JP5471541B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device using a developer composed of toner and a carrier, a process cartridge using the developing device, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having at least two functions thereof. is there.

  In the image forming apparatus of the above type, in recent years, it has become the mainstream to employ a two-component developing type developing device composed of toner and carrier. Many developing devices of this type are configured by arranging two screws arranged horizontally as described in FIG. Of these two screws, the first screw located closer to the photosensitive drum supplies the developer to the developer carrying member (developing sleeve) and collects the developer after passing through the developing section. Used for. The second conveying screw is used for mixing and stirring the developer collected from the developing sleeve and the newly supplied developer.

  On the other hand, in recent years, in an image forming apparatus using an electrophotographic system such as a copying machine or a printer, there has been an increasing demand for downsizing the apparatus main body in order to achieve space saving. However, since a plurality of developing devices are used, the size of the developing device is larger than that of a monochrome device. However, it is desired to reduce the size as much as possible.

  In order to meet this demand, Patent Document 1 proposes a developing device in which two conveying screws, which are circulation means for agitating and conveying the developer and circulating in the developing container, are arranged in the vertical direction. This developing device includes a developing container containing a developer, and has a developing sleeve as a developer carrying member at an opening facing the photosensitive drum of the developing container. A developing transport chamber and a stirring transport chamber partitioned by a partition are formed vertically on the side opposite to the opening in the developing container. The developing transport chamber and the stirring transport chamber are circulating means. First and second conveying screws are respectively installed. The first conveying screw conveys the developer in the developing and conveying chamber, and the second conveying screw is supplied from the toner supply port into the agitating and conveying chamber and the toner supplied to the upstream side of the second conveying screw and the agitating and conveying chamber. The existing developer is conveyed while stirring to make the toner density of the developer uniform.

  In the vertical stirring type developing device as described above, since the developing transport chamber and the stirring transport chamber are arranged obliquely in the vertical direction in the vertical direction, the space occupied in the horizontal direction can be small. In a color image forming apparatus such as a tandem system in which the apparatuses are mounted in parallel in the horizontal direction, advantages such as contributing to downsizing of the apparatus are obtained.

  The flow of the developer in the vertical stirring type developing device will be described. Supply toner accompanying toner consumption is supplied into the device from a toner supply port provided in a part of the stirring conveyance chamber. The replenished toner is agitated and mixed by the second conveying screw together with the existing developer in the agitating and conveying chamber, and the toner concentration of the developer is made uniform. The developer having a uniform toner concentration is dropped and moved from the feeding portion of the agitating and conveying chamber downstream in the developer conveying direction to the developing and conveying chamber, and is fixedly arranged inside while being conveyed by the first conveying screw. It is pumped over the entire length of the developing sleeve by the magnetic pole of the magnetic roll. The amount of the developer that has been pumped up is regulated by the developer regulating member, and the developer that finally adheres to the developing sleeve and does not reach the development area is agitated and conveyed from the delivery section downstream in the developer conveying direction of the developer conveying chamber. Returned to the room. Further, the developer that has adhered to the developing sleeve and has reached the developing area but has not moved to the image carrier is separated from the developing sleeve by the agent separating magnetic pole and returned to the upper agitating and conveying chamber.

  By the way, it is necessary to install toner density detecting means for detecting the toner density in the developer in the developing device in which the developer is circulated, and the detection accuracy of the toner density detecting means is inappropriate. In addition, there is a problem of causing problems such as background contamination and toner scattering due to excessive toner concentration.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus in which the above-described conventional problems can be solved and the toner density detecting means can detect an appropriate toner density.

In order to solve the above-described problems, the present invention provides a developer carrier that is disposed opposite to an image carrier that carries an electrostatic latent image and contains a magnetic field generating unit, a toner carrier located below the developer carrier, and a toner And a developer transport chamber having a first transport member that transports the developer comprising the carrier along the direction of the rotation axis while supplying the developer to the developer carrier, and is arranged to face the lower side of the developer carrier. And a developer regulating member that regulates the amount of developer carried on the developer carrying member, partitioned by the development conveyance chamber and a partition, and disposed above the development conveyance chamber, and The developer separated from the developer carrying member at a position past the image carrying member is collected and conveyed in the direction opposite to the first conveying member along the rotation axis direction of the developer carrying member. A stirring and conveying chamber having two conveying members. A feeding section for feeding the developer in the agitation transport chamber to the developer transport chamber is provided on the downstream side in the developer transport direction of the transport chamber and outside the developer carrier, and on the downstream side of the developer transport chamber in the developer transport direction. In the developing device in which a delivery unit for delivering the developer in the development transport chamber to the agitation transport chamber is provided outside the developer carrier, the first transport member is moved from the feeding section of the development transport chamber to the The toner density detecting means is formed so as to reach the delivery section, and a toner density detecting means for detecting the toner density in the developer is installed on the wall surface of the developing conveyance chamber facing the feeding section. A developing device is proposed.

  In the present invention, the rotation direction of the first conveyance member is the same as the rotation direction of the developer carrier, and the installation position of the toner concentration detection means is lower than the lowest position in the gravity direction on the wall surface of the development conveyance chamber. It is also advantageous if the position is shifted to the downstream side in the rotational direction of the first conveying member.

  Further, according to the present invention, the developing transport chamber is located obliquely below the agitation transport chamber, and the first transport member and the second transport member are disposed on the upper inclined wall surface of the feed port through which the developer passes. It is advantageous if a convex shape with a height reaching a straight line connecting the axes is formed.

  In order to solve the above-described problem, the present invention provides a process cartridge that is detachably installed on an apparatus main body of an image forming apparatus, and the developing device according to any one of claims 1 to 3. A process cartridge is proposed in which the image carrier is integrated.

  In order to solve the above problems, the present invention proposes an image forming apparatus comprising the developing device according to any one of claims 1 to 3 and the image carrier.

According to the present invention, the first conveying member is formed to have a length that extends from the feeding portion of the developing conveyance chamber to the delivery portion, and the wall of the developing conveyance chamber that faces the feeding portion contains a developer in the developer. Since the toner density detecting means for detecting the toner density is installed, the toner density detecting means can detect the toner density at a stable position where the bulk fluctuation of the developer is small .

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows an image creation part. It is sectional drawing which shows a developing device. It is explanatory drawing which shows the flow of the developer in a developing device. FIG. 4 is a cross-sectional explanatory view of a feeding portion of the developing device showing an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a vertical cross-sectional view showing an example of an electrophotographic image forming apparatus. The image forming apparatus shown here includes first to fourth drum-shaped photoconductors arranged in an apparatus main body 1. And image transfer bodies 2Y, 2M, 2C, and 2K, and an intermediate transfer body configured as an endless intermediate transfer belt 3 that is also disposed in the apparatus main body 1. The intermediate transfer belt 3 is wound around the support rollers 4, 5, 6 and 7 and rotated in the direction of arrow A.

  The intermediate transfer belt 3 is positioned above the image carriers 2Y to 2K, and the lower running side of the intermediate transfer belt 3 is in contact with the peripheral surface of the image carriers 2Y to 2K. It constitutes an example of a transfer material on which toner images of different colors respectively formed on the surface of the carrier can be transferred.

  The configuration in which a toner image is formed on each of the first to fourth image carriers 2Y, 2M, 2C, and 2K and the toner image is transferred to the intermediate transfer belt 3 is substantially different only in the color of the toner image. Since all of them are the same, only the configuration for forming a toner image on the first image carrier 2Y and transferring the toner image to the intermediate transfer belt 3 will be described. The subscripts Y, M, C, and K indicate yellow, magenta, cyan, and black colors, and these subscripts are omitted as necessary.

  Although FIG. 2 omits the suffix “Y”, the image carrier 2 corresponding to yellow and each image forming device for forming a toner image on the surface of the image carrier 2 are enlarged. FIG. The image carrier 2 is rotationally driven in the clockwise direction in FIG. 2, and at this time, the image carrier 2 is charged to a predetermined polarity by a charging device including a charging roller 8 to which a charging voltage is applied. The charged image carrier 2 is irradiated with a light-modulated laser beam L emitted from an optical writing device (not shown), whereby an electrostatic latent image is formed on the image carrier 2. The electrostatic latent image is visualized as a yellow toner image by the developing device 20 described in detail later.

  A primary transfer roller 9 is disposed on the side opposite to the image carrier 2 with the intermediate transfer belt 3 interposed therebetween, and a transfer voltage is applied to the primary transfer roller 9 so that the toner image on the image carrier 2 is changed to an arrow. Primary transfer is performed on the intermediate transfer belt 3 rotating in the A direction. The transfer residual toner adhering to the image carrier 2 after the toner image transfer is removed by the cleaning device 10. Further, the electric charge remaining on the image carrier 2 is removed by a static eliminator (not shown) to prepare for the next image formation.

  In exactly the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are respectively formed on the second to fourth image carriers 2M, 2C, and 2K shown in FIG. Are sequentially superposed on the intermediate transfer belt 3 to which the yellow toner image has been transferred, and are primarily transferred to form a composite toner image on the intermediate transfer belt 3. The transfer residual toner on each of the image carriers 2M, 2C, 2K after the toner image transfer is removed by the cleaning device 10 is not different from the case of the first image carrier 2Y.

  On the other hand, as shown in FIG. 1, a paper feed cassette 11 containing a recording medium P made of, for example, transfer paper and a paper feed device 13 having a paper feed roller 12 are arranged at the lower part in the apparatus main body 1. As the paper roller 12 rotates, the uppermost recording medium P is sent in the direction of arrow B. The fed recording medium is fed by a registration roller pair 13 between a portion of the intermediate transfer belt 3 wound around the support roller 6 at a predetermined timing and a secondary transfer roller 14 disposed on the intermediate transfer belt 3. The At this time, a predetermined transfer voltage is applied to the secondary transfer roller 14, whereby the composite toner image on the intermediate transfer belt 3 is secondarily transferred to the recording medium P.

  The recording medium P on which the composite toner image has been secondarily transferred is further conveyed upward and passes through the fixing device 15. At this time, the toner image on the recording medium P is fixed by the action of heat and pressure. The recording medium P that has passed through the fixing device 15 is discharged by a paper discharge roller pair 16 to a paper discharge unit 17 at the top of the apparatus main body 1. Further, the transfer residual toner adhering to the intermediate transfer belt 3 after the toner image transfer is removed by the cleaning device 18. Note that the image forming apparatus shown in FIG. 2 is configured as a process cartridge and can also be mounted on a device.

  As shown in FIG. 3, the developing device 20 is filled with a fixed amount (225 g) of a developer in which toner (5.8 μm) mainly composed of a polyester resin and a carrier (35 μm) as magnetic fine particles are uniformly mixed to 7 wt%. The developing case 21 and a developing roller 22 as a developer carrying member that is rotatably supported by the developing case 21 and is disposed in close proximity to the image carrier 2 through an opening formed in the developing case 21. The developing roller 22 includes a developing sleeve 23 that rotates counterclockwise in FIG. 2 and a magnetic roll 24 that is fixed in the sleeve and has five magnetic poles P1 to P5. Yes. The toner is preferably a polymerized toner having a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180.

  FIG. 3 shows the positions where the magnetic forces of the five magnetic poles P1 to P5 are peaked. A doctor blade 25 as a developer restricting member supported by the developing case 21 is disposed close to the lower side of the developing roller 22, and the amount of developer on the developing roller 22 is regulated by the doctor blade 25. The developing device 20 is provided with a developing and conveying chamber 26 obliquely below the developing roller 22 and a stirring and conveying chamber 27 that is substantially horizontal and above the developing and conveying chamber 26. A first transport screw 28 as a developer transport member is disposed in the development transport chamber 26, and a second transport screw 29 as a developer transport member is disposed in the agitation transport chamber 27. The first and second conveying screws 28 and 29 have their axes parallel to the axis of the developing roller 22, and the first conveying screw 28 is adjacent to the entire length of the developing roller 22 in the axial direction. The length of the conveying screw 28 in the axial direction is set to a length that reaches from a later-described feeding portion to a delivery portion. Similarly, the second conveying screw 29 adjacent to the entire length of the developing roller 22 in the axial direction may be the same length as the first conveying screw 28. However, in the present embodiment, the length of the second conveying screw 29 is the toner supply port. The length 30 is set to be longer than the first conveying screw 28 by the amount provided outside. The first and second conveying screws 28 and 29 are rotated at 600 to 800 rpm to convey the developer while stirring, thereby uniformly mixing the toner and the carrier and applying the charge. Further, the rotation direction of the first conveyance screw 28 is the same as the rotation direction of the developing sleeve 23 and is the counterclockwise direction in FIG. 3, whereas the second conveyance screw 29 is rotated in the opposite clockwise direction.

FIG. 4 is a development explanatory view showing the flow of the developer in the developing device according to the present invention.
In FIG. 4, a toner concentration sensor 40 (shown in FIG. 5) is provided in the developing device 20, and when the sensor detects an insufficient toner concentration, the developer conveyance direction upstream side of the stirring conveyance chamber 27 (the left end in the figure). The toner according to the amount of toner consumption is replenished from a toner replenishing port 30 serving as a toner replenishing section provided in. The agitating / conveying chamber 27 is provided with a transfer portion 31 through which the developer conveying chamber 26 and the agitating / conveying chamber 27 communicate with each other after the toner supply port 30, and the transfer blade 31 scrapes the doctor blade 25 within the developing and conveying chamber 26. Dropped developer or the like is sent. The developer that has been carried on the developing roller 22 and reached the developing area but has not been developed is returned to the agitating / conveying chamber 27 that has passed the transfer section 31 via a collection guide 32 formed in the developing case 21. Then, the return developer covers almost the entire length of the developing roller 22, and these developers are conveyed to the right in the drawing by the rotation of the second conveying screw 29.

  By being transported while being stirred by the second transport screw 29, the developer in the stirring transport chamber 27 in which the toner density becomes uniform is fed into the developing transport chamber 26 from a feeding portion 33 provided on the downstream side in the transport direction. . Since the agitating / conveying chamber 27 is located above the developing / conveying chamber 26 in the feeding portion 33, the developer is fed by its own weight drop. Note that the positions of the transfer portion 31 and the feeding portion 33 are provided at positions beyond the left end and the right end of the developing roller 22, respectively.

  As described above, the developing device 20 employs a system in which the developer is supplied to the developing roller 22 while being agitated and conveyed by the first conveying screw 28 and is collected by the second conveying screw 29. As described above, the developer accumulation state in the developing and conveying chamber 26 and the agitating and conveying chamber 27 becomes oblique (the amount of developer in the supply screw decreases in the downstream direction). When the developer conveyance amount capability obtained from the diameter, pitch and rotation speed of the first conveyance screw 28 is Wm, and the developer conveyance amount on the developing roller 22 is Ws, the developer is obtained when the relationship between the two becomes Wm> Ws. Are uniformly conveyed onto the developing roller 22. If this condition is not satisfied, the developer is insufficient on the downstream side of the first conveying screw 28, and the developer cannot be supplied to the developing roller 22.

  In this way, the developing device 20 to which the developer is transported replenishes new toner from the toner replenishing port 30 when detecting the toner concentration in the developer and detecting that the concentration has decreased due to toner consumption. The toner density sensor 40 used for this purpose is optimally installed at a location where the toner density is uniform and the developer is stably concentrated in the detection area.

Therefore, in the present invention, the toner concentration sensor 40 is disposed opposite to the feeding portion 33 that feeds the developer in the stirring and conveying chamber 27 into the developing and conveying chamber 26. As shown in FIG. 4, the feeding portion 33 is provided at the most downstream portion in the developer conveying direction of the agitating / conveying chamber 27, so that the developer conveyed in the agitating / conveying chamber 27 is sufficiently agitated. Since the density is stable and the transfer is switched, the developer is hardly interrupted, but the toner density sensor 40 is provided with favorable conditions. In this case, the feeding portion as the installation location of the toner density sensor 40 in the developing transport chamber 26 is from the right end of the developing transport chamber 26 to the right end of the developing roller 22 in FIG. Accuracy is obtained.

  In this embodiment, as shown in FIG. 5, the toner concentration sensor 40 is installed at a position shifted from the lowest position in the direction of gravity on the wall surface of the development conveyance chamber 26 to the downstream side in the rotation direction of the first conveyance screw 28. ing. This installation position is a position where the developer is most likely to accumulate when the first conveyance screw 28 rotates in the clockwise direction shown in FIG. 5 in the wall surface of the development conveyance chamber 26 opposite to the second conveyance screw 29. . Therefore, this position is a position at which the bulk of the developer that has been stirred and conveyed by the second conveying screw 29 and has a uniform density is unlikely to fluctuate, and the toner density sensor 40 installed here continues to have a highly accurate detection result. Obtained. Therefore, it is possible to prevent the occurrence of problems such as ground contamination and toner scattering due to the detection error of the sensor.

  Further, as shown in FIG. 5, the feed opening 34 of the feed section 33 is formed obliquely downward, and at this time reaches a straight line connecting the axis of the second transport screw 29 and the first transport screw 28 to the upper side wall surface. An approximately convex shape 35 is formed. This convex shape 35 can narrow the developer opening in a portion where the toner concentration detection sensor 40 is installed by narrowing the opening to such an extent that the delivery opening 34 is made too narrow and does not hinder the delivery of the developer. It is possible to reliably suppress erroneous detection of the toner concentration due to the bulk fluctuation of the agent.

  As described above, according to the present invention, it is possible to provide a stable image forming apparatus that does not cause scumming or toner scattering due to excessive toner concentration by appropriately detecting the toner concentration in the developing device. Is.

1 image forming apparatus body (apparatus body),
2 image carrier 20 developing device 22 developing roller (developer carrier),
25 Doctor blade (developer regulating member)
26 Developing transport chamber 27 Stirring transport chamber 28 First transport screw (first transport member)
29 Second conveying screw (second conveying member)
31 delivery section,
33 Feeding portion 35 Convex shape 40 Toner density sensor

Japanese Patent Laid-Open No. 11-174810 JP 2008-26408 A

Claims (5)

A developer carrying body disposed opposite to an image carrying body carrying an electrostatic latent image and containing magnetic field generating means;
A developing conveyance chamber provided with a first conveying member that is positioned below the developer carrying member and conveys the developer composed of toner and carrier along the rotational axis while supplying the developer carrying member to the developer carrying member;
A developer regulating member disposed to face the lower side of the developer carrying member and regulating the amount of developer carried on the developer carrying member;
The developer is separated from the developer carrying chamber and separated from the developer carrying body at a position past the image carrying body by being partitioned by the partition and separated from the development carrying chamber. And a stirring and conveying chamber provided with a second conveying member that conveys the developer carrying member in a direction opposite to the first conveying member along the rotation axis direction of the developer carrier,
A feeding section for feeding the developer in the stirring and conveying chamber into the developing and conveying chamber on the outside of the developer carrier on the downstream side in the developer conveying direction of the stirring and conveying chamber;
In the developing device provided with a delivery section for delivering the developer in the developer transport chamber to the agitating transport chamber outside the developer carrier on the downstream side in the developer transport direction of the developer transport chamber,
The first conveying member is formed to have a length that extends from the feeding portion to the delivery portion of the developing conveyance chamber, and the toner concentration in the developer is reduced on the wall surface of the developing conveyance chamber facing the feeding portion. A developing device comprising toner density detecting means for detecting.   2. The developing device according to claim 1, wherein the rotation direction of the first conveying member is the same as the rotation direction of the developer carrying member, and the installation position of the toner concentration detection unit is a gravitational direction on the wall surface of the developing conveyance chamber. 2. A developing device according to claim 1, wherein the developing device is located at a position shifted from the lowest position to the downstream side in the rotation direction of the first conveying member.   3. The developing device according to claim 1, wherein the developing transport chamber is located obliquely below the agitating transport chamber, and the first transport member and the upper inclined wall surface are connected to a feed port through which the developer of the feed section passes. A developing device having a height that reaches a straight line connecting the axes of the second conveying members. A process cartridge that is detachably installed on the main body of the image forming apparatus,
4. A process cartridge, wherein the developing device according to claim 1 and the image carrier are integrated.   An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

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