JP6693440B2 - 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, titanium oxide, which is an external additive, is preferentially moved to the photosensitive drum side while the toner mother particles are left on the developing roller in the developing device as much as possible, and is supplied to the rubbing roller. There is 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, which has the same chargeability as the toner base particles and a smaller chargeability (charge amount per unit weight) compared to the toner base particles, is used, and a normal developing bias ( A bias smaller than that of the toner and titanium oxide) is applied.

JP, 2011-169995, A

  By the way, in the above image forming apparatus, the charging condition of the photosensitive drum in the refresh mode (polishing mode) is the same as the charging condition of the photosensitive drum in the image formation. Therefore, the charging device of the image forming apparatus described above generates the same discharge products as in the image formation in the polishing mode.

  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 and consumption of mother particles constituting a toner in the polishing mode of a carrier.

  A first image forming apparatus of the present invention includes a revolving carrier, a charging member that is in contact with the carrier and is applied with a voltage obtained by superimposing an AC voltage on a DC voltage, and a charging member that charges the carrier. An exposure device that exposes the carrier charged by a member to form a latent image on the carrier, and a voltage that is opposed to the carrier and rotates around an axis, and a voltage in which an AC voltage is superimposed on a DC voltage is applied. And a developing device for developing the latent image as a toner image by using a toner containing a mother particle adhered to the developing member and an abrasive having a polarity opposite to that of the mother particle. A charging member that polishes the carrier, a transfer device that transfers the toner image to a medium, and a fixing device that fixes the toner image to the medium, and a discharge start voltage is applied to the charging member during non-image formation. Orbiting by applying only the following AC voltage Wherein while the carrier is charged that, by applying a voltage to an AC voltage is superimposed on a DC voltage of said developing member at the time of image formation and opposite polarity, it is polished mode of polishing the carrier by the polishing member.

  A second image forming apparatus of the present invention includes a revolving carrier, a charging member that is in contact with the carrier and is applied with a voltage in which an AC voltage is superimposed on a DC voltage to charge the carrier, and the charging member. An exposure device that exposes the carrier charged by a member to form a latent image on the carrier, and a voltage that is opposed to the carrier and rotates around an axis, and a voltage in which an AC voltage is superimposed on a DC voltage is applied. And a developing device for developing the latent image as a toner image by using a toner containing a mother particle adhered to the developing member and an abrasive having a polarity opposite to that of the mother particle. A charging member that polishes the carrier, a transfer device that transfers the toner image to a medium, and a fixing device that fixes the toner image to the medium, and a discharge start voltage is applied to the charging member during non-image formation. Orbiting by applying only the following AC voltage While charging the carrier, a voltage in which an AC voltage is superimposed on a DC voltage that repeats a DC voltage having the same polarity as that at the time of image formation and a DC voltage having the opposite polarity is applied to the developing member by the polishing member. A polishing mode for polishing the carrier is performed.

  A third image forming apparatus of the present invention is the first or second image forming apparatus, wherein the carrier is a photosensitive body made of amorphous silicon.

  The image forming apparatus of the present invention can perform the polishing mode while suppressing generation of discharge products and consumption of the mother particles constituting the toner in the polishing mode of the carrier.

FIG. 3 is a schematic view of the image forming apparatus of the first embodiment as seen from the front side. FIG. 3 is a schematic view of the photoconductor and its peripheral portion that form the image forming apparatus of the first embodiment as seen from the front side. FIG. 3 is a block diagram showing a relationship between a control device forming the image forming apparatus of the first embodiment and each component forming the image forming apparatus. FIG. 3 is a schematic diagram of toner used in the image forming apparatus of the first embodiment. FIG. 6 is a schematic diagram for explaining the relationship between the surface potential of the photoconductor and the potential applied to the developing roller in the image forming operation by the image forming apparatus of the first embodiment. FIG. 6 is a schematic diagram for explaining a voltage applied to a charging roller in an image forming operation by the image forming apparatus of the first embodiment. Schematic diagram for explaining the relationship between the surface potential of the photoconductor, the voltage applied to the charging roller, and the voltage applied to the developing roller in the polishing operation performed during non-image formation by the image forming apparatus of the first embodiment. Is. FIG. 6 is a schematic diagram for explaining a voltage applied to a charging roller in a polishing operation performed during non-image formation by the image forming apparatus of the first embodiment. In the image forming apparatus of the first embodiment, the relationship between the surface potential of the photoconductor during image formation and the voltage applied to the developing roller and the relationship between the surface potential of the photoconductor during the polishing mode and the voltage applied to the developing roller are described. It is a summary table. In the polishing operation performed during non-image formation by the image forming apparatus of the second embodiment, the surface potential of the photoconductor, the voltage applied to the charging roller, and the voltage applied to the developing roller (change of DC voltage with time) It is a schematic diagram for demonstrating a relationship.

<< Overview >>
Hereinafter, the first embodiment, the second embodiment, and the modified examples will be described in the order of description.

«First embodiment»
First, the configuration, image forming operation, polishing operation (operation in polishing mode) and effects 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 arrow Fr and the arrow Rr in the drawing are the front side and the rear side in the device depth direction, the directions indicated by the arrow R and the arrow L are the right and left sides in the device width direction, and the arrow U and the arrow Lo, respectively. The directions shown are the upper side and the lower side in the device height direction, respectively. Further, in this specification, a state in which the image forming apparatus 10 is viewed from the front side in the apparatus depth direction will be described as a front surface of the image forming apparatus 10.

<Structure 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 conveyance device 50, a fixing device 60, a power supply PS, and a control device CU. It is said that the electrophotographic apparatus is configured to include the.

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

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

  The photoconductor PC has a drum shape and carries a latent image formed by the exposure device 34, and is driven by a drive source (not shown) to orbit clockwise when viewed from the front side. The photoconductor PC of the present embodiment is, for example, a photoconductor made of amorphous silicon. The photoconductor PC of this embodiment is, for example, a so-called positive charging type photoconductor.

  The charging roller 32 has a function of contacting the photoconductor PC while being applied with a voltage from the power source PS and charging the photoconductor PC. The voltage applied from the power supply PS to the charging roller 32 is, for example, a voltage obtained by superimposing an AC voltage on a DC voltage (see FIG. 5B).

  The exposure device 34 has a function of exposing the photoconductor PC charged by the charging roller 32 to form a latent image on the photoconductor PC.

  The developing device 36 has a function of developing the 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 36A (an example of a developing member) that faces the photoconductor PC and rotates around an axis (see FIGS. 1 and 2), and uses a toner T attached to the outer periphery of the developing roller 36A to form a toner image. Is developed. Further, the developing device 36 causes the toner T on the outer periphery of the developing roller 36A to fly and move to the photoconductor PC by applying a voltage in which the AC voltage is superimposed on the DC voltage from the power source PS to the developing roller 36A. 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 mother particles Ta containing a resin as a main component and an abrasive Tb. The average charge amount distribution of the toner T is a positive charge amount. Here, the mother particles Ta are particles whose average charge amount distribution has a positive charge amount. The abrasive Tb is a particle having a negative charge amount in the average charge amount distribution, that is, a particle having a polarity opposite to that of the mother particle. In addition, the developing method of the present embodiment is a reversal developing method using a positively charged photoreceptor and positively charged toner (see FIG. 5A).

  The static eliminator 37 has a function of irradiating the photoconductor PC that has passed through the transfer position (the position where the photoconductor PC comes into contact with the belt TB) with light to eliminate the charge on the photoconductor PC.

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

  The polishing roller 39 has a function of polishing the photoconductor PC. The polishing roller 39 is, for example, a sponge roller having a shaft covered with a foam (sponge). It should be noted that the polishing roller 39 is adapted to rotate around the axis at a peripheral speed higher than that of the photoconductor PC while being in contact with the photoconductor PC.

  Descriptions of the charging roller 32, the developing device 36, the charge eliminating device 37, the polishing roller 39, and the cleaning blade CB around the photoconductor PC when viewed from the front side are included in the toner image forming unit 30 except for the photoconductor PC. They are arranged clockwise in order (see FIG. 2). The exposure device 34 forms a latent image between the charging roller 32 and the developing device 36 in the photoconductor PC. Note that, in FIG. 1, reference numerals of the monochromatic units 31M, 31C, 31K other than the monochromatic unit 31Y are omitted.

  The transfer device 40 has an endless belt TB, 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. 1 and is held by the belt TB. It has a function of secondarily transferring the toner image to the medium S. That is, the transfer device 40 has a function of transferring the toner image onto the medium S.

  The transport device 50 has a function of transporting the medium S contained in the paper feed cassette 20 along a transport path (two-dot chain line P in FIG. 1). 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 onto the medium S by the transfer device 40 onto the medium S.

  The power supply PS has a function of applying a voltage to each of the charging roller 32 and the developing device 36 (the developing roller 36A thereof) under the control of the control unit CU.

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

<Image forming operation>
Next, an image forming operation by the image forming apparatus 10 of the present exemplary embodiment will be described with reference to FIGS. 1, 2, 3, 5A and 5B, and 7.

  Upon receiving the image data from the external device (not shown), the control unit CU operates each unit 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 photoconductor PC, the exposure device 34 exposes the photoconductor PC, and the developing device 36 exposes the photoconductor 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 source PS to the charging roller 32 so as to charge the charging roller 32 to + 250V, for example, the surface potential (Vopc in FIG. 5) of the photoconductor PC. Specifically, as shown in FIG. 5B, the control unit CU uses, as an example, a DC voltage VAdc of + 250V and VApp (a value that is twice the amplitude, that is, VApp / 2 is the discharge start voltage). A sine wave voltage of 1200 V, which is more than double, is superimposed and applied. Further, as shown in FIG. 5A, the control unit CU controls the developing roller 36A to have a DC voltage VBave of + 190V as an example, and VBpp (a value twice the amplitude, that is, the amplitude is VBpp / 2) of 1650V. The rectangular wave voltage of is superimposed and applied. Then, the surface potential of the photoconductor PC exposed by the exposure device 34 to form a latent image is less than +60 V (+20 V as an example), and the surface of the photoconductor PC on which the potential contrast is formed is transferred from the developing roller 36A. The toner T moves (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 onto the belt TB. Further, the medium S accommodated in the paper feeding cassette 20 is conveyed by the conveying device 50 at the timing when the toner image primarily transferred to the belt TB is secondarily transferred, and the toner held on the belt TB is conveyed. The image is secondarily transferred to the medium S. The medium S to which the toner image is secondarily transferred is conveyed by the conveying device 50 toward the fixing device 60.

  Next, when the fixing device 60 is operated and the medium S to which the toner image is secondarily transferred is conveyed to the fixing device 60, the toner image secondarily transferred to the medium S is fixed to the medium S (to the medium S). 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 to the outside of the image forming apparatus 10 by the conveying device 50, and the image forming operation is completed.

<Polishing operation (operation in polishing mode)>
Next, the polishing operation of this embodiment will be described with reference to FIGS. 6A and 6B and FIG. 7. The polishing operation of this embodiment is performed during non-image formation. The inside of the control unit CU is set by a temperature / humidity sensor (not shown) after the image forming operation for a predetermined number (for example, 100 sheets of A4 size medium S) of the medium S is completed. If the temperature is high or high, and the inside of the device is high or high, which is set by the temperature / humidity sensor (not shown) when the power of the device is turned on, the user can select from the panel (not shown) provided in the device. The polishing operation is performed when a polishing mode execution command is issued by. It should be noted that the polishing operation is a phenomenon called a so-called image deletion, which is accompanied by a decrease in the surface resistance of the photoconductor PC due to the fact that the discharge product generated on the photoconductor PC absorbs water in a high temperature and high humidity environment. This is to suppress the generation. In particular, the image deletion remarkably appears in the case of an inorganic photoconductor such as the photoconductor made of amorphous silicon of the present embodiment.

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

  When the toner image forming unit 30 is operated, the surface potential Vopc of each of the single color units 31Y, 31M, 31C and 31K is set to 0V by the charging roller 32 as shown in FIGS. 6A, 6B and 7. Charge the photoconductor PC. Specifically, as shown in FIG. 6B, the control unit CU applies a direct current voltage of 0 V from the power source PS to the charging roller 32 (in other words, while turning off the direct current voltage), the amplitude is increased. An alternating voltage having a (VApp / 2) of 500 V (an example of a voltage equal to or lower than the discharge start voltage) is applied. That is, the control unit CU applies only an AC voltage equal to or lower than the discharge start voltage from the power source PS to the charging roller 32 to charge the orbiting photoconductor PC.

Further, as shown in FIG. 6A, the control unit CU applies an AC voltage of 825V from the power source PS to the developing roller 36A, in which the DC voltage of -60V has an amplitude (V B pp / 2) as an example. That is, the control unit CU applies a voltage obtained by superimposing an AC voltage on a DC voltage having a polarity opposite to that at the time of image formation from the power source PS to the developing roller 36A.

  Then, the control unit CU rotates the photoconductor PC a predetermined number of times while applying the above voltage to the charging roller 32 and the developing roller 36A from the power supply PS for a predetermined period, and the polishing operation of the present embodiment is performed. finish.

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

  For example, when the charging condition of the photosensitive drum in the polishing mode and the charging condition of the photosensitive drum in the image formation are the same as in the image forming apparatus of the above-mentioned Patent Document 1 (hereinafter, in the case of the comparative embodiment) The amount of discharge products generated from the charging device in the polishing mode is equal to the amount of discharge products generated from the charging device during image formation.

  On the other hand, in the case of the present embodiment, the charging condition of the photosensitive drum in the polishing mode and the charging condition of the photosensitive drum in the image formation are different. Specifically, in the case of the present embodiment, as shown in FIG. 6B, in the polishing mode, the charging roller 32 applies only an AC voltage equal to or lower than the discharge start voltage to charge the orbiting photoreceptor PC. Therefore, in the case of the present embodiment, the discharge product is not generated from the charging roller 32 in the polishing mode (or even if generated, it is smaller than that during image formation).

  Further, in the case of the present embodiment, the DC voltage VBave applied to the developing roller 36A in the polishing mode is set to a voltage having the opposite polarity to the DC voltage VBave applied to the developing roller 36A during image formation. In addition, in the case of the present embodiment, since the surface potential Vopc of (the entire outer periphery of) the photoconductor PC is 0 V, the mother particles Ta of the toner T having an average positive charge amount are not easily transferred to the photoconductor PC. The abrasive Tb whose average charge amount is negative is easily (selectively) transferred to the photoconductor PC. As a result, in the case of the present embodiment, the abrasive Tb of the toner T is selectively attached to the photoconductor PC, and the photoconductor PC is efficiently polished by the polishing roller 39.

  Therefore, the image forming apparatus 10 of the present embodiment suppresses generation of discharge products and consumption of the mother particles Ta forming the toner T in the polishing mode of the photoconductor PC, as compared with the image forming apparatus of the comparative example. A polishing mode can be performed. This effect can be said to be effective when the photoconductor PC is a photoconductor made of amorphous silicon as in the case of the present embodiment.

«Second embodiment»
Next, the configuration of the image forming apparatus of the second embodiment (see FIG. 1 because the mechanical configuration is the same as that of the first embodiment), the image forming operation, the polishing operation, and the effect thereof are mainly described with reference to FIG. Will be described in the order of description. In the present embodiment, 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 DC voltage VBave applied to the developing roller 36A in the polishing mode is a DC voltage in which the DC voltage having the same polarity and the opposite polarity as in the image formation is repeated as shown in FIG. Specifically, in the case of the present embodiment, the control unit CU supplies the alternating current voltage equal to or lower than the discharge start voltage to the charging roller 32 by the power source PS while charging the orbiting photoreceptor PC while the power source PS is in the polishing mode. An AC voltage (as an example, the same as in the first embodiment, omitted in FIG. 8) is applied to the DC voltage VB2ave in which the DC voltage having the same polarity and the DC voltage having the opposite polarity, which are the same as those at the time of image formation, are repeatedly applied to the developing roller 36A by PS. The photosensitive drum PC is polished by the polishing roller 39 by applying the superimposed voltage. The points in which the present embodiment is different from the first embodiment are as described above.

<Effect>
In the case of the present embodiment, in FIG. 8, while the positive DC voltage VB2ave (+60 V in the figure) is being applied from the power source PS to the developing roller 36A, the toner T (base particles Ta that has adhered to the developing roller 36A is applied. And the polishing agent Tb) moves to the photoconductor PC. As a result, the mother particles Ta that have moved to the photoconductor PC absorb (absorb) the water adsorbed on (the outer periphery of) the photoconductor PC. Next, in the case of the present embodiment, after the period in which the positive DC voltage VB2ave (+60 V in the drawing) is applied from the power supply PS to the developing roller 36A, the negative DC voltage VB2ave (in the drawing) is applied to the developing roller 36A. -60 V) is applied. Therefore, according to the present embodiment, by the same mechanism as in the case of the first embodiment (see FIG. 6A), the photosensitive member is exposed while the negative DC voltage VB2ave (−60V in the drawing) is applied to the developing roller 36A. The abrasive Tb of the toner T is selectively attached to the PC, and the PC is efficiently polished by the polishing roller 39.

  Therefore, as compared with the image forming apparatus of the comparative embodiment, the image forming apparatus of the present embodiment absorbs moisture that causes the generation of discharge products during the polishing mode of the photoconductor PC, thereby generating the discharge products. The polishing mode can be performed while suppressing the consumption of the mother particles Ta forming the toner T. In other words, the image forming apparatus according to the present exemplary embodiment has the same effect as the image forming apparatus according to the first exemplary embodiment, and absorbs water that causes generation of discharge products during the polishing mode of the photoconductor PC. be able to. This effect can be said to be effective when the photoconductor PC is a photoconductor made of amorphous silicon as in the case of the present embodiment.

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

  For example, in each of the embodiments, an example of the photoconductor PC has been described as the photoconductor PC made of amorphous silicon. However, since the image deletion is a phenomenon that occurs even when the photoconductor PC is not made of amorphous silicon, the photoconductor PC does not have to be a photoconductor made of amorphous silicon. For example, it may be an organic photoconductor (so-called OPC photoconductor).

  In each embodiment, the surface potential Vopc of the photoconductor PC and the applied voltage of the developing roller 36A are set as shown in FIGS. 5A, 6A, 7 and 8 during image formation and polishing mode. explained. However, since these voltage conditions are an example of the reversal development method using the positive charging type photoconductor, the polarity is the same as that of the present embodiment in the case of the reversal development method using the negative charging type photoconductor. It goes without saying that the relationship is reversed.

  Moreover, in each embodiment, the polishing roller 39 is described as an example of the polishing member. However, the polishing roller 39 may not be an example of the polishing member as long as it has a function of polishing the outer periphery of the photoconductor PC. For example, the cleaning blade CB may be removed as an example of the polishing member by removing the polishing roller 39 from the image forming apparatus of each embodiment and polishing the photoconductor PC with the cleaning blade CB. From another perspective, any member having a function of polishing the photoconductor PC may be regarded as an example of the polishing member.

10 image forming apparatus 32 charging roller (an example of charging member)
34 exposure device 36 developing device 36A developing roller (an example of developing member)
39 polishing roller (an example of polishing member)
40 transfer device 60 fixing device PC photoconductor (an example of carrier)
S medium VApp AC voltage below discharge start voltage VBave DC voltage VBpp AC voltage of opposite polarity to that during image formation

Claims (2)

An orbiting carrier,
A charging member that is in contact with the carrier and is applied with a voltage in which an alternating voltage is superimposed on a direct current voltage to charge the carrier,
An exposure device that exposes the carrier charged by the charging member to form a latent image on the carrier;
Opposing the carrier, rotating around an axis, having a developing member to which a voltage obtained by superimposing an AC voltage on a DC voltage is applied, and a mother particle attached to the developing member and having a polarity opposite to that of the mother particle. A developing device for developing the latent image as a toner image by using a toner containing a charged abrasive.
A polishing member for polishing the carrier,
A transfer device for transferring the toner image onto a medium,
A fixing device for fixing the toner image on a medium;
Equipped with
During non-image formation, an AC voltage is superposed on a DC voltage having a reverse polarity to that at the time of image formation on the developing member while charging only the alternating voltage below the discharge start voltage to the charging member to charge the circulating carrier. Voltage is applied to perform a polishing mode in which the carrier is polished by the polishing member,
Image forming apparatus. The carrier is a photoconductor made of amorphous silicon,
The image forming apparatus according to claim 1 .

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