U.S. patent number 9,674,934 [Application Number 14/782,930] was granted by the patent office on 2017-06-06 for ion generator.
This patent grant is currently assigned to KOGANEI CORPORATION. The grantee listed for this patent is KOGANEI CORPORATION. Invention is credited to Yoshinari Fukada, Kazuyoshi Onezawa.
United States Patent |
9,674,934 |
Fukada , et al. |
June 6, 2017 |
Ion generator
Abstract
Provided is an ion generator that has a potential sensor
provided integrally inside the main body of the ion generator, and
that can measure, with the potential sensor, an electric field that
reaches the potential sensor from a member from which static charge
is to be eliminated, without being affected by an electric field
between a discharge electrode and an opposing electrode. This ion
generator comprises a discharge electrode, an opposing electrode,
and a main body part including these electrodes, the ion generator
sending out, toward a member from which static charge is to be
eliminated, air ions generated by applying a high voltage between
the electrodes. A potential sensor that measures the potential of
the member from which static charge is to be eliminated is provided
integrally to the main body part, and a projecting
electrostatic-shielding plate that projects from the main body part
is provided between the potential sensor and a discharge part
constituted by the discharge electrode and the opposing
electrode.
Inventors: |
Fukada; Yoshinari (Koganei,
JP), Onezawa; Kazuyoshi (Koganei, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KOGANEI CORPORATION |
Koganei-shi, Tokyo |
N/A |
JP |
|
|
Assignee: |
KOGANEI CORPORATION (Tokyo,
JP)
|
Family
ID: |
51689566 |
Appl.
No.: |
14/782,930 |
Filed: |
April 9, 2014 |
PCT
Filed: |
April 09, 2014 |
PCT No.: |
PCT/JP2014/060242 |
371(c)(1),(2),(4) Date: |
October 07, 2015 |
PCT
Pub. No.: |
WO2014/168160 |
PCT
Pub. Date: |
October 16, 2014 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20160044770 A1 |
Feb 11, 2016 |
|
Foreign Application Priority Data
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|
|
|
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Apr 11, 2013 [JP] |
|
|
2013-083022 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05F
3/06 (20130101); H01T 19/04 (20130101); H01T
23/00 (20130101) |
Current International
Class: |
H05F
3/06 (20060101); H01T 23/00 (20060101); H01T
19/04 (20060101) |
Field of
Search: |
;250/423R,424,423F
;315/111.01,111.81 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2005294178 |
|
Oct 2005 |
|
JP |
|
2006315770 |
|
Nov 2006 |
|
JP |
|
2010085393 |
|
Apr 2010 |
|
JP |
|
2012242094 |
|
Dec 2012 |
|
JP |
|
20010040133 |
|
May 2001 |
|
KR |
|
1020070055393 |
|
May 2007 |
|
KR |
|
Other References
International Search Report corresponding to Application No.
PCT/JP2014/060242; Date of Mailing: Jul. 8, 2014. cited by
applicant .
Korean Office Action for Application No. 10-2015-7031097; Dated:
Nov. 18, 2016, with English translation. cited by
applicant.
|
Primary Examiner: Ippolito; Nicole
Attorney, Agent or Firm: Cantor Colburn LLP
Claims
The invention claimed is:
1. An ion generator that blows air ions generated by applying a
high voltage to a discharge unit including discharge electrodes and
counter electrodes, toward a charged member, the ion generator
comprising: a main body comprising: a potential sensor housing
portion; a potential sensor accommodated in the potential sensor
housing portion and structured to measure potential of the charged
member; a detection window communicating with the potential sensor
housing portion; and a blow-off opening to blow-off the air ions;
and a projecting electrostatic shield plate disposed between the
discharge unit and the potential sensor to project from the main
body unit; wherein the discharge unit is attached to the main
body.
2. The ion generator according to claim 1, wherein a projection
length of the projecting electrostatic shield plate is in a range
of 8 to 10 mm.
3. The ion generator according to claim 1, wherein an aperture
window communicating with the detection window is formed in the
potential sensor to take in an electric field from the charged
member.
4. The ion generator according to claim 3, wherein a plurality of
the discharge electrodes is disposed at intervals along the
blow-off opening, and the projecting electrostatic shield plate
intervenes between any of the discharge electrodes and the aperture
window.
5. The ion generator according to claim 4, wherein the blow-off
opening and the aperture window are disposed on same plane in the
main body.
6. The ion generator according to claim 3, wherein a distance from
the projecting electrostatic shield plate to the aperture window in
the potential sensor is 2 mm or less.
7. The ion generator according to claim 1, wherein the blow-off
opening and the potential sensor are disposed to be opposed to the
charged member.
Description
This is a U.S. national stage of application No. PCT/JP2014/060242,
filed on Apr. 9, 2014. Priority under 35 U.S.C. .sctn.119(a) and 35
U.S.C. .sctn.365(b) is claimed from Japanese Patent Applications
No. 2013-083022 filed on Apr. 11, 2013, the disclosure of which is
also incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to an ion generator that neutralizes
charge of an electrically-charged body as an object required to be
electrically neutralized (hereinafter "charged member"). The ion
generator blows positive or negative air ions generated by corona
discharge against the charged member. The present invention relates
to, especially an ion generator having an integral potential sensor
integrally provided therewith.
BACKGROUND ART
The ion generator is called ionizer or static charge eliminator as
well. The ion generator blows air ions against a charged target and
eliminates charge. In a manufacture line in which manufacture and
assembly of electronic components are conducted, electronic
components and manufacture assembly jigs are charged. The
electronic components and manufacture assembly jigs are regarded as
a charged member, and the ion generator is used. Blowing air ions
against the charged member prevents foreign matters from adhering
to electronic components by static electricity, prevents electronic
components from being destroyed by static electricity, and prevents
foreign matters from adhering to jigs.
It is known to measure the potential of the charged member, by
using a potential sensor (see, for example, Patent Literatures 1
and 2). If such a potential sensor is used together with the ion
generator, it is possible to eliminate charge in the charged
member, while measuring the potential of the charged member by
using the potential sensor. Such a potential sensor is usually
attached separately from the ion generator or externally to the ion
generator and used.
CITATION LIST
Patent Literature
{PTL 1} Japan Unexamined Patent Application Publication
2012-242094
{PTL 2} Japan Unexamined Patent Application Publication
2010-85393
SUMMARY OF THE INVENTION
Technical Problem
In a case where the ion generator and the potential sensor are
provided separately, the installation space is large. On the other
hand, in a case where the ion generator and the potential sensor
are provided integrally, the installation space is small. If the
ion generator and the potential sensor are provided integrally,
however, a problem is posed. For example, since a discharge
electrode and an opposite electrode are disposed near the potential
sensor, an electric field between the discharge electrode and the
opposite electrode with a high voltage applied reaches the
potential sensor. The electric field is superposed on an electric
field that reaches the potential sensor from the charged member,
i.e., an electric field to be measured, and becomes noise.
Therefore, it is not possible to measure the potential of the
charged member, accurately.
An object of the present invention is to provide, an ion generator
that measures potential of a charged member, by using a potential
sensor without being influenced by an electric field between a
discharge electrode and an opposite electrode, i.e., noise,
although the ion generator and the potential sensor are provided
integrally.
Solution to Problem
In order to solve the problem, the present invention provides an
ion generator that blows air ions generated by applying a high
voltage to a discharge unit including discharge electrodes and
opposite electrodes, toward a charged member. The ion generator
includes a potential sensor provided integrally in a main body unit
to measure potential of the charged member, and a projecting
electrostatic shield plate disposed between the discharge unit and
the potential sensor to project from the main body unit.
It is possible to set a projection length of the projecting
electrostatic shield plate in a range of 8 to 10 mm.
An aperture window is formed in the potential sensor to take in an
electric field from the charged member. It is possible to set a
distance from the projecting electrostatic shield plate to the
aperture window in the potential sensor equal to 2 mm or less.
A blow-off opening is formed in the main body unit to blow off the
air ions. A plurality of the discharge electrodes is disposed at
intervals along the blow-off opening. It is possible to cause the
projecting electrostatic shield plate to intervene between any of
the discharge electrodes and the aperture window.
It is possible to cause the blow-off opening and the aperture
window to be disposed on the same plane in the main body.
Advantageous Effects of the Invention
In the ion generator according to the present invention, the
potential sensor is provided integrally in the main body unit.
Potential of the charged member is measured by the potential
sensor. The discharge unit includes the discharge electrodes and
the opposite electrodes. The projecting electrostatic shield plate
is provided between the discharge unit and the potential sensor.
The projecting electrostatic shield plate projects toward an ion
blow-off direction from the main body unit. The high voltage is
applied between the discharge electrode and the opposite electrode,
and an electric field is generated. The electric field is shielded
by the projecting electrostatic shield plate, and the electric
field does not reach the potential sensor. Therefore, the potential
of the charged member is measured by the potential sensor without
being influenced by the electric field between the discharge
electrode and the opposite electrode, i.e., noise.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a general perspective view obtained by viewing an ion
generator according to an embodiment of the present invention from
a front side.
FIG. 2 is a general perspective view obtained by viewing the ion
generator illustrated in FIG. 1 from a rear side;
FIG. 3 is a front view of the ion generator.
FIG. 4 is a plan view of FIG. 3.
FIG. 5 is a rear view of FIG. 3.
FIG. 6 is a perspective view illustrating a single substance of a
discharge electrode unit.
FIG. 7 is a sectional view taking along line A-A in FIG. 1.
FIG. 8 is an enlarged view of an X portion in FIG. 3.
FIG. 9 is a perspective view of FIG. 8.
FIG. 10 is a perspective view illustrating the whole of a potential
sensor.
FIG. 11 is a plan view illustrating a configuration of the
potential sensor.
FIG. 12 is a front sectional view of the potential sensor
illustrated in FIG. 11, illustrating a state in which the potential
sensor is cut along a line indicated by arrows 2-2.
FIG. 13 is a side sectional view of the potential sensor
illustrated in FIG. 11, illustrating a state in which the potential
sensor is cut along a line indicated by arrows 3-3.
FIG. 14 is a plan view of the potential sensor illustrated in FIG.
11 in a state in which an electrostatic shield plate is
removed.
FIG. 15 is a side view of the potential sensor illustrated in FIG.
11 in the state in which the electrostatic shield plate is
removed.
FIG. 16 is a diagram illustrating relations between a position of a
projecting electrostatic shield plate and a projection length
thereof.
FIG. 17 is a graphic diagram illustrating relations between the
length of the projecting electrostatic shield plate and noise
voltage.
FIG. 18 is a graphic diagram illustrating relations between the
length of the projecting electrostatic shield plate and signal
voltage.
DESCRIPTION OF EMBODIMENTS
Hereafter, an ion generator according to an embodiment of the
present invention will be described in detail with reference to the
drawings. "Up-down direction," "left/right direction (width
direction)," and "depth direction" used in the following
description refer to directions viewed from a front side where the
front side (surface side) is this side in FIG. 1. In the embodiment
stated hereafter, a product of wide type will be described. The
product of wide type blows off generated air ions from a laterally
long blow-off opening.
The whole of an ion generator 1 is illustrated in FIGS. 1 to 5. The
ion generator 1 includes a main body unit 10, a discharge electrode
unit 20 (see FIG. 6), and a potential sensor unit 40. The discharge
electrode unit 20 is detachably attached to the main body unit 10
from a blow-off opening 11. The potential sensor unit 40 is housed
in the main body unit 10.
The main body unit 10 is formed into the shape of nearly a
rectangular parallelepiped, and the main body unit 10 extends in
the left/right direction. As illustrated in FIGS. 1, 3, 4 and 7,
the blow-off opening 11 is formed in an upper portion of the front
of the main body unit 10 on this side. The blow-off opening 11
extends in the left/right direction.
As illustrated in FIG. 7, a discharge electrode unit mounting
portion 12 is formed within the rear portion of the blow-off
opening 11. The discharge electrode unit mounting portion 12 is
recessed in the depth direction, and has the same width as that of
the blow-off opening 11. The discharge electrode unit mounting
portion 12 is formed into a rectangular recessed shape. The
discharge electrode unit 20 (see FIG. 6) is fitted in the discharge
electrode unit mounting portion 12.
As illustrated in FIG. 7, an air supply chamber 13 is provided
further behind the discharge electrode unit mounting portion 12.
The air supply chamber 13 is formed over the whole length of the
blow-off opening 11 in the left/right direction. As illustrated in
FIGS. 1 to 5, the air supply chamber 13 is supplied with jet air
from an air supply port 13A provided on a left side of the main
body unit 10 via a tube 13B.
As illustrated in FIGS. 7 to 9, an air discharge opening 16 is
provided in an upper portion of the front side of the air supply
chamber 13. The air discharge opening 16 communicates from inside
of the air supply chamber 13 to a back portion of the discharge
electrode unit mounting portion 12. The air discharge opening 16
takes the shape of a rectangular hole or a round hole. As
illustrated in FIGS. 8 and 9, two air discharge openings 16 are
provided on lower sides of the left and right of each of discharge
electrodes 21. Details of the air discharge openings 16 will be
described later. The jet air is jetted forward from the air
discharge openings 16.
As illustrated in FIG. 7, an air guide portion 17 is provided on an
upper portion of the air discharge opening 16. The air guide
portion 17 projects to the upper side of the front of the air
discharge opening 16. The air guide portion 17 enhances the
straight advancing property of the jet air blown off from the air
discharge opening 16.
A top face cover 14 is provided over the air supply chamber 13 and
the discharge electrode unit mounting portion 12. As illustrated in
FIGS. 1 to 3, 5 and 7, an air flow path 15 is formed between the
top face cover 14 and the air supply chamber 13. The air flow path
15 is also formed between the top face cover 14 and the discharge
electrode unit mounting portion 12. The air flow path 15 passes
through from a back face of the main body unit 10 to a front face.
The air flow path 15 is parallel to a direction in which the
above-described air guide portion 17 leads the jet air. In other
words, a direction of the jet air flow discharged from the air
discharge opening 16 becomes the same as a direction of flow of an
external air which flows in the air flow path 15. The external air
is an air rolled from the circumference of the ion generator 1 by
the flow of the jet air.
As illustrated in FIGS. 2, 5 and 7, an upper portion of the air
supply chamber 13 is formed into a curved shape. As a result, an
inlet 15A on the rear face side of the air flow path 15 is spread
toward behind. As a result, it is facilitated to take external air
behind the ion generator 1 into the air flow path 15.
On the other hand, as illustrated in FIG. 6, a plurality of (four
in FIG. 6) discharge electrodes 21 is disposed in the discharge
electrode unit 20 at intervals. The discharge electrode 21 is
formed in a fine wire form or a needle form. The rectilinear
discharge electrode 21 extends toward the blow-off opening 11 on
this side in FIG. 6. Opening portion 22 are formed on a top face of
the discharge electrode unit 20 to correspond to respective
discharge electrodes 21. The respective discharge electrodes 21 is
exposed from the top face of the discharge electrode unit 20 via
the opening portion 22.
As illustrated in FIGS. 1, 3 and 6 to 9, an opposite electrode 23
is provided on the front side of the discharge electrode unit 20.
The opposite electrode 23 is formed of metal having conductivity
and formed into the shape of a plate. The opposite electrode 23 is
disposed in a lengthwise direction of the discharge electrode unit
20.
As illustrated in FIGS. 3, 6, 8 and 9, the opposite electrode 23 is
provided on a side lower than the discharge electrode 21 when
viewed from the front side of the ion generator 1. A notched
portion 23A is formed in a nearly half circle shape centered the
discharge electrode 21 to correspond to the discharge electrode 21.
In other words, the discharge electrode 21 and the opposite
electrode 23 are disposed via a gap 25 having a determinate length
interposed therebetween.
As illustrated in FIG. 7, an air supply path 24 is formed within
the discharge electrode unit 20. The jet air flows through the air
supply path 24 which extends from the air discharge opening 16
toward the gap 25.
As illustrated in FIG. 7, a separation space 26 is provided in a
state in which the discharge electrode unit 20 is attached to the
main body unit 10. The separation space 26 is a space extending
from a front side tip portion of the air guide portion 17 to a back
end portion of the air supply path 24. The jet air flows fast from
the air discharge opening 16 toward the air supply path 24. The jet
air flowing fast and the external air in the air flow path 15 are
brought into contact with each other in the separation space 26 and
the opening portion 22.
Power is supplied from an external power supply to the ion
generator 1 via a power supply cable 27 (see FIG. 1). A high
voltage is applied between the discharge electrode 21 and the
opposite electrode 23. As a result, corona discharge occurs and air
ions are generated. As for an internal configuration for applying a
high voltage, detailed description thereof will be omitted.
As illustrated in FIG. 7, a potential sensor unit housing portion
18 is provided on a lower side within the main body unit 10, i.e.,
under the air supply chamber 13 and the discharge electrode unit
mounting portion 12. The potential sensor unit housing portion 18
is provided over the left/right direction of the ion generator 1. A
detection window 18A is provided in a front side wall of the
potential sensor unit housing portion 18. The detection window 18A
communicates with the potential sensor unit housing portion 18. The
potential sensor unit 40 is attached to the potential sensor unit
housing portion 18. The potential sensor unit 40 measures the
potential of the charged member P disposed opposite to the blow-off
opening 11.
The potential sensor unit 40 includes a potential sensor 41 and a
power supply unit (not illustrated) that supplies power to the
potential sensor 41. The potential sensor 41 and the power supply
unit are attached within the potential sensor unit housing portion
18.
As illustrated in FIG. 10, the potential sensor 41 includes a
printed circuit board 111 on which a detection electrode 114 (see
FIG. 12) and so forth are mounted, and an electrostatic shield
plate 43 to which the printed circuit board 111 is attached. A
lengthwise direction of the printed circuit board 111 extends in
the left/right direction of the main body unit 10 in the ion
generator 1. By the way, as for the printed circuit board 111
illustrated in FIGS. 11 to 15, a portion is illustrated, and other
portions are omitted.
A rectangular shaped aperture window 113 is formed in the
electrostatic shield plate 43. As illustrated in FIG. 11, the
aperture window 113 is formed by notching the electrostatic shield
plate 43. All main slits 131 are exposed to the outside via the
aperture window 113, and all main slits 131 is visible from the
outside. A position of the aperture window 113 coincides with a
position of the detection window 18A in the potential sensor unit
housing portion 18.
As illustrated in FIGS. 10 to 12, a projecting electrostatic shield
plate 43A is provided continuously from the electrostatic shield
plate 43. The projecting electrostatic shield plate 43A is provided
over the whole length in the left/right direction of the
electrostatic shield plate 43. The projecting electrostatic shield
plate 43A is projected from the ion generator 1. Details of the
projecting electrostatic shield plate 43A will be described
later.
As illustrated in FIGS. 11 to 13, the detection electrode 114 is
attached to the printed circuit board 111. A flange portion 114a of
the detection electrode 114 is fixed to the printed circuit board
111. In addition, a standing portion 114b extending from the flange
portion 114a is nearly perpendicular to the printed circuit board
111. An electrode portion 114c extends from the standing portion
114b in parallel with the printed circuit board 111. The electrode
portion 114c opposes to the aperture window 113. The detection
electrode 114 is one of elements included in a detection circuit
(not illustrated). At least the electrode portion 114c included in
the detection electrode 114 forms an electric field between a
charged substance and the electrode portion 114c.
A fixed shutter 115 made of a conductive material is attached to
the printed circuit board 111. The fixed shutter 115 covers the
detection electrode 114. A main body portion 116 of the fixed
shutter 115 is provided in parallel with the electrode portion 114c
of the detection electrode 114. The main body portion 116 is formed
into a nearly rectangular shape. Side wall portions 117 and end
wall portions 118 are bent from the main body portion 116 at right
angles and are integral with the main body portion 116. As
illustrated in FIG. 12, tip portions of the side wall portions 117
are inserted into mounting holes formed through the printed circuit
board 111, and the fixed shutter 115 is fixed to the printed
circuit board 111.
Aperture slits 119 are formed in the main body portion 116 of the
fixed shutter 115. The aperture slits 119 extend in the lengthwise
direction (left/right direction) of the electrostatic shield plate
43. Five aperture slits 119 are formed in a width direction
(up-down direction) of the main body portion 116. The aperture
slits 119 are disposed at constant intervals.
As illustrated in FIGS. 12 to 15, a movable shutter 121 is provided
on the printed circuit board 111. The movable shutter 121 is
provided outside the fixed shutter 115 to cover the fixed shutter
115. The movable shutter 121 moves between two positions: a full
open position in which the slits 131 and slits 132 of the movable
shutter 121 coincide with the aperture slits 119 of the fixed
shutter 115, and an interruption position in which the aperture
slits 119 of the fixed shutter 115 are closed. A change of an
aperture area of the shutters depending upon the full open position
and the interruption position gives a change in an electric field
formed between a charged substance and the detection electrode 114
(the electrode portion 114c).
A center line (not illustrated) of the aperture slits 119 in the
lengthwise direction (left/right direction) is referred to as
aperture slit center line. A center line (not illustrated) of the
slits 131 and 132 in the lengthwise direction (left/right
direction) is referred to as main slit center line. A position of
the movable shutter 121 in which the aperture slit center line and
the main slit center line coincide with each other is referred to
as "full open position."
A center line in the lengthwise direction (left/right direction) of
a shield portion (reference numeral is omitted) existing between
two main slits 131 is referred to as main shield portion center
line. A center line (not illustrated) in the lengthwise direction
(left/right direction) of a shield portion (reference numeral is
omitted) existing between a main slit 131 and a subsidiary slit 132
is referred to as subsidiary shield portion center line. A position
of the movable shutter 121 in which the aperture slit center line
coincides with the main shield portion center line or the
subsidiary shield portion center line is referred to as
"interruption position."
The movable shutter 121 is formed of a material having
conductivity. The movable shutter 121 reciprocates in an open-close
direction (up-down direction). The movable shutter 121 includes a
fixed end portion 122 fixed to the printed circuit board 111. Leg
pieces 123 are integrally provided on both sides of the fixed end
portion 122. The leg pieces 123 are inserted into mounting holes
formed in the printed circuit board 111. The fixed end portion 122
of the movable shutter 121 is attached to the printed circuit board
111.
An arm portion 124 is provided integrally in each of the leg pieces
123 in the fixed end portion 122. The arm portion 124 extends to
one end side (right side) in the lengthwise direction (left/right
direction) of the printed circuit board 111. As illustrated in FIG.
14, two arm portions 124 are provided at a predetermined interval
in the present embodiment. Each of the arm portions 124 is formed
of a flexible plate shaped member. A main body portion 125 is
provided integrally on tips of the arm portions 124. As illustrated
in FIGS. 12 and 13, the main body portion 116 of the fixed shutter
115 is disposed outside the detection electrode 114. The main body
portion 116 covers the detection electrode 114. The main body
portion 125 of the movable shutter 121 is disposed outside the
fixed shutter 115. In addition, the main body portion 125 is
exposed to the outside via the aperture window 113. The main body
portion 125 of the movable shutter 121 reciprocates in an
open-close direction indicated by an arrow N, and opens and closes
the aperture slits 119.
At least the main body portion 116 of the fixed shutter 115 is
grounded. And at least the main body portion 125 of the movable
shutter 121 is also grounded.
As illustrated in FIGS. 13 and 14, a magnet 127 functioning as a
magnetic substance is attached to an end wall 126 provided
integrally in the main body portion 125. The magnet 127 has a
function of driving the movable shutter 121 to open and close. As
indicated by solid lines and dashed lines in FIG. 14, a U-shaped
yoke 128 is attached to one end side (right side) of the printed
circuit board 111. One pair of coils 129a and 129b is wound round
the yoke 128 via bobbins 281. The coils 129a and 129b are connected
to a power supply unit, which is not illustrated. An alternating
current is flown through each of the coils 129a and 129b. As a
result, magnetic fields that are inverse in direction to each other
are formed on two magnetic pole surfaces 128a and 128b. Therefore,
the magnet 127 moves between a position opposed to one magnetic
pole surface 128a and a position opposed to the other magnetic pole
surface 128b. In this way, a drive means that drives the movable
shutter 121 in the reciprocation direction N to open and close is
formed by the coils 129a and 129b wound round the yoke 128 and the
magnet 127.
Five main slits 131 are formed in the main body portion 125 in the
movable shutter 121. The five main slits 131 correspond to the five
aperture slits 119 formed in the fixed shutter 115. The respective
main slits 131 extend in the same direction as that of the aperture
slits 119. Adjacent main slits 131 are disposed at a constant
interval. The interval is the same as that of the aperture slits
119.
The movable shutter 121 conducts reciprocal vibration, and moves
between the full open position and the interruption position.
FIG. 12 illustrates a state in which the movable shutter 121 is in
a neutral position. At this time, all of the five main slits 131
are opposed to the aperture slits 119. One subsidiary slit 132 is
formed on each of outsides of main slits 131 located on both ends
of the reciprocation direction N (up-down direction). Each
subsidiary slit 132 takes the same shape as that of the main slit
131. Intervals between the five main slits 131 are the same as
intervals between the main slits 131 and the subsidiary slits 132.
The five main slits 131 and the two subsidiary slits 132 take the
same shape. These seven slits 131 and 132 formed on the movable
shutter 121 take the same shape as that of the aperture slits 119
formed on the fixed shutter 115. When the movable shutter 121
reciprocates, therefore, the aperture slits 119 are opened and
closed by the subsidiary slits 132.
In this way, one subsidiary slit 132 is formed on the outside of
the two main slits 131 located at both ends of the reciprocation
direction N, i.e., in an extension direction of the reciprocation
direction N. During one period of movement of the movable shutter
121, the movable shutter 121 moves from the neutral position
illustrated in FIG. 12 to a reciprocation end in a left direction
in FIG. 12, then the movable shutter 121 moves to a position of a
reciprocation end in a right direction, and returns to the neutral
position. During the one period, the five aperture slits 119 on the
fixed shutter 115 are opened and closed four times. In other words,
the aperture slits 119 are opened and closed with a frequency that
is four times the drive frequency of the movable shutter 121.
A current detection circuit is connected to the detection electrode
114. In a state in which the detection electrode 114 is opposed to
a charged substance via the aperture window 113, an alternating
current in the range of, for example, 600 to 800 Hz is applied to
the coils 129a and 129b to cause the movable shutter 121 to conduct
reciprocal vibration. As a result, the aperture slits 119 on the
fixed shutter 115 are opened and closed with a frequency that is
four times the drive frequency of the movable shutter 121. With
this open/close frequency, an electric field between the detection
electrode 114 and the charged substance changes, and an alternating
voltage is generated in the detection electrode 114.
The projecting electrostatic shield plate 43A provided on the
electrostatic shield plate 43 will now be described. In the ion
generator 1 with the potential sensor 41 integrally mounted
thereon, charge elimination is conducted by blowing generated air
ions against the charged member P (see FIG. 7). At the same time,
the potential sensor 41 measures surface potential of the charged
member P. In other words, since the ion generator 1 and the
potential sensor 41 are provided in the same casing, it is more
convenient to use as compared with the case where the ion generator
1 and the potential sensor 41 are provided separately.
It is necessary to dispose both the blow-off opening 11 of air ions
and the potential sensor 41 to be opposed to the charged member P.
Therefore, the discharge unit (the discharge electrodes 21 and the
opposite electrodes 23) and the aperture window 113 of the
potential sensor 41 are provided on the same plane of the main body
unit 10. As a result, not only an electric field from the charged
member P but also an electric field between the discharge electrode
21 and the opposite electrode 23, i.e., a discharge electric field
reaches the potential sensor 41. The discharge electric field
becomes noise. In the present embodiment, the blow-off opening 11
and the aperture window 113 of the potential sensor 41 are provided
on the same plane of the main body unit 10. In addition, the
projecting electrostatic shield plate 43A is projected and provided
between the blow-off opening 11 and the aperture window 113 to
conduct electrostatic shielding between the discharge unit and the
potential sensor 41.
A length S1 of the forward projection of the projecting
electrostatic shield plate 43A influences a noise voltage and a
signal voltage of the potential sensor 41. Graphs in FIG. 17
represent a ratio of a noise voltage Vn to Vn0 (Vn/Vn0) and a
projection length S1 of the projecting electrostatic shield plate
43A, where Vn0 is the noise voltage in a case where the projection
length S1 of the projecting electrostatic shield plate 43A is 0 mm.
A distance S2 (2, 4, 6 and 10 mm) between the projecting
electrostatic shield plate 43A and the aperture window 113 is set
to be a parameter. The ratio Vn/Vn0 does not largely depend upon
the distance S2 between the projecting electrostatic shield plate
43A and the aperture window 113. The ratio Vn/Vn0 decreases, the
longer the projection length S1 of the projecting electrostatic
shield plate 43A is made. For example, in a case where the
projection length S1 of the projecting electrostatic shield plate
43A is set equal to 8 or 10 mm, Vn/Vn0 decreases to 35% or 50%.
Graphs in FIG. 18 represent a ratio of a sensor signal voltage Vs
to Vs0 (Vs/Vs0) and a function of the projection length S1 of the
projecting electrostatic shield plate 43A, where Vs0 is the signal
voltage in a case where the projection length S1 of the projecting
electrostatic shield plate 43A is 0 mm. A distance S2 (2, 4, 6 and
10 mm) between the projecting electrostatic shield plate 43A and
the aperture window 113 is set to be a parameter. In a case where
the distance S2 between the projecting electrostatic shield plate
43A and the aperture window 113 is as short as 2 mm, the signal
decreases by approximately 20% as compared with a case where the
distance is 10 mm.
The length of the projecting electrostatic shield plate 43A in the
left/right direction is made long enough to be also effective to a
plurality of discharge electrodes 21 disposed at intervals along
the lengthwise direction of the blow-off opening 11. Relations
between the length of the projecting electrostatic shield plate 43A
and the distance S2 between the projecting electrostatic shield
plate 43A and the aperture window 113 will be described hereafter.
When the projection length of the projecting electrostatic shield
plate 43A is prolonged gradually from 0 mm to 10 mm, attenuation of
the sensor signal is in the range of 0% to at most approximately
20% (the distance S2=2 mm). Whereas attenuation of the noise
voltage is in the range of 30% (the distance S2=10 mm) to 50% (the
distance S2=2 mm). In other words, the sensor signal attenuates
little whereas the attenuation of the noise voltage is large.
Especially in a case where the projecting electrostatic shield
plate 43A and the aperture window 113 are made close to each other
so as to have the distance S2 that is approximately 2 mm and the
projection length of the projecting electrostatic shield plate 43A
is set equal to 10 mm, attenuation of the sensor signal is
approximately 20%. On the other hand, attenuation of the noise
voltage is approximately 50%. Therefore, the signal to noise ratio
is improved by 0.8/0.5=1.6, i.e., 60%.
In the ion generator according to the embodiment of the present
invention, the potential sensor 41, which measures the potential of
the charged member P, is provided integrally in the main body unit
10. In addition, the projecting electrostatic shield plate 43A
projecting from the main body unit 10 is provided between the
discharge unit formed of the discharge electrodes 21 and the
opposite electrodes 23, and the potential sensor 41. Therefore, the
electric field between the discharge electrode 21 and the opposite
electrode 23 is electrostatically shielded by the projecting
electrostatic shield plate 43A. Accordingly, the electric field is
hard to reach the potential sensor 41. As a result, superposition
of noise caused by the electric field between the discharge
electrode 21 and the opposite electrode 23 on a value measured by
the potential sensor 41 is suppressed. Therefore, the voltage of
the charged member P is measured accurately.
The discharge unit formed of the discharge electrodes 21 and the
opposite electrodes 23, and the aperture window 113 of the
potential sensor 41 are disposed on the same plane. As a result, a
depth dimension L (see FIG. 7) of the ion generator 1 can be made
small. Accordingly, it becomes possible to design an ion generator
1 having a smaller size.
The projection length S1 of the projecting electrostatic shield
plate 43A is set in the range of 8 to 10 mm from the aperture
window 113 of the potential sensor 41. As compared with the case
where the projecting electrostatic shield plate 43A is not
provided, therefore, it is possible to decrease the ratio of the
noise voltage Vn to Vn0 represented by Vn/Vn0 to a range of 35 to
50%. In addition, the distance S2 from the projecting electrostatic
shield plate 43A to the aperture window 113 is set equal to or less
than 2 mm. As a result, it is possible to suppress the decrease in
the ratio of the signal voltage Vs to Vs0 represented by Vs/Vs0 to
approximately 20%.
In addition, the blow-off opening 11 is formed to be long. And a
plurality of discharge electrodes 21 is disposed at intervals along
the lengthwise direction of the blow-off opening 11. In such a
configuration, the projecting electrostatic shield plate 43A is
made to intervene between all of the discharge electrodes 21 and
the aperture window 113. As a result, it is possible to suppress
noise generation effectively.
Heretofore, the ion generator according to the embodiment of the
present invention has been described. However, the present
invention is not restricted to the embodiment described above, but
various modifications and changes can be made on the basis of the
technical thought of the present invention.
For example, in the present embodiment, the ion generator 1 having
a plurality of discharge electrodes 21 along the lengthwise
direction has been described. However, the present invention can
also be applied to an ion generator having one discharge electrode
21 (an ion generator that blows off air ions in a spot way).
REFERENCE SIGNS LIST
1 Ion generator 10 Main body unit 11 Blow-off opening 12 Discharge
electrode unit mounting portion 13 Air supply chamber 13A Air
supply port 13B Tube 14 Top face cover 15 Air flow path 16 Air
discharge opening 17 Air guide portion 18 Potential sensor unit
housing portion 18A Detection window 20 Discharge electrode unit 21
Discharge electrode 22 Opening portion 23 Opposite electrode 24 Air
supply path 25 Gap 26 Separation space 27 Power supply cable 40
Potential sensor unit 41 Potential sensor 43 Electrostatic shield
plate 43A Projecting electrostatic shield plate 111 Printed circuit
board 113 Aperture window 114 Detection electrode 114a Flange
portion 114b Standing portion 114c Electrode portion 115 Fixed
shutter 116 Main body portion 117 Side wall portion 118 End wall
portion 119 Aperture slit 121 Movable shutter 122 Fixed end portion
123 Leg piece 124 Arm portion 125 Main body portion 126 End wall
127 Magnet 128 Yoke 128a Magnetic pole surface 128b Magnetic pole
surface 129a Coil 131 Slit 131 Main slit 132 Subsidiary slit 281
Bobbin S1 Projection length of projecting electrostatic shield
plate S2 Distance from projecting electrostatic shield plate to
aperture window Vn Noise voltage Vn0 Noise voltage in case where
projecting electrostatic shield plate is not provided Vs Signal
voltage Vs0 Signal voltage in case where projecting electrostatic
shield plate is not provided L Depth dimension N Reciprocation
direction P Charged member
* * * * *