Magnet roller, developing roller, and image forming apparatus

Abstract

To provide a magnet roller that can improve the productivity of a developing roller.SOLUTION: A magnet roller 1 comprises a shaft 30, a plurality of magnets 10, and an adhesive. The plurality of magnets 10 are arranged side by side in a circumferential direction D2 of a shaft core of the shaft 30 on an outer surface 30e of the shaft 30. The adhesive bonds the shaft 30 and the plurality of magnets 10 to each other. At least one magnet 11 has recesses 13 depressed relative to a surface 12 that faces the outer surface 30e of the shaft 30.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Conventionally, in a developing unit of an image forming apparatus, a developer is supplied onto a photosensitive drum to form a toner image on the photosensitive drum. Specifically, the developing unit uses a developing roller to supply the developer to the photosensitive drum. Patent Document 1 describes a magnetic roller used as the developing roller.

[0003] The magnetic roller of the developing roller described in Patent Document 1 has multiple magnetic poles. The developing roller further has a sleeve that rotatably covers the outer periphery of the magnetic roller. The multiple magnetic poles are formed by multiple different magnets. The magnetic roller is assembled by adhering these multiple magnets to a shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-20305 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, when multiple magnets are attached to a shaft, if a large amount of adhesive is applied to the magnets, the adhesive will harden while spilling out onto the sides of the magnets. This can cause the shaft to become loose from the other magnets. This can result in assembly defects in the developing roller, which can reduce productivity.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a technique that can improve the productivity of developing rollers. [Means for solving the problem]

[0007] According to one aspect of the present invention, a magnetic roller includes a shaft, magnets, and an adhesive. The magnets are arranged on the outer surface of the shaft in a circumferential direction of the shaft's axis. The adhesive bonds the shaft and the magnets to each other. At least one of the magnets has a recess that is recessed into a surface facing the outer surface of the shaft.

[0008] According to another aspect of the present invention, a developing roller includes the magnet roller and a cylindrical sleeve. The sleeve houses the magnet roller therein and is supported rotatably around the circumferential direction.

[0009] According to yet another aspect of the present invention, an image forming apparatus includes the above-described developing roller. [Effects of the Invention]

[0010] According to the present invention, a technique capable of improving the productivity of developing rollers can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the internal configuration of an image forming apparatus equipped with a magnet roller according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating the configuration of a developing unit equipped with the magnet roller. [Figure 3] FIG. 2 is a perspective view showing the configuration of the magnet roller. [Figure 4] FIG. 2 is a perspective view showing the configuration of the magnet of the magnet roller. [Figure 5A] 10A to 10C are diagrams showing the assembly procedure of the magnet roller. [Figure 5B] 10A to 10C are diagrams showing the assembly procedure of the magnet roller. [Figure 5C]10A to 10C are diagrams showing the assembly procedure of the magnet roller. [Figure 6] FIG. 10 is a plan view showing the configuration of a magnet roller according to a second embodiment of the present invention. [Figure 7A] FIG. 10 is a diagram showing a test method for confirming the adhesive strength between the magnet and the shaft. [Figure 7B] FIG. 2 is a diagram showing an example of measurement results of the magnetic properties of the magnet roller. [Figure 8A] FIG. 10 is a diagram showing an example of measurement results of adhesive strength and magnetic properties of the magnet. [Figure 8B] FIG. 10 is a diagram showing an example of measurement results of adhesive strength and magnetic properties of the magnet. DETAILED DESCRIPTION OF THE INVENTION

[0012] A magnet roller 1 according to an embodiment of the present invention will be described below with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated. Furthermore, in the following description, terms indicating positions or directions, such as "upper," "lower," "horizontal," and "vertical," may be used. These terms are used for convenience to facilitate understanding of the embodiment, and are not limited to positions or directions when actually implemented.

[0013] (First embodiment) An image forming apparatus 100 equipped with a magnet roller 1 according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a diagram showing the internal configuration of an image forming apparatus 100 equipped with a magnet roller 1 according to the first embodiment of the present invention.

[0014] As shown in Figure 1, the image forming apparatus 100 has a paper feeder 61 that supplies a sheet S, a transport path 62 along which the sheet S supplied from the paper feeder 61 is transported, a transport roller 63 that transports the sheet S in the transport path 62, an image forming unit 5 that is provided midway along the transport path 62 and forms a toner image on the sheet S, a fixing unit 64 that fixes the toner image formed on the sheet S, and an output tray 65 onto which the sheet S with the fixed image is discharged.

[0015] The image forming unit 5 has a photosensitive drum 8, an exposure unit (not shown), a developing unit 4, and a transfer roller 60. A toner image corresponding to image data is formed on the surface of the photosensitive drum 8 by the exposure unit and the developing unit 4. The image data is, for example, image data read by a document reading unit 67 or image data received by an external communication unit 68. The external communication unit 68 is controlled by a control unit 69.

[0016] The transfer roller 60 is pressed against the photosensitive drum 8, forming a transfer nip region N1 between itself and the photosensitive drum 8. A transfer voltage is applied to the surface of the transfer roller 60. When the toner image on the surface of the photosensitive drum 8 passes through the transfer nip region N1 together with the sheet S, the toner image is transferred to the sheet S by the electrostatic attraction of the transfer roller 60, and an image is formed on the sheet S. The sheet S with the image formed thereon is transported to a fixing unit 64.

[0017] The fixing unit 64 has a fixing roller 64b with a built-in heater and a pressure roller 64c. The pressure roller 64c is in pressure contact with the fixing roller 64b, forming a fixing nip area N2 between the pressure roller 64c and the fixing roller 64b. When the sheet S on which an image has been formed passes through the fixing nip area N2, the image is fixed to the sheet S by the pressure and heat applied by the rollers 64b and 64c. The sheet S on which the image has been fixed is transported to a discharge tray 65.

[0018] Next, the configuration of the developing unit 4 will be described with reference to Fig. 2. Fig. 2 is a diagram showing a schematic configuration of the developing unit 4 equipped with the magnet roller 1 according to the present invention.

[0019] In FIG. 2, the developing unit 4 has a developer storage section 6 that stores developer A, a developing roller 3 that adsorbs developer A from the developer storage section 6, and a regulating member 7 that scrapes off the amount of developer A adsorbed to the developing roller 3 to regulate it to a fixed amount.

[0020] The developing roller 3 supplies the attracted and regulated developer A to the photosensitive drum 8. The developing roller 3 has a magnet roller 1 with multiple magnetic poles and a sleeve 2 that rotatably covers the outer periphery of the magnet roller 1. The magnet roller 1 has a cylindrical shaft 30 and multiple magnets 10 arranged side by side in a circumferential direction D2 of the shaft 30 (an example of a circumferential direction of the shaft center).

[0021] The magnet 10 is provided facing the outer surface 30e of the shaft 30 and extending in the axial direction D1 of the shaft 30. The multiple magnets 10 have inner surfaces facing the outer surface 30e of the shaft 30, and the inner surfaces of the multiple magnets 10 and the outer surface 30e of the shaft 30 are bonded together with an adhesive (not shown).

[0022] In this embodiment, the magnet 10 includes a first magnet 11, a second magnet 21, a third magnet 31, a fourth magnet 41, and a fifth magnet 51. In this embodiment, the first magnet 11, the third magnet 31, and the fifth magnet 51 have their north poles facing radially outward, and the second magnet 21 and the fourth magnet 41 have their south poles facing radially outward.

[0023] Each magnetic pole included in the magnet roller 1 has its own role, and is required to make the magnetic force pattern on the surface of the sleeve 2 into a desired magnetic force waveform.

[0024] Specifically, each magnet, such as the first magnet 11, corresponds to one of a pumping pole, a transport pole, a regulating pole, a developing pole, and a peeling pole. The pumping pole, the transport pole, the regulating pole, the developing pole, and the peeling pole are arranged in the above-mentioned order along the direction of the arrow D4 (the rotation direction of the sleeve 2) shown in FIG.

[0025] Developer A is composed of toner and carrier (magnetic particles) that is magnetically attracted to magnet roller 1 while carrying the toner. Developer A is charged by a charging device (not shown), and is magnetically attracted to the scooping pole and adheres to sleeve 2. Developer A that has adhered to sleeve 2 is transported by the transport pole toward the regulating pole.

[0026] The transported developer A is scraped off by the regulating member 7, making the amount of developer A transported uniform. After passing through the regulating pole, the developer A is transported to the developing pole. At the developing pole, the toner in the developer A is magnetically attracted and adheres to the photosensitive drum 8, which rotates in the direction of arrow D5 shown in FIG. 2. An electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 8 by charging it with a charging device and exposing it to laser light, for example. The toner is attracted to the portion of the surface of the photosensitive drum 8 where the electrostatic latent image is formed. Therefore, a toner image corresponding to the image data is developed on the surface of the photosensitive drum 8.

[0027] The developer A remaining on the sleeve 2 is then transported to the peeling pole. The peeling pole is configured to weaken the magnetic field, and the developer A transported to the peeling pole is peeled off from the sleeve 2.

[0028] Next, the configuration of the magnet roller 1 will be further described with reference to Fig. 3. Fig. 3 is a perspective view showing the configuration of the magnet roller 1.

[0029] In FIG. 3, the shaft 30 has a notch 30n, which serves as a reference for positioning the shaft 30 in the circumferential direction D2, in a part of the outer surface 30e at the end in the axial direction D1.

[0030] In order to form a desired magnetic force pattern on the surface of the sleeve 2 (see FIG. 2) in the circumferential direction D2 of the shaft 30, each magnet must be accurately positioned in the circumferential direction D2 and adhered to the shaft 30. In this embodiment, each of the first magnet 11, second magnet 21, third magnet 31, fourth magnet 41, and fifth magnet 51 must be accurately positioned with reference to the cutout portion 30n of the shaft 30.

[0031] Specifically, first, the first magnet 11 is adhered to the shaft 30 at a desired position in the circumferential direction D2, using the cutout 30n as a reference. Then, the second magnet 21, the third magnet 31, the fourth magnet 41, and the fifth magnet 51 are adhered to the shaft 30 in sequence, using the position of the side surface 15 of the first magnet 11 as a reference (details will be described later). The first magnet 11, the second magnet 21, the third magnet 31, the fourth magnet 41, and the fifth magnet 51 are adhered while being arranged at desired positions in the circumferential direction D2, using the position of the cutout 30n as a reference. Therefore, a desired magnetic pole pattern is formed on the surface of the sleeve 2 that covers the magnet roller 1.

[0032] Next, the configuration of the first magnet 11 of the magnet roller 1 of the present invention will be described with reference to Fig. 4. Fig. 4 is a perspective view showing the configuration of the first magnet 11 of the magnets 10 of the magnet roller 1.

[0033] As shown in Fig. 4, the first magnet 11 has an inner surface 12 (an example of a surface), an outer surface 16, and two side surfaces 15. The inner surface 12 has an arc-shaped cross section facing the outer surface 30e of the shaft 30. The outer surface 16 is located outside the inner surface 12 and has a curved cross section. The two side surfaces 15 connect the inner surface 12 and the outer surface 16 in the radial direction D3 of the shaft 30.

[0034] Two grooves 13 (one example of a plurality of recesses) extending in the axial direction D1 are provided on the inner surface 12. The two grooves 13 are provided at positions spaced apart from each other in the circumferential direction D2 on the inner surface 12. The two grooves 13 divide the inner surface 12 into an inner inner surface 12i and an outer inner surface 12e in the circumferential direction D2.

[0035] Next, the assembly procedure and operation of the above-described magnet roller 1 will be described with reference to Figures 5A, 5B, and 5C. Figures 5A, 5B, and 5C are diagrams showing the assembly procedure for the magnet roller 1.

[0036] As explained above, when bonding the magnet 10 to the shaft 30, the first magnet 11 is bonded to the shaft 30 first. Then, the second magnet 21, the third magnet 31, the fourth magnet 41, and the fifth magnet 51 are bonded to the shaft 30 in this order.

[0037] 5A, when bonding the first magnet 11 to the shaft 30, adhesive G is applied to the inner surface 12i of the first magnet 11. Then, as shown by the imaginary line in the figure, the shaft 30 is pressed against the inner surface 12i of the first magnet 11. When the outer surface 30e of the cutout 30n is pressed against the inner surface 12i of the first magnet 11 when bonding the first magnet 11 to the shaft 30, the position of the first magnet 11 in the circumferential direction D2 relative to the shaft 30 is accurately determined.

[0038] The design value of the amount of adhesive G to be applied should be determined from the viewpoint of obtaining the recommended adhesive thickness so as to maximize the adhesive strength. The design value of the amount of adhesive G to be applied should preferably be set within a certain range depending on the requirements for production (such as reliability of work and cost).

[0039] The second magnet 21 and subsequent magnets are bonded sequentially using the side surface 15 of the first magnet 11 for which bonding has been completed as a reference surface for positioning. Therefore, it is preferable that the adhesive G be solidified and the bonding between the first magnet 11 and the shaft 30 be completed before the second magnet 21 is bonded.

[0040] FIG. 5B shows the state where the first magnet 11 and shaft 30 have been bonded together. As shown in the enlarged view of FIG. 5B, excess adhesive G from the applied adhesive G flows into the groove 13 and does not spill out of the groove 13. As a result, the adhesive G does not spill out onto the side surface 15 of the first magnet 11, as in the past. If the width and depth of the groove 13 are appropriately set, the magnet roller 1 can be configured so that the adhesive G does not spill out onto the side surface 15 of the magnet 10 within the range of the design value for the amount of adhesive G to be applied.

[0041] Furthermore, as shown in Figure 5C, when the second second magnet 21 is attached, the side surface 15 of the already positioned first magnet 11 serves as a reference for positioning the second magnet 21 in the circumferential direction D2. Therefore, the second magnet 21 is positioned with high precision and attached to the shaft 30. As a result, it is possible to prevent the occurrence of gaps and floating that are seen in conventional magnets. Because the second magnet 21 is positioned with high precision, the third magnet 31 and subsequent magnets can also be positioned with high precision and attached to the shaft 30.

[0042] As a result, the magnet roller 1 prevents a decrease in the adhesive strength between the magnet 10 and the shaft 30 because the adhesive area between the magnet 10 and the shaft 30 does not decrease, and prevents the magnet 10 from peeling off and becoming detached from the shaft 30 during assembly of the developing roller 3. In other words, the magnet roller 1 can improve the productivity of the developing roller 3.

[0043] As in the present embodiment, two grooves 13 are provided at positions spaced apart from each other in the circumferential direction D2 on the inner surface 12 of the first magnet 11, thereby forming an inner inner surface 12i on the magnet 10. By forming the inner inner surface 12i, the adhesive G is prevented from spilling out from both sides of the inner surface 12 in the circumferential direction D2, so that the adhesive G is reliably prevented from spilling out onto the side surface 15 of the first magnet 11.

[0044] Although the shaft 30 according to this embodiment is cylindrical, it may be polygonal, such as a square prism. In this case, it is preferable that the inner surface of the magnet 10, which faces the outer surface 30e of the shaft 30, is configured to have a shape corresponding to the shape of the outer surface 30e of the shaft 30.

[0045] Furthermore, the magnet roller 1 according to this embodiment is configured so that the grooves 13 are provided only in the first magnet 11 among the magnets 10, but the magnets on which the grooves 13 are provided are not limited to the first magnet 11. The magnet roller 1 may be configured so that the grooves 13 are provided in any of the magnets 10 among the second magnet 21, the second magnet 21, the third magnet 31, the fourth magnet 41, and the fifth magnet 51.

[0046] In addition, in the magnet roller 1 of this embodiment, the grooves 13 are formed on the inner surface 12 of the magnet 10, but the grooves 13 may also be formed on the outer surface 30e of the shaft 30, or may be formed on both the inner surface of the magnet 10 and the outer surface 30e of the shaft 30.

[0047] Even when the grooves 13 are formed on the outer surface of the shaft 30, as described above, excess adhesive G from the applied adhesive G flows into the grooves 13 and does not spill out of the grooves 13. Therefore, the magnetic roller 1 can achieve the same effects as those described above.

[0048] (Second embodiment) Next, the configuration of a magnet roller 1d according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a plan view showing the configuration of a magnet roller 1d according to the second embodiment of the present invention.

[0049] As shown in FIG. 6, the first magnet 11d of the magnet roller 1d is further defined in terms of the range of the groove width 13w and groove depth 13d compared to the first magnet 11 of the magnet roller 1 according to the first embodiment.

[0050] Specifically, the ratio of the sum of the widths of the multiple grooves 13 in the circumferential direction D2 to the width 12w of the inner surface 12 of the first magnet 11d in the circumferential direction D2 of the shaft 30 (hereinafter referred to as the "groove width ratio") is 12% or more and 25% or less.

[0051] Furthermore, the ratio of the depth of each of the plurality of grooves 13 to the height 15h (an example of a dimension) of the first magnet 11d in the radial direction D3 of the shaft 30 (hereinafter referred to as "groove depth ratio") is not less than 7% and not more than 14%.

[0052] The effects of the configuration of the magnet roller 1d described above will be explained below with reference to test results regarding the adhesive strength of the magnet roller 1d and the magnetic properties of the magnet roller 1d.

[0053] First, the respective test methods will be described with reference to Figures 7A and 7B. Figure 7A shows a test method for confirming the adhesive strength of the magnet roller 1d. Figure 7B shows an example of the measurement results of the magnetic properties of the magnet roller 1d.

[0054] The adhesive strength is measured based on, for example, "Testing Method for Tensile Adhesive Strength of Adhesives" (JIS K 6849-1994). Specifically, as shown in FIG. 7A, the adhesive strength test is performed by supporting the first magnet 11d adhered to the shaft 30 with a jig J and using a push-pull gauge P ("PS-10Kg" manufactured by Imada Manufacturing Co., Ltd.). The push-pull gauge P pulls the shaft 30 in a direction away from the first magnet 11d, and the maximum load required until the shaft 30 peels off from the first magnet 11d is measured as the "adhesive strength."

[0055] Although not shown, a probe using a Hall element is placed on a magnet 10d attached to a shaft 30, and the shaft 30 is rotated to detect the magnetic characteristics of the attached magnet 10d. The relationship between the rotation angle of the shaft 30 and the magnetic flux density detected by the Hall element is then obtained, as shown in Figure 7B. Specifically, the measurement device used is an "Automatic Magnetic Field Distribution Measurement Device: 6800ROLL2" manufactured by Nippon Denji Sokki Co., Ltd. The probe is placed 10 mm from the center of the shaft 30 in the radial direction D3, and the rotation speed of the shaft 30 is approximately 6 seconds per rotation. Then, under the same conditions as above, measurements are also taken when the probe is placed at nine positions in the axial direction D1 of the magnet 10, dividing the length of the magnet 10 into ten equal parts.

[0056] In the measured waveform obtained as shown in Figure 7B, the maximum value of the magnetic flux density waveform shown is determined as the "maximum magnetic force." The rotation angle at the center of the two rotation angles θ3 and θ4, at which the magnetic flux density is 80% of the maximum magnetic force, is determined as the "magnetic central angle." In other words, these "maximum magnetic force" and "magnetic central angle" are confirmed as magnetic characteristics.

[0057] Next, referring again to FIG. 6, the first magnet 11d, shaft 30, and adhesive G used in the test will be described in detail. The first magnet 11d has a sector shape with an opening angle θ1 of 90° as shown in the cross section. The first magnet 11d has a height 15h of 5.7 mm, an axial length of 300 mm, an outer diameter of the arc forming the inner surface 12 of Φ6 mm, and an outer diameter of the arc forming the outer surface 16 of Φ17.4 mm. The grooves 13 are arranged at positions in the circumferential direction D2 of the first magnet 11d where the angle θ2 of the circumferential direction D2 with respect to the center line C is 25°. The groove depth 13d of the groove 13 is 0.3 mm, and the groove width 13w is 0.6 mm. The material of the first magnet 11d is primarily polychloroethylene, with 85% by mass of anisotropic ferrite as magnetic powder. The shaft 30 has an outer diameter of Φ6 mm and an axial length of 330 mm. The shaft 30 is made of SUM23 and is nickel-plated. Aron Alpha (registered trademark) 800 series, for example, is used as the adhesive G. The adhesive G is applied in an amount of, for example, 100 gm, and is applied to a position on the inner surface 12i of the shaft 30 along the center line C shown in the figure. The adhesive G dries for at least one hour at room temperature.

[0058] The test results under the above test conditions will be explained with reference to Figures 8A and 8B. Figure 8A shows an example of the measurement results of the adhesive strength and magnetic properties of the same magnet 10 when the above-mentioned "groove width ratio" is at various levels. Figure 8B shows an example of the measurement results of the adhesive strength and magnetic properties of the same magnet 10 when the above-mentioned "groove depth ratio" is at various levels.

[0059] 8A and 8B show measurement results of the magnetic characteristics (maximum magnetic force, magnetic central angle) of the first magnet 11d and the adhesive strength between the first magnet 11d and the shaft 30 when only the first magnet 11d is adhered to the shaft 30. Also shown are measurement results of the magnetic characteristics of the second magnet 21 (see FIG. 3) when, in addition to the first magnet 11d, the second magnet 21 is adhered to the shaft 30. Note that the reference rotation angle (0°) for the "magnetic central angle" in FIGS. 8A and 8B is the angle at which the first magnet 11d overlaps with the center line C (see FIG. 6) in the circumferential direction D2.

[0060] 8A, when the groove width ratio is 12% or more and 25% or less as described above, the magnetic properties and adhesive strength of the first magnet 11d and the magnetic properties of the second magnet 21 are stable and fall within a more preferable range. Therefore, if the groove width ratio of the magnet roller 1d is in the above-mentioned range of 12% or more and 25% or less, the product performance is stably ensured, and quality is improved.

[0061] 8B, when the groove depth ratio is between 7% and 14% as described above, the magnetic properties and adhesive strength of the first magnet 11d and the magnetic properties of the second magnet 21 are stable and fall within a more preferable range. Therefore, if the groove width ratio of the magnet roller 1d is within the above-mentioned range between 7% and 14%, the product performance is ensured stably, and quality is improved.

[0062] The groove 13 described in the first embodiment of the present invention is an example of a recess, and the shape of the recess is not limited to a groove shape. The recess may have a curved bottom, an R-shaped bottom, or a rounded bottom. Even if the recess is configured in this manner, excess adhesive G from the applied adhesive G flows into the recess, thereby achieving the same effects as those described above. Also, in the second embodiment, as long as the groove width 13w and groove depth 13d of the groove 13 are within the ranges described above, the edges and corners of the bottom of the groove 13 may be chamfered or may have a rounded shape.

[0063] In the first and second embodiments, the magnets 10, 10d may be formed from a mixture containing magnetic powder and resin, and the magnetic powder may contain ferrite. This allows the magnets 10, 10d to be formed with the grooves 13 of the present invention by injection molding or the like.

[0064] Furthermore, the multiple magnets 10, 10d may be molded from a mixture containing magnetic powder and resin, and the magnetic powder may be a mixture of ferrite and rare earth magnetic powder. Rare earth magnetic powder generally has stronger magnetic force and better temperature characteristics than ferrite magnetic powder. Therefore, by using a mixture of ferrite and rare earth magnetic powder for the magnetic powder, it is possible to further improve the compactness, lightness, and performance depending on the usage environment, and to increase the degree of freedom in design.

[0065] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit and scope of the present invention. The drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the materials, shapes, dimensions, etc. of each component shown in the above embodiments are merely examples and are not particularly limited, and various modifications are possible within a scope that does not substantially deviate from the configuration of the present invention. [Industrial Applicability]

[0066] The magnet roller, the developing roller, and the image forming apparatus according to the present invention have industrial applicability. [Explanation of symbols]

[0067] 1 magnetic roller 2 sleeves 3 Developing roller 4 Development section 5 Image forming unit 10 Magnets 11 First magnet (an example of a first magnet) 12 Inner 13 Groove 13w groove width 13d groove depth 15 Side 16 Exterior 21 Second Magnet 31 Third Magnet 41 4th Magnet 51 5th Magnet

Claims

1. A shaft, a plurality of magnets arranged on an outer surface of the shaft in a circumferential direction of an axis of the shaft; an adhesive that bonds the shaft and the plurality of magnets to each other; Equipped with At least one of the magnets has a recess recessed into a surface facing the outer surface of the shaft. Magnetic roller.

2. At least one of the magnets has a plurality of the recesses on the surface, The magnetic roller according to claim 1 , wherein the plurality of recesses are spaced apart from one another in the circumferential direction.

3. a ratio of a sum of widths of the plurality of recesses in the circumferential direction to a width of the surface in the circumferential direction is 12% or more and 25% or less; The magnetic roller according to claim 1 or 2.

4. a ratio of the depth of each of the plurality of recesses to the dimension of the magnet in the radial direction of the axis is 7% or more and 14% or less; The magnetic roller according to claim 1 or 2.

5. The plurality of magnets are molded from a mixture containing magnetic powder and resin, The magnetic powder includes ferrite. The magnetic roller according to claim 1 or 2.

6. The plurality of magnets are molded from a mixture containing magnetic powder and resin, The magnetic powder is a mixture of ferrite and rare earth magnetic powder. The magnetic roller according to claim 1 or 2.

7. The magnetic roller according to claim 1 or 2; a cylindrical sleeve that houses the magnet roller and is supported rotatably around the circumferential direction; A developing roller having

8. An image forming apparatus comprising the developing roller according to claim 7 .

Images