JP2005010526A - Charging device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanism that realizes more speedy, satisfactory electrification without requiring a complex device structure and a control process. <P>SOLUTION: The apparatus suitably performs a discharging process in which wettability is improved by applying an AC voltage from a power supply 13, thereby discharging and exposing the surface of a charging member 11. Thus, in the subsequent charging process, a uniform thin film of an ionic conductive medium is formed on the surface of the charging member 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric.
[0002]
[Prior art]
In image forming apparatuses such as electrophotographic copying machines and laser beam printers, corotrons are widely used as charging devices for charging an image carrier. When the corotron is used, there is an advantage that the image carrier can be uniformly charged by the action of corona discharge, but there is also the following problem. First, in order to charge the image carrier to a predetermined potential by the corotron, it is necessary to apply a relatively high voltage of several kV, so that a high voltage power source capable of applying such a high voltage is required. . Further, it is known that discharge products such as ozone generated by corona discharge cause deterioration of the image carrier. Furthermore, since an ozone filter is necessary so that the generated ozone is not discharged outside the image forming apparatus, there is a problem that the manufacturing cost increases.
[0003]
Therefore, a so-called contact-type charging device has been developed as a charging device replacing the corotron. The contact type charging device has a conductive member such as a roll shape, a brush shape, a blade shape, a film shape or a belt shape, and a minute gap near the contact portion between the conductive member and the image carrier. The image carrier is charged by generating a discharge. Since such a contact-type charging device does not use corona discharge, there is an advantage that generation of ozone is extremely small and a power supply voltage lower than that of the corotron is sufficient.
[0004]
By the way, in the contact-type charging device, when the DC (direct current) voltage is applied to the conductive member to charge the image carrier, the charging uniformity is not so good, and the charging is opposite to the applied voltage. It is known that toner or the like adheres to the image carrier. Therefore, a general method is to apply a voltage in which an AC (alternating current) voltage is superimposed on a DC voltage to the conductive member of the contact-type charging device, thereby charging the image carrier. However, if the moving speed (process speed) of the surface of the image carrier is high, uneven charging (so-called AC ripple) corresponding to the frequency of the AC voltage increases, and this becomes uneven density and appears in the image quality of the recording paper. Therefore, it is necessary to set the frequency of the AC voltage as high as possible so that density unevenness is not noticeable.
[0005]
However, since the image carrier originally has the characteristic of being easily damaged by the AC voltage, if the frequency of the AC voltage is increased as described above, the AC voltage flowing through the image carrier also increases, and the image carrier. Will receive considerable damage. Furthermore, the discharge products increase with the increase of the AC voltage. However, if the strength of the cleaner blade is increased to remove such a large amount of discharge products, the friction with the cleaner blade eventually results. The surface of the image carrier is worn. Accordingly, in the current situation, a contact charging device that applies a voltage obtained by superimposing an AC voltage on a DC voltage cannot be mounted on an image forming apparatus such as a medium-to-high speed copying machine having a high process speed.
[0006]
Therefore, as a charging device that solves these problems of the contact charging device, for example, there are those described in Patent Documents 1 to 3. The charging devices described in these Patent Documents 1 to 3 impregnate a sponge roller with a liquid such as water, and charge the image carrier by applying a voltage while the sponge roller is in contact with the image carrier. That's it.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 05-119583
[Patent Document 2]
Japanese Patent Laid-Open No. 07-140729
[Patent Document 3]
Japanese Patent Laid-Open No. 08-62932
[0008]
[Problems to be solved by the invention]
In this type of charging device, the amount of liquid impregnated in the sponge roller must be adjusted very closely. This is because, if the amount of liquid impregnated in the sponge roller is too small, charging failure will naturally occur. If the amount of liquid impregnated in the sponge roller is too large, a large amount of liquid adheres to the image carrier. This is because the liquid flows directly into the developing device via the image carrier and causes image quality defects. Thus, in order to appropriately adjust the amount of liquid, a dedicated device such as a highly accurate sensor or pump is required, resulting in an increase in manufacturing cost.
[0009]
Patent Documents 1 to 3 disclose both a charging device that constantly supplies liquid to the sponge roller and a charging device that stops supplying liquid to the sponge roller when not in use. . In the former type of charging device, in order to prevent the evaporation of the liquid due to the sponge roller being exposed to the atmosphere, a means for shielding contact with the outside air is necessary or the evaporated liquid is replenished. There is a concern about inconveniences such as a high frequency. Further, the latter type of charging device has a problem that it takes a considerable amount of time to sufficiently absorb the liquid again in the sponge roll that has already been dried because the unused state continues for a long time. is there.
[0010]
The present invention has been made under such a background, and the object of the present invention is to provide a mechanism for realizing good charging processing more quickly without requiring a complicated apparatus configuration and control processing. It is to provide.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a charging member for charging a charge acceptor, a supply means for supplying an ionic conductive medium to the charging member, and a potential difference with respect to a reference potential. A voltage applying means for generating the member, and when charging the charge receptor, the supplying means supplies the ionic conductive medium to the charging member, and the voltage applying means When the first potential difference is generated in the charging member while the surface of the charging member is exposed to discharge, the supply means does not supply the ionic conductive medium to the charging member, and the voltage applying means Provides a charging device that causes the charging member to generate a second potential difference with respect to the reference potential.
When the surface of the charging member is exposed to discharge, the wettability is promoted, so that a thin film of the ionic conductive medium can be formed quickly and uniformly. This makes it possible to charge the charge acceptor quickly and satisfactorily.
[0012]
According to a preferred aspect of the present invention, in the above-described charging device, the supply unit includes a holding member that holds the ionic conductive medium and a position where the holding member contacts the charging member. Driving means for moving the charging member to a position separated from the charging member, and when the surface of the charging member is exposed to discharge, the driving means moves the holding member to a position spaced from the charging member, The ionic conductive medium is not supplied to the charging member.
[0013]
The present invention can also be applied to an image forming apparatus using the above-described charging device as a charging unit.
[0014]
Further, as a desirable aspect of the present invention, in the above-described image forming apparatus, a measuring unit that measures the frequency with which the charging member is used, and a surface of the charging member based on the frequency measured by the measuring unit. And a control unit that causes the charging device to perform a process of exposing to discharge.
As a result, the surface of the charging member is exposed to discharge according to the frequency of use, so that the wettability can be maintained in a good state.
[0015]
According to a preferred aspect of the present invention, the image forming apparatus includes a rotation speed control unit that controls a rotation speed of the image carrier and a rotation speed of a developing roll provided in the developing device. When the surface of the charging member is exposed to discharge, the speed control means reduces the rotational speed of the image carrier or charges the charge receptor as compared to charging the charge receptor. The number of rotations of the developing roll is increased as compared with the case.
Thereby, since the amount of the discharge product adhering to the surface of the image carrier can be reduced, it is possible to suppress image defects caused by the adhesion of the discharge product.
[0016]
Further, as a desirable aspect of the present invention, in the above-described image forming apparatus, the removal is performed between the charging device and the exposure device to remove the ionic conductive medium attached to the surface of the image carrier. Means.
As a result, it is possible to prevent the ionic conductive medium from adhering to an apparatus or member responsible for an image forming process after the exposure process.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(1) Configuration
First, the configuration of a charging device and an image forming apparatus using the same according to an embodiment of the present invention will be described.
[0018]
(1-1) Image forming apparatus
FIG. 1 is a diagram illustrating a configuration of the image forming apparatus 100. As shown in the figure, the image forming apparatus 100 includes a charging device 1, a photosensitive drum 2, an ionic conductive medium removing device 3, an exposure device 4, a developing device 5, a recording medium 6, A transfer roll 7 and a cleaning device 8 are provided.
[0019]
The charging device 1 includes a charging member 11, an ionic conductive medium supply device 12, a power source 13, and a rotation speed detection device 14, and the charging member 11 is in contact with the surface of the photosensitive drum 2. Is installed. The ionic conductive medium supply device 12 includes a holding member 121 that applies an ionic conductive medium such as water in contact with the charging member 11, and a dropping device 122 that drops the ionic conductive medium on the holding member 121. A motor 123 is provided for bringing the holding member 121 into contact with or separating from the charging member 11. When a voltage is applied between the charging member 11 and the photosensitive drum 2 by the power source 13 in a state where the ionic conductive medium is applied to the surface of the charging member 11, the charge moves in a nip region where both are in contact. As a result, the surface of the photosensitive drum 2 is uniformly charged. The detailed configuration of the charging device 1 will be described later. In this specification, for the sake of convenience, applying a voltage between the photosensitive drum and the charging member is “applying a voltage to the charging member” or “a potential difference with respect to the reference potential is applied to the charging member. Express ". In the latter case, the reference potential is the potential of the photosensitive drum.
[0020]
The photosensitive drum 2 has a roll shape, and its rotation shaft is supported by support means (not shown) and is rotated in the direction of arrow A in the figure by drive means (not shown). The photoconductive drum 2 is formed by forming, for example, two to three photoconductive layers including a charge generation layer and a charge transport layer made of OPC (Organic Photo Conductor) as a charge acceptor on a conductive substrate. The conductor substrate is electrically grounded.
[0021]
The ionic conductive medium removing device 3 is provided with a blade-like elastic member, and this elastic member extends in a direction parallel to the axial direction of the photosensitive drum 2 and is in contact therewith. The photosensitive drum 2 is charged by being charged with an ionic conductive medium such as water, but the ionic conductive medium remains on the surface of the photosensitive drum 2 even after the charging. The remaining ionic conductive medium adversely affects an exposure process and a development process to be performed later. The ionic conductive medium removing device 3 is provided to remove such an ionic conductive medium, and removes the ionic conductive medium on the surface of the photosensitive drum 2 by scraping. The removed ionic conductive medium is recovered by an ionic conductive medium recovery device (not shown).
[0022]
The exposure device 4 includes, for example, an LED (Light Emitting Diode) and the like, and the charge is lost by irradiating the uniformly charged surface of the photosensitive drum 2 with light. Forming an electrostatic latent image).
[0023]
The developing device 5 includes a developing roll 51, and this developing roll 51 is in contact with the photosensitive drum 2. The developing roll 51 is charged with the opposite polarity to the surface of the photosensitive drum 2, and the toner is charged by supplying the toner to the developing roll 51. In the nip region between the photosensitive drum 2 and the developing roll 51, the charged toner adheres to the portion of the photosensitive drum 2 having a charge of the electrostatic latent image by electrostatic force, and a toner image is formed here.
[0024]
The recording medium 6 is a recording medium capable of transferring toner, such as recording paper, and proceeds in the direction of arrow B in the drawing by a conveyance belt (not shown).
[0025]
The transfer roll 7 is connected to a power source 71 and faces the photosensitive drum 2 with the recording medium 6 interposed therebetween. The power source 71 applies a voltage between the photosensitive drum 2 and the transfer roll 7. As a result, an electric field is formed between the transfer roll 7 and the photosensitive drum 2 so that the charged toner image is attracted from the photosensitive drum 2 to the recording medium 6, and the toner image on the photosensitive drum 2 is Transferred to the recording medium 6. The toner image transferred to the recording medium 6 is fixed on the recording medium 6 by being heated by a fixing device (not shown).
[0026]
The cleaning device 8 includes a disturber brush 81 and a cleaning blade 82. The disturber brush 81 is roll-shaped and has brush fibers implanted on the surface thereof, and extends in a direction parallel to the axial direction of the photosensitive drum 2. The disturber brush 81 is supported at both ends by support means (not shown), and rotates substantially in synchronization with the photosensitive drum 2. The cleaning blade 82 has a blade shape, extends in a direction parallel to the axial direction of the photosensitive drum 2, and contacts the cleaning drum 82.
The toner remaining on the photosensitive drum 2 is first reduced in adhesion by the disturber brush 81 and then scraped off from the surface of the photosensitive drum 2 by the cleaning blade 82. The toner scraped off is collected by a collecting device (not shown). By cleaning the photosensitive drum 2 in this way, preparation for the next image forming process is performed.
[0027]
With the above-described configuration, the image forming apparatus 100 forms an image through a process of charging, exposure, development, transfer, fixing, and cleaning.
[0028]
FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 100. As illustrated in FIG. 1, the image forming apparatus 100 includes a control unit 101, a power supply unit 102, a drive unit 103, and a measurement unit 104.
The control unit 101 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the operation of each unit of the image forming apparatus 100. The power source unit 102 includes various power sources such as the power source 13 and the power source 71 described above, and supplies power to each unit of the image forming apparatus 100 under the control of the control unit 101. The driving unit 103 includes a plurality of driving devices such as a motor, and rotates the photosensitive drum 2 and the developing roll 51 under the control of the control unit 101, or the holding member of the ionic conductive medium supply device 12 described above. An operation such as moving 121 is performed. The measurement unit 104 includes various measurement devices such as the rotation speed detection device 14 described above. The control unit 101 performs various arithmetic processes using the measurement values obtained by the measurement unit 104.
[0029]
(1-2) Charging device
Next, the configuration of the charging device 1 will be described in detail with reference to FIG.
The charging member 11 has a roll shape, and a lower portion thereof is in contact with the surface of the photosensitive drum 2. As the material of the charging member 11, a material (for example, an elastic body such as semiconductive rubber) that has conductivity and forms a good nip with the photosensitive drum 2 is appropriately used. The charging member 11 is supported by a support means (not shown), and is rotated in synchronization with the rotation of the photosensitive drum 2. That is, when the photosensitive drum 2 rotates in the direction of arrow C in the figure, the charging member 11 rotates in the direction of arrow D in the figure.
[0030]
The holding member 121 is a columnar member extending in a direction parallel to the axial direction of the charging member 11 and having a length equal to or longer than the charging region of the charging member 11, and is an ion for applying to the charging member 11. The conductive conductive medium is held. The holding member 121 is preferably made of a material that can ensure appropriate water content, and is made of, for example, sponge-like porous PVA (polyvinyl alcohol). However, as the volume of the holding member 121 increases, it takes time to sufficiently absorb the ionic conductive medium from the dry state. Therefore, the holding member 121 may be as small as possible while satisfying a sufficient holding amount. desirable. The holding member is moved by the motor 123 to either a position in contact with the charging member 11 as shown in FIG. 3 or a position separated from the charging member 11 as shown in FIG. The dropping device 122 stores an ionic conductive medium, and drops and supplies it to the holding member 121. The dropping device 122 is provided in the vicinity of the holding member, and is made of a pipe having the same length as the holding member 121. A number of holes are provided along the axial direction at positions facing the charging member 11 of the pipe, and an ionic conductive medium is dropped onto the holding member.
[0031]
As the ionic conductive medium, water such as pure water, distilled water, tap water, or a liquid in which an electrolyte or ionizable gas molecules are dissolved in a solvent such as water or alcohol can be used as appropriate. As an electrolyte dissolved in the above-mentioned solvent such as water and alcohol, LiClO₄, Na₂SO₄, Na₂CO₃, NaHCO₃, NaCl, KCl, LiCl, MgCl₂, CaCl₃, (NH₄)₂SO₄An electrolyte such as can be used. Examples of the ionizable gas molecules include CO.₂Is mentioned. This CO₂As the ionizable gas molecule, one that is naturally dissolved in a solvent such as water may be used, or one that is actively dissolved may of course be used.
[0032]
One end of the power supply 13 is electrically grounded, and the other end is connected to the charging member 11. The power source 13 has both an AC power source and a DC power source, and can apply an AC voltage or a DC voltage to the charging member 11.
[0033]
The rotation speed detection device 14 includes an optical sensor (not shown), and measures the rotation speed of the charging member 11 by reading a sensor mark SM provided on a part of the outer peripheral surface of the charging member 11.
[0034]
(2) Operation
Under the configuration described above, the charging device 1 according to the present embodiment operates as follows.
The charging device 1 of the present embodiment has a charging processing mode and a discharging processing mode as processing modes. The charging processing mode is a processing mode for charging the photosensitive drum 2, and is an operation executed in the above-described charging process. On the other hand, the discharge processing mode is a processing mode that is executed to improve and maintain the charging performance of the charging device 1, and is an operation that is appropriately executed at a predetermined timing other than during image formation. Hereinafter, the operation in each processing mode will be described with reference to the drawings.
[0035]
(2-1) Charge processing mode
In the charging processing mode, the charging device 1 is in the state shown in FIG. As shown in the figure, in the charging process mode, the power source 13 applies a DC voltage to the charging member 11 under the control of the control unit 101, while the holding member 121 of the ionic conductive medium supply device 12 is An ionic conductive medium is applied in contact with the charging member 11.
[0036]
At this time, the ionic conductive medium is ionized on the surface of the charging member 11. As an example, carbon dioxide (CO₂) Dissolved pure water (H₂In the case of using O), in this case, in the ionic conductive medium, carbon dioxide and water are ionized as shown in the following chemical formulas 1 to 4.
[0037]
[Chemical 1]
H₂O ⇔ H⁺+ OH⁻
[Chemical formula 2]
CO₂+ H₂O ⇔ H₂CO₃
[Chemical Formula 3]
H₂CO₃  ⇔ H⁺+ HCO₃ ⁻
[Formula 4]
HCO₃ ⁻  ⇔ H⁺+ CO₃ ^2-
[0038]
Here, by applying a voltage to the charging member 11, ions in the ionic conductive medium can be moved. Specifically, for example, when the power source 13 applies a voltage (first potential difference) so that the surface of the charging member 11 is negative, negatively charged anions repel the charging member 11 and the photosensitive member. It adheres to the surface of the drum 2 by electrostatic force. As a result, a negative charge is applied to the surface of the photosensitive drum 2.
[0039]
The charging process in this embodiment is performed in this way. Although both DC voltage and AC voltage can be used for this charging process, it is possible to prevent various problems caused by using the AC voltage by using the DC voltage. That is, it is possible to prevent wear of the photosensitive drum 2 and occurrence of AC ripple due to application of an AC voltage. This makes it possible to apply the present invention to a medium / high speed image forming apparatus.
[0040]
From the above, it can be seen that the time required for charging the photosensitive drum 2 depends on the moving speed of ions in the ionic conductive medium. That is, the larger the resistivity of the ionic conductive medium, the longer the time required for charging. Therefore, when used in an image forming apparatus with a high process speed, the resistivity of the ionic conductive medium is 10.⁹Desirably less than Ωcm.
[0041]
(2-2) Discharge treatment mode
Next, the operation in the discharge processing mode will be described.
In the discharge processing mode, the charging device 1 is in the state shown in FIG. As shown in the figure, in the discharge processing mode, the holding member 121 is separated from the charging member 11. This is because an unnecessary ionic conductive medium is prevented from being supplied to the surface of the charging member 11, and a current leaks to the holding member 121 when a voltage is applied to the charging member 11 by the power source 13 described later. The purpose is to prevent.
[0042]
At this time, an AC voltage (second potential difference) exceeding a predetermined discharge start voltage is applied to the charging member 11 by the power source 13 under the control of the control unit 101. As a result, discharge occurs near the portion where the charging member 11 and the photosensitive drum 2 are in contact with each other. When the surface of the charging member 11 is exposed to electric discharge, surface modification proceeds physically and chemically, and wettability is promoted. When the wettability is promoted, when the ionic conductive medium is applied to the charging member 11 in the above-described charging process, a uniform ionic conductive medium thin film is stably and rapidly formed on the surface of the charging member 11. It becomes possible to form. This thin film is maintained up to the contact (nip) region between the charging member 11 and the photosensitive drum 2 as the charging member 11 rotates. If a uniform thin film is formed in the nip region, the photosensitive drum 2 can be uniformly and stably charged.
[0043]
The discharge process in this embodiment is performed in this way. This discharge process has the following effects by being appropriately executed before or between the above-described charging processes.
In other words, the wettability is promoted by this discharge process, and a uniform thin film made of an ionic conductive medium is formed on the surface of the charging member 11, so that the ionic conductive medium required for the charging process is the minimum necessary. It becomes the amount of. Therefore, the frequency of replenishing the ionic conductive medium can be reduced.
Furthermore, the fact that the wettability is promoted means that the thin film formation of the ionic conductive medium on the surface of the charging member 11 is performed more rapidly, and the operation time until the charging process can be shortened. In particular, in the present embodiment, a semiconductive elastic roll is used for the charging member 11 instead of a water-absorbing sponge roll, and coupled with this, when the image forming apparatus is started or after a long period of non-use. The effect of shortening the waiting time at the time of the return of the operation remarkably appears.
[0044]
During the operation in the discharge processing mode, the photosensitive drum 2 is also exposed to discharge, and there is a risk of image quality defects due to adhesion of discharge products. However, the discharge process in this embodiment is extremely short and limited as compared with the time during which the image forming process is performed. In the conventional image forming apparatus, it can be said that the amount of discharge products generated in the present embodiment is negligibly small in view of the generation of discharge products during the image forming process.
[0045]
(2-3) Example of operation
The two processing modes described above are executed, for example, as shown below.
FIG. 5 is a flowchart illustrating an example of a process for periodically performing the discharge process. This process is an interrupt process periodically executed by the control unit 101 of the image forming apparatus during image formation. Hereinafter, a description will be given with reference to FIG.
[0046]
First, when this process is started, the control unit 101 refers to the measurement unit 104 to obtain the rotation number of the charging member 11 (step S1). Subsequently, the control unit 101 compares the number of rotations measured by the measurement unit 104 with a preset value, and determines whether or not the number of rotations of the charging member 11 exceeds the set value (step S2). ).
[0047]
If this determination is affirmative (step S2: YES), the control unit 101 sends an instruction to execute the above-described discharge processing mode (step S3), and sets the rotation speed value measured by the measurement unit 104 to “0”. (Step S4). If this determination is negative (step S2: NO), the control unit 101 updates the counter by incrementing the value (step S5).
[0048]
After updating the counter value (steps S4 and S5), an image forming process is executed (step S6). This series of processes is periodically repeated until the image forming process is completed.
By performing the above processing, it becomes possible to always maintain the wettability of the surface of the charging member 11 at a certain level or higher. In addition, by appropriately determining the execution interval of the process and the set value described above, it is possible to prevent a charging failure due to a decrease in wettability of the surface of the charging member 11, and to prevent an image quality defect due to a charging failure. In addition, the charging uniformity of the surface of the charging member 11 can be maintained for a long time.
[0049]
(3) Modification
In addition, this invention is not limited to embodiment mentioned above, The following various changes are possible.
(3-1) Modification 1
In the above-described embodiment, since the photosensitive drum 2 is also exposed to discharge, there is a concern about image defects due to adhesion of discharge products. However, this can be reduced by appropriately adjusting the rotational speeds of the photosensitive drum 2 and the developing roll 51 during image formation and discharge processing. Specifically, the rotation speed of the photosensitive drum 2 is higher during image formation than during discharge processing, or the rotation speed of the developing roll 51 is slower than during discharge processing, so that the discharge product The influence can be reduced. Only one of the rotation speeds of the photosensitive drum 2 and the developing roll 51 may be adjusted, or both may be simultaneously performed.
[0050]
(3-2) Modification 2
In the above-described embodiment, the voltage (second potential difference) applied to the charging member 11 by the power source 13 during the discharge process is an AC voltage, but it is not necessarily an AC voltage. The voltage applied to the charging member 11 during the discharge process may be a DC voltage exceeding the discharge start voltage or a voltage obtained by superimposing the DC voltage and the AC voltage.
[0051]
(3-3) Modification 3
In the above-described embodiment, the recording medium 6 is a recording sheet, and the recording medium 6 is conveyed by the conveyance belt. However, an intermediate transfer belt may be used as the recording medium 6. In this case, the toner image is primarily transferred from the photosensitive drum 2 to the intermediate transfer belt by the transfer roll 7, and then secondarily transferred from the intermediate transfer belt to the recording paper by a secondary transfer roll (not shown).
[0052]
(3-4) Modification 4
In the above-described embodiment, in order to easily understand the configuration of the charging device 1, the rotation speed detection device 14 detects the rotation speed of the charging member 11 using an optical sensor. However, conventionally, an image forming apparatus is generally provided with a measuring unit that measures the number of printed sheets. This measuring unit measures, for example, the number of rotations of a rotating image carrier (photosensitive drum). ing. Since the charging member 11 of the present embodiment is rotated substantially following the photosensitive drum 2, it is possible to determine the approximate frequency of use of the charging member 11 based on the measurement value obtained by the conventional measuring means. It is. According to such an aspect, the frequency of use of the charging member 11 can be measured only by storing the rotation ratio of the charging member 11 and the photosensitive drum 2 in the control unit 101, so that the configuration of the image forming apparatus 100 is complicated. The present invention can be applied without conversion.
Further, the method of measuring the usage frequency of the charging member 11 is not limited to the number of rotations of the charging member 11.
[0053]
(3-5) Modification 5
In the above-described embodiment, the ionic conductive medium supply device 12 is configured to apply the ionic conductive medium to the charging member 11. However, the aspect in which the ionic conductive medium supply device 12 supplies the ionic conductive medium is not limited to the above-described aspect, and supply by dropping or supply by spraying may be used.
The same applies to the dropping device 122, and the manner in which the dropping device 122 supplies the ionic conductive medium to the holding member 121 can be various as described above.
[0054]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a good charging process more quickly without requiring a complicated apparatus configuration or control process.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a functional block diagram of the image forming apparatus according to the embodiment.
FIG. 3 is a diagram showing a configuration of a charging device according to the embodiment.
FIG. 4 is a view showing a state in a discharge processing mode of the charging device according to the embodiment;
FIG. 5 is a flowchart showing an example of a process for periodically performing a discharge process in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 1 ... Charging device, 2 ... Photoconductor drum, 3 ... Ionic conductive medium removing device, 4 ... Exposure device, 5 ... Developing device, 6 ... Recording medium, 7 ... Transfer roll, 8 ... Cleaning DESCRIPTION OF SYMBOLS 11 ... Charging member, 12 ... Ionic conductive medium supply device, 121 ... Holding member, 122 ... Dropping device, 123 ... Motor, 13 ... Power source, 14 ... Number-of-rotations detector

Claims (6)

A charging member for charging the charge receptor;
Supply means for supplying an ionic conductive medium to the charging member;
Voltage applying means for causing the charging member to generate a potential difference with respect to a reference potential,
When charging the charge receptor, the supplying means supplies the ionic conductive medium to the charging member, and the voltage applying means generates a first potential difference in the charging member with respect to the reference potential. While letting
When the surface of the charging member is exposed to discharge, the supplying means does not supply the ionic conductive medium to the charging member, and the voltage applying means charges the second potential difference with respect to the reference potential. A charging device generated in a member. The supply means includes
A holding member that holds the ionic conductive medium in a state including the ionic conductive medium;
Driving means for moving the holding member to a position in contact with the charging member or a position spaced from the charging member;
In the case where the surface of the charging member is exposed to discharge, the driving unit moves the holding member to a position separated from the charging member so that the ionic conductive medium is not supplied to the charging member. The charging device according to claim 1. In an image forming apparatus comprising a photoconductive image carrier, a charging device, an exposure device, a developing device, and a transfer device,
The charging device is:
A charging member for charging the image carrier;
Supply means for supplying an ionic conductive medium to the charging member;
Voltage application means for applying a voltage between the image carrier and the charging member;
When charging the image carrier, the supply means supplies the ionic conductive medium to the charging member, and the voltage applying means has a first voltage between the image carrier and the charging member. While applying
When the surface of the charging member is exposed to discharge, the supplying means does not supply the ionic conductive medium to the charging member, and the voltage applying means is not connected between the image carrier and the charging member. 2. An image forming apparatus that applies a voltage of 2. Measuring means for measuring the frequency of use of the charging member;
The image forming apparatus according to claim 3, further comprising: a control unit that causes the charging device to perform a process of exposing the surface of the charging member to discharge based on the frequency measured by the measuring unit. Rotational speed control means for controlling the rotational speed of the image carrier and the rotational speed of the developing roll provided in the developing device,
When the surface of the charging member is exposed to discharge, the rotation speed control means reduces the rotation speed of the image carrier or charges the charge receptor as compared to charging the charge receptor. The image forming apparatus according to claim 3, wherein the number of rotations of the developing roll is increased as compared with the case of forming the developing roll. The image forming apparatus according to claim 3, further comprising a removing unit that is disposed between the charging device and the exposure device and removes the ionic conductive medium attached to the surface of the image carrier.

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