JP2010197592A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of accurately adjusting toner concentration in a developer storage part, and an image forming apparatus using the same. <P>SOLUTION: In the developing device which has: a developing part 10 which performs development by developer having toner and a carrier; and a plurality of developer storage parts 45, 46 which are provided outside the developing part 10 and store a part of the developer, and supplies the developer from the developer storage parts 45, 46 to the developing part 10 by the airflow, the developer is circulated between arbitrary one of the plurality of developer storage parts 45, 46 and the developing part 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, and a multi-function machine thereof.

  As a developing device used in an image forming apparatus, an apparatus that develops and visualizes an electrostatic latent image formed on an image carrier using a two-component developer composed of toner and carrier is known. In this developing device, the developer that has undergone development processing in the development area and has consumed the toner is collected, mixed and stirred with the replenished toner, and again used for development. The developer used in such a developing device needs to maintain a constant toner density and charge amount in order to obtain a stable toner image. The toner density is adjusted by the toner consumed in development and the amount of replenished toner, and the charge amount is given by frictional charging during mixing of the carrier and the toner. The developing device sufficiently stirs the two-component developer composed of toner and carrier to equalize the toner concentration and charge the toner to stabilize the toner image.

  In a general developing device, toner is dispersed and charged by utilizing the stirring effect of the rotation of two screws during a short time until the replenished toner is pumped up to the developing roller. In particular, when the toner balance is large, the replenished toner is not sufficiently dispersed. In this state, the toner is pumped up to the developing roller, and quality problems such as background contamination and toner scattering occur.

  In order to solve this problem, a separate stirring unit is provided at a location away from the developing unit, the developing unit and the stirring unit are connected by a circulation means, and the stirring unit performs stirring according to the state of the developer, For example, “Patent Document 1”, “Patent Document 2”, and “Patent Document 3” disclose a developing device that supplies a developer with an appropriately adjusted charge amount to a developing unit.

  As described above, in the configuration in which a developer storage unit is provided outside and stirring is performed and the developer is transported again to the development unit, when there is only one developer storage unit, the developer falls down the storage unit ( It is stirred while being circulated). Here, the amount of toner to be replenished is determined based on the detection signal from the toner density detecting means provided in the developing unit or the output image pattern. There is a possibility of being discharged without being sufficiently dispersed, and it is impossible to grasp whether the toner density of the discharged developer has a desired value. Even if the toner density detecting means is provided in the storage section, the developer is circulated and cannot be adjusted again based on the detection result.

  SUMMARY An advantage of some aspects of the invention is that it solves the above-described problems and provides a developing device capable of accurately adjusting the toner density in the developer storage unit and an image forming apparatus using the developing device.

  The invention according to claim 1 includes a developing unit that performs development with a developer having toner and a carrier, and a plurality of developer accommodating units that are provided outside the developing unit and accommodate a part of the developer. In the developing device that supplies the developer to the developing unit by an air flow from the developer accommodating unit, the developer circulates between any one of the plurality of developer accommodating units and the developing unit. It is characterized by being.

  According to a second aspect of the present invention, in the developing device according to the first aspect, in the developer accommodating portion where the developer does not circulate between the developing portions of the plurality of developer accommodating portions, toner replenishment and The toner density is adjusted by stirring.

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, the developing device further includes a switching valve that changes a flow of the developer collected from the developing unit, and the plurality of developing units are switched by switching the switching valve. The developer flows into one of the agent storage portions.

  According to a fourth aspect of the present invention, in the developing device according to the third aspect, the operation of the switching valve is controlled based on the amount of toner consumed in the developing unit.

  According to a fifth aspect of the present invention, there is provided the developing device according to any one of the first to fourth aspects, further comprising an open state and a closed state for controlling the outflow of the developer from the plurality of developer accommodating portions. Two opening / closing valves are provided for each developer storage section, and one of the opening / closing valves occupies an open state, and the other occupies a closed state.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the plurality of developer accommodating portions are formed to have a symmetrical shape having at least one wall surface. It is characterized by that.

  A seventh aspect of the invention is an image forming apparatus having the developing device according to any one of the first to sixth aspects.

  According to the present invention, the developer is circulated between any one of the plurality of developer accommodating portions and the developing portion, the flow of the developer is stopped in the other developer accommodating portions, and the toner concentration is reliably adjusted. By alternately switching these, it is possible to reliably adjust the toner density while continuously circulating the developer.

1 is a schematic view of a developing device employing an embodiment of the present invention. It is sectional drawing of the image development part used for one Embodiment of this invention. It is sectional drawing of the developer accommodating part used for one Embodiment of this invention. It is sectional drawing of the developer accommodating part used for one Embodiment of this invention. It is sectional drawing of the developer accommodating part used for one Embodiment of this invention. It is a timing chart explaining the opening / closing operation | movement of the switching valve in one Embodiment of this invention. 1 is a schematic view showing an image forming apparatus to which a developing device shown in an embodiment of the present invention can be applied.

  FIG. 1 is a schematic view of a developing apparatus employing an embodiment of the present invention. In the figure, reference numeral 10 denotes a casing constituting a developing device as a developing unit, and a two-component developer in which toner and a carrier are mixed is stored in the casing 10. Further, inside the casing 10, as shown in FIG. 2, two conveying screws 11, 12 having spiral fins and a developing roller 13 are rotatably arranged. The transport screw 11 transports the developer from the front to the back in FIG. 2, a part of which is adsorbed on the surface of the developing roller 13 by magnetic force, and the adsorbed developer is uniformly uniformed by the doctor blade 14. By subsequently contacting a photoconductor (not shown), the electrostatic latent image on the photoconductor is developed and a toner image is formed.

  The developed developer is transported from the back to the front of FIG. 2 by the transport screw 12 and discharged from a discharge hole (not shown) formed at the downstream end of the transport screw 12 in the developer transport direction, and then the circulation path 30. To the developer storage section 40. A toner density detection unit (not shown) is provided at the most downstream position in the developer conveyance direction of the conveyance screw 12, and toner is replenished from the toner cartridge 20 based on a signal generated from the toner concentration detection unit. Toner replenishment is performed by the operation of two motors 21 provided in the toner hopper 22, and when the motor 21 is operated, the toner hopper 22 and the developer storage unit 40 are connected to the two toner replenishment paths 34 and 35, respectively. The provided shaftless screw rotates, and toner is replenished from the toner hopper 22 to the developer storage section 40 by this rotation.

  In the developer storage section 40, the developed developer and the replenished toner are mixed and stirred to become a developer having an appropriate toner concentration and charge amount. As shown in FIG. 3, the developer in the developer storage unit 40 falls to the developer and air merging portion 32 disposed below the developer storage portion 40, and is supplied by air sent from the air pump 60 via the circulation path 33. It is returned again to the casing 10 through the circulation path 31.

  As shown in FIG. 3, the developer storage section 40 has two developer storage sections 45 and 46 that store the developer. Above the developer storage sections 45 and 46, A shown by a solid line. A switching valve 49 that selectively occupies the position and the B position indicated by a broken line is provided. The developer supplied from the circulation path 30 to the developer storage unit 40 is developed when the switching valve 49 occupies the A position, and is developed when the switching valve 49 occupies the B position. Each is supplied to the agent storage unit 46. With this configuration, the flow direction of the developer can be easily controlled, and the developer can be easily distributed to the plurality of developer storage portions 45 and 46.

  Two developer agitating members 43 and 44 for agitating the supplied developer are disposed in the developer accommodating portions 45 and 46, respectively. The developer is agitated by the rotation of the agitating members 43 and 44, and the toner is agitated. Is distributed. The agitating members 43 and 44 have a blade shape in which two plate-like members made of resin, metal, or the like are combined, and are rotated by driving means such as a motor (not shown). Toner supply ports 47, 48 are provided above the developer storage portions 45, 46. The toner supply port 47 is connected to the toner supply channel 34, and the toner supply port 48 is connected to the toner supply channel 35. Thus, the toner from the toner cartridge 20 is replenished. Under the developer accommodating portions 45 and 46, toner concentration detection sensors 41 and 42 for detecting the toner concentration in the developer accommodating portions 45 and 46 are disposed, respectively.

  An opening / closing valve that selectively occupies a closed state that blocks outflow of the developer from the developer storage portions 45 and 46 and an open state that allows the developer to flow out, under the developer storage portions 45 and 46. Two 50 and 51 are arranged vertically in each developer accommodating portion 45 and 46. The on-off valves 50A and 50B and the on-off valves 51A and 51B are so-called butterfly valves whose on / off state is switched by rotation. As a result, one of the on-off valves 50A and 51B and the on-off valves 51A and 51B occupies a closed state, so that air from the merging portion 32 can be prevented from flowing into the developer accommodating portions 45 and 46. . In the above-described configuration, the space in the developer storage unit 40 is divided by the single wall surface 52 to form the two developer storage portions 45 and 46 that have symmetrical shapes. The volume of the developer storage section 40 can be reduced.

  Next, the flow of the developer and the toner density adjusting operation, which are the features of the present invention, will be described with reference to FIGS. 3, 4, 5, and 6. FIG. FIG. 3 shows a state in which the developing section is stopped. Developer is accommodated in the developer accommodating sections 45, 46, and the stirring members 43, 44 and the on-off valves 50A, 50B, 51A, 51B are shown. Operation has stopped. This state is indicated by state number 0 in the timing chart shown in FIG.

  When the developing unit is driven, the on-off valves 50A and 50B and the air pump 60 are driven, and the on-off valve 50A and the on-off valve 50B can take the open state and the closed state, thereby developing from within the developer storage unit 45. The discharged developer is sent to the casing 10 through the circulation path 31 by the air flow generated from the air pump 60. At this time, the switching valve 49 occupies the A position, and the developer recovered from the casing 10 is supplied into the developer storage portion 45 via the circulation path 30. This state is indicated by state numbers 1 to 6 in FIG. At this time, the developer collected after the development is performed and the toner is consumed has a low toner concentration. When the developer initially stored in the developer storage portion 45 is almost discharged, the switching valve 49 moves to the B position as shown in FIG. 5, and the developer collected from the casing 10 is in the circulation path 30. To be supplied into the developer storage section 46. This state is indicated by state number 7 in FIG.

  When the switching valve 49 occupies the B position, both the on-off valves 50A and 50B are closed as shown in FIG. 5, and the discharge of the developer from the developer storage unit 45 is stopped and the agitating member 43 is actuated. The toner density of the developer in the agent storage unit 45 is adjusted. Toner density adjustment is performed by the stirring member 43 while supplying toner from the toner supply port 47 so that the toner density detection sensor 41 detects the toner density in the current developer storage unit 45 and returns to the desired toner density. The developer is agitated, and when the toner concentration in the developer accommodating portion 45 reaches a desired toner concentration based on the detection result of the toner concentration detection sensor 41, the toner replenishment and the operation of the agitating member 43 are stopped. . This state is indicated by state numbers 7 to 13 in FIG. At this time, the amount of toner to be replenished first is determined based not only on the detection result of the toner concentration detection sensor 41 but also on the estimated value of the consumed toner amount based on the output image and the detection result of the toner concentration detection sensor installed in the casing 10. By determining, the toner density can be adjusted more accurately and in a short time.

  At this time, in the developer accommodating portion 46, the on-off valves 51A and 51B are operated and the operation of the stirring member 44 is stopped, and the developer is collected and discharged, that is, the developer is circulated between the developer accommodating portion 46 and the casing 10. Is started. When the developer initially stored in the developer storage portion 46 is almost discharged, the switching valve 49 moves to the position A as shown in FIG. 4, and the developer collected from the casing 10 is in the circulation path 30. Then, the toner is again supplied into the developer accommodating portion 45. This state is indicated by state number 14 in FIG.

  As described above, the developer storage section 40 is divided into two developer storage sections 45 and 46, and on the other hand, the developer is circulated, and on the other hand, the flow of the developer is stopped and the toner density is adjusted reliably. By alternately switching the toner density, it is possible to reliably adjust the toner density while continuously circulating the developer. In the case where an image is not output, for example, in a developing unit of a color that is not used in a full-color machine, only the developer is circulated and toner is not consumed. Therefore, the switching valve 49 is not operated and only one developer storage unit is operated. It is preferable to use it. This is because the agitating operation of the toner due to the rotation of the agitating member slightly damages the developer, and it is better not to operate the agitating member when the toner is not replenished.

  FIG. 7 shows an image forming apparatus that can employ the developing device of the present invention. This image forming apparatus is a multifunction machine having a copying function and other functions such as a printer function and a facsimile function, and the copying function, the printer function, and the facsimile function can be switched by a switching key provided in an operation unit (not shown). It is configured. The image forming apparatus includes a main body 100, a writing unit 118 disposed on the top of the main body 100, an image reading unit 106 disposed on the top of the writing unit 118, and an ADF 101 disposed on the top of the image reading unit 106. Have.

  The operation during the copying function will be described below. When a document bundle is placed on the document table 102 of the ADF 101 with the image surface facing up, and a start key on an operation unit (not shown) is pressed, the lowest document is fed by the feeding roller 103 and the feeding belt 104. It is fed to a predetermined position on the contact glass 105. After the image information is read by the image reading unit 106, the document on the contact glass 105 is discharged onto the paper discharge tray 108 by the feeding belt 104 and the discharge roller 107. When the document detection sensor 109 detects that the next document exists on the document table 102, the document is fed onto the contact glass 105 as described above.

  The image reading unit 106 performs line scanning on the image information of the original in the sub-scanning direction while irradiating the original on the contact glass 105 with the two lamps 128, and uses the reflected light as image data as the first mirror 129 and the second mirror. 130, the light is reflected in a predetermined direction by the third mirror 131, and sent to the CCD 133 via the lens unit 132 for reducing and forming an image. The image data read by the image reading unit 106 is sent to a writing unit 118 having a laser light emitting device 134, an fθ lens 135, a reflecting mirror 136, and the like via an image processing unit (not shown), and the photosensitive drum 117 is read by the writing unit 118. An electrostatic latent image corresponding to the original image is formed on the top.

  Inside the main body 100, a photosensitive drum 117, a developing device having a casing 10, a fixing unit 121, a paper discharge unit 122, first to third paper supply devices 110, 111, and 112, a vertical conveyance unit 116, and the like are disposed. Has been. The photosensitive drum 117 is uniformly charged by a charger (not shown) and then exposed to light information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image is developed by a developing device and is toner. An image is formed.

  A conveyor belt 120 is disposed below the photosensitive drum 117. The conveyance belt 120 also serves as conveyance means and transfer means for transfer paper as a recording medium. A transfer bias is applied from a power source (not shown), and the transfer paper from the vertical conveyance unit 116 is conveyed at a constant speed with the photosensitive drum 117. The toner image on the photosensitive drum 117 is transferred to the transfer paper. The toner image transferred to the transfer paper is fixed on the transfer paper in the fixing unit, and the transfer paper on which the image is fixed is discharged onto the paper discharge tray 123 via the paper discharge unit 122. The photosensitive drum 117 is cleaned by a cleaning unit (not shown) after the toner image is transferred, and is prepared for the next image formation.

  The paper discharge unit 122 includes a reversing unit 125 that feeds the transfer paper from the middle thereof by a pair of transport rollers 124, an image forming side transport path 126 that transports the transfer paper reversed by the reversing unit 125 to the vertical transport unit 116 side, and a reversal. A double-sided conveyance path having a paper discharge conveyance path 127 and the like for returning the transferred transfer paper to the paper discharge unit 122 again is provided. With this double-sided conveyance path, images can be formed on both sides of the transfer paper, or discharged onto the paper discharge tray 123 with the image-formed side down.

  When selected, the first to third paper feeding devices 110, 111, and 112 feed transfer sheets stacked on the first tray 113, the second tray 114, and the third tray 115, respectively. The fed transfer paper is conveyed to a position where it comes into contact with the photosensitive drum 17 by the vertical conveyance unit 116.

  In this image forming apparatus, image data from the outside is input to the writing unit 118 instead of the image data from the image processing means during the printer function, and an image is formed on the transfer paper by the image forming means. During the facsimile function, the image data from the image reading unit 106 is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit, and is sent to the writing unit 118 instead of the image data from the image processing means. As a result of the input, the image forming means operates to form an image on the transfer paper.

  In the above-described configuration, an example in which a multifunction peripheral is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited thereto, and other image forming apparatuses such as a copying apparatus, a printer, a facsimile machine, and a plotter. In addition, the present invention is applicable.

10 Development section (casing)
45, 46 Developer accommodating portion 49 Switching valve 50A, 50B, 51A, 51B On-off valve

Japanese Patent No. 3733496 Japanese Patent No. 3349286 JP-A-11-143196

Claims (7)

A developing unit that performs development using a developer having toner and a carrier; and a plurality of developer storage units that are provided outside the development unit and store a part of the developer. In the developing device for supplying the developer to the developing unit by flow,
A developing device, wherein the developer circulates between any one of the plurality of developer accommodating portions and the developing portion. The developing device according to claim 1,
A developing device in which toner concentration is adjusted by toner replenishment and agitation in a developer accommodating portion in which the developer does not circulate among the plurality of developer accommodating portions. The developing device according to claim 1 or 2,
A developing device, comprising: a switching valve that changes a flow of the developer collected from the developing unit, wherein the developer flows into one of the plurality of developer accommodating units by switching the switching valve. The developing device according to claim 3.
The operation of the switching valve is controlled based on the amount of toner consumed in the developing unit. In the developing device according to any one of claims 1 to 4,
Each of the developer storage portions has two open / close valves each capable of taking an open state and a closed state for controlling the outflow of the developer from the plurality of developer storage portions, and one of the open / close valves is opened. A developing device characterized in that when occupied, the other occupies a closed state. The developing device according to any one of claims 1 to 5,
The developing device, wherein the plurality of developer accommodating portions are formed to have a symmetrical shape having at least one wall surface.   An image forming apparatus comprising the developing device according to claim 1.

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