JP2019026872A - Method for producing sintered gear - Google Patents

Abstract

To provide a sintered gear having increased strength while suppressing generation of cracks and emboly damages of a stock.SOLUTION: Provided is a method for producing a sintered gear comprising a rolling step where a stock 13 for a gear is subjected to rolling, and before the rolling step, a preliminary rolling step is implemented to the rolling the dedendum part 13d so that the dedendum part 13d of the stock 13 for a gear has a prescribed thickness for rolling. Rolling the vicinity of the dedendum 13d of the stock 13 for a gear using a first rolling die 11A in advance can reduce an amount of the stock flowing through a tooth bottom 13e in the rolling step.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a sintered gear.

  Conventionally, there is JP, 2006-523775, A as a technique of such a field. This publication discloses a manufacturing technique including a rolling process of rolling a gear material. A sintered gear that is refined by compressing and sintering metal powder with a mold may require high strength. One way to increase the strength of the sintered gear is to densify the tooth profile by rolling.

JP 2006-523775 A

However, in the manufacturing technology of sintered gears using a rolling process, the effect of increasing strength can be expected by increasing the amount of rolling. There is a problem that defects tend to occur. Specifically, when the amount of rolling is increased, the amount of material that is pushed and stretched in the direction of the tooth tip increases, the material does not fully stretch and breaks and cracks occur, and the tooth surface and the vicinity of the tooth root When the amount of the material flowing from the tooth root toward the tooth bottom increases, the tooth bottom covers the tooth bottom, which may cause cracking of the tooth bottom or a turn-up wound.
The present invention provides a method for manufacturing a sintered gear with improved strength while improving defects such as cracks in the material and occurrence of cracks.

The method for manufacturing a sintered gear according to the present invention includes a rolling step of rolling a gear material, and before the rolling step, a predetermined rolling wall thickness is applied to a tooth bottom portion of the gear material. A pre-rolling step of rolling the tooth bottom portion in a state of holding is provided.
Thereby, by rolling the vicinity of the tooth base of the gear material using the first rolling die in advance, the amount of material flowing to the tooth bottom in the rolling process can be reduced.

  Thereby, the sintered gear which improved the intensity | strength can be provided, suppressing generation | occurrence | production of the crack of a raw material, or a turning-up crack.

It is the schematic of the rolling apparatus used for a preliminary rolling process. It is the schematic of the rolling apparatus used for a rolling process. It is a figure which shows the tooth | gear part of a rolling raw material. It is a figure which shows an example of the shape of the tooth | gear part of a 1st rolling type | mold. It is a figure which shows the rolling amount and rolling location of the rolling raw material in a prior rolling process and a rolling process. It is a figure which shows an example of rolling of the rolling raw material using a 2nd rolling die. It is a figure which shows the relationship between the elongation amount of a tooth tip, and generation | occurrence | production of a crack. It is a figure which shows an example of a turn-up wound. It is a figure which shows the example of generation | occurrence | production of the crack by elongation of a rolling raw material.

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the rolling device 1 includes a pair of rolling dies 11 and a rolling machine 12. In addition, the rolling raw material 13 is set between the pair of rolling molds 11 in the rolling device 1, and the processing of the rolling raw material 13 is executed by two processes of the preliminary rolling process and the rolling process. .

  The rolling die 11 has a disk shape having a thickness, and a plurality of concave and convex teeth portions continuous along the circumferential direction are formed on the outer peripheral portion thereof. The pair of rolling dies 11 rotate around their axes by the power given from the rolling machine 12. Here, the pair of rolling dies 11 are arranged so that the axial directions are substantially parallel. The pair of rolling dies 11 operates so that the distance between the rolling dies 11 is narrowed with the rolling raw material 13 sandwiched therebetween, and the teeth of the rolling dies 11 press the rolling raw material 13 around the axis. The rolled material 13 is processed by performing the rotating operation. The axial direction of the pair of rolling dies 11 and the axial direction of the substantially cylindrical rolling material 13 set in the rolling device 1 are substantially parallel.

  As shown in FIG. 3, between the tooth tip 13 b and the tooth bottom 13 e of the tooth portion 13 a of the rolled material 13, the intermediate portion near the tooth tip 13 b is the tooth surface 13 c and the intermediate portion near the tooth bottom 13 e is the tooth root ( (Tooth base part) 13d is demonstrated. The same applies to the tooth tip, tooth surface, tooth root, and tooth bottom of the rolling die 11, and the tooth tip 21b, tooth surface 21c, tooth root 21d, tooth bottom of the tooth portion 21a of the first rolling die 11A described later. 21e (see FIG. 4), and the tooth tip 22b, tooth surface 22c, tooth root 22d, and tooth bottom 22e (see FIG. 6 (a)) of the tooth portion 22a of the second rolling mold 11B.

  Here, the pair of rolling dies 11 is used by switching between the first rolling die 11A used in the pre-rolling step and the second rolling die 11B used in the post-rolling step by attaching and detaching in the rolling device 1. To do. FIG. 1 shows a state where the first rolling die 11A is set in the rolling device 1, and FIG. 2 shows a state where the second rolling die 11B is set in the rolling device 1. As shown in FIG. 5A, the first rolling die 11A is used for processing the tooth root 13d of the rolling material 13 in the preliminary rolling process. Moreover, as shown in FIG.5 (b), the 2nd rolling type | mold 11B is used in order to process the tooth tip 13b, the tooth surface 13c, and the tooth root 13d of the tooth part 13a of the rolling raw material 13 in a rolling process. .

  For example, the same number of teeth is used for the teeth of the first rolling mold 11A and the second rolling mold 11B. Further, for example, when the tooth portions of the first rolling mold 11A and the second rolling mold 11B are compared, the gradient of the portion forming the tooth surface from the tooth base of the second rolling mold 11B is formed large. The tooth tip of the second rolling die 11B is formed to be smaller than the first rolling die 11A. That is, as shown in FIG. 4, the shape of the tooth portion 21a of the first rolling mold 11A is the same as that of the first rolling mold 11A when the rolling material 13 and the first rolling mold 11A are moved closer to each other. The tooth surface 21 c has a shape that abuts only on the tooth root 13 d of the rolled material 13.

  On the other hand, the shape of the tooth portion 22a of the second rolling die 11B is such that when the second rolling die 11B is moved toward the rolling material 13, the portion from the tooth surface 22c to the tooth root 22d is It is a shape which contacts the tooth surface 13c from the tooth root 13d of the rolling material 13. For example, the tooth length from the tooth bottom 22e to the tooth tip 22b of the tooth portion 22a of the second rolling mold 11B is shorter than the length from the tooth bottom 13e to the tooth tip 13b of the rolling material 13 before the rolling process. . In addition, the tooth portion of the second rolling die 11B has the tooth tip 13b of the rolling material 13 when the rolling material 13 is processed in the rolling process and the length from the tooth bottom 13e to the tooth tip 13b is extended. It is formed with a length that contacts the tooth bottom 22e of the second rolling die 11B.

  The rolling machine 12 generates power for operating the rolling mold 11. That is, the rolling machine 12 is operated so that the space between the respective rolling dies 11 is narrowed, and the respective rolling dies 11 are rotated around the axis. The rolling machine 12 is operated so that each of the rolling molds 11 has the same rotational direction around the axis. For example, when viewed as A in FIG. 1, both of the rolling dies 11 rotate counterclockwise. In addition, the rolling machine 12 is operated so that the rolling material 13 rotates clockwise in the view A.

  The rolling material (gear material) 13 has, for example, a substantially cylindrical shape. The length of the diameter of the rolled material 13 in the vicinity of the center in the axial direction is formed to be longer than the length of the diameter at both ends in the axial direction. Hereinafter, a portion having a long diameter near the center portion is referred to as a processing portion 13A, and a portion having a short diameter arranged so as to sandwich the processing portion 13A is referred to as a shaft portion 13B. The processed part 13A is formed with tooth parts 13a having a plurality of concave and convex shapes continuous in the circumferential direction by rolling with the rolling molds 11A and 11B. That is, as shown in FIG. 3, in the preliminary rolling process, the teeth 13a of the rolling material 13 are engaged with the teeth 21a of the rolling die 11A, and the rolling material 11 is sandwiched while the rolling die 11A rotates. By pressing in such a state, the processing of the tooth portion 13a is executed. In the rolling process, the teeth 13a of the rolling material 13 are engaged with the teeth 22a of the rolling die 11B, and the rolling die 11B is pressed while sandwiching the rolling material 13 while rotating. Thus, the processing of the tooth portion 13a is executed.

  Next, the manufacturing method of the sintered gear using the rolling method of the rolling raw material 13 which consists of two processes of a preliminary rolling process and a rolling process is demonstrated.

  In the preliminary rolling process, as shown in FIG. 1, the tooth base 13 d of the rolled material 13 is processed by using the first rolling die 11 </ b> A in the rolling device 1.

  A pair of first rolling molds 11A is set in the rolling device 1, and a rolling material 13 is disposed so as to be sandwiched between the pair of first rolling molds 11A.

  The rolling machine 12 makes the first rolling die 11A approach the rolling material 13 while rotating the first rolling mold 11A around each axis.

  The tooth portion 21a of the first rolling mold 11A comes into contact with the tooth portion 13a of the rolling material 13. At this time, the tooth surface 21c of the first rolling die 11A comes into contact with the tooth base 13d of the rolling material 13, and the other parts do not come into contact with each other, and the rolling of the tooth base 13d is executed. In the rolling of the tooth root 13d, processing may be performed including the vicinity of the tooth root 13d. As a result, the tooth base 13d of the rolled material 13 is processed so as to have a thickness for rolling.

  When the rolling of the rolling material 13 by the first rolling die 11A is completed, the first rolling die 11A is separated from the rolling material 13.

  Next, the rolling process will be described. In the rolling process, as shown in FIG. 2, the second tip 11B is used in the rolling device 1 to process the tooth tip 13b, the tooth surface 13c and the tooth base 13d of the rolling material 13.

  First, the pair of first rolling dies 11A is removed from the rolling device 1, and the pair of second rolling dies 11B is mounted.

  The rolling machine 12 brings the second rolling die 11B closer to the rolling material 13 while rotating the second rolling die 11B around each axis.

  As shown in FIG. 6A, the tooth portion 22 a of the second rolling mold 11 </ b> B comes into contact with the tooth portion of the rolled material 13. At this time, from the tooth root 22d of the second rolling die 11B to the tooth surface 22c, the tooth surface 13c of the rolling material 13 contacts the tooth base 13d. Thereby, the tooth surface 13c of the rolling material 13 is pressed by the tooth base 21d, and the material flows to the tooth tip 13b.

  Here, as shown in FIG. 6 (b), the tooth portion 22a of the second rolling die 11B has a tooth tip 13b of the tooth of the second rolling die 11B when the tooth tip 13b of the rolling material 13 extends. It is formed in such a length as to contact the bottom 22e, and the tooth tip 13b contacts the tooth bottom of the second rolling die 11B.

  Thereafter, as shown in FIG. 6 (c), the tooth tip 13b of the rolling material 13 is pushed into the target position while being in contact with the tooth bottom of the tooth portion of the second rolling die 11B. The tooth tip 13b is pressed, and the tooth surface 13c and the tooth root 13d are rolled. At this time, the material flows through the root 13e by rolling.

  Here, when the rolling amount of the tooth surface 13c of the rolling material 13 increases, the elongation of the tooth tip 13b increases. However, when the elongation amount increases too much, a crack occurs. For example, as shown in FIG. 7, it is investigated in advance that cracking occurs when the elongation amount of the tooth tip 13b of the rolling material 13 exceeds 0.23 mm. Before the 13 tooth tips 13b extend beyond 0.23 mm, the tooth tips 13b are in contact with the rolling roots 22e.

  In this way, by rolling the vicinity of the tooth root 13d of the rolling material 13 first using the first rolling mold 11A, the tooth root is rolled from the tooth surface using the second rolling mold 11B. This reduces the amount of material that flows when When the rolling process is performed after the preliminary rolling process is performed, the amount of material flowing so as to cover the tooth bottom 13e is reduced as compared with the case where the rolling process is performed without performing the preliminary rolling process. For this reason, the generation of cracks in the bottom of the teeth and the turn-up wound as shown in FIG. 8 is suppressed. As a result, the strength of the product after rolling can be improved.

  Further, in the rolling process, considering the amount of elongation of the tooth tip 13b of the rolling material 13, by using a second rolling die 11B having an appropriate length from the tooth bottom to the tooth tip, the tooth tip 13b. It is possible to avoid the occurrence of cracks due to the elongation of the rolled material 13 as shown in FIGS. 9 (a) to 9 (c).

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, as the rolling mold 11 used in the rolling machine 12, the first rolling mold 11A and the second rolling mold 11B are attached to and detached from the rolling mold 11, so that the first rolling mold 11A is used in the rolling process in the preliminary rolling process. Although explained as using the second rolling die 11B, for example, two rolling devices are prepared, and one rolling device performs the first rolling step using the first rolling die 11A, and the other rolling die. The apparatus may perform the rolling process using a second rolling mold.

DESCRIPTION OF SYMBOLS 1 Rolling apparatus 11A 1st rolling mold 11B 2nd rolling mold 12 Rolling machine 13 Rolling raw material 13A Processing part 13B Shaft part

Claims (1)

Including a rolling process for rolling gear materials,
Prior to the rolling step, a pre-rolling step of rolling the root portion is performed so that the tooth root portion of the gear material has a predetermined rolling thickness. .