BICYCLE CRANK ARRANGEMENT

Abstract

A bicycle crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) comprising: a crankshaft (20) with an inner cavity (SA) and a pivot axis (CA); a crank arm (22) coupled to the crankshaft (20); a sprocket mounting element (24) to which a bicycle sprocket (12) is attached; a first sprocket tooth displacement structure (26) arranged at least partially within the inner cavity (SA) of the crankshaft (20); and a second sprocket tooth displacement structure (28) arranged outside the inner cavity (SA) of the crankshaft (20); wherein the sprocket mounting element (24) is configured to be displaceable by the first sprocket tooth displacement structure (26) and the second sprocket tooth displacement structure (28) with respect to the crankshaft (20) and the crank arm (22) in a first axial direction (DA) with respect to the rotational center axis (CA).

Description

The present invention relates to a bicycle crank assembly. US patent 2017 / 0167542A1 discloses technology related to a bicycle crank assembly. In the bicycle crank assembly, a bicycle chainring moves axially relative to a crankshaft. The pedaling torque is transmitted to a sliding axle that rotates integrally with the bicycle chainring within the crankshaft. The conventional bicycle crank moves the bicycle chainring using a complex mechanism. The present invention provides a bicycle crank assembly with a simple bicycle chainring displacement structure. A bicycle crank assembly according to a first aspect of the present invention comprises a crankshaft with an inner cavity and an axis of rotation, a crank arm coupled to the crankshaft, a sprocket mounting element on which a bicycle sprocket is mounted, a first sprocket tooth displacement structure arranged at least partially within the inner cavity of the crankshaft, and a second sprocket tooth displacement structure arranged outside the inner cavity of the crankshaft. The sprocket mounting element is configured to be displaceable in a first axial direction with respect to the axis of rotation through the first sprocket tooth displacement structure and the second sprocket tooth displacement structure with respect to the crankshaft and the crank arm. According to the bicycle crank design of the first aspect, the displacement structure is divided into the first chainring tooth displacement structure and the second chainring tooth displacement structure, in order to position the first and second chainring tooth displacement structures at different sections in the bicycle crank design. This simplifies the structures of the first and second chainring tooth displacement structures and reduces the number of parts and the weight. According to a second aspect of the present invention, in the crank arrangement according to the first aspect, the second sprocket tooth displacement structure is configured to transmit the pedaling torque between the crankshaft and the sprocket mounting element. According to the crank arrangement of the second aspect, the second sprocket tooth displacement structure has a pedaling torque transmission function. This simplifies the first sprocket tooth displacement structure. According to a third aspect of the present invention, the crank arrangement according to the first or second aspect is configured such that the first sprocket tooth displacement structure includes a first sliding axis that is located at least partially within the inner cavity of the crankshaft; and the first sliding axis is displaceable relative to the crankshaft and coupled to the sprocket mounting element. According to the crank arrangement of the third aspect, the axial sliding is stable. According to a fourth aspect of the present invention, the crank assembly according to one of the first to third aspects is configured such that the first sprocket tooth displacement structure has a first sliding surface extending in the first axial direction, and the second sprocket tooth displacement structure has a second sliding surface extending in the first axial direction. According to the crank assembly of the fourth aspect, the sprocket mounting element slides on the two sliding surfaces. This enables stable axial sliding. According to a fifth aspect of the present invention, the crank arrangement according to one of the first to fourth aspects is configured such that the first sprocket tooth displacement structure includes at least one first sliding element arranged within the inner cavity of the crankshaft. According to the crank arrangement of the fifth aspect, axial sliding is smooth. According to a sixth aspect of the present invention, the crank arrangement according to the fifth aspect is configured such that the at least one first sliding element comprises a plurality of first sliding elements. According to the crank arrangement of the sixth aspect, axial sliding is smooth. According to a seventh aspect of the present invention, the crank arrangement according to the sixth aspect is configured such that the plurality of first sliding elements is arranged such that the plurality of first sliding elements are spaced apart from one another in the first axial direction. According to the crank arrangement of the seventh aspect, the axial sliding is smooth. According to an eighth aspect of the present invention, the crank assembly according to one of the first to seventh aspects is configured such that the second chainring tooth displacement structure includes a sliding hole in the crank arm and a second sliding axis for passage through the sliding hole. The second sliding axis is coupled to the chainring mounting element and the bicycle chainring. According to the crank assembly of the eighth aspect, the axial sliding is smooth and stable. According to a ninth aspect of the present invention, the crank arrangement according to the eighth aspect is configured such that the second sprocket tooth displacement structure further includes a tubular element with a tubular hole. The second sliding axis is configured to pass through the tubular hole. According to the crank arrangement of the ninth aspect, the axial sliding is stable. According to a tenth aspect of the present invention, in the crank assembly according to the ninth aspect, the tubular element is configured to be positioned in the first axial direction between the chainring mounting element and the bicycle chainring when the bicycle crank assembly is assembled. According to the crank assembly of the tenth aspect, the movement of the crank arm relative to the chainring mounting element and the bicycle chainring is uniform between the chainring mounting element and the bicycle chainring. Thus, the axial sliding is stable. According to an eleventh aspect of the present invention, the crank assembly according to one of the eighth to tenth aspects is configured such that the second sliding axis includes a first axis element and a second axis element coupled to the first axis element. According to the crank assembly of the eleventh aspect, the bicycle crank assembly can be easily disassembled. This facilitates maintenance and the replacement of parts. According to a twelfth aspect of the present invention, in the crank assembly according to the eleventh aspect, the first axle element is configured to extend in a second axial direction with respect to a central axis of the second sliding axis through a through-hole associated with one of the chainring mounting element and the bicycle chainring, and the second axle element is configured to extend in a second axial direction through a through-hole associated with the other of the chainring mounting element and the bicycle chainring. According to the crank assembly of the twelfth aspect, the bicycle crank assembly can be easily disassembled. This facilitates maintenance and the replacement of parts. According to a thirteenth aspect of the present invention, the bicycle crank assembly according to the eleventh or twelfth aspect is configured such that the first axle element includes a first axle end and, on a side opposite the first axle end in a second axial direction with respect to a central axis of the second sliding axis, a second axle end. The second axle element includes a third axle end and a fourth axle end on a side opposite the third axle end in the second axial direction. A first threaded section is provided on the first axle end of the first axle element. A second threaded section is provided on the third axle end of the second axle element and is configured to engage with the first threaded section. According to the crank assembly of the thirteenth aspect, the first axle element and the second axle element are coupled via a threaded structure.This makes maintenance and parts replacement easier. According to a fourteenth aspect of the present invention, the crank arrangement according to the thirteenth aspect is configured such that a first projection extending radially outward from the second axle end with respect to the central axis of the second sliding axis is provided at the second axle end of the first axle element, and a second projection is provided at the fourth axle end of the second figure-eight element to extend radially outward from the fourth axle end with respect to the central axis of the second sliding axis, wherein the first projection is configured to bear against one of the chainring mounting element and the bicycle chainring in the second axial direction, and the second projection is configured to bear against the other of the chainring mounting element and the bicycle chainring in the second axial direction.According to the crank arrangement of the fourteenth aspect, the first and second axle elements are easily positioned by the stop of the first projection and the stop of the second projection. This allows for easy assembly of the first and second axle elements, thus facilitating maintenance and parts replacement. According to a fifteenth aspect of the present invention, the crank arrangement according to the fourteenth aspect is configured such that the first projection extends circumferentially around the second axial end of the first figure-eight element with respect to the central axis of the second sliding axis, and the second projection extends circumferentially around the fourth axial end of the second figure-eight element with respect to the central axis of the second sliding axis. According to the crank arrangement of the fifteenth aspect, the first and second axial elements can be easily positioned during assembly. This facilitates maintenance and the replacement of parts. According to a sixteenth aspect of the present invention, the crank assembly according to one of the eleventh to fifteenth aspects is configured such that the first axle element has a first tool engagement section and the second axle element has a second tool engagement section. According to the bicycle crank assembly of the sixteenth aspect, the first axle element and the second axle element can be easily attached to and detached from the chainring mounting element or the bicycle chainring using a tool. This facilitates maintenance and the replacement of parts. According to a seventeenth aspect of the present invention, the crank assembly according to any of the first to sixteenth aspects further comprises a displacement stroke adjustment structure configured to adjust the total displacement stroke of the bicycle chainring relative to the crankshaft and crank arm. According to the crank assembly of the seventeenth aspect, the interference between the bicycle chainring and the bicycle frame is reduced by adjusting the total displacement stroke of the bicycle chainring. Thus, the present crank assembly can be mounted on bicycle frames of various shapes. According to an eighteenth aspect of the present invention, the displacement stroke adjustment structure in the crank assembly according to the seventeenth aspect comprises a threaded hole provided on one side of the sprocket mounting element and the crank arm, and a threaded element configured to engage in the threaded hole, be displaceable within the threaded hole, and come into contact with the other side of the sprocket mounting element and the crank arm. According to the crank assembly of the eighteenth aspect, the structure of the displacement stroke adjustment structure is simplified. According to a nineteenth aspect of the present invention, the displacement stroke adjustment structure in the crank assembly according to the eighteenth aspect further comprises an elastic element configured to be provided on the other side of the sprocket mounting element and the crank arm and to come into contact with the threaded element. According to the crank assembly of the nineteenth aspect, the elastic element reduces the impact noise generated by the threaded element during the movement of the sprocket mounting element. This reduces unnecessary noise. According to a twentieth aspect of the present invention, in the crank arrangement according to any of the first to nineteenth aspects, the first sprocket tooth displacement structure and the second sprocket tooth displacement structure are configured to displace the bicycle sprocket relative to the crankshaft and the crank arm in the first axial direction. According to the crank arrangement of the twentieth aspect, the bicycle sprocket is displaced smoothly with respect to the crankshaft and the crank arm, compared to a case in which the bicycle sprocket is displaced in the direction that intersects the first axial direction. A bicycle crank assembly according to a twenty-first aspect of the present invention comprises a crankshaft with an inner cavity and a pivot axis, a crank arm coupled to one end of the crankshaft, a sprocket mounting element on which a bicycle sprocket is mounted, a sprocket tooth displacement structure arranged at least partially within the inner cavity of the crankshaft, and a torque transmission structure arranged outside the inner cavity of the crankshaft and configured to transmit the pedaling torque between the crank arm and the sprocket mounting element. The sprocket mounting element is configured to be displaceable in a first axial direction with respect to the crankshaft and the crank arm in relation to the pivot axis by the sprocket tooth displacement structure.According to the twenty-first aspect of the bicycle crank design, the torque transmission structure is separate from the chainring tooth displacement structure. This simplifies the chainring tooth displacement structure and reduces the number of parts and weight. According to a twenty-second aspect of the present invention, in the bicycle crank assembly according to the twenty-first aspect, the chainring tooth displacement structure is configured to displace the bicycle chainring relative to the crankshaft and crank arm in the first axial direction. According to the bicycle crank assembly of the twenty-second aspect, the bicycle chainring is displaced smoothly relative to the crankshaft and crank arm, compared to a case in which the bicycle chainring is displaced in the direction intersecting the first axial direction. According to the bicycle crank arrangement of the present invention, the structure of the displacement structure of the bicycle chainring is simplified. A more comprehensive assessment of the invention and many of its associated advantages is easily achieved, as it is better understood through the following detailed description when considered in conjunction with the accompanying drawings, wherein Fig. 1 is a schematic representation of a bicycle seen from above; Fig. 2 is a schematic representation of a bicycle crank assembly; Fig. 3 is a perspective view of a bicycle crank assembly according to a first embodiment; Fig. 4 is a top view of the bicycle crank assembly according to the first embodiment; Fig. 5 is a cross-sectional view of the bicycle crank assembly according to the first embodiment along line VV in Fig. 4; Fig. 6 is a perspective exploded view of the bicycle crank assembly according to the first embodiment; Fig. 7 is a cross-sectional view of a second sliding axis; Fig.8 is a cross-sectional view of the bicycle crank assembly according to the first embodiment along line VIII-VIII in Fig. 4; Fig. 9 is a side view of the bicycle crank assembly in a case where the chainring is located on the outermost side; Fig. 10 is a side view of the bicycle crank assembly in a case where the chainring is located on the innermost side; Fig. 11 is a perspective view of a bicycle crank assembly according to a second embodiment; Fig. 12 is a top view of a bicycle crank assembly according to the second embodiment; Fig. 13 is a perspective exploded view of a bicycle crank assembly according to the second embodiment; Fig. 14 is a top view of a bicycle crank assembly according to a third embodiment; Fig. 15 is a top view of a bicycle crank assembly according to a fourth embodiment; Fig. 16 is a top view of a bicycle crank assembly according to a fifth embodiment; Fig.Figure 17 is a top view of a bicycle crank assembly according to a sixth embodiment; Figure 18 is a top view of a bicycle crank assembly according to a seventh embodiment; Figure 19 is a cross-sectional view of a bicycle crank assembly with a first modified example of a second sliding axis; Figure 20 is a cross-sectional view of a bicycle crank assembly with a second modified example of the second sliding axis; Figure 21 is a cross-sectional view of a bicycle crank assembly with a third modified example of the second sliding axis; and Figure 22 is a cross-sectional view of a bicycle crank assembly with a modified example of a first sliding axis. Selected embodiments are now described with reference to the associated drawings, where identical reference numbers denote corresponding or identical elements in the different drawings. The phrase “at least one of” used in this revelation means “one or more” of a desired choice. For example, the phrase “at least one of,” as used in this revelation, means “only a single choice” or “both of two choices” when the number of choices is two. In another example, the phrase “at least one of,” as used in this revelation, means “only a single choice” or “any combination of two or more choices” when the number of choices is three or more. A human-powered vehicle to which a bicycle crank assembly is attached will now be described with reference to Fig. 1. Figure 1 is a diagram of a bicycle A, which is an example of a human-powered vehicle, viewed from above. Here, a human-powered vehicle refers to a vehicle that uses at least some human power as its driving force. Human-powered vehicles include those that assist human power with electrical energy. Human-powered vehicles do not include those that use only a propulsion motor other than human power. In particular, human-powered vehicles do not include those that use only an internal combustion engine as their propulsion motor. A typical human-powered vehicle is a compact, light vehicle that does not require a driver's license to operate on public roads. The illustrated human-powered vehicle includes a bicycle A. In particular, the human-powered vehicle is a bicycle A.Bicycle A includes a drivetrain B. The drive train B is of the chain drive type. The drive train B includes a bicycle crank assembly 10. The bicycle crank assembly 10 rotates a bicycle chainring 12. The bicycle chainring 12 has chainring teeth that engage with a bicycle chain 14. In the present embodiment, the bicycle chainring 12 includes a front chainring 16. The torque of the front chainring 16 is transmitted via the bicycle chain 14 to a rear chainring 18. When the bicycle crank assembly 10 is subjected to pedaling force, the bicycle chainring 12 is rotated in the forward direction DR (see Fig. 4) to move the bicycle A forward. The bicycle crank assembly 10 will now be described with reference to Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. 9. As shown in Fig. 2, the bicycle crank assembly 10 includes a crankshaft 20 with an inner cavity SA and a pivot axis CA, crank arms 22 coupled to the crankshaft 20, a sprocket mounting element 24 on which the bicycle sprocket 12 is mounted, a first sprocket tooth displacement structure 26 which is at least partially located in the inner cavity SA of the crankshaft 20, and a second sprocket tooth displacement structure 28 which is located outside the inner cavity SA of the crankshaft 20. The crankshaft 20 is rotatably held by a bottom bracket of the bicycle frame. The crank arms 22 are each mounted at two ends of the crankshaft 20. The crank arm 22 has a base section 22a that is attached to the crankshaft 20. In particular, the base section 22a of the crankshaft 20 has an end that is inserted into an engagement hole 22c in the base section 22a of the crank arm 22. A pedal is rotatably mounted to an end 22b of the crank arm 22 that is located on the side opposite the base section 22a. The crankshaft 20 and the crank arm 22 rotate together about the axis of rotation CA. The crankshaft 20 has a first end 20a on the side of the bicycle sprocket 12 and a second end 20b on the side opposite the first end 20a in a first axial direction DA with respect to the axis of rotation CA. The inner cavity SA of the crankshaft 20 extends along the axis of rotation CA from the first end 20a. The sprocket mounting element 24 has a pivot axis CB. The sprocket mounting element 24 is positioned on the bicycle frame such that the pivot axis CA of the crankshaft 20 and the pivot axis CB are coaxial. The sprocket mounting element 24 is rotatable about the pivot axis CB relative to the bicycle frame. The sprocket mounting element 24 is configured to be displaceable relative to the crankshaft 20 and the crank arm 22 in the first axial direction DA with respect to the axis of rotation CA by the first sprocket tooth displacement structure 26 and the second sprocket tooth displacement structure 28. Preferably, the first sprocket tooth displacement structure 26 and the second sprocket tooth displacement structure 28 are configured to displace the bicycle sprocket 12 relative to the crankshaft 20 and the crank arm 22 in the first axial direction DA. As shown in Figures 3 and 4, the sprocket mounting element 24 comprises a main body 24a provided with the first sprocket tooth displacement structure 26, a plurality of arms 24b extending radially from the main body 24a with respect to the axis of rotation CB for supporting the bicycle sprocket 12, and a support section 24c extending radially from the main body 24a with respect to the central axis of rotation CB for supporting the second sprocket tooth displacement structure 28. Each arm 24b has a distal end section defining a mounting section 24d that is attached to the bicycle sprocket 12. In a state where the bicycle chainring 12 is mounted on the chainring mounting element 24, an arm space SB is formed between the main body 24a of the chainring mounting element 24 and the bicycle chainring 12, into which the crank arm 22 is inserted. The arm space SB is surrounded by the main body 24a, the bicycle chainring 12 and two of the arms 24b. A mounting section 24e, on which the first sprocket tooth displacement structure 26 is mounted, is provided on a central section of the main body 24a through which the axis of rotation CB extends. In the present embodiment, the mounting section 24e is configured as a toothed through-hole extending in the first axial direction DA. The sprocket mounting element 24 is supported on the crankshaft 20 by the first sprocket tooth displacement structure 26. The sprocket mounting element 24 is located on the outside of the crank arm 22 in the first axial direction DA with respect to a bicycle centerline. At least the base section 22a of the crank arm 22 is positioned in the first axial direction DA between the bicycle sprocket 12 and the sprocket mounting element 24. In a case where the first sprocket tooth displacement structure 26 moves the bicycle sprocket 12 in the first axial direction DA, the path of the teeth of the bicycle sprocket 12 is moved. In the present embodiment, the circular path of the teeth of the bicycle sprocket 12 is displaced in the first axial direction DA in a state where the central axis of the circular path is parallel to the first axial direction DA. As shown in Figs. 5 and 6, the first sprocket tooth displacement structure 26 includes a first sliding axis 30, which is at least partially located in the inner cavity SA of the crankshaft 20. The first sliding axis 30 is displaceable relative to the crankshaft 20 and coupled to the sprocket mounting element 24. A first end 30a of the first sliding axis 30 is attached to the mounting section 24e of the sprocket mounting element 24. A cap element 31 is provided at a second end 30b opposite the first end 30a of the first sliding axis 30. The first sliding axis 30 is mounted on the sprocket mounting element 24 such that the longitudinal direction of the first sliding axis 30 lies along the rotational center axis CB of the sprocket mounting element 24. The first sprocket tooth displacement structure 26 has a first sliding surface 26a extending in the first axial direction DA. For example, the first sliding surface 26a is cylindrical. In the present embodiment, an outer circumferential surface 30c of the first sliding axis 30 is configured as the first sliding surface 26a. The outer circumferential surface 30c is cylindrical. The first sliding surface 26a is configured to contact the cylindrical inner circumferential surface of the crankshaft 20 in the inner cavity SA or to contact the first sliding element 32 received in the inner cavity SA. The first sliding surface 26a is not limited to the shape of the present embodiment. For example, the first sliding surface 26a need not be cylindrical and can be formed into a polygonal cross-section. Preferably, the first sprocket tooth displacement structure 26 includes at least one first sliding element 32 arranged within the inner cavity SA of the crankshaft 20. Here, the "at least one first sliding element 32" can include a plurality of first sliding elements 32. Preferably, the first sprocket tooth displacement structure 26 can have a plurality of first sliding elements 32. For example, the first sliding element 32 is designed as at least one rolling element or as a cylindrical bushing. The first sliding element 32 is arranged in the inner cavity SA of the crankshaft 20 such that it is axially oriented with respect to the rotational axis CA of the crankshaft 20. In a state arranged within the inner cavity SA, a fastening element 34 holds the first sliding element 32 in the inner cavity SA. Furthermore, a sealing element 36 with a lip is provided on the inner circumferential section of the fastening element 34.The lip of the sealing element 36 is in sliding contact with the outer circumferential surface 30c of the first sliding axis 30. At least one first sliding element 32 is arranged on the outer circumferential surface of the first sliding axis 30. In the present embodiment, at least one first sliding element 32 is a spherical rolling element. Preferably, in a case where the first sprocket tooth displacement structure 26 includes a plurality of first sliding elements 32, the plurality of first sliding elements 32A are arranged such that they are spaced apart from one another in the first axial direction DA. For example, a holder 33 separates the plurality of first sliding elements 32A from one another in the first axial direction DA. The second sprocket tooth displacement structure 28 is configured to transmit the pedaling torque between the crankshaft 22 and the sprocket mounting element 24. The pedaling torque refers to a rotational force based on the pedaling force exerted on the pedal by the user riding the bicycle. Preferably, the second sprocket tooth displacement structure 28 guides the bicycle sprocket 12 such that the bicycle sprocket 12 moves in the first axial direction DA. Preferably, the second sprocket tooth displacement structure 28 is configured, as in the present embodiment, to transmit the pedaling torque from the crankshaft 22 to both the sprocket mounting element 24 and the bicycle sprocket 12. In this case, the pedaling torque is transmitted through the crank 22 to both the sprocket mounting element 24 and the bicycle sprocket 12. The second sprocket tooth displacement structure 28 has a second sliding surface 28a extending in the first axial direction DA. The second sliding surface 28a is radially spaced from the rotational axis CA of the crankshaft 20. The second sliding surface 28a is located on a first rotating structure with the crank arm 22 and a second rotating structure with the bicycle sprocket 12. Furthermore, the second sliding surface 28a is configured as a surface that contacts the other surface of both the first and second rotating structures. The pedaling torque of the crankshaft 22 is transmitted from the first rotating structure to the second rotating structure via the second sprocket tooth displacement structure 28. In the present embodiment, the first rotating structure includes the crank arm 22 and the bushing 41.In the present embodiment, the second rotating structure includes the bicycle chainring 12, the chainring mounting element 24, a second sliding axle 42, and a tubular element 44. In the present embodiment, the second sliding surface 28a is configured as the outer circumferential surface 44b of the tubular element 44. The second sprocket tooth displacement structure 28 includes a sliding hole 40 provided in the crank arm 22 and the second sliding axle 42 configured to pass through the sliding hole 40. The sliding hole 40 is provided in the crank arm 22 in a region where the crank arm 22, the bicycle chainring 12, and the chainring mounting element 24 overlap in the first axial direction DA. The sliding hole 40 includes a sliding inner circumferential surface 40a. The sliding inner circumferential surface 40a extends in the first axial direction DA. The sliding inner circumferential surface 40a is defined by the inner circumferential surface of the bushing 41. The bushing 41 is mounted on a mounting hole 22d of the crank arm 22, so that it is part of the sliding hole 40. The sealing elements 43a and 43b, each including a lip, are located in the mounting hole 22d, respectively, on the side of the bushing 41 closer to the bicycle chainring 12 and on the side of the bushing 41 closer to the chainring mounting element 24 in the second axial direction DB. Socket 41 can be omitted. Preferably, as shown in Fig. 5, the second sprocket tooth displacement structure 28 further comprises a tubular element 44 with a tubular hole 44a. The second sliding axis 42 is configured to pass through the tubular hole 44a. The tubular element 44 is configured to be positioned in the first axial direction DA between the sprocket mounting element 24 and the bicycle sprocket 12 in a mounted state of the bicycle crank assembly 10. The tubular element 44 moves together with the chainring mounting element 24 and the bicycle chainring 12 along the first axial direction DA. The tubular element 44 is rotatable about a central axis CC of the second sliding axis 42 and can be attached to at least one of the chainring mounting element 24 and the bicycle chainring 12. The outer circumferential surface 44b of the tubular element 44 slides with respect to the sliding hole 40 of the crank arm 22. The outer circumferential surface 44b of the tubular element 44 and the sliding inner circumferential surface 40a of the sliding hole 40 are in sliding contact with each other. The second sliding axle 42 will now be described with reference to Figures 5, 6 to 7. The second sliding axle 42 is attached to at least one of the chainring mounting elements 24 and the bicycle chainring 12. Alternatively, the second sliding axle 42 can be attached to the crank arm 22 (see Figure 21). As shown in Fig. 5, in the present embodiment the second sliding axis 42 is coupled to the chain wheel mounting element 24 and the bicycle chain wheel 12. The second sliding axis 42 can be configured as a single element or as a coupled body consisting of a plurality of elements. In the present embodiment, the second sliding axis 42 comprises a first axis element 46 and a second axis element 48 coupled to the first axis element 46. The first axis element 46 is configured to extend in the second axial direction DB with respect to the central axis CC of the second sliding axis 42 through a through-hole 50A provided on one of the chainring mounting element 24 and the bicycle chainring 12. The second axis element 48 is configured to extend in the second axial direction DB through a through-hole 50B provided on the other of the chainring mounting element 24 and the bicycle chainring 12. In the present embodiment, the first axle element 46 passes through a first through-hole 52A (through-hole 50A) provided in the sprocket mounting element 24. The second axle element 48 passes through a second through-hole 52B (through-hole 50B) provided in the bicycle sprocket 12. In the present embodiment, the second through-hole 52B is provided in a projection 16a that extends from the inner circumferential edge of the ring of the bicycle sprocket 12 towards the center of the bicycle sprocket 12 (see Fig. 6). As shown in Fig. 7, the first axis element 46 has a first axis end 46a and, in the second axial direction DB with respect to the central axis CC of the second sliding axis 42, a second axis end 46b opposite the first axis end 46a. The second axis element 48 has a third axis end 48a and, in the second axial direction DB opposite the third axis end 48a, a fourth axis end 48b. A first threaded section 46c is provided at the first axis end 46a of the first axis element 46. A second threaded section 48c is provided at the third axis end 48a of the second axis element 48 and is configured to engage thread-wise with the first threaded section 46c. A first projection 46d is provided at the second axial end 46b of the first axial element 46 to extend radially outward from the second axial end 46b with respect to the central axis CC of the second sliding axis 42. A second projection 48d is provided at the fourth axial end 48b of the second axial element 48 to extend radially outward from the fourth axial end 48b with respect to the central axis CC of the second sliding axis 42. The first projection 46d is configured to bear against one of the chainring mounting element 24 and the bicycle chainring 12 in the second axial direction DB. The second projection 48d is configured to bear against the other of the chainring mounting element 24 and the bicycle chainring 12 in the second axial direction DB. In the present embodiment, the first projection 46d is configured to bear against the chainring mounting element 24 in the second axial direction DB.The second projection 48d is configured to bear against the bicycle chainring 12 in the second axial direction DB. The first projection 46d extends circumferentially around the second axis end 46b of the first axis element 46 with respect to the central axis CC of the second sliding axis 42. The second projection 48d extends circumferentially around the fourth axis end 48b of the second axis element 48 with respect to the central axis CC of the second sliding axis 42. Preferably, the first axis element 46 has a first tool engagement area 46e. The second axis element 48 has a second tool engagement area 48e. For example, the first tool engagement section 46e is configured as a hole into which a hexagonal key is inserted into the end face of the second axis end 46b of the first figure-eight element 46. The second tool engagement section 48e is configured as a hole into which a hexagonal key is inserted into the end face of the fourth axis end 48b of the second figure-eight element 48. Preferably, the bicycle crank assembly 10 further includes a displacement stroke adjustment structure 56 configured to adjust a total displacement stroke DL of the bicycle chainring 12 with respect to the crankshaft 20 and the crank arm 22. The total displacement stroke DL specifies the distance between the innermost position of the bicycle chainring 12 and the outermost position of the bicycle chainring 12 in the first axial direction DA (see Fig. 9 and Fig. 10). The innermost position is the position of the bicycle chainring 12 when the chainring mounting element 24 is in its innermost position in the first axial direction DA. The outermost position is the position of the bicycle chainring 12 when the chainring mounting element 24 is in its outermost position in the first axial direction DA. As shown in Fig. 5, the displacement stroke adjustment structure 56 includes a threaded hole 58 and a threaded element 60. The threaded hole 58 is provided on one side of the chainring mounting element 24 and the crank arm 22. The threaded element 60 is configured to contact the other side of the chainring mounting element 24 and the crank arm 22. Furthermore, the threaded element 60 is configured to engage in the threaded hole 58, which is displaceable within the threaded hole 58. Preferably, the displacement stroke adjustment structure 56 also includes an elastic element 62, which is configured to be provided on the other side of the chainring mounting element 24 and the crank arm 22 and to contact the threaded element 60. In the present embodiment, the threaded hole 58 is provided on the sprocket mounting element 24. The elastic element 62 is provided on the crank arm 22. The threaded element 60 has a head that is located in the space between the chainring mounting element 24 and the crank arm 22. The position of the head of the threaded element 60 is adjusted by setting the depth to which the threaded element 60 engages in the threaded hole 58. The elastic element 62 is attached to the crank arm 22 such that it faces the threaded hole 58. The elastic element 62 is made, for example, of rubber or an elastomer. In a case where the chainring mounting element 24 moves towards the bottom bracket of the bicycle frame in the first axial direction DA in the direction DX1, the threaded element 60 and the elastic element 62 come into contact with each other and limit the movement of the chainring mounting element 24 and the bicycle chainring 12 with respect to the crankshaft 20 and the crank arm 22. In addition, the elastic element 62 reduces the impact noise that occurs when the threaded element 60 and the elastic element 62 come into contact. Preferably, as shown in Fig. 8, the displacement stroke adjustment structure 56 can further include an additional elastic element 66, which is provided on one of the bicycle chainring 12 and the crank arm 22 to contact the other of the bicycle chainring 12 and the crank arm 22. In the present embodiment, the additional elastic element 66 is provided on the crank arm 22. In particular, an additional elastic element 66 is provided on the crank arm 22 that faces the projection 16a of the bicycle chainring 12. The additional elastic element 66 is, for example, made of rubber or an elastomer. The additional elastic element 66 projects in the first axial direction DA from the section of the crank arm 22 to the bicycle chainring 12. In a case where the chainring mounting element 24 is displaced in the first axial direction DA in the direction DX2 away from the bottom bracket of the bicycle frame, the bicycle chainring 12 and the additional elastic element 66 come into contact with each other. This restricts the movement of the chainring mounting element 24 and the bicycle chainring 12 with respect to the crankshaft 20 and the crank arm 22. The functioning of the bicycle crank assembly 10 will now be described with reference to Fig. 9 and Fig. 10. Fig. 9 shows the bicycle crank assembly 10 in a state where the chainring mounting element 24 is in its outermost position. In this case, the bicycle chainring 12 is in its outermost position. The double-dashed line in Fig. 9 shows the innermost position of the bicycle chainring 12 when the chainring mounting element 24 is in its innermost position. Fig. 10 shows the bicycle crank assembly 10 in a state where the chainring mounting element 24 is in its innermost position. In this case, the bicycle chainring 12 is in its innermost position. The double-dashed line in Fig. 10 shows the outermost position of the bicycle chainring 12 when the chainring mounting element 24 is in its outermost position. The rotation of the crank 22 about the central axis CA generated by the pedaling force transmits the pedaling torque to the bicycle chainring 12 and the chainring mounting element 24 via the second sliding axis 42 and the tubular element 44 of the second chainring tooth displacement structure 28. The torque of the bicycle chainring 12 is transmitted to the chainring 18 via the bicycle chain 14. In a case where a chain change is performed on the rear sprocket 18 while the bicycle A is in motion, a force in the first axial direction DA acts through the bicycle chain 14 on the bicycle sprocket 12. This causes the bicycle sprocket 12 and the sprocket mounting element 24 to move in the chain shifting direction. The sprocket mounting element 24 is supported by the first sliding axis 30 such that it is displaceable in the first axial direction DA. This causes the bicycle sprocket 12 and the sprocket mounting element 24 to displace in the first axial direction DA. Furthermore, in the present embodiment, the first sprocket tooth displacement structure 26 includes at least one first sliding element 32, which is arranged within the inner cavity SA. This allows the bicycle sprocket 12 and the sprocket mounting element 24 to displace smoothly in the first axial direction DA. Moreover, the first sprocket tooth displacement structure 26 is at least partially located within the inner cavity SA of the crankshaft 20. Thus, the bicycle crank assembly 10 is compact. Furthermore, in the present embodiment, the displacement structure for moving the bicycle chainring 12 separates the first chainring tooth displacement structure 26 and the second chainring tooth displacement structure 28. Moreover, the first chainring tooth displacement structure 26 and the second chainring tooth displacement structure 28 are located at different sections within the bicycle crank assembly 10. Thus, the structures of the first chainring tooth displacement structure 26 and the second chainring tooth displacement structure 28 are simpler than in a case where the displacement structure is configured at a single location within the bicycle crank assembly 10. A bicycle crank assembly 10A according to a second embodiment is now described with reference to Figures 11, 12 to 13. The components that are identical to the corresponding components of the first embodiment are given the same reference numbers. A detailed description of these components is omitted. The bicycle crank assembly 10A according to the second embodiment differs from the first embodiment in the design of the second chainring tooth displacement structure 28. The second sprocket tooth displacement structure 28 includes a second sliding surface 70a, which is provided on the sprocket mounting element 24. The second sliding surface 70a includes an upstream sliding surface 70b and a downstream oriented sliding surface 70c. The upstream sliding surface 70b is provided on the side of the downstream sliding surface 70c that is upstream of the sprocket mounting element 24 in the forward direction of rotation DR. The upstream sliding surface 70b is provided on one of the two arms 24b that encloses the arm space SB in the sprocket mounting element 24, which is located on the side upstream DR in the forward direction of rotation. The downstream sliding surface 70c is provided on one of the two arms 24b that encloses the arm space SB in the sprocket mounting element 24, which is located on the side downstream DR in the forward direction of rotation. As shown in Fig. 12, the upstream sliding surface 70b is configured such that it is in sliding contact with an upstream contact surface 72a on the crank arm 22. In the assembled state of the bicycle crank assembly 10A, the upstream sliding surface 70b extends radially to the axis of rotation CA. In particular, a plane SX encompassing the upstream sliding surface 70b extends through the axis of rotation CA. The downstream sliding surface 70c is configured to be in sliding contact with a downstream contact surface 72b provided on the crank arm 22. In the assembled state of the bicycle crank assembly 10A, the downstream sliding surface 70c extends radially to the axis of rotation CA. In particular, a plane SY encompassing the downstream sliding surface 70c extends through the axis of rotation CA. The upstream contact surface 72a is located on the side of the crank arm 22 that is forward of the direction of rotation DR. The upstream contact surface 72a is formed by a forward projection 74A of the crank arm 22. The downstream contact surface 72b is located on the side of the crank arm 22 that is downstream of the direction of rotation DR. The downstream contact surface 72b is formed by a downstream projection 74B of the crank arm 22. As shown in Fig. 13, the upstream projection 74A and the downstream projection 74B can be configured by an element separate from the crank arm 22. In the present embodiment, a contact element 76 is mounted on the crank arm 22. The contact element 76 includes the upstream projection 74A, the downstream projection 74B, and a connecting section 74C that connects the upstream projection 74A and the downstream projection 74B. The contact element 76 is mounted on the crank arm 22 by engaging with the engagement projections 78 provided on the crank arm 22. The engagement projections 78 can be omitted, and the contact element can be fastened to the crank arm 22 with a screw, adhesive, or the like. A bicycle crank assembly 10B according to a third embodiment is now described with reference to Fig. 14. The bicycle crank assembly 10B according to the third embodiment is a modification of the bicycle crank assembly 10A according to the second embodiment. The components that are identical to the corresponding components of the second embodiment are given the same reference numbers. A detailed description of these components is omitted. In the second embodiment, the upstream contact surface 72a and the downstream contact surface 72b are provided on the upstream projection 74A and the downstream projection 74B of the crank arm 22. In the present embodiment, the upstream contact surface 72a is provided on a side surface of the crank arm 22 on the side facing forward in the direction of forward rotation DR. The downstream contact surface 72b is provided on a side surface of the crank arm 22 on the side facing backward in the direction of forward rotation DR. The upstream sliding surface 70b is provided on a third projection 80A, which extends towards the downstream side of the arm 24b, located on the upstream side of the arm space SB. The downstream sliding surface 70c is provided on a fourth projection 80B, which extends towards the upstream side of the arm 24b, located on the downstream side relative to the arm space SB. A bicycle crank assembly 10C according to a fourth embodiment is now described with reference to Fig. 15. The bicycle crank assembly 10C according to the fourth embodiment is a further modification of the bicycle crank assembly 10B according to the third embodiment. The components that are identical to the corresponding components of the third embodiment are given the same reference numbers. A detailed description of these components is omitted. In the present embodiment, the third projection 80A of the sprocket mounting element 24 is provided with a pressure element 82 that projects from the upstream sliding surface 70b. The pressure element 82 is, for example, designed as a plunger. The pressure element 82 includes a distal end section 82a with a spherical surface. Furthermore, the pressure element 82 includes a main body 82b, which is housed in the third projection 80A. The distal end section 82a of the pressure element 82 is exposed from the upstream sliding surface 70b and presses against the upstream contact surface 72a of the crank arm 22. The pressure element 82 presses against the upstream contact surface 72a of the crank arm 22. These limitations are reduced when force is applied to the downstream sliding surface 70c of the sprocket mounting element 24 against the downstream contact surface 72b of the crank arm 22. A bicycle crank assembly 10D according to a fifth embodiment is now described with reference to Fig. 16. The bicycle crank assembly 10D according to the fifth embodiment is a further modification of the bicycle crank assembly 10B according to the third embodiment. The components that are identical to the corresponding components of the third embodiment are given the same reference numbers. A detailed description of these components is omitted. In the third embodiment, the upstream sliding surface 70b and the downstream sliding surface 70c, which are provided on the sprocket mounting element 24, are designed as flat surfaces. In the present embodiment, the upstream sliding surface 70b and the downstream sliding surface 70c are designed as rotatable curved surfaces. In particular, the upstream sliding surface 70b is configured by an outer circumferential surface of a first roller 84A. The first roller 84A is rotatably mounted by a first rotary axis element 86A. The first rotary axis element 86A is mounted on the third projection 80A such that the longitudinal direction of the first rotary axis element 86A is parallel to the upstream contact surface 72a. Similarly, the downstream sliding surface 70c is configured as the outer circumferential surface of a second roller 84B. The second roller 84B is rotatably mounted by the second rotary axis element 86B. The second rotary axis element 86B is mounted on the fourth projection 80B such that the longitudinal direction of the second rotary axis element 86B is parallel to the downstream contact surface 72b. A bicycle crank assembly 10E according to a sixth embodiment is now described with reference to Fig. 17. The components that are identical to the corresponding components of the first embodiment are given the same reference numbers. A detailed description of these components is omitted. The bicycle crank assembly 10E according to the sixth embodiment differs from the first embodiment in the structure of the second chainring tooth displacement structure 28. In the first embodiment, the second sprocket tooth displacement structure 28 includes a second sliding surface 28a extending in the first axial direction DA. The second sprocket tooth displacement structure 28 of the present embodiment has two second sliding surfaces 28a extending in the first axial direction DA. The structure of the second sliding surface 28a corresponds to that of the first embodiment. In particular, each of the two second sliding surfaces 28a is configured by the outer circumferential surface 44b of a tubular element 44. The two second sliding surfaces 28a are located in the longitudinal direction of the crank arm 22, closer to the end 22b of the crank arm 22 than the axis of rotation CA.Furthermore, the distance between the central axis CR of one of the second sliding surfaces 28a and the rotational axis CA of the crankshaft 20 is equal to the distance between the central axis CS of the other of the second sliding surfaces 28a and the rotational axis CA of the crankshaft 20. A bicycle crank assembly 10F according to a seventh embodiment is now described with reference to Fig. 18. The bicycle crank assembly 10F according to the seventh embodiment is a further modification of the bicycle crank assembly 10E according to the sixth embodiment. The components that are identical to the corresponding components of the sixth embodiment are given the same reference numbers. A detailed description of these components is omitted. In the sixth embodiment, viewed in the direction of the axis of rotation CA, the two cylindrical second sliding surfaces 28a are located closer to the end 22b of the crank arm 22 than the axis of rotation CA in the direction of extension of the crank arm 22. In the present embodiment, the two second sliding surfaces 28a are located at point-symmetrical positions, the center of which is the axis of rotation CA. The distance between the central axis CX of one of the second sliding surfaces 28a and the axis of rotation CA of the crankshaft 20 is equal to the distance between the central axis CY of the other second sliding surface 28a and the axis of rotation CA of the crankshaft 20. In the present embodiment, the two second sliding surfaces 28a are arranged at point-symmetrical positions, the center of which is the axis of rotation CA. Thus, the crank arm 22 includes an extended section 90. The extended section 90 extends in a direction opposite to the direction extending from the base section 22a of the crank arm 22 to the pedal. The extended section 90 is provided with a sliding hole corresponding to the sliding hole 40 shown in the first embodiment. The description relating to the embodiments above illustrates, without intending to limit, one applicable form of a bicycle crank assembly 10 and 10A to 10F according to the present invention. In addition to the embodiments described above, the bicycle crank assembly 10 and 10A to 10F according to the present invention applies, for example, to modified examples of the embodiments described above and combinations of at least two of the modified examples that do not contradict each other. In the modified examples described below, the components that are identical to the corresponding components of the embodiments above are given the same reference numbers. A detailed description of these components is omitted. A modified example for the second sliding axis 42 will now be described with reference to Fig. 19. In the first, sixth, and seventh embodiments, the second sliding axis 42 is coupled to the chainring mounting element 24 and the bicycle chainring 12. In the present modified example, the second sliding axis 42A is coupled only to the bicycle chainring 12. The second sliding surface 28a of the second chainring tooth displacement structure 28 is formed on the outer circumferential surface of the second sliding axis 42A. The modified example shown in Fig. 19 can be applied to each of the first, sixth, and seventh embodiments. A modified example for the second sliding axis 42 will now be described with reference to Fig. 20. In the first, sixth, and seventh embodiments, the second sliding axis 42 is coupled to the chainring mounting element 24 and the bicycle chainring 12. In the present modified example, the second sliding axis 42B is coupled only to the chainring mounting element 24. The second sliding surface 28a of the second chainring tooth displacement structure 28 is formed by the outer circumferential surface of the second sliding axis 42B. The modified example shown in Fig. 20 can be applied to each of the first, sixth, and seventh embodiments. A modified example for the second sliding axis 42 will now be described with reference to Fig. 21. In the first, sixth, and seventh embodiments, the second sliding axis 42 is coupled to the chainring mounting element 24 and the bicycle chainring 12, and the second sliding axis 42 extends through the sliding hole 40 of the crank arm 22. In the present modified example, the second sliding axis 42C is provided on the crank arm 22. The second sliding axis 42C includes a first sliding projection 92A, which projects from the crank arm 22 in one direction in the second axial direction DB, and a second sliding projection 92B, which projects from the crank arm 22 in the other direction in the second axial direction DB. The first sliding projection 92A is inserted through a first sliding hole 94A of the chainring mounting element 24. The second sliding projection 92B is inserted through a second sliding hole 94B of the bicycle chainring 12.The second sliding surface 28a of the second sprocket tooth displacement structure 28 is formed by the outer circumferential surface of the first sliding projection 92A and the outer circumferential surface of the second sliding projection 92B. The modified example shown in Fig. 21 can be applied to each of the first, sixth, and seventh embodiments. A modified example of the first sliding element 32 will now be described with reference to Fig. 22. In the first embodiment, the first sprocket tooth displacement structure 26 includes the first sliding element 32, which is designed as a spherical roller body. In the present modified example, the first sprocket tooth displacement structure 26 includes an annular first sliding element 32A. The plurality of first sliding elements 32A are arranged such that they are spaced apart from one another in the first axial direction DA. The first sliding element 32A includes a bushing. The modified example shown in Fig. 22 can be applied to any of the first through seventh embodiments. The bicycle crank assembly 10 can be configured as described below. The bicycle crank assembly 10 comprises a crankshaft 20 with an inner cavity SA and a rotational axis CA, a crank arm 22 coupled to the crankshaft 20, a sprocket mounting element 24 to which a bicycle sprocket 12 is attached, a sprocket tooth displacement structure located at least partially within the inner cavity SA of the crankshaft 20, and a torque transmission structure located outside the inner cavity SA of the crankshaft 20 and designed to transmit the pedaling torque between the crank arm 22 and the sprocket mounting element 24. The sprocket mounting element 24 is configured to be displaceable relative to the crankshaft 20 and the crank arm 22 in the first axial direction DA with respect to the rotational axis CA by the sprocket tooth displacement structure. The bicycle crank assembly 10 includes the first to seventh embodiments. The chainring tooth displacement structure includes the first chainring tooth displacement structure 26, which is described in the first to seventh embodiments. The torque transmission structure includes the second chainring tooth displacement structure 28, which is described in the first to seventh embodiments and the modified examples thereof. The torque transmission structure is not limited to these examples. In the first to seventh embodiments, the pedaling torque is transmitted to the bicycle chainring 12 via the crank 22. The torque transmission structure includes further mechanisms. One example of a further mechanism includes a mechanism for transmitting the pedaling torque to the bicycle chainring 12 by means of an extension arm section that extends radially outward with respect to the axis of rotation CA in the crankshaft 20.The extension arm section is provided with a sliding axis which corresponds to the second sliding axis 42 described in the first embodiment. The bicycle crank assembly 10 can also be applied to a bicycle A, in which the bicycle chainring 12 includes a chainring tooth displacement structure pivoted about an axis of rotation. In this case, the bicycle chainring 12 is configured to be displaceable and pivotable in the first axial direction DA. The chainring tooth displacement structure pivots the bicycle chainring 12 about an axis of rotation that is a line parallel to a line that intersects the centerline of the bicycle orthogonally, extending in the front and rear directions of the bicycle A, and a line that lies along the first axial direction DA. Accordingly, such an axis of rotation is oriented to extend in the vertical direction of the bicycle. REFERENCE NUMBERSA Bicycle B Drivetrain CA Pivot axis CB Pivot axis CC Center axis CR Center axis CS Center axis CX Center axis CY Center axis DA First axial direction DB Second axial direction DL Total displacement stroke DR Forward rotation direction DX1 direction DX2 direction SA Inner cavity SB Arm space SX Plane 10- 10F Bicycle crank assembly 12 Bicycle sprocket 14 Bicycle chain 16 Front sprocket 16a Projection 18 Rear sprocket 20 Crankshaft 20a First end 20b Second end 22 Crank arm 22a Base section 22b End 22c Engagement hole 22d Mounting hole 24 Sprocket mounting element 24a Main body 24b Arm 24c Support section 24d Mounting section 24e Mounting section 26 First sprocket tooth displacement structure 26a First sliding surface 28 Second sprocket tooth displacement structure 28a Second sliding surface 30 First sliding axis 30a First End 30b second end 30c outer circumferential surface 31 cap element 32 first sliding element 32A first sliding element 33 holder 34 fastening element 36Sealing element 40 Sliding hole 40a Sliding inner circumferential surface 41 Bushing 42 Second sliding axis 42A Second sliding axis 42B Second sliding axis 42C Second sliding axis 43a Sealing element 43b Sealing element 44 Tubular element 44a Tubular hole 44b Outer circumferential surface 46 First axis element 46a First axis end 46b Second axis end 46c First threaded section 46d First projection 46e First tool engagement section 48 Second axis element 48a Third axis end 48b Fourth axis end 48c Second threaded section 48d Second projection 48e Second tool engagement area 50A Through hole 50B Through hole 52A First through hole 52B Second through hole 56 Displacement stroke adjustment structure 58 Threaded hole 60 Threaded element 62 Elastic element 66 Additional elastic element 70a second sliding surface 70b upstream sliding surface 70c downstream sliding surface 72a upstream contact surface 72b downstream contact surface 74A upstream projection 74B downstreamProjection 76 Contact element 78 Engagement projection 80A Third projection 80B Fourth projection 82 Pressure element 82a Distal end section 82b Main body 84A First roller 84B Second roller 86A First pivot element 86B Second pivot element 90 Extended section 92A First sliding projection 92B Second sliding projection 94A First sliding hole 94B Second sliding hole

Claims

A bicycle crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) comprising: a crankshaft (20) with an inner cavity (SA) and a pivot axis (CA); a crank arm (22) coupled to the crankshaft (20); a sprocket mounting element (24) to which a bicycle sprocket (12) is attached; a first sprocket tooth displacement structure (26) arranged at least partially within the inner cavity (SA) of the crankshaft (20); and a second sprocket tooth displacement structure (28) arranged outside the inner cavity (SA) of the crankshaft (20); wherein the sprocket mounting element (24) is configured to be displaceable by the first sprocket tooth displacement structure (26) and the second sprocket tooth displacement structure (28) with respect to the crankshaft (20) and the crank arm (22) in a first axial direction (DA) with respect to the rotational center axis (CA). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 1, wherein the second sprocket tooth displacement structure (28) is configured to transmit a pedaling torque between the crankshaft (22) and the sprocket mounting element (24). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 1 or 2, wherein the first sprocket tooth displacement structure (26) includes a first sliding axis (30) which is arranged at least partially within the inner cavity (SA) of the crankshaft (20); and the first sliding axis (30) is displaceable relative to the crankshaft (20) and coupled to the sprocket mounting element (24). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to any one of claims 1 to 3, wherein the first sprocket tooth displacement structure (26) has a first sliding surface (26a) extending in the first axial direction (DA); and the second sprocket tooth displacement structure (28) has a second sliding surface (28a) extending in the first axial direction (DA). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to one of claims 1 to 4, wherein the first sprocket tooth displacement structure (26) includes at least one first sliding element (32) arranged within the inner cavity (SA) of the crankshaft (20). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 5, wherein the at least one first sliding element (32) comprises a plurality of first sliding elements (32A). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 6, wherein the plurality of first sliding elements (32A) are arranged such that the plurality of first sliding elements (32A) are spaced apart from each other in the first axial direction (DA). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to any one of claims 1 to 7, wherein the second chainring tooth displacement structure (28) includes a sliding hole (40) provided on the crank arm (22) and a second sliding axis (42, 42A, 42B, 42C) configured to pass through the sliding hole (40); and the second sliding axis (42, 42A, 42B, 42C) is coupled to the chainring mounting element (24) and the bicycle chainring (12). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 8, wherein the second sprocket tooth displacement structure (28) further comprises a tubular element (44) with a tubular hole (44a); and the second sliding axis (42, 42A, 42B, 42C) is configured to pass through the tubular hole (44a). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 9, wherein the tubular element (44) is configured to be positioned in the first axial direction (DA) between the chain wheel mounting element (24) and the bicycle chain wheel (12) in an assembled state of the bicycle crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F). The crank arrangement (10, 10A, 10B, 10C, 100, 10E, 10F) according to one of claims 8 to 10, wherein the second sliding axis (42, 42A, 42B, 42C) includes a first axis element (46) and a second axis element (48) coupled to the first axis element (46). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 11, wherein the first axle element (46) is configured to guide in a second axial direction (DB) with respect to a central axis (CC) of the second sliding axis (42, 42A, 42B, 42C) through a through hole (50A) provided on one of the chainring mounting element (24) and the bicycle chainring (12); and the second axle element (48) is configured to guide in the second axial direction (DB) through a through hole (50B) provided on the other of the chainring mounting element (24) and the bicycle chainring (12). The crank assembly (10, 10A, 10B, 10C, 100, 10E, 10F) according to claim 11 or 12, wherein the first axle element (46) has a first axle end (46a) and, in a second axial direction (DB) with respect to a central axis (CC) of the second sliding axis (42, 42B, 42C, 42D) opposite the first axle end (46a), a second axle end (46b); the second axle element (46) has a third axle end (48a) and, in the second axial direction (DB) opposite the third axle end (48a), a fourth axle end (48b); a first threaded section (46c) is provided on the first axle end (46a) of the first axle element (46); and a second threaded section (48c) is provided at the third axis end (48a) of the second axis element (48) and is configured to engage thread-wise with the first threaded end (48c). The crank assembly (10, 10A, 10B, 10C, 100, 10E, 10F) according to claim 13, wherein a first projection (46d) is provided at the second axle end (46b) of the first axle element (46) to extend radially outward from the second axle end (46b) with respect to the central axis (CC) of the second sliding axle (42, 42A, 42B, 42C); a second projection (48d) is provided at the fourth axle end (48b) of the second axle element (48) to extend radially outward from the fourth axle end (48b) with respect to the central axis (CC) of the second sliding axle (42, 42A, 42B, 42C); the first projection (46d) is configured to engage in the second axial direction (DB) with one of the sprocket mounting elements (24) and the bicycle chainring (12); and the second projection (48d) is configured to abut in the second axial direction (DB) against the other of the chainring mounting element (24) and the bicycle chainring (12). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 14, wherein the first projection (46d) extends circumferentially around the second axis end (46b) of the first axis element (46) with respect to the central axis (CC) of the second sliding axis (42, 42A, 42B, 42C); and the second projection (48d) extends circumferentially around the fourth axis end (48b) of the second axis element (48) with respect to the central axis (CC) of the second sliding axis (42, 42A, 42B, 42C). The crank arrangement (10, 10A, 10B, 10C, 10D, 10E, 10F) according to one of claims 11 to 15, wherein the first axle element (46) has a first tool engagement section (46e); and the second axle element (48) has a second tool engagement section (48e). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to any one of claims 1 to 16, further comprising: a displacement stroke adjustment structure (56) configured to adjust an entire displacement stroke of the bicycle chainring (12) with respect to the crankshaft (20) and the crank arm (22). The crank assembly (10, 10A, 10B, 10C, 10D, 10D, 10E, 10F) according to claim 17, wherein the displacement stroke adjustment structure (56) comprises: a threaded hole (58) provided on one of the chainring mounting element (24) and the crank arm (22); and a threaded element (60) configured to engage with the threaded hole (58), to be displaceable within the threaded hole (58), and to contact the other of the chainring mounting element (24) and the crank arm (22). The crank assembly (10, 10A, 10B, 10C, 10D, 10D, 10E, 10F) according to claim 18, wherein the displacement stroke adjustment structure (56) further includes an elastic element (62) configured to be provided on the other of the sprocket mounting element (24) and the crank arm (22) and to come into contact with the threaded element (60). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to any one of claims 1 to 19, wherein the first sprocket tooth displacement structure (26) and the second sprocket tooth displacement structure (28) are configured to displace the bicycle sprocket (12) in the first axial direction (DA) with respect to the crankshaft (20) and the crank arm (22). A bicycle crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F), comprising: a crankshaft (20) with an inner cavity (SA) and a pivot axis (CA); a crank arm (22) coupled to one end of the crankshaft (20); a sprocket mounting element (24) to which a bicycle sprocket (12) is attached; a sprocket tooth displacement structure (26) arranged at least partially within the inner cavity (SA) of the crankshaft (20); and a torque transmission structure (28) which is arranged and configured outside the inner cavity (SA) of the crankshaft (20) to transmit pedaling torque between the crankshaft (22) and the sprocket mounting element (24); wherein the sprocket mounting element (24) is configured to be displaceable in a first axial direction (DA) with respect to the rotational center axis (CA) through the sprocket tooth displacement structure (26) with respect to the crankshaft (20) and the crank arm (22). The crank assembly (10, 10A, 10B, 10C, 10D, 10E, 10F) according to claim 21, wherein the sprocket tooth displacement structure (26) is configured to displace the bicycle sprocket (12) in the first axial direction (DA) with respect to the crankshaft (20) and the crank arm (22).

Images