JP4026949B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer. More specifically, the present invention relates to an image forming apparatus that prevents toner in a toner container from flowing out to a developing device other than during toner replenishment. .
[0002]
[Prior art]
Conventionally, a rotating developer unit having a plurality of developing units and rotatably provided in the vicinity of the latent image carrier, and a plurality of toner storage chambers corresponding one-to-one to the plurality of developing units, respectively. And a revolver developing device comprising a rotating toner accommodating unit coaxially provided at one end of the rotating developer unit, and a toner conveying means for connecting the toner accommodating chambers and the developing units. (See, for example, Japanese Patent Application Laid-Open Nos. 62-251772, 63-78170 and 63-41164). As the toner conveying means, a toner conveying path provided between the toner containing chamber and the developing device is connected. Forming toner transport pipe And the toner transport pipe A toner conveying member arranged inside is known, and the toner in the toner container is conveyed to the developing unit as needed by the toner conveying member.
[0003]
As the toner conveying member, for example, in Japanese Utility Model Laid-Open No. 3-129968 and Japanese Patent Application No. 4-345373, a screw in which a spiral blade portion is formed on a shaft (hereinafter referred to as a conveying screw) is applied. Has been disclosed. These are toner transport pipe By using the toner conveying means constituted by the conveying screw or the like provided in the toner, the toner in the toner container can be conveyed to a place away from the toner container. The degree of freedom in laying out each apparatus within the image forming apparatus, such as being arranged on the side of the developing device, can be increased, and the image forming apparatus can be reduced in size.
[0004]
The conveying screw and the conveying path as described above are conventionally configured to have a certain amount of clearance between them so that the conveying screw rotates smoothly. This is because when the two interfere with each other, there is a possibility that abnormal noise may be generated due to interference or locking may be caused during rotation driving.
[0005]
[Problems to be solved by the invention]
However, as described above, the transport screw and toner transport pipe When there is a clearance between the toner and the toner whose fluidity increases as the developing device rotates, pipe When the toner enters, the toner flows out to the developing device through the clearance. Also, even if the toner fluidity is not high, the toner can be transported at once. pipe When entering, toner transport pipe There is a problem in that the air inside is difficult to escape and the toner is pushed out to the developing device by the pressure. Further, the toner conveyance pipe The toner in the vicinity of the opening facing the developing device may flow out to the developing device due to vibration during rotation of the developing device. Since such spilled toner flows out to the developing device at any time regardless of the toner replenishment signal of the image forming apparatus main body, if more toner flows out than the toner consumption amount, the toner density in the developing device becomes high. As a result, there are a number of problems such as excessive image density and background stains, and the developer being locked due to the increase in toner volume in the developer.
[0006]
Such defects are caused by the conveyance screw and the toner conveyance. pipe However, since there is a limit due to manufacturing tolerance of each part, the above problem has not been solved.
Also, toner transport member and toner transport pipe Even if there is a clearance between pipe There is a method in which a shutter is provided at the opening to the developing unit, and the shutter is opened when the toner is replenished, and the shutter is closed when the toner is not replenished to prevent unnecessary toner from flowing out to the developing unit. In addition, the configuration of the shutter is complicated, and it is necessary to provide a driving unit for the shutter, which causes a problem in terms of cost and space.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a toner transport member and a toner transport. pipe When of while of clearance Through , Toner in the toner container Is It is an object of the present invention to provide an image forming apparatus capable of preventing the toner from flowing into the developing device except when the toner is replenished.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention provides a magnetic developer comprising a plurality of developing devices, rotatably provided near a latent image carrier, and comprising a toner and a magnetic carrier. Rotating type developing device Place A plurality of toner containers that are detachably attached to the developing device and rotate integrally with the developing device, corresponding to the developing devices on a one-to-one basis. vessel , as well as, Connecting each toner container and each developing device Ruto Conveyor pipe When And provided inside the toner transport pipe so that there is a clearance between the toner transport pipe and the toner transport pipe. Toner conveying member When Toner transporter consisting of Step In the image forming apparatus provided, the rotary developing device is configured to convey each of the toners by rotating the rotary developing device. pipe And the above and each developing device has a configuration that the vertical positional relationship changes, Each of the toner transport pipes has an opening with respect to the developer of each of the toner transport pipes when an inlet of the toner transport pipe communicated with the toner container is directed upward by rotation of the rotary developing device. Configured to face downward, the above For fixing the magnetic developer in each toner conveying pipe A magnetic field generating means is provided.
[0009]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the magnetic field generating means is composed of a magnet.
[0010]
In the image forming apparatus according to claim 1 or 2, , Magnetism By providing a boundary generating means, the transporting device is rotated during rotation of the developing device. pipe The magnetic developer in the developer that flows into the toner is conveyed by the magnetic field. pipe Fixed inside. Therefore, this toner transport pipe The magnetic developer fixed inside Toner transport pipe The toner conveying member and the toner conveying pipe When of while of clearance Through Each developer side Heto Na But Outflow Do Can be prevented. Further, by preventing the toner from flowing out, it is possible to prevent the toner density in each developing device from becoming high, so that it is possible to prevent the occurrence of excessive image density and background contamination. In addition, toner transport pipe In addition, it is possible to prevent the magnetic developer from flowing back into the toner container.
[0011]
In particular, in the image forming apparatus of the second aspect, since the magnet is used as the magnetic field generating means, it is possible to reliably prevent the toner from flowing out to the developing device with a simple configuration.
[0012]
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the toner conveying unit is capable of conveying the magnetic developer restrained by the magnetic field generating unit by driving the toner conveying member. It is characterized by this.
[0013]
In the image forming apparatus according to claim 3, when the toner transporting unit is configured to transport the magnetic developer restrained by the magnetic field generating unit by driving the toner transporting member, Toner transport automatically pipe Are opened. That is, by using the magnetic field generating means, the opening is kept closed except when the toner is replenished. Further, by using the toner conveying member according to claim 3, the opening is maintained when the toner is replenished. The part can be opened. According to this, toner transport pipe As a method for opening and closing the communication portion of each developing device, since it is a simple configuration that uses the driving of the toner conveying member originally provided in the developing device and only includes the magnetic field generating means, Compared to a configuration in which a shutter mechanism, a shutter drive unit, and the like are provided, this is advantageous in terms of cost and space.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter referred to as a color copying machine) which is an image forming apparatus will be described.
First, the schematic configuration and operation of the color copying machine according to the present embodiment will be described with reference to FIG. The color copying machine includes a color image reading device (hereinafter referred to as a color scanner) 1, a color image recording device (hereinafter referred to as a color printer) 2, a paper feed bank 3, and the like.
[0015]
The color scanner 1 forms an image of the document 4 on the contact glass 101 on the color sensor 105 through the illumination lamp 102, the mirror groups 103a, 103b, and 103c, and the lens 104, and the color image information of the document 4 is obtained. For example, red: red, green: green, and blue: blue (hereinafter referred to as R, G, and B), respectively, are read and converted into electrical image signals. Here, the color sensor 105 is composed of R, G, B color separation means and a photoelectric conversion element such as a CCD in this example, and simultaneously reads three color images obtained by color separation of the image of the document 4. . Then, based on the color separation image signal intensity levels of R, G, and B obtained by the color scanner 1, color conversion processing is performed by an image processing unit (not shown), Black: black (hereinafter referred to as Bk), Cyan : Color image data of cyan (hereinafter referred to as C), Magenta: magenta (hereinafter referred to as M), and Yellow: yellow (hereinafter referred to as Y) are obtained.
[0016]
The operation of the color scanner 1 for obtaining the Bk, C, M, and Y color image data is as follows. In response to a scanner start signal that takes the operation and timing of the color printer 2 to be described later, the optical system including the illumination lamp 102 and the mirror groups 103a, 103b, and 103c scans the document 4 in the left direction of the arrow, and once. One color image data is obtained for each scanning. By repeating this operation a total of four times, color image data of four colors is sequentially obtained. Each time, the color printer 2 sequentially visualizes the images and superimposes them to form a final four-color full-color image.
[0017]
The color printer 2 includes a photosensitive drum 200 as an image carrier, a writing optical unit 220, a revolver developing device 230, an intermediate transfer device 260, a fixing device 270, and the like.
[0018]
The photosensitive drum 200 rotates counterclockwise as indicated by an arrow, and around the photosensitive drum 201, a static elimination lamp 202, a charger 203, a potential sensor 204, and a selected developing device of the revolver developing device 230. Further, a development density pattern detector 205, an intermediate transfer belt 261 of the intermediate transfer device 260, and the like are arranged.
[0019]
The writing optical unit 220 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the image of the document 4, and forms an electrostatic latent image on the photosensitive drum 200. The writing optical unit 220 includes a semiconductor laser 221 as a light source, a laser light emission drive control unit (not shown), a polygon mirror 222 and its rotation motor 223, an f / θ lens 224, a reflection mirror 225, and the like.
[0020]
The revolver developing device 230 includes a Bk developing unit 231K, a C developing unit 231C, an M developing unit 231M, and a Y developing unit 231Y, and a revolver rotation driving unit described below that rotates each developing unit in the counterclockwise direction indicated by an arrow. It is configured. Each developing device includes a developing sleeve that rotates by contacting a developer ear with the surface of the photosensitive drum 200 in order to develop the electrostatic latent image, and a developer that rotates to pump up and stir the developer. It consists of paddles. The toner in each developing device 231 is negatively charged by stirring with a magnetic carrier, and each developing sleeve has a developing bias in which an AC voltage Vac is superimposed on a negative DC voltage Vdc by a developing bias power source (not shown). Is applied, and the developing sleeve is biased to a predetermined potential with respect to the metal substrate layer of the photosensitive drum 200. In the standby state of the copying machine main body, the revolver developing device 230 has the Bk developing unit 231K set at the developing position, and when the copying operation is started, the color scanner 1 reads Bk color image data from a predetermined timing. Then, based on the color image data, optical writing by laser light and electrostatic latent image formation start (hereinafter, the electrostatic latent image by Bk image data is referred to as a Bk latent image. The same applies to C, M, and Y). Before the leading edge of the electrostatic latent image reaches the Bk development position so that the leading edge of the Bk electrostatic latent image can be developed, the Bk developing sleeve starts to rotate, and the Bk electrostatic latent image is converted into Bk toner. Develop with. Thereafter, the development operation of the Bk electrostatic latent image area is continued. When the trailing edge of the electrostatic latent image passes the Bk development position, the revolver development is performed until the next color developing device immediately reaches the development position. The device 230 rotates. This is completed at least before the leading edge of the electrostatic latent image by the next image data arrives.
The revolver developing device 230 will be described in detail later.
[0021]
The intermediate transfer device 260 includes an intermediate transfer belt 261, a belt cleaning device 262, a primary transfer corona discharger (hereinafter referred to as a primary transfer device) 263, and the like. The intermediate transfer belt 261 is stretched around a drive roller 264a, a transfer counter roller 264b, a cleaning counter roller 264c, and a driven roller group, and is driven and controlled by a drive motor (not shown). The belt cleaning device 262 includes an inlet seal, a rubber blade, a discharge coil, an inlet seal, a rubber blade contact / separation mechanism, and the like, and a Bk image of the first color is transferred to the intermediate transfer belt 261. During the primary transfer of the second, third, and fourth color images after the transfer, the entrance seal and blade are separated from the surface of the intermediate transfer belt 261 by the contact / separation mechanism. The paper transfer unit 263 applies an AC voltage + DC voltage or a DC voltage by a corona discharge method, and collectively transfers (secondary transfer) the superimposed toner images on the intermediate transfer belt 261 onto the transfer paper.
[0022]
The transfer paper cassette 207 in the color printer 2 and the transfer paper cassettes 300a, 300b, and 300c in the paper supply bank 3 store transfer paper 5 of various sizes, and transfer paper cassettes of designated sizes. Are fed and conveyed in the direction of the registration roller pair 209 by the sheet feeding rollers 208, 301a, 301b, and 301c. Further, a manual feed tray 210 for manual paper feed such as OHP paper or thick paper is provided on the right side of the printer 2.
[0023]
In the color copying machine having the above configuration, when an image forming cycle is started, first, the photosensitive drum 200 is rotated counterclockwise as indicated by an arrow, and the intermediate transfer belt 261 is rotated clockwise as indicated by an arrow by a drive motor (not shown). . As the intermediate transfer belt 261 rotates, Bk toner image formation, C toner image formation, M toner image formation, and Y toner image formation are performed, and finally, on the intermediate transfer belt 261 in the order of Bk, C, M, and Y. A toner image is formed in an overlapping manner.
[0024]
The Bk toner image formation is performed as follows. The charger 203 uniformly charges the photosensitive drum 200 to about −700 V with a negative charge by corona discharge. The semiconductor laser 221 performs raster exposure based on the Bk color image signal. When this raster image is exposed, the charge proportional to the exposure light amount disappears in the exposed portion of the photosensitive drum 200 that is initially uniformly charged, and a Bk electrostatic latent image is formed. When the negatively charged Bk toner on the Bk developing sleeve comes into contact with the Bk electrostatic latent image, the toner does not adhere to the remaining portion of the photosensitive drum 200, and the portion without the charge, that is, the exposure. Bk toner is attracted to the portion thus formed, and a Bk toner image similar to the electrostatic latent image is formed. The Bk toner image formed on the photosensitive drum 200 is primarily transferred by the primary transfer unit 263 to the surface of the intermediate transfer belt 261 that is driven at a constant speed in contact with the photosensitive drum 200.
[0025]
Some untransferred residual toner on the photoreceptor drum 200 is cleaned by the photoreceptor cleaning device 201 in preparation for the reuse of the photoreceptor drum 200. The collected toner is stored in a waste toner tank (not shown) via a collection pipe.
[0026]
On the side of the photosensitive drum 200, the process proceeds to the C image forming process after the Bk image forming process, and C image data reading by the color scanner 1 is started at a predetermined timing, and the C electrostatic latent image is written by laser light writing with the C image data. Form. Then, after the rear end portion of the previous Bk electrostatic latent image passes and before the front end portion of the C electrostatic latent image reaches, the revolver developing device 230 is rotated, and the C developing unit 231C develops. The C electrostatic latent image is developed with C toner. Thereafter, the development of the C electrostatic latent image area is continued, but when the rear end of the C electrostatic latent image passes, the revolver developing device 230 is rotated in the same manner as in the case of the previous Bk developing unit 231B. The next M developing unit 231M is moved to the developing position. This is also completed before the leading edge of the next M electrostatic latent image reaches the developing position.
Note that the M and Y image forming steps are the same as the above-described steps BK and C, respectively, because the operations of reading color image data, forming an electrostatic latent image, and developing are the same as those described above.
[0027]
On the intermediate transfer belt 261, toner images of Bk, C, M, and Y that are sequentially formed on the photosensitive drum 200 are sequentially aligned on the same surface to form a four-color superimposed toner image for the next transfer. In the process, the four-color toner images are collectively secondary-transferred onto the transfer paper by the secondary transfer device 265.
[0028]
At the time when the image forming operation is started, the transfer paper is fed from either the transfer paper cassette or the manual feed tray and is waiting at the nip of the registration roller pair 209. When the leading edge of the toner image on the intermediate transfer belt 261 approaches the secondary transfer unit 265, the registration roller pair 209 is driven so that the leading edge of the transfer paper coincides with the leading edge of the toner image, and the transfer paper and the toner are transferred. Registration with the image is performed. Then, the transfer paper is superimposed on the toner image on the intermediate transfer belt 261 and passes over the secondary transfer device 265 having a positive potential. At this time, the transfer paper is charged with a positive charge by the corona discharge current, and most of the toner image is transferred onto the transfer paper. Subsequently, when the paper passes through a portion facing an AC + DC corona separation / discharger (not shown) disposed on the left side of the secondary transfer unit 265, the transfer sheet is discharged, peeled off from the intermediate transfer belt 261, and transferred to the conveyance belt 211.
[0029]
Then, the transfer paper onto which the four-color superimposed toner images are collectively transferred from the surface of the intermediate transfer belt 261 is transported to the fixing device 270 by the paper transport belt 211, and the fixing roller 271 and the pressure roller controlled to a predetermined temperature. The toner image is melted and fixed at the nip portion of the roller 272, sent out of the apparatus main body by the discharge roller pair 212, and stacked on a copy tray (not shown) so as to obtain a full color copy.
[0030]
On the other hand, the surface of the photosensitive drum 200 after the primary transfer is cleaned by the photosensitive member cleaning device 201 (brush roller, rubber blade), and is uniformly discharged by the discharging lamp 202. Further, the surface of the intermediate transfer belt 261 after the toner image is transferred to the transfer paper is cleaned by pressing the blade of the belt cleaning device 262 again with the blade contact / separation mechanism.
[0031]
Here, in the case of repeat copy, the operation of the color scanner 1 and the image formation on the photosensitive drum 200 are performed at a predetermined timing following the image formation process for the fourth color (Y) of the first sheet. The first color (Bk) image forming process proceeds. In addition, the intermediate transfer belt 261 continues to the area of the surface that has been cleaned by the belt cleaning device 262 on the surface following the batch transfer process of the first four-color superimposed toner image to the transfer paper. The Bk toner image is primarily transferred. After that, the operation is the same as the first sheet.
(Hereinafter, blank space)
[0032]
The above is a copy mode for obtaining a four-color full-color copy. However, in the case of a three-color copy mode and a two-color copy mode, the above-described items for the designated color and number of times are described above. A similar operation is performed. In the case of the single color copy mode, only the predetermined color developer of the revolver developing device 230 is set in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning device 262 is placed in the intermediate state. The copying operation is continuously performed on the transfer belt 261 while being pressed. In the A3 size full-color copy mode, it is desirable to form a one-color toner image each time the intermediate transfer belt 261 makes one turn, and form a four-color toner image by four rotations. In order to reduce the overall size of the apparatus, that is, to suppress the circumferential length of the intermediate transfer belt 261, to ensure the copy speed in the case of a small size and to prevent the maximum size of the copy speed from being lowered, the intermediate transfer belt 261 has 2 It is preferable to form a one-color toner image during the circumference. In this case, after the Bk toner image is transferred to the intermediate transfer belt 261, the next intermediate transfer belt 261 rotates idly without being developed and transferred in the color printer 2, and in the next one turn. Development is performed with C toner of the next color, and the C toner image is sequentially transferred to the intermediate transfer belt 261. At this time, the rotating operation of the revolver developing device 230 for switching the developing device is performed during the idling rotation.
[0033]
Next, the revolver developing device 230 will be described.
2A is a cross-sectional view showing the internal structure of the revolver developing device 230 in which the developing units 231K, 231C, 231M, and 231Y are integrated, and FIG. 3 is a schematic perspective view showing the appearance of the revolver developing device 230. is there. The developing units 231K, 231C, 231M, and 231Y of the revolver developing device 230 are respectively supported by hollow square cylindrical stay members provided between front and rear end plates 230a and 230b having a substantially disk shape as shown in FIG. ing. Further, the developing devices 231K, 231C, 231M, and 231Y are provided with developing device casing portions 283, 283C, 283M, and 283Y of the same type, respectively. Each of the developing device casing portions 283, 283C, 283M, and 283Y contains a two-component developer composed of a magnetic carrier as a magnetic developer and toner of each color. In the example shown in the drawing, the developing position facing the photosensitive drum 200 is a black developing unit 231K containing black toner and a magnetic carrier, and a yellow developing unit containing yellow toner and a magnetic carrier in the counterclockwise order in the figure. 231Y, a magenta developing unit 231M containing magenta toner and a magnetic carrier, and a cyan developing unit 231C containing cyan toner and a magnetic carrier.
[0034]
Here, since the internal structure of each of the four developing devices is exactly the same, the internal structure will be described below by taking the black developing device 231K at the developing position as an example in FIG. Regarding the structure, the reference numerals of the corresponding members are indicated by the same numerals as those in the black developing unit, with the subscripts Y, M, and C added to distinguish the yellow, magenta, and cyan developing units. The description is omitted.
[0035]
In the black developing device 231K at the developing position in the drawing, an opening toward the photosensitive drum 200 is formed in the developing device casing portion 283, and the developing device casing portion is exposed so that a part is exposed through the opening. A developing roller 284 is provided as a developer carrying member including a developing sleeve in which a magnet is disposed. Further, in the developer casing portion, a doctor blade 285 that regulates the amount of developer carried on the developing roller 284 and conveyed to the portion facing the photosensitive drum 200, and regulated by the doctor blade 285, is regulated in the developer casing. While stirring a part of the held developer, the first agitating screw 286 is conveyed forward and backward along the central axis direction, and is opposite to the first agitating screw 286 along the central axis direction. A second agitation screw 291 is provided to convey the developer while agitating in the direction. A developer concentration sensor (not shown) for detecting the toner concentration of the developer stored in the developer casing portion 283 is installed in the developer casing portion 283 below the second stirring screw 291.
[0036]
FIG. 4 is a vertical cross-sectional view of the black developing unit 231 </ b> K by a plane including the central axis of the first and second stirring screws 286 and 291. In FIG. 4, the first and second stirring screws 286 and 291 rotate in predetermined directions, so that the magnetic developer accommodated in the developing device casing portion 283 is stirred while the developing agent casing portion 283 is in the developing device casing portion 283. It is circulated and conveyed. The magnetic developer conveyed in a circulating manner is carried and conveyed on the sleeve by the rotation of the sleeve of the developing roller 284, and is thinned by the doctor blade 285. Supply the toner.
[0037]
Further, as shown in FIG. 5, the revolver developing device 230 is supported by an image forming device support 21 that can be pulled out from the color copying machine main body by a slide. The image forming device support 21 in the illustrated example also functions as a support for the photoconductor unit 22 including the photoconductor drum 200, and the photoconductor unit 22 is configured as shown by an arrow A in FIG. Mounted on the support 21.
[0038]
The image forming device support 21 includes a front side plate 21a, a rear side plate 21b, and a total of four stay members 21c on the left and right and in the center. Acculide slide rails (not shown) are attached to both side portions of the image forming device support 21 so that the image forming device support 21 can be slid to the front side of the apparatus main body. ing. As shown in FIG. 3, each of the developing devices described above is detachably attached to the support of the revolver developing device 230 supported by the image forming device support 21, and with respect to the support, FIG. It is mounted as shown by arrow B in FIG. Further, as shown in FIG. 5, the image forming device support 21 is pulled out to the front side of the device, and the developing unit of the revolver developing device 230 supported thereby is completely exposed outside the apparatus. In this way, the slide unit can be pulled out more than the entire length of the developing device.
[0039]
On the other hand, as shown in FIG. 6, a developing bias power source is provided at a fixed position on the rear plate 20a of the color printer main body 20 facing the end of the developing roller shaft 284a as a developing bias input portion of the developing device located at the developing position. A developing bias terminal 24 composed of a conductive rod-shaped terminal for applying a developing bias connected to 23 is attached by a bracket 25 so as to be retractable in the sliding direction (thrust direction) of the image forming apparatus support 21 and biasing means. Is pushed and urged to the front side of the color copying machine main body by a conductive spring 25a. The tip of the developing bias terminal 24 is formed in a hemispherical shape, and the shaft end of the developing roller shaft 41a that is in contact with the tip of the developing bias terminal 24 has a circular arc shape with a slightly larger radius of curvature than the hemisphere. A dent is formed. As a result, when the revolver developing device 230 rotates, the shaft end of the developing roller shaft 284a of the developing roller 284 that reaches the portion facing the developing bias terminal 24 and the tip of the developing bias terminal 24 are disengaged. Reduction of contact addition and contact stability during engagement are achieved.
[0040]
The developing bias terminal 24 applies a developing bias only to the developing device at the developing position. When the predetermined developing device is set at the developing position, the developer on the developing roller 284 is set. When the developing bias terminal 24 and the shaft end of the developing roller shaft 284a of the developing roller 284 are securely in contact with each other before the developer drum 200 contacts the photosensitive drum 200, and when the developing device moves away from the developing position, The developing bias terminal 24 and the shaft end portion of the developing roller shaft 284a of the developing roller 284 are configured to reliably contact each other until the developer on the developing roller 284 is completely separated from the photosensitive drum 200.
[0041]
The developing bias power source 23 is configured to apply a developing bias in which an AC voltage is superimposed on a DC voltage to the developing bias terminal 24. The output of the AC voltage from the developing bias power source 23 can be switched ON / OFF independently of the DC voltage at a predetermined timing based on a control signal from a control unit (not shown). Can be changed at a predetermined timing. For example, in the color printer having the above-described configuration, before the revolver motor 295 of the revolver developing device 230 is rotated, that is, in a state where the developer on the developing roller 284 is in contact with the photosensitive drum 200, an AC (AC ) Application of the component is turned off, and then the revolver rotating motor is turned on to rotate the revolver developing device 230, and the developer is separated from the surface of the photosensitive drum 200. Then, after the developer on the developing roller 41C of the next color developing device comes into contact with the surface of the photosensitive drum 200 and the revolver rotating motor is turned off, the application of the alternating current (AC) component of the developing bias is turned on.
[0042]
As described above, when the developer on the developing roller 41 and the photosensitive drum 200 are brought into contact with and separated from each other with the rotation of the revolver developing device 230, the application of the alternating current (AC) component of the developing bias is turned off, so that the alternating current component is applied. Since the action of activating the developer to make it easy to move is suppressed, adhesion of the carrier and toner to the photosensitive drum 200 can be prevented.
A method for rotationally driving the revolver developing device 230 will be described in detail below.
[0043]
Next, the configuration and operation of toner supply to the developing device according to the present invention will be described.
As shown in FIG. 5, the toner container unit 240 is disposed on the front side of the revolver developing device 230 in the center axis direction with the front plate 21 so as to be substantially coaxial with the revolver developing device 230. It is attached. A cross-sectional view of the toner container unit 240 is shown in FIG. The toner container unit 240 is detachably provided with toner cartridges 241K, 241C, 241M, and 241Y as toner containers that store toners of different colors in one-to-one correspondence with the developing devices. In addition, toner hoppers 242K, 242C, 242M, and 242Y that receive toner from the toner cartridges 241K, 241C, 241M, and 241Y are also fixed.
[0044]
As shown in FIGS. 3 and 4, the revolver developing device 230 is rotatably supported by revolver support bearings 293a and 293b attached to the front and rear end plates 230a and 230b. The revolver gear 294 disposed on the rear end plate 230b is driven by the drive gear 296 driven by the revolver motor 295, so that the developing units 231K, 231Y, 231M, and 231C are moved to predetermined positions, respectively. Then stopped. When the revolver developing device 230 rotates, the four developing units, the four toner cartridges, and the four toner hoppers rotate together, and the rotation causes the toner in each toner cartridge to be agitated.
[0045]
FIG. 8 is a cross-sectional view illustrating a state where the toner cartridge 241K is mounted on the toner hopper 242K. The toner cartridge 241K is slidably coupled with the toner hopper 242K and engaged with each other so that the openings 300a and 300b coincide with each other via a seal member that prevents toner leakage. When the revolver developing device 230 rotates in this state, the toner inside the toner cartridge 241K flows into the toner hopper 242K by the synergistic action of the rotation and gravity.
[0046]
Further, as shown in FIG. 7, toner transport paths for transporting toner from the four toner hoppers 242K, 242C, 242M, and 242Y to the corresponding developing units, respectively. Form The toner transport pipes 245K, 245C, 245M, and 245Y communicate with each other. The toner transport pipes 245K, 245C, 245M, and 245Y are provided with toner transport screws 250K, 250C, 250M, and 250Y as toner transport members, and extend into the respective toner hoppers 242. is doing. The toner conveying screws 250K, 250C, 250M, and 250Y are arranged so as to be positioned almost immediately above the extending portion of the first stirring screw 286 in the corresponding developing device when the corresponding developing device is positioned at the developing position. Is set to FIG. 7 shows the developing device 231K, the toner hopper 242K, and the toner conveying screw 250K for one color (black) as a representative.
[0047]
As shown in FIG. 5, the rotating shaft 248a of the toner conveying screw 250 and the toner conveying pipe 245 pass through the holes of the front end plate 230a and the disk-shaped unit face plate 240a of the revolver developing device 230, and the revolver developing device. It protrudes to the 230 side. The pipe opening 300c of the toner transport pipe 245 communicates with the developing device opening 300d of the developing device in a form that collapses the seal member 310 provided in the developing device, and replenishes toner to the developing device (FIG. 10). reference). The rotation shaft 248a has a replenishing gear 284 fixed to the end thereof, and meshes with the toner replenishing driving gear 298a for driving input shown in FIG. When the toner replenishing drive gear 298a is driven through a plurality of gears such as a toner replenishing drive idler gear 298b driven by a replenishing motor attached to the main body rear plate 21b, replenishment provided for each toner conveying screw 250 is provided. Of the gears 284, the replenishment gear 284 corresponding to the developing device at the development position is a replenishment drive gear 298a. When Engage. As a result, the toner conveying screw 250 at the developing position is rotationally driven, and the toner conveyed from the toner hopper 245K is supplied into the developing device 231K. Then, as described above, the magnetic carrier in the developing device casing 283 is agitated and used as a magnetic developer for development.
[0048]
Here, as shown in FIG. 9, the conventional toner conveying screw 250 and the toner conveying pipe 245 are configured to have a clearance between them so that the toner conveying screw 250 rotates smoothly. . This is because if the toner conveying screw 250 and the toner conveying pipe 245 interfere with each other, an abnormal noise is generated during driving or a lock is caused.
[0049]
However, as described above, when there is a clearance between the toner conveying screw 250 and the toner conveying pipe 245, when the fluidity of the toner increases with the rotation of the revolver developing device 230, the toner enters the toner hopper 242 at once. There arises a problem that the toner flows out to the developing device through the clearance. Even when the toner fluidity is not high, if the toner enters the toner hopper 242 at a time, there is a problem that the air in the toner transport pipe 245 is difficult to escape and the toner is pushed out to the developing device by pressure. . Further, the toner in the vicinity of the pipe opening 300 c of the toner transport pipe 245 may flow out to the developing device due to vibration during rotation of the revolver developing device 230.
[0050]
Therefore, in the present embodiment, a configuration that can prevent the outflow of toner to the developing device is employed even when there is a clearance between the toner conveying screw 250 and the toner conveying pipe.
Hereinafter, a configuration for preventing toner from flowing into the developing device 231 will be described with reference to FIGS. 10 and 11. FIG. 11 is an enlarged view of a communication portion between the toner conveying pipe 245 and the developing unit 231 shown in FIG. As shown in each figure, a magnet 400 as a magnetic field generating means is attached in the vicinity of the pipe opening 300c of the toner transport pipe 245. 10 and 11, when the vertical positional relationship between the toner transport pipe 245 and the developing device 231 changes due to the rotation of the revolver developing device 230, the magnetic developer 320 in the developing device 231 flows toward the toner transport pipe 245. . At this time, the magnet 400 generates a magnetic field in the vicinity of the pipe opening 300c of the toner transport pipe 245, and the magnetic developer 320 is attracted and fixed to the magnetic field. After that, even if the revolver developing device 230 further rotates and the developing device 231 moves to the developing position, the magnetic developer 320 does not fall into the developing device 231 due to gravity, but the toner transport pipe 245 by the magnetic field. It is fastened inside.
[0051]
As described above, when the magnetic developer 320 is retained in the toner transport pipe 245, the communication portion between the toner transport pipe 245 and the developing device 231 is blocked, and the revolver developing device 230 as described above. The toner can be prevented from flowing out to the developing unit 231 due to the rotation of.
[0052]
The magnetic developer 320 fixed in the toner conveyance pipe 245 is scraped off by the screw 250 when the toner conveyance screw 250 is rotated by the toner replenishment signal of the copying machine main body, and is moved into the developing device 231 by gravity. Fall. Therefore, at the time of toner replenishment, the toner transport pipe 245 and the developing device 231 communicate with each other again, and the toner can be replenished to the developing device 231.
[0053]
As described above, according to the embodiment, the magnet 400 is transported with toner. pipe As a result, the communicating portion between the toner transport pipe 245 and the developing device 231 is always closed by the magnetic developer 320 except when the toner is replenished. Therefore, the toner transport pipe 245 and the toner transport screw 250 of Even when there is a clearance between them, it is possible to prevent toner from flowing out to the developing device 231 other than during toner replenishment. When the toner is replenished, the communicating portion is opened by driving the toner conveying screw 250. Therefore, as a method for opening and closing the communication portion, since it has a simple configuration using the originally provided conveying screw 250 and only having the toner magnet 400 attached thereto, a complicated shutter mechanism and the shutter driving portion are provided. This is advantageous in terms of both cost and space as compared with the configuration in which the above is provided.
[0054]
Further, by providing the magnet 400, it is possible to prevent the magnetic developer 320 from flowing back into the toner transport pipe 245 and the toner cartridge 241 at the same time.
[0055]
Furthermore, by preventing the toner from flowing out, it is possible to prevent the toner density in the developing device from becoming high, and thus it is possible to prevent the occurrence of excessive image density and scumming.
[0056]
In this embodiment, the image forming apparatus that develops using a two-component magnetic developer composed of toner and a magnetic carrier has been described. However, the present invention can also be applied to an image forming apparatus that uses a one-component magnetic developer.
[0057]
【The invention's effect】
[0058]
【The invention's effect】
According to the first and second aspects of the present invention, the toner transport member and the toner transport pipe When of while of clearance Through It is possible to prevent the toner from flowing out to the developing device side. In addition, it is possible to prevent excessive image density and background contamination. Furthermore, the current magnetic image agent in the developing unit is pipe In addition, backflow into the toner container can be prevented at the same time.
[0059]
In particular, according to the second aspect of the invention, there is an excellent effect that the toner outflow to each developing device can be surely prevented with a simple configuration.
[0060]
According to the invention of claim 3, the toner is automatically conveyed when the toner is replenished. pipe Can be opened. Therefore, toner transport pipe As for the method of opening and closing the communication portion of each developing device, since it is a simple configuration that uses the drive of the toner conveying member originally provided in the developing device and only includes the magnetic field generating means, it is complicated. Compared to a configuration in which a simple shutter mechanism and the shutter drive unit are provided, it is advantageous in terms of cost and space.
[Brief description of the drawings]
FIG. 1 is a front view showing a schematic configuration of a color copying machine according to an embodiment of the present invention.
FIG. 2A is a sectional view of a revolver developing device of the color copying machine.
FIG. 4B is a front view of the toner storage unit of the revolver developing device of the color copying machine.
FIG. 3 is a schematic perspective view of the revolver developing device.
FIG. 4 is a schematic plan view of a toner conveying unit and a driving unit of the revolver developing device.
FIG. 5 is a schematic perspective view showing a state in which an image forming apparatus support of the color copying machine is pulled out from a color printer main body.
FIG. 6 is a cross-sectional view of a main part showing a conventional bias applying mechanism of the developing unit of the revolver developing device.
FIG. 7 is a longitudinal sectional view showing a toner container unit portion and a toner transport portion of the revolver developing device.
FIG. 8 is a cross-sectional view showing an internal configuration of a toner container unit of the revolver developing device.
FIG. 9 is an explanatory diagram for explaining a conventional defect.
FIG. 10 is a side cross-sectional view showing a state where the toner transport pipe and the developing device according to the present embodiment are communicated with each other.
11 is an enlarged view of a communication portion of the toner conveying pipe and the developing device shown in FIG.
[Explanation of symbols]
1 Color scanner
2 Color printer
3 Feeding bank
200 Photosensitive drum
220 Writing optical unit
230 Revolver developing device
231K, 231C, 231M, 231Y Developer
240 Toner container unit
241K, 241C, 241M, 241Y Toner cartridge
242K, 242C, 242M, 242Y Toner hopper
245K, 245C, 245M, 245Y Toner transport pipe
250K, 250C, 250M, 250Y Toner conveying screw
260 Intermediate transfer device
261 Intermediate transfer belt
270 Fixing device
284 Development roller
286 First stirring screw
291 Second stirring screw
294 Revolver gear
295 Revolver motor
296 Drive gear
300a Toner cartridge opening
300b Toner hopper opening
300c Toner transport pipe opening
300d Developer opening
310 Seal member
320 Developer
400 magnet

Claims (3)

A plurality of developing units, provided rotatably in proximity to the latent image bearing member, and the rotating developing equipment for performing development using a magnetic developer comprising a toner and a magnetic carrier,
A plurality of toner containers that are detachably attached to the developing device and rotate integrally with the developing device ;
From respective toner container in and the belt donor conveying pipe to connect the respective developing device, a toner conveying member provided inside the toner conveying pipe so clearance is present between the toner conveying pipe an image forming apparatus having a toner conveying hand stage comprising,
The rotary developing device has a configuration in which the vertical positional relationship between the toner transport pipes and the developing devices is changed by the rotation of the rotary developing device.
Each of the toner transport pipes has an opening with respect to the developer of each of the toner transport pipes when an inlet of the toner transport pipe communicated with the toner container is directed upward by rotation of the rotary developing device. Configured to face downward,
An image forming apparatus comprising a magnetic field generating means for fixing the magnetic developer in each of the toner conveying pipes . The image forming apparatus according to claim 1.
An image forming apparatus, wherein the magnetic field generating means is composed of a magnet. The image forming apparatus according to claim 1.
An image forming apparatus using the toner conveying unit capable of conveying a magnetic developer restrained by the magnetic field generating unit by driving the toner conveying member.

Images