JP2009058597A - Development device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device capable of feeding a uniform developer to a developer carrier by uniformly setting height of a developer face of the developer in a feed carrying passage in the development device for delivering the developer passing a development region to the developer carrying passage different from the feed carrying passage by being fed to the developer carrier from the feed carrying passage, and to provide an image forming apparatus provided with the development device. <P>SOLUTION: The development device 4 having: a development sleeve for feeding a toner on latent images on a photoreceptor; the feed carrying passage 7 for carrying the developer along an axis line direction of the development sleeve while feeding the developer on the development sleeve; a feed screw 9 for giving carrying force to the developer in the feed carrying passage 7; a circulation carrying passage 8 for carrying the developer reaching the downstream end of a carrying direction of the feed carrying passage 7 to the upstream end of a carrying direction of the feed carrying passage 7; and a circulation screw 10 for giving carrying force to the developer 2 in the circulation carrying passage 8, wherein a feed bottom face 7b being a bottom face of the feed carrying passage 7 is inclined so as to be higher toward the downstream side of the carrying direction of the feed carrying passage 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like and an image forming apparatus using the developing device.

  Conventionally, an image forming apparatus including a developing device using a two-component developer composed of toner and a magnetic carrier has been widely used. As a developing device using a two-component developer, the developer conveying member is conveyed in parallel to the axial direction of the developing sleeve, which is a developing carrier, and the developer is supplied to the developing sleeve, and reaches the downstream end of the supplying conveying path. A developer having a circulating conveyance path for conveying the developed developer to the upstream end of the supply conveyance path is known.

  As a developing device including a supply conveyance path and a circulation conveyance path, the developer supplied from the supply conveyance path to the developing sleeve passes through a development region which is a facing portion between the photosensitive member as the latent image carrier and the development sleeve. After that, there is something that is delivered to the supply conveyance path. Since the developer that has passed through the development area supplies toner to the latent image on the photoconductor and the toner density is lowered, the developer that has passed through the development area returns to the supply conveyance path. The toner concentration in the developer decreases toward the downstream side in the transport direction. In particular, in an image with a high printing rate, a decrease in the toner concentration of the developer after passing through the development region is larger than that before the passage through the development region, and the toner concentration on the downstream side in the transport direction of the supply transport path There is a problem that the image quality is deteriorated.

  The developing device described in Patent Document 1 includes two developer conveying paths parallel to the developing sleeve of the supply conveying path and the circulation conveying path, and the developer supplied to the developing sleeve and passing through the developing region is circulated and conveyed. Passed to the road. In such a developing device, the developer whose toner density has decreased after passing through the developing region does not return to the supply conveyance path, but is transferred to the circulation conveyance path. The problem of lowering the toner density does not occur.

  The developing device described in Patent Document 2 includes three developer conveyance paths parallel to the development sleeves of the supply conveyance path, the circulation conveyance path, and the recovery conveyance path, and is supplied to the development sleeve and passes through the development region. The developer is transferred to the collection conveyance path. The developer in the collection conveyance path is conveyed in the same direction as the supply conveyance path, and the developer that has reached the downstream end of the supply conveyance path and the developer that has reached the downstream end of the collection conveyance path are transferred to the circulation conveyance path. . In such a developing device, the developer whose toner density has decreased after passing through the developing region does not return to the supply conveyance path, but is delivered to the collection conveyance path. The problem of lowering the toner density does not occur.

In the developing devices described in Patent Document 1 and Patent Document 2, since the developer supplied from the supply conveyance path to the developing sleeve does not return to the supply conveyance path, the amount of developer decreases toward the downstream side in the conveyance direction of the supply conveyance path. Less. When the developer conveying member that conveys the developer in the supply conveyance path has a uniform shape throughout the conveyance direction, and the supply conveyance path has a uniform shape throughout the conveyance direction, Problems arise. That is, the height of the developer surface becomes lower toward the downstream side in the transport direction where the amount of the developer is smaller. If deviation occurs in the developer level between the upstream and downstream sides in the conveyance direction in the supply conveyance path, unevenness in the supply to the developing sleeve can occur, and the amount of developer supplied to the developing sleeve can also be reduced. Deviation occurs in the axial direction of the developing sleeve.
That is, on the upstream side of the supply conveyance path where the developer surface is high, the amount of developer supplied to the developing sleeve is stable and the image density is constant. On the other hand, on the downstream side of the supply conveyance path where the developer surface is low, the supply amount of the developer to the developing sleeve becomes unstable, causing density unevenness in the image and causing an image defect.

  In the developing device of Patent Document 1, the developer transport amount in the supply transport path and the circulation transport path is sufficiently larger than the supply amount to the developing sleeve, whereby the developer is supplied by supplying the developer to the developing sleeve. The rate of decrease is reduced. Thereby, the deviation of the height of the developer surface in the supply conveyance path is reduced, and the occurrence of density unevenness in the image is suppressed. However, in Patent Document 1, as a method of increasing the developer conveyance amount, the developer conveyance speed by the developer conveyance members in the supply conveyance path and the circulation conveyance path is increased. As described above, increasing the transport speed of the developer transport member in the supply transport path and the circulation transport path to increase the transport amount of the developer leads to an increase in stress on the developer. Further, when a transport screw is used as the developer transport member, increasing the rotational speed to increase the transport speed of the developer leads to an increase in the rotational torque of the transport screw. As described above, since the stress on the developer increases and the rotational torque of the conveying screw increases, there is a problem that the amount of developer conveyed between the supply conveyance path and the circulation conveyance path cannot be increased too much.

On the other hand, Patent Document 2 describes a developing device that includes a screw-like supply screw as a developer conveyance member in a supply conveyance path, and uses a conveyance screw whose pitch width becomes narrower toward the downstream side in the conveyance direction as the supply screw. Yes. When transporting developer using a transport screw, the narrower the pitch width of the screw, the shorter the distance that the developer moves each time the screw rotates, and if there is no increase or decrease in the developer, the narrower the pitch width of the screw, the smaller the developer. Becomes bulky. Therefore, by using a conveyance screw having a narrower pitch width toward the downstream side as the supply screw of the supply conveyance path in which the amount of developer decreases toward the downstream side in the conveyance direction, development on the upstream and downstream sides in the conveyance direction within the supply conveyance path. The deviation in the height of the surface of the agent can be reduced. As a result, the amount of developer supplied to the developing sleeve can also be reduced in the axial direction of the developing sleeve, and the amount of developer supplied to the developing sleeve is small on the downstream side of the supply conveyance path. It is possible to prevent the occurrence of image defects due to density unevenness.
Note that the configuration in which the transport screw whose pitch width is narrower toward the downstream side in the transport direction is used as the supply screw is not limited to the developing device including three developer transport paths as in Patent Document 2, and the transport path as in Patent Document 1. Is also applicable to two developing devices.

JP-A-5-333691 Japanese Patent Publication No. 2006-251440

However, the configuration using the transport screw whose pitch width becomes narrower toward the downstream side in the transport direction has the following problems.
That is, the amount of developer in the supply conveyance path that decreases by being supplied to the developing sleeve can be calculated, but it is difficult to calculate the amount of increase in the developer volume by narrowing the pitch width. For this reason, it is difficult to create a supply screw in which the developer surface in the supply conveyance path in which the developer amount decreases toward the downstream side in the conveyance direction by supplying the developer to the developing sleeve is horizontal. . Therefore, in the configuration in which the conveyance screw whose pitch width is narrower toward the downstream side in the conveyance direction is used as the supply screw, the deviation in the height of the developer surface on the upstream side and the downstream side in the conveyance direction in the supply conveyance path can be reduced. It is difficult to make the height of the agent surface uniform.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developer in which the developer supplied from the supply conveyance path to the developer carrying member and passed through the development region is different from the supply conveyance path. A developing device that can deliver a uniform developer to the developer carrying member by setting the height of the developer surface of the developer in the supply conveying path to be more uniform by a developing device delivered to the conveying path. And an image forming apparatus provided with the developing device.

In order to achieve the above object, the invention according to claim 1 is characterized in that the developer is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the latent image carrier at a position facing the latent image carrier. A developer carrying body to be developed, a supply carrying path for carrying the developer along the axial direction of the developer carrying body while supplying the developer to the developer carrying body, and development in the supply carrying path A supply conveyance member that applies conveyance force to the agent, a circulation conveyance path that conveys the developer that has reached the downstream end in the conveyance direction of the supply conveyance path, to the upstream end in the conveyance direction of the supply conveyance path, and the circulation conveyance path In the developing device having a circulation conveyance member that applies a conveyance force to the developer inside, the bottom surface of the supply conveyance path is inclined so as to become higher toward the downstream side in the conveyance direction of the supply conveyance path. It is what.
According to a second aspect of the present invention, there is provided a developer for carrying and developing a developer on the surface thereof, supplying toner to the latent image on the surface of the latent image carrier and developing it at a position facing the latent image carrier. A carrier, a supply conveyance path for conveying the developer along the axial direction of the developer carrier while supplying the developer to the developer carrier, and a conveyance force for the developer in the supply conveyance path A supply conveyance member for supplying the developer, a circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the supply conveyance path to the upstream end in the conveyance direction of the supply conveyance path, and a developer in the circulation conveyance path A developing device having a circulating conveying member for applying a conveying force, wherein a lowermost portion of a region to which the supplying and conveying member applies a conveying force becomes higher toward a downstream side in the conveying direction of the supply conveying path. It is.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the supply / conveying member includes a rotation shaft and a wing portion spirally provided on the rotation shaft, and the rotation is performed by rotating the supply / conveyance member. The supply screw includes a screw member that conveys the developer in the axial direction of the shaft.
According to a fourth aspect of the present invention, in the developing device according to the third aspect, the supply screw has a shape in which the outer diameter of the wing portion becomes smaller toward the downstream side in the conveyance direction of the supply conveyance path. is there.
Further, the invention of claim 5 is the developing device according to claim 4, wherein the supply screw and the supply screw are arranged so that the rotation shaft of the supply screw approaches the developer carrier toward the downstream side of the supply conveyance path in the conveyance direction. A supply conveyance path is arranged.
According to a sixth aspect of the present invention, there is provided at least a latent image carrier, a charging unit 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. 6. An image forming apparatus comprising: a developing device for developing the electrostatic latent image into a toner image; and the developing device according to claim 1, 2, 3, 4 or 5 as the developing device. It is characterized by using.

In the developing device having the above-described configuration, the bottom surface of the supply conveyance path is inclined so as to become higher toward the downstream side in the conveyance direction of the supply conveyance path, so that the developer amount is smaller toward the downstream side of the supply conveyance path. However, the deviation of the height of the agent surface can be reduced. And since the height of the preparation surface on the downstream side in the conveying direction is increased by the inclination, the increase in the height of the preparation surface by changing the inclination can be easily calculated, and the height of the preparation surface Is easy to set. For this reason, the height of the surface of the supply conveyance path can be set more uniformly than in the conventional developing device.
Further, in the developing device having the configuration according to claim 2, the lowermost portion of the region where the supply conveyance member applies the conveyance force becomes higher toward the downstream side in the conveyance direction of the supply conveyance path. A dead space, which is an area where no conveyance force is applied from the supply conveyance member, below the lowermost part of the conveyance area, which is an area where the member imparts conveyance force, becomes higher toward the downstream side of the supply conveyance path in the conveyance direction. In the dead space, the developer stagnating without being imparted with the conveying force is accumulated along the lowermost part of the conveying region, so that the developer accumulated in the dead space becomes a slope that becomes higher toward the downstream side in the conveying direction of the supply conveying path. . Since the developer is transported on the slope of the deposited developer, the state is similar to the configuration in which the bottom surface of the supply transport path is inclined so as to become higher toward the downstream side in the transport direction of the supply transport path. For this reason, even if the amount of the developer is smaller toward the downstream side of the supply conveyance path, the deviation of the height of the agent surface can be reduced. Since the developer surface on the downstream side in the conveying direction is raised by the inclination of the accumulated developer, the increase in the height of the agent surface by changing the inclination can be easily calculated. Easy to set the height even. For this reason, the height of the surface of the supply conveyance path can be set more uniformly than in the conventional developing device. In addition, since the slope of the deposited developer has a shape along the lowermost inclination of the region where the supply and transport member applies the transport force, the slope of the deposited developer is changed by changing the arrangement or shape of the supply and transport member. You can change the slope.

  According to the first to sixth aspects of the present invention, the height of the developer surface of the developer in the supply conveyance path can be set to be more uniform than that of the conventional developing device, and the developer carrying member can be uniformly developed. There is an excellent effect that the agent can be supplied.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color laser copier (hereinafter simply referred to as “copier 500”) in which a plurality of photoconductors are arranged in parallel will be described.
FIG. 1 is a schematic configuration diagram of a copying machine 500 according to the present embodiment. The copier 500 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 includes an image forming unit 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). 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 laser light onto a surface of a photoconductor described later based on image data.
The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photoreceptor 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. Thereby, the potential of the surface of the photoreceptor 1Y of the irradiation part (exposure part) is attenuated. Due to the attenuation of the surface potential, 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, 18C, and 18K.

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 medium tension roller 114, 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 a medium tension stretching roller 114. 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 photoreceptor 1 and the primary transfer bias roller 62 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 medium 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 500 main body, a plurality of paper feeding cassettes 44 in which a plurality of transfer sheets can be stacked and stored in a bundle of sheets are arranged so as to overlap each other in the vertical direction. It is installed. 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 delivered from the paper feed cassette 44 includes a plurality of transport roller pairs 47 and a registration roller pair 49 provided near the end in the paper feed path 46. 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 heats the fixing belt 26 by the generated heat. The heated 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 subjected to the fixing process in the fixing device 25 is stacked on the stack portion 57 provided outside the left side plate in the drawing of the printer housing, or forms a toner image on the other surface. 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 a document reading operation, each device in each of the process cartridges 18Y, 18M, 18C, 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 starts driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, and K toner images are formed on the respective photoreceptors 1Y, 1M, 1C, and 1K. Is done. 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.

  When the copier 500 forms a multicolor image composed of toners of two or more colors, the intermediate transfer belt 110 is stretched so that the upper stretched surface thereof is substantially horizontal, and all the upper stretched surface is placed on the upper stretched surface. Photoconductors 1Y, 1M, 1C, and 1K are brought into contact with each other. 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, not only the photosensitive member 1 but also the developing device 4 is stopped, and each member of the photosensitive member 1 and the developing device 4 and the developer in the developing device 4 are unnecessarily consumed. To prevent.

  The copier 500 includes a control unit (not shown) composed of a CPU and the like that controls each device in the copier 500, and an operation display unit (not shown) composed of 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 of the developing device 4 and the photoreceptor 1 provided in one of the four process cartridges 18Y, 18M, 18C, and 18K as viewed from the back side in FIG. Since the four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the colors of the toners to be handled are different, the subscripts Y, M, C, and K added to “4” in FIG. Is omitted.
The developing device 4 is disposed opposite to the drum-shaped photoconductor 1 which is a latent image carrier, and the photoconductor 1 is rotated in the clockwise direction in FIG. 2 as indicated by an arrow a in the figure. The surface of the photoreceptor 1 is charged by a charging device (not shown) while rotating. An electrostatic latent image is formed on the surface of the charged photoreceptor 1 by the laser beam emitted from the optical writing unit 21 serving as an exposure device.

  A developing container 3 which is a casing of the developing device 4 contains a powdery two-component developer 2 made of a magnetic carrier and magnetic or nonmagnetic toner. The developing device 4 supplies toner to the electrostatic latent image formed on the surface of the photoreceptor 1 and carries the developer 2 in the developing container 3 to the developing area A where the development is performed, and transports the surface by moving the surface. A developing sleeve 14a is provided as a developer carrying member. Further, a magnet roller 14b made of a plurality of magnets fixed to the developing device 4 is provided inside the developing sleeve 14a. Furthermore, it has an agent regulating member 5 that regulates the layer thickness of the developer carried on the developing sleeve 14a.

  As two conveying screws as developer conveying means, a supply screw 9 and a circulating screw 10 are provided substantially parallel to the axial direction of the developing sleeve 14a. Each transport screw includes a rotation shaft and a blade portion spirally provided on the rotation shaft, and rotates to transport the developer in one direction along the axial direction of the rotation shaft. A space is partitioned by the inner wall of the developing container 3 and the partition wall 6, and a supply transport path 7 and a circulation transport path 8 are formed vertically with the partition wall 6 interposed therebetween as developer transport paths. Further, openings are respectively provided at both ends of the partition wall 6 on the front side and the back side in FIG. 2, and the supply conveyance path 7 and the circulation conveyance path 8 are communicated with each other by two openings. Yes.

As shown in FIG. 2, a supply screw 9 and a circulation screw 10 are arranged in the supply conveyance path 7 and the circulation conveyance path 8, respectively, and the developer 2 in the developing container 3 is supplied to the supply conveyance path 7 and the circulation conveyance path 8. Is housed in. The circulation screw 10 is disposed substantially parallel to the supply screw 9, and the developer in the circulation conveyance path 8 is conveyed by the circulation screw 10 in a direction opposite to the conveyance direction of the supply screw 9.
The developer 2 in the developing container 3 is circulated between the supply conveyance path 7 and the circulation conveyance path 8 through openings provided at both ends of the partition wall 6 by conveyance by rotation of the supply screw 9 and the circulation screw 10. .

  Of the developer 2 in the developer container 3, the developer in the supply conveyance path 7 is supplied to the surface of the developing sleeve 14 a while being conveyed by the rotation of the supply screw 9. The developer 2 is supplied from the supply conveyance path 7 to the developing sleeve 14a by the rotation of the supplying screw 9 over the partition wall 13 between the supplying screw 9 and the developing sleeve 14a, or the developer 2 is moved into the developing sleeve 14a. This is performed by the developer 2 being attracted to the developing sleeve 14a by the magnetic force of the magnet roller 14b provided.

  The developer 2 supplied to the developing sleeve 14a is conveyed in the direction of arrow B in FIG. 2 while being carried on the developing sleeve 14a by the rotation of the developing sleeve 14a and the magnetic force of the magnet roller 14b provided therein. The That is, the developer 2 supplied and carried on the developing sleeve 14a passes through the agent regulating member 5 as indicated by an arrow B while being carried on the developing sleeve 14a. The developer 2 carried on the surface of the developing sleeve 14a is scraped off when the developer 2 passes through a portion facing the agent regulating member 5 as indicated by an arrow B1 in FIG.

The appropriate amount of the developer 2 that has passed through the agent regulating member 5 passes through the developing region A between the developing sleeve 14a and the photosensitive member 1 as shown by an arrow B2 in FIG. It flows to the bottom 3 b of the container 3 and is delivered to the circulation conveyance path 8.
That is, the developer 2 that is carried on the developing sleeve 14a, conveyed to the developing area A, passes through the developing area A, and remains on the developing sleeve 14a without being supplied to the surface of the photoreceptor 1 in the developing area A. Instead of being collected again in the supply conveyance path 7 with the rotation of the developing sleeve 14a, it is once collected in the circulation conveyance path 8. For this reason, only the developer sufficiently stirred in the circulation conveyance path 8 always exists in the supply conveyance path 7.

  The developer 2 that has reached the downstream end of the supply conveyance path 7 and the developer that has passed through the development region A and separated from the developing sleeve 14 a are conveyed by the circulation conveyance path 8 and received at the upstream end of the supply conveyance path 7. Passed. Since the developer 2 in the circulation conveyance path 8 contains the developer 2 that has passed through the development region A and has a reduced toner concentration, it is necessary to replenish the toner. Therefore, by supplying toner to the developer in the circulation conveyance path 8 according to the toner consumption calculated from the image information of the latent image or the measurement result of the toner density of the developer in the circulation conveyance path 8, an appropriate amount is obtained. The developer 2 having a toner density can be transferred to the supply conveyance path 7.

FIG. 3 is a schematic diagram illustrating the flow of the developer 2 in the developing container 3 when the developing device 4 is viewed from the direction of arrow C in FIG. The arrows in FIG. 3 indicate the flow of the developer 2 in the developing container 3.
As shown in FIGS. 2 and 3, in the developing device 4, the supply conveyance path 7 and the circulation conveyance path 8 are arranged in the vertical direction. For this reason, in the opening 12 provided at both ends of the partition wall 6, the developer 2 flows upward from the downstream end of the supply conveyance path 7 to the upstream end of the circulation conveyance path 8 at the right opening in FIG. Move down from. On the other hand, at the lifting port 11 which is the opening on the left side in FIG. 3 among the openings provided at both ends of the partition wall 6, the developer 2 flows from the bottom to the upstream end of the supply conveyance path 7 from the downstream end of the circulation conveyance path 8. Move up. The developer moves from the circulation conveyance path 8 to the supply conveyance path 7 by the lift 11 so that the developer is pushed upward from below by the pressure of the developer 2 accumulated at the downstream end in the conveyance direction in the circulation conveyance path 8. The drug is delivered.

In the developing device 4, not all of the developer 2 transferred from the circulation conveyance path 8 to the supply conveyance path 7 reaches the downstream end in the conveyance direction of the supply screw 9 in the supply conveyance path 7. As indicated by an arrow B in FIG. 3, there is a component that is supplied to the surface of the developing sleeve 14 a while being transported in the supply transport path 7, passes through the development region A, and is collected in the circulation transport path 8. To do. The delivery of the developer 2 to the surface of the developing sleeve 14a is performed over substantially the entire width of the developing sleeve 14a in the axial direction.
For this reason, the amount of the developer 2 that is transported with the transport force applied by the supply screw 9 in the supply transport path 7 tends to gradually decrease from the upstream end to the downstream end in the supply transport path 7. .
On the other hand, the amount of the developer 2 that is conveyed with the conveying force applied by the circulation screw 10 in the circulation conveyance path 8 tends to gradually increase from the upstream end to the downstream end in the circulation conveyance path 8. That is, there is a deviation in the distribution of the developer 2 in the developing device 4.

FIG. 4 is an explanatory diagram of the distribution of the developer 2 in the supply conveyance path 7 and the circulation conveyance path 8 in the conventional developing device 4.
As shown in FIG. 4, in the conventional developing device 4, the supply screw 9 has a uniform shape throughout the transport direction, and the supply transport path 7 also has a uniform shape throughout the transport direction. As described above, in the developing device 4, the amount of the developer 2 in the supply conveyance path 7 gradually decreases from the upstream end to the downstream end in the supply conveyance path 7. The height of the second agent surface 2f becomes lower toward the downstream side in the transport direction. As shown in FIG. 4, if the height of the developer surface 2f of the developer 2 is uneven between the upstream side and the downstream side in the transport direction in the supply transport path 7, the developer supply to the developing sleeve 14a is uneven. In addition, the amount of the developer 2 supplied to the developing sleeve 14a is also shifted in the axial direction of the developing sleeve 14a and becomes non-uniform.

  Due to the non-uniform amount of the developer 2 supplied to the developing sleeve 14a, the density of the formed image differs in the axial direction of the developing sleeve 14a. That is, on the upstream side in the supply conveyance path 7 where the height of the developer surface 2f of the developer 2 is high, the supply amount of the developer 2 to the developing sleeve 14a is stable and the image density is constant. However, on the downstream side in the supply conveyance path 7 where the height of the developer surface 2f of the developer 2 is low, the amount of the developer 2 supplied to the developing sleeve 14a is small, resulting in density unevenness in the image and image failure.

[Example 1]
Next, a first example (hereinafter referred to as Example 1) provided with the characteristic part of the present embodiment will be described.
FIG. 5 is an explanatory side sectional view of the supply conveyance path 7 and the circulation conveyance path 8 of the developing device 4 of the first embodiment.
As shown in FIG. 5, in the developing device 4 of Example 1, the supply bottom surface 7 b that is the bottom surface of the supply conveyance path 7 is inclined so as to become higher toward the downstream side of the supply conveyance path 7 in the conveyance direction.

FIG. 6 is a schematic diagram for explaining the distribution of the developer 2 in the developing container 3 of the developing device 4 of the first embodiment shown in FIG.
FIG. 6A is a schematic diagram in a state where the developer 2 is not supplied to the developing sleeve 14a, and FIG. 6B is a schematic diagram in a state where the developer 2 is supplied to the developing sleeve 14a. It is.
Here, the movement of the developer 2 in the supply conveyance path 7 will be described again.
In the conventional developing device 4 described with reference to FIG. 4, the supply screw 9 has a uniform shape throughout the conveyance direction, and the supply conveyance path 7 also has a uniform shape throughout the conveyance direction. For this reason, the conveyance force of the supply screw 9 arranged in the supply conveyance path 7 is constant with respect to the developer conveyance direction. Further, since the supply bottom surface 7 b of the supply conveyance path 7 is not inclined, the developer 2 in the supply conveyance path 7 is conveyed in the supply conveyance path 7 at a constant speed by the rotation of the supply screw 9. For this reason, if the developer 2 is not supplied to the developing sleeve 14a, the height of the developer surface 2f of the developer 2 in the supply conveyance path 7 is uniform. However, as described above, the developer 2 conveyed by the supply screw 9 of the developing device 4 is gradually supplied to the developing sleeve 14a from the upstream side of the supply conveyance path 7 to the downstream side. Gradually decreases. Therefore, in the developing device 4 of Example 1, the inclination of the supply bottom surface 7b of the supply conveyance path 7 is changed in order to eliminate the deviation of the developer surface 2f of the developer 2.

  That is, when the supply conveyance path 7 is inclined with respect to the developing sleeve 14a, if no developer is supplied to the developing sleeve 14a, the developer surface 2f of the developer 2 in the supply conveyance path 7 as viewed from the developing sleeve 14a. As shown in FIG. 6A, the height increases from upstream to downstream. At this time, if the amount of the developer 2 supplied to the developing sleeve 14a is the same as the inclination amount of the agent surface 2f in FIG. 6A, the developer 2 is supplied to the developing sleeve 14a. The height of the developer surface 2f of the developer 2 becomes uniform.

  Therefore, in the developing device 4 of the first embodiment, the height of the developer surface 2f of the developer 2 in the supply conveyance path 7 is substantially the same as that of the developing sleeve 14a, which is caused by the deviation of the developer amount distribution. This configuration eliminates the deviation of the supply of the developer 2 to the developing sleeve 14a. That is, in the developing device 4 according to the first embodiment, the height of the developer surface 2f of the developer 2 becomes uniform by arranging the supply bottom surface 7b of the supply conveyance path 7 so as to be inclined with respect to the developing sleeve 14a.

Next, the developer reduction amount M [kg / m] per unit length in the supply conveyance path 7 will be described.
The developer transport amount W [kg / sec] of the developing sleeve 14a is determined by the developer amount B [kg / m ² ] regulated by the agent regulating member 5, the radius r [m] of the developing sleeve, and the rotation speed R [rpm]. And the length L [m] of the developing sleeve,
W = B × 2πr × R × L / 60
Suppose that
Further, when the transport amount of the developer in the supply transport path 7 is expressed as C [m / sec], the decrease amount of the developer 2 per unit length in the supply transport path 7 is
M = W / C [kg / m]
Can be expressed as

Based on this relationship, if the supply conveyance path 7 is inclined with respect to the developing sleeve 14 a, the developer 2 in the supply conveyance path 7 can be used in the developing apparatus in which the developer circulates in a so-called one direction as in the developing apparatus 4. The agent surface 2f can be made substantially uniform with respect to the developing sleeve 14a, and a stable image can be obtained.
For example, a transport screw (type 1) having a developer transport amount of 0.40 [m / sec] and a transport screw (type 2) having a developer transport amount of 0.25 [m / sec] are supplied. Assume that the screw 9 is used.

  FIG. 7 is a graph showing the amount of decrease in the developer surface 2f of the developer 2 when the type 1 conveying screw and the type 2 conveying screw are used in the conventional developing device 4 shown in FIG. By setting the inclination of the supply bottom surface 7b of the supply conveyance path 7 in accordance with the amount of decrease in the agent level as shown in the graph of FIG. 7, the height of the developer surface 2f of the developer 2 in the supply conveyance path 7 is set. It becomes uniform and a uniform developer can be supplied to the developing sleeve 14a. By supplying a uniform developer to the developing sleeve 14a, a stable image can be obtained.

[Modification 1]
The supply screw 9 according to the first embodiment is a transport screw having a uniform shape in the transport direction as shown in FIG. Hereinafter, as a first modification, a configuration in which the screw pitch of the supply screw 9 becomes narrower toward the downstream side in the transport direction will be described.
Since the first modification is common to the first embodiment except that the shape of the supply screw 9 is different, the description of the common points is omitted, and only the different points will be described.
FIG. 8 is an explanatory view of a conveying screw used for the supply screw 9 of the first modification. In the developing device of Modification 1, a supply screw 9 shown in FIG. 8 is used instead of the supply screw 9 of the developing device 4 of Example 1 shown in FIG.
In the developing device 4 of Modification 1, in addition to the configuration in which the supply bottom surface 7b of the supply conveyance path 7 is inclined, the conveyance speed by the supply screw 9 is reduced toward the downstream side of the supply conveyance path 7 in the conveyance direction.
It is known that when the developer is transported by the transport screw, the transport speed of the developer 2 changes when the screw pitch length of the transport screw is changed. That is, if the pitch of the transport screw is increased, the distance to which the developer is pushed out when the screw rotates once is increased, so that the transport speed is increased. Conversely, if the pitch is shortened, the transport speed is decreased.
If the developer 2 is not supplied to the developing sleeve 14a, the bulk of the developer 2 is increased in the portion where the screw pitch is low and the screw pitch is short compared to the portion where the screw pitch is high. Thus, the surface 2f is increased. Therefore, if the supply screw 9 is used in which the supply bottom surface 7b is inclined and the screw pitch becomes shorter toward the downstream side in the transport direction as in the developing device 4 in the first modification, the downstream in the transport direction than the developing device 4 in the first embodiment. The side surface 2f becomes higher. That is, when the developer surface 2f of the developer 2 in the supply conveyance path 7 has a uniform height in the developing device 4 in which the supply bottom surface 7b is inclined as in the first embodiment, in the first modification, the downstream side in the conveyance direction. As a result, the developer surface 2f of the developer 2 in the supply conveyance path 7 becomes higher, and the height of the developer surface 2f becomes uneven. However, when the supply bottom surface 7b is not sufficiently inclined, or when a part of the developer 2 slips to the upstream side in the conveyance direction due to the inclination of the supply bottom surface 7b, the agent surface 2f on the downstream side of the supply conveyance path 7 is desired. A supply screw 9 shown in FIG. 8 may be used as an auxiliary configuration in the case where the height is not reached.

As in the first modification, the developing device 4 in which the screw pitch of the supply screw 9 is shortened toward the downstream side has the following advantages.
In the developing device in which the developer circulates in a so-called one direction like the developing device 4, in order for the developer to circulate without being clogged in the developer conveying path, between the two conveying screws (between the two developer conveying paths) ) It is necessary to smoothly deliver the developer. In particular, the configuration in which two screws are arranged in the vertical direction (vertical direction) as in the developing device 4 has an advantage that the lateral width (horizontal width) of the developing device can be reduced.
However, as shown in FIGS. 3 and 4, the developer is transferred in the upward direction by pressing the developer against the lifting port 11 which is a communication portion provided in the partition wall 6 between the screws. If the developer is excessively present in the vicinity of the lifting opening 11, the developer is likely to be clogged. If delivery of the developer at the lifting port 11 is not smoothly performed, the developer deteriorates at the delivery portion, and the developer moves slowly and the developer is not sufficiently stirred. In order to solve this problem, it is necessary to transport the developer after passing through the lifting opening 11 to the downstream side earlier and to reduce the amount of the developer entering the lifting opening 11.
In the case of a conveyance screw having the same screw pitch, for example, even if the rotation speed of the supply screw 9 is increased and the developer after passing through the lifting port 11 is passed early, the developing sleeve is provided downstream of the supply conveyance path 7. Since the amount of the developer that has not been supplied to 14a also increases, the developer that enters the dropping port 12 increases, and the developer tends to be clogged after all.
On the other hand, when it is changed between the upstream and downstream of the conveying screw as in Modification 1, there are the following merits. That is, since the conveyance amount of the supply screw 9 is large upstream of the supply conveyance path 7, the developer is quickly conveyed downstream, and the developer is not easily clogged. Further, downstream of the supply conveyance path 7, since the conveyance amount of the supply screw 9 is small, the developer tends to accumulate in the supply conveyance path 7 and does not excessively enter the drop opening 12. The delivery of the developer through the lifting port 11 and the dropping port 12 is smoothly performed.

[Example 2]
Next, a second example (hereinafter referred to as Example 2) including the characteristic part of the present embodiment will be described.
FIG. 9 is an explanatory side sectional view of the supply conveyance path 7 and the circulation conveyance path 8 of the developing device 4 according to the second embodiment.
As shown in FIG. 9, in the developing device 4 of Example 2, the supply bottom surface 7 b of the supply conveyance path 7 is inclined so as to become higher toward the downstream side of the supply conveyance path 7 in the conveyance direction, and further outside the wing portion of the supply screw 9. The diameter is smaller toward the downstream side in the conveyance direction of the supply conveyance path 7.
When transporting developer using a transport screw, increasing the outer diameter of the wing increases the area of the wing that comes into contact with the developer, and can provide transport force when the screw rotates once. The upper limit of the amount is also increased. On the other hand, when the outer diameter of the wing portion is reduced, the upper limit of the amount of developer that can impart the conveying force when the screw rotates once is also reduced. Therefore, if a conveying screw having a smaller outer diameter on the downstream side, such as the supply screw 9 in FIG. 9, is used in the developer conveying path in which the amount of developer to be conveyed does not change, the following problems occur. Can happen. That is, when an amount of developer that can be conveyed on the upstream side where the outer diameter of the wing part is large is input and conveyed to the downstream side, the upper limit of the amount that can be conveyed on the downstream side where the outer diameter of the wing part is small is exceeded. End up. Even if the developer is transported from the upstream side to the location where the upper limit of the transport amount is exceeded, the developer is not given a transport force beyond the upper limit of the transport amount, is stagnated, and exceeds the upper limit of the transport amount. If a certain amount of developer is continuously conveyed from the upstream side, the developer becomes clogged and cannot be conveyed.

On the other hand, in the supply transport path 7 in which the amount of developer transported decreases toward the downstream side in the transport direction as in the developing device 4 of the present embodiment, transport is performed such that the outer diameter of the wing portion decreases toward the downstream side as shown in FIG. It is possible to use a screw.
The supply screw 9 of the developing device 4 of Example 1 has a uniform outer diameter from the upstream end to the downstream end. Therefore, when the supply bottom surface 7b is increased toward the downstream side, the supply conveyance is performed as shown in FIG. The upper part of the casing on the downstream side of the path 7 may be made higher than the upstream side, leading to an increase in the size of the developing device 4. On the other hand, if the supply screw 9 is a conveyance screw in which the outer diameter of the wing portion decreases toward the downstream side as in the developing device 4 of the second embodiment, the downstream side of the supply conveyance path 7 even if the supply bottom surface 7b is increased toward the downstream side. There is no need to raise the top of the side casing. As a result, it is possible to prevent an increase in the size of the developing device 4 that raises the supply bottom surface 7b of the supply conveyance path 7 toward the downstream side.

Next, the positional relationship between the supply screw 9 and the developing sleeve 14a in which the outer diameter of the wing portion becomes smaller toward the downstream side of the developing device 4 according to the second embodiment will be described.
FIG. 10 is a schematic diagram for explaining the positional relationship among the supply screw 9, the developing sleeve 14a, and the partition wall 13 when the developing device 4 is viewed from above.
FIG. 10A is a schematic diagram of an arrangement in which the rotation axis of the supply screw 9 and the rotation axis of the developing sleeve 14a are parallel, and the partition wall 13 is parallel to the rotation axes of the supply screw 9 and the developing sleeve 14a. In the arrangement of FIG. 10A, the partition wall 13 is further away from the end 9a (the straight line connecting the ends of the wings) of the conveyance region by the supply screw 9 toward the downstream in the conveyance direction. The efficiency of the developer inside the partition wall 13 is reduced by the rotation of the supply screw 9. In addition, the amount of developer supplied to the developing sleeve 14a may be reduced.

  FIG. 10B is a schematic view of the arrangement in which the rotation axis of the supply screw 9 and the rotation axis of the developing sleeve 14 a are parallel, and the partition wall 13 is parallel to the end 9 a of the conveyance region by the supply screw 9. 10B, unlike the case of FIG. 10A, the partition wall 13 has a shape along the outer diameter of the supply screw 9, so that the developer is partitioned by the rotation of the supply screw 9 toward the downstream side in the transport direction. It is possible to prevent the efficiency over the wall 13 from being lowered. However, since the distance between the developing sleeve 14a and the partition wall 13 is further away toward the downstream side in the transport direction, the developer that has crossed the partition wall 13 does not contact the developing sleeve 14a on the downstream side, or due to the magnetic force of the magnet roller 14b. When the pulling force becomes weak, the amount of developer supplied to the developing sleeve 14a becomes unstable. As a result, the amount of developer supplied to the developing sleeve 14a becomes non-uniform, resulting in an image defect.

  FIG. 10C is a schematic diagram illustrating the positional relationship among the supply screw 9, the developing sleeve 14 a, and the partition wall 13 of the developing device 4 according to the second embodiment. As illustrated in FIG. 10C, in the second embodiment, the supply screw 9 and the supply conveyance path 7 are arranged so that the rotation shaft of the supply screw 9 approaches the developing sleeve 14 a toward the downstream side of the supply conveyance path 7 in the conveyance direction. ing. That is, the line connecting the tips of the wings of the supply screw 9 and the rotation axis of the developing sleeve 14a are parallel to each other, and the partition wall 13 is also arranged to be parallel to the rotating shaft of the developing sleeve 14a. As shown in FIG. 10C, the partition wall 13 is parallel to the straight line connecting the tips of the wings of the supply screw 9, and the partition wall 13 has a shape along the outer diameter of the supply screw 9. It is possible to prevent the efficiency that the developer passes over the partition wall 13 by the rotation of the supply screw 9 toward the downstream side in the direction. Furthermore, since the partition wall 13 is also parallel to the rotation axis of the developing sleeve 14a, the distance between the partition wall 13 and the developing sleeve 14a is uniform in the axial direction of the developing sleeve 14a, and the developer 2 that has passed over the partition wall 13 is removed. It can be transferred to the surface of the developing sleeve 14a satisfactorily. As a result, it is possible to prevent the occurrence of image defects that may occur in the arrangements of FIGS. 10A and 10B.

[Modification 2]
In the above-described first and second embodiments and the first modification, the configuration in which the supply bottom surface 7b that is the bottom surface of the supply conveyance path 7 is stronger toward the downstream side in the conveyance direction of the supply conveyance path 7 has been described. Hereinafter, as a modified example 2, a configuration in which the supply bottom surface 7b has a horizontal shape and the lowermost portion of the region where the supply screw 9 as a supply conveyance member applies conveyance force becomes higher toward the downstream side in the conveyance direction of the supply conveyance path 7 will be described. .

FIG. 11 is an explanatory side sectional view of the supply conveyance path 7 and the circulation conveyance path 8 of the developing device 4 of Modification 2.
As shown in FIG. 11, in the developing device 4 according to the second modification, the conveyance region lower end 9 e, which is the lowest part of the region to which the supply screw 9 as the supply conveyance member applies the conveyance force, is closer to the conveyance direction downstream side of the supply conveyance path 7. The supply screw 9 is disposed obliquely so as to be higher. In the developing device 4 of Modification 2, the supply bottom surface 7 b is horizontal, whereas the supply screw 9 is arranged obliquely, and the conveyance region lower end 9 e becomes higher toward the downstream side of the supply conveyance path 7 in the conveyance direction. Yes. For this reason, there exists a dead space α between which the conveyance force is not applied from the supply screw 9 between the conveyance region lower end 9e and the supply bottom surface 7b. Then, since the developer entering the dead space α is not imparted with a conveyance force, the developer stagnates and accumulates along the lowermost portion of the region where the supply conveyance member imparts the conveyance force.

FIG. 12 is a schematic diagram illustrating a state where a developer is deposited in the dead space α of the developing device 4 according to the second modification.
In the developing device 4 of Modification 2, the lower end 9e of the transport region becomes higher toward the downstream side in the transport direction of the supply transport path 7, so that the deposition which is the upper surface of the deposited developer T deposited in the dead space as shown in FIG. The agent surface Tf becomes an inclined surface that becomes higher toward the downstream side in the conveyance direction of the supply conveyance path 7. Since the developer is transported on the deposition agent surface Tf that has become the inclined surface, the same state as the developing device 4 of the first embodiment in which the supply bottom surface 7b is inclined so as to become higher toward the downstream side of the supply transport path 7 in the transport direction. Become.

  For this reason, by supplying the developer to the developing sleeve 14 a as in the developing device 4 of the first embodiment, the amount of developer to which the conveying force is applied from the supply screw 9 is smaller toward the downstream side of the supply conveying path 7. Also, the deviation of the height of the surface 2f can be reduced. Then, since the agent surface 2f on the downstream side in the transport direction is raised by the inclination of the depositing agent surface Tf of the deposited developer T, the height of the agent surface 2f is raised by changing the inclination of the depositing agent surface Tf. Can be easily calculated. For this reason, it is easy to perform the setting that makes the height of the agent surface uniform as in the first embodiment. For this reason, the height of the surface of the supply conveyance path 7 can be set more uniformly than in the conventional developing device.

The depositing agent surface Tf, which is the slope of the deposited developer T, has a shape along the inclination of the conveyance region lower end 9e, which is the lowest part of the region to which the supply screw 9 imparts conveyance force. By changing the shape, the inclination of the deposition agent surface Tf can be changed.
Further, the supply screw 9 of the second modification is not limited to the uniform attachment of the wings to the rotating shaft as shown in FIGS. 11 and 12, and the pitch width becomes narrower toward the downstream side as in the first modification. A screw or a screw whose outer diameter is smaller toward the downstream side as in Example 2 can be used.

  In the above-described embodiment, the configuration in which the two conveying screws of the supply screw 9 and the circulation screw 10 are arranged in the vertical direction has been described. However, the configuration of the developing device to which the characteristic portion of the present invention can be applied is not limited thereto. is not. The so-called one-way circulation type in which the developer once supplied to the developer carrying member from the supply carrying path for supplying the developer to the developer carrying member is always transferred to the developer carrying path different from the supply carrying path. Any developing device can be applied. Therefore, the number of developer transport paths and the positional relationship of the developer transport paths to be written are not limited to the configurations described in the embodiments.

  For example, as shown in FIG. 13, the present invention can also be applied to the developing device 4 including three developer conveyance paths including a supply conveyance path 7, a circulation conveyance path 8, and a collection conveyance path 8a. In the developing device 4 shown in FIG. 13, the developer supplied from the supply conveyance path 7 to the developing sleeve 14 a and passed through the development area A is transferred to the collection conveyance path 8 a and is in the same direction as the developer in the supply conveyance path 7. Is conveyed by the recovery screw 10a. The developer that has reached the downstream end in the transport direction of the supply transport path 7 and the downstream end in the transport direction of the recovery transport path 8a is delivered to the upstream end of the circulation transport path 8 in the transport direction. Then, the developer conveyed to the circulation screw 10 and reaching the downstream end in the conveyance direction of the circulation conveyance path 8 is delivered to the upstream end of the supply conveyance path 7.

Further, as shown in FIG. 14, the present invention can also be applied to the developing device 4 in which the supply conveyance path 7 and the circulation conveyance path 8 which are two developer conveyance paths are arranged side by side in the horizontal direction.
Also in the developing device 4 as shown in FIGS. 13 and 14, the deviation of the height of the surface 2 f of the developer 2 in the supply conveyance path 7 can be reduced by applying the characteristic portion of the present embodiment. Image quality can be improved.
In the developing device 4 shown in Embodiments 1 and 2, Modifications 1 and 2, and FIGS. 13 and 14, the axial direction of the rotating shaft of the photosensitive member 1 and the rotating shaft of the developing sleeve 14a is horizontal. When the rotation axis of the photosensitive member 1 and the rotation axis of the developing sleeve 14a are inclined, the developer surface 2f of the developer without the developing device 4 is also set to have a developer distribution that matches the inclination of the developing sleeve 14a. .

As described above, according to the present embodiment, the developer 2 is carried and rotated on the surface, and the latent image on the surface of the photoconductor 1 is formed in the development area A that is a portion facing the photoconductor 1 that is the latent image carrier. A developing sleeve 14a that is a developer carrying member for supplying and developing toner; a supply conveying path 7 that conveys the developer along the axial direction of the developing sleeve 14a while supplying the developer to the developing sleeve 14a; A supply screw 9 that is a supply conveyance member that applies a conveyance force to the developer 2 in the path 7, and a developer that has reached the downstream end in the conveyance direction of the supply conveyance path 7 is transferred to the upstream end in the conveyance direction of the supply conveyance path 7. In the developing device 4 having a circulation conveyance path 8 for conveyance and a circulation screw 10 that is a circulation conveyance member that applies a conveyance force to the developer 2 in the circulation conveyance path 8, the supply conveyance path 7 is downstream in the conveyance direction. Of the supply conveyance path 7 so as to become higher For supplying bottom 7b is a plane is inclined, it is possible to reduce the deviation of the downstream side as the developer amount less also developer surface 2f height of the supply path 7. Since the height of the drug surface 2f on the downstream side in the transport direction is increased by the inclination of the supply bottom surface 7b, the level of increase of the drug surface by changing the inclination can be easily calculated. Easy to set the surface height to be uniform. For this reason, the height of the surface of the supply conveyance path 7 can be set more uniformly than in the conventional developing device. Thus, the height of the developer surface 2f of the developer 2 in the supply conveyance path 7 can be set to be more uniform than that of the conventional developing device 4, and the uniform developer is supplied to the developing sleeve 14a. be able to.
In addition, as in Modification 2, the conveyance region lower end 9e, which is the lowest part of the region to which the supply screw 9 as the supply conveyance member applies the conveyance force, becomes higher toward the downstream side in the conveyance direction of the supply conveyance path 7. By disposing the supply screw 9 diagonally, the deposition agent surface Tf of the deposited developer T deposited in the dead space α below the conveyance region lower end 9 e is inclined so as to become higher toward the downstream side in the conveyance direction of the supply conveyance path 7. Similarly to the configuration in which the supply bottom surface 7b is inclined, the deviation of the height of the agent surface 2f is reduced even if the amount of developer applied to the supply screw 9 is smaller toward the downstream side of the supply conveyance path 7. I can do it. As a result, as in the first embodiment, the height of the developer surface 2f of the developer 2 in the supply conveyance path 7 can be set to be more uniform than that of the conventional developing device 4, and the developing sleeve 14a is uniform. A simple developer can be supplied.
In addition, the supply conveyance member is a supply screw 9 that includes a rotation shaft and a wing portion spirally provided on the rotation shaft, and includes a screw member that conveys the developer in the axial direction of the rotation shaft by rotating. Thus, the developer 2 in the supply conveyance path 7 can be conveyed by a space-saving conveyance member.
Further, as in the second embodiment, the supply screw 9 has a shape in which the outer diameter of the wing portion becomes smaller toward the downstream side in the conveyance direction of the supply conveyance path 7, so that the developing device 4 that inclines the supply bottom surface 7 b. It can prevent becoming larger than the conventional developing device 4.
Further, as described in the second embodiment with reference to FIG. 10C, the rotation axis of the supply screw 9 is closer to the developing sleeve 14 a that is a developer carrier on the downstream side in the conveyance direction of the supply conveyance path 7. By disposing the supply screw 9 and the supply conveyance path 7, even if the supply screw 9 has a shape in which the outer diameter of the wing portion decreases toward the downstream side in the conveyance direction of the supply conveyance path 7, the developer 2 is removed from the developing sleeve 14 a. It can be transferred to the surface satisfactorily and the occurrence of image defects can be prevented.
Further, at least a photosensitive member 1 as a latent image carrier, a charger as a charging unit for charging the surface of the photosensitive member 1, and a latent image forming unit for forming an electrostatic latent image on the photosensitive member 1. A copying machine 500, which is an image forming apparatus having a certain optical writing unit 21 and a developing unit for developing an electrostatic latent image into a toner image, uses the developing device 4 as a developing unit to develop the image. Since the developer can be uniformly supplied to the sleeve 14a, it is possible to prevent unevenness in image density and to form a good image.

1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating a developing device and a photoconductor. FIG. 3 is a schematic diagram illustrating the flow of a developer in a developing container. Explanatory drawing of the distribution of the developer of the supply conveyance path and the circulation conveyance path in the conventional developing device. FIG. 3 is an explanatory side sectional view of a supply conveyance path and a circulation conveyance path of the developing device according to the first exemplary embodiment. Schematic diagram illustrating the distribution of the developer in the developing container of the developing device of Example 1, (a) is a schematic diagram in a state where the developer is not supplied to the developing sleeve, (b) is a schematic diagram of the developing sleeve FIG. 3 is a schematic diagram illustrating a state where a developer is supplied. The graph which shows the fall amount of the agent surface at the time of using 2 types of screws. Explanatory drawing of the conveyance screw used for the supply screw of the modification 1. FIG. FIG. 6 is a side cross-sectional explanatory view of a supply conveyance path and a circulation conveyance path of the developing device of Embodiment 2. Schematic diagram illustrating the positional relationship between the supply screw, the developing sleeve, and the partition wall, (a) and (b) are schematic diagrams in which the rotation axis of the supply screw and the rotation axis of the developing sleeve are arranged in parallel, and (c) FIG. 5 is a schematic diagram for explaining the positional relationship among a supply screw, a developing sleeve, and a partition wall in Example 2. FIG. 10 is a side cross-sectional explanatory view of a supply conveyance path and a circulation conveyance path of a developing device according to Modification 2; FIG. 9 is a schematic diagram illustrating a state where a developer is accumulated in a dead space of a developing device according to Modification 2. Schematic explanatory drawing of a developing device provided with three developer conveyance paths. FIG. 3 is a schematic explanatory diagram of a developing device in which two developer conveying paths are arranged in a horizontal direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developer 2f Agent surface 3 Developing container 3b Bottom part 4 Developing apparatus 5 Agent control member 6 Bulkhead 7 Supply conveyance path 7b Supply bottom face 8 Circulation conveyance path 9 Supply screw 9a End of conveyance area 10 Circulating screw 11 Lifting port 12 Drop port 13 Partition wall 14a Developing sleeve 14b Magnet 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 Stretching roller 24 Paper transport belt 25 Fixing device 90 Belt cleaning device 100 Printer unit 110 Intermediate transfer belt 500 Copying machine T Deposited developer Tf Deposited agent surface

Claims (6)

A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A supply conveyance path for conveying the developer along the axial direction of the developer carrier while supplying the developer to the developer carrier;
A supply conveyance member that applies conveyance force to the developer in the supply conveyance path;
A circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the supply conveyance path to the upstream end in the conveyance direction of the supply conveyance path;
In the developing device having a circulation conveyance member that applies a conveyance force to the developer in the circulation conveyance path,
A developing device, wherein a bottom surface of the supply conveyance path is inclined so as to be higher toward a downstream side in the conveyance direction of the supply conveyance path. A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A supply conveyance path for conveying the developer along the axial direction of the developer carrier while supplying the developer to the developer carrier;
A supply conveyance member that applies conveyance force to the developer in the supply conveyance path;
A circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the supply conveyance path to the upstream end in the conveyance direction of the supply conveyance path;
In the developing device having a circulation conveyance member that applies a conveyance force to the developer in the circulation conveyance path,
2. A developing device according to claim 1, wherein a lowermost portion of an area to which the supply conveyance member applies a conveyance force becomes higher toward a downstream side in the conveyance direction of the supply conveyance path. The developing device according to claim 1 or 2,
The supply conveyance member is a supply screw including a rotation shaft and a blade provided spirally on the rotation shaft, and comprising a screw member that conveys the developer in the axial direction of the rotation shaft by rotating. A developing device. The developing device according to claim 3.
The developing device according to claim 1, wherein the supply screw has a shape in which the outer diameter of the wing portion becomes smaller toward the downstream side in the conveyance direction of the supply conveyance path. The developing device according to claim 4.
The developing device, wherein the supply screw and the supply conveyance path are arranged so that the rotation shaft of the supply screw approaches the developer carrier toward the downstream side in the conveyance direction of the supply conveyance 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 means.

Images