JPH038529A - Formation of internal gear - Google Patents

Abstract

PURPOSE:To form an internal gear excellent in shape and accuracy by rotating a gear forming punch on the inside of a cylindrical base material for forming an internal gear, pressurizing the cylindrical base material and reducing its diameter. CONSTITUTION:The punch 12 having a tooth form corresponding to the tooth form of the internal gear is fitted in the internal circumferential surface of the cylindrical base material 22 to form the internal gear, plural recessed forming dies 20 which can move in the radial direction of the punch 12 and whose surfaces on the punch side nearly correspond to the external circumferential surface of the internal gear approach to or separate from the punch 12 several times as an amount of approach to the punch 12 is increase gradually, when the forming dies 20 are separated from the cylindrical base material 22, the punch 12, the cylindrical base material 22 and the forming dies 20 are rotated mutually and a part corresponding to a clearance between the external circumferential surface of the cylindrical base material 22 and the adjacent forming dies is changed to reduce the diameter of the cylindrical base material 22. The adhesion of the punch to the internal circumferential surface of the cylindrical base material 22 is improved, further, the distribution of stresses in the base material is uniformized, and a gear excellent in dimensional accuracy can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of forming gears, and particularly to a technique for improving the processing accuracy thereof.

Conventional technology Japanese Patent Application Publication No. 1983. Japanese Patent No. 221144 describes a method for forming an outer ring of Rebrozigiint. The outer ring of the Rebro joint consists of two parts: an outer race part and a shaft part, and the outer race part is almost cylindrical with a bottom.
It has a plurality of cross grooves on its inner peripheral surface. In the above method, the bottomed cylindrical part of the material forming the shape of the outer ring is
Cross grooves are formed on the inner circumferential surface of the bottomed cylindrical portion by placing the punch over a punch having a plurality of cross grooves on the outer circumferential surface and tightening the punch from the outside with a plurality of molds to reduce the diameter. Therefore, the mold is movable in the radial direction of the punch, and the surface on the punch side is a concave surface that substantially corresponds to the outer circumferential surface of the outer race portion.

This method can also be used to form gears.

Since the inner gear is cylindrical and has a plurality of teeth on its inner circumferential surface, the cross groove type of the punch for the outer race was changed to the tooth shape of the inner gear, and the punch for the outer race was changed to the tooth shape of the outer race. If the cylindrical material of the gear is fitted into a gear punch and molded in the same manner, the inner circumferential surface of the cylindrical material is pressed against the outer circumferential surface of the punch to form teeth.

Moreover, according to the above method, compared to broaching, extrusion, etc., less friction occurs between the material and the tooth mold during molding. Therefore, damage in the tooth trace direction of the gear due to friction is avoided, and the effect of increasing the strength of the teeth is obtained. In addition, since there is less friction between the material and the tooth pattern, it is possible to use simple lubricants such as lubricating oil instead of solid lubricants such as molybdenum disulfide, and the lubrication that accompanies the application of lubricant during molding. Gears can be processed with high precision without being affected by film thickness or unevenness. Furthermore, there is an advantage that the amount of wear on the punch is small and it can be used for a long time.

Problems to be Solved by the Invention Although the various advantages described above can be obtained by molding a gear by the molding method disclosed in the above-mentioned publication, there are still points to be improved.

That is, in the above molding method, it is difficult to uniformly press each part of the outer peripheral surface of the material, and there is a limit to the improvement in the dimensional accuracy of the product. In addition, since forming is performed by approaching and separating the molds once, the material deforms rapidly, and burrs are likely to occur in areas of the outer circumferential surface of the material that are not pressed, that is, areas that correspond to the gaps between adjacent molds. Another problem is that it is difficult to mold gears with large teeth.

The present invention solves the above problems by applying pressing force to a cylindrical material multiple times and making the pressing force as uniform as possible in the circumferential direction, and provides a method that allows even gears with large teeth to be formed with high precision. This was done with the aim of providing this service.

Means for Solving the Problems The gist of the present invention is to fit a cylindrical material into a punch having a tooth pattern corresponding to the teeth of a gear on its outer peripheral surface, and to move the material in the radial direction of the punch. A plurality of molds, each of which has a concave surface that roughly corresponds to the outer circumferential surface of the gear on the punch side, were brought close to and separated from each other several times while gradually increasing the amount of approach to the punch, and the molds were separated from the cylindrical material. In this state, the punch, the cylindrical material, and the mold are rotated relative to each other to change the portion of the outer peripheral surface of the cylindrical material that corresponds to the gap between adjacent molds, thereby reducing the diameter of the cylindrical material and increasing its inner periphery. The purpose is to form multiple teeth on a surface.

It is desirable that the plurality of molds have a central part of the punch side surface as a partial cylindrical surface corresponding to the outer circumferential surface of the gear, and the following side parts as relief surfaces extending in the tangential direction of the partial cylindrical surface.

As described above, in the method of the present invention, the mold approaches the punch, presses the cylindrical material, and then moves away multiple times, increasing the amount of approach to the punch and gradually reducing the diameter of the material. let In addition, the punch or the mold rotates while the mold is separated from the punch, and the part of the outer peripheral surface of the cylindrical material that corresponds to the gap between adjacent molds changes, so the entire outer peripheral surface of the material is pressed uniformly. .

Effects of the Invention Therefore, compared to the conventional forming method described in the above-mentioned publication, the degree of adhesion of the inner circumferential surface of the cylindrical material to the punch is improved, and the stress distribution within the material is made uniform, resulting in a molded gear as a product. Improves dimensional accuracy. In addition, since the diameter of the material is gradually reduced and the part of the outer peripheral surface of the cylindrical material that corresponds to the gap between adjacent molds changes, it is possible to form gears with relatively large teeth while avoiding the generation of burrs. It becomes possible to do so.

In particular, when the punch-side surface of multiple molds is a concave surface including a partial cylindrical surface and a relief surface, at the initial stage of processing,
Since both sides of the partial cylindrical surface, which has a smaller radius of curvature than the outer circumferential surface of the cylindrical material, are prevented from digging into the outer circumferential surface of the cylindrical material, unevenness on the outer circumferential surface of the cylindrical material is avoided, and the outer periphery A gear with a smoother surface shape can be obtained.

EXAMPLE Hereinafter, an example in which the present invention is applied to the molding of a ring-shaped helical gear will be described in detail based on the drawings.

FIG. 1 is a diagram showing the main parts of a press device used in this embodiment. In the figure, a fixed mold 10 constitutes a part of a lower mold 11, and the entire lower mold 11 is attached to a bolster (not shown). A mandrel punch (hereinafter simply referred to as punch) 12 is attached to the center of the fixed mold 10. The punch 12 has a circular cross section, and has tooth patterns 14 formed on its outer circumferential surface to correspond to a plurality of teeth formed on the inner circumferential surface of the helical gear to be formed. A rotary shaft 16 extends from the lower end of the punch 12, and a fixed mold 10
The punch 12 is connected to a motor 18 fixed to the punch 12.
is rotated.

A plurality of molds 20 are disposed around the outer periphery of the punch 12 and are movable in the radial direction of the punch 12.

The surface of each mold 20 on the punch 12 side is a pressing surface 24 that approaches the punch 12 and presses the cylindrical material 22 fitted to the punch 12, and these pressing surfaces 24 are formed by a helical ring gear. It forms a partial cylindrical surface that roughly corresponds to the outer circumferential surface of. Moreover, the surface 26 of the mold 20 opposite to the pressing surface 24 is
The lower portion is shaped to form part of a tapered surface where the diameter increases.

These molds 20 are biased away from the outer peripheral surface of the punch 12 by a biasing member made of a spring, an elastic body, or the like, although not shown.

Furthermore, an extrusion device 30 is disposed below the punch 12 in the fixed mold 10 . The extrusion device 30 includes the punch 12
It consists of a cylindrical extrusion member 32 fitted to the outer peripheral surface of the cylinder, and a hydraulic cylinder (not shown) that moves the extrusion member 32 up and down via a rod 34. The hydraulic cylinder is provided on a member of the lower mold 11 below the fixed mold 10, and the rod 34 is normally retracted into the cylinder, so that when the punch 12 is in a non-operating position, the extrusion member 32 is in the non-operating position as shown in the figure.
It is located near the lower end of. In this non-operating position, the upper end surface of the extrusion member 32 supports the cylindrical material 22 fitted into the punch 12, and when forming is completed, the rod 34 is extended by the operation of the hydraulic cylinder, and the extrusion member 32
2 rises to separate the gear from the punch 12 after forming. The extrusion member 32 has a slightly smaller diameter at the upper part of the outer circumferential surface so as not to interfere with the pressing surface 24 of the mold 20 during molding of the cylindrical material 22.

An upper mold 36 is disposed above the punch 12. The upper die 36 includes a latch mold 42. Support mold 44 above the latch mold 42. It consists of a rod-shaped presser mold 46, etc., and is repeatedly raised and lowered in partial strokes by a ram (not shown). The lower surface of the support mold 44 is an inclined surface 47, and a wedge member 48 is disposed between the inclined surface 47 and the upper surface of the latch mold 42. The wedge member 48 is connected to the upper mold by a hydraulic cylinder 50. The support mold 44 has an inclined surface 49 that rises from the tip side toward the cylinder 50 side in correspondence with the inclined surface 47 . Therefore, by gradually advancing the wedge member 48 for each stroke of the ram, the amount of descent of the latch mold 42 is gradually increased. is immovable relative to each other and is guided so as to be relatively movable in the vertical direction, and the wedge member 48 and the latch mold 42
In order to prevent a gap from forming between the wedge member 48 and the wedge member 48, the wedge member 48 is constantly pulled up by a lifting plate 54 which is urged upward by a pair of hydraulic cylinders 52.

The support type 44. Through holes 56, 58 and 60 are formed in the wedge member 48 and the latch mold 42, respectively, and the presser mold 46 is disposed through these holes. The presser mold 46 is attached to the ram via a cushion device (not shown), and is lowered during molding and is pressed against the punch 1.
2, and cooperates with the extrusion member 32 to position the cylindrical material 22 in the axial direction. The presser die 46 reaches the lower end before the latch die 42 acts on the mold 20, and starts rising after the latch die 42 is separated from the mold 20. Note that the through hole 58 of the wedge member 48 is formed by the movement of the wedge member 48 so that the presser mold 46 and the wedge member 4
It is made to be long so that it does not interfere with 8.

The method for forming helical gears will be explained below.

First, while positioning the extrusion member 32 at the lower end,
The upper mold 36 is raised. In this state, when the cylindrical material 22 is fitted to the punch 12 and the upper mold 36 is lowered, the presser mold 46 first contacts the punch 12 and the cylindrical material 22 is inserted into the punch 12.
axial positioning. Thereafter, the action of the cushion device allows the latch die 42 to move downward relative to the presser die 46, and the tapered surface 38 of the latch part 40 brings the mold 20 closer to the punch 12. During this first stroke, the wedge member 48 is positioned at the retreating end, and from the second stroke, the wedge member 48 is gradually advanced, and the upper die 3
The amount of descent of the latch mold 42 at the bottom dead center of No. 6 is gradually increased.

Along with this, the smaller diameter portion of the tapered surface 38 engages with the surface 26 of the mold 20 and pushes out the mold 20, so that the amount of approach of the mold 20 to the punch 12 becomes as shown in FIG. The molding die 20 presses the cylindrical material 22 by a certain amount each time the upper mold 36 moves up and down, and the material 22 is processed. Further, while the upper die 36 is rising, the latch die 42 is separated from the forming die 20, and the forming die 20 is pushed against the punch 12 by the urging force of the urging member.
At the same time, the presser die 46 also separates from the punch 12 and the cylindrical material 22, so during this time, the punch 1
2, for example, by rotating half the central angle corresponding to each mold 20 to change the portion of the outer circumferential surface of the cylindrical material 22 corresponding to the gap between adjacent molds 20. All parts of the outer peripheral surface of the mold 22 are pressed, and each part of the outer peripheral surface is not pressed only by the same part of the same mold 20.

When the molding is completed, the upper mold 36 is raised and separated from the punch 12 so that the punch 12 can freely rotate, and the extrusion device 30 is operated to raise the extrusion member 32 and remove the tooth trace of the gear. The formed gear is removed from the punch 12 while rotating the punch 12 along the direction.

It is also possible to use the press device shown in FIG. 3 instead of the press device described above. This press device will be described below, but the same members as those in the device described above will be designated by the same reference numerals and detailed explanations will be omitted.

In FIG. 3, the upper die 70 is the latch die 42. Holder mold 46
The lower mold 72 approaches and separates from the punch 12 by a certain amount. A movable mold 74 having a mold 20 and the like can be moved gradually toward an upper mold 70, and a holding mold 76 that movably holds the movable mold 74. A wedge member 78 with a through hole 77 and a hydraulic cylinder 80 are disposed between the movable mold 74 and the holding mold 76, as in the above device, and each time the upper mold 70 rises, the wedge member 78 By gradually advancing the member 78, the movable mold 74 is raised, and the amount of action of the latch mold 42 on the mold 20 is gradually increased. According to this device, a gap is prevented from being generated between the movable die 74 and the wedge member 78 due to its own weight, so there is no need to provide the hydraulic cylinder 52 and the lifting plate 54 in the device of the embodiment. In addition, in the apparatus of this embodiment, the extrusion device 30
During molding, both the head side chamber and the rod side chamber of the hydraulic cylinder communicate with the tank, and the movable mold 7
4 is allowed to extend as the rod 34 rises. Alternatively, the hydraulic cylinder may extend the rods 34 by simply abutting a connecting plate connecting the lower ends of the plurality of rods 34.
In this case, the piston rod of the hydraulic cylinder may be kept in a contracted state during molding, and it may be expanded after molding is completed and wedge member 78 has retreated to the retracted end.

In addition, like the above two press devices, the upper mold 36 and the lower mold 7
Instead of providing wedge members 48, 78, etc. on the upper die or the lower die, the stroke amount of the upper die or the lower die itself may be gradually changed.

Next, another embodiment of the present invention will be described.

Since the press apparatus used in this embodiment is almost the same as the press apparatus shown in FIG. 1, a detailed explanation will be omitted, and only the characteristic mold 90 will be taken out and shown in FIG. 4.

In each mold 90 of this embodiment, the pressing surface 92 on the punch 12 side consists of a partial cylindrical surface 94 at the center and release surfaces 96 at both sides. The partial cylindrical surface 94 has a radius of curvature approximately equal to the outer peripheral surface of the helical gear, and the relief surfaces 96 are planes extending tangentially from both ends of the partial cylindrical surface 94. It is desirable that the partial cylindrical surface 94 and relief surface 96 be formed to satisfy the condition of equation (1).

However, θ: central angle of the pressing surface 92 θ: central angle of the partial cylindrical surface 94 On the other hand, the surface of the mold 90 opposite to the pressing surface 92 is similar to the surface 26 of the mold 20, although not shown. The lower part is shaped to form part of a tapered surface where the diameter increases.
The punch 12 is biased away from the outer circumferential surface of the punch 12 by a biasing member made of a spring, an elastic body, or the like.

Also when molding a gear in a press apparatus equipped with the mold 90 as described above, the latch mold 42 separates from the mold 90 while the upper mold 36 is rising, and the mold 90 absorbs the biasing force of the biasing member. At the same time, the presser mold 46 also separates from the punch 12 and the cylindrical material 22, so during this time, the punch 12 is rotated by a certain angle,
The part of the outer peripheral surface of the cylindrical material 22 corresponding to the gap between adjacent molds 90 is changed so that all parts of the outer peripheral surface of the cylindrical material 22 are pressed, and each part of the outer peripheral surface Parts are prevented from being pressed only by the same part of the same mold 90.

At this time, in the initial stage of processing, as shown in Fig. 5,
A portion of the pressing surface 92 near the boundary between the partial cylindrical surface 94 and the relief surface 96 presses the outer peripheral surface of the cylindrical material 22, but since the partial cylindrical surface 94 and the relief surface 96 are smoothly continuous. , a partial cylindrical surface 9 is formed on the outer peripheral surface of the cylindrical material 22.
This prevents the both sides of 4 from digging in and creating unevenness.

Further, since the relief surface 96 does not contact the cylindrical material 22, the machining load is reduced even if the machining surface pressure is the same. Note that as the processing of the cylindrical material 22 progresses, the pressing surface 92 gradually comes to press the material 22 at a portion near the center of the partial cylindrical surface 94.

In this embodiment, since unevenness is well prevented from being formed on the outer circumferential surface of the ring gear during molding, the machining allowance for the outer circumferential surface can be reduced in subsequent steps. When the outer diameter tolerance of the internal gear is set to about the general tolerance level, it is also possible to omit machining of the outer circumferential surface.

Using the above-mentioned press apparatus, an experiment was conducted to compare the dimensional accuracy of molded gears with and without a relief surface in the mold. The results are shown in FIG. The mold is divided into six parts, and the pressing surface 92 consists of a partial cylindrical surface 94 and a relief surface 96, and the central angle θ of the pressing surface 92 is 60.
mold 9 whose central angle θ of the partial cylindrical surface 94 is 30 degrees.
0 and the mold 20 of the embodiment shown in FIG. 1 in which the entire pressing surface 24 is a partially cylindrical surface were used. In addition, the comparison between the two is based on the tooth tip diameter of the gear (the diameter between the tips of the opposing teeth) among the 80 teeth formed by each mold 90.20.
This was done by measuring.

As is clear from the figure, the mold 9 has a relief surface 96.
0, the tooth tip diameter tends to vary and the dimensional accuracy tends to decrease compared to the mold 20 without a relief surface.

Therefore, further experiments were conducted in order to find conditions under which good molding could be performed even with the relief surface 96 provided. mold 90
Using the same thing as in the previous experiment, the rotation angle of the punch was 15 degrees and 30 degrees, respectively.
The ratio of one machining allowance (the increment in the amount of approach of the mold 90 to the punch 12 at each pressing time) to the total tooth height is 2%,
Three types of molding were performed at 4% and 6%, and the tip diameter of each formed gear was measured. Further, for comparison, a similar experiment was conducted using a mold 20 without a relief surface, with the punch rotation angle set at 15 degrees. The results of the experiment are shown in FIGS. 7 and 8.

As is clear from Figure 7, when the rotation angle of the punch is 15 degrees, the variation in the tooth tip diameter is 115.1 m when the machining allowance for one time with the mold 90 is 2% and 4%.
m to 115.3 mm, but when it is set to 6%, the maximum value of the tooth tip diameter reaches 115.8 mm, and the dimensional error becomes larger than when no relief surface is provided. On the other hand, when using the mold 20, the dimensional error does not become large even if the machining allowance for one time is 6%. In addition, when the rotation angle shown in Fig. 8 is 30 degrees, the maximum tooth tip diameter is 116.2 + nm and the minimum tooth tip diameter is 115.1 mm, which varies greatly regardless of the size of the machining allowance. Accuracy decreases.

As is clear from these experimental results, it is desirable that the rotation angle of the punch be less than half of the central angle θ of the partial cylindrical surface 92 and that the machining allowance for one time be less than 5%.

If molding is performed within this range, it is possible to suppress a decrease in dimensional accuracy, similar to the mold 20 without a relief surface,
Furthermore, it is possible to obtain an internal gear with a smooth outer peripheral surface compared to a mold without a relief surface.

Although the relief surface 96 of the pressing surface 92 was made flat, it is preferable that both ends of the pressing surface 92 do not dig into the outer peripheral surface when the pressing surface 92 is pressed against the outer peripheral surface of the cylindrical material 22. It is also possible to have a convex or concave surface with a sufficiently large radius of curvature. In other words, regardless of whether the relief surface 96 is a concave surface, a flat surface, or a convex surface, it is sufficient that the pressing surface 92 is a concave surface that substantially corresponds to the outer peripheral surface of the gear when viewed as a whole.

Also, instead of keeping the increment of the approach of the mold to the cylindrical material constant from the beginning to the end of processing, it is possible to change it as appropriate, for example, by making the increment larger at the beginning and smaller at the end. It is. Further, the amount of rotation of the punch each time can be changed as appropriate, such as starting small and increasing it at the end.

Further, the increment of the approach amount of the mold and the rotation amount of the punch may be changed as appropriate depending on the diameter of the cylindrical material and the number of teeth.

In addition, if the central angle of the pressing surface of the mold is made smaller, that is, if the mold is divided into smaller pieces, the bending stress applied to the punch teeth during processing will be reduced, reducing the amount of wear on the punch and extending its life. Effects can be obtained.

Note that the punch may be fixed to the lower die and the forming die may be rotated, or by changing the shape of the teeth of the punch, it is also possible to immediately form a ring gear.

In addition, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a front cross-sectional view showing the main parts of a press device used for forming a helical gear according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the position of the shifting die and time in the above-mentioned apparatus, and FIG. 3 is a front sectional view showing the main parts of the press apparatus used in another embodiment of the present invention. FIG. 4 is a partially enlarged plan sectional view showing a mold of a press device used in still another embodiment of the present invention, and FIG. FIG. FIG. 6, FIG. 7, and FIG. 8 are graphs showing the results of experiments conducted using the above-mentioned apparatus, respectively. 12: Mandrel punch 14: Teeth mold 20: Molding mold 22: Cylindrical material 90: Molding mold

Claims (1)

[Claims] A method for forming a gear having a plurality of teeth on its inner peripheral surface, the method comprising: fitting a cylindrical material into a punch having a tooth pattern corresponding to the teeth on its outer peripheral surface; A plurality of molds, which are movable in the radial direction of the punch and whose punch-side surface has a concave surface substantially corresponding to the outer circumferential surface of the inner gear, are brought close to and separated from each other multiple times while gradually increasing the amount of contact with the punch. With,
By rotating the punch, the cylindrical material, and the mold relative to each other while the mold is separated from the cylindrical material, and changing the portion of the outer peripheral surface of the cylindrical material that corresponds to the gap between adjacent molds, the cylindrical material can be removed. A method for forming a gear, the method comprising: reducing the diameter of the gear to form the plurality of teeth on the inner circumferential surface of the gear.