JP2007156311A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of demonstrating satisfactory cleaning performance for a long period of time. <P>SOLUTION: The image forming apparatus includes; a cleaning brush 81b which has a voltage applied thereto to attract residual toner; a power source 83 for brush which applies a voltage to the cleaning brush 81b; a recovery roll 85 which has a voltage applied thereto to recover the residual toner on the cleaning brush 81b; a power source 87 for roll which applies a voltage to the recovery roll 85; an ammeter 84 which measures a current flowing between the power source 83 for brush and the cleaning brush 81b; and a control part 90 which controls the voltage applied to the recovery roll 85 from the power source 87 for roll into a voltage corresponding to the current measured by the ammeter 84. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system.

  As an example of an image forming apparatus using an electrophotographic system, a copying machine, a facsimile, a printer, and the like can be given. In these image forming apparatuses, an electrostatic latent image is formed by charging the image bearing surface, irradiating the image bearing surface with exposure light, and supplying the charged toner to the electrostatic latent image to reduce the static electricity. The electrostatic latent image is developed to obtain a toner image, and the toner image is transferred and fixed on the recording medium to form an image composed of the fixed toner image on the recording medium.

  Here, the toner that could not be transferred remains on the image bearing surface after the transfer of the toner image, and this residual toner (residual toner) can be removed prior to the formation of the next toner image. I need it.

  Various cleaning methods for removing residual toner have been proposed, but a brush cleaning method using a conductive brush having a plurality of conductive fibers is widely known as an effective method. . The brush cleaning method is a method in which the residual toner is adsorbed and removed by rubbing the image bearing surface with a conductive brush charged to a polarity opposite to the charged polarity of the toner.

  By the way, in such a brush cleaning system, various devices have been conventionally made in order to improve the cleaning performance.

  For example, conventionally, a technique has been proposed in which a conductive brush, which has been often charged in an electrically floating state, is stably charged with a current suppressed to such an extent that the image bearing surface is not damaged (for example, (See Patent Document 1). According to this technique, since the charged state of the conductive brush is stabilized, the cleaning performance for the image bearing surface is improved.

  Further, for example, a technique has been proposed in which the residual toner adsorbed on the conductive brush is recharged (see, for example, Patent Document 2). In the brush cleaning method, the residual toner adsorbed on the conductive brush is often collected by being adsorbed on a collecting member charged with a polarity opposite to that of the residual toner. According to the technique of Patent Document 2, The charged state of the residual toner in the conductive brush is stable, and the recovery by the recovery member is good. Thereby, the accumulation of residual toner on the conductive brush is suppressed, and the cleaning performance for the image bearing surface is improved.

  In addition, for example, a technique has been proposed in which a voltage for charging a conductive brush is controlled to suppress a change with time of the charged state of the conductive brush (see, for example, Patent Document 3). This technique also stabilizes the charged state of the conductive brush, thereby improving the cleaning performance for the image bearing surface.

  Further, for example, a technique has been proposed in which the surface of the recovery member is covered with a medium resistance material for stably maintaining the potential difference between the conductive brush and the recovery member regardless of environmental changes such as humidity. (For example, refer to Patent Document 4). According to this technique, since the collection of the residual toner by the collection member is stable, the accumulation of the residual toner on the conductive brush is suppressed, and the cleaning performance for the image bearing surface is improved.

  In addition, for example, a technique of covering the surface of the recovery member with a thin film of a high resistance material for preventing an overcurrent from occurring due to an environmental change such as humidity between the conductive brush and the recovery member. Has been proposed (see, for example, Patent Document 5). According to this technique, since the life of the recovery member is extended, the cleaning performance is maintained for a long time.

In the brush cleaning method, the residual toner adsorbed on the collecting member is often mechanically scraped and collected from the collecting member. For example, the collecting member is mechanically scraped off. A technique has been proposed in which the charging potential of the toner is switched to a potential that weakens the attractive force with respect to the residual toner to promote toner separation (see, for example, Patent Document 6). According to this technique, the residual toner is prevented from being adsorbed on the recovery member, so that the recovery by the recovery member is good, and as a result, the cleaning performance is improved.
JP-A-62-94884 Japanese Patent Laid-Open No. 3-181984 JP-A-4-174488 JP 2002-278400 A JP 2004-184863 A JP 2004-102002 A

  By the way, in the brush cleaning system, the residual toner that the collecting member could not adsorb gradually accumulates on the conductive brush by repeated cleaning. Therefore, conventionally, for example, when the image forming apparatus is turned on, the cleaning operation is performed in a state where there is little transfer of residual toner from the image bearing surface, thereby removing the residual toner accumulated on the conductive brush. The cleaning brush itself is being cleaned.

  However, if the amount of residual toner deposited on the conductive brush is large, the residual toner receives charge injection from the conductive brush and the like, and is charged with the opposite polarity, that is, the same polarity as the conductive brush. May end up. Such residual toner charged to the opposite polarity is not collected by the cleaning of the conductive brush itself as described above, but remains in the conductive brush. Such residual toner charged to the opposite polarity changes the apparent electrical resistance of the conductive brush and fluctuates the current for charging the conductive brush, leading to a reduction in cleaning performance for the image bearing surface. Therefore, removing such residual toner charged to the opposite polarity from the conductive brush is an important issue in maintaining the cleaning performance of the brush cleaning method in a good state for a long time. At present, no specific technique for removing such residual toner charged to the opposite polarity has been proposed.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of exhibiting good cleaning performance over a long period of time.

The image forming apparatus of the present invention that achieves the above object forms an electrostatic latent image by charging the image carrying surface and irradiating the image carrying surface with exposure light, and the electrostatic latent image is charged with the charged toner. In the image forming apparatus, the electrostatic latent image is developed by supplying the toner image to obtain a toner image, and the toner image is transferred and fixed on the recording medium to form an image composed of the fixed toner image on the recording medium. ,
An adsorbing member that is charged by applying a voltage and adsorbs residual toner remaining on the image carrying surface by rubbing the image carrying surface after the toner image is transferred;
A power supply for the suction member that applies a voltage to the suction member so that the suction member is charged to a polarity opposite to the charging polarity of the toner during development;
A collecting member that collects residual toner adsorbed on the adsorbing member by contacting the adsorbing member that is charged by applying a voltage;
A power supply for a recovery member that applies a voltage to the recovery member to charge the recovery member;
A current measuring unit for measuring a current flowing between the power supply for the adsorbing member and the adsorbing member;
And an application control unit that controls a voltage applied by the recovery member power source to the recovery member to a voltage corresponding to the current measured by the current measurement unit.

Further, in the image forming apparatus of the present invention, “the adsorbing member comprises a plurality of conductive fibers, and the conductive fibers rub the image bearing surface,
The form that the said collection | recovery member has a roll shape and the surrounding surface of the roll shape contacts the said conductive fiber is a typical form.

  According to the image forming apparatus of the present invention, the adsorption performance of the adsorption member is monitored by measuring the current flowing between the adsorption member power source and the adsorption member. The main cause of the decrease in the adsorption performance is that the residual toner accumulated on the adsorption member is charged with a polarity opposite to that of the former. According to the image forming apparatus of the present invention, when a decrease in the suction performance of the suction member is detected, the voltage applied by the power supply for the recovery member is appropriately controlled to reduce the suction performance of the suction member. By urging the residual toner to be transferred from the suction member to the recovery member, such residual toner can be removed from the suction member, etc., and the cleaning performance in the image forming apparatus is good over a long period of time. Can be maintained.

In the image forming apparatus of the present invention, “the power supply for the recovery member is such that the recovery member is charged to a potential for recovering the residual toner having the same polarity as that of the toner at the time of development from the adsorption member. A voltage of 1 and a second voltage at which the collecting member is charged from the adsorption member to a potential for collecting the residual toner having a polarity opposite to the charging polarity of the toner at the time of development are selectively applied. Yes,
The form that the said application control part selects the voltage according to the electric current measured by the said electric current measurement part among the said 1st voltage and the said 2nd voltage is a preferable form.

  According to this preferred embodiment of the image forming apparatus, the application controller only needs to select one of the first voltage and the second voltage, and the control is very easy. Further, according to this preferred embodiment of the image forming apparatus, since only the voltage suitable for collecting the residual toner is applied to the collecting member, the collecting effect is great.

  In the image forming apparatus of the present invention, “the voltage applied by the recovery member power source to the recovery member is determined by the application control unit between the current measured by the current measurement unit and a predetermined threshold value”. The form of “controlling the voltage according to the relationship” is a preferable form.

  According to this preferred embodiment of the image forming apparatus, the residual power that is generated by the residual toner charged to the opposite polarity to the charged polarity of the toner at the time of development in the suction member is provided between the suction member power source and the suction member. The voltage can be accurately controlled according to the fluctuation of the current flowing through the.

  In the image forming apparatus of a preferable form using this threshold value, it is more preferable that “the application control unit updates the threshold value directly or indirectly at a predetermined timing”.

  The current between the power supply for the adsorbing member and the adsorbing member may leave a minute fluctuation within an allowable range even after the toner charged to the opposite polarity is sufficiently removed from the adsorbing member. There is. According to the image forming apparatus of the preferred embodiment, the threshold value is appropriately updated, so that it is possible to cope with such a variation.

Further, in the image forming apparatus of the present invention, “the suction member has a predetermined rotation axis,
The recovery member has a rotation axis extending along the rotation axis of the adsorption member;
An adsorbing member drive unit that rotationally drives the adsorbing member at a predetermined rotational speed around the rotation axis of the adsorbing member;
A recovery member drive unit that rotationally drives the recovery member around a rotation axis of the recovery member;
A rotation control unit that controls the rotation drive of the recovery member drive unit relative to the recovery member so that the rotation speed of the recovery member becomes a rotation rate according to the current measured by the current measurement unit; The form “is” is also a preferable form.

  Residual toner charged to the opposite polarity is weakly charged as compared to the residual toner having the same polarity as that of the toner at the time of development as it is adsorbed by the adsorption member. It often takes more time than the residual toner having the same polarity as the charged polarity of the toner. According to the preferred embodiment of the image forming apparatus, for example, when collecting the residual toner charged to the opposite polarity from the adsorption member, the rotation speed of the collection member is decreased and the residual toner is taken over time. Operations such as reliable collection can be easily realized.

  Further, in the image forming apparatus that performs such rotation control, “the rotation control unit controls the rotation drive of the collection member driving unit with respect to the collection member, and the rotation speed of the collection member is Of the first rotation speed higher than the rotation speed of the member and the second rotation speed lower than the rotation speed of the attracting member, the rotation speed is switched to the rotation speed corresponding to the current measured by the current measuring unit. The form “is” is a preferred form.

  According to this preferred embodiment of the image forming apparatus, the residual toner having the same polarity as the charged polarity of the toner at the time of development as it is adsorbed by the adsorbing member is rotationally driven at the first rotational speed. Residual toner that is quickly collected by the member and charged to the opposite polarity to the charged polarity of the toner at the time of development in the adsorption member is taken over by the collecting member that is rotationally driven at the second rotational speed. It can be reliably recovered.

Further, in the image forming apparatus in which the rotation control is performed, “the rotation control unit performs rotation driving of the recovery member driving unit with respect to the recovery member, and the rotation speed of the recovery member is measured by the current measuring unit. Is preferably controlled so as to have a rotational speed according to the magnitude relationship between and a predetermined threshold value,
It is further preferable that the rotation control unit updates the threshold value directly or indirectly at a predetermined timing.

  According to these preferred embodiments of the image forming apparatus, the residual power charged between the suction member and the suction member is caused by the residual toner charged in the opposite polarity to the charged polarity of the toner at the time of development in the suction member. Rotational drive control according to fluctuations in the current flowing through can be performed accurately.

Further, in the image forming apparatus of the present invention, it is also preferable that the above-mentioned recovery member has an electrical resistance of 10 ⁶ Ω or more and 10 ⁸ Ω or less,
A form in which “the recovery member has a surface formed of a phenol resin” is also preferable.

  According to the former form, it is possible to obtain good chargeability on the surface of the collecting member, and according to the latter form, it is possible to obtain good wear resistance on the surface of the collecting member.

In the image forming apparatus of the present invention, “the adsorbing member has 50,000 or more conductive fibers having an electric resistance of 10 ⁷ Ω or more and 10 ¹² Ω or less per 1 inch ² (about 6.45 cm ² ). The form of “provided by density” is also preferable.

  According to this preferable embodiment, it is possible to obtain good adsorptivity for the adsorbing member.

  As described above, according to the present invention, good cleaning performance can be exhibited over a long period of time.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  An image forming apparatus 1 shown in FIG. 1 includes a drum-shaped photoconductor 10 that rotates in the clockwise direction indicated by an arrow A around a grounded rotary shaft 10a. A charger 20, an exposure device 30, a developing device 40, a transfer charger 50, a pre-cleaning charger 60, a pre-cleaning static eliminator 70, and a cleaning device 80 are arranged. The image forming apparatus 1 also includes a control unit 90 and a fixing device 110.

  A photoreceptor 10 shown in FIG. 1 is obtained by laminating a photosensitive layer including an undercoat layer, a charge generation layer, and a charge transport layer on a conductive support on a cylinder. The photoreceptor 10 rotates in the clockwise direction indicated by the arrow A around the rotation shaft 10a. The surface of the photoreceptor 10 corresponds to an example of the image carrying surface referred to in the present invention.

  The photoreceptor charger 20 is a non-contact charging type corotron charger. A negative polarity charging bias voltage is applied to the photosensitive member charging device 20 from a high voltage power supply 21 for charging the photosensitive member, and the negative polarity charging bias voltage causes the surface of the photosensitive member to have a negative polarity at a predetermined charging position P1. Is charged.

  The exposure device 30 irradiates the surface of the photoreceptor with laser light modulated based on image information. When the surface of the photosensitive member charged to the negative polarity is irradiated with the laser beam from the exposure device 30 at the exposure position P2 on the downstream side of the charging position P1 in the path of movement of the surface as the photosensitive member 10 rotates. Then, the potential on the surface of the photoreceptor is removed to the shape of the image represented by the image information. As a result, an electrostatic latent image that electrostatically represents the image is formed.

  The developing device 40 carries a developer containing body 41 containing a developer containing toner and a fine particle external additive that exhibits a polishing effect and the like, and carries a toner charged to a negative polarity in the developer containing body 41. A developing roll 42 that rotates while facing the surface of the photoreceptor is provided. Here, the negative polarity which is the charging polarity of the toner in the developer container 41 corresponds to an example of “the charging polarity of the toner during development” according to the present invention.

  The toner charged in the negative polarity in the developer container 41 has the developing roll 42 and the photoconductor 10 at the developing position P3 downstream of the exposure position P2 where the developing roll 42 and the photoconductor 10 are close to each other. Due to the potential difference, the surface shifts to the photoreceptor surface. At this time, the toner adheres to the portion of the electrostatic latent image where the potential is removed, avoiding the negatively charged portion on the surface of the photoreceptor. As a result, the electrostatic latent image is developed with toner.

  In FIG. 1, the recording paper P is conveyed in the direction indicated by the arrow B. The conveyed recording paper P is sent to a transfer position P4 between the photoreceptor 10 and a transfer charger 50 which is a non-contact charging type corotron charger. The transfer charging device 50 is applied with a transfer bias voltage having a polarity opposite to the toner charging polarity in the developing device 40, that is, a positive polarity, from a high voltage power supply 51 for transfer charging. The toner image formed on the surface is transferred from the surface of the photoreceptor to the recording paper P at the transfer position P4.

  In the present embodiment, a transfer system using the transfer charger 50 is employed. However, the image forming apparatus of the present invention is not limited to an image forming apparatus employing such a transfer system. For example, an image forming apparatus that employs a transfer method using a transfer roll to which a bias voltage is applied may be used.

  Further, in the image forming apparatus 1 shown in FIG. 1, the fixing device 110 is disposed downstream of the transfer position P4 in the paper transport direction. The fixing device 110 includes a fixing roll 111 having a heating mechanism and a pressure roll 112 provided so as to face the fixing roll 111. The recording paper P that has passed the transfer position P4 is conveyed between the fixing roll 111 and the pressure roll 112 that face each other. The toner constituting the toner image on the recording paper P is melted by the heating mechanism of the fixing roll 111 and is fixed on the recording paper P by receiving the pressure from the pressure roll 112 to form an image composed of the fixing toner image.

  On the other hand, residual toner that could not be transferred to the recording paper P at the transfer position P4 adheres to the surface of the photoconductor 10 that has passed through the transfer region.

  A cleaning device 80 shown in FIG. 1 is a device for removing the residual toner, and is located downstream of the transfer path P4 in the movement path of the surface of the photoconductor, and rotated by the photoconductor than the photoconductor charger 20. It is arranged to remove the residual toner at the cleaning position P7 on the upstream side in the direction. Further, a pre-cleaning charger 60 and a pre-cleaning static eliminator 70 are provided in front of the cleaning device 80. Here, the residual toner is toner that remains without being attracted to the potential of the transfer charger 50, and the charged state is disturbed. For this reason, the pre-cleaning charger 60 to which a negative-polarity bias voltage is applied from the pre-charging high-voltage power supply 61 causes the residual toner to have a negative polarity at the pre-charging position P5 downstream of the transfer position P4. Further, the pre-cleaning static eliminator 70 lowers the residual potential level on the surface of the photosensitive member at the static elimination position P6 on the downstream side of the pre-charging position P5. By these processes, the residual toner is easily removed by the cleaning device 80.

  A cleaning device 80 shown in FIG. 1 includes a cleaning brush 81, a brush drive motor 82, a brush power supply 83, an ammeter 84, a collection roll 85, a roll drive motor 86, a roll power supply 87, and a scraper member 88.

  Here, the cleaning brush 81, the brush drive motor 82, the brush power supply 83, the ammeter 84, the collection roll 85, the roll drive motor 86, and the roll power supply 87 are the suction member, suction member drive unit, It corresponds to an example of a power supply for an adsorption member, a current measurement unit, a recovery member, a recovery member drive unit, and a recovery member power source.

  The cleaning brush 81 has conductive fibers 81b extending radially about a brush rotation shaft 81a extending in parallel with the rotation shaft 10a of the photoconductor 10. The cleaning brush 81 is installed in a state in which the leading end of the conductive fiber 81b bites into both the circumferential surface of the photoconductor 10 and the circumferential surface of the collecting roll 85, and is driven to rotate around the brush rotation shaft 81a by the brush drive motor 82. Is done. The conductive fiber 81b corresponds to an example of the conductive fiber referred to in the present invention.

  Here, in this embodiment, the amount of biting of the cleaning brush 81 into the surface of the photosensitive member, the material of the conductive fiber 81b of the cleaning brush 81, the method of imparting conductivity to the conductive fiber 81b, The electrical resistance of the conductive fiber 81b, the thickness of the conductive fiber 81b, and the density of the conductive fiber 81b are not particularly limited, and only some preferred examples will be introduced.

The amount of biting of the cleaning brush 81 into the surface of the photoconductor is desirably in the range of 0.1 mm to 2.5 mm, preferably in the range of 0.5 mm to 2.0 mm, and more preferably in the range of 0.8 mm. It is in the range of 9 mm to 1.8 mm. Examples of the material of the conductive fibers 81b of the cleaning brush 81 include resin fibers such as nylon (registered trademark), acrylic, polyolefin, and polyester. In addition, regarding the method of imparting conductivity to the conductive fiber 81b of the cleaning brush 81, the resin fiber is mixed with a conductive powder or an ionic conductive material to impart conductivity, or the inside of the resin fiber or Although the method of providing electroconductivity by forming a conductive layer in the surface is mentioned, As a preferable method, there exists the method of mix | blending the material which provides electroconductivity uniformly in a resin fiber. Further, the electrical resistance of the conductive fiber 81b of the cleaning brush 81 is desirably in the range of 10 ⁵ Ω to 10 ¹⁵ Ω, and more preferably in the range of 10 ⁷ Ω to 10 ¹² Ω. In addition, the thickness of the conductive fiber 81b of the cleaning brush 81 is desirably 30 denier (about 66 μm) or less, and preferably 10 denier (about 38 μm) or less. The density of the conductive fibers 81b of the cleaning brush 81 is desirably 20,000 or more per 1 inch ² (about 6.45 cm ² ), and preferably 50,000 or more per 1 inch ² (about 6.45 cm ² ). It is preferable that Specific conductive resin fibers employed as the conductive fibers 81b of the cleaning brush 81 include Beltron (registered trademark: manufactured by Kanebo), SA-7 (registered trademark: manufactured by Toray), UU nylon (registered trademark). : Manufactured by Unitika).

  When collecting the residual toner, in order to attract the residual toner on the surface of the photosensitive member to the conductive fiber 81b of the cleaning brush 81, a brush bias voltage having a positive polarity opposite to the charged polarity of the residual toner is applied to the brush power source 83. To the conductive fiber 81b through the brush rotating shaft 81a of the cleaning brush 81.

  Residual toner on the surface of the photosensitive member is attracted by the conductive fibers 81b by the action of the brush bias voltage and scraped off by the conductive fibers 81b. This cleaning brush 81 is less susceptible to deterioration in cleaning performance with time, and is more advantageous than a plate-shaped cleaning blade, particularly in a high-speed machine. Further, since the cleaning brush 81 shown in FIG. 1 is a cleaning method that actively uses an electric field, it is superior to cleaning of spherical toner, which is difficult with a cleaning blade that mechanically scrapes without using an electrical action. There is. The residual toner transferred to the conductive fibers 81b of the cleaning brush 81 is held on the conductive fibers 81b by the action of the brush bias voltage.

  In the present embodiment, the current flowing between the brush power supply 83 and the cleaning brush 81 is measured by the ammeter 84. The current value measured by the ammeter 84 is transmitted to the control unit 90 and used for later-described control in the control unit 90. The control unit 90 corresponds to a combination of an example of the application control unit and an example of the rotation control unit according to the present invention.

  The collection roll 85 collects residual toner held on the conductive fibers 81 b of the cleaning brush 81. The collection roll 85 is rotationally driven by a roll drive motor 86 around a roll rotation shaft 85a extending in parallel with the rotation shaft 10a of the photoconductor 10.

  Further, a roll bias voltage, which will be described later, is supplied to the surface of the collection roll 85 from a roll power supply 87 via a roll rotation shaft 85a. The collection roll 85 collects the residual toner held on the conductive fibers 81b of the cleaning brush 81 by pulling stronger than the holding force of the conductive fibers 81b by this roll bias voltage.

  Here, in this embodiment, the material of the collection roll 85 is not particularly limited, and only some preferred examples will be introduced. First, properties related to elasticity, properties related to wear, properties related to hardness, and properties related to electrical resistance required for the material of the collection roll 85 will be described.

First, as for the properties related to elasticity, the collection roll 85 is required to have a rigidity that does not cause bending, and specifically, the bending elastic modulus according to JIS-K7171: 94 is 700 Kpa or more. preferable. As for the properties related to wear, the collection roll 85 is constantly in contact with the cleaning brush 71 and a scraper member 88 described later, and therefore it is required to be resistant to wear. Specifically, the wear amount in JIS-K6902: 98 is required. Is preferably 20 mg or less. As for the properties relating to hardness, it is required that molding with high dimensional accuracy is possible at the time of manufacturing the collecting roll 85, and it is required to be strong against scraping at the time of use, and Rockwell hardness (M scale) in JIS-K7202: 95. Is preferably 100 or more. As for the properties relating to the electric resistance, it is required that the residual toner transferred to the cleaning brush 81 can be adsorbed satisfactorily, and the specific resistance value is desirably in the range of 10 ⁵ Ω to ^{10 10} Ω, preferably Is in the range of 10 ⁶ Ω to 10 ⁸ Ω. Next, a preferable example of the material of the collection roll 85 that satisfies these properties will be described.

  First, as a material satisfying the properties of elasticity, wear, and hardness related to the recovery roll 85, the recovery roll has good dimensional accuracy because it is hard to shrink after molding because it is cured (crosslinked) by heating during molding. A thermosetting resin from which 85 is obtained is preferred. Examples of such thermosetting resins include phenolic resin, urea resin, melamine resin, unsaturated polyester, epoxy resin, polyimide resin, etc. Among them, phenolic resin has good dimensional accuracy and smooth surface. It is particularly preferable because an excellent molded product can be obtained at low cost. Furthermore, in order to satisfy the above-mentioned properties relating to electric resistance, the following fillers can be mentioned as those incorporated in the thermosetting resin as described above. First, carbon black, carbon powder, graphite, magnetic powder, metal oxides such as zinc oxide, tin oxide and titanium oxide, metal sulfides such as copper sulfide and zinc sulfide, so-called hard ferrites such as strontium, barium and rare earth, magnetite, Examples thereof include ferrites such as copper, zinc, nickel and manganese, and those obtained by subjecting the surface of the above substances to a conductive treatment as required. In addition, high temperature oxides, hydroxides, carbonates, metal compounds, etc. containing different metal elements such as copper, iron, manganese, nickel, zinc, cobalt, barium, aluminum, tin, lithium, magnesium, silicon, phosphorus, etc. Also included are so-called mixed metal oxides which are solid solutions of metal oxides obtained by firing in the medium. Furthermore, metal powder, metal fiber, glass fiber, etc., such as tin, iron, and aluminum, are mentioned. In order to satisfy the above-described properties relating to electric resistance, any one of these fillers may be used alone, or a plurality of types may be mixed and used.

  The scraper member 88 is a thin metal plate that plays a role of scraping off the residual toner collected by the collection roll 85 from the collection roll 85. In the present embodiment, the material and thickness of the scraper member 88 are not particularly limited, and only some preferred examples will be introduced. The material of the scraper member 88 is preferably stainless steel or phosphor bronze from the viewpoint of durability and cost, and the thickness is desirably 0.02 mm to 2 mm, preferably 0.05 mm to 1 mm. .

  In the cleaning device 80 described above, residual toner that cannot be fully collected by the collection roll gradually accumulates on the cleaning brush 81 due to repeated cleaning. If the amount of residual toner accumulated in this way increases, the residual toner may receive charge injection from the cleaning brush 81 or the like and be charged with a reverse polarity, that is, a positive polarity. is there. If this state is left as it is, the apparent electrical resistance of the cleaning brush 81 increases, the current from the brush power supply 83 decreases, and the cleaning performance deteriorates. Hereinafter, the residual toner having a negative polarity as it is adsorbed to the cleaning brush 81 is referred to as a normally charged toner, and the residual toner having a positive polarity is referred to as a reversely charged toner.

  In the image forming apparatus 1 of the present embodiment, the cleaning brush 81 in the cleaning device 80 is cleaned at the timing when the image forming apparatus 1 is powered on. During the cleaning, the control unit 90 controls the operation of the cleaning device 80 as described below to sufficiently remove not only the normally charged toner but also the reversely charged toner from the cleaning brush 81. Thus, the cleaning performance of the cleaning device 80 is maintained good for a long time. The control unit 90 controls the overall operation of the image forming apparatus 1 according to the present embodiment in addition to the control for the cleaning device 80. The control contents other than the control for the cleaning device 80 are described in this book. The description is omitted because it is not the subject of the invention.

  FIG. 2 is a flowchart showing a cleaning flow of the cleaning brush 81 shown in FIG. In the following description, the components shown in FIG.

  As described above, the processing shown in this flowchart is started when the image forming apparatus 1 is turned on. When the process is started, the control unit 90 controls the cleaning device 80 as follows so that the normal cleaning operation in which the recovery roller 85 recovers the normally charged toner from the cleaning brush 81 is executed in the cleaning device 80. (Step S101).

  In a normal cleaning operation, the roll power supply 87 is controlled to supply a voltage higher than the brush bias voltage to the collection roll 85 as a roll bias voltage.

  In this normal cleaning operation, the roll drive motor 86 and the brush drive motor 82 are controlled by the control unit 90 so that the collection roll 85 rotates faster than the cleaning brush 81. In the present embodiment, this control is executed based on the following equation.

Rotation speed of collection roll 85 / (rotation speed of cleaning brush 81 + rotation speed of collection roll 85)> 0.5
In this normal cleaning operation, the normally charged toner having a negative polarity is charged to a positive polarity higher than the cleaning brush 81 by the roll bias voltage, and is quickly recovered by the recovery roll 85 that rotates faster than the cleaning brush 81. The

  When this normal cleaning operation is executed, a flag indicating which one of the normal cleaning operation and the reversely charged toner cleaning operation described later is executed indicates that the normal cleaning operation is executed. Set to level.

  As a result of the control in step S101, a normal cleaning operation is executed for a predetermined time.

  When the normal cleaning operation is finished, it is next determined whether or not the elapsed time from the start of the process of this flowchart has exceeded a predetermined specified time (step S102).

  If it is determined in step S102 that the elapsed time has not yet exceeded the specified time (No determination in step S102), the value of the current flowing from the brush power supply 83 toward the brush rotation shaft 81a is obtained by the ammeter 84. It is measured (step S103).

  Then, it is determined whether or not the difference between the current value obtained by the measurement and a preset initial current value exceeds a predetermined allowable value Va (step S104).

  In the present embodiment, whether the residual toner accumulated on the cleaning brush 81 is charged with a polarity opposite to that of the current due to the determination in step S104, that is, whether or not the current decrease is more than a predetermined value, that is, the reverse charging described above. It is determined whether or not the toner is generated more than allowable.

  When it is determined in step S104 that the above difference exceeds the predetermined allowable value Va (Yes determination in step S104), the control unit 90 determines that the reversely charged toner is more than allowable. to decide. Then, in the cleaning device 80, the control unit 90 controls the cleaning device 80 as follows so that the recovery roller 85 performs the cleaning operation for the reversely charged toner in which the reversely charged toner is recovered from the cleaning brush 81 (see FIG. Step S105).

  The cleaning operation for the reversely charged toner is controlled such that the roll power supply 87 supplies a voltage lower than the brush bias voltage to the collection roll 85 as the roll bias voltage. In the description here, the roll bias voltage in the cleaning operation for the reversely charged toner is not particularly limited, but the roll bias voltage is preferably such that the difference from the brush bias voltage is 200 V or more. .

  In the cleaning operation for the reversely charged toner, the roll drive motor 86 and the brush drive motor 82 are controlled by the control unit 90 so that the collection roll 85 rotates slower than the cleaning brush 81. In the present embodiment, this control is executed based on the following equation.

Rotation speed of collection roll 85 / (rotation speed of cleaning brush 81 + rotation speed of collection roll 85) ≦ 0.5
In the cleaning operation for the reversely charged toner, the reversely charged toner having a positive polarity is recovered by moving to the recovery roll 85 having a lower potential than the cleaning brush 81.

  Further, the charge of the reversely charged toner is weaker than that of the normally charged toner, and the electrostatic movement of the reversely charged toner takes longer than the movement of the normally charged toner. In the present embodiment, when the reversely charged toner is collected by the collection roll 85, the collection roll 85 rotates slower than the cleaning brush 81 as described above. As a result, the reversely charged toner is reliably collected over the collection roll 85 over time.

  When the reverse charging toner cleaning operation is executed, the flag is set to an H level indicating the execution of the reverse charging toner cleaning operation.

  In step S105, the cleaning device 80 is controlled by the control unit 90 so that the cleaning operation for the reversely charged toner is performed over a predetermined time.

  Here, in the present embodiment, the processes from step S103 to step S105 are repeated as appropriate. In the repetition, every time the cleaning operation for the reversely charged toner in step S105 is executed, the reversely charged toner is removed stepwise from the cleaning brush 81. Finally, the reversely charged toner is almost removed from the cleaning brush 81. After being removed, the current from the brush power supply 83 is restored until it becomes substantially equal to the initial current value.

  The return of the current is confirmed by determining whether or not the above difference is a predetermined allowable value Va in step S104. Here, the value obtained by adding the initial current value to the allowable value Va corresponds to an example of the threshold according to the present invention. That is, this embodiment corresponds to an example in which the threshold value according to the present invention is indirectly updated.

  Here, even if the return of the current is confirmed in step S104, the current from the brush power supply 83 is not completely equal to the initial current value, and a slight variation with time remains. Therefore, in the present embodiment, as will be described below, every time the return of this current is confirmed, the initial current value used in the determination in step S104 becomes a current value including the above-described fluctuation over time. Updated.

  If it is determined in step S104 that the difference is equal to or less than a predetermined allowable value Va (No determination in step S104), it is then determined whether or not the flag is set to H level. (Step S106).

  If the flag is set at the H level (Yes determination in step S106), since the reversely charged toner removal process has been performed, the initial current value is the latest measured in the reversely charged toner removal process. The current value is updated (step S107). Thereafter, the process returns to step S101, and the normal cleaning operation is resumed.

  On the other hand, if the flag remains at the L level (No determination in step S106), the process of removing the reversely charged toner is not performed, so the process of step S107 is omitted and the process returns to step S101.

  The processing from step S101 to step S107 is repeated until it is determined in step S102 that the elapsed time from the start of the processing of this flowchart has exceeded a predetermined specified time (Yes determination in step S102). If it is determined in step S102 that the elapsed time has exceeded the specified time, the processing of this flowchart ends.

  As described above, in the image forming apparatus 1 of the present embodiment, both the normally charged toner and the reversely charged toner accumulated on the cleaning brush 81 are removed each time the power is turned on by the control of the control unit 90. As a result, the image forming apparatus 1 can exhibit good cleaning performance over a long period of time.

In the above description, the cleaning operation as shown in the flowchart of FIG. 2 is executed at the timing when the power is turned on to the image forming apparatus as a combination of each example of the application control unit and the rotation control unit according to the present invention. Although the control part 90 was illustrated, this invention is not limited to this. The application control unit and the rotation control unit of the present invention may perform such a cleaning operation periodically, for example, while the power is turned on, or each time image formation is performed. It may be a thing.
(Example)
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Example 1]
As a testing machine, a color DocuTech60V (registered trademark) manufactured by Fuji Xerox was remodeled like the image forming apparatus shown in FIG. That is, the cleaning device shown in FIG. 1 provided with a cleaning brush, a brush drive motor, a brush power source, a collection roll, a roll drive motor, a roll power source, a scraper member, and an ammeter was used. Hereinafter, details of the cleaning brush, the brush drive motor, the brush power supply, the collection roll, the roll drive motor, the roll power supply, and the scraper member will be described. The ammeter will not be described in detail because it does not particularly affect the evaluation results of the examples.

(1) Cleaning brush Brush material: conductive nylon (registered trademark), fiber thickness: 2 denier (about 17 μm), electric resistance: 10 ⁸ Ω, length of hair leg: 3.5 mm, fiber density: 1 inch ² (about 120,000 per 6.45 cm ² ), biting into the photoreceptor: approx. 0.5 mm
(2) Brush drive motor Rotation direction: Reverse rotation with respect to the rotation direction of the photoconductor, and rotationally drive the cleaning brush at a rotation speed of 171 mm / s. (3) Brush power supply Brush bias voltage: + 260V
(4) Recovery roll Material: phenol resin in which conductive carbon is dispersed, electric resistance: 10 ⁸ Ω, flexural modulus (JIS K7171: 94): 100 MPa, wear amount (JIS K6902: 98): 2 mg, Rockwell hardness ( JIS K7202: 95, M scale): 120, biting amount into the cleaning brush: 1.0 mm
(5) Roll drive motor The collection roll is rotationally driven under the following conditions. Rotation direction: reverse rotation with the cleaning brush (a) Rotational speed during normal cleaning operation: 201 mm / s
(B) Rotational speed during cleaning operation for reversely charged toner: 171 mm / s
(6) Roll power supply Roll bias voltage during normal cleaning operation: 660 V
Roll bias voltage during cleaning operation for reversely charged toner: 0V
(7) Scraper member Material: SUS304, thickness: 80 μm, amount of biting into the collecting roll: 1.3 mm, free length (free length): 8.0 mm

  As described above, in the image forming apparatus shown in detail in (1) to (7), after outputting 100,000 images on which three bands with image densities of 5%, 50%, and 100% are drawn, once Then, the image forming apparatus is turned off and restarted. Then, after the cleaning operation for the cleaning brush executed at the time of restarting was completed, the amount of residual toner on the photosensitive member and the amount of toner accumulated on the cleaning brush in the cleaning device were visually evaluated. After that, two A3-sized solid images are output by the image forming apparatus, and then a 10% halftone image is further output, and the image quality of the 10% halftone image is visually checked to evaluate the cleaning performance. did. These evaluation results are shown in Table 1. Table 1 also shows evaluation results for Example 2 and Comparative Example described later.

  The evaluation criteria in Table 1 are as follows.

[Residual toner amount on photoconductor]
○: It is impossible to visually confirm that toner remains on the surface of the photoreceptor.
X: The presence of toner on the surface of the photoreceptor can be confirmed visually.

[Toner amount accumulated on the cleaning brush]
○: The amount of toner accumulated on the cleaning brush is small by visual judgment.
X: The amount of toner accumulated on the cleaning brush is large by visual judgment.

[Cleaning performance]
○: The presence of color streaks cannot be visually confirmed in the 10% halftone image.
X: The presence of color streaks can be visually confirmed in a 10% halftone image.
[Example 2]
The cleaning brush was replaced with one having the same structure as the cleaning brush of Example 1 except that the fiber density was 240,000 per 1 inch ² (about 6.45 cm ² ), and during the cleaning operation for the reversely charged toner Using the same image forming apparatus as in Example 1, except that the rotation speed of the collecting roll was changed to 152 mm / s, and the roll bias voltage at the time of the cleaning operation for the reversely charged toner in the roll power supply was changed to 100 V. Tests and evaluations similar to those in Example 1 were performed. The results are shown in Table 1.
[Comparative example]
An example using the same image forming apparatus as in Example 1 except that the rotation speed of the collection roll is always changed to 201 mm / s and the roll bias voltage in the roll power source is always changed to 600 V. Tests and evaluations similar to 1 were performed. The results are shown in Table 1.

  Hereinafter, the evaluation results in the two examples and the comparative example will be described with reference to Table 1.

  In the two examples and comparative examples described above, the residual toner on the photoconductor generated in the output of 100,000 images was satisfactorily removed by the cleaning device. You can see from the results.

  However, from the evaluation results with respect to the toner amount on the cleaning brush in Table 1, in the two examples, the residual toner accumulated on the cleaning brush is well removed in the cleaning operation for the cleaning brush executed at the time of restart. In contrast, in the comparative example, it can be seen that residual toner remains accumulated on the cleaning brush. This result is due to the following reason.

  When 100,000 sheets of images are output, the amount of residual toner accumulated on the cleaning brush is large. Therefore, the residual toner on the cleaning brush is charged with a reverse polarity, and the reversely charged toner is generated. In the above comparative example, in the cleaning operation at the time of restart, a higher roll bias voltage than that of the cleaning brush is always applied to the collection roll. Therefore, in the cleaning operation, the reversely charged toner remains on the cleaning brush without moving to the collecting roll.

  As a result, as shown in the evaluation results for the cleaning performance in Table 1, the cleaning performance at the time of image output after restart is low, the surface of the photoreceptor is not sufficiently cleaned, and unnecessary color streaks are generated. An image will be output.

  On the other hand, in the two embodiments, in the cleaning operation at the time of restart, the deterioration of the cleaning performance due to the occurrence of the reversely charged toner on the cleaning brush is detected by measuring the current flowing into the cleaning brush. When a decrease in cleaning performance is detected, the cleaning operation for the reversely charged toner is performed, and the reversely charged toner is recovered from the cleaning brush to the recovery roll.

  Here, in Example 1, a large potential gradient of a potential difference of 260 V is formed between the collection roll and the cleaning brush. For this reason, the reversely charged toner is promptly transferred to the collecting roll by being urged by this large potential gradient, and thus is easily removed even if the rotating speed of the collecting roll is the same as the rotating speed of the cleaning brush.

  On the other hand, in Example 2, the potential difference between the collection roll and the cleaning brush is 160 V, and the potential gradient is smaller than that in Example 1 described above. However, since the rotation speed of the collection roll is slower than the rotation speed of the cleaning brush, the reverse charge toner is satisfactorily removed even if it takes some time to transfer the reverse charge toner to the collection roll.

  As described above, in the two embodiments, the residual toner accumulated on the cleaning brush is well removed in the cleaning operation at the time of restart. Therefore, as can be seen from the evaluation result of the cleaning performance in Table 1, after the restart, In the image output to be executed, good cleaning performance is exhibited and an image with good image quality is output.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a flowchart which shows the flow of cleaning of the cleaning brush 81 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Photoconductor 10a Rotating shaft 20 Photoconductor charger 21 Photoconductor charging high-voltage power supply 30 Exposure unit 40 Developer 41 Developer container 42 Developing roll 50 Transfer charger 51 Transfer charging high-voltage power supply 60 Cleaning Pre-charger 61 Pre-charge high-voltage power supply 70 Pre-cleaning static eliminator 80 Cleaning device 81 Cleaning brush 81a Brush rotation shaft 81b Conductive fiber 82 Brush drive motor 83 Brush power supply 84 Ammeter 85 Recovery roll 85a Roll rotation shaft 86 Roll drive motor 87 Power supply for roll 88 Scraper member 90 Control unit 110 Fixing device 111 Fixing roll 112 Pressure roll

Claims (1)

An electrostatic latent image is formed by charging the image bearing surface and irradiating the image bearing surface with exposure light, and developing the electrostatic latent image by supplying charged toner to the electrostatic latent image. In an image forming apparatus that forms a toner image on a recording medium by obtaining a toner image, transferring the toner image, and fixing the toner image on the recording medium.
An adsorbing member that is charged by applying a voltage and adsorbs residual toner remaining on the image carrying surface by rubbing the image carrying surface after the toner image is transferred;
A power supply for the suction member that applies a voltage to the suction member so that the suction member is charged to a polarity opposite to the charging polarity of the toner during development;
A collecting member that collects residual toner adsorbed on the adsorbing member by contacting the adsorbing member that is charged by applying a voltage;
A power supply for a recovery member that applies a voltage to the recovery member to charge the recovery member;
A current measuring unit for measuring a current flowing between the power supply for the adsorbing member and the adsorbing member;
An image forming apparatus comprising: an application control unit configured to control a voltage applied by the recovery member power source to the recovery member to a voltage corresponding to the current measured by the current measurement unit.

Images