Patent Publication Number: US-11661141-B2

Title: Derailleur for human-powered vehicle

Description:
BACKGROUND 
     The present disclosure relates to a human-powered vehicle derailleur. 
     Patent Document 1 discloses an example of a human-powered vehicle derailleur including a pulley assembly biasing member. The pulley assembly biasing member biases a pulley assembly so that the position of the pulley assembly relative to a movable member shifts from a second rotational position toward a first rotational position.
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2016-7905   

     SUMMARY 
     One object of the present disclosure is to provide a human-powered vehicle derailleur that sets rotational force of a pulley assembly in a preferred state. 
     In accordance with a first aspect of the present disclosure, a human-powered vehicle derailleur comprises a base member configured to be attached to a human-powered vehicle frame, a movable member movable relative to the base member, a linkage structure operatively connecting the movable member to the base member, a pulley assembly attached to the movable member so that the pulley assembly is pivotally movable relative to the movable member about a pivot axis in a first direction and a second direction opposite to the first direction with respect to the pivot axis, and a rotational force control structure configured to control rotational force of the pulley assembly relative to the movable member. The pulley assembly has a first pivotal position and a second pivotal position. The pulley assembly is configured to move in the first direction upon moving from the second pivotal position toward the first pivotal position. The rotational force control structure includes a cam member having a first cam surface, an abutment member configured to abut the first cam surface, and a biasing member configured to bias the abutment member. The abutment member is configured to abut the first cam surface by the biasing member so as to apply first additional force to the pulley assembly in the first direction while the pulley assembly is in the first pivotal position. 
     The derailleur according to the first aspect is configured to apply the first additional force to the pulley assembly in the first direction while the pulley assembly is in the first rotational position. This facilitates movement of the pulley in the first direction while the pulley assembly is in the first rotational position. Thus, rotational force of the pulley assembly relative to the movable member is set in a preferred state. 
     In accordance with a second aspect of the present disclosure, in the derailleur according to the first aspect, the pulley assembly is configured to be in the first pivotal position while a human-powered vehicle chain engages with a smallest sprocket of a human-powered vehicle rear sprocket assembly. The pulley assembly is configured to be in the second pivotal position while the human-powered vehicle chain engages with a largest sprocket of the human-powered vehicle rear sprocket assembly. 
     The derailleur according to the second aspect sets rotational force of the pulley assembly, which moves between the first rotational position corresponding to the smallest sprocket and the second rotational position corresponding to the largest sprocket, in a preferred state. 
     In accordance with a third aspect of the present disclosure, the derailleur according to the first aspect is configured so that the cam member has a second cam surface. The abutment member is configured to abut the second cam surface by the biasing member so as to apply second additional force to the pulley assembly in the second direction while the pulley assembly is in the second pivotal position. 
     The derailleur according to the third aspect sets rotational force of the pulley assembly that is in the second rotational position in a preferred state. 
     In accordance with a fourth aspect of the present disclosure, the derailleur according to the third aspect is configured so that the cam member has a transit portion positioned between the first cam surface and the second cam surface. 
     In the derailleur according to the fourth aspect, the transit portion forms the first cam surface and the second cam surface in a preferred manner. 
     In accordance with a fifth aspect of the present disclosure, the derailleur according to the first aspect is configured so that the biasing member has a first end and a second end. The first end is attached to one of the abutment member and the pulley assembly. The second end is attached to the other of the abutment member and the pulley assembly. 
     In the derailleur according to the fifth aspect, the biasing member is attached to the abutment member and the pulley assembly in a preferred manner. 
     In accordance with a sixth aspect of the present disclosure, the derailleur according to the first aspect is configured so that the abutment member has a rotational axis and is rotatable about the rotational axis in a third direction and a fourth direction opposite to the third direction with respect to the rotational axis. The biasing member is configured to bias the abutment member in the third direction so that the abutment member abuts the first cam surface of the cam member. 
     In the derailleur according to the sixth aspect, the biasing member causes the abutment member to abut the first cam surface of the cam member in a preferred manner. 
     In accordance with a seventh aspect of the present disclosure, the derailleur according to the third aspect is configured so that the abutment member has a rotational axis and is rotatable about the rotational axis in a third direction and a fourth direction opposite to the third direction with respect to the rotational axis. The biasing member is configured to bias the abutment member in the third direction so that the abutment member abuts each of the first cam surface and the second cam surface of the cam member. 
     In the derailleur according to the seventh aspect, the biasing member causes the abutment member to abut the first cam surface and the second cam surface of the cam member in a preferred manner. 
     In accordance with an eighth aspect of the present disclosure, the derailleur according to the sixth aspect is configured so that a first reference line is defined to extend between the pivot axis and the rotational axis while the pulley assembly is in the first pivotal position. A first tangential line is defined with respect to the first cam surface at a first intersection of the first cam surface and the first reference line. A first apex angle is defined at the first intersection between the first reference line and the first tangential line. The first apex angle is smaller than 90 degrees. 
     In the derailleur according to the eighth aspect, the pulley assembly and the abutment member are configured so that the first apex is smaller than 90 degrees. 
     In accordance with a ninth aspect of the present disclosure, the derailleur according to the seventh aspect is configured so that a second reference line is defined to extend between the pivot axis and the rotational axis while the pulley assembly is in the second pivotal position. A second tangential line is defined with respect to the second cam surface at a second intersection of the second cam surface and the second reference line. A second apex angle is defined at the second intersection between the second reference line and the second tangential line. The second apex angle is smaller than 90 degrees. 
     In the derailleur according to the ninth aspect, the pulley assembly and the abutment member are configured so that the second apex is smaller than 90 degrees. 
     In accordance with a tenth aspect of the present disclosure, the derailleur according to the seventh aspect is configured so that a first reference line is defined to extend between the pivot axis and the rotational axis while the pulley assembly is in the first pivotal position. A first tangential line is defined with respect to the first cam surface at a first intersection of the first cam surface and the first reference line. A first apex angle is defined at the first intersection between the first reference line and the first tangential line. The first apex angle is smaller than 90 degrees. A second reference line is defined to extend between the pivot axis and the rotational axis while the pulley assembly is in the second pivotal position. A second tangential line is defined with respect to the second cam surface at a second intersection of the second cam surface and the second reference line. A second apex angle is defined at the second intersection between the second reference line and the second tangential line. The second apex angle is smaller than 90 degrees. 
     In the derailleur according to the tenth aspect, the pulley assembly and the abutment member are configured so that the first apex is smaller than 90 degrees and so that the second apex is smaller than 90 degrees. 
     In accordance with an eleventh aspect of the present disclosure, a human-powered vehicle derailleur comprises a base member configured to be attached to a human-powered vehicle frame, a movable member movable relative to the base member, a linkage structure operatively connecting the movable member to the base member, a pulley assembly attached to the movable member so that the pulley assembly is pivotally movable relative to the movable member about a pivot axis in a first direction and a second direction opposite to the first direction with respect to the pivot axis, and a rotational force control structure configured to control rotational force of the pulley assembly relative to the movable member. The pulley assembly has a first pivotal position and a second pivotal position. The pulley assembly is configured to move in the first direction upon moving from the second pivotal position toward the first pivotal position. The rotational force control structure includes a resistance applying member movably attached to the movable member, a contact member attached to the pulley assembly and configured to contact the resistance applying member as the pulley assembly moves in the second direction from the first pivotal position toward the second pivotal position, and a first biasing member configured to bias the resistance applying member from a first retracted position toward a first extended position in a first biasing direction. 
     In the derailleur according to the eleventh aspect, the contact member contacts the resistance applying member so that rotational force of the pulley assembly is set in a preferred state. 
     In accordance with a twelfth aspect of the present disclosure, in the derailleur according to the eleventh aspect, the pulley assembly is configured to be in the first pivotal position while a human-powered vehicle chain engages with a smallest sprocket of a human-powered vehicle rear sprocket assembly. The pulley assembly is configured to be in the second pivotal position while the human-powered vehicle chain engages with a largest sprocket of the human-powered vehicle rear sprocket assembly. 
     The derailleur according to the twelfth aspect sets rotational force of the pulley assembly, which rotates between the first rotational position corresponding to the smallest sprocket and the second rotational position corresponding to the largest sprocket, in a preferred state. 
     In accordance with a thirteenth aspect of the present disclosure, the derailleur according to the eleventh aspect is configured so that the first biasing member is attached to the movable member. 
     In the derailleur according to the thirteenth aspect, the first biasing member is attached to the movable member so that the first biasing member biases the resistance applying member in a preferred manner. 
     In accordance with a fourteenth aspect of the present disclosure, the derailleur according to the eleventh aspect is configured so that the rotational force control structure further includes a second biasing member configured to bias the resistance applying member from a second retracted position toward a second extended position in a second biasing direction that is different from the first biasing direction. 
     In the derailleur according to the fourteenth aspect, the second biasing member biases the resistance applying member in a preferred manner. 
     In accordance with a fifteenth aspect of the present disclosure, the derailleur according to the fourteenth aspect is configured so that the second biasing member is attached to the movable member. 
     In the derailleur according to the fifteenth aspect, the second biasing member is attached to the movable member so that the second biasing member biases the resistance applying member in a preferred manner. 
     In accordance with a sixteenth aspect of the present disclosure, in the derailleur according to the eleventh aspect, the contact member is configured to pass through the resistance applying member by moving the resistance applying member toward the first retracted position as the pulley assembly moves in the second direction from the first pivotal position toward the second pivotal position. 
     In the derailleur according to the sixteenth aspect, the contact member moves the resistance applying member toward the first retracted position, so that the pulley assembly moves in the second direction in a preferred manner. 
     In accordance with a seventeenth aspect of the present disclosure, in the human-powered vehicle derailleur according to the fourteenth aspect, the contact member is configured to pass through the resistance applying member by moving the resistance applying member toward the first retracted position and the second retracted position as the pulley assembly moves in the second direction from the first pivotal position toward the second pivotal position. 
     In the derailleur according to the seventeenth aspect, the contact member moves the resistance applying member toward the first retracted position and the second retracted position, so that the pulley assembly moves in the second direction in a preferred manner. 
     In accordance with an eighteenth aspect of the present disclosure, a human-powered vehicle derailleur comprises a base member configured to be attached to a human-powered vehicle frame, a movable member movable relative to the base member, a linkage structure operatively connecting the movable member to the base member, a pulley assembly attached to the movable member so that the pulley assembly is pivotally movable relative to the movable member about a pivot axis in a first direction and a second direction opposite to the first direction with respect to the pivot axis, a pulley assembly biasing member configured to apply rotational force to the pulley assembly in the first direction, and a rotational force control structure configured to control rotational force of the pulley assembly relative to the movable member. The pulley assembly has a first pivotal position and a second pivotal position. The pulley assembly is configured to move in the first direction upon moving from the second pivotal position toward the first pivotal position. The rotational force control structure includes a cam member, an abutment member configured to abut the cam member, and a biasing member configured to bias the abutment member. The abutment member is configured to abut the cam member by the biasing member so as to reduce rotational force by the pulley assembly biasing member while the pulley assembly is in the second pivotal position. 
     In the derailleur according to the eighteenth aspect, while the pulley assembly is in the second rotational position, the biasing member reduces rotational force of the pulley assembly biasing member, so that rotational force of the pulley assembly is set in a preferred state. 
     In accordance with a nineteenth aspect of the present disclosure, a human-powered vehicle derailleur comprises a base member configured to be attached to a human-powered vehicle frame, a movable member movable relative to the base member, a linkage structure operatively connecting the movable member to the base member, a pulley assembly attached to the movable member so that the pulley assembly is pivotally movable relative to the movable member about a pivot axis in a first direction and a second direction opposite to the first direction with respect to the pivot axis, and a rotational force control structure configured to control rotational force of the pulley assembly relative to the movable member. The pulley assembly has a first pivotal position and a second pivotal position. The pulley assembly is configured to move in the first direction upon moving from the second pivotal position toward the first pivotal position. The rotational force control structure includes a resistance applying member attached to the movable member and a contact member attached to the pulley assembly. The contact member is configured to contact the resistance applying member as the pulley assembly moves in the second direction from the first pivotal position toward the second pivotal position. The resistance applying member is elastically deformable. 
     In the derailleur according to the nineteenth aspect, the resistance applying member that is elastically deformable sets rotational force of the pulley assembly in a preferred state. 
     The human-powered vehicle derailleur of the present disclosure sets rotational force of the pulley assembly in a preferred state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a human-powered vehicle including an embodiment of a human-powered vehicle derailleur. 
         FIG.  2    is a perspective view showing a state in which a pulley assembly of the human-powered vehicle derailleur of the embodiment is in a first pivotal position. 
         FIG.  3    is a perspective view showing a state in which the pulley assembly of the human-powered vehicle derailleur of the embodiment is in a second pivotal position. 
         FIG.  4    is a first schematic diagram showing a first example of a rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  5    is a second schematic diagram showing the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  6    is a diagram showing a relationship between a cam surface of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2    and first additional force and second additional force. 
         FIG.  7    is a diagram showing a positional relationship between the cam surface and an abutment member of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  8    is a graph showing a relationship between a plate rotational angle and biasing return force. 
         FIG.  9    is a first schematic diagram showing a first modified example of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  10    is a second schematic diagram showing the first modified example of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  11    is a third schematic diagram showing the first modified example of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  12    is a second schematic diagram showing a second modified example of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  13    is a second schematic diagram showing the second modified example of the first example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  14    is a second schematic diagram showing a second example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  15    is a second schematic diagram showing the second example of the rotational force control structure of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  16    is a perspective view showing a first example of a pulley assembly biasing member of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  17    is a perspective view showing a second example of a pulley assembly biasing member of the human-powered vehicle derailleur shown in  FIG.  2   . 
         FIG.  18    is a perspective view showing a modified example of the pulley assembly biasing member shown in FIG.  17 . 
         FIG.  19    is a side view of a human-powered vehicle including a first modified example of a human-powered vehicle derailleur. 
         FIG.  20    is a block diagram showing the electrical configuration of a human-powered vehicle including a second modified example of a human-powered vehicle derailleur. 
         FIG.  21    is a block diagram showing the electrical configuration of a human-powered vehicle including a third modified example of a human-powered vehicle derailleur. 
         FIG.  22    is a block diagram showing the electrical configuration of a human-powered vehicle including a fourth modified example of a human-powered vehicle derailleur. 
     
    
    
     EMBODIMENTS OF THE DISCLOSURE 
     Embodiment 
     An embodiment of a human-powered vehicle derailleur  40  will now be described with reference to  FIGS.  1  to  18   . A human-powered vehicle  10  is a vehicle that can be driven by at least human driving force. The number of wheels on the human-powered vehicle  10  is not limited. The human-powered vehicle  10  includes, for example, a monocycle and a vehicle having three or more wheels. The human-powered vehicle  10  includes, for example, various types of bicycles such as a mountain bike, a road bike, a city bike, a cargo bike, and a recumbent bike. The bicycle can be an electric bicycle (E-bike). The electric bicycle includes an electric assist bicycle that assists propulsion of the vehicle with an electric motor. In the embodiment described below, the human-powered vehicle  10  refers to a bicycle. 
     The human-powered vehicle  10  includes a crank  12 , wheels  14 , and a vehicle body  16 . The wheels  14  include a rear wheel  14 A and a front wheel  14 B. The vehicle body  16  includes a frame  18 . The crank  12  includes a crankshaft  12 A configured to rotate relative to the frame  18  and crank arms  12 B provided on opposite axial ends of the crankshaft  12 A. A pedal  20  is coupled to each of the crank arms  12 B. The rear wheel  14 A is driven in accordance with rotation of the crank  12 . The rear wheel  14 A is supported by the frame  18 . The crank  12  and the rear wheel  14 A are coupled by a drive mechanism  22 . The drive mechanism  22  includes a front sprocket  24  coupled to the crankshaft  12 A. The crankshaft  12 A and the front sprocket  24  can be coupled by a first one-way clutch. The first one-way clutch is configured to allow forward rotation of the front sprocket  24  in a case in which the crank  12  is rotated forward, and prohibit rearward rotation of the front sprocket  24  in a case in which the crank  12  is rotated rearward. The drive mechanism  22  further includes a rear sprocket  26  and a chain  28 . The chain  28  transmits rotational force of the front sprocket  24  to the rear sprocket  26 . The drive mechanism  22  includes multiple rear sprockets  26 . The rear sprockets  26  configure a rear sprocket assembly  26 A. 
     The rear sprockets  26  are coupled to the rear wheel  14 A. Preferably, a second one-way clutch is provided between the rear sprockets  26  and the rear wheel  14 A. The second one-way clutch is configured to allow forward rotation of the rear wheel  14 A in a case in which the rear sprockets  26  are rotated forward, and prohibit rearward rotation of the rear wheel  14 A in a case in which the rear sprockets  26  are rotated rearward. 
     The front wheel  14 B is attached to the frame  18  by a front fork  30 . A handlebar  34  is coupled to the front fork  30  by a stem  32 . In the present embodiment, the rear wheel  14 A is coupled to the crank  12  by the drive mechanism  22 . However, at least one of the rear wheel  14 A and the front wheel  14 B can be coupled to the crank  12  by the drive mechanism  22 . 
     The human-powered vehicle  10  can include a battery  36  for a human-powered vehicle. The battery  36  includes one or more battery elements. The battery elements include a rechargeable battery. The battery  36  supplies electric power to an assist motor  38 . Preferably, the assist motor  38  is connected to a controller to perform wired or wireless communication with the controller. The assist motor  38  is configured to perform, for example, power line communication (PLC) with the controller. 
     The human-powered vehicle  10  can include the assist motor  38  that applies propulsion force to the human-powered vehicle  10 . The assist motor  38  includes one or more electric motors. The assist motor  38  is configured to transmit rotation to at least one of the front wheel  14 B and a power transmission path that extends from the pedals  20  to the rear wheel  14 A. The power transmission path extending from the pedals  20  to the rear wheel  14 A includes the rear wheel  14 A. In the present embodiment, the assist motor  38  is provided on the frame  18  of the human-powered vehicle  10  and is configured to transmit rotation to the sprocket  24 . A drive unit is configured to include the assist motor  38  and a housing on which the assist motor  38  is provided. Preferably, a one-way clutch is provided on the power transmission path between the assist motor  38  and the crankshaft  12 A so that in a case in which the crankshaft  12 A is rotated in a direction in which the human-powered vehicle  10  travels forward, the rotational force of the crank  12  will not rotate the assist motor  38 . In a case in which the assist motor  38  is provided on at least one of the rear wheel  14 A and the front wheel  14 B, the assist motor  38  can include a hub motor. The assist motor  38  can be omitted from the human-powered vehicle  10 . 
     The human-powered vehicle  10  includes the derailleur  40 . The derailleur  40  is configured to change a transmission ratio R, which is the ratio of rotational speed of the rear wheel  14 A to rotational speed of the crank  12 . In the present embodiment, the derailleur  40  includes a rear derailleur. The derailleur  40  can include a front derailleur. The derailleur  40  moves the chain  28  from one of the rear sprockets  26  to another one of the rear sprockets  26  included in the rear sprocket assembly  26 A. 
     The derailleur  40  includes a base member  42 , a movable member  44 , a linkage structure  46 , and a pulley assembly  48 . The pulley assembly  48  includes at least one plate member  52 . The pulley assembly  48  is configured to be pivotally movable relative to the movable member  44  so that a rotational angle of the pulley assembly  48  is movable with respect to the movable member  44 . The plate member  52  is configured to be pivotally movable relative to the movable member  44  so that a rotational angle of the plate member  52  is movable with respect to the movable member  44 . The rotational angle of the plate member  52  with respect to the movable member  44  is defined as a plate rotational angle X. 
       FIG.  8    shows a relationship between the plate rotational angle X and biasing return force M in a first direction A 1 . 
     In a typical derailleur, as shown in  FIG.  8    by the double-dashed line, as the plate rotational angle X moves in a second direction, the biasing return force M is linearly increased by a pulley assembly biasing member  66 , which attempts to rotate the plate rotational angle X of the pulley assembly  48  with respect to the movable member  44  in the first direction A 1 . Preferably, in a state in which the plate rotational angle X is a first rotational angle, the biasing return force M is less than in a state in which the plate rotational angle X is a second rotational angle. In a state in which the plate rotational angle X is the first rotational angle, the pulley assembly  48  is located in a first pivotal position P 1 . In a state in which the plate rotational angle X is the second rotational angle, the pulley assembly  48  is located in a second pivotal position P 2 . The second rotational angle is greater than the first rotational angle. Preferably, in a state in which the pulley assembly  48  is located in the second pivotal position P 2 , the biasing return force M is greater than in a state in which the pulley assembly  48  is located in the first pivotal position P 1 . 
     The derailleur  40  includes at least one of a mechanism that increases the biasing return force M in the first pivotal position P 1  and an adjustment mechanism that causes the biasing return force M in the second pivotal position P 2  to be equal to or smaller than a predetermined torque. The plate rotational angle X corresponds to a rotational amount of the pulley assembly  48  rotating about a pivot axis  48 X from the first pivotal position P 1  toward the second pivotal position P 2 . The biasing return force M is defined by rotational force of the pulley assembly  48  relative to the movable member  44 . 
     A first example of the adjustment mechanism is a variable mechanism that varies the relationship between the plate rotational angle X and the biasing return force M in the first direction A 1  at a predetermined plate rotational angle XA. The solid line in  FIG.  8    shows an example of the relationship between the plate rotational angle X and the biasing return force M of the derailleur  40  using the variable mechanism. The variable mechanism varies the ratio of a change amount of the biasing return force M to a change amount of the plate rotational angle X between a state in which the plate rotational angle X is greater than the plate rotational angle XA and a state in which the plate rotational angle X is equal to or smaller than the plate rotational angle XA. The variable mechanism is configured, for example, so that in a state in which the plate rotational angle X is greater than the plate rotational angle XA, the ratio of the change amount of the biasing return force M to the change amount of the plate rotational angle X is less than in a state in which the plate rotational angle X is equal to or smaller than the plate rotational angle XA. The variable mechanism can be configured not to change the biasing return force M even if the plate rotational angle X is changed in a state in which the plate rotational angle X is greater than the plate rotational angle XA. 
     A first example of the variable mechanism includes a rotational force control structure  50 . The derailleur  40  includes the rotational force control structure  50 . 
     The base member  42  is configured to be attached to the frame  18  of the human-powered vehicle  10 . The movable member  44  is movable relative to the base member  42 . The linkage structure  46  operatively connects the movable member  44  to the base member  42 . The pulley assembly  48  is attached to the movable member  44  to be pivotally movable relative to the movable member  44 . The linkage structure  46  includes a first link  46 A, a second link  46 B, and a connecting pin  46 C. One end of the first link  46 A is swingably attached to the base member  42  by the connecting pin  46 C. The other end of the first link  46 A is swingably attached to the movable member  44  by the connecting pin  46 C. One end of the second link  46 B is swingably attached to the base member  42  by the connecting pin  46 C. The other end of the second link  46 B is swingably attached to the movable member  44  by the connecting pin  46 C. 
     The pulley assembly  48  is pivotally movable relative to the movable member  44  about the pivot axis  48 X in the first direction A 1  and a second direction A 2  opposite to the first direction with respect to the pivot axis  48 X. The pulley assembly  48  has the first pivotal position P 1  and the second pivotal position P 2 . The pulley assembly  48  is configured to move in the first direction A 1  upon moving from the second pivotal position P 2  toward the first pivotal position P 1 . 
     The pulley assembly  48  is configured to be in the first pivotal position P 1  while the chain  28  of the human-powered vehicle  10  engages with a smallest sprocket  26  of the rear sprocket assembly  26 A of the human-powered vehicle  10 . The pulley assembly  48  is also configured to be in the second pivotal position P 2  while the chain  28  of the human-powered vehicle  10  engages with a largest sprocket  26  of the rear sprocket assembly  26 A of the human-powered vehicle  10 . 
     The pulley assembly  48  includes the plate member  52 , a first pulley  54  having a first pulley axis  54 X, and a second pulley  56  having a second pulley axis  56 X. The plate member  52  is pivotally supported by the movable member  44 . The first pulley  54  and the second pulley  56  are supported by the plate member  52  and pivotally movable relative to the plate member  52 . The first pulley  54  is attached to the plate member  52  at a position closer to the movable member  44  than the second pulley  56 . The chain  28  runs on the first pulley  54  and the second pulley  56 . The plate member  52  includes a first plate  52 A and a second plate  52 B. The first pulley  54  and the second pulley  56  are located between the first plate  52 A and the second plate  52 B. 
     The derailleur  40  can include a mechanical derailleur that is driven in accordance with operation of a cable. The derailleur  40  can include an electrical derailleur that actuates in accordance with driving of an actuator. 
     The derailleur  40  includes the pulley assembly biasing member  66  configured to apply rotational force to the pulley assembly  48  in the first direction A 1 . The pulley assembly biasing member  66  is provided, for example, on the pivot axis  48 X. The pulley assembly biasing member  66  can be a coil spring, a plate spring, or a rubber member. Preferably, the pulley assembly biasing member  66  has a first end portion and a second end portion. The first end portion is connected with the movable member  44 . The second end portion is connected with the pulley assembly  48 . 
     Rotational force of the pulley assembly  48  is formed by a total force of biasing force of the pulley assembly biasing member  66  and biasing force of the rotational force control structure  50 . 
     The rotational force control structure  50  is configured to control the rotational force of the pulley assembly  48  relative to the movable member  44 . The rotational force control structure  50  includes a cam member  60 , an abutment member  62 , and a biasing member  64 . The cam member  60  has a first cam surface  60 A. The abutment member  62  is configured to abut the first cam surface  60 A. The abutment member  62  is configured to abut the first cam surface  60 A by the biasing member  64  so as to apply first additional force F 11  to the pulley assembly  48  in the first direction A 1  while the pulley assembly  48  is in the first pivotal position P 1 . The first additional force F 11  corresponds to a component of force F 1  in the first direction A 1 . The force F 1  is applied from the biasing member  64  to the pulley assembly  48  through the abutment member  62  while the pulley assembly  48  is in the first pivotal position P 1 . The first cam surface  60 A can be a flat surface or a curved surface. Preferably, the cam member  60  is provided on the movable member  44  to move integrally with the movable member  44 . The cam member  60  can be formed integrally with the movable member  44 . The cam member  60  can be formed separately from the movable member  44  and attached to the movable member  44 . 
     The cam member  60  has a second cam surface  60 B. The abutment member  62  is configured to abut the second cam surface  60 B by the biasing member  64  so as to apply second additional force F 21  to the pulley assembly  48  in the second direction A 2  while the pulley assembly  48  is in the second pivotal position P 2 . The second cam surface  60 B can be a flat surface or a curved surface. The cam member  60  has a transit portion  60 C between the first cam surface  60 A and the second cam surface  60 B. The transit portion  60 C includes, for example, a projection formed between the first cam surface  60 A and the second cam surface  60 B. The second additional force F 21  corresponds to a component of force F 2  in the second direction A 2 . The force F 2  is applied from the biasing member  64  to the pulley assembly  48  through the abutment member  62  while the pulley assembly  48  is in the second pivotal position P 2 . 
     Preferably, the rotational force control structure  50  includes the cam member  60 , the abutment member  62 , and the biasing member  64 . The abutment member  62  is configured to abut the cam member  60 . The biasing member  64  is configured to bias the abutment member  62 . The abutment member  62  is configured to abut the cam member  60  by the biasing member  64  to reduce rotational force of the pulley assembly biasing member  66  while the pulley assembly  48  is in the second pivotal position P 2 . 
       FIGS.  4  and  5    show a first example of the rotational force control structure  50 . 
     The biasing member  64  has a first end  64 A and a second end  64 B. The first end  64 A is attached to one of the abutment member  62  and the pulley assembly  48 . The second end  64 B is attached to the other of the abutment member  62  and the pulley assembly  48 . The biasing member  64  includes at least one of a coil spring, a plate spring, and an elastic member. 
     The abutment member  62  has a rotational axis  62 X and is rotatable about the rotational axis  62 X in a third direction A 3  and a fourth direction A 4  opposite to the third direction A 3 . The biasing member  64  is configured to bias the abutment member  62  in the third direction A 3  so that the abutment member  62  abuts the first cam surface  60 A of the cam member  60 . In a case in which the biasing member  64  includes a coil spring, the biasing member  64  can be provided around a shaft connected to the abutment member  62  and the pulley assembly  48 . For example, the shaft extends along the rotational axis  62 X of the abutment member  62 . The shaft can be provided on the pulley assembly  48  or can be provided on the abutment member  62 . The biasing member  64  can be, for example, fitted to the shaft, and the first end  64 A is attached to the abutment member  62  and the second end  64 B is attached to the pulley assembly  48 . The abutment member  62  has a distal end provided opposite to the shaft to abut the first cam surface  60 A of the cam member  60 . The biasing member  64  is configured to bias the abutment member  62  in the third direction A 3  so that the distal end of the abutment member  62  abuts the first cam surface  60 A of the cam member  60 . Preferably, the biasing member  64  is configured not to bias the abutment member  62  in a direction opposite to the third direction A 3 . The abutment member  62  is attached to the pulley assembly  48  via the shaft and is rotatable relative to the pulley assembly  48 . 
     The biasing member  64  is configured to bias the abutment member  62  in the third direction A 3  so that the abutment member  62  abuts each of the first cam surface  60 A and the second cam surface  60 B of the cam member  60 . 
     A first reference line LX is defined to extend between the pivot axis  48 X and the rotational axis  62 X while the pulley assembly  48  is in the first pivotal position P 1 . A first tangential line S 1  is defined with respect to the first cam surface  60 A at a first intersection C 1  of the first cam surface  60 A and the first reference line LX. A first apex angle D 1  is defined at the first intersection C 1  between the first reference line LX and the first tangential line S 1 . Preferably, the first apex angle D 1  is smaller than 90 degrees. The first apex angle D 1  is an acute angle and is formed by the first reference line LX and the first tangential line S 1 . The first apex angle D 1  is formed between a portion of the first reference line LX located toward the pivot axis  48 X and a portion of the first tangential line S 1  located opposite to the transit portion  60 C. 
     A second reference line LY is defined to extend between the pivot axis  48 X and the rotational axis  62 X while the pulley assembly  48  is in the second pivotal position P 2 . A second tangential line S 2  is defined with respect to the second cam surface  60 B at a second intersection C 2  of the second cam surface  60 B and the second reference line LY. A second apex angle D 2  is defined at the second intersection C 2  between the second reference line LY and the second tangential line S 2 . Preferably, the second apex angle D 2  is smaller than 90 degrees. Preferably, the first apex angle D 1  is smaller than 90 degrees, and the second apex angle D 2  is smaller than 90 degrees. The second apex angle D 2  is an acute angle and is formed by the second reference line LY and the second tangential line S 2 . The second apex angle D 2  is formed between a portion of the second reference line LY located toward the pivot axis  48 X and a portion of the second tangential line S 2  located opposite to the transit portion  60 C. 
     Preferably, a first distance L 1 , which extends from the cam member  60  to the rotational axis  62 X of the abutment member  62 , is less than a second distance L 2 , which extends from a contact point of the abutment member  62  with the cam member  60  to the rotational axis  62 X of the abutment member  62 . The configuration in which the first distance L 1  is less the second distance L 2  limits separation of the abutment member  62  from the cam member  60 . 
     The first distance L 1  can be configured to be equal to or larger than the second distance L 2 . In this case, as shown in  FIGS.  9  to  11   , the derailleur  40  can include an auxiliary biasing member  68 . While the pulley assembly  48  is in the second pivotal position P 2 , the auxiliary biasing member  68  is in contact with the abutment member  62  and biases the abutment member  62  so that the abutment member  62  will not separate from the second cam surface  60 B. 
     In the derailleur  40  including the first example of the rotational force control structure  50 , while the pulley assembly  48  is in the first pivotal position P 1 , the pulley assembly  48  is readily rotated in the first direction A 1  by the first additional force F 11 . While the pulley assembly  48  is in the second pivotal position P 2 , the pulley assembly  48  is readily rotated in the second direction A 2  by the second additional force F 21 . Preferably, the predetermined plate rotational angle XA corresponds to the plate rotational angle X of the pulley assembly  48  in which the abutment member  62  is in contact with the transit portion  60 C. While the pulley assembly  48  is in the first pivotal position P 1 , the biasing return force M is increased, so that the derailleur  40  increases tension of the chain  28 . Increased tension of the chain  28  sets rotational force of the pulley assembly  48  relative to the movable member  44  in a preferred state. This limits unintentional shifting. In addition, in a state in which the pulley assembly  48  is in the first pivotal position P 1 , the first additional force F 11  restricts rotation of the pulley assembly in the second direction A 2  caused by vibration generated, for example, during travelling. 
     While the pulley assembly  48  is in the second pivotal position P 2 , the derailleur  40  limits increases in the biasing return force M. This reduces driving loss of a shifting operation of the derailleur  40  and driving loss caused by friction generated in the chain  28 . The derailleur  40  limits decreases in the shifting performance during a shifting operation that moves the chain  28  to another one of the sprockets  26  and also limits decreases in the driving efficiency during rotation of the annular chain  28  extending between the front sprocket  24  and the rear sprockets  26 . Thus, rotational force of the pulley assembly  48  relative to the movable member  44  is set in a preferred state. While the pulley assembly  48  is in the second pivotal position P 2 , the second additional force F 21  partially compensates for biasing force of the pulley assembly biasing member  66 . This reduces friction generated between plates and chain rollers that configure the chain  28 . Hence, decreases in the driving efficiency are limited. For example, if the biasing return force M is increased while the pulley assembly  48  is in the second pivotal position P 2 , tension of the chain  28  is increased while the pulley assembly  48  is in the second pivotal position P 2 . This increases friction resistance caused by sliding of the plates and chain rollers of the chain  28 . In addition, energy loss is increased. As a result, the driving efficiency is lowered. While the pulley assembly  48  is in the second pivotal position P 2 , the derailleur  40  limits increases in the biasing return force M. Decreases in the driving efficiency are limited while the pulley assembly  48  is in the second pivotal position P 2 . 
     The biasing return force M is adjusted to a value appropriate for, for example, at least one of the material, shape, and size of a biasing member included in the rotational force control structure  50 . 
     As shown in  FIGS.  12  and  13   , in the first example of the rotational force control structure  50 , the rotational force control structure  50  can include a resistance applying member  70  that is elastically deformable. In this case, the rotational force control structure  50  is configured to control rotational force of the pulley assembly relative to the movable member. The rotational force control structure  50  includes the resistance applying member  70  and the abutment member  62 . The resistance applying member  70  is attached to the movable member  44 . The abutment member  62  is attached to the pulley assembly  48  and configured to contact the resistance applying member  70  as the pulley assembly  48  moves in the second direction A 2  from the first pivotal position P 1  toward the second pivotal position P 2 . The resistance applying member  70  is elastically deformable. The resistance applying member  70  is extendable toward the abutment member  62 . The resistance applying member  70  is configured so that the extension state changes in accordance with a state of contact with the abutment member  62 . The resistance applying member  70  can be formed integrally with the movable member  44 . The resistance applying member  70  can be formed separately from the movable member  44  and attached to the movable member  44 . In a case in which the resistance applying member  70  is formed separately from the movable member  44 , the resistance applying member  70  can be biased by biasing force of a biasing member separate from the resistance applying member  70 . The resistance applying member  70  is provided on a portion corresponding to the transit portion  60 C. While the pulley assembly  48  is in the second pivotal position P 2 , the derailleur  40  limits increases in the biasing return force M using the resistance applying member  70 . This reduces driving loss of shifting operation of the derailleur  40 . 
       FIGS.  14  and  15    show a second example of the rotational force control structure  50 . 
     The rotational force control structure  50  shown in  FIGS.  14  and  15    is configured to control rotational force of the pulley assembly relative to the movable member. The rotational force control structure  50 A includes a resistance applying member  72 , a contact member  74 , and a first biasing member  76 . The resistance applying member  72  is movably attached to the movable member  44 . The contact member  74  is attached to the pulley assembly  48  and configured to contact the resistance applying member  72  as the pulley assembly  48  moves in the second direction A 2  from the first pivotal position P 1  toward the second pivotal position P 2 . The first biasing member  76  is configured to bias the resistance applying member  72  from a first retracted position Q 11  toward a first extended position Q 21  in a first biasing direction B 1 . Preferably, the resistance applying member  72  of the rotational force control structure  50 A is configured to contact the pulley assembly  48  by biasing force of one or both of the biasing member  76  and a biasing member  78 . 
     The first biasing member  76  is attached to the movable member  44 . The first biasing member  76  can be a coil spring, a plate spring, or a rubber member. 
     The rotational force control structure  50  further includes a second biasing member  78 . The second biasing member  78  is configured to bias the resistance applying member  72  from a second retracted position Q 12  toward a second extended position Q 22  in a second biasing direction B 2  that is different from the first biasing direction B 1 . As viewed from the pulley assembly  48 , the first retracted position Q 11  can be different from the second retracted position Q 12 . Preferably, as viewed from the movable member  44 , the first retracted position Q 11  is the same as the second retracted position Q 12 . As viewed from the pulley assembly  48 , the first extended position Q 21  can be different from the second extended position Q 22 . Preferably, as viewed from the movable member  44 , the first extended position Q 21  is the same as the second extended position Q 22 . 
     The second biasing member  78  is attached to the movable member  44 . The second biasing member  78  can be a coil spring, a plate spring, or a rubber member. While the pulley assembly  48  is in the second pivotal position P 2 , the second biasing member  78  biases the resistance applying member  72  so that the resistance applying member  72  is contactable with the contact member  74 . The second biasing member  78  is configured to bias the resistance applying member  72  in the second biasing direction B 2  using the contact member  74  while the pulley assembly  48  is in the second pivotal position P 2 . 
     Preferably, the contact member  74  is configured to pass through the resistance applying member  72  by moving the resistance applying member  72  toward the first retracted position Q 11  as the pulley assembly  48  moves in the second direction A 2  from the first pivotal position P 1  toward the second pivotal position P 2 . Preferably, the contact member  74  is configured to pass through the resistance applying member  72  by moving the resistance applying member  72  toward the first retracted position Q 11  and the second retracted position Q 12  as the pulley assembly  48  moves in the second direction A 2  from the first pivotal position P 1  toward the second pivotal position P 2 . 
     In the derailleur  40  having the second example of the rotational force control structure  50 , during rotation of the pulley assembly  48  from the first pivotal position P 1  to the second pivotal position P 2 , the first biasing member  76  is compressed to apply force that pushes the resistance applying member  72  onto the contact member  74 . This increases friction force generated between the resistance applying member  72  and the contact member  74  and hinders movement of the pulley assembly  48  in the first direction A 1 . As a result, increases in the biasing return force M are limited, thereby reducing loss of driving power of the derailleur  40  during a shifting operation and loss of driving power caused by friction generated in the chain. In the derailleur  40  having the second example of the rotational force control structure  50 , during rotation of the pulley assembly  48 , contact of the resistance applying member  72  with the contact member  74  resists movement of the pulley assembly  48 . This compensates for biasing force of the pulley assembly biasing member  66  during movement of the pulley assembly  48  in the first direction A 1  and the second direction A 2 . 
     A second example of the variable mechanism includes a biasing member  80  that applies biasing force to the pulley assembly  48 . The biasing member  80  corresponds to the pulley assembly biasing member  66  of the derailleur  40 . A derailleur  40 A includes a base member  42 , a movable member  44 , a pulley assembly  48 , and the biasing member  80 . The base member  42  is configured to be attached to the frame  18  of the human-powered vehicle  10 . The movable member  44  is movable relative to the base member  42 . The pulley assembly  48  is configured to be attached to the movable member  44  and rotatable about the pivot axis  48 X. The biasing member  80  includes a first biasing member  82  and a second biasing member  84  that apply biasing force to the pulley assembly  48 . 
     The first biasing member  82  has a first spring rate K 1 . The second biasing member  84  has a second spring rate K 2 . Preferably, the first spring rate K 1  is different from the second spring rate K 2 . Preferably, the second spring rate K 2  is less than the first spring rate K 1 . The second spring rate K 2  can be equal to or larger than the first spring rate K 1 . 
     Preferably, the first biasing member  82  and the second biasing member  84  are configured to engage with each other. The second biasing member  84  can be configured not to directly contact the first biasing member  82  and can indirectly bias the first biasing member  82  using another member. 
     Preferably, one of the first biasing member  82  and the second biasing member  84  is connected to the pulley assembly  48 , and the other of the first biasing member  82  and the second biasing member  84  is connected to the movable member  44 . The first biasing member  82  has a first end portion  82 X and a second end portion  82 Y. The second biasing member  84  has a third end portion  84 X and a fourth end portion  84 Y. 
     The first biasing member  82  is connected to the second biasing member  84  at portions excluding the first end portion  82 X and the fourth end portion  84 Y. The first end portion  82 X of the first biasing member  82  is connected to the movable member  44 . The second end portion  82 Y of the first biasing member  82  is connected to the third end portion  84 X of the second biasing member  84 . The fourth end portion  84 Y of the second biasing member  84  can be connected to the pulley assembly  48 . The first end portion  82 X of the first biasing member  82  corresponds to the first end portion of the pulley assembly biasing member  66 . The fourth end portion  84 Y of the second biasing member  84  corresponds to the second end portion of the pulley assembly biasing member  66 . 
     The first biasing member  82  can be made of a first material, and the second biasing member  84  can be made of a second material that is different from the first material. The first biasing member  82  can be made of the first material, and the second biasing member  84  can be made of the first material. The first biasing member  82  can have a first cross-sectional area, and the second biasing member  84  can have a second cross-sectional area that is different from the first cross-sectional area. The first biasing member  82  can have the first cross-sectional area, and the second biasing member  84  can have the first cross-sectional area. 
       FIG.  16    shows a first example in which the first biasing member  82  and the second biasing member  84  are both coil springs. In a case in which the first biasing member  82  and the second biasing member  84  are coil springs, the first biasing member  82  has a first coiling diameter, and the second biasing member  84  has a second coiling diameter that is different from the first coiling diameter. Preferably, the second coiling diameter of the second biasing member  84  is smaller than the first coiling diameter of the first biasing member  82 . In a case in which the first biasing member  82  and the second biasing member  84  are coil springs, the first biasing member  82  and the second biasing member  84  can be different in at least one of the numbers of turns in coil springs, the average coil diameter, the coil diameter, and the material so that the first spring rate K 1  is different from the second spring rate K 2 . 
     The first biasing member  82  has a first coil center axis. The second biasing member  84  has a second coil center axis that coincides with the first coil center axis to form a coil center axis. Preferably, the second biasing member  84  is disposed radially inward from the first biasing member  82  with respect to the coil center axis. At least part of the first biasing member  82  is located in the second biasing member  84 . Preferably, the first coil center axis and the second coil center axis substantially coincide with the pivot axis  48 X. 
     In the first example shown in  FIG.  16   , the number of turns in the coil spring of the first biasing member  82 B is less than the number of turns in the coil spring of the second biasing member  84 B. Preferably, the third end portion  84 X of the second biasing member  84 B projects radially outward from the coil center axis, and the second end portion  82 Y of the first biasing member  82 B projects along the coil center axis. The third end portion  84 X of the second biasing member  84 B and the second end portion  82 Y of the first biasing member  82 B are provided in positions contactable with each other. For example, the first biasing member  82 B includes a biasing member having nonlinear characteristics. In an example of a biasing member having nonlinear characteristics, while the pulley assembly  48  is in the first pivotal position P 1 , the third end portion  84 X of the second biasing member  84 B is in contact with the second end portion  82 Y of the first biasing member  82  and receives first biasing force from the first biasing member  82 . While the pulley assembly  48  is in the second pivotal position P 2 , the first biasing force received from the first biasing member  82  is increased as compared to while the pulley assembly  48  is in the first pivotal position P 1 . This reduces the biasing return force M in the entirety of the biasing member  80 . 
       FIG.  17    shows a second example in which one of the first biasing member  82  and the second biasing member  84  is a coil spring, and the other of the first biasing member  82  and the second biasing member  84  is a plate spring. For example, the second biasing member  84 C is a coil spring, and the first biasing member  82 C is a plate spring. The first biasing member  82 C is provided in a direction in which the coil spring of the second biasing member  84 C extends. The fourth end portion  84 Y of the second biasing member  84 C projects radially outward from the coil center axis. While the pulley assembly  48  is in the first pivotal position P 1 , the fourth end portion  84 Y of the second biasing member  84 C is in contact with the first end portion  82 X of the first biasing member  82 C. While the pulley assembly  48  is in the first pivotal position P 1 , the elastic deformation amount of the first biasing member  82 C is less than while the pulley assembly  48  is in the second pivotal position P 2 . While the pulley assembly  48  is in the second pivotal position P 2 , the elastic deformation amount of the first biasing member  82 C is greater than while the pulley assembly  48  is in the first pivotal position P 1 . Therefore, while the pulley assembly  48  is in the second pivotal position P 2 , the deformation amount of each of the first biasing member  82 C and the second biasing member  84 C is less than the deformation amount of the pulley assembly biasing member  66  in a case in which the pulley assembly biasing member  66  is provided. Therefore, a total force of the biasing return force M of the first biasing member  82 C and the second biasing member  84 C is less than the biasing return force M of the pulley assembly biasing member  66 . This reduces the biasing return force M in the entirety of the biasing member  80 . 
     As shown in  FIG.  18   , the first biasing member  82 C and the second biasing member  84 C can be formed integrally. In this case, in the same manner as the second example shown in  FIG.  17   , while the pulley assembly  48  is in the first pivotal position P 1 , the total elastic deformation amount of the elastic deformation amount of the first biasing member  82 C and the elastic deformation amount of the second biasing member  84 C is less than while the pulley assembly  48  is in the second pivotal position P 2 . While the pulley assembly  48  is in the second pivotal position P 2 , both the first biasing member  82 C and the second biasing member  84 C elastically deform. This reduces the biasing return force M in the entirety of the biasing member  80 . Thus, the pulley assembly  48  appropriately controls the biasing return force. 
     In a second example of the adjustment mechanism, a pulley assembly biasing member  66  is configured so that at least one of the biasing return force M and biasing tension force N in the second pivotal position P 2  sets rotational force of the pulley assembly  48  relative to the movable member  44  in a preferred state. 
     The derailleur  40  includes a base member  42 , a movable member  44 , a pulley assembly  48 , and the pulley assembly biasing member  66 . The base member  42  is configured to be attached to the frame  18  of the human-powered vehicle  10 . The movable member  44  is movable relative to the base member  42 . The pulley assembly  48  is attached to the movable member  44  and rotatable in the first direction A 1  and the second direction A 2  opposite to the first direction A 1 . The pulley assembly  48  includes a first pulley  54  having a first pulley axis  54 X and a second pulley  56  having a second pulley axis  56 X. The pulley assembly biasing member  66  is configured to bias the pulley assembly  48  with respect to the movable member  44  in the first direction A 1 . 
     In a first example of the second example of the adjustment mechanism, the derailleur  40  has a pulley distance LP (centimeter), biasing return force F (newton), and a return value K. The pulley distance LP is defined between the first pulley axis  54 X and the second pulley axis  56 X. The biasing return force M is defined by rotational force of the pulley assembly  48  relative to the movable member  44 . The return value K is defined by the biasing return force M multiplied by the pulley distance LP. 
     Measurement Process of Biasing Return Force M 
     The biasing return force M is measured by a first step, a second step, a third step, and a fourth step. The second step can be executed before the first step or simultaneously with the first step. The third step is executed after the first step and the second step. The fourth step is executed after the third step. 
     The first step includes fixing the base member  42  of the derailleur  40  to a measurement device and rotating the pulley assembly  48  relative to the movable member  44  so that a line PA connecting the first pulley axis  54 X of the first pulley  54  and the second pulley axis  56 X of the second pulley  56  is parallel to the connecting pin  46 C of the linkage structure  46  on a projection plane orthogonal to the pivot axis  48 X. The base member  42  is fixed to the measurement device in the same manner as the base member  42  is fixed to the frame  18 . 
     The second step includes setting a tension gauge to a predetermined hook position. The predetermined hook position is the position of a shaft member used to attach the second pulley  56  to the plate member  52 . 
     The third step includes pulling the pulley assembly  48  using the tension gauge in a direction that is orthogonal to the connecting pin  46 C in which the second pulley  56  moves away from the base member  42  on a projection plane orthogonal to the pivot axis  48 X. In the third step, on the projection plane orthogonal to the pivot axis  48 X, the position of the pulley assembly  48  is held in a position so that the line PA is parallel to the connecting pin  46 C of the linkage structure  46 . 
     The fourth step includes attenuating force applied to the tension gauge and measuring torque at which the pulley assembly  48  starts to move in the first direction A 1 . The torque measured in the fourth step is the biasing return force M. 
     The return value K is equal to or larger than 136. Preferably, the return value K is equal to or larger than 300. Preferably, the return value K is equal to or smaller than 750. 
     The steps of measuring the biasing return force M can be changed as follows. 
     In the first step, the movable member  44  of the derailleur  40  can be fixed to a measurement device. Both the base member  42  and the movable member  44  of the derailleur  40  can be fixed to a measurement device. In a case in which the movable member  44  is fixed to a measurement device, the measurement device includes, for example, a clamp and the clamp is used to fix the movable member  44  to the measurement device. 
     The first step can include rotating the pulley assembly  48  relative to the movable member  44  so that the line PA is parallel to the connecting pin  46 C of the linkage structure  46  as viewed in a direction orthogonal to the extension direction of the first plate  52 A. 
     In the second step, the predetermined hook position can be concentric with the second pulley axis  56 X of the second pulley  56 . 
     The third step can include pulling the pulley assembly  48  using a tension gauge in a direction that is orthogonal to the connecting pin  46 C in a direction in which the second pulley  56  separates away from the base member  42  as viewed in a direction orthogonal to the extension direction of the first plate  52 A. 
     In a first example of the second example of the adjustment mechanism, preferably, the pulley distance LP ranges from 4.55 centimeters to 15 centimeters. More preferably, the pulley distance LP ranges from 7 centimeters to 14 centimeters. 
     In the first example of the second example of the adjustment mechanism, preferably, the biasing return force M is equal to or larger than 30 newtons. Preferably, the biasing return force is equal to or smaller than 50 newtons. 
     In a second example of the second example of the adjustment mechanism, the derailleur  40  has the pulley distance LP (centimeter), the biasing tension force N (newton), and a tension value S. The biasing tension force N is defined by rotational force of the pulley assembly  48  relative to the movable member  44 . The tension value S is defined by the biasing tension force N multiplied by the pulley distance LP. 
     Measurement Process of Biasing Tension Force N 
     The biasing tension force N is measured by a fifth step, a sixth step, a seventh step, and an eighth step. The sixth step can be executed before the fifth step or simultaneously with the fifth step. The seventh step is executed after the fifth step and the sixth step. The eighth step is executed after the seventh step. 
     The fifth step is executed in the same manner as the first step in the measurement process of the biasing return force M. 
     The sixth step is executed in the same manner as the second step in the measurement process of the biasing return force M. 
     The seventh step is executed in the same manner as the third step in the measurement process of the biasing return force M. 
     The eighth step includes measuring the maximum force using a tension gauge during 20-millimeter movement of the second pulley  56  away from the base member  42  in a direction orthogonal to the connecting pin  46 C. The maximum force measured in the eighth step is the biasing tension force N. 
     The steps of measuring the biasing tension force N can be changed as follows. 
     In the fifth step, the movable member  44  of the derailleur  40  can be fixed to a measurement device. Both the base member  42  and the movable member  44  of the derailleur  40  can be fixed to a measurement device. In a case in which the movable member  44  is fixed to a measurement device, the measurement device includes, for example, a clamp and the clamp is used to fix the movable member  44  to the measurement device. 
     The fifth step can include rotating the pulley assembly  48  relative to the movable member  44  so that the line PA is parallel to the connecting pin  46 C of the linkage structure  46  as viewed in a direction orthogonal to the extension direction of the first plate  52 A. 
     In the sixth step, the predetermined hook position can be concentric with the second pulley axis  56 X of the second pulley  56 . 
     The seventh step can include pulling the pulley assembly  48  using a tension gauge in a direction that is orthogonal to the connecting pin  46 C in a direction in which the second pulley  56  separates away from the base member  42  as viewed in a direction orthogonal to the extension direction of the first plate  52 A. 
     The tension value S is equal to or larger than 136. Preferably, the tension value S is equal to or larger than 300. Preferably, the tension value S is equal to or smaller than 750. 
     In the second example of the second example of the adjustment mechanism, preferably, the pulley distance LP ranges from 4.55 centimeters to 15 centimeters. More preferably, the pulley distance LP ranges from 7 centimeters to 14 centimeters. 
     In the second example of the second example of the adjustment mechanism, preferably, the biasing tension force N is equal to or larger than 30 newtons. More preferably, the biasing tension force N is equal to or smaller than 50. 
     Only one of the first example of the adjustment mechanism, a modified example of the first example of the adjustment mechanism, the second example of the adjustment mechanism, and a modified example of the second example of the adjustment mechanism can be used to set rotational force of the pulley assembly  48  relative to the movable member  44  in a preferred state. At least two of the first example of the adjustment mechanism, a modified example of the first example of the adjustment mechanism, the second example of the adjustment mechanism, and a modified example of the second example of the adjustment mechanism can be combined and used. 
     MODIFIED EXAMPLES 
     The description related to the above embodiment exemplifies, without any intention to limit, applicable forms of a human-powered vehicle derailleur according to the present disclosure. The human-powered vehicle derailleur according to the present disclosure can be applied to, for example, modified examples of the embodiment that are described below and combinations of at least two of the modified examples that do not contradict each other. In the following modified examples, the same reference characters are given to those elements that are the same as the corresponding elements of the above embodiment. Such elements will not be described in detail. 
     As shown in  FIG.  19   , the derailleur  40  can be changed to a derailleur  40 A further including a motor  88  configured to move the movable member  44  relative to the base member  42 . Preferably, the motor  88  is provided on the base member  42 . The motor  88  can be provided on at least one of the movable member  44 , the linkage structure  46 , and the pulley assembly  48 . The motor  88  can be configured to be supplied with electric power from the battery  36  disposed apart from the derailleur  40 . In a case in which the derailleur  40  includes the motor  88 , preferably, the human-powered vehicle  10  includes a control device. The control device can be provided on the derailleur  40 . The control device includes an arithmetic processing device that executes a predetermined control program. The arithmetic processing device includes, for example, a central processing unit (CPU) or a micro processing unit (MPU). Arithmetic processing devices can be provided at different positions separate from each other. The control device can include one or more microcomputers. Preferably, the control device further includes storage. The storage stores information used for various control programs and various control processes. The storage includes, for example, a nonvolatile memory and a volatile memory. The nonvolatile memory includes, for example, at least one of a read-only memory (ROM), an erasable programmable read only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), and a flash memory. The volatile memory includes, for example, a random access memory (RAM). 
     In the modified example shown in  FIG.  19   , the derailleur  40 A can further include a battery  90  that supplies electric power to the motor  88  as shown in  FIG.  20   . Preferably, the battery  90  is provided on the base member  42 . The battery  90  can be provided on at least one of the movable member  44 , the linkage structure  46 , and the pulley assembly  48 . 
     As shown in  FIG.  21   , the battery  90  can further be provided to supply electric power to the assist motor  38  configured to apply propulsion force to the human-powered vehicle  10 . The modified example shown in  FIG.  21    can be applied to the derailleur  40  that has the motor  88  and the derailleur  40  that does not have the motor  88 . 
     As shown in  FIG.  22   , the derailleurs  40  and  40 A can further include a wireless unit  92  configured to perform wireless communication with an electric component of the human-powered vehicle  10 . Preferably, the wireless unit  92  is provided on the base member  42 . The battery  90  can be provided on at least one of the movable member  44 , the linkage structure  46 , and the pulley assembly  48 . The wireless unit  92  can be detachably attached to the derailleurs  40  and  40 A. 
     In this specification, the phrase “at least one of” as used in this disclosure means “one or more” of a desired choice. For one example, the phrase “at least one of” as used in this disclosure means “only one single choice” or “both of two choices” if the number of its choices is two. For other example, the phrase “at least one of” as used in this disclosure means “only one single choice” or “any combination of equal to or more than two choices” if the number of its choices is equal to or more than three. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
         
           
               10 ) human-powered vehicle,  18 ) frame,  26 ) sprocket,  26 A) rear sprocket assembly,  36 ) battery,  38 ) assist motor,  40 ) derailleur,  42 ) base member,  44 ) movable member,  46 ) linkage structure,  48 ) pulley assembly,  48 X) pivot axis,  54 ) first pulley,  56 ) second pulley,  50 ) rotational force control structure,  60 ) cam member,  60 A) first cam surface,  60 B) second cam surface,  60 C) transition portion,  62 ) abutment member,  62 X) rotational axis,  64 ) biasing member,  66 ) pulley assembly biasing member,  70 ) resistance applying member,  72 ) resistance applying member,  74 ) contact member,  76 ) first biasing member,  78 ) second biasing member,  80 ) pulley assembly biasing member,  82 ) first biasing member,  82 X) first end portion,  82 Y) second end portion,  84 ) second biasing member,  84 X) third end portion,  84 Y) fourth end portion,  88 ) motor,  90 ) battery,  92 ) wireless unit