JP2010175944A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of suppressing density variation of a conveyed developer without reducing conveyance properties of the developer and suppressing the fluctuation of a magnetic permeability sensor output, and an image forming apparatus using the developing device. <P>SOLUTION: In the developing device 2 including a development tank 111 storing the 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 supplying toner to a photoreceptor drum 3, and a toner density detection sensor 119 detecting the toner density of the developer in the development tank 111, the second conveyance member 113 comprises an auger screw including a single spiral blade 113aa with a single spiral structure and a double spiral blade 113ab with a double spiral structure. The outer diameter of the double spiral blade 113ab is smaller than that of the single spiral blade 113aa, and the toner density detection sensor 119 is arranged at a position facing the double spiral blade 113ab. <P>COPYRIGHT: (C)2010,JPO&INPIT

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. The developer is composed of toner and carrier, and the toner and the 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 quickly transport 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 system in which a circulation type developing device including a conveyance path and two developer stirring members that convey the developer while stirring the developer in the developer conveyance path is mounted (see Patent Document 1). ).

JP-A-2005-24592

  However, in the above-described developing device, a magnetic permeability sensor is generally used to detect the toner concentration of the developer in the developing tank. However, if an auger screw having spiral blades is used as a developer conveying member, the sensor output There was a problem that became unstable.

  This is considered to be because the output value of the magnetic permeability sensor changes due to the local change in the density of the developer passing on the detection surface of the magnetic permeability sensor. That is, when the developer is transported by an auger screw, the pressure applied to the developer is high near the spiral blade and low near the spiral blade, so the density of the developer depends on the local pressure fluctuation. It is considered that it varies locally and causes variations in the permeability sensor output.

  The present invention has been made in view of the above-described conventional problems, and can suppress changes in the density of the developer being conveyed without deteriorating the developer conveyance performance, and variations in the permeability sensor output. An object of the present invention is to provide a developing device capable of suppressing the above and an image forming apparatus 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 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; In the developing device including a magnetic permeability sensor for detecting the toner concentration of the developer in the developer transport path, the developer transport member includes a rotating shaft and a spiral blade provided on an outer periphery of the rotating shaft. An auger screw is provided, and the spiral blade includes a single spiral blade having a single spiral structure and a multiple spiral blade having a multiple spiral structure, and an outer diameter of the multiple spiral blade is defined by the single spiral blade. Formed smaller than the outer diameter The magnetic permeability sensor, is characterized in that the arrangement in the multi-spiral blade facing position.

  In the present invention, it is preferable that the spiral pitch of the multiple spiral blades is formed at the same pitch as the spiral pitch of the single spiral blade.

  In the present invention, it is preferable that the multiple spiral blade is formed such that one spiral blade of the multiple spiral blades constituting the multiple spiral blade is continuous with the single spiral blade.

  In the present invention, it is preferable that the outer diameter of the multiple spiral blade be 0.8 to 0.9 times the outer diameter of the single spiral blade.

  In the present invention, it is preferable that the multiple spiral blades are provided so that the phase differences of all adjacent spiral blades are equal.

  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 electrophotography, wherein the developing device according to any one of claims 1 to 5 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 A developer conveying member which is provided on the developer conveying member in a predetermined direction while stirring the developer, and a developing roller which 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 a toner concentration of the developer in the developer transport path, wherein the developer transport member includes a rotation shaft, and a spiral blade provided on an outer periphery of the rotation shaft. The spiral blade includes a single spiral blade having a single spiral structure and a multiple spiral blade having a multiple spiral structure, and the outer diameter of the multiple spiral blade is defined by the single spiral. Smaller than the outer diameter of the blade The magnetic permeability sensor is disposed at a position facing the multiple spiral blades, thereby providing a gap between the outer peripheral tip of the multiple spiral blades and the magnetic permeability sensor, thereby transporting the developer. Without reducing the performance, it is possible to suppress the density change of the developer that occurs when the outer peripheral tip of the multiple spiral blade passes over the detection surface of the magnetic permeability sensor, and as a result, the output of the magnetic permeability sensor Can be suppressed.

  Further, according to the present invention, the spiral pitch of the multiple spiral blades is formed at the same pitch as the spiral pitch of the single spiral blade, so that the vicinity of the magnetic permeability sensor can be reduced without reducing the developer transportability. Since the developer can be conveyed, it is possible to suppress a change in the density of the developer that occurs when the outer peripheral tip of the multiple spiral blade passes over the detection surface of the magnetic permeability sensor.

  Further, according to the present invention, the multiple spiral blade is formed such that one spiral blade of the plurality of spiral blades constituting the multiple spiral blade is continuously formed with the single spiral blade. Since no discontinuity occurs between the spiral blade and the single spiral blade, the occurrence of irregular turbulence can be suppressed, and variations in the output of the magnetic permeability sensor can be suppressed.

  Also, according to the present invention, the outer diameter of the multiple spiral blade is formed to be 0.8 times or more and 0.9 times or less than the outer diameter of the single spiral blade, thereby reducing developer transportability. Therefore, pressure unevenness can be reduced. When the outer diameter of the multiple spiral blade is less than 0.8 times the outer diameter of the single spiral blade, the developer transportability is reduced and turbulence is likely to occur, and the sensitivity of the magnetic permeability sensor. Variations are likely to occur. Conversely, when the outer diameter of the multiple spiral blade exceeds 0.9 times the outer diameter of the single spiral blade, the density change of the developer tends to occur.

  Further, according to the present invention, the multiple spiral blades are arranged so that all adjacent spiral blades have the same phase difference, for example, 180 degrees for a double spiral blade and 120 degrees for a triple spiral blade. By providing in this way, the intervals between the plurality of spiral blades forming the multiple spiral blades are constant, so that the developer conveyance speed is stabilized and variations in the output of the magnetic permeability sensor can be suppressed.

  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 an electrophotographic method, wherein the developing device according to any one of claims 1 to 5 is used as the developing device. Thus, the developer can be transported without degrading the transportability, and the density change of the transported developer can be suppressed, so that the toner density of the developer can be controlled with high accuracy, so that a stable image density can be obtained. obtain Door can be.

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.

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 includes 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 illustrating a schematic configuration of a toner replenishing device constituting the image forming apparatus according to the present embodiment, and FIG. 3 is a cross-sectional view taken along a line CC in 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 toner concentration detection sensor (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.

  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 developing roller 114 is provided so as to face the photosensitive drum 3 and be separated from the photosensitive drum 3 with a gap. 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 116 is disposed at a position close to the surface of the developing roller 114. The doctor blade 116 is a rectangular plate-like member that extends parallel to the axial direction of the developing roller 114, one end 116 b in the short direction is supported by the developing tank cover 115, and the tip 116 a is against the surface of the developing roller 114. It is provided so as to be separated 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 FIG. 5, the first conveying member 112 includes an auger screw including a spiral first conveying blade 112a and a first rotating shaft 112b, and a gear 112c. As shown in FIG. 5, the second transport member 113 includes an auger screw composed of 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.

  The second conveying blade 113a includes a single spiral blade 113aa spirally provided on the outer periphery of the second rotating shaft 113b, and a double spiral blade 113ab that is smaller in diameter and forms a double spiral structure. .

  As shown in FIGS. 5 and 6, the double spiral blade 113ab is composed of two spiral blades 113ab1 and 113ab2, and a toner concentration detection sensor 119 is disposed at a substantially central portion of the second transport path Q in the developer transport direction. It is provided at an opposing position.

  The single spiral blade 113aa and the double spiral blade 113ab are both formed at the same spiral pitch. Of the two spiral blades 113ab1 and 113ab2 forming the double spiral blade 113ab, one spiral blade 113ab1 is 1 It is configured to be continuous with the heavy spiral blade 113aa.

  The ratio of the diameter of the double spiral blade 113ab to the single spiral blade 113aa is preferably 0.8 or more and 0.9 or less. In the present embodiment, the outer diameter of the double spiral blade 113ab is 0.9 times the outer diameter of the single spiral blade 113aa.

  Incidentally, if the ratio of the diameter of the double spiral blade 113ab to the single spiral blade 113aa is less than 0.8, the transportability tends to be lowered, and conversely if the ratio of the diameter exceeds 0.9, the toner concentration detection sensor 119. Above, the pressure fluctuation of the developer tends to occur.

  The two spiral blades 113ab1 and 113ab2 forming the double spiral blade 113ab are formed with a phase difference of 180 degrees. In the present embodiment, the phase difference means that one spiral blade (for example, the spiral blade 113ab1) of the two spiral blades 113ab1 and 113ab2 forming the double spiral blade 113ab from the upstream side in the developer transport direction. The angle when the other spiral blade (for example, the spiral blade 113ab2) overlaps when rotated in the clockwise direction while seeing the axial direction of the two rotation shaft 113b.

  The toner concentration detection sensor 119 is mounted at a substantially central portion in the developer conveying direction on the bottom surface of the developing tank 111 below the second conveying member 113 in the vertical direction, and is provided so that the sensor surface is exposed inside the developing tank 111. The toner concentration detection sensor 119 is electrically connected to a toner concentration control means (not shown). As shown in FIG. 3, the toner concentration control means rotates the toner discharge member 122 in accordance with the toner concentration measurement value detected by the toner concentration detection sensor 119, and enters the developing tank 111 through the toner discharge port 123. Control to supply toner.

  If it is determined that the toner density measurement value by the toner density detection sensor 119 is lower than the toner density setting value, a control signal is sent to the driving means for driving the toner discharge member 122 to rotate, and the toner discharge member 122 is driven to rotate. As the toner concentration detection sensor 119, a general toner concentration detection sensor can be used, and examples thereof include a transmitted light detection sensor, a reflected light detection sensor, and a magnetic permeability detection sensor. Among these, a magnetic permeability detection sensor is preferable.

  A power supply (not shown) is connected to the magnetic permeability detection sensor. The power supply applies a drive voltage for driving the magnetic permeability detection sensor and a control voltage for outputting the 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.

  Further, as shown in FIG. 4, a removable developer tank cover 115 is provided on the upper side of the developer tank 111. Further, the developing tank cover 115 is provided with a toner supply port 115 a for supplying unused toner into the developing tank 111.

  As shown in FIG. 1, the toner stored in the toner replenishing device 22 is transferred into the developing tank 111 via the toner transfer mechanism 102 and the toner replenishing port 115a, whereby the toner is supplied to the developing tank 111. It has come to be.

  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 Then, as shown in FIG. 5, the first transport member 112 transports the 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. Is set to

  The toner replenishing port 115a is a region in the first conveyance path P and is formed at a position on the arrow X direction side from the second communication path b. That is, in the first transport path P, the toner is replenished downstream of the second communication path b.

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 to the first transport path P from the toner replenishing port 115a. The replenished toner is mixed and stirred with the developer existing in the first conveyance path P.

  Next, the operation of the developing device 2 according to this embodiment when the developer is conveyed will be described with reference to the drawings.

  According to the developing device 2 of the present embodiment, as shown in FIG. 5, the developer in the developing tank 111 is moved in the direction of arrow X in the first transport path P by the first transport member 112 and the second transport member 113. In the second conveyance path Q, the sheet is conveyed in the arrow Y direction.

  At this time, the developer is stirred and conveyed by the single spiral blade 113aa and the double spiral blade 113ab of the second transport member 113 in the second transport path Q. Specifically, the developer is conveyed by the single spiral blade 113aa on the upstream side in the developer conveyance direction in the second conveyance path Q, that is, on the upstream side of the toner concentration detection sensor 119.

  In addition, the developer is transported by the double spiral blade 113ab in a substantially central portion of the second transport path Q in the developer transport direction, that is, in the vicinity of the toner concentration detection sensor 119.

  Further, on the downstream side in the developer conveyance direction in the second conveyance path Q, that is, on the downstream side of the toner concentration detection sensor 119, the developer is conveyed by the single spiral blade 113aa as in the upstream side.

  In other words, in the vicinity of the toner concentration detection sensor 119 at the substantially central portion in the developer conveyance direction in the second conveyance path Q, the developer uses two spiral blades 113ab to form two spirals of one spiral blade 113aa. The blades 113ab1 and 113ab2 are subdivided and conveyed by stirring.

  Furthermore, since the outer diameter of the double spiral blade 113ab is smaller than the outer diameter of the single spiral blade 113aa, the second conveying member 112 has an outer peripheral front end portion of the double spiral blade 113ab and a toner concentration detection sensor 119. The developer can be stirred and conveyed without deteriorating the developer conveyance performance.

  Therefore, according to the developing device 2 of the present embodiment, the developer is stirred and conveyed by the double spiral blade 113ab while suppressing a change in the density of the developer without degrading the developer conveying property.

  Since it comprised as mentioned above, according to this embodiment, in the developing device 2, as a structure of the 2nd conveyance member 113, the single spiral blade 113aa of a single spiral structure and the double spiral blade of a double spiral structure 113ab, the outer diameter of the double spiral blade 113ab is smaller than the outer diameter of the single spiral blade 113aa, and the double spiral blade 113ab is disposed at a position facing the toner concentration detection sensor 119. A gap is provided between the outer peripheral tip of the double spiral blade 113ab and the toner concentration detection sensor 119, so that the outer peripheral tip of the double spiral blade 113ab does not deteriorate the developer transportability. It is possible to suppress the density change of the developer that occurs when passing over the detection surface. As a result, it is possible to perform stable density measurement while suppressing variations in the output of the toner density detection sensor 119.

  Therefore, according to the image forming apparatus 100 of this embodiment, the toner density of the developer can be controlled with high accuracy, so that a stable image density can be obtained.

  In the present embodiment, the second conveying member 113 includes a single spiral blade 113aa and a double spiral blade 113ab configured by two spiral blades 113ab1 and 113ab2. However, the present invention provides a developer. As long as multiple spiral blades are used for the configuration of the conveying member, the invention is not limited to this. For example, a triple spiral blade composed of three spiral blades is used instead of the double spiral blade 113ab. May be. This triple spiral blade is preferably provided at 120 degrees so that the phase differences of all adjacent spiral blades are equal.

  With this configuration, the interval between the three spiral blades forming the triple spiral blade is constant, so that the developer conveyance speed is stabilized and the toner density detection sensor ( Variation in the output of the magnetic permeability sensor) 119 can be suppressed.

  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 changed to the toner. The image forming apparatus using the developing device 2 that is detected by the density detection sensor 119 is not limited to the image forming apparatus and the copying machine having the above-described configuration, and can be developed to other image forming apparatuses. 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)
112 First conveying member (developer conveying member)
113 Second conveying member (developer conveying member)
113a Second conveying blade 113aa Single spiral blade 113ab Double spiral blade (multiple spiral blade)
113ab1, 113ab2 Spiral blade 119 Toner concentration detection sensor (permeability sensor)
P 1st conveyance path Q 2nd conveyance path

Claims (6)

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 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 conveying A developing device including a magnetic permeability sensor for detecting a toner concentration of a developer in a path;
The developer conveying member is composed of an auger screw including a rotating shaft and a spiral blade provided on the outer periphery of the rotating shaft,
The spiral blade includes a single spiral blade having a single spiral structure and a multiple spiral blade having a multiple spiral structure, and an outer diameter of the multiple spiral blade is smaller than an outer diameter of the single spiral blade,
The developing device according to claim 1, wherein the magnetic permeability sensor is disposed at a position facing the multiple spiral blades.   The developing device according to claim 1, wherein a spiral pitch of the multiple spiral blades is the same as a spiral pitch of the single spiral blade.   3. The multi-spiral blade according to claim 1, wherein one of the plurality of spiral blades constituting the multi-spiral blade is formed continuously with the single spiral blade. Development device.   4. The outer diameter of the multiple spiral blade is formed to be 0.8 to 0.9 times the outer diameter of the single spiral blade. 5. The developing device described.   The developing device according to claim 1, wherein the multiple spiral blades have the same phase difference between all adjacent spiral blades. 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.