1. Field of the Invention
The present invention relates to a rotary connector.
2. Description of the Related Art
Conventionally, a rotary connector is used for electrically connecting power lines, signal lines, and the like, between two relatively rotating members (for example, see Japanese Patent Application Laid-Open (kokai) No. H5-82223). This kind of rotary connector can maintain electrical connection irrespective of a relative rotation angle of the rotating members.
In
Also, a circular retainer 303 is rotatably placed relative to the inner ring 301 and the outer ring 302 between the inner ring 301 and the outer ring 302. Wheels 304 made of electrically conductive metal are mounted in the retainer 303. The wheels 304 are rotatably mounted relative to the retainer 303 at three points in the retainer through mounting shafts 305.
The wheels 304 roll along the outer circumference surface of the inner ring 301 and the inner circumference surface of the outer ring 302 when the inner ring 301 and the outer ring 302 relatively rotate. Thereby, the wheels 304 can electrically connect the relatively rotating inner ring 301 and outer ring 302 irrespective of the rotation angle therebetween.
However, since the wheels 304 in the conventional rotary connector are rigid and do not deform in the radial direction thereof, electrical connection can be momentarily broken between the inner ring 301 and the outer ring 302. Theoretically speaking, the inner ring 301 and the outer ring 302 are always electrically connected through the wheels 304, if the wheels, which have a diameter equal to a difference between the radius of the outer circumference of the inner ring 301 and the radius of the inner circumference of the outer ring 302, are rotatably placed in equally-spaced three points between the outer circumference of the inner ring 301 and the inner circumference of the outer ring 302. However, in practice, dimensional errors in manufacturing and assembling the inner ring 301, the outer ring 302, and the wheels 304 causes backlash between the inner ring 301, the outer ring 302, and the wheels 304. This causes all the wheels 304 to be separated, even though momentarily, from the outer circumference surface of the inner ring 301 or the inner circumference surface of the outer ring 302, and thus may result in electrical disconnection in some cases.
Therefore, in order to provide higher reliability in electrical connection, Japanese Patent Application Laid-open (kokai) No. H5-82223 discloses a rotary connector, in which flange portions in the outermost circumferences of each of the wheels 304 slidingly contact the side surfaces of both the inner ring 301 and the outer ring 302 in such a way as to hold the side surfaces thereof between the flange portions. However, since the flange portions of each of the wheels 304 slidingly contact the side surfaces of the inner ring 301 and the outer ring 302 on both sides thereof, substantial resistance occurs to relative rotation of the inner ring 301 and the outer ring 302. Moreover, it causes wear of the flange portions of the wheels 304 or of the side surfaces of the inner ring 301 and the outer ring 302, and thus bad electrical contact occurs after long-term use.
The present invention has been made with a view to solving the above problems of the conventional rotary connectors. It is therefore an object of the present invention to provide a simply-structured, low-cost, and widely applicable rotary connector, which is highly reliable in electrical connection since it is free from electrical disconnection, even if momentarily, between the ring-shaped inside terminal and the ring-shaped outside terminal through a ring-shaped connection terminal by allowing the ring-shaped connection terminal, which abuts the outer circumference portion of a ring-shaped inside terminal and the inner circumference portion of a ring-shaped outside terminal, to deform elastically along the radial direction so as to absorb errors in the members.
In order to achieve the above object, the present invention provides a rotary connector for electrically connecting wires of two relatively rotating connection target members, including: a ring-shaped outside terminal having a circular inner circumference portion and connected to the wire of one connection target member; a ring-shaped inside terminal having a circular outer circumference portion, which is concentric with the inner circumference portion of the ring-shaped outside terminal, and connected to the wire of the other connection target member; and a rotatable ring-shaped connection terminal electrically connecting the ring-shaped outside terminal and the ring-shaped inside terminal, wherein the ring-shaped connection terminal elastically deforms along a radial direction thereof, and an outer circumference portion of the ring-shaped connection terminal abuts the inner circumference portion of the ring-shaped outside terminal and the outer circumference portion of the ring-shaped inside terminal.
Preferably, the ring-shaped connection terminal rolls around the inner circumference of the ring-shaped outside terminal and the outer circumference of the ring-shaped inside terminal while elastically deforming along the radial direction of the ring-shaped connection terminal, when the ring-shaped outside terminal and the ring-shaped inside terminal relatively rotate.
Preferably, the ring-shaped connection terminal is mounted rotatably around a rod-like bearing member extending parallel to an axis of the ring-shaped outside terminal and the ring-shaped inside terminal and so as to be elastically deformable along the radial direction of the ring-shaped connection terminal.
Preferably, the ring-shaped connection terminal is positioned along the axial direction by insulators alternately superimposed on the ring-shaped outside terminal and the ring-shaped inside terminal.
Preferably, the ring-shaped outside terminal is superimposed alternately on the ring-shaped outside insulator having an inner circumference portion smaller in diameter than the inner circumference portion of the ring-shaped outside terminal, the ring-shaped inside terminal is superimposed alternately on the ring-shaped inside insulator having an outer circumference portion larger in diameter than the outer circumference portion of the ring-shaped inside terminal, and the ring-shaped connection terminal is positioned along the axial direction by the ring-shaped outside insulator and the ring-shaped inside insulator.
Preferably, the ring-shaped outside terminal and the ring-shaped inside terminal are superimposed alternately on the ring-shaped intermediate insulator having an outer circumference portion larger in diameter than the inner circumference portion of the ring-shaped outside terminal, an inner circumference portion smaller in diameter than the outer circumference portion of the ring-shaped inside terminal, and openings for inserting the rod-like bearing members, and the ring-shaped connection terminal is supported by an edge of the opening, and positioned by the ring-shaped intermediate insulator along the axial direction.
According to the present invention, the rotary connector has a ring-shaped connection terminal, which abuts the outer circumference portion of the ring-shaped inside terminal and the inner circumference portion of the ring-shaped outside terminal, are elastically deformable along the radial direction. Thereby, errors in the members can be absorbed, and it is therefore possible to achieve a simply-structured, low-cost, and widely applicable rotary connector, which is highly reliable in electrical connection since it is free from electrical disconnection, even if momentarily, between the ring-shaped inside terminal and the ring-shaped outside terminal through the ring-shaped connection terminal.
An embodiment of the present invention is described below in detail with reference to the accompanying drawings.
In the figures, reference numeral 10 designates the rotary connector, according to the embodiment, for use in electrically connecting wires, such as a power line, a signal line, and the like, of relatively rotating connection target members. The relatively rotating connection target members can be members of any kind of apparatus, and of any size. For example, the relatively rotating members can be a body part or a display part of a small electrical device such as a mobile phone, personal computer, PDA (Personal Digital Assistant), digital camera, video camera, music player, mobile game machine and the like, wherein the body part or the display part is rotatably linked by a hinge member and the like. Further, the relatively rotating members can be a steering wheel and a steering column rotatably supporting the steering wheel. Further, the relatively rotating members can be a rotating member of a large apparatus such as an assembly robot or a machine tool, and the like, and a supporting member thereof.
In this embodiment, representations of directions such as “up”, “down”, “left”, “right”, “front”, “rear”, and the like, used for explaining a structure and movement of each part of the rotary connector 10, are not absolute, but relative. These representations are appropriate when the rotary connecter 10 is in the position shown in the figures. If the position of the rotary connector 10 changes, however, it is assumed that these representations are to be changed according to the change of the position of the rotary connector 10.
As shown in
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The outside diameter of the ring-shaped outside insulator 36 is equal to the outside diameter of the ring-shaped outside terminal 31, and the inside diameter of the ring-shaped outside insulator 36 is slightly smaller than the inside diameter of the ring-shaped outside terminal 31. Specifically, the diameter of the hole 37 of the ring-shaped outside insulator 36 is slightly smaller than the diameter of the hole 32 of the ring-shaped outside terminal 31. Therefore, as shown in
As shown in
As shown in
The outside diameter of the ring-shaped inside insulator 26 is formed slightly larger than the outside diameter of the ring-shaped inside terminal 21. Further, the diameter of the hole 37 in the ring-shaped outside insulator 36 is slightly smaller than the diameter of the hole 32 in the ring-shaped outside terminal 31. Therefore, as shown in
In the state where the ring-shaped outside terminals 31, the ring-shaped outside insulators 36, the ring-shaped inside terminals 21 and the ring-shaped inside insulators 26 are placed inside the cover 11, the locations of the ring-shaped outside terminals 31 and the ring-shaped inside terminals 21 correspond to each other, and also the locations of the ring-shaped outside insulators 36 and the ring-shaped inside insulators 26 correspond to each other, with respect to the axial direction of the rotary connector 10. Specifically, the ring-shaped outside terminals 31 and the ring-shaped inside terminals 21 face each other, and also the ring-shaped outside insulators 36 and the ring-shaped inside insulators 26 face each other. Then, the ring-shaped connection terminals 42 are placed between the ring-shaped outside terminals 31 and the ring-shaped inside terminals 21, which are facing each other.
Each ring-shaped connection terminal 42 is a ring-shaped member made of elastic, electrically conductive metal, and can deform elastically in the radial direction of the ring-shaped connection terminal 42. That is, if the ring-shaped connection terminal 42 is subjected to external force along the radial direction thereof, the ring-shaped connection terminal 42 deforms along the radial direction, and goes back to its original shape when the external force ceases. Therefore, preferably the ring-shaped connection terminal 42 is thin in the radial thickness and is a seamless ring. For example, the ring-shaped connection terminal 42 could be manufactured by slicing a thin-walled seamless metal pipe. For example, when the rotary connector 10 is used in a small electronic device such as a mobile telephone, the outside diameter of the ring-shaped connection terminal 42 would be in the order of 0.5 mm and the radial thickness thereof would be in the order of 0.01 mm. This sort of metal pipe or a metal ring small in diameter and thin-walled can be made by, for example, electroforming.
For example, if the ring-shaped connection terminal 42 is a pipe-shaped connection terminal, the pipe-shaped connection terminal is placed so that the outer circumference surface of the pipe-shaped connection terminal abuts the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21. In this case, the outside diameter of the ring-shaped connection terminal 42 is set larger than the gap between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21. Specifically, the outside diameter of the ring-shaped connection terminal 42 is set larger than one-half of the difference between the inside diameter of the hole 32 of the ring-shaped outside terminal 31 and the outside diameter of the ring-shaped inside terminal 21. Therefore, the ring-shaped connection terminal 42 is subjected to external force, along the radial direction thereof, from the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21, thereby deforming along the radial direction. Then, when the ring-shaped outside terminal 31 and the ring-shaped inside terminal 21 rotate relatively, the ring-shaped connection terminals 42 roll between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21.
If the gap between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21 becomes smaller than a reference value, the deformation of the ring-shaped connection terminal 42 becomes larger, and thus abutment between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21 is maintained. On the other hand, if the gap becomes larger than the reference value, the deformation of the ring-shaped connection terminal 42 becomes smaller, and still abutment between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21 is maintained. Thus, since the ring-shaped connection terminal 42 can elastically deform along the radial direction thereof, electrical connection between the ring-shaped outside terminal 31 and the ring-shaped inside terminal 21 via the ring-shaped connection terminal 42 can be maintained without fail even if there is a change in the gap between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21.
Further, a plurality of, for example, six shaft bearings 41 are placed at even intervals between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21. As shown in
In the shown example, the same shaft bearings as the shaft bearings 41 placed between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21 are inserted in the engagement holes 23 of the ring-shaped inside terminal 21. However, rod-like members different from the shaft bearings 41 can be inserted in the engagement holes 23 of the ring-shaped inside terminal 21. Also, in the example, all the shaft bearings 41 placed between the inner circumference surface of the ring-shaped outside terminal 31 and the outer circumference surface of the ring-shaped inside terminal 21 are the same in this example, however, the shaft bearing 41 with no ring-shaped connection terminal 42 around can be a different rod-like member from the shaft bearing 41.
A process of assembling the rotary connector 10 is explained in the following.
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Subsequently, the front shaft 15b is mounted as shown in
Finally, the front cover 11b is mounted and thereby the rotary connecter 10 as shown in
As described hereinabove, in this embodiment, the rotary connector 10 includes a ring-shaped outside terminal 31 having a circular inner circumference portion and connected to the wire of one connection target member, a ring-shaped inside terminal 21 having a circular outer circumference portion, which is concentric with the inner circumference portion of the ring-shaped outside terminal 31, and connected to the wire of the other connection target member, and a rotatable ring-shaped connection terminal 42 electrically connecting the ring-shaped outside terminal 31 and the ring-shaped inside terminal 21, wherein the ring-shaped connection terminal 42 elastically deforms along a radial direction thereof, and an outer circumference portion of the ring-shaped connection terminal 42 abuts the inner circumference portion of the ring-shaped outside terminal 31 and the outer circumference portion of the ring-shaped inside terminal 21. Therefore, even if there are manufacturing or assembling errors in members of the rotary connector 10, the errors can be absorbed and therefore no electrical disconnection occurs, even if momentarily, between the ring-shaped inside terminal 21 and the ring-shaped outside terminal 31 through the ring-shaped connection terminals 42. Thereby, it is possible to achieve a simply-structured, low-cost, and widely applicable rotary connector, which is highly reliable in electrical connection.
Further the ring-shaped connection terminal 42 rolls around the inner circumference of the ring-shaped outside terminal 31 and the outer circumference of the ring-shaped inside terminal 21 while elastically deforming along the radial direction of the ring-shaped connection terminal 42, when the ring-shaped outside terminal 31 and the ring-shaped inside terminal 21 relatively rotate. Therefore, the ring-shaped connection terminal 42 not only absorbs errors by elastically deforming so as to reliably maintain the electrical connection between the ring-shaped inside terminal 21 and the ring-shaped outside terminal 31, but can reduce the resistance since the ring-shaped inside terminal 21 does not slidingly contact the ring-shaped outside terminal 31. Furthermore, since the ring-shaped connection terminals 42 do not slidingly contact the ring-shaped inside terminal 21 and the ring-shaped outside terminal 31, the ring-shaped inside terminal 21 and the ring-shaped outside terminal 31 do not wear out.
Further, the ring-shaped connection terminal 42 is mounted rotatably around a shaft bearing 41 extending parallel to an axis of the ring-shaped outside terminal 31 and the ring-shaped inside terminal 21 and mounted so as to be elastically deformable along the radial direction of the ring-shaped connection terminal 42. Moreover, the ring-shaped connection terminal 42 is positioned by a ring-shaped inside insulator 26 and a ring-shaped outside insulator 36 along the axial direction. Therefore, it is possible to maintain the ring-shaped connection terminal 42 with a simple structure, to simplify the structure of the rotary connector 10, and to reduce the cost.
In the embodiment described above, a ring-shaped outside insulator 36 is inserted between each pair of ring-shaped outside terminals 31, and a ring-shaped inside insulator 26 between each pair of ring-shaped inside terminals 21, so as to restrict movement of the ring-shaped connection terminals 42 along the axial direction. The ring-shaped outside insulator 36 and the ring-shaped inside insulator 26 are used to form an annular space therebetween so as to allow the ring-shaped connection terminal 42 mounted on the shaft bearing 41 to roll around the ring-shaped inside terminal 21 while maintaining the relative locations of the ring-shaped connection terminals 42.
Thus the ring-shaped connection terminal 42 rolls around the ring-shaped inside terminal 21, thereby reducing loss of rotation caused by the ring-shaped connection terminal 42 sliding on the outer circumference of the ring-shaped inside terminal 21 and the inner circumference of the ring-shaped outside terminal 31.
An insulator with a structure shown in
The ring-shaped insulator 50 shown in
Holes 53 for inserting the shaft bearings 41 are provided in the annular part 54 so as to match the locations of the shaft bearings 41.
The diameter of each hole 53 is almost the same as the size of the shaft bearing 41. The hole 53 is large enough for the shaft bearing 41 to pass through it, and also smaller than the outer diameter of the ring-shaped connection terminal 42. Thereby, the end of the ring-shaped connection terminal 42 is supported on the surface of the annular part 54.
The ring-shaped insulator 50 serves as an insulator for insulating each of the connection terminals superimposed on each other, and it can be used as a retainer of the shaft bearings 41, that is, as a retainer used when the ring-shaped connection terminals 42 roll around the ring-shaped inside terminal 21. Thereby, the number of members used as insulators can be reduced.
It should be noted here that the present invention is not limited to the above embodiment, but can be variously modified and changed within the gist of the invention. Thus the modifications and changes are not excluded from the scope of the present invention.
Number | Date | Country | Kind |
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2005-334364 | Nov 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2006/060905 | 11/15/2006 | WO | 00 | 6/12/2009 |