JP2003118159A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a toner jet type imaging apparatus in which an image can be formed with a high resolution by suppressing scattering of flying toner. SOLUTION: The center CE of a transfer electrostatic field E is formed in the center of a ring-like control electrode 43 and a toner passing hole 41 is bored at such a position as the center line CA thereof passes through the upstream side (left side of fig. 5 (b)) of the center of electric field CE in the direction D of carrying toner. Toner T1 deviated from toner T flying from a developing roller 12 to the downstream side of the center CE of the transfer electrostatic field E due to inertia in the direction D of carrying toner cannot pass through the toner passing hole 41 and since only toners T3 and T4 flying in the direction parallel with the transfer electrostatic field E fly toward a back electrode 3, flying direction of toner is narrowed down.

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.

[0005]

However, in such a toner-jet type image forming apparatus, since the particle diameter and the charge amount of the toner used are varied, each toner flying by the action of the transfer electrostatic field is dispersed. The flight trajectory is not constant. For this reason, the landing positions of a plurality of toner particles that should converge on one point on the image receptor have spread (scattering) in a certain range, and therefore the size of the smallest dot that can be formed on the image receptor is It depends on the scattering. That is, it can be said that the amount of toner scattering is one of the major factors that determine the resolution of the toner image. Therefore, in order to obtain an image with high resolution, it is desired to establish a technique for suppressing the scattering of the toner that has landed on the image receiver.

The present invention has been made in view of the above problems, and an object thereof is to provide a toner jet type image forming apparatus capable of suppressing the scattering of flying toner and forming an image with a good image quality.

[0007]

In order to achieve the above-mentioned object, an image forming apparatus according to the present invention is a toner which carries a back electrode and a toner and moves in a predetermined moving direction to face the back electrode. The toner carrier that conveys the toner to the flying start position is disposed between the back electrode and the toner carrier to control the toner flying from the toner flying start position of the toner carrier to the back electrode. The toner fly control means for forming a toner image by landing toner on the image receiving body conveyed between the back electrode and the back electrode, and the toner fly control means,
A toner passage hole for passing the toner, and a control electrode provided around the toner passage hole and applied with a control voltage for controlling the flight of the toner from the toner carrier to the back electrode. And a center of an electric field formed in the vicinity of the toner passage hole by a control voltage applied to the control electrode so as to fly the toner carried on the toner carrier toward the back electrode, It is characterized in that it is arranged on the downstream side in the moving direction with respect to the center of the hole (Claim 1).

In such an image forming apparatus, it is desirable that the toner carried on the toner carrier flies straight from the toner flying start position toward the back electrode. But,
According to an experiment by the inventor of the present application, in an actual image forming apparatus,
It has been clarified that the toner flying from the toner carrier contains a large amount of toner flying with a velocity component toward the downstream side (hereinafter simply referred to as “downstream side”) in the toner transport direction. The reason why such a velocity component to the downstream side is generated is that the toner carried by the toner carrier to the toner flying start position has inertia in the carrying direction and the flying velocity before reaching the toner flying start position. It is conceivable that the toner that has started is subjected to a force toward the center of the electric field (which is located on the downstream side of the position where the toner flies) by the transfer electrostatic field. As described above, since the flying toner has a velocity component in the toner conveying direction, the flying locus deviates to the downstream side from the center of the electric field, which is one of the causes of the above-mentioned toner scattering.

Therefore, in the present invention, the geometric center of the opening of the toner passage hole is located upstream of the electric field center of the transfer electrostatic field by the control electrode. Therefore, as described above, the toner that has largely deviated to the downstream side from the center of the electric field cannot pass through the toner passage hole,
It will collide with the surface of the toner flying control means on the side of the toner carrier. By thus restricting the passage of the toner whose flight direction is largely deviated to the downstream side through the toner passage hole, variations in the flight direction of the toner that has passed through the toner passage hole can be suppressed to a low level. An image with high resolution can be formed with less scattering.

By the way, there are variations in the particle size of the toner used in such an image forming apparatus, and those having a relatively small particle size often fly toward the downstream side in this way. In general, a toner having a small particle size has a smaller amount of charge and a smaller force received from the transfer electrostatic field than a toner having a large particle size, so that the velocity component to the downstream side due to inertia with respect to the flight direction of the toner This is because the contribution becomes larger.

When a toner containing a large number of small-diameter toner particles having such flying characteristics is used as it is in a conventional image forming apparatus, the small-diameter toner particles fly away from the center of the electric field toward the downstream side and fly to land on the image receptor. Since the toner adheres, the amount of toner scattered on the image receiver becomes large, the outline of the toner image becomes unclear, and the resolution of the image decreases. for that reason,
In a conventional image forming apparatus, it is necessary to use a toner having a low content of toner particles having a small particle diameter, and as a result, the cost of the toner and the running cost of the apparatus increase.

On the other hand, in the image forming apparatus of the present invention, as described above, the passage of the toner particles largely deviated to the downstream side is restricted, so that the toner having such a small particle diameter is regulated. Even if a large amount of particles are contained, the resolution of the image is not deteriorated by that.

As such a toner, for example, a toner having a particle diameter of 5 μm or less and a content of toner of 10 number% or more may be used (claim 2). By making it possible to use such a toner, it is not necessary to prepare a special toner as described above in the image forming apparatus of the present invention, and therefore, the running cost of the apparatus can be kept low and the toner can be dispersed with a clear toner. Image formation can be performed.

[0014]

1 is a diagram showing an 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 main controller 1
The engine controller 102 controls each part of the developing device 1 in accordance with a signal from 01, so that the two rollers 21,
The toner flies and adheres to the intermediate transfer belt 23 that is stretched around the sheet 22 to form a toner image corresponding to the image signal. Thus, in this embodiment, the intermediate transfer belt 23
Is functioning 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 a charged toner (that is, charged particles for image formation) T, and rotates at a predetermined peripheral speed in a direction D of an arrow in FIG. 1 to face a rear electrode 3 described later (toner). 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.

Further, in this embodiment, in order to control the flying 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 (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. Although the toner passage holes 41 are arranged in one row in this embodiment, they may be arranged in plural rows. The shape of the toner passage hole 41 may be a rectangle as in this embodiment, or may be a square, a circle, an ellipse, or another polygon.

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 (direction Y shown in FIG. 4) orthogonal to the arrangement direction of the toner passage holes 41. The shape of the control electrode 43 is not limited to a rectangle, but may be any shape, and may be, for example, a square, a circle, an ellipse, or another polygon, and is not a complete ring, but a part thereof is missing. It may be one.

Here, as shown in FIG. 4, the toner passage hole 41 is not formed at the center of the ring-shaped control electrode 43, but is formed at a position slightly shifted to the upstream side (downward in FIG. 4). The reason for this will be described later in detail.

On the side of the back electrode 3 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.

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, and an appropriate control voltage is selectively applied according to an opening / closing control signal from the CPU 105 of the engine controller 102, thereby The toner passage hole 41 is opened and closed electrostatically. 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 has a 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) Leftward deflection: Of the deflection electrodes 45L and 45R indicated by 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) Right 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, 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 (see FIG. 3). The spacer 5 spread over the entire length in the vertical direction X) is inserted to the front side of the toner passage hole 41 of the FPC 4, and a part of the spacer 5 is held on the developing roller 12 by the toner layer TL.
The gap GP between the developing roller 12 and the toner passage hole 41 of the FPC 4 is regulated to a constant value by abutting against.

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.

Next, the reason why the toner passage hole 41 and the control electrode 43 are provided in the FPC 4 so that the center of the toner passage hole 41 and the center of the control electrode 43 are displaced from each other will be described with reference to FIG. To do. FIG. 5 is a diagram schematically showing how the toner passes through the toner passage hole in this image forming apparatus. Here, in order to facilitate understanding, a model in which the structure of the apparatus is simplified is used in FIG. 5, and there is no deflection in the toner flight direction, that is, the same voltage is applied to the deflection electrodes 45L and 45R. A case where the toner T is caused to fly straight as indicated by the arrow P1 is described, but the same applies to a case where the toner T is deflected by giving a potential difference between the deflection electrodes 45L and 45R.

Similar to the conventional image forming apparatus described above, also in this image forming apparatus, the toner T starts to fly when the developing roller 12, which is a toner carrier, rotates in the direction D shown in FIG. 5A. It is transported to position J. Then, the control voltage applied to the control electrode 43 separates the developing roller 12 from the developing roller 12 by the force received from the electrostatic transfer field E formed in the vicinity of the toner flying start position J, and starts flying toward the back electrode 3. As described above, some of the flying toner has a velocity component in the downstream direction (to the right in the figure) (reference numeral T in the figure).
1) Such toner T1 does not go straight to the back electrode 3, but flies toward the downstream side as indicated by an arrow D1 shown in FIG.

Here, in this image forming apparatus, as shown in FIG.
As shown in (b), the toner passage hole 41 is formed such that the center line CA of the toner passage hole 41 is slightly displaced from the center of the ring-shaped control electrode 43 to the upstream side (left side in the figure). Has been done. Therefore, the electric field center CE of the transfer electrostatic field E formed at the center of the ring of the control electrode 43 is
The toner passage hole 41 is located slightly downstream of the center line CA (on the right side in the figure). Therefore, as described above, the toner T1 flying while diverging from the electric field center CE to the downstream side does not enter the toner passage hole 41,
It collides with the upper surface of the FPC 4 (reference T4). On the other hand, the toners T2 and T3 flying along the direction of the transfer electrostatic field E are
The toner particles pass through the toner passage hole 41 and fly toward the back electrode 3, and land and adhere to the intermediate transfer belt 23 (FIG. 3) which is an image receiver to form a toner image.

As described above, in this image forming apparatus, the toner passage hole 41 provided in the FPC 4 serving as the toner flying control means is arranged inside the ring-shaped control electrode 43 at a position offset toward the upstream side. , The toner T1 whose flying direction is largely deviated to the downstream side is the toner passage hole 4
1 is restricted, while toners T2 and T3 flying along the direction of the electrostatic field E are allowed to pass through the toner passage hole 41. In this way, the flying direction of the toner T that flies toward the back electrode 3 through the toner passage hole 41 is narrowed down, and the scattering of the toner that has landed on the intermediate transfer belt 23 (FIG. 3), which is an image receiver, is reduced. As a result, a clear toner image with high resolution can be obtained.

The FPC 4 having the function of limiting the toner flying direction can be formed by manufacturing the FPC 4 with the positional relationship between the control electrode 43 and the toner passage hole 41 defined as described above. Therefore, for example, it is not necessary to add any special configuration to the conventional image forming apparatus having a toner passage hole formed in the center of the inside of the control electrode in the configuration of the apparatus and the manufacturing process thereof. It is possible to realize such an excellent function at a device cost comparable to the above.

By the way, as described above, among the toner particles having various particle diameters contained in the toner T, the toner particles having a small diameter are likely to deviate in the downstream direction and fly. Therefore, when the toner containing a large amount of such small-diameter toner particles is used in the conventional image forming apparatus, the toner scattering on the image receiver becomes large and the image quality is deteriorated.

On the other hand, in the image forming apparatus of this embodiment, as described above, since the toner T1 that deviates and flies to the downstream side is restricted from passing through the toner passage hole 41, such a configuration is adopted. Even if a toner containing a large amount of small-sized toner particles is used, it is possible to suppress the scattering of the toner on the image receiver. Therefore, as the toner T, for example, one toner particle having a particle diameter of 5 μm or less, which is not suitable for use in the conventional image forming apparatus, is used.
A toner containing about 0% by number or more may be used. Such a toner can be manufactured at low cost because there are few restrictions on the manufacturing method such as synthesis and classification. By using such a low cost toner, the running cost of the image forming apparatus is reduced. be able to.

Of course, also in this image forming apparatus,
It goes without saying that a toner image having a good image quality can be formed by using a toner having a small content of small-diameter toner particles used in a conventional image forming apparatus. In addition, not only small-diameter toner particles but also toner having a large particle size may fly in such a manner that the toner diverted to the downstream side flies, so even if such toner is used, The effect of suppressing the scattering of the toner on the image receiving body by controlling the passage of the toner that deviates to the side and fly through the toner passage hole 41 can be obtained.

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 toner passage hole 41 and the control electrode 43 may have various shapes and arrangements other than those in the above-described embodiment. However, in the toner transport direction, the toner may fly away from the electric field center of the transfer electrostatic field toward the downstream side. In order to regulate the passage of toner, the center of the toner passage hole is located upstream of the center of the electrostatic transfer field, and all of them are included in the scope of the technical idea of the present invention.

That is, the shape of the toner passage hole 41 is, for example, a square (FIG. 6 (a)), a circle (FIG. 6 (b)), an ellipse (FIG. 6 (c)), or another shape not shown in FIG. Even in this case, the center line of the toner passage hole 41 in the direction Y, which is indicated by the alternate long and short dash line in FIG. The one configured so that the center of the transfer electrostatic field is located on the right side (for example, the mark x shown in FIG.
It is included in the scope of the technical idea of the present invention. Regarding the direction X of the toner passage hole 41, the center of the electric field does not necessarily have to be on the center line, and may be displaced upward or downward in FIG.

Further, for example, in the above embodiment, after the toner image is formed on the transfer medium such as the intermediate transfer belt 23,
The present invention is applied to an intermediate transfer type image forming apparatus that transfers the toner image on the transfer medium to the sheet S. However, the charged toner T flying from the developing device 1 is directly landed on the sheet S to form an image. The present invention may be applied to an image forming apparatus to be formed.

In the above embodiment, the semiconductive layer 49 is used.
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.

Further, 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.
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.

Further, in the above-described embodiment, the present invention is applied to an image forming apparatus for forming an image with one developing device 1, that is, for executing so-called single-color 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.

[0048]

As described above, according to the present invention, among the toners flying from the toner carrier, the toners that have largely deviated to the downstream side in the toner transport direction and fly are restricted from passing through the toner passage holes. Therefore, the dispersion of the flying direction of the toner flying toward the back electrode after passing through the toner passage hole can be suppressed to a low level, and the scattering of the toner on the image receiving body can be reduced to form an image with high resolution.

Further, since a toner containing a large amount of small-diameter toner particles in which the flying direction deviates to the downstream side and is likely to be scattered, it is possible to suppress the manufacturing cost of the toner and reduce the running cost of the apparatus. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing an 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.

FIG. 5 is a diagram schematically showing how toner passes through a toner passage hole in this image forming apparatus.

FIG. 6 is a diagram illustrating another shape of a toner passage hole.

[Explanation of symbols]

3 ... Back electrode 4 ... FPC (toner flying control means) 12 ... Developing roller (toner carrier) 23 ... Intermediate transfer belt (image receptor) 41 ... Toner passage hole 43 ... Control electrode CA ... Center line (of toner passage hole 41) CE ... Electric field center (of transfer electrostatic field E) D: Toner transport direction E ... Transfer electrostatic field J: Toner flight start position T ... toner

Continued front page    F-term (reference) 2C162 AE02 AE25 AE31 AE74 AE81                       AH03 AH12 AJ09 CA02 CA11                       CA12 CA23 CA24                 2H029 DB00

Claims (2)

[Claims] 1. A back electrode, a toner carrier that carries toner while moving in a predetermined moving direction, and transports the toner to a toner flying start position facing the back electrode, the back electrode and the toner. It is arranged between the carrier and
Toner flight control for forming a toner image by landing toner on an image receiver conveyed between the toner carrier and the back electrode by controlling the flight of the toner from the toner flight start position to the back electrode. Further, the toner flight control means is provided around the toner passage hole for passing the toner and the toner passage hole to prevent the toner from flying from the toner carrier to the back electrode. A control electrode to which a control voltage for controlling is applied, and the toner passing hole is controlled by the control voltage applied to the control electrode to fly the toner carried on the toner carrier toward the back electrode. Is configured so that the center of the electric field formed in the vicinity of is located on the downstream side in the moving direction with respect to the center of the toner passage hole. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the content of the toner having a particle diameter of 5 μm or less is 10% by number or more.