WO2018180184A1 - Resin gear and gear mechanism - Google Patents

Abstract

An embodiment of a resin gear according to the invention is made of a mixed material including a resin material and a carbon material, wherein the carbon material is a spherical amorphous carbon.

Description

Resin gear and gear mechanism

The present invention relates to a resin gear and a gear mechanism.

Conventionally, in the case of gears using metal materials, vibration and noise caused by backlash have been a problem. Therefore, in order to reduce vibration and noise caused by backlash, in recent years, it has been proposed to apply a gear using a resin material. *

Further, in order to transmit a large stress, there is a demand for improvement in durability and wear resistance of the resin gear. As one means for improving the durability and wear resistance of a resin gear, for example, as in Patent Documents 1 and 2, a method for improving durability and wear resistance by adding reinforcing fibers to a resin material Is being considered.

JP 2014-77541 A Republished WO 2004-015309

However, when the gear is small, there is no space for providing a rolling bearing, so that the resin gear itself needs high lubricity. *

In view of the above problems, one aspect of the present invention includes a resin gear that has sufficient durability and wear resistance and good lubricity even when it is small, and includes a reinforcing fiber. Another object is to provide a gear mechanism.

One aspect of the resin gear of the present invention is made of a mixed material of a resin material and a carbon material, and the carbon material is spherical amorphous carbon.

According to one aspect of the present invention, it is possible to provide a resin gear having sufficient durability and wear resistance and good lubricity, and a gear mechanism including the resin gear, even if it is small.

The figure which shows the structure of a part of small reduction gear 100 which applied the resin gear of embodiment as the external gear 20. FIG. The figure which shows the external gear 20. FIG. The figure which shows the internal gear 10. FIG. The enlarged view which shows a part of inner peripheral surface 24a of the shaft insertion hole 24 of the external gear 20 before use. The enlarged view which shows a part of inner peripheral surface 24a of the shaft insertion hole 24 of the external gear 20 after use. The enlarged view which shows a part of inner peripheral surface 24a of the shaft insertion hole 24 of the external gear 20 and the shaft 7 after use.

The resin gear according to the present invention is made of a mixed material of a resin material and a carbon material. Spherical amorphous carbon is used as the carbon material, and many spherical amorphous carbons are mixed in the resin material. Such a resin gear can be suitably used as a gear having a sliding bearing function, such as an external gear 20 of a small reduction gear 100 as shown in FIG. *

Hereinafter, the configuration of a small reduction gear 100 including 20 external gears, which is an embodiment of the resin gear according to the present invention, will be described with reference to the drawings. The scope of the present invention is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, the actual structure may be different from the scale, number, or the like in each structure. *

In the drawings, an XYZ coordinate system is appropriately shown as a three-dimensional orthogonal coordinate system. In the XYZ coordinate system, the Z-axis direction is a direction parallel to the axial directions of the first central axis J1 and the second central axis J2 shown in FIG. The X-axis direction is a direction orthogonal to the Z-axis direction and is the left-right direction in FIG. The Y-axis direction is a direction orthogonal to both the X-axis direction and the Z-axis direction, and is the vertical direction in FIG. *

In the following description, a direction parallel to the first central axis J1 and the second central axis (Z-axis direction) is simply referred to as an “axial direction” and is centered on the first central axis J1 or the second central axis. The radial direction is simply referred to as “radial direction”, and the circumferential direction around the first central axis J1 or the second central axis, that is, the circumference of the first central axis J1 or the second central axis is simply referred to as “circumferential direction”. Call. *

(Small Reducer) FIG. 1 is a diagram showing a partial configuration of a small reducer 100 to which the resin gear according to the present invention is applied as the external gear 20. 1, the small reduction gear (gear mechanism) 100 includes at least an internal gear 10, an external gear 20, a shaft 7, and a plurality of support pins 8. The shaft 7 is an input shaft of the small reduction gear 100, and a shaft main body (not shown) extending along the first central axis J1 and an eccentric portion 7B provided at the tip of the shaft main body and extending along the second central axis J2. And have. *

(External gear 20) FIG. 2 is a diagram showing the external gear 20. As shown in FIG. External gear (resin gear) 20 is a cycloid gear. As shown in FIGS. 1 and 2, the external gear 20 has a substantially annular plate shape that extends radially from the second central axis J <b> 2. A plurality of external teeth 22 projecting outward in the radial direction are provided on the outer periphery of the external gear 20. Further, between the adjacent external teeth 22 in the circumferential direction, an inter-external tooth groove 23 that is recessed inward in the radial direction is provided. The external teeth 22 and the external inter-tooth grooves 23 exist alternately around the second central axis J2. The tip diameter of the external gear 20 is, for example, 2 mm or more and 12 mm or less. *

The external gear 20 has a shaft insertion hole (first through hole) 24 that penetrates in the central direction in the axial direction (Z-axis direction). The shaft insertion hole 24 is an axial hole that rotatably supports the eccentric portion 7B of the shaft (first shaft) 7 extending along the second central axis J2. The shaft insertion hole 24 is a sliding bearing and holds the lubricating oil 19 (FIG. 6) on the inside. *

The external gear 20 has a plurality of through holes 25 around the shaft insertion hole 24. The plurality of through-holes (second through-holes) 25 are arranged at equal intervals along the circumferential direction centering on the second central axis J2 at positions spaced radially outward from the shaft insertion hole 24. Further, the radial positions of the through holes 25 are the same. *

In the present embodiment, about 10 through holes 25 are provided, but the number is not limited thereto. The shape of the through hole 25 viewed from the axial direction (Z-axis direction) is circular. The plurality of through holes 25 are sliding bearings and hold the lubricating oil 19 (FIG. 6) inside. *

A support pin (second shaft) 8 shown in FIG. 1 is inserted into each of the plurality of through holes 25. The inner diameter of the through hole 25 is larger than the outer diameter of the support pin 8. The outer peripheral surface 8 b of the support pin 8 is in contact with the inner peripheral surface 25 a of the through hole 25. The support pin 8 restricts free rotation of the external gear 20 and swings the external gear 20 around the first central axis J1. The support pin 8 is connected to the output shaft of the small speed reducer 100. The external gear 20 is meshed with the internal gear 10 disposed on the radially outer side. *

(Material of External Gear 20) The external gear 20 is an embodiment of a resin gear according to the present invention. The external gear 20 is a resin gear made of a reinforced resin containing a carbon material. As the material of the external gear 20, the resin material 11 (FIG. 4) is used as a base material, and spherical amorphous carbon is used as an additive to the base material. Hereinafter, this additive is simply referred to as spherical amorphous carbon (carbon material) 12 (FIG. 4). *

As the resin material 11 used for the base material, a polymer material having excellent moldability and high mechanical strength is selected. Specific examples of the resin material 11 include, for example, PEEK (Poly ether ether ketone) polyether ether ketone resin (crystalline super engineering plastic), LCP (Liquid Crystal Polymer liquid crystal polymer), PPS (Poly Phenylene Sulfide Resin polyphenylene sulfide resin). And one or more materials selected from the group consisting of polyamide resins such as semi-aromatic nylon (PA4T, PA6T, PA9T, PA10T) and polyamide 46 (PA46). *

The spherical amorphous carbon 12 is a carbon fine particle having an average aspect ratio of 2 or less. The average particle diameter of the spherical amorphous carbon 12 is 5 to 10 μm. *

Here, the average aspect ratio means that the length in the radial direction orthogonal to the major axis direction of the spherical amorphous carbon 12 is the minor axis r (μm), and the length of the spherical amorphous carbon 12 in the major axis direction is the major axis L (μm). It is a value obtained by averaging the L / r ratio at the time of a plurality of particles included in a predetermined range. The aspect ratio of one particle can be calculated by observing the spherical amorphous carbon 12 and dividing the major axis of the spherical amorphous carbon 12 by the minor axis. *

The size of the spherical amorphous carbon 12 can be measured using an optical microscope or an electron microscope. For example, using a scanning electron microscope (SEM), for example, 100 arbitrary spherical amorphous carbons 12 are selected from the spherical amorphous carbons dispersed in the base material, and the major axis and minor axis of these spherical amorphous carbons 12 are selected. And measure. From the measured major axis and minor axis, the aspect ratio of 100 spherical amorphous carbons 12 can be obtained, and the average aspect ratio can be calculated as the average value of the aspect ratios. *

The finely divided spherical amorphous carbon 12 has a small aspect ratio and has a very good dispersibility with respect to the resin material 11 and is distributed in the resin material 11 in a uniform state. Further, since the aspect ratio is small, anisotropy does not appear in the dispersion direction of the spherical amorphous carbon 12 in the resin material 11, and the external gear 20 with high dimensional accuracy and high strength can be obtained. *

In the external gear 20 of the present embodiment, 20 to 70% by volume of spherical amorphous carbon 12 that is a carbon material (reinforcing material) is contained in the base material of the resin material. More preferably, it is 30 to 60% by volume. More preferably, it is 50%. If the content of the spherical amorphous carbon 12 is less than 20% by volume, the desired effect cannot be obtained. On the other hand, when the content of the spherical amorphous carbon 12 exceeds 70% by weight, the resin material 11 is reduced with respect to the spherical amorphous carbon 12, and the resin amount that fills the gap is insufficient. There is a risk. Therefore, by adding the spherical amorphous carbon 12 to the resin material 11 at a ratio within the above range, the external gear 20 with high dimensional accuracy can be obtained. *

Further, by adding the spherical amorphous carbon 12 to the resin material 11, the thermal expansion coefficient becomes lower than that of the resin material 11 alone. Therefore, the dimensional change of the external gear 20 due to heat generation during use can be suppressed. *

(Internal gear 10) FIG. 3 is a diagram showing the internal gear 10. As shown in FIGS. 1 and 3, the internal gear 10 includes a cylindrical internal gear main body 10A centered on the first central axis J1, a fixed portion 10B extending from a part of the internal gear main body 10A, It consists of a single member having A plurality of internal teeth 13 projecting radially outward from the inner peripheral surface 10a is provided on the inner peripheral surface 10a of the internal gear main body 10A. Between the internal teeth 13 adjacent in the circumferential direction, an internal inter-tooth groove 14 that is recessed toward the radially inner side (inner peripheral surface 10a) is provided. The inner teeth 13 and the inter-inner teeth grooves 14 are alternately present around the first central axis J1. The tip diameter of the internal gear 10 is, for example, not less than 2 mm and not more than 12 mm. *

The internal gear main body 10A surrounds the radially outer side of the external gear 20 as shown in FIG. The internal teeth 13 of the internal gear main body 10 </ b> A face the external teeth 22 of the external gear 20 and partially mesh with each other sequentially in the circumferential direction in accordance with the swinging operation of the external gear 20. *

(Material of Internal Gear 10) As the material of the internal gear 10, a polymer material having excellent moldability and high mechanical strength is selected. Specific resin materials include, for example, PEEK (Poly ether ether ketone) polyether ether ketone resin (crystalline super engineering plastic), LCP (Liquid Crystal Polymer liquid crystal polymer), PPS (Poly Phenylene Sulfide Resin polyphenylene sulfide resin), and the like. And one or more materials selected from the group consisting of polyamide resins such as semi-aromatic nylon (PA4T, PA6T, PA9T, PA10T) and polyamide 46 (PA46). The internal gear 10 can be manufactured by injection molding a resin material.

The internal gear 10 preferably contains a carbon material. The durability of the internal gear 10 can be enhanced by using a fiber-reinforced mixed material in which carbon fiber (not shown) is added to the above-described resin material as the material of the internal gear 10. As the carbon fiber, it is preferable to use a short fiber having a fiber length of 100 μm or less. *

As the base material of the external gear 20 described above, the same material as the base material of the internal gear 10 may be used, or may be different. *

In the small speed reducer 100 according to the present embodiment, when the shaft 7 shown in FIG. 1 rotates around the first central axis J1, the inner peripheral surface of the through-hole 25 of the external gear 20 supported by the eccentric portion of the shaft 7. The external gear 20 oscillates in the radial direction while the inscribed position between 25a and the outer peripheral surface 8b of the support pin 8 changes. By this swinging, the position where the external teeth 22 of the external gear 20 and the internal teeth 13 of the internal gear 10 mesh with each other changes in the circumferential direction. Here, every time the shaft 7 makes one rotation around the second central axis J2, the position where the teeth mesh with each other in the circumferential direction shifts. As a result, the output shaft connected to the support pin 8 rotates at a speed 1/30 of the shaft 7, for example. The operation of the small speed reducer 100 described above is an example, and may be configured to perform other operations. *

FIG. 4 is an enlarged view showing a part of the inner peripheral surface 24a of the shaft insertion hole 24 of the external gear 20 before use. FIG. 5 is an enlarged view showing a part of the inner peripheral surface 24a of the shaft insertion hole 24 of the external gear 20 after use. FIG. 6 is an enlarged view showing a part of the inner peripheral surface 24 a of the shaft insertion hole 24 of the external gear 20 and the shaft 7 after use. *

Conventionally, when the external gear 20 is made of only a resin material, oil shortage occurs between the shaft 7 and the inner peripheral surface of the shaft insertion hole 24 is damaged. *

On the other hand, in the present embodiment, the spherical gear 12 having a hardness higher than that of the resin material 11 is added to the resin material 11 to form the external gear 20. When the shaft 7 rotates, friction is generated between the shaft 7 and the external gear 20, and the inner peripheral surface 24 a of the shaft insertion hole 24 of the external gear 20 is worn. *

In addition, the external gear 20 that rotates with the rotation of the shaft 7 includes a plurality of support pins 8 inserted into the respective through holes 25 of the external gear 20. The rotation is restricted by contacting the surface 25a. Thus, the inner peripheral surface 25a of each through-hole 25 is also abraded when the support pin 8 contacts. *

Since the relatively soft resin material 11 is preferentially scraped when the external gear 20 is worn, the hard spherical amorphous carbon 12 partially protrudes radially inward of the inner peripheral surfaces 24a and 25a. *

In each of the inner peripheral surface 24a of the shaft insertion hole 24 and the inner peripheral surface 25a of each through hole 25, when the resin material 11 on each surface is scraped, the hardness that is buried in the resin material 11 as shown in FIG. As shown in FIG. 5, the spherical amorphous carbon 12 appears on the surface, and a gap 15 is generated between the spherical amorphous carbon 12 and the resin material 11. Then, the lubricating oil 19 (FIG. 6) is held in the gap 15 formed in each inner peripheral surface 24a, 25a by capillary action. 4 and 5, a part of the inner peripheral surface 24a of the shaft insertion hole 24 is shown in an enlarged manner, but the inner peripheral surface 25a of the through hole 25 has a similar surface. *

Further, as shown in FIG. 6, a gap 16 is generated between the shaft 7 and the shaft insertion hole 24 by the spherical amorphous carbon 12 partially protruding inward in the radial direction of the shaft insertion hole 24. The lubricating oil 19 is also retained in the gap 16 by capillary action. *

As described above, the concave and convex portions (the gap 15 and the gap 16 described above) are formed on the inner peripheral surface 24a of the shaft insertion hole 24 and the inner peripheral surface 25a of the plurality of through holes 25 in the external gear 20 by driving the small reduction gear 100. Etc.), the lubricating oil 19 can be retained by utilizing the capillary phenomenon. With respect to the support pin 8 having a diameter smaller than the diameter of the through hole 25, the external gear 20 is held on the inner peripheral surface 25 a of the through hole 25 while receiving a load by making point contact with the support pin 8. The lubricating oil 19 can be adapted around the support pin 8. *

As a result, the external gear 20 can be used for a long time without cutting the oil film between the shaft 7 and the plurality of support pins 8, and the external gear having good lubricity with respect to the shaft 7 and the plurality of support pins 8. 20 As a result, since the external gear 20 can function as a sliding bearing in the small reduction gear 100, fatigue of the external gear 20 due to friction can be suppressed, and the life can be extended. *

Moreover, since the carbon material added to the resin material 11 is spherical amorphous carbon, even if the spherical amorphous carbon 12 is exposed from the resin material 11 during use, the shaft 7 and the plurality of support pins 8 are damaged. There is nothing. *

Since the small reduction gear 100 of the present embodiment includes the internal gear 10 including carbon fiber and the external gear 20 including the spherical amorphous carbon 12, sufficient durability and wear resistance can be achieved even if it is small. Is obtained, and a highly reliable small reduction gear 100 can be obtained. *

In particular, since the external gear 20 receives both compression force and shear force, durability and wear resistance are important. Spherical amorphous carbon is hard to break and hard to cut. Therefore, the durability and wear resistance of the external gear 20 can be improved by adding the spherical amorphous carbon 12 to the resin material 11. *

Although one embodiment of the present invention has been described above, each configuration in the embodiment and combinations thereof are examples, and addition, omission, replacement, and other configurations of the configuration are within the scope not departing from the gist of the present invention. It can be changed. Further, the present invention is not limited by the embodiment. *

For example, in the above-described embodiment, in the external gear 20, only the spherical amorphous carbon 12 is included in the resin material 11 as the carbon material. However, not only the spherical amorphous carbon 12 but also carbon fibers may be mixed in the resin material 11. Good. The amount of spherical amorphous carbon 12 and carbon fiber mixed with the resin material 11 is appropriately selected in consideration of the moldability and dimensional accuracy of the external gear 20. *

Thus, the density of the carbon material in the resin material 11 is improved by mixing not only the spherical amorphous carbon 12 but also the carbon fiber in the resin material 11. Accordingly, the strength of the external gear 20 can be increased, so that the durability and wear resistance of the external gear 20 are further improved. *

In the case of this configuration, when the resin material 11 on the outermost surface of the external gear 20 is scraped by the rotation of the external gear 20, carbon fibers also appear together with the spherical amorphous carbon 12, and between these carbon material and the resin material 11. In this case, the gaps 15 are increased, and the lubricating oil 19 is held in the numerous gaps 15. Thereby, the slidability of the external gear 20 with respect to the shaft 7 and the plurality of support pins 8 can be further improved. *

Further, in the internal gear 10, only the carbon fiber is mixed with the resin material 11, but not only the carbon fiber but also spherical amorphous carbon may be mixed.

DESCRIPTION OF SYMBOLS 7 ... Shaft (1st shaft), 10 ... Internal gear, 11 ... Resin material, 12 ... Spherical amorphous carbon (carbon material), 15 ... Clearance, 20 ... External gear (resin gear), 24 ... Shaft insertion hole (First through hole), 25 ... through hole (second through hole), 100 ... small reduction gear (gear mechanism)

Claims (9)

A resin gear comprising a mixed material of a resin material and a carbon material, wherein the carbon material is spherical amorphous carbon. It is an external gear, and has a plurality of external teeth protruding outward in the radial direction and at least one through hole penetrating in the axial direction. The through hole is a sliding bearing that rotatably supports the shaft. The resin gear according to claim 1. The external gear is a cycloid gear, and has a first through hole formed in the center and rotatably supporting the first shaft, and at least one formed around the first through hole and a second The resin gear according to claim 2, further comprising a second through hole that rotatably supports the shaft. 4. The resin gear according to claim 2, wherein lubricating oil is held in the through hole, and a gap is provided between the carbon material located on a surface of the inner wall surface of the through hole and the resin material. . The resin gear according to any one of claims 2 to 4, wherein an outer diameter is 12 mm or less. The resin gear according to any one of claims 1 to 5, wherein an average aspect ratio of the carbon material is 2 or less. The resin gear according to any one of claims 1 to 6, further comprising a carbon fiber having an aspect ratio of 5 to 15 inclusive of 100 µm or less. The resin gear according to any one of claims 1 to 7, wherein a content of the carbon material in the resin material is in a range of 20 wt% to 60 wt%. The resin gear according to any one of claims 1 to 8 is an external gear, and is a gear mechanism having an internal gear that is disposed on a radially outer side of the external gear, and the internal gear includes a resin material and A gear mechanism made of a mixed material with carbon fibers having a fiber length of 100 μm or less.

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