JP2010026110A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is configured to apply a protective agent to a photoreceptor, which is able to prevent ingress of the protective agent into a developing means and hence transfer of the protective agent to a transfer member in a transfer section, and which recovers deteriorated protective agent with a cleaning means, thereby preventing the deteriorated protective agent from staying on the photoreceptor. <P>SOLUTION: The image forming apparatus includes: a rotatable image carrier; a protective agent supply means for supplying a protective agent to the image carrier; a first charging means for charging the image carrier to the same polarity as the charging polarity of toner; a second charging means for charging the protective agent, supplied to the image carrier, to the reverse polarity to the charging polarity of the toner; a cleaning means for cleaning the image carrier by means of an electric field; an exposure means for forming an electrostatic latent image on the image carrier; a developing means for developing the electrostatic latent image on the image carrier; and a transfer means for transferring the image on the image carrier. The first charging means, the cleaning means, the protective agent supply means, the second charging means, the exposure means, the developing means, and the transfer means are arranged in that order in the rotating direction of the image carrier. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer. More specifically, the present invention relates to an image carrier, a charging unit that charges the image carrier, and an image carrier charged by the charging unit by exposure. An image bearing unit comprising: an exposure unit that forms an electrostatic latent image; a developing unit that develops the electrostatic latent image formed by the exposure unit; and a transfer unit that transfers an image developed by the developing unit. In an image forming apparatus for applying a protective agent to a body, the charging polarity of the protective agent applied on the image carrier is controlled to suppress the mixing of the protective agent into the developing unit, thereby preventing filming and image unevenness. It is to prevent.

  By applying a protective agent such as stearic acid on the photoconductor, it is possible to suppress the deterioration of the resin constituting the photoconductive layer and the generation of discharge products adhering to the surface of the photoconductor, thus extending the life of the photoconductor. Is possible. Further, in a process having a cleaner blade, the blade tip contact portion is worn and the driving torque of the photosensitive member is reduced, so that a configuration in which a protective agent is applied is becoming more common in high speed machines and large machines.

  However, many higher fatty acids (such as stearic acid) often used as a protective agent have a low melting point, and there is a problem that mixing into a developing device causes filming. Particularly in a high-speed machine, since the rotation speed of the developing roller becomes high, the heat generation temperature of the developing roller itself such as heat generation at the gear portion and frictional heat at the seal portion becomes high, and filming is more likely to occur.

  Furthermore, in a one-component development system, if a large amount of protective agent is mixed in the developing device, the frictional force changes at the contact portion with the supply member or the contact portion with the regulating member, so that the toner can be supplied and the toner can be transported without filming. In some cases, the chargeability is affected, causing image quality deterioration, fogging, scattering, and leakage. In the contact development using a rubber roller, the protective agent applied on the photosensitive member comes into direct contact with the developing roller or the toner conveyed on the developing roller, so that the protective agent applied on the photosensitive member is more easily mixed into the developing device. The above issues were more serious problems.

  For these reasons, in a one-component development system, it has been difficult to extend the life of the photosensitive member by applying a protective agent on the photosensitive member. On the other hand, even in the two-component development system, since the magnetic spikes contact the photoconductor, it is not possible to completely prevent the protective agent on the photoconductor from being mixed into the developing device. It could not be applied on the photoreceptor. In addition to the movement due to physical adhesion caused by the contact between the photosensitive member and the developing roller as described above, the protective agent is mixed between the photosensitive member and the developing roller when the protective material is charged. Therefore, it is not possible to prevent the protective agent from being mixed into the developing device by simply bringing the developing roller and the photosensitive member into non-contact with each other. In addition, for the protective agent remaining on the photosensitive member, if the protective agent is charged to the same polarity as the normal polarity of the toner, it will prevent the toner from adhering to the exposed portion on the photosensitive member. As a result, the toner density is lowered or the density becomes uneven. Further, when the toner adheres to a transfer roller or the like, the transferability is deteriorated, or the transferability of the transfer material is lowered, causing a paper jam. Further, in a color machine, the transfer belt as an intermediate transfer member and the surface layer of the transfer drum are contaminated, causing non-uniform transfer.

  Further, in the image forming apparatus that cleans the transfer residual toner on the photoconductor with a cleaning blade, when the cleaning blade, the charging unit, and the protective agent supply unit are arranged in this order on the photoconductor, Is removed together with the residual toner by the cleaning blade, so that a sufficient protective agent cannot be supplied to the charged portion, and partial discharge product adhesion and photosensitive layer deterioration occur, resulting in image unevenness.

  Further, if the charging unit, the cleaning blade, and the protective agent supplying unit are arranged in this order on the photosensitive member, the residual toner on the photosensitive member is charged by the charging unit, so that the adhesion between the photosensitive member and the residual toner increases, and the cleaning blade The cleaning effect is reduced and cleaning defects are likely to occur. Occurrence of toner cleaning failure causes toner filming on the photosensitive member and degrades image quality.

When the charging unit, the protective agent supply unit, and the cleaning blade are arranged in this order on the photoreceptor,
The transfer residual toner remaining on the photosensitive member adheres to the protective agent supply means, the protective agent scraping ability is insufficient, and the supply amount of the protective agent to the photosensitive member is reduced. Further, by supplying the residual toner adhered to the protective agent supplying means to the surface of the protective agent, the supply amount of the protective agent onto the photoreceptor is further reduced.

  In the first place, with a small particle diameter toner having a particle diameter of less than 5 μm or a toner having a high circularity with a circularity exceeding 0.96, there is a limit to the cleaning performance with the cleaning blade. When the contact pressure of the cleaning blade is increased or the contact angle is increased, especially when a protective agent is applied, changes in the viscosity of the protective agent due to changes in the temperature of the machine and the retention state of the protective agent at the blade tip In order to prevent the deterioration of the protective agent or to strictly control the application amount of the protective agent, there are problems such as the tip of the cleaning blade turning up or the torque at the blade contact portion increasing due to the change in In addition, it is necessary to consume toner regularly between papers and before and after the start of an image forming operation.

As a conventional technique for applying a protective agent to a photoconductor, Japanese Patent Application Laid-Open No. 2007-86262 discloses an image in which a developing process exists after applying a protective agent with a coating member after charging and making the protective agent uniform with a leveling member. A forming apparatus is disclosed. Japanese Patent Application Laid-Open No. 9-81005 discloses an image forming apparatus that charges a photoreceptor after applying a protective agent. In JP-A-2006-235563 and JP-A-2007-93983, a cleaning blade is used and a protective agent is applied to a photoconductor, which is not necessary for image formation on a regular basis or periodically due to image occupancy. A toner is applied on a photoconductor to refresh the residue on the photoconductor. Japanese Patent Application Laid-Open No. 2006-39380 discloses a device in which a protective agent applied to a photoreceptor is removed by a contact member.
JP 2007-86262 A JP-A-9-81005 JP 2006-235563 A JP 2007-93983 A JP 2006-39380 A

  However, what is disclosed in Japanese Patent Application Laid-Open No. 2007-86262 has no means for preventing the transfer of the protective agent to the developing device or the transfer member, and can prevent development filming and transfer member contamination. Can not. Further, since the abutting member exists after the image carrier is charged, the charging uniformity of the image carrier is lost due to friction on the abutting member and streaks and unevenness occur, which is a problem in improving the image quality. In addition, depending on the charge train of the contact member, the protective material may be charged by friction with the contact member, which may promote mixing into the developing device. Further, when a cleaning failure occurs due to environmental changes or the like, the protective agent supply means is contaminated with residual toner, and the function of the protective agent is reduced.

  In addition, in Japanese Patent Laid-Open No. 9-81005, the surface of the photoconductor is charged after the protective agent is applied, so that the uniformity of the charging potential of the photoconductor is ensured. The protective agent charged to the same polarity as that of the toner and deteriorated in the charging unit is conveyed to the downstream developing unit as it is, and the protective agent is mixed in the developing unit in the developing unit to deteriorate the filming of the developing roller. In particular, the protective agent deteriorated at the charging portion also loses the lubricity and further deteriorates filming. However, in this case, even if a cleaning failure occurs, the cleaning failure toner is recovered by development, so that the protective agent supply means is not contaminated by the residual toner.

  In addition, those disclosed in Japanese Patent Application Laid-Open Nos. 2006-235563 and 2007-93983 are both configured using a cleaner blade and applying a protective agent on a photoconductor. Depending on the printing rate, toner that is not originally required for image formation is applied to the photoconductor to refresh the residue on the photoconductor. However, depending on the print pattern used by the user, the number of printable sheets may be less than the specified number. In order to avoid this, it is necessary to initially fill with excess toner, and the container for collecting the consumed toner has to be enlarged.

  In addition, in the device disclosed in Japanese Patent Application Laid-Open No. 2006-39380, a contact member for removing the protective agent after the photosensitive member is charged is disposed. When the removal member is in the shape of a roller, the charged potential fluctuates with the roller cycle, which is a problem on the image. Furthermore, when the cleaning unit is provided downstream of the protective agent supply unit, there is an essential problem that the lubricant cannot be sufficiently supplied to the charging unit. Even in the configuration in which the protective agent supplying means is disposed downstream of the cleaning member, when the removing member is a roller member, the protective agent is not completely removed, and the worn protective agent has the same polarity as the toner by the charger. The photosensitive member is transported to the developing unit and the transfer unit while being charged, and the recovery at the developing roller and the transfer to the transfer material at the transfer unit may occur. Also, when removing the protective agent using a blade, the protective agent is charged at the charging section, so that the adhesion to the photoconductor becomes strong and cannot be completely removed. When strengthened, the protective agent was fixed on the photoreceptor as a fixed layer, making it difficult to remove the deteriorated protective agent.

  The present invention solves the problems of the prior art, and is configured to apply a protective agent to the photoconductor, and can prevent the protective agent from being mixed into the developing means and the transfer of the protective agent to the transfer member at the transfer portion, An object of the present invention is to provide an image forming apparatus capable of collecting a protective agent deteriorated by a cleaning unit and preventing the deteriorated protective agent from staying on a photoreceptor.

  In order to solve the above problems, an image forming apparatus of the present invention includes a rotatable image carrier, protective agent supply means for supplying a protective agent to the image carrier, and the image carrier having a charging polarity of toner. First charging means for charging to the same polarity, second charging means for charging the protective agent supplied to the image carrier to a polarity opposite to the charge polarity of the toner, and cleaning means for cleaning the image carrier by an electric field And an exposure unit that forms an electrostatic latent image on the image carrier, a developing unit that develops the electrostatic latent image on the image carrier, and a transfer unit that transfers the image on the image carrier. The first charging unit, the cleaning unit, the protective agent supply unit, the second charging unit, the exposure unit, the developing unit, and the transfer unit are arranged in this order with respect to the rotation direction of the image carrier. Thereby, since the protective agent applied on the image carrier is charged by the second charging unit to a polarity opposite to the normal charging polarity of the toner, recovery of the protective agent at the developing unit and the transfer unit is suppressed, Sufficient protective agent can be supplied to the contact portion between the photosensitive member and the first charging unit. Since the first charging means charges not only the transfer residual toner but also the protective agent, the deteriorated protective agent and the excessive protective agent can be cleaned and recovered by the force of the electric field. Can be prevented from staying on the photoreceptor. Further, since the protective agent that has not been charged by the first charging means or the undegraded protective agent is not cleaned by the force of the electric field, it can remain on the photoconductor, and it is not necessary to supply an unnecessary protective agent. Since no blade is used as the cleaning means, the deteriorated protective agent is not rubbed onto the photoconductor, and toner filming of the photoconductor and adhesion of the deterioration protective agent to the photoconductor can be prevented.

  In the image forming apparatus according to the present invention, the second charging unit may charge the image carrier to a potential smaller in absolute value than the potential charged by the first charging unit. As a result, the second charging unit charges the protective agent to a polarity opposite to the normal charging polarity of the toner while maintaining the charging polarity of the image carrier at the same polarity as the normal charging polarity of the toner charged by the first charging unit. To do.

  The image forming apparatus of the present invention is characterized in that the cleaning means is a conductive brush roller. Thereby, since no blade is used, the deteriorated protective agent is not applied on the photoconductor 20Y, and toner filming of the photoconductor 20Y and adhesion of the deterioration protective agent to the photoconductor can be prevented.

  In the image forming apparatus according to the present invention, the cleaning unit / protective agent supply unit includes a single conductive brush roller that serves as both the cleaning unit and the protective agent supply unit. Thereby, the cleaning and the application of the protective agent can be performed at the same time, and the space can be saved. Further, since the process of contacting the photoreceptor is reduced, it is advantageous for the abrasion of the photoreceptor. Since the contact state is stabilized by the brush roller, the coating uniformity and cleaning properties are excellent. Since the surface of the cleaning means is coated with a protective agent, it is possible not only to suppress local micro-discharge generated between the photoconductor and the voltage when the cleaning means is applied, but also to prevent deterioration in cleaning properties. It is possible to prevent the charged potential of the photoreceptor from becoming non-uniform due to the discharge. Further, the cleaning electric field can be increased by increasing the bias applied to the cleaning means / protective agent supply means, so that the cleaning property is improved.

  In the image forming apparatus of the present invention, the first charging unit is a conductive brush roller. Accordingly, the protective agent on the surface of the photosensitive member can be charged while handbilling, so that a fixing layer of the protective agent is hardly generated on the photosensitive member, and the recoverability by the cleaning unit is improved.

  In the image forming apparatus of the present invention, the second charging unit is a scorotron charger, a bias having the same polarity as the normal charging polarity of the toner is applied to the grid, and the wire has a polarity opposite to the normal charging polarity of the toner. It is characterized by flowing an electric current. As a result, while maintaining the charging potential of the image carrier at the same polarity as the normal charging polarity of the toner, the corona having the opposite polarity to the normal charging polarity of the toner can be swung on the image carrier, The toner can be charged to a polarity opposite to the normal charging polarity of the toner. Further, since the charged potential of the image carrier is in an equilibrium state with the grid voltage, the charged potential of the image carrier that has become non-uniform due to the rubbing of the protective agent supply means or the application of the protective agent can be made uniform. Further, the second charging unit removes electricity by the potential that fills the non-uniform charge generated by the charging in the first charging unit, thereby generating ozone, generating discharge products in the auxiliary charging unit, and deteriorating the photosensitive layer. Can be minimized. Further, since the non-contact scorotron charger is used, the protective agent is not fixed to the charger, the deterioration of the charging performance of the second charging means can be prevented, and the life can be extended.

  The image forming apparatus of the present invention is characterized in that a leveling member is brought into contact with the image carrier between the cleaning unit / protective agent supply unit and the second charging unit. As a result, toner cleaning properties are not required, so the degree of freedom in setting the contact angle, contact direction, and contact load is high, and the protective agent becomes a fixed layer or the deteriorated protective agent adheres to the photoreceptor. Can be prevented. Further, the protective agent can be made uniform, and local deterioration of the surface of the photoreceptor can be reduced. Further, since the leveling member is brought into contact with the downstream of the cleaning means / protective agent supply means, there is no residual toner on the photosensitive member, and there is no concern about filming at the portion.

  In the image forming apparatus of the present invention, the developing unit is not in contact with the image carrier. Mixing of a physical protective agent due to contact of the developing member can be prevented. Further, even when the charge of the protective agent is weak, it is easy to prevent and suppress mixing into the developing device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the entire image forming apparatus of the present invention.

  As shown in FIG. 1, the image forming apparatus 10 includes four image forming stations 15 (Y, M, C, K), an intermediate transfer belt 70, and a secondary transfer unit 80, and further includes a fixing unit 90, a user. And a control unit 100 that controls these units and operates as an image forming apparatus.

  The image forming station 15 (Y, M, C, K) has a function of forming an image with toners of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Since the configuration of the image forming station 15 (Y, M, C, K) is the same, the image forming station 15Y will be described below.

  As shown in FIG. 1, the image forming station 15Y includes a charging unit 30Y, an exposure unit 40Y, a developing unit 50Y, and a primary transfer unit along the rotation direction of a photoconductor 20Y as an example of an image carrier. .

  The photoreceptor 20Y has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In the present embodiment, the photoreceptor 20Y rotates clockwise as indicated by an arrow. To do.

  The charging unit 30Y is a device for charging the photoconductor 20Y. From the exposure unit 40Y, a latent image is formed on the charged photoreceptor 20Y by irradiating a laser.

  The exposure unit 40Y has a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and is charged with a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 20Y.

  The development unit 50Y is a device for developing the latent image formed on the photoreceptor 20Y using yellow (Y) toner. In the developing unit 50Y, a developing roller and a toner supply roller are arranged in a developing chamber to which new toner is supplied from a replaceable toner cartridge, and a regulating blade comes into contact with the developing roller to thin the toner on the developing roller. .

  In the primary transfer unit, a primary transfer bias is applied by the primary transfer roller 65Y in the primary transfer portion B1, and the yellow toner image formed on the photoreceptor 20Y is transferred to the intermediate transfer belt 70. When the four color toners are sequentially transferred in the primary transfer portions B 1, B 2, B 3 and B 4, a full color toner image is formed on the intermediate transfer belt 70.

  The intermediate transfer belt 70 is an endless belt stretched around a belt driving roller 71a and a driven roller 71b, and is rotationally driven while being in contact with the photoreceptor 20 (Y, M, C, K).

  The secondary transfer unit 80 is a device for transferring a single color toner image or a full color toner image formed on the intermediate transfer belt 70 onto a transfer material such as paper, film, or cloth.

  The fixing unit 90 includes a fixing roller 90a and a pressure roller 90b, and is a device for fusing a single color toner image or a full color toner image transferred onto a transfer material to the transfer material to form a permanent image.

  Next, the operation of the image forming apparatus 10 configured as described above will be described.

  First, when an image signal and a control signal from a host computer (not shown) are input to the main controller of the image forming apparatus via an interface, the photoconductor 20Y and the developing unit are controlled by a unit controller based on a command from the main controller. The developing roller provided in 50Y, the intermediate transfer belt 70, and the like rotate. The photoconductor 20Y is sequentially charged by the charging unit 30Y at the charging position while rotating.

  The charged area of the photoconductor 20Y reaches the exposure position as the photoconductor 20Y rotates, and a latent image corresponding to yellow Y image information is formed in the area by the exposure unit 40Y.

  The latent image formed on the photoreceptor 20Y reaches the development position as the photoreceptor 20Y rotates, and is developed by the development unit 50Y. Thereby, a toner image is formed on the photoreceptor 20Y.

  The toner image formed on the photoconductor 20Y reaches the position of the primary transfer portion B1 as the photoconductor 20Y rotates, and is transferred to the intermediate transfer belt 70 by the primary transfer unit. At this time, in the primary transfer unit, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the primary transfer roller 65Y. As a result, the four color toner images formed on the respective photoreceptors 20 (Y, M, C, K) are transferred to overlap the intermediate transfer belt 70, and a full color toner image is formed on the intermediate transfer belt 70. Is done.

  The intermediate transfer belt 70 is driven by transmitting a driving force from a belt driving unit such as a motor via a belt driving roller 71a.

  The full color toner image formed on the intermediate transfer belt 70 is transferred to a transfer material such as paper by the secondary transfer unit 80. Such a transfer material is conveyed from the paper feed tray to the secondary transfer unit 80 via the paper feed roller 94a and the registration roller 94b.

  The full-color toner image transferred to the transfer material is heated and pressed by the fixing unit 90 and fused to the transfer material. After passing through the fixing unit 90, the paper is discharged by a paper discharge roller 94c.

  On the other hand, the photosensitive member 20 (Y, M, C, K) is neutralized by a neutralizing unit (not shown) after passing through the primary transfer portions B1, B2, B3, B4 to form the next latent image. To prepare for charging.

  An intermediate transfer belt cleaning device (not shown) is installed on the driven roller 71b side of the intermediate transfer belt 70 after the secondary transfer, and cleans the intermediate transfer belt 70 after the secondary transfer.

  Although the description has been given based on the embodiment of the intermediate transfer system using the intermediate transfer belt, a direct transfer image forming apparatus may be used.

  In such an image forming apparatus 10, by applying a protective agent such as stearic acid on the photoconductor 20 (Y, M, C, K), deterioration of the resin constituting the photoconductive layer or the photoconductor 20 (Y , M, C, K) Since the generation of discharge products adhering to the surface can be suppressed, the life of the photoconductor 20 (Y, M, C, K) can be extended.

  FIG. 2 shows an image forming apparatus according to a first embodiment for solving the problems of the prior art in the image forming apparatus 10 that applies a protective agent to the photoconductor 20 (Y, M, C, K). Although the image forming apparatus according to the first exemplary embodiment can be applied to a single-color image forming apparatus, FIG. 2 illustrates a yellow image forming unit 15Y of the color image forming apparatus as an example.

  The photoreceptor 20Y has a cylindrical conductive substrate and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In the first embodiment shown in FIG. Rotate counterclockwise so that.

  The photoreceptor 20Y is neutralized by disposing a charge eliminating unit 110Y downstream of the primary transfer portion B1. A first charging unit 112Y, which is a main charging unit, is disposed downstream of the charge removal unit 110Y. The first charging unit 112Y charges the photoconductor 20Y and the residue on the photoconductor 20Y to the same polarity as the normal charging polarity of the toner. The first charging unit 112Y of the first embodiment is a conductive brush roller. The conductive brush roller as the first charging unit 112Y rotates in the clockwise direction opposite to the rotation direction of the photoconductor 20Y, and the DC bias of −1500 V exceeding the discharge limit of the photoconductor used in this embodiment is 600V. Is applied to the photoreceptor, and the potential of the photoreceptor 20Y is charged to -900V. In the charging process by the first charging means, the untransferred toner remaining on the photosensitive member and the protective agent applied on the photosensitive member are charged to a negative polarity which is the same as the normal charging polarity of the toner.

  A cleaning unit 114Y is disposed downstream of the first charging unit 112Y. The cleaning unit 114Y is a conductive brush roller. An electric field of −700 V is applied to the conductive brush roller, and the residue on the photoconductor 20Y is caused by a potential difference of 200 V from the charged potential of the photoconductor charged by the first charging unit. The conductive brush roller collects the electric field generated. The conductive brush which is the cleaning unit 114Y rotates in the same counterclockwise direction as the rotation direction of the photoconductor 20Y. Residues collected by the cleaning means 114Y by the force of the electric field are removed by a flicker member 115Y made of conductive sheet metal that comes into contact with the conductive brush roller.

  A protective agent supply unit 111Y is disposed downstream of the cleaning unit 114Y. The protective agent protects the photosensitive layer of the photoreceptor 20Y and at the same time provides a lubricating effect. As the protective agent, a fatty acid metal salt can be used, and it can be used in the form of powder or solid depending on the supply mode to the photoreceptor 20Y. In order to eliminate problems such as scattering, it is desirable to use it in a solid state. Examples of the metal element constituting the fatty acid metal salt include zinc, lithium, sodium, magnesium, aluminum, lead and nickel. Examples of the fatty acid constituting the fatty acid metal salt include stearic acid and lauric acid. And palmitic acid. Of these, zinc stearate is preferred when used as a solid. In Example 1, as the protective agent supply unit 111Y, a block of zinc stearate is brought into contact with the photoconductor 20Y, and the protective agent is supplied to the photoconductor 20Y.

  A second charging unit 113Y as an auxiliary charging unit is disposed downstream of the protective agent supply unit 111Y. The second charging unit 113Y charges the protective agent supplied to the photoreceptor 20Y by the protective agent supply unit 111Y to a polarity opposite to the normal charging polarity of the toner. The second charging unit 113Y of Embodiment 1 uses a non-contact type scorotron charger. In the scorotron charger, a bias of −500 V having the same polarity as the normal charging polarity of the toner is applied to the grid, and a current of +200 μA having a polarity opposite to that of the normal charging polarity of the toner is applied to the wire. While keeping the same polarity as the normal charging polarity of the toner charged by the first charging means, a corona having a polarity opposite to the normal charging polarity of the toner is passed over the photoreceptor, and the protective agent is defined as the normal charging polarity of the toner. Charge to the opposite polarity. The potential of the photoconductor 20Y after passing through the second charging unit 113Y becomes −500V. The second charging unit 113Y charges the charged potential of the photoconductor 20Y to a potential that is smaller in absolute value than the potential charged by the first charging unit 112Y.

  An exposure unit 40Y is disposed downstream of the second charging unit. The exposure unit 40Y has a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and is charged with a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 20Y.

  A developing unit 50Y is disposed downstream of the exposure unit 40Y. The developing unit 50Y develops the photoconductor 20Y in which a latent image corresponding to yellow Y image information is formed in the region by the exposure unit 40Y. The developing unit 50Y of Embodiment 1 is a non-contact type, and a developing roller 51Y is disposed with a predetermined developing gap with the photoreceptor 20Y. A thin toner layer charged by a toner supply roller and a regulating blade is formed on the developing roller 51Y. A developing bias in which AC is superimposed on DC is applied to the developing roller 51Y, the toner is caused to fly to the surface of the photoreceptor 20Y, and the latent image on the photoreceptor 20Y is developed.

  A primary transfer unit is disposed downstream of the developing unit 50Y. In the primary transfer unit, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the primary transfer roller 65Y that is in contact with the photoconductor 20Y at the primary transfer portion B1 via the intermediate transfer belt 70, and the image of the photoconductor 20Y is applied. Is transferred to the intermediate transfer belt 70.

  The image forming process operation of Example 1 is shown in Table 1 below.

  In the image forming apparatus according to the first exemplary embodiment, the first charging unit 112Y, the cleaning unit 114Y, the protective agent supply unit 111Y, and the second charging unit 113Y are arranged in this order on the photoconductor 20Y. The surface of 20Y and the residue on the photoreceptor 20Y are charged to the same polarity as the normal charging polarity of the toner (Example-).

  The cleaning unit 114Y contacts the photoconductor 20Y and removes the residue on the photoconductor 20Y charged by the first charging unit 112Y by the force of an electric field. The second charging unit 113Y is configured to adjust the charging potential of the photoconductor 20Y to a potential that is smaller in absolute value than the potential charged by the first charging unit. A means for discharging a charge having a polarity opposite to that of the charged polarity (Example-) (Example +), and a protective agent supplying means 111Y for applying a protective agent on the photoreceptor 20Y is provided downstream of the cleaning means 114Y. It was provided upstream of the two charging means 113Y.

  Since the protective agent applied on the photoreceptor 20Y by the protective agent supply unit 111Y is charged by the second charging unit 113Y to a polarity opposite to the normal charging polarity of the toner, the protective agent in the developing unit 50Y and the primary transfer unit Recovery is suppressed, and a sufficient protective agent can be supplied to the contact portion between the photoconductor 20Y and the first charging unit 112Y. Since the first charging unit 112Y charges not only the transfer residual toner but also the protective agent, the deteriorated protective agent and the excessive protective agent can be collected in the cleaning unit 114Y by the force of the electric field. Can prevent a protective agent from staying on the photoreceptor.

  Further, the protective agent that has not been charged by the first charging unit 112Y or the undegraded protective agent is not cleaned by the electric field force of the cleaning unit 114Y, so that it can remain on the photoconductor 20Y, and an excessive protective agent is supplied. You do n’t have to. Since no blade is used as the cleaning unit 114Y, the deteriorated protective agent is not rubbed onto the photoconductor 20Y, and toner filming of the photoconductor 20Y and adhesion of the deterioration protective agent to the photoconductor 20Y can be prevented.

  In the image forming apparatus according to the first exemplary embodiment, the first charging unit can be charged while using a conductive brush roller as the first charging unit while fliering the protective agent on the surface of the photoconductor 20Y. Therefore, a fixing layer of the protective agent is provided on the photoconductor 20Y. It becomes difficult to generate, and the recoverability by the cleaning means 114Y becomes good.

In the image forming apparatus according to the first exemplary embodiment, the second charging unit 113Y is a scorotron charger, a bias having the same polarity as the normal charging polarity of the toner is applied to the grid, and the polarity opposite to the normal charging polarity of the toner is applied to the wire. Therefore, while maintaining the charged potential of the photoconductor 20Y at the same polarity as the normal charging polarity of the toner, a corona having a polarity opposite to the normal charging polarity of the toner can be applied on the photoconductor to protect the photoconductor 20Y. The agent can be charged to a polarity opposite to the normal charging polarity of the toner. Since the charging potential of the photoconductor 20Y is in an equilibrium state with the grid voltage, the charging potential of the photoconductor 20Y that has become non-uniform by applying the protective agent can be made uniform. In the second charging means, the charge is removed by an amount corresponding to the potential that fills up the non-uniform charge generated by the charging in the first charging means, generating ozone, generating discharge products in the second charging means, and deteriorating the photosensitive layer. Can be minimized.

  In the image forming apparatus according to the first exemplary embodiment, the developing unit is not in contact with the photoconductor 20Y, so that it is possible to prevent the physical protective agent from being mixed due to the contact of the developing member. Further, even when the charge of the protective agent is weak, it is easy to prevent and suppress mixing into the developing device.

  FIG. 3 shows an image forming apparatus according to a second embodiment for solving the problems of the prior art in the image forming apparatus 10 that applies a protective agent to the photoconductor 20 (Y, M, C, K). The image forming apparatus according to the second embodiment can be applied to a single-color image forming apparatus, but FIG. 3 illustrates the yellow image forming unit 15Y of the color image forming apparatus as an example.

  In the image forming apparatus according to the second exemplary embodiment, as in the image forming apparatus according to the first exemplary embodiment, the charge removal unit 110Y is disposed downstream of the primary transfer unit B1 and is discharged. A first charging unit 112Y, which is a main charging unit, is disposed downstream of the charge removal unit 110Y. The first charging unit 112Y charges the photoconductor 20Y to the same polarity as the normal charging polarity of the toner. The first charging unit 112Y of the first embodiment is a conductive brush roller. The conductive brush roller as the first charging unit 112Y rotates in the clockwise direction opposite to the rotation direction of the photoconductor 20Y, and the DC bias of −1500 V exceeding the discharge limit of the photoconductor used in this embodiment is 600V. Is applied to the photoreceptor, and the potential of the photoreceptor 20Y is charged to -900V.

  In the image forming apparatus according to the second exemplary embodiment, a cleaning unit / protective agent supply unit 116Y including a conductive brush roller that also serves as the cleaning unit 114Y and the protective agent supply unit 111Y is disposed downstream of the first charging unit 112Y. An electric field of −700 V is applied to the conductive brush roller which is the cleaning means / protective agent supply means 116Y, and the electric field force generated by the electric potential difference of 200 V from the charged potential of the photoconductor charged by the first charging means on the photoconductor 20Y. The residue is collected on a conductive brush roller. The conductive brush which is the cleaning means / protective agent supply means 116Y rotates in the same clockwise direction as the rotation direction of the photoconductor 20Y. Residues collected by the force of the electric field are removed by a flicker member 115Y made of conductive sheet metal that comes into contact with the conductive brush roller. A block of zinc stearate, which is a protective agent, is brought into contact downstream of the contact position of the flicker member 115Y of the conductive brush roller in the rotational direction, and the protective agent is applied to the conductive brush roller after the collected material is removed by the flicker member. It is applied and a protective agent is supplied onto the photoreceptor 20Y.

  As in the first embodiment, a second charging unit composed of a scorotron charger, an exposure unit 40Y, a developing unit 50Y, and a primary transfer unit are disposed downstream of the conductive brush roller serving as the cleaning unit / protective agent supply unit 116Y. The

  Table 2 below shows an image forming process operation diagram of the second embodiment.

  In the image forming apparatus according to the second embodiment, the cleaning unit / protective agent supply unit 116Y is constituted by one conductive brush roller that also serves as the cleaning unit 114Y and the protective agent supply unit 111Y. Can be carried out simultaneously, and space saving is possible. Further, since the process of contacting the photoconductor 20Y is reduced, it is advantageous for the wear of the photoconductor 20Y. Furthermore, since the contact state is stabilized by the conductive brush roller, the application uniformity of the protective agent and the cleaning property are excellent. Further, since the surface of the brush roller, which is a cleaning means, is coated with a protective agent, local micro-discharge generated between the photosensitive member and the cleaning means / protective agent supply means 116Y is suppressed, and the cleaning performance is improved. In addition to preventing the decrease, it is possible to prevent the charged potential of the photosensitive member from becoming non-uniform due to the minute discharge. Further, the cleaning electric field can be increased by increasing the bias applied to the cleaning / protecting agent supply unit 116Y as described above, so that the cleaning property is improved. Other configurations are the same as those of the image forming apparatus according to the first embodiment, and thus the description of the operation is omitted.

  FIG. 4 shows an image forming apparatus according to a third embodiment for solving the problems of the prior art in the image forming apparatus 10 that applies a protective agent to the photoconductor 20 (Y, M, C, K). The image forming apparatus according to the third embodiment can be applied to a single-color image forming apparatus, but FIG. 4 illustrates a yellow image forming unit 15Y of the color image forming apparatus as an example.

  In the image forming apparatus of the third embodiment, the photosensitive member 20Y between the conductive brush roller which is the cleaning unit / protective agent supplying unit 116Y of the image forming apparatus of the second example and the second charging unit 113Y including the scorotron charger is provided. A leveling member 117Y that makes the protective agent applied to the photoconductor 20Y uniform is brought into contact. Since other configurations are the same as those of the image forming apparatus of the second embodiment, description thereof is omitted.

  The image forming process operation of Example 3 is shown in Table 3 below.

  A leveling member 117Y for uniformizing the protective agent applied to the photoconductor 20Y is brought into contact between the conductive brush roller as the cleaning means / protective agent supply means 116Y and the second charging means 113Y comprising the scorotron charger. . Since the leveling member 117Y does not require toner cleaning properties, the degree of freedom in setting the contact angle, the contact direction, and the contact load is high, and the protective agent becomes a stationary phase or a deteriorated protective agent is present on the photoreceptor 20Y. Can be prevented, the protective agent can be made uniform, and local deterioration of the surface layer of the photoreceptor 20Y can be reduced. Since the leveling member 117Y is disposed downstream of the cleaning / protective agent supply unit 116Y, there is no residual toner on the photoconductor 20Y, and there is no concern about toner filming in this portion.

  As described above, according to the image forming apparatus of the present invention, the protective agent is applied to the photoconductor 20Y, and the protective agent is applied to the developing device by applying a charge opposite to the normal charging polarity of the toner to the protective agent. Prevents contamination and transfer of the protective agent to the transfer member at the transfer portion. Further, a first charging unit 112Y is provided to make the charging polarity of the protective agent the same as the normal charging polarity of the toner upstream of the photoconductor cleaning unit (114Y, 116Y), and the protective agent deteriorated by the photoconductor cleaning unit due to an electric field is collected. Therefore, it is possible to prevent the deteriorated protective agent from staying on the photoreceptor 20Y.

1 is a diagram illustrating an entire image forming apparatus of the present invention. It is a figure which shows embodiment of this invention. It is a figure which shows embodiment of this invention. It is a figure which shows embodiment of this invention.

Explanation of symbols

  10: image forming apparatus, 15 (Y, M, C, K): image forming station, 20 (Y, M, C, K): photoconductor, 30 (Y, M, C, K): charging unit, 40 (Y, M, C, K): exposure unit, 50 (Y, M, C, K): development unit, 70: intermediate transfer belt, 80: secondary transfer unit, 90: fixing unit, 110Y: static elimination unit, 111Y: protective agent supply means, 112Y: first charging means, 113Y: second charging means, 114Y: cleaning means, 115Y: flicker member, 116Y: cleaning means / protective agent supply means, 117Y: leveling member

Claims (8)

A rotatable image carrier;
Protective agent supply means for supplying a protective agent to the image carrier;
First charging means for charging the image carrier to the same polarity as the charging polarity of the toner;
A second charging means for charging the protective agent supplied to the image carrier to a polarity opposite to a charging polarity of toner;
Cleaning means for cleaning the image carrier by an electric field;
Exposure means for forming an electrostatic latent image on the image carrier;
Developing means for developing an electrostatic latent image of the image carrier;
Transfer means for transferring an image of the image carrier;
With
An image forming apparatus comprising: a first charging unit, a cleaning unit, a protective agent supply unit, a second charging unit, an exposure unit, a developing unit, and a transfer unit in the order of rotation of the image carrier. . 2. The image forming apparatus according to claim 1, wherein the second charging unit charges the image carrier to a potential smaller in absolute value than the potential charged by the first charging unit. The image forming apparatus according to claim 1, wherein the cleaning unit is a conductive brush roller. The image forming apparatus according to claim 1, wherein the cleaning unit / protective agent supply unit includes a conductive brush roller that serves as both the cleaning unit and the protective agent supply unit. apparatus. The image forming apparatus according to claim 1, wherein the first charging unit is a conductive brush roller. The second charging means is a scorotron charger, a bias having the same polarity as the normal charging polarity of the toner is applied to the grid, and a current having a polarity opposite to the normal charging polarity of the toner is supplied to the wire. The image forming apparatus according to any one of 1 to 5. 7. The image forming apparatus according to claim 4, wherein a leveling member is brought into contact with the image carrier between the cleaning unit / protective agent supply unit and the second charging unit. The image forming apparatus according to claim 1, wherein the developing unit is a non-contact type with the image carrier.

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