JP2008083092A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of surely collecting developer inside the developing device without deteriorating productivity in image-forming even when monochrome image forming operation is consecutively performed. <P>SOLUTION: The developing device includes: a developing unit with a collecting port for collecting excess developer; and a rotator rotating while holding a plurality of developing units, and performs development processing by rotationally driving the rotator, so that the predetermined developing unit may be successively moved to a developing position where it is opposed to an image carrier. In the developing device, when collecting the excess developer by moving the developing unit which collects the excess developer to a collecting position where the collecting port of the developing unit is positioned downward in a gravity direction, the rotator is rotated in a reverse direction to the rotating direction when performing image-forming to thereby move the developing unit which collects the excess developer to the collecting position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions, which employs an electrophotographic method, and more particularly, a two-component consisting of a carrier and a toner. The present invention relates to a developing device using a developer.

JP 2004-294527 A JP 9-218575 A

  Conventionally, various types of developing devices have been proposed for use in image forming apparatuses such as printers, copiers or facsimiles that employ this type of electrophotographic system, and also multifunctional machines that have these functions. In addition, it has been commercialized and introduced into an actual image forming apparatus. These developing devices include a developing device using a one-component developer consisting only of toner and a developing device using a two-component developer consisting of a carrier and toner, and an electrostatic latent image formed on a photosensitive drum. In order to develop an image satisfactorily, it is necessary to sufficiently stir the developer such as toner contained in the main body of the developing device to maintain the developer in an appropriate state.

  By the way, as the developing device, a plurality of developing devices having different colors are arranged along the circumferential direction of the rotating body, and the rotating body is driven to rotate at a predetermined timing, thereby photosensitive the desired developing device. Some are configured to be developed by moving to a development position facing the body drum.

  In such a developing device, when a developing process using the developing device of the same color is repeated, such as when performing monochromatic printing continuously for a large number of sheets, a rotating body in which a plurality of developing devices are arranged in the circumferential direction is not rotationally driven. Therefore, the developer contained in the developing device may not be sufficiently stirred.

  Therefore, in the above developing device, as a technique for sufficiently stirring the developer such as toner accommodated in the developing device and maintaining the developer in an appropriate state, for example, Japanese Patent Application Laid-Open No. 2004-294527 is disclosed. What has been disclosed has already been proposed.

  An image forming apparatus according to Japanese Patent Application Laid-Open No. 2004-294527 includes a plurality of developer accommodating bodies for accommodating different color developers, and a rotatable rotating body that is detachable and rotatable. In an image forming apparatus capable of continuously forming an image on a plurality of sheets of media using a developer housed in a developer container mounted on a rotating body, when an image is continuously formed on a plurality of sheets of media using a single color developer. Is configured to rotate the rotating body one or more times at least at the start of continuous image formation or at the end of continuous image formation.

  However, the image forming apparatus according to Japanese Patent Application Laid-Open No. 2004-294527 discloses that when an image is continuously formed on a plurality of sheets of media using a single color developer, when the continuous image formation starts or when the continuous image formation ends. However, the image forming apparatus is not configured to discharge the developer to the outside, and the developing device is configured to rotate the rotating body at least one turn. However, there is a problem that the image quality deteriorates due to the increase in the developer.

  Therefore, as a technique capable of solving such a problem, a technique disclosed in Japanese Patent Laid-Open No. 9-218575 has already been proposed.

  A rotary developing device according to Japanese Patent Application Laid-Open No. 9-218575 includes a developer that transports the developer to a developing roll while containing and circulating the developer including at least toner and a carrier, and a plurality of the developers. In a rotary developing device that forms a multicolor image by sequentially rotating the rotating body and facing the photosensitive drum by the rotation of the rotating body, the developer is replenished with developer. A developer replenishing means is provided, and the developer in the developing device is discharged by the rotation of the rotating body.

  However, the conventional technique has the following problems. That is, in the case of the rotary developing device according to the above-mentioned Japanese Patent Application Laid-Open No. 9-218575, if single color printing is performed continuously, the number of rotations of the rotating body is reduced as compared with multi-color printing. In order to discharge only the necessary amount of developer, it is necessary to perform a lot of idling processing of the rotating body and discharge excess developer. Therefore, in the image forming apparatus using the rotary developing device, it takes a long time to idle the rotating body of the rotary developing device, and during that time, the image forming operation cannot be performed, and the print productivity is increased. It had the problem of decreasing.

  To explain further, in the case of a conventional rotary developing device, in order to discharge a surplus developer by a necessary amount, for example, as shown in FIG. In other words, it takes a long time to rotate and rotate the rotating body of the rotary developing device. During this time, the image forming operation cannot be performed, and printing productivity is lowered.

  Further, when the rotary member of the rotary developing device is idled, the developer other than the required developer is discharged, and there is a possibility that the excess developer may be discharged more than necessary. Also had.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to improve the productivity of image formation even when a single-color image forming operation is continuously performed. It is an object of the present invention to provide a developing device capable of reliably collecting the developer in the developing device without lowering.

That is, the invention described in claim 1 includes a developing device including a recovery port for recovering excess developer,
A rotating body that holds and rotates a plurality of the developing devices,
In a developing device for performing development processing by sequentially moving a predetermined developing device to a developing position facing the image carrier by rotationally driving the rotating body,
When collecting the excess developer by moving the developer that collects the excess developer to a collection position where the collection port of the developer is located below the gravitational direction,
In the developing device, the rotating body is rotated in a direction opposite to a rotation direction at the time of image formation, and a developing unit that collects the excess developer is moved to a collection position.

  The invention described in claim 2 is characterized in that the developer carrying member of the developing device for collecting the excess developer is not driven to rotate in accordance with the operation of collecting the excess developer. The developing device described in 1.

  Furthermore, the invention described in claim 3 collects the excess developer according to the image density of the image to be developed by the developing device of the developing device and the number of recording media to be continuously developed. 3. The developing device according to claim 1, wherein the number of times the developing device is moved to the collection position is changed.

  According to a fourth aspect of the present invention, the number of times the developing device that collects the excess developer is moved to the collection position is such that the image density of the image to be developed is high and the development is continuously performed. 4. The developing device according to claim 1, wherein a larger value is set as the number of recording media is larger.

Further, in the fifth aspect of the present invention, when the development is continuously performed by a single developing device, the development is performed without rotating the rotating body until the development corresponding to the predetermined number of recording media is performed. 5. The developing device according to claim 1, wherein the processing is continued.

  Further, in the invention described in claim 6, the recovery port of the developing device is formed in a nozzle shape protruding inside the developing device, and the nozzle-shaped opening portion is substantially tangential to the rotating body, The developing device according to claim 1, wherein the developing device is set within a range of ± 45 degrees with respect to the upstream side in the rotation direction of the rotating body.

  Further, in the invention described in claim 7, the home position of the developing device is set to a position on the downstream side of 30 degrees or more from the collection position along the rotation direction during the developing operation of the rotating body. The developing device according to claim 1, wherein the developing device is a developing device.

  According to the present invention, there is provided a developing device capable of reliably collecting the developer in the developing device without degrading the image forming productivity even when the monochrome image forming operation is continuously performed. can do.

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

Embodiment 1
FIG. 2 shows a four-cycle full-color printer as an image forming apparatus to which the developing device according to Embodiment 1 of the present invention is applied.

  In FIG. 2, reference numeral 1 denotes a main body of a full-color printer as an image forming apparatus main body. Inside the full-color printer main body 1, a photosensitive drum 2 as an image carrier is located slightly above the center. It is rotatably arranged. As this photosensitive drum 2, for example, a drum made of a conductive cylinder having a diameter of about 47 mm whose surface is coated with a photosensitive layer made of OPC or the like is used. It is rotationally driven at a process speed of about 150 mm / sec. The surface of the photosensitive drum 2 is charged to a predetermined potential by a charging roll 3 serving as a charging unit disposed almost directly below the photosensitive drum 2, and then at a position just below the photosensitive drum 2. Image exposure by a laser beam (LB) is performed by ROS4 (Raster Output Scanner) as the arranged exposure means, and an electrostatic latent image corresponding to image information is formed. The electrostatic latent image formed on the photosensitive drum 2 passes through the developing devices 5Y, 5M, 5C, and 5K of yellow (Y), magenta (M), cyan (C), and black (K) in the circumferential direction. The toner is developed by a rotary developing device 5 disposed along the toner image to form a toner image of a predetermined color. The developing devices 5Y, 5M, 5C, and 5K for the respective colors are supplied with developer containing at least the corresponding color toner from the developer cartridges 45Y, 45M, 45C, and 45K disposed adjacent to each other. It is configured as follows. In this embodiment, a two-component developer composed of a toner and a carrier is supplied as the developer. In the first embodiment, there are four developer cartridges, but they may be increased or decreased as necessary.

At this time, charging, exposure and development processes are repeated a predetermined number of times on the surface of the photosensitive drum 2 in accordance with the color of the image to be formed. In the rotary developing device 5, the corresponding color developing devices 5 </ b> Y, 5 </ b> M, 5 </ b> C, and 5 </ b> K move to a developing position facing the photosensitive drum 2. For example, when a full-color image is formed, the charging, exposure, and development processes are performed on the surface of the photosensitive drum 2 in yellow (Y), magenta (M), cyan (C), and black (K) colors. The toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is sequentially formed on the surface of the photosensitive drum 2. The The number of rotations of the photosensitive drum 2 in forming the toner image differs depending on the size of the image. For example, in the case of A4 size, one image is obtained by rotating the photosensitive drum 2 a plurality of times. Is formed. That is, a toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the surface of the photosensitive drum 2 every time the photosensitive drum 2 rotates a predetermined number of times. Are sequentially formed.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drum 2 are intermediately formed on the surface of the photosensitive drum 2 as an intermediate transfer member. At the primary transfer position where the transfer belt 6 abuts, the primary transfer is performed by the primary transfer roll 7 while being superimposed on the intermediate transfer belt 6. The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 6 are fed by the secondary transfer roll 8 at a predetermined timing. The recording sheet 9 is secondarily transferred in a lump. The recording paper 9 is fed by a feed roll 11 from a paper feed cassette 10 disposed at the lower part of the full-color printer main body 1 and is fed in a state where the recording paper 9 is rolled one by one by the feed roll 11 and the retard roll 12. The toner image is transferred to the secondary transfer position of the intermediate transfer belt 6 through the conveyance guide 15 in a state in which the toner image is transferred onto the intermediate transfer belt 6 by the registration roll 14 via the paper conveyance path 13. 2, reference numerals 16 and 17 denote a temperature sensor and a humidity sensor for detecting the temperature and humidity in the printer main body 1, respectively.

  The intermediate transfer belt 6 is stretched by a plurality of rolls and is rotationally driven so as to circulate and move at a predetermined process speed (about 150 mm / sec). The intermediate transfer belt 6 includes a drive roll 19 that is rotated by a motor (not shown), a primary transfer roll 7 that transfers a toner image formed on the photosensitive drum 2 onto the intermediate transfer belt 6, and a secondary transfer roll. 8 is stretched with a predetermined tension by a backup roll 20, which is in contact with the intermediate transfer belt 6 via the intermediate transfer belt 6, a first idle roll 22, and a second idle roll 23.

  The intermediate transfer belt 6 is stretched around the plurality of rolls 7 and 19 to 23 as described above. In this embodiment, the intermediate transfer belt 6 is used in order to reduce the size of the full-color printer main body 1. The cross-sectional shape on which is stretched is configured to be a flat and elongated rectangular shape.

  Furthermore, in this embodiment, as shown in FIG. 2, the entire full-color printer is miniaturized as much as possible, but the rotary developing device 5 occupies a large space of the full-color printer main body 1. Therefore, the full-color printer main body 1 is designed to improve the maintainability of the intermediate transfer belt 6 and the rotary developing device 5 while achieving downsizing of the device. Specifically, as shown in FIG. 3, the intermediate transfer belt 6 includes the photosensitive drum 2, the charging roll 3, and the secondary transfer roll 8, and integrally constitutes an image forming unit 24 as an exchange unit. The entire image forming unit 24 can be attached to and detached from the full color printer main body 1 by opening the upper cover 25 of the full color printer main body 1. In the image forming unit 24, an intermediate transfer unit 26 including the intermediate transfer belt 6 and a photosensitive unit 28 including a photosensitive drum 2, a charging roll 3, and a cleaning device 27 can be separately attached and detached. It is also possible to replace the photoconductor unit 28 alone. In addition, an unused detection sensor 29 that detects whether or not the developer cartridges 45Y, 45M, 45C, and 45K are unused is disposed above the developing device 5. As shown in FIG. 2, the upper cover 25 is configured to open and close around a fulcrum 25a, and an open / close detection sensor 25b for detecting the opening and closing of the upper cover 25 is provided in the vicinity of the fulcrum 25a. Is provided.

  Further, as shown in FIG. 2, the cleaning device 21 for the intermediate transfer belt 6 includes a scraper 30 disposed so as to contact the surface of the intermediate transfer belt 6 stretched by a first idle roll 22, and a first scraper 30. 2 and a cleaning brush 31 arranged so as to be in pressure contact with the surface of the intermediate transfer belt 6 stretched by the idle roll 23. Residual toner and paper powder removed by the scraper 30 and the cleaning brush 31 are It is collected inside the cleaning device 21. The cleaning device 21 is disposed so as to be able to swing counterclockwise around the swing shaft 32, and until the secondary transfer of the final color toner image is completed, the intermediate transfer is performed. The belt 6 is retracted to a position separated from the surface of the belt 6 and is configured to come into contact with the surface of the intermediate transfer belt 6 when the secondary transfer of the final color toner image is completed.

  Further, as shown in FIG. 2, the recording paper 9 onto which the toner image has been transferred from the intermediate transfer belt 6 is conveyed to a fixing device 33, where heat and pressure are applied by a heating roll 33a and a pressure member 33b of the fixing device 33. The toner image is fixed on the recording paper 9 by the pressure, and is discharged onto a discharge tray 37 provided on the upper portion of the printer main body 1 through a discharge port 36 by a discharge roll 35 provided in the fixing unit 34.

  Note that the surface of the photosensitive drum 2 after the toner image transfer process is completed, the cleaning blade 38 of the cleaning device 27 disposed obliquely below the photosensitive drum 2 every time the photosensitive drum 2 rotates once. As a result, residual toner and the like are removed to prepare for the next image forming process.

  FIG. 4 is an external perspective view showing a specific example of the rotary developing device 5 as the developing device according to this embodiment. FIG. 4 shows a state in which one developing device 5Y and developer cartridge 45Y are mounted on the developing device body for convenience.

  As shown in FIGS. 5 and 6, the rotary developing device 5 includes a developing device main body 40 as a rotating body that is rotatably arranged in a vertical plane. The developing device main body 40 includes a cylindrical rotating shaft member 41 disposed along the longitudinal direction at the center thereof, and a front side disposed at an end portion on the near side in the longitudinal direction of the rotating shaft member 41. Formed by a flange member 42, a rear flange member 43 disposed at the end in the longitudinal direction of the rotary shaft member 41, and the rotary shaft member 41 and front and rear flange members 42, 43. And a partition member 44 that divides the cylindrical space S into four sections every 90 degrees. A driven gear 43a for rotationally driving the developing device main body 40 is provided on the outer periphery of the rear flange member 43 as shown in FIG. The driven gear 43a is meshed with a drive gear attached to a drive shaft of a drive motor disposed on the printer body 1 side, and can rotate forward and reverse by rotating the drive motor. ing.

  As shown in FIG. 6, the developing device main body 40 is attached to the printer main body 1 so as to be normally driven to rotate in the counterclockwise direction as shown in FIG. As shown in FIG. 6, the developing device main body 40 includes four developing devices 5Y, 5M, yellow (Y), magenta (M), cyan (C), and black (K) in the clockwise direction. 5C and 5K are mounted along the circumferential direction, and yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the developing devices 5Y, 5M, 5C, and 5K. The four developer cartridges 45Y, 45M, 45C, and 45K are mounted along the circumferential direction.

  Since these developing devices 5Y, 5M, 5C, and 5K are all configured in the same manner, here, the yellow (Y) developing device 5Y will be described as an example. As shown in FIG. 7, a developing device main body 46 is provided, and a new developer is supplied to the developing device main body 46 from a developer cartridge 45Y.

  As shown in FIGS. 7 and 8, the developing device main body 46 is disposed so that a part thereof is exposed to an opening 47 provided facing the outer periphery of the developing device main body 46, and is perpendicular to the paper surface. A developing roll 48 that is long in any direction, and two spiral augers 49 and 50 that are positioned obliquely below the developing roll 48 and extend parallel to the developing roll 48 are disposed. As shown in FIG. 8, the developing roll 48 is disposed over substantially the entire length of the developing device main body 46. In the developing device 5Y, as shown in FIG. 8, when the developing roll 48 rotates, the spiral auger 49 on the back side conveys the developer 51 accommodated in the developing device main body 46 while stirring in one direction. . On the other hand, the spiral auger 50 conveys the developer 51 while stirring the developer 51 in the direction opposite to the conveying direction of the spiral auger 49 and supplies the developer 51 evenly to the developing roll 48. The developer 51 supplied to the surface of the developing roll 48 is regulated in layer thickness by a layer thickness regulating member 52, and is conveyed to a developing area facing the photosensitive drum 2 as the developing roll 48 rotates. The In this embodiment, a two-component developer composed of a toner and a carrier is used as the developer 51. However, the developer 51 only needs to contain at least toner, and is composed only of toner. Of course, a one-component developer may be used.

  As shown in FIG. 7, the developing roll 48 attracts carriers contained in the developer 51 with a magnetic force by a magnet roll 48 a disposed in a fixed state inside, and develops on the surface of the developing roll 48. A magnetic brush of the agent 51 is formed, and the toner adsorbed on the carrier is conveyed to a developing area facing the photosensitive drum 2. The electrostatic latent image formed on the photosensitive drum 2 is visualized by a magnetic brush of a developer 51 composed of a carrier and toner formed on the surface of the developing roll 48.

  Further, as shown in FIGS. 9 and 10, the developer cartridge 45 is formed of a long cylindrical container having a cylindrical cross section. As shown in FIG. 10, the interior of the developer cartridge 45 is divided into a developer accommodating portion 53 for accommodating a new developer 52 and a developer collecting portion 55 for recovering a used developer 54. It is partitioned by a cap 56. In the illustrated embodiment, the developer container 53 is set to occupy about 4/5 of the entire length of the developer cartridge 45, and the developer recovery unit 55 is set to occupy about 1/5. Of course, the ratios of the lengths of the developer accommodating portion 53 and the developer collecting portion 55 may be other ratios.

  As shown in FIGS. 9 and 10, the developer container 53 is provided with a supply port 65 for supplying a new developer 52 to the outside at a slightly inclined position at the end on the developer recovery unit 55 side. Is opened in a rectangular shape. In addition, a spiral agitator 66 that conveys the new developer 52 accommodated in the developer accommodating portion 53 while being stirred is rotatably disposed in the developer accommodating portion 53. The developer 52 is transported by the agitator 66 and supplied to the outside from the supply port 65. A gear 67 for rotationally driving the agitator 66 is provided at the rear end of the developer cartridge 45 so that a part of the gear 67 is exposed to the outside. As shown in FIG. 11, the gear 67 engages with a gear 67a provided in the developing device main body 46 in a state where the developer cartridge 45 is mounted on the developing device main body 46, so that the agitator 66 is driven to rotate. It is configured.

  As shown in FIG. 11, the developer 5Y to which the developer 52 is supplied from the developer cartridge 45 has a developer-side shutter plate 68 that contacts the portion corresponding to the supply port 65 of the developer cartridge 45. Are provided in a curved state in a substantially arc shape. The shutter plate 68 is slidably attached to the developing device main body 46 along the arrow direction. The shutter plate 68 has a replenishment receiving port 69 for receiving a new developer 52 supplied from the developer cartridge 45, and a projecting piece 69 a is formed at the outer peripheral end of the replenishment receiving port 69. It protrudes toward the inside. As shown in FIGS. 6 and 7, the developing device 5Y supplied with the developer 52 from the replenishment receiving port 69 is disposed over a predetermined length at the upper part on the back side of the developing device main body 46, and the developer is provided at the entrance. The replenishing auger 71 (see FIG. 11) having a replenishing port (not shown) is conveyed by a predetermined distance along the longitudinal direction of the developing device main body 46, and is then provided on the upper portion on the back side of the developing device main body 46. The toner is supplied into the developing device main body 46 through a supply opening (not shown).

  Further, as shown in FIG. 7, the developing unit 5Y has an upper portion on the back side of the developing device main body 46 in order to collect used developer out of the developer 51 accommodated in the developing device main body 46. Is provided with a recovery opening 95, and when the developing device 5Y rotates and moves to the position C (developer recovery position) in FIG. Is configured to recover. As shown in FIG. 11, the used developer 54 collected from the developing unit 5 is opened in the developer port 45 opened in the shutter plate 68 and in the developer cartridge 45 as shown in FIG. As shown in FIG. 7, it is configured to be collected in the developer collecting portion 55 of the developer cartridge 45 through the collection port 74. In addition, as shown in FIG. 11, a convex piece 70a is projected inward toward the discharge outlet 70 for collecting the developer.

  In this embodiment, as shown in FIGS. 7 and 10, the developer container 53 is formed on the outer periphery of the developer container 53 and the developer recovery part 55 formed in the cylindrical shape of the developer cartridge 45. A handle member 75 as an opening / closing member that opens and closes the supply port 65 and the recovery port 74 of the developer recovery unit 55 is fitted in a rotatable manner along the circumferential direction. The handle member 75 is formed in a cylindrical shape, similar to the developer accommodating portion 53 and the developer collecting portion 55 of the developer cartridge 45, but the inner diameter of the handle member 75 is outside the developer collecting portion 55. It is slightly larger than the diameter, and is formed in a circular shape that is substantially inscribed in a space other than the developing device 5Y out of the space allocated to one developing device 5Y of the developing device main body 46 in which the developer cartridge 45 is mounted. .

  As shown in FIG. 10, the handle member 75 has a supply opening 76 and a recovery opening 77 at positions corresponding to the supply port 65 and the recovery port 74 of the developer cartridge 45. The handle member 75 can be rotated along the outer periphery of the developer recovery portion 55 of the developer cartridge 45 to open and close the supply port 65 and the recovery port 74 of the developer cartridge 45 at the same time. It has become. Convex pieces 76a and 77a project outward from the edges of the supply opening 76 and the recovery opening 77 of the handle member 75.

  Further, as shown in FIG. 8, the handle member 75 is operated to rotate the handle member 75 in a part of its circumferential direction, and holds the developer cartridge 45 and is attached to the developing device main body 46 as shown in FIG. A grip 78 for projecting is projected outward in the radial direction. On the side surface of the handle 78, a non-slip portion 79 made of a plurality of ridges is provided so as to facilitate gripping.

  By the way, in this embodiment, there is provided a developing device having a recovery port for recovering excess developer, and a rotating body that holds and rotates a plurality of the developing devices, and rotates the rotating body to obtain a predetermined value. In the developing device for performing development processing by sequentially moving the developing devices to the developing position facing the image carrier, the collecting port of the developing device is positioned below the gravitational direction in the developing device for collecting the excess developer. When the surplus developer is collected by moving it to the collection position, the developer that collects the excess developer is moved to the collection position by rotating the rotating body in a direction opposite to the rotation direction during image formation. It is configured to let you.

  That is, in the rotary developing device 5 according to this embodiment, as shown in FIG. 6, the developing device main body 40 normally rotates in the counterclockwise direction, so that desired developing devices 5Y, 5M, 5C, 5K is moved to a developing position A facing the photosensitive drum 2. Further, in the rotary developing device 5, the position D upstream of the developing position A by a predetermined angle (for example, 90 degrees) in the clockwise direction is the home position. The rotary developing device 5 is normally set to stop in a state where the black developing device 5K is located at the home position.

  The home position of the rotary developing device 5 is 30 degrees or more from the collection position C along the rotational direction during the developing operation of the developing device main body 40, and in this embodiment, the home position is 90 degrees downstream. Is set. Here, the reason why the home position should be set at a position on the downstream side of 30 degrees or more from the collection position C is that the developing device main body 40 is rotated in the reverse direction at the time of collecting the excess developer. This is because a sufficient recovery effect of the excess developer can be obtained if the rotation is more than a predetermined degree.

  At the collection position C, the developing units 5Y, 5M, 5C, and 5K are in an upside-down state, so the developer contained in the developing units 5Y, 5M, 5C, and 5K is on the ceiling side. It is to move.

  Here, as shown in FIGS. 8 and 14, the recovery port 70 of the developing units 5Y, 5M, 5C, and 5K is a spiral auger on the side away from the developing roll 48 of the two spiral augers 49 and 50. 49, which is disposed on the most upstream side of the spiral auger 49 in the developer conveying direction. Further, normally, the developer conveyed by the other spiral auger 50 is directly conveyed on the most upstream side of the spiral auger 49 in the developer conveying direction, so that a large amount of developer exists at the developer collecting position. Then, when the developing devices 5Y, 5M, 5C, and 5K move to the collection position, the developer in the developing devices 5Y, 5M, 5C, and 5K may be excessively collected.

  Therefore, in this embodiment, the developer in the developing devices 5Y, 5M, 5C, and 5K is prevented from being excessively collected, and the developer amount in the developing devices 5Y, 5M, 5C, and 5K is shown in FIG. As shown in FIG. 15, when the amount exceeds a certain amount, only the excess developer exceeding the certain amount is collected.

  Specifically, as shown in FIG. 14, the development of the spiral auger 49 is avoided in order to prevent the developer from being directly conveyed by the other spiral auger 50 to the most upstream side of the spiral auger 49 in the developer conveying direction. A developer movement preventing wall 60 is provided on the uppermost stream side in the agent transport direction so as to partition the other spiral auger 50 and prevent the developer from moving. Therefore, the developer conveyed by the spiral auger 50 does not move directly to the position where the recovery port 70 is provided, but moves to the spiral auger 49 side through the passage 91 opened in front of the developer. It is supposed to be. Further, an auger 50 a in the reverse direction is provided at the downstream end of the spiral auger 50 so that the developer conveyed by the spiral auger 50 is returned to the passage 91.

  In the developing units 5Y, 5M, 5C, and 5K, when the developer in the developing units 5Y, 5M, 5C, and 5K exceeds a certain amount, the developer in the spiral auger 49 is increased according to the increase in volume. It moves to the most upstream side in the transport direction, and is collected from the collection port 70 at the position on the most upstream side.

  Further, in this embodiment, the collection port is not a simple opening 70, but a rectangular column-shaped nozzle protruding obliquely downward from the ceiling of the developing devices 5Y, 5M, 5C, and 5K as shown in FIG. It is formed in a shape. Therefore, even when the developing devices 5Y, 5M, 5C, and 5K move to the recovery position, the recovery port 70 formed in the shape of a square columnar nozzle has the developing device 5Y with the top and bottom reversed. Since it is in a state of projecting obliquely downward from the bottom of 5M, 5C, and 5K, the developer in the developing units 5Y, 5M, 5C, and 5K is avoided from being excessively introduced into the collection port 70. It has become.

  However, in this embodiment, since the excess developer at the collection position of the developing units 5Y, 5M, 5C, and 5K is set to a certain amount, the developer positioned above the nozzle-shaped collection port 70 is It is configured to be collected in the collection port 70.

  Moreover, in this embodiment, the nozzle-shaped recovery port 70 is within a range of ± 45 degrees with respect to the upstream side in the rotational direction of the rotating body 40 in the substantially tangential direction of the rotating body, as shown in FIG. It is set to face.

  More specifically, in this embodiment, as shown in FIG. 12, the nozzle-shaped collection port 70 is set so as to face the substantially tangential direction of the rotating body 40. In this way, by setting the nozzle-shaped collection port 70 so as to face the substantially tangential direction of the rotating body 40, the spiral of the developing devices 5Y, 5M, 5C, and 5K when moving from the home position to the collection position. In the vicinity of the most upstream side of the auger 49 in the developer transport direction, the developer that is about to move toward the developer movement prevention wall side can be collected by the nozzle-shaped collection port 70 so as to be excessively developed. A large recovery amount of the agent can be set. At that time, the recovery amount of the excess developer can be arbitrarily set according to the set angle of the nozzle-shaped recovery port 70, the area of the opening, or the like. The recovery amount of the excess developer can be set to a desired value. The value can be controlled.

  That is, if the set angle of the nozzle-shaped collection port 70 is moved in the clockwise direction with respect to the tangential direction, the recovery amount of the excess developer tends to be reduced, and conversely, it is counter to the tangential direction. If it is moved in the clockwise direction, the amount of excess developer collected tends to increase. Further, if the opening area of the nozzle-shaped collection port 70 is reduced, the recovery amount of excess developer tends to be reduced. Conversely, if the opening area of the recovery port 70 is increased, the recovery amount tends to increase. It is in. Furthermore, if the height of the nozzle-shaped recovery port 70 is set high, the amount of excess developer recovered tends to decrease, and conversely, if the height of the recovery port 70 is decreased, the recovery amount increases. There is a tendency.

  FIG. 16 is a block diagram showing a control circuit of the full color printer.

  In the figure, 200 is a CPU for controlling the image forming operation of the printer, 201 is a controller for setting printing conditions such as the type of recording medium of the printer and the number of prints, and 202 is a control program executed by the CPU 200 and the developing device 5. A ROM that stores parameters for controlling the operation as a table, 203 a RAM for temporarily storing data such as parameters for controlling the operation of the printer, and 204 a drive motor for driving the rotary developing device 5. The drive motor 204 is configured to be capable of forward and reverse rotation.

  In the above-described configuration, the full-color printer according to this embodiment does not reduce the productivity of image formation even when a single-color image forming operation is continuously performed as follows. It is possible to reliably collect the developer.

  That is, in the full-color printer according to this embodiment, as shown in FIG. 17, for example, when a monochrome single-color image is continuously formed, the rotary developing device 5 is driven to rotate counterclockwise. Then, the black developing device 5K located at the home position is moved to the developing position A facing the photosensitive drum 2, and the printing operation is performed.

  At this time, when the toner in the black developing device 5K is consumed in accordance with the printing operation, the toner or the developer is replenished from the toner cartridge according to the amount of toner consumption. Here, in the present embodiment, the developer in which not only the toner but also the carrier is mixed is replenished from the toner cartridge, and the carrier is not consumed in the development process. The amount of the developer inside increases gradually.

  Therefore, in the full-color printer according to this embodiment, as shown in FIG. 18, after performing the printing process (steps 101 to 104), it is determined whether or not it is time to perform the idling of the rotary developing device 5 by the CPU 200. Is determined (step 105), and if it is not time to idle the rotary developing device 5, the black developing device 5K is driven to rotate counterclockwise and moved to the home position (step 108). ), The printing operation is terminated (step 109).

  If the CPU 200 determines that it is time to perform the idling of the rotary developing device 5 after performing the printing process, the CPU 200 rotates the black developing device 5K counterclockwise as shown in FIG. As shown in FIG. 1, the black developer 5K is driven to rotate clockwise to move to the recovery position (step 107). 107).

  At that time, the CPU 200 refers to a table as shown in FIG. 19 according to the area coverage (AC) indicating the image density and the number of prints, and rotates the black developing device 5K in the clockwise direction to collect it. The number of times of movement to the position is determined (step 107).

  Here, the number of idling operations for moving the developing device to the collection position is basically an amount proportional to the consumption amount of toner or developer in the toner cartridge, and as shown in FIGS. Increases with increasing or decreases with increasing area coverage (AC) indicating image density.

  Accordingly, in consideration of these characteristics, the number of times of idling to move the developing device to the collection position is determined according to the area coverage (AC) indicating the image density and the number of prints as shown in FIG. .

  As described above, in the above embodiment, when the surplus developer is collected, for example, the black developing device 5K is rotated in the clockwise direction opposite to the normal direction to move to the collection position. As shown in FIG. 1, the developer in the black developing device 5K from which the excess developer is to be collected moves to the opposite side to the direction of movement in the normal rotation direction, and the normal rotation is performed. A large amount of excess developer can be collected at a time by the nozzle-like collection port 70 installed on the opposite side to the direction of movement in the direction.

  Therefore, even when an image having a high area coverage (AC) indicating the image density or when a large number of prints are printed, as shown in FIG. Excess developer can be collected, and even when single-color image forming operations are performed continuously, it is possible to reliably collect the developer in the developing device without reducing image formation productivity. High quality images can be maintained over a long period of time.

FIG. 1 is an explanatory view showing the operation of the developing apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a four-cycle full-color printer as an image forming apparatus to which the developing device according to Embodiment 1 of the present invention is applied. FIG. 3 is an explanatory view showing the attachment / detachment state of the image forming member in the four-cycle full-color printer as the image forming apparatus to which the developing device according to Embodiment 1 of the present invention is applied. FIG. 4 is an external perspective view showing a specific example of the rotary developing device 5 as the developing device according to this embodiment. FIG. 5 is a front view showing the rotary developing device according to the first embodiment of the present invention. FIG. 6 is a cross-sectional configuration diagram showing a rotary developing device according to Embodiment 1 of the present invention. FIG. 7 is a longitudinal sectional view showing the developing device and developer cartridge of the rotary type developing apparatus according to Embodiment 1 of the present invention. FIG. 8 is a cross-sectional configuration diagram showing the developing device of the rotary developing device according to the first embodiment of the present invention. FIG. 9 is a longitudinal sectional view showing a developer cartridge of the rotary type developing apparatus according to Embodiment 1 of the present invention. FIG. 10 is a longitudinal sectional configuration diagram along the longitudinal direction showing the developer cartridge of the rotary developing device according to the first embodiment of the present invention. FIG. 11 is a perspective configuration diagram showing the developing device of the rotary developing device according to the first embodiment of the present invention. FIG. 12 is an explanatory view showing the operation of the rotary developing device according to Embodiment 1 of the present invention. FIG. 13 is a block diagram showing the shape of the opening of the developing device. FIG. 14 is a cross-sectional view showing the developing device of the rotary developing device according to Embodiment 1 of the present invention. FIG. 15 is a graph showing the relationship between the developer amount and the discharge amount in the developing device. FIG. 16 is a block diagram showing a control circuit of a 4-cycle full-color printer as an image forming apparatus to which the developing device according to Embodiment 1 of the present invention is applied. FIG. 17 is an explanatory view showing the operation of the rotary developing device according to the first embodiment of the present invention. FIG. 18 is a flowchart showing the operation of the rotary developing device according to the first embodiment of the present invention. FIG. 19 is a chart showing the number of times of operation of the rotary developing device according to the first embodiment of the present invention. FIG. 20 is a graph showing the relationship between the number of prints and the rotational speed of the rotary. FIG. 21 is a graph showing the relationship between image density and rotary speed. FIG. 22 is a table showing the number of times of operation of the rotary developing device according to the first embodiment of the present invention.

Explanation of symbols

  5: Rotating developing device, 5Y, 5M, 5C, 5K: Developer, 45: Developer cartridge, 70: Collection port, A: Development position, C: Collection position, D: Home position.

Claims (7)

A developing device having a recovery port for recovering excess developer;
A rotating body that holds and rotates a plurality of the developing devices,
In a developing device for performing development processing by sequentially moving a predetermined developing device to a developing position facing the image carrier by rotationally driving the rotating body,
When collecting the excess developer by moving the developer that collects the excess developer to a collection position where the collection port of the developer is located below the gravitational direction,
A developing device, wherein the rotating member is rotated in a direction opposite to a rotating direction at the time of image formation, and a developing device for collecting the excess developer is moved to a collecting position. 2. The developing device according to claim 1, wherein the developer carrying member of the developing unit that collects the excess developer is not driven to rotate in accordance with the operation of collecting the excess developer. The number of times the developing device for collecting the excess developer is moved to the collecting position is changed according to the image density of the image to be developed by the developing device of the developing device and the number of recording media to be continuously developed. The developing device according to claim 1, wherein: The number of times the developer that collects the excess developer is moved to the collection position is set to a larger value as the image density of the image to be developed is higher and the number of recording media to be continuously developed is larger. The developing device according to claim 1, wherein the developing device is provided. 2. The development processing is continued without rotating the rotating body until the development corresponding to a predetermined number of recording media is performed when the development is continuously performed by a single developing device. 5. The developing device according to any one of 4 to 4. The recovery port of the developing device is formed in a nozzle shape protruding into the developing device, and the nozzle-shaped opening is in a direction substantially tangent to the rotating body, and ±± with respect to the upstream side in the rotation direction of the rotating body. 6. The developing device according to claim 1, wherein the developing device is set within a range of 45 degrees. 7. The home position of the developing device is set at a position downstream of the collection position by 30 degrees or more along the rotation direction during the developing operation of the rotating body. The developing device according to any one of the above.

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