JP2010217328A - Developing device, image-forming device, and process cartridge - Google Patents

Abstract

A developing device capable of stably and accurately detecting a toner concentration of a developer in an apparatus, an image forming apparatus including the developing device, and a process cartridge are provided.
In a developing device, a supply conveyance path is disposed above the agitation conveyance path, and the agitation conveyance path is supplied to a position near the downstream end in the developer conveyance direction in the agitation conveyance path. A supply opening 91 that is an opening that communicates with the conveyance path 9 is provided, and a toner concentration sensor 201 that is a toner concentration detection unit is disposed on the downstream side in the developer conveyance direction in the agitation conveyance path 10.
[Selection] Figure 4

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 and a process cartridge using the developing device.

Conventionally, an image forming apparatus including a developing device using a two-component developer including toner and a magnetic carrier has been widely used. In this type of image forming apparatus, the developer in the developing device that consumes toner accompanying development is replenished with toner from the toner container as required by the toner replenishing device, so that the toner concentration of the developer Is maintained within a predetermined range.
When the toner density is lower than the predetermined range, problems such as insufficient image density and blurring of characters / line drawings occur. On the contrary, when the toner concentration is higher than the predetermined range, the image density is excessive or the characters / line drawings are crushed or ground. Problems such as contamination occur. Further, there is a problem that a target hue cannot be obtained when the toner density fluctuates in a multi-color superimposed image in a color image forming apparatus using a plurality of developing devices. In order to prevent the occurrence of these problems, it is necessary to appropriately control the toner replenishment amount. For this purpose, it is necessary to accurately detect the toner concentration of the developer in the developing device.

As a toner concentration detection means for detecting the toner concentration of a two-component developer containing toner and a magnetic carrier, the magnetic permeability of the developer changes due to a change in toner concentration as in the toner concentration sensor described in Patent Document 1. Toner density sensors that focus on the above are known.
As a developing device provided with such a toner density sensor, for example, there is a developing device described in Patent Document 2.

However, when the height of the developer at the position where the detection unit of the toner density sensor in the developing device is changed, even if the toner density of the developer is the same, the apparent magnetic permeability that is detected changes. In some cases, the toner density sensor cannot accurately detect the toner density.
As a case where the height of the developer changes at the position where the detection unit is provided, there is a case where the height of the developer changes when toner density fluctuation, developer deterioration, environmental fluctuation, or the like occurs. Also, in the premix system in which the deteriorated developer is discharged little by little and the new developer is replenished, if the balance between discharge and replenishment temporarily shifts, the amount of developer in the developing device fluctuates and the detection unit The height of the developer changes as the amount of the developer at the position where is provided. Further, the height of the developer also varies depending on the blade period of the screw as the developer conveying member that conveys the developer. Further, when the developer is fluidized through a long image forming operation, the amount of air contained between the developer particles increases, so that the volume of the developer increases and the height of the developer increases. Then, even if the amount of toner with respect to the carrier in the developer is the same, the apparent permeability changes and the same problem may occur.

  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 that can stably and accurately detect the toner concentration of the developer in the apparatus, and image formation including the developing device. An apparatus and a process cartridge are provided.

In order to achieve the above-mentioned object, the invention according to claim 1 is the latent image carrier at a position facing the latent image carrier and rotating with a two-component developer composed of toner and magnetic carrier on the surface. A developer carrying member for supplying toner to the latent image on the surface of the developer for development, a developer containing unit for containing the developer supplied to the developer carrying member, and a plurality of developers for conveying the developer in the developer containing unit And a toner concentration detecting means for detecting the ratio of the toner in the developer in the vicinity of the toner concentration detecting portion disposed in the developer accommodating portion, the space in the developer accommodating portion. The developer transport member has a partition member that forms a plurality of developer transport paths arranged in the space, and the developer transport members are arranged above and below the partition member as the plurality of developer transport members. Upper developer transport member and lower developer transport A lower developer conveying path in which the lower developer conveying member is disposed by the partition member and an upper developer conveying path in which the upper developer conveying member is disposed in the space in the developer accommodating portion. And an opening that communicates the lower developer transport path and the upper developer transport path at a position near the downstream end in the developer transport direction in the lower developer transport path of the partition member. And the toner density detector is disposed downstream of the developer transport path in the developer transport direction.
According to a second aspect of the present invention, in the developing device according to the first aspect, the position where the toner concentration detection unit is disposed in the lower developer transport path is the position in the developer transport direction in the lower developer transport path. It is a position upstream of the position where the opening is provided in the developer transport direction in the lower developer transport path.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the space portion in which the toner density detecting portion is disposed in the internal space of the lower developer conveyance path is filled with the developer. It is characterized by being.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the lower developer conveying member rotates by fixing a helical wing portion to a shaft portion. A screw member for conveying the developer in the axial direction, wherein the toner density detecting portion is disposed on the lower developer conveying path at a height of the shaft portion of the lower developer conveying member from a bottom surface in the lower developer conveying path. It arrange | positions between the side surfaces.
According to a fifth aspect of the present invention, there is provided the developing device according to the fourth aspect, wherein the toner density detecting portion is moved from the bottom surface center position vertically below the shaft portion in the bottom surface in the lower developer transport path to the center of the bottom surface. It is characterized in that it is arranged between the position of the side surface having the same height as the shaft portion on the downstream side in the rotation direction of the lower developer conveying member with respect to the position.
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. A developing apparatus according to claim 1, wherein the developing unit includes a developing unit and a developing unit for developing the electrostatic latent image into a toner image. It is characterized by this.
According to a seventh aspect of the present invention, at least the latent image carrier and the development in an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier. 6. The developing device according to claim 1, wherein the developing unit is a process cartridge that is held by a common holding member as a unit and is detachable from the image forming apparatus main body. It is characterized by using.

In the developing device of the present invention, an opening communicating the lower developer transport path and the upper developer transport path is provided at a position near the downstream end of the developer transport direction in the lower developer transport path of the partition member. Provided. The developer that has reached the vicinity of the downstream end of the developer transport direction of the lower developer transport path by the lower developer transport member is pushed up by the developer coming later and reaches the height of the opening of the partition member. Passed to the upper developer conveyance path. Therefore, the developer exists up to the height of the opening in the lower developer transport path at the position where the opening is provided in the partition member when the developing device is driven.
Further, when the bulk of the developer in the entire developing device increases, the height of the developer increases in the entire developer transport path in the device, but at the position where the opening is provided in the partition member. In the lower developer conveyance path, the developer exceeding the height of the opening is transferred to the upper developer conveyance path.
Thus, in the state where the developing device is driven in the lower developer conveyance path in the vicinity of the position where the opening is provided in the partition member, the developer exists up to the height of the opening, and the interior space is filled with the developer. Therefore, even if the volume of the developer in the entire apparatus changes, the height of the developer in the lower developer conveyance path in the vicinity of the position where the opening is provided in the partition member hardly changes. . In the lower developer conveyance path, the amount of change in the height of the developer at that position with respect to the amount of change in the volume of the developer in the entire apparatus is closer to the position where the opening is provided in the partition member. Get smaller. By providing the toner density detection unit at a position where the amount of change in the developer height becomes small, the influence of the change in apparent permeability caused by the change in the developer height is suppressed. Can do.

  According to the present invention, the height of the developer is changed by providing the toner density detection portion on the downstream side in the developer transport direction in the lower developer transport path, where the amount of change in the developer height is small. As a result, it is possible to suppress the influence of the apparent magnetic permeability change caused by this, so that the toner concentration of the developer in the apparatus can be stably and accurately compared with the configuration in which the toner concentration detection unit is provided at another position. There is an excellent effect that it can be detected.

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. Cross-sectional explanatory drawing of a developing device. FIG. 5 is a schematic diagram of a developer flow in a developing device having a shape different from that in FIG. 4. FIG. FIG. 6 is a perspective explanatory view of the vicinity of the front end in a state where the stirring screw, the recovery screw, and the developing doctor are removed from the developing device. Explanatory drawing of a discharge developer transfer pipe. Explanatory drawing of the position which can arrange | position a toner density sensor. FIG. 3 is a perspective explanatory view of a process cartridge in a state where a developing device is temporarily positioned. FIG. 6 is an explanatory perspective view of a process cartridge to which a positioning plate is attached.

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 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. 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 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 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. Return 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 500, 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 illustrating the developing device 4 and the photosensitive member 1 included in one of the four process cartridges 18Y, 18M, 18C, and 18K. 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.
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. The developing roller 5 includes a rotatable developing sleeve, and a magnetic body (not shown) including a plurality of magnetic poles is disposed therein. The magnetic material is necessary for holding the developer on the surface of the developing roller 5.
Further, a supply screw 8 is provided as a supply conveyance member that conveys the developer in the front direction of FIG. 2 along the axial direction of the development roller 5 while supplying the developer to the development roller 5.
A doctor blade 12 as a developer regulating means 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.
A collection conveyance path 7 that collects the developed developer that has passed through the developing area and separated from the surface of the developing roller 5 on the downstream side in the surface movement direction from the developing area that is the portion of the developing roller 5 facing the photoreceptor 1. Faces the developing roller 5. The collection conveyance path 7 is a collection conveyance member that conveys the collected developer collected in the same direction as the supply screw 8 along the axial direction of the developing roller 5, and a spiral collection screw 6 arranged in parallel to the axial direction. I have. A supply conveyance path 9 provided with the supply screw 8 is arranged in the lateral direction of the developing roller 5, and a collection conveyance path 7 provided with the collection screw 6 is arranged in parallel below the development roller 5.
The developer can be separated from the developing roller 5 by setting the magnetic body in the developing sleeve described above to a state where there is no magnetic pole only at a position where the developer is desired to be separated. Yes. Further, a magnetic body having a magnetic pole arrangement in which a repulsive magnetic field is formed at a location to be separated may be used.

  The developing device 4 is provided with a stirring conveyance path 10 in parallel with the collection conveyance path 7 below the supply conveyance path 9. The agitating / conveying path 10 is arranged in parallel to the axial direction as an agitating / conveying member that conveys the developer along the axial direction of the developing roller 5 and conveys the developer to the back side in the figure, which is opposite to the supply screw 8. The screw-shaped stirring screw 11 having a helical stirring blade portion 11b fixed to the stirring shaft portion 11a is provided.

The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition wall. As for the part which partitions the supply conveyance path 9 and the stirring conveyance path 10 of the first partition wall 133, both ends of the front side and the back side in the figure are openings, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. is 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 recovery conveyance path 7 of the first partition wall 133 are partitioned. Absent.
In addition, the two developer conveyance paths of the agitation conveyance path 10 and the recovery 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 stirring conveyance path 10 and the collection conveyance path 7 communicate with each other.
The developer screw, supply screw 8, recovery screw 6 and stirring screw 11 are made of resin or metal screws, and each screw has a diameter of φ22 [mm] and a screw pitch of 50 [mm]. The winding, the recovery screw 6 and the stirring screw 11 are set to a single winding of 25 [mm], and the number of rotations is all set to about 600 [rpm].
Further, in the developing device 4 of the present embodiment, the total length of the stirring conveyance path 10 is 410 [mm], and the total length of the supply conveyance path 9 is 320 [mm].

The developer thinned by the doctor blade 12 made of stainless steel on the developing roller 5 is transported to a developing area which is a portion facing the photosensitive member 1 for development. The surface of the developing roller 5 is V-grooved or sandblasted, and is made of an Al or SUS element tube of φ25 [mm], and the gap between the doctor blade 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 second partition wall 134 provided in the non-image area portion. Developer is transferred. Note that toner is supplied to the stirring and conveying path 10 from a toner replenishing port 95 (described later) provided on the upper side of the stirring and conveying path 10 in the vicinity of the opening of the second partition wall 134 on the upstream side in the developer conveying direction in the stirring and conveying path 10. Supplied.

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 developer conveyance direction of the supply screw 8 while supplying the developer to the developing roller 5. Then, the excess developer that has not been supplied to the developing roller 5 and has been conveyed to the downstream end of the supply conveyance path 9 in the developer conveyance direction is supplied to the agitation conveyance path 10 from the excessive opening 92 of the first partition wall 133. (Arrow E in FIG. 4).
On the other hand, the developer supplied to the developing roller 5 is used for development in the developing region, and then separated / separated from the developing roller 5 and delivered to the collection conveyance path 7. The collected developer that has been transferred from the developing roller 5 to the collection conveyance path 7 and conveyed to the downstream end in the developer conveyance direction of the collection conveyance path 7 by the collection screw 6 is stirred from the collection opening 93 of the second partition wall 134. It is supplied to the conveyance path 10 (arrow F in FIG. 4).
The agitating and conveying path 10 agitates the supplied excess developer and the recovered developer, conveys the agitating screw 11 downstream in the developer conveying direction, conveys the supplying screw 8 upstream in the developer conveying direction, It is supplied to the supply conveyance path 9 from the supply opening 91 of the first partition wall 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 transported to the upstream side in the developer transport direction of the supply transport path 9 communicating with the supply opening 91 on the downstream side in the developer transport direction. A toner concentration sensor 201 composed of a magnetic permeability sensor is provided below the agitation transport path 10, and a toner replenishment control device (not shown) is operated by the sensor output to replenish toner from a toner storage portion (not shown). Yes. Details of the height of the developer in the developing device 4 and the arrangement of the toner density sensor 201 will be described later.

  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. For this reason, it is possible to prevent the toner concentration of the developer supplied to the developing roller 5 from decreasing toward the downstream side of the supply conveyance path 9 in the developer conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and the agitation are performed in different developer conveyance paths, the developed developer does not fall in the middle of the agitation. Thereby, since the sufficiently stirred 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 stirred. 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, so that the image density during development can be reduced. 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 the arrow D is to push the developer into the downstream side of the agitation transport path 10 by the rotation of the agitation screw 11 so that the developer rises and supplies the developer to the supply transport 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, the life of the developer can be extended by reducing the stress of the developer in the movement of the developer indicated by the arrow D. 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.

In the developing device 4 of this embodiment, as shown in FIG. 2, the supply conveyance path 9 is disposed obliquely above the stirring conveyance path 10. By disposing it obliquely above, it is possible to reduce the developer stress in the movement of the developer indicated by the arrow D, as compared with 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 agitation conveyance path 10 causes the developer to be stressed because the developer is lifted by the pressure of the agitation 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, the developer can be delivered more efficiently from the stirring conveyance path 10 to the supply conveyance path 9.

Further, in the developing device 4, the supply conveyance path 9 and the agitation are stirred so that the center distance A between the development roller 5 and the supply conveyance path 9 is shorter than the center distance B between the development roller 5 and the agitation conveyance path 10. A conveyance path 10 is arranged. As a result, 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 rotates counterclockwise as viewed from the front side in FIG. 2 (the arrow C direction 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.

FIG. 5 is a cross-sectional explanatory view of the cross section at the rotation center of the supply screw 8 of the developing device 4 as viewed from the direction of arrow J in FIG. In the figure, H denotes a developing region in which the developing roller 5 that is a developer carrying member supplies toner to the photosensitive member 1 that is a latent image carrying member. The width in the axial direction of the rotation axis of the developing roller 5 in the developing area H is the developing area width α.
As shown in FIG. 5, the developing device 4 includes a supply opening 91 that is a part for lifting the developer from the agitation conveyance path 10 to the supply conveyance path 9, and a surplus for dropping the developer from the supply conveyance path 9 to the agitation conveyance path 10. Both of the openings 92 are provided in the development region width α.

FIG. 6 is a schematic diagram of the developer flow in the developing device 4 having a configuration different from that in FIG. 4.
The developing device 4 shown in FIG. 6 is provided with a supply opening 91 and a surplus opening 92 outside the developing region width α. Since the supply opening 91 is provided outside the development area width α, the upstream side of the supply conveyance path 9 in the developer conveyance direction is longer than the development roller 5 by the supply conveyance path upstream area β. Further, since the surplus opening 92 is provided outside the developing region width α, the downstream side of the supply transport path 9 in the developer transport direction is longer than the developing roller 5 by the region γ on the downstream side of the supply transport path.

On the other hand, in the developing device 4 configured as shown in FIG. 4, the supply opening 91 is provided in the developing region width α, so that the upstream side in the developer transport direction of the supply transport path 9 is supplied from the developing device 4 in FIG. 6. It can be shortened by the conveyance path upstream side region β. Further, since the surplus opening 92 is provided in the developing region width α, the downstream side in the developer transport direction of the supply transport path 9 may be shorter than the developing device 4 in FIG. 6 by the downstream transport region γ. it can.
4 is provided with the supply opening 91 and the surplus opening 92 within the developing region width α, the upper portion of the developing device 4 is higher than that of the developing device 4 shown in FIG. Space saving can be achieved.

Next, the position at which toner is supplied to the developer conveyance path including the supply conveyance path 9, the agitation conveyance path 10, and the recovery conveyance path 7 of the developing device 4 will be described. FIG. 7 is an external perspective view of the developing device 4.
As shown in FIG. 7, a toner replenishing port 95 for replenishing toner is provided above the upstream end portion in the developer transport direction of the stirring transport path 10 including the stirring screw 11. Since the toner replenishing port 95 is provided outside the end portion in the width direction of the developing roller 5, it is outside the developing region width α.
The portion where the toner replenishing port 95 is provided is on an extension line in the conveyance direction of the supply conveyance path 9 and corresponds to a vacant space in the region γ on the downstream side of the supply conveyance path in FIG. Providing the toner replenishment port 95 in an empty space by providing the surplus opening 92 within the developing region width α makes it possible to reduce the size of the developing device 4.
Further, the toner replenishing port 95 is not limited to a position above the upstream end of the agitation transport path 10 in the developer transport direction, and may be provided above the downstream end of the recovery transport path 7.
Further, a toner replenishing port 95 may be provided just above the collection opening 93 which is a place where the developer is transferred from the collection conveyance path 7 to the stirring conveyance path 10. Since the space directly above the collection opening 93 is also an empty space provided by providing the surplus opening 92 within the developing region width α, the toner replenishing port 95 is provided at this position to reduce the size of the developing device 4. Can be planned. Furthermore, since the developer is likely to be mixed in the collection opening 93 which is a delivery unit, the developer can be more efficiently stirred by replenishing at this position.

As in the developing device 4 described with reference to FIG. 4, the supply opening that delivers the developer from the downstream end of the agitation transport path 10 in the developer transport direction to the upstream end of the supply transport path 9 in the developer transport direction 91 and a surplus opening 92 for delivering the developer from the downstream end of the supply transport path 9 in the developer transport direction to the upstream end of the stirring transport path 10 in the developer transport direction is provided in the development region width α. Therefore, compared to the conventional developing device 4, the space above the developing device 4 can be saved, and the space of the entire developing device 4 can be saved.
Also, by providing the toner replenishment port 95 in the empty space by providing the surplus opening 92 within the development region width α, the development device 4 can be downsized.
Further, the developer can be more efficiently stirred by replenishing the toner from above the recovery opening 93 which is a developer delivery portion from the recovery transport path 7 to the stirring transport path 10.
Further, by providing the developing device 4 as the developing means of the printer unit 100 of the copying machine 500 as an image forming apparatus, it is possible to save the space of the entire apparatus.

  A toner replenishment control device (not shown) that is a developer replenishing unit replenishes toner in a toner storage unit (not shown) to the developing device 4 from the toner replenishing port 95. In the developing device 4 of this embodiment, a developer including toner and a carrier is supplied from a toner supply port 95 of the developing device 4. Hereinafter, the developer in which the toner supplied to the developing device 4 and the carrier are mixed is referred to as premix toner.

FIG. 8 is a perspective explanatory view of the vicinity of the front side end portion in a state where the discharge screw 2a, the stirring screw 11, the recovery screw 6, and the doctor blade 12 as the discharge conveyance member are removed from the developing device 4.
In the developing device 4 of the present embodiment, the circulation conveyance path that conveys the excess developer that has reached the downstream end of the supply conveyance path 9 in the developer conveyance direction to the upstream end of the supply conveyance path 9 in the developer conveyance direction is stirred. This is the conveyance path 10. In addition, the circulating and conveying member that applies a conveying force to the developer in the agitating and conveying path 10 that is the circulating and conveying path is the agitating screw 11. Further, a surplus opening 92 is a circulation opening provided in the vicinity of the downstream end of the supply conveyance path 9 in the developer conveyance direction and through which the passed developer is transferred to the stirring conveyance path 10 which is a circulation conveyance path. Further, the developing device 4 is provided with a developer discharge port 94 as a developer discharge means in which the developer that has passed is discharged to the outside of the developing device 4 in the supply conveyance path 9. The developer that has passed through the developer discharge port 94 is delivered as a discharged developer to the discharge conveyance path 2, and the discharge screw 2 a rotates to move in the conveyance direction of the supply conveyance path 9 (on the front side in FIGS. 2 and 8). It is conveyed in the opposite direction (the direction toward the back side in FIG. 2 and FIG. 8).
The discharge conveyance path 2 is arranged on the downstream side of the supply conveyance path 9 in the developer conveyance direction so as to be adjacent to the supply conveyance path 9 with the discharge partition wall 135 interposed therebetween, and the developer discharge port 94 is connected to the supply conveyance path 9 and discharge conveyance. It is an opening provided in the discharge partition wall 135 so as to communicate with the path 2.

  Further, the developing device 4 reaches the vicinity of the downstream end of the supply conveyance path 9 in the developer conveyance direction, and retains the developer that has not entered the excessive opening 92 that is the circulation opening in the vicinity of the excessive opening 92. A supply downstream side end wall surface 80 as a developer retaining means is provided. Further, the developer discharge port 94 that is a discharge opening reaches the position of the developer discharge port 94 among the staying developer that is located above the surplus opening 92 and is retained by the supply downstream end wall surface 80. The developer is passed through. In other words, the developer that has reached the vicinity of the downstream end of the supply transport path 9 in the developer transport direction cannot enter the surplus opening 92 and the surplus developer overflowing from the surplus opening 92 is supplied downstream. It is blocked by the end wall surface 80 and becomes a staying developer. When the volume of the staying developer increases, the developer that reaches the developer discharge port 94 provided above the surplus opening 92 is discharged to the discharge conveyance path 2 through the developer discharge port 94. Is done.

FIG. 9 shows a discharge conveyance for receiving the discharged developer conveyed to the outside of the developing casing of the developing device 4 through the discharge conveyance path 2 and conveying the discharged developer to a discharged developer tank 600 which is a discharged developer storage unit. FIG. 6 is an explanatory diagram of a discharged developer transfer pipe 601 that is a path.
What is the developer discharge port 94 from the supply conveyance path 9 in each developing device 4 (Y, M, C, K) through the developer discharge port 94 and each discharge conveyance path 2 (Y, M, C, K)? The developer is conveyed to the end of the developing device 4 on the opposite side, and the discharged developer is discharged out of the developing casing of the developing device 4.
The developer transported to the downstream end portion in the developer transport direction of each discharge transport path 2 (Y, M, C, K) and discharged from the casing of the developing device 4 is a developer receiving port 604 (Y, M, C). , K) enters the discharged developer transfer pipe 601. The discharged developer transfer pipe 601 includes a discharge storage screw 602 that is a discharge storage transport member that applies a transport force to the discharged developer in the discharge developer transfer pipe 601. A discharge developer screw drive source 603 is provided at one end of the discharge developer transfer pipe 601, and the developer in the discharge developer transfer pipe 601 is sequentially transferred by the rotation of the discharge storage screw 602, and discharged and developed outside the developing device 4. Is accommodated in a discharged developer tank 600 which is an agent accommodating portion.
Although FIG. 9 shows a configuration in which the discharged developer conveyed by each discharge conveyance path 2 (Y, M, C, K) is conveyed to one discharge developer tank 600, each discharge conveyance path 2 is shown. A discharge developer tank 600 for each color corresponding to each of (Y, M, C, K) may be provided individually.

Next, the characteristic part of this embodiment is demonstrated.
Changes in the height of the developer in the developing device 4 of the present embodiment will be described with reference to FIG.
The hatched areas in the supply conveyance path 9, the agitation conveyance path 10, and the recovery conveyance path 7 in FIG. 4 schematically show the height of the developer in each conveyance path. 2 is a cross-sectional view at a position where the toner density sensor 201 is provided in the developer conveyance direction, and the description of the developer is omitted in FIG.
First, the supply conveyance path 9 has a large amount of developer at the upstream end portion in the developer conveyance direction, and the supply conveyance path 9 conveys the developer while supplying the developer to the developing roller 5. The developer amount decreases as the time goes. For this reason, the height of the developer in the supply conveyance path 9 is higher on the upstream side in the developer conveyance direction and lower on the downstream side in the developer conveyance direction.
As for the collection conveyance path 7, the amount of developer is small on the upstream side in the developer conveyance direction, and the developer conveyance path 7 conveys the developer while collecting the developer from the developing roller 5. The amount of increases. For this reason, the height of the developer in the collection transport path 7 is low on the upstream side in the developer transport direction, and is higher on the downstream side in the developer transport direction.

  On the other hand, the amount of the developer in the agitating / conveying path 10 is little changed from the upstream to the middle in the developer conveying direction, and the difference in the height of the developer due to the difference in the position in the developer conveying direction is small. However, since the developer is lifted up to the supply conveyance path 9 above the supply opening 91, the developer stagnates near the downstream end of the agitating conveyance path 10 in the developer conveyance direction, and the amount of the developer is large. is there. For this reason, the height is rapidly increased toward the downstream side in the developer conveyance direction of the agitation conveyance path 10 and the developer is filled up to the upper part of the agitation conveyance path 10.

Here, the amount of the developer in the developing device 4 increases or the amount of air contained between the developer particles increases, so that the bulk of the developer in the entire developing device 4 increases. In this case, the height of the developer increases up to the area indicated by the broken line in FIG. That is, when the volume of the developer in the entire developing device 4 increases, the height of the developer in the supply conveyance path 9 increases. In the agitating and conveying path 10, the width of the area where the developer is filled to the upper part is widened, and the height of the developer as a whole increases even in the area where the developer does not reach the upper part of the conveying path. Further, since the height of the developer rises as a whole even in the region where the developer in the agitation transport path 10 does not reach the upper part, even at the position of the recovery opening 93 at the upstream end in the developer transport direction of the agitation transport path 10. The height of the developer increases. Here, if the height of the developer on the stirring and conveying path 10 side is higher than the height of the developer on the collecting and conveying path 7 side across the collection opening 93, the developer from the collecting and conveying path 7 to the stirring and conveying path 10 Since the delivery is not performed, if the height of the developer rises at the position of the collection opening 93 at the upstream end in the developer conveyance direction of the agitation conveyance path 10, the developer conveyance direction of the collection conveyance path 7 is affected by the influence. The height of the developer near the downstream end also increases.
Note that the change in the height of the developer at each position of each developer transport path when the bulk of the developer in the entire developing device 4 is reduced is reversed.
Further, when the flowability of the developer changes over time, the amount of developer passing through the gap between the developing roller 5 and the doctor blade 12 changes, and the amount of developer passing through the developing region also changes, so the supply conveyance path 9 and the amount of the developer in the recovery transport path 7 change, and the height of the developer in the recovery transport path 7 varies not only in the vicinity of the downstream end portion in the developer transport direction but also in the developer transport direction.

Here, the developer is filled when the bulk of the developer in the entire developing device 4 is the smallest in the vicinity of the downstream end portion in the developer conveyance direction of the agitation conveyance path 10 and within a range in which image formation can be followed. In the state region, the height of the developer is substantially constant even if the bulk of the developer in the entire developing device 4 changes or the flowability of the developer changes. By disposing the toner concentration sensor 201 at a position in a region where the developer is filled when the bulk of the developer in the entire developing device 4 is the smallest, the developer in the agitating and conveying path 10 Of these, the amount of developer present in the range in which the toner concentration sensor 201 detects the magnetic permeability becomes substantially constant, so that the toner concentration can be accurately detected.
Even in the full region, it is desirable to dispose the toner density sensor 201 at a position other than the position where the supply opening 91 is provided. This is due to the following reason.
That is, when the toner concentration sensor 201 is disposed below the supply opening 91, the developer in the supply conveyance path 9 further above the supply opening 91 may be within the detection range. When the bulk of the developer in the entire developing device 4 changes, the height of the developer in the supply conveyance path 9 changes as a whole, so that the detection range of the toner density sensor 201 extends to the developer in the supply conveyance path 9. This is because the toner density cannot be accurately detected if it is included. Further, since the developer can move from the supply opening 91 to the supply conveyance path 9 at the position where the supply opening 91 is provided, the pressure in the developer escapes and the density of the developer becomes rough. Therefore, it is desirable to arrange the toner density sensor 201 at a position other than the position where the supply opening 91 is provided.

Further, the height of the developer in the developer transport path varies depending on whether the developing device 4 is driven or stopped even if the amount is the same. This is because when the developing device 4 is driven, the developer rises by the rotation of the screw. In the position where the supply opening 91 of the developing device 4 of the present embodiment is provided, the transfer from the stirring conveyance path 10 to the upper supply conveyance path 9 can be performed in a state where the apparatus is driven so that the image formation can be followed. The height of the developer to be performed is required. For this reason, the developer is present up to a height at which the supply opening 91 is immersed in the developer at the position where the supply opening 91 is provided when the apparatus is driven.
In this embodiment, the state where the developer is present up to the same height as the developer at the position where the supply opening 91 is provided in a state where the apparatus is driven is referred to as a state where the developer is filled.
Since the supply opening 91 is located at a position higher than the upper end of the stirring screw 11, in the region where the developer is filled, the position of the developer surface in the state where the apparatus is driven is the stirring screw. 11 is higher than the upper end of 11.

In the developing device 4 of the present embodiment, a supply opening 91 (width in the axial direction: 50 [mm]) is disposed at the downstream end of the developer transport direction in the 410 [mm] agitation transport path 10, and the developer. The toner density sensor 201 is disposed at a position of 70 mm from the wall surface at the downstream end in the transport direction.
In the developing device 4 of the present embodiment, the position where the toner density sensor 201 is disposed is 90 mm from the wall surface of the downstream end portion in the developer transport direction at a position upstream of the supply opening 91 in the developer transport direction. It was confirmed that the toner density can be detected satisfactorily by disposing it in the range up to the position of [].

FIG. 10 is an explanatory diagram of positions where the toner density sensor 201 can be arranged.
Since the toner density sensor 201 is disposed at a position where the developer is filled, it can be installed at any position a to d in FIG. The range of a to d in FIG. 10 is a range from the bottom surface of the stirring conveyance path 10 to the height of the stirring shaft portion 11 a of the stirring screw 11. When the stirring shaft 11a is in the range up to the height as described above, the developer tends to be tightened by the weight of the developer, and the centrifugal force due to the rotation of the stirring screw 11 is directed toward the wall surface forming the stirring conveyance path 10. Therefore, when the developer is fluidized, it is possible to accurately detect the toner concentration in which bubbles are difficult to enter. Further, since the developer present in the region above the stirring blade portion 11b of the stirring screw 11 is difficult to be drawn downward and may not be sufficiently stirred, the toner concentration sensor 201 is shown in FIG. It installs in the range of ad.
Even in the range of a to d in FIG. 10, the best position for disposing the toner density sensor 201 is the position c in FIG. 10 as in the developing device 4 of the embodiment shown in FIG. 2. In the developing device 4 of the present embodiment, the stirring screw 11 rotates in the clockwise direction in the drawing, and therefore, the stirring shaft portion 11a is downstream of the stirring screw 11 in the rotation direction with respect to the lowest position of the stirring conveyance path 10. The position c in FIG. 10, which is a position lower than the height of the toner, can accurately detect the toner concentration at which the pressure applied to the developer is the highest and bubbles are difficult to enter when the developer is fluidized. It becomes possible.

11 and 12 are perspective explanatory views of the process cartridge 18.
As shown in FIG. 11, the developing device 4 is temporarily positioned on the frame of the process cartridge 18 and then positioned on the surface opposite to the drive side of the frame of the process cartridge 18 as shown in FIG. 905 is attached and positioned. The photoreceptor 1 and the developing roller 5 are correctly positioned by the positioning plate 905, and the process cartridge 18 in which the photoreceptor 1 and the developing device 4 are integrated is configured. In addition, the distance between the central axis of the photoreceptor 1 and the central axis of the developing roller 5 is correctly regulated by the positioning plate 905. As a result, when the photosensitive member 1 and the developing roller 5 are arranged to face each other with a minute gap, the gap is correctly maintained, and a high-quality toner image is developed on the photosensitive member 1. be able to. Further, when the photosensitive member 1 and the developing roller 5 are configured to contact each other and face each other, the contact pressure is correctly regulated, and a high-quality toner image is developed on the photosensitive member 1. Can do.

As the two-component developer used in the developing device 4 of the present embodiment, a magnetic carrier containing a small particle diameter carrier can be used.
In recent years, there has been an increasing demand for further stabilization and higher image quality of electrophotographic images. In particular, attempts have been made to minimize and increase the density of the minimum latent image unit (1 dot) for the purpose of improving the image quality. To that end, it is important to faithfully develop the minimized latent image. It has become. Further, for stable image quality, it is an important issue to reduce variation in the charge amount distribution of the developer.
In order to reduce the variation in the charge distribution of the developer and faithfully develop the latent image, it is considered that reducing the particle size of the carrier is effective.
Examples of small particle size carriers include the following.
A carrier comprising core particles and a coating layer covering the particles, wherein the carrier has a weight average particle diameter Dw of 22 [μm] or more and 32 [μm] or less, and a number average particle diameter Dp and a weight average particle diameter Dw The ratio Dw / Dp is 1.00 ≦ Dw / Dp ≦ 1.20, the particle size x [μm] is in the range of 0 <x <20, the particle content is 7% by weight or less, and the particle size y [ μm] is a carrier in which the content of particles in the range of 0 <y <36 is 90 [wt%] or more and 100 [wt% or less].
Note that the small particle size carrier is not limited to this, and the developer used in the developing device 4 having the features of the present invention is not limited to the small particle size carrier.
A developer containing a carrier having a small particle diameter is used for improving the image quality. However, the developer containing a carrier having a small particle diameter easily changes in fluidity due to deterioration with time, and air between the developer particles. However, with the developing device 4 of the present embodiment, it is possible to accurately detect the toner density even when the flowability of the developer changes due to deterioration over time.

As described above, the developing device 4 of the present embodiment carries the two-component developer composed of the toner and the magnetic carrier on the surface and rotates, and the photosensitive member 1 at a position facing the photosensitive member 1 that is a latent image carrier. A developing roller 5 that is a developer carrying member that supplies toner to a latent image on the surface of the toner and develops it, a developing casing that forms a developer containing portion that contains the developer supplied to the developing roller 5, Toner density detection that detects the ratio of toner in the developer in the vicinity of each of the screws (6, 8 and 11), which are a plurality of developer conveying members that convey the developer, and the toner density detecting unit disposed in the developing casing. And a toner density sensor 201 as means. The developing device 4 is a partition member that partitions the space in the developing casing and forms a plurality of developer transport paths (7, 9 and 10) in which the screws (6, 8 and 11) are arranged in the space. A supply screw 8 that is an upper developer conveying member that has a certain first partition wall 133 and a second partition wall 134 and is arranged vertically with a first partition wall 133 that is a partition member as a plurality of screws. And a stirring screw 11 which is a developer conveying member. Further, in the space in the developing casing, there are an agitation conveyance path 10 which is a lower developer conveyance path where the agitation screw 11 is arranged by the first partition wall 133 and an upper developer conveyance path where the supply screw 8 is arranged. The supply conveyance path 9 is formed, and an opening that communicates the agitation conveyance path 10 and the supply conveyance path 9 at a position near the downstream end in the developer conveyance direction in the agitation conveyance path 10 in the first partition wall 133. Is provided, and a toner concentration sensor 201 as a toner concentration detection unit is disposed on the downstream side in the developer conveyance direction in the agitation conveyance path 10. In such a developing device 4, the developer that has reached the vicinity of the downstream end of the agitating / conveying path 10 in the developer conveying direction by the agitating screw 11 is pushed up by the developer coming later and is supplied to the first partition wall 133. When it reaches the height of the portion 91, it passes through the supply opening 91 and is delivered to the supply conveyance path 9. Therefore, the developer is present up to the height of the supply opening 91 when the developing device 4 is driven in the agitation transport path 10 at the position where the supply opening 91 is provided in the first partition wall 133.
Further, when the bulk of the developer in the entire developing device 4 increases, the height of the developer in the entire developer transport path (7, 9 and 10) in the device increases. In the agitation transport path 10 at the position where the supply opening 91 is provided on the wall 133, the developer exceeding the height of the supply opening 91 is delivered to the supply transport path 9.
Thus, in the stirring conveyance path 10 in the vicinity of the position where the supply opening 91 is provided in the first partition wall 133, the developer exists up to the height of the supply opening 91 in a state where the developing device 4 is driven. Since the developer is filled in the internal space, the stirring conveyance path 10 in the vicinity of the position where the supply opening 91 is provided in the first partition wall 133 even if the volume of the developer in the entire apparatus changes. The height of the developer in the inside hardly changes. In the agitating and conveying path 10, the closer to the position where the supply opening 91 is provided in the first partition wall 133, the height of the developer at that position relative to the amount of change in the developer bulk in the entire apparatus. The amount of change of becomes smaller. In the developing device 4, the height of the developer is changed by providing the toner concentration sensor 201 on the downstream side in the developer conveyance direction in the agitation conveyance path 10 where the change amount of the developer becomes small. The influence of the apparent change in permeability can be suppressed. Therefore, the toner concentration of the developer in the apparatus can be detected stably and accurately as compared with the configuration in which the toner concentration sensor 201 is provided at another position.
Further, stable and good development can be performed by controlling the toner supply based on the detection result.
The state in which the supply screw 8 and the stirring screw 11 are arranged above and below means that the supply screw 8 is above the stirring screw 11, and at least a part of the vertical projection surface of the supply screw 8 and the stirring screw 11. In this state, at least a part of the projection surface in the vertical direction is arranged so as to overlap.

  Further, in the developing device 4, the position where the toner concentration sensor 201 is disposed in the stirring conveyance path 10 is located in the stirring conveyance path 10 with respect to the position in the stirring conveyance path 10 where the supply opening 91 is provided in the developer conveyance direction. Is a position upstream of the developer conveyance direction. As a result, the toner density can be accurately detected without being affected by the change in the height of the developer in the supply conveyance path 9.

  Further, in the developing device 4, the space in which the toner density sensor 201 is arranged in the internal space of the agitation transport path 10 is in a state where the developer is filled, so that the amount of developer in the developing device 4 changes. Even if the developer fluidity changes, the toner density can be detected at a location where the amount of displacement of the developer is small.

Further, in the developing device 4, the toner concentration sensor 201 is located between the bottom surface in the stirring and conveying path 10 and the side surface of the stirring and conveying path 10 that is the height of the stirring shaft portion 11 a of the stirring screw 11. By disposing in this range, it is possible to accurately detect the toner concentration where bubbles are difficult to enter when the developer is fluidized.
Furthermore, the stirring conveyance path which becomes the same height as the stirring shaft part 11a on the downstream side in the rotation direction of the stirring screw 11 from the bottom surface center position which is vertically below the stirring shaft part 11a on the bottom surface in the stirring conveyance path 10 When the toner concentration sensor 201 is disposed at a position c in FIG. 10 up to the position of the side surface 10, the pressure applied to the developer becomes the highest and bubbles are generated when the developer is fluidized. It is possible to accurately detect the toner concentration where it is difficult to enter.

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 an optical writing unit 21 and a developing unit for developing an electrostatic latent image into a toner image, includes the developing unit 4 as a developing unit. The toner concentration of the developer in the apparatus 4 can be detected stably and accurately, and a good image can be stably obtained by controlling toner supply based on the detection result.
In addition, at least the photosensitive member 1 and the developing unit in the copying machine 500 that is an image forming apparatus including the photosensitive member 1 that is a latent image carrier that carries a latent image and a developing unit that develops the latent image on the photosensitive member 1. The process cartridge 18 that is held on a common holding body as a unit and is detachable from the copying machine 500 main body includes the developing device 4 as the developing means, thereby stabilizing the toner concentration of the developer in the device. By accurately detecting and controlling toner replenishment based on the detection result, it is possible to easily attach and detach the developing device 4 capable of performing stable and good development to the copier 500.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Discharge conveyance path 2a Discharge screw 4 Developing apparatus 5 Developing roller 6 Collecting screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 11a Stirring shaft part 11b Stirring blade part 12 Doctor blade 14 Tension 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 26 Fixing belt 27 Pressure roller 80 downstream end wall surface 90 belt cleaning device 91 supply opening 92 surplus opening 93 recovery opening 94 developer discharge port 95 toner supply port 100 printer unit 110 intermediate transfer belt 133 first partition wall 134 second partition wall 135 discharge Partition wall 201 Toner concentration sensor 500 Copier 600 Discharged developer tank 601 Discharged developer transfer pipe 602 Discharge containing screw 603 Discharge containing screw drive source 604 Developer receiving port

JP 2005-31119 A JP 2007-34043 A

Claims (7)

A developer that carries a two-component developer comprising toner and a magnetic carrier on the surface, rotates, supplies the toner to the latent image on the surface of the latent image carrier, and develops it at a location facing the latent image carrier. A carrier,
A developer accommodating portion for accommodating a developer to be supplied to the developer carrying member;
A plurality of developer conveying members for conveying the developer in the developer accommodating portion;
A developing device having toner concentration detecting means for detecting a ratio of toner in the developer in the vicinity of the toner concentration detecting portion disposed in the developer containing portion;
A partition member that partitions the space in the developer accommodating portion and forms a plurality of developer transport paths in which the developer transport member is disposed in the space;
As the plurality of developer conveying members, an upper developer conveying member and a lower developer conveying member disposed above and below the partition member,
A lower developer transport path in which the lower developer transport member is disposed by the partition member and an upper developer transport path in which the upper developer transport member is disposed are formed in the space in the developer accommodating portion,
An opening for communicating the lower developer transport path and the upper developer transport path is provided at a position near the downstream end of the developer transport direction in the lower developer transport path in the partition member;
2. A developing apparatus according to claim 1, wherein the toner density detecting section is arranged on the downstream side in the developer conveying direction in the lower developer conveying path. The developing device according to claim 1.
The position where the toner density detection unit is arranged in the lower developer conveyance path is located in the lower developer conveyance path with respect to the position where the opening is provided in the developer conveyance direction in the lower developer conveyance path. A developing device, wherein the developing device is located upstream of the developer conveying direction. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein a space portion in which the toner density detection unit is disposed in an internal space of the lower developer conveyance path is in a state where the developer is filled. The developing device according to any one of claims 1 to 3,
The lower developer conveying member is a screw member that conveys the developer in the axial direction by rotating and fixing a helical wing to the shaft part,
The development is characterized in that the toner density detecting portion is arranged between a bottom surface in the lower developer transport path and a side surface of the lower developer transport path which is the height of the shaft portion of the lower developer transport member. apparatus. The developing device according to claim 4.
The toner concentration detection unit is disposed on the downstream side in the rotational direction of the lower developer transport member from the bottom surface center position that is vertically below the shaft portion on the bottom surface in the lower developer transport path with respect to the bottom surface center position. A developing device, wherein the developing device is disposed up to the position of the side surface having the same height as the shaft portion. 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. In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, at least the latent image carrier and the developing unit are shared as one unit. In the process cartridge that is held by the holding body and is detachable from the image forming apparatus main body,
6. A process cartridge using the developing device according to claim 1 as the developing means.

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