JPH0234817Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of use This invention relates to a molding device for anisotropic ferrite magnets, which increases the difference in the magnetic properties of both planes of an annular anisotropic ferrite magnet, and increases the magnetic properties of one plane side. The present invention relates to a molding device that can improve the properties of the molded product, prevent micro-cracks, etc. in the sintered body, and significantly improve the crushing strength of the molded body. BACKGROUND ART A molding device that is commonly used for molding an anisotropic ferrite magnet in the form of an annular body fills a molding space in a die with a slurry-like raw material powder, and then passes the raw material powder through an upper punch and a lower punch in a magnetic field. It is configured to be compressed using a punch. In general, when an anisotropic ferrite magnet is molded using a molding device with the above configuration, the ferromagnetic end surface becomes relatively ferromagnetic due to the influence of water removal during compression molding or the difference in molding density between the upper punch side and the lower punch side. and a weakly magnetic end face were formed, resulting in a difference in magnetic properties between the two planes. Active uses of magnets with such a difference in magnetic properties include flat type motors, magnetrons, hysteresis couplings, etc., and there is a desire to further expand the difference in magnetic properties between the two planes of the shaped magnet. However, no means has been established to actively set the strength and weakness of the magnetic properties on both sides of an anisotropic ferrite magnet with a desired difference.
Only a few methods have been proposed for controlling the strength of the magnetic properties by changing the area ratio of the upper and lower punch pole faces during compression molding in a magnetic field. In addition, annular anisotropic ferrite magnets are used in applications such as magnetrons, magnetic couplings, and flat motors, and it is strongly desired to improve the strength of the magnet body in practical use. Fine cracks in the direction or in layers tend to occur, and it has been difficult to significantly improve the crushing strength. Purpose of the invention This invention, in an anisotropic ferrite magnet molding device, is capable of expanding the difference in magnetic properties between both planes of a flat annular magnet, and greatly improving the magnetic properties of the plane side. The object is a molding device that can prevent the occurrence of cracks and improve the crushing strength of molded bodies. Structure and Effects of the Device This device was developed as a result of various studies on means of creating a difference in magnetic properties on both planes of an annular flat anisotropic ferrite magnet, as well as means of preventing micro-cracks and improving strength. By making the tip of the upper punch a non-magnetic material, placing an iron core in the non-magnetic core, and compression molding, the difference in magnetic properties between both sides of the obtained magnet can be increased, and the magnetic properties of one side can be increased. can be improved, and
It is possible to prevent the occurrence of minute cracks in the sintered molded body.
Furthermore, it was discovered that the crushing strength was significantly improved. That is, this invention is a molding device for anisotropic ferrite magnets that fills a molding space in a die with slurry-like raw material powder and compresses and molds the raw material powder in a magnetic field using an upper punch and a lower punch. A molding device for an anisotropic ferrite magnet, characterized in that the body is placed at the tip of the upper punch molding space, and a ferromagnetic core material is arranged concentrically within a non-magnetic core inserted into the molding space. It is. More specifically, this invention is a molding device for an annular anisotropic ferrite magnet, in which a non-magnetic material is provided at the tip of the upper punch on the molding space side, or in addition,
A ring-shaped magnetic body is provided concentrically outside the inner peripheral surface of the molding space on the non-magnetic body or the outer periphery of the non-magnetic body at the tip of the upper punch, and a core inserted into the molding space is a non-magnetic cylindrical core. This is an anisotropic ferrite magnet molding device characterized by fitting and inserting a ferromagnetic core material such as an iron core concentrically into the core. The magnetic properties of the ferromagnetic end face can be improved by widening the property difference, and there are no microcracks in the sintered molded body, and the crushing strength is greatly improved. Preferred Embodiment of the Invention In this invention, the non-magnetic material interposed between the magnetic pole surface of the upper punch and the raw material powder and the ferromagnetic core material in the non-magnetic core are provided in advance in the magnetic pole surface of the upper punch and in the core. In addition, it may be inserted at any time during compression molding, and the non-magnetic material on the punch surface must be configured to prevent the raw material powder filled into the molding space from leaking, and should be selected as appropriate depending on the workability of molding. do it. Furthermore, any known configuration of the compression molding device can be applied. Furthermore, the thickness of the non-magnetic material can be selected appropriately depending on the shape of the molded body, but if it is too thick, it will require a lot of current to form an appropriate magnetic field, causing various problems in terms of efficiency, and if it is too thin, it will not be sufficient. However, it is necessary to select the size appropriately in conjunction with the preferred dimensions of the annular magnetic body. In this invention, by providing an annular magnetic body concentrically outside the inner peripheral surface of the molding space in the non-magnetic body or the outer periphery of the non-magnetic body at the tip of the upper punch,
It is possible to improve the magnetic properties of the ferromagnetic end face by expanding the difference in characteristics between the ferromagnetic end face and the weakly magnetic end face.
The height of the annular magnetic material is the same as the thickness of the non-magnetic material described above, and when the die inner diameter is D, it is preferably 0.2D to 2.0D, more preferably 0.5D to 1.5D, and the inner diameter of the annular magnetic material is 1D to 1.5D is desirable, preferably 1.1D to 1.2D, and the thickness is 0.02D to
0.3D is preferred, 0.1D-0.2D is most preferred,
A non-magnetic material may be provided on the contact surface with the filled raw material powder, and a magnetic material may be arranged annularly around the outer periphery of the non-magnetic material, which may be appropriately selected in consideration of the shape of the object to be molded and workability. It is desirable that the non-magnetic core material inserted into the molding space has a Rockwell hardness HRC of 40 or higher so that it will not wear out due to friction with the lower punch during pressing and cause practical problems. In addition, if the diameter _d1 of the ferromagnetic core material that fits or loosely inserts concentrically into the non-magnetic core is less than 0.2d, where d is the diameter of the non-magnetic core, it will not be affected by the applied magnetic field during magnetic field forming. As a result, it becomes magnetically saturated, making it impossible to obtain the full effect of this invention. Also, if it exceeds 0.8d, the magnetic field orientation near the molded body is partially disturbed, causing minute cracks in the molded body. occurs, which is undesirable, so d ₁ is set to 0.2d to 0.8d,
More preferably, d ₁ =0.4d to 0.6d. In addition, the ferromagnetic core material is preferably arranged within the non-magnetic core so that its upper surface tip position is at the same height as the core and at a height where it contacts the upper punch surface, and the length of the ferromagnetic core material is The thickness is preferably 4 times or more the thickness of the molded body after pressing. DISCLOSURE OF THE INVENTION BASED ON DRAWINGS FIG. 1 is a longitudinal sectional view of a molding apparatus according to this invention. The molding space is created by fitting a hollow cylindrical lower punch 2 made of a magnetic material into a cylindrical space provided in a die 1 made of a non-magnetic material, and inserting a cylindrical non-magnetic core made of a non-magnetic material into the hollow part of the lower punch 2. 3 and further inserting the iron core 7 into the axis of the non-magnetic core 3, the core 7 is formed inside the die 1, and the raw material powder is filled in the same space. Further, an upper punch 5 having a non-magnetic plate 4, which is a disc having the same diameter as the upper punch 5, is provided on the magnetic pole surface of the upper punch 5 comes into contact with the upper end surface of the die 1. Furthermore, a ring-shaped annular magnetic body having an inner diameter larger than the inner diameter of the die 1 serving as the molding space may be provided in the non-magnetic plate 4 concentrically with the molding space. Further, the upper punch 5 and the lower punch 2 are provided with hydraulic cylinders (not shown) that move in the vertical direction to apply pressure, and an electromagnetic coil 6 for forming a magnetic field is provided on the outer circumference of the die 1. After filling the molding space in the die 1 with slurry-like raw material powder, the coil 6 is excited to form a magnetic field, and the die 1, upper punch 5, and core 3 are lowered to perform compression molding. At this time, the water in the slurry-like raw material powder may be drained, for example, from a drainage hole provided in the non-magnetic plate 4, or by interposing a filter such as a filter cloth between the non-magnetic plate 4 and the raw material powder. It's also good. In addition, the area Su of the magnetic pole surface of the upper punch and the cross-sectional area Sd (π/4・
D ² ), Su/Sd, is 1 or more, the effect of this invention is fully exhibited. Furthermore, by providing multiple molding spaces within the die,
Even in devices that produce multiple molded bodies in one molding process, there is usually only one upper punch, so the Su/Sd ratio of each molding space was calculated assuming that there is only one upper punch. Think of it as the value obtained by dividing the ratio by the number of molding spaces. On the other hand, although the case where the electromagnetic coil is provided on the outer periphery of the die has been described, it may also be provided on the outer periphery of the upper and lower punches. In this case, the balance of magnetomotive force between the upper and lower coils is the same, or the lower side is stronger. The case is good. Alternatively, if the magnetomotive force is sufficiently large, it may be provided around only the lower punch. Examples Example 1 The axial center of a non-magnetic core (d=24 mm) was molded using a molding device in which a non-magnetic plate of 80 mmφ and the same size as the magnetic pole surface was attached to the magnetic pole surface of the upper punch shown in FIG. To,
By inserting iron cores of various outer diameters (d ₁ ), SrO9.5%,
Slurry raw material powder containing 88% Fe ₂ O ₃ is
In a magnetic field of 8 kOe, a pressure of 0.5 t/cm ² was applied, and the outer diameter
It was molded into dimensions of 65 mm x inner diameter 24 mm x height 18 mm, and the resulting ring-shaped molded body was sintered at 1250°C for 1 hour to obtain an anisotropic ferrite magnet. Furthermore, an anisotropic ferrite magnet was obtained using the conventional apparatus by molding and sintering under exactly the same conditions except that the iron core was not inserted into the non-magnetic core. The residual magnetic flux density of each obtained magnet was measured, and the ratio of the ferromagnetic surface to the weakly magnetic surface was compared with the ratio of the comparative example as 1, and the measurement results are shown in Table 1. As is clear from Table 1, according to this invented device, the magnetic properties of the weakly magnetic end face of the ring-shaped anisotropic ferrite magnet are greatly attenuated, the difference in the magnetic properties of both planes is increased, and the ferromagnetic end face is We were able to significantly improve the magnetic properties. Note that when _d1 is 23 mm, the Br ratio improves, but cracks occur, which is not preferable. Example 2 100 anisotropic ferrite magnets obtained in Example 1 under various conditions using the invented device and 100 anisotropic ferrite magnets obtained using the conventional device were visually inspected to determine the incidence of cracks. A crushing strength test was conducted. The inspection and test results are shown in Table 1. For the crushing strength test, 50 pieces with no cracks were selected, and each was placed on a base 12 via two stainless steel pins 11 (diameter 8 mmφ) with test magnets 10 arranged at a predetermined interval, as shown in Figure 2. Place magnet 1
Apply the angle material 13 to the top surface of 0 and press 14
The test was carried out by applying a load at the time of failure and measuring the load at the time of failure. From the results shown in Table 1, it can be seen that the annular anisotropic ferrite magnet produced by this device was prevented from generating minute cracks, and had significantly improved crushing strength compared to conventional magnets. Note that when _d1 is 2.4 mm, no cracks occur, but the Br ratio cannot be improved, which is not preferable. 【table】

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the molding apparatus according to this invention. FIG. 2 is a schematic diagram of the crushing strength measuring device. 1... Dice, 2... Lower punch, 3... Core,
4... Non-magnetic plate, 5... Upper punch, 6... Electromagnetic coil, 7... Iron core, 10... Test magnet, 11...
Stainless steel pin, 12... base, 13... angle material, 14... press.

Claims (1)

[Scope of utility model registration request] In a molding device for an anisotropic ferrite magnet having an annular body, a slurry-like raw material powder is filled into a molding space in a die, and the raw material powder is compressed and molded in a magnetic field using an upper punch and a lower punch. 1. A molding device for an anisotropic ferrite magnet, characterized in that a ferromagnetic core material is arranged concentrically within a non-magnetic core that is placed at the tip end of a punch molding space and inserted into the molding space.