JP2008170786A - Developing device and image forming apparatus using the same - Google Patents

Abstract

A developing device capable of supplying toner to a developing device without overflowing with a simple configuration without overflowing, and capable of reliably mixing and stirring the supplied toner and a developer. An image forming apparatus is provided.
A housing 234 that contains a developer, a developing roller 231 that supplies toner to a photosensitive drum 21 on which an electrostatic latent image is formed, and a developer that agitates and conveys the developer in the housing 234. In a developing device 23 that includes a first toner conveying shaft 232 and a second toner conveying shaft 233 and visualizes the electrostatic latent image formed on the photosensitive drum 21 with toner, toner is applied to the housing 234 from the outside. A toner introduction port 234a to be introduced is provided, and a magnet 250 is disposed adjacent to the toner introduction port 234a.
[Selection] Figure 2

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device and an image forming apparatus using the developing device. A developing device that visualizes the electrostatic latent image formed on the photosensitive drum with toner, and a developing device configured to stir the developer in the developer containing portion without any unevenness. The present invention relates to the image forming apparatus used.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a facsimile machine using toner, toner is supplied to a developing device by a toner replenishing device such as a toner cartridge, and continuous operation of image output is performed.

  For supplying toner to the developing device by the toner replenishing device, a system is known in which toner is supplied from a toner cartridge via a toner conveying device. In such a toner conveying device, a toner cartridge is provided above the developing device, and a toner conveying path extending in the vertical direction is formed to convey the toner to the developing device below.

  Incidentally, in recent years, image quality has been improved in image forming apparatuses, and accordingly, the particle diameter of toner has been reduced. The fine toner generally has poor fluidity, and toner stagnation and coagulation easily occur in the toner conveyance path of the toner conveyance device.

  In addition, the toner contains WAX having a lower melting point than that of the main resin in order to ensure low-temperature fixability. However, for the purpose of oilless fixing and compatibility with recent high-speed machines, more WAX may be added or the lower melting point may be added. Tend to use WAX. Along with this, the fluidity of the toner is lowered, and aggregation easily occurs.

When the toner aggregation state continues as described above, the toner transport capability is lowered, and there is a problem that newly supplied toner cannot be fed into the developing device.
In particular, due to the influence of high heat generated during high-speed conveyance of toner, in the worst case, a phenomenon in which toner adheres / fuses to a conveyance member or the like may occur.

  2. Description of the Related Art Conventionally, an image forming apparatus that employs an intermediate transfer member often has a structure in which a toner hopper that replenishes toner and a developing device (developing tank) are separated, and the toner supplied from the toner hopper is supplied to the toner via a transport pipe. It is configured to be fed into the developing tank from the replenishing port.

  The toner supplied from the toner replenishing port is mixed and agitated with the developer in the developing tank and conveyed to the developing roller. However, due to the reduction in capacity of the developing tank itself accompanying the recent downsizing of the apparatus, Since a sufficient space for mixing and stirring the toner and the developer cannot be obtained, the toner is more likely to agglomerate. In some cases, the toner overflows from the toner supply port.

Therefore, as a countermeasure against such a conventional problem, for example, a method has been proposed in which a coil spring is used in a toner hopper to improve toner conveyance. Specifically, in order to prevent toner aggregation near the toner replenishing port of the toner hopper, the coil spring is brought into contact with the fin of the conveying shaft to be moved / returned (see Patent Document 1).
JP-A-6-167880

  However, although the above-described conventional configuration can improve toner transportability, it does not have a structure that contributes to the mixing and stirring of the toner replenished from the toner hopper and the developer. Further, even when a sheet-like member made of polyethylene resin such as PET is wound around the rotating shaft of the toner conveying member and the toner is mixed with the developer by the rotating force, the ability to take in the toner is weak and a sufficient effect is obtained. Absent.

  In other words, the conventional configuration basically transports only the toner, and does not consider mixing and stirring of the replenished toner and the developer. Therefore, it has not been assumed that the toner having a low specific gravity when the toner is stirred in the developing tank causes the upper slip of the developer to overflow and the toner that is not carried into the developing tank overflows.

  The present invention has been made in view of the above-described conventional problems, and can be supplied into the developing device with a simple configuration without overflowing the toner replenished in the developing device. An object of the present invention is to provide a developing device capable of reliably performing mixing and stirring, and an image forming apparatus using the same.

  Each configuration of the developing device and the image forming apparatus using the developing device according to the present invention for solving the above-described problems is as follows.

  The developing device according to claim 1 supplies toner to a developer containing portion that contains a developer containing a chargeable toner and a magnetic carrier, and an electrostatic latent image carrier on which an electrostatic latent image is formed. And a developing device that visualizes the electrostatic latent image formed on the electrostatic latent image carrier with toner, the developing roller comprising: a developing roller that stirs and transports the developer in the developer container The toner container is provided with a toner inlet for introducing toner into the developer container from outside, and magnetic force generating means for forming a magnetic brush with a magnetic carrier is disposed adjacent to the toner inlet. It is characterized by this.

  The developing device described in claim 2 is characterized in that, in addition to the configuration described in claim 1, the magnetic force generating means is disposed at a position lower than the upper layer surface of the developer stored in the developer accommodating portion. To do.

  The developing device described in claim 3 is characterized in that, in addition to the configuration described in claim 1 or 2, the magnetic force generating means is disposed below the transport path of the introduced toner.

  According to a fourth aspect of the present invention, in addition to the configuration described in any one of the first to third aspects, the developing device is arranged such that the agitating and conveying means is disposed along the axial direction of the developing roller and rotates. The developer is agitated and conveyed by the operation, and the magnetic force generating means is arranged in the vicinity of the agitating and conveying means and on the upstream side in the rotation direction on the side where the rotation operation of the agitating and conveying means is directed downward from above. It is characterized by this.

  According to a fifth aspect of the present invention, in addition to the configuration described in any one of the first to fourth aspects, the magnetic force generating means is disposed outside the developer accommodating portion. To do.

  In addition to the structure described in any one of claims 1 to 5, the developing device described in claim 6 uses a permanent magnet as the magnetic force generating means.

  The developing device described in claim 7 is characterized in that, in addition to the configuration described in claim 6, a neodymium magnet, an alnico magnet, a ferrite magnet, or a sumakoba magnet is used as the permanent magnet.

  In addition to the configuration described in any one of claims 1 to 5, the developing device described in claim 8 is configured such that the magnetic force generating means is electrically energized using an electric magnetic force generating means, for example, an electromagnet. It is characterized in that it can be turned on / off.

  According to a ninth aspect of the present invention, in addition to the configuration described in the eighth aspect, the magnetic force generating means controls the magnetic force generation state to be variable according to the amount of toner introduced. It is.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus comprising: a developer containing portion that contains a developer containing a chargeable toner and a magnetic carrier; and an electrostatic latent image carrier on which an electrostatic latent image is formed. A developing roller that supplies toner; and a stirring and conveying unit that stirs and conveys the developer in the developer container. The electrostatic latent image formed on the electrostatic latent image carrier is visualized with toner. In the image forming apparatus that outputs the image by transferring the developer image formed on the surface of the electrostatic latent image carrier by the electrophotographic method onto the transfer medium, the developing device includes: A developing device according to any one of claims 1 to 9 is used.

  According to the first aspect of the present invention, the toner is applied to the developer accommodating portion that accommodates the developer containing the chargeable toner and the magnetic carrier, and the electrostatic latent image carrier on which the electrostatic latent image is formed. Development that includes a developing roller to be supplied and an agitating / conveying means for agitating and conveying the developer in the developer accommodating portion, and developing the electrostatic latent image formed on the electrostatic latent image carrier with a toner. In the apparatus, the developer accommodating portion is provided with a toner introducing port for introducing toner into the developer accommodating portion from the outside, and magnetic force generating means is disposed adjacent to the toner introducing port, so that the introduced toner is removed. Since it can be smoothly mixed with the developer by the magnetic brush by the magnetic carrier formed by the magnetic force generating means, an appropriate developer concentration (toner concentration) can be reached in a short time. Further, since the toner does not stay near the toner introduction port by the magnetic brush by the magnetic force generating means, it is possible to prevent toner clogging at the toner introduction port. Furthermore, since the magnetic force generating means can also affect the magnetic force of the corner portion of the developer that is difficult to be stirred by the stirring and conveying means of the developer storage portion, it is possible to generate a stagnant developer that does not contribute to development. , The developer can be effectively stirred.

  Moreover, in addition to the common effect obtained by the inventions according to claims 1 to 10, the following effects can be obtained according to the inventions described in each claim.

Specifically, according to the second aspect of the invention, in addition to the effect obtained by the first aspect of the invention, the magnetic force generating means is positioned lower than the upper layer surface of the developer stored in the developer containing portion. Since the magnetic brush can be formed in a wide range in the developer, the toner and the developer can be mixed and stirred efficiently.
That is, if it is placed at a position higher than the developer, the amount of magnetic brush formation will be reduced, so the mixing and stirring of the toner and developer will be reduced. The amount of brush formation can be increased.

  According to a third aspect of the present invention, in addition to the effect obtained by the first or second aspect of the present invention, the developing device can be dropped from above by arranging the magnetic force generating means below the toner conveyance path. The supplied replenishing toner can be efficiently stirred.

  According to a fourth aspect of the present invention, in addition to the effect obtained by the invention according to any one of the first to third aspects, the agitating and conveying means is provided along the axial direction of the developing roller. The developer is arranged so as to stir and convey the developer by a rotating operation, and the magnetic force generating means is close to the agitating and conveying means, and the rotating operation of the agitating and conveying means is upstream in the rotational direction on the side from the top to the bottom. By disposing on the side, the introduced toner can be stirred and conveyed downward, so that stirring can be performed effectively.

  According to a fifth aspect of the present invention, in addition to the effect obtained by the invention according to any one of the first to fourth aspects, the magnetic force generating means is disposed outside the developer accommodating portion. As a result, it is possible to efficiently carry out stirring and conveyance without interfering with the stirring and conveyance of the developer.

  In addition to the effect obtained by the invention according to any one of claims 1 to 5, the developing device according to claim 6 has a complicated apparatus configuration by using a permanent magnet as the magnetic force generating means. It can be configured easily without having to.

  In addition to the effects obtained by the invention according to claim 6, the developing device according to claim 7 is a neodymium magnet, an alnico magnet, a ferrite magnet, or a sumakoba that has a high magnetic force among sintered magnets as the permanent magnet. By using a magnet, a large magnetic brush can be formed even from the outside of the developer container, so that the effect of mixing and stirring the toner and developer can be obtained.

  In addition to the effect obtained by the invention according to any one of claims 1 to 5, the developing device described in claim 8 uses an electric magnetic force generator, for example, an electromagnet. By configuring so that the energized state can be turned on / off, the toner stirring action by the magnetic force generating means can be adjusted according to the stirring state of the toner.

In addition to the effect obtained by the invention described in claim 8, the developing device described in claim 9 controls the magnetic force generation means so that the magnetic force generation state can be varied according to the amount of toner introduced. The toner can be effectively stirred according to the supply amount of the toner.
The variable control of the magnetic force generating means may be controlled according to the operation time of the apparatus and the number of output sheets.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus comprising: a developer containing portion that contains a developer containing a chargeable toner and a magnetic carrier; and an electrostatic latent image carrier on which an electrostatic latent image is formed. A developing roller that supplies toner; and a stirring and conveying unit that stirs and conveys the developer in the developer container. The electrostatic latent image formed on the electrostatic latent image carrier is visualized with toner. In the image forming apparatus that outputs the image by transferring the developer image formed on the surface of the electrostatic latent image carrier by the electrophotographic method onto the transfer medium, the developing device includes: By using the developing device according to any one of claims 1 to 9, the introduced toner can be smoothly mixed with the developer by a magnetic brush made of a magnetic carrier formed by the magnetic force generating means. it can In so short time to reach the appropriate developer density (toner density) can be always output a stable high-quality image by the developer concentration.

  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 view showing the overall configuration of an image forming apparatus employing a developing device according to the present invention.

  In this embodiment, as shown in FIG. 1, the developer image formed on the photosensitive drum 21 (21a, 21b, 21c, 21d) based on the image data by the developer supplied by the developing roller 231 is transferred. Then, a developing device 23 (23a, 23b, 23c, 23d) used in the image forming apparatus 1 that transfers to a recording sheet, and a toner bottle (toner storage unit) 200 (200a, 200b, 200c, 200d) in which toner is stored. ) And a toner replenishing portion mounting mechanism 600 (600a, 600b, 600c, 600d) as a toner supply device that stores and agitates the toner supplied from the toner bottle 200 and supplies the toner to the developing device 23, and replenishment as a toner transport device Toner replenishing device 100 (612a, 612b, 612c, 612d) 00a, 100b, 100c, 100d) mounted to a constitution that the toner in the developing device 23 to be automatically supplied.

  As shown in FIG. 1, the image forming apparatus 1 to which the developing device 23 according to the present embodiment is attached uses a developer (hereinafter referred to as toner) that matches each hue in accordance with color-separated image information. A photosensitive drum 21 (21a, 21b, 21c, 21d) on which a formed developer image (hereinafter referred to as a toner image) is formed, and a developing device that supplies the developer onto the surface of the photosensitive drum 21. 23 (23a, 23b, 23c, 23d), and a plurality of process printing units (image forming means) 20 (20a, 20b, 20c, 20d). A transfer belt comprising an exposure unit (optical scanning device) 10 for generating an electrostatic latent image by irradiating a laser beam (beam) onto the body drum 21 and an endless transfer belt 31 for conveying the supplied recording paper. Knit 30, and a fixing unit 27 for thermally fixing the toner image transferred to the recording sheet by heat roller 27a and pressing roller 27b.

  First, the overall configuration of the image forming apparatus 1 will be described.

  An image forming apparatus 1 according to the present embodiment is a so-called digital color printer, which color-separates image information, forms an image for each hue, and outputs a color image, as shown in FIG. The image forming unit 108 and the sheet feeding unit 109 are roughly configured, and a multicolor image or a single color image is recorded on a recording sheet based on a print job from an information processing apparatus (not shown) such as a personal computer connected to the outside. Is formed.

  The image forming unit 108 uses an electrophotographic method to form a multicolor image using each color of yellow (Y), magenta (M), cyan (C), and black (BK). The unit 10, the process printing unit 20, the fixing unit 27, a transfer belt unit 30 as a transfer means including a transfer belt 31, a transfer roller 36, and a transfer belt cleaning unit 37 are configured.

  The schematic configuration of the image forming unit 108 is that a fixing unit 27 is disposed on the upper end of one end of the casing 1 a of the image forming apparatus 1, and is transferred below the fixing unit 27 from one end to the other end of the casing 1 a. A belt unit 30 is disposed, a process printing unit 20 is disposed below the transfer belt unit 30, and an exposure unit 10 is disposed below the process printing unit 20.

  A transfer belt cleaning unit 37 is provided on the other end side of the transfer belt unit 30. Further, a paper discharge tray 43 is provided adjacent to the fixing unit 27 above the image forming unit 108. A paper feeding unit 109 is configured below the image forming unit 108.

  In the present embodiment, four process printing units 20a, 20b, 20c, and 20d corresponding to the respective colors of black (BK), cyan (C), magenta (M), and yellow (Y) are transferred as the process printing unit 20. The belts 31 are sequentially provided along the belt 31.

  These process printing units 20 (20a, 20b, 20c, 20d) are arranged in parallel in a substantially horizontal direction (left-right direction in the figure) in the housing 1a, and a photosensitive drum 21 serving as an image carrier for each color. (21a, 21b, 21c, 21d), a charger (charging means) 22 (22a, 22b, 22c, 22d) for charging the photosensitive drum 21, and a developing device (developing means) 23 (23a, 23b, 23c, 23d) ), Cleaner units 24 (24a, 24b, 24c, 24d) and the like.

  Here, the symbols a, b, c, and d attached to the components corresponding to the respective colors correspond to the respective colors of black (BK), cyan (C), magenta (M), and yellow (Y). However, in the following description, the constituent elements provided for the respective colors are collectively shown in the photosensitive drum 21, except for the case where the constituent elements corresponding to a specific color are specified. The charger 22, the developing device 23, and the cleaner unit 24 are described.

  The photosensitive drum 21 is disposed such that a part of the outer peripheral surface thereof is in contact with the surface of the transfer belt 31, and the charger 22, the developing device 23, and the cleaner unit as an electric field generating unit along the outer peripheral surface of the drum. 24 are arranged close to each other.

  As the charger 22, a corona wire charger type charger is used, and is arranged close to the outer peripheral surface of the photosensitive drum 21 on the substantially opposite side to the position where the transfer belt unit 30 is arranged with the photosensitive drum 21 interposed therebetween. . In the present embodiment, a corona wire charger type charger is used as the charger 22. However, instead of the corona wire charger type charger, a fur brush type charger, a magnetic brush type charger, a roller type charger, a saw tooth Any type charger, ion generating charging device, or the like can be used without particular limitation as long as it can impart desired chargeability to the photosensitive drum.

  The developing device 23 stores toner of each color of black (BK), cyan (C), magenta (M), and yellow (Y) for each of the developing devices 23a, 23b, 23c, and 23d. It is arranged downstream of the charger 22 in the rotational direction (the direction of arrow A in the figure).

  The developing devices 23a, 23b, 23c, and 23d are provided with five toner replenishing units for replenishing the developing devices 23a, 23b, 23c, and 23d with each other so as to be capable of high-speed and mass printing. Toner replenishing devices 100a, 100b, 100c, and 100d having 500a, 500b, 500c, and 500d are provided, and developing rollers 231a, 231b, 231c, and 231d are disposed to face the photosensitive drums 21a, 21b, 21c, and 21d, respectively. Thus, each color toner is supplied to the electrostatic latent images formed on the outer peripheral surfaces of the photosensitive drums 21a, 21b, 21c, and 21d so as to be visualized (visualized).

  As a developer for replenishment, the toner replenisher 500a has a black (BK) developer, the toner replenisher 500b has a cyan (C) developer, and the toner replenisher 500c has a magenta (M) developer. The replenishing section 500d contains yellow (Y) developer.

  Note that two toner replenishing portions 500a for black (BK) developer are provided in parallel so that a large amount of printing can be performed in consideration of normally used mono black printing.

  Each toner replenishing section 500 is disposed almost directly above the developing device 23 that develops using the corresponding developer, and the developer replenishment passage body ( Toner conveying devices) 612 (612a, 612b, 612c, 612d) are connected.

  The supply passage body 612a for supplying black (BK) developer is structured to supply the developer from the two toner supply devices 100a and 100a together to the developing device 23a. ing.

  The cleaner unit 24 is disposed on the upstream side of the charger 22 in the rotation direction of the photosensitive drum. In addition, the cleaner unit 24 includes a cleaning blade 241, and the cleaning blade 241 is disposed in contact with the outer peripheral surface of the photoconductive drum 21 to scrape and collect residual toner on the photoconductive drum 21. Has been. Reference numeral 242 in the figure denotes a conveying screw that conveys the collected toner.

  Although the cleaning blade 241 is used in this embodiment, the present invention is not particularly limited to these configurations, and one or more cleaning blades may be used, or a fur brush or a magnetic brush may be used alone. A cleaning blade, a fur brush, and a magnetic brush may be used in combination. Any device configured to scrape and collect residual toner on the photosensitive drum 21 can be used.

  The exposure unit 10 mainly includes a box-shaped housing 10a, a laser scanning unit (LSU) 11 having a laser irradiation unit 11a disposed therein, a polygon mirror 12, and laser light for each color. Mirrors 13a, 13b, 13c, 13d, 14a, 14b, 14c and the like.

  The laser light emitted from the laser irradiation unit of the laser scanning unit 11 is color-separated by a polygon mirror and an fθ lens (not shown), and then reflected by the reflection mirrors 13a to 13c. 21b, 21c, and 21d are irradiated.

  The laser scanning unit 11 may be configured to use a writing head in which light emitting elements such as EL (Electro Luminescence) and LED (Light Emitting Diode) are arranged in an array instead of the laser irradiation unit, or a light source The liquid crystal shutter may be used, and any means capable of forming an electrostatic latent image on the photosensitive drum 21 can be used.

  As shown in FIG. 1, the transfer belt unit 30 mainly includes a transfer belt 31, a transfer belt drive roller 32, a transfer belt driven roller 33, and intermediate transfer rollers 35a, 35b, 35c, and 35d.

  In the following description, the intermediate transfer rollers 35a, 35b, 35c, and 35d are collectively referred to as the intermediate transfer roller 35 when used.

  The transfer belt 31 is endlessly formed using a film having a thickness of about 75 μm to 120 μm. As the material of the transfer belt 31, polyimide, polycarbonate, a thermoplastic elastomer alloy, or the like is mainly used.

  The transfer belt 31 is stretched by a transfer belt driving roller 32, a transfer belt driven roller 33, and an intermediate transfer roller 35 so that the surface thereof is in contact with the outer peripheral surface of the photosensitive drum 21, and the transfer belt driving roller 32. It is configured to move in the sub-scanning direction (in the direction of arrow B in the figure) by the driving force of.

  The transfer belt driving roller 32 is disposed on one end side of the housing 1a, drives the transfer belt 31 to convey the transfer belt 31, and transfers the transfer belt 31 in a state where the transfer belt 31 and the recording paper are overlapped. The recording paper is conveyed while being pressed between and pressed.

  The transfer belt driven roller 33 is disposed on the other end side of the housing 1a, and the transfer belt 31 and the transfer belt driving roller 32 are laid substantially horizontally from the fixing unit 27 side to the other end side of the housing 1a. In order to reduce the dimension in the width direction of the image forming apparatus 1 in FIG. 1 or to save the space in the so-called width direction, the transfer belt 31 together with the transfer belt drive roller 32 is mounted from the fixing unit 27 side. The other side of the body 1a can be inclined, and one of them can be provided with an appropriate arrangement, size, etc., such as a photoreceptor, development, laser irradiation unit, fixing, etc. It doesn't matter.

  The intermediate transfer roller 35 is disposed in the inner space of the transfer belt 31 that is wound from the transfer belt driving roller 32 to the transfer belt driven roller 33. The transfer belt 31 is disposed at a position shifted to the downstream side in the moving direction, presses the inner surface of the transfer belt 31, and the outer surface of the transfer belt 31 winds a part of the outer peripheral surface of the photosensitive drum 21. You may provide so that a predetermined | prescribed nip amount may be obtained.

  The intermediate transfer roller 35 includes a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm, and the outer peripheral surface of the metal shaft is coated with a conductive elastic material such as EPDM or urethane foam. It is not necessary to limit to these elastic materials.

  The intermediate transfer roller 35 configured as described above has a high voltage transfer bias for transferring the toner image formed on the photosensitive drum 21 to the transfer belt 31, that is, a polarity opposite to the charging polarity (−) of the toner. A high voltage (+) is applied, and the high voltage is uniformly applied to the transfer belt 31 by an elastic material.

  A visualized toner image (electrostatic image) corresponding to each hue on each of the above-described photosensitive drums 21 is laminated on the transfer belt 31 and becomes image information input to the apparatus. The stacked image information is transferred onto a recording sheet by a transfer roller 36 disposed at a contact position of the transfer belt 31.

  The transfer roller 36 constituting the transfer means constitutes a transfer means for transferring the developer image transferred to the transfer belt 31 onto a recording sheet, and is opposed to the transfer belt drive roller 32 substantially horizontally and in parallel. The multi-color toner image formed on the transfer belt 31 is transferred onto a recording sheet and is arranged so as to be pressed against the transfer belt 31 wound around the transfer belt drive roller 32 at a predetermined nip. In other words, a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner is applied.

  Further, in order to obtain a nip between the transfer belt 31 and the transfer roller 36 steadily, either the transfer belt drive roller 32 or the transfer roller 36 is made of a hard material such as metal, and the other roller Is made of a soft material such as elastic rubber or foamable resin.

  A registration roller 26 is provided below the transfer belt driving roller 32 and the transfer roller 36. The registration roller 26 is configured to align the leading edge of the recording paper supplied from the paper feeding unit 109 and the leading edge of the toner image on the transfer belt 31 and convey the toner to the transfer roller 36 side.

  Further, as described above, the toner adhering to the transfer belt 31 due to contact with the photosensitive drum 21 or the toner remaining on the transfer belt 31 without being transferred onto the recording paper by the transfer roller 36 is mixed with toner in the next step. Therefore, the transfer belt cleaning unit 37 is set to be removed and collected.

  The transfer belt cleaning unit 37 is provided in the vicinity of the transfer belt driven roller 33 and disposed so as to be in contact (or sliding contact) with the transfer belt 31, and the residual on the transfer belt 31 by the cleaning blade 37a. A box-shaped toner collecting portion 37b that temporarily stores the toner (waste toner) that has been scraped off the toner, and scrapes and collects the residual toner on the transfer belt 31.

  Further, the transfer belt cleaning unit 37 is disposed in the vicinity of the process printing unit 20a on the upstream side in the moving direction of the transfer belt 31 from the process printing unit 20a. The portion of the transfer belt 31 where the cleaning blade 37 a contacts the outer surface is supported by the transfer belt driven roller 33 on the inner surface.

  As shown in FIG. 1, the fixing unit 27 includes a pair of fixing rollers 271 configured by a heating roller 27a and a pressure roller 27b, and a conveying roller 27c above the fixing roller 271. It is carried in from below 271 and carried out above carrying roller 27c.

  Further, a paper discharge roller 28 is provided above the fixing unit 27, and the recording paper conveyed from the conveyance roller 27 c is discharged onto the paper discharge tray 43 by the paper discharge roller 28. .

  The fixing of the toner image by the fixing unit 27 is controlled by controlling heating means (not shown) such as a heater lamp provided inside or close to the heating roller 27a based on a detection value of a temperature detector (not shown). The heating roller 27a is maintained at a predetermined temperature (fixing temperature), and the recording paper on which the toner image has been transferred is heated and pressed while being rotated and conveyed by being sandwiched between the heating roller 27a and the pressure roller 27b. The toner image is thermally fixed.

  Adjacent to the fixing unit 27, a double-sided document conveying path S3 for double-sided printing is formed from the rear to the bottom of the fixing unit 27 to the vicinity of the paper feed unit 109, and is arranged in the vertical direction on the double-sided document conveying path S3. The recording paper is reversed toward the transfer roller 36 in a state where the recording paper is reversed by the provided conveying rollers 29a and 29b.

  Specifically, the transport roller 29a is disposed behind the fixing unit 27, and the transport roller 29b is disposed below the transport roller 29a in the vertical direction and is disposed at substantially the same position as the registration roller 26 in the lateral direction. Yes.

  In this embodiment, the heating roller 27a and the pressure roller 27b, which are heating means such as a heater lamp, are used. However, an induction heating method may be used or they may be used in combination. Further, any means may be used as long as it is an appropriate method capable of uniformly heat-fixing the toner image on the recording paper without disturbing the toner image without using a roller.

  The paper feed unit 109 includes a manual feed tray 41 and a paper feed cassette 42 for storing recording paper used for image formation. The image forming unit 108 feeds recording paper from the manual feed tray 41 and the paper feed cassette 42 one by one. To be supplied to.

  As shown in FIG. 1, the manual feed tray 41 is expanded to one side end (right side in the drawing) of the casing 1 a of the image forming apparatus 1. A small number (necessary number) of recording sheets of the type desired by the user are placed and taken into the housing 1a of the image forming apparatus 1 one by one.

  A pickup roller 41a is provided on the side of the exposure unit 10 in the casing 1a of the image forming apparatus 1 on the downstream side of the paper feeding direction of the recording paper by the manual feed tray 41 (the direction of arrow C in the figure). A conveyance roller 41b is provided substantially horizontally on the downstream side in the paper direction.

  The pickup roller 41a comes into contact with the surface of one end portion of the recording paper fed from the manual feed tray 41 and reliably conveys the paper one by one by the frictional resistance of the roller.

  The above-described pickup roller 41a and transport rollers 41b, 41c, and 41d constitute a recording paper transport path S1.

  On the other hand, the paper feed cassette 42 is provided below the image forming unit 108 and the exposure unit 10 in the housing 1a, and records a large amount of recording paper having a size defined by the specifications of the apparatus or a size predetermined by the user. Can be accommodated.

  A pickup roller 42a is provided on one end portion (left end portion in the figure) of the paper feed cassette 42, and a conveyance roller 42b is provided downstream of the pickup roller 42a in the recording paper conveyance direction.

  The pickup roller 42a contacts the surface of one end of the recording paper at the top of the recording paper set in the paper feeding cassette 42 in response to an output request, and reliably feeds out one by one by the frictional resistance of the roller. It is supposed to be.

  The conveyance roller 42b is configured to convey the recording sheet fed from the pickup roller 42a upward to the image forming unit 108 along the recording sheet conveyance path S2 formed on one end side in the housing 1a. .

Next, the configuration of the toner supply device 100 and the characteristic developing device 23 constituting the image forming apparatus according to the present embodiment will be described in detail with reference to the drawings.
FIG. 2 is a schematic side sectional view showing the configuration of the developing device and the toner replenishing device constituting the image forming apparatus of the present embodiment, and FIG. 3 is a schematic diagram seen from the front showing the configuration of the developing device and the toner replenishing device. .

  As shown in FIGS. 2 and 3, the toner replenishing device 100 mainly includes a toner bottle (toner containing portion) 200 containing toner as a developer, and the toner bottle 200 can be rotated on one end side. A toner replenishing section 500 having a bottle support member 300 supported on the toner supply section, a toner replenishing section mounting mechanism (toner supplying apparatus) 600 that is mounted with the toner replenishing section 500 and supplies toner to the developing device 23, and a replenishment passage body 612. It is comprised by.

  In this embodiment, the toner replenishing units 500a, 500b, 500c, and 500d constituting the toner replenishing device 100 (100a, 100b, 100c, and 100d) mounted on the image forming apparatus 1 have the same structure.

  The toner bottle 200 includes a main body portion 201 formed in a substantially cylindrical shape, and a tip portion thereof is supported by a bottle support member 300. The bottle support member 300 is formed in a substantially cylindrical shape and is configured to cover the front end portion of the main body portion 201.

  As shown in FIG. 1, the toner replenishing portion mounting mechanism 600 is configured to dispose the toner replenishing portion 500 so as to face the developing device 23 substantially in parallel with the transfer belt unit 30 interposed therebetween, as shown in FIG. In addition, it extends long in a direction substantially perpendicular to the transfer belt conveyance direction (transfer belt width direction). The toner replenishing portion mounting mechanism 600 for black toner can be mounted together with two toner replenishing portions 500a for storing black toner.

  In the toner replenishing unit mounting mechanism 600, a toner introduction port 611 is formed on one end side of the toner replenishing unit 500 where the bottle support member 300 is mounted, and the lower surface of the toner replenishing unit mounting mechanism 600 has a toner introduction port 611. A replenishment passage body 612 (612a, 612b, 612c, 612d) for toner conveyance that communicates with the developing device 23 provided below is provided.

  As shown in FIG. 3, the toner replenishing unit mounting mechanism 600 is configured to supply toner supplied from the toner replenishing unit 500 through a toner introduction port 611 provided outside the transfer belt width W in the direction perpendicular to the transfer belt conveyance direction. It has come to introduce.

  The toner replenishing portion mounting mechanism 600 includes a housing 610a formed in a box shape long in the transfer belt width direction, and a toner agitation shaft (not shown) for agitating the toner is disposed inside the housing 610a. ing. The toner stirring shaft is rotated by a drive motor (not shown).

  In one end side 610a1 of the housing 610a, a toner introduction port 611 for introducing toner supplied from the toner bottle 200 disposed above, and a replenishment passage body 612 disposed below for introducing toner into the developing device 23 are provided. And a toner supply port 610a4 for supplying toner inside the housing 610a.

  A toner introduction port 612b1 for introducing toner is formed in the upper portion of the replenishment passage body 612, and a toner passage (toner transport) through which the toner passes from the toner introduction port 612b1 to a toner discharge port 612a1 formed in the lower portion. Road) 612c1 is provided in a substantially straight line in the vertical direction.

Next, a characteristic developing device 23b according to the present embodiment will be described with reference to the drawings.
FIG. 4 is an explanatory diagram showing the configuration of the developing device according to the present embodiment, and is a cross-sectional view taken along the line EE of FIG. 2, and FIG.

  As shown in FIGS. 2 and 3, the developing device 23 includes a housing (developer housing portion) 234 that forms an exterior portion and stores developer, and is replenished to the upper portion of the housing 234. A toner introduction port 234a for introducing toner is formed as an opening, and a first toner conveyance shaft 232, a second toner conveyance shaft 233, and a developing roller 231 are disposed inside the casing 234 as agitating and conveying means. The roller 231 is attached to the image forming apparatus main body in a state where the roller 231 is opposed to or brought close to the photosensitive drum 21. The toner introduction port 234a is formed outside the transfer belt width W on the same side as the toner introduction port 611 of the toner supply unit mounting mechanism 600.

  The housing 234 has a long box shape in a direction (transfer belt width direction) perpendicular to a transfer direction (transfer belt conveyance direction) in a state of being mounted on the image forming apparatus main body, and the developing device 23 is connected to the image forming apparatus. An opening 235 is formed so that the developing roller 231 and the photosensitive drum 21 that are present in the state of being mounted on the main body face each other.

  The opening 235 is formed to be long in the width direction of the housing 234 along the axial direction of the developing roller 231 so that at least the developing roller 231 can come into contact with the photosensitive drum 21. A blade 236 is provided along the axial direction of the developing roller 231 at the lower edge of the opening 235 in the drawing. The blade 236 is provided so as to form a predetermined gap between the edge of the blade 236 and the surface of the developing roller 231, and a predetermined amount of toner is supplied to the surface of the developing roller 231 through this gap. ing.

  The first toner transport shaft 232 and the second toner transport shaft 233 are arranged in parallel with each other along the axial direction of the developing roller 231 on the bottom side in the housing 234, and develop the toner supplied into the housing 234. The developer is conveyed to the developing roller 231 while stirring together with the agent. The developing roller 231 is disposed on the upper side of the second toner conveying shaft 233 so as to be exposed from the opening 235.

  A partition wall 234b is disposed between the first toner transport shaft 232 and the second toner transport shaft 233, and the inside of the housing 234 is axially directed to the first toner transport shaft 232 side and the second toner transport shaft 233 side. It is divided along.

  The first toner transport shaft 232 and the second toner transport shaft 233 are provided with screw bodies 232a and 233a for stirring and transporting toner, respectively, and drive gears 232b and 233b provided on the other end side 234c2 of the housing 234. And is driven to rotate by a drive motor (not shown).

As shown in FIG. 4, the first toner transport shaft 232 is configured such that the end of one end 234 c 1 of the housing 234 is longer than the second toner transport shaft 233.
A toner introduction portion 234d is formed on one end side 234c1 of the housing 234 so as to protrude sideways corresponding to the long end portion of the first toner conveyance shaft 232, and the toner introduction portion 234d has an upper portion on the toner introduction portion 234d. An introduction port 234a is formed as an opening. The replenishment toner is supplied from the toner introduction port 234a to the first toner conveyance shaft 232 side.

  As shown in FIGS. 4 and 5, a magnet (magnetic force generating means) 250 is disposed outside the toner introducing portion 234 d. The magnet 250 is a developer stored in the housing 234 below the toner introduction port 234a opposite to the side (the photosensitive drum 21 side) where the developing roller 231 of the toner introduction unit 234d is disposed. It is arranged at a position lower than the upper layer surface 23G. That is, the magnet 250 is disposed below the toner conveyance path to be supplied to the first toner conveyance shaft 232 side.

Further, as shown in FIG. 5, the magnet 250 performs the rotation operation (arrow A <b> 1) of the first toner conveyance shaft 232 at a position close to and opposed to the lower side of the axis (rotation center) of the first toner conveyance shaft 232. It arrange | positions in the rotation direction upstream at the side which goes to the downward direction from upper direction.
The toner replenishing device 100 is disposed on the upper side of the developing device 23 configured as described above.

Next, the agitating action of the replenishment toner by the developing device 23 according to this embodiment will be described with reference to the drawings.
In the developing device 23 and the toner replenishing device 100, the toner concentration of the developer in the housing 234 is detected by a toner concentration sensor (not shown) disposed in the housing 234, and the developer in the developing device 23 is in operation. When the toner density of the toner drops, the toner supply signal from the toner density sensor is received and the toner supply device 100 is controlled to supply toner to the developing device 23.

  As shown in FIG. 2, the toner supplied from the toner replenishing device 100 is supplied from the upper part of the housing 234 to the inside through the toner introduction port 234 a of the developing device 23 through the replenishment passage body 612. The supplied toner is put on top of the developer stored so as to cover the first toner transport shaft 232.

  At this time, the toner concentration of the developer near the upper portion of the first toner conveyance shaft 232 is in a very high state. This is because the specific gravity of the toner is usually smaller than that of other materials such as a carrier constituting the developer, so that much of the charged toner does not enter the developer and the surface of the developer. This is because it exists in the vicinity.

  Toner (hereinafter referred to as replenishment toner) charged into the housing 234 is agitated and conveyed by the first toner conveying shaft 232 together with the stored developer. At this time, inside the developer, as shown in FIG. 4, a magnetic brush 250 a is formed by a magnet 250 disposed below the side of the first toner transport shaft 232.

  As shown in FIG. 5, the replenishment toner is agitated toward the inside of the developer in the clockwise direction (in the drawing) from the upper portion of the stored developer by rotating the first toner conveying shaft 232 in the direction of the arrow A1. It is conveyed and held inside the developer by the magnetic brush 250a.

  The replenishment toner held by the magnetic brush 250a formed by the magnet 250 inside the developer is conveyed while being further stirred inside the developer by the conveying action of the screw body 232a of the first toner conveying shaft 232. The mixing and stirring is effectively performed with the developer on the upstream side in the direction. That is, the replenishment toner stirred and transported into the developer by the first toner transport shaft 232 is transported while being mixed and stirred with the developer without being lifted by the magnetic force of the magnet 250.

  In the portion where the magnetic brush 250a inside the developer is formed, a gap is opened, and the developer density is apparently lowered. When the replenishment toner enters the gap, the developer and the replenishment toner are mixed. Then, the replenishment toner is pushed toward the bottom of the developer in the housing 234 by the rotational force and conveying action of the screw body 232a as the first conveying shaft 232 rotates.

  In this way, the newly supplied replenishment toner is agitated by the first toner conveyance shaft 232 and continuously agitated to the inner side of the housing 234 without staying in the vicinity of the toner introduction port 234a by continuing the agitation and conveyance action. It is sent. Specifically, as shown in FIG. 4, the replenishment toner is gradually sent to the right side along the first conveying shaft 232 and mixed with the developer on the right side to lower the toner concentration and return. At the time of moving to the second transport shaft 233, the specified toner density is set to 6.0% by weight.

  With the configuration as described above, according to the developing device 23 according to the present embodiment, when the magnet 250 is not provided, 40 to 70K sheets of toner overflowed, but when the magnet 250 is provided, 150K sheets are provided. Even with the above, the apparatus could be operated without overflowing the toner.

Here, an embodiment in which the magnet 250 is disposed in the housing 234 of the developing device 23 will be described with reference to the drawings.
FIG. 6 is a comparison table showing the surface magnetic flux dependency according to the specifications of the magnet arranged in the housing of the developing device according to the present embodiment, and FIG. 7 is a comparison table showing the magnet arrangement dependency according to the mounting position of the magnet. FIG. 8 is a comparison table showing magnet dependence according to a plurality of types of permanent magnets employed as the magnet.

  In the embodiment, ABS is used as a resin agent for forming the housing 234, the length of the toner introduction part 234d into which the toner is introduced: L2 = 35 mm, the width of the toner introduction part 234d: W2 = 20 mm, and the magnet 250 are arranged. Wall surface thickness: t2 = 2 mm.

  As the magnet 250, a neodymium magnet (permanent magnet) having a magnetic force of 1000 G is used, the thickness is t = 3 mm, the height along the depth direction of the developer is h = 5 mm, and the first toner transport shaft 232 has an axial width. : L = 11 mm, and the center line CL1 passing through the center of the magnet 250 at a position below the developer level (upper surface) is perpendicular to the first toner transport shaft 232 (vertical line CL2). ) So as to be at a position inclined by 60 °.

  As a developer carrier, a ferrite carrier of 60 μm and 65 emu is used. The magnet 250 forms a magnetic brush with a ferrite carrier in the developer.

First, the surface magnetic flux density dependency of the magnet 250 in this example was verified by changing the thickness of the magnet 250.
As shown in FIG. 6, the thickness of the magnet 250 is 1 mm, 1.5 mm, 2 mm, 2, 5 mm, 3 mm, respectively, when the toner replenishment amount is 5 g and the magnet 250 is not attached and when the magnet 250 is attached. For 7 conditions when the thickness is 5 mm, the density of toner at the center and the other end of the housing 234 was measured and compared.

  In this embodiment, the magnet 250 is a neodymium magnet manufactured by Nikko Manufacturing Co., Ltd., the toner concentration to be charged is 5.5 wt%, the residual magnetic flux density (Br) is 1.2 T (12 kG), It is assumed that 1T (Tesla) = 10000 G (Gauss).

  According to the measurement result, when the thickness of the magnet 250 is 1.5 to 3 mm under the conditions of this embodiment, the surface magnetic flux density is 0.1190 to 0.1859 (T), and the developer in the housing 234 It can be seen that the toner density becomes substantially uniform at 5.9 to 6.0 wt%.

  On the other hand, when the magnet 250 is not attached or when the thickness of the magnet 250 is as thin as 1 mm, the surface magnetic flux density is 0 to 0.0868 (T) and the toner concentration is 5.6 to 5.7 wt. Little effect of mixing and stirring toner and developer.

  When the magnet 250 is as thick as 5 mm, the surface magnetic flux density is 0 to 0.0868, the toner concentration is 5.6 to 5.7 wt%, and the carrier spike is too strong, so Little effect of mixing and stirring with developer.

  From this, the mixing and stirring action of the replenishing toner and the developer is promoted by mounting the magnet 250. In particular, the surface magnetic flux density is set according to the installation conditions of the magnet 250 and the thickness of the magnet 250, and the toner replenishment amount, etc. It can be seen that the optimum toner and developer can be mixed and stirred uniformly with the replenishment toner and the developer.

Next, the placement dependency of the magnet 250 in this example was verified by changing the placement angle of the magnet 250.
As shown in FIG. 7, the toner replenishment amount is 5 g, the magnet 250 is not installed, and the magnet 250 is installed at 40 °, 45 °, 60 °, 75 °, and 90 ° when the magnet 250 is attached. , 105 °, and 120 °, the toner concentrations at the center and the other end of the housing 234 were measured and compared.

  According to the measurement result, when the installation angle of the magnet 250 is 40 °, 45 °, 60 °, 75 °, and 90 ° under the conditions of the present embodiment, the toner concentration of the developer in the housing 234 is 5.9 to 5.9. It turns out that it becomes substantially uniform at 6.0 wt%.

  On the other hand, when the magnet 250 is not mounted or when the magnet 250 is installed at a position with a small inclination of 40 ° and close to the bottom, the toner concentration becomes 5.6 to 5.8 wt% and the replenishing toner and the development are developed. The effect of mixing and stirring with the agent is small. That is, the influence of the magnetic brush on the replenishment toner in the upper part in the developer is small.

  In addition, when the installation angle of the magnet 250 is set to a position higher than the horizontal state of 105 ° and 120 °, the toner concentration becomes 5.7 to 5.8 wt% and 5.6 to 5.7 wt%. The higher the position, the less effective the mixing and stirring of the replenishment toner and the developer. In other words, the influence of the magnetic brush on the replenishment toner at the upper part in the developer is too great, and the toner prevents stirring downward in the developer.

Next, the magnet dependence of the magnet 250 in this example was verified by changing the type of magnet used for the magnet 250.
As shown in FIG. 8, the toner replenishment amount is 5 g, and the toner at the center and the other end of the housing 234 is subjected to four conditions when a neodymium magnet, ferrite magnet, sumakoba magnet, and alnico magnet are used for the magnet 250, respectively. The concentration of was measured and compared.

  According to the measurement results, when a neodymium magnet and an alnico magnet are used as the magnet 250 under the conditions of the present embodiment, the toner concentration of the developer in the housing 234 becomes substantially uniform at 6.0 to 6.1 wt%. I understand that.

  On the other hand, in the case where a ferrite magnet and a Samacoba magnet are used as the magnet 250, the toner concentration becomes 5.8 to 5.9 wt%, and the effect of mixing and stirring the replenishment toner and the developer is small. In addition, a ferrite magnet is cheap compared with two types in which the effect of mixing and stirring is good, and a sumaboba magnet is easily cracked. Alnico magnets have the disadvantage that they are easy to demagnetize although the effect of mixing and stirring is good and the dimensional accuracy is high.

  As described above, according to the present embodiment and the example, in the developing device 23, the magnet 250 is adjacent to the toner introduction port 234 a in the housing 234 from the outside in the housing 234 that is a developer container. Since the replenishment toner and the developer can be smoothly mixed and stirred by the magnetic brush 250a by the magnetic carrier formed by the magnet 250, the toner density of the appropriate developer can be reached in a short time.

  Further, according to the present embodiment, a magnet (permanent magnet) 250 is adopted as the magnetic force generating means constituting the developing device 23, and a neodymium magnet is used for the magnet 250, so that the configuration is simple and inexpensive and efficient. The replenishment toner and the developer can be mixed and stirred well.

  Furthermore, according to the embodiment, since the magnet 250 is arranged on the upstream side in the rotation direction on the side where the rotation operation of the first toner conveyance shaft 232 is directed from the upper side to the lower side, the replenishment toner is agitated and conveyed downward in the developer. Therefore, mixing and stirring can be performed effectively.

  In the present embodiment and example, the magnet 250 is provided outside the housing 234. However, the magnet 250 is disposed in the housing 234 within a range that does not affect the stirring and transport of the developer by the first toner transport shaft 232. It is also possible to do.

  Further, in the present embodiment and examples, a permanent magnet is used for the magnet 250 as the magnetic force generation means according to the present invention. However, the present invention is not limited to the configuration of the magnetic force generation means. As an alternative, instead of the magnet 250, an electromagnet may be employed as the electric magnetic force generation means.

Hereinafter, a developing device that employs an electromagnet as an electric magnetic force generation unit in place of the magnet 250 according to the embodiment described above as a modification will be described in detail with reference to the drawings.
FIG. 9 is an explanatory diagram showing a configuration of a modified example of the magnetic force generating means constituting the developing device according to the present invention, and FIG. 10 is a block diagram showing a configuration related to toner replenishment control in the developing device.

  As shown in FIG. 9, the developing device 123 according to the modified example employs an electromagnet 350 as an electric magnetic force generating unit instead of the magnet 250 of the developing device 23 according to the above-described embodiment. In addition, in the developing device 123, what has the same configuration as the developing device 23 according to the above-described embodiment is denoted by the same reference numeral, and description thereof is omitted.

  The housing 234 constituting the developing device 123 is formed with a toner introducing portion 234d as in the above-described embodiment, and an electromagnet (electric magnetic force generating means) is formed outside the toner introducing portion 234d as shown in FIG. 350 is arranged.

  The electromagnet 350 is a developer stored in the housing 234 under the toner introduction port 234a opposite to the side (the photosensitive drum 21 side) where the developing roller 231 of the toner introduction unit 234d is disposed. It is arranged at a position lower than the upper layer surface 23G. That is, the electromagnet 350 is disposed below the path for transporting toner to be supplied to the first toner transport shaft 232 side.

In addition, the electromagnet 350 is located close to and opposite to the lower side of the axis (rotation center) of the first toner conveyance shaft 232, and the rotation operation (arrow A1) of the first toner conveyance shaft 232 is directed from the upper side to the lower side. Arranged upstream in the rotational direction.
The operation of the electromagnet 350 configured as described above is controlled by the electromagnet driving means 351 so that the energized state can be turned on / off.

Next, operation control of the electromagnet 350 will be described with reference to a block diagram.
Operation control of the electromagnet 350 is controlled by a control unit 400 that controls each driving unit related to driving of the developing device 23 as shown in FIG.

  The control unit 400 determines whether or not the toner concentration of the developer in the developing device 23 is appropriate, and toner supply control means that controls the operation of the toner replenishing device 100 based on the determination result by the determination unit 410. 420 is provided.

The determination unit 410 determines whether the toner density is an appropriate value based on a detection signal from the toner density sensor 430 disposed in the housing 234.
The toner supply control means 420 controls the operation of the toner replenishment drive means 440 that drives the toner replenishing device 100 based on the determination result by the determination means 410, and includes the developing roller 231, the first toner transport shaft 232, and the second toner transport shaft. It controls the operation of the development drive means 450 that drives 233.

When the toner supply operation is performed by the toner replenishment drive unit 440, the electromagnet drive unit 351 is driven to energize the electromagnet 350 in accordance with toner replenishment.
The energization operation of the electromagnet 350 by the electromagnet driving means 351 may be controlled so that the magnetic force generation state can be varied according to the amount of toner supplied from the toner supply device 100.

  Since the developing device 123 includes the electromagnet 350, the replenishment toner and the developer can be mixed and stirred effectively according to the supply amount of the replenishment toner. Further, by variably controlling the magnetic force generation state of the electromagnet 350 by the electromagnet driving means 351, an optimal magnetic brush can be formed according to the stirring state of the replenishing toner and developer, and the replenishing toner can be mixed and stirred.

  In this way, by adopting the electric magnetic force generating means, it becomes possible to control the operation according to the operating time of the developing device and the number of output sheets of paper, and to variably control the magnetic force generating state. Detailed operation control according to the state and operation status becomes possible.

  In the above-described embodiments, examples, and modifications, the example in which the developing devices 23 and 123 are applied to the image forming apparatus as shown in FIG. 1 has been described. However, the present invention is not limited to this example. 11 may be applied to the copying machine 101 as shown in FIG.

As shown in FIG. 11, the copier 101 has an image reading device (scanner) 110 disposed above an image forming unit 108 having a configuration substantially similar to that of the image forming apparatus 1 according to the present embodiment. The first paper feed cassette 142a, the second paper feed cassette 142b, the third paper feed cassette 142c, and the fourth paper feed cassette 142d corresponding to a plurality of types of paper are disposed below the 108, and each has a developing device. The process printing units 20a, 20b, 20c, and 20d are configured to automatically perform a variety of mass printing while supplying toner.
Reference numeral 120 in the figure denotes a waste toner box that collects waste toner.
Incidentally, in the copying machine 101, those having the same configuration as that of the image forming apparatus 1 according to the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

  According to the copying machine 101 configured as described above, the same effects as those of the image forming apparatus 1 according to the above-described embodiment can be achieved by employing the developing device according to the present invention.

  Furthermore, the present invention is not limited to the image forming apparatus and the copying machine having the above-described configuration as long as the image forming apparatus has a developing device that replenishes toner, and can be applied to other image forming apparatuses. Is possible.

  As described above, the present invention is not limited to the above-described embodiments, examples, modifications, and the like, and various modifications are possible within the scope indicated in 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.

  For example, in the above-described embodiment, the present invention is applied to a color image forming apparatus in which a plurality of developing devices are installed. However, the present invention may be applied to an image forming apparatus in which a monochrome developing device is installed. Is possible.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus employing a developing device according to the present invention. FIG. 2 is a schematic side cross-sectional view illustrating a configuration of a developing device and a toner replenishing device that constitute the image forming apparatus. FIG. 3 is a schematic view of a configuration of the developing device and a toner replenishing device viewed from the front. It is explanatory drawing which shows the structure of the said developing device, Comprising: It is EE sectional drawing of FIG. It is F arrow line view of FIG. It is a comparison table | surface which shows the surface magnetic flux dependence according to the specification of the magnet arrange | positioned in the housing | casing of the said developing device. It is a comparison table | surface which shows the magnet arrangement | positioning dependence according to the attachment position of the said magnet. It is a comparison table | surface which shows the magnet dependence according to the multiple types of permanent magnet employ | adopted as the said magnet. It is explanatory drawing which shows the structure of the modification of the magnetic force generation means which comprises the developing device which concerns on this invention. FIG. 4 is a block diagram illustrating a configuration relating to toner supply control in the developing device. It is explanatory drawing which shows the structure of the whole copying machine which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20, 20a, 20b, 20c, 20d Process printing unit 23, 23a, 23b, 23c, 23d Developing device 23G Upper surface 100, 100a, 100b, 100c, 100d Toner replenishing device 101 Copier 123 Developing device 231 Developing Roller 232 First toner conveying shaft (stirring conveying means)
232a, 233a Screw bodies 232b, 233b Drive gear 233 Second toner conveying shaft (stirring conveying means)
234 housing (developer housing part)
234a Toner introduction port 234b Partition body 234d Toner introduction part 250 Magnet (magnetic force generating means)
250a Magnetic brush 350 Electromagnet (electrical magnetic force generating means)
351 Electromagnet Drive Unit 400 Control Unit 410 Determination Unit 420 Toner Supply Control Unit 430 Toner Concentration Sensor 440 Toner Supply Drive Unit 450 Development Drive Unit

Claims (10)

A developer container that contains a developer containing a chargeable toner and a magnetic carrier; a developing roller that supplies toner to an electrostatic latent image carrier on which an electrostatic latent image is formed; and the developer container A developing and conveying device that stirs and conveys the developer, and visualizes the electrostatic latent image formed on the electrostatic latent image carrier with toner,
2. A developing device according to claim 1, wherein a toner introduction port for introducing toner from the outside into the developer accommodation unit is provided in the developer accommodation unit, and a magnetic force generating means is disposed adjacent to the toner introduction port.   The developing device according to claim 1, wherein the magnetic force generating unit is disposed at a position lower than an upper layer surface of the developer stored in the developer accommodating portion.   The developing device according to claim 1, wherein the magnetic force generation unit is disposed below a conveyance path of toner to be introduced. The agitating and conveying means is arranged along the axial direction of the developing roller and is configured to agitate and convey the developer by a rotating operation,
The magnetic force generating means is arranged in the vicinity of the stirring and conveying means, and arranged on the upstream side in the rotational direction on the side from which the rotating operation of the stirring and conveying means is directed downward from above. The developing device according to any one of the above.   5. The developing device according to claim 1, wherein the magnetic force generating unit is disposed outside the developer accommodating portion.   The developing device according to claim 1, wherein the magnetic force generation unit uses a permanent magnet.   The developing device according to claim 6, wherein the permanent magnet is a neodymium magnet, an alnico magnet, a ferrite magnet, or a sumakoba magnet.   The developing device according to claim 1, wherein the magnetic force generation unit is an electric magnetic force generation unit and is configured to be turned on / off.   The developing device according to claim 8, wherein the magnetic force generation unit is controlled to be able to change a magnetic force generation state in accordance with the amount of toner introduced. A developer container that contains a developer containing a chargeable toner and a magnetic carrier; a developing roller that supplies toner to an electrostatic latent image carrier on which an electrostatic latent image is formed; and the developer container An agitating / conveying means for agitating and conveying the developer, and a developing device that visualizes the electrostatic latent image formed on the electrostatic latent image bearing member with toner, and the static image is obtained by electrophotography. In an image forming apparatus that outputs an image by transferring a developer image formed on the surface of an electrostatic latent image carrier onto a transfer medium,
An image forming apparatus using the developing device according to claim 1 as the developing device.

Images