JP6693620B2 - Powder molding machine and powder filling method - Google Patents

Description

The present invention relates to a powder molding machine and a powder filling method.
This application claims the priority right based on Japanese application No. 2015-172915 filed on September 2, 2015, and incorporates all the contents described in the Japanese application.

  The following Patent Documents 1 and 2 disclose that the powder feeding box is accompanied by a vibrator (vibration generator) to vibrate the powder feeding box when the powder is charged.

Japanese Utility Model Publication No. 2-25537 Japanese Patent No. 3063499

The powder molding machine according to the present disclosure has a mold in which a cavity is formed, a die plate for holding the mold, and a lower outlet having the same shape as the upper inlet shape of the cavity, and is installed on the die plate. And a shaker connected to the powder feeding box and vibrating in the vertical direction, and a shutter installed at the lower outlet of the powder feeding box.

FIG. 1 is a sectional view showing a main part of a powder molding machine according to an embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. 1 of the powder feeding box according to the embodiment. FIG. 3 is a cross-sectional view of a state in which the powder feeding box is arranged above the cavity. FIG. 4 is a plan view of the powder feeding box of FIG. FIG. 5 is a partially cutaway enlarged plan view of the engaging portion of the powder feeding box and the drive lever of the drive mechanism according to the embodiment.

The powder molding machine includes a powder feeding box that moves from a standby position to a powder feeding position and feeds raw material powder (hereinafter simply referred to as powder) into a cavity of a mold.

  Generally, the powder is put into the cavity from the powder feeding box by spontaneous fall, but in this method, the phenomenon that the powders form an arch structure, so-called bridge, is concerned about the dispersion of the packing density. ..

  Therefore, Patent Documents 1 and 2 propose to attach a vibrating machine (vibration generator) to the powder feeding box to vibrate the powder feeding box when the powder is charged.

  The powder molding machine (powder pressing device) described in Patent Document 1 is provided with a sieve at the bottom of the powder feeding box, and the powder to be introduced into the cavity is sieved so that bridging is less likely to occur and uneven feeding is performed. It suppresses.

  Further, in the powder molding machine described in Patent Document 2, the inside of the lower portion of the powder feeding box is divided into a plurality of chambers by vertical and horizontal partition plates, and the powder feeding box is vibrated when the powder is charged into the cavity. Vibration is propagated to the charged powder through the partition plate to break the bridge generated in the charged powder.

  In the production of sintered parts, it is important not only to make the packing density of the powder in the cavity of the mold uniform, but also to reduce the amount of air trapped in the packed powder (so-called inclusion amount).

  This is because, especially in high-density molding and high-precision molding of powder, when air is trapped inside the powder filled in the cavity, the enclosed air is compressed by the molding pressure, and when the molded body is extracted from the mold, This is because the air may expand and the molded body may be damaged.

  The expansion of the enclosed air occurs even when the molded body is heat-treated, and the molded body may be damaged or deformed (expanded) during the heat treatment.

  In order to solve the problem, it is required to reduce the amount of air contained in the compact in the production of high-density parts and high-precision parts. In the conventional powder molding machine and the above-mentioned Patent Documents 1 and 2, The powder molding machine described does not give the expected effect.

  Since the powder molding machine of Patent Document 1 only sifts the powder to be charged and causes the powder to fall naturally, the effect of rearranging the powder cannot be obtained, and the amount of entrapped air increases.

  Further, in the powder molding machine of Patent Document 2, the vibration from the powder feeding box is transmitted to the powder put into the cavity, but due to the structure of the powder feeding box, the vibration is lateral vibration. Therefore, the rearrangement of the powder put into the cavity does not proceed effectively, and it is difficult for the molding machine of Patent Document 2 to sufficiently reduce the air inclusion amount.

For example, in a dust core (powder core) used in a motor, a reactor, or the like, in order to obtain better magnetic characteristics, it is desired to apply a high molding pressure to increase the molding density as much as possible.
In order to meet the demand, it is necessary to solve the above-mentioned problems of damage and deformation due to the contained air.

Therefore, an embodiment of the present invention has an object to provide a powder molding machine and a powder filling method in which an air inclusion amount of input powder is reduced and high density filling of powder into a cavity is realized.
[Means for solving the problem]

  A powder molding machine according to the present disclosure has a mold in which a cavity is formed, a die plate for holding the mold, and a lower outlet having the same shape as the upper inlet shape of the cavity, and is installed on the die plate. And a shaker connected to the powder feeding box and vibrating in the vertical direction, and a shutter installed at the lower outlet of the powder feeding box.

Further, the powder filling method according to one aspect of the present invention taps the powder in the powder feeding box by vertically vibrating the powder feeding box of the powder molding machine according to one aspect of the present invention by the vibrator. The method includes a vibrating step for increasing the density and a charging step for opening the shutter below the powder feeding box and charging powder having a tap density into the cavity of the mold.
[The invention's effect]

According to the powder molding machine and the powder filling method according to the aspect of the present invention, the powder is densely filled in the cavity of the mold.
[Description of Embodiments of the Present Invention]
A powder molding machine according to one embodiment of the present invention is listed below. The powder molding machine includes a mold, a die plate that holds the mold, and a powder feeding box that moves on the die plate. The mold includes a die, a punch, and a core rod that is additionally provided if necessary. The powder feeding box moves on the die plate from the standby position toward the powder feeding position, and feeds the powder into the cavity of the die at the powder feeding position. The powder feeding box has a lower outlet that has the same shape as the upper inlet shape of the cavity. Equipped with a shutter that opens and closes. Here, to vibrate vertically means to vibrate in a direction parallel to the axis of the cavity.

  Here, the powder feeding box having a lower outlet having the same shape as the upper inlet shape of the cavity means a powder feeding box having a lower outlet having the same planar contour shape or a similar shape as the planar contour shape of the upper inlet of the cavity. Say For example, if the cavity has a ring-shaped upper inlet in plan view, the powder feeding box has a ring-shaped lower outlet.

The size of the lower outlet of the powder feeding box may be equal to the size of the inlet of the cavity, but rather than that, in consideration of the springback amount when the powder having the tap density comes out from the powder feeding box. It is preferable that the size is smaller than the size of the upper inlet of the cavity.
Here, the tap density is a density in a state where the container is vibrated after the powder is put into the container and the volume of the powder is no longer reduced. The measuring method is according to ISO 3953: 2011.

  The powder feeding box is vibrated by the vibration exciter with the shutter closed.

  The supply of powder to the powder feeding box and the vibration of the powder feeding box by the vibrator may be performed with respect to the powder feeding box moved to the standby position, or the powder feeding box is It may be performed at any position in the moving area.

  The vibration of the powder feeding box may be performed at any time before the powder feeding into the cavity is started. By vibrating the powder feeding box, vertical vibration is applied to the powder put in the powder feeding box, and the vibration causes the rearrangement of the powder in the powder feeding box to be forced and effective. ..

  Since the powder in the powder supply box is supported by the shutter that closes the lower outlet, the entire area of the powder supplied to the powder supply box vibrates uniformly.

  Due to the rearrangement of the powder due to the vibration, the powder in the powder feeding box has a tap density, and is then charged into the cavity. Since the lower outlet of the powder feeding box has the same shape as the upper inlet of the cavity, the powder having the tap density can be fed without being broken.

  Therefore, the amount of air contained in the powder filled in the cavity is reduced, and even if the obtained molded body has a high density, damage or deformation (swelling during heat treatment) due to the contained air is prevented. It

  In addition, when the powder having the tap density is introduced, the packing density of the powder with respect to the volume of the cavity is higher than that of the conventional powder molding machine. The total length of the die can be shortened by reducing the volume of powder to be filled. Along with that, the total length of the upper and lower punches can be shortened to reduce the distortion of the punches at the time of forming, which leads to an improvement in forming accuracy.

  In addition, since the packing density of the powder with respect to the volume of the cavity is increased, the variation in the amount of air inevitably contained in the filled powder is reduced, and the variation in the weight of the compact is also suppressed.

  It is preferable that the side wall of the powder feeding box has a taper angle (this is referred to as an inverse taper angle) such that the upper space is narrowed. More preferably, a reverse taper angle having a value larger than the springback amount of the powder having the tap density is provided to make it difficult to generate frictional resistance when the powder is charged into the cavity. A preferable inverse taper angle is 0.05 ° to 1 °.

When the inverse taper angle is 0.05 ° or less, the effect of reducing the frictional resistance when the powder is charged into the cavity is small, and when it is about 1 °, the effect is saturated.

  Further, it is preferable that the size of the lower outlet of the powder feeding box is slightly smaller than the size of the upper inlet of the cavity (preferably, a sliding gap is secured between the powder and the cavity). With these treatments, the powder can be smoothly put into the cavity from the powder feeding box. The difference between the size of the lower outlet and the size of the upper inlet is preferably 0.01 mm to 1.0 mm in the radial direction.

  In the powder molding machine according to one aspect of the present invention, it is preferable that a drive mechanism for moving the powder feeding box is installed on the die plate. More preferably, the drive mechanism has a drive lever connected to the powder feeding box, and the connection between the drive lever and the powder feeding box is permitted relative movement in the vertical direction and is restricted from relative movement in the push-pull direction. ing. More preferably, the drive mechanism includes a connector provided in the powder feeding box and having a vertically extending slot, and a drive lever inserted into the slot.

  Since the powder feeding box is not constrained in the vertical direction, the powder feeding box can vibrate vertically without receiving the load of the drive mechanism and the drive lever.

  In the powder filling method according to one aspect of the present invention, the powder feeding box provided with the shaker and the shutter that opens and closes the lower outlet is vibrated in the vertical direction by the shaker so that The powder is filled in the cavity through a step of making the powder have a tap density and a step of opening the shutter below the powder feeding box and introducing the powder having the tap density into the cavity of the mold.

  In this method, the powder may be introduced into the cavity from the powder supply box by either dropping powder supply or suction powder supply. The drop powder feeding is a method of feeding powder from the powder feeding box into the cavity having a defined volume.

  The suction dusting is the following dusting method. First, the die is lowered to a position where the upper surface of the die and the upper end of the lower punch are aligned. Next, the volume is expanded while raising the die, and at the same time, powder is charged into the cavity from the powder feeding box. According to the suction powdering, the effect of high-density filling is exhibited by the above-mentioned action.

  In the powder filling method according to one aspect of the present invention, the scraping of the powder charged in the cavity can be performed by a die and the powder feeding box that returns to the standby position after the powder is charged. Preferably, after the powder is charged into the cavity, the lower outlet is closed by the shutter that is in contact with the upper surface of the die, and the shutter is used for scraping.

  When the powder is scraped off by the shutter, the weight of the powder in the cavity does not change due to the powder remaining in the powder feeding box falling into the cavity. Therefore, the difference in density of the filled powder before and after the powder feeding box in the advancing / retreating direction is suppressed to be smaller, and the accuracy (coaxiality, etc.) and performance of the product obtained by sintering the obtained molded body are improved.

A powder molding machine according to an aspect of the present invention is a die having an inner peripheral surface that cuts vertically, a core rod inserted into the die, a die plate that holds the die, and a shape of the inner peripheral surface of the die that is similar to the die. -Shaped lower outlet and a cylinder having a shape similar to the outer peripheral surface shape of the core rod, a powder feeding box installed on the die plate, a vibrator that is connected to the powder feeding box and vibrates in the vertical direction, and A shutter installed at the lower outlet of the powder feeding box, a connector having a vertically extending slot installed in the powder feeding box, and a drive lever inserted into the slot.

With such a configuration, the cavity of the mold is densely filled with powder.

[Details of the embodiment of the present invention]
Specific examples of a powder molding machine and a powder filling method according to an aspect of the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples and is shown by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

  The powder molding machine 1 shown in FIG. 1 is configured by combining a die 2, a upper punch 3, a lower punch 4, a core rod 5, a powder feeding box 6 and a vibrating machine 7 which constitute a mold.

  The die 2 is supported by a die plate 8. The upper punch 3 is supported by an upper punch plate 9 driven by an upper ram (not shown) of the press machine, and the lower punch 4 is supported by a base plate 10.

  Further, the die plate 8 is connected via a connecting rod 12 to a yoke plate 11 driven by a lower ram (also not shown) of the pressing machine.

  The upper surface of the die 2 supported by the die plate 8 can be lowered by driving the yoke plate 11 until it is aligned with the upper end of the lower punch 4.

  The cavity 13 is formed by the inner peripheral surface 24 of the die 2, the upper end of the lower punch 4, and the outer peripheral surface 25 of the core rod 5.

As shown in FIG. 4, in the powder feeding box 6, the shape of the lower outlet 23 in plan view is similar to the shape of the upper inlet 22 of the cavity 13 (that of the illustrated powder molding machine has an inner contour and an outer shape). Concentric circles) are provided. The size of the lower outlet 23 is set to be 0.5 mm smaller than the inner peripheral surface 24 in the radial direction.

  As shown in FIG. 2, the side wall 6a of the powder feeding box 6 is provided with an inverse taper angle θ that narrows the upper gap. The inverse taper angle θ is set to about 0.05 ° to 1 °. When the inverse taper angle θ is 0.05 ° or less, the effect of reducing the frictional resistance when the powder is charged into the cavity 13 is small, and when it is about 1 °, the effect is saturated.

  Further, at the lower part of the powder feeding box 6, there is provided a shutter 14 formed of a thin flat plate for opening and closing the lower outlet 23 for powder.

  An actuator 15 that drives the shutter 14 is attached to the powder feeding box 6 and moves on the die plate 8 together with the powder feeding box 6.

In the powder molding machine 1, as shown in FIG. 1, the drive lever 16a of the drive mechanism 16 installed on the die plate 8 is connected to the rear of the side wall 6a of the powder feeding box 6. The movement from the standby position on the die plate 8 to the powder charging position on the cavity 13 and the return from the powder charging position to the standby position are performed by advancing and retracting the drive lever 16a.

    As shown in FIG. 2, the powder feeding box 6 is a box whose upper end is opened, and is pushed by the drive lever 16a and slides on the die plate 8 to move from the standby position to the powder feeding position. Move towards. Here, the powder feeding box 6 has a cylinder 6c extending in the vertical direction. The cylinder 6c is supported by the side wall 6a of the powder feeding box 6 at a position corresponding to the core rod 5 via a support pin 6b and the like.

 As shown in FIG. 3, the cylinder 6c has an upper surface and a side surface 26. The tube may have a lower surface.

As shown in FIG. 4, the outer peripheral shape of the lower end of the side surface 26 is similar to the outer peripheral surface 25 of the upper end of the core rod 5. The size of the lower end of the side surface 26 is set to be 0.5 mm larger than the outer peripheral surface 25 in the radial direction.

  The powder molding machine 1 is a molding machine using an NC servo press machine, and when the powder feeding box 6 is at the standby position, a fixed amount of powder is supplied from the hopper 17 at the upper portion to the powder feeding box 6. It

  Further, in the powder molding machine 1, the vibrator 7 is attached to the outer surface of the side wall 6 a of the powder feeding box 6, and the vibrator 7 vertically vibrates the powder feeding box 6.

  The vibrator 7 may be a commercially available linear vibration type air vibrator or the like. The drive lever 16a is connected to the powder feeding box 6 so that the load of the lever is not applied so as not to hinder the vibration of the vibrator 7.

  In the powder molding machine 1, as shown in detail in FIGS. 4 and 5, a connector 18 is attached to the rear portion of the powder feeding box 6. The T-shaped slot 19 provided in the driving lever 16a in the T-shaped slot 19 extending in the vertical direction, which is provided in the connecting tool, allows relative movement of the head portion 20 having the T-shaped plan view in the vertical direction with respect to the powder feeding box 6. Are connected so that relative movement in the push-pull direction is restricted. Therefore, the powder feeding box 6 can vibrate up and down without receiving the load of the drive lever 16a.

  It is preferable that a ball plunger 21 is provided on the connecting tool 18 in contact with the surface of the head portion 20 to reduce the sliding resistance of the vertical movement of the powder feeding box 6 and guide the ball feeding box 6.

  In the powder molding machine 1 configured as described above, a fixed amount of powder is supplied to the powder feeding box 6 when the powder feeding box 6 is at the standby position. At this time, the shutter 14 is closed.

  When the supply is completed, the powder feeding box 6 is vertically vibrated by the vibrator 7 with the shutter 14 closed. The powder feeding box 6 may be vibrated when it is at the standby position, or may be vibrated while the powder feeding box 6 is moving toward the powder feeding position. Although it may be vibrated after moving to the powder feeding position, if the vibration is completed before reaching the powder feeding position, the time required for the molding process is reduced.

  Due to this vibration, the powder supported by the shutter 14 in the powder feeding box 6 vibrates. The powder is rearranged to a tap density by repeating the operation of lifting and dropping the powder.

  When the powder in the powder feeding box 6 has a tap density due to the vibration for a predetermined time (the time may be several seconds depending on the size of the powder feeding box, the application condition of the vibration, etc.), the shutter 14 is opened to open the powder. Is charged into the cavity 13.

  This charging is performed by either drop powder feeding or suction powder feeding. Since the side wall 6a of the powder feeding box 6 has the reverse taper angle θ, the powder can be smoothly introduced into the cavity 13 by either powder feeding method.

  When the powder is put into the cavity 13, the upper surface of the put powder is scraped off in order to make the filling amount of the powder in the cavity 13 constant.

  In the powder molding machine 1, the powder is scraped off by the shutter 14. Specifically, the powder is rubbed off by closing the shutter 14 in contact with the upper surface of the die 2. As a result, the powder protruding from the cavity 13 is separated from the powder in the cavity 13.

  It is also possible to scrape off the powder by the side wall 6a on the front side of the powder supply box 6 when the powder supply box 6 moves to the standby position. However, when the powder is scraped off by the shutter 14, the powder remaining in the powder feeding box 6 is not received by the shutter 14 and the powder remaining does not fall into the cavity 13. It is more preferable for homogenizing the density.

  In the powder feeding box 6, since the lower outlet 23 has the same shape as the upper inlet 22 of the cavity 13, powder having a tap density is thrown into the cavity 13 without breaking, and air is fed to the charged powder. The situation of being newly mixed is avoided.

  The powder can be supplied to the powder supply box 6 by connecting the powder supply box 6 and the hopper (not shown) that is a powder supply source through a hose. However, the method of supplying the powder to the powder feeding box 6 at the standby position is preferable to this method because the powder is less likely to be biased in the powder feeding box 6.

After feeding the powder into the cavity 13, the powder feeding box 6 slides on the die plate 8 and returns to the standby position. Then, the upper punch 3 descends and the powder in the cavity 13 is pressure-molded.

-Example 1-
The results of the evaluation test of the powder molding machine and powder filling method of the present invention are shown below. The evaluation test was performed using the three types of powders shown in Table 1. Table 1 shows each density and the ratio of each density to the intimacy degree.

  In this test, the prepared powder was prepared by using a die having an inner diameter = φ50 mm, a core rod having an outer diameter = φ30 mm, an upper punch having inner and outer diameters set to values that ensure sliding clearance between the die and the core rod, and Using a die provided with a lower punch, 30 ring-shaped compacts of No. 1 to No. 23 under the combination conditions of Table 2 having an outer diameter of 50 mm, an inner diameter of 30 mm and a thickness of 15 mm were molded.

  As shown in Table 2, the powder molding machine has a powder feeding box having a square outlet in plan view larger than the inlet shape of the cavity, and the same shape as the upper inlet of the cavity in plan view. The one having an outlet of () is used.

  In addition, if the powder feeding box has a lower outlet in the shape of a product, the powder feeding box performs three patterns of vibration without vibration, horizontal vibration, and vertical vibration, depending on the presence or absence of vibration and the difference in vibration direction. I investigated the effect.

  Furthermore, the effects of the reverse taper of the side wall of the powder feeding box and the presence or absence of scraping of the powder introduced into the cavity by the shutter were also investigated.

  Powder A was non-lubricated, and powders B and C were formed by spraying a solution (lubricant) of zinc stearate dissolved in alcohol on a mold. Further, the powder was introduced into the cavity by suction powder feeding while raising the die lowered to a position where the upper surface of the die and the upper end of the lower punch were aligned.

  Further, as the vibrator for vibrating the powder feeding box, a linear vibration type air vibrator {Piston air vibrator 3/4 "ACM (vibration frequency 60 Hz) manufactured by Uras Techno Co., Ltd.] was used.

  With respect to the vibration of the powder feeding box by the vibrator, in the case of vertical vibration, the powder in the powder feeding box could be made to have a tap density in 2 to 3 seconds. With this time, there is little influence on the molding time of mass-produced products.

  The results of this test are shown in Table 2.

  From the test results shown in Table 2, it can be seen that according to the present invention, the packing density of the molded body is increased and the amount of air contained therein is decreased. The decrease in the amount of included air makes it less likely that damage due to high pressure and the amount of included air in the high-density molded article will occur during ejection from the mold, damage during heat treatment, and swelling.

  Further, it can be seen that since the filling depth of the powder into the cavity becomes shallower than that in the case where there is no vibration or the vibration in the lateral direction, it is possible to reduce the size of the mold (die) and also to expect the distortion of the mold to be reduced.

  Furthermore, it can be seen that when the vibration of the powder feeding box in the vertical direction, the impartation of an inverse taper to the side wall of the box, and the scraping of the input powder by the shutter are used together, the coaxiality (fluctuation) of the outer peripheral surface and the inner peripheral surface of the compact is significantly increased.

-Example 2-
The molded articles of Nos. 9 to 23 of Example 1 were heated to 250 ° C., including those having swelling, and the occurrence of deformation and damage after heating was examined. The results are shown in Table 2 as X, Y and Z. Here, X is one in which no swelling occurs in 30 pieces, Y is less than 10 in 30 pieces in which a bulge occurs and the molded body is chipped, and Z is swelling occurs The number of bodies lacking more than 10 out of 30 is shown.

It can be seen that when the vibration of the powder feeding box in the vertical direction, the provision of an inverse taper to the side wall of the box, and the scraping of the input powder by the shutter are used together, chipping of the compact does not occur.

1 Powder Forming Machine 2 Die 3 Upper Punch 4 Lower Punch 5 Core Rod 6 Powder Feeding Box 6a Side Wall 6b Support Pin 6c Cylinder 7 Vibrator 8 Die Plate 9 Upper Punch Plate 10 Base Plate 11 Yoke Plate 12 Connecting Rod 13 Cavity 14 Shutter 15 Actuator 16 Drive mechanism 16a Drive lever 17 Hopper 18 Connecting tool 19 Slot 20 Head part 21 Ball plunger 22 Upper inlet 23 Lower outlet 24 Inner peripheral surface 25 Outer peripheral surface 26 Side surface θ Reverse taper angle

Claims (7)

A mold with a cavity,
A die plate for holding the mold,
A powder feeding box installed on the die plate, having a lower outlet having the same shape as the upper inlet shape of the cavity,
A vibrator that is connected to the powder feeding box and vibrates vertically.
A shutter installed at the lower exit of the powder feeding box ,
Side walls of the paper powder box, flour powder molding machine that have a reverse taper values in excess of 0.05 °. The powder molding machine according to claim 1 , wherein a driving mechanism for moving the powder feeding box is installed on the die plate. The drive mechanism comprises a drive lever coupled to the feed powder box, connecting the feed powder box and said drive lever is relative movement in the vertical direction is allowed, the claims relative movement of the push pull direction is prevented 2 The powder molding machine described in 1. The powder molding machine according to any one of claims 2 to 3 , wherein the drive mechanism includes a connecting member having a vertically extending slot installed in the powder feeding box, and a drive lever connecting with the connecting member. A powder filling method for charging powder into a cavity of a mold using the powder molding machine according to any one of claims 1 to 4 ,
A vibration step in which the powder feeding box is vibrated in the vertical direction by the vibrator to make the powder in the powder feeding box have a tap density,
A charging step of opening a shutter below the powder feeding box and charging powder having a tap density into the cavity of the mold. The powder filling method according to claim 5 , further comprising a scraping step of scraping off the powder on the upper surface of the cavity with the shutter after the charging step. A die having an inner peripheral surface that penetrates vertically,
A core rod inserted into the die,
A die plate for holding the die,
Having a lower outlet similar to the inner peripheral surface shape of the die and a cylinder similar to the outer peripheral surface shape of the core rod, a powder feeding box installed on the die plate,
A vibrator that is connected to the powder feeding box and vibrates vertically.
A shutter installed at the lower exit of the powder feeding box,
A connector having a slot installed in the powder feeding box and extending in the vertical direction,
A powder molding machine comprising: a drive lever inserted into the slot.

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