JP4688323B2 - Image forming apparatus and image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus and an image forming method.
[0002]
[Prior art]
In an image forming apparatus, for example, an electrophotographic printer, the inside becomes hotter than the outside during operation due to heat generated by an exposure element, a fixing unit or a motor. At the same time, in the electrophotographic printer, the water in the paper evaporates due to the heating of the paper in the fixing unit, and the inside may become more humid than the outside.
[0003]
For this reason, when the operation of the electrophotographic printer is stopped, the internal temperature may decrease, and condensation may occur inside the printer.
In addition, in an electrophotographic printer, a discharge device for charging or discharging a photosensitive member is disposed inside, and nitrogen oxide (NOx) may be generated to a slight extent with the discharge operation of the discharge device. .
[0004]
[Problems to be solved by the invention]
By the way, in the electrophotographic printer, condensation may occur inside when stopped as described above. If this condensation occurs on the surface of the photosensitive member or in the vicinity of the photosensitive member, a print defect occurs in the condensed portion at the restart. There was a problem. This printing defect may occur due to the moisture adhering to the surface of the photoconductor due to the moisture, but the image formation may be hindered. It may appear as a printing defect on the top.
[0005]
On the other hand, as described above, in an electrophotographic printer, NOx may be generated along with the discharge operation of the internal discharge device, and this NOx and moisture due to condensation react to generate nitric acid. May react with metals to form metal nitrates. When this nitric acid or metal nitrate adheres to the surface of the photoconductor, the electrical characteristics of the photoconductor of that portion change, and when printing, this portion is developed black, or conversely, there is a print defect that becomes white without being developed. There was a problem that occurred.
[0006]
In addition, when the electrophotographic printer has a fixing device using a flash fixing method, a part of the flash light is reflected directly or on a conveying device or paper during the printing operation, and is irradiated to the photosensitive drum as leakage light, There is a case where a printing defect occurs in which the portion irradiated with the leaking light is developed black, or conversely, white portions are not developed but developed. If the print defect due to the leaked light and the print defect caused by condensation or NOx described above occur at the same position on the surface of the photoconductor, they are developed blacker or whiter than when they occur individually. There was a problem of missing. Further, the electrophotographic printer has a problem that if the paper conveyance path is substantially linear, the amount of leakage light may increase, resulting in a further black development or whiteout.
[0007]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming method in which occurrence of a print defect due to condensation or nitrogen oxide (NOx) is suppressed.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present inventor has made extensive studies on the state of occurrence of print defects caused by condensation and nitrogen oxides (NOx) with respect to the image forming apparatus. As a result, in the image forming apparatus, it is found that a metal member exists in the vicinity of the photosensitive member, and the above-described print defect due to condensation or NOx is likely to occur in a portion facing the metal member. It was.
[0009]
The present invention has been made on the basis of the above knowledge, and is an image forming apparatus having an organic photoreceptor, and at least the organic photosensitive member disposed in the vicinity of the organic photoreceptor and not directly involved in image formation. The part which opposes a body is comprised with the heat insulation member.
In this specification, “close to the organic photoconductor” refers to a position where the distance from the surface of the organic photoconductor is approximately 7% or less of the entire length of the organic photoconductor. For example, when the organic photoconductor is a photosensitive drum having a diameter of 120 mm, the distance close to the organic photoconductor is about 1/5 of the diameter.
[0010]
In addition to the above definition of proximity, by configuring the portion facing the organic photoconductor with a heat insulating member, portions that result undesirable image forming process, for example, for the developing roll, its location Even if it is in a position close to the organic photoreceptor, it is better not to use a heat insulating member.
Preferably, the heat insulating member is rubber.
[0011]
Preferably, the heat insulating member is a foam material.
Further, if the organic photoreceptor is a single layer type organic photoreceptor, it is more effective.
If the single layer type organic photoreceptor is of a positively charged type, it is more effective.
Further, it is more effective if a fixing device for fixing an unfixed image formed on the recording medium is provided and the fixing device is of a flash fixing system.
[0012]
Furthermore, the image forming apparatus includes a transport unit that transports the recording medium in a substantially straight line.
In order to achieve the above object, the present invention is an image forming method in which an electrostatic latent image formed on an organic photoreceptor is developed into a toner image, and the toner image is fixed on a recording medium to form an image. Thus, at least a portion of the metal member that is disposed in the vicinity of the organic photoreceptor and does not directly participate in image formation is opposed to the organic photoreceptor.
[0013]
[Action]
When the metal member that is close to the organic photoconductor and faces at least the organic photoconductor is configured as a heat insulating member or a heat insulating state , this portion cools faster than the surroundings when the temperature in the apparatus decreases due to the stoppage of operation. Therefore, it is considered that this part and the surface of the organic photoconductor facing this part are not at a lower temperature than the surroundings, and condensation is unlikely to occur.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image forming apparatus and an image forming method according to an embodiment of the present invention will be described in detail based on an electrophotographic printer 1 shown in FIGS.
The electrophotographic printer 1 achieves the first object of the present invention. As shown in FIGS. 1 and 2, a main charger 3, an LED print head 4, and a developing device around a photosensitive drum 2 in a housing 1a. The unit 5, the transfer charger 6, the separation charger 7, the pre-cleaning charger 8, the carrier recovery unit 9, the cleaning unit 10, and the charge removal lamp 11 are arranged, and the photosensitive drum 2 downstream of the conveyance path through which the recording medium MRC is conveyed. The fixing unit 20 is disposed on the front side. Further, the electrophotographic printer 1 is provided with a guide plate 13 and a tractor 14 on the upstream side of the photosensitive drum 2 in the conveyance path, and a conveyance unit 15 at a position facing the fixing unit 20 in the conveyance path.
[0015]
Here, in the electrophotographic printer 1, continuous paper is used as the recording medium MRC, but cut paper can also be used. As shown in the figure, the recording medium MRC is introduced from the inlet 1b on the right side of the housing 1a and discharged from the outlet 1c on the left side.
In the photosensitive drum 2, an organic photoreceptor layer made of a positively charged single-layer photoelectric material is formed on the surface of a cylindrical drum (conductive substrate), and an electrostatic latent image is generated by light emitted from the LED print head 4. Is formed on the surface. The illustrated photosensitive drum 2 uses Emerald-1 manufactured by Kyocera Mita Corporation as an organic photoreceptor.
[0016]
The surface of the photosensitive drum 2 is uniformly charged by the main charger 3 and the surface of the photosensitive drum 2 is exposed by the light beam from the LED print head 4 to form an electrostatic latent image corresponding to the recording information.
Here, on the downstream side of the LED print head 4, there is a support bracket 4a that supports a surface potential sensor that monitors the surface potential of the photosensitive drum 2, as shown in the figure. The support bracket 4 a is adjacent to the photosensitive drum 2, and a heat insulating member Ab is attached to a portion facing the photosensitive drum 2. In this embodiment, a chloroprene rubber sponge having a thickness of 1.0 mm is used as the heat insulating member Ab. As the material of the heat insulating member Ab, other rubber materials, synthetic resins or foams thereof, paper, leather, wood, cloth / nonwoven fabric may be used, but in consideration of ozone generated inside the printer during printing. It is preferable to use a material having ozone resistance.
[0017]
As the rubber material, in addition to the chloroprene rubber, silicone rubber, butyl rubber, ethylene propylene rubber and the like can be used. As the synthetic resin, polystyrene resin, urea resin, polyurethane resin, phenol resin, polyvinyl acetal resin, vinyl chloride resin, polyethylene resin, epoxy resin and the like can be used.
[0018]
The heat insulating member Ab may be a foamed material of the rubber material and synthetic resin.
The developing unit 5 is disposed to face the photosensitive drum 2, and stores a developing roller 5c in the lower part of the housing 5a and a two-component developer (not shown) in which a carrier is mixed with toner in an appropriate mixing ratio. Developing roller 5c directs the two-component developer on the photosensitive drum 2, and carrying and conveying, with a roller made of a rotatable sleeve (metal tube of non-magnetic) for developing the electrostatic latent image in the interior A rotatable magnet 5d is provided. The magnet 5d is a permanent magnet that is long in the axial direction, and a plurality of poles are arranged in the circumferential direction. A toner cartridge 5b is removably inserted in the housing 5a. A replenishment toner is accommodated in the toner cartridge 5b. A replenishment toner is appropriately supplied to the developer by a replenishment mechanism (not shown), and the mixing ratio of the toner and the carrier is adjusted. Maintains the expected range.
[0019]
The transfer charger 6 discharges with a polarity opposite to the charged polarity of the toner, and transfers the unfixed toner image developed on the photosensitive drum 2 to the recording medium MRC.
The separation charger 7 is a charger that electrically separates the recording medium MRC from the photosensitive drum 2, and a corotron charger to which an alternating voltage is applied is used. Further, a separation claw 12 for mechanically separating the head of the recording medium MRC from the photosensitive drum 2 is provided between the separation charger 7 on the outer periphery of the photosensitive drum 2 and the pre-cleaning charger 8.
[0020]
The pre-cleaning charger 8 is a brush in a cleaning unit 10 which will be described later with toner remaining on the surface of the photosensitive drum 2 without being transferred to the recording medium MRC, slightly existing carriers, additives to the developer, paper dust and the like. It is charged with a polarity opposite to the bias voltage of the roller 10b and is easily removed by the brush roller 10b.
Here, as shown in the drawing, the pre-cleaning charger 8 is disposed in the vicinity of the photosensitive drum 2 and a heat insulating member Ab between the stay 1e which is a portion facing the photosensitive drum 2.
[0021]
The carrier recovery unit 9 is a housing in which a recovery roller 9a and a blade are housed in a housing, and the blade scrapes off the carrier recovered by the recovery roller 9a from the surface of the recovery roller.
The cleaning unit 10 is provided with a brush roller 10b and a collection roller 10c in a housing 10a. The brush roller 10b is cleaned by scraping the toner remaining from the surface of the photosensitive drum 2 with a brush. The collection roller 10c is applied with a bias voltage and electrostatically collects the toner collected by the brush roller 10b. The collected toner is scraped off from the collection roller 10c by a blade (not shown).
[0022]
The static elimination lamp 11 has a configuration in which a plurality of LED chips are arranged on the substrate at appropriate intervals, and removes residual charges from the surface of the photosensitive drum 2 by light irradiation.
At this time, as shown in FIG. 2, a heat insulating member Ab is stuck to the lamp housing 11 a that is close to the photosensitive drum 2 and faces the photosensitive drum 2.
[0023]
The conveyance unit 15 is configured by a conveyance belt 15b being stretched between two conveyance rollers 15a supported by a casing 15c made of a steel plate (that is, a ferromagnetic material). As shown in FIG. 1, the electrophotographic printer 1 is configured such that the conveyance path for conveying the recording medium MRC is substantially straight and substantially horizontal before and after the conveyance unit 15, and the recording medium MRC is a pair of recording media MRC. Tension for conveyance is given by the scarf roller 16. However, the transport unit 15 is arranged with the auxiliary roller 15d slightly biased upward in the middle.
[0024]
In the fixing unit 20, two flash lamps 21 serving as a radiant heat source, a reflection plate 22, and heat radiation fins 23 for cooling the reflection plate 22 are provided in the housing 20 a, and a protection is provided on the front surface of the housing 20 a facing the conveyance unit 15. Glass 24 is arranged. In the fixing unit 20, a magnet 25 is disposed at a position substantially equidistant from the surface of the protective glass 24 when viewed from the recording medium MRC on the carry-in side of the recording medium MRC and the printing surface side. A suction duct 26 for sucking air is provided on the downstream side of the magnet 25 when viewed in the direction.
[0025]
The reflecting plate 22 is formed by processing a metal such as aluminum having a high reflectance on the inner surface thereof. However, if the reflection plate 22 is a metal, it is difficult to be formed into an arbitrary shape because the metal plate has a low degree of freedom in shape and becomes heavy. For this reason, the reflection plate 22 may be formed of a heat-resistant resin such as polyimide deposited with metal. For example, a polyimide film having a thickness of about 0.1 to 0.5 mm is integrally formed into a desired reflector shape by vacuum forming, and a metal such as aluminum, silver, or gold is deposited on the inner surface.
[0026]
The magnet 25 is a permanent magnet provided for the purpose of reducing dirt on the protective glass 24 by capturing the scattered toner and reducing the toner adhering to the protective glass 24. At this time, as for the conveyance unit 15, the housing | casing 15c consists of a ferromagnetic material as mentioned above. For this reason, the magnet 25 has a shape in which the lines of magnetic force cross the recording medium MRC, so that the scattered toner can be captured more effectively. Therefore, the magnet 25 may be provided closer to the recording medium MRC than the surface of the protective glass 24 for the above purpose.
[0027]
1, the suction duct 26 is disposed in the front and back direction of the housing 1a in FIG. 1, has an opening on the transport unit 15 side, and is connected to the outside of the housing 1a through suction means such as a filter and a blower (not shown) for deodorizing and removing smoke. Communicate. The suction duct 26 sucks the air around the fixing unit 20 in this way, and discharges it outside the housing 1a through a filter for deodorizing / desmokinging, thereby fixing the unfixed toner image in the fixing unit 20 mainly. The unpleasant odor and smoke of the toner component generated by the toner is removed.
[0028]
Here, the photosensitive drum 2, the main charger 3, the LED print head 4, the developing unit 5, the pre-cleaning charger 8, the carrier recovery unit 9, the cleaning unit 10, and the charge eliminating lamp 11 form an unfixed image on the recording medium MRC. The image forming unit PIF to be used.
In the electrophotographic printer 1, stays 1e and 1f are disposed between a pair of side plates 1d of the housing 1a, and shielding plates 1g and 1h are provided between the stays 1e and 1f and the housing 1a.
[0029]
The shielding plates 1g and 1h are provided for the purpose of shielding the airflow between the image forming unit PIF and the fixing unit 20. However, in the electrophotographic printer 1, as is clear from FIG. 1, this airflow mainly flows on the upper side of the image forming portion PIF, so that at least the shielding plate 1g may be provided. As described above, in the electrophotographic printer 1, the image forming portion PIF is disposed in a substantially closed space formed by the pair of side plates 1d, stays 1e and 1f, shielding plates 1g and 1h, and the conveyance path for conveying the recording medium MRC. Will be.
[0030]
As shown in the figure, the electrophotographic printer 1 is provided with a fan 17 between the image forming unit PIF and the fixing unit 20, that is, between the upper portion of the stay 1e and the upper portion of the fixing unit 20.
The fan 17 blows an airflow toward the image forming surface on the upper surface of the recording medium MRC in FIG. 1, and generates an airflow toward at least one of the image forming unit PIF and the fixing unit 20 along the recording medium MRC. At this time, as shown in FIG. 1, the outside air of the electrophotographic printer 1 is introduced into the fan 17 through the discharge port 1c. In addition, an opening, a duct, or the like that guides outside air to the fan 17 may be provided in the housing 1a.
[0031]
The electrophotographic printer 1 is configured as described above, and performs a desired print by fixing an unfixed toner image on the recording medium MRC by the electrophotographic method described below.
First, the surface of the photosensitive drum 2 whose surface is cleaned by the cleaning unit 10 and rotated at a constant speed in the direction of the arrow is charged by the main charger 3 after the residual charge on the surface is removed by the charge eliminating lamp 11.
[0032]
Next, the LED print head 4 irradiates the photosensitive drum 2 with a light beam to form an electrostatic latent image corresponding to the recording information on the surface of the photosensitive drum 2. The electrostatic latent image is developed by the developing unit 5 by the rotation of the photosensitive drum 2 and becomes an unfixed toner image (visible image).
The unfixed toner image developed on the photosensitive drum 2 is transferred by the transfer charger 6 onto the recording medium MRC conveyed along the conveyance path indicated by the arrow. The recording medium MRC to which the unfixed toner image is transferred is separated from the photosensitive drum 2 by the separation charger 7 and conveyed to the fixing unit 20 by the conveyance unit 15.
[0033]
In the fixing unit 20, the flash lamp 21 emits light, and the unfixed toner image is melted and fixed on the recording medium MRC by the generated heat.
In the electrophotographic printer 1, as described above, an image corresponding to the recording information is formed on the recording medium MRC, charged by the pre-cleaning charger 8, the carrier recovery by the carrier recovery unit 9, and the cleaning unit 10. After the surface cleaning of the photosensitive drum 2, the residual latent image on the photosensitive drum 2 is erased by the charge eliminating lamp 11 and is used for the next subsequent image formation.
[0034]
At this time, the electrophotographic printer 1 has a higher temperature inside the apparatus than outside due to the printing operation. At the same time, in the electrophotographic printer 1, due to the heating of the recording medium MRC (paper) in the fixing unit 20, the moisture in the recording medium MRC evaporates, and the inside of the apparatus becomes humider than the outside.
However, the electrophotographic printer 1 is close to the optical drum 2 and at least the support bracket 4 a of the LED print head 4 facing the photosensitive drum 2, between the pre-cleaning charger 8 and the stay 1 e and the lamp housing 11 a of the static elimination lamp 11. The heat insulating member Ab is attached to or disposed on.
[0035]
For this reason, even if the temperature in the apparatus is lowered due to the stop of the printing operation, the electrophotographic printer 1 is provided between the support bracket 4a to which the heat insulating member Ab is attached, the lamp housing 11a and the pre-cleaning charger 8 and the stay 1e. The part does not cool faster than the surroundings. Therefore, in the electrophotographic printer 1, the surface of the photosensitive drum 2 facing these portions does not reach a lower temperature than the surroundings, so that the occurrence of condensation is suppressed.
[0036]
In addition, a print defect caused by the overlap of the potential drop caused by the part of the flash light being applied to the photosensitive drum 2 and the potential drop caused by the reaction between the condensation and nitrogen oxide (NOx) is caused by condensation and nitrogen oxide ( Since the potential drop due to the reaction with NOx) is suppressed, the generation is reduced.
[0037]
【The invention's effect】
According to the first to eighth aspects of the present invention, it is possible to provide an image forming apparatus and an image forming method that suppress the occurrence of printing defects caused by condensation or nitrogen oxides (NOx).
[Brief description of the drawings]
FIG. 1 is a cross-sectional front view illustrating a schematic configuration of an electrophotographic printer according to an embodiment of an image forming apparatus and an image forming method of the present invention.
2 is an enlarged cross-sectional front view centering on a photosensitive drum in the electrophotographic printer of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electrophotographic printer 1d Side plate 1e, 1f Stay 1g, 1h Shield plate 2 Photosensitive drum 3 Main charger 4 LED print head 5 Development unit 5c Developing roll 5d Magnet 6 Transfer charger 7 Separation charger 8 Pre-cleaning charger 9 Carrier recovery Unit 10 Cleaning unit 10b Brush roller 11 Static elimination lamp 12 Separation claw 13 Guide plate 14 Tractor 15 Transport unit 16 Scuff flora 17 Fan 20 Fixing unit 21 Flash lamp 22 Reflector plate 23 Radiation fin 24 Protective glass 25 Magnet 26 Suction duct Ab Heat insulation member PIF Image forming unit

Claims (8)

An image forming apparatus having an organophotoreceptor, wherein at least a portion of the metal member that is disposed in the vicinity of the organophotoreceptor and does not directly participate in image formation is opposed to the organophotoreceptor. An image forming apparatus. The image forming apparatus according to claim 1, wherein the heat insulating member is rubber. The image forming apparatus according to claim 1, wherein the heat insulating member is a foam material. The image forming apparatus according to claim 1, wherein the organic photoreceptor is a single layer type organic photoreceptor. The image forming apparatus according to claim 4, wherein the single-layer type organic photoreceptor is a positively charged type. 6. The image forming apparatus according to claim 1, further comprising a fixing device for fixing an unfixed image formed on the recording medium, wherein the fixing device is of a flash fixing system. The image forming apparatus according to claim 6, further comprising a conveying unit that conveys the recording medium substantially linearly. An image forming method of developing an electrostatic latent image formed on an organic photoreceptor into a toner image and fixing the toner image on a recording medium to form an image, the image forming method being disposed in proximity to the organic photoreceptor and An image forming method characterized in that at least a portion of a metal member not directly involved in image formation is opposed to the organic photoreceptor.

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