Patent Description:
A parallel link mechanism is described in, for example, Patent Literature <NUM> (<CIT>). The parallel link mechanism described in Patent Literature <NUM> includes a proximal end link hub, a distal end link hub, and a plurality of link mechanisms.

Each of the plurality of link mechanisms includes a first end link member, a second end link member, and an intermediate link member. One end of the first end link member is rotatably coupled to the proximal end link hub. One end of the second end link member is rotatably coupled to the distal end link hub. One end and the other end of the intermediate link member are respectively rotatably coupled to the other end of the first link member and the other end of the second link member. The parallel link mechanism described in Patent Literature <NUM> is a spherical surface link mechanism. That is, the distal end link hub moves on a spherical surface centering on a spherical surface link center point.

Document <CIT> discloses a parallel link mechanism according to the preamble of claim <NUM>.

In the parallel link mechanism described in Patent Literature <NUM>, intermediate link members of the plurality of link mechanisms are not coupled to one another. Therefore, the parallel link mechanism described in Patent Literature <NUM> has room of improvement in rigidity.

The present invention has been devised in view of the problems of the related art described above. More specifically, the present invention provides a spherical surface link mechanism and a spherical surface actuating device having improved rigidity.

A spherical surface link mechanism of the present invention includes a proximal end link hub, a distal end link hub, a plurality of links, a plurality of intermediate link hubs, and a shaft member. Each of the plurality of links includes a first end link member, a second end link member, and an intermediate link member. The first end link member is coupled, at one end, to the proximal end link hub to be rotatable about a first rotation axis. The second end link member is coupled, at one end, to the distal end link hub to be rotatable about a second rotation axis. The intermediate link member is coupled, at one end, to another end of the first end link member to be rotatable about a third rotation axis and is coupled to, at another end, another end of the second end link member about a fourth rotation axis. A center axis of the proximal end link hub, the first rotation axis, and the third rotation axis cross at a first spherical surface link center point. A center axis of the distal end link hub, the second rotation axis, and the fourth rotation axis cross at a second spherical surface link center point. Each of the plurality of intermediate link hubs is connected to the intermediate link member of each of the plurality of links. The plurality of intermediate link hubs are coupled to one another by a shaft member to be rotatable about a fifth rotation axis that passes the first spherical surface link center point and the second spherical surface link center point. A through hole is formed in the shaft member so as for the through hole to pierce through the shaft member along the fifth rotation axis.

The spherical surface link mechanism explained above may further include a bearing that reduces friction between at least one of the plurality of intermediate link hubs and the shaft member.

In the spherical surface link mechanism explained above, the bearing may be a rolling bearing. In the spherical surface link mechanism explained above, the bearing may be a slide bearing.

In the spherical surface link mechanism explained above, a through-hole piercing through the shaft member along the fifth rotation axis may be formed in the shaft member.

In the spherical surface link mechanism explained above, the shaft member may be formed integrally with one of the plurality of intermediate link hubs. In the spherical surface link mechanism explained above, the shaft member may be a member separate from the plurality of intermediate link hubs.

A spherical surface link actuating device of the present invention includes the spherical surface link mechanism and at least two or more driving sources. A position and a posture of at least one of the proximal end link hub and the distal end link hub are determined by the at least two or more driving sources.

In the spherical surface link actuating device explained above, each of the at least two or more driving sources may rotate the first end link member of each of the plurality of links about the first rotation axis.

In the spherical surface link actuating device explained above, each of the at least two or more driving sources may rotate each of the plurality of intermediate link hubs about the fifth rotation axis.

With the spherical surface link mechanism and the spherical surface link actuating device of the present invention, it is possible to improve the rigidity of the spherical surface link mechanism.

Details of embodiments of the present invention are explained with reference to the drawings. In the drawings referred to below, the same or equivalent portions are denoted by the same reference numerals and signs and redundant explanation is not repeated.

A spherical surface link mechanism (hereinafter "spherical surface link mechanism <NUM>") according to a first embodiment is explained.

A configuration of a spherical surface link mechanism <NUM> is explained below.

<FIG> is a perspective view of spherical surface link mechanism <NUM>. <FIG> is a front view of spherical surface link mechanism <NUM>. <FIG> is a plan view of spherical surface link mechanism <NUM>. <FIG> is a sectional view in IV-IV in <FIG>. <FIG> is an enlarged sectional view in V-V in <FIG>.

As shown in <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>, spherical surface link mechanism <NUM> includes a proximal end link hub <NUM>, a distal end link hub <NUM>, a plurality of links <NUM>, a plurality of intermediate link hubs <NUM>, and bearings <NUM>.

Proximal end link hub <NUM> has, for example, a plate-like shape. Proximal end link hub <NUM> includes a first surface 10a and a second surface 10b. Second surface 10b is the opposite surface of first surface 10a. A projecting section 10c is provided in proximal end link hub <NUM>. Projecting section 10c is provided on first surface 10a. Projecting section 10c projects in a direction from second surface 10b to first surface 10a. A through-hole (not shown) is formed in projecting section 10c. In the following explanation, the center axis of proximal end link hub <NUM> is sometimes referred to as a center axis CL1.

Distal end link hub <NUM> has, for example, a plate-like shape. Distal end link hub <NUM> includes a first surface 20a and a second surface 20b. Second surface 20b is the opposite surface of first surface 20a and faces the first surface 10a side. A projecting section 20c is provided in distal end link hub <NUM>. Projecting section 20c is provided on second surface 20b. Projecting section 20c projects in a direction from first surface 20a to second surface 20b. A through-hole (not shown) is formed in projecting section 20c. In the following explanation, the center axis of distal end link hub <NUM> is sometimes referred to as a center axis CL2. Although not shown, an end effector is attached to the first surface 20a side of distal end link hub <NUM>.

Each of plurality of links <NUM> includes a first end link member <NUM>, a second end link member <NUM>, and an intermediate link member <NUM>. The number of plurality of links <NUM> is, for example, three. However, the number of plurality of links <NUM> may be two or four or more. Plurality of links <NUM> preferably have the same shape.

First end link member <NUM> is rotatably coupled, at one end, to proximal end link hub <NUM>. More specifically, a through-hole (not shown) is formed at one end of first end link member <NUM>. A shaft member <NUM> is inserted through both of the through-hole formed at one end of first end link member <NUM> and the through-hole formed in projecting section 10c. Consequently, first end link member <NUM> is coupled, at one end, to proximal end link hub <NUM> to be rotatable about the center axis of shaft member <NUM> (hereinafter sometimes referred to as a first rotation axis RA1). First end link member <NUM> has, for example, an L shape.

Second end link member <NUM> is rotatably coupled, at one end, to distal end link hub <NUM>. More specifically, a through-hole (not shown) is formed at one end of second end link member <NUM>. A shaft member <NUM> is inserted through both of the through-hole formed at one end of second end link member <NUM> and through-hole formed in projecting section 20c. Consequently, second end link member <NUM> is coupled, at one end, to distal end link hub <NUM> to be rotatable about the center axis of shaft member <NUM> (hereinafter sometimes referred to as a second rotation axis RA2). Second end link member <NUM> has, for example, an L shape.

Intermediate link member <NUM> is rotatably coupled, at one end, to the other end of first end link member <NUM>. More specifically, a through-hole (not shown) is formed at one end of intermediate link member <NUM>. A through-hole (not shown) is formed at the other end of first end link member <NUM>. A shaft member <NUM> is inserted through both of the through-hole formed at one end of intermediate link member <NUM> and the through-hole formed at the other end of first end link member <NUM>.

Consequently, intermediate link member <NUM> is coupled, at one end, to the other end of first end link member <NUM> to be rotatable about the center axis of shaft member <NUM> (hereinafter sometimes referred to as a third rotation axis RA3).

Intermediate link member <NUM> is rotatably coupled, at the other end, to the other end of the second end link member <NUM>. More specifically, a through-hole (not shown) is formed at the other end of intermediate link member <NUM>. A through-hole (not shown) is formed at the other end of second end link member <NUM>. A shaft member <NUM> is inserted through both of the through-hole formed at the other end of intermediate link member <NUM> and the through-hole formed at the other end of second end link member <NUM>.

Consequently, intermediate link member <NUM> is coupled, at the other end, to the other end of second end link member <NUM> to be rotatable about the center axis of shaft member <NUM> (hereinafter sometimes referred to as a fourth rotation axis RA4).

Each of plurality of intermediate link hubs <NUM> includes a coupling section <NUM> and a beam section <NUM>. A through-hole 41a is formed in coupling section <NUM>. Beam section <NUM> is connected, at one end, to coupling section <NUM> and connected, at the other end, to intermediate link member <NUM>. Coupling section <NUM> is located on the inner side of plurality of links <NUM>. Intermediate link member <NUM> and intermediate link hubs <NUM> are, for example, one member.

Plurality of intermediate link hubs <NUM> are mutually rotatably coupled in coupling sections <NUM>. More specifically, a shaft member <NUM> is inserted through through-hole 41a of each of plurality of intermediate link hubs <NUM>. Consequently, plurality of intermediate link hubs <NUM> are coupled to one another to be rotatable about the center axis of shaft member <NUM> (hereinafter sometimes referred to as a fifth rotation axis RA5).

A through-hole 38a is formed in shaft member <NUM>. Through-hole 38a pierces through shaft member <NUM> along fifth rotation axis RA5. From another viewpoint, shaft member <NUM> is a hollow member. Although not shown, a cable connected to the end effector attached to distal end link hub <NUM> is inserted through through-hole 38a.

Retaining rings 38b are attached to both the end portions of shaft member <NUM>. Consequently, plurality of intermediate link hubs <NUM> (coupling sections <NUM>) are prevented from coming off shaft member <NUM>. Retaining rings 38b are, for example, C rings or E rings. Spacers 38c are attached to shaft member <NUM>. Consequently, plurality of intermediate link hubs <NUM> (coupling sections <NUM>) are separated from one another.

Bearings <NUM> are disposed on the inside of through-hole 41a. Consequently, friction between shaft member <NUM> and intermediate link hubs <NUM> (coupling sections <NUM>) is reduced. Bearings <NUM> are not particularly limited if bearings <NUM> can reduce the friction between shaft member <NUM> and intermediate link hubs <NUM> (coupling sections <NUM>).

Bearings <NUM> are, for example, rolling bearings or slide bearings. The rolling bearings are capable of supporting a radial load (a load in a direction orthogonal to fifth rotation axis RA5) and an axial load (a load in a direction parallel to fifth rotation axis RA5). Note that bearings <NUM> only have to be provided between at least one of plurality of intermediate link hubs <NUM> and shaft member <NUM>.

<FIG> is a schematic diagram showing a mutual relation between center axis CL1 and center axis CL2 and first rotation axis RA1 to fifth rotation axis RA5. As shown in <FIG>, center axis CL1, first rotation axis RA1, and third rotation axis RA3 cross at one point. This one point is referred to as a spherical surface link center point P1. Center axis CL2, second rotation axis RA2, and fourth rotation axis RA4 cross at one point. This one point is referred to as a spherical surface link center point P2.

A spherical surface centering on spherical surface link center point P1 is referred to as a moving spherical surface SP1. Proximal end link hub <NUM> moves on moving spherical surface SP1. A spherical surface centering on spherical surface link center point P2 is referred to as a moving spherical surface SP2. Distal end link hub <NUM> moves on moving spherical surface SP2. That is, spherical surface link mechanism <NUM> has structure in which two spherical surface link mechanisms are combined.

Fifth rotation axis RA5 passes both of spherical surface link center point P1 and spherical surface link center point P2. From another viewpoint, fifth rotation axis RA5 passes the center of a surface (an intermediate plane IP having a circular shape) where moving spherical surface SP1 and moving spherical surface SP1 cross and is orthogonal to intermediate plane IP. The relation explained above always holds irrespective of the positions and the postures of proximal end link hub <NUM> and distal end link hub <NUM>.

Effects of spherical surface link mechanism <NUM> are explained below in comparison with a spherical surface link mechanism according to a comparative example.

A configuration of the spherical surface link mechanism according to the comparative example is the same as the configuration of spherical surface link mechanism <NUM> except that the spherical surface link mechanism according to the comparative example does not include intermediate link hubs <NUM>.

In spherical surface link mechanism <NUM>, intermediate link members <NUM> of plurality of links <NUM> are mutually rotatably coupled by plurality of intermediate link hubs <NUM>. However, fifth rotation axis RA5 passes spherical surface link center point P1 and spherical surface link center point P2. Therefore, with spherical surface link mechanism <NUM>, it is possible to move proximal end link hub <NUM> and distal end link hub <NUM> as in the spherical surface link mechanism according to the comparative example.

In the spherical surface link mechanism according to the comparative example, intermediate link members <NUM> of plurality of links <NUM> are not coupled to one another. Therefore, in the spherical surface link mechanism according to the comparative example, in order to improve rigidity, it is necessary to improve the rigidity of the link members (first end link member <NUM>, second end link member <NUM>, and intermediate link member <NUM>) and the coupling sections among the link members. However, there is a limitation in the volume of the link members and the coupling sections among the link members in order to avoid interference among plurality of links <NUM>. Therefore, there is a limitation in the rigidity improvement.

On the other hand, in spherical surface link mechanism <NUM>, plurality of links <NUM> are coupled to one another by intermediate link hubs <NUM>. In spherical surface link mechanism <NUM>, rigidity is improved by coupling plurality of intermediate link hubs <NUM> to one another. Therefore, the rigidity improvement is less easily affected by the volume of the link members and the coupling sections among the link members. In this way, with spherical surface link mechanism <NUM>, it is possible to improve the rigidity without compromising the operation of the spherical surface link mechanism.

Note that, since the rigidity of spherical surface link mechanism <NUM> is improved, positioning accuracy of distal end link hub <NUM> (proximal end link hub <NUM>) is improved and the operation of spherical surface link mechanism <NUM> becomes smooth.

In the spherical surface link mechanism according to the comparative example, a region into which link <NUM> does not intrude is present on the inside. For example, the cable connected to the end effector can be inserted through the region. However, this region cannot be viewed in the spherical surface link mechanism according to the comparative example. On the other hand, in spherical surface link mechanism <NUM>, plurality of intermediate link hubs <NUM> coupled to one another are located in a region into which link <NUM> does not intrude. Therefore, with spherical surface link mechanism <NUM>, it is easy to recognize the region into which link <NUM> does not intrude present on the inside.

In spherical surface link mechanism <NUM>, since the cable can be inserted through through-hole 38a, it is possible to protect the cable. As a result of the cable being inserted through through-hole 38a, deflection of the cable is suppressed and interference between the cable and link <NUM> is suppressed. Since through-hole 38a is formed in shaft member <NUM>, it is possible to reduce shaft member <NUM> in weight.

In spherical surface link mechanism <NUM>, since shaft member <NUM> is a member separate from intermediate link hubs <NUM>, it is possible to simplify structure for coupling plurality of intermediate link hubs <NUM> one another. Eventually, it is possible to reduce manufacturing cost of spherical surface link mechanism <NUM>. Since shaft member <NUM> follows movement of the cable when the cable is inserted through through-hole 38a, a load on the cable and friction with the cable decrease.

In spherical surface link mechanism <NUM>, since the friction between intermediate link hubs <NUM> and shaft member <NUM> is reduced by bearings <NUM>, the life of spherical surface link mechanism <NUM> is improved. Heat generation from spherical surface link mechanism <NUM> during operation can be suppressed by this friction reduction.

If the volume of the coupling sections of the link members is increased, interference sometimes occurs among plurality of links <NUM>. However, interference less easily occurs even if the volume of the coupling sections of plurality of intermediate link hubs <NUM> is increased. Therefore, bearings larger than bearings used in the coupling sections of the link members can be used as bearings <NUM>. As a result, it is possible to further improve the rigidity of spherical surface link mechanism <NUM>.

When bearings <NUM> are rolling bearings, bearings <NUM> can support an axial load in addition to a radial load. When bearings <NUM> are slide bearings, bearings <NUM> can be reduced in weight and vibration is less easily transmitted between shaft member <NUM> and intermediate link hubs <NUM>.

A simulation for applying a load of <NUM> N between proximal end link hub <NUM> and distal end link hub <NUM> in a state in which proximal end link hub <NUM> and distal end link hub <NUM> are opposed and calculating stress and displacement in the members of the spherical surface link mechanism was implemented using a finite element analysis method. Note that, in this simulation, the members constituting the spherical surface link mechanism according to the comparative example and spherical surface link mechanism <NUM> were formed by steel.

According to a result of the simulation explained above, in the spherical surface link mechanism according to the comparative example, distal end link hub <NUM> was displaced <NUM> toward the proximal end link hub <NUM> side. On the other hand, in spherical surface link mechanism <NUM>, distal end link hub <NUM> was displaced <NUM> toward proximal end link hub <NUM>. In this way, a displacement amount of distal end link hub <NUM> in spherical surface link mechanism <NUM> was less than <NUM> percent of a displacement amount of distal end link hub <NUM> in the spherical surface link mechanism according to the comparative example.

In the simulation explained above, a safety factor (a value obtained by dividing yield stress of a material constituting the members constituting the spherical surface link mechanism by maximum stress applied to the members) of the spherical surface link mechanism according to the comparative example was <NUM>. On the other hand, a safety factor of spherical surface link mechanism <NUM> was <NUM>. In this way, with spherical surface link mechanism <NUM>, it has been clarified in the simulation that the displacement of distal end link hub <NUM> is suppressed and the load of distal end link hub <NUM> is dispersed and the safety factor increases, that is, the rigidity is improved.

A spherical surface link mechanism according to a second embodiment (hereinafter, "spherical surface link mechanism <NUM>") is explained. Here, differences from spherical surface link mechanism <NUM> are mainly explained and redundant explanation is not repeated.

A configuration of spherical surface link mechanism <NUM> is explained below.

Spherical surface link mechanism <NUM> includes proximal end link hub <NUM>, distal end link hub <NUM>, plurality of links <NUM>, plurality of intermediate link hubs <NUM>, and bearings <NUM>. In this regard, the configuration of spherical surface link mechanism <NUM> is common to the configuration of spherical surface link mechanism <NUM>.

<FIG> is an enlarged sectional view of spherical surface link mechanism <NUM>. In <FIG>, an enlarged sectional view of spherical surface link mechanism <NUM> in a position corresponding to <FIG> is shown. As shown in <FIG>, in spherical surface link mechanism <NUM>, shaft member <NUM> is formed integrally with one of plurality of intermediate link hubs <NUM> (shaft member <NUM> is a part of one of plurality of intermediate link hubs <NUM>). In this regard, the configuration of spherical surface link mechanism <NUM> is different from the configuration of spherical surface link mechanism <NUM>.

Effects of spherical surface link mechanism <NUM> are explained below.

In spherical surface link mechanism <NUM>, since shaft member <NUM> is formed integrally with one of plurality of intermediate link hubs <NUM>, it is possible to reduce the number of bearings <NUM>. More specifically, in spherical surface link mechanism <NUM>, since shaft member <NUM> is the member separate from intermediate link hubs <NUM>, three bearings <NUM> in total are necessary. On the other hand, in spherical surface link mechanism <NUM>, since shaft member <NUM> is formed integrally with one of plurality of intermediate link hubs <NUM>, two number of bearings <NUM> are enough. In this way, with spherical surface link mechanism <NUM>, it is possible to reduce the number of bearings <NUM>. Therefore, it is possible to reduce manufacturing cost.

A spherical surface link mechanism according to a third embodiment (hereinafter, "spherical surface link mechanism <NUM>") is explained. Here, differences from spherical surface link mechanism <NUM> are mainly explained and redundant explanation is not repeated.

Spherical surface link mechanism <NUM> includes proximal end link hub <NUM>, distal end link hub <NUM>, plurality of links <NUM>, plurality of intermediate link hubs <NUM>, and bearings <NUM> (not shown in <FIG>). In this regard, the configuration of spherical surface link mechanism <NUM> is common to the configuration of spherical surface link mechanism <NUM>.

<FIG> is a perspective view of spherical surface link mechanism <NUM>. As shown in <FIG>, in spherical surface link mechanism <NUM>, coupling sections <NUM> are located on the outer side of plurality of links <NUM>. In this regard, the configuration of spherical surface link mechanism <NUM> is different from the configuration of spherical surface link mechanism <NUM>.

<FIG> is an enlarged sectional view of spherical surface link mechanism <NUM>. In <FIG>, illustration of the components other than intermediate link member <NUM>, shaft member <NUM>, and intermediate link hubs <NUM> is omitted. As shown in <FIG>, in spherical surface link mechanism <NUM>, shaft member <NUM> is inserted through through-hole 41a, whereby coupling sections <NUM> of plurality of intermediate link hubs <NUM> are coupled to be rotatable about fifth rotation axis RA5. However, in spherical surface link mechanism <NUM>, a through-hole 38d for inserting through beam section <NUM> is formed in shaft member <NUM>.

<FIG> is an enlarged sectional view of spherical surface link mechanism <NUM> according to a first modification. In <FIG>, illustration of the components other than intermediate link members <NUM>, an outer ring <NUM>, and intermediate link hubs <NUM> is omitted. As shown in <FIG>, spherical surface link mechanism <NUM> may include outer ring <NUM> instead of shaft member <NUM>. Outer ring <NUM> is disposed on the outer side of coupling section <NUM> of each of plurality of intermediate link hubs <NUM> and holds coupling section <NUM> of each of plurality of intermediate link hubs <NUM> to be rotatable about fifth rotation axis RA5. More specifically, outer ring <NUM> includes a first member 39a and a second member 39b. First member 39a and second member 39b are coupled to each other in a state in which coupling section <NUM> of each of plurality of intermediate link hubs <NUM> is sandwiched between first member 39a and second member 39b.

<FIG> is an enlarged sectional view of spherical surface link mechanism <NUM> according to a second modification. In <FIG>, illustration of the components other than intermediate link members <NUM>, a falling-off preventing ring 60a, a falling-off preventing ring 60b, and intermediate link hubs <NUM> is omitted. As shown in <FIG>, spherical surface link mechanism <NUM> may include falling-off preventing ring 60a and falling-off preventing ring 60b instead of outer ring <NUM>.

Coupling section <NUM> of one intermediate link hub <NUM> is sandwiched by coupling sections <NUM> of other two intermediate link hubs <NUM>. Falling-off preventing ring 60a and falling-off preventing ring 60b are attached to coupling section <NUM> of one intermediate link hub <NUM>. Falling-off preventing ring 60a and falling-off preventing ring 60b sandwich coupling section <NUM> of each of plurality of intermediate link hubs <NUM>. Consequently, coupling section <NUM> of each of plurality of intermediate link hubs <NUM> is held to be rotatable about fifth rotation axis RA5.

In spherical surface link mechanism <NUM> and spherical surface link mechanism <NUM>, by rotating each of plurality of intermediate link hubs <NUM> about fifth rotation axis RA5 with a driving source (not shown), it is possible to respectively symmetrically move proximal end link hub <NUM> and distal end link hub <NUM> with respect to intermediate plane IP.

However, in spherical surface link mechanism <NUM>, since plurality of intermediate link hubs <NUM> are present on the inner side of plurality of links <NUM>, it is difficult to install driving sources for driving plurality of intermediate link hubs <NUM>. On the other hand, in spherical surface link mechanism <NUM>, since plurality of intermediate link hubs <NUM> are present on the outer side of plurality of links <NUM>, it is easy to install the driving sources for driving plurality of intermediate link hubs <NUM>.

A spherical surface link actuating device according to a fourth embodiment (hereinafter, "spherical surface link actuating device <NUM>") is explained.

<FIG> is a perspective view of spherical surface link actuating device <NUM>. As shown in <FIG>, spherical surface link actuating device <NUM> includes spherical surface link mechanism <NUM> and a plurality of driving sources <NUM>. The number of plurality of driving sources <NUM> is two or more. When the number of plurality of links <NUM> included in spherical surface link mechanism <NUM> is three or more, the number of plurality of driving sources <NUM> may be smaller than the number of plurality of links <NUM>.

Driving source <NUM> is, for example, a motor. Plurality of driving sources <NUM> are attached to spherical surface link mechanism <NUM>. Each of plurality of driving sources <NUM> rotates first end link member <NUM> of each of plurality of links <NUM> about first rotation axis RA1. Consequently, it is possible to change the position and the posture of distal end link hub <NUM> with respect to proximal end link hub <NUM>. Although not shown, each of plurality of driving sources <NUM> may rotate second end link member <NUM> of each of plurality of links <NUM> about second rotation axis RA2. Consequently, it is possible to change the position and the posture of proximal end link hub <NUM> with respect to distal end link hub <NUM>.

In spherical surface link actuating device <NUM>, spherical surface link mechanism <NUM> may be used instead of spherical surface link mechanism <NUM>. In spherical surface link actuating device <NUM>, spherical surface link mechanism <NUM> may be used instead of spherical surface link mechanism <NUM>. Although not shown, when spherical surface link mechanism <NUM> is used in spherical surface link actuating device <NUM>, each of plurality of driving sources <NUM> can respectively symmetrically move proximal end link hub <NUM> and distal end link hub <NUM> with respect to intermediate plane IP by rotating each of plurality of intermediate link hubs <NUM> about fifth rotation axis RA5.

In spherical surface link actuating device <NUM>, when each of plurality of driving sources <NUM> rotates first end link member <NUM> of each of plurality of links <NUM> about first rotation axis RA1 to thereby change the position and the posture of distal end link hub <NUM> with respect to proximal end link hub <NUM>, it is possible to reduce an inertial moment involved in the movement of distal end link hub <NUM>.

On the other hand, in spherical surface link actuating device <NUM>, when each of plurality of driving sources <NUM> rotates each of plurality of intermediate link hubs <NUM> about fifth rotation axis RA5 to thereby change the position and the posture of distal end link hub <NUM> with respect to proximal end link hub <NUM>, since proximal end link hub <NUM> and distal end link hub <NUM> are symmetrically moved, it is possible to reduce accumulation of errors such as backlash.

A link actuating device according to a fifth embodiment (hereinafter referred to as "link actuating device <NUM>") is explained.

<FIG> is a perspective view of link actuating device <NUM>. <FIG> is a front view of link actuating device <NUM>. <FIG> is a side view of link actuating device <NUM>. <FIG> is a sectional view in XVI-XVI in <FIG>. <FIG> is a plan view of link actuating device <NUM>. <FIG> is a sectional view in XVIII-XVIII in <FIG>. As shown in <FIG>, link actuating device <NUM> includes a spherical surface link mechanism <NUM>, an origin positioning member <NUM>, and a driving source <NUM>.

Spherical surface link mechanism <NUM> includes a proximal end link hub <NUM>, a distal end link hub <NUM>, a plurality of links <NUM>, and a plurality of intermediate link hubs <NUM>.

Proximal end link hub <NUM> and distal end link hub <NUM> are, for example, flat. However, the shape of proximal end link hub <NUM> and distal end link hub <NUM> is not limited to this. In the following explanation, the center axis of proximal end link hub <NUM> is referred to as a first center axis and the center axis of distal end link hub <NUM> is referred to as a second center axis. Although not shown, an end effector is attached to, for example, distal end link hub <NUM>.

The number of plurality of links <NUM> is, for example, three. However, the number of plurality of links <NUM> may be four or more. Plurality of links <NUM> are disposed, for example, at equal intervals, in a direction along a circumference centering on the first center axis. Link <NUM> includes a first end link member 613a, a second end link member 613b, and an intermediate link member 613c.

First end link member 613a is coupled, at one end of first end link member 613a, to proximal end link hub <NUM> to be rotatable about a first rotation axis. Second end link member 613b is coupled, at one end of second end link member 613b, to distal end link hub <NUM> to be rotatable about a second rotation axis. First end link member 613a and second end link member 613b are, for example, L-shaped.

Intermediate link member 613c is coupled, at one end of intermediate link member 613c, to the other end of first end link member 613a to be rotatable about a third rotation axis. Intermediate link member 613c is coupled, at the other end of intermediate link member 613c, to the other end of second end link member 613b to be rotatable about a fourth rotation axis. Intermediate link member 613c has, for example, an L shape.

The first rotation axis, the third rotation axis, and the first center axis cross at a first spherical surface link center point. The second rotation axis, the fourth rotation axis, and the second center axis cross at a second spherical surface link center point. Therefore, proximal end link hub <NUM> moves on a spherical surface (a first moving spherical surface) centering on the first spherical surface link center point and distal end link hub <NUM> moves on a spherical surface (a second moving spherical surface) centering on the second spherical surface link center point. That is, spherical surface link mechanism <NUM> has structure in which two spherical surface link mechanisms are combined.

The number of plurality of intermediate link hubs <NUM> is equal to the number of plurality of links <NUM>. Intermediate link hub <NUM> includes a coupling section 614a and a beam section 614b. Coupling section 614a is disposed on the inner side of plurality of links <NUM>.

Coupling sections 614a of plurality of intermediate link hubs <NUM> are coupled to one another to be rotatable about a fifth rotation axis. The fifth rotation axis passes both of the first spherical surface link center point and the second spherical surface link center point. From another viewpoint, the fifth rotation axis passes the center of a surface (an intermediate plane having a circular shape) where the first moving spherical surface and the second moving spherical surface cross and is orthogonal to the intermediate plane. This always holds irrespective of the positions and the postures of proximal end link hub <NUM> and distal end link hub <NUM>. Therefore, spherical surface link mechanism <NUM> is capable of performing the same operation as an operation performed when spherical surface link mechanism <NUM> does not include plurality of intermediate link hubs <NUM>.

A first through-hole 614aa is formed in coupling section 614a. First through-hole 614aa pierces through coupling section 614a in the direction of the fifth rotation axis. First through-holes 614aa of plurality of intermediate link hubs <NUM> overlap one another.

A first groove 614ab and a second groove 614ac are formed on the inner wall surface of first through-hole 614aa. First groove 614ab and second groove 614ac extend from the inner wall surface of first through-hole 614aa toward the radial direction outer side of first through-hole 614aa. First groove 614ab and second groove 614ac are present in positions symmetrical with respect to the center of first through-hole 614aa.

First groove 614ab and second groove 614ac of each of plurality of intermediate link hubs <NUM> are formed to overlap each other when distal end link hub <NUM> is present in an origin position. Distal end link hub <NUM> is present in the origin position when the second center axis is present on the same straight line as the first center axis (when a bending angle of spherical surface link mechanism <NUM> is <NUM>°).

Beam section 614b is connected, at one end of beam section 614b, to coupling section 614a. Beam section 614b is connected, at the other end of beam section 614b, to intermediate link member 613c. Intermediate link hub <NUM> (coupling section 614a and beam section 614b) may be formed integrally with intermediate link member 613c.

Origin positioning member <NUM> is plate-like. Origin positioning member <NUM> includes a first end 620a and a second end 620b. First end 620a and second end 620b are ends in the longitudinal direction of origin positioning member <NUM>. Second end 620b is an end on the opposite side of first end 620a.

Origin positioning member <NUM> includes a first portion <NUM> and a second portion <NUM>. First portion <NUM> is a portion on the first end 620a side of origin positioning member <NUM>. Second portion <NUM> is a portion on the second end 620b side of origin positioning member <NUM>. The width of first portion <NUM> in a direction orthogonal to the longitudinal direction of origin positioning member <NUM> is larger than the width of second portion <NUM> in the direction orthogonal to the longitudinal direction of origin positioning member <NUM>. The width of first portion <NUM> in the direction orthogonal to the longitudinal direction of origin positioning member <NUM> decreases toward first end 620a.

Origin positioning member <NUM> is inserted into first through-hole 614aa (more specifically, first groove 614ab and second groove 614ac) of each of intermediate link hubs <NUM> when distal end link hub <NUM> is present in the origin position, whereby plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis.

When plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis, the positions and the postures of proximal end link hub <NUM>, distal end link hub <NUM>, and plurality of links <NUM> are fixed, whereby distal end link hub <NUM> is fixed to the origin position. Note that it is sufficient that origin positioning member <NUM> disables at least two or more among plurality of intermediate link hubs <NUM> to rotate about the fifth rotation axis.

Driving source <NUM> is, for example, a motor. The number of plurality of driving sources <NUM> is equal to, for example, the number of plurality of links <NUM>. However, the number of plurality of driving sources <NUM> may be smaller than the number of plurality of links <NUM> if the number of plurality of driving sources <NUM> is two or more. Each of plurality of driving sources <NUM> rotates first end link member 613a of each of plurality of links <NUM> about the first rotation axis. The position and the posture of distal end link hub <NUM> are changed by changing an amount of the rotation.

<FIG> is a flowchart showing an origin positioning method in link actuating device <NUM>. As shown in <FIG>, the origin positioning method in link actuating device <NUM> includes a preparation step S1, an origin positioning member insertion step S2, a preload step S3, and a recording step S4. Origin positioning member insertion step S2 is performed after preparation step S1. Preload step S3 is performed after origin positioning member insertion step S2. Recording step S4 is performed after preload step S3.

In preparation step S1, link actuating device <NUM> is prepared. In origin positioning member insertion step S2, first, driving source <NUM> adjusts an amount of rotating first end link member 613a about the first rotation axis to thereby move distal end link hub <NUM> to the origin position. In origin positioning member insertion step S2, secondly, origin positioning member <NUM> is inserted into first through-hole 614aa (first groove 614ab and second groove 614ac) of each of plurality of intermediate link hubs <NUM>. Consequently, origin positioning member <NUM> becomes incapable of rotating about the fifth rotation axis of plurality of intermediate link hubs <NUM>. Distal end link hub <NUM> is fixed to the origin position.

In preload step S3, each of plurality of driving sources <NUM> generates torque for rotating first end link member 613a of each of plurality of links <NUM> about the first rotation axis, whereby preload is applied on each of plurality of links <NUM>. In recording step S4, torque of each of plurality of driving sources <NUM> in a state in which the preload explained above is applied is recorded or output.

In recording step S4, an operation amount of each of plurality of driving sources <NUM> may be recorded or output or the position of each of plurality of links <NUM> may be recorded or output instead of the torque of each of plurality of driving sources <NUM>. At this time, the recorded or output torque of each of plurality of driving sources <NUM> (the operation amount of each of plurality of driving sources <NUM> or the position of each of plurality of links <NUM>) is reflected on an output of each of plurality of driving sources <NUM> during the operation of link actuating device <NUM>. Consequently, it is possible to suppress backlash of rotation pair units during the operation of link actuating device <NUM>.

In link actuating device <NUM>, by inserting origin positioning member <NUM> into first through-holes 614aa of plurality of intermediate link hubs <NUM>, it is possible to perform origin positioning for distal end link hub <NUM>. Therefore, in link actuating device <NUM>, in the origin positioning for distal end link hub <NUM>, origin positioning member <NUM> is suppressed from interfering with the end effector attached to distal end link hub <NUM>.

A link actuating device according to a sixth embodiment (hereinafter referred to as "link actuating device 600A") is explained. Here, differences from link actuating device <NUM> are mainly explained and redundant explanation is not repeated.

<FIG> is a perspective view of link actuating device 600A. <FIG> is a front view of link actuating device 600A. <FIG> is a sectional view in XXII-XXII in <FIG>. <FIG> is a plan view of link actuating device 600A. <FIG> is a sectional view in XXIV-XXIV in <FIG>. Note that, in <FIG>, illustration of driving source <NUM> is omitted. As shown in <FIG>, in link actuating device 600A, a second through-hole 614ad is formed in coupling section 614a of each of plurality of intermediate link hubs <NUM>.

Second through-hole 614ad pierces through coupling section 614a in the direction of the fifth rotation axis. Second through-hole 614ad is present in a position deviating from the center of coupling section 614a. Second through-holes 614ad of plurality of intermediate link hubs <NUM> are formed to overlap one another when distal end link hub <NUM> is present in the origin position.

In link actuating device 600A, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad of each of plurality of intermediate link hubs <NUM>. Consequently, plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis. Note that, in link actuating device 600A, origin positioning member <NUM> is bar-like.

In link actuating device 600A, a third through-hole 611a is formed in proximal end link hub <NUM> and a fourth through-hole 612a is formed in distal end link hub <NUM>. Third through-hole 611a is formed in a position deviating from the center of proximal end link hub <NUM>. Fourth through-hole 612a is present in a position deviating from the center of distal end link hub <NUM>. When distal end link hub <NUM> is present in the origin position, third through-hole 611a and fourth through-hole 612a are present in positions where third through-hole 611a and fourth through-hole 612a overlap second through-hole 614ad of each of plurality of intermediate link hubs <NUM>. When distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into third through-hole 611a and fourth through-hole 612a in addition to second through-hole 614ad of each of plurality of intermediate link hubs <NUM>.

In link actuating device 600A, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad of each of plurality of intermediate link hubs <NUM>, whereby plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis. Therefore, in link actuating device 600A, in the origin positioning for distal end link hub <NUM>, origin positioning member <NUM> is suppressed from interfering with the end effector attached to distal end link hub <NUM>.

In link actuating device 600A, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into third through-hole 611a and fourth through-hole 612a in addition to second through-hole 614ad of each of plurality of intermediate link hubs <NUM>. Therefore, in link actuating device 600A, the origin positioning for distal end link hub <NUM> by origin positioning member <NUM> is more firmly performed. Note that, since fourth through-hole 612a is present in a position deviating from the center of distal end link hub <NUM>, in the origin positioning for distal end link hub <NUM>, origin positioning member <NUM> less easily interferes with the end effector attached to distal end link hub <NUM>.

A link actuating device according to a seventh embodiment (hereinafter referred to as "link actuating device 600B") is explained. Here, differences from link actuating device 600A are mainly explained and redundant explanation is not repeated.

<FIG> is a perspective view of link actuating device 600B. <FIG> is a front view of link actuating device 600B. <FIG> is a plan view of link actuating device 600B. <FIG> is a sectional view in XXVIII-XXVIII in <FIG>. <FIG> is a sectional view in XXIX-XXIX in <FIG>. As shown in <FIG>, in link actuating device 600B, coupling section 614a is disposed on the outer side of plurality of links <NUM>. In link actuating device 600B, coupling section 614a is annular.

In link actuating device 600B, second through-hole 614ad is formed in a slit shape on the outer circumferential surface of coupling section 614a. In link actuating device 600B, second through-hole 614ad extends from the outer circumferential surface of coupling section 614a to the radial direction inner side of coupling section 614a.

In link actuating device 600B, origin positioning member <NUM> is plate-like. In link actuating device 600B, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad of each of plurality of intermediate link hubs <NUM>. Consequently, plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis.

As explained above, in link actuating device 600B, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad of each of plurality of intermediate link hubs <NUM>, whereby plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis. In link actuating device 600B, coupling section 614a is disposed on the outer side of plurality of links <NUM>. Therefore, in link actuating device 600B, in the origin positioning for distal end link hub <NUM>, origin positioning member <NUM> is suppressed from interfering with the end effector attached to distal end link hub <NUM>.

In a link actuating device according to an eighth embodiment (hereinafter referred to as "link actuating device 600C") is explained. Here, differences from link actuating device 600A are mainly explained and redundant explanation is not repeated.

<FIG> is a perspective view of link actuating device 600C. <FIG> is a front view of link actuating device 600C. <FIG> is a side view of link actuating device 600C. <FIG> is a sectional view in XXXIII-XXXIII in <FIG>. <FIG> is a sectional view in XXXIV-XXXIV in <FIG>. <FIG> is an enlarged view in a region XXXV in <FIG>. As shown in <FIG>, in link actuating device 600C, spherical surface link mechanism <NUM> further includes a housing member <NUM>. Housing member <NUM> is attached to proximal end link hub <NUM>.

In link actuating device 600C, one intermediate link hub <NUM> among plurality of intermediate link hubs <NUM> is referred to as a first intermediate link hub and other intermediate link hubs <NUM> among plurality of intermediate link hubs <NUM> are referred to as second intermediate link hubs. In link actuating device 600C, coupling section 614a of the first intermediate link hub includes a shaft section 614c. Shaft section 614c has a tubular shape extending in the direction of the fifth rotation axis.

Coupling section 614a of the second intermediate link hub is attached to shaft section 614c to be rotatable about shaft section 614c. Consequently, coupling sections 614a of plurality of intermediate link hubs <NUM> are capable of mutually rotating about the fifth rotation axis. Note that rotation resistance reducing members <NUM> are disposed between shaft section 614c and coupling section 614a of the second intermediate link hub. Consequently, rotation resistance between shaft section 614c and coupling section 614a of the second intermediate link hub is reduced. Rotation resistance reducing members <NUM> are, for example, rolling bearings or slide bearings.

In link actuating device 600C, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad. Consequently, plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis. Note that, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> may be inserted into shaft section 614c in addition to second through-hole 614ad.

In link actuating device 600C, origin positioning member <NUM> may include a grasping section <NUM>. In link actuating device 600C, by lifting grasping section <NUM> upward when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad and shaft section 614c.

In link actuating device 600C, origin positioning member <NUM> is housed in housing member <NUM>. That is, in link actuating device 600C, origin positioning member <NUM> is held by spherical surface link mechanism <NUM>. However, in origin positioning member <NUM>, a portion inserted into second through-hole 614ad and shaft section 614c and grasping section <NUM> are located on the outside of housing member <NUM>.

As explained above, in link actuating device 600C, when distal end link hub <NUM> is present in the origin position, origin positioning member <NUM> is inserted into second through-hole 614ad of each of plurality of intermediate link hubs <NUM>, whereby plurality of intermediate link hubs <NUM> become incapable of mutually rotating about the fifth rotation axis. Therefore, in link actuating device 600B, in origin positioning for distal end link hub <NUM>, origin positioning member <NUM> is suppressed from interfering with the end effector attached to distal end link hub <NUM>.

In link actuating device 600C, origin positioning member <NUM> is held by spherical surface link mechanism <NUM> (housing member <NUM>). Therefore, in link actuating device 600C, loss and drop of origin positioning member <NUM> are suppressed.

A link actuating device according to a ninth embodiment (hereinafter referred to as "link actuating device 600D") is explained. Here, differences from link actuating device 600A are mainly explained and redundant explanation is not repeated.

<FIG> is a perspective view of link actuating device 600D. <FIG> is a plan view of link actuating device 600D. <FIG> is a sectional view in XXXVIII-XXXVIII in <FIG>. As shown in <FIG>, link actuating device 600D includes a light source <NUM>, a detector <NUM>, and a stand <NUM>. However, link actuating device 600D does not include origin positioning member <NUM>.

In link actuating device 600D, spherical surface link mechanism <NUM> and detector <NUM> are disposed on stand <NUM>. In link actuating device 600D, coupling section 614a is disposed on the outer side of plurality of links <NUM>. In link actuating device 600D, coupling section 614a is annular.

Light source <NUM> generates light <NUM>. Light source <NUM> is, for example, a laser oscillator. Light <NUM> is laser light. Second through-holes 614ad of plurality of intermediate link hubs <NUM> overlap one another when distal end link hub <NUM> is present in the origin position. Light <NUM> is applied to detector <NUM> passing through second through-hole 614ad of each of plurality of intermediate link hubs <NUM> when distal end link hub <NUM> is present in the origin position. On the other hand, if distal end link hub <NUM> is absent from the origin position, light <NUM> is blocked by coupling section 614a of each of plurality of intermediate link hubs <NUM> and is not applied to detector <NUM>.

Light <NUM> is applied to detector <NUM>, whereby detector <NUM> outputs a signal indicating that light <NUM> is applied. Detector <NUM> is for example, a photodiode. Therefore, it is detected based on the output signal from detector <NUM> that distal end link hub <NUM> is present in the origin position.

An encoder 614ae is provided in coupling section 614a. When distal end link hub <NUM> is present in the origin position, a value of encoder 614ae is recorded. By comparing a value of encoder 614ae at the time when link actuating device 600D is operating and a value of encoder 614ae recorded when distal end link hub <NUM> is present in the origin position, it is possible to determine a position of distal end link hub <NUM> during the operation of link actuating device 600D.

In link actuating device 600D, by allowing light <NUM> to pass through second through-holes 614ad of plurality of intermediate link hubs <NUM>, it is possible to perform the origin positioning for distal end link hub <NUM>. Therefore, in link actuating device <NUM>, it is unnecessary to use origin positioning member <NUM> in origin positioning for distal end link hub <NUM>. Origin positioning member <NUM> is suppressed from interfering the end effector attached to distal end link hub <NUM>.

The embodiments of the present invention are explained above. However, it is also possible to variously modify the embodiments explained above. The scope of the present invention is not limited to the embodiments explained above. The scope of the present invention is indicated by the claims and is intended to include all changes within the scope of the claims.

The embodiments explained above can be particularly advantageously applied to a spherical surface link mechanism, a spherical surface link actuating device, a link actuating device, and an origin positioning method.

Claim 1:
A spherical surface link mechanism (<NUM>, <NUM>, <NUM>) comprising:
a proximal end link hub (<NUM>);
a distal end link hub (<NUM>);
a plurality of links (<NUM>);
a plurality of intermediate link hubs (<NUM>); and
a shaft member (<NUM>), wherein
each of the plurality of links (<NUM>) includes a first end link member (<NUM>), a second end link member (<NUM>), and an intermediate link member (<NUM>),
the first end link member (<NUM>) is coupled, at one end, to the proximal end link hub (<NUM>) to be rotatable about a first rotation axis (RA1),
the second end link member (<NUM>) is coupled, at one end, to the distal end link hub (<NUM>) to be rotatable about a second rotation axis (RA2),
the intermediate link member (<NUM>) is coupled, at one end, to another end of the first end link member (<NUM>) to be rotatable about a third rotation axis (RA3) and is coupled to, at another end, another end of the second end link member (<NUM>) about a fourth rotation axis (RA4),
a center axis of the proximal end link hub (<NUM>), the first rotation axis (RA1), and the third rotation axis (RA3) cross at a first spherical surface link center point (P1),
a center axis of the distal end link hub (<NUM>), the second rotation axis (RA2), and the fourth rotation axis (RA4) cross at a second spherical surface link center point (P2),
each of the plurality of intermediate link hubs (<NUM>) is connected to the intermediate link member (<NUM>) of each of the plurality of links (<NUM>), and
the plurality of intermediate link hubs (<NUM>) are coupled to one another by the shaft member ( (<NUM>, <NUM>, <NUM>, <NUM>) to be rotatable about a fifth rotation axis (RA5) that passes the first spherical surface link center point (P1) and the second spherical surface link center point (P2), and characterised in that
a through hole (38a) is formed in the shaft member (<NUM>) so as for the through hole (38a) to pierce through the shaft member (<NUM>) along the fifth rotation axis (RA5).