Static eliminator

Abstract

[Problem] To make it possible to stabilize the distance between an electrode needle and a prevention member for preventing an induced voltage from being generated in a workpiece. [Solution] A static eliminator 1 makes it possible, by using an electrically conductive plate 6 (front prevention member) of each of a plurality of needle cap members 3 that are provided to the front side Df(+) (needle tip direction) of an electrode needle 33, to prevent an induced voltage from being generated in a workpiece. Moreover, by providing a plurality of electrically conductive plates 6, each electrically conductive plate 6 can be formed to be short in a width direction Dw. Therefore, bending of the electrically conductive plates 6 is suppressed, and the distance between the electrically conductive plates 6 and the electrode needle 33 can be stabilized.

Description

Static eliminator

[0001] The present invention relates to a bar-type static eliminator that generates ions by applying a high voltage to a plurality of electrode needles arranged in a row in an arrangement direction.

[0002] A static eliminator neutralizes a workpiece with ions generated by applying a high voltage to a needle electrode. During this process, an induced voltage generated in the workpiece may cause an imbalance between positive and negative ions. Therefore, in Patent Document 1, a plate-shaped conductive member is provided facing the needle electrode from the front side to prevent the generation of induced voltage.

[0003] Patent No. 6725938

[0004] However, a bar-type static eliminator in which a plurality of electrode needles are arranged in a row in the arrangement direction, as in Patent Document 1, has the following problem: In other words, bar-type static eliminators tend to be long in the arrangement direction of the electrode needles. In contrast, when the preventive member for preventing the generation of induced voltage (the plate-shaped conductive member in Patent Document 1) is long, there are problems such as the trouble of maintenance for cleaning and replacing each individual electrode needle, and the problem of the preventive member bending, making the distance between the electrode needle and the preventive member unstable.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a technique that makes it possible to stabilize the distance between a prevention member that prevents the generation of induced voltage in a workpiece and an electrode needle.

[0006] The static eliminator of the present invention is a bar-type static eliminator that generates ions by applying a high voltage to a plurality of electrode needles arranged in a row in the arrangement direction, and comprises a frame that holds the plurality of electrode needles with the tips of each of the electrode needles facing toward the needle tip direction, side prevention members that are attached to the frame, positioned to the sides of the electrode needles, and conductive to ground, and a plurality of front prevention members that are arranged in a row in the arrangement direction and attached to the frame, positioned toward the needle tips of the electrode needles, and conductive to the side prevention members.

[0007] In the present invention configured as described above, the generation of induced voltage in the workpiece can be prevented by the multiple front prevention members provided in the direction of the needle tip from the electrode needle. Moreover, by providing multiple front prevention members, each front prevention member can be formed to be short. This makes it possible to suppress the deflection of the front prevention members and stabilize the distance between the front prevention members and the electrode needle.

[0008] As described above, according to the present invention, it is possible to stabilize the distance between the electrode needle and the preventing member that prevents the generation of induced voltage in the workpiece.

[0009] 11. A perspective view showing the external configuration of a bar-type static eliminator according to the present invention. A front perspective view of a needle cap member. A rear perspective view of the needle cap member. An exploded perspective view of the needle cap member. A partial cross-sectional view of the needle cap member. A partial cross-sectional view of the needle cap member. A partial cross-sectional view of the needle cap member. A block diagram showing the electrical configuration of the static eliminator. A block diagram showing the internal configuration of a controller. A flowchart showing an example of operation during ion balance control executed by the controller of FIG. 9. A perspective view showing the external configuration of a modified bar-type static eliminator according to the present invention. A perspective view showing the internal configuration of the static eliminator of FIG. 11. A perspective view showing a cap unit included in the static eliminator of FIG. 11. A perspective view showing a cap unit included in the static eliminator of FIG. 11. A diagram showing an attachment procedure for attaching the cap unit to a pair of mounting plates. A diagram showing an attachment procedure for attaching the cap unit to a pair of mounting plates. A diagram showing an attachment procedure for attaching the cap unit to a pair of mounting plates.

[0010] FIG. 1 is a perspective view showing the external configuration of a bar-type static eliminator according to the present invention. In this embodiment, the longitudinal direction Dl, width direction Dw, and airflow direction Df of the static eliminator 1 are shown. Here, the longitudinal direction Dl, width direction Dw, and airflow direction Df are perpendicular to each other. Furthermore, the front side Df(+) and rear side Dd(-) of the airflow direction Df are shown. Here, the front side Df(+) and rear side Dd(-) face in opposite directions.

[0011] The static eliminator 1 has a housing 2 that is elongated in the longitudinal direction Dl. The housing 2 has a base cover 21 that opens to the front side Df(+) in the airflow direction Df, a top cover 25 that is attached to the base cover 21 so as to cover the base cover 21 from the front side Df(+), and a pair of side covers 29 that are attached to both ends of the base cover 21 and the top cover 25 in the longitudinal direction Dl. Each of the base cover 21 and the top cover 25 has an elongated shape in the longitudinal direction Dl.

[0012] The top cover 25 has a front plate 26 perpendicular to the airflow direction Df, and a pair of side plates 27 extending from both ends of the front plate 26 in the width direction Dw to the rear side Dd(-), and is open between the pair of side plates 27. The front plate 26 faces the base cover 21 from the front side Df(+), and the pair of side plates 27 sandwich the base cover 21 from the width direction Dw.

[0013] The static eliminator 1 also includes a plurality of needle cap members 3 arranged at a predetermined pitch in the longitudinal direction D1 on the front plate 26 of the top cover 25. Fig. 2 is a front perspective view of the needle cap member, Fig. 3 is a rear perspective view of the needle cap member, Fig. 4 is an exploded perspective view of the needle cap member, and Figs. 5 to 7 are partial cross-sectional views of the needle cap member.

[0014] The needle cap member 3 includes a base portion 4, a front cover 5 attached to the base portion 4 from the front side Df(+), and a conductive plate 6 disposed between the base portion 4 and the front cover 5. The base portion 4 and the front cover 5 are made of resin.

[0015] The structure of the flow path F through which air passes will be described using Figure 5. The base portion 4 covers the through holes Hp, which extend in the air blowing direction Df, from the sides (longitudinal direction Dl and width direction Dw). The through holes Hp constitute the flow path F through which air passing in the air blowing direction Df passes. In other words, the base portion 4 covers the flow path F from the sides, through which air passing in the air blowing direction Df passes.

[0016] The flow path F has a large-diameter flow path Fl located at the front end Df(+), a small-diameter flow path Fs located at the rear end Dd(-), and a tapered flow path Ft located between the large-diameter flow path Fl and the small-diameter flow path Fs. The large-diameter flow path Fl, the tapered flow path Ft, and the small-diameter flow path Fs are arranged concentrically around the central axis C of the needle cap member 3, which is parallel to the airflow direction Df. The cross-sectional area of ​​the large-diameter flow path Fl is larger than the cross-sectional areas of the small-diameter flow path Fs and the tapered flow path Ft. The cross-sectional area of ​​the tapered flow path Ft increases toward the front side Df(+). The cross-sectional area of ​​the tapered flow path Ft at the front end Df(+) is smaller than that of the large-diameter flow path Fl, and the cross-sectional area of ​​the tapered flow path Ft at the rear end Dd(-) is the same as that of the small-diameter flow path Fs. Here, the cross-sectional area is the area of ​​a cross section in a plane perpendicular to the airflow direction Df.

[0017] The base portion 4 has a flange portion 41 having an octagonal outer shape when viewed from the airflow direction Df, and a rod portion 45 extending rearward Dd(-) from the flange portion 41. The flange portion 41 protrudes laterally from the rod portion 45, and the rod portion 45 protrudes rearward Dd(-) from the center of the flange portion 41.

[0018] The flange portion 41 has a flange frame 411, and a through hole Hf, which is the front side Df(+) portion of the through hole Hp, penetrates the flange frame 411 in the airflow direction Df. That is, the flange frame 411 surrounds the through hole Hf from the side. The flange frame 411 has a front end surface 412 provided at the end of the front side Df(+) and a bottom surface 413 provided on the rear side Dd(-) of the front end surface 412. The front end surface 412 and the bottom surface 413 are each planes perpendicular to the airflow direction Df. In a plan view from the front side Df(+), the front end surface 412 surrounds the large-diameter flow path Fl from the side, and the bottom surface 413 surrounds the tapered flow path Ft from the side.

[0019] The flange frame 411 has a wall surface 414 extending in the airflow direction Df between the inner periphery of the front end surface 412 and the outer periphery of the bottom surface 413. This wall surface 414 laterally surrounds the large-diameter flow path Fl. The flange frame 411 also has a tapered wall surface 415 tapered from the inner periphery of the bottom surface 413 toward the rear side Dd(-). The cross-sectional area of ​​the tapered wall surface 415 decreases toward the rear side Dd(-). This tapered wall surface 415 is provided along the front end (the end on the front side Df(+)) of the tapered flow path Ft and laterally surrounds the front end of the tapered flow path Ft. In this way, the through hole Hf of the flange portion 41 includes the large-diameter flow path Fl and the front end of the tapered flow path Ft.

[0020] Furthermore, a protrusion 416 and a recess 417 are provided at the end of the front side Df(+) of the flange frame 411. The protrusion 416 protrudes toward the front side Df(+), and the recess 417 is recessed toward the rear side Dd(-) relative to the protrusion 416. The protrusions 416 and the recesses 417 are arranged alternately around the central axis C of the needle cap member 3. Furthermore, the flange portion 41 has multiple (two) screw insertion holes 418 provided in the flange frame 411 at equal angular intervals around the central axis C of the needle cap member 3. Each screw insertion hole 418 penetrates the flange frame 411 in the air blowing direction Df. The flange portion 41 also has two insertion openings A41 ( FIG. 4 ) that penetrate the flange frame 411 in the air blowing direction Df. The insertion opening A41 extends in the airflow direction Df between an end face 419 on the rear side Dd(-) of the flange frame 411 and the bottom face 413.

[0021] The rod portion 45 has a rod frame 451, and a through hole Hr, which is the rear Dd(-) portion of the through hole Hp, penetrates the rod frame 451 in the air blowing direction Df. In other words, the rod frame 451 surrounds the through hole Hr from the side. The rod frame 451 has a flange 452 that protrudes inward from the through hole Hr, and an insertion opening A452 opens inside the flange 452 in a plan view from the air blowing direction Df.

[0022] The rod frame 451 has a tapered wall surface 453 provided at the front side Df(+) end and a wall surface 454 provided on the rear side Dd(-) of the tapered wall surface 453. This tapered wall surface 453 is provided along the rear end (end on the rear side Dd(-)) of the tapered flow passage Ft and surrounds the rear end of the tapered flow passage Ft from the side. The wall surface 454 also surrounds the small-diameter flow passage Fs from the side. In this way, the through hole Hr of the rod portion 45 surrounds the rear end of the tapered flow passage Ft and the small-diameter flow passage Fs from the side. The wall surface 454 also extends from the small-diameter flow passage Fs to the rear side Dd(-), and a radius is provided between the wall surface 454 and the front end face of the flange 452 (the end face on the front side Df(+)).

[0023] The rod frame 451 also has a plurality of (four) engaging protrusions 458 that protrude outward (on the opposite side of the through-hole Hr). The engaging protrusions 458 are arranged at regular angles around the central axis C of the needle cap member 3.

[0024] The needle cap member 3 includes a flow path member 31 attached to a flange 452 of the rod portion 45. The flow path member 31 has a member body 311 tapered toward the front side Df(+) and a flange 312 protruding outward from the end of the rear side Dd(-) of the member body 311. The member body 311 is inserted into an insertion opening A452 on the inside of the flange 452 and engages with the flange 452. The flange 312 abuts against the end face of the rear side Dd(-) of the flange 452 from the rear side Dd(-).

[0025] The flow path member 31 also has an insertion hole Hn that penetrates the member body 311 and the flange 312 in the airflow direction Df. The insertion hole Hn has a tapered insertion hole Hnt provided at the end on the front side Df(+) and a cylindrical insertion hole Hnl provided on the rear side Dd(-) of the tapered insertion hole Hnt. The cross-sectional area of ​​the tapered insertion hole Hnt decreases toward the front side Df(+). The cross-sectional area of ​​the end on the rear side Dd(-) of the tapered insertion hole Hnt matches the cross-sectional area of ​​the cylindrical insertion hole Hnl.

[0026] Furthermore, the needle cap member 3 includes a needle electrode 33. The needle electrode 33 is inserted into the insertion hole Hn so that a tip 331 of the needle electrode 33 faces the front side Df(+), and the tip 331 of the needle electrode 33 protrudes from the flow path member 31 toward the front side Df(+). The needle electrode 33 has a tip portion 332 extending from the tip 331 toward the rear side Dd(-), and a cylindrical portion 333 extending from the tip portion 332 to the rear side Dd(-). The cross-sectional area of ​​the tip portion 332 becomes smaller toward the front side Df(+) (in other words, toward the tip 331). The cross-sectional area of ​​the tip portion 332 on the rear side Dd(-) is the same as the cross-sectional area of ​​the cylindrical portion 333.

[0027] Air passing through the insertion hole Hn in the airflow direction Df is formed. That is, a gap that functions as a flow path f is formed between the inner wall of the insertion hole Hn of the flow path member 31 and the electrode needle 33 inserted into the insertion hole Hn. The air passes through the flow path f in the airflow direction Df and is ejected from the front end (the end of the front side Df(+)) of the flow path member 31 toward the front side Df(+). A high voltage is applied to the electrode needle 33, causing ions to be generated from the electrode needle 33. These ions travel through the flow path F toward the front side Df(+) by the air ejected from the front end of the flow path member 31.

[0028] The front cover 5 has an opening 51 that overlaps the flow path F in a plan view from the front side Df(+). Ions traveling through the flow path F to the front side Df(+) pass through this opening 51 to the front side Df(+) and reach the target for static elimination (workpiece). The front cover 5 also has an annular cover frame 52 that laterally surrounds the opening 51 in the plan view. A convex portion 521 and a concave portion 522 are provided at the end of the rear side Dd(-) of the cover frame 52. The convex portion 521 protrudes toward the rear side Dd(-), and the concave portion 522 is recessed toward the front side Df(+) relative to the convex portion 521. These convex portions 521 and concave portions 522 are alternately arranged around the central axis C of the needle cap member 3. Furthermore, the cover frame 52 is provided with a plurality of screw covers 524 at equal intervals around the central axis C of the needle cap member 3. Each screw cover 524 is provided with a screw insertion hole 525 extending in the airflow direction Df, and the screw insertion hole 525 opens to the rear side Dd(-).

[0029] The conductive plate 6 is made of a conductive material such as metal. The conductive plate 6 has an opening 61 that overlaps the flow path F in a plan view from the front side Df(+). Ions traveling through the flow path F to the front side Df(+) pass through this opening 61 to the front side Df(+) and then pass through the opening 51 in the front cover 5. In a plan view from the front side Df(+), the conductive plate 6 has an annular outer frame 62 that surrounds the opening 61 and an annular inner frame 63 provided at the center of the outer frame 62. The outer frame 62 and the inner frame 63 have concentric circular shapes centered on the central axis C of the needle cap member 3, and the diameter of the inner frame 63 is smaller than the diameter of the outer frame 62.

[0030] An opening 64 penetrating the inside of the inner frame 63 in the airflow direction Df functions as a flow path through which ions pass to the front side Df(+). In addition, in a plan view from the front side Df(+), the opening 64 of the inner frame 63 faces the tip 331 of the electrode needle 33. The opening 64 has a circular shape, and the diameter of the opening 64 is larger than the diameter of the electrode needle 33 (the diameter of the cylindrical portion 333). The electrode needle 33 is located inside and at the center of the opening 64. This opening 64 functions as a maintenance opening for inserting a maintenance member such as a cotton swab to clean the tip 331 of the electrode needle 33.

[0031] The conductive plate 6 also has multiple connection frames 65 extending radially from the inner frame 63 to the outer frame 62. The multiple connection frames 65 are arranged at equal angular intervals around the central axis C of the needle cap member 3, and openings 66 between adjacent connection frames 65 function as flow paths through which ions pass to the front side Df(+). Furthermore, the conductive plate 6 has multiple (four) screw insertion holes 67 arranged in the outer frame 62 at equal angular intervals around the central axis C of the needle cap member 3. Each screw insertion hole 67 penetrates the outer frame 62 in the air blowing direction Df.

[0032] Furthermore, the needle cap member 3 has a leaf spring 35 made of a conductive material such as metal. The leaf spring 35 has a wave washer 351 (wave spring) having a wavy annular shape, and an opening 352 is provided on the inside of the wave washer 351. When the rod portion 45 is inserted into the opening 352 from the front side Df(+), the leaf spring 35 fits onto the rod portion 45 from the outside.

[0033] The leaf spring 35 also has multiple (two) protrusions 353 spaced at equal angles around the central axis C of the needle cap member 3. Each protrusion 353 protrudes from the wave washer 351 toward the front side Df(+). The protrusion 353 has an extension piece 354 extending from the wave washer 351 toward the front side Df(+) and an engagement piece 355 extending outward from the extension piece 354. The leaf spring 35 also has multiple (two) insertion holes 356 formed in the wave washer 351 at equal angles around the central axis C of the needle cap member 3. Each insertion hole 356 penetrates the wave washer 351 in the air blowing direction Df.

[0034] The needle cap member 3 configured as described above is assembled as follows. The conductive plate 6 is fitted between the multiple protrusions 521 of the front cover 5 and faces the opening 51 of the front cover 5 from the rear side Dd(-). Two screws 37 are inserted into two of the four screw insertion holes 67 of the conductive plate 6 from the rear side Dd(-). Furthermore, two screws 37 are fastened into two of the four screw insertion holes 525 provided in the front cover 5 from the rear side Dd(-). In this way, the conductive plate 6 is fixed to the front cover 5.

[0035] Furthermore, with the conductive plate 6 sandwiched between the base unit 4 and the front cover 5, the base unit 4 is attached to the front cover 5 from the rear side Dd(-). That is, the convex portion 416 of the base unit 4 fits into the concave portion 522 of the front cover 5 from the rear side Dd(-), and the convex portion 521 of the front cover 5 fits into the concave portion 417 of the base unit 4 from the front side Df(+). This positions the base unit 4 and the front cover 5 relative to each other.

[0036] Furthermore, the two protrusions 353 of the leaf spring 35 are inserted into the two insertion openings A41 of the base 4 from the rear side Dd(-), and the engagement pieces 355 of each protrusion 353 engage with the bottom surface 413 of the base 4. In other words, the leaf spring 35 is attached to the base 4 by the engagement pieces 355.

[0037] The wave washer 351 of the leaf spring 35 contacts the base portion 4 from the rear side Dd(-). Two screws 38 are inserted from the rear side Dd(-) into the two insertion holes 356 of the leaf spring 35 and the two screw insertion holes 418 of the base portion 4, and are fastened from the rear side Dd(-) into the two screw insertion holes 67 of the conductive plate 6. At this time, the screws 38 are fastened to the conductive plate 6 against the elastic force generated by the wave washer 351 of the leaf spring 35 contacting the base portion 4. In addition, the tips of the two screws 38 are inserted from the rear side Dd(-) into the two screw insertion holes 525 of the front cover 5. The screws 38 are made of a conductive material such as metal and contact both the leaf spring 35 and the conductive plate 6. This electrically connects the leaf spring 35 and the conductive plate 6, establishing electrical conduction between them.

[0038] 7, the housing 2 has a cap attachment opening A2 that opens in the airflow direction Df, and the needle cap member 3 is inserted into the cap attachment opening A2 from the front side Df(+). The front cover 5, conductive plate 6, and flange portion 41 of the base portion 4 are supported and exposed above the housing 2. The rod portion 45 of the base portion 4 is accommodated within the housing 2, and the pair of base covers 21 of the housing 2 face the rod portion 45 in the width direction Dw.

[0039] A cap supporter 11 is accommodated inside the housing 2. The cap supporter 11 has a base plate 111 supported horizontally by the housing 2 and a cylindrical side wall 112 extending from the base plate 111 to the front side Df(+). A rod insertion space 113 is provided inside the side wall 112. The end of the rear side Dd(-) of the rod portion 45 of the needle cap member 3 is inserted into the rod insertion space 113 from the front side Df(+). In response to this, the cap supporter 11 has multiple (four) protrusions 114 provided at equal intervals around the central axis C of the needle cap member 3. Each protrusion 114 protrudes inward from the end of the front side Df(+) of the side wall 112. The multiple protrusions 114 are provided to correspond to the multiple engaging protrusions 458. Each protrusion 114 is located further forward Df(+) than the corresponding engaging protrusion 458 and overlaps the engaging protrusion 458 in a plan view from the front side Df(+). This prevents the rod portion 45 from slipping out of the rod insertion space 113 toward the front side Df(+). Furthermore, by rotating the needle cap member 3 around the central axis C, the multiple engaging protrusions 458 can be retracted from the multiple protrusions 114 in a plan view from the front side Df(+). This allows the rod portion 45 to slip out of the rod insertion space 113 toward the front side Df(+), and the needle cap member 3 can be removed from the cap supporter 11. In other words, the needle cap member 3 is removably attached to the housing 2.

[0040] The static eliminator 1 also includes two ground plates 13 (corresponding to the side plates 27 in FIG. 1 ) arranged to sandwich the electrode needles 33 in the width direction Dw. The ground plates 13 are provided on the surface of the housing 2. That is, the two ground plates 13 face the electrode needles 33 from both sides in the width direction Dw. In a side view from the width direction Dw, the ground plates 13 overlap the entire electrode needles 33; in other words, the electrode needles 33 are hidden by the ground plates 13.

[0041] The ground plate 13 is provided outside the base cover 21 and along the base cover 21. In particular, the ground plate 13 extends in the airflow direction Df from a front end position P(+) on the front side Df(+) of the electrode needle 33 (i.e., the tip 331) to a rear end position P(-) on the rear side Dd(-) of the electrode needle 33 (i.e., the rear end 334). The ground plate 13 is made of a conductive material such as metal and is shorted to ground. The front end Df(+) of the ground plate 13 contacts the leaf spring 35. In this way, the leaf spring 35 is shorted to ground by the ground plate 13.

[0042] 8 is a block diagram showing the electrical configuration of the static eliminator 1. As shown in FIG. 8, the static eliminator 1 includes a high-voltage power supply circuit 16 that supplies a high voltage to the electrode needle 33, and a controller 17 that controls the high-voltage power supply circuit 16.

[0043] The high-voltage power supply circuit 16 has a switching circuit 161 and a high-voltage generation circuit 162. The switching circuit 161 turns on and off the power supply to the high-voltage generation circuit 162. The high-voltage generation circuit 162 has a primary step-up circuit 163 and a secondary step-up rectifier circuit 164. The primary step-up circuit 163 steps up the power supply voltage supplied via the switching circuit 161, and the secondary step-up rectifier circuit 164 steps up and rectifies the voltage output from the primary step-up circuit 163 to generate a high voltage. The high voltage (negative drive voltage V2) generated by the secondary step-up rectifier circuit 164 is applied to the electrode needle 33.

[0044] The high-voltage power supply circuit 16 has a switching circuit 165 and a high-voltage generation circuit 166. The switching circuit 165 turns on and off the power supply to the high-voltage generation circuit 166. The high-voltage generation circuit 166 has a primary step-up circuit 167 and a secondary step-up rectifier circuit 168. The primary step-up circuit 167 steps up the power supply voltage supplied via the switching circuit 165, and the secondary step-up rectifier circuit 168 steps up and rectifies the voltage output from the primary step-up circuit 167 to generate a high voltage. The high voltage (positive-side drive voltage V1) generated by the primary step-up circuit 167 is applied to the electrode needle 33 via the secondary step-up rectifier circuit 164.

[0045] Controller 17 generates PWM signal SWn that controls the on / off of power supply by switching circuit 161, and PWM signal SWp that controls the on / off of power supply by switching circuit 165. Controller 17 generates PWM signal SWn and PWM signal SWp so that negative drive voltage V2 and positive drive voltage V1 are alternately applied to electrode needle 33. Controller 17 is configured by, for example, a processor.

[0046] 9 is a block diagram showing the internal configuration of the controller. The controller 17 has target value storage units 171 and 174, an ion balance error extraction unit 172, an average potential calculation unit 173, an average potential error extraction unit 175, a drive control unit 176, a voltage value adjustment unit 177, an application time adjustment unit 178, and a PWM signal generation unit 179. The target value storage unit 171 stores a target value for ion balance, and the target value storage unit 174 stores a target value for average potential V0. These target values ​​are set based on, for example, a user operation.

[0047] The ion balance error extraction unit 172 compares the detected ion balance value Vf with the corresponding target value, calculates an ion balance control error, and outputs the result to the drive control unit 176. Specifically, the ion balance error extraction unit 172 obtains the detected value Vf by converting the charge flowing into the static eliminator 1 via the grounded electrode into a voltage. The voltage value adjustment unit 177 adjusts the voltage values ​​of the positive drive voltage V1 and the negative drive voltage V2 applied to the electrode needle 33 based on the ion balance control error. The average potential calculation unit 173 obtains a detected value Vn obtained by converting the current flowing from the transformer of the primary boost circuit 163 to ground into a voltage, and a detected value Vp obtained by converting the current flowing from the transformer of the primary boost circuit 167 to ground into a voltage. The average potential calculation unit 173 then calculates an average potential V0 from the detected values ​​Vn and Vp, and outputs the average potential error extraction unit 175. The average potential V0 is calculated by V0 = Vp - Vn.

[0048] The average potential error extractor 175 compares the average potential V0 calculated by the average potential calculator 173 with a corresponding target value, calculates a control error for the average potential, and outputs the control error to the drive controller 176. The application time adjuster 178 adjusts the application time Tp of the positive drive voltage V1 and the application time Tn of the negative drive voltage V2 based on the control error for the average potential.

[0049] The drive control unit 176 controls the adjustment amounts of the voltage values ​​of the drive voltages V1 and V2 and the application times Tp and Tn based on the control errors of the ion balance and the average potential. The PWM signal generation unit 179 generates PWM signals SWp and SWn based on the outputs of the voltage value adjustment unit 177 and the application time adjustment unit 178.

[0050] Specifically, the duty ratio Ds = Tn / T1 of the application time and the duty ratio Dp = T12 / T11 of each of the PWM pulses Pp and Pn are determined so that the ion balance and the average potential V0 coincide with their respective target values. At this time, the drive control unit 176 adjusts the duty ratios Ds and Dp so that the average potential V0 is kept constant.

[0051] Fig. 10 is a flowchart showing an example of the operation during ion balance control executed by the controller of Fig. 9. Fig. 10 shows a process for adjusting the duty ratio Dp of each of the PWM pulses Pp and Pn based on the detected value of ion balance.

[0052] In step S101, the controller 17 acquires the detected value Vf of the ion balance. In step S102, the controller 17 compares the detected value Vf with a target value. If Vf is greater than the target value ("YES" in step S103), the controller 17 increases the duty ratio Dp of the PWM pulses Pp and decreases the duty ratio Dp of the PWM pulses Pn in order to increase the positive ions and eliminate the excess negative ions (step S104). On the other hand, if Vf is less than the target value ("YES" in step S106), the controller 17 decreases the duty ratio Dp of the PWM pulses Pp and increases the duty ratio Dp of the PWM pulses Pn in order to increase the negative ions and eliminate the excess positive ions (step S107). The controller 17 repeats steps S101 to S104, S106, and S107 until Vf matches the target value (step S105).

[0053] In the static eliminator 1 configured in this manner, the generation of induced voltage in the workpiece can be prevented by the conductive plates 6 (front prevention members) of each of the multiple needle cap members 3 provided on the front side Df(+) (needle tip direction) of the electrode needle 33. Moreover, by providing multiple conductive plates 6, each conductive plate 6 can be formed to be short in the width direction Dw. Therefore, when maintenance is performed on an individual electrode needle 33, the corresponding conductive plate 75 can be selectively attached and detached. Furthermore, bending of the conductive plates 6 can be suppressed, making it possible to stabilize the distance between the conductive plates 6 and the electrode needle 33.

[0054] In the static eliminator 1 disclosed in this embodiment, the conductive plate 6 is disposed, thereby reducing the temporal change in ion balance that occurs in response to the operating frequency of voltage application by the drive control unit 176. This temporal change in ion balance is called the swing voltage, and corresponds to the difference between the maximum and minimum values ​​for one drive cycle. Because this temporal change in ion balance occurs in response to the operating frequency, it is a change that can occur even if the ion balance is kept constant by the control of the drive control unit 176. In the static eliminator 1 disclosed in this embodiment, experimental results have shown that the swing voltage is reduced from 140 V to 2 V by disposing the conductive plate 6.

[0055] The conductive plate 6 is detachably attached to the housing 2 (frame) by the cap supporter 11. This allows easy removal of only the conductive plate 6 out of the ground plate 13 (side protection member) and the conductive plate 6.

[0056] Also provided is a needle cap member 3 that holds the electrode needle 33 (first electrode needle) and the conductive plate 6 (first front prevention member) and is detachably attached to the housing 2 by a cap supporter 11. In this configuration, the conductive plate 6 and the electrode needle 33 can be positioned relative to each other by the needle cap member 3, and the distance between them can be stabilized.

[0057] Furthermore, when the needle cap member 3 is attached to the housing 2 by the cap supporter 11, the front Df(+) end of the ground plate 13 is located Df(+) forward of the tip 331 of the electrode needle 33. This allows the ground plate 13 to cover the entire length of the electrode needle 33 from the sides, preventing the electric field generated by the electrode needle 33 from spreading sideways.

[0058] The needle cap member 3 also includes a flow path member 31 that surrounds the electrode needle 33 from the side. The flow path f between the electrode needle 33 and the flow path member 31 has a narrowed shape in which the area of ​​the flow path f decreases toward the front side Df(+). Providing this flow path member 31 allows for the generation of a high-speed airflow. Generally, the neutralization time required to reduce the potential of a charged workpiece to a certain level is used as an indicator of the performance of a static eliminator. By providing the conductive plate 6 on the front side Df(+) of the electrode needle 33, some of the ions generated by the electrode needle 33 are absorbed by the conductive plate 6, thereby reducing the number of ions reaching the workpiece and shortening the neutralization time. Furthermore, if the airflow velocity decreases due to the conductive plate 6 being provided on the front side Df(+), the number of ions reaching the workpiece per given time decreases, shortening the neutralization time. Generating a high-speed airflow allows for the reduction of the neutralization time.

[0059] Furthermore, the conductive plate 6 has an opening 64 (maintenance opening) that opens at a position overlapping with the electrode needle 33 when viewed from the front side Df(+). The diameter of the opening 64 is larger than the diameter of the electrode needle 33. Therefore, maintenance of the electrode needle 33 can be easily performed by inserting a maintenance member such as a cotton swab through the opening 64.

[0060] The needle cap member 3 also has a base portion 4 (a resin member) that laterally surrounds a flow path F that is provided on the front side Df(+) from the electrode needle 33. The flow path F that is surrounded by the base portion 4 has a widening shape in which the area of ​​the flow path F increases toward the front side Df(+). By giving the base portion 4 such a widening shape, it is possible to prevent the base portion 4 from being charged by ions passing through the flow path F.

[0061] The static eliminator 1 is also provided with an ion balance error extraction unit 172 (charge detection unit) that detects the amount of charge flowing from the grounded electrode into the static eliminator 1. The controller 17 (control unit) controls the voltage applied to the electrode needle 33 based on the amount of charge detected by the ion balance error extraction unit 172. By using this type of ion balance control in combination with the conductive plate 6, a good ion balance can be achieved.

[0062] Fig. 11 is a perspective view showing the external configuration of a modified bar-type static eliminator according to the present invention, Fig. 12 is a perspective view showing the internal configuration of the static eliminator of Fig. 11, and Figs. 13 and 14 are perspective views showing a cap unit included in the static eliminator of Fig. 11. The static eliminator 7 of Fig. 11 includes a housing 71 that is elongated in the width direction Dw. The housing 71 includes a bottom frame 711 extending in the width direction Dw and a pair of side plates 712 provided at both ends of the bottom frame 711 in the longitudinal direction Dl. The bottom frame 711 incorporates a plurality of electrode needles 33 arranged in the longitudinal direction Dl, with the tip 331 of each electrode needle 33 facing the front side Df(+). Furthermore, similar to the above, a pair of ground plates 13 are provided on the bottom frame 711 facing the electrode needles 33 from both sides in the width direction Dw and overlapping the entire electrode needles 33 in a side view from the width direction Dw.

[0063] The static eliminator 7 also includes a pair of mounting plates 72 spaced apart in the width direction Dw. Each mounting plate 72 is made of a conductive material such as metal and is shorted to ground. The pair of mounting plates 72 protrude from the front side Df(+) end of the bottom frame 711 toward the front side Df(+) and are located at both ends of the bottom frame 711 in the width direction Dw. The mounting plates 72 have multiple cutouts 721 arranged in the longitudinal direction Dl. Each cutout 721 has an introduction groove 722 extending in the airflow direction Df from the front side Df(+) end of the mounting plate 72 toward the rear side Dd(-) and an engagement groove 723 extending from the rear side Dd(-) end of the introduction groove 722 to one side in the longitudinal direction Dl.

[0064] The static eliminator 7 has a plurality of cap units 73 arranged in the longitudinal direction Dl. Each cap unit 73 is mounted on a pair of mounting plates 72 in the width direction Dw and faces the bottom frame 711 from the front side Df(+). Each cap unit 73 is detachably attached to the mounting plate 72.

[0065] The cap unit 73 includes a unit frame 74. The unit frame 74 has a top cover 741 that faces the bottom frame 711 from the front side Df(+). The top cover 741 has multiple (two in the example shown in FIG. 13 ) openings 742 arranged in the longitudinal direction Dl, and each opening 742 opens in the airflow direction Df. The unit frame 74 also has a pair of side covers 743 that extend from both ends of the top cover 741 in the width direction Dw to the rear side Dd(-). The pair of side covers 743 are provided corresponding to the pair of mounting plates 72, and each side cover 743 faces the corresponding mounting plate 72 from the outside in the width direction Dw. The unit frame 74 also has multiple engagement protrusions 744 aligned in the airflow direction Df. In the example shown in FIG. 14 , two engagement protrusions 744 are provided for each side cover 743. Each engagement protrusion 744 protrudes from the side cover 743 inward in the width direction Dw (i.e., toward the mounting plate 72).

[0066] The cap unit 73 also has a conductive plate 75 attached to the unit frame 74. The conductive plate 75 is made of a conductive material such as metal and is short-circuited to the ground plate 13. The conductive plate 75 has multiple openings 751 (two in the example of FIG. 13 ) arranged in the longitudinal direction Dl. Each opening 751 overlaps one electrode needle 33 in the bottom frame 711 in a plan view from the front side Df(+). Therefore, ions generated by the electrode needle 33 pass through the opening 751 toward the front side Df(+) on the airflow traveling toward the front side Df(+) in the airflow direction Df. In a plan view from the front side Df(+), the conductive plate 75 has an annular outer frame 752 surrounding the opening 751 and an annular inner frame 753 disposed at the center of the opening 751.

[0067] An opening 754 penetrating in the air blowing direction Df is provided inside the inner frame 753. This opening 754 functions as a flow path through which ions pass to the front side Df(+). In addition, in a plan view from the front side Df(+), the opening 754 of the inner frame 753 faces the tip 331 of the electrode needle 33. The opening 754 has a circular shape, and the diameter of the opening 754 is larger than the diameter of the electrode needle 33 (the diameter of the cylindrical portion 333). The electrode needle 33 is located inside and at the center of the opening 754. This opening 754 functions as a maintenance opening for inserting a maintenance member such as a cotton swab to clean the tip 331 of the electrode needle 33.

[0068] The conductive plate 75 also has a plurality of connection frames 755 extending radially from the inner frame 753 to the outer frame 752. The plurality of connection frames 755 are arranged at equal angular intervals around a center line that passes through the center of the circular opening 751 and is parallel to the airflow direction Df, and openings 756 between adjacent connection frames 755 function as flow paths through which ions pass to the front side Df(+).

[0069] The cap unit 73 also has a leaf spring 76 attached to the rear side Dd(-) surface of the conductive plate 75. The leaf spring 76 is made of a conductive material such as metal. The center of the leaf spring 76 is held to the conductive plate 75 by a spring holding portion 745 of the unit frame 74 and is in contact with the conductive plate 75. Both ends of the leaf spring 76 are bent toward the rear side Dd(-) and separated from the conductive plate 75. When the cap unit 73 is attached to the pair of mounting plates 72, both ends of the leaf spring 76 contact the mounting plates 72 and are shorted to ground. As a result, the conductive plate 75 is shorted to ground via the leaf spring 76 and the mounting plates 72.

[0070] 15A to 15C illustrate the procedure for attaching the cap unit to a pair of mounting plates. First, the engaging protrusion 744 of the cap unit 73 is positioned facing the guide groove 722 of the mounting plate 72 from the front side Df(+) (FIG. 15A). Next, the engaging protrusion 744 of the cap unit 73 is inserted into the guide groove 722 of the mounting plate 72 from the rear side Dd(-) (FIG. 15B). At this time, the engaging protrusion 744 is inserted into the guide groove 722 against the elastic force generated by the leaf spring 76. Finally, the cap unit 73 is moved in the longitudinal direction Dl to engage the engaging protrusion 744 of the cap unit 73 with the engaging groove 723 of the mounting plate 72 (FIG. 15C). In this way, the mounting plate 72 is attached to the pair of mounting plates 72. The cap unit 73 can be removed from the pair of mounting plates 72 by performing the reverse procedure.

[0071] In the static eliminator 7 configured in this manner, the generation of induced voltage in the workpiece can be prevented by the conductive plates 75 (front prevention members) of each of the multiple cap units 73 provided on the front side Df(+) (needle tip direction) of the electrode needle 33. Moreover, by providing multiple conductive plates 75, each conductive plate 75 can be formed to be short in the longitudinal direction Dl. Therefore, when maintenance is performed on an individual electrode needle 33, the corresponding conductive plate 75 can be selectively attached and detached. Furthermore, bending of the conductive plates 75 can be suppressed, making it possible to stabilize the distance between the conductive plates 75 and the electrode needle 33.

[0072] Furthermore, multiple cap units 73 (first unit, second unit) are arranged in the longitudinal direction Dl. Each cap unit 73 has a conductive plate 75 located on the front side Df(+) of the multiple electrode needles 33 (first electrode needle, second electrode needle, third electrode needle, fourth electrode needle). When each cap unit 73 is attached to a pair of mounting plates 72 (frames), the conductive plate 75 of each cap unit 73 is electrically connected to the mounting plate 72 (side protection member). This allows multiple conductive plates 75 to be provided for one mounting plate 72 in the longitudinal direction Dl, thereby shortening each conductive plate 75 in the longitudinal direction Dl. Therefore, for example, in an environment in which the static eliminator 7 is used with the front side Df(+) facing downward, deflection of the conductive plate 75 can be prevented, and the distance between the conductive plate 75 and the electrode needles 33 can be stabilized.

[0073] Further, the mounting plate 72 is provided with a cutout portion 721, and the cap unit 73 is attached to the mounting plate 72 by engaging with the cutout portion 721. Therefore, the cap unit 73 can be easily attached and detached.

[0074] The present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described embodiment without departing from the spirit of the present invention. For example, the number of electrode needles 33 may be changed as appropriate.

[0075] Furthermore, the specific configuration for attaching and detaching the needle cap member 3 and the cap unit 73 is not limited to the above example, and can be modified as appropriate.

[0076] Furthermore, the number of openings 751 provided in the conductive plate 75 is not limited to the above example, and can be changed as appropriate.

[0077] The present invention is applicable to the general technology of bar-type static eliminators that generate ions by applying a high voltage to a plurality of electrode needles arranged in a row in the arrangement direction.

Claims

1. A bar-type static eliminator that generates ions by applying a high voltage to a plurality of electrode needles arranged in a row in an arrangement direction, comprising: a frame that holds the plurality of electrode needles with the tips of each of the electrode needles facing in the needle tip direction; side prevention members that are attached to the frame, positioned to the sides of the electrode needles, and conductive to ground; and a plurality of front prevention members that are arranged in a row in the arrangement direction and attached to the frame, positioned in the needle tip direction from the electrode needles, and conductive to the side prevention members.

2. The static eliminator according to claim 1, wherein the front prevention member is detachably attached to the frame.

3. The static eliminator according to claim 2, further comprising a needle cap member that holds a first electrode needle included in the plurality of electrode needles and a first front prevention member included in the plurality of front prevention members, and that is removably attached to the frame.

4. The static eliminator according to claim 3, wherein when the needle cap member is attached to the frame, the end of the side prevention member in the needle tip direction is positioned further in the needle tip direction than the tip of the first electrode needle.

5. The static eliminator according to claim 3, wherein the needle cap member has a flow path member that surrounds the first electrode needle from the side, and the flow path between the first electrode needle and the flow path member has a narrowed shape in which the area of ​​the flow path decreases toward the needle tip.

6. The static eliminator according to claim 3, wherein the front prevention member has a maintenance opening that opens at a position overlapping with the first electrode needle when viewed from the needle tip direction, and the diameter of the maintenance opening is larger than the diameter of the first electrode needle.

7. The static eliminator according to claim 3, wherein the needle cap member has a resin member that laterally surrounds a flow path that extends from the first electrode needle toward the needle tip, and the flow path surrounded by the resin member has a widening shape in which the area of ​​the flow path increases toward the needle tip.

8. A static eliminator as described in claim 1, comprising: a first unit having a first front prevention member located in the direction of the needle tips of a first electrode needle and a second electrode needle among the plurality of electrode needles; and a second unit having a second front prevention member located in the direction of the needle tips of a third electrode needle and a fourth electrode needle among the plurality of electrode needles, wherein when the first unit and the second unit are attached to the frame, the first front prevention member and the second front prevention member are conductive to the side prevention member.

9. The static eliminator according to claim 8, wherein the side prevention member is provided with a notch, and the first unit and the second unit are attached to the frame by engaging with the notch.

10. The static eliminator according to claim 1, further comprising a flow path member that surrounds the electrode needle from the side, and the flow path between the electrode needle and the flow path member has a narrowed shape in which the area of ​​the flow path decreases toward the tip of the needle.

11. A static eliminator as claimed in any one of claims 1 to 10, comprising: a charge detection unit that detects the amount of charge flowing into the static eliminator from a grounded electrode; and a control unit that controls the voltage applied to the electrode needle based on the amount of charge detected by the charge detection unit.

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