JP2009092834A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve satisfactory image formation by eliminating a difference between charging amount of toner just after starting printing and that during consecutive printing, and making the charging amount of the toner stable. <P>SOLUTION: A developing device 100 includes a developing roller 120 forming an image on a photoreceptor 11 by conveying developer to the photoreceptor 11 while carrying the developer on its surface, and a doctor blade 150 arranged on a more upstream side of the developing roller 120 than a spot to form an image on the photoreceptor 11 and regulating the amount of the developer to the photoreceptor 11. A pre-regulation member 160 capable of changing dimension of space between the developing roller 120 and the member 160 itself is arranged on the upstream side of the doctor blade 150. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to a developer carrying member that carries a developer on a surface thereof, conveys the developer to a latent image carrier, and forms an image on the latent image carrier. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device having a developer regulating member disposed upstream of a developer carrying member from an image forming portion on the image carrying member and regulating the amount of developer on the developer carrying member, and an image forming apparatus including the developing device. .

  In recent years, in image forming apparatuses such as copying machines and laser printers, high image quality is demanded, and at the same time, high speed, high durability, and high stability are also desired. In order to meet this demand, the image forming apparatus is required to form a stable image over time with little change in image quality due to environmental changes and even at high speed.

  2. Description of the Related Art Conventionally, an image forming apparatus, particularly a high-speed machine, is widely used to develop a photosensitive member, which is a latent image carrier, using a two-component developer composed of a non-magnetic toner and a magnetic carrier.

  In such an image forming apparatus, the two-component developer is applied to the photoreceptor by a developing roller that is a developer carrying member. Here, the developing roller includes a magnetic pole to form a magnetic brush, and the two-component developer is attached to the photoconductor to which a developing bias is applied by the magnetic brush. At this time, the toner is charged, and the charged toner adheres to the electrostatic latent image on the latent image carrier and is formed as a toner image on the developing roller.

  Here, the toner is charged upstream of the developer carrier, and the developer that regulates the amount of developer on the surface of the developer carrier in the stirring device that uniformly stirs the magnetic carrier and the replenished toner. This is performed by frictional charging in a gap between a regulating member (hereinafter referred to as a doctor blade) and a developer carrier (hereinafter referred to as a doctor gap).

  Hereinafter, an example of the two-component developing device will be described. FIG. 5 is a schematic sectional view showing the structure of a conventional developing device. In this developing device, the developing device 400 according to this example is a two-component developing device, and a housing 410 contains a developer made of a carrier that is a magnetic material and toner that is a non-magnetic material. The housing 410 includes a developing roller 420, a stirring roller 430, and a doctor blade 450 that is a developer regulating member. In this example, the toner of the developer is replenished from the toner replenishing unit 440.

  The developing roller 420 conveys the developer to the developing position, and attaches toner to the latent image on the photoreceptor 460 that is an image carrier to form a visible image. Further, the developing roller 420 includes a non-magnetic developing sleeve 421 that is driven to rotate counterclockwise in the drawing, and a magnet roller 422 that is a magnetic force generating means fixed inside the sleeve so as not to be rotated. In addition, a part of the peripheral surface is exposed from the opening of the housing 410 so as to keep a predetermined distance from the photoconductor 460.

  The doctor blade 450 is disposed at a predetermined interval from the developing roller 420 and regulates the amount of developer held on the developing roller 420.

  The developer carried on the developing roller 420 by the magnetic force is regulated by the doctor blade 450 with the layer thickness on the developing roller 420, transported to the developing area close to the photosensitive member 460, and the toner is latent on the developing roller 420. Supply to the image and develop.

  The developer that has completed the development passes below the developing roller 420 to the stirring roller 430, is replenished with toner, and repeats the above circulation.

As such a developing device, Patent Document 1 discloses a developing device that performs development by transferring the developer on the surface of the developer carrying member to the developing region of the image carrying member, and is close to the developer carrying member. In a developing device having two plate-like members arranged and restricting the amount of developer carried out by the developer carrying member, or mixing and stirring the developer, within the corner of the tip of the plate-like member, It is described that the corner closest to the developer carrying member has a roundness with a minute radius at least upstream in the rotation direction of the developer carrying member.
JP-A-9-34250

  By the way, in such a developing device, when the developing roller is driven at a high speed and the doctor gap with the doctor blade is narrow, the toner is largely charged by friction charging of the doctor gap.

  Therefore, compared to the state where the developing roller rotates continuously and the developer is evenly circulated as in continuous printing, the amount of toner that is not passing through the doctor gap immediately after the start of printing is large. The charge amount will be low. For this reason, problems such as excessive density in the image area, toner adhesion to the non-image area, and toner blowing are likely to occur due to development failure immediately after the start of printing.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device and an image forming apparatus capable of eliminating the difference in toner charge amount immediately after the start of printing and during continuous printing, stabilizing the toner charge amount, and forming a good image.

  According to the first aspect of the present invention, there is provided a developer carrier for carrying a developer on the surface and transporting the developer to the latent image carrier and forming an image on the latent image carrier, and an image on the latent image carrier. And a developer regulating member that regulates the amount of the developer on the developer carrier disposed upstream of the developer carrying member, and the developer upstream of the developer regulating member. The developing device is characterized in that a front regulating member capable of changing a distance between the carrier and the carrier is disposed.

  According to a second aspect of the present invention, in the developing device according to the first aspect, the pre-described member includes a restriction member disposed in proximity to the developer carrier, and the restriction member is attached to the developer carrier. It is characterized by comprising an interval adjusting member that adjustably holds the gap interval.

  According to a third aspect of the present invention, in the developing device according to the second aspect, the regulating member is a flat plate member.

  According to a fourth aspect of the present invention, in the developing device according to the second aspect, the restricting member is a columnar member.

  According to a fifth aspect of the present invention, in the developing device according to the third aspect, the interval adjusting member can hold the restricting member so as to be slidable and adjust an interval dimension between the restricting member and the developer carrier. It is characterized by doing.

  According to a sixth aspect of the present invention, in the developing device according to the third or fourth aspect, the interval adjusting member adjusts an interval dimension between the restricting member and the developer carrying member by rotatably supporting the restricting member. It is possible to make it possible.

  A seventh aspect of the present invention is an image forming apparatus comprising the developing device according to any one of the first to sixth aspects.

  According to the developing device and the image forming apparatus according to the present invention, since the front regulating member that can adjust the distance between the developer carrying member and the developer regulating member is arranged on the upstream side of the developer regulating member, Therefore, the toner charge amount is stabilized by eliminating the difference between the toner charge amount immediately after the start of printing and during continuous printing, and good image formation can be performed.

  Embodiments as the best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. The image forming apparatus 10 includes a charging device 12 that uniformly charges the photoconductor 11 around the photoconductor 11 that is an image carrier, and exposure from an exposure device that is not shown in the uniformly charged photoconductor 11. 13, a developing device 100 that develops the latent image formed to form a toner image, a contact-type transfer device 15 that transfers the formed toner image to the transfer paper P, a P sensor 14, and a photosensitive after transfer. A cleaning device 16 that cleans residual toner on the body 11 and a charge removal device 17 are provided.

  A fixing device 18 for fixing the toner image formed on the transfer paper P with heat and pressure is disposed downstream of the transfer device 15 in the transfer material conveyance direction. In FIG. 1, illustrations of the paper feeding unit (paper feeding cassette, paper feeding tray, etc.) and paper feeding device (paper feeding roller, transport roller, registration roller, etc.) of the transfer paper P are omitted.

  In this example, the photosensitive member 11 is a drum-shaped photosensitive member. As the photoconductor 11, a belt-like photoconductor or the like can be used. As the charging device 12, for example, a contact charging type such as a charging roller is used, but a non-contact charging type such as a corona charger can be used.

  An exposure apparatus (not shown) employs a method in which an image is written by exposing the photosensitive member 11 with laser light modulated in accordance with image information by a laser scanning optical system, or a light emitting diode (LED) array corresponding to image information. Various methods such as a method of writing an image by driving the like can be used.

  The developing device 100 develops the latent image on the photoconductor 11 with a two-component developer composed of toner and carrier to make a visible image, and carries and conveys the two-component developer and developer in the housing 110. The developing roller 120, the stirring roller 130, the toner replenishing unit 140, the doctor blade 150, and the front regulating member 160 are configured.

  In the image forming apparatus according to this embodiment, when an image forming (copying or printing) operation is started, the photosensitive member 11 is first uniformly charged by the charging device 12, and the electrostatic latent image is obtained by the exposure 13 from the exposure device. Is formed. The latent image on the photoconductor 11 is developed with a developer carried by the developing roller 120 of the developing device 100 to be visualized. Then, the transfer paper P is fed to the transfer device 15 from a paper supply unit (not shown) at the timing when the visible image (toner image) on the photoconductor 11 comes to the position of the transfer device 15. The toner image on the photoconductor 11 is transferred to the transfer paper P at the belt nip portion.

  Then, the transferred transfer paper P is conveyed toward the fixing device 18 by the transfer belt, and the toner image is fixed on the transfer paper P by the fixing device 18. On the other hand, the residual toner is removed from the surface of the photoconductor 11 after the transfer by the cleaning device 16, and the residual charge is removed by the charge eliminating device 17.

  Next, the developing device according to the embodiment will be described. FIG. 2 is a schematic cross-sectional view illustrating the configuration of the developing device according to the embodiment. The developing device 100 includes a housing 110 that includes a developing roller 120, a stirring roller 130, a toner replenishing unit 140, a doctor blade 150, and a front regulating member 160.

  The developing roller 120 conveys the developer to the developing position, and attaches toner to the latent image on the photoreceptor 11 as an image carrier to form a visible image. Further, the developing roller 120 includes a non-magnetic developing sleeve 121 that is driven to rotate counterclockwise in the figure, and a magnet roller 122 that is a magnetic force generating means fixed inside the sleeve so as not to be rotated. And a part of the peripheral surface is exposed from the opening of the housing 110 so as to be kept at a predetermined distance from the photoreceptor 11.

  The agitation roller 130 agitates the developer and mixes the toner replenished from the toner replenishing unit 140 with the carrier.

  Toner is supplied from the toner supply unit 140. As a result, the toner consumed by the repeated development is replenished and mixed into the developer by the stirring roller 130 to keep the toner concentration in the developer at a certain value or higher.

  The doctor blade 150 is a plate-like member, and is fixedly disposed with a predetermined interval between the doctor roller 120 and regulates the amount of developer held on the developer roller 120.

  The front regulating member 160 is arranged on the upstream side of the doctor blade 150. The front restricting member 160 includes a plate-like pre-doctor blade 161 that is a restricting member, and a driving device 162 that is an interval adjusting member that variably holds the pre-doctor blade 161 with the developing roller 120. Has been. The driving device 162 includes a solenoid, a motor, and the like, and adjusts the distance between the predoctor blade 161 and the developing roller 120 by slidingly driving the predoctor blade 161 (arrow A in the figure). A lever or a cam may be arranged between the pre-doctor blade 161 and the driving device 162.

  In this example, the front regulating member 160 is driven as follows. At the start of printing, the driving device 162 sets the distance between the pre-doctor blade 161 and the developing roller 120 (referred to as a pre-doctor gap) to a position that is substantially equal to the distance between the doctor blade 150 and the developing roller 120 (doctor gap). The pre-doctor blade 161 is moved and fixed. At this time, if the size of the pre-doctor gap is smaller than the size of the doctor gap, the amount of the developer on the developing roller 120 is smaller than a predetermined amount, and therefore the size of the pre-doctor gap may be equal to or larger than the size of the doctor gap. desirable.

  In this state, the developer sent from the stirring roller 130 to the developing roller 120 is first charged in the pre-doctor gap and then further charged in the doctor gap, so that the charging efficiency of the toner is increased and the charge amount of the toner is increased. Can be increased rapidly.

  Thereafter, when the toner charge amount reaches the saturation charge amount when charged only by the doctor, the size of the pre-doctor gap is increased. The time until the toner charge amount reaches saturation varies depending on the properties of the magnetic carrier used, the printing speed, and the usage environment. Therefore, the timing for moving the pre-doctor gap is determined according to each condition, and the driving device 162 is set. Control. This control can be executed by setting the control device of the image forming apparatus 10 in advance and controlling the driving device 162 with this control device. Further, the developing device 100 may be provided with a control unit, and the control unit may control the driving device 162.

  It should be noted that a device for measuring the toner charge amount may be arranged in the developing device 100, and the toner charge amount may be constantly monitored to determine the timing for driving the pre-doctor blade 161.

  According to the developing device 100 according to this example, immediately after the start of printing, the pre-doctor gap, which is the distance between the pre-doctor blade 161 and the developing roller 120, is reduced to increase the toner charge amount, and the toner charge immediately after the start of printing. It is possible to compensate for the shortage of the amount, eliminate the difference in the toner charge amount immediately after the start of printing and during continuous printing, stabilize the toner charge amount, and perform good image formation.

  Next, a developing device according to a second embodiment will be described. FIG. 3 is a schematic cross-sectional view showing the configuration of the image forming apparatus according to the second embodiment. In the developing device 200, a front regulating member 260 having a pre-doctor blade 261 as a regulating member is disposed in the housing 110, and similarly to the developing device 100 according to the first embodiment, the developing roller 120, the stirring roller 130, a toner replenishing unit 140, and a doctor blade 150 are arranged.

  In this example, the pre-doctor blade 261 is connected to a shaft 262 that is a distance adjusting member and a driving device (not shown) that drives the shaft 262 to swing. With such a configuration, the distance from the developing roller 120 can be changed by swinging the pre-doctor blade 261.

  According to the developing device of this example, the distance between the pre-doctor blade 261 and the developing roller 120 can be adjusted by rotating the shaft 262, and the charge amount of the toner immediately after the start of printing, as in the first embodiment. Can compensate for the shortage of toner, eliminate the difference in toner charge amount immediately after the start of printing and during continuous printing, stabilize the toner charge amount, and achieve good image formation

  In addition, the shape of the member employ | adopted as a front-position control member is not restricted to a plate-shaped person, The thing of another shape can be used. FIG. 5 is a schematic sectional view showing a developing apparatus according to the third embodiment. In this example, the front restricting member 360 uses a columnar restricting member 361 as a restricting member, and supports the restricting member 361 with a shaft 362 at an eccentric position, and the shaft 362 is not illustrated. It is supported so that it can swing.

  According to the developing device of this example, the interval between the regulating member 361 and the developing roller 120 can be adjusted by rotating the shaft 362, and the toner charge amount is insufficient immediately after the start of printing, as in the first embodiment. Therefore, the toner charge amount can be stabilized by eliminating the difference between the toner charge amount immediately after the start of printing and during continuous printing, and good image formation can be performed.

  In the above example, the shape of the member used for the front restricting member has been described as a plate shape or a cylindrical shape. However, the shape is not limited to this shape, and other shape members can be used.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment. It is a schematic sectional drawing which shows the structure of the developing device which concerns on an Example. It is a schematic sectional drawing which shows the structure of the developing device which concerns on a 2nd Example. It is a schematic sectional drawing which shows the structure of the developing device which concerns on a 3rd Example. It is a schematic sectional drawing which shows the structure of the conventional image development apparatus.

Explanation of symbols

10 Image forming apparatus 11 Photosensitive member (latent image carrier)
DESCRIPTION OF SYMBOLS 12 Charging device 13 Exposure 14 P sensor 15 Transfer device 16 Cleaning device 17 Static elimination device 18 Fixing device 100 Developing device 110 Housing 120 Developing roller (Developer carrier)
121 Developing Sleeve 122 Magnet Roller 130 Stirring Roller 140 Toner Supplying Unit 150 Doctor Blade (Developer Restricting Member)
160 Pre-regulation member 161 Pre-doctor blade (regulation member)
162 Drive device (spacing adjustment member)
200 Developing device 260 Pre-regulating member 261 Pre-doctor blade (regulating member)
262 shaft (spacing adjustment member)
360 Front Restriction Member 361 Restriction Member 362 Axis (Spacing Adjustment Member)

Claims (7)

A developer carrying member for carrying the developer on the surface and transporting the developer to the latent image carrying member to form an image on the latent image carrying member; and a developer carrying member from an image forming portion on the latent image carrying member. A developer regulating member that is disposed upstream and regulates the amount of developer on the developer carrying member;
A developing device, wherein a front regulating member capable of changing a distance between the developer carrying member and an upstream side of the developer regulating member is disposed.   The pre-described member is composed of a regulating member arranged in the vicinity of the developer carrying member, and an interval adjusting member that holds the regulating member so that the gap interval to the developer carrying member can be adjusted. The developing device according to claim 1, wherein:   The developing device according to claim 2, wherein the regulating member is a flat plate member.   The developing device according to claim 2, wherein the regulating member is a columnar member.   The developing device according to claim 3, wherein the interval adjusting member is configured to adjust the interval dimension between the restricting member and the developer carrying member by slidably holding the restricting member.   5. The developing device according to claim 3, wherein the interval adjusting member is configured to adjust the interval dimension between the restricting member and the developer carrying member by rotatably supporting the restricting member. An image forming apparatus comprising the developing device according to claim 1.