WO2009151856A1

WO2009151856A1 - Neutralization device having cleaning system

Info

Publication number: WO2009151856A1
Application number: PCT/US2009/043732
Authority: WO
Inventors: Masahiko Ito; Toshikazu Numaguchi
Original assignee: 3M Innovative Properties Company
Priority date: 2008-06-12
Filing date: 2009-05-13
Publication date: 2009-12-17
Also published as: JP2009301851A

Abstract

To provide a neutralization device capable of automatically cleaning an electrode needle thereof and having a structure for preventing dust or particles generated when cleaning the electrode needle from dispersing. During a cleaning operation, an electric motor (731) rotates so as to move a shutter member (71) from a first position to a second position, whereby a first opening (22) of a housing (2) is closed. Then, electric motor (731) alternates between normal and inverse rotations in a short stroke, whereby shutter member (71) reciprocates in a short stroke such that brushes (72a, 72b) clean corresponding electrode needle (42a, 42b) in both directions along the moving direction of the shutter member. During reciprocating, shutter member (71) does not open first opening (22). Therefore, when each electrode needle is cleaned, dust or particles removed from the electrode needle do not disperse from first opening (22).

Description

NEUTRALIZATION DEVICE HAVING CLEANING SYSTEM

TECHNICAL FIELD

The present invention relates to a neutralization device having a cleaning system for cleaning an electrode needle of the device. BACKGROUND ART

Various types of neutralization devices or ionizers, for generating plus or minus ions by corona discharging and for neutralizing static electricity on an object with air flow including the ions by means of a fan, have been developed. These devices may be used in an assembling process of a semiconductor component or an electronic device, in order to prevent the component or the device from being damaged by electrostatic discharging thereof. Various types of fans may be used as the fan for the neutralization device. For example, Japanese Unexamined Patent Publication (Kokai) No. 2002-151293 discloses an electrostatic eliminator and describes that "As a fan, a centrifugal sirocco fan or an axial cross-flow fan is used." The above neutralization device has an electrode needle (or a discharging needle) for generating corona discharging. The discharging performance of the electrode needle may be deteriorated, after use, when dust in the air is adsorbed on the tip of the needle. Therefore, it is necessary to clean the electrode needle periodically. For example, Japanese Unexamined Patent Publication (Kokai) No. 2004-234972 discloses an air-flow type ionizer and describes that "a fin portion receives an air flow and a movable member is activated. Then, a brush member attached to the movable member comes into contact with the tip of a discharging needle, whereby the dust adsorbed on the tip of the needle is removed."

Depending on usage, the neutralization device may be installed at a very narrow place or a place where an operator cannot easily access. In such a case, it is difficult to detach the device from the installation place in order to clean an electrode thereof.

On the other hand, as in the ionizer disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2004-234972, it may be possible to automatically clean the electrode needle without detaching the device from the installation place. However, when the device is used in an environment, such as a semiconductor manufacturing process, where even a slight amount of dust or particles may cause a significant affect, it is desired to prevent the dust or particles generated by cleaning the electrode from dispersing. SUMMARY

The invention provides a neutralization device capable of automatically cleaning an electrode needle thereof and having a structure for preventing dust or particles generated by cleaning the electrode needle from dispersing. In order to achieve the object of the invention described above, according to one aspect of the invention, there is provided a neutralization device comprising: at least one electrode needle for generating ions by corona discharging; an air generating part for conveying air flow by which the ions are conveyed; a housing having a flow path through which generated air flows, and a first opening communicated with the flow path; a cleaning system for cleaning the electrode needle, the cleaning system comprising a shutter member capable of moving between a first position where the shutter member opens the first opening and a second position where the shutter member closes the first opening, and at least one cleaning part configured to clean the electrode needle when the shutter member is positioned at the second position; and a dust-collecting air filter through which air flow from the air generating part to the exterior passes when the shutter member is positioned at the second position.

In the neutralization device according to one aspect of the invention, air flow from an air generating part passes through a dust collecting air filter while an electrode needle is cleaned, whereby dust or particles generated by cleaning are collected by the air filter and prevented from dispersing. Therefore, the neutralization device of the invention is useful even in a case, such as a semiconductor manufacturing process, in which dust or particles are highly undesirable.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of a neutralization device according to a first embodiment of the present invention.

Fig. 2 is a view showing an example of the constitution of an electrode.

Fig. 3 shows cleaning operations of an electrode needle: (a) normal operation is carried out, (b) a shutter member is reciprocated to clean the electrode needle, (c) a shutter member is reciprocated to clean the electrode needle and (d) the shutter member is returned to its original position after cleaning.

Fig. 4 is similar to Fig. 1, showing the state in which a shutter member closes a first opening.

Fig. 5 is a schematic view of a neutralization device according to a second embodiment of the present invention.

Fig. 6 is similar to Fig. 5, showing the state in which a shutter member closes a first opening.

DETAILED DESCRIPTION

Fig. 1 shows a schematic configuration of a neutralization device according to a first embodiment of the present invention. This embodiment may be applied to either DC type or AC type. A neutralization device 1 has a housing 2 schematically illustrated, an air generating part or a centrifugal fan such as a sirocco fan 3 arranged within housing 2, one or more electrode 4 for generating ions by corona discharging, and a high- voltage power supply 5 for applying high voltage to electrode 4. As air generating part 3, an axial fan or the like may also be used. However, since the direction of a rotation axis of a centrifugal fan is different from the direction of air flow generated by the fan, the largest surface of the neutralization device (a surface parallel to the paper surface of Fig. 1) may be closely attached to a wall or the like. Therefore, the centrifugal fan allows greater flexibility of installation.

The airflow generated by centrifugal fan 3 passes through a flow path 21 formed in housing 2 and flows out from a first opening 22 communicated with flow path 21 toward an object to be neutralized. Housing 2 has a second opening 23 communicated with flow path 21, and a dust-collecting air filter such as a HEPA filter 6 is arranged such that the filter covers second opening 23. Therefore, at least a part, preferably all, of air flow passing through second opening 23 also passes through HEPA filter 6 before flowing outside the device. As shown in Fig. 2, electrode 4 has a hollow electrode box 41 (the illustrated embodiment has a rectangular box shape from which one pair of opposing surfaces are removed), at least one electrode needle (two electrode needles 42a and 42b in this embodiment), a support member 43 arranged within the box 41 for supporting each electrode needle, and an electric wire 44 connected to high- voltage power supply 5. Electrode box 41 is positioned in flow path 21 such that air flow from centrifugal fan 3 may pass through electrode box 41. High- voltage form power supply 5 is applied to each electrode needle via wire 44, whereby corona discharging is generated between each electrode and electrode box 41 which may function as an opposed electrode. Electrode box 41 is grounded by means of a connecting member (not shown) via housing 2. Air ions generated by corona discharging are conveyed with air flow from centrifugal fan 3 toward an object (not shown) to be neutralized.

Neutralization device 1 has a cleaning system 7 for cleaning each electrode needle. Cleaning system 7 has a shutter member 71 configured to close or open flow path 21 (first opening 22 in the embodiment) of housing 2, at least one cleaning part 72 (two brushes 72a, 72b in the embodiment) arranged on shutter member 71, a drive unit 73 for moving shutter member 71, and a control unit 74 for controlling drive unit 73. In the embodiment, although the number of brushes is the same as the number of the electrode needles, the two numbers may be different. For example, the two electrode needles may be cleaned by one brush. In addition, a polishing member such as a polishing film may be used instead of the brush. Shutter member 71 is configured to move between a first position where shutter member 71 opens first opening 22 (Fig. 1) and a second position where shutter member 71 closes first opening 22 (Fig. 4). Shutter member 71 in the embodiment is a plate member positioned within housing 2 near a one side or a lower surface 24 (on which first opening 24 is formed), and configured to move parallel to lower surface 24. Brushes 72a, 72b are positioned so as to clean corresponding electrode needle 42a, 42b when shutter member 71 is positioned at the second position. Shutter member 71 may have another constitution as long as the shutter member may close or open the first opening.

Drive unit 73 is used for move shutter member 71 between the first and second positions. In the embodiment, drive unit 73 has an electric motor 731 and a gear 732 attached to a rotation shaft of electric motor 731. On the other hand, shutter member 71 has a toothed belt 711 at an end thereof opposed to first opening 22, and electric motor 731 is positioned such that gear 732 engages with toothed belt 711. As electric motor 731 , a stepping motor or a solenoid may be used. Electric motor 731 may be controlled by control unit 74 schematically illustrated. Drive unit may have another constitution as long as the drive unit may move shutter member between the first and second positions.

Next, the operation of neutralization device 1 will be explained with reference to Fig. 3. First, when a main switch (not shown) of device 1 is turned on, centrifugal fan 3 rotates and generated air flow passes through in flow path 21 of housing 2. On the other hand, ions are generated at electrode 4 and the generated ions are conveyed and flow out from first opening 22 with air flow by centrifugal fan 3, toward the object (not shown) to be neutralized. During such a normal operation, shutter member 71 is positioned at the first position, as shown in Figs. 1 or 3 (a).

After the normal operation is carried out for a period of time or the dust or dirt adheres to the electrode needle, the normal operation is once stopped and the cleaning operation of the electrode is carried out. At this point, as shown in Fig. 4 or 3(b), electric motor 731 rotates so as to move shutter member 71 from the first position to the second position, whereby first opening 22 of housing 2 is closed. Then, electric motor 731 alternates between normal and inverse rotations in a short stroke, as shown in Figs. 3(b) and 3(c), whereby shutter member 71 reciprocates in a short stroke such that brushes 72a, 72b clean corresponding electrode needle 42a, 42b in both directions (right and left directions in the embodiment) along the moving direction of the shutter member. At this point, during reciprocating, shutter member 71 does not open first opening 22. Therefore, during each electrode needle is cleaned, dust or particles removed from the electrode needle does not disperse from first opening 22.

It is preferable that centrifugal fan 3 continuously rotates while the shutter member reciprocates (or the electrode needle is cleaned), as shown in Figs. 3(b) and 3(c). Since first opening 22 is closed while the shutter member reciprocates, as shown in Fig. 4, air flow from centrifugal fan 3 pass through second opening 23 and HEPA filter 6 positioned at second opening 23 before flowing out. Therefore, dust or particles removed from the electrode needle are collected by HEPA filter 6 and does not disperse outside the device. The above reciprocating movement of the shutter member may be carried out only once or several times, depending on the usage environment and/or the operating time of the neutralization device. By carrying out such a cleaning operation at proper time intervals (for example, once every 12-24 hours), each electrode needle may be maintained clean sufficiently to have the properties thereof. After each electrode needle is cleaned, as shown in Fig. 3(d), the drive unit moves shutter member 71 to the first position. The position of shutter member 71 may be detected by a position detecting part such as a photo sensor 25 arranged within housing 2 near the shutter member. In addition, after the cleaning and before shutter member 71 is moved to the first position, air flow may be continued for certain period of time. Due to this, dust or particles removed from the electrode may be collected by the filter more surely.

According to the neutralization device of the invention, since dust or particles generated by cleaning the electrode needle does not disperse outside the device, the device is useful, in particular, in a manufacturing environment in which dust or particles are highly undesirable. Further, since the series of operations as shown in Figs. 3(a) to 3(d) may be automatically carried out, the device does not need to be detached from the installation position thereof in order to clean the electrode, whereby the labor of the operations may be greatly reduced. In the above embodiment, the brush is positioned on the shutter member. Instead, the shutter member and the brush may be separately constituted, and the brush may be configured to clean the electrode needle after the shutter closes the first opening of the housing. However, by the brush is positioned on the shutter member, another means for supporting and moving the brush is not necessary, whereby the number of components of the device may be reduced.

In the normal operation (when first opening 22 is opened), air flow from centrifugal fan 3 may flow out from both the first and second opening. However, due to a pressure loss of HEPA filter 6 arranged at the second opening, most of the air flow from centrifugal fan 3 flows out from first opening 22. Therefore, in order that the air flow may effectively flow out from first opening 22, first opening 22 is preferably positioned on an extended line along the longitudinal direction (or the air- flow direction) of a part of flow path 21 where the flow path is communicated with the first opening, as shown in Fig 1 or 4.

In the above first embodiment, the shutter member may close the first opening, and further, support and move the brush. However, as in a second embodiment explained below with reference to Figs. 5 and 6, a means for closing the first opening and a means for supporting and moving the brush may be separately constituted. In the second embodiment, electrode 4 having the electrode needle is positioned at an upstream side in flow path 21 more than the first embodiment, and thus, cleaning system 7 is positioned at the position where the cleaning system may clean the electrode needle. Further, in the second embodiment, a shutter member 26 is arranged which is configured to close or open first opening 22. Shutter member 26 is configured to move between a third position (Fig. 5) where shutter member 26 opens first opening 22 and a fourth position (Fig. 6) where the shutter member closes the first opening. For example, shutter member 26 may be rotated about a shaft 27 arranged at a corner of housing 2. The movement of shutter member 26 may be controlled by a control unit (not shown). While cleaning system 7 cleans the electrode needle, shutter member 26 is controlled to be positioned at the fourth position. Therefore, in the second embodiment, the cleaning system needs not to have a structure for closing or opening the first opening.

Shutter member 26 at the third position may close the second opening communicated with HEPA filter 6, whereby dust or particles adhered to a sucking surface of the filter may be prevented from dropping from the surface and being conveyed with the air flow. Further, it may be avoided that the amount of air flow to be directed to the object to be neutralized is reduced due to that a part of the air flow enters the filter. In the above both embodiments, housing 2 has two openings and the shutter member may switch the direction of air flow from the fan in order to collect dust or particles generated by cleaning the electrode. At this point, housing 2 may not have the second opening and HEPA filter arranged at the second opening, instead, an opening may be formed on at least part of the shutter member and a filter such as HEPA filter may be arranged at the opening of the shutter member. Due to this, while the electrode is cleaned, air flow from the fan may pass through the filter arranged at the opening on the shutter member.

The neutralization device according to the above embodiments is an AC type neutralization device having two electrode needles. In the AC type device, it is not necessary to position each electrode needle opposed each other. For example, the AC type device may have only one electrode needle. Further, all of the electrode needles may be connected to one AC power supply so as to generate corona discharging between each electrode needle and an electrode opposed to each electrode needle. Needless to say, the invention may also be applied to a DC type neutralization device.

The positional relation between the electrode and the cleaning member is not limited to that disclosed in the drawings. Any type of cleaning member may be used, as long as the cleaning member is positioned the position where the cleaning member does not become an obstacle to air flow from the fan while neutralizing, and is moved to the position where the cleaning member can clean the electrode needle while cleaning. Further, the motion of the cleaning member is not limited to the linear motion as described above. For example, the cleaning member may be rotated to clean the electrode needle.

By using two neutralization devices according to the invention or by arranging the two neutralization devices in one housing, and by making the timing of cleaning the electrode needle in one device different from the other, neutralizing of an object may be carried out even when an electrode needle of one of the devices is cleaned.

Claims

1. A neutralization device comprising: at least one electrode needle for generating ions by corona discharging; an air generating part for conveying air flow by which the ions are conveyed; a housing having a flow path through which generated air flows, and a first opening communicated with the flow path; a cleaning system for cleaning the electrode needle, the cleaning system comprising a shutter member capable of moving between a first position where the shutter member opens the first opening and a second position where the shutter member closes the first opening, and at least one cleaning part configured to clean the electrode needle when the shutter member is positioned at the second position; and a dust-collecting air filter through which air flow from the air generating part to the exterior passes when the shutter member is positioned at the second position.

2. The neutralization device according to claim 1, wherein the air filter is arranged on the housing such that the air filter covers a second opening communicated with the flow path of the housing.

3. The neutralization device according to claim 1, wherein the air filter is positioned at an opening portion formed on at lease a part of the shutter member.

4. The neutralization device according to any one of claims 1 to 3, wherein the at least one cleaning part is positioned on the shutter member.

5. The neutralization device according to claim 4, wherein the shutter member is configured to reciprocate in a short stroke at the second position.

6. The neutralization device according to any one of claims 1 to 5, wherein the first opening is positioned on an extended line along the longitudinal direction of a part of the flow path where the flow path is communicated with the first opening.