JP7115066B2 - Magnet rollers, developing rollers, developing devices and image forming devices - Google Patents

Description

The present disclosure relates to a magnet roller, a developing roller, a developing device, and an image forming device used for conveying toner.

2. Description of the Related Art In an image forming apparatus, a developing roller is used to supply developer to a photoreceptor. The developing roller includes a magnet roller having a plurality of magnetic poles and a cylindrical developing sleeve rotatably covering the magnet roller.

Each magnetic pole included in the magnet roller has a role, and is required to make the magnetic force pattern on the surface of the developing sleeve into a desired magnetic force waveform. Some magnet rollers have magnetic poles formed of different parts and these separate parts are attached around a shaft.

When manufacturing a magnet roller with a plurality of separate parts, a manufacturing process is required to attach each part to the shaft, which may increase the manufacturing cost and cause misalignment of the attachment positions of the parts.

Therefore, in order to simplify the manufacturing process and to suppress the relative positional deviation between the magnet portion and the shaft portion, a magnet roller in which the magnet portion and the shaft portion are integrally molded with a magnetic material has been developed.

An example of a document disclosing a magnet roller in which a magnet portion and a shaft portion are integrally formed in this manner is Japanese Patent Application Laid-Open No. 2016-153813 (Patent Document 1).

In the magnet roller disclosed in Patent Literature 1, two grooves extending in the axial direction of the magnet roller are provided side by side in the circumferential direction so as to determine the width of the magnetic pole with the largest magnetic force.

JP 2016-153813 A

When magnetizing a magnet roller in which a magnet portion and a shaft portion are integrally formed, the magnetic force of the magnetized magnetic poles may deviate from a desired value. In such a case, the width of the magnetic pole fluctuates, and the positions at which two adjacent magnetic poles are switched are shifted.

In the magnet roller disclosed in Patent Document 1, although the width of the main pole is determined by the two grooves, if the magnetic force of the main pole varies during magnetization, the width of the main pole may vary depending on the shape of the groove. It is possible that the switching position between adjacent magnetic poles fluctuates.

The present disclosure has been made in view of the problems described above, and an object of the present disclosure is to provide a magnet roller, a developing roller, a developing device, and An object of the present invention is to provide an image forming apparatus.

A magnet roller according to the present disclosure includes a magnet portion having a central axis and including a plurality of magnetic poles arranged around the central axis. The magnet portion has an outer peripheral surface surrounding the central axis, and is integrally formed of a magnetic composition containing magnetic particles and resin. Magnetic forces possessed by the magnetic poles adjacent to each other are different from each other. A plurality of sets of two adjacent magnetic poles are present by arranging the plurality of magnetic poles around the central axis, and at least one of the plurality of sets of two adjacent magnetic poles is formed on the outer peripheral surface of the magnet portion. A groove extending in a direction parallel to the axial direction of the central axis is provided between a pair of two adjacent magnetic poles. The groove portion has a first inclined surface and a second inclined surface facing each other and inclined so as to approach each other toward the central axis. The first inclined surface is located on the side of the magnetic pole having the smaller magnetic force among the two adjacent magnetic poles, and the second inclined surface is located on the side of the magnetic pole having the larger magnetic force among the two adjacent magnetic poles. Located in In a cross section of the magnet portion orthogonal to the central axis in the portion where the groove portion is provided, the angle formed by the first imaginary line passing through the lower end of the first inclined surface and the central axis and the first inclined surface The smaller angle is defined as the first groove angle, and the smaller angle formed by the second slant surface and a second imaginary line passing through the lower end of the second slant surface and the central axis is the second groove angle. In terms of angles, the first groove angle is smaller than the second groove angle.

In the magnet roller based on the present disclosure, the grooves may be formed between two or more pairs of adjacent magnetic poles among the plurality of pairs of adjacent magnetic poles.

In the magnet roller based on the present disclosure, the difference between the first groove angle and the second groove angle in the groove provided between the two adjacent magnetic poles having a large difference in magnetic force is The difference between the first groove angle and the second groove angle in the groove provided between two adjacent magnetic poles having a small difference in magnetic force may be larger.

In the magnet roller based on the present disclosure, the depth of the groove provided between the two adjacent magnetic poles with a large difference in magnetic force is the depth between the two adjacent magnetic poles with a small difference in magnetic force. It may be deeper than the depth of the provided groove.

Preferably, the magnet roller based on the present disclosure further includes shaft portions that protrude along the axial direction from both ends of the magnet portion in the axial direction of the central axis. In this case, the magnet portion and the shaft portion may be integrally molded from the magnetic composition.

In the magnet roller based on the present disclosure, it is preferable that the groove portion is provided from one end of the magnet portion to the other end of the magnet portion along a direction parallel to the axial direction.

A developing roller based on the present disclosure includes the magnet roller and a cylindrical developing sleeve that covers the outer peripheral surface of the magnet portion.

A developing device according to the present disclosure includes the developing roller and a developer regulating member that regulates the amount of developer carried on the developing roller.

An image forming apparatus according to the present disclosure includes the developing device and a transfer member for transferring the toner image developed by the developing device onto a recording medium.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a magnet roller, a developing roller, a developing device, and an image forming apparatus capable of suppressing displacement of switching positions of two adjacent magnetic poles.

1 is a schematic diagram of an image forming apparatus according to Embodiment 1; FIG. 1 is a schematic diagram of a developing device according to Embodiment 1; FIG. 4 is a diagram showing the magnetic force distribution of the developing roller according to Embodiment 1; FIG. 1 is a schematic perspective view of a magnet roller according to Embodiment 1; FIG. 1 is a schematic cross-sectional view of a magnet roller according to Embodiment 1; FIG. 5 is a diagram showing the magnetic force distribution of two adjacent magnetic poles when the magnetic force of the magnetic poles magnetized in the magnet roller according to Embodiment 1 varies. FIG. FIG. 8 is a schematic cross-sectional view of a magnet roller according to Embodiment 2; It is a figure which shows the conditions and result of the verification experiment performed in order to verify the effect of embodiment. 4A and 4B are schematic cross-sectional views of magnet rollers in Comparative Examples 1A and 1B; 4A and 4B are schematic cross-sectional views of magnet rollers in Comparative Examples 2A and 2B;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments shown below, the same or common parts are denoted by the same reference numerals in the drawings, and the description thereof will not be repeated.

(Embodiment 1)
[Image forming apparatus]
FIG. 1 is a schematic diagram of an image forming apparatus. An image forming apparatus 100 according to an embodiment will be described with reference to FIG.

FIG. 1 shows an image forming apparatus 100 as a color printer. Although the image forming apparatus 100 as a color printer will be described below, the image forming apparatus 100 is not limited to a color printer. For example, image forming apparatus 100 may be a monochrome printer, a FAX, or a multi-functional peripheral (MFP: Multi-Functional Peripheral) of monochrome printer, color printer, and FAX.

The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33 as a transfer member, a cleaning device 36, a cassette 37, A fixing device 40 and a control device 101 are provided.

The image forming unit 1Y receives supply of toner from the toner bottle 15Y and forms a yellow (Y) toner image. The image forming unit 1M receives supply of toner from the toner bottle 15M and forms a magenta (M) toner image. The image forming unit 1C receives supply of toner from the toner bottle 15C and forms a cyan (C) toner image. The image forming unit 1K receives supply of toner from the toner bottle 15K and forms a black (BK) toner image.

The image forming units 1Y, 1M, 1C, and 1K are arranged in order along the rotation direction of the intermediate transfer belt 30, respectively. The image forming units 1Y, 1M, 1C, and 1K each include a photoreceptor 10, a charging device 11, an exposure device 12, a cleaning device 17, and a developing device .

The photoreceptor 10 is an image carrier that carries a toner image. As an example, the photoreceptor 10 has a drum shape. A photosensitive layer is formed on the surface of the photoreceptor 10 . The charging device 11 uniformly charges the surface of the photoreceptor 10 . The exposure device 12 irradiates the photoreceptor 10 with a laser according to a control signal from the control device 101, and exposes the surface of the photoreceptor 10 according to a designated image pattern. Thereby, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 10 . The electrostatic latent image formed on the photoreceptor 10 is developed as a toner image by the developing device 50 . Details of the developing device 50 will be described later.

The photoreceptor 10 and the intermediate transfer belt 30 are in contact with each other at the portion where the primary transfer roller 31 is provided. The toner image developed on the photoreceptor 10 is transferred to the intermediate transfer belt 30 by the transfer bias applied to this contact portion. At this time, a yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred onto the intermediate transfer belt 30 . Thereby, a color toner image is formed on the intermediate transfer belt 30 .

The cleaning device 17 has a cleaning blade. The cleaning blade is pressed against the photoreceptor 10 and collects toner remaining on the surface of the photoreceptor 10 after the toner image is transferred.

Sheets S are set in the cassette 37 . Sheets S are fed one by one from cassette 37 to secondary transfer roller 33 . The secondary transfer roller 33 transfers the toner image transferred to the intermediate transfer belt 30 onto the sheet S. As shown in FIG. By synchronizing the timing of feeding and transporting the paper S with the position of the toner image on the intermediate transfer belt 30, the toner image is transferred to the appropriate position on the paper S. FIG. After that, the paper S is sent to the fixing device 40 .

The fixing device 40 presses and heats the paper S. As shown in FIG. As a result, the toner image is melted on the sheet S and fixed thereon. After that, the sheet S is discharged to the tray 48 .

The cleaning device 36 has a cleaning blade. The cleaning blade is pressed against the intermediate transfer belt 30 and collects toner remaining on the intermediate transfer belt 30 after the toner image is transferred. The collected toner is transported by a transport screw (not shown) and stored in a waste toner container (not shown).

Control device 101 controls, for example, a motor (not shown) for rotating developing roller 60 (see FIG. 2) in developing device 50, and controls the amount of developer supplied from developing device 50 to photoreceptor 10. to adjust.

Note that the structure of the image forming apparatus 100 is not limited to the example shown in FIG. For example, the image forming apparatus 100 may be composed of one photoreceptor 10 and a plurality of rotatable developing devices 50 . In this case, the image forming apparatus 100 rotates the developing devices 50 to sequentially guide the developing devices 50 to the photoreceptor 10 . As a result, a toner image of each color is developed on the photosensitive member 10 to form a color image.

[Developing device]
FIG. 2 is a schematic diagram of the developing device according to the embodiment. A developing device 50 according to the embodiment will be described with reference to FIG.

As shown in FIG. 2, the developing device 50 has a housing 51 . Inside the housing 51, a partition wall 51A, a first stirring member 54A, a second stirring member 55A, and a developing roller 60 are provided.

The partition wall 51A is provided along the axial direction of the developing roller 60 . The interior of the housing 51 is separated into a first transfer chamber 54 and a second transfer chamber 55 by a partition wall 51A. The developer D is stored inside the first transport chamber 54 and the second transport chamber 55 . The developer D is composed of toner and magnetic carrier.

A first stirring member 54A is provided inside the first transfer chamber 54 . The first stirring member 54A transports the developer D from the first transport chamber 54 to the second transport chamber 55 while stirring the developer D. As shown in FIG. A second stirring member 55A is provided inside the second transfer chamber 55 . The second stirring member 55A conveys the developer D to the developing roller 60 while stirring the developer D. As shown in FIG. By rotating the first stirring member 54A and the second stirring member 55A in mutually opposite directions, the developer D flows through the first transfer chamber 54 and the second transfer chamber 54 through circulation ports (not shown) provided at both ends of the partition wall 51A. It circulates with the transfer chamber 55 .

The developing roller 60 is provided so as to face the photoreceptor 10 with a required space therebetween. Developing roller 60 includes magnet roller 52 and developing sleeve 53 . Magnet roller 52 attracts developer D from first transport chamber 54 . A detailed shape of the magnet roller 52 will be described later with reference to FIGS. 4 and 5. FIG.

The developing sleeve 53 has a cylindrical shape and covers an outer peripheral surface 521a (see FIG. 4) of a magnet portion 521 (see FIG. 3) which will be described later. The developing sleeve 53 is rotatably provided around the magnet roller 52 . The sleeve diameter is, for example, 16 mm.

A plurality of grooves (not shown) are provided on the outer peripheral surface of the developing sleeve 53 . For example, 40 grooves are provided. The plurality of grooves are provided side by side in the circumferential direction. The groove depth is, for example, 75 μm. Note that the number and depth of the grooves can be changed as appropriate. It should be noted that blasting may be performed without forming grooves on the outer peripheral surface of the developing sleeve 53 .

The housing 51 of the developing device 50 is provided with a regulating member 56 for regulating (regulating) the transport amount of the developer D. As shown in FIG. One end of the restricting member 56 is fixed to the housing 51 . The regulating member 56 is plate-shaped, for example, and is arranged so that the plate surface is orthogonal to the rotation surface of the developing sleeve 53 . Note that the restricting member 56 is not limited to a plate shape, and may be a round bar shape. The regulating member 56 is provided along the axial direction of the developing roller 60 .

The regulating member 56 is provided so as to face the surface of the developing sleeve 53 of the developing roller 60 . More specifically, the regulating member 56 is provided at a distance Db from the developing sleeve 53 at a portion facing the regulating pole S1 of the magnet roller 52, which will be described later.

The restricting member 56 is preferably made of a magnetic material. As a result, a magnetic field is formed between the regulating member 56 and the developing roller 60 , and a magnetic attraction force acts on the surface of the regulating member 56 . As a result, the developer D can be easily scraped off, and the layer thickness of the developer D can be easily adjusted.

FIG. 3 is a diagram showing the magnetic force distribution of the developing roller according to the embodiment. The function of the developing roller 60 will be described with reference to FIG.

As shown in FIG. 3, the magnetic force distribution of the developing roller 60 has a plurality of peaks arranged in the circumferential direction. The magnetic force distribution of the developing roller 60 is formed by the magnetic force generated from the magnet portion 521 of the magnet roller 52, which will be described later. A plurality of peaks are formed by a plurality of magnetic poles of the magnet portion 521 .

The multiple magnetic poles include a pumping pole S2, a transport pole N2, a regulation pole S1, a development pole N1, and a separation pole S3. The drawing pole S2, the transport pole N2, the regulation pole S1, the development pole N1, and the separation pole S3 are arranged in order along the direction of the arrow DR1 shown in FIG. 3 (the circumferential direction of the magnet roller 52).

The developer D generates static electricity and is charged by being agitated. The charged developer D is attracted to the scooping pole S2 and adheres to the developing sleeve 53 . The developer D adhering to the developing sleeve 53 is transported toward the regulation pole S1 by the transport pole N2.

The conveyed developer D receives a magnetic force from the regulating pole S<b>1 and extends vertically toward the photoreceptor 10 on the surface of the developing sleeve 53 . As a result, the developer D is scraped off by the regulating member 56, and the transport amount of the developer D becomes uniform.

The developer D is conveyed to the development pole N1 after passing through the regulation pole S1. The developer D receives a magnetic force from the development pole N1 and becomes continuous in the direction of the magnetic force. That is, the developing pole N1 forms a magnetic brush by causing the developer carried on the developing sleeve 53 to stand.

The toner forming the developer D is negatively charged, and the carrier forming the developer D is positively charged. The electrostatic latent image formed on the photoreceptor 10 is negatively charged, but the potential is higher than the developing potential applied to the developing roller 60 . Therefore, the toner adheres to the photoreceptor 10 . As a result, the electrostatic latent image formed on the photoreceptor 10 is developed as a toner image. After that, the developer D remaining on the developing sleeve 53 is conveyed to the separation pole S3. The developer D conveyed to the separation pole S3 is separated from the developing sleeve 53 by the magnetic field weakening from the latter half of the separation pole S3 and continuing to be close to zero.

[Magnet roller]
4 is a schematic perspective view of a magnet roller according to Embodiment 1. FIG. FIG. 5 is a schematic cross-sectional view of the magnet roller according to Embodiment 1. FIG. 5 is a cross-sectional view of the magnet portion taken along line VV shown in FIG. 4. FIG. A specific structure of the magnet roller 52 according to the first embodiment will be described with reference to FIGS. 4 and 5. FIG.

As shown in FIG. 4 , the magnet roller 52 has a magnet portion 521 and a shaft portion 522 .

Shaft portion 522 is configured by, for example, a metal core. Shaft portion 522 has a cylindrical shape. The shaft portion 522 extends along the axial direction of the central axis C of the magnet portion 521 . The shaft portion 522 protrudes from both ends of the magnet portion 521 in the axial direction of the central axis C along the axial direction.

The magnet portion 521 is integrally molded with a magnetic composition containing magnetic particles and a binder. The magnetic particles can be selected from ferrite, rare earth (SmCo, NdFeB), MnAlC, alnico, and SmFeN. A thermoplastic resin, a thermosetting resin, a low melting point alloy, or the like can be used as the binder.

The magnet portion 521 includes a plurality of magnetic poles (drawing pole S2, transport pole N2, regulation pole S1, development pole N1, and separation pole S3) arranged around the central axis C. As shown in FIG. The plurality of magnetic poles generate magnetic force such that a plurality of peaks are formed in the magnetic force distribution in the circumferential direction of the magnet roller 52 . The magnetic forces of magnetic poles adjacent to each other are different.

For example, the scooping pole S2 is magnetized so that the magnetic force on the surface of the developing sleeve 53 is approximately 40 mT. The transport pole N2 is magnetized so that the magnetic force on the surface of the developing sleeve 53 is approximately 35 mT. The regulation pole S1 is magnetized so that the magnetic force on the surface of the developing sleeve 53 is approximately 40 mT. The developing pole N1 is magnetized so that the magnetic force on the surface of the developing sleeve 53 is approximately 100 mT. The separation pole S3 is magnetized so that the magnetic force on the surface of the developing sleeve 53 is approximately 60 mT.

Magnet portion 521 has a cylindrical shape. The magnet portion 521 is attached to the shaft portion 522 while the shaft portion 522 is inserted therethrough. The magnet portion 521 has an outer peripheral surface 521a surrounding the central axis C. As shown in FIG. A groove portion 523 is provided on the outer peripheral surface 521 a of the magnet portion 521 .

The groove portion 523 is provided on the outer peripheral surface 521 a of the magnet portion 521 . The groove portion 523 extends along a direction parallel to the axial direction of the central axis C of the magnet portion 521 . The groove portion 523 is provided from one end of the magnet portion 521 to the other end of the magnet portion 521 along the axial direction.

As shown in FIG. 5, the groove 523 is provided between at least one set of two adjacent magnetic poles out of a plurality of sets of two adjacent magnetic poles. Specifically, it is provided between the regulation pole S1 and the development pole N1. The magnitude of the magnetic force of the development pole N1 is greater than the magnitude of the magnetic force of the regulation pole S1. The magnitude of magnetic force means the absolute value of magnetic force.

The groove portion 523 has a substantially V shape. The groove portion 523 has a first inclined surface 523a and a second inclined surface 523b that are opposed to each other and inclined to approach each other toward the center.

The first inclined surface 523a is positioned on the side of the magnetic pole having the smaller magnetic force among the two adjacent magnetic poles. Specifically, the first inclined surface 523a is located on the regulation pole S1 side between the regulation pole S1 and the development pole N1.

The second inclined surface 523b is located on the side of the magnetic pole having the larger magnetic force among the two adjacent magnetic poles. Specifically, the second inclined surface 523b is located on the development pole N1 side between the regulation pole S1 and the development pole N1.

In the cross section of the magnet portion 521 orthogonal to the central axis C in the portion where the groove portion 523 is provided, the angle formed by the first virtual line VL1 passing through the lower end of the first inclined surface 523a and the central axis C and the first inclined surface 523a Let the smaller angle be the first groove angle θ1, and the smaller one of the angles formed by the second slant surface 523b and the second virtual line VL2 passing through the lower end of the second slant surface 523b and the central axis C Given the second groove angle θ2, the first groove angle θ1 is smaller than the second groove angle θ2.

FIG. 6 is a diagram showing the magnetic force distribution of two adjacent magnetic poles when the magnetic force of the magnetic poles magnetized in the magnet roller according to Embodiment 1 varies. Specifically, FIG. 6 shows the magnetic force distribution from the regulation pole S1 to the development pole N1.

The vertical axis in FIG. 6 represents the magnetic force, with the magnetic force on the S pole side being positive and the magnetic force on the N pole side being negative. The horizontal axis in FIG. 6 indicates the center angle of the magnet portion 521 . When a predetermined position on the outer peripheral surface 521a of the magnet portion 521 is assumed to be 0 degree as the center angle of the magnet portion 521, the position on the outer peripheral surface 521a of the magnet portion 521 is represented by the center angle.

As shown in FIG. 6, when magnetizing the plurality of magnetic poles in each magnet portion 521 after integrally molding the plurality of magnet portions 521 with the above-described magnetic composition, each magnet portion 521 was magnetized. The magnetic force of the magnetic pole may vary. In FIG. 6, the solid line indicates the magnetic force distribution in the first magnetized state, and the dashed line indicates the magnetic force distribution in the second magnetized state.

Due to variations in magnetization, the magnitude (absolute value) of the magnetic force of the development pole N1 in the first magnetized state is larger than the magnitude (absolute value) of the magnetic force of the development pole N1 in the second magnetized state. It's getting bigger.

In general, when the magnitude of the magnetic force increases, the width of the magnetic pole also increases, and the switching position of two adjacent magnetic poles (center angle of the position where the magnetic force becomes 0 in FIG. 6) is displaced.

Here, in the embodiment, as described above, the groove portion 523 is formed on the outer peripheral surface 521a of the magnet portion 521 between two adjacent magnetic poles so that the first groove angle θ1 is smaller than the second groove angle θ2. is provided.

Therefore, the diameter r1 of the magnet portion 521 on the first inclined surface 523a moved toward the regulation pole S1 side by a predetermined center angle of the magnet portion 521 with the position of the bottom portion of the groove portion 523 as a reference is the position of the bottom portion of the groove portion 523. As a reference, it is larger than the diameter r2 of the magnet portion 521 on the second inclined surface 523b moved toward the development pole N1 by the same angle as the predetermined central angle.

In the magnet portion 521, the larger the diameter, the stronger the magnetic force. Therefore, even when the magnetic force of the development pole N1 increases, the above-mentioned diameter r1 is larger than the diameter r2, so that the width of the magnetic force of the development pole N1 can be suppressed from increasing. As a result, it is possible to prevent the switching position between the regulation pole S1 and the development pole N1 from being pushed toward the regulation pole S1 and moving.

As described above, in the magnet roller 52 and the developing roller 60, the developing device 50, and the image forming apparatus 100 using the magnet roller 52 according to the first embodiment, the displacement of the switching positions of the two adjacent magnetic poles is suppressed. can do.

(Embodiment 2)
FIG. 7 is a schematic cross-sectional view of a magnet roller according to Embodiment 2. FIG. A magnet roller 52A according to the second embodiment will be described with reference to FIG.

Magnet roller 52A according to the second embodiment differs from magnet roller 52 according to the first embodiment in the shape of magnet portion 521A. Other shapes are substantially the same.

In the magnet portion 521A, two groove portions 523 and 524 are provided on the outer peripheral surface 521a. The groove portion 523 is provided between the regulation pole S1 and the development pole N1, and the groove portion 524 is provided between the development pole N1 and the separation pole S3. That is, grooves are provided between two sets of two adjacent magnetic poles out of a plurality of sets of two adjacent magnetic poles.

Groove portion 523 is configured substantially in the same manner as in the first embodiment. The groove portion 524 has a substantially V shape. The groove portion 524 has a first inclined surface 524a and a second inclined surface 524b that are opposed to each other and inclined to approach each other toward the center.

The first inclined surface 524a is located on the side of the magnetic pole having the smaller magnetic force among the two adjacent magnetic poles. Specifically, the first inclined surface 524a is located on the separation pole S3 side between the development pole N1 and the separation pole S3.

The second inclined surface 524b is located on the side of the magnetic pole having the larger magnetic force among the two adjacent magnetic poles. Specifically, the second inclined surface 524b is located on the development pole N1 side between the development pole N1 and the separation pole S3.

In the cross section of the magnet portion 521A perpendicular to the central axis C in the portion where the groove portion 524 is provided, the angle formed by the first inclined surface 524a and a third virtual line VL3 passing through the lower end of the first inclined surface 524a and the central axis C Let the smaller angle be the first groove angle θ1a, and the smaller one of the angles formed by the second inclined surface 523b and the fourth imaginary line VL4 passing through the lower end of the second inclined surface 524b and the central axis C Given the second groove angle θ2a, the first groove angle θ1a is smaller than the second groove angle θ2a.

Further, the difference between the first groove angle and the second groove angle in the groove provided between two adjacent magnetic poles with a large difference in magnetic force is the same as the difference between the first groove angle and the second groove angle in the groove provided between two adjacent magnetic poles with a small difference in magnetic force. is larger than the difference between the first groove angle and the second groove angle in .

Specifically, the difference in magnetic force between the regulation pole S1 and the development pole N1 is larger than the difference in magnetic force between the development pole N1 and the separation pole S3. In this case, the difference between the first groove angle θ1 and the second groove angle θ2 in the groove portion 523 provided between the regulation pole S1 and the development pole N1 is the difference provided between the development pole N1 and the separation pole S3. is greater than the difference between the first groove angle θ1a and the second groove angle θ2a in the groove portion 524.

Furthermore, the depth of the groove provided between two adjacent magnetic poles with a large magnetic force difference is deeper than the depth of the groove provided between two adjacent magnetic poles with a small magnetic force difference.

Specifically, the depth of the groove 523 provided between the regulation pole S1 and the development pole N1 is deeper than the depth of the groove 524 provided between the development pole N1 and the separation pole S3. .

By being configured as described above, the magnet roller 52A according to the second embodiment can obtain effects equal to or greater than those of the magnet roller 52 according to the first embodiment.

Specifically, grooves are provided between two or more pairs of adjacent magnetic poles out of a plurality of pairs of adjacent magnetic poles. It is possible to suppress the displacement of the switching positions of the two magnetic poles.

In general, the larger the magnetic force difference between two adjacent magnetic poles, the easier it is to switch to the smaller magnetic force and move the position.

As in Embodiment 2, the difference between the first groove angle θ1 and the second groove angle θ2 in the groove provided between two adjacent magnetic poles with a large difference in magnetic force is the same as that of the two adjacent magnetic poles with a small difference in magnetic force. By making the difference between the first groove angle θ1a and the second groove angle θ2a larger than the difference between the first groove angle θ1a and the second groove angle θ2a in the groove provided between the two magnetic poles, it is possible to suppress the movement of the switching position to the lower magnetic force.

Furthermore, by making the depth of the groove provided between two adjacent magnetic poles with a large difference in magnetic force greater than the depth of the groove provided between two adjacent magnetic poles with a small difference in magnetic force, the magnetic force is reduced. It is possible to suppress the movement of the switching position to the smaller one.

(Verification experiment)
FIG. 8 is a diagram showing conditions and results of a verification experiment conducted to verify the effects of the embodiment. With reference to FIG. 8, conditions and results of verification experiments conducted to verify the effects of the embodiment will be described.

As shown in FIG. 8, in the verification experiment, magnet rollers according to Comparative Example 1A, Comparative Example 1B, Comparative Example 2A, Comparative Example 2B, Example 1A and Example 1B were prepared. In each of the combinations of Comparative Examples 1A and 1B, the combination of Comparative Examples 2A and 2B, and the combination of Examples 1A and 1B, the magnetic force of the development pole N1, which is the main magnetic pole, is varied to obtain the control pole S1 and the development pole. The position where the magnetic force with N1 switches was confirmed. The position at which the magnetic force switches was confirmed by measuring the magnetic force around the central axis C of the magnet portion 521 with a gauss meter.

As the magnet roller in Examples 1A and 1B, the magnet roller 52 according to Embodiment 1 was prepared. In Examples 1A and 1B, the first groove angle θ1 was set to 30° and the second groove angle θ2 was set to 45°.

FIG. 9 is a schematic cross-sectional view of magnet rollers in Comparative Examples 1A and 1B. As shown in FIG. 9, as the magnet roller 52X in Comparative Examples 1A and 1B, magnet portions 521 in which grooves were not provided were prepared.

FIG. 10 is a schematic cross-sectional view of magnet rollers in Comparative Examples 2A and 2B. As shown in FIG. 10, as the magnet roller 52Y in Comparative Examples 2A and 2B, a groove portion 523 provided between the regulation pole S1 and the development pole N1 on the outer peripheral surface 521a of the magnet portion 521 is prepared. did. In Comparative Examples 2A and 2B, the first groove angle .theta.1 and the second groove angle .theta.2 of the groove portion 523 were the same, and the first groove angle .theta.1 and the second groove angle .theta.2 were set to 45 degrees (see FIG. 8).

As shown in FIG. 8 again, in Comparative Examples 1A and 1B, since the groove is not provided, the magnetic force of the developing pole N1 varies. The center angle of the magnet portion 521 was moved by 5.8°.

In Comparative Examples 2A and 2B, although grooves are provided, the first groove angle θ1 and the second groove angle θ2 are the same. The position at which the magnetic force with N1 is switched has moved by 5.3° in terms of the center angle of the magnet portion 521 .

In Examples 1A and 1B, since the first groove angle θ1 is smaller than the second groove angle θ2, even if the magnetic force of the developing pole N1 varies, the magnetic force between the regulating pole S1 and the developing pole N1 does not change. The switching position moved by only 0.8° in terms of the center angle of the magnet portion 521 .

From the above results, by providing a groove portion extending in a direction parallel to the axial direction of the central axis between two adjacent magnetic poles and making the first groove angle smaller than the second groove angle, It can be said that it was experimentally confirmed that the displacement of the switching positions of the two adjacent magnetic poles can be suppressed.

In Embodiments 1 and 2 described above, the magnet portion 521 has a cylindrical shape and is attached to the shaft portion 522 while the shaft portion 522 is inserted therethrough. is not limited to The magnet portion 521 and the shaft portion 522 may be integrally molded with a magnetic composition. In this case, it is not necessary to attach the magnet portion 521 to the shaft portion 522, so the manufacturing cost of the magnet portion 521 can be reduced.

In Embodiment 1 described above, the case where the groove is provided between the regulating pole S1 and the development pole N1 has been described as an example, but the present invention is not limited to this. The groove portion may be provided between the development pole N1 and the separation pole S3, may be provided between the separation pole S3 and the scooping pole S2, or may be provided between the scooping pole S2 and the transport pole N2. It may be provided between the transport pole N2 and the regulation pole S1. That is, as long as the first groove angle θ1 is smaller than the second groove angle element θ2, at least one pair of adjacent magnetic poles out of a plurality of pairs of adjacent magnetic poles will have a central axis between the two adjacent magnetic poles. It suffices that a groove extending along a direction parallel to the axial direction is provided.

When grooves are provided between three or more pairs of adjacent magnetic poles, the difference between the first groove angle and the second groove angle in the grooves provided between the two adjacent magnetic poles increases as the magnetic force difference increases. can be increased. Further, the depth of the groove provided between two adjacent magnetic poles may be increased as the magnetic force difference increases.

As described above, the embodiments disclosed this time are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the scope of claims, and includes all modifications within the meaning and scope of equivalence to the scope of claims.

1C, 1K, 1M, 1Y image forming unit 10 photoreceptor 11 charging device 12 exposure device 15C, 15K, 15M, 15Y toner bottle 17 cleaning device 30 intermediate transfer belt 31 primary transfer roller 33 secondary Transfer roller 36 Cleaning device 37 Cassette 40 Fixing device 48 Tray 50 Developing device 51 Housing 51A Partition wall 52, 52A, 52X, 52Y Magnet roller 53 Developing sleeve 54 First transport chamber 54A First Stirring member 55 Second transport chamber 55A Second stirring member 56 Regulating member 60 Developing roller 100 Image forming apparatus 101 Control device 521, 521A Magnet portion 521a Peripheral surface 522 Shaft portion 523 Groove portion 523a First inclined surface 523b Second inclined surface 524 Groove 524a First inclined surface 524b Second inclined surface.

Claims (10)

A magnet unit having a central axis and including a plurality of magnetic poles arranged around the central axis,
The magnet part has an outer peripheral surface surrounding the central axis, and is integrally formed of a magnetic composition containing magnetic particles and a binder,
The magnetic forces of the magnetic poles adjacent to each other are different from each other,
By arranging the plurality of magnetic poles around the central axis, there are a plurality of sets of two adjacent magnetic poles,
On the outer peripheral surface of the magnet part, between at least two pairs of the adjacent magnetic poles among the plurality of pairs of the adjacent magnetic poles, along a direction parallel to the axial direction of the central axis. each provided with a groove extending through the
each of the grooves has a first inclined surface and a second inclined surface facing each other and inclined to approach each other toward the central axis;
the first inclined surface is located on the side of the magnetic pole having the smaller magnetic force among the two adjacent magnetic poles,
the second inclined surface is positioned on the side of the magnetic pole having the larger magnetic force among the two adjacent magnetic poles,
In the cross section of the magnet portion orthogonal to the central axis at the portion where the groove portions are provided, an angle formed between the first slanted surface and a first imaginary line passing through the lower end of the first slanted surface and the central axis The smaller angle is defined as the first groove angle, and the smaller angle among the angles formed by the second slant surface and the second imaginary line passing through the lower end of the second slant surface and the central axis is the second groove angle. The magnet roller, wherein the first groove angle is smaller than the second groove angle when expressed as a groove angle. The difference between the first groove angle and the second groove angle in the groove provided between the two adjacent magnetic poles having a large magnetic force difference is the difference between the two adjacent magnetic poles having a small magnetic force difference. 2. The magnet roller according to claim 1 , which is larger than a difference between said first groove angle and said second groove angle in said groove provided in said groove. The groove provided between two adjacent magnetic poles with a large difference in magnetic force is deeper than the depth of the groove provided between two adjacent magnetic poles with a small difference in magnetic force. Item 3. The magnet roller according to Item 1 or 2 . further comprising a shaft portion protruding along the axial direction from both ends of the magnet portion in the axial direction of the central axis;
The magnet roller according to any one of claims 1 to 3 , wherein the magnet portion and the shaft portion are integrally molded from the magnetic composition. The magnet roller according to any one of claims 1 to 4 , wherein the groove is provided from one end of the magnet portion to the other end of the magnet portion along a direction parallel to the axial direction. A magnet roller according to any one of claims 1 to 5 ;
and a cylindrical developing sleeve that covers the outer peripheral surface of the magnet portion. a developing roller according to claim 6 ;
and a developer regulating member that regulates the amount of developer carried on the developing roller. An image forming apparatus comprising: the developing device according to claim 7 ; and a transfer member for transferring the toner image developed by the developing device onto a recording medium. A magnet unit having a central axis and including a plurality of magnetic poles arranged around the central axis,
The magnet part has an outer peripheral surface surrounding the central axis, and is integrally formed of a magnetic composition containing magnetic particles and a binder,
The magnetic forces of the magnetic poles adjacent to each other are different from each other,
By arranging the plurality of magnetic poles around the central axis, there are a plurality of sets of two adjacent magnetic poles,
On the outer peripheral surface of the magnet portion, between at least any two pairs of the adjacent magnetic poles among the plurality of pairs of the adjacent magnetic poles, along a direction parallel to the axial direction of the central axis. each provided with a groove extending through the
each of the grooves has a first inclined surface and a second inclined surface facing each other and inclined to approach each other toward the central axis;
the first inclined surface is located on the side of the magnetic pole having the smaller magnetic force among the two adjacent magnetic poles,
the second inclined surface is positioned on the side of the magnetic pole having the larger magnetic force among the two adjacent magnetic poles,
In the cross section of the magnet portion orthogonal to the central axis at the portion where the groove portions are provided, an angle formed between the first slanted surface and a first imaginary line passing through the lower end of the first slanted surface and the central axis The smaller angle is defined as the first groove angle, and the smaller angle among the angles formed by the second slant surface and a second imaginary line passing through the lower end of the second slant surface and the central axis is the second groove angle. In terms of groove angle, the first groove angle is smaller than the second groove angle,
The difference between the first groove angle and the second groove angle in the groove provided between the two adjacent magnetic poles with a large difference in magnetic force is the difference between the two adjacent magnetic poles with a small difference in magnetic force. a magnet roller that is larger than the difference between the first groove angle and the second groove angle in the groove provided in the magnet roller. A magnet unit having a central axis and including a plurality of magnetic poles arranged around the central axis,
The magnet part has an outer peripheral surface surrounding the central axis, and is integrally formed of a magnetic composition containing magnetic particles and a binder,
The magnetic forces possessed by the magnetic poles adjacent to each other are different from each other,
By arranging the plurality of magnetic poles around the central axis, there are a plurality of sets of two adjacent magnetic poles,
On the outer peripheral surface of the magnet portion, between at least any two pairs of the adjacent magnetic poles among the plurality of pairs of the adjacent magnetic poles, along a direction parallel to the axial direction of the central axis. a groove extending through the
each of the grooves has a first inclined surface and a second inclined surface facing each other and inclined to approach each other toward the central axis;
the first inclined surface is located on the side of the magnetic pole having the smaller magnetic force among the two adjacent magnetic poles,
the second inclined surface is positioned on the side of the magnetic pole having the larger magnetic force among the two adjacent magnetic poles,
In the cross section of the magnet portion orthogonal to the central axis at the portion where the groove portions are provided, an angle formed between the first slanted surface and a first imaginary line passing through the lower end of the first slanted surface and the central axis The smaller angle is defined as the first groove angle, and the smaller angle among the angles formed by the second slant surface and the second imaginary line passing through the lower end of the second slant surface and the central axis is the second groove angle. In terms of groove angle, the first groove angle is smaller than the second groove angle,
The magnet, wherein the depth of the groove provided between two adjacent magnetic poles having a large difference in magnetic force is greater than the depth of the groove provided between two adjacent magnetic poles having a small difference in magnetic force. roller.

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