to the electric field forming electrode 35 changes to a negative voltage (time t24 in FIG. 7C).

  In the engine 2 according to the second embodiment, a charging film 33 that is more easily charged than the insulating film 32 is formed. As a result, the electric field formed in the combustion chamber 22 is stronger than that of the engine 1 according to the first embodiment, so that the flame of the combustion chamber 22 having the positive electrode property further repels the piston surface 31, and the flame further extends from the piston surface. Leave. Therefore, in addition to the effects of the first embodiment, the cooling loss can be further reduced.

  In the engine 2, in the initial stage of combustion, a positive voltage is applied to the electrolysis forming electrode 35 to charge the charging film 33 positively. As a result, the flame in the combustion chamber 22 repels the piston 30 and the flame separates from the piston 30. On the other hand, in the latter stage of combustion, a negative voltage is applied to the electric field forming electrode 35, and an electric field in the direction from the charged film 33 to the electric field forming electrode 35 is formed in the combustion chamber 22. As a result, an electric field stronger than the electric field formed in the initial stage of combustion is formed in the combustion chamber 22, the flame in the combustion chamber 22 further repels the piston 30, and the flame separates from the piston 30. Thus, in the engine 2, the polarity of the voltage applied to the electric field forming electrode 35 is controlled separately in the early stage and the late stage of combustion, and the electric field formed in the combustion chamber 22 is further strengthened. Therefore, the engine 2 can control the position of the flame generated in the combustion chamber 22 by forming an electric field in the combustion chamber 22 in the combustion stroke in addition to charging the charging film 33 in the exhaust stroke and the intake stroke.

(Third embodiment)
Next, an internal combustion engine according to a third embodiment of the present invention will be described with reference to FIG. The third embodiment is different from the second embodiment in the position where the insulating film and the charging film are formed. In addition, the same code | symbol is attached | subjected to the site | part substantially the same as 2nd Embodiment, and description is abbreviate | omitted.

  In the engine 3 according to the third embodiment, in addition to the insulating film 32 and the charging film 33 on the piston surface 31, the insulating film 242 and the charging film 243 are provided on the inner wall surface 241 of the cylinder head portion 24 that forms the combustion chamber 22. Yes. An insulating film 262 and a charging film 263 are provided on the inner wall surface 261 of the cylinder liner portion 26 that forms the combustion chamber 22. Further, an insulating film 182 and a charging film 183 are provided on the intake valve end surface 181 of the intake valve 18 that forms the combustion chamber 22. An insulating film 482 and a charging film 483 are formed on the exhaust valve end surface 481 of the exhaust valve 48 that forms the combustion chamber 22.

  The electric field forming electrode 35 of the engine 3 has a plurality of protrusions 351 at positions facing the inner wall surface 241 of the cylinder head portion 24 and the inner wall surface 261 of the cylinder liner portion 26. Each of the plurality of protrusions 351 is formed so that the length thereof is substantially the same as the distance from the charging films 33, 243, 263, 183, and 483.

  In the engine 3 according to the third embodiment, the piston surface 31 forming the combustion chamber 22, the inner wall surface 241 of the cylinder head portion 24, the inner wall surface 261 of the cylinder liner portion 26, the intake valve end surface 181 of the intake valve 18, and the exhaust valve Insulating films 32, 242, 262, 182, 482 and charging films 33, 243, 263, 183, 483 are formed on all the exhaust valve end faces 481 of 48. As a result, when the charging films 33, 243, 263, 183, and 483 are positively charged, the flame repels the piston surface 31, the inner wall surfaces 241, 261, the intake valve end surface 181, and the exhaust valve end surface 481, and causes the combustion chamber 22 to enter. Move away from these surfaces to form. Therefore, in addition to the effects of the first embodiment, the cooling loss can be further reduced.

(Other embodiments)
(A) In the above-described embodiment, the engine is a direct injection type four-stroke engine using light oil as fuel. However, the type of fuel and the type of engine are not limited to this. In the case of a diesel engine, it may be a compression ignition type engine or an engine equipped with a glow plug. Further, an engine using gasoline as fuel may be used. In the case of a gasoline engine, it may be a direct injection engine that directly injects gasoline into the combustion chamber, a PFI type that injects gasoline into the intake passage, or a gas engine that uses natural gas as fuel. For example, an engine using a mixed fuel of alcohol and gasoline as fuel may be used. A two-stroke engine may also be used.

  (A) In the above-described embodiment, the insulating film has a constant thickness, and the plurality of protrusions of the electric field forming electrode are formed so that the distance from the surface of the insulating film is substantially the same. However, the distance between the projection of the electric field forming electrode and the surface of the insulating film is not limited to this. The insulating strength is changed by changing the thickness and material of the insulating film depending on the location. In this way, it is only necessary to change the distance between the protrusion and the insulating film according to the charging property of the insulating film that changes depending on the location, and to form a constant charged state in the vicinity of the piston surface.

  (C) In the above-described embodiment, the control unit calculates the optimum voltage value and current value for forming an electric field in the combustion chamber based on the opening degree of the throttle valve, the exhaust temperature, and the crank angle. However, the parameters based on when the control unit calculates the optimum voltage value and current value are not limited to this. For example, the pressure in the combustion chamber used when calculating the optimum voltage value and current value may be calculated based on the accelerator opening of the accelerator device, the EGR amount based on the map, the compression ratio, and the like. Further, the temperature of the combustion chamber used when calculating the optimum voltage value and current value may be calculated based on the EGR amount based on the map.

  (D) In the first embodiment, the voltage is applied to the electric field forming electrode 35 from the exhaust stroke to the intake stroke and in the compression stroke. In the second embodiment, the voltage is applied to the electric field forming electrode 35 from the exhaust stroke to the intake stroke, in the compression stroke, and in the combustion stroke. However, the timing at which the voltage is applied to the electric field forming electrode 35 is not limited to this. The voltage may be applied during the intake stroke or the exhaust stroke. At this time, since the intake valve is opened during the intake stroke and the exhaust valve is opened during the exhaust stroke, the voltage applied to the electric field forming electrode is set to be relatively low. On the other hand, when the intake valve and the exhaust valve are closed, the voltage applied to the electric field forming electrode is set to be relatively high. Thereby, an insulating film or a charging film can be charged efficiently.

  (E) In the above-described embodiment, the control unit applies a voltage that increases in accordance with the pressure in the combustion chamber to the electric field forming electrode in the compression stroke. However, the magnitude of the voltage is not limited to this.

  (F) In the above-described embodiment, the electric field forming electrode has a plurality of protrusions. However, the shape of the electrode forming the electric field is not limited to this. An electrode without protrusions may be used.

  (G) In the above-described embodiment, the electric field forming electrode is provided on the fuel injection valve. However, the position where the electric field forming electrode is provided is not limited to this. According to the shape of the combustion chamber, it may be provided on the inner wall surface of the cylinder head portion or the cylinder liner portion. One electric field forming electrode may be provided, or a plurality of electric field forming electrodes may be provided.

  (K) In the above embodiment, the piston surface is formed in a toroidal shape. However, the shape of the piston surface is not limited to this. It may be a reentrant type or a dish type.

  (K) In the above-described embodiment, the fuel injected by the fuel injection valve is charged. However, the fuel may not be charged.

  (E) In the above-described embodiment, the insulating film is formed of aluminum oxide. However, the material for forming the insulating film is not limited to this. For example, any insulating material or semiconductor material may be used as long as it is a material having high heat resistance, which is mainly made of silicon oxide such as glass, and is relatively easily charged.

  As mentioned above, this invention is not limited to such embodiment, It can implement with a various form in the range which does not deviate from the summary.

1 ... Engine (internal combustion engine),
18 ・ ・ ・ Intake valve,
181 ... Inlet valve end face,
20 ... Cylinder,
22 ... combustion chamber,
25 ... Fuel injection valve (fuel supply means),
30 ・ ・ ・ Piston,
31 ... piston surface,
32, 242, 262, 182, 482 ... insulating film,
33, 243, 263, 183, 483 ... charged film,
35 ... Electric field forming electrode (electric field forming means),
48 ... exhaust valve,
481 ... exhaust valve end face.

Claims (17)

A reciprocating piston (30);
A cylinder (20) that houses the piston and forms a combustion chamber (22) whose volume is variable by reciprocating movement of the piston;
Fuel supply means (25) for supplying fuel to the combustion chamber;
Electric field forming means (35) provided in the cylinder for forming an electric field in the combustion chamber;
With
The internal combustion engine, wherein the piston has a chargeable insulating film (32) formed on a piston surface (31) forming the combustion chamber.   2. The internal combustion engine according to claim 1, wherein the cylinder is provided with a chargeable insulating film (242, 262) on an inner wall surface (241, 261) forming the combustion chamber. An intake valve (18) for supplying at least air to the combustion chamber;
The internal combustion engine according to claim 1 or 2, wherein the intake valve has a chargeable insulating film (182) formed on an intake valve end surface (181) forming the combustion chamber. An exhaust valve (48) for exhausting the exhaust of the combustion chamber;
The internal combustion engine according to any one of claims 1 to 3, wherein the exhaust valve has a chargeable insulating film (482) formed on an exhaust valve end surface (481) forming the combustion chamber. .   5. The internal combustion engine according to claim 1, wherein the insulating film is formed from an insulating material or a semiconductor material mainly composed of aluminum oxide or silicon oxide. 6.   The internal combustion engine according to claim 1, wherein the insulating film is formed in an uneven shape.   The charging film (33, 243, 263, 183, 483) that is more easily charged than the insulating film is formed on the insulating film, according to any one of claims 1 to 6. Internal combustion engine.   The internal combustion engine according to any one of claims 1 to 7, wherein the electric field forming means forms an electric field in the combustion chamber when a high voltage is applied. Charging means (251) for charging fuel supplied to the combustion chamber;
The internal combustion engine according to any one of claims 1 to 8, wherein the fuel supply means supplies charged fuel to the combustion chamber.   The internal combustion engine according to any one of claims 1 to 9, further comprising a control unit (50) for controlling an intensity of an electric field formed by the electric field forming unit and a time for forming the electric field. A control method for an internal combustion engine according to claim 10,
The method of controlling an internal combustion engine, wherein the electric field forming means forms an electric field in the combustion chamber in at least one of an exhaust stroke, an intake stroke, and a compression stroke.   The control of the internal combustion engine according to claim 11, wherein the electric field forming means forms an electric field in the combustion chamber when the piston is at a top dead center between an exhaust stroke and an intake stroke. Method.   The method of controlling an internal combustion engine according to claim 11 or 12, wherein the electric field forming means forms an electric field in the combustion chamber during a compression stroke.   14. The control of an internal combustion engine according to claim 11, wherein the electric field forming unit charges the insulating film or the charging film negatively for a predetermined time from the start of the internal combustion engine. Method.   15. The internal combustion engine according to claim 11, wherein the electric field forming unit charges the insulating film or the charging film positively after a predetermined time has elapsed since the start of the internal combustion engine. How to control the engine.   The internal combustion engine according to any one of claims 11 to 15, wherein the control unit controls the strength of an electric field formed in the combustion chamber in accordance with a magnitude of the pressure in the combustion chamber. Control method.   The method of controlling an internal combustion engine according to any one of claims 11 to 16, wherein the electric field forming means forms an electric field of the combustion chamber in a combustion stroke.

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