JP2007271689A - Developing device and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more securely suppress the quantity of developer remaining in a developing device from being erroneously detected. <P>SOLUTION: The developing device 27 includes a second stirring spiral 49, a housing 41, a remaining toner quantity sensor 48, and a cleaning spring 46. The second stirring spiral 49 has a rotation shaft 71 and a spiral portion 73 formed along the periphery of the rotation shaft 71. The housing 41 stores toner, and has a side 41b supporting the rotation shaft 71 of the second stirring spiral and an arcuate bottom 41c formed along the lower portion of the second stirring spiral 49 in the radial direction of the spiral 49. The remaining toner quantity sensor 48 is disposed on the internal wall of the side 41b of the housing 41 so as to expose its surface, and is used to detect a quantity of toner remaining in the housing 41. The cleaning spring 46 is attached to the sensor 48 side end of the rotation shaft 71 of the second stirring spiral 49 so as to clean the internal wall of the side 41b accompanying the rotation of the second stirring spiral 49. The cleaning spring 46 is rotated so that its perimetral end follows a locus C1 that has a diameter greater than that of the arcuate bottom 41c. The cleaning spring 46 is elastic. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus including the developing device.

  Image forming apparatuses such as copying machines and printers that employ an electrophotographic system generally include a photosensitive drum (image carrier) and a developing device that supplies toner to the photosensitive drum for development. The developing device usually includes a housing that accommodates the developer, a stirring member that stirs the developer in the housing, and a remaining amount sensor that detects the amount of the developer in the housing. As the remaining amount sensor, a piezoelectric sensor arranged on the inner wall of the side portion of the housing is usually employed.

In such a developing device, cleaning is performed to clean the side of the housing where the remaining amount sensor is arranged so that a developer may adhere to the remaining amount sensor or toner blocking may occur in the vicinity of the remaining amount sensor to prevent erroneous detection. An apparatus further provided with a member has already been proposed (see, for example, Patent Documents 1 to 6). The cleaning member is usually attached to the rotating shaft of the stirring member and rotates integrally with the stirring member so that the vicinity of the remaining amount sensor can be cleaned simultaneously with stirring.
JP-A-8-110694 JP-A-7-306580 JP 2003-167420 A Noto 2584467 JP-A-10-198255 Japanese Patent Laid-Open No. 10-198254

  In the developing device described in Patent Document 1, a wire having a spiral cross section in the radial direction is used as the cleaning member. However, when the stirring member stops, depending on the stop position of the spiral wire in front of the remaining amount sensor. May cause false detection.

  Patent Documents 2 to 6 describe various configurations of developing devices, but the configuration is complicated, and screws and other fixing parts are required to attach the cleaning member to the stirring member. As a result, the number of parts is large, leading to increased costs.

  An object of the present invention is to more reliably suppress erroneous detection of the developer remaining amount in the developing device.

  The developing device according to a first aspect includes a stirring member, a housing, a detection unit, and a cleaning member. The stirring member has a rotating shaft and a blade member provided on the outer periphery of the rotating shaft. The housing contains a developer and has a side portion that supports the rotating shaft of the stirring member, and an arcuate bottom portion that is formed along a lower portion in the radial direction of the stirring member. The detector is disposed with the surface exposed on the inner wall of the side of the housing, and detects the amount of developer in the housing. The cleaning member is attached to the end portion of the rotating shaft of the stirring member on the detection portion side so as to clean the inner wall of the side portion as the stirring member rotates, and the outer peripheral end has a locus having a diameter larger than the diameter of the arc-shaped bottom portion. It rotates to follow and has elasticity.

  In this developing device, the developer in the housing is agitated by the rotation of the agitating member, and the cleaning member also rotates integrally therewith, thereby cleaning the inner wall of the side portion and also cleaning the surface of the detecting portion. Is done.

  In such a cleaning operation, the cleaning member rotates following a trajectory having a diameter larger than the diameter of the arc-shaped bottom portion. Therefore, when the cleaning member reaches the arc-shaped bottom portion in the middle of the rotation operation, the cleaning member is elastically deformed, and is caused by the arc-shaped bottom portion. Rotates in a bent state due to reaction. The cleaning member is removed from the bottom of the circular arc shape and at the same time receives the elastic force to return the bending to vigorously rotate, so even if the toner fluidity is reduced and blocking occurs, It can be understood, and erroneous detection by the detection unit can be avoided.

  Moreover, since the cleaning member rotates vigorously as described above in the circumferential region other than the arcuate bottom, it is possible to prevent the cleaning member from stopping in front of the detection unit, and to avoid erroneous detection.

  Furthermore, since the cleaning member can more reliably remove the toner around the detection portion using the elastic force without securing a large diameter of the arc-shaped bottom portion, it contributes to downsizing of the developing device.

  According to a second aspect of the present invention, in the apparatus of the first aspect, the cleaning member is a metal wire having a spring property that extends from the rotating shaft of the stirring member to the outer peripheral side.

  In this developing device, since the cleaning member has a simple configuration, the cost can be reduced.

  According to a third aspect of the present invention, in the apparatus of the second aspect, the cleaning member has a coil spring portion attached to the rotating shaft of the stirring member.

  In this developing device, since the cleaning member has the coil spring portion, the amount of elastic deformation when passing through the arc-shaped bottom portion is increased, thereby obtaining a strong repulsive force when leaving the arc-shaped region. Thus, the blocked toner can be broken down more reliably, and a stop in front of the detection surface can be avoided.

  According to a fourth aspect of the present invention, in the apparatus according to any one of the first to third aspects, the detection unit is a piezoelectric sensor.

  In this developing device, since the piezoelectric sensor is used as the detection unit, it is necessary to arrange the sensor on the side portion of the housing, and therefore, it is necessary to avoid toner blocking around the inner wall of the side portion. . In this developing device, by including the cleaning member having the above-described configuration, even when a piezoelectric sensor is employed, erroneous detection can be prevented and the amount of developer can be detected satisfactorily.

  An image forming apparatus according to a fifth aspect includes an image carrier, a developing device, and a transfer device. 5. The developing device according to claim 1, wherein the developing device supplies a developer to the image carrier. The transfer device is a device for transferring an image formed on the image carrier to a recording medium.

  Since this image forming apparatus includes the developing device according to any one of claims 1 to 4, erroneous detection of the developer amount is suppressed, and an appropriate developing operation, and thus an image forming operation is ensured. In addition, since the diameter of the arc-shaped bottom portion of the developing device can be kept small by utilizing the elasticity of the cleaning member, the developing device or the entire image forming apparatus can be downsized.

  According to the developing device of the present invention, the cleaning member rotates following a trajectory having a diameter larger than the diameter of the arcuate bottom portion. Therefore, when the cleaning member reaches the arcuate bottom portion in the middle of the rotation operation, the cleaning member is elastically deformed and is arcuate. It rotates in a bent state due to the reaction by the bottom. The cleaning member is removed from the bottom of the circular arc shape and at the same time receives the elastic force to return the bending to vigorously rotate, so even if the toner fluidity is reduced and blocking occurs, It can be understood, and erroneous detection by the detection unit can be avoided.

  Moreover, since the cleaning member rotates vigorously as described above in the circumferential region other than the arcuate bottom, it is possible to prevent the cleaning member from stopping in front of the detection unit, and to avoid erroneous detection.

  Furthermore, since the cleaning member can more reliably remove the toner around the detection portion using the elastic force without securing a large diameter of the arc-shaped bottom portion, it contributes to downsizing of the developing device.

<Configuration of MFP>
FIG. 1 shows a multifunction machine 1 as an image forming apparatus in which an embodiment of the present invention is adopted.

  The multifunction machine 1 is an image forming apparatus having functions as a copying machine, a printer, a facsimile machine, and a scanner, and includes an operation panel (not shown), an image reading unit 5, a control unit (not shown), a feeding unit. A paper unit 9, an image forming unit 11, a fixing unit 13, and a paper discharge unit 15 are provided.

  The operation panel has a start key for instructing copying and reading of a document, a setting key for setting various printing conditions, and the like. The operation panel has a touch panel type liquid crystal display on which various operation screens are displayed.

  The image reading unit 5 is for reading image information of a document on the document table 2 on the upper surface of the multifunction machine main body 1a, and has an optical system, a CCD, etc. (not shown).

  The control unit includes a microcomputer including a CPU, a RAM, a ROM, and the like, and performs control of input / output units such as the image reading unit 5 and the image forming unit 11, image processing for image information, and the like. Various program data for these operations are stored in the ROM, read out to the RAM by the CPU, and executed.

  The paper feed unit 9 has a plurality of paper feed cassettes 10 arranged at the bottom of the multifunction machine main body 1a, and a manual feed tray 12 provided on the side of the multifunction machine main body 1a. A sheet feeding roller 8 for conveying the recording medium) to the image forming unit 11 one by one and a driving motor (not shown) for driving the sheet feeding roller 8 are provided.

  The image forming unit 11 forms a toner image on a sheet conveyed from the sheet feeding unit 9 by an electrophotographic process, and is a photosensitive drum 21 (rotated in a predetermined rotation direction (arrow X direction)). An image carrier), and a main charging device 23, an exposure device 25, a developing device 27, a transfer device 29, a cleaning device 31, and a charge eliminating device 33, which are arranged around the photosensitive drum 21 in order from the upstream side in the rotation direction. ing.

  The photosensitive drum 21 is a rotating body having a photosensitive layer on its surface, and rotates at a predetermined rotation speed in response to an image formation command.

  The main charging device 23 has a charging wire to which a high voltage is applied. By applying a predetermined potential to the surface of the photosensitive drum 21 by corona discharge by the charging wire, the photosensitive drum 21 is uniformly charged. .

  The exposure device 25 includes a laser light source, a polygon mirror, and the like, and the surface potential of the photosensitive drum 21 is selectively attenuated by irradiating the charged photosensitive drum 21 with laser light based on image information. An electrostatic latent image is formed.

  The developing device 27 is a device for supplying toner to the photosensitive drum 21 to visualize the electrostatic latent image on the surface of the photosensitive drum 21. Details will be described later.

  The transfer device 29 is a device for transferring the toner image formed on the surface of the photosensitive drum 21 to the paper side by a transfer bias.

  The cleaning device 31 includes a housing 32, a cleaning blade 30 that contacts the surface of the photosensitive drum 21, and agitation for conveying the toner scraped off in the housing 32 to one side in the axial direction (the back side in FIG. 1). It has a spiral (not shown), and scrapes off and collects the toner remaining on the surface of the photosensitive drum 21.

  The neutralization device 33 is for removing the residual potential on the surface of the photosensitive drum 21.

  The fixing unit 13 is disposed on the downstream side of the image forming unit 11 in the sheet conveyance direction, and includes a heating roller 16 and a pressure roller 18 incorporating a heater, and the sheet onto which the toner image has been transferred is applied to both the rollers 16 and 18. The toner image is melted and fixed by being nipped.

  The paper discharge unit 15 is for discharging the paper that has passed through the fixing unit 13 to the paper discharge tray 14 on the side of the multifunction machine main body 1a, and includes a roller and a drive motor that drives the roller. .

  The multifunction machine 1 further includes an automatic document feeder 17 and a toner replenishing device (not shown) as other input / output units. The automatic document feeder 17 is mounted on the upper surface of the multifunction machine main body 1a so as to be openable and closable, and can continuously feed a plurality of documents one by one to the document table 2. The toner replenishing device is for replenishing toner from a toner cartridge (not shown) disposed above the developing device 27, and the remaining amount of toner is detected by a remaining amount detection sensor (not shown) of the developing device 27. When it is detected that the amount has decreased, the replenishment operation is performed.

<Developing device>
Next, the developing device 27 will be described in detail with reference to FIGS.

  FIG. 2 is a perspective view of the developing device 27 as viewed from above the rear end. For convenience of explanation, the rear end (the end opposite to the photosensitive drum is shown in FIG. 3, the upper surface portion of the left end portion is omitted. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a plan view showing main parts of the stirring member and the cleaning member.

  The developing device 27 performs development using toner as a one-component developer, and includes a housing 41, a developing roller 43, a layer thickness regulating blade 45, a first stirring spiral 47, and a second stirring spiral. 49 (stirring member), a cleaning spring 46 (cleaning member), and a toner remaining amount sensor 48 (detection unit).

  The housing 41 is a housing made of resin or metal, and a space for accommodating toner is formed inside. The front end of the housing 41 (the end on the photosensitive drum side, the upper right side in FIG. 2 and the right end in FIG. 3) is opened, and the upper surface of the rear end communicates with a toner cartridge (not shown). Has been. Further, the housing 41 has a partition wall 41a formed between the first and second stirring spirals 47 and 49 so as to extend in a vertical direction and extend over a region excluding both end portions in the axial direction. Further, the housing 41 rotatably supports the rotating shaft 71 of the second stirring spiral 49 at the side portions 41b at both ends in the axial direction (the depth direction in FIG. 3). Further, the housing 41 has an arcuate bottom portion 41 c formed in an arc shape along the lower portion in the radial direction of the second stirring spiral 49.

  The developing roller 43 is rotatably mounted in the opening portion of the front end portion of the housing 41 and is disposed adjacent to the photosensitive drum 21. The developing roller 43 supplies toner in the housing 41 to the photosensitive drum 21, and is fixedly disposed on the inner peripheral side of the developing sleeve 43a that is rotationally driven and the developing sleeve 43a, and has a predetermined circumferential position. And a magnet roller 43b having a plurality of magnetic poles.

  The layer thickness regulating blade 45 is a member for regulating the thickness of the toner layer supplied to the developing sleeve 43a, and is disposed with a predetermined gap between the tip portion and the developing sleeve 43a.

  The second agitating spiral 49 conveys the toner in the housing 41 to one side in the axial direction (the direction from the front side to the back side in FIG. 3) while agitating the toner. The toner in 41 is circulated and conveyed. The second agitation spiral 49 is arranged in parallel with the first agitation spiral 47 via the partition wall 41a, and is arranged rotatably in the housing 41. The second stirring spiral 49 has a rotating shaft 71 and a spiral spiral 73 (blade member) formed on the outer peripheral portion of the rotating shaft 71.

  The first agitation spiral 47 conveys the toner in the housing 41 to the other side in the axial direction (the direction from the back side to the front side in FIG. 3) while agitating the toner. The first agitation spiral 47 is rotatably arranged in the housing 41. Has been. The first stirring spiral 47 includes a shaft 61 and a spiral 63 formed in a spiral shape on the outer peripheral surface of the shaft 61.

  The cleaning spring 46 is made of a metal wire having a spring property (for example, SUS304), a coil spring portion 46a attached to the rotating shaft 71 of the second stirring spiral 49, and a tangential direction of the rotating shaft 71 from the coil spring portion 46a. And a distal end portion 46c formed to extend further from the outer peripheral end of the extension portion 46b. The cleaning spring 46 is attached to the coil spring portion 46 a by inserting the end portion of the rotating shaft 71 of the second stirring spiral 49 on the toner remaining amount sensor 48 side. The tip 46c has a shape that extends slightly in the axial direction so that even a blocked toner can be effectively unwound.

  The cleaning spring 46 rotates in the direction of the arrow integrally with the second stirring spiral 49 so that the extending portion 46 b can slide on the inner wall of the side portion 41 b of the housing 41. In FIG. 3, C1 indicates the locus of the outer peripheral end of the cleaning spring 46 when the cleaning spring 46 rotates about the rotation shaft 71 of the second stirring spiral 49, and has a larger diameter than the arcuate bottom 41c. It is an arc. C2 indicates the locus of the outer peripheral end of the cleaning spring when another cleaning spring as a reference example rotates about the rotation shaft 71, and is an arc having the same diameter as the arcuate bottom 41c.

  The toner remaining amount sensor 48 is for detecting the toner remaining amount in the housing 41, and here, a piezoelectric sensor is used. The toner remaining amount sensor 48 is disposed with its surface exposed on the inner wall of the side portion 41 b of the housing 41.

<Operation of MFP>
Next, the operation of the multifunction device 1 will be described.

  When the multifunction device 1 is turned on, various parameters are initialized in the control unit, and the heater of the fixing unit 13 is heated, and the initial operation is performed. When the initial operation is completed, a predetermined print standby screen is displayed on the operation panel.

  In this state, for example, when a document is placed on the document table 2 and the start key is pressed, the image information of the document is read and the sheet is fed from the sheet feeding cassette 10. At this time, in the image forming unit 11, the photosensitive drum 21 is rotationally driven, charged, and then exposed based on the read image information to form an electrostatic latent image. Then, toner is supplied from the developing device 27. Thus, a toner image is formed. Then, at a predetermined timing, the sheet is conveyed to the image forming unit 11 and the toner image is transferred from the photosensitive drum 21. The sheet on which the toner image is transferred is further conveyed downstream, and the toner image is melted and fixed by passing through the fixing unit 13, and is discharged onto the discharge tray 14 by the discharge unit 15.

  During this series of image forming operations, in the developing device 27, the two agitating spirals 47 and 49 convey toner in opposite directions while agitating the toner, whereby the toner is circulated and conveyed in the housing 41. At the same time, a part of the toner is supplied from the first stirring spiral 47 to the developing roller 43 side.

  Further, in the developing device 27, the cleaning spring 46 rotates integrally with the second stirring spiral 49, whereby the toner existing in the vicinity of the side portion 41b is removed, and the surface of the toner remaining amount sensor 48 is also cleaned. The

  In such a cleaning operation, the cleaning spring 46 rotates following a trajectory having a diameter larger than the diameter of the arcuate bottom portion 41c. Therefore, when the cleaning spring 46 reaches the arcuate bottom portion 41c in the middle of the rotation operation, the cleaning spring 46 is elastically deformed, It rotates in a bent state due to the reaction of the arc-shaped bottom 41c. Therefore, at the same time as it escapes from the arc-shaped bottom portion 41c, it is rotated vigorously by receiving the elastic force to return the deformation to the original, so that even when the toner fluidity is lowered and blocking occurs, this can be solved. And erroneous detection by the toner remaining amount sensor 48 can be avoided.

  Further, since the cleaning spring 46 rotates vigorously in the circumferential region other than the arc-shaped bottom portion 41c, it is possible to prevent the cleaning spring 46 from stopping in front of the toner remaining amount sensor 48 and to avoid erroneous detection due to this.

  Further, the cleaning spring 46 can more reliably remove the toner around the toner remaining amount sensor 48 using the elastic force without securing a large diameter of the arc-shaped bottom portion 41c. It will contribute to the downsizing.

<Other embodiments>
(A) The shape, material, radial length and the like of the cleaning member are not limited to those described above.

  (B) The developer accommodated in the developing device is not limited to a one-component developer, and may be a two-component developer, and may be magnetic or non-magnetic.

  (C) The developing device is not limited to the circulating stirring type, and may be one having only one stirring member.

  (D) The image forming apparatus is not limited to a multifunction peripheral, and may be a copying machine, a printer, or a facsimile apparatus.

1 is a longitudinal sectional view showing a multifunction machine in which an embodiment of the present invention is adopted. FIG. 3 is a perspective view of the developing device of the multi-function machine, partly broken and viewed from above the rear end side. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. The top view which shows the principal part of the stirring member and cleaning member of the said developing device.

Explanation of symbols

1 MFP (image forming device)
27 Developing device 29 Transfer device 21 Photosensitive drum (image carrier)
41 Housing 46 Cleaning spring (cleaning member)
48 Toner level sensor (detection unit)
49 2nd stirring spiral (2nd stirring conveyance member)
71 Rotating shaft 73 Spiral (blade member)

Claims (5)

A stirring member having a rotating shaft and a blade member provided on an outer peripheral portion of the rotating shaft;
A housing containing developer therein and supporting a rotating shaft of the stirring member; and an arcuate bottom formed along a radially lower portion of the stirring member;
A detection portion that is disposed with an exposed surface on an inner wall of a side portion of the housing and detects the amount of the developer in the housing;
The end of the rotating shaft of the stirring member is attached to the end on the detection unit side so as to clean the inner wall of the side with the rotation of the stirring member, and the outer peripheral end has a larger locus than the diameter of the arcuate bottom. A cleaning member that rotates and follows elasticity, and
A developing device comprising:   The developing device according to claim 1, wherein the cleaning member is a metal wire having a spring property that extends from a rotating shaft of the stirring member to an outer peripheral side.   The developing device according to claim 2, wherein the cleaning member has a coil spring portion attached to a rotation shaft of the stirring member.   The developing device according to claim 1, wherein the detection unit is a piezoelectric sensor. An image carrier;
The developing device according to claim 1, wherein a developer is supplied to the image carrier.
A transfer device for transferring an image formed on the image carrier to a recording medium;
An image forming apparatus.

Images