Planetary gear mechanism and method for manufacturing the same

Abstract

To reduce vibration and noise.SOLUTION: A planetary gear mechanism 100 comprises a planetary gear 2, a shaft 4 that rotatably supports the planetary gear, and a bearing 20 provided between the planetary gear and the shaft, which is a resin radial-type slide bearing. A radial clearance between the planetary gear and the bearing and a radial clearance between the shaft and the bearing are both set to zero.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a planetary gear mechanism and a method for manufacturing the same.

Background Art

[0002] For example, planetary gear mechanisms are used as speed reducers for machine tools. The planetary gear mechanism is advantageous from the perspective of space efficiency because the sun gear, planetary gears and ring gear are arranged coaxially and aligned in the radial direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, the planetary gear is rotatably supported by a shaft attached to a carrier. On the other hand, a needle roller bearing, which is a rolling bearing, is generally provided between the planetary gear and the shaft.

[0005] However, radial clearances exist between the plurality of needles of the needle roller bearing, the planetary gear and the shaft. In addition, circumferential clearances exist between the plurality of needles. There is a problem that backlash occurs due to these clearances, leading to increased vibration and noise.

[0006] The present disclosure has been devised in view of such circumstances, and an object thereof is to provide a planetary gear mechanism capable of reducing vibration and noise, and a method for manufacturing the same.

Means for Solving the Problems

[0007] According to one aspect of the present disclosure, Planetary Gear and A shaft that rotatably supports the planetary gear, A bearing provided between the planetary gear and the shaft, which is a resin-made radial-type sliding bearing, Equipped with, The radial clearance between the planetary gear and the bearing, and the radial clearance between the shaft and the bearing are set to zero. A planetary gear mechanism characterized by the above is provided.

[0008] Preferably, the bearing is integrally provided with either the planetary gear or the shaft.

[0009] Preferably, the bearing is formed by a resin coating layer provided on either the planetary gear or the shaft.

[0010] Preferably, an oil groove is provided on the bearing surface of the bearing.

[0011] Preferably, the planetary gear and the shaft are made of metal.

[0012] Preferably, the planetary gear mechanism is applied to a machine tool or a robot.

[0013] According to other aspects of this disclosure, A manufacturing method for producing the aforementioned planetary gear mechanism, The procedure includes coating one of the planetary gear and the shaft with the resin that forms the bearing. A method for manufacturing a planetary gear mechanism is provided, characterized by the following features. [Effects of the Invention]

[0014] According to this disclosure, vibration and noise can be reduced. [Brief explanation of the drawing]

[0015] [Figure 1] FIG. 1 is a schematic front view showing a planetary gear mechanism according to a basic embodiment of the present disclosure. [Figure 2] FIG. 2 is a longitudinal side view showing the planetary gear mechanism. [Figure 3] FIG. 3 is a longitudinal side view showing a shaft and a bearing. [Figure 4] FIG. 4 is a schematic front view showing the present embodiment and a comparative example. [Figure 5] FIG. 5 is a longitudinal side view showing a first modified example. [Figure 6] FIG. 6 is a longitudinal side view showing a planetary gear and a bearing. [Figure 7] FIG. 7 is a longitudinal side view showing a first example of an oil groove in a second modified example. [Figure 8] FIG. 8 is a longitudinal side view showing a second example of an oil groove in the second modified example. [Figure 9] FIG. 9 is a longitudinal side view showing a third example of an oil groove in the second modified example. [Figure 10] FIG. 10 is a longitudinal side view showing a fourth example of an oil groove in the second modified example. [Figure 11] FIG. 11 is a longitudinal side view showing a fifth example of an oil groove in the second modified example. [Description of Embodiments]

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the following embodiments.

[0017] [Basic Embodiment] FIG. 1 and FIG. 2 show a planetary gear mechanism 100 of the basic embodiment. The planetary gear mechanism 100 of the present embodiment is applied to a machine tool or a robot (particularly an industrial robot). However, its application is arbitrary.

[0018] The symbol C1 indicates the central axis of the planetary gear mechanism 100. Hereafter, unless otherwise specified, the axial, radial, and circumferential directions relative to axis C1 will simply be referred to as the axial, radial, and circumferential directions. Also, one end in the direction of axis C1 (right side in Figure 2) will be considered the front, and the other end (left side in Figure 2) will be considered the rear. Figure 1 is a schematic front view as seen from the axial front.

[0019] The planetary gear mechanism 100 comprises a sun gear 1 located at the radial center, a plurality (four) of planetary gears 2 located radially outside the sun gear 1 and meshing with the sun gear 1, and a ring gear 3 located radially outside these planetary gears 2 and meshing with the planetary gears 2. The planetary gear mechanism 100 also comprises a plurality (four) of shafts 4 that rotatably support the plurality of planetary gears 2, and a carrier 5 to which these shafts 4 are attached. The symbol C2 indicates the central axis of the shaft 4, i.e., the rotation center of the planetary gear 2. The planetary gears 2 and shafts 4 are arranged at equal intervals in the circumferential direction.

[0020] In the planetary gear mechanism 100, the sun gear 1 is integrally formed with the front end of the input shaft 6. The rear end of the output shaft 7 is coaxially and rotatably inserted into the front end of the input shaft 6 via a needle bearing 8. The input shaft 6 and the output shaft 7 are arranged coaxially with shaft C1. The planetary gear mechanism 100 functions as a reduction gear, reducing the rotational input transmitted from the input shaft 6 and outputting it from the output shaft 7.

[0021] The carrier 5 is spline-fitted from the rear to a spline 9 provided at the rear end of the output shaft 7. The carrier 5 is then sandwiched from the front and rear in the axial direction by the flange 10 of the output shaft 7 and the snap ring 11, thereby restricting its axial movement. The snap ring 11 is fitted into a ring groove 12 provided in the spline 9.

[0022] The front end of the shaft 4 is press-fitted into the carrier hole 13 of the carrier 5 and secured. The middle portion of the shaft 4 is inserted into the gear hole 14 provided in the center of the planetary gear 2. The rear end of the shaft 4 is press-fitted into the plate hole 16 provided in the ring-shaped back plate 15 and secured. In this way, the planetary gear 2 is positioned in the axial direction between the front carrier 5 and the rear back plate 15.

[0023] The carrier 5, shaft 4, and backplate 15 are assembled as a single unit onto the output shaft 7 and rotate together with the output shaft 7. The planetary gear 2 then rotates relative to the shaft 4. The backplate 15 can be considered as part of the carrier 5.

[0024] A ring-shaped carrier-side shim 17 is fitted to the shaft 4 at a position between the planetary gear 2 and the carrier 5 in the axial direction. Similarly, a ring-shaped plate-side shim 18 is fitted to the shaft 4 at a position between the planetary gear 2 and the back plate 15 in the axial direction. These shims 17 and 18 optimally adjust the axial clearance between the planetary gear 2 and the carrier 5, and the axial clearance between the planetary gear 2 and the back plate 15.

[0025] The planetary gear mechanism 100 includes a bearing 20 provided between the planetary gear 2 and the shaft 4. The bearing 20 is a resin radial type sliding bearing. The bearing 20 is made of nylon, for example, but may be made of other resins such as rubber. In the planetary gear mechanism 100 of this embodiment, all parts other than the bearing 20 are made of metal (for example, iron). In particular, the planetary gear 2 and the shaft 4 are made of metal (for example, iron).

[0026] As shown in Figure 3, the bearing 20 is cylindrical with its center extending axially, and has a constant thickness t and an axial dimension equal to the gear hole 14. The bearing 20 is located radially between the planetary gear 2 and the shaft 4. In this embodiment, the bearing 20 is integrally provided on the shaft 4. That is, the manufacturing method for producing the planetary gear mechanism 100 of this embodiment includes the step of coating the shaft 4 with the resin that will form the bearing 20. By coating the outer circumferential surface of the shaft 4 with the resin that will form the bearing 20, a relatively thin resin bearing 20 is integrally formed. Thus, the bearing 20 is formed by a resin coating layer provided on the outer circumferential surface of the shaft 4.

[0027] Since the bearing 20 is integrally fixed to the shaft 4, naturally there is no radial clearance between the bearing 20 and the shaft 4; it is zero. On the other hand, when the shaft 4 with the bearing 20 (referred to as the shaft assembly) is fitted into the gear hole 14 of the planetary gear 2, there is no radial clearance between the bearing 20 and the inner circumferential surface of the gear hole 14; it is zero. In other words, the outer diameter of the bearing 20 or the inner diameter of the gear hole 14 is set to achieve this.

[0028] Thus, the radial clearance between the shaft 4, the bearing 20, and the planetary gear 2 is set to zero.

[0029] The ring gear 3 has an outer circumferential surface portion on which protrusions 21 are formed at equal intervals in the circumferential direction, so as to be fixed to equipment to which the planetary gear mechanism 100 is applied.

[0030] Sun gear 1 and planetary gear 2 have outer teeth 22 and 23 made of helical teeth, and ring gear 3 has inner teeth 24 made of helical teeth.

[0031] To supply lubricating oil to the needle bearing 8, an oil hole 25 is provided in the input shaft 6 and an oil hole 26 is provided in the output shaft 7. In addition, the sliding surfaces of the bearing 20 and the planetary gear 2 are lubricated by oil scattered from the surrounding area near the planetary gear 2 penetrating the surface.

[0032] As shown in Figure 1, the back plate 15 has multiple spoke-shaped reinforcing portions 27 that protrude axially forward between the planetary gears 2. Also, as shown in Figure 2, the output shaft 7 has multiple (two) splines 28, 29 formed on it for spline fitting with the mating member.

[0033] In this embodiment of the planetary gear mechanism 100, a resin bearing 20 is provided between the planetary gear 2 and the shaft 4, replacing the conventional needle roller bearing. The radial clearance between the planetary gear 2 and the bearing 20, and the radial clearance between the shaft 4 and the bearing 20 are set to zero. Furthermore, there is naturally no circumferential clearance between the needles, as was present in conventional needle roller bearings. Therefore, no play caused by radial or circumferential clearance occurs, and vibration and noise during use can be reduced.

[0034] Furthermore, the planetary gear mechanism 100 of this embodiment can achieve improved rigidity compared to conventional planetary gear mechanisms.

[0035] Figure 4 shows a comparison of the planetary gear support portion of the planetary gear mechanism 100 of this embodiment and a conventional planetary gear mechanism (referred to as a comparative example), where (A) and (C) represent this embodiment and (B) represents the comparative example. For convenience, the same reference numerals 2 and 4 are used for the planetary gear and shaft of the comparative example as in this embodiment.

[0036] As shown in (B), in the comparative example, a needle roller bearing 30 is provided between the planetary gear 2 and the shaft 4. In this case, there is a radial clearance greater than zero between the planetary gear 2 and the needle 31, and between the shaft 4 and the needle 31. The figure shows the total radial clearance CL1. The radial distance CL3 between the planetary gear 2 and the shaft 4 is greater than the outer diameter D1 of the needle 31. There is also a circumferential clearance CL2 greater than zero between each needle 31. The figure exaggerates the clearances CL1 and CL2.

[0037] Incidentally, in the comparative example, the presence of these clearances CL1 and CL2 causes looseness, resulting in relatively high vibration and noise during use.

[0038] In contrast, in this embodiment shown in Figure 4(A), a resin bearing 20 is provided between the planetary gear 2 and the shaft 4. There is no radial clearance between the planetary gear 2 and the bearing 20, and between the shaft 4 and the bearing 20. The radial distance CL3 between the planetary gear 2 and the shaft 4 is equal to the thickness t of the bearing 20. Naturally, there is no circumferential clearance in the bearing 20.

[0039] Therefore, in this embodiment, the diameter of the shaft 4 can be increased because there is no radial clearance CL1. In the illustrated example, the inner diameter D2 of the gear hole 14 of the planetary gear 2 is kept the same as in the comparative example, while the outer diameter of the shaft 4 is increased by the amount of the radial clearance CL1, resulting in an outer diameter D3 that is larger than that of the comparative example.

[0040] By increasing the diameter of the shaft 4 in this way, the rigidity of the shaft 4 can be improved.

[0041] The shaft 4 can also be made larger in diameter. For example, if the inner diameter D2 of the gear hole 14 of the planetary gear 2 is the same as in the comparative example, the thinner the thickness t of the bearing 20 is made compared to the outer diameter D1 of the needle 31, the larger the diameter of the shaft 4 can be made. The thickness t of the bearing 20 can be made relatively easily thinned, mainly insofar as durability requirements are met, so the diameter of the shaft 4 can be made relatively easily.

[0042] On the other hand, in this embodiment shown in Figure 4(C), the gear hole 14 (i.e., inner diameter) of the planetary gear 2 is reduced in diameter because there is no radial clearance CL1. In the illustrated example, the outer diameter D4 of the shaft 4 is kept the same as that of the comparative example, while the inner diameter of the gear hole 14 is reduced by the amount of the radial clearance CL1, resulting in an inner diameter D5 that is smaller than that of the comparative example.

[0043] By reducing the diameter of the gear hole 14 of the planetary gear 2, the rigidity of the planetary gear 2 can be improved.

[0044] The gear hole 14 of the planetary gear 2 can also be made smaller in diameter. For example, if the outer diameter D4 of the shaft 4 is the same as in the comparative example, the thinner the thickness t of the bearing 20 is made compared to the outer diameter D1 of the needle 31, the smaller the diameter of the gear hole 14 can be made. As mentioned above, the thickness t of the bearing 20 can be made relatively easily, so the diameter of the gear hole 14 can be made relatively easily.

[0045] Although not shown in the diagram, it is also possible to simultaneously increase the diameter of the shaft 4 and decrease the diameter of the gear hole 14 of the planetary gear 2.

[0046] In this way, the rigidity of at least one of the shaft 4 and the planetary gear 2 can be improved, and this improvement in rigidity can be reallocated to reduce the size, thereby enabling miniaturization. Specifically, the number of teeth and outer diameter of the planetary gear 2 can be reduced, and the distance between the gears' axes can be shortened, thereby reducing the overall size.

[0047] Thus, the planetary gear mechanism 100 of this embodiment not only reduces vibration and noise, but also improves rigidity and achieves miniaturization.

[0048] Next, modified examples of the present disclosure will be described. Parts identical to those in the basic embodiment will be denoted by the same reference numerals in the figures and their descriptions will be omitted. The following will primarily describe the differences from the basic embodiment.

[0049] [First variation] In the first modified example described here, as shown in Figure 6, the bearing 20 is integrally provided on the inner circumferential surface of the planetary gear 2, particularly the gear hole 14. That is, the manufacturing method for producing the planetary gear mechanism 100 of this modified example includes a step of coating the planetary gear 2 with the resin that will form the bearing 20. By coating the inner circumferential surface of the gear hole 14 of the planetary gear 2 with the resin that will form the bearing 20, a relatively thin resin bearing 20 is integrally formed. Thus, the bearing 20 is formed by a resin coating layer provided on the inner circumferential surface of the gear hole 14 of the planetary gear 2.

[0050] A schematic front view of this modified example is shown in Figure 1, which is the same as that of the basic embodiment. A longitudinal side view of this modified example is shown in Figure 5, and a longitudinal side view of the gear hole 14 of the planetary gear 2 and the bearing 20 is shown in Figure 6.

[0051] The bearing 20 is cylindrical with its center extending axially and has a constant thickness t. Since the bearing 20 is integrally fixed to the planetary gear 2, naturally there is no radial clearance between the bearing 20 and the planetary gear 2; it is zero. On the other hand, when the planetary gear 2 (referred to as the gear assembly), which has the bearing 20 integral to it, is fitted onto the shaft 4, there is no radial clearance between the bearing 20 and the outer surface of the shaft 4; it is zero. In other words, the inner diameter of the bearing 20 or the outer diameter of the shaft 4 is set to achieve this.

[0052] In this modified example, the radial clearance between the shaft 4, the bearing 20, and the planetary gear 2 is also set to zero.

[0053] In this modified example, oil holes 40 and 41 are provided in the shaft 4 and the back plate 15, respectively, to more actively supply oil to the sliding surfaces of the bearing 20 and the shaft 4. Oil scattered from the outside is supplied to the sliding surfaces through the oil holes 40 and 41. As with the basic embodiment described above, the planetary gear mechanism 100 is provided inside the gearbox of the equipment, and the inside of the gearbox is in an oily atmosphere.

[0054] The oil hole 40 of the shaft 4 includes a first hole 42 that extends axially from the axial rear end (base end) to the middle part in the center of the shaft 4, a plurality (two) of second holes 43 that extend radially outward and inward from the rear end of the first hole 42, and a third hole 44 that extends radially outward from the front end (tip) of the first hole 42 and opens on the outer circumferential surface of the shaft 4. The oil hole 41 of the back plate 15 includes a fourth hole 45 that penetrates radially at the position of the plate hole 16 and communicates coaxially with the second hole 43.

[0055] By providing these oil holes 40 and 41, oil can be actively supplied to the sliding surface, thereby suppressing heat generation on the sliding surface.

[0056] This modified version can also achieve the same effects and advantages as the basic embodiment.

[0057] [Second variation] In the second modification described here, an oil groove is provided on the bearing surface of the bearing 20. The bearing surface refers to the sliding surface that slides against the mating member (shaft 4 or planetary gear 2).

[0058] Figure 7 shows a first example of the oil groove in this modified example. In the basic embodiment, the oil groove can be provided on the outer circumferential surface of the bearing 20, and in the first modified example, it can be provided on the inner circumferential surface of the bearing 20. Since these can be configured similarly, for convenience, only the case where it is provided on the outer circumferential surface of the bearing 20 will be described here. That is, the oil groove is provided on the outer circumferential surface of the bearing 20 which is integrally provided on the shaft 4.

[0059] The oil groove 51 in the first example shown in Figure 7 is provided on the outer circumferential surface of the bearing 20 perpendicular to the axis C2 direction and along the circumferential direction, and multiple grooves are provided at equal intervals in the axial direction. The cross-sectional shape of the oil groove 51 is rectangular, but other shapes such as semicircular may also be used.

[0060] By providing these oil grooves 51, oil can be stored within the oil grooves 51, allowing for more active oil retention on the outer surface, which is the bearing surface, and effectively suppressing heat generation on the sliding surface.

[0061] Figures 8 to 10 show the second to fourth examples of oil grooves. In the second example shown in Figure 8, a single helical oil groove 52 is provided on the outer circumferential surface of the bearing 20. This oil groove 52 promotes the flow and exchange of oil within the groove 52, further suppressing heat generation on the sliding surface.

[0062] In the third example shown in Figure 9, two helical oil grooves 53 and 54 are provided on the outer circumferential surface of the bearing 20. The helical pitch of these oil grooves 53 and 54 is the same, but the helical direction is opposite, and these oil grooves 53 and 54 intersect each other at equally spaced positions in the axial direction. These oil grooves 53 and 54 further promote the flow and exchange of oil within the oil grooves 53 and 54, thereby further suppressing heat generation on the sliding surface.

[0063] Figure 10 shows the appearance of the fourth example. In this fourth example, the bearing 20 is provided with a plurality of oil grooves 55 extending parallel to the axial direction on its outer circumferential surface. These oil grooves 55 are arranged at equal intervals in the circumferential direction. These oil grooves 55 also actively retain oil on the outer circumferential surface, thereby suppressing heat generation on the sliding surface.

[0064] In the above example, the depth to of the oil groove (see Figure 7) was made smaller than the thickness t of the bearing 20. However, in the fifth example shown in Figure 11, the depth to of the oil groove 56 is made equal to the thickness t of the bearing 20. That is, the resin forming the bearing 20 is eliminated in the oil groove 56 portion, making it appear as if the bearing 20 is intermittently installed. In this case, by masking the portion that will become the oil groove 56 and coating it with resin, the intermittent bearing 20 can be easily manufactured. Other effects are the same as described above.

[0065] The example shown in Figure 11 is a modification of the first example, but the second to fourth examples can be similarly modified.

[0066] Although not shown in the diagram, as mentioned above, the oil grooves 51-56 described above can also be provided on the inner circumferential surface of the bearing 20 in the first modified example (Figure 6).

[0067] Although embodiments of this disclosure have been described in detail above, various other embodiments and modifications of this disclosure are conceivable.

[0068] (1) For example, the bearing does not have to be integrally mounted with the planetary gear or shaft, and may be mounted separately if the durability requirements are met. In this case, the bearing is slidably fitted into the gap between the planetary gear and the shaft so that there is zero clearance.

[0069] (2) When bearings are integrally mounted on planetary gears or shafts, they can be mounted by methods other than coating. For example, a separate bearing may be integrally fixed to the planetary gear or shaft by adhesive.

[0070] The configurations of each embodiment and each variation described above can be combined in part or in whole, as long as there is no particular contradiction. The embodiments of this disclosure are not limited to those described above, but include any variations, applications, and equivalents that are encompassed within the spirit of this disclosure as defined by the claims. Therefore, this disclosure should not be constrained and may be applied to any other art that falls within the scope of the spirit of this disclosure. [Explanation of Symbols]

[0071] 2 Planetary Gear 4 shafts 20 bearings 51-56 Oil groove 100 Planetary gear mechanism

Claims

1. Planetary Gear and A shaft that rotatably supports the planetary gear, A bearing provided between the planetary gear and the shaft, which is a resin-made radial-type sliding bearing, Equipped with, The radial clearance between the planetary gear and the bearing, and the radial clearance between the shaft and the bearing are set to zero. A planetary gear mechanism characterized by the following features.

2. The bearing is integrally provided on either the planetary gear or the shaft. The planetary gear mechanism according to claim 1.

3. The bearing is formed by a resin coating layer provided on either the planetary gear or the shaft. The planetary gear mechanism according to claim 1.

4. An oil groove is provided on the bearing surface of the bearing. The planetary gear mechanism according to claim 1.

5. The planetary gear and the shaft are made of metal. The planetary gear mechanism according to claim 1.

6. Applicable to machine tools or robots The planetary gear mechanism according to claim 1.

7. A manufacturing method for producing the planetary gear mechanism described in claim 1, The procedure includes coating one of the planetary gear and the shaft with the resin that forms the bearing. A method for manufacturing a planetary gear mechanism characterized by the above.

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