JP2012089314A - Electric field generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the surface shape of a first electrode (e.g. a positive electrode) in an electric field generator suitable for generating a substantially uniform strong electric field simultaneously at a large number of portions.SOLUTION: A large number of pointed portions are formed on a plane (an end face facing a second electrode (e.g. a negative electrode)) of a chip pasted to the tip at the proximal region of a first electrode (e.g. a positive electrode). The distance from the plane (base surface) of the chip to the tip of the pointed portion is H, and the distance (pitch) between the tips of adjoining pointed portions is P. When relations "H≥50 μm, and H/P≥0.5" are satisfied, the surface shape of the first electrode suitable for generating a substantially uniform strong electric field (i.e. generating a substantially uniform plasma) simultaneously near the tips of a large number of pointed portions is obtained. Material of the pointed portions is preferably a conductive ceramics composed of a single crystal.

Description

  The present invention relates to an electric field generator, and preferably relates to an apparatus in which a plasma region is generated by a generated electric field.

  Conventionally, a voltage is applied between a first electrode (for example, an anode) disposed at a position facing a second electrode (for example, a cathode), the first electrode, and the second electrode, and the first electrode An electric field generator including a power source that forms an electric field in a space between second electrodes is widely known (see, for example, Patent Documents 1 to 3).

  In the space where the electric field is generated by the electric field generator (the space between the first and second electrodes), plasma (ionized state) can be generated at a portion where the electric field strength (electric field strength) exceeds a certain level. . Plasma has the characteristic of maintaining an electrically neutral state as a whole while having particles (cations, electrons, etc.) having a charge inside.

  In recent years, in various devices (all of which are also electric field generators) such as an ignition device for an internal combustion engine, a sterilizer, an ozone generator, a surface reformer, an air cleaner, and a gas phase reaction accelerator, the above plasma is used. These characteristics have been utilized to improve their performance.

  Various apparatuses using the characteristics of the plasma are required to generate substantially uniform plasma at a number of locations at the same time in order to further improve performance. For this purpose, it is necessary to generate a substantially uniform strong electric field simultaneously at a number of locations.

JP 2006-70830 A JP 2009-36125 A Japanese Patent No. 4217933

  The inventor has found the shape of the surface of the first electrode suitable for generating a substantially uniform strong electric field simultaneously at a number of locations in an electric field generator.

  The electric field generator according to the present invention applies a voltage between the first electrode disposed at a predetermined position with respect to the second electrode, the first electrode, and the second electrode, as described above, and And a power source for forming an electric field in a space between the first and second electrodes.

  The electric field generator according to the present invention is characterized in that a plurality of pointed heads are formed in at least a part of the surface of the first electrode, the height of the pointed heads is H, and the adjacent pointed heads When the pitch between the tips of P is P, the relationship of H / P ≧ 0.5 is established. In this case, it is preferable that the relationship of H ≧ 50 μm is established.

  It is most preferable that the two relations are established at all the sites in the region, but the relationship may be established only at some sites in the region. The surface corresponding to the region (the base surface on which the plurality of pointed heads are formed) may be a flat surface or a curved surface. The first electrode has a rod shape, a columnar shape, a cone shape, a needle shape, or the like, and the plurality of cusps are formed on a plane that is an end surface of the first electrode facing the second electrode. It is preferable that the part is formed.

  The inventor has a shape of the surface of the first electrode according to the above configuration that is suitable for simultaneously obtaining an abrupt potential change (and hence a strong electric field) in the space near the tips of each of the plurality of cusps. I found out. Details of this point will be described later. That is, according to the above configuration, a substantially uniform strong electric field can be generated simultaneously at a number of locations. As a result, it is possible to generate substantially uniform plasma at a number of locations simultaneously.

  In the electric field generator according to the present invention, the height of the plurality of cusps is reduced as the position of the corresponding cusp moves from the center of the region to the outer edge of the region. It is preferable to be configured.

  As will be described in detail later, generally, “the smaller the height of the cusp, the weaker the electric field near the tip of the cusp”, and “the closer the position of the cusp is to the outer edge in the region, There is a tendency that the electric field near the tip of the pointed head becomes stronger. In view of these points, when the height of the cusp is reduced as the position of the cusp moves from the center of the region to the outer edge of the region, the height of the plurality of cusps is constant As compared with, the strength of the electric field in the vicinity of the tip of each of the plurality of cusps can be made more uniform. The above configuration is based on such knowledge.

  In this case, it is preferable that the pitch between the tips of the plurality of adjacent cusps is also configured to decrease as the position of the corresponding pitch moves from the central portion of the region to the outer edge portion of the region. It is. According to this, the number of pointed heads in the region can be increased. That is, the number of places where a substantially uniform strong electric field can be obtained can be increased.

  As described above, the height of the plurality of cusps and the pitch become smaller as the position of the corresponding cusp and the corresponding position of the pitch move from the center of the region to the outer edge of the region. Consider the case where the plurality of pointed heads are formed on the end surface (plane) of the first electrode having a rod shape. In this case, the height and the pitch of the cusp are 5% to 50% each time the position of the corresponding cusp and the corresponding position of the pitch move to an adjacent position on the outer edge side of the region. It is suitable that it is configured to decrease at a rate of 5%, preferably 5 to 25%.

  In addition, in this case, the region where the plurality of pointed heads are formed exists in the center of the plane and does not exist in the outer edge of the plane, and extends from the center of the plane to the outer edge of the plane. When the distance is L and the distance from the center of the plane to the outer edge of the region is B, it is preferable that the relationship of 0.3 ≦ B / L ≦ 0.9 is established. This is because when an apex is formed from the center of the plane to the outer edge of the plane, the electric field near the apex of the apex of the outer edge of the plane becomes an electric field near the apex of the apex of the center of the plane. Based on becoming extremely strong compared to. That is, even if an attempt is made to reduce the strength of the electric field in the vicinity of the tip of the cusp at the outer edge of the plane by utilizing the above-mentioned “electric field strength reducing effect” by reducing the height of the cusp, Cannot be reduced to the same level as the electric field strength in the vicinity of the tip of the cusp at the central portion.

  As described above, while focusing on the shape of the surface of the first electrode, conditions suitable for generating a substantially uniform strong electric field at a number of locations simultaneously have been described. In addition to this condition, it is more preferable that the second electrode is arranged and configured with respect to the first electrode so that the following condition is satisfied. The condition is “1 ≦ Dmax / Dmin, where Dmax and Dmin are the maximum value and the minimum value, respectively, of the shortest distances between the tips of the plurality of cusps and the second electrode. The relationship of ≦ 1.3 is established ”.

  The strength of the electric field in the vicinity of the tip of each cusp depends greatly on the shortest distance between the tip of the cusp and the second electrode. Therefore, as in the above configuration, in the state where there is no large difference in the shortest distances between the respective tips of the plurality of peak portions and the second electrode, the plurality of peak points is compared with the state where there is a large difference. The strength of the electric field in the vicinity of each tip of the part can be made more uniform.

  By the way, it is preferable that the material of the plurality of pointed portions of the first electrode is a conductive ceramic made of a single crystal. In this case, for example, silicon carbide SiC made of a single crystal can be used as the conductive ceramic made of the single crystal.

  When the material of the plurality of cusps is metal (for example, SUS material), after using the device for a long time, only the tip of the cusp tends to be consumed, and the kurtosis at the tip of the cusp tends to decrease greatly. is there. When the kurtosis at the tip of the cusp decreases, the strength of the electric field near the tip of the cusp decreases. On the other hand, when the material of the plurality of cusps is a conductive ceramic made of a single crystal, compared to the case of metal (for example, SUS material), the tip of the cusp tip is also used after a long period of use of the device. The kurtosis is difficult to decrease. This is based on the fact that the overall shape of the pointed head is similarly reduced by an anisotropic etching action based on a single crystal after the device has been used for a long time. Therefore, by using conductive ceramics made of a single crystal as the material of the plurality of pointed heads, it is possible to suppress a reduction in the strength of the electric field near the tip of the pointed head after the device has been used for a long time.

It is the schematic diagram which showed the whole structure of the electric field generator or plasma generator which concerns on embodiment of this invention. It is a perspective view of the chip | tip stuck on the front-end | tip of the base part of the 1st electrode shown in FIG. FIG. 3 is a plan view of the chip shown in FIG. 2. FIG. 3 is a side view of the chip shown in FIG. 2. FIG. 5 is a schematic diagram corresponding to the section 5-5 in FIG. 3 for explaining the heights and pitches of a plurality of pointed heads formed on the plane of the chip. It is a graph for demonstrating the basis of the lower limit of ratio of the height of a cusp and pitch. It is a graph for demonstrating the basis of the upper limit of the ratio of the height and pitch of a cusp. It is a figure which shows the result of having calculated the electric potential distribution of the vicinity of the tip of a cusp for various combinations between the heights and pitches of a plurality of cusps by simulation. It is the schematic diagram which showed arrangement | positioning / structure of the 2nd electrode used for the simulation performed in order to obtain distribution of the electric field strength of the vicinity of the front-end | tip of each cusp from the center part of a chip | tip to an outer edge part. . It is a graph which shows the result of having calculated the intensity distribution of the electric field of the tip vicinity of each cusp from the center part of a chip | tip to an outer edge part by simulation. FIG. 6 is a schematic diagram corresponding to FIG. 5 for a modified example for making the electric field strength distribution in the vicinity of the tip of each pointed head from the center to the outer edge of the chip more uniform. It is the schematic diagram which showed a preferable example of arrangement | positioning / structure of a 2nd electrode. It is the figure which showed an example of the shape before and behind consumption of a pointed head at the time of using a metal as a material of a pointed head. It is the figure which showed an example of the shape before and behind consumption of a pointed head at the time of using the conductive ceramics which consist of a single crystal as a material of a pointed head.

(Constitution)
FIG. 1 shows an overall configuration of an electric field generator or a plasma generator according to an embodiment of the present invention. This apparatus includes a mounting portion 10 and a power source 20. The attachment portion 10 includes a main body 11 and a first electrode 12 (for example, an anode) fixed to the main body 11. The main body 11 has a substantially cylindrical shape, for example. The first electrode 12 has, for example, a rod shape and is coaxially fixed to the main body 11.

  The main body 11 is fixed to, for example, a protrusion (not shown) from the wall surface of the gas phase reactor. In this case, the inner wall of the gas phase reactor can be used as the second electrode 30 (for example, the cathode).

  The first electrode 12 includes a rod-like base portion 12a fixed to the main body 11 and a chip 12b attached to the tip of the base portion 12a. The base 12a is made of metal. The chip 12b may be made of metal, but is preferably made of “conductive ceramic made of a single crystal” as described later.

  As shown in FIGS. 2 to 4, a large number of cusps are formed on the plane of the chip 12 b (the surface opposite to the attachment surface, corresponding to the end surface of the first electrode 12 facing the second electrode 30). Is formed. In this example, the planar shape (see FIG. 3) of the chip 12b is a square (one side: 3 mm). Over the entire area of the plane of the chip 12b, 15 × 15 identical cusp portions pass through the center O and are symmetrical with respect to each of the symmetry lines C1-C1 and C2-C2 in a matrix. Aligned and arranged. In this example, each pointed head has a quadrangular pyramid shape protruding in a direction perpendicular to the plane of the chip 12b.

  The power source 20 is a well-known pulse power source or a well-known RF power source. The power source 20 is electrically connected to the first electrode 12. By applying a voltage to the first electrode 12 by the power supply 20, a potential difference is applied between the chip 12 b located at the tip of the first electrode 12 and the second electrode 30. As a result, an electric field is formed in the space between the chip 12b and the second electrode 30.

  When a large number of pointed heads are formed on the plane of the chip 12b as in this example, an abrupt change in potential is obtained in the space near the tips of the number of pointed heads. The strength of the electric field (electric field strength) is equal to the potential gradient. Therefore, in the space between the tip 12b and the second electrode 30, a particularly strong electric field can be obtained in the vicinity of the tips of the many cusps. That is, a substantially uniform strong electric field can be generated simultaneously at a number of locations.

  A plasma (ionization state) can be generated in a portion where the strength of the electric field exceeds a certain level. Therefore, in this example, a substantially uniform plasma region can be generated at the same time in the vicinity of the tips of a large number of pointed heads. In other words, a substantially uniform plasma region can be generated simultaneously at a number of locations. When a plasma region is generated in the vicinity of the tip of each cusp, each plasma region grows toward the second electrode 30. An aggregate of plasma regions in this growth process is also called a streamer. When each streamer reaches the second electrode, discharge occurs over a wide area. This discharge is called streamer discharge.

  In this way, streamer discharges occur almost simultaneously at a number of locations. Then, starting from these many streamer discharges, activation of chemical species that are raw materials supplied to the gas phase reactor is promoted. This brings about various beneficial effects such as an increase in reaction rate, an improvement in product yield, and an improvement in controllability of the reaction atmosphere.

(Preferred relationship between the height of the cusp and the pitch)
As in this example, a case is assumed in which a large number of pointed heads are formed on the end surface (plane) of the distal end portion (in this example, the chip 12b) of the first electrode 12 facing the second electrode 30. Hereinafter, as shown in FIG. 5, the distance from the plane (base surface) of the chip 12b to the tip of the cusp is H, and the distance (pitch) between the tips of adjacent cusps is P.

  The present inventor searches for the shape of the surface of the first electrode 12 suitable for generating substantially uniform plasma at the same time in the vicinity of the tips of each of a large number of cusps, that is, In order to find the shape of the surface of the first electrode 12 suitable for generating a substantially uniform strong electric field at the same time in the vicinity of the tip of the head, attention was paid to the relationship between the height H of the apex and the pitch P.

  For each of a plurality of chips 12b having different values “H / P” (the pitch P is the same and the height H is different), the electric field in the vicinity of the tip of the pointed head was calculated by simulation. In this simulation, each cusp of the first electrode 12 has an elongated cylindrical shape. The pitch P was constant at 188 μm. A constant voltage of 20 kV was applied to the first electrode 12. That is, the surface of the first electrode 12 (the base surface and the tip of the tip 12b) are all at an equipotential of 20 kV (the potential difference between the first electrode 12 and the second electrode 30 is 20 kV). As the second electrode 30, as shown in FIG. 9, a rotationally symmetric one was used. The arrangement relationship between the chip 12b and the second electrode 30 is as shown in FIG.

  FIG. 6 shows the relationship between the height H of the cusp and the electric field strength near the tip of the cusp. As can be understood from FIG. 6, when the height H is 100 μm (H / P = 0.53) or more, the electric field strength is sufficiently high. Therefore, “0.5” was adopted as the lower limit of H / P.

  In addition, the potential distribution between adjacent peaks in the model was calculated by simulation. FIG. 7 shows the relationship between the height H of the cusp and the equipotential surface depression depth. “Equipotential surface recess depth” means a position where the potential becomes 99% of the applied voltage on a line segment passing through the midpoint between adjacent cusps and perpendicular to the bottom surface (base surface) of the chip. This is the difference in height from the tip of the head. In other words, “equipotential surface depression depth” represents “the degree of depression below the equipotential surface”. As will be described later, this value is an index representing the strength of the electric field in the vicinity of the tip of the cusp.

  As can be understood from FIG. 7, the ratio of the increase in the “equipotential surface recess depth” to the increase in the height H of the cusp, that is, “near the tip of the cusp relative to the increase in the height H of the cusp The degree of increase in the electric field strength ”greatly decreases when the height H is around 300 μm (H / P = 1.60). From this, it is considered preferable to provide an upper limit for H / P.

  The grounds of “H / P ≧ 0.5” described above are verified from other viewpoints. For each of the four types of chips 12b having different values “H / P” (the pitch P is the same and the height H is different), the potential distribution in the vicinity of the tip of the cusp is calculated by simulation. FIG. 8 shows the result.

  As can be understood from FIGS. 8A to 8D, a rapid change in potential is observed in the space near the tip of each pointed head. That is, a strong electric field is generated in the space near the tip of each cusp. Here, as an index representing the strength of the electric field in the vicinity of the tip of the cusp, “the degree of depression below the equipotential surface” formed in the space between the tips of adjacent cusps can be employed. That is, the greater the “degree of depression below the equipotential surface”, the more sudden the potential change in the space near the tip of the cusp, that is, the stronger the electric field strength in the space near the tip of the cusp. It can be considered large.

  As can be understood from FIGS. 8A to 8D, FIG. 8B shows a lower dent below the equipotential surface than FIG. 8B and FIG. 8B shows FIG. "Degree" is small. Accordingly, generally speaking, “the smaller the height of the peak (ie, the smaller H / P), the smaller the degree of depression below the equipotential surface”, that is, “the height of the peak. It can be said that the smaller the value is (that is, the smaller the H / P is), the weaker the electric field near the tip of the pointed head is. This is because the smaller the height of the cusp (ie, the smaller H / P), the closer the space between the tips of adjacent cusps is closer to the “base surface of the chip 12b having a high potential”. It is considered that the equipotential surface between adjacent tips is pushed upward.

  As can be understood from FIG. 8A, when the H / P is reduced to about 0.27, the equipotential surface formed in the space between the adjacent tips of the cusps approaches horizontal. This can be a second basis for adopting “0.5” as the lower limit of H / P.

  On the other hand, as can be understood from the comparison between FIG. 8C and FIG. 8D, in the range where H / P is larger than about 1.6, the height of the apex is increased (that is, H / P is increased). Even if / P is increased), “the degree of depression below the equipotential surface” does not increase. In other words, in the range where H / P is larger than about 1.6, when the height of the cusp is increased (that is, when H / P is increased), the space between adjacent cusps (especially adjacent In the space between the matching apex root portions), useless areas that do not contribute to the generation of a strong electric field near the apex of the apex increase. In addition, as the height of the pointed head increases, a structure in which the pointed head is weak against vibration or the like can be obtained. This can be a second basis that it is preferable to set an upper limit for H / P.

  In principle, the present inventor, regardless of the magnitude of H, as long as the relationship of H / P ≧ 0.5 is established, a strong electric field that is substantially uniform at the same time in the vicinity of the tips of a large number of cusps. Has been confirmed to occur. However, when H ≦ 50 μm, even if the relationship of H / P ≧ 0.5 is established, it has been confirmed that the equipotential surface formed in the space between the adjacent tips of the cusps approaches horizontal. . This is considered to be based on the fact that, when H ≦ 50 μm, the above-described “effect of pushing up the equipotential surface by the base surface of the chip 12b having a high potential” acts strongly regardless of the value of H / P.

  As described above, when the relationship of H ≧ 50 μm and H / P ≧ 0.5 is established, a substantially uniform strong electric field is generated near the tips of each of a large number of pointed heads (that is, A suitable surface shape of the first electrode 12 can be obtained (to generate a substantially uniform plasma). The above relationship is most preferably established in all the parts on the plane (base surface) of the chip 12b, but may be established only in a part of the parts on the plane (base surface).

(Electric field strength distribution near the tip of the cusp)
Next, the electric field strength distribution in the vicinity of the tip of each pointed head existing in the section from the center O of the plane of the chip 12b to the outer edge (section shown in FIG. 5, see line 5-5 in FIG. 3). Was calculated by simulation. First, as Example A of the chip, as shown in FIGS. 2 to 5, 15 × 15 pointed heads are symmetrical lines C1-C1, C2-C2 (see FIG. Chips that are aligned and arranged in a matrix in line symmetry with respect to each of the two chips (see 3), and H and P are all equal in the section from the center O of the plane of the chip 12b to the outer edge (the plane shape is 3 mm on a side) Square). The relationship of H ≧ 50 μm and H / P ≧ 0.5 holds for all the cusps on the plane of the chip 12b.

  As the second electrode 30, as shown in FIG. 9, one having a rotationally symmetric shape was used. The arrangement relationship between the chip 12b and the second electrode 30 is as shown in FIG. A constant voltage of 20 kV was applied to the chip 12b (first electrode 12, anode). That is, the potential difference between the chip 12b (first electrode 12) and the second electrode 30 (cathode) is 20 kV.

  The simulation results for Example A are indicated by round dots in FIG. As can be understood from FIG. 10, when the height H and the pitch P of the cusp are all equal in the section from the center O of the plane of the chip 12b to the outer edge, “the position of the cusp is from the center O of the chip 12b. There is a tendency that the electric field near the tip of the cusp becomes stronger as it approaches the outer edge. This is because the closer the tip of the tip 12b is to the outer edge of the chip 12b, the number of “tips with high potential” existing around the tip of the tip (ie, the tip of the tip). (The number of objects that affect the direction in which the electric field in the vicinity is weakened) relatively decreases, so that the electric lines of force generated from the pointed head easily extend linearly toward the closest part of the second electrode 30. As a result, it is considered that the gradient of the potential in the space near the tip of the pointed head is increased.

  In the following, it is considered that the electric field strength distribution in the vicinity of the tip of each pointed head existing in the section from the center O of the plane of the chip 12b to the outer edge is made more uniform than in the embodiment A. For this purpose, it is necessary to weaken the electric field in the vicinity of the tip of the pointed head existing on the outer edge side of the flat surface of the chip 12b. Here, as described above, there is a tendency that “the smaller the height of the peak, the weaker the electric field near the tip of the peak is”. In view of this tendency, when the height of the cusp is reduced as the position of the cusp moves from the center O of the plane of the chip 12b to the outer edge, each of the plurality of cusps is compared with Example A. It is considered that the electric field strength near the tip can be made more uniform.

  In addition, as can be understood from the distribution of round dots in FIG. 10, the electric field in the vicinity of the tip of the tip near the outer edge of the plane of the chip 12b is the electric field in the vicinity of the tip of the tip in the center of the plane of the chip 12b. Compared to extreme strength. In view of this tendency, the strength of the electric field in the vicinity of the tip of the tip of the outer edge of the plane of the chip 12b using the above-mentioned “effect of reducing the strength of the electric field” by reducing the height of the tip. Even if it is going to reduce, it is thought that it cannot reduce to the same level as the strength of the electric field in the vicinity of the tip of the tip of the center of the chip 12b. In other words, in order to make the distribution of the electric field strength in the vicinity of each tip of the pointed head extremely uniform, it is preferable not to form the pointed head in the vicinity of the outer edge of the plane of the chip 12b. Conceivable.

  From the above, as Example B of the chip, as shown in FIG. 11 corresponding to FIG. 5, it covers the area excluding the outer edge of the plane of the chip 12b (hereinafter referred to as “pointed head forming area”). 15 × 15 pointed heads are arranged and arranged in a matrix symmetrically with respect to C1-C1 and C2-C2 (see FIG. 3), and the positions of H and P are on the outer edge side. A chip (a square whose planar shape is 3 mm on a side) in which H and P are decreased at a predetermined rate each time it moves to an adjacent position was adopted. The relationship of H ≧ 50 μm and H / P ≧ 0.5 is established for all the cusps in the cusp formation region on the plane of the chip 12b.

  The simulation results for Example B are shown by square dots in FIG. The shape of the second electrode 30, the positional relationship between the chip 12b and the second electrode 30, the condition of the voltage applied to the chip 12b, and the like are the same as in the case of Example A. As can be understood from FIG. 10, in Example B, the distribution of the electric field strength in the vicinity of the tip of each pointed head existing on the plane of the chip 12b is extremely uniform.

  The present inventor considers a preferable range of the reduction ratio of H and P when H and P decrease each time the position of H and P moves to the adjacent position on the outer edge side. did. As a result, it has been found that this reduction ratio is preferably 5 to 50% in order to make the distribution of the electric field strength in the vicinity of each tip of the pointed head uniform. When a large number of cusps (for example, 10 × 10 or more cusps) are formed on the chip 12b, it is more preferable that the reduction ratio is 5 to 25%.

  In addition, the inventor considered a preferable range of the apex formation region on the plane of 12b in Example B. As shown in FIG. 11, the distance from the center O of the plane of the chip 12b to the outer edge of the plane is L, and the distance from the center O of the plane to the outer edge of the pointed head forming region is B. As a result, it has been found that it is preferable that the relationship of “0.3 ≦ B / L ≦ 0.9” is satisfied in order to make the distribution of the electric field strength in the vicinity of the tip of each pointed head uniform. is doing.

(Arrangement and configuration of second electrode)
As described above, the conditions necessary for making the distribution of the electric field strength in the vicinity of each tip of the tip on the tip 12b uniform have been described from the viewpoint of “arrangement / shape of the tip”. Next, conditions necessary for this will be briefly described from the viewpoint of “arrangement / configuration of second electrode 30”. In general, the strength of the electric field in the vicinity of the tip of each peak on the plane of the chip 12 b largely depends on the shortest distance between the tip of the peak and the second electrode 30. Therefore, it is considered that it is not preferable that there is a large difference in the shortest distances between the tips of the plurality of cusps and the second electrode.

  From the above, assuming that the maximum value and the minimum value of the shortest distances between the tips of the plurality of pointed heads and the second electrode 30 are Dmax and Dmin, respectively, the present inventor In order to make the distribution of the electric field strength in the vicinity of the tip of each of the cusps of the head uniform, it is preferable that the relationship “1 ≦ Dmax / Dmin ≦ 1.3” is satisfied.

  In addition, as indicated by the hatched area in FIG. 12, when the plane of the chip 12b (tip of the first electrode 12) is viewed from the direction perpendicular to the plane of the chip 12b, the second electrode is formed in the area outside the plane of the chip 12b. It is preferred that at least a portion of 30 is present. Thereby, the region where the above-described streamer discharge is formed is widened, and streamer discharge can be generated substantially simultaneously in a wide range.

(Pointed head material)
Hereinafter, the material of the chip 12b (that is, the material of the pointed head) will be additionally described. The chip 12b can be made of metal. However, when the material of the cusp is metal (for example, SUS material), as shown in FIG. 13, after the device has been used for a long time, only the tip of the cusp is consumed and the tip of the cusp The degree tends to decrease greatly. When the kurtosis at the tip of the cusp decreases, the strength of the electric field near the tip of the cusp decreases.

  On the other hand, the material of the chip 12b is preferably “conductive ceramic made of a single crystal”. As an example of “conductive ceramic made of single crystal”, silicon carbide SiC made of single crystal can be used.

  In this case, compared with the case of metal (for example, SUS material), the kurtosis at the tip of the cusp is less likely to be lowered even after the device is used for a long time. This is because, as shown in FIG. 14, the overall shape of the pointed head is similarly reduced by the anisotropic etching action based on the single crystal after the device is used for a long time. From the above, by using “conductive ceramics made of single crystal” as the material of the pointed tip (material of the chip 12b), the strength of the electric field near the tip of the pointed tip after a long period of use of the device is reduced. Can be suppressed.

  In addition, this invention is not limited to the said embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, in the above embodiment, each pointed head has a quadrangular pyramid shape protruding in a direction perpendicular to the plane of the chip 12b (see FIGS. 2 to 4 and the like). It may be in the shape of a cylinder, a cylinder, a needle, or a bar.

Moreover, in the said embodiment, although the base surface in which the some pointed head in the chip | tip 12b is formed is a plane, a curved surface (for example, spherical surface) etc. may be sufficient. In addition, although the first and second electrodes 12 and 30 are an anode and a cathode, respectively, the first and second electrodes 12 and 30 may be a cathode and an anode, respectively.

  Further, the present invention is not limited to the above-described embodiment, and various types relating to the generation of electric fields such as an ignition device for an internal combustion engine, a sterilizer, an ozone generator, a surface reformer, an air purifier, and a gas phase reaction accelerator. It can be applied to other devices.

  Further, as in the above embodiment, the electric field generator according to the present invention is mainly assumed to generate a strong electric field for generating a plasma region over a wide range. However, the plasma region is not generated. A mode in which a strong electric field is generated over a wide range is also included in the electric field generator according to the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Attachment part, 11 ... Main body, 12 ... 1st electrode, 12a ... Base part, 12b ... Chip | tip, 20 ... Power supply, 30 ... 2nd electrode

Claims (9)

A first electrode disposed at a predetermined position with respect to the second electrode;
A power source that applies a voltage between the first electrode and the second electrode to form an electric field in a space between the first and second electrodes;
An electric field generator comprising:
When a plurality of cusps are formed in at least a partial region of the surface of the first electrode, the height of the cusps is H, and the pitch between the tips of the adjacent cusps is P, An electric field generator in which the relationship of H / P ≧ 0.5 is established. The electric field generator according to claim 1,
An electric field generator in which the relationship of H ≧ 50 μm is established. In the electric field generator according to claim 1 or 2,
The electric field generator configured to reduce the heights of the plurality of cusps as the positions of the corresponding cusps move from the center of the region to the outer edge of the region. The electric field generator according to claim 3,
The electric field generator configured to reduce a pitch between tips of the plurality of adjacent cusps as the position of the corresponding pitch moves from a central portion of the region to an outer edge portion of the region. The electric field generator according to claim 4,
The first electrode has a rod shape, a cylindrical shape, a cone shape, or a needle shape, and the plurality of pointed heads are formed on a plane that is an end surface of the first electrode facing the second electrode,
The height of the plurality of cusps and the pitch between the tips of the adjacent cusps are such that the position of the corresponding cusp and the position of the corresponding pitch are adjacent to the outer edge side of the region. An electric field generator configured to decrease at a rate of 5 to 50% every time it moves to a position. The electric field generator according to claim 5,
The region where the plurality of cusps are formed is present at the center of the plane and not at the outer edge of the plane, and the distance from the center of the plane to the outer edge of the plane is L, An electric field generation device in which a relationship of 0.3 ≦ B / L ≦ 0.9 is established, where B is a distance from the center of the plane to the outer edge of the region. In the electric field generator according to any one of claims 1 to 6,
The second electrode is relative to the first electrode.
The relationship of 1 ≦ Dmax / Dmin ≦ 1.3, where Dmax and Dmin are the maximum and minimum values, respectively, of the shortest distances between the tips of the plurality of cusps and the second electrode, respectively. An electric field generator arranged and configured so that In the electric field generator according to any one of claims 1 to 7,
The electric field generator, wherein a material of the plurality of pointed heads of the first electrode is a conductive ceramic made of a single crystal. The electric field generator according to claim 8,
The electric field generator, wherein the conductive ceramic made of a single crystal is silicon carbide SiC made of a single crystal.