Patent Description:
Conventionally, it has been known to form a slide-plating layer having high slidability with respect to a sliding member of a bicycle, and for example, it has been devised to form the slide-plating layer on an outer link plate of a chain as the sliding member (see <CIT>).

Since the outer link plate of the bicycle chain slides on the side surface of the tooth of the sprocket at the time of shifting, it is possible to reduce the sliding resistance with respect to the side surface of the tooth of the sprocket by forming the slide-plating layer as in <CIT> Other examples of prior art chains are shown in <CIT> and <CIT>.

On the other hand, it has also been required to reduce the sliding resistance with the side surface of the tooth of the sprocket by another method.

The present invention in its one aspect provides a bicycle chain as specified in claims <NUM> to <NUM>.

A bicycle chain transmission device <NUM> shown in <FIG> includes a front sprocket <NUM>, an exterior rear multistage transmission <NUM>, and a chain <NUM>. The rear multistage transmission <NUM> includes a rear sprocket unit <NUM> and a rear derailleur <NUM>, and the rear sprocket unit <NUM> is configured such that a plurality of rear sprockets <NUM> having different diameters disposed so as to decrease in diameter from the rear side (the hub side of the tire) toward the front side (the outside) in the axial direction rotate integrally. The rear derailleur <NUM> is movable in the lateral direction (axial direction) with respect to the driving direction of the chain <NUM>.

The bicycle chain <NUM> is endlessly wound around the front sprocket <NUM> and the rear sprocket <NUM>, so that the bicycle chain transmission device <NUM> transmits the driving force generated in the front sprocket <NUM> to the rear sprocket <NUM> via the bicycle chain <NUM>.

In addition, the chain transmission device <NUM> shifts the speed of the bicycle by changing the chain <NUM> to the rear sprocket <NUM> having a different diameter using the rear derailleur <NUM>. Specifically, a downshift is performed by changing the chain <NUM> from the small-diameter rear sprocket <NUM> to the large-diameter rear sprocket <NUM>, and an upshift is performed by changing the chain <NUM> from the large-diameter rear sprocket <NUM> to the small-diameter rear sprocket <NUM>.

The rear sprocket <NUM> is provided with a groove at a predetermined position on the circumference in a direction in which the chain <NUM> rises from the small-diameter sprocket <NUM> toward the large-diameter sprocket <NUM>. The rear sprocket <NUM> is provided with a groove at a predetermined position different from the downshift groove in a direction in which the chain <NUM> falls from the large-diameter sprocket <NUM> toward the small-diameter sprocket <NUM>. Therefore, both the upshift and downshift are performed only at predetermined positions corresponding to the upshift/downshift grooves on the sprocket <NUM>.

Next, the configuration of the bicycle chain <NUM> will be described. As shown in <FIG>, the bicycle chain <NUM> is configured such that an inner link <NUM> and an outer link <NUM> are alternately connected by a chain pin <NUM>. As shown in <FIG>, the inner link <NUM> includes a pair of inner link plates <NUM> and <NUM> facing each other in the axial direction of the chain pin <NUM>, and a roller <NUM>. Each of the pair of inner link plates <NUM> and <NUM> includes a first inner link end <NUM> provided at one end of the inner link plate <NUM> in the longitudinal direction, a second inner link end <NUM> provided at an end opposite to the one end in the longitudinal direction, and an inner link intermediate portion <NUM> connecting the first inner link end <NUM> and the second inner link end <NUM>.

Each of the first inner link end <NUM> and the second inner link end <NUM> has a substantially circular shape, a first fitting insertion hole 511a is formed at the first inner link end <NUM>, and a second fitting insertion hole 512a is formed at the second inner link end <NUM>. The first inner link end <NUM> and the second inner link end <NUM> are provided with sleeve portions 511b and 512b protruding in the axial direction on inner surfaces thereof (surfaces facing the other inner link plate).

The first sleeve 511b is a cylindrical portion whose inner periphery protrudes so as to form a part of the first fitting insertion hole 511a, and the second sleeve 512b is a cylindrical portion whose inner periphery protrudes so as to form a part of the second fitting insertion hole 512a. Further, the roller <NUM> is configured to be fitted to the first and second sleeves 511b and 512b, and when the protrusion amount of the first sleeve 511b and the second sleeve 512b is P and the thickness of the roller <NUM> in the axial direction is D, D>2P is satisfied. Thus, the end surfaces of the opposing sleeve portions do not slide during assembly of the chain <NUM>.

The inner link intermediate portion <NUM> is formed so as to be recessed toward the pitch line connecting the centers of the first fitting insertion hole 511a and the second fitting insertion hole 512a in relation to the first inner link end <NUM> and the second inner link end <NUM>. Therefore, the inner link plate <NUM> has a substantially <NUM> shape when viewed from the axial direction of the chain pin <NUM>. In the inner link intermediate portion <NUM>, an end edge forming an outer edge of the inner link plate <NUM> is C-chamfered. Specifically, upper and lower end edges 513a and 513b of the inner link plate <NUM> in the lateral direction are formed on the inner surface of the inner link intermediate portion <NUM> in a tapered shape so as to be thinner in the direction away from the pitch line in the lateral direction of the inner link plate <NUM>. Similarly, upper and lower end edges 513c and 513d in the lateral direction are formed on the outer surface of the inner link intermediate portion <NUM> on the opposite side in the axial direction from the inner surface in a tapered shape so as to be thinner in the direction away from the pitch line in the lateral direction of the inner link plate <NUM>.

The outer link <NUM> includes a pair of outer link plates <NUM> and <NUM> facing each other in the axial direction of the chain pin <NUM>, and the chain pin <NUM>. Each of the pair of outer link plates <NUM> includes a first outer link end <NUM> provided at one end in the longitudinal direction of the outer link plate <NUM>, a second outer link end <NUM> provided at another end opposite to the one end in the longitudinal direction, and an outer link intermediate portion <NUM> connecting the first outer link end <NUM> and the second outer link end <NUM>.

Each of the first outer link end <NUM> and the second outer link end <NUM> has a substantially circular shape, a first pin hole 611a is formed at the first outer link end <NUM>, and a second pin hole 612a is formed at the second outer link end <NUM>. In addition, the outer link intermediate portion <NUM> is formed so as to be recessed toward the pitch line connecting the centers of the first pin hole 611a and the second pin hole 612a in relation to the first outer link end <NUM> and the second outer link end <NUM>. Therefore, the outer link plate <NUM> has a substantially <NUM> shape when viewed from the axial direction of the chain pin <NUM>.

The chain pin <NUM> is configured to be press-fitted and fixed to the first pin hole 611a and the second pin hole 612a of the outer link plate <NUM>. The chain pin <NUM> is configured to be loosely fitted by being fitted into the first fitting insertion hole 511a and the second fitting insertion hole 512a of the inner link plate <NUM>. For example, in the example of <FIG>, both ends of the chain pin <NUM> are press-fitted into the first pin holes 611a and 611a of the pair of outer link plates <NUM> and <NUM>, and are fitted into the second fitting insertion holes 512a and 512a of the pair of inner link plates <NUM> and <NUM> between the pair of outer link plates <NUM> and <NUM>. Both ends of the other chain pin <NUM> are press-fitted into the second pin holes 612a and 612a of the pair of outer link plates <NUM>, and are fitted into the first fitting insertion holes 511a and 511a of the pair of inner link plates <NUM> and <NUM> between the pair of outer link plates <NUM> and <NUM>. Thus, the outer link <NUM> and the inner link <NUM> are configured to be relatively bendable.

Next, a detailed configuration of the outer link plate <NUM> will be described with reference to <FIG>. In the following description, at the time of assembling the chain, a side surface of the outer link plate <NUM> positioned on the axial outside of the chain pin <NUM> is referred to as an outer surface (see <FIG>), and a side surface opposite to the outer surface is referred to as an inner surface (see <FIG>).

The outer surface of the outer link plate <NUM> is a sliding region where the outer surface slides on the side surface of the tooth of the large-diameter rear sprocket <NUM> at the end of shifting in both the downshift (small-diameter rear sprocket → large-diameter rear sprocket) and the upshift (large-diameter rear sprocket → small-diameter rear sprocket). Therefore, in order to reduce resistance and noise during sliding, the outer link plate <NUM> of the present embodiment has an uneven pattern <NUM> formed on the outer surface as shown in <FIG>.

More specifically, the uneven pattern <NUM> is formed on the outer surface of the outer link intermediate portion <NUM> positioned between the first outer link end <NUM> and the second outer link end <NUM> in the longitudinal direction (pitch line direction) of the outer link plate <NUM> orthogonal to the axial direction of the chain pin <NUM>, and the outer surface of the outer link intermediate portion <NUM> has an uneven region 613a in which the uneven pattern <NUM> is formed and a peripheral region 613b which surrounds the uneven region 613a.

In the uneven region 613a, a plurality of irregularities is continuously arranged in a predetermined pattern to form the uneven pattern <NUM>, and in the present embodiment, a plurality of protrusion portions <NUM> and a plurality of groove portions <NUM> form the uneven pattern <NUM> having a waveform. Specifically, the protrusion portion <NUM> is a ridge with an arc-shaped cross section and extends in the longitudinal direction of the outer link plate <NUM>, and the plurality of protrusion portions is arranged in the lateral direction of the outer link plate <NUM> with a predetermined pitch. Further, a space between the protrusion portions <NUM> parallel to the longitudinal direction is formed by the groove portion <NUM> continuously connected to the protrusion portions <NUM> by a curved surface or at substantially a right angle, and the protrusion portions <NUM> and the groove portions <NUM> are alternately arranged in the lateral direction to form the uneven pattern <NUM> having the waveform.

The uneven region 613a is defined by a pair of upper and lower constricted edges 613a1 extending along the constricted shape of the outer link intermediate portion <NUM> when viewed in <FIG>, a pair of left and right arc-shaped edges 613a2 extending along the contours of the first pin hole 611a and the second pin hole 612a, and four corner portions 613a3 connecting the constricted edge and the arc-shaped edge. In the figure, each corner portion 613a3 has a constricted shape of the outer link intermediate portion <NUM> and a shape protruding from the outer link intermediate portion <NUM> toward the first and second outer link ends <NUM> and <NUM> along the first and second pin holes 611a and 612a. The uneven region 613a may have a rectangular region shape in which the corner portion 613a3 does not protrude.

On the other hand, the peripheral region 613b is constituted by a plane having no uneven pattern, and this plane is a plane continuous with the outer surfaces of the first outer link end <NUM> and the second outer link end <NUM>. The outer surfaces of the first outer link end <NUM> and the second outer link end <NUM> are flat surfaces in order to improve workability during pressing. For shifting, an upper end edge 611b in the lateral direction is chamfered on the outer surface of the first outer link end <NUM>, and a lower end edge 612b in the lateral direction is chamfered on the outer surface of the second outer link end <NUM> (see <FIG>).

In <FIG> described above, in order to make the shape of the uneven pattern <NUM> in the uneven region 613a easy to understand, the change in the curved surface of the surface of the uneven pattern <NUM> formed by the curved surface is indicated by a ridge line. On the other hand, <FIG> are six surface views showing the outer link plate <NUM> only in outline. <FIG> is a perspective view of the outer link plate <NUM>, in which a shade is indicated by a thin line so that the three-dimensional shape of the outer link plate <NUM> including the uneven pattern <NUM> can be seen. More specifically, the thin lines shown near the outer edge of the outer link plate <NUM>, the pin holes 611a and 612a, and the uneven region 613a in <FIG> are all for specifying the shape of the three-dimensional surface.

As described above, since the uneven pattern <NUM> is formed on the outer surface in the outer link plate <NUM> of the present embodiment, the sliding area between the outer link plate and the side surface of the tooth of the sprocket <NUM> at the time of shifting is reduced, so that the friction coefficient can be reduced. Accordingly, it is possible to reduce the sliding resistance with respect to the side surface of the tooth of the sprocket and to reduce the noise at the time of shifting.

Next, the configuration of the inner surface of the outer link plate <NUM> will be described. As shown in <FIG>, a thin portion <NUM> recessed toward the outer surface side in the thickness direction than the first outer link end <NUM> and the second outer link end <NUM> is formed in the outer link intermediate portion <NUM> on the inner surface of the outer link plate <NUM>.

The thin portion <NUM> is configured such that a center portion <NUM> positioned on a center side (pitch line side) of the outer link plate <NUM> is the thickest and an end edge <NUM> which is an outer edge of the outer link plate <NUM> is thinnest, and the center portion <NUM> and the end edge <NUM> are connected by a gentle curved surface. Therefore, as shown in <FIG>, when the thickness of the outer link plate <NUM> at the end edge <NUM> is X1, the thickness of the outer link plate <NUM> at the center portion <NUM> is X2, the thickness of the outer link plate <NUM> at the first outer link end <NUM> is Y1, and the thickness of the outer link plate <NUM> at the second outer link end <NUM> is Y2, the relationship between these thicknesses is X1<X2<Y1=Y2.

More specifically, the thickness (for example, X1 and X2) of the outer link plate <NUM> in the thin portion <NUM> is <NUM>% to <NUM>% of the thickness (for example, Y1 and Y2) of the thickest portion of the outer link plate <NUM>. For example, the thickness X1 of the thinnest portion of the outer link plate <NUM> can be set to <NUM>% of the thicknesses Y1 and Y2 of the thickest portions of the outer link plate <NUM>.

As described above, in the present embodiment, the thin portion <NUM> is formed on the inner surface of the outer link intermediate portion <NUM>, and as shown in <FIG>, the gap Z between the pair of outer link plates <NUM> and <NUM> constituting the outer link <NUM> is configured to be large. When the chain <NUM> is changed from the small-diameter sprocket <NUM> to the large-diameter sprocket <NUM> (at the time of triggering the shift), the teeth of the large-diameter sprocket <NUM> always enter the gap Z between the outer link plates <NUM> first. However, in the present embodiment, since the gap Z is large, the teeth of the large-diameter sprocket <NUM> can be smoothly inserted between the outer link plates <NUM> and <NUM> at the time of the downshift.

In addition, the teeth that first enter the gap Z between the outer link plates <NUM> at the time of the downshift are teeth arranged at positions corresponding to the above-described downshift grooves, and the teeth of the rear sprocket <NUM> are offset from the other adjacent teeth on the front side (outer side) in the axial direction and are formed to be thinner. Therefore, in combination with the wide gap Z, the teeth of the sprocket <NUM> can be smoothly inserted into the gap Z during the downshift speed change, and the speed change performance during the downshift can be improved.

On the other hand, at the time of upshift, the gear shift is triggered by deviation of the teeth of the large-diameter rear sprocket <NUM> from the gap N between the pair of inner link plates <NUM> and <NUM> of the inner link <NUM> formed narrower than the gap Z (see <FIG>). Even in this case, as shown in <FIG>, since the end edges 513c and 513d are chamfered on the outer surface of the inner link intermediate portion <NUM> in the chain <NUM> according to the present embodiment, the chain <NUM> is easily detached from the teeth of the large-diameter rear sprocket <NUM>. As a result, it is possible to improve the shifting performance at the time of upshift.

Next, a second embodiment will be described. The present embodiment is different from the first embodiment only in that an uneven pattern of an outer link plate is different. Therefore, in the following description, only differences from the first embodiment will be described, and description of other parts will be omitted.

As shown in <FIG>, the uneven pattern <NUM> according to the present embodiment is provided in the uneven region 613a of the outer surface of the outer link intermediate portion <NUM>, and is formed by a plurality of V groove portions <NUM> and a plurality of protrusion portions <NUM>. Specifically, as shown in <FIG> and <FIG>, the V groove portion <NUM> is a groove portion having a V-shaped cross section, and extends in the longitudinal direction of the outer link plate <NUM>. The plurality of V groove portions <NUM> is arranged side by side in the lateral direction of the outer link plate <NUM> with a predetermined pitch, and a space between the V groove portions <NUM> is the protrusion portion <NUM>. The cross-sectional shape of the groove portion <NUM> is not limited to the V shape, and may be a U shape.

The protrusion portion <NUM> is a convex portion protruding with respect to the V groove portion <NUM>, and is constituted by a plane having the same height as the peripheral region 613b. The V groove portions <NUM> and the protrusion portions <NUM> are alternately arranged in the lateral direction to form the uneven pattern <NUM>. That is, in the present embodiment, the uneven pattern <NUM> is formed by forming the plurality of V groove portions <NUM> extending in parallel in the longitudinal direction in the uneven region 613a of the outer surface of the outer link intermediate portion <NUM>. As described above, in the present embodiment, the uneven pattern <NUM> can be provided only by forming the V groove on the outer surface of the outer link plate <NUM>.

The uneven region 613a according to the present embodiment is defined by an imaginary line indicated by a two-dot chain line in <FIG>. Specifically, as in the first embodiment shown in <FIG>, the imaginary line is defined by the pair of upper and lower constricted edges 613a1, the pair of left and right arc-shaped edges 613a2, and four corner portions 613a3 connecting the constricted edge 613a1 and the arc-shaped edge 613a2. Each corner portion 613a3 has a protruding shape as in the first embodiment. The uneven region 613a may have a rectangular region shape in which no corner portion protrudes. <FIG> show <FIG> in a state in which the imaginary line indicating the uneven region 613a is erased and only the outline is indicated.

Next, a third embodiment will be described. The present embodiment is different from the first embodiment only in that an uneven pattern of an outer link plate is different. Therefore, in the following description, only differences from the first embodiment will be described, and description of other parts will be omitted.

As shown in <FIG>, in the uneven pattern <NUM> according to the present embodiment, the uneven pattern <NUM> is formed not only on the outer link intermediate portion <NUM> but also on substantially the entire outer surface of the outer link plate <NUM> from the first outer link end <NUM> to the second outer link end <NUM>. More specifically, in the uneven pattern <NUM>, an uneven pattern having a waveform is formed by a plurality of protrusion portions <NUM> and a plurality of groove portions <NUM>.

The protrusion portion <NUM> has an arc-shaped cross section and extends from the first outer link end <NUM> to the second outer link end <NUM> via the outer link intermediate portion <NUM> in the longitudinal direction of the outer link plate <NUM>. In addition, the plurality of protrusion portions <NUM> is arranged in the lateral direction of the outer link plate <NUM> with a predetermined pitch, and the parallel protrusion portions <NUM> form the groove portions <NUM> continuously connected to the protrusion portions <NUM> at a curved surface or substantially a right angle. The protrusion portions <NUM> and the groove portions <NUM> are alternately arranged in the lateral direction to form the uneven pattern <NUM> having the waveform.

Further, the peripheral region 613b is formed around the uneven region 613a where the uneven pattern <NUM> is formed, and the peripheral region 613b is constituted by a plane having no uneven pattern. In the present embodiment, the plane of the peripheral region 613b is configured to have the same height as the vertex of the protrusion portion <NUM> as in the first embodiment, but may be configured to be lower than the vertex of the protrusion portion <NUM>.

In this manner, the sliding area with the side surface of the tooth of the rear sprocket <NUM> can be more effectively reduced by forming the uneven pattern <NUM> on substantially the entire outer surface of the outer link plate <NUM>.

Next, a fourth embodiment will be described. The present embodiment is different from the third embodiment only in that an uneven pattern of an outer link plate is different. Therefore, in the following description, only differences from the first embodiment will be described, and description of other parts will be omitted.

As shown in <FIG>, in the uneven pattern <NUM> according to the present embodiment, the uneven pattern <NUM> is formed not only on the outer link intermediate portion <NUM> but also on substantially the entire outer surface of the outer link plate <NUM> from the first outer link end <NUM> to the second outer link end <NUM>. More specifically, in the uneven pattern <NUM>, an uneven pattern is formed by a plurality of protrusion portions <NUM> and a plurality of groove portions <NUM>.

The protrusion portion <NUM> has an arc-shaped cross section and extends in the oblique direction intersecting the longitudinal direction of the outer link plate <NUM>. The plurality of protrusion portions <NUM> extending in the oblique direction is arranged in the longitudinal direction of the outer link plate <NUM> with a predetermined pitch, and are provided from the first outer link end <NUM> to the second outer link end <NUM> via the outer link intermediate portion <NUM>. In addition, a space between the protrusion portions <NUM> is formed by the groove portion <NUM> continuously connected to the adjacent protrusion portions <NUM> by a curved surface or at a substantially right angle. The protrusion portions <NUM> and the groove portions <NUM> are alternately arranged to form the uneven pattern <NUM>. Although not shown, each of the protrusion portions <NUM> may extend in the oblique direction so as to cross the longitudinal direction of the outer link plate <NUM> at an angle different from each other.

Next, a fifth embodiment will be described. The present embodiment is different from the fourth embodiment only in that an uneven pattern of an outer link plate is different. Therefore, in the following description, only differences from the first embodiment will be described, and description of other parts will be omitted.

The protrusion portion <NUM> has an arc-shaped cross section and extends in the lateral direction of the outer link plate <NUM>. The plurality of protrusion portions <NUM> extending in the lateral direction are arranged in the longitudinal direction of the outer link plate <NUM> with a predetermined pitch, and are provided from the first outer link end <NUM> to the second outer link end <NUM> via the outer link intermediate portion <NUM>. In addition, the plurality of protrusion portions <NUM> form the groove portions <NUM> continuously connected to the adjacent protrusion portions <NUM> at a curved surface or a substantially right angle. The protrusion portions <NUM> and the groove portions <NUM> are alternately arranged to form the uneven pattern <NUM>. In the present embodiment, the peripheral region 613b does not exist, and the plurality of protrusion portions <NUM> and groove portions <NUM> extend to the outer edge of the outer link plate <NUM>.

Next, a sixth embodiment will be described. The present embodiment is different from the fourth embodiment only in that an uneven pattern of an outer link plate is different. Therefore, in the following description, only differences from the first embodiment will be described, and description of other parts will be omitted.

As shown in <FIG>, in the uneven pattern <NUM> according to the present embodiment, the uneven pattern <NUM> is formed not only on the outer link intermediate portion <NUM> but also on substantially the entire outer surface of the outer link plate <NUM> from the first outer link end <NUM> to the second outer link end <NUM>. More specifically, in the uneven pattern <NUM>, an uneven pattern is formed by a plurality of first protrusion portions <NUM>, a plurality of second protrusion portions <NUM>, and a plurality of concave portions <NUM> between the first protrusion portions <NUM> and the second protrusion portions <NUM>.

The first protrusion portion <NUM> has an arc-shaped cross section and extends in a first oblique direction inclined obliquely with respect to the longitudinal direction of the outer link plate <NUM>. The second protrusion portion <NUM> has a substantially semicircular cross section and extends in a second oblique direction inclined at an angle different from the first oblique direction with respect to the longitudinal direction of the outer link plate <NUM>. The plurality of first and second protrusion portions <NUM> and <NUM> are arranged in the longitudinal direction of the outer link plate <NUM> with a predetermined pitch, and are provided from the first outer link end <NUM> to the second outer link end <NUM> via the outer link intermediate portion <NUM>.

Further, in the uneven pattern <NUM>, an intersection point <NUM> formed by the first protrusion portion <NUM> and the second protrusion portion <NUM> intersecting with each other and orthogonal to each other, for example, serves as a vertex, and a region surrounded by the first protrusion portion <NUM> and the second protrusion portion <NUM> serves as the concave portion <NUM>. As described above, the intersection point <NUM> between the first protrusion portion <NUM> and the second protrusion portion <NUM> is formed as the vertex protruding to the outermost side in the uneven pattern <NUM>, so that the contact with the side surface of the tooth of the rear sprocket <NUM> can be made point contact, and the sliding area with the side surface of the tooth of the rear sprocket <NUM> can be effectively reduced.

Next, a seventh embodiment will be described. The present embodiment is different from the fourth embodiment only in that an uneven pattern of an outer link plate is different. Therefore, in the following description, only differences from the first embodiment will be described, and description of other parts will be omitted.

As shown in <FIG>, in the uneven pattern <NUM> according to the present embodiment, the uneven pattern <NUM> is formed not only on the outer link intermediate portion <NUM> but also on substantially the entire outer surface of the outer link plate <NUM> from the first outer link end <NUM> to the second outer link end <NUM>. More specifically, in the uneven pattern <NUM>, an uneven pattern is formed by the plurality of dimples <NUM> and a plurality of convex portions <NUM>.

In the present embodiment, the dimple <NUM> is a recess recessed in a circular shape, and is provided from the first outer link end <NUM> to the second outer link end <NUM> via the outer link intermediate portion <NUM> at a predetermined interval. In addition, a space between the plurality of dimples <NUM> is a convex portion <NUM> protruding to the outermost side in the uneven pattern <NUM>. In the present embodiment, since the convex portion <NUM> makes point contact with the side surface of the tooth of the rear sprocket <NUM> at the time of shifting, the sliding area with the side surface of the tooth of the rear sprocket <NUM> can be effectively reduced. The dimple <NUM> may be a recess recessed in a substantially rectangular shape.

Furthermore, in the above-described embodiment, an example in which the transmission is provided only on the rear side has been described. However, the front sprocket may be provided in multiple stages, and the transmission may also be provided on the front side. In addition, power from an electric assist motor may be input to the front side. Further, the bicycle chain <NUM> may be a chain with a bush.

Further, the uneven pattern formed on the outer surface of the outer link plate <NUM> is not limited to the example described above, and for example, the uneven pattern may be formed by providing convex portions concentrically at a predetermined pitch on the outer surface of the outer link plate <NUM> or arranging a plurality of dot-shaped convex portions. Further, the uneven pattern may be formed on the entire outer surface of the outer link plate <NUM> or a part thereof. In addition, the inventions described in the above-described embodiments may be combined in any way.

Claim 1:
A bicycle chain (<NUM>) comprising:
an inner link (<NUM>) which includes a pair of inner link plates (<NUM>); and
an outer link (<NUM>) which includes a pair of outer link plates (<NUM>) and a chain pin (<NUM>),
wherein the inner link (<NUM>) and the outer link (<NUM>) are bendably connected by the chain pin (<NUM>), characterized in that
the outer link plate (<NUM>) includes an inner side surface facing the inner link (<NUM>) in an axial direction of the chain pin (<NUM>) and an outer side surface opposite to the inner side surface in the axial direction of the chain pin (<NUM>), the outer side surface of the outer link plate (<NUM>) including a sliding region that slides on a side surface of a tooth of a sprocket (<NUM>), and
wherein an uneven pattern (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in which a plurality of irregularities is continuously arranged in a predetermined pattern is provided in the sliding region of the outer link plate (<NUM>) for reducing a sliding resistance between the sliding region of the outer side surface of the outer link plate (<NUM>) and the side surface of the tooth of the sprocket (<NUM>).