JP5677046B2 - Developing device and image forming apparatus - Google Patents

Description

The present invention relates to a developing device for forming an image using an electrophotographic system such as a copying machine, a printer, a FAX, and a multifunction machine, and an image forming apparatus using the developing device .

  As a developing device used in a conventional image forming apparatus, there is a developing device 4 using a two-component developer as shown in FIGS. The developing device 4 includes a developing container 41 that stores a developer. The developing container 41 is divided into a developing chamber (developer conveying path) 41a and an agitating chamber (developer conveying path) 41b by a partition wall 41c extending in the vertical direction. A first developer transport stirring member 42 and a second developer transport stirring member 43 are disposed in the developing chamber 41a and the stirring chamber 41b, respectively. In addition, delivery portions (developer transport paths) 41d and 41e that allow the developer to pass between the developing chamber 41a and the stirring chamber 41b are provided at the end in the longitudinal direction of the partition wall 41c. The first and second developer conveying and stirring members (screws) 42 and 43 convey the developer while stirring and circulate the developer container 41. A developing sleeve 44 as a developer carrying member is rotatably disposed at a position facing the photosensitive drum 1 of the developing container 41. The developing sleeve 44 incorporates a magnet 45 as a magnetic field generating means.

  The magnet 45 is configured in the order of S1, N1, S2, N2, and N3 poles in the rotation direction of the developing sleeve 44. The developer stirred by the screw 42 is restrained by the magnetic force of the conveying magnetic pole (pumping pole) N2 for pumping, and is transported to the developer reservoir 48 by the rotation of the developing sleeve 44. The amount of the developer conveyed to the developer reservoir 48 is regulated by the developer return member 47, and in order to constrain the stable developer, a conveying magnetic pole (cut pole) having a certain magnetic flux density above a certain level. It is sufficiently restrained at S2 and is conveyed while forming a magnetic brush. Since the magnetic pole of the developer is changed by the magnetic forces of S and N, the attractive force acts on both the magnetic poles of S and N and is restrained.

  Next, the amount of the developer is optimized by cutting off the magnetic spike by the regulating blade 46, conveyed by the conveying magnetic pole N1, conveyed to the portion facing the photosensitive drum 1, and developed by the developing pole S1. To be served. At the opposing portion, only the toner is transferred to the electrostatic latent image formed on the surface of the photosensitive drum 1 by the developing bias applied to the developing sleeve 44, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 1. The

  As shown in FIG. 3, the magnet 45 is arranged in the developing container 41 so that the same poles (N2 and N3) are adjacent to each other. As a result, a repulsive force is generated on the developing sleeve 44 in the developing container 41. As a result, the developer having a low toner concentration used for forming the toner image is collected by the screw 42. The collected developer is stirred again to return the toner density to the original level, and then supplied to the developing sleeve 44 again. Thereby, screw pitch unevenness and image density are suppressed from being lowered.

  However, in the developing device 4 in which such a magnet 45 is used, there is a problem that the developer is biased or scattered during transportation. Therefore, in the technique disclosed in Patent Document 1, a magnetic sheet is placed under the developing device 4 so that the magnetic force of the magnetic sheet restrains the developer under the developing device 4 and biases the developer during transportation. And the scattering is suppressed.

JP 2003-330269 A

  However, the technique of Patent Document 1 requires a disposable magnet sheet. Further, when it is necessary to pull out again after attaching the developing device 4 or the process cartridge including the developing device 4 and removing the magnetic sheet, the developer is inclined and biased depending on how to hold and put it. Sometimes.

  As shown in FIG. 4, when the developing device 4 is detached from the main body of the image forming apparatus and tilted perpendicularly to the developer transport direction, the developer is biased to almost half of the entire length direction. . When the developing device 4 or the process cartridge including the developing device 4 is installed in such a state that the developer is biased and the sleeve 44 and the screws 42 and 43 are rotated, uneven coating on the sleeve (image defect) and the screws 42 and 43 May occur (developing device lock).

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and an image forming apparatus that can suppress bias of the developer when the developing device is detached with a simple configuration, and can suppress image defects and developing device lock.

In order to solve the above-mentioned problems, a typical configuration of an image forming apparatus according to the present invention is a rotatable developer that carries a two-component developer containing toner and a carrier and conveys it to a development area facing the image carrier. A carrier, a developer conveying and agitating member for conveying and agitating the developer , a plurality of magnetic poles provided in the developer carrying body, and a region for restraining the two-component developer and the two-component developer; and a multipolar magnet having a region that is not, in the developing apparatus detachably mountable to an image forming apparatus main body, when they are detached from the image forming apparatus main body, the area for restraining the developer of the multipolar magnet, Rotating to a position facing the developer conveying and agitating member .

  According to the present invention, the bias of the developer when the developing device is detached can be suppressed with a simple configuration, and image defects and the developing device lock can be suppressed.

1 is a configuration diagram of an image forming apparatus according to a first embodiment. It is sectional drawing of the image development apparatus of the former and 1st Embodiment. It is a cross-sectional view of a conventional developing device. FIG. 10 is a diagram illustrating an example in which a developer is biased depending on how to hold and place in a conventional developing device. It is a block diagram of the developing device showing a magnet arrangement according to the first embodiment. It is a figure which shows the relationship between the position in the rotation direction of the magnet which concerns on 1st Embodiment, and magnetic force. FIG. 5 is a distribution diagram of a developer achieved by the first embodiment. The flowchart at the time of rotating the magnet of 1st Embodiment. It is a figure which shows an example of the rotation method of the magnet of 1st Embodiment. It is a block diagram of the developing device showing a magnet arrangement according to the second embodiment.

[First embodiment]
A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment.

  As shown in FIG. 1, an image forming apparatus 100 using an electrophotographic method uniformly charges the surface of a photosensitive drum (image carrier) 1 with a charger 2, and the charged photosensitive drum 1 is exposed with an exposure device 3. Exposure is performed according to image information, and an electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is visualized as a toner image by the toner in the developer using the developing device 4. The visualized toner image is transferred to the recording medium S by the transfer device 5. The toner image transferred to the recording medium S is fixed by heat and pressure by the fixing device 6.

  After the toner image is transferred, the toner remaining on the photosensitive drum 1 is removed by the cleaning device 7, and the charge remaining on the photosensitive drum 1 is further removed by the charge eliminating device 8, whereby the photosensitive drum 1 is moved to the next time. Prepare for the image forming process.

  As the developer, a two-component developer including nonmagnetic toner particles (toner) and magnetic carrier particles (carrier) is used. In particular, in a color image forming apparatus, a two-component developer is widely used because the toner does not need to contain a magnetic material and the color tone is good. The image forming apparatus of the present invention may be a color image forming apparatus.

(Developing device 4)
FIG. 2 is a cross-sectional view of the developing device of this embodiment. FIG. 5A is a configuration diagram when the developing device 4 of the present embodiment is installed (at the time of image formation). FIG. 5B is a configuration diagram when the developing device 4 of the present embodiment is detached. FIG. 6A is a diagram showing the relationship between the position in the rotation direction of the magnet 45, the magnetic force (N), and the magnetic flux density (GR) at the time of installation corresponding to FIG. 5A. FIG. 6B is a diagram showing the relationship between the position of the magnet 45 in the rotational direction, the magnetic force (N), and the magnetic flux density (GR) at the time of separation corresponding to FIG. 5B. In FIG. 6, Fr (thin line) indicates magnetic force, and Br (thick line) indicates magnetic flux density.

  As shown in FIGS. 2 and 5A, the developing device 4 includes a developing container 41 that contains a developer. The developing container 41 is divided into a developing chamber (developer conveying path) 41a and an agitating chamber (developer conveying path) 41b by a partition wall 41c extending in the vertical direction. A first developer transport stirring member 42 and a second developer transport stirring member 43 are disposed in the developing chamber 41a and the stirring chamber 41b, respectively. In addition, delivery portions (developer transport paths) 41d and 41e that allow the developer to pass between the developing chamber 41a and the stirring chamber 41b are provided at the end in the longitudinal direction of the partition wall 41c. The first and second developer conveying and stirring members (screws) 42 and 43 convey the developer while stirring and circulate the developer container 41. A developing sleeve 44 as a developer carrying member is rotatably disposed at a position facing the photosensitive drum 1 of the developing container 41. The developing sleeve 44 incorporates a magnet (multipolar magnet) 45 as a magnetic field generating means.

  The magnet 45 provided in the developer carrying body is configured in the order of S1, N1, S2, N2, and N3 poles in the rotation direction of the developing sleeve 44. The developer stirred by the screw 42 is restrained by the magnetic force of the conveying magnetic pole (pumping pole) N2 for pumping, and is transported to the developer reservoir 48 by the rotation of the developing sleeve 44. The amount of the developer conveyed to the developer reservoir 48 is regulated by the developer return member 47, and in order to constrain the stable developer, a conveying magnetic pole (cut pole) having a certain magnetic flux density above a certain level. It is sufficiently restrained at S2 and is conveyed while forming a magnetic brush. Next, the amount of the developer is optimized by cutting off the magnetic spikes with the regulating blade 46, transported with the transport magnetic pole N <b> 1, transported to a portion (development region) facing the photosensitive drum 1, and developed. It is used for development at the pole S1. At the opposing portion, only the toner is transferred to the electrostatic latent image formed on the surface of the photosensitive drum 1 by the developing bias applied to the developing sleeve 44, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 1. The

  As shown in FIGS. 5A and 6A, in the state where the developing device 4 is installed in the apparatus main body (when forming an image), the magnet 45 is adjacent to the same pole (N2 and N3) in the developing container 41. Arrange to fit. In the region where the same poles (N2 and N3) at the position facing the screw 42 are adjacent, the force applied to the carrier by the magnet (the magnetic flux density in FIG. 6A is almost 0) does not work. As a result, the developer having a low toner concentration used for forming the toner image falls by gravity and is collected by the screw 42. The collected developer is stirred again to return the toner density to the original level, and then supplied to the developing sleeve 44 again. Thereby, screw pitch unevenness and image density are suppressed from being lowered.

  However, when the developing device 4 is removed from the apparatus main body in the state shown in FIG. 5A, the developer may be inclined and biased depending on how the developing device 4 is held or placed. If the developing device 4 is installed with the developer biased and the sleeve 44 and the screws 42 and 43 are rotated, uneven coating (image defect) on the sleeve, locking of the screws 42 and 43 (developing device lock), etc. occur. There is a fear.

  Therefore, in the present embodiment, as shown in FIGS. 5B and 6B, when the developing device 4 is detached from the image forming apparatus 100, the S1 pole is located at a position facing the screw 42. The magnet 45 is rotated. Thereby, the attractive force applied to the carrier by the magnet 45 at the position of the developing sleeve 44 facing the screw 42 becomes strong, and the developer can be restrained. Thereby, the bias of the developer can be suppressed regardless of how the developing device 4 is held or placed when the developing device 4 is detached from the image forming apparatus 100.

  Although the configuration in which the S1 pole is located at the position facing the screw 42 has been described, when the magnet 45 is rotated to a position that restrains the two-component developer in the developing device when it is detached from the image forming apparatus main body. Good. Further, it is desirable that the position where the two-component developer is restrained in the developing device is a place where the two-component developer is most accumulated. As a result, more developer can be restrained, and deviation of the developer can be effectively suppressed. Further, the electrode is not limited to the S1 electrode, and may be any electrode that can restrain the developer. If the pole having the maximum magnetic flux density among the plurality of poles of the magnet 45 is arranged at a position facing the screw 42, the developer can be made stronger and faster, which is preferable.

  FIG. 9 is a diagram showing an example of rotation of the magnet motor 86 that drives the magnet 45. As shown in FIG. 1, the image forming apparatus 100 includes a control unit 50 that controls the rotation of the magnet 45. As shown in FIG. 9A, the magnet motor 86 supports the shaft end portion 84 of the magnet 45 so as to be rotatable about the axis of the magnet 45. The shaft end portion 84 is provided in the developing device 4 by a positioning sheet metal 85.

  When the developing device 4 is attached to and detached from the apparatus main body, the positioning sheet metal 85 is biased by the positioning sheet metal stopper 82 by the force by which the spring 83 contracts. At this time, the S1 pole is in a position facing the screw 42, and the developer is restrained.

  When the control unit 50 determines that the door for attaching and detaching the developing device 4 is closed, the rotation signal of the magnet motor 86 is turned ON, and the shaft end 84 rotates to the state shown in FIG. At this time, the positioning sheet metal 85 abuts against the positioning sheet metal stopper 81, and the magnet 45 stops rotating at a position suitable for image formation.

  FIG. 8 is a flowchart for rotating the magnet 45. As shown in FIG. 8, when the image forming apparatus 100 is turned on (S1) and the control unit 50 determines that the door of the image forming apparatus 100 is closed (S2), a magnet rotation signal for turning the magnet 45 is generated. Turn it on. Then, the magnet 45 rotates to the state shown in FIGS. 5A and 6A, and the image forming operation is performed.

  On the other hand, if it is determined that the door of the image forming apparatus 100 is open (S2), the magnet rotation signal for turning the magnet 45 is turned off. Then, the magnet 45 rotates to the state shown in FIG. 5B and FIG. 6B, and the developing device 4 can be attached and detached while the bias of the developer can be suppressed.

  FIG. 7 is a distribution diagram of the developer in the developing device 4 according to this embodiment. FIG. 7 shows the deviation of the developer when the developing device 4 of the present embodiment is kept stationary for a while in a state of being perpendicular to the developer transport direction and returned to the image forming state. As shown in FIG. 7, in the fourth embodiment, it is possible to eliminate the bias of the developer as compared with the conventional developing device 4 shown in FIG.

  In this state, the magnet 45 was rotated to return to the optimal arrangement for image formation, and when image formation was performed, coating unevenness on the developing sleeve 44 and locking of the screw 42 did not occur. Further, neither screw pitch unevenness nor image density reduction occurred.

  As a more severe condition, the developing device 4 is kept standing for a while in a state of being perpendicular to the developer conveying direction, and after that, the developing device 4 is shaken up and down several times, and then the magnet 45 is rotated to be optimal for image formation. The image was formed after returning to the arrangement. Similarly, in the result, coating unevenness on the developing sleeve 44 and locking of the screw 42 did not occur. Further, neither screw pitch unevenness nor image density reduction occurred.

  In the present embodiment, the configuration in which the magnet 45 is rotated by controlling the magnet motor 86 has been described. However, when the developing device 4 is disposed at a predetermined position, the force is automatically pressed by a lever or a protrusion. The structure which rotates the magnet 45 may be sufficient. Further, in the present embodiment, the system in which the developing device 4 is independent is described. However, at least the process cartridge including the developing device 4 may be configured to be detachable from the apparatus main body.

[Second Embodiment]
Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. The same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted. FIG. 10A is a diagram showing a magnet arrangement when the developing device according to the present embodiment is installed. FIG. 10B is a diagram showing a magnet arrangement when the developing device according to this embodiment is attached / detached.

  As shown in FIG. 10A and FIG. 10B, the developing device 4 of the present embodiment has the screws 42 and 43 arranged in the horizontal direction of the developing device 4 of the first embodiment up and down (vertical direction). )). In the present embodiment, since the two screws 42 and 43 are arranged above and below, the two screws 42 and 43 exist closer to the developing sleeve 44 than when arranged on the left and right. Therefore, as shown in FIG. 10A, the S1 pole is substantially opposite to the photosensitive drum 1 during image formation. In the developing container 41, the magnet 45 is adjacent to the same polarity (N2, N3), and repulsive force is generated on the developing sleeve 44 between the same polarity (N2, N3).

  As shown in FIG. 10B, when the developing device 4 is detached, two of the plurality of poles constituting the magnet 45 for each of the upper and lower screws 42 and 43 (S1, N1) Can be arranged substantially opposite to each other. As a result, the developer that exists above and below can hold the developer with a strong restraining force, and therefore, how the developing device 4 is held and placed when the developing device 4 is detached from the image forming apparatus 100. Even in the state, the bias of the developer can be further reduced as compared with the first embodiment.

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 4 ... Developing device 41 ... Developing container 41a, 41b ... Agitation chamber 41c ... Partition 41d, 41e ... Delivery part 42 ... 1st developer conveyance stirring member 43 ... 2nd developer conveyance stirring member 44 ... Development Sleeve 45 ... Magnet 46 ... Regulating blade 47 ... Developer return member 48 ... Developer reservoir 50 ... Control part 82 ... Sheet metal stopper 83 ... Spring 84 ... Shaft end 85 ... Sheet metal 86 ... Magnet motor 100 ... Image forming apparatus

Claims (9)

A rotatable developer carrying member that carries a two-component developer containing toner and a carrier and conveys it to a developing region facing the image carrier;
A developer carrying and stirring member for carrying and stirring the developer;
A multi-pole magnet provided in the developer carrying body, having a plurality of magnetic poles, and having a region that restrains the two-component developer and a region that does not restrain the two-component developer; In a detachable developing device,
The developing device characterized in that when separated from the main body of the image forming apparatus, the region of the multipolar magnet that restrains the developer is rotated to a position facing the developer conveying and stirring member.   2. The magnetic pole having the highest magnetic flux density is a region that restrains the developer of the multipolar magnet that faces the developer conveying and stirring member when detached from the image forming apparatus main body. The developing device according to 1.   When the developer conveying stirring member has two in the vertical direction and is separated from the main body of the image forming apparatus, the regions of the multipolar magnet for restraining the developer are respectively the two developer conveying stirring members. The developing device according to claim 1, wherein the developing device is opposed to the developing device. Wherein the developer conveying agitating member has two horizontally, while detached from the image forming apparatus main body, the area for restraining the developer of the multi-pole magnet is closer to the multi-pole magnet the developing The developing device according to claim 1, wherein the developing device faces the agent conveyance stirring member . A rotatable developer carrying member carrying a two-component developer containing toner and a carrier and carrying the developer to a developing region facing the image carrier, a developer carrying stirring member for carrying and stirring the developer, and the developer carrying A developing device provided in the body, having a plurality of magnetic poles, and having a multipolar magnet having a region that restrains the two-component developer and a region that does not restrain the two-component developer can be attached to and detached from the image forming apparatus main body In the image forming apparatus,
A rotation means for rotating the multipolar magnet has a region where the developer of the multipolar magnet is constrained to the developer conveying agitating member when the developing device is detached from the image forming apparatus main body. An image forming apparatus that rotates as described above.   The region that restrains the developer of the multipolar magnet that faces the developer conveyance stirring member when the developing device is detached from the main body of the image forming apparatus is a magnetic pole having the highest magnetic flux density. Item 6. The image forming apparatus according to Item 5. The developing device has two developer conveying stirring members in the vertical direction,
The rotation area of the multi-pole magnet is restricted so as to oppose each of the two developer conveying and stirring members when the developing device is detached from the main body of the image forming apparatus. The image forming apparatus according to claim 5 or 6. Two developer conveying stirring members in the horizontal direction,
6. The rotation of the multipolar magnet so as to oppose the developer conveying and stirring member on the side close to the multipolar magnet when the developer is separated from the image forming apparatus. Alternatively, the image forming apparatus according to claim 6.   A door for attaching and detaching the developing device is provided, and when the door is opened, a region for restraining the developer of the multipolar magnet is rotated so as to face the developer transport stirring member. The image forming apparatus according to claim 5.

Images