JP2003145825A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which an image of good image quality can be formed stably by removing toner adhering to a toner flight control means effectively. SOLUTION: The imaging apparatus is arranged such that adhesion of toner to an intermediate transfer belt 23 is higher than adhesion of toner to an FPC 4. In the imaging apparatus, a DC potential is applied to a developing roller 12 and a control electrode 43 and toner is reciprocated between a back face electrode 3 and the FPC 4 by applying a cleaning voltage Vc1 of rectangular AC voltage from a back face bias generating section 104 to the back face electrode 3, but since toner exhibits higher adhesion to the back face electrode 3, almost all toner eventually adheres to the back face electrode 3 and toner adhering to the FPC 4 is removed.

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 such as a copying machine, a facsimile or a printer, and more particularly to an image forming apparatus for forming an image by controlling toner flying from a toner carrier to a back electrode. .

[0002]

2. Description of the Related Art As an image forming method using toner,
Conventionally, the jumping type and the projection type have been most widely used. In this type of image forming method, an electrostatic latent image corresponding to an image is formed on a photoconductor, and toner as an image forming agent is adhered to the electrostatic latent image on the photoconductor from a toner carrier such as a developing roller. To obtain a toner image, and then transfer the toner image to copy paper, transfer paper, copy paper,
It is to be transferred onto recording paper. However, these image forming methods require a step (photosensitive process) of forming an electrostatic latent image on the surface of the photoconductor, which involves a problem that the apparatus configuration is complicated and the apparatus cost and running cost are high. There is. Therefore, in recent years, as described in U.S. Pat. Nos. 3,689,935 and 5,036,341 and Japanese Patent Laid-Open No. 2001-505146, toner is copied by a function of an electric field, recording paper or intermediate paper. An image forming apparatus of a so-called "toner jet (registered trademark)" system, which forms an image by flying on an image receiving body such as a transfer belt, has been attracting attention.

In this image forming apparatus, a toner carrying member such as a developing roller for carrying toner in a predetermined moving direction is provided, and a toner regulating blade is provided so as to contact the surface of the toner carrying member. ing. Therefore, the toner on the toner carrier is triboelectrically charged by the toner regulating blade and, after being regulated to a predetermined thickness, is transported to the toner flying start position facing the back electrode.

Further, in this image forming apparatus, a flexible printed circuit board (Flexible Printed Circuit) having a plurality of toner passage holes for passing charged toner is disposed between the toner carrier and the back electrode. At the same time, an image receiver such as a recording paper or a transfer medium is arranged between the flexible printed circuit board and the back electrode. Then, a potential difference is applied between the toner carrier and the back electrode to form a transfer electrostatic field that causes the charged toner to fly from the toner carrier to the back electrode. Also,
In the flexible printed circuit board, control electrodes are arranged around each toner passage hole, and each toner passage hole is electrostatically opened and closed by controlling a control voltage applied to each control electrode according to an image signal. Corresponding to the image signal, the charged toner is caused to fly from the toner carrier to the back electrode through the toner passage hole and adhere to the image receiver. As described above, the toner flying is controlled by the flexible printed circuit board, that is, the board functions as the toner flying control means, so that the toner image corresponding to the image signal is formed on the image receiving body.

[0005]

By the way, in the image forming apparatus constructed as described above, a part of the flying toner adheres to and deposits on the surface of the flexible printed circuit board to deteriorate the image quality or cause the printing. There was a problem such as not being able to perform. That is, the control voltage applied to the control electrode corresponding to the image signal is shielded by the accumulated charge of the toner, the flight of the toner cannot be correctly controlled, or the toner passage hole is blocked by the toner. Toner image formation may not be possible. In particular, since the toner particles charged to the opposite polarity to the desired polarity are attracted to the control electrode by the application of the control voltage, the surface of the flexible printed circuit board opposite to the toner carrier, that is, the back electrode is opposed. In some cases, toner adheres to the surface of the surface.

When the toner adhered to the flexible printed circuit board is scattered by the action of mechanical vibration or electrostatic force of the apparatus and adheres to the image receptor, the toner image formed on the image receptor is stained.

In order to solve such problems and to stably form an image of good quality, it is required to establish a technique for removing the toner adhering to the toner flying control means.

The present invention has been made in view of the above problems, and provides an image forming apparatus capable of effectively removing the toner attached to the toner flying control means and stably forming an image of good quality. The purpose is to do.

[0009]

In order to achieve the above object, an image forming apparatus according to the present invention carries a back electrode and charged toner and moves in a predetermined moving direction to face the back electrode. The toner carrier that conveys the toner to the toner flying start position and the rear electrode and the toner carrier are disposed to prevent the toner flying from the toner flying start position of the toner carrier to the back electrode. Toner flight control means for controlling, a transfer medium is sent between the toner flight control means and the back electrode, and the flying toner is landed to temporarily carry a toner image on the surface, and A transfer means for transferring the toner image to the image receiving body, and an electric field generating means for generating an alternating electric field between the toner flying control means and the transfer medium are provided, and the transfer means is provided for the transfer medium. Adhesion of the toner is characterized by greater than adhesion of the toner to the toner flying control means.

According to the invention thus constructed, when an alternating electric field is generated between the toner flying control means and the transfer medium by the electric field generating means, the charged toner attached to the toner flying control means becomes a toner. The force received from the alternating electric field generated between the flight control means and the transfer medium causes the toner flight control means and the transfer medium to reciprocate. Further, since the adhesion force of the toner to the transfer medium is set to be larger than the adhesion force of the toner to the toner flight control unit, the probability that the toner adheres to the transfer medium is higher than the probability that the toner adheres to the toner flight control unit. ing. Therefore, while repeating the reciprocating motion, the toner attached to the toner flying control means gradually moves to the transfer medium side, and finally, most of the toner attaches to the transfer medium, and as a result, the toner flying control is performed. The toner adhering to the means is removed.

Since an alternating electric field is applied, any toner having any charging polarity can be effectively released from the toner flying control means and attached to the transfer medium.

In this way, by performing the cleaning for removing the toner attached to the toner flying control means,
In this image forming apparatus, it is possible to stably form an image with good image quality.

The adhesion of the toner particles to other substances is caused by various causes such as electrostatic force and van der Waals force. The kind and amount of external additives added to the toner, and the surface condition of the mating substance. The size greatly changes depending on the like. Various proposals have been made for the measuring method (for example, the measuring method described in JP 2001-228075 A), but the "adhesive force" referred to in the present specification is a force resulting from these various causes. For example, “Study on toner adhesion-effect of external additives” (Haruo Iimura, Ricoh Technical Report, No. 2).
6, Nov., 2000) or “Measurement of particle adhesion force by electric field desorption method (II)” (Masashi Nagayama et al., Japan Hardcopy 2000, 1
The evaluation can be performed by the electric field desorption method described in pages 37-140 of the Imaging Society of Japan), but other evaluation methods may also be used.

The image forming apparatus according to the present invention is
To achieve the above object, a back electrode, a toner carrier that carries a charged toner, moves in a predetermined moving direction, and conveys the toner to a toner flying start position facing the back electrode, and the back electrode. A toner flight control unit that is disposed between an electrode and the toner carrier and controls the toner flight from the toner flight start position of the toner carrier to the back electrode, and a carrier medium that holds an image receiver is the toner. Between the toner fly control means and the carrier medium, a carrier means for sending the flying toner between the flight control means and the back electrode to land the flying toner on the surface of the image receiving body to form a toner image. An electric field generating means for generating an alternating electric field, and the adhesion force of the toner to the conveying medium is larger than the adhesion force of the toner to the toner flying control means. It is characterized in.

In the invention thus constructed, when an alternating electric field is generated between the toner flying control means and the carrier medium by the electric field generating means as required, the charged toner attached to the toner flying control means becomes a toner. The force received from the alternating electric field generated between the flight control means and the transport medium causes the toner flight control means and the transport medium to reciprocate. Further, since the adhesion force of the toner to the conveying medium is set to be larger than the adhesion force of the toner to the toner flying control unit, the probability that the toner adheres to the conveying medium becomes higher than the probability that the toner adheres to the toner flying control unit. ing. Therefore, while repeating the reciprocating motion, the toner that has adhered to the toner flying control means gradually moves to the carrying medium side, and eventually most of the toner adheres to the carrying medium, resulting in toner flying control. The toner adhering to the means is removed.

At this time, the electric field generating means generates an alternating electric field while an area of the surface of the carrier medium exposed without holding the image receiver is located between the toner flying control means and the back electrode. It may be generated. By doing so, the toner attached to the toner flight control means can be surely transferred to the surface of the transport medium, so that the toner flight control means can be cleaned while preventing unnecessary toner attachment to the image receiving body. .

As described above, by performing the cleaning for removing the toner attached to the toner flying control means,
In this image forming apparatus, it is possible to stably form an image with good image quality.

If desired, a cleaning unit may be provided in the transfer unit or the transport unit to remove the toner adhering to the transfer medium or the transport medium from the surface thereof. By doing so, unnecessary toner that has moved to the transfer medium or the transport medium is reliably removed, and the toner image formed on the surface of the image receiving body is not contaminated, and an image with good image quality can be formed.

Here, when the toner flying control means is provided with a control electrode to which a control voltage for controlling the flying of the toner to the back electrode is applied, the electric field generating means is connected to the back electrode. The alternating electric field may be generated by applying an alternating voltage to the control electrode.

Further, when the toner flying control means is provided with a semiconductive layer provided on at least a surface facing the back electrode, the electric field generating means includes the back electrode and the semiconductive layer. The alternating electric field may be generated by applying an alternating voltage between them.

In these inventions, an alternating voltage is applied between the back electrode and the control electrode or semi-conductive layer which is essential for image formation without providing a special member for cleaning. By doing so, it is possible to effectively clean the toner flying control means.

The alternating voltage may be, for example, a voltage whose polarity is opposite to that of the polarity during which a voltage is applied to the charged toner to exert a force in the direction from the toner fly control means to the back electrode. It may be longer than the application period. By doing so, it is possible to more reliably attract the toner to the back electrode side, attach it to the transfer medium or the transport medium, and collect it.

[0023]

1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. In this image forming apparatus, when an image signal is given to the main controller 101 of the control unit 100 from an external device such as a host computer, the engine controller 1 responds to the signal from the main controller 101.
02 controls each part of the developing device 1 so that two rollers 21 and 22 are rotatably driven by a drive motor (not shown).
Toner is ejected onto and adheres to the surface of the intermediate transfer belt 23 that is laid over the toner to form a toner image corresponding to the image signal.

In this developing device 1, in the housing 11,
The toner T as a developer is stored, and the developing roller 12, the supply roller 13, and the regulation blade 14 are housed. The developing roller 12 carries charged toner (that is, charged particles for image formation) T, and rotates at a predetermined peripheral speed in the direction of arrow D in FIG. Flight start position) J
It is a toner carrier to be transported to. This developing roller 12
Is formed in a cylindrical shape with a metal or alloy such as aluminum or iron, and a DC voltage is applied from the developing roller bias generator 103 provided in the engine controller 102.

The supply roller 13 is brought into contact with the outer peripheral surface of the developing roller 12 and rotates in the opposite direction to the developing roller 12,
The toner T is supplied to the developing roller 12 and the excess toner T is dropped from the developing roller 12. The supply roller 13 is made of, for example, a metal core wrapped with synthetic rubber such as urethane sponge, and also has a function of charging the toner T to a predetermined polarity by frictionally contacting the developing roller 12. In the present embodiment, the toner T will be described below as being negatively charged.

The regulating blade 14 is applied to the outer peripheral surface of the developing roller 12 on the downstream side of the supply roller 13 in the rotation direction D of the developing roller 12, and negatively charges the toner T by friction with the developing roller 12. The amount of toner T carried on the developing roller 12 is regulated. More specifically, the regulation blade 14 is constituted by a plate-shaped metal piece 141 having one end fixed to the housing 11, and an elastic member 142 attached to the other end of the plate-shaped metal piece 141. Contact the surface, toner T
Are regulated.

The back electrode 3 is opposed to the developing roller 12.
Are arranged. More specifically, the back electrode 3 is shown in FIG.
As shown in FIG. 3, the intermediate transfer belt 23 is sandwiched between the developing roller 12 and the developing roller 12. Then, a voltage is applied to the back electrode 3 from the back bias generator 104 provided in the engine controller 102 according to the operating condition. For example, a DC voltage higher than the voltage applied to the developing roller 12 is applied during image formation, and the charged toner T is transferred between the developing roller 12 and the back electrode 3 toward the back electrode 3. A transfer electrostatic field is formed. For this reason, the charged electrostatic toner T flies from the developing roller 12 toward the back surface electrode 3 at the toner flying start position J by the transfer electrostatic field, and landed and adheres to the surface of the intermediate transfer belt 23 that functions as a transfer medium. Further, during cleaning, which will be described later, an alternating voltage is applied to remove the toner T from the FPC 4.

A cleaner 24 is provided at a position near the roller 21 around which the intermediate transfer belt 23 is stretched (FIG. 1). More specifically, the cleaner 24 is
The cleaner housing 241 and a cleaner blade 242 made of, for example, polyurethane attached to the cleaner housing 241 are included in the roller blade 21.
The intermediate transfer belt 23 is abutted against the surface of the intermediate transfer belt 23 by sandwiching the intermediate transfer belt 23 with the surface of the intermediate transfer belt 23 to scrape off the toner T adhering to the surface of the belt 23, and the cleaner housing 241 collects the scraped toner T. To do. Thus, on the intermediate transfer belt 23 from which the residual toner is removed,
New toner image formation is performed. As described above, in this embodiment, the rollers 21, 22, the intermediate transfer belt 23, the cleaner 24 as a cleaning unit, and the drive motor (not shown) constitute a transfer unit.

Further, in this embodiment, in order to control the flight of the charged toner T onto the intermediate transfer belt 23, a flexible printed circuit board (hereinafter referred to as FPC) 4 is provided between the developing roller 12 and the back electrode 3. It is arranged. Hereinafter, the configuration and operation of the FPC 4 will be described with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing a partially enlarged cross section of a flexible printed circuit board and a flying model of charged toner. Further, FIG. 4 is a view showing control electrodes and deflection electrodes formed on the flexible printed circuit board. This F
In the PC 4, a toner passage hole 41 for guiding the charged toner T from the developing roller 12 to the back electrode 3 is formed in a base 42 made of an electrically insulating material such as polyimide.
Although only one toner passage hole 41 is shown in FIG. 3, a plurality of toner passage holes 41 are provided in a line at equal intervals in the vertical direction X of the paper surface of FIG. 3 in this embodiment. The charged toner T can pass through the toner passage holes 41 toward the back electrode 3 side. In this embodiment, the toner passage holes 41 are arranged in one line,
It may be arranged in a plurality of rows. Further, the toner passage hole 41
The shape may be circular as in this embodiment, or may be elliptical or polygonal.

Here, in the image forming apparatus according to the present invention, the adhesive force of the toner to the surface of the toner flying control means is selected to be smaller than the adhesive force of the toner to the transfer medium. In the toner T used in the apparatus of the present embodiment, for example, a combination of a base body 42 (of the FPC 4 which is a toner flight control means) made of polyimide and an intermediate transfer belt 23 which is a transfer medium made of polycarbonate in which carbon black is dispersed is used. The above conditions can be satisfied by the above, but the adhesive force of toner depends on the material of the toner and the other substance, the surface condition, etc., and these should be changed appropriately according to the specifications of the toner and the device used. May be.

On the developing roller 12 side of the substrate 42, a ring-shaped control electrode 43 is formed so as to surround each toner passage hole 41. In addition, each control electrode 43
The lead wire 44 extends in the direction orthogonal to the arrangement direction of the toner passage holes 41. The shape of the control electrode 43 is not limited to the circular shape, but may be any shape, and may be, for example, an elliptical shape or a polygonal shape. Further, the control electrode 43 may have a partial cutout instead of a perfect ring. .

On the back electrode 3 side of the base 42,
A pair of deflection electrodes 45L, 4L is provided for each toner passage hole 41.
As shown in FIG. 4, 5R is provided so as to be diagonally opposed to the conveyance direction Y of the intermediate transfer belt 23 (direction orthogonal to the toner passage hole array), and the deflection electrodes 45L, 4L,
Lead wires 46L and 46R are extended from 5R, respectively.

Further, although not shown in FIGS. 3 and 4, the high-voltage driver IC is provided on the base body 42.
And a control bias generator 47 (FIG. 2), an L deflection bias generator 48L (FIG. 2), and an R deflection bias generator 48R (FIG. 2). Of these, the control bias generator 47 is electrically connected to each control electrode 43, and the CPU 105 of the engine controller 102.
An appropriate voltage is selectively applied in accordance with the open / close control signal from to open and close the toner passage hole 41 electrostatically. That is, the charged toner T is ejected from the developing roller 12 for each control electrode 43, and the toner passage hole 41 is formed.
The transfer electrostatic field passing through the toner passing hole 41 is exposed between the developing roller 12 and the back electrode 3 so as to fly toward the back electrode 3 after passing through, and the exposure is limited.

The L deflection bias generator 48L is electrically connected to the deflection electrode 45L, and the R deflection bias generator 48R is electrically connected to the deflection electrode 45R. The engine controller 102 controls deflection. By appropriately applying an appropriate voltage to each of the deflection electrodes 45L and 45R according to the signal, the charged toner T
The flight direction of is switched to the following three directions.

(1) No deflection: When the same voltage is applied to both the deflection electrodes 45L and 45R of the arrow P1 in FIG. 3, the charged toner T becomes the toner passage hole 41 as shown by the arrow P1 in FIG. Straight through the intermediate transfer belt 23
And fly to a position corresponding to the toner passage hole 41 on the above.

(2) Left deflection: Among the deflection electrodes 45L and 45R indicated by the arrow P2 in FIG. 3, the deflection electrode 45L disposed on the left side of the toner passage hole 41 on the right side with respect to the conveyance direction Y of the intermediate transfer belt 23 is on the right side. Deflection electrode 45 arranged
When a voltage relatively higher than R is applied, the charged toner T charged in the negative polarity has a static charge for deflection generated between the electrodes 45L and 45R as shown by an arrow P2 in FIG. It is deflected to the left by the electric field.

(3) Rightward deflection: Among the deflection electrodes 45L and 45R indicated by the arrow P3 in FIG. 3, the deflection electrode 45R disposed on the right side of the toner passage hole 41 on the left side with respect to the conveyance direction Y of the intermediate transfer belt 23 is on the left side. Deflection electrode 45 arranged
When a voltage relatively higher than L is applied, the charged toner T, which is negatively charged, is deflected statically between the electrodes 45L and 45R as shown by the arrow P3 in FIG. It is deflected to the right by the electric field.

As described above, in this embodiment, the flying direction of the charged toner T is switched to the three directions, and the charged toner T is landed on the intermediate transfer belt 23 at the landing position PI of the intermediate transfer belt 23 including the deflection range. I am letting you.

However, as described above, the deflection electrodes 45L, 45
Since R is diagonally opposed to the transport direction Y of the intermediary transfer belt 23, the intermediary transfer belt 23 is formed by the three modes of (1) no deflection, (2) left deflection, and (3) right deflection. When 23 is stopped, the intermediate transfer belt 23
On the intermediate transfer belt 23, three dots lined up obliquely with respect to the transport direction Y of. In this case, the transport speed is determined so that the intermediate transfer belt 23 is transported by the displacement amount (distance) of the adjacent dots in the cycle (time) of hitting the dots, so that the three dots are transferred to the intermediate transfer belt 23. They can be arranged linearly in the direction orthogonal to the transport direction Y. Therefore, three dots can be formed with one toner passage hole 41, and the density of the dots can be increased.

Further, on the upstream side of the toner flying start position J in the rotation direction D of the developing roller 12, between the FPC 4 and the developing roller 12 configured as described above, the longitudinal direction of the developing roller 12 (see the plane of FIG. 3). The spacer 5 spread over the entire length in the vertical direction X) is inserted in the front side in the rotation direction D with respect to the toner passage hole 41 of the FPC 4, and a part of the spacer 5 is carried on the developing roller 12 by the toner layer TL. By contacting with the developing roller 12 and the FP
The gap GP with the toner passage hole 41 of C4 is regulated to a constant value.

In the image forming apparatus configured as described above, when an image signal is given from the external device to the main controller 101 of the control unit 100, the CPU 105 of the engine controller 102 responds to the signal from the main controller 101. The control signal corresponding to the image signal is supplied to the control bias generator 47 and the L deflection bias generator 4.
The toner T is applied to the 8L and R deflection bias generators 48R to fly and adhere to the intermediate transfer belt 23 to form a toner image corresponding to the image signal. Then, regarding the toner image, in the predetermined transfer region TR, the cassette 7
The image is transferred onto a sheet S that is an image receiver such as a copy sheet, a transfer sheet, and an OHP transparent sheet taken out from the sheet (FIG. 1). The sheet S on which the image is thus formed is conveyed to the discharge tray (not shown) via the fixing unit 8.

Next, FIGS. 5 to 7 will be described with respect to the cleaning operation which is performed at any time to remove the toner T adhering to the surface of the FPC 4 facing the back electrode 3 in the image forming apparatus having the above-described configuration. The description will be made with reference. FIG. 5 is a diagram showing potentials applied to each part in the cleaning operation of the image forming apparatus of FIG. 1, and FIG.
It is a figure which shows an example of the waveform of a cleaning voltage. Also,
FIG. 7 is a schematic diagram showing the behavior of the toner during the cleaning operation.

In the cleaning operation of this device, the CPU
Based on the control command from 105, as shown in FIG.
Control bias generator 47, L deflection bias generator 48
The L and R deflection bias generator 48R and the developing roller bias generator 103 each output a predetermined negative voltage.
Thereby, for example, the potential Vr of the developing roller 12 is -1.
00V, the potential Vg of the control electrode 43 is set to -300V, and the potential Vd of the deflection electrodes 45L and 45R is set to -200V. 5 and 7, the L deflection electrode 4
Although the description of the L deflection bias generator 48L connected to 5L is omitted, this L deflection bias generator 48L is also
The same voltage Vd as that of the R deflection bias generator 48R is generated, and the L deflection electrode 45L has the same potential as the R deflection electrode 45R.

On the other hand, the back bias generator 104 outputs the cleaning voltage Vc1. Therefore, the developing roller 12
Is applied with a cleaning voltage Vc1. The cleaning voltage Vc1 is a rectangular wave voltage shown in FIG. 6, and the peak-to-peak voltage Vpp can be set to 1.5 kV and the repetition frequency can be set to 3 kHz. As shown in FIG. 6, the cleaning voltage Vc1 has a period t1 in which the voltage is positive and a period t2 in which the voltage is negative in each cycle, where t1 <t2.
And the duty ratio is 40%, that is, t
It can be set so that 1: t2 = 4: 6. Although the reason for doing so will be described later, the above-described potentials and cleaning voltages Vc1 of the respective parts are not limited to these, and can be appropriately changed according to the device configuration.

As described above, the FPC 4 is cleaned by applying the predetermined voltage to each part of the apparatus, and the toner T attached to the FPC 4 is removed. Less than,
The reason why the toner T is removed from the FPC 4 is shown in FIG.
It will be described in detail with reference to FIG.

First, during the period t1 when the cleaning voltage Vc1 applied to the back electrode 3 is positive, the electric field E is generated between the intermediate transfer belt 23 and the FPC 4 in the direction of the arrow shown in FIG. 7A. , The negatively charged toner Tn among the toners T attached to the FPC 4 is transferred from the FPC 4 to the intermediate transfer belt 2
3, the positively charged toner Tp receives a force Fp1 in the opposite direction.

Next, when the voltage Vc1 shifts to the negative period t2,
As shown in FIG. 7B, the direction of the electric field E is opposite to that described above, and the negatively charged toner Tn receives the force Fn2 in the direction from the intermediate transfer belt 23 to the FPC4, while the positively charged toner Tp comes from the FPC4. The force Fp2 in the direction toward the intermediate transfer belt 23 is received.

As described above, the force that each toner T receives from the electric field E is larger than the adhesion force of each toner particle T to the adhered substance (that is, the intermediate transfer belt 23 or the FPC 4), and its direction is that direction. When the toner T is separated from the adhered substance, the toner T is separated from the adhered substance and starts flying. For example, FIG.
When the force Fn1 received from the electric field E is larger than the adhesion force to the FPC4, the negatively charged toner Tn shown in FIG.
To fly to the intermediate transfer belt 23. Then, when the direction of the electric field E is reversed (FIG. 7B), the flight direction of the toner Tn is opposite to the above. That is, the toner Tn reciprocates between the FPC 4 and the intermediate transfer belt 23 as the direction of the electric field E changes periodically.
The same applies to the positively charged toner Tp, but the flying direction is opposite to that of the negatively charged toner Tn.

Here, as described above, in the image forming apparatus of this embodiment, the toner T on the intermediate transfer belt 23 is used.
Of the toner T is larger than that of the toner T to the FPC 4. Therefore, the probability that the toner T that reciprocates between the FPC 4 and the intermediate transfer belt 23 due to the action of the alternating electric field E formed by the cleaning voltage Vc1 adheres to the intermediate transfer belt 23 side is FP.
It is higher than the probability of adhering to the C4 side. Therefore, when the cleaning voltage Vc1 is continuously applied for a predetermined period of time, the reciprocating toner T gradually adheres to the intermediate transfer belt 23, and finally, as shown in FIG. The toner T adheres to the intermediate transfer belt 23 and is collected regardless of the charging polarity, and thus the toner T adhered to the FPC 4 is removed.

These toners T are conveyed to the downstream side by the movement of the intermediate transfer belt 23 in the direction of the arrow Y in FIG. 7C, and finally the intermediate transfer belt 23.
5 is scraped off by the cleaner blade 242 (FIG. 5) that comes into contact with the surface of the cleaning roller 242 and collected in the cleaner housing 241. Thus, the cleaning operation in this embodiment is completed.

As described above, in this embodiment, the cleaning voltage Vc1 is the period t1 when the voltage is positive.
Is set to be shorter than the period t2 in which is negative, the time for the positively charged toner Tp to fly from the FPC 4 toward the intermediate transfer belt 23 is set to be longer than the time for flying in the opposite direction. ing. Therefore, even if there is a time delay in the change of the electric field due to the relatively large electric resistance of the intermediate transfer belt 23, the positively charged toner Tp can be reliably attracted to the intermediate transfer belt 23 side and collected.

As described above, in the image forming apparatus of the first embodiment described above, a predetermined DC voltage is applied to the control electrode 43 and the deflection electrodes 45L and 45R formed on the FPC 4, while the back electrode 3 is cleaned for cleaning. Alternating voltage Vc1
An alternating electric field E is generated by applying
The toner T attached to the surface of the FPC 4 is collected on the intermediate transfer belt 23 having a larger adhesive force, and the FPC 4 is cleaned. Therefore, the toner T is attached to the rear electrode side surface of the FPC 4.
And effectively prevent problems that occur in conventional image forming apparatuses, such as the control voltage being blocked and the toner flight being unable to be correctly controlled, and the toner passage hole being blocked. It is possible to stably form an image with good image quality.

In the above embodiment, the developing roller 1
2, the control electrode 43 and the deflecting electrodes 45L and 45R are applied with the above-described DC potential, and the back electrode 3 is applied with the cleaning voltage Vc1 shown in FIG. However, the developing roller 12 and the control electrode 43 are not limited thereto.
The potentials of the deflecting electrodes 45L and 45R may be appropriately changed or may be grounded. In addition, a DC voltage may be superimposed on the cleaning voltage Vc1, or the waveform may be a sine wave voltage other than a rectangular wave.

Although the peak-to-peak voltage Vpp of the cleaning voltage Vc1 may have other values, the force Fn1 exerted on each charged toner particle by the electric field E formed by applying the voltage Vc1.
It is desirable to set the voltage value such that the above is larger than the adhesive force of the toner T to the FPC 4 and smaller than the adhesive force to the intermediate transfer belt 23.

In the above embodiment, the alternating electric field E is generated by fixing the potentials of the control electrode 43 and the deflection electrodes 45L and 45R and applying the cleaning voltage Vc1 to the back electrode 3, but this is not the case. Conversely, the back electrode 3 may be grounded or kept at a predetermined DC potential, and an alternating voltage may be applied to the control electrode 43 and / or the deflection electrodes 45L and 45R. However, the control electrode 43 and the deflection electrode 4 are restricted due to the limitation of the withstand voltage of the driver IC or the like that constitutes the FPC 4.
Since a very high voltage cannot be applied to 5L and 45R, it is realistic to apply the cleaning voltage Vc1 to the back electrode 3 as in the above embodiment.

Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 8 shows a second image forming apparatus according to the present invention.
9 is a diagram showing an embodiment, and FIG. 9 is a diagram showing a partially enlarged cross section of a flexible printed circuit board in the image forming apparatus of FIG. 8. Further, FIG. 10 is a diagram showing potentials applied to respective portions in the cleaning operation of the image forming apparatus of FIG. 8, and FIG. 11 is a diagram showing an example of a waveform of the cleaning voltage.

The image forming apparatus of this embodiment differs from the image forming apparatus of the first embodiment in the following three points in terms of its configuration. Firstly, the apparatus of the first embodiment is provided with the intermediate transfer belt 23, and the toner image is once formed on the belt 23, and then transferred to the sheet S which is an image receiver in the transfer region TR, so that the sheet S is transferred. In contrast to the above-described toner image formation, in the apparatus of this embodiment, as shown in FIG. 8, a sheet conveying belt 26 made of polyurethane, for example, is provided instead of the intermediate transfer belt. Then, the sheet S, which is an image receiving body that is supplied from the cassette 7 through the feed roller 25 and is held on the sheet conveying belt 26, moves along with the movement of the sheet conveying belt 26 in the Y direction.
Image formation is performed while passing an image receiving position between the back electrode 3 and the back electrode 3. That is, the toner T flying from the toner flying start position J directly impacts and adheres to the sheet S,
A toner image is formed on the sheet S. As described above, in this embodiment, the sheet conveying belt 26 functions as a conveying medium, and the rollers 21 and 22 and the sheet conveying belt 26 form the main part of the conveying means of the present invention.

Secondly, the cleaner 24, which is a cleaning unit provided in the above-mentioned conveying means, is provided at a position close to the roller 22, and the cleaner blade 242 causes the toner adhered to the surface of the sheet conveying belt 26. While the toner T is scraped off, the cleaner housing 241 collects the scraped toner T.

The third difference is that, as shown in FIG. 9, a semiconductive layer 49 is provided on the surface 422 of the substrate 42 of the FPC 4 on the back electrode 3 side. The semi-conductive layer 49 is electrically grounded, exhibits an optimum resistance value at a preset temperature (initial setting temperature), and generates a triboelectric charge generated by the flying charged toner T coming into contact with the FPC 4. The FPC 4 is configured so that it can escape from the FPC 4 and effectively prevent the FPC 4 from being charged, and can suppress the influence on the electrostatic transfer field and the deflection electric field.
That is, good print quality can be ensured while the temperature of the semiconductive layer 49 is maintained within the initial set temperature or the allowable temperature range.

Further, the semiconductive layer 49 is made of toner T
The adhesive force of the sheet to the semiconductive layer 49 is
6 is made of a material having a smaller adhesive force with respect to 6, for example, a sheet conveying belt 26 made of polyurethane,
As the semiconductive layer 49, for example, polyimide containing carbon or lead can be used. Since the configuration other than the above is the same as that of the image forming apparatus of the first embodiment shown in FIG. 1, the same components are designated by the same reference numerals and the description thereof will be omitted.

In the image forming apparatus of this embodiment,
The FPC 4 is cleaned as follows.
That is, as shown in FIG. 10, a DC voltage (for example, -200 V) is applied to the developing roller 12 from the developing roller bias generator 103, while the control electrodes 43, L and R are applied.
The deflection electrodes 45L and 45R and the semiconductive layer 49 are grounded. Then, a cleaning voltage V having a rectangular waveform shown in FIG. 11 is applied to the back electrode 3 from the back bias generator 104.
c2 is applied. As this cleaning voltage Vc2,
For example, the peak-to-peak voltage Vpp is 2 kV and the repetition frequency is 3
Since the sheet conveying belt 26 is an insulator, the duty ratio may be 50%, that is, t1 = t2.

By applying such a cleaning voltage Vc2 to the back electrode 3, an alternating electric field is formed between the FPC 4 and the sheet conveying belt 26, and the FPC 4 is the same as in the apparatus of the first embodiment described above. Of the toner T adhered to the surface of the rear electrode 3 side of the
Moves to the sheet conveying belt 26, and cleaning of the FPC 4 is achieved.

The cleaning operation is performed on at least the toner passage hole 41 on the surface of the sheet conveying belt 26.
It is preferable that the sheet S is not held in a portion located between the back electrode 3 and the back electrode 3 and the surface of the sheet conveying belt 26 is exposed. By doing so, the FPC 4 can be cleaned without contaminating the sheet S, and the FPC 4 and the sheet conveying belt 26 having a larger adhesive force than the FPC 4 always face each other during the cleaning operation. The adhered toner can be reliably removed.

Even when a plurality of toner images are continuously formed, the toner is attached to the sheet conveying belt 26 exposed between the plurality of continuously conveyed sheets S and collected. As a result, the FPC 4 is always kept in a state where no toner adheres, and stable toner image formation can be continuously performed.

Also in this embodiment, the developing roller 1
2. The DC potentials of the control electrode 43 and the deflection electrodes 45L and 45R are not limited to the above values, and the applied voltage may be changed or grounded as appropriate. In addition, the back electrode 3 is grounded or fixed to an appropriate DC potential, and the semiconductive layer 49
Alternatively, the cleaning voltage Vc2 may be applied.

Further, in the above-described embodiment, an example in which the sheet conveying belt 26 is used as the conveying medium of the present invention has been described, but the conveying medium is not limited to such a belt, but may be a roller or a drum. May be. Further, in the case where this is made of a conductive material and the output voltage from the back bias generator 104 is applied,
The function as a carrier medium and the function as a back electrode can be provided at the same time, and the number of parts can be reduced and the apparatus can be downsized.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the duty ratio of the cleaning voltage Vc1 is set to 40% in the first embodiment and the duty ratio of the cleaning voltage Vc2 is set to 50% in the second embodiment, but these may be modified as appropriate, for example, as the voltage Vc1. Figure 1
The voltage waveform with the duty ratio of 50% shown in 1 may be used, or the voltage having another duty ratio may be used.

Further, in the first embodiment, the intermediate transfer belt 23 is provided, and the FPC 4 is not provided with the semiconductive layer. In the second embodiment, the sheet conveying belt 2 is used.
6 and the configuration in which the FPC 4 is provided with the semiconductive layer 49 has been described, but the application target of the present invention is not limited to this. For example, in addition to this, the intermediate transfer belt 23 is included. However, the FPC 4 may be provided with a semiconductive layer, or the FPC 4 may be provided with the sheet conveying belt 26 and not provided with the semiconductive layer. Further, not only one side of the FPC 4 but also the toner passage hole 41 may be formed. A semiconductive layer may be provided on the inner wall surface and the surface of the developing roller 12 side.

The materials of the respective members such as the intermediate transfer belt 23, the sheet conveying belt 26, the base 42 of the FPC 4 and the semiconductive layer 49 exemplified in the respective embodiments are not limited to the above but may be used. The adhesive force of the toner to each member may be appropriately changed depending on the property of the toner as long as the relationship defined in the present invention is satisfied.

Further, for example, the voltage applied to the control electrode 43 and the deflection electrodes 45L and 45R is the toner passage hole 41.
In order to prevent the influence of the electric field other than the periphery of F,
When the shield electrode is provided on at least the surface of the PC 4 on the back electrode 3 side, a voltage for cleaning may be applied between the shield electrode and the back electrode 3.

In each of the above embodiments, the deflection electrode 45 is used.
The flying directions of the charged toner T are three directions P by L and 45R.
Although the present invention is applied to an image forming apparatus that can switch between 1, P2, and P3, the application target of the present invention is not limited to this, and an image in which the flight direction of the charged toner T is fixed is used. The present invention can be applied to a forming apparatus.

Furthermore, in each of the above-described embodiments, the present invention is applied to an image forming apparatus that forms an image with one developing device 1, that is, so-called monochromatic printing. However, for example, when forming a full-color image. Is a so-called tandem type color image forming apparatus in which the same developing devices 1 for four types of toners of yellow, magenta, cyan and black are arranged in a line in the conveyance direction Y of the intermediate transfer belt 23 or the sheet S. The present invention can also be applied to it.

[0074]

As described above, according to the present invention, the adhesive force of the toner to the transfer medium or the conveying medium is set to be larger than the adhesive force of the toner to the toner flying control means. The probability of adhering to the medium or the conveying medium side is higher than the probability of adhering to the toner flying control means side, and the transfer medium or the conveying medium and the toner flying control are performed by the force that the charged toner adhering to the toner flying control means receives from the alternating electric field. While the reciprocating motion with the means is repeated, the toner attached to the toner flight control means gradually moves to the transfer medium or the transport medium side, and the toner attached to the toner flight control means is removed. .

By performing the cleaning for removing the toner attached to the toner flying control means in this way, it is possible to stably form an image of good quality in this image forming apparatus.

Even if the toner contains a toner that is charged to the opposite polarity to the original charging polarity, it is effective even if the toner has any charging polarity by applying an alternating electric field. It can be removed from the toner flying control means.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG.

FIG. 3 is a diagram showing a partially enlarged cross section of a flexible printed circuit board and a flying model of charged toner.

FIG. 4 is a diagram showing control electrodes and deflection electrodes formed on a flexible printed circuit board.

5A and 5B are diagrams showing potentials applied to respective portions in a cleaning operation of the image forming apparatus of FIG.

FIG. 6 is a diagram showing an example of a waveform of a cleaning voltage.

FIG. 7 is a schematic diagram showing the behavior of toner during a cleaning operation.

FIG. 8 is a diagram showing a second embodiment of an image forming apparatus according to the present invention.

9 is a diagram showing a partially enlarged cross section of a flexible printed circuit board in the image forming apparatus of FIG.

FIG. 10 is a diagram showing potentials applied to respective parts in a cleaning operation of the image forming apparatus of FIG.

FIG. 11 is a diagram showing another example of the waveform of the cleaning voltage.

[Explanation of symbols]

3 ... Back electrode 4 ... FPC (toner flying control means) 12 ... Developing roller (toner carrier) 23 ... Intermediate transfer belt (transfer medium) 24 ... Cleaner (cleaning section) 26 ... Sheet transport belt (transport medium) 41 ... Toner passage hole 42 ... Base 43 ... Control electrode 49 ... Semi-conductive layer 104 ... Back bias generator (electric field generator) T ... toner Tn ... Negatively charged toner Tp ... Positively charged toner

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C162 AE04 AE12 AE25 AE31 AE47                       AE69 AE92 AH03 AH15 AH20                       AJ05 AJ16 AJ23 CA03 CA12                       CA24 CA25                 2H029 DB00                 2H200 JB23 JB42 JC03 JC12 LB02                       LB08 LB13

Claims (8)

[Claims] 1. A back electrode, a toner carrier that carries a charged toner, moves in a predetermined moving direction, and conveys the toner to a toner flying start position facing the back electrode, and the back electrode. A toner flying control means arranged between the toner carrying body and the toner flying control means for controlling the toner flying from the toner flying start position of the toner carrying body to the back electrode, and between the toner flying control means and the back electrode. A transfer medium for sending a transfer medium to the surface of the toner to temporarily hold the toner image on the surface of the toner, and transfer the toner image to an image receiving body; An electric field generating unit that generates an alternating electric field between the transfer medium and the transfer medium; An image forming apparatus comprising greater than the force. 2. The image forming apparatus according to claim 1, wherein the transfer unit has a cleaning unit that removes toner adhering to the transfer medium from a surface of the transfer medium. 3. A back electrode, a toner carrier that carries a charged toner and moves in a predetermined moving direction to convey the toner to a toner flying start position facing the back electrode, and the back electrode. A toner flying control means which is disposed between the toner carrying body and controls the toner flying from the toner flying start position of the toner carrying body to the back electrode, and a carrier medium which holds an image receiving body, Between the toner flying control means and the carrying medium, a carrying means for sending the flying toner onto the surface of the image receiving body to form a toner image by sending the flying toner between the controlling means and the back electrode. Electric field generating means for generating an alternating electric field, wherein the adhesion force of the toner to the transport medium is larger than the adhesion force of the toner to the toner flying control means. An image forming apparatus. 4. The electric field generating means generates an alternating electric field while a region of the surface of the carrier medium exposed without holding the image receiving body is located between the toner flying control means and the back electrode. The image forming apparatus according to claim 3, wherein the image forming apparatus is configured to: 5. The image forming apparatus according to claim 4, wherein the transport unit has a cleaning unit that removes toner adhering to the transport medium from a surface of the transport medium. 6. The toner flight control means includes a control electrode to which a control voltage for controlling the flight of the toner to the back electrode is applied, and the electric field generation means includes the back electrode and the control electrode. 6. The image forming apparatus according to claim 1, wherein the alternating electric field is generated by applying an alternating voltage between and. 7. A semiconductive layer provided on at least a surface of the toner flying control means facing the back electrode, wherein the electric field generating means is provided between the back electrode and the semiconductive layer. The image forming apparatus according to claim 1, wherein the alternating electric field is generated by applying an alternating voltage. 8. The alternating voltage has a polarity voltage application period in which a force is applied to the charged toner in a direction from the toner flight control unit to the back electrode, and a polarity voltage application period is opposite to the polarity voltage application period. The image forming apparatus according to claim 6, which is long.