JP5891987B2 - Charging device and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device and an image forming apparatus.

  In an image forming apparatus such as a copying machine or a printer, the surface of a photoconductor as a charge receptor is charged by a charging device, an electrostatic latent image is formed on the surface by irradiation of image light, and the electrostatic latent image is formed by adhesion of a developer. Visualize the image. As a charging device for charging the photoconductor of such an image forming apparatus, a corotron, a scorotron, or the like that charges the photoconductor using corona discharge is used.

  This corotron is an effective device for uniformly charging an image carrier such as a photoconductor, but in order to charge to a surface potential, a high voltage must be applied and a high-voltage power supply is required. It becomes. As a charging device replacing the corotron or the like, there is one using an endless film for charging to which a bias voltage is applied (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 06-194926 Japanese Patent Laid-Open No. 10-239946

  In a charging device in which conductive fibers are electrostatically flocked onto an endless film, the conductive fibers are laid by pressing a shaft member inside the film with a spring load. The electrostatically implanted conductive fibers cannot be said to be firmly adhered to the film, and the conductive fibers may be pressed out as described above, so that the conductive fibers may come off from the film.

  The present invention has been made in view of such a point, and the photosensitive fiber is not pressed against the photosensitive member, and the photosensitive member is charged by suppressing the generation of uneven charging. A charging device and an image forming apparatus are provided.

  According to the first aspect of the present invention, an endless film and conductive fibers are planted on the surface of the film, and the conductive fibers are arranged so as to come into contact with a rotating photoreceptor, and the rotation of the photoreceptor is performed. And a power supply member that applies a voltage to the conductive fiber, and the conductive fiber is in contact with the surface of the photoconductor by an electrostatic adsorption force, and in the contact area, The photosensitive member is charged, and the power supply member applies a first voltage when a substitute value corresponding to a cumulative contact time between the conductive fiber and the surface of the photoreceptor is less than a predetermined substitute value, and the substitute member When the value is equal to or greater than the predetermined substitute value, a second voltage lower than the first voltage is applied.

According to a second aspect of the present invention, the first voltage is V, the length of the conductive fiber is P, the cross-sectional radius is r, the Young's modulus is E, and the photoconductor and the conductive fiber are in contact with each other. When the number of flocks in the portion is F, the nip width is N, the length in the nip axis direction is L, the dielectric constant of the photoconductor is ε ′, the dielectric constant of vacuum is ε ₀ , and the film thickness of the photoconductor is d 2. The charging device according to claim 1, wherein the first voltage V is a voltage satisfying an expression shown in the following formula 1.

  Invention of Claim 3 is provided in the inside of the said film, It rotates with the said film, It has a shaft member which supports the said film, The said shaft member serves as the said electric power feeding member, Through the said film The charging device according to claim 1, wherein a voltage is applied to the conductive fiber.

  According to a fourth aspect of the present invention, there is provided a shaft member that is provided inside the film, rotates together with the film, and supports the film, and the power feeding member is in contact with the conductive fiber outside the film. The charging device according to claim 1, wherein the charging device is rotated by applying a voltage to the conductive fiber.

  The invention described in claim 5 is provided inside the film, rotates together with the film, and has a shaft member that supports the film, and the power feeding member contacts the conductive fiber outside the film. The charging device according to claim 1, wherein a voltage is applied to the conductive fiber.

  The invention according to claim 6 includes a film support case that is provided outside the film and supports the rotating conductive fibers so as to surround the film, and the power supply member is attached to the film support case. The charging device according to claim 1, wherein the charging device is provided in contact with the conductive fiber and applies a voltage to the conductive fiber.

  A seventh aspect of the present invention is an image forming apparatus comprising the charging device according to any one of the first to sixth aspects, wherein an image is formed on a supplied recording medium. .

According to the first aspect of the present invention, it is possible to provide a charging device capable of suppressing uneven charging as compared with the case where the present configuration is not provided.
According to the invention described in claim 2, the first voltage can be set to an optimum value.
According to invention of Claim 3, it can be set as the structure which can be reduced in size by providing an electric power feeding member in the inside of a film support part.
According to invention of Claim 4 and Claim 5, it can be set as a simple structure by providing an electric power feeding member outside.
According to invention of Claim 6, it can be set as a simpler structure by providing a film support part in the exterior of an endless film.
According to the image forming apparatus of the seventh aspect, compared with the case where the charging device described in any one of the first to sixth aspects is not provided, the image quality is deteriorated due to uneven charging. Can be suppressed.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus using a charging device of the present invention. It is a schematic diagram which shows the charging device of embodiment. It is a table which shows an example of a comparison with an Example and a reference example. It is a schematic diagram which shows the charging device of other embodiment.

(Embodiment)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus using the charging device of the present invention. The image forming apparatus 1 according to the embodiment includes a control unit 2, a photoreceptor 10, a charging device 20, an exposure unit 30, a developing unit 40, a transfer unit 50, a fixing unit 60, a cleaning unit 70, a paper storage unit 80, and a paper supply. An image is formed on a sheet P that is a recording medium based on supplied image information.

The control unit 2 is a CPU (Central
An arithmetic device such as a processing unit) and a memory are provided, and the operation of each component of the image forming apparatus 1 is controlled. The photosensitive member 10 is a cylindrical rotating member having a photosensitive layer formed of an organic photosensitive material for holding an image and rotating in the direction of the arrow shown in FIG.

The charging device 20 supports the film 21 so that the endless film 21, the conductive fibers 22 planted on the surface of the film 21, and the film 21 rotate, and supplies power to the conductive fibers 22 through the film 21. A power supply member 23 is included. Here, the power supply member 23 also serves as a shaft member that supports the film 21.
A specific embodiment of the charging device 20 will be described later.

  The exposure unit 30 irradiates the surface of the photoconductor 10 charged by the charging device 20 with light corresponding to image data that has been processed with respect to the input data, and thereby a static image consisting of a latent image potential based on a potential difference. An electrostatic latent image is formed. The electrostatic latent image moves to a position where the developing unit 40 is disposed as the photoconductor 10 rotates.

  The developing unit 40 has a rotating developing roll 41, and the toner adsorbed on the developing roll 41 moves to the photoconductor 10. That is, the toner moves to the surface of the photoconductor 10 due to a potential difference between the electrostatic latent image formed on the photoconductor 10 and the charged toner. In this way, a toner image is formed on the photoconductor 10, and the toner image moves to a position where the transfer unit 50 is disposed as the photoconductor 10 rotates.

  The transfer unit 50 electrostatically transfers the toner image formed on the photoconductor 10 to the paper P conveyed by the conveyance roll 91. The paper P on which the toner image is transferred by the transfer unit 50 is conveyed to the fixing unit 60 by the conveyance roll 91. In the fixing unit 60, the toner image that has not been fixed is pressed and heated by the heating roller 92, and the toner image is fixed to the paper P. The paper P fixed by the fixing unit 60 is transported and stored by the transport roll 91.

  The fixing unit 60 includes a heating roll 92 and transfers the toner image formed on the photoconductor 10 onto a sheet P that is a recording medium. That is, the fixing unit 60 fixes the toner image on the paper P by applying pressure and heating to the toner image transferred onto the paper P by the transfer unit 50 with the heating roll 92. The cleaning unit 70 removes the toner remaining on the surface of the photoreceptor 10 after the toner image is transferred to the paper P.

  The paper storage unit 80 stores paper P, which is a plurality of recording media, and the paper supply unit 81 supplies the paper P manually. The paper P is taken out from the paper storage unit 80 or the paper supply unit 81 by the paper feed roll 90 and is transported to the transfer unit 50 by the transport roll 91. In the transfer unit 50, an image that is a toner image is transferred to the paper P, and this image is fixed in the fixing unit 60. A one-dot chain line shown in FIG. The recording medium of the object forming the image used in the embodiment is the paper P, but may be a transparent sheet, an OHP sheet, or the like, for example.

  Next, the charging device 20 according to the embodiment will be described with reference to FIGS. 2 and 3. As described above, the charging device 20 illustrated in FIG. 2A includes the film 21, the conductive fiber 22, and the power supply member 23.

  The film 21 is formed in a belt shape, and a member of this film is formed by mixing conductive particles such as carbon black or an ionic conductive agent into a polymer material such as polyester, polyamide, polyimide, or the like. ing. In this embodiment, the film 21 is conductive. However, in other embodiments described later, an insulating film member into which conductive particles such as carbon black are not mixed may be used.

The conductive fiber 22 is a fiber in which carbon is mixed into nylon, and is electrostatically implanted in the film 21 at a predetermined interval such as 100,000 pieces / inch ² . Thus, the conductive fibers 22 electrostatically implanted in the film 21 come into contact with the photosensitive member 10 by the electrostatic adsorption force with the rotating photosensitive member 10 and rotate in conjunction with the rotation of the photosensitive member 10. Are arranged.

  As shown in FIG. 2 (a), the conductive fiber 22 is in an area K that is in contact with the surface of the rotating photoreceptor 10 in a collapsed state, that is, in a sleeping state, due to an electrostatic attraction force generated between the conductive fiber 22 and the surface. have. The conductive fiber 22 charges the photoconductor 10 through the contact region K and the vicinity thereof.

  The power feeding member 23 is rotatably provided inside the film 21, and rotates together with the film 21 to support the film 21. The power supply member 23 applies a voltage to the conductive fiber 22.

The power supply member 23 applies a first voltage when the substitute value corresponding to the cumulative contact time between the conductive fiber 22 and the surface of the photoconductor 10 is less than the predetermined substitute value, and the substitute value is equal to or greater than the predetermined substitute value. In this case, the second voltage lower than that of the first voltage is applied.
For example, a predetermined paper usage amount of the paper P that is a recording medium can be used as a substitute value for the accumulated contact time. In addition, as a substitute value, the cumulative driving time of the photoconductor 10, the time when the voltage is applied by the power supply member, and the like can be used.
Further, for example, power is supplied to the power supply member 23 from a power source (not shown) controlled by the control unit 2.

  Next, the contact area | region K is demonstrated using FIG.2 (b) and FIG.2 (c). FIGS. 2B and 2C show a state in which the conductive fiber 22 is in contact with the photosensitive member 10 by electrostatic adsorption force. For convenience of explanation, one conductive fiber 22 in the contact region K is shown. The electrostatic adsorption state is shown. FIG. 2B shows a state where electrostatic adsorption is not sufficient, and the area of electrostatic adsorption in this case is a contact area Ka. Further, FIG. 2C shows a state where electrostatic attraction is sufficient, and the area of electrostatic attraction in this case is defined as a contact area Kb.

  In the state of the contact area Ka, the adsorbing force is insufficient as described above, and the conductive fiber 22 is not completely in a sleeping state, the contact area Ka is small, and uneven charging of the photoconductor 10 is caused. Arise. Such a contact area Ka occurs when the accumulated contact time between the conductive fiber 22 and the surface of the photoconductor 10 is short and the conductive fiber 22 is not sufficiently laid down.

  On the other hand, in the state of the contact area Kb, the adsorbing force is sufficient as described above, and the conductive fiber 22 is in a sleeping state. Reduces uneven charging. Such a contact area Kb occurs when the accumulated contact time between the conductive fiber 22 and the surface of the photosensitive member is long and the conductive fiber 22 is sufficiently laid down.

  When the substitute value is less than the predetermined substitute value, the charging device 20 applies a voltage from the power supply member 23 to the conductive fiber 22 so as not to be in the contact area Ka as described above. The voltage is set to 1. That is, in the charging device 20, the application of the voltage from the power supply member 23 to the conductive fiber 22 is set to a predetermined first voltage, and the region of contact Kb is suppressed, thereby suppressing charging unevenness. . The first voltage is a voltage that makes the contact area Kb.

  When the first voltage is continuously applied from the power supply member 23 to the conductive fiber 22 when the substitute value is equal to or greater than the predetermined substitute value, the voltage is applied in a state where the conductive fiber 22 is laid down. It becomes. In such a state, the adsorption force due to the application of this voltage becomes larger than the repulsive force of the conductive fiber 22, which may damage the photoconductor 10.

  An example of the operation of the charging device 20 having such a function will be described with reference to FIG. FIG. 3 shows the occurrence of uneven charging in the embodiment of the image forming apparatus 1 using the power supply member 23 of the present invention, and the uneven charging in Reference Examples 1 and 2 when the applied voltage is fixed using the power supply member 23. The occurrence of

  The sheet usage shown in FIG. 3 is the number of sheets P used for image processing by the image forming apparatus, and is used as a substitute value for the accumulated contact time. In this example, the predetermined substitute value is 1000 sheets. Note that the amount of paper used, which is a substitute value for the cumulative contact time, is also affected by the material of the conductive fiber 22 and the like, and is not limited to the above example. For example, the charging unevenness can be evaluated and determined according to the material of the conductive fiber 22 through experiments or the like.

  In the embodiment, when the number of sheets P used is less than 1000, the first voltage from the power supply member 23 to the conductive fiber 22 is set to -1300V, and the potential of the photoconductor 10 at this time is set to -850V. When the number of sheets P used is 1000 or more and up to 30000, the second voltage from the power supply member 23 is −900V, and the potential of the photoconductor 10 is −450V. By changing the voltage applied from the power supply member 23 in this way, when the amount of paper used is less than a predetermined number of sheets, uneven density due to the occurrence of potential unevenness is suppressed, and when the amount of used paper is greater than or equal to the predetermined number of sheets. Also, the occurrence of image loss due to scratching or filming on the photoreceptor 10 is suppressed.

  On the other hand, in Reference Example 1, as shown in FIG. 3, when the voltage applied to the conductive fiber 22 is fixed at −900 V and the photoreceptor potential is fixed at −450 V, the inclination of the conductive fiber 22 in the initial state is Insufficient density unevenness due to initial potential unevenness occurs. In this case, when the amount of paper used is equal to or greater than a predetermined number, the conductive fibers 22 tend to tilt and are laid down, and density unevenness is suppressed.

  In Reference Example 2, when the voltage applied to the conductive fiber 22 is fixed at -1300 V and the photoreceptor potential is fixed at -850 V, the applied voltage is high in the initial state and the electrostatic adsorption force is large. The inclination of the conductive fiber 22 is sufficient, and the occurrence of initial potential unevenness is suppressed. However, in this case, when the amount of paper used is a predetermined number or more, the state in which the applied voltage is high and the electrostatic attraction force is large is maintained even though the conductive fibers 22 are inclined and lie down. As described above, the conductive fibers 22 scratch the surface of the photoreceptor 10. This example is an example of the present embodiment, and the above numerical values such as the applied voltage are not limited to this.

Next, the setting of the value of the first voltage of the charging device 20 will be described using the following equations 2 and 3. V shown in Equation 2 is a predetermined first voltage. P is the length of the conductive fiber 22, r is the cross-sectional radius of the conductive fiber 22, E is the Young's modulus of the conductive fiber 22, and F is the conductivity of the portion where the photoconductor 10 and the conductive fiber 22 are in contact. N is the nip (NIP) width, L is the nip (NIP) axial length, ε ′ is the dielectric constant of the photoreceptor, ε ₀ is the vacuum dielectric constant, and d is the photoreceptor 10 It is the film thickness. By setting the above V to a value that satisfies the following equation (2), the charging device 20 suppresses the occurrence of uneven charging when the amount of paper used is less than a predetermined number.

Further, the following Equation 3 shows a case where the following numerical value is used for Equation 2 above. The numerical values used in Equation 3 are as follows: V is −1300 V, P is 0.8 mm, r is 16 μm, E is 180 Kg / mm ² , F is 100 K / inch ² , N is 1 mm, L is 224 mm, and ε ′ is 3.3, ε ₀ is 8.85 × 10 ⁻¹² m ⁻³ Kg ⁻¹ S ⁴ A ² , and d is 24 μm. The numerical value of the dielectric constant ε ₀ of the vacuum is well known and will not be described.

  As shown in the above equation 3, by setting the initial voltage to −1300 V, the electrostatic adsorption force becomes 1.93 kg. On the other hand, the repulsive force of the conductive fiber 22 is 1.18 kg, and thus the electrostatic attracting force by the first voltage is larger than the initial fiber repulsive force. For example, as shown in FIG. It has the area | region Kb which contacts.

  The above is the description of the charging device 20 of the embodiment. According to such an embodiment, at the initial stage, the conductive fibers 22 are not sufficiently laid in the lying direction. Therefore, at this initial stage, the applied voltage is increased so as to obtain a large electrostatic attraction force. Lay down 22 and put it down. The applied voltage is lowered when the conductive fiber 22 is sufficiently laid after a certain period of time. With such a configuration, uneven charging is suppressed in the initial stage, and the occurrence of scratches and filming of the photoconductor 10 is suppressed when the amount of paper used is a predetermined number or more.

  Further, the image forming apparatus 1 using such a charging device 20 can stably reduce the cost by eliminating the need to adjust the amount of charge before transfer because the charging of the photoconductor 10 is stably performed. Further, by stabilizing the charging of the photoconductor 10, it is possible to reduce the cost by making it unnecessary to adjust the developing gap between the photoconductor 10 and the developing unit 40.

(Other embodiments)
The charging device of the present invention and the image forming apparatus using the same are not limited to the above-described embodiments, and other embodiments are possible. Hereinafter, other embodiments of the charging device will be described with reference to FIGS.

  The charging device 20 a shown in FIG. 4A is provided so as to be in contact with the conductive fiber 22 outside the film 21, the conductive fiber 22, the shaft member 24, and the conductive fiber 22. A rotatable power supply member 24a for applying the voltage.

  In the charging device 20a, the power supply member 23 of the charging device 20 is a power supply member 24a. The power supply member 24 a is provided so as to be in contact with the conductive fiber 22 while rotating outside the film 21, and a voltage is directly applied to the conductive fiber 22 from the power supply member 24 a. In the charging device 20a, the film 21 may be insulative, and in this case, the configuration is simple.

The charging device 20 b shown in FIG. 4B is provided so as to be in contact with the conductive fiber 22 outside the film 21, the conductive fiber 22, the shaft member 24, and the conductive fiber 22. It has the electric power feeding member 24b which applies.

  In the charging device 20b, the power supply member 23 of the charging device 20 is a power supply member 24b. As described above, the power supply member 24b is fixedly provided outside the film 21 so as to be in contact with the conductive fiber 22, and a voltage is directly applied to the conductive fiber 22 from the power supply member 24b. In the charging device 20b, the film 21 may be insulative, and in this case, the configuration is simple.

The charging device 20c shown in FIG. 4C has a film support case 23a that is provided outside the film 21, the conductive fiber 22, and the film 21, is in contact with the rotating conductive fiber 22, and surrounds the film 21. . The charging device 20 includes a power supply member 24 c that is provided on the film support case 23 a so as to be in contact with the conductive fibers 22 and applies a voltage to the conductive fibers 22.

  In the charging device 20c, the power supply member 23 that also serves as a shaft member that supports the film of the charging device 20 is a film support case 23a, and the power supply member 23 is a power supply member 24c. The power supply member 24 c is fixed to the film support case 23 a outside the film 21, and a voltage is directly applied from the power supply member 24 c to the conductive fiber 22. In the charging device 20c, the film 21 may be insulative, and in this case, the configuration is simple. Further, the charging device 20c has a configuration in which the power supply member 23 is not provided inside the film 21, and is more inexpensive.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Control apparatus 10 Photoconductor 20,20a, 20b, 20c Charging apparatus 21 Film 22 Conductive fiber 23 Power supply member 23a Film support case 24 Shaft member 24a Power supply member 24b Power supply member 24c Power supply member 30 Exposure part 40 Development part 41 Development Roll 50 Transfer Unit 60 Fixing Unit 70 Cleaning Unit 80 Paper Storage Unit 81 Paper Supply Unit 90 Paper Feed Roll 91 Carrying Roll 92 Heating Roll K, Ka, Kb Area P in Contact P Paper

Claims (7)

An endless film and conductive fibers are planted on the surface of the film, and the conductive fibers are arranged so as to be in contact with a rotating photoconductor, and rotate in conjunction with the rotation of the photoconductor. A power supply member for applying a voltage to the conductive fiber,
The conductive fiber comes into contact with the surface of the photoconductor by electrostatic attraction, and charges the photoconductor in the contact area,
The power supply member applies a first voltage when a substitute value corresponding to a cumulative contact time between the conductive fiber and the surface of the photoreceptor is less than a predetermined substitute value, and the substitute value is the predetermined substitute value. When the value is equal to or greater than the value, a second voltage lower than the first voltage is applied. The first voltage is V, the length of the conductive fiber is P, the cross-sectional radius is r, the Young's modulus is E, the number of flocks at the portion where the photoconductor and the conductive fiber are in contact is F, and the nip When the width is N, the length in the nip axis direction is L, the dielectric constant of the photosensitive member is ε ′, the dielectric constant of vacuum is ε ₀ , and the film thickness of the photosensitive member is d, the first voltage V is The charging device according to claim 1, wherein the voltage satisfies a formula represented by the following formula 1.

Provided inside the film, rotating with the film, and having a shaft member that supports the film,
The charging device according to claim 1, wherein the shaft member also serves as the power feeding member and applies a voltage to the conductive fiber through the film. Provided inside the film, rotating with the film, and having a shaft member that supports the film,
The charging device according to claim 1, wherein the power supply member is provided outside the film so as to be in contact with the conductive fiber, and applies a voltage to the conductive fiber to rotate. . Provided inside the film, rotating with the film, and having a shaft member that supports the film,
The charging device according to claim 1, wherein the power supply member is provided outside the film so as to be in contact with the conductive fiber, and applies a voltage to the conductive fiber. A film support case provided outside the film and supporting the rotating conductive fiber so as to surround the film;
The charging device according to claim 1, wherein the power supply member is provided on the film support case so as to be in contact with the conductive fiber, and applies a voltage to the conductive fiber.   An image forming apparatus comprising the charging device according to claim 1, and forming an image on a supplied recording medium.

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