JP2005172217A - Shaft coupling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft coupling, having a structure compact in the axial direction, having no limitation of transmission power and eccentric amount, inexpensive and having excellent assembling nature. <P>SOLUTION: Two or more guide grooves 5, 6 are provided on the opposite surfaces of plates 1, 2 fitted to the shaft end parts of the opposite input and output shafts A, B to intersect perpendicularly to the guide grooves in the corresponding positions of the counterpart plate. Steel balls 3 disposed in the intersecting positions of the guide grooves 5, 6 in both plates 1, 2 are pressed to a retainer 4 to be restrained from moving in the radial direction of the plate by the drive side plate 1, and rolled in the guide grooves 5, 6 to press the driven side plate 2 and transmit the power. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a shaft coupling that connects two parallel shafts and transmits power between the two shafts.

  A shaft joint that connects two shafts of a general mechanical device and transmits power from the drive side to the driven side has a different structure depending on the positional relationship between the two shafts to be connected. And those that are parallel to each other (and not concentric).

  Of these, an Oldham coupling is well known as a shaft coupling for connecting two parallel axes. However, when the Oldham coupling transmits a large amount of power, poor lubrication may occur on the friction surface between the sliders interposed between the two shafts, and the power transmission may not be performed smoothly, and a large amount of eccentricity (2 There is also a problem that the amount of deviation of the shaft in the radial direction cannot be allowed.

  There is also a method of connecting two parallel axes by combining two constant velocity joints instead of Oldham joints. However, in this method, since the operating angle of the constant velocity joint is limited, a large amount of eccentricity is required. When it is going to obtain, an axial direction length becomes long and an apparatus is easy to enlarge.

  On the other hand, a plate is inserted between two rotating members (disks) that face each other in the axial direction, and linear guides are placed at a plurality of locations on the front and back surfaces of the plate so that their operating directions are perpendicular to each other on the front and back surfaces of the plate. If a mechanism for transmitting power between the rotating members via the plate and the linear motion guide is adopted, the structure becomes compact in the axial direction, and the apparatus can be downsized. In addition, the required amount of eccentricity can be obtained simply by changing the length of the linear motion guide, and a large amount of power can be obtained by arranging a plurality of steel balls on the surfaces of the linear motion guide that move relative to each other. It can also be transmitted smoothly (see Patent Document 1).

However, in the shaft coupling having the above-described mechanism, a large number of linear guides are used, so that the manufacturing cost of the entire coupling is considerably increased. Each linear guide consists of a guide member and a rail member that move relative to each other, and one of them needs to be aligned and fixed to the rotating member and the other to the plate. There is also a problem that it is difficult to assemble with high precision so as to move, and that the assembling work is very time-consuming.
JP 2003-260902 A

  An object of the present invention is to provide a shaft coupling that has a compact structure in the axial direction, has few restrictions on transmission power and eccentricity, is inexpensive, and has excellent assemblability.

  In order to solve the above-described problems, the shaft coupling of the present invention has a plurality of guide grooves formed on the opposing surfaces of the two rotating members which are opposed in the axial direction and are held in a state where the rotating shafts are parallel to each other and not concentric. Are arranged so as to be orthogonal to the guide grooves at corresponding positions of the rotating member on the other side, and rolling elements that roll while being guided by the guide grooves are arranged at positions where the guide grooves of the two rotating members intersect. A cage for restricting the movement of each rolling element in the radial direction of the rotating member is provided so that power is transmitted between the rotating members via each rolling element (claim 1).

  In other words, the rolling elements arranged at the intersecting positions of the guide grooves of the two rotating members are pushed by the driving-side rotating member in a state where the movement of the rotating member in the radial direction is constrained by the cage and roll in the guide grooves. By pushing the driven side rotating member while transmitting power, the frictional resistance during power transmission is reduced so that large power can be transmitted smoothly and the length of the guide groove is changed. The necessary amount of eccentricity was obtained. Moreover, by using only the rolling elements and the cage as the parts arranged between the two rotating members, the structure is reduced in the axial direction, the manufacturing cost is reduced, and the assemblability is improved.

  In the above configuration, each rotating member, rolling element, and cage is formed of a metal material, and the surface thereof is subjected to a curing process, so that the contact portion of each member is caused by stress acting between the members during power transmission. It is possible to prevent plastic deformation and surface damage (claim 2).

  By forming each guide groove linearly in the longitudinal direction, the guide groove can be easily processed, and the contact surface pressure between the guide groove and the rolling element is kept constant, thereby preventing the generation of excessive surface pressure. (Claim 3). At this time, if each of the guide grooves is formed to extend in a direction that forms 45 degrees with the radial direction of the rotating member, the guide groove processing becomes easier and the contact surface pressure between the guide groove and the rolling element is kept constant. It becomes easy and generation | occurrence | production of excessive surface pressure can be prevented more reliably (Claim 4).

  By using the rolling element as a sphere, the rolling element can be prevented from being twisted (Claims 5 and 6). At this time, if the cross-sectional shape of the guide groove is formed by a curved surface having a radius of curvature larger than the radius of the rolling element, the contact surface pressure between the guide groove and the rolling element can be kept low. If the cross-sectional shape of the contact surface with the rolling element of the cage is a curved surface having a radius of curvature larger than the radius of the rolling element, the contact surface pressure between the cage and the rolling element can be kept low. (Claim 6). On the other hand, if the contact surface of the cage with the rolling element is formed as a flat surface, the cage can be easily manufactured.

  At least one of the contact surface between the guide groove and the rolling element and the contact surface between the cage and the rolling element is dry plating, wet plating, melting treatment, thermal spraying, ion implantation, sulfurization treatment, chemical conversion treatment, surface One or more surface treatments of heat treatment and shot peening are applied to reduce the friction coefficient of the contact surface (Claim 8), between the contact surface of the guide groove and the rolling element, and the cage Between the contact surfaces of the rolling elements and the contact surfaces of the rolling elements with a lubricant (claim 9). Abrasion and heat generation due to friction can be suppressed, and the resistance against relative movement when the rotation axes of both rotating members are shifted can be reduced.

  Further, by providing an axial restraint mechanism that restrains changes in the axial spacing between the rotating members, it is possible to integrate the members and further improve the assemblability (claim 10).

  As the axial direction restraining mechanism, a mechanism that is disposed on the opposite side of the opposing surface of each rotating member and that sandwiches both rotating members with two restraining members connected to each other can be adopted.

  In the axial direction restraint mechanism having the above configuration, any one or more of the same types of surface treatment as in claim 8 may be applied to the contact surface of at least one of the contact surfaces of the rotating member and the restraint member. And reducing the friction coefficient of the contact surface (Claim 12), or interposing a lubricant or a sliding material between the rotating member and the restraining member (Claims 13 and 14), The frictional force acting between each rotating member and the restraining member when the rotating shafts of both rotating members are displaced can be reduced.

  Further, if the distance between the two restraining members is variable and the force with which the two restraining members sandwich the rotating member can be adjusted, the frictional force acting between each rotating member and the restraining member can be easily reduced. (Claim 15). Here, as means for making the interval between the two restraining members variable, a means for screwing both the restraining members can be employed. In addition, if the restraining members are provided with a force by which both the restraining members sandwich the rotating member by an elastic member that urges each restraining member in the direction of pressing the opposing rotating member, the space between each rotating member and the restraining member. Generation of rattling can be prevented (claim 17).

  On the other hand, if the both restraining members are fixed so that the distance between them is constant, the force with which the both restraining members pinch the rotating member can be maintained at a constant level without adjusting over a long period of time. ).

  Furthermore, in the structure according to claim 9 or 13, the friction resistance between the members in use is provided by holding the lubricant inside the joint and preventing the foreign matter from entering from the outside of the joint. Can be prevented (claim 19).

  As described above, the shaft coupling according to the present invention transmits power between the rotating members via the rolling elements arranged at the intersecting positions of the guide grooves of the rotating members. The frictional resistance of the member is small, large power can be transmitted smoothly, and the amount of eccentricity can be easily increased by increasing the length of the guide groove. Moreover, since there are few components arrange | positioned between both rotation members, it can be set as a structure compact in an axial direction. In addition, since expensive parts such as a linear motion guide that require high assembly accuracy are not used, they can be manufactured at low cost and the assembly work is easy.

  In addition, according to any one of claims 2 to 6, it is possible to increase the power that can be transmitted and extend the life of the joint. Among these, in the invention of claim 3 or 4, since the guide groove can be easily processed, the manufacturing cost can be further reduced.

  On the other hand, if the invention of claim 7 is applied, it becomes easy to manufacture the cage, so that the manufacturing cost can be reduced.

  Furthermore, by applying the invention of claim 8 or 9, wear and heat generation on the contact surface between the guide groove and the cage and the rolling element can be suppressed, so that the joint can be used stably over a long period of time. Since the resistance against the relative movement of the rotating member is reduced, it is not necessary to increase the rigidity of each component of the bearing and the joint that supports each rotating member, and the cost can be reduced.

  According to the invention of claim 10, since the members are integrated by the axial direction restraining mechanism, the assemblability is further improved, and the entire joint can be exchanged together at the time of maintenance. At this time, if the invention of claim 11 is applied, the structure of the axial restraint mechanism is simplified.

  In the structure of claim 11, by applying the invention of any one of claims 12 to 16, it is possible to suppress wear and heat generation of the contact surfaces of the rotating members and the restraining member, and to resist the relative movement of the rotating members. Therefore, the joint performance can be stabilized and the cost can be reduced as in the inventions of claims 8 and 9. In addition, by applying the invention of claim 17, the rotating member can be securely clamped by both the restraining members and the interval between the rotating members can be prevented from being expanded, so that smoother power transmission can be achieved. On the other hand, if the invention of claim 18 is applied, the frequency of maintenance can be reduced.

  In addition, according to the nineteenth aspect of the present invention, it is possible to prevent an increase in the frictional resistance between the members in use, so that it is possible to further extend the period during which stable joint performance is maintained.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3 show a first embodiment. As shown in FIGS. 1 (a), 1 (b), and 2, this shaft coupling has the same diameter input / output shafts A and B that face each other in the axial direction and whose rotating shafts are held parallel to each other. Plates 1 and 2 as rotating members fitted to the respective shaft end portions, steel balls 3 as a plurality of rolling elements arranged between both plates 1 and 2, and movement of each steel ball 3 in the plate radial direction , And a power transmission between the plates 1 and 2 via each steel ball 3. Each of the plates 1 and 2 and the cage 4 is made of a metal material, and each member obtained by adding a steel ball 3 to the surface is subjected to a hardening process such as heat treatment or shot peening. FIG. 1 shows the state where the input / output shafts A and B are concentric for the sake of explanation, but normally, the input / output shafts A and B are used in a state where the rotation shafts are shifted (eccentric) as described later. Is done.

  Each of the plates 1 and 2 is a donut-shaped disk, and is fitted into the shaft end portions of the input shaft A and the output shaft B with a cylindrical portion formed on the inner periphery, and fixed in a state of being opposed in the axial direction. .

  As shown in FIG. 1 (a) and FIG. 2, eight guide grooves 5 and 6 are formed on the opposing surfaces of the plates 1 and 2, respectively, at corresponding positions on the counterpart plate at equal intervals in the circumferential direction. It is provided so as to be orthogonal to the guide grooves, and the steel balls 3 arranged at the positions where the guide grooves 5 and 6 of both plates 1 and 2 intersect are guided and rolled by the guide grooves 5 and 6. It has become. The reason why the guide grooves 5 and 6 are provided symmetrically in the circumferential direction is to prevent the force acting between the plates 1 and 2 and the steel balls 3 from being biased in the plates 1 and 2. is there.

  Each of the guide grooves 5 and 6 is formed so as to extend linearly in a direction that forms 45 degrees with the plate radial direction, and the cross-sectional shape thereof is an arc surface having a radius of curvature larger than the radius of the steel ball 3. Consists of.

  The cage 4 is formed in an annular shape, and elongated holes 7 extending linearly in a direction orthogonal to the radial direction are provided at eight positions at equal intervals in the circumferential direction. The steel ball 3 is fitted into the. The cross-sectional shape of the contact surface of each elongated hole 7 with the steel ball 3 is an arc surface having a radius of curvature larger than the radius of the steel ball 3.

  Further, the guide grooves 5 and 6 of the plates 1 and 2 and the long hole 7 of the cage 4 set the diameter of the steel ball 3 to the maximum moving distance in the plate radial direction when the rotation axes of the input / output shafts A and B are shifted. It is formed to the added length.

  This shaft coupling has the above-described configuration. When the input shaft A is driven to rotate and the plate 1 fixed thereto rotates, the steel ball 3 pushed from the circumferential direction into the guide groove 5 of the input side plate 1. However, in a state where the movement in the plate radial direction is restricted by the cage 4, power is transmitted to the output shaft B by pushing the guide groove 6 of the plate 2 fixed to the output shaft B and rotating the output side plate 2. Is done. Even if the rotation direction of the input shaft A changes or the driving side and the driven side of the input / output shafts A and B are reversed, power transmission is performed by the same mechanism.

  The power transmission mechanism described above is basically the same even in a normal use state in which the rotation axes of the input / output shafts A and B are shifted as shown in FIGS. 3 (a) and 3 (b). In the state of FIG. 3, the crossing position of the guide grooves 5 and 6 is changed in the circumferential direction of the plate due to the shift of the rotation axis of each of the plates 1 and 2. Power is transmitted between the plates 1 and 2 while rolling in the long holes 7 of the four.

  As described above, in this shaft coupling, power is transmitted only by the two plates 1 and 2 fixed to the input / output shafts A and B, and the steel balls 3 and the cage 4 disposed between the plates 1 and 2. Since the structure is extremely compact in the axial direction, each member has a simple structure, and the assembly position is automatically determined according to the shape of each, so the manufacturing cost is low and the assembly work is not time-consuming. .

  Also, even when power transmission is performed with the rotational axis shifted, there is no member that slides just by rolling the steel ball 3, so there is less frictional resistance of each member, and large power can be transmitted smoothly, It is possible to smoothly follow fluctuations in the amount of eccentricity of the rotating shaft. In addition, since the eccentric amount of the rotating shaft can be freely set within the range of the length of the guide grooves 5 and 6 and the long hole 7 of the cage 4, the guide groove can be used even when the required eccentric amount of the rotating shaft is large. This can be easily handled by lengthening the long holes 7 of the retainers 4.

  In addition, since each member is made of metal and the surface is hardened, there is little possibility that the contact portion of each member will be plastically deformed or cause surface damage due to the stress acting between the members. Further, since the guide grooves 5 and 6 are formed so as to extend in the direction of 45 degrees with the plate radial direction, the guide groove processing is easy and the contact surface pressure between the guide grooves 5 and 6 and the steel ball 3 is reduced. The cross-sectional shape of the guide grooves 5 and 6 and the long hole 7 of the cage 4 is formed by a curved surface having a radius of curvature larger than the radius of the steel ball 3, and is in contact with the steel ball 3. Since the pressure is kept low, there is no possibility that an excessive surface pressure is generated at the contact portion of each member. Furthermore, since the rolling elements that transmit power between the plates 1 and 2 are the steel balls 3, there is no fear that the rolling elements will be twisted. From these things, it is possible to transmit large power stably for a long time.

  In addition, when it is not necessary to transmit large motive power, mass production can be achieved and weight can be reduced by forming each member with a synthetic resin material such as engineering plastic. In addition, it is possible to reduce the manufacturing cost by forming the contact surface of the cage with the steel ball as a flat surface to facilitate the production of the cage.

  4 and 5 show a second embodiment. In this embodiment, as shown in FIGS. 4 (a) and 4 (b), the two plates 1 and 2 of the shaft coupling are fitted on the outer circumferences of the shaft end portions of the input / output shafts A and B having different diameters, respectively. Accordingly, there are provided three axial restraining mechanisms 8 for restraining changes in the axial spacing between the plates 1 and 2. Since other basic configurations and mechanisms of power transmission are the same as those in the first embodiment, differences from the first embodiment will be described below.

  The contact surfaces of the steel ball 3 surface of the shaft coupling and the steel balls 3 of the guide grooves 5 and 6 of the plates 1 and 2 and the long hole 7 of the cage 4 are dry plating, wet plating, melting treatment, thermal spraying, One or a plurality of surface treatments of ion implantation, sulfurization treatment, chemical conversion treatment, surface heat treatment, and shot peening are performed to form a surface having a small friction coefficient. Further, a lubricant is interposed between the contact surfaces of the guide grooves 5 and 6 and the steel balls 3 and between the long holes 7 of the cage 4 and the contact surfaces of the steel balls 3. An outer diameter boot 9, an inner diameter seal 10, an outer cover 11 and an inner cover 12 are provided as means for holding the lubricant inside the joint and preventing foreign matter from entering from the outside of the joint. As a result, even if the steel ball 3 moves partially in the guide grooves 5 and 6 and the long hole 7 of the cage 4, even if it is partially slipped, wear and heat generation due to sliding friction are suppressed over a long period of time. The drag force against relative movement when the rotation axes of 1 and 2 are shifted can be reduced.

Here, among the above surface treatments, dry plating includes PVD treatment (physical vapor deposition) and CVD treatment (chemical vapor deposition). In PVD treatment, TiN, ZrN, CrN, TiC, TiCN, TiAlN, Al ₂ O ₃ , DLC (Diamond Like Carbon) film, etc., CVD process, TiC, TiN, TiCN, TiCNO film, or TiC / TiN, TiC / Al ₂ O ₃ , TiC / TiCNO, TiC / TiCN / A composite film such as TiN, TiC / TiCNO / TiN, TiC / TiCN / Al ₂ O ₃ , TiC / Al ₂ O ₃ / TiN may be formed. Wet plating includes electroplating and electroless plating, and types of plating include industrial chromium, electroless chromium, and composite plating.

  Melting processes include cladding, alloying, and glazing. Thermal spraying includes gas spraying and electric spraying, and types of coating include chromium oxide, titanium oxide, and zirconia. Ion implantation includes high energy implantation and medium energy implantation. In the sulfuration treatment, a composite treatment using a layer containing molybdenum disulfide, which is a solid lubricant, as a film is effective. The chemical conversion treatment includes phosphate treatment, iron phosphate treatment, manganese phosphate treatment, chromate treatment and the like. The surface heat treatment includes surface quenching, carburizing quenching, nitriding treatment, sulfurizing treatment and the like.

  Among these treatments, dry plating, sulfurization treatment, and chemical conversion treatment are particularly effective in reducing the friction coefficient of the contact surface. On the other hand, in the heat treatment such as nitriding, the friction coefficient can be reduced and the wear resistance can be improved.

  In addition, grease is used as the lubricant. The grease composition uses mineral oil, synthetic oil, or a mixture of both as the base oil, urea-based thickener as the thickener, and molybdenum disulfide, tungsten disulfide, Melamine cyanurate, graphite, boron nitride, etc. are added, and molybdenum dithiocarbamate, zinc dithiocarbamate, zinc dithiophosphonate, sulfur-based additive, phosphorus-based additive, oily agent, dispersant, antioxidant are added . In addition, it is preferable that a portion of the guide grooves 5 and 6 where the steel ball 3 does not pass is subjected to groove processing or the like to form a grease reservoir, so that more stable grease can be supplied.

  Each of the axial direction restraint mechanisms 8 is formed integrally with two restraint plates (constraint members) 8a and 8b disposed on the opposite side of the opposing surfaces of the plates 1 and 2, and the restraint plate 8a on the input side, Each plate 1, 2 includes a retainer 4 and a screw 8c that passes through the output-side restraint plate 8b, and a lock nut 8d that is coupled to the screw 8c to connect the restraint plates 8a and 8b. By inserting, both plates 1 and 2 are sandwiched between the restraining plates 8a and 8b on both sides. In addition, since this axial direction restraint mechanism 8 was provided at equal intervals in the plate circumferential direction, the guide grooves 5 and 6 of the plates 1 and 2, the long hole 7 of the cage 4 and the steel ball 3 are connected to each restraint mechanism. Two are arranged between the eight, and six sets as a whole are provided symmetrically in the circumferential direction.

  Although not shown, an elastic member such as a leaf spring is sandwiched between the output side restraint plate 8b and the lock nut 8d, and this elastic member faces the restraint plates 8a and 8b, respectively. It is biased in the direction of pressing against the plates 1 and 2.

  That is, the axial direction restraint mechanism 8 changes the distance between the restraint plates 8a and 8b and the restraint plates 8a and 8b through the elastic member by changing the tightening amount of the lock nut 8d to the screw 8c. 2 can be easily adjusted.

  On the other hand, in each of the plates 1 and 2, the guide holes 13 and 14 through which the screw 8 c of the axial direction restraining mechanism 8 passes are linearly extended in a direction forming 45 degrees with the plate radial direction, like the guide grooves 5 and 6. The concavities 15 and 16 into which the restricting plates 8a and 8b are fitted along the peripheral edges of the guide holes 13 and 14 are provided on the surfaces of the plates 1 and 2 facing the restricting plates 8a and 8b. ing.

  As a result, as shown in FIGS. 5A and 5B, when the rotational axes of the input and output shafts A and B are shifted, the axial restraint mechanism 8 is accompanied by the rotation of the plates 1 and 2. The screw 8c moves in the guide holes 13 and 14 of the plates 1 and 2 so that each restraint plate 8a and 8b slides on the plate recesses 15 and 16 to transmit power.

  Therefore, if the tightening amount of the lock nut 8d of the axial direction restraint mechanism 8 is appropriately set, the rattling between the restraint members 8a and 8b and the plates 1 and 2 is eliminated, and the plate is formed by both restraint members 8a and 8b. The frictional force acting between each of the restraining plates 8a and 8b and the plate recesses 15 and 16 can be kept low while securely sandwiching the plates 1 and 2 to suppress the spread of the space between the plates 1 and 2.

  Further, in order to further reduce the frictional force between each of the restraining plates 8a and 8b and the plate recesses 15 and 16, the above-described countermeasure against the sliding friction between the steel ball 3 and the guide grooves 5 and 6 and the cage 4 is provided. Similarly, one or more of the above-mentioned types of surface treatments are applied to both contact surfaces to form a surface having a small friction coefficient, and the grease is used as a lubricant between the contact surfaces. Filled. Further, although not shown in the drawings, the contact surfaces of both are grooved as a grease reservoir so that more stable grease supply is performed. In addition to this, for example, a synthetic resin-based sheet excellent in slidability such as PTFE (polytetrafluoroethylene) is attached to at least one of both, such as interposing a sliding material between the two, The frictional force can be reduced by interposing a small-diameter steel ball between the two.

  On the other hand, if it is not necessary to adjust the distance between the two restraint plates during mass production, the axial length of the joint can be further shortened by fixing the two restraint plates by caulking so that the distance between them is constant. The force with which the two restraining plates sandwich the plate can be maintained at a constant level over a long period of time, and the frequency of maintenance can be reduced.

  The shaft coupling according to this embodiment has the above-described configuration, and the members are integrated by the axially restricting mechanism 8 having a simple structure. Therefore, the shaft coupling is superior to the first embodiment, and the entire joint is maintained during maintenance. Can be exchanged together.

  In addition, since wear and heat generation due to sliding friction between the steel ball 3 and the guide grooves 5 and 6 and the cage 4 and between the restraint plates 8a and 8b and the plate recesses 15 and 16 are suppressed, it is stable over a long period of time. The joint performance can be maintained, and the drag when the two plates 1 and 2 move relative to each other is small. Therefore, it is necessary to increase the rigidity of bearings (not shown) that support the input / output shafts A and B and the joint parts. It can be manufactured at low cost.

Side view of shaft coupling of first embodiment (rotary shafts are concentric) Sectional drawing along the II line | wire of Fig.1 (a) 1 is an exploded side view of the shaft coupling of FIG. 1 is a side view showing the usage state of the shaft coupling of FIG. 1 (rotary shaft is eccentric) Sectional drawing along the III-III line of Fig.3 (a) Side view of essential parts of shaft coupling of second embodiment (rotary shafts are concentric) Sectional view along line IV-IV in Fig. 4 (a) 4 is a side view of the main part showing the usage state of the shaft coupling of FIG. 4 (the rotation shaft is eccentric). Sectional drawing along the VV line of Fig.5 (a)

Explanation of symbols

1, 2 Plate 3 Steel ball 4 Cage 5, 6 Guide groove 7 Long hole 8 Axial restraint mechanism 8a, 8b Restraint plate 8c Screw 8d Lock nut 13, 14 Guide hole 15, 16 Recess A Input shaft B Output shaft

Claims (19)

  A plurality of guide grooves are orthogonal to the guide grooves at corresponding positions of the counterpart rotating member on the opposing surfaces of the two rotating members that are axially opposed and are held in a state where the rotation axes are parallel to each other and not concentric. A rolling element that rolls while being guided by each guide groove at a position where the guide grooves of the two rotating members intersect with each other, and that holds the rolling members in the radial direction of the rotating member. A shaft coupling in which power is transmitted between the rotating members via the rolling elements.   2. The shaft coupling according to claim 1, wherein each of the rotating members, the rolling elements, and the cage is made of a metal material, and the surface thereof is hardened.   The shaft coupling according to claim 1, wherein each guide groove is formed linearly in the longitudinal direction.   The shaft coupling according to claim 3, wherein each guide groove is formed to extend in a direction that forms 45 degrees with the radial direction of the rotating member.   The shaft coupling according to claim 3 or 4, wherein the rolling element is a sphere, and a cross-sectional shape of the guide groove is a curved surface having a radius of curvature larger than a radius of the rolling element.   6. The rolling element according to claim 1, wherein the rolling element is a sphere, and a cross-sectional shape of a contact surface of the cage with the rolling element is a curved surface having a radius of curvature larger than a radius of the rolling element. A shaft coupling according to any one of the above.   The shaft coupling according to any one of claims 1 to 5, wherein a contact surface of the cage with the rolling element is formed as a flat surface.   At least one of the contact surface between the guide groove and the rolling element and the contact surface between the cage and the rolling element is dry plating, wet plating, melting treatment, thermal spraying, ion implantation, sulfurization treatment, chemical conversion treatment, surface The shaft coupling according to any one of claims 1 to 7, wherein one or a plurality of surface treatments of heat treatment and shot peening are performed to reduce a friction coefficient of the contact surface.   The lubricant is interposed between at least one contact surface between the guide groove and the contact surface of the rolling element and between the contact surface of the cage and the rolling element. Shaft coupling according to crab.   The shaft coupling according to any one of claims 1 to 9, further comprising an axial direction restraining mechanism for restraining a change in an axial distance between the rotating members.   The said axial direction restraint mechanism is arrange | positioned on the opposite side to the opposing surface of each said rotation member, and clamps both rotation members with the two restraint members connected mutually. Shaft coupling.   Any one of dry plating, wet plating, fusion treatment, thermal spraying, ion implantation, sulfurization treatment, chemical conversion treatment, surface heat treatment, and shot peening is applied to the contact surface of at least one of the contact surfaces of the rotating member and the restraining member. The shaft coupling according to claim 11, wherein one or a plurality of surface treatments are performed to reduce a coefficient of friction of the contact surface.   The shaft coupling according to claim 11 or 12, wherein a lubricant is interposed between contact surfaces of the rotating member and the restraining member.   The shaft coupling according to any one of claims 11 to 13, wherein a sliding member is interposed between the rotating member and the restraining member.   The shaft coupling according to any one of claims 11 to 14, wherein an interval between the two restricting members is variable, and a force with which the restricting members sandwich the rotating member can be adjusted.   The shaft coupling according to claim 15, wherein the means for making the interval between the both restraining members variable is to couple both the restraining members with screws.   The shaft coupling according to claim 15, wherein the force by which both the restraining members sandwich the rotating member is given by an elastic member that urges each restraining member in a direction in which the restraining member is pressed against the opposing rotating member.   The shaft coupling according to any one of claims 11 to 14, wherein the both restraining members are fixed so that a distance between them is constant.   The shaft coupling according to claim 9 or 13, further comprising means for holding the lubricant inside the joint and preventing foreign matter from entering from the outside of the joint.

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