JP2005224807A - Powder forming apparatus, formed body made by the same, and sintered component made from the same formed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder forming apparatus which can improve the concentricity of the outside and inside diameters and the run-out of the end face of a sintered component. <P>SOLUTION: A core holder 21 is mounted on a die plate 16 holding a die 13 at a position nearer a cavity than a base plate 15. A core 14 is held by the core holder 21. In addition, a plurality of legs extending downward from a lower punch 12 are connected at an interval in the peripheral direction. The legs are inserted into through holes so as to vertically move, the through holes being provided on the core holder 21 so as to correspond to the respective legs. The lower punch 12 is held by supporting the lower portions of the legs 12b by means of a base plate 15. By this constitution, the stiffness and supporting stability of the core 14 affecting the concentricity of the outside and inside diameters and the run-out of the end face of the formed body can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a powder molding apparatus used in powder metallurgy, a molded body molded by the apparatus, and a sintered part such as a pump rotor obtained by sintering the molded body.

  For example, when a rotor of an internal gear pump is manufactured by a powder metallurgy method, a powder forming apparatus having an upper punch, a lower punch, a die and a core rod is used. An outline of a conventional example of the powder molding apparatus is shown in FIG.

  In the figure, 1 is an upper punch, 2 is a lower punch, 3 is a die, and 4 is a core rod.

  The upper punch 1 is attached to an upper ram (not shown) of the press machine. The lower punch 2 is fixed on the base plate 5, the die 3 is held by the die plate 6, and the core rod 4 is attached to the yoke plate 7.

  The die plate 6 and the yoke plate 7 are connected to each other via a connecting rod 8, so that the die 3 and the core rod 4 move in synchronization.

  In this conventional powder molding apparatus, a material powder is filled in a cavity 9 formed between a lower punch 2, a die 3 and a core rod 4, and then molding is performed by lowering the upper punch 1. When the upper punch 1 is inserted into the die 3 as far as there is, the die 3 and the core rod 4 begin to move down following the movement of the upper punch 1 due to friction generated between the upper punch 1 and the upper punch 1 is moved in this state. Lowering to the bottom dead center completes molding. Thereafter, the die 3 and the core rod 4 are further lowered, and the completed molded body is extracted from the cavity 9.

  When such a conventional powder molding apparatus is designed so that it can be used with a general-purpose press, the entire length of the core rod 4 becomes long and the support of the core rod 4 becomes unstable.

  The upper part of the core rod 4 is guided by the lower punch 2, but there is a sliding gap as a lateral movement allowance with the lower punch 2, so that the core rod 4 is moved in one direction by the force acting during powder molding. Alternatively, the core rod 4 is tilted (inclined), which causes the inner and outer diameters of the molded body to be misaligned, and the deflection accuracy (perpendicularity) of the end surface with respect to the inner and outer diameters is deteriorated. To do.

In addition, the following Patent Document 1 describes that the centering and positioning with a die (upper and lower punches) can be facilitated by giving flexibility to the attachment of a very long core rod. It is difficult to solve the above problem no matter how accurately the alignment and alignment are performed.
JP-A-8-257799

  The present invention relates to a powder molding apparatus and a molding apparatus that can perform molding while minimizing the deviation between the inner and outer diameter shaft centers of the molded body and the fluctuation of the end surface with respect to the inner and outer diameter shaft centers. An object of the present invention is to provide a high-precision sintered part such as a pump rotor formed by molding.

  In order to solve the above problems, in the present invention, an upper punch, a lower punch, a die, and a core are provided, and a core holder is attached to a die plate that holds the die at a position closer to the cavity than a base plate, and the core holder uses the core holder. In addition, a plurality of legs suspended at the lower part of the lower punch are connected at intervals in the circumferential direction, and the plurality of legs can be moved up and down in the through holes provided in the core holder corresponding to each leg. A powder molding apparatus is provided in which the lower part of the foot is supported by a base plate and the lower punch is held.

  In this powder molding apparatus, a protrusion projecting radially outward is provided on the outer periphery of the lower punch holder provided on the base plate, and a circumferential position in which the height position is aligned with the outer periphery near the lower end of each foot of the lower punch. A groove is provided, and a half ring is attached to the outer periphery of the lower punch holder and the lower punch foot, and a first claw provided on the inner surface side of the half ring is provided in the groove on the outer periphery of each foot. It is desirable that the claws are engaged with the convex portions on the outer periphery of the lower punch holder, and a detachable binding ring is fitted on the outer periphery of the half ring to attach the lower punch to the base plate.

  In a molded body such as a pump rotor produced by performing powder molding before sintering with the powder molding apparatus of the present invention, the deflection of the inner and outer diameter shaft centers is suppressed to 0.03 mm or less. The present invention also provides the molded body and a sintered part obtained by sintering the molded body.

  In the powder molding apparatus of the present invention, the core holder that does not interfere with the lower punch is attached to the die plate at a position closer to the cavity than the base plate, and the core is supported by the die plate. This increases the rigidity and support stability of the core, and reduces the displacement and collapse of the core due to the molding pressure. The concentricity and the runout accuracy of the end surface with respect to the inner and outer diameter shaft centers are increased.

  In addition, if the structure desired in the above is adopted, the mold can be easily and quickly replaced. Detailed explanation on this will be given in the next section.

  Hereinafter, an embodiment of the powder molding apparatus of the present invention will be described with reference to FIGS. 1 and 2. In the figure, 11 is an upper punch, 12 is a lower punch, 13 is a die, and 14 is a core.

  The upper punch 11 is attached to an upper ram (not shown) of the press machine. The lower punch 12 is attached to the base plate 15 using a lower punch holder 19 and a punch connector 20, and the die 13 is held by the die plate 16.

  The die plate 16 and the yoke plate 17 are connected to each other via a connecting rod 18 slidably inserted into the base plate 15 and move in synchronization.

  The core 14 has a core holder 21 attached to the die plate 16 and is attached to the core holder 21 with bolts 22. The illustrated core 14 has a spacer 31 interposed between the core holder 21 and the height of the core 14 can be adjusted by exchanging the spacer. However, the spacer 31 may be provided as necessary. The core holder 21 is provided at a position closer to the cavity than the base plate 15.

  As shown in FIG. 2, the lower punch 12 has a structure in which a plurality of suspended legs 12b are continuously provided at intervals in the circumferential direction below a main portion 12a involved in powder molding. Although the main portion 12a is represented by a simple cylindrical shape, it is actually formed into a shape corresponding to the cross-sectional shape of the product. For example, when the object to be molded is an outer rotor of an internal gear pump, the cross-sectional shape of the main portion 12a is such that the outer periphery is a perfect circle and the inner periphery has teeth and tooth grooves alternately arranged.

  If the foot 12b is provided in a portion where the radial thickness of the main portion 12a is large, it is easy to ensure the strength. For example, when there are the aforementioned teeth and tooth gaps on the inner periphery of the main portion 12a, it is easy to ensure the strength by providing the legs 12b with the teeth of the main portion extended. If interference with the die 13 and the core holder 21 does not occur, the radial thickness of the foot 12b may be made larger than the thickness of the corresponding portion of the main portion 12a, and this method can also increase the strength of the foot 12b.

  The core holder 21 is provided with through holes 21a corresponding to the respective legs 12b of the lower punch 12, and the lower punch legs 12b are passed through the through holes 21a so as to be movable up and down. 19 is connected.

  When the connection is performed using the illustrated punch connector 20 including the half ring 23 and the bundling ring 24, the mold can be easily and quickly replaced.

  The illustrated punch connector 20 is provided with a convex portion 25 such as a heel projecting radially outward on the outer periphery of the lower punch holder 19, and a circumferential groove 26 with a height position aligned on the outer periphery of each foot 12 b. Furthermore, the 1st nail | claw 27 and the 2nd nail | claw 28 corresponding to the convex part 25 and the groove | channel 26 are provided in the inner surface side of the half ring 23. FIG. The first and second claws 27 and 28 may be inner flanges or claws scattered in the circumferential direction.

  This punch connector 20 has a half ring 23 attached to the outer periphery of the lower punch holder 19 and the lower punch foot 12b, and the second pawl 28 is attached to the convex portion 25 on the outer periphery of the lower punch holder 19 to each foot 12b. The first claws 27 are engaged with the outer circumferential grooves 26, respectively. After that, the bundling ring 24 is fitted on the outer side so that the connection state by the half ring 23 is maintained. By simply removing the bundling ring 24, the half ring 23 is removed and the lower punch 12 with respect to the lower punch holder 19 is removed. Can be disconnected.

  The die 13 is pressed and fixed by a pressing plate 29. Therefore, the lower punch 12 is disconnected by the punch connecting tool 20, and the fastener (bolt 30 in the figure) between the pressing plate 29 and the die plate 16 is removed. The lower punch 12, die 13 and core 14 can be easily and collectively replaced.

  The illustrated powder molding apparatus configured as described above performs powder molding and extraction of the molded body from the die by the same procedure as in the conventional apparatus.

  Next, a confirmation test result will be described as an effect of the powder molding apparatus of the present invention. The test was obtained by molding 30 outer rotors of an internal gear pump having an outer diameter of 90 mm, a tip diameter of 70 mm, and 10 teeth using the powder molding apparatus of the present invention and a conventional powder molding apparatus. We investigated the deflection accuracy at the center of the outer diameter and the deflection accuracy of the end face.

As shown in FIG. 3, the center and outer diameter accuracy of the inner and outer diameters was measured by measuring the thickness (diameter dimension a) of each of No. 1 to No. 10 teeth of the molded outer rotor R, and 30 samples. No. 1 to No. 10 were evaluated by calculating the difference between the maximum thickness (a _max ) and the minimum thickness (a _min ) of each tooth.

  In addition, the runout accuracy of the end face is determined by examining the total length of the tip of each tooth (the axial length of the center of the tip), and the maximum length and minimum length in the compression molding direction by punching the teeth of No. 1 to No. 10. The difference in length (full length difference) was determined and evaluated.

  Table 1 shows the total length difference and thickness difference of each tooth of the outer rotor formed by the powder forming apparatus of the present invention in which the core is supported by the die plate and the conventional powder forming apparatus in which the core is supported by the yoke plate.

  In Table 1, A represents an inventive product molded with the powder molding apparatus of the invention, and B represents a comparative product molded with a conventional powder molding apparatus. The unit of numerical values in the table is (mm).

  As can be seen from the results of this comparative test, the invention product A molded with the powder molding apparatus of the present invention has both a maximum value and a minimum value for both the overall length difference and the wall thickness difference compared to the comparative product B molded with the conventional powder molding apparatus. The difference is almost halved, and the effect of improving accuracy is great. The maximum value of the total length difference of Invention Product A is 0.027 mm, which is smaller than the minimum value of the total length difference of Comparative Product B of 0.034 mm. Moreover, the maximum value of the thickness difference of the invention product A is 0.013 mm, which is smaller than the minimum value of 0.015 mm of the thickness difference of the comparative product B. In the present invention, a molded body such as a pump rotor having an inner and outer diameter shaft center deflection of 0.03 mm or less produced by molding with the powder molding apparatus of the present invention, and a sintered part obtained by sintering the molded body Also provided.

  In the internal gear pump, the discharge performance and the like greatly depend on the degree of concentricity of the outer diameter of the inner rotor and the outer rotor, and the accuracy of the end face runout. Therefore, the powder molding apparatus of the present invention can be expected to have a great effect when used for molding a pump rotor that is made by sintering. In addition, a great effect can be expected even when used for molding sintered parts other than the rotor for pumps that require the concentricity of the inner and outer diameters and the deflection accuracy of the end face.

Sectional drawing which shows the outline | summary of an example of the powder shaping | molding apparatus of this invention The disassembled perspective view which shows the lower punch of the apparatus of FIG. 1, a lower punch holder, and a punch coupling tool Side view showing an example of an outer rotor molded by the apparatus of the present invention The figure which shows the outline | summary of an example of the conventional general powder shaping | molding apparatus.

Explanation of symbols

11 Upper punch 12 Lower punch 12a Main portion 12b Foot 13 Die 14 Core 15 Base plate 16 Die plate 17 Yoke plate 18 Connecting rod 19 Lower punch holder 20 Punch connector 21 Core holder 21a Through hole 22, 30 Bolt 23 Half ring 24 Binding ring 25 Convex 26 Groove 27 First Claw 28 Second Claw 29 Holding Plate 31 Spacer

Claims (4)

  An upper punch, a lower punch, a die, and a core are provided. A core holder is attached to a die plate that holds the die at a position closer to the cavity than the base plate, the core holder is used to hold the core, and the core is suspended below the lower punch. A plurality of legs are connected in series in the circumferential direction, and the plurality of legs are passed through through holes provided in the core holder so as to correspond to the legs, and the lower part of the legs is supported by a base plate. Powder molding machine holding the lower punch.   A protrusion projecting radially outward is provided on the outer periphery of the lower punch holder provided on the base plate, and a circumferential groove having a height position is provided on the outer periphery near the lower end of each foot of the lower punch. A half ring is attached to the outer periphery of the legs of the punch holder and the lower punch, and a first claw provided on the inner surface side of the half ring is placed in the groove on the outer circumference of each leg, and a second claw is placed on the lower punch holder 2. The powder molding apparatus according to claim 1, wherein the lower punch is attached to the base plate by engaging each of the protrusions on the outer periphery of the ring and further fitting a detachable binding ring on the outer periphery of the half ring.   A molded body produced by performing powder molding before sintering with the powder molding apparatus according to claim 1 and having a deflection of the inner and outer diameter shaft centers of 0.03 mm or less.   A sintered part obtained by sintering the molded body according to claim 3.

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