JP2938390B2 - Gear shot peening method and gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shot peening method for a gear, in which a gear is rotated to make shots of shot grains toward the outer surface of the gear and the outer surface is hardened, and the shot peening process is performed. This is related to a gear consisting of:

[0002]

2. Description of the Related Art In recent years, for example, in response to a demand for miniaturization of an automobile engine, it has been necessary to reduce the size of a gear used. However, various studies have been made to improve the strength of gears, because simply reducing the size cannot withstand loads such as rotational torque. Shot peening is known as one means for improving the strength of the gear. The shot peening is a process in which shot grains such as steel balls collide with the outer peripheral surface of a gear by an impeller or a nozzle to harden the gear.

FIG. 7 shows an example of nozzle type shot peening. In FIG. 7, a shot grain 101 such as a steel ball collides against the outer surface of the gear 100. Here, the gear 100 has a tooth top surface 102, a tooth bottom surface 103, a tooth profile surface 104 constituted by, for example, an involute curve bent from the tooth bottom surface 103 toward the tooth tip surface 102, Surface 104
Chamfered surface 105 provided between the tooth tip surface 102 and
The shot particles 101 are shot from the nozzle 106. The shot direction 107 of the shot grain 101 from the nozzle 106 is a direction substantially perpendicular to the tooth bottom surface 103 with respect to the rotating gear 100.

[0004]

However, in this conventional shot peening method, the plasticity due to the impact at the time of collision of the shot grains 101 at the tip of the gear 100, particularly at the ridgeline between the tooth profile surface 104 and the chamfered surface 105, is considered. There is a problem that deformation occurs and a small protrusion 108 is formed on the tooth profile surface 104 side. If this small projection 108 is formed, other gears meshing with the gear 100 will be damaged, and the life of the gear will be shortened. Further, when such protrusions 108 are formed, there is a problem that noise is generated when the gears mesh with each other.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a method of shot peening a gear capable of hardening the gear without forming a projection on a tooth tip of the gear, and It is an object of the present invention to provide a high-strength gear hardened by the shot peening method.

[0006]

In order to achieve the above-mentioned object, a method of shot peening a gear according to the present invention comprises the steps of: adding a tooth apex surface, a tooth bottom surface; A gear having a tooth surface curved toward the front and a chamfered surface provided between the tooth surface and the tooth tip surface is rotated, and a shot of a shot grain is shot toward the outer surface of the gear to perform the shot. A shot peening method of a gear for hardening an outer surface, wherein a preliminary shot step of performing shot of the shot grain so that the shot grain selectively collides with a tip of the gear, and after the preliminary shot step, A tooth bottom aiming step of performing shots of the shot particles substantially perpendicular to the tooth bottom so that the shot particles collide with the entire gear.

According to the shot peening method for a gear according to the present invention, prior to a root aiming shot in which shot grains collide in a direction substantially perpendicular to a tooth bottom face of the gear, a shot grain is prepared as a preliminary shot on a tooth tip of the gear. , The tip of the gear is pre-hardened. Therefore, even if the shot particles collide with the tooth tip in the shot aimed at the tooth bottom, no protrusion is formed on the tooth tip, and the degree of hardening is further increased. In this way, the life of other gears meshing with this gear can be shortened,
In addition, it is possible to eliminate problems such as generation of noise when the gears mesh with each other.

In the present invention, in a plane perpendicular to the axis of the gear, the shot of the shot grain in the preliminary shot step aims at a ridge point between a chamfer line at the front of the gear in the rotational direction and a tooth profile line. The nozzle axis for the shot is located in a region sandwiched between a straight line connecting the inner angle bisector having the ridge point as a corner and the uppermost point of another tooth facing the ridge point. Is preferably located.

By setting the shot direction of the shot grains in the preliminary shot step as described above, the vicinity of the ridge point between the chamfer line and the tooth profile line where the projection is particularly likely to be formed is hardened and crushed to form a corner. Since it is removed or deformed so as to have a more obtuse angle, the formation of protrusions on the tooth surface is more effectively suppressed. In this case, when the axis of the shot grain in the shot direction goes outside beyond the inner angle bisector having the ridge point as a corner, the impact force of the shot grain at the ridge line between the chamfered surface and the tooth profile surface increases the tooth profile surface. Since the protrusions are biased to the side, projections tend to be formed on the tooth profile side. When the axis in the shot direction goes outside beyond a straight line connecting the uppermost point of the other tooth facing the ridge point, the other tooth facing the obstacle interferes with the shot aiming at the ridge point. become unable.

In the present invention, in a plane perpendicular to the axis of the gear, the shot of the shot grain in the preliminary shot step may be formed by setting a ridge point between a chamfer line and a tooth profile line at a rear part in the rotation direction of the gear. The nozzle axis for the shot may be located in a region which is aimed at and is sandwiched between an extension of the tooth tip line and an extension of the chamfering line at the rear in the rotation direction.

In the setting of the shot direction of the shot grain in the preliminary shot step in this way, when the axis of the shot grain in the shot direction exceeds an extension of the chamfered line at the rear of the gear in the rotation direction, the rotation direction is changed. Since shot particles collide with the ridge point between the rear chamfer line and the tooth profile line adjacent to the chamfer line from the lateral direction, projections tend to be formed on the tooth profile surface side from the ridge point portion. Further, if the axis in the shot direction exceeds the extension of the tooth tip line, a shot aiming at the ridge point between the tooth tip line and the chamfer line at the rear of the gear in the rotation direction cannot be performed.

[0012] Next, the gear according to the present invention provides a tooth tip surface, a tooth bottom surface, a tooth profile surface bent from the tooth bottom surface toward the tooth tip surface, and the tooth profile surface and the tooth tip surface. A gear having an outer surface having a chamfered surface provided between the gears and having the outer surface subjected to a shot peening process by collision of shot particles, wherein the shot peening process is performed on a tooth tip of the gear. A preliminary shot in which the shot grains are shot so that the shot grains collide with each other, and a shot of the shot grains substantially perpendicular to the tooth bottom surface so that the shot grains collide with the entire gear after the preliminary shot. The processing is characterized by including a root aim shot.

In the gear according to the present invention, prior to the root aiming shot in which the shot grains collide with the gear in a direction orthogonal to the tooth bottom face of the gear, the shot grains collide with the tooth tip of the gear as a preliminary shot. Thus, since the tooth tip of the gear is obtained by previously hardening the tooth tip, no projection is formed on the tooth tip.

In the gear according to the present invention, in a plane perpendicular to the axis of the gear, the shot of the shot grain in the preliminary shot aims at a ridge point between a chamfer line at a front portion in a rotational direction of the gear and a tooth profile line. The nozzle axis for the shot is located in a region sandwiched between a straight line connecting the inner angle bisector having the ridge point as a corner and the uppermost point of another tooth facing the ridge point. Is preferably positioned.

[0015] Further, in a plane orthogonal to the axis of the gear, the shot of the shot grain in the preliminary shot step is formed by aiming at a ridge point between a chamfer line and a tooth profile line at a rear portion in the rotation direction of the gear, and A nozzle axis for the shot may be located in a region sandwiched between an extension line of the tooth tip line and an extension line of the chamfer line at the rear part in the rotation direction.

[0016] In the present invention, the tooth bottom of the arc height value of aimed shots to above 0.6MmA, and formed by the tooth tip protrusion amount generated the ridge of the tooth surface and the chamfered surface below 5μ gear It can be.

According to such a gear, the amount of tooth tip protrusion generated on the ridge between the tooth profile surface and the chamfered surface is 5 μm or less, which is an allowable protrusion amount when examined from the surface roughness of the tooth surface. In addition, the arc height value is set to 0.6 mmA or more, and a high compressive residual stress called hard shot peening is given to achieve high strength. Therefore, it is possible to obtain a gear that can achieve both the strength and accuracy as a product.

[0018] Other objects of the present invention will become apparent from the following detailed description. However, while the detailed description and specific examples describe the most preferred embodiments, various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from the detailed description, and This is described as an example.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a gear shot peening method according to the present invention;

FIG. 1 is a partial side view showing a preliminary shot step of a gear according to an embodiment of the present invention.

In the gear of the present embodiment, the outer surfaces are a tooth top surface 1, a tooth bottom surface 2, and the tooth bottom surface 2 from the tooth bottom surface 2.
Having left and right involute surfaces 4a, 4b forming side surfaces of the teeth 3A, and chamfered surfaces 5a, 5b provided between the involute surfaces 4a, 4b and the tooth tip surface 1. It has been. In FIG. 1, a ridge formed by the left involute surface 4a and the chamfered surface 5a (hereinafter, for simplicity of description, the ridge will be described as a point (ridge point) 6a in a plane orthogonal to the axis of the gear. The air nozzle 7 for the shot of the shot grain (steel ball in the present embodiment) is arranged so as to aim at the above), in other words, the axis 8 of the steel ball shot from the air nozzle 7 passes through the ridge 6a. The air nozzle 7 is provided.

The axis 8 of the air nozzle 7 is divided into a bisector 9 of the inner angle of the corner of the ridge 6a and the ridge 6a.
Is located in an area sandwiched by a straight line 10 connecting the uppermost point of the tooth 3B opposed to. Here, the gear is
Is rotated counterclockwise, and the ridge 6a, the chamfered surface 5a, and the involute surface 4a are
Move to face. Note that the state shown in FIG. 1 captures an instantaneous state. Therefore, the steel ball shot from the air nozzle 7 collides with the ridge 6a and the area around the ridge 6a, in other words, the tip of the tooth 3A and hardens the tip. In particular, at the ridge 6a, the involute surface 4a on which the protrusion 108 is easily formed as shown in the above-described conventional example (FIG. 7).
The sides are crushed and become sharp or obtuse. As a result, a projection is not formed on the involute surface 4a side of the ridge point 6a in a root aim shot described later.

Here, when the axis 8 of the air nozzle 7 comes out of the straight line 10 (the lower side in the figure), the teeth 3B become an obstacle and the ridge point 6 cannot be aimed at. The axis 8 is outside the bisector 9 (upper side in the figure)
, It becomes easy to form a projection on the involute surface 4a side of the ridge point 6.

Preferably, the gear is rotated counterclockwise as shown in FIG. 1 and the tip is hardened, and then turned upside down to perform a similar preliminary shot. By doing so, the teeth 3A are hardened symmetrically on the left and right, and the strength is uniformly improved on the left and right.

FIG. 2 shows another embodiment of the air nozzle 7 in the shot direction. In the example shown in FIG. 2, the axis 8 of the air nozzle 7 is
With respect to the chamfered surface 5a coming inward, it passes through the ridge point 11 between the chamfered surface 5b at the rear part in the rotation direction of the gear and the tooth tip surface 1, and the extension line 12 of the tooth tip surface 1 and the chamfered surface at the rear part in the rotation direction. 5b is located in an area sandwiched by the extension lines 13 of FIG. The state of FIG. 2 also captures a moment, and in fact, the steel ball collides with the entire tip of the tooth 3A.

Here, if the axis 8 of the air nozzle 7 comes out of the extension line 12 (the lower side in the figure), the ridge point 11 cannot be aimed at, and the axis 8 of the air nozzle 7 cannot be aimed at.
Comes out of the extension line 13 (upper side in the figure), a projection is formed on the involute surface 4b side of the ridge 6b formed by the right chamfer surface 5b and the involute surface 4b.

Also in this embodiment, preferably,
After the gear rotates in the counterclockwise direction as shown in FIG. 2 and the tooth tip is hardened, it is preferable that the same reverse shot is performed by turning the gear upside down. By doing so, the teeth 3A are hardened symmetrically on the left and right, and the strength is uniformly improved on the left and right.

Next, as shown in FIGS. 1 and 2, a preliminary shot is performed to harden the tip of the gear, and then, as shown in FIG. 3, the axis 8 'of the air nozzle 7'.
The air nozzle 7 ′ is arranged so that is perpendicular to the tooth bottom 2, and a shot aimed at the tooth bottom is performed. Since the gear is also rotating at the time of this tooth bottom aiming shot, the steel ball is placed on the tooth bottom 2, the involute surfaces 4a and 4b, and the chamfer surfaces 5a and 5
b, Collision with all of the tooth tip surface 1 hardens the entire gear. In the shot aimed at the bottom of the tooth, the tip is hardened by the preliminary shot, so that no projection is formed on the tip.

FIG. 4 shows the positional relationship between the gears and the air nozzles 7, 7 '. As an example, the diameter of the gear is 105.88 mm, and the width of the air nozzle 7 for shooting the steel ball 20 (the distance from the left end 21 to the right end 22 of the shot area) is 20 mm. The position of the air nozzle 7 is such that the left end 21 of the shot area is
Radial line segment 2 of the gear perpendicular to the axis 8 of the air nozzle 7
The position is in contact with the tip of the radius line segment 24 which forms an angle of 34 ° with 3. As a result, the distance between the axis of the air nozzle 7 and the center 25 of the gear is 59 mm. The position of the air nozzle 7 with respect to the gear is shown in FIG.
Is a position for performing the preliminary shot shown in FIG.

In FIG. 4, the air nozzle 7 'for the shot aimed at the bottom of the tooth has the same size as the air nozzle 7 and is arranged in parallel with the air nozzle 7. The axis 8 'of the air nozzle 7' for the root aiming shot passes through the center 25 of the gear, and the axis 8 'of the air nozzle 7'
The distance between the air nozzle 7 and the axis 8 is 59 mm.

Next, a specific example in which the gear is subjected to shot peening using the apparatus shown in FIG. 4 will be described with reference to FIGS. As the gear, a spur gear having a diameter of 105.88 mm (module: 3.
0, pressure angle: 20 °, number of teeth: 33, material: SNCM22
0H, heat treatment, carbonitriding, quenching and tempering).
With respect to this gear, a preliminary shot and a tooth bottom aiming shot are performed using the air nozzle 7 and the air nozzle 7 'on the upper half shown in FIG. Make the bottom shot. Each shot is performed for various arc height values (indicators indicating the strength of shots) and is performed 10 times for the same arc height value. Table 1 shows the test procedures of the upper half and the lower half in the order of steps.

[0032]

[Table 1]

In this test, the preliminary shot is 2k
At g / cm ² , steel balls are used as shot grains. The purpose of this preliminary shot is to averagely cure the entire tooth tip portion, and there are no particular restrictions on the conditions, but in practice, the aim of the tooth bottom is to prevent the surface roughness of the tooth profile surface from being greatly reduced. It is preferable to carry out with an arc height value not exceeding the arc height value. FIGS. 5A and 5B show the results of this test in comparison with the case where there is a spare shot and the case where there is no spare shot. (A) is a graph showing the relationship between the arc height value and the maximum amount of tip protrusion and compressive residual stress, and (b) is a graph showing the relationship between the arc height value and the average amount of tip protrusion.

As is clear from the graph of FIG. 5, when there is no preliminary shot, the compressive residual stress increases as the arc height value increases, but conversely, the amount of tooth tip protrusion also increases.
It can be seen that while the strength is improved, the tooth profile is reduced. In addition, it can be seen that when the preliminary shot is performed, even when the arc height value is increased, both the maximum amount of tip protrusion and the average amount of tip protrusion are suppressed to be small.

By the way, generally, the allowable amount of tooth tip protrusion is about 5 μm when examined from the viewpoint of surface roughness or the like. Therefore, if the arc height value is less than 0.6 mmA, there is no practical problem even without the preliminary shot. A gear called hard shot peening, which imparts a high compressive residual stress to increase the strength, requires a compressive stress of 100 kg / mm ² (indicated by a negative value in FIG. 5) or more. When converted to an arc height value, a strength of 0.6 mmA or more is required. That is, when manufacturing a high-strength gear having an arc height value of 0.6 mmA or more,
Since the tip protrusion amount is 5 μ or more, it can be said that the preliminary shot of the present embodiment is indispensable. The preliminary shot is effective even when the arc height value exceeds 1.0 mmA, but in practice, it is 1.0 mmA at which the compressive residual stress is saturated.
It is common to operate at the following arc height values.

In this embodiment, the air nozzle 7 'for the shot aiming at the root is used separately from the air nozzle 7 for the preliminary shot, but one shot peening apparatus uses the air nozzle 7' for the preliminary shot. The installation angle of the air nozzle 7 may be changed to use it for a shot aimed at the bottom of the tooth. In addition, instead of turning the gear upside down in order to harden the left and right sides evenly in the preliminary shot of the gear teeth, the air nozzle 7 has a preliminary shot aiming at the left side and a preliminary shot aiming at the right side. May be provided. Further, the direction of one air nozzle may be changed so that preliminary shots can be made from the left and right sides.

In the present embodiment, the steel balls are used as shot grains. However, other than the steel balls, glass beads, alumina spheres, cemented spheres or the like may be used. Also, there is no particular limitation on the size of shot grains in the preliminary shot. However, those having a diameter of 1.2 mm or less are generally used.

In this embodiment, the involute curve is described as the tooth profile curve.
There are various other types such as a cycloid curve and a straight line. The present invention is also effective when applied to those various tooth profile curves.

As described above, it is apparent that the present invention can be variously modified. Such modifications do not depart from the spirit and scope of the invention and all such modifications and changes that are obvious to those skilled in the art are included in the claims.

[Brief description of the drawings]

FIG. 1 is a partial side view showing a preliminary shot step in the present embodiment.

FIG. 2 is a partial side view showing another preliminary shot step in the present embodiment.

FIG. 3 is a partial side view showing a tooth bottom aiming shot step in the present embodiment.

FIG. 4 is a schematic configuration diagram for implementing the gear shot peening method of the present embodiment.

FIGS. 5A and 5B are graphs showing test results of shot peening according to the present embodiment.

FIG. 6 is a perspective view of a gear that is hardened in the present embodiment.

FIG. 7 is a diagram showing a problem of the related art.

[Explanation of symbols]

 1 tooth tip surface 2 tooth bottom surface 3A, 3B tooth 4a, 4b involute surface 5a, 5b chamfered surface 6a, 6b, 11 ridge point 7, 7 'air nozzle 8, 8' axis 20 steel ball

Continuation of front page (56) References JP-A-2-301513 (JP, A) JP-A-3-256672 (JP, A) JP-A-1-97568 (JP, A) JP-A-7-242994 (JP) JP-A-4-21757 (JP, A) JP-A-4-141521 (JP, A) JP-A-6-254765 (JP, A) JP-A-3-107418 (JP, A) 5-33047 (JP, A) JP-A-61-290272 (JP, A) JP-A-63-123673 (JP, A) JP-A-3-120366 (JP, U) JP-B-62-7245 (JP, A) B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) B24C 1/10 F16H 55/06 C21D 7/06

Claims (7)

(57) [Claims] 1. A tooth tip surface, a tooth bottom surface, a tooth profile surface bent from the tooth bottom surface toward the tooth tip surface, and a chamfered surface provided between the tooth profile surface and the tooth tip surface. Is a shot peening method for a gear, in which a shot having shots is shot toward the outer surface of the gear and the outer surface is hardened, wherein the shot grains are selectively formed on the tooth tip of the gear. A preliminary shot step of performing a shot of the shot grain so as to collide with the gear; and a root bottom aiming to perform a shot of the shot grain substantially perpendicular to the tooth bottom so that the shot grain collides with the entire gear after the preliminary shot step. A shot peening method for a gear, comprising: a shot step. 2. In a plane orthogonal to the axis of the gear, the shot of the shot grain in the preliminary shot step is formed by aiming at a ridge point between a chamfer line and a tooth profile line at a front part in a rotation direction of the gear. In addition, the nozzle axis for the shot is located in the area sandwiched by the bisector of the inner angle with the ridge point as the corner and the straight line connecting the uppermost point of the other teeth facing this ridge point. The method of claim 1, wherein the shot peening is performed. 3. In a plane perpendicular to the axis of the gear, the shot of the shot grain in the preliminary shot step is formed by aiming at a ridge point between a chamfer line and a tooth profile line at a rear part in the rotation direction of the gear, and 2. The gear shot according to claim 1, wherein a nozzle axis for the shot is located in a region sandwiched between an extension of the tooth tip line and an extension of the chamfer line at the rear in the rotation direction. Peening method. 4. A tooth tip surface, a tooth bottom surface, a tooth profile surface bent from the tooth bottom surface toward the tooth tip surface, and a chamfered surface provided between the tooth profile surface and the tooth tip surface. A gear having an outer surface having: a shot peening process performed by collision of shot particles on the outer surface, wherein the shot peening process selectively collides with a shot tip of the gear. And a root aiming shot for performing the shot of the shot grain substantially perpendicular to the tooth bottom so that the shot grain collides with the entire gear after the preliminary shot. Gears characterized by processing. 5. A shot of the shot grain in the preliminary shot in a plane orthogonal to the axis of the gear, aiming at a ridge point between a chamfer line and a tooth profile line at a front portion in the rotation direction of the gear, and The nozzle axis for the shot is located in the area between the bisector of the interior angle with the ridge point as the corner and the straight line connecting the highest point of the other tooth opposite to this ridge point The gear according to claim 4, wherein the gear is a gear. 6. A shot of the shot grain in the preliminary shot step in a plane orthogonal to an axis of the gear, aiming at a ridge point between a chamfer line and a tooth line at a rear part in a rotation direction of the gear, and The nozzle axis for the shot is located in a region sandwiched between an extension of the tooth tip line and an extension of the chamfer line at the rear in the rotation direction, according to claim 4, wherein the nozzle axis for the shot is positioned. gear. 7. The method according to claim 4, wherein an arc height value of said root aiming shot is 0.6 mmA or more, and an amount of tooth tip protrusion generated at a ridge between said tooth profile surface and said chamfer surface is 5 μm or less . A gear according to any one of the preceding claims.