JP2016098860A - Eccentric oscillation type reduction gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eccentric oscillation type reduction gear capable of greatly prolonging the lifetime of an eccentric body shaft.SOLUTION: An eccentric oscillation type reduction gear 12 has external tooth gears (oscillation gear) 24A, 24B, an eccentric body shaft 20 having eccentric bodies 22A, 22B, and rolls (eccentric body bearing) 26A, 26B arranged between the external tooth gears and eccentric bodies, and oscillates the external tooth gears eccentrically or with deflection through eccentric bodies of eccentric body shaft. The eccentric body shaft is subjected to hardening processing, in which when the eccentric body shaft is thermally loaded such that material characteristic thereof change, a surface part of the eccentric shaft is larger in carbide amount after being thermally loaded than before thermally loaded.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an eccentric oscillating speed reducer.

  Patent Document 1 discloses an eccentric rocking type speed reducer. This reduction device has a rocking gear, an eccentric shaft having an eccentric body, and an eccentric bearing provided between the rocking gear and the eccentric body. The speed reducer eccentrically oscillates the oscillating gear via the eccentric body of the eccentric body shaft.

  In Patent Document 1, an external gear is adopted as the oscillating gear, and the external gear meshes with the internal gear while oscillating with the internal gear. A plurality of eccentric body shafts for swinging the external gear are provided at positions offset from the axis of the internal gear.

  Patent Document 1 discloses a technique for increasing the life of an eccentric body shaft by subjecting the eccentric body shaft to a specific hardening process in such an eccentric oscillating speed reducer.

JP 2011-158073 A (paragraphs [0009] to [0012], etc.)

  Various methods for curing the eccentric shaft, including the method of Patent Document 1, have been known.

  This invention makes it the subject to provide the eccentric rocking | fluctuation type reduction gear which can extend the lifetime of an eccentric body axis | shaft greatly.

  The present invention includes an oscillating gear, an eccentric body shaft having an eccentric body, and an eccentric body bearing disposed between the oscillating gear and the eccentric body, and the eccentric body of the eccentric body shaft. In the eccentric oscillating type speed reducer in which the oscillating gear is eccentrically oscillated or flexibly oscillated via a shaft, the eccentric body shaft is cured, and the curing process is performed with respect to the eccentric body shaft. The eccentric body after applying the thermal load, when the thermal load that changes the material characteristics of the eccentric body shaft is applied, rather than the amount of carbide on the surface portion of the eccentric body shaft before applying the thermal load. The above problem is solved by adopting a configuration in which the amount of carbide on the surface portion of the shaft is increased.

  In the present invention, the eccentric body after applying the thermal load to the eccentric body shaft, rather than the amount of carbide on the surface portion of the eccentric body shaft before applying the thermal load that changes the characteristics of the material. A hardening process is performed to increase the amount of carbide on the surface of the shaft.

  Thereby, durability of an eccentric body axis | shaft can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the eccentric rocking | swiveling type reduction gear which can extend the lifetime of an eccentric body axis | shaft greatly can be obtained.

List of composition and specifications of various curing treatments Image showing precipitation of carbide Image showing the precipitation of nitride Sectional drawing which shows the eccentric rocking | fluctuation type reduction gear which concerns on an example of embodiment of this invention Sectional drawing which follows the arrow VV line of FIG. Time chart showing an example of application of thermal load of various curing processes in the manufacturing process of the eccentric body shaft of the eccentric oscillating speed reducer

  Hereinafter, an example of an embodiment of the present invention will be described in detail based on the drawings.

  First, the basic configuration of an eccentric oscillating speed reducer according to an example of an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

  4 is a cross-sectional view of the eccentric oscillating speed reducer, and FIG. 5 is a cross-sectional view taken along the line VV in FIG.

  The eccentric oscillating speed reducer 12 includes external gears (oscillating gears) 24A and 24B, an eccentric body shaft 20 integrally including the eccentric bodies 22A and 22B, and the external gears 24A and 24B and the eccentric body 22A. , 22 </ b> B (rollers of eccentric body bearings) 26 </ b> A, 26 </ b> B and an internal gear 28. The external gears 24A and 24B are internally meshed with the internal gear 28 while being eccentrically swung by the eccentric bodies 22A and 22B of the eccentric body shaft 20. The output of the speed reducer 12 is taken out from the first and second carriers 32 and 34 as the rotation components of the external gears 24A and 24B. Details will be described below.

  The input shaft 14 can be connected to an output shaft of a motor (not shown). A sun gear 16 is integrally formed at the tip of the input shaft 14. The sun gear 16 meshes simultaneously with a plurality (three in this example) of transmission gears 18.

  Each transmission gear 18 is incorporated into a plurality of (three in this example) eccentric body shafts 20 and can drive the three eccentric body shafts 20 simultaneously and in the same direction. Eccentric bodies 22A and 22B are integrally provided on the eccentric body shafts 20 in the axial direction so as to have a 180 degree phase. Further, the eccentric bodies 22A and the eccentric bodies 22B located at the same position in the axial direction of the eccentric body shafts 20 are incorporated so as to be rotatable in the same direction with the same phase.

  Between the external gear 24A and the three eccentric bodies 22A, a roller (rolling element) 26A constituting an eccentric body bearing is disposed. Between the external gear 24B and the three eccentric bodies 22B, a roller (rolling element) 26B constituting an eccentric body bearing is also arranged. The eccentric bodies 22A and 22B of each eccentric body shaft 20 rotate synchronously, and the external gears 24A and 24B swing eccentrically via the eccentric bodies 22A and 22B of the eccentric body shaft 20 that rotates eccentrically synchronously. However, it is possible to internally mesh with the internal gear 28.

  The internal gear 28 is integrated with the casing 30 and includes roller-shaped pins 28P as “internal teeth”. The pin 28P can mesh with the external gears 24A and 24B, respectively. The number of internal teeth of the internal gear 28 (the number of pins 28P) is slightly larger (only 1 in this example) than the number of external teeth of the external gears 24A and 24B.

  First and second carriers 32 and 34 are arranged on both axial sides of the external gears 24A and 24B. The first and second carriers 32 and 34 are connected to each other via a carrier pin 34A and a bolt 40 which are formed by press-fitting from the second carrier 34 side, and the whole is rotated to the casing 30 via bearings 36 and 38. Supported as possible.

  Next, the operation of the eccentric oscillating speed reducer 12 will be described.

  When the input shaft 14 rotates, the three eccentric body shafts 20 simultaneously rotate at a reduced speed through the transmission gear 18 meshing with the sun gear 16 of the input shaft 14. As a result, the eccentric bodies 22A and the eccentric bodies 22B integrally attached to the eccentric body shafts 20 rotate in the same phase, and the external gears 24A and 24B are inscribed in the internal gear 28, respectively. It swings and rotates while maintaining a phase difference of 180 degrees. Since the internal gear 28 is integrated with the casing 30 and is in a fixed state, when the eccentric body shaft 20 rotates, the external gears 24A and 24B swing and rotate via the eccentric bodies 22A and 22B. A phenomenon occurs in which the meshing positions of the gears 24A and 24B and the pin 28P, which is the internal tooth of the internal gear 28, sequentially move.

  The number of teeth of the external gears 24 </ b> A and 24 </ b> B is one less than the number of teeth of the internal gear 28. Therefore, due to the movement of the meshing position, the phases of the external gears 24A and 24B are shifted (rotated) by one tooth corresponding to the difference in the number of teeth with respect to the internal gear 28 in the fixed state. As a result, the eccentric body shaft 20 revolves around the input shaft 14 at a speed corresponding to the rotation component, and the first and second carriers 32 and 34 supporting the eccentric body shaft 20 correspond to the revolution speed. Rotate at the speed you want. The first and second carriers 32 and 34 are connected via carrier pins 34 </ b> A and bolts 40. Therefore, the first and second carriers 32 and 34 are integrally rotated (as one large output body) and slowly rotate to connect a not-shown counterpart machine (driven machine) connected via the bolt hole 42. To drive.

  As in this embodiment, when the casing 30 (internal gear 28) is fixed, the relative displacement between the external gears 24A and 24B and the internal gear 28 is changed to the first and second carriers 32 and 34 side. When the rotation of the first and second carriers 32 and 34 is constrained, the relative displacement can be reduced through the swinging (rotation constrained) of the external gears 24A and 24B. It can be taken out as rotation on the casing 30 side (frame rotation).

  Here, the radial clearance between the eccentric body 22A (22B) -the roller 26A (26B) -the external gear 24A (24B) is set to about -3 μm to 3 μm in this embodiment, and the manufacturing error absorption margin is set. Is extremely small. Moreover, since the eccentric body shaft 20 rotates at a high speed, the DmN value, that is, the value of the rotational speed (rpm) of the eccentric body shaft 20 × the pitch circle diameter (mm) of the rollers 26A and 26B is 10,000. It is in a state of exceeding.

  Under this condition, the eccentric body shaft 20 is always subjected to “high-speed fluctuating load torque” when the external gears 24A and 24B are swung and rotated via the eccentric bodies 22A and 22B and the rollers 26A and 26B. For this reason, the eccentric body axis | shaft 20 exists in the very severe condition thermally (it becomes very high temperature).

  Therefore, in the present embodiment, a specific curing process is performed on the eccentric body shaft 20. In order to facilitate understanding, first, for the purpose of comparison, a general curing process P that has been conventionally performed on this type of eccentric body shaft (20) will be described.

  Conventionally, the following hardening process P was generally performed with respect to the eccentric body axis | shaft.

  The material of the eccentric body shaft subjected to the curing treatment P is iron (Fe), C: 0.18 to 0.23% by weight, Si: 0.15 to 0.35% by weight, Mn: 0.60. 0.90 wt%, P: 0.030 wt% or less, S: 0.030 wt% or less, Ni: 0.25 wt% or less, Cr: 0.90 to 1.20 wt%, Mo: 0.15 Up to 0.25% by weight.

  This curing process P includes: a) an eccentric body axis, together with a material containing carbon (a solid material such as charcoal, a gas material such as natural gas or petroleum gas, or a liquid material), B) Reduce the heating temperature to 830 ° C. and maintain this state; c) Then put the eccentric body shaft into oil (may be water) and quench (quenching); d) Again 170 ° C. The process of heating to and maintaining the tempering temperature is followed by tempering.

  Here, the inventor simulated the heat load that is expected to be applied by the speed reducer operation on the curing process P similar to the above and the eccentric body shaft subjected to the curing process disclosed in Patent Document 1 described above. The test was intentionally given a heat load (“test heat load” of 3 hours exposure to 300 ° C., which is considered to change the material properties of the eccentric body shaft).

  Then, the amount of carbide on the surface portion of the conventional eccentric body shaft subjected to the test heat load was measured. Then, in the conventional eccentric body shaft, before and after applying the test heat load, the carbide itself does not exist in the first place, or the amount of carbide after applying the test heat load is before the test heat load is applied. It was possible to confirm a qualitative tendency that the amount was smaller than the amount of carbide.

  In response to this result, the inventor conversely, the surface portion of the eccentric body shaft before applying a thermal load (thermal load for testing) in which the material characteristics of the eccentric body shaft change. The eccentric body shaft is used by applying a hardening treatment that increases the amount of carbide on the surface of the eccentric body shaft after applying the test thermal load. It was hypothesized that it would be possible to improve the properties after the material properties changed, and to extend the life significantly.

  First, various curing treatments were actually performed, and the existence of a heat treatment exhibiting such a qualitative tendency was searched. As a result, for at least the following four curing treatment examples 1 to 4, “the eccentricity after applying the test thermal load rather than the carbide amount of the surface portion of the eccentric body shaft before applying the test thermal load. It was confirmed that the eccentric body shaft 20 having the characteristic that the amount of carbide on the surface portion of the body shaft increases is obtained. Hereinafter, it demonstrates in order.

[Curing treatment example 1]
In the curing process example 1, the process as shown in FIG. 6 (A) was performed. Here, the material of the eccentric body shaft 20 subjected to the curing process example 1 is the same as that of the eccentric body shaft subjected to the curing process P.

  First, the eccentric body shaft 20 is heated to 930 ° C. in an atmosphere of a hydrocarbon gas (for example, methane, propane, ethylene, acetylene, etc.) and the state is maintained (first step S1a). The maintenance time here is set according to the required curing treatment depth. Usually, it is set appropriately from the range of about 2 to 40 hours according to the required curing treatment depth.

  Next, after the heating temperature is lowered by gas cooling (second step S2a), the temperature is raised again to 850 ° C. and this temperature is maintained (third step S3a). The maintenance time here is also set according to the required curing treatment depth, and is usually set appropriately from a range of about 1 to 10 hours.

After temporarily lowering the heating temperature again by gas cooling (fourth step S4a), this time, the heating temperature is once again set at 850 ° C. in an atmosphere containing hydrocarbon gas and NH ₃ gas (ammonia gas). Ascending and maintaining up to (5th step S5a). The maintenance time here is substantially the same as the third step S3a.

  Thereafter, the eccentric body shaft 20 is put into oil (or water) and rapidly cooled (quenched) (sixth step S6a). And after heating and maintaining again to the low temperature tempering temperature of 180 degreeC, it tempers (7th process S7a).

  Through the above treatment, carbon and nitrogen enter and diffuse into the surface portion of the eccentric shaft 20, and fine carbides and fine nitrides are precipitated. Further, the amount of retained austenite as will be described later is also present on the surface portion of the eccentric body shaft 20.

  And the eccentric body shaft 20 manufactured by the hardening process example 1 which has the above process is the eccentric body shaft 20 before giving the thermal load (the said thermal load for a test) from which the material characteristic of this eccentric body shaft 20 changes. It was confirmed that the amount of carbide on the surface portion of the eccentric body shaft 20 after the application of the heat load is larger than the amount of carbide on the surface portion. That is, a heat treatment in which the amount of carbide on the surface portion of the eccentric body shaft 20 after application of the thermal load is larger than the amount of carbide on the surface portion of the eccentric body shaft 20 before application of the test thermal load, It was confirmed that it actually exists.

  In the following description, the amount of carbide on the surface portion of the eccentric body shaft after application of the test thermal load is larger than the amount of carbide on the surface portion of the eccentric body shaft before application of the test thermal load. "Characteristic" is simply referred to as "carbide increasing characteristic".

[Curing treatment example 2]
In the curing process example 2, a process as shown in FIG. 6B was performed.

  The material of the eccentric body shaft 20 subjected to the curing process example 2 is also the same as the eccentric body shaft subjected to the curing process P.

  Also in the curing processing example 2, first, the eccentric body shaft 20 is heated to 940 ° C. in an atmosphere of a hydrocarbon-based gas (for example, methane, propane, ethylene, acetylene, etc.) and the state is maintained (first) One step S1b). The maintenance time here is set according to the required curing treatment depth. Usually, it is set appropriately from the range of about 2 to 40 hours according to the required curing treatment depth.

  Next, after the heating temperature is lowered by gas cooling (second step S2b), the temperature is raised again to 850 ° C. and this temperature is maintained (third step S3b). The maintenance time here is also set according to the required curing treatment depth, and is usually set appropriately from a range of about 1 to 10 hours.

After temporarily lowering the heating temperature again by gas cooling (fourth step S4b), this time, the heating temperature is once again set at 850 ° C. in an atmosphere containing hydrocarbon gas and NH ₃ gas (ammonia gas). (5th process S5b). The maintenance time here is substantially the same as the third step S3b.

Here, in this curing process example 2, after the fifth step S5b, the temperature is temporarily lowered by gas cooling (sixth step S6b), and then the same atmosphere (hydrocarbon gas) as the fifth step S5b. In the atmosphere containing + NH ₃ gas), the heating temperature is raised to 880 ° C. and maintained (seventh step S7b). The maintenance time here is also substantially equivalent to the third step S3b.

  Then, quenching is performed (eighth step S8b). The tempering temperature is set to 220 ° C., slightly higher than the tempering temperature (180 ° C.) in the curing processing example 1 (9th step S9b).

  Through the above treatment, carbon and nitrogen enter and diffuse into the surface portion of the eccentric shaft 20, and fine carbides and fine nitrides are precipitated. Further, the amount of retained austenite as will be described later is also present on the surface portion of the eccentric body shaft 20.

  Also according to the above-described curing treatment example 2, the “characteristic of increasing the amount of carbide” could be confirmed.

[Curing treatment example 3]
In the curing process example 3, the process as shown in FIG. 6C was performed.

  The material of the eccentric body shaft 20 subjected to the curing process example 3 is the same as that of the eccentric body shaft subjected to the curing process P.

  Also in the curing processing example 3, first, the eccentric body shaft 20 is heated to 940 ° C. under an atmosphere of a hydrocarbon-based gas (for example, methane, propane, ethylene, acetylene, etc.), and the state is maintained (No. 1). One step S1c). The maintenance time here is set according to the required curing treatment depth. Usually, it is set appropriately from the range of about 2 to 40 hours according to the required curing treatment depth.

  Next, after the heating temperature is lowered by gas cooling (second step S2c), the temperature is raised again to 850 ° C. and this temperature is maintained (third step S3c). The maintenance time here is also set according to the required curing treatment depth, and is usually set appropriately from a range of about 1 to 10 hours.

After temporarily lowering the heating temperature again by gas cooling (fourth step S4c), this time, the heating temperature is raised and maintained to 650 ° C. in an atmosphere containing NH ₃ gas (ammonia gas) ( 5th process S5c). The maintenance time here is substantially equivalent to the third step S3c.

That is, in the fifth step S5c of the curing process example 3, unlike the curing process example 2, the atmosphere includes only the NH ₃ gas (not the atmosphere including the hydrocarbon gas + NH ₃ gas), and the temperature is It is 650 degreeC lower than 850 degreeC.

Thereafter, in this curing treatment example 3, the temperature is temporarily lowered by gas cooling (sixth step S6c), and the heating temperature is increased to 850 ° C. again in an atmosphere containing hydrocarbon-based gas + NH ₃ gas. -Maintain (7th process S7c). The maintenance time here is also substantially equivalent to the third step S3c.

  Then, quenching is performed (eighth step S8c). The tempering temperature after quenching is set to 180 ° C. that is slightly lower than the tempering temperature (220 ° C.) of the curing process example 2 (9th step S9c).

  Through the above treatment, carbon and nitrogen enter and diffuse into the surface portion of the eccentric shaft 20, and fine carbides and fine nitrides are precipitated. Further, the amount of retained austenite as will be described later is also present on the surface portion of the eccentric body shaft 20.

  Also according to the above-described curing treatment example 3, the “characteristic of increasing the amount of carbide” could be confirmed.

[Curing treatment example 4]
In the curing process example 4, the process as shown in FIG. 6D was performed.

  The material of the eccentric body shaft 20 subjected to the curing process example 4 is the same as that of the eccentric body shaft subjected to the curing process P.

  Also in the curing treatment example 4, first, the eccentric body shaft 20 was heated to 930 ° C. in an atmosphere of a hydrocarbon-based gas (for example, methane, propane, ethylene, acetylene, etc.), and the state was maintained (No. One step S1d). The maintenance time here is set according to the required curing treatment depth. Usually, it is set appropriately from the range of about 2 to 40 hours according to the required curing treatment depth.

  And in the hardening process example 4, it enters into furnace cooling as it is (2nd process S2d).

Thereafter, the heating temperature is once again increased to 850 ° C. and maintained in an atmosphere containing hydrocarbon gas and NH ₃ gas (ammonia gas) (third step S3d). The maintenance time here is also set according to the required curing treatment depth, and is usually set appropriately from a range of about 1 to 10 hours.

  Then, quenching is performed (fourth step S4d). The tempering temperature after quenching is set to 180 ° C. equivalent to the tempering temperature in the curing processing example 1 (fifth step S5d).

  Through the above treatment, carbon and nitrogen enter and diffuse into the surface portion of the eccentric shaft 20, and fine carbides and fine nitrides are precipitated. Further, the amount of retained austenite as will be described later is also present on the surface portion of the eccentric body shaft 20.

  Also according to the above-described curing treatment example 4, the “characteristic of increasing the amount of carbide” could be confirmed.

  That is, all of the illustrated curing treatment examples 1 to 4 are more than the amount of carbide on the surface portion of the eccentric body shaft 20 before applying a thermal load (a thermal load for testing) in which the material characteristics of the eccentric body shaft 20 change. In addition, the “carbide content increase characteristic” was observed in which the amount of carbide on the surface portion of the eccentric body shaft 20 after the thermal load was applied was increased. In other words, there are at least four examples of the curing process that satisfies the “characteristic of increasing the amount of carbide”. If variations are included, it is considered that there are more curing methods.

  For example, when the content of various additives included in the iron (Fe) is changed not only in the heat treatment method but also in the material of the eccentric body shaft 20, the heat treatment differs from the above, It is considered that there is a possibility that "characteristic" can be obtained. In this sense, the material of the eccentric body shaft 20 includes carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), nitrogen (N), chromium contained in iron (Fe). Changing the content of (Cr), molybdenum (Mo), nickel (Ni), etc., and then applying heat treatment is an effective technique for searching for “increased char content”.

  In this way, the results obtained by actually measuring various compositions and specifications for many eccentric body shafts 20 (5 samples of Sample A to Sample E) from which the “characteristic of increasing the amount of carbide” was obtained. An example of the numerical value is shown in FIG. Here, the eccentric body shaft 20 is thermally strained by the above-described curing process. Therefore, the eccentric body shaft 20 is subjected to cutting and polishing of the surface portion by about 50 to 150 μm after the curing process, and the thermal strain is removed. In the present embodiment, the surface portion of the eccentric body shaft 20 after cutting and polishing (that is, the eccentric body shaft 20 in a state of being incorporated in a speed reducer as a product) is measured.

  In each item of FIG. 1, “the amount of carbide before application” is the eccentric body before applying “thermal load for test” that is exposed to 300 ° C. for 3 hours, which is understood that the material properties of the eccentric body shaft 20 change. The amount of (fine) carbide deposited on the surface portion of the shaft 20 (of the eccentric bodies 22A and 22B), “the amount of carbide after application” is also the same as that of the eccentric body shaft 20 (of the test thermal load) It means the amount of (fine) carbide deposited on the surface of the eccentric bodies 22A, 22B). The unit is area%.

  The amount of carbide on the surface portion of the eccentric body shaft 20 is obtained by imaging the surface of the eccentric body shaft 20 and measuring the area ratio occupied by the carbide in the captured image. However, for example, when the outer diameter of the eccentric body shaft is small and the image of the peripheral portion is not in focus and analysis becomes difficult, the eccentric body shaft is cut, and “the depth from the surface is 50˜ You may make it measure by the cross section parallel to the axis | shaft in a site | part of about 100 micrometers. If it is the depth to about 50-100 micrometers, the precipitation aspect of a carbide | carbonized_material will hardly change with the surface. Rather, in some cases, the amount of carbide (area%) on the surface portion can be measured with a smaller error.

  The image example of FIG. 2 captures the (fine) carbide precipitation state on the surface portion of the eccentric body shaft 20 by “a cross section parallel to the axis at a portion having a depth of about 50 to 100 μm from the surface” from this viewpoint. Is. The upper part on the left side of FIG. 2 is a carbide precipitation image of the cross section of the surface portion imaged before applying a thermal load (test thermal load) that changes material characteristics to a specific sample (eccentric body axis 20). is there. The lower part of the left side of FIG. 2 is a precipitation image of carbide on the surface imaged after applying a test heat load to the sample. Moreover, the upper stage of the right side of FIG. 2 is the precipitation image of the carbide | carbonized_material of the surface part imaged before giving the thermal load for a test similarly to another sample. The lower part on the right side of FIG. 2 is a precipitation image of carbide on the surface imaged after applying a test heat load to the sample.

  In the image of FIG. 2, the dark black portion is carbide. In any of the samples, the eccentric body shaft 20 according to the present embodiment has a heat resistance higher than the amount of carbide on the surface portion of the eccentric body shaft 20 before applying a heat load that changes the material characteristics of the eccentric body shaft 20. It can be seen that the amount of carbide on the surface portion of the eccentric body shaft 20 after application of the load is increased.

  In the specification table of FIG. 1, for example, the column of sample A shows the following contents. That is, the “amount of carbide before application” was 6.3 (area%), the “amount of carbide after application” was 8.8 (area%), and thus the rate of increase in the amount of carbide was 140%. The eccentric body shaft 20 of sample A has a retained austenite (residual γ) of 43 (volume%), a surface hardness (Vickers hardness) of 62.5 HV, and a carbon concentration of the surface of 1.2 (wt%). ), The nitrogen concentration in the surface portion was 0.08 (wt%), and the lifetime was 6.2 times that of the eccentric body shaft treated by the conventional curing treatment P. The view of Samples B to E is the same.

  When the specifications table of FIG. 1 is seen as a whole, in samples A to E, the amount of carbide is 6.3 → 8.8 (increase rate 140%), 6.0 → 6.6 (110%), 8.8 → 13.0 (148%), 10.0 → 11.2 (112%), and 9.8 → 10.0 (102%). That is, in all cases, the amount of carbide is increased after applying the test heat load than before applying the test heat load. As described above, the samples A to E having the “characteristics of increasing the amount of carbide” have a lifetime of the eccentric body shaft (life multiple) of 6.2 compared to the sample by the conventional curing treatment P, respectively. Times, 3.6 times, 4.5 times, 4.1 times, and 5.2 times, and a great increase in lifetime is obtained.

  In samples A to E in this test, the retained austenite (residual γ) is measured by analyzing the surface of the eccentric body shaft 20 (the eccentric body) of samples A to E with X-rays. Since the X-ray penetrates in the depth direction of the sample (in order to pick up information in the depth direction), the measurement result is volume%. In addition, the retained austenite here is a value in a state completed as a product (a state in which a test heat load is not applied: an unoperated state).

  In samples A to E in this test, the retained austenite has a value between 36 and 45 (volume%).

  Here, the amount of retained austenite is 36 to 45% by volume, which is considerably larger than the amount of retained austenite that has been considered to be optimal in the past. When the amount of retained austenite increases, the effect of suppressing the height of the indentation when the indentation is generated can be obtained, but the required hardness cannot be ensured. Therefore, conventionally, the amount of retained austenite lower than 36 to 45% by volume was considered optimal.

  However, the present inventor, even if the amount of retained austenite is large, by precipitating fine carbide (or fine nitride), it can compensate for the decrease in hardness and ensure the required hardness (the synergistic effect of retained austenite and fine carbide) ). In fact, in the present embodiment, while the amount of retained austenite is set to 36 to 45% by volume, the necessary hardness is ensured by precipitating fine carbides, and the effect that the height of the indentation can be kept low is also enjoyed. .

  In samples A to E in this test, it can be confirmed that the Vickers hardness (HV) shows a stable hardness between 60.8 HV and 63.3 HV. Here, the Vickers hardness is a value in a state where the product is completed (a state where a test heat load is not applied: an unoperated state).

  Moreover, in sample AE in this test, it can confirm that the carbon concentration of the surface part was a value between 1.0-1.6 (weight%). In this test, the carbon concentration of the surface portion is measured by cutting the surface portion by about 50 μm to 100 μm by machining, dissolving the shaving powder, and performing wet analysis.

  The carbon concentration of the surface portion is measured both before and after applying the test heat load. However, it has been confirmed by the inventor that there is almost no change (same) before and after applying the test heat load with respect to the carbon concentration of the surface portion. In other words, in Samples A to E, the carbon content in the surface portion increased before and after the test thermal load was applied, although the carbon concentration in the surface portion of the eccentric body shaft was substantially the same. It can be understood that the curing process is being performed.

  Moreover, in samples A to E in this test, the nitrogen concentration in the surface portion is a value between 0.08 and 0.28 (% by weight). That is, in samples A to E in this test, it can be confirmed that the nitrogen concentration in the surface portion was a value between approximately 0.07 and 0.30 (% by weight). Here, the value of the nitrogen concentration in the surface portion is a value in a state where the product is completed (a state where a test heat load is not applied: an unoperated state). The method for measuring the nitrogen concentration in the surface portion is the same as the method for measuring the carbon concentration.

  For some of the samples that satisfy the “characteristic of increasing the amount of carbide”, as in the samples on the left and right sides shown in FIG. 3, before applying the “test thermal load” to the eccentric body axis. It was observed that the amount of nitride on the surface portion of the eccentric body shaft (lower stage) after the application of the “thermal load for test” was higher than the amount of nitride on the surface portion of the eccentric body shaft in FIG. In FIG. 3, the portion that appears white is nitride. And it was confirmed that the sample in which such a tendency is seen has a longer life than the sample in which the nitride amount does not change (or decreases) before and after applying the “test thermal load”.

  In the present invention, the test thermal load is a test load that is applied to the eccentric body shaft during use of the speed reducer, and what should be the base is loaded according to the actual usage mode. Heat load. However, since the purpose is to apply a thermal load to the extent that the material characteristics of the eccentric body shaft change as in the case of using the speed reducer, the heat load actually applied to the speed reducer is not necessarily It doesn't have to be fully linked.

  In short, a qualitative tendency to increase or decrease the amount of carbide on the surface portion of the eccentric body shaft can be grasped if the heat load changes the material characteristics of the eccentric body shaft. Rather, it is easier to compare the increase and decrease of the carbide before and after the application when the heat load for testing is higher than the actual heat load, for example, the condition that the temperature is higher than the low temperature tempering temperature (150 ° C. to 200 ° C.). Tend to be. In this sense, it can be said that the condition adopted by the inventor, for example, “exposure to 300 ° C. for 3 hours” is an appropriate heat load in which a qualitative tendency is noticeable. In this sense, the term “low temperature tempering temperature” does not mean the tempering temperature itself when the eccentric body shaft itself is actually heat-treated (hardening treatment).

  Further, the specific speed reduction structure of the eccentric oscillating speed reducer according to the present invention is not limited to the above example. For example, only one eccentric body shaft is provided at the central portion in the radial direction of the speed reducer. A speed reduction structure in which the external gear is oscillated and rotated via an eccentric body of an eccentric body shaft arranged at the center of the machine may be used. In addition to the type in which the external gear swings as a swing gear as in the above example, an eccentric swing type speed reducer in which the internal gear swings is also known. The present invention is also applicable to an eccentric oscillating speed reducer in which such an internal gear oscillates as an oscillating gear. Furthermore, the present invention can also be applied to a so-called bending-meshing type eccentric oscillating speed reducer in which an external gear is bent and internally meshed with an internal gear. In this case, the shaft integrally provided with the eccentric body (non-circular body) for bending the external gear can be regarded as the “eccentric body shaft” according to the present invention.

DESCRIPTION OF SYMBOLS 12 ... Eccentric oscillation type reduction gear 14 ... Input shaft 16 ... Sun gear 18 ... Transmission gear 20 ... Eccentric body shaft 22A, 22B ... Eccentric body 24A, 24B ... External gear 26A, 26B ... Roller 28 ... Internal gear

Claims (6)

An oscillating gear, an eccentric body shaft having an eccentric body, and an eccentric body bearing disposed between the oscillating gear and the eccentric body, and through the eccentric body of the eccentric body shaft In an eccentric oscillating type speed reducer in which the oscillating gear is eccentrically or flexibly oscillated,
The eccentric body shaft is subjected to a curing treatment,
The curing treatment is performed more than the amount of carbide on the surface portion of the eccentric body shaft before applying the thermal load when the thermal load is applied to the eccentric body shaft so that the material characteristics of the eccentric body shaft change. An eccentric oscillating type speed reducer, characterized in that it is a hardening process in which the amount of carbide on the surface portion of the eccentric body shaft after application of the thermal load is increased. In claim 1,
The curing process is a curing process in which the amount of nitride on the surface portion of the eccentric body shaft after application of the thermal load is larger than the amount of nitride on the surface portion of the eccentric body shaft before application of the thermal load. An eccentric rocking type speed reducer characterized by that. In claim 1 or 2,
The eccentric oscillation type speed reducer, wherein the thermal load that changes the material characteristics of the eccentric body shaft is a thermal load in which the eccentric body shaft is exposed to a temperature of 300 ° C. or more for 3 hours or more. In any one of Claims 1-3,
Eccentric rocking-type speed reducer, wherein the retained austenite on the surface portion of the eccentric body shaft is 36 to 45% by volume. In any one of Claims 1-4,
The eccentric oscillating type speed reducer, wherein the curing process is a curing process in which the carbon concentration of the surface portion of the eccentric body shaft is the same before and after applying the thermal load. In any one of Claims 1-5,
The eccentric oscillating type speed reducer, wherein a nitrogen concentration in a surface portion of the eccentric body shaft is 0.07 to 0.30% by weight.