Abstract:
A multiple-speed transmission wheel hub for imparting torque to a drive wheel includes a hub shell formed around a wheel axis and a clutch wheel formed around the wheel axis and axially movable between at least first and second speed positions. First gearing couples the clutch wheel to the hub shell when the clutch wheel is in the first position producing a first transmission speed. Second gearing couples the clutch wheel in the second speed position with the hub shell producing a second transmission speed. A speed-shifting cam is disposed on the axis and axially rotatable between at least first and second speed positions, with helical segments formed on a surface of the clutch wheel facing the cam, the helical segments coupling to the cam to translate rotation of the cam into axial displacement of the clutch wheel both from the second speed position to the first speed position and from the first speed position to the second speed position.

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/125,011, filed Mar. 18, 1999. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The invention pertains to the use of a servo principle for a three-speed hub to shift between three speeds regardless of the load through the transmission and with negligible effort to actuate the shift. The invention uses a sloped, periodic camming action to force the shifts in both the upshifting direction and in the downshifting direction. 
     BACKGROUND OF THE INVENTION 
     In conventional three speed internal hub transmissions used on bicycles, the load path and therefore the gear ratio is controlled by the position of an element called the “clutch wheel” or “claw clutch”. The clutch wheel moves axially along the axle between three axial positions. In conventional designs which are currently in use in the marketplace, the axial position of the clutch wheel is controlled in one direction by a pull chain, cable, or pushrod/bell crank mechanism and in the other direction by a return spring. 
     When the transmission is transmitting a load, the splines at each end of the clutch wheel are loaded circumferentially and the resulting friction prevents easy axial movement. In order to make the transmission shift under more than zero load, the preload in the return spring is increased. In order to make the transmission shift under more load than this, the preload must be increased proportionally to the load through the transmission. This increase in preload of the return spring must ultimately be overcome by effort at the hand actuator on the handlebar. The preload needed to make the conventional design shift under load makes this effort excessive. 
     It is therefore desirable to find another source of axial force or forces to move the clutch wheel in both the up and down shifting directions. Ideally it would also be desirable to find a source of axial force that is always proportional to the load through the transmission and is therefore always great enough to overcome the frictional forces that oppose this movement. 
     European Patent Application 876953 discloses a mechanism which uses a servo principle to move the clutch wheel. As shown in FIGS. 1-4, this mechanism upshifts in a conventional manner using no servo effect to “force” the upshift. Movement of the clutch wheel in the upshifting direction is effected by a displacement of the control cable  73   b  toward the handlebar actuator. This rotates a bellcrank  71  which pushes on pushrod assembly  69  and  68  (FIG.  2 ). A preloaded spring  60  is therefore compressed below its installed length and transfers the force to control element assembly  66  and  49 . The axial force is then transferred to a clutch wheel  45  by means of a snap ring  63  (FIG.  3 ). The force to move the clutch wheel  45  in the upshifting axial direction is the result of the energy put into the hand actuator on the handlebar minus the inefficiencies of all the interactions between the handlebar actuator and the clutch wheel. The control elements  69 ,  68 ,  60 ,  66  and  49  must move axially to displace the clutch wheel  45  the same axial distance. 
     The mechanism downshifts in a servo manner. To initiate a downshift, the cable  73   b  and the bell crank  71  release the control elements  69 ,  68 ,  60 ,  66 , and  49  so that another preloaded spring  61  can apply an unopposed force on an element  49 . When the cam lobes on the inside diameter of the clutch wheel permit it, element  49  moves into a valley  47   a  between the cam lobes. Element  49  simultaneously slides along helical slot  21   b  in the axle. The angles between the helical slot  21  in the axle and the helical cam inside the clutch wheel cooperate in such a way that the control element  49  becomes axially fixed and therefore the rotation of the clutch wheel is converted to axial displacement as control element  49  slides up helical cam ramp  47   c . As in the case of the upshifting sequence, elements  69 ,  68 ,  60 ,  66 , and  49  move axially to accomplish a displacement of the clutch wheel the same axial distance. 
     One feature that distinguishes the present invention from the device disclosed in EP 876953 is that the helical camming servo effect works in one direction only in the aforementioned prior art. Furthermore, in this prior art construction, to be fully enabled to both up and down shift, the device must use both the helical camming servo effect and the conventional simple non-servo pushing method. 
     The use of an axially moving control element also has certain drawbacks. In a three-speed hub, it must protrude out of the end of the axle at least as much as the combined stroke of two shifts. This is a very vulnerable place to put a delicate, protruding control element. It is also awkward to convert cable displacement into control element displacement because of the 90-degree difference in orientation. The axially moving control element is also awkward to control with a gear motor since a gear motor in its simplest form is most suitable to deliver rotation, not sliding, axial movement. Also, as a general engineering principle, rotation is preferable to sliding because it is less susceptible to cocking and jamming. 
     SUMMARY OF THE INVENTION 
     The present invention answers these deficiencies because it employs a helical camming servo effect for moving the clutch wheel in both the up and down shifting directions and completely eliminates the need for the conventional control element to push the clutch wheel by moving axially itself. The present invention also uses a control element which is simply rotates. 
     A multiple-speed planetary hub mechanism according to the invention comprises a rotatable control cam having a plurality of axially noncylindrical camming surfaces. A clutch wheel is located about the control cam, and a plurality of ball sets are located between the clutch wheel and the control cam. As the control cam rotates, the ball sets engage selectively are radially urged outwardly by the control cam camming surface and selectively interact with camming surfaces on the clutch wheel. The movement of the ball sets against the camming surfaces produces an axial movement of the clutch wheel. The change of axial position of the clutch wheel alters the transmission load path through the hub assembly. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of an internal hub transmission according to the prior art. 
     FIG. 2 is a detailed view of the internal hub transmission shown in FIG.  1 . 
     FIG. 3 is an oblique view of portion of the hub transmission shown in FIG.  1 . 
     FIG. 4 is schematic view illustrating the operation of the shift key and cam surface in the hub transmission shown in FIG.  1 . 
     FIG. 5 is an axial view of an entire hub assembly according to one embodiment of the present invention. 
     FIG. 6 is a detailed axial view of the clutch wheel, axle, and control elements shown in FIG.  4 . 
     FIG. 7 is a schematic view of the control ball pair dispositions for each of the three gear selections. 
     FIG. 8 is a view of the inside diameter of the clutch wheel as if it were unrolled, showing the relative locations of the ball pairs for different gear positions. 
     FIG. 9 is a view of the turning mechanism for rotating the control cam between gear positions. 
     FIG. 10 is a side view of the control cam and ball pairs when the hub mechanism is in the low gear position. 
     FIG. 11 is a right end view of the control cam of FIG.  10 . 
     FIG. 12 is a side view of the control cam and ball pairs when the hub mechanism is in an intermediate gear position. 
     FIG. 13 is a right end view of the control cam of FIG.  12 . 
     FIG. 14 is a side view of the control cam and ball pairs when the hub mechanism is in a high gear position. 
     FIG. 15 is a right end view of the control cam of FIG.  14 . 
     FIG. 16 is a sectional end view of the control cam along lines  16 — 16  of FIG.  14 . 
     FIG. 17 is a sectional end view of the control cam along lines  17 — 17  of FIG.  14 . 
     FIG. 18 is a sectional end view of the control cam along lines  18 — 18  of FIG.  14 . 
     FIG. 19 is a sectional end view of the control cam along lines  19 — 19  of FIG.  14 . 
     FIG. 20 is a view of the snap ring arrangement for maintaining the clutch wheel in the low gear position. 
     FIG. 21 is a side view of the snap ring of FIG. 20, 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The elements of the hub assembly  102  are shown in FIG.  5 . Elements  10  and  180  are bicycle frame members or dropouts for holding an axle  5 . The hub assembly is retained in the dropouts by threaded axle nuts  230  and  220 . 
     The hub assembly  102  is built on the axle  5  by first installing four control ball pairs,  290 ,  300 ,  320 , and  330 . Then a control cam  390  is installed by inserting it into the tubular axle  5 . The control cam  390  is rotated to a low gear position so that control ball pairs  320  and  330  are retracted into grooves  104  and  106  and flush with the outside diameter of the axle  5 . In this position a clutch wheel  305  can be slid into place. 
     A planet carrier body  112  consists of elements  270 ,  100 , and  110 . The main body  270  of the planet carrier  112  supports a plurality of one way ratchet pawls  70  and planet shafts  260 . The ratchet pawls are spring loaded (springs not shown) in the radially outward direction. Planet carrier body elements  100  and  110  are preferably formed to be integral with the main body  270 ; in this cross section they appear to be separate, but that is only because of recess  114  required for the planet gear  90 . Element  100  supports the other end of planet shaft  260 , and element  110  is a castellation oriented axially and formed on element  100 . Another set of one-way ratchet pawls  140  (one shown) is installed into pockets  116  in the outside diameter of a ring gear  80 . The pawls  140  are spring loaded (spring not shown) in the radially outward direction. 
     A slip ring  130  is snapped past a ridge  135  of a hub shell  40  and is trapped axially between ridge  135  and a set of ratchet teeth  120  formed in the hub shell  40 . Another set of ratchet teeth  60  are integral with the hub shell  40  and engage with ratchet pawls  70 . Radially outwardly projecting spoke flanges  50  are also integral with the hub shell  40  and are used for mounting the spokes of the bicycle wheel. 
     An input sprocket  170  is installed onto an input shell  190 . A snap ring  340  is installed into a snap ring retention groove  350 . The ring gear  80  is slid over the clutch wheel  310 . Next, a helical ring gear spring  150  is placed against the ring gear  80  and bearing balls  160  (as trapped in a carrier, not shown) are placed over the spring. An input shell  190  is then installed over the splines  375  formed on the outboard end of the claw clutch  305 . Bearing balls  200  (trapped in a carrier, not shown) are then placed against the bearing race formed into the outboard end of the input shell  190 . Then, an outboard bearing cone  210  is threaded onto the axle  230  and retained with axle nut  215 . 
     Next, the hub shell  40  is placed so that the bearing race  118  on the drive (in FIG. 5, rightward) end of the shell  40  is against bearing balls  160 . Then the planet carrier  270  is placed over the axle  5  and against the non-drive (leftward) side of a sun gear  285  that is preferably formed to be integral with the axle  5 . In this position, the planet gears  90  are meshed with the sun gear  285  and the ring gear  80 . Then bearing balls  30  are placed against the bearing race  122  on the non drive (leftward) end of the hub shell  40 . Next, a helical planet carrier positioning spring  250  is installed over the axle  5 . A non-drive side bearing cone  25  is then threaded onto the axle  5 , trapping and preloading spring  250  and loading all of the bearing balls  30 ,  160 , and  200 . Locknuts  20  are threaded onto the non-drive end of axle  5  to adjust and secure the position of cone  25 . The hub assembly is secured to the bicycle dropouts  10  and  180  by tightening axle nuts  230  and  220 . 
     The method of operation is shown in FIGS. 5-7. When the load path and corresponding gear ratio are in low gear (as shown in FIG.  5 ), the load path starts at the input sprocket  170  (which is engaged to a conventional bicycle chain) and is transferred to the input shell  190  by splines (not shown) between the input sprocket  170  and the input shell  190 . Then the load is transferred by means of splines  375  on the inside diameter of the input shell  190  to the splines on the outboard end of the clutch wheel  305 . The load is then transferred to the ring gear  80  by means of inboard splines  315  on the clutch wheel  305  and corresponding splines  145  on the ring gear  80 . The ring gear  80  then turns the planet gears  90  around the sun gear  285 . This rotates the planet carrier  270  at a slower speed than the input sprocket  170 . The planet carrier  270  then rotates the hub by means of one way ratchet pawls  70  engaging ratchet teeth  60  in the hub  40 . 
     In the low gear position, the snap ring  340  engages a specially shaped spline  500  on the clutch wheel  305  to form a detent or temporary retention mechanism to oppose the effect of ring gear return spring  150 . The spline  500  is contoured in order to cooperate with the D-shaped snap ring  340 . The detent is just strong enough to overcome return spring  150 . During a shift from low to middle gear the detent releases the clutch wheel  305  from the input shell  190  to permit it to move to the left to engage middle gear. The interaction of the spline  500  and the snap ring  340  is shown in detail in FIGS. 20-21. 
     When it is desired to shift the transmission from low to middle gear, the following sequence occurs. First the rotating control cam  390  is rotated to allow control balls  300  to recess inside the axle and then the control cam  390  displaces and locks control balls  330  radially outwardly. As shown in FIG. 9, this is accomplished by use of a spool  400  that is biased by a spring  440  against a cable (not shown). The cable originates from the hand controls near the front of the bicycle. A saver spring  410  urges the control cam  390  to match the rotational position of the spool  400 . This occurs due to the saver spring&#39;s  410  tendency to keep the spool pin  420  and cam pin  430  in alignment with each other. The saver spring  410  also has some flexibility in one embodiment of the invention in order t o allow a temporary misalignment when the control cam rotation cannot be accomplished immediately. In this position the control balls  330  will interact with the outboard sloped, periodic camming surfaces  370  on the inside diameter of the clutch wheel  305  in such a way as to convert rotation of the clutch wheel  305  into leftward (as seen in FIG. 5) axial displacement of the clutch wheel  305 . FIG. 5 further shows the relative placement of each of the control balls  290 ,  300 ,  320 , and  330  and the rotating control cam  390  in low gear. 
     The camming surfaces  370  and  380  are not helical when taken as a whole, but rather are composed of a series of alternating right-handed and left-handed helical segments of substantially equal length which are joined together by several transitions which make peaks and valleys. FIGS. 10-15 show the relative positions of the transitions and ball pairs when the control cam  390  is in the low, intermediate, and high gear positions. FIGS. 16-19 show various cross-sections of the control cam  390  when the hub mechanism  2  is in a high gear position. As can be seen in the drawings the two middle ball pairs  300  and  320  are prominent and active for one of three positions and retracted and inactive for the other two positions. It is for this reason that the valleys  610  and  620  shown in FIGS. 17 and 18 are smaller than the valleys  600  and  630  shown in FIGS. 16 and 19. A schematic of the helical camming surfaces on the inside diameter of the clutch wheel  305  is shown in FIG.  8 . FIG. 8 shows the inside diameter of clutch wheel  305  as if it were unrolled or laid flat. The axial distance from a peak to a valley of the cammed surface  370  or  380  corresponds to the stroke required for one shift. In the illustrated embodiment, the stroke for the shift from low to middle gear is substantially the same as for the shift from middle to high gear. Also the strokes from high to middle and from middle to low are substantially the same. This need not be the case. The same upshifting camming surfaces  370  are used for the shifts from low to middle and from middle to high. For the first shift from low to middle, the cammed surface  370  interacts with balls  330 . For the shift from middle to high the cammed surface  370  interacts with balls  320 . The relative positions of each of the balls  290 ,  300 ,  320  and  330  for the low, middle, and high gears is shown in FIG.  6 . 
     When the clutch wheel  305  moves to the left, the ring gear  80  is forced to follow by the ring gear return spring  150 . Ring gear ratchets  140  drag slip ring  130  to the left until the slip ring  130  is stopped by the ratchet teeth  120 . At this point, the ring gear  80  and ratchets  140  continue to move to the left placing the ratchets  140  under the ratchet teeth  120  then escaping from under the slip ring  130  so that the ratchets engage the ratchet teeth  120 . 
     For the load path corresponding to middle gear, the load path is transferred directly from the ring gear  80  to the hub by means of the ratchet teeth  140 . The planetary gear system is bypassed and the hub shell  40  rotates at the same speed as the input sprocket  170 . In this condition the transmission is in “lock out” or in a one to one condition. In this condition, the ratchets  70  are overdriven. 
     When it is desired to shift the transmission from middle gear to high gear, the following sequence occurs. First the rotating control cam  390  is rotated to allow control balls  290  to drop below the outside diameter of the axle  230 . Then the control cam  390  displaces control balls  320  into the up and locked position. In this position, the control balls  320  interact with the helical camming surfaces  370  on the inside face of the clutch wheel  305 . This interaction converts the rotation of the clutch wheel  305  into axial motion to the left in FIG. 4 or in the upshifting, axial direction. The ring gear  80  is prevented from moving as far to the left as the clutch wheel  305  because it comes up against the planet carrier  270 . This causes the splines  145  on the ring gear  80  to disengage from the splines  315  on the clutch wheel  305 . Another set of splines  310  on the clutch wheel  305  then engage corresponding castellations  110  on the planet carrier  270 . 
     For a load path corresponding to high gear, when the castellations  110  on the planet carrier  270  are driven by the splines  310  on the clutch wheel  305 , the load is transferred from the clutch wheel  305  to the planet carrier  270 . This is the overdrive condition. The planet carrier  270  and rotating planet gears  90  drive the ring gear  80  at a higher speed than the input sprocket. The load is transmitted from the ring gear to the hub by means of the ratchets  140  and ratchet teeth  120 . In this condition the ratchets  70  are overdriven. 
     When it is desired to shift the transmission from high to middle gear, the following sequence occurs: First, the rotating cam  390  is rotated to allow control balls  320  to drop below the outside diameter of the axle  230  and then control balls  290  are displaced into the up and locked position. In this position, the balls  290  interact with the down shifting camming surfaces  380 . Rotation of the clutch wheel  305  is converted into axial movement of the clutch wheel  305  in the downshifting (in FIG. 5, rightward) direction. As was the case with upshifting, the downshifting camming surfaces  380  are used twice: once for the shift from high to middle and once more for the shift from middle to low. 
     The load path in middle gear has already been described above and is not influenced by whether it is arrived at by an upshift or a downshift. 
     When it is desired to shift from middle to low gear, the control cam  390  is rotated to drop balls  330  and raise and balls  300 . The camming action between balls  300  and downshifting camming surface  380  converts rotation of the clutch wheel  305  into axial motion of the clutch wheel  305  in the downshifting direction. The leftmost splines  310  on the clutch wheel  305  pull the ring gear  80  to the right so that ratchets  130  are disengaged from ratchet teeth  120 . They are completely disengaged at about half the shift stroke. During the rest of the stroke to the right, the ratchets are trapped and pinned under the slip ring  130 . The system arrives at the condition shown in FIG. 4 with the ratchets  140  trapped and the slip ring  130  rotating with the ratchets  140 . The ratchets will be released when the transmission is shifted into middle gear as described above. 
     The load path for low gear has been described above. 
     Regarding the control cam or control cam rod  390 , the deployment of control balls in the “up and locked” position is “opportunistic”. By this it is meant that depending on the position of the helical cam surfaces  380  and  370 , the control balls cannot be arbitrarily forced into the up and locked position. For example they may start up and then get jammed down before they get into the “locked” position. In this case the control rod  390  must be free to return to the start position and try again. Presumably the next try will be successful since the “window of opportunity” at the bottom of a valley in the cams  370  and  380  will reappear. The trick is to use a saver spring, shown in FIG. 9, to gently preload the control cam in the desired direction but not force it until the window of opportunity is wide open. 
     The “up and locked” position of control balls is achieved by configuring the cam lobes so that the contact angle between the lobe and the ball is tangential to the control cam rod. This way, forces downward on the ball resulting from the strong interaction with the helical camming surfaces  370  and  380  cannot apply a rotational force on the control cam rod  390 . It becomes a matter of strength of materials only. Short of the “locked” position, it is desirable that the downward force on the ball can exert a rotational force on the control cam rod  390  to counter rotate it to the start of its motion so it can try again without jamming the whole control mechanism. 
     Additionally, it is may also be desirable to configure the cam lobes so that the balls being retracted are nearly fully retracted before the balls being deployed up begin to go up. 
     While several preferred embodiments have been shown and described, it is understood that changes and modifications can be made to the invention without departing from the invention&#39;s broader aspects. Thus, it is apparent that alternative embodiments are available to most skilled and development art. Therefore, the present invention is not limited to the described and illustrated embodiment but only by the scope and spirit of independent and dependent claims.