JP5033534B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like, and more particularly to a developing device using a two-component developer composed of toner and a magnetic carrier and an image forming apparatus using the same.

Conventionally, as a developing device using a two-component developer composed of a toner and a magnetic carrier, the one shown in FIG. The developing device 4 shown in FIG. 6 is provided with a conveyance path for supplying the developer to the developing roller, which is a developer carrying member, and a conveyance path for agitating the developer, and the developer is reversed in the two conveyance paths. The developer is circulated by being conveyed in the direction.
In the developing device shown in FIG. 6, a conveyance path for supplying the developer to the developing roller and a conveyance path for collecting the developer supplied to the developing roller and passing through the development area are common. Therefore, there is a problem that the toner concentration of the developer supplied to the developing roller decreases toward the downstream side in the conveying direction of the conveying path supplied to the developing roller. When the toner density supplied to the developing roller decreases, the image density during development also decreases.

  Such a problem is solved by providing a developer auger for supplying the developer to the developing roller and a developer auger for collecting the developed developer in different developer transport paths as in the developing device described in Patent Document 1. can do. The configuration of the developing device described in Patent Document 1 will be described below.

FIG. 7 is a schematic configuration diagram showing a developing device described in Patent Document 1.
In the developing device 4 shown in FIG. 7, a developer supply conveyance path 9 that supplies the developer to the developing roller 5 and a developer collection conveyance path 7 that collects the developer that has passed through the development area are provided separately. Further, the developer transported to the most downstream side of the developer supply transport path 9 and the recovered developer transported to the most downstream side of the developer recovery transport path 7 are agitated and reverse to the developer supply transport path 9. A developer stirring / conveying path 10 for conveying the developer in the direction is provided.
In such a developing device 4, the developed developer is sent to the developer recovery transport path 7, so that it does not enter the developer supply transport path 9. Thus, the toner concentration of the developer supplied to the developing roller 5 is constant without changing the toner concentration of the developer in the developer supply conveyance path 9.
Furthermore, the recovered developer is not immediately supplied to the developer supply / conveyance path 9, but is stirred in the developer stirring / conveyance path 10 and then the developer is supplied to the developer supply / conveyance path 9, so that the developer is sufficiently stirred. The developer in the state can be supplied to the developer supply conveyance path 9. As a result, it is possible to prevent non-uniform image density and lower image density during development, which are problems of the developing device 4 described with reference to FIG.

JP-A-11-167260 (FIG. 1)

  In the developing device 4 described in Patent Document 1, the developer recovered from the developing roller 5 by the rotation of the recovery screw 6 that is a developer recovery transport member disposed in the developer recovery transport path 7 is on the front side in the figure. The developer is conveyed from the upstream side of the developer collection conveyance path toward the downstream side in the drawing. For this reason, the amount of developer on the downstream side is larger than that on the upstream side of the developer recovery conveyance path, and the ratio of the gaps in the developer recovery conveyance path on the downstream side is smaller than that on the upstream side. As a result, the internal pressure in the developer recovery transport path increases from the upstream side to the downstream side of the developer recovery transport path, and the internal pressure in the developer recovery transport path becomes non-uniform in the axial direction. Usually, the internal pressure in the developer recovery conveyance path is increased by the pressure of the air flow generated on the surface of the developing roller by the rotation of the developing roller 5 and blown into the gap 406 between the developing roller 5 and the case on the downstream side of the developing region. In addition, the developer in the developer recovery conveyance is suppressed from blowing out from the gap 406. However, as described above, when the internal pressure in the developer recovery conveyance path becomes non-uniform in the axial direction, the airflow blown into the gap 406 between the developing roller 5 and the case flows to the upstream side of the developer recovery conveyance path where the internal pressure is low. End up. As a result, the pressure due to the blown airflow downstream of the developer recovery conveyance path in the gap 406 decreases, and the internal pressure downstream of the developer recovery conveyance path becomes larger. As a result, there is a problem in that a blowout air current blown out from the gap 406 to the latent image carrier side is generated on the downstream side of the developer collection conveyance path, and toner scattering occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of suppressing non-uniformity of internal pressure in the developer recovery conveyance path and suppressing toner scattering. An image forming apparatus is provided.

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a two-component developer comprising a magnetic carrier and a toner is carried on the surface and rotated, and the latent image carrier is located at a position facing the latent image carrier. A developer carrying member that supplies toner to the latent image on the surface of the developer for development, and a developer supply that conveys the developer along the axial direction of the developer carrying member and supplies the developer to the developer carrying member The developer recovered from the developer carrying body after passing through the developer supply carrying path provided with the carrying member and the portion facing the latent image carrying body along the axial direction of the developer carrying body. And a developer recovery transport path including a developer recovery transport member that transports in the same direction as the developer supply transport member, and transports to the downstream side in the transport direction of the developer supply transport path without being used for development. Excess developer and the transport direction of the developer recovery transport path recovered from the developer carrier Receiving the supply of the collected developer conveyed to the downstream side, along the axial direction of the developer carrier, and while stirring the excess developer and the collected developer, Comprises a developer agitating and conveying member that conveys the developer in the reverse direction, and has a developer agitating and conveying path for supplying the developer to the developer supply and conveying path, and the developer agitating and conveying path and the developer collecting and conveying path A developing device in which the developer supply transport path is positioned above the other two developer transport paths, and toner is supplied to the developer transport path. In this embodiment, the cross-sectional area of the developer recovery transport path on the downstream side of the developer recovery transport path is larger than that on the upstream side of the developer recovery transport path.
According to a second aspect of the present invention, in the developing device of the first aspect, the developer agitation transport path and the developer supply transport path are partitioned by a partition member, and the stirring developer opening provided in the partition member The developer is delivered from the developer stirring and conveying path to the developer supply and conveying path through a section.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the three developer conveyance paths including the developer recovery conveyance path, the developer supply conveyance path, and the developer agitation conveyance path are partitioned. It is characterized by being partitioned by a member.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the developer agitating and conveying member is not used for development and is conveyed to the most downstream side in the conveying direction of the developer supply conveying path. The supplied excess developer and the recovered developer recovered from the developer carrier and transported to the most downstream side in the transport direction of the developer recovery transport path are supplied along the axial direction of the developer carrier. In addition, the excess developer and the recovered developer are conveyed in the opposite direction to the developer supply and conveyance member while stirring.
According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, a space in the developer recovery transport path is filled from the upstream of the developer recovery transport path to at least a central portion of the developer recovery transport path. The embedding member is provided.
According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the developer conveyance speed on the downstream side of the developer collection conveyance path is higher than that on the upstream side of the developer collection conveyance path. The developer collecting and conveying member is configured .
Also, the invention of claim 7, in any one of the developing apparatus according to claim 1 to 6, the developer supply conveyance path, which is characterized in that provided in the obliquely upward with respect to the developer agitation path It is.
The invention according to claim 8 provides at least a latent image carrier, charging means for charging the surface of the latent image carrier, and formation of a latent image for forming an electrostatic latent image on the latent image carrier. means, in an image forming apparatus having a developing means for toners Zoka by developing the electrostatic latent image, as the developing means, characterized by using one of the developing apparatus according to claim 1 to 7 Is.

According to the onset bright, by increasing the cross-sectional area of the developer collection conveyance path of the developer collection conveyance path downstream than the developer collection conveyance path upstream side, the downstream side as compared with the collection conveyance path upstream side In a state where the amount of the developer is large, it is possible to suppress the ratio of the gaps in the downstream developer collection and conveyance path from becoming smaller than the ratio of the gaps in the downstream developer collection and conveyance path. As a result, it is possible to prevent the internal pressure in the recovery conveyance path from becoming non-uniform in the axial direction, and the blowing generated in the gap between the developer carrier and the case downstream of the development region due to the rotation of the developer carrier. It is possible to suppress the flow of air to the upstream side of the developer recovery conveyance path. As a result, the pressure drop of the blown airflow in the gap between the developer carrier and the case on the downstream side of the development region can be suppressed, and the pressure of the blown airflow on the downstream side of the developer recovery conveyance path is reduced to the downstream side of the developer collection conveyance path It can be maintained higher than the internal pressure. Thereby, it is possible to suppress the generation of a blowing air current that blows out from the gap toward the latent image carrier, thereby suppressing toner scattering.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color laser copying machine (hereinafter simply referred to as “copying machine”) in which a plurality of photoconductors are arranged in parallel will be described.
FIG. 1 is a schematic configuration diagram of a copying machine according to the present embodiment. The copier includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is placed, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 fixed on the scanner 300 is also provided.

  The printer unit 100 forms an image including four sets of process cartridges 18Y, 18M, 18C, and 18K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). A unit 20 is provided. Y, M, C, and K attached to the numbers of the respective symbols indicate members for yellow, cyan, magenta, and black (the same applies hereinafter). In addition to the process cartridges 18Y, 18M, 18C, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a resist roller pair 49, a belt fixing type fixing device 25, and the like are disposed. .

  The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of a photoreceptor to be described later with laser light based on image data.

  The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photosensitive member 1, a charger, a developing device 4, a drum cleaning device, a static eliminator, and the like.

Hereinafter, the yellow process cartridge 18 will be described.
The surface of the photoreceptor 1Y is uniformly charged by a charger as charging means. The surface of the photoreceptor 1 </ b> Y that has been subjected to charging processing is irradiated with laser light that has been modulated and deflected by the optical writing unit 21. Then, the potential of the irradiation part (exposure part) is attenuated. By this attenuation, an electrostatic latent image for Y is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed by the developing device 4Y as developing means to become a Y toner image.
The Y toner image formed on the Y photoconductor 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photoreceptor 1Y after the primary transfer is cleaned of the transfer residual toner by a drum cleaning device.
In the Y process cartridge 18Y, the photoconductor 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges (18M, C, K).

Next, the intermediate transfer unit will be described.
The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 90, and the like. Further, it also includes a tension roller 14, a driving roller 15, a secondary transfer backup roller 16, four primary transfer bias rollers 62Y, M, C, and K.
The intermediate transfer belt 110 is tensioned by a plurality of rollers including the tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).
The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photoreceptors 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photosensitive member and the primary transfer bias roller due to the influence of the primary transfer bias.
The above-described Y toner image formed on the Y photoconductor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, K toner images formed on the M, C, K photoconductors 1M, C, K are sequentially superposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt 110.
The four-color toner image superimposed and transferred onto the intermediate transfer belt 110 is secondarily transferred onto a transfer sheet (not shown) as a recording sheet at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 90 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

Next, the secondary transfer device 22 will be described.
Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers 23. One of the two stretching rollers 23 arranged on the right side in the drawing sandwiches the intermediate transfer belt 110 and the paper transport belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is out. By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 110 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. A secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown). By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt 110 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip. A next transfer electric field is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt 110 by a registration roller pair 49 to be described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

  In the paper feeding device 200 provided at the lower part of the copying machine main body, a plurality of paper feeding cassettes 44 in which a plurality of transfer sheets can be stacked and accommodated in a bundle of sheets are arranged so as to overlap in the vertical direction. Has been. Each paper feed cassette 44 presses the paper feed roller 42 against the uppermost transfer paper in the paper bundle. Then, by rotating the paper feed roller 42, the uppermost transfer paper is sent out toward the paper feed path 46.

  The paper feed path 46 that receives the transfer paper fed from the paper feed cassette 44 has a plurality of conveying roller pairs 47 and a registration roller pair 49 provided near the end in the path. Then, the transfer paper is conveyed toward the registration roller pair 49. The transfer sheet conveyed toward the registration roller pair 49 is sandwiched between the rollers of the registration roller pair 49. On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 110 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip. Thereby, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which the full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and then is sent from the paper transport belt 24 to the fixing device 25.

  The fixing device 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward one roller of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper transport belt 24 is sandwiched therebetween. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller 27 has a heat source (not shown) inside, and pressurizes the fixing belt 26 by the generated heat. The pressed fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  The transfer paper that has been subjected to the fixing process in the fixing device 25 is stacked on a stack portion 57 that protrudes from the left side plate in the drawing of the printer housing or forms a toner image on the other surface. Therefore, it is returned to the secondary transfer nip described above.

  When a document (not shown) is copied, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.

  When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner 300 starts. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation. In the document reading operation, first, the first traveling body 33 and the second traveling body 34 start traveling together, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.

  In parallel with such document reading operation, each device in each process cartridge (18Y, M, C, K), the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 start driving. Then, based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, K toner images are formed on the respective photosensitive members (40Y, M, C, K). Is formed. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer sheets are separated one by one by the separation roller 45 and enter the reverse feeding path 46, and then conveyed toward the secondary transfer nip by the conveyance roller pair 47. In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the manual feed roller 50 is selectively rotated to feed the transfer paper on the manual feed tray 51, the separation roller 52 separates the transfer paper one by one and feeds it to the manual feed path 53 of the printer unit 100. Make paper.

  In the case of forming another color image composed of two or more colors of toner, the copying machine stretches the intermediate transfer belt 110 so that the upper stretched surface thereof is substantially horizontal, Photoconductors (1Y, M, C, K). On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, the driving of not only the photoconductor but also the developing device is stopped to prevent unnecessary consumption of the photoconductor and the developer.

  The copying machine includes a control unit (not shown) configured by a CPU or the like that controls the following devices in the copying machine, and an operation display unit (not shown) configured by a liquid crystal display, various key buttons, and the like. The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

FIG. 2 is an enlarged configuration diagram showing the developing device 4 and the photoreceptor 1 provided in one of the four process cartridges 18 (Y, M, C, K). The four process cartridges 18 (Y, M, C, K) have substantially the same configuration except that the colors of the toners to be handled are different from each other. Therefore, Y, M, C denoted by “4” in FIG. , K are omitted.
As shown in FIG. 2, the surface of the photosensitive member 1 is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. The charged surface of the photoreceptor 1 is supplied with toner from the developing device 4 to a latent image on which an electrostatic latent image is formed by laser light emitted from an exposure device (not shown), thereby forming a toner image.

The developing device 4 has a developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photoreceptor 1 while moving the surface in the direction of arrow I in the drawing. Further, a supply screw 8 is provided as a developer supply / conveying member that conveys the developer in the depth direction of FIG. 2 while supplying the developer to the developing roller 5.
A developing doctor 12 as a developer regulating member for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided on the downstream side of the surface moving direction from the portion facing the supply screw 8 of the developing roller 5. ing.
The developed developer that has passed through the developing section is collected downstream from the developing section, which is the facing portion of the developing roller 5 with respect to the photoconductor 1, and the collected developer is collected in the same direction as the supply screw 8. A recovery screw 6 is provided as a developer recovery / conveying member. A supply conveyance path 9, which is a developer supply conveyance path provided with a supply screw 8, is in the lateral direction of the developing roller 5, and a recovery conveyance path 7 as a developer collection conveyance path provided with a collection screw 6 is below the development roller 5. It is installed side by side.

The developing device 4 is provided with an agitation conveyance path 10 that is a developer agitation conveyance path in parallel with the recovery conveyance path 7 below the supply conveyance path 9. The agitating and conveying path 10 includes an agitating screw 11 as a developer agitating and conveying member that conveys the developer to the front side in the figure, which is in the opposite direction to the supply screw 8 while agitating the developer.
The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition member. In the first partition wall 133, the supply conveyance path 9 and the agitation conveyance path 10 are partitioned at both ends on the front side and the back side in the drawing, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. doing.
The supply conveyance path 9 and the recovery conveyance path 7 are both partitioned by the first partition wall 133, but an opening is provided at a location where the supply conveyance path 9 and the agitation conveyance path 7 of the first partition wall 133 are partitioned. Absent.
Further, the two conveyance paths of the stirring conveyance path 10 and the collection conveyance path 7 are partitioned by a second partition wall 134 as a partition member. The second partition wall 134 has an opening on the front side in the figure, and the agitation transport path 10 and the collection transport path 7 communicate with each other.
The supply screw 8, the recovery screw 6 and the stirring screw 11, which are developer conveying members, are made of resin screws. Each screw diameter is φ18 [mm], screw pitch is 25 [mm], and the rotation speed is 600 [rpm]. It is set above.

The developer thinned by the developing doctor 12 made of stainless steel on the developing roller 5 is transported to a developing area which is a portion facing the photoreceptor 1 for development. The surface of the developing roller 5 is V-groove or sandblasted and is made of an Al [aluminum] element tube with a diameter of 25 [mm], and the gap between the developing doctor 12 and the photoreceptor 1 is about 0.3 [mm]. .
The developer after the development is collected in the collection conveyance path 7, conveyed to the front side of the cross section in FIG. 2, and to the agitation conveyance path 10 through the opening of the first partition wall 133 provided in the non-image area portion. Developer is transferred. In addition, toner is supplied to the stirring and conveying path 10 from a toner replenishing port provided on the upper side of the stirring and conveying path 10 in the vicinity of the opening of the first partition wall 133 on the upstream side in the developer conveying direction in the stirring and conveying path 10.

Next, the circulation of the developer in the three developer conveyance paths will be described.
FIG. 3 is a perspective sectional view of the developing device 4 for explaining the flow of the developer in the developer transport path. Each arrow in the figure indicates the moving direction of the developer.
4 is a schematic diagram of the flow of the developer in the developing device 4. Like FIG. 3, each arrow in the drawing indicates the moving direction of the developer.

In the supply conveyance path 9 that has been supplied with the developer from the agitation conveyance path 10, the developer is conveyed downstream in the conveyance direction of the supply screw 8 while supplying the developer to the developing roller 5. Then, the excess developer that is supplied to the developing roller 5 and is not used for development and is transported to the downstream end in the transport direction of the supply transport path 9 is supplied to the stirring transport path 10 from the opening of the first partition wall 133 (FIG. 4). Middle arrow E).
The collected developer that is sent from the developing roller 5 to the collection conveyance path 7 and conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6 is supplied to the stirring conveyance path 10 from the opening of the second partition wall 134. (Arrow F in FIG. 4).
The agitating and conveying path 10 agitates the supplied surplus developer and the recovered developer, conveys the agitating screw 11 to the downstream side in the conveying direction, and conveys it to the upstream side in the conveying direction of the supplying screw 8. It is supplied to the supply conveyance path 9 from the opening part 133 (arrow D in FIG. 4).
In the agitating and conveying path 10, the agitating screw 11 agitates and conveys the collected developer, the surplus developer, and the toner replenished as necessary in the transfer unit in the direction opposite to the developer in the collecting and conveying path 7 and the supply conveying path 9. . Then, the agitated developer is transferred to the upstream side in the conveyance direction of the supply conveyance path 9 communicating with the downstream side in the conveyance direction. A toner concentration sensor (not shown) is provided below the agitation transport path 10, and a toner supply control device (not shown) is operated by the sensor output to supply toner from a toner storage portion (not shown).

  In the developing device 4 shown in FIG. 4, a supply conveyance path 9 and a collection conveyance path 7 are provided, and developer supply and collection are performed in different developer conveyance paths, so that the developed developer is supplied to the supply conveyance path 9. There is no contamination. Accordingly, it is possible to prevent the toner density of the developer supplied to the developing roller 5 from decreasing toward the downstream side of the supply conveyance path 9 in the conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Therefore, since the sufficiently agitated developer is supplied to the supply conveyance path 9, it is possible to prevent the developer supplied to the agent supply conveyance path 9 from being insufficiently agitated. In this way, the toner density of the developer in the supply conveyance path 9 can be prevented from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred. Can be constant.

As shown in FIG. 4, the developer moves from the lower part to the upper part of the developing device 4 only by the arrow D. The movement of the developer indicated by an arrow D is to push the developer by rotating the stirring screw 11 so that the developer is raised and supplied to the supply conveyance path 9.
Such movement of the developer gives stress to the developer and contributes to a decrease in the life of the developer.
When the developer is lifted from the bottom to the top, stress is applied to the developer, and the carrier film in the developer is scraped off and the toner is spent on the spot. Accordingly, the stability of the image quality is maintained. It will disappear.
Therefore, if the developer stress in the movement of the developer indicated by the arrow D can be reduced, the life of the developer can be extended. By prolonging the life of the developer, it is possible to provide a developing device that prevents deterioration of the developer and is always stable in image quality without image density unevenness.

Therefore, in the developing device 4 of the present embodiment, the supply conveyance path 9 is disposed obliquely above the stirring conveyance path 10 as shown in FIG. By disposing it obliquely above, it is possible to reduce the developer stress in the movement of the developer indicated by the arrow D, compared to the case where the supply conveyance path 9 is provided vertically above the stirring conveyance path 10 and the developer is lifted. .
Further, in the developing device 4, the supply conveyance path 9 and the agitation conveyance path 10 are arranged obliquely so that the upper wall surface of the agitation conveyance path 10 is higher than the lower wall surface of the supply conveyance path 9 as shown in FIG. 2. It arranges so that it may become a position.
Lifting the supply conveyance path 9 vertically upward with respect to the stirring conveyance path 10 causes the developer to be stressed because the developer is lifted by the pressure of the stirring screw 11 against gravity. On the other hand, the developer present at the highest point of the agitating and conveying path 10 is placed at the bottom of the supplying and conveying path 9 by arranging the upper wall surface of the agitating and conveying path 10 to be higher than the lower wall surface of the supplying and conveying path 9. Since the point can flow without being against gravity, the stress applied to the developer can be reduced.
Note that a fin member may be provided on the shaft of the stirring screw 11 in a portion where the stirring transport path 10 and the supply transport path 9 communicate with each other on the downstream side of the developer transport path of the stirring transport path 10. This fin member is a plate-like member composed of a side parallel to the axial direction of the stirring screw 11 and a side perpendicular to the axial direction of the stirring screw. By scooping up the developer with this fin member, it is possible to more efficiently deliver the developer from the stirring conveyance path 10 to the supply conveyance path 9.

Further, in the developing device 4, the distance between the center A between the developing roller 5 and the supply conveyance path 9 is shorter than the distance B between the center between the development roller 5 and the agitation conveyance path 10. A conveyance path 10 is arranged. Thus, the developer can be supplied without difficulty from the supply conveyance path 9 to the developing roller 5, and the apparatus can be downsized.
Further, the stirring screw 11 is rotated counterclockwise as viewed from the front side in FIG. 2 (the direction of arrow C in the figure), and the developer is supplied by lifting the developer along the shape of the stirring screw 11. It is transferred to the conveyance path 9. As a result, the developer can be lifted efficiently, and the stress on the developer can be further reduced.

Next, features of the present embodiment will be described.
As shown in FIGS. 2 and 5, a filling member 135 is provided that extends from the upstream side in the developer conveyance direction of the collection conveyance path 7 to the central portion in the axial direction of the collection conveyance path 7 and fills the space of the collection conveyance path 7. Yes. The filling member 135 extends from the second partition wall 134 to the first partition wall 133 and is provided so as to cover the recovery screw 6. In this way, by filling the upstream space in the developer transport direction of the collection transport path 7 with the filling member, the cross-sectional area on the upstream side in the developer transport direction of the recovery transport path 7 is changed to the cross-sectional area in the downstream of the developer transport direction. Can be made smaller.

  The developer is collected almost uniformly from the developing roller 5 to the collection conveyance path. However, since the collected developer is conveyed from the upstream of the collection conveyance path 7 to the downstream side, the developer is upstream of the collection conveyance path 7. In comparison, the amount of developer on the downstream side increases. When the cross-sectional area of the recovery conveyance path 7 is uniform in the axial direction as shown in FIG. 7, the ratio of the gap in the developer recovery conveyance path on the downstream side is smaller than that on the upstream side, and the recovery conveyance path 7 is recovered. The internal pressure on the downstream side in the transport path becomes higher than that on the upstream side, and the internal pressure in the recovery transport path 7 becomes non-uniform in the axial direction. As a result, the rotation of the developing roller 5 causes the blowing airflow that blows into the gap between the developing roller 5 and the case on the downstream side of the developing region to flow to the upstream side of the recovery conveyance path 7 where the internal pressure is low, and the downstream side of the developer recovery conveyance path The pressure of the insufflation airflow will decrease. As a result, on the downstream side of the developer recovery transport, the internal pressure on the downstream side of the developer recovery transport path becomes larger than the pressure of the blown air flow, and a blowout air stream that blows out from the gap toward the photoreceptor 1 is generated, causing toner scattering.

  However, in the present embodiment, the space on the upstream side of the developer conveyance direction of the collection conveyance path 7 is filled with the filling member, and the cross-sectional area of the collection conveyance path 7 on the upstream side in the developer conveyance direction is set on the downstream side in the developer conveyance direction. By making it smaller than the cross-sectional area, the ratio of the gap in the downstream collection conveyance path 7 is increased in the upstream side in the state where the amount of developer on the downstream side is larger than the upstream side of the collection conveyance path 7. It can suppress that it becomes small compared. As a result, it is possible to suppress the internal pressure on the downstream side in the collection conveyance path from becoming higher than that on the upstream side, and the blowing that blows into the gap between the developing roller 5 and the case on the downstream side of the developing region by the rotation of the developing roller 5. It is possible to suppress the airflow from flowing into the upstream side of the collection conveyance path 7. As a result, it is possible to suppress the pressure drop due to the blown airflow on the downstream side of the recovery conveyance path, and to maintain the pressure due to the blown airflow on the downstream side of the recovery conveyance path higher than the internal pressure on the downstream side of the recovery conveyance path. . Accordingly, it is possible to suppress the generation of a blown air current that blows out from the gap between the developing roller and the case on the downstream side of the developing region to the photosensitive member side, thereby suppressing toner scattering.

  In addition, the amount of developer at each position in the collection conveyance path is grasped, and based on this, the filling member is formed so that the ratio of the gap in the collection conveyance path 7 is the same at each position in the collection conveyance path. Is preferred. Thereby, the internal pressure of the collection conveyance path 7 can be made uniform, and the blown airflow can be reliably suppressed from flowing into the upstream side of the collection conveyance path 7.

  Further, in this embodiment, the space on the upstream side in the developer conveyance direction of the collection conveyance path 7 is filled with the filling member, so that the internal pressure in the collection conveyance path 7 is suppressed from becoming non-uniform in the axial direction. For example, the second partition wall 134 and the first partition wall 133 may be tapered walls such that the cross-sectional area of the recovery transport path 7 increases from the upstream side of the recovery transport path 7 toward the downstream side.

  Further, by configuring the recovery screw so that the developer transport speed on the downstream side of the recovery transport path is higher than that on the upstream side of the recovery transport path, the ratio of the gaps in the downstream recovery transport path 7 is higher than that on the upstream side. Can be further suppressed. In the present embodiment, the recovery screw 6 is rotated at a high speed of 600 [rpm] or more, more specifically, 690 [rpm] or 729 [rpm]. Thus, when the collection screw 6 is rotated at a high speed of 600 [rpm] or more, the screw pitch on the downstream side in the developer conveyance direction of the collection screw 6 is made shorter than the upstream side in the developer conveyance direction, Compared to the upstream side of the recovery transport path, the result is that the developer transport speed on the downstream side of the recovery transport path can be increased. Therefore, by making the screw pitch downstream of the recovery screw 6 in the developer transport direction shorter than the upstream side of the developer transport direction, the developer transport speed on the downstream side of the recovery transport can be increased, and the developer transport direction The amount of developer on the downstream side can be reduced as compared with a developer having a uniform developer conveyance speed. Thereby, it can further suppress that the ratio of the space | gap in the collection | recovery conveyance path 7 of a downstream is small compared with an upstream.

  In the developing device in which the number of rotations of the collection screw 6 is 300 to 500 [rpm], the screw pitch on the downstream side in the developer conveyance direction of the collection screw 6 is made longer than that on the upstream side in the developer conveyance direction. The developer transport speed on the downstream side of the recovery transport path can be increased compared to the upstream side of the recovery transport path.

As described above, according to the present embodiment, the developer transport path 9 has the supply transport path 9 as the developer supply transport path and the recovery transport path 7 as the developer recovery transport path, and the developer transport path differs between the developer supply and recovery. Therefore, the developed developer is not mixed into the supply conveyance path 9. Thereby, it is possible to prevent the toner concentration of the developer supplied to the developing roller from decreasing toward the downstream side in the transport direction of the developer supply transport path. In addition, the developer conveyance path 7 and the agitation conveyance path 10 that is the developer agitation conveyance path are provided, and the developer collection and agitation are performed separately in the collection conveyance path 7 and the agitation conveyance path 10, so that the developed Developer does not fall during stirring. Therefore, since the sufficiently agitated developer is supplied to the supply conveyance path 9, it is possible to prevent the developer supplied to the supply conveyance path 9 from being insufficiently agitated. In this way, the toner density of the developer in the supply conveyance path 9 can be prevented from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred. Can be constant.
Furthermore, since the cross-sectional area of the collection conveyance path downstream of the collection conveyance path 7 is made larger than that upstream of the collection conveyance path 7, the amount of developer on the downstream side is larger than that upstream of the collection conveyance path 7. In this state, it is possible to suppress the ratio of the voids in the downstream collection conveyance path 7 from becoming smaller than that on the upstream side. As a result, it is possible to prevent the internal pressure in the collection conveyance path from becoming uneven, and the blowing airflow that blows into the gap between the developing roller 5 and the case on the downstream side of the development region flows into the collection conveyance path 7 upstream side. Can be suppressed. As a result, it is possible to suppress the pressure drop due to the blown airflow on the downstream side of the recovery conveyance path, and to maintain the pressure due to the blown airflow on the downstream side of the recovery conveyance path higher than the internal pressure on the downstream side of the recovery conveyance path. . Accordingly, it is possible to suppress the generation of a blown air current that blows out from the gap between the developing roller and the case on the downstream side of the developing region to the photosensitive member side, thereby suppressing toner scattering.

  Further, by filling the space in the collection conveyance path from the upstream of the collection conveyance path to at least the central portion of the collection conveyance path with a filling member, the cross-sectional area on the downstream side of the collection conveyance path 7 can be reduced compared to the upstream side of the collection conveyance path 7. Can be bigger.

  Further, the developer screw 6 as a developer collecting and conveying member is configured so that the developer conveying speed on the downstream side of the collecting and conveying path is higher than that on the upstream side of the collecting and conveying path 7, thereby developing the developer on the downstream side in the developer conveying direction. The amount can be reduced as compared with a uniform developer conveying speed. Thereby, it can further suppress that the ratio of the space | gap in the collection | recovery conveyance path 7 of a downstream is small compared with an upstream.

  Further, in the collection screw 6 that rotates at a rotational speed of 600 [rpm] or more, the collection pitch 6 has a screw pitch on the downstream side in the developer conveyance direction that is shorter than that on the upstream side in the developer conveyance direction. Compared to the upstream side of the path 7, the developer transport speed on the downstream side of the recovery transport path can be increased.

  Further, by providing the supply conveyance path 9 obliquely above the agitation conveyance path 10, it is possible to reduce the stress applied to the developer as compared with the case where the developer is lifted vertically upward. As a result, the life of the developer can be extended.

1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 2 is a schematic configuration diagram of a developing device and a photoreceptor. FIG. 3 is a perspective cross-sectional view of the developing device for explaining the flow of the developer. FIG. 3 is a schematic diagram of a developer flow in a developing device. The perspective view which shows the filling member in a developing device. 1 is a schematic configuration diagram of a conventionally known developing device. 1 is a schematic configuration diagram of a developing device described in Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing device 5 Developing roller 6 Collection screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 12 Developing doctor 14 Stretching roller 15 Driving roller 16 Secondary transfer backup roller 17 Intermediate transfer unit 18 Process Cartridge 20 Image Forming Unit 21 Optical Writing Unit 22 Secondary Transfer Device 23 Tension Roller 24 Paper Conveying Belt 25 Fixing Device 26 Fixing Belt 27 Pressure Roller 30 Document Stand 32 Contact Glass 33 First Traveling Body 34 Second Traveling Body 35 Imaging lens 36 Reading sensor 42 Paper feed roller 44 Paper feed cassette 46 Paper feed path 47 Transport roller pair 49 Registration roller pair 57 Stack part 62 Primary transfer bias roller 90 Belt cleaning device 100 Printer part 110 Intermediate transfer bell 133 first partition wall 134 a second partition wall 200 paper feeder 300 Scanner 400 automatic document feeder

Claims (8)

A two-component developer comprising a magnetic carrier and a toner is carried on the surface and rotated, and the developer is developed by supplying toner to the latent image on the surface of the latent image carrier at a location facing the latent image carrier. A carrier,
A developer supply transport path including a developer supply transport member that transports the developer along the axial direction of the developer support and supplies the developer to the developer support;
The developer recovered from the developer carrier after passing through the portion facing the latent image carrier is along the axial direction of the developer carrier and in the same direction as the developer supply / conveying member. A developer recovery transport path including a developer recovery transport member for transporting
The excess developer that has not been used for development and is transported to the downstream side in the transport direction of the developer supply transport path, and is recovered from the developer carrier and transported to the downstream side in the transport direction of the developer recovery transport path. The developer is supplied with the recovered developer, and is conveyed along the axial direction of the developer carrying member and in the direction opposite to the developer supply / conveying member while stirring the excess developer and the collected developer. A developer agitating and conveying member that has a developer agitating and conveying path for supplying the developer to the developer supply and conveying path;
The developer agitation transport path and the developer recovery transport path are provided at substantially the same height, and the developer supply transport path is provided so as to be positioned above the other two developer transport paths, In a developing device in which toner is replenished to the developer conveyance path,
A developing device having a larger cross-sectional area of a developer recovery transport path on the downstream side of the developer recovery transport path than on the upstream side of the developer recovery transport path. The developing device according to claim 1.
The developer agitation transport path and the developer supply transport path are partitioned by a partition member, and the developer supply transport from the developer agitation transport path via a stirring developer opening provided in the partition member. A developing device for delivering a developer to a path. The developing device according to claim 1 or 2,
3. A developing device characterized in that three developer transport paths comprising the developer recovery transport path, the developer supply transport path, and the developer agitation transport path are each partitioned by a partition member. The developing device according to any one of claims 1 to 3,
The developer agitating / conveying member is not used for development and is transported to the most downstream side in the transport direction of the developer supply transport path, and the developer recovery transport path recovered from the developer carrier. The developer is supplied with the recovered developer conveyed to the most downstream side in the conveying direction of the developer, and the developer is stirred along the axial direction of the developer carrier and the excess developer and the recovered developer. A developing device that transports in a direction opposite to a supply transport member. In the developing device according to any one of claims 1 to 4,
A developing device, comprising: a filling member that fills a space in the developer recovery transport path from the upstream of the developer recovery transport path to at least a central portion of the developer recovery transport path . The developing device according to any one of claims 1 to 5,
2. A developing device comprising: a developer collecting and conveying member configured to increase a developer conveying speed on a downstream side of the developer collecting and conveying path as compared with an upstream side of the developer collecting and conveying path. The developing device according to any one of claims 1 to 6,
2. A developing device according to claim 1, wherein the developer supply transport path is provided obliquely above the developer agitation transport path. At least a latent image carrier;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the latent image carrier;
In an image forming apparatus having developing means for developing the electrostatic latent image into a toner image,
An image forming apparatus using the developing device according to claim 1 as the developing unit.