JP2006301437A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress production of an abnormal image with spots which rarely occurs in the first sheet on forming an image first in the morning. <P>SOLUTION: The image forming apparatus charges a photoreceptor drum 2 by using a charging roller 3 in contact with or in proximity to the drum 2, wherein the apparatus is equipped with a current measuring unit 102 to detect a current flowing in the charging roller 3, and with a controller 100 to determine a preliminary operation time prior to image formation based on the current detected by the current measuring unit 102 during the preliminary operation prior to image formation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine having at least two functions of these.

  In an image forming apparatus using a general electrophotographic method, when an image is output immediately after the power is turned on, a spotted pattern having a diameter of about 1 to 2 mm, which is rarely referred to as spot unevenness, may appear on the image. One of the causes of this uneven spot is a charging process. In the charging process, the image carrier is charged so as to have a uniform potential. However, when the abnormal image is generated, a portion that is not charged to a predetermined potential is generated. For this reason, when development is performed, the toner is developed in the portion that did not reach the predetermined potential, and a spot-like image appears in the final image. This non-uniformity does not occur every time under the same charging roller and the same output conditions, that is, temperature, humidity, toner conditions, and the like.

  Further, even after the power is turned on, it does not occur when output is performed when the image forming apparatus is sufficiently warm, such as after the second sheet or in the standby mode. For this reason, although a detailed cause is unknown, it is thought that stability of the energization state of a charging member is related.

JP 2003-057924 A Japanese Patent Laid-Open No. 11-084824

  In the configuration of Patent Document 1, the environment around the apparatus is detected and controlled so as to prevent a charging failure with a small discharge amount in a low temperature and low humidity environment. As a result, the occurrence of unevenness can be suppressed, but the voltage may be controlled even when the unevenness does not occur under environmental conditions. Then, not only is the efficiency low, but also the life of the image carrier is shortened, which is contrary to resource saving.

Further, in Patent Document 2, a stable image without density unevenness is obtained even when used in a place where the ambient temperature changes greatly.
For this reason, when the temperature of the charging roller or the temperature in the vicinity thereof changes due to the change in the environmental temperature where the image forming apparatus is placed, the charging potential on the photosensitive member is stabilized after the voltage is applied to the charging roller. Even in such a case, the temperature detection sensor detects the temperature of the charging roller or a temperature in the vicinity thereof, and the pre-charging time control means applies a voltage to the charging roller according to the detected temperature. Then, by varying the time from the start of image formation on the photoconductor to optimize the time, the charging potential in one image can be made constant, so that density unevenness can be reduced. No stable image is obtained.

  Even with this method, an optimum image can be obtained. However, depending on the selection of the material of the charging roller, an abnormal image may not be obtained even if the environment changes. That is, even if a charging roller that generates a spot unevenness rarely due to a change in environment is used, even if a spot unevenness does not occur in the configuration of Patent Document 2, the voltage is controlled when the environmental condition changes. That is, there is a case where the voltage is controlled even when no unevenness occurs. Then, under specific environmental conditions, not only the time until image formation is always increased, but also the life of the image carrier is shortened, which is contrary to resource saving.

  SUMMARY OF THE INVENTION In view of the circumstances described above, an object of the present invention is to provide an image forming apparatus capable of suppressing the occurrence of an abnormal image of a spot unevenness that occurs very rarely when the first image is displayed in the morning. And

  In order to achieve the above object, the present invention provides an image forming apparatus for charging an image carrier using a charging member in contact with or close to the image carrier, and a current measuring unit for detecting a current flowing through the charging member. And a control unit that determines the time of the preliminary operation before the image formation based on the current detected by the current measuring unit during the preliminary operation before the image formation.

  According to the present invention, when the current measuring unit detects a current flowing through the charging member during a preliminary operation before image formation and a spike-like current pulse is detected, the control unit is predetermined. It is effective to extend the preliminary operation standard time before the image formation.

  Further, according to the present invention, a humidity detector is provided to detect the humidity during the preliminary operation before image formation, and when the detected humidity is lower than a predetermined value, the current measuring unit is charged during the preliminary operation before image formation. When the current flowing through the member is detected and a spike-like current pulse is detected, it is effective that the control unit extends the predetermined preliminary operation standard time before the image formation.

  Furthermore, the present invention provides a temperature detection means for detecting the temperature during the preliminary operation before image formation, and when the detected temperature is lower than a predetermined value, the current measuring unit is configured during the preliminary operation before image formation. When the current flowing through the charging member is detected and a spike-like current pulse is detected, it is effective if the control unit extends the predetermined preliminary operation standard time before the image formation.

  Furthermore, the present invention provides a humidity detection means and a temperature detection means for detecting the humidity and temperature during the preliminary operation before image formation, and when at least one of the detected humidity and temperature is lower than a predetermined value, When the current measuring unit detects a current flowing through the charging member during the preliminary operation before image formation, and when a spike-like current pulse is detected, the control unit sets a predetermined preliminary operation standard time before the image formation. It is effective to extend.

  Furthermore, according to the present invention, the control unit increases the length of time of the preliminary operation according to the sum of the counts or peak values of spike-like current pulses detected by the current measurement unit during the preliminary operation before image formation. Setting the size is effective.

  Furthermore, the present invention is an ammeter in which the current measuring unit measures a current pulse, and the ammeter is effective when installed between a circuit for applying a voltage to the charging member and the charging member. It is.

Furthermore, the present invention is effective when the current measuring unit is an ammeter for measuring a current pulse, and the ammeter is installed between the image carrier and the ground.
Furthermore, the present invention provides an electrode member whose surface is made of a resistor or an insulator, and is close to or in contact with the charging member, and a current for determining a pre-operation time is generated between the charging member and the electrode member. It is effective based on the current flowing between them.

Furthermore, the present invention is effective when a charging roller is used as the charging member.
Furthermore, according to the present invention, the charging member is a member having a small change in hardness due to the environment, and the surface is disposed close to the surface of the image carrier so that the discharge is performed in the adjacent space formed by the gap. It is effective to charge the image carrier by causing

Furthermore, the present invention is effective when a toner image is formed on the image carrier and the toner used has a circularity of 0.96 or more.
Furthermore, the present invention includes a cleaning means including a fur brush made of conductive fibers in contact with the image carrier, a recovery roller in contact with the fur brush, and a scraper member in contact with the recovery roller. It is effective to collect the toner from the image carrier using an electric field by applying a voltage to at least one of the fur brush or the collecting roller of the means.

Furthermore, the present invention is effective when the image carrier is made of amorphous silicon.
Furthermore, the present invention is effective when the surface layer of the image carrier disperses and strengthens the filler.

Furthermore, the present invention is effective when an organic photoreceptor using a crosslinkable charge transport material is used for the image carrier.
Furthermore, the present invention is effective when at least the surface layer of the image carrier is made of polyarylate resin.

Furthermore, the present invention is effective when a toner image is formed on the image carrier and the toner to be used is an oilless toner.
Furthermore, the present invention is effective when it has a process cartridge in which an image carrier and at least one image forming means for forming a toner image on the image carrier are integrally assembled.

  Furthermore, the present invention is effective when an image is formed by overlapping toners a plurality of times.

  An abnormal image that occurs accidentally can be prevented in advance.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an example of an image forming apparatus 1 to which the present invention is applied.
1, an image forming apparatus 1 includes a photosensitive drum 2 as an image carrier that is rotated in a clockwise direction in FIG. 1 in a main body housing (not shown), and around the photosensitive drum 2. A charging unit 3, a writing unit 4, a developing unit 5, a transfer unit 6, a cleaning 7, and a photoreceptor charge eliminating unit 8 are provided in the rotation direction.

  Although not shown, the image forming apparatus 1 includes a paper feeding cassette that stores a plurality of recording papers. The recording paper in the paper feeding cassette is timed by a pair of registration rollers (not shown) one by one by a paper feeding roller (not shown). After the adjustment, the paper is transferred between the paper transfer section (7) and the image carrier 2.

  The image forming apparatus 1 is uniformly charged by the charging unit 3 when the photosensitive drum 2 is driven to rotate clockwise, and the charged portion is irradiated with a laser modulated by image data by the writing unit 4. An electrostatic latent image is formed on the photosensitive drum 2. The electrostatic latent image formed on the photosensitive drum 2 is visualized by attaching toner to the developing unit 5, thereby forming a toner image. In synchronization with the toner image, the recording paper is fed toward the transfer unit 6 of the photosensitive drum 2, and the toner image is transferred under the action of the transfer unit 6 and conveyed to a fixing unit (not shown). Then, the fixed recording paper is discharged onto a paper discharge tray (not shown).

  On the other hand, the toner that is not transferred remains on the photosensitive drum 2 after transfer, and this residual toner is removed by the cleaning unit 7. The cleaning unit 7 of this example includes a blade, and the toner is scraped off and removed by the blade. After the toner is removed, the residual charge is removed from the photosensitive drum 2 by the charge removing unit 8 to prepare for the next image formation. The cleaning unit 7 is not limited to the one that scrapes off the residual toner on the photosensitive drum 2 with a blade, and may be one that scrapes off the residual toner on the photosensitive drum 2 with a fur brush, for example. Reference numeral 9 denotes a lubricant application unit that applies a lubricant to the photosensitive drum 2.

  In the image forming apparatus 1, the charging unit 3 may be a contact charging roller, a non-contact charging roller, a brush charger, a blade charger, or the like, but is preferably arranged with a small gap with respect to the photosensitive drum. It consists of a hard conductive roller.

FIG. 2 is an example of a configuration in which the charging unit of the image forming apparatus 1 of the present invention is implemented in a roller shape.
For example, the charging roller 3 as a charging unit includes a conductive substrate 201 and a surrounding resistance layer 202. The conductive substrate 201 is a cylindrical member made of stainless steel (hereinafter also referred to as SUS) having a diameter of 8 to 20 mm. Note that the conductive substrate 201 may be reduced in weight by using aluminum or a conductive resin of 10 3 Ω · cm or less.

  The resistance layer 202 is made of a polymer material obtained by kneading a conductive material into a resin such as ABS or PP, and the surface thereof is coated with, for example, a fluorine-based resin as a thin layer 203. Examples of conductive materials include metal ion complexes, carbon black, and ionic molecules. In addition, a material capable of performing uniform charging may be used.

  The surface of the charging roller 3 moves in the same direction as the surface of the photosensitive drum 2. Of course, the charging roller 3 may be stationary without rotating together with the photosensitive drum 2. The length of the charging roller 3 in the longitudinal direction (axial direction) is set slightly longer than the maximum image width A4 side (about 290 mm). The charging roller 3 is provided with spacers (not shown) at both ends in the longitudinal direction, and the charged surfaces on the surface of the photosensitive drum 2 are brought into contact with the non-image forming regions at both ends of the photosensitive drum 2. The gap H between the charging roller 3 and the charging surface of the charging roller 3 is held such that the distance at the closest portion is 5 to 150 μm. This closest distance is more preferably set to 30 to 75 μm, and is set to 50 μm in this embodiment.

  A charging power source 210 is connected to the charging roller 3. As a result, the surface to be charged is uniformly charged by discharge in the gap H between the surface to be charged on the surface of the photosensitive drum 2 and the surface to be charged on the surface of the charging roller 3. The applied voltage bias is preferably a voltage waveform in which an AC voltage is superimposed on a DC voltage, and the peak-to-peak voltage of the AC voltage is preferably at least twice the charging start voltage. Moreover, you may use DC voltage and the voltage of a constant current system as needed.

FIG. 3 is an explanatory diagram showing an example of a method of maintaining the gap H with a minute gap.
In FIG. 3, the spacer member 302 is configured by winding a film around both ends of the charging roller 3. The spacer member 302 is brought into contact with the photosensitive surface of the photosensitive drum 2 so as to obtain a certain minute gap in the image area of the charging roller 3 and the photosensitive drum 2. The applied bias applies an AC superposition type voltage to charge the photosensitive drum by electric discharge generated in a minute gap between the charging roller and the photosensitive drum. Furthermore, by pressing the shaft 204 of the charging roller 3 with a spring 303 or the like, the maintenance accuracy of the minute gap is improved.

  Further, the charging roller 3 provided with the spacer member 302 by integral molding may be used. At this time, at least the surface of the spacer member 302 is preferably an insulator. With this configuration, the discharge is eliminated in the gap portion, the discharge product is deposited on the spacer member 302, and the toner adheres to the gap portion due to the adhesiveness to the discharge product, so that the gap is not widened.

  The spacer member 302 may be a heat shrinkable tube. As the heat-shrinkable tube, for example, a Sumitube (trade name: F105 ° C, manufactured by Sumitomo Chemical Co., Ltd.) for 105 ° C is used. The thickness of the heat-shrinkable tube is 300 μm, and depending on the diameter of the charging roller 3 to be mounted, the heat-shrinkable tube exhibits a shrinkage rate of about 50 to 60% and increases by about 0 to 200 μm due to heat shrinkage. The roller 3 needs to be cut in consideration of the increase. For example, when the spacer member 302 is mounted on the charging roller 3 having a diameter of 12 mm, a heat shrinkable tube having a cutting depth of 350 μm and an inner diameter of about 15 mm may be used. After mounting the heat shrinkable tube on the cutting part at the end of the charging roller 3, the charging member is rotated and inwardly heated from the end surface and heated with a heat source at 120 to 130 ° C. to uniformly shrink the heat, The gap H between the photosensitive drums can be set to about 50 μm. The heat-shrinkable and fixed heat-shrinkable tube does not come off during use, but for prevention, a liquid adhesive such as cyanoacrylate resin (for example, Aron Alpha, cyanobond, etc., both trade names) is used at the end. Can be poured and fixed.

  Since the heat-shrinkable tube has a thickness, when the spacer member 302 is used, the step 401 is taken as shown in FIG. 4 and the spacer member 302 is attached, or a part of the end of the resistance layer is left as shown in FIG. The groove 402 is formed, and a square ring spacer member 302 having endless stretchability is attached to the groove 402. Further, the groove in FIG. 5 may be rounded and cut, and a circular ring-shaped (usually referred to as O-ring) spacer member 302 may be attached. It is desirable that the end portion is sharpened to facilitate insertion of the spacer member 302, and it is also possible to cut completely and fix it with an adhesive. In the case where the spacer member 302 is mounted and fixed to a portion where a cut portion or a groove is formed, it is desirable to use an adhesive such as a two-component epoxy resin in addition to the liquid adhesive described above.

  As shown in FIG. 6, the spacer member may be a roller member 601 into which a member having a diameter larger than that of the charging roller is inserted later. As the material of the roller member 601, polycarbonate (PC), polyacetal (POM), polypropylene (PP), polyethylene (PE), ultrahigh molecular weight polyethylene (UHMW-PE), polyamide 6 (PA6), polyamide 66 (PA66), Modified polyphenylene ether (m-PPE), ABS, polyarylate (PAR), PTFE, phenol resin, bakelite, Teflon resin polysulfone (PSF), polyethersulfone (PES), polyphenylene sulfide (PPS), polyarylate (PAR) , Polyamideimide (PAI), polyetherimide (PEI), polyetheretherketone (PEEK), thermoplastic polyimide (TPI), polybenzimidazole (PBI), polymethylpentene (TPX), polyester Cyclohexylene-dimethylene terephthalate (PCT), syndiotactic polystyrene (SPS), Polyamide 6T (PA6T), polyamide 9T (PA9T), polyamide 11,12 (PA11,12), and the like fluororesin. Also, a roller member 601 may be obtained by mixing a blend of these resins or the same resin but having different grades.

  FIG. 10 is a schematic configuration diagram for explaining the layer configuration of the amorphous silicon photoconductor. In the electrophotographic photoreceptor 500 shown in FIG. 10A, a photoconductive layer 502 made of a-Si: H, X and having photoconductivity is provided on a support 501. An electrophotographic photoreceptor 500 shown in FIG. 10B includes a photoconductive layer 502 made of a-Si: H, X and having photoconductivity on a support 501, and an amorphous silicon-based surface layer 503. It is configured. An electrophotographic photoreceptor 500 shown in FIG. 10C has a photoconductive layer 502 made of a-Si: H, X and having photoconductivity on a support 501, an amorphous silicon-based surface layer 503, And an amorphous silicon based charge injection blocking layer 504. In the electrophotographic photoreceptor 500 shown in FIG. 10D, a photoconductive layer 502 is provided on a support 501. The photoconductive layer 502 includes a charge generation layer 505 made of a-Si: H, X and a charge transport layer 506, and an amorphous silicon-based surface layer 503 is provided thereon.

  In addition, an organic photoreceptor using a crosslinkable charge transport material can be used as the photoreceptor. In this photoreceptor, a protective layer having a crosslinked structure is also effectively used as a binder constitution of the protective layer. Regarding the formation of a cross-linked structure, a reactive monomer having a plurality of cross-linkable functional groups in one molecule is used to cause a cross-linking reaction using light or thermal energy to form a three-dimensional network structure. is there. This network structure functions as a binder resin and exhibits high wear resistance.

  From the viewpoint of electrical stability, printing durability, and life, it is a very effective means to use a monomer having a charge transporting ability in whole or in part as the reactive monomer. By using such a monomer, a charge transporting site is formed in the network structure, and the function as a protective layer can be sufficiently expressed.

  The reactive monomer having charge transporting ability includes a compound containing at least one charge transporting component and a silicon atom having a hydrolyzable substituent in the same molecule, and a charge transporting component in the same molecule. A compound containing a hydroxyl group, a compound containing a charge transporting component and a carboxyl group in the same molecule, a compound containing a charge transporting component and an epoxy group in the same molecule, a charge transporting component in the same molecule And a compound containing an isocyanate group. These charge transport materials having a reactive group may be used alone or in combination of two or more.

  More preferably, a reactive monomer having a triarylamine structure is effectively used as the monomer having a charge transporting ability because of high electrical and chemical stability and high carrier mobility.

  In addition to this, monofunctional and bifunctional polymerizable monomers and polymerizable oligomers are used in combination for the purpose of viscosity adjustment during coating, stress relaxation of the cross-linked charge transport layer, low surface energy, and reduction of friction coefficient. be able to. As these polymerizable monomers and oligomers, known ones can be used.

  In the present invention, the hole transporting compound is polymerized or cross-linked using heat or light. When the polymerization reaction is performed by heat, the polymerization initiator may be used in the case where the polymerization reaction proceeds only with thermal energy. Although it may be necessary, in order to advance the reaction efficiently at a lower temperature, it is preferable to add an initiator.

  In the case of polymerization by light, it is preferable to use ultraviolet light as light, but the reaction rarely proceeds only with light energy, and generally a photopolymerization initiator is used in combination.

  The polymerization initiator in this case mainly absorbs ultraviolet rays having a wavelength of 400 nm or less to generate active species such as radicals and ions, and initiates polymerization. In the present invention, the aforementioned heat and photopolymerization initiator can be used in combination.

  The charge transport layer having a network structure formed in this manner has high wear resistance, but has a large volume shrinkage during the crosslinking reaction, and if it is too thick, it may cause cracks. In such a case, the protective layer may be a laminated structure, a low molecular dispersion polymer protective layer may be used for the lower layer (photosensitive layer side), and a protective layer having a crosslinked structure may be formed on the upper layer (surface side). good.

  In the electrophotographic photosensitive member 1, an electrophotographic photosensitive member A was prepared in the same manner as the electrophotographic photosensitive member 1, except that the protective layer coating solution, film thickness, and preparation conditions were changed as follows. 182 parts of methyltrimethoxysilane, 40 parts of dihydroxymethyltriphenylamine, 225 parts of 2-propanol, 106 parts of 2% acetic acid, and 1 part of aluminum trisacetylacetonate were mixed to prepare a coating solution for the protective layer. This coating solution was applied onto the charge transport layer and dried, and then heat-cured at 110 ° C. for 1 hour to form a protective layer having a thickness of 3 μm.

In the electrophotographic photosensitive member 1, an electrophotographic photosensitive member B was prepared in the same manner as the electrophotographic photosensitive member 1, except that the protective layer coating solution, film thickness, and preparation conditions were changed as follows.
30 parts of a hole transporting compound (the following structural formula (I)), 0.6 part of an acrylic monomer (the following structural formula (II)) and a photopolymerization initiator (1-hydroxy-cyclohexyl-phenyl-ketone) It was dissolved in a mixed solvent of 50 parts of chlorobenzene / 50 parts of dichloromethane to prepare a coating material for the surface protective layer. This paint was applied on the previous charge transport layer by spray coating, and cured for 30 seconds at a light intensity of 500 mW / cm ² using a metal halide lamp to form a surface protective layer having a thickness of 5 μm.

  By the way, in an image forming apparatus, when an image is output immediately after the power is turned on, a spotted pattern having a diameter of about 1 to 2 mm, which is rarely referred to as spot unevenness, may appear on the image.

  Therefore, the inventor of the present application examined the waveform of the current flowing through the charging roller when normal and when uneven spots occur. The result is shown in FIG. FIG. 8 is a screen of an oscilloscope, and the waveform is a current waveform that flows from the charging roller 3 to the photosensitive member 2 when the photosensitive member is charged. When spot unevenness occurs, spike-like pulses are generated as shown in FIG. 8B, but when the photosensitive member 2 is uniformly charged (during normal operation), it is shown in FIG. A current waveform without spike-like pulses as shown was observed.

  In this experiment, the same charging roller 3 was used, but the waveform shown in FIG. 8 (b) was rarely generated in a plurality of measurements, and it may or may not occur even if the conditions are very similar. I understood. In addition, it was found that spot unevenness occurs when the temperature and humidity are low. Furthermore, spike-like pulses that generate uneven spots are generated only at a certain time after the power is turned on. In other words, it has been found that after a certain period of time has elapsed, it disappears.

If a charging roller in which the spike-like pulse is detected in the current waveform is handled as a defective product in order to prevent the occurrence of spot unevenness, the yield of the charging roller is deteriorated.
Therefore, in the present invention, when the spike-like pulse is detected, the preliminary operation time of the photosensitive member, which is a preliminary operation before image formation, is extended. The preliminary operation is process control (hereinafter abbreviated as “procon”) performed when the image forming apparatus is started up. In general, process control is used to always set image forming conditions appropriately in an image forming apparatus. Specifically, with respect to the detection result of the toner adhesion amount and the surface potential of the photosensitive drum 2, the light emission amount of the writing unit 4, the charging potential of the photosensitive drum 2, the developing bias, and the toner replenishment In addition to control for setting the amount and the like, the color image forming apparatus includes control for matching the color of each color toner image. In this professional computer, for example, the charging roller 3 and the photosensitive member 2 are rotated, a voltage is applied to the charging roller 3, and a state in which discharge is generated between the charging roller 3 and the photosensitive member 2 is continued for a certain time. At this time, since it is not necessary to uniformly charge the photosensitive member, the lowest voltage (Vpp or the like) at which discharge occurs or the AC frequency lower than usual may be used. Alternatively, discharging may be performed by applying only a DC voltage.

9 to 12 show a configuration for detecting a current waveform flowing through the charging roller.
In FIG. 9, reference numeral 101 denotes a voltage applying unit that applies a voltage to the charging roller 3. A current measuring unit 102 is provided between the voltage applying unit 101 and the charging roller 3, and the current measuring unit 102 uses the spike-like current pulse. Is detected. Reference numeral 100 denotes a controller, 103 denotes a driving motor for the charging roller 3, 104 denotes a driving motor for the photosensitive drum 2, and the driving of these motors is controlled by the controller 100.

  FIG. 10 is different from FIG. 9 in that the current measuring unit 102 is provided on the ground side on the photosensitive member 2 side, but the other configurations are the same as those in FIG. It is attached.

  Furthermore, in FIG. 11, a counter electrode 110 is provided between the charging roller 3 and the photosensitive member 2, and a current pulse of a current flowing between the charging roller 3 and the counter electrode 110 is detected by the current measuring unit 102. . The counter electrode 110 is inserted between the charging roller 3 and the photosensitive member 2 during the process control. Then, during the subsequent image formation, the counter electrode 110 is retracted to a position that does not hinder the uniform charging of the photoreceptor 2.

  Furthermore, FIG. 12 is a diagram in which a memory 120 is connected to the controller 100, and the memory 120 can store the number of current pulses detected by the current measuring unit 102. The memory 120 can also store the peak value of the current pulse detected by the current measuring unit 102.

Next, a control example for determining the process control time will be described based on the flow of FIGS.
In FIG. 13, after the main power source is turned on (step 1) and the motor and voltage application unit 101 are turned on (step 2), the current measuring unit 102 detects the presence or absence of spike-like current pulses (step 3). Then, the presence / absence of a spike-like current pulse is determined (step 4), and when the spike-like current pulse is detected, the time of the process control is determined (step 4).

  Further, when the normal control time is determined, the control time may be controlled to be extended only when a current pulse is detected by the current detection unit 102 as shown in FIG.

  In the flowcharts of FIGS. 13 and 14, the control time is determined and extended only when the main power is turned on. However, when the control is performed even when there is no printing operation for a certain time other than when the main power is turned on, the same applies. You may control.

  In addition, since spot unevenness occurs only when at least one of temperature and humidity is low, the flow chart shown in FIG. 15 is provided with a sensor capable of detecting the temperature in the vicinity of the charging roller 3, and 15 ° C. or less is regarded as a low temperature. Only when the temperature is 15 ° C. or lower, the process control time is determined and extended.

  Furthermore, in the flowchart shown in FIG. 16, a sensor capable of detecting the humidity in the vicinity of the charging roller 3 is provided, and 35% or less is regarded as low humidity, and the control time is determined and extended only when the humidity is 35% or less. I do.

  Of course, both the temperature and humidity sensors may be installed in the vicinity of the charging roller 3, and when both values or at least one value falls below a certain value, the determination of the process control time and the extension control may be performed.

Furthermore, the flow chart of FIG. 17 shows the control for determining the length of the extended time when the normal control time is determined and when the current pulse is detected, the control time is extended. At the time of the process control, the number of current pulses is counted (n) for a certain time (for example, 10 seconds). Then, the length of the process control time is determined by the relationship shown in Table 1 below according to the count number (value of n). Table 1 is an example, and n may be associated with the preliminary rotation time on a one-to-one basis without dividing n into sections.

Further, the length of the extension time can be determined by adding the peak values of the current pulses detected by the current measuring unit 102.
FIG. 18 is an explanatory diagram showing an example of a tandem type full-color image forming apparatus 1 to which the present invention is applied.

  18, the image forming apparatus 1 includes first to fourth image forming units 11A to 11D having drum-shaped image carriers 12A to 12D that rotate counterclockwise, and each of the image forming units 11A to 11D. A yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on the image carriers 12A to 12D, respectively. An intermediate transfer belt 13 is disposed opposite to the image carrier 12 of each image forming means 11, and this intermediate transfer belt 13 is wound around a plurality of rollers 14, and one of the rollers is driven by a driving means (not shown). By being driven to rotate, the vehicle is driven in the direction of arrow A.

  Since the operation is substantially the same as the configuration for forming the toner image on each of the first to fourth image carriers 12A to 12D, only the configuration for forming the toner image on the first image carrier 12A is used. Will be explained. The image carrier 12A is driven to rotate counterclockwise in FIG. 1, and at this time, the surface of the image carrier is uniformly charged to a predetermined polarity by the charging roller 15. Next, the charged surface is irradiated with a light-modulated laser beam emitted from the laser writing unit 16. As a result, an electrostatic latent image is formed on the image carrier 12, and the electrostatic latent image is visualized as a yellow toner image by the developing device 17. A transfer roller (not shown) is disposed at a position substantially opposite to the image carrier 12A with the intermediate transfer belt 13 interposed therebetween. The transfer roller has a polarity opposite to the charging polarity of the toner on the image carrier 2A. A voltage is applied, whereby the yellow toner image on the image carrier 2A is transferred onto the intermediate transfer belt 13. The transfer residual toner that is not transferred to the intermediate transfer belt 13 and remains on the image carrier 2Y is removed by the cleaning device 18.

  In exactly the same manner, a cyan toner image, a magenta toner image, and a black toner image are formed on the second to fourth image carriers 12B to 12D, respectively, and these toner images are transferred to the yellow toner image. The images are sequentially superimposed on the belt 3 and transferred.

  On the other hand, the image forming apparatus 1 is provided with a paper feed cassette that stores a plurality of recording papers (not shown), and the recording paper in the paper feeding cassette is not shown by a registration roller (not shown) one by one by a paper feeding roller (not shown). After the timing is adjusted in pairs, the paper is fed between the paper transfer unit 19 and the intermediate transfer belt 13. Then, the superimposed toner image formed on the intermediate transfer belt 13 is transferred to the recording paper P, and the recording paper on which the toner image is transferred is discharged outside the apparatus after fixing.

  FIG. 19 is an explanatory view showing a revolver type full-color image forming apparatus, which is different from the image forming apparatus 1 in FIG. 1 in that four developing units 24 for forming toner images of yellow, cyan, magenta and black. And a toner image formed on the photosensitive drum 22 is sequentially transferred onto the intermediate transfer belt 28 in a superimposed manner.

  When a full-color copy is obtained in this revolver type image forming apparatus, an image for each color is formed on the photosensitive drum 22 and transferred onto the intermediate transfer belt 28 in an overlapping manner. At this time, the developing unit 24 selectively activates the developing unit 24 of the color to be formed by switching the operation. When the full-color toner image is superimposed and transferred onto the intermediate transfer belt 28, the toner image is collectively transferred to the recording paper in the secondary transfer unit 29, and the recording paper P on which the toner image is transferred is fixed to a fixing unit (not shown). ) To obtain a fixed image.

FIG. 20 shows a schematic configuration of an image forming apparatus having a process cartridge of the present invention.
In FIG. 20, 30 is the entire process cartridge, 2 is a photosensitive member, 3 is a charging means, 5 is a developing means, 7 is a cleaning means, and 9 is a lubricant application device.

  Among the constituent elements of the above-described photoreceptor 2, charging means 3, developing means 3, cleaning means 7, and solid lubricant application device 9, a plurality of them are integrally combined as a process cartridge, The process cartridge is configured to be detachable from the image forming apparatus main body such as a copying machine or a printer. Further, in the case of a process cartridge, when parts are replaced due to spot unevenness, replacement is performed in units of cartridges, resulting in a large number of parts and waste.

  As described above, the present invention can prevent abnormal images that occur accidentally. Therefore, the waste of paper and the waste of time, such as recognizing an abnormal image for the first time after forming the image and starting output again, are eliminated.

In addition, when the ammeter for measuring the current pulse is installed between the charging member and the circuit for applying a voltage to the charging member, the ammeter efficiently detects the spike-like current pulse related to the unevenness.
Furthermore, an ammeter for measuring current pulses is detected on the ground side when installed between the image carrier and the earth, so that a special insulation process is not required, and the configuration of the detection unit can be simplified.

  When a dedicated counter electrode is provided for current pulse detection, even if the surface of the image carrier changes due to filming, etc., a dedicated component is used to detect the current pulse of the current flowing between the charging member and the dedicated component. As a result, spike-like current pulses can be reliably detected.

  When the charging member and the image carrier are in contact, a spike-like current pulse is generated at the contact portion. This current waveform is a spike-like pulse waveform. For this reason, it is indistinguishable from the spike-like current waveform generated by the spotted unevenness, and even when the current is detected, the spotted unevenness may not be prevented. Alternatively, a current pulse due to a current flowing between the charging member and the toner is detected, and the preliminary operation time becomes long regardless of the occurrence of spot unevenness, but the charging member and the image carrier are in contact with each other. Therefore, no current pulse is generated that is not related to the unevenness.

  In the present invention, when a circularity of 0.96 or more is used as the toner, there is almost no untransferred toner, so there is no background toner. Thereby, it is possible to reliably detect the current pulse related to the spotted unevenness.

Further, the present invention provides an image forming apparatus having at least an image carrier, a charging unit, and a cleaning unit, wherein the cleaning unit in contact with the image carrier is a fur brush made of conductive fibers, and a cleaning device A cleaning roller that is in contact with the fur brush and a scraper member thereof, and a cleaning unit that collects toner from the image carrier using an electric field by applying a voltage to the fur brush and / or the collecting roller. Even when the surface state changes due to NOx or the like adhering to the surface of the image carrier, or the static friction coefficient changes, the cleaning member deforms and contacts with the surface state, so that a good cleaning property is maintained. be able to. Furthermore, the toner on the image carrier can be cleaned well without causing a reduction in the cleaning margin due to fluctuations in the amount of input toner.
Even if the toner for developing the latent image on the two-image carrier is a toner having a circularity of 0.96 or more, it can be easily cleaned.

  As described above, the toner on the storage carrier is well cleaned, and the background toner is reduced on the image carrier. Thereby, it is possible to reliably detect the current pulse related to the spotted unevenness.

  In the present invention, the use of amorphous silicon for the image carrier dramatically improves the smoothness of the image carrier. Therefore, no current pulse is generated that is not related to spot unevenness. For this reason, it is possible to reliably detect a current pulse due to spot unevenness.

  In the present invention, when an image carrier in which filler is dispersed and strengthened on the surface layer is used as the image carrier, the image carrier in which filler is dispersed and strengthened on the surface layer having excellent hardness is used. Unevenness is unlikely to occur on the surface. Therefore, no current pulse is generated that is not related to spot unevenness. For this reason, it is possible to reliably detect a current pulse due to spot unevenness.

  In the present invention, if an organic photoreceptor using the above-described crosslinkable charge transport material is used, an image carrier having a cross-linked structure with a surface layer having excellent hardness is used. Unevenness is unlikely to occur on the surface. Therefore, no current pulse is generated that is not related to spot unevenness. For this reason, it is possible to reliably detect a current pulse due to spot unevenness.

  In the present invention, when at least the surface layer of the image carrier is made of polyarylate resin, an image carrier having a cross-linked structure with a surface layer having excellent hardness is used. Hateful. Therefore, no current pulse is generated that is not related to spot unevenness. For this reason, it is possible to reliably detect a current pulse due to spot unevenness.

  Furthermore, according to the present invention, when an oilless toner is used, no current pulse is generated during image formation, so that the type agent does not ooze out on the image carrier.

1 is a schematic view showing a main part of an image forming apparatus according to the present invention. FIG. 4 is an enlarged explanatory view showing a relationship between a charging roller and a photoreceptor. FIG. 4 is an explanatory diagram showing a gap between a charging roller and a photosensitive member. It is explanatory drawing which shows the other example of a charging roller. It is explanatory drawing which shows the further another example of a charging roller. It is explanatory drawing which shows the further another example of a charging roller. (A)-(d) is explanatory drawing which shows the structure of the photoreceptor of the image forming apparatus which concerns on this invention. It is a graph which shows the result of having detected the electric current which flows into a charging roller with an oscilloscope. 1 is an explanatory diagram of a main part showing an embodiment of an image forming apparatus according to the present invention. It is explanatory drawing of the principal part which shows other embodiment of the image forming apparatus which concerns on this invention. It is explanatory drawing of the principal part which shows other embodiment of the image forming apparatus which concerns on this invention. It is explanatory drawing of the principal part which shows other embodiment of the image forming apparatus which concerns on this invention. 6 is a flowchart illustrating a control example of the image forming apparatus according to the present invention. 6 is a flowchart illustrating another control example of the image forming apparatus according to the present invention. 10 is a flowchart illustrating still another example of control of the image forming apparatus according to the present invention. 10 is a flowchart illustrating still another example of control of the image forming apparatus according to the present invention. 10 is a flowchart illustrating still another example of control of the image forming apparatus according to the present invention. 1 is a schematic view showing a color image forming apparatus according to the present invention. 1 is a schematic view showing a color image forming apparatus according to the present invention. 1 is a schematic view of a process cartridge of an image forming apparatus according to the present invention.

Explanation of symbols

2 Photosensitive drum 3 Charging roller 100 Controller 101 Voltage application unit 102 Current measurement unit 110 Counter electrode

Claims (20)

In an image forming apparatus for charging an image carrier using a charging member that is in contact with or close to the image carrier,
A current measurement unit that detects a current flowing through the charging member, and a control unit that determines a pre-operation time before the image formation based on the current detected by the current measurement unit during the pre-operation before the image formation. An image forming apparatus comprising: The image forming apparatus according to claim 1.
When the current measuring unit detects a current flowing through the charging member during a preliminary operation before image formation, and when a spike-like current pulse is detected, the control unit determines a preliminary before the image formation. An image forming apparatus characterized by extending an operation standard time. The image forming apparatus according to claim 1, wherein
Humidity detection means is provided to detect the humidity during the preliminary operation before image formation, and when the detected humidity is lower than the predetermined value, the current measuring unit detects the current flowing through the charging member during the preliminary operation before image formation When the spike-like current pulse is detected, the control unit extends a predetermined preliminary operation standard time before the image formation in advance. The image forming apparatus according to claim 1, wherein
A temperature detector is provided to detect the temperature during the preliminary operation before image formation, and when the detected temperature is lower than a predetermined value, the current measuring unit detects the current flowing through the charging member during the preliminary operation before image formation. When the spike-like current pulse is detected, the control unit extends a predetermined preliminary operation standard time before the image formation in advance. The image forming apparatus according to claim 1, wherein
Humidity detection means and temperature detection means are provided to detect the humidity and temperature during the preliminary operation before image formation. When at least one of the detected humidity and temperature is lower than a predetermined value, the current measurement unit In this preliminary operation, the current flowing through the charging member is detected, and when a spike-like current pulse is detected, the control unit extends a predetermined preliminary operation standard time before the image formation. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 5,
The control unit sets the length of time for the preliminary operation according to a value obtained by adding the count number or peak value of spike-like current pulses detected by the current measurement unit during the preliminary operation before image formation. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus, wherein the current measuring unit is an ammeter that measures a current pulse, and the ammeter is installed between a circuit that applies a voltage to the charging member and the charging member. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus, wherein the current measuring unit is an ammeter for measuring a current pulse, and the ammeter is installed between the image carrier and ground. The image forming apparatus according to claim 1,
An electrode member that has a surface made of a resistor or an insulator and that is close to or in contact with the charging member is provided. Based on the current flowing between the charging member and the electrode member, the current for determining the pre-operation time is determined. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 9,
An image forming apparatus using a charging roller as the charging member. The image forming apparatus according to claim 1,
The charging member is a member having a small change in hardness due to the environment, and the surface is provided close to the surface of the image carrier, and a discharge is generated in the adjacent space formed by the gap. An image forming apparatus characterized by charging the battery. The image forming apparatus according to claim 1, wherein:
An image forming apparatus, wherein a toner image is formed on the image carrier, and the toner used has a circularity of 0.96 or more. The image forming apparatus according to any one of claims 1, 8, 11 and 12.
A cleaning means comprising a fur brush made of conductive fibers in contact with the image carrier, a recovery roller in contact with the fur brush, and a scraper member in contact with the recovery roller, the fur brush or recovery of the cleaning means An image forming apparatus which collects toner from an image carrier using an electric field by applying a voltage to at least one of rollers. The image forming apparatus according to any one of claims 1, 8, 11 to 13,
An image forming apparatus, wherein the image carrier is made of amorphous silicon. The image forming apparatus according to any one of claims 1, 8, 11 to 14,
An image forming apparatus, wherein a surface layer of the image bearing member is dispersed and strengthened. The image forming apparatus according to any one of claims 1, 8, 11 to 15,
An image forming apparatus using an organic photoreceptor using a cross-linked charge transport material for the image carrier. The image forming apparatus according to any one of claims 1, 8, 11 to 16,
An image forming apparatus, wherein at least a surface layer of the image carrier is made of polyarylate resin. The image forming apparatus according to any one of claims 1, 8, 11 to 17,
An image forming apparatus, wherein a toner image is formed on the image carrier, and the toner to be used is an oilless toner. The image forming apparatus according to any one of claims 1 to 18,
An image forming apparatus comprising: a process cartridge in which an image carrier and at least one image forming unit for forming a toner image on the image carrier are integrally assembled. The image forming apparatus according to claim 1,
An image forming apparatus that forms an image by superimposing toner a plurality of times.

Images