Sprocket and power transmission device

Abstract

This sprocket comprises: a plurality of first sprocket teeth which engage with links of a chain; and a plurality of second sprocket teeth which are separated from the first sprocket teeth at an interval in the direction of extension of the rotational center line of the sprocket and which engage with the links. The first sprocket teeth are each provided with a first contact part that contacts a link on the forward rotation direction side of the sprocket, and are each provided with a first clearance part that is for avoiding contact with the links on the reverse rotation direction side. The second sprocket teeth are each provided with a second contact part that contacts a link on the reverse rotation direction side of the sprocket, and are each provided with a second clearance part that is for avoiding contact with the links on the forward rotation direction side.

Description

Sprockets and power transmission devices

[0001] The present disclosure relates to sprockets and power transmission devices.

[0002] For example, various types of chains that engage with sprockets are known, such as roller chains and silent chains. Meanwhile, a new chain, a chain with a spiral structure, is described in Patent Document 1. In the spiral chain described in Patent Document 1, a plurality of links are rotatably connected in series to form a spiral link assembly that extends in a spiral shape.

[0003] Patent No. 7478912

[0004] However, no sprocket suitable for a spiral chain in which multiple links are connected in a spiral configuration, as described in Patent Document 1, has yet been proposed.

[0005] Therefore, an object of the present disclosure is to realize a sprocket that can engage with a chain having a spiral structure in which multiple links are connected in a spiral shape.

[0006] In order to solve the above-mentioned problems, according to one aspect of the present disclosure, there is provided a sprocket that can engage with a chain having a spiral structure in which a plurality of links are spirally connected, comprising: a plurality of first sprocket teeth that engage with the links of the chain; and a plurality of second sprocket teeth that are spaced apart from the first sprocket teeth in the direction of extension of the rotational centerline of the sprocket and engage with the links of the chain, wherein each of the first sprocket teeth has a first contact portion on the forward rotation direction side of the sprocket that contacts the link of the chain, and a first relief portion on the reverse rotation direction side that avoids contact with the link of the chain, and each of the second sprocket teeth has a second contact portion on the reverse rotation direction side of the sprocket that contacts the link of the chain, and a second relief portion on the forward rotation direction side that avoids contact with the link of the chain.

[0007] According to another aspect of the present disclosure, there is provided a power transmission device comprising: a chain having a spiral structure in which a plurality of links are spirally connected; and a sprocket engageable with the chain, wherein the chain includes: a plurality of first sprocket teeth that engage with the links of the chain; and a plurality of second sprocket teeth that are spaced apart from the first sprocket teeth in the direction of extension of the rotational center line of the sprocket and engage with the links of the chain, wherein each of the first sprocket teeth has a first contact portion on the forward rotation direction side of the sprocket that contacts the link of the chain, and a first relief portion on the reverse rotation direction side that avoids contact with the link of the chain, and each of the second sprocket teeth has a second contact portion on the reverse rotation direction side of the sprocket that contacts the link of the chain, and a second relief portion on the forward rotation direction side that avoids contact with the link of the chain.

[0008] According to the present disclosure, it is possible to realize a sprocket that can engage with a chain having a spiral structure in which multiple links are connected in a spiral shape.

[0009] 1A and 1B are front and right perspective views of a sprocket according to an embodiment of the present disclosure with an example chain engaged; 1C are front and left perspective views of a sprocket according to an embodiment of the present disclosure with an example chain engaged; 1D are perspective views of a portion of the example chain; 1E are top views of a portion of the example chain; 1F are exploded perspective views of a portion of the example chain; 1G are perspective views of a plurality of first links in the example chain connected to one another; 1H are front views of a plurality of first links (first spiral link combinations) in the example chain connected to one another; 1H are exploded perspective views of a plurality of first links in the example chain; 15A is a perspective view of a first and second spiral link assembly in which a plurality of first and second links are connected via a connecting member in an example chain; 15B is an exploded perspective view illustrating the connection of a plurality of first and second links via a plurality of connecting members in an example chain; 15C is a cross-sectional view of an example chain taken along line S1-S1 in FIG. 2; 15D is a cross-sectional view of an example chain taken along line S2-S2 in FIG. 2; 15E is a perspective view of a portion of an example chain bending to one side in the width direction; 15F is a perspective view of a portion of an example chain bending to the other side in the width direction; 15G is a perspective view of a portion of an example chain bending to one side in the thickness direction; 15H is a perspective view of a portion of an example chain bending to the other side in the thickness direction;1 shows an exploded perspective view of a sprocket; 2 shows a right side view of a sprocket with an example chain engaged; 3 shows a left side view of a sprocket with an example chain engaged; 4 shows a perspective view of the first and second links of an example chain in contact with the first and second sprocket teeth for one cycle; 5 shows a partial cross-sectional view of a sprocket with an example chain engaged; 6 shows a right front perspective view of a sprocket according to another embodiment with an example chain engaged; 7 shows a left front perspective view of a sprocket according to another embodiment with an example chain engaged; 8 shows a perspective view of a portion of an example chain; 9 shows an exploded perspective view of a portion of an example chain; 10 shows a front view of multiple first links (first spiral link combinations) that are connected to each other in an example chain; 11 shows a front view of multiple second links (second spiral link combinations) that are connected to each other in an example chain 20A and 20B are cross-sectional views of another example of a chain taken along lines S3-S3, respectively; 20B and 20C are cross-sectional views of another example of a chain taken along lines S4-S4, respectively; 20C are right-front perspective views of a sprocket according to another embodiment of the invention with a still further example of a chain engaged; 20C are left-front perspective views of a sprocket according to another embodiment of the invention with a still further example of a chain engaged; 20C are perspective views of a portion of a still further example of a chain; 20C are exploded perspective views of a portion of a still further example of a chain; 20C are front views of a plurality of first links (first spiral link assembly) connected to each other in a still further example of a chain; 20C are front views of a plurality of second links (second spiral link assembly) connected to each other in a still further example of a chain;

[0010] A sprocket according to one aspect of the present disclosure is a sprocket that can engage with a spiral chain in which multiple links are connected in a spiral shape, and includes a plurality of first sprocket teeth that engage with the links of the chain, and a plurality of second sprocket teeth that are spaced apart from the first sprocket teeth in the direction of extension of the center line of rotation of the sprocket and engage with the links of the chain, wherein each of the first sprocket teeth has a first contact portion on the forward rotation side of the sprocket that contacts the link of the chain, and a first relief portion on the reverse rotation side that avoids contact with the link of the chain, and each of the second sprocket teeth has a second contact portion on the reverse rotation side of the sprocket that contacts the link of the chain, and a second relief portion on the forward rotation side that avoids contact with the link of the chain.

[0011] According to this aspect, it is possible to realize a sprocket that can be engaged with a chain having a spiral structure in which a plurality of links are connected in a spiral shape.

[0012] For example, the first contact portion may be a flat surface facing in the forward rotation direction and outward from the sprocket, and the second contact portion may be a flat surface facing in the reverse rotation direction and outward from the sprocket.

[0013] For example, the sprocket may have a guide member that faces the chain in the direction of extension of the rotation center line when the chain is engaged with the sprocket, and that guides the chain.

[0014] For example, the sprocket may have a first rotating body including a disk-shaped first body portion and a plurality of the first sprocket teeth arranged along the outer periphery of the first body portion, a second rotating body including a disk-shaped second body portion and a plurality of the second sprocket teeth arranged along the outer periphery of the second body portion, and a spacer arranged between the first rotating body and the second rotating body to space the first sprocket teeth and the second sprocket teeth from each other in the direction of extension of the rotation center line.

[0015] For example, the chain may include a plurality of first links rotatably connected to each other to form a first spiral link assembly extending in a spiral, a plurality of second links rotatably connected to each other to form a second spiral link assembly extending in a spiral, and a plurality of connecting members that connect corresponding first links and second links, respectively, to connect the first and second spiral link assembly, thereby forming a double spiral structure, wherein the plurality of first sprocket teeth alternately contact the first links and the second links, and the plurality of second sprocket teeth alternately contact the first links and the second links.

[0016] For example, the sprocket may have markers that indicate the spiral direction of the chain when engaging the chain with the first and second sprocket teeth.

[0017] A power transmission device according to another aspect of the present disclosure includes a chain having a spiral structure in which a plurality of links are spirally connected, and a sprocket engageable with the chain, wherein the chain includes a plurality of first sprocket teeth that engage with the links of the chain, and a plurality of second sprocket teeth that are spaced apart from the first sprocket teeth in the direction of extension of the rotational centerline of the sprocket and engage with the links of the chain, each of the first sprocket teeth having a first contact portion on the forward rotation direction side of the sprocket that contacts the link of the chain, and a first relief portion on the reverse rotation direction side that avoids contact with the link of the chain, and each of the second sprocket teeth having a second contact portion on the reverse rotation direction side of the sprocket that contacts the link of the chain, and a second relief portion on the forward rotation direction side that avoids contact with the link of the chain.

[0018] According to this aspect, it is possible to realize a power transmission device having a chain with a spiral structure in which a plurality of links are connected in a spiral shape, and a sprocket with which the chain can be engaged.

[0019] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings.

[0020] 1A and 1B are right and left front perspective views of a sprocket according to one embodiment of the present disclosure with an example chain engaged therewith.

[0021] The X-Y-Z Cartesian coordinate system shown in the figure is intended to facilitate understanding of the embodiments of the present disclosure and is not intended to limit the embodiments of the present disclosure. The X-axis direction indicates the extension direction of the rotational centerline of the sprocket, and the Y-axis and Z-axis directions indicate the radial directions of the sprocket.

[0022] 1A and 1B, a sprocket 10 according to this embodiment is configured to be engageable with a spiral chain 110. This configuration forms a power transmission device including the sprocket 10 and the chain 110. Before describing the specific configuration of the sprocket 10, the characteristics of the chain 110 that engages with the sprocket 10 will be described.

[0023] Figure 2 is a perspective view of a portion of an example chain. Figure 3 is a top view of a portion of the example chain. Figure 4 is an exploded perspective view of the example chain. Note that the UVW orthogonal coordinate system shown in the figures is intended to facilitate understanding of the embodiments of the present disclosure and does not limit the embodiments of the present disclosure. The U-axis direction indicates the width direction of the chain, the V-axis direction indicates the thickness direction of the chain, and the W-axis direction indicates the extension direction of the chain.

[0024] In this specification, the extending direction of the chain (W-axis direction) is the direction in which the chain moves when the chain is in use. When the chain moves along a straight path, the extending direction of the chain corresponds to the extending direction of the straight path. When the chain moves along a curved path, the extending direction of the chain corresponds to the tangent direction of the curved path. In addition, in some drawings, the traveling direction (forward direction) of the chain is indicated by a white arrow FD to facilitate understanding of the embodiments of the present disclosure.

[0025] As shown in FIGS. 2 to 4, the chain 110 has a plurality of first links 120 and a plurality of second links 130 .

[0026] Figure 5A is a perspective view of a plurality of first links in an example chain in a connected state, Figure 5B is a front view of a plurality of first links (first spiral link combinations) in an example chain in a connected state, and Figure 5C is an exploded perspective view of a plurality of first links in an example chain.

[0027] 5A to 5C, in one example of a chain 110, the multiple first links 120 have the same shape. The first links 120 extend in the extension direction (W-axis direction) of the chain 110, but are bent when viewed in the extension direction of the chain 110. In other words, the first links 120 have an L-shape when viewed in the extension direction of the chain 110.

[0028] 4 and 5A to 5C, the multiple first links 120 are connected in series. That is, each first link 120 is connected to the other side of another first link 120 at one side in the extension direction (W-axis direction) of the chain 110, and is also connected to the one side of another first link 120 at the other side. Specific details of the connection method will be described later.

[0029] Furthermore, each of the first links 120 rotates around first and second rotation center lines C1 and C2. Specifically, each of the first links 120 is connected to one of the other first links 120 so as to be rotatable around the first rotation center line C1, and is connected to the other of the other first links 120 so as to be rotatable around the second rotation center line C2.

[0030] The first and second rotational center lines C1 and C2 extend in different directions. Specifically, the first and second rotational center lines C1 and C2 intersect when viewed in the extension direction (W-axis direction) of the chain 110. In one example of the chain 110, the extension direction of the first and second rotational center lines C1 and C2 (V-axis direction) intersect at a substantially 90-degree angle when viewed in the extension direction of the chain 110.

[0031] When each of the plurality of first links 120 is connected in series to other first links 120 so as to be rotatable about the first and second rotation center lines C1, C2, a first spiral link assembly 140 extending in a spiral shape is formed, as shown in Fig. 4. The first spiral link assembly 140 is a deformable link assembly having a plurality of first rotation center lines C1 and a plurality of second rotation center lines C2 arranged alternately in the extension direction of the chain 110 (W-axis direction).

[0032] In this specification, the term "spiral" refers to a three-dimensional curve that goes around a reference line extending in one direction and moves in the extension direction of the reference line. In this disclosure, the reference line of the spiral corresponds to a line that extends in the extension direction (W-axis direction) of the chain 110 and passes through the cross-sectional shape of the chain 110 perpendicular to the extension direction (i.e., a line that is located within the outline of the cross-sectional shape when viewed in the extension direction).

[0033] As described above, in the example chain 110, the multiple first links 120 have the same shape, and the first and second rotation center lines C1, C2 are substantially perpendicular to each other when viewed in the extension direction (W-axis direction) of the chain 110. Therefore, as shown in Fig. 5A, four consecutive first links 120 correspond to one period (one pitch) of the first spiral link assembly 140. Furthermore, as shown in Fig. 5B, the four consecutive first links 120, i.e., the first spiral link assembly 140, have a substantially square outline when viewed in the extension direction (W-axis direction) of the chain 110.

[0034] Figure 6A is a perspective view of a plurality of second links in an example chain in a connected state, Figure 6B is a front view of a plurality of second links (a second spiral link assembly) in an example chain in a connected state, and Figure 6C is an exploded perspective view of a plurality of second links in an example chain.

[0035] As shown in Figures 6A to 6C, in the example chain 110, the multiple second links 130 have the same shape. Furthermore, the first links 120 and the second links 130 have the same shape. In other words, the example chain 110 is composed of one type of link. Therefore, the second links 130 also extend in the extension direction of the chain 110 (W-axis direction), but are bent when viewed in the extension direction of the chain 110. In other words, the second links 130 also have an L-shape when viewed in the extension direction of the chain 110.

[0036] 4 and 6A to 6C, the second links 130 are connected in series. That is, each second link 130 is connected to the other side of another second link 130 at one side in the extension direction (W-axis direction) of the chain 110, and is also connected to the one side of another second link 130 at the other side. The specific connection method will be described in detail later.

[0037] Furthermore, each second link 130 is rotatably connected to the other second link 130 connected to it around a third rotation center line C3, and is rotatably connected to the other second link 130 connected to it around a fourth rotation center line C4.

[0038] The third rotation center line C3 and the fourth rotation center line C4 extend in different directions. Specifically, the third rotation center line C3 and the fourth rotation center line C4 intersect when viewed in the extension direction of the chain 110 (W-axis direction). The extension direction of the third rotation center line C3 (U-axis direction) and the extension direction of the fourth rotation center line C4 (V-axis direction) intersect at an angle of substantially 90 degrees when viewed in the extension direction of the chain 110.

[0039] When each of the plurality of second links 130 is connected in series to other second links 130 so as to be rotatable about the third and fourth rotation center lines C3 and C4, a second spiral link assembly 150 extending in a spiral shape is formed, as shown in Fig. 4. The second spiral link assembly 150 is a deformable link assembly having a plurality of third rotation center lines C3 and a plurality of fourth rotation center lines C4 arranged alternately in the extension direction of the chain 110 (W-axis direction).

[0040] As described above, in the example chain 110, the multiple second links 130 have the same shape, and the third and fourth rotation center lines C3, C4 are substantially perpendicular to each other when viewed in the extension direction (W-axis direction) of the chain 110. Therefore, as shown in Fig. 6A, four consecutive second links 130 correspond to one period of the second spiral link assembly 150. Furthermore, the four consecutive second links 130, i.e., the second spiral link assembly 150, has a substantially square outline when viewed in the extension direction (W-axis direction) of the chain 110, as shown in Fig. 6B.

[0041] A first spiral link assembly 140 formed from a plurality of first links 120 and a second spiral link assembly 150 formed from a plurality of second links 130 are connected by a connecting member to form the chain 110. Specifically, the first spiral link assembly 140 and the second spiral link assembly 150 are connected to form a double spiral structure.

[0042] FIG. 7 is a perspective view of an example chain showing first and second helical link connections forming a double helix structure.

[0043] As shown in FIG. 7, the first spiral link connection 140 and the second spiral link connection 150 form a double spiral structure without being in direct contact with each other.

[0044] Specifically, the first rotation center line C1 of the first link 120 forming the first spiral link assembly 140 and the third rotation center line C3 of the second link 130 forming the second spiral link assembly 150 are aligned on the same straight line. Furthermore, the second rotation center line C2 of the first link 120 and the fourth rotation center line C4 of the second link 130 are aligned on the same straight line. This allows the first spiral link assembly 140 and the second spiral link assembly 150 to form a double helix structure without coming into direct contact with each other. Strictly speaking, it is only necessary that the first spiral link assembly 140 and the second spiral link assembly 150 do not come into direct contact with each other, at least when the chain 110 is extending linearly. Otherwise, the chain 110 would not be able to bend.

[0045] The first spiral link connector 140 and the second spiral link connector 150 are connected to each other via a connecting member.

[0046] Fig. 8 is a perspective view showing first and second links in an example chain connected via a connecting member. Fig. 9 is an exploded perspective view illustrating the connection of multiple first and second links in an example chain via multiple connecting members. Fig. 10A is a cross-sectional view of the example chain taken along line S1-S1 in Fig. 2. Fig. 10B is a cross-sectional view of the example chain taken along line S2-S2 in Fig. 2.

[0047] 8 to 10B, an example chain 110 has first and second pins 160, 162 as connecting members. The first link 120 in the first spiral link assembly 140 and the second link 130 in the second spiral link assembly 150 are connected via the first and second pins 160, 162.

[0048] The first pin 160 rotatably supports the first link 120 while rotatably supporting the second link 130. Specifically, the first pin 160 supports the first link 120 at one of the base end and the tip end so that it can rotate about a first rotation center line C1. The first pin 160 also supports the second link 130 at the other of the base end and the tip end so that it can rotate about a third rotation center line C3. Due to this support by the first pin 160, the first rotation center line C1 of the first link 120 and the third rotation center line C3 of the second link 130 are positioned on the same straight line.

[0049] Furthermore, the first pin 160 supports each of two consecutive first links 120 so that they can rotate about the first rotation center line C1. This allows each of the two consecutive first links 120 to be connected to each other so that they can rotate about the first rotation center line C1. At the same time, the first pin 160 supports each of two consecutive second links 130 so that they can rotate about the third rotation center line C3. This allows each of the two consecutive second links 130 to be connected to each other so that they can rotate about the third rotation center line C3. In other words, the first pin 160 rotatably supports the two first links 120 and the two second links 130.

[0050] The second pin 162 also rotatably supports the first link 120 and the second link 130. Specifically, the second pin 162 rotatably supports the first link 120 at one of the base end and the tip end about a second rotation center line C2. The second pin 162 also rotatably supports the second link 130 at the other of the second base end and the tip end about a fourth rotation center line C4. Due to this support by the second pin 162, the second rotation center line C2 of the first link 120 and the fourth rotation center line C4 of the second link 130 are positioned on the same straight line.

[0051] Furthermore, the second pin 162 supports each of two consecutive first links 120 so that they can rotate about the second rotation center line C2. This allows each of the two consecutive first links 120 to be connected to each other so that they can rotate about the second rotation center line C2. At the same time, the second pin 162 supports each of two consecutive second links 130 so that they can rotate about the fourth rotation center line C4. This allows each of the two consecutive second links 130 to be connected to each other so that they can rotate about the fourth rotation center line C4. In other words, the second pin 162 rotatably supports the two first links 120 and the two second links 130.

[0052] In the exemplary chain 110, the first and second pins 160, 162 have the same shape.

[0053] 9, the first and second links 120, 130 are each formed with two through holes 120a, 130a into which the first and second pins 160, 162 are inserted, so as to be rotatably supported by the first and second pins 160, 162. In the first link 120, one through hole 120a extends in the direction of extension of the first rotation center line C1, and the other through hole 120a extends in the direction of extension of the second rotation center line C2. In the second link 130, one through hole 130a extends in the direction of extension of the third rotation center line C3, and the other through hole 130a extends in the direction of extension of the fourth rotation center line C4. By inserting the first and second pins 160, 162 into the through-hole 120a, the first pin 160 supports the first link 120 rotatably about the first rotation center line C1, and the second pin 162 supports the first link 120 rotatably about the second rotation center line C2. Similarly, by inserting the first and second pins 160, 162 into the through-hole 130a, the first pin 160 supports the second link 130 rotatably about the third rotation center line C3, and the second pin 162 supports the second link 130 rotatably about the fourth rotation center line C4.

[0054] Snap rings 164 are attached to the tips of the first and second pins 160, 162 to prevent the first and second pins 160, 162 from slipping out of the first and second links 120, 130. In one example chain 110, as shown in FIGS. 10A and 10B , rollers 166 are attached to the first and second pins 160, 162 via bushings 168. Both the rollers 166 and the bushings 168 may be provided, or both may be omitted, as needed. Alternatively, only the rollers 166 may be provided, as needed. Furthermore, the method for preventing the first and second pins 160, 162 from slipping out of the first and second links 120, 130 is not limited to the use of snap rings 164; for example, split pins or the like may also be used. Furthermore, the first and second pins 160, 162 and the first and second links 120, 130 may be joined by, for example, crimping without using any other parts.

[0055] In the example chain 110, each of the plurality of first and second pins 160, 162 rotatably supports each of the two first links 120 and the two second links 130. Alternatively, the first and second pins 160, 162 may be integrally provided on the first link 120 and the second link 130.

[0056] 10A and 10B , each first link 120 has an inner portion disposed on the inside relative to another first link 120 connected to it, and an outer portion disposed on the outside relative to another first link 120 connected to it. Similarly, each second link 130 has an inner portion disposed on the inside relative to another second link 130 connected to it, and an outer portion disposed on the outside relative to another second link 130 connected to it. For example, bushings 168 may be integrally provided on the inner portions of the first link 120 and the second link 130, and first and second pins 160, 162 may be integrally provided on the outer portions of the first link 120 and the second link 130 while passing through the bushings 168. That is, with the bush 168 supported non-rotatably on the inner portions of the first and second links 120, 130, respectively, the first and second pins 160, 162, which are supported non-rotatably on the outer portions of the first and second links 120, 130, respectively, are rotatably supported on the bush 168.

[0057] Note that one method for integrally providing the first and second pins 160, 162 to the first and second links 120, 130, respectively, is to use an "interference fit," for example. Briefly explaining the "interference fit," first, through holes are formed in the first and second links 120, 130. The first and second pins 160, 162 are press-fit into these through holes. As a result, the first and second pins 160, 162 are supported in the through holes so that they cannot rotate.

[0058] 11A-11D are perspective views each showing a portion of an example chain bending in a different direction.

[0059] As shown in Figures 11A and 11B, when the first link 120 (120A) rotates to one side or the other in the width direction (X-axis direction) around the second rotation center line C2 (C2A), the corresponding second link 130 (130A) rotates in the same direction around the fourth rotation center line C4 (C4A) that is located on the same straight line as the second rotation center line C2 (C2A).

[0060] In this specification, a "correspondence" is defined between a first link and a second link when the relative position of one link with respect to the other is maintained substantially constant, i.e., one link cannot move relative to the other. In an example chain 110, as shown in Figure 8, a first link 120 and a second link 130 supported by common first and second pins 160, 162 are in a correspondence relationship.

[0061] Also, as shown in Figures 11C and 11D, when the first link 120 (120B) rotates in one direction or the other in the thickness direction (Y-axis direction) around the first rotation center line C1 (C1B), the corresponding second link 130 (130B) rotates around the third rotation center line C3 (C3B) located on the same straight line as the first rotation center line C1 (C1B).

[0062] As a result of the first link 120 and the corresponding second link 130 rotating synchronously in this manner, the chain 110 can bend in the width direction (X-axis direction) and thickness direction (Y-axis direction) when viewed in its extension direction (Z-axis direction). In other words, the exemplary chain 110 can bend in four directions when viewed in its extension direction. This allows the chain 110 to freely change its traveling direction. As a result, the chain 110 can move along a straight path as well as a complex path with complex bends, i.e., it can wrap around the sprocket 10. Furthermore, because the chain 110 has a spiral, i.e., periodic, structure, the sprocket 10 can engage with the chain 110 from four directions.

[0063] In order to engage with such a spirally structured chain 110, the sprocket 10 according to this embodiment has the following features.

[0064] Figures 12A and 12B are right-front and left-front perspective views of the sprocket. Figures 13A and 13B are right-side and left-side views of the sprocket. Figure 14 is a front view of the sprocket. Figures 15A and 15B are exploded perspective views of the sprocket from different perspectives. Each of Figures 12A to 14 shows a shaft DS that connects a power source such as a motor (not shown) to the sprocket 10 and drives the sprocket 10 to rotate. The sprocket 10 may also be connected to a load via the shaft DS rather than the power source.

[0065] As shown in Figures 12A to 15B, the sprocket 10 of this embodiment has a disk-shaped first rotating body 12 having first sprocket teeth 12a and a disk-shaped second rotating body 14 having second sprocket teeth 14a.

[0066] Specifically, the first rotating body 12 includes a disk-shaped first main body portion 12b that rotates about the rotational centerline C0 of the sprocket 10 and a plurality of first sprocket teeth 12a provided at intervals along the outer periphery of the first main body portion 12b. The second rotating body 14 includes a disk-shaped second main body portion 14b that rotates about the rotational centerline C0 and a plurality of second sprocket teeth 14a provided at intervals along the outer periphery of the second main body portion 14b.

[0067] Additionally, the first sprocket tooth 12a and the second sprocket tooth 14a are located at different positions in the direction (X-axis direction) of the rotational centerline C0 of the sprocket 10. That is, the first sprocket tooth 12a and the second sprocket tooth 14a are spaced apart from each other in the direction of the rotational centerline C0.

[0068] In this embodiment, the sprocket 10 includes a cylindrical spacer 16 disposed between the first main body 12b of the first rotating body 12 and the second main body 14b of the second rotating body 14 to separate the first rotating body 12 and the second rotating body 14. The spacer 16 separates the first sprocket teeth 12a and the second sprocket teeth 14a from each other in the direction of the rotational centerline C0 of the sprocket 10. The first rotating body 12 and the second rotating body 14 are fixed to the spacer 16 via, for example, screws (not shown).

[0069] Furthermore, in this embodiment, the sprocket 10 includes an annular guide member 18 that guides the chain 110 engaged with the sprocket 10, as will be described in detail later.

[0070] In this embodiment, the sprocket 10 is made up of multiple components, but it can also be made as a single component. Also, any one of the first rotating body 12, the second rotating body 14, the spacer 16, and the guide member 18 may be integrated into a single component.

[0071] The first rotating body 12, the second rotating body 14, and the spacer 16 each have a through-hole 12c, 14c, 16a through which a shaft DS connected to a power source such as a motor (not shown) is inserted. When the shaft DS rotates, the first and second rotating bodies 12, 14, i.e., the first and second sprocket teeth 12a, 14a, rotate synchronously.

[0072] First and second sprocket teeth 12 a , 14 a of sprocket 10 engage first and second links 120 , 130 of spiral chain 110 .

[0073] 16A and 16B are right and left side views of an example sprocket with a chain engaged therewith, omitting all components other than the guide member 18 of the sprocket 10 and the first and second links 120, 130 of the chain 110.

[0074] 16A and 16B, the sprocket 10 engages with the chain 110 so that the width direction (U-axis direction) of the chain 110 is parallel to the extension direction of the rotational center line C0 of the sprocket 10 (X-axis direction). Note that because the chain 110 has a periodic structure, the sprocket 10 can also engage with the chain 110 so that the height direction (V-axis direction) of the chain 110 is parallel to the extension direction of the rotational center line C0 of the sprocket 10 (X-axis direction).

[0075] 16A , the first links 120 and second links 130 of the chain 110 alternately contact the multiple first sprocket teeth 12a of the sprocket 10. In other words, the first sprocket teeth 12a contacting the first links 120 and the first sprocket teeth 12a contacting the second links 130 alternate in the rotational direction of the sprocket 10.

[0076] Strictly speaking, in this embodiment, the first sprocket teeth 12 a contact some of the first links 120 and some of the second links 130 of the chain 110 .

[0077] FIG. 17 is a perspective view illustrating contact between the first and second links and the first and second sprocket teeth for one cycle of an example chain.

[0078] 17 and 5A to 6C, the first sprocket teeth 12a contact the first links 120 (120C) that have portions located between the first sprocket teeth 12a in one cycle of four consecutive first links 120. Similarly, the first sprocket teeth 12a contact the second links 130 (130C) that have portions located between the first sprocket teeth 12a in one cycle of four consecutive second links 130.

[0079] 16A and 17 , each of the first sprocket teeth 12a of the sprocket 10 has a first contact portion 12d that contacts the first and second links 120, 130 of the chain 110 in the forward rotation direction R1 of the sprocket 10. In this embodiment, the first contact portion 12d is a flat surface that faces in the forward rotation direction R1 and outward from the sprocket 10.

[0080] 16A and 17, the first contact portions 12d of each of the first sprocket teeth 12a of the sprocket 10 contact the rear end faces 120b, 130b of the first and second links 120, 130 of the advancing chain 110. In this specification, the direction of the chain 110 moving in the forward rotation direction R1 of the sprocket 10 is referred to as the forward direction FD.

[0081] On the other hand, as shown in FIG. 16A , each of the first sprocket teeth 12a of the sprocket 10 does not contact the first and second links 120, 130 of the chain 110 in the reverse direction R2 of the sprocket 10 (i.e., the direction opposite to the forward rotation direction R1). For example, a first sprocket tooth 12a that contacts the first link 120 in the forward rotation direction R1 does not contact the second link 130 in the reverse rotation direction R2. To this end, each of the first sprocket teeth 12a has a first relief portion 12e on the reverse rotation direction R2 side to avoid contact with the first and second links 120, 130. In this embodiment, the first relief portion 12e is a relief surface. Therefore, each of the first sprocket teeth 12a does not contact both the first link 120 and the second link 130 at the same time, i.e., it is not sandwiched between the first link 120 and the second link 130. The reason why the first sprocket tooth 12a has such a first recess 12e will be described later.

[0082] 16B , the first links 120 and the second links 130 of the chain 110 alternately contact the second sprocket teeth 14a of the sprocket 10. In other words, the second sprocket teeth 14a contacting the first links 120 and the second sprocket teeth 14a contacting the second links 130 alternate in the rotational direction of the sprocket 10.

[0083] Strictly speaking, in this embodiment, the second sprocket teeth 14 a contact some of the first links 120 and some of the second links 130 of the chain 110 .

[0084] 16B and 17, the second sprocket teeth 14a contact the first links 120 (120D) that have portions located between the second sprocket teeth 14a in one cycle of four consecutive first links 120. Similarly, the second sprocket teeth 14a contact the second links 130 (130D) that have portions located between the second sprocket teeth 14a in one cycle of four consecutive second links 130.

[0085] 16B and 17, each of the second sprocket teeth 14a of the sprocket 10 has a second contact portion 14d that contacts the first and second links 120, 130 of the chain 110 in the reverse rotation direction R2 of the sprocket 10. In this embodiment, the second contact portion 14d is a flat surface that faces in the reverse rotation direction R2 and outward from the sprocket 10.

[0086] Also, as shown in FIG. 16B, the second contact portions 14d of each of the plurality of second sprocket teeth 14a of the sprocket 10 contact the front end faces 120c, 130c of the first and second links 120, 130 of the advancing chain 110.

[0087] On the other hand, as shown in FIG. 16B , each of the second sprocket teeth 14a of the sprocket 10 does not contact the first and second links 120, 130 of the chain 110 in the forward rotation direction R1 of the sprocket 10 (i.e., the direction opposite to the reverse direction R2). For example, a second sprocket tooth 14a that contacts the second link 130 in the reverse direction R2 does not contact the first link 120 in the forward rotation direction R1. To avoid this, each of the second sprocket teeth 14a has a second relief portion 14e on the forward rotation direction R1 side to avoid contact with the first and second links 120, 130. In this embodiment, the second relief portion 14e is a relief surface. Therefore, each of the second sprocket teeth 14a does not contact both the first link 120 and the second link 130 at the same time, i.e., it is not sandwiched between the first link 120 and the second link 130. The reason why the second sprocket tooth 14a has such a second relief portion 14e will be described later.

[0088] 16A and 16B, the reason why the first and second sprocket teeth 12a, 14a are provided with the first and second relief portions 12e, 14e on different rotational directions will be explained. For this purpose, comparative examples 1 and 2 that are different from this embodiment will be presented.

[0089] Unlike the present embodiment, the first and second relief portions 12e, 14e are provided on the same side (e.g., the forward rotation direction R1) of the first and second sprocket teeth 12a, 14a, respectively. In Comparative Example 1, the chain 110 attached to the sprocket 10 wobbles in its extension direction, resulting in a decrease in the power transmission efficiency between the sprocket 10 and the chain 110.

[0090] Also, unlike the present embodiment, a case will be described as Comparative Example 2 in which the first and second sprocket teeth 12a, 14a do not have the first and second relief portions 12e, 14e, respectively. In this Comparative Example 2, the first and second sprocket teeth 12a, 14a simultaneously contact both the first and second links 120, 130 of the chain 110 in the rotational direction of the sprocket 10. In other words, the first and second sprocket teeth 12a, 14a are sandwiched between the first and second links 120, 130, respectively.

[0091] Because the chain 110 that engages the sprocket has a deformable spiral structure, any slight bending changes the distance between the first link 120 and the second link 130. This is similar to how a coil spring changes its pitch when it bends.

[0092] 16A and 16B , when the first and second links 120, 130 rotate even slightly around the rotation center lines C2, C4 extending radially of the sprocket 10 (e.g., when tension is applied to the chain 110), the first link 120 and the second link 130, which are consecutive in the rotation direction of the sprocket 10, move closer to each other. In the case of Comparative Example 2, which does not have the first and second relief portions 12e, 14e, the first link 120 and the second link 130 that are close to each other may continue to hold the first sprocket tooth 12a therebetween with a strong force. As a result, in the case of Comparative Example 2, the chain 110 does not smoothly separate from the sprocket 10, which may reduce the power transmission efficiency between the sprocket 10 and the chain 110. Furthermore, the first and second links 120, 130 of the chain 110 just before engaging with the sprocket 10 may ride up onto the first and second sprocket teeth 12a, 14a, causing the chain 110 to come off the sprocket 10.

[0093] Taking into account the comparative examples 1 and 2, in this embodiment, as shown in Figures 16A and 16B, the first sprocket tooth 12a has a first recess 12e on the reverse rotation direction R2 side, and the second sprocket tooth 14a has a second recess 14e on the forward rotation direction R1 side. That is, each of the first sprocket teeth 12a only contacts the portion of the first and second links 120, 130 (120C, 130C) located between them in the forward rotation direction R1. Furthermore, each of the second sprocket teeth 14a only contacts the portion of the first and second links 120, 130 (120D, 130D) located between them in the reverse rotation direction R2. This allows the chain 110 to engage with the sprocket 10 without rattling in its extension direction. Furthermore, the deformable spiral structure of the chain 110 allows it to smoothly separate from the sprocket 10 and is less likely to come off the sprocket 10.

[0094] In this embodiment, as shown in Figure 16A, the first sprocket tooth 12a of the sprocket 10 does not contact the first and second links 120, 130 of the chain 110 over the entire portion thereof on the forward rotation direction R1 side. Also, as shown in Figure 16B, the second sprocket tooth 14a does not contact the first and second links 120, 130 over the entire portion thereof on the reverse rotation direction R2 side.

[0095] Specifically, the tip-side portion (outer peripheral portion) of the first sprocket tooth 12a on the forward rotation direction R1 side (i.e., first contact portion 12d) contacts the first and second links 120, 130, while the root portion (center portion) on the forward rotation direction R1 side does not contact the first and second links 120, 130. That is, the root portion of the first sprocket tooth 12a has a relief portion 12f on the forward rotation direction R1 side to avoid contact with the first and second links 120, 130. Also, the tip-side portion of the second sprocket tooth 14a on the reverse direction R2 side (i.e., second contact portion 14d) contacts the first and second links 120, 130, while the root portion on the reverse direction R2 side does not contact the first and second links 120, 130. That is, a recess 14f for avoiding contact with the first and second links 120, 130 is provided on the reverse rotation direction R2 side of the tooth base of the second sprocket tooth 14a.

[0096] 16A, the tooth roots of the sprocket 10 (first rotating body 12) located between two adjacent first sprocket teeth 12a also do not contact the first and second links 120, 130. That is, the tooth roots of the sprocket 10 located between two adjacent first sprocket teeth 12a also have clearances 12g to avoid contact with the first and second links 120, 130. Similarly, as shown in FIG. 16B, the tooth roots of the sprocket 10 (second rotating body 14) located between two adjacent second sprocket teeth 14a also have clearances 14g to avoid contact with the first and second links 120, 130.

[0097] The spiral chain 110 can smoothly separate from the sprocket 10 and is less likely to come off the sprocket 10 thanks to the relief portions 12f, 12g, 14f, and 14g provided in the forward direction R1 side portion of the root portion of the first sprocket tooth 12a, the tooth root portion between two adjacent first sprocket teeth 12a, the reverse direction R2 side portion of the root portion of the second sprocket tooth 14a, and the tooth root portion between two adjacent second sprocket teeth 14a.

[0098] The detailed shapes of the first and second recesses 12e, 14e and the recesses 12f, 12g, 14f, 14g are determined taking into consideration the shapes of the first and second links 120, 130, as well as the change in the rotation direction of the sprocket 10, the interchange of the tensioned and slackened portions of the chain due to the change in rotation direction, gravity acting on the chain, and the like.

[0099] As described above, the first contact portions 12d of the first sprocket teeth 12a facing in the forward rotation direction R1 and the second contact portions 14d of the second sprocket teeth 14a facing in the reverse rotation direction R2 allow the chain 110 to engage with the sprocket 10 without displacement in the extension direction (without rattle). In contrast, displacement of the chain 110 in the extension direction of the rotation center line C0 of the sprocket 10 (X-axis direction) is suppressed by the first rotating body 12 and the guide member 18.

[0100] FIG. 18 is a partial cross-sectional view of an example sprocket engaged with a chain.

[0101] Figure 18 shows one cycle of four consecutive first links 120 (120C to 120F). As described above and as shown in Figure 17, the first sprocket tooth 12a of the first link 120 (120C) contacts the sprocket 10 in the reverse direction R2. The second sprocket tooth 14a of another first link 120 (120D) contacts the sprocket 10 in the forward direction R1. In other words, these two first links 120 (120C, 120D) are driven by the first and second sprocket teeth 12a, 14a.

[0102] The remaining two first links 120 (120E, 120F) are guided by the first rotating body 12 and the guide member 18 of the sprocket 10. Specifically, as shown in FIG. 18 , one of the first links 120 (120E) is located between the first rotating body 12 and the second rotating body 14 and faces the inner surface 12h of the first rotating body 12 in the direction of the rotation center line C0 of the sprocket 10 (X-axis direction). The other first link 120 (120F) faces the inner surface 18a of the guide member 18 attached to the outer surface of the second rotating body 14 in the direction of the rotation center line C0. Therefore, a first spiral link assembly 140 formed by the multiple first links 120 is guided by the inner surface 12h of the first rotating body 12 and the inner surface 18a of the guide member 18 and moves between them. Therefore, displacement of the first spiral link assembly 140 in the direction of extension of the rotation center line C0 is suppressed, and as a result, the first link 120 (120C, 120D) is suppressed from coming off the first and second contact portions 12d, 14d of the first and second sprocket teeth 12a, 14a.

[0103] Similarly, the second links 130 (130E, 130F) are also guided by the first rotating body 12 and the guide member 18 of the sprocket 10. Therefore, the second spiral link assembly 150 formed from multiple second links 130 moves between the inner surface 12h of the first rotating body 12 and the inner surface 18a of the guide member 18, and displacement in the direction of extension of the rotation center line C0 (X-axis direction) is suppressed. As a result, the second links (130C, 130D) are suppressed from coming off the first and second contact portions 12d, 14d of the first and second sprocket teeth 12a, 14a.

[0104] Because the chain 110 has a helical structure, the helical direction in which it can engage with the sprocket 10 is uniquely determined. In this embodiment, as shown in FIGS. 1A and 1B , the chain 110 must be engaged with the sprocket 10 so that the first and second helical link structures 140, 150 extend forward while rotating clockwise as viewed from the front. If the chain 110 with a double helical structure is considered a twisted wire, the first and second helical link structures 140, 150 of the chain 110 engaged with the sprocket 10 have an S-twist when viewed in the direction of the rotational centerline C0 of the sprocket 10. As shown in FIGS. 13B and 16B , a marker 14h indicating the helical direction in which it can engage with the sprocket 10 is formed on the outer surface of the second rotating body 14. Note that the marker indicating the helical direction may be provided on another member, such as the outer surface of the first rotating body 12, in addition to or instead of the second rotating body 14. Such markers 14h allow the user to properly attach the chain 110 to the sprocket 10.

[0105] According to the present embodiment as described above, it is possible to realize a sprocket that can be engaged with a chain having a spiral structure in which a plurality of links are connected in a spiral shape.

[0106] It should be noted that the chain that can be engaged with the sprocket according to the embodiment of the present disclosure is not limited to the example chain 110 shown in FIGS. 2 to 11D.

[0107] 19A and 19B are left and right front perspective views of an alternative embodiment of a sprocket with an alternative chain engaged therewith.

[0108] 19A and 19B, a sprocket 210 according to another embodiment has a different shape for the first and second sprocket teeth, but is substantially identical in function to the sprocket 10 according to the above-described embodiment. Therefore, a detailed description of the configuration of the sprocket 210 according to another embodiment will be omitted, and instead, a description will be given of another example chain 310 that engages with the sprocket 210.

[0109] 2 to 11D, the first spiral link assembly 140 is made up of a single type of first links 120. The second spiral link assembly 150 is also made up of a single type of second links 130. In contrast, the second spiral link assembly 150 is made up of a single type of first links 120. The second spiral link assembly 150 is made up of a single type of second links 130. In contrast, the second spiral link assembly 310 is made up of a single type of first links 120. The second spiral link assembly 150 is made up of a single type of second links 130. The second spiral link assembly 310 is made up of a single type of second links 130. In other respects, the second spiral link assembly 310 is almost the same as the first spiral link assembly 110.

[0110] Figure 20 is a perspective view of a portion of a chain of another example. Also, Figure 21 is an exploded perspective view of a portion of a chain of another example. Furthermore, Figures 22A and 22B are front views of a plurality of first and second links (first and second spiral link combinations) that are connected to each other in a chain of another example. Finally, Figures 23A and 23B are cross-sectional views of the chain of another example taken along lines S3-S3 and S4-S4, respectively, shown in Figure 20.

[0111] 20 to 23B, in another example of a chain 310, a first spiral link assembly 340 is formed from a plurality of different shaped first links 320, 322. A second spiral link assembly 350 is formed from a plurality of different shaped second links 330, 332.

[0112] 21 and 22A , first link 322 is smaller than first link 320. Furthermore, first link 322, which is relatively smaller, is entirely disposed inside first link 320. Furthermore, first links 320, 322 are alternately connected to form first spiral link assembly 340.

[0113] 21 and 22B , second link 332 is smaller than second link 330. Furthermore, second link 332, which is relatively smaller, is entirely disposed inside second link 330. Furthermore, second links 330, 332 are alternately connected to form second spiral link assembly 350.

[0114] In the case of the chain 310 of the alternative example, the first link 320 and the second link 330 have the same shape, and the first link 322 and the second link 332 have the same shape. In other words, the chain 310 of the alternative example is composed of two types of links.

[0115] As shown in Figures 23A and 23B, the first links 320, 322 and the second links 330, 332 are connected to and supported by the first and second pins 360, 362 so that the first rotation center line C1 and the third rotation center line C3 are aligned on the same line, and the second rotation center line C2 and the fourth rotation center line C4 are aligned on the same line.

[0116] 19A and 19B, the first sprocket tooth 212a of the sprocket 210 contacts the first and second links 320, 330 of the alternative chain 310 only in the forward direction R1, and the second sprocket tooth 214a contacts the first and second links 322, 332 only in the reverse direction R2.

[0117] 24A and 24B are left and right front perspective views of yet another embodiment of a sprocket with yet another example chain engaged therewith.

[0118] 24A and 24B, a sprocket 410 according to yet another embodiment is substantially identical in function to the sprocket 10 according to the above-described embodiment, except for the number, size, and shape of the first and second sprocket teeth. Therefore, a detailed description of the configuration of the sprocket 410 according to this embodiment will be omitted, and instead, a description will be given of yet another example chain 510 that engages with the sprocket 410.

[0119] In the example chain 110, each of the multiple first links 120 has a first rotation center line C1 and a second rotation center line C2 that are perpendicular to each other, as shown in FIG. 5B . Also, as shown in FIG. 6B , each of the multiple second links 130 has a third rotation center line C3 and a fourth rotation center line C4 that are perpendicular to each other. In contrast, in another example chain 510 shown in FIGS. 24A and 24B , the first and second rotation center lines in each first link intersect at an angle other than 90 degrees, and the third and fourth rotation center lines in each second link also intersect at an angle other than 90 degrees. The remaining features of the chain 110 are almost identical to those of the example chain 110. Therefore, the description of the another example chain 510 will focus on these differences.

[0120] Fig. 25 is a perspective view of a portion of a chain according to yet another example. Fig. 26 is an exploded perspective view of a portion of a chain according to yet another example. Furthermore, Figs. 27A and 27B are front views of a plurality of first and second links (first and second spiral link connectors) connected to each other in a chain according to yet another example. Fig. 28 is an exploded perspective view illustrating the connection of a plurality of first and second links via a plurality of connecting members in a chain according to yet another example.

[0121] 25 to 28, in yet another example of a chain 510, a first spiral link assembly 540 is formed by connecting a plurality of first links 520 having the same shape. Also, a second spiral link assembly 550 is formed by connecting a plurality of second links 530 having the same shape. In yet another example of the chain 510, the first and second links 520, 530 have the same shape. In other words, the yet another example of the chain 510 is composed of a single type of link.

[0122] 26 and 27A, each of the first links 520 rotates about first and second rotation center lines C1 and C2. Specifically, each of the first links 520 rotates about the first rotation center line C1 relative to the other first link 520 connected to it, and also rotates about the second rotation center line C2 relative to the other first link 520 connected to it. As shown in FIG. 27A, the first rotation center line C1 and the second rotation center line C2 intersect at an angle of substantially 60 degrees when viewed in the extension direction (W-axis direction) of the chain 510.

[0123] According to such first links 520 , six consecutive first links 520 correspond to one period of the first spiral link assembly 540 .

[0124] 26 and 27B, each of the second links 530 rotates about third and fourth rotation center lines C3 and C4. Specifically, each of the second links 530 rotates about the third rotation center line C3 relative to the other second link 530 connected to it, and also rotates about the fourth rotation center line C4 relative to the other second link 530 connected to it. As shown in FIG. 27B, the third rotation center line C3 and the fourth rotation center line C4 intersect at an angle of substantially 60 degrees when viewed in the extension direction (W-axis direction) of the chain 510.

[0125] According to such second links 530 , six consecutive second links 530 correspond to one period of the second spiral link assembly 550 .

[0126] As shown in FIG. 28, the first link 520 and the second link 530 are connected to and supported by the first and second pins 560, 562 so that the first rotation center line C1 and the third rotation center line C3 are aligned on the same line, and the second rotation center line C2 and the fourth rotation center line C4 are aligned on the same line.

[0127] Furthermore, the chain 510 of this further example can bend in six directions when viewed in the extending direction of the chain 510 (W-axis direction).

[0128] 24A and 24B, the first sprocket tooth 412a of the sprocket 410 contacts the first and second links 520, 530 of another example chain 510 only in the forward direction R1, and the second sprocket tooth 414a contacts the first and second links 320, 330 only in the reverse direction R2.

[0129] Additionally, when viewed in the extending direction of the chain, the angle at which the first rotation center line intersects with the second rotation center line and the angle at which the third rotation center line intersects with the fourth rotation center line are not limited to 90 degrees or 60 degrees, and may be any angle. However, it is preferable that these angles be integer multiples of 360 degrees. In other words, it is preferable that one cycle of the first and second spiral link assembly is formed by an integer number of first and second links. This makes it easier to design a corresponding sprocket.

[0130] In the sprocket 10 of the above-described embodiment, the first and second contact portions 12d, 14d of the first and second sprocket teeth 12a, 14a are flat. The portions of the first and second links of the chain that contact the flat first and second contact portions 12d, 14d are also flat. However, the embodiments of the present disclosure are not limited to this. For example, the first and second contact portions of the sprocket may be curved. In this case, the portions of the first and second links of the chain that contact the curved first and second contact portions may also be curved. For example, the first and second contact portions may have a recess (e.g., a groove) centrally located along the sprocket's rotational centerline. In this case, the portions of the first and second links that contact the first and second contact portions have a protrusion (e.g., a ridge) that engages with the recess (e.g., a ridge that engages with the groove). The engagement of the recesses of the first and second contact portions with the protrusions of the first and second links suppresses displacement of the chain relative to the sprocket in the direction of the center line of rotation of the chain, making it possible to omit the guide member.

[0131] Furthermore, in the above-described embodiment, as shown in Figures 16A and 16B, the sprocket 10 includes relief portions 12f, 12g, 14f, and 14g to avoid contact with the first and second links 120 and 130 of the chain 10 at the root (inner peripheral portion) of the first sprocket tooth 12a on the forward rotation direction R1 side, the tooth root between two adjacent first sprocket teeth 12a, the tooth root between two adjacent second sprocket teeth 14a on the reverse rotation direction R2 side of the root of the second sprocket tooth 14a, and the tooth root between two adjacent second sprocket teeth 14a. However, the present disclosure is not limited to this. These sprocket portions may come into contact depending on the shape of the links of the spiral chain. In other words, even if the links come into contact with these sprocket portions, relief portions may not be provided at these sprocket portions as long as the links have a shape that allows the chain to smoothly engage and disengage from the sprocket.

[0132] In other words, the sprocket according to the embodiment of the present disclosure is, in a broad sense, a sprocket that can engage with a chain having a spiral structure in which a plurality of links are connected in a spiral shape, and includes a plurality of first sprocket teeth that engage with the links of the chain, and a plurality of second sprocket teeth that are spaced apart from the first sprocket teeth in the direction of extension of the center line of rotation of the sprocket and engage with the links of the chain, wherein each of the first sprocket teeth has a first contact portion on the forward rotation side of the sprocket that contacts the link of the chain, and a first relief portion on the reverse rotation side that avoids contact with the link of the chain, and each of the second sprocket teeth has a second contact portion on the reverse rotation side of the sprocket that contacts the link of the chain, and a second relief portion on the forward rotation side that avoids contact with the link of the chain.

[0133] By appropriately combining any of the above-described embodiments and various modifications, it is possible to achieve the effects of each of the embodiments and modifications.

[0134] Although the present disclosure has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, various variations and modifications will be apparent to those skilled in the art. Such variations and modifications should be understood to be included within the scope of the present disclosure as defined by the appended claims, unless they depart therefrom. Furthermore, changes in the combination and order of elements in each embodiment may be made without departing from the scope and spirit of the present disclosure.

[0135] The present disclosure is applicable to sprockets that engage with chains having a spiral structure in which multiple links are connected in a spiral fashion.

[0136] 10 Sprocket 12a First sprocket tooth 14a Second sprocket tooth 110 Chain (example chain) 120 Link (first link) 130 Link (second link) C0 Rotation center line R1 Normal rotation direction R2 Reverse rotation direction

Claims

1. A sprocket capable of engaging with a spiral chain in which a number of links are connected in a spiral shape, comprising: a number of first sprocket teeth which engage with the links of the chain; and a number of second sprocket teeth which are spaced apart from the first sprocket teeth in the direction of the extension of the center line of the rotation of the sprocket and engage with the links of the chain, wherein each of the first sprocket teeth has a first contact portion on the forward rotation direction side of the sprocket that contacts the link of the chain, and a first relief portion on the reverse rotation direction side to avoid contact with the link of the chain, and each of the second sprocket teeth has a second contact portion on the reverse rotation direction side of the sprocket that contacts the link of the chain, and a second relief portion on the forward rotation direction to avoid contact with the link of the chain.

2. A sprocket according to claim 1, wherein said first contact portion is a planar surface facing in said forward rotation direction and outwardly of said sprocket, and said second contact portion is a planar surface facing in said reverse rotation direction and outwardly of said sprocket.

3. A sprocket as set forth in claim 1, further comprising a guide member that faces the chain in the direction of extension of the rotation center line when the chain is engaged with the sprocket and guides the chain.

4. A sprocket as described in claim 1, comprising: a first rotating body including a disk-shaped first body portion and a plurality of the first sprocket teeth provided along the outer periphery of the first body portion; a second rotating body including a disk-shaped second body portion and a plurality of the second sprocket teeth provided along the outer periphery of the second body portion; and a spacer disposed between the first rotating body and the second rotating body, spacing the first sprocket teeth and the second sprocket teeth from each other in the direction of extension of the rotation center line.

5. The sprocket of claim 1, wherein said chain includes a plurality of first links rotatably connected to one another to form a first spiral link assembly extending in a spiral manner; a plurality of second links rotatably connected to one another to form a second spiral link assembly extending in a spiral manner; and a plurality of connecting members connecting corresponding first links and second links, respectively, to connect said first and second spiral link assembly to form a double helix structure, wherein said plurality of first sprocket teeth alternately contact said first links and said second links, and said plurality of second sprocket teeth alternately contact said first links and said second links.

6. A sprocket according to claim 1, having a marker indicating the spiral direction of said chain as it engages said first and second sprocket teeth.

7. A power transmission device comprising: a chain having a spiral structure in which a plurality of links are connected in a spiral shape; and a sprocket engageable with the chain, wherein the chain includes: a plurality of first sprocket teeth that engage with the links of the chain; and a plurality of second sprocket teeth that are spaced apart from the first sprocket teeth in the direction of extension of the center line of rotation of the sprocket and engage with the links of the chain, each of the first sprocket teeth having a first contact portion that contacts the link of the chain on the forward rotation direction side of the sprocket, and a first relief portion that avoids contact with the link of the chain on the reverse rotation direction side, and each of the second sprocket teeth having a second contact portion that contacts the link of the chain on the reverse rotation direction side of the sprocket, and a second relief portion that avoids contact with the link of the chain on the forward rotation direction side.

Images