JP2006093174A - Magnet piece and magnet roll, and magnet piece magnetizing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnet piece for a magnet roll that constitutes a magnet roll having a magnetic characteristic that a repulsion pole is extremely feeble enough and planar with the number of poles required for design. <P>SOLUTION: In a method of magnetizing a magnet piece for a magnet roll, a magnetic pole is formed on the outer periphery of a composite magnetic body 30 having an almost fan-shaped or rectangular-shaped cross section. A first and a second magnet generating sources 10, 20 are used that face each other to generate different magnetic poles, a magnetization yoke 21 facing one side of the composite magnetic body 30 is added to the magnet generating source 20 that is disposed on the side opposing the inner side of the composite magnetic body 30, and the composite magnetic body 30 is disposed between the first and second magnet generating sources 10 and 20 for performing magnetization. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnet piece and a magnet roll for a magnet roll used in an electrophotographic copying machine, a laser printer, a facsimile, and the like, and a magnet piece magnetizing method and apparatus.

  A magnet roll having a magnet body is used for applications such as a developing device that visualizes an electrostatic latent image on a photosensitive drum such as a copying machine or a printer. For example, in the developing device, a magnet roll having a predetermined magnetic flux pattern is disposed inside a rotating cylindrical sleeve.

  A magnet roll using a resin magnet composition (hereinafter referred to as a composite magnet body) in which magnetic powder and a binder are mixed as the magnet body includes a shaft passing through the center of a composite magnet body formed into a hollow cylindrical shape, and a cross section. Is roughly divided into those in which a plurality of composite magnet bodies each having a substantially sector shape are bonded to a shaft.

  In a magnet roll made of one composite magnet body, the composite magnet body is integrally formed in a hollow cylindrical shape on the shaft, or the composite magnet body is formed in a hollow cylindrical shape, and then the shaft is fixed to the center.

  Also, as a magnet roll composed of a plurality of composite magnet bodies, when magnetic powder and a binder are mixed to form a composite magnet body having a substantially fan-shaped cross section, the magnetization of the magnetic powder toward the central part of the substantially arc-shaped arc surface Patent Document 1 below discloses a configuration in which a composite magnet body is produced by orienting directions and a plurality of obtained composite magnet bodies are bonded to the outer periphery of a shaft.

JP-A-62-282423

  Moreover, after bonding a magnet body to a shaft, the method of magnetizing like the following patent document 2 is disclosed. However, it is necessary to change the magnetizing device depending on the required magnetizing pattern and the shape of the magnet roll.

JP 2001-34069 A

  Moreover, in the mag roll which consists of several fan-shaped magnet bodies, the method of magnetizing a fan-shaped magnet body one by one is shown by patent document 3, Furthermore, patent document 4 also has various magnetization patterns. It is disclosed.

JP 2001-291628 A JP 2004-87644 A

  FIG. 7 shows Conventional Example 1 of a magnet roll used as a developing roll for visualizing an electrostatic latent image on a photosensitive drum. This magnet roll includes magnet pieces P1, P2, P3, P4, and P5 constituting the pumping pole 1, the layer regulating pole 2, the developing pole 3, the recovery pole 4 and the peeling pole 5, respectively, between the pumping pole 1 and the peeling pole 5. The magnet pieces P1 and P5 positioned on both sides of the gap 8 have the same magnetic force on the left and right side surfaces in the circumferential direction (the center position of the outer peripheral surface of the magnet piece). And magnetized so that the magnetic flux distribution is symmetrical. The shaft 7 is usually a magnetic material such as iron.

  The magnetized pattern (on the circumferential surface surrounding the magnet roll) when the surface magnetic force of the magnet roll of FIG. 7 is measured along the circumferential direction (on the circumferential surface corresponding to the cylindrical sleeve that houses the magnet roll). The relationship between the angle and the surface magnetic flux density is as shown in the graph of FIG. 8A shows a case where the gap 8 has a width of 45 ° with respect to the shaft center, and FIG. 8B shows a case where the gap 8 has a width of 15 °. In either case, there is a problem that a repulsion pole (reverse pole) is likely to occur in the gap 8.

  FIG. 9 shows a second conventional example of a magnet roll. In this magnet roll, in addition to the magnet pieces P1 to P5 of the conventional example 1 in FIG. 7 described above, the magnet piece P6 for suppressing the reverse pole is pumped, and the cross section of the magnet roll is circular between the pole 1 and the peeling pole 5. It sticks together on the outer periphery of the shaft 7 so that it may become. As the magnet piece P6, a magnet having a cross section having a substantially fan-shaped side surface, a magnetic pole having the same polarity, and a magnetized so that the inner peripheral surface is opposite to the side surface is used. Others are the same as the prior art example 1.

  The magnetized pattern (on the circumferential surface surrounding the magnet roll) when the surface magnetic force of the magnet roll in FIG. 9 is measured along the circumferential direction (on the circumferential surface corresponding to the cylindrical sleeve that houses the magnet roll). The relationship between the angle and the surface magnetic flux density is as shown in the graph of FIG. 10 (when the magnet piece P6 has a width of 45 ° with respect to the shaft center). In this conventional example 2, the occurrence of repulsive poles can be prevented by providing the magnet piece P6 for suppressing the reverse pole. In addition, there is the following Patent Document 5 as a known document corresponding to Conventional Example 2 in FIG.

JP 2002-50515 A

  In the case of a magnet roll composed of an odd number of poles, especially the above five poles, the pumping pole and the peeling pole are the same pole, and there is a countermeasure against the occurrence of a repulsive pole due to the repulsive force between the two poles. Indispensable. Due to this repulsion pole, the recovery rate of the carrier (magnetic powder such as iron powder) for transporting the toner decreases, and the supply of toner to the photosensitive drum becomes unstable due to the unrecovered carrier, resulting in image defects. There is a risk of waking up. Therefore, it is necessary to control the repulsion pole to 10 mT (100 gauss) or less on the surface of the cylindrical sleeve, and the carrier recovery rate is improved by flattening the region of 10 mT or less. Conventionally, as a method for controlling the repulsion pole, as described in the conventional example 2, a magnetic pole having the same polarity is provided between the same poles of the magnet roll (region where the repulsion pole is generated) and the side surface has a substantially fan-shaped cross section. However, it has been proposed to arrange a magnet piece whose inner peripheral surface is opposite to the side surface. However, in this case, one more magnet piece must be added to the number of poles required in the design, resulting in a complicated configuration, an increase in weight, and an increase in cost. In addition, when magnet pieces are arranged for repulsive pole control, the magnetic properties at both ends in the longitudinal direction of the magnet roll tend to increase, which also deteriorates the carrier recovery rate.

  Therefore, in view of the above points, the present invention provides a magnet piece for a magnet roll for constituting a magnet roll having a flat magnetic characteristic with a repulsive pole sufficiently weak (10 mT or less) with the number of poles required for design. It is a first object to provide

  A second object of the present invention is to provide a magnet roll capable of realizing a flat magnetic characteristic with sufficiently weak repulsion poles and the number of poles required in design by using the magnet piece. To do.

  Furthermore, a third object of the present invention is to provide a magnetizing method and apparatus for magnetizing a magnet piece for a magnet roll for constituting a magnet roll having a sufficiently weak repulsion pole and flat magnetic characteristics. .

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, a magnet piece for a magnet roll according to the present invention is composed of a composite magnet body having a substantially fan-shaped or substantially rectangular cross section whose inner peripheral side is fixed to a shaft and whose outer peripheral surface is close to and opposed to a cylindrical sleeve. In
When the magnetic flux density peak point on the outer peripheral surface is at a position where the outer peripheral surface is divided into length A and length B,
A / B> Φ _A / Φ _B
(However, A ≦ B and Φ _A is the magnetic flux density peak value on the cylindrical sleeve due to the magnetic force of the side surface on the length A side of the composite magnet body, and Φ _B is the length B side of the composite magnet body. Magnetic flux density peak value on the cylindrical sleeve due to the magnetic force of the side surface of
It is characterized by being.

  The composite magnet body is a mixture of anisotropic magnet powder and resin or rubber, and is concentrated in the vicinity of the position that becomes the magnetic flux density peak point of the outer peripheral surface, or the composite magnet body is A mixture of isotropic magnet powder and resin or rubber may be used.

  The magnet roll according to the present invention has a configuration in which a plurality of magnet pieces are fixedly arranged on the outer periphery of a shaft, and at least one of the plurality of magnet pieces is a magnet piece according to the present invention.

  Further, the magnet roll according to the present invention provides a gap without a magnet piece in a predetermined angular range on the outer periphery of the shaft, and a plurality of magnet pieces are fixedly arranged on the outer periphery of the shaft, and the magnet pieces on both sides of the gap are the main pieces. The magnet piece according to the invention is characterized in that the magnet pieces on both sides of the gap have the same magnetic poles on the outer peripheral surface, and the side surface facing the gap has a weaker magnetic force than the side surface on the opposite side. .

In the magnetizing method of the magnet piece for the magnet roll according to the present invention, when the magnetic pole is formed on the outer peripheral surface of the composite magnet body having a substantially sectoral cross section or a substantially rectangular cross section,
The first and second magnetic field generating sources that generate different magnetic poles facing each other are used, and the magnetic field generating source on the side facing the inner peripheral side of the composite magnet body is opposed to one side surface of the composite magnet body. Add a magnetizing yoke
The composite magnet body is disposed between the first and second magnetic field generation sources.

  In the magnetizing method of the magnet piece for the magnet roll, the composite magnet body may be passed between the first and second magnetic field generation sources and magnetized.

  In the magnetizing method of the magnet piece for the magnet roll, a linear direction passing through a desired position on the inner peripheral surface of the composite magnet body and a concentrated orientation position on the outer peripheral surface, and a magnetic field generated by the first and second magnetic field generation sources. It is better to set the direction of

A magnetizing device for a magnet piece for a magnet roll according to the present invention has a configuration in which magnetic poles are formed on the outer peripheral surface of a composite magnet body having a substantially sectoral or substantially rectangular cross section.
One side surface of the composite magnet body, which is added to the first and second magnetic field generation sources that generate different magnetic poles facing each other and the magnetic field generation source on the side facing the inner peripheral side of the composite magnet body And a magnetized yoke opposite to each other.

  In the magnetizing apparatus for the magnet piece for the magnet roll, the lengths of the first and second magnetic field generation sources and the magnetizing yoke are shorter than the length of the composite magnet body, and the first and second magnetic fields are It is preferable to further include a through gauge for passing the magnet body between the generation sources.

  According to the magnet piece for a magnet roll according to the present invention, the magnetic force on one side of the composite magnet body having a substantially sectoral or substantially rectangular cross section can be weakened (the magnetic force on the other side is increased). In addition, when a composite magnet body that is concentrated and oriented using anisotropic magnet powder is used and the concentrated orientation position is offset from the center of the outer peripheral surface of the magnet piece to the left or right of the circumferential direction, the magnetic path in the composite magnet body Due to the difference, a magnetic force difference occurs between the left side surface and the right side surface. However, according to the present invention, a magnetic force difference is generated between the left and right side surfaces more than the position ratio (angle ratio) where the concentrated orientation position is offset. This is particularly effective for controlling the repulsion pole in the magnet roll.

  According to the magnet roll of the present invention, by using the magnet piece, even when a gap is left in the magnet roll, the repulsion pole generated in the gap portion can be effectively suppressed. As a result, it is possible to realize a magnet roll having flat magnetic characteristics with a repulsive pole sufficiently weak (for example, 10 mT or less on the outer periphery of the cylindrical sleeve) with only the number of poles required for design. Further, by providing a gap, it is possible to suppress the rise of magnetic characteristics at both ends of the magnet roll in the longitudinal direction. Furthermore, compared with the structure in which the magnet piece is provided in all the cylindrical shapes of the magnet roll, by leaving the gap portion, the costly magnet body portion can be reduced and the weight can be reduced.

  According to the magnetizing method and apparatus for a magnet piece for a magnet roll according to the present invention, the magnetic force of one of the side surfaces of the composite magnet body having a substantially sectoral or substantially rectangular cross section is weakened (the magnetic force of the other side surface is increased). Is possible. Moreover, when using the composite magnet body concentratedly oriented using anisotropic magnet powder, the magnetic force difference can be generated between the left and right side surfaces more than the position ratio (angle ratio) where the concentrated orientation position is offset.

  Hereinafter, as a best mode for carrying out the present invention, embodiments of a magnet piece and a magnet roll, and a magnet piece magnetizing method and apparatus will be described with reference to the drawings.

  1 and 2 show a first embodiment of the present invention, which shows a magnetizing method and apparatus for a magnet piece for a magnet roll, and a magnet piece obtained thereby. In FIG. 1, reference numeral 11 denotes an upper support of the magnetizing device, 12 denotes a lower support of the magnetizing device, and the upper support 11 generates a magnetic field for magnetization as a first magnetic field generating source 10. A permanent magnet or an electromagnet is fixed, and a permanent magnet or an electromagnet that generates a magnetic field for magnetization as the second magnetic field generation source 20 faces the lower support 12 in parallel with the first magnetic field generation source 10. It is fixed. In addition, a magnetized yoke 21 is added to and joined to the upper side surface of the second magnetic field generation source 20 (on the side facing the first magnetic field generation source 10). The first magnetic field generation source 10 and the second magnetic field generation source 20 generate different magnetic poles. For example, if the first magnetic field generation source 10 is the S pole, the second magnetic field generation source 20 is N Generate poles.

  Here, the magnetizing yoke 21 is opposed to one of the side surfaces in the circumferential direction of the composite magnet body 30 formed by mixing magnet powder and a binder with a substantially fan-shaped cross section as an object to be magnetized (including proximity facing and contact facing). It is arrangement to do. Preferably, as shown in the figure, the cross-sectional triangular shape (the shape in which the cross-sectional area gradually decreases from the magnetic field generation source 20 toward the tip) is in contact with the substantially lower half (the inner peripheral portion) of one side surface of the composite magnet body 30. ing. The magnetized yoke material is iron, iron-cobalt alloy (trade name: pamenjour), or the like.

  The composite magnet body 30 as an object to be magnetized has a substantially sectoral cross section and is a mixture of isotropic or anisotropic magnet powder and a binder such as rubber or resin, and becomes a magnet piece for a magnet roll by magnetization processing. It is. FIG. 1A shows a correct arrangement of the composite magnet body 30 as a magnetized object with respect to the magnetizing device. For example, when the composite magnetic body 30 has a symmetrical fan shape, the first and second magnetic field generation sources 10 are used. , 20 has a center line passing from the center of the outer peripheral surface to the center of the inner peripheral surface of the composite magnet body 30 (this center line passes through the center of the shaft when the composite magnetic body 30 is mounted on the shaft). It is parallel to the direction of the magnetic field between the second magnetic field generation sources 10 and 20. The same arrangement is used when the composite magnet body 30 is an anisotropic composite magnet body using anisotropic magnet powder and is concentrated and oriented at the center position of the outer peripheral surface. At that time, one side surface of the composite magnet body 30 is opposed to the magnetizing yoke 21 to perform magnetization.

  The magnetic field generated by the first and second magnetic field generation sources 10 and 20 depends on the material and shape of the magnetic powder used in the composite magnet body 30, but it is applied when the magnetic field is 400 to 2000 kA / m (5 to 25 kOe). Magnetism is possible. When the composite magnet body 30 is concentrated and oriented with an anisotropic composite magnet body using anisotropic magnet powder, it is not shown, but it is preferable to dispose the upper magnetized yoke so as to face the position. .

  The first magnetic field generation source 10 and the second magnetic field generation source 20 are permanent magnets, and the depth lengths of the first and second magnetic field generation sources 10 and 20 and the magnetizing yoke 21 (perpendicular to the plane of FIG. 1). If the direction) is larger than the length of the composite magnet body 30, magnetization can be achieved by simply disposing the composite magnet body 30 as shown in FIG. Further, when the length of the composite magnet body 30 is larger than the depth length of the first and second magnetic field generation sources 10 and 20 and the magnetizing yoke 21, it is between the first and second magnetic field generation sources 10 and 20. By allowing the composite magnet body 30 to pass through, it is possible to cope with the magnetization of the long composite magnet body 30.

  If the first magnetic field generation source 10 and the second magnetic field generation source 20 are electromagnets, the depth lengths of the first and second magnetic field generation sources 10, 20 and the magnetizing yoke 21 are set to the composite magnet body 30. Magnetization can be performed by energizing a magnetizing current to the electromagnets serving as the magnetic field generation sources 10 and 20 in advance.

  In FIG. 1A, the direction of the center line passing from the center of the outer peripheral surface of the composite magnet body 30 to the center of the inner peripheral surface (the central orientation of the shaft to which the composite magnetic body 30 should be attached and the concentrated orientation of the outer peripheral surface of the composite magnetic body 30) The direction of the straight line passing through the position) and the direction of the magnetic field generated by the first and second magnetic field generation sources 10 and 20 are substantially parallel, which is a preferable positional relationship. Thus, the direction of the center line of the composite magnet body 30 with respect to the direction of the magnetic field generated by the first and second magnetic field generation sources 10 and 20 (the direction of the straight line passing through the shaft center and the concentrated orientation position of the outer peripheral surface) It is also possible to carry out magnetization by tilting. However, in the case of FIGS. 1B and 1C, there is a possibility that the magnetic force drop of the magnetic pole formed on the outer peripheral surface of the composite magnet body 30 and the influence of the surface magnetic flux density on the waveform may occur.

  When the composite magnet body 30 is an anisotropic composite magnet body using anisotropic magnet powder and the concentrated orientation is deviated from the direction of the center line, the first and the second In some cases, it is preferable to match the direction of the magnetic field between the second magnetic field generation sources 10 and 20 with the direction of a straight line passing through the shaft center and the concentrated orientation position of the outer peripheral surface. For example, when the magnetized yoke 21 is placed in contact with the side surface of the composite magnet body 30, the concentrated and oriented position on the outer peripheral surface of the composite magnet body 30 is preferably substantially directly above. In order to obtain such a state, the apex angle of the triangular magnetized yoke 21 in FIG. 1 may be appropriately set in accordance with the side surface angle of the composite magnet body 30. When the magnetization shown in FIG. 1 is performed in a state in which the position of concentrated orientation is shifted from almost directly above, there is a decrease in the magnetic force of the magnetic pole formed on the outer peripheral surface of the composite magnet body 30 and an adverse effect on the waveform of the surface magnetic flux density. .

  Needless to say, the composite magnet body 30 can be magnetized in the same manner even when the configuration of the magnetizing apparatus shown in FIG.

  2 is a magnet piece obtained by magnetizing the composite magnet body 30 with the magnetizing apparatus of FIG. 1, and FIG. 2 (A) passes from the center of the outer peripheral surface of the composite magnet body 30 to the center of the inner peripheral surface. This is the case where the anisotropic composite magnet body concentrated and oriented in the center line direction is magnetized, and a large amount of magnetic flux flows on the side surface facing the magnetizing yoke 21 during the magnetization process (the flow of magnetic flux on the opposite side surface). However, the magnetic force on the side surface on the magnetizing yoke 21 side increases compared to the case without the magnetizing yoke 21, and the magnetic force on the opposite side surface decreases.

At this time, it is assumed that the magnetic flux density peak point on the outer peripheral surface of the composite magnet body 30 is at a position where the outer peripheral surface is divided into length A: length B, and the magnetic force on the side surface on the length A side of the composite magnet body 30 The magnetic flux density peak value on the cylindrical sleeve (arranged on the outer periphery of the magnet roll composed of magnet pieces in the developing device) is Φ _A , and the magnetic force on the side surface on the length B side of the composite magnet body 30 is When the magnetic flux density peak values on the cylindrical sleeve and [Phi _B, the following equation (1) is satisfied.
A / B> Φ _A / Φ _B (1)
(However, the side surface on the B side faces the magnetized yoke)
That is, in the magnet piece of FIG. 2A, the magnetic flux density peak point on the outer peripheral surface of the composite magnet body 30 is the center of the outer peripheral surface, and A = B, and the left side A / B = 1 in the equation (1) It is. By providing the magnetized yoke 21, Φ _A <Φ _B is satisfied, so that the right side Φ _A / Φ _B <1 of equation (1) is satisfied, and equation (1) is established.

  The magnet piece of FIG. 2 (B) is magnetized on an anisotropic composite magnet body in which the position of concentrated orientation is slightly shifted from the center line direction passing from the center of the outer peripheral surface of the composite magnet body 30 to the center of the inner peripheral surface. . Also in this case, since a large amount of magnetic flux flows on the side surface facing the magnetized yoke 21 during the magnetizing process (the flow of magnetic flux on the opposite side surface is reduced), the magnetic force on the side surface on the magnetized yoke 21 side is the magnetized yoke. It increases compared to the case without 21 and the magnetic force on the opposite side surface decreases.

Also at this time, the above equation (1) holds. That is, in the magnet piece of FIG. 2B, the magnetic flux density peak point on the outer peripheral surface of the composite magnet body 30 is in the vicinity of the concentrated orientation position on the outer peripheral surface, and A <B, and the left side A / B <1. When the concentrated orientation position is shifted to the left or right in the circumferential direction from the center of the outer peripheral surface, a magnetic force difference is generated between the left side surface and the right side surface due to the difference in the magnetic path in the composite magnet body. By providing, more than the position ratio (angle ratio) where the concentrated orientation position is offset, a difference in magnetic force can be generated between the left and right side surfaces,
The right side Φ _A / Φ _B <1 of equation (1) is smaller than A / B, and equation (1) is established.

  According to the first embodiment, the following effects can be obtained.

(A) While using the 1st and 2nd magnetic field generation sources 10 and 20 which generate a different magnetic pole facing each other, the composite magnetic body is used for the magnetic field generation source 20 on the side facing the inner peripheral side of the composite magnet body 30. A magnetizing yoke 21 that opposes (including proximity opposition and contact opposition) is added to one side face of 20, and a composite magnet body 30 is disposed between the first and second magnetic field generation sources 10, 20 for magnetization processing. Therefore, the magnetic force on one side of the composite magnet body 30 having a substantially sectoral cross section can be weakened (the magnetic force on the other side facing the yoke 21 is increased).

(B) When a composite magnet body concentratedly oriented using anisotropic magnet powder is used and the concentrated orientation position is offset from the center of the outer peripheral surface of the magnet piece to the left or right in the circumferential direction, the magnetic path in the composite magnet body However, according to the present embodiment, the magnetic force difference between the left and right side surfaces is greater than the position ratio (angle ratio) where the concentrated orientation position is offset. Can be generated. This is particularly effective for controlling the repulsion pole in the magnet roll, which will be described in detail later.

  3 and 4 show Embodiment 2 of the present invention, and shows a magnetizing method and apparatus for a magnet piece for a magnet roll suitable for through magnetization. In this case, in order to move the composite magnet body 30 between the magnetized yoke 31 added to the first magnetic field generation source 10 and the second magnetic field generation source 20, the through gauge 25 is fixedly arranged. The through gauge 25 slidably guides the composite magnet body 30 so that the center position of the outer peripheral surface of the composite magnet body 30 is the center position of the facing surface width of the magnetizing yoke 31. The magnetizing yoke 31 is disposed so as to face the outer peripheral surface which is an arc surface of the composite magnet body 30 (including proximity facing and contact facing), and has a cross-sectional area from the magnetic field generation source 10 toward the magnetized object. 3 is a trapezoid whose cross section is symmetrical (specifically downward) as shown in FIG. 3, and has a function of strengthening the magnetizing magnetic field at the center position of the outer peripheral surface of the composite magnet body 30.

  The configuration for performing this magnetization is suitable in both cases where an electromagnet and a permanent magnet are used for the first magnetic field generation source 10 and the second magnetic field generation source 20, and the first magnetic field generation source 10 and The depth length of the magnetized yoke 31 and the depth lengths of the second magnetic field generation source 20 and the magnetized yoke 21 may be sufficiently shorter than the composite magnet body 30.

  Then, the composite magnet body 30 is passed between the magnetizing yoke 31 and the second magnetic field generation source 20 by using the through gauge 25 to perform magnetization.

  Other configurations are the same as those of the first embodiment described above, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  According to the second embodiment, since the structure has the through gauge 25, the through magnetization process of the composite magnet body 30 can be executed efficiently in a short time. In addition, since the magnetizing device may be magnetized through the composite magnet body 30, it can be very miniaturized.

  Further, by adding a magnetizing yoke 31 which is substantially trapezoidal and has a width opposite to the outer peripheral surface of the composite magnet body to be magnetized smaller than the outer peripheral surface width to the first magnetic field generating source 10, Even when the generated magnetic field is low (for example, when a rare earth permanent magnet is used), it is possible to sufficiently magnetize the composite magnet body 30 composed of the rare earth magnetic powder and the binder.

  The magnetized yoke 31 used in the second embodiment may be used in the first embodiment described above.

  In the first and second embodiments, the magnetizing yoke having a triangular cross section is used as the magnetizing yoke facing one side surface of the composite magnet body 30, but a magnetizing yoke having a circular cross section, a trapezoidal cross section, or the like can be used. . Moreover, it is also possible to use a shape having a portion facing not only one side surface of the composite magnet body 30 but also a part of its inner peripheral surface (the lower surface of the composite magnet body 30 in FIG. 1) as the magnetizing yoke. is there.

  FIG. 5 is a third embodiment of the present invention, and shows a configuration of a magnet roll using the magnet piece obtained in the first embodiment or the second embodiment. The magnet roll shown in FIG. 5 is used as a developing roll for visualizing the electrostatic latent image on the photosensitive drum, and includes a pumping electrode 1, a layer regulating electrode 2, a developing electrode 3, a collecting electrode 4, and a peeling electrode 5. Magnet pieces P 1, P 2, P 3, P 4, and P 5 are bonded to the outer periphery of the shaft 7 so as to provide a gap 8 between the pumping pole 1 and the peeling pole 5, but located on both sides of the gap 8. As the magnet pieces P1 and P5, the magnet pieces 40 having asymmetrical magnetic forces on the left and right side surfaces in the circumferential direction shown in FIG. The magnet piece 40 is arranged so that the side surface 40a on which the magnetic force of the magnet piece 40 is weak faces the face 8 (facing). The shaft 7 is usually a magnetic material such as iron.

  Thus, the magnet piece 40 obtained in the first or second embodiment is used as the magnet piece P1 (pumping pole 1) and the magnet piece P5 (peeling pole 5) on both sides of the gap 8 provided in the magnet roll. By arranging the side surface of the magnet piece 40 having a weak magnetic force so as to face (facing) the gap 8, the repulsive pole in the gap 8 can be suppressed. As a result, only the number of poles required in the design can be obtained. Thus, it is possible to realize a magnet roll having a repulsive pole sufficiently weak (for example, 10 mT or less on the outer periphery of the cylindrical sleeve) and flat magnetic characteristics. In particular, when a magnet piece in which the position of concentrated orientation is shifted in the left-right direction from the center of the outer peripheral surface as shown in FIG.

Hereinafter, the configuration of the magnet roll will be described in detail in Example 1.
1st magnet body Magnetic powder: Anisotropic Sr ferrite magnet powder Binder: Polyamide resin (nylon 12)
Molding: Concentrated orientation, injection molding (section is generally fan-shaped, rod-shaped)
2nd magnet body Magnetic powder: Anisotropic Sr ferrite magnet powder Binder: Nitrile rubber Molding: Concentrated orientation, extrusion molding (section is substantially fan-shaped, rod-shaped)
Magnetization Method The first magnet body is magnetized in the conventional predetermined magnetic field (the magnetizing yoke 21 of FIG. 1 or FIG. 3 is not used). The first magnet body thus magnetized is used for the developing pole 3.

  As shown in FIG. 1 or FIG. 3, the second magnet body is subjected to a magnetizing process in which a magnetic field is applied in a state where the magnetizing yoke 21 is disposed on the side surface of the magnet body. By such magnetization, it is possible to reduce (weaken) the magnetic force generated on the side surface opposite to the side surface on which the magnetized yoke 21 is disposed. The second magnet body magnetized in this way is used for the pumping pole 1 and the peeling pole 5. A second magnet body magnetized in a conventional predetermined magnetic field (without using the magnetizing yoke 21 of FIG. 1 or FIG. 3) is used for the layer regulating pole 2 and the recovery pole 4.

  The first and second magnet bodies produced as described above are bonded to an Fe shaft (diameter 6 mm) with an adhesive (the magnet roll diameter after bonding is 16 mm). A first magnet body is formed on the developing pole 3 in FIG. 5, a second magnet body (conventional magnetization) is formed on the layer regulating pole 2 and the recovery pole 4, and a second magnet body (see FIG. 1 or the magnetizing yoke 21 of FIG. 3). At this time, the second magnet body used for the pumping pole 1 and the separation pole 5 is disposed such that the magnetized yoke 21 is disposed in the direction in which the gap 8 is present and the opposite side surface is aligned with the magnetized side surface.

  Magnetization pattern (on the circumferential surface surrounding the magnet roll) when the surface magnetic force of the magnet roll configured in this way is measured along the circumferential direction (on the circumferential surface corresponding to the cylindrical sleeve containing the magnet roll) The relationship between the angle and the surface magnetic flux density is as shown in the graph of FIG. 6 (A) or (B). 6A shows a case where the gap 8 has a width of 45 ° with respect to the shaft center, and FIG. 6B shows a case where the gap 8 has a width of 15 °. In either case, the repulsion pole (reverse pole) in the gap 8 is suppressed to 10 mT or less. In this way, the repulsion pole can be controlled without reducing the magnetic force between the pumping pole 1 and the separation pole 5.

  In each of the embodiments and examples of the present invention, the magnet piece has been described as having a substantially sectoral cross section. However, the magnet piece has a substantially rectangular shape in which the radius of curvature of one or both of the sectoral outer peripheral surface and the inner peripheral surface is infinite. The present invention can be applied even to a magnet piece having a cross-sectional shape.

  Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

Embodiment 1 of the present invention, which is a magnetizing method and apparatus for a magnet piece for a magnet roll, wherein (A) is a preferred arrangement in which the direction of concentrated orientation of the composite magnet body and the generated magnetic field are substantially parallel, (B) And (C) is a front view which respectively shows the arrangement | positioning which inclined the direction of the concentrated orientation of a composite magnet body with respect to the generated magnetic field. It is the orientation image of the magnet piece for magnet rolls obtained by Embodiment 1 of this invention, Comprising: (A) is an orientation image in the case of being concentrated-oriented at the outer peripheral surface center, (B) is the left-right direction from the outer peripheral surface center. It is a front view which shows the orientation image in the case of having shifted | deviated to concentrated orientation. It is Embodiment 2 of this invention, Comprising: It is a front view which shows the magnetization method and apparatus of the magnet piece for magnet rolls. It is the same side view. It is Embodiment 3 of this invention, Comprising: It is a cross-sectional view of the magnet roll using the said magnet piece. 6 is a graph showing a magnetization pattern in the case of a magnet roll according to a third embodiment. It is a cross-sectional view of the magnet roll of Conventional Example 1. It is a graph which shows the magnetization pattern in the case of the prior art example 1. FIG. It is a cross-sectional view showing a magnet roll of Conventional Example 2. It is a graph which shows the magnetization pattern in the case of the prior art example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pumping pole 2 Layer regulation pole 3 Developing pole 4 Recovery pole 5 Separation pole 7 Shaft 8 Gap 10 First magnetic field generation source 11 Upper support body 12 Lower support body 21, 31 Magnetization yoke 20 Second magnetic field generation source 25 Through gauge 30 Composite magnet body 40 Magnet piece P1 to P6 Magnet piece

Claims (10)

In the magnet piece for the magnet roll, which is composed of a composite magnet body having a substantially sectoral cross section or a substantially rectangular cross section in which the inner peripheral side is fixed to the shaft and the outer peripheral surface is close to and opposed to the cylindrical sleeve,
When the magnetic flux density peak point on the outer peripheral surface is at a position where the outer peripheral surface is divided into length A and length B,
A / B> Φ _A / Φ _B
(However, A ≦ B and Φ _A is the magnetic flux density peak value on the cylindrical sleeve due to the magnetic force of the side surface on the length A side of the composite magnet body, and Φ _B is the length B side of the composite magnet body. Magnetic flux density peak value on the cylindrical sleeve due to the magnetic force of the side surface of
A magnet piece for a magnet roll.   2. The magnet piece according to claim 1, wherein the composite magnet body is a mixture of anisotropic magnet powder and resin or rubber, and is concentratedly oriented in the vicinity of a position that becomes a magnetic flux density peak point on the outer peripheral surface.   The magnet piece according to claim 1, wherein the composite magnet body is a mixture of isotropic magnet powder and resin or rubber.   A magnet roll having a plurality of magnet pieces fixedly arranged on an outer periphery of a shaft, wherein at least one of the plurality of magnet pieces is the magnet piece according to claim 1, 2, or 3.   The magnet piece according to claim 1, 2 or 3, wherein a gap without a magnet piece is provided in a predetermined angular range of the outer periphery of the shaft, and a plurality of magnet pieces are fixedly arranged on the outer periphery of the shaft, and the magnet pieces on both sides of the gap are arranged. In addition, the magnet pieces on both sides of the gap have the same magnetic poles on the outer peripheral surface, and the side face facing the gap has a weaker magnetic force than the opposite side face. In a magnetizing method for a magnet piece for a magnet roll that forms a magnetic pole on the outer peripheral surface of a composite magnet body having a substantially sectoral cross section or a substantially rectangular cross section,
The first and second magnetic field generating sources that generate different magnetic poles facing each other are used, and the magnetic field generating source on the side facing the inner peripheral side of the composite magnet body is opposed to one side surface of the composite magnet body. Add a magnetizing yoke
A method of magnetizing a magnet piece for a magnet roll, wherein the composite magnet body is disposed between the first and second magnetic field generation sources.   The method of magnetizing a magnet piece for a magnet roll according to claim 6, wherein the composite magnet body is passed between the first and second magnetic field generation sources and magnetized.   The linear direction passing through a desired position on the inner peripheral surface of the composite magnet body and a concentrated orientation position on the outer peripheral surface, and the direction of the magnetic field generated by the first and second magnetic field generation sources are substantially parallel. Magnetization method of the magnet piece for magnet rolls of description. In a magnetizing device for a magnet piece for a magnet roll that forms a magnetic pole on the outer peripheral surface of a composite magnet body having a substantially sectoral or rectangular cross section,
One side surface of the composite magnet body, which is added to the first and second magnetic field generation sources that generate different magnetic poles facing each other and the magnetic field generation source on the side facing the inner peripheral side of the composite magnet body A magnetizing device for a magnet piece for a magnet roll, characterized in that a magnetizing yoke is provided.   The lengths of the first and second magnetic field generation sources and the magnetizing yoke are shorter than the length of the composite magnet body, and a through gauge that allows the magnet body to pass between the first and second magnetic field generation sources. The magnetizing device for a magnet piece for a magnet roll according to claim 9 further comprising:

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