JP2013215790A - Device for powder forming helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for powder-forming a helical gear having helical teeth in an outer circumference which comes axially on the halfway from one end face and concaves in the other end face, respectively, in which forming can achieved without causing density difference in opposite walls on both sides in circumferential directions of the concaves.SOLUTION: A device for powder-forming a helical gear includes: a rotatable die 1 adapted to form helical teeth which come axially on the halfway from one end face of an outer circumference of the helical gear and an outer circumferential surface of a circular-cylindrical portion on the other end side; a lower punch 2 adapted to form one end face of the helical gear inclusive of end faces of the helical teeth; an upper punch 4 adapted to form the other end face of the helical gear and the concaves shaped in the other end face; and a rotary guide 12 adapted to guide the die 1 using a guiding face of the same lead as the teeth in the portion for the helical teeth of the die to be formed and rotate the die, in a compression process of the powder P poured into a cavity 5, wherein the upper punch 4 is rotatably supported.

Description

  The present invention relates to a powder molding apparatus used when a helical gear having a bevel at part of the outer periphery and a recess at the other end face is manufactured by a powder metallurgy method.

  Among the helical gears manufactured by the powder metallurgy method, there is one as shown in FIG. A helical gear 20 shown in the figure is a sun gear employed in a power transmission system of a vehicle, and has inclined teeth 21 on the outer periphery of a region extending from one end to the middle in the axial direction. Moreover, it has the recessed part 22 in the other end surface. Reference numeral 23 denotes a cylindrical portion on the other end side where no inclined teeth are formed.

  The helical gear of FIG. 4 has conventionally employed a method of forming raw material powder using a die that is rotatably supported, a lower punch, a core, and an upper punch that is non-rotatably fixed to an upper punch plate. .

  In manufacturing helical gears by powder metallurgy, powder forming apparatuses as shown in Patent Documents 1 and 2 below are used. The powder molding apparatus described in these patent documents supports a die and an upper punch in a rotatable manner, and is a rotary guide having a guide surface with the same lead as an inclined tooth in the compression process of the powder. Molding while guiding and rotating.

Japanese Patent Laid-Open No. 11-58087 JP 2000-140990 A

  The powder forming apparatus shown in the above-mentioned Patent Documents 1 and 2 forms a helical gear in which inclined teeth formed on the outer periphery extend from one end to the other end.

  In the helical gear as shown in FIG. 4, the inclined teeth 21 do not reach the other end, and in addition, there is a recess 22 that needs to be formed with the upper punch on the other end surface, so that the upper punch is forcibly rotated. For this reason, conventionally, a powder molding apparatus in which only the die is rotated and the upper punch is fixed to the upper punch plate and cannot be rotated is used.

  However, it was found that when the helical gear of FIG. 4 was molded with the powder molding apparatus with the upper punch fixed, a density difference was produced at the opposing wall portions on both sides in the circumferential direction of the concave portion at the other end of the obtained helical gear.

  When the die is rotated during the powder compression process, the powder in the cavity flows in the rotational direction by the rotation of the die. On the other hand, the upper punch only moves vertically up and down, and as a result, the above-described density difference occurs. The density difference is not preferable in terms of product quality.

  In view of this, the present invention has a helical gear in which the outer peripheral inclined teeth do not reach the other end, and there is a concave portion formed by the upper punch on the other end surface, causing a difference in density between opposing wall portions on both sides in the circumferential direction of the concave portion. The problem is that it becomes possible to form without any problem.

  In order to solve the above-described problems, in the present invention, a helical gear molding apparatus having an inclined tooth on the outer periphery extending from one end face to the middle in the axial direction and further having a recess on the other end face, more specifically, the inclined tooth A rotatable die for forming the outer peripheral surface of the cylindrical portion on the other end side than the inclined teeth, a lower punch for forming one end surface of the helical gear including the end surfaces of the inclined teeth, the other end surface and the other end surfaces of the helical gear An upper punch for forming the concave portion formed on the die, and a rotation guide for rotating the die by guiding it with the guide surface of the same lead as the teeth of the inclined tooth forming portion of the die in the compression process of the powder put into the cavity. The helical gear powder molding apparatus provided was improved, and the upper punch of the apparatus was supported rotatably.

  In the helical gear powder molding apparatus according to the present invention, when the die rotates in the powder compression process and the powder in the cavity flows in the rotation direction, the upper punch rotates by being dragged by the flow. Therefore, the flow of the powder is not blocked by the convex part for forming the concave part of the upper punch (cause of causing the density difference), and molding that does not cause the density difference in the opposing wall part of the concave part on the other end face of the gear is possible. Become.

Sectional drawing which shows an example of the powder molding apparatus of this invention 1 is an enlarged cross-sectional view showing the main part of the powder molding apparatus of FIG. Enlarged cross-sectional view of the recessed portion of the helical gear (A) A perspective view showing an example of a helical gear molded by the powder molding apparatus of the present invention, (b) a sectional view of the helical gear same as the above.

  Hereinafter, an embodiment of a powder molding apparatus for a helical gear according to the present invention will be described with reference to FIGS. 1 and 2 of the accompanying drawings.

  The helical gear powder forming apparatus shown in FIG. 4 is for forming the helical gear 20 shown in FIG. 4, and is configured using a die in which a die 1, a lower punch 2, a core rod 3 and an upper punch 4 are combined.

  The die 1, the lower punch 2, and the core rod 3 form a cavity 5 between the three members, and the powder P put into the cavity 5 is compressed by the upper punch 4 to be molded.

  The die 1 is rotatably attached to the die plate 6 using a bearing 7. The lower punch 2 is fixed to a lower punch plate 8 and the core rod 3 is fixed to a yoke 9 driven by a lower ram (not shown).

  Further, the upper punch 4 is rotatably attached to an upper punch plate 10 driven by an upper ram (also not shown) using a bearing 11.

  In the die 1, an inner peripheral lower portion is configured as an inclined tooth forming portion that forms an inclined tooth of a helical gear, and an inner peripheral upper portion is configured as a forming portion on the outer peripheral surface of the other end side cylindrical portion of the helical gear.

  Further, teeth that mesh with the teeth of the inclined tooth forming portion of the die 1 are provided on the upper outer periphery of the lower punch 2. Further, a guide groove gg having a guide surface with the same lead as the inclined teeth of the helical gear to be formed is provided on the outer periphery of the lower portion of the lower punch 2.

  The guide groove gg guides a guide pin gp provided at the lower part of the die 1, and the guide groove gg and the guide pin gp constitute a rotating guide 12 that rotates the die 1 in the powder compression process. ing.

  The upper punch 4 is a punch provided with a molding convex portion 4a corresponding to the concave portion on the other end surface of the helical gear, and is supported on the upper punch plate 10 by a bearing 11 so as to be free to rotate. Since the rotation is free, it is not guaranteed that the phase of the convex portion 4a is always constant. However, no problem occurs when the phase difference between the concave portion provided on the other end face of the helical gear and the inclined tooth is allowed.

  Reference numeral 13 in FIG. 1 denotes a punch guide that slidably supports the outer periphery of the upper punch 4 in the axial direction to prevent the upper punch 4 and the die 1 from being misaligned. The punch guide 13 is provided as necessary, and is supported by the die plate 6.

  A guide rod 14 fixed to the die plate 6 is slidably inserted into the punch guide 13, and a guide pin 15 erected on the punch guide 13 is slidably inserted into the upper punch plate 10. As a result, the die plate 6, the upper punch plate 10, and the punch guide 13 are coaxially positioned to prevent the axial centers of the die 1 and the upper punch 4 from being displaced.

  The punch guide 13 is provided as necessary and is not an essential element.

  The inventive powder molding apparatus shown in FIG. 1 was prototyped, and the helical gear shown in FIG. 3 was molded using the apparatus and a conventional apparatus to which the upper punch was fixed. Then, the obtained powder compact is sintered, and then the helical gear is cut at the position of the concave portion on the other end surface, and holes around the opposing walls 22f and 22r on both sides in the circumferential direction of the concave portion 22 shown in FIG. The existence situation of was investigated. The opposing wall 22f is a wall in front of the direction in which the molding convex part moves during molding, and the opposing wall 22r is a wall in front of the direction in which the molding convex part moves during molding.

  As a result, the helical gear formed by the conventional device had more holes on the opposite wall 22r side than the holes on the rear wall 22f side (the density on the rear wall 22f side was higher), whereas the helical gear formed by the conventional device was an invented device. It was confirmed that the molded helical gear had almost no difference in the presence of holes around the opposing walls 22f and 22r, and the density in both regions was almost the same.

DESCRIPTION OF SYMBOLS 1 Die 2 Lower punch 3 Core rod 4 Upper punch 4a Molding convex part 5 Cavity 6 Die plates 7, 11 Bearing 8 Lower punch plate 9 Yoke 10 Upper punch plate 12 Rotation guide gg Guide groove gp Guide pin 13 Punch guide 14 Guide rod 15 Guide pin 20 Helical gear 21 Oblique teeth 22 Recesses 22f, 22r Opposing walls 23 on both sides in the circumferential direction Cylindrical portion

Claims (1)

  An apparatus for forming a helical gear having an inclined tooth (21) on an outer periphery extending in the axial direction from one end face and further having a recess (22) on the other end face, which is more than the inclined tooth (21) and the inclined tooth. A rotatable die (1) for forming the outer peripheral surface of the cylindrical portion (23) on the other end side, a lower punch (2) for forming one end surface of the helical gear (20) including the end face of the inclined teeth, The upper punch (4) for forming the recess (22) formed on the other end face and the other end face of the helical gear, and the die (1) in the compression stroke of the powder charged into the cavity (5) A helical gear powder molding apparatus comprising a rotation guide (12) that is rotated by being guided by a guide surface having the same lead as the teeth of the tooth molding unit, and wherein the upper punch (4) is rotatably supported.

Images