阅读说明：本技术 偏心摆动型减速装置及偏心体的制造方法 (Eccentric oscillating type speed reducer and method for manufacturing eccentric body ) 是由 为永淳 阿部瞬 松永健嗣 于 2020-01-21 设计创作，主要内容包括：若对偏心体的表面实施磨削加工,则根据加工条件有时会导致偏心体的寿命变短。本发明是鉴于这种课题而完成的,其目的在于提供一种能够抑制偏心体的寿命下降的偏心摆动型减速装置。偏心摆动型减速装置(10)具备内齿轮(16)、外齿轮(14)及使外齿轮(14)摆动的偏心体(12a),其中,偏心体(12a)的距表面20μm的处残余应力为压缩应力。(When the surface of the eccentric member is ground, the life of the eccentric member may be shortened depending on the machining conditions. The present invention has been made in view of the above problems, and an object thereof is to provide an eccentric oscillating type reduction gear device capable of suppressing a reduction in the life of an eccentric body. An eccentric oscillation type reduction gear (10) is provided with an internal gear (16), an external gear (14), and an eccentric body (12a) that oscillates the external gear (14), wherein the residual stress at a position 20 [ mu ] m from the surface of the eccentric body (12a) is compressive stress.)

1. An eccentric oscillating type reduction gear device comprising an internal gear, an external gear, and an eccentric body that oscillates the external gear, characterized in that,

the residual stress of the eccentric body at 20 μm from the surface is compressive stress.

2. The eccentric oscillating type reduction gear according to claim 1,

the residual stress of the eccentric body at a position 20 mu m away from the surface is below-200 MPa.

3. The eccentric oscillating type reduction gear according to claim 1 or 2,

the amount of retained austenite at a position of 20 [ mu ] m from the surface of the eccentric body is 30-45 vol%.

4. The eccentric oscillating type reduction gear according to any one of claims 1 to 3,

the residual stress on the surface of the eccentric body is-800 MPa or less.

5. The eccentric oscillating type reduction gear according to any one of claims 1 to 4,

the amount of retained austenite on the surface of the eccentric body is 25 to 40 vol%.

6. A method of manufacturing an eccentric body of an eccentric oscillating reduction gear having an internal gear, an external gear, and an eccentric body that oscillates the external gear, the method comprising:

a heat treatment step of performing heat treatment on the eccentric body; and

a grinding step of grinding the heat-treated eccentric body,

in the grinding step, grinding is performed under grinding conditions such that the residual stress of the eccentric body after grinding is negative at a distance of 20 μm from the surface.

7. The method of manufacturing an eccentric body according to claim 6,

in the grinding step, grinding is performed with the average chip thickness set to 0.01 [ mu ] m or less.

Technical Field

The present invention relates to an eccentric oscillating type reduction gear and a method of manufacturing an eccentric body.

Background

The present applicant discloses, in patent document 1, an eccentrically oscillating speed reducer including an external gear and an eccentric body shaft having an eccentric body, and eccentrically oscillating the external gear via the eccentric body of the eccentric body shaft. The reduction gear described in patent document 1 has an eccentric roller bearing disposed between an external gear and an eccentric body, and a special curing treatment is applied to the eccentric body so that the material properties of the eccentric body change when a thermal load is applied to the eccentric body.

Patent document 1: japanese laid-open patent publication No. 2016-098860

In the eccentric body subjected to the heat treatment, since thermal deformation occurs at the time of the heat treatment, the surface of the eccentric body after the heat treatment may be ground to eliminate the thermal deformation. As the grinding of the eccentric body, various methods including a method based on cutting and polishing described in patent document 1 can be employed. However, depending on the grinding conditions, the life of the eccentric body may be shortened.

Disclosure of Invention

The invention aims to provide an eccentric swinging type speed reducer capable of restraining the service life reduction of an eccentric body.

In order to solve the above problem, an eccentric oscillating type speed reduction device according to an embodiment of the present invention includes an internal gear, an external gear, and an eccentric body that oscillates the external gear, and in the eccentric oscillating type speed reduction device, a residual stress of the eccentric body at a distance of 20 μm from a surface is a compressive stress.

Another embodiment of the present invention is a method of manufacturing an eccentric body. The eccentric body is an eccentric body of an eccentric oscillating type reduction gear device including an internal gear, an external gear, and an eccentric body oscillating the external gear, and includes: a heat treatment step of performing heat treatment on the eccentric body; and a grinding step of grinding the heat-treated eccentric body. In the grinding step, grinding is performed under grinding conditions such that the residual stress of the eccentric body after grinding is negative at a distance of 20 μm from the surface.

In addition, any combination of the above-described constituent elements or a mode in which the constituent elements or expressions of the present invention are interchanged with each other between methods, systems, and the like is also effective as an embodiment of the present invention.

According to the present invention, an eccentric oscillating type reduction gear capable of suppressing a reduction in the life of an eccentric body is provided.

Drawings

Fig. 1 is a side sectional view schematically showing an eccentric oscillating type reduction gear transmission according to embodiment 1.

Fig. 2 is a table showing the results of the residual stress and durability test of the eccentric body of fig. 1.

Fig. 3 is a graph showing residual stress of the eccentric body of fig. 1.

Fig. 4 is a graph showing the retained austenite amount of the eccentric body of fig. 1.

Fig. 5 is a graph showing the residual austenite amount and the residual stress of the eccentric body of fig. 1.

Fig. 6 is a schematic view schematically showing a grinding process of the eccentric body of fig. 1.

Fig. 7 is a scatter diagram showing a relationship between the average chip thickness and the residual stress of the eccentric body of fig. 1.

Fig. 8 is a side sectional view showing the eccentric rocking type reduction gear according to embodiment 2.

In the figure: 10-eccentric oscillating type speed reducing device, 12-input shaft, 12 a-eccentric body, 14-external gear, 16-internal gear, 18, 20-wheel carrier, 24, 26-main bearing, 32-internal pin and 70-input gear.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the embodiment, the comparative example, and the modification, the same or equivalent constituent elements and components are denoted by the same reference numerals, and overlapping description is appropriately omitted. In the drawings, the dimensions of the components are shown enlarged or reduced as appropriate for the convenience of understanding. In the drawings, parts that are not essential to the description of embodiment 1 are omitted.

Further, although the terms including the numbers 1, 2, and the like are used to describe various components, the terms are used only for the purpose of distinguishing one component from another component, and the terms are not used to limit the components.

[ embodiment 1 ]

Hereinafter, the structure of the eccentric rocking type reduction gear transmission 10 according to embodiment 1 will be described with reference to the drawings. Fig. 1 is a side sectional view showing an eccentric rocking type reduction gear transmission 10 according to embodiment 1. The eccentric oscillating type reduction gear 10 of the present embodiment is configured to oscillate the external gear meshing with the internal gear, thereby rotating one of the internal gear and the external gear, and outputting the generated motion component from the output member to the driven device.

The eccentric oscillating type reduction gear 10 mainly includes: an input shaft 12; an outer gear 14; an internal gear 16; wheel frames 18, 20; a housing 22; and main bearings 24, 26. Hereinafter, a direction along the central axis La of the internal gear 16 is referred to as an "axial direction", and a circumferential direction and a radial direction of a circle centered on the central axis La are referred to as a "circumferential direction" and a "radial direction", respectively. For convenience of explanation, hereinafter, one side (right side in the drawing) in the axial direction is referred to as an input side, and the other side (left side in the drawing) is referred to as an opposite-to-input side.

The input shaft 12 is rotated about a rotation center line by rotational power input from a driving device (not shown). The eccentric oscillating type reduction gear 10 of the present embodiment is a center crank type eccentric oscillating type reduction gear in which the rotation center line of the input shaft 12 and the center axis line La of the internal gear 16 are provided on the same axis. The driving device is, for example, a motor, a gear motor, an engine, or the like.

The input shaft 12 of the present embodiment is an eccentric body shaft having a plurality of eccentric bodies 12a for oscillating the external gear 14. The axis of the eccentric body 12a is eccentric with respect to the rotation center line of the input shaft 12. In the present embodiment, three eccentric bodies 12a are provided, and the eccentric phases of the adjacent eccentric bodies 12a are shifted by 120 ° from each other. A spline 12b for receiving power from an output member of the drive device is formed at an input-side end portion of the input shaft 12.

Three external gears 14 are assembled to the outer periphery of the eccentric body 12a via roller bearings 30. Each external gear 14 internally meshes with the internal gear 16. The external gears 14 are assembled in three rows in order to increase the transmission capacity, and to reduce vibration and noise due to the eccentric phase shift. The structures of the external gears of the respective rows are the same except for the difference in eccentric phase.

The external gears 14 are provided corresponding to the respective eccentric bodies 12 a. The external gear 14 is rotatably supported by the corresponding eccentric body 12a via a roller bearing 30. The external gear 14 is provided with a 1 st through hole 13 through which the inner pin 32 passes and a 2 nd through hole 15 which abuts against the roller bearing 30.

The 1 st through hole 13 is provided at a position offset from the center of the external gear 14. The 1 st through hole 13 is provided in plural corresponding to an inner pin 32 described later. In this example, six 1 st through-holes 13 are provided at 60 ° intervals in the circumferential direction. The 2 nd through hole 15 is provided in the center of the external gear 14, and is a hole through which the eccentric body 12a is inserted.

As shown in fig. 1, the housing 22 is cylindrical as a whole, and the internal gear 16 is provided on the inner peripheral portion thereof. The internal gear 16 meshes with the external gear 14. The internal gear 16 of the present embodiment includes an internal gear main body integrated with the case 22, and outer pins 16a (pin members) rotatably supported by the internal gear main body and constituting internal teeth of the internal gear 16. The number of internal teeth of the internal gear 16 (the number of the outer pins 16 a) is slightly larger than the number of external teeth of the external gear 14 (in this example, only 1 more).

The carriers 18, 20 are disposed on the axial side portions of the external gear 14. The carriers 18, 20 include a 1 st carrier 18 disposed on the side of the input side of the external gear 14 and a 2 nd carrier 20 disposed on the side of the input opposite side of the external gear 14. The carriers 18 and 20 have a disk shape, and rotatably support the input shaft 12 via an input shaft bearing 34.

The 1 st carrier 18 and the 2 nd carrier 20 are coupled together via inner pins 32. The inner pin 32 penetrates the plurality of external gears 14 in the axial direction at a position radially offset from the axial center of the external gear 14. The inner pin 32 of the present embodiment is formed integrally with the 2 nd wheel carrier 20. The inner pin 32 may be provided separately from the wheel frames 18, 20. The inner pins 32 are provided in plural at predetermined intervals around the central axis La of the internal gear 16. In the present embodiment, six inner pins 32 are provided at intervals of 60 ° in the circumferential direction.

The inner pin 32 has a tip end portion fitted into a bottomed recess 18c formed in the 1 st carrier 18, and couples the 1 st carrier 18 and the 2 nd carrier 20 together with a bolt 36 inserted from the input side of the 1 st carrier 18.

The inner pin 32 penetrates the 1 st penetration hole 13 formed in the outer gear 14. A roller 35 is rotatably fitted over the outer peripheral surface 32s of the inner pin 32 as a sliding promoting member. The axial movement of the roller 35 is restricted by the input-side opposite side of the 1 st carrier 18 and the input side of the 2 nd carrier 20. A gap that is a clearance for absorbing a swing component of the external gear 14 is provided between the roller 35 and the 1 st through hole 13. The roller 35 is partially in contact with the inner wall surface of the 1 st penetration hole 13.

Here, a member that outputs rotational power to a driven device (not shown) is referred to as an output member, and a member that is fixed to an external member for supporting the eccentric rocking type reduction gear transmission 10 is referred to as a fixed member. The output member of the present embodiment is the 2 nd carrier 20, and the fixed member is the casing 22. The output member is rotatably supported by the fixed member via main bearings 24 and 26.

The main bearings 24 and 26 include a 1 st main bearing 24 disposed between the 1 st carrier 18 and the casing 22, and a 2 nd main bearing 26 disposed between the 2 nd carrier 20 and the casing 22. In the present embodiment, the main bearings 24 and 26 are arranged in a so-called back-to-back combination state. The outer peripheries of the 1 st carrier 18 and the 2 nd carrier 20 form the inner rings of the 1 st main bearing 24 and the 2 nd main bearing 26, respectively. In the present embodiment, angular ball bearings having spherical rolling bodies 42 are exemplified as the main bearings 24 and 26. The main bearings 24 and 26 may be roller bearings such as tapered roller bearings and angular contact roller bearings.

Next, the operation of the eccentric rocking type reduction gear transmission 10 configured as described above will be described. When the rotational power is transmitted from the driving device to the input shaft 12, the eccentric body 12a of the input shaft 12 rotates about the rotational center line passing through the input shaft 12. The eccentric body 12a performing eccentric motion partially contacts the 2 nd penetration hole 15 to swing the external gear 14. At this time, the external gear 14 oscillates so that its axial center rotates around the rotation center line of the input shaft 12. When the external gear 14 oscillates, the meshing positions of the external gear 14 and the internal gear 16 sequentially deviate. As a result, one of the external gear 14 and the internal gear 16 rotates on its own axis by the difference in the number of teeth between the external gear 14 and the internal gear 16 per rotation of the input shaft 12. In the present embodiment, the external gear 14 rotates and outputs the decelerated rotation from the 2 nd carrier 20 via the inner pin 32.

Next, the durability of the eccentric body 12a will be described with reference to fig. 2 to 5. The inventors have studied and confirmed that the durability of the eccentric body 12a changes depending on the residual stress after grinding (hereinafter, sometimes referred to as "Sr") and the residual austenite amount after grinding (hereinafter, sometimes referred to as "residual γ"). Therefore, the present inventors produced samples a to D having different residual stresses Sr and residual γ, and performed durability tests on the samples.

In the following, when the residual stress is represented numerically, the compressive stress is represented by a negative numerical value denoted by "-", and the tensile stress is represented by a positive numerical value not denoted by a symbol. Further, "a value equal to or larger than a certain value" indicates a value on the positive direction side from the certain value, "a value equal to or smaller than a certain value" indicates a value on the negative direction side from the certain value, and "a value smaller than a certain value" indicates a value on the negative direction side from the certain value. The compressive residual stress "higher than a certain value" indicates that the residual stress is a value on the negative direction side of the value, and the compressive residual stress "lower than a certain value" indicates that the residual stress is a value on the positive direction side of the value.

FIG. 2 is a table showing the results of the residual stress and durability tests of samples A to D. Fig. 3 is a graph showing the residual stress after grinding of samples a to D. Fig. 4 is a graph showing the retained austenite amounts after grinding of samples a to D. In fig. 3 and 4, the horizontal axis represents the measurement position, and the vertical axis represents the measurement result. The residual stress in fig. 2 represents the residual stress Sr after grinding at 20 μm from the surface. The cutting depth, the workpiece rotation speed, and the chip thickness in fig. 2 are indices indicating conditions of a grinding process described later.

As for samples a to D, eccentric bodies (hereinafter, referred to as "workpieces") subjected to heat treatment under the same heat treatment conditions (for example, solidification treatment example 1 described in patent document 1) were ground under conditions of different machining stresses. In fig. 3 and 4, the measurement positions indicate depths from the surface, the surface layer is gradually removed from the surface by electropolishing, and data at each depth is acquired every 20 μm from the surface.

Fig. 5 is a graph showing the correlation between the residual γ and the residual stress Sr of the samples a to D. As is clear from this figure, the residual stress Sr is displaced toward the negative direction side at a distance of 20 μm from the surface as the residual γ increases. Also, the residual γ and the residual stress Sr have the same tendency even on the surface.

The durability test results of fig. 2 will be explained. This result is used as an index indicating durability. The durability test is a so-called acceleration test in which a stress load, which is interpreted to be the same as a rated load applied during a rated use period, is repeatedly applied to a sample. The durability test results show the aging state after the test with symbols. In fig. 2, symbol × represents a case where the test is interrupted due to the occurrence of abnormal noise in the durability test. The symbol Δ indicates that cracking (surface damage) was observed after the durability test. The symbol quality indicates that slight damage in a practically usable range is observed after the durability test. The symbol "represents a case where almost no damage is observed after the durability test.

In the results of the durability test, as shown in fig. 2, sample a was "x", sample B was "Δ", sample C was "good", and sample D was "excellent". That is, sample A, B has a large influence of grinding burn, resulting in poor durability, and sample C, D has durability in a range that can be practically used. Therefore, it can be said that the eccentric body 12a with reduced influence of the grinding burn can be provided as long as the sample C, D can be distinguished from the sample A, B.

As shown in fig. 3 and 5, sample A, B can be distinguished from sample C, D by the residual stress Sr at 20 μm from the surface. The reference range can be determined with reference to the residual stress Sr of the sample C at 20 μm from the surface. From this viewpoint, in the present embodiment, the residual stress Sr at 20 μm from the surface of the eccentric body 12a is set to a compressive stress (Sr < 0MPa), thereby controlling the durability to a level better than that of the sample C. By setting the residual stress Sr at 20 μm from the surface to a compressive stress, the influence of grinding burn can be suppressed, and practical durability of the eccentric body 12a can be achieved.

From the viewpoint of having a margin against variations in manufacturing or variations in use conditions, the residual stress Sr at a distance of 20 μm from the surface may be-200 MPa or less. For example, sample D has a residual stress Sr of-374 MPa, which achieves this condition. In this case, the influence of the grinding burn can be further suppressed, and the practical durability of the eccentric body 12a can be realized even in consideration of variations in manufacturing and variations in use conditions.

As shown in fig. 4 and 5, sample A, B can also be distinguished from sample C, D by the residual γ at 20 μm from the surface. For example, the reference range may be determined with reference to the residual γ of the sample C at 20 μm from the surface. From this viewpoint, the retained austenite amount of the eccentric body 12a at a distance of 20 μm from the surface may be 30 to 45 vol%. At this time, since another index of the residual γ is used in addition to the residual stress Sr, the eccentric body 12a having further improved durability can be provided.

As shown in fig. 3 and 5, the sample A, B can be distinguished from the sample C, D according to the residual stress Sr on the surface. For example, the reference range may be determined with reference to the residual stress Sr of the sample D of the surface. From this viewpoint, the residual stress Sr on the surface of the eccentric body 12a can be set to-800 MPa or less. At this time, since the residual stress Sr on the surface is used in addition to the residual stress Sr at 20 μm from the surface, the eccentric body 12a further improved in durability can be provided.

As shown in fig. 4 and 5, sample A, B can also be distinguished from sample C, D by the residue γ on the surface. For example, the reference range may be determined with reference to the residual γ of the sample C on the surface. From this viewpoint, the amount of retained austenite on the surface of the eccentric body 12a can be set to 25 to 40 vol%. At this time, since the amount of retained austenite on the surface is used in addition to the residual stress Sr at 20 μm from the surface, the eccentric body 12a further improved in durability can be provided.

Next, a method for manufacturing the eccentric body 12a will be described. The manufacturing method mainly includes a rough machining step of forming a material contour by machining, a heat treatment step of performing heat treatment on the eccentric body 12a, and a grinding step of grinding the eccentric body 12a after the heat treatment. The eccentric body 12a in this example is manufactured integrally with the input shaft 12.

The heat treatment step will be explained. Although the heat treatment of the eccentric body 12a is not limited, the heat treatment in the heat treatment step may be a curing treatment having a property of increasing the amount of carbide, for example. The increasing property of the carbide amount means: the surface portion of the eccentric body 12a after the heat load is given a property of increasing the amount of carbide as compared with before the heat load (test heat load) for changing the material properties is given. By applying a thermal load for testing, the increase characteristic of the carbide amount can be easily confirmed. As the curing treatment that can satisfy the characteristic of increasing the amount of carbide, for example, curing treatment examples 1 to 4 and modifications thereof described in patent document 1 can be adopted. Although not limited to the thermal load for the test, the thermal load for the test may be, for example, a thermal load that is generated by irradiating the eccentric body 12a with radiation at 300 ℃ or higher for 3 hours or longer.

Next, the grinding process will be described with reference to fig. 6 and 7. Fig. 6 is a schematic view schematically showing the grinding step of the present embodiment. As shown in fig. 6, in the grinding step, the rotating grinding wheel 82 is moved relative to the surface of the eccentric body (hereinafter, referred to as "workpiece 81" in this description) by a predetermined depth of cut Ae, thereby grinding the surface of the workpiece 81. As a result of the study by the inventors, it was confirmed that the residual stress Sr after grinding is mainly related to the circumferential velocity Vc (m/s) of the grinding wheel 82, the feed velocity Vw (mm/min) of the workpiece 81, and the depth of cut ae (mm) per pass of the grinding wheel 82. That is, by adjusting these grinding conditions, the desired residual stress Sr can be achieved. Thus, in the grinding step of the present embodiment, grinding is performed under grinding conditions such that the residual stress Sr at 20 μm from the surface of the eccentric body after grinding is negative (Sr < 0 MPa). In addition, the residual stress Sr being negative means that the residual stress Sr is a compressive stress. By making the residual stress Sr 20 μm from the surface negative, the influence of grinding burn can be suppressed, and practical durability of the eccentric body 12a can be achieved.

The inventors evaluated the residual stress Sr by changing the cutting depth Ae, and found that the grinding conditions can be effectively set by adjusting the average chip thickness hm. Fig. 7 is a scatter diagram showing the relationship between the average chip thickness hm and the residual stress Sr at 20 μm from the surface. In fig. 7, the white point indicated by the symbol K is the result when the cutting depth Ae is 0.015mm, and the black point indicated by the symbol J is the result when the cutting depth Ae is 0.010 mm. And, the broken line represents a regression line M between the average chip thickness hm and the residual stress Sr.

The result of the symbol K, J deviates less from the regression line M, and therefore it can be said that the residual stress Sr can be controlled in accordance with the average chip thickness hm at any depth of cut Ae. The above-described grinding conditions (negative residual stress Sr at 20 μ M from the surface (Sr < 0MPa)) can be achieved if the average chip thickness hm deviates from the regression line M by 0.01 μ M or less. Thus, in the grinding step of the present embodiment, grinding is performed with the average chip thickness set to 0.01 μm or less.

Next, the average chip thickness hm will be described with reference to fig. 6. During one rotation of the grinding wheel 82, the grinding wheel 82 is relatively moved from the position of the solid line to the position of the broken line (actually, the workpiece 81 is moving). The average chip thickness hm is an average of the thicknesses of chips generated from the start of cutting by the grinding wheel 82 to the end of cutting, and can be calculated by the following equation 1.

hm＝(Ae·Vw)/(Vc·60·1000)……(1)

(wherein hm is an average chip thickness [ mm ], Ae is a cutting depth [ mm ] in each stroke of the grinding wheel 82, Vw is a feed speed [ mm/min ] of the workpiece 81, and Vc is a peripheral speed Vc [ m/s ] of the grinding wheel 82.)

As shown in formula 1, the average chip thickness hm is an index proportional to the cutting depth Ae and the speed Vw and inversely proportional to the peripheral speed Vc, and is an index combining these grinding conditions. By using the average chip thickness hm, the grinding conditions can be set efficiently.

Fig. 2 is further illustrated. Samples E to G in fig. 2 show the durability test results of samples in which the cutting depths Ae and the like were adjusted so that the average chip thickness hm became 0.009 μm to 0.010 μm. In these samples, the residual stress Sr is in the range of-200 MPa to-500 MPa, and the damage after the durability test is hardly observed, and the state is good. The results for samples E to G also support the above grinding conditions to be appropriate. From the viewpoint of ensuring productivity, the residual stress Sr at 20 μm from the surface may be-1000 MPa or more, and the average chip thickness hm may be 0.001 μm or more.

The above is the description of embodiment 1. According to the eccentric oscillating type speed reduction device 10 of embodiment 1, an eccentric oscillating type speed reduction device is provided which can suppress the influence of grinding burn on the eccentric body 12a and can suppress the reduction of the life of the eccentric body 12 a.

[ 2 nd embodiment ]

Next, the structure of the eccentric rocking type reduction gear transmission 10 according to embodiment 2 will be described with reference to fig. 8. In the drawings and the description of embodiment 2, the same or equivalent constituent elements and components as those of embodiment 1 are denoted by the same reference numerals. Description of the structure different from embodiment 1 will be omitted as appropriate, and the description will be repeated. Fig. 8 is a side sectional view showing the eccentric rocking type reduction gear transmission 10 according to embodiment 2, which corresponds to fig. 1.

In embodiment 1, an eccentric oscillating type reduction gear of a center crank type is exemplified. The eccentric oscillating type reduction gear of the present embodiment is a so-called distributed type eccentric oscillating type reduction gear. The eccentric oscillating type reduction gear 10 mainly includes: an input gear 70; an input shaft 12; an outer gear 14; an internal gear 16; wheel carriers 18, 20; a housing 22; and main bearings 24, 26. The present embodiment is mainly different from embodiment 1 in that a plurality of input gears 70 and input shafts 12 are provided, and the number of external gears 14 is different.

The plurality of input gears 70 are arranged around the central axis La of the internal gear 16. Only one input gear 70 is shown in fig. 8. The input gear 70 is supported by the input shaft 12 inserted in the center portion thereof, and is provided so as to be rotatable integrally with the input shaft 12. The input gear 70 meshes with an external tooth portion of a rotary shaft (not shown) provided on the center axis La. The rotational power is transmitted to the rotary shaft from a driving device not shown, and the input gear 70 rotates integrally with the input shaft 12 by the rotation of the rotary shaft.

The input shaft 12 of the present embodiment is disposed in a plurality of (for example, three) positions offset from the central axis La of the internal gear 16 at intervals in the circumferential direction. Only one input shaft 12 is shown in fig. 8. Two eccentric bodies 12a having eccentric phases shifted by 180 ° from each other are axially arranged on each input shaft 12.

Two external gears 14 are assembled to the outer periphery of the eccentric body 12a via roller bearings 30. Each external gear 14 internally meshes with the internal gear 16. The structures of the external gears 14 are the same except for the eccentric phases.

Next, the operation of the eccentric rocking type reduction gear transmission 10 of the present embodiment will be described. When the rotational power is transmitted from the driving device to the rotating shaft, the rotational power is distributed from the rotating shaft to the plurality of input gears 70, and the input gears 70 rotate in the same phase. When each input gear 70 rotates, the eccentric body 12a of the input shaft 12 rotates about the rotation center line passing through the input shaft 12, and the eccentric body 12a causes the external gear 14 to oscillate. When the external gear 14 oscillates, the meshing positions of the external gear 14 and the internal gear 16 are sequentially shifted, and one of the external gear 14 and the internal gear 16 rotates, as in embodiment 1. The rotation of the input shaft 12 is reduced in speed at a reduction gear ratio corresponding to the difference in the number of teeth between the external gear 14 and the internal gear 16, and then output from the output member to the driven device.

The eccentric body 12a of the present embodiment also has the characteristics of the residual stress Sr and the residual γ of the eccentric body 12a described in embodiment 1.

The method for manufacturing the eccentric body 12a described in embodiment 1 can be applied to the eccentric body 12a of the present embodiment.

The above is the description of embodiment 2. According to the eccentric rocking type reduction gear 10 of embodiment 2, the same operational effects as those of embodiment 1 are obtained, and an eccentric rocking type reduction gear in which the influence of the grinding burn on the eccentric body 12a can be suppressed and the reduction in the life of the eccentric body 12a can be suppressed is provided.

The above description explains an example of the embodiment of the present invention in detail. The above-described embodiments are merely specific examples for carrying out the present invention. The contents of the embodiments do not limit the technical scope of the present invention, and various design changes such as changes, additions, deletions, and the like of the constituent elements can be made without departing from the scope of the inventive concept defined in the claims. In the above-described embodiments, the terms "in the embodiments" and "in the embodiments" are given to the contents in which such a design change is possible, but this does not mean that the design change is not permitted without the contents of such terms.

Hereinafter, a modified example will be described. In the drawings and the description of the modified examples, the same or equivalent constituent elements and components as those of the embodiment are denoted by the same reference numerals. Description of the embodiment will be omitted as appropriate, and a description of a structure different from that of embodiment 1 will be repeated.

Although the example in which three external gears 14 are provided is shown in embodiment 1 and the example in which two external gears 14 are provided is shown in embodiment 2, one external gear 14 may be provided or four or more external gears 14 may be provided according to desired characteristics.

In embodiment 1, an example in which the 1 st main bearing 24 and the 2 nd main bearing 26 do not have an inner ring is described, but the present invention is not limited to this. At least one of the 1 st main bearing 24 and the 2 nd main bearing 26 may be a bearing having an inner race.

In the above, an example in which the output member of the embodiment is the carrier 18, 20 and the case 22 is fixed to the external member has been described. The case 22 may be an output member, and the carriers 18 and 20 may be fixed to an external member.

The above modifications also have the same operational effects as those of embodiment 1.

Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. The new embodiment which is produced by the combination has the effects of the combined embodiments and the modifications.