JP2008310019A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device, capable of removing a charging product without enlargement and complication of the device and impairing a user's convenience. <P>SOLUTION: A heating wire 25 is disposed on a grid mesh 23 of an electrifier 20 for charging a photosensitive drum 10. An exhaust unit 9 for discharging the internal air is attached to an exhaust port 22d of the electrifier 20. When the heating wire 25 is heated by current carrying after completion of image forming, the grid mesh 23 is heated to about 40°C to decompose and vaporize a charging product such as NOx adhered to the grid mesh 23. The vaporized charging product is sucked and discharged through the exhaust port 22d by the exhaust unit 9 to prevent adhesion thereof to the photosensitive drum 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for preventing image quality deterioration caused by a charged product.

The image forming apparatus charges the surface of the photoconductor prior to forming an electrostatic latent image on the photoconductor. Ozone and nitrogen oxides (NOx) are generated by corona discharge in this charging process. Nitrogen oxides react with moisture in the air to form nitrates that adhere to the photoreceptor, charger stabilizer, grid mesh, and the like.
Nitrate has a low vaporization temperature, vaporizes at about 30 ° C., and adheres to the surface of the photoreceptor. When the charged product adheres to the surface of the photoconductor, the surface resistance of the photoconductor decreases, and image noise such as image flow, background fogging, and white spots occurs.

In order to solve such a problem, for example, a technique has been developed in which a heat source is provided inside the photosensitive drum, the photosensitive member is heated, and the charged product attached to the photosensitive member is removed by volatilization. In this case, the charged product that cannot be removed only by heating is wiped off from the photosensitive member by the cleaning blade. Further, in order to prevent the temperature of the photoconductor from being changed by heating, the photoconductor temperature is controlled to fall within a certain range.
JP 05-188706 A

However, if a heat source is provided inside the photosensitive drum, the image forming apparatus becomes large and the structure thereof is complicated. Further, in order to remove the charged product, not only a heat source but also a cleaning blade is required, which increases the cost.
Furthermore, since the charged product is removed when the power is turned on or during the image forming operation, a dead time occurs before the image forming operation is started, and user convenience is impaired. In addition, the heat source may be overheated due to poor control or the like, causing damage to the photoreceptor.

  The present invention has been made in view of the above-described problems, and provides an image forming apparatus that removes a charged product without increasing the size and complexity of the apparatus and without impairing user convenience. The purpose is to do.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus including a charger for charging a photoconductor, and the charger includes a grid mesh and a grid for uniformly charging the surface of the photoconductor. Heating means for heating the mesh, and heating the grid mesh with the heating means to vaporize the charged product attached to the grid mesh.

In this way, unlike the prior art, there is no need to dispose a heating means in the photosensitive drum, so that the charged product can be removed without increasing the size and complexity of the image forming apparatus. .
In this case, it is preferable to provide discharge means for discharging the charged product evaporated by heating to the outside of the apparatus. Further, the discharge means includes an exhaust pipe that communicates the inside of the charger with the outside of the machine, and a blower provided in the middle of the exhaust pipe, and discharges air in the charger to generate a charge. Items may be discharged out of the machine.

The image forming apparatus according to the present invention further includes a stopping unit that stops the heating unit from heating the grid mesh. If it does in this way, the electric power for heating a grid mesh can be saved.
The image forming apparatus according to the present invention is characterized in that the heating unit heats the grid mesh when the charger completes the charging of the photosensitive member. In this way, it is possible to avoid the dead time associated with the removal of the charged product and improve the convenience for the user.

The image forming apparatus according to the present invention includes a driving unit that rotationally drives the photosensitive member in a heating period in which the grid mesh is heated by the heating unit and a predetermined period after the heating is stopped by the stopping unit. Features. In this way, uneven charging can be prevented by avoiding that the charged product adheres unevenly on the photoreceptor.
In the image forming apparatus according to the present invention, the charger includes a discharge electrode and a stabilization plate that stores the discharge electrode together with the grid mesh, and the heating unit heats the stabilization plate together with the grid mesh. It is characterized by doing. In this way, the charged product adhering to the stabilizing plate can also be removed, and the problems caused by the charged product can be solved.

  In addition, it is suitable if the said heating means heats a grid mesh using a heating wire.

Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment.

As shown in FIG. 1, the image forming apparatus 1 is an electrophotographic tandem type full-color digital printer, and includes an intermediate transfer member 3, a plurality of process units 4, and a plurality of units accommodated inside the apparatus main body 2. Developer cartridge 5, sheet feeding means 6, secondary transfer roller 7, fixing device 8, and exhaust unit 9 as a ventilation means.
The intermediate transfer member 3 is an endless belt formed of a sheet material made of an insulating resin, and is stretched around a plurality of rollers (not shown). The intermediate transfer body 3 is rotationally driven in the direction A of the arrow by rotating one of the rollers by a driving means (not shown).

  There are four process units 4 for yellow, magenta, cyan, and black. The process units 4 are arranged in series along the intermediate transfer body 3 at predetermined intervals so as to face each other. . Each process unit 4 includes a photosensitive drum 10 as an image carrier, a charger 20, an exposure device 30, a developing device 40, a primary transfer roller 50, a cleaner 60, and the like, and forms a toner image of each color.

The photosensitive drum 10 has a cylindrical shape with a photosensitive layer formed on the surface thereof, and is driven to rotate in the direction of arrow B. The charger 20, the exposure device 30, the developing device 40, the primary transfer roller 50, and the cleaner 60 are sequentially arranged on the outer periphery of the photosensitive drum 10 along the rotation direction of the photosensitive drum 10.
The charger 20 is a non-contact type charger provided with a discharge electrode 21 and uniformly charges the surface of the rotating photosensitive drum 1 to a predetermined potential. Details of the charger 20 will be described later.

The exposure device 30 irradiates the surface of the photosensitive drum 10 with a laser beam corresponding to the time-series electric digital pixel signal of the image information, and changes the charged potential of the exposed portion to form an electrostatic latent image.
The developing device 40 causes toner to adhere to the surface of the photosensitive drum 10 by an electric field or the like to visualize the electrostatic latent image. The developing device 40 may be a contact type or a non-contact type, and the developing method may be a two-component developing method comprising a toner and a carrier or a one-component developing method not including a carrier, and the toner may be a negatively charged toner or a positively charged toner. But it ’s okay.

The primary transfer roller 50 is disposed to face the photosensitive drum 10 with the intermediate transfer belt 3 interposed therebetween, and transfers the toner image on the surface of the photosensitive drum 10 to the intermediate transfer member 3 by an electric field and pressure.
The cleaner 60 brings the blade 61 into contact with the surface of the photosensitive drum 10 and scrapes off and removes unnecessary toner from the surface. Unnecessary toner is untransferred toner due to transfer failure, toner dust, and the like. The removed toner is collected in the cleaner 60.

The developer cartridge 5 is filled with a developer of a color corresponding to each process unit 4, and the developer is supplied to each process unit 4 through a conveyance path 51.
The paper feeding means 6 conveys the recording paper (not shown) to the secondary transfer position in accordance with the secondary transfer timing.
The secondary transfer roller 7 transfers the toner image on the surface of the intermediate transfer body 3 to the recording paper conveyed to the secondary transfer position.

The fixing device 8 includes a pair of fixing rollers 81 and 82 that are arranged to face each other and rotate in contact with each other. When the recording paper passes between the fixing rollers 81 and 82, the recording paper is heated and pressurized to fix the toner on the recording paper. .
The exhaust unit 9 includes a duct 91 as a ventilation path, a connection portion 92 provided on the upstream side of the duct 91, and a fan 93 provided on the downstream side of the duct 91. Details of the exhaust unit 9 will be described later.

[2] Configuration of Charger 20 Next, the charger 20 and the exhaust unit 9 will be described in detail.
FIG. 2 is a cross-sectional view schematically showing the configuration of the charger 20. FIG. 3 is an external perspective view of the charger 20.
As shown in FIGS. 2 and 3, the charger 20 includes a discharge electrode 21, a casing member 22, a grid mesh 23, a sealing material 24, and a heating wire 25.

  The discharge electrode 21 is a corona discharge electrode, and is horizontally mounted in the discharge space 22a inside the casing member 22 along the photosensitive drum axial direction. The discharge electrode 21 is applied with a voltage of −5 to −7 KV by supplying a current of −700 μA, for example, from a power source (not shown) during the image forming operation. Corona discharge occurs. As the discharge electrode 21, for example, a sawtooth electrode, a discharge wire, or a pin electrode can be considered.

The casing member 22 is a box-shaped member having a discharge space 22a for housing the discharge electrode 21, and supports the stabilization electrode 22b for stabilizing the air discharge of the discharge electrode 21 and the discharge electrode 21 from both ends. And a pair of holders 22c, and the stabilizing plate 22b and the pair of holders 22c form a discharge space 22a.
The casing member 22 is open on the photosensitive drum side, and electrons generated from the discharge electrode 21 are efficiently emitted to the photosensitive drum 10. Further, the casing member 22 is provided with an exhaust port 22d along the rotation axis of the photosensitive drum on the surface opposite to the photosensitive drum.

The stabilization plate 22b is formed by bending a metal plate into a U shape, and surrounds the discharge electrode 21 from three sides except for the photosensitive drum side. The pair of holders 22c are attached to the stabilization plate 22b so as to close both ends of the stabilization plate 22b in the rotation axis direction of the photosensitive drum.
The grid mesh 23 is made of thin stainless steel having a thickness of about 0.1 to 0.2 mm, and is attached at a position between the discharge electrode 21 and the photosensitive drum 10 so as to cover an open portion of the casing member 22. It has been. During the image forming operation, for example, a voltage of −400 to −1200 V is applied to the grid mesh 23 from a power source (not shown) different from that for the discharge electrode 21 to control the surface potential of the photosensitive drum 10.

The sealing material 24 is a belt-like member for closing the gap between the casing member 22 and the photosensitive drum 10, and is provided on the photosensitive drum side of the casing member along the rotation axis of the photosensitive drum. The side of the sealing material 24 opposite to the side fixed to the casing member 22 is in contact with the photosensitive drum 10.
The heating wire 25 is fixed to the grid mesh 23 in an electrically insulated state. The heating wire 25 is, for example, a nichrome wire covered with a ceramic cover, and a voltage of 24 V is appropriately applied from a low voltage source (not shown).

  FIG. 4 is an external perspective view of the heating wire 25. As shown in FIG. 4, the heating wire 25 is routed around the periphery of the grid mesh 23, and the entire grid mesh 23 is heated by heating the periphery of the grid mesh 23. The image forming apparatus 1 starts and ends heating of the grid mesh 23 by turning on and off the switch of the heating wire 25.

[3] Exhaust System Next, a configuration for exhausting the gas inside the charger 20 will be described.
FIG. 5 is a perspective view showing the charger 20 and the exhaust unit 9. FIG. 6 is a diagram illustrating a connection state between the charger 20 and the exhaust unit 9.
As shown in FIG. 5, in the exhaust unit 9, the upstream side of the duct 91 is branched into four, and a connecting portion 92 is provided at the tip of each branch. Further, downstream of the duct 91, a filter unit 94 and a fan 93 are sequentially provided for removing discharge products such as nitrogen oxides and ozone and nitrate compounds such as nitric acid.

  As shown in FIG. 6, the connection portion 92 is provided with a connection port 92a having substantially the same shape and size as the exhaust port 22d, and the exhaust port 22d and the connection port 92a are aligned with each other. When the connecting portion 92 is brought into contact with the side opposite to the photosensitive drum 10, a pair of locking claws 22e provided on the casing member 22 are provided at locations corresponding to the locking claws 22e of the connecting portion 92. The charger 20 and the duct 91 are connected via the connection portion 92 by engaging with the pair of locking grooves 92 b. As a result, the discharge space 22 a and the internal space of the duct 91 communicate with each other via the internal space of the connection portion 92.

When the fan 93 is rotated, an air flow is generated, and the air in the discharge space 22 a passes through the connection portion 92, the duct 91, and the filter portion 94 and is discharged to the outside of the image forming apparatus 1. On the other hand, air is sucked into the discharge space 22 a from a portion where the sealing material 24 is not disposed between the photosensitive drum 10 and the casing member 22.
The airflow generated by the exhaust unit 9 is, for example, a wind speed of 0.5 to 0.6 m / sec at the connection portion 92.

As a result, nitrogen oxides and nitrate compounds are discharged from the discharge space 22a, pass through the connection portion 92 and the duct 91, and trapped by the filter portion 94, so that the nitrogen oxides and nitrate compounds are removed from the discharge space 22a. The
[4] Operation of Image Forming Apparatus 1 Next, the operation of the image forming apparatus 1 will be described.

FIG. 7 is a flowchart showing main operations of the image forming apparatus 1. As shown in FIG. 7, the image forming apparatus 1 executes an image forming process (S601), and then sets a timer (S602). The timer is set almost at the same time as the charging process of the photosensitive drum 10 by the charger 20 is stopped in the image forming process.
In the present embodiment, the time set in the timer is determined from the cumulative discharge time of the charger 20 and the environmental conditions. That is, the image forming apparatus 1 has a higher temperature and a higher humidity than a low temperature and a low humidity, and the longer the accumulated discharge time, the longer the time set in the timer. FIG. 8 is a table illustrating the relationship between the environmental conditions and the accumulated discharge time and the time set in the timer.

  This is because nitrogen oxide is more easily generated at higher temperature and humidity than at low temperature and low humidity, and more ozone and nitrogen oxide are generated by the discharge electrode as the cumulative discharge time is longer. Further, the time set in the timer should be appropriately adjusted according to the capacity of the heating wire 25 and the heat capacity of the grid mesh 23. In the present embodiment, the effect can be obtained by heating for a maximum of 20 seconds.

  Next, the image forming apparatus 1 starts heating by energizing the heating wire 25 (S603). By this heating, the grid mesh 23 is set to around 40 ° C., so that the charged product attached to the grid mesh 23 is decomposed and vaporized. The exhaust unit 9 continues the exhaust operation after the image forming process, and sucks and exhausts the vaporized charged product so as not to adhere to the photosensitive drum 10.

In this way, it is possible to eliminate the dead time that makes the user wait to remove the charged product.
Thereafter, when a time-out occurs (S604: Yes), a new timer is set (S605), energization to the heating wire 25 is stopped to finish heating (S606), the fan 93 is started, and the charger The air in 20 is exhausted outside the apparatus (S607).

In this case, a time required for sucking and exhausting the charged product decomposed and vaporized by heating with the heating wire 25 is set in the timer. The time required for exhausting the charged product is preferably set to an appropriate value in accordance with the performance of the exhaust unit 9 and the volume of the discharge space 22a of the charger 20, and is set to 5 seconds in this embodiment.
Further, when a time-out occurs (S608: Yes), the fan 93 is stopped and the discharge of the charged product is finished (S609).

[5] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above embodiment, the case where the charged product is removed by exhausting the air in the charger 20 by the exhaust unit 9 to prevent uneven charging of the photoreceptor has been described. It goes without saying that the invention is not limited to this, and the following may be used instead.

FIG. 9 is a flowchart showing main operations of the image forming apparatus according to this modification. As shown in FIG. 9, after executing the image forming process (S801), the image forming apparatus 1 sets a timer (S802) and starts rotating the photosensitive drum 10 (S803).
Next, the image forming apparatus 1 starts heating by energizing the heating wire 25 (S804). By this heating, the charged product adhering to the grid mesh 23 is decomposed and vaporized. Further, the vaporized charged product is agitated by the air flow generated by the rotation of the photosensitive drum 10.

Thereafter, when a time-out occurs (S804: Yes), a new timer is set (S805), energization of the heating wire 25 is stopped, and heating is ended (S806). Further, when a timeout occurs (S808: Yes), the rotation of the photosensitive drum 10 is stopped (S809).
In this way, the vaporized charged product adheres to the inside of the charger 20 and the surface of the photosensitive member. However, since the photosensitive drum 10 continues to rotate, the charged product remains on the surface of the photosensitive drum 10. It adheres evenly. Therefore, problems such as charging unevenness can be solved.

(2) In the above embodiment, the case where the exhaust unit 9 exhausts air after the heating by the heating wire 25 has been described in the above embodiment, but the present invention is not limited to this. Instead of this, the following may be used.
FIG. 10 is a flowchart showing main operations of the image forming apparatus according to this modification. As shown in FIG. 10, after executing the image forming process (S901), the image forming apparatus 1 sets a timer (S902) and starts exhausting by the exhaust unit 9 (S903). Next, the image forming apparatus 1 starts heating with the heating wire 25 (S904). By this heating, the vaporized charged product is immediately exhausted.

Thereafter, when a timeout occurs (S904: Yes), a new timer is set (S905), and the heating is terminated (S906). Further, when a timeout occurs (S908: Yes), the exhaust is terminated (S909).
In this way, since the vaporized charged product is immediately exhausted, it is possible to prevent the charged product from adhering to the inside of the charger 20 again. In addition, since the heat release of the grid mesh 23 is promoted by the exhaust, it is more preferable to increase the amount of energization to the heating wire 25 than when exhausting after heating.

(3) Although the case where the grid mesh 23 is exclusively heated has been described in the above embodiment, it goes without saying that the present invention is not limited to this, and the stabilizer 22b may also be heated in addition to this.
Since the stabilizing plate 22b faces the discharge space 22a as well as the grid mesh 23, the charged product adheres to the photosensitive drum 10 even if it is not as large as the grid mesh 23. Therefore, by heating the stabilizing plate 22b together with the grid mesh 23 to remove the charged product, problems such as uneven charging of the photosensitive drum can be solved and the image quality can be further improved.

(4) Although not particularly mentioned in the above embodiment, it is desirable to stop the rotation of the photosensitive drum 10 when the charged product is exhausted by the exhaust unit 9. As described above, when the photosensitive drum 10 is rotated, an air flow is generated in the charger 10 and it is difficult to suck and discharge the charged product.
(5) Although the tandem type full-color digital printer has been described as an example in the above embodiment, the present invention is not limited to this, and the present invention is applied to image forming apparatuses other than the tandem type such as a four-cycle type. It may be applied. Even if the present invention is applied to an image forming apparatus other than full color such as monochrome, the effect can be obtained. Needless to say, the present invention can be applied to any image forming apparatus provided with a photoreceptor and a charger, even if it is other than a printer.

  (6) In the above embodiment, the case where the heating wire is used as the means for heating the grid mesh 23 has been described. However, it goes without saying that the present invention is not limited to this, and the grid mesh is used using a means other than the heating wire. 23 may be heated.

  The image forming apparatus according to the present invention is useful as a technique for preventing image quality deterioration caused by a charged product.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows typically the structure of the charger 20 which concerns on embodiment of this invention. 1 is an external perspective view of a charger 20 according to an embodiment of the present invention. It is an external appearance perspective view of the heating wire 25 which concerns on embodiment of this invention. It is a perspective view which shows the charger 20 and the exhaust unit 9 which concern on embodiment of this invention. It is a figure explaining the connection state of the charger 20 and the exhaust unit 9 which concern on embodiment of this invention. 3 is a flowchart showing main operations of the image forming apparatus 1 according to the embodiment of the present invention. It is a table | surface which illustrates the relationship between the environmental conditions in embodiment of this invention, accumulated discharge time, and the time set to a timer. It is a flowchart which shows main operation | movement of the image forming apparatus which concerns on the modification (1) of this invention. It is a flowchart which shows the main operation | movement of the image forming apparatus which concerns on the modification (2) of this invention.

Explanation of symbols

1 ………… Image forming device 2 ………… Device main body 3 ………… Intermediate transfer member 4 ………… Process unit 5 ………… Developer cartridge 6 ………… Supply Paper means 7 ............ Secondary transfer roller 8 ............ Fixer 9 ...... …… Exhaust unit 10 ………… Photoreceptor drum 20 ………… Charger 21 ………… Discharge electrode 22 ………… Casing member 22a ………… Discharge space 22b ………… Stabilizer plate 22c ……… Holder 22d ……… Exhaust port 22e ……… Locking claw 23 ………… Grid mesh 24 ………… Seal Material 25... Heating wire 30... Exposure unit 40... Developer 50... Primary transfer roller 51... Transport path 60. , 82 ... Fixing roller 91 ... Duct 92 ... Connection 92a ... Connection port 92b ... Groove 93 ............ fan 94 ............ filter unit

Claims (8)

An image forming apparatus including a charger for charging a photoconductor,
The charger is a grid mesh that uniformly charges the photoreceptor surface,
Heating means for heating the grid mesh,
An image forming apparatus, wherein the charged product attached to the grid mesh is vaporized by heating the grid mesh with the heating means. 2. The image forming apparatus according to claim 1, further comprising discharge means for discharging the charged product vaporized by heating to the outside of the apparatus. The discharging means is
An exhaust pipe communicating between the inside of the charger and the outside of the machine;
A blower provided in the middle of the exhaust pipe,
The image forming apparatus according to claim 2, wherein the charged product is discharged out of the apparatus by exhausting air in the charger. The image forming apparatus according to claim 1, further comprising a stopping unit that stops the heating unit from heating the grid mesh. The image forming apparatus according to claim 4, wherein the heating unit heats the grid mesh when the charger completes charging of the photosensitive member. 5. The driving device according to claim 4, further comprising a driving unit that rotationally drives the photosensitive member during a heating period in which the heating unit heats the grid mesh and a predetermined period after heating is stopped by the stopping unit. Image forming apparatus. The charger includes a discharge electrode;
A stabilizing plate for storing the discharge electrode together with the grid mesh,
The image forming apparatus according to claim 1, wherein the heating unit heats the stabilizing plate in addition to the grid mesh. The image forming apparatus according to claim 1, wherein the heating unit heats the grid mesh using a heating wire.

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