JP2010038939A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of reducing toner scattering and image fogging by suppressing toner which is not sufficiently electrified from being supplied to a developing roller, in the developing device and to provide an image forming apparatus using the developing device. <P>SOLUTION: The developing device 2 includes: a developing tank 111 storing a developer D including a toner and a magnetic carrier; a first conveying path P and a second conveying path Q in which the developer D is conveyed; a first conveying member 112 provided in the first conveying path P and conveying the developer D, while stirring it; a second conveying path 113 provided in the second conveying path Q and conveying the developer D, while stirring it; and a toner replenishing port 118 for replenishing the toner to the first conveying path P. In the developer device 2, the first conveying member 112 and the second conveying member 113 are provided with spiral blades 112a and 113a conveying the developer and the spiral blades 112a and 113a are formed so that a spiral pitch may be periodically changed. <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.

  This 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.

  Furthermore, recently, there has been a demand for speeding up and downsizing of an image forming apparatus, and it has become necessary to quickly and sufficiently charge the developer and to quickly transport the developer.

In view of this, in the image forming apparatus, a circulation type developing device is employed in order to instantly disperse the replenished toner in the developer and impart an appropriate charge amount. The circulation type developing device includes a developer conveying path that is a path through which the developer is circulated and a developer conveying member that conveys the developer while stirring the developer in the developer conveying path (Patent Document 1). See).
JP-A-10-63081

  In the above-described circulation type developing device, when the toner concentration of the developer in the developing device falls below a predetermined value, the toner is supplied from the toner hopper to the developer conveying path.

  However, since the specific gravity of the toner of the developer is considerably smaller than the specific gravity of the carrier (about 1/3), the replenished toner easily floats on the developer. When the amount of replenished toner replenished from the toner hopper to the developer conveyance path is large, there is a problem that the toner is conveyed in a lump on the developer.

  As a result, a situation has occurred in which toner that is not sufficiently mixed with the carrier (a lowly charged toner that is not sufficiently charged) is supplied to the developing roller.

  That is, if toner that is not sufficiently charged is supplied to the developing roller, the toner easily scatters from the developing roller, causing a problem that the image forming apparatus and an image formed on the sheet are stained.

  Further, if toner that is not sufficiently charged is supplied to the developer carrying member, the electrostatic force for holding the toner on the carrier surface is reduced, and the toner adheres to the non-image area and is likely to be fogged. The problem arises.

  The present invention has been made in view of the above-described conventional problems. In the developing device, toner that is not sufficiently charged is prevented from being supplied to the developing roller, thereby reducing toner scattering and image fogging. An object of the present invention is to provide a developing device capable of performing 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 provides a developer containing portion for containing a developer containing toner and a magnetic carrier, a developer carrying path for carrying the developer, and the developer provided in the developer carrying path. A developer carrying member that carries the developer in a predetermined direction while stirring; a developer carrying member that carries the developer in the developer carrying path and supplies toner contained in the developer to the photosensitive drum; and the developer carrying In a developing device having a toner replenishing port for replenishing toner to a path, the developer conveying member includes a spiral blade that transports developer, and the spiral pitch of the spiral blade changes periodically. It is formed as follows.

  In the present invention, it is preferable that the spiral pitch of the spiral blade is such that the minimum value is not less than 0.3 times and not more than 0.7 times the maximum value.

  In the present invention, it is preferable that the toner supply port is provided in an upper portion of the developer conveying member at a position where the spiral pitch of the spiral blade is maximized.

  According to the present invention, the developer transport path includes a first transport path and a second transport path arranged side by side, and the first transport path and the second transport path have the first transport path at both ends. A first communication path and a second communication path that communicate between the first conveyance path and the second conveyance path are formed, and the developer conveyance member is provided in the first conveyance path as a configuration of the developer conveyance member. A first conveying member that conveys the developer in a predetermined direction while stirring the developer; and a developer conveying direction that is provided in the second conveying path and is stirred by the first conveying member while stirring the developer in the second conveying path; Includes a second conveying member that conveys in the opposite direction, and the developer is conveyed from the first conveying path to the second conveying path via the first communicating path, and from the second conveying path to the second communicating path. It is configured to be transported to the first transport path, and the spiral pin of the spiral blade on the first communication path side of the first transport member. Is configured to be shorter than the spiral pitch of the spiral blades on the first communication path side of the second transport member facing the second transport member, and the spiral pitch of the spiral blades on the second communication path side of the first transport member is opposed to the spiral pitch. Preferably, the second conveying member is configured to be longer than the helical pitch of the helical blades on the second communication path side.

  In addition, the present invention provides a developer accommodating portion that accommodates a developer containing toner and a magnetic carrier, a developer conveying path that conveys the developer, and a developer conveying path provided in the developer conveying path. A developer carrying member that carries the developer in a predetermined direction while stirring the developer, a developer carrying member that carries the developer in the developer carrying path and supplies toner contained in the developer to the photosensitive drum, and the development In the developing device having a toner supply port for supplying toner to the developer transport path, the developer transport member includes a spiral blade for transporting the developer and a rotating shaft on which the spiral blade is provided. The rotating shaft is formed such that its shaft diameter periodically changes along the axial direction.

  In the present invention, it is preferable that the toner replenishing port is provided in an upper portion of the developer conveying member at a position where the shaft diameter of the rotating shaft is minimized.

  According to the present invention, the developer transport path includes a first transport path and a second transport path arranged side by side, and the first transport path and the second transport path have the first transport path at both ends. A first communication path and a second communication path that communicate between the first conveyance path and the second conveyance path are formed, and the developer conveyance member is provided in the first conveyance path as a configuration of the developer conveyance member. A first conveying member that conveys the developer in a predetermined direction while stirring the developer; and a developer conveying direction that is provided in the second conveying path and is stirred by the first conveying member while stirring the developer in the second conveying path; Includes a second conveying member that conveys in the opposite direction, and the developer is conveyed from the first conveying path to the second conveying path via the first communicating path, and from the second conveying path to the second communicating path. It is configured to be transported to the first transport path, and the shaft diameter of the rotary shaft on the first communication path side of the first transport member is The diameter of the rotating shaft on the second communication path side of the first conveying member is opposed to this, and the diameter of the rotating shaft on the second communication path side of the first conveying member is opposed to this. It is preferable that the second conveying member has a smaller diameter than the diameter of the rotating shaft on the second communication path side.

  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. Developing device for supplying toner to electrostatic latent image on drum surface to form toner image, toner replenishing device for replenishing toner to developing device, and transfer device for transferring toner image on photosensitive drum surface to recording medium And a fixing device for fixing the toner image on the recording medium, wherein the developing device is an image forming apparatus that forms an image using toner by electrophotography. The developing device described above is used.

  According to the present invention, a developer accommodating portion that accommodates a developer containing toner and a magnetic carrier, a developer conveying path for conveying the developer, and the developer provided in the developer conveying path. A developer carrying member that carries the developer in a predetermined direction while stirring the developer, a developer carrying member that carries the developer in the developer carrying path and supplies toner contained in the developer to the photosensitive drum, and the development In the developing device having a toner replenishing port for replenishing toner to the developer transport path, the developer transport member includes a spiral blade that transports the developer, and the spiral pitch is periodically set to the spiral blade. By forming it to change, the developer conveyance amount per rotation by the spiral blade changes periodically, that is, the developer conveyance amount is large in the part where the helical pitch is long, and in the part where the helical pitch is short Present Since the amount of the image agent transported is reduced, the developer surface is wavy and the stirring of the developer surface or the developer in the vertical direction is promoted. As a result, even when the amount of replenished toner is large, it is possible to prevent the replenished toner from being conveyed while floating on the developer surface, and to prevent toner scattering due to uncharged toner.

  According to the present invention, the spiral pitch of the spiral blade is minimized by setting the spiral pitch of the spiral blade to a minimum value that is not less than 0.3 times and not more than 0.7 times the maximum value. In part, the flow of the developer is extremely reduced, so that wavy undulations can be formed on the developer surface without applying excessive stress. As a result, stirring of the developer surface or the developer in the vertical direction is promoted.

  According to the present invention, the toner replenishing port is provided in an upper portion of the developer conveying member where the spiral pitch of the spiral blade is maximized, so that toner is replenished at a portion where the developer surface is lowered. Therefore, the replenished toner is easily mixed in the developer in the developer transport path.

  Further, according to the present invention, as a configuration of the developer transport path, the developer transport path includes a first transport path and a second transport path arranged in parallel, and at both ends of the first transport path and the second transport path, A first communication path and a second communication path that connect the first conveyance path and the second conveyance path are formed, and the first conveyance path is provided in the first conveyance path as a configuration of the developer conveyance member. A first conveying member that conveys the developer in the path in a predetermined direction while stirring, and a developer conveyance that is provided in the second conveying path and that is stirred by the first conveying member while stirring the developer in the second conveying path. A second conveying member that conveys in a direction opposite to the direction, and the developer is conveyed from the first conveying path to the second conveying path via the first communicating path, and from the second conveying path to the second communicating path. Through the first conveying path, and the screw of the spiral blade on the first communication path side of the first conveying member. The pitch is configured to be shorter than the spiral pitch of the spiral blade on the first communication path side of the second transport member facing the second transport member, and the spiral pitch of the spiral blade on the second communication path side of the first transport member is By configuring the second conveying member to be longer than the helical pitch of the spiral blades on the second communication path side of the opposing second conveying member, the upstream developer surface in the developer conveying direction is downstream in the first communicating path and the second communicating path. Since it becomes higher than the developer surface on the side, the developer can be moved quickly, so that the developer can be transported efficiently.

  Further, according to the present invention, a developer accommodating portion that accommodates a developer containing toner and a magnetic carrier, a developer conveying path for conveying the developer, and a developer conveying path are provided in the developer conveying path. A developer conveying member that conveys the developer in a predetermined direction while stirring; a developer carrying member 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 toner supply port for supplying toner to the developer transport path, the developer transport member includes a spiral blade that transports the developer, and a rotation shaft provided with the spiral blade. And the rotation shaft is formed such that its shaft diameter periodically changes along the axial direction, so that the developer conveyance amount per rotation by the spiral blade periodically changes, that is, In parts where the shaft diameter is thin Since the developer transport amount is large and the developer transport amount is small in the portion where the shaft diameter is thick, the developer surface is wavy and the developer surface or the developer in the vertical direction is promoted. As a result, even when the amount of replenished toner is large, it is possible to prevent the replenished toner from being conveyed while floating on the developer surface, and to prevent toner scattering due to uncharged toner.

  According to the present invention, the toner replenishing port is provided above the position where the shaft diameter of the rotating shaft is minimized in the developer conveying member, so that the toner is replenished at a portion where the developer surface is lowered. Therefore, the replenished toner is easily mixed in the developer in the developer transport path.

  Further, according to the present invention, as a configuration of the developer transport path, the developer transport path includes a first transport path and a second transport path arranged in parallel, and at both ends of the first transport path and the second transport path, A first communication path and a second communication path that connect the first conveyance path and the second conveyance path are formed, and the first conveyance path is provided in the first conveyance path as a configuration of the developer conveyance member. A first conveying member that conveys the developer in the path in a predetermined direction while stirring, and a developer conveyance that is provided in the second conveying path and that is stirred by the first conveying member while stirring the developer in the second conveying path. A second conveying member that conveys in a direction opposite to the direction, and the developer is conveyed from the first conveying path to the second conveying path via the first communicating path, and from the second conveying path to the second communicating path. The shaft diameter of the rotary shaft on the first communication path side of the first transport member is configured to be transported to the first transport path via The diameter of the rotating shaft on the second communicating path side of the first conveying member is larger than the diameter of the rotating shaft on the first communicating path side of the second conveying member facing the second conveying member. By configuring the opposing second transport member to have a diameter smaller than the shaft diameter of the rotating shaft on the second communication path side, the developer surface on the upstream side in the developer transport direction in the first communication path and the second communication path. Since it becomes higher than the developer surface on the downstream side, the developer can be moved quickly, so that the developer can be transported efficiently.

  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 toner replenishing device that supplies toner to the developing device, and a toner image on the surface of the photosensitive drum is transferred to a recording medium. 8. An image forming apparatus that includes a transfer device and a fixing device that fixes a toner image on a recording medium, and forms an image using toner by an electrophotographic method, and the developing device is any one of claims 1 to 7. By using the developing device described in the item, the replenishment toner can be mixed with the carrier (developer) without significantly increasing stress on the developer. Accordingly, toner scattering and image fogging caused by toner that is not sufficiently charged can be reduced, and a good image can be obtained.

(First embodiment)
The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is an example of an embodiment for carrying out the invention, and is an explanatory diagram showing an overall configuration of an image forming apparatus using a developing device according to a first embodiment of the present invention.

  In the first embodiment, as shown in FIG. 1, a photosensitive drum 3 on which an electrostatic latent image is formed, a charger (charging device) 5 that charges the surface of the photosensitive drum 3, and the photosensitive drum 3. An exposure unit (exposure device) 1 for forming an electrostatic latent image on the surface, a developing device 2 for supplying toner to the electrostatic latent image on the surface of the photosensitive drum 3 to form a toner image, and a toner for the developing device 2 A toner hopper (toner replenishing device) 101 for replenishing, 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) for fixing the toner image on the recording medium. In the image forming apparatus 100 that forms an image using toner by electrophotography, the developing device 2 according to the present invention is employed 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), so that a black image, cyan image, magenta 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, 3d). 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. The developing device 2 (2a, 2b, 2c, 2d) includes a toner hopper 101 (101a, 101b, 101c, 101d), a toner transfer mechanism 102 (102a, 102b, 102c, 102d), and a developing tank (developer container) 111. (111a, 111b, 111c, 111d).

  The toner hopper 101 is arranged on the H direction side of the developing tank 111 and stores unused toner (powder toner). The toner is supplied from the toner hopper 101 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 characteristic developing device 2 of the first embodiment will be described with reference to the drawings.
2 is a cross-sectional view showing the configuration of the developing device constituting the image forming apparatus according to the first embodiment, FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line BB in FIG. FIG.

  As shown in FIG. 2, the developing device 2 has a developing roller (developer carrying member) 114 disposed in the developing tank 111 so as to face the photosensitive drum 3. 3 is a device for supplying (developing) an electrostatic latent image formed on the surface of the photosensitive drum 3 by supplying toner to 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 118, a doctor blade 116, a first conveying member 112, a second conveying member 113, and a partition plate (partition wall) 117. I have.

  The developing tank 111 is a tank that stores a developer containing toner and a carrier. 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 rotating magnet roller that pumps and carries the developer in the developing tank 111 on the surface and supplies toner contained in the developer carried on the surface to the photosensitive drum 3. A doctor blade (layer thickness regulating blade) 116 is disposed at a position close to the surface of the developing roller 114.

  Further, as shown in FIGS. 2 and 4, a detachable developing tank cover 115 is provided above the developing tank 111. Further, as shown in FIG. 4, the developing tank cover 115 is formed with a toner supply port 118 for supplying unused toner to the developing tank 111.

  As shown in FIG. 1, the toner accommodated in the toner hopper 101 is transferred to the developing tank 111 through the toner transfer mechanism 102 and the toner supply port 118, whereby the toner is supplied to the developing tank 111. It is like that.

  Further, as shown in FIGS. 2, 3, and 4, the first transport member 112 and the second transport member 113 are spiral transport blades (spiral blades) for stirring and transporting the developer in the developing tank 111. ) 112a and 113a, and a rotating shaft 112b is rotationally driven by a driving means (not shown) such as a motor so that the developer is stirred and conveyed.

  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. 3, 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

  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. Hereinafter, as illustrated in FIG. 4, 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.

  As shown in FIGS. 3 and 4, the first transport member 112 includes a spiral transport blade (hereinafter referred to as “spiral blade”) 112a for transporting the developer, and a rotating shaft 112b on which the spiral blade 112a is provided. And the portion of the spiral blade 112a1 having a long spiral pitch and the portion of the spiral blade 112a2 having a short spiral pitch are alternately provided. As a result, the developer transport amount per rotation of the first transport member 112 periodically changes, so that wave-like undulation is formed on the developer surface.

  In the first embodiment, as shown in FIG. 4, the first transport member 112 sets the spiral pitch P2 of the spiral blade 112a2 having a short spiral pitch to 0.5 times the spiral pitch P1 of the spiral blade 112a1 having a long spiral pitch. Yes.

The second transport member 113 is configured in substantially the same manner as the first transport member 112.
Accordingly, the second transport member 113 also includes a spiral blade 113a for transporting the developer and a rotating shaft 113b on which the spiral blade 113a is provided, as shown in FIGS. 3 and 4, similarly to the first transport member 112. The portions of the spiral blade 113a1 having a long spiral pitch and the portions of the spiral blade 113a2 having a short spiral pitch are alternately provided.

  Further, as shown in FIG. 4, the second transport member 113 sets the spiral pitch P2 of the spiral blade 113a2 having a short spiral pitch to 0.5 times the spiral pitch P1 of the spiral blade 113a1 having a long spiral pitch.

  The spiral pitch P2 of the spiral blade 112a2 on the first communication path a side of the first transport member 112 is configured to be shorter than the spiral pitch P1 of the spiral blade 113a1 on the first communication path a side of the second transport member 113 facing this. ing.

  Further, the spiral pitch P1 of the spiral blade 112a1 on the second communication path b side of the first transport member 112 is longer than the spiral pitch P2 of the spiral blade 113a2 on the second communication path b side of the second transport member 113 facing this. It is configured.

  In the first embodiment, the toner supply port 118 is a region in the first transport 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 direction of arrow X 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 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 118 to the first transport path P. The replenished toner is mixed and agitated with the developer existing in the first conveyance path P.

Here, the mixing and stirring action of the replenishing toner T and the developer D in the developing tank 111 of the developing device 2 according to the first embodiment will be described with reference to the drawings.
FIG. 5 is an explanatory diagram illustrating a state in which the developer surface is wavy and the replenishment toner is mixed with the developer in the developing device of the image forming apparatus according to the first embodiment.

  In the developing device 2, the first transport member 112 and the second transport member 113 have the same function, and thus the first transport member 112 will be described as an example.

  As shown in FIG. 5, the first conveying member 112 has a developer conveying amount per rotation of the first conveying member 112 between the portion of the spiral blade 112 a 1 having a long spiral pitch and the spiral blade 112 a 2 having a short spiral pitch. Due to the difference, a wave-like undulation is formed in the developer D.

  That is, the developer D has a higher developer surface in the portion of the spiral blade 112a2 with a shorter spiral pitch in the first conveying member 112 and lower in the portion of the spiral blade 112a1 with a longer pitch. Usually, since the developer D flows from the higher side to the lower side, the vertical direction of the developer D is caused by the difference in the height of the developer surface caused by the difference in the length of the helical pitches P1 and P2 in the spiral blades 112a1 and 112a2. Agitation is promoted.

  Since it comprised as mentioned above, according to 1st Embodiment, in 1st conveyance member 112 and 2nd conveyance member 113, spiral blade 112a1, so that the spiral pitch of spiral blade 112a, 113a may be changed periodically. Since the spiral pitches 113a1 and 112a2 and 113a2 are alternately formed as P1 and P2, wavy undulations are generated on the developer surface to promote stirring of the replenishment toner T in the developer surface or in the vertical direction of the developer. Can do.

  Therefore, even when the amount of the replenished toner is large, the replenishment toner T is prevented from being conveyed while being floated on the developer surface, and the first conveying member in the first conveying path P and the second conveying path Q is suppressed. Since the necessary charge amount can be obtained by sufficiently stirring the developer D and the replenishment toner T by the 112 and the second conveying member 113, it is possible to prevent toner scattering due to uncharged toner.

  In the first embodiment, as shown in FIG. 5, the height of the developer tank cover 115 is set to such a height that the developer surface of the spiral blade 112 a 2 having a short spiral pitch is loosely in contact with the developer tank cover 115. Therefore, even if the replenished toner (supplementary toner) T is in a lump state, it is crushed between the developer surface and the developer tank cover 115, so that it is conveyed on the developer surface in a lump state. Can be prevented.

(Second Embodiment)
Next, a developing device according to a second embodiment of the present invention will be described with reference to the drawings.
FIG. 6 is a cross-sectional view showing the configuration of the developing device according to the second embodiment of the present invention, and FIG. 7 is a cross-sectional view taken along the line CC in FIG.
6 is a cross-sectional view corresponding to FIG. 3 in the developing device 2 of the first embodiment described above, and FIG. 7 is a cross-sectional view corresponding to FIG. 4 in the developing device 2.

  As shown in FIGS. 6 and 7, the developing device 200 according to the second embodiment includes the developing roller 114, the developing tank cover 115, the toner supply port 118, the first transport member 212, and the second transport in addition to the developing roller 114. A member 213 and a partition plate (partition wall) 117 are provided.

  The developing device 200 has the same configuration as the developing device 2 except that the configurations of the first transport member 112 and the second transport member 113 in the developing device 2 according to the first embodiment described above are different. Members having the same configuration other than the first transport member 212 and the second transport member 213 are denoted by the same reference numerals and description thereof is omitted.

  The first transport member 212 and the second transport member 213 are disposed in the first transport path P and the second transport path Q, respectively, as shown in FIG.

  As shown in FIGS. 6 and 7, the first transport member 212 and the second transport member 213 are configured by screw augers including rotating shafts 212 b and 213 b and spiral transport blades (spiral blades) 212 a and 213 a. The rotation shafts 212b and 213b are rotationally driven by a driving means (not shown) such as a motor, whereby the developer is stirred and conveyed.

  The first transport member 212 and the second transport member 213 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. 6, the first transport member 212 transports the developer in the arrow X direction, and the second transport member 213 transports the developer in the arrow Y direction opposite to the arrow X direction. Is set to

  As shown in FIGS. 6 and 7, the first conveying member 212 includes a rotating shaft 212b whose axis diameter periodically changes along the axial direction, and includes a portion 212b1 having a small shaft diameter and a portion 212b2 having a large shaft diameter. And are provided alternately. As a result, the developer transport amount per rotation of the first transport member 212 periodically changes, so that undulations are formed on the developer surface.

  In the second embodiment, as shown in FIG. 6, the first conveying member 212 has a ratio of the diameters of the spiral blade 212a, the diameter portion 212b2 of the rotation shaft 212b, and the diameter portion 212b1 of the rotation shaft 212b. 3: 2: 1.

The second transport member 213 is configured in substantially the same manner as the first transport member 112.
Accordingly, as shown in FIG. 6, the second conveying member 213 also includes a rotating shaft 212b whose axis diameter periodically changes along the axial direction, as in the case of the first conveying member 212, and a portion 212b1 having a small axial diameter. And portions 212b2 having a large shaft diameter are alternately provided.

  Further, as shown in FIG. 6, the second conveying member 213 has a ratio of the diameters of the spiral blade 213a, the thick shaft portion 213b2 of the rotating shaft 213b, and the thin shaft portion 213b1 to 3: 2: 1 is assumed.

  A portion 212b2 having a large shaft diameter of the rotation shaft 212b on the first communication path a side of the first transport member 212 is thin, and a shaft diameter of the rotation shaft 213b on the first communication path a side of the second transport member 213 opposite thereto is small. It has a larger diameter than the portion 213b1.

  In addition, the portion 212b1 having a small shaft diameter of the rotation shaft 212b on the second communication path b side of the first transport member 212 is the shaft diameter of the rotation shaft 213b on the second communication path b side of the second transport member 213 facing the portion 212b1. It has a smaller diameter than the thick part 213b2

Next, the mixing and stirring action of the replenishing toner T and the developer D in the developing tank 111 of the developing device 200 according to the second embodiment will be described with reference to the drawings.
FIG. 8 is an explanatory diagram showing a state in which the developer surface is wavy and the replenishment toner is mixed with the developer in the developing device of the image forming apparatus according to the second embodiment.

  In the developing device 200, the first transport member 212 and the second transport member 213 have the same function, and thus the first transport member 212 will be described as an example.

  As shown in FIG. 8, the first conveying member 212 has a developer conveying amount per one rotation of the first conveying member 212 in a portion 212b1 having a thin shaft diameter 212b1 and a portion 212b2 having a large shaft diameter. Due to the difference, wave-like undulations are formed on the developer surface.

  That is, the developer D has a higher developer surface above the portion 212b2 with a large shaft diameter of the rotating shaft 212b and lower at the portion 212b1 with a small shaft diameter. Usually, since the developer D flows from the higher side to the lower side, the developer D is agitated in the vertical direction due to the difference in height of the developer surface caused by the difference in the shaft diameter (outer diameter) of the rotating shaft 212b. Is promoted.

  Since it comprised as mentioned above, according to 2nd Embodiment, in the 1st conveyance member 212 and the 2nd conveyance member 213, a shaft diameter is large so that the shaft diameter of rotating shaft 212b, 213b may be changed periodically. Since the portions 212b2 and 213b2 and the thin portions 212b1 and 213b1 are formed alternately, a wavy wave is generated on the developer surface to promote the stirring of the replenishment toner T in the developer surface or in the vertical direction of the developer. Can be made.

  Therefore, even when the amount of the replenished toner is large, the replenishment toner T is prevented from being conveyed while being floated on the developer surface, and the first conveying member in the first conveying path P and the second conveying path Q is suppressed. Since the required charge amount can be obtained by sufficiently stirring the developer D and the replenishment toner T by the 212 and the second conveying member 213, toner scattering due to uncharged toner can be prevented.

  Further, in the second embodiment, as shown in FIG. 8, the height of the developing tank cover 115 is set high enough that the developer surface in the portion 212b2 having a large shaft diameter of the rotating shaft 212b is loosely in contact with the developing tank cover 115. Therefore, even if the replenished toner (supplementary toner) T is in a lump state, it is crushed between the developer surface and the developer tank cover 115, so that the lump state is formed on the developer surface. It can be prevented from being conveyed as it is.

  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 illustrated in FIG. 1 has been described. However, an image for supplying toner to the developing device 2 using the toner hopper 101 is described. The forming apparatus 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.

  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 is an explanatory diagram illustrating an overall configuration of an image forming apparatus in which a developing device according to a first embodiment of the present invention is used. FIG. 2 is a cross-sectional view illustrating a configuration of a developing device that constitutes the image forming apparatus. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2. It is a BB cross-sectional arrow view of FIG. FIG. 4 is an explanatory diagram illustrating a state where waviness is generated on the developer surface in the developing device and replenishment toner is mixed with the developer. It is sectional drawing which shows the structure of the developing device which concerns on 2nd Embodiment of this invention. It is CC sectional view taken on the line of FIG. FIG. 4 is an explanatory diagram illustrating a state where waviness is generated on the developer surface in the developing device and replenishment toner is mixed with the developer.

Explanation of symbols

1 Exposure unit (exposure equipment)
2,200 Development device 3 Photosensitive drum 5 Charger (charging device)
8 Intermediate transfer belt unit (transfer device)
12 Fixing unit (fixing device)
100 Image forming apparatus 101 Toner hopper (toner supply device)
111 Developer tank (developer container)
112, 212 First conveying member (developer conveying member)
112a, 112a1, 112a2, 212a Spiral blade 112b Rotating shaft 113, 213 Second conveying member (developer conveying member)
113a, 113a1, 113a2, 213a Spiral blade 114 Developing roller (developer carrying member)
118 Toner supply ports 212b and 213b Rotating shafts 212b1 and 213b1 Thin portions 212b2 and 213b2 Thick portions 213b Rotating shaft a First communication path b Second communication path D Developer P First transport path (Developer transport path)
P1, P2 Spiral pitch Q Second transport path (developer transport path)
T Supply toner

Claims (8)

A developer containing portion for containing a developer containing toner and a magnetic carrier; a developer carrying path for carrying the developer; and a predetermined position while stirring the developer provided in the developer carrying path A developer conveying member that conveys the toner in a direction, a developer carrying member that carries the developer in the developer conveying path and supplies toner contained in the developer to the photosensitive drum, and a toner in the developer conveying path. In a developing device having a toner replenishing port for replenishment,
The developer transport member includes a spiral blade that transports the developer,
The developing device according to claim 1, wherein the spiral blade is formed such that a spiral pitch changes periodically.   2. The developing device according to claim 1, wherein the spiral pitch of the spiral blade has a minimum value not less than 0.3 times and not more than 0.7 times a maximum value.   3. The developing device according to claim 1, wherein the toner supply port is provided in an upper portion of the developer transport member at a position where a spiral pitch of the spiral blade is maximized. 4. The developer transport path has a first transport path and a second transport path arranged in parallel,
A first communication path and a second communication path that connect the first transport path and the second transport path are formed at both ends of the first transport path and the second transport path,
The developer conveying member is provided in the first conveying path, and is provided in the second conveying path, and a first conveying member that conveys the developer in the first conveying path in a predetermined direction while stirring. A second transport member that transports in a direction opposite to the developer transport direction by the first transport member while stirring the developer in the second transport path;
The developer is transported from the first transport path to the second transport path via the first communication path, and is transported from the second transport path to the first transport path via the second communication path,
The spiral pitch of the spiral blades on the first communication path side of the first transport member is configured to be shorter than the spiral pitch of the spiral blades on the first communication path side of the second transport member facing it,
The spiral pitch of the spiral blade on the second communication path side of the first transport member is configured to be longer than the spiral pitch of the spiral blade on the second communication path side of the second transport member facing the first transport member. The developing device according to any one of claims 1 to 3. A developer containing portion for containing a developer containing toner and a magnetic carrier; a developer carrying path for carrying the developer; and a predetermined position while stirring the developer provided in the developer carrying path A developer conveying member that conveys the toner in a direction, a developer carrying member that carries the developer in the developer conveying path and supplies toner contained in the developer to the photosensitive drum, and a toner in the developer conveying path. In a developing device having a toner replenishing port for replenishment,
The developer transport member includes a spiral blade that transports the developer, and a rotation shaft provided with the spiral blade.
The developing device according to claim 1, wherein the rotation shaft is formed such that an axial diameter thereof periodically changes along an axial direction.   The developing device according to claim 5, wherein the toner replenishing port is provided in an upper portion of the developer conveying member at a position where the shaft diameter of the rotating shaft is minimized. The developer transport path has a first transport path and a second transport path arranged in parallel,
A first communication path and a second communication path that connect the first transport path and the second transport path are formed at both ends of the first transport path and the second transport path,
The developer conveying member is provided in the first conveying path, and is provided in the second conveying path, and a first conveying member that conveys the developer in the first conveying path in a predetermined direction while stirring. A second transport member that transports in a direction opposite to the developer transport direction by the first transport member while stirring the developer in the second transport path;
The developer is transported from the first transport path to the second transport path via the first communication path, and is transported from the second transport path to the first transport path via the second communication path,
The shaft diameter of the rotating shaft on the first communicating path side of the first conveying member is configured to be larger than the shaft diameter of the rotating shaft on the first communicating path side of the second conveying member facing it.
The shaft diameter of the rotation shaft on the second communication path side of the first transport member is configured to be smaller than the shaft diameter of the rotation shaft on the second communication path side of the second transport member facing the first transport member. The developing device according to claim 5 or 6. 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 that supplies toner to an image to form a toner image, a toner replenishing device that replenishes toner to the developing device, a transfer device that transfers the toner image on the surface of the photosensitive drum to a recording medium, and a toner image recording In an image forming apparatus comprising a fixing device for fixing to a medium and forming an image using toner by an electrophotographic method,
An image forming apparatus using the developing device according to claim 1 as the developing device.

Images