JP2003080760A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which a toner image can be formed on an image receiving body with a sufficient image density by preventing toner from standing in a preflight space located between the toner carrier side end part of a toner pass hole and a gap regulating means. SOLUTION: By applying AC electric fields E1 and E2 in a preflight space SP, a developing roller 12 is rotary driven to carry toner T to a toner flight start position J. Even if the toner T at a part of a toner layer TL is separated from the developing roller 12 due to contact with a spacer 5, the toner T is prevented from depositing on an FPC 4 by the AC electric fields E1 and E2 and moved to the downstream side of the developing roller 12 in the rotational direction D. Consequently, the toner T is preventing from standing in the preflight space SP and the image density of a toner image being formed on an intermediate transfer belt 23 can be prevented from lowering.

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 copying paper, transfer paper, copying paper, recording paper by controlling the toner flying from the toner carrier to the back electrode. The present invention relates to an image forming apparatus that forms an image by attaching toner to an image receiving body such as a transfer medium.

[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 / closed by controlling the voltage applied to each control electrode according to an image signal. Corresponding to the 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. By doing so, a toner image corresponding to the image signal is formed on the image receiving body.

In this type of image forming apparatus, in order to stably form a toner image, it is necessary to keep the gap between the toner carrier and the flexible printed circuit board constant.
Therefore, as described in, for example, Japanese Patent No. 3045295, Japanese Patent Laid-Open No. 2000-211180, a spacer (gap defining means) is arranged on the upstream side in the moving direction with respect to the toner flying start position. Therefore, a gap management technique for keeping the above gap constant is proposed. That is, the spacer is arranged so as to contact with the toner layer carried on the toner carrier between the toner regulating blade and the toner flying start position, whereby the gap between the toner carrier and the toner flying control means is provided. Is prescribed.

[0006]

By the way, in the image forming apparatus constructed as described above, the toner layer carried on the toner carrier is conveyed before being conveyed to the toner flying start position by the toner carrier. Since it is always in contact with the spacer, a part of the toner is separated from the toner layer by the contact, and the space between the end of the toner passage hole on the toner carrier side and the spacer (hereinafter referred to as "pre-flight space") is reached. It may stay. As a result, there is a problem that the toner is not sufficiently supplied to the toner flying start position, a sufficient image density cannot be obtained, and the image quality is deteriorated.

The present invention has been made in view of the above problems, and it is sufficient to prevent the toner from staying in the pre-flight space located between the end of the toner passage hole on the toner carrier side and the gap defining means. An object of the present invention is to provide an image forming apparatus capable of forming a toner image on an image receiving body with an image density.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention carries a back electrode and a toner, and moves the toner in a predetermined moving direction at a toner flying start position facing the back electrode. Is provided on the base member so as to surround a toner carrier that conveys the toner, a base member that is disposed between the toner carrier member and the back electrode, and a toner passage hole that is formed through the base member from the toner carrier member to the back electrode. And a control electrode for controlling the flight of toner from the toner carrier to the back electrode to land the toner on the image receiving body conveyed between the back electrode and the substrate to form a toner image. And a gap for defining a gap between the toner carrier and the toner flying control means by contacting the toner layer carried on the toner carrier on the upstream side in the moving direction with respect to the toner flying start position. A fixing means, and an alternating electric field generating means for generating an alternating electric field between the toner carrier and the toner flying control means in the pre-flight space located between the toner carrier side end of the toner passage hole and the gap defining means. Is provided (Claim 1).

In the invention thus constructed, an alternating electric field is generated between the toner carrier and the toner flight control means in the pre-flying space, so that the toner separated from the toner carrier is transferred to the toner flight control means. The toner is transported to the toner flying start position without being accumulated. For this reason, the retention of toner in the pre-flying space is suppressed, and a decrease in image density is prevented.

Here, the alternating electric field generating means applies an alternating voltage between the electrode portion and the electrode portion provided on the base so as to face the toner carrier so as to sandwich the pre-flying space, and between the electrode portion and the toner carrier. And an AC bias generator (claim 2). In this case, the toner carrier and the electrode section are arranged to face each other through the pre-flying space, and an alternating electric field is generated between the toner carrier and the electrode section, that is, the pre-flying space, by the AC voltage applied from the AC bias generator. .

Here, as the electrode portion, a dedicated electrode for generating an alternating electric field may be provided, or a base member facing the toner carrier so as to sandwich a part of the lead wire in the pre-flying space. It may be arranged at the above position to function as an electrode portion (claim 3). In particular, when a part of the lead wire (alternating electrode portion) is made to function as an electrode portion, the control bias generating means for changing the bias applied to the control electrode in accordance with the toner image to be formed on the image receiving body is an AC bias generating portion. Can be made to function, and the device configuration can be simplified. This is because the control bias generating means changes the bias applied to the control electrode according to the toner image as described above, so that the bias is generated between the alternating electrode portion of the lead wire and the toner carrier. This is because the direction of the electric field changes alternately and an alternating electric field is generated in the space before flight.

Further, according to the present invention, the toner carrying member carrying the toner is moved in a predetermined moving direction to convey the toner to a toner flying start position facing the back electrode.
Between the back electrode and the toner flight control means by controlling the toner flight from the toner carrier to the back electrode by means of the toner flight control means arranged between the toner carrier and the back electrode. An image forming apparatus for forming a toner image by landing toner on a conveyed image receiving body, wherein a control bias is generated to change an output bias according to a toner image to be formed on the image receiving body in order to achieve the above object. And a toner passing hole formed through the base from the toner carrier to the back electrode, the base having the toner flying control means disposed between the toner carrier and the back electrode. And a control electrode provided on the base so as to surround the toner carrier and a part of the control electrode facing the toner carrier so as to sandwich the pre-flight space. Its dependent configured to include a lead wire for electrically connecting the control electrode and the control bias generator (claim 4).

In the invention thus constructed, a part of the lead wire faces the toner carrier so as to sandwich the pre-flying space, and the bias is applied to the control electrode from the control bias generating means via the lead wire. Is given. Since this bias changes according to the toner image to be formed on the image receiving body, an alternating electric field is generated between a part of the lead wire and the toner carrier in accordance with the change in the bias. Therefore, the toner separated from the toner carrier is conveyed to the toner flying start position without accumulating on the toner flying control means, and the retention of the toner in the pre-flying space is suppressed and the image density is prevented from lowering.

Further, when the substrate is provided with a plurality of lead wires, the alternating electrode portion of each lead wire is kept insulated from the alternating electrode portion of the adjacent lead wire or the adjacent control electrode before flying. It is desirable that the base be provided so as to overlap in the width direction in the space (claim 5).
With such a configuration, an alternating electric field is generated over the entire width direction in the pre-flight space, and toner retention in the pre-flight space can be suppressed evenly, and uneven image density in the width direction can be suppressed. The toner image can be formed on the image receptor with better quality.

[0015]

1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. 2 is shown in FIG.
3 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 102 is responsive to the signal from the main controller 101.
Controls each part of the developing device 1 so that the two rollers 2
Toner is ejected to and adheres to the intermediate transfer belt 23 that is stretched around the first and second toner particles 22 to form a toner image corresponding to the image signal. Thus, in this embodiment, the intermediate transfer belt 2
3 functions as an image receiver.

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. The back bias generator 104 provided in the engine controller 102
Therefore, a DC voltage higher than the voltage applied to the developing roller 12 is applied, and a transfer electrostatic field for transferring the charged toner T toward the back electrode 3 is applied between the developing roller 12 and the back electrode 3. Has been formed. For this reason, the charged electrostatic toner T at the toner flying start position J is generated by the transfer electrostatic field.
Flies from the developing roller 12 toward the back electrode 3 and is deposited and attached to the surface of the intermediate transfer belt 23 that functions as an image receiver.

In this embodiment, a flexible printed circuit board (hereinafter referred to as FPC) 4 is provided between the developing roller 12 and the back electrode 3 in order to control the flight of the charged toner T onto the intermediate transfer belt 23. 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 lead wires 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.

Further, on the side of the developing roller 12 of the base 42, a control electrode 43 is formed in a ring shape 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 and further to the upstream side (-D) of the rotation direction D of the developing roller 12 (corresponding to the moving direction of the invention).
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 side of the back electrode 3 of the base 42,
A pair of deflection electrodes 45L, 4 is provided for each toner passage hole 41.
5R is provided so as to be obliquely opposed to the conveyance direction Y of the intermediate transfer belt 23 (direction orthogonal to the toner passage hole array).

Although not shown in FIGS. 3 and 4, the substrate 42 includes a control bias generator 47 (FIG. 2) and an L deflection bias generator 48L (FIG. 2), which are high voltage driver ICs and the like. And R deflection bias generator 48
R (FIG. 2) is provided. Of these, the control bias generator 47 is electrically connected to each control electrode 43 by each lead wire 44, and the engine controller 102
An appropriate voltage is selectively applied according to the opening / closing control signal from the CPU 105 to electrostatically open / close the toner passage hole 41. That is, for each control electrode 43, the charged toner T is ejected from the developing roller 12, passes through the toner passage hole 41, and is ejected toward the back electrode 3, so that the toner is between the developing roller 12 and the back electrode 3. It exposes the transfer electrostatic field passing through the passage hole 41 and limits the exposure.

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 is 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 of the deflection electrode 45L on the right side of the conveyance direction Y of the intermediate transfer belt 23 as a reference. Deflection electrode 45 arranged
When a voltage relatively higher than R is applied, the charged toner T, which is negatively charged, as shown by 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 arranged on the right side of the toner passage hole 41 on the left side of the deflection electrode 45R arranged on the right side of the conveyance direction Y of the intermediate transfer belt 23 is used as a reference. Deflection electrode 45 arranged
When a voltage relatively higher than L is applied, the negatively charged toner T is charged by the static toner for deflection generated 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, while changing the flying direction of the charged toner T to three directions, 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.

In the base 42 of the FPC 4, the developing roller 12
On the surface 421 on the side and the surface 422 on the side of the back electrode 3, a semiconductive layer 49 for antistatic is formed and a ground potential is given. These semi-conductive layers 4
Reference numeral 9 indicates an optimum resistance value at a preset temperature (initial setting temperature). The frictional charge generated when the charged toner T flying as described above comes into contact with the FPC 4 is indicated by the FPC 4
The FPC 4 can be effectively prevented from being discharged from the above, and the influence on the electrostatic transfer field and the deflection electric field can be suppressed. 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, 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, that is, the width direction. The spacer 5 spread over the entire length of X is the toner passage hole 41 of the FPC 4.
The toner layer T, which is inserted on the front side in the rotation direction D with respect to the developing roller 12, has a part of the spacer 5 carried on the developing roller 12.
By making contact with L, the gap GP between the developing roller 12 and the toner passage hole 41 of the FPC 4 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. Applies a control signal corresponding to the image signal to the control bias generation unit 47, the L deflection bias generation unit 48L and the R deflection bias generation unit 48R to cause the toner T to fly and adhere onto the intermediate transfer belt 23 to correspond to the image signal. The formed toner image is formed. Then, the toner image is transferred onto a sheet S such as a copy sheet, a transfer sheet, and an OHP transparent sheet taken out from the cassette 7 in a predetermined transfer region TR. Further, the sheet S on which the image is thus formed is conveyed to the discharge tray (not shown) via the fixing unit 8.

By the way, the gap management technique is adopted also in this embodiment, that is, the spacer 5 is provided on the upstream side of the toner flying start position J in the rotation direction D of the developing roller 12 (corresponding to the moving direction of the present invention). As a result, the gap GP between the developing roller 12 and the toner passage hole 41 of the FPC 4 is regulated to a constant value. Therefore, like the conventional device, when the toner layer TL contacts the spacer 5, the toner T separates from the developing roller 12 and is located between the developing roller side end 41 a of the toner passage hole 41 and the spacer 5. There is a possibility of staying in the pre-flight space SP. Therefore, in this embodiment, the lead wire 44 is extended to the upstream side (−D) in the rotation direction D of the developing roller 12 as described above, thereby suppressing the retention of the toner in the pre-flying space SP. Hereinafter, the configuration and the operation effect will be described in detail.

As a result of various verifications by the present inventor, most of the toner staying in the pre-flying space SP has a polarity opposite to the polarity of the toner originally used to form a toner image (negative electrode in this embodiment). It was found that the toner was a toner of No. 1 (positively charged toner in this embodiment), and the amount of charge was very small. That is, with respect to the staying toner, the reverse polarity toner that easily spills from the developing roller 12 is dominant, and since the image force with the developing roller 12 is weak, it easily separates from the developing roller 12 by contact with the spacer 5. It is considered that it will be deposited on the FPC 4.

Therefore, in the present embodiment, the lead wire 44 is extended to the upstream side (-D) in the rotation direction D of the developing roller 12 as described above, so that a part 4 of the lead wire 44 is formed.
4a (FIGS. 3 and 4) is provided on the base 42 so as to face the developing roller 12 with the pre-flying space SP interposed therebetween. In this image forming apparatus, in order to form a desired toner image on the intermediate transfer belt 23, when the control bias generator 47 turns on the control electrode 43 via the lead wire 44 in accordance with the opening / closing control signal (toner is caused to fly). Voltage) or an OFF voltage (when the toner is not caused to fly) is applied, but the lead wire 44 is changed by the voltage that changes according to the open / close control signal.
An alternating electric field is generated between the part 44a of the sheet and the developing roller 12. That is, a relatively high positive voltage, for example, a voltage of about 300V is applied to the control electrode 43 via the lead wire 44 in order to cause the toner T to fly to the intermediate transfer belt 23 at a certain timing. An electric field E1 is generated at SP. On the other hand, at a different timing, in order to prohibit the toner T from flying onto the intermediate transfer belt 23, a negative voltage, for example, -50V is applied to the control electrode 43 via the lead wire 44.
A voltage of about a certain degree is applied, but at this time, an electric field E2 opposite to the electric field E1 is generated in the pre-flight space SP. As described above, in this embodiment, the part 44a of the lead wire 44 corresponds to the "alternating electrode portion" of the present invention, and functions as the "electrode portion" of the present invention, and the alternating electric field E1 in the pre-flight space SP. ，
E2 is generated.

As described above, in this embodiment, while the alternating electric fields E1 and E2 are applied in the pre-flying space SP, the developing roller 12 is rotationally driven to carry the toner T and is conveyed to the toner flying start position J. There is. Therefore, even if a part of the toner T in the toner layer TL separates from the developing roller 12 due to the contact with the spacer 5, the toner T is not deposited on the FPC 4 by the alternating electric fields E1 and E2, and the developing roller 12 does not. Moving toward the downstream side (+ D) in the rotation direction D of. As a result, the retention of the toner T in the pre-flight space SP is suppressed, and the image density of the toner image formed on the intermediate transfer belt 23 can be prevented from lowering.

Further, in this embodiment, the lead wire 44 not only plays a role of electrically connecting the control bias generator 47 and the control electrode 43, but also functions as an electrode portion, and the control bias generator 47. Not only generates a bias voltage for controlling the toner flight, but also the electrode portion (the alternating electrode portion 44a of the lead wire 44) and the developing roller 1.
Since it also functions as an AC bias generator that applies an AC voltage between the two and generate alternating electric fields E1 and E2, an electrode portion and an AC bias generator are separately provided as in the second embodiment described later. It is possible to provide at low cost an image forming apparatus that can form a toner image on the intermediate transfer belt 23 with sufficient image density without the need.

In the first embodiment, the lead wire 44
Is extended in parallel with the rotation direction D of the developing roller 12, the lead wire 44 may be provided so as to be inclined with respect to the rotation direction D as shown in FIG. The region formed is wider, which is more preferable. That is, when the lead wire 44 is provided parallel to the rotation direction D of the developing roller 12 as shown in FIG. 4, the area in the pre-flying space SP where the alternating electric field is formed is limited to the width of the lead wire 44. , A region where the effect of the alternating electric field extends and a region where the effect is difficult are formed in the width direction X. On the other hand, in the improved embodiment shown in FIG. 5, since the lead wire 44 is arranged so as to be inclined with respect to the rotation direction D, the region R44 in which the effect of the alternating electric field is extended in the width direction X is widened to the pre-flight space SP. The retention of the toner T can be suppressed more effectively.

Here, since a part of the control electrode 43 exists in the pre-flight space SP, the effect of the alternating electric field is exerted in the range of the region R43 in FIG. Therefore, as shown in the figure, when the alternating electrode portions 44a of the lead wires 44 are provided so as to overlap the adjacent control electrodes 43 in the width direction X in the pre-flight space SP in the width direction X, a region R43 is formed.
And the region R44 overlap each other, an alternating electric field is generated over the entire width direction X in the pre-flying space SP, and toner retention in the pre-flying space SP can be uniformly suppressed, and unevenness in image density in the width direction X can be suppressed. A toner image can be formed on the intermediate transfer belt 23 with better quality.

Further, in the first embodiment (FIG. 4) and the improved embodiment (FIG. 5), the alternating electrode portion 4 of the lead wire 44 is formed.
Although 4a has a line shape that extends straight in a plan view, the shape is arbitrary, and may be finished in a cross shape in a plan view as shown in FIG. 6, for example.
By finishing the shape to have a spread, the range of the alternating electric field in the width direction X is expanded, and the retention of the toner T in the pre-flying space SP can be suppressed more effectively.

Further, it is desirable that each alternating electrode portion 44a is provided so as to overlap the alternating electrode portion 44a of the adjacent lead wire 44 in the width direction X in the pre-flight space SP. The reason is the same as in the case of the improved embodiment (FIG. 5) described above. That is, in the improved embodiment shown in FIG.
Since the adjacent alternating electrode portions 44a overlap each other in the width direction X, the region R44 in which the effect of the alternating electric field extends in the width direction by providing each alternating electrode portion 44a.
It is possible to more effectively suppress the retention of the toner T in the pre-flight space SP by overlapping each other.

Further, in the first embodiment (FIG. 4) and the improved embodiment (FIGS. 5 and 6), the lead wire 44 with respect to the control electrode 43 is in the (-D) direction or in the (-D) direction. Is extended to the spacer 5 side while being inclined, the control electrode 43 is formed as shown in FIG. 7, FIG. 8 or FIG.
In order to electrically connect the lead wire 44 to the control bias generator 47, the lead wire 44 is connected to the downstream side (+
D) may be extended. In this case, a part 44a of the lead wire 44 is extended to the spacer 5 side beyond the control electrode 43 so that the first embodiment (FIG. 4) or the improved embodiment described above. The same operation and effect as (FIGS. 5 and 6) can be obtained.

FIG. 10 is a diagram showing a second embodiment of the image forming apparatus according to the present invention. 11 is a block diagram showing the electrical configuration of the image forming apparatus of FIG. This image forming apparatus is provided with a dedicated alternating electric field generating means for forming an alternating electric field in the pre-flight space SP, and thus a part of the lead wire 44 (alternating electrode portion) 44a and the control bias generating portion 47 are provided. This is largely different from the first embodiment, which is used not only for toner flight control but also as an alternating electric field generating means. That is, in the second embodiment, the lead wire 44 is connected to the downstream side (+ D) in the rotation direction D of the developing roller 12.
The lead wire 44 is not extended at a position corresponding to the pre-flight space SP, but an electrode portion 40 is arranged instead of the lead wire 44. The electrode portion 40 and the developing roller are arranged. There is a pre-flight space SP at 12. An AC bias generator 106 is electrically connected to the electrode unit 40. By applying an AC voltage to the electrode unit 40, an alternating electric field is generated between the electrode unit 40 and the developing roller 12 to which the DC voltage is applied. Is configured to occur.

As described above, in the second embodiment, the electrode portion 4
0 and the AC bias generator 106 constitute an alternating electric field generating means, and by operating the AC bias generator 106 at an appropriate timing, the developing roller 12 is rotationally driven while giving an alternating electric field in the pre-flying space SP. Then, when the toner T is carried and conveyed to the toner flying start position J, the pre-flying space SP is provided, as in the first embodiment.
Of the toner T on the intermediate transfer belt 23
It is possible to prevent the image density of the toner image formed above from being lowered.

Further, according to the second embodiment, since the dedicated electrode portion 40 is provided for generating the alternating electric field,
An alternating electric field can be applied to the entire pre-flight space SP,
The application area of the alternating electric field is the alternating electrode portion 44 of the lead wire 44.
The retention of the toner T in the pre-flight space SP can be more reliably suppressed as compared with the first embodiment in which the area corresponding to a is limited.

Furthermore, in the first embodiment, since the control bias generator 47 functions as the "AC bias generator" of the present invention as described above, the timing at which the direction of the electric field in the pre-flight space SP switches is the image signal. Therefore, the alternating electric field suitable for suppressing the retention of the toner T is not always applied to the pre-flying space SP. On the other hand, in the second embodiment, by providing the exclusive AC bias generator 106, an alternating electric field suitable for suppressing the retention of the toner T can be always applied to the pre-flying space SP. Also, it is advantageous in more reliably suppressing the retention of the toner T in the pre-flying space SP.

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, in the above embodiment, the present invention is applied to an intermediate transfer type image forming apparatus that forms a toner image on a transfer medium such as the intermediate transfer belt 23 and then transfers the toner image on the transfer medium to the sheet S. However, the present invention may be applied to an image forming apparatus in which the charged toner T flying from the developing unit 1 is directly landed on the sheet S to form an image.

Further, in the above embodiment, the semiconductive layer 49.
The present invention is applied to an image forming apparatus in which the FPC 4 is provided with antistatic property, but the application target of the present invention is not limited to this, and an antistatic semiconductive layer is provided. The present invention can be applied to an image forming apparatus which is not provided.

In the above embodiment, the deflection electrode 45 is used.
The flying directions of the charged toner T are three directions P by L and 45R.
The present invention is applied to an image forming apparatus capable of switching to 1, P2, and P3, but 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 provided. The present invention can be applied to a forming apparatus.

Further, in the above embodiment, the developing roller 12
Although a predetermined DC voltage is applied from the developing roller bias generation unit 103, it may be grounded or an AC voltage may be applied.

Furthermore, in the above-described embodiment, the present invention is applied to an image forming apparatus which forms an image with one developing device 1, that is, which executes so-called monochromatic printing. However, in the case of forming a full-color image, for example. In contrast to 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, However, the present invention can be applied.

[0053]

As described above, according to the present invention, the alternating electric field is generated between the toner carrier and the toner flying control means in the pre-flight space.
By abutting the gap defining means, the toner separated from the toner carrier can be conveyed to the toner flying start position without being deposited on the toner flying control means. As a result, it is possible to prevent the toner from staying in the pre-flying space, prevent a decrease in image density, and form a toner image on the image receiving body with a sufficient image density.

[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.

3 is a diagram showing a partially enlarged cross section of a flexible printed circuit board used in the image forming apparatus of FIG. 1 and a flying model of charged toner.

FIG. 4 is a view showing control electrodes and lead wires formed on a flexible printed circuit board.

FIG. 5 is a diagram showing an improved form of the first embodiment.

FIG. 6 is a diagram showing another improvement of the first embodiment.

FIG. 7 is a diagram showing another improvement of the first embodiment.

FIG. 8 is a diagram showing still another improvement of the first embodiment.

FIG. 9 is a view showing still another improved mode of the first embodiment.

FIG. 10 is a diagram showing a second embodiment of an image forming apparatus according to the present invention.

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

[Explanation of symbols]

3 ... Back electrode 4 ... FPC (toner flying control means) 5 ... Spacer (gap defining means) 12 ... Developing roller (toner carrier) 23 ... Intermediate transfer belt (image receptor) 40 ... Electrode part 41 ... Toner passage hole 41a ... Edge of developing roller (toner passage hole 41) 42 ... Base 43 ... Control electrode 44 ... Lead wire 44a ... Alternating electric field region 47 ... Control bias generator 106 ... AC bias generator D ... Rotation direction (of the developing roller 12) GP ... Gap J: Toner flight start position SP: Space before flight T ... toner TL ... toner layer X ... Width direction

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C162 AE04 AE09 AE25 AE31 AE89                       AF02 AF70 AF71 AH03 AH12                       AH23 AH29 AJ02 AJ05 AJ07                       AJ10 AJ21                 2H029 DB04

Claims (5)

[Claims] 1. A back electrode, a toner carrier that carries a toner and moves in a predetermined moving direction to convey the toner to a toner flying start position facing the back electrode, the toner carrier and the toner carrier. A substrate disposed between the back electrode and a control electrode provided on the substrate so as to surround a toner passage hole formed through the substrate from the toner carrier to the back electrode, A toner flight control means for forming a toner image by landing toner on an image receiving body conveyed between the back electrode and the base by controlling the flight of toner from the toner carrier to the back electrode; The gap between the toner carrier and the toner flying control means is defined by contacting the toner layer carried on the toner carrier on the upstream side in the moving direction with respect to the toner flying start position. In the space before the flight, which is located between the gap defining means and the toner carrying body side end of the toner passage hole and the gap defining means, an alternating electric field is applied between the toner carrying body and the toner flying control means. An image forming apparatus comprising: an alternating electric field generating means for generating the alternating electric field. 2. The alternating electric field generating means includes an electrode portion provided on the base so as to face the toner carrier so as to sandwich the pre-flying space, and between the electrode portion and the toner carrier. The image forming apparatus according to claim 1, further comprising an AC bias generator that applies an AC voltage. 3. A control bias generation unit that changes a bias applied to the control electrode in accordance with a toner image to be formed on the image receiving body, wherein the toner fly control unit includes the control bias generation unit and the control electrode. And a lead wire for electrically connecting to each other, and a part of the lead wire is arranged on the base so as to face the toner carrier so as to sandwich the pre-flying space, and functions as the electrode portion. The image forming apparatus according to claim 2, wherein the control bias generating unit functions as the AC bias generating unit. 4. A toner carrying member carrying a toner is moved in a predetermined moving direction to convey the toner to a toner flying start position facing the back electrode, and between the toner carrying member and the back electrode. By controlling the toner flight from the toner carrier to the back electrode by the toner flight control means arranged, the toner is made to land on the image receiving body conveyed between the back electrode and the toner flight control means. In an image forming apparatus for forming an image, a control bias generating unit that changes an output bias according to a toner image to be formed on the image receiving body is provided, and the toner flying control unit includes a toner carrier and a back electrode. The base disposed so as to surround the toner passing hole formed through the base from the toner carrier to the back electrode. And a control electrode provided on the base, and a part of which faces the toner carrier so as to sandwich the pre-flying space, and is electrically connected to the control bias generating means and the control electrode. An image forming apparatus, comprising: 5. A plurality of toner passage holes are formed in a row in the width direction substantially orthogonal to the moving direction in the base, and the control electrode is provided for each toner passage hole and The image forming apparatus according to claim 3 or 4, wherein the control electrode is electrically connected to the control bias generating means by the lead wire, when a portion of each lead wire that functions as the electrode portion is an alternating electrode portion. The image provided on the base body so that the alternating electrode portion of each lead wire overlaps with the alternating electrode portion of the adjacent lead wire or the adjacent control electrode in the width direction in the pre-flight space while maintaining an insulating state. Forming equipment.