Planetary gear device

Abstract

To provide a planetary gear device capable of permanently supplying lubricating oil between a planetary gear and a planetary shaft with a simple structure.SOLUTION: The oil holding grooves 37a and 37b are formed on the outer peripheral surfaces of the press-fitting portions 31a and 31b, which are press-fitted into the through-holes 35a and 35b of the carriers 24, over the entire lengths of the press-fitting portions 35a and 35b, and the oil holding grooves 35a and communicate with the oil supplying grooves 38 on one side of the press-fitting portions and. 35b 37a 37b, the lubricant L can flow into the oil holding groove 35a, 35b from the space 40a, 40b on the other side of the press-in part 37a, 37b.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a planetary gear device. [Background technology]

[0002] In a typical planetary gear device, planetary gears are rotatably supported on planetary shafts held by a carrier, but because the planetary gears and the carrier are close to each other, there is a problem in that the lubricating oil stored in the casing does not easily reach between the planetary gears and the planetary shafts. To address this problem, it has been proposed to provide an oil reservoir that holds lubricating oil on the inner circumferential surface of the planetary gear (for example, Patent Document 1). It has also been proposed to drill a lubricating oil supply path in the center of the planetary shaft (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-70864 [Patent Document 2] Japanese Patent Publication No. 2022-7748 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, the amount of lubricating oil that can be supplied from the oil reservoir is limited, so the lubrication performance does not last. On the other hand, the configuration of Patent Document 2 allows for a continuous supply of lubricating oil, but requires complex machining of the planetary shaft, making it difficult to adopt unless the device is relatively large or in a high price range.

[0005] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide a planetary gear device that can permanently supply lubricating oil between the planet gears and the planet shafts with a simple configuration. [Means for solving the problem]

[0006] The present invention is a planetary gear device comprising a casing containing a sun gear, an internal gear arranged around the sun gear, planetary gears arranged between the sun gear and the internal gear, planetary shafts that rotatably support the planetary gears, and a carrier that supports at least one end of the planetary shafts, and wherein lubricating oil is stored inside the casing, wherein at least one end of the planetary shafts is press-fitted into a through hole formed in the carrier, and the planetary shafts have an oil supply groove formed on the outer surface of an axial hole fitting portion that fits into the axial hole of the planet gear, which can supply the lubricating oil between the planet gears and the planet shaft, and an oil retention groove filled with the lubricating oil is formed on the outer surface of a press-fit portion that is press-fitted into the through hole, and the oil retention groove is formed over the entire length of the press-fit portion, communicates with the oil supply groove on one side of the press-fit portion, and the lubricating oil can flow in from a space on the other side of the press-fit portion.

[0007] In this configuration, lubricating oil is supplied between the planet gears and planet shafts from the oil supply groove, but the lubricating oil supplied from the oil supply groove is replenished from the oil retention groove, and the oil replenished from the oil retention groove to the oil supply groove flows in from the other side of the press-fit portion, so lubricating oil can be continuously supplied between the planet gears and planet shafts without running out. Furthermore, the oil supply groove and oil retention groove according to the present invention have a simple configuration and can be easily formed on the outer peripheral surface of the planet shaft by rolling, cutting, etc., so they can be suitably used in small and low-cost devices.

[0008] In the present invention, it is proposed that the oil retention groove is configured so as to be able to retain the lubricating oil by capillary force.

[0009] The capillary force acting on the lubricating oil in the Oil Retention Groove is not affected by the orientation of the planetary shaft, so with this configuration, the Oil Retention Groove can be reliably filled with lubricating oil no matter what orientation the planetary gear unit is positioned in. Furthermore, the capillary force acting on the lubricating oil in the Oil Retention Groove is determined based on the cross-sectional area of ​​the Oil Retention Groove, as well as the surface tension, specific gravity, contact angle, etc. of the lubricating oil, so if the cross-sectional area, etc. of the Oil Retention Groove are set appropriately, it is possible to retain lubricating oil throughout the entire length of the Oil Retention Groove by capillary force alone.

[0010] In the present invention, it is also proposed that the planet shaft slides on a slide bearing disposed in a shaft hole of the planet gear, or on the shaft hole of the planet gear.

[0011] In this configuration, the gap between the outer peripheral surface of the planetary shaft and the inner peripheral surface of the sliding bearing or shaft hole is extremely small, making it easy for the lubricating oil to spread throughout the oil supply groove due to capillary force.

[0012] Furthermore, in the present invention, it is proposed that the carrier is arranged on both axial sides of the planetary gear, the planetary shaft is pressed into a through hole formed in the carrier at both ends, the oil retention groove is formed on the outer peripheral surface of the press-fit portion at both ends of the planetary shaft, and the oil supply groove is formed over the entire length of the shaft hole fitting portion and is connected to the oil retention groove on both sides of the shaft hole fitting portion.

[0013] In this configuration, lubricating oil can be supplied to the oil supply groove from both ends of the planetary shaft, so that lubricating oil can be stably supplied to the oil supply groove regardless of the orientation of the planetary shaft. [Effects of the Invention]

[0014] As described above, according to the present invention, a simple configuration makes it possible to continuously supply lubricating oil between the planetary gear and the planetary shaft, thereby making it possible to suitably improve the lubrication performance of small devices and low-priced devices. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing the internal structure of a planetary gear device 1 according to an embodiment. [Figure 2] FIG. 2 is an enlarged view of the X portion in FIG. [Figure 3] 1A is a side view of the planetary shaft 23, and FIG. 1B is a development view of the outer circumferential surface of the planetary shaft 23. FIG. [Figure 4] 1A is a cross-sectional view of the planetary shaft 23 and the like cut at the press-fit portions 35a and 35b, and FIG. 1B is a cross-sectional view of the planetary shaft 23 and the like cut at the shaft hole fitting portion 36. FIG. [Figure 5] 3 is an explanatory diagram showing the supply direction of lubricating oil L. FIG. [Figure 6] 10 is a development view of the outer circumferential surface of the planetary shaft 23, showing modified examples of the oil retention grooves 37a and 37b and the oil supply groove 38. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] The embodiments of the present invention will be described below with reference to the following examples. In the following examples, the through holes according to the present invention correspond to the shaft support holes 31a and 31b of the carrier 24. The spaces on the other side of the press-fit portions according to the present invention correspond to the oil storage spaces 40a and 40b.

[0017] A planetary gear device 1 of this embodiment is used as a reducer. FIG. 1 is a cross-sectional view of the planetary gear device 1 of this embodiment. The planetary gear device 1 includes an input shaft 2, an output shaft 3, and a planetary gear mechanism 4. The planetary gear mechanism 4 is housed in a casing 6, with the input shaft 2 protruding from one side of the casing 6 and the output shaft 3 protruding from the other side of the casing 6. The casing 6 is formed by assembling a first case member 7 on the output shaft 3 side and a second case member 8 on the input shaft 2 side, and a fixing bracket 9 is attached to the second case member 8. The configuration of the planetary gear device 1 is the same as that of existing planetary gear devices, except for the configuration related to the main parts of the present invention, which will be described later.

[0018] The planetary gear mechanism 4 includes a sun gear 20, an internal gear 21 disposed around the sun gear 20, planetary gears 22 disposed between the sun gear 20 and the internal gear 21, planetary shafts 23 that rotatably support each planetary gear 22, and carriers 24 that support both ends of each planetary shaft 23. The sun gear 20 is connected to the input shaft 2, and the carrier 24 is connected to the output shaft 3. The internal gear 21 is fixed inside the casing 6. In the planetary gear mechanism 4, when the sun gear 20 rotates together with the input shaft 2, each planetary gear 22 revolves around the sun gear 20, and the carrier 24 rotates in conjunction with this orbital motion, causing the output shaft 3 to rotate at a slower speed than the input shaft 2.

[0019] The carrier 24 is made of a single metal member. The carrier 24 has shaft support portions 30a, 30b that support one end and the other end of the planetary shaft 23. Although only one pair of the shaft support portions 30a, 30b is shown in Fig. 1, the carrier 4 is provided with three pairs of shaft support portions 30a, 30b around the axis of the planetary gear mechanism 4, and each of the shaft support portions 30a, 30b supports a planetary shaft 23 that pivotally supports a planetary gear 22.

[0020] 2, shaft supports 30a and 30b supporting one end and the other end of the planetary shaft 23 are disposed opposite to each other in the axial direction of the planetary gear 22 across a gap of the tooth width of the planetary gear 22. Shaft support holes 31a and 31b that penetrate the planetary gear 22 in the axial direction are formed in the shaft supports 30a and 30b, respectively. Then, with the planetary gear 22 fitted between the shaft support holes 31a and 31b, the planetary shaft 23 is inserted through the shaft hole 33 of the planetary gear 22 and the shaft support holes 31a and 31b.

[0021] The planetary gear 22 is a spur gear having a round shaft hole 33, and the planetary shaft 23 is a solid round bar. The outer diameter of the planetary shaft 23 is slightly smaller than the inner diameter of the shaft hole 33 of the planetary gear 22, and the planetary shaft 23 is fitted into the shaft hole 33 of the planetary gear 22 without any bearing parts and is configured to slide directly against the inner circumferential surface of the shaft hole 33 of the planetary gear 22. On the other hand, the shaft support holes 31a, 31b are round holes of approximately the same diameter as the planetary shaft 23, and both ends of the planetary shaft 23 are press-fitted into the shaft support holes 31a, 31b, so that the outer circumferential surfaces of the planetary shaft 23 are in close contact with the inner circumferential surfaces of the shaft support holes 31a, 31b.

[0022] As shown in Fig. 1, the planetary gear device 1 has bearings 10, 11, and 12 arranged around the input shaft 2 and carrier 24. As shown in Fig. 2, lubricating oil L is stored in the internal space of the casing 6, and the lubricating oil L is supplied to each part of the planetary gear mechanism 4 by an oil bath lubrication method. The portions where the input shaft 2 and the output shaft 3 pass through the casing 6 are sealed with oil seals 17 and 18 to prevent leakage of the lubricating oil L. There are no particular restrictions on the amount of lubricating oil L filled in the casing 6, but it is preferable that more than 70% of the internal space be filled with the lubricating oil L.

[0023] The essential configuration of the present invention will be described below. As described above, the planetary gear device 1 has the lubricating oil L stored inside the casing 6, and as the planetary gears 22 revolve, the lubricating oil L is supplied to various locations in the planetary gear mechanism 4. Here, as shown in Fig. 2, the shaft support portions 30a, 30b of the carrier 24 are adjacent to both side surfaces of the planetary gears 22, making it difficult to supply the lubricating oil L to the sliding surfaces of the planetary gears 22 and the planet shafts 23 from between the planetary gears 22 and the shaft support portions 30a, 30b. For this reason, this embodiment is configured so that the lubricating oil L inside the casing 6 can be supplied between the planetary gears 22 and the planet shafts 23 through the outer peripheral surfaces of the planet shafts 23.

[0024] Specifically, as shown in FIG. 2, the shaft support holes 31a, 31b of the carrier 24 open on both sides of the shaft support portions 30a, 30b and communicate with oil storage spaces 40a, 40b on the side opposite the planetary gear 22. The oil storage spaces 40a, 40b are spaces in which lubricating oil L is stored to lubricate the planetary gear mechanism 4 using an oil bath lubrication system, and a sufficient amount of lubricating oil is stored in the oil storage spaces 40a, 40b. Furthermore, oil retention grooves 37a, 37b filled with lubricating oil L are formed on the outer peripheral surfaces of the press-fit portions 35a, 35b of the planetary shaft 23 that are press-fitted into the shaft support holes 31a, 31b. Furthermore, an oil supply groove 38 is formed on the outer peripheral surface of the shaft hole fitting portion 36 that fits into the shaft hole 33 of the planetary gear 22 to supply lubricating oil L between the planetary gear 22 and the planetary shaft 23.

[0025] As shown in Figures 3 and 4(A), the oil retention grooves 37a, 37b are recessed grooves with a semicircular cross section that extend linearly in the axial direction of the planetary shaft 23. Eight oil retention grooves 37a, 37b are formed at equal intervals in each press-fit portion 35a, 35b. As shown in Figure 4(A), when press-fitted into the shaft support holes 31a, 31b, the outer peripheral surfaces of the press-fit portions 35a, 35b, excluding the oil retention grooves 37a, 37b, are in tight contact with the inner peripheral surfaces of the shaft support holes 31a, 31b, and the oil retention grooves 37a, 37b are in the form of narrow tubes that are sealed all around.

[0026] 2, each oil retention groove 37a, 37b is formed over the entire length of the press-fit portion 35a, 35b, and communicates with the oil supply groove 38 on one side of the press-fit portion 35a, 35b and with the oil storage spaces 40a, 40b on the other side of the press-fit portion 35a, 35b. Because the oil retention grooves 37a, 37b are tubular, the lubricating oil L flows into the oil retention grooves 37a, 37b from the oil storage spaces 40a, 40b by capillary force and is retained therein. Even when the planetary shaft 23 is positioned vertically, the oil retention grooves 37a, 37b are configured to suck up the lubricating oil L from the oil storage spaces 40a, 40b below by capillary force and retain the lubricating oil L over the entire length of the oil retention grooves 37a, 37b. Since the capillary force is inversely proportional to the cross-sectional area of ​​the thin tube, the capillary force acting on the oil retention grooves 37a and 37b can be set to a required strength by appropriately setting the cross-sectional area of ​​the oil retention grooves 37a and 37b.

[0027] 3 and 4(B), the oil supply grooves 38 are recessed grooves that extend spirally in the axial direction of the planetary shaft 23, and eight oil supply grooves 38 are formed at equal intervals in the shaft hole fitting portion 36. Each oil supply groove 38 is formed over the entire length of the shaft hole fitting portion 36, and communicates with the ends of the oil retention grooves 37a, 37b at both ends of the shaft hole fitting portion 36.

[0028] 4(B), the cross section of the oil supply groove 38 is formed in a semicircular shape of the same size as the oil retention grooves 37a, 37b. Here, because there is a gap 25 between the outer peripheral surfaces of the press-fit portions 35a, 35b and the inner peripheral surface of the axial hole 33, the oil supply groove 38 is not in the form of a sealed capillary tube, but because the gap 25 is extremely small, the lubricating oil L is supplied from the oil retention grooves 37a, 37b into the oil supply groove 38 by capillary force, and the lubricating oil L is retained inside the oil supply groove 38 throughout its entire length.

[0029] In this configuration, when the lubricating oil L in the gap 25 between the planetary gear 22 and the planetary shaft 23 decreases, the lubricating oil L held in the oil supply groove 38 flows out into the gap 25, replenishing the lubricating oil L in the gap 25, thereby preventing oil shortage on the sliding surfaces. Then, when the lubricating oil L flows out from the oil supply groove 38, the leaked lubricating oil L is replenished by capillary force or the like from the lubricating oil L held in the oil retention grooves 37a, 37b on both sides, as shown in Fig. 5. Then, the lubricating oil L replenished to the oil supply groove 38 from the oil retention grooves 37a, 37b is replenished from the oil storage spaces 40a, 40b to the oil retention grooves 37a, 37b by capillary force or the like, so that the oil retention grooves 37a, 37b are maintained in a state filled with lubricating oil L.

[0030] In this way, in this embodiment, when lubricating oil L is supplied from the oil supply groove 38 between the planetary gear 22 and the planetary shaft 23, the supplied amount of lubricating oil L is replenished from the oil retention grooves 37a, 37b, and the amount of lubricating oil replenished from the oil retention groove 38 to the oil supply grooves 37a, 37b is replenished from the oil storage spaces 40a, 40b, so that lubricating oil can be continuously supplied between the planetary gear 22 and the planetary shaft 23 without running out of lubricating oil.

[0031] Furthermore, the oil retention grooves 37a, 37b and the oil supply groove 38 of this embodiment have a simple configuration and can be easily formed by rolling, cutting, or the like, making them suitable for improving the lubrication performance of small planetary gear devices and low-priced planetary gear devices.

[0032] Furthermore, the oil retention grooves 37a, 37b in this embodiment are configured to be able to retain the lubricating oil L over their entire length by capillary force, so that the inside of the oil retention grooves 37a, 37b can be reliably filled with the lubricating oil L regardless of the orientation of the planetary shaft 23.

[0033] Furthermore, in this embodiment, the planetary shaft 23 slides directly against the axial hole 33 of the planetary gear 22 without any bearing parts, and the gap 25 between the outer surface of the planetary shaft 23 and the inner surface of the axial hole 33 is extremely small, so that the lubricating oil L can be spread throughout the entire oil supply groove 38 by capillary force and retained inside the oil supply groove 38.

[0034] Furthermore, this embodiment has the advantage that the supply of lubricating oil L to the oil retention grooves 37a, 37b and the oil supply groove 38 can continue due to capillary force even when the planetary gear mechanism 4 is stopped.

[0035] In addition, in this embodiment, the oil supply groove 38 is connected to the oil retention grooves 37a, 37b on both sides of the planetary shaft 23, and lubricating oil L is supplied to the oil supply groove 38 from the oil retention grooves 37a, 37b on both sides, so that lubricating oil L can be stably supplied to the oil supply groove 38 regardless of the orientation of the planetary shaft 23.

[0036] <Evaluation test> The durability of the planetary gear device 1 of the embodiment was evaluated using as a comparative example a planetary gear device having the same configuration as the embodiment except that it does not have the oil retention grooves 37a, 37b and the oil supply groove 38. Specifically, the durability of the planetary gear device 1 of the embodiment was evaluated using a surface pressure of 7.88 N / mm 2 An acceleration test was carried out under the condition of a sliding speed of 0.18 m / sec, and the durability time (time until seizure occurs) of the example and the comparative example was compared.

[0037] As a result of the evaluation test, the durability of the example was 3.5 times or more that of the comparative example. This result shows that by forming the oil retention grooves 37a, 37b and the oil supply groove 38 in the planetary shaft 23, the life of the planetary gear device can be significantly extended.

[0038] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate within the scope of the present invention.

[0039] For example, the shape of the oil supply groove 38 according to the present invention is not limited to a spiral shape and can be variously modified. For example, it may be a mesh shape as shown in FIG. 6(A) or a bent shape as shown in FIG. 6(B). The shapes of the oil retention grooves 37a and 37b according to the present invention are not limited to a linear shape along the axial direction and can be variously modified. For example, it may be a mesh shape as shown in FIG. 6(C) or a spiral shape as shown in FIG. 6(D). The oil retention grooves 37a and 37b according to the present invention and the oil supply groove 38 may have the same shape as shown in FIGS. 6(C) and 6(D). The oil retention groove 37a according to the present invention may be formed in only one press-fitting portion 35a as shown in FIG. 6(E). The oil supply groove 38 according to the present invention does not have to be formed over the entire length of the shaft hole fitting portion 36 as shown in FIG. 6(E). 6(F), the oil retention groove 37a in the press-fit portion 35a on one side and the oil retention groove 37b in the press-fit portion 35b on the other side may communicate with different oil supply grooves 38. In the above embodiment, eight oil retention grooves 37a, 37b and eight oil supply grooves 38 are formed on the outer circumferential surface of the planetary shaft 23, but it is sufficient that one or more oil retention grooves 37a, 37b and one or more oil supply grooves 38 are formed on the planetary shaft 23.

[0040] Furthermore, although the oil retention grooves 37a, 37b and the oil supply groove 38 in the embodiment have semicircular cross sections, there are no particular limitations on the cross-sectional shapes of the oil retention grooves 37a, 37b and the oil supply groove 38, and they may be triangular or rectangular. Furthermore, the cross-sectional shapes and cross-sectional areas of the oil retention grooves 37a, 37b and the oil supply groove 38 do not need to be constant and may vary depending on the location.

[0041] Furthermore, although the above embodiment is configured such that the planetary gear 22 and the planetary shaft 23 slide directly against each other, the present invention can also be applied to a configuration in which bearing parts such as sliding bearings or rolling bearings are disposed between the planetary gear 22 and the planetary shaft 23.

[0042] In addition, in the above embodiment, both sides of the planetary shaft 23 are press-fitted into the carrier 24, but only one side of the planetary shaft 23 may be press-fitted into the shaft support holes 31a, 31b of the carrier 24. Furthermore, the tip of the planetary shaft 23 press-fitted into the shaft support holes 31a, 31b may penetrate the shaft support portions 30a, 30b and protrude into the oil storage spaces 40a, 40b. Furthermore, although the carrier 24 in the embodiment is a single metal member, the carrier 24 may be composed of multiple members.

[0043] In addition, in the planetary gear device of the present invention, in addition to the oil retention grooves 37a, 37b and the oil supply groove 38, it is possible to provide a structure such as an oil reservoir for supplying lubricating oil L between the planet gear 22 and the planet shaft 23. [Explanation of symbols]

[0044] 1 Planetary gear unit 2 input shafts 3 output shaft 4 Planetary gear mechanism 6 Casing 7 First case member 8 Second case member 9 Bracket 10~12 bearings 15,16 Opening 17,18 Oil seal 20 Sun Gear 21 Internal gear 22 Planetary gear 23 Planetary shaft 24 Career 25 Gap 30a, 30b Shaft support portion 31a, 31b Shaft support hole (through hole) 33 Shaft hole 35a, 35b press-fit portion 36 Shaft hole fitting part 37a,37b Oil retaining groove 38 Oil supply groove 40a, 40b Oil storage space

Claims

1. The sun gear and an internal gear disposed around the sun gear; a planetary gear disposed between the sun gear and the internal gear; a planetary shaft that rotatably supports the planetary gear; a carrier that supports at least one end of the planetary shaft; The casing is provided with A planetary gear device in which lubricating oil is stored inside the casing, At least one end of the planetary shaft is press-fitted into a through hole formed in the carrier, The planetary shaft an oil supply groove capable of supplying the lubricating oil between the planet gear and the planet shaft is formed on an outer peripheral surface of a shaft hole fitting portion that fits into the shaft hole of the planet gear; an oil retention groove filled with the lubricating oil is formed on an outer peripheral surface of a press-fit portion press-fitted into the through hole, the oil retention groove is formed over the entire length of the press-fit portion, communicates with the oil supply groove on one side of the press-fit portion, and allows the lubricating oil to flow in from a space on the other side of the press-fit portion.

2. 2. The planetary gear device according to claim 1, wherein the oil retention groove is configured to retain the lubricating oil by capillary force.

3. 3. The planetary gear device according to claim 1, wherein the planet shaft slides on a plain bearing disposed in a shaft hole of the planet gear, or on the shaft hole of the planet gear.

4. the carriers are disposed on both axial sides of the planetary gears, The planetary shaft is press-fitted at both ends into through holes formed in the carrier, The oil retention groove is formed on the outer circumferential surface of the press-fit portion on both ends of the planetary shaft, 3. The planetary gear device according to claim 1, wherein the oil supply groove is formed over the entire length of the shaft hole fitting portion and communicates with the oil retention groove on both sides of the shaft hole fitting portion.

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