JP2007040518A - Harmonic speed reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a harmonic speed reducer increased in durability, reduced in weight, and manufacturable easily. <P>SOLUTION: This harmonic speed reducer comprises an annular rigid internal gear 2, a flexible external gear 3 disposed on the inside thereof, and a wave generator 4 disposed on the inside thereof. The flexible external gear 3 comprises a tubular body part 31 radially deformable and having flexibility, a tubular tooth part 30 having external teeth formed formed continuously with one end of the body part 31 thereof, an annular diaphragm 32 radially extending continuously with the other end of the body part 31, and a boss 33 continued with the diaphragm. The flexible external gear 3 comprises a body part of which outer diameter is 7 mm or smaller and is formed of a titanium alloy containing 30 to 60 mass% vanadium group elements or a metal glass containing zirconium and nickel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a harmonized speed reducer including a flexible external gear with a reduced diameter and improved durability.

There are cup-type, top-hat type, and flat-type harmonic reducers depending on the shape of the flexible external gear incorporated therein. A typical example conventionally proposed for a cup-type harmonic reduction gear is shown in FIG. 1 (see, for example, Patent Document 1).
Hereinafter, an example of the cup-type harmonic speed reducer disclosed in Patent Document 1 will be described. FIG. 1 is a side sectional view showing an outline of a cup-type harmonic reduction gear, and FIG. 2 is a front view thereof.
The cup-type harmonic speed reducer 1 includes an annular rigid internal gear 2, a cup-shaped flexible external gear 3 disposed on the inside thereof, and an elliptical wave generator 4 fitted on the inside thereof. Have. The cup-shaped flexible external gear 3 includes a cylindrical body portion 31, a cylindrical tooth portion 30 in which external teeth 34 are formed continuously at one end of the body portion 31, and the body portion 31. An annular diaphragm 32 that seals the end, and a boss 33 that is integrally formed at the center of the diaphragm 32 are provided.

  The flexible external gear 3 is bent to a certain strain in an elliptical shape by the wave generator 4, and the external teeth 34 at both ends in the major axis direction of the elliptical shape are formed on the inner peripheral surface of the internal gear 2. It meshes with the formed internal teeth 21. When the wave generator 4 is rotated by a motor rotating shaft or the like, the meshing position of both gears moves in the circumferential direction. Since the number of teeth of the internal teeth 21 and the external teeth 34 is different by 2N (N is a positive integer), relative rotation corresponding to the difference in the number of teeth occurs between the two gears. In general, since the side of the internal gear 2 is fixed, rotation that is greatly decelerated according to the difference in the number of teeth of both gears is output from the side of the cup-shaped flexible external gear 3. For such operations, the flexible external gear 3 is generally made of special steel having excellent mechanical strength in practical use.

The harmonic speed reducer has been described above by taking the cup type as an example, but the principle of operation is the same for the top hat type and the flat type.
Such a harmonic reduction gear is generally commercially available in Japan with a flexible external gear having an outer diameter of about 10 mm or more.
JP 2000-55147 A (page 3, FIG. 1)

However, since the above-described harmonic reduction gear is used in a driving device such as a robot, it is required to improve the durability and reduce the diameter and weight. In particular, when it is used for a robot hand, it is required to improve durability as well as to reduce the diameter. The flexible cylindrical body that can be deformed in the radial direction of the flexible external gear used in the harmonic reduction gear is usually made of special steel such as nickel chrome molybdenum steel (Young's modulus E = 200 GPa). ing. In an apparatus in which the cylindrical body is subjected to constant strain, the applied stress increases when the diameter is reduced, and fatigue failure occurs in short-time use, so the outer diameter of about 8 to 10 mm is the limit. That is, since the deformation amount ΔD of the flexible external gear is operated constant regardless of the outer diameter D, when the outer diameter of the flexible external gear becomes smaller, ΔD / D, that is, the strain ε increases. On the other hand, when the Young's modulus is E, the stress σ applied to the flexible external gear becomes larger as the diameter becomes smaller due to the relationship of σ = εE. As a result, the fatigue strength of the flexible external gear becomes a problem.
In view of this point, an object of the present invention is to provide a small-diameter harmonic reduction device.

In order to solve the above problems, the present invention is configured as follows.
The invention described in claim 1 includes an annular rigid internal gear, a flexible external gear disposed inside the annular rigid gear, and a wave generator disposed further inside. The tooth gear includes a cylindrical barrel portion that is deformable in the radial direction and has flexibility, a cylindrical tooth portion in which external teeth are formed continuously at one end of the cylindrical barrel portion, and the barrel portion. In the harmonic reduction gear including an annular diaphragm extending in the radial direction continuously to the other end of the shaft and a boss continuing to the diaphragm, the flexible external gear has an outer diameter of 7 mm. It is made of a titanium alloy containing the following and 30 to 60% by mass of a vanadium group element.
According to a second aspect of the present invention, the titanium alloy contains 1 to 20% by mass in total of one or more elements in a metal element group composed of zirconium, hafnium, and scandium.
According to a third aspect of the present invention, the titanium alloy contains 0.08 to 0.6% by mass of oxygen.
The invention according to claim 4 includes an annular rigid internal gear, a flexible external gear disposed inside the annular rigid gear, and a wave generator disposed inside the rigid external gear, and the flexible external gear. The tooth gear includes a cylindrical barrel portion that is deformable in the radial direction and has flexibility, a cylindrical tooth portion in which external teeth are formed continuously at one end of the cylindrical barrel portion, and the barrel portion. In the harmonic reduction gear including an annular diaphragm extending in the radial direction continuously to the other end of the shaft and a boss continuing to the diaphragm, the flexible external gear has an outer diameter of 7 mm. A harmonized speed reducer characterized in that it is made of a metal material having an elastic strain of 0.015 to 0.03 and a tensile strength of 750 MPa or more.
The invention according to claim 5 is the harmonic speed reducer, wherein the metallic material is metallic glass.
The invention according to claim 6 is the harmonic speed reducer characterized in that the metallic glass contains 5 to 60% by mass of zirconium and nickel in the balance.

According to the inventions described in claims 1 to 3, the titanium alloy used for the flexible external gear has been used so far as the strength is equivalent to that of the special steel compared to other titanium alloys and the Young's modulus is about 40 GPa. Since the Young's modulus is less than about 200 GPa such as nickel chrome molybdenum steel, when the flexible external gear is subjected to the same strain ε, the stress σ generated in this member is lower as apparent from σ = εE. Become. That is, even a flexible external gear having an outer diameter of 7 mm or less, which has been difficult with the conventional configuration, has a lower stress applied to the member, and a small-diameter harmonic reduction gear can be configured.
According to the inventions of claims 4 to 6, the elastic strain of the metallic glass used for the flexible external gear is 0.015 to 0.03, which is larger than about 0.007 of the conventional special steel, and Since the tensile strength is GPa or more, the tensile strength is about 750 MPa, so the same effect as described above can be obtained, and a small-diameter harmonic reduction device can be configured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are cup-type harmonic reduction gears using the present invention. Since the shape is the same as the conventional one, the description of the reference numerals of each part is omitted. The annular rigid internal gear 2, the wave generator 4, and other components are produced by the same method as before.
The flexible external gear 3 is manufactured by setting the cup outer diameter of the flexible external gear 3 to 3, 5, 7, and 8 mm, and plate materials of four types of titanium alloys # 1 to # 4 shown below. And # 5 to # 6 metallic glass plate materials were formed by the cold deep drawing method. The deep drawing ratio is about 70 to 90%. After this processing, annealing at 100 to 400 ° C. was used as necessary. As the tensile strength of the metallic glass, one having an elastic strain divided by an elastic modulus of 0.015 to 0.03 was used. A numerical value represents the mass% of an alloy component.
(1) # 1: Ti-35Nb-10V-0.35O
(2) # 2: Ti-40Nb-6V-4Ta-0.28O
(3) # 3: Ti-20Nb-5V-10Ta-5Zr-5Hf-0.29O
(4) # 4: Ti-35Nb-5Ta-3Sc-0.27O
(5) # 5: Zr-30Cu-10Al-5Ni
(6) # 6: Ni-20Nb-10Ti-8Zr-6Co-3Cu
(7) # 7: Nickel chromium molybdenum steel Note that # 7 is a comparative example produced by a conventional method.

Next, the produced flexible external gear 3 was incorporated in the rigid internal gear 2 and the wave generator 4, and the durability of the harmonic reduction gear 1 was evaluated with a reduction ratio of 100.
In the evaluation method, the output end, that is, the boss 33 of the flexible external gear 3 is fixed, and the input end, that is, the generation of the wave is applied to the output side so that torque corresponding to each size is continuously applied in the positive and negative directions. Judgment was made based on whether or not the applied torque could be input 1000 times or more without breaking the instrument 4.
The durability evaluation results are shown in Table 1.

As can be seen from Table 1, # 1 to # 6 of the examples of the present invention passed in the standard level of the implementation, but in the comparative example, the outer diameter of 7 mm was broken less than 1000 times, and 3 mm and 5 mm. The external gear was destroyed when it was incorporated into the internal gear. Thus, it can be seen that the present invention is effective in reducing the diameter of the wave reducer.
In addition, although the titanium alloy used for the flexible external gear 3 made vanadium group elements 30 to 60% by mass, if it is less than 30% by mass, the average Young's modulus is not sufficiently lowered, and exceeds 60% by mass. Material segregation becomes remarkable and the properties of strength, toughness and ductility are not satisfied. In addition, one or more elements in the metal element group consisting of zirconium, hafnium and scandium are contained in total in an amount of 1 to 20% by mass. And does not satisfy the properties of ductility. Further, the oxygen content is set to 0.08 to 0.6% by mass. However, when the oxygen content is less than 0.08% by mass, the strength of the titanium alloy is not sufficiently increased. It is not preferable because it causes embrittlement.
Further, the metal glass used for the flexible external gear 3 has an elastic strain of 0.015 to 0.03 obtained by dividing the tensile strength by the elastic modulus. This is not preferable because the Young's modulus is not sufficient to be used in the present invention. Further, although the tensile strength is set to 750 MPa or more, it is not preferable that the tensile strength is 750 MPa or less because the strength is not sufficient to be used in the present invention.

  Thus, according to the present invention, the Young's modulus of the constituent member of the flexible external gear is reduced, and even when the stress received by this member to bend and operate is less than the outer diameter of 7 mm, the stress limit of the member is reduced. Therefore, a small-diameter harmonic reduction gear can be configured.

  Since the amount of strain can be increased with respect to the surface stress of the flexible external gear, it can also be applied as an element of a flexible external gear of a harmonic reduction gear having a force detection function by attaching a strain gauge.

It is a sectional side view which shows the cup type | mold harmonic reduction gear used for this invention. It is a front view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Harmonic reduction gear 2 Internal gear 21 Internal tooth 3 Flexible external gear 30 Teeth part 31 Body part 32 Diaphragm 33 Boss 34 External tooth 4 Wave generator

Claims (6)

An annular rigid internal gear, a flexible external gear disposed on the inner side thereof, and a wave generator disposed on the inner side thereof, wherein the flexible external gear is deformed in the radial direction. A flexible cylindrical barrel, a cylindrical tooth formed with external teeth continuous at one end of the cylindrical barrel, and a radius continuously at the other end of the barrel In a harmonic speed reducer including an annular diaphragm extending in a direction and a boss continuous with the diaphragm,
The flexible external gear is a harmonic speed reducer characterized in that the outer diameter of its body is 7 mm or less and is made of a titanium alloy containing 30 to 60% by mass of a vanadium group element.   2. The harmonic speed reducer according to claim 1, wherein the titanium alloy contains 1 to 20 mass% in total of one or more elements in a metal element group composed of zirconium, hafnium, and scandium.   The said titanium alloy contains 0.08-0.6 mass% oxygen, The harmony speed reducer of Claim 1 or 2 characterized by the above-mentioned. An annular rigid internal gear, a flexible external gear disposed on the inner side thereof, and a wave generator disposed on the inner side thereof, wherein the flexible external gear is deformed in the radial direction. A flexible cylindrical barrel, a cylindrical tooth formed with external teeth continuous at one end of the cylindrical barrel, and a radius continuously at the other end of the barrel In a harmonic speed reducer including an annular diaphragm extending in a direction and a boss continuous with the diaphragm,
The flexible external gear is a metal having an outer diameter of a body portion of 7 mm or less, an elastic strain obtained by dividing a tensile strength by an elastic modulus, 0.015 to 0.03, and a tensile strength of 750 MPa or more. Harmonic reducer characterized by being composed of materials.   The harmonic reduction gear according to claim 4, wherein the metallic material is metallic glass.   6. The harmonic reduction gear according to claim 5, wherein the metallic glass contains 5 to 60% by mass of zirconium and the remainder contains nickel.

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