JP4768561B2 - SEALING DEVICE AND DEVELOPING DEVICE - Google Patents

Description

  The present invention relates to a sealing device and a developing device for preventing leakage of magnetic particles.

  In an image forming apparatus using an electrophotographic system, an electrostatic latent image formed on the surface of a photosensitive drum is developed using a developing device and visualized as a toner image.

  A typical developing device includes a developing tank for storing a developer, a conveying screw, and a developing roller. The developing tank is divided into a developing chamber and a stirring chamber by a partition wall. Each of the developing chamber and the stirring chamber is provided with a conveying screw. Each conveying screw is rotatably supported by the developing tank and is driven to rotate. By rotating each conveying screw, the developer in the developing tank is circulated through the developing chamber and the agitating chamber while being agitated. An opening communicating with the developing chamber is formed in the developing tank, and a developing roller is provided in the opening. The developing roller faces the photosensitive drum. The developing roller is rotatably supported by the developing tank and is driven to rotate. When the developing roller is driven to rotate, the developer in the developing chamber is pumped up by the developing roller, and thus the developer is supplied to the photosensitive drum.

  In such a developing device, the developer enters the bearing portion of the rotating shaft of the developing roller and the bearing portion of the rotating shaft of each conveying screw. The developer that has entered the bearing portion is melted by frictional heat due to rubbing. When the molten developer adheres to the bearing portion, there is a problem that the rotational load on the developing roller and each conveying screw increases.

  As a technique for solving this problem, Patent Document 1 discloses a technique of forming a magnetic brush. In this technique, a rotating member that rotates while contacting the developer in the container is supported by the bearing member in the container that stores the developer. A magnet member is provided at a position closer to the inside of the container than the bearing member so as to surround the rotating member. Techniques similar to the technique disclosed in Patent Document 1 are also disclosed in Patent Documents 2 and 3.

  As another technique for solving the above problem, Patent Document 4 provides a pair of ring magnets so that the same poles face each other across the bearing, and a developer repels the bearing by a repulsive magnetic field. A technique for preventing this is disclosed. A technique similar to the technique disclosed in Patent Document 4 is also disclosed in Patent Document 5.

Japanese Patent Laid-Open No. 3-251882 JP-A-4-245269 JP-A-4-245270 JP 60-28673 A JP 2005-84344 A

  In the technique disclosed in Patent Document 1, since the developer that has once entered the gap between the magnet member and the rotating member cannot be returned to the inside of the container, the developer accumulates in the gap, Has a problem that the developer is pushed out to the opposite side. Each technique disclosed in Patent Documents 2 to 5 has the same problem.

  An object of the present invention is to provide a sealing device and a developing device that can prevent leakage of magnetic particles as much as possible.

The present invention is an insertion hole forming portion in which a straight cylindrical insertion hole is formed, and is inserted into the insertion hole of the insertion hole forming portion, is formed in a right cylindrical shape or a right cylindrical shape, and has a straight line common to its axis. The magnetic particles are prevented from leaking through a gap between the insertion portion and the insertion portion that is rotated relative to the insertion hole forming portion around a rotation axis that extends parallel to the extending direction of the insertion hole. A sealing device for
It is formed in a right cylindrical shape, and the insertion portion is inserted into the inner hole thereof, is provided coaxially with the rotation axis, is interposed between the insertion hole forming portion and the insertion portion, and has no gap with respect to the insertion hole forming portion. A magnetic pole that is fixed and has an inner peripheral surface that faces the insertion portion and extends so as to incline toward one side in the extending direction of the insertion hole as it becomes downstream in the rotation direction of the insertion portion with respect to the insertion hole forming portion. There includes a magnetic pole forming portions to be formed,
One of the N pole and the S pole is a sealing device in which a plurality of the magnetic poles are arranged in the rotation direction as the magnetic poles .
Further, the present invention is provided so as to protrude from the outer peripheral surface of the insertion portion, and is inclined to one side in the extending direction of the insertion hole as it becomes downstream in the rotation direction of the insertion hole forming portion with respect to the insertion portion. And a protrusion formed in a spiral shape along the rotation axis.

  In the invention, it is preferable that the magnetic pole forming portion is formed of a resin magnet formed using a mixed material of resin and magnetic material.

  The present invention is further characterized by further comprising a yoke part interposed between the insertion hole forming part and the magnetic pole forming part.

The present invention also includes the sealing device,
A container having the insertion hole forming portion and having a storage space for storing the developer;
A developer carrying body having the insertion portion, provided in the accommodation space, and carrying a developer;
A bearing portion interposed between the insertion hole forming portion and the insertion portion, disposed on the opposite side of the housing space with respect to the sealing device, and rotatably supporting the insertion portion with respect to the insertion hole forming portion. This is a developing device.

  In the invention, it is preferable that the developer is a two-component developer including a carrier and a toner, and the toner coverage on the carrier surface is less than 100%.

  According to the present invention, the insertion hole forming portion is formed with a straight cylindrical insertion hole, and the insertion portion formed in a right cylindrical shape or a right columnar shape is inserted into the insertion hole. The insertion portion is rotated relative to the insertion hole forming portion about a rotation axis that extends in parallel with the extending direction of the insertion hole and forms a straight line common to the axis.

  A magnetic pole forming portion is interposed between the insertion hole forming portion and the insertion portion. The magnetic pole forming portion is formed in a right cylindrical shape, and the insertion portion is inserted through the inner hole thereof. The magnetic pole forming portion is provided coaxially with the rotation axis, and is fixed to the insertion hole forming portion without a gap.

  A magnetic pole is formed on the inner peripheral surface of the magnetic pole forming portion facing the insertion portion. Therefore, when magnetic particles enter the gap between the magnetic pole forming portion and the insertion portion, a magnetic brush made of magnetic particles is formed in the gap by the action of the magnetic field of the magnetic pole. Since the magnetic brush is formed in this way, it is possible to prevent the magnetic particles from leaking through the gap, and thus to prevent the magnetic particles from leaking through the gap between the insertion hole forming portion and the insertion portion. Can do.

Moreover, the magnetic pole extends so as to incline toward one side in the extending direction of the insertion hole as it becomes downstream in the rotation direction of the insertion part with respect to the insertion hole forming part. Therefore, the magnetic particles that have entered the gap between the magnetic pole forming portion and the insertion portion move along the magnetic pole while moving in the rotation direction together with the insertion portion when the insertion portion is rotated with respect to the insertion hole formation portion. And move to one side in the extending direction of the insertion hole. As described above, since the magnetic particles move to one side in the extending direction of the insertion hole, it is possible to prevent the magnetic particles from leaking to the other side in the extending direction of the insertion hole as much as possible. It is possible to prevent the magnetic particles from leaking to the other side in the extending direction of the insertion hole through the gap between the insertion hole forming portion and the insertion portion as much as possible.
In the present invention, any one of the N pole and the S pole is arranged in the rotation direction as the magnetic pole. Accordingly, the magnetic particles can be moved to one side in the extending direction of the insertion hole at a plurality of positions with respect to the rotation direction. Therefore, leakage of magnetic particles can be prevented more reliably.
Furthermore, since any one of the N pole and the S pole is arranged as the magnetic pole in the rotation direction, it is possible to eliminate the position where the magnetic field strength by each magnetic pole is zero with respect to the rotation direction. Therefore, the leakage of the developer can be prevented over the entire rotation direction.
Moreover, according to this invention, a protrusion part is provided in the outer peripheral surface of the said insertion part. The protruding portion is provided so as to protrude from the outer peripheral surface, and is spirally formed so as to be inclined toward one side in the extending direction of the insertion hole toward the downstream side in the rotation direction of the insertion hole forming portion with respect to the insertion portion. Formed. Therefore, the magnetic particles that have entered the gap between the magnetic pole forming portion and the insertion portion move in the rotation direction together with the magnetic pole formation portion when the insertion hole formation portion is rotated with respect to the insertion portion. It moves to one side of the extending direction of the said insertion hole along. As described above, since the magnetic particles move to one side in the extending direction of the insertion hole, it is possible to prevent the magnetic particles from leaking to the other side in the extending direction of the insertion hole as much as possible. It is possible to prevent the magnetic particles from leaking to the other side in the extending direction of the insertion hole through the gap between the insertion hole forming portion and the insertion portion as much as possible.

  Further, according to the present invention, the magnetic pole forming portion is made of a resin magnet formed using a mixed material of resin and magnetic material, so that the dimensional accuracy of the magnetic pole forming portion can be easily improved.

  According to the invention, a yoke portion is interposed between the insertion hole forming portion and the magnetic pole forming portion. By forming a part of the magnetic circuit by the yoke portion, it is possible to efficiently form a magnetic field by the magnetic pole of the magnetic pole forming portion.

  According to the invention, the container is provided with a storage space for storing the developer. The container has the insertion hole forming part. A developer carrying body for carrying the developer is provided in the storage space of the container. The developer carrier has the insertion portion. Between the insertion hole forming part and the insertion part, there is a bearing part that rotatably supports the insertion part with respect to the insertion hole forming part. The bearing portion is disposed on the opposite side of the housing space with respect to the sealing device. Therefore, the developer can be prevented from leaking to the bearing portion side by the sealing device.

  When the developer leaks to the bearing portion side, the developer that has entered the bearing portion is melted by frictional heat due to rubbing. When the melted developer adheres to the bearing portion, there arises a problem that the rotational load of the insertion portion with respect to the insertion hole forming portion increases. In the present invention, since it is possible to prevent the developer from leaking to the bearing portion as much as possible, the above-described problems can be avoided.

  According to the invention, the developer is realized by the two-component developer including the carrier and the toner. Since the toner coverage on the carrier surface is selected to be less than 100%, the toner adheres to the carrier and is moved together with the carrier. Therefore, the toner can be prevented from leaking to the bearing portion side. When the toner coverage on the carrier surface becomes 100% or more, the toner with poor charging increases rapidly. The poorly charged toner is detached from the carrier. Therefore, the toner easily leaks to the bearing portion side.

  FIG. 1 is a cross-sectional view showing the vicinity of a sealing device 101 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a simplified configuration of the developing device 2 that is a developing device including the sealing device 101 shown in FIG. The developing device 2 is mounted on the image forming apparatus 100 using the electrophotographic method, and supplies developer to the surface of the photosensitive drum 3 on which the electrostatic latent image is formed to develop the electrostatic latent image. Used. In this embodiment, a two-component developer containing a carrier and toner is used as the developer. The carrier is a magnetic particle.

  The developing device 2 includes a developing tank 112 that is a container in which a storage space 111 that stores a developer is formed, and a developing roller that is provided in the storage space 111 and is rotationally driven to support the developer. 113, a doctor blade 114 that is a layer thickness regulating member that regulates the layer thickness of the developer carried and conveyed by the developing roller 113, and is provided in the housing space 111 and is driven to rotate while stirring the developer. First and second screws 115 and 116, which are stirring and conveying members that are conveyed and circulated, are provided.

  The developing tank 112 is made of resin, for example. The developing tank 112 is formed to extend. The developing tank 112 is disposed horizontally in the installed state. The storage space 111 of the developing tank 112 is partitioned into first and second storage chambers 121 and 122 by a partition wall 120 extending in the extending direction of the developing tank 112. The first and second storage chambers 121 and 122 communicate with each other at both ends in the extending direction. The developing tank 112 is formed with an opening 123 that opens to face the photosensitive drum 3. The opening 123 communicates with the first storage chamber 121. The developing tank 112 is provided with a toner supply port 124 for supplying toner. The toner supply port 124 communicates with the second storage chamber 122.

  The developing roller 113 is provided in the opening 123 of the developing tank 112 and faces the photosensitive drum 3. The developing roller 113 includes a roller main body 126 formed in a right cylindrical shape, and a roller shaft portion 127 formed in a right cylindrical shape or a right cylindrical shape and provided coaxially with the roller main body 126. The roller shaft 127 is made of a magnetic material such as iron. The roller body 126 includes a developing sleeve 128 made of a nonmagnetic material, and a magnet roller 129 that is fitted in the developing sleeve 128 and has a plurality of magnetic poles. On the outer peripheral surface of the developing sleeve 128, the carrier, to which the developer, specifically the toner, is attached, is magnetically attracted by the action of the magnetic field of each magnetic pole of the magnet roller 129.

  Such a developing roller 113 is supported so as to be rotatable about a first rotation axis L <b> 1 that extends in parallel to the extending direction of the developing tank 112 and forms a straight line common to the developing tank 113 with respect to the developing tank 112. Is done. The developing roller 113 is driven to rotate in the direction of the arrow R1 in FIG. 2 around the first rotation axis L1. As the developing roller 113 is driven to rotate in this way, the developer in the first storage chamber 121 is pumped up, and this developer is supplied to the photosensitive drum 3.

  The doctor blade 114 is disposed on the upstream side in the rotation direction R1 of the developing roller 113 from the position P where the developing sleeve 128 is closest to the photosensitive drum 3. The doctor blade 114 is fixed to the developing tank 112 with a predetermined gap with respect to the outer peripheral surface of the developing sleeve 128. Such a doctor blade 114 regulates the layer thickness of the developer that is attracted to the outer peripheral surface of the developing sleeve 128 and conveyed.

  The first and second screws 115 and 116 are provided on a screw shaft portion 131 formed in a right cylindrical shape or a right column shape, and an outer peripheral surface of the screw shaft portion 131, and spiral along the axial direction of the screw shaft portion 131. Screw blade 132 formed in a shape. The screw shaft 131 is made of a magnetic material such as iron.

  The first screw 115 is provided in the first storage chamber 121 of the developing tank 112. The first screw 115 is supported so as to be rotatable about a second rotation axis L <b> 2 that extends in parallel to the extending direction of the developing tank 112 and forms a straight line with the axis of the first screw 115 with respect to the developing tank 112. The The first screw 115 is driven to rotate in the direction of the arrow R2 in FIG. 2 around the second rotation axis L2. By rotating the first screw 115 in this manner, the developer in the first storage chamber 121 is conveyed in a direction from one end to the other end in the extending direction of the developing tank 112 while being stirred. At the other end in the extending direction, the second storage chamber 122 is moved.

  The second screw 116 is provided in the second storage chamber 122 of the developing tank 112. The second screw 116 is supported by the developing tank 112 so as to be rotatable about a third rotation axis L <b> 3 that forms a straight line common to the axis of the second screw 116 and extends parallel to the extending direction of the developing tank 112. The The second screw 116 is rotationally driven around the third rotation axis L3 in the direction of the arrow R3 in FIG. By rotating the second screw 116 in this way, the developer in the second storage chamber 122 is conveyed in a direction from the other end in the extending direction of the developing tank 112 toward one end while being agitated. At one end in the extending direction, the first storage chamber 121 is moved.

  Referring to FIG. 1, FIG. 1 shows an enlarged bearing portion of the developing roller 113. The developing tank 112 includes a developing tank main body 136 and an insertion hole forming portion 138 that protrudes outward from the developing tank main body 136 and in which an insertion hole 137 is formed. The roller shaft 127 of the developing roller 113 is inserted through the insertion hole 137. A portion of the roller shaft portion 127 that is inserted through the insertion hole 137 is an insertion portion 139. The insertion hole 137 has a straight cylindrical shape and is formed extending along the first rotation axis L1. In the present embodiment, the insertion hole 137 has a right cylindrical shape and is coaxial with the first rotation axis L1. The insertion part 139 is supported by the insertion hole forming part 138 via the bearing part 140.

  The sealing device 101 according to the present embodiment includes a magnetic pole forming unit 141. The magnetic pole forming portion 141 is interposed between the insertion hole forming portion 138 and the insertion portion 139 and is disposed closer to the accommodation space 111 with respect to the bearing portion 140. The magnetic pole forming portion 141 is formed in a right cylindrical shape, and the insertion portion 139 is inserted through the inner hole 142 thereof. The magnetic pole forming portion 141 is provided coaxially with the first rotation axis L1 and is fixed to the insertion hole forming portion 138 without any gap.

  The magnetic pole forming portion 141 is made of a resin magnet that is molded using a mixed material of resin and magnetic material. Examples of the resin include polyoxymethylene (POM), high density polyethylene (PEHD), acrylonitrile-butadiene-styrene copolymer (ABS), and polypropylene (PP). Examples of the magnetic material include ferrite and neodymium. The magnetic pole forming part 141 is formed by, for example, compression molding or injection molding. Therefore, the dimensional accuracy of the magnetic pole forming portion 141 can be easily improved.

  A magnetic pole is formed on the inner peripheral surface 143 of the magnetic pole forming portion 141 facing the insertion portion 139. Therefore, when the developer enters the gap 144 between the magnetic pole forming portion 141 and the insertion portion 139, a magnetic brush made of the developer is formed in the gap 144 by the action of the magnetic field by the magnetic pole. Since the magnetic brush is formed in this way, it is possible to prevent the developer from leaking through the gap 144, and thus the developer from leaking through the gap between the insertion hole forming portion 138 and the insertion portion 139. Can be prevented.

  FIG. 3 is a developed view of the inner peripheral surface 143 of the magnetic pole forming portion 141. The magnetic pole extends so as to incline toward the accommodation space 111, which is one side in the extending direction of the insertion hole 137, toward the downstream side in the rotation direction R <b> 1 of the insertion part 139 relative to the insertion hole forming part 138. In the present embodiment, the magnetic pole is formed in a spiral shape along the first rotation axis L1. Therefore, the developer that has entered the gap 144 between the magnetic pole forming portion 141 and the insertion portion 139 moves in the rotation direction R1 together with the insertion portion 139 when the insertion portion 139 is rotated with respect to the insertion hole formation portion 138. However, it moves to the accommodation space 111 side along the magnetic pole. Since the developer moves to the accommodation space 111 in this way, it is possible to prevent the developer from leaking to the bearing portion 140 side that is the other side in the extending direction of the insertion hole 137 through the gap 144 as much as possible. As a result, it is possible to prevent the developer from leaking to the bearing portion 140 side as much as possible through the gap between the insertion hole forming portion 138 and the insertion portion 139.

  In the present embodiment, a plurality of the magnetic poles are arranged in the rotation direction R1. Since the plurality of magnetic poles are arranged in the rotation direction R1 in this way, the developer can be moved to the accommodation space 111 side at a plurality of positions with respect to the rotation direction R1. Therefore, leakage of the developer can be prevented more reliably.

  In the present embodiment, the N pole and the S pole are alternately arranged in the rotation direction R1 as the magnetic pole. Thus, since the N pole and the S pole are alternately arranged as the magnetic poles in the rotation direction R1, a magnetic field by each magnetic pole can be efficiently formed.

Furthermore, in the present embodiment, the pitch between magnetic poles of the same polarity is p1, the distance between the magnetic pole forming portion 141 and the insertion portion 139 in the rotational radius direction (radial direction) around the first rotation axis R1 is g1, When the thickness dimension of the magnetic pole forming portion 141 in the rotational radius direction around one rotational axis R1 is Lm1,
4.g1 ≦ Lm1 ≦ p1 / 4
Is satisfied. Thereby, the magnetic field by each magnetic pole can be formed suitably, Therefore The leak of a developer can be prevented reliably.

  When Lm1 is less than 4 · g1, in other words, the distance g1 of the gap 144 is larger than 1/4 of the thickness dimension Lm1 in the magnetization direction (radial direction) of the magnetic pole forming portion 141, the gap 144 has a sufficient magnetic flux density. Cannot be secured, and the magnetic attractive force to the developer is insufficient.

  When Lm1 is less than or equal to p1 / 4, in other words, when the pitch p1 is greater than or equal to four times the thickness dimension Lm1 of the magnetic pole forming portion 141, a substantially trapezoidal magnetic flux density distribution that is not affected by the adjacent magnetic poles is obtained. However, when Lm1 exceeds p1 / 4, in other words, when the pitch p1 is less than 4 times the thickness dimension Lm1 of the magnetic pole forming portion 141, an approximate sinusoidal magnetic flux density distribution is obtained due to interference of adjacent magnetic poles at the magnetic pole center portion, and the maximum magnetic flux density Decreases, and a sufficient magnetic flux density cannot be secured, resulting in insufficient magnetic attraction to the developer.

  Thus, when deviating from the range of 4 · g1 ≦ Lm1 ≦ p1 / 4, the magnetic attractive force to the developer is insufficient, and the developer is likely to leak.

  Furthermore, in this embodiment, the toner concentration of the developer is selected so that the toner coverage on the carrier surface is less than 100%. Since the toner coverage on the carrier surface is selected to be less than 100%, the toner adheres to the carrier and is moved together with the carrier. Therefore, the toner can be prevented from leaking to the bearing portion 140 side. When the toner coverage on the carrier surface becomes 100% or more, the toner with poor charging increases rapidly. The poorly charged toner is detached from the carrier. Therefore, the toner tends to leak to the bearing portion 140 side.

In the present embodiment, as described in Japanese Patent No. 3710801, the average volume diameter of the magnetic carrier is Dcav_vol (μm), the average volume diameter of the toner is Dtav_vol (μm), and the magnetic carrier specific gravity is When γc and toner specific gravity are γt, the toner is replenished to the developer so that the toner density TD (%) falls within the range defined by the following equation (1).
TD ≦ {γt · Vt / Nt / (γc · Vc)} × 100 (1)
In equation (1),
Vt (toner volume) = (π / 6) · (Dtav_vol) ³
Sc (magnetic material carrier surface area) = π · (Dcav_vol + Dtav_vol) ²
Nt (number of dense lines) = Sc / [(3 ^0.5 / 2) · (Dtav_vol) ² ] / 2
Vc (magnetic carrier volume) = (π / 6) · (Dcav_vol) ³

Using the average volume diameter Dcav_vol (μm) of the magnetic carrier and the average volume diameter Dtav_vol (μm) of the toner, a prescribed range in which the measured toner concentration TD (%) should be stored is set based on the above formula (1). By doing so, it is possible to accurately set the target specified range, and it is possible to always accurately control the toner density.

  Next, the reason why the prescribed range of the target toner density is accurate will be described. First, it is assumed that the magnetic carrier c has a large spherical shape and the toner t has a small spherical shape. In addition, a large number of toners t adhere to the surface of the magnetic carrier c, the surface of the magnetic carrier c is completely covered, and there is no more room for the toner to adhere to the surface of the magnetic carrier c. c When there is no excess toner not attached to the surface and one toner is shared by two adjacent magnetic carriers, the coverage of the toner is 100%, and an accurate toner density at that time The upper limit value TD100% is set.

In this state, if the average volume diameter of the magnetic carrier is Dcav_vol (μm), the average volume diameter of the toner is Dtav_vol (μm), the magnetic carrier specific gravity is γc, and the toner specific gravity is γt, the following equation is theoretically obtained. (2) It is possible to calculate an accurate upper limit value TD100% of toner density.
TD100% = {γt · Vt / Nt / (γc · Vc)} × 100 (2)

  The right term of the above formula (1) and the right term of the above formula (2) are the same. Therefore, the above formula (1) indicates that the acquired toner density TD (%) is maintained at the upper limit value TD100% or less of the accurate toner density of the above formula (2), while the toner density TD (%) is set to the upper limit value TD100. It suggests that it is always close to%.

  If there is excess toner t, the measured toner density TD (%) deviates from the specified range of the above formula (1). In this case, the toner with poor charging increases rapidly.

  FIG. 4 is a schematic diagram illustrating a configuration of the image forming apparatus 100 including the developing device 2 illustrated in FIG. The image forming apparatus 100 forms multi-color and single-color images on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside. The image forming apparatus 100 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a charger 5, a cleaner unit 4, an intermediate transfer belt unit 8, a fixing unit 12, a paper transport path S, a paper feed tray 10, and a paper discharge tray. 15 is comprised.

  Note that image data handled in the image forming apparatus 100 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, the developing device 2 (2a, 2b, 2c, 2d), the photosensitive drum 3 (3a, 3b, 3c, 3d), the charger 5 (5a, 5b, 5c, 5d), and the cleaner unit 4 (4a, 4b, 4c). , 4d) are provided to form four types of latent images corresponding to the respective colors, and a is set to black, b is set to cyan, c is set to magenta, and d is set to yellow. An image station is configured.

  The photosensitive drum 3 is disposed (mounted) on the upper part of the image forming apparatus 100. The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. As shown in FIG. 4, in addition to a contact roller type or brush type charger, a charger type charger is used. A vessel may be used. The exposure unit 1 uses, for example, an EL or LED writing head in which light emitting elements are arranged in an array, in addition to a method using a laser scanning unit (LSU) provided with a laser irradiation unit and a reflection mirror as shown in FIG. There is also a technique. The exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with (K, C, M, Y) toner. The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 8 disposed above the photosensitive drum 3 includes an intermediate transfer belt 7, an intermediate transfer belt driving roller 71, an intermediate transfer belt tension mechanism 73, an intermediate transfer belt driven roller 72, and an intermediate transfer roller 6 (6a). , 6b, 6c, 6d), and an intermediate transfer belt cleaning unit 9.

  The intermediate transfer belt drive roller 71, the intermediate transfer belt tension roller 73, the intermediate transfer roller 6, the intermediate transfer belt driven roller 72, etc. stretch the intermediate transfer belt 7 and rotate it in the direction of arrow B.

  The intermediate transfer roller 6 is rotatably supported by the intermediate transfer roller mounting portion of the intermediate transfer belt tension mechanism 73 of the intermediate transfer belt unit 8, and transfers the toner image on the photosensitive drum 3 onto the intermediate transfer belt 7. A transfer bias for the transfer.

  The intermediate transfer belt 7 is provided so as to be in contact with each photosensitive drum 3. The intermediate transfer belt 7 sequentially superimposes and transfers the toner images of each color formed on the photosensitive drum 3 onto the intermediate transfer belt 7, whereby a color toner image (multicolor toner image) is formed on the intermediate transfer belt 7. It has the function to form. The intermediate transfer belt 7 is formed in an endless shape using a film having a thickness of about 100 μm to 150 μm.

  Transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 7 is performed by the intermediate transfer roller 6 in contact with the back side of the intermediate transfer belt 7. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 6 in order to transfer the toner image. The intermediate transfer roller 6 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt. In this embodiment, a roller shape is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic images visualized according to the hues on the photosensitive drums 3 are stacked on the intermediate transfer belt 7 and become image information input to the apparatus. As described above, the laminated image information is transferred onto the sheet by the rotation of the intermediate transfer belt 7 by the transfer roller 11 disposed at the contact position between the sheet and the intermediate transfer belt 7 described later.

  At this time, the intermediate transfer belt 7 and the transfer roller 11 are pressed against each other at a predetermined nip, and a voltage for transferring the toner onto the sheet is applied to the transfer roller 11 (the polarity opposite to the toner charging polarity (−)). (+) High voltage). Further, in order to obtain the nip constantly, the transfer roller 11 uses one of the transfer roller 11 and the intermediate transfer belt drive roller 71 as a hard material (metal or the like), and the other as a soft material such as an elastic roller (elastic rubber roller). Or a foaming resin roller).

  As described above, the toner adhered to the intermediate transfer belt 7 by contact with the photosensitive drum 3 or the toner that is not transferred onto the sheet by the transfer roller 11 and remains on the intermediate transfer belt 7 Therefore, the intermediate transfer belt cleaning unit 9 is configured to remove and collect the toner. The intermediate transfer belt cleaning unit 9 is provided with a cleaning blade as a cleaning member that comes into contact with the intermediate transfer belt 7. The intermediate transfer belt 7 in contact with the cleaning blade is supported by an intermediate transfer belt driven roller 72 from the back side. ing.

  The paper feed tray 10 is a tray for storing sheets (recording paper) used for image formation, and is provided below the image forming unit and the exposure unit 1 of the image forming apparatus 100. A paper discharge tray 15 provided on the upper part of the image forming apparatus 100 is a tray for placing printed sheets face down.

  In addition, the image forming apparatus 100 is provided with a substantially vertical sheet conveyance path S for sending the sheet in the sheet feeding tray 10 to the sheet discharge tray 15 via the transfer unit 11 and the fixing unit 12. Further, a pickup roller 16, a registration roller 14, a transfer unit 11, a fixing unit 12, a conveyance roller 25 that conveys a sheet, and the like are disposed in the vicinity of the sheet conveyance path S from the paper feed tray 10 to the paper discharge tray 15. Yes.

  The conveyance roller 25 is a small roller for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 25 are provided along the sheet conveyance path S. The pickup roller 16 is a drawing roller that is provided at the end of the paper feed tray 10 and supplies sheets from the paper feed tray 10 to the paper transport path S one by one.

  Further, the registration roller 14 temporarily holds the sheet being conveyed on the sheet conveyance path S. The sheet has a function of conveying the sheet to the transfer unit at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned.

  The fixing unit 12 includes a heat roller 31, a pressure roller 32, and the like, and the heat roller 31 and the pressure roller 32 rotate with a sheet interposed therebetween.

  The heat roller 31 is set to a predetermined fixing temperature by the control unit based on a signal from a temperature detector (not shown), and is transferred to the sheet by thermocompression bonding the sheet together with the pressure roller 33. The multicolor toner image is melted, mixed, and pressed to be thermally fixed to the sheet.

  The sheet after the fixing of the multicolor toner image is conveyed to the reverse paper discharge path of the paper transport path S by the transport roller 25, and in a reversed state (with the multicolor toner image facing downward), the paper discharge tray. 15 is discharged to the top.

  Next, the sheet conveyance path will be described in detail. The image forming apparatus 100 includes a paper feed cassette 10 that stores sheets in advance, and a manual feed tray 20 that does not need to open and close the paper feed cassette 10 when a user prints a small number of sheets. Has been placed. In both the paper feeding methods, the pickup roller 16 is disposed, and each sheet is guided to the conveyance path.

  When the printing request content is a single-sided printing request, the sheet conveyed from the sheet feeding cassette 10 is conveyed to the registration roller 14 by the conveying roller 25-1 in the conveying path, and the image information on the leading edge of the sheet and the intermediate transfer belt 7 is conveyed. Are transferred to the transfer roller 11 at the timing of aligning the leading edges of the toner and image information is written on the sheet. Thereafter, the sheet passes through the fixing unit 12 so that unfixed toner on the sheet is melted and fixed by heat, and is discharged from the discharge roller 25-3 onto the discharge tray 15 via the conveying roller 25-2. .

  The sheets stacked on the manual paper feed tray 20 are fed by the pickup roller 16-2, reach the registration roller 14 through a plurality of transport rollers (25-6, 25-5, 25-4), and thereafter. Is discharged to the paper discharge tray 15 through the same process as that of the sheet fed from the paper feed cassette.

  When the content of the print request is a double-sided print request, as described above, the trailing edge of the sheet that has finished single-sided printing and has passed through the fixing unit 12 is chucked by the paper discharge roller 25-3, and the paper discharge roller rotates reversely. Then, after being guided to the transport rollers (25-7, 25-8), the back side printing is performed through the registration rollers 14, and the paper is discharged to the paper discharge tray 15.

  FIG. 5 is a developed view of the inner peripheral surface 153 of the magnetic pole forming portion 152 provided in the sealing device 151 according to the second embodiment of the present invention. Since this embodiment is similar to the first embodiment described above, the corresponding parts are denoted by the same reference numerals, and only different points will be described.

  In the present embodiment, N poles are arranged in the rotation direction R1 as the magnetic poles. Thus, since the N poles are arranged as the magnetic poles in the rotation direction R1, it is possible to eliminate the position where the magnetic field strength by each magnetic pole becomes zero with respect to the rotation direction R1. Therefore, the leakage of the developer can be prevented over the entire rotation direction R1.

  In the present embodiment, the N pole is arranged as the magnetic pole in the rotation direction R1, but the S pole may be arranged as the magnetic pole in the rotation direction R1. Even in this case, the same effect can be achieved.

  FIG. 6 is a cross-sectional view showing the vicinity of the sealing device 156 according to the third embodiment of the present invention. Since this embodiment is similar to the first embodiment described above, the corresponding parts are denoted by the same reference numerals, and only different points will be described.

  In the present embodiment, sealing device 156 further includes a yoke portion 157. The yoke part 157 is interposed between the insertion hole forming part 138 and the magnetic pole forming part 141. The yoke part 157 is formed in a right cylindrical shape, and the magnetic pole forming part 141 is inserted into the inner hole 158 thereof. The yoke portion 141 is provided coaxially with the first rotation axis L1 and is fixed to the insertion hole forming portion 138 and the magnetic pole forming portion 141 without a gap. By forming a part of the magnetic circuit by such a yoke portion 157, the magnetic field generated by the magnetic poles of the magnetic pole forming portion 141 can be efficiently formed.

  FIG. 7 is a cross-sectional view showing the vicinity of the sealing device 161 according to the fourth embodiment of the present invention. Since this embodiment is similar to the first embodiment described above, the corresponding parts are denoted by the same reference numerals, and only different points will be described.

  In the present embodiment, the magnetic pole forming portion 162 is fixed to the insertion portion 139 instead of the insertion hole forming portion 138 without any gap. A magnetic pole is formed on the outer peripheral surface 163 of the magnetic pole forming part 162 facing the insertion part 139. Therefore, when the developer enters the gap 164 between the magnetic pole forming portion 141 and the insertion hole forming portion 138, a magnetic brush made of the developer is formed in the gap 164 by the action of the magnetic field by the magnetic pole. Since the magnetic brush is formed in this way, it is possible to prevent the developer from leaking through the gap 164 and to prevent the developer from leaking through the gap between the insertion hole forming portion 138 and the insertion portion 139. Can be prevented.

  Moreover, the magnetic pole extends so as to incline toward the accommodation space 111, which is one side in the extending direction of the insertion hole, toward the downstream side in the rotation direction R11 of the insertion hole forming portion 138 with respect to the insertion portion 139. In the present embodiment, the magnetic pole is formed in a spiral shape along the first rotation axis L1. Therefore, the developer that has entered the gap 164 between the magnetic pole forming portion 162 and the insertion hole forming portion 138 rotates together with the insertion hole forming portion 138 when the insertion hole forming portion 138 is rotated with respect to the insertion portion 139. While moving in the direction R11, it moves toward the accommodation space 111 along the magnetic pole. Since the developer moves to the accommodation space 111 side in this way, it is possible to prevent the developer from leaking to the bearing portion 140 side that is the other side in the extending direction of the insertion hole 137 through the gap 164 as much as possible. As a result, it is possible to prevent the developer from leaking to the bearing portion 140 side as much as possible through the gap between the insertion hole forming portion 138 and the insertion portion 139.

  In the present embodiment, the plurality of magnetic poles are arranged in the rotation direction R11. Since the plurality of magnetic poles are arranged in the rotation direction R11 in this way, the developer can be moved toward the accommodation space 111 at a plurality of positions with respect to the rotation direction R11. Therefore, leakage of the developer can be prevented more reliably.

  In the present embodiment, the N pole and the S pole are alternately arranged in the rotation direction R11 as the magnetic pole. As described above, since the N pole and the S pole are alternately arranged in the rotation direction R11 as the magnetic pole, the magnetic field by each magnetic pole can be efficiently formed.

Furthermore, in the present embodiment, the pitch between the magnetic poles of the same polarity is p2, the distance between the magnetic pole forming portion 162 and the insertion portion 139 in the rotational radius direction (radial direction) around the first rotation axis R1 is g2, When the thickness dimension of the magnetic pole forming part 162 in the rotational radius direction around one rotational axis R1 is Lm2,
4 · g2 ≦ Lm2 ≦ p2 / 4
Is satisfied. Thereby, the magnetic field by each magnetic pole can be formed suitably, Therefore The leak of a developer can be prevented reliably.

  When Lm2 is less than 4 · g2, in other words, the distance g2 of the gap 164 becomes larger than 1/4 of the thickness dimension Lm2 in the magnetization direction (radial direction) of the magnetic pole forming portion 162, the gap 164 has a sufficient magnetic flux density. Cannot be secured, and the magnetic attractive force to the developer is insufficient.

  When Lm2 is equal to or smaller than p2 / 4, in other words, when the pitch p2 is equal to or larger than four times the thickness dimension Lm2 of the magnetic pole forming portion 162, a substantially trapezoidal magnetic flux density distribution that is not affected by the adjacent magnetic poles is obtained. However, when Lm2 exceeds p2 / 4, in other words, when the pitch p2 is less than 4 times the thickness dimension Lm2 of the magnetic pole forming portion 162, an approximate sinusoidal magnetic flux density distribution occurs due to the interference of adjacent magnetic poles at the magnetic pole center portion, and the maximum magnetic flux density Decreases, and a sufficient magnetic flux density cannot be secured, resulting in insufficient magnetic attraction to the developer.

  Thus, when deviating from the range of 4 · g2 ≦ Lm2 ≦ p2 / 4, the magnetic attractive force to the developer is insufficient, and the developer is likely to leak.

  In the present embodiment, the N pole and the S pole are alternately arranged in the rotation direction R11 as the magnetic pole, but either the N pole or the S pole may be arranged in the rotation direction R11 as the magnetic pole. In this case, the position where the strength of the magnetic field by each magnetic pole becomes zero with respect to the rotation direction R11 can be eliminated. Therefore, the leakage of the developer can be prevented over the entire rotation direction R11.

  FIG. 8 is a cross-sectional view showing the vicinity of the sealing device 166 according to the fifth embodiment of the present invention. Since this embodiment is similar to the first embodiment described above, the corresponding parts are denoted by the same reference numerals, and only different points will be described.

  In the present embodiment, each magnetic pole may be formed on the inner peripheral surface 168 of the magnetic pole forming portion 167 as in the first embodiment, or one magnetic pole is formed over the entire rotation direction R1. May be.

  The sealing device 166 according to the present embodiment further includes a protrusion 170 provided to protrude from the outer peripheral surface 169 of the insertion portion 139 facing the magnetic pole forming portion 167. The projecting portion 170 extends so as to incline toward the accommodation space 111, which is one side in the extending direction of the insertion hole 137, toward the downstream side in the rotation direction R 11 of the insertion hole forming portion 138 with respect to the insertion portion 139. . In the present embodiment, the protrusion 170 is formed in a spiral shape along the first rotation axis L1.

  Since the protruding portion 170 is provided in this way, the developer that has entered the gap 144 between the magnetic pole forming portion 167 and the insertion portion 139 is rotated when the insertion hole formation portion 138 is rotated with respect to the insertion portion 139. While moving in the rotation direction R <b> 11 together with the magnetic pole forming part 167, it moves along the protruding part 170 to the accommodation space 111 side that is one side in the extending direction of the insertion hole 137. Since the developer moves to the accommodation space 111 in this way, it is possible to prevent the developer from leaking to the bearing portion 140 side that is the other side in the extending direction of the insertion hole 137 through the gap 144 as much as possible. As a result, it is possible to prevent the developer from leaking to the bearing portion 140 side as much as possible through the gap between the insertion hole forming portion 138 and the insertion portion 139.

  In the present embodiment, the plurality of protrusions 170 are arranged in the rotation direction R11. As described above, since the plurality of protrusions 170 are arranged in the rotation direction R11, the developer can be moved toward the accommodation space 111 at a plurality of positions with respect to the rotation direction R11. Therefore, leakage of the developer can be prevented more reliably.

  FIG. 9 is a cross-sectional view showing the vicinity of the sealing device 171 according to the sixth embodiment of the present invention. Since this embodiment is similar to the above-described fourth embodiment, the same reference numerals are given to corresponding portions, and only different points will be described.

  In the present embodiment, each magnetic pole may be formed on the outer peripheral surface 173 of the magnetic pole forming portion 172 in the same manner as in the fourth embodiment described above, or one magnetic pole is formed over the entire rotation axis R1. Also good.

  The seal device 171 according to the present embodiment further includes a protruding portion 175 provided to protrude from the inner peripheral surface 174 of the insertion hole forming portion 138 facing the magnetic pole forming portion 172. The projecting portion 175 extends so as to incline toward the accommodation space 111, which is one side in the extending direction of the insertion hole 137, toward the downstream side in the rotation direction R 1 of the insertion portion 139 with respect to the insertion hole forming portion 138. . In the present embodiment, the protrusion 175 is formed in a spiral shape along the first rotation axis L1.

  Since the protruding portion 175 is provided in this way, the developer that has entered the gap 164 between the magnetic pole forming portion 172 and the insertion hole forming portion 138 causes the insertion portion 139 to rotate with respect to the insertion hole forming portion 138. Then, while moving in the rotation direction R <b> 1 together with the magnetic pole forming part 172, it moves along the protruding part 175 to the accommodation space 111 side, which is one side in the extending direction of the insertion hole 137. Since the developer moves to the accommodation space 111 side in this way, it is possible to prevent the developer from leaking to the bearing portion 140 side that is the other side in the extending direction of the insertion hole 137 through the gap 164 as much as possible. As a result, it is possible to prevent the developer from leaking to the bearing portion 140 side as much as possible through the gap between the insertion hole forming portion 138 and the insertion portion 139.

  In the present embodiment, the plurality of protrusions 175 are arranged in the rotation direction R1. As described above, since the plurality of protrusions 175 are arranged in the rotation direction R1, the developer can be moved toward the accommodation space 111 at a plurality of positions with respect to the rotation direction R1. Therefore, leakage of the developer can be prevented more reliably.

  Each of the embodiments described above is merely an example of the present invention, and the configuration can be changed within the scope of the present invention. For example, the developer may be a one-component developer. The roller shaft portion 127 may be made of magnetic stainless steel. Further, the roller shaft portion 127 is not limited to a magnetic material, and may be made of a nonmagnetic material.

  Further, the screw shaft portions 131 of the first and second screws 115 and 116 may be provided with a sealing device as in the above-described embodiments. The screw shaft portion 131 may be made of magnetic stainless steel. The screw shaft 131 is not limited to a magnetic material but may be made of a nonmagnetic material.

It is sectional drawing which shows the vicinity of the sealing device 101 which is 1st Embodiment of this invention. FIG. 2 is a cross-sectional view illustrating a simplified configuration of a developing device 2 that is a developing device including the seal device 101 illustrated in FIG. 1. FIG. 6 is a diagram showing an inner peripheral surface 143 of a magnetic pole forming part 141 in an expanded state. FIG. 3 is a schematic diagram illustrating a configuration of an image forming apparatus 100 including the developing device 2 illustrated in FIG. 2. It is a figure which expand | deploys and shows the internal peripheral surface 153 of the magnetic pole formation part 152 with which the sealing apparatus 151 which is 2nd Embodiment of this invention is provided. It is sectional drawing which shows the vicinity of the sealing device 156 which is the 3rd Embodiment of this invention. It is sectional drawing which shows the vicinity of the sealing device 161 which is 4th Embodiment of this invention. It is sectional drawing which shows the vicinity of the sealing device 166 which is 5th Embodiment of this invention. It is sectional drawing which shows the vicinity of the sealing device 171 which is the 6th Embodiment of this invention.

Explanation of symbols

2 Developing devices 101, 151, 156, 161, 166, 171 Sealing device 112 Developing tank 113 Developing roller 137 Insertion hole 138 Insertion hole forming part 139 Insertion part 140 Bearing part 141, 152, 162, 167, 172 Magnetic pole formation part 157 Joint Iron part 170,175 Protruding part

Claims (6)

An insertion hole forming portion in which a straight cylindrical insertion hole is formed, and the insertion hole forming portion is inserted into the insertion hole, and is formed in a straight cylinder shape or a right column shape, and forms a straight line common to the axis thereof. Sealing device for preventing magnetic particles from leaking through a gap between the insertion portion rotated relative to the insertion hole forming portion around a rotation axis extending parallel to the extending direction of the insertion hole Because
It is formed in a right cylindrical shape, and the insertion portion is inserted into the inner hole thereof, is provided coaxially with the rotation axis, is interposed between the insertion hole forming portion and the insertion portion, and has no gap with respect to the insertion hole forming portion. A magnetic pole that is fixed and has an inner peripheral surface that faces the insertion portion and extends so as to incline toward one side in the extending direction of the insertion hole as it becomes downstream in the rotation direction of the insertion portion with respect to the insertion hole forming portion. There includes a magnetic pole forming portions to be formed,
One of N poles and S poles is arranged as a plurality of the magnetic poles in the rotation direction . Projecting from the outer peripheral surface of the insertion portion, the rotation axis is inclined so as to incline to one side in the extending direction of the insertion hole as it becomes downstream in the rotation direction of the insertion hole forming portion with respect to the insertion portion. The sealing device according to claim 1 , further comprising a protrusion formed in a spiral shape along the protrusion . The magnetic pole forming portions, the sealing device according to claim 1 or 2, characterized by comprising a resin magnet molded by using a mixed material of resin and magnetic material. The seal device according to any one of claims 1 to 3, further comprising a yoke portion interposed between the insertion hole forming portion and the magnetic pole forming portion. A sealing device according to any one of claims 1 to 4 ,
A container having the insertion hole forming portion and having a storage space for storing the developer;
A developer carrying body having the insertion portion, provided in the accommodation space, and carrying a developer;
A bearing portion interposed between the insertion hole forming portion and the insertion portion, disposed on the opposite side of the housing space with respect to the sealing device, and rotatably supporting the insertion portion with respect to the insertion hole forming portion. A developing device. The developing device according to claim 5 , wherein the developer is a two-component developer including a carrier and a toner, and a toner coverage on the carrier surface is less than 100%.

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