JP2008233892A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device having a simple configuration by which a desired amount of developer can be delivered to an image bearing member, and an image forming apparatus. <P>SOLUTION: The developing device 1 includes: a developing roller 17 by which the two-component developer is borne and delivered to a photoreceptor drum 8; a layer thickness-regulating member 20 regulating a layer thickness of the developer; a magnetism-generating member 22 for generating magnetism; and a control part 23 for controlling an amount of displacement of the magnetism-generating member 22. Since the control part 23 controls an amount of displacement of the magnetism-generating member 22 relative to a development sleeve 27, the control on the amount of displacement allows for the control on the influences of the magnetism which the magnetism-generating member 22 generates toward the development sleeve 27, and controls the amount of the developer which passes through a gap between the magnetism-generating member 22 and the developing sleeve 27. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device that develops an electrostatic latent image using a two-component developer and an image forming apparatus including the developing device.

  An electrophotographic image forming apparatus that forms an image by electrophotography includes a developing device that develops an electrostatic latent image formed on a photoreceptor. As a developing device, there is a developing device that develops an electrostatic latent image using a two-component developer (hereinafter also referred to as “developer”) composed of toner and a carrier. In such a two-component developing device, a developer contained in a developer container is carried on a developer carrying member and conveyed to a developing region facing the photosensitive member, and toner in the developer is transferred to the photosensitive member in the developing region. To develop the electrostatic latent image. In the developing device, the developer is carried on the developer carrying member by the magnetic force of a magnet roller contained in the developer carrying member.

  In the two-component developing device, the toner is consumed as the image is formed, and the carrier is repeatedly used for a certain period. The carrier deteriorates under various stresses during repeated use. The stress regulates, for example, environmental changes such as temperature and humidity at which the image forming apparatus is installed, heat generation from each part in the image forming apparatus caused by operating the image forming apparatus for a long time, and developer layer thickness. For example, pressure due to the developer moving at high speed in a narrow gap formed by the layer thickness regulating member. The toner is always electrically attached to the surface of the carrier due to its mirror image force, but this stress causes the toner on the carrier surface to cover the carrier surface over time without leaving the carrier, so-called spent. A phenomenon occurs. There also occurs a phenomenon that the coating material covering the surface of the carrier is peeled off. Therefore, the fluidity of the developer is deteriorated, and the amount of the developer conveyed by the developer carrier is reduced. Along with this, the layer thickness of the toner layer regulated by the layer thickness regulating member is also reduced, so that the development amount for developing the electrostatic latent image on the photosensitive member is reduced and the image density is lowered.

  Also, the carrier and the toner are charged by friction with each other, and the charge amount is maintained by the insulating properties of both the toner and the carrier. However, due to changes in the surrounding environment, the charge amount of the toner is greatly affected. For example, the charge amount of the developer decreases under high temperature and high humidity conditions. Occur.

  A conventional developing device that solves such a problem has been disclosed. In this conventional developing device, an electromagnet is disposed upstream of the developer conveying direction of the magnetic blade so that image defects such as density unevenness and image fog do not occur even if the atmosphere changes. The toner layer thickness is controlled by controlling the energization amount to the electromagnet according to the atmosphere and changing the magnetic force induced in the magnetic blade (see, for example, Patent Document 1).

  In the developing device described in Patent Document 2, a magnet body in which at least two magnetic poles, that is, an S pole and an N pole are formed on the upstream side in the sleeve rotation direction of the layer thickness regulating member is arranged facing the rotating sleeve and fixed during development. The magnet body is arranged so that one magnetic pole of the magnet roller and one magnetic pole of the magnet body have the same polarity, thereby regulating the amount of toner flowing into the layer thickness regulating member.

  At the time of non-development, the magnetic body is driven to rotate in a predetermined rotation direction, the magnetic field distribution formed between the magnet body and the fixed magnet roller is changed by the rotation of the magnet body, and the toner aggregate is vibrated by vibrating the toner aggregate. I am trying to relax. As a result, image defects due to clogging of toner aggregates in the gap between the rotating sleeve and the layer thickness regulating member are prevented.

JP 2005-106874 A JP 2005-134774 A

  In the developing device described in Patent Document 1, since the electromagnet has a coil, toner easily clogs the coil, and there is a problem that the developer cannot be taken out when the developer is replaced. Further, when the coil is constantly in contact with the developer at a high pressure, the coil is liable to be deteriorated. Therefore, the coil needs to be frequently replaced, and it is difficult to maintain the performance. Further, since the electromagnet is provided in the direction in which the developer carrying member extends, there is a problem that the electromagnet is enlarged, the structure is complicated, and the cost is high.

  Further, in the developing device described in Patent Document 2, the amount of toner flowing into the layer thickness regulating member is regulated by installing the magnet body and rotating the magnet body. With such a configuration, there is an effect of loosening toner aggregates in the vicinity of the layer thickness regulating member, but since agitation characteristics for new replenishing toner in the developing tank are not taken into consideration, an original with a high printing rate is long. In the case of continuous output, there is a problem that an image defect occurs with a decrease in stirring characteristics.

  Accordingly, an object of the present invention is to provide a developing device and an image forming apparatus that can convey a desired amount of developer to an image carrier with a simple configuration.

The present invention is a developing device for developing an electrostatic latent image formed on an image carrier using a two-component developer,
A developer provided rotatably around a predetermined first axis, carrying a two-component developer and transporting it to an image carrier, and a magnet roller provided in the developer sleeve and generating magnetism A carrier,
A layer thickness regulating member provided facing the developing sleeve and regulating the layer thickness of the two-component developer carried by the developing sleeve;
A magnetism generating member that is disposed upstream of the layer thickness regulating member in the rotational direction of the developing sleeve and is displaceable facing the developing sleeve;
And a control unit that controls a displacement amount of the magnetism generating member with respect to the developing sleeve.

In the present invention, the magnetism generating member is configured to be displaceable at least in the horizontal direction.
The control means controls the amount of displacement of the magnetism generating member in the horizontal direction.

In the present invention, the magnetism generating member is
A cylindrical body that is provided so as to be angularly displaceable around a predetermined second axis and is formed into a cylindrical shape;
A magnetic pole forming portion for forming magnetic poles at a plurality of circumferential positions of the cylindrical body inside the cylindrical body,
The control means controls the amount of angular displacement around the second axis of the cylindrical body.

  Furthermore, the invention is characterized in that the length of the magnetic generating member in the direction in which the first axis extends is equal to the length of the developer carrier in the direction in which the first axis extends.

  Furthermore, the invention is characterized in that the length of the magnetism generating member in the direction in which the first axis extends is larger than the length of the developer carrier in the direction in which the first axis extends.

  Further, the present invention is characterized in that the control means controls the displacement amount of the magnetism generating member based on the toner density detected by the density detecting means for detecting the toner density developed on the image carrier. To do.

  Furthermore, the invention is characterized in that the surface roughness of the magnetism generating member is different from the surface roughness of the developing sleeve.

  Further, the present invention is characterized in that a diameter of the cylindrical body is smaller than a diameter of the developing sleeve.

  Further, the present invention is characterized in that a diameter of the cylindrical body is equal to a diameter of the developing sleeve.

Furthermore, the present invention is characterized in that the magnetic force of the magnet roller in the developing sleeve at a position facing the magnetic generating member is set larger than the magnetic force of the magnetic generating member at a position facing the developing sleeve. To do.
Furthermore, the present invention is an image forming apparatus comprising the developing device.

  According to the present invention, the developing device regulates the developer carrying member that carries a two-component developer (hereinafter sometimes referred to as “developer”) and conveys it to the image carrying member, and the layer thickness of the developer. A layer thickness regulating member, a magnetism generating member that generates magnetism, and a control unit that controls the amount of displacement of the magnetism generating member relative to the developing sleeve are configured. The developer carrying member is provided to be rotatable around the first axis, and includes a developing sleeve and a magnet roller provided in the developing sleeve and generating magnetism. With this magnet roller, the developer can be carried on the surface of the developing sleeve, and the developer can be conveyed to the image carrier. The magnetism generating member is provided upstream of the layer thickness regulating member in the rotation direction of the developing sleeve and displaceably facing the developing sleeve. Since the magnetism generating member generates magnetism, the layer thickness of the developer carried on the developing sleeve can be controlled by the magnetism. Since the control means controls the amount of displacement of the magnetism generating member relative to the developing sleeve, the influence of magnetism generated by the magnetism generating member on the developing sleeve can be controlled by controlling the amount of displacement. Therefore, it is possible to control the amount of developer passing between the magnetism generating member and the developing sleeve. Thus, the layer thickness of the developer can be reliably regulated to a desired layer thickness by the layer thickness regulating member on the downstream side in the rotation direction of the magnetism generating member. As a result, it is possible to control the amount of movement of the developer to the image carrier. Therefore, it is possible to realize a developing device that can convey a desired amount to the image carrier with a simple configuration.

  According to the invention, the magnetism generating member is configured to be displaceable at least in the horizontal direction, and the amount of displacement in the horizontal direction is controlled by the control means.

  By appropriately adjusting the distance between the magnetic generating member and the predetermined magnetic pole of the magnet roller, and the surface magnetic force of the magnetic generating member and the predetermined magnetic pole, the repulsive magnetic force generated between the magnetic generating member magnetic pole and the magnetic roller magnetic pole The amount of the developer that moves from the surface of the developing sleeve to above the stirring member can be adjusted.

  On the other hand, since the new toner for replenishment into the developing tank is set to fall from above the agitating member, the developer moved from the developing sleeve and the replenishing toner that falls are encountered at substantially the same location. The replenishing toner is mixed with the developer and stirred by the stirring member.

  The controllability of the magnetic force changes depending on how the magnetism generating member is displaced, but the controllability is improved by changing the distance between the magnetism generating member and the developing sleeve, particularly by displacing the magnetism generating member in a horizontal direction. It becomes possible.

  Further, according to the present invention, the magnetism generating member includes a cylindrical body provided so as to be angularly displaceable about the second axis, and an inner side of the cylindrical body, and magnetic poles at a plurality of circumferential positions of the cylindrical body. And a magnetic pole forming part for forming The control means controls the amount of angular displacement around the second axis of the cylindrical body. The control unit can oppose the developing sleeve to the portion that generates the optimum magnetism among the plurality of magnetic poles by controlling the angular displacement amount. Thereby, the magnetic force between the developer carrier and the layer thickness regulating member can be controlled. Further, since the magnetic pole forming portion is provided inside the cylindrical body, it is possible to prevent the developer from undesirably adhering to the magnetic pole forming portion. Therefore, there is no possibility that the developer is clogged by the magnetism generating member, and stable development performance can be exhibited even if the number of developments is increased. In addition, by moving the magnetism generating member in the horizontal direction while rotating, the amount of developer moved by the developing sleeve and the position where it encounters the replenishing toner are precisely adjusted and controlled according to the characteristics and usage environment of the developer. As a result, optimum developer agitation characteristics can be obtained.

  Further, according to the present invention, the length of the magnetic generating member in the direction in which the first axis extends is equal to the length of the developer carrier in the direction in which the first axis extends. This makes it possible to control the amount of developer passing between the magnetism generating member and the developing sleeve over the entire developing area of the developer carrying member. Therefore, it is possible to eliminate the unevenness of the amount of developer carried over the entire area of the developer carrying member. As a result, development without unevenness can be realized.

  Furthermore, according to the present invention, the length of the magnetism generating member in the direction in which the first axis extends is greater than the length of the developer carrier in the direction in which the first axis extends. Since both ends of the magnetism generating member may reduce the ability to control the amount of developer movement relative to the center due to the nature of magnetism generated by the magnetism generating member, the length of the magnetism generating member may be If it is the same as the length of the body, the amount of developer at the end of the development area may be different from the center. On the other hand, in the present invention, by making the length of the magnetic generating member longer than that of the developer carrier, the amount of the developer at the end portion and the central portion of the developing region can be made equal. Therefore, it is possible to eliminate the unevenness of the amount of developer carried over the entire area of the developer carrying member. As a result, development without unevenness can be realized.

  Further, according to the present invention, the control means controls the amount of displacement of the magnetism generating member based on the toner density detected by the density detecting means for detecting the toner density developed on the image carrier. As a result, the developer transport amount can be controlled based on the toner density detected in real time in accordance with environmental fluctuations and developer deterioration. As a result, the developer transport amount can be controlled in real time so that the optimum developer transport amount is obtained.

  Furthermore, according to the present invention, the surface roughness of the magnetism generating member is different from the surface roughness of the developing sleeve. Thus, by making the surface roughness different between the magnetism generating member and the developing sleeve, the amount of developer carried and moved on the surfaces of both members can be made different. Therefore, for example, by making the surface roughness of the developing sleeve rougher than that of the magnetism generating member, it is possible to increase the amount of developer transported to the developing sleeve, so that the developer transport capability is greater than that of the magnetism generating member. Can be set. Thereby, the amount of the developer conveyed by the developer carrier can be set to a desired amount.

  Furthermore, according to the present invention, the diameter of the cylindrical body is smaller than the diameter of the developing sleeve. As a result, the entire developing device can be reduced in size.

  Furthermore, according to the present invention, the diameter of the cylindrical body is equal to the diameter of the developing sleeve. Therefore, the cylindrical body and the developing sleeve can be shared, and the cost can be reduced.

  Further, according to the present invention, the magnetic force of the magnet roller in the developing sleeve at the position facing the magnetic generating member is set larger than the magnetic force of the magnetic generating member at the position facing the developing sleeve. Therefore, the developer carried on the developer carrying member can be prevented from being undesirably carried on the magnetism generating member. As a result, it is possible to prevent the amount of the developer carried by the developer carrying body from becoming too small, and to reliably transport the developer to the image carrying body.

  Furthermore, according to the present invention, since the image forming apparatus includes the developing device, it is possible to realize an image forming apparatus that achieves the excellent effects described above.

  Hereinafter, a plurality of embodiments for carrying out the present invention will be described with reference to the drawings. Portions corresponding to the matters described in the preceding forms in each embodiment are denoted by the same reference numerals, and overlapping description may be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in the preceding section. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

  FIG. 1 is a front view schematically showing the developing device 1 according to the first embodiment of the present invention. FIG. 2 is a front view schematically showing an image forming apparatus 2 that is an application example of the developing device 1. The image forming apparatus 2 of the present embodiment is realized by a dry electrophotographic color image forming apparatus 2. The image forming apparatus 2 forms a multicolor or single color image on a predetermined recording sheet 3 based on, for example, image data transmitted from each terminal device on the network. The image forming apparatus 2 includes four visible image forming units 4Y, 4M, 4C, and 4B (hereinafter sometimes collectively referred to as “visible image forming unit 4”), a recording paper transport unit 5, and a fixing device 6. , And a supply tray 7.

  A plurality of recording papers 3 can be placed on the supply tray 7. The plurality of recording papers 3 placed on the supply tray 7 are separated one by one, and the visible image forming unit 4Y closest to the supply tray 7 is provided. To supply.

  Each visible image forming unit 4 corresponds to four colors of yellow (Y), magenta (M), cyan (C), and black (B), respectively, and four visible image forming units 4Y, 4M, 4C, 4B. Are arranged side by side. The visible image forming unit 4Y forms an image using yellow (Y) toner T, and the visible image forming unit 4M forms an image using magenta (M) toner T to form a visible image. The unit 4C forms an image using cyan (C) toner T, and the visible image forming unit 4B forms an image using black (B) toner T. A specific arrangement is a so-called tandem type in which four visible image forming units 4 are arranged along a conveyance path of the recording paper 3 that connects the supply tray 7 of the recording paper 3 and the fixing device 6.

  Each visible image forming unit 4 has substantially the same configuration, and includes a developing device 1, a photosensitive drum 8, a charger 9, laser light irradiation means 10, a transfer roller 11, and a cleaner unit 12. Is provided. Each visible image forming unit 4 multiplex-transfers each color toner T onto the recording paper 3 conveyed from the supply tray 7.

  The photosensitive drum 8 carries an image to be formed. The charger 9 uniformly charges the surface of the photosensitive drum 8 to a predetermined potential. The laser light irradiation means 10 exposes the surface of the photosensitive drum 8 charged by the charger 9 according to the image data input to the image forming apparatus 2, and an electrostatic latent image is formed on the surface of the photosensitive drum 8. Form. The developing device 1 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 8 with the toner T of each color. The transfer roller 11 is applied with a bias voltage having a polarity opposite to that of the toner T, and transfers the formed toner image onto the recording paper 3 conveyed by the recording paper conveying means 5 described later. The drum cleaner unit 12 removes and collects the toner T remaining on the surface of the photosensitive drum 8 after the development processing in the developing device 1 and the transfer of the image formed on the photosensitive drum 8. The transfer of the toner image to the recording paper 3 as described above is repeated four times for four colors.

  The recording paper transport means 5 includes a driving roller 13, an idling roller 14 and a transport belt 15, and recording supplied from the supply tray 7 so that a toner image is formed on the recording paper 3 by the visible image forming unit 4. The paper 3 is conveyed. The driving roller 13 and the idling roller 14 stretch the endless conveyance belt 15, and the endless conveyance belt 15 is rotated by rotating the drive roller 13 at a predetermined peripheral speed. Yes. The transport belt 15 generates static electricity on the outer surface, and transports the recording paper 3 while electrostatically attracting the recording paper 3.

  In this way, the recording paper 3 is transferred to the conveying belt 15 while being transferred with the toner image, and then peeled off from the conveying belt 15 by the curvature of the driving roller 13 and conveyed to the fixing device 6. The fixing device 6 applies appropriate heat and pressure to the recording paper 3 to dissolve the toner T and fix it to the recording paper 3, thereby forming a robust image.

  Next, the configuration of the developing device 1 will be described with reference to FIG. The developing device 1 includes a developing container 16, a developing roller 17, a paddle 18, a stirring roller 19, a layer thickness regulating member 20, an exhaust unit 21, a magnetism generating member 22, and a control unit 23. The developing container 16 is a container-like member formed of, for example, a synthetic resin. The developing roller 17, the paddle 18, the stirring roller 19, and the layer thickness regulating member 20 are accommodated in the internal space of the developing container 16. Containing a two-component developer (hereinafter also referred to as “developer”). An opening 24 extending in parallel with the axial direction of the photosensitive drum 8 is formed on a side surface of the developing container 16 facing the photosensitive drum 8. A developer receiving port 25 is formed on the wall of the developing container 16 above the stirring roller 19 in the vertical direction. A developer hopper (not shown) is provided above the developer receiving port 25 in the vertical direction.

  The developer hopper is provided so that the developer receiving port 25 and a toner replenishing port (not shown) formed at the lower portion in the vertical direction of the developer hopper are connected to each other. As a result, the internal space of the developer container 16 and the internal space of the developer hopper communicate with each other. The developer hopper is a container-like member formed of, for example, a synthetic resin and stores the toner T in the internal space. The toner T is stored in the developer hopper, and the toner T is supplied into the developer container 16 through the developer receiving port 25 according to the consumption state of the toner T in the developer container 16. An exhaust port 26 is formed in the wall of the developing container 16 below the developing roller 17 in the vertical direction. The function of the exhaust port 26 will be described later.

  The agitation roller 19 agitates the toner T supplied from the developer hopper to the developing container 16 according to the consumption state of the toner T, and transports it around the paddle 18 in a uniform state. The stirring roller 19 is a screw-like roller member that is provided so as to face the developing roller 17 through the paddle 18 and is rotatably supported by the developing container 16, for example.

  The paddle 18 stirs and conveys the developer conveyed from the stirring roller 5 and supplies it to the developing roller 17. The paddle 18 is a roller member that is provided so as to face the photosensitive drum 8 with the developing roller 17 interposed therebetween, and is supported by the developing container 16 so as to be rotatable about an axis. As the paddle 18 rotates, the developer in the developing container 16 is supplied around the developing roller 17, and a developer layer is formed on the surface of the developing roller 17.

  The developing roller 17 is a developer carrying member, and is rotatably provided around a predetermined first axis L1. The developing roller 27 carries a two-component developer and conveys it to the photosensitive drum 8, and a developing sleeve. 27 and a magnet roller 28 that generates magnetism. The developing roller 17 is spaced apart from the photosensitive drum 8 through, for example, an opening 24 formed facing the photosensitive drum 8 in the developing container 16, and the axis of the photosensitive drum 8 and the developing roller 17 are separated from each other. It is a roller member provided so that the 1st axis line L1 may become parallel. The developing sleeve 27 is a cylindrical member that is rotatably fitted to the magnet roller 28, and is a cylindrical member in the present embodiment. The developing sleeve 27 is made of metal such as aluminum and stainless steel. A potential is applied to the developing sleeve 27 from a power source (not shown) so that a potential difference is generated between the developing sleeve 27 and the photosensitive drum 8.

  The magnet roller 28 is fixedly provided so as to be included in the developing sleeve 27, and forms a magnetic pole inside the developing sleeve 27. The magnet roller 28 is formed by alternately arranging magnet members having different magnetic poles in the circumferential direction. In the present embodiment, the magnet roller 28 uses a permanent magnet such as ferrite, and has seven magnetic poles S1, N1, S2, N3, S4, S3, and N2.

  The developing sleeve 27 is rotationally driven in the direction of the arrow A in the counterclockwise direction toward the paper surface of FIG. 1 by the driving means 29 (see FIG. 3), and the other end is supported by, for example, the sliding bearing 30. Has been. The developing sleeve 27 rotates in the same direction as the photosensitive drum 8 in a developing region (developing nip portion) formed at the closest portion to the photosensitive drum 8. That is, the rotation direction of the developing sleeve 27 about the axis L1 is opposite to the rotation direction of the photosensitive drum 8 about the axis. Hereinafter, in order to simplify the description, the rotation direction of the developing sleeve 27 may be referred to as the rotation direction of the developing roller 17. The developing roller 17 magnetically attracts the carrier by the magnetic force of the magnetic pole formed by the magnet roller 28, and the magnetic material composed of the carrier and the toner T is formed on the radially outer surface portion of the developing sleeve 27. Form a brush. The magnetic brush is formed along the magnetic field radiated from the magnetic pole formed by the magnet roller 28. The developing roller 17 rotates the developing sleeve 27 in the direction of arrow A to convey the developer to the developing nip portion that is the closest facing portion between the developing roller 17 and the photosensitive drum 8, and the toner in the magnetic brush T is supplied to the surface portion of the photosensitive drum 8.

  The layer thickness regulating member 20 is provided to face the developing sleeve 27 and regulates the layer thickness of the developer carried on the developing sleeve 27. By such a layer thickness regulating member 20, the developer layer thickness is adjusted to a desired value. The layer thickness regulating member 20 is mounted on the surface of the developing roller 17 with one end in the short direction being attached to the developing container 16 and the other end being a free end with a gap on the surface of the developing roller 17. A thin plate member provided in contact with the developer layer. The separation distance W1 between the layer thickness regulating member 20 and the developing roller 17 is the shortest distance between the developing roller 17 and the layer thickness regulating member 20 in the radial direction of the developing roller 17. The separation distance W1 is not less than 0.5 mm and not more than 1.0 mm, for example. For the layer thickness regulating member 20, for example, a thin plate formed of a nonmagnetic elastic material can be used. The elastic material is not particularly limited, and examples thereof include elastic metals (aluminum, stainless steel such as SUS316), and synthetic resins having elasticity. Moreover, the layer thickness control member 20 which consists of magnetic stainless steels, such as SUS430, can also be used for further image quality improvement. A predetermined amount of developer passing through the gap between the layer thickness regulating member 20 and the developing roller 17 is conveyed to the developing nip portion by the rotation of the developing roller 17.

  The exhaust means 21 sucks the air in the developing container 16 and discharges it to the outside. The exhaust means 21 includes an exhaust port 26, an exhaust fan 31, and an exhaust duct 32. The exhaust fan 31 is provided at a position facing the developing roller 17 through the wall of the developing container 16 in the vertical direction. The exhaust fan 31 sucks the air in the developing container 16 through the intake / exhaust port 26 and the exhaust duct 32 and discharges it to the outside of the developing container 16. As a result, the inside of the developing container 16 has a negative pressure, and external air can be introduced into the developing container 16 from the opening 24. Each of the exhaust ports 26 is a band-shaped opening formed on the wall of the developing container 16 below the developing roller 17 in the vertical direction so as to extend in parallel to the axis L1 of the developing roller 17 and in the longitudinal direction of the developing container 16. is there. The exhaust port 26 is also formed in parallel. The exhaust port 26 is a passage for discharging outside air introduced into the developing container 16 from the opening 24 to the outside of the developing container 16. The exhaust duct 32 is provided outside the developing container 16 adjacent to the exhaust port 26, and temporarily stores air discharged from the exhaust port 26. According to the exhaust unit 21, the air flowing into the developing container 16 through the opening 24 from the gap between the photosensitive drum 8 and the developing container 16 flows around the developing roller 17, passes through the exhaust port 26, and the exhaust duct 32. Then, the exhaust fan 31 discharges the developer container 16 to the outside. Since air flowing through the air flow path in the developing container 16 is removed by a filter (not shown) provided in the flow path, it may be discharged to the outside of the developing container 16 as it is.

  FIG. 3 is a cross-sectional view showing the magnetism generating member 22 and the developing roller 17 in a simplified manner. The magnetism generating member 22 will be described with reference to FIG. In FIG. 3, the magnetism generating member 22 and the developing roller 17 are shown apart from each other for easy understanding. The magnetism generating member 22 is disposed upstream of the layer thickness regulating member 20 in the rotation direction of the developing sleeve 27 and is disposed so as to be opposed to the developing sleeve 27. The magnetism generating member 22 is provided at a position vertically above the developer level 33 and close to the paddle 18. The magnetism generating member 22 is provided so as to be angularly displaceable around a predetermined second axis L2, and is formed in a cylindrical shape, a cylindrical body 34, and an inner side of the cylindrical body 34. And a magnetic pole forming portion 35 for forming magnetic poles at a plurality of circumferential positions.

  In the present embodiment, cylindrical body 34 is formed in a cylindrical shape, for example. The cylindrical body 34 is not limited to such a cylindrical shape, and may be a polygonal shape. The cylindrical body 34 is spaced from the developing sleeve 27 with a gap, and is provided so that the axis L1 of the developing sleeve 27 and the axis L2 of the cylindrical body 34 are parallel to each other. The shortest distance W2 between the outer peripheral surface of the cylindrical body 34 and the outer peripheral surface of the developing sleeve 27 is selected based on the layer thickness of the developer carried on the developing sleeve 27, the magnetic force of the magnetism generating member 22, and the like, for example 5 mm It is set to 10 mm or less. The cylindrical body 34 is rotatably fitted on the magnetic pole forming portion 35. The cylindrical body 34 is formed of a metal such as aluminum and stainless steel. The diameter of the cylindrical body 34 is set to be smaller than or equal to the diameter of the developing sleeve 27. In the present embodiment, the diameter of the cylindrical body 34 is set smaller than the diameter of the developing sleeve 27. For example, the diameter of the cylindrical body 34 is set to 10 mm, and the diameter of the developing sleeve 27 is set to 30 mm. . Thus, by making the diameter of the cylindrical body 34 smaller than the diameter of the developing sleeve 27, the entire developing device 1 can be reduced in size.

  The magnetic pole forming portion 35 is provided so as to be angularly displaceable around the axis of the cylindrical body 34 so as to be included in the cylindrical body 34, and forms a magnetic pole inside the cylindrical body 34. The magnetic pole forming part 35 is formed by arranging magnet members having different magnetic poles in the circumferential direction almost alternately. In the present embodiment, the magnetic pole forming portion 35 is made of a permanent magnet made of, for example, ferrite, alkoni, and rare earth, and has two magnetic poles having the polarity of N pole and three magnetic poles having the polarity of S pole. . As shown in FIG. 1, the magnetic pole having the polarity of N pole is arranged so as to be located on a line segment connecting the rotation center of the developing sleeve 27 and the rotation center of the cylindrical body 34. In addition, at least one of the five magnetic poles of the magnetic pole forming unit 35 is set to be smaller than the magnetic force of the magnet roller 28 at a position facing the magnetism generating member 22. Accordingly, by causing the magnetic pole forming portion 35 to be angularly displaced, the magnetic force of the magnet roller 28 at the position facing the magnetism generating member 22 can be made larger than the magnetic force of the magnetic pole forming portion 35 at the position facing the developing sleeve 27. it can. The magnetic pole forming portion 35 is configured such that one end portion in the axial direction can be angularly displaced by a magnetic pole forming portion driving means 36 to a desired angular displacement amount. The magnetic pole forming unit driving means 36 is realized by, for example, a stepping motor.

  The cylindrical body 34 is rotationally driven in the direction of the arrow B, for example, clockwise by the driving means 29 toward the paper surface of FIG. The rotation direction of the cylindrical body 34 may be clockwise or counterclockwise. The rotation direction of the cylindrical body 34 is appropriately determined by the total balance of the surface shape, magnetic force, distance, and the like of the developing sleeve 27 and the cylindrical body 34. The cylindrical body 34 is configured to be able to transmit a driving force by being mechanically connected to a driving means 29 for driving the developing sleeve 27 via a gear. With this configuration, the developing sleeve 27 and the cylindrical body 34 can be driven by one driving means 29, and the configuration can be simplified.

  In the present embodiment, as shown in FIG. 3, the length W3 of the magnetism generating member 22 in the direction in which the first axis L1 extends is greater than the length W4 of the developing roller 17 in the direction in which the first axis L1 extends. Each dimension is set so as to increase.

  FIG. 4 is a front view for explaining the magnetic relationship between the developing roller 17 and the magnetism generating member 22. The amount of the developer carried by the developing sleeve 27 and passing between the developing sleeve 27 and the cylindrical body 34 has a correlation with the magnetic force distribution formed by the magnet roller 28 and the magnetic pole forming portion 35. For example, as shown in FIG. 4A, when the magnetic pole of the magnet roller 28 is N-pole and the magnetic pole of the magnetic pole forming part 35 closest to the developing roller 17 is also N-pole, the magnetic pole forming part repels each other. The magnetic flux density between 35 and the magnet roller 28 becomes small. In such a case, the developer conveying force is reduced, and the amount of developer passing between the developing sleeve 27 and the cylindrical body 34 is reduced.

  From the state shown in FIG. 4 (1), the magnetic pole forming portion 35 is angularly displaced around the axis L2, and as shown in FIG. 4 (2), the magnetic roller 28 has the N pole and the closest distance to the developing roller 17. When the magnetic poles of the magnetic pole forming part 35 are S poles, the magnetic flux density between the magnetic pole forming part 35 and the magnet roller 28 increases by attracting each other. In such a case, the developer conveying force increases, and the amount of developer passing between the developing sleeve 27 and the cylindrical body 34 increases. Therefore, by controlling the angular displacement amount of the magnetic pole forming portion 35, the developer conveying force by the developing roller 17 can be controlled.

  Further, the magnetic flux density between the magnetic pole forming portion 35 and the magnet roller 28 is also affected by the magnitude of the magnetic flux density between the magnetic pole forming portion 35 itself and the magnet roller 28 itself. When the magnetic force between the magnet roller 28 and the magnetic pole forming portion 35 is increased and the developer conveying force is increased, the pressure on the developer is increased, so that the charge amount of the developer is increased. Therefore, the magnetism generating member 22 also has a function of controlling the charge amount of the developer.

  FIG. 5 is a block diagram showing a simplified electrical configuration related to the magnetism generating member 22. The controller 23 controls the distance between the magnetism generating member 22 and the developing sleeve 27. In the present embodiment, the control unit 23 controls the amount of angular displacement around the axis L2 of the cylindrical body 34. The control unit 23 controls the amount of angular displacement of the magnetism generating member 22 based on the toner density detected by the density detecting means 37 that detects the toner density developed on the photosensitive drum 8. As a result, the magnetism generating member 22 controls the magnetic force with the developing roller 17 in accordance with the measurement result of the patch on the photosensitive drum 8, and controls the amount of toner supplied to the layer thickness regulating member 20. Controls development fluctuations due to humidity and developer deterioration.

  The density detection unit 37 is realized by, for example, a light emitting element 38 that irradiates infrared light toward the photosensitive drum 8 and a light receiving element 39 that receives reflected infrared light from the photosensitive drum 8. Therefore, the light emitted from the light emitting element 38 is reflected on the toner image on the photosensitive drum 8, and the light is detected by the light receiving element 39. The control unit 23 gives a drive command to the magnetic pole forming unit driving means 36 in accordance with the value detected by the light receiving element 39. As a result, the magnetic pole forming portion 35 is angularly displaced, for example, from several degrees to 180 degrees around the axis by the magnetic pole forming portion driving means 36.

  In the developing device 1 using a two-component developer, the toner T is consumed as the image is formed, and the carrier is repeatedly used for a certain period. The carrier deteriorates under various stresses during repeated use. When the developer is deteriorated as described above, the fluidity of the developer is deteriorated and the chargeability of the developer is also deteriorated, so that the toner density on the photosensitive drum 8 is lowered. When the toner concentration becomes low, the control unit 23 gives a drive command to the magnetic pole forming unit driving means 36 so that the magnetic flux density between the magnetic pole forming unit 35 and the magnet roller 28 is increased as shown in FIG. The amount of angular displacement of the magnetic pole forming portion 35 is controlled so as to increase. As a result, the developer conveying force can be increased, and the toner density on the photosensitive drum 8 can be increased to control the toner density to a desired level. Further, the control unit 23 gives a drive command to the magnetic pole forming unit driving means 36 when the charge amount of the toner T is reduced due to environmental changes, for example, high temperature and humidity, and the toner density on the photosensitive drum 8 is increased. 4 (1), the angular displacement amount of the magnetic pole forming portion 35 is controlled so that the magnetic flux density between the magnetic pole forming portion 35 and the magnet roller 28 becomes small. As a result, the developer conveying force can be reduced, the toner density on the photosensitive drum 8 can be lowered, and the toner density can be controlled to a desired level. Further, the control unit 23 gives a drive command to the magnetic pole forming unit driving means 36 when the charge amount of the toner T becomes high and the toner density on the photosensitive drum 8 becomes low due to the environmental change, for example, low temperature and low humidity. 4 (2), the angular displacement amount of the magnetic pole forming portion 35 is controlled so that the magnetic flux density between the magnetic pole forming portion 35 and the magnet roller 28 is increased. As a result, the developer conveying force can be increased, and the toner density on the photosensitive drum 8 can be increased to control the toner density to a desired level.

  The control unit 23 controls the angular displacement amount based on a data map stored in advance in order to control the angular displacement amount of the magnetic pole forming unit 35 as described above. In the data map, the relationship between the amount of angular displacement and the toner concentration is related to the surrounding environment, and the optimum amount of angular displacement is searched based on the detected environmental load and toner concentration. Easily remembered. By using such a data map, the controller 23 can shorten the calculation time of the displacement amount and can control the magnetism generating member 22 in real time based on the toner concentration.

  As described above, in the developing device 1 of the present embodiment, the developing device 1 carries the two-component developer and conveys it to the photosensitive drum 8, and the layer that regulates the layer thickness of the developer. A thickness regulating member 20, a magnetism generating member 22 that generates magnetism, and a control unit 23 that controls the amount of displacement of the magnetism generating member 22 are configured. The developing roller 17 is provided rotatably around the first axis L1, and includes a developing sleeve 27 and a magnet roller 28 provided in the developing sleeve 27 and generating magnetism. With the magnet roller 28, the developer can be carried on the surface of the developing sleeve 27 and conveyed to the photosensitive drum 8. The magnetism generating member 22 is disposed upstream of the layer thickness regulating member 20 in the rotation direction of the developing sleeve 27 and is disposed so as to be opposed to the developing sleeve 27. Since the magnetism generating member 22 generates magnetism, the layer thickness of the developer carried on the developing sleeve 27 can be controlled by this magnetism. Since the controller 23 controls the amount of displacement of the magnetism generating member 22 relative to the developing sleeve 27, the influence of magnetism generated by the magnetism generating member 22 on the developing sleeve 27 can be controlled by controlling the amount of displacement. Therefore, the amount of developer passing between the magnetism generating member 22 and the developing sleeve 27 can be controlled. Accordingly, the layer thickness of the developer can be reliably regulated to a desired layer thickness by the layer thickness regulating member 20 on the downstream side in the rotation direction of the magnetism generating member 22. As a result, the amount of developer moved to the photosensitive drum 8 can also be controlled. Therefore, the developing device 1 capable of transporting a desired amount to the photosensitive drum 8 with a simple configuration can be realized. Further, by providing the developing device 1 as described above in the image forming apparatus 2, it is possible to provide the image forming apparatus 2 that can obtain a stable printed image even if the temperature and humidity environment changes and the developer deteriorates.

  Further, in the present embodiment, the cylindrical body 34 is rotationally driven by the same driving means 29 as the developing sleeve 27, so that even when the developer adheres to the cylindrical body 34, the cylindrical body 34 is attached by the rotation. Since the detachment and the adhesion are repeated without being maintained, the cylindrical body 34 can be prevented from being undesirably covered with the developer. As a result, the magnetism generating member 22 can be prevented from being damaged by the developer adhering thereto, and maintenance can be facilitated.

  Further, in the present embodiment, the magnetism generating member 22 includes a cylindrical body 34 provided so as to be angularly displaceable around the second axis L2, and an inner side of the cylindrical body 34, and a plurality of the cylindrical body 34 And a magnetic pole forming portion 35 for forming a magnetic pole at a circumferential position. The control unit 23 controls the amount of angular displacement around the second axis L2 of the cylindrical body 34. The controller 23 can oppose the developing sleeve 27 to the portion that generates the optimum magnetism among the plurality of magnetic poles by controlling the amount of angular displacement. Thereby, the magnetic force between the developing roller 17 and the layer thickness regulating member 20 can be controlled. Further, since the magnetic pole forming portion 35 is provided inside the cylindrical body 34, it is possible to prevent the developer from adhering to the magnetic pole forming portion 35 undesirably. Therefore, there is no possibility that the magnetic generation member 22 is clogged with the developer, and stable development performance can be exhibited even if the number of developments is increased.

  In the present embodiment, the magnetism generating member 22 is provided at a position vertically above the developer level 33 and close to the paddle 18. By providing the magnetism generating member 22 at a position close to the paddle 18 as described above, the developer generating amount is controlled by the magnetism generating member 22 at a position where the amount of the developer supplied to the developing roller 17 by the paddle 18 is large. can do.

  Furthermore, in the present embodiment, the length W3 of the magnetism generating member 22 in the direction in which the first axis L1 extends is larger than the length W4 of the developing roller 17 in the direction in which the first axis L1 extends. Since both ends of the magnetism generating member 22 may have reduced ability to control the amount of movement of the developer relative to the center due to the property of magnetism generated by the magnetism generating member 22, the length W3 of the magnetism generating member 22 may be reduced. Is the same as the length W4 of the developing roller 17, the amount of the developer at the end of the developing region may be different from the central portion. On the other hand, in the present invention, by making the length W3 of the magnetism generating member 22 longer than that of the developing roller 17, the amount of developer at the end portion and the central portion of the developing region can be made equal. Accordingly, it is possible to eliminate the unevenness of the amount of the developer carried over the entire area of the developing roller 17. As a result, development without unevenness can be realized.

  Further, in the present embodiment, the control unit 23 controls the amount of displacement of the magnetism generating member 22 based on the toner density detected by the density detecting means 37 that detects the toner density developed on the photosensitive drum 8. . As a result, the developer transport amount can be controlled based on the toner density detected in real time in accordance with environmental fluctuations and developer deterioration. As a result, the developer transport amount can be controlled in real time so that the optimum developer transport amount is obtained.

  Further, in the present embodiment, the magnetic force of the magnet roller 28 in the developing sleeve 27 at a position facing the magnetic generating member 22 is set to be larger than the magnetic force of the magnetic generating member 22 in a position facing the developing sleeve 27. Can do. Therefore, the developer carried on the developing roller 17 can be prevented from being carried on the magnetism generating member 22 undesirably. As a result, it is possible to prevent the amount of developer carried by the developing roller 17 from becoming too small, and the developer can be reliably conveyed to the photosensitive drum 8.

  In the present embodiment, the developer conveyed toward the layer thickness regulating member 20 by the developing roller 17 has a magnetic attraction force that depends on the rotation direction of the developing sleeve 27 depending on the amount of angular displacement of the magnetic pole forming portion 35. May work in the opposite direction. Since the magnetic attraction force by the magnetic pole forming portion 35 acts as a brake against the movement of the developer in the rotation direction of the developing sleeve 27, the speed of the developer when colliding with the layer thickness regulating member 20 and the staying developer. Can be made smaller than when the magnetism generating member 22 is not provided. As a result, when colliding with the layer thickness regulating member 20 and the staying developer, the pressure applied from the developer to the layer thickness regulating member 20 and the staying developer can be weakened. The load applied to the conveyed developer from 20 and the staying developer can be reduced. As described above, in this embodiment, the load applied to the developer when colliding with the layer thickness regulating member 20 and the staying developer can be reduced, and the deterioration of the developer, more specifically, the deterioration of the carrier is suppressed. In addition, image degradation can be suppressed.

  In this embodiment, the length of the magnetism generating member 22 in the direction in which the first axis L1 extends is set to be larger than the length of the developing roller 17 in the direction in which the first axis L1 extends. Instead, the length of the magnetism generating member 22 in the direction in which the first axis L1 extends may be set equal to the length of the developing roller 17 in the direction in which the first axis L1 extends. As a result, the amount of developer passing between the magnetism generating member 22 and the developing sleeve 27 can be controlled over the entire developing area of the developing roller 17. Accordingly, it is possible to eliminate the unevenness of the amount of the developer carried over the entire area of the developing roller 17. As a result, development without unevenness can be realized. Further, the developing device 1 can be miniaturized.

  In this embodiment, the diameter of the cylindrical body 34 is set smaller than the diameter of the developing sleeve 27. However, the diameter is not limited to this, and the diameter of the cylindrical body 34 and the diameter of the developing sleeve 27 are set equal. May be. Accordingly, the configuration of the cylindrical body 34 and the developing sleeve 27 can be made common, and the cost can be reduced.

  Next, the developing device 1 according to the second embodiment of the present invention will be described. FIG. 6 is a simplified cross-sectional view of the magnetism generating member 22A. FIG. 7 is a front view showing the magnetism generating member 22A in a simplified manner. In the present embodiment, the magnetism generating member 22A is integrally provided with a cylindrical body 34 and a magnetic pole forming portion 35A provided inside the cylindrical body 34. Accordingly, when the cylindrical body 34 is angularly displaced about the axis L2, the magnetic pole forming portion 35A is also angularly displaced about the axis L2 of the cylindrical body 34. The developing device 1 of the present embodiment further includes a slide displacing means 40 that causes the magnetic pole forming portion 35A to displace the developing sleeve 27 in a sliding direction C perpendicular to the axis of the cylindrical body 34. The magnetic pole forming portion 35 </ b> A can be displaced in the sliding direction C with respect to the developing sleeve 27 by the slide displacing means 40.

  The magnetic pole forming portion 35A is realized by a permanent magnet, for example. The magnetic pole forming portion 35A has a prismatic shape, and the cross-sectional shape in a virtual plane perpendicular to the axis is a rectangular shape. The shape of the magnetic pole forming portion 35A is not limited to this, and for example, the cross-sectional shape in a virtual plane perpendicular to the axis may be a square shape. The magnetic pole forming portion 35 </ b> A is arranged so that the axis is parallel to the axis L <b> 1 of the developing sleeve 27. The magnetic pole forming portion 35A forms the S pole on one surface portion in the direction perpendicular to the axis and forms the N pole on the other surface portion over the entire axial direction. The magnetic pole forming part 35 </ b> A is disposed on one side of the cylindrical body 34 in the radial direction. In the magnetic pole forming portion 35A, the S pole is disposed on the radially inner side, and the N pole is disposed on the radially outer side.

  The control unit 23 does not control the magnetic pole forming unit driving unit 36 so that the cylindrical body 34 integrated with the magnetic pole forming unit 35A is always rotated around the axis, and the toner density detected by the density detecting unit 37 is adjusted. Based on this, the angular displacement amount of the magnetism generating member 22A is controlled. Further, the control unit 23 controls the slide displacement amount in the direction perpendicular to the axis of the cylindrical body 34 based on the toner density detected by the density detecting unit 37, thereby setting the distance of the magnetism generating member 22A to the developing sleeve 27. Change.

  As described above, the amount of the developer carried by the developing sleeve 27 and passing between the developing sleeve 27 and the cylindrical body 34 has a correlation with the magnetic force distribution formed by the magnet roller 28 and the magnetic pole forming portion 35A. is there. When the magnetic roller 28 has an N pole and the magnetic pole forming portion 35A closest to the developing roller 17 has an N pole, the magnetic flux density between the magnetic pole forming portion 35A and the magnet roller 28 repels each other. Becomes smaller. Further, in such a case, as the distance between the magnetism generating member 22A and the developing roller 17 becomes smaller, the magnetic flux density becomes further smaller, so that the developer conveying force becomes smaller, and the developing sleeve 27 and the cylindrical body 34 are less affected. The amount of developer passing between them is reduced.

  Further, when the magnetic pole forming part 35A is angularly displaced about the axis, and the magnetic pole of the magnet roller 28 is N pole and the magnetic pole of the magnetic pole forming part 35A closest to the developing roller 17 is S pole, it attracts each other to form the magnetic pole. The magnetic flux density between the portion 35A and the magnet roller 28 increases. In such a case, as the distance between the magnetism generating member 22A and the developing roller 17 decreases, the magnetic flux density further increases, so that the developer conveying force increases, and the developing sleeve 27 and the cylindrical body 34 are separated from each other. The amount of developer passing between them increases. Therefore, by controlling the angular displacement amount and the slide displacement amount of the magnetic pole forming portion 35A, the developer conveying force by the developing roller 17 can be controlled.

  FIG. 8 is a cross-sectional view schematically showing an example of the slide displacement means 40. The slide displacement means 40 of this example includes a guide means 41 for guiding the magnetism generating member 22A along the sliding direction C, a pressing means 42 for pressing the magnetism generating member 22A toward one side in the sliding direction C, and the magnetism generating member 22A. Is configured to include a spring member 43 that applies a spring force toward the other side in the sliding direction C. A shaft member 44 that transmits a driving force from the magnetic pole forming unit driving means 36 to the cylindrical body 34 is connected to the cylindrical body 34 coaxially with the cylindrical body 34. The guide means 41 guides the shaft member 44 along the slide direction C. In this embodiment, the guide means 41 is realized by a slide hole extending along the slide direction C. The shaft member 44 is inserted into the slide hole, and the slide hole The shaft member 44 is configured to be displaceable in the slide direction C.

  The pressing means 42 is realized by, for example, a solenoid, and the shaft member 44 is displaced so that both ends in the axial direction of the shaft member 44 are displaced toward one side in the slide direction C by a slide amount based on a control command from the control unit 23. Press. The spring member 43 applies a spring force to the shaft member 44 toward the other side in the sliding direction C, and applies a spring force so that the shaft member 44 is always in contact with the pressing means 42. Therefore, the pressing means 42 can dispose the shaft member 44 at a predetermined position by applying a pressing force against the spring force of the spring member 43. By configuring the slide displacement means 40 in this way, the shaft member 44 can be displaced along the slide hole. As a result, the distance between the magnetism generating member 22A and the developing roller 17 can be changed.

  FIG. 9 is a cross-sectional view schematically showing another example of the slide displacement means 40A. FIG. 10 is a diagram for explaining the operation of the slide displacement means 40A. The slide displacement means 40A of this example is a guide means 41 for guiding the magnetism generating member 22A along the slide direction C, a cam member 45 provided in contact with the shaft member 44, and an angular displacement of the cam member 45 about the cam shaft 46. It includes an angular displacement means 47 to be moved, and a spring member 43 that applies a spring force toward the other side in the sliding direction C to the magnetism generating member 22A. The guide means 41 guides the shaft member 44 along the slide direction C. In the present embodiment, a slide hole extending along the slide direction C is provided as the guide means 41, and the shaft member 44 is inserted into the slide hole. Thus, the shaft member 44 is configured to be displaceable in the sliding direction C by being guided by the slide hole.

  The cam members 45 are provided at both ends in the axial direction of the cam shaft 46 so as to be angularly displaceable around the axis of the cam shaft 46 parallel to the axis L 2 of the cylindrical body 34, and the outer peripheral surface portions are both ends in the axial direction of the shaft member 44. It is provided in contact with the outer peripheral surface portion of the portion. The angular displacement means 47 angularly displaces the cam member 45 so that both ends in the axial direction of the shaft member 44 are displaced toward one side in the slide direction C by a slide amount based on a control command from the control unit 23. The shaft member 44 is pressed. The spring member 43 applies a spring force to the shaft member 44 toward the other side in the sliding direction C, and applies a spring force so that the shaft member 44 is always in contact with the cam member 45. Therefore, as shown in FIG. 10 (1), the cam member 45 is angularly displaced by the angular displacement means 47 from the state where the cam member 45 is disposed so as to extend in the direction orthogonal to the sliding direction C. 45 can apply a pressing force to the shaft member 44 against the spring force of the spring member 43. As a result, as shown in FIG. 10 (2), the shaft member 44 can be displaced in one of the sliding directions C, and the shaft member 44 can be arranged at a predetermined position. By configuring the slide displacement means 40A in this way, the shaft member 44 can be displaced along the slide hole. As a result, the distance between the magnetism generating member 22A and the developing roller 17 can be changed.

  FIG. 11 is an enlarged and simplified sectional view showing still another example of the slide displacement means 40B. FIG. 12 is a diagram for explaining the operation of the slide displacement means 40B. In the sliding means of this example, the sliding direction C is not a direction orthogonal to the axis of the cylindrical body 34, but a direction along an arc that rotates about the axis L1 of the developing sleeve 27. Accordingly, the slide displacing means 40B of this example displaces the magnetism generating member 22A along the outer periphery of the developing sleeve 27 while maintaining a predetermined distance. The slide displacement means 40B of this example includes a guide means 41 for guiding the magnetism generating member 22A along the slide direction C, a cam member 45 provided in contact with the shaft member 44, and the cam member 45 around the axis of the cam shaft 46. An angular displacement means 47 that angularly displaces and a spring member 43 that applies a spring force toward the other side in the sliding direction C to the magnetism generating member 22A. The guide means 41 guides the shaft member 44 along the slide direction C. In the present embodiment, an arcuate slide hole extending along the slide direction C is provided as the guide means 41, and the shaft member 44 is provided in the slide hole. Is inserted and guided in the slide hole, and the shaft member 44 is configured to be displaceable in the slide direction C.

  Accordingly, as in the other examples described above, the cam member 45 is pivoted by angularly displacing the cam member 45 by the angular displacement means 47 from the state where the cam member 45 is disposed as shown in FIG. A pressing force can be applied to the member 44 against the spring force of the spring member 43. As a result, as shown in FIG. 10 (2), the shaft member 44 can be disposed in a predetermined position by displacing the shaft member 44 in one of the sliding directions C along the arcuate slide hole. By configuring the slide displacement means 40B in this way, the shaft member 44 can be displaced along the slide hole. Thus, the magnetism generating member 22A can be changed along the outer periphery of the developing sleeve 27 while maintaining a predetermined distance. Thus, by displacing the magnetism generating member 22A and the developing sleeve 27 along the outer circumference, the magnet roller 28 has different magnetic poles in the circumferential direction, so that the magnetic flux density between the magnetizing member 22A and the developing roller 17 can be changed. it can. As a result, the above-described effect due to the change in magnetic flux density can be achieved.

  Next, the developing device according to the third embodiment of the present invention will be described. FIG. 13 is a front view schematically showing the developing device 1 according to the third embodiment of the present invention. The developing device 1 according to the present embodiment includes a magnet moving means 60 that displaces the magnetism generating member 22B in the horizontal direction x with respect to the developing sleeve 27.

  The magnetism generating member 22B is realized by a permanent magnet, for example. The magnetic generation member 22B has a prismatic shape, and the cross-sectional shape in a virtual plane perpendicular to the axis is a rectangular shape. The shape of the magnetic generation member 22B is not limited to this, and for example, the cross-sectional shape in a virtual plane perpendicular to the axis may be a square shape. The magnetism generating member 22B is provided at the tip of a line L obtained by extending the center line of the N2 magnetic pole of the magnet roller 28 so as to face the magnet roller 28. In the magnetism generating member 22B, the N pole is arranged on the surface facing the magnet roller 28, and the S pole is arranged on the opposite side.

  The control unit controls the amount of displacement of the magnetism generating member 22B in the horizontal direction with respect to the developing sleeve 27 based on the toner density detected by the density detecting means.

  The magnet moving means 60 can be used as long as the magnetism generating member 22B such as a solenoid, a hydraulic cylinder, or a pneumatic cylinder can be displaced in a linear direction, and the control unit adjusts the current value, hydraulic pressure, and air pressure. The amount of displacement of the magnetism generating member 22B in the horizontal direction is controlled.

  The amount of developer carried by the developing sleeve 27 and passing between the developing sleeve 27 and the magnetism generating member 22B depends on the magnetic force distribution formed by the magnet roller 28 and the magnetism generating member 22B. Since the magnetic pole of the magnet roller 28 is N pole and the magnetic pole of the magnetism generating member 22B that is closest to the magnet roller 28 is also N pole, the magnetic flux density between the magnetism generating member 22B and the magnet roller 28 repels each other. Becomes smaller. Further, in such a case, as the distance between the magnetism generating member 22B and the magnet roller 28 is decreased by moving the magnetism generating member 22B in the horizontal direction, the magnetic flux density is further reduced, so that the developer conveying force is reduced. The amount of developer passing between the developing sleeve 27 and the magnetism generating member 22B is reduced.

  The toner for new replenishment into the developing container 16 is set so as to drop from above the stirring member. In the present embodiment, the toner drops almost in the middle of the paddle 18 and the stirring roller 19. The developer moved from the developing sleeve 27 and the replenishing toner that falls are almost encountered at the above-mentioned locations, and the replenishing toner is mixed and stirred with the developer by both the paddle 18 and the stirring roller 19.

  Although the controllability of the magnetic force changes depending on how the magnetic generation member 22B is displaced, the magnetic generation member 22B moves from the development sleeve 27 by changing the distance between the magnetic generation member 22B and the development sleeve 27, particularly by displacing in the horizontal direction. Since the amount of the developer can be controlled, precise stirring control according to the amount of toner to be supplied, fluidity, and the like becomes possible.

  For example, when a document with a high printing rate is continuously printed, the amount of toner replenishment is several times the normal amount. In such a case, sufficient agitation is possible. Further, under the condition that toner particles are likely to aggregate in a high temperature and high humidity environment, the agitation can be improved by moving the developer from the developing sleeve 27 more than the normal setting.

  Next, the developing device 1 according to the fourth embodiment of the present invention will be described. FIG. 14 is a front view schematically showing the developing device 1 according to the fourth embodiment of the present invention. This embodiment has a configuration similar to that of the developing device 1 of the first embodiment shown in FIG. 1, and includes a magnet moving means 60 for displacing the magnetism generating member 22 with respect to the developing sleeve 27 in the horizontal direction x. Only the inclusion in the configuration is different.

  In the present embodiment, when the cylindrical body 34 is angularly displaced about the axis, the magnetic pole forming portion 35 is also angularly displaced about the axis of the cylindrical body 34. In addition, the magnetism generating member 22 is displaced in the horizontal direction with respect to the developing sleeve 27 by the magnet moving means 60.

  The magnetic pole forming part 35 is realized by a permanent magnet, for example. The magnetic pole forming portion 35 has a prismatic shape, and the cross-sectional shape in a virtual plane perpendicular to the axis is a rectangular shape. The shape of the magnetic pole forming portion 35 is not limited to this, and for example, the cross-sectional shape in a virtual plane perpendicular to the axis may be a square shape. The magnetic pole forming portion 35 is disposed so that the axis is parallel to the axis of the developing sleeve 27. The magnetic pole forming portion 35 forms the S pole on one surface portion in the direction perpendicular to the axis and forms the N pole on the other surface portion over the entire axial direction. The magnetic pole forming portion 35 is disposed on one side of the cylindrical body 34 in the radial direction. In the magnetic pole forming part 35, the S pole is arranged on the radially inner side, and the N pole is arranged on the radially outer side.

  The magnet moving means 60 can be used as long as the magnetism generating member 22B such as a solenoid, a hydraulic cylinder, or a pneumatic cylinder can be displaced in a linear direction, and the control unit adjusts the current value, hydraulic pressure, and air pressure. The amount of displacement of the magnetism generating member 22B in the horizontal direction is controlled.

  The control unit does not control the magnetic pole forming unit driving unit 36 so as to always rotate the cylindrical body 34 integrated with the magnetic pole forming unit 35 around the axis, but based on the toner density detected by the density detecting unit. The amount of angular displacement of the magnetism generating member 22 is controlled. The control unit also controls the magnet moving unit 60 to control the amount of displacement of the magnetism generating member 22 in the horizontal direction relative to the developing sleeve 27 based on the toner density detected by the density detecting unit.

  As described above, the amount of developer carried by the developing sleeve 27 and passing between the developing sleeve 27 and the cylindrical body 34 depends on the magnetic force distribution formed by the magnet roller 28 and the magnetic pole forming portion 35. . When the magnetic roller 28 has an N pole and the magnetic generating member 22 located closest to the magnet roller 28 also has an N pole, the magnetic flux density between the magnetic generating member 22 and the magnet roller 28 repels each other. Becomes smaller. Further, in such a case, as the distance between the magnetism generating member 22 and the magnet roller 28 is decreased by moving the magnetism generating member 22B in the horizontal direction, the magnetic flux density is further reduced, so that the developer conveying force is reduced. The amount of developer passing between the developing sleeve 27 and the magnetism generating member 22 is reduced.

  Further, when the magnetic pole forming portion 35 is angularly displaced about the axis, and the magnetic pole of the magnet roller 28 is N pole and the magnetic pole of the magnetic pole forming portion 35 closest to the magnet roller 28 is S pole, the magnetic pole formation is attracted to each other. The magnetic flux density between the portion 35 and the magnet roller 28 increases. In such a case, as the distance between the magnetism generating member 22 and the magnet roller 28 is reduced, the magnetic flux density is further increased, so that the developer conveying force is increased, and the developer sleeve 27 and the cylindrical body 34 are separated from each other. The amount of developer passing between them increases. Therefore, by controlling the angular displacement amount and the horizontal displacement amount of the magnetic pole forming portion 35, the developer conveying force by the developing roller can be precisely controlled.

  The toner for new replenishment into the developing container 16 is set so as to drop from above the stirring member. In the present embodiment, the toner drops almost in the middle of the paddle 18 and the stirring roller 19. The developer moved from the developing sleeve 27 and the replenishing toner that falls are almost encountered at the above-mentioned locations, and the replenishing toner is mixed and stirred with the developer by both the paddle 18 and the stirring roller 19.

  Although the controllability of the magnetic force varies depending on how the magnetic generating member 22 is displaced, the amount of the developer that moves from the developing sleeve 27 and the replenishment by moving the magnetic generating member 22 in the horizontal direction while rotating. Since the encounter position with the toner can be finely adjusted and controlled according to the characteristics of the developer and the usage environment, the optimum developer agitation performance can be obtained.

  Next, the developing device 1 according to the fifth embodiment of the present invention will be described. FIG. 15 is an enlarged front view showing the surface of the cylindrical body 34 and the surface of the developing sleeve 27 according to the present embodiment. The present embodiment is characterized in that the surface roughness of the magnetism generating member 22 is different from the surface roughness of the developing sleeve 27.

  FIG. 15 (1) is a diagram showing the surface of the cylindrical body 34. As shown in FIG. 15 (1), for example, the surface of the cylindrical body 34 has a rectangular groove extending along the axial direction. A plurality of 48 are formed. The depth of the groove 48 of the cylindrical body 34 is, for example, 1 mm, and the interval between the grooves 48 is, for example, 1 mm. FIG. 15 (2) is a diagram showing the surface of the developing sleeve 27. As shown in FIG. 15 (2), for example, the surface of the developing sleeve 27 has a rectangular groove 49 extending along the axial direction. A plurality are formed. The depth of the groove 49 of the developing sleeve 27 is, for example, 3 mm, and the interval between the grooves 49 is, for example, 3 mm. Thus, the surface roughness of the cylindrical body 34 is configured to be different from the surface roughness of the developing sleeve 27. Further, as shown in FIGS. 15A and 15B, the surface roughness of the cylindrical body 34 is not limited to the configuration in which the surface roughness of the cylindrical body 34 is smaller than the surface roughness of the developing sleeve 27. May be larger.

  Further, as shown in FIG. 15 (3), the shape of the grooves 48 and 49 is not limited to the rectangular shape as shown in FIG. 15 (2), and may be a V-shaped groove 50. Further, as shown in FIG. 15 (4), the surface may be sandblasted to form grooves 51 having a surface roughness Rz of several μm or more and several hundreds of μm or less. The rectangular and V-shaped grooves 48, 49, and 50 can be formed by, for example, providing the mold in advance in a mold for molding in the drawing method. Sand blasting is a method of creating grooves by spraying an abrasive such as glass beads on the surface.

  The developer conveying force by the developing sleeve 27 and the cylindrical body 34 can be arbitrarily changed depending on the shape and size of the groove and the interval between the grooves. As a method for determining the developer transport amount, for example, using an external idle machine, the developing roller 17 is rotated for 3 minutes at a predetermined condition, for example, 400 rpm, and then the developer weight per unit area is measured. Judgment can be made.

  Thus, in the present embodiment, the surface roughness of the magnetism generating member 22 is different from the surface roughness of the developing sleeve 27. Thus, by making the surface roughness different between the magnetism generating member 22 and the developing sleeve 27, the amount of developer carried and moved on the surfaces of both members can be made different. Therefore, for example, by making the surface roughness of the developing sleeve 27 rougher than that of the magnetism generating member 22, it is possible to increase the transport amount of the developer transported to the developing sleeve 27. It can be set larger than the member 22. As a result, the amount of developer conveyed by the developing roller 17 can be set to a desired amount.

It is a front view which simplifies and shows developing device 1 of a 1st embodiment of the present invention. FIG. 2 is a front view schematically showing an image forming apparatus 2 as an application example of the developing device 1. FIG. 4 is a cross-sectional view schematically showing a magnetism generating member 22 and a developing roller 17. FIG. 6 is a front view for explaining the relationship between the developing roller 17 and the magnetism generating member 22 relating to magnetism. 3 is a block diagram showing a simplified electrical configuration related to a magnetism generating member 22. FIG. It is sectional drawing which simplifies and shows the magnetism generating member 22A. It is a front view which simplifies and shows the magnetism generating member 22A. FIG. 4 is a cross-sectional view schematically showing an example of slide displacement means 40. It is sectional drawing which simplifies and shows the other example of the slide displacement means 40A. It is a figure for demonstrating operation | movement of the slide displacement means 40A. It is sectional drawing which expands and simplifies and shows another example of the slide displacement means 40B. It is a figure for demonstrating operation | movement of the slide displacement means 40B. It is a front view which simplifies and shows the developing device 1 of the 3rd Embodiment of this invention. It is a front view which simplifies and shows the developing device 1 of the 4th Embodiment of this invention. 2 is an enlarged front view showing the surface of a cylindrical body 34 and the surface of a developing sleeve 27. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Image forming apparatus 8 Photosensitive drum 17 Developing roller 20 Layer thickness control member 22 Magnetic generation member 23 Control part 27 Developing sleeve 28 Magnet roller 34 Cylindrical body 35 Magnetic pole formation part 40 Slide displacement means

Claims (11)

A developing device for developing an electrostatic latent image formed on an image carrier using a two-component developer,
A developer provided rotatably around a predetermined first axis, carrying a two-component developer and transporting it to an image carrier, and a magnet roller provided in the developer sleeve and generating magnetism A carrier,
A layer thickness regulating member that is provided facing the developing sleeve and regulates the layer thickness of the two-component developer carried on the developing sleeve;
A magnetism generating member that is disposed upstream of the layer thickness regulating member in the rotational direction of the developing sleeve and is displaceable facing the developing sleeve;
And a control unit that controls a displacement amount of the magnetism generating member with respect to the developing sleeve. The magnetism generating member is configured to be displaceable at least in the horizontal direction,
The developing device according to claim 1, wherein the control unit controls a displacement amount of the magnetism generating member in a horizontal direction. The magnetism generating member is
A cylindrical body that is provided so as to be angularly displaceable around a predetermined second axis and is formed into a cylindrical shape;
A magnetic pole forming portion for forming magnetic poles at a plurality of circumferential positions of the cylindrical body inside the cylindrical body,
The developing device according to claim 1, wherein the control unit controls an amount of angular displacement around a second axis of the cylindrical body.   The length of the magnetism generating member in the direction in which the first axis extends is equal to the length of the developer carrier in the direction in which the first axis extends. Development device.   The length of the magnetism generating member in the direction in which the first axis extends is larger than the length of the developer carrier in the direction in which the first axis extends. Development device.   The control means controls the amount of displacement of the magnetism generating member based on the toner density detected by the density detecting means for detecting the toner density developed on the image carrier. 5. The developing device according to any one of 5 above.   The developing device according to claim 1, wherein the surface roughness of the magnetism generating member is different from the surface roughness of the developing sleeve.   The developing device according to claim 3, wherein a diameter of the cylindrical body is smaller than a diameter of the developing sleeve.   The developing device according to claim 3, wherein a diameter of the cylindrical body is equal to a diameter of the developing sleeve.   The magnetic force of the magnet roller in the developing sleeve at a position facing the magnetic generating member is set to be larger than the magnetic force of the magnetic generating member at a position facing the developing sleeve. The developing device according to any one of 9.   An image forming apparatus comprising the developing device according to claim 1.

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