JP2008087008A - Powder molding device and powder molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder molding device and a powder molding method, capable of preventing the generation of an overshoot phenomenon while attaining high speed of the whole powder molding cycle. <P>SOLUTION: The powder molding device 1 is equipped with: a die 3 and a lower punch 5 combined in a relatively movable relation each other; an upper punch applying pressurizing force to a molding chamber 15 demarcated by them; a servomotor 9 driving the upper punch; a crank mechanism 11 arranged between the servomotor and the upper punch and transmitting the driving force of the servomotor to the upper punch; and a control part 13 allowing the servomotor to perform a non-uniform rotary operation within one powder molding cycle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a powder molding apparatus and a powder molding method.

  In powder molding, a raw material in which metal powder is blended with predetermined components is filled into a molding die, and compression molding is performed with a press to obtain a molded body. An example of a conventional powder molding machine for performing such powder molding is disclosed in Patent Document 1.

  In this powder molding machine, a die whose upper part is opened is constituted by a die that mainly molds the side surface of the molded body and a lower punch that mainly molds the bottom surface of the molded body. In addition, an upper punch for applying pressure from above is provided in a molding chamber defined by the die and the lower punch. For the fixed die, the lower punch and the upper punch are supported so as to be able to reciprocate, and when both punches approach each other, it is possible to carry out double-pressing that pressurizes in two opposite directions. it can.

The lower punch and the upper punch are supported so as to reciprocate on one axis by a lower punch ball screw and an upper punch ball screw, respectively. The ball screw is driven by two motors provided corresponding to each ball screw. These motors ensure synchronization between the lower punch and the upper punch. It is used.
Japanese Patent Application Laid-Open No. 8-206891

  The powder molding cycle mainly includes a plurality of processes with different functions such as a powder filling process, a pressing process, and a molded body extraction process, and the cycle time itself required for one cycle is shortened. An increase in the number of moldings per hour is desired.

  On the other hand, according to the study of the present inventors, in the existing powder molding, if the entire powder molding cycle is simply speeded up uniformly, the following problems will newly arise. The maximum pressing force in the pressurizing process is calculated and set based on the position of the bottom dead center where the upper punch is most lowered. However, in the conventional powder molding described above, when the motor rotational speed is simply increased to uniformly speed up the entire cycle, the high-speed rotation of the ball screw instantaneously stops at a predetermined timing. It becomes difficult. For this reason, in the pressurizing step, the ball screw over-rotates with a surplus force, and accordingly, an overshoot phenomenon occurs in which the upper punch is further lowered from the original bottom dead center. When such a phenomenon occurs, too much pressure is applied, which may cause a problem in the molded body.

  The present invention has been made in view of such circumstances, and provides a powder molding apparatus and a powder molding method capable of preventing the occurrence of an overshoot phenomenon while increasing the speed of the entire powder molding cycle. For the purpose.

  In order to solve the above-described problems, a powder molding apparatus according to the present invention applies pressure to a die and a lower punch that are combined in a mutually movable relationship, and a molding chamber defined by the die and the lower punch. An upper punch, a servo motor that drives the upper punch, a crank mechanism or a cam mechanism that is disposed between the servo motor and the upper punch, and transmits the driving force of the servo motor to the upper punch, and single powder molding And a controller that causes the servomotor to rotate at a non-constant speed in a cycle.

  In order to achieve the same object, the present invention also provides a powder molding method. That is, in a method of forming a powder by applying pressure with an upper punch to a molding chamber defined by a die and a lower punch, a servo motor and a crank mechanism or a cam mechanism are prepared, and within one powder molding cycle The servo motor is rotated at a non-uniform speed, and the upper punch is operated by the servo motor via the crank mechanism or cam mechanism.

  Preferably, the one powder molding cycle includes a raw material powder filling step, a pressurizing step, a molded body extraction step, and a transient step between these steps. The servo motor is rotated at a higher speed in the transient process than in the filling process, the pressurizing process, and the extracting process.

  Preferably, the one powder molding cycle includes at least a raw material powder filling step, a pressurizing step, and a molded body extraction step, and the control unit includes the servo motor and the filling step. And at the time of an extraction process, it is made to rotate at high speed rather than the said pressurization process.

  Further, a powder box for supplying raw material powder to the molding chamber, and a link mechanism that is disposed between the crank mechanism or cam mechanism and the powder box and operates the powder box by the driving force of the servo motor are used. May be.

  According to the present invention described above, it is possible to reliably prevent the occurrence of the overshoot phenomenon while increasing the speed of the entire powder molding cycle.

  The other features of the present invention and the operational effects thereof will be described in more detail with reference to the accompanying drawings.

  Embodiments of a powder molding apparatus and a powder molding method according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a diagram schematically showing a configuration of a powder molding apparatus according to the present embodiment. The powder molding apparatus 1 includes a die 3, a lower punch 5, an upper punch 7, a first servo motor 9, a crank mechanism 11, and a control unit 13. The die 3 and the lower punch 5 are combined so as to be movable relative to each other. More specifically, in the present embodiment, the lower punch 5 is provided in a fixed manner in order to perform the withdrawal method, while the die 3 is provided movably with respect to the lower punch 5.

  The die 3 is mainly responsible for forming the side surface of the molded body, and the lower punch 5 is mainly responsible for forming the bottom surface of the molded body. Therefore, the die 3 and the lower punch 5 are combined to obtain a mold whose upper part is opened. The die 3 has a through space having a predetermined shape, and the lower punch 5 is inserted into the through space from below. Thus, the through space functions as a molding chamber 15 which is defined by the space forming surface of the die 3 and mainly the upper surface of the lower punch 5 and is opened upward.

  The die 3 is driven in the vertical direction by the vertical movement mechanism 17. As an example, the vertical movement mechanism 17 includes a transmission unit 19, a ball screw 21, and a second servo motor 23. While the die 3 is connected to the transmission portion 19, a ball screw 21 is screwed together. When the ball screw 21 rotates, the rotational torque is converted into a linear driving force, and the die 3 moves up and down via the transmission unit 19. Further, the ball screw 21 is rotated by the second servo motor 23.

  A powder box 25 is arranged above the die 3. The powder box 25 accommodates the powder used as the raw material of the molded body, and supplies the raw material powder into the molding chamber 15 at a predetermined timing. A link mechanism 27 is provided between the powder box 25 and the crank mechanism 11. For example, the link mechanism 27 includes a plurality of connecting rods, a cam that engages with the crankshaft 29, and the like. With the link mechanism 27, the powder box 25 can be operated between the supply position and the retracted position by the driving force of the first servo motor 9.

  The upper punch 7 is disposed above the lower punch 5 and is supported coaxially with the lower punch 5 so as to be vertically movable. More specifically, the upper punch 7 can be inserted into and withdrawn from above with respect to the through space of the die 3, and applies pressure to the molding chamber 15 when inserted into the through space of the die 3.

  A crank mechanism 11 is provided between the upper punch 7 and the first servomotor 9. The crank mechanism 11 transmits the driving force of the first servo motor 9 to the upper punch 7 and includes a crankshaft 29 and a connecting frame 31 as an example. Further, the crankshaft 29 has a main shaft portion 33 and a wheel portion 35.

  One end side of the main shaft portion 33 is connected to the first servo motor 9, and the other end side is connected to the wheel portion 35 to provide a rotation center of the wheel portion 35. One end side of the connecting frame 31 is connected to the wheel portion 35, and the other end side of the connecting frame 31 supports the upper punch 7. The connection point 35 a between the wheel portion 35 and the connecting frame 31 is eccentric from the center of rotation of the wheel portion 35, whereby the rotational torque of the wheel portion 35 is converted into a linear driving force to the connecting frame 31. The connecting frame 31 is simply vibrated. The upper punch 7 is moved up and down by the linear movement of the connecting frame 31.

  The first servo motor 9 and the second servo motor 23 are each connected to the control unit 13 via connection lines. The control unit 13 controls the rotation speeds of the first servo motor 9 and the second servo motor 23, and obtains information on the rotation amounts (rotation angles) of the first servo motor 9 and the second servo motor 23. It is possible to do.

  Next, the operation of the powder molding apparatus according to the present embodiment, that is, the implementation of the powder molding method will be described. First, the mechanical operation of the powder molding apparatus will be described, and then the operation of the powder molding apparatus corresponding to the powder molding cycle will be described.

  FIG. 1 shows a state in which the powder raw material is supplied and filled into the molding chamber 15 from the powder box 25, and the operation proceeding from here will be described. When the servo motor 9 is rotated from the state shown in FIG. 1, the wheel portion 35 is rotated as indicated by an arrow in the drawing. As a result, the connecting frame 31 is lowered as shown in FIG. The punch 7 also descends and enters the through space of the die 3, that is, pressurizes the powder raw material filled in the molding chamber 15. In parallel with this, the second servomotor 23 is rotated, and the transmission unit 19 and the die 3 are lowered as the ball screw 21 rotates.

  In this way, the raw material powder is pressurized in the withdrawal method, and the molded body 41 is obtained in the molding chamber 15.

  Further, during this time, the link mechanism 27 operates as the wheel portion 35 rotates, and the powder box 25 retreats from between the upper punch 7 and the lower punch 5 and moves further away. This state is the state shown in FIG.

  When the first servo motor 9 further operates from the state of FIG. 2, the upper punch 7 rises through the connecting frame 31 as the wheel portion 35 rotates. Thereby, the upper part of the molding chamber 15 is opened, and the molded body 41 obtained in the molding chamber 15 can be extracted from the die 3. In parallel with this, the powder box 25 is operated via the link mechanism 27 and approaches the molding chamber 15 for supplying the raw material powder used for the next pressurization. Furthermore, in parallel with these, the second servomotor 23 rotates in the reverse direction when the die descends, so that the ball screw 21 also rotates in the reverse direction, and the die 3 is raised in preparation for the next pressurization. By such an operation, the powder molding apparatus 1 finally returns to the state shown in FIG. 1, and the operation is repeated thereafter.

  Next, the operation of the powder molding apparatus corresponding to the powder molding cycle will be described. As understood from the mechanical operation of the above powder molding apparatus, the powder molding cycle includes the filling process of the raw material powder, the pressurizing process, the pressurizing and holding process, and the removal of the compact as the upper punch rises. The process can be divided into an outgoing process and a transient process between these processes. In the present invention, the servo motor 9 is driven to rotate at a non-constant speed by the control unit 13 in such a powder molding cycle.

  This will be described more specifically with reference to FIG. In FIG. 3, the diagrams indicated by reference numerals P7, P3, and P25 indicate the position of the upper punch 7, the position of the die 3, and the position of the powder box 25, respectively, in the powder molding cycle. The vertical axis indicates the respective movement modes, and the position P7 of the upper punch 7 and the position P3 of the die 3 are shown based on the reference symbol D on the vertical axis, and the vertical axis indicates the vertical position. ing. The position P25 of the powder box 25 is indicated on the basis of the reference symbol F on the vertical axis, and the vertical axis represents the approach to the molding chamber 15 as it goes upward.

  The horizontal axis indicates the rotational angle position of the wheel portion 35, that is, the main shaft portion 33 in the powder molding cycle. One powder molding cycle is executed from 300 (−60) degrees to the next 300 degrees when the top punch point at the position P7 of the upper punch 7 is set to 0 degrees.

  First, the rotation angle of the main shaft portion 33 is from −60 degrees to 30 degrees in the raw material powder filling step, and the servo motor 9 is operated at the rotation speed V1. In the filling step, the upper punch 7 starts to descend slightly after rising and reaching top dead center. The die 3 ascends to provide a molding chamber 15 having a sufficient depth, and thereafter descends corresponding to the upper punch 7. The powder box 25 approaches the molding chamber 15 and drops the raw material powder into the molding chamber 15 where a sufficient depth is secured. At this time, the upper punch 7 is largely retracted upward, and the powder box 25 is prevented from interfering with the upper punch 7. Further, as can be seen from the diagram, the powder box 25 performs a shaking motion so that the raw material powder is efficiently dropped into the molding chamber 15.

  Next, when the rotation angle of the main shaft portion 33 is 30 degrees to 137 degrees, the first transient process is performed, and the servo motor 9 is operated at the rotation speed V4. In the first transient process, the upper punch 7 is lowered and the powder box 25 is separated from the molding chamber 15.

  Subsequently, the rotation process of the main shaft portion 33 is performed at a pressure of 137 to 180 degrees, and the servo motor 9 is operated at the rotation speed V2. In the pressurizing step, the upper punch 7 and the die 3 are lowered, and the raw material powder is compressed to form a compact. In the present embodiment, the servo motor 9 is temporarily stopped for a predetermined time at around 180 degrees as the pressurizing and holding process, and the pressurizing state is held.

  Subsequently, when the rotation angle of the main shaft portion 33 is 180 degrees to 250 degrees, the extraction process is performed, and the servo motor 9 is operated at the rotation speed V3. In the extraction process, the die 3 is lowered, the upper punch 7 is raised, and the exposed portion of the molded body is increased so that the extraction from the die 3 can be easily performed.

  Further, the molded body is extracted, and the second transient process is performed when the rotation angle of the main shaft portion 33 is 250 to 300 degrees, and the servo motor 9 is operated at the rotation speed V4. In the second transition process, the upper punch 7 is further raised, and the powder box 25 approaches the molding chamber 15.

  Thereafter, the raw material powder filling process, the first transient process, the pressurizing process, the pressurizing and holding process, the extraction process, and the second transient process are repeated.

  Further, the rotational speeds V1, V2, V3, and V4 are not constant, that is, the control unit 13 causes the servo motor 9 to perform non-constant speed rotation operation within one powder molding cycle. Specifically, the control unit 13 causes the servo motor 9 to rotate at a higher speed than the pressurization process during the filling process and the extraction process, and further than the filling process, the pressurization process, and the extraction process in the transient process. Operate at high speed. As an example of the rotation speed, the rotation speed V1 = 50 [rpm], the rotation speed V2 = 40 [rpm], the rotation speed V3 = 50 [rpm], and the rotation speed V4 = 60 [rpm]. .

  According to the powder molding apparatus and the powder molding method according to the present embodiment as described above, the upper punch 7 is configured to receive a driving force from the driving source via the crank mechanism 11, and therefore the servo motor 9 is used as the driving source. Even if is used, there is no possibility of causing an overshoot phenomenon that descends further than the original bottom dead center. That is, the bottom dead center of the upper punch 7 is not realized when the servo motor 9 is stopped, but is realized at the rotation angle position of the main shaft portion 33 by the servo motor 9. It will not descend. And since the possibility of the overshoot phenomenon is eliminated and the servo motor 9 can be used, the servo motor 9 is operated at a non-constant speed in one powder molding cycle, and there is no defect in the molded body. Speeding up can be achieved, thereby speeding up the entire powder molding cycle.

  Specifically, in the transient process, the rotation process is performed at a higher speed than the filling process, the pressurizing process, and the extracting process. As a result, a section that does not perform a particular function in the powder molding cycle can be shortened, and the entire powder molding cycle can be speeded up while ensuring the filling, pressurization, and extraction. In addition, during the filling process and the extraction process, the rotating process is performed at a higher speed than in the pressurizing process. As a result, the entire powder molding cycle can be speeded up while securing a sufficient pressurizing time to ensure the molding.

  Although the contents of the present invention have been specifically described with reference to the preferred embodiments, various modifications can be made by those skilled in the art based on the basic technical idea and teachings of the present invention. It is self-explanatory.

  For example, in the above-described embodiment, the crank mechanism is exemplified as the mechanism for transmitting the driving force of the servo motor to the upper punch. However, the present invention is not limited to this, and the position of the upper punch is not limited to this. Any mode can be used as long as it can be defined by a periodic function depending on at least the rotation angle of the main shaft portion. For example, a cam mechanism can be used.

  Moreover, as a mechanism which transmits the drive force of a servomotor to a powder box, it is not limited to a link mechanism, Other modes may be sufficient as long as mechanical interlocking is ensured.

  Further, the present invention can also be applied to double pressing other than the withdrawal method.

It is a figure which shows typically the structure of the powder shaping | molding apparatus which concerns on embodiment of this invention. It is a figure of the same aspect as FIG. 1 which shows the state of a pressurization process. It is a figure which shows operation | movement of an upper punch, die | dye, and a powder box in a powder molding cycle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Powder molding apparatus 3 Die 5 Lower punch 7 Upper punch 9 Servo motor 11 Crank mechanism 13 Control part 25 Powder box 27 Link mechanism

Claims (8)

A die and a lower punch which are combined in a mutually movable relationship, and
An upper punch for applying pressure to a molding chamber defined by the die and the lower punch;
A servo motor for driving the upper punch;
A crank mechanism or a cam mechanism that is disposed between the servo motor and the upper punch and transmits a driving force of the servo motor to the upper punch;
A powder molding apparatus comprising: a control unit that operates the servo motor to rotate at a non-constant speed in one powder molding cycle. The one powder molding cycle includes a raw material powder filling step, a pressing step, a molded body extraction step, and a transient step between these steps,
The powder molding apparatus according to claim 1, wherein the control unit causes the servo motor to rotate at a higher speed in the transient process than in the filling process, the pressurizing process, and the extracting process. The one powder molding cycle includes at least a raw material powder filling step, a pressing step, and a molded body extraction step,
The powder molding apparatus according to claim 1, wherein the control unit causes the servo motor to rotate at a higher speed than the pressurization step during the filling step and the extraction step. A powder box for supplying raw powder to the molding chamber;
The link mechanism which is arrange | positioned between the said crank mechanism or cam mechanism, and the said powder box, and operates this powder box with the drive force of this servomotor is further provided. Powder molding equipment. In a method of forming a powder by applying pressure with an upper punch to a molding chamber defined by a die and a lower punch,
Servo motor and crank mechanism or cam mechanism are prepared.
A powder molding method in which the servomotor is operated at a non-constant speed in one powder molding cycle, and the upper punch is operated by the servomotor via the crank mechanism or cam mechanism. The one powder molding cycle includes a raw material powder filling step, a pressing step, a molded body extraction step, and a transient step between these steps,
The powder molding method according to claim 5, wherein the control unit causes the servo motor to rotate at a higher speed in the transient process than in the filling process, the pressurizing process, and the extracting process. The one powder molding cycle includes at least a raw material powder filling step, a pressing step, and a molded body extraction step,
The powder forming method according to claim 5 or 6, wherein the control unit causes the servo motor to rotate at a higher speed than the pressurizing step during the filling step and the extracting step. While preparing a powder box for supplying raw powder to the molding chamber, preparing a link mechanism disposed between the powder box and the crank mechanism or cam mechanism,
The powder molding method according to any one of claims 5 to 7, wherein the powder box is operated by the servo motor via the link mechanism.

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