JP2013125125A - Developing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device configured to prevent developer from being accumulated on a sensor sensing surface without using a soft material for cleaning the sensing surface of a magnetic permeability sensor, and to prevent a change in density of developer to be sensed, while preventing a reduction in reliability of an output of a magnetic permeability sensor, and to provide an image forming device using the same.SOLUTION: A developing device 2 includes a developer tank 111 for housing developer, a first conveyance path P, a second conveyance path Q, a first conveyance member 112, a second conveyance member 113, a developing roller 114 for supplying toner to a photoreceptor drum 3, and a magnetic permeability sensor 119 for detecting toner density of the developer in the developer tank 111. The vicinity of the sensing surface 119a of the magnetic permeability sensor 119 is protruded. The outer diameter of a second conveyance blade 113a of the second conveyance member 113 facing the protruded part is made smaller. An inclination part 111a is formed, which inclines toward the vicinity of the protruded sensing surface 119a.

Description

  The present invention relates to a developing device and an image forming apparatus using the same, and more particularly to an image forming apparatus such as an electrostatic copying machine, a laser printer, and a facsimile machine that forms an image using toner by an electrophotographic method. The present invention relates to a developing device using a two-component developer containing a magnetic carrier and an image forming apparatus using the developing device.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses such as copying machines, printers, and facsimiles are known. An electrophotographic image forming apparatus forms an electrostatic latent image on the surface of a photosensitive drum (toner image carrier), and develops the electrostatic latent image by supplying toner to the photosensitive drum by a developing device. The toner image formed on the photosensitive drum by development is transferred to a sheet such as paper, and the toner image is fixed on the sheet by a fixing device.

  2. Description of the Related Art In recent years, two-component developers (hereinafter simply referred to as “developers”) that are excellent in toner charge stability are often used in image forming apparatuses that support full color and high image quality. This developer is composed of toner and a magnetic carrier, and the toner and the magnetic carrier are rubbed by stirring them in the developing device, and a properly charged toner is obtained by this friction.

  In the developing device, the charged toner is supplied to the surface of a developer carrying member, for example, a developing roller. The toner supplied to the developing roller moves to an electrostatic latent image formed on the photosensitive drum by an electrostatic attraction force. As a result, a toner image based on the electrostatic latent image is formed on the photosensitive drum.

  Further, such an image forming apparatus is required to be increased in speed and reduced in size, and it is necessary to quickly and sufficiently charge the developer and to rapidly carry and stir the developer.

  Therefore, as a conventional technique, in the image forming apparatus, in order to immediately disperse the replenished toner in the developer and to provide an appropriate charge amount, two developers that form a path through which the developer is circulated and conveyed A device in which a circulation type developing device including a conveyance path and two developer agitating / conveying members that convey the developer while stirring the developer in the developer conveyance path is mounted (Patent Document 1). reference).

However, in the above-described developing device, a magnetic permeability sensor is generally used to detect the toner concentration of the developer in the developer accommodating portion. However, in the magnetic permeability sensor, circulation of the developer on the detection surface is delayed. There is a problem that the reliability of the sensor output decreases.
This is because the sensor output is adjusted based on the developer density in a state where the sensor is stably circulated and transported at a predetermined speed. Therefore, if the developer density changes due to stagnation of the circulatory transport, the output value of the permeability sensor and the toner This is because the correlation coefficient of density decreases.

  Therefore, as a countermeasure against this problem, there is known a method of attaching a soft material such as urethane at a position facing the magnetic permeability sensor detection surface of the developer stirring and conveying member for the purpose of cleaning the sensor detection surface.

  However, in this method, the soft material repeats physical contact with the sensor detection surface as the stirring / conveying member is driven to rotate. Therefore, when the rotational speed of the stirring / conveying member increases as the speed of the image forming apparatus increases, the soft material becomes the sensor detection surface. The mechanical stress applied to the sensor increases, and the sensor detection surface is damaged. In addition, if the strength of the soft material is lowered to prevent this, deterioration of the soft material due to long-term use is unavoidable, and if the free length of the soft material is extended, the effect of preventing the retention of the developer is lost. was there.

  Therefore, as a conventional technique, in the developing device, a part of the stirring blade in the axial direction of the screw that stirs and conveys the developer is a stirring blade having a reduced diameter with respect to the other part, and the reduced diameter part is faced. Thus, there has been proposed a sensor surface of a magnetic sensor for detecting the toner density in the developer (see Patent Document 2).

  With this configuration, a developer bulge is formed that has a small change in toner concentration in the developer and has a smooth conveyance force, and the toner concentration of the developer is adjusted by a magnetic sensor provided on the side surface side. By detecting it, the filling amount of the developer in the developing device can be set small.

  As another technique, in the developing device, the toner concentration detection member is protruded from the inner wall of the developing tank, and the gap g between the mixing roller and the detection surface of the toner concentration detecting member and the gap G between the inner wall of the developing tank and There have been proposed those in which g = 0.2 to 1.0 mm and G = 0.3 to 2.5 mm, respectively (see Patent Document 3).

By configuring in this way, the detection accuracy of the toner concentration in the developer is improved,
High responsiveness that can immediately follow the change in toner density is possible.

  Furthermore, as another technique, a developing device has been proposed in which the gap G between the stirring member and the magnetic sensor is 0.5 mm or less (see Patent Document 4).

  With this configuration, the developer stays on the sensor surface of the magnetic sensor and the magnetic sensor accurately detects the toner concentration in the stirring member region, so that appropriate toner concentration control can be realized.

JP 2006-106194 A Japanese Patent Laid-Open No. 8-21725 Japanese Patent Laid-Open No. 1-252065 JP 2009-37181 A

  However, according to the above-described prior art, since the toner concentration detection member such as a magnetic sensor is protruded in the developing tank, the toner adheres to the detection surface, or the developer is placed around the protruded toner concentration detection member. The problem of stagnation arises.

  The present invention has been made in view of the above-described conventional problems, and suppresses the retention of developer on the sensor detection surface without attaching a soft material to the developer agitating and conveying member. It is an object of the present invention to provide a developing device in which reliability is not lowered and an image forming device using the same.

  The developing device and the image forming apparatus using the same according to the present invention for solving the above-described problems are as follows.

  The present invention is provided with a developer accommodating portion in which a developer containing toner and a magnetic carrier is accommodated, a developer conveying path in which the developer is conveyed in the developer accommodating portion, and a developer conveying path. A developer agitating and conveying member that conveys the developer in a predetermined direction while agitating the developer; a developing roller that carries the developer in the developer conveying path and supplies toner contained in the developer to the photosensitive drum; And a magnetic permeability sensor for detecting the toner concentration of the developer in the developer conveyance path, wherein the magnetic permeability sensor is located at a position facing the developer agitating and conveying member in the developer accommodating portion. The developer agitating and conveying member is arranged so that the periphery of the detecting surface protrudes from other than the periphery of the detecting surface, and the outer diameter of the developer agitating and conveying member at a position facing the periphery of the detecting surface is Not facing The developer agitating / conveying member and the developing member other than the periphery of the detection surface are configured such that the protruding distance from the inner wall surface of the developer accommodating portion around the detection surface of the magnetic permeability sensor is smaller than the outer diameter of the developer sensor. It is configured to be larger than the gap distance from the inner wall surface of the agent storage portion.

  Further, the present invention provides an outer diameter of the developer stirring / conveying member at a position facing the periphery of the detection surface of the magnetic permeability sensor and an outer diameter of the developer stirring / transporting member at a position other than the position facing the periphery of the detecting surface. It is preferable that the difference be smaller than one third of the outer diameter of the developer agitating / conveying member other than the position facing the periphery of the detection surface.

  In addition, the present invention provides an inclination having an inclination angle (gradient) of 5 ° or more and less than 60 ° from the periphery of the protruding detection surface of the magnetic permeability sensor to the inner wall surface (other than the periphery of the detection surface) of the developer container. It is preferable to provide a part.

  The present invention also provides a photosensitive drum on which an electrostatic latent image is formed, a charging device that charges the surface of the photosensitive drum, an exposure device that forms an electrostatic latent image on the surface of the photosensitive drum, and a photosensitive member. A developing device that supplies toner to the electrostatic latent image on the drum surface to form a toner image, a transfer device that transfers the toner image on the surface of the photosensitive drum to a recording medium, and the transferred toner image is fixed to the recording medium. An image forming apparatus comprising a fixing device and forming an image using toner by an electrophotographic method, wherein the developing device according to any one of claims 1 to 3 is used as the developing device. It is what.

  According to the present invention, a developer containing portion that contains a developer containing toner and a magnetic carrier, a developer carrying path in which the developer is carried in the developer containing portion, and the developer carrying path And a developer agitating / conveying member that conveys the developer in a predetermined direction while agitating the developer, and that carries the developer in the developer conveying path and supplies the toner contained in the developer to the photosensitive drum. In a developing device including a roller and a magnetic permeability sensor that detects a toner concentration of the developer in the developer conveyance path, the magnetic permeability sensor is located at a position facing the developer agitating and conveying member in the developer container. The outer periphery of the developer agitating / conveying member at a position facing the periphery of the detecting surface is arranged such that the periphery of the detecting surface protrudes from the vicinity of other than the periphery of the detecting surface. Do not face the periphery And the developer agitating and conveying member other than the periphery of the detection surface and the protrusion distance from the inner wall surface of the developer accommodating portion around the detection surface of the magnetic permeability sensor, By configuring the distance larger than the gap distance from the inner wall surface of the developer accommodating portion, a safe gap is provided between the developer agitating and conveying member even if the sensor detection surface is disposed so as to protrude. Therefore, even if the developer agitating / conveying member is shaken or bent during rotation, physical contact with the sensor detection surface can be prevented, and the circulated and conveyed developer stays on the sensor detection surface. Can be suppressed. Thereby, since the density change of the developer does not occur, a highly reliable sensor output can be obtained without reducing the correlation coefficient with respect to the toner density.

  Further, according to the present invention, the outer diameter of the developer agitating / conveying member at a position facing the periphery of the detection surface of the magnetic permeability sensor and the outer diameter of the developer agitating / conveying member at a position other than the position facing the periphery of the detecting surface. Is smaller than one third of the outer diameter of the developer agitating / conveying member other than the position facing the periphery of the detection surface, so that the developer conveying speed due to the difference in local outer diameter can be reduced. It is possible to obtain a highly reliable sensor output while maintaining a stable developer circulation without causing a decrease.

  Further, according to the present invention, the inclined portion having an inclination angle of 5 ° or more and less than 60 ° from the periphery of the protruding detection surface of the magnetic permeability sensor to the inner wall surface (other than the periphery of the detection surface) of the developer containing portion. Unlike the case of projecting at an angle close to a right angle, the developer is not accumulated in the blind spot, and the developer transport speed is not slowed at the projecting position, and the developer is developed in the developer transport path. The agent can be circulated stably.

  Further, according to the present invention, a photosensitive drum on which an electrostatic latent image is formed, a charging device that charges the surface of the photosensitive drum, an exposure device that forms an electrostatic latent image on the surface of the photosensitive drum, A developing device that supplies toner to the electrostatic latent image on the surface of the photosensitive drum to form a toner image, a transfer device that transfers the toner image on the surface of the photosensitive drum to a recording medium, and the transferred toner image on the recording medium An image forming apparatus comprising a fixing device for fixing and forming an image using toner by electrophotography, wherein the developing device according to claim 1 is used as the developing device. Therefore, since it is possible to suppress a decrease in the reliability of the sensor output, stable toner density control can be performed.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus in which a developing device according to an embodiment of the present invention is used. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a toner replenishing device constituting the image forming apparatus. It is CC sectional view taken on the line of FIG. FIG. 2 is a cross-sectional view illustrating a configuration of a developing device that constitutes the image forming apparatus. It is an AA cross-sectional arrow view of FIG. It is a BB cross-sectional arrow view of FIG. It is explanatory drawing which shows the structure of the magnetic permeability sensor provided in the developing tank of the said developing device, and a 2nd conveyance member.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an example of an embodiment for carrying out the invention, and is an explanatory view showing the overall configuration of an image forming apparatus using a developing device according to an embodiment of the present invention.

  In the present embodiment, as shown in FIG. 1, a photosensitive drum 3 on which an electrostatic latent image is formed, a charger (charging device) 5 for charging the surface of the photosensitive drum 3, and the surface of the photosensitive drum 3 An exposure unit (exposure device) 1 that forms an electrostatic latent image on the surface, a developing device 2 that forms a toner image by supplying toner to the electrostatic latent image on the surface of the photosensitive drum 3, and a toner supply to the developing device 2 A toner replenishing device 22, an intermediate transfer belt unit (transfer device) 8 for transferring the toner image on the surface of the photosensitive drum 3 to a recording medium, and a fixing unit (fixing device) 12 for fixing the toner image on the recording medium. In the image forming apparatus 100 that forms an image using toner by electrophotography, the configuration of the developing device according to the present invention is adopted as the developing device 2.

  The image forming apparatus 100 forms a multicolor or single color image on a predetermined sheet (recording paper, recording medium) according to image data transmitted from the outside. A scanner or the like may be provided above the image forming apparatus 100.

First, the overall configuration of the image forming apparatus 100 will be described.
As shown in FIG. 1, the image forming apparatus 100 handles image data for each color component of black (K), cyan (C), magenta (M), and yellow (Y). An image and a yellow image are formed, and a color image is formed by superimposing the images of the respective color components.

  Accordingly, in the image forming apparatus 100, as shown in FIG. 1, the developing device 2 (2a, 2b, 2c, 2d) and the photosensitive drum 3 (3a, 3b, 3c) are formed so that images of the respective color components are formed. , 3d), four chargers 5 (5a, 5b, 5c, 5d) and four cleaner units 4 (4a, 4b, 4c, 4d). In other words, four image forming stations (image forming units) each including the developing device 2, the photosensitive drum 3, the charger 5, and the cleaner unit 4 are provided.

  The symbols a to d indicate that a is a member for forming a black image, b is a member for forming a cyan image, c is a member for forming a magenta image, and d is a member for forming a yellow image. It is a thing. Further, the image forming apparatus 100 includes an exposure unit 1, a fixing unit 12, a sheet conveyance path S, a paper feed tray 10, and a paper discharge tray 15.

The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential.
As the charger 5, a contact brush type charger or a non-contact charger type charger may be used in addition to the contact roller type charger shown in FIG.

  As shown in FIG. 1, the exposure unit 1 is a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror. However, in addition to the laser scanning unit, the exposure unit 1 may be an EL (electroluminescence) in which light emitting elements are arranged in an array or an LED writing head. The exposure unit 1 exposes the charged photosensitive drum 3 according to the input image data, thereby forming an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 3.

  The developing device 2 visualizes (develops) the electrostatic latent image formed on the photosensitive drum 3 with one of K, C, M, and Y toners. Above the developing device 2 (2a, 2b, 2c, 2d), there are a toner transfer mechanism 102 (102a, 102b, 102c, 102d), a toner replenishing device 22 (22a, 22b, 22c, 22d), a developing tank (developer). (Container) 111 (111a, 111b, 111c, 111d).

  The toner replenishing device 22 is disposed above the developing tank 111 and stores unused toner (powdered toner). The toner is supplied from the toner supply device 22 to the developing tank 111 via the toner transfer mechanism 102.

  The cleaner unit 4 removes and collects the toner remaining on the surface of the photosensitive drum 3 after the development and image transfer processes.

  An intermediate transfer belt unit 8 is disposed above the photosensitive drum 3. The intermediate transfer belt unit 8 includes an intermediate transfer roller 6 (6a, 6b, 6c, 6d), an intermediate transfer belt 7, an intermediate transfer belt driving roller 71, an intermediate transfer belt driven roller 72, an intermediate transfer belt tension mechanism 73, and an intermediate transfer. A belt cleaning unit 9 is provided.

  The intermediate transfer belt 6, the intermediate transfer belt drive roller 71, the intermediate transfer belt driven roller 72, and the intermediate transfer belt tension mechanism 73 stretch the intermediate transfer belt 7 and rotationally drive the intermediate transfer belt 7 in the direction of arrow B in FIG. It is something to be made.

  The intermediate transfer roller 6 is rotatably supported by an intermediate transfer roller mounting portion in the intermediate transfer belt tension mechanism 73 of the intermediate transfer belt unit 8. A transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 7 is applied to the intermediate transfer roller 6.

  The intermediate transfer belt 7 is provided so as to be in contact with each photosensitive drum 3. A color toner image (multicolor toner image) is formed on the intermediate transfer belt 7 by sequentially superimposing and transferring the toner images of the respective color components formed on the photosensitive drum 3. The intermediate transfer belt 7 is formed in an endless shape using a film having a thickness of, for example, about 100 μm to 150 μm.

  Transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 7 is performed by the intermediate transfer roller 6 in contact with the back side of the intermediate transfer belt 7. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 6 in order to transfer the toner image.

  The intermediate transfer roller 6 is formed based on a metal (for example, stainless steel) shaft having a diameter of, for example, 8 to 10 mm, and the surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, the intermediate transfer roller 6 can uniformly apply a high voltage to the intermediate transfer belt 7. In this embodiment, a roller-shaped transfer electrode (intermediate transfer roller 6) is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic latent images on the respective photosensitive drums 3 are visualized with toners corresponding to the respective color components to become toner images, and these toner images are superimposed and laminated on the intermediate transfer belt 7. As described above, the stacked toner images are moved to a contact position (transfer portion) between the conveyed paper and the intermediate transfer belt 7 by the rotation of the intermediate transfer belt 7, and the transfer roller disposed at this position is moved. 11 is transferred onto the paper. In this case, the intermediate transfer belt 7 and the transfer roller 11 are pressed against each other at a predetermined nip, and a voltage for transferring the toner image onto the sheet is applied to the transfer roller 11. This voltage is a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner.

  In order to obtain the nip constantly, either the transfer roller 11 or the intermediate transfer belt drive roller 71 is made of a hard material such as metal, and the other is a soft material such as an elastic roller (elastic rubber roller or foamable resin roller). Etc.).

  The toner adhering to the intermediate transfer belt 7 due to the contact between the intermediate transfer belt 7 and the photosensitive drum 3 and the toner image remaining on the intermediate transfer belt 7 without being transferred when the toner image is transferred from the intermediate transfer belt 7 to the sheet. The toner is removed and collected by the intermediate transfer belt cleaning unit 9 because it causes toner color mixing in the next step.

  The intermediate transfer belt cleaning unit 9 is provided with a cleaning blade (cleaning member) that contacts the intermediate transfer belt 7. The portion of the intermediate transfer belt 7 that is in contact with the cleaning blade is supported by the intermediate transfer belt driven roller 72 from the back side.

  The paper feed tray 10 is for storing sheets (for example, recording paper) used for image formation, and is provided below the image forming unit and the exposure unit 1. On the other hand, a paper discharge tray 15 provided in the upper part of the image forming apparatus 100 is for placing printed sheets face down.

  Further, the image forming apparatus 100 is provided with a sheet conveyance path S for guiding the sheet of the paper feed tray 10 and the sheet of the manual feed tray 20 to the paper discharge tray 15 via the transfer unit and the fixing unit 12. . The transfer unit is located between the intermediate transfer belt driving roller 71 and the transfer roller 11.

  Further, a pickup roller 16 (16a, 16b), a registration roller 14, a transfer unit, a fixing unit 12, a conveyance roller 25 (25a to 25h), and the like are arranged in the sheet conveyance path S.

  The conveyance rollers 25 are small rollers for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 25 are provided along the sheet conveyance path S. The pickup roller 16 a is a pull-in roller that is provided at the end of the paper feed tray 10 and supplies sheets one by one from the paper feed tray 10 to the sheet conveyance path S. The pickup roller 16 b is a drawing roller that is provided near the manual feed tray 20 and supplies sheets from the manual feed tray 20 to the sheet conveyance path S one by one. The registration roller 14 temporarily holds the sheet conveyed in the sheet conveyance path S, and conveys the sheet to the transfer unit at a timing when the leading edge of the toner image on the intermediate transfer belt 7 and the leading edge of the sheet are aligned.

  The fixing unit 12 includes a heat roller 81, a pressure roller 82, and the like. The heat roller 81 and the pressure roller 82 rotate with the sheet interposed therebetween. The heat roller 81 is controlled by a control unit (not shown) so as to have a predetermined fixing temperature. This control unit controls the temperature of the heat roller 81 based on a detection signal from a temperature detector (not shown).

  The heat roller 81 heat-presses the sheet together with the pressure roller 82 to melt, mix, and press the color toner images transferred to the sheet, and heat-fix the sheet. The sheet on which the multicolor toner image (each color toner image) is fixed is conveyed to the reverse sheet discharge path of the sheet conveyance path S by the plurality of conveyance rollers 25 and is reversed (the multicolor toner image is on the lower side). Are discharged onto the paper discharge tray 15.

Next, the sheet conveying operation by the sheet conveying path S will be described.
As shown in FIG. 1, the image forming apparatus 100 is provided with a paper feed tray 10 that stores sheets in advance and a manual feed tray 20 that is used when printing a small number of sheets as described above. Pickup rollers 16 (16a, 16b) are disposed on both trays, and the pickup rollers 16 supply sheets one by one to the sheet conveyance path S.

  In the case of single-sided printing, the sheet conveyed from the sheet feeding tray 10 is conveyed to the registration roller 14 by the conveyance roller 25a in the sheet conveyance path S, and is stacked on the leading edge of the sheet and the intermediate transfer belt 7 by the registration roller 14. Then, the toner image is conveyed to a transfer portion (contact position between the transfer roller 11 and the intermediate transfer belt 7) at a timing when the leading edge of the toner image is aligned. In the transfer portion, a toner image is transferred onto the sheet, and this toner image is fixed on the sheet by the fixing unit 12. Thereafter, the sheet is discharged onto the discharge tray 15 from the discharge roller 25c via the conveyance roller 25b.

  Further, the sheet conveyed from the manual feed tray 20 is conveyed to the registration roller 14 by a plurality of conveying rollers 25 (25f, 25e, 25d). Subsequent sheet conveyance operations are discharged to the sheet discharge tray 15 through a process similar to that for the sheets supplied from the sheet feed tray 10 described above.

  On the other hand, in the case of double-sided printing, the trailing edge of the sheet that has completed single-sided printing and passed through the fixing unit 12 as described above is chucked by the paper discharge roller 25c. Next, the sheet is guided to the conveying rollers 25g and 25h by the reverse rotation of the paper discharge roller 25c, and after the printing on the back surface is again performed through the registration roller 14, it is discharged to the paper discharge tray 15.

Next, the configuration of the toner supply device 22 of the present embodiment will be specifically described.
FIG. 2 is a cross-sectional view showing a schematic configuration of a toner replenishing device constituting the image forming apparatus according to the present embodiment, and FIG.

  As shown in FIG. 2, the toner supply device 22 includes a toner container 121, a toner stirring member 125, a toner discharge member 122, and a toner discharge port 123. The toner replenishing device 22 is disposed above the developing tank 111 and stores unused toner (powdered toner). The toner in the toner replenishing device 22 is supplied from the toner discharge port 123 to the developing tank 111 through the toner transfer mechanism 102 by rotating a toner discharge member (discharge screw) 122.

  The toner storage container 121 is a substantially semi-cylindrical container member having an internal space, and rotatably supports the toner stirring member 125 and the toner discharge member 122 to store the toner. The toner discharge port 123 is a substantially rectangular opening provided below the toner discharge member 122 and from the central portion in the axial direction, and is disposed at a position facing the toner transfer mechanism 102.

  The toner agitating member 125 rotates around the rotating shaft 125 a to draw up the toner in the toner container 121 and convey it to the toner discharge member 122 while agitating the toner accommodated in the toner container 121. And a toner pumping member 125b at the tip. The toner pumping member 125 b is made of a flexible polyethylene terephthalate (PET) sheet and is attached to both ends of the toner stirring member 125.

  The toner discharge member 122 supplies the toner in the toner container 121 from the toner discharge port 123 to the developing tank 111. As shown in FIG. 3, the toner discharge member 122 includes an auger including a toner transport blade 122a and a toner discharge member rotating shaft 122b. A screw and a toner discharge member rotating gear 122c are included. The toner discharge member 122 is rotationally driven by a toner discharge member drive motor (not shown). The direction of the auger screw is set so that the toner is conveyed from both ends in the axial direction of the toner discharge member 122 toward the toner discharge port 123.

  A toner discharge member partition wall 124 is provided between the toner discharge member 122 and the toner stirring member 125. Accordingly, the toner pumped up by the toner stirring member 125 can hold an appropriate amount of toner around the toner discharge member 122.

  As shown in FIG. 2, the toner stirring member 125 rotates in the direction of arrow Z, stirs the toner, and pumps the toner toward the toner discharge member 122. At this time, the toner scooping member 125b rotates and slides along the inner wall of the toner container 121 due to its flexibility, and supplies the toner to the toner discharge member 122 side. The supplied toner is guided to the toner discharge port 123 by the rotation of the toner discharge member 122.

Next, the characteristic developing device 2 of the present embodiment will be described with reference to the drawings.
4 is a cross-sectional view showing the configuration of the developing device constituting the image forming apparatus according to the present embodiment, FIG. 5 is a cross-sectional view taken along the line AA in FIG. 4, and FIG. 6 is a cross-sectional view taken along the line BB in FIG. It is.

  As shown in FIG. 4, the developing device 2 has a developing roller 114 disposed in the developing tank 111 so as to face the photosensitive drum 3, and the developing roller 114 applies toner to the surface of the photosensitive drum 3. The apparatus supplies and develops (develops) the electrostatic latent image formed on the surface of the photosensitive drum 3.

  In addition to the developing roller 114, the developing device 2 includes a developing tank 111, a developing tank cover 115, a toner supply port 115a, a doctor blade 116, a first conveying member 112, a second conveying member 113, a partition plate (partition wall) 117, A magnetic permeability sensor 119 is provided.

  The developing tank 111 is a tank for storing a two-component developer containing toner and carrier (hereinafter simply referred to as “developer”). The developing tank 111 is provided with a developing roller 114, a first conveying member 112, a second conveying member 113, and the like. Note that the carrier of this embodiment is a magnetic carrier having magnetism.

  A removable developer tank cover 115 is provided on the upper side of the developer tank 111 as shown in FIGS. Further, the developing tank cover 115 is provided with a toner supply port 115a for supplying unused toner to the preliminary stirring unit 115b in the developing tank 111.

  In the developing tank 111, a partition plate 117 is disposed between the first transport member 112 and the second transport member 113. The partition plate 117 extends in parallel with each axial direction (each rotational axis direction) of the first transport member 112 and the second transport member 113. The interior of the developing tank 111 is partitioned by a partition plate 117 into a first transport path P in which the first transport member 112 is disposed and a second transport path Q in which the second transport member 113 is disposed.

  The partition plate 117 is disposed away from the inner wall surface of the developing tank 111 at both axial ends of the first transport member 112 and the second transport member 113. Thereby, in the developing tank 111, a communication path that connects the first transport path P and the second transport path Q is formed in the vicinity of both axial ends of the first transport member 112 and the second transport member 113. ing. In the following, as shown in FIG. 5, the communication path formed on the arrow X direction side is referred to as a first communication path a, and the communication path formed on the arrow Y direction side is referred to as a second communication path b.

  The first transport member 112 and the second transport member 113 are arranged in parallel so that their peripheral surfaces face each other via the partition plate 117 and their axes are parallel to each other, and rotate in opposite directions. Is set to As shown in FIG. 5, the first transport member 112 transports the two-component developer in the arrow X direction, and the second transport member 113 transports the developer in the arrow Y direction opposite to the arrow X direction. It is set to be.

  As shown in FIG. 5, the first transport member 112 includes a screw auger including a spiral first transport blade 112a and a first rotating shaft 112b, and a gear 112c. As shown in FIG. 5, the second transport member 113 includes a screw auger including a spiral second transport blade 113a and a second rotating shaft 113b, and a gear 113c. The first transport member 112 and the second transport member 113 are rotated and driven by a driving unit (not shown) such as a motor to stir and transport the developer.

  Further, as shown in FIG. 6, the first conveying member 112 has an angle formed by the first rotating shaft 112 b axis and the outer periphery of the first conveying blade 112 a when the first rotating shaft 112 b is viewed from the vertical direction, that is, The inclination angle θ of the spiral blade is 30 degrees or more and 60 degrees or less.

  Specifically, when the inclination angle θ of the spiral blade of the first conveying member 112 is not less than 30 degrees and not more than 60 degrees, the developer is replenished because the force for stirring the developer in the rotation direction of the first conveying member 112 is strong. “Floating toner” that is conveyed while the toner floats on the developer is less likely to occur. Accordingly, the toner concentration of the developer can be accurately detected by the magnetic permeability sensor 119 even after the toner is replenished.

  On the other hand, when the inclination angle θ of the spiral blade is less than 30 degrees, the developer transport speed by the first transport member 112 is decreased, so that the developer is quickly worn. When the inclination angle θ of the spiral blade exceeds 60 degrees, the developer transport speed by the first transport member 112 becomes too fast, and thus floating toner is likely to be generated.

  The developing roller 114 is a magnet roller that is rotationally driven around a shaft center by a driving unit (not shown). The developer in the developing tank 111 is pumped and carried on the surface, and toner contained in the developer carried on the surface is photosensitive. This is supplied to the body drum 3.

  The developer conveyed by the developing roller 114 comes into contact with the photosensitive drum 3 at the closest portion. This contact area is the development nip N, and a development bias voltage is applied to the development roller 114 from a power source (not shown) connected to the development roller 114, and the developer on the surface of the development roller 114 is exposed to light. Toner is supplied to the electrostatic latent image on the surface of the body drum 3.

  A doctor blade (layer thickness regulating blade) 116 is disposed at a position close to the surface of the developing roller 114.

  The doctor blade 116 is a plate-like member that extends parallel to the axial direction of the developing roller 114. One end in the short direction is supported by the developing tank 111 and the other end is the developing roller below the developing roller 114 in the vertical direction. 114 is provided to be separated from the surface with a gap. As the material of the doctor blade 116, stainless steel can be used, but aluminum or synthetic resin can also be used.

  As shown in FIGS. 4 and 6, the magnetic permeability sensor 119 includes a second conveying member 113 in the preliminary agitating unit 115 b near the toner supply port 115 a and downstream of the developer conveying direction (arrow Y direction) below. Is attached to the bottom surface of the developing tank 111 on the lower side in the vertical direction, that is, the bottom surface of the second transport path Q, and is provided so that the detection surface 119 a is exposed to the inside of the developing tank 111.

  Further, the magnetic permeability sensor 119 is electrically connected to a toner concentration control means (not shown). The magnetic permeability sensor 119 in the present embodiment can be replaced with a general toner concentration detection sensor, for example, a transmitted light detection sensor, a reflected light detection sensor, and the like. Among these, the magnetic permeability detection sensor is preferable.

  A power supply (not shown) is connected to the magnetic permeability detection sensor. The power source applies a drive voltage for driving the magnetic permeability detection sensor and a control voltage for outputting a detection result of the toner density to the control means. Application of a voltage to the magnetic permeability detection sensor by the power source is controlled by the control means. The permeability detection sensor is a type of sensor that receives the control voltage and outputs the toner density detection result as an output voltage value. Basically, the sensitivity near the median value of the output voltage is good. It is used by applying a control voltage to obtain a voltage. Such type of magnetic permeability detection sensors are commercially available, and examples thereof include TS-L, TS-A, TS-K (all are trade names, manufactured by TDK Corporation) and the like.

Next, the conveyance of the developer in the developing tank of the developing device 2 will be described.
As shown in FIG. 4, the toner accommodated in the toner replenishing device 22 is transferred into the developing tank 111 through the toner transfer mechanism 102 and the toner replenishing port 115a, and thereby the toner is supplied to the developing tank 111. .

  In the developing tank 111, the first transport member 112 and the second transport member 113 are rotationally driven by a driving means (not shown) such as a motor to transport the developer. Specifically, in the first transport path P, the developer is transported in the arrow X direction while being stirred by the first transport member 112 and reaches the first communication path a. The developer that has reached the first communication path a passes through the first communication path a and is conveyed to the second conveyance path Q.

On the other hand, in the second transport path Q, the developer is transported in the direction of the arrow Y while being stirred by the second transport member 113 and reaches the second communication path b. Then, the developer that has reached the second communication path b passes through the second communication path b and is conveyed to the first conveyance path P.
That is, the first transport member 112 and the second transport member 113 transport the developer in the opposite directions while stirring the developer.

  In this way, the developer passes through the first conveyance path P, the first communication path a, the second conveyance path Q, and the second communication path b in the developing tank 111 from the first conveyance path P to the first communication path. Circulating movement is performed in the order of a → second conveyance path Q → second communication path b. Then, while the developer is being conveyed in the second conveyance path Q, the developer is carried on the surface by the rotation of the developing roller 114 and pumped up, and the toner in the developer that has been pumped up is transferred to the photosensitive drum 3. It moves and is consumed sequentially.

  In order to make up for the consumed toner, unused toner is replenished from the toner replenishing port 115a to the second transport path Q. The replenished toner is mixed and agitated with the existing developer while circulating in the order of the second conveyance path Q → second communication path b → first conveyance path P → first communication path a. . Thereafter, the developer mixed with unused toner is transported again to the second transport path Q, carried on the surface of the developing roller 114, and pumped up.

Next, the configuration of the characteristic magnetic permeability sensor 119 and the second conveying member 113 in the developing device 2 in the present embodiment will be described with reference to the drawings.
FIG. 7 is an explanatory diagram showing a configuration of a magnetic permeability sensor and a second conveying member provided in the developing tank of the developing device according to the present embodiment.

  According to the developing device 2 of the present embodiment, as shown in FIG. 7, the detection surface 119 a of the magnetic permeability sensor 119 and its periphery face the second conveying member 113 with respect to the bottom surface of the developing tank 111. And a distance (hereinafter referred to as “projection distance”) δ1.

  In general, as a feature of the developing device using a spiral blade, also in this embodiment, the ability to transport the developer becomes weaker as the distance from the second transport blade 113a increases. In particular, the developer tends to stay on the bottom surface of the developing tank 111. Therefore, by causing the detection surface 119a of the magnetic permeability sensor 119 to protrude from the bottom surface of the developing tank 111, the detection surface 119a of the magnetic permeability sensor 119 is disposed at a position away from the bottom surface where the developer is stably conveyed. Therefore, the influence on the sensor output due to the retention of the developer described above can be suppressed.

  In this embodiment, the protrusion distance δ1 around the detection surface 119a of the magnetic permeability sensor 119 is detected by the magnetic permeability sensor 119 in order to effectively suppress the retention of the developer on the detection surface 119a of the magnetic permeability sensor 119. It is preferable that the distance between the second conveying blade 113a and the bottom surface of the developing tank 111 other than the periphery of the surface 119a (hereinafter referred to as “gap distance”) δ0 is larger.

  According to the developing device 2 of the present embodiment, the gap distance δ0 is set to 0.5 mm, the protrusion distance δ1 is set to 0.5 mm or more (preferably about 0.5 to 2 mm), and the magnetic permeability sensor. It was confirmed that when the 119 was arranged, a decrease in the reliability of the sensor output could be effectively suppressed.

  Further, according to the developing device 2 of the present embodiment, the second conveying member 113 is arranged in FIG. 7 so that physical contact between the vicinity of the detection surface 119a of the magnetic permeability sensor 119 and the second conveying blade 113a does not occur. As shown, the outer diameter of the second conveying blade 113a is reduced by the length δ2 only in the spiral blade (hereinafter referred to as “opposing spiral blade”) 113a1 at a position facing the protruded portion.

In the present embodiment, the gap distance δ0 is set between the second conveyance blade 113a and the bottom surface of the developing tank 111 in consideration of touch and bending during rotation driving of the second conveyance member 113.
In addition, it is preferable that the gap distance δ3 between the opposing spiral blade 113a1 is set to be δ0 or more also around the detection surface 119a of the magnetic permeability sensor 119. Therefore, it is preferable that the length δ2 is equal to or larger than the protrusion distance δ1.

  Here, when the length δ2 is excessively increased, that is, when the outer diameter of the opposing spiral blade 113a1 is excessively decreased, the developer transport capability is locally reduced at this position, so that the developer transport described above is performed. This affects the circulation of the developer in the entire path. In order to suppress such a problem, the length δ2 is preferably smaller than one third of the outer diameter φ of the second conveying blade 113a.

  According to the developing device 2 of the present embodiment, the outer diameter φ of the second conveying blade 113a is set to 14.0 mm, and the length δ2 of the second conveying blade 113a is one third of the outer diameter φ. It was confirmed that by making it smaller than 4.7 mm, the developer circulation in the entire developer conveyance path was not affected.

As a comparative example of the present embodiment, when the periphery of the detection surface 119a of the magnetic permeability sensor 119 is projected at an angle close to a right angle, development is performed on a dead angle portion between the protruding portion and the non-projecting portion (around the base portion of the protruding portion) It was confirmed that the developer stays at the protruding position or the developer conveying speed becomes slow at the protruding position.
In such a case, the effect of stabilizing the developer density on the detection surface 119a by projecting the periphery of the detection surface 119a of the magnetic permeability sensor 119 is reduced.

  In order to suppress the above problem, according to the developing device 2 of the present embodiment, an inclination having an inclination angle (gradient) α from the bottom surface of the developing tank 111 with respect to the periphery of the protruding detection surface 119a of the magnetic permeability sensor 119. A portion 111a is provided. The inclination angle α is preferably 5 ° or more and less than 60 °.

  Accordingly, the transmittance sensor 119 can satisfactorily sense the state of the developer conveyed by the second conveying blade 113a, and the developer conveyed even when a toner film or other foreign matter adheres to the detection surface 119a. Scraping / removing effect can be expected, so that stable sensing can be performed without causing trouble.

  With the configuration described above, according to the present embodiment, in the developing device 2 of the image forming apparatus 100, the magnetic permeability sensor 119 is opposed to the second conveying blade 113 a of the second conveying member 113 in the developing tank 111. It arrange | positions in the position so that the detection surface 119a periphery may protrude rather than the detection surface 119a periphery, and as a structure of a 2nd conveyance member, the 2nd conveyance blade 113a is the opposing spiral blade 113a1 in the position which opposes the detection surface 119a periphery. Is configured to be smaller than the outer diameter of the second conveying blade 113a at a position not facing the periphery of the detection surface 119a, and the protruding distance δ1 from the inner wall surface of the developing tank 111 around the detection surface 119a of the magnetic permeability sensor 119. Is configured to be larger than the gap distance δ0 between the second conveying blade 113a and the inner wall surface of the developing tank 111 outside the periphery of the detection surface 119a. Even if it is arranged so that the periphery of the 19 detection surfaces 119a protrudes, a safe gap is provided between the second conveying member 113 and the second conveying blade 113a. Even if bending occurs, physical contact with the detection surface 119a can be prevented, and the developer that is circulated and conveyed can be prevented from staying on the detection surface 119a. Thereby, since the density change of the developer does not occur, a highly reliable sensor output can be obtained without reducing the correlation coefficient with respect to the toner density.

  In the above-described embodiment, the example in which the developing device 2 according to the present invention is applied to the image forming apparatus 100 as shown in FIG. 1 has been described. However, the toner concentration of the developer stirred in the developing tank 111 is transparent. As long as the image forming apparatus uses the developing device 2 that is detected by the magnetic sensor 119, the image forming apparatus is not limited to the image forming apparatus and the copying machine having the above-described configuration. Is possible.

  As described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope not departing from the gist of the present invention are also included in the technical scope of the present invention.

1 Exposure unit (exposure equipment)
2 Developing device 3 Photosensitive drum 5 Charger (charging device)
8 Intermediate transfer belt unit (transfer device)
12 Fixing unit (fixing device)
22 Toner supply device 100 Image forming device 111 Developer tank (developer container)
111a Inclined portion 112 First conveying member (developer conveying member)
113 Second conveying member (developer conveying member)
113a Second conveying blade 113a1 Opposing spiral blade 115a Toner replenishing port 115b Pre-stirring section 119 Magnetic permeability sensor 119a Detection surface P First conveying path Q Second conveying path α Inclination angle δ0 Gap distance δ1 Projection distance δ2 Length δ3 Gap distance

Claims (4)

A developer containing portion for containing a developer containing toner and a magnetic carrier; a developer carrying path for carrying the developer in the developer containing portion; and the development provided in the developer carrying path. A developer agitating and conveying member that conveys the developer in a predetermined direction while stirring the developer, a developing roller that carries the developer in the developer conveying path and supplies toner contained in the developer to the photosensitive drum, and the developer In a developing device including a magnetic permeability sensor that detects a toner concentration of a developer in a conveyance path,
The magnetic permeability sensor is disposed at a position facing the developer agitating and conveying member in the developer accommodating portion so that the periphery of the detection surface protrudes more than the periphery of the detection surface,
The developer stirring and conveying member is configured such that an outer diameter of the developer stirring and conveying member at a position facing the periphery of the detection surface is smaller than an outer diameter of a position not facing the detection surface and the periphery.
The protrusion distance from the inner wall surface of the developer accommodating portion around the detection surface of the magnetic permeability sensor is larger than the gap distance between the developer agitating and conveying member and the inner wall surface of the developer accommodating portion outside the periphery of the detection surface. A developing device having a large structure.   The difference between the outer diameter of the developer stirring and conveying member at a position facing the periphery of the detection surface of the magnetic permeability sensor and the outer diameter of the developer stirring and conveying member at a position other than the position facing the periphery of the detecting surface is determined by the detection surface. The developing device according to claim 1, wherein the developing device is smaller than one third of the outer diameter of the developer agitating and conveying member at a position other than a position facing the periphery.   The inclined portion having an inclination angle of 5 ° or more and less than 60 ° from the vicinity of the protruding detection surface of the magnetic permeability sensor to the inner wall surface of the developer containing portion is provided. Development device. A photosensitive drum on which an electrostatic latent image is formed, a charging device for charging the surface of the photosensitive drum, an exposure device for forming an electrostatic latent image on the surface of the photosensitive drum, and an electrostatic latent image on the surface of the photosensitive drum A developing device for supplying toner to the image to form a toner image, a transfer device for transferring the toner image on the surface of the photosensitive drum to a recording medium, and a fixing device for fixing the transferred toner image to the recording medium, In an image forming apparatus that forms an image using toner by electrophotography,
An image forming apparatus using the developing device according to claim 1 as the developing device.

Images