SHAFT COUPLING ARRANGEMENT

Abstract

Shaft coupling arrangement in which a second shaft (16) is inserted into a cylindrical part (18) provided in a first shaft (12) so that they are coupled together, wherein a bushing (52) is inserted between an inner circumference of the first shaft (12) and an outer circumference of the second shaft (16), and wherein the first shaft (12) and the second shaft (16) are coupled together by a combination of a spring coupling and a clamping coupling, wherein the first shaft (12) has a spring groove (56; 62K) with which a spring (54) engages, and a shaft recess (62S; 62S1) formed in the cylindrical part (18) by cutting out a portion thereof in an axial direction, wherein a fastening device (58) for the clamping coupling is mounted on a portion of the outer circumference of the first shaft (12) in which the shaft recess (62; 62S; 62S1) is formed. is, wherein the socket (52) has a socket recess (64;64A) which coincides with the spring groove (56; 62K); and wherein, after the clamping coupling is closed, the bushing recess (64; 64A) of the bushing (52) has a width (Bc1) which is greater than a width (Sc1) of the spring groove (56; 62K) of the first shaft (12).;

Description

BACKGROUND Technical field The present invention relates to a shaft coupling arrangement. Description of the related technique The related technology discloses a shaft coupling arrangement in which a motor shaft is inserted into a hollow part provided in an input or drive shaft which are to be coupled together. In the shaft coupling arrangement, a spring groove is formed in both the drive shaft and the motor shaft, and a slot is formed in the drive shaft. The drive shaft and the motor shaft are coupled together by a combination of a spring coupling and a clamping coupling. Power transmission is carried out via the spring, and the clamp bridges a gap between the spring and the spring groove, thereby helping to reduce vibration and noise. Since the shaft coupling arrangement described above required preparation for each type of motor shaft, it was likely that the costs would be high. In certain embodiments of the present invention, it is desirable to provide a shaft coupling arrangement that can be applied to a coupling between different types of shafts at low cost by a combination of a spring coupling and a clamping coupling. Furthermore, reference should be made to JP 2009-257 543 A, which discloses a rotary shaft connection structure and a geared motor, wherein spacers between a shaft keyway and a shaft and between a keyway and a key prevent possible phase shifts caused by abrupt load changes between the shaft and the geared motor. Furthermore, JP 2002-206 560 A shows a connection structure of a hollow shaft on a shaft connected to each other by a power transmission element (tongue and groove connection), wherein a non-metallic bushing is arranged between the hollow shaft and the shaft, but not between the tongue and groove. Furthermore, JP 2010-190 412 A discloses a power transmission mechanism and a manufacturing process for a hollow shaft of a power transmission mechanism, wherein a coating is applied to the inner circumferential surface of a hollow shaft. The coating is a composite material of Fluoresin® PTFE dispersed in the base material nickel. Finally, DE 101 38 220 C1 discloses a connection between a slotted hollow shaft and a mating part engaging in it, wherein the slotted hollow shaft is, for example, provided with a pinion and is clamped to a mating part, the hollow shaft having a slotted area in the connection area into which the mating part engages in the operating position. To bridge the difference between the inner diameter of the hollow shaft and the outer diameter of the mating part, a reducing bushing with axially extending slots for radial compliance during the clamping process is arranged between them. The length of the slots of the reducing bushing is equal to or greater than the effective axial extent of the clamping area of ​​a clamping or clamping element. SUMMARY The object of the present invention is achieved by a shaft coupling arrangement according to claim 1. The dependent claims relate to preferred embodiments of the invention. According to one embodiment of the present invention, a shaft coupling arrangement is provided in which a second shaft is inserted into a cylindrical part provided in a first shaft so that they are coupled together. The first shaft and the second shaft are coupled together by a combination of a spring coupling and a clamping coupling, wherein a bushing is inserted between an inner circumference of the first shaft and an outer circumference of the second shaft. The first shaft has a spring groove with which the spring engages, as well as a shaft recess formed in the cylindrical part by cutting out a portion of it in the axial direction.A fastening device for the clamping coupling is mounted on a portion of the outer circumference of the first shaft, in which the shaft recess is formed. The sleeve or bushing has a bushing recess that corresponds to the spring groove. In the embodiment of the present invention, when the second shaft is coupled to the inner circumference of the first shaft, wherein the bushing is inserted between the inner circumference of the first shaft and the outer circumference of the second shaft, the coupling is implemented based on the combination of the spring coupling and the clamping coupling. At this point, the first shaft has the spring groove and the shaft cut, which is formed in the cylindrical part by cutting out a portion of it in the axial direction, and the fastening device for the clamping coupling is attached to a portion of the outer circumference of the first shaft in which the shaft cut is formed. On the other hand, the bushing has the bushing cut, which corresponds to the spring groove of the first shaft. Accordingly, enjoying the advantages of both the spring coupling and the clamp coupling, a first shaft and a second shaft of different shapes and sizes can be coupled together at a lower cost if a bushing that corresponds to the shafts of the different shapes and sizes is simply inserted between them. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a main part of a shaft coupling arrangement according to an exemplary embodiment of the present invention and is an enlarged cross-sectional view taken along line II in Fig. 2. Fig. 2 is a cross-sectional view showing an exemplary configuration in which the shaft coupling arrangement according to the exemplary embodiment of the present invention is applied to a coupling between a motor shaft of a motor and a drive shaft of a speed reducer. Fig. 3 is an explanatory drawing that schematically illustrates a size relationship between the widths of a bushing recess, a spring groove, and a spring. Fig. 4 is an enlarged cross-sectional view, corresponding to Fig. 1, according to another exemplary embodiment of the present invention. Fig. 5A shows a cross-sectional view of a bushing taken along a line perpendicular to the axis shown in Fig.Figure 5B shows a cross-sectional view of the bushing taken along the arrows VB-VB in Fig. 5A, according to yet another exemplary embodiment of the present invention. DETAILED DESCRIPTION An exemplary embodiment of the present invention is described in detail below with reference to the accompanying drawings. Fig. 2 is a cross-sectional view showing an exemplary configuration in which a shaft coupling arrangement according to an exemplary embodiment of the present invention is applied to a coupling between a motor shaft of a motor and a drive shaft of a speed reducer. A coupling arrangement between a drive shaft 12 (a first shaft) of a speed reducer 10 and a motor shaft 16 (a second shaft) of a motor 14 will be described later, and first a schematic configuration of the power transmission system of the speed reducer 10 will be briefly described with reference to Fig. 2. The speed reducer 10 is a speed reducer of an eccentrically oscillating design and is widely used in robot articulated drives and machine tool drive systems. The drive shaft 12 of the speed reducer 10 is located at the center point O1 of an internal gear 22. An eccentric body 26 is integrally formed with the drive shaft 12. An external gear 20 is attached to the outer circumference of the eccentric body 26 via a roller 28. The external gear 20 meshes internally with the internal gear 22. The internal gear 22 is integrated with a housing 30. The external gear 20 has fewer teeth (down to just one in this example) than the internal gear 22. A pin-shaped link 32 passes through each of the external gears 20. On both sides of the external gear 20, a pair of a first support 34 and a second support 36 are rotatably mounted in the axial direction through the housing 30 via bearings 38 and 40. The first support 34 and the second support 36 are coupled to each other via the pin-shaped link 32 and a bolt 42. A driven link, not shown, is coupled to the first support 34 via a keyway or a threaded bore 34A. The operation of the power transmission system of the speed reducer 10 is briefly described. When the input or drive shaft 12 is rotated, the eccentric body 26, which is integrated with the drive shaft, rotates, and the external gear 20 oscillates over the roller 28. As a result, a phenomenon occurs in which the engagement position of the external gear 20 shifts sequentially relative to the internal gear 22. Since the number of teeth on the external gear 20 is at least one less than the number of teeth on the internal gear 22, the external gear 20 shifts out of phase by at least one tooth relative to the internal gear whenever the drive shaft 12 is rotated. The rotational component is transmitted to the first support 34 and the second support 36 via the pin-like link 32, thereby driving the driven link, which is coupled to the drive link via the first support 34 and the threaded bore 34A. The following describes in detail, with reference to Figures 1 to 3B, a coupling arrangement between the drive shaft 12 (the first shaft) of the speed reducer 10 and the motor shaft 16 (the second shaft) of the motor 14 according to the exemplary embodiment. The dimensions of the gaps and similar features do not necessarily correspond to the actual dimensions of these, so that the exemplary embodiment of the present invention can be understood in a simplified manner. In the coupling arrangement, the drive shaft 12 and the motor shaft 16 are coupled to each other by inserting the tip of the motor shaft 16 into a hollow (cylindrical) part 18 provided in the drive shaft 12. A sleeve or bushing 52 is inserted between an inner circumference 12A of the drive shaft 12 and an outer circumference 16A of the motor shaft 16, and the drive shaft 12 and the motor shaft 16 are coupled to each other by a combination of a clutch via a spring 54 and a clamping clutch via a fastening device 58. The motor shaft 16 of the motor 14 has a spring groove 56 formed along its outer circumference 16A in the axial direction. In the exemplary embodiment, a universal motor is used as the motor 14, and the motor shaft 16 and the spring groove 56 of the universal motor 14 are used as originally configured. The drive shaft 12 of the speed reducer 10 is supported by the first support 34 and the second support 36 via ball bearings 44 and 46. The drive shaft 12 has the hollow section 18 on a side opposite a load side in the axial direction (on the side of the motor 14). The drive shaft 12 has a stepped section on the side of the motor 14, which is formed by a substantially axial center position of the hollow section 18 via two steps 12K1 and 12K2, and the stepped section has a thinner wall thickness than the rest of the hollow section 18. The drive shaft 12 has a spring groove 62K, which extends from an end surface 12E on the motor side to an axial position slightly beyond steps 12K1 and 12K2, where the spring 54 engages with the spring groove 62K, and has a clamping shaft recess 62S, which is formed by cutting out a portion of the hollow part 18 in the axial direction. In the exemplary embodiment, however, a single shaft groove 62 serves as both the spring groove 62K and the shaft recess 62S (the shaft groove 62, the spring groove 62K, and the shaft recess 62S refer to the same single part). That is, in appearance, the drive shaft 12 has the single shaft groove 62 that serves as both the spring groove 62K and the shaft recess 62S. For the sake of simplicity, the physical “shaft groove 62” will be appropriately referred to in the description as the spring groove 62K when the shaft groove is focused on serving as a spring groove, and as the shaft notch 62S when the shaft groove is focused on serving as a shaft notch. On the other hand, the bushing 52 has a cylindrical shape, a flange or collar 52P, and a bushing recess 64, which is formed such that it extends through these in the axial direction, and the bushing recess 64 corresponds to the spring groove 62K (shaft groove 62) of the drive shaft 12. The bushing recess 64 is designed in such a way that the spring 54 can extend beyond the bushing 52 in the radial direction and engage with both the spring groove 56 of the motor shaft 16 and the spring groove 62K of the drive shaft. The collar 52P is clamped between the end surface 12E of the drive shaft 12 and a snap ring 68, which is engaged in the motor shaft 16, thereby positioning the bushing 52 in the axial direction. The fastening device 58 for the clamping coupling is mounted on a part on an outer circumference 12B of the drive shaft 12, in which the shaft recess 62S is formed. The fastening device 58 has recessed sections 70 and 71 for reducing the diameter of the shaft and tightens the drive shaft 12 from the radial outside by tightening a bolt 72, thereby reducing the diameter of the drive shaft 12. In the exemplary embodiment, the tightening is carried out in a state where the recessed sections 70 and 71 of the fastening device 58 are arranged in positions P2 and P3 at a substantially 90° angle to position P1, where the shaft groove 62, which serves as both the spring groove 62K and the shaft recess 62S, is located. The bushing 52 has an axial length L1 (axial length of the bushing recess 64) which is longer than an axial length L2 of the fastening device 58 (refer to Fig. 1). The following describes, with reference to Fig. 3A and Fig. 3B, a size relationship between each part in the exemplary embodiment. The symbols are defined as follows: Bf1: the width of the bushing recess 64 of the bushing 52 in a free state (before clamping is performed); Bc1: the width of the bushing recess 64 of the bushing 52 after clamping is completed; Sf1: the width of the shaft groove 62 (= the spring groove 62K = the shaft recess 62S) of the drive shaft 12 in a free state; Sc1: the width of the shaft groove 62 (= the spring groove 62K = the shaft recess 62S) of the drive shaft 12 after clamping is completed; K1: the width of a spring; M1: the width of the spring groove 56 of the motor shaft 16 Since the shaft groove 62 of the drive shaft 12 becomes small due to a reduction in the diameter of the drive shaft 12 after the clamping process is complete, compared to a free state (before clamping), the width Sc1 becomes smaller than the width Sf1, where Sc1 is the width of the shaft groove 62 after the clamping process is complete, and Sf1 is the width of the shaft groove 62 in a free state (Sc1 <Sf1) ist. In ähnlicher Weise ist die Breite Bc1 kleiner als die Breite Bf1, wo Bc1 die Breite des Buchseneinschnitts 64 ist, nachdem das Festklemmen abgeschlossen ist, und Bf1 die Breite des Buchseneinschnitts 64 in einem freien Zustand ist (Bc1<Bf1). In the embodiment, after the clamping coupling is completed, the bushing recess 64 of the bushing 52 has a width Bc1 that is larger than the width Sc1 of the spring groove 62K of the drive shaft 12 (Bc1>Sc1). Even after the clamping coupling is closed, the spring groove 62K of the drive shaft 12 also has a width Sc1 that is larger than the width K1 of the spring 54 (Sc1>K1). Furthermore, the width Bc1 is greater than the width Sf1, where Bc1 is the width of the bushing recess 64 after the clamping is complete and Sf1 is the width of the shaft groove 62 of the drive shaft 12 in a free state (Bc1>Sf1). As a result, as can be seen in Fig. 3A, a relationship BF1>Bc1>Sf1>Sc1>K1 is formed. After clamping is complete, the shaft groove 62 is adjusted in the exemplary embodiment such that the width Sc1 is identical to the width M1 of the spring groove 56 of the motor shaft 16 (Sc1 ≅ M1). However, after clamping is complete, it is not necessarily required for the shaft groove 62 to have a width Sc1 identical to the width M1 of the spring groove 56 of the motor shaft 16, and it can, for example, be adjusted to have a width greater than the width M1 of the spring groove 56 of the motor shaft 16. The following describes the operation of the shaft coupling arrangement. In the shaft coupling arrangement according to the exemplary embodiment, the bushing 52 and the spring 54 are inserted between the inner circumference 12A of the drive shaft 12 and the outer circumference 16A of the motor shaft 16. The bushing 52 and the spring 54 are pre-assembled onto either the drive shaft 12 or the motor shaft 16, and in the pre-assembled state, the motor shaft 16 is fitted into the hollow part 18 of the drive shaft 12. For example, first the position (position P1 in Fig. 1) of the bushing recess 64 of the bushing 52 is aligned with the shaft groove 62 (as the spring groove 62K) of the drive shaft 12. Then the bushing 52 is mounted onto the inner circumference 12A of the drive shaft 12. In this state, the spring 54 is mounted in the spring groove 56 of the motor shaft 16, the position of the spring 54 is aligned with position P1 of the shaft groove 62 of the drive shaft 12, and then the motor shaft 16 together with the spring 54 is inserted into the hollow part 18 of the drive shaft 12. The fastening device 58 is attached to a part of the outer circumference of the drive shaft 12 in which the shaft groove 62 (as shaft recess 62S) is formed, and the drive shaft 12 is tightened by screwing in the bolt 72 of the fastening device 58 (diameter reduction). At this point, the width of the shaft groove 62 of the drive shaft 12 is reduced from Sf1 to Sc1, but, since the shaft groove 62 is set so that the width Sc1 is greater than the width K1 of the spring 54, even after the clamping coupling is completed (as well as in a free state), there is no possibility that the shaft groove 62 of the drive shaft 12 will come into contact with the spring 54 in the middle of the clamping process, thus preventing the diameter of the drive shaft 12 from being reduced further. Additionally, since the bushing recess 64 of the bushing 52 always has a width Bc1 that is larger than the width Sc1 of the shaft groove 62 after clamping is complete, there is no possibility that the bushing recess 64 of the bushing 52 will come into contact with the spring 54 while the shaft groove 62 of the drive shaft 12 is being reduced in diameter. Therefore, the diameter of the drive shaft 12 cannot be reduced further without friction. That is, regardless of the fact that the bushing 52 is inserted between the drive shaft 12 and the motor shaft 16, the reduction in diameter of the drive shaft 12 can be reliably carried out by the fastening device 58 without being affected by the presence of the spring 54 and the presence of the bushing 52. As is evident from the operation of the coupling described above, in this embodiment a gap exists between the spring 54 and the spring groove 62K and between the spring 54 and the bushing recess 64, even after clamping is complete. Accordingly, power transmission is based on the clamping coupling. In particular, power transmission is achieved by the frictional clamping force between the outer circumference 16A of the motor shaft 16 and the inner circumference of the bushing 52, as well as by the frictional clamping force between the outer circumference of the bushing 52 and the inner circumference 12A of the drive shaft 12. The spring 54 does not contribute to power transmission between the motor shaft 16 and the drive shaft 12 (during normal operation). In this respect, for example, the exemplary embodiment differs considerably in the technical concepts of the coupling from an arrangement with a combination of spring and clamping in the related technology described above. That is, in the shaft coupling arrangement of the related technology, "the power transmission is essentially carried out via the spring, and the clamping bridges a gap between the spring and the spring groove, thereby preventing vibration and noise," and the spring assumes the role of power transmission.However, when this configuration is applied to a configuration where the bushing is inserted between the motor shaft and the drive shaft, the diameter reductions of the drive shaft and the bushing are not only prone to interfering with each other via the spring while the diameter reduction is being carried out, but also (since the bushing exists between the spring groove of the motor shaft and the spring groove of the drive shaft) the gaps in either spring groove are prone to being incompletely bridged and remaining. That is, the arrangement according to the related technique described above is generally not suitable for the arrangement where the bushing is inserted. Even in a free state, or even during or after clamping, this embodiment is configured in such a way that there is essentially no interference between the spring 54 and the shaft groove 62, or between the spring 54 and the bushing recess 64. In this way, clamping (diameter reduction) of the drive shaft 12 can be carried out smoothly, even with the bushing 52 inserted. Furthermore, since power transmission is essentially achieved by relying on the clamping coupling, the advantages of the clamping coupling, such as the absence of backlash, low vibration, and low noise, can be fully utilized. Additionally, even in the event that the frictional transmission force is lost due to unknown causes, a coupling via the spring 54 serves as a safeguard or support, thus preventing a driven machine coupled to the drive element from behaving unexpectedly. In such a configuration, where the spring coupling and the clamp coupling are combined, the configuration can be applied to a coupling between different types of shafts at low cost simply by appropriately designing the bushing. More precisely, if a coupling between the drive shaft 12 (the first shaft) of the speed reducer 10 and the motor shaft 16 (the second shaft) is described as an example, the motor shaft 16 can have a diameter of various sizes, but a type of drive shaft 12 can serve the motor shaft 16 with such a wide range of diameters by providing a variety of bushing types 52 with an inner diameter corresponding to the diameter of the motor shaft 16. Additionally, since the motor shaft can have a cylindrical shape, it can also have a chamfered or tapered shape.Even in such a case, the drive shaft 12 with a cylindrical, hollow part can operate the motor shaft of any shape by preparing the bushing with a tapered inner circumference. A second embodiment of the present invention is described below. The same reference numerals and symbols are assigned to the same or similar parts of the first embodiment. Fig. 4 shows an example in which a shaft cut 62S1 is added to the drive shaft 12 (the first shaft) and as a result a plurality of shaft cuts (2 pieces) are formed in conjunction with the same shaft cut 62S (which also serves as a spring groove) as in the first embodiment. The additional shaft groove 62S1 is formed in a position opposite the shaft groove 62S (180° opposite position), which also serves as a spring groove. In the embodiment, irrespective of the fact that the plurality of shaft recesses 62S and 62S1 are formed in the drive shaft 12, the bushing 52 does not have a plurality of bushing recesses 64, but has only one bushing recess 64, wherein the bushing recess 64 also serves as the same shaft recess as in the first embodiment. One intention of the configuration is as follows. That is, if the multiple shaft grooves 62S and 62S1 are formed in the drive shaft 12, the advantage is that a uniform reduction in the diameter of the drive shaft 12 is achieved much more easily compared to if only one shaft groove is formed. Accordingly, an offset between the drive shaft 12 and the shaft groove 62 can be suppressed, and stress concentration near the shaft groove 62 can be reduced. Additionally, the shaft grooves 62S and 62S1 formed in the drive shaft 12 (the first shaft) can be machined relatively easily by clamping a portion of the drive shaft 12 on one side opposite the motor side in the axial direction.On the other hand, if the multiple bushing slots are formed in the bushing 52, the bushing is not prone to clamping in many cases during machining, and consequently, the bushing slots are not necessarily formed (machined) in a simple manner. Additionally, since the bushing 52 absorbs the diameter-reducing force from the fastening device 58 via the drive shaft 12, the uniform diameter-reducing force of the drive shaft 12 essentially enables a relatively uniform diameter reduction of the bushing 52. Accordingly, if a configuration is made such that the drive shaft 12 (the first shaft) has the shaft slots 62S and 62S1, and the bushing 52 has only one bushing slot 64, it can be said that the configuration exhibits realistic machinability and uniform clamping, which are compatible with each other. The drive shaft 12 can have three or more shaft slots (as long as the strength or rigidity necessary for power transmission is ensured). In terms of quality, the more shaft slots the drive shaft 12 has, the more uniformly its diameter can be reduced. Additionally, in the example shown in Fig. 4, similar to the first embodiment, a shaft groove 62 is formed, which serves both as the spring groove 62K and the shaft recess 62S. Furthermore, a shaft recess 62S1 (which does not serve as a spring groove) is formed with a width smaller than 62K. However, as in Fig. 4, the additional shaft recess can also be formed such that it has a width (the width Sf1 in a free state and the width Sc1 after clamping is complete) that the additional shaft recess can serve as the same spring groove as the shaft groove 62. In this case, since the shaft recesses can be machined continuously using the same tool, manufacturing can be made much simpler. Fig. 5 shows a modification example of the bushing. As described above, due to the challenging clamping or similar aspects, it is not necessarily easy in practice to shape the bushing cut in the bushing in such a way that it passes through it in the axial direction or to form the multitude of bushing cuts of a long length in the bushing. In the bushing 52, shown in Fig. 5, a plurality of the bushing recess 64 and one bushing recess 64A each have different axial lengths L4 and L5. That is, since the bushing recess 64 passes through the bushing 52 in the axial direction, the bushing recess 64 has an axial length L4 that is identical to the axial length L1 of the bushing 52. However, the bushing recess 64A does not pass through the bushing 52 in the axial direction, and the bushing recess 64A has an axial length L5 that is smaller than the axial length L4 of the bushing recess 64 (L4 > L5). Since the strength of the bushing 52, which is necessary for clamping it, can be ensured when the processing is carried out, easy processing and uniform clamping, which are compatible with each other, can accordingly be achieved. In the bushing 52 according to the exemplary embodiment, if the bushing recess 64 extends through the bushing 52 and is long, the bushing recess 64 becomes a wide bushing recess with which the spring 54 (not shown in Fig. 5) can engage, and if the bushing recess 64 does not extend through the bushing 52 and is short, the bushing recess 64 becomes a narrow bushing recess with which the spring 54 cannot engage. Similar to the modification example, the additional bushing recess can also be a wide bushing recess with which the spring 54 can engage. The bushing can have three or more bushing recesses. As such, in the plurality of bushing slots, even if there is one bushing slot that does not extend through, the bushing slot preferably has an axial length (L5 in this case) that is longer than the axial length L2 of the fastening device 58 (not shown in Fig. 5, and reference is made to Fig. 2). Accordingly, partial contact of the fastening device 58 can be prevented when clamping is carried out. The following section, again with reference to Fig. 3A and Fig. 3B, describes a size relationship between the widths of a bushing recess, a spring groove and a spring. As described above, in Fig. 3A, after the clamping is complete, the bushing recess 64 is adjusted to have a width Bc1 that is greater than the width Sf1 of the shaft groove 62 of the drive shaft 12 in a free state (Bc1 > Sf1). However, the exact size relationship shown, for example, in Fig. 3B is not necessarily required. If, in summary, a relationship is maintained "in which, after the clamping coupling is complete, the bushing recess 64 has a width Bc2 that is greater than a width Sf1 of the spring groove 64K of the drive shaft 12," there are hardly any concerns regarding practicality.Although, for example, the bushing recess 64 in a free state has a width Bf2 which is smaller than a width Sf2 of the spring groove 62K in a free state, there are no concerns as long as the bushing recess 64, after the clamping is complete, has a width Bc2 which is larger than the width Sc2 of the spring groove 62K after the clamping is complete. In all of Figs. 3A to 3B, it is necessary to maintain a configuration, even after the clamping is complete, in which the spring groove 62K of the drive shaft 12 has a width Sc1 or Sc2 that is greater than the width K1 of the spring 54 (Sc1>K1 or Sc2>K1) and consequently the clamping is carried out reliably throughout the entire operation. In some embodiments of the present invention, however, a reversal of the size relationship (Sc1>K1 or Sc2>K1) is not completely excluded. That is, after the clamping is complete, the spring groove 62K of the drive shaft 12 can be designed to have a width Sc1 that is smaller than the width K1 of the spring 54 (Sc1 <k1). in diesem fall dient das festklemmen durch die befestigungsvorrichtung 58 dazu, einen spalt zwischen der feder 54 und federnut 62k zu entfernen. demgemäß kann eine leistungsübertragung, leistungsübertragung umfasst, bewerkstelligt werden. selbst in fall, wenn reibungsbefestigungskraft selbst perfekter weise aufrecht erhalten wird ausgelegt ist, um beständig auf basis klemmkraft ausgeführt werden, geeignete einstellung abmessungen jedes glieds einfacher gesteuert zusätzlich, nachdem abgeschlossen breite sc1 (sc2) besitzen, identisch bc1 des buchseneinschnitts ist oder < aufweisen.In the embodiments described above, the groove in the drive shaft serves as the spring groove of the drive shaft, but in certain embodiments of the present invention, the shaft groove is not necessarily required to serve as a spring groove. For example, a groove serving only as a spring groove may be individually formed in a circumferential position that differs from a circumferential position where a groove serving only as a groove is formed; otherwise, the spring groove may be formed in the same circumferential position, and the groove may be formed outside the circumference of the spring groove such that it has a width that is smaller than the spring groove. In addition, in the embodiments described above, certain embodiments of the present invention are applied to a coupling between a motor shaft and a drive shaft of a speed reducer, but are not limited to the coupling between the motor shaft and the drive shaft of the speed reducer. Certainly, a speed reducer configuration is not limited to the configuration described above. For example, in a speed reducer of the eccentrically oscillating type with a plurality of eccentric body shafts (each possessing an eccentric body) at positions offset from the center point of an internal gear shaft, or of a so-called distribution type, certain embodiments of the present invention can be applied, for example, to a part where the drive shaft of the speed reducer is coupled to a motor.In addition, certain embodiments of the present invention are not limited exclusively to the speed reducer, but can collectively find broad application in a shaft coupling arrangement where a second shaft is inserted into a cylindrical part provided in a first shaft, so that they are coupled together. It should be understood that the invention is not limited to the embodiment described above, but can be modified in various ways based on the teachings of the invention. These modifications are additionally included within the scope of the invention.

Claims

Shaft coupling arrangement in which a second shaft (16) is inserted into a cylindrical part (18) provided in a first shaft (12) so that they are coupled together, wherein a bushing (52) is inserted between an inner circumference of the first shaft (12) and an outer circumference of the second shaft (16), and wherein the first shaft (12) and the second shaft (16) are coupled together by a combination of a spring coupling and a clamping coupling, wherein the first shaft (12) has a spring groove (56; 62K) with which a spring (54) engages, and a shaft recess (62S; 62S1) formed in the cylindrical part (18) by cutting out a portion thereof in an axial direction, wherein a fastening device (58) for the clamping coupling is mounted on a portion of the outer circumference of the first shaft (12) in which the shaft recess (62; 62S; 62S1) is formed. is, wherein the socket (52) has a socket recess (64;64A) which coincides with the spring groove (56; 62K); and wherein, after the clamping coupling is closed, the bushing recess (64; 64A) of the bushing (52) has a width (Bc1) which is greater than a width (Sc1) of the spring groove (56; 62K) of the first shaft (12).; Shaft coupling arrangement according to claim 1, wherein a single groove serves both as the spring groove (56; 62K) of the first shaft (12) and as the shaft recess (62S; 62S1). Shaft coupling arrangement according to claim 1, wherein even after the clamping coupling is closed, the spring groove (56; 62K) of the first shaft (12) has a width (M1) that is greater than a width (K1) of the spring (54). Shaft coupling arrangement according to claim 1, wherein the first shaft (12) has a plurality of shaft slots (62S; 62S1; 62S1), and the bushing (52) has only one bushing slot (64; 64A). Shaft coupling arrangement according to claim 1, wherein the bushing (52) has a plurality of bushing slots (64; 64A), and at least two bushing slots (64; 64A) have axial lengths that differ from each other. Shaft coupling arrangement according to claim 5, wherein within the plurality of bushing cuts (64; 64A) a bushing cut is formed such that it passes through the bushing (52) in the axial direction. Shaft coupling arrangement according to claim 6, wherein within the plurality of bushing cuts (64; 64A), the bushing cuts which do not pass through the bushing (52) have axial lengths which are longer than an axial length of the fastening device (58).

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