JP2018040907A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce variations in toner density of a two-component developer stored in a developer storage container due to a change in the amount of carrier in the developer, compared with a case where a developing device does not include an operating body that is arranged at a supply port of a carrier storage container and operates to close the supply port when the height of the surface of the developer inside the developer storage container reaches a predetermined value or more.SOLUTION: A developing device comprises: a device housing 140 that stores a two-component developer 4 including toner and carrier: a developing roll 141 that holds the developer 4; a carrier storage container 170 that stores a carrier CA and has a supply port for supplying the carrier CA into the device housing 140 at a lower end part; and a valve body 173 that is arranged at the supply port of the carrier storage container 170 and operates to close the supply port when the height of the surface of the developer inside the device housing 140 reaches a predetermined value or more.SELECTED DRAWING: Figure 3

Description

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

  2. Description of the Related Art Conventionally, as a developing device, a two-component developer containing toner and a carrier is accommodated in an apparatus main body, and an electrostatic latent image formed on a photosensitive drum is developed with a two-component developer. is there. As a technique for adjusting the amount of developer in the apparatus main body in such a developing apparatus, for example, those disclosed in Patent Documents 1 and 2 have already been proposed.

  In Patent Document 1, a developer in a developer container storing a two-component developer containing toner and a carrier is supported on a developer carrier by a magnetic force, and is carried on the developer carrier by a developer regulating member. After regulating the amount of the developer, the developer is transported to the developing area facing the latent image carrier by rotation, and the toner container is connected to the developer container via the toner intake port. In the developing device that takes in the toner by movement of the developer, a valve that can be opened and closed is provided at the toner taking-in port, and the valve opens and closes according to a change in the volume of the developer in the developer accommodating portion.

  Patent Document 2 discloses a developer container that contains a developer, a developer carrier that supplies the developer in the developer container to the development target, and a developer transport member that transports the developer in the developer container. A developer container having a developer discharge port for discharging the developer in the developer container by overflowing the developer container, and a developer supply means for supplying the developer to the developer container. The developing container is configured to be provided with detecting means for detecting the surface of the developer in the developing container.

Japanese Patent Laid-Open No. 11-194596 JP 2005-292511 A

  An object of the present invention is to provide an operating body that is disposed at a replenishing port of a carrier container and that operates to close the replenishing port when the height of the developer surface in the developer containing container exceeds a predetermined value. Compared to the case where the developer is not provided, the toner concentration of the two-component developer accommodated in the developer accommodating container is prevented from fluctuating due to a change in the carrier amount in the developer.

The invention described in claim 1 is a developer container that contains a two-component developer containing toner and a carrier;
A developer holder for holding the developer;
A carrier container that contains the carrier and has a replenishing port at the lower end for replenishing the carrier into the developer container;
An actuating element disposed at the replenishing port of the carrier containing container and operating to close the replenishing port when the height of the developer surface in the developer containing container is equal to or greater than a predetermined value;
Is a developing device.

According to a second aspect of the present invention, there is provided a developer storage container for storing a two-component developer containing toner and a carrier;
A developer holder that is rotatably arranged in the opening of the developer container and holds the developer;
A toner container having a supply port for containing the toner and supplying the toner into the developer container;
An outer periphery that is rotatably disposed at the supply port of the toner storage container and closes the supply port when the height of the developer surface in the developer storage container exceeds a predetermined first value. A rotating body that rotates while holding developer,
A carrier container that contains the carrier and has a replenishing port at the lower end for replenishing the carrier into the developer container;
When the height of the developer surface in the developer container is equal to or higher than a predetermined second value that is lower than the first value, the replenishment port is disposed at the replenishment port of the carrier container. An actuating body that operates to close;
Is a developing device.

  According to a third aspect of the present invention, there is provided the developer according to the third aspect, wherein the developer acts on the developer when the height of the developer surface in the developer container reaches or exceeds a predetermined value. The developing device according to claim 1, wherein the developing device operates to close the replenishing port by buoyancy.

  According to a fourth aspect of the present invention, the operating body is rotatably disposed at the replenishing port of the carrier container, and the height of the developer surface in the developer container is greater than or equal to the second value. 3. The developing device according to claim 1, further comprising a rotating body that rotates while holding a developer on an outer periphery so as to close the replenishing port.

The invention described in claim 5 includes an image holding body for holding an electrostatic latent image;
Developing means for developing the electrostatic latent image held on the image carrier;
With
An image forming apparatus using the developing device according to claim 1 as the developing unit.

  According to the first aspect of the present invention, the replenishment port is closed when the height of the developer surface in the developer storage container becomes equal to or higher than a predetermined value, which is disposed at the replenishment port of the carrier storage container. As compared with the case where the operating body is not provided, the toner concentration of the two-component developer stored in the developer container is suppressed from fluctuating due to the change in the carrier amount in the developer. be able to.

  According to the second aspect of the present invention, when the height of the developer surface in the developer container is greater than or equal to the second value which is lower than the first value. The toner concentration of the two-component developer contained in the developer container changes due to the change in the carrier amount in the developer, compared with the case where the operating body that operates to close the supply port is not provided. Can be suppressed.

  According to the third aspect of the present invention, the carrier can be replenished inside the developer container with a simple configuration.

  According to the fourth aspect of the present invention, the carrier can be stably replenished inside the developer container.

  According to the fifth aspect of the present invention, it is possible to suppress a decrease in image quality due to a change in the toner density of the developer in the developing device.

1 is a schematic configuration diagram showing an image forming apparatus to which a developing device according to Embodiment 1 of the present invention is applied. 1 is a configuration diagram illustrating an image forming unit of an image forming apparatus to which a developing device according to Embodiment 1 of the present invention is applied. 1 is a cross-sectional configuration diagram illustrating a developing device according to a first embodiment of the present invention. 1 is a plan configuration diagram illustrating a developing device according to Embodiment 1 of the present invention; It is a schematic diagram which shows a developing agent. It is an expanded sectional view which shows the developing device concerning Embodiment 1 of this invention. It is an expanded sectional view of the operation of the developing device according to the first embodiment of the present invention. It is a schematic diagram which shows the change of the bulk density of a developing agent. It is a schematic diagram which shows the discharge | release phenomenon of a carrier. 6 is a graph showing the relationship between toner density and developer bulk density. It is an expanded sectional view which shows the effect | action of the developing device which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the change of the bulk density of the developer accompanying supply of a carrier. It is an expanded sectional view which shows the effect | action of the developing device which concerns on Embodiment 2 of this invention. It is a plane block diagram which shows the effect | action of the developing device which concerns on Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
1 and 2 show an image forming apparatus to which the developing device according to the first embodiment is applied. FIG. 1 shows an outline of the entire image forming apparatus, and FIG. 2 shows an enlarged main part (image forming apparatus, etc.) in the image forming apparatus.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 according to the first embodiment is configured as a color printer, for example. The image forming apparatus 1 includes a plurality of image forming apparatuses 10 that form toner images developed with toner constituting the developer, and the toner images formed by the respective image forming apparatuses 10 for final recording. An intermediate transfer device 20 that transports to a secondary transfer position for secondary transfer to a recording sheet 5 as an example of a medium, and a required recording sheet 5 to be supplied to the secondary transfer position of the intermediate transfer device 20 are accommodated and transported. A sheet feeding device 50 and a fixing device 40 for fixing the toner image on the recording paper 5 secondarily transferred by the intermediate transfer device 20 are provided. In the figure, reference numeral 1a denotes an apparatus main body of the image forming apparatus 1. The apparatus main body 1a is formed of a support structure member, an exterior cover, or the like. In addition, a two-dot chain line in the figure indicates a main conveyance path through which the recording paper 5 is conveyed in the apparatus main body 1a.

  The image forming device 10 includes four image forming devices 10Y, 10M, 10C, and 10K that respectively form four color toner images exclusively for yellow (Y), magenta (M), cyan (C), and black (K). It is configured. These four image forming apparatuses 10 (Y, M, C, K) are arranged so as to be arranged in a line in an inclined state in the internal space of the apparatus main body 1a.

  As shown in FIG. 1, each image forming device 10 (Y, M, C, K) includes a photosensitive drum 11 that holds and rotates an electrostatic latent image as an example of an image holding member. Around the photosensitive drum 11, each apparatus as an example of the following toner image forming means is mainly arranged. The main devices are a charging device 12 that charges a peripheral surface (image holding surface) on the photosensitive drum 11 on which an image can be formed to a required potential, and image information (on the charged peripheral surface of the photosensitive drum 11). The exposure device 13 that irradiates the light LB based on the signal) to form an electrostatic latent image for each color having a potential difference, and the developer of the corresponding color (Y, M, C, K). A developing device 14 (Y, M, C, K) as an example of a developing unit that develops with toner to form a toner image, and a primary transfer as an example of a primary transfer unit that transfers each toner image to the intermediate transfer device 20 A device 15 (Y, M, C, K) and a drum cleaning device 16 (Y, M, K) that removes and removes adhering substances such as toner remaining on the image holding surface of the photosensitive drum 11 after the primary transfer. C, K) and the like.

  The photosensitive drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar base material to be grounded. The photosensitive drum 11 is supported so as to rotate in a direction indicated by an arrow A when power is transmitted from a driving device (not shown).

  The charging device 12 includes a contact-type charging roll that is disposed in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. As the charging voltage, when the developing device 14 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied. As the charging device 12, a non-contact type charging device such as a scorotron disposed in a non-contact state on the surface of the photosensitive drum 11 may be used.

  The exposure device 13 forms an electrostatic latent image by irradiating the charged surface of the photosensitive drum 11 with light LB configured according to image information input to the image forming device 1. To do. In this embodiment, one exposure device 13 common to the four image forming devices 10Y, 10M, 10C, and 10K of yellow (Y), magenta (M), cyan (C), and black (K) is used. . When the latent image is formed, the exposure device 13 receives information (signal) of an image that is input to the image forming device 1 by any means and is subjected to image processing by an image processing unit (not shown). The exposure device 13 irradiates the photosensitive drum 11 with light corresponding to image information by LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of each photosensitive drum 11. An LED print head that forms an electrostatic latent image may be used. In this case, the exposure device 13 is arranged corresponding to each photosensitive drum 11.

  As shown in FIG. 2, each of the developing devices 14 (Y, M, C, K) holds the developer 4 inside an apparatus housing 140 in which an opening and a storage chamber for the developer 4 are formed. A developing roll 141 that conveys the developer 4 to a developing area facing the photosensitive drum 11, a supply conveying member 142 such as two screw augers that convey the developer 4 so as to pass through the developing roll 141 while stirring, and an agitating and conveying member 143. A layer thickness regulating member 144 that regulates the amount (layer thickness) of the developer 4 held on the developing roll 141 is arranged. A developing voltage is supplied to the developing device 14 between a developing roll 141 and the photosensitive drum 11 from a power supply device (not shown). Further, the developing roll 141, the supply conveyance member 142, and the agitation conveyance member 143 are rotated in a required direction when power is transmitted from a driving device (not shown). Further, as the four-color developer 4 (Y, M, C, K), a two-component developer containing a non-magnetic toner and a magnetic carrier is used. The developing device 14 will be described in detail later.

  The primary transfer device 15 (Y, M, C, K) is in contact with the periphery of the photosensitive drum 11 via an intermediate transfer belt 21 and rotates, and a contact type provided with a primary transfer roll to which a primary transfer voltage is supplied. This is a transfer device. As the primary transfer voltage, a DC voltage having a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

  The drum cleaning device 16 is disposed so as to come into contact with the container-shaped main body, which is partially open, and the peripheral surface of the photosensitive drum 11 after the primary transfer at a required pressure, and removes adhered matters such as residual toner to clean the drum. And a delivery member such as a screw auger that collects and removes deposits such as toner removed by the cleaning plate and sends them to a collection system (not shown).

  As shown in FIG. 1, the intermediate transfer device 20 is arranged to be present at a position above each image forming device 10 (Y, M, C, K). The intermediate transfer device 20 includes an intermediate transfer belt 21 that rotates in a direction indicated by an arrow B while passing a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll), and an intermediate transfer belt 21. A plurality of belt support rolls 22 to 25 that are held in a desired state from their inner surfaces and are rotatably supported, and an outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support roll 25. A secondary transfer device 30 as an example of a secondary transfer means for secondary transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5, and the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30. The belt cleaning device 26 is mainly composed of a cleaning device 26 that removes and removes adhering matters such as toner and paper dust that remain and adhere.

  As the intermediate transfer belt 21, for example, an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. Further, the belt support roll 22 is configured as a drive roll that is rotationally driven by a driving device (not shown), the belt support roll 23 is configured as a surface roll that holds the traveling position of the intermediate transfer belt 21, and the belt support roll 24 is The belt is provided as a tension applying roll that applies tension to the intermediate transfer belt 21, and the belt support roll 25 is configured as a backup roll constituting secondary transfer means.

  As shown in FIG. 1, the secondary transfer device 30 is configured to move the intermediate transfer belt 21 at a secondary transfer position that is an outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roll 25 in the intermediate transfer device 20. The contact type transfer device includes a secondary transfer roll 31 that constitutes a secondary transfer unit that rotates in contact with a peripheral surface and is supplied with a secondary transfer voltage. The secondary transfer device 30 includes a secondary transfer roll 31 and a belt support roll 25 as a backup roll. The secondary transfer roll 31 or the belt support roll 25 is supplied with a DC voltage having a polarity opposite or the same as the charging polarity of the toner as a secondary transfer voltage.

  The belt cleaning device 26 is disposed so as to be in contact with the peripheral surface of the intermediate transfer belt 21 after the secondary transfer and the container-shaped main body, which is partially opened, with a required pressure, and removes deposits such as residual toner. The cleaning plate is composed of a cleaning member to be cleaned and a delivery member such as a screw auger that transports the adhering material such as toner removed by the cleaning plate so as to collect it and send it to a collecting system (not shown).

  The fixing device 40 includes a drum-shaped or belt-shaped heating rotator 41 heated by a heating unit so that the surface temperature is maintained at a required temperature, and a predetermined state in a state substantially along the axial direction of the heating rotator 41. A drum-type or belt-type pressurizing rotating body 42 that rotates in contact with the pressure is arranged. In the fixing device 40, a contact portion where the heating rotator 41 and the pressing rotator 42 come into contact becomes a fixing processing unit that performs a required fixing process (heating and pressing).

  The sheet feeding device 50 exists at a position below the image forming devices 10 (Y, M, C, K) and the exposure device 13 for yellow (Y), magenta (M), cyan (C), and black (K). To be arranged. The paper feeding device 50 is a single (or plural) paper container 51 that accommodates recording paper 5 of a desired size, type, etc., and a sending device that sends out the recording paper 5 from the paper container 51 one by one. 52 and 53. The paper container 51 is attached, for example, so that it can be pulled out to the front side (side surface on which the user faces during operation) of the main body 1a.

  Examples of the recording paper 5 include plain paper, OHP sheets, and thin paper such as tracing paper used in electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, the surface of the recording paper 5 is preferably as smooth as possible. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. So-called cardboard having a relatively large basis weight can be used.

  Between the paper feeding device 50 and the secondary transfer device 30, a single (or plural) paper conveyance roll pair 54 for conveying the recording paper 5 delivered from the paper feeding device 50 to the secondary transfer position, or a conveyance guide (not shown). A paper feeding / conveying path 55 is provided. The pair of paper transport rolls 54 is configured as, for example, a roll (registration roll) that adjusts the transport timing of the recording paper 5. Further, at a portion near the discharge port of the recording paper 5 formed on the apparatus main body 1a, the recording paper 5 after fixing sent out from the fixing device 40 is discharged to a paper discharge portion 56 provided on the upper portion of the apparatus main body 1a. For this purpose, a pair of paper discharge rolls 57 is disposed.

  The pair of paper discharge rolls 57 is configured such that the rotation direction can be switched between a normal rotation direction (discharge direction) and a reverse rotation direction. When images are formed on both sides of the recording paper 5, the rotation direction of the paper discharge roll pair 57 is changed while the rear end of the recording paper 5 with the image formed on one side is held by the paper discharge roll pair 57. Switch from forward direction (discharge direction) to reverse direction. The recording paper 5 conveyed in the reverse direction by the paper discharge roll pair 57 is again transferred to the paper conveyance roll pair 54 in a state where the conveyance path is switched by a switching gate (not shown) and the front and back sides are reversed via the double-side conveyance path 58. Be transported.

  Reference numeral 100 in FIG. 1 denotes a control device that controls the operation of the image forming apparatus 1 in an integrated manner. The control device 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a bus connecting these CPU and ROM, a communication interface, and the like (not shown).

<Operation of Image Forming Apparatus>
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

  Here, using the four image forming devices 10 (Y, M, C, K), an operation of forming a full-color image configured by combining toner images of four colors (Y, M, C, K). Will be described.

  When the image forming apparatus 1 receives command information for requesting an image forming operation (printing), the four image forming apparatuses 10 (Y, M, C, K), the intermediate transfer apparatus 20, the secondary transfer apparatus 30, and the fixing apparatus. 40 etc. starts.

  In each image forming device 10 (Y, M, C, K), each photosensitive drum 11 first rotates in the direction indicated by arrow A, and each charging device 12 causes the surface of each photosensitive drum 11 to have a required polarity. (Embodiment 1 has negative polarity) and a potential. Subsequently, the exposure apparatus 13 converts the image information input to the image forming apparatus 1 into each color component (Y, M, C, K) with respect to the surface of the photosensitive drum 11 after charging. The light LB emitted based on this signal is irradiated, and an electrostatic latent image of each color component composed of a required potential difference is formed on the surface thereof.

  Subsequently, each image forming device 10 (Y, M, C, K) corresponds to the electrostatic latent image of each color component formed on the photosensitive drum 11 charged to a required polarity (minus polarity). Color (Y, M, C, K) toner is supplied from the developing roll 141 and electrostatically attached to perform development. By this development, the electrostatic latent images of the respective color components formed on the respective photosensitive drums 11 are visualized as toner images of four colors (Y, M, C, K) respectively developed with the corresponding color toners. It becomes.

  Subsequently, when each color toner image formed on the photosensitive drum 11 of each image forming device 10 (Y, M, C, K) is conveyed to the primary transfer position, the primary transfer device 15 causes each color image. The toner image is primarily transferred in a state where the toner image is sequentially superimposed on the intermediate transfer belt 21 rotating in the direction indicated by the arrow B of the intermediate transfer device 20.

  Further, in each image forming apparatus 10 for which the primary transfer has been completed, the drum cleaning device 16 cleans the surface of the photosensitive drum 11 by removing the adhered material so as to scrape off. Thereby, each image forming apparatus 10 is brought into a state in which the next image forming operation can be performed.

  Subsequently, in the intermediate transfer device 20, the toner image primarily transferred by the rotation of the intermediate transfer belt 21 is held and conveyed to the secondary transfer position. On the other hand, the paper feeding device 50 sends out the required recording paper 5 to the paper feeding conveyance path 55 in accordance with the image forming operation. In the paper feed transport path 55, a pair of paper transport rolls 54 as registration rolls feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

  At the secondary transfer position, the secondary transfer roll 31 of the secondary transfer device 30 collectively transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5. Further, in the intermediate transfer device 20 after the secondary transfer is completed, the belt cleaning device 26 removes the adhering matter such as toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer, and cleans it.

  Subsequently, the recording paper 5 on which the toner image is secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 31 and then conveyed to the fixing device 40. In the fixing device 40, the necessary fixing process (heating and heating) is performed by introducing and passing the recording sheet 5 after the secondary transfer through the contact portion between the rotating rotating body 41 for heating and the rotating body 42 for pressing. The unfixed toner image is fixed on the recording paper 5 by applying pressure. Finally, the recording paper 5 after the fixing is completed is ejected by the paper ejection roll pair 57 at the upper part of the apparatus main body 1a in the image forming operation only for forming an image on one side. It is discharged to the unit 56.

  When images are formed on both sides of the recording paper 5, the recording paper 5 with the image formed on one side is not discharged to the paper discharging unit 56 by the paper discharging roll pair 57, but the paper discharging roll pair 57 is used for the recording paper. While the rear end of the sheet 5 is held, the rotation direction of the sheet discharge roll pair 57 is switched to the reverse direction. The recording paper 5 transported in the reverse direction by the paper discharge roll pair 57 is transported again to the paper transport roll pair 54 in a state where the front and back sides are reversed via the double-side transport path 58. The pair of paper transporting rolls 54 feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing, forms an image on the back surface of the recording paper 5, and forms the image on the back of the apparatus main body 1 a by the paper discharge roll pair 57. The paper is discharged to the installed paper discharge unit 56.

  Through the above operation, the recording paper 5 on which a full color image formed by combining four color toner images is output. Note that the image forming apparatus 1 may naturally form a monochrome image on the recording paper 5 using only the black (K) image forming apparatus 10K.

<Configuration of developing device>
FIG. 3 is a sectional view showing the developing device according to the first embodiment.

  As shown in FIG. 3, the developing device 14 includes a device housing 140 as an example of a developer container. The apparatus housing 140 is roughly divided into a lower housing 140 a disposed at the lower portion of the developing device 14 and an upper housing 140 b disposed at the upper portion of the developing device 14. A developer accommodating chamber 150 for accommodating the two-component developer 4 is formed inside the apparatus housing 140 including the lower housing 140a and the upper housing 140b. The two-component developer 4 includes a carrier CA made of magnetic particles and a nonmagnetic toner T. The carrier CA has a particle size larger than that of the nonmagnetic toner T. An opening 151 is provided in a region of the apparatus housing 140 facing the photosensitive drum 11. Further, inside the apparatus housing 140, a developing roll 141 as an example of a developer holder is disposed so as to be rotatable along the arrow C direction so that a part of the developing roll 141 is exposed to the opening 151. The developing roll 141 is fixed inside and has a magnet roll 141a as an example of a magnetic field generating member in which a magnetic pole having a required polarity is arranged at a required position along the circumferential direction, and an arrow C on the outer periphery of the magnet roll 141a. And a cylindrical developing sleeve 141b as an example of a developer conveying member that is rotatably arranged along the direction at a required rotational speed. The developing sleeve 141b is formed in a cylindrical shape from a nonmagnetic material made of aluminum alloy, nonmagnetic stainless steel, or the like.

  In this embodiment, the rotation direction of the developing sleeve 141b is set to be the same as the rotation direction of the photosensitive drum 11. That is, the rotation direction of the photosensitive drum 11 is set in the clockwise direction as shown in FIG. The rotation direction of the developing sleeve 141b is also set in the clockwise direction. As a result, the outer peripheral surface of the developing sleeve 141 b moves in the direction opposite to the moving direction of the surface of the photosensitive drum 11 in the developing region facing the photosensitive drum 11. Note that the rotation direction of the developing sleeve 141b may be set in a direction opposite to the rotation direction of the photosensitive drum 11.

  In the apparatus housing 140, a supply conveyance member 142 made up of a screw auger (supply auger) or the like that pumps up the developer 4 stored in the developer storage chamber 150 and supplies the developer 4 to the developing roll 141. It is arranged obliquely downward along the direction. The supply conveyance member 142 is rotationally driven in a clockwise direction by a driving device (not shown). Further, inside the apparatus housing 140, an agitating and conveying member 143 composed of a screw auger (admix auger) that conveys the developer 4 supplied to the inside of the apparatus housing 140 while stirring is provided on the rear surface of the supplying and conveying member 142. Arranged on the side. The agitating / conveying member 143 is rotationally driven in a clockwise direction by a driving device (not shown). The amount (layer thickness) of the developer 4 supplied to the surface of the developing roll 141 by the supply conveyance member 142 is regulated by the cylindrical layer thickness regulating member 144.

  The lower housing 140 a is provided with a supply chamber 147 and a stirring chamber 148 that house the supply transport member 142 and the stirring transport member 143. The supply chamber 147 and the stirring chamber 148 are partitioned by a partition wall 152 provided in the lower housing 140a.

  As shown in FIG. 4, first and second passage portions 153 that transfer the developer 4 between the supply conveyance member 142 and the agitation conveyance member 143 are provided at both ends along the longitudinal direction of the partition wall 152. , 154 are provided.

  By the way, the developing device 14 according to this embodiment does not include a dedicated drive motor for supplying toner from the toner container to the inside of the developing device, and the height (bulk density) of the developer surface inside the developing device. The toner is configured as a two-component developing device of an autonomous toner supply type that autonomously supplies toner in response to the above. As shown in FIG. 5, the bulk density of the developer 4 is a case where the carrier CA and the toner T constituting the developer 4 and the gap formed between the carrier CA and the toner T are considered as a volume. Density. Therefore, even if the volume density (height) of the developer 4 is the same as the amount of the carrier CA constituting the developer 4, if the amount of the toner T is changed, the carrier CA and the toner T constituting the developer 4 are changed. It changes according to the volume of the space | gap formed between. Further, the bulk density (height) of the developer 4 has different values even when the amount of the carrier CA constituting the developer 4 is changed.

  Basically, if the volume of the device housing 140 of the developing device 14, the weight of the developer 4, and the amount of the carrier CA are the same, the height (bulk density) of the developer surface in the device housing 140 is the same. Become. However, even if the height (bulk density) of the developer surface in the apparatus housing 140 is the same, the concentration of the toner T in the developer 4 differs if the amount of the carrier CA in the apparatus housing 140 is different.

  As shown in FIG. 3, a toner cartridge 160 as an example of a toner storage container that stores toner T to be supplied to the inside of the apparatus housing 140 is disposed on the rear side of the developing device 14. The toner cartridge 160 is disposed along the longitudinal direction of the developing device 14 over substantially the entire length of the developing device 14. The toner cartridge 160 includes a toner cartridge main body 161. The toner T is accommodated in the toner cartridge main body 161. Further, a supply port 162 for supplying the accommodated toner T to the inside of the developing device 14 is opened at the bottom (lower end) of the toner cartridge main body 161. The supply port 162 is formed integrally with the toner cartridge body 161, and has an upstream side wall portion 162a located on the upstream side along the rotation direction of a supply roll 165, which will be described later, and a downstream side wall portion 162b located on the downstream side. doing. Further, inside the toner cartridge main body 161, a conveying member 163 composed of an agitator or the like for conveying the toner T accommodated therein to the supply port 162 while being agitated is rotatably mounted. The conveying member 163 is driven in synchronism with the operation of the developing device 14 by a driving device such as a driving motor (not shown) that rotationally drives the developing roll 141 and the like.

  The supply port 162 of the toner cartridge body 161 is provided with an autonomous supply unit 164 that autonomously supplies the toner T into the inside of the device housing 140 according to the height (bulk density) of the developer 4 in the device housing 140. Has been.

  The autonomous supply unit 164 includes a supply roll 165 as an example of a rotating body that supplies the toner T from the supply port 162 to the inside of the apparatus housing 140 according to the height (bulk density) of the developer 4 in the apparatus housing 140. . The supply roll 165 is disposed so that a part of the supply roll 165 is located above a preset first height (value) L1 which is the surface of the developer 4 in the stirring chamber 148. The set height L1 is a height at which the supply roll 165 starts to hold the developer 4 in the stirring chamber 148 on the outer periphery by the action described later when the developer 4 increases from the height.

  The supply roll 165 is formed in a cylindrical shape from a metal such as an aluminum alloy or nonmagnetic stainless steel. As shown in FIG. 4, the supply roll 165 is rotatably attached to the apparatus housing 140 via rotary shafts 165 a and 165 b provided at both ends along the axial direction. The supply roll 165 is set to be longer than the opening length of the supply port 162 of the toner cartridge main body 161 (the length along the direction perpendicular to the paper surface of FIG. 3), and covers the supply port 162. On the outer peripheral surface of the supply roll 165, a plurality of grooves 165c formed linearly along the axial direction for transporting the developer 4 are formed over the entire circumference at a predetermined pitch along the circumferential direction. Yes. In the developer 4 used in this embodiment, the volume average particle diameter of the carrier CA is 35 μm. The average depth and average width of the groove 165c are set to values larger than the volume average particle diameter of the carrier CA. For example, the groove portion 165c has an average depth of 90 μm and an average width in the rotation direction of 75 μm.

  As shown in FIG. 3, the supply roll 165 has a predetermined height (distance from the bottom surface of the stirring chamber 148) corresponding to the upper side of the stirring and conveying member 143 on the back side of the stirring chamber 148 in the apparatus housing 140. It is arrange | positioned in the position which has. As shown in FIG. 4, the device housing 140 is an extended portion in which a region 140 c in which the supply roll 165 is disposed is extended to the back side. The height of the surface of the developer 4 located below the supply roll 165 always matches the height of the surface of the developer 4 accommodated in the stirring chamber 148 of the apparatus housing 140. Further, the supply roll 165 is disposed at an upstream end portion of the stirring and conveying member 143 along the developer conveying direction. In the illustrated embodiment, the supply roll 165 is positioned immediately downstream of the first passage portion 153 along the developer conveyance direction. The supply roll 165 receives a driving force from a driving device such as a driving motor (not shown) that rotationally drives the developing roll 141 and the like, and a required rotation speed is synchronized with the operation of the developing device 14 along the clockwise direction in FIG. It is driven by.

  Further, as shown in an enlarged view in FIG. 6, the supply roll 165 is separated from the lower end portion of the supply port 162 through which the toner T filled in the toner cartridge 160 passes through a required gap. Opposite. More specifically, the supply roll 165 is disposed so as to face the lower end surfaces of the upstream side wall part 162a and the downstream side wall part 162b in the supply port 162 with a minute gap therebetween. The minute gap is set to a value (for example, about several hundred μm) larger than the volume average particle diameter of the carrier CA in the developer 4.

  As shown in FIG. 6, a magnet (magnet roll) 166 formed in a columnar shape is disposed inside the supply roll 165 in a fixed state. The magnet 166 attracts the developer 4 existing above the set height L1 against the gravity, and attracts the developer 4 to the outer periphery of the supply roll 165, and the magnetic pole N1 (pickup pole) It has a magnetic pole S1 (transport pole) for transporting the developer 4 while holding it on the outer periphery of the supply roll 165.

  On the outer periphery of the supply roll 165, a bundle of magnetic lines (magnetic field) from the magnetic pole N1 toward the magnetic pole S1 is formed. The developer 4 adsorbed on the outer periphery of the supply roll 165 is held by this magnetic field. The magnetic pole S <b> 1 is disposed on the downstream side in the rotation direction of the supply roll 165 with respect to the magnetic pole N <b> 1 and inside the supply port 162.

  In the supply roll 165, a position corresponding to the magnetic pole N <b> 1 of the magnet 166 is an adsorption region A <b> 1 that adsorbs the developer 4. Further, in the supply roll 165, the gravity of the developer 4 becomes larger than the magnetic force of the magnetic pole S <b> 1 that attracts the developer 4 at a position downstream of the magnetic pole S <b> 1 of the magnet 166 along the rotation direction of the supply roll 165. It becomes peeling area A2 which peels the agent 4. FIG.

  Thereby, when the height (bulk density) of the surface of the developer 4 in the stirring chamber 148 increases to the set height L1 or more, the supply roll 165 holds the increase on the outer periphery of the supply roll 165 by the adsorption region A1. In addition, as the supply roll 165 rotates, the increase is conveyed to the supply port 162, and the supply port 162 is closed by the developer 4 held on the outer periphery of the supply roll 165. In this way, the supply port 162 is closed by the developer 4 held on the outer periphery of the supply roll 165, whereby the supply of the toner T from the supply port 162 to the inside of the stirring chamber 148 is stopped.

  The increased amount of the developer 4 held on the outer periphery of the supply roll 165 by the adsorption region A1 is caused to fall into the stirring chamber 148 in the separation region A2 by its own weight when conveyed beyond the supply port 162. It has become. When the surface of the developer 4 is lower than the set height L1, the supply roll 165 does not adsorb the developer 4 in the agitation chamber 148 in the adsorption area A1, and toner is supplied from the supply port 162 to the inside of the agitation chamber 148. T is supplied.

  Further, in this embodiment, as shown in FIG. 6, a carrier storage container 170 having a supply port 171 for storing the carrier CA and supplying the carrier CA inside the apparatus housing 140 is provided. The carrier storage container 170 is formed in, for example, a cylindrical shape, and a carrier CA is stored therein. A cap 172 is attached to the upper end portion of the carrier storage container 170. Further, as shown in FIG. 4, the carrier storage container 170 is disposed on the upstream side of the supply roll 165 along the conveyance direction of the agitation conveyance member 143. The carrier storage container 170 is located between the stirring and conveying member 143 and the apparatus housing 140. As described above, the planar circular supply port 171 is opened at the bottom (lower end) of the carrier storage container 170. When the height of the surface of the developer 4 in the stirring chamber 148 becomes equal to or higher than a second value L2 lower than the first value L1, as shown in FIG. A disc-shaped valve body 173 as an example of an operating body that operates so as to close the supply port 171 is mounted so as to be freely opened and closed by a hinge member (not shown). Here, the second value L2 is a height corresponding to the case where the developer initial filling amount is the lower limit value of the tolerance, or the lower limit value (for example, 5%) of the toner density allowed for the developing device 14. Is set to a value corresponding to at least one of the heights corresponding to.

  The valve body 173 operates so as to close the replenishing port 171 by the buoyancy of the developer 4 acting on the valve body 173 when the height of the surface of the developer 4 in the stirring chamber 148 becomes the second value L2 or more. To do. However, a carrier CA having a specific gravity greater than that of the developer 4 is accommodated inside the carrier accommodating container 170, and the weight of the carrier CA accommodated in the carrier accommodating container 170 acts on the valve body 173. Yes. Therefore, the buoyancy of the developer 4 acting on the valve body 173 is usually smaller than the weight of the carrier CA, and in the state as it is, the height of the surface of the developer 4 in the stirring chamber 148 is equal to or greater than the second value L2. Even when the carrier container 170 is embedded in the developer 4, the valve body 173 operates in the opening direction.

  Therefore, in this embodiment, when the height of the surface of the developer 4 in the stirring chamber 148 is equal to or greater than the second value L2, a coil spring (not shown) is provided so that the valve body 173 does not open due to the weight of the carrier CA. It is urged in the closing direction by an urging means such as. However, when the urging force is excessive due to the urging means such as a coil spring, the height of the surface of the developer 4 in the stirring chamber 148 becomes less than the second value L2, and the developer 4 is applied to the valve body 173. Even when the buoyancy is not applied, the valve body 173 does not open and the carrier CA may not be supplied into the stirring chamber 148. Therefore, the biasing means such as a coil spring is used when the height of the surface of the developer 4 in the stirring chamber 148 becomes lower than the second value L2 and the buoyancy of the developer 4 does not act on the valve body 173. When the valve body 173 is opened and the height of the surface of the developer 4 in the stirring chamber 148 is equal to or higher than the second value L2, the buoyancy of the developer 4 acts on the valve body 173 so that the valve body 173 is closed. Is set to The weight of the carrier CA acting on the valve body 173 varies depending on the amount of the carrier CA stored in the carrier storage container 170, but the amount of the carrier CA replenished from the carrier storage container 170 into the stirring chamber 148 is as follows. In general, since the amount of the carrier CA is very small, the amount of the carrier CA in the carrier container 170 can be regarded as substantially constant. Therefore, the valve body 173 opens and closes according to the height of the developer 4 in the stirring chamber 148, and the carrier CA can be supplied to the inside of the stirring chamber 148. It should be noted that the carrier CA can be more stably replenished into the stirring chamber 148 by adopting the carrier container 170 according to the second embodiment to be described later.

<Operation of developing device>
In the developing device according to the first embodiment, the carrier is replenished inside the device housing as follows.

  As shown in FIG. 3, in the developing device 14, when the developing operation is started, the developing roll 141 is rotationally driven along the direction of arrow C by a driving motor (not shown). As the developing roll 141 rotates, the supply conveyance member 142, the agitation conveyance member 143, and the supply roll 165 are also driven to rotate along the arrow directions. The electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 11 is developed as a toner image by the toner T of the developer 4 supplied from the developing roll 141. As a result, the developing device 14 consumes an amount of toner T corresponding to the developed toner image.

  In the meantime, the developer 4 conveyed to the supply chamber 147 without being supplied to the developing roller 141 is conveyed to the stirring chamber 148 (see FIG. 3) via the first passage portion 153 as shown in FIG. Then, it is conveyed to the downstream end along the axial direction by the agitating and conveying member 143 disposed inside the agitating chamber 148. The developer 4 transported to the downstream end along the axial direction by the stirring transport member 143 is transported to the supply chamber 147 (see FIG. 3) via the second passage portion 154. The developer 4 conveyed to the inside of the supply chamber 147 is supplied to the developing roll 141 while being conveyed to the downstream side along the axial direction by the supply conveyance member 142.

  Incidentally, the supply roll 165 disposed inside the stirring chamber 148 is rotated while being in contact with the toner T accumulated in the region facing the supply port 162 as shown in FIG. The toner T is electrostatically attached to the outer peripheral surface of the supply roll 165 passing through the region facing the supply port 162 via the developer 4 adsorbed on the outer peripheral surface. The toner T attached to the outer peripheral surface of the supply roll 165 is conveyed to the peeling area A2 as the supply roll 165 rotates while being regulated by the downstream side wall portion 162b of the supply port 162. The toner T conveyed to the peeling area A2 mainly falls under gravity and falls into the stirring chamber 148 together with the developer 4. As a result, the toner T conveyed from the supply port 162 of the toner cartridge 160 is supplied into the developing device 14. It should be noted that the toner T that has come into contact with the region facing the supply port 162 is not limited to the case where the toner T adheres to the outer peripheral surface of the supply roll 165 via the developer 4, and the toner T of the supply roll 165 does not pass through the developer 4. There is also a case of being directly attached to the outer peripheral surface and transported.

  Next, a case where the total amount of toner T consumed as a result of the developing operation is smaller than the total amount of toner T replenished from the supply port 162 will be described. In this case, the amount of the developer 4 in the stirring chamber 148 is increased as compared with that before the developing operation, and the upper surface of the developer 4 in the stirring chamber 148 may be equal to or higher than the predetermined height L1.

  In this case, when the upper surface of the developer 4 in the stirring chamber 148 reaches the height L1, the developer 4 in the stirring chamber 148 is formed by the magnet 166 in the adsorption region A1, as shown in FIG. Receives magnetic attraction by magnetic force. Then, it is adsorbed on the outer peripheral surface of the supply roll 165 and conveyed into the supply port 162. Part of the developer 4 transported into the supply port 162 is adsorbed by the supply roll 165, is regulated by the downstream side wall portion 162 b of the supply port 162, and is transported to the peeling area A <b> 2 together with the supply roll 165. Dropped into the stirring chamber 148. On the other hand, the remaining developer 4 transported into the supply port 162 is restricted in movement by the downstream side wall portion 162 b and stays in the supply port 162.

  Therefore, as long as the upper surface of the developer 4 in the stirring chamber 148 is equal to or higher than the height L 1, the toner T in the supply port 162 is retained by the developer 4 staying in the supply port 162. Adherence to the surface is inhibited. That is, the supply of the toner T in the supply port 162 into the stirring chamber 148 is restricted (stopped).

  Further, when the developing operation is performed in this state and the upper surface of the developer 4 in the stirring chamber 148 becomes lower than the height L1, the developer 4 in the stirring chamber 148 again becomes the adsorption region as shown in FIG. It is not adsorbed at A1 (see FIG. 6). Then, since the developer 4 in the stirring chamber 148 is not transported into the supply port 162, the developer 4 that has previously accumulated in the supply port 162 is gradually supplied by the supply roll 165. It is conveyed from the inside to the peeling area A2. Thereafter, as the developer 4 staying in the supply port 162 is reduced from the supply port 162, the amount of toner T in which the toner T in the supply port 162 is gradually conveyed by the outer peripheral surface of the supply roll 165 is increased. Will be increased. In this way, the toner T in the toner cartridge body 161 is supplied into the stirring chamber 148.

  By the way, in the developing device 14 configured as described above, due to the tolerance of the initial filling amount of the developer 4, the dimensional tolerance of the device housing 140, and the ejection of the carrier from the developing device 14 while the image forming apparatus 1 is in use, etc. There is a possibility that the amount of carrier CA in the apparatus housing 140 changes, the bulk density of the developer 4 in the apparatus housing 140 changes, and the converged toner density changes.

  More specifically, in the developing device 14, as schematically shown in FIG. 8, the two-component developer 4 is initially filled in the device housing 140 so that the bulk density is Ag / cc. To do. In this case, assuming that the total weight of the developer 4 is 100 g and the toner concentration is 8%, the toner 8 g and the carrier 92 g are filled in the apparatus housing 140. In the developing device 14, assuming that the toner T is rapidly consumed by the continuous development process of the solid image and the toner concentration is reduced to 5%, the developer in the stirring chamber 148 is consumed as the toner T is consumed. 4 is lowered, the toner T is supplied into the agitating chamber 148 by the operation of the supply roll 165, and the developer 4 in the agitating chamber 148 has a predetermined developer amount at which the height L1 becomes the height L1. Toner is supplied to a certain original toner concentration of 8%.

  On the other hand, in the developing device 14, there is a tolerance in the total amount of the developer 4 that is initially filled in the device housing 140 at the time of manufacture, and the initial filling amount of the developer 4 is larger than the original amount. There may be few cases. Then, since the toner concentration of the developer 4 initially filled in the apparatus housing 140 is constant (for example, 8%), as a result, the initial filling amount of the developer 4 is smaller than the original amount. Accordingly, the amount of the carrier CA in the two-component developer 4 existing inside the apparatus housing 140 is reduced.

  In this case, as in the case described above, the upper surface of the developer 4 in the stirring chamber 148 is lowered as the toner is consumed, so that the volume of the developer 4 is increased as shown in FIG. When the density is reduced to a predetermined value (for example, Bg / cc), the supply roll 165 is operated to supply toner into the apparatus housing 140.

  However, in this case, since the amount of the carrier CA in the two-component developer 4 is different (small) due to the tolerance of the initial filling amount of the developer 4, the bulk density of the developer 4 is the same as B (g / cc). When it decreases, as shown in FIG. 8C, for example, the value becomes higher than 5%, for example, 8%, which is a case where the toner density is normal. In this state, when the supply roll 165 is operated and the toner T is supplied, the toner density in the apparatus housing 140 is increased from a predetermined value as shown in FIG. When the supply of toner by the roll 165 is completed, there is a possibility that the toner density becomes a high value such as 12%. Therefore, the toner density in the developing device 14 becomes too high, and an image quality abnormality such as fogging may occur in the image developed on the outer peripheral surface of the photosensitive drum 11.

  Such a problem is not limited to the case where there is a tolerance in the initial filling amount of the developer 4, but the dimensional tolerance of the device housing 140 and the photosensitive drum from the developing device 4 while the image forming apparatus 1 is continuously used. 11 is also caused in the same manner by so-called BCO (Beads Carry Over) or the like in which the carrier CA jumps out on the 11. That is, if there is a dimensional tolerance in the size (capacity) of the apparatus housing 140, the height of the surface of the developer 4 differs by an amount corresponding to the dimensional tolerance of the capacity even when a predetermined amount of the developer 4 is filled. When the toner T is replenished in conjunction with the rotation of the supply roll 165, the replenishment amount of the toner T varies and the toner density varies.

  Further, while the developing device 14 is being used over time, the carrier CA jumps out of the developing device 4 onto the photosensitive drum as shown in FIG. The amount of carrier CA present inside the housing 140 is similarly reduced.

  In this embodiment, as shown in FIG. 10, when the amount of carrier CA existing inside the apparatus housing 140 decreases, the developer 4 in the apparatus housing 140 decreases as the toner concentration of the developer 4 decreases. The surface height (bulk density) is drastically reduced as compared with the case where the amount of carrier CA is appropriate.

  Therefore, in the developing device 14, as shown in FIG. 11, the amount of carrier CA existing inside the device housing 140 is reduced, and a large number of solid images are continuously developed. The height (bulk density) of the surface of the developer 4 is rapidly reduced. When the height (bulk density) of the surface of the developer 4 in the stirring chamber 148 becomes less than the second value L2, the valve body 173 of the carrier container 170 is opened, and the carrier CA is replenished inside the stirring chamber 148. Is done.

  When the carrier CA is supplied into the stirring chamber 148, as shown in FIG. 12C, the developer in the stirring chamber 148 is developed while the developer 4 in the stirring chamber 148 is stirred by the stirring and conveying member 143. The bulk density of the developer 4 increases, and the height (bulk density) of the surface of the developer 4 becomes equal to or greater than the second value L2, and the carrier container 173 is shown in FIG. 7 and FIG. 170 replenishment port 171 (see FIG. 7) is closed, and the replenishment of carrier CA autonomously stops.

  Therefore, the developer 4 in the apparatus housing 140 increases in the amount of the carrier CA and approaches an appropriate value, and as shown in FIG. 10, the developer in the stirring chamber 148 is changed with the change in the toner concentration. The variation in the height (bulk density) of the surface 4 becomes large, and the height (bulk density) of the surface of the developer 4 in the stirring chamber 148 becomes less than the first value L1 due to the consumption of the toner T in the development process. Thus, the toner T is supplied into the stirring chamber 148 by the supply roll 165. As a result, the toner concentration of the developer 4 in the device housing 140 in the developing device 14 is maintained at an appropriate value. Therefore, the toner density of the developer 4 in the apparatus housing 140 becomes too high, and the occurrence of an image quality abnormality such as fogging on the image developed on the outer peripheral surface of the photosensitive drum 11 is suppressed.

[Embodiment 2]
FIG. 13 is a cross-sectional configuration diagram illustrating a developing device according to the second embodiment.

  As shown in FIG. 13, the developing device 14 according to Embodiment 2 includes a supply roll 180 at the bottom of the carrier container 170. The supply roll 180 is configured similarly to the supply roll 165.

  That is, the replenishing roll 180 is formed in a cylindrical shape from a metal such as an aluminum alloy or nonmagnetic stainless steel. As shown in FIG. 14, the replenishing roll 180 is rotatably mounted on the apparatus housing 140 via rotating shafts 180a and 180b provided at both ends along the axial direction. The supply roll 180 is set longer than the opening length of the supply port 171 of the carrier storage container 170 and covers the supply port 171. On the outer peripheral surface of the supply roll 180, a plurality of groove portions 180c formed linearly along the axial direction for transporting the developer 4 are formed over the entire circumference at a predetermined pitch along the circumferential direction. Yes.

  As shown in FIG. 13, the replenishing roll 180 has a predetermined height (distance from the bottom surface of the stirring chamber 148) corresponding to the upper side of the stirring and conveying member 143 on the back side of the stirring chamber 148 in the apparatus housing 140. It is arrange | positioned in the position which has. As shown in FIG. 14, the apparatus housing 140 is an extended portion in which a region 140 d where the supply roll 180 is arranged is extended to the back side, and the height of the surface of the developer 4 where the supply roll 180 is located is as follows. The surface height of the developer 4 accommodated in the stirring chamber 148 of the apparatus housing 140 always coincides with the surface height. Further, the replenishing roll 180 is disposed at the upstream end of the agitating and conveying member 143 along the developer conveying direction. In the illustrated embodiment, the replenishment roll 180 is located immediately below the downstream side of the first passage portion 153 along the developer conveyance direction. Further, the supply roll 165 is disposed on the downstream side of the stirring and conveying member 143 along the developer conveying direction. The replenishing roll 180 receives driving force from a driving device such as a driving motor (not shown) that rotationally drives the developing roll 141 and the like, and a required rotational speed is synchronized with the operation of the developing device 14 along the clockwise direction in FIG. It is driven by.

  Further, as shown in an enlarged view in FIG. 13, the supply roll 180 is separated from the lower end portion of the supply port 171 through which the carrier CA filled in the carrier container 170 passes through a required gap. Are facing each other.

  Inside the replenishing roll 180, a magnet (magnet roll) 181 formed in a cylindrical shape is arranged in a fixed state. The magnet 181 attracts the developer 4 present at a set height L2 or more against the gravity, and attracts the developer 4 to the outer periphery of the supply roll 180, and the developer. 4 is held on the outer periphery of the supply roll 180 and has a magnetic pole S1.

  On the outer periphery of the supply roll 180, a bundle of magnetic lines (magnetic field) from the magnetic pole N1 toward the magnetic pole S1 is formed. By this magnetic field, the developer 4 adsorbed on the outer periphery of the supply roll 180 is held. The magnetic pole S1 is disposed on the downstream side in the rotation direction of the supply roll 180 with respect to the magnetic pole N1, and is positioned inside the supply port 171.

  Thus, the replenishing roll 180 has a suction area A1 where the developer 4 is sucked at a position corresponding to the magnetic pole N1 of the magnet 181. Further, in the supply roll 180, the gravity of the developer 4 becomes larger than the magnetic force of the magnetic pole S1 that adsorbs the developer 4 at the downstream position along the rotation direction of the supply roll 180 relative to the magnetic pole S1 of the magnet 181. It becomes peeling area A2 which peels the agent 4. FIG.

  As a result, when the height (bulk density) of the surface of the developer 4 in the stirring chamber 148 increases to a set height L2 or more, the supply roll 180 holds the increase on the outer periphery of the supply roll 180 by the adsorption region A1. In addition, the increase is conveyed to the supply port 171 as the supply roll 180 rotates, and the supply port 171 is closed by the developer 4 held on the outer periphery of the supply roll 180. In this way, the supply port 171 is closed by the developer 4 held on the outer periphery of the supply roll 180, whereby the supply of the carrier CA from the supply port 171 to the inside of the stirring chamber 148 is stopped.

  Further, since the supply roll 180 is arranged on the upstream side of the supply roll 165 along the axial direction of the stirring conveyance member 143, the developer 4 in the stirring chamber 148 before the toner T is supplied by the supply roll 165. The carrier CA can be supplied into the stirring chamber 148 in accordance with the change in the surface height (bulk density).

  As described above, in the second embodiment, the supply roll 180 is rotatably provided in the supply port 171 of the carrier container 170 so that the supply roll 180 operates in the same manner as the supply roll 165, and the developer in the stirring chamber 148. When the height (bulk density) of the surface No. 4 increases to the set height L2 or more, the supply port 171 of the carrier container 170 is closed by the supply roll 180, and the supply of the carrier CA can be reliably stopped.

  In the above-described embodiment, the full-color image forming apparatus that forms four color toner images of yellow (Y), magenta (M), cyan (C), and black (K) has been described as the image forming apparatus. Of course, the present invention can be similarly applied to the image forming apparatus.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 1a ... Image forming apparatus main body 11 ... Photosensitive drum 14 ... Developing apparatus 141 ... Developing roll 142 ... Supply conveyance member 143 ... Agitation conveyance member 165 ... Supply roll

Claims (5)

A developer container for containing a two-component developer containing toner and a carrier;
A developer holder for holding the developer;
A carrier container that contains the carrier and has a replenishing port at the lower end for replenishing the carrier into the developer container;
An actuating element disposed at the replenishing port of the carrier containing container and operating to close the replenishing port when the height of the developer surface in the developer containing container is equal to or greater than a predetermined value;
A developing device comprising: A developer container for containing a two-component developer containing toner and a carrier;
A developer holder that is rotatably arranged in the opening of the developer container and holds the developer;
A toner container having a supply port for containing the toner and supplying the toner into the developer container;
An outer periphery that is rotatably disposed at the supply port of the toner storage container and closes the supply port when the height of the developer surface in the developer storage container exceeds a predetermined first value. A rotating body that rotates while holding developer,
A carrier container that contains the carrier and has a replenishing port at the lower end for replenishing the carrier into the developer container;
When the height of the developer surface in the developer container is equal to or higher than a predetermined second value that is lower than the first value, the replenishment port is disposed at the replenishment port of the carrier container. An actuating body that operates to close;
A developing device comprising:   The operating body operates to close the replenishing port by the buoyancy of the developer acting on the operating body when the height of the developer surface in the developer containing container becomes equal to or higher than a predetermined value. The developing device according to claim 1 or 2.   The operating body is rotatably disposed at a supply port of the carrier container, and closes the supply port when the height of the developer surface in the developer container reaches the second value or more. The developing device according to claim 1, comprising a rotating body that rotates while holding the developer on the outer periphery. An image carrier for holding an electrostatic latent image;
Developing means for developing the electrostatic latent image held on the image carrier;
With
An image forming apparatus using the developing device according to claim 1 as the developing unit.

Images