This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2005-306677. The entire disclosure of Japanese Patent Application No. 2005-306677 is hereby incorporated herein by reference.
1. Field of the Invention
This invention generally relates to a bicycle freewheel to be mounted to a hub of a bicycle. More specifically, the present invention relates to a bicycle freewheel with a one-way clutch in which the lost motion of the one-way clutch is minimized.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. The bicycle drive train has been extensively redesigned.
In many bicycles with multiple speeds, a wheel of the bicycle, typically the rear wheel, is provided with a freewheel that is arranged on a hub of the wheel. The freewheel is arranged either as an integral part of the hub body or as a separate member. The freewheel usually has a one-way clutch function whereby it only transfers torque in one direction. One well-known conventional type of freewheel is provided with a pawl-type one-way clutch that includes ratchet teeth and clutch pawls configured to mesh with the ratchet teeth. In pawl-type one-way clutches, the clutch pawls are forced (spring loaded) toward engaging positions where they mesh with the ratchet teeth. Pawl-type one-way clutches have a characteristic called an “angle of lost motion” which indicates the timing delay with which the clutch pawls reach the engagement angle and mesh with the ratchet teeth. For example, if there is one clutch pawl and the angular distance between adjacent ratchet teeth (i.e., the angular pitch of the ratchet teeth) is 20°, then a maximum possible angle of lost motion of 20° exists between the current position and the position where the clutch pawl meshes with the ratchet tooth.
There is a demand for reducing the angle of lost motion of the one-way clutch as much as possible in the case of road racing bicycles, mountain bikes, and other competition oriented bicycles that are used under such severe conditions as rapid acceleration, extreme variations of the slope of the riding surface, and sharp cornering. Competition oriented bicycles used under severe conditions also require a freewheel that can withstand large loads because the freewheels of such bicycles are subjected to conditions that require a high degree of strength and a high resistance to impact. There are known freewheel configurations that have a small angle of lost motion and satisfy the aforementioned strength requirements (e.g., European Patent Application Publication No. 0777060).
A conventional freewheel structure is disclosed in European Patent Application Publication No. 0777060 (see,
In such conventional freewheels, the clutch pawls are arranged such that the clutch pawls are spaced apart in the circumferential direction so as to have an angular phase difference with respect to the ratchet teeth. As a result, the clutch pawls are enabled to mesh with the ratchet teeth after moving through a smaller rotational angle than the angular pitch of the ratchet teeth. In other words, the angle of lost motion is reduced and the angular interval traversed in order for the clutch pawls to mesh with the ratchet teeth is shortened. In addition to arranging a one-way clutch between the inner tubular member and the outer tubular member, the freewheel can be enabled to bear large loads by providing bearing assemblies between the inner tubular member and outer tubular member on both sides of the one-way clutch.
Since the conventional freewheel structure described above has one force applying member for each clutch pawl, the internal structure of the freewheel becomes complex and the process of assembling the one-way clutch becomes troublesome in cases where the space inside the freewheel is greatly limited.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved bicycle freewheel. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
One object of the present invention is to provide a freewheel having a plurality of clutch pawls that has a small angle of lost motion, a simple internal structure, and a high degree of strength.
In accordance with a first aspect of the present invention, the foregoing object can basically be attained by providing a bicycle freewheel that basically comprises an inner tubular member, an outer tubular member, at least one bearing assembly and a one-way clutch. The inner tubular member is configured to be coupled to a bicycle hub. The outer tubular member is arranged around an outer side circumference of the inner tubular member. The at least one bearing assembly is disposed between the inner tubular member and the outer tubular member to couple the outer tubular member to the inner tubular member in a rotatable manner such that the outer tubular member rotates freely with respect to the inner tubular member. The one-way clutch includes a plurality of ratchet teeth, at least three clutch pawls and at least one force applying member. The ratchet teeth are provided on an internal circumferential surface of the outer tubular member. The at least three clutch pawls are circumferentially spaced apart around the outer side circumference of the inner tubular member and each freely movable between an engagement position in which the clutch pawls engage the ratchet teeth to transmit torque from the outer tubular member to the inner tubular member and a disengagement position in which the clutch pawls are disengaged from the ratchet teeth. The at least one force applying member applies a force against at least two of the clutch pawls in a direction oriented away from the outer side circumference of the inner tubular member and toward the engagement position. The clutch pawls are arranged such that an angle of lost motion of the freewheel is 10° or less.
With this freewheel, when the outer tubular member is rotated, the outer tubular member undergoes not more than 10° of lost motion before the rotation of the outer tubular member begins being transferred to the inner tubular member by the one-way clutch and the hub, i.e., the wheel, begins to rotate. In order to assemble the freewheel, first the clutch pawls are arranged on the inner tubular member. From this state, the force applying member is installed in the inner tubular member so as to exert a force against at least two of the n clutch pawls in a direction oriented away from the external circumference of the inner tubular member and toward the engagement position. Thus, since the force applying member applies an outwardly force against two or more of the n clutch pawls simultaneously, two or more clutch pawls can be urged toward the engagement position simultaneously by simply installing one or more force applying member in the inner tubular member. As a result, a freewheel can be obtained which has a small angle of lost motion, a simple internal structure, and a high degree of strength.
A bicycle freewheel in accordance with a second aspect of the present invention is a bicycle freewheel according to the first aspect of the present invention, wherein the at least one bearing assembly includes a first bearing assembly and a second bearing assembly with the first and second bearing assemblies being spaced apart from each other in an axial direction of the freewheel, and the ratchet teeth and the clutch pawls being disposed between the first and second bearing assemblies. With this bicycle freewheel, since the one-way clutch is arranged between the bearing assemblies, the amount of rotational play is smaller during power transmission and larger loads can be withstood.
A bicycle freewheel in accordance with a third aspect of the present invention is a bicycle freewheel according to the first or second aspects of the present invention, wherein the outer tubular member includes a sprocket mounting part on an external circumferential surface of the outer tubular member, the sprocket mounting part being configured to mount a sprocket thereon such that the sprocket rotates as an integral unit with the outer tubular member. This aspect of the invention makes it possible to provide a freewheel having a high degree of strength on which a sprocket can be mounted.
A bicycle freewheel in accordance with a fourth aspect of the present invention is a bicycle freewheel according to anyone of the first to third aspects of the present invention, wherein two adjacent ones of the clutch pawls are angular spaced apart by a first angular distance that is larger than other angular distances between any other adjacent pair of the clutch pawls among the clutch pawls. With this bicycle freewheel, the angular distance between the first clutch pawl and the last (nth) clutch pawl is larger than the angular distance between any other pair of adjacent clutch pawls. As a result, the degree of design freedom and the degree of arrangement freedom are increased with respect to the force applying members.
A bicycle freewheel in accordance with a fifth aspect of the present invention is a bicycle freewheel according to the fourth aspect of the present invention, wherein the other angular distances between each of the other adjacent pairs of the clutch pawls among the clutch pawls are equal to one another. With this bicycle freewheel, the strength is maintained in a well-balanced fashion and variation among the forces applied against the clutch pawls by the force applying member(s) can be suppressed.
A bicycle freewheel in accordance with a sixth aspect of the present invention is a bicycle freewheel according to anyone of the first to fifth aspects of the present invention, wherein the clutch pawls and the ratchet teeth are configured and arranged such that a maximum number of the clutch pawls that simultaneously mesh with the ratchet teeth is one less than a total number of the clutch pawls. With this bicycle freewheel, the angle of lost motion can be reduced without increasing the number of clutch pawls.
A bicycle freewheel in accordance with a seventh aspect of the present invention is a bicycle freewheel according to the sixth aspect of the present invention, wherein the maximum number of the clutch pawls that simultaneously mesh with the ratchet teeth is two. With this bicycle freewheel, the angle of lost motion can be reduced while ensuring sufficient rigidity.
A bicycle freewheel in accordance with an eighth aspect of the present invention is a bicycle freewheel according to the sixth aspect of the present invention, wherein the maximum number of the clutch pawls that simultaneously mesh with the ratchet teeth is one. With this bicycle freewheel, the angle of lost motion can be reduced as much as possible without increasing the original number of clutch pawls.
A bicycle freewheel in accordance with a ninth aspect of the present invention is a bicycle freewheel according to anyone of the first to eighth aspects of the present invention, wherein each of the clutch pawls includes a claw-like part configured to selectively mesh with the ratchet teeth, and a spring engaging part arranged on one side of the claw-like part and engaged with the force applying member. With this bicycle freewheel, there is a higher degree of freedom regarding the shape of the claw-like part because the claw-like part and the spring engaging part of each clutch pawl are provided separately.
A bicycle freewheel in accordance with a tenth aspect of the present invention is a bicycle freewheel according to anyone of the first to eighth aspects of the present invention, wherein the at least one force applying member includes a first force applying member and a second force applying member, with the first and second force applying members being arranged to apply forces to alternate ones of the clutch pawls, respectively. With this bicycle freewheel, the forces applied by the force applying members can be stabilized even when the number of clutch pawls is large because the clutch pawls can be divided into two groups, each group being forced by a different force applying member. As a result, the plurality of clutch pawls can be urged toward the engagement position in a stable manner.
A bicycle freewheel in accordance with an eleventh aspect of the present invention is a bicycle freewheel according to the tenth aspect of the present invention, wherein each of the clutch pawls includes a claw-like part configured to selectively mesh with the ratchet teeth, and a spring engaging part arranged on a side of the claw-like part and engaged with one of the first and second force applying members, with the spring engaging parts of adjacent ones of the clutch pawls being provided on opposite sides of respective ones of the claw-like parts. With this bicycle freewheel, the forces applied by the force applying members are stabilized and the degree of freedom regarding the design of the claw-like parts is increased.
With this invention, since the force applying member applies an outwardly force (i.e., outward from the inner tubular member) against two or more clutch pawls simultaneously, a number n of clutch pawls can be urged toward the engagement position simultaneously by simply installing one or more force applying member in the inner tubular member. As a result, a freewheel can be provided which has a small angle of lost motion, a simple internal structure, and a high degree of strength.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.
Referring now to the attached drawings which form a part of this original disclosure:
Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Referring initially to
As shown in
The hub axle 40 is a quick-release hub axle having a hollow axle main body 44 that has a right-hand (for example) external thread 44a arranged to span from a position slightly axially inward of the portion where the first bearing assembly 42a is installed to the axially outward end of the axle main body 44. The hollow axle main body 44 also has a right-hand external thread 44b that spans from a position slightly axially inward of the portion where the freewheel 43 is mounted to the axially outward end of the axle main body 44. The hub axle 40 also has a quick-release hub rod 44c, an adjustment nut 45 and a cam lever 46. The quick-release hub rod 44c is arranged so as to pass through the hollow axle main body 44. The adjustment nut 45 screws onto one end of the quick-release hub rod 44c. The cam lever 46 engages with the other end of the quick-release hub rod 44c. A first volute spring 46a is installed between one end (right-hand end in
The hub body 41 is a generally cylindrical member made of, for example, an aluminum alloy. The hub body 41 has a pair of hub flanges 41a and 41b provided on both ends of the external circumference of the hub body 41. The hub flanges 41a and 41b are configured for connecting the spokes 99 thereto. A bearing installation section 41c is formed in one end face (left-hand end face in
The first bearing assembly 42a is a ball bearing that comprises a first outer race 47a, a first inner race 48a, and a plurality of spherical bodies (balls) 49a. The spherical bodies (balls) 49a are arranged between the two races 47a and 48a. Similarly, the second bearing assembly 42b is a ball bearing that comprises a second outer race 47b, a second inner race 48b, and a plurality of spherical bodies (balls) 49b. The spherical bodies (balls) 49b are arranged between the two races 47b and 48b. Each set of spherical balls 49a and 49b is held by a retainer (not shown) such that adjacent balls of each set maintain a prescribed circumferential spacing therebetween.
The first outer race 47a is press fitted into the bearing installation section 41c formed in the hub body 41. The second outer race 47b is screwed onto and, thereby, fastened to a bearing installation section 50b (see
As shown in
The inner tubular member 50 is a step-shaped cylindrical member made of chromium-molybdenum steel or other comparatively high-strength steel material. The inner tubular member 50 is non-rotatably coupled with respect to the hub body 41 by a cylindrical coupling member 54 having serrations 54a formed on the external circumferential surface thereof. Serrations 50a and 41d configured to mesh with the serrations 54a of the coupling member 54 are provided on the internal surface of a larger diameter section of the left-hand end of the inner tubular member 50 (i.e., left-hand end as viewed in
The bearing installation section 50b for installing the second bearing assembly 42b is formed on the external circumferential surface of the right-hand end of the inner tubular member 50 (i.e., the right-hand end when viewed as shown in
The outer tubular member 51 has a sprocket mounting part 51a configured for the rear sprocket cluster RP to be mounted on the external circumference thereof. The outer tubular member 51 is supported in a freely rotatable manner on the external circumference of the inner tubular member 50. As shown in
The third and fourth bearing assemblies 52a and 52b are arranged between the inner tubular member 50 and the outer tubular member 51 and serve to mount the outer tubular member 51 onto the inner tubular member 50 such that the outer tubular member 51 can rotate freely with respect to the inner tubular member 50. The third bearing assembly 52a is a ball bearing that comprises the ball bearing surface 65a, the ball pushing surface 66a and a plurality of spherical bodies (balls) 67a. The ball bearing surface 65a is formed on the internal circumferential surface of the outer tubular member 51 and serves as an outer race. The ball pushing surface 66a is formed on the external circumferential surface of the inner tubular member 50 and serves as an inner race. The spherical bodies (balls) 67a are arranged between the ball bearing surface 65a and the ball pushing surface 66a. Likewise, the fourth bearing assembly 52b is a ball bearing that comprises the ball bearing surface 65b, the ball pushing surface 66b and a plurality of spherical bodies (balls) 67b. The ball bearing surface 65b is formed on the internal circumferential surface of the outer tubular member 51 and serves as an outer race. The ball pushing surface 66b is formed on the external circumferential surface of the outer race 47b of the second bearing assembly 42b and serves as an inner race. The spherical bodies (balls) 67b are arranged between the ball bearing surface 65b and the ball pushing surface 66b. Each set of spherical balls 67a and 67b is held by a retainer (not shown) such that adjacent balls of each set maintain a prescribed circumferential spacing therebetween.
The one-way clutch 53 serves to transfer only forward rotation of the outer tubular member 51 to the inner tubular member 50. As shown in
The ratchet teeth 60 are arranged on the portion of the internal surface of the outer tubular member 51 that is located between the third and fourth bearing assemblies 52a and 52b. The ratchet teeth 60 are arranged so as to be spaced apart from one another along a circumferential direction. In the embodiment shown in
In this embodiment, there are four of the clutch pawls 61 arranged to be spaced apart from one another along a circumferential direction. To facilitate explaining the arrangement of the clutch pawls 61, the first to fourth clutch pawls 61 are numbered 61a, 61b, 61c, and 61d and arranged in the clockwise direction in
In order to achieve this angle of lost motion, the clutch pawls 61 are arranged such that the angular distance β1 between the first and second clutch pawls 61a and 61b, the second and third clutch pawls 61b and 61c, and the third and fourth clutch pawls 61c and 61d is smaller than the angular distance γ1 between the first and fourth clutch pawls 61a and 61d (the angular distance γ1 is measured on the opposite side where the second and third clutch pawls 61b and 61c are not located, i.e., all angular distances are measured the direction in which no other clutch pawls exist between the two clutch pawls whose angular distance is being measured). More specifically, in this embodiment, the angular distances β1 between the adjacent pairs of clutch pawls 61a and 61b, 61b and 61c, and 61c and 61d are all 70° and the angular distance γ1 between the first and fourth clutch pawls 61a and 61d is 150°.
By arranging the first to fourth clutch pawls 61a to 61d in this way, the first and third clutch pawls 61a and 61c mesh with the ratchet teeth 60 simultaneously and the second and fourth clutch pawls 61b and 61d mesh with the ratchet teeth 60 simultaneously. More specifically, since the angular distance β1 between each of the adjacent pairs of clutch pawls 61a and 61b, 61b and 61c, and 61c and 61d is 70°, the angular distance between the non-adjacent first and third clutch pawls 61a and 61c is 140° and the angular distance between the non-adjacent second and fourth clutch pawls 61b and 61d is 140°. Since 140 is evenly divisible by 20, the non-adjacent pair of clutch pawls 61a and 61c and the non-adjacent pair of clutch pawls 61b and 61d each mesh with the ratchet teeth simultaneously. Additionally, since the angular distance β1 is 70°, when one of the adjacent clutch pawls 61a and 61b is meshed with one of the ratchet teeth 60, the other is positioned 10° out of phase with the nearest one of the ratchet teeth 60. Likewise, when one of the adjacent clutch pawls 61c and 61d is meshed with one of the ratchet teeth 60, the other is positioned 10° out of phase with the nearest one of the ratchet teeth 60. Consequently, the angle of lost motion is 10°. Since two of the clutch pawls 61 mesh with the ratchet teeth 60 simultaneously, the required rigidity can be maintained while reducing the angle of lost motion.
As shown in
In this embodiment, the force applying member 62 comprises the two spring members 62a and 62b that are configured and arranged to spring load the first to fourth clutch pawls 61a to 61d simultaneously in a direction oriented away from the external circumference of the inner tubular member 50 and toward the engagement position. Each of the two spring members 62a and 62b is made of a metal elastic wire-like material that has been bent into a C-shape such that it can be installed in one of the circular spring arrangement grooves 50f. Consequently, each of the spring members 62a and 62b has an open end part 62c and is thus shaped like a circle from which one small section has been cut out (i.e., a split ring). As shown in
More specifically, the spring member 62a spring loads the first clutch pawl 61a and the third clutch pawl 61c and the spring member 62b spring loads the second clutch pawl 61b and the fourth clutch pawl 61d. Thus, by spring loading a plurality of clutch pawls 61 simultaneously with the spring members 62a and 62b in such a fashion that alternate clutch pawls 61 are spring loaded with a different one of the spring members 62a and 62b, respectively, the clutch pawls 61 spring loaded by the spring members (force applying member) 62a and 62b can be divided into two groups. Consequently, the spring members 62a and 62b can apply stable forces to the clutch pawls 61 even when the number of clutch pawls 61 is large. As a result, a plurality of clutch pawls 61 can be urged (spring loaded) toward their respective engagement positions in a stable fashion and rotation (torque) can be transferred through the clutch pawls 61 in a stable fashion.
The operation of the freewheel 43 will now be described. When a rider pedals the pedals PD and rotates the rear sprocket cluster RP, the outer tubular member 51 rotates together with the rear sprocket cluster RP and two of the clutch pawls 61 of the one-way clutch 53 mesh with two of the ratchet teeth 60 of the one-way clutch 53. Since the angle of lost motion is 10°, the outer tubular member 51 will rotate not more than a maximum of 10° before two of the clutch pawls 61 mesh with the ratchet teeth 60 and the rotation of the outer tubular member 51 is transferred to the inner tubular member 50, thereby causing the wheel to rotate. Meanwhile, if the rider stops pedaling the pedals PD, the inner tubular member 50 will rotate relative to the outer tubular member 51 in the direction depicted as the clockwise direction in
A typical assembly procedure for the freewheel 43 will now be described. First, the spherical balls 67a of the third bearing assembly 52a, which are held by a retainer, are arranged on the ball pushing surface 66a of the inner tubular member 50. Next, the clutch pawls 61 are mounted in the smaller circular arc-shaped recessed sections 50e of the clutch pawl installation recesses 50c. Clutch pawls 61 having the spring engaging parts 64 provided on opposite sides thereof are arranged adjacent to one another so that the side on which the spring engagement part 64 is provided alternates as one moves from one clutch pawl 61 to another. Then, after putting the clutch pawls 61 in a lying-down state, the inner tubular member 50 is grasped with one hand and the spring members 62a and 62b are installed into the spring arrangement grooves 50f one at a time with the other hand by putting each spring member 62a and 62b onto the inner tubular member 50 from the end of the inner tubular member 50 depicted as the right-hand end in
After the spherical balls 67a, the clutch pawls 61, and the spring members 62a and 62b have be installed onto the external circumference of the inner tubular member 50 as described above, the inner tubular member 50 is inserted into the outer tubular member 51 from the end depicted as the left-hand end in
Since a separate spring member is not provide for each of the clutch pawls 61 but, instead, a plurality of the clutch pawls 61 are spring loaded simultaneously (together) with one of the spring members 62a and 62b, the internal structure of the freewheel 43 is prevented from becoming complex and the force applying member 62 can be installed more easily during the assembly process of the freewheel 43.
Now other embodiments will now be explained with reference to
Although the previously described embodiment is configured such that two of the clutch pawls 61 mesh with the ratchet teeth 60 simultaneously in order to ensure the necessary rigidity while reducing the angle of lost motion, it is acceptable to configure the freewheel such that only one of the clutch pawl 61 meshes with the ratchet teeth 60 at a time in order to achieve a small angle of lost motion.
With this arrangement of the first to fourth clutch pawls 61a to 61d, only one of the first to fourth clutch pawls 61a to 61d meshes with the ratchet teeth 60 at a time. More specifically, since the angular distance β2 between each of the adjacent pairs of the clutch pawls 61a and 61b, 61b and 61c, and 61c and 61d is 75°, there are no two of the clutch pawls 61 that are separated by an angular distance that is evenly divisible by 20°. Consequently, when one of the clutch pawls 61 meshes with one of the ratchet teeth 60, all of the other of the clutch pawls 61 are out of phase with respect to the ratchet teeth 60. Furthermore, since the angular distance β2 is 75°, when the first clutch pawl 61a is meshed with one of the ratchet teeth 60, the second to fourth of the clutch pawls 61b to 61d are arranged so as to be successively closer in 5° increments to meshing with the one of the ratchet teeth 60 that is nearest in the counterclockwise direction. Consequently, the angle of lost motion is 5°. With this bicycle freewheel, since only one of the clutch pawl 61 meshes with the ratchet teeth 60 at a time, the angle of lost motion can be reduced as much as possible without increasing the original number of the clutch pawls.
Also, similarly to the previous embodiment, alternate ones of the clutch pawls 61 are spring loaded by either a first spring member 62a or a second spring member 62b, respectively.
Although the previously described embodiments have four of the clutch pawls 61, the number of the clutch pawls 61 can be any number equal to or larger than 3.
In the embodiment shown in
With this arrangement of the first to sixth of the clutch pawls 61a to 61f, the following pairs of the clutch pawls 61 mesh with the ratchet teeth 60 simultaneously: the first and fourth clutch pawls 61a and 61d, the second and fifth clutch pawls 61b and 61e, and the third and sixth of the clutch pawls 61c and 61f. More specifically, since the angular distance β3 between each of the adjacent pairs of the clutch pawls 61a and 61b, 61b and 61c, and 61c and 61d, 61d and 61e, and 61e and 61f is 53°20′, the angular distance between the first and fourth of the clutch pawls 61a and 61d is 160°, the angular distance between the second and fifth of the clutch pawls 61b and 61e is 160°, and the angular distance between the third and sixth of the clutch pawls 61a and 61d is 160°. Since 160 is evenly divisible by 20, each of the pairs of the clutch pawls 61a and 61d, 61b and 61e, and 61c and 61f meshes with the ratchet teeth 60 simultaneously. Additionally, since the angular distance β3 is 53°20′, when one of the clutch pawls 61 of any pair of adjacent ones of the clutch pawls 61 (e.g., 61a and 61b or 61b and 61c) is meshed with one of the ratchet teeth 60, the other clutch pawl 61 is positioned 6°40′ out of phase with the nearest one of the ratchet teeth 60. Consequently, the angle of lost motion is 6°40′. Since two clutch pawls 61 mesh with the ratchet teeth 60 simultaneously, the required rigidity can be maintained while reducing the angle of lost motion. Additionally, it is also acceptable configure the one-way clutch such that three clutch pawls mesh with the ratchet teeth simultaneously and the angle of lost motion is 10°.
In the embodiment shown in
With this arrangement of the first to sixth of the clutch pawls 61a to 61f, only one of the first to sixth of the clutch pawls 61a to 61f meshes with the ratchet teeth 60 at a time. More specifically, since the angular distance β4 between each of the adjacent pairs of the clutch pawls 61a and 61b, 61b and 61c, 61c and 61d, 61d and 61e, and 61e and 61f is 56°40′, there are no two of the clutch pawls 61 that are separated by an angular distance that is evenly divisible by 20°. Consequently, when one of the clutch pawls 61 meshes with one of the ratchet teeth 60, all of the other of the clutch pawls 61 are out of phase with respect to the ratchet teeth 60. Furthermore, since the angular distance β4 is 56°40′, when the first clutch pawl 61a is meshed with one of the ratchet teeth 60, the second to sixth of the clutch pawls 61b to 61f are arranged so as to be positioned successively closer in 3°20′ increments to meshing with the one of the ratchet teeth 60 that is nearest in the counterclockwise direction. Consequently, the angle of lost motion is 3°20′. With this bicycle freewheel, since only one of the clutch pawls 61 meshes with the ratchet teeth 60 at a time, the angle of lost motion can be reduced as much as possible without increasing the original number of clutch pawls.
In the embodiment shown in
With this arrangement of the first to fifth of the clutch pawls 61a to 61e, only one of the first to fifth of the clutch pawls 61a to 61e meshes with the ratchet teeth 60 at a time. More specifically, since the angular distance γ5 between each of the adjacent pairs of the clutch pawls 61a and 61b, 61b and 61c, 61c and 61d, and 61d and 61e is 68°, there are no two of the clutch pawls 61 that are separated by an angular distance that is evenly divisible by 20°. Consequently, when one clutch pawl 61 meshes with one of the ratchet teeth 60, all of the other clutch pawls 61 are out of phase with respect to the ratchet teeth 60. Furthermore, since the angular distance β5 is 68°, when the clutch pawl 61a is meshed with one of the ratchet teeth 60, the clutch pawls 61b to 61e are arranged such that the angular distance between each of the clutch pawls 61b to 61e and the respective one of the ratchet teeth 60 that is nearest in, for example, the counterclockwise direction varies in 4° increments. More specifically, when the first of the clutch pawls 61a meshes with one of the ratchet teeth 60, the fourth of the clutch pawls 61d is positioned 4° away from the nearest one of the ratchet teeth 60 (in the counterclockwise direction from pawl to tooth), the second of the clutch pawls 61b is positioned 8° away from the nearest one of the ratchet teeth 60, the fifth of the clutch pawls 61e is positioned 12° away from the nearest one of the ratchet teeth 60, and the third of the clutch pawls 61c is positioned 16° away from the nearest one of the ratchet teeth 60. Consequently, the angle of lost motion is 4°. With this bicycle freewheel, since only one of the clutch pawls 61 meshes with one of the ratchet teeth 60 at a time, the angle of lost motion can be reduced as much as possible without increasing the original number of clutch pawls. It is also possible to obtain an angle of lost motion equal to 4° by setting both of the angular distances β5 and γ5 to 72° such that the first to fifth of the clutch pawls 61a to 61e are all equally spaced apart.
Also, similarly to the previously described embodiment, in the embodiments shown in FIGS. 8 to 10, alternate ones of the clutch pawls 61 are spring loaded by the first and second spring members 62a and 62b, respectively. Also, in the embodiment shown in
Although in the previously described embodiment the spring engaging part 64 of each clutch pawl 61 is arranged on a side portion of the claw-like part 63 of the clutch pawl 61, the invention is not limited to such an arrangement of the spring engagement parts.
The spring engaging groove 164a indicated with a broken line is configured to slant upward to the right when viewed as shown in
Although in the previously described embodiment two C-shaped spring members 62a and 62b are used as the force applying member 62, the invention is not limited to such a force applying member 62.
The length of the coil spring 162a is set such that the coil spring 162a is elongated beyond its natural length when it is installed with the hooks 162b hooked together. The coil spring 162a is installed by hooking the hooks 162b together and placing the coil spring 162a into the spring arrangement groove 50f from the end of the inner tubular member 50 depicted as the right-hand end in
Although in the previously described embodiment each of the two force applying members 62a and 62b serves to urge (apply forces against) a plurality of clutch pawls 61 toward their respective engagement positions, one or more force applying members can be arranged to urge only one claw pawl each so long as at least one force applying member is configured and arranged to urge a plurality of clutch pawls simultaneously.
In understanding the scope of the present invention, the term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. As used herein to describe the present invention, the following directional terms “forward, rearward, above, downward, vertical, horizontal, below and transverse” as well as any other similar directional terms refer to those directions of a bicycle equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a bicycle equipped with the present invention as used in the normal riding position. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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2005-306677 | Oct 2005 | JP | national |