Rubber magnet, developing magnet roller, developing device, and image forming device

Abstract

To provide a rubber magnet in which magnetic characteristics are improved by reducing a half width while maintaining magnetic flux density, a developing magnet roller, a developing device, and an image forming device.SOLUTION: An end surface portion 51 of a rubber magnet 50 includes: a first end surface portion 510 formed in an annular fan shape; and a second end surface portion 511 formed in an annular fan shape and connected to the first end surface portion 510 by a top surface portion 53, a side surface portion 52, and a bottom surface portion 54. The side surface portion 52 includes a left side surface portion 520 and a right side surface portion 521. The left side surface portion 520 connects the first end surface portion 510 and the second end surface portion 511, and further connects the top surface portion 53 and the bottom surface portion 54. The right side surface portion 521 connects the first end surface portion 510 and the second end surface portion 511, and further connects the top surface portion 53 and the bottom surface portion 54. The top surface portion 53 is formed by a combination of partial arcs of a plurality of outer circles (80, 81, and 83) having different center points from each other.SELECTED DRAWING: Figure 17

Description

[Technical field]

[0001] The present invention relates to a rubber magnet, a developing magnet roller, a developing device, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses the shape of the magnet part of a magnet roller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-3640 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 does not disclose a method for improving the magnetic properties of the developing roller, such as reducing the half-value width while maintaining the magnetic flux density.

[0005] An object of the present invention is to provide a rubber magnet, a developing magnet roller, a developing device, and an image forming apparatus, in which the magnetic characteristics are improved by reducing the half-width while maintaining the magnetic flux density. [Means for solving the problem]

[0006] According to the present invention, the rubber magnet includes an end surface portion, a side surface portion, a top surface portion, and a bottom surface portion. The end surface portion has a first end surface portion formed in an annular sector shape, and a second end surface portion formed in an annular sector shape and connected to the first end surface portion by the top surface portion, the side surface portion, and the bottom surface portion. The side surface portion has a left side surface portion and a right side surface portion. The left side surface portion connects the first end surface portion to the second end surface portion, and further connects the top surface portion to the bottom surface portion. The right side surface portion connects the first end surface portion to the second end surface portion, and further connects the top surface portion to the bottom surface portion. The top surface portion is made up of a combination of arcs that are part of a plurality of outer circles whose center points are different from each other.

[0007] The developing magnet roller according to the present invention includes a shaft and a rubber magnet. The shaft is cylindrical. A plurality of the rubber magnets are arranged such that the bottom surface of the rubber magnet contacts the circumferential surface of the shaft.

[0008] The developing device according to the present invention includes a developing magnet roller.

[0009] The image forming apparatus according to the present invention includes a developing device. Effect of the Invention

[0010] According to the present invention, it is possible to provide a rubber magnet, a developing magnet roller, a developing device, and an image forming apparatus, in which the magnetic properties are improved by reducing the half-value width while maintaining the magnetic flux density. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a multifunction peripheral including an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a developing device according to the first embodiment. [Diagram 3] FIG. 1 is a diagram showing a typical developing magnet roller. [Figure 4] FIG. 1 is a diagram showing the standards of common rubber magnets. [Diagram 5] 1(a) to 1(c) are diagrams showing a general method of magnetizing a rubber magnet. [Figure 6] 13(a) and 13(b) are diagrams showing a comparative example of a rubber magnet. [Figure 7] 13(a) to 13(d) are diagrams showing the direction and orientation of magnetic field lines of a rubber magnet according to a comparative example. [Figure 8] 1(a) to 1(c) are diagrams showing a rubber magnet according to a first embodiment. [Figure 9] 1(a) to 1(c) are diagrams illustrating a magnetizing method for a rubber magnet according to embodiment 1. [Figure 10] FIG. 4 is a diagram showing a method for testing the magnetic flux density of the rubber magnet according to embodiment 1. [Figure 11] 4(a) to 4(d) are diagrams showing the magnetic flux density and orientation of the rubber magnet according to the first embodiment. [Figure 12] FIG. 11 is a diagram showing a comparison of the characteristics of the rubber magnet according to the first embodiment and a comparative example when no additional magnetization is performed. [Figure 13] FIG. 11 is a diagram showing a comparison of the characteristics of the rubber magnet according to the first embodiment and a comparative example when additional magnetization is performed. [Figure 14] 1(a) to 1(e) are diagrams showing a developing magnet roller according to embodiment 1. FIG. [Figure 15] FIG. 11 is a diagram showing a rubber magnet according to a second embodiment. [Figure 16] 1A to 1E are diagrams showing developing magnet rollers according to comparative examples. [Figure 17] 13(a) and (b) are diagrams showing a rubber magnet according to a third embodiment. [Figure 18] 1(a) and (b) are diagrams showing a typical rubber magnet. [Figure 19] FIG. 11 is a diagram showing a rubber magnet according to a third embodiment. [Figure 20] FIG. 11 is a diagram showing a rubber magnet according to a third embodiment. [Figure 21]13(a) and (b) are diagrams showing a rubber magnet according to a third embodiment. [Figure 22] FIG. 11 is a diagram showing a rubber magnet according to a third embodiment. [Diagram 23] FIG. 11 is a diagram showing a rubber magnet according to a third embodiment. [Figure 24] 13(a) to 13(c) are diagrams comparing rubber magnets according to a third embodiment. [Diagram 25] 13(a) to 13(c) are diagrams comparing rubber magnets according to a third embodiment. [Figure 26] FIG. 4 is a diagram showing changes in magnetic properties. [Figure 27] FIG. 4 is a diagram showing changes in magnetic properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0013] The description of embodiment 1 and the matters shown in the drawings related to embodiment 1 may be applied to all other embodiments and the matters shown in the drawings related to all other embodiments, as necessary.

[0014] The matters described in the description of embodiment 1 and the drawings related to embodiment 1 may be referenced to all other embodiments and the matters described in the drawings related to all other embodiments.

[0015] An image forming apparatus 3 according to the first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a diagram showing a multifunction peripheral 1 including an image forming apparatus 3 according to the first embodiment of the present invention.

[0016] As shown in FIG. 1, the multifunction device 1 includes a document reading device 2 and an image forming device 3.

[0017] The document reading device 2 reads the document G and outputs image data.

[0018] The document reading device 2 includes a document transport device 20 and an optical device 21 .

[0019] The document transport device 20 transports the document G to the optical device 21. An example of the document transport device 20 is an ADF (Auto Document Feeder).

[0020] The optical device 21 reads an image formed on the document G and generates image information. The optical device 21 has a light emitting section, an optical system, an actuator that drives the optical system, and a light receiving section.

[0021] The image forming device 3 forms an image on a sheet.

[0022] The image forming apparatus 3 includes a feeding section 4, an image forming section 5, a fixing section 6, a sheet ejection section 7, and a sheet ejection tray 8.

[0023] The feeding section 4 feeds the sheet toward the image forming section 5 .

[0024] The image forming section 5 forms an image on the sheet fed from the feeding section 4 .

[0025] The image forming section 5 includes a toner supply unit 10 and an image forming section 11 .

[0026] The toner supply unit 10 has, for example, cyan, magenta, yellow, and black toner cartridges (not shown). Each toner cartridge has a toner bottle and a toner supply mechanism (not shown).

[0027] The toner supply unit 10 supplies toner from a toner bottle to the image forming section 11 by a toner supply mechanism.

[0028] The image forming unit 11 forms a toner image, which is created based on image data, on a sheet by, for example, electrophotography.

[0029] The image forming section 11 includes a charging device 30, an exposure device 31, a developing device 32, a photoconductor 33, and a cleaning device .

[0030] The charging device 30 charges the peripheral surface of the photoconductor 33. The exposure device 31 irradiates the charged peripheral surface of the photoconductor 33 with laser light based on image data, forming an electrostatic latent image.

[0031] The developing device 32 develops the electrostatic latent image on the photoconductor 33 with the toner supplied from the toner supply unit 10 .

[0032] The photoconductor 33 transfers the toner image onto a sheet by a direct transfer method or an indirect transfer method.

[0033] The cleaning device 34 cleans the remaining toner from the photoconductor 33 and also removes electricity from the peripheral surface of the photoconductor 33 .

[0034] The sheet onto which the toner image has been transferred is transported to the fixing unit 6. The fixing unit 6 applies heat and pressure to the sheet by a fixing roller and a pressure roller, thereby fixing the toner image formed on the sheet onto the sheet.

[0035] The sheet that has passed through the fixing unit 6 is conveyed to the sheet discharge unit 7 and discharged onto the sheet discharge tray 8. The sheet discharge tray 8 stores the discharged sheets.

[0036] Next, the developing device 32 according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing the developing device 32 according to the first embodiment.

[0037] As shown in FIG. 2, the developing device 32 includes a housing 40, a developing magnet roller 41, a first agitating member 42, and a second agitating member 43.

[0038] The housing 40 contains a developer such as toner, an example of which is a one-component magnetic toner.

[0039] The developing magnet roller 41 is disposed at a position facing the photoconductor 33 (FIG. 1).

[0040] The first agitating member 42 and the second agitating member 43 agitate the developer.

[0041] The first stirring member 42 and the second stirring member 43 are each composed of a screw connected to a driving device such as a motor (not shown). The first stirring member 42 and the second stirring member 43 each have a rotating shaft and a stirring blade provided around the rotating shaft.

[0042] A control device (not shown) controls the operation of a drive device (not shown) to rotate the first agitating member 42 around the rotation axis, thereby transporting the toner supplied from the toner supply unit 10 in the axial direction of the rotation axis while stirring it.

[0043] The control device controls the operation of the drive device to rotate the second agitating member 43 around the rotation axis, thereby transporting the toner transported by the first agitating member 42 in the axial direction of the rotation axis, opposite to the transport direction of the first agitating member 42.

[0044] The developing magnet roller 41 operates according to the control of the control unit, thereby recovering the toner conveyed by the second stirring member 43 by magnetic force and supplying the toner to the developing magnet roller 41 .

[0045] The developing magnet roller 41 operates under the control of the control unit, thereby supplying the supplied toner to the electrostatic latent image formed on the circumferential surface of the photoconductor 33 .

[0046] Next, with reference to FIGS. 3 to 7(b), a general rubber magnet 102 and magnet shaft 100, which are different from the rubber magnet 50 and developing magnet roller 41 according to the first embodiment, will be described.

[0047] Fig. 3 is a diagram showing a general magnet shaft 100. Fig. 4 is a diagram showing the standards of a general rubber magnet 102. Figs. 5(a) to (c) are diagrams showing a magnetization method of a general rubber magnet 102. Figs. 6(a) and (b) are diagrams showing comparative examples of the general rubber magnet 102 and the general rubber magnet 103. Figs. 7(a) to (d) are diagrams showing the magnetic flux density and orientation of the general rubber magnet 102 and the general rubber magnet 103 according to the comparative examples.

[0048] As shown in FIG. 3, a general magnet shaft 100 includes a general shaft 101 and a general rubber magnet 102.

[0049] The magnet shaft 100 has, for example, four to six rubber magnets 102 attached to the circumferential surface of a shaft 101.

[0050] The magnet shaft 100 is disposed inside a typical developing device and transports magnetic toner to a typical photoconductor.

[0051] The end face of rubber magnet 102 in the axial direction of shaft 101 is substantially annular sector-shaped. The bottom surface of rubber magnet 102 is in contact with the circumferential surface of shaft 101. The top surface of rubber magnet 102's annular sector is formed into a curved surface.

[0052] A typical "annular sector" is a sector surrounded by two circles (the top and bottom surfaces of the rubber magnet 102) with a common center on the axis of the shaft 101, and two straight lines extending radially from the common center.

[0053] The rubber magnet 102 has magnetism. The rubber magnet 102 has a major axis in the axial direction (longitudinal direction) of the shaft 101 and a minor axis in the circumferential direction (transverse direction) of the shaft 101.

[0054] As shown in Figure 4, magnetic property standards are established for each common rubber magnet 102. As shown in Figure 4, magnetic properties are shown by taking the angle (°) on the horizontal axis and the magnetic flux density (mT) on the vertical axis.

[0055] One of the magnetic property standards is the "magnetic angle standard" (°).

[0056] The change in magnetic flux density of rubber magnet 102 when magnet shaft 100 shown in FIG. 3 is rotated in the direction of the arrow around the axis of rotation of shaft 101 is the magnetic angle standard shown in FIG.

[0057] As an example, as shown by the bold line in Fig. 4, the magnetic flux density is 0 (mT) at a rotation angle of 0° at one end of the rubber magnet 102, gradually increases as the rotation angle increases, and has a maximum magnetic force at a rotation angle of about 90°. The magnetic flux density further gradually decreases after the rotation angle exceeds about 90°, and is 0 (mT) at the other end of the rubber magnet 102 when the rotation angle is about 180°.

[0058] The magnetic flux density at a rotation angle of approximately 90°±(2° to 5°) is referred to as the "magnetic center." The magnetic center is in the range of 90°±(2° to 5°), which is the rotation angle at which the rubber magnet 102 shows a magnetic flux density of 80% or more of the maximum magnetic flux density X when the rotation angle at which the rubber magnet 102 shows a maximum magnetic flux density X is 90°.

[0059] Another magnetic property standard is the "magnetic flux density standard." The rubber magnet 102 exhibits a maximum magnetic flux density X (mT) when the rotation angle is approximately 90°±(2° to 5°). The magnetic flux density standard requires that the magnetic flux density be maximum magnetic flux density X±5 (mT) when the rotation angle of the rubber magnet 102 is approximately 90°±(2° to 5°).

[0060] Another important magnetic property standard is called the "half-value width." The half-value width is the rotation angle width (°) of the rubber magnet 102 when the magnetic flux density of the rubber magnet 102 is 50% of the maximum magnetic flux density X (mT).

[0061] Next, a method for producing and magnetizing a general rubber magnet 102 will be described as shown in FIGS. 5(a) to 5(c).

[0062] A typical rubber magnet 102 is produced by an extrusion method in which a mixture of resin and magnetic powder is extruded while being heated into a mold 112 as shown in FIG. 5(a).

[0063] For example, there are two types of magnetization methods for orienting a general rubber magnet 102.

[0064] As shown in FIG. 5( a ), with the rubber magnet 102 placed in a metal mold 112 , a yoke 110 is placed on the upper side of the metal mold 112 , and a yoke 111 is placed on the lower side of the metal mold 112 .

[0065] When magnetic lines of force are generated from yoke 111 toward yoke 110, the apex portion of the top surface of rubber magnet 102 of mold 112 is magnetized in an oriented manner.

[0066] Furthermore, as shown in FIG. 5(b), two yokes 111a and 111b are arranged below the mold 112, and one yoke 110 is arranged above the mold 112.

[0067] When magnetic lines of force are generated from the two yokes 111a and 111b toward the yoke 110, the apex portion of the top surface of the rubber magnet 102 of the mold 112 is magnetized in an oriented manner.

[0068] Furthermore, as shown in FIG. 5(c), for example, there is a method in which a yoke 121 is placed in an iron container 70 and the rubber magnet 102 is additionally magnetized.

[0069] Rubber magnet 102 is placed on iron container 70 so that the apex of the top surface of rubber magnet 102 is in contact with iron container 70, and yoke 121a and yoke 121b are arranged at the position where the apex of the top surface of rubber magnet 102 is in contact with iron container 70.

[0070] The apex portion of the top surface of the rubber magnet 102 is further magnetized by the magnetic field lines emitted from the yokes 121a and 121b.

[0071] Figures 6(a) and (b) show comparative examples for the rubber magnet 50 according to embodiment 1. Figure 6(a) is an end face of a rubber magnet 102 viewed in the axial direction of the shaft 101 (Figure 3). Figure 6(b) is an end face of a rubber magnet 103 according to the comparative example viewed in the axial direction of the shaft 101 (Figure 3).

[0072] 6(a) shows a rubber magnet 102 having a generally annular sector-shaped end surface, with a bottom surface 102a, a side surface 102b, and a top surface 102c. The bottom surface 102a and the top surface 102c are curved surfaces. The side surface 102b is flat.

[0073] A rubber magnet 103 shown in FIG. 6(b) is a modified example of the rubber magnet 102 shown in FIG. 6(a).

[0074] The end face of the rubber magnet 103 according to the comparative example shown in Fig. 6(b) is a polyhedron and has a bottom face 103a, a side face 103b, and a top face 103c and a top face 103d. The bottom face 103a is a curved surface. The side face 103b, the top face 103c, and the top face 103d are flat surfaces.

[0075] Top surface 103c and top surface 103d of rubber magnet 103 in the comparative example shown in Figure 6(b) are prepared by cutting top surface 102c of rubber magnet 102 shown in Figure 6(a) to create top surface 103c, which is a horizontal surface, and further cutting both sides of top surface 103c in the short direction of the axial direction of shaft 101 (Figure 3) to create top surface 103d.

[0076] FIG. 7(a) is a diagram showing the top surface 102c of the rubber magnet 102 shown in FIG. 6(a).

[0077] As shown in FIG. 7(d), a Hall element 130 is disposed facing the top surface 102c of the rubber magnet 102, making it possible to measure the state and orientation of the magnetic lines of force.

[0078] When the rubber magnet 102 shown in FIG. 6(a) is magnetized using the method described in FIG. 5(a) and (b), there is variation in the magnetic angle (°) of the magnetic field lines generated on the top surface 102c, as shown in FIG. 7(a).

[0079] Furthermore, as explained in Fig. 5(c), when the top surface 102c of the rubber magnet 102 is placed facing the iron container 120 in which the yokes 121a and 121b are arranged and additional magnetization is performed, the rubber magnet 102 may tilt as shown in Fig. 7(b). Therefore, the orientation of the magnetic field lines on the top surface 102c of the rubber magnet 102 tilts as shown in Fig. 7(c).

[0080] The magnetic flux density and orientation of the top surface 103c (FIG. 6(b)) of the rubber magnet 103 according to the comparative example shown in FIG. 6(b) can also be measured using the method described in FIG. 7(d).

[0081] 12 and 13 show diagrams comparing the magnetic properties of the rubber magnet 50 according to the first embodiment (FIG. 8) with the rubber magnet 103 according to a comparative example.

[0082] Fig. 12 is a diagram showing a comparison of magnetic properties between the rubber magnet 50 according to embodiment 1 when there is no additional magnetization and the rubber magnet 103 according to the comparative example. Fig. 13 is a diagram showing a comparison of magnetic properties between the rubber magnet 50 according to embodiment 1 when there is additional magnetization and the rubber magnet 103 according to the comparative example.

[0083] 12 and 13 show the measurement results of the rubber magnet 50 according to the first embodiment and the measurement results of the rubber magnet 103 according to the comparative example, respectively.

[0084] Figures 12 and 13 each show the short-side width (mm) of the horizontal surface portion 531 (Figure 8(a)) of the rubber magnet 50 of embodiment 1, and the magnetic force (mT) per width (mm) of the horizontal surface length, the magnetic angle variation (°), and the half-value width (°) for the rubber magnet 50 of embodiment 1 and the rubber magnet 103 of the comparative example.

[0085] The results of this measurement are compared with the magnetic property standards explained in Figure 4. It is necessary to maintain the magnetic force and half-width while suppressing the variation in the magnetic angle, and here, if there is no additional magnetization, the variation in the magnetic angle is required to be 0±3°, in which case the magnetic force is required to be 55±5 (mT) and the half-width is required to be 50±5°.

[0086] In the rubber magnet 50 without additional magnetization according to embodiment 1 shown in FIG. 12, even when the horizontal plane length is 5 mm, the magnetic force and half-value width are within the required ranges mentioned above and are better than the rubber magnet 103 of the comparative example.

[0087] On the other hand, the measurement result of the rubber magnet 103 according to the comparative example without additional magnetization shown in FIG. 12 is that the half-width is 43° when the length of the horizontal plane is 0.2 mm and 0.3 mm, which is outside the required range of half-width (50±5°).

[0088] Next, when additional magnetization as shown in FIG. 13 is performed, the variation in magnetic angle is required to be 0±3°, the magnetic flux density is required to be 58±5mT, and the half-value width is required to be 45±5°.

[0089] The measurement results of the rubber magnet 103 according to the comparative example with additional magnetization in Figure 13 show that when the length of the horizontal plane is 0.2 mm or more, both the magnetic flux density and the half-value width are outside the range required by the magnetic property standards.

[0090] Next, the rubber magnet 50 according to the first embodiment will be described with reference to Figs. 8(a) to 13.

[0091] Figs. 8(a)-(c) are diagrams showing the rubber magnet 50 according to embodiment 1. Figs. 9(a)-(c) are diagrams showing a magnetization method for the rubber magnet 50 according to embodiment 1. Fig. 10 is a diagram showing a method for testing the magnetic flux density and orientation of the rubber magnet 50 according to embodiment 1. Figs. 11(a)-(d) are diagrams showing the magnetic flux density and orientation of the rubber magnet 50 according to embodiment 1. Fig. 12 is a diagram showing a comparison of the characteristics of the rubber magnet 50 according to embodiment 1 in the absence of additional magnetization and a comparative example. Fig. 13 is a diagram showing a comparison of the characteristics of the rubber magnet 50 according to embodiment 1 in the presence of additional magnetization and a comparative example.

[0092] First, the configuration of the rubber magnet 50 according to the first embodiment will be described with reference to FIGS. 8(a) to (c).

[0093] 8(a), the rubber magnet 50 according to the first embodiment includes an end surface portion 51, a side surface portion 52, a top surface portion 53, and a bottom surface portion 54. Here, the end surface portion 51, the side surface portion 52, the top surface portion 53, and the bottom surface portion 54 may be perpendicular to one another.

[0094] The end surface portion 51 has a first end surface portion 510 and a second end surface portion 511. The first end surface portion 510 and the second end surface portion 511 are flat surfaces extending in the short-side direction of the rubber magnet 50 according to embodiment 1. The first end surface portion 510 may be parallel to the second end surface portion 511.

[0095] The first end surface portion 510 is formed in an annular sector shape.

[0096] The second end surface portion 511 is formed in an annular sector shape, and is connected to the first end surface portion 510 by a top surface portion 53, a side surface portion 52, and a bottom surface portion .

[0097] The “annular sector” in this embodiment is an annular sector surrounded by two circles (top surface 53 and bottom surface 54 of rubber magnet 102) with a common center on the axis of shaft 56 (Figure 10) and two straight lines extending radially from the common center.

[0098] The side surface portion 52 has a left side surface portion 520 and a right side surface portion 521. The left side surface portion 520 and the right side surface portion 521 are flat surfaces extending in the longitudinal direction of the rubber magnet 50 according to the first embodiment.

[0099] The top surface portion 53 has a left curved surface portion 530 and a right curved surface portion 532. The left curved surface portion 530 and the right curved surface portion 532 are curved surfaces that extend in the longitudinal direction of the rubber magnet 50 according to the first embodiment.

[0100] The left side surface portion 520 of the side surface portion 52 connects the first end surface portion 510 and the second end surface portion 511, and further connects the left curved surface portion 530 of the top surface portion 53 and the bottom surface portion 54. The bottom surface portion 54 is a curved surface that extends in the longitudinal direction of the rubber magnet 50 according to the first embodiment.

[0101] The right side surface portion 521 of the side surface portion 52 connects the first end surface portion 510 and the second end surface portion 511 of the end surface portion 51, and further connects the right curved surface portion 532 of the top surface portion 53 and the bottom surface portion 54.

[0102] Top surface portion 53 further has a horizontal surface portion 531 formed between left curved surface portion 530 and right curved surface portion 532. Horizontal surface portion 531 is horizontal when top surface portion 53 of rubber magnet 50 faces vertically upward. Horizontal surface portion 531 is horizontal, for example, when rubber magnet 50 is placed on a horizontal surface with bottom surface portion 54 facing vertically downward.

[0103] According to the first embodiment, by forming the horizontal surface portion 531 on the top surface portion 53, the magnetic properties of the rubber magnet 50 can be improved.

[0104] More specifically, as shown in FIG. 8(b), first end surface portion 510 of end surface portion 51 is surrounded by first connection portion 510A, first connection portion 510B, first connection portion 510C, first connection portion 510D, first connection portion 510E, and first connection portion 510F.

[0105] A first end surface portion 510 of the end surface portion 51 is connected to the bottom surface portion 54 at a first connection portion 510A. The first connection portion 510A is a curved line.

[0106] A first end surface portion 510 of the end surface portion 51 is connected to a left side surface portion 520 of the side surface portion 52 at a first connection portion 510B. The first connection portion 510B may be a straight line.

[0107] The first end surface portion 510 of the end surface portion 51 is connected to the right side surface portion 521 of the side surface portion 52 at a first connection portion 510C. The first connection portion 510C may be a straight line.

[0108] First end surface portion 510 of end surface portion 51 is connected to left curved surface portion 530 of top surface portion 53 at a first connection portion 510D. First connection portion 510D is a curved line.

[0109] First end surface portion 510 of end surface portion 51 is connected to right curved surface portion 532 of top surface portion 53 at a first connection portion 510E. First connection portion 510E is a curved line.

[0110] A first end surface portion 510 of the end surface portion 51 is connected to a horizontal surface portion 531 of the top surface portion 53 at a first connection portion 510F. The first connection portion 510F is a straight line.

[0111] Similarly, as shown in Figure 8 (b), the second end surface portion 511 of the end surface portion 51 is surrounded by the second connection portion 511A, the second connection portion 511B, the second connection portion 511C, the second connection portion 511D, the second connection portion 511E, and the second connection portion 511F.

[0112] The second end surface portion 511 of the end surface portion 51 is connected to the bottom surface portion 54 at a second connection portion 511A. The second connection portion 511A is curved.

[0113] The second end surface portion 511 of the end surface portion 51 is connected to the left side surface portion 520 of the side surface portion 52 at a second connection portion 511B. The second connection portion 511B may be a straight line.

[0114] The second end surface portion 511 of the end surface portion 51 is connected to the right side surface portion 521 of the side surface portion 52 at a second connection portion 511C. The second connection portion 511C may be a straight line.

[0115] The second end surface portion 511 of the end surface portion 51 is connected to the left curved surface portion 530 of the top surface portion 53 at a second connection portion 511D. The second connection portion 511D is curved.

[0116] The second end surface portion 511 of the end surface portion 51 is connected to the right curved surface portion 532 of the top surface portion 53 at a second connection portion 511E. The second connection portion 511E is curved.

[0117] The second end surface portion 511 of the end surface portion 51 is connected to the horizontal surface portion 531 of the top surface portion 53 at a second connection portion 511F. The second connection portion 511F is a straight line.

[0118] 8(c), the left side surface portion 520 of the side surface portion 52 is connected to the left curved surface portion 530 of the top surface portion 53 at the third connection portion 53A. The third connection portion 53A is a straight line. The third connection portion 53A extends from the first end surface portion 510 of the end surface portion 51 to the second end surface portion 511 of the end surface portion 51.

[0119] The right side surface portion 521 of the side surface portion 52 is connected to the right curved surface portion 532 of the top surface portion 53 at the third connection portion 53B. The third connection portion 53B is a straight line. The third connection portion 53B extends from the first end surface portion 510 of the end surface portion 51 to the second end surface portion 511 of the end surface portion 51.

[0120] When the rubber magnet 50 is placed on a horizontal surface with the bottom surface 54 facing vertically downward, the left side surface 520 and the right side surface 521 of the side surface portion 52 are symmetrical with respect to the vertical direction.

[0121] The horizontal surface portion 531 of the top surface portion 53 is connected to the left curved surface portion 530 of the top surface portion 53 at a third connection portion 53C. The third connection portion 53C is a straight line. The third connection portion 53C extends from the first end surface portion 510 of the end surface portion 51 to the second end surface portion 511 of the end surface portion 51.

[0122] The horizontal surface portion 531 of the top surface portion 53 is connected to the right curved surface portion 532 of the top surface portion 53 at a third connection portion 53D. The third connection portion 53D is a straight line. The third connection portion 53D extends from the first end surface portion 510 of the end surface portion 51 to the second end surface portion 511 of the end surface portion 51.

[0123] The bottom surface portion 54 is connected to the left side surface portion 520 of the side surface portion 52 at the fourth connection portion 54A. The fourth connection portion 54A is straight. The fourth connection portion 54A extends from the first end surface portion 510 of the end surface portion 51 to the second end surface portion 511 of the end surface portion 51.

[0124] The bottom surface portion 54 is connected to the right side surface portion 521 of the side surface portion 52 at the fourth connection portion 54B. The fourth connection portion 54B is straight. The fourth connection portion 54B extends from the first end surface portion 510 of the end surface portion 51 to the second end surface portion 511 of the end surface portion 51.

[0125] Next, as shown in Figs. 9(a) to (c), a method for producing and magnetizing the rubber magnet 50 according to the first embodiment will be described.

[0126] The rubber magnet 50 according to the first embodiment is produced by an extrusion method in which a material made of a mixture of resin and magnetic powder is extruded while being heated into a mold 62 as shown in FIG. 9(a).

[0127] For the rubber magnet 50 according to the first embodiment, there are two types of alignment and magnetization methods, for example.

[0128] As shown in FIG. 9( a ), with the rubber magnet 50 placed in a metal mold 62 , a yoke 60 is placed on the upper side of the metal mold 62 , and a yoke 61 is placed on the lower side of the metal mold 62 .

[0129] When magnetic lines of force are generated from the yoke 61 toward the yoke 60, the apex portion of the top surface of the rubber magnet 50 of the mold 62 is magnetized in an oriented manner.

[0130] Furthermore, as shown in FIG. 9(b), two yokes 61a and 61b are arranged below the die 62, and one yoke 60 is arranged above the die 62.

[0131] When magnetic lines of force are emitted from the two yokes 61a and 61b toward the yoke 60, the apex portion of the top surface of the rubber magnet 50 of the mold 62 is magnetized in an oriented manner.

[0132] Furthermore, as shown in FIG. 9(c), for example, there is a method in which a yoke 61 is placed in an iron container 70 and the rubber magnet 50 is additionally magnetized.

[0133] The rubber magnet 50 is placed so that the apex of the top surface of the rubber magnet 50 is in contact with the iron container 70, and the yoke 61a and the yoke 61b are arranged at the position where the apex of the top surface of the rubber magnet 50 is in contact with the iron container 70.

[0134] The apex portion of the top surface of the rubber magnet 50 is further magnetized by the magnetic field lines emitted from the yoke 61a and the yoke 61b.

[0135] As shown in FIG. 9( c ), the rubber magnet 50 according to the first embodiment may have a magnetic flux density center 55 on the horizontal surface portion 531 of the top surface portion 53 .

[0136] According to the first embodiment, the orientation of the magnetic field lines in the horizontal surface portion 531 can be improved.

[0137] The magnetic property standards described in FIG. 4 can also be applied to the rubber magnet 50 according to the first embodiment.

[0138] The magnetic properties of the rubber magnet 50 according to the first embodiment can be measured by the method shown in Fig. 10. A redundant explanation of the magnetic property standards will be omitted.

[0139] As shown in FIGS. 10 and 11(d), a Hall element 90 is brought into contact with a developing magnet roller 41, which will be described later with reference to FIG.

[0140] Specifically, as will be described later with reference to FIG. 14, the developing magnet roller 41 is formed by attaching a rubber magnet 50 to the circumferential surface of a shaft 56 and inserting the rubber magnet 50 into a sleeve tube 57 .

[0141] As described in FIG. 8, the horizontal surface portion 531 is formed on the top surface portion 53 of the rubber magnet 50 according to the first embodiment.

[0142] A magnetic flux density center 55 is formed around a horizontal surface portion 531 of a top surface portion 53 of the rubber magnet 50 according to the first embodiment.

[0143] The magnetic characteristics of the horizontal surface portion 531 of the top surface portion 53 of the rubber magnet 50 are measured by the Hall element 90 through the sleeve tube 57. The distance between the Hall element 90 and the horizontal surface portion 531 is 0.1 mm to 0.3 mm.

[0144] By the magnetization and additional magnetization of the rubber magnet 50 described with reference to FIGS. 9(a) to (c), magnetic lines of force are generated on the horizontal surface portion 531 of the top surface portion 53 of the rubber magnet 50, as shown in FIG. 11(a).

[0145] As shown in FIG. 11(a), by providing the horizontal surface portion 531 on the top surface portion 53, the magnetic flux density of the magnetic lines of force generated on the horizontal surface portion 531 can be suitably controlled.

[0146] As shown in FIGS. 11(b) and (c), the orientation of the magnetic field lines generated on the horizontal surface portion 531 is preferably oriented in a direction perpendicular to the horizontal surface portion 531.

[0147] The magnetic characteristics of the rubber magnet 50 according to the first embodiment in which the horizontal surface portion 531 is provided on the top surface portion 53 in this way will be described again with reference to FIG. 12 and FIG.

[0148] As magnetic characteristic standards when there is no additional magnetization on horizontal surface portion 531 of top surface portion 53, a magnetic flux density of 55±5 (mT) is required. The magnetic angle variation is required to be 0±3°. The half-value width is required to be 50±5°.

[0149] As shown in FIG. 12, the magnetic properties of the rubber magnet 50 of embodiment 1 in the absence of additional magnetization are a magnetic flux density of 55 mT to 52 mT when the short-side length of the horizontal surface portion 531 is 0.2 mm to 3.0 mm, which is superior to the rubber magnet 103 made of a polyhedron of the comparative example.

[0150] When the short-side length of horizontal surface portion 531 is 0.2 mm or more, the variation in magnetic angle is 3° or less, which is superior to rubber magnet 103 according to the comparative example.

[0151] When the length of the horizontal surface portion 531 in the short side direction is 0.2 mm to 5.0 mm, the half-width is 45° to 50°, which is superior to the rubber magnet 103 according to the comparative example.

[0152] Therefore, in the case where no additional magnetization is performed, when the length of the horizontal surface portion 531 in the short direction is 0.2 mm to 3.0 mm, this is superior to the rubber magnet 103 according to the comparative example.

[0153] Next, as shown in Figure 13, when additional magnetization is performed, the magnetic property standard requires a magnetic flux density of 58±5 (mT). The magnetic angle variation is required to be 0±3°. The half-value width is required to be 45±5°.

[0154] As shown in FIG. 13, when the horizontal surface portion 531 of the top surface portion 53 has additional magnetization, the magnetic characteristics of the rubber magnet 50 of embodiment 1 are such that when the short-side length of the horizontal surface portion 531 is 0.5 mm to 5.0 mm, the magnetic flux density is 58 mT to 53 mT, which is superior to the rubber magnet 103 of the comparative example.

[0155] When the short-side length of horizontal surface portion 531 is 0.5 mm or more, the variation in magnetic angle is 3° or less, which is superior to rubber magnet 103 according to the comparative example.

[0156] When the length of the horizontal surface portion 531 in the short side direction is 0.5 mm to 5.0 mm, the half-width is 42° to 45°, which is superior to the rubber magnet 103 according to the comparative example.

[0157] Therefore, in the case where additional magnetization is performed, when the length of the horizontal surface portion 531 in the short direction is 0.5 mm to 5.0 mm, this is superior to the rubber magnet 103 according to the comparative example.

[0158] Therefore, by additionally magnetizing the horizontal surface portion 531 of the top surface portion 53, the width in the short side direction of the horizontal surface portion 531 of the top surface portion 53 is preferably 0.5 mm to 5 mm.

[0159] According to the first embodiment, it is possible to obtain a rubber magnet 50 that satisfies magnetic property standards.

[0160] The rubber magnet 50 according to the first embodiment is made of magnetic powder, and the magnetic powder is ferrite.

[0161] According to the first embodiment, the magnetic force of the rubber magnet 50 can be strengthened.

[0162] The magnetic powder forming the rubber magnet 50 may further include rare earth magnetic powder.

[0163] According to the first embodiment, the magnetic force of the rubber magnet 50 can be further strengthened.

[0164] The developing magnet roller 41 has a shaft 56 formed in a cylindrical shape, and a plurality of rubber magnets 50 are arranged such that the bottom surface 54 of the rubber magnets 50 contacts the circumferential surface of the shaft 56 .

[0165] According to the first embodiment, the orientation of the magnetic lines of force of the developing magnet roller 41 can be improved, and the developing magnet roller 41 can be easily manufactured.

[0166] The horizontal surface portion 531 of the top surface portion 53 is formed perpendicular to normal lines extending from the circumferential surface of the shaft 56 to both side surface portions 52 at the same distance.

[0167] According to the first embodiment, the variation in the magnetic angle of the magnetic field lines of the rubber magnet 50 can be suppressed.

[0168] Next, the developing magnet roller 41 according to the first embodiment will be described with reference to Fig. 14. Figs. 14(a) to (e) are diagrams showing the developing magnet roller 41 according to the first embodiment.

[0169] The developing magnet roller 41 according to the first embodiment is formed by attaching a plurality of rubber magnets 50 shown in FIG. 14(a) to the circumferential surface of a shaft 56 shown in FIG. 14(b) to form a so-called mag shaft.

[0170] Next, as shown by the arrow in FIG. 14(c), the mag shaft is covered with a tube-shaped sleeve pipe 57 made of aluminum.

[0171] For example, a groove may be formed on the outer surface of the sleeve tube 57 .

[0172] For example, the outer surface of the sleeve pipe 57 may be subjected to a blasting treatment.

[0173] The blasting process is a surface treatment in which an abrasive material is sprayed at high speed against the outer surface of the sleeve tube 57 to polish or harden the outer surface of the sleeve tube 57. Examples of the abrasive material include steel balls, sand, or glass beads.

[0174] Next, as shown by the arrows in FIG. 14(d), the mag shaft is fixed from both axial sides of the shaft 56 by flanges 58 made of aluminum.

[0175] Through these steps, the developing magnet roller 41 shown in FIG. 14(e) is assembled.

[0176] (Embodiment 2) Next, a rubber magnet 50 according to the second embodiment will be described with reference to Fig. 15. Fig. 15 is a diagram showing the rubber magnet 50 according to the second embodiment.

[0177] The configuration of the rubber magnet 50 according to the second embodiment shown in Fig. 15 is a modified example of the rubber magnet 50 according to the first embodiment described in Figs. 8(a) to (c). For the configuration of the rubber magnet 50 according to the second embodiment shown in Fig. 15, refer to the configurations in Figs. 8(a) to (c).

[0178] In addition, the details described in the description of embodiment 2 and the drawings related to embodiment 2 may be applied to all other embodiments and the details described in the drawings related to all other embodiments, as necessary.

[0179] The matters described in the description of the second embodiment and the drawings related to the second embodiment may be referenced to all other embodiments and the matters described in the drawings related to all other embodiments.

[0180] 15, first joint portion 510G is a joint between first connection portion 510A and first connection portion 510B. First joint portion 510G has a curve or a curved surface and has an R shape, but may be chamfered.

[0181] First joint portion 510H is a joint between first connection portion 510A and first connection portion 510C. First joint portion 510H has a curved line or a curved surface, and has an R shape.

[0182] First joint portion 510I is a joint between first connection portion 510B and first connection portion 510D. First joint portion 510I has a curved line or a curved surface and has an R shape.

[0183] First joint portion 510J is a joint between first connection portion 510C and first connection portion 510E. First joint portion 510J has a curved line or a curved surface and has an R shape.

[0184] The second joint portion 511G is a joint between the second connection portion 511A and the second connection portion 511B. The second joint portion 511G has a curved line or a curved surface and has an R-shape.

[0185] The second joint portion 511H is a joint between the second connection portion 511A and the second connection portion 511C. The second joint portion 511H has a curved line or a curved surface and has an R-shape.

[0186] The second joint portion 511I is a joint between the second connection portion 511B and the second connection portion 511D. The second joint portion 511I has a curved line or a curved surface and has an R shape.

[0187] The second joint portion 511J is a joint between the second connection portion 511C and the second connection portion 511E. The second joint portion 511J has a curved line or a curved surface and has an R-shape.

[0188] The mark portion 520A is formed on the left side surface portion 520 of the side surface portion 52. An example of the mark portion 520A is a notch or an unevenness. As an example, the mark portion 520A is used for the ID, serial number, etc. of the rubber magnet 50.

[0189] Mark portion 520B is formed on right side surface portion 521 of side surface portion 52. An example of mark portion 520B is a notch or an unevenness. Mark portion 520B is used, for example, for the ID, serial number, etc. of rubber magnet 50.

[0190] (Embodiment 3) Next, a rubber magnet 50 according to a third embodiment will be described with reference to FIGS. 16 to 27 in addition to FIGS. 1 to 15.

[0191] In addition, the matters described in the description of embodiment 3 and the drawings related to embodiment 3 may be applied to all other embodiments and the matters described in the drawings related to all other embodiments, as necessary.

[0192] The matters described in the description of embodiment 3 and the drawings related to embodiment 3 may be referenced to all other embodiments and the matters described in the drawings related to all other embodiments.

[0193] Figures 16(a) to (c) are diagrams showing a magnet shaft 100 according to a comparative example. Figures 17(a) and (b) are diagrams showing a rubber magnet 50 according to embodiment 3. Figures 18(a) and (b) are diagrams showing a general rubber magnet 102.

[0194] Fig. 19 is a diagram showing a rubber magnet 50 according to embodiment 3. Fig. 20 is a diagram showing a rubber magnet 50 according to embodiment 3. Figs. 21(a) and (b) are diagrams showing a rubber magnet 50 according to embodiment 3. Fig. 22 is a diagram showing a rubber magnet 50 according to embodiment 3. Fig. 23 is a diagram showing a rubber magnet 50 according to embodiment 3.

[0195] Figures 24(a) to (c) are diagrams comparing rubber magnets 50 according to embodiment 3. Figures 25(a) to (c) are diagrams comparing rubber magnets 50 according to embodiment 3. Figure 26 is a diagram showing changes in magnetic properties. Figure 27 is a diagram showing changes in magnetic properties.

[0196] The rubber magnet 50 of the developing magnet roller 41 has three magnetic characteristics, namely, magnetic flux density, half-width, and magnetic angle, and it is desirable to freely control the magnetic characteristics.

[0197] The half width contributes to image quality.

[0198] That is, if the width of rubber magnet 102(a) is increased, as in the case of rubber magnet 102(a) shown in FIG. 16(a), the half-value width increases, the magnetic flux density decreases, and the practicality decreases.

[0199] If the width is narrowed as in the case of rubber magnet 102(b) shown in FIG. 16(b), the half-value width becomes smaller, but the magnetic flux density also becomes smaller, reducing its practicality.

[0200] If the width is narrowed and the height is increased as in rubber magnet 102(c) shown in FIG. 16(c), the half-value width becomes smaller and the magnetic flux density increases, but the rubber magnet 102(c) may collide with sleeve 104, causing a breakdown.

[0201] Therefore, in the third embodiment, a new configuration is proposed for the shape of the top surface portion 53 of the rubber magnet 50.

[0202] First, the rubber magnet 102 will be described with reference to Figures 18(a) and (b). As shown in Figures 18(a) and (b), the top surface 102c is part of an arc of an outer circle 105 having a radius R4 from the center 107. The bottom surface 102a is part of an arc of an inner circle 106 having a radius R5 from the center 107.

[0203] The rubber magnet 102 shown in Figures 18(a) and (b) is in the shape of an annular sector surrounded by a bottom surface 102a, a top surface 102c, and a side surface 102b extending from the inner circle 106 to the outer circle 105 in a straight line extending from the center 107 of the inner circle 106 toward the inner circle 106 and the outer circle 105.

[0204] 17(a) and (b), a rubber magnet 50 according to embodiment 3 will be described. The rubber magnet 50 according to embodiment 3 is characterized in that the top surface 53 is composed of a reference arc portion 533 and a first deformed arc portion 534.

[0205] For the rubber magnet 50 according to embodiment 3, reference is made to Figures 8(a) to 8(c) for configurations common to the rubber magnet 50 according to embodiment 1. The rubber magnet 50 according to embodiment 3 includes an end surface portion 51 (Figure 8(a)), a side surface portion 52 (Figure 8(a)), a top surface portion 53 (Figure 17(a)), and a bottom surface portion 54 (Figure 17(a)). The end surface portion 51, the side surface portion 52, the top surface portion 53, and the bottom surface portion 54 may be connected perpendicularly to one another.

[0206] 8(a), the end surface portion 51 has a first end surface portion 510 and a second end surface portion 511. The first end surface portion 510 and the second end surface portion 511 are flat surfaces extending in the short-side direction of the rubber magnet 50 according to embodiment 3. The first end surface portion 510 may be parallel to the second end surface portion 511.

[0207] The first end surface portion 510 is formed in an annular sector shape.

[0208] As shown in FIG. 8(a), the second end surface portion 511 is formed in an annular sector shape, and is connected to the first end surface portion 510 by a top surface portion 53, a side surface portion 52, and a bottom surface portion .

[0209] As shown in FIG. 8(a), the second end surface portion 511 is formed in an annular sector shape, and is connected to the first end surface portion 510 by a top surface portion 53, a side surface portion 52, and a bottom surface portion .

[0210] 8(a), the side surface portion 52 has a left side surface portion 520 and a right side surface portion 521. The left side surface portion 520 and the right side surface portion 521 are flat surfaces extending in the longitudinal direction of the rubber magnet 50 according to the third embodiment.

[0211] 17(a), the top surface portion 53 has a reference arc portion 533 and a first deformed arc portion 534. The top surface portion 53 is a curved surface that expands in the longitudinal direction of the rubber magnet 50, as described with reference to FIG.

[0212] The reference arc portion 533 has a magnetic center. The first deformed arc portion 534 has no magnetic center.

[0213] As shown in Fig. 8(a), the left side surface portion 520 of the side surface portion 52 connects the first end surface portion 510 and the second end surface portion 511, and further, as shown in Fig. 8(b), the left side surface portion 520 of the side surface portion 52 connects the top surface portion 53 and the bottom surface portion 54. The bottom surface portion 54 is a curved surface that expands in the longitudinal direction of the rubber magnet 50 according to the third embodiment.

[0214] As shown in FIG. 8(a), the right side surface portion 521 of the side surface portion 52 connects the first end surface portion 510 and the second end surface portion 511 of the end surface portion 51, and further connects the top surface portion 53 and the bottom surface portion .

[0215] As shown in FIG. 17(b), the top surface portion 53 is composed of a combination of multiple outer circles 80 each having a reference center point 536 and a first deformed center point 535 that are different from one another, and a portion of an arc (reference arc portion 533 and first deformed arc portion 534) between the outer circle 81.

[0216] 17(b), the reference arc portion 533 is part of the arc of the outer circle 80 having a reference center point 536 as its center. The first deformed arc portion 534 is part of the arc of the outer circle 81 having a first deformed center point 535 as its center. By forming the top surface portion 53 by combining the reference arc portion 533 and the first deformed arc portion 534, the rubber magnet 50 shown in FIG. 17(a) can reduce the half-width while maintaining the magnetic flux density.

[0217] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density.

[0218] In other words, according to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while minimizing the decrease in magnetic flux density.

[0219] 17(a), the top surface portion 53 has a reference arc portion 533 and a first deformed arc portion 534. The top surface portion 53 is formed by a combination of the reference arc portion 533 and the first deformed arc portion 534. The reference arc portion 533 and the first deformed arc portion 534 are end portions that connect the top surface portion 53 and the first end surface portion 510 of the end surface portion 51.

[0220] 17(b), the reference arc portion 533 is a part of the arc of the outer circle 80 whose center is a reference center point 536. The first deformed arc portion 534 is a part of the arc of the outer circle 81 whose center is a first deformed center point 535 different from the reference center point 536.

[0221] That is, as shown in Fig. 17(b), a first deformed center point 535 of the outer circle 81 is offset from a reference center point 536 of the outer circle 80. As shown in Fig. 17(a), the top surface portion 53 can be formed by a reference arc portion 533 and a first deformed arc portion 534 which is an arc different from the reference arc portion 533. Therefore, the rubber magnet 50 can reduce the half-width while maintaining the magnetic flux density.

[0222] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density. Also, according to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while suppressing the decrease in magnetic flux density.

[0223] The first modified arc portion 534 is disposed on the side where the reference center point 536 is disposed relative to the arc of the outer circle 80 that includes the reference arc portion 533 .

[0224] The first deformed arc portion 534 can also be described as being disposed inside the arc of the outer circle 80 including the reference arc portion 533. In other words, the sharpness of the top surface portion 53 is increased when the top surface portion 53 is formed by a combination of the arc of the reference arc portion 533 and the arc of the first deformed arc portion 534, compared to when the top surface portion 53 is formed only by the arc of the reference arc portion 533. Therefore, the half-width can be reduced while suppressing the decrease in magnetic flux density as much as possible.

[0225] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density.

[0226] As shown in FIG. 17(b), a radius R2 of an outer circle 80 whose center is the reference center point 536 and a radius R1 of an outer circle 81 whose center is the first deformation center point 535 may be the same.

[0227] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density.

[0228] As shown in FIG. 17(b), a radius R1 of an outer circle 81 having a center at the first deformation center point 535 may be smaller than a radius R2 of an outer circle 80 having a center at the reference center point 536.

[0229] With this configuration, the sharpness of the top surface portion 53 is further increased, and therefore the half-value width can be further reduced while maintaining the magnetic flux density.

[0230] According to this embodiment, it is possible to further reduce the half-value width while maintaining the magnetic flux density, and to obtain a rubber magnet 50 with improved magnetic properties.

[0231] The arc of the bottom surface portion 54 is part of the arc of the inner circle 82 , and the center of the inner circle 82 may coincide with the reference center point 536 .

[0232] According to this embodiment, the top surface portion 53 and the bottom surface portion 54 of the rubber magnet 50 can be formed into an annular sector shape including a part of an arc of a concentric circle.

[0233] The arc portion where the magnetic center of the top surface portion 53 exists may be the reference arc portion 533 .

[0234] One of the arcuate portions of the top surface portion 53 where no magnetic center exists is a first deformed arcuate portion 534 .

[0235] According to this embodiment, the first deformed arc portion 534 of the top surface portion 53 is disposed inside the arc of the outer circle 80 including the reference arc portion 533. Therefore, the sharpness of the top surface portion 53 is increased, and the half-width can be further reduced while maintaining the magnetic flux density.

[0236] The arc of the bottom surface portion 54 is part of the arc of the inner circle 82 , and the reference center point 536 and the first deformation center point 535 may both be located inside the inner circle 82 .

[0237] According to this embodiment, the sharpness of the top surface portion 53 can be adjusted to a suitable degree.

[0238] As shown in FIG. 19, the radial deviation between the reference arc portion 533 and the first modified arc portion 534 may be 0.5 mm or less.

[0239] That is, as shown in FIG. 19, the maximum deviation between the first modified arc portion 534 and an outer circle 80 having the reference center point 536 as its center may be 0.5 mm or less.

[0240] In other words, the distance between the first joint 510I (FIG. 15) of the left side portion 520 of the rubber magnet 50 shown in FIG. 19 and the point where a straight line extending from the left side portion 520 toward the outer circle 80 intersects with the outer circle 80 may be 0.5 mm or less.

[0241] According to this embodiment, the sharpness of the top surface portion 53 can be adjusted to a suitable degree.

[0242] The difference between the diameter ΦY of the outer circle 81 including the first deformed arc portion 534 and the diameter ΦX of the outer circle 80 including the reference arc portion 533 may be within −2%.

[0243] Furthermore, the radius R1 of the outer circle 81 including the first deformed arc portion 534 relative to the radius R2 of the outer circle 80 including the reference arc portion 533 may be within −2%.

[0244] According to this embodiment, the sharpness of the top surface portion 53 can be adjusted to a suitable degree.

[0245] Next, the rubber magnet 50 according to embodiment 3 will be described with reference to Fig. 21(a) to Fig. 23. The rubber magnet 50 according to embodiment 3 shown in Fig. 21(a) to Fig. 23 is characterized in that the top surface 53 is composed of a reference arc portion 533, a first deformed arc portion 534, and a second deformed arc portion 538.

[0246] 21(a), the top surface portion 53 has a reference arc portion 533, a first deformed arc portion 534, and further a second deformed arc portion 538. The top surface portion 53 is made up of a combination of the reference arc portion 533, the first deformed arc portion 534, and the second deformed arc portion 538. The reference arc portion 533, the first deformed arc portion 534, and the second deformed arc portion 538 are end portions that connect the top surface portion 53 and the first end surface portion 510 of the end surface portion 51.

[0247] 21(b), the reference arc portion 533 is part of an outer circle 80 whose center is a reference center point 536. The first modified arc portion 534 is part of an outer circle 81 whose center is a first modified center point 535 that is different from the reference center point 536. The second modified arc portion 538 is part of an outer circle 83 whose center is a second modified center point 539 that is different from both the reference center point 536 and the first modified center point 535.

[0248] 21(b), a first deformation center point 535 of the outer circle 81 is shifted from a reference center point 536 of the outer circle 80. A second deformation center point 539 of the outer circle 83 is shifted from both the reference center point 536 of the outer circle 80 and the first deformation center point 535 of the outer circle 81.

[0249] As a result, as shown in Figure 21 (a), the top surface portion 53 can be formed by a reference arc portion 533, a first deformed arc portion 534 which is an arc different from the reference arc portion 533, and a second deformed arc portion 538 which is an arc different from both the reference arc portion 533 and the first deformed arc portion 534.

[0250] Therefore, the rubber magnet 50 can reduce the half-value width while maintaining the magnetic flux density.

[0251] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density.

[0252] The second modified arc portion 538 is disposed on the side where the reference center point 536 is disposed relative to the arc of the outer circle 80 that includes the reference arc portion 533 .

[0253] The second deformed arc portion 538 can also be described as being disposed inside the arc of the outer circle 80 including the reference arc portion 533. In other words, the sharpness of the top surface portion 53 is further increased when the top surface portion 53 is formed by the reference arc portion 533, the first deformed arc portion 534, and the second deformed arc portion 538, compared to when the top surface portion 53 is formed only by the reference arc portion 533. Therefore, the half-width can be reduced while suppressing the decrease in magnetic flux density as much as possible.

[0254] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density.

[0255] As shown in FIG. 21(b), the radius R2 of the outer circle 80 whose center is the reference center point 536 and the radius R6 of the outer circle 83 whose center is the second deformation center point 539 may be the same.

[0256] According to this embodiment, it is possible to obtain a rubber magnet 50 with improved magnetic properties by reducing the half-value width while maintaining the magnetic flux density.

[0257] As shown in FIG. 21(b), a radius R6 of an outer circle 83 having a center at the second deformation center point 539 may be smaller than a radius R2 of an outer circle 80 having a center at the reference center point 536.

[0258] With this configuration, the sharpness of the top surface portion 53 is further increased, and therefore the half-value width can be further reduced while maintaining the magnetic flux density.

[0259] According to this embodiment, it is possible to further reduce the half-value width while maintaining the magnetic flux density, and to obtain a rubber magnet 50 with improved magnetic properties.

[0260] The arc portion where the magnetic center of the top surface portion 53 exists may be the reference arc portion 533 .

[0261] Of the arcuate portions of the top surface portion 53 where the magnetic center is not present, the portion opposite the first deformed arcuate portion 534 with respect to the reference arcuate portion 533 is a second deformed arcuate portion 538 .

[0262] According to this embodiment, the second deformed arc portion 538 of the top surface portion 53 is disposed inside the arc of the outer circle 80 including the reference arc portion 533. Therefore, the sharpness of the top surface portion 53 is increased, and the half-width can be further reduced while maintaining the magnetic flux density.

[0263] As shown in FIG. 21( b ), the arc of the bottom surface portion 54 is part of the arc of the inner circle 82 , and the reference center point 536 and the second deformation center point 539 may both be located inside the inner circle 82 .

[0264] According to this embodiment, the sharpness of the top surface portion 53 can be adjusted to a suitable degree.

[0265] As shown in FIG. 22, the radial deviation between the reference arc portion 533 and the second modified arc portion 538 may be 0.5 mm or less.

[0266] That is, as shown in FIG. 22, the maximum deviation between the first modified arc portion 534 and an outer circle 80 having the reference center point 536 as its center may be 0.5 mm or less.

[0267] In other words, the distance between the first joint 510I (FIG. 15) of the left side portion 520 of the rubber magnet 50 shown in FIG. 22 and the point where a straight line extending from the left side portion 520 toward the outer circle 80 intersects with the outer circle 80 may be 0.5 mm or less.

[0268] In addition, the distance between the first joint 510J (FIG. 15) of the right side surface portion 521 of the rubber magnet 50 shown in FIG. 22 and the point where a straight line extending from the right side surface portion 521 toward the outer circle 80 intersects with the outer circle 80 may be 0.5 mm or less.

[0269] According to this embodiment, the sharpness of the top surface portion 53 can be adjusted to a suitable degree.

[0270] As shown in FIG. 23, the diameter ΦZ of the outer circle 83 including the second deformed arc portion 538 relative to the diameter ΦX of the outer circle 80 including the reference arc portion 533 may be within −2%.

[0271] Furthermore, as shown in FIG. 21(b), the radius R6 of the outer circle 83 including the second deformed arc portion 538 relative to the radius R2 of the outer circle 80 including the reference arc portion 533 may be within −2%.

[0272] According to this embodiment, the sharpness of the top surface portion 53 can be adjusted to a suitable degree.

[0273] Next, with reference to Figs. 24(a) to (c) and Fig. 26, an experimental example in which the magnetic properties of the rubber magnet 50 according to embodiment 3 were measured will be described.

[0274] Fig. 24(c) shows the rubber magnet 102 described in Fig. 18(a) and (b). Fig. 24(b) shows an example of the rubber magnet 50 according to embodiment 3, in which the top surface portion 53 is cut out at the reference arc portion 533 and a straight line 537 (plane 537). Fig. 24(a) shows an example of the rubber magnet 50 according to embodiment 3 described with reference to Figs. 17(a) and (b), 19, and 20.

[0275] FIG. 24(a) shows a rubber magnet 50 according to a third embodiment, in which the top surface portion 53 is formed from a reference arc portion 533 and a first deformed arc portion 534. As shown in FIG.

[0276] The rubber magnet 50 according to embodiment 3 shown in Figures 24(a) and (b) has an open angle of 90°. The rubber magnet 102 shown in Figure 21(c) has an open angle of 90°.

[0277] The distance from the bottom surface 54 to the top surface 53 (FIG. 19) of the rubber magnet 50 according to embodiment 3 shown in Figures 24(a) and (b) is 5.7 mm. The distance from the bottom surface 102a to the top surface 102c of the rubber magnet 102 shown in Figure 24(c) is 5.7 mm.

[0278] FIG. 26 is a diagram comparing the magnetic properties of the rubber magnets 50 according to the embodiment 3 shown in FIGS. 24(a) to (c).

[0279] In Fig. 26, the inner ring misalignment (mm) is sampled from 0 (mm) to 0.7 (mm). The inner ring misalignment indicates the amount of deviation between reference center point 536 and first deformed center point 535 shown in Fig. 24(a). The inner ring misalignment may be the amount of deviation in the radial direction between first deformed arc portion 534 described with reference to Fig. 19 and the arc of outer circle 80.

[0280] The first column from the left in Fig. 26 shows the magnetic force (mT) and half-width (°) versus the inner ring misalignment amount of the rubber magnet 50 according to embodiment 3 shown in Fig. 24(a). The second column from the left shows the magnetic force (mT) and half-width (°) versus the inner ring misalignment amount of the rubber magnet 50 shown in Fig. 24(b).

[0281] As shown in the second column from the left in Fig. 26, the rubber magnet 50 in which the top surface portion 53 shown in Fig. 24(b) is cut out by the reference arc portion 533 and a straight line 537 (plane 537) shares the reference center point 536 with the reference arc portion 533. Therefore, the amount of inner wheel deviation is 0 (mm).

[0282] Starting from a state in which the amount of inner wheel deviation is 0 (mm), as in Figure 24(a), when the center point is shifted from the reference center point 536 to the first deformation center point 535 and the amount of inner wheel deviation is increased, the inclination of the straight line 537 (plane 537) with respect to the reference arc portion 533 becomes larger.

[0283] When the inner ring misalignment amount is changed from 0 mm to 0.5 mm, the magnetic force changes from 54 mT to 49 mT. The half-value width changes from 49° to 42°.

[0284] Next, as shown in the first column from the left in Fig. 26, the rubber magnet 50 in which the top surface portion 53 shown in Fig. 24(a) is formed by a reference arc portion 533 and a first deformed arc portion 534 has a reference center point 536 and a first deformed center point 535. Therefore, there is no experimental value when the inner ring misalignment amount is 0 (mm).

[0285] As shown in FIG. 24(a), when the first deformation center point 535 is gradually shifted from the reference center point 536, the top surface portion 53 becomes sharper.

[0286] When the inner ring misalignment is changed from 0.1 mm to 0.5 mm, the magnetic force changes from 55 mT to 51 mT. The half-value width changes from 49° to 43°.

[0287] That is, it can be seen that the rubber magnet 50 shown in FIG. 24(a) can reduce the half-width while suppressing the decrease in magnetic force more than the rubber magnet 50 shown in FIG. 24(b).

[0288] Next, with reference to Figs. 25(a) to (c) and Fig. 27, an experimental example in which the magnetic properties of the rubber magnet 50 according to the third embodiment were measured and compared will be described.

[0289] Fig. 25(c) shows the rubber magnet 102 described in Fig. 18(a) and (b). Fig. 25(b) shows an example of the rubber magnet 50 according to embodiment 3, in which the top surface portion 53 is cut out by straight lines 537 (planes 537) in addition to the reference arc portion 533, on both sides of the reference arc portion 533. Fig. 25(a) shows an example of the rubber magnet 50 according to embodiment 3 described with reference to Figs. 21(a) to 23.

[0290] FIG. 25(a) shows a rubber magnet 50 according to embodiment 3, in which the top surface portion 53 is formed from a reference arc portion 533, a first deformed arc portion 534, and a second deformed arc portion 538. As shown in FIG.

[0291] The rubber magnet 50 according to the third embodiment shown in Figures 25(a) and (b) has an opening angle of 90°. The rubber magnet 102 shown in Figure 21(c) has an opening angle of 90°.

[0292] The distance from the bottom surface 54 to the top surface 53 (FIG. 19) of the rubber magnet 50 according to embodiment 3 shown in Figures 25(a) and (b) is 5.7 mm. The distance from the bottom surface 102a to the top surface 102c of the rubber magnet 102 shown in Figure 25(c) is 5.7 mm.

[0293] The configuration in FIG. 27 is the same as the configuration in FIG. 26, so a duplicated description will be omitted.

[0294] As shown in the second column from the left in Fig. 27, the rubber magnet 50 in which the top surface portion 53 shown in Fig. 25(b) is cut out at the reference arc portion 533 and two straight lines 537 (flat surfaces 537) shares the reference center point 536 with the reference arc portion 533. Therefore, the amount of inner wheel deviation is 0 (mm).

[0295] Starting from a state in which the amount of inner wheel deviation is 0 (mm), as in Figure 25 (a), by shifting the center point from the reference center point 536 to the first deformation center point 535 and the second deformation center point 539 and increasing the amount of inner wheel deviation, the inclinations of the two straight lines 537 (planes 537) relative to the reference arc portion 533 each become larger.

[0296] When the inner ring misalignment amount is changed from 0 mm to 0.5 mm, the magnetic force changes from 53 mT to 48 mT. The half-value width changes from 48° to 40°.

[0297] Next, as shown in the first column from the left in Fig. 27, the rubber magnet 50 in which the top surface portion 53 shown in Fig. 25(a) is formed by a reference arc portion 533, a first deformed arc portion 534, and a second deformed arc portion 538 has a reference center point 536, a first deformed center point 535, and a second deformed center point 539. Therefore, there are no experimental values ​​when the inner ring misalignment amount is 0 (mm).

[0298] As shown in FIG. 25(a), when the first deformation center point 535 and the second deformation center point 539 are gradually shifted from the reference center point 536, the top surface portion 53 becomes sharper.

[0299] As shown in the first column from the left in Fig. 27, when the inner ring misalignment amount is changed from 0.1 mm to 0.5 mm, the magnetic force changes from 54 mT to 50 mT. The half-value width changes from 48° to 40°.

[0300] That is, it can be seen that the rubber magnet 50 shown in FIG. 25(a) is able to maintain a higher magnetic force relative to the amount of reduction in the half-value width than the rubber magnet 50 shown in FIG. 25(b).

[0301] Furthermore, when comparing the portion surrounded by the dashed line in Figure 26 with the portion surrounded by the dashed line in Figure 27, it can be seen that the rubber magnet 50 of embodiment 3 shown in Figure 25(a), in which the top surface portion 53 is formed from the reference arc portion 533, the first deformed arc portion 534, and the second deformed arc portion 538, has a smaller half-width while maintaining the desired magnetic force than the rubber magnet 50 of embodiment 3 shown in Figure 24(a), in which the top surface portion 53 is formed from the reference arc portion 533 and the first deformed arc portion 534.

[0302] The embodiments of the invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the spirit of the present invention. The drawings are mainly schematic illustrations of the respective components for ease of understanding, and the number of each component shown in the drawings may differ from the actual number due to the convenience of drawing. Furthermore, the components shown in the above embodiments are merely examples, and are not particularly limited, and various modifications are possible without substantially departing from the effects of the present invention. [Industrial Applicability]

[0303] The present invention can be used in the fields of rubber magnets, developing magnet rollers, developing devices, and image forming apparatuses. [Explanation of symbols]

[0304] 3. Image forming device 11 Image forming section 32 Developing device 42 Developing magnet roller 50 Rubber Magnet 53 Top section 533 Reference arc part 534 First deformed arc section 535 Reference center point 536 First transformation center point 538 Second deformed arc section 54 Bottom part 55 Magnetic flux density center

Claims

1. A rubber magnet having end surfaces, side surfaces, a top surface, and a bottom surface, The end surface portion is A first end surface portion formed in an annular sector shape; a second end surface portion formed in the annular sector shape and connected to the first end surface portion by the top surface portion, the side surface portion, and the bottom surface portion; having The side surface portion has a left side surface portion and a right side surface portion, the left side surface portion connects the first end surface portion and the second end surface portion, and further connects the top surface portion and the bottom surface portion; the right side surface portion connects the first end surface portion and the second end surface portion, and further connects the top surface portion and the bottom surface portion; The top surface portion is a rubber magnet formed by a combination of arcs that are portions of multiple outer circles each having a different center point.

2. The top surface portion has a reference arc portion and a first deformed arc portion, the reference arc portion is a part of an arc of an outer circle having a reference center point as a center of the circle, The rubber magnet according to claim 1 , wherein the first deformation arc portion is a part of an arc of an outer circle having a center of a first deformation center point different from the reference center point.

3. The rubber magnet according to claim 2 , wherein the first deformed arc portion is disposed on a side where the reference center point is disposed, relative to an outer circle including the reference arc portion.

4. The rubber magnet according to claim 2 , wherein a radius of an outer circle having a center at the reference center point is the same as a radius of an outer circle having a center at the first deformation center point.

5. The rubber magnet according to claim 2 , wherein a radius of an outer circle having a center at the first deformation center point is smaller than a radius of an outer circle having a center at the reference center point.

6. The rubber magnet according to claim 2 , wherein the arc of the bottom surface portion is a part of an arc of an inner circle, and the center of the inner circle coincides with the reference center point.

7. the arc portion where the magnetic center of the top surface portion exists is the reference arc portion, 3. The rubber magnet according to claim 2, wherein one of the arcuate portions of the top surface portion in which the magnetic center is not present is the first deformed arcuate portion.

8. The rubber magnet according to claim 2 , wherein the arc of the bottom surface portion is a part of an arc of an inner circle, and the reference center point and the first deformation center point are both located inside the inner circle.

9. 3. The rubber magnet according to claim 2, wherein a radial deviation between the reference arc portion and the first deformed arc portion is 0.5 mm or less.

10. 3. The rubber magnet according to claim 2, wherein a diameter of an outer circle including the first deformed arc portion is within −2% of a diameter of an outer circle including the reference arc portion.

11. The top surface portion further has a second deformed arc portion, The rubber magnet according to claim 2 , wherein the second deformation arc portion is a part of an outer circle having a center at a second deformation center point different from the reference center point and the first deformation center point.

12. The rubber magnet according to claim 11 , wherein the second deformed arc portion is disposed on a side where the reference center point is disposed relative to an arc of an outer circle that includes the reference arc portion.

13. The rubber magnet according to claim 11, wherein a radius of an outer circle having a center at the reference center point is the same as a radius of an outer circle having a center at the second deformation center point.

14. The rubber magnet according to claim 11, wherein a radius of an outer circle having a center at the second deformation center point is smaller than a radius of an outer circle having a center at the reference center point.

15. the arc portion where the magnetic center of the top surface portion exists is the reference arc portion, The rubber magnet according to claim 11 , wherein, of the arc portions of the top surface portion where the magnetic center is not present, the second deformed arc portion is located on the opposite side of the first deformed arc portion with respect to the reference arc portion.

16. The rubber magnet according to claim 11 , wherein the arc of the bottom surface portion is a part of an arc of an inner circle, and the reference center point and the second deformation center point are both located inside the inner circle.

17. The rubber magnet according to claim 11 , wherein a radial deviation between the reference arc portion and the second deformed arc portion is 0.5 mm or less.

18. The rubber magnet according to claim 11, wherein the diameter of the outer circle including the second deformed arc portion is within −2% of the diameter of the outer circle including the reference arc portion.

19. 2. The rubber magnet according to claim 1, which is made of magnetic powder, the magnetic powder being ferrite.

20. The rubber magnet according to claim 19, wherein the magnetic powder further includes rare earth magnetic powder.

21. A cylindrical shaft; A developing magnet roller, comprising a plurality of rubber magnets according to claim 1 arranged so that the bottom surface of the rubber magnets contacts the circumferential surface of the shaft.

22. A developing device comprising the developing magnet roller according to claim 20.

23. A developing device comprising the developing magnet roller according to claim 21.

24. An image forming apparatus comprising the developing device according to claim 22.

25. An image forming apparatus comprising the developing device according to claim 23.

Images