JP5487732B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly, to a developing mechanism that uses a two-component developer containing toner and a carrier.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member as a latent image carrier is subjected to visible image processing by a developing device, and the visible image is converted into a sheet. A recording output can be obtained by transferring to the above.

  As a developer used for development, there is a two-component developer obtained by mixing a toner and a carrier in addition to a one-component developer containing only magnetic or non-magnetic toner.

  The two-component developer is composed of a toner and a carrier that carries the toner, and the toner can be electrostatically attracted to the electrostatic latent image on the photosensitive member by charging the toner by a frictional charging effect that occurs during stirring and mixing. It is said.

  In the developing device, a developing sleeve as a developer carrying member for supplying developer toward the electrostatic latent image on the photosensitive member by causing the developer to rise on the peripheral surface by magnetic force, and agitating and mixing the developing sleeve A configuration including a stirring member such as a screw auger for supplying a developer is known. The developer carried on the developing sleeve is supplied to the electrostatic latent image on the photosensitive member after a carrying amount (layer thickness) is defined by a regulating member such as a doctor blade.

  As a configuration of a developing device using a two-component developer, there is a configuration shown in FIG. 18 (for example, Patent Document 1).

  In the configuration shown in FIG. 18, a developer supplying auger 401 is disposed below the position where the developing sleeve 5 as the developer carrying member is disposed, and is parallel to the axis of the developer supplying auger 401 in the horizontal direction. An auger 402 for stirring is arranged. Each of the augers 401 and 402 for supply and agitation communicates with each other in the space where these augers are arranged at the end in the axial direction.

  In the configuration shown in FIG. 18, the developer is circulated between the spaces where the augers are arranged by transferring the developer in the direction in which the screw augers oppose each other. Thus, the developer is pumped from the supply auger 401 to the developing sleeve 5 and the developer carried on the developing sleeve 5 after development is collected.

  As a configuration for supplying and collecting the developer described above, development is performed on the developing sleeve 5 in the developing sleeve 5 along the circumferential direction so that a magnetic brush is raised in opposition to the developing sleeve 5. A separation magnetic pole capable of forming a repulsive magnetic field for separating the developer from the conveying magnetic pole to which the agent is moved and the sleeve peripheral surface after development is provided. By providing the repulsive magnetic pole, an odd number of poles, specifically 7 A pole magnet is used.

  The developer peeled off and collected from the peripheral surface of the developing sleeve 5 by the repellent magnetic pole once passes through the conveyance path 401P and is collected by the supply auger 401 as indicated by the one-dot chain line arrow F1. Then, it is pumped up by the conveying magnetic pole and supplied to the peripheral surface of the developing sleeve 5. As a result, the developer is conveyed in the axial direction of the auger while circulating between the supply conveyance path and the collection conveyance path existing at the same position, and while facing the magnetic pole on the developing sleeve side many times in the process. Moving. The developer is in a spiked state when facing the magnetic pole, and when separated from the magnetic pole, the spikes collapse and condense, and the frictional contact between the carrier and the toner is performed, and the toner is triboelectrically charged. Is called.

  The developer in which the frictional contact due to the rising state and the rising state collapses and condenses is repeated, for example, in the axial direction of the auger. Therefore, if the toner consumption increases in the conveying process in that direction, the developer is conveyed. The toner density on the downstream side in the direction decreases.

  For example, when developing an image with a large image area, the toner consumption in the auger axial direction is likely to be consumed in large quantities on the supply side, and the developer is contained on the downstream side in the transport direction. The amount of toner is reduced. For this reason, a uniform toner density may not be maintained in the axial direction of the developing sleeve. Insufficient toner density leads to a decrease in image quality.

  The above-described problems are caused by the common use of the developer supply conveyance path and the recovery conveyance path. In other words, the collected developer is insufficient in toner, and if such developer is conveyed again to the supply conveyance path, the carrier content ratio in the supplied developer becomes high, The ratio of the carrier and the toner in the supplied developer is different from the predetermined ratio.

  Accordingly, a configuration is proposed in which a part of the configuration shown in FIG. 18 is changed so that the developer supply and recovery paths are distinguished from each other so that the collected developer is not mixed in the supply and transfer paths. (For example, Patent Document 1).

  FIG. 19 shows the main part of the developing device disclosed in Patent Document 1. In FIG. 19, the housing of the developing device 4 is partitioned in a vertical direction by a partition wall 403 in the first direction. Agitation chambers 401P and 402P are provided to accommodate the auger 401 and the second auger 402, respectively.

  On the other hand, as disclosed in Patent Document 1, there is a configuration disclosed in Patent Document 2 as another example of a configuration in which the stirring chamber that houses the auger is partitioned by a partition wall.

  FIG. 20 is a diagram showing a configuration disclosed in Patent Document 2. In FIG. 20, a supply auger 401 and a developer for supplying developer to the developing sleeve 5 are provided in the housing of the developing device 4. In addition to the stirring auger 402, a collecting auger 404 for collecting the developer on the developing sleeve 5 that has passed through the developing region is provided, and a supply conveyance path 401P ′ where the supplying auger 401 is located and the collecting auger 404 are positioned. The recovery transport path 404P is partitioned by a partition wall 405, and the stirring transport path 402P ′ where the stirring auger 402 is located and the recovery transport path 404P are partitioned by a partition wall 406.

  In the configuration disclosed in Patent Document 1, the collected developer is transported in the axial direction by the auger 402 for stirring and is transported as it is to the auger 401 for supply, so that new toner is replenished. Even in this case, the stirring by the auger 402 for stirring tends to be insufficient, and there is a possibility that the image density becomes uneven or the density is lowered due to insufficient charging of the toner. This is particularly noticeable when forming an image with a high printing rate in which the toner concentration of the collected developer tends to decrease.

  On the other hand, in the configuration disclosed in Patent Document 2, the developer recovered from the developing sleeve is transported to the recovery transport path 404P and is not mixed into the supply transport path 401P ′, and is further recovered. Since the developer does not enter the stirring conveyance path 402P ′ as it is and is stirred and then conveyed toward the supply conveyance path 401P ′, it is possible to eliminate the problem caused by the configuration shown in FIG. I can expect.

  However, the configuration of the developing sleeve, which is a developer carrier used in the configuration disclosed in these patent documents, has the following problems.

  The developing sleeve disclosed in each patent document is provided with a magnetic pole for forming a magnetic brush, that is, a developer to make it stand up. The number of magnetic poles is shown in Patent Document 1 as shown in the figure. Although it is made of five poles and is not shown in Patent Document 2, it is described that the developer moves toward a collecting screw that collects the developed developer that has passed through the developing section. In the case shown in FIG. 18 or in the same manner as in Patent Document 1, it can be expected to be about 5 or 7 poles.

  On the other hand, in the configuration disclosed in Patent Document 1, unlike the case shown in FIG. 18, the supply conveyance path and the recovery conveyance path are not common and are independent, The developer cannot be circulated between the supply / recovery conveyance path.

  For this reason, the collected developer is collected in a state where the number of times of passing through the magnetic pole is only 5 to 7 times, and the frictional contact at the time of repeated rise and fall of the rise is caused. An extremely low state is obtained. As a result, there arises a problem that the frictional charging due to the opportunity of frictional contact becomes insufficient and a long time is required for charging the toner.

  In the configuration disclosed in Patent Document 2, since the agitation conveyance path is provided independently, it is possible to improve the agitation efficiency for the collected developer. Since the charge amount of the toner tends to be lost when the toner is left as it is, the adhesion to the carrier is reduced and the toner tends to be scattered. As a result, there is a possibility of causing contamination in the apparatus.

  By the way, in this type of developing device, after the developer remaining on the developing sleeve 5 that has passed through the developing region is collected, the development carried on the developer sleeve 5 by receiving a new developer supply. It is necessary to keep the concentration of the agent constant.

  However, if the developer cannot be recovered satisfactorily from the developing sleeve 5 that has passed through the developing region, the concentration of the developer carried on the developing sleeve changes and a problem arises that an image with a predetermined density cannot be obtained. That is, the developer concentration remaining on the developing sleeve 5 is lowered due to the consumption of the toner, and if the developer concentration is used as it is, a ghost image having a reduced concentration is obtained. .

  SUMMARY OF THE INVENTION In view of the above-described problems in the conventional developing device, the present invention provides a developing device having a configuration that can easily remove the developer from the developer carrying member and reliably collect the developer. is there.

In order to achieve this object, the present invention has the following configuration.
(1) A developing device including a developer carrier for supplying a two-component developer containing toner and a carrier to an electrostatic latent image formed on the image carrier,
Inside the developer carrying member, a rotatable magnetic field generating means having a magnetic pole for causing the developer to stand up and transported is disposed,
The magnetic field generating means is arranged with its center of the cross section decentered in a direction approaching the image carrier with respect to the center of the cross section of the developer carrier.
A magnetic shielding member capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. And the magnetic shielding member is configured such that the edge along the rotation direction of the magnetic field generating means is not parallel to the magnetic pole provided on the magnetic field generating means .
(2) A developing device including a developer carrier for supplying a two-component developer containing toner and a carrier to an electrostatic latent image formed on the image carrier,
Inside the developer carrying member, a rotatable magnetic field generating means having a magnetic pole for causing the developer to stand up and transported is disposed,
The magnetic field generating means is arranged with its center of the cross section decentered in a direction approaching the image carrier with respect to the center of the cross section of the developer carrier.
A magnetic shielding member capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. And the magnetic shielding member is configured by arranging a plurality of magnetic poles along the longitudinal direction of the magnetic field generating means .
(3) A developing device including a developer carrier for supplying a two-component developer containing toner and carrier to the electrostatic latent image formed on the image carrier,
Inside the developer carrying member, a rotatable magnetic field generating means having a magnetic pole for causing the developer to stand up and transported is disposed,
The magnetic field generating means is arranged with its center of the cross section decentered in a direction approaching the image carrier with respect to the center of the cross section of the developer carrier.
A magnetic shielding member capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. The developing device is characterized in that a plate-like member is used as the magnetic shielding member, and the plate-like member has a different thickness in the longitudinal direction .
(4) The developing device according to any one of (1) to (3), wherein the magnetic field generating unit includes even-numbered magnetic poles arranged along a rotation direction thereof .
(5) Of the above (1) to (4), the magnetic shielding member is provided with a shielding angle larger than an angle between magnetic poles provided in the magnetic field generating means . The developing device according to any one of the above.
(6) The plurality of magnetic poles provided in the magnetic shielding member have a polarity capable of suppressing flexural vibration along the longitudinal direction of the shielding member due to the magnetic force from the magnetic pole provided in the magnetic field generating means. The developing device according to (5), which is set.
(7) The developing device according to (5) or (6), wherein a magnetic sheet having a plurality of magnetic poles is attached to the magnetic shielding member.
(8) The magnetic shielding member may be configured such that the developer carrier inner surface is closer to the magnetic field generating unit than the magnetic field generating unit in a gap space between the surface of the magnetic field generating unit opposite to the side biased to the image carrier and the inner surface of the developer carrier. The developing device according to any one of (1) to (7), wherein the developing device is arranged close to the side .
(9) The magnetic field generating means can be rotated in the same direction or relative direction as the developer carrying member, and when rotating in the same direction, a relative speed difference is set to rotate (1) ) To (3) .
(10) An image forming apparatus using the developing device according to any one of (1) to (9).
(11) The image forming apparatus according to (10), further comprising a process cartridge that collectively accommodates at least the developing device and the image carrier .

  According to the present invention, magnetic field generating means is provided that is rotatably provided in the developer carrying body and is eccentric in a direction approaching the latent image carrying body with respect to the center of the cross section of the developer carrying body. Since a magnetic shielding member capable of covering a part of the magnetic field generation means is provided in the gap space in the developer carrier formed by the eccentricity of the magnetic field generation means, it is difficult to exert a magnetic force on the surface of the image carrier. Thus, the developer can be easily peeled off. In particular, when the developer can be easily recovered due to the ease of peeling, the apparatus can be increased in size and the developer can be scraped off by simply providing a magnetic shielding member in the gap space obtained by the eccentricity. This can be performed reliably without requiring a structure or the like.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus using a developing device according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the configuration and operation of a developing device used in the image forming apparatus shown in FIG. 1. FIG. 3 is a perspective view illustrating an appearance of a main part of the developing device illustrated in FIG. 2. FIG. 3 is a schematic diagram for explaining the flow of developer in the developing device shown in FIG. 2. FIG. 4 is a schematic diagram illustrating a cross section viewed from a direction indicated by an arrow J in FIG. 3. FIG. 5 is a schematic diagram for explaining another example of the developer flow in the developing device shown in FIG. 2. FIG. 3 is a perspective view of relevant parts for explaining the configuration of a toner replenishing unit in the developing device shown in FIG. 2. FIG. 4 is a perspective view of main parts showing a state in which some members in the developing device shown in FIG. 3 are removed. FIG. 3 is a schematic side view for explaining a characteristic part in the developing device shown in FIG. 2. It is a perspective view for demonstrating the structure of the developer carrier used for the characteristic part shown in FIG. FIG. 10 is a waist cross-sectional view for explaining a support structure of the developer carrying member shown in FIG. 9 and a magnetic field generating unit included in the developer carrying member. FIG. 10 is a table showing a result of an experiment relating to the number of passages between the developer and the magnetic poles of the magnetic field generating means by the feature shown in FIG. It is a perspective view for demonstrating one structure of the magnetic shielding member used for the characteristic part shown in FIG. FIG. 14 is an operation diagram showing a facing relationship between a magnetic shielding member and a magnetic field generating means for explaining a problem due to the configuration shown in FIG. 13. It is a perspective view equivalent to FIG. 13 for demonstrating the structure which eliminated the malfunction by the magnetic shielding member shown in FIG. It is a perspective view equivalent to FIG. 13 which shows the principal part modification of the magnetic shielding member shown in FIG. It is a schematic diagram for demonstrating the opposing relationship of the magnetic shielding member and magnetism generation means for demonstrating another example for eliminating the malfunction which arises by the structure shown in FIG. It is a schematic diagram for demonstrating the prior art example of the developer supply mechanism in a developing device. It is a schematic diagram for demonstrating one structure known conventionally in order to eliminate the malfunction in the prior art example shown in FIG. It is a schematic diagram for demonstrating an example different from FIG. It is a schematic diagram for demonstrating the structure of the reference example using the magnetic shielding member shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows an image forming apparatus using a developing device according to the present invention. The image forming apparatus shown in FIG. 1 is a tandem full-color printer. However, the present invention is not limited to this, and the present invention is not limited thereto. It can also be applied to devices.

FIG. 1 is a schematic configuration diagram of a full-color printer (hereinafter referred to as a copying machine for convenience) 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 mounted, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 is fixed on the scanner 300.

  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 photoconductor 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 17 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 48.

  The paper feed path 48 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 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. Any one of the transport modes to be returned to the secondary transfer nip is selected.

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

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

  In parallel with such a document reading operation, each device in each of the process cartridges 18Y, 18M, 18C, 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 starts driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, and K toner images are formed on the respective photoreceptors 1Y, 1M, 1C, and 1K. Is done. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

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

  When the copier 500 forms a multicolor image composed of toners of two or more colors, the intermediate transfer belt 110 is stretched so that the upper stretched surface thereof is substantially horizontal, and all the upper stretched surface is placed on the upper stretched surface. Photoconductors 1Y, 1M, 1C, and 1K are brought into contact with each other. On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member 1 but also the developing device 4 is stopped, and each member of the photosensitive member 1 and the developing device 4 and the developer in the developing device 4 are unnecessarily consumed. To prevent.

  The copier 500 includes a control unit (not shown) composed of a CPU and the like that controls each device in the copier 500, and an operation display unit (not shown) composed of a liquid crystal display, various key buttons, and the like. . The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

  FIG. 2 is an enlarged configuration diagram showing the developing device 4 and the photoreceptor 1 provided in each 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 and developing toner to the latent image on the surface of the photoreceptor 1 while conveying the developer in the direction of arrow I in the drawing.

  The developing roller 5 includes a rotatable developing sleeve 81, and includes a magnet roller 82 which is composed of a plurality of magnetic poles and serves as magnetism generating means which can rotate in the direction of arrow J in the figure. The developing roller 5 is a feature of the present invention and will be described in detail later.

  Further, while supplying the developer to the developing roller 5, the front side of the paper surface shown in FIG. 2 along the axial direction of the developing roller 5 (hereinafter, sometimes referred to as the front side in the figure or the front side in FIG. 2 for convenience). A supply screw 8 is provided as a supply / conveyance member that conveys the developer toward the substrate.

  A doctor blade 12 serving as a developer regulating means for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided downstream of the developing roller 5 facing the supply screw 8 in the developer transport direction. I have.

  A recovery conveyance path that collects the developed developer that has passed through the development area and separated from the surface of the development roller 5 on the downstream side in the developer conveyance direction from the development area that is the portion of the development roller 5 facing the photoreceptor 1Y. 7 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. 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 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 and conveying path 10 is in the direction opposite to the supply screw 8 while agitating the developer along the axial direction of the developing roller 5 (referred to as the back side in the drawing for the sake of convenience). As a stirring and transporting member that transports toward (sometimes), a spiral stirring screw 11 that is arranged in parallel to the axial direction 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. The supply conveyance path 9 and the agitation conveyance path 10 of the first partition wall 133 have openings at the front and back sides in the figure, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. Yes.

  The supply conveyance path 9 and the recovery conveyance path 7 are also partitioned by the first partition wall 133, but an opening portion is provided at a location where the supply conveyance path 9 and the recovery conveyance path 7 are partitioned on the first partition wall 133. Is not provided.

  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 agitation transport path 10 and the collection transport path 7 communicate with each other.

  The supply screw 8, the recovery screw 6, and the stirring screw 11, which are developer conveying members, are made of resin or metal screws, and each screw diameter is φ22 (mm) and the screw pitch is 2 (50 mm). The winding, the collecting screw 6 and the stirring screw 11 are one winding of 25 (mm), and the number of rotations is all set to about 600 (rpm).

  The developer carried on the developing roller 5 is thinned by a doctor blade 12 made of stainless steel, and is then transported to a developing area which is a portion facing the photoreceptor 1 for development.

  The diameter of the developing roller 5 is φ25 (mm), and the gap between the doctor blade 12 and the photoreceptor 1 is about 0.3 (mm).

  The developed developer is collected in the collection conveyance path 7, conveyed to the front side in FIG. 2, and developed to the agitation conveyance path 10 through the opening of the second partition wall 134 provided in the non-image area. The agent is transferred. In the vicinity of the opening of the second partition wall 134 on the upstream side in the developer conveyance direction in the agitation conveyance path 10 and above the agitation conveyance path 10, as shown in FIG. Toner is supplied to the path 10.

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

  4 is a schematic diagram of the flow of the developer in the developing device 4. Like FIG. 3, each arrow in the drawing indicates the moving direction of the developer.

  In the supply conveyance path 9 that receives the developer supplied from the agitation conveyance path 10, the developer is supplied in contact with the developing roller 5 while moving.

  The surplus developer that has moved to the downstream end in the transport direction of the supply transport path 9 without being supplied to the developing roller 5 is supplied to the stirring transport path 10 from the surplus opening 92 of the first partition wall 133 (arrow in FIG. 4). E).

  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 conveyance direction of the collection conveyance path 7 by the collection screw 6 enters the stirring conveyance path 10 from the collection opening 93 of the second partition wall 134. Supplied (arrow F in FIG. 4).

  In the agitation transport path 10, excess developer supplied from the supply transport path 9, recovered developer recovered in the recovery transport path 7, and toner replenished from a toner replenishment port 95 (see FIG. 7) described later. The agitated developer is conveyed downstream in the conveying direction of the agitating screw 11 and upstream in the conveying direction of the supply screw 8, and is supplied from the supply opening 91 of the first partition wall 133 to the supply conveying path 9. (Arrow D in FIG. 4).

  A toner concentration sensor 13 (see FIG. 2) including a magnetic permeability sensor is provided below the agitation conveyance path 10, and a toner replenishment control device (not shown) is operated by the sensor output from a toner storage unit (not shown). Toner is being replenished.

  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 suppress a decrease in the toner concentration of the developer supplied to the developing roller 5 toward the downstream side of the supply conveyance path 9 in the conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Thereby, since the sufficiently stirred developer is supplied to the supply conveyance path 9, it is possible to suppress 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 suppressed from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred, so 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 an arrow D is to push the developer downstream of the agitation transport path 10 by the rotation of the agitation screw 11 so that the developer is raised and supplied 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.

  In this way, when the developer is lifted from below to above, the developer is stressed, and the carrier film in the developer is scraped off and the toner is spent at that point, and the stability of the image quality is maintained accordingly. 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 suppresses the deterioration of the developer and always has stable image quality without image density unevenness.

  In the developing device 4 of the present 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, compared to the case where the supply conveyance path 9 is provided vertically above the stirring conveyance path 10 and the developer is lifted. .

  Further, in the developing device 4, the supply conveyance path 9 and the agitation conveyance path 10 are arranged obliquely so that the upper wall surface of the agitation conveyance path 10 is higher than the lower wall surface of the supply conveyance path 9 as shown in FIG. 2. It arranges so that it may become a position. In other words, a part of the space constituting the agitation transport path 10 has advanced into a part of the space constituting the supply transport path 9 in the vertical direction.

  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 it can flow toward the point without resisting gravity, the stress applied to the developer can be reduced.

  As shown in FIG. 5, a fin member is provided on the shaft of the stirring screw 11 in the part 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. Also good. 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 more efficiently delivered from the agitation transport path 10 to the supply transport path 9.

  In the developing device 4, the supply conveyance path 9 and the agitation conveyance path are set such that the distance between the centers of the development roller 5 and the supply conveyance path 9 is shorter than the distance between the centers of the development roller 5 and the agitation conveyance path 10. 10 are 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 reduced in size.

  Further, the agitating screw 11 rotates in the clockwise direction as viewed from the front side in FIG. 2 (the arrow C direction in the figure), and the developer lifts the developer along the shape of the agitating screw 11 and feeds and conveys it. It is transferred to the road 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 the 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 has 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 that drops 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 developing region width α, the upstream side in the transport direction of the supply transport path 9 is longer than the developing roller 5 by the upstream region β of the supply transport path. Further, since the surplus opening 92 is provided outside the developing region width α, the downstream side in the transport direction of the supply transport path 9 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 having the configuration shown in FIG. 4, since the supply opening 91 is provided within the developing region width α, the upstream side in the transport direction of the supply transport path 9 is on the supply transport path than the developing device 4 in FIG. The flow side region β can be shortened. Further, since the surplus opening 92 is provided in the developing area width α, the downstream side in the transport direction of the supply transport path 9 can be made shorter by the area γ on the downstream side of the supply transport path than the developing device 4 in FIG.

  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 can be saved.

  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 collection 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, the toner replenishing port 95 for replenishing toner is provided above the upstream end of the agitating and conveying path 10 including the agitating screw 11 in the conveying direction. 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.

  A portion where the toner supply port 95 is provided is on an extension line in the conveyance direction of the supply conveyance path 9 and corresponds to an empty 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 the position above the upstream end portion in the transport direction of the stirring transport path 10 and may be provided above the downstream end portion of the collection transport path 7.

  Further, a toner replenishing port 95 may be provided directly above the collection opening 93 (see FIG. 4), 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. You can plan. Furthermore, since the developer is likely to be mixed in the collection opening 93 serving as a delivery unit, the developer can be more efficiently stirred by replenishing at this position.

  In the developing device 4 described with reference to FIG. 4, as described above, the supply opening 91 that delivers the developer from the downstream end in the transport direction of the stirring transport path 10 to the upstream end in the transport direction of the supply transport path 9, and the supply Since the surplus opening 92 for transferring the developer from the downstream end of the transport path 9 to the upstream end of the stirring transport path 10 in the transport direction is provided in the development region width α, the development apparatus is more in comparison with the conventional development apparatus 4. 4 can be saved in space, and the entire developing device 4 can be saved in space.

  In addition, by providing the toner replenishing port 95 in an empty space by providing the surplus opening 92 within the developing region width α, the developing device 4 can be reduced in size.

  Further, the developer can be efficiently stirred by replenishing the toner from above the collection opening 93 which is a delivery portion of the developer from the collection conveyance path 7 to the stirring conveyance path 10.

  Further, by providing the developing device 4 as the developing means of the printer unit 100 of the copying machine as the 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 the present embodiment, the developer including toner and carrier is supplied from the 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. Such a replenishment developer is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-203814, which is a prior application of the present applicant.

  FIG. 8 is an explanatory perspective view of the vicinity of the front end in a state in which the discharge screw 2 a, the stirring screw 11, the recovery screw 6, and the doctor blade 12 that are discharge conveyance members 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 in the conveyance direction of the supply conveyance path 9 to the upstream end in the conveyance direction of the supply conveyance path 9 is the agitation conveyance path 10. The circulating conveying member that applies a conveying force to the developer in the agitating and conveying path 10 that is the circulating conveying path is the agitating screw 11. Further, the circulation opening provided near the downstream end in the conveyance direction of the supply conveyance path 9 and through which the passed developer is transferred to the agitation conveyance path 10 which is a circulation conveyance path is a surplus opening 92. 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 disposed on the downstream side in the conveyance direction of the supply conveyance path 9 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 the discharge conveyance path 2. Are openings provided in the discharge partition wall 135 so as to communicate with each other.

  Further, the developing device 4 reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, and retains the developer that has not entered the surplus opening 92 that is the circulation opening near the surplus opening 92. As a supply downstream end wall surface 80 (see FIGS. 4 and 6). Further, in FIGS. 4 and 6, the developer discharge port 94 which is a discharge opening is above the surplus opening 92 and out of the staying developer retained by the supply downstream end wall surface 80, the developer discharge port 94. It is provided so that the developer having reached the position can be passed. In other words, the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path 9 cannot enter the surplus opening 92, and the surplus developer overflowing from the surplus opening 92 is blocked by the supply downstream end wall surface 80. Stopped and becomes a stagnant 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.

  Next, the main part of the developing roller 5, which is a characteristic part of the present embodiment, will be described with reference to FIG.

  The developing roller 5 includes a cylindrical developing sleeve 81 that carries a developer and a magnet roller 82 that is included in the developing sleeve 81 and serves as a magnetic field generating unit that attracts the developer by magnetic force.

  The developing sleeve 81 is made of a nonmagnetic and conductive material such as aluminum, austenitic stainless steel or magnesium.

  The surface may be smooth, but in a high-speed machine, the following roughening treatment / processing may be performed to suppress developer slip.

(A) Groove extrusion processing such as V-groove or U-groove, machining of various concave shapes or laser processing or edging processing (B) Blasting processing (C) Thermal spraying processing of metal or ceramic etc. Magnet roller 82 is in the developer transport direction It is provided so as to be rotatable in the direction of arrow J opposite to P, and an even number of magnets 83 are arranged at equal intervals (10 magnets are arranged in the configuration of the embodiment shown in FIG. 9), and their polarities are adjacent to each other. They are oriented in opposite directions so as to attract each other.

  In the present embodiment, the driving relationship between the magnet roller 82 and the developing sleeve 81 can be selected from either the same or relative rotational direction, and the rotational relationship is carried on the surface of the developing sleeve 81. The developer is set on the condition that the number of facings between the developer and the magnet 83 on the magnet roller 82 side increases.

  Due to the increase in the number of times the developer faces the magnet of the magnet roller 82 obtained by setting the drive relationship described above, a spike is formed when the developer is opposed to the magnetic pole, and the spike is broken when the developer is separated from the magnetic pole. The number of repetitions of the phenomenon is increased, and the charging property of the toner can be improved by increasing the chance of frictional contact between the toner and the carrier.

  In this case, the increase in the number of facings can be obtained by setting the rotational direction of the magnet roller 83 and the developing sleeve 81, setting the speed difference, or the like as described above. That is, when both rotate in the same direction, the number of times the developer faces the magnet 83 can be increased by setting a speed difference between them, and the opposite direction without setting the speed difference. In this case, the number of times the developer faces the magnet 83 can be increased in the same manner.

  The experimental results based on such a rotational direction or speed difference will be described with reference to FIG.

  For the above-described magnet 83, a conventional inexpensive ferrite magnet can be used, but a stronger rare earth magnet such as a samarium cobalt magnet or a neodymium magnet can also be used for downsizing and speeding up. The magnet 83 may be supported on the magnet holder 84 by adhesion, and the outer periphery thereof may be protected by a heat shrinkable tube or the like (not shown).

  If the magnet holder 84 is made of a magnetic material, the magnetic force of the magnet 83 can be slightly improved. However, since the cost is high and magnetic materials mainly composed of iron are generally high in specific gravity, the moment of inertia increases at the time of high-speed rotation, which may cause a problem in the durability of the drive unit. Therefore, although the magnetic force of the magnet 83 is slightly reduced, nonmagnetic and light specific gravity aluminum or magnesium may be used as a material.

  In FIG. 9, the rotation center P 'of the magnet roller 82 in this embodiment is eccentrically positioned at a position away from the rotation center P of the developing sleeve 81 by a distance (T).

  The direction of eccentricity is set so that the developer carried on the surface of the developing roller 5 can be closest to the inner surface of the developing roller 81 at a position before transferring to the photosensitive member 1 and is indicated by the above-mentioned symbol T. The amount of eccentricity corresponding to the distance is an amount that can suppress the carrier from moving to the photosensitive member 1 in the developing region by the magnetic force from the magnetic pole. As a result, the developer transferred to the photosensitive member 1 can be contacted in a state in which the rising is ensured upon contact with the photosensitive member, and carrier transfer is prevented by the magnetic force from the approaching magnetic pole so that only the toner is transferred to the photosensitive member. It moves so that it may be supplied to the latent image.

  On the other hand, the magnetic force can be kept low on the side opposite to the eccentric direction. For this reason, the developer carried on the surface of the developing sleeve 5 can be easily peeled off.

  By providing such an eccentric structure, the developer can be easily peeled off without using external mechanical external force.

  Further, by decentering the magnet roller 82, a gap space U is formed between the developing sleeve 81 and the magnet roller 82, and a magnetic shield plate 85 corresponding to a magnetic shielding member is disposed in this space U.

  The magnetic shield plate 85 is preferably a ferromagnetic material having a relative magnetic permeability of about 100 to 100,000 and a soft magnetic material having a coercive force of 100 or less, and a material such as iron, silicon steel, permalloy, sendust, ferrite, and amorphous is selected. Is possible. Furthermore, a material obtained by dispersing the soft magnetic material in a resin material such as polycarbonate, ABS, polystyrene, nylon, etc., and dissolving and molding it can also be used.

  The magnetic shield plate 85 is exposed to the attractive force from the magnet roller 82 due to its magnetic characteristics. As will be described later, if the suction force is strong and the strength is weak because the two ends are supported, there is a concern that the center portion bends and contacts the magnet roller 82. In order to reduce the attraction force, it is preferable to dispose the magnet sleeve 82 away from the developing roller 81 as long as it does not contact the developing sleeve 81. Further, the thickness of about 0.2 mm to 2 mm can be used, but about 1 mm is preferable from the viewpoint of strength.

  By the way, as described above, the magnetic shield plate 85 bends each time it faces the magnetic pole when the magnet roller 82 rotates, so that vibration occurs in the so-called longitudinal direction. Therefore, in the present embodiment, as described above, a configuration that avoids contact with the magnet roller 82 due to bending and suppresses bending vibration is also employed. This configuration will be described later with reference to FIG. 13 and subsequent drawings. To do.

  A configuration in which a magnetic shield member is provided between the developing sleeve and the magnet roller is proposed in, for example, Reference 1 (Japanese Utility Model Laid-Open No. 60-39053).

  However, in this configuration, the main purpose is to select whether or not the magnetic force from the magnet roller is applied to the surface of the developing sleeve.

  Specifically, among the plurality of developing rollers, the magnetic shield member is separated from the developing area so as to be able to act on the developing roller in use, and the above-described case is described in the case of non-use. Contrary to the case, the magnetic shield member is opposed to the developing region so that the magnetic force does not reach.

  For this reason, the rotation of the magnet roller is not performed, and the configuration of the number of times the developer is opposed to the magnetic pole is merely intended to eliminate the spike and the spike of the magnetic brush on the surface in the rotation of the developing sleeve. There is nothing, and there is no idea of facilitating the peeling of the developer in the process of promoting the charging of the toner to the carrier in the developer.

  On the other hand, in a developing device in which the magnet roller does not rotate, it is well known that a repulsive magnetic field is formed by the same polarity by using an odd number of magnetic poles as in the conventional configuration shown in FIGS. And can be easily implemented.

  However, in this embodiment, it is assumed that the magnet roller is rotated, and as described above, unlike the case of using a repulsive magnetic field when an odd number of magnetic poles are provided, FIG. As shown, the number of magnetic poles is an even number. For this reason, the developer cannot be peeled off by forming a repulsive magnetic field with the same polarity when an odd number of magnetic poles are used.

  Therefore, in order to peel off the developer when an even number of magnetic poles are used, a method of peeling off the developer by bringing a flexible scraper into contact with the developing sleeve 81 can be considered. Then, the magnet roller 82 is eccentric so that the magnetic pole facing the developer peeling position is separated from the inner surface of the developing sleeve 81. Thereby, it is possible to prevent a problem in mechanical durability from occurring as in the case of using a scraper.

  By the way, as configurations in which the developer peeling action is obtained by the difference in the magnetic force, Reference Patent Document 2 (Japanese Patent Laid-Open No. 57-190974) and Reference Patent Document 3 (Japanese Patent Publication No. 04-65379). ).

  However, in order to completely separate the developer using such an eccentric structure of the magnet roller, it is necessary to increase the diameter of the developing sleeve 81 and increase the amount of eccentricity, which may increase the size of the apparatus.

  In this embodiment, a magnetic shield plate 85 is fixedly disposed in the vicinity of a rotating magnet roller that is eccentric with respect to the developing sleeve so as not to increase the size of the developing sleeve.

  Therefore, unlike the case of combining the above reference patent documents, the repulsive magnetic field for peeling the developer is not formed in the case where the number of times the magnetic pole and the developer are opposed to each other by rotation and the even number of poles is set. However, the present invention is not limited to suppressing the action of magnetic force by eccentricity, but is characterized in that the magnetic attraction of the developer is almost eliminated by providing a magnetic shield plate.

Next, the transfer of the developer in the present embodiment will be described with reference to FIG.
The developer supplied to the developing roller 5 by the supply screw 8 is attracted onto the developing sleeve 81 by the magnetic force of the magnet roller 82 and arranged along the lines of magnetic force. That is, magnetic spikes are generated on the magnet 83 as indicated by reference symbol B1, and the magnetic spikes fall between the magnets 83 as indicated by reference symbol B2.

  When the rotation direction of the magnet roller 82 is a direction opposite to the rotation direction (I) of the developing sleeve 81 as indicated by the symbol J, while the magnet roller 82 rotates, the magnetic spikes are in a so-called flip flap shape. It rotates and proceeds in the direction of arrow F opposite to the direction indicated by arrow J, which is the direction of rotation of the magnet roller 82. At this time, the developing sleeve 81 may be supplementarily rotated in the direction of arrow I at a relatively low speed.

  The developer is regulated by the doctor 12 so that the height of the magnetic head is kept constant, and the excess developer is returned to the supply screw 8 in the flow of the arrow M and supplied to the developing roller 5 again while being conveyed in the axial direction.

  As the developer passing through the developing doctor 12 continues to rotate, the magnetic roller 82 is decentered to gradually increase the attracting force to the developer sleeve 81 and suppress the carrier from being transferred to the photosensitive drum. As the magnet roller 82 rotates more rapidly, the developer is vigorously stirred at the opposite portion of the photosensitive drum 1, so that the toner can be transferred efficiently according to the latent image.

  As the developer continues to rotate, the attracting force to the developer sleeve 81 gradually decreases due to the eccentricity of the magnet roller 82 and is separated from the developing sleeve 81 by its own weight in the supply conveyance path 7, but the developer is developed by the slightly remaining attracting force. Some developer remains on the sleeve 81.

  The lines of magnetic force generated from the magnet 83 in the vicinity of the magnetic shield plate 85 pass through the magnetic shield plate 85 having a higher magnetic permeability, and there is no leakage magnetic field to the outside of the developing sleeve 81.

  Here, all the remaining developer falls, and the developing sleeve 81 completes preparation for the next developer conveyance. As a result, the developer once used for development is not transported as it is toward the development area again, so that the problem that the toner concentration of the developer is lowered can be suppressed.

  By the way, when the width | variety of the magnetic shield board 85, ie, the width along the circumferential direction of the magnet roller 82, is small, the problem that a vibration generate | occur | produces with rotation of the magnet roller 82 is estimated.

  The magnet 83 acting on the magnetic shield plate 85 becomes a single pole, and the magnet 83 is located on the upstream side in the rotational direction and the downstream side in the rotational direction within the width along the circumferential direction of the magnetic shield plate 85. This is because the direction of the attractive force acting on the magnetic shield plate 85 is switched. The vibration propagated to the developing device and became an abnormal image or noise in the form of horizontal stripes.

  Therefore, in this embodiment, the relationship between the installation angle (R °) corresponding to the width in the circumferential direction of the magnetic shield plate 85 and the arrangement angle (Q °) of the magnetic pole 83 is set as follows. Yes.

R °> Q °
Where R °: each end portion in the circumferential direction of the magnetic shield plate 85 from the rotation center of the magnet roller 82
The angle formed by the line connecting
Q °: formed by a line connecting the center of two magnets from the rotation center of the magnet roller 82
As a result, an attractive force is always generated from the plurality of magnets 83 on the magnetic shield plate 85, and the force is averaged to suppress vibration.

  Since this embodiment is configured as described above, the apparatus can be reduced in size. That is, in order to completely remove the developer from the developing sleeve 81 without using the magnetic shield plate, which is a feature of the present invention, the eccentric amount of the included magnet roller 82 is set. It must be increased to prevent the magnetic force from reaching.

  However, the magnet roller 82 has a limit in reducing the diameter in order to exhibit the function of conveying the developer. Instead, it is necessary to increase the diameter of the developing sleeve 81.

  In this embodiment, the diameter of the magnet roller 83 is about φ17.6 mm. However, if the magnetic shield plate 85 is not provided, the diameter of the developing sleeve 81 needs to be about φ28 to 30 mm.

  On the other hand, when the magnetic shield plate 85 is provided, the diameter of the developing sleeve 81 can be set to φ25 mm, which makes it possible to reduce the size of the developing device. In particular, as shown in FIG. In the case of a color laser copying machine of the type, it is possible to obtain a result that the entire copying machine can be downsized.

  Next, the configuration in the longitudinal direction of the developing roller 5 used in this embodiment will be described with reference to FIG.

  In FIG. 10, the lower right corresponds to the back side of the image forming apparatus, and flanges 86 are press-fitted into both ends of the rotatable developing sleeve 81, and the developing sleeve 81 and the flange 86 can be rotated together. A bias applying brush 88 is pressed against the flange 86 on the front side to apply the developing bias to the developing sleeve 81.

  A driven gear 89 is fixed to the rear flange 86, and the drive is transmitted from a drive gear (not shown) to the developing sleeve 81. Further, supporters 87 are provided at both ends, and the supporters 87 are fixedly supported by the developing device 4.

  Next, the longitudinal sectional structure on the back side of the developing roller 5 used in the present embodiment will be described with reference to FIG. Since the front side cross section has almost the same configuration, the description thereof is omitted.

  In FIG. 11, the outer ring of the ball bearing 91 is press-fitted into the flange 86, and the support sleeve 87 is press-fitted into the inner ring of the ball bearing 91, whereby the developing sleeve 81 is rotatably supported.

  On the other hand, the outer rings of the ball bearings 92 and 93 are press-fitted at positions eccentric from the ball bearing 91 near the center of the supporter 87, and the shaft 90 press-fitted into the magnet roller 82 is supported. A coupling or gear (not shown) is attached to the tip of the shaft 90 to transmit the drive to the magnet roller. Note that the ball bearings 91 and 92 are displaced in the longitudinal direction to reduce the diameter of the developing roller. The magnetic shield plate 85 is fixedly supported by inserting a pin protruding from a supporter 87 (not shown).

Using the developing device 4 configured as described above, an experiment was performed on the number of times the developer faces the magnetic pole using a high-speed copying machine having a continuous print number of 60 to 70 (sheets / min), and the result shown in FIG. . Note that the result shown in FIG. 12A is for the case where the developing sleeve 81 and the magnet roller 83 rotate in opposite directions as shown in FIG. In this case, both directions may be the same. In this case, it is desirable to increase the number of times the developer and the magnetic pole face each other by providing a speed difference between the two. The experimental result in the latter case is shown in FIG. In FIG. 12 (B), Example 4 shows the case of rotating in opposite directions, and Example 5 shows the case of the same rotation direction (speed difference is set).
Further, as a comparative example (shown as a conventional example in FIG. 12), the developing device having the configuration shown in FIG. 20 was used as a target. In the configuration shown in FIG. 20, the magnet roller is fixed.

  In FIG. 12A, in the conventional developing device, the magnet roller arranged in a fixed manner has five magnetic poles, and is set to 60 to 70 (sheets / minute), which is the number of continuous prints described above. In order to obtain the copying speed, the developing sleeve had to be rotated at 400 rpm. At this time, the number of times the magnetic pole passes through the path from the supply conveyance path to the collection conveyance path is only five, and there is a problem of toner scattering after the developer replacement or after leaving in a high humidity environment.

  On the other hand, in the developing device of Example 1, when the number of magnetic poles is 10 and the magnet roller is rotated at 600 rpm, the developing sleeve can obtain an image density equivalent to that of the conventional example at 300 rpm, and is collected and conveyed from the supply conveyance path. The number of passes of the magnetic pole in the path leading to the path was obtained about 15 times, and there was no problem of toner scattering even after changing the developer or leaving it in a high humidity environment.

  In the developing device of Example 2, when the number of magnetic poles is the same 10 and the magnet roller is rotated at 1200 rpm, the developing sleeve can obtain an image density equivalent to that of the conventional example at 180 rpm, and from the supply conveyance path to the recovery conveyance path. The number of times the magnetic poles passed through the route was about 30 times, and there was no problem of toner scattering even after changing the developer or after leaving for a long time in a high humidity environment.

  In the developing device of Example 3, when the magnetic roller is rotated at 2000 rpm with the same number of magnetic poles, the image density equivalent to that of the conventional example can be obtained even if the developing sleeve is fixed, and from the supply conveyance path to the recovery conveyance path. The number of passes of the magnetic poles in the route reached was about 50 times, and there was no problem of toner scattering even after the developer replacement or after leaving for a long period of time in a high humidity environment, but noise of high-speed rotation of the magnet roller was generated.

  On the other hand, in FIG. 12B, when rotating in the opposite direction, even when the rotation speed is the same, the number of facings is greater than in the conventional example in FIG. It can also be seen that the number of facings can be increased according to the speed difference.

  From the above description, it can be seen that there are a plurality of appropriate rotation speed conditions, and these may be set as appropriate. Also, suitable conditions can be set as needed even when the copying speed is different or the developing sleeve diameter is different. The same applies to the rotation direction.

  Further, the above embodiment is a case where the present invention is applied to the developing device having the supply conveyance path, the recovery conveyance path, and the agitation conveyance path in the configuration shown in FIG. The present invention can also be applied to a developing device having only the supply conveyance path and the recovery conveyance path, which is shown in the drawing.

  When applied, the developer that has been sent to the collection transport path is supplied to the supply transport path as it is. It becomes possible to prevent uniformity and density reduction.

  By the way, in this embodiment, as described above, the magnetic shielding member is disposed in the gap space U between the magnet roller 67 formed by the eccentricity with respect to the center of the cross section of the developing sleeve 81 and the inner surface of the developing sleeve 81. The magnetic shield plate 85 is flexibly vibrated by repeatedly receiving a magnetic attractive force from the magnet roller 82 side.

  Therefore, in this embodiment, as described above, even when bending deformation occurs, it is arranged in a range that does not contact the inner surface of the magnet roller 82, and the occupation range of the magnetic shield plate 85 along the rotation direction of the magnet roller. Is selected to have a relationship of R °> Q ° as described above.

  However, in the case of a long magnetic shield plate, the span between the supporting positions becomes large and is easily affected by a bending moment, which causes remarkable bending vibration.

  In this embodiment, such a phenomenon can be suppressed, and its configuration will be described below.

  FIG. 13 is a diagram showing an arrangement configuration of the magnetic shield plate 85 with respect to the magnet on the magnet roller 67 side when the vibration suppression measure in this embodiment is not used.

  In the figure, the magnetic shield plate 85 is positioned in a state in which the rotation direction edge of the magnet roller 82 (see FIG. 9) is parallel to the longitudinal direction of the magnet 83 in the longitudinal direction.

  For this reason, as shown in FIG. 14, the magnetic shield plate 85 is in the same state as the beam structure in which both ends are supported, and in the longitudinal direction, the center in the longitudinal direction is most easily bent by the magnetic attractive force from the magnet side. This bending and the return to the original shape occur each time the magnets face each other, and vibration is generated by this repetition.

  In this embodiment, the edge along the rotation direction of the magnet roller 82 is formed so as not to be parallel to the magnet 83 on the magnet roller 82 side.

  FIG. 15 shows a configuration in which the edge of a magnetic shield plate (indicated by reference numeral 85 ′ for convenience) along the rotation direction of the magnet roller 82 is twisted along the longitudinal direction so as not to be parallel to the extending direction of the magnet 83 of the magnet roller 82. It is shown.

  In this configuration, the period in which the magnetic attractive force from the magnet 83 on the magnet roller 82 side acts on the edge of the magnetic shield plate 85 ′ is different in the longitudinal direction of the magnetic shield plate 85 ′, and is uniform in the longitudinal direction. In other words, in other words, the bending deformation cycle of the edge of the magnetic shield plate 85 ′ is different from the case where the suction cycles operate in the longitudinal direction. As a result, the bending moment does not occur intensively at the longitudinal center of the magnetic shield plate as in the case where a magnetic attractive force with a uniform period is applied, and the vibration that occurs when the bending moment is concentrated. It is to be suppressed.

  Such a configuration in which the action period of the magnetic attractive force at the edge along the longitudinal direction is varied is not limited to twisting the linear edge shown in FIG. 15, but as shown in FIG. It is also possible to form the edge shape into an uneven shape, a sawtooth shape or a zigzag shape. In addition, when the structure in which the magnetic shield plate 85 ′ supports both ends in the longitudinal direction (longitudinal direction) is targeted, the thickness is varied from the support position side toward the center, specifically, the support position side is the most. The section rigidity may be increased by increasing the thickness.

  In the above-described embodiment, the shape of the edge portion of the magnetic shield plate 85 ′ is devised to suppress the occurrence of flexural vibration due to the magnetic attractive force from the magnet roller 67. The power itself may be neutralized.

  FIG. 17 shows the configuration in this case. In the drawing, a plurality of magnetic poles (indicated by N and S) are provided along the longitudinal direction on the surface of the magnetic shield plate facing the magnet 83 on the magnet roller 82 (see FIG. 9) side.

  As a configuration in which a plurality of magnetic poles are provided, a configuration in which a magnet sheet 96 is attached to the surface of the magnetic shield plate 85 is employed. The magnet sheet 96 is obtained by mixing a ferrite magnet or rare earth magnet powder into an elastic material such as rubber and molding it into a thin sheet. The magnet sheet 96 is excellent in flexibility, and is adhered to the magnetic shield plate 85 with an adhesive tape.

Magnetization is single-sided multi-pole magnetization (FIG. 17) or double-sided multi-pole magnetization, and the magnetization pitch is about 2 to 8 mm. it can. FIG. 17 shows a state in which the N pole of the magnet 83 faces the magnet sheet 96, but the S pole of the magnet sheet 96 is attracted in the same manner as the configuration shown in FIG. To do.
As a result, the force acting on the magnetic shield plate 85 can be reduced by canceling the attractive force and the repulsive force.
As described above, the magnet arrangement on the magnetic shield plate 85 side is not limited to arranging a plurality of magnets along the longitudinal direction, and may be arranged along the rotation direction of the magnet roller 82, for example. In short, any arrangement configuration may be used as long as the magnetic attractive force from the magnet roller 82 side is relaxed and the magnetic shield plate 85 is not deformed.

  By the way, there is a configuration disclosed in Reference Patent Document 4 (Japanese Patent Laid-Open No. 09-211992) as a configuration approximate to a configuration in which the magnetic shield plate 85 is disposed in the gap space U, which is the configuration of the present embodiment.

  In this document, as shown in FIG. 21, a magnetic shield plate 134 is provided in a space between the developing sleeve 133 and the magnet roller 132a on the side of the magnet roller 132a that rotates inside the developing sleeve 133 that faces the image carrier. A configuration in which is arranged is disclosed.

  However, this configuration does not correspond to a configuration in which the magnet roller 132a is eccentrically arranged with respect to the developing sleeve 133, and the developing sleeve 133 and the magnet roller 132a are similar to those in Reference Documents 2 and 3. It is designed to rotate in the same direction. For this reason, it can be said that the number of times the developer faces the magnet roller when rotating in the same direction is not so many. In particular, in Reference Patent Document 4, since the main purpose is to move the developer in a spiked state toward the development region while remaining in the spiked state, the rotational movement of the developer ( The developer sleeve and the magnet roller are rotated at the same speed because the developer is not moved by rolling), and in such a configuration, the developer and the magnetic pole on the magnet roller side are hardly opposed. I can say no. For this reason, it can be said that there is no idea of increasing the number of oppositions between the developer and the magnet to be obtained in the present embodiment and increasing the chance of frictional contact.

  Accordingly, from Reference Patent Document 4, the effect of increasing the number of frictional contact between the toner and the carrier by increasing the number of times the developer and the magnet roller face the magnetic pole is increased by providing a difference in the rotation speed between the developing sleeve and the magnet roller. It cannot be expected.

  In the embodiment as described above, the developer on the developing sleeve is used even when the magnetic shield plate is simply provided in the space between the developing sleeve and the magnet roller so as not to exert a magnetic force on the surface of the developing sleeve. Since the number of times that the magnetic roller and the magnetic pole on the magnet roller side face each other can be increased, the number of frictional contact between the carrier contained in the developer and the toner can be increased to ensure the toner charge amount. Can be prevented. In addition, even when the even-numbered magnetic pole is provided on the magnet roller and the repulsive magnetic pole is not provided, the developer can be easily peeled off from the developing sleeve. Furthermore, it is possible to obtain a developing device that prevents vibration when the magnetic shield plate used for peeling of the developer is opposed to the magnetic pole of the magnet roller and does not generate noise.

  The developer used in this embodiment has the following configuration.

The toner used in this embodiment contains at least a binder resin and a colorant, and if necessary, a release agent, a charge control agent, and other components. In addition to the above-mentioned additives, a fluidity improver and other components are added as necessary. For these materials, all known materials are possible.
Examples of the binder resin include styrene, parachlorostyrene, vinyl toluene, vinyl chloride, vinyl acetate, vinyl propionate, methyl (meth) acrylate, ethyl (meth) tacrylate, propyl (meth) acrylate, (meth ) N-butyl acrylate, isobutyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) Hydroxypropyl acrylate, 2-chloroethyl (meth) acrylate, (meth) acrylonitrile acid, (meth) acrylamide, (meth) acrylic acid, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether. Examples include a weight body of monomers such as vinyl methyl ketone, N-vinyl pyrrolidone, N-vinyl pyridine and butadiene, a copolymer composed of two or more of these monomers, or a mixture thereof. In addition, polyester resin, polyol resin, polyurethane resin, polyamide resin, epoxy resin, rosin, modified rosin, terbene resin, phenol resin, hydrogenated petroleum resin, ionomer resin, silicone resin, ketone resin, xylene resin, etc. alone or in combination Can be used.

  As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R) ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Se Red, Parachlor Ortonito Aniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmin Min BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Tolujing Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake , Thioindigo red B, thioindigo maroon, oil red, quinacridone red, pyrazolone red, Riazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Cyanine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

Examples of the charge control agent include nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (including fluorine-modified quaternary ammonium salts). .), Alkylamide, phosphorus simple substance or compound, tungsten simple substance or compound, fluorine-based activator, salicylic acid metal salt, metal salt of salicylic acid derivative, and the like.
The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 2 to 5 parts by weight is preferable. If the amount is less than 0.1 parts by weight, the toner is not practically negatively charged. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, and the electrostatic attraction force with the carrier increases, leading to a decrease in developer fluidity and a decrease in image density.

Examples of release agents include low molecular weight polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, beeswax, carnauba wax, candelilla wax, rice wax, and montan wax. Natural waxes such as paraffin wax, petroleum wax such as microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid, myristic acid, metal salts of higher fatty acids, higher fatty acid amides, and various modified waxes thereof. Can be mentioned.

  These may be used alone or in combination of two or more, but it is preferable to use those having a melting point in the range of 70 to 125 ° C. By setting the melting point to 70 ° C. or more, a toner having excellent transferability and durability can be obtained, and by setting the melting point to 125 ° C. or less, the toner can be melted quickly at the time of fixing and a reliable release effect can be exhibited. The amount of these release agents used is preferably 1 to 15% by weight based on the toner. If it is less than 1% by weight, the effect of preventing offset is insufficient, and if it is 15% by weight or more, transferability and durability are deteriorated.

As an additive (external additive), at least a fine particle having a volume average particle diameter of 50 to 500 nm and a bulk density of 0.3 g / cm ³ or more is added. The amount of external addition is preferably 0.2 to 3% by weight based on the toner base. If the amount is less than this range, the effect of forming an appropriate gap between the toners or between the toner and the others is not exhibited. On the other hand, when the amount is large, the fluidity is inhibited or the amount of desorption increases, so that an aggregate of external additives is formed, and the image quality is deteriorated.
In addition to the above-mentioned additives, additives outside this range can be added, and it is preferable to add fine particles having a small volume average particle diameter for the purpose of improving fluidity.

In the additive in the present embodiment, as the inorganic _{compound, SiO2, TiO 2, Al 2} O 3, MgO, CuO, ZnO, SnO 2, CeO 2, Fe 2 O 3, BaO, CaO, K 2 O, Na ₂ O, ZrO ₂ , CaO.SiO ₂ , K ₂ O (TiO ₂ ) n, Al ₂ O ₃ .2SO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _3, etc. _{preferably, SiO 2, TiO 2, Al} 2 O 3 and the like. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like.
The organic compound additive may be a thermoplastic resin or a thermosetting resin. For example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin. , Urea resin, aniline resin, ionomer resin, polycarbonate resin and the like. As the resin fine particles, two or more of the above resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained.

  Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like.

  The additive (fine particles) in this embodiment is excellent as a toner for a developer in the developing device. That is, the contact area with the toner particles, the photoconductor drum, and the charge imparting member is very small and contacts evenly, so the effect of reducing adhesion is great and effective in improving development / transfer efficiency. Furthermore, since it acts as a roller, it is buried in the toner particles even when cleaning the cleaning drum and the photosensitive drum under high stress (high load, high speed, etc.) without wearing or damaging the photosensitive drum. It is difficult to remove or return even after being buried a little, so that stable characteristics can be obtained over a long period of time. Further, the toner is moderately detached from the surface of the toner and accumulated at the tip of the cleaning blade, and the so-called dam effect has an effect of preventing a phenomenon that the toner passes from the blade.

  As a method for producing the toner in the present embodiment, a method obtained by melting and kneading a toner constituent material and then pulverizing and classifying is generally used as a conventional method, but is not limited to this method. A method is possible.

  As the polymerization method, a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, and the like are possible. Although different from the polymerization method, in addition to a dissolution suspension method, a polymer suspension method, etc., an extension reaction method or the like can be used. .

  Other than the conventional method is preferable in that the toner having the above-described particle size range and circularity can be easily obtained. Further, the circularity may be adjusted by subjecting the toner after pulverization and classification to heat treatment.

  The method for adding the additive in the present embodiment is not particularly limited, and a method in which the toner base particles and the additive are mechanically mixed and adhered using various known mixing devices, or a toner base in a liquid phase. There is a method in which particles and additives are uniformly dispersed with a surfactant or the like, and after an adhesion treatment, dried.

  The particle size distribution of the toner described above can be measured by using a toner particle size distribution measuring apparatus by the Coulter counter method. Examples of these devices include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.

  First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the weight and number of toner particles or toner are measured with the above-described measuring apparatus using a 100 μm aperture as the aperture. Calculate weight distribution and number distribution. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.

  As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

The circularity of the toner described above is a value obtained by the following equation.
Circularity = (perimeter of a circle having the same area as the projected area of the particle) / (perimeter of the projected particle image)
This circularity is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is a perfect sphere, and the circularity becomes smaller as the surface shape becomes more complicated.

  Circularity can be measured using a flow type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. As a specific measuring method, 0.1 to 0.5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of water from which impure solids have been previously removed, and further measurement is performed. Add about 0.1-0.5g of sample. The suspension in which the sample is dispersed is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape of the toner is measured with the above-mentioned apparatus with the dispersion concentration being 3000 to 10000 / μl.

Hereinafter, the carrier used in this embodiment will be described supplementarily.
The carrier used in this embodiment is formed so that the weight average particle diameter is 20 to 60 μm (preferably 20 to 45 μm). This particle size range is also excellent as a carrier for the developer in the developing device.

  When the average particle diameter of the carrier is less than 20 μm, fine powder is increased in the distribution of the carrier particles, and the magnetization per particle may be lowered to cause carrier scattering. On the other hand, if the average particle size of the carrier exceeds 45 μm, the carrier spikes during the development process become rough, and the uniformity of solid and halftone may be inferior (particularly, the average particle size exceeds 60 μm). And become prominent.) In addition, since the specific surface area is reduced, toner scattering may occur in a small particle size toner.

  The carrier is not particularly limited except for the particle diameter, and can be appropriately selected according to the purpose. However, a carrier having a core material and a resin layer covering the core material is preferable.

  There is no restriction | limiting in particular as a material of a core material, It can select suitably from well-known things, for example, 50-90 emu / g manganese-strontium (Mn-Sr) type material, manganese-magnesium (Mn-Mg) ) Based materials are preferred, and in terms of securing image density, highly magnetized materials such as iron powder (100 emu / g or more), magnetite (75 to 120 emu / g) are preferred. In addition, weak magnetization such as copper-zinc (Cu-Zn) (30 to 80 emu / g) is advantageous in that it can weaken the contact with the photosensitive drum in which the toner is in a spiked state and is advantageous in improving the image quality. Material is preferred. These may be used alone or in combination of two or more.

  The material for the resin layer of the carrier is not particularly limited and can be appropriately selected from known resins according to the purpose. Examples thereof include amino resins, polyvinyl resins, polystyrene resins, and halogenated olefin resins. Polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, fluoride Examples thereof include a copolymer of vinylidene and vinyl fluoride, a fluoroterpolymer such as a terpolymer of tetrafluoroethylene, vinylidene fluoride, and a non-fluorinated monomer, and a silicone resin. These may be used individually by 1 type and may use 2 or more types together.

  The resin layer may contain conductive powder or the like as necessary. Examples of the conductive powder include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. The average particle diameter of these conductive powders is preferably 1 μm or less. When the average particle diameter exceeds 1 μm, it may be difficult to control the electric resistance.

  The carrier resin layer is prepared, for example, by dissolving the silicone resin in a solvent to prepare a coating solution, and then uniformly coating the coating solution on the surface of the core by a known coating method, drying, and baking. It can form by performing. Examples of the application method include a dipping method, a spray method, and a brush coating method.

  The amount of the resin layer in the carrier is preferably 0.01 to 5.0% by mass. If the amount of the resin layer is less than 0.01% by mass, a uniform resin layer may not be formed on the surface of the core material. If the amount exceeds 5.0% by mass, the resin layer becomes too thick. As a result, granulation of carriers occurs, and uniform carrier particles may not be obtained.

  The developer (premix toner) used in this embodiment is a mixture of the above-described toner and carrier. The toner and the carrier are triboelectrically charged by mixing. Mixing can be performed using a known mixer.

  The developer (initial agent) stored in advance in the developing device is also a mixture of the above-described toner and carrier. There is no restriction | limiting in particular as content (carrier density | concentration) of the carrier in a developing agent, According to the objective, it can select suitably. For example, 90-98 mass% is preferable and 93-97 mass% is more preferable.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 4 Developing device 81 Developing sleeve 82 Magnet roller 85, 85 'Magnetic shield plate 96 Magnetic sheet T Eccentricity U Gap space between developing sleeve and magnet roller

Japanese Patent No. 3127594 JP 2007-101797 A

Claims (11)

A developing device including a developer carrier for supplying a two-component developer containing toner and a carrier to an electrostatic latent image formed on the image carrier,
Inside the developer carrying member, a rotatable magnetic field generating means having a magnetic pole for causing the developer to stand up and transported is disposed,
The magnetic field generating means is arranged with its center of the cross section decentered in a direction approaching the image carrier with respect to the center of the cross section of the developer carrier.
A magnetic shielding member capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. And the magnetic shielding member is configured such that the edge along the rotation direction of the magnetic field generating means is not parallel to the magnetic pole provided on the magnetic field generating means . A developing device including a developer carrier for supplying a two-component developer containing toner and a carrier to an electrostatic latent image formed on the image carrier,
Inside the developer carrying member, a rotatable magnetic field generating means having a magnetic pole for causing the developer to stand up and transported is disposed,
The magnetic field generating means is arranged with its center of the cross section decentered in a direction approaching the image carrier with respect to the center of the cross section of the developer carrier.
A magnetic shielding member capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. And the magnetic shielding member is configured by arranging a plurality of magnetic poles along the longitudinal direction of the magnetic field generating means . A developing device including a developer carrier for supplying a two-component developer containing toner and a carrier to an electrostatic latent image formed on the image carrier,
Inside the developer carrying member, a rotatable magnetic field generating means having a magnetic pole for causing the developer to stand up and transported is disposed,
The magnetic field generating means is arranged with its center of the cross section decentered in a direction approaching the image carrier with respect to the center of the cross section of the developer carrier.
A magnetic shielding member capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. The developing device is characterized in that a plate-like member is used as the magnetic shielding member, and the plate-like member has a different thickness in the longitudinal direction . 4. The developing device according to claim 1, wherein the magnetic field generating unit includes even-numbered magnetic poles arranged along a rotation direction thereof . 5. 5. The magnetic shielding member according to claim 1, wherein the magnetic shielding member is provided with a shielding angle larger than an angle between magnetic poles provided in the magnetic field generation unit. The developing device described.   The plurality of magnetic poles provided on the magnetic shielding member are set to polarities capable of suppressing flexural vibration along the longitudinal direction of the shielding member due to the magnetic force from the magnetic pole provided on the magnetic field generating means. The developing device according to claim 5, wherein:   7. The developing device according to claim 5, wherein a magnetic sheet having a plurality of magnetic poles is attached to the magnetic shielding member. The magnetic shielding member is closer to the inner side of the developer carrier than the magnetic field generator in a gap space between the surface of the magnetic field generating unit opposite to the side biased to the image carrier and the inner surface of the developer carrier. The developing device according to claim 1 , wherein the developing device is arranged in such a manner. 4. The magnetic field generating means is rotatable in the same direction or relative direction as the developer carrying member, and when rotating in the same direction, a relative speed difference is set to rotate. The developing device according to any one of the above. An image forming apparatus using the developing device according to claim 1 . The image forming apparatus according to claim 10, further comprising a process cartridge that collectively accommodates at least the developing device and the image carrier .

Images