JP2015203128A - Sinter component production method and sinter component produced by it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sinter component having irregularities on an outer periphery, and effectively enhance circularity of a sinter component to which silence of high level is required by rolling correction.SOLUTION: A sinter component 10 has irregularities arranged in a regular state in a peripheral direction on an outer periphery. Strain correction by performing rolling using a correction gearwheel is performed with setting in which, a rolling margin of rolling becomes larger on bottoms 14 of recess parts than on tip ends 13 of salient parts, in the outer periphery.

Description

  The present invention relates to a method for manufacturing a sintered part having irregularities such as meshing teeth regularly arranged in the circumferential direction on the outer periphery, and more specifically, a manufacturing method in which both the reinforcement of the tooth surface and the correction of the outer diameter are achieved. And a sintered part such as a sintered gear manufactured by the method.

  For example, a sintered gear manufactured by the powder metallurgy method is shipped after removing the distortion and increasing the roundness after sintering. A method of removing the strain by rolling was studied.

  As for a sintered gear, it has been proposed to refine the structure of the surface layer portion of the tooth tip and the bottom of the tooth as a measure for reinforcing the tooth portion (for example, see Patent Document 1 below).

  In the sintered part, voids remain in the metal matrix. The strength of the tooth portion can be increased by reducing the residual holes by densification of the tissue.

  Patent document 1 cites rolling as an example of a method for densifying the surface structure. The densification of the surface layer of the tooth tip and the bottom of the tooth is generally performed so that the densification layer of the tooth tip is thick and the densification layer of the tooth base is a thin layer, the purpose of which is during rolling This can be achieved by making the rolling allowance of the tooth tip part larger than the rolling allowance of the tooth bottom part.

Japanese Patent No. 4160561

  As described above, as for the sintered gear, if the rolling allowance (the amount of buildup of the tooth tip) in the rolling is made larger than the amount of buildup of the tooth bottom, the densification of the tooth tip is performed as in Patent Document 1. A structure in which the layer is thicker than the densified layer of the root can be produced by rolling.

  However, if you try to correct distortion at the same time as strengthening the tooth surface with this rolling, the distortion correction effect is not fully demonstrated, and high accuracy is required for the roundness of the tooth tip and root Found that there was a case where the request could not be satisfied.

  In the case of meshing machine parts such as gears, if the roundness of the tooth portion is poor, the meshing position is shifted and noise (abnormal noise) is generated.

  Accordingly, the present invention provides a tooth part surface formed by rolling for sintered parts having irregularities such as meshing teeth regularly arranged in the circumferential direction on the outer periphery, particularly sintered parts having a high requirement for quietness of meshing. At the same time, the roundness is effectively increased by the rolling.

  In order to solve the above-mentioned problems, a sintered part having irregularities regularly arranged in the circumferential direction on the outer periphery is manufactured by strengthening the tooth surface and correcting the distortion by a rolling method. And the manufacture is performed with the setting that the rolling allowance in rolling is larger at the bottom of the recess than at the tip of the outer periphery.

  With this method, the sintered parts whose tooth surfaces are strengthened and distortions are corrected, the material is plastically deformed on the surface of the irregularities on the outer periphery regularly arranged in the circumferential direction, and the porosity is higher than that of the other parts. A smaller densified layer is formed, and the thickness (depth) at the bottom of the concave portion of the densified layer is larger than the thickness at the tip of the convex portion. The present invention also provides such a sintered part.

  According to the manufacturing method described above, the roundness of the obtained sintered part is larger than the roundness obtained by the densification method in which the rolling allowance in rolling is larger at the tip of the convex portion than at the bottom of the concave portion. improves.

It is a principle figure which shows an example of the manufacturing method of this invention. It is a side view which shows a part of example (it is a sintered gear of the figure) of the sintered component which strengthens a tooth | gear part surface and corrects a distortion by the manufacturing method of this invention. It is sectional drawing which shows the densification layer produced in the sintered component of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a method for correcting a sintered part according to the present invention and a sintered part obtained by correcting the sintered part will be described with reference to FIGS. 1 to 3 of the accompanying drawings.

  In this invention, the surface of the tooth portion is strengthened and the distortion is corrected by rolling a sintered part having irregularities regularly arranged in the circumferential direction. It is set so that it is larger at the bottom of the recess than at the tip.

  FIG. 1 shows an example of manufacturing a sintered gear. In the figure, reference numeral 10 denotes a sintered gear obtained by sintering a powder compact, and strengthening and distortion correction of the tooth surface after sintering is performed by rolling.

  As shown in the figure, the teeth surface is strengthened and the distortion is corrected by rolling gears 1 and 2 having a parallel arrangement of sintered gears 10 each having a shaft hole 11 at the center and meshing teeth 12 on the outer periphery. It is arranged between a kind of molds) and meshed with the rolling gears 1 and 2.

  Then, in this state, the rolled gears 1 and 2 are rotated to rotate the sintered gear 10 following the rotation. By making the rolling gears 1 and 2 relatively approach while advancing the rotation, the tooth tip portion and the bottom portion of the meshing tooth 12 on the outer periphery of the sintered gear 10 are compressed and plastically deformed, and the surface texture is changed. It can be densified and at the same time correct the distortion.

  As an example of a sintered gear with poor roundness, an elliptical gear is now considered. If the shape of the sintered gear 10 in FIG. 1 is the elliptical shape, when the major axis side of the ellipse is sandwiched between the rolling gears 1 and 2, the amount of compression by the rolled gears 1 and 2 is reduced on the minor axis side of the ellipse. It becomes larger than when sandwiched between the artificial gears 1 and 2.

  As a result, the tip circle diameter and root circle diameter on the major axis side of the ellipse are reduced to be larger than the tip circle diameter and root circle diameter on the minor axis side of the ellipse, and on the major axis side and the minor axis side of the ellipse. The difference between the tip diameter and the root diameter is reduced and the roundness of the gear is improved.

  In strengthening and correcting the tooth surface by rolling, a difference is made between the rolling allowance of the tooth tip and the rolling allowance of the tooth bottom. In order to cause a difference in the rolling allowance, the build-up amount of the tooth tip and the build-up amount of the tooth bottom of the sintered gear before distortion correction are made different.

  In the present invention, as shown in FIG. 2, for the sintered gear 10, the rolling allowance d <b> 2 of the tooth bottom portion 14 is made larger than the rolling allowance d <b> 1 of the tooth tip portion 13 of the meshing tooth 12, and the tooth tip portion thereof. A sintered gear having different rolling allowances of 13 and the tooth bottom portion 14 is made, and the tooth surface is strengthened and the distortion is corrected by rolling.

  As can be seen from FIG. 2, in the sintered gear 10, the radial thickness t <b> 1 of the tooth bottom portion 14 is smaller than the radial thickness t <b> 2 of the tooth tip portion 13. From this, it can be seen that the rigidity of the tooth bottom portion 14 is lower than that of the tooth tip portion 13 and is easily plastically deformed.

  In the present invention, the tooth bottom portion 14 is smoothly plastically deformed by applying a compressive force equivalent to that of the tooth tip portion 13 from the outside in the radial direction to the tooth bottom portion 14 having low rigidity and easily deformable.

  And the tooth tip part 13 side is also deformed by utilizing the deformation of the tooth bottom part 14, and the diameter of the part bulging excessively in the radial direction is reduced.

  In this way, the sintered parts that have been reinforced and corrected for the tooth surface have materials on the surface of the irregularities on the outer periphery (for gears, the tooth tip and the tooth bottom) that are regularly arranged in the circumferential direction. A densified layer having a porosity smaller than the other part is formed by plastic deformation, and the thickness of the bottom of the concave part (in the case of gears) of the densified layer is such that the tip part of the convex part (gear of the gear) In this case, it becomes thicker than the thickness at the tooth tip).

According to this method, the roundness of the sintered part that has been rolled is higher than the correction of distortion in the rolling process in which the rolling allowance of the tooth tip part is larger than that of the root part. In order to make the correction force strongly work on the site that is difficult to deform in rolling with the rolling allowance of the tooth tip part larger than the root part, a situation where distortion is not sufficiently corrected can occur, but according to the illustrated method, The trouble does not occur.

  The effect of improving the roundness by this method is particularly noticeable when the thickness of the densified layer 15 (see FIG. 3) formed by plastic deformation is 0.3 mm or more at the tooth bottom.

  Therefore, the thickness of the densified layer 15 at the tooth bottom portion is 0.3 mm or more and the thickness of the densified layer 15 at the tooth tip portion is 0.3 mm or less, so that the amount of prior build-up of the tooth tip portion and the tooth bottom portion is 0.3 mm or less. It is better to set and roll.

An evaluation test of the method of the present invention was conducted. For the test, the following external tooth sintered gears were used.
・ Rolling target gear tooth tip circle: 64mm
Tooth round: 56mm
Inner diameter: 48 mm
Module: 2
Number of teeth: 30
Pressure angle: 20 °
Transition coefficient: 0

The material of the gear is 2 wt% Cu-0.6 wt% C-residual Fe. The density of the powder compact before sintering is 7.1 g / cm ³ . The molded body was sintered at 1130 ° C. and subjected to distortion correction by rolling.

  Compression (densification of the structure) accompanied by plastic deformation in rolling was performed so that only the tooth tip, only the tooth bottom, and the tooth surface had the layer thicknesses shown in Table 1. Then, the roundness of the gear before the correction by the rolling and the roundness of the gear after the correction were examined. The results are also shown in Table 1.

  The roundness in Table 1 is the difference between the maximum and minimum portions of the tip circle diameter. The correction amount in Table 1 represents the correction amount of roundness.

  As can be seen from the test results, the compression and plastic deformation emphasizing the tooth bottom part is more effective in improving the roundness than the compression and plastic deformation emphasizing the tooth tip part.

  In the rolling performed so that the thickness of the densified layer at the tooth bottom is 0.3 mm or more, the effect of improving the roundness is particularly great.

  Tooth surface compression and plastic deformation have no effect on the improvement of roundness.

  In addition, although the above description gave and demonstrated the distortion correction of the sintered gear, this invention is applicable also to distortion correction of sintered parts other than a sintered gear.

  The above-described sintered sprocket wheel and sintered rotor for gear pumps (which may also be considered as a kind of gear) are required to have high roundness for smooth engagement and quietness improvement.

  This sintered sprocket wheel and sintered rotor for gear pumps have shaft holes at the center and irregularities regularly arranged in the circumferential direction on the outer circumference, similar to sintered gears. Correction is possible.

  These sintered parts are also distorted in the sintering process and the roundness is lowered. Therefore, even if the present invention is applied to these parts, there is an effect.

1, 2 Rolled gear 10 Sintered gear 11 Shaft hole 12 Engagement tooth 13 Tooth tip portion 14 Tooth bottom portion 15 Densified layer d1 Tooth tip portion rolling allowance d2 Tooth tip portion rolling allowance t1 Tooth bottom portion radial thickness t2 Tooth tip portion radial thickness

Claims (4)

  A method for manufacturing sintered parts having irregularities regularly arranged in the circumferential direction on the outer circumference by reinforcing the surface of the irregularities and correcting the distortion by a rolling method. A method for manufacturing a sintered part, which is performed by setting so that is larger at the bottom of the recess than at the tip of the outer periphery.   By compressing the bottom of the recess by rolling, a densified layer having a smaller porosity than the other part having a thickness of 0.3 mm or more is formed at the bottom of the recess by plastic deformation of the component due to the compression. The manufacturing method of the sintered component of Claim 1 to perform.   A sintered part manufactured by strengthening and correcting the surface of the concavo-convex portion by the manufacturing method according to claim 1 or 2, wherein the material is formed on a surface layer of the concavo-convex portion on the outer periphery regularly arranged in the circumferential direction. Sintering in which the densified layer is formed by plastic deformation and the porosity is smaller than the other part, and the thickness of the bottom of the concave part of the densified layer is thicker than the thickness of the tip part of the convex part parts.   The sintered part according to claim 3, wherein the densified layer of the recess has a thickness of 0.3 mm or more.

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