WO2001052278A1

WO2001052278A1 - Magnet roller

Info

Publication number: WO2001052278A1
Application number: PCT/JP2000/005939
Authority: WO
Inventors: Masaharu Iwai
Original assignee: Kaneka Corporation; Tochigi Kaneka Corporation
Priority date: 2000-01-06
Filing date: 2000-09-01
Publication date: 2001-07-19
Also published as: EP1253604A1; EP1253604A4

Abstract

A magnet roller produced at low cost, capable of exhibiting a strong magnetic force even if the magnet roller is magnetized in a relatively weak magnetic field and of exhibiting a magnetic force (800 G or more) practically sufficient for development even if a plurality of magnetic poles are provided in a main magnetic pole part, and having a good resistance to oxidation. The magnetic roller (1) comprises a body part (3) and a shaft part (2) supporting both ends of the body part. A plurality of magnetic poles (N1, S2, N2, S1) are provided in the outer peripheral face of the body part (3). The body part (3) is made up of a rare-earth bond magnet made of rare-earth magnetic power having a composite phase of a hard magnetic phase and a soft magnetic phase both magnetically exchange-interacting with each other and having a coercive force (iHc) of 5 Koe or less and a residual magnetic flux density (Br) of 5 KG or more.

Description

Description Magnet roller Technical field

The present invention relates to a magnet roller incorporated in an electrophotographic apparatus employing an electrophotographic process in an image forming apparatus such as a copying machine, a laser printer or a facsimile receiving apparatus. Background art

A magnet roller incorporated in an electrophotographic apparatus supplies a toner to an electrostatic latent image carrier and develops the electrostatic latent image by developing the toner, and a developing roller after transferring the developed toner image onto paper. It is applied to a cleaning roller for removing residual toner on an electrostatic latent image carrier. For example, when a magnet roller is used as a developing roller, as shown in FIG. 9, the magnet roller 31 is formed by forming a main body 33 made of a magnet material on the outer periphery of a shaft (shaft) 32. It is used by being incorporated in a hollow cylindrical sleeve 34 made of an aluminum alloy or the like. A plurality of magnetic poles are formed on the outer peripheral surface of the main body 33 of the magnet roller 31. Of these magnetic poles, the one having the highest surface magnetic flux density is called the main magnetic pole, and the developing pole is Often used as Thus, the conventional magnet roller forms a main magnetic pole (developing pole) consisting of one magnetic pole on the main body, and its surface magnetic flux density curve (magnetic force distribution curve) forms a single high peak. In addition, two main magnetic poles of the same polarity were juxtaposed to form a main magnetic pole (development pole), and the magnetic force distribution curve formed two high peaks (W peaks).

In addition, strontium-based or barium-based ferrite magnetic powder, rare-earth-based magnetic powder (Nd-Fe-B-based magnetic powder, Sm-Co-based magnetic powder, etc.) are formed in the main body of such a conventional magnet roller. A typical example is a bonded magnet formed by kneading a resin binder such as a thermoplastic resin by means such as injection molding or extrusion molding. The magnetic properties required for the magnet roller are determined at the time of molding or after molding. Outside the body It was obtained by applying a partial magnetic field and magnetizing.

However, the conventional magnet roller has mainly the following problems (1) to (4). (1) A magnet roller using ferrite-based magnetic powder could not meet the demand for high magnetic force. In the case of a magnet roller composed of a single magnetic pole as the main magnetic pole, for example, the magnetic force of a magnet roller with an outer diameter of 13.6 mm is less than 850 G at maximum, and a high magnetic field (Approximately 30 K〇e), it was difficult to obtain a high magnetic force of 850 G or more due to magnetic saturation.

(2) In recent years, a magnet roller having a main magnetic pole composed of a plurality of magnetic poles has been developed.The magnetic force at the main magnetic pole is 600 G or less, and the magnetic roller plays a role as a developing pole. It was not a level that could be fulfilled. The reason why the main magnetic pole is composed of a plurality of poles is that the range of the width of the developer in the circumferential direction is widened, and this has an advantage of increasing the development efficiency.

(3) On the other hand, in a magnet roller using rare-earth magnetic powder, since the coercive force of the rare-earth magnetic powder is relatively high (intrinsic coercive force (iHc) of 5 KOe or more), low magnetism (7 (Approximately 0 G), and a high applied magnetic field (approximately 20 to 3 O KOe) is required to obtain a high magnetic force, which inevitably increases the size and power of the magnetizing device. This complicates the magnetizing process and is a factor in increasing the cost.

(4) In addition, conventional rare-earth magnetic powders have a low Curie point of about 330 ° C, so their working limit temperature is limited to about 13 O, or conventional rare-earth magnetic powders Because of the poor corrosion resistance and oxidation resistance of the steel, magnetic properties are degraded due to the formation of 鲭, so surface coating such as plating is required to prevent the occurrence of 鲭, etc. It was a factor of high.

An object of the present invention is to provide a magnet roller which can obtain a high magnetic force even when magnetized in a relatively low magnetic field and can be manufactured at low cost. . In particular, the magnetic force of the main pole consisting of a single magnetic pole should be set to a high magnetic force of more than 850 G even if it is magnetized at 15 K〇e or less. The purpose is to make it practically sufficient. At the same time, it is another object of the present invention to obtain a magnet roller having good corrosion resistance and oxidation resistance without requiring surface coating such as plating. Disclosure of the invention

In order to achieve the above object, the present inventor has focused on a “nanocomposite magnet” which is composed of a soft magnetic material and a hard magnetic material having a small coercive force, and the order of the crystal grain size of the soft magnetic material is nanometer. As a result of intensive studies, they have found that this nanocomposite magnet is suitable as a magnet material for a magnet roller, and have reached the present invention.

That is, the present invention is a magnet roller comprising a main body portion and a shaft portion supporting both ends of the main body portion, wherein a plurality of magnetic poles are formed on an outer peripheral surface of the main body portion in a circumferential direction. The whole or a part of the main body has a magnetically exchangeable interaction between a hard magnetic phase and a soft magnetic phase, and has a coercive force (iHc) of 5 K〇e or less and a residual magnetic flux of 5 KG or more. It is characterized by comprising a rare-earth bonded magnet using a rare-earth magnetic powder having a high density and a resin binder. Therefore, it is possible to obtain a magnet roller having low coercive force (iHc) due to the presence of the soft magnetic phase and high remanence (Br) magnetic properties due to magnetic exchange interaction.

Further, it is more preferable that the rare earth magnetic powder is made of exchange spring magnetic powder. "Exchange spring magnetism" means that when a large amount of soft magnetic phase exists in a magnet, the magnetization of the crystal grains of the soft magnetic phase and the hard magnetic phase are connected to each other through exchange interaction, thereby providing a low coercive force. First, the magnetization of the soft magnetic phase, which easily reverses the magnetization in the reverse magnetic field, becomes difficult to reverse even in the reverse magnetic field, and shows a mode in which both phases are connected by a spring. Refers to magnetic properties such as

R. Coehoorn, KH J. Buschow etal .: J. de Phys., 49 (1988) C8-669). Such rare-earth magnetic powders include a rare-earth iron-boron compound phase as a hard magnetic phase, an iron phase or an iron-boron compound phase as a soft magnetic phase, or a rare-earth iron-nitrogen compound as a hard magnetic phase. Those using an iron phase as the compound phase and the soft magnetic phase are preferred. Since this kind of rare-earth magnetic powder contains a large amount of soft magnetic phase, one point of curi, which is an index of the temperature dependence of remanent magnetization, is mainly governed by the temperature dependence of the soft magnetic phase. Therefore, the Curie point of the rare earth magnetic powder is a high value of about 400 or more, and the temperature dependence of remanent magnetization is low. Can be

Further, it is desirable that cobalt (Co) is added to the rare earth magnetic powder in an amount of 1 to 16 wt%. As a result, the bonded magnet made of the rare-earth magnetic powder has a higher Co content than the rare-earth Nd-Fe-B-based magnet mainly composed of the conventional hard magnetic phase, so that the corrosion resistance and the oxidation resistance are improved. And the occurrence of 鲭 can be prevented even if there is no surface coating such as plating. That is, if the content of Co is less than 1 wt%, the oxidation resistance of the bonded magnet is reduced, and the likelihood of occurrence is increased. On the other hand, if the content of Co exceeds 16 wt%, the bonded magnet is protected. The magnetic force decreases, making it difficult to secure the magnetic properties required for the magnet roller.

When the main magnetic pole is composed of a plurality of magnetic poles, it is desirable that the polarities of adjacent magnetic poles among the plurality of magnetic poles constituting the main magnetic pole be opposite to each other. By making the polarities of the adjacent magnetic poles opposite to each other, the magnetic polarities in the developing zone (the area where the developer rises toward the photoreceptor on the main magnetic pole) with the rotation of the magnet roller during use There is an advantage that the developer is reversed (rotated) due to the change, and the efficiency of supplying the developer to the photoconductor can be increased.

In order to control the magnetic force distribution of the magnet roller, it is also preferable that a magnet piece made of the rare earth bonded magnet is disposed in a groove formed along an axis near the main magnetic pole on the outer peripheral surface of the main body. The rare earth bonded magnet can be composed of one or a plurality of magnet pieces. When the main magnetic pole is composed of a plurality of rare-earth bonded magnet pieces, it is desirable that adjacent rare-earth bonded magnet pieces have opposite polarities.

Further, a magnet roller may be formed by attaching a plurality of magnet pieces including the rare earth bonded magnet to the outer peripheral surface of the shaft portion. For example, a magnet piece with a C-shaped cross section made of a conventional ferrite resin magnet or the like is attached to the outer peripheral surface of the shaft, and the rare-earth bonded magnet piece is placed in the C-shaped opening (near the main magnetic pole) of the magnet piece. Alternatively, a magnet roller can be formed by fitting a plurality of magnet rollers. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view showing one embodiment of the magnet roller according to the present invention. FIG. 2 is a schematic view showing another embodiment of the magnet roller according to the present invention. FIG. 3 is a schematic diagram showing still another embodiment of the magnet roller according to the present invention. FIG. 4 is a schematic view showing still another embodiment of the magnet roller according to the present invention. FIG. 5 is a schematic view showing still another embodiment of the magnet roller according to the present invention. FIG. 6 is a schematic view showing still another embodiment of the magnet roller according to the present invention. FIG. 7 is a schematic diagram illustrating a magnetic force distribution in a circumferential direction of the magnet roller of the example.

FIG. 8 is a schematic diagram showing a magnetic force distribution in a circumferential direction of a magnet roller of another embodiment.

FIG. 9 is a schematic sectional view showing a developing roller incorporated in a conventional sleeve. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a magnet roller according to the present invention will be described below with reference to the drawings.

Referring to the schematic cross-sectional view of FIG. 1, the magnet roller 1 according to the present invention has a main body 3 formed on the outer periphery of a shaft 2 made of SUS, an aluminum alloy, a resin, or the like. The main body 3 has a complex phase of a hard magnetic phase and a soft magnetic phase that magnetically exchange and interact with each other, and has a coercive force (iHc) of 5 KOe or less and a residual magnetic flux density (Br) of 5 KG or more. It is composed of a rare earth pound magnet formed using the rare earth magnetic powder. It is more preferable that the rare earth magnetic powder is an exchange spring magnetic powder in which the crystal grain size of the soft magnetic phase is adjusted to several tens nm in order to make the exchange interaction effective. Further, a plurality of magnetic poles (NS ₂ , N ₂ , four-pole magnetized) are formed on the outer peripheral surface of the main body 3, and the main magnetic pole (in this embodiment, In this example, four poles were formed at equal intervals, but the present invention does not limit the number of poles and pole positions at all. The number of poles and pole positions may be appropriately set according to the desired magnetic characteristics.

The magnet material of the magnet roller main body 3 is mainly composed of a mixture of 50 to 95% by weight of the rare earth magnetic powder and 5 to 50% by weight of a resin binder. Depending on the silane or titanate type as a surface treatment agent for magnetic powder It is preferable to add a coupling agent described above, an amide-based lubricant as a lubricant for improving the fluidity of the molten magnet material, a stabilizer for preventing thermal decomposition of the resin binder, or a flame retardant. If the content of the rare earth magnetic powder is less than 50% by weight, the magnetic properties of the magnet roller are reduced due to insufficient magnetic powder, and a desired magnetic force (850 G or more at the main magnetic pole) cannot be obtained. If the content exceeds 95% by weight, the binder becomes insufficient and the moldability of the main body 3 is impaired. Examples of the resin binder include an ethylene-ethyl acrylate resin, a polyamide resin, a polyethylene resin, a polystyrene resin, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and PPS (polyphenylene sulfide). ), EVA (ethylene-vinyl acetate copolymer), EVOH (ethylene-vinyl alcohol copolymer), PVC (polyvinyl chloride), etc. One or more types, or epoxy resin, phenol resin One or two or more of thermosetting resins such as urea resin, melamine resin, furan resin, unsaturated polyester resin, and polyimide resin can be used.

The rare earth magnetic powder includes a rare earth (R) —iron (Fe) —nitrogen (N) alloy or a rare earth (R) —iron (Fe) —boron (B) alloy containing a hard magnetic phase and a soft magnetic phase. A spring magnetic powder is preferable, and an exchange spring magnetic powder of a rare earth (R) —iron (Fe) —cobalt (Co) alloy may be used. Preferably, R is Sm, Nd, or one or a combination of two or more of Pr, Dy, Tb, and the like. Co, Ni, Cu, Zn, Ga, Ge, A1, Si, Sc, Ti, V, Cr, Mn, Zr, Nb, Mo , Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Hf, Ta, W, Re, 〇s, Ir, Pt, Au, Hg, T1, Pb, One or more elements such as B i may be added. More specifically, Nd-Fe-B alloys (soft magnetic phase: Fe-B alloy, aFe), Sm-Fe-N alloys (soft magnetic phase: Fe), Nd-Fe- Replacement spring magnetic powders such as Co-Cu-Nb-B alloy (soft magnetic phase: Fe_B alloy, aFe), Nd—Fe—Co alloy (soft magnetic phase: aFe, etc.) are suitable. Nd ₄ Fe ₈ , especially from the viewpoint of reducing the coercive force (iHc) and increasing the residual magnetic flux density (Br). B _{2 ()} alloy (Soft magnetic phase: F An exchange spring magnetic powder of e ₃ B, a _Fe ) or _Sm ₂ _{Fe 17} N ₃ alloy (soft magnetic phase: _aFe ) is preferable.

In addition, it is particularly preferable to add Co to the exchange spring magnetic powder in an amount of 1 to 16 wt%, more preferably 3 to 13 wt%. As a result, in the bonded magnet made of the rare earth magnetic powder, the magnetic properties are improved by adding Co, and the corrosion resistance and oxidation resistance are improved. Occurrence can be suppressed.

As a method for producing such an exchange spring magnetic powder, a high-speed quenching method, mechanical opening (mechanical alloying), or the like is used. Specifically, each raw material element is weighed, a heat treatment is performed on the alloy powder obtained by mechanical alloying, and a nitriding treatment is performed as necessary. After pulverizing an alloy containing an amorphous or near-amorphous microstructure obtained by performing a rapid quenching method, a heat treatment is performed to precipitate crystals, and a nitriding treatment is performed as necessary. By appropriately adjusting quenching conditions (roll speed, etc.), crushing conditions, heat treatment conditions (treatment time, temperature), etc., it is possible to produce exchange spring magnetic powder having a soft magnetic phase with a crystal grain size of several tens of nm. Incidentally, the nitriding treatment is necessary when producing the R_Fe-N-based exchange spring magnetic powder.

The magnet roller according to the present invention and a magnet piece (stone piece) to be described later are pelletized after melting and kneading the magnet material, and are molded from the pellet by an extrusion molding method or an injection molding method. Further, the magnet material may be formed by a compression molding method. Magnetization of the magnet roller and magnet pieces can be performed at the same time as injection molding or extrusion molding. It is obtained by magnetizing after molding without magnetizing. Also, in forming and assembling the magnet roller, the main body and the shaft may be integrally formed, the shafts may be attached to both ends of the main body, or the shaft may be provided through the cylindrical body axis. Alternatively, a magnet piece formed in a different shape such as a camber or fan may be attached to a shaft having a circular, elliptical or polygonal cross section to form a magnet roller.

For example, as shown in the schematic sectional view of Fig. 2 (or Fig. 3), It is also preferable to dispose a magnet piece 7 (11) made of the above rare earth pound magnet in a groove 6 (10) formed along the axis near the main magnetic pole in the main body 5 (9). These magnet pieces are desirably a square piece 7 having a square sectional shape as shown in FIG. 2 or a semi-segment piece 11 having a semi-fan shape as shown in FIG. This is because such a shape is easy to be shared with other magnet roller pieces, and improves moldability and sticking property (adhesive property).

When the main magnetic pole is composed of a plurality of magnetic poles, a plurality of magnetic poles (N-pole, S-pole, N-pole, S-pole) are formed on the outer surface of the shaft 12 as shown in the schematic sectional view of FIG. The main body 13 is formed with a groove 14 having a sectoral cross-sectional shape, and the above-mentioned rare earth pound magnet is formed in the groove 14 to form the S pole, N pole and S pole on the surface. The main magnetic poles may be formed by arranging and adhering the magnet pieces 15A, 158, and 150 having the respective magnetic poles so that the magnetic polarities of the adjacent magnet pieces are opposite to each other. Or, as shown in the schematic cross-sectional view of FIG. A ferrite pound magnet 17 is attached, and a magnet piece 18A made of the above-mentioned rare earth bonded magnet and having S, N, and S poles on the surface in the C-shaped opening (near the main magnetic pole) of the ferrite pound magnet 17 is attached. , 18B and 18C may be arranged and bonded so that the magnetic polarities of adjacent magnet pieces are opposite to each other to form a main magnetic pole.

Further, as shown in the schematic cross-sectional view of FIG. 6, magnet pieces 21 A, 21 B, which are made of the above-mentioned rare earth bonded magnet on the outer peripheral surface of the shaft portion 19 and have S, N, and S poles on the surface, respectively. A main magnetic pole is formed by disposing and bonding 21 C, and a ferrite bond magnet piece 2 OA, 20 B, 2 OA ′, 20 B ′ having another magnetic pole is bonded on the outer peripheral surface of the shaft portion 19, A magnet roller may be manufactured.

In the present invention, the shape of the magnet piece is not limited at all, and the shape can be appropriately changed according to desired magnetic characteristics (magnetic force, magnetic force distribution waveform, etc.). As a method for manufacturing such a magnet roller, two injection molding machines are used, a main body is molded by a first injection molding machine, and a magnet piece is inserted into a groove by a second injection molding machine. Molding, a so-called two-color molding method, can also be adopted. This method is effective for greatly simplifying the manufacturing process. Further, as the magnetic field orientation of the magnet pieces, random orientation, linear orientation as shown by arrows in FIGS. 2 (b) and 3 (b), and arrows shown in FIGS. 2 (c) and 3 (c) Such a radial orientation is a typical example. Also, although not explicitly shown in the figure, the magnetic flux density of the applied magnetic field is converged to control the amount of orientation magnetization from any side of the magnet piece 7 (1 1), from the back side to the front side. Thereby, the magnetic force distribution of the magnet roller can be controlled. This control is effective when the magnetic force distribution waveform at the main pole is made asymmetric. Further, a magnet roller may be configured by combining magnet pieces having these different orientations, and the combination may be appropriately selected according to required specifications.

In addition, when the isotropic rare earth magnetic powder according to the present invention is used and magnetized after molding the magnet roller, it is easy to magnetize to a desired magnetic force at a desired position of the magnet roller. preferable. In particular, since there is no need to construct a magnetic circuit in the molding apparatus, the molding die is inexpensive, and since the bonded magnet is not deformed by the applied magnetic field during molding, the dimensional accuracy after molding is increased, so the magnetizing is performed. And the pole position can be determined with high accuracy.

[Example]

Hereinafter, more specific examples and comparative examples according to the present invention will be described, but the following examples do not limit the present invention in any way.

The magnet rollers of Examples 1 to 3 and Comparative Examples 1 to 4 described below were mixed with 10% by weight of a resin binder (nylon 12) and 90% by weight of magnetic powder, melt-kneaded, and formed into pellets. After forming a roller (diameter: 13.6 mm; total length: 320 mm) from the pellets by injection molding, an external magnetic field was applied, and a four-pole (Ν ,, S ₂ , N ₂ , S,) It was produced by magnetizing. The magnetic force distribution of the magnet opening was measured while the magnet opening was housed in the aluminum alloy sleeve 12. In FIG. 7, N and pole are main magnetic poles, reference numeral 13 is a shaft portion, 14 is a main body portion, 15 is a distribution waveform of magnetic force, and point A indicates the maximum value of the magnetic force distribution at the main magnetic pole.

(Example 1)

Nylon 12 as resin binder and NcLF e ₈ as magnetic powder. B _2. Exchange Magnetic powder (intrinsic coercive force iHc: 3. OKOe, residual magnetic flux density Br: 12KG, Co content: 2wt%), kneaded, pelletized, and formed by injection molding to form a roller. It is a magnet roller magnetized at 8K〇e to 15KOe.

(Example 2)

Nd ₅ F as magnetic powder

A magnet roller manufactured in the same manner as in Example 1 except that ring magnetic powder (intrinsic coercive force iHc: 4.8 KOe, residual magnetic flux density Br: 5.2 KG, Co content: 6 wt%) was used. (Example 3)

Example 1 was the same as Example 1 except that Sm ₂ Fe ₁₇ N ₃ exchange spring magnetic powder (coercive force iHc: 4.0 KOe, residual magnetic flux density Br: 7.8 KG, Co content: lwt%) was used as the magnetic powder. This is a magnet roller manufactured similarly.

(Comparative Example 1)

Ferrite magnetic powders _{S r O · 6 F e 2} 0 3 as the magnetic powder (coercivity iHc: 3 kOe, the residual magnetic flux density Br: 4. 8KG, Co content: 0 wt%) except for using, as in Example 1 This is a manufactured magnet roller.

(Comparative Example 2)

Ferrite magnetic powders S r O · 6 F e ₂ 〇 ₃ as magnetic powder (coercivity iHc: 3K_〇_E remanence Br: 4. 8KG, Co content: 0 wt%) with, the intensity of the applied magnetic field A magnet roller manufactured in the same manner as in Example 1 except that 2 OKOe to 3 OKOe were used.

(Comparative Example 3)

Rare earth magnetic powder as a magnetic powder _{_{_{(Nd 13 5 Fe l 7 B}}} 4 8; coercive force iHc:.. 14 kOe, residual magnetic flux density Br: 8. 4KG, Co content: 0. 5 wt%), except using, implementation This is a magnet roller manufactured in the same manner as in Example 1.

(Comparative Example 4)

Rare earth magnetic powder (Nd ^ FeuB; coercive force iHc: 14KOe, residual magnetic flux density Br: 8.4KG, Co content: 0.5wt%) was used as the magnetic powder, and the applied magnetic field strength was 20KOe to 3OKOe. Except that the magnet was manufactured in the same manner as in Example 1. Trolla.

Next, as shown in FIG. 8, the magnet apertures of Example 4 and Comparative Example 5, which will be described in detail below, are magnet pieces 29A to 29C, 28A, 28B on the outer peripheral surface of the shaft portion 26. , 28 Α ', 28 B' are bonded together (diameter φ 13.6 mm; overall length 320 mm). Each magnet piece is mixed with 10% by weight of a resin binder (nylon 12) and 90% by weight of magnetic powder, melt-kneaded and formed into pellets, and the pellets are shaped by injection molding using this belt. It was fabricated by applying an external magnetic field and magnetizing after molding. In Fig. 8, S, P, N, and S ₂ poles are main poles, 26 is a shaft, 28A, 28B, 28A 'and 28B' are ferrite pole magnet pieces, and 29A to 29C are rare earth elements. The pound magnet piece, 30 indicates the magnetic force distribution waveform, and points B, C, and D indicate the highest values of the magnetic force distribution at the main pole. In FIG. 8, the angle (0 ₂ ) between the magnetic force peak position (point B) at the upstream side of the developer conveyance and the magnetic force peak position (point D) at the downstream side of the developer conveyance is 60 °. Set to. The angle between the points B and C (θ is 30 °. If the angle between the points Β and D (θ ₂ ) exceeds 60 °, the point C is Since the brushing of the nearby developer is coarse, it does not change from the brushing state of the conventional magnet roller in the developing zone, and at the same time, the reversal (rotation) of the developer due to the change in the magnetic polarity becomes noticeable. Higher image quality cannot be achieved due to a decrease in the amount of toner supplied to the photoreceptor. On the other hand, when the gap angle (0 ₂ ) is less than 30 °, the rare-earth bonded magnet piece is used for the main magnetic pole. No high magnetic force could be obtained, and it was confirmed that it was difficult to achieve high image quality.

(Example 4)

Ν d ₄ Fe _8Q B ₂ as magnetic powder for magnet pieces having S, P, P and S ₂ poles as main poles. Using an exchange spring magnetic powder (intrinsic coercive force iHc: 3.0 K〇e, residual magnetic flux density Br: 12 KG, Co content: 2 wt%), both were mixed and kneaded using nylon 12 as a resin binder. The pellets are then formed into pellets, and the pellets are used to form magnet pieces having a fan-shaped cross section by an injection molding method. The magnet pieces are magnetized by applying an external magnetic field. I stuck them together. Ferrite magnetic powder S r〇6Fe ₂ 0 ₃ (coercive force iHc) is used as a magnetic powder for a magnet piece having N ₂ poles, S ₃ poles, S ₄ poles, and N ₃ poles constituting magnetic poles other than the main magnetic pole.

: 3KOe, residual magnetic flux density Br: 4.8KG), using Nylon 12 as a resin binder, mixing and kneading the two, pelletizing, and forming a magnet piece with a fan-shaped cross section by injection molding. After performing orientation magnetization at the same time as molding, the magnet piece was bonded to the outer peripheral surface of the shaft portion 26.

(Comparative Example 5)

The main magnetic pole in the Example 4 (S, poles, N, pole, S _2-pole) the exchange spring magnetic powder used in the magnet pieces which constitute the ferrite magnetic powder S R_〇, 6 Fe ₂ 〇 ₃ (coercivity iHc : 3KOe, residual magnetic flux density Br: 4.8KG, Co content: 0 wt%), mixed with nylon 12 and kneaded, pelletized, and injection molded using these pellets to form a fan-shaped cross section This is a magnet roller manufactured in the same manner as in Example 4 except that the magnet piece is formed and orientation magnetization is performed simultaneously with the forming.

The magnetic force distributions of the above Examples and Comparative Examples were measured using a Gauss meter with a probe at a position 1.2 mm radially away from the magnet roller surface (at a position 8.0 mm radially away from the center axis of the magnet roller). The magnet roller was rotated in the circumferential direction and measured. Tables 1 and 2 show the magnetic properties of the magnetic powder and the magnet aperture used in the examples and comparative examples, and Table 3 shows the oxidation resistance. Regarding the oxidation resistance, after the produced magnet roller was left in the air for 168 hours, the presence or absence of mackerel on the surface of the magnet roller was visually checked. The magnetic properties in Tables 1 and 2 are as follows: `` intrinsic coercive force iHc '' and `` residual magnetic flux density Br '' of the magnetic powder, magnet roller `` intrinsic coercive force iHc after molding '' and `` residual magnetic flux density Br '' And the "magnetic force of the main pole" at points A to D after magnetization.

(table 1)

(Table 2)

(Table 3) Example Example Example Example Example

1 2 3 4

発生 outbreak

Yes No No No No Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example 1 2 3 4 5

Yes to No Yes Yes Yes No (Evaluation of Examples 1 to 3 and Comparative Examples 1 to 4 in which the main magnetic pole is composed of a single pole) As is clear from the results shown in Table 1, the magnets using the exchange spring magnetic powders of Examples 1 to 3 were used. In the case of the rollers, when magnetized in a low magnetic field (15 K〇e), all magnetic forces of more than 850 G were obtained, whereas the magnet rollers made of the conventional ferrite bonded magnets of Comparative Examples 1 and 2 Then, only 800 G of magnetic force was obtained regardless of whether the magnet was magnetized in a low magnetic field (15 KO e) or a high magnetic field (30 K〇e). Also, with the magnet rollers made of the conventional rare-earth bonded magnets of Comparative Examples 3 and 4, when magnetized with a high magnetic field (30 KO e) as in Comparative Example 4, a high magnetic force of 135 G can be obtained. When magnetized in a low magnetic field (15 K〇e) as in Comparative Example 3, only a magnetic force of 700 G was obtained. Therefore, it was confirmed that the magnet roller of the present example can provide a high magnetic force (850 G or more) with a low magnetic field (15 K〇e or less). Further, as is clear from the results shown in Table 3, there was no occurrence of mackerel in Examples 1 to 3 using the exchange spring magnetic powder and Comparative Examples 1 and 2 using the conventional ferrite magnetic powder. On the other hand, in Comparative Examples 3 and 4 using rare earth magnetic powder mainly composed of a hard magnetic phase, generation of 鲭 was confirmed.

(Evaluation of Example 4 and Comparative Example 5 in which the main magnetic pole is composed of three poles)

As is evident from the results shown in Table 2, the magnetic force of the three poles constituting the main pole in Example 4 was 800 G or more, whereas the three poles constituting the main pole were in Comparative Example 5. Had a magnetic force of less than 600 G. Therefore, the magnet roller of Example 4 can obtain a high magnetic force (800 G or more) sufficient for developing even if three magnetic poles are arranged within a range of 60 ° around the main magnetic pole, and It was confirmed that the developer was close to the point near point C.

Further, according to Table 3, there was no occurrence of mackerel in Example 4 using the exchange spring magnetic powder and Comparative Example 5 using the conventional ferrite magnetic powder. Industrial applicability

According to the magnet roller of the present invention, the main body has a multiple phase of a hard magnetic phase and a soft magnetic phase that magnetically exchange and interact with each other, and has a coercive force (iHc) of 5 KOe or less and Since a rare-earth bonded magnet using a rare-earth magnetic powder having a residual magnetic flux density of 5 KG or more is used, the low coercive force of the soft magnetic phase and the magnetization higher than that of the hard magnetic phase can be used. High magnetic force can be obtained even when magnetized. In particular, when the main magnetic pole is composed of a single pole, even if it is magnetized in a low magnetic field of 8 KOe to 15 KOe, a high magnetic force of 850 G or more can be obtained. Even when the magnetic pole is composed of a plurality of poles, a high magnetic force of 800 G or more can be obtained, so that a magnet roller with high development efficiency can be obtained. Since the main magnetic pole can be magnetized in a low magnetic field in this way, it is possible to avoid an increase in the size and power of the magnetizing device, and to obtain a magnet roller with excellent magnetic properties while keeping manufacturing costs low. It becomes possible.

Also, by adding 1 to 16 wt% of cobalt to the rare earth magnetic powder, a magnet roller having good corrosion resistance and oxidation resistance can be obtained without requiring surface coating such as plating, and as a result, the magnet Rollers can obtain stable magnetic properties over a long period of time.

Further, by configuring the main magnetic pole by a plurality of magnetic poles and setting the polarities of the adjacent magnetic poles of the plurality of magnetic poles constituting the main magnetic pole to be opposite to each other, the vicinity of the main magnetic pole in use is reduced. The developer can be made denser, and the reversal (rotation) of the developer due to the change in magnetic polarity in the development zone becomes more active, so that the efficiency of supplying the developer to the photoreceptor is increased and the image quality is improved. Becomes possible.

Claims

The scope of the claims

1. A magnet roller comprising a main body, and a shaft supporting both ends of the main body, wherein a plurality of magnetic poles are formed on an outer peripheral surface of the main body in a circumferential direction. All or a part of it has a magnetic and exchange interaction of a hard magnetic phase and a soft magnetic phase, and has a coercive force (iHc) of 5 KOe or less and a residual magnetic flux density of 5 KG or more. A magnet roller comprising a rare earth bonded magnet using a rare earth magnetic powder and a resin binder.

2. The magnet roller according to claim 1, wherein the rare earth magnetic powder is made of exchange spring magnetic powder.

3. The magnet roller according to claim 1, wherein a rare-earth iron-boron compound phase is used as the hard magnetic phase, and an iron phase or iron-boron compound phase is used as the soft magnetic phase.

4. The magnet roller according to claim 1, wherein a rare-earth iron-nitrogen compound phase is used as a hard magnetic phase and an iron phase is used as a soft magnetic phase.

5. The magnet roller according to any one of claims 1 to 4, wherein cobalt is added to the rare earth magnetic powder in an amount of 1 to 16 wt%.

6. The main magnetic pole is constituted by a plurality of magnetic poles, and the polarities of adjacent magnetic poles among a plurality of magnetic poles constituting the main magnetic pole are set to mutually opposite polarities. The magnet roller according to the item.

7. The magnet piece made of the rare earth bonded magnet is disposed in a groove formed along an axis near the main magnetic pole on the outer peripheral surface of the main body. Magnet roller.

8. The magnet roller according to any one of claims 1 to 6, wherein a plurality of magnet pieces including the rare earth bonded magnet are attached to an outer peripheral surface of the shaft portion.