Speed Change Hub and Braking Construction

1. Field of the Invention

The present invention relates to a speed-change hub for use in e.g. a bicycle, and more particularly to a speed-change hub including a fixed shaft, a hub body rotatably mounted on the fixed shaft, a drive member rotatably mounted on the fixed shaft for transmitting a drive force to the hub body selectively through a plurality of transmission channels and a clutch for selecting one of the transmission channels.

2. Description of the Related Art

A known speed-change hub of the above-specified type includes first and second sun gears rotatable relative to a fixed shaft and having different diameters and a lock control mechanism for locking the sun gears to and releasing the same from the fixed shaft. The fixed shaft further includes an axially movable first control portion having a control portion for controlling a clutch element and externally operable at one distal end of the hub body and an axially movable second control portion having a control portion for activating the lock control mechanism to lock either the first or second sun gear to the fixed shaft. Accordingly, by moving the first control portion, the clutch is operated to select a desired transmission channel. Also, by moving the second control portion, one of the first and second sun gears is locked to the fixed shaft. In this way, the hub provides a plurality of speeds (Japanese published patent gazette No. 53-14820).

Recently, the prior art has suggested a further type of speed-change hub having only one one control portion (West Germany laid-open patent gazette No. 2458871). With this speed-change hub, the control portion is rotated to axially move a sun gear and a planet gear meshing therewith.

One problem occurs with the above speed-change hub however. That is, since the speed-changing operation is effected by operating the sun gear and the planet gear which are being rotated in union (more particularly, the planet gear, the sun gear and also the hub body are acting on each other), the control portion tends to be subjected to a relatively large load which results in a `heavy` speed-change operation feel. In this sense, this speed-change hub still has room for improvement.

The present invention attends to the abovedescribed drawback of the prior art. Hence, the invention's primary object is to provide an improved speed-change hub which provides a light speed-changing operation feel to the user because of an effectively reduced load acting on the control portion of the hub.

For accomplishing the above-noted object, the invention provides in a speed-change hub comprising: a fixed shaft; a hub body rotatably mounted on the fixed shaft; a drive member rotatably mounted on the fixed shaft for transmitting a drive force to the hub body selectively through a plurality of transmission channels; a clutch for selecting one of the transmission channels; a plurality of sun gears rotatably mounted on the fixed shaft and having diameters differing from each other; a lock control mechanism for controlling locking and releasing of the sun gears relative to the fixed shaft, sun gears having axial movements which are substantially limited; and a control member rotatably mounted on the fixed shaft, the control member including a first control portion for controlling the clutch and second and third control portions for activating the lock control mechanism for selectively locking the sun gears to the fixed shaft, the control member being operable externally of the hub body for providing a plurality of speeds through the selection of the transmission channel and the selection of the sun gear to be locked by the lock control mechanism.

Functions and effects of the above construction will now be described.

As the control member is rotatably operated (or moved axially), the first control portion acts to select the transmission channel while the second and third control portions act to select the sun gear to be locked by the lock control mechanism.

As described above, the invention's speed-change hub includes the sun gears having different diameters, the lock control mechanism for controlling locking and releasing of the sun gears relative to the fixed shaft and the clutch for selecting the transmission channel from the drive member to the hub body. Yet, with the above-described construction, the selection of the transmission channel and also that of the sun gears to be locked to the fixed shaft can both be effected by the very simple rotational operation of the control member. Consequently, the speed-change hub of the invention provides a light operational feel and also reliable and error-free operation.

Further, in a braking construction used in a speed-change hub having a fixed shaft, a hub body rotatably mounted on the fixed shaft, a drive member rotatably mounted on the fixed shaft for transmitting a drive force to the hub body selectively through a plurality of transmission channels, clutches for selecting one of the transmission channels and a braking mechanism for releasing engagement between the drive member and the hub body through reverse rotation of the drive member relative to a driving direction, the mechanism including a braking member for braking rotation of said hub body, the braking construction of the present invention is characterized in that the releasing action of the engagement between the drive member and the hub body is effected through an interaction of a plurality of transmission claws supported to the drive member.

The above-described braking constructon achieves an easy operation while maintaining the light speed-change operation feel of the hub body rotation.

Further and other objects, features and effects of the invention will become more apparent from the following more detailed description of the embodiments of the invention taken with reference to the accompanying drawings.

FIG. 1 is a partially cutaway front view showing a speed-change hub relating to one preferred embodiment of the present invention,

FIG. 2 is a perspective view showing only control portions and lock control portions of a control member used in the hub of FIG. 1,

FIG. 3 is a section view of FIG. 2,

FIGS. 4(a) through 4(d) are views illustrating a relationship between the control member and a lock control mechanism,

FIG. 5 is a partially cutaway front view showing a fixed shaft alone,

FIG. 6 is a section view taken along a line A--A of FIG. 5,

FIG. 7 is a section view taken along a line B--B of FIG. 5,

FIG. 8 is a section view of the control member,

FIG. 9 is a section view taken along a line C--C of FIG. 8,

FIG. 10 is a section view taken along a line D--D of FIG. 8,

FIG. 11 is a section view taken along a line E--E of FIG. 8,

FIG. 12 is a section view taken along a line F--F of FIG. 8,

FIG. 13 is a section view taken along a line G--G of FIG. 8,

FIG. 14 is a section view taken along a line H--H of FIG. 8,

FIG. 15 is a perspective view of a first control portion,

FIG. 16 is a perspective view of a ball pushing element,

FIG. 17 is a perspective view of a spacer,

FIG. 18 is a perspective view of a control portion,

FIGS. 19(a) and 19(b) are views illustrating engagement/disengagement relationship among a clutch, a drive member and a ring gear when the drive member is rotated in a reverse direction,

FIG. 20 is a partially enlarged front view showing a modified arrangement of the lock control portions,

FIG. 21 is a section view showing only a fixed shaft, lock claws and sleeves of the arrangement of FIG. 20,

FIG. 22 is a partial front view showing a clutch and a control member according to a still further modified arrangement,

FIG. 23 is a partial front view showing a further modified arrangement of the clutch and the control member,

FIG. 24 is an enlarged front view showing a ring gear and a drive member of a modified arrangement when the drive member is rotated reversely,

FIGS. 25 through 26 are partial section views illustrating engaging relationship between the ring gear and the drive member of the arrangement of FIG. 24; in which,

FIGS. 25(a) and 25(b) are views showing the ring gear being engaged with the drive member through a transmission claw,

FIGS. 26(a) and 26(b) are views showing a condition where the ring gear and the drive member break the power transmission,

FIG. 27 is a partially enlarged front view showing a ring gear and a drive member of a still further modified arrangement when the drive member is rotated reversely,

FIGS. 28 through 29 are partial section views illustrating engagement relationship between the ring gear and the drive member of the arrangement of FIG. 27,

FIG. 22 is a partial front view showing a clutch and a control member according to a still further modified arrangement,

FIG. 23 is a partial front view showing a further modified arrangement of the clutch and the control member,

FIG. 24 is an enlarged front view showing a ring gear and a drive member of a modified arrangement when the drive member is rotated reversely,

FIGS. 25 through 26 are partial section views illustrating engaging relationship between the ring gear and the drive member of the arrangement of FIG. 24; in which,

FIGS. 25(a) and 25(b) are views showing the ring gear being engaged with the drive member through a transmission claw,

FIGS. 26(a) and 26(b) are views showing a condition where the ring gear and the drive member break the power transmission,

FIG. 27 is a partially enlarged front view showing a ring gear and a drive member of a still further modified arrangement when the drive member is rotated reversely,

FIGS. 28 through 29 are partial section views illustrating engagement relationship between the ring gear and the drive member of the arrangement of FIG. 27; in which,

FIGS. 28(a) and 28(b) are views showing the ring gear being engaged with the drive member through a transmission claw, and

FIGS. 29(a) and 29(b) are views showing a condition where the ring gear and the drive member break the power transmission.

Preferred embodiments of the present invention will be now described in particular with reference to the accompanying drawings.

FIG. 1 shows a five-speed, speed-change hub capable of providing two high speeds, one middle speed and two low speeds for use in a bicycle. This change-speed hub mainly includes a fixed shaft 1 to be fixed to a bicycle frame, a cylindrical hub body 2 rotatably mounted on the fixed shaft 1, a drive member 3 rotatably mounted on the fixed shaft 1, a cylindrical gear carrier 4 accommodated in the hub body 2 and carrying planet gears meshing with sun gears to be described later, a ring gear 5 accommodated in the hub body 2 and having an internal gear 51 meshable with the planet gears, a relay member 6 for relaying a rotational force from the drive member 3 to the gear carrier 4, a first transmission claw 7 projectably and retractably disposed between the drive member 3 and the relay member 6, a second transmission claw 8 projectably and retractably disposed between the drive member 3 and the ring gear 5, a third transmission claw 9 projectably and retractably disposed between the hub body 2 and the ring gear 5 and a fourth transmission claw 10 projectably and retractably disposed between the hub body 2 and the gear carrier 4. Further, a clutch 20 is provided for selectively transmitting the force of the drive member 3 either through a transmission channel via the gear carrier 4 to the hub body 2 or through a further transmission channel via the ring gear 5 to the hub body 2 without passing the gear carrier 4.

At a longitudinal middle position of the fixed shaft 1, there is provided a key 30 axially movable within an elongated slot extending radially. On an inner peripheral face of the hub body 2, there are provided a first ratchet 21 engageable with the third transmission claw 9 and a second ratchet 22 engageable with the fourth transmission claw 10, with the ratchets 21 and 22 being disposed with a predetermined axial distance therebetween.

At one distal external end of the drive member 3, there is provided a chain gear 31 engageable with a drive chain of the bicycle. At a longitudinal intermediate position of the drive member 3, there is supported the second transmission claw 8. Whereas, the first transmission claw 7 is supported to the inner peripheral face of the drive member 3, with the claw 7 being urged toward the relay member 6 by means of a claw spring. Also, the second transmission claw 8 is urged to the inner peripheral face of the ring gear 5 by means of a claw spring.

On the inner peripheral face of the gear carrier 4 on the side of the drive member 3, there is provided an internal gear 41 meshable with a gear 61 mounted on an end portion of the outer periphery of the relay member 6. Further, on the outer periphery opposite to the drive member 3, there is supported the fourth transmission claw 10, with the claw 10 being urged toward the ratchet 22 by means of a claw spring.

On the inner peripheral face of the ring gear 5 on the side of the drive member 3, there is provided a ratchet 52 engageable with the second transmission claw 8. On the opposite side of the inner peripheral face of the ring gear 5, there is provided the internal gear 51. At a longitudinal intermediate position thereof, the third transmission claw 9 is supported, with the claw 9 being urged towards the ratchet 21 by means of a claw spring.

On the outer peripheral face of the relay member 6 on the side of the drive member 3, there is provided a ratchet 62 engageable with the first transmission claw 7. At an intermediate position of the outer peripheral face, there is formed a control face which comes into contact with a leg portion of the third transmission claw 9 opposed to its claw portion during the axial movement for controlling the third transmission claw 9.

The clutch 20 is constructed as a cylindrical member having a large diameter portion and a small diameter portion divided across a stepped portion. On a face of the large diameter portion opposing to the transmission claw 7, there is formed a cam face. Also, on an inner periphery of the small diameter portion, there is provided a stopper portion engageable with the key 30 for stopping rotation.

Further, the fixed shaft 1 rotatably mounts, at axially different intermediate positions thereof, a first sun gear 11 and a second sun gear 12. Both the sun gears have a cylindrical shape and define teeth on its outer periphery and the first sun gear 11 is larger in diameter than the second sun gear 12. On the other hand, the gear carrier 4 rotatably mounts a first planet gear 13 meshable with the first sun gear 11 and a second planet gear 14 meshable with the second sun gear 12, with the first planet gear 13 being smaller in diameter than the second planet gear 14. At axially different positions of the outer peripheral face of the fixed shaft 1, as illustrated in FIGS. 5 through 7, there are provided a first regulating projection 71 and a second regulating projection 72.

On the inner peripheral face of the first sun gear 11, there are provided two pairs of first lock claws 73 engageable with the first regulating projection 71, with the two claws 73 of each pair having leading ends directed in opposite directions. Similarly, on the inner peripheral face of the second sun gear 12, there are provided two pairs of second lock claws 74 engageable with the second regulating projection 72, with the two claws 74 of each pair having leading ends directed in opposite directions. These first and second regulating projections 71, 72 and the first and second lock claws 73, 74 together constitute a lock control mechanism 70 for selectively locking and releasing the sun gears 11 and 12 relative to the fixed shaft 1. On the outer periphery of the fixed shaft 1, there is rotatably mounted a control member 80 which is operable externally of the hub body 2. This control member 80 includes a first control portion 81 for controlling the clutch 20, a second control portion 82 for causing the lock control mechanism 70 to lock the first sun gear 11 to the fixed shaft 1 and a third control portion 83 for locking the second sun gear 12 to the fixed shaft 1. Then, with a rotational operation on this control member 80, both the selection of the transmission channel and also that of the sun gears to be locked to the fixed shaft can be readily effected for providing a plurality of speeds.

Further, the first sun gear 11 and the second sun gear 12 are rotatable relative to each other. Also, the lock claws 73 and 74 supported to the inner peripheral faces of the respective sun gears 11, 12 are urged to the outer peripheral face of the fixed shaft 1 by means of the claw springs. Incidentally, these two pairs of the lock claws 73 and 74 can be substituted by one pair for each.

The first planet gear 13 and the second planet gear 14 are formed integrally with each other and are supported to the gear carrier 4 through a single common shaft. Further, the first planet gear 13 is meshed with the internal teeth 51 of the ring gear 5.

The control member 80 has a length extending from one distal end of the fixed shaft 1 to a portion of the shaft 1 carrying the second regulating projection 72. Also, the control member 80 is loosely, i.e. rotatably mounted on the fixed shaft 1.

On a distal end of the control member 80, there is provided a disc-shaped control portion 84 having a stopper portion for stopping an end of a speed-change control cable. At the other end of the member 80, there are provided the second and third control portions 82 and 83. Moreover, at intermediate positions of the control member 80, there are provided the first control portion 81 and an elongated inserting slot 85 for receiving the key 30.

The first control portion 81, as best shown in FIG. 15, includes a first cam face 81a, a second cam face 81b continuous with the first cam face, a third cam face 81d continuous with the second cam face 81b through a stepped portion 81c therebetween, and a fourth cam face 81e, with the first through fourth cam faces and the stepped portion being dispersed peripherally in said order. The first cam face 81a is formed normal to the axis of the fixed shaft 1. Further, this first control portion 81 is formed independently of a cylindrical body 80a having the control portion. Specifically, the control portion 81 is formed as a cylindrical member including a radially extending, disc-shaped flange portion and a cylindrical portion extending axially from one end of the flange portion. This cylindrical control portion 81 includes, in its inner peripheral face, a pair of opposed engaging grooves 86, 86 engageable with fork portions 80g (to be described later) of the cylindrical body 80a, such that the first control portion 81 is unrotatably connected with the cylindrical body 80a.

The second and third control portions 82 and 83 are formed as axially extending projections comprised of partial cutouts of the cylindrical body 80a. More particularly, as illustrated in FIG. 2 and also in FIGS. 8 through 12, at the leading end of the cylindrical body 80a, there are formed a peripheral groove 80b extending in the peripheral direction and a plurality of axial grooves 80c extending from the peripheral groove 80b toward the control portion 84. Thus, the projecting portions between these grooves 80b and 80c constitute the second control portion 82. On the other hand, there are formed a plurality of axial grooves 80d extending from the leading edge of the cylindrical body 80a to the control portion 84. Then, the projections between these grooves 80d constitute the third control portion 83. Also, there is formed a communicating groove 80e extending from the peripheral groove 80b to the leading edge, so that the first regulating projection 71 is positioned in the peripheral groove 80b. Then, as the peripheral groove 80b receives the first regulating projection 71, as shown in FIGS. 2 and 3, the first regulating projection 71 and the second control portion 82 are axially aligned with each other. Further, as the second regulating projection 72 is positioned externally of the leading edge of the cylindrical body 80a, as shown in FIGS. 2 and 3, the second regulating projection 72 and the third control portion 83 are axially aligned with each other. Consequently, the first lock claws 73 are engageable with the first regulating projection 71 and the second control portion 82; whereas, the second lock claws 74 are engageable with the second regulating projection 72 and the third control portion 83. Then, by varying the peripheral positions of the second and third control portions 82 and 83 relative to the respective regulating projections 71 and 72, the respective lock claws 73 and 74 are controlled as illustrated in FIGS. 4(a) through 4(e).

On the side of the control portion 84, as shown in FIGS. 8, 13 and 14, the control member 80 is forked shaped. Specifically, the control member 80 includes, at this portion thereof, a pair of axially extending slits 80f and a pair of the fork portions 80g formed between the slits 80f. Further, at an intermediate inner portion of each fork portion 80g, there is formed an abutment 80h which comes into abutment against a stepped portion 1a formed on the fixed shaft 1 for limiting the axial movement of the control member 80.

A ball pushing element 15 is provided for supporting the drive member 3 to the fixed shaft 1. In an inner peripheral face of this ball pushing element 15, as shown in FIG. 16, there is formed a peripherally extending guide groove 15a. Then, as the fork portion 80g is inserted into the guide groove 15 along the engaging groove 86, the control member 80 is held rotatable relative to the ball pushing element 15. Incidentally, the ball pushing element 15 is axially slidably yet unrotatably fitted on the fixed shaft 1.

The control portion 84 is formed independently of the cylindrical body 80a. On the inner peripheral face of the control portion 84, as shown in FIG. 18, there are a pair of projections 87 including engaging grooves 87a into which the leading ends of the fork portions 80g are engaged. Further, on the inner side of this control portion 84, there is provided a spacer 16 having a peripheral guide groove 16a for guiding the projection 87 (see FIG. 17), so that this spacer 16 is only axially movable relative to the fixed shaft 1.

In this embodiment, between the drive member 3 and the relay member 6, there is provided a projectable/retractable fifth transmission claw 17 for transmitting rotational force of the drive member 3 through the relay member 6 to the gear carrier 4 when the drive member 3 is rotated in the reverse direction. The hub body 2 includes, in its inner periphery, a braking face 23. Whereas, the gear carrier 4 includes, in its end periphery, a cam face 42. Further, between this cam face 42 and the braking face 23, there is provided a braking shoe 18, as a braking element, radially movable via a rotary member, so that the reverse rotation of the drive member 3 activates the shoe 18 for braking.

In this case, as illustrated in FIG. 19, with the reverse rotation of the drive member 3, the fifth transmission claw 17 as one transmission claw becomes engaged with a reverse tooth formed at an intermediate position of the outer peripheral face of the relay member 6. Then, the second transmission claw 8 as the other transmission claw supported to the drive member 3 becomes depressed as the claw end of this claw 8 supported to the drive member 3 comes into contact with the fifth transmission claw 17, so that the depressed second transmission claw 8 breaks the power transmission between the drive member 3 and the ring gear 5. That is, when the drive member 3 is rotated in the forward direction, i.e. the driving direction, as illustrated in FIG. 19(a), the fifth transmission claw 17 becomes engaged with the drive member 3 and the second transmission claw 8 becomes engaged with the ring gear 5. Conversely, when the drive member 3 is rotated in the reverse direction, i.e. the braking direction, as illustrated in FIG. 19(b), the fifth transmission claw 17 comes into contact with the second transmission claw 8 to break power transmission between the drive member 3 and the ring gear 5.

In FIG. 1, a reference numeral 19 denotes a return spring for returning the control member 80. A numeral 40 denotes a return spring for returning the clutch 20. By means of this return spring 40, the clutch 20 is engaged with the first control portion 81 via the key 30. Further, a reference numeral 50 denotes a return spring for returning the relay member 6. A numeral 60 denotes a control ring unrotatably supported to the inner peripheral face of the hub body 2 and for depressing the third transmission claw 9 when the drive member 3 is rotated in the reverse direction.

Functions and operations of the speed-change hub having the above-described characterizing construction of the invention will be particularly described next.

In the condition shown in FIG. 1, the speed-change hub is in the highest speed stage. In this condition, the clutch 20 and the relay member 6 are located at their rightmost positions. The first lock claws 73 of the lock control mechanism 70 are controlled by the second control portion 82 so that the claws 73 are engaged with the first regulating projection 71 (see FIG. 4(b)) thereby to lock the first sun gear 11 against rotation. As the first transmission claw 7 engages with the ratchet 62 of the relay member 6, the power from the drive member 3 is transmitted via the first transmission claw 7 and the relay member 6 to the gear carrier 4. Then, this power transmitted to the gear carrier 4 is further transmitted via the first planet gear 13 to the ring gear 5 and the third transmission claw 9 engaged with the first ratchet 21 to consequently the hub body 2 for rotating the same at the top speed.

In the above operation, the second planet gear 14 is rotated in the same direction as the first planet gear 13. However, since the rotational speed transmitted from the second planet gear 14 to the second sun gear 12 is lower than that transmitted from the first planet gear 13 to the ring gear 5, as illustrated in FIG. 14(a), the second sun gear 12 is rotated in the opposite direction to that of the force acting on the first sun gear 11, the second sun gear 12 is not locked.

Further, in the above operation, the second transmission claw 8 becomes engaged with the ratchet 52 of the ring gear 5. However, since the rotational speed transmitted from the gear carrier 4 to the ring gear 5 is higher than that transmitted from the drive member 3 via the second transmission claw 8 to the ring gear 5, the second transmission claw 8 only slides.

For effecting a change speed operation from the above-described top speed stage to a second highest speed stage, the control member 80 is rotated so that, as illustrated in FIG. 4(c), the third control portion 83 causes the second lock claw 74 of the lock control mechanism 70 to come into engagement with the second regulating projection 72 thereby to lock the second sun gear 12 against rotation. Further, the second control portion 82 acts to release the engagement between the first lock claw 73 and the first regulating projection 71 as shown in FIG. 4(d) thereby to release the locked condition of the first sun gear 11.

Accordingly, the power transmitted through the first transmission claw 7, the relay member 6 and the gear carrier 4 is further transmitted via the second planet gear 14, the ring gear 5 and the third transmission claw 9 to consequently the hub body for rotating the same at the second highest speed. Incidentally, in the above operation, the key 30 engaged with the first control portion 81 effects only a peripheral displacement along the first cam face 81a of the first control portion 81 and the clutch 20 does not effect axial movement. Also, in the above speed-change operation, the second transmission claw 8 comes into engagement with the ratchet 52 of the ring gear 5. However, since the rotational speed transmitted from the gear carrier 4 to the ring gear 5 is higher than that transmitted from the drive member 3 via the second transmission claw 8 to the ring gear 5, similarly to the foregoing case, the second transmission claw 8 only slides.

For effecting a speed-change operation from the above second highest speed stage to the middle speed stage, the control member 80 is further rotated for causing the second cam face 81b of the first control portion 81 to move the clutch 20 toward the gear carrier 4 so that the cam face of the clutch 20 depresses the first transmission claw 7 to break the power transmission from the drive member 3 to the relay member 6. Accordingly, the power of the drive member 3 is transmitted via the second transmission claw 8, the ring gear 5 and the third transmission claw 9 to consequently the hub body 2 for rotating the same at the middle speed. In this case, as illustrated in FIG. 4(c), the third control portion 83 causes the second lock claw 74 of the lock control mechanism 70 to come into engagement with the second regulating projection 72 thereby to lock the second sun gear 12 against rotation.

Also, in the above operations, the second control portion 82 acts as shown in FIG. 4(f) to release the engagement between the first lock claw 73 and the first regulating projection 71, whereby the locked condition of the first sun gear 11 is released.

The intermediate stepped portion of the clutch 20 is placed in contact with the terminal edge of the relay member 6.

For effecting a speed-change operation from the above middle speed stage to the second lowest speed, the control member 80 is further rotated to cause the third cam face 81d of the first control portion 81 to move the clutch 20 further toward the gear carrier 4. Further, as illustrated in FIG. 4(g), the third control portion 83 causes the second lock claw 74 of the lock control mechanism 70 to come into engagement with the second regulating projection 72 thereby to lock the second sun gear 12 against rotation. Also, the second control portion 82 acts as shown in FIG. 4(h) to release the engagement between the first lock claw 73 and the first regulating projection 71 thereby to release the first sun gear 11. Accordingly, with the above movement of the clutch 20, the relay member 6 moves toward the gear carrier 4 and the outer peripheral control face of this relay member 6 depresses the third transmission claw 9 to break the power transmission from the ring gear 5 to the hub body 2. Thus, the power of the drive member 3 is transmitted via the second transmission claw 8, the ring gear 5, the second planet gear 14, the gear carrier 4 and the fourth transmission claw 10 consequently to the hub body 2 for rotating the same at the second lowest speed.

In the above operation, the first planet gear 13 rotates in the same direction as the second planet gear 14. However, since the rotational speed transmitted from this first planet gear 13 to the first sun gear 11 is lower than that transmitted from the ring gear 5 to the second planet gear 14, the first planet gear 13 rotates in the opposite direction to that of the force acting on the second sun gear 12, whereby the first sun gear 11 is not locked.

For effecting a speed-change operation from the above second lowest speed stage to the lowest speed stage, the control member 80 is further rotated to cause the second control portion 82, as illustrated in FIG. 4(j), to bring the first lock claw 73 of the lock control mechanism 70 into engagement with the first regulating projection 71 thereby to lock the first sun gear 11 against rotation. Further, as shown in FIG. 4(i) the third control portion 83 acts to release the engagement between the second lock claw 74 and the second regulating projection 72 thereby to release the second sun gear 12. Accordingly, the power transmitted from the drive member 3 via the second transmission claw 8 to the ring gear 5 is further transmitted via the first planet gear 13, the gear carrier 4 and the fourth transmission claw 10 consequently to the hub body 2 for rotating the same at the lowest speed. Incidentally, in the above operations, the key 30 engaged with the first control portion 81 effects only a peripheral displacement along the fourth cam face 81e continuous with the third cam face 81d of the first control portion 81 and the clutch 20 does not move in the axial direction.

The above-described various transmission channels are summarized in the table below, in which a circle mark denotes an active state of each claw, a cross mark denotes an inactive state of the claw where the claw is released from engagement by the clutch 20 and the control portions 81 through 83. A triangular mark denotes a partial engagement of the claw where the claw is only partially engaged in the power transmission and effects a sliding movement due to a speed difference.

In the foregoing embodiment, the speed-change hub is designed to provide five speeds including two high speeds, a middle speed and two low speeds. Instead, the hub can be designed to provide three speeds including two high speeds and one middle speed, or two low speeds and one middle speed, or the hub can be designed to provide four speeds including two high speeds and two low speeds.

In the foregoing embodiment, two sun gears are employed. Instead, the specific number of sun gears can vary conveniently.

Further, the operations of the control member 80 by the control portion 84 are effected from one direction in the foregoing embodiment. Alternately, it is also conceivable for the operations to be effected from the two opposite directions, i.e. the right and left directions. For this modified arrangement, for example, in FIG. 1, it is conceivable to arrange the lock claw 73 of the first sun gear 11 so that it is controlled by the control portion disposed at the right side of FIG. 1 while the lock claw 74 of the second sun gear 12 is controlled by the further control portion disposed at the left side of FIG. 1.

Further, in the foregoing embodiment, the lock claws 73 and 74 are supported respectively to the first and second sun gears 11 and 12. Instead, as illustrated in FIGS. 20 and 21, these lock claws can be supported respectively to the fixed shaft 1. In this case, the control operations of these lock claws relative to the sun gears are effected by means of sleeves 80i and 80j provided to the control member 80, respectively.

Moreover, the speed-change operations by using the control portion can vary in many other ways than those described in the foregoing embodiment. For instance, as illustrated in FIG. 22, the speed-change operations can be effected by operating a control bar 89 along the fixed shaft 1. In this case, as shown in FIG. 1, instead of moving the clutch 20 through the rotation of the first control portion 81 having a plurality of cam faces displaced peripherally of the fixed shaft relative to each other, the control bar 89 acts in place of the first control portion 81. Then, by moving this control bar 89 along the axis of the fixed shaft 1, two separate clutches 92 are selectively moved for operating the control member 80. More specifically, by pushing the control bar 89 in the axial direction, a rear poriton 92a of the clutch 92 is pushed via the key 30 and then a front portion 92b having a cam face of the clutch 92 and directly connected with the control member 80 is rotated. That is, this front portion 92b, when pushed by the clutch rear portion 92a, rotates about the fixed shaft 1 together with the control member 80.

The above axial operation of the control bar 89 is carried out by the user's operation of an unillustrated speed-change lever directly connected via a control cable with a bell crank (not shown) for pushing and pulling the control bar 89. Then, when the control bar 89 is pushed, the clutch 92 is pushed via the key 30 and then the control member 80 is rotated. Thus, in this modified construction, the control portion 84 such as illustrated in FIG. 1 is not necessary.

Further, as illustrated in FIG. 23, it is also conceivable that the axial movement of the control member 88 having cam faces 88a, 88b forwardly thereof causes engagement and disengagement of the lock claws 73 and 74 supported to the respective sun gears. That is, the axial pushing operation of the control bar 89 pushes the clutch 20 via the key 30 against the urging force of the return spring 40 and simultaneously therewith the control member 88 effects an axial movement to engage or disengage the lock claws 73 and 74. This modified construction is advantageous for its simpleness, since the clutch and the control member are not rotatably operated.

Further, if the user can effect the speed-change operations by such straight line motions rather than the rotary motions, the user can benefit from greater easiness in the operations.

The construction of the ball pushing element 15 can also vary in many ways. In its construction illustrated in FIG. 1, the element 15 includes a ball receiving face in its inclined outer peripheral face and a plurality of balls are peripherally dispersed and received in the receiving face so that the balls per se are movable in the peripheral direction. In place of this, for example, it is conceivable to define a plurality of recesses in the ball receiving face of the element 5 for receiving the balls while limiting peripheral movements of the same.

Further, according to the braking construction described in the foregoing embodiment, the reverse rotation of the drive member 3 causes the fifth transmission claw 17 as the one transmission claw to come into contact with the second transmission claw 8 supported to the drive member 3 as the other transmission claw for depressing this second transmission claw 8 thereby to break the power transmission from the drive member 3 to the ring gear 5. However, this operation for breaking the power transmission between the drive member 3 and the ring gear 5 can be carried out in many other ways.

For instance, as illustrated in FIGS. 24 through 26, a claw cage 91 is attached to an intermediate portion on the outer peripheral face of the drive member 3 and also a slide spring 93 is attached to the ring gear 5. So that, the claw cage 91 is moved via the fifth transmission claw 17 to come into contact with the second transmission claw 8 for depressing the same.

After a braking operation in the middle or low speed stages, the second transmission claw 8 is returned in the following manner. That is, when the drive member 3 is rotated in the forward direction, i.e. the driving direction, this drive member 3 per se effects free rotation relative to the ring gear 5. However, as shown in FIGS. 25 and 26, since the claw cage 91 is unmovable because of the slide spring 93 fitted on the ring gear 5, there occurs mutual rotation between the claw cage 91 and the drive member 3 thereby to return the second transmission claw 8. Incidentally, when the drive member 3 and the ring gear 5 are rotated relative to each other as in the high speed stages, the claw cage 91 is placed in abutment against the drive member 3 and therefore the slide spring 93 slides relative to the ring gear 5.

The operation for breaking the power transmission between the drive member 3 and the ring gear 5 can be effected still alternately as described below.

In this further modified construction, as shown in FIG. 27, the slide spring 93 is fitted on the relay member 6 so as to limit movement of the claw cage 94 having a guide portion 94a projecting from the leading end of its claw portion. This construction effects the same functions as that shown in FIG. 24. In this case, when the drive member 3 is rotated in the braking, i.e. reverse direction, the drive member 3 effects a free rotation relative to the relay member 6. On the other hand, since the claw cage 94 has its movement limited by the slide spring 93, the cage 94 is rotated ralative to the drive member 3. Accordingly, the fifth transmission claw 17, as shown in FIG. 29(a), causes the drive member 3 to come into engagement with the relay member 6 while the second transmission claw 8, as shown in FIG. 29(b), acts to release the engagement between the drive member 3 and the ring gear 5 thereby to break the power transmission between the drive member 3 and the ring gear 5. Incidentally, in the middle and low speed stages, the operations will occur in the opposite manners to those described above. That is, as shown in FIG. 28(b), the second transmission claw 8 causes the drive member 3 and the ring gear 5 to come into engagement with each other and acts also to release the engagement between the drive member 3 and the ring gear 5 as shown in FIG. 28(a).

In the above construction, the slide spring 93 is fitted on the relay member 6. Alternately, as shown in FIG. 24, the slide spring 93 can be fitted on the ring gear 5.

The invention may be embodied in other specific forms without departing from the sprit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.