JP2007240595A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of forming a high-quality image that an abutting mark on a developer carrier does not appear on an image even when the abutting mark is left on the developer carrier because the apparatus is left in an unused state over a long term. <P>SOLUTION: In the image forming apparatus, the developer is carried on the developer carrier 104a having an elastic layer, and conveyed to a developing part opposed to a latent image carrier 101 while it is regulated by a regulation member 104b abutting on the developer carrier, whereby a latent image on the latent image carrier is made visible. The image forming apparatus is equipped with a storage means 120 in which the history of application of the developer carrier is stored, and the regulation member has a conductive layer and an insulating layer formed at least on its surface coming into contact with the latent image carrier. A control means controls oscillating electric field applied between the conductive layer of the regulation member and the developer carrier in accordance with the history of application stored in the storage means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and in particular, an image such as an electrophotographic apparatus or an electrostatic recording apparatus in which a developer regulating member is disposed in contact with a developer carrier. The present invention relates to a forming apparatus.

FIG. 8 is a diagram showing a schematic configuration of a typical example of a conventional image forming apparatus. The image forming apparatus of this example is a copier or printer using a non-magnetic one-component contact development system.
In FIG. 8, reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven in the direction of arrow r1 with a predetermined peripheral speed (process speed). An image forming process of charging, image exposure, development, transfer, and cleaning is applied to the photosensitive drum 1.

  That is, the surface of the rotationally driven photosensitive drum 1 is uniformly charged with a predetermined polarity and potential by the primary charger 2. In this example, a case where a negatively charged photosensitive drum is used will be described.

Next, image exposure is performed on the charging processing surface by an image exposure apparatus (such as a document image projection exposure apparatus or an image-modulated laser beam scanning exposure apparatus) 3 as an image information writing apparatus. As a result, the charged potential of the exposed bright portion is attenuated, and an electrostatic latent image corresponding to the exposure image information is formed on the surface of the photosensitive drum 1.
The electrostatic latent image is visualized as a transferable toner image (visualized image) by the developing device 4 at the development site n1.

  In this conventional example, the developing device 4 includes a developing roller 4a, a regulating blade 4b, and a supply roller 4c that are integrated into a cartridge, and is configured to be detachable from the image forming apparatus main body.

  The developing roller 4a is pressed against the elasticity of the elastic layer of the photosensitive drum 1 with a predetermined pressing force to form a developing portion n (developing nip portion). The developing roller 4a is driven not shown while maintaining a constant peripheral speed difference from the rotational peripheral speed of the photosensitive drum 1 in the forward direction with respect to the rotation of the photosensitive drum 1, while the amount of toner carried by the regulating blade 4b is regulated. It is rotationally driven by the device. The surface of the developing roller 4a has a certain surface roughness to ensure toner transportability.

  The toner image visualized on the photosensitive drum 1 is transferred to a transfer material (transfer paper) by a transfer device at the transfer portion n1.

  When the transfer material exits the transfer site n1, it is separated from the surface of the rotating photosensitive drum 1, conveyed to the fixing device 12, fixed on the transfer material surface as a permanently fixed image, and discharged as an image formed product (copy, print). Is done.

  After the transfer material is separated, the surface of the photosensitive drum 1 is cleaned by the cleaner 10 after removal of adhering contaminants such as residual toner and paper dust, and is repeatedly used for image formation.

  Here, the regulating blade 4b is in contact with the developing roller 4a made of a cored bar and a medium-resistance elastic layer formed around the cored bar with a constant pressure, and left in this state for a long time. In this case, a contact mark of the regulating blade 4b is generated on the developing roller 1. An image defect (hereinafter, referred to as a set image) that causes uneven stripe density in the longitudinal direction of the developing roller appeared, and the image quality was remarkably deteriorated. In particular, since the period from when the developing device 4 is assembled at the factory until it is used by the user is long, the probability that a set image is generated increases.

Therefore, conventionally, it has been proposed to make the toner layer thickness uniform on the developing roller 4a by generating an oscillating electric field (applying an oscillating voltage) between the regulating blade 4b and the developing roller 4a (Patent Document 1). reference).
JP 58-153972 A

  According to the proposal, the set image does not appear even with the developing roller whose elastic layer is deformed. However, due to the influence of the oscillating electric field, the non-deteriorated toner is selectively carried on the developing roller 4a, and when the life of the developing device is approached, the deteriorated toner remains in the developing container, causing image defects due to transfer defects and the like. There was a problem that occurred.

  The present invention has been made under such circumstances, and prevents drum scraping and image defects. Even if the developer carrier is left unusable for a long time and a contact mark is generated on the developer carrier, It is an object of the present invention to provide an image forming apparatus capable of forming a high-quality image that is not affected by the contact mark.

  In order to solve the above-described problems, in the present invention, an image forming apparatus is configured as described in (1) below.

(1) A developer is carried on a developer carrier having an elastic layer, and the developer is opposed to the latent image carrier while the developer is regulated by a regulating member in contact with the developer carrier. In the image forming apparatus for visualizing the latent image on the latent image carrier,
Storage means for storing a history of use of the developer carrier,
The regulating member has a conductive layer and an insulating layer formed on a surface thereof in contact with at least the latent image carrier,
The image forming apparatus that controls an oscillating electric field applied between the conductive layer of the restricting member and the developer carrying member according to the usage history stored in the storage unit.

  According to the present invention, it is possible to form a high-quality image in which the influence of the contact trace does not appear in the image even when the developer carrying member is left unused for a long period of time and a contact trace is generated.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 2 is a sectional view of the “image forming apparatus” according to the first embodiment. The image forming apparatus shown in the figure is an electrophotographic copying machine or a laser beam printer. In the following description, a case will be described in which reversal development is performed using the negatively charged photosensitive drum 101 and a negatively charged toner.

  The image forming apparatus shown in FIG. 2 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 101 as an image carrier. The photosensitive drum 101 is rotatably supported by an image forming apparatus main body (hereinafter simply referred to as “apparatus main body”), and is driven to rotate in the direction of arrow R1 by a driving device (not shown). Around the photosensitive drum 101, the following devices are arranged almost in order along the rotation direction. A primary charger 102 for uniformly charging the surface of the photosensitive drum 101; and an exposure device 103 for forming an electrostatic latent image corresponding to image information on the surface of the photosensitive drum 101 after charging. Further, a developing device 104 that develops the electrostatic latent image, a transfer device 109 that transfers the toner image on the photosensitive drum 101 to a transfer material such as paper, and a cleaning device 110 that removes the primary transfer residual toner on the photosensitive drum 101.

  Further, the developing device 104 is provided with a memory 120 that can store the assembly date and the last use date. As the memory, a non-volatile memory, a non-contact type non-volatile memory, and a volatile memory equipped with a power source can be used.

Subsequently, supplementary explanation will be given briefly for each of the above-described members.
The photosensitive drum 101 is configured by providing, for example, an OPC (organic optical semiconductor) photosensitive layer having a negative charging polarity on the surface of an aluminum cylindrical cored bar.
The primary charger 102 has a charging roller disposed in contact with the surface of the photosensitive drum 101 and a DC voltage corresponding to a desired dark portion potential VD, which is equal to or higher than 2 × Vth (Vth is a discharge start voltage of the photosensitive drum). And a power supply for applying an oscillating voltage on which a peak-to-peak voltage is superimposed. As a result, the surface of the photosensitive drum 101 is uniformly charged.

  The exposure apparatus 103 includes, for example, a laser oscillator that emits laser light according to image information, a polygon mirror, and the like, and scans the surface of the photosensitive drum 101 after charging to remove electrostatic charges from the light irradiation portion. A latent image is formed.

  The developing device 104 stores negative toner that is negatively charged due to friction, and is attached to a portion of the surface of the photosensitive drum 101 from which the charge of the electrostatic latent image has been removed. Thereby, the electrostatic latent image is developed as a toner image.

  The developing roller 104a includes, for example, a cored bar and a medium-resistance elastic layer formed around the cored bar, and has a certain surface roughness to ensure toner transportability. Then, the development portion n1 (development nip portion) is formed by contacting the photosensitive drum 101 with a predetermined pressing force against the elasticity of the elastic layer. The developing roller 104a is rotated in the forward direction by the rotation of the photosensitive drum 101 by a driving device (not shown) while maintaining a constant peripheral speed difference from the rotational peripheral speed of the photosensitive drum 101.

  The regulating blade 104b is made of a conductive thin plate and an insulating thin layer formed on the surface in contact with the developing roller 104a, and is in contact with the developing roller 104a at a linear pressure of about 30 gf / cm.

  The cleaning device 110 includes a cleaning blade that abuts on the surface of the photosensitive drum 101 and scrapes off the primary transfer residual toner adhering to the surface of the photosensitive drum 101.

Next, the operation of the image forming apparatus having the above configuration will be described.
For example, the surface of the photosensitive drum 101 is uniformly charged to -700 V by the primary charger 102 applied with an oscillating voltage obtained by superimposing an AC voltage having a peak-to-peak voltage of 1200 V corresponding to 2 × Vth on a DC voltage of −700 V. Next, exposure according to image information by the exposure device 103 is performed to form an electrostatic latent image. On the surface of the photosensitive drum 101 after exposure, the dark portion potential VD of the unexposed portion is −700 V, and the bright portion potential VL of the exposed portion is −100 V. A developing bias of −400 V is applied to the developing sleeve 104 a of the developing device 104. As a result, the negatively charged negative toner does not adhere to the unexposed portion (hereinafter referred to as “VD portion”) of the surface of the photosensitive drum 101, but adheres to the exposed portion (hereinafter referred to as “VL portion”) as a toner image. It is visualized (developed). The photosensitive drum 101 and the transfer roller 109 rotate in the same direction at the same peripheral speed, and a primary transfer bias T1 is applied to the transfer roller 109 by a high voltage power source (not shown). As a result, the toner image on the photosensitive drum 101 is transferred from the surface of the photosensitive drum 101 to a transfer material such as paper conveyed from the sheet feeding device 113 by the potential difference between the photosensitive drum 101 and the transfer roller 109 in the transfer nip portion n1. At this time, the transfer residual toner that is not primarily transferred to the transfer material and remains on the surface of the photosensitive drum 101 is removed by the cleaning blade 110 of the cleaning device 110 and stored in the waste toner container 111.
The transfer material is heated and fixed by the fixing device 112 and is discharged out of the image forming apparatus as a permanently fixed image.

Next, the bias control of the regulating blade, which is a feature of this embodiment, will be described.
If the regulating blade continues to contact the developing roller for a long time, the elastic layer is deformed at the contact portion and appears as a streak set image.

  As shown in FIG. 3, the set image does not appear in the image when the number of elapsed days in the pressurized state is small, and gradually becomes a noticeable set image as the number of elapsed days increases, and becomes saturated after a certain period of time has elapsed. There is a feature. On the other hand, as shown in FIG. 4, after the pressure of the regulating blade is released, the pressure is eased every time the number of days elapsed after the release, and after a sufficient number of days has elapsed, it does not appear in the image.

  Here, it is known that the thickness of the toner layer on the developing roller 104a is made uniform by generating an oscillating electric field (applying an oscillating voltage) between the regulating blade 104b and the developing roller 104a. Can be improved. On the other hand, non-deteriorated toner is selectively carried on the developing roller 4a due to the influence of the oscillating electric field, and when the life of the developing device is approached, the deteriorated toner remains in the developing container, causing image defects due to transfer defects and the like. There was a problem that occurred.

  Therefore, in the memory 120 (FIGS. 1 and 2), the last use date a for determining the period during which the regulating blade 104b is in contact with the same part of the developing roller 104a and the period after the set part is released. The pressure release date b for determining is stored.

  In this embodiment, the memory 120 attached to the developing device 104 stores the last use date a and the pressure release date b as the date when the developing device was last driven and the date when the contact portion was released. Suppose you are. It is assumed that the date of manufacture is stored as the last use date a at the time of factory shipment. In this embodiment, it is assumed that information is read out from the memory 120 and updated at the same time when the driving start of the developing roller 104a is detected.

Here, details of the control contents will be described with reference to the drawings.
First, a description will be given of when an image forming operation is started with a new developing device. In the case of a new developing device, the memory 120 stores the date of manufacture as the last use date a.

The developing roller 104a is rotated in the direction of the arrow by a driving device (not shown). Before and after this, the last use date a (manufacturing date) and the pressure release date b stored in the memory 120 are read, and the calculation unit 122-1 of the main body control unit 122 uses the last use date a, The number of days d (FIG. 3) from the date of manufacture is calculated.
Thereafter, the date of use date is updated as the last use date a of the memory 120.

  The set profile of the developing roller is known in advance. For example, as shown in FIG. 3, since it is known that a set image does not appear when d <30, the control is not performed by the oscillating electric field. The same DC voltage as the bias is applied. The pressure release date b is not updated.

  Similarly, since it is known that a set image appears when d ≧ 30, the main body control unit 122 is configured to generate an oscillating electric field (apply an oscillating voltage) between the regulating blade 104b and the developing roller 104a. An instruction is issued (see FIG. 5). At this time, the pressure release date b is updated to the date of use date.

  Here, in order to generate the oscillating electric field, depending on the characteristics of the developing roller 104a, in this embodiment, the regulating blade is set to have a peak-to-peak voltage of 800 Vpp, a frequency of 1.5 kHz, and a DC component of 0 V. An oscillating voltage was applied (see FIG. 6).

Next, a case where a print job is performed will be described.
After d ≧ 30 and blade bias control is performed, the date of use date is stored in the last use date a and the pressure release date b of the memory 120, respectively.
When a job is started in this state, since d = 0, blade bias control is not performed. However, as shown in FIG. 4, it is known that a set image appears without blade bias control until about 40 days have passed after pressure release.
Therefore, the calculation unit 122-1 of the main body control unit 122 uses the pressure release date b to calculate the number of days d ′ elapsed since the pressure release, and when d ′ <40, the main body control unit 122 performs blade bias control. To instruct

  FIG. 7 shows a summary of whether or not control is performed for each combination of the elapsed days d in the pressurized state and the elapsed days d ′ after release of pressure, which has been described above for blade bias control.

  As described above, this blade bias control confirms the number of days that have elapsed since the previous set position was released while confirming the occurrence of the set image by confirming the period during which the regulating blade presses the developing roller. In this way, the recovery situation can be obtained.

This control makes it possible to make the toner layer on the surface of the developing roller 4a uniform by an oscillating electric field so that it does not appear in the image in a state where an image defect occurs due to deformation of the elastic layer of the developing roller. Further, in a state where no image defect occurs, toner selection by an oscillating electric field does not occur, and a good image can be maintained even in the latter half of the lifetime.
The regulating member is not limited to the blade, and any shape that regulates the toner layer has the same effect.

  In this embodiment, control is performed so that an oscillating electric field is not applied between the regulating blade and the developing roller when no image is set, but the same effect can be obtained when the AC electric field is reduced.

  Furthermore, in the present embodiment, a monochrome machine has been described. However, a full-color image forming apparatus is similarly effective when applied to each color developing apparatus.

Further, the information update operation to the memory 120 may be performed at any timing as long as the information is read out and after the start of the developing roller driving is detected and before and after the end of the print job. Further, it is not necessary to update the date for each print job. Once the update operation is performed, the date update operation can be prevented from being performed until the date changes.
Further, as the use history, the developing roller rotation speed, driving time, bias application time after pressure release, the number of printed sheets, and the like can be applied according to the set recovery characteristics of the developing roller.
Further, in this embodiment, an example of the process cartridge integrated type has been described. However, the process cartridge and the developing cartridge separation type and the replenishment type for replenishing toner are also effective.

The figure which shows the structure of the control system in Example 1. FIG. Sectional drawing which shows schematic structure of Example 1. FIG. The figure which shows the relationship between the elapsed days in pressurization state and the set image level The figure which shows the relationship between the elapsed days after pressure release and the set image level Illustration of the main unit control unit Explanatory drawing of developing device Diagram showing the relationship between usage history and control Sectional drawing which shows schematic structure of a prior art example

Explanation of symbols

101 Photosensitive drum 104a Developing roller 104b Restricting blade 120 Memory 122 Main body control unit

Claims (5)

A developing unit that carries a developer on a developer carrying member having an elastic layer and controls the developer by a regulating member that is in contact with the developer carrying member, and that faces the latent image carrier. In the image forming apparatus that visualizes the latent image on the latent image carrier,
Storage means for storing a history of use of the developer carrier,
The regulating member has a conductive layer and an insulating layer formed on a surface thereof in contact with at least the latent image carrier,
The control unit controls an oscillating electric field applied between the conductive layer of the regulating member and the developer carrying member according to the use history stored in the storage unit. apparatus. The image forming apparatus according to claim 1.
A cartridge having the developer carrier, the regulating member, and the storage means is detachable from the image forming apparatus,
The image forming apparatus, wherein the storage unit stores a manufacturing date of the cartridge. The image forming apparatus according to claim 1.
A cartridge having the developer carrier, the regulating member, and the storage means is detachable from the image forming apparatus,
The developed image forming apparatus, wherein the storage unit stores a last use date of the cartridge and a pressurization release date of the regulating member. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the control of the oscillating electric field by the control means is control of the presence or absence of the oscillating electric field. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the control of the oscillating electric field by the control means is control of the magnitude of the oscillating electric field.

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