JP5158473B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like and an image forming apparatus 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. As an image forming apparatus of this type, the toner density of the developer is kept within a predetermined range by supplying toner from the toner container as necessary to the developer in the developing apparatus that consumes toner with development. There is something to keep in. In such a configuration, the carrier in the developer is hardly consumed and used repeatedly, and therefore the carrier deteriorates as the image is output. Specifically, the coating film on the carrier surface is scraped by mechanical stress or the toner component is spent on the carrier surface. When the carrier is deteriorated, the ability of the carrier to charge the toner gradually decreases, causing an abnormal image such as background stain, image density reduction, and uneven image density, and image quality reduction such as toner scattering. For this reason, in this type of image forming apparatus, a service person regularly visits the user to exchange carriers. For this reason, maintenance costs are incurred, and the unit price for image formation is high.

  In Patent Document 1 and Patent Document 2, a premix developer in which a carrier and toner are mixed is supplied to the developer in the developing device to restore the toner density, and an increased amount of developer is removed from the developing device. A developing device to be discharged is described. In such a configuration, a new carrier in the premix developer is replenished to the developer in the developing device while the carrier that has become old due to the discharge of the developer is gradually discharged from the developing device. Then, the carrier replacement work can be omitted by replacing the carrier in the developer gradually with a new one by such discharge and replenishment.

  In the developing device described in Patent Document 1, a sensor for detecting the amount of developer is provided in a developer transport path through which the developer circulates in the developing device, and a shutter mechanism for opening and closing the developer discharge portion. In normal operation, the shutter is closed so that the developer is not discharged, and when the sensor detects that the volume of the developer exceeds a certain level, the shutter opens and the developer is discharged. ing. However, in this method, the configuration becomes complicated and the cost increases.

  In the developing device described in Patent Document 2, the developer is supplied to the developing roller on the side wall on the downstream side of the position where the developer is supplied to the developing roller in the supply conveyance path that conveys the developer in the axial direction of the developing roller. The developer is discharged out of the developing device from the provided developer discharge port. A circulation opening that communicates with the circulation conveyance path that delivers the developer to the upstream end of the supply conveyance path is provided downstream of the position where the developer discharge port is provided. In this developing device, when the premix developer is supplied and the amount of developer in the developing device increases, the bulk of the developer in the supply conveyance path increases. At this time, the developer that reaches the height of the developer discharge port at the position where the developer discharge port is provided is discharged from the developer discharge port to the outside of the developing device, and is not discharged at the position where the developer discharge port is provided. The developer is fed to the circulation conveyance path through the circulation opening. Further, in the state where the volume of the developer in the supply conveyance path does not change, the developer does not reach the height of the developer discharge port at the developer discharge port, so the developer is not discharged, and the supply conveyance path The developer that reaches the downstream side of the toner is sent to the circulation conveyance path.

  In such a developing device, the increased amount of developer supplied by the premix developer is discharged from the developer discharge port, so that the carrier in the developer in the device is gradually replaced with a new one. Can continue. Further, since the developer is not discharged in a state where the volume of the developer in the supply conveyance path does not change, it is possible to prevent the developer amount in the developing device from decreasing. Further, when the volume of the developer reaches the height of the developer discharge port at the position of the developer discharge port, the developer that has reached the height of the developer discharge port is naturally discharged from the developer discharge port to the outside of the apparatus. . For this reason, a complicated developer discharging mechanism including a sensor and a shutter as in the developing device described in Patent Document 1 is not required, and it is possible to prevent the configuration from becoming complicated and costly.

Japanese Patent No. 2891845 JP 2000-112238 A

  However, if the developer fluidity decreases due to environmental fluctuations and the like and the developer aggregates, it becomes difficult to smoothly feed the developer sent from the supply conveyance path to the developer discharge port. For this reason, there is a problem that the excess developer due to the replenishment of the developer is not properly discharged from the developer discharge port, and the amount of developer in the developing device becomes larger than necessary.

  So far, an example in which both the toner and the carrier are supplied to the developing device using the premix developer has been described, but the same problem may occur in the following cases. That is, there are a case where the toner and the carrier are replenished separately, and a case where one of the toner and the carrier and the premix developer are replenished.

  Further, in a developing device using a one-component developer composed only of toner, the developer is replenished in the developing device, and the excess developer due to the replenishment is discharged from the developer discharge port to the outside of the device. Then, the same problem as described above may occur.

  SUMMARY OF THE INVENTION 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 and a developing device capable of appropriately discharging the developer to the outside of the apparatus even if the fluidity is reduced and the developer is aggregated Is provided.

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 member for developing and a developer carrying member for carrying the developer, and in the developer supply region for supplying the developer to the developer carrying member, the developer is supplied to the developer carrying member. The developer transport path for transporting the developer, and a predetermined height at a location in the developer transport path where the volume of the developer increases or decreases in accordance with the increase or decrease of the developer amount in the entire developer transport path. In addition, in the developing device that includes a developer discharging unit that discharges the developer to the outside of the device, and the developer is sent to the developer discharging unit by increasing the volume of the developer, and discharges the developer to the outside of the device. A developer loosening means for loosening the developer sent to the developer discharge section is provided in the vicinity of the developer discharge section. Parallel to the conveying member, and, as soak in the developer conveyance path in the developer conveyance direction downstream side of the developer, and provided separately from the developer conveying member, the same direction as the developer conveying member The developer loosening means is operated so as to transport the developer to the top.
According to a second aspect of the present invention, in the developing device of the first aspect, the developer loosening means is a screw member.
According to a third aspect of the present invention, in the developing device of the second aspect, the screw member is a two-thread screw.
The invention of claim 4 is the developing device according to claim 2 or 3, wherein the axial length of the screw member is shorter than the length of the developer transport member in the developer transport direction. It is.
According to a fifth aspect of the present invention, in the developing device of the second, third, or fourth aspect, the developing device further includes a control unit that controls the rotation operation of the screw member, and the control unit intermittently rotates the screw member. It is what is controlled.
According to a sixth aspect of the present invention, in the developing device of the fifth aspect, the control means performs the intermittent control in accordance with an output image.
According to a seventh aspect of the present invention, in the developing device of the second, third, fourth, fifth or sixth aspect, the screw member is made of a metal material.
According to an eighth aspect of the present invention, in the developing device of the seventh aspect, the screw member is grounded.
According to a ninth aspect of the present invention, there is provided a latent image carrier that carries a latent image, a developing unit that develops the latent image carried on the latent image carrier, and a developer supply that replenishes the developer with a developer. In the image forming apparatus, the developing device according to the first, second, third, fourth, fifth, sixth, seventh, or eighth aspect is used as the developing unit.

  In the present invention, the developer sent to the developer discharge portion can be loosened by the developer loosening means provided in the vicinity of the developer discharge portion. As a result, even if the developer fluidity is reduced and the developer aggregates, the developer is loosened by the developer loosening means and sent to the developer carry-out portion, so that the developer is smoothly sent to the developer discharge portion. be able to. Therefore, the developer can be appropriately discharged from the development discharge unit to the outside of the apparatus.

  As described above, according to the present invention, even when the fluidity is reduced and the developer is aggregated, the developer can be appropriately discharged to the outside of the apparatus, and the amount of the developer in the developing apparatus can be suppressed from being increased more than necessary. There is an effect.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color laser copying machine (hereinafter simply referred to as “copying machine”) in which a plurality of photoconductors 1 are arranged in parallel will be described.

  FIG. 2 is a schematic configuration diagram of the copying machine according to the present embodiment. The copier includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is placed, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 fixed on the scanner 300 is also provided.

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

  The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates a laser beam onto the surface of the photoreceptor 1 described later 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 north surface of the photoreceptor 1Y is uniformly charged by a charger as charging means. The surface of the photoreceptor 1 </ b> Y that has been subjected to charging processing is irradiated with laser light that has been modulated and deflected by the optical writing unit 21. Then, the potential of the irradiation part (exposure part) is attenuated. By this attenuation, an electrostatic latent image for Y is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed by the developing device 4Y as developing means to become a Y toner image.

  The Y toner image formed on the Y photoconductor 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photoreceptor 1Y after the primary transfer is cleaned of the transfer residual toner by a drum cleaning device.

  In the Y process cartridge 18Y, the photoconductor 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges (18M, C, K).

Next, the intermediate transfer unit will be described.
The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 90, and the like. Further, it also includes a tension roller 14, a driving roller 15, a secondary transfer backup roller 16, four primary transfer bias rollers 62Y, M, C, and K.

  The intermediate transfer belt 110 is tensioned by a plurality of rollers including the tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).

  The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photoreceptors 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photoreceptor 1 and the primary transfer bias roller due to the influence of the primary transfer bias.

  The above-described Y toner image formed on the Y photoconductor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, K toner images formed on the M, C, K photoconductors 1M, C, K are sequentially superposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt 110.

  The four-color toner image superimposed and transferred onto the intermediate transfer belt 110 is secondarily transferred onto a transfer sheet (not shown) as a recording sheet at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 90 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

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

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

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

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

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

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

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

  In parallel with such document reading operation, each device in each process cartridge (18Y, M, C, K), the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 start driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled so that Y, M, C, and K toner images are formed on the respective photosensitive members (1Y, M, C, and K). It is formed. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

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

  In the case of forming another color image composed of two or more colors of toner, the copying machine stretches the intermediate transfer belt 110 so that the upper stretched surface thereof is substantially horizontal, Photoconductors (1Y, M, C, K). On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member 1 but also the developing device 4 is stopped to prevent unnecessary consumption of the photosensitive member 1 and the developer.

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

  As shown in FIG. 1, the developing device 4 used in this embodiment includes a supply screw 8 as a developer supply / conveying member that conveys the developer in the depth direction of FIG. 1 while supplying the developer to the developing roller 5. Have. A developing doctor 12 is provided as a developer regulating member for regulating the developer supplied to the developing roller 5 to a thickness suitable for development, on the downstream side in the surface movement direction from the portion facing the supply screw 8 of the developing roller 5. Yes.

  The developed developer that has passed through the developing section is collected downstream from the developing section, which is the facing portion of the developing roller 5 with respect to the photoconductor 1, and the collected developer is collected in the same direction as the supply screw 8. A recovery screw 6 is provided as a developer recovery / conveying member. A supply conveyance path 9, which is a developer supply conveyance path provided with a supply screw 8, is in the lateral direction of the developing roller 5, and a recovery conveyance path 7 as a developer collection conveyance path provided with a collection screw 6 is below the development roller 5. It is installed side by side.

  The developing device 4 is provided with an agitation conveyance path 10 that is a developer agitation conveyance path in parallel with the recovery conveyance path 7 below the supply conveyance path 9. The agitating and conveying path 10 includes an agitating screw 11 as a developer agitating and conveying member that conveys the developer to the front side in the figure, which is in the opposite direction to the supply screw 8 while agitating the developer.

  The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall as a partition member. In the first partition wall, the supply conveyance path 9 and the agitation conveyance path 10 are partitioned at both ends on the front side and the back side in the figure, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. ing. In addition, although the supply conveyance path 9 and the collection | recovery conveyance path 7 are divided by the 1st partition member, the location which partitions off the supply conveyance path 9 and the stirring conveyance path 10 of a 1st partition wall is not provided. Further, the two conveyance paths of the agitation conveyance path 10 and the collection conveyance path 7 are partitioned by a second partition wall as a partition member. The second partition wall 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 case of the developing device 4 is formed of aluminum with t = 2 [mm].

  The supply screw 8, the recovery screw 6 and the stirring screw 11, which are developer conveying members, are made of metal screws. Each screw diameter is φ22 [mm], the screw pitch is 25 [mm], and the rotation speed is about 600 [rpm]. ] Is set.

  The developer thinned by the developing doctor 12 made of stainless steel on the developing roller 5 is transported to a developing area which is a portion facing the photoreceptor 1 for development. The surface of the developing roller 5 is V-groove or sandblasted and is made of an Al [aluminum] element tube with a diameter of 25 [mm], and the gap between the developing doctor 12 and the photoreceptor 1 is 0.3 [mm].

  The developer after development is collected in the collection conveyance path 7, conveyed to the front side of the cross section in FIG. 1, and developed to the agitation conveyance path 10 at the opening of the first partition wall provided in the non-image area portion. The agent is transferred. The toner is supplied from a toner replenishing port T provided on the supply conveyance path 9 on the upstream side in the developer conveyance direction (may be downstream in the collection screw 6 developer conveyance direction or upstream on the stirring screw 11).

  For toner replenishment, the toner concentration of the stirring screw 11 in the developing device 4 is detected by the toner concentration sensor 79 of FIG. The replenished toner is stirred and mixed with the existing developer by the stirring screw 11 to obtain a uniform toner density. The developer in which the toner is uniformly dispersed is lifted to the supply screw 8, and the developer is supplied to the developing roller 5. The developer roller 5 supplied is regulated in developer amount by the development doctor 12 and the toner and carrier are rubbed by an appropriate amount to charge the toner, and the charged toner is transferred to the photoreceptor 1 on which an electrostatic latent image is formed. Moving. The developer used for the development is recovered by the recovery screw 6, supplied with toner, and transferred to the stirring screw 11. That is, the developer in the developer transport path moves and circulates between the developer transport paths in the directions of arrows A, B, and C shown in FIG. 3, and image formation is performed by repeating the above operation.

  In the toner replenishment in the present embodiment, a premix toner (not shown) having a container (STC) that is easily deformed and filled with a premix toner in which toner and carrier are dispersed at a constant concentration, and a suction pump. The supply device supplies toner and carrier to the developing device 4 in the form of premix toner. The premix toner supply device sucks the premix toner with a suction pump and supplies the premix toner to the developing device 4. As a result, the toner stirring operation in the toner cartridge is eliminated, and the toner can be replenished without any stirring operation at all times.

  In the premix toner supply device, the void ratio in the container when the premix toner is left standing for 24 hours is preferably 12% or more. Thus, since the toner is not packed like a vacuum pack, the toner can be discharged from the STC stably at a constant amount with a uniform density.

  In the premix toner, the weight ratio of the carrier to the toner is 3 [wt%] to 20 [wt%]. As a result, the specific gravity of the toner increases and the carrier also acts as a lubricant, so that the rushed toner flows smoothly, so that a constant amount of premix toner with a uniform density is stably supplied from the premix toner supply device to the developing device 4. Can be supplied.

  Further, the amount of lubricant added to the premix toner is set to 0.3 [wt%] to 3.0 [wt%], whereby the fluidity of the premix toner can be maintained. Can be stably supplied to the developing device 4 at a uniform density.

  In addition, a premix toner having an accelerated aggregation degree of 10% or less is used, so that the premix toner supply device to the developing device 4 can be used regardless of the additive formulation, toner material, and charging characteristics. A constant amount can be stably supplied at a uniform concentration.

  As in this embodiment, by using the premix toner as described above, a constant amount of premix toner is always supplied from the premix toner supply device to the developing device 4, so that the developer deterioration rate is increased. It is possible to suppress the occurrence of abnormal images.

  In the developing device 4 shown in FIG. 1, a supply conveyance path 9 and a collection conveyance path 7 are provided, and developer supply and collection are performed in different developer conveyance paths, so that the developed developer is supplied to the supply conveyance path 9. There is no contamination. Accordingly, it is possible to prevent the toner density of the developer supplied to the developing roller 5 from decreasing toward the downstream side of the supply conveyance path 9 in the developer conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Therefore, since the sufficiently agitated developer is supplied to the supply conveyance path 9, it is possible to prevent the developer supplied to the supply conveyance path 9 from being insufficiently agitated. In this way, the toner density of the developer in the supply conveyance path 9 can be prevented from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred. Can be constant.

  In this embodiment, as described above, the carrier is supplied simultaneously with the toner by the premix toner. Therefore, the amount of developer in the developing device 4 increases with toner replenishment. If the amount of the developer continues to increase permanently, the developer overflows in the collection screw 6 and the developer moves along with the developing roller 5 to affect the image density.

  Therefore, in this embodiment, as shown in FIG. 4, the supply is at a predetermined height at a location in the supply conveyance path where the volume of the developer increases or decreases in accordance with the increase or decrease in the developer amount in the entire developer conveyance path. A developer discharge port 75 that connects the supply conveyance path 9 and the discharge conveyance path 2 is provided at a predetermined position of the partition wall 135 that partitions the conveyance path and the discharge conveyance path 76 that conveys the developer to the outside of the apparatus. .

  Then, by controlling the moving speed when the developer remaining on the downstream side in the developer conveyance direction of the supply conveyance path 9 that has not been supplied to the developing roller 5 is moved to the stirring screw 11, the development of the supply conveyance path 9 is performed. The bulk of the developer is varied on the downstream side in the agent transport direction to increase the bulk as shown in FIG. Thus, the developer is pumped up to the discharge conveyance path 76 via the developer discharge port 75 by increasing the volume of the developer on the downstream side of the supply conveyance path 9 in the developer conveyance direction. Then, the deteriorated developer pumped up to the discharge conveyance path 76 is conveyed by the discharge screw 77 and discharged to the outside of the apparatus. Thereby, it is possible to prevent the developer from overflowing in the recovery screw 6.

  Further, by providing the developer discharge port 75 at the above position as in this embodiment, the apparent developer amount such as an increase in toner density due to an increase in toner concentration due to environmental fluctuations or the like can be obtained. The developer is not discharged from the developer discharge port 75 only by increasing the number. For this reason, it is possible to prevent the developer from being discharged to the outside of the apparatus and the developer amount in the developing apparatus from being reduced more than necessary even when the developer is not replenished. Therefore, it is possible to suppress an abnormal image that is generated when the amount of developer supplied from the supply conveyance path 9 to the developing roller 5 is reduced.

  The discharge conveyance path 76 is provided above the supply conveyance path 9 so that the rotation axis center of the discharge screw 77 is higher than the rotation axis center of the developing roller 5. Further, the discharge screw 77 is set to φ8 [mm], the screw pitch is 25 [mm], the number of strips is one, and the rotation speed is about 50 [rpm]. Further, the rotation of the discharge screw 77 is intermittently controlled by the control unit. When the developer in the developing device is not discharged outside the device, the rotation is not performed, thereby saving energy and preventing the deterioration of the discharge screw 77. It can be performed.

  However, if the developer fluidity decreases and the developer aggregates on the downstream side of the supply conveyance path 9 in the developer conveyance direction (in the vicinity of the discharge screw 77), the developer discharge port 75 is connected to the supply conveyance path 9. Thus, the developer cannot be smoothly moved to the discharge conveyance path 76.

  Therefore, in the present embodiment, as shown in FIG. 1, development that is pumped up to the discharge conveyance path 76 via the developer discharge port 75 by increasing the volume of the developer on the downstream side of the supply conveyance path 9 in the developer conveyance direction. As shown in FIG. 6, a loosening screw 78 is used in the vicinity of the developer discharge port 75 as shown in FIG. It is installed in. This makes it possible to smoothly move the developer from the supply conveyance path 9 to the discharge conveyance path 76 via the developer discharge port 75 while unraveling the aggregated developer.

  The number of strips of the loosening screw 78 is more effective for loosening the developer in which the two-row screw is agglomerated than the single-row screw. Therefore, in this embodiment, the loosening screw 78 is set to φ8 [mm], the screw pitch is 25 [mm], the number of strips is 2, and the rotational speed is about 50 [rpm].

  Further, in the present embodiment, the loosening screw 78 is rotated so as to convey the developer in the same direction as the developer conveying direction of the supply screw 8, and more specifically, a left-handed screw toward the developer conveying direction of the supply screw 8. Rotate left. Further, by rotating the loosening screw 78 in this way, the developer is also pumped up by the rotation of the loosening screw 78, and the efficiency of pumping the developer from the supply conveyance path 9 to the discharge conveyance path 76 can be enhanced.

  Note that the screw winding direction and the rotation direction of the loosening screw 8 are not limited to those described above. That is, it is sufficient that at least the developer pumped from the supply conveyance path 9 to the discharge conveyance path 76 can be loosened, and the screw winding direction and the rotation direction of the loosening screw 8 are not limited.

  As shown in FIG. 3, the axial length of the loosening screw 78 is preferably shorter than half the axial length of the supply screw 8 (the length of the supply conveyance path 9 in the developer conveyance direction). Furthermore, it is preferable to provide the loosening screw 78 on the downstream side in the developer conveyance direction of the supply conveyance path 9 (downstream in the developer conveyance direction of the supply screw 8). If the axial length of the loosening screw 78 is the same as the total length of the supply screw 8, the developer may be discharged more than necessary. Further, the transport force for transporting the developer in the supply transport path 9 to the downstream side in the developer transport direction of the supply transport path 9 is generated not only by the supply screw 8 but also by the loosening screw 78, and the transport force becomes too large. This is because the supply amount of the developer supplied from the supply conveyance path 9 to the developing roller 5 may be different (decreased) from the set value.

  Further, when the image is output under a certain condition, the developer supply amount and the developer state are substantially the same, so that the developer can be discharged stably. However, in reality, the image area ratio may be different, the carrier supply amount may be changed, or the duty may be different, and the developer deterioration rate may be different. Therefore, there are cases where more developer than necessary moves to the discharge screw 77 that discharges the developer, or too little. When the developer moves to the discharge screw 77 more than necessary, it becomes necessary to control the discharge amount by some method. Therefore, in this embodiment, the rotation speed of the discharge screw 77 and the loosening screw 78 is intermittently controlled by the control unit. Thereby, the amount of the developer moving to the discharge screw 77 is suppressed, and the discharge amount of the developer can be reduced. Further, by calculating the carrier supply amount according to the output image and controlling the rotation speed of the discharge screw 77 and the loosening screw 78, the developer discharge amount can be controlled with higher accuracy.

  Further, the developer staying in the developing device 4 for a long time is often in a highly charged state. For this reason, the aggregation between the developers may not be easily loosened. In such a case, it is possible to easily release the aggregation state by releasing the charge from the highly charged developer. As a means for releasing the charge from the highly charged developer, a loosening screw 78 made of a conductive metal material may be used. As a result, the charge is loosened from the highly charged developer and escaped to the screw 78. Thus, it is possible to easily unravel the aggregation state of the developer. In addition, by grounding the rotating shaft of the loosening screw 78, the electric charge easily moves from the developer to the loosening screw 78, so that the state of aggregation of the developer can be more easily released.

Moreover, the stable dischargeability of the developer with respect to the change of the developer state in the developing device 4 was evaluated at high humidity and low humidity. The results are shown in Table 1. In the column of discharge performance in Table 1, when there is no excessive discharge or low discharge of the developer, and stable discharge performance is always obtained, ○ is indicated, and excessive discharge or low discharge of the developer is indicated. X is shown when stable discharge performance cannot be obtained. As can be seen from Table 1, by providing the loosening screw 78 even if there is an environmental fluctuation in the developing device 4, it is possible to always obtain a stable discharge performance. As a result, there is no effect on the image density due to these.

As described above, according to the present embodiment, the developer is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the photoconductor 1 at a position facing the photoconductor 1 as the latent image carrier and developed. A developing roller 5 that is a developer carrying member, and a supply screw 8 that is a developer conveying member that conveys the developer. In the developer supply region where the developer is supplied to the developer roller 5, the developing roller 5 is developed. A supply conveyance path 9 that is a developer conveyance path for conveying the developer while supplying the developer, and a location in the developer conveyance path where the volume of the developer increases or decreases according to the increase or decrease in the amount of the developer in the entire developer conveyance path In the developing device 4 provided with a discharge conveyance path 76, a discharge screw 77, and a developer discharge port 75 that constitute a discharge conveyance unit that conveys the developer to the outside of the apparatus provided at a predetermined height of the developer. Due to the increase in volume, the developer conveyance port 9 passes through the developer discharge port 75. Out loosening of the developer fed to the conveying path 76, a loosening screw 78 is loosened developer means parallel to the supply screw 8, and, as soak in developer conveyance direction downstream side of the developer supply conveyance path 9, The unwinding screw 78 is provided separately from the supply screw 8 and operates the loosening screw 78 so as to convey the developer in the same direction as the supply screw 8. This is sent to the discharge conveyance path 76 through the developer outlet 75 from the supply conveyance path 9 while loosened developer by the flow of the developer is reduced even developer are agglomerated, loosening screw 7 8 Therefore, the developer can be smoothly fed from the supply conveyance path 9 to the discharge conveyance path 76. Therefore, the developer can be appropriately discharged from the discharge conveyance path 76 to the outside of the apparatus by the discharge screw 77. Therefore, even if the fluidity is lowered and the developer is aggregated, the developer can be appropriately discharged out of the apparatus.
Further, according to the present embodiment, by using the loosening screw 78 as the developer loosening means, the aggregated developer can be loosened efficiently. Furthermore, the efficiency of pumping the developer from the supply conveyance path 9 to the discharge conveyance path 76 via the developer discharge port 75 can be increased.
Moreover, according to this embodiment, since the loosening screw 78 is a two-thread screw, the aggregated developer can be loosened more efficiently.
Further, according to the present embodiment, the axial length of the loosening screw 78 is shorter than the axial length of the supply screw 8 (length in the developer transport direction), so that the developer is discharged more than necessary. Can be suppressed. Further, the transport force for transporting the developer in the supply transport path 9 to the downstream side in the developer transport direction of the supply transport path 9 is generated not only by the supply screw 8 but also by the loosening screw 78, and the transport force becomes too large. Thus, it is possible to suppress the supply amount of the developer supplied from the supply conveyance path 9 to the developing roller 5 from being different from the set value.
Moreover, according to this embodiment, it has a control means which controls the rotational operation of the loosening screw 78, and the said control means controls intermittently the rotational operation of the loosening screw 78. As a result, it is possible to adjust the amount of developer moved to the discharge screw 77, thereby suppressing an excessive amount of developer from moving to the discharge screw 77, suppressing excessive discharge, and moving to the discharge screw 77. By increasing the amount of the developer to be discharged, it is possible to suppress an excessive discharge.
Further, according to the present embodiment, the control means performs the intermittent control according to the output image. For example, the supply amount of the carrier is calculated according to the output image, and the rotational speed of the loosening screw 78 or the like. By controlling this, it is possible to more accurately control the developer discharge amount.
Further, according to the present embodiment, since the loosening screw 78 is made of a metal material, it is possible to loosen the electric charge from the highly charged developer and release it to the screw 78, and to easily release the aggregation state of the developer. be able to.
Further, according to the present embodiment, the loosening screw 78 is grounded, so that the electric charge is easily transferred from the developer to the loosening screw 78, and the developer aggregation state can be more easily released.
Further, according to the present embodiment, the photosensitive member 1 that is a latent image carrier that carries a latent image, the developing unit that develops the latent image carried on the photosensitive member 1, and the developer is supplied to the developing unit. In a copying machine that is an image forming apparatus provided with a premix toner supply device that is a developer replenishing means, the use of the developing device 4 of the present invention as the developing means reduces the fluidity and causes the developer to aggregate. Since the developer can be appropriately discharged to the outside of the apparatus, the amount of the developer in the developing apparatus can be appropriately maintained even when the premix toner is supplied by the premix toner supply apparatus. As a result, the pumping of the developer to the developing roller 5 and the detachment of the developer used for the development from the developing roller 5 are appropriately performed, so that the latent image on the photoreceptor 1 is appropriately developed and a good image is obtained. Can be obtained.

1 is a schematic configuration diagram of a developing device that is a characteristic part of the present invention. FIG. 1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 3 is a route diagram illustrating a developer conveyance route. FIG. 6 is a perspective explanatory view of the vicinity of the front end of the developing device with each screw and developing doctor removed. Sectional drawing of the developer in the supply conveyance path | route which showed the state which made the bulk of the developer high in the developer conveyance direction downstream of a supply conveyance path | route. Sectional drawing of the developer in the supply conveyance path which showed the arrangement position of a loosening screw.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing device 5 Developing roller 6 Collection screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 12 Developing doctor 75 Developer discharge port 76 Discharge conveyance path 77 Discharge screw 78 Unraveling screw 79 Toner Concentration sensor 135 Partition wall

Claims (9)

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 developer transport path having a developer transport member for transporting the developer and transporting the developer while supplying the developer to the developer carrier in the developer supply region for supplying the developer to the developer carrier. When,
Developer that discharges the developer to the outside of the apparatus provided at a predetermined height in the developer transport path where the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire developer transport path A discharge section,
In the developing device in which the developer is sent to the developer discharge portion by increasing the volume of the developer, and the developer is discharged to the outside of the device.
The developer sent to the developer discharge section is loosened, and the developer loosening means is in the vicinity of the developer discharge section, parallel to the developer transport member, and downstream of the developer transport path in the developer transport direction. The developer conveying member is provided separately from the developer conveying member so as to be in contact with the developer, and the developer loosening means is operated so as to convey the developer in the same direction as the developer conveying member. Development device. The developing device according to claim 1.
The developing device, wherein the developer loosening means is a screw member. The developing device according to claim 2.
The developing device according to claim 1, wherein the screw member is a two-thread screw. The developing device according to claim 2 or 3,
The length of the screw member in the axial direction is shorter than the length of the developer transport member in the developer transport direction. The developing device according to claim 2, 3 or 4,
Having a control means for controlling the rotational operation of the screw member;
The developing device characterized in that the control means intermittently controls the rotational operation of the screw member. The developing device according to claim 5.
The developing device according to claim 1, wherein the control means performs the intermittent control according to an output image. The developing device according to claim 2, 3, 4, 5 or 6.
The developing device according to claim 1, wherein the screw member is made of a metal material. The developing device according to claim 7.
A developing device, wherein the screw member is grounded. A latent image carrier for carrying a latent image;
Developing means for developing the latent image carried on the latent image carrier;
In an image forming apparatus provided with a developer replenishing means for replenishing developer to the developing means,
An image forming apparatus using the developing device of claim 1, 2, 3, 4, 5, 6, 7, or 8 as the developing means.

Images