TWI503258B - A bicycle sprocket - Google Patents

Description

Bicycle sprocket

The present invention is a sprocket, and more particularly to a bicycle sprocket provided for driving a bicycle.

In the bicycle, a front sprocket and a rear sprocket for transmitting the rotation of the crankshaft to the rear wheel are provided. The front sprocket system rotates integrally with the crankshaft, and the rotation of the crankshaft is transmitted to the rear sprocket provided on the rear wheel via the chain. In the bicycle sprocket including the front sprocket and the rear sprocket, a technique for reducing the weight and maintaining rigidity has been conventionally known (for example, Japanese Patent No. 12881097). A conventional bicycle sprocket includes a metal tooth portion and a synthetic resin base portion. The base portion is attached to a rotary drive portion of the bicycle.

In the conventional bicycle sprocket, since the tooth portion required to maintain rigidity is made of metal and the base portion is made of synthetic resin, it is possible to reduce the weight of the bicycle sprocket and maintain rigidity.

An object of the present invention is to ensure the required rigidity and further reduce the weight in the bicycle sprocket in which the tooth portion is made of metal.

The bicycle sprocket according to the present invention includes a metal tooth portion and a non-metal base portion. The base portion has a surface, a back surface, and a cavity portion, and supports the tooth portion.

In this bicycle sprocket, the required rigidity can be ensured by the metal tooth portion. Further, since the base portion is made of a non-metal and the base portion has a cavity portion, the base portion can be further reduced in weight. Therefore, in the bicycle sprocket in which the tooth portion is made of metal, the required rigidity is secured and further weight reduction is performed.

It is also possible to have a covering member that covers the base portion. When the base member is covered by the covering member, for example, the covering member is made of a lightweight metal, and even if the base portion is made of synthetic resin, the rigidity of the bicycle sprocket can be effectively ensured by the covering member, and further weight reduction can be achieved. .

Preferably, the covering member is disposed on the surface of the base portion. In this case, it is possible to enhance the design feeling of the surface which becomes the outer side surface of the sprocket.

A bicycle sprocket according to another aspect of the present invention includes a metal tooth portion, a non-metal base portion, and a covering member. The base portion has at least one through hole penetrating the surface and the back surface and supporting the tooth portion. The cover member covers the surface of the base portion.

In this bicycle sprocket, the required rigidity can be ensured by the metal tooth portion. Further, since the base portion is made of a non-metal and the base portion has a through hole, the base portion can be further reduced in weight. Furthermore, the surface side of the through hole is covered by the covering member. Therefore, the through hole is reinforced by the covering member, and in the bicycle sprocket in which the tooth portion is made of metal, the required rigidity is secured and further weight reduction is performed.

According to the present invention, the required rigidity can be ensured by the metal tooth portion. Further, since the base portion is made of synthetic resin and the base portion has a cavity portion, the base portion can be further reduced in weight. Therefore, in the bicycle sprocket whose teeth are made of metal, the required rigidity is ensured and further Lightweight.

<First Embodiment>

In the first embodiment, the right crankshaft 10 for a bicycle according to the first embodiment of the present invention includes a crank portion 12, a first sprocket 14 which is a bicycle sprocket according to an embodiment of the present invention, and a second sprocket. 16. The first sprocket 14 and the second sprocket 16 are front sprockets. The crankshaft portion 12 includes a crank arm 20 that extends in the radial direction and a sprocket mounting portion 22 that is formed integrally with the crank arm 20 . The front end of the crank arm 20 has a pedal mounting portion 20a, and the base end of the crank arm 20 has a crank mounting portion 20b. The sprocket mounting portion 22 has a plurality of (for example, four) mounting arms 22a extending radially around the crank mounting portion 20b, and a sprocket fixing portion 22b provided at a front end portion of each of the mounting arms 22a. A through hole 22c is formed in the sprocket fixing portion 22b, and a fixing screw member (for example, a bolt member) 24 (see the fourth drawing) penetrates the through hole 22c.

The number of teeth of the first sprocket 14 is larger than that of the second sprocket 16 as shown in the second, third, fourth and fifth figures. The first sprocket 14 includes a metal tooth portion 30, a non-metallic base portion 32 that supports the tooth portion 30, and a covering member 34. The metal tooth portion 30 is made of, for example, iron or a lightweight metal having a small specific gravity such as titanium or aluminum. In this embodiment, the tooth portion 30 is made of titanium. The tooth portion 30 has a ring shape, and the outer peripheral portion of the tooth portion 30 has a plurality of sprocket teeth 30a, and these sprocket teeth 30a are arranged in the circumferential direction at intervals. The inner peripheral portion of the tooth portion 30 has a joint portion 30b joined to the base portion 32 as shown in the fourth figure, and the joint portion 30b is He is partly thin. A plurality of (for example, five) spikes 40 are attached to the back side of the tooth portion 30, and the spikes 40 are used when the chain of the shifting operation is released from the sprocket.

As shown in the fourth and fifth figures, the base portion 32 is an annular member joined to the tooth portion 30 by an integral molding method using a mold such as outsert molding or insert molding. . The non-metal base portion 32 is made of a synthetic resin such as a polyamide resin, a polyacetal resin, or a carbon fiber reinforced resin. In this embodiment, the base portion 32 is made of carbon fiber reinforced resin. The base portion 32 is configured to support the tooth portion 30. The base portion 32 has a surface 32a, a back surface 32b, a cavity portion 32c, a plurality of (for example, four) crank arm mounting portions 32d, a plurality of (for example, four) nut members 36, and a plurality of (for example, six) chain guides 38. . The surface 32a of the base portion 32, as shown in the fourth figure, is covered by the covering member 34. The surface 32a is a side exposed to the outside when the first sprocket 14 is attached to the bicycle. The back surface 32b is disposed on the side of the second sprocket 16 to be exposed. A recessed annular recess 32e is formed in the outer peripheral portion between the surface 32a and the back surface 32b, and the recess 32e is joined to the joint portion 30b of the tooth portion 30.

The cavity portion 32c is formed in a ring shape extending in the circumferential direction between the surface 32a and the back surface 32b. The cavity portion 32c is formed, for example, by a gas ejected from a mold at the time of molding. On the surface 32a side of the cavity portion 32c, as shown in Fig. 5, a gas hole 32f for discharging gas from the mold to the inside of the base portion 32 is formed. At least a part of the cavity portion 32c is disposed radially outward of the crank arm attachment portion 32d.

The four crank arm mounting portions 32d are attached to the mounting arm 22a Minute. As shown in the second and third figures, the crank arm attachment portion 32d is formed on the inner peripheral portion of the base portion 32 and protrudes inward in the radial direction. The four crank arm attachment portions 32d are disposed in the circumferential direction at intervals to be attachable to the attachment arm 22a. In the first embodiment, the four crank arm attachment portions 32d are arranged at equal intervals, but they may be arranged such that the intervals between the adjacent crank arm attachment portions 32d are different.

As shown in the fourth figure, the plurality of nut members 36 are metal substantially cylindrical members that are respectively embedded in the four crank arm attachment portions 32d. The inner peripheral surface of the nut member 36 has a female screw portion 36a, and the female screw portion 36a is screwed to the screw member 24. Further, an axial center alignment portion 36b is formed on the outer peripheral surface of the distal end, and the axial alignment portion 36b is fitted to the through hole 22c to align the axial center of the first sprocket 14. The nut member 36 is embedded in the crank arm attachment portion 32d when the base portion 32 is molded.

As shown in the third figure, the chain guide 38 is configured to guide the unillustrated chain that is engageable with the tooth portion 30 during movement to move between the first sprocket 14 and the second sprocket 16. A plurality of chain guides 38 are recessed in an appropriate shape to form the back surface 32b of the base portion 32.

The cover member 34 is, for example, an aluminum member that covers the base portion 32. In this embodiment, the covering member 34 is disposed on the surface 32a and covers the surface 32a of the base portion 32. The covering member 34 is formed to cover the surface 32a of the base portion 32 by, for example, press working. The covering member 34 is fixed to the base portion 32 by, for example, a suitable fixing means. As shown in the second, fourth, and fifth figures, the cover member 34 covers the surface 32a of the base portion 32, and includes a crank arm attachment portion 32d from the outer peripheral side to the inner peripheral side. In the crank arm mounting portion 32d, three of the crank arm mounting portions 32d are covered. The side does not include the inner peripheral portion close to the mounting arm 22a. The portion from the outer peripheral portion of the surface 32a to the inner peripheral portion facing the rear surface 32b is covered in a portion excluding the crank arm mounting portion 32d of the base portion 32. Therefore, when the first sprocket 14 is viewed from the outside, the portion including the tooth portion 30 of the first sprocket 14 is completely covered by the covering member 34.

The second sprocket 16 is made of, for example, aluminum, and is fixed to the mounting arm 22a by the screw member 24 together with the first sprocket 14. Here, the first sprocket 14 is attached to the outer side surface of the mounting arm 22a (the surface on the right side of the fourth drawing), and the second sprocket 16 is attached to the inner side surface of the mounting arm 22a (the surface on the left side of the fourth drawing) .

In the first sprocket 14 of the first embodiment configured as described above, the required rigidity can be ensured by the metal tooth portion 30. Further, since the base portion 32 is made of a non-metal such as synthetic resin, and the base portion 32 has the cavity portion 32c, the base portion 32 can be further reduced in weight. Therefore, the rigidity required for the first sprocket 14 can be ensured and the first sprocket 14 can be further reduced in weight.

Since the metal cover member 34 covering the base portion 32 is provided, even if the base portion 32 is made of synthetic resin, the rigidity of the first sprocket 14 can be effectively ensured by the cover member 34, and further weight reduction can be achieved. Furthermore, by the cover member 34, the design feeling of the first sprocket 14 can be improved.

Since the covering member 34 is disposed on the surface 32a of the base portion 32, the design of the surface of the first sprocket 14 on the side exposed when the bicycle is exposed can be improved.

<Second embodiment>

In the first embodiment, the weight is reduced by the cavity portion 32c. In the second embodiment, the weight is reduced by the through hole 132c. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

As shown in the sixth, seventh, and eighth figures, the first sprocket 114 includes a metal tooth portion 130, a non-metal base portion 132, a supporting tooth portion 130, and a covering member 134. The metal tooth portion 130 is made of, for example, iron or a lightweight metal having a small specific gravity such as titanium or aluminum. In this embodiment, the tooth portion 130 is made of titanium. The tooth portion 130 has a ring shape, and the outer peripheral portion of the tooth portion 130 has a plurality of sprocket teeth 130a, and these sprocket teeth 130a are arranged in the circumferential direction at intervals. The inner peripheral portion of the tooth portion 130 has a joint portion 130b thinner than the other portions as shown in the eighth diagram, and the joint portion 130b is joined to the base portion 132. A plurality of (for example, five) spikes 40 are attached to the back side of the tooth portion 130, and the spikes 40 are used when the chain of the shifting operation is disengaged from the sprocket.

As shown in the seventh and eighth drawings, the base portion 132 is an annular member that is joined to the tooth portion 130 by an integral molding method using a mold such as an insert molding or an insert molding. The non-metal base portion 132 is made of a synthetic resin such as a polyamide resin, a polyacetal resin, or a carbon fiber reinforced resin. In this embodiment, the base portion 132 is made of carbon fiber reinforced resin. The base portion 132 is configured to support the tooth portion 130. The base portion 132 has a surface 132a, a back surface 132b, a through hole 132c, a plurality of (for example, four) crank arm mounting portions 132d, and a plurality of (for example, four) nut members 136. The surface 132a of the base portion 132, as shown in the eighth figure, is covered by the covering member 134. The surface 132a is a side exposed to the outside when the first sprocket 114 is attached to the bicycle. The back side 132b is equipped It is exposed on the side of the second sprocket 116. A recessed annular recess 132e is formed in an outer peripheral portion between the surface 132a and the back surface 132b, and the recess 132e is joined to the joint portion 130b of the tooth portion 130.

The through hole 132c penetrates the surface 132a and the back surface 132b. The through hole 132c is integrally formed when molded by a mold. The through hole 132c provided in the portion where the crank arm attachment portion 132d is disposed extends inward in the radial direction from the other through holes 132c.

The four crank arm mounting portions 132d are portions that are attached to the mounting arms not shown. As shown in FIG. 6 and FIG. 7 , the crank arm attachment portion 132 d is formed on the inner peripheral portion of the base portion 132 and protrudes inward in the radial direction. The four crank arm attachment portions 132d are arranged in the circumferential direction at intervals. In the second embodiment, the four crank arm mounting portions 132d are alternately arranged at a wide interval and a narrow interval. Of course, it is also possible to arrange at equal intervals like the four crank arm mounting portions 132d of the first embodiment.

The plurality of nut members 136 have substantially the same structure as the nut members 36 of the first embodiment shown in the fourth embodiment.

The cover member 134 is, for example, an aluminum member that covers the surface 132a of the base portion 132. The cover member 134 is formed to cover the surface 132a of the base portion 132 by, for example, press working. The covering member 134 is fixed to the base portion 132 by, for example, a suitable fixing means, for example. As shown in the sixth and eighth figures, the covering member 134 covers the surface 132a of the base portion 132, and includes a crank arm mounting portion 132d from the outer peripheral side to the inner peripheral side. The crank arm attachment portion 132d covers all three sides of the crank arm attachment portion 132d, and does not include an inner peripheral portion that is close to the attachment arm. Covering the surface 132a from the portion of the crank arm mounting portion 132d that does not include the base portion 132 The outer peripheral portion faces the inner peripheral portion of the rear surface 132b. Therefore, when the first sprocket 114 is viewed from the outside, the portion including the tooth portion 130 of the first sprocket 114 is completely covered by the covering member 134.

In the second embodiment, the first sprocket 114 having the above configuration can ensure the required rigidity by the metal tooth portion 130. Further, since the base portion 132 is made of a non-metal such as synthetic resin, and the base portion 132 has the through hole 132c, the base portion 132 can be further reduced in weight. Therefore, the rigidity required for the first sprocket 114 and the further weight reduction of the first sprocket 114 can be ensured.

Since the metal cover member 134 covering the base portion 132 is provided, even if the base portion 132 is made of synthetic resin and the through hole 132c is exposed on the back side 132b, the rigidity of the first sprocket 114 can be effectively ensured by the cover member 134. Achieve further lightweighting. Furthermore, since the through hole 132c is covered by the covering member 134, the design feeling of the first sprocket 114 can be improved.

Since the covering member 134 is disposed on the surface 132a of the base portion 132, the design of the surface of the first sprocket 114 on the exposed side when the first sprocket 114 is attached to the bicycle can be improved.

<Other Embodiments>

The first and second embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

(a) In the first embodiment, the cavity portion 32c is formed by a gas, but the method of forming the cavity portion is not limited thereto.

In the ninth diagram, in the first sprocket 214, for example, gas can be stored The balloon 242 is disposed inside when the base portion 232 is molded, and the balloon 242 is inflated to form a cavity portion 232c. The balloon 242 is left in the cavity portion 232c after the internal gas is released after molding. On the surface 232a side of the base portion 232, a bleed hole 232f for venting air in the mold when the balloon 242 is inflated is formed.

Further, in the tenth diagram, in the first sprocket 314, the base portion 332 is divided into two portions, and a cavity portion 332c is disposed therebetween. Specifically, the base portion 332 has a first base member 344 and a second base member 346 which can form a cavity portion 332c together with the first base member 344. For example, the first base member 344 is integrally joined to the tooth portion 30. The second base member 346 is fixed to the first base member 344 by an appropriate fixing means such as screwing or the like.

(b) In the first and second embodiments, the tooth portions 30 and 130 are made of titanium, but the tooth portion 30 may be made of aluminum or iron.

(c) In the first and second embodiments, the base portions 32 and 132 are made of carbon fiber reinforced resin, but the present invention is not limited thereto. The base portion may be made of other non-metallic materials such as polyamide resin or polyacetal resin.

(d) In the first embodiment, the cover member 34 is provided. However, in the case where the base portion 32 is made of a non-metal such as a carbon fiber reinforced resin that can obtain a high-grade appearance, the cover member may not be provided.

(e) In the first and second embodiments, the present invention will be described by taking the front sprocket provided on the right crankshaft as an example. However, any sprocket can be applied to the bicycle sprocket. For example, the present invention is also applicable to a rear sprocket that is mounted on a rear hub.

(f) In the first and second embodiments, the cover member 34 is not disposed (or covered), that is, the back surface 32b (or the back surface 132b) of the base portion 32 (or the base portion 132) on the side where the bicycle is not exposed. Component 134), but the invention is not limited thereto. It is also possible to configure the cover part on the back.

(g) In the first embodiment, although one hollow portion 32c is formed in a ring shape extending in the circumferential direction, the present invention is not limited thereto. For example, as shown in the eleventh diagram, a plurality of (for example, eight) reinforcing ribs 432g arranged at intervals in the circumferential direction may be formed, and a plurality of (for example, eight) hollow portions 432c may be intermittently formed in the circumferential direction. . In this case, since the reinforcing ribs 432g are formed between the adjacent hollow portions 432c, the rigidity can be more effectively ensured in the first sprocket 414.

10‧‧‧Bicycle right crankshaft

12‧‧‧Crankshaft

14, 114, 214, 314, 414‧‧‧ first sprocket (an example of a bicycle sprocket)

16, 116‧‧‧Second sprocket

20‧‧‧ crank arm

20a‧‧‧Pedal installation

20b‧‧‧Crankshaft installation

22‧‧‧Sprocket installation

22a‧‧‧Installation arm

22b‧‧‧Sprocket fixing

22c, 132c‧‧‧through holes

24‧‧‧ screw parts

30, 130‧‧‧ teeth

30a, 130a‧‧‧ sprocket

30b, 130b‧‧‧ joints

32, 132, 232, 332‧‧‧ base body

32a, 132a, 232a‧‧‧ surface

32b, 132b‧‧‧ back

32c, 232c, 332c, 432c‧‧‧ cavity

32d, 132d‧‧‧ crankshaft arm installation

32e, 132e‧‧‧ recess

32f‧‧‧ gas hole

34, 134‧‧‧ Covering parts

36, 136‧‧‧ nut parts

36a‧‧‧ Female thread

36b‧‧‧Axis alignment

38‧‧‧Chain guides

40‧‧‧ spikes

232f‧‧‧ vent hole

242‧‧‧ Balloon

344‧‧‧First base parts

346‧‧‧Second base parts

432g‧‧‧ reinforcing ribs

First Fig.: Front view of a right crankshaft according to a first embodiment of the present invention.

Second drawing: A front view of a bicycle sprocket according to a first embodiment of the present invention.

Third picture: its rear view.

Fourth: A cross-sectional view taken from the cut line IV-IV of the second figure.

Fig. 5 is a cross-sectional view taken from the cut line V-V of the second figure.

Fig. 6 is a view corresponding to the second diagram of the second embodiment.

Fig. 7 is a view corresponding to the third diagram of the second embodiment.

Fig. 8 is a cross-sectional view taken from the cut line VIII-VIII of the seventh figure.

Fig. 9 is a view corresponding to the fifth figure of another embodiment.

Fig. 10 is a view corresponding to the fifth diagram of still another embodiment.

Fig. 11 is a view corresponding to the third figure of still another embodiment.

14‧‧‧First sprocket

16‧‧‧Second sprocket

22a‧‧‧Installation arm

22c‧‧‧through hole

24‧‧‧ screw parts

30‧‧‧ teeth

30a‧‧‧Sprocket teeth

30b‧‧‧Interface

32‧‧‧Base Department

32a‧‧‧ surface

32b‧‧‧Back

32c‧‧·The Ministry of the Cavity

32d‧‧‧ crankshaft arm installation

32e‧‧‧ recess

34‧‧‧ Covering parts

36‧‧‧ Nut parts

36a‧‧‧ Female thread

36b‧‧‧Axis alignment

Claims (34)

A bicycle sprocket comprising: a metal tooth portion; and a non-metal base portion having a surface, a back surface, and a cavity portion, and supporting the tooth portion; the base portion being joined to the tooth portion by an integral molding method . The bicycle sprocket according to claim 1, further comprising: a covering member covering the base portion. The bicycle sprocket according to claim 2, wherein the covering member is disposed on the surface of the base portion. The bicycle sprocket according to claim 3, wherein the covering member is made of metal. The bicycle sprocket according to claim 4, wherein the cover member comprises aluminum. The bicycle sprocket according to claim 1, wherein the base portion is formed of a single member. The bicycle sprocket according to claim 1, wherein the base portion has a first base member and a second base member that can form the cavity portion together with the first base member. The bicycle sprocket according to claim 1, wherein the base portion is made of carbon fiber reinforced resin. The bicycle sprocket according to claim 1, wherein the base portion has a crank arm mounting portion. The bicycle sprocket according to claim 9, wherein the base portion has a nut member embedded in the crank arm Installation department. The bicycle sprocket according to claim 9, wherein at least a part of the hollow portion is disposed radially outward of the crank arm mounting portion. The bicycle sprocket according to claim 1, wherein the base portion has a chain guide that guides a chain engageable with the tooth portion. The bicycle sprocket according to claim 1, wherein the tooth portion comprises iron. The bicycle sprocket according to claim 1, wherein the tooth portion comprises aluminum. The bicycle sprocket according to claim 1, wherein the tooth portion comprises titanium. The bicycle sprocket according to claim 1, wherein the cavity portion is formed in a ring shape continuous in the circumferential direction. The bicycle sprocket according to claim 1, wherein the plurality of the hollow portions are intermittently formed in the circumferential direction. The bicycle sprocket according to claim 17, wherein the reinforcing rib is formed between the adjacent hollow portions. The bicycle sprocket according to claim 1, wherein the bicycle sprocket is a front sprocket. The bicycle sprocket according to claim 1, wherein the bicycle sprocket is a rear sprocket. A bicycle sprocket comprising: a metal tooth portion; a non-metal base portion having a surface, a back surface, and at least a continuous hole penetrating the surface and the back surface, and supporting the tooth portion; And the covering member covers the surface of the base portion; the base portion is joined to the tooth portion by an integral molding method. The bicycle sprocket according to claim 21, wherein the through holes are provided in plural at intervals in the circumferential direction. The bicycle sprocket according to claim 21, wherein at least one of the through holes extends inward in the radial direction of the other through holes. The bicycle sprocket according to claim 21, wherein the covering member is made of metal. The bicycle sprocket according to claim 24, wherein the cover member comprises aluminum. The bicycle sprocket according to claim 21, wherein the base portion is made of carbon fiber reinforced resin. The bicycle sprocket according to claim 21, wherein the base portion has a crank arm mounting portion. The bicycle sprocket according to claim 27, wherein the base portion has a nut member and is embedded in the crank arm attachment portion. The bicycle sprocket according to claim 21, wherein the tooth portion comprises iron. The bicycle sprocket according to claim 21, wherein the tooth portion comprises aluminum. The bicycle sprocket according to claim 21, wherein the tooth portion comprises titanium. The bicycle sprocket according to claim 21, wherein the plurality of through holes are intermittently formed in the circumferential direction. The bicycle sprocket according to claim 21, wherein the bicycle sprocket is a front sprocket. The bicycle sprocket according to claim 21, wherein the bicycle sprocket is a rear sprocket.