JP5009660B2 - Developing device and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device provided in an image forming apparatus such as a copying machine, a printer, and a facsimile that employs an electrophotographic system, and a multifunction machine that includes these functionally, and an image forming apparatus that includes the developing device.

  Conventionally, as the replenishing toner accommodated in the toner container, one that is supplied to the photosensitive drum via the developing device is generally employed (see, for example, Patent Document 1).

  7 to 9 show an example of such a conventional developing device, FIG. 7 is an explanatory view of an image forming unit provided with the conventional developing device, FIG. 8 is a plan view of the conventional developing device, and FIG. It is sectional drawing of the conventional image development apparatus.

  In the figure, reference numeral 61 denotes a photosensitive drum as an image carrier. The surface of the photosensitive drum 61 is charged with positive polarity by the action of the corona discharger 62, and then the laser beam irradiated to the photosensitive drum 61 from the exposure device 63 corresponding to the image to be formed. The electrostatic latent image is formed by selectively eliminating the charges.

  Further, the photosensitive drum 61 visualizes the electrostatic latent image as a toner image with the toner supplied from the developing device 64, and then transfers the toner image to a transfer sheet (not shown).

  The developing device 64 is supplied with replenishing toner from a first toner replenishing unit 66 and a second toner replenishing unit 67 of the toner container 65.

  The first toner replenishing portion 66 is disposed above the second toner replenishing portion 67, and a first spiral 69 is provided below the first toner replenishing portion 66 via a first replenishing port 68 of the developing device 64. A second spiral 71 is provided below the second toner replenishing portion 67 via a second replenishing port 70.

  The first spiral 69 and the second spiral 71 agitate the toner while circulating (reciprocating) the toner inside the developing device 64 by conveying the replenished toner from the toner container 65 along the axial direction thereof. Further, the toner is supplied to the photosensitive drum 61 while being appropriately stirred so as not to aggregate by the developing roller 72 adjacent to the photosensitive drum 61.

  The first supply port 68 and the second supply port 70 are opened and closed by shutters 74 and 75 controlled by a control circuit (not shown) according to the toner detection density from the toner sensor 73.

  In the developing roller 72, a plurality of magnets S1, S2, N1, and N2 are disposed on the rotating sleeve 76, and the toner on the rotating sleeve 76 is attached and conveyed by the magnetic restraining force of the magnets S1, S2, N1, and N2. To do. The layer thickness of the toner conveyed by the rotating sleeve 76 is regulated by a magnetic blade 77 facing the rotating sleeve 76 with a certain gap, and the toner is charged by friction.

When replenishment toner is replenished from the toner container 65 to the developing device 64, toner replenishing rollers (not shown) provided in the toner container 65 and the toner replenishing portions 66 and 67 are connected to the driving systems of the developing device 64. The toner is rotated in synchronism with the rotation, and a constant amount of replenishment toner is constantly replenished from the toner container 65 to the developing device 64, and the shape of the first spiral 69 and the second spiral 71 in the developing device 64 is oversupplied or insufficiently replenished. Is preventing.
JP 2005-043523 A

  However, in the developing device 64 configured as described above, the toner in the developing device 64 can be supplied even if the replenishment amount of the replenishing toner from the toner container 65 is continuously performed at a high printing rate. When setting is made such that a stable toner amount can be maintained without being too small, the amount of toner consumed in the developing device 64 is reduced when image forming processing at a low printing rate is continuously performed. Nevertheless, the toner container 65 is replenished with the same amount of toner as in the image forming process according to the printing rate higher than the actual printing rate, and the amount of toner in the developing device 64 becomes excessive as compared with the normal case. There was a problem.

  On the contrary, even if the replenishment amount of the replenishment toner from the toner container 65 is continuously performed at a low printing rate, the toner amount in the developing device 64 is stable without being excessive. If the setting is such that the toner amount can be maintained, when the image forming process at a high printing rate is continuously performed, the toner container 65 actually consumes a large amount of toner in the developing device 64. As a result, only the same amount of toner as in the image forming process conforming to a printing rate lower than the printing rate is replenished, and the amount of toner in the developing device 64 becomes less than usual.

  As a result, when the toner amount becomes excessive, the density is lowered due to deterioration caused by the toner load during circulation in the developing device 64, and when the toner amount becomes excessive, the rotating sleeve 76 is used. An image defect may occur, such as image fading due to insufficient toner supply to the printer.

  Therefore, in consideration of the above circumstances, the present invention can suppress the occurrence of image defects due to excessive toner and insufficient toner by adjusting the toner amount in the developing device and uniformity of charging in accordance with the printing rate. An object of the present invention is to provide a developing device capable of realizing a long life.

  In the developing device of the present invention, the replenishment toner contained in the toner container is agitated and supplied to the photoconductor, and the opening area of the toner replenishing port to which the replenishment toner is supplied from the toner container is defined as a printing rate. It is characterized by having a shutter that can be changed according to the above.

  At this time, the toner replenishing port includes two toner replenishing ports having different opening areas, and the shutter opens one of the two different toner replenishing ports according to the printing rate and closes the other. Preferably, when the printing rate is small, the shutter opens the smaller opening area of the toner supply port and closes the larger opening area of the toner supply port, and when the printing rate is high, the shutter It is preferable to open the larger opening area of the toner supply port and close the smaller opening area of the toner supply port.

  Preferably, the toner replenishing port has one toner replenishing port having a large opening area, and the shutter preferably adjusts an actual opening area of the toner replenishing port according to a printing rate. When the rate is small, it is preferable to reduce the opening area of the toner supply port, and when the printing rate is high, it is preferable to increase the opening area of the toner supply port.

  Further, it is desirable that the toner replenishing port has a large opening area near the starting end of the toner stirring path.

  Furthermore, the present invention can be an image forming apparatus employing a developing device having any one of the above-described configurations.

  The developing device of the present invention can suppress the occurrence of image defects due to excessive toner and insufficient toner by adjusting the toner amount in the developing device according to the printing rate and uniformity of charging, and realizing a long life. can do.

  Next, a developing device according to an embodiment of the present invention is applied to a multifunction machine as an image forming apparatus and will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a multifunction peripheral as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of a developing device according to an embodiment of the present invention with a toner supply port having a small opening area opened. FIG. 3 is a plan view of a developing device according to an embodiment of the present invention in a state where a toner replenishing port having a large opening area is opened, and FIG. 4 is a cross-sectional view of the developing device according to an embodiment of the present invention.

(Overall configuration of MFP)
As shown in FIG. 1, a multi-function machine 1 as an image forming apparatus according to an embodiment of the present invention includes a plurality of transfer paper storage apparatuses 3, 4, 5 that can be pulled out from the front surface of an apparatus body 2, and the transfer apparatus. In order to make it possible to use transfer paper different from the paper storage devices 3, 4, and 5, a manual feed tray 6 provided on one side of the apparatus body 2 so as to be openable and closable, and various types of copiers, facsimiles, and scanners. An automatic document feeder (ADF) 7 used when reading a document as a function, and an operation unit 9 having a display screen 8 and performing setting / selection operations of various functions and the like are provided.

  Note that the shape, configuration, function, and the like of the multifunction machine 1 are not limited to those shown in the drawings. Further, for example, it does not hinder the installation of optional equipment such as a sorter.

(Internal structure of MFP)
Further, the apparatus main body 2 takes out the transfer paper (not shown) stored in the transfer paper storage devices 3, 4, 5 or the manual feed tray 6 into the apparatus main body 2 and is disposed on the other side surface of the apparatus main body 2. A transport path 11 that transports the paper toward the paper tray 10, a registration sensor 12 that is disposed upstream of the transport path 11 in the transfer paper transport direction and detects the transfer paper, and a transfer paper transport direction in the transport path 11 relative to the resist sensor 12 The pair of registration rollers 13 disposed on the downstream side, the image forming unit 14 disposed on the downstream side of the conveyance path 11 in the transfer sheet conveyance direction with respect to the registration sensor 12, and the image forming unit 14 are transferred to the surface of the transfer sheet. The fixing unit 15 for fixing the toner image on the surface of the transfer paper, the branch path 16 disposed on the downstream side of the transport path 11 in the transfer paper transport direction from the fixing section 15, and the transfer paper guided to the branch path 16 are switched. After a single-sided printing process when there are a plurality of originals set on the ADF 7 and a reverse path 18 that returns to the transport path 11 upstream of the registration sensor 12 in the transfer paper transport direction with the front and back reversed via the back path 17. And a reverse discharge path 19 for discharging the transfer sheet to the discharge tray 10 in a state where the discharge surface of the transfer sheet is aligned with the document order.

  The registration sensor 12 detects the transfer paper and synchronizes the position of the leading edge of the transfer paper with the position of the toner image formed on the surface of the photosensitive drum 20, and the registration sensor 12 detects the leading edge of the transfer paper. Then, the rotation driving of the registration roller pair 13 is started after a lapse of a predetermined time, and the rotation driving of the registration roller pair 13 is stopped after the lapse of a predetermined time after the registration sensor 12 detects the trailing edge of the transfer paper.

  The registration roller pair 13 is connected to a drive source (not shown) such as a motor. Then, in a stationary state, the registration roller pair 13 instantaneously stops the transfer paper when the leading edge of the transfer paper is nipped, and corrects the oblique feeding of the transfer paper by bending the transfer paper. .

  The image forming unit 14 includes a photosensitive drum 20, a charging device 21, an exposure device 22, a developing device (developing apparatus) 23, a transfer device 24, a cleaning device 25, and a static eliminating device 26 arranged around the photosensitive drum 20. I have.

  As a result, in the image forming unit 14, the photosensitive drum 20 is rotationally driven at a predetermined process speed (circumferential speed) by a driving unit (not shown), and the surface thereof is uniformly charged to a predetermined polarity and potential by the charging device 21. .

An electrostatic latent image is formed on the surface of the charged photosensitive drum 20 by the exposure device 22. Here, for example, the exposure device 22 is connected via a communication line such as a print data read by a scanner unit using the ADF 7 by a copying machine function, a print data received through a telephone line by a facsimile function, or a network by a printer function. Based on the print data output from a personal computer or the like, the surface of the photosensitive drum 20 is irradiated with laser light, and the charge of the laser light irradiated portion on the surface of the photosensitive drum 20 is removed to reduce the static according to the image information. An electrostatic latent image is formed.
The electrostatic latent image formed on the surface of the photosensitive drum 20 is developed as a toner image by electrostatically attaching a charged toner by the developing device 23. Further, the toner image is transferred onto the transfer paper as a transfer image by the transfer device 24.

  At this time, the photosensitive drum 20 having the toner image transferred onto the transfer paper is removed by the cleaning device 25 and the charge is removed by the charge removal device 26 for charging at the next image formation.

(Configuration of developing device 23)
The developing device 23 supplies the toner for replenishment stored in a toner container 27 detachable (replaceable) to the multifunction machine main body 2 to the photosensitive drum 20 while stirring, as shown in FIGS. 2 and 4. In addition, a lid 30 having two large and small toner replenishing ports 28 and 29 having different opening areas to which replenishment toner is supplied from the toner container 27, a spiral container 31 covered with the lid 30, a toner replenishing port 28, 29 adjacent to the first spiral 32 so that the first spiral 32 and the partition wall 33 formed in the spiral container 31 are sandwiched between the first spiral 32 and the first spiral 32 rotatably held in the spiral container 31. The second spiral 34 rotatably held in the spiral container 31 and the spiral container 31 rotatably held so as to be adjacent to the second spiral 34. And a developing roller 35.

  In the present embodiment, the toner replenishing ports 28 and 29 are, for example, when the printing rate is low based on the printing rate calculated by a control circuit (not shown) based on image data for image forming processing (for example, A toner replenishing port 28 having a small opening area so that the replenishment toner is replenished from the toner container 27 at a printing rate of less than 1%, and when the printing rate is high (for example, a printing rate of 1% or more) ) Is a toner replenishing port 29 having a large opening area in which the opening area is set so that the toner for replenishment is replenished from the toner container 27. Each toner supply port 28, 29 is opened and closed by a single shutter 37.

  The shutter 37 is connected via an arm 39 and a shutter driving member 38 such as a solenoid that can be expanded and contracted (see arrow A in FIG. 2), and when the printing rate of the image forming process is low, as shown in FIG. In addition, when the toner replenishing port 28 is opened and the toner replenishing port 29 is closed due to the contraction of the shutter driving member 38 and the printing rate of the image forming process is high, the shutter driving member 38 has a high printing rate as shown in FIG. The toner supply port 29 is opened by the extension, and the toner supply port 28 is closed. In this embodiment, the toner replenishing port 29 having a large opening area is about 8 mm × 2 mm, and the toner replenishing port 28 having a small opening area is about 1/3 of the toner replenishing port 29 (for example, 2.5 mm). ˜3.0 mm × 2 mm).

  Both ends of the partition wall 33 formed inside the spiral container 31 communicate with the spirals 32 and 34, and are directed to one side of the developing device 23 by the first spiral 32 provided below the toner supply holes 28 and 29. (See arrow B in FIG. 2), the toner is stirred and conveyed (forward path), and then folded from the gap on one side and directed toward the other side of the developing device 23 by the second spiral 34 (see arrow C in FIG. 2). ) A circulation path is formed in which the toner is stirred and conveyed (return path) and turned back again in the gap on the other side.

  Further, in the present embodiment, the first spiral 32 is formed in a clockwise spiral in order to supply toner along the axial direction by rotating counterclockwise in FIG. Further, the second spiral 34 is formed in a counterclockwise spiral in order to supply the toner along the axial direction by rotating in the counterclockwise direction in the figure.

  Therefore, when the first spiral 32 rotates counterclockwise, the toner is conveyed in the depth direction of the paper surface of FIG. 4, whereas when the second spiral 34 rotates counterclockwise, the toner is conveyed forward of the paper surface. Will be. Thus, the toner is circulated and conveyed through the gaps at both ends of the partition wall 33 so as to wrap around the inside of the developing device 23, and the toner conveyed by the second spiral 34 is supplied to the developing roller 35.

  Thus, the toner replenishing port 28 having a small opening area is formed near the center of the lid 30 having a short circulation path, and the toner replenishing port 29 having a large opening area is formed near the end of the lid 30 having a long circulation path. As a result, the length of the toner reaching path from the second spiral 34 via the developing roller 35 to the photosensitive drum 20 is secured according to the amount of toner replenished, so that the charge of the toner due to agitation is made uniform and fogging due to insufficient charge is generated. Can be suppressed. Each spiral 32, 34 can be reversed in the direction of toner circulation by reversing the direction of rotation thereof.

  The developing roller 35 is disposed so that the peripheral surface thereof faces the peripheral surface of the photosensitive drum 20. Therefore, the toner being conveyed to the developing roller 35 is supplied to the peripheral surface of the photosensitive drum 20 via the developing roller 35, and thereby a toner image is formed on the peripheral surface of the photosensitive drum 20. At this time, the developing roller 35 supplies the photosensitive drum 20 with proper stirring so as not to aggregate the toner, and includes a rotating sleeve 36 in which a plurality of magnets S1, S2, N1, and N2 are arranged. The toner on the rotating sleeve 36 is attached and transported by the magnetic restraining force of S1, S2, N1, and N2. The layer thickness of the toner conveyed by the rotary sleeve 36 is regulated by the magnetic blade 40 facing the rotary sleeve 36 with a certain gap, and the toner is charged by friction.

  As described above, according to the developing device (developing device 23) of the present invention, when the replenishment toner is replenished from the toner container 27 to the developing device 23, the control circuit calculates in advance based on the image data for the image forming process. For example, when the printing rate is low, the toner is supplied from the toner supply port 28 having a small opening area. When the printing rate is high, the toner is supplied from the toner supply port 29 having a large opening area. Therefore, it is possible to suppress oversupply and undersupply at the time of toner replenishment, and therefore, it is possible to achieve toner amount adjustment in the developing device 23 according to the printing rate and uniformity of charging, due to excessive toner and insufficient toner. In addition to suppressing the occurrence of image defects, the life of the developing device 23 can be extended.

  By the way, in the above-described embodiment, the one having two large and small toner supply ports 28 and 29 having different opening areas is disclosed. For example, as shown in FIGS. 5 and 6, only the toner supply port 29 having a large opening area is provided. When the printing rate of the image forming process is low, as shown in FIG. 5, a part of the toner replenishing port 29 is opened so that the opening area is reduced by the extension of the shutter driving member 38, and the image forming process is performed. 6, all of the toner replenishing port 29 is opened so that the opening area is increased by contraction of the shutter driving member 38, and the actual opening area of the toner replenishing port 29 is set as shown in FIG. 6. The present invention is not limited to the above-described embodiment, such as being configured to adjust according to the printing rate.

1 is an explanatory diagram of a multifunction peripheral as an image forming apparatus according to an embodiment of the present disclosure. FIG. 6 is a plan view of a developing device according to an embodiment of the present invention with a toner supply port having a small opening area opened. FIG. 6 is a plan view of a developing device according to an embodiment of the present invention with a toner supply port having a large opening area opened. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention. FIG. 10 is a plan view of a state in which a part of one toner replenishing port is opened so that the opening area in another developing device according to an embodiment of the present invention is reduced. FIG. 10 is a plan view of a state in which all of one toner replenishing port is opened so that an opening area in another developing device according to an embodiment of the present invention is increased. It is explanatory drawing of the image forming part provided with the conventional developing device. It is a top view of the conventional developing device. It is sectional drawing of the conventional image development apparatus.

Explanation of symbols

1 ... Multifunction machine (image forming device)
20 ... Photosensitive drum (photosensitive member)
23. Developing device (developing device)
28 ... Toner supply port 29 ... Toner supply port 37 ... Shutter 38 ... Shutter drive member

Claims (4)

In the developing device for supplying the toner for replenishment stored in the toner container to the photosensitive member while stirring,
The toner supply port is provided with a shutter that varies an opening area of a toner supply port to which supply toner is supplied from the toner container in accordance with a printing rate. The toner supply port includes two toner supply ports having different opening areas. developing apparatus is characterized in closing to Rukoto an open and the other one of said large and small two different toner supply port in accordance with the printing ratio. The shutter opens the smaller opening area of the toner replenishing port and closes the larger opening area of the toner replenishing port when the printing rate is small, and the toner replenishing when the printing rate is large. 2. The developing device according to claim 1, wherein the one having a larger opening area is opened and the one having a smaller opening area is closed. The developing device according to claim 1 , wherein the toner replenishing port has a large opening area near a starting end portion of a toner stirring path . An image forming apparatus comprising the developing device according to claim 1 .

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