Shifting Apparatus for Operating Front and Rear Derailleurs With a Single Manual Level

1. Field of the Invention

The present invention relates to a shifting apparatus for a multispeed bicycle having a plurality of front chainwheels, a plurality of rear gears, and front and rear derailleurs. This shifting apparatus is operable with a single manual lever to actuate the two derailleurs.

2. Description of the Related Art

A known shifting apparatus for a multispeed bicycle as noted above is disclosed in U.S. Pat. No. 4,194,408, for example. The bicycle has two front chainwheels, five rear gears, and front and rear derailleurs for changing a chain among these chainwheels and gears. The shifting apparatus includes a pair of change speed cams rotatable by a single manual lever, a pivot link pivotable by one of the change speed cams to pull or relax a control cable connected to the front derailleur, and a pivot link pivotable by the other change speed cam to pull or relax a control cable connected to the rear derailleur. When the manual lever is operated, the pair of change speed cams cause one or both of the derailleurs to change the chain among the front chainwheels and/or rear gears. Thus, the shifting apparatus provides 10 speed stages.

With an operation of the shifting apparatus, the chain may be changed both between the front chainwheels and between the rear gears. For example, the chain may be changed from the smaller front chainwheel to the larger front chainwheel and from the smallest rear gear to the largest rear gear, or from the larger front chainwheel to the smaller front chainwheel and from the largest rear gear to the smallest rear gear. A relatively long time is required to complete the actual shifting operation. For an interval of time must be set between the change at the front and the change at the rear, e.g. the chain is changed at the front and thereafter at the rear. This is necessary to avoid the chain coming off the chainwheels or gears which tends to occur when the chain is changed simultaneously at the front and the rear.

The object of the present invention is to provide a shifting apparatus for a bicycle which causes front and rear derailleurs to produce quickly and reliably all speed stages available from combinations of a plurality of front chainwheels and a plurality of rear gears.

The above object is fulfilled, according to the present invention, by a shifting apparatus for a bicycle having a first actuating mechanism for actuating a front derailleur, a second actuating mechanism for actuating a rear derailleur, and a single manual lever, the shifting apparatus comprising a shift controller responsive to operation of the manual lever to drive the first actuating mechanism or the second actuating mechanism to produce a speed stage, and responsive to repeated operation of the manual lever to produce all speed stages corresponding to all combinations of the front chainwheels and rear gears.

With this shifting apparatus, when the manual lever is operated, only the front derailleur or rear derailleur changes the chain to establish a speed stage corresponding to the lever operation. Such lever operations produce all speed stages by combinations of the front chainwheels and rear gears.

Thus, simple shifting operations to control the single manual lever produce all speed stages by the combinations of the front chainwheels and rear gears. These speed stages may be used effectively to make subtle speed adjustments in response to subtle variations in running load, for example, to realize smooth running. Since the chain is changed by action of only the front derailleur or the rear derailleur to provide a new speed stage, there is little chance of the chain coming off the front chainwheels or rear gears, and shifting operations may be effected with excellent responsivity at all times.

Other features and advantages of the present invention will be apparent from the following description of an embodiment to be had with reference to the drawings.

FIG. 1 is a schematic side view of a bicycle having a shifting apparatus according to the present invention.

FIG. 2 is a schematic perspective view of an actuating mechanism.

FIG. 3 is a sectional view of a proximal portion of a manual lever.

FIG. 4 is a block diagram of a control system for controlling the shifting apparatus.

FIG. 5 is an explanatory view of a change speed pattern.

FIG. 1 shows a change speed system of a multispeed bicycle. This system includes three front chainwheels F1, F2 and F3 having different numbers of teeth, which are rotatably mounted on a bottom bracket of a bicycle body frame 1 and driven by a crank 2; a front derailleur 3 attached to a seat tube of the body frame 1 by a clamp band 3a and having a chain guide 3b for changing a chain 4 among the front chainwheels F1, F2 and F3; seven rear gears G1-G7 having different numbers of teeth, which are rotatably mounted on a rear fork end of the body frame 1 and rotated by the front chainwheels F1, F2 and F3 through the chain 4 to drive a rear wheel of the bicycle; a rear derailleur 5 attached to the rear fork end by a bracket 5a and having a guide pulley 5b for changing the chain 4 among the rear gears G1-G7; and a shifting device particularly described hereunder.

As shown in FIG. 1, the shifting device includes a front actuating mechanism 20 attached to the seat tube of the body frame 1 for actuating the front derailleur 3, a rear actuating mechanism 30 attached to a back fork of the body frame 1 for actuating the rear derailleur 5, and a shift controller 40 for controlling the front actuating mechanism 20 and rear actuating mechanism 30. The shift controller 40 is mounted in a case 21 of the front actuating mechanism 20. A single manual lever 10 is attached to a brake lever bracket 9 along with a brake lever 7 to be disposed adjacent a grip 8a of a handlebar 8. Operation of the manual lever 10 is transmitted to the shift controller 40 as particularly described hereinafter.

As shown in FIG. 1, the front actuating mechanism 20 has the case 21 attached to the seat tube. Referring to FIG. 2, the case 21 contains a takeup element 22, a reduction mechanism 23, a reversible electric motor 24, a drive circuit 25, a battery power source 26 and a rotary potentiometer 27. The potentiometer 27 detects a rotational position of the takeup element 22 and produces an electric signal indicative of a front speed stage based on the detection. The drive circuit 25 is operable in response to a predetermined signal received from the shift controller 40 to rotate the electric motor 24 forward or backward. Then the electric motor 24 transmits a torque, which is reduced by the reduction mechanism 23, to the takeup element 22 whereby the takeup element 22 winds or unwinds a control cable 6a. When the takeup element 22 winds the control cable 6a, a pulling force of the control cable 6a causes a pivot link 3c between the chain guide 3b and band 3a of the front derailleur 3 to pivot inwardly of the body frame 1 relative to the band 3a. As a result, the chain guide 3b pushes the chain 4 to change from a larger one to a smaller one of the front chainwheels F1, F2 and F3. When the takeup element 22 unwinds the control cable 6a, a return spring (not shown) of the front derailleur 3 causes the pivot link 3c to pivot outwardly of the body frame 1 relative to the band 3a. As a result, the chain guide 3b pushes the chain 4 to change from a smaller one to a larger one of the front chainwheels F1, F2 and F3. When a selected speed stage is established with the chain 4 placed in engagement with one of the front chainwheels F1, F2 and F3, the shift controller 40 transmits a signal based on a result of detection by the potentiometer 27 to the drive circuit 25. Then, the drive circuit 25 stops the electric motor 24 whereupon the takeup element 22 stops winding or unwinding the control cable 6a. The control cable 6a or return spring becomes inoperative to complete the operation of chain guide 3b to change the chain 4. Thus, in response to a signal from the shift controller 40, the front actuating mechanism 20 actuates the front derailleur 3 through the control cable 6a.

The rear actuating mechanism 30 has substantially the same construction as the front actuating mechanism 20, and will be described referring again to FIG. 2 showing the front actuating mechanism 20. In FIG. 2, numerals in parentheses denote the components of the rear actuating mechanism 30. As shown in FIG. 1, the rear actuating mechanism 30 has a case 31 fixed to the back fork of the body frame 1. Referring to FIG. 2, the case 31 contains a takeup element 32, a reduction mechanism 33, a reversible electric motor 34, a drive circuit 35, a battery power source 36 and a rotary potentiometer 37. The potentiometer 37 detects a rotational position of the takeup element 32 and produces an electric signal indicative of a rear speed stage based on the detection. The drive circuit 35 is operable in response to a predetermined signal received from the shift controller 40 to rotate the electric motor 34, whereby the takeup element 32 winds or unwinds a control cable 6b. When the takeup element 32 winds the control cable 6b, a pulling force of the control cable 6b causes a pivot link 5d between the bracket 5a of the rear derailleur 5 and a support 5c of the guide pulley 5b to pivot inwardly of the body frame 1 relative to the bracket 5a. As a result, the guide pulley 5b pushes the chain 4 to change from a larger one to a smaller one of the rear gears G1-G7. When the takeup element 32 unwinds the control cable 6b, a return spring (not shown) of the rear derailleur 5 causes the pivot link 5d to pivot outwardly of the body frame 1 relative to the bracket 5a. As a result, the guide pulley 5b pushes the chain 4 to change from a smaller one to a larger one of the rear gears G1-G7. When a selected speed stage is established with the chain 4 placed in engagement with one of the rear gears G1-G7, the shift controller 40 transmits a signal based on a result of detection by the potentiometer 37 to the drive circuit 35. Then, the drive circuit 35 stops the electric motor 34 whereupon the takeup element 32 stops winding or unwinding the control cable 6b. The control cable 6b or return spring becomes inoperative to complete the operation of guide pulley 5b to change the chain 4. Thus, in response to a signal from the shift controller 40, the rear actuating mechanism 30 actuates the rear derailleur 5 through the control cable 6b.

As shown in FIG. 3, the manual lever 10 has a proximal end 10a thereof rotatably attached to a lever support 9a of the lever bracket 9. Thus, the manual lever 10 is pivotable about an axis 11 by the rider's hand holding the grip 8a of the handlebar 8, between an accelerating position U and a decelerating position D across a neutral position N. The proximal end 10a of the manual lever 10 includes a switch operator 10b. When the manual lever 10 is in the accelerating position U, the switch controller 10b contacts a stopper 9b formed in the lever bracket 9. When the manual lever 10 is in the decelerating position D, the switch controller 10b contacts a stopper 9c formed in the lever bracket 9.

A return spring 12 is disposed on a side wall of the proximal end 10a of the manual lever 10. The proximal ends 10a includes a spring presser 10c while the lever support 9a includes a spring bearing 9d. When the manual lever 10 is operated to the accelerating position U, the spring bearing 9d supports one end of the return spring 12, and the spring presser 10c pushes the other end of the return spring 12. This elastically deforms the return spring 12 to bias the manual lever 10 toward the neutral position N. When the manual lever 10 is operated to the decelerating position D, the spring bearing 9d supports the other end of the return spring 12, and the spring presser 10c pushes the one end of the return spring 12. This elastically deforms the return spring 12 to bias the manual lever 10 toward the neutral position N. That is, the return spring 12 is operable to maintain the manual lever 10 in the neutral position N, and to return the manual lever 10 automatically from the accelerating position U or decelerating position D to the neutral position N.

The lever support 9a further supports a pair of detection switches 13a and 13b. When the manual lever 10 is operated to the accelerating position U, the switch operator 10b presses upon one of the detection switches 13a. When the manual lever 10 is operated to the decelerating position D, the switch operator 10b presses upon the other detection switch 13b. Thus, a shifting operation effected in the accelerating direction is detected by one of the detection switches 13a which transmits a corresponding electric signal to the shift controller 40. A shifting operation effected in the decelerating direction is detected by the other detection switches 13b which transmits a corresponding electric signal to the shift controller 40.

As shown in FIG. 4, the shift controller 40 includes a microcomputer as a central component thereof, which essentially is programmed to provide a processing unit 41, a shifting operation detecting unit 42, a front speed detecting unit 43, a rear speed detecting unit 44 and a speed setting unit 45.

When the manual lever 10 is operated to the accelerating position U or decelerating position D, the processing unit 41 and shifting operation detecting unit 42 process the signal received from the detection switch 13a or 13b. The shifting operation detecting unit 42 determines whether the manual lever 10 is operated to the accelerating position U or to the decelerating position D. The processing unit 41, front speed detecting unit 43 and rear speed detecting unit 44 process the signals received from the potentiometers 27 and 37. The front speed detecting unit 43 determines a current front speed stage, i.e. one of top speed T, middle speed M and low speed L. The rear speed detecting unit 44 determines a current rear speed stage, i.e. one of the first to seventh speeds. The speed setting unit 45 sets a target speed to be attained, based on the direction of a shifting operation detected by the shifting operation detecting unit 42, the front speed stage detected by the front speed detecting unit 43, the rear speed stage detected by the rear speed detecting unit 44, and a change speed pattern inputted in advance. FIG. 5 shows the change speed pattern inputted in advance for setting a target speed. This pattern provides a first to a twenty-first speed stages based on various combinations of the three front chainwheels F1, F2 and F3 and seven rear gears G1-G7. One of the twenty-one speed stages is set as the target speed. When the manual lever 10 is operated to the accelerating position U, the target speed is a speed stage next in the direction of a solid line arrow to a speed stage functioning before the shifting operation. When the manual lever 10 is operated to the decelerating position D, the target speed is a speed stage next in the direction of a broken line arrow to a speed stage functioning before the shifting operation. The processing unit 41 outputs signals to the drive circuits 25 and 35 to move or stop the front derailleur 3 and rear derailleur 5 to/at positions to produce the target speed set by the speed setting unit 45.

In FIG. 5, low speed L, middle speed M and top speed T are the front speed stages. The low speed L is the speed stage provided when the chain 4 is engaged with the smallest F3 of the front chainwheels F1, F2 and F3. The middle speed M is the speed stage provided when the chain 4 is engaged with the intermediate front chainwheel F2. The top speed T is the speed stage provided when the chain 4 is engaged with the largest front chainwheel F1. The first to seventh speeds are the rear speed stages. The first speed is provided when the chain 4 is engaged with the largest G1 of the rear gears G1-G7. The second speed is provided when the chain 4 is engaged with the second largest rear gear G2. The third speed is provided when the chain 4 is engaged with the third largest rear gear G3. The fourth speed is provided when the chain 4 is engaged with the fourth rear gear G4. The fifth speed is provided when the chain 4 is engaged with the fifth rear gear G5. The sixth speed is provided when the chain 4 is engaged with the sixth rear gear G6. The seventh speed is provided when the chain 4 is engaged with the seventh or smallest rear gear G7. The first to twenty-first speeds are the speed stages of the shifting device as a whole, which are produced by the combinations of the front and rear speed stages. The first to seventh speeds are provided when the front speed stage is low speed L and the rear speed stage is the first to seventh speeds. The eighth to fourteenth speeds are provided when the front speed stage is middle speed M and the rear speed is the first to seventh speeds. The fifteenth to twenty-first speeds are provided when the front speed stage is top speed T and the rear speed is the first to seventh speeds. For example, the first speed is provided when the front speed stage is low speed L and the rear speed stage is the first speed. The seventh speed is provided when the front speed stage is low speed L and the rear speed stage is the seventh speed. The eighth speed is provided when the front speed stage is middle speed M and the rear speed stage is the first speed. The fourteenth speed is provided when the front speed stage is middle speed M and the rear speed stage is the seventh speed. The fifteenth speed is provided when the front speed stage is top speed T and the rear speed stage is the first speed. The twenty-first speed is provided when the front speed stage is top speed T and the rear speed stage is the seventh speed.

That is, when the manual lever 10 is operated to the accelerating position U, the shift controller 40 sets a target speed as shown in FIG. 5, and transmits predetermined signals to the front actuating mechanism 20 and rear actuating mechanism 30. As a result, depending on a speed stage functioning before the shifting operation, the front derailleur 3 or rear derailleur 5 is operated to establish a next speed stage in the direction of a solid line arrow shown in FIG. 5. When the manual lever 10 is operated to the decelerating position D, the shift controller 40 sets a target speed as shown in FIG. 5, and transmits predetermined signals to the front actuating mechanism 20 and rear actuating mechanism 30. As a result, depending on a speed stage functioning before the shifting operation, the front derailleur 3 or rear derailleur 5 is operated to establish a next speed stage in the direction of a broken line arrow shown in FIG. 5. As a whole, the shift controller 40 is operable to set target speeds as shown in FIG. 5, whereby all of the first to twenty-first speed stages may be established by combinations of the three front chainwheels F1-F3 and seven rear gears G1-G7.

When a shifting operation is repeatedly carded out in the accelerating direction in a state in which the chain 4 is engaged with the smallest front chainwheel F3 and the largest rear gear G1 to provide the first speed stage, the front derailleur 3 remains out of operation to maintain the chain 4 on the smallest front chainwheel F3, and the rear derailleur 5 is operated to change the chain 4 successively to the smaller rear gears, thereby successively to switch from the first speed stage to the seventh speed stage. When a shifting operation is repeatedly carded out in the accelerating direction after the chain 4 is engaged with the smallest rear gear G7 providing the seventh speed stage, the rear derailleur 5 is stopped to maintain the chain 4 on the smallest rear gear G7, and the front derailleur 3 is operated to change the chain 4 successively to the larger front chainwheels, thereby to switch from the seventh speed stage to the fourteenth speed stage and to the twenty-first speed stage. When a shifting operation is repeatedly carded out in the accelerating direction in a state in which the chain 4 is engaged with the intermediate front chainwheel F2 and the largest rear gears G1 to provide the eighth speed stage, the front derailleur 3 remains out of operation to maintain the chain 4 on the intermediate front chainwheel F2, and the rear derailleur 5 is operated to change the chain 4 successively to the smaller rear gears, thereby successively to switch from the eighth speed stage to the fourteenth speed stage. When a shifting operation is carried out in the accelerating direction after the chain 4 is engaged with the smallest rear gear G7 providing the fourteenth speed stage, the rear derailleur 5 is stopped to maintain the chain 4 on the smallest rear gear G7, and the front derailleur 3 is operated to change the chain 4 to the largest front chainwheels F1, thereby to switch from the fourteenth speed stage to the twenty-first speed stage. When a shifting operation is carried out in the accelerating direction with the chain 4 engaged with the largest front chainwheel F1 and largest rear gear G1 providing the fifteenth speed stage, the front derailleur 3 is stopped to maintain the chain 4 on the largest front chainwheel F1, and the rear derailleur 5 is operated to change the chain 4 successively to the smaller rear gears, thereby successively to switch from the fifteenth speed stage to the twenty-first speed stage.

When a shifting operation is repeatedly carried out in the decelerating direction in a state in which the chain 4 is engaged with the largest front chainwheel F1 and the smallest rear gear G7 to provide the twenty-first speed stage, the front derailleur 3 remains out of operation to maintain the chain 4 on the largest front chainwheel F1, and the rear derailleur 5 is operated to change the chain 4 successively to the larger rear gears, thereby successively to switch from the twenty-first speed stage to the fifteenth speed stage. When a shifting operation is repeatedly carried out in the decelerating direction after the fifteen speed stage is established, the rear derailleur 5 is stopped to maintain the chain 4 on the largest rear gear G1, and the front derailleur 3 is operated to change the chain 4 successively to the smaller front chainwheels, thereby to switch from the fifteenth speed stage to the eighth speed stage and to the first speed stage. When a shifting operation is repeatedly carried out in the decelerating direction in a state in which the chain 4 is engaged with the intermediate front chainwheel F2 and the smallest rear gears G7 to provide the fourteenth speed stage, the front derailleur 3 remains out of operation to maintain the chain 4 on the intermediate front chainwheel F2, and the rear derailleur 5 is operated to change the chain 4 successively to the larger rear gears, thereby successively to switch from the fourteenth speed stage to the eighth speed stage. When a shifting operation is carried out in the decelerating direction after the eighth speed stage is established, the rear derailleur 5 is stopped to maintain the chain 4 on the largest rear gear G1, and the front derailleur 3 is operated to change the chain 4 to the smallest front chainwheel F3, thereby to switch from the eighth speed stage to the first speed stage. When a shifting operation is carried out in the decelerating direction with the chain 4 engaged with the smallest front chainwheel F3 and smallest rear gear G7 providing the seventh speed stage, the front derailleur 3 is stopped to maintain the chain 4 on the smallest front chainwheel F3, and the rear derailleur 5 is operated to change the chain 4 successively to the larger rear gears, thereby successively to switch from the seventh speed stage to the first speed stage.

The front actuating mechanism or rear actuating mechanism may be replaced with a mechanism for convening the bicycle driving torque of the chain, gears or wheels into power for operating the chain guide or guide pulley. This converting mechanism may be operable by a control mechanism switchable between operative state and inoperative state by electric signals. When a predetermined electric signal is inputted, the chain guide or guide pulley is operated by the bicycle driving power to change the chain. Instead of the electrical connection between the single manual lever and the two derailleurs, a mechanical interlocking structure may be employed to transmit an operating force of the manual lever to the derailleurs through a cam mechanism and control cables. In this modification, the two derailleurs are operable only by a manual operating force applied to the single manual lever. In the described embodiment, the shifting apparatus provides a total of 21 speed stages by combinations of the three front chainwheels and seven rear gears. The number of front chainwheels may be two instead of three, and the number of rear gears may be six or eight instead of seven. Thus, the present invention is applicable also to a shifting apparatus constructed to provide more than or less than 21 speed stages.