JPH07164669A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus capable of preventing image clogging of apertures of an aperture board due to toner and enabling stable image formation for a long period of time. [Structure] Aperture board 10 in which a plurality of openings 12 and individual electrodes 13 and a common electrode 14 are provided in an insulating layer 11.
Is used to supply the charged toner 16 from the toner conveying member 15 to the opening 12, the signal voltage according to the image signal is applied from the signal voltage source 19 to the individual electrode 13, and the common electrode 14 and the back electrode 17 are connected. In the image forming apparatus that forms a toner image on the recording paper 18 by applying a DC bias voltage from the DC power supply 21 between the common electrode 14 and the rear electrode 1.
By applying a bias voltage in which a DC voltage is superimposed on an AC voltage from the cleaning bias power source 22 between the cleaning bias power supply 7 and 7, an alternating electric field is generated in the opening 12 to remove the toner in the opening 12, and The toner is adsorbed to the back electrode 17 and collected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used for a printer or the like, and more particularly to recording by using a control member for controlling passage of powder developer (hereinafter referred to as toner) according to an image signal. The present invention relates to an image forming apparatus that directly forms a toner image on a body.

[0002]

2. Description of the Related Art A technique for directly forming a toner image on a recording paper without passing through an exposure process is disclosed in, for example, US Pat.
89,935, U.S. Pat. No. 4,568,955. In the image forming apparatus described in these known documents, a large number of openings are arranged in an insulating layer, and individual electrodes corresponding to the respective openings are formed on one surface of the insulating layer and a common electrode is formed on the other surface. A control member called an aperture board is used. Then, toner charged to a predetermined polarity is supplied to the apertures of this aperture board, and a signal voltage corresponding to the image signal is applied to the individual electrodes to form an electric field in the apertures, so that the toner passes through the apertures. By controlling, a toner image is formed on the recording paper arranged on the side opposite to the toner supply source with respect to the aperture board.

[0003]

In the above-described conventional image forming apparatus, since the aperture diameter of the aperture board needs to be extremely small, about 100 μm, toner adheres to the inner wall of the aperture and clogging with the toner occurs. There is a problem of doing. When such clogging of the apertures occurs, the amount of toner that can pass through the apertures decreases, and in the extreme case, the toner cannot pass through at all, so the toner image on the recording paper deteriorates significantly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which prevents clogging of apertures of an aperture board due to toner and enables stable image formation for a long period of time.

[0005]

In order to achieve the above object, the present invention has as its essence the fact that an alternating electric field is generated in the opening of the control member to remove the toner adhering to the inner wall of the opening. To do. That is, the image forming apparatus according to the present invention includes a control member including a plurality of holes in the insulating layer and individual electrodes for generating electric fields in the holes, respectively.
A developer supply unit that is provided so as to face one surface of the control member and supplies the powder developer charged to a predetermined polarity to the opening, and a recording medium on the other surface of the control member. Passing through the opening between the back electrode facing each other, a signal voltage applying means for applying a signal voltage according to an image signal so as to generate the electric field to the individual electrode, and between the control member and the back electrode. An alternating electric field is provided between the control member and the back electrode between the first bias applying means for applying a DC bias voltage for forming an electric field for guiding the powder developer to the recording medium and the control electrode. And a second bias applying means for applying a bias voltage for forming.

[0006]

In the image forming apparatus according to the present invention configured as described above, by applying the AC voltage alone or by superposing the DC voltage as the cleaning bias voltage between the control member and the back electrode, An alternating electric field is formed in the opening of the control member along the longitudinal direction of the opening. By the action of this alternating electric field, the toner adhering to the inner wall of the opening reciprocates in the length direction of the opening and is separated. Therefore, when a DC electric field is superimposed on this alternating electric field, the toner separated from the inner wall of the opening is discharged to the outside of the opening.
By cleaning the control member in this manner, clogging of the openings due to the toner is eliminated, and a good toner image is formed for a long period of time.

In this case, if the frequency of the cleaning bias voltage is changed from a low frequency to a high frequency in response to changes in the toner charge amount and charge polarity, the cleaning effect of the control member is further improved, and the cleaning effect is uniform. An even toner image is obtained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the principle configuration of a recording element for one pixel of an image forming apparatus according to an embodiment of the present invention.
In FIG. 1, an aperture board 10 which is a control member
2A and 2B are plan views and sectional views, a plurality of openings 12 are formed in a zigzag pattern in the insulating layer 11, and the insulating layer 11 is formed on one surface of the insulating layer 11. The individual electrode 13 is formed so as to surround the periphery of the opening 12, and the insulating layer 1 is further formed.
The common electrode 14 is uniformly formed on the other surface of the first electrode 1. The insulating layer 11 is formed of, for example, an epoxy resin or a ceramic material, and includes the individual electrode 13 and the common electrode 14.
Is formed of, for example, a copper thin film or a gold thin film.

A toner conveying member 15 made of a non-magnetic material such as ceramic, copper, or aluminum is arranged facing the lower surface of the aperture board 10, that is, the side where the common electrode 14 is formed. This toner conveying member 1
In FIG. 5, a one-component non-magnetic toner (hereinafter, simply referred to as a toner) 16 charged to a predetermined polarity is applied as a uniform layer, and the toner 16 is conveyed to the lower portion of the aperture board 10.

On the other hand, a rear electrode 17 formed of, for example, aluminum or copper is located on the upper surface of the aperture board 10, that is, opposite to the side on which the individual electrodes 13 are formed, that is, on the opposite side of the toner carrying member 15. It is arranged. At the time of image formation, the recording paper 18, which is a recording medium, is guided in close contact with the back electrode 17 between the back electrode 17 and the aperture board 10.

A signal voltage corresponding to an image signal is applied from the signal voltage source 19 between the individual electrode 13 and the common electrode 14 of the aperture board 10 during image formation. On the other hand, a DC power supply 21 or a cleaning bias power supply 2 is provided between the common electrode 14 and the back electrode 17 via a switch 20.
The DC bias voltage or the cleaning bias voltage from 2 is selectively applied. That is, the switch 20 is controlled by a controller (not shown) according to the operation mode of the image forming apparatus, and is switched to the side a during image formation, thereby connecting the DC power supply 21 to the back electrode 17.
When the aperture board 10 is cleaned, the cleaning bias power supply 22 is switched to the side b.
Is connected to the back electrode 17.

Next, the operation of the image forming apparatus of this embodiment will be described. In the image forming mode, a signal voltage corresponding to an image signal is applied from the signal voltage source 19 between the individual electrode 13 and the common electrode 14 at the position where the image point is to be formed. Further, the switch 20 is switched to the a side, and a DC bias voltage is applied between the common electrode 14 and the back electrode 17 from the DC power supply 21.

Here, the polarities of the signal voltage and the DC bias voltage are set according to the charging polarity of the toner 16.
For example, when the charge polarity of the toner 16 is negative, the signal voltage applied by the signal voltage source 19 has a positive polarity on the individual electrode 13 side and a negative polarity on the common electrode 14 side, and the DC power supply 21.
The DC bias voltage applied by is set such that the common electrode 14 side is negative and the back electrode 17 side is positive. When the charging polarity of the toner 16 is positive, the polarities of the signal voltage and the DC bias voltage are set opposite to the above. Although the reference potential, that is, the ground potential may be basically any electrode, the common electrode 14 is the reference potential in this embodiment.

When the signal voltage and the DC bias voltage are applied in this manner, the toner 16 conveyed below the aperture board 10 by the toner conveying member 15 is applied between the individual electrode 13 and the common electrode 14. The electric field due to the signal voltage passes through the aperture 12, and is further accelerated by the electric field due to the DC bias voltage applied between the common electrode 14 and the back electrode 17 to adhere onto the recording paper 18. When the signal voltage is not applied between the individual electrode 13 and the common electrode 14 or when the voltage of the opposite polarity is applied, the toner 16 does not pass through the opening 12.

In this way, the toner 16 is attached onto the recording paper 18 according to the image signal to be recorded, and a toner image is formed. After that, the toner image is fixed on the recording paper 18 by heat fixing or pressure fixing, and a series of image forming steps is completed.

Next, the step of cleaning the aperture board 10 will be described. In the cleaning mode, the switch 20 is switched to the b side and the common electrode 14
Bias power supply 2 for cleaning between the back electrode 17 and the back electrode 17.
A cleaning bias voltage is applied from 2. As the cleaning bias voltage, a voltage obtained by superimposing a DC voltage having a predetermined polarity on an AC voltage having an appropriate frequency is applied. Now, assuming that toner adheres to the inner wall of the opening 12 of the aperture board 10, the alternating electric field formed along the longitudinal direction of the opening 12 by the alternating voltage in the bias voltage for cleaning causes the opening 12 to be opened. Since the toner attached to the inner wall of the opening is forcibly reciprocated, the toner is separated from the inner wall of the opening 12.

The toner separated from the inner wall of the opening 12 is attracted to the back electrode 17 by the DC electric field formed between the common electrode 14 and the back electrode 17 by the DC voltage in the cleaning bias voltage. The toner attached to the back electrode 17 is removed and collected by a cleaning device (not shown). The collected toner is reused if necessary. In the cleaning bias power source 22, the polarity of the cleaning bias voltage, that is, the polarity of the DC voltage superimposed on the AC voltage is negative on the common electrode 14 side when the charging polarity of the toner 16 is negative,
The polarity is set to be a positive polarity on the back electrode 17 side, and when the charging polarity of the toner 16 is positive, the polarity is set to the opposite.

By applying the cleaning bias voltage in this manner, the clogging of the opening 12 with the toner 16 can be eliminated. Therefore, by performing the cleaning process by applying the cleaning bias voltage as needed, the toner 16 at the time of image formation smoothly passes through the opening 12 and is transferred onto the recording paper 18, so that stable image formation is always performed. It becomes possible.

Next, a more specific embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a diagram more specifically showing the image forming apparatus according to the present invention, and the portions corresponding to those in FIG. 1 are designated by the same reference numerals.

In FIG. 3, the structure of the aperture board 10 is as shown in FIG. 2, but it will be described in more detail as follows. The opening 12 formed in the insulating layer 11 has a diameter of about 100 μm, and extends along the direction (main scanning direction) shown by the arrow X orthogonal to the transfer direction (sub-scanning direction) of the recording paper 18 shown by the arrow Y. They are arranged in a zigzag pattern in 6 rows at a density of about 300 / inch. For example, recording paper 1
When the width of 8 in the main scanning direction is 297 mm, 3,508 holes 12 are provided along the main scanning direction.
The thickness of the insulating layer 11 can be appropriately set within a range of about 50 μm to 1 mm, and is 400 μm in this embodiment. Insulation layer 1
An individual electrode 13 is formed on one surface of the first electrode 1 so as to surround each of the openings 12, and each of the individual electrodes 13 is connected to a signal voltage source 19 via an individual wiring or a matrix wiring. . A common electrode 14 is formed on the other surface of the insulating layer 11, and the common electrode 14 is grounded.

A plurality of transport electrodes 31, 32 are formed on the toner transport member 15 made of a non-magnetic member. For example, an odd-numbered transport electrode 31 among them is a toner transport power source 33 made of, for example, an AC power source. Are connected, and the even-numbered transport electrodes 32 are grounded. A suitable interval between the common electrode 14 of the aperture board 10 and the transport electrodes 31, 32 on the toner transport member 15 is in the range of 10 μm to 500 μm, and this interval is the toner 16 from the viewpoint of improving the image density and recording speed. It is better to be as narrow as possible without agglomerating. In this embodiment, this interval is 100 μm.

When the toner 16 charged from the left end in the drawing is supplied onto the toner conveying member 15, the toner 16 is transferred to the right in the drawing and becomes a smoke. The smoked toner 16 passes through the opening 12 by the electric field generated by the signal voltage applied from the signal voltage source 19 between the individual electrode 13 and the common electrode 14 of the aperture board 10, and is further grounded. It is attached onto the recording paper 18 by the electric field between 14 and the back electrode 18 to which a DC bias voltage is applied by the DC power supply 21. That is,
While moving the recording paper 18 in the sub-scanning direction indicated by the arrow Y at a speed of, for example, about 100 μm / sec, the signal voltage source 1
The signal voltage pulse corresponding to the image signal from 9 is applied to the individual electrode 13
When applied to the recording paper 18, the toner 16 adheres to the recording paper 18.
As a result, a toner image is formed on the recording paper 18 corresponding to the image signal. The toner image thus formed on the recording paper 18 is heated or pressure-fixed by a fixing device (not shown).

In the present embodiment, the back electrode 17 is composed of, for example, a conductive roller made of aluminum. Then, the cleaning device 34 is provided near the back electrode 17.
Is provided. The cleaning device 34 is the blade 3
5, the blade 35 scrapes off and collects the toner adhering to the surface of the back electrode 17.

If the above-mentioned image forming process is carried out for a long period of time, the toner 16 adheres to the inner wall of the aperture 12 of the aperture board 10 and the passage of the toner 16 through the aperture 12 is not smooth. The quality of the toner image formed above deteriorates, and in the worst case, the toner 16 cannot pass through the opening 12 at all, and the toner image is not formed. Therefore, when such a state occurs, or before the image forming process, the switch 20 is periodically switched to the b side, and the cleaning bias power source 2
2 to the back electrode 17 to connect the common electrode 14 and the back electrode 1
By applying a cleaning bias voltage to and from 7, the toner adhering to the inner wall of the opening 12 is reciprocated to be removed, thereby eliminating clogging of the opening 12 due to the toner.

Here, the cleaning bias voltage may be an AC voltage only, but the effective value is 500V to 20V.
It is more preferable to superimpose a DC voltage in the range of 10V to 1000V on an AC voltage in the range of 00V. Further, the maximum cleaning efficiency can be obtained by changing the frequency of the AC voltage in the cleaning bias voltage according to the degree of clogging and the environment (particularly humidity), and also the difference in the charge amount and particle size of the toner 16. Can be set. In this embodiment, a cleaning bias voltage in which a DC voltage of 100 V is superimposed on an AC voltage of 1500 V and 2 kHz is used.

The toner removed from the opening 12 by applying such a cleaning bias voltage is attracted to the back electrode 17. The toner adhering to the back electrode 17 is removed by the cleaning device 34.
Removed and recovered. The collected toner may be discarded or supplied to the toner conveying member 15 for reuse.

FIG. 4 is a view showing the arrangement of an image forming apparatus according to another embodiment of the present invention, in which the common electrode is removed from the aperture board 10 and only the individual electrode 13 is covered by the insulating layer 1.
2 is formed by adhesion. In this case, for example, the common electrode 40 may be arranged on the back surface side of the toner conveying member 15 as shown in the figure. The connection relation of each electrode and the operation of the device are the same as those in the embodiment of FIG.

The present invention can be implemented with various modifications. For example, in the above-described embodiment, the example in which the toner image is directly formed on the recording paper 18 has been described, but the toner image may be formed on the intermediate transfer body and the toner image on the intermediate transfer body may be transferred onto the recording paper. . In that case, the intermediate transfer member can also serve as the back electrode.

Further, the developer supplying means is not limited to the structure shown in the embodiment, but may be any structure as long as it can supply the charged toner to the opening 12 of the aperture board 10.

In the above embodiment, the one-component non-magnetic toner is used as the developer, but the two-component toner may be used. In that case, the toner can be supplied to the opening 12 of the aperture board 10 by using a conventional developing device such as a cascade magnetic brush, and the same as in the case of using the one-component non-magnetic toner described in the above embodiment. The result of is obtained.

Further, in the above-described embodiment, the toner separated from the opening 12 of the aperture board 10 is separated from the rear electrode 17 by the toner.
However, for example, in a cleaning mode, an appropriate insulating sheet is inserted in front of the back electrode 17, and the toner is attached to the insulating sheet by using the DC electric field between the common electrode 14 and the back electrode 17. After that, the insulating sheet may be collected.

[0032]

As described above, according to the present invention, an alternating electric field is generated inside the aperture of the aperture board along the longitudinal direction of the aperture to separate the toner attached to the inner wall of the aperture. The toner image can be removed and a stable toner image can be formed over a long period of time.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing a detailed configuration of an aperture board used in this embodiment and a cross-sectional view taken along the line II of FIG.

FIG. 3 is a diagram more specifically showing a configuration of the image forming apparatus in FIG.

FIG. 4 is a diagram showing a schematic configuration of an image forming apparatus according to another embodiment of the present invention.

[Explanation of symbols]

10 ... Aperture board 11 ... Insulating layer 12 ... Opening hole 13 ... Individual electrode 14 ... Common electrode 15 ... Toner conveying member 16 ... Toner 17 ... Back electrode 18 ... Recording paper 19 ... Signal voltage source 20 ... Mode change switch 21 ... DC power supply 22 ... Bias power supply for cleaning 31, 32 ... Transport electrode 33 ... Toner transport power supply 34 ... Cleaning device 35 ... Blade 40 ... Common electrode

Claims (1)

[Claims] 1. A control member comprising a plurality of openings in an insulating layer and individual electrodes for generating an electric field in the openings respectively, and a control member provided on one surface of the control member so as to face the control member. A developer supplying means for supplying the powder developer charged with polarity to the opening, a back electrode facing the other surface of the control member via a recording medium, and an electric field generated in the individual electrode. A signal voltage applying means for applying a signal voltage according to an image signal, and an electric field for guiding the powder developer passing through the opening to the recording medium are formed between the control member and the back electrode. Bias applying means for applying a DC bias voltage for controlling the bias voltage, and second bias applying means for applying a bias voltage for forming an alternating electric field in the opening between the control member and the back electrode. And comprising That the image forming apparatus.