JP3823788B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, an image receiving body such as copying paper, transfer paper, copy paper, recording paper, and transfer medium by controlling toner flying from a toner carrier to a back electrode. The present invention relates to an image forming apparatus that forms an image by attaching toner to the toner.
[0002]
[Prior art]
As an image forming method using toner, a jumping method and a projection method are most widely used. In this type of image forming method, an electrostatic latent image corresponding to an image is formed on a photosensitive member, and toner as an image forming agent is attached to the electrostatic latent image on the photosensitive member from a toner carrier such as a developing roller. After the toner image is obtained, the toner image is transferred to copy paper, transfer paper, copy paper, recording paper, and the like. However, these image forming methods require a process (photosensitive process) for forming an electrostatic latent image on the surface of the photosensitive member, which includes problems that the apparatus configuration is complicated, and the apparatus cost and running cost are high. Yes. Therefore, in recent years, as described in U.S. Pat. Nos. 3,689,935, 5,036,341, and Japanese Translation of PCT International Publication No. 2001-505146, toner is applied to copy paper, recording paper, and intermediate paper by the action of an electric field. An image forming apparatus of a so-called “toner jet (registered trademark)” type that forms an image by flying on an image receiving member such as a transfer belt has attracted attention.
[0003]
In this image forming apparatus, a toner carrier such as a developing roller that carries toner in a predetermined moving direction while carrying toner is provided, and a toner regulating blade is provided so as to contact the surface of the toner carrier. For this reason, 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 flight start position facing the back electrode.
[0004]
In this image forming apparatus, a flexible printed circuit having a plurality of toner passage holes for allowing charged toner to pass therethrough is disposed between the toner carrier and the back electrode. An image receiver such as a recording paper or a transfer medium is disposed between the flexible printed circuit board and the back electrode. 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. Further, 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 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. By doing so, a toner image corresponding to the image signal is formed on the image receiver.
[0005]
[Problems to be solved by the invention]
By the way, in the image forming apparatus configured as described above, not all of the toner transported to the toner flying start position by the movement of the toner carrier flies, and the toner that has not flew may pass through the flying start position. It remains carried on the toner carrier. If the toner thus charged remains on the toner carrying member, the next new toner layer formation is hindered. Therefore, these toners are scraped off once and collected, and are again used for toner layer formation. .
[0006]
However, since a bias voltage is applied to the toner carrying member to attract the charged toner, it is necessary to provide a cleaning member such as a blade or a rotating brush in order to scrape off the toner reliably. Since the member serves as a resistance against the movement of the toner carrier, the burden on the motor or the like for driving the toner carrier increases, resulting in an increase in the cost of the apparatus.
[0007]
Further, by repeating the collection and reuse of charged toner, the amount of charged toner mixed into unused toner gradually increases, so that a uniformly charged toner layer is stably formed on the toner carrier. It becomes difficult.
[0008]
The present invention has been made in view of the above problems, and provides an image forming apparatus capable of stably forming a uniform toner layer by removing the charge of the toner remaining on the toner carrier and obtaining good image quality. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention achieves the above-described object, and a toner carrying body that carries a toner to a toner flying start position that moves in a predetermined movement direction and faces the back electrode while carrying the back electrode and charged toner. A regulating blade for regulating the thickness and charge amount of the toner carried on the toner carrying body upstream of the toner flying start position in the moving direction, and the back electrode and the toner carrying body The toner is landed on the image receiving body which is disposed between and is transported between the back electrode by controlling the toner flying from the toner flying start position of the toner carrying body to the back electrode, thereby forming a toner image. A toner flying control means to be formed, and sandwiched between the toner carrier and the toner flying control means on the downstream side in the moving direction with respect to the toner flying start position, And a neutralizing member that defines a gap between the toner carrier and the toner flying control means, and neutralizes the charge of the toner that forms the toner layer in contact with the toner layer carried on the toner carrier. (Claim 1).
[0010]
In the invention configured as described above, the toner that did not fly at the toner flying start position loses electric charge by being brought into contact with the charge removing member provided on the downstream side from the toner flying start position, and is discharged. The toner thus neutralized does not generate an attractive force due to the Coulomb force with the toner carrying member, so that it is easy to peel off from the toner carrying member, and does not hinder the formation of a new toner layer on the toner carrying member. Mixing of the charged toner into the used toner can be suppressed. Therefore, a uniform toner layer is always formed on the toner carrier, and good image quality can be obtained. In addition, since the neutralizing member also has a function as a gap defining unit that keeps the gap between the toner carrier and the toner flight control unit constant, a uniform toner layer can be always formed on the toner carrier, Since the gap can be kept constant, more stable image formation can be performed. In addition, it is not necessary to separately provide the gap defining means and the charge eliminating member, and the apparatus configuration is simplified.
[0011]
Here, when the toner is a positively charged toner that is positively charged, the charge removal member may be formed of a material having a work function smaller than the work function of the toner. At this time, the electrons move to the toner side having a larger work function, that is, easily charged negatively, so that the electrons move from the discharging member to the charged toner by friction between the toner layer and the discharging member, and the positively charged toner The toner is neutralized and the toner is neutralized.
[0012]
On the other hand, when the toner is a negatively charged toner that is negatively charged, the neutralizing member may be formed of a material having a work function larger than that of the toner. By doing so, contrary to the above, the electron transfer from the charged toner to the charge removal member occurs due to the friction between the toner layer and the charge removal member, so that the charge of the negatively charged toner is neutralized. .
[0013]
The charge removal member may be formed of a conductive material, and may further include a voltage application unit that applies a DC voltage for discharging the toner between the toner carrier and the charge removal member. Item 4). In the invention thus configured, a voltage for removing the charge of the toner is applied between the toner carrier and the charge removal member, and the charge removal member and the toner layer are brought into contact with each other, whereby the toner and the charge removal member are brought into contact with each other. Charge transfer between the toners occurs and the charge of the toner is neutralized. For example, when the toner is a negatively charged toner that is negatively charged, the negative charge accumulated in the charged toner moves to the high potential neutralization member by applying a voltage that causes the neutralization member to have a high potential from the toner carrier. Then, the toner is discharged.
[0014]
In addition, by providing a regulating blade upstream of the toner flying start position in the toner carrier moving direction, the charge amount and thickness of the toner reaching the toner flying start position can be kept constant, so that the stable Image formation can be performed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
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. 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 controls each part of the developing device 1 in accordance with the signal from the main controller 101. As a result, the toner flies and adheres to the intermediate transfer belt 23 stretched around the two rollers 21 and 22 to form a toner image corresponding to the image signal. Thus, in this embodiment, the intermediate transfer belt 23 functions as an image receiver.
[0016]
In the developing device 1, toner T as a developer is stored in a housing 11, and a developing roller 12, a supply roller 13, and a regulating blade 14 are accommodated. The developing roller 12 carries charged toner (that is, charged particles for image formation) T, and rotates at a predetermined peripheral speed in the arrow direction D of FIG. The toner carrying member conveyed to the flight start position (J). The developing roller 12 is formed in a cylindrical shape from a metal or alloy such as aluminum or iron, and a DC voltage is applied from a developing roller bias generator 103 provided in the engine controller 102.
[0017]
The supply roller 13 is in contact with the outer peripheral surface of the developing roller 12 and rotates in the opposite direction to the developing roller 12 to supply the toner T to the developing roller 12 and to drop excess toner T from the developing roller 12. Is. The supply roller 13 is made of, for example, a synthetic rubber such as urethane sponge wound around a metal core, and has a function of charging the toner T to a predetermined polarity by frictional contact with the developing roller 12. In the present embodiment, the following description will be made assuming that the toner T is negatively charged.
[0018]
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 due to friction with the developing roller 12. The amount of the toner T carried on the toner 12 is regulated. More specifically, the regulating blade 14 is configured by attaching an elastic member 142 to the other end of the plate-shaped metal piece 141 whose one end is fixed to the housing 11, and the elastic member 142 is an outer periphery of the developing roller 12. It abuts against the surface and regulates the toner T.
[0019]
A back electrode 3 is disposed opposite to the developing roller 12. More specifically, as shown in FIG. 1, the back electrode 3 is disposed on the opposite side of the developing roller 12 with the intermediate transfer belt 23 interposed therebetween. A DC voltage higher than the voltage applied to the developing roller 12 is applied from the back bias generation unit 104 provided in the engine controller 102, and the charged toner T is applied between the developing roller 12 and the back electrode 3. A transfer electrostatic field for transfer toward the back electrode 3 is formed. For this reason, this charged electrostatic field causes the charged toner T to fly from the developing roller 12 toward the back electrode 3 at the toner flying start position J and land on and adhere to the surface of the intermediate transfer belt 23 that functions as an image receiver.
[0020]
In this embodiment, a flexible printed circuit board (hereinafter referred to as FPC) 4 is disposed between the developing roller 12 and the back electrode 3 in order to control the flying of the charged toner T to the intermediate transfer belt 23. Yes. Hereinafter, the configuration and operation of the FPC 4 will be described with reference to FIGS. 3 and 4.
[0021]
FIG. 3 is a diagram showing a partially enlarged cross section of the flexible printed circuit board and a flying model of charged toner. FIG. 4 is a diagram showing control electrodes and deflection electrodes formed on the flexible printed circuit board. In this FPC 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. In FIG. 3, only one toner passage hole 41 is shown. However, in this embodiment, a plurality of toner passage holes 41 are provided in a line at equal intervals in the vertical direction of FIG. 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 row, but may be provided in a plurality of rows. The shape of the toner passage hole 41 may be circular as in this embodiment, or may be oval or polygonal.
[0022]
A control electrode 43 is formed in a ring shape on the developing roller 12 side of the base 42 so as to surround each toner passage hole 41. A lead wire 44 extends from each control electrode 43 in a direction perpendicular to the arrangement direction of the toner passage holes 41. Note that the shape of the control electrode 43 is not limited to a circular shape, and is arbitrary. For example, the control electrode 43 may be an elliptical shape or a polygonal shape. .
[0023]
Further, on the back electrode 3 side of the base 42, for each toner passage hole 41, a pair of deflection electrodes 45L and 45R are transported in the intermediate transfer belt 23 (direction perpendicular to the toner passage hole row) as shown in FIG. The lead wires 46L and 46R extend from the deflection electrodes 45L and 45R, respectively, so as to be diagonally opposed to Y.
[0024]
Although not shown in FIGS. 3 and 4, the base 42 is provided with a control bias generator 47 (FIG. 2), an L deflection bias generator 48 L (FIG. 2), and an R deflection composed of a high voltage driver IC or the like. A bias generator 48R (FIG. 2) is provided. Among these, the control bias generator 47 is electrically connected to each control electrode 43, and an appropriate voltage is selectively applied according to an open / close control signal from the CPU 105 of the engine controller 102, whereby the toner is The passage hole 41 is electrostatically opened and closed. That is, for each control electrode 43, the toner between the developing roller 12 and the back electrode 3 so that the charged toner T jumps out of the developing roller 12, passes through the toner passage hole 41 and flies toward the back electrode 3. The transfer electrostatic field passing through the passage hole 41 is exposed, and the exposure is limited.
[0025]
Further, 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, and corresponds to the deflection control signal from the engine controller 102. By selectively applying appropriate voltages to the deflection electrodes 45L and 45R, the flying direction of the charged toner T is switched to the following three directions.
[0026]
(1) No deflection: arrow P1 in FIG.
When the same voltage is applied to both the deflection electrodes 45L and 45R, the charged toner T passes straight through the toner passage hole 41 as shown by an arrow P1 in FIG. 3, and passes through the toner on the intermediate transfer belt 23. Fly to a position corresponding to the hole 41.
[0027]
(2) Left deflection: arrow P2 in FIG.
A voltage higher than the deflection electrode 45R arranged on the right side is applied to the deflection electrode 45L arranged on the left side of the toner passage hole 41 with respect to the conveyance direction Y of the intermediate transfer belt 23 as a reference. In this case, the charged toner T charged to the negative polarity is deflected to the left side by an electrostatic field for deflection generated between the electrodes 45L and 45R, as indicated by an arrow P2 in FIG.
[0028]
(3) Right deflection: arrow P3 in FIG.
A voltage higher than the deflection electrode 45L arranged on the left side is applied to the deflection electrode 45R arranged on the right side of the toner passage hole 41 with respect to the conveyance direction Y of the intermediate transfer belt 23 as a reference among the deflection electrodes 45L and 45R. In this case, the negatively charged charged toner T is deflected to the right side by a deflecting electrostatic field generated between the electrodes 45L and 45R as indicated by an arrow P3 in FIG.
[0029]
Thus, in this embodiment, 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 while switching the flying direction of the charged toner T to three directions. .
[0030]
However, as described above, the deflection electrodes 45L and 45R are disposed opposite to each other in the oblique direction with respect to the conveyance direction Y of the intermediate transfer belt 23, so that (1) no deflection, (2) left deflection, and (3) right deflection. With these three modes, when the intermediate transfer belt 23 is stopped, three dots arranged linearly obliquely with respect to the transport direction Y of the intermediate transfer belt 23 are formed on the intermediate transfer belt 23. In this case, by determining the transport speed so that the intermediate transfer belt 23 is transported by the shift amount (distance) of adjacent dots in the period (time) of hitting the dots, the three dots are transferred to the intermediate transfer belt 23. They can be arranged linearly in a direction orthogonal to the transport direction Y. Therefore, three dots can be formed by one toner passage hole 41, and the density of the dots can be increased.
[0031]
In the base 42 of the FPC 4, an antistatic semiconductive layer 49 is formed on the surface 421 on the developing roller 12 side and the surface 422 on the back electrode 3 side, and a ground potential is applied. These semiconductive layers 49 exhibit an optimum resistance value at a preset temperature (initial setting temperature), and friction charges generated when the charged toner T flying as described above comes into contact with the FPC 4 are generated from the FPC 4. It is configured to escape and effectively prevent the FPC 4 from being charged, and to suppress the influence on the transfer electrostatic field and the deflection electric field. That is, it is possible to ensure good print quality while the temperature of the semiconductive layer 49 is maintained within the initial set temperature or the allowable temperature range.
[0032]
Further, in the rotation direction D of the developing roller 12, on the upstream side of the toner flying start position J, the longitudinal direction of the developing roller 12 (the direction perpendicular to the paper surface of FIG. 3) between the FPC 4 and the developing roller 12 configured as described above. And the spacer 5 extending over the entire length of the FPC 4 is inserted in front of the toner passage hole 41 of the FPC 4 in the rotational direction D, and a part of the spacer 5 comes into contact with the toner layer TL carried on the developing roller 12. Thus, the gap GP between the developing roller 12 and the toner passage hole 41 of the FPC 4 is defined to a constant value.
[0033]
Here, the spacer 5 is preferably formed of a material having a work function substantially equal to the work function of the toner T. This is because if the work functions of the two are greatly different, the toner T charged by the friction between the supply roller 13 and the toner regulating blade 14 is brought into frictional contact with the spacer 5. This is because charge transfer occurs and the charged state of the toner T changes, and uniform image formation cannot be performed. On the other hand, when the work functions of the two are substantially the same, such charge transfer does not occur and the charged state of the toner T is not disturbed. As a material satisfying such conditions, for example, for a toner having a work function of 5.62 eV, for example, a polyamide having carbon dispersedly coated (work function: 5.52 eV) or a urethane having carbon dispersedly coated. Can be used (work function: 5.64 eV).
[0034]
On the other hand, a toner discharging blade 15 is fixed to the outer edge portion of the housing 11 located downstream of the toner flight start position J. The toner charge removal blade 15 will be described in detail later.
[0035]
In the image forming apparatus configured as described above, when an image signal is supplied from an external device to the main controller 101 of the control unit 100, the CPU 105 of the engine controller 102 converts the image signal into the image signal in accordance with the signal from the main controller 101. A corresponding control signal is supplied to the control bias generator 47, L deflection bias generator 48L, and R deflection bias generator 48R to cause the toner T to fly and adhere to the intermediate transfer belt 23 to form a toner image corresponding to the image signal. To do. Then, the toner image is transferred onto a sheet S such as copy paper, transfer paper, and OHP transparent sheet taken out from the cassette 7 in a predetermined transfer region TR. Further, the sheet S on which an image is formed in this way is conveyed to a discharge tray (not shown) via the fixing unit 8.
[0036]
Next, the toner discharging blade 15 provided on the downstream side of the toner flying start position J will be described with reference to FIG. FIG. 5 is a partially enlarged sectional view in the vicinity of the toner charge removal blade 15.
[0037]
The toner charge removal blade 15 is formed of a material having a work function larger than that of the toner T. For this reason, the electrons accumulated in the toner T have a larger work function, that is, negatively, due to frictional contact between the charged toner T on the developing roller 12 that did not fly at the toner flying start position J and the toner discharging blade 15. The toner moves toward the toner neutralizing blade 15 which has a higher tendency to be charged. As a result, the charged toner T loses part or all of its charge, and therefore it is easy to peel off from the developing roller 12, and an increase in charge in the toner T stored in the housing 11 is suppressed. .
[0038]
Further, as shown in FIG. 5, the toner neutralizing blade 15 is disposed so as to be in contact with the toner layer TL on the developing roller 12 at the plane portion P thereof. This is because when the toner neutralization blade 15 and the toner layer TL are brought into contact with each other at a sharp portion such as the edge portion E, the toner T that has been neutralized and has weakened the attractive force to the developing roller 12 is developed by the edge. This is because they are scraped off 12 and scattered around and may adhere to the inside of the apparatus, in particular, the FPC 4 to cause disturbance of the electric field, or may adhere to the intermediate transfer belt 23 serving as the image receiving body and stain the image.
[0039]
In this embodiment, the toner charge removal blade 15 also serves as a seal member that prevents the toner T from spilling out of the housing 11, and is brought into contact with the toner layer TL at the flat surface portion P to scrape off the toner described above. However, it is not necessarily limited to such a shape. For example, when the toner discharging blade 15 is configured to be completely accommodated inside the housing 11 by providing a seal member separately, the edge portion E of the toner discharging blade 15 is brought into contact with the toner layer TL, The toner T may be scraped off from the developing roller 12 while discharging electricity.
[0040]
As described above, in the image forming apparatus according to this embodiment, the toner charge removal blade 15 formed of a material having a work function larger than that of the toner T is provided on the downstream side of the toner flying start position J. Therefore, the charged toner T that does not fly at the toner flying start position J and remains on the developing roller 12 is discharged by contacting the toner discharging blade 15. Since the toner T is neutralized in this way, the toner T is easily peeled off from the developing roller 12 and charges are not accumulated in the toner T in the housing 11, so that a uniform and stable toner layer can be continuously supplied. And good quality image formation can be performed.
[0041]
Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 6 is a view showing the image forming apparatus of this embodiment. FIG. 7 is a partially enlarged sectional view of the image forming apparatus of FIG.
[0042]
In this embodiment, as shown in FIG. 6, in the image forming apparatus (FIG. 1) of the first embodiment described above, it is provided upstream of the toner flying start position J in the rotation direction D of the developing roller 12. The spacer 5 and the toner neutralizing blade 15 provided on the downstream side are omitted, and a spacer 51 is provided on the downstream side instead of them, which is different from the apparatus of the first embodiment. Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted. Here, differences in structure and operation based on the above differences will be described. To do.
[0043]
In this embodiment, as shown in FIG. 7, the spacer 51 that keeps the gap GP between the developing roller 12 and the toner passage hole 41 of the FPC 4 constant is located downstream of the toner passage hole 41 in the rotation direction D of the developing roller 12. Is provided. By doing this, the toner flying start position J is reached without disturbing the charge amount and thickness of the toner layer TL regulated by the toner regulating blade 14. For this reason, the charge amount and thickness of the toner layer TL at the toner flying start position J can always be kept constant, so that stable image formation can be performed.
[0044]
The spacer 51 is formed using a material having a work function larger than that of the toner T. When the negatively charged toner T comes into contact with the spacer 51, electrons move from the toner T to the spacer 51, As a result, the toner T is neutralized. In FIG. 7, in order to distinguish the charged / uncharged state of the toner T, the charged toner is indicated by a circle with hatching, and the uncharged toner is indicated by a circle without hatching.
[0045]
Further, the spacer 51 is formed in a tapered shape whose upper surface is inclined toward the upstream side, and the inclined surface S is in contact with the toner layer TL. For this reason, scraping off of the toner T by the edge of the spacer 51 is suppressed similarly to the toner charge removal blade 15 (FIG. 5) in the apparatus of the first embodiment described above. In this embodiment, the spacer 51 must be provided outside the housing 11 because of the structure. Therefore, the toner T scraped off by the spacer 51 is scattered inside the apparatus. Therefore, it is desired to keep the toner scraping at the spacer 51 as low as possible. Further, the spacer 51 is also used in this sense in order to suppress the fluctuation of the gap GP due to the unevenness generated in the toner layer TL due to the flying of the toner T corresponding to the image signal. It is preferable to use a simple shape. Of course, it goes without saying that even if the spacer 51 has such a shape, the effect of keeping the gap GP constant is not changed. Further, the inclined surface S is not limited to the above-described flat surface, and may be, for example, an upward convex curved surface in FIG. 7 or a downward convex curved surface having a smaller curvature than the developing roller 12.
[0046]
As described above, in the image forming apparatus according to this embodiment, the spacer 51 provided on the downstream side keeps the gap GP between the developing roller 12 and the toner passage hole 41 constant and removes the toner T remaining on the developing roller 12. This makes it possible to continuously form a stable toner layer TL. In this manner, the gap GP and the toner layer TL are stabilized, so that good image formation can be stably performed.
[0047]
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 negatively charged toner is discharged by using a material having a work function larger than that of the toner as the material of the toner discharging blade in the first embodiment and the spacer in the second embodiment. In addition, for example, these are formed of a conductive material such as copper or stainless steel, and a DC voltage having a higher potential than that of the developing roller is applied from a separately provided DC power source so that the charge accumulated in the toner is removed. It may be.
[0048]
Further, in each of the above-described embodiments, the case where the toner is a negatively charged toner having a property of being negatively charged has been illustrated, but even if the charging polarity of the toner and its work function are different, The present invention can be applied to an apparatus using toner different from the above by appropriately adjusting the polarity and magnitude of the bias voltage applied to each part.
[0049]
Further, for example, in the above embodiment, the present invention is applied to an intermediate transfer type image forming apparatus in which a toner image is formed on a transfer medium such as the intermediate transfer belt 23 and then the toner image on the transfer medium is transferred to the sheet S. However, the present invention may be applied to an image forming apparatus that forms an image by directly landing the charged toner T flying from the developing device 1 on the sheet S.
[0050]
In the above embodiment, the present invention is applied to the image forming apparatus in which the semiconductive layer 49 is provided to prevent the FPC 4 from being charged. However, the scope of application of the present invention is not limited to this. Instead, the present invention can also be applied to an image forming apparatus that does not have an antistatic semiconductive layer.
[0051]
In the above embodiment, the present invention is applied to an image forming apparatus in which the flying direction of the charged toner T can be switched to the three directions P1, P2, and P3 by the deflection electrodes 45L and 45R. The object is not limited to this, and the present invention can also be applied to an image forming apparatus in which the flying direction of the charged toner T is fixed.
[0052]
In the above embodiment, a predetermined DC voltage is applied to the developing roller 12 from the developing roller bias generator 103. However, the developing roller 12 may be configured to be grounded or an AC voltage.
[0053]
Furthermore, in the above-described embodiment, the present invention is applied to an image forming apparatus that performs so-called single-color printing, in which an image is formed by one developing device 1. For example, when forming a full-color image, yellow, The present invention is also applied to a so-called tandem type color image forming apparatus in which the same developing devices 1 for four types of magenta, cyan and black toners are arranged in a line in the conveying direction Y of the intermediate transfer belt 23 and the sheet S. The invention can be applied.
[0054]
【The invention's effect】
As described above, according to the present invention, the toner that did not fly at the toner flying start position loses electric charge by being brought into contact with the discharging member provided on the downstream side from the toner flying start position, and is discharged. The toner thus neutralized is easily peeled off from the toner carrying member, so that the formation of a new toner layer on the toner carrying member is not hindered, and mixing of charged toner into unused toner can be suppressed. Therefore, a uniform toner layer is always formed on the toner carrier, and good image quality can be obtained.
[0055]
As such a charge eliminating member, a material that easily charges the toner to a polarity opposite to its charged polarity, that is, a material having a work function smaller than that of the toner for positively charged toner, and a material for negatively charged toner. Can use a material having a work function larger than that of the toner. Further, the toner can be removed by applying a bias voltage that cancels the charging of the toner to the charge removing member.
[0056]
Further, by sandwiching the charge eliminating member between the toner carrier and the toner flight control means, the gap between the toner carrier and the toner flight control means becomes constant, and it is possible to perform stable image formation with a simple configuration. Become.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating 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.
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 illustrating control electrodes and deflection electrodes formed on a flexible printed circuit board.
FIG. 5 is a partial enlarged cross-sectional view in the vicinity of a toner charge removal blade.
FIG. 6 is a diagram showing a second embodiment of the image forming apparatus according to the present invention.
7 is a partially enlarged cross-sectional view of the image forming apparatus of FIG.
[Explanation of symbols]
3 ... Back electrode 4 ... FPC
5 ... Spacer 12 ... Developing roller (toner carrier)
15 ... Toner static elimination blade (static elimination member)
23. Intermediate transfer belt (image receiver)
41 ... Toner passage hole 51 ... Spacer (static elimination member)
D: Development roller moving direction (toner transport direction)
J: Toner flight start position T ... Toner TL ... Toner layer

Claims (4)

A back electrode;
A toner carrier that moves in a predetermined movement direction and carries the toner to a toner flying start position facing the back electrode while carrying the charged toner;
A regulating blade that regulates the thickness and charge amount of the toner carried on the toner carrying body upstream of the toner flying start position in the moving direction;
An image receiver that is disposed between the back electrode and the toner carrying member and is conveyed between the back electrode by controlling the toner flying from the toner flying start position of the toner carrying member to the back electrode. Toner flying control means for forming toner images by landing toner on the body;
A gap between the toner carrier and the toner flight control means is defined by being sandwiched between the toner carrier and the toner flight control means on the downstream side in the moving direction with respect to the toner flight start position. An image forming apparatus comprising: a charge eliminating member that neutralizes the charge of the toner that forms the toner layer in contact with the toner layer carried on the toner carrying member.   The image forming apparatus according to claim 1, wherein the toner is a positively charged toner that is positively charged, and the charge removal member is formed of a material having a work function smaller than a work function of the toner.   The image forming apparatus according to claim 1, wherein the toner is a negatively charged toner that is negatively charged, and the charge removal member is formed of a material having a work function larger than a work function of the toner. The static elimination member is made of a conductive material,
The image forming apparatus according to claim 1, further comprising a voltage applying unit that applies a DC voltage for discharging the toner between the toner carrier and the discharging member. .

Images