JP6635008B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus.

  At the time of non-transfer to the recording medium, while the toner base particles remain as much as possible on the developing roller in the developing device, titanium oxide as an external additive is preferentially moved to the photosensitive drum side and supplied to the rubbing roller. There has been known an image forming apparatus capable of executing a refresh mode for polishing the surface of a photosensitive drum (see Patent Document 1). In this image forming apparatus, titanium oxide having the same polarity as the toner base particles and having a smaller chargeability (charge amount per unit weight) than the toner base particles is used. (Same polarity as toner and titanium oxide).

JP 2011-169995 A

  By the way, in the above-described image forming apparatus, the charging condition of the photosensitive drum in the refresh mode (the polishing mode) is the same as the charging condition of the photosensitive drum in the image formation. Therefore, in the case of the above-described image forming apparatus, the charging device generates a discharge product in a polishing mode equivalent to that in image formation.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of performing a polishing mode while suppressing generation of discharge products in a polishing mode of a carrier.

  The first image forming apparatus according to the present invention includes a rotating carrier, a charging roller that contacts the carrier, and a voltage in which an AC voltage is superimposed on a DC voltage is applied to charge the carrier. An exposure device that exposes the carrier charged by a roller to form a latent image, and a developing roller that faces the carrier, rotates around an axis, and is applied with a voltage obtained by superimposing an AC voltage on a DC voltage. A developing device that develops the latent image as a toner image using a toner containing base particles and an abrasive attached to the developing roller, a transfer device that transfers the toner image to a medium, A fixing device for fixing the toner image to the medium, and a polishing member for polishing the carrier, and a DC voltage applied to the developing roller during image formation without applying a voltage to the charging roller during non-image formation. Reverse polarity of voltage Voltage AC voltage is superimposed on a DC voltage is applied for, it is polished mode of polishing the carrier by the polishing member.

  In the second image forming apparatus of the present invention, the AC voltage applied to the developing roller is a rectangular wave, and moves the toner in the rectangular wave from the carrier to the developing roller in the polishing mode. The ratio is set to be larger than the ratio of moving the toner in the rectangular wave from the carrier to the developing roller during image formation.

  The third image forming apparatus of the present invention further applies the developing roller to the developing roller during image formation without charging the carrier to the charging roller during a part of the period in the polishing mode. A DC voltage having the same polarity as the DC voltage is applied to move the toner from the developing roller to the carrier.

  The image forming apparatus of the present invention can perform the polishing mode while suppressing the generation of discharge products during the polishing mode of the carrier.

FIG. 2 is a schematic view of the image forming apparatus according to the first embodiment as viewed from the front side. FIG. 2 is a schematic view of a photoconductor and its peripheral portion constituting the image forming apparatus according to the first embodiment as viewed from the front side. FIG. 2 is a block diagram illustrating a relationship between a control device included in the image forming apparatus according to the first embodiment and each component included in the image forming apparatus. FIG. 2 is a schematic diagram of a toner used by the image forming apparatus according to the first embodiment. FIG. 4 is a schematic diagram for explaining a relationship between a surface potential of a photoconductor and a potential applied to a developing roller in an image forming operation (at the time of image formation) by the image forming apparatus according to the first embodiment. FIG. 3 is a schematic diagram for explaining a voltage applied to a developing roller in an image forming operation (at the time of image formation) by the image forming apparatus according to the first embodiment. FIG. 3 is a schematic diagram for explaining a relationship between a surface potential of a photoconductor and a potential applied to a developing roller during a polishing operation performed during non-image formation by the image forming apparatus according to the first embodiment. FIG. 3 is a schematic diagram for explaining a voltage applied to a developing roller during a polishing operation performed during non-image formation by the image forming apparatus according to the first embodiment. In the image forming apparatus of the first embodiment, the surface potential of the photoconductor during image formation, the applied voltage of the charging roller and the applied voltage of the developing roller, and the surface potential of the photoconductor and the applied voltage of the developing roller during the polishing mode are determined. This is a summarized table. FIG. 9 is a schematic diagram for explaining a voltage applied to a developing roller during a polishing operation performed during non-image formation by the image forming apparatus according to the second embodiment. In the image forming apparatus according to the second embodiment, the surface potential of the photoconductor during image formation, the applied voltage of the charging roller and the applied voltage of the developing roller, and the surface potential of the photoconductor and the applied voltage of the developing roller during the polishing mode are determined. This is a summarized table. FIG. 9 is a schematic diagram for explaining a relationship between a surface potential of a photoconductor and a voltage applied to a developing roller during a polishing operation performed during non-image formation by an image forming apparatus according to a modification.

≪Overview≫
Hereinafter, the first embodiment, the second embodiment, and the modifications will be described in the order of description.

<< 1st Embodiment >>
First, the configuration, image forming operation, polishing operation, and effect of the image forming apparatus 10 (see FIG. 1) of the first embodiment will be described in the order of description with reference to the drawings.

  In the following description, the directions indicated by the arrows Fr and Rr in the figure are respectively the near side and the back side in the apparatus depth direction, the directions indicated by the arrows R and L are the right and left sides in the apparatus width direction, and the arrows U and Lo, respectively. The directions shown are the upper side and the lower side in the apparatus height direction, respectively. In this specification, a state in which the image forming apparatus 10 is viewed from the near side in the apparatus depth direction will be described as the front of the image forming apparatus 10.

<Configuration of Image Forming Apparatus>
As shown in FIG. 1, the image forming apparatus 10 includes a paper feed cassette 20, a toner image forming unit 30, a transfer device 40, a transport device 50, a fixing device 60, a control device CU, a power supply PS, , And is an electrophotographic apparatus.

  The paper feed cassette 20 has a function of storing the medium S.

  The toner image forming unit 30 has a function of performing each step of charging, exposing, and developing to form a toner image to be held on a belt TB described later. The toner image forming unit 30 includes single color units 31Y, 31M, 31C, and 31K that form toner images of different colors (Y (yellow), M (magenta), C (cyan), and K (black)). I have. As shown in FIG. 1, each of the single-color units 31Y, 31M, 31C, and 31K includes a photoconductor PC (an example of a carrier), a charging roller 32, an exposing device 34, a developing device 36, and a charge removing device. 37, a cleaning device 38, and a polishing roller 39 (an example of a polishing member).

  The photoconductor PC is formed in a drum shape and carries a latent image formed by the exposure device 34, and is driven by a driving source (not shown) to rotate clockwise as viewed from the front side. The photoconductor PC of the present embodiment is an amorphous silicon photoconductor as an example. That is, the photoconductor PC of the present embodiment is a so-called positive charging type photoconductor.

  The charging roller 32 has a function of charging the photoconductor PC while a voltage is applied from the power supply PS. The voltage applied from the power source PS to the charging roller 32 is, for example, a voltage obtained by superimposing an AC voltage on a DC voltage (see FIG. 7).

  The developing device 36 has a function of developing a latent image formed on the photoconductor PC by the exposure device 34 using the toner T (see FIG. 4) as a toner image. The developing device 36 has a developing roller 36A that faces the photoconductor PC and rotates around an axis (see FIGS. 1 and 2), and develops a toner image using the toner T attached to the outer periphery thereof. ing. Further, the developing device 36 is configured to apply a voltage in which an AC voltage is superimposed on a DC voltage from the power supply PS to the developing roller 36A so that the toner T on the outer periphery of the developing roller 36A flies to the photoconductor PC and moves. It has become.

  Here, as shown in FIG. 4, the toner T used by the developing device 36 of the present embodiment is configured to include base particles Ta having a resin as a main component and an abrasive Tb. The base particles Ta and the abrasive Tb are both particles whose average charge amount distribution has a positive charge amount. That is, the average charge amount distribution of the toner T is a positive charge amount. The developing method of the present embodiment is a reversal developing method using a positively charged photoconductor and a positively charged toner (see FIG. 5A). The abrasive Tb is, for example, titanium oxide, and has a lower electric resistance than the base particles Ta.

  The static eliminator 37 has a function of irradiating the photoconductor PC with light after passing through the transfer position (the position at which the photoconductor PC comes into contact with the belt TB) to neutralize the photoconductor PC.

  The cleaning device 38 has a function of removing residual toner remaining on the photoconductor PC (toner not transferred to the belt TB and remaining attached to the photoconductor PC) from the photoconductor PC. The cleaning device 38 includes a cleaning blade CB (see FIG. 2).

  The polishing roller 39 has a function of polishing the photoconductor PC. The polishing roller 39 is, for example, a sponge roller in which the outer periphery of a shaft is covered with a foam (sponge). The polishing roller 39 rotates around the axis at a higher peripheral speed than the photoconductor PC in a state of being in contact with the photoconductor PC.

  The components of the toner image forming unit 30 other than the photoconductor PC include a charging roller 32, a developing device 36, a static eliminator 37, a polishing roller 39, and a cleaning blade CB around the photoconductor PC when viewed from the front side. They are arranged clockwise in this order (see FIG. 2). The exposure device 34 forms a latent image between the charging roller 32 and the developing device 36 of the photoconductor PC. In FIG. 1, reference numerals of the single color units 31M, 31C, 31K other than the single color unit 31Y are omitted.

  The transfer device 40 has an endless belt TB, and primary-transfers the toner image formed by the toner image forming unit 30 onto the belt TB that rotates in the direction of arrow X in FIG. 1, and is held by the belt TB. And a second transfer function of transferring the transferred toner image onto the medium S.

  The transport device 50 has a function of transporting the medium S stored in the sheet cassette 20 along a transport path (two-dot line P in FIG. 1). Note that the arrow Y in FIG. 1 indicates the transport direction of the medium S.

  The fixing device 60 has a function of fixing the toner image secondarily transferred to the medium S by the transfer device 40 to the medium S.

  The control unit CU has a function of controlling each unit constituting the image forming apparatus 10 (see FIG. 3 described later). The function of the control unit CU will be described later in the description of the image forming operation and the polishing operation (operation in the polishing mode).

<Image forming operation>
Next, an image forming operation by the image forming apparatus 10 according to the present embodiment will be described with reference to FIGS. 1, 2, 3, 5A, and 5B.

  The control device CU that has received the image data from the external device (not shown) activates each unit of the image forming apparatus 10 (see FIG. 3).

  When the toner image forming unit 30 is operated, in each of the monochrome units 31Y, 31M, 31C, and 31K, the charging roller 32 charges the photosensitive member PC, the exposing device 34 exposes the photosensitive member PC, and the developing device 36 exposes the photosensitive member PC. The latent image on the body PC is developed as a toner image. As a result, a toner image is formed on each photoconductor PC. In this case, the control unit CU applies a voltage from the power supply PS to the charging roller 32 so as to charge the charging roller 32 to +230 V as an example of the surface potential (Vopc in FIG. 5) of the photoconductor PC. Specifically, a sine-wave voltage of 1000 V whose VApp (double the amplitude) is more than twice the so-called discharge start voltage is applied to the DC voltage VAdc of +200 V (see FIG. 7). In addition, the control device CU has, for example, a central value VBctr (or DC voltage VBctr) of +60 V and a double amplitude VBpp (VBpp / 2 means amplitude) of 1000 V on the developing roller 36 </ b> A. A rectangular wave voltage is applied (see FIGS. 5A and 5B). In this case, of the rectangular wave of the AC voltage applied to the developing roller 36A, the ratio of the positive time (meaning the time for moving the toner T from the photoconductor PC to the developing roller 36A) to the ratio. The ratio of the negative time is 60% to 40%. Then, the surface potential of the photoconductor PC on which the latent image is formed by exposure by the exposure device 34 becomes less than +60 V (for example, about +20 V), and the developing roller 36A is formed on the surface of the photoconductor PC on which the potential contrast is formed. The toner T moves from the position (hatched portion in FIG. 5A).

  Next, when the transfer device 40 and the transport device 50 are operated, the toner image formed by the toner image forming unit 30 is primarily transferred to the belt TB. Further, the medium S stored in the sheet cassette 20 is transported by the transport device 50 at the timing when the toner image primary-transferred onto the belt TB is secondary-transferred, and the toner held on the belt TB is transferred. The image is secondarily transferred to the medium S. The medium S to which the toner image has been secondarily transferred is transported by the transport device 50 toward the fixing device 60.

  Next, when the fixing device 60 is operated and the medium S on which the toner image is secondarily transferred is conveyed to the fixing device 60, the toner image secondarily transferred onto the medium S is fixed on the medium S (on the medium S). An image is formed).

  Then, the medium S on which the toner image is fixed (the medium S on which the image is formed) is discharged out of the image forming apparatus 10 by the transport device 50, and the image forming operation ends.

<Polishing operation (operation in polishing mode)>
Next, the polishing operation of the present embodiment will be described with reference to FIGS. 6A, 6B, and 7. FIG. The polishing operation according to the present embodiment is performed during non-image formation. After the image forming operation on the predetermined number of the mediums S (for example, equivalent to 100 A4 size media S) is completed, the control unit CU determines the inside of the apparatus by the temperature and humidity sensor (not shown). When the temperature is higher than the humidity, the internal temperature of the apparatus is higher than the high temperature and high humidity determined by the temperature and humidity sensor (not shown) when the power supply of the apparatus is turned on. The polishing operation is performed, for example, when a mode execution command is issued. Note that the polishing operation is a phenomenon called a so-called image flow caused by lowering the surface resistance of the photoconductor PC due to a discharge product generated on the photoconductor PC absorbing moisture in a high-temperature and high-humidity environment. This is for suppressing the occurrence. In particular, the image deletion remarkably appears in the case of an inorganic photoconductor such as the amorphous silicon photoconductor of the present embodiment.

  First, for example, when the image forming operation for a predetermined number of the media S is completed, the control device CU of the present embodiment activates each unit except the exposure device 34, the transport device 50, and the fixing device 60.

    When the toner image forming unit 30 is operated, the single-color units 31Y, 31M, 31C, and 31K do not apply the voltage from the power supply PS to the charging roller 32 as shown in FIGS. Therefore, the surface potential Vopc of the photoconductor PC becomes, for example, 0 V (see FIG. 6A). Further, the control device CU supplies the developing roller 36A with a DC voltage having an opposite polarity to the DC voltage (+60 V which is VBctr in FIG. 5) applied at the time of image formation (as an example, in FIGS. 6A, 6B, and 7). A voltage in which an AC voltage (as an example, a rectangular wave whose amplitude is twice VBpp and whose voltage is 1000 V) is applied to VBctr (−170 V).

  As a result, the latent image (potential contrast) of the photoconductor PC at the time of image formation is not formed on the photoconductor PC in the polishing mode, and the toner T of the developing roller 36A hardly moves to the photoconductor PC (by VBpp). Although the toner reciprocates between the developing roller 36A and the photoconductor PC, as a result, most of the toner T returns to the developing roller 36A). However, as described above, the toner T is composed of the base particles Ta and the abrasive Tb, and since the abrasive Tb has a lower resistance than the base particles Ta, the abrasive Tb of the toner T has priority. Is easily moved to the photoconductor PC and remains.

  Next, the abrasive Tb that has moved to the photoconductor PC and left on the photoconductor PC circulates together with the photoconductor PC, reaches a contact portion between the polishing roller 39 and the photoconductor PC, and polishes the outer periphery of the polishing roller 39. The agent Tb adheres. As a result, the polishing roller 39 rotates with a peripheral speed difference from the photoconductor PC with the abrasive Tb adhered to the outer periphery thereof, and polishes the photoconductor PC. Then, when the above operation is performed for a predetermined period, the polishing operation of the present embodiment ends.

  At the time of the polishing operation, the control device CU controls the transfer device 40 so as to rotate the belt TB of the transfer device 40 but not to perform the primary transfer.

<Effect>
Next, effects of the present embodiment will be described with reference to the drawings.

  For example, at the time of the polishing operation, for example, when a large amount of toner T is moved to the photoconductor PC after forming a large-area potential contrast on the photoconductor PC (hereinafter, referred to as Comparative Example 1), a large amount is performed. Of toner T is consumed. Further, when the photosensitive drum is charged in the polishing mode (hereinafter, referred to as Comparative Example 2) as in the image forming apparatus of Patent Document 1 described above, the charging device in the polishing mode is the same as in the image formation. Discharge products are generated.

  In contrast, in the case of the present embodiment, no voltage is applied to the charging roller 32 during the polishing mode (see FIGS. 6A and 7), and thus no discharge from the charging roller 32 occurs during the polishing mode. In the case of the present embodiment, the DC voltage VBctr (= −170 V) having the same polarity as the toner T is applied to the developing roller 36A in the polishing mode (see FIGS. 6A, 6B, and 7). Sometimes it is difficult to move to the toner T photoconductor PC side. In this embodiment, since the electrical resistance of the abrasive Tb is lower than the electrical resistance of the base particles Ta, the abrasive Tb of the toner T is preferentially moved to the photoconductor PC.

  Therefore, according to the present embodiment, it is possible to perform the polishing mode while suppressing the generation of discharge products during the polishing mode of the photoconductor PC. Further, according to the present embodiment, the polishing mode is performed while suppressing the consumption of the toner T (or the base particles Ta of the toner T) in the polishing mode and suppressing the generation of discharge products in the polishing mode of the photoconductor PC. It can be said that it is possible.

<< 2nd Embodiment >>
Next, the configuration, image forming operation, polishing operation, and effect of the image forming apparatus according to the second embodiment (see FIG. 1 because the mechanical configuration is the same as the first embodiment) will be described with reference to FIGS. 8A and 8B. The description will be made in the order of these descriptions. In the present embodiment, only the parts different from the first embodiment will be described.

<Structure, image forming operation and polishing operation>
In the case of the present embodiment, the ratio of the positive polarity time (70% shown in FIGS. 8A and 8B) of the rectangular wave of the AC voltage applied to the developing roller 36A in the polishing mode is determined by the developing roller 36A during image formation. Is larger than the ratio of the positive polarity time (60% shown in FIG. 5B and FIG. 7) in the rectangular wave of the AC voltage applied to This embodiment is different from the first embodiment in the above.

<Effect>
For example, as in the image forming apparatus of Patent Document 1, in the polishing mode, the waveform of the rectangular wave of the AC voltage applied to the developing roller is the same as the waveform of the rectangular wave of the AC voltage during the image forming operation ( Hereinafter, this will be referred to as Comparative Example 3.) Also, the mother particles can move to the photoconductor side together with the titanium oxide.

  On the other hand, in the case of the present embodiment, the ratio of the positive polarity time in the rectangular wave of the AC voltage of the developing roller 36A in the polishing mode is larger than that in the image formation. Therefore, in the case of the present embodiment, the amount of the base particles Ta moving to the photoconductor PC side is smaller than in the case of Comparative Example 3. Further, as described above, in the case of the present embodiment, the electric resistance of the abrasive Tb is lower than the electric resistance of the base particles Ta. Therefore, the abrasive Tb is more likely to move toward the photoconductor PC than the base particles Ta.

  Therefore, according to the present embodiment, it is possible to perform the polishing mode (polishing the surface of the photoconductor PC) while further suppressing the consumption of the toner T in the polishing mode of the photoconductor PC.

  As described above, the embodiments of the present invention have been described as examples, but the technical scope of the present invention is not limited to the embodiments. For example, the technical scope of the present invention includes the following embodiments.

  For example, in each embodiment, an example of the photoconductor PC has been described as an amorphous silicon photoconductor. However, since the image flow is a phenomenon that occurs without using the amorphous silicon photoconductor, the photoconductor PC may be another photoconductor. For example, an organic photoconductor (so-called OPC) may be used.

  In each embodiment, the surface potential Vopc of the photoconductor PC and the voltage applied to the developing roller 36A during the image formation and the polishing mode are shown in FIGS. 5A, 5B, 6A, 6B, 7, and 7. 8A and 8B. However, these voltage conditions are an example of a reversal development method using a positively charged photoconductor. That is, it is needless to say that the polarity is reversed when the negatively charged photoreceptor is used in the present embodiment.

  Further, in each embodiment, an example of the DC voltage of the opposite polarity applied to the developing roller 36A in the polishing mode is −170 V. However, a spark discharge (leak) must be generated between the developing roller 36A and the photoconductor PC. For example, the DC voltage of the opposite polarity need not be -170V.

  As a modification of the second embodiment (see FIG. 9), the charging of the photoconductor PC by the charging roller 32 is stopped during a part of the polishing mode (last fixed period). Instead, a DC voltage Vctr (for example, +60 V) having the same polarity as the DC voltage applied during image formation may be applied to the developing roller 36A to move the toner T from the developing roller 36A to the photoconductor PC. . Thus, the toner T having a small ratio of the abrasive Tb adhered to the developing roller 34A in the polishing mode can be collected by the cleaning device 38, so that the occurrence of image formation failure at the next and subsequent image forming operations can be suppressed. Note that, in this case, it is desirable that the process be performed at least for the time during which the developing roller 34A makes one rotation.

10 Image Forming Apparatus 32 Photoconductor (Example of Carrier)
36 Developing device 36A Developing roller 39 Polishing roller (an example of a polishing member)
40 Transfer device 60 Fixing device PC Photoconductor (an example of a carrier)
S medium VBpp / 2 Amplitude of AC voltage of developing roller VBctr DC voltage of developing roller

Claims (2)

A rotating carrier;
A charging roller that contacts the carrier, a voltage in which an AC voltage is superimposed on a DC voltage is applied, and a charging roller that charges the carrier;
An exposure device that forms a latent image by exposing the carrier charged by the charging roller,
Opposite to the carrier, rotated around an axis, has a developing roller to which a voltage obtained by superimposing an AC voltage on a DC voltage is applied, and includes a toner containing base particles and an abrasive attached to the developing roller. A developing device for developing the latent image as a toner image using the developing device;
A transfer device for transferring the toner image to a medium,
A fixing device for fixing the toner image to a medium,
A polishing member for polishing the carrier,
With
At the time of non-image formation, without applying a voltage to the charging roller, applying a voltage obtained by superimposing an AC voltage on a DC voltage having a polarity opposite to the DC voltage applied at the time of image formation to the developing roller, There rows polishing mode for polishing the bearing member,
The AC voltage applied to the developing roller is a rectangular wave,
The ratio of moving the toner in the rectangular wave from the carrier side to the developing roller side in the polishing mode is set to be larger than the ratio of moving the toner in the rectangular wave from the carrier side to the developing roller side during image formation .
Image forming device. During a part of the polishing mode, without charging the carrier to the charging roller, applying a DC voltage of the same polarity as the DC voltage applied to the developing roller at the time of image formation to the developing roller, Moving the toner from the developing roller to the carrier;
The image forming apparatus according to claim 1 .

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