Abstract:
A driving apparatus having a small charging load, capable of reducing the size of the appratus is disclosed. A present invention discloses a driving apparatus comprises a driving source, a driven member, an energizing member which energizes the driven member in a predetermined direction, a lever member rotatable by receiving the driving force from the driving source at an input portion, which contacts and charges the driven member and a main body which includes a first engaging portion and a second engaging portion and supports the lever member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a driving apparatus, shutter apparatus and camera which moves a driven member having a moving load from an initial position of charging to a position of completion of charging against the load. 
     2. Description of Related Art 
     A conventional charge mechanism which moves a driven member having a moving load from an initial position of charging to a position of completion of charging against the moving load is constructed in such a way that a lever member  401  rotates about one rotation axis as shown in FIG.  23 . 
     With reference to FIG. 23 which is a perspective view showing an entire conventional charge mechanism, the conventional charge mechanism will be explained in detail. 
     Reference numeral  401  denotes a lever member which is supported in a manner rotatable about an axial portion  402   a  laid on a first base plate  402  as the rotation axis, pressed in the thrust direction of the axial portion  402   a  by a dropout prevention member (not shown) with a tiny gap. Reference numeral  401   a  denotes an input side arm portion of the lever member  401 ,  401   b  denotes an input pin laid in an integrated fashion on the input side arm portion  401   a  and  401   c  denotes an output side arm portion of the lever member  401 . 
     Reference numeral  403  denotes a driven member, which is supported in a manner rotatable about an axial portion  402   b  laid on the first base plate  402  as the rotation axis, pressed in the thrust direction of the axial portion  402   b  by a dropout prevention member (not shown) with a tiny gap. At one end of the driven member  403 , the axial portion  403   a  is laid in an integrated fashion and a roller  404  is attached in a manner rotatable about the axial portion  403   a  as the rotation axis. The dropout prevention member (not shown) acts on the roller  404  in the same way. 
     Reference numeral  405  denotes a power spring (torsion spring) located on the driven member  403  in such a way as to be coaxial with the axial portion  402   b  and its one end contacts a spring stopper  402   c  laid on the first base plate  402  and its other end contacts a spring stopper  403   b  of the driven member  403  and gives the driven member  403  clockwise torque about the axial portion  402   b  as the rotation axis. 
     Reference numeral  406  denotes a charge input lever and is supported in a manner rotatable about an axial portion  407   a  as the rotation axis, laid on a second base plate  407  which is placed orthogonal to the first base plate  402  and pressed in the thrust direction of the axial portion  407   a  by a dropout prevention member (not shown) with a tiny gap. Reference numeral  406   a  denotes an input side arm portion of the charge input lever  406  and receives a force Fch which rotates the charge input lever  406  counterclockwise about the axial portion  407   a  as the rotation axis to charge this charge mechanism. 
     Reference numeral  406   b  denotes an output side arm portion of the charge input lever  406 .  406   c  denotes an output pin laid in an integrated fashion on the output side arm portion  406   b , which contacts the input pin  401   b  of the lever member  401  and transmits power to the lever member  401 . Reference numeral  408  denotes a return spring, one end of which is supported by a spring stopper portion  407   b  laid on the second base plate  407  and the other end of which is hooked on to a hole  406   d  of the charge input lever  406 . Hereby the return spring  408  gives the charge input lever  406  clockwise torque about the axial portion  407   a  as the rotation axis. 
     Reference numeral  407   c  denotes a stopper provided on the second base plate  407  which contacts the side of the output side arm portion  406   b  of the charge input lever  406  and blocks the clockwise rotation of the charge input lever  406  by the return spring  408 . 
     Then, the operation of the conventional charge mechanism in the above described configuration will be explained. 
     First, when a force Fch is applied to the input side arm portion  406   a  of the charge input lever  406 , the charge input lever  406  rotates counterclockwise about the axial portion  407   a  as the rotation axis. In this way, the input pin  401   b  on the input side arm portion  401   a  is pressed by the output pin  406   c  on the output side arm portion  406  and the lever member  401  rotates clockwise about the axial portion  402   a  as the rotation axis. This causes the output side arm portion  401   c  of the lever member  401  to press the roller  404  against the force of the power spring  405  and rotate the driven member  403  counterclockwise about the axial portion  402   b  as the rotation axis. 
     Then, charging is finished when the driven member  403  has rotated by a predetermined angle. 
     Then, the operation of the conventional charge mechanism will be explained in detail with the state of a charging load in operation taken into consideration. The power spring  405  is a torsion spring but it will be expressed as a tensile coil spring in the figures used in the following explanations as required. 
     FIG. 24 is a plane view of charge mechanism (charge input lever  406  placed on the second base plate  407 , etc., is omitted) indicating the lever member  401  and the driven member  403  placed on the first base plate  402  when charging is started, and both the rotation angle of the lever member  401  (driving member) and the rotation angle of the driven member  403  are 0°. 
     In the same figure, components have dimensions as indicated in the figure and suppose the rotation moment that the power spring  405  gives to the driven member  403  is kθ1 when charging is started. Here, k denotes a spring constant of the power spring  405  per unit rotation angle when the driven member  403  rotates. Furthermore, θ1 denotes a displacement angle from a free state of the driven member  403 . 
     F in the figure denotes a force that the input pin  401   b  of the lever member  401  receives from the output pin  406   c  of the charge input lever  406  to balance with kθ1, P10 denotes the force that the roller  404  receives from the output side arm portion  401   c  of the lever member  401 , which is equal to a reaction force by the force of the power spring  405  that the output side arm portion  401   c  of the lever member  401  receives through the roller  404 . 
     From a balance relationship between forces, the following expressions are obtained. Here, for simplicity of explanation, frictions of various portions are ignored. 
     
       
         ( F ·cos 29.16°)×3.90 =P 10×5.79  (1.1) 
       
     
     
       
         ( P 10·cos 54.35°)×10.00 =kθ 1  (1.2) 
       
     
     From expressions (1.1) and (1.2), F=0.292kθ1 is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]), θ1=10°. Then, F=2.92[gf](=2860[dyn]) is obtained. 
     FIG. 25 is a plane view of charge mechanism in a first half charging state after charging has further advanced from the state in FIG.  24 . The rotation angle of the lever member (driving member)  401  is 14° and the rotation angle of the driven member is 10° after charging is started. 
     In the same figure, components have dimensions as shown in the figure and the rotation moment that the power spring  405  gives to the driven member  403  is k(θ1+10°). Reference character F denotes a force that the input pin  401   b  of the lever member  401  receives from the output pin  406   c  of the charge input lever  406  to balance with k(θ1+10°), P20 denotes a force that the roller  404  receives from the output side arm portion  401   c  of the lever member  401 , which is equal to the reaction force by the force of the power spring  405  that the output side arm portion  401   c  of the lever member  401  receives through the roller  404 . 
     The following expressions are obtained from the relationship of balance between forces. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F ·cos 15.16°)×3.90 =P 20×4.98  (1.3) 
       
     
     
       
         ( P 20·cos 30.35°)×10.00 =k (θ1+10°)  (1.4) 
       
     
     From Expressions (1.3) and (1.4), F=0.153k(θ1+10°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]), θ1=10°. Then, F=3.07[gf](=3000[dyn]) is obtained. 
     FIG. 26 is a plane view of charge mechanism in an intermediate charging state after charging has further advanced from the state in FIG.  25 . The rotation angle of the lever member (driving member)  401  is 30.2° and the rotation angle of the driven member  403  is 18.5° after charging is started. 
     In the same figure, components have dimensions as shown in the figure. In the intermediate state of charging, the rotation moment that the power spring  405  gives to the driven member  403  is k(θ1+18.5°). Reference character F denotes a force that the input pin  401   b  of the lever member  401  receives from the output pin  406   c  of the charge input lever  406  to balance with k(θ1+18.5°), P30 denotes a force that the roller  404  receives from the output side arm portion  401   c  of the lever member  401 , which is equal to the reaction force by the force of the power spring  405  that the output side arm portion  401   c  of the lever member  401  receives through the roller  404 . 
     The following expressions are obtained from the relationship of balance between forces. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F ·cos 1.04°)×3.90 =P 30×4.94  (1.5) 
       
     
     
       
         ( P 30·cos 5.65°)×10.00 k (θ1+18.5°)  (1.6) 
       
     
     From expressions (1.5) and (1.6), F=0.127k(θ1+18.5°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=3.63[gf](=3560[dyn]) is obtained. 
     FIG. 27 is a plane view of charge mechanism in a second half charging state after charging has further advanced from the state in FIG.  26 . The rotation angle of the lever member (driving member)  401  is 55.5° and the rotation angle of the driven member is 33° after charging is started. 
     In the same figure, components have dimensions as shown in the figure. In the second half charging state, the rotation moment that the power spring  405  gives to the driven member  403  is k(θ1+33°). Reference character F denotes a force that the input pin  401   b  of the lever members  401  receives from the output pin  406   c  of the charge input lever  406  to balance with k(θ1+33°), P40 denotes a force that the roller  404  receives from the output side arm portion  401   c  of the lever member  401 , which is equal to the reaction force by the force of the power spring  405  that the output side arm portion  401   c  of the lever member  401  receives through the roller  404 . 
     The following expressions are obtained from the relationship of balance between forces. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F ·cos 26.34°)×3.90 =P 40×6.25  (1.7) 
       
     
     
       
         ( P 40·cos 34.15°)×10.00 =k (θ1+33°)  (1.8) 
       
     
     From expressions (1.7) and (1.8), F=0.216k(θ1+33°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=9.29[gf](=9110[dyn]) is obtained. 
     FIG. 28 is a plane view of charge mechanism in a charging completion state after charging has further advanced from the state in FIG.  27 . The rotation angle of the lever member (driving member)  401  is 66.5° and the rotation angle of the driven member is 44° after charging is started. 
     In the same figure, components have dimensions as shown in the figure. In the charging completion state, the rotation moment that the power spring  405  gives to the driven member  403  is k(θ1+44°). Reference character F denotes a force that the input pin  401   b  of the lever member  401  receives from the output pin  406   c  of the charge input lever  406  to balance with k(θ1+44°), P50 denotes a force that the roller  404  receives from the output side arm portion  401   c  of the lever member  401 , which is equal to the reaction force by the force of the power spring  405  that the output side arm portion  401   c  of the lever member  401  receives through the roller  404 . 
     The following expressions are obtained from the relationship of balance between forces. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F·cos  37.34°)×3.90 =P 50×7.90  (1.9) 
       
     
     
       
         ( P 50·cos 56.15°)×10.00 =k (θ1+44°)  (1.10) 
       
     
     From expressions (1.9) and (1.10), F=0.457k(θ1+44°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=24.7[gf](=24200([dyn]) is obtained. 
     Based on the above described results, the graphs shown in FIGS. 7A and 7B give a summary of the relationship between the rotation angle of the driven member and input load of the lever member (which will be described later). 
     Here, suppose a shutter apparatus provided with the above described charge mechanism (e.g., see Japanese Patent Publication No. S62(1987)-17737 (pp2-5, FIG. 2) and Japanese Utility Model Application Laid-Open No. H4(1992)-17930 (pp2-3, FIG. 1)). 
     FIG. 30 to FIG. 36 show a conventional charge mechanism of a focal plane shutter (hereinafter simply referred to as a “shutter apparatus”) mounted on a single-lens reflex camera. The focal-plane shutter has a front curtain and a rear curtain. FIG. 30 is a perspective view indicating main components of the shutter apparatus, FIG. 31 is a plane view of the shutter apparatus showing a state after completion of running until charging is started, FIG. 32 is a plane view of the shutter apparatus in a first half charging state, FIG. 33 is a plane view of the shutter apparatus in an intermediate state of charging (switching of charge lever axes), FIG. 34 is a plane view of the shutter apparatus showing a second half charging state, FIG. 35 is a plane view of the shutter apparatus in a state immediately before completion of charging and FIG. 36 is a plane view of the shutter apparatus in a state of overcharge. In these FIGS. 31 to  36 , suppose straight lines H 5 , H 6  and H 7  are common straight lines. 
     In FIGS. 30 to  36 , reference numeral  501  denotes a charge lever (lever member) which is supported to an axial portion  502   a  laid on a shutter base plate  502  in a rotatable manner and pressed in the thrust direction of the axial portion  502   a  by a dropout prevention member (not shown) with a tiny gap. Reference numeral  501   a  denotes an input side arm portion of the charge lever  501 ,  501   b  denotes an input pin (input portion) laid in an integrated fashion on the input side arm portion  501   a ,  501   c   1  denotes a front curtain side output arm portion of the charge lever  501 ,  501   c   2  denotes a rear curtain side output arm portion of the charge lever  501 . 
     Reference numeral  503  denotes a front curtain driving lever (driven member) which is supported to an axial portion  512   a  laid on the shutter base plate  502  in a rotatable manner and pressed in the thrust direction of the axial portion  512   a  by a dropout prevention member (not shown) with a tiny gap. At the end of the one arm portion  503   c  of the front curtain driving lever  503 , an axial portion  503   a  is laid in an integrated fashion and a roller  504  is supported to the axial portion  503   a  in a rotatable manner. This shutter base plate  502  acts as a dropout prevention member of the roller  504 . 
     At the end of the other arm portion  503   d  of the front curtain driving lever  503 , a front curtain driving pin  503   e  is laid in an integrated fashion. On the front curtain driving lever (driven member)  503 , a power spring (torsion spring)  505  is located in such a way as to be coaxial to the axial portion  512   a.    
     One end of the power spring  505  is supported to a shutter speed adjustment member (not shown) and the other end is hooked on to a spring stopper (not shown) of the front curtain driving lever  503 . Hereby, the power spring  505  gives the front curtain driving lever  503  clockwise torque about the axial portion  512   a  as the rotation axis. A front curtain main arm  516  is supported to an axial portion  502   g  laid on the shutter base plate  502  in a rotatable manner. Furthermore, a front curtain sub-arm  517  is supported to an axial portion  502   h  laid on the shutter base plate  502  in a rotatable manner. Then, a slit formation blade (first blade)  518   a  of a blade group  518  making up the front curtain has a slit formation portion  518   e.    
     Of the blade group  518 , a second blade  518   b , a third blade  518   c  and a fourth blade  518   d  are supported to the front curtain main arm  516  and front curtain sub-arm  517  in a rotatable manner using a caulking dowel  519   a , etc., and both arms  516 ,  517  and each blade together forms a parallel link (publicly known configuration). Furthermore, an armature holding portion  503   f  is formed above the arm portion  503   d  of the front curtain driving lever  503  to hold a magnet armature  523  by means of an armature axis  524  with a certain degree of freedom. Then, a yoke  525  wound with a coil  526  is fixed to a base plate (not shown), which attracts and holds the armature  523  when power is supplied to the coil  526 , and releases the armature  523  when the power supply to the coil  526  is interrupted. Shutter timing is controlled using the above described operation. 
     Reference numeral  513  denotes a rear curtain driving lever (driven member), which is supported to an axial portion  512   b  laid on the shutter base plate  502  in a rotatable manner and pressed in the thrust direction of the axial portion  512   b  by a dropout prevention member (not shown) with a tiny gap. At one end of the arm portion  513   c  of the rear curtain driving lever  513 , an axial portion  513   a  is laid in an integrated fashion and a roller  514  is supported to the axial portion  513   a  in a rotatable manner. 
     The shutter base plate  502  acts as a dropout prevention member for the roller  514 . At one end of the arm portion  513   d  of the rear curtain driving lever  513 , a rear curtain driving pin  513   e  is laid in an integrated fashion. On the rear curtain driving lever (driven member)  513 , a power spring (torsion spring)  515  is located in such a way as to be coaxial with the axial portion  512   b . One end of the power spring  515  is supported to a shutter speed adjustment member (not shown) and the other end is hooked on to a spring stopper (not shown) of the rear curtain driving lever  513 . Hereby the power spring  513  gives the rear curtain driving lever  513  clockwise torque about the axial portion  512   b  as the rotation axis. The rear curtain main arm  520  is supported to an axial portion  502   i  laid on the shutter base plate  502  in a rotatable manner. Furthermore, a rear curtain sub-arm  521  is supported to an axial portion  502   j  laid on the shutter base plate  502  in a rotatable manner. 
     Furthermore, a blade group  522  making up the rear curtain is constructed of four blades as in the case of the front curtain. Reference numeral  522   e  in FIGS. 32 to  35  denotes a slit formation portion in the blade group  522 . Each blade of the blade group  522  is supported to the rear curtain main arm  520  and the rear curtain sub-arm  521  in a rotatable manner using a caulking dowel  519   b , etc., and both arms  520 ,  521  and each blade together forms a parallel link (publicly known configuration). Furthermore, an armature holding portion  513   f  is formed above the arm portion  513   c  of the rear curtain driving lever  513  and the armature holding portion  513   f  holds a magnet armature  527  by means of an armature axis  528  with a certain degree of freedom of movement. 
     A yoke  529  wounded with a coil  530  is fixed to a base plate (not shown), which attracts and holds the armature  527  when power is supplied to the coil  530 , and releases the armature  527  when the power supply to the coil  530  is interrupted. Shutter timing is controlled using the above described operation. Reference numeral  502   d  denotes an aperture formed on the shutter base plate  502  through which a light passes and  502   e  denotes a long hole portion which is formed on the shutter base plate along a movement track of the front curtain driving pin  503   e  and  502   f  denotes a long hole portion which is formed on the shutter base plate along a movement track of the rear curtain driving pin  513   e.  Reference numerals  511   a  and  511   b  denote buffering members for receiving the front curtain driving pin  503   e  and rear curtain driving pin  513   e  when running of the front curtain is completed. 
     The charge mechanism of the conventional shutter apparatus as described above sets a maximum width from the input pin  501   b  laid in an integrated fashion on the input side arm portion  501   a  to the left end of the shutter apparatus to 12.6 mm (see FIG. 33) and sets the stroke of the input pin  501   b  (distance between straight line H 5  and straight line H 6 ) to 4.25 mm. 
     Furthermore, a charge input lever (not shown) which contacts the input pin  501   b  of the charge lever  501  to give the charge lever  501  torque in the same relationship as reference numeral  406  in FIG. 23 is provided. 
     The above described charge mechanism in which the lever member  401  simply rotates around one rotation axis involves inconvenience that when charging is started and when charging is completed, an angle formed between the straight line (L in FIGS. 24 to  29 ) connecting the central axis of the input pin  401   b  of the lever member  401  and the center of the axial portion  402   a , and the line (H in FIGS. 24 to  29 ) orthogonal to the direction of the force F increases and the component force in the direction of the rotation axis  402   a  of the lever member  401  of the force that the input pin  401   b  receives from the output pin  406   c  of the charge input lever  406  is large (that is, axial loss is large), causing the force that rotates the lever member in the charge direction (clockwise direction) to be lost. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a small driving apparatus with a low charging load. The present invention is especially designed to reduce axial loss by reducing the component force in the axial direction during charging, reduce displacement at the input end in the direction orthogonal to the direction of the input load and thereby increase the driving efficiency. 
     One aspect of the driving apparatus of the present invention includes the following: A driving source, a driven member, an energizing member which energizes the driven member in a predetermined direction, a lever member rotatable by receiving the driving force from the driving source at an input portion, which contacts and charges the driven member, and a main body which includes a first engaging portion and a second engaging portion and supports the lever member. Here, the lever member includes a first engaged portion which engages with the first engaging portion and a second engaged portion which engages with the second engaging portion, and the lever member is rotated around a first axis by engaging the first engaging portion and the first engaged portion with each other, and in the middle of rotation, the lever member is rotated around a second axis by engaging the second engaging portion and the second engaged portion with each other. 
     One aspect of the shutter apparatus of the present invention includes the following: A driving source, a front curtain constructed of a plurality of blades, a rear curtain constructed of a plurality of blades, a first driving lever which drives charging of the front curtain, a second driving lever which drives charging of the rear curtain; and a driving force transmission member rotatable by receiving the driving force from the driving source, which includes a first arm portion which contacts the first driving lever and transmit the driving force and a second arm portion which contacts the second driving lever and transmits driving force. Here, the driving force transmission member starts charging when the distance between the rotation center and the point of contact with the first driving lever is greater than the distance between the rotation center and the point of contact with the second driving lever and is set through switching of the rotation center at some midpoint so that the distance between the rotation center and the point of contact with the second driving lever is greater than the distance between the rotation center and the point of contact with the first driving lever. 
     One aspect of the camera of the present invention includes the above described shutter apparatus. 
     Features of the driving apparatus, shutter apparatus and camera of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an entire charge mechanism which is a first embodiment of the present invention; 
     FIG. 2 is a plane view of the charge mechanism in a charging start state according to the first embodiment of the present invention; 
     FIG. 3 is a plane view of the charge mechanism in a first half charging state according to the first embodiment of the present invention; 
     FIG. 4 is a plane view of the charge mechanism in an intermediate charging (axis switching) state according to the first embodiment of the present invention; 
     FIG. 5 is a plane view of the charge mechanism in a second half charging state according to the first embodiment of the present invention; 
     FIG. 6 is a plane view of the charge mechanism in a charging completion state according to the first embodiment of the present invention; 
     FIGS.  7 (A) and  7 (B) illustrate a relationship between the rotation angle of a driven member and an input load of the lever member; 
     FIG. 8 is a plane view of the charge mechanism in illustrating a relationship between a charge input member and lever member according to the first embodiment of the present invention; 
     FIG. 9 is a perspective view of an entire charge mechanism which is a second embodiment of the present invention; 
     FIG. 10 is a plane view of the charge mechanism in a charging start state according to the second embodiment of the present invention; 
     FIG. 11 is a plane view of the charge mechanism in an intermediate charging (axis switching) state according to the second embodiment of the present invention; 
     FIG. 12 is a plane view of the charge mechanism in a charging completion state according to the second embodiment of the present invention; 
     FIG. 13 is a plane view of the charge mechanism in illustrating a relationship between the charge input member and lever member according to the second embodiment of the present invention; 
     FIG. 14 is an outside perspective view of a shutter apparatus according to a third embodiment of the present invention; 
     FIG. 15 is a front view of part of the shutter apparatus in a charging start state; 
     FIG. 16 is a front view of part of the shutter apparatus in a first half charging state; 
     FIG. 17 is a front view of part of the shutter apparatus in an intermediate charging (axis switching) state; 
     FIG. 18 is a front view of part of the shutter apparatus in a second half charging state; 
     FIG. 19 is a front view of part of the shutter apparatus in a state immediately before completion of charging; 
     FIG. 20 is a front view of part of the shutter apparatus in an overcharge state; 
     FIG. 21 is an outside perspective of a camera; 
     FIG. 22 is a longitudinal sectional view of the camera body; 
     FIG. 23 is a perspective view of an entire charge mechanism of a conventional technology; 
     FIG. 24 is a plane view of a conventional charge mechanism in a charging start state; 
     FIG. 25 is a plane view of the conventional charge mechanism in a first half charging state; 
     FIG. 26 is a plane view of the conventional charge mechanism in an intermediate charging (axis switching) state; 
     FIG. 27 is a plane view of the conventional charge mechanism in a second half charging state; 
     FIG. 28 is a plane view of the conventional charge mechanism in a charging completion state; 
     FIG. 29 is a plane view of the conventional charge mechanism illustrating a relationship between the charge input member and lever member; 
     FIG. 30 is an outside perspective view of the shutter apparatus of the conventional technology; 
     FIG. 31 is a front view of part of the conventional shutter apparatus in a charging start state; 
     FIG. 32 is a front view of part of the conventional shutter apparatus in a first half charging state; 
     FIG. 33 is a front view of part of the conventional shutter apparatus in an intermediate charging (axis switching) state; 
     FIG. 34 is a front view of part of the conventional shutter apparatus in a second half charging state; 
     FIG. 35 is a front view of part of the conventional shutter apparatus in a state immediately before completion of charging; and 
     FIG. 36 is a front view of part of the conventional shutter apparatus in an overcharge state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (First Embodiment) 
     A charge mechanism according to this embodiment will be explained. 
     FIGS. 1 to  8  illustrate the charge mechanism according to the first embodiment of the present invention. FIG. 1 is a perspective view of the entire charge mechanism, FIG. 2 is a plane view of the charge mechanism which a lever member  1  and driven member  3  are placed on the first base plate  2  in a charging start state, FIG. 3 is a plane view of the charge mechanism in a first half charging state, FIG. 4 is a plane view of the charge mechanism in an intermediate charging (axis switching) state, FIG. 5 is a plane view of the charge mechanism in a second half charging state and FIG. 6 is a plane view of the charge mechanism in a charging completion state. 
     FIG. 7 illustrates a relationship between the rotation angle of a driven member and an input load of the lever member, FIG. 7A is a table and FIG. 7B is a graph. FIG. 8 is a plane view of the charge mechanism illustrating a relationship between a charge input member and lever member. 
     In FIG. 1, reference numeral  1  denotes a lever member, which is supported in a manner rotatable about a first axial portion (a first engaging portion)  2   a   1  and a second axial portion (a second engaging portion)  2   a   2  laid on a first base plate  2  as rotation axes and pressed in the thrust directions of the first axial portion  2   a   1  and second axial portion  2   a   2  by a dropout prevention member (not shown) with a tiny gap. Reference numeral  1   a  denotes an input side arm portion of the lever member  1 ,  1   b  denotes an input pin (input portion) laid on the input side arm portion  1   a  in an integrated fashion and  1   c  denotes an output side arm portion of the lever member  1 . 
     Reference numeral  1   d   1  denotes a first bearing portion (a first engaged portion) which engages with the first axial portion  2   a   1  and makes the lever member  1  rotatable about the first axial portion  2   a   1  as the rotation axis (first rotation axis) and  1   d   2  denotes a second bearing portion (a second engaged portion) which engages with the second axial portion  2   a   2  and makes the lever member  1  rotatable about the second axial portion  2   a   2  as the rotation axis (second rotation axis). 
     The first bearing portion  1   d   1  is hidden in the perspective view of FIG. 1, but formed inside (side facing the first base plate  2 ) the lever member  1  as shown with the dotted lines and formed in a position different from the second bearing portion  1   d   2  which penetrates the lever member  1 . 
     That is, the position of engagement between the first axial portion  2   a   1  and first bearing portion  1   d   1  and position of engagement between the second axial portion  2   a   2  and second bearing portion  1   d   2  are set to be different in the thickness direction of the lever member  1 . This allows the rotation center of the lever member  1  to be switched smoothly with a smaller space. 
     Reference numeral  3  denotes a driven member which is supported in a manner rotatable about an axial portion  2   b  laid on the first base plate  2  as the rotation axis and pressed in the thrust direction of the axial portion  2   b  by a dropout prevention member (not shown) with a tiny gap. At one end of the driven member  3 , the axial portion  3   a  is laid in an integrated fashion and a roller  4  is attached to the axial portion  3   a  in a rotatable manner. A dropout prevention member (not shown) acts on the roller  4  in the same way. 
     Reference numeral  5  denotes a torsion spring (power spring) provided on the driven member  3  in such a way as to be coaxial with the axial portion  2   b  and its one end contacts a spring stopper  2   c  laid on the first base plate  2  and its other end contacts a spring stopper  3   b  of the driven member  3 . The power spring  5  placed in this way gives the driven member  3  clockwise torque about the axial portion  2   b  as the rotation axis. 
     Reference numeral  6  denotes a charge input lever (transmission member) and is supported in a manner rotatable about an axial portion  7   a  laid on a second base plate  7  (placed orthogonal to the first base plate  2 ) as the rotation axis and pressed in the thrust direction of the axial portion  7   a  by a dropout prevention member (not shown) with a tiny gap. Reference numeral  6   a  denotes an input side arm portion of the charge input lever  6 , which receives a force Fch transmitted from a driving source (not shown) and rotates the charge input lever  6  counterclockwise about the axial portion  7   a  as the rotation axis. 
     Reference numeral  6   b  denotes an output side arm portion of the charge input lever  6 .  6   c  denotes an output pin laid on the output side arm portion  6   b  in an integrated fashion, which contacts the input pin  1   b  of the lever member  1  and transmits power to the lever member  1 . 
     Reference numeral  8  denotes a return spring, one end of which is supported by a spring stopper  7   b  laid on the second base plate  7  and the other end of which is hooked on to a hole  6   d  of the charge input lever  6 . This causes the return spring  8  to give the charge input lever  6  clockwise torque about the axial portion  7   a  as the rotation axis. Reference numeral  7   c  denotes a stopper provided on the second base plate  7  which contacts the side of the output side arm portion  6   b  of the charge input lever  6  and blocks the clockwise rotation of the charge input lever  6  by the return spring  8  (see FIG.  1 ). 
     The distance between the center of the first axial portion  2   a   1  and the center of the input pin  1   b  is 4.00 mm and the distance between the center of the second axial portion  2   a   2  and the center of the input pin  1   b  is 3.77 mm, that is, these distances are set to substantially the same length. This can suppress drastic variations of load when the rotation center of the lever member  1  is switched from the first axial portion  2   a   1  to the second axial portion  2   a   2  in the middle of rotation of the lever member  1 . 
     Furthermore, to reduce (that is, reduce axial loss) the component force in the direction of the first and second rotation axis of the lever member  1  of the driving force transmitted from the output pin  6   c  of the charge input lever  6  to the input pin  1   b , the total rotation angle (sum of rotation angles) of the lever member  1  about the first axial portion  2   a   1  and second axial portion  2   a   2  as the rotation axes is set to 65° (31°+34°). 
     That is, the total rotation angle is set to be greater than 39.77° which is the sum of angle 17.46° formed by the straight line (L) connecting the center of the first axial portion  2   a   1  and the center of the input pin  1   b  when charging is started (see FIG. 2) and the straight line (H) orthogonal to the direction of the force applied to the input pin  1   b , and angle 22.31° formed by the straight line (L) connecting the center of the second axial portion  2   a   2  and the center of the input pin  1   b  when charging is completed (see FIG. 6) and the straight line (H) orthogonal to the direction of the force applied to the input pin  1   b.    
     Then, the operation of the charge mechanism in such a configuration will be explained in detail below. 
     First, when a driving force Fch is applied to the input side arm portion  6   a  of the charge input lever  6 , the charge input lever  6  rotates counterclockwise in FIG. 1 about the axial portion  7   a  as the rotation axis. This causes the output pin  6   c  on the output side arm portion  6   b  to push in the input pin  1   b  on the input side arm portion  1   a , causes the first bearing portion  1   d   1  to contact the first axial portion  2   a   1 , making the lever member  1  rotate clockwise about the first axial portion  2   a   1  as the rotation axis. This causes the output side arm portion  1   c  of the lever member  1  to push the roller  4  and makes the driven member  3  rotate counterclockwise about the axial portion  2   b  as the rotation axis against the force of the power spring  5 . 
     Here, if the second bearing portion  1   d   2  contacts the second axial portion  2   a   2  in the middle of rotation of the lever member  1 , the first bearing portion  1   d   1  disengages from the first axial portion  2   a   1  and the lever member  1  rotates clockwise about the second axial portion  2   a   2  as the rotation axis (that is, by switching the rotation center from the first axial portion to the second axial portion). Then, charging is finished when the lever member  1  has rotated a predetermined angle. 
     On the other hand, when the force Fch is no longer applied in a charging completion state, the lever member  1  goes the opposite way of the charging process by the force of the power spring  5  and returns to the charging start state. 
     The operation of the charge mechanism according to this embodiment will be explained sequentially in detail with the state of charging load in the middle of the operation taken into consideration. The power spring  5  is a torsion spring, but will be expressed as a tensile coil spring in the figures (FIGS. 2 to  6 ) used in the following explanations. 
     FIG. 2 is a plane view of the charge lever member  1  and the driven member  3  placed on the first base plate  2  in the charge starting state (the charge input lever  6 , etc., placed on the second base plate  7  is omitted) and shows the case where both the rotation angle of the lever member and the rotation angle of the driven member are 0°. 
     In FIG. 2, components have dimensions as indicated in the figure and suppose the rotation moment that the power spring  5  gives to the driven member  3  is kθ1 when charging is started. Here, k denotes a spring constant of the power spring  5  per unit rotation angle when the driven member  3  rotates. Furthermore, θ1 denotes an angle by which the power spring  5  has displaced from a free state rotating about the axial portion  2   b.    
     Reference character F indicated by the arrow in FIG. 2 denotes a force (that is, the driving force transmitted from the driving source) that the input pin  1   b  of the lever member  1  receives from the output pin  6   c  of the charge input lever  6  to balance with kθ1, P1 indicated by the arrow denotes the force that the roller  4  receives from the output side arm portion  1   c  of the lever member  1 , which is equal to a reaction force by the force of the power spring  5  that the output side arm portion  1   c  of the lever member  1  receives through the roller  4 . F1 indicated by the arrow is a force component around the first axial portion  2   a   1  to generate P1. 
     From the relationship of balance between forces, the following expressions are obtained. Here, for simplicity of explanation, frictions of various portions are ignored. 
     
       
         ( F ·cos 17.46°)×4.00 =F 1×5.94  (2.1) 
       
     
     
       
           F 1·cos 8.32 °=P 1  (2.2) 
       
     
     
       
         ( P 1·cos 53.15°)×10.00 =kθ 1  (2.3) 
       
     
     From expressions (2.1), (2.2) and (2.3), F=0.262kθ1 is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=2.62[gf](=2570[dyn]) is obtained. 
     FIG. 3 is a plane view of the charge mechanism in a first half charging state after charging has advanced from the state in FIG.  2 . Here, the first half charging state means the range after charging is started until the rotation center of the lever member  1  is switched from the first axial portion to the second axial portion. The rotation angle of the lever member  1  after charging is started is 14° and the rotation angle of the driven member  3  is 10° in the state shown in FIG.  3 . 
     In the same figure, components have dimensions as shown in the figure and the rotation moment that the power spring  5  gives to the driven member  3  is k(θ1+10°). Reference character F indicated by the arrow in the figure denotes a force that the input pin  1   b  of the lever member  1  receives from the output pin  6   c  of the charge input lever  6  to balance with k(θ1+10°), P2 indicated by the arrow denotes a force that the roller  4  receives from the output side arm portion  1   c  of the lever member  1 , which is equal to the reaction force by the force of the power spring  5  that the output side arm portion  1   c  of the lever member  1  receives through the roller  4 . F2 indicated by the arrow denotes a force component around the first axial portion  2   a   1  to generate P2. 
     The following expressions are obtained from the relationship of balance between forces. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F ·cos 3.46°)×4.00 =F 2×4.95  (2.4) 
       
     
     
       
           F 2·cos 10.00° =P 2  (2.5) 
       
     
     
       
         ( P 2·cos 29.15°)×10.00 =k (θ1+10°)  (2.6) 
       
     
     From expressions (2.4), (2.5) and (2.6), F=0.144k(θ1+10°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=2.88[gf](=2820[dyn]) is obtained. 
     FIG. 4 is a plane view of the charge mechanism in an intermediate charging (range in which the rotation center of the lever member  1  is switched from the first axial portion to the second axial portion) state after charging has advanced from the state in FIG.  3 . The rotation angle of the lever member  1  after charging is started is 31° and the rotation angle of the driven member is 18.5° in the state shown in FIG.  4 . 
     In the same figure, components have dimensions as shown in the figure and the rotation moment that the power spring  5  gives to the driven member  3  is k(θ1+18.5°). Reference character F indicated by the arrow in the figure denotes a force that the input pin  1   b  of the lever member  1  receives from the output pin  6   c  of the charge input lever  6  to balance with k(θ1+18.5°), P3 indicated by the arrow denotes a force that the roller  4  receives from the output side arm portion  1   c  of the lever member  1 , which is equal to the reaction force by the force of the power spring  5  that the output side arm portion  1   c  of the lever member  1  receives through the roller  4 . F31 indicated by the arrow denotes a force component around the axial portion  2   a   1  to generate P3 and F32 indicated by the arrow denotes a force component around the axial portion  2   a   2  to generate P3. 
     From the balance relationship between forces, the following expressions are obtained. Here, for simplicity of explanation, frictions of various portions are ignored. 
     The following expression are obtained around the axial portion  2   a   1 : 
     
       
         ( F ·cos 13.54°)×4.00 =F 31×4.72  (2.7) 
       
     
     
       
           F 31·cos 10.48° =P 3  (2.8) 
       
     
     
       
         ( P 3·cos 3.65°)×10.00 =k (θ1+18.5°)  (2.9) 
       
     
     From expressions (2.7), (2.8) and (2.9), F=0.124k(θ1+18.5°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then F=3.52[gf](=3450[dyn]) 
     The following expressions are obtained around the axial portion  2   a   2 : 
     
       
         ( F ·cos 11.69°)×3.77 =F 32×5.03  (2.10) 
       
     
     
       
           F 32·cos 9.41° =P 3  (2.11) 
       
     
     
       
         ( P 3·cos 3.65°)×10.00 =k (θ1+18.5°)  (2.12) 
       
     
     From expressions (2.10), (2.11) and (2.12), F=0.138k(θ1+18.5°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]), θ1=10°. Then, F=3.94[gf](=3860[dyn]) is obtained. 
     FIG. 5 is a plane view of the charge mechanism in a second half charging (that is, after the rotation center of the lever member  1  is switched from the first axial portion to the second axial portion until the charge operation is completed) state after charging has advanced from the state in FIG.  4 . In the state shown in FIG. 5, the rotation angle of the lever member  1  is 31°+24° and the rotation angle of the driven member  3  is 33° after charging is started. 
     In the same figure, components have dimensions as shown in the figure and the rotation moment that the power spring  5  gives to the driven member  3  is k(θ1+33°). Reference character F indicated by the arrow in the figure denotes a force that the input pin  1   b  of the lever member  1  receives from the output pin  6   c  of the charge input lever  6  to balance with k(θ1+33°), P4 indicated by the arrow denotes a force that the roller  4  receives from the output side arm portion  1   c  of the lever member  1 , which is equal to the reaction force by the force of the power spring  5  that the output side arm portion  1   c  of the lever member  1  receives through the roller  4 . F4 indicated by the arrow is the force component around the axial portion  2   a   2  to generate P4. 
     From the relationship of balance between forces, the following expressions are obtained. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F ·cos 12.31°)×3.77 =F 4×6.70  (2.13) 
       
     
       F 4·cos 7.05 °=P 4  (2.14) 
     
       
         ( P 4·cos 34.85°)×10.00 =k (θ1+33°)  (2.15) 
       
     
     From Expressions (2.13), (2.14) and (2.15), F=0.223k(θ1+33°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=9.60[gf](=9410[dyn]) is obtained. 
     FIG. 6 is a plane view of the charge mechanism in a charging completion state after charging has advanced from the state in FIG.  5 . The rotation angle of the lever member  1  after charging is started is 31°+34° and the rotation angle of the driven member  3  is 44° in the state shown in FIG.  6 . 
     In the same figure, components have dimensions as shown in the figure and the rotation moment that the power spring  5  gives to the driven member  3  is k(θ1+44°). Reference character F indicated by the arrow in the figure denotes a force that the input pin  1   b  of the lever member  1  receives from the output pin  6   c  of the charge input lever  6  to balance with k(θ1+44°), P5 indicated by the arrow denotes a force that the roller  4  receives from the output side arm portion  1   c  of the lever member  1 , which is equal to the reaction force by the force of the power spring  5  that the output side arm portion  1   c  of the lever member  1  receives through the roller  4 . F5 indicated by the arrow is the force component around the axial portion  2   a   2  to generate P5. 
     From the relationship of balance between forces, the following expressions are obtained. Here, for simplicity of explanation, frictions of various components are ignored. 
     
       
         ( F ·cos 22.31°)×3.77 =F 4×8.47  (2.16) 
       
     
     
       
           F 5·cos 5.57 °=P 5  (2.17) 
       
     
     
       
         ( P 5·cos 55.85°)×10.00 =k (θ1+44°)  (2.18) 
       
     
     From Expressions (2.16), (2.17) and (2.18), F=0.435k(θ1+44°) is obtained. 
     Here, suppose k=1[gf/deg](=980[dyn/deg]) and θ1=10°. Then, F=23.5[gf](=23000[dyn]) is obtained. 
     FIG. 7 compares the results about the charge mechanism in this embodiment obtained as shown above with the charge mechanism in the above described conventional technology and summarizes the relationship between the rotation angle of the driven member ( 3 ,  403 ) and input load of the lever member ( 1 ,  401 ) as a table (FIG. 7A) and graph (FIG.  7 B). 
     From above, the input load of the charge mechanism in this embodiment increases by a little less than 10% in the middle (near 18.5 to 33 deg) of the rotation angle (charge) of the driven member compared to the charge mechanism in the conventional technology, but it decreases by 3 to 10% in the first half charging state (0 to 18.5 deg), and definitely decreases from the second half charging state (near 40 deg) to the final state (44 deg) and the load peak which is important to the charge mechanism (44 deg at the final part of the rotation angle) decrease by not less than approximately 5%. 
     In addition, in the relationship between the charge input lever ( 6 ,  406 ) and the lever member ( 1 ,  401 ) during charging, the operation positional relationship between the output pin ( 6   c ,  406   c ) and input pin ( 1   b ,  401   b ) will be compared in FIG.  8  and FIG.  29 . Here, FIG. 8 is a plane view of the charge mechanism in this embodiment showing the positional relationship between the charge input lever  6  and lever member  1 . FIG. 29 is a plane view of the conventional charge mechanism showing the positional relationship between the charge input lever  406  and lever member  401 . 
     In these figures, solid lines show the lever member ( 1 , 401 ) and the driven member ( 3 ,  403 ) in the charging start state and two-dot dashed lines show the lever member ( 1 ,  401 ) and driven member ( 3 ,  403 ) in the state at some midpoint of charging and state of completion of charge. For simplicity of explanation and ease of understanding of the figure, only the charging start state of the charge input lever ( 6 ,  406 ) is shown. In the middle of charging or when the charge operation is completed, the output pin ( 6   c ,  406   c ) moves downward while remaining in contact with the input pin ( 1   b ,  401   b ). 
     Here, assuming that the shortest distance between the lever surface ( 6   f ,  406   f ) of the charge input lever ( 6 ,  406 ) and the input pin ( 1   b ,  401   b ) of the lever member ( 1 ,  401 ) is 1.00 mm, the positional relationship between the output pin ( 6   c ,  406   c ) and input pin ( 1   b ,  401   b ) during charging will be examined. 
     With the charge mechanism of the conventional technology, the central position of the input pin  401   b  is farthest from the lever surface  406   f  of the charge input lever  406  when charging is completed and the distance is 2.60 mm. Since the distance is 1.80 mm at the most proximate position in the middle of charging, the width of movement while the output pin  406   c  is in contact with the input pin  401   b  during charging is 0.80 mm. 
     On the other hand, with the charge mechanism of this embodiment, the central position of the input pin  1   b  is farthest from the lever surface  6   f  of the charge input lever  6  when the charge operation is completed and the distance is 2.11 mm (81% of the value of the charge mechanism of the conventional technology). Since the distance is 1.80 mm at the most proximate position during charging, the width of movement while the output pin  6   c  is in contact with the input pin  1   b  is 0.31 mm (39% of the charge mechanism of the conventional technology). 
     Therefore, the charge mechanism according to this embodiment has the merit compared to the conventional technology as follows. 
     First, since the torsion moment applied to the charge input lever  6  is by far small and the charge input lever  6  is not tilted, axial loss during rotation and friction loss due to contact between the charge input lever  6  and the second base plate  7  during rotation are small and the operation efficiency is high. 
     Furthermore, loss by friction between the output pin  6   c  and input pin  1   b  is small and the operation efficiency is high, which allows the overall charging load in the charge mechanism to be reduced drastically. Furthermore, the width direction is reduced by 2.60 (above described conventional value)−2.11 (value in this embodiment)=0.49 mm, thus contributing to miniaturization. 
     (Second Embodiment) 
     FIG. 9 to FIG. 12 illustrate a charge mechanism according to a second embodiment of the present invention. FIG. 9 is a perspective view of the entire charge mechanism, FIG. 10 is a plane view of the charge mechanism which a lever member  201  and driven member  203  are placed on a first base plate  202  in a charging start state, FIG. 11 is a plane view of the charge mechanism in an intermediate charging (axis switching) state, FIG. 12 is a plane view of the charge mechanism in a charging completion state and FIG. 13 is a plane view of the charge mechanism illustrating a positional relationship between the charge input member and lever member. 
     The charge mechanism according to this embodiment is an application of the above described first embodiment. While the first embodiment includes the first and second bearing portions formed on the lever member  1  side, this embodiment includes the first and second axial portions formed on the lever member side. The members having the same functions as those in the above described first embodiment are indicated by reference numerals with  200  added to the reference numerals assigned in the first embodiment. 
     In FIG. 9, reference numeral  201  denotes a lever member which is supported in a rotatable manner to a first bearing portion  202   a   1  and second bearing portion  202   a   2  laid on the first base plate  202  and pressed in the thrust directions of the first bearing portion  202   a   1  and second bearing portion  202   a   2  by a dropout prevention member (not shown) with a tiny gap. 
     Reference numeral  201   a  denotes an input side arm portion of the lever member  201  and  201   b  denotes an input pin laid on the input side arm portion  201   a  in an integrated fashion and  201   c  denotes an output side arm portion of the lever member  201 . 
     Reference numeral  201   d   1  denotes a first axial portion which engages with the first bearing portion  202   a   1  and makes the lever member  201  rotatable about the center of the first bearing portion  202   a   1  as the rotation center and  201   d   2  denotes a second axial portion which engages with the second bearing portion  202   a   2  and makes the lever member  201  rotatable about the center of the second bearing portion  202   a   2  as the rotation center. 
     The first axial portion  201   d   1  engages with the substantially entire first bearing portion  202   a   1 . The second axial portion  201   d   2  is formed shorter than the first axial portion  201   d   1  and engages with the second bearing portion  202   a   2  formed as the side wall of a terrace. 
     That is, the position of engagement between the first bearing portion  202   a   1  and first axial portion  201   d   1  and the position of engagement between the second bearing portion  202   a   2  and second axial portion  201   d   2  are provided in such a way as to be different in the thickness direction (e.g., in stepped form) of the lever member  201 . This allows the rotation center of the lever member  201  to be switched between the first bearing portion  202   a   1  and second bearing portion  202   a   2  smoothly with a smaller space. 
     Reference numeral  203  denotes a driven member, which is supported in a manner rotatable about an axial portion  202   b  laid on the first base plate  202  as the rotation axis and pressed in the thrust direction of the axial portion  202   b  by a dropout prevention member (not shown) with a tiny gap. At one end of the driven member  203 , an axial portion  203   a  is laid in an integrated fashion and a roller  204  is supported to the axial portion  203   a  in a rotatable manner. A dropout prevention member (not shown) also acts on the roller  204  in the same way. 
     Reference numeral  205  denotes a power spring (torsion spring) provided on the driven member  203  in such a way as to be coaxial with the axial portion  202   b  and its one end contacts a spring stopper  202   c  laid on a first base plate  202  and its other end contacts a spring stopper  203   b  of the driven member  203 . In this way, the power spring  205  gives the driven member  203  clockwise torque about the axial portion  202   b  as the rotation axis. 
     Reference numeral  206  denotes a charge input lever and is supported in a manner rotatable about an axial portion  207   a  laid on a second base plate  207  (placed orthogonal to the first base plate  202 ) as the rotation axis and pressed in the thrust direction of the axial portion  207   a  by a dropout prevention member (not shown) with a tiny gap. Reference numeral  206   a  denotes an input side arm portion of the charge input lever  206 , which receives a force Fch which rotates the charge input lever  206  counterclockwise about the axial portion  207   a  as the rotation axis. 
     Reference numeral  206   b  denotes an output side arm portion of the charge input lever  206 .  206   c  denotes an output pin laid on the output side arm portion  206   b  in an integrated fashion, which contacts the input pin  201   b  of the lever member  201  and transmits the driving force to the lever member  201 . Reference numeral  208  denotes a return spring, one end of which is supported by a spring stopper  207   b  laid on the second base plate  207  and the other end of which is hooked on to a hole  206   d  of the charge input lever  206 . This causes the return spring  208  to give the charge input lever  206  clockwise torque about the axial portion  207   a  as the rotation axis. 
     Reference numeral  207   c  denotes a stopper provided on the second base plate  207  which contacts the side of the output side arm portion  206   b  of the charge input lever  206  and blocks the clockwise rotation of the charge input lever  206  by the return spring  208 . 
     As described above, the charge mechanism in this embodiment has a configuration with the axial portion and the bearing portion of the charge mechanism in the first embodiment switched round. 
     Here, the distance between the center of the first bearing portion  202   a   1  and the center of the input pin  201   b  is 4.00 mm and the distance between the center of the second bearing portion  202   a   2  and the center of the input pin  201   b  is 3.77 mm, that is, these distances are set to substantially the same length. This can suppress drastic variations of load when the engagement between the first axial portion  201   d   1  and the first bearing portion  202   a   1  is switched to the engagement between the second axial portion  201   d   2  and the second bearing portion  202   a   2  during the rotation of the lever member  201 . 
     Furthermore, to reduce (that is, reduce axial loss) the component force in the direction of the rotation axis of the lever member  1  of the force that the input pin  201   b  receives from the output pin  206   c  of the charge input lever  206 , the total rotation angle of the lever member  201  about the first bearing portion  202   a   1  and second bearing portion  202   a   2  as the rotation axes is set to 65° (31°+34°). 
     That is, the total rotation angle of the lever member  201  is set to be greater than 39.77° which is the sum of angle 17.46° formed by the straight line (L) connecting the center of the first bearing portion  202   a   1  and the center of the input pin  201   b  at the start of charging (see FIG. 10) and the straight line (H) orthogonal to the direction of the force applied to the input pin  201   b , and angle 22.31° formed by the straight line (L) connecting the center of the second bearing portion  202   a   2  and the center of the input pin  201   b  when charging is completed (see FIG. 12) and the straight line (H) orthogonal to the direction of the force applied to the input pin  201   b.    
     Then, the operation of the charge mechanism in such a configuration will be explained below. 
     First, when a force Fch is applied to the input side arm portion  206   a  of the charge input lever  206 , the charge input lever  206  rotates counterclockwise (FIG. 9) about the axial portion  207   a  as the rotation axis. This causes the output pin  206   c  on the output side arm portion  206   b  to push the input pin  201   b  on the input side arm portion  201   a , causes the first axial portion  201   d   1  to contact the first bearing portion  202   a   1 , making the lever member  201  rotate clockwise about the first bearing portion  202   a   1  as the rotation axis. 
     This causes the output side arm portion  201   c  of the lever member  201  to push the roller  204  against the force of the power spring  205  and makes the driven member  203  rotate counterclockwise about the axial portion  202   b  as the rotation axis. 
     Here, if the second axial portion  201   d   2  contacts the second bearing portion  202   a   2  in the middle of rotation of the lever member  201 , the first engaged portion  202   a   1  disengages from the first axial portion  201   d   1  and the lever member  201  rotates clockwise about the second bearing portion  202   a   2  as the rotation axis. That is, the rotation center of the lever member  201  is switched from the first axial portion to the second axial portion. Then, charging is finished when the lever member  201  has rotated a predetermined angle. 
     On the other hand, when the force Fch is no longer applied in a charging completion state, the lever member  201  goes the opposite way of the charging process by the force of the power spring  205  and returns to the charging start state. 
     The operation of the charge mechanism and charging load (FIGS. 10 to  13 ) according to this embodiment are the same as the operation of the charge mechanism (FIGS. 2 to  6 , FIG. 8) according to the first embodiment including the dimensional relationship, and therefore explanations thereof will be omitted. 
     The table and graph showing the relationship between the rotation angle of the driven member  203  and the input load of the lever member  201  are the same as those in FIG.  7 . Therefore, the charge mechanism according to this embodiment has the following merits compared to the conventional charge mechanism. 
     First, since the torsion moment applied to the charge input lever  206  is by far small and the charge input lever  206  is not tilted, axial loss during rotation and friction loss due to contact between the charge input lever  206  and the second base plate  207  during rotation are small and the operation efficiency is high. 
     Furthermore, loss by friction between the output pin  206   c  and input pin  201   b  is small and the operation efficiency is high, which allows the overall charging load in the charge mechanism to be reduced drastically. Furthermore, the size in the width direction is reduced by 2.60 (conventional value)−2.11 (value in this embodiment)=0.49 mm, thus contributing to miniaturization. 
     (Third Embodiment) 
     A third embodiment of the present invention relates to a focal plane shutter (hereinafter simply referred to as a “shutter apparatus”) provided with the charge mechanism according to the first embodiment. The shutter apparatus according to this embodiment is mounted on the single-lens reflex camera, etc., shown in FIG.  21  and FIG.  22 . 
     In FIG.  21  and FIG. 22, a lens apparatus  602  provided with an image-taking lens is mounted on a camera body  601  in an attachable/detachable manner. As shown in FIG. 22, the camera body  601  is provided with a shutter apparatus  603  of this embodiment. 
     Here, when a reflective mirror  606  is placed diagonally in the image-taking optical path, an object beam L which has pass d through the lens apparatus  602  is reflected at the reflective mirror  606  and led to an eyepiece  604  through a pentaprism  605 . On the other hand, when the reflective mirror  606  is out of the image-taking optical path, the object beam L is directed toward the shutter apparatus  602  and an image is taken by running of a shutter of the shutter apparatus  602 . 
     The shutter apparatus of this embodiment will be explained using FIGS. 14 to  20  below. The charge mechanism used for the shutter apparatus which will be described below differs from the charge mechanism of the first embodiment in some points, but has the same basic configuration and function. Furthermore, of the components of the shutter apparatus which will be explained below, suppose the components with the same names as those of the components of the aforementioned charge mechanism of the first embodiment have the same functions. 
     FIG. 14 is an outside perspective view of the shutter apparatus of this embodiment, FIG. 15 is a plane view of the shutter apparatus from completion of running to a charging start state and FIG. 16 is a plane view of the shutter apparatus in a first half charging state. FIG. 17 is a plane view of the shutter apparatus in an intermediate charging (range in which the rotation center of the charge lever changes from the first axial portion to the second axial portion) state. 
     FIG. 18 is a plane view of the shutter apparatus in a second half charging state, FIG. 19 is a plane view of the shutter apparatus in a state immediately before completion of charging and FIG. 20 is a plane view of the shutter apparatus in an overcharge state. 
     In FIG. 14 to FIG. 20, reference numeral  101  denotes a charge lever (corresponds to the lever member  1  in the first embodiment), which is supported in a manner rotatable about a first axial portion  102   a   1  and a second axial portion  102   a   2  laid on a shutter base plate  102  as the rotation axes and pressed in the thrust directions of these axial portions  102   a   1  and  102   a   2  by a dropout prevention member (not shown) with a tiny gap. 
     Reference numeral  101   a  denotes an input side arm portion (corresponds to the input side arm portion  1   a ) of the charge lever  101 ,  101   b  denotes an input pin laid on the input side arm portion  101   a  in an integrated fashion,  101   c   1  denotes a front curtain side output arm portion (corresponds to the output side arm portion  1   c ) of the charge lever  101 ,  101   c   2  denotes a rear curtain side output arm portion (corresponds to the output side arm portion  1   c ) of the charge lever  101 . 
     Reference numeral  101   d   1  denotes a first bearing portion which engages with the first axial portion  102   a   1  and makes the charge lever  101  rotatable about the first axial portion  102   a   1  and  101   d   2  denotes a second bearing portion which engages with the second axial portion  102   a   2  and makes the charge lever  101  rotatable about the second axial portion  102   a   2 . 
     The first bearing portion  101   d   1  is hidden in FIGS. 15 to  20  and expressed with a dotted line. It is formed inside the charge lever  101  (side facing the shutter base plate  102 ), provided in a position different from the second bearing portion  101   d   2  in the height direction (direction perpendicular to the plane of the sheet in FIGS. 15 to  20 ). Then, the first bearing portion  101   d   1  and the second bearing portion  101   d   2  are formed in a staircase pattern. 
     That is, the position of engagement between the first axial portion  102   a   1  and first bearing portion  101   d   1  differs from the position of engagement between the second axial portion  102   a   2  and second bearing portion  101   d   2  in the axial directions of the first and second axial portions. 
     This allows the rotation center of the charge lever  101  to be switched between the first axial portion  102   a   1  and second axial portion  102   a   2  smoothly with a smaller space. Reference numeral  103  denotes a front curtain driving lever (corresponds to the driven member  3 ) which is supported in a manner rotatable about the axial portion  112   a  as the rotation axis which is laid on the shutter base plate  102  and is pressed in the thrust direction of the axial portion  112   a  by a dropout prevention member (not shown) with a tiny gap. 
     At the end of an arm portion  103   c  of the front curtain driving lever  103 , an axial portion  103   a  is laid in an integrated fashion and a roller  104  is supported to the axial portion  103   a  in a rotatable manner. Here, the shutter base plate  102  acts as a dropout stopper of the roller  104 . 
     At the end of the other arm portion  103   d  of the front curtain driving lever  103 , the front curtain driving pin  103   e  is laid in an integrated fashion. Reference numeral  105  denotes a power spring (torsion spring) which is provided on the front curtain driving lever  103  in such a way as to be coaxial with the axial portion  112   a . This one end contacts a shutter speed adjustment member (not shown) and the other end contacts a spring stopper (not shown) of the front curtain driving lever  103 . This causes the power spring  105  to give the front curtain driving lever  103  clockwise torque about the axial portion  112   a  as the rotation axis. 
     Reference numeral  116  denotes a front curtain main arm, which is supported in a manner rotatable about an axial portion  102   g  as the rotation axis laid on the shutter base plate  102 . Reference numeral  117  denotes a front curtain sub-arm, which is supported in a manner rotatable about the axial portion  102   h  as the rotation axis laid on the shutter base plate  102 . 
     Reference numeral  118  denotes a blade group making up the front curtain and reference numeral  118   a  of this blade group denotes a slit formation blade (first blade) and includes a slit formation portion  118   e . Reference numeral  118   b  denotes a second blade,  118   c  denotes a third blade and  118   d  denotes a fourth blade. Each blade of the blade group  118  is supported in a rotatable manner to the front curtain main arm  116  and front curtain sub-arm  117  by a caulking dowel  119   a  etc., and both arms  116  and  117  and each blade forms a parallel link (publicly known configuration). 
     Furthermore, as shown in FIG. 14, an armature holding portion  103   f  is formed above the arm portion  103   d  of the front curtain driving lever  103  and the armature holding portion  103   f  holds a magnet armature  123  by means of an armature axis  124  with a certain degree of freedom of movement. 
     Reference numeral  125  denotes a yoke and  126  denotes a coil wound around the yoke  125  and these are fixed to a base plate (not shown). When power is supplied to the coil  126 , the yoke  125  attracts and holds the armature  123  and releases the armature  123  when the power supply to the coil  126  is interrupted. Shutter timing is controlled using this operation. 
     Reference numeral  113  denotes a rear curtain driving lever, which is supported in a manner rotatable about an axial portion  112   b  as the rotation axis laid on the shutter base plate  102  and pressed in the thrust direction of the axial portion  112   b  by a dropout suppression member (not shown) with a tiny gap. At one arm portion  113   c  of the rear curtain driving lever  113 , an axial portion  113   a  is laid in an integrated fashion and the roller  114  is supported to the axial portion  113   a  in a rotatable manner. 
     The shutter base plate  102  operates as a dropout prevention member for the roller  114 . At the end of the other arm portion  113   d  of the rear curtain driving lever  113 , a rear curtain driving pin  113   e  is laid in an integrated fashion. Reference numeral  115  denotes a power spring (torsion spring), which is placed on the rear curtain driving lever  113  in such a way as to be coaxial with the axial portion  112   b.    
     One end of the power spring  115  contacts a shutter speed adjustment member (not shown) and the other end contacts a spring stopper (not shown) of the rear curtain driving lever, which gives the rear curtain driving lever  113  clockwise torque about the axial portion  112   b  as the rotation axis. 
     Reference numeral  120  denotes a rear curtain main arm, which is supported in a manner rotatable about an axial portion  102   i  as the rotation axis laid on the shutter base plate  102 . Reference numeral  121  denotes a rear curtain sub-arm, which is supported in a manner rotatable about an axial portion  102   j  as the rotation axis laid on the shutter base plate  102 . 
     Reference numeral  122  denotes a blade group constituting a rear curtain which is constructed of four blades as in the case of the front curtain. One of the blade group  122  includes a slit formation portion (indicated by reference numeral  122   e  in FIG. 16 to FIG. 18) which forms a slit together with the slit formation blade  118   a . Each blade of the blade group  122  is supported in a rotatable manner to the above described rear curtain main arm  120  and rear curtain sub-arm  121  using a caulking dowel  119   b , etc., and both arms  120  and  121  and each blade together forms a parallel link (publicly known configuration). 
     Furthermore, an armature holding portion  113   f  is formed above the arm portion  113   c  of the rear curtain driving lever and an armature holding portion  113   f  holds a magnet armature  127  by means of the armature axis  128  with a certain degree of freedom of movement. 
     Reference numeral  129  denotes a yoke and  130  denotes a coil wounded around the yoke  129 , which are fixed to a base plate (not shown). The yoke  129  attracts and holds the armature  127  when power is supplied to the coil  130  and releases the armature  127  when the power supply to the coil  130  is interrupted. Shutter timing is controlled using the above described operation. 
     Reference numeral  102   d  denotes an aperture through which light passes formed on the shutter base plate  102 . Reference numeral  102   e  denotes a long hole portion which is formed on the shutter base plate along a movement track of the front curtain driving pin  103   e  and  102   f  denotes a long hole portion which is formed on the shutter base plate  102  along a movement track of the rear curtain driving pin  113   e . Reference numerals  111   a  and  111   b  denote buffering members which receive the front curtain driving pin  103   e  and rear curtain driving pin  113   e  respectively when running of each shutter (front curtain and rear curtain) is completed. 
     The charge mechanism of the shutter apparatus of this embodiment reduces the size of the apparatus by setting the width from the input pin  101   b  laid on the input side arm portion  101   a  in an integrated fashion to the end of the shutter apparatus (left end of the shutter apparatus) to 12.6 mm and setting the stroke of the input pin  101   b  (distance between straight line H 2  and straight line H 4 ) in the longitudinal direction in FIGS. 15 to  20  to 4.25 mm. 
     Furthermore, a charge input lever (not shown) which contacts the input pin  101   b  of the charge lever  101  and gives the charge lever  101  torque in the same configuration as the charge input lever  6  in FIG.  1 . 
     The distance between the center of the first axial portion  102   a   1  and the center of the input pin  101   b  is 4.00 mm and the distance between the center of the second axial portion  102   a   2  and the center of the input pin  101   b  is 3.77 mm, that is, these distances are set to substantially the same length. This can suppress drastic variations of load when the rotation center of the charge lever member  101  is switched from the first axial portion  102   a   1  to the second axial portion  102   a   2  in the middle of rotation of the charge lever member  101 . 
     Furthermore, to reduce (that is, reduce axial loss) the component force in the direction of the rotation axis of the charge lever member  101  of the force that the input pin  101   b  receives from the output pin of the charge input lever (not shown), the total rotation angle of the charge lever  101  about the first axial portion  102   a   1  and second axial portion  102   a   2  as the rotation axes is set to 66° (31°+35°). 
     That is, the total rotation angle of the charge lever  101  is set to be greater than 39.77° which is the sum of angle 17.46° formed by the straight line (L) connecting the center of the first axial portion  102   a   1  and the center of the input pin  101   b  at the start of charging and the straight line (H) orthogonal to the direction of the force applied to the input pin  101   b , and angle 22.31° formed by the straight line (L) connecting the center of the second axial portion  102   a   2  and the center of the input pin  101   b  when charging is completed and the straight line (H) orthogonal to the direction of the force applied to the input pin  101   b.    
     Then, the operation of the shutter apparatus and charge mechanism thereof in such a configuration will be explained. First, when a charging force Fch (not shown) is applied to the charge input lever (not shown) from the charging start state in FIG. 15 as in case of the charge mechanism according to the first embodiment, the charge input lever pushes the input pin  101   b  on the input side arm portion  101   a  of the charge lever  101 . 
     This causes the first bearing portion  101   d   1  to contact the first axial portion  102   a   1 , making the charge lever  101  rotate clockwise about the first axial portion  102   a   1  as the rotation axis. 
     This causes the front curtain side output arm portion  101   c  of the charge lever  101  to push the roller  104  and makes the front curtain driving lever  103  rotate counterclockwise about the axial portion  112   b  as the rotation axis against the force of the power spring  105 . Furthermore, the rear curtain side output arm portion  101   c   2  pushes the roller  114  and makes the rear curtain driving lever  113  rotate counterclockwise about the axial portion  112   b  as the rotation axis against the force of the power spring  115 . This is the first half charging state shown in FIG.  16 . 
     When compared to the state diagram of the first half charging state of the shutter apparatus using the conventional charge mechanism, the charging force is reduced by approximately 10% and the amount of overlapping (indicated by the distance between the slit formation portions  118   e  and  122   e  of the front curtain and rear curtain) between the front curtain and rear curtain in the first half charging state is 7 mm as shown in FIG.  16  and FIG. 17, which is 2 mm greater than 5 mm of the conventional shutter apparatus (FIG. 30) and provides high light-shielding performance. 
     Furthermore, in the middle of charging, when the rotatable axis of the charge lever  101  in FIG. 17 is switched, the moment the first bearing portion  101   d   1  engages with the first axial portion  102   a   1 , the second bearing portion  101   d   2  engages the second axial portion  102   a   2 . 
     Compared to the state diagram in the middle of charging of the shutter apparatus using the conventional charge mechanism, the charging force remains substantially the same, but the amount of overlapping between the front curtain and rear curtain during charging (indicated by the distance between the slit formation portion  118   e  of the front curtain and the slit formation sections  122   e  of the rear curtain) is 7 mm, which is 1.5 mm greater than 5.5 mm of the conventional shutter apparatus (FIG. 31) and provides high light-shielding performance. 
     After a while, the first bearing portion  101   d   1  is disengaged from the first axial portion  102   a   1  and the charge lever  101  rotates clockwise about the second axial portion  102   a   2  as the rotation axis (that is, the rotation center of the charge lever is switched from the first rotation axis to the second rotation axis). This is the second half charging state shown in FIG.  18 . 
     As is apparent from the same figure, compared to the state diagram of the second half charging state of the shutter apparatus using the conventional charge mechanism, the charging force is reduced by approximately 5%, the amount of overlapping between the front curtain and rear curtain (indicated by the distance between the slit formation portions  118   e  of the front curtain and the slit formation portion  122   e  of the rear curtain) is 6 mm, which is 1 mm greater than 5 mm of the conventional shutter apparatus (FIG. 32) and provides high light shielding performance. 
     Furthermore, in the state immediately before charging is completed in FIG. 19, the charge lever  101  rotates clockwise about the second axial portion  102   a   2  as the rotation axis and the front curtain has already completed charging. 
     Compared to the state immediately before charging is completed of the shutter apparatus using the conventional charge mechanism, the charging force is reduced by approximately 10% and the amount of overlapping between the front curtain and rear curtain in the middle of charging (indicated by the distance between the slit formation portions  118   e  of the front curtain and the slit formation portion  122   e  of the rear curtain) is 5.0 mm, which is 1.5 mm greater than 3.5 mm of the conventional shutter apparatus and provides high light shielding performance. 
     According to this embodiment, in the second half of charging the position of overlapping between the front curtain and rear curtain is above a shutter exposure aperture  102   d . In the case of a single-lens reflex camera, a main mirror for splitting the optical path for the finder is normally provided on the image-taking lens side immediately before the shutter apparatus and the light shielding performance in the upper section of the shutter exposure aperture  102   d  where a hinge for the main mirror is provided is higher than that in the lower portion. Therefore, it is possible to reduce the amount of overlapping between the front curtain and rear curtain in the second half of charging. 
     Then, when the charge lever  101  has rotated a predetermined angle, an overcharge state is set as shown in FIG.  20  and the charging ends. 
     When the photographer presses the release button of a camera provided with the shutter apparatus and the camera starts an image-taking operation, power is supplied to the coils  126  and  130  of the timing control magnet and armatures  123  and  127  are attracted and held. 
     Then, as in the case of the charge mechanism according to this embodiment, the charge input lever (not shown) goes the opposite way of the charging process by the force of a return spring (mirror up spring, not shown), moves the main mirror (not shown) which is placed diagonally on the image-taking optical path away from the image-taking optical path to the image-taking position (mirror up). Caused by this mirror up, the charge lever  101  is restored to the charging start state by a returning mechanism (not shown) interlocked with the charge input lever. 
     The shutter is ready for running in this state, and after a predetermined exposure time the front curtain runs first, then the rear curtain runs to carry out an exposure operation. That is, after a predetermined exposure time, the power supply to the coils  126  and  130  is interrupted, the armatures  123  and  127  are released, the unfolded front curtain is folded to open the shutter exposure aperture  102   d , while the folded rear curtain is unfolded to close the shutter exposure aperture  102   d.    
     According to the above described configuration, the driving force transmission member starts charging when the distance between the rotation center and the point of contact with the front curtain driving lever is longer than the distance between the rotation center and the point of contact with the rear curtain driving lever and the distance between the rotation center and the point of contact with the rear curtain driving lever is set to be longer than the distance between the rotation center and the point of contact with the front curtain driving lever because the rotation center is switched midway through the process. 
     Adopting the above described configuration of this embodiment can provide a shutter apparatus including a charge mechanism having a greater degree of freedom in changing the charging phase between the front curtain and rear curtain than the conventional one, capable of shifting the peaks of the charging forces of the front curtain and rear curtain and thereby suppressing the peak of the overall charging force. 
     This embodiment has described the shutter apparatus provided with the charge mechanism according to the first embodiment, but it can also be adapted so as to mount the charge mechanism according to the second embodiment on the shutter apparatus. 
     According to the shutter apparatus of the above described embodiments, at least in the first half of a charge operation (that is, after charging is started until the rotation center of the driving force transmission member is switched), to take advantage of the fact that the distance between the rotation center and the point of contact with the front curtain driving lever is longer than the distance between the rotation center and the point of contact with the rear curtain driving lever, it is possible to drive the front curtain so that the amount of charging is greater than that of the rear curtain and drive the front curtain to close to the position at which charging is completed in an early stage after charging is started. That is, it is possible to increase the amount of overlapping of the slit formation portions of the front curtain and rear curtain in the middle of the charging and thereby improve the light shielding performance in the middle of charging. 
     On the other hand, in the second half of charging (that is, after the rotation center of the driving force transmission member is switched until charging is completed), to take advantage of the fact that the distance between the rotation center and the point of contact with the front curtain driving lever is shorter than the distance between the rotation center and the point of contact with the rear curtain driving lever, it is possible to drive the rear curtain so that the amount of charging is greater (so as to increase the driving speed) than that of the front curtain and drive it to close to the position at which charging is completed. 
     Furthermore, shortening the distance the point of contact between the charge input lever and the input portion travels sliding over the charge input lever can reduce the distance from the uppersurface (surface on which the output pin is laid) to the above described point of contact when charging is started and when charging is completed and further reduce tilting of the charge input lever and thereby reduce frictional loss. 
     Especially, the use of a small charge mechanism with improved efficiency can alleviate the component force in the axial direction during charging, and thereby reduce axial loss. Furthermore, the charge mechanism as described above can reduce displacement at the input end in the direction orthogonal to the direction of the input load and thereby improve the efficiency. 
     Reducing axial loss due to alleviation of the component force in the axial direction during charging can improve the efficiency of a charging and alleviate the charging load. 
     It also has the effects of reducing displacement at the input end in the direction orthogonal to the direction of the input load, further improving the efficiency and reducing the charging load. In addition, it also has the effect of reducing the size of the charge mechanism (in width direction). 
     It is further possible to keep the width of the shutter apparatus small, increase the amount of overlapping of the slit formation portions of the front curtain and rear curtain during charging and thereby improve the light shielding performance during charging. 
     Furthermore, incorporating the shutter apparatus according to the above described embodiments in a camera can provide a camera which has the above described effects.