JP4144072B2 - Magnetic powder molding apparatus and magnetic powder molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic powder molding apparatus and a magnetic powder molding method capable of making the pressure acting on each magnetic powder uniform when simultaneously compressing and molding a plurality of magnetic powders.
[0002]
[Prior art]
The following steps are known as one of the processes for manufacturing a permanent magnet. That is,
1) The raw material is melted at a high temperature to form a raw material alloy having a predetermined component.
2) This raw material alloy is pulverized into a fine magnetic powder.
3) The magnetic powder is pressed in a magnetic field to align the direction of the particles, and a compressed body having a predetermined shape is produced.
4) This compressed body is sintered at a high temperature of 1000 ° C. or higher to obtain a magnet material.
5) A heat treatment called aging treatment is performed in order to improve the magnetic properties.
6) Finishing by polishing and adjusting the dimensions and shape.
[0003]
Although manufactured through the steps as described above, the present invention relates to a magnetic powder molding apparatus used in a step of making a compressed body of a predetermined shape. The basic configuration of this apparatus is that a die is provided with a molding space (cavity), magnetic powder is introduced into the molding space, and the magnetic powder is compressed by a lower punch and an upper punch. And in order to improve production efficiency, many pieces are taken. That is, a plurality of molding spaces are formed in the die, and a plurality of upper punches and lower punches corresponding to the number of molding spaces are provided. An important point in taking a large number of pieces is to compress and mold the magnetic powder so that the density is constant at a uniform pressure when the magnetic powder is compressed in each molding space. Thereby, the product quality molded in each molding space can be made predetermined, and the yield can be improved.
[0004]
However, it is difficult to make the amount of magnetic powder filled in each molding space exactly the same, so that it is difficult to perform compression molding with uniform pressure in each molding space. As a conventional technique for solving this problem, there is a powder molding press apparatus disclosed in Japanese Patent Laid-Open No. 9-168899.
[0005]
This apparatus is configured to operate a plurality of upper punches individually, and at the same time, is equipped with a pressurizing force stabilizing means for compressing and molding a powder compact at the same pressure, thereby making the density of the plurality of powder compacts constant. I try to keep it. Specifically, a hydraulic cylinder, a plurality of pistons arranged in parallel therein, and an upper punch are provided at the tip of each piston. A constant pressure is applied to each piston so that it is pressed simultaneously at the same pressure, and each powder compact is molded at a uniform pressure. Therefore, the upper punch can be moved individually.
[0006]
[Problems to be solved by the invention]
However, the above prior art has the following problems. First, since each of the plurality of upper punches is individually driven by a cylinder, play is likely to occur in the upper punch. Therefore, when the upper punch enters the die, there arises a problem that the die and the upper punch come into contact with each other to cause chipping in the upper punch, or that the inner surface of the die forming space is seized or scratched.
[0007]
Secondly, in a configuration in which a plurality of upper punches are individually backed up with fluid pressure by a hydraulic cylinder, there is a limit to the size of the piston acting surface on which the fluid pressure acts in order to bring the plurality of upper punches as close as possible. It cannot be increased.) Therefore, high pressure is applied to the working surface. In other words, if the same load is applied to the upper punch, it is necessary to increase the hydraulic pressure, and thus there arises a problem that it becomes difficult to seal between the piston operating surface and the cylinder.
[0008]
Third, since the magnetic powder molding apparatus performs molding in a magnetic field, it is difficult to form a punch having a complicated structure in the magnetic field. The mechanism for individually operating the upper punch by the hydraulic cylinder of the prior art complicates the mechanism for operating the upper punch and cannot be said to be suitable for molding magnetic powder.
[0009]
The present invention solves the above-mentioned problems of the prior art, and by adopting a configuration that replaces the configuration in which the upper punch is individually operated by a hydraulic cylinder, the problems associated with the adoption of the hydraulic cylinder are solved, and a plurality of It is an object of the present invention to provide a magnetic powder molding apparatus and a magnetic powder molding method capable of compressing and molding magnetic powder with a uniform pressure.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a magnetic powder molding apparatus according to the present invention comprises:
A die having a plurality of molding space portions for compressing and molding a plurality of magnetic powders, a plurality of upper punches inserted into the molding space portion from above and compressing the magnetic powder at the lower end surface thereof, A plurality of lower punches that are inserted into the molding space from below and compress the magnetic powder at the upper end surface thereof, a pressure medium that acts in common on the lower end surfaces of the plurality of lower punches, and the pressure medium are accommodated A holding space for holding and a pressure medium holding body provided with a lower punch guide portion for guiding and holding the lower end surface side of the plurality of lower punches are provided.
[0011]
According to this configuration, the pressure medium acting in common on the lower end surfaces of the plurality of lower punches is provided, and this pressure medium acts so as to apply a uniform pressure during compression molding of the magnetic powder. For the sake of simplicity, it is assumed that there are two molding spaces for compressing and molding the magnetic powder. The lower end surfaces of the two lower punches are supported by a pressure medium, and when the magnetic powder is filled in the molding space and subjected to a compression action by pressing the upper punch, the lower end surfaces of the lower punches are subjected to pressure from the pressure medium. Works. At this time, the amount of the filled magnetic powder is different in the two molding spaces, and even if there is a difference in the compression amount, the pressure medium is deformed so that the pressure acting on all the punches becomes the same. The compression density of the molded body is made the same.
[0012]
Since the above configuration only provides a pressure medium acting on the lower end surface of the lower punch, the upper punch may have the same configuration as the conventional one, compared to a configuration in which the upper punch is driven by a hydraulic cylinder, and the structure is simple and magnetic powder is used. It can be said that it is suitable for compression molding of the body.
[0013]
  The present inventionIsThe lower punch guide portion of the pressure medium holderProvided inA restricting portion for restricting the upper limit movement position of the lower punchIs further provided.
[0014]
In order to supply magnetic powder into the molding space, (A) a case of using a quantitative supply device that measures the supplied powder for each cavity, and (B) a scraping method that measures by the capacity of each cavity. There are two cases. In the case of (A), the upper end surface of the lower punch does not necessarily have to be aligned, but it is necessary to provide a fixed quantity supply device separately. On the other hand, in the case of (B), the quantity can be easily determined, but it is necessary to align the upper end surfaces of the lower punches. However, just placing the lower punch on the pressure medium does not align the upper end surfaces of the multiple lower punches, and therefore the filling depth varies from one molding space to another and varies in the amount of magnetic powder to be filled. There is a problem that is likely to occur. When filling the molding space with magnetic powder, if the upper limit movement position of the lower punch is controlled by the restricting portion, the upper punch is lifted by the action of the pressure medium when the upper punch load is released. Since the position of the end face can be located at a predetermined position, it is possible to reduce the variation factor of the filled magnetic powder.
[0015]
In addition, as a method of supplying magnetic powder to the molding space, a dropping method of supplying magnetic powder after first forming the molding space with the die and the upper end of the lower punch, and moving the lower punch downward relative to the die Any known method such as a suction method for supplying magnetic powder using the attractive force can be used without limitation.
[0016]
  The present inventionIsDuring the compression molding process of the magnetic powder, the entire pressure mediumTheMoves downward by the compression action of the upper punchLetMechanismMore. When the above-described restricting portion is provided and the pressure medium is always in contact with the restricting portion when the pressure of the upper punch is not applied, the pressure medium is compressed during compression molding of the magnetic powder. Then, at least one of the lower punches is pushed downward from the contact state with the restricting portion, and the same pressure acts on all the lower punches. This embodiment has the following problems.
[0017]
B) After the compression molding is completed, the load of the upper punch is reduced to a predetermined value, and at the same time, when the die is moved downward for demolding, the molded body remains under the pressure from the upper punch and the pressure from the spring back of the pressure medium. Release from restraint from the die. The force of the pressure medium due to the spring back is quite strong, and if the upper punch load adjustment is insufficient, the die is not constrained, and cracks may occur in the molded body.
[0018]
B) Since the movement of the lower punch is limited to the amount of compression deformation of the pressure medium, the movement stroke is small. For this reason, the stroke of the lower punch cannot follow until the molded body is completely removed from the die, the upper punch is separated from the molded body, and a crack may occur in the molded body due to the spring back of the molded body itself.
[0019]
In order to solve these problems, the entire pressure medium is moved downward by the compression action of the upper punch during the compression molding process. Then, the action of the spring back of the pressure medium can be surely reduced by the amount that can be moved downward, and the moving stroke of the lower punch can be made sufficiently long. As a result, the upper and lower punches can be taken out from the die while holding the molded body at a predetermined pressure sufficient to prevent spring back of the molded body itself, thereby preventing the molded body from cracking. And the defect of a molded object can be reduced reliably.
[0020]
As another preferred embodiment of the present invention, there is one in which a seal member for sealing a gap between the lower punch guide portion and the lower punch is provided on the outer periphery of the lower end surface of the lower punch. As a result, it is possible to prevent the pressure medium from entering the gap between the lower punch guide portion and the lower punch and thereby deteriorating the movement of the lower punch, and to prevent the pressure medium from being worn.
[0021]
Another magnetic powder molding apparatus according to the present invention is:
A die having a plurality of molding space portions for compressing and molding a plurality of magnetic powders, a plurality of upper punches inserted into the molding space portion from above and compressing the magnetic powder at the lower end surface thereof, A plurality of lower punches that are inserted into the molding space portion from below and compress the magnetic powder at the upper end surface thereof, an intermediate member provided on the lower end surface of the plurality of lower punches, and the intermediate member A pressure medium acting in common on the lower end surfaces of the plurality of lower punches, a holding space for storing and holding the pressure medium, and a pressure medium holding body provided with an intermediate member guide portion for guiding and holding the intermediate member, And a lower punch holder having a lower punch guide portion that is provided above the pressure medium holder and guides and holds the lower end surfaces of the plurality of lower punches.
[0022]
A major feature of this configuration is that a pressure medium is also provided. However, the pressure medium does not act directly on the lower end surface of the lower punch, but acts via the intermediate member. The intermediate member is guided and held by the pressure medium holder, while the lower punch is guided and held by the lower punch holder. The reason for adopting this configuration is as follows.
[0023]
That is, when changing the size and cross-sectional shape of the magnetic powder compression molded body, it is necessary to replace the upper punch, the lower punch, and the die, and it is necessary to make the replacement work easy. In particular, if a mechanism is adopted in which the lower punch is directly guided and held by the pressure medium holding body and the regulating portion is provided in the guide portion, it is necessary to remove the pressure medium in order to replace the lower punch. It is necessary to prepare the entire molding apparatus for each shape or size of the molded body. Therefore, if the lower punch is held by a lower punch holding body different from the pressure medium holding body, the lower punch and the like can be replaced without placing a hand on the pressure medium. It is possible to easily and easily cope with a change in shape.
[0024]
As described above, when the lower punch is guided and held by the lower punch holder, the restricting portion for restricting the upper limit movement position of the lower punch is provided in the lower punch guide portion of the lower punch holder.
[0025]
  The present inventionIsA mechanism for moving the entire pressure medium downward by a predetermined amount by the compression action of the upper punch during the compression molding process of the magnetic powder;BecauseThe lower punch can move in any of the vertical directions, and a uniform pressure can be reliably realized. “Uniform” includes a range in which the force acting on all the lower punches is substantially uniform.
[0026]
In this case, it is preferable to provide a support body that can move in the vertical direction that supports the entire lower surface of the pressure medium, and a biasing mechanism that biases the support body in the upward direction. When such a mechanism is employed, the pressure medium is urged upward when the magnetic powder is filled, so that the lower punch is regulated by the regulating portion. Thereby, the filling depth of the magnetic powder in each molding space can be made uniform.
[0027]
Furthermore, if a space for applying fluid pressure is provided on the lower surface of the support, the fluid pressure can be applied over a wide area of the lower surface of the support, and even if the fluid pressure is low, A desired urging force can be applied, and the holding force of the molded body by the upper and lower punches can be easily adjusted. Moreover, since the moving stroke of the lower punch can be made sufficiently large, it is possible to remove the mold easily while preventing the cracking of the molded body.
[0028]
Moreover, it is preferable that a seal member for sealing a gap between the intermediate member guide portion and the intermediate member is provided on the outer periphery of the lower end surface of the intermediate member. Thereby, it is possible to prevent the pressure medium from entering the gap between the intermediate member guide portion and the intermediate member.
[0029]
As a specific example of the pressure medium, it is preferable to select a resin having a crosslinked structure and a Shore-A hardness of 50 or less. Thereby, the leakage of the pressure medium from the clearance between the lower punch and the lower punch guide portion can be easily prevented, and at the same time, the nonuniformity of the molding pressure due to the variation in the filling of the magnetic powder can be effectively eliminated.
[0030]
The magnetic powder molding method of the present invention comprises a die having a plurality of molding space portions for compressing and molding a plurality of magnetic powders, and filling the molding powder with the magnetic powder, Inserting the plurality of upper punches from above in the molding space, the lower end surface of the upper punch, and the upper end surfaces of the plurality of lower punches inserted from below into the molding spaces. And a step of making the compressive force of the magnetic powder uniform in each molding space by a pressure medium acting in common on the lower end surfaces of the plurality of lower punches. Is.
[0031]
  Further, the magnetic powder molding method described above further includes a step of aligning upper end surfaces of the plurality of lower punches inserted in the molding spaces, prior to the step of filling the magnetic powder. Furthermore, in the compression molding step of the magnetic powder, there is a step of moving the entire pressure medium downward by the compression action of the upper punch.It is characterized by. These methods are described in claims 1 to 1.8The described forming apparatus is used, and the above-described effects can be obtained.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
<Configuration of First Embodiment>
First, a conceptual diagram of an embodiment of a basic magnetic powder molding apparatus will be described with reference to FIG. This apparatus includes an upper punch 1, a lower punch 2, a die 3, a pressure medium holding body 4, and a pressure medium 5. The upper punch 1 is fixedly attached to the upper punch fixing washer 6. The plurality of upper punches 1 are configured not to move individually but to move together integrally. A plurality of molding spaces 3a are formed in the die 3, and the spaces are filled with magnetic powder and compressed. The magnetic powder is compressed by the lower end surface 1 a of the upper punch 1 and the upper end surface 2 a of the lower punch 2. The pressure medium holding body 4 is provided with a storage space 4a in which the pressure medium 5 is filled and held, and a lower punch guide portion 4b for guiding and holding the lower end surface 2b side of the lower punch 2. The lower end surface 2 b of the lower punch 2 is configured to be supported from below by the pressure medium 5. In a state as shown in FIG. 1 (a), a predetermined amount of magnetic powder is filled in the molding space 3a, and the upper punch 1 is lowered and compressed from above as shown in FIG. 1 (b).
[0033]
Examples of the magnetic powder include those mainly composed of rare earth elements, iron, and boron. However, the fluidity is poor, and it is difficult to uniformly fill the molding spaces 3a of the die 3 when a large number of them are taken. There is. The sintered magnet is subjected to a sintering process after compression molding. However, the amount of magnetic powder filled in the molding space 3a is small, and if the molded powder is sintered with a weak compression force, the shrinkage ratio increases. However, there is a problem that the yield cannot be obtained because of the expected size. Therefore, it is important to improve the yield by making the molding pressure uniform.
[0034]
Here, in FIG. 1, if the right molding space 3a is filled with a larger amount of magnetic powder, the right lower punch 2 is lowered than the left lower punch by the action of the pressure medium. As a result, the magnetic powders on both the left and right sides are compressed with the same pressure, so that the density becomes uniform.
[0035]
<Specific examples of pressure medium>
As the pressure medium used in the present invention, the filling amount of the magnetic powder in a certain molding space is relatively large, and when the compressive force acting on the lower punch becomes high, the pressure is relatively small. Anything that is transmitted to the lower part of the lower punch and deforms so as to be uniform can be used without any particular limitation. In particular, an elastic body or a viscoelastic body having a low hardness or a fluid having a high viscosity is easy to use and is preferable.
[0036]
As the low-hardness elastic body or viscoelastic body, an organic high molecular weight compound is suitable, and a material in which the high molecular weight compound itself has low hardness, or a material in which the high molecular weight compound is reduced in hardness by an additive such as a plasticizer is used. Is possible.
[0037]
As the material having a low hardness as the high molecular weight compound itself, it is preferable to use a polymer having a glass transition temperature of room temperature or lower, preferably 0 ° C. or lower and having a low elastic modulus at the room temperature of use. Examples include silicon rubber, polyurethane, and polyvinyl acetate.
[0038]
As a material whose molecular weight compound is reduced in hardness by an additive such as a plasticizer, a polymer having a low elastic modulus at room temperature, which is a use temperature, can be used by adding a plasticizer or the like. Specifically, polyurethane, polyvinyl chloride, polyvinyl acetate, vinyl chloride / vinyl acetate with a phthalate plasticizer added such as dioctyl phthalate (DOP), dioctyl adipate (DOA), dibutyl phthalate (DBP), etc. Examples thereof include polymers and polyvinyl butyral. Further, diene or olefin rubber materials such as polynorbornene rubber and ethylene propylene rubber which are filled with a process oil such as naphthene or aroma and cross-linked as necessary can also be used. The kind and addition amount of the plasticizer and process oil are appropriately selected in consideration of the compatibility with the polymer, the plasticizing performance, the required hardness of the elastic body, and the like.
[0039]
Examples of the high viscosity fluid include low molecular weight polymers such as high viscosity machine oil, liquid polybutadiene, and liquid polyisoprene.
[0040]
The pressure medium is preferably capable of easily preventing leakage from the clearance between the lower punch 2 and the lower punch guide portion 4b, and is a partially crosslinked molecule, a so-called flexible gel. Is preferred. The polymer having a low modulus of elasticity, a plasticized polymer, a soft gel-like body, and the like have a hardness of 50 or less in Shore A hardness.
[0041]
In addition to the above-described pressure medium, it is also preferable to use a liquid seal type pressure medium in which a liquid is sealed in a hollow film having flexibility. Such a liquid sealing type pressure medium has a high compression ratio, an adjustment of the lower punch position is easy, and there is an advantage that accuracy can be improved. Furthermore, since the viscosity of the liquid is low, the height of the pressure medium accommodation space can be lowered, and a compact molding apparatus can be obtained. The liquid seal type pressure medium is preferably formed in a shape along the pressure medium accommodation space.
[0042]
As a flexible material for forming a hollow film constituting a liquid seal type pressure medium, a synthetic resin forming a flexible film is suitable. Polyolefins such as polyethylene and polybutene, polyurethane elastomers, styrene butadiene Examples thereof include rubbers such as rubber, natural rubber and polybutadiene, and thermoplastic elastomers such as SBS and SES. These resins and rubbers are molded into a hollow body by known means such as compression molding, injection molding, blow molding, vacuum molding and the like. The hollow body does not have to be a seamless hollow body, and may be formed by sealing into a plurality of shapes and then containing a liquid described later.
[0043]
The liquid used for the liquid seal type pressure medium can be used at normal temperature and pressure without limitation, and examples thereof include various oils, organic compounds such as fats and oils, mercury, water, and the like. These liquids are preferably enclosed under a slight pressure, that is, in a state where the hollow body containing the liquid is stretched.
[0044]
<Punch, Dice>
The dies and punches used in the molding apparatus of the present invention may be composed entirely of the same material or may be composed of a plurality of members. For example, only the portion in contact with the magnetic powder may be made of a material having excellent wear resistance and may be a separate member from the pressure medium contact portion.
[0045]
<Configuration of Second Embodiment>
Next, a conceptual diagram of the second embodiment will be described. The feature of the second embodiment is that a regulating portion 4c is formed on the lower punch guide portion 4b in the first embodiment. The lower punch 2 receives a slight pressure from the pressure medium 5, and the step 2c of the lower punch 2 is in contact with the restricting portion 4c. That is, the height at which the upper end surface 2a of the lower punch 2 is inserted into the molding space 3a is aligned, and when the magnetic powder is filled by the scraping method, it is effective to eliminate variations in the filling depth.
[0046]
In the configuration of FIG. 1, only the lower end surface 2b of the lower punch 2 is placed on the pressure medium 5, so that the position of the upper end surface 2a of the lower punch 2 varies after molding due to permanent deformation of the pressure medium. Sometimes it is not stable. That is, it is difficult to align the upper end surface 2a of the lower punch 2 at the same height. This is because the filling depth of each molding space 3a varies when it is filled not by a constant supply device but by a scraping method, but the second embodiment solves this problem.
[0047]
FIG. 2 (b) shows a state in which the magnetic powder is compressed. The step 2c of the left or right lower punch 2 is in a state of being separated from the restricting portion 4c, and the pressure medium 5 is compressed, and the left and right magnetic powders are compressed with the same pressure by the deformation.
[0048]
<Problem of the second embodiment>
Although the configuration in which the restricting portion 4c is provided as in the second embodiment has an advantage that the filling depth is uniform, another problem may occur. This will be described with reference to FIG.
[0049]
FIG. 3 (a) shows a state in which it has already been compressed, but the right side is a case where the filling amount of the magnetic powder is larger than that of the left molding space 3a. Compression molding.
[0050]
After completion of compression molding, when the pressure for adjusting the load of the upper punch is lowered to a predetermined value and at the same time the die is moved downward for demolding, the molded magnetic body is exposed from the die as in (b) . At this time, the molded magnetic powder receives a compressive force due to the load due to the spring back when the pressure medium returns to the original volume, and only the compressive force due to the upper and lower punches is released from the restriction from the die. In some cases, the load of the upper punch may be released rapidly due to a shortage of the movement stroke of the lower punch, and the molded body may be cracked. This is a major cause of reducing the product yield.
[0051]
In order to avoid such a phenomenon, the load applied to the upper punch can be adjusted to such an extent that the molded body is not damaged. However, it is necessary to detect and control the force caused by the spring back of the pressure medium one by one. The equipment becomes expensive and complicated. Moreover, the stroke of the lower punch cannot be changed only with this configuration.
[0052]
<Configuration of Third Embodiment>
The conceptual diagram of 3rd Embodiment which solved the problem that a molded object cracks is shown in FIG. Only a configuration different from the second embodiment will be described. A support plate 11 is provided over the entire lower surface of the pressure medium 5 so that the entire pressure medium 5 can be moved downward by a dimension h as shown in FIG. Further, a mechanism is provided that acts to lift the entire pressure medium 5 upward. In other words, a space 12 is provided for allowing the fluid supply means 13 and the supplied fluid pressure to act on the lower surface of the support plate 11.
[0053]
FIG. 4B shows a state where compression molding is performed. Since the compression force by the upper punch 1 is larger than the fluid pressure by the fluid supply means 13, the pressure medium 5 is surely lowered by the dimension h. Be lowered. As a result, the lower punch 2 is also surely lowered by the dimension h, so that the step 2c and the restricting portion 4c of the lower punch 2 are reliably separated. Therefore, even if the load of the upper punch is reduced to a predetermined value and the die is moved downward at the same time, the spring back action of the pressure medium is absorbed by the action of the mechanism acting to lift the entire pressure medium 5 upward, and compression molding The molded body thus formed is removed from the molding space 3a without cracking in a state where it is held at a pressure that does not cause the upper punch 1 and the lower punch 2 to be broken even in a portion released from the die restraint. Further, the moving stroke of the lower punch is sufficiently large, and the holding force of the upper and lower punches can be maintained until the lower punch is removed from the die, so that the molded body can be easily removed from the die without cracking due to its own springback.
[0054]
<Configuration of Fourth Embodiment>
FIG. 5 is a conceptual diagram of the fourth embodiment. The difference between this embodiment and the embodiment of FIG. 2 is that the lower punch and the lower punch holding material are configured to be separable from the pressure medium and its accommodating portion, and by configuring in this way, It becomes possible to easily cope with the change of the shaped body.
[0055]
Specifically, in the fourth embodiment, the lower punch 2 is supported by the lower punch holder 8. The upper end surface 7 a of the lower punch fixing washer 7 (intermediate member) is in contact with the lower end surface 2 b of the lower punch 2. The lower punch holder 8 is formed with a lower punch guide portion 8a and a restricting portion 8b, and the upward movement of the lower punch 2 is restricted by the step 2c of the lower punch 2 coming into contact with the restricting portion 8b. Has been. By providing this restricting portion 8b, the height of the upper end surface 2a of the lower punch 2 is made uniform. The pressure medium support 4 is formed with a storage space 4 a for storing the pressure medium 5 and a guide portion 4 d for guiding and holding the lower punch fixing washer 7. The lower punch holder 8 is fastened and fixed to the upper side of the pressure medium holder 4 with a bolt (not shown) or the like.
[0056]
The lower end surface 7 b of the lower punch fixed washer 7 is placed on the pressure medium 5, and the pressure of the pressure medium 5 is transmitted to the lower punch 2 through the lower punch fixed washer 7. Further, a seal material 9 is provided on the outer periphery of the lower end surface 7b of the lower punch fixed washer 7 to prevent the pressure medium 5 from entering the gap between the guide portion 4d and the lower punch fixed washer 7. The upper punch 1 is supported by an upper punch fixed washer 6, and an orientation coil 10 is provided on the upper side and on the outer periphery of the pressure medium holding body 4, which gives a magnetic field to the magnetic powder filled in the molding space 3a. Is.
[0057]
The sealing material 9 is deformed by the pressure received from the pressure medium 5 and prevents the pressure medium 5 from entering the clearance portion between the lower punch fixed washer 7 and the guide portion 4d that guides and supports the lower punch fixed washer 7. Those having can be used without any particular limitation. However, the hardness needs to be higher than that of the pressure medium 5. Preferably, the Shore-A hardness is 60 or more and the Shore-D hardness is about 60 or less. Specifically, rubber materials such as natural rubber, styrene butadiene rubber, ethylene propylene rubber, and fluoro rubber, thermosetting resins such as polyurethane elastomers and elastic epoxy resins, various thermoplastic elastomers, and the like are exemplified.
[0058]
<Molding Operation of Fourth Embodiment>
Next, a forming operation when the configuration of the fourth embodiment is adopted will be briefly described. In FIG. 6A, the upper punch 1, the upper punch fixing washer 6, and the upper orientation coil 10 are released upward. Then, the die 3 is lifted to form the molding space 3a. At this time, the lower punch fixing washer 7 and the lower punch 2 are lifted upward by a minute initial load by the pressure medium 5, and the step 2c of the lower punch 2 is in contact with the restricting portion 8b. Therefore, the filling depth in the molding space 3a is constant. In this state, a magnetic powder is filled by a dropping method using a feeder. At this time, the filling amount of the magnetic powder to be filled is constant, but variation may occur in each molding space 3a.
[0059]
In FIG. 6B, the upper punch 1, the upper punch support plate 6, and the upper orientation coil 10 are integrally lowered, and the orientation coil 10 is energized when the upper punch 1 contacts the upper surface of the die 3. A magnetic field is applied to the magnetic powder in 3a to perform orientation treatment.
[0060]
In FIG. 7C, the lower punch 1 is further lowered to apply a compressive force to the magnetic powder. Accordingly, the lower punch 2 and the lower punch fixing washer 7 are lowered, and the step 2c of the lower punch 2 is in a state of being separated from the restricting portion 8b. In this figure, the left molding space 3a is filled with a lot of magnetic powder, and the lower punch 2 and the lower punch fixing washer 7 on the left side are further lowered than on the right side. At this time, the pressure medium 5 is in a slightly contracted state, and the same pressure acts in both molding spaces 3a. Further, the pressure medium 5 is sealed by the sealing material 9 so that the pressure medium 5 does not enter the gap between the guide portion 8a and the lower punch fixing washer 7 in a state where pressure is applied. Then, when the predetermined forming density is reached, a reverse magnetic field is applied to the orientation coil 10 to demagnetize the magnetic powder compact, and then the energization to the orientation coil 10 is stopped.
[0061]
In FIG. 7D, the molded body can be taken out by letting the upper punch 1 escape upward and further lowering the die 3 downward. In this state, no pressure is applied by the upper punch 1, and therefore the lower punch 2 is regulated by the regulating portion 8b by the action of the pressure medium 5.
[0062]
<When changing the size and shape of a molded product>
In this apparatus, it is necessary to replace the upper punch 1, the lower punch 2, and the die 3 when changing the size / shape of the molded product. In particular, when replacing the lower punch 2, the lower punch holding body 8 may be removed from the pressure medium holding body 4, and it is not necessary to touch the pressure medium holding body 4. Therefore, the replacement work is facilitated.
[0063]
<Fifth Embodiment>
FIG. 8 is a diagram showing a fifth embodiment. The fifth embodiment is different from the example shown in FIG. 5 in that the pressure medium 5 is provided with a support 11 and a fluid supply means 13 to the lower part as an urging means. With such a configuration, it is possible to reduce defects due to cracks generated in the molded body due to the spring back of the pressure medium, and at the same time, the movement stroke of the lower punch is increased by the movement stroke of the support body 11, and predetermined by the upper and lower punches. The molded body can be completely taken out from the die while being held under pressure, and cracks due to the spring back of the molded body itself can be prevented. The same members as those already described have the same reference numerals. Here, three molding spaces 3 a are formed in the die 3. Correspondingly, three upper punches 1, lower punches 2, and lower punch fixing washers 7 are also provided. The pressure medium 5 may be configured as an integral member, but the main body 5a and the protrusions 5b (there are three locations) may be configured separately. Moreover, in order to give durability, the inner surface part which comprises the shaping | molding space 3a of the die | dye 3 is good also as a separate material structure from another part as a hard material. For the same reason, the tip portion of the lower punch 2 may be made of a hard material and separate from the other portions.
[0064]
<Molding Operation of Fifth Embodiment>
Next, the molding operation according to the fifth embodiment will be described. In FIG. 8, the upper punch 1 is retracted upward. The die 3 is lifted to the position shown in the figure to form a molding space 3a and filled with magnetic powder. The amount filled in each molding space 3a is the largest on the left side, followed by the middle and the right side. Further, a fluid (oil or air) is supplied to the space portion 12 by the fluid supply means 13, and pressure is applied so as to lift the pressure medium 5. As a result, the step 2 c of the lower punch 2 is in contact with the restricting portion 8 b of the lower punch holder 8. The pressure by the fluid supply means 13 may be a low pressure.
[0065]
In FIG. 9A, the upper punch 1 is lowered to compress the magnetic powder. This applied pressure is larger than the pressure by the fluid supply means 13. Accordingly, the entire pressure medium 5 is reliably lowered together with the support 11 by the dimension h (see FIG. 8). Further, the lower punch 2 and the lower punch fixing washer 7 are lowered according to the respective filling amounts. As shown in the figure, the left lower punch 2 is the lowest. Further, the lower punch 2 on the right side with the smallest filling amount is also lowered, and a gap is surely formed between the step 2c of the lower punch 2 and the restricting portion 8b. In the compressed state, the same pressure acts on each magnetic powder, and the density of all the compacts becomes equal.
[0066]
As shown in FIG. 9B, the upper punch 1 is slightly raised. The lower punch 2 on the right side is in a state where the step 2c and the restricting portion 8b are in contact with each other. The other lower punches 2 are also raised slightly but have not yet come into contact with the restricting portion 8b. Similarly, the lower punch fixing washer 7, the pressure medium 5 and the support 11 are also raised by a small amount. In any case, the compact that has been compression-molded rises slightly while the upper punch 1 and the lower punch 2 are held.
[0067]
Next, as shown in FIG. 10A, the die is lowered while maintaining the position of the upper punch 1. At this time, the molded body is held at the adjusted pressure by the upper and lower punches by the pressure from the fluid supply means 13, and the molded body is prevented from being crushed or cracked.
[0068]
Next, as shown in FIG. 10B, the upper punch 1 is retracted completely upward. Thereby, the lower punch 2 is lifted to a position regulated by the regulating portion 8b by the pressure from the fluid supply means 13, and the molded body can be taken out.
[0069]
【The invention's effect】
Since the lower end surfaces of the plurality of lower punches constituting the magnetic powder molding space are supported from below by the pressure medium, the effect that the compacts can have the same compression density can be obtained.
[0070]
By providing the lower punch guide portion with a restriction portion for restricting the upper limit movement position of the lower punch, the position of the upper end surface of the lower punch is determined in advance to supply the magnetic powder into the molding space by the scraping method. Since it can be in a predetermined position, the effect that the dispersion | variation factor of the magnetic powder with which it fills can be reduced is acquired.
[0071]
A mechanism in which the entire pressure medium is moved downward by the compression action of the upper punch during the compression molding step of the magnetic powder, particularly preferably a support body that is movable in the vertical direction to support the entire lower surface of the pressure medium; By providing an urging mechanism that urges the support upward, it is possible to absorb the action of the spring back of the pressure medium after completion of compression molding and prevent the molded body from cracking. Furthermore, since the movement stroke of the lower punch is sufficiently secured, the holding force of the upper and lower punches can be maintained, and the mold can be removed from the die without causing a crack generated by the spring back of the molded body itself. As a result, defects in the molded product can be reliably reduced.
[0072]
The manufacturing method of the present invention includes a molding apparatus having the above-described configuration, and has an effect of reducing defects in the molded body.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing the configuration of a first embodiment.
FIG. 2 is a conceptual diagram showing a configuration of a second embodiment.
FIG. 3 is a conceptual diagram illustrating a problem of the second embodiment.
FIG. 4 is a conceptual diagram showing the configuration of the third embodiment.
FIG. 5 is a conceptual diagram showing the configuration of the fourth embodiment.
FIG. 6 is a view for explaining a molding operation according to the fourth embodiment.
FIG. 7 is a view for explaining a molding operation according to the fourth embodiment.
FIG. 8 is a diagram showing the configuration of the fifth embodiment.
FIG. 9 is a view for explaining a molding operation according to the fifth embodiment.
FIG. 10 is a view for explaining a molding operation according to the fifth embodiment.
[Explanation of symbols]
1 Top punch
2 Lower punch
3 dice
4 Pressure medium holder
5 Pressure medium
6 Upper punch fixing washer
7 Lower punch fixing washer (intermediate member)
8 Lower punch support
9 Sealing material
10 Oriented coil
11 Support plate
12 Space

Claims (10)

A die having a plurality of molding space portions for compression molding a plurality of magnetic powders;
A plurality of upper punches inserted into the molding space from above and compressing the magnetic powder at the lower end surface thereof,
A plurality of lower punches inserted into the molding space from below and compressing the magnetic powder at the upper end surface thereof;
A pressure medium acting in common on the lower end surfaces of the plurality of lower punches, and comprising a low-hardness elastic body or viscoelastic body ;
A holding space for storing and holding the pressure medium, and a pressure medium holding body provided with a lower punch guide portion for guiding and holding lower end surfaces of the plurality of lower punches ;
A restricting portion that is provided in the lower punch guide portion of the pressure medium holder and restricts an upper limit movement position of the lower punch;
A mechanism for moving the entire pressure medium downward by the compression action of the upper punch during the compression molding step of the magnetic powder,
A support plate for supporting the pressure medium over the entire lower surface;
A magnetic powder molding apparatus comprising: fluid supply means for applying fluid pressure to the lower surface of the support plate . 2. The magnetic powder molding according to claim 1, wherein a liquid seal type pressure medium in which a liquid is enclosed in a flexible hollow film is used instead of the pressure medium made of the low-hardness elastic body or viscoelastic body. apparatus. The magnetic powder molding apparatus according to claim 1, wherein a seal member that seals a gap between the lower punch guide portion and the lower punch is provided on an outer periphery of a lower end surface of the lower punch. A die having a plurality of molding space portions for compression molding a plurality of magnetic powders;
A plurality of upper punches inserted into the molding space from above and compressing the magnetic powder at the lower end surface thereof,
A plurality of lower punches inserted into the molding space from below and compressing the magnetic powder at the upper end surface thereof;
An intermediate member provided on a lower end surface of the plurality of lower punches;
A pressure medium that acts in common on the lower end surfaces of the plurality of lower punches via the intermediate member, and is made of a low-hardness elastic body or viscoelastic body ;
A holding space for storing and holding the pressure medium, and a pressure medium holding body provided with an intermediate member guide portion for guiding and holding the intermediate member;
A lower punch holding body provided above the pressure medium holding body, and having a lower punch guide portion for guiding and holding lower end surface sides of the plurality of lower punches ;
A restriction part that is provided in the lower punch guide part of the lower punch holder and restricts an upper limit movement position of the lower punch;
A mechanism for moving the entire pressure medium downward by a predetermined amount by the compression action of the upper punch during the compression molding step of the magnetic powder,
A support body that is movable in the vertical direction and supports the entire lower surface of the pressure medium;
And a biasing mechanism that biases the support upward . 5. The magnetic powder molding according to claim 4 , wherein a liquid-sealed pressure medium in which a liquid is sealed in a hollow film having flexibility is used instead of the pressure medium made of the low hardness elastic body or viscoelastic body. apparatus. The magnetic powder molding apparatus according to claim 4 , wherein the biasing mechanism includes a space for applying fluid pressure to the lower surface of the support. The magnetic powder molding apparatus according to any one of claims 4 to 6 , wherein a seal member that seals a gap between the intermediate member guide portion and the intermediate member is provided on an outer periphery of a lower end surface of the intermediate member. The magnetic powder molding apparatus according to claim 4 , wherein the pressure medium is a resin having a crosslinked structure and a Shore A hardness of 50 or less. Filling the magnetic powder into a molding space constituted by a die and a lower punch fitted to the die; and
Inserting a plurality of upper punches from above in the plurality of molding spaces;
Compressing the magnetic powder at the lower end surface of the upper punch and the upper end surfaces of a plurality of lower punches inserted from below into each molding space;
The step of making the compressive force of the magnetic powder in each molding space substantially uniform by a pressure medium that acts in common on the lower end surfaces of the plurality of lower punches and is made of a low-hardness elastic body or viscoelastic body ;
Prior to the step of filling the magnetic powder, aligning upper end surfaces of the plurality of lower punches inserted in the molding spaces;
In the compression molding step of the magnetic powder, the entire pressure medium is moved downward by the compression action of the upper punch,
Applying a fluid pressure to the lower surface of the support plate that supports the pressure medium over the entire lower surface . 10. The magnetic powder molding according to claim 9 , wherein a liquid seal type pressure medium in which a liquid is sealed in a flexible hollow film is used instead of the pressure medium made of the low-hardness elastic body or viscoelastic body. Method.

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