Planetary gear reducer

Abstract

Provided is a gear reducer that has high rigidity and can suppress the occurrence of vibration and noise. Provided is a planetary gear reducer (W1) provided with: an input shaft (10) having a first eccentric part (12) and a second eccentric part (14), which form a pair; a stationary sun gear (20) comprising an external gear provided coaxially with the input shaft (10); a first planetary gear (30) having an internal gear that meshes with the stationary sun gear (20) and provided on the first eccentric part (12); a driven sun gear (40) disposed coaxially with the axis of rotation of the input shaft (10) and comprising an external gear that outputs a speed reducing output; a second planetary gear (70) that has an internal gear that meshes with the driven sun gear (40), is configured to have a gear ratio different from that of the first planetary gear (30), and can receive eccentric input from the second eccentric part (14); and a coupling member (60) of a crankshaft disposed between the first planetary gear (30) and the second planetary gear (70). The coupling member (60) moves the planetary gears integrally with each other so that the same work as counterweights, and restricts the rotation of the planetary gears.

Description

Planetary gear reducer

[0001] The present invention relates to a planetary gear reducer, and more particularly to a hypocycloid reducer.

[0002] A planetary gear reducer can achieve a high speed reduction ratio with a single stage and is small and lightweight, but has a large number of parts, making the structure complex and causing concerns about rigidity (Patent Document 1).

[0003] On the other hand, there is a reducer that uses a 2K-H type planetary gear mechanism (Patent Document 2). The planetary gear mechanism in Patent Document 2 uses two sets of combinations of an internal gear and an external gear that meshes with it, and has high rigidity with a small number of gears used, and can also significantly reduce speed in a single stage.

[0004] JP 2012-97903 A JP 2017-106596 A

[0005] However, the speed reducer of Patent Document 2 has a problem in that the center of gravity of the planetary gear is offset from the center of rotation of the input shaft, which makes it prone to vibration and noise. Adding many parts to address this problem would only lead to complexity and a loss of rigidity, which would defeat the purpose.

[0006] The present invention has been made in view of this, and provides a reducer that has high rigidity and can suppress the generation of vibration and noise.

[0007] In order to solve the above problems, in one aspect of the present disclosure, there is provided an input shaft having a pair of first and second eccentric portions, a fixed sun gear consisting of an external gear provided coaxially with the input shaft, a first planetary gear having an internal gear that meshes with the fixed sun gear and provided on the first eccentric portion of the input shaft, a driven sun gear consisting of an external gear that is disposed coaxially with the rotation axis of the input shaft and outputs a reduced output, and an internal gear that meshes with the driven sun gear and is configured with a gear ratio different from that of the first planetary gear, and a connecting member disposed between the first planetary gear and the second planetary gear, wherein the connecting member is configured such that the central axis of one end is offset from the central axis of the other end, and the one end is rotatably supported by the first planetary gear and the other end is rotatably supported by the second planetary gear, so that the first planetary gear and the second planetary gear move together as a unit and the rotation of the second planetary gear is restricted.

[0008] According to this aspect, the first planetary gear and the second planetary gear rotate in opposite phases due to the connecting member, and act as counterweights to each other. This makes it possible to suppress the generation of vibration and noise. Furthermore, the reducer configured as described above has a small number of parts and can maintain high rigidity.

[0009] According to another aspect, the second planetary gear is arranged in the opposite phase to the first planetary gear so that the eccentricity of the internal gear of the second planetary gear is in the same phase and with the same amount of eccentricity as the second eccentric portion, and the second planetary gear is configured to accept the rotation of the second eccentric portion via the connecting member.

[0010] According to one aspect, the connecting member is provided on the second eccentric portion, and one end is arranged circumferentially inside the first planetary gear and rotatably supported, and the other end is arranged circumferentially outside the second planetary gear and rotatably supported.

[0011] According to another aspect, the internal gear of the first planetary gear and the internal gear of the second planetary gear are configured based on a trochoid curve, and the difference in the number of teeth between the first planetary gear and the fixed sun gear, and between the second planetary gear and the driven sun gear, is configured to be an integer of 2 or greater and to have a meshing ratio of 2 or greater. According to this aspect, it is possible to ensure both quietness and a good meshing ratio.

[0012] As is clear from the above description, a reducer that has high rigidity and can suppress the generation of vibration and noise is provided.

[0013] FIG. 1 is a perspective view (partially cut away) of a reducer according to the configuration of the present disclosure. FIG. 2 is a cross-sectional view of a reducer according to the configuration of the present disclosure. FIG. 3 is an exploded front perspective view of the reducer. FIG. 4 is an exploded rear perspective view of the reducer. FIG. 5 is a skeleton diagram showing the configuration of the reducer. FIG. 6 shows a fixed sun gear. FIG. 6(A) is a front view of the fixed sun gear. FIG. 6(B) is a side view of the fixed sun gear. FIG. 6(C) is a cross-sectional view of the fixed sun gear. FIG. 7 shows an input shaft. FIG. 7(A) is a front view of the input shaft. FIG. 7(B) is a side view of the input shaft. FIG. 7(C) is a rear view of the input shaft. FIG. 8 shows a driven sun gear. FIG. 8(A) is a front view of the driven sun gear. FIG. 8(B) is a side view of the driven sun gear. FIG. 8(C) is a cross-sectional view of the driven sun gear. FIG. 9 shows a first planetary gear. FIG. 10(A) is a front view of the first planetary gear. FIG. 10(B) is a side view of the first planetary gear. FIG. 10(C) is a cross-sectional view of the first planetary gear. 9(D) is a rear view of the first planetary gear. It shows a connecting member. 10(A) is a front view of the connecting member. 10(B) is a side view of the connecting member. 10(C) is a cross-sectional view of the connecting member. 10(D) is a rear view of the connecting member. It shows a second planetary gear. 11(A) is a side view of the second planetary gear. 11(B) is a cross-sectional view of the second planetary gear. 11(C) is a rear view of the second planetary gear. It is a cross-sectional view taken along line A-A in FIG. 2. It mainly shows the driven sun gear and the first planetary gear. It is a cross-sectional view taken along line B-B in FIG. 2. It mainly shows the first planetary gear and the first shaft of the connecting member. It is a cross-sectional view taken along line CC in FIG. 2. It mainly shows the second shaft of the connecting member, the second planetary gear, and the driven sun gear. It is a skeleton diagram of a modified example.

[0014] Specific embodiments of the present invention will be described below with reference to the drawings. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. In addition, in the following description of the embodiments and modifications, the same components are designated by the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0015] (Embodiment) Fig. 1 is a perspective view (partially cutaway) of a reducer W1 according to the configuration of the present disclosure. Fig. 2 is a cross-sectional view of the reducer W1. Fig. 3 is an exploded front perspective view of the reducer W1. Fig. 4 is an exploded rear perspective view of the reducer W1. Fig. 5 is a skeleton diagram showing the configuration of the reducer W1. Note that in each drawing, directions are described with the output shaft side as the front (FR) and the input shaft side as the rear (RE) based on the input shaft and output shaft (driven sun gear) arranged side by side in the axial direction of the reducer W1.

[0016] 1 to 5, the reducer W1 is a 2K-H type hypocycloid reducer having a planetary gear mechanism. The reducer W1 mainly includes an input shaft 10, a fixed sun gear 20, a first planetary gear 30, a driven sun gear 40, a housing 50, a connecting member 60, and a second planetary gear 70.

[0017] 2, the reducer W1 is mounted on a wheel drive unit of a vehicle and is interposed between a motor M and a wheel hub H. The reducer W1 has an input shaft 10 as an input shaft and a driven sun gear 40 as an output shaft, and the rotation of the input shaft 10 is reduced and output from the driven sun gear 40.

[0018] The input shaft 10 is inserted into the motor M, and is rotated by the rotation of the motor M. The driven sun gear 40 is connected to a wheel hub H to which a wheel (not shown) is connected, and the rotation of the driven sun gear 40 is transmitted to the wheel through the wheel hub H. The rotation of the motor M is reduced in speed by a reducer W1 and transmitted to the wheel, causing the wheel to rotate. The input shaft 10 may be directly driven as a rotating shaft on the motor M side, or may be connected to a rotating shaft of the motor M and driven. Similarly, in addition to the configuration in which the driven sun gear 40 is directly connected to the wheel hub H to transmit driving force, a configuration in which a transmission shaft is provided to be connected to the driven sun gear 40 and connected to the wheel hub H via the transmission shaft to drive the wheel may also be used.

[0019] (Housing) The fixed sun gear 20 is made up of a housing cover portion 21 and a fixed sun gear main body 22. The housing cover portion 21, together with the housing 50, constitutes the housing of the reducer W1.

[0020] The housing 50 is composed of a cylindrical portion 51 having a substantially cylindrical shape and an end face 52 that closes one end of the cylindrical portion 51. A substantially disk-shaped housing cover portion 21 is attached with bolts (not shown) so as to close the opening of the cylindrical portion 51 (the end opposite the end face 52). Each component is held in the substantially cylindrical internal space defined thereby.

[0021] A portion of the input shaft 10 is inserted into and rotatably held in a bearing hole 28 provided in the center of the housing cover portion 21. A portion of the driven sun gear 40, which is provided coaxially with the input shaft 10, is inserted into and rotatably held in a bearing hole 58 provided in an end face 52 of the housing 50.

[0022] (Fixed Sun Gear) The configuration of the fixed sun gear 20 will be described with reference to Fig. 6. Fig. 6 shows the fixed sun gear 20. Fig. 6(A) is a front view of the fixed sun gear 20. Fig. 6(B) is a side view of the fixed sun gear 20. Fig. 6(C) is a cross-sectional view of the fixed sun gear 20.

[0023] As described above, the fixed sun gear 20 is made up of the housing cover portion 21 and the fixed sun gear main body 22. The fixed sun gear 20 is formed integrally with the substantially disk-shaped housing cover portion 21 and the ring-shaped fixed sun gear main body 22, which has a smaller diameter than the housing cover portion 21, arranged side by side in the axial direction with their axes aligned. The fixed sun gear main body 22 is provided on the surface of the housing cover portion 21 facing the housing 50. When the housing cover portion 21 is fastened to the housing 50, the fixed sun gear main body 22 is positioned inside the housing.

[0024] A plurality of screw holes 29 are formed at equal intervals on the same circumference on the side edge of the housing cover portion 21. Bolts (not shown) are inserted into these screw holes 29 and fastened to openings in the housing 50, thereby fixing the fixed sun gear 20 in place.

[0025] The fixed sun gear main body 22 is an external gear with an external gear G1 formed on its ring-shaped outer circumferential surface. The fixed sun gear main body 22 is a trochoid gear that uses a trochoid curve in its gear shape and is a spur gear with tooth traces cut parallel to the axis.

[0026] Not only the fixed sun gear main body 22, but all the gears of the reducer W1 are spur gears using a trochoid curve. Trochoid gears have a better meshing ratio and a smaller slip ratio than involute gears. In this embodiment, a meshing ratio of 2 or more is ensured for each gear, ensuring both a high meshing ratio and quiet operation. Note that spur gears are not essential; helical gears or cogwheels may be used to increase the meshing ratio.

[0027] (Input Shaft) The configuration of the input shaft 10 will be described with reference to Fig. 7. Fig. 7 shows the input shaft 10. Fig. 7(A) is a front view of the input shaft 10. Fig. 7(B) is a side view of the input shaft 10. Fig. 7(C) is a rear view of the input shaft 10.

[0028] As shown in Figure 7, the input shaft 10 has a connecting shaft portion 11, a first eccentric portion 12, a spacer portion 13, a second eccentric portion 14, and a support shaft portion 15, each of which is configured as an approximately cylindrical column, and these are arranged in order in the axial direction and formed integrally.

[0029] The connecting shaft 11 constitutes one end of the input shaft 10. The tip side of the connecting shaft 11 protrudes from a bearing hole 28 in the housing cover part 21 and is inserted into and fixed to the motor M. The base end side of the connecting shaft 11 is supported in the bearing hole 28 of the fixed sun gear 20 via a bearing BR1, so that the input shaft 10 is rotatably supported by the fixed sun gear 20.

[0030] The first eccentric portion 12 is provided eccentric by an input shaft eccentricity amount e1 with respect to the central axis X, which is the rotational axis of the input shaft 10. When the input shaft 10 rotates, the first eccentric portion 12 rotates about a first eccentricity center X1 while being eccentric from the central axis X by the input shaft eccentricity amount e1.

[0031] The spacer portion 13 is thin and has an expanded diameter and is provided between the first eccentric portion 12 and the second eccentric portion 14, and serves as a spacer to guide the arrangement of the bearings of the first eccentric portion 12 and the second eccentric portion 14 and to prevent interference and friction between parts when the input shaft 10 rotates.

[0032] The second eccentric portion 14 is eccentric with respect to the central axis X by the input shaft eccentricity amount e1 and is provided at a phase that is 180 degrees different from that of the first eccentric portion 12. When the input shaft 10 rotates, the second eccentric portion 14 rotates about a second eccentric center X2, which is the rotation center of the second eccentric portion 14, while being eccentric from the central axis X by the input shaft eccentricity amount e1.

[0033] The amount of eccentricity of the first eccentric portion 12 is equal to the amount of eccentricity of the second eccentric portion 14, and the first eccentric portion 12 and the second eccentric portion 14 are arranged in opposite phases, and the first eccentric portion 12 and the second eccentric portion 14 are arranged in a pair on the input shaft 10.

[0034] The support shaft 15 constitutes the other end of the input shaft 10. The support shaft 15 is engaged with a circular recess 48 provided in the center of one end (rear side) of the driven sun gear 40 via a bearing BR2, with the rotational axis of the driven sun gear 40 aligned (see FIG. 2). As a result, the input shaft 10 and the driven sun gear 40 are coupled to each other so that their rotational axes are aligned and they can rotate relative to each other.

[0035] (Driven Sun Gear) The configuration of the driven sun gear 40 will be described with reference to Fig. 8. Fig. 8 shows the driven sun gear 40. Fig. 8(A) is a front view of the driven sun gear 40. Fig. 8(B) is a side view of the driven sun gear 40. Fig. 8(C) is a cross-sectional view of the driven sun gear 40.

[0036] The driven sun gear 40 is formed integrally with a cylindrical output shaft portion 41 and a generally disk-shaped driven sun gear main body 42 that is larger in diameter than the output shaft portion 41, with their central axes aligned in the axial direction. The driven sun gear 40 is arranged with the driven sun gear main body 42 side facing the input shaft 10 side.

[0037] The output shaft 41 is inserted into a bearing hole 58 formed in the center of an end face 52 of the housing 50, with its tip protruding outside the housing 50 and rotatably held via a collar C1. The end face 52 of the housing 50 has a protrusion 53 formed by extending the peripheral wall of the bearing hole 58 from the surface of the end face 52. The output shaft 41 is disposed in the bearing hole 58 extended by the protrusion 53, so that the driven sun gear 40 is stably held in the housing 50 and rotatably. Note that although the collar C1 is used for the output shaft 41 as a bearing for a location requiring rigidity where a shear load is applied, a bearing may also be used for the bearing.

[0038] A wheel hub H is connected to the output shaft portion 41 that protrudes from the housing 50, and rotation input from the input shaft 10 is reduced and output from the driven sun gear 40, causing the wheel connected to the wheel hub H to rotate. A key groove is formed in the inner hole 43 of the cylindrical output shaft portion 41, and the wheel hub H is fitted into the outer circumferential surface of the output shaft portion 41 and the inner hole 43 for connection.

[0039] The driven sun gear body 42 is disposed within the housing. A circular recess 48 is formed in the center of the end face of the driven sun gear body 42 for coupling with the input shaft 10. The support shaft portion 15 of the input shaft 10 is fitted into the circular recess 48 via a bearing BR6, and the two are coupled to each other so as to be rotatable about the central axis X.

[0040] The driven sun gear main body 42 is an external gear with the external gear G3 formed on the outer circumferential surface of a substantially circular disk shape. The rotational input received by the driven sun gear main body 42 causes the driven sun gear 40 to rotate (spin) about the central axis X.

[0041] (First Planetary Gear) The configuration of the first planetary gear 30 will be described with reference to Fig. 9. Fig. 9(A) is a front view of the first planetary gear 30. Fig. 9(B) is a side view of the first planetary gear 30. Fig. 9(C) is a vertical cross-sectional view of the first planetary gear 30. Fig. 9(D) is a rear view of the first planetary gear 30. See also the perspective views of the first planetary gear 30 shown in Figs. 3 and 4.

[0042] The first planetary gear 30 has a flat, generally cylindrical outer shape with an axial length shorter than its circumferential length. A bearing hole 38 is formed in the center of the generally cylindrical first planetary gear 30, penetrating it in the axial direction, into which the first eccentric portion 12 of the input shaft 10 is inserted via a bearing BR2. As a result, the first planetary gear 30 is mounted on the first eccentric portion 12, and when the input shaft 10 rotates, the first planetary gear 30 receives an eccentric input from the first eccentric portion 12.

[0043] The input shaft side (rear) of the first planetary gear 30 constitutes a first planetary gear main body 35. An internal gear G2 that meshes with the fixed sun gear main body 22 is provided on the inner peripheral side surface of a rear circular recess 31 provided in the center of the rear end face of the first planetary gear 30. The number of teeth of the first planetary gear main body 35 is configured to be two or more more than the number of teeth of the fixed sun gear 20.

[0044] The output shaft side (front) of the first planetary gear 30 constitutes a holding portion 39. A front circular recess 32 is provided on the end face of the holding portion 39, which is the front end face of the first planetary gear 30, and is provided in communication with the bearing hole 38. The front circular recess 32 is eccentric to the bearing hole 38 and is provided with a diameter that is significantly larger than the bearing hole 38. One end of a connecting member 60 is rotatably supported in the front circular recess 32, which is inside the holding portion 39.

[0045] (Connecting member) The configuration of the connecting member 60 will be described with reference to Fig. 10. Fig. 10(A) is a front view of the connecting member 60. Fig. 10(B) is a side view of the connecting member 60. Fig. 10(C) is a vertical cross-sectional view of the connecting member 60. Fig. 10(D) is a rear view of the connecting member 60. The thick light ink line indicates the central axis of the connecting member 60.

[0046] The connecting member 60 is formed integrally by arranging two circular plates, one large and one small, side by side in the axial direction with the central axes of the circular outer plates offset.

[0047] The connecting member 60 is arranged between the first planetary gear 30 and the second planetary gear 70, with the first shaft body 61, which is a circular plate with a small diameter, facing the first planetary gear 30 and the second shaft body 62, which is a circular plate with a large diameter, facing the second planetary gear 70.

[0048] The connecting member 60 has a circular through-hole formed as a bearing hole 68 that extends in the axial direction and is eccentric to the center of the disk-shaped outer shape of the first shaft body 61. The center line of the bearing hole 68 is defined as a connecting member center X4.

[0049] The connecting member 60 is rotatably supported on the second eccentric portion 14 via the bearing BR3 by inserting the second eccentric portion 14 of the input shaft 10 into the bearing hole 68. That is, when the connecting member 60 is disposed in the reducer W1, the connecting member 60 is supported with the connecting member center X4 coinciding with the second eccentric center X2 (connecting member center X4 = second eccentric center X2), and rotates eccentrically around the second eccentric center X2 of the second eccentric portion 14.

[0050] A circular fitting recess 65 is formed in the second shaft 62 of the connecting member 60, recessed in the axial direction from the end face. The fitting recess 65 communicates with a bearing hole 68, and is provided eccentrically with respect to the bearing hole 68.

[0051] If the central axis of the outer circumferential surface of the first shaft body 61 is defined as a first connecting axis a1, the first connecting axis a1 is provided away from the connecting member center X4 by a first offset amount d1.

[0052] If the central axis of the inner surface of the mating recess 65 of the second shaft body 62 is defined as the second connecting axis a2, the second connecting axis a2 is positioned 180 degrees out of phase with the first shaft body 61, away from the connecting member center X4 by a second offset amount d2.

[0053] The connecting member 60 is supported by the second eccentric portion 14 through the bearing hole 68, with the first shaft body 61 rotatably supported by the first planetary gear 30 and the second shaft body 62 rotatably supported by the second planetary gear 70.

[0054] Specifically, the first shaft 61 fits inside the front circular recess 32 of the first planetary gear 30, and its outer circumferential surface is supported via a bearing BR4. A disk-shaped second planetary gear 70 is rotatably fitted inside the fitting recess 65 of the second shaft 62 via a bearing BR5. The first planetary gear 30 and the first shaft 61, and the second planetary gear 70 and the second shaft 62 are supported so as to be able to rotate relative to each other. The first shaft 61 is disposed circumferentially inside the first planetary gear 30 and rotatably supported, and the second shaft 62 is disposed circumferentially outside the second planetary gear 70 and rotatably supported.

[0055] The rotation center of the first shaft body 61 is the first connecting shaft a1, and the rotation center of the second shaft body 62 is the second connecting shaft a2. The first connecting shaft a1 and the second connecting shaft a2 are configured to be offset from each other in parallel.

[0056] (Second Planetary Gear) The configuration of the second planetary gear 70 will be described with reference to Fig. 11. Fig. 11(A) is a side view of the second planetary gear 70. Fig. 11(B) is a cross-sectional view of the second planetary gear 70. Fig. 11(C) is a rear view of the second planetary gear 70.

[0057] The second planetary gear 70 is an internal gear having a generally disk-shaped outer shape, with an internal gear G4 that meshes with the driven sun gear main body 42 of the driven sun gear 40 provided on the inner peripheral surface of a through hole 71 that penetrates the second planetary gear 70 in the axial direction. The number of teeth of the second planetary gear 70 is two or more more than the number of teeth of the driven sun gear 40, and is different from the number of teeth of the first planetary gear 30. In other words, the first planetary gear 30 and the second planetary gear 70 are configured to have different gear ratios.

[0058] The through hole 71 of the second planetary gear 70 is provided eccentrically with respect to the center of the substantially disk-shaped outer shape.

[0059] As described above, the second planetary gear 70 is rotatably disposed via the bearing BR5, with its outer peripheral surface supported inside the fitting recess 65 of the connecting member 60. To ensure stable disposition, a flange portion 74 is provided at the opening of the second planetary gear 70.

[0060] The second planetary gear 70 is an internal gear, and the driven sun gear body 42 is disposed in the through hole 71 so as to mesh with the driven sun gear body 42 which is an external gear.

[0061] As shown in FIG. 2 , the second shaft 62 is disposed on the outer periphery of the second planetary gear 70, and the driven sun gear main body 42 is disposed on the inner periphery of the second planetary gear 70. The second planetary gear 70 is disposed circumferentially sandwiched between the connecting member 60 and the driven sun gear 40. The eccentric direction of the second planetary gear 70 is disposed in the opposite phase to that of the first planetary gear 30. If the center line of the through hole 71 is the second planetary gear center X5, the second planetary gear center X5 is disposed to coincide with the second eccentric center X2 when disposed in the reducer W1 (second planetary gear center X5 = second eccentric center X2). That is, the second planetary gear 70 is disposed in the reducer W1 so that the eccentricity of the internal gear is in phase with and the same amount of eccentricity as the second eccentric portion 14 with respect to the central axis X.

[0062] (Function of the connecting member) The function of the connecting member 60 will be explained with reference to Figure 2. The eccentricity direction of each component of the reducer W1 is configured to be arranged on a straight line, although there may be a difference in positive or negative (direction) with respect to the central axis X. In Figure 2, the eccentricity direction of each component is the up-down direction, and in this explanation, the eccentricity direction will be referred to as the up-down direction with respect to the central axis X. The thick light-ink line in Figure 2 indicates the central axis of the connecting member 60.

[0063] The following description will focus on the rotation axes of each component. The input shaft 10 has a pair of eccentric portions, a first eccentric portion 12 and a second eccentric portion 14. The first eccentric portion 12 is provided eccentrically upward by an input shaft eccentricity amount e1 with respect to the central axis X, which is the rotation axis of the input shaft 10. The second eccentric portion 14 is provided eccentrically downward by an input shaft eccentricity amount e1 with respect to the central axis X, which is the rotation axis of the input shaft 10.

[0064] Since the first planetary gear 30 is provided in the first eccentric portion 12, the first planetary gear 30 rotates around the first eccentric center X1, which is the rotation center of the first eccentric portion 12, while being eccentric upward from the central axis X by the input shaft eccentricity amount e1.

[0065] Since the connecting member 60 is provided on the second eccentric portion 14, the connecting member 60 rotates around the second eccentric center X2 while being eccentric downward from the central axis X by the input shaft eccentricity amount e1.

[0066] Since the first eccentric portion 12 and the second eccentric portion 14 are provided in opposite phases, the connecting member 60 rotates in the opposite phase to the first planetary gear 30 .

[0067] A first shaft 61, which is one (rear) end of the connecting member 60, is provided eccentrically on the first planetary gear 30 and engages with the front circular recess 32. The first shaft 61 is provided largely eccentrically with respect to the connecting member center X4 (= second eccentric center X2), and when the first shaft 61 is engaged with the first planetary gear 30, the first connecting shaft a1 is positioned above the first eccentric center X1.

[0068] At this time, since the second connecting shaft a2 of the second shaft body 62 is arranged eccentrically downward relative to the connecting member center X4 (= second eccentric center X2), the second connecting shaft a2 is positioned further downward than the second eccentric center X2.

[0069] When the second planetary gear 70 is disposed in the through hole 71 of the second shaft 62, the second planetary gear center X5 of the second planetary gear 70 coincides with the second eccentric center X2. The second planetary gear 70 receives eccentric rotation about the second eccentric center X2 via the connecting member 60.

[0070] As shown by the thick, light-inked line in Figure 2, the central axis of the connecting member 60 is crank-shaped, and although the external shape of the connecting member 60 is generally disk-shaped, the connecting member 60 functions as a crankshaft. The central axis of the first shaft 61 of the connecting member 60 is the first connecting axis a1, and the rotation axis (first eccentric center X1) of the first planetary gear 30 connected to the first shaft 61 does not coincide with the first connecting axis a1, so that the rotation of the first planetary gear 30 is restricted. Similarly, the central axis of the second shaft of the connecting member 60 is the second connecting axis a2, and the rotation axis (second eccentric center X2) of the second planetary gear 70 connected to the second shaft 62 does not coincide with the second connecting axis a2, so that the rotation of the second planetary gear 70 is also restricted.

[0071] The connecting member 60 rotates eccentrically about the second eccentric center X2, but only rotates on its axis and does not revolve. The second planetary gears 70, which receive rotational input via the connecting member 60, are restricted from rotating on their axes and only revolve. When the first planetary gears 30 are rotated on their axes by the fixed sun gear 20, the second planetary gears 70 rotate in conjunction with it.

[0072] The amount of eccentricity between the first planetary gear 30 and the connecting member 60 is configured to be equal to the amount of eccentricity between the second planetary gear 70 and the connecting member 60. In other words, the distance from the first eccentric center X1, which is the central axis of the first planetary gear on the first shaft 61, to the first connecting axis a1 is configured to be equal to the distance from the second eccentric center X2, which is the central axis of the second planetary gear on the second shaft 62, to the second connecting axis a2. In other words, the first connecting axis a1 and the second connecting axis a2 are configured to be equal to each other with respect to the central axis X (d1 - e1 = d2 + e1).

[0073] With the above-described configuration, the connecting member 60 allows the first planetary gear 30 and the second planetary gear 70 to move together, and also restricts the rotation of the first planetary gear 30 and the second planetary gear 70 on their axes.

[0074] The connecting member 60 is disposed between the first planetary gear 30 and the second planetary gear 70, and both ends are supported by the first planetary gear 30 and the second planetary gear 70, integrally connecting the first planetary gear 30 and the second planetary gear 70. Because the second planetary gear 70 is disposed in the opposite phase to the first planetary gear 30, the first planetary gear 30 and the second planetary gear 70 act as counterweights that rotate in opposite phases to each other, thereby suppressing the generation of vibration and noise.

[0075] In a conventional 2H-K type planetary gear mechanism, when the planetary gears are combined in an internal + external or external + internal configuration, the total gear ratio of the reducer is the sum of the gear ratio of the first planetary gear and the gear ratio of the second planetary gear, making it impossible to obtain a large reduction ratio. In this embodiment, the planetary gears of the internal gears are connected together using the connecting member 60, so the total reduction ratio i of the reducer W1 is the difference between the gear ratio of the first planetary gear 30 and the gear ratio of the second planetary gear 70, making it possible to achieve a large reduction ratio.

[0076] The connecting member 60 is provided directly on the input shaft 10 and is configured to be roughly the same size as the other parts, and serves as a counterweight and restricts the rotation of the second planetary gear 70 with just one part, while also having high rigidity.

[0077] (Movement of the Reducer) The movement of the reducer W1 configured as described above will be explained using the skeleton diagram of Fig. 5 and Figs. 12 to 14. Fig. 12 is a cross-sectional view taken along line A-A in Fig. 2. It mainly shows the fixed sun gear main body 22 and the first planetary gear main body 35. Fig. 13 is a cross-sectional view taken along line B-B in Fig. 2. It mainly shows the first planetary gear 30 and the first shaft body 61 of the connecting member 60. Fig. 14 is a cross-sectional view taken along line CC in Fig. 2. It mainly shows the second shaft body 62 of the connecting member 60, the second planetary gear 70, and the driven sun gear main body 42.

[0078] 5, the reducer W1 is a hypocycloid reducer having a 2K-H planetary gear mechanism. The reducer W1 includes an input shaft 10 having a pair of first eccentric portions 12 and second eccentric portions 14, a fixed sun gear 20 consisting of an external gear provided coaxially with the input shaft 10, a first planetary gear 30 having an internal gear that meshes with the fixed sun gear 20, a driven sun gear 40 having an external gear that outputs a reduced output, a second planetary gear 70 having an internal gear that meshes with the driven sun gear 40, and a connecting member 60 disposed between the first planetary gear 30 and the second planetary gear 70.

[0079] The first planetary gear 30 is provided on the first eccentric portion 12, and the connecting member 60 is provided on the second eccentric portion 14. The second planetary gear 70 is provided in the opposite phase to the first planetary gear 30 and is arranged coaxially with the second eccentric portion 14, and receives the rotation of the second eccentric portion 14 via the connecting member 60.

[0080] The connecting member 60 is configured such that a first connecting shaft a1, which is the central axis of one end, and a second connecting shaft a2, which is the central axis of the other end, are offset from each other. The first connecting shaft a1 is rotatably supported by the first planetary gear 30, and the second connecting shaft a2 is rotatably supported by the second planetary gear 70. As a result, the connecting member 60 allows the first planetary gear 30 and the second planetary gear 70 to move integrally with each other, and restricts the rotation of the second planetary gear 70.

[0081] The first planetary gear 30 and the first shaft 61 of the connecting member 60 are relatively eccentric, and as the first planetary gear 30 rotates, the connecting member 60 also rotates relative to it by the same amount as the first planetary gear 30 rotates on its axis. However, since the second planetary gear 70 and the second shaft 62 of the connecting member 60 are also relatively eccentric, the relative positions of the first planetary gear 30 and the second planetary gear 70 are maintained.

[0082] When the rotational input of the motor M is transmitted to the input shaft 10, the first eccentric portion 12 performs eccentric rotational motion around the first eccentric center X1. This eccentric rotational motion is transmitted to the first planetary gear 30 via the bearing BR2. As the fixed sun gear main body 22 fixed to the housing 50 meshes with the first planetary gear 30, the first planetary gear 30 is decelerated by the gear ratio between the first planetary gear 30 and the fixed sun gear main body 22. The first planetary gear 30 then rotates by the amount of gear meshing while revolving around the fixed sun gear main body 22 due to the eccentric rotation of the first eccentric portion 12. The decelerated rotation of the first planetary gear 30 is transmitted to a connecting member 60 connected to the first planetary gear 30.

[0083] Since the connecting member 60 is provided on the second eccentric portion 14, it rotates eccentrically about the second eccentric center X2 while receiving a deceleration input from the first planetary gear 30. At this time, the connecting member 60 only rotates on its own axis using the offset shafts at both ends.

[0084] The second planetary gear 70 accepts eccentric motion around the second eccentric center X2. The eccentric motion of only revolution around the second eccentric center X2 is transmitted from the connecting member 60 to the second planetary gear 70 connected to the connecting member 60.

[0085] The second planetary gear 70 meshes with the driven sun gear main body 42 in conjunction with the transmitted orbital motion, and the power is output at a reduced speed by the gear ratio between the second planetary gear 70 and the driven sun gear main body 42. The eccentric motion of the orbiting second planetary gear 70 causes the driven sun gear main body 42 to rotate on its axis.

[0086] At this time, the second planetary gear 70 rotates at a reduced speed by the gear ratio between the first planetary gear 30 and the fixed sun gear main body 22, and the rotation of the driven sun gear main body 42 is output at a further reduced speed by the gear ratio between the driven sun gear main body 42 and the second planetary gear 70.

[0087] (Effects) The first planetary gear 30 and the second planetary gear 70 are eccentrically arranged in opposite phases via the connecting member 60. The reduction ratio based on the number of teeth Z1 of the fixed sun gear main body 22 and the number of teeth Z2 of the first planetary gear 30 is defined as the first reduction ratio R1, and the reduction ratio based on the number of teeth Z3 of the second planetary gear 70 and the number of teeth Z4 of the driven sun gear main body 42 is defined as the second reduction ratio R2. Because the planetary gears are arranged in opposite phases via the connecting member 60, the difference between the first reduction ratio R1 and the second reduction ratio R2 is the total reduction ratio i of the reducer W1. This allows for a very large reduction ratio. Conventionally, in 2KH-type planetary gears, the first planetary gear and the second planetary gear tend to vibrate in phase. Because the reducer W1 is arranged in opposite phases via the connecting member 60, the total reduction ratio i is the difference between the first reduction ratio and the second reduction ratio. With the configuration of the present disclosure, the planetary gears act as counterweights to suppress vibrations, and a large reduction ratio can be obtained.

[0088] The difference in the number of teeth between the two sets of gears in the reducer W1 is 2 or more. If the difference in the number of teeth is 1, a larger reduction ratio can be obtained, but the amount of eccentricity must be reduced, which poses a problem of high load on the bearings provided in the eccentric portion. By setting the difference in the number of teeth to 2 or more, the above configuration ensures a large reduction ratio while keeping the amount of eccentricity within a reasonable range.

[0089] An example of the number of teeth in this embodiment and the corresponding total reduction ratio i are as follows: Number of teeth Z1 of the fixed sun gear main body 22 = 55 Number of teeth Z2 of the first planetary gear 30 = 53 Number of teeth Z3 of the second planetary gear 70 = 39 Number of teeth Z4 of the driven sun gear main body 42 = 37 Here, 1 / i = 1 / (39 / (39-37)) - 1 / (55 / (55-53)), so the total reduction ratio i of the reducer W1 = 67

[0090] Additionally, in the reducer W1, the driven sun gear 40 that extracts the reduced output is configured as an external gear, so it can be configured to be shorter in the axial direction than if it were configured as an internal gear. An internal gear is provided to protrude in the axial direction from a disk-shaped base, but an external gear does not require a base and can be directly installed on the outer circumferential surface of the disk. For the same tooth width, the internal gear can be configured to be shorter in the axial direction. In the reducer W1, by configuring the driven sun gear main body 42 as an external gear, the structure inside the housing is shortened in the axial direction.

[0091] The reducer W1 has a small number of parts, and each part is roughly the same size and arranged axially, making it highly rigid. Furthermore, it can achieve a large reduction ratio without increasing its circumferential size.

[0092] (Modification) A reduction gear W2, which is a modification of the configuration described above, will be described with reference to Fig. 15. Fig. 15 is a skeleton diagram of the reduction gear W2. Components having the same configuration are given the same reference numerals, and descriptions thereof will be omitted.

[0093] The first planetary gear 130 is provided on the first eccentric portion 12 and meshes with the fixed sun gear 20. Except for the connection portion with the connection member 160, the first planetary gear 130 is the same as the first planetary gear 30.

[0094] The second planetary gear 170 is an internal gear that meshes with the driven sun gear 40, and is rotatably supported by the second eccentric portion 14. The second planetary gear 170 is disposed in the opposite phase to the first planetary gear 130. The second planetary gear 170 has a configuration in which the connecting member 60 and the second planetary gear 70 are integrated, except that the second planetary gear 170 is not connected to the first planetary gear 30.

[0095] The connecting member 160 is a crankshaft. It is disposed between the first planetary gear 130 and the second planetary gear 170. One end of the connecting member 160 is rotatably supported by the first planetary gear 130, and the other end of the connecting member 160 is rotatably supported by the second planetary gear 170.

[0096] The first planetary gear 130 and the second planetary gear 170 are provided in opposite phases and act as counterweights to each other. Despite being in opposite phases, a large reduction ratio can be achieved. The connecting member 160 allows the first planetary gear 130 and the second planetary gear 170 to move together and restricts the rotation of the first planetary gear 130 and the second planetary gear 170. There may be only one connecting member 160, or two or more may be provided at equal intervals in the circumferential direction.

[0097] The above describes preferred embodiments of the present invention, but the above embodiments are merely examples of the present invention, and these can be combined based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention.

[0098] W1: reducer, 10: input shaft, 12: first eccentric portion, 14: second eccentric portion, 20: fixed sun gear, 30: first planetary gear, 40: driven sun gear, 60: connecting member, 70: second planetary gear

Claims

1. an input shaft having a pair of first and second eccentric portions; a fixed sun gear including an external gear provided coaxially with the input shaft; a first planetary gear having an internal gear meshing with the fixed sun gear and provided on the first eccentric portion of the input shaft; a driven sun gear arranged coaxially with the rotation axis of the input shaft and configured as an external gear for outputting a reduced output; a second planetary gear having an internal gear that meshes with the driven sun gear and is capable of receiving an eccentric input from the second eccentric portion; a connecting member disposed between the first planetary gear and the second planetary gear; Equipped with a gear ratio between the second planetary gear and the driven sun gear is different from a gear ratio between the first planetary gear and the fixed sun gear, the connecting member is configured such that a central axis of one end and a central axis of the other end are offset, the one end is rotatably supported by the first planetary gear, and the other end is rotatably supported by the second planetary gear, so that the first planetary gear and the second planetary gear move together as a unit and the rotation of the second planetary gear is restricted, the connecting member is provided on the second eccentric portion, the one end of the connecting member is disposed on the circumferential inner side of the first planetary gear and rotatably supported, and the other end of the connecting member is disposed on the circumferential outer side of the second planetary gear and rotatably supported. A planetary gear reducer characterized by:

2. the second planetary gear is provided in an opposite phase to the first planetary gear so that an eccentricity of an internal gear of the second planetary gear is in phase with and has the same amount of eccentricity as the second eccentric portion, and the second planetary gear receives rotation of the second eccentric portion via the connecting member.

2. The planetary gear reducer according to claim 1 .

3. (delete)

4. the internal gear of the first planetary gear and the internal gear of the second planetary gear are configured based on a trochoid curve, a difference in the number of teeth between the first planetary gear and the fixed sun gear, and between the second planetary gear and the driven sun gear, is an integer of 2 or more, and a meshing ratio is 2 or more; 4. The planetary gear reducer according to claim 1, wherein the first and second gears are arranged in a first direction.