JP6444833B2 - Ignition plug and ignition device for internal combustion engine having the same - Google Patents

Description

  The present invention relates to a spark plug that performs dielectric barrier discharge and arc discharge, and an ignition device for an internal combustion engine including the same.

  In order to increase the thermal efficiency of the internal combustion engine, it is effective to increase the combustion rate and increase the isovolume. In order to increase the combustion rate, low temperature plasma (non-equilibrium plasma) is generated by corona discharge or glow discharge in the spark plug, and active species (radical reaction field) due to high energy electrons contributing to the combustion reaction are generated in the combustion chamber. It is known that the flame propagation to the entire combustion chamber can be promoted.

  As an ignition plug of an internal combustion engine capable of generating low temperature plasma by dielectric barrier discharge, a high voltage electrode (anode) having an exposed surface exposed to the combustion chamber and a coated surface covered with a coating material, and an exposed exposed to the combustion chamber A device including an induction electrode (cathode) having a surface and a coating surface covered with a coating material is known (see Patent Document 1). This spark plug generates a precursor discharge (dielectric barrier discharge) between the coated surfaces of both electrodes by applying a pulse voltage between both electrodes, followed by a main discharge (exposed to the exposed surfaces of both electrodes). Arc discharge). Thus, the arc discharge is stably generated by using the space where the low temperature plasma generating the active species is generated as a path of the arc discharge.

  Further, as an ignition plug capable of switching between a discharge mode for generating low-temperature plasma and a discharge mode for generating thermal plasma, a spark plug having a center electrode held by an insulator and an outer electrode located on the outer peripheral side of the center electrode Is known (see Patent Document 2). In FIG. 13 of Patent Document 2, there is an ignition plug arranged such that the center electrode protrudes toward the combustion chamber with respect to the outer electrode, and the outer electrode is exposed to the combustion chamber at a position along the top wall surface of the combustion chamber. It is disclosed. This spark plug generates a streamer (low temperature plasma) around the center electrode by applying a relatively low voltage between both electrodes, and the center electrode and the outer electrode by increasing the applied voltage relatively. A thermal plasma is generated by arc discharge that short-circuits with and.

JP 2012-48889 A JP 2013-238129 A

  However, in the spark plugs described in Patent Documents 1 and 2, the location where the dielectric barrier discharge and the arc discharge are generated is common, and the arc discharge includes creeping discharge that travels on the surface of the coating material. Melting and scraping occur due to arc discharge (thermal plasma). Therefore, not only does the covering material deteriorate, but the covering material eventually penetrates and cracks, and the spark plug may be destroyed. Further, since the discharge mode shifts to creeping arc discharge during the generation of the dielectric barrier discharge, active species generated by the dielectric barrier discharge are immediately consumed by the arc discharge. That is, active species effective for combustion cannot be stored in the combustion chamber, and the combustion improvement effect by the dielectric barrier discharge is small.

  In view of such a background, an object of the present invention is to provide an ignition plug having high durability and high combustion stability and an ignition device for an internal combustion engine including the same.

  In order to solve such a problem, the spark plug (11, 31) according to the present invention is formed of a conductive material, and is covered with a covering portion (21a) covered with a dielectric (25) and the dielectric. A high voltage electrode (21) having no exposed portion (21b), a dielectric barrier discharge electrode (22) disposed opposite to the covering portion of the high voltage electrode with the dielectric interposed therebetween, And an arc discharge electrode (23) disposed opposite to the exposed portion of the voltage electrode.

  According to this configuration, dielectric barrier discharge (non-equilibrium plasma discharge) and arc discharge are possible with a single spark plug, and ignition with high combustion stability at low cost and low volume is possible. In addition, since the arc discharge electrode is provided separately from the dielectric barrier discharge electrode, damage to the dielectric is suppressed and durability is improved as compared with the conventional plasma spark plug in which the arc discharge includes creeping discharge.

  In the above invention, the high voltage electrode (21) may have the exposed portion (21b) on the distal end side and the covering portion (21a) on the proximal end side.

  According to this configuration, ignition by arc discharge is performed on the tip side of the dielectric, that is, the combustion chamber side where the mixed gas exists, so that thermal damage to the dielectric is suppressed.

  In the above invention, the distance from the dielectric barrier discharge electrode (22) to the dielectric (25) is A, and the region from the region (P) facing the dielectric barrier discharge electrode in the dielectric. The shortest creepage distance along the outer surface (21b) of the high voltage electrode (21) to the exposed portion (21b) is B, and the distance between the arc discharge electrode (23) and the exposed portion of the high voltage electrode is B. When the distance is defined as C, it is preferable that A <C <B.

  According to this configuration, the dielectric barrier discharge can be performed prior to the arc discharge while preventing the creeping discharge.

  In the above invention, the dielectric barrier discharge electrode (22) and the arc discharge electrode (23) may be provided so as to face each other with the high voltage electrode (21) interposed therebetween.

  According to this configuration, an increase in the size of the spark plug can be prevented.

  In the above invention, the dielectric barrier discharge electrode (22) may be provided in plural.

  According to this configuration, a radical reaction field can be formed over a wide range, and flame propagation to the entire combustion chamber can be promoted.

  In the above invention, the high-voltage electrode (21) includes the exposed portion (21B) including the exposed portion (21b) and the exposed portion separated from each other by an element (32) for limiting an arc current. The dielectric barrier discharge electrode (22) is disposed opposite to the power supply side portion, and the arc discharge electrode (23) is disposed opposite to the exposed side portion. It can be set as the structure made.

  During arc discharge, electromagnetic waves that can interfere with other devices are generated. According to this configuration, energy loss due to the element is not caused during dielectric barrier discharge, and electromagnetic interference due to arc discharge can be suppressed by passing a current through the element during arc discharge.

  In order to solve the above problems, an ignition device (10) for an internal combustion engine (1) according to the present invention includes the ignition plug (31) and a control device (12) for controlling a voltage applied to the ignition plug. The control device applies a pulse voltage to the high voltage electrode (21).

  When the voltage for dielectric barrier discharge is increased, arc discharge may occur depending on environmental conditions such as pressure and temperature. According to this configuration, since the RC circuit is formed by the resistance component of the element on the arc discharge electrode side due to the capacitance component of the spark plug, the dielectric barrier discharge voltage can be increased. A radical reaction field having high energy can be generated by discharge.

  In order to solve the above problems, an ignition device (10) of an internal combustion engine (1) according to the present invention includes a spark plug (11, 31) and a control device that controls a voltage applied to the spark plug ( 12), the controller applies a short time pulse to the high voltage electrode (21) to perform dielectric barrier discharge, and then applies a long time pulse to the high voltage electrode to cause arc discharge. The configuration is to be performed.

  According to this configuration, the control device can control both the dielectric barrier discharge and the arc discharge by pulse-controlling the voltage applied to the high voltage electrode.

  In order to solve the above problems, an ignition device (10) of an internal combustion engine (1) according to the present invention includes a spark plug (11, 31) and a control device that controls a voltage applied to the spark plug ( 12), and the controller performs a dielectric barrier discharge by applying a relatively low voltage to the high voltage electrode, and then performs an arc discharge by applying a relatively high voltage to the high voltage electrode. The configuration.

  According to this configuration, both the dielectric barrier discharge and the arc discharge can be performed by the control device controlling the voltage applied to the high voltage electrode.

  As described above, according to the present invention, it is possible to provide an ignition plug having high durability and high combustion stability and an ignition device for an internal combustion engine including the same.

1 is a schematic cross-sectional view of an internal combustion engine including an ignition device according to a first embodiment. Fig. 1 is an enlarged sectional view of the waist of the spark plug shown in Fig. 1. Graph showing the correlation between discharge generation voltage and pressure at various distances Graph showing the correlation between discharge generation voltage and pressure Time chart showing applied voltage Time chart showing other examples of applied voltage Graph showing the correlation between discharge generation voltage and pressure in various voltage application modes Bottom view of spark plug according to modification The waist expanded sectional view of the ignition plug concerning a 2nd embodiment. Action explanatory drawing of the spark plug shown in FIG. Action explanatory drawing of the spark plug shown in FIG. Waist enlarged sectional view of a spark plug according to a modified example

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the internal combustion engine 1 and its ignition device 10 mounted on the vehicle according to the illustrated direction will be described, but the mounting posture of the internal combustion engine 1 is not limited to the illustrated one.

<< First Embodiment >>
First, an ignition device 10 for an internal combustion engine 1 according to the first embodiment will be described with reference to FIGS. As shown in FIG. 1, the internal combustion engine 1 is a four-stroke gasoline engine, and includes a cylinder block 2 that defines a cylindrical cylinder 2a, a cylinder head 3 joined to the upper surface of the cylinder block 2, and a cylinder 2a. The piston 4 is provided so as to be slidable. The number of cylinders and the cylinder row of the internal combustion engine 1 may be arbitrary.

  A combustion chamber recess 3 a that is a curved depression is formed at a position corresponding to the cylinder 2 a on the lower surface of the cylinder head 3. A combustion chamber 5 is formed by a space surrounded by the combustion chamber recess 3 a, the cylinder 2 a and the top surface of the piston 4. That is, the combustion chamber recess 3 a defines the top of the combustion chamber 5.

  A spark plug insertion hole 3b extending from the upper surface of the cylinder head 3 to the combustion chamber 5 is formed substantially at the center of the cylinder head 3. In the present embodiment, one spark plug insertion hole 3b is formed for one cylinder 2a. The spark plug insertion hole 3b is formed on the cylinder axis so as to open in the center of the combustion chamber recess 3a. A cylindrical plug guide 6 is press-fitted into the spark plug insertion hole 3 b of the cylinder head 3, and the spark plug insertion hole 3 b is extended upward by the plug guide 6.

  The cylinder head 3 is formed with an intake port 3c that opens to the left side and opens to the combustion chamber recess 3a, and an exhaust port 3d that opens to the combustion chamber recess 3a and opens to the right side. In the present embodiment, two intake ports 3c and two exhaust ports 3d are formed for one cylinder 2a. The cylinder head 3 is slidably provided with an intake valve 7 that opens and closes each intake port 3c and an exhaust valve 8 that opens and closes each exhaust port 3d.

  An exhaust device 9 is joined to the right side surface of the cylinder head 3. The exhaust device 9 includes, in addition to an exhaust pipe 9a connected to the exhaust port 3d and forming an exhaust passage, a catalytic converter 9b and a silencer (not shown) in order from the upstream side of the exhaust passage. The catalytic converter 9b may be a three-way catalyst, for example. The catalytic converter 9b is provided with a temperature sensor 9c for detecting the catalyst temperature.

  The internal combustion engine 1 is provided with an ignition device 10 that ignites a mixed gas drawn into the combustion chamber 5 from the intake port 3c. The ignition device 10 is inserted into the ignition plug insertion hole 3b, and is connected to the ignition plug 11 from the power source 13 (13a, 13b). And a control device 12 for controlling the applied voltage. In this embodiment, a short pulse high frequency power supply 13a and a long pulse power supply 13b are provided as the power supply 13, and the control device 12 controls the voltage applied to the spark plug 11 from both the power supplies 13a and 13b.

  The spark plug 11 has a base end held by a plug cap 15 and is screwed into a female screw formed in the lower portion of the spark plug insertion hole 3b. A terminal portion 16 is formed at the base end (upper end) of the spark plug 11. The terminal portion 16 is electrically connected to the power source 13 by the high voltage conductive member 17 made of a coil spring housed in the plug cap 15 being in elastic contact with the terminal portion 16.

  As shown in FIG. 2, the spark plug 11 has three electrodes 21 to 23 (hereinafter referred to as a first electrode 21, a second electrode 22, and a third electrode 23) at the tip (lower end). Yes. The first electrode 21 disposed on the center axis of the spark plug 11 is a center electrode that is electrically connected to the power source 13 via the terminal portion 16 and is applied with a high voltage.

  The distal end portion of the spark plug 11 is formed with a male screw (not shown) on the outer periphery, a cylindrical main body 24 that is electrically connected to the cylinder head 3, and a cylindrical insulation inserted into the main body 24. And an insulator 25. An insulating film 26 made of a material having a lower dielectric constant than that of the insulator 25 is formed on the inner surface of the main body 24. The insulator 25 has a cylindrical shape and houses therein a first electrode 21 that forms a high-voltage electrode, and acts as an insulator as will be described later. The insulator 25 extends below the front end surface 24 a of the main body 24, and this extended portion is exposed to the combustion chamber 5. The second electrode 22 and the third electrode 23 are integrally provided on the distal end surface 24a of the main body 24 so as to extend downward. The second electrode 22 and the third electrode 23 are arranged at positions facing each other with the first electrode 21 interposed therebetween.

  The first electrode 21 extends further downward than the tip 25a of the insulator 25, and then bends and extends radially outward. That is, the first electrode 21 is disposed on the distal end side with respect to the base end side covering portion 21a covered with the insulator 25 and exposed to the combustion chamber 5 without being covered with the insulator 25. Part 21b. The exposed portion 21b has a radially outer end portion 21c at the tip of the bent portion.

  The second electrode 22 extends linearly shorter than the third electrode 23 downward from the outer peripheral portion of the main body 24 and then bends and extends radially inward. An inward leading end 22 a (a radially inner end face) of the bent portion of the second electrode 22 is disposed closer to the outer surface 25 b of the insulator 25 than the third electrode 23. The second electrode 22 is a ground electrode (positive electrode) that is electrically connected to the cylinder head 3 via the main body 24, and is an insulator that covers the first electrode 21 between the first electrode 21 and more precisely. 25 is a dielectric barrier discharge electrode for generating a dielectric barrier discharge between the outer surface 25b and the outer surface 25b.

  The third electrode 23 has a rod shape and extends downward from the outer peripheral portion of the main body portion 24 in a straight line. The third electrode 23 is formed longer than the second electrode 22, and the tip 23 a is disposed in the vicinity of the radially outer end 21 c of the first electrode 21. The third electrode 23 is a ground electrode (positive electrode) that is electrically connected to the cylinder head 3 via the main body 24, and is an arc discharge electrode that generates an arc discharge with the first electrode 21.

  Here, the arrangement of the electrodes 21 to 23 will be described in more detail. The distance from the second electrode 22 to the insulator 25 is defined as a first distance A, and the outermost surface 25b of the insulator 25 has the most distal side (on the exposed portion 21b side of the first electrode 21) in the region facing the second electrode 22. ) Is a shortest creepage distance along the outer surface 25b from the point P to the exposed portion 21b of the first electrode 21 as a second distance B, and a distance from the third electrode 23 to the exposed portion 21b of the high voltage electrode is a third distance. Defined as C. At this time, the first to third electrodes 21 to 23 are arranged to have a relationship of A <C <B.

  The relationship between these first to third distances A to C is determined based on the following idea.

  That is, the first distance A is a discharge gap of the dielectric barrier discharge generated between the first electrode 21 (insulator 25) and the second electrode 22. The second distance B, which is the distance from the point P facing the second electrode 22 in the insulator 25 where the dielectric barrier discharge is generated, to the exposed portion 21b of the first electrode 21 is the outer surface 25b of the insulator 25. It is a cap for preventing the occurrence of creeping arc discharge. The third distance C is a discharge gap of arc discharge generated between the exposed portion 21 b of the first electrode 21 and the third electrode 23.

  The withstand voltage of the insulator 25 has a correlation with the thickness of the insulator 25 that increases as the thickness increases under the same pressure condition. Therefore, the thickness and material of the insulator 25 are selected so that the withstand voltage is 45 kV or more and 50 kV or less. On the other hand, the generated voltage of the dielectric barrier discharge at the first distance A has a correlation with the thickness of the insulator 25 that increases as the thickness increases under the same pressure condition. When the thickness of the insulator 25 is set as described above, in order to generate the dielectric barrier discharge and the spatial arc discharge separately, the generated voltage of the dielectric barrier discharge at the first distance A is set to the third distance C. It is necessary to make it less than or equal to the arc discharge generation voltage (first condition), and the generation voltage of the spatial arc discharge at the third distance C must be less than the generation voltage of the creeping arc discharge at the second distance B (second). conditions).

  FIG. 3 shows the arc discharge generation voltage when the third distance C is changed to 2.0 mm, 1.5 mm, 1.1 mm, 0.8 mm and 0.6 mm, and the creeping surface when the second distance B is 10 mm. The correlation between each of the arc discharge generation voltage and the dielectric barrier discharge generation voltage when the first distance A is 0.3 mm and the pressure is shown. As shown in FIG. 3, each discharge generation voltage tends to increase as the pressure increases. Further, compared to the dielectric barrier discharge generation voltage at the discharge gap of the first distance A = 0.3 mm and the creeping arc discharge generation voltage at the second distance B of 10 mm, the spatial arc discharge generation voltage at the second distance B is a pressure. It tends to increase as the value increases.

  On the other hand, when the third distance C is set to these values, the general value of the combustion chamber pressure is 0.8 MPa to 1.6 MPa in all cases where the third distance C is 0.6 mm to 2.0 mm. The first and second conditions are satisfied in the range. Further, when the third distance C is 0.8 mm to 1.5 mm, the first and second conditions are satisfied in the range of 0.8 MPa to 2.0 MPa.

  For this reason, in the present invention, the first electrode 21 (insulator 25), the second electrode 22, and the first electrode 21 are arranged such that the first to third electrodes 21 to 23 have a relationship of A <C <B. It is possible to individually generate the dielectric barrier discharge generated between the first electrode 21 and the arc discharge generated between the exposed portion 21b of the first electrode 21 and the third electrode 23 without generating creeping arc discharge. Yes.

  This will be further described with a specific example. When the thickness of the insulator 25 is 1.2 mm (withstand voltage when the pressure is 2 MPa: 50 kV), for example, the first distance A = 0.3 mm (dielectric barrier discharge generation voltage when the pressure is 2 MPa: 30 kV, 3, the second distance B = 10 mm (creeping arc discharge generation voltage at a pressure of MPa: 48 kV), the third distance C = 1.5 mm (space arc discharge generation voltage at a pressure of 2 MPa: 45 kV) ).

  FIG. 4 shows the correlation between dielectric barrier discharge generation voltage and arc discharge generation voltage and pressure in this case. Also in this example, the first to third electrodes 21 to 23 are arranged to have a relationship of A <C <B, and a dielectric barrier discharge is generated between the first electrode 21 and the second electrode 22 and Arc discharge can be generated between the first electrode 21 and the third electrode 23 without generating arc discharge.

  In the ignition device 10 in which the ignition plug 11 is configured in this way, the control device 12 controls the applied voltage of the ignition plug 11, the pulse width of the applied voltage, etc., so that the discharge form between the pair of electrodes is not balanced. Switch between plasma discharge and arc discharge, and ignite the mixture by arc discharge.

  Specifically, as shown in FIG. 5, the control device 12 first applies a relatively short high-frequency pulse with a relatively low voltage from the short-pulse high-frequency power source 13 a to the spark plug 11, thereby A non-equilibrium plasma discharge is generated between the first electrode 21, that is, between the inward tip portion 22 a of the second electrode 22 and the outer surface 25 b of the insulator 25. The wavelength of the low voltage pulse can be set to about 200 nsec, for example. Thereafter, the control device 12 applies a high-frequency short-time pulse with a relatively high voltage from the short-pulse high-frequency power source 13a to the spark plug 11, thereby causing the third electrode 23 to be connected between the third electrode 23 and the first electrode 21. An arc discharge is generated between the tip portion 23a of the first electrode 21 and the radially outer end portion 21c of the first electrode 21. The wavelength of the high voltage pulse can also be set to about 200 nsec, for example.

  When such a discharge control is performed by the control device 12, the ignition of the mixed gas by the spark plug 11 and the combustion of the ignited mixed gas proceed as follows. That is, the spark plug 11 first performs non-equilibrium plasma discharge (corona discharge or glow discharge) accompanied by generation of non-equilibrium plasma that generates radicals between the second electrode 22 and the first electrode 21, thereby igniting. An active field is generated around the tip of the plug 11. The active field is increased by being generated by the continuation of the discharge while being flown by the main flow of the air-fuel mixture and spreading into the combustion chamber 5. Thereafter, the spark plug 11 ignites the air-fuel mixture by performing arc discharge between the third electrode 23 and the first electrode 21. The flame ignited at the tip of the spark plug 11 (between the pair of electrodes 21 and 23) propagates in the active field so as to spread from the center of the combustion chamber 5 at high speed, and combustion of the air-fuel mixture is completed at an early stage.

  Thus, the spark plug 11 is formed of a conductive material, and is a first electrode that is a high-voltage electrode having a covering portion 21a that is covered with an insulator 25 that is a dielectric and an exposed portion 21b that is not covered with the insulator 25. 21, the second electrode 22, which is a dielectric barrier discharge electrode disposed opposite to the covering portion 21 a of the first electrode 21 with the insulator 25 interposed therebetween, and the exposed portion 21 b of the first electrode 21. By providing the third electrode 23 which is an arc discharge electrode, a single spark plug 11 can perform dielectric barrier discharge (non-equilibrium plasma discharge) and arc discharge, and can stabilize combustion at low cost and low volume. High-quality ignition is possible. Further, the third electrode 23 for arc discharge is provided separately from the second electrode 22 for dielectric barrier discharge, so that the insulator 25 is damaged as compared with the conventional plasma spark plug in which the arc discharge includes creeping discharge. It is suppressed and durability is improved.

  Further, since the first electrode 21 has the exposed portion 21b on the distal end side and the covering portion 21a on the proximal end side, an arc is generated on the distal end side of the insulator 25, that is, the combustion chamber 5 side where the mixed gas exists. Since ignition by discharge is performed, thermal damage to the insulator 25 is suppressed.

  Further, as described above, the first to third electrodes 21 to 23 are arranged so as to satisfy the relationship of A <C <B, thereby preventing the arc discharge while preventing the creeping discharge along the outer surface 25b of the insulator 25. Prior to the discharge, it is possible to perform a dielectric barrier discharge.

  Further, the second electrode 22 for dielectric barrier discharge and the third electrode 23 for arc discharge are provided so as to face each other with the first electrode 21 which is a high voltage electrode interposed therebetween, so that the spark plug 11 An increase in size is prevented.

  The controller 12 applies a short-time pulse to the first electrode 21 that is a high-voltage electrode to perform dielectric barrier discharge, and then applies a long-time pulse to the first electrode 21 to perform arc discharge. Thus, both dielectric barrier discharge and arc discharge can be carried out only by pulse-controlling the voltage applied to the high voltage electrode.

  Alternatively, the control device 12 may control the applied voltage as shown in FIG. That is, the control device 12 first applies a high-frequency short-time pulse having a relatively low voltage to the spark plug 11 from the short-pulse high-frequency power source 13a. The generation of non-equilibrium plasma discharge by this is the same as in FIG. On the other hand, the control device 12 then generates an arc discharge between the third electrode 23 and the first electrode 21 by applying a long pulse with a relatively high voltage to the spark plug 11 from the long pulse power supply 13b. . While the wavelength of the low voltage pulse is about 200 nsec, the wavelength of the high voltage pulse can be set to about 100 μsec, for example.

  As shown in FIG. 7, the arc discharge generation voltage when a long-time pulse is applied is lower than the arc discharge generation voltage when a high-frequency short-time pulse as shown in FIG. 5 is applied. Therefore, when the control device 12 controls such an applied voltage, the arc discharge can be generated at a lower applied voltage than when the arc discharge is generated by the applied voltage of the high-frequency short-time pulse shown in FIG. it can. Thereby, the withstand voltage which should be ensured for the insulator 25 can be reduced. That is, by reducing the thickness of the insulator 25, as shown in FIG. 5, the dielectric barrier discharge generation voltage can be reduced as much as the insulator 25 is thinned.

  As described above, the controller 12 applies a relatively low voltage to the first electrode 21 to perform dielectric barrier discharge, and then applies a relatively high voltage to the first electrode 21 to perform arc discharge. Both dielectric barrier discharge and arc discharge can be performed only by controlling the voltage applied to the first electrode 21 which is a high voltage electrode.

  Moreover, in the said embodiment, although the 2nd electrode 22 is provided only in the position facing the 3rd electrode 23 on both sides of the 1st electrode 21, as FIG. 8 shows, the 2nd electrode 22 is provided. A plurality (two in the illustrated example) may be provided. In this case, the plurality of second electrodes 22 may be arranged at different positions in the circumferential direction on the distal end surface 24 a of the main body 24.

  As described above, the spark plug 11 includes a plurality of the second electrodes 22 for dielectric barrier discharge, thereby forming a radical reaction field by the dielectric barrier discharge in a wide range and promoting the flame propagation to the entire combustion chamber 5. Can do.

<< Second Embodiment >>
Next, the ignition device 10 according to the second embodiment will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the element which is the same or the same as that of 1st Embodiment, or a function, and the overlapping description is abbreviate | omitted.

  In the ignition device 10 of the present embodiment, the configuration of the spark plug 31 is different from that of the above embodiment. FIG. 9 is a cross-sectional view corresponding to FIG. 2 showing the waist portion on the tip (lower end) side of the spark plug 31. As shown in the figure, in the spark plug 31 of the present embodiment, the first electrode 21 is provided with a resistor 32, and the first electrode 21 (conductive material constituting the first electrode 21) is formed by the resistor 32. It is divided into an exposed side portion 21B including the exposed portion 21b and a power source side portion 21A not including the exposed portion 21b. The resistor 32 is disposed on the distal end side of the first electrode 21 with respect to the position facing the inward distal end portion 22a of the second electrode 22. Therefore, the second electrode 22 is disposed so that the inward tip portion 22 a faces the power supply side portion 21 </ b> A of the first electrode 21. The resistor 32 is set to 5 kΩ, for example.

  As described with reference to FIG. 6 in the first embodiment, the control device 12 first applies a relatively high-frequency short-time pulse of a relatively low voltage from the short-pulse high-frequency power source 13a to the spark plug 31, thereby A non-equilibrium plasma discharge is generated between the electrode 22 and the first electrode 21. Thereafter, the control device 12 applies a long pulse with a relatively high voltage from the long pulse power supply 13 b to the spark plug 31, thereby generating arc discharge between the third electrode 23 and the first electrode 21.

  In the ignition device 10 configured as described above, the control device 12 applies a high-frequency short-time pulse with a relatively low voltage to the ignition plug 31, and between the power supply side portion 21 </ b> A of the first electrode 21 and the second electrode 22. When a dielectric barrier discharge is performed, no current passes through the resistor 32. On the other hand, when the control device 12 applies a long pulse with a relatively high voltage to the spark plug 31, and arc discharge is performed between the tip of the first electrode 21 (exposed side portion 21 </ b> B) and the third electrode 23. Current passes through the resistor 32. That is, the arc current is limited by the resistor 32. Therefore, as shown in FIG. 10, the spark plug 31 acts as a capacitor (capacitor), and the spark plug 31 forms an RC circuit (resistor-capacitor circuit).

Accordingly, as shown in FIG. 11A, when the control device 12 applies a high-frequency short-time pulse to the spark plug 31, the high-frequency short-time having the input voltage Vin input to the terminal portion 16 is obtained. The pulse is a high-frequency short-time pulse having a first output voltage Vout ₁ having the same magnitude as the input voltage Vin at the first output portion 41 formed in the power supply side portion 21A of the first electrode 21 facing the second electrode 22. Is output as

On the other hand, in the second output portion 42 formed in the exposed side portion 21B of the first electrode 21 that is disposed close to the third electrode 23, the high-frequency short-time pulse of the input voltage Vin is the capacitance (for example, the spark plug 31). 5 pF) with a time constant τ (τ = 0.7 × 5 kΩ × 5 pF = 1.8 × 10 ⁻⁸ sec). At this time, the second output voltage Vout ₂ of the high-frequency short-time pulse decreases by about 20% as shown by a broken line in FIG. For this reason, when the control device 12 applies a high-frequency short-time pulse to the spark plug 31, arc discharge is unlikely to occur between the first electrode 21 and the third electrode 23, and the voltage for dielectric barrier discharge is increased. It can be set to generate a high energy dielectric barrier discharge.

On the other hand, when the control device 12 applies a long-time pulse to the spark plug 31, the long-time pulse of the input voltage Vin is still input to the input voltage at the first output unit 41 as shown in FIG. It is output as a long-time pulse having the first output voltage Vout ₁ having the same magnitude as Vin. On the other hand, in the second output unit 42, the long-time pulse of the input voltage Vin is transmitted with a time constant τ as shown by the broken line in FIG. It is output as a long-time pulse having a second output voltage Vout ₂ that is approximately the same as the voltage Vin. Therefore, arc discharge does not easily occur between the first electrode 21 and the third electrode 23.

  Thus, the first electrode 21 which is a high voltage electrode has an exposed side portion 21B including the exposed portion 21b and a power source side portion 21A not including the exposed portion 21b, which are separated from each other by the resistor 32, and has a dielectric barrier. By disposing the second electrode 22 for discharge so as to face the power source side portion 21A and the third electrode 23 for arc discharge so as to face the exposed side portion 21B, the following actions and effects can be obtained. In other words, electromagnetic waves that can interfere with other devices are generated during arc discharge, but with the above configuration, energy loss due to the resistor 32 does not occur during dielectric barrier discharge, and arc discharge occurs when current flows through the resistor 32 during arc discharge. Electromagnetic interference due to is suppressed. Other elements such as a coil may be used instead of the resistor 32 as an element for limiting the arc current.

  In addition, when the dielectric barrier discharge voltage is set high, arc discharge may occur depending on environmental conditions such as pressure and temperature. In this embodiment, the control device 12 applies a pulse voltage to the spark plug 31. Is applied, the arc RC circuit is formed on the side of the arc discharge third electrode 23 due to the capacitance component of the spark plug 31, so that the dielectric barrier discharge voltage can be increased, and the dielectric barrier A radical reaction field having high energy can be generated by discharge.

  In order to obtain the same operation and effect, the configuration of the spark plug 31 may be as shown in FIG. That is, as shown in the figure, in the spark plug 31, the first electrode 21 (the conductive material constituting the first electrode 21) is divided into an exposed side portion 21B and a power source side portion 21A. Although the resistor 32 is provided, the position of the resistor 32 is closer to the base end side than the point P of the first electrode 21 facing the inwardly leading end portion 22a of the second electrode 22 in the first electrode 21. ing. On the other hand, the power supply side portion 21A of the first electrode 21 extends from the position where the resistor 32 is provided toward the distal end side in parallel with the exposed side portion 21B and away from the exposed side portion 21B. It has an extending portion 33 that reaches a position corresponding to the point P facing the inward tip portion 22a.

Even if the spark plug 31 is configured in this way, when the control device 12 applies a high-frequency short-time pulse with a relatively low voltage to the spark plug 31, the first output portion 41 formed in the extension portion 33. the first reduces the output voltage Vout ₁ of the second output voltage Vout ₂ of the second output section 42 which is formed on the exposed portion 21B can be reduced. Further, when the control device 12 applies a long pulse of a relatively high voltage to the spark plug 31, it is possible to generate arc discharge without reducing the second output voltage Vout ₂ of the second output unit 42. it can. As a result, the dielectric barrier discharge voltage can be set high to generate a high-energy dielectric barrier discharge.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above embodiment, a DC pulse voltage is applied as a high-frequency short-time pulse, but an AC voltage may be applied. In addition, the specific configuration, arrangement, quantity, material, control procedure, and the like of each member and part can be changed as appropriate without departing from the spirit of the present invention. In addition, all the constituent elements shown in the above embodiment are not necessarily essential, and can be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Ignition apparatus 11 Spark plug 12 Control apparatus 21 1st electrode (high voltage electrode)
21A Power supply side portion 21B Exposed side portion 21a Cover portion 21b Exposed portion 22 Second electrode (electrode for dielectric barrier discharge)
23 Third electrode (electrode for arc discharge)
25 Insulator (dielectric)
25b Outer surface 31 Spark plug 32 Resistance (element for limiting arc current)
A 1st distance (distance from the 2nd electrode 22 to the insulator 25)
B second distance (the shortest creepage distance along the outer surface 25b from the point P to the exposed portion 21b of the first electrode 21)
C 3rd distance (distance from the 3rd electrode 23 to the exposed part 21b of the 1st electrode 21)
Point P (the most distal point in the region facing the second electrode 22 on the outer surface 252b of the insulator 25)

Claims (8)

A high voltage electrode formed of a conductive material and having a covering portion covered by a dielectric and an exposed portion not covered by the dielectric;
A dielectric barrier discharge electrode disposed opposite to the covering portion of the high-voltage electrode with the dielectric interposed therebetween;
An arc discharge electrode disposed opposite to the exposed portion of the high voltage electrode ;
The spark plug according to claim 1, wherein the dielectric barrier discharge electrode and the arc discharge electrode are provided so as to face each other with the high voltage electrode interposed therebetween . A high voltage electrode formed of a conductive material and having a covering portion covered by a dielectric and an exposed portion not covered by the dielectric;
A dielectric barrier discharge electrode disposed opposite to the covering portion of the high-voltage electrode with the dielectric interposed therebetween;
An arc discharge electrode disposed opposite to the exposed portion of the high voltage electrode ;
The high voltage electrode has an exposed side portion including the exposed portion and a power source side portion not including the exposed portion, which are separated from each other by an element for limiting an arc current.
The dielectric barrier discharge electrode is disposed opposite to the power supply side portion,
A spark plug characterized in that the arc discharge electrode is disposed opposite to the exposed side portion . The spark plug according to claim 1 or 2 , wherein the high-voltage electrode has the exposed portion on a distal end side and the covering portion on a proximal end side. A distance from the dielectric barrier discharge electrode to the dielectric is A,
The shortest creepage distance along the outer surface from the region facing the dielectric barrier discharge electrode in the dielectric to the exposed portion of the high voltage electrode is B,
When the distance from the arc discharge electrode to the exposed portion of the high voltage electrode is defined as C,
The spark plug according to any one of claims 1 to 3, wherein A <C <B. The spark plug according to any one of claims 1 to 4 , comprising a plurality of dielectric barrier discharge electrodes. A spark plug according to claim 2 ;
A control device for controlling the voltage applied to the spark plug,
An ignition device for an internal combustion engine, wherein the control device applies a pulse voltage to the high voltage electrode. The spark plug according to any one of claims 1 to 5 ,
A control device for controlling the voltage applied to the spark plug,
An internal combustion engine characterized in that the controller performs a dielectric barrier discharge by applying a short-time pulse to the high-voltage electrode, and then performs an arc discharge by applying a long-time pulse to the high-voltage electrode. Ignition device. The spark plug according to any one of claims 1 to 5 ,
A control device for controlling the voltage applied to the spark plug,
The internal combustion engine characterized in that the controller performs a dielectric barrier discharge by applying a relatively low voltage to the high voltage electrode, and then performs an arc discharge by applying a relatively high voltage to the high voltage electrode. Engine ignition device.

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