JPH07297028A - Magnet roll - Google Patents

Abstract

PURPOSE:To hold reliably the magnetic characteristics and strength of a magnet roll even if the magnet roll is a small-diameter one and to manufacture the magnet roll at low cost by a method wherein a fitting part is provided on the end part on at least one side of the end parts of a permanent magnet member and a cap having a shaft part is fitted on this fitting part by a plate processing means. CONSTITUTION:A permanent magnet member 1 is formed in an isoparametric solid cylindier form extending over its whole length by an extrusion molding means and fiting parts 8 are respctively provided on both ends of the member 1. These parts 8 are formed by a grinding work, for example, with the outer peripheral surface of the member 1 as their reference. Caps 21 and 22 formed into the form of a bowl of an outside diameter dimension of the same dimension or shorter as the outside diameter dimension of the member 1 by a plate processing means are respectively fitted on these parts 8. A shaft 23 is coaxially secured on the chip 21 and at the same time, a shaft part 24 is made to project on the cap 22 coaxially and integrally with the cap 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roll used as a developing roll or a cleaning roll in electrophotography, electrostatic recording, etc., and particularly, a magnet roll which can be manufactured with a small diameter at low cost. It is about.

[0002]

2. Description of the Related Art Conventionally, in electrophotography, electrostatic recording, etc., a magnet roll used as a developing roll or a cleaning roll is most commonly one having a structure as shown in FIG. In FIG. 6, reference numeral 1 denotes a permanent magnet member, which is formed into a hollow cylindrical shape by a sintered powder permanent magnet material such as hard ferrite or a mixed material of a ferromagnetic powder material and a binder, and has a shaft at the center. 2 is fixed coaxially.

A plurality of magnetic poles (not shown) extending in the axial direction are provided on the outer peripheral surface of the permanent magnet member 1, and these are arranged at equal or unequal intervals in the circumferential direction.
Next, a flat plate-shaped flange 3 and a shaft-equipped flange 4 are rotatably mounted on both ends 2a and 2b of the shaft 2 via bearings 5 and 5, and are attached to the outer circumferences of the flat-plate-shaped flange 3 and the shaft-equipped flange 4. Is fitted with a sleeve 6 formed in a hollow cylindrical shape.

The plate-like flange 3, the shaft-equipped flange 4 and the sleeve 6 are made of a non-magnetic material such as aluminum alloy or stainless steel. 7
Is a seal member and is fitted between the flat plate-shaped flange 3 and the end portion 2 a of the shaft 2. Further, the permanent magnet member 1 often has a diameter of 10 to 60 mm and a length of 200 to 350 mm.

With the above configuration, the relative rotation between the permanent magnet member 1 and the sleeve 6 (for example, the permanent magnet member 1 is fixed and the sleeve 6 is rotated by the flange 4 with the shaft) causes the outer peripheral surface of the sleeve 6 to be rotated. Adsorb magnetic developer to form a magnetic brush and perform predetermined development work,
Alternatively, the excess magnetic developer after transfer is adsorbed from the surface of the photoconductor to perform a predetermined cleaning operation.

It should be noted that the flat flange 3 in FIG. 6 has a structure in which a hollow cylindrical projecting portion 3a is provided in the central portion as shown in FIG. 7, the seal member 7 (see FIG. 6) is omitted, and this projecting It may be used for driving the sleeve 6 or supporting the sleeve 6 via the portion 3a.

[0007]

When forming the permanent magnet member 1 having the above-mentioned structure, first, in the case of using a sintered powder magnet material such as hard ferrite, for example, an appropriate amount of polyvinyl alcohol (P) is added to barium ferrite particles.
VA) is added and kneaded with a double-arm kneader, and then granulated and dried raw material powder is prepared. Next, this raw material powder is filled into a bag of a thin film made of rubber or plastic, which has a core rod in the center and is put into a liquid such as oil, glycerin, or water, and liquid pressure is applied. Pressure molding (hydrostatic pressure molding or rubber pressing) is performed from the surroundings and firing is performed to mold a hollow cylindrical material.

A shaft (see reference numeral 2 in FIG. 6) separately prepared is fixed to the hollow hole of the above material with an adhesive, and then subjected to predetermined processing to provide a plurality of magnetic poles extending in the axial direction on the outer peripheral surface. Of.

However, when the above means is used, the work of molding the raw material from the raw material powder is relatively complicated, and the work of fixing the shaft to the hollow hole of the raw material is also complicated, and the number of manufacturing and assembling steps is increased. However, there is a problem in that the manufacturing cost rises due to the large size. Especially, since the hollow hole of the material and the shaft are in a loose state, it is necessary to completely fill the gap between them with the adhesive. Therefore, when the material and the shaft are combined, excess adhesive is removed and cleaned. There is a need to. Further, there is a drawback that heating is required to cure the adhesive.

On the other hand, a means for molding the permanent magnet member 1 by a so-called bonded magnet containing a mixture of ferrite particles and a thermoplastic resin material as a main component is also commonly used. In this case, a mold for injection molding is used, the shaft 2 is previously inserted in a predetermined portion of the molding space, the thermoplastic resin material is heated and melted, and is injected and filled into the molding space, followed by cooling. It can be taken out after solidification. In addition, in order to improve the magnetic characteristics, a magnetic field forming means for providing anisotropy by providing a magnetic field generating means in the injection molding die is commonly used.

The permanent magnet member manufactured by the anisotropic bonded magnet as described above has advantages of relatively small manufacturing steps and light weight, but on the other hand, the injection molding die becomes complicated. At the same time, when the number of magnetic poles is large, there may occur a situation where molding in a magnetic field is impossible. In particular, if the permanent magnet member has a small diameter of, for example, 20 mm or less, the magnetic field generating means may come close to or come into contact with each other, and it may be substantially impossible to manufacture an injection molding die. Therefore, there is a problem that the degree of freedom of the magnetization pattern is small.

Further, as an example of the magnet roll using the bonded magnet as described above, the shaft 2 in the central portion is omitted,
In addition, there has been proposed one having a uniform diameter over the entire length (for example, Japanese Unexamined Patent Publication No. 62-81009, Japanese Utility Model Laid-Open No. 5-504).
69 publication). With this configuration,
It is said that the shaft 2 is not required, magnetic design can be easily performed, and sufficient magnetic force can be obtained even with a small diameter.

However, in the case of a magnet roll having a bonded magnet without the shaft 2 as described above, when the outer diameter of the permanent magnet member 1 is, for example, 10 mm or less, the doctor blade has a magnetic material ( When it is made of iron or steel, there is a problem that the magnetic attraction force of the permanent magnet member 1 acts and the permanent magnet member 1 is bent and interferes with the inner surface of the sleeve 6.
Further, since the bonded magnet is used while being anisotropy, it is difficult to obtain a uniform magnetic field orientation.

In order to solve the strength problem of the above-mentioned bonded magnet, the present applicant forms an integral cylindrical body over the entire length by using a ferrite-based sintered magnet material, and forms an intermediate body at both ends of this cylindrical body. A proposal is made to form a shaft portion having a diameter smaller than that of the shaft portion (Japanese Patent Application No. 5-137153).
issue).

According to the above proposal, it is possible to expect an effect that a magnet roll having high magnetic characteristics and a large degree of freedom of a magnetizing pattern can be relatively easily manufactured, but there are still some problems.

That is, since the cylindrical body made of the ferrite-based sintered magnet material is hard, it is necessary to rely on the grinding work to form the shaft portions at both ends, and the grinding allowance for forming the shaft portion is required. Since it is large, there is a problem that the grinding work takes time. Further, since the sintered ferrite magnet material is brittle, the strength of the shaft portion formed by grinding is insufficient, and undesired breakage, chipping, etc. may occur during handling in the magnetizing step and other working steps after grinding. There is a problem that accidents are likely to occur.

The present invention solves the problems existing in the above-mentioned prior art and improved invention, and provides a magnet roll which can be manufactured at a low cost while ensuring the magnetic characteristics and strength even with a small diameter. With the goal.

[0018]

In order to achieve the above object, in the first aspect of the present invention, first, a permanent magnet member is formed in a cylindrical shape and has a plurality of magnetic poles extending axially on the outer peripheral surface thereof. In a magnet roll in which a hollow cylindrical sleeve made of a non-magnetic material is coaxially and relatively rotatably fitted through flanges arranged at both ends, a ferrite-based sintered magnet material has an equal diameter. At least one end of the permanent magnet member formed in the above is provided with a fitting portion having an outer diameter dimension smaller than the outer diameter dimension of the permanent magnet member. A technical means of fitting a cap having a shaft portion and having a diameter smaller than the outer diameter of the member is adopted.

Next, in the second invention, a permanent magnet member formed in a cylindrical shape and provided with a plurality of magnetic poles extending in the axial direction on the outer peripheral surface, and a sleeve formed of a nonmagnetic material in a hollow cylindrical shape. In a magnet roll coaxially and relatively rotatably fitted through flanges arranged at both ends, at least one end of a permanent magnet member formed to have an equal diameter by a ferrite-based sintered magnet material. A fitting portion having an outer diameter smaller than the outer diameter of the permanent magnet member is provided, and the outer diameter of the fitting is smaller than the outer diameter of the permanent magnet member by a plate material processing means. The shaft-equipped flange is formed by integrally fitting a cap portion formed by the plate material processing means and a shaft having a shaft portion protruding into the cap portion. The shaft portion of the flange into engagement with a bearing provided in said cap, adopting the technical means of.

[0020]

With the above structure, since the outer peripheral surface of the cap does not protrude from the outer peripheral surface of the permanent magnet member, interference between the cap and the sleeve can be prevented. Further, by ensuring the strength of the permanent magnet member, it is possible to prevent the axial line from bending, and it is possible to easily and accurately form the shaft portion or the shaft portion at both ends of the permanent magnet member.

[0021]

1 is a longitudinal sectional view of a partially omitted main part showing a permanent magnet member according to a first embodiment of the present invention, and the same parts are designated by the same reference numerals as those in FIG. In FIG. 1, the permanent magnet member 1 is formed into a solid columnar shape having an equal diameter over the entire length by an extrusion molding means described later, and fitting portions 8 are provided at both ends thereof. The fitting portion 8 is formed by, for example, grinding with the outer peripheral surface of the permanent magnet member 1 as a reference. However, if the depth t of the fitting portion 8 is too large, the number of processing steps becomes large, so the depth t is preferably 1 mm or less.

The fitting portion 8 has a cap 21 or 2 formed in a bowl shape having an outer diameter equal to or smaller than the outer diameter of the permanent magnet member 1 by means of a plate material processing means.
2 is fitted, the shaft 23 is coaxially fixed to the cap 21, and the shaft portion 24 is coaxially and integrally protruded from the cap 22. The caps 21 and 22
The fixing means to the permanent magnet member 1 may be only the press-fitting means, but an adhesive may be used together. Also cap 2
It is also possible to separately form the second shaft portion 24 as a shaft so as to have the same structure as the cap 21 side and to make the permanent magnet member 1 have a structure with shafts at both ends.

When it is necessary to project the shafts at both ends of the permanent magnet member 1 due to the mounting structure, members similar to the cap 21 and the shaft 23 may be provided instead of the cap 22. Further, either one of the caps 21 and 22 may be used only at one end of the permanent magnet member, and a member by another means may be provided at the other end.

The caps 21 and 22 are made of, for example, austenitic stainless steel (SUS304, 316, etc.) and aluminum alloys (Al-Cu, Al-Mg,
A plate material having a thickness of 0.1 to 1.0 mm, preferably 0.3 to 0.8 mm, made of a non-magnetic metal material such as Al-Mg-Si system) is drawn and punched using, for example, a press and a molding die. It can be formed by processing a plate material such as processing and punching. Depending on the application, the caps 21 and 2 may be used.
It is also possible to form 2 by a magnetic metal material such as SPCC, prevent leakage magnetic flux at the end, and obtain a magnetic shield effect.

A hole 25 is bored in the center of the cap 21, a small diameter portion 26 provided at the end of the shaft 23 is fitted, and both are integrally formed by means such as spot welding or soldering. The shaft 23 fixed to the cap 21 penetrates the bearing 5 provided on the flat plate-shaped flange 3 shown in FIG. 6 or 7 and projects outward, while the shaft portion 24 projecting from the cap 22 is shown in FIG. It engages with a bearing 5 provided on the shaft-equipped flange 4 shown.

Next, FIG. 2 is a cross-sectional view of an essential part showing an example of extrusion molding means of a cylindrical body constituting the permanent magnet member in FIG. In FIG. 2, 11 is a kneading chamber, 12 is a vacuum chamber, and 13
Is an extrusion molding die, which is connected in this order to form extrusion molding means. A hopper 14 is provided above the entrance of the kneading chamber 11.
And the kneading screw 15 is installed in the kneading chamber 11.
Built in. A shredder 16 is provided at the exit of the kneading chamber 11. It is also possible to form a hollow cylindrical molded body by providing the extrusion molding die 13 with a concentric core.

Reference numeral 17 denotes an extrusion screw, which is used in the vacuum chamber 12
It is provided inside. 18 is a vacuum pump, which is a vacuum chamber 12
It is connected so that the air inside can be discharged. Reference numeral 19 denotes a tapered portion, which is provided near the outlet of the vacuum chamber 12. Reference numeral 20 denotes a cutter, which is provided in the vicinity of the exit of the extrusion molding die 13 and is for cutting a cylindrical molded body described later into a predetermined length.

Next, the raw materials constituting the permanent magnet member will be described. First, ferrite particles (MO · nF) having a magnetoplumbite type crystal structure with a particle size of 0.7 to 1.5 μm.
e ₂ O ₃ : M = one or more of Ba, Sr, and Pb, n = 5
~ 6) and a mixed solution such as water and alcohol are thoroughly mixed to prepare a mud-like or ointment-like raw material. In this case, if the particle size of the ferrite particles is too small, the formability at the time of extrusion molding is lowered, while if the particle size is too large, the density of the sintered body is lowered and the magnetic properties are lowered, which is not preferable. Therefore, it is preferable to use particles having a particle size in the range of 0.7 to 1.5 μm.

If the amount of the mixed liquid added to the ferrite particles is too small, the viscosity of the raw material becomes large, the moldability at the time of extrusion molding is deteriorated, and the density of the molded body is locally varied, and at the time of sintering. In this case, cracks will be generated, which is not preferable. On the other hand, if the amount of the mixed solution added is too large, cracks occur when the molded body is dried, and high density during molding cannot be obtained, which is inconvenient. Therefore, the addition amount of the mixed solution is 1 with respect to the ferrite particles.
It is preferable to set it in the range of 0 to 30% by weight.

The ferrite particles contain methyl cellulose,
Moldability can be improved by adding an organic binder such as carboxymethyl cellulose. However, if the amount of the organic binder added is too large, cracks occur during extrusion molding, and these cracks develop during sintering, which is not preferable. Therefore, the amount of the above organic binder added to the ferrite particles is 2% by weight.
The following is preferably 0.5 to 1.0% by weight.

Further, 0.1 to 3% by weight of B is added to the ferrite particles.
By adding an oxide such as ₂ O ₃ , CaO or SiO ₂ , the density of the sintered body can be improved and the magnetic characteristics can be improved.

The raw materials prepared as described above are shown in FIG.
It is supplied into the kneading chamber 11 through the hopper 14 shown in FIG.
It is crushed through and supplied to the vacuum chamber 12. Since the inside of the vacuum chamber 12 is decompressed by the vacuum pump 18, the raw material supplied into the vacuum chamber 12 is deaerated, and the extrusion screw 17 through the taper portion 19 causes the extrusion molding die 13 to pass through.
Filled inside.

The solid cylindrical molded body extruded from the extrusion molding die 13 is cut into a predetermined size by a cutter 20 provided near the exit of the extrusion molding die 13,
It is a material for permanent magnet members. This material is then dried to remove the mixed solution and is sintered at a predetermined temperature to form a sintered body.

The sintered body formed as described above is then finished to a predetermined size after smoothing the outer peripheral surface by grinding as in the prior art. The sintered body for forming the permanent magnet member is a long cylindrical body having a large axial length dimension as compared with the diameter dimension, and the sintered body has a high hardness. Therefore, dimensional accuracy (frame etc.)
From this point of view, it is preferable that the outer peripheral surface is processed by centerless grinding. According to the above coreless grinding process, the outer diameter dimension tolerance is 2
A cylindrical permanent magnet member having a high straightness can be obtained which can be processed with high accuracy of 0 to 50 μm.

The fitting portion 8 is formed on the basis of the outer peripheral surface of the permanent magnet member 1 which is ground with high precision as described above, and the caps 21 and 22 shown in FIG. 1 are fitted to the fitting portion 8. Therefore, the shaft 23 and the shaft portion 24 and the permanent magnet member 1 are coaxial with each other.

3 and 4 are vertical sectional views showing modified examples of the caps 21 and 22 in FIG. 1, and the same parts are designated by the same reference numerals as those in FIG. First, as shown in FIG. 3A, a concave portion 27 is formed on the outer end surface of the central portion of the cap 21, and the small diameter portion 26 of the shaft 23 is fitted into the concave portion 27. Reference numeral 28 is a flange portion for positioning the shaft 23 in the axial direction.

In the structure shown in FIG. 3B, a concave portion 27 is formed in a protruding portion 29 which is bulged on the outer end surface of the cap 21,
The small diameter portion 26 of the shaft 23 is fitted. As shown in FIG. 3C, a projection 30 is integrally formed on the outer end surface of the cap 21, and the projection 30 is fitted into a recess 31 provided on the end surface of the shaft 23. Figure 4
Is an example in which the outer end surface of the cap 22 is formed flat.

FIG. 5 is a longitudinal cross-sectional view of essential parts showing the constituent members in the second embodiment of the present invention in an exploded manner, and the same portions are designated by the same reference numerals as those in FIGS. 1 and 6. In FIG. 5, reference numeral 31 denotes a bearing portion, which coaxially and integrally projects on the outer end surface of the cap 22 to accommodate the bearing 5. Next, reference numeral 32 denotes a cap portion, which is made of a non-magnetic metal material similar to that of the cap 22 and is formed into a bowl shape by sheet metal working means.

A hole 33 is formed in the center of the cap portion 32, a fitting portion 35 provided near the end portion of the shaft 34 is fitted, and both are integrally formed by a fixing means such as spot welding. The flange with shaft 4 is used. Reference numeral 36 is a flange portion for positioning, and 37 is a shaft portion. Then, when the permanent magnet member 1 is assembled in the direction of the arrow, the shaft portion 37 becomes the bearing 5
It enters and engages inside.

In this embodiment, an example in which the permanent magnet member 1 is formed in a solid cylindrical shape has been described, but a through hole having a diameter of 1 to 2 mm may be provided in the central portion. In order to provide such a small diameter through hole, the extrusion molding die 13 shown in FIG.
If a core metal having an outer diameter corresponding to the through hole is installed therein, the through hole can be formed in the molded body during extrusion molding. Further, in the case of a relatively large-diameter permanent magnet member having an outer diameter of about 15 mm or more, it is desirable to provide a through hole having a larger size. This through hole acts as a degassing port when the molded body is sintered, so it is effective in promoting the sintering in the central portion, and the through hole is provided when the outer diameter is relatively large. It is preferable.

Although the caps 21 and 22 and the shaft 23 that are fitted to both ends of the permanent magnet member 1 are made of metal material, one or both of them may be made of plastic material.

[0042]

EFFECTS OF THE INVENTION Since the present invention has the structure and operation as described above, the following effects can be obtained.

(1) Since the outer peripheral surface of the cap fitted to both ends of the permanent magnet member does not project from the outer peripheral surface of the permanent magnet member, there is no interference with the sleeve. (2) Since the permanent magnet member can be formed into a substantially solid cylindrical shape, the magnetic characteristics can be improved by the volume effect.

(3) Even in the case of a multi-pole type which is difficult to form in a magnetic field, the degree of freedom of the magnetization pattern is large, and even a small-diameter type can be easily manufactured. (4) Since the permanent magnet member is made of a ferrite-based sintered magnet material, the rigidity can be ensured even if it has a small diameter, and undesired bending does not occur.

(5) Since the caps fitted to both ends of the permanent magnet member can be easily manufactured by the sheet metal working means, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal cross-sectional view of a partially omitted main part showing a permanent magnet member according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts showing an example of extrusion molding means for a cylindrical body forming the permanent magnet member in FIG.

FIG. 3 is a vertical cross-sectional view showing a modified example of the cap 21 in FIG.

FIG. 4 is a vertical sectional view showing a modified example of the cap 22 in FIG.

FIG. 5 is a longitudinal sectional view of an essential part showing an exploded view of constituent members in a second embodiment of the present invention.

FIG. 6 is a partially omitted vertical sectional view showing an example of a conventional magnet roll.

FIG. 7 is a longitudinal sectional view of a main part showing another example of a conventional magnet roll.

[Explanation of symbols]

 1 Permanent Magnet Member 3 Flat Flange 4 Flange with Shaft 21, 22 Cap 23 Shaft 24 Shaft Part

Claims (2)

[Claims] 1. A permanent magnet member formed in a cylindrical shape and provided with a plurality of magnetic poles extending in the axial direction on an outer peripheral surface, and a hollow cylindrical sleeve made of a nonmagnetic material are arranged at both ends. In a magnet roll that is coaxially and relatively rotatably fitted via a flange, at least one end of the permanent magnet member formed with a ferrite-based sintered magnet material to the same diameter has an outer diameter of the permanent magnet member. A fitting portion having an outer diameter smaller than the dimension is provided, and a cap having a shaft portion and having an outer diameter smaller than or equal to the outer diameter of the permanent magnet member is fitted to the fitting portion by plate material processing means. A magnet roll featuring. 2. A permanent magnet member formed into a cylindrical shape and provided with a plurality of magnetic poles extending in the axial direction on the outer peripheral surface thereof, and a sleeve formed into a hollow cylindrical shape from a non-magnetic material are arranged at both ends. In a magnet roll that is coaxially and relatively rotatably fitted via a flange, at least one end of the permanent magnet member formed with a ferrite-based sintered magnet material to the same diameter has an outer diameter of the permanent magnet member. A fitting portion having an outer diameter smaller than the dimension is provided, and a cap having an outer diameter smaller than the outer diameter of the permanent magnet member and having a bearing portion is fitted to the fitting portion by plate material processing means. The shaft-equipped flange is formed by integrally fixing a cap portion formed by the plate material processing means and a shaft having a shaft portion protruding into the cap portion, and the shaft portion of the shaft-equipped flange is formed by the cap member. Magnet roll which is characterized in that engaged a bearing provided in the flop.