JPH11144947A - Magnet roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a large dispersion of magnetic flux density in the longitudinal direction of a magnet roll from occurring, by providing a taper from one side to the other side in the longitudinal direction of a magnet roll body in the magnet roll. SOLUTION: A magnet roll 1 is integrally formed with a magnet material, wherein reducing shafts 3 and 4 are formed to protrude from both sides of a roll body 2 with circular cross-section, a notch 5 for positioning or transmitting a driving force is formed on the shaft 3. Difference X-Y between external diameter dimension X in one side and external diameter dimension Y in the other side of the roll body 2 is set to 0.01-0.3 mm, and connecting the both sides enables a taper to be formed from one side to the other side of the roll body 2. Shaft centers in the both sides of the roll body 2 are set to align each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnet roll used for an electrophotographic developing device such as a copying machine, a facsimile, a printer, and the like, and a magnet roll used for other purposes.

[0002]

2. Description of the Related Art When forming the above magnet roll, for example, as shown in FIG. 7A, a molten magnet material is injected into a split mold 22 composed of a movable mold 20 and a fixed mold 21. After the injected molten magnet material is solidified, the movable mold 20 is moved away from the fixed mold 21,
As shown in FIG. 7B, the formed magnet roll 1 is taken out by projecting the projecting pins 23. Numeral 10 shown in the figure is a magnetic field orienting means for aligning the directions of the magnetic particles of the filled molten magnet material. And the magnet roll 1 formed by the injection molding or the like
As shown in FIG. 6 (a), the roller body 2 includes shaft portions 3 and 4 located at both ends of the roll body portion 2, respectively. Fig. 6 shows the magnetic flux density
As shown in (b), it was found that the magnetic flux density gradually decreased from one end to the other end in the longitudinal direction of the roll body 2. At this time, the variation width h of the magnetic flux density in the longitudinal direction of the roll main body 2 is as large as 80 G, and there is a problem that a density difference appears at both ends of the image.

[0003] As described above, the large variation in the magnetic flux density in the longitudinal direction of the magnet roll occurs because the molten magnet material injected from one end of the mold comes into contact with the inner surface of the mold near the injection port early. Because it will be hardened, the orientation of the magnetic particles in that part cannot be sufficiently exerted,
The magnetic particles cannot be oriented as desired. As a result, the magnetic flux density in the vicinity of one end of the formed magnet roll is extremely reduced, and the above-mentioned inconvenience occurs.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has an object to solve the problem by suppressing a large variation in magnetic flux density in a longitudinal direction of a magnet roll. .

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a roll body portion and shaft portions located at both ends of the roll body portion, and a mold is filled with a molten magnet material. And a taper is provided from one end to the other end in the longitudinal direction of the roll main body. By providing the taper, the diameter of the roll body increases toward one end. From this, since the amount of the molten magnet material gradually increases and the magnetic flux density can gradually increase, the taper angle (the angle between the horizontal plane and the taper surface) is adjusted in accordance with the gradient of the increase and decrease of the magnetic flux density distribution. ), The magnitude of the magnetic flux density can be aligned in the longitudinal direction of the roll body at the developing action position (sleeve surface), and the amount of increase or decrease in the magnetic flux density can be adjusted in the longitudinal direction of the roll body. Can be kept small. Further, the magnetic flux density can be increased only at one end.

[0006] By forming the taper so that the cross-sectional shape in the direction perpendicular to the longitudinal direction of the roll main body is circular, and the diameter becomes larger as the magnetic flux density becomes lower in the longitudinal direction of the roll main body. Since the amount of the molten magnet material on the low magnetic flux density side can be increased, the value can be made equal to or close to the value on the high magnetic flux density side.

The difference in outer diameter of the roll body is 0.01 mm.
Preferably, it is set to 0.3 mm. If an outer diameter difference of more than 0.3 mm is provided, molding failure occurs, magnetic flux density is reduced, and the magnetic flux density width in the longitudinal direction is increased.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a magnet roll according to the present invention. The magnet roll 1 is formed by projecting shaft portions 3 and 4 having reduced diameters at both ends of a roll body 2 having a circular cross section. A notch 5 for positioning or driving force transmission is formed in the portion 3 and is integrally formed using a magnet material. Then, as shown in FIG. 2A, the outer diameter X of one end of the roll body 2 is set to 13.5 mm, the outer diameter Y of the other end is set to 13.7 mm, and both ends are connected to each other. It is configured such that a taper is formed from one end to the other end of the roll body 2. The axial centers at both ends of the roll body 2 are set so as to be located on the same line. By providing the taper in this manner, the amount of the magnet material increases in the other end portion and in the right side in the figure, and as shown in FIG. 2B, the change width H of the magnetic flux density in the longitudinal direction of the roll body 2 is 40 G It is possible to do the following. By setting the outer diameter difference between the both ends to 0.2 mm, the variation width H of the magnetic flux density is set to 40 G or less. However, the outer diameter difference is considered in accordance with the change in the magnetic flux density. .01mm
It will be set to 0.3 mm. In addition, as the magnet roll 1, the roll part 2 is not a cylinder but a polygonal pillar, the other shaft part 4, the one in which the notches 5 are formed in both shaft parts 3, 4, or the magnet part 1 The present invention can be similarly applied to a case in which the center of the shaft and the center of the shafts 3 and 4 are intentionally decentered.

The magnetic material constituting the magnet roll 1 is mainly composed of a magnetic powder and a binder for binding the magnetic powder, and a silane-based or titanate-based coupling agent for strengthening the bond, A mixture containing a small amount of a lubricant to improve fluidity, a stabilizer to prevent thermal decomposition of the binder, etc.It is also possible to add a flame retardant, a reinforcing agent, etc. if necessary. , Rare earth (SmCo, NdFeB)
System), MnAIC system, alnico system, SmFeN system, etc., and as the binder, a thermoplastic resin, a thermosetting resin, a low melting point alloy or the like can be used.

The magnet roll 1 is used as a developing roll and a cleaning roll in an electrophotographic developing device such as a copying machine, a facsimile, and a printer, but can be used for other purposes.

The outline of the apparatus for manufacturing the magnet roll 1 will be described below. As shown in FIGS. 3 to 5, a cylindrical fixed-side main forming die 6 for forming the roll body 2 of the magnet roll 1 is provided. A movable end forming die 7 for forming the shaft portion 3 of the magnet roll 1 which is disposed at one end of the main forming die 6 and is disposed in the main forming die 6 so as to be able to move back and forth. In addition, with the filling of the molten magnet material into the molding space 9 formed by the main mold 6, it moves to the retreat side to form the end of the magnet roll 1, that is, the shaft 4. And a slide die 8 for forming a magnet roll. There is provided a magnetic field orientation means 10 for aligning the direction of the magnetic particles during a period until the molten magnet material provided in the main mold 6 and filled in the molding space is solidified. As the magnetic field orienting means 10, various existing configurations such as a permanent magnet, an electromagnet, or a combination thereof can be used. The molten magnet material is supplied from an injection cylinder (not shown) into the molding space via the injection port 11 shown in the drawing.

Next, a method of forming the magnet roll 1 will be described. First, as shown in FIG.
Is driven to move the slide die 8 to the forward position. As the actuator 14, for example, an air compressor, a hydraulic cylinder, a pneumatic cylinder, a screw screw, a rack and pinion gear, a linear motor, or the like can be used. Next, as shown in FIG. 4, the injection cylinder is driven to inject and inject the molten magnet material into the molding space 9 through the injection port 11 shown in FIG. The molten space is filled with the molten magnet material while the slide die 8 is retracted to the retracted position by the combined force with the driving force. When a hydraulic cylinder is used as the actuator 12, the working oil is leaked while being throttled to apply a braking force to the backward movement of the slide die 8, so that the molding space is filled with the molten magnet material without gaps. It is possible to go. However, a braking force applying means for applying a braking force by friction or the like may be provided to apply the braking force when the slide die 8 moves backward. Further, the slide die 8 may be retracted while applying a braking force by the actuator 12 according to the injection and injection speed of the molten magnet material.
Further, when the molten magnet material is filled, the driving by the actuator 12 may be stopped. The molding space 9
During the period until the molten magnet material filled in the inside is solidified, the directions of the magnetic particles are aligned by the magnetic field orientation means 10. The shape of the slide die 8 is as follows.
Although it may be straight, an elastic heat-resistant rubber or heat-resistant resin may be attached to the tip of the slide mold in order to fit into the tapered molding space.

As shown in FIG. 5, after the molten magnet material injected and solidified is solidified, the main mold 6 is moved away from the end mold 7, and the slide mold 8 is advanced to move the magnet roll. One is disengaged. The end molding 7 may be moved away from the main molding 6.

In the above embodiment, the shaft portion and the roll portion are integrally formed. However, the present invention is also applicable to a shaft insert type magnet roll in which a metal or synthetic resin shaft is inserted. be able to.

In the above embodiment, the magnet roll 1 formed by using the slide die 8 is detached from the main forming die 6, but the slide die 8 may be omitted. That is, as shown in FIG. 7A, a split mold including a movable mold and a fixed mold is used,
The magnet roll 1 formed in this split mold may be separated from the fixed mold by moving the movable mold, and then the magnet roll 1 may be ejected by the ejecting pin. In this case, the inner surface of the split mold is formed to be tapered.

[0016]

According to the first aspect of the present invention, since the amount of the molten magnet material can be adjusted by providing the taper, the magnitude of the magnetic flux density can be aligned in the longitudinal direction of the roll body. It is possible to reduce the amount of increase and decrease of the magnetic flux density in the longitudinal direction of the roll body,
It is possible to reliably avoid troubles such as a difference in density at both ends of an image. Another advantage is that the magnetic flux density can be increased only at one end.

According to the second aspect, the taper is formed so that the diameter becomes larger as the magnetic flux density becomes lower in the longitudinal direction of the roll main body, thereby increasing the amount of the molten magnet material having the lower magnetic flux density. Because you can
The magnetic flux density can be set to a value equal to or close to the higher magnetic flux density, and the magnetic flux density in the longitudinal direction can be made uniform over the entire area.

[Brief description of the drawings]

FIG. 1 is a perspective view of a magnet roll.

2A is a side view of the magnet roll, and FIG. 2B is a graph showing the magnetic flux density of the magnet roll of FIG.

FIG. 3 is a schematic cross-sectional view showing a main part of a manufacturing apparatus showing a state immediately before pouring a magnet material.

FIG. 4 is a schematic cross-sectional view of the manufacturing apparatus showing a state in which the injection of the molten magnet material is completed.

FIG. 5 is a schematic cross-sectional view of the manufacturing apparatus showing a state where a formed magnet roll is detached.

6A is a perspective view showing a conventional magnet roll, and FIG. 6B is a graph showing the magnetic flux density of the conventional magnet roll shown in FIG.

7A is a cross-sectional view schematically showing a manufacturing apparatus for manufacturing a conventional magnet roll, and FIG. 7B is a view showing a state where the magnet roll formed by the manufacturing apparatus of FIG. Sectional drawing which shows the outline of an apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnet roll 2 Roll body part 3, 4 Shaft part 5 Notch part 6 Main molding die 7 End molding die 8 Slide die 9 Molding space 10 Magnetic field orienting means 11 Inlet 12 Actuator H, h change width

Claims (3)

[Claims] 1. A magnet roll comprising a roll body portion and shaft portions located at both ends of the roll body portion, wherein the magnet roll is formed by filling a molten magnet material in a mold, wherein the length of the roll body portion is A magnet roll characterized in that a taper is provided from one end to the other end in the direction. 2. The taper is formed such that a cross-sectional shape in a direction orthogonal to a longitudinal direction of the roll main body is circular, and the diameter becomes larger as the magnetic flux density becomes lower in the longitudinal direction of the roll main body. The magnet roll according to claim 1. 3. The difference in outer diameter of the roll main body is 0.01 m.
3. The magnet roll according to claim 2, which is set to have a length of m to 0.3 mm.