JPH0376764B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magnetic brush developing roller or a magnetic brush used as a conveying means for magnetic developer in a dry image reproducing apparatus such as an electrophotographic copying machine, a facsimile machine, or a printer. This invention relates to a magnetic roller such as a cleaning roller and its manufacturing method.

(Prior art) As shown in FIG. 7, a conventional molded magnet roller is formed by insert-molding a core shaft 1 with magnet powder 2 to form a circular magnet roller, and locally anisotropically orients the axis of easy magnetization. It has been proposed that the magnetic pole 3 is formed on the circumferential surface of the magnet by magnetization (Japanese Patent Application Laid-open No. 108207-1983).

Although this magnet roll has the advantages of being easy to manufacture and magnetically homogeneous, it also has the following problems.

In other words, the width of the magnetic pole 3 extends not only to the magnetized area but also to a certain extent on both sides, and as the width of the magnetic pole 3 increases and the boundary becomes blurred, the magnetic pole position of the magnetic roller is limited to a predetermined range. It was difficult to do so, and the magnetic flux density decreased accordingly. In addition, when magnet powder orients the axis of easy magnetization, the lines of magnetic force are oriented in the magnetic field through a free curved path from one magnetic pole N to the opposite magnetic pole S, and are not concentrated in one direction, resulting in magnetic anisotropy. Improvement in sexual performance was still insufficient.

This is because expensive magnetic powder is used in the intermediate region 4 between the magnetic poles 3 and 3 on the circumferential surface of the magnetic roller and in its vicinity, although almost no lines of magnetic force pass through it and it does not function as a magnetic roller. , it was a waste of material.

Furthermore, the conventional equipment for manufacturing the above-mentioned molded magnet roller has a magnet roller cavity 5 as shown in FIG.
An injection mold 6 is used, with magnetic members 7 at the locations corresponding to the magnetic poles and non-magnetic members 8 at other locations.
Each magnetic member 7 has an electromagnetic yoke 9.
It is connected to. The magnetic roller is manufactured by inserting the core shaft 1 into the cavity 5, injecting magnet powder, which is a molten mixture of ferromagnetic powder and thermoplastic resin, into the cavity, and simultaneously energizing each electromagnetic coil at the same time. A magnetic field was generated in the yoke, and the magnetic field was oriented along a magnetic path from one magnetic pole N to the opposite magnetic pole S.

This magnetic roller manufacturing method requires a strong electromagnetic coil 10 to generate a magnetic field independently for each yoke.
Therefore, it was unreasonable in terms of space to arrange a plurality of large electromagnetic coils 10 in a narrow space around the mold of an injection molding machine.

(Problems to be Solved) The present invention is a shaped magnet roller, which is an anisotropic magnet roller in which the magnetic poles can be limited to a predetermined range and the magnetic field orientation is concentrated in one direction.

The present invention further discloses a method of manufacturing a magnetic roller that can orient the magnetic field to all magnetic poles of the magnetic roller using only two yokes, and that can impart magnetic anisotropy concentrated in one direction to each magnetic pole.

(Means for Solving the Problems) The magnet roller of the present invention is insert-molded with a core shaft 1 of a magnetic material and a magnet powder compact 2, and the magnet powder compact is inserted into a thin film that covers the core shaft. It is composed of a boss portion 11 and a plurality of magnetic pole protrusions 12 that protrude radially over a predetermined angular range of the boss portion.

To manufacture the magnetic roller, molds 13 and 14 having the magnetic roller cavity 5 are attached to a pair of electromagnetic yokes 15 and 16 that can be moved closer to each other.
The space between each magnetic pole protrusion tip 17 and the yokes 16, 16 is made of magnetic material, and the other parts are made of non-magnetic material 8 to form a magnetic path between the yoke and the magnetic pole protrusion tip 17, A magnetic core shaft 1 is inserted and supported in the mold, and a molten mixture of ferromagnetic powder and a polymer compound is injected into the cavity of the mold to insert mold the core shaft 1, and during injection or injection. When the molten mixed material is still in a molten state in the cavity, a magnetic field is generated between the yokes 15 and 16, and the axis of easy magnetization of the ferromagnetic powder in the magnetic pole piece 12 is moved from the tip of the magnetic pole piece to the base. A magnetic field is oriented toward the end, and after the resin has solidified, a magnetic field in the opposite direction is generated between the yokes to demagnetize the molded body, and the molded body is taken out of the mold and each magnetic pole protrusion piece is magnetized.

(Function) When the magnetic roller of the present invention is anisotropically oriented, the lines of magnetic force are one yoke 15 → the magnetic material 7 of one mold 13 → one magnetic pole protrusion 12 → the core axis 1 → the other magnetic pole protrusion. The pieces 12 → the magnetic material 7 of the other mold 14 → the other yoke 16 → the yoke 15 are passed in this order to form a magnetic closed circuit, and the axis of easy magnetization of the ferromagnetic powder in the magnetic pole piece is aligned in the direction of the lines of magnetic force. Orient it so that it matches.

The magnetic circuit resistance is large in the boss portion 11 because the passage width is narrow. On the other hand, since the core shaft has a large diameter and low resistance, most of the magnetic lines of force pass from the magnetic pole protrusion 12 through the core shaft 1 as shown in Figure 4, and the orientation of the axis of easy magnetization is based on the tip of the magnetic pole protrusion. Strong anisotropy concentrates in one direction toward the edge.

The lines of magnetic force of the magnetized roller come to pass from the tip 17 of the magnetic pole protrusion through the core shaft 1 to the opposite magnetic pole as shown in Fig. 5, and the lines of magnetic force are concentrated in one direction within the magnetic pole protrusion. , a magnetic field is generated only at the tip of the protrusion.

(Effect) The magnetic roller generates a magnetic field only at the tip of the magnetic pole protrusion 12, and there is no magnetic field generated from other places, so the boundary between the magnetic poles is clear, and the magnetic field is concentrated to that extent, resulting in a strong magnetic effect. can demonstrate.

In addition, the orientation of the axis of easy magnetization is achieved at once by a pair of electromagnetic coils for a large number of magnetic poles, and there is no need to arrange an electromagnetic coil for each magnetic pole as in the past, so the equipment is inexpensive and easy to implement. can.

(Example) The drawings and the following description are for illustrating the present invention, and are not intended to be interpreted as narrowly limiting the invention.

Figure 1 shows the toner case 18 of an electronic dry copying machine.
The present invention is implemented in a magnetic roller 19 therein, and as is well known, a case 18 containing toner is placed close to a drum 20 on which an electrostatic latent image is formed. Toner case 18
Inside are a non-magnetic rotating roller 21 and a magnetic roller 1.
9 are arranged concentrically, the magnetic roller 19 is fixed to the case, and the rotating roller 21 is driven by a drive device (not shown).
The drum 20 rotates in synchronization with the drum 20.

The toner is attracted to the magnetic poles of the magnetic roller, stands in spikes on the circumferential surface of the non-magnetic rotating roller 21, and is conveyed as the roller rotates. During conveyance, the height of the toner spikes is made uniform by the doctor knife 22, and when the spikes rub the surface of the drum 20, a portion of the toner transfers to the cylinder surface, and the remaining toner is transported downstream. It is peeled off from the roller surface by a doctor knife 23 .

Although the above structure is known, the present invention has the magnet roller 19 in the shape shown in FIG.
What is new is that magnetic field orientation is performed using the equipment shown in Figure 3.

The core shaft 1 of the magnet roller 19 is made of a magnetic material such as free-cutting steel, and may be formed into a shaft shape or a hollow pipe shape as required.

The molded body of magnet powder 2 is formed by insert molding the core shaft 1, and at the same time, the axis of easy magnetization is oriented from the tip to the base end of the magnetic pole protrusion 12, resulting in magnetic anisotropy. Each piece 12 is magnetized to a predetermined polarity and strength.

Magnet powder 2 is a ferromagnetic powder such as ferrite magnet powder such as Sr-ferrite, alloy magnet powder such as rare earth-transition metal, or other ferromagnetic material with a large magnetic anisotropy constant such as Mn-Al-C magnet powder. Powder is used, and the blending amount is preferably 80% by weight or more.

The binder resin to be kneaded with the ferromagnetic powder is
Any thermoplastic resin such as polyethylene, polyvinyl chloride, polyamide, or thermosetting resin such as epoxy resin or phenolic resin can be used as long as it can firmly bind the magnet powder in a small amount.

Additives such as organic silicon compounds and organic titanate compounds are added as lubricants if necessary.

The number, position, width, and polarity of magnetic poles to be formed on the surface of the magnetic roller 19 vary depending on the specifications of the copying machine. In the example shown in FIG. 5, N ₁ ,
Give the polarity of S ₁ , N ₂ , S ₃ , S ₂ , the width is 12 mm for N ₁ ,
Others are 6mm. The position of each magnetic pole is based on the straight line connecting the center of the core axis and the center of magnetic pole N ₁ , and the angle made by the center of the magnetic pole is 71° for S ₁ , 150° for N ₂ , 185° for S ₃ ,
S ₂ is −82°.

The diameter of the core shaft 1 is 21 mm, and the thickness of the boss part 11 is 2.5 mm.
mm, N The tip 17 of the magnetic pole piece 12 constituting the ₁ pole is
It is a circular arc surface or plane concentric with the core axis 1, and the radius length from the center of the core axis is 15.0 mm, but the other magnetic poles are
_N Make the rotating roller 21 1 to 2 mm shorter than the 1st pole.
Appropriately weaken the magnetic field acting on the surface.

The shaping of the magnetic roller and the magnetic field orientation are performed in the second
This is carried out using a known magnetic field injection molding machine (Model TSD 100 manufactured by Nissei Jushi Kogyo Co., Ltd.) shown in Figs.

Although not shown, the molding machine includes an upper yoke 15 and a lower yoke 16 that are magnetically connected to each other at a position outside the magnetized space, and an electromagnetic coil 24 that generates a strong magnetic field between the upper and lower yokes. One yoke, for example, the upper yoke 15, is provided so as to be able to slide within the electromagnetic coil 24, and moves toward and away from the lower yoke.

A base plate 25 made of a magnetic material and injection molds 13 and 14 are attached to opposing surfaces of each yoke 15 and 16, respectively. The molds 13 and 14 have mold surfaces that form the magnet roller cavity 5, and both ends of the core shaft 1 are inserted and supported by members 27 and 27 formed of a non-magnetic material. Also, on the side of the mold,
An injection molding machine that uses magnetic powder as raw material will be installed.

The upper and lower molds 13 and 14 are made of a non-magnetic material 8, and the parts between the mold surface 26 corresponding to the tip 17 of the magnetic pole protrusion of the magnet roller cavity and the base plates 25 and 25 are made of a magnetic material, respectively. 7, and constitutes a magnetic path from the yoke to the tip 17 of the magnetic pole protrusion.

To mold the magnetic roller, first, the magnetic powder melted in the cylinder 28 of the injection molding machine is passed through the nozzle 29,
It is injected from the runner 30 into the cavity 5. The magnetic powder is inserted into the core shaft 1 and formed into the shape of a magnetic roller, filling the cavity.

Before injection or when the magnet powder in the cavity is still in a molten state and the ferromagnetic powder can move freely, the electromagnetic coil 24 is energized to close the yokes 15 and 16.
A magnetic field with a strength of 10KOe or more is generated between the two.

Upper yoke 15 → base plate 25 → member 7 → all magnetic pole protrusions 12 in the upper mold → core shaft 1 → all magnetic pole protrusions 12 in the lower mold → member 7 → base plate 25 → lower yoke 16
→Since a magnetic closed circuit is formed around the upper yoke 25, a strong magnetic field can be generated, and the ferromagnetic powder in each magnetic pole piece 12 is concentrated in one direction from the tip to the base. orientation of the easy axis of magnetization. When the resin solidifies, the orientation is fixed and the magnet becomes anisotropic.

At this point, the molded magnetic roller is attracted to the mold and cannot be separated, so the magnet roller is demagnetized by passing a current in the opposite direction to the magnetic field orientation to the electromagnetic coil 24 to prevent it from adhering to the mold. remove.

Next, the rod 30, which is driven by a hydraulic system (not shown), is raised from the lower yoke 16 side, and the knockout pins 32, 32 attached to the magnetic member 31 at the tip of the rod protrude. Remove the magnetic roller from the mold.

The removed magnet roller 19 is completed by magnetizing each magnetic pole protrusion 12 as is well known.

Since the magnetic roller of the present invention is formed to have strong anisotropy, the surface magnetic flux density appearing at the tip of the magnetic pole protrusion is large, and is as follows.

N ₁ is 800G N ₂ is 600G S ₁ is 700G S ₂ is 700G S ₃ is 600G It goes without saying that the present invention is not limited to the above description and drawings, and many modifications can be made. be.

For example, the molds 13 and 14 should have a split structure;
The injection magnetic field forming machine can be a rigid type, and the magnetizing machine can be a horizontal type.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a state in which a magnetic roller is applied to a developing magnetic brush roller for a copying machine, Fig. 2 is a front sectional view of the manufacturing equipment, Fig. 3 is a sectional view taken along the - line in Fig. 2, 4 is a front sectional view of the magnetic orientation process, FIG. 5 is a front view of a magnetic roller, FIG. 6 is a front sectional view of conventional manufacturing equipment, and FIG. 7 is a front view of a conventional magnetic roller. DESCRIPTION OF SYMBOLS 1... Core shaft, 19... Magnet roller, 2... Magnet powder, 21... Rotating roller, 11... Boss part, 2
4... Electromagnetic coil, 7... Magnetic member, 8... Non-magnetic member, 12... Magnetic pole protrusion, 13, 14...
Upper and lower molds, 15, 16...upper and lower yokes.

Claims (1)

[Scope of Claims] 1 Consists of a magnetic core shaft 1 and a magnet powder molded body 2 in which the core shaft is insert-molded, and the molded body 2 has a thin boss portion 11 that covers the core shaft. A plurality of magnetic pole protrusions 12 are provided that protrude radially over a predetermined angular range of the boss portion, and each magnetic pole protrusion is magnetically anisotropically arranged and magnetized from the tip to the base end. Molded magnet roller. 2 A pair of electromagnetic yokes 15 and 16 that can be moved closer and closer to each other
Molds 13 and 14 each having a cavity for a magnet roller from which a plurality of magnetic pole protrusions protrude radially are installed, and the molds are made of a magnetic material or other material between the tip 17 of each magnetic pole protrusion and the yoke. The part is formed of a non-magnetic material to form a magnetic path between the yoke and the tip of the magnetic pole protrusion, insert and support the magnetic core shaft 1 in the mold, and insert it into the cavity of the mold. The molten magnet powder is injected and the core shaft is insert-molded, and the yokes 15, 1 are formed during injection or when the injected molten magnet powder is still in a molten state in the cavity.
A magnetic field is generated between 6 and 6 to orient the easy magnetization axis of the ferromagnetic powder in the magnet powder in the magnetic pole protrusion 12 from the tip to the base of the magnetic pole protrusion, and after the magnet powder is solidified, the yoke A method for producing a magnetic roller, characterized in that a magnetic field in the opposite direction is generated between the molded bodies to demagnetize the molded body, the molded body is taken out from the mold, and each magnetic pole protrusion piece is magnetized.