JPH0533802B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a magnet roller, which is a resin magnet used in a magnetic brush developing roller used in a copying machine, a printer, etc., and a mold that can be used therein. [Prior art] Magnetic rollers conventionally used in copying machines and other equipment have generally been made of isotropic or anisotropic sintered magnets or resin magnets pasted or press-fitted onto a core metal. It was spot on.
In addition, in recent years, the injection molding method has been used to
-28287 and Japanese Patent Publication No. 56-108207, which has integrated polar anisotropic orientation molding inside.
A large number of applications have been filed. However, in bonding sintered magnets in the conventional example, there were problems such as easy chipping, troublesome bonding, and high cost. Furthermore, sintered integrally molded magnets also have problems such as poor yields and poor dimensional accuracy due to quenching cracks and warping, as well as problems such as being heavy and requiring high costs due to secondary processing. Further, even when bonding resin magnets with rubber or plastic, there are still problems such as high cost due to adhesion, secondary processing, etc. For this reason, in recent years, one-piece molded magnets made of resin magnets have also appeared. However, isotropic materials currently lack magnetic force. Therefore, many attempts have been made to make magnetic rollers anisotropic. [Problems to be solved by the invention] However, since radial orientation is impossible with long, solid or hollow magnetic rollers,
Integration by applying polar anisotropic orientation or bipolar orientation, which has been attempted in motor rollers, is generally performed. Regarding polar anisotropic orientation, methods have been proposed in which a coil is placed inside or outside the mold, or a permanent magnet is placed, but these methods have the following practical problems. A method in which a coil that generates a pulsed magnetic field is built into the mold is ideal because the device is small, but because the pulse width is short, the degree of orientation does not improve and high performance cannot be obtained. . In particular, magnetic rollers for electrostatic phenomena require a high surface magnetic flux density, so a molding material with a high content of magnetic powder is used, so the apparent viscosity of the molding material is extremely high, and it must be oriented using a pulsed magnetic field. In reality, this would have been almost impossible. The method of incorporating a permanent magnet inside the mold is effective because it is relatively small in terms of equipment, but since the viscosity of the molding material is high in the magnetic roller, it is difficult to completely orient the magnetic powder. I couldn't let it go. In addition, during mass production, the molded product is strongly attracted to the mold, so if the cycle is not extended until it is completely cooled when it is released from the mold, warping and other deformations will occur, resulting in a very low yield. In terms of mass production, there were problems due to inefficiency. Regarding the method in which a coil that generates a static magnetic field is built into a mold, if the number of poles is more than two and the polar orientation is anisotropic, the arrangement of the magnetic poles in the mold can be arranged in various directions as shown in Figure 9. Since the cavities cannot be lined up on the partying line, the space required around the cavities becomes large, and a large space is also required to house the coil. In addition, the number of pieces to be produced was limited, resulting in very low productivity in mass production. When installing a coil that generates a static magnetic field outside the mold, if the magnet has more poles than a two-pole magnet and is oriented anisotropically, the magnetic pole arrangement near the cavity will be the same as above, resulting in the same problem. In addition to this, the magnetic path for connecting to the coil outside the mold spreads inside and outside the mold, so there is the problem that the space required to form one cavity becomes larger than with the internal mold type. It was hot. Therefore, since it is very difficult to produce a large number of pieces, it has the disadvantage that productivity is very poor. Furthermore, in terms of the performance of the magnetic roller, if the number of poles is greater than 4, the degree of orientation will decrease, which is a drawback of polar anisotropic orientation, and the oriented portion will only be near the surface layer.
The disadvantage is that magnetic efficiency decreases because the magnetic powder near the center is not effectively utilized. This is due to the following two major theoretical drawbacks. a○ As shown in Figure 12, as the number of poles increases, the shortest distance between adjacent magnetic pole pairs, which forms a magnetic circuit which is the principle of polar anisotropic orientation, becomes the chord connecting them over the shortest distance. The more the number of poles increases, the more the part where the magnetic field is strongly applied moves toward the outer surface relative to the center of the cavity. For this reason, in the center, there is a very weak leakage defined by the permeance between the gaps of the magnetic poles, and orientation can only be achieved by magnetic flux. Since the apparent clay content was very high, the magnetic powder could not be perfectly oriented, resulting in a decrease in properties. b○ As the number of magnetic poles further increases, the pairs of magnetic poles are no longer placed facing each other, so the lines of magnetic force do not pass through the gap in the cavity between the magnetic poles, which forms an adjacent magnetic circuit, and instead flow as shown by the arrow in Figure 13. However, there is a drawback that leakage occurs directly between the magnetic poles around the cavity. For this reason, the efficiency of the magnetic circuit within the mold has been greatly reduced. As a result, there was a drawback that the degree of orientation was lowered and the properties were lowered. Furthermore, as a method of manufacturing rotors for motors rather than for electrostatic phenomena, a method was developed in which two poles are molded and oriented in one direction, and multiple poles are used for magnetization.
38159 and Japanese Patent Application Laid-open No. 112310/1983.
It is not stated that these can solve the problem of the magnetic poles spreading in multiple directions within the mold, but it can be easily inferred by analogy. However, these conventional methods have had the following problems when producing a magnetic roller for electrostatic phenomena. (A) Magnetism is weak. In the case of polar anisotropic orientation, in order to effectively use most of the volume of the magnetic roller, it is possible to increase the degree of orientation with good magnetic efficiency even in the mold, unless the magnetic roller is particularly multipole. However, in the case of two-pole orientation multipolar magnetization, since orientation is performed using a uniformly parallel magnetic field as shown in FIG. 10, the molded product becomes as shown in FIG. 11. For this reason, in areas where the energy of each magnetic powder in the magnet roller requires a high value as surface magnetic flux, the energy of each magnetic powder in the magnet roller is not all in a straight line, but is located a little far from the magnetic pole position on the magnet. In terms of position, the direction of the magnetic path differs from the position where the surface magnetic flux density is required, so as a result, although the magnetic efficiency is similar to radial orientation and the degree of orientation is high, the vector is shifted. When magnetizing, the deviated part is not a magnetic path, so the vector shifts and each magnetic powder is not fully magnetized to the maximum value of magnetic force that it can exert, so even if it looks good at first glance, the result is has the disadvantage that it is considerably inferior to polar anisotropic orientation. (B) Distribution characteristics cannot be controlled. In addition to the above-mentioned high surface magnetic flux density, the required characteristics of a magnetic roller for electrostatic phenomena include:
What particularly affects the image characteristics is the quality of the distribution of the magnetic flux emitted into space from the magnetic roller. Although polar anisotropic orientation has no problems in this respect, it has been found that bipolar orientation and multipolar magnetized rollers have various drawbacks. In other words, as a magnetic roller, it is necessary to have uniform and straight spikes of toner in the phenomenon area, and it is also necessary to suddenly increase the surface magnetic flux density locally in the circumferential direction distribution. It is necessary by design to lower or lower it.
However, in the method of performing bipolar oriented multipole magnetization, the anisotropy direction of the magnetic powder is oriented in a single direction at the required magnetic pole position on the magnet roller, as described above. The surface magnetic flux density waveform also has a distribution uniquely determined by the magnetic powder oriented in a single direction because it is not focused to the required waveform. It was extremely difficult to control the magnet simply by changing the shape of the yoke and the strength of magnetization. Moreover, it was impossible to perform full-power magnetization and control the distribution waveform at the same time in order to increase the absolute value of the surface magnetic flux density. In other words, in a magnetic roller that applies polar anisotropic orientation, it is possible to simultaneously satisfy the surface magnetic flux density distribution and height when the number of poles is small, but industrial productivity is extremely low. There are drawbacks, such as the fact that although the productivity is high, it is impossible to produce a magnetic roller that uses two-pole oriented multi-pole magnetization, but has a high surface magnetic flux density and clear distribution characteristics. The present invention has been made in view of the above-mentioned problems, and its purpose is to make it possible to obtain strong magnetic force even with a high content of magnetic powder by oriented with a high degree of orientation, and to obtain a strong magnetic force with a high surface magnetic flux density. It is an object of the present invention to provide a method for manufacturing a magnetic roller, which can control the thickness and distribution, has a good yield, can be manufactured in large numbers, and has good productivity, and a mold that can be used therein. [Means for Solving the Problems] The above object of the present invention is to provide a plurality of magnetic pole pairs constituting three or more of magnetic pole pairs consisting of a pair of opposing magnetomotive poles and a magnetization pole in the peripheral part in a cross section perpendicular to the axis. has magnetic poles, and the magnetic poles are arranged so that straight lines connecting the magnetizing pole and the final magnetizing pole in each pair of magnetic poles are substantially parallel to each other on the cross section, and adjacent magnetic poles have different magnetisms, and , magnetic powder is oriented in a direction that converges toward the center of the magnetic peak of each magnetic pole in the peripheral part of the cross section, and in the central part of the cross section connects the magnetizing pole and the final magnetizing pole of each pair of magnetic poles. A method for manufacturing a magnetic roller oriented substantially parallel to a straight line, comprising: a. A plurality of orienting magnetic pole pairs consisting of a magnetizing pole and a magnetizing pole being oriented on one side with a roller molding cavity in between. The magnetic poles are arranged so that the final magnetic pole is lined up on the other side and correspond to the arrangement of the magnetic pole pairs of the magnetic roller, and magnetic fluxes in the same direction and substantially parallel to each other are applied to the cavity from these orienting magnetic pole pairs. A resin material containing the injected magnetic powder is molded to have magnetic poles at positions corresponding to the respective orientation magnetic poles, and the magnetic powder is directed toward the center of the magnetic peak of each orientation magnetic pole in the vicinity of each orientation magnetic pole. a step of obtaining a roller-shaped molded product that is oriented substantially parallel in a direction in which the magnetic fluxes are converged, and which are otherwise substantially parallel to each other in response to the substantially parallel magnetic flux generated from each pair of magnetic poles; b. the roller obtained in step a; This is achieved by a method for manufacturing a magnetic roller, which comprises the steps of reversing the magnetism of a part of the magnetic poles of a shaped molded product and magnetizing adjacent magnetic poles so that they are different. Moreover, the mold of the present invention that can be used in the above step a,
In order to mold a magnet roller in which a resin material containing magnetic powder is molded and oriented, a magnetomotive pole member for orientation and a final magnetization pole member for orientation are respectively provided on the left and right sides of a line passing through the center of the cross section of a cavity made of a magnetic material, and each of the above-mentioned In order to divide the magnetic pole member into at least three parts, a spacer made of a non-magnetic pole material having a longitudinal shape parallel to the center line is provided so that the longitudinal direction of each spacer is parallel to the center line of the cavity cross section, and
The tip of each spacer is arranged so as to constitute a part of the cavity, and the lines of magnetic force from the magnetomotive pole member are divided by the spacer and the magnetic powder in the cavity is divided into the magnetomotive pole and the final magnetization pole. The magnetic poles are arranged to be substantially parallel to each other in the cross section along a straight line connecting the magnetic poles, and to converge toward the center of the magnetic peak of each magnetic pole. In the method of the present invention, conventionally known resin magnet materials (ferromagnetic powder and binder) are used, but the orienting force is applied by flowing magnetic lines of force in one direction to the molded product during molding orientation. Since it is large and all of the magnetic powder in the center of the magnet roller is oriented, materials with a high content of ferromagnetic powder can be used without difficulty. In the present invention, the surface magnetic flux density of the molded product is improved by changing the material of the ferromagnetic material forming the magnetic poles for applying the magnetic lines of force for orientation, by changing the cross-sectional area of the magnetic poles, or by changing both. can be easily controlled. In other words, by changing the amount of magnetic flux passing between each magnetic pole using the method described above, and changing the volume ratio of the magnetic powder oriented due to the magnetic chain occurring at each pole inside the molded product, the surface magnetic flux density can be increased. This means that the distribution can be controlled without changing the strength of magnetization, with each pole fully magnetized, and the maximum energy of all the magnetic powder inside the magnet roller can be extracted. Hereinafter, the present invention will be specifically described with reference to the drawings. [Example] FIGS. 1 to 6 schematically show each process of an example of the present invention. Further, FIGS. 9 to 11 show conventional embodiments. Figure 1 is a drawing of the cavity in the mold that best represents the features of the present invention. In the figure, 1 and 4 are for orientation of magnetic powder made of ferromagnetic materials facing each other with the cavity in between. This is a magnetic pole (magnetic pole member) for guiding the magnetic flux from the magnetic field generating coils shown at 24 and 18 in the molding machine shown in FIG. 8 through the molding machine platen shown at 25 and 20 to the mold cavity. . Furthermore, 7, 8, 9 and 10, 11, 12 are
This is a magnetic pole portion that is integrally constructed with the magnetic poles 1 and 4 above, and is arranged to substantially face each other across a cylindrical cavity space indicated by 14. That is, magnetic pole parts 7, 8, and 9, which serve as magnetomotive poles through which lines of magnetic force flow, and magnetic pole parts 10, 11, and 12, which serve as final magnetic poles into which lines of magnetic force flow, are lined up facing each other. and 12 each form a pair of magnetic poles, and a line connecting 7 and 10,
Each magnetic pole part is arranged so that the line connecting 8 and 11 and the line connecting 9 and 12 are substantially on the same plane and are substantially parallel. Here, each magnetic pole is constructed of a ferromagnetic material as is conventionally known. Also 2, 3, 5,
6 is a spacer made of a non-magnetic material. That is, the mold of the molding machine shown in FIG. 8 is characterized by having a pair of magnetic poles 1 and 4 facing each other with the cavity in between, and having a magnetic pole part separated by a spacer made of a non-magnetic material at the end on the cavity side. There is. By having such a configuration in the mold, it becomes possible to distribute and arrange the magnetic pole parts on both sides of the parting part in the molding machine, creating extra space along the parting surface in the molding machine, and making it possible to By using this method, a large number of cavities can be parallelized to enable multi-cavity production. In such a configuration, 18,
When a current is applied to the magnetic field generating coil 24, the magnetic flux (magnetic field lines) generated there passes through the movable molding machine platen 20, and is transferred from the magnetic pole 1 made of the ferromagnetic material in the mold to the magnetic flux 2, It is divided into 8 and 9 magnetic pole parts (magnetic poles), flows into 14 cavities, and flows according to the permeance distribution between the gaps as shown at 13 in Figure 1, and the opposing 10, 11, 1
The current flows to gather at the second magnetic pole (final magnetic pole). The magnetic flux passes through the magnetic pole 4, the fixed platen shown at 25 in FIG. 8, and the tie bar shown at 19.
It is configured to be a closed loop. With the magnetic flux forming a closed loop as described above, when molten resin magnet material (ferromagnetic powder and binder) is injected into the 14 cavities, the magnetic flux shown in Fig. 2 is obtained. The orientation of the powder 15 occurs according to the flow of magnetic field lines shown in FIG. As shown in Figure 1, the lines of magnetic force spread inside the cavity and converge at the magnetic pole, so
The magnetic powder is also oriented in a converged state at the magnetic pole portion, as shown in FIG. Because of this orientation, the magnetic powder inside the molded product is effectively used and the lines of magnetic force are concentrated at desired positions of the molded product, so that a magnetic roller with a high surface magnetic flux density and strong magnetic force can be obtained. When the magnetic powder is cooled and solidified while maintaining its orientation as shown in FIG. 2, and taken out, a molded article shown in FIG. 3 is obtained. At this time, the distribution of surface magnetic flux density of the molded product shown in FIG. 3 becomes as shown in the upper part of FIG. 5. Next, using a conventionally known magnetizer mainly consisting of a yoke 16 and a magnetizing coil 17 as shown in FIG. 6, the molded product shown in FIG. If you match the N-pole (magnetizing pole) applying part of the magnetizer to the magnetic pole (magnetic pole) and the S-pole applying part of the magnetizer to the middle N pole on the right side, magnetize while applying a sufficiently strong current. The S and N poles of the molded product are reversed, and a magnetic roller is obtained in which the S and N poles are alternately magnetized on the peripheral surface of the molded product, as shown in the lower part of FIG. That is, the magnetism of some of the magnetic poles of the molded product is left intact and used, and the magnetism of other magnetic poles is reversed to form a desired magnetic pole arrangement. The surface magnetic flux density distribution of the molded product shown in the lower row of FIG. 5 is as shown in FIG. 4. Four-pole and six-pole plastic magnet rollers were created using the method described above and evaluated. The evaluation is compared with the typical specifications generally required for a copying machine roller, which has a maximum surface magnetic flux density of 900 [G] or more and a width at half-life of 60% or less. Note that the half-life time width is expressed by the following formula using A and B shown in FIG. Width at half-life = (A/B) x 100 [%] (The larger this value is, the wider the waveform is) As test 1, the 4-pole magnetic roller of the present invention, the conventional polar anisotropically oriented product, and the 2-pole The oriented products were tested, and as Test 2, the 6-pole magnetic roller of the present invention, the conventional polar anisotropically oriented product, and the bipolar oriented product were tested, and the results are shown in Tables 1 and 2.
All samples were made using a well-known plastic magnet material mixed with 90wt% strontium ferrite, and the mold temperature was 110%.
Two types of magnetic rollers with a diameter of 20 mm and 14 mm were manufactured by injection molding at a molding temperature of 280 °C.

【table】

〔Effect of the invention〕

As explained above, according to the method for manufacturing a magnetic roller of the present invention, all of the magnetic pole parts in the mold have a magnetic pole structure in which they face each other in substantially the same direction, so that there is sufficient space along the parting surface. It is easy to produce a large number of pieces, and productivity can be increased by 3 to 6 times. In addition, since the orientation magnetic flux is focused where the magnetic force is needed, and the vector of the easy axis of magnetization of the magnetic powder (the central axis of the magnetic powder that is oriented along the lines of magnetic force) is focused, the characteristics of the surface magnetic flux density are Significant performance improvements are achieved. In addition, since a demagnetizing process is not required, a demagnetizing device is not required, resulting in good productivity. In addition, by changing the amount of magnetic flux passing between the magnetic pole parts and changing the volume ratio of the magnetic powder used, it is possible to control the distribution of surface magnetization density in a fully magnetized state. is possible.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the vicinity of the cavity of the mold of the present invention, Fig. 2 is a sectional view of the resin magnet material injected and oriented into the cavity, and Fig. 3 is a sectional view of the magnet roller after being removed from the mold. , Fig. 4 is a cross-sectional view of the magnet roller after magnetization, Fig. 5 is a magnetic flux distribution graph on the circumferential surface of the magnet roller (the upper part of Fig. 5 shows the magnetic flux distribution after molding,
The lower row shows the magnetic flux distribution after magnetization), the sixth
The figure is a schematic diagram of the magnetizer, and Figure 7 is the same as Figure 2.
FIG. 8 is a schematic diagram showing the magnetic field injection molding apparatus and mold part used in this example, FIG. 9 is a schematic diagram showing the orientation method using conventional polar anisotropic orientation molding, and FIG. The figure is a schematic diagram explaining bipolar orientation.
Figure 1 is a cross-sectional view of a magnetic roller obtained by demagnetizing and re-magnetizing a bipolar oriented product, Figure 12 is a cross-sectional view of a polar anisotropically oriented product, and Figure 13 is a cross-sectional view of a magnetic roller produced by conventional polar anisotropically oriented molding. FIG. 14 is a diagram illustrating the half-width, and FIG. 15 is a schematic diagram showing the part where the magnetic roller is attached to the developing machine. 1, 4...Magnetic pole (magnetic pole member) (1 is the magnetizing pole member, 4 is the final magnetizing pole member), 2, 3, 5, 6
... Spacer (non-magnetic material), 7, 8, 9... Magnetic pole part (magnetic pole), 10, 11, 12... Magnetic pole part (final magnetic pole),
13...Flow of magnetic flux (lines of magnetic force), 14...Mold cavity, 15...Magnetic powder, 16...Yoke, 17...
Magnetizing coil, 18, 24... Magnetic field generation coil, 2
0...Movable side molding machine platen, 21...Fixed side mold,
23... Movable side mold, 25... Fixed side molding machine platen, 26, 27, 28... Magnetic pole.

Claims (1)

[Scope of Claims] 1. A plurality of magnetic poles constituting three or more of magnetic pole pairs consisting of a pair of opposing magnetomotive poles and a magnetization pole, are provided in a peripheral portion in a cross section perpendicular to the axis, and the magnetic poles are , straight lines connecting the magnetizing pole and the final magnetizing pole in each pair of magnetic poles are arranged so that they are substantially parallel to each other on the cross section, and adjacent magnetic poles have different magnetisms; It is oriented in a direction that converges toward the center of the magnetic peak of each magnetic pole in the peripheral part, and in the central part of the cross section, it is almost parallel to a straight line connecting the magnetizing pole and the final magnetizing pole of each pair of magnetic poles. A method for manufacturing an oriented magnetic roller, comprising: a. A plurality of pairs of orienting magnetic poles each consisting of a magnetomotive pole and a final magnetization pole, with the magnetomotive pole on one side and the final magnetization pole on the other side with a roller molding cavity in between. A resin containing magnetic powder, which is arranged so that the magnetic poles are aligned and corresponds to the arrangement of the magnetic pole pairs of the magnetic roller, and is injected into the cavity while applying magnetic flux in the same direction and substantially parallel to each other from the orienting magnetic pole pairs. Molding a material, having a magnetic pole at a position corresponding to each orientation magnetic pole, and in a direction in which the magnetic powder converges toward the center of the magnetic peak of each orientation magnetic pole in the vicinity of each orientation magnetic pole; The part includes a step of obtaining a roller-shaped molded product that is oriented substantially parallel in response to the nearly parallel magnetic flux generated from each pair of magnetic poles, and (b) a part of the magnetic pole of the roller-shaped molded product obtained in step a. 1. A method for manufacturing a magnetic roller, comprising the step of reversing the magnetism of the magnetic roller and magnetizing adjacent magnetic poles so that they are different from each other. 2. In order to mold a magnet roller in which a resin material containing magnetic powder is molded and oriented, a magnetizing pole member for orientation and a final magnetizing pole member for orientation are respectively provided on the left and right sides of a line passing through the center of the cross section of a cavity made of a magnetic material, and the above-mentioned. In order to divide each magnetic pole member into at least three parts, a spacer made of a non-magnetic pole material having a longitudinal shape parallel to the center line is provided so that the longitudinal direction of each spacer is parallel to the center line of the cavity cross section, and
The tip of each spacer is arranged so as to constitute a part of the cavity, and the lines of magnetic force from the magnetomotive pole member are divided by the spacer and the magnetic powder in the cavity is divided into the magnetomotive pole and the final magnetization pole. A mold for molding a magnetic roller, characterized in that the cross section is substantially parallel to each other along a straight line connecting the magnetic poles, and converges toward the center of the magnetic peak of each magnetic pole.