JP2018092104A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that requires short time for a refresh mode for carriers.SOLUTION: An image forming apparatus comprises: carriers that individually carry latent images; developing devices that individually are opposed to the carriers, have developing rollers rotating around axes, and develop the latent images as toner images by using toner including a polishing agent; first polishing parts that individually polish the carriers; a transfer device that includes a rotating intermediate transfer body and a second polishing part that polishes the intermediate transfer body, and secondarily transfers the primarily transferred toner images; and a fixing device that fixes the secondarily transferred toner images to a medium. During a non-image forming period, the image forming apparatus performs a refresh mode of moving the toner from the developing rollers to the carriers while rotating the carriers, and primarily transferring, from the carriers to the intermediate transfer body, part of the toner moved to the carriers while rotating the intermediate transfer body, so as to cause the second polishing part to polish the intermediate transfer body while causing the first polishing parts to polish the carriers.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus.

  For example, when discharge products adhering to the photoreceptor in a high humidity environment absorb moisture in the air, the surface resistance of the photoreceptor decreases, and image formation (image blur) may occur when an image is formed in this state. Are known. Therefore, a method is known in which water is removed from the surface of the photoreceptor by attaching toner to the surface of the photoreceptor and polishing the surface of the photoreceptor using the toner.

  In the case of an image forming apparatus that primarily transfers a toner image formed on a photosensitive member to an intermediate transfer belt (intermediate transfer member) and then secondarily transfers the toner image that has been primarily transferred to the intermediate transfer belt to a medium. The intermediate transfer belt also absorbs moisture in the air. For this reason, in this image forming apparatus, since water moves from the intermediate transfer belt to the photoconductor, it takes time to remove water from the surface of the photoconductor.

  Therefore, in order to remove the moisture adsorbed on the intermediate transfer belt, for example, as described in Patent Document 1, when an image forming cycle is not performed, an abrasive-containing toner is adhered on the photosensitive member to thereby perform photosensitivity. There is a method in which the toner adhering to the body is temporarily transferred onto the intermediate transfer body, then reversely transferred from the intermediate transfer body onto the photoreceptor, and the moisture on the surface of the photoreceptor is removed after removing moisture from the intermediate transfer body. Proposed.

JP 2004-279902 A

  However, the above method is inefficient because it takes time to refresh because the moisture on the photoreceptor is removed after the moisture on the intermediate transfer member is removed.

  An object of the present invention is to provide an image forming apparatus in which the time required for the refresh mode of the carrier is short.

  The first image forming apparatus of the present invention includes a carrier that circulates while carrying a latent image, a developing roller that faces the carrier and rotates about an axis, and is a mother particle attached to the developing roller. And a developing device that develops the latent image as a toner image using a toner including a polishing agent, a first polishing unit that is disposed in contact with the carrier and polishes the carrier, and is endless. An intermediate transfer member that is circulated and a second polishing unit that is disposed in contact with the intermediate transfer member and polishes the intermediate transfer member, and the toner image that has been primarily transferred to the intermediate transfer member is subjected to secondary transfer onto a medium. And a fixing device that fixes the toner image secondarily transferred to the medium to the medium, and moves the toner from the developing roller to the carrier while rotating the carrier during non-image formation. Further, the intermediate transfer member is circulated. First, a part of the toner moved from the carrier to the intermediate transfer member is primarily transferred, and the intermediate transfer member is polished by the second polishing unit while the carrier is polished by the first polishing unit. A refresh mode is executed to polish the surface.

  In the second image forming apparatus of the present invention, the transfer device is disposed on the opposite side of the carrier with the intermediate transfer member interposed therebetween, and a voltage is applied to transfer the toner image on the carrier to the intermediate A primary transfer member for primary transfer to the transfer body, and a voltage applied to the primary transfer member is set to a predetermined voltage so that the toner from the carrier to the intermediate transfer body in the refresh mode is The primary transfer efficiency is made lower than the primary transfer efficiency of toner from the carrier to the intermediate transfer member during image formation.

  In the third image forming apparatus of the present invention, the second polishing unit further includes a conductive fur brush that contacts the intermediate transfer member, and a rotating member that contacts the fur brush and is applied with a voltage. At the time of image formation, a voltage is applied to the rotating member to remove the toner that remains on the intermediate transfer member without being secondarily transferred from the intermediate transfer member to the medium and is removed from the intermediate transfer member by the fur brush. In the refresh mode, no voltage is applied to the rotating member, so that the fur brush removes the toner removed from the intermediate transfer member by the fur brush.

  In the fourth image forming apparatus of the present invention, the carrier is an amorphous silicon type photoreceptor.

  In the image forming apparatus of the present invention, the time required for the refresh mode of the carrier is short.

1 is a schematic view of an image forming apparatus according to an embodiment as viewed from the front side. FIG. 2 is a schematic view of a photosensitive member and its peripheral portion constituting the image forming apparatus of the present embodiment as viewed from the front side. FIG. 2 is a block diagram illustrating a relationship between a control device configuring the image forming apparatus of the present embodiment and each unit configuring the image forming apparatus. 2 is a schematic diagram of toner used by the image forming apparatus according to the exemplary embodiment. FIG. 6 is a timing chart of the operation of each unit in a refresh mode executed by the image forming apparatus of the present embodiment during non-image formation. 12 is a timing chart of the operation of each unit in a refresh mode executed by the image forming apparatus according to the first modification during non-image formation. It is the schematic which looked at the image forming apparatus of the 2nd modification from the front side.

≪Overview≫

  Hereinafter, the configuration, image forming operation, refresh operation (refresh mode execution operation) and effects of the image forming apparatus 10 (see FIG. 1) according to the present 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 drawing are the front and back sides of the apparatus depth direction, the directions indicated by the arrows R and L are the right and left sides of the apparatus width direction, the arrows U and the arrow Lo, respectively. The directions shown are the upper side and the lower side of the apparatus height direction, respectively. Further, in this specification, the state in which the image forming apparatus 10 is viewed from the front side in the apparatus depth direction will be described as the front of the image forming apparatus 10.

<< Configuration of image forming apparatus >>
Hereinafter, the configuration of the image forming apparatus 10 will be described with reference to FIG. 1 unless otherwise specified. The image forming apparatus 10 includes an electronic paper cassette 20, a toner image forming unit 30, a transfer device 40, a transport device 50, a fixing device 60, a control device CU, and a power source PS. It is a photographic system.

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

  The toner image forming unit 30 has a function of forming a toner image to be held on a belt TB described later by performing each process of charging, exposure, and development. 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)). Yes. As shown in FIG. 1, each of the single color units 31Y, 31M, 31C, and 31K includes a photosensitive member PC (an example of a carrier), a charging roller 32, an exposure device 34, a developing device 36, and a cleaning device, respectively. 38 and a polishing roller 39 (an example of a first polishing unit).

  The photoconductor PC has a drum shape, and is driven by a drive source (not shown) while carrying a latent image formed by the exposure device 34, and rotates clockwise when viewed from the front side. The photoconductor PC of this embodiment is, for example, an amorphous silicon type photoconductor. That is, the photoconductor PC of the present embodiment is a so-called positively charged type and is an inorganic photoconductor.

  The charging roller 32 has a function of charging the photoreceptor PC while a voltage is applied from the power source PS (see FIG. 2). Note that 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.

  The developing device 36 has a function of developing a latent image formed on the photoconductor PC by the exposure device 34 as a toner image using the toner T (see FIG. 4). The developing device 36 has a developing roller 36 </ b> A that faces the photoreceptor PC and rotates around its axis (see FIGS. 1 and 2), and develops a toner image using toner T attached to the outer periphery thereof. ing. Further, in the developing device 36, a voltage obtained by superimposing an AC voltage on a DC voltage is applied from the power source PS to the developing roller 36A (see FIG. 2), so that the toner T on the outer periphery of the developing roller 36A jumps to the photoreceptor PC. It is supposed to be moved.

  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 mainly composed of a resin and an abrasive Tb. Note that the base particle Ta and the abrasive Tb are both particles having an average charge amount distribution with 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 photoreceptor and a positively charged toner T. Note that the abrasive Tb is, for example, titanium oxide.

  The cleaning device 38 has a function of removing toner T remaining on the photoconductor PC (toner T remaining on the photoconductor PC without being primarily transferred to the belt TB and remaining on 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 has a function of removing the toner T remaining on the photoreceptor PC from the photoreceptor PC. For example, the polishing roller 39 is a sponge roller in which the outer periphery of the shaft is covered with a foam (sponge). The polishing roller 39 is disposed in contact with the photoconductor PC, and rotates around the axis at a faster peripheral speed than the photoconductor PC.

  Each part other than the photoreceptor PC constituting the toner image forming unit 30 is clockwise in the order of description of the charging roller 32, the developing device 36, the polishing roller 39, and the cleaning blade CB around the photoreceptor PC when viewed from the front side. (See FIGS. 1 and 2). The exposure device 34 forms a latent image between the charging roller 32 and the developing device 36 in the photoreceptor PC. In FIGS. 1 and 2, the reference numerals of the single color units 31M, 31C, and 31K other than the single color unit 31Y are omitted.

  The transfer device 40 has an endless belt TB (an example of an intermediate transfer member), and primarily transfers the toner image formed by the toner image forming unit 30 onto the belt TB that circulates in the direction of arrow X in FIG. Thus, the toner image held on the belt TB has a function of secondary transfer to the medium S. In addition to the belt TB described above, the transfer device 40 includes primary transfer rollers 42Y, 42M, 42C, and 42K (an example of a primary transfer member), a secondary transfer roller 44, and a cleaning device 46 (a second polishing unit). An example).

  Primary transfer rollers 42Y, 42M, 42C, and 42K (hereinafter referred to as primary transfer rollers 42) are respectively arranged on the opposite sides of the photoreceptors PC of the respective colors across the belt TB and on the inner periphery of the belt TB. Arranged in contact. Each primary transfer roller 42 is configured to primarily transfer the toner image on the photosensitive member PC of each color onto the belt TB by applying a primary transfer voltage from the power source PS. The secondary transfer roller 44 comes into contact with the outer periphery of the belt TB and is driven by the belt TB to rotate around the axis. The secondary transfer roller 44 is configured to secondarily transfer the toner image primarily transferred to the belt TB to the medium S by applying a secondary transfer voltage from the power source PS. In this embodiment, the primary transfer efficiency (= {(amount of toner T primarily transferred to the belt TB−primary transfer is not performed) when the toner T on the photoreceptor PC is primarily transferred to the belt TB. The amount of toner T remaining on the photoreceptor PC) / the amount of toner T developed on the belt TB (before primary transfer) × 100%) is set to be 95% or more.

  The cleaning device 46 is in contact with the belt TB, a conductive fur brush 46A that rotates around the axis, and a metal roller 46B that contacts the fur brush 46A and rotates around the axis while being applied with a voltage from the power source PS (rotating member). For example). The fur brush 46A has a function of removing toner remaining on the belt TB without being secondarily transferred from the belt TB to the medium S from the belt TB. Further, the metal roller 46B has a function of collecting the toner T removed from the belt TB by the fur brush 46A from the fur brush 46A. The cleaning device 46 applies the voltage from the power source PS to the metal roller 46B during image formation, so that the toner T removed by the fur brush 46A from the belt TB is collected by the metal roller 46B, and the belt TB is removed. Cleaning (removal of the residual toner T remaining on the belt TB from the belt TB) is performed.

  The transport device 50 has a function of transporting the medium S accommodated in the paper feed cassette 20 along the transport path (two-dot chain line P in FIG. 1). Note that the arrow Y in FIG. 1 means 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 FIGS. 3 and 5 described later). The function of the control unit CU will be described in the description of the image forming operation and the refresh operation described later.

≪Image formation operation≫
Next, an image forming operation by the image forming apparatus 10 of the present embodiment will be described with reference to FIGS.

  Receiving the image data from the external device (not shown), the control unit CU operates each part of the image forming apparatus 10 (see FIG. 3).

  When the toner image forming unit 30 is operated, in each of the single color units 31Y, 31M, 31C, and 31K, the charging roller 32 charges the photosensitive member PC, the exposure device 34 exposes the photosensitive member PC, and the developing device 36 photosensitive. The latent image of the body PC is developed as a toner image. As a result, a toner image is formed on each photoconductor PC.

  Next, when the transfer device 40 and the conveyance device 50 are operated, the toner image formed by the toner image forming unit 30 is primarily transferred to the belt TB. In this case, a primary transfer voltage is applied to each primary transfer roller 42 from the power source PS, so that the toner images on the photoreceptors PC of the respective colors are primarily transferred to the belt TB. In addition, in accordance with the timing at which the toner image primarily transferred onto the belt TB is secondarily transferred, the medium S accommodated in the sheet feeding cassette 20 is conveyed by the conveying device 50 and is held on the belt TB. The image is secondarily transferred to the medium S. In this case, a secondary transfer voltage is applied to the secondary transfer roller 44 from the power source PS, whereby the toner image on the belt TB is secondarily transferred to the medium S. Then, the medium S on which the toner image is secondarily transferred is transported toward the fixing device 60 by the transport device 50.

  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 is completed.

≪Refresh operation≫
Next, the refresh operation of this embodiment will be described with reference to FIGS. The refresh operation of this embodiment is performed during non-image formation. For example, the control unit CU determines whether the inside of the apparatus is determined by a humidity sensor (not shown) after the image forming operation for a predetermined amount (for example, 100 sheets of A4 size medium S) is completed. If it is above the humidity, if the humidity inside the device is higher than the humidity determined by the humidity sensor when the device is turned on, a refresh command is issued by the user from the panel (not shown) provided on the device. The refresh operation is performed in such a case. The refresh operation is a phenomenon referred to as so-called image flow that is accompanied by a decrease in the surface resistance of the photoconductor PC due to the discharge product generated on the photoconductor PC sucking moisture in a high temperature and high humidity environment. This is to suppress the occurrence. In particular, the image flow appears remarkably in the case of an inorganic photoconductor such as the amorphous silicon type photoconductor of the present embodiment.

  First, for example, when the image forming operation with respect to a predetermined number of media S is completed, the control unit CU according to the present embodiment, except for the exposure device 34, the transport device 50, and the fixing device 60, that is, the toner image forming unit 30. And the transfer device 40 is operated.

  Specifically, the control unit CU applies a primary transfer bias (primary transfer voltage) from the power source PS to each primary transfer roller 42 of the transfer device 40 (time t1). As shown in FIG. 5, the primary transfer voltage applied in this case is a primary transfer voltage (hereinafter referred to as reverse bias) having a polarity opposite to that of the primary transfer voltage at the time of image formation. Further, the control device CU applies a voltage at the time of image formation from the power source PS to the metal roller 46B of the cleaning device 46, whereby a voltage at the time of image formation is applied to the fur brush 46A (time t1).

  Next, the control unit CU operates the toner image forming unit 30 as shown in FIG. Specifically, the control unit CU drives each color photoconductor PC by each drive source and drives each developing roller 36A (time t2). Further, the control device CU applies a voltage to be applied to the developing roller 36A during image formation from the power source PS to the developing roller 36A (time t2). Further, the control unit CU drives the belt TB by the drive source (time t2). As a result, the toner T moves from the developing roller 36 </ b> A to the circulating photoconductor PC.

  Next, as shown in FIG. 5, the control unit CU applies the reverse bias voltage applied to each primary transfer roller 42 from the power source PS to a voltage having the same polarity as that during image formation (hereinafter referred to as a positive bias). (Time t3). In this case, the magnitude of the switched positive bias is set smaller than the magnitude of the primary transfer voltage (corresponding to the primary transfer bias indicated by a two-dot chain line in FIG. 5) at the time of image formation. For this reason, the primary transfer efficiency of the toner T during the refresh operation is lower than the primary transfer efficiency of the toner T during image formation (as an example, 50%). In addition, the control unit CU causes the power supply PS to stop applying the voltage to the metal roller 46B (time t3). As a result, a part of the toner T moved to the photoreceptor PC is primarily transferred onto the belt TB that circulates. That is, a part of the toner T moved from the developing roller 36A remains attached to the photoconductor PC. In the photosensitive member PC, the toner T that is not primarily transferred to the belt TB and remains on the photosensitive member PC moves together with the photosensitive member PC and adheres to the polishing roller 39. Accordingly, the polishing roller 39 polishes the photoconductor PC with the toner T (or the abrasive Tb contained in the toner T) attached thereto. On the other hand, the toner T primarily transferred to the belt TB moves together with the belt TB and reaches the cleaning device 46. Accordingly, the fur brush 46A polishes the belt TB while holding the toner T (or the abrasive Tb contained in the toner T) removed from the belt TB. That is, in the present embodiment, the belt TB is polished by the fur brush 46A while the photosensitive roller PC is polished by the polishing roller 39.

  Next, as shown in FIG. 5, the control unit CU causes the power supply PS to stop applying the voltage to the developing roller 36A (time t4).

  Next, after maintaining the above state for a period longer than the period from t1 to t4, the control unit CU causes the power supply PS to apply a voltage to the metal roller 46B (time t5) as shown in FIG. ). As a result, the toner T adhering to the fur brush 46A is collected by the metal roller 46B.

  Next, as shown in FIG. 5, the control unit CU causes the power supply PS to stop applying the voltage to the metal roller 46B (time t6). Further, the control unit CU stops the operation of each unit (time t6). Then, the refresh operation of this embodiment is completed.

≪Effect≫
Next, the effect of this embodiment will be described with reference to the drawings.

<First effect>
For example, in the case of Patent Document 1 described above, the refresh operation of the photoconductor is performed after the refresh operation of the intermediate transfer member, so that the refresh operation takes time.

  On the other hand, in the present embodiment, the belt TB is polished on the fur brush 46A while the polishing roller 39 is polishing the photoconductor PC (time t4 to t5 in FIG. 5).

  Therefore, according to the image forming apparatus 10 of the present embodiment, the time required for the refresh mode (refresh operation) of the photoreceptor PC is short.

<Second effect>
In the case of the present embodiment, by setting (adjusting) the primary transfer voltage during the refresh operation to a predetermined voltage, the primary transfer efficiency of the toner T during the refresh operation is set to the toner T during image formation. The primary transfer efficiency is set to be lower. For example, in this embodiment, by adjusting the primary transfer voltage, the amount of toner T remaining after primary transfer on all the photoreceptors PC is equal to the amount of toner T that is primarily transferred to the belt TB. It is set to be. Therefore, according to the present embodiment, the toner T can be attached to the photoreceptor PC and the belt TB in parallel by a simple setting method.

<Third effect>
In the case of the present embodiment, the voltage to the metal roller 46B that collects the toner T adhering to the fur brush 46A is not applied during the period of time t3 to t5 during the refresh operation. Therefore, during the period of time t3 to t5, the fur brush 46A can polish the belt TB while holding the toner T (or the abrasive Tb contained in the toner T) removed from the belt TB. Therefore, according to the present embodiment, the belt TB can be polished by a simple setting method while the photoconductor PC is being polished while the fur brush 46A holds the abrasive Tb.

  As described above, the present embodiment has been described by taking the present embodiment as an example, but the technical scope of the present invention is not limited to the present embodiment. For example, the following forms are also included in the technical scope of the present invention.

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

  In the present embodiment, the magnitude of the positive bias applied to each primary transfer roller 42 during the period of time t3 to t5 during the refresh operation is the primary transfer voltage during image formation (two points in FIG. 5). It has been described that it is set smaller than the size of the primary transfer bias indicated by a chain line (see FIG. 5). However, if a part of the toner T on the photoconductor PC can be primarily transferred to the belt TB during the refresh operation, the voltage setting need not be the same as in the present embodiment. For example, as in the modification of FIG. 6, the voltage applied to each primary transfer roller 42 during the period from time t3 to t5 during the refresh operation may be an alternating current whose effective value does not exceed the primary transfer bias. Good.

  Further, in the present embodiment, it has been described that there are a plurality of photoreceptors PC corresponding to the toner T of each color. However, as in the modification of FIG. 7, the photoreceptor PC (toner image forming unit 30) may be an image forming apparatus for one color. In this case, for example, as in the case of the present embodiment, if the primary transfer efficiency of the toner T during the refresh operation is 50%, the amount of toner T attached to the photoreceptor PC and the belt TB are attached. This is equivalent to the amount of toner T.

10 Image forming apparatus PC Photosensitive member (an example of a carrier)
36 Developing device 36A Developing roller 39 Polishing roller (an example of a first polishing unit)
40 Transfer Device 42 Primary Transfer Roller (Primary Transfer Member)
46 Cleaning device (example of second polishing section)
46A Fur brush 46B Metal roller (an example of a recovery member)
60 fixing device PC photoconductor (an example of a carrier)
S Medium TB belt (an example of an intermediate transfer member)

Claims (4)

A carrier that circulates while carrying a latent image;
A developing device that has a developing roller that faces the carrier and rotates about an axis, and that develops the latent image as a toner image using a toner containing mother particles and an abrasive attached to the developing roller. ,
A first polishing section disposed in contact with the carrier and polishing the carrier;
An intermediate transfer member that is endless and circulates, and a second polishing unit that is disposed in contact with the intermediate transfer member and polishes the intermediate transfer member, and a toner image that is primarily transferred to the intermediate transfer member is a medium A transfer device for secondary transfer to
A fixing device for fixing the toner image secondarily transferred to the medium to the medium;
With
During non-image formation, the toner was moved from the developing roller to the carrier while rotating the carrier, and further, the toner was moved from the carrier to the intermediate transfer member while rotating the intermediate transfer member. Executing a refresh mode in which a part of the toner is primarily transferred, and the intermediate transfer member is polished by the second polishing unit while the carrier is polished by the first polishing unit;
Image forming apparatus. The transfer device is disposed on the opposite side of the carrier with the intermediate transfer member interposed therebetween, and has a primary transfer member for primary transfer of a toner image on the carrier to the intermediate transfer member by applying a voltage. And
The voltage applied to the primary transfer member is set to a predetermined voltage, and the primary transfer efficiency of the toner from the carrier to the intermediate transfer member in the refresh mode is determined from the carrier in the image formation. Lower than the primary transfer efficiency of the toner to the intermediate transfer member,
The image forming apparatus according to claim 1. The second polishing unit includes a conductive fur brush that contacts the intermediate transfer member and a rotating member that contacts the fur brush and is applied with a voltage.
At the time of image formation, a voltage is applied to the rotating member to remove the toner that remains on the intermediate transfer member without being secondarily transferred from the intermediate transfer member to the medium and is removed from the intermediate transfer member by the fur brush. To collect,
In the refresh mode, by applying no voltage to the rotating member, the fur brush holds the toner removed from the intermediate transfer member by the fur brush.
The image forming apparatus according to claim 1. The carrier is an amorphous silicon type photoreceptor,
The image forming apparatus according to claim 1.

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