Deceleration mechanism

Abstract

The present invention provides a deceleration mechanism for achieving a self-lock function without the use of a worm gear. An input shaft 2 of this deceleration mechanism 1 comprises a general section 21 and an eccentric section 22 that is eccentric with respect to the general section 21. An external gear 3 is rotatably supported by the eccentric section 22 so that the central axis of the external gear 3 coincides with that of the eccentric section 22, and a torque disk 4 is disposed between the external gear 3 and a fixed hub 5. The fixed hub 5 is fixed in the deceleration mechanism 1. An internal gear 6 is disposed on the outer peripheral side of the external gear 3 so that teeth of the internal gear 6 and the external gear 3 mutually mesh, and the internal diameter of the internal gear 6 is greater than the external diameter of the external gear 3. The external gear 3 fits onto the torque disk 4 so that the direction of movement of the external gear 3 with respect to the torque disk 4 within a plane orthogonal to the input shaft 2 is restricted to a first direction. The torque disk 4 fits onto the fixed hub 5 so that the direction of movement of the torque disk 4 with respect to the fixed hub 5 within a plane orthogonal to the input shaft 2 is restricted to a second direction that is orthogonal to the first direction.

Description

Reduction mechanism

[0001] The present invention relates to a speed reduction mechanism and the like.

[0002] Patent Document 1 discloses a KHV type reduction mechanism, which has an external gear disposed inside an internal gear, an eccentric portion of an input shaft inserted into the external gear, and the external gear, which revolves as the input shaft rotates, meshes with the internal gear, causing the internal gear on the output side to rotate on its axis.

[0003] In the above reduction mechanism, the input shaft is rotated by a motor, but it is important that the input shaft does not rotate when the reduction mechanism is stopped, even when a rotational force is applied to the internal gear on the output side. This is called a self-locking function, and without this function, a holding torque would be required to resist the torque applied to the input shaft by the above rotational force, which would result in the motor consuming power even when the reduction mechanism is stopped.

[0004] Worm gears are commonly known as speed reduction mechanisms with a self-locking function (see, for example, Patent Documents 2 and 3). A worm gear is a mechanism in which a worm (a screw gear) and a worm wheel (a helical gear) are meshed together, and the self-locking function is achieved by the friction between them.

[0005] JP 2013-87781 A JP 2018-100716 A JP 2006-205950 A

[0006] However, worm gears with self-locking functions generally have a large reduction ratio (around 60), and also suffer from large losses due to friction and other factors, resulting in low transmission efficiency. This limits their range of application, making it difficult to widely use them in robots, automobiles, etc.

[0007] The present invention has been made in view of the above problems, and has as its object to provide a speed reduction mechanism or the like that achieves a self-locking function without using a worm gear.

[0008] In order to solve the above-mentioned problems, the present invention provides a reduction mechanism having an input shaft, an external gear, a torque disc, a fixed portion, and an internal gear, wherein the input shaft has a general portion and an eccentric portion that is eccentric relative to the general portion, the central axis of the external gear coincides with the eccentric portion and is rotatably supported by the eccentric portion, the torque disc is disposed between the external gear and the fixed portion, and the fixed portion is fixed in the reduction mechanism, the internal gear is disposed on the outer periphery of the external gear so that some teeth of the internal gear and the external gear mesh with each other, the external gear is engaged with the torque disc, so that the direction in which the external gear can move relative to the torque disc in a plane perpendicular to the input shaft is restricted to a first direction, and the torque disc is engaged with the fixed portion so that the direction in which the torque disc can move relative to the fixed portion in a plane perpendicular to the input shaft is restricted to a second direction perpendicular to the first direction, and when the general portion of the input shaft rotates, the external gear revolves along the inner periphery of the internal gear without rotating on its own axis.

[0009] In the reduction gear mechanism of the present invention, when the general portion of the input shaft rotates, the external gear revolves around the inner circumference of the internal gear without rotating on its axis, due to the eccentricity of the eccentric portion of the input shaft and the aforementioned fixed portion-torque disc-external gear engagement structure. The internal gear on the output side rotates along its axis as the external gear revolves. Here, when a rotational force is applied to the internal gear with the reduction gear mechanism stopped, the external gear does not rotate (spin), and the force is transmitted to the eccentric portion. However, in the present invention, the eccentric distance between the general portion and the eccentric portion of the input shaft can be reduced, so the torque applied to the general portion of the input shaft due to the force is reduced, and the general portion hardly rotates. In this way, the present invention achieves a self-locking function with a highly efficient transmission mechanism that does not use a worm gear, and the power consumption of the motor required to apply holding torque to the general portion of the input shaft can be reduced to almost zero. Furthermore, the compact configuration and low reduction ratio make it applicable to a variety of devices.

[0010] For example, the engagement between the external gear and the torque disc, and the engagement between the torque disc and the fixed portion are achieved by linear grooves on either side of a hole through which the input shaft passes, and ridges that fit into the grooves, with the ridges being provided on one of the external gear and the torque disc, and one of the torque disc and the fixed portion, and the groove being provided on the other. The above-mentioned engagement structure is a novel structure inspired by Oldham couplings, and can suitably achieve revolution without rotation of the external gear and a self-locking function.

[0011] It is desirable that a pair of ridges be formed on either the external gear or the torque disc, sandwiching the hole. Alternatively, it is also desirable that the ridges be formed on only one side of the hole on either the external gear or the torque disc. In the former case, when the rotational force is applied, the reaction force applied from the torque disc to the external gear via the ridges is canceled out between the pair of ridges, and does not affect the self-locking function. In the latter case, the external gear revolves a certain amount, and the external gear reaches a position where the reaction force applied from the torque disc to the external gear via the ridges balances the rotational force, thereby locking the rotation of the general portion of the input shaft and reliably achieving the self-locking function.

[0012] It is desirable that the input shaft, the external gear, the torque disc, and the internal gear are disposed within a casing having the fixed portion, the internal gear having a ring-shaped main body and an output shaft, the general portion of the input shaft being rotatably supported in a hole in the fixed portion by multiple rows of bearings arranged in the axial direction of the input shaft, and the output shaft being rotatably supported in a hole in the casing by multiple rows of bearings arranged in the axial direction of the output shaft.It is also desirable that the input shaft, the external gear, the torque disc, and the internal gear are disposed within a casing having the fixed portion, the internal gear having a ring-shaped main body, an output shaft, and an end plate closing the output shaft side of the main body, the general portion of the input shaft being rotatably supported in a single row of bearings in the hole in the fixed portion, an auxiliary device provided at the tip of the eccentric portion of the input shaft being rotatably supported by a bearing provided in an internal space of the end plate, and the output shaft being rotatably supported in a single row of bearings in the hole in the casing. These structures suppress shaft deflection of the input and output shafts of the reduction gear mechanism, preventing performance degradation due to shaft deflection.

[0013] The present invention can provide a speed reduction mechanism or the like that achieves a self-locking function without using a worm gear.

[0014] A diagram showing the reduction mechanism 1. A diagram showing the input shaft 2. A diagram showing the external gear 3 and the internal gear 6. A diagram showing the torque disc 4. A diagram showing the fixed hub 5. A diagram explaining the fitting structure in the reduction mechanism 1. A diagram explaining the revolution of the external gear 3. A diagram explaining the self-locking function of the reduction mechanism 1. A diagram showing the external gear 3'. A diagram showing the reduction mechanism 1a. A diagram showing the external gear 3a and the internal gear 6a. A diagram showing the fixed plate 5a. A diagram explaining the self-locking function of the reduction mechanism 1a. A diagram showing the reduction mechanism 10. A diagram showing the reduction mechanism 10. A diagram showing the torque disc 40. A diagram showing the reduction mechanism 10a.

[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0016] [First embodiment] (1. Reduction mechanism 1) Figure 1 shows a reduction mechanism 1 according to a first embodiment of the present invention, and Figures 1(a) and 1(b) are perspective views of the reduction mechanism 1 as seen diagonally from the left and right, respectively.

[0017] 1(a) and 1(b), the reduction mechanism 1 includes an input shaft 2, an external gear 3, a torque disc 4, a fixed hub 5, and an internal gear 6. The reduction mechanism 1 is housed in a casing (not shown).

[0018] FIG. 2 is a diagram showing the input shaft 2. As shown in FIG. 2, the input shaft 2 has a general portion 21 and an eccentric portion 22. The general portion 21 is a cylindrical portion of approximately the same diameter. The eccentric portion 22 is provided midway in the axial direction of the general portion 21, is a cylindrical portion with a larger diameter than the general portion 21, and has a central axis 221 that is offset from the central axis 211 of the general portion 21 (i.e., is eccentric). The general portion 21 is disposed within a cross section (hereinafter simply referred to as a cross section) that is perpendicular to the axial direction of the eccentric portion 22.

[0019] Fig. 3 is a diagram showing the external gear 3 and the internal gear 6. As shown in Fig. 3, the external gear 3 is a disk-shaped member with teeth on its outer periphery, and a pair of ridges 31 is formed on one surface of the body (the surface facing the torque disc 4). The external gear 3 also has a hole 32 that penetrates the body in the thickness direction. Note that although the external gear 3 in this embodiment is a spur gear, it may also be a helical gear.

[0020] The ridges 31 extend radially from the center of the external gear 3. The pair of ridges 31 are formed on the same straight line with the hole 32 therebetween.

[0021] The hole 32 is provided at the center of the external gear 3. As shown in FIG. 1( b), the eccentric portion 22 of the input shaft 2 passes through this hole 32, and the external gear 3 is rotatably supported by the eccentric portion 22. Although not shown, a bearing or other support may be disposed between the hole 32 and the eccentric portion 22. The central axis 221 of the eccentric portion 22 (see FIG. 2) coincides with the central axis of the hole 32, i.e., the central axis 33 of the external gear 3.

[0022] The internal gear 6 is disposed on the outer periphery of the external gear 3. The internal gear 6 has teeth on the inner periphery of its ring-shaped body that mesh with the teeth of the external gear 3, and the number of teeth is greater than the number of teeth of the external gear 3. The inner diameter of the internal gear 6 is larger than the outer diameter of the external gear 3, and the central axis 61 of the internal gear 6 is offset from the central axis 33 of the external gear 3. Therefore, the external gear 3 and the internal gear 6 are configured so that some of the teeth mesh with each other.

[0023] 4 is a diagram showing the torque disc 4. The torque disc 4 is a disk-shaped member, and has a pair of grooves 41 formed on one surface of the main body (the surface facing the external gear 3), and a pair of grooves 42 formed on the other surface (the surface facing the fixed hub 5). The torque disc 4 also has a hole 43 formed therein that penetrates the main body in the thickness direction.

[0024] Grooves 41 and 42 both extend radially from the center of torque disc 4 and are formed linearly across hole 43. The extension direction of groove 41 and the extension direction of groove 42 intersect at right angles at the center of hole 43.

[0025] The hole 43 is provided in the center of the torque disc 4. The general portion 21 of the input shaft 2 passes through the hole 43. The diameter of the hole 43 is larger than the diameter of the general portion 21.

[0026] 5 is a diagram showing the fixed hub 5. The fixed hub 5 is a disc-shaped member, and a ridge 51 is formed on one surface of the body (the surface facing the torque disc 4). The fixed hub 5 also has a hole 52 that penetrates the body in the thickness direction.

[0027] The ridges 51 extend radially from the center of the fixed hub 5. The pair of ridges 51 are formed on the same straight line with the hole 52 therebetween.

[0028] The hole 52 is provided in the center of the fixed hub 5, and the general portion 21 of the input shaft 2 is passed through the hole 52. The diameter of the hole 52 is approximately the same as the diameter of the general portion 21.

[0029] The fixed hub 5 is a fixed part that is fixed within the reduction gear mechanism 1, and does not rotate around the input shaft 2 or move in the axial direction of the input shaft 2 or in a direction perpendicular to this.

[0030] As shown in Figure 6, in the reduction gear mechanism 1, the torque disc 4 is disposed between the external gear 3 and the fixed hub 5. The torque disc 4 comes into contact with the external gear 3 and the fixed hub 5, with the ridges 31 of the external gear 3 fitting into the grooves 41 and the ridges 51 of the fixed hub 5 fitting into the grooves 42. In this way, the external gear 3 and the torque disc 4 are fitted together, and the torque disc 4 and the fixed hub 5 are fitted together.

[0031] Due to this fitting structure, the external gear 3 moves only in the extension direction (first direction) of the groove 41 indicated by arrow a relative to the torque disc 4 on a plane perpendicular to the input shaft 2, and the torque disc 4 moves only in the extension direction (second direction) of the groove 42 indicated by arrow b relative to the fixed hub 5 on a plane perpendicular to the input shaft 2. Therefore, when viewed from the fixed hub 5, the external gear 3 can move only in directions a and b of the grooves 41 and 42 which are perpendicular to each other. Due to this restriction of the movement direction, the external gear 3 is configured not to rotate on its own axis.

[0032] In the reduction gear mechanism 1, when the general portion 21 of the input shaft 2 is rotated by a motor (not shown), the position of the eccentric portion 22 relative to the general portion 21 changes, as shown in FIG. 7 , causing the external gear 3 to revolve within the internal gear 6 while meshing with the internal gear 6. This causes the output-side internal gear 6 to rotate, and any position A in the circumferential direction of the internal gear 6 makes one full rotation. The motor and reduction gear mechanism 1 constitute a drive device. Furthermore, the external gear 3 revolves without rotating, by moving the external gear 3 along the directions a and b described above. Therefore, the positional relationship between any position B on the external gear 3 and the hole 32 does not change during the external gear 3's revolution.

[0033] (2. Self-locking function of reduction mechanism 1) In this embodiment, when a rotational force F is applied to the internal gear 6 on the output side while the reduction mechanism 1 is stopped, as shown in Figure 8, the external gear 3 does not rotate, so the force F is transmitted to the eccentric portion 22, and a torque that tends to rotate the general portion 21 of the input shaft 2 is generated.

[0034] The magnitude of this torque is the product F×Δd of the rotational force F and the eccentric distance Δd between the general portion 21 and eccentric portion 22 of the input shaft 2, but in the reduction gear mechanism 1 of this embodiment, the eccentric distance Δd can be made small, so the torque generated in the general portion 21 of the input shaft 2 is very small. In addition, due to the presence of friction of the external gear 3 and the like, the general portion 21 of the input shaft 2 will not rotate unless a large rotational force F is applied.

[0035] As described above, in the reduction gear mechanism 1 of this embodiment, when the general portion 21 of the input shaft 2 rotates, the external gear 3 revolves around the inner circumference of the internal gear 6 without rotating on its own axis due to the eccentricity of the eccentric portion 22 on the input shaft 2 and the above-mentioned fitting structure of the fixed hub 5, torque disc 4, and external gear 3, and the internal gear 6 on the output side rotates on its own axis in conjunction with the revolution of the external gear 3. Here, when a rotational force F is applied to the internal gear 6 with the reduction gear mechanism 1 stopped, the external gear 3 does not rotate (rotate), and therefore the force F is transmitted to the eccentric portion 22. However, in this embodiment, the eccentric distance Δd between the general portion 21 and eccentric portion 22 of the input shaft 2 can be made small, so the torque applied to the general portion 21 of the input shaft 2 by the force F is small, and the general portion 21 hardly rotates.

[0036] In this way, in this embodiment, a self-locking function can be achieved in a highly efficient transmission mechanism that does not use a worm gear, and the power consumption of the motor for applying holding torque to the general portion 21 of the input shaft 2 can be reduced to almost zero. Furthermore, because the configuration is compact and the reduction ratio can be made low, the device can be widely applied to a variety of devices such as factory assembly robots, small mobility vehicles, automobiles, and construction machinery, and can widely contribute to energy conservation.

[0037] The fitting structure used in this embodiment has the torque disc 4 sandwiched between the external gear 3 and the fixed hub 5, and these are fitted together by the ridges 31, 51 and the grooves 41, 42. This is a novel structure inspired by the Oldham coupling, and can effectively realize revolution without rotation of the external gear 3 and a self-locking function.

[0038] However, the present invention is not limited to the above embodiment. For example, as shown in Fig. 9, the ridges 31 of the external gear 3' may be provided on a cylindrical portion 34 that protrudes from the main body of the external gear 3 toward the torque disc 4 (corresponding to the left side of Fig. 9). The hole 32 of the external gear 3 is also provided so as to pass through this cylindrical portion 34.

[0039] In addition, in this embodiment, the ridges 31, 51 are formed on the external gear 3 and the fixed hub 5, and the grooves 41, 42 are formed on the torque disc 4, but this is not limitative, and it is sufficient to form a ridge on either the external gear 3 or the torque disc 4, or either the torque disc 4 or the fixed hub 5, and then form a groove into which the ridge fits on the other. For example, it is also possible to form a ridge on the torque disc 4 side.

[0040] Additionally, the shape of the input shaft 2 is not particularly limited as long as the eccentric portion 22 is eccentric with respect to the general portion 21. For example, it is also possible to configure the eccentric portion 22, which has a smaller diameter than the general portion 21, to be provided within the cross section of the general portion 21.

[0041] Below, other examples having different configurations of the speed reduction mechanism 1 will be described as second and third embodiments. In the second and third embodiments, differences from the first embodiment will be described, and similar configurations will be denoted by the same reference numerals in the drawings and the like, and description thereof will be omitted. Furthermore, the configurations described in each embodiment, including the first embodiment, can be combined as necessary.

[0042] 10 is a diagram showing a speed reduction mechanism 1a according to a second embodiment of the present invention. The speed reduction mechanism 1a includes an input shaft 2, an external gear, a torque disc 4, a fixed plate 5a, an internal gear 6a, etc.

[0043] 11 is a diagram showing an external gear 3a and an internal gear 6a. The external gear 3a of this embodiment also has the same ridge 31 and hole 32 as described above, but differs from the first embodiment in that the ridge 31 is provided on only one side of the hole 32. An eccentric portion 22 (see FIG. 13 ) provided on the end of the general portion 21 of the input shaft 2 is inserted into the hole 32, and the external gear 3a is rotatably supported by the eccentric portion 22 as described above.

[0044] Similarly to the above, the internal gear 6a has a ring-shaped main body that is disposed on the outer periphery of the external gear 3a, but differs from the above-described internal gear 6 in that the side of the main body opposite the torque disc 4 (corresponding to the right side in FIG. 11 ) is closed by an end plate 62. An output shaft 63 is fixed to the surface of the end plate 62 opposite the torque disc 4. The output shaft 63 is provided on the central axis 61 of the internal gear 6.

[0045] 12 is a view showing the fixed plate 5a. The fixed plate 5a is a plate-shaped fixed portion that is fixed in the reduction gear mechanism 1a, and in this embodiment, it is part of the casing C (see FIG. 10). One surface of the fixed plate 5a (the surface facing the torque disc 4) is provided with a protrusion 51 similar to that of the fixed hub 5 described above, and a hole 52 that penetrates the fixed plate 5a in the thickness direction is also formed in the same manner as described above.

[0046] In this reduction gear mechanism 1a as well, the ridges 31 of the external gear 3a fit into the grooves 41 of the torque disc 4, and the ridges 51 of the fixed plate 5a fit into the grooves 42 of the torque disc 4. Therefore, as the general portion 21 of the input shaft 2 rotates, the external gear 3a revolves within the internal gear 6a without rotating while meshing with the main body of the internal gear 6a.

[0047] (2. Self-locking function of reduction mechanism 1a) In this embodiment, when a large rotational force F is applied to the output side internal gear 6a as shown in Figure 13 while the reduction mechanism 1a is stopped, the external gear 3a revolves a certain amount, and when the convex rib 31 reaches a position where the reaction force c, etc. applied to the external gear 3a from the torque disc 4 via the convex rib 31 is balanced with the rotational force F, the external gear 3a stops revolving, and thereafter the rotation of the general portion 21 of the input shaft 2 is locked.

[0048] In the first embodiment as well, a reaction force c is applied from the torque disc 4 to the external gear 3 via the ridges 31 (see FIG. 8 ). However, because a pair of ridges 31 are provided on either side of the hole 32 in the external gear 3, the reaction forces c applied to these ridges 31 cancel each other out and have almost no effect on the self-locking function.

[0049] In this way, the speed reduction mechanism 1a of this embodiment also achieves a self-locking function in a highly efficient transmission mechanism that does not use a worm gear, and provides the same effects as in the first embodiment. Furthermore, in this embodiment, the self-locking function is reliably achieved by balancing the reaction force c and the like with the rotational force F, eliminating the need to apply a holding torque to the general portion 21 of the input shaft 2 by a motor.

[0050] 14 and 15 are views showing a reduction gear mechanism 10 according to a third embodiment of the present invention. Fig. 14 shows a cross section taken along line B-B in Fig. 15, and Fig. 15 shows a cross section taken along line A-A in Fig. 14. The third embodiment is an example characterized mainly by the method of supporting the input and output shafts of the reduction gear mechanism 10.

[0051] In the reduction mechanism 10, the input shaft 20, the external gear 30, the torque disc 40, the internal gear 60, etc. are arranged inside the casing C.

[0052] The input shaft 20 has a general portion 21 and an eccentric portion 22a. The eccentric portion 22a is provided so as to continue from an end portion of the general portion 21. The eccentric portion 22a is a cylindrical portion having a diameter approximately the same as that of the general portion 21, but its central axis 221 is disposed offset from the central axis 211 of the general portion 21.

[0053] The external gear 30 has a disk-shaped main body provided with ridges 31 and holes 32 similar to those of the external gear 3a of the second embodiment. The ridges 31 are provided on one side of the holes 32, but the ridges 31 may be provided on both sides of the holes 32, similar to the external gear 3 of the first embodiment.

[0054] The external gear 30 rotatably supports the eccentric portion 22a of the input shaft 20, which is inserted through the hole 32, via a bearing 100 (100a). The bearing 100 (100a) of this embodiment is a rolling bearing, with rolling elements 103 provided between an inner ring 101 and an outer ring 102. The inner ring 101 and the outer ring 102 are annular members formed from metal, and the outer ring 102 is disposed outside the inner ring 101. The outer ring 102 is fixed along the inner circumferential surface of the hole 32, and the inner ring 101 is fixed along the outer circumferential surface of the eccentric portion 22a of the input shaft 20. The rolling elements 103 are spherical bodies formed from metal, and multiple rolling elements 103 are spaced apart circumferentially around the inner ring 101 (and outer ring 102) and are held rotatably between the inner ring 101 and the outer ring 102. The rolling elements 103 may be cylindrical bodies (rollers). The cylindrical body is arranged so that its axial direction is aligned with the axial direction of the input shaft 20 .

[0055] The internal gear 60 has a ring-shaped main body 64 that is positioned on the outer periphery of the external gear 30. As in the second embodiment, the side of the main body 64 opposite the torque disc 40 (corresponding to the right side in Figures 14 and 15) is closed by an end plate 62a. A cylindrical output shaft 63a is fixed to the surface of the end plate 62a opposite the torque disc 40. The output shaft 63a is mounted on the central axis 61 of the internal gear 60. The end plate 62a is a truncated conical dish-shaped member that tapers toward the output shaft 63a. The output shaft 63a is configured such that a large diameter portion 631 located on the end plate 62a side is continuous with a small diameter portion 632 that is smaller in diameter than the large diameter portion 631.

[0056] FIG. 16 is a diagram showing the torque disc 40. Like the torque disc 4 described above, the torque disc 40 is a disk-shaped member with a hole 43 in the center, and a pair of grooves 41 is formed on one surface of the main body (the surface facing the external gear 30). The ridge 31 of the external gear 30 is inserted into one of these grooves 41. A pair of arc-shaped wall portions 44 is provided along the outer periphery on the other surface of the main body (the surface opposite the external gear 30), and a groove 42 is formed between both ends of this pair of wall portions 44. The grooves 42 are arranged at positions facing each other across the hole 43.

[0057] The casing C has an input side case 50, an output side case 70, and a case body 80. In the reduction gear mechanism 10, the casing C is fixed to the installation surface by a fixing bracket 90.

[0058] The input side case 50 (fixed portion) is provided at the end of the casing C on the input shaft 20 side. The input side case 50 is a disk-shaped member, and similar to the fixed plate 5a of the second embodiment, a pair of ridges 51 are provided on the same line with a hole 52 therebetween. These ridges 51 are inserted into the respective grooves 42 of the torque disc 40.

[0059] The input side case 50 rotatably supports the general portion 21 of the input shaft 20, which is inserted through the hole 52, with bearings 100 (100b, 100c). The outer ring 102 of the bearing 100 is fixed along the inner circumferential surface of the hole 52, and the inner ring 101 is fixed along the outer circumferential surface of the general portion 21 of the input shaft 20. In this embodiment, multiple rows of bearings 100 (two rows in the illustrated example) are provided within the hole 52. These bearings 100 are arranged side by side in the axial direction of the input shaft 20.

[0060] The output side case 70 is provided at the end of the casing C on the output shaft 63a side. The output side case 70 is a cylindrical member, and its hole is composed of, in order from the input shaft 20 side, a large diameter portion 71 and a small diameter portion 72 having a smaller diameter than the large diameter portion 71. The main body 64 and end plate 62a of the internal gear 60 are disposed in the large diameter portion 71. The large diameter portion 631 of the output shaft 63a of the internal gear 60 is disposed in the small diameter portion 72. The small diameter portion 632 of the output shaft 63a protrudes outward from the output side case 70.

[0061] The large diameter portion 631 of the output shaft 63a is rotatably supported by bearings 100 (100d, 100e) within the small diameter portion 72 of the output side case 70. The outer ring 102 of the bearing 100 is fixed along the inner circumferential surface of the small diameter portion 72, and the inner ring 101 is fixed along the outer circumferential surface of the large diameter portion 631 of the output shaft 63a. A plurality of rows of bearings 100 (two rows in the illustrated example) are provided within the small diameter portion 72. These bearings 100 are arranged side by side in the axial direction of the output shaft 63a.

[0062] The case body 80 is a cylindrical member provided to connect the outer peripheries of the input case 50 and the output case 70 to each other.

[0063] As described above, in this embodiment, the input shaft 20 and the output shaft 63a of the reduction gear mechanism 10 are supported by multiple rows of bearings 100 in the input side case 50 and the output side case 70 of the casing C, respectively. If these bearings 100 were in a single row, the input and output shafts of the reduction gear mechanism 10 would be cantilevered, raising concerns about performance degradation due to shaft deflection. However, in this embodiment, the input and output shafts are supported by multiple rows of bearings 100, which suppresses shaft deflection and prevents performance degradation of the reduction gear mechanism 10.

[0064] In this embodiment, rolling bearings are used as the bearings 100, but this is not a limitation and plain bearings may also be used. Furthermore, the method of supporting the input and output shafts is not limited to the above. For example, as shown in the reduction gear mechanism 10a in FIG. 17 , the bearings 100 in the hole 52 of the input side case 50 that supports the general portion 21 of the input shaft 20a and the bearings 100 in the small diameter portion 72 of the output side case 70 that supports the large diameter portion 631 of the output shaft 63a are arranged in a single row rather than in multiple rows. Alternatively, the input shaft 20a may be further supported by a bearing 100 (100A) provided inside the end plate 62b of the internal gear 60a.

[0065] 17, the end plate 62b of the internal gear 60a is a truncated cone-shaped dish-shaped member that narrows toward the output shaft 63a, and its internal space has, in order from the input shaft 20a side, a large diameter portion 621 and a small diameter portion 622. The large diameter portion 621 and the small diameter portion 622 are cylindrical hollow portions, and the diameter of the small diameter portion 622 is smaller than that of the large diameter portion 621.

[0066] An auxiliary tool 23 is provided at the tip of the eccentric portion 22a of the input shaft 20a. The auxiliary tool 23 is a cylindrical metal member arranged in the internal space of the end plate 62b, and the tip of the auxiliary tool 23 is inserted into the small diameter portion 622 of the internal space. The tip of the auxiliary tool 23 is rotatably supported within the small diameter portion 622 by a bearing 100 (100A). The outer ring 102 of the bearing 100 is fixed along the inner circumferential surface of the small diameter portion 622, and the inner ring 101 is fixed to the outer circumferential surface of the tip of the auxiliary tool 23. The bearings 100 are arranged in a row within the small diameter portion 622.

[0067] In this case, too, the above-mentioned bearing 100 (100A) can prevent the input and output shafts of the reduction gear mechanism 10a from being supported in a cantilevered manner. In addition, since the bearings 100 of the input side case 50 and the output side case 70 can be aligned in a single row, a more compact casing C can be realized compared to the reduction gear mechanism 10 described above.

[0068] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that those skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas disclosed herein, and it is understood that these modifications also fall within the technical scope of the present invention.

[0069] 1, 1a, 10, 10a: Reduction mechanism 2, 20, 20a: Input shaft 3, 3', 3a, 30: External gear 4, 40: Torque disc 5: Fixed hub 5a: Fixed plate 6, 6a, 60, 60a: Internal gear 21: General part 22, 22a: Eccentric part 23: Auxiliary tool 31, 51: Convex rib 32, 43, 52: Hole 41, 42: Groove 50: Input side case 100: Bearing

Claims

1. A reduction mechanism comprising an input shaft, an external gear, a torque disc, a fixed portion, and an internal gear, wherein the input shaft has a general portion and an eccentric portion that is eccentric relative to the general portion, the external gear has a central axis that coincides with the eccentric portion and is rotatably supported by the eccentric portion, the torque disc is disposed between the external gear and the fixed portion, and the fixed portion is fixed in the reduction mechanism, the internal gear is disposed on the outer periphery of the external gear so that some of the teeth of the internal gear and the external gear mesh with each other, the external gear is engaged with the torque disc so that the direction in which the external gear can move relative to the torque disc in a plane perpendicular to the input shaft is restricted to a first direction, and the torque disc is engaged with the fixed portion so that the direction in which the external gear can move relative to the fixed portion in a plane perpendicular to the input shaft is restricted to a second direction perpendicular to the first direction, and when the general portion of the input shaft rotates, the external gear revolves along the inner circumference of the internal gear without rotating.

2. The reduction gear mechanism according to claim 1, characterized in that the engagement between the external gear and the torque disc, and the engagement between the torque disc and the fixed portion are achieved by a groove provided in a straight line on either side of a hole through which the input shaft passes, and a protrusion that fits into the groove, and the protrusion is provided on one of the external gear and the torque disc, and one of the torque disc and the fixed portion, and the groove is provided on the remaining other one.

3. The reduction gear mechanism according to claim 2, wherein a pair of said ridges are formed on either side of said hole on either said external gear or said torque disc.

4. The reduction mechanism according to claim 2, wherein the ridge is formed on only one side of the hole in one of the external gear and the torque disc.

5. The reduction gear mechanism according to claim 1, characterized in that the input shaft, the external gear, the torque disc, and the internal gear are disposed within a casing having the fixed portion, the internal gear has a ring-shaped main body and an output shaft, the general portion of the input shaft is rotatably supported within a hole in the fixed portion by bearings arranged in multiple rows in the axial direction of the input shaft, and the output shaft is rotatably supported within a hole in the casing by bearings arranged in multiple rows in the axial direction of the output shaft.

6. The reduction gear mechanism according to claim 1, characterized in that the input shaft, the external gear, the torque disc, and the internal gear are disposed within a casing having the fixed portion, the internal gear has a ring-shaped main body, an output shaft, and an end plate closing the output shaft side of the main body, the general portion of the input shaft is rotatably supported by bearings arranged in a row within a hole in the fixed portion, an auxiliary device provided at the tip of the eccentric portion of the input shaft is rotatably supported by bearings provided in an internal space of the end plate, and the output shaft is rotatably supported by bearings arranged in a row within a hole in the casing.