JPH06213287A - Flexible meshing type gear meshing construction - Google Patents

Abstract

PURPOSE:To restrain deformation resistance of an external gear to be small in a flexible meshing type gear meshing construction, even in case of setting difference of the number of teeth between an internal gear and an external gear to be small. CONSTITUTION:When difference of the number of teeth between an internal gear 132 and an external gear 128 is set as (i), difference of the number of teeth between the internal gear 132 and a virtual external gear 134 inscribedly meshing with the internal gear 132 and having rigidity is set as (j), and relation of (i)<(j) is set, the tooth profile of the external gear after bending in the part meshing with the internal gear is set to be formed into equal tooth profile of the virtual external gear, and the deformed curvature at the meshing part of the external gear with the internal gear is set to be equal to the curvature of that of the virtual external gear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible mesh type gear meshing structure, that is, a so-called wave gear structure, which is suitable for application to a small speed reducer or a speed increaser.

[0002]

2. Description of the Related Art Conventionally, for example, a technique disclosed in Japanese Patent Laid-Open No. 63-130949 is known as a technique relating to a flexural meshing gear meshing structure. This will be described below.

FIG. 5 is a sectional view showing the structure of this prior art,
FIG. 6 is a sectional view taken along line VI-VI of FIG. This structure is generally called a wave gear structure.

The input rotary shaft 21 is provided with an outer spline 22A, and the outer spline 22A is connected to an inner spline 22B provided on an eccentric body 23 which serves as a wave generator. Eccentric body bearings 24 are provided on the outer circumferences of these eccentric bodies 23. An external gear 28 is provided on the outer periphery of the eccentric body bearing 24, and the external gear 28 is composed of a flange portion 29, an annular portion 30, and an external tooth portion 31. The external tooth portion 31 of the external gear 28 is located on the outer circumference of the outer ring 27 of the eccentric body bearing 24.

In the above, the outer ring 27, the annular portion 30 and the outer tooth portion 31 are elastically deformable. The external tooth 31A provided on the external tooth portion 31 has a trochoidal tooth profile or the like, and the external tooth 31A meshes with an internal tooth 33A formed by a pin rotatably supported by an internal gear 32. There is.

The number of external teeth 31A is smaller by two than the number of internal teeth (pins) 33A of the internal gear 32.
The shape of the external teeth 31A is such that two epitrochoid parallel curves having a radius ratio of an inversion circle and a base circle are integers are overlapped with their phases shifted, and the innermost curve portion of the overlapping individual curves is This is a tooth profile curve, and the tooth profile itself is Japanese Patent Publication No. 58-42382 (Patent No. 120854).
No. 8).

The rotation of the input rotary shaft 21 becomes the rotation of the wave generator (eccentric body 23), and the eccentric body 23 deforms the external tooth portion 31 of the external gear 28 through the eccentric bearing 24. The outer tooth portion 31 deformed by the convex portion of the eccentric body 23 has its outer tooth 31A meshing with the inner tooth (pin) 33A, and the tooth of the outer tooth 31A and the pin 33A is rotated during one rotation of the eccentric body 23. The phase shifts by a number difference, and the shift becomes rotation of the external gear 28 and is transmitted to the output shaft 34. In this example, specifically, there are 100 external teeth 31A and 102 internal teeth (pins) 33A, the difference in the number of teeth is 2, and the reduction ratio is (-2 / 100 = -1 / 50).
Becomes In addition, "-" indicates that the input and output are in a reverse rotation relationship.

The internal gear 32 is fixed in this embodiment. However, when one of the external gear 28 and the internal gear 32 is fixed, the other is the output side, and the input rotary shaft is the output that is accelerated and taken out when the output shaft is the input side. It also serves as an axis.

By the way, in this type of flexible mesh type gear device, the tooth profile used for the external gear 28 and the internal gear 32 is ideally the one disclosed in Japanese Patent Publication No. 58-42382 mentioned above. It is said that. This Japanese Patent Sho 58-423
The tooth profile disclosed in Japanese Unexamined Patent Publication No. 82 is originally applied to a planetary gear reducer (known as a registered trademark “Cyclo reducer” owned by the applicant) having an internal gear having rigidity and an external gear having rigidity. It was invented for the purpose of use.

That is, even in the flexural gear type gear device, in order to make the external gear 28 and the internal gear 32 mesh theoretically and accurately, at least the external gear 28 and the internal gear 32 mesh with each other. That is, the same state as the meshing state of the planetary gear reducer related to the combination of the external gear and the internal gear having the above-mentioned rigidity must be formed in the portion where the gears are engaged.

Specifically, this is a perfect circular state before the external gear 28 has a shape (radius of curvature) at least at a portion meshing with the internal gear 32 before the external gear 28 is bent (deformed). It means that it must have the same shape (curvature radius) as in.

[0012]

However, such an idea has the following drawbacks.

This will be described with reference to FIG.

FIG. 7 conceptually shows a deformed state of an external gear in a flex mesh type gear meshing structure.
As shown, points A, B, C on external gear 28,
Deformation moves to points A2, B2, C2, D2.
Here, in the portions indicated by the curves A2-D2 and B2-C2, the external teeth 31A of the external gear 28 and the internal gear 32 are shown.
It is necessary that the internal teeth (pins) 33A of the gears theoretically mesh accurately.

Here, comparing the curves of the external gear 28 before and after the deformation, the curve A-D (curve B-C) is translated to the curve A2-D2 (curve B2-C2). Therefore, between A2-B2 (between C2-D2) is between A-B (C-D
The curve A2-B2 (curve C2-D2) has a tangent slope at points A2 and B2 (points C2 and D2) equal to the slope at A and B (C and D). Up to this point, the curve AB (curve CD) is extended in the X-axis direction.

Therefore, it can be seen that the shape of the deformed external gear 28 has a sharply reduced radius of curvature in the vicinity of the points A2, B2, C2 and D2.

This is because the entire circumference before and after deformation is constant, and within a certain range (here, curve A2-D2 and curve B2-C2), the radius of curvature before deformation is maintained even after deformation. This is a phenomenon that inevitably occurs because it has to be done (this also determines the shape of the eccentric body 23A).

Therefore, in the external gear 28, a large bending stress is generated in the vicinity of the points A2, B2, C2, and D2 due to the deformation, and it is unavoidable that the transmissible torque is limited. There wasn't.

The present invention has been made in view of such a conventional problem, and in a flex meshing type gear meshing structure in which the flexure of the external gear is essential, the external gear is deformed. The purpose is to suppress bending stress as much as possible, improve transmission efficiency, and increase transmittable torque.

[0020]

SUMMARY OF THE INVENTION According to the present invention, a rigid internal gear, an external gear having flexibility capable of intermeshing with the internal gear, and a flexural deformation of the external gear. In the flexural mesh type gear meshing structure including a wave generator that realizes internal meshing of the internal gear and the external gear by doing, a difference in the number of teeth between the internal gear and the external gear Let i be j and the difference in the number of teeth from the internal gear is larger than i (i <
j), and assuming a virtual external gear having rigidity that meshes internally with the internal gear, the tooth profile of the external gear is the portion that meshes with the internal gear as a result of bending of the external gear. In addition to forming a shape that is equal to the tooth profile of the virtual external gear in
The problem described above is solved by setting the deformation curvature in the portion of the external gear that meshes with the internal gear to be equal to the curvature of the virtual external gear.

[0021]

In the present invention, the difference in the number of teeth between the external gear and the internal gear is
When i, the conventional design concept of deciding the tooth profile and curvature of the internal gear and the external gear by focusing on the tooth number difference i is revised, and the tooth number difference j larger than this tooth number difference i The external gear that would be

This virtual external gear has a basic shape that is a perfect circle and has rigidity. Therefore, as a type, it corresponds to an external gear of a conventionally known planetary gear reducer (cyclo reducer: registered trademark). You can think of it as something.

FIG. 3 is a view showing a deformed shape of the external gear according to the present invention, corresponding to FIG. 7 (conventional example).

3 and 7, point P and point Q are the same. That is, the external tooth portion of the external gear that was located at the point P on the X-axis in the state of a perfect circle before the deformation moves to the position of the point Q when meshing.

Further, the curve A1-D1 (curve B1-C in FIG. 3 is
The radius of curvature of 1) is the curve A2-D2 (curve B2-) of FIG.
It is smaller than the radius of curvature of C2) (= the radius of curvature of the curve A-D (curve B-C)), and the ratio thereof corresponds to "the number of teeth of the virtual external gear / the number of teeth of the external gear".

Therefore, A → A1 (B → B1, C →) rather than the moving distance in the X-axis direction from point A → point A2 (point B → point B2, point C → point C2, point D → point D2). The moving distance in the X-axis direction from C1, D → D1) becomes shorter. Moreover, since θ1 is (number of teeth of external gear / number of teeth of virtual external gear) × θ, θ1> θ. Therefore, curve AB → curve A1-
The transformation from B1 (curve C-D to curve C1-D1) is A
-A1 and A-A2 distance difference in the X-axis direction, and the slope of the tangent to the curve A1-B1 at points A1 and B1 and point A
2, the difference in the tangent slopes of the curve A2-B2 at B2, the curve AB → the curve A2-B2 (curve CD → curve C2
-D2) can be performed more easily.

Therefore, the bending stress due to the deformation of the external gear is reduced accordingly, and the transmissible torque limited by the bending stress of the external gear can be increased.

In addition, at the meshing portion, the external gear is deformed to the radius of curvature of the virtual external gear, and the tooth profile of the meshing portion is formed in advance so as to have the same shape as that of the virtual external gear. The internal gear and the external gear will be in perfect theoretical mesh (although the difference in the number of teeth is actually i) as if the difference in the number of teeth is j.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In the gear meshing structure of this embodiment, the external gear 1
28 and the shape of the eccentric body 123 corresponding thereto are shown in FIGS. 5 and 6 (Japanese Patent Laid-Open No. 63-13094).
The basic structure is the same as the prior art, except for 9). Therefore, redundant description will be omitted, and only different parts will be described by replacing the reference numerals.

FIG. 1 is a sectional view of the main part of the structure of this embodiment, which corresponds to the section taken along the line VI-VI of FIG. or,
FIG. 2 shows a meshing relationship between the internal gear 132 and the virtual external gear 134.

Incidentally, FIG. 8 shows a conventional technique having the same reduction ratio as that of FIG. 1 as a comparative example in order to make it easier to understand the difference between the present invention and the conventional example.

The relationship between the external gear 128, the internal gear 132, and the virtual external gear 134 is as follows.

First, with respect to the number of teeth (58) of the external teeth 131A of the external gear 128, the internal teeth (pins) 1 of the internal gear 132 are
The number of teeth (60) of 33A is two more. That is, the difference in the number of teeth i = 6
0-58 = 2.

On the other hand, the number of teeth of the virtual external gear 134 (56)
Is four less than the number of teeth (60) of the internal gear 132.
That is, j = 60−56 = 4 (i <j).

The external gear 128 is based on the "tooth profile" of the virtual external gear 134 having four teeth less than the number (60) of the internal teeth (pins) 133A of the internal gear 132. , Two teeth of the same shape are added to this, and the internal gear 132
The difference in the number of teeth with is 2.

In order to achieve a theoretically accurate meshing between the external teeth 131A of the external gear 128 and the internal teeth 133A of the internal gear 132, which have such a relationship, the external gear 128 at the meshing portion. The radius of curvature needs to be equal to the radius of curvature of the virtual external gear 134. Therefore, in this embodiment, as shown in FIG. 3, the curvature radii of the meshing ranges A1 to D1 and B1 to C1 of the external gear 128 are set to the external gear 128.
Virtual external gear 1 which is two teeth less than the external teeth 131A of
It is set to be the same as the radius of curvature of 34. The radius of curvature of the virtual external gear is the number of teeth of the virtual external gear (56) / the number of teeth of the external gear (5) with respect to the radius of curvature of the conventional external gear 128.
8) Only smaller.

The specific shape of the virtual external gear 134 is such that four epitrochoid parallel curves in which the radius ratio of the rolling circle and the base circle is an integer are overlapped with each other by shifting the phase, and the overlapped individual curves are formed. Of these, the innermost curved portion is a tooth profile curve.
It is known from Japanese Patent No. 42382.

That is, the shape of the virtual external gear 134 is
When this is used in an internally meshing planetary gear device (eg, cyclo gear reducer (registered trademark)), the internal teeth 13 of the internal gear 132 are
3A is an external gear having a difference in the number of teeth of 4 (having rigidity) and has a shape capable of theoretical meshing (see FIG. 2).

As described above, the reduction gear ratios of the speed reducer according to this embodiment and the speed reducer according to the comparative example shown in FIG. 8 are both external teeth 131A, 1A of the external gears 128, 128 ', as described above.
Since 31A 'is 58 and the internal teeth (pins) 133A, 133A' of the internal gears 132, 132 'are 60, the difference in the number of teeth is 2, so both speed reducers are -2 / 58 = -1 /. Two
It becomes 9. It should be noted that "-" indicates that the input and output have a reverse rotation relationship.

However, in the speed reducer according to this embodiment, the deformed shape of the external teeth in the meshing range of the external gear is actually four less than the number of teeth 60 of the internal gear 132 after the deformation. It is the same. Therefore, the entire shape of the external gear 128 when deformed in the speed reducer according to the comparative example is changed from a shape close to a rectangle to a shape closer to a perfect circle. As described above, the deformation resistance can be reduced by changing the actual tooth number difference (reduction ratio) and adopting the tooth profile relating to the combination having a larger tooth number difference and the deformation curve matching the tooth profile. Moreover, as described above, the internal gear 132
The external gear 128 and the external gear 128 are completely theoretically meshed as if they are meshed with each other according to the combination of the tooth number difference j.

Next, FIG. 4 shows a second embodiment of the present invention. The difference between the second embodiment and the above embodiment is that the internal teeth are cut directly on the main body, instead of using pins as the internal teeth of the internal gear. The internal teeth in this case are set so as to theoretically mesh with the virtual external gear. Specifically, the internal teeth 2 of the internal gear 232 in this case
33A and the external teeth of the virtual external gear (that is, the actual external gear 2
As the external tooth 231A) in the meshing portion of 28, the tooth profile proposed in Japanese Patent Application No. 4-202295 (unknown) can be adopted.

That is, when the difference in the number of teeth between the virtual external gear and the internal gear 232 is N (2 in the example of FIG. 4), the tooth profile of the virtual external gear has N epitrochoid parallel curves in phase. The tooth profile of the internal gear 232 is composed of N inner trochoidal envelopes meshing with the epitrochoid parallel curve, which are formed by using the innermost curve formed when they are overlapped with each other.
It is configured based on the innermost curve formed when the virtual external gears are superposed with the same phase shift.

Since the other construction is basically the same as that of the above-described embodiment, the same reference numerals are allotted to the same portions in the drawings, and the duplicated description will be omitted.

When the present invention is carried out, the external gear may interfere with the internal gear at a portion other than the portion having the same radius of curvature as the virtual external gear, depending on the difference in the number of teeth to be set. May occur. In this case, in order to prevent this interference, it is preferable to correct the tooth profile by appropriately rounding the tip of the external gear.

In each of the above two embodiments, the difference i between the number of internal teeth of the internal gear and the number of external teeth of the external gear is set to 2, but in the present invention, this difference is set. The difference i is not limited to 2, and may be any number as long as it is 1 or more. or,
Also in the present invention, the number of teeth of the virtual external gear may be an appropriate number as long as it is smaller than the actual number of external teeth of the external gear.

[0047]

As described above, according to the present invention, the actual external gear has a larger difference in the number of teeth while maintaining a small difference in the actual number of teeth, that is, while ensuring a large reduction ratio. The shape can be made almost the same as that of the case, and since the deformation resistance of the external gear can be reduced by that much, it becomes possible to further increase the transmissible torque which was limited by the deformation resistance in the conventional durability. Excellent effect can be obtained.

Further, since the deformation resistance is reduced, heat generation in the external gear can be further reduced, and the transmission efficiency can be further improved.

[Brief description of drawings]

FIG. 1 is a sectional view corresponding to FIG. 6 or 8 showing a main part of a flexible meshing gear meshing structure to which the present invention is applied.

FIG. 2 is a meshing diagram of an internal gear and a virtual external gear in the above embodiment.

FIG. 3 is a diagram showing the relationship between the external gear before deformation (before bending) and after deformation (after bending) in the above embodiment.

FIG. 4 is a sectional view corresponding to FIG. 1 showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing an overall structure of an example of a conventional flexible meshing gear meshing structure (this embodiment also has the same basic structure except for the number of teeth and tooth profile).

6 is a sectional view taken along the line VI-VI in FIG.

FIG. 7 is a diagram corresponding to FIG. 3 showing the relationship of a conventional external gear before deformation (before bending) and after deformation (after bending).

8 is a sectional view showing a conventional example (comparative example) having the same reduction ratio as that of the embodiment of the present invention shown in FIG.

[Explanation of symbols]

 123 ... Eccentric body (wave generator) 128, 228 ... External gear 131A ... External teeth 132, 232 ... Internal gear 133A ... Internal teeth 134 ... Virtual external gear 140A ... External teeth of virtual external gear

Claims (1)

[Claims] 1. An internal gear having rigidity, an external gear having flexibility capable of being internally meshed with the internal gear, and the internal gear having the external gear flexibly deformed. In a flexural meshing gear meshing structure including a wave generator that achieves internal meshing with an external gear, when the difference in the number of teeth between the internal gear and the external gear is i,
If the difference in the number of teeth from the internal gear is larger than i (i <j
), And assuming a virtual external gear having rigidity that meshes internally with the internal gear, the tooth profile of the external gear is a portion that meshes with the internal gear as a result of bending of the external gear. The flexure is formed in a shape that is equal to the tooth profile of the virtual external gear, and the deformation curvature of the portion of the external gear that meshes with the internal gear is set to be equal to the curvature of the virtual external gear. Meshing gear meshing structure.