JP7020377B2 - Bevel gear manufacturing method - Google Patents

Description

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

In recent years, bevel gears formed by forging have been used. When the tooth profile of the bevel gear is formed by forging, if the shape of the tooth tip is sharp, the molding pressure exerts an unacceptable stress on the die, and repeated states may lead to breakage.

Conventionally, there is Japanese Patent Publication No. 2007-509761 as a technique in such a field. In the bevel gear described in this publication, stress concentration can be prevented by gently forming the radius of the tooth tip. This bevel gear is formed by reducing the filling degree of the mold and filling the mold.

Japanese Patent Publication No. 2007-509761

However, it is difficult to control the shape of the above-mentioned conventional bevel gear because the mold is manufactured in a state where the filling degree of the mold is reduced and the mold is deficient. In addition, it is possible that the meshing rate changes due to uneven thickness. It should be noted that stress exceeding the permissible amount is applied to the mold, and cracks are likely to occur in the tooth tip portion, but there is a problem that the manufacturing cost increases if the mold cracks at an early stage.

Here, in order to reduce the stress of the mold, it is effective to smooth the shape of the tooth tip to prevent stress concentration, but if the radius of the tooth tip is increased, the tooth surface length of the product becomes smaller and the meshing ratio becomes smaller. As a result, the product function is adversely affected.
The present invention provides a method for manufacturing a bevel gear in which stress concentration on a die during manufacturing by forging is reduced while ensuring a required tooth surface length of a sufficient length.

The method for manufacturing a bevel gear according to the present invention is a method for manufacturing a bevel gear in which a bevel gear having a gradually changing R-shaped tooth tip is manufactured by using a mold. The teeth are continuously arranged, and the teeth are arranged between a tooth tip having a substantially flat shape in the pitch direction and a tooth bottom and the tooth tip, and a tooth surface arranged so as to sandwich the tooth tip. In the tooth before forming the gradually changing R shape, an O point is set at the end of the tooth tip having a substantially flat shape and the end of the tooth surface, and the tooth has a substantially flat shape. A point T is set on an intermediate surface between both ends of a certain tooth tip, a required tooth surface length on the tooth surface is set, and the required tooth surface length is secured from the tooth bottom side on the tooth tip side. The end is set as the S point, the point where the vertical line from the O point intersects with respect to the straight line connecting the T point and the S point is set as the P point, and the straight line connecting the O point and the P point is set. Therefore, when the point where the stress generated in the mold is minimized by 3D modeling / CAE analysis is set as the Q point, the distance between the O point and the Q point is the O point and the P point. The Q point is set so as to be 30 to 50% of the connected distance, the spline curve connecting the S point, the Q point and the T point is set, and the setting of the spline curve is set from the inner end of the tooth to the outside. This is performed continuously toward the end to define the shape of the tooth whose tip is a gradually changing R shape.
Thereby, the shape of the bevel gear whose tooth tip has a gradually changing R shape can be defined.

This makes it possible to provide a method for manufacturing a bevel gear in which stress concentration on a die during manufacturing by forging is reduced while ensuring a required tooth surface length of a sufficient length.

It is a figure which showed the bevel gear. It is sectional drawing of the tooth of a bevel gear. It is an enlarged view of the cross section of the tooth before defining the gradual change R shape in the tip. It is an enlarged view of the cross section of a tooth after defining the gradual change R shape in the tip. It is a figure which showed the procedure which defines the gradual change R shape in the tooth of a bevel gear.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the bevel gear 1 is a gear formed by forging using a die. A plurality of teeth 11 continuous in the pitch direction are formed on the bevel gear 1.

Here, FIG. 2 is a cross-sectional view of one tooth 11. 3 and 4 are enlarged views of the tooth tip 21 of the tooth 11 and the tooth surface 22 arranged so as to sandwich the tooth tip 21. That is, FIGS. 3 and 4 are enlarged views of the dotted square portion of FIG. 2. 3 is an enlarged view of the tooth 11 in which the gradual change R is not set in the tooth tip 21, and FIG. 4 is a tooth in which the gradual change R is set from the state of the tooth shown in FIG. 11 is shown. In the following, it is assumed that the tooth tip 21 has a substantially flat shape in the pitch direction in the tooth 11 in the state where the gradual change R is not set.

Here, as shown in FIG. 3, when a normal bevel gear in which the gradual change R is not set on the tooth tip 21 is created by forging, the stress σ1 in the direction perpendicular to the tooth tip 21 surface and the tooth surface 22 are applied. A vertical stress σ2 is generated. Therefore, the mold is liable to be damaged starting from the point O, which is the end of the tooth tip 21 and the end of the tooth surface 22.

Next, a method of defining the gradually changing R shape of the tooth tip 21 when forming the bevel gear 1 by forging will be described. Hereinafter, as shown in FIG. 2, a predetermined cross section of the tooth 11 will be described.

A bevel gear in which the gradual change R is not set for the tooth tip 21 is used as a reference bevel gear. That is, the reference bevel gear is a bevel gear in which a high stress is applied to the mold starting from the apex between the tooth tip 21 and the tooth surface 22. For example, as shown in FIG. 4, the tooth 11 having a gradually changing R shape on the tooth tip 21 has a shape in which a part of the tooth tip 21 and the tooth surface 22 of the reference bevel gear tooth is cut off.

First, the O point is set (step S1). Specifically, as shown in FIGS. 2 and 3, it is the apex between the tooth tip 21 of the reference bevel gear and one tooth surface 22a, and is the starting point of mold breakage when forging is performed. The point to be becomes the first O point. In other words, the first point O is a substantially flat end portion of the tooth tip 21 and a portion of the end portion of the tooth surface 22a.

Similarly, as shown in FIG. 2, the second O point is the apex between the tooth tip 21 and the other tooth surface 22b, which is the starting point of mold breakage when forging is performed. And.

Next, the T point is set (step S2). For example, the position on the tooth tip 21 is set as the T point, which is between the first O point and the second O point, equidistant from the first O point and the second O point. The method of setting the T point is not limited to this method. For example, if the tooth 11 has a line-symmetrical shape as shown in FIG. 2, the point on the symmetric line and on the tooth tip 21 is the T point. It may be set as. Here, it is assumed that the T point is set at a position substantially at the center of both ends on the tooth tip 21.

Next, the S point is set (step S3). As shown in FIGS. 2 and 4, in order to set the S point, the required tooth surface length is set on the tooth surface 22. The required tooth surface length is a length in the direction of the tooth tip 21 set from the tooth root or the vicinity of the tooth root of the tooth 11, and can be changed according to the functional product requirements.

Here, when the required tooth surface length is set, assuming a line segment on the tooth surface 22a indicating the required tooth surface length from the tooth root to the tooth tip 21, the tooth tip 21 in this line segment is assumed. The end on the side is set as the S point. Further, a straight line ST connecting the S point and the T point is set.

Next, the P point is set (step S4). A point where a perpendicular line is drawn from the point O and intersects the straight line ST is set as the point P. In addition, a straight line OP connecting points O and P is set.

Set the Q point that minimizes the stress (step S5). Here, the Q point is set on the straight line OP, and the distance of the line segment OQ connecting the O point and the Q point is 30% to 50% of the distance of the line segment OP. Set a point.

At this time, the Q point is the Q point where the stress generated in the mold is minimized when the 3D modeling of the bevel gear 1 is constructed and the bevel gear 1 is formed by using the mold by CAE (Computer Aided Engineering). It is set by calculating the position of.

A spline curve connecting points S, Q, and T is set (step S6). The spline curve is set so that the points S and T are in tangent contact with each other.

Here, the setting of the spline curve by the processing of steps S1 to S6 is continuously executed not only from the predetermined cross section of the tooth 11 but also from the inner end to the outer end of the tooth 11 of the bevel gear (step S7). This sets multiple spline curves. Then, the gradual change R shape of the tooth 11 is defined so that the set of lines drawn by these spline curves becomes the surface of the tooth tip 21 and the tooth surface 22a. For example, the inner end is the large end of the tooth of the umbrella-shaped bevel gear, and the outer end is the small end.

After that, a die is formed as a forging of a bevel gear having a tooth tip 21 having a gradually changing R shape defined by setting a spline curve.

This makes it possible to propose a product shape that meets the conflicting forging manufacturing requirements of reducing the concentration of stress applied to the die during forging manufacturing while ensuring the required tooth surface length with the mating gear. In other words, the bevel gear formed by forging can suppress the decrease in the meshing ratio, and can suppress the early occurrence of cracking of the die during forging, so that the manufacturing cost can be reduced. ..

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.

For example, in step S6, the gradual change R shape is set by setting the spline curve, but the spline curve is not limited to the other curve. Further, what is forged by defining the gradually changing R shape by this method is not limited to the bevel gear, and may be used when manufacturing other types of gears.

For example, in the above-mentioned bevel gear 1, the tooth tip 21 has been described as having a substantially flat shape, but when actually used as a product, the shape of the tooth tip 21 should be a conical shape coaxial with the product center axis. Can be done. The conical shape of the tooth tip 21 can be treated as being close to a substantially flat shape, and a gradually changing R shape can be set for the tooth tip 21 by the above method.

Further, the setting of the T point has been described as being set as the center position on the tooth tip 21, but the setting is not limited to this. For example, an arbitrary position between the first O point and the second O point may be set as the T point on the tooth tip 21.

1 Bevel gear 11 Tooth 21 Tooth tip 22 Tooth surface 22a First tooth surface 22b Second tooth surface

Claims (1)

It is a method of manufacturing a bevel gear that manufactures a bevel gear whose tooth tip has a gradually changing R shape using a mold.
In the tooth part of the bevel gear, multiple teeth are continuously arranged in the pitch direction.
The tooth
Tooth tips that have a substantially flat shape in the pitch direction,
It has a tooth surface that is arranged between the tooth bottom and the tooth tip and is arranged so as to sandwich the tooth tip.
In the tooth before forming the gradually changing R shape,
An O point is set at the end of the tooth tip having a substantially flat shape and at the end of the tooth surface.
A point T is set on the intermediate surface between both ends of the tooth tip, which has a substantially flat shape.
The required tooth surface length on the tooth surface is set, and the end portion on the tooth tip side when the required tooth surface length is secured from the tooth bottom side is set as the S point.
The point where the perpendicular line from the O point intersects with respect to the straight line connecting the T point and the S point is set as the P point.
The distance between the O point and the Q point when setting the point on the straight line connecting the O point and the P point where the stress generated in the mold by 3D modeling / CAE analysis is minimized as the Q point. However, the Q point is set so as to be 30 to 50% of the distance connecting the O point and the P point.
A spline curve connecting the S point, the Q point, and the T point is set.
The spline curve is continuously set from the inner end to the outer end of the tooth, and the shape of the tooth whose tip is a gradually changing R shape is defined.
How to manufacture bevel gears.

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