Abstract:
A timepiece bearing has a bearing member of unitary construction that is provided at least at one end portion of a shaft member for undergoing rotation around an axis and that regulates movement of the shaft member in axial and radial directions of the shaft member. An elastic member applies an urging force in an axial direction of the bearing member to hold the bearing member in contact with the shaft member. A frame member supported by and fixed to a support member contains the bearing member. The elastic member is provided so as to establish connection between the bearing member and the frame member. The shaft member is configured to undergo rotation around the rotational axis while the shaft member and the bearing member are held in contact with each other by the elastic member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a timepiece bearing, a movement, and a portable timepiece. 
     2. Description of the Related Art 
     Conventionally, a rotating mechanical component such as a gear used in a portable timepiece, such as a wristwatch or a pocket watch, is formed such that a bearing is arranged so as to contain rotation shaft ends thereof and that the rotation shaft is rotated while guided by the bearing to transmit torque, thereby ticking away the time. 
     Here, as the construction of a conventional timepiece bearing, a construction as shown in  FIG. 21  is known (See, for example, JP-A-2004-294320).  FIG. 21  is a sectional view of a balance with hairspring. 
     As shown in  FIG. 21 , a balance with hairspring  520  includes a balance staff  523  whose thin small-diameter portions  521  and  522  at both ends thereof are supported so as to be rotatable around a center axis C by a timepiece bearing  510  formed in a balance bridge  505  and a main plate  504  so as to extend along the center axis C, a balance wheel  528  equipped with an annular rim portion  524  constituting a balance wheel main body and an arm portion  525  whose both ends are connected to the rim portion  524  and which extends in the diametrical direction of the rim portion  524 , with an intermediate portion  526  of the arm portion  525  being fixed to a central shaft portion  527  of the balance staff  523 , a collet  550 , and a double roller  554  retaining an impulse pin  552 . 
     The timepiece bearing  510  has an outer side bearing frame  512  retained by the inner peripheral surface of the balance bridge  505 , an inner bearing frame  511  arranged inside the outer bearing frame  512 , a hole jewel  514  arranged in a medium diameter recess of the inner bearing frame  511  and serving as a journal bearing for the small diameter shaft portion  522  at the upper end of the balance staff  523 , a cap jewel  515  arranged in a large diameter recess of the inner side bearing frame  515  and serving as a thrust bearing for the small diameter shaft portion  522  of the balance staff  523 , and a presser spring  516  locked to a groove of the outer side bearing frame  512  and retaining the cap jewel  515  in the large diameter recess of the inner side bearing frame  511 . 
     To permit rotation of the shaft, the above-described conventional timepiece bearing  510  requires a gap or space between the shaft (the small diameter shaft portion  522 ) and the bearing (the cap jewel  515 ). Due to the presence of this space, when the attitude of the timepiece is changed or an impact is applied thereto, the position of the shaft fluctuates. Then, the torque transmitted from a barrel drum to the balance with hairspring fluctuates, resulting in fluctuation in the oscillation angle and the rate. As a result, the time indication accuracy of the timepiece deteriorates. 
     The present invention has been made in view of the above problem. It is an object of the present invention to provide a timepiece bearing, a movement, and a portable timepiece helping to achieve an improvement in terms of time indication accuracy. 
     SUMMARY OF THE INVENTION 
     To solve the above problem, the present invention provides the following techniques. 
     According to the present invention, there is provided a timepiece bearing comprising: a bearing member provided at at least one end portion of a shaft member rotating around an axis and regulating movement of the shaft member in axial and radial directions; an elastic member having an force facing in axial direction to the bearing member; and a frame member containing the bearing member, wherein the elastic member is provided so as to establish connection between the bearing member and the frame member; the frame member is supported by and fixed to a support member; and the shaft member is rotatable around the axis, with the shaft member and the bearing member being held in contact with each other by the elastic member. 
     Due to this construction, it is possible to rotate the shaft member around the axis, with no space formed between the shaft member and the bearing member. Thus, even if the attitude of the timepiece bearing is changed or an impact is applied thereto, it is possible to suppress fluctuation in the position of the shaft member. As a result, it is possible to suppress fluctuation in torque, so that it is possible to achieve an improvement in terms of the time indication accuracy of the timepiece. 
     Further, the elastic member is equipped with an inner ring portion inserted to surroundings of and fixed to the bearing member, and a plurality of spring portions extending radially outwards from the inner ring portion, and the forward ends of the spring portions can be supported by the frame member. 
     Due to this construction, it is possible to support and fix the elastic member in a position between the bearing member and the frame member, making it possible to impart an urging force between the bearing member and the frame member due to the spring portions. Further, the frame member is supported by and fixed to the support member, so that the bearing member strives to move in an urging direction with respect to the frame member. Thus, by urging the spring portions toward the shaft member, it is possible to urge the bearing member reliably in the direction of the shaft member, making it possible to bring the bearing member and the shaft member into contact with each other. As a result, it is possible to suppress fluctuation in the position of the shaft member, and to suppress fluctuation in torque, so that it is possible to improve the time indication accuracy of the timepiece. 
     Further, the above-mentioned elastic member is equipped with an outer ring portion inserted to inner in and fixed to the frame member, and a plurality of spring portions extending radially inwards from the outer ring portion, and the forward ends of the spring portions can be supported by the bearing member. 
     Due to this construction, it is possible to support and fix the elastic member in position between the bearing member and the frame member, and it is possible to impart an urging force between the bearing member and the frame member due to the spring portions. Further, since the frame member is supported by and fixed to the support member, the bearing member strives to move in the urging direction with respect to the frame member. Thus, by urging the spring portions toward the shaft member, it is possible to reliably urge the bearing member in the direction of the shaft member, making it possible to bring the bearing member and the shaft member into contact with each other. As a result, it is possible to suppress fluctuation in the position of the shaft member, and to suppress fluctuation in torque, so that it is possible to achieve an improvement in the time indication accuracy of the timepiece. 
     Further, there is provided a pressurization adjustment mechanism capable of adjusting the pressure applied by a force from the bearing member toward the shaft member. 
     Due to this construction, it is easily possible to effect setting to a pressure allowing the shaft member to rotate around the axis while holding the bearing member and the shaft member in contact with each other. 
     Further, the pressurization adjustment mechanism is formed by a screw portion formed between the outer peripheral surface of the frame member and the inner peripheral surface of the support member. 
     Due to this construction, the threaded engagement ratio of the frame member with respect to the support member is adjusted, whereby it is possible to easily adjust the pressure with which urging is effected from the bearing member toward the shaft member. 
     Further, the pressurization adjustment mechanism is formed by a plurality of spring support recesses formed in the inner peripheral surface of the frame member at axially deviated positions. 
     Due to this construction, by selecting the positions for supporting the spring portions of the elastic member from the plurality of spring support recesses formed at axially deviated positions, it is possible to easily adjust the pressure with which urging is effected from the bearing member toward the shaft member. 
     Further, the pressurization adjustment mechanism consists of a spirally formed spring support groove portion formed in the inner peripheral surface of the frame member. 
     Due to this construction, by moving the forward ends of the spring portions of the elastic member along the spring support groove portion, it is possible to easily adjust the pressure with which urging is effected from the bearing member toward the shaft member. 
     Further, there is provided an attachment/detachment mechanism allowing attachment and detachment of the elastic member to and from the frame member. 
     Due to this construction, when performing maintenance on the timepiece bearing, it is possible to easily remove the elastic member from the frame member, making it possible to perform maintenance on each member. Thus, it is possible to achieve an improvement in terms of maintenance efficiency. 
     Further, the attachment/detachment mechanism is equipped with fit-engagement protrusions formed at the forward ends of the spring portions of the elastic member, and a fit-engagement recess formed in one axial end surface of the frame member, and, after the fit-engagement protrusions of the elastic member have passed the fit-engagement recess of the frame member, the elastic member is rotated along the engagement groove portion formed in the peripheral direction in the inner peripheral surface of the frame member, whereby the elastic member is supported by the frame member. 
     Due to this construction, by rotating the elastic member along the engagement groove portion of the frame member and mating the fit-engagement protrusion and the fit-engagement recess with each other to draw it out, it is possible to easily attach and detach the elastic member to and from the frame member. Thus, it is possible to achieve an improvement in terms of maintenance efficiency. 
     Further, there is provided an attachment/detachment mechanism allowing attachment and detachment of the elastic member to and from the bearing member. 
     Due to this construction, when performing maintenance on the timepiece bearing, it is possible to easily remove the elastic member from the bearing member, making it possible to perform maintenance on each member. Thus, it is possible to achieve an improvement in terms of maintenance efficiency. 
     Further, the attachment/detachment mechanism is equipped with fit-engagement protrusions formed at the forward ends of the spring portions of the elastic member, and a fit-engagement recess formed in one axial end surface of the bearing member, and, after the fit-engagement protrusions of the elastic member have passed the fit-engagement recess of the bearing member, the elastic member is rotated along the engagement groove portion formed in the peripheral direction in the outer peripheral surface of the bearing member, whereby the elastic member is supported by the bearing member. 
     Due to this construction, by rotating the elastic member along the engagement groove portion of the bearing member and mating the fit-engagement protrusion and the fit-engagement recess with each other to draw it out, it is possible to easily attach and detach the elastic member to and from the bearing member. Thus, it is possible to achieve an improvement in terms of maintenance efficiency. 
     Further, on the opposite side of the shaft member through the intermediation of the bearing member, there is provided a stopper member regulating the axial displacement amount of the bearing member. 
     Due to this construction, even if the attitude of the timepiece is changed or an impact is applied thereto, it is possible to suppress axial displacement of the bearing member. As a result, it is possible to suppress fluctuation in the position of the shaft member and to suppress fluctuation in torque, so that it is possible to achieve an improvement in terms of the time indication accuracy of the timepiece. 
     Further, the stopper member is fixed to the frame member, and is arranged with an axial gap between itself and the bearing member. 
     Due to this construction, it is possible to arrange the stopper member without affecting the pressure with which urging is effected from the bearing member toward the shaft member. Thus, it is possible to achieve an improvement in terms of the time indication accuracy of the timepiece. 
     Further, there is provided a guide member restricting the movable direction of the bearing member to the axial direction. 
     Due to this construction, it is possible to reliably prevent displacement of the shaft member in a radial direction that is orthogonal to the axial direction. Thus, it is possible to achieve an improvement in terms of the time indication accuracy of the timepiece. 
     Further, the guide member is fixed to the inner peripheral surface of the frame member. 
     Due to this construction, solely by fixing the guide member to the inner peripheral surface of the frame member, it is possible to reliably prevent the shaft member from being displaced in the radial direction that is orthogonal to the axial direction. Thus, it is possible to achieve an improvement in terms of the time indication accuracy of the timepiece with a simple construction. 
     Further, the bearing member and the elastic member are formed integrally. 
     Due to this construction, it is possible to reduce the number of components, and to achieve an improvement in terms of the production efficiency at the time of production and the maintenance efficiency at the time of maintenance. 
     Further, the elastic member and the frame member are formed integrally. 
     Due to this construction, it is possible to reduce the number of components, and to achieve an improvement in terms of the production efficiency at the time of production and the maintenance efficiency at the time of maintenance. 
     Further, the frame member and the stopper member are formed integrally. 
     Due to this construction, it is possible to reduce the number of components, and to achieve an improvement in terms of the production efficiency at the time of production and the maintenance efficiency at the time of maintenance. 
     Further, the bearing member and the stopper member are formed integrally. 
     Due to this construction, it is possible to reduce the number of components, and to achieve an improvement in terms of the production efficiency at the time of production and the maintenance efficiency at the time of maintenance. 
     Further, the bearing member and the guide member are formed integrally. 
     Due to this construction, it is possible to reduce the number of components, and to achieve an improvement in terms of the production efficiency at the time of production and the maintenance efficiency at the time of maintenance. 
     Further, the frame member and the guide member are formed integrally. 
     Due to this construction, it is possible to reduce the number of components, and to achieve an improvement in terms of the production efficiency at the time of production and the maintenance efficiency at the time of maintenance. 
     Further, a movement according to the present invention is a timepiece movement equipped with a barrel drum, wheels &amp; pinions, an escape wheel &amp; pinion, a pallet fork, and a balance with hairspring, and, a timepiece bearing as described above is used at least as the bearing of the balance with hairspring. 
     Due to this construction, it is possible to rotate the shaft member around the axis with no space formed between the shaft member and the bearing member, so that, even if the attitude of the timepiece bearing is changed or an impact is applied thereto, it is possible to suppress fluctuation in the position of the shaft member. As a result, it is possible to suppress fluctuation in torque, so that it is possible to provide a movement helping to achieve an improvement in term of the time indication accuracy of the timepiece. 
     A portable timepiece according to the present invention is equipped with the above-described movement, and a casing containing the movement. 
     Due to this construction, it is possible to rotate the shaft member around the axis with no space formed between the shaft member and the bearing member, so that, even if the attitude of the timepiece bearing is changed or an impact is applied thereto, it is possible to suppress fluctuation in the position of the shaft member. As a result, it is possible to suppress fluctuation in torque, so that it is possible to provide a portable timepiece helping to achieve an improvement in term of the time indication accuracy of the timepiece. 
     In the timepiece bearing of the present invention, it is possible to rotate the shaft member around the axis with no space formed between the shaft member and the bearing member, so that, even if the attitude of the timepiece bearing is changed or an impact is applied thereto, it is possible to suppress fluctuation in the position of the shaft member. As a result, it is possible to suppress fluctuation in torque, so that it is possible to achieve an improvement in term of the time indication accuracy of the timepiece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the front side of a movement of a mechanical timepiece according to an embodiment of the present invention (A part of the components are omitted, and a bridge member is indicated by a phantom line); 
         FIG. 2  is a schematic partial sectional view showing a portion extending from a barrel drum to an escape wheel &amp; pinion according to an embodiment of the present invention; 
         FIG. 3  is a schematic partial sectional view showing a portion from an escape wheel &amp; pinion to a balance with hairspring according to an embodiment of the present invention; 
         FIG. 4  is a perspective view of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 5  is an exploded perspective view of a bearing according to an embodiment of the present invention; 
         FIG. 6  is a sectional view of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 7  is an exploded perspective view of another form (1) of a bearing according to an embodiment of the present invention; 
         FIG. 8  is a sectional view of the other form (1) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 9  is a perspective view of another form (2) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 10  is an exploded perspective view of the other form (2) of a bearing according to an embodiment of the present invention; 
         FIG. 11  is a sectional view of the other form (2) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 12  is a perspective view of another form (3) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 13  is an exploded perspective view of the other form (3) of a bearing according to an embodiment of the present invention; 
         FIG. 14  is a sectional view of the other form (3) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 15  is a perspective view of another form (4) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 16  is a sectional view of the other form (4) of a balance with hairspring and a bearing according to an embodiment of the present invention; 
         FIG. 17  is a perspective view of another form (5) of a frame member according to an embodiment of the present invention; 
         FIG. 18  is an exploded perspective view of the other form (5) of a frame member according to an embodiment of the present invention; 
         FIG. 19  is a perspective view of another form (6) of a frame member according to an embodiment of the present invention; 
         FIG. 20  is a sectional view of another form (7) of a balance with hairspring and a bearing according to an embodiment of the present invention; and 
         FIG. 21  is a schematic partial sectional view showing the construction of a conventional balance with hairspring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, a timepiece bearing according to an embodiment of the present invention will be described with reference to  FIGS. 1 through 20 . In this embodiment, described below, the timepiece bearing is applied to a portable mechanical timepiece such as a wristwatch. 
     (Mechanical Timepiece) 
     As shown in  FIGS. 1 through 3 , a movement  100  of a mechanical timepiece has a main plate  102  constituting a base plate of the movement  100 . A winding stem  110  is rotatably incorporated into a winding stem guide hole  102   a  of the main plate  102 . A dial  104  (See  FIG. 2 ) is mounted to the movement  100 . Generally speaking, of the two sides of the main plate  102 , the side where the dial  104  is arranged is referred to as the back side of the movement  100 , and the side opposite to the side where the dial  104  is arranged is referred to as the front side of the movement  100 . A train wheel assembled to the front side of the movement  100  is referred to as the front train wheel, and a train wheel assembled to the back side of the movement  100  is referred to as the back train wheel. By providing the movement  100  with a casing (not shown), the timepiece is formed as a portable timepiece. 
     The position in the axial direction of the winding stem  110  is determined by a switching device including a setting lever  190 , a yoke  192 , a yoke spring  194 , and a setting lever jumper  196 . A winding pinion  112  is rotatably provided on the guide shaft portion of the winding stem  110 . When the winding stem  110  is rotated, with the winding stem  110  being at a first winding stem position (0 th  step) nearest to the inner side of the movement  100  in the direction of the rotation axis, the winding pinion  112  is rotated via rotation of a clutch wheel. A crown wheel  114  is rotated through rotation of the winding pinion  112 . Through rotation of a ratchet wheel  116 , a mainspring  122  (See  FIG. 2 ) accommodated in a movement barrel  120  is wound up. 
     A center wheel &amp; pinion  124  is rotated through rotation of the movement barrel  120 . An escape wheel &amp; pinion  130  is rotated through rotation of a second wheel &amp; pinion  128 , a third wheel &amp; pinion  126 , and the center wheel &amp; pinion  124 . The movement barrel  120 , the center wheel &amp; pinion  124 , the third wheel &amp; pinion  126 , and the second wheel &amp; pinion  128  constitute the front train wheel. 
     An escapement/governor for controlling the rotation of the front train wheel includes a balance with hairspring  140 , an escape wheel &amp; pinion  130 , and a pallet fork  142 . Based on the rotation of the center wheel &amp; pinion  124 , a cannon pinion  150  rotates simultaneously. A minute hand  152  mounted to the cannon pinion  150  indicates “minute.” The cannon pinion  150  is provided with a slip mechanism with respect to the center wheel &amp; pinion  124 . Based on the rotation of the cannon pinion  150 , an hour wheel  154  is rotated through rotation of a minute wheel. An hour hand  156  mounted to the hour wheel  154  indicates “hour.” 
     The movement barrel  120  is equipped with a barrel cogwheel  120   d , a barrel arbor  120   f , and a mainspring  122 . The barrel arbor  120   f  includes an upper shaft portion  120   a  and a lower shaft portion  120   b . The barrel arbor  120   f  is formed of a metal such as carbon steel. The barrel cogwheel  120   d  is formed of a metal such as brass. 
     The center wheel &amp; pinion  124  includes an upper shaft portion  124   a , a lower shaft portion  124   b , a pinion portion  124   c , a cogwheel portion  124   d , and a bead portion  124   h . The pinion portion  124   c  of the center wheel &amp; pinion  124  is in mesh with the barrel cogwheel  120   d . The upper shaft portion  124   a , the lower shaft portion  124   b , and the bead portion  124   h  are formed of a metal such as carbon steel. The cogwheel portion  124   d  is formed of a metal such a nickel. 
     The third wheel &amp; pinion  126  includes an upper shaft portion  126   a , a lower shaft portion  126   b , a pinion portion  126   c , and a cogwheel portion  126   d . The pinion portion  126   c  of the third wheel &amp; pinion  126  is in mesh with the cogwheel portion  124   d.    
     The second wheel &amp; pinion  128  includes an upper shaft portion  128   a , a lower shaft portion  128   b , a pinion portion  128   c , and a cogwheel portion  128   d . The pinion portion  128   c  of the second wheel &amp; pinion  128  is in mesh with the cogwheel portion  126   d . The upper shaft portion  128   a  and the lower shaft portion  128   b  are formed of a metal such as carbon steel. The cogwheel portion  128   d  is formed of a metal such as nickel. 
     The escape wheel &amp; pinion  130  includes an upper shaft portion  130   a , a lower shaft portion  130   b , a pinion portion  130   c , and a cogwheel portion  130   d . The pinion portion  130   c  of the escape wheel &amp; pinion  130  is in mesh with the cogwheel portion  128   d . The pallet fork  142  is equipped with a body of pallet fork  142   d , and a pallet staff  142   f . The pallet staff  142   f  includes an upper shaft portion  142   a  and a lower shaft portion  142   b.    
     The movement barrel  120  is supported so as to be rotatable with respect to the main plate  102  and a barrel bridge  160 . That is, the upper shaft portion  120   a  of the barrel arbor  120   f  is supported so as to be rotatable with respect to the barrel bridge  160 . The lower shaft portion  120   b  of the barrel arbor  120   f  is supported so as to be rotatable with respect to the main plate  102 . The center wheel &amp; pinion  124 , the third wheel &amp; pinion  126 , the second wheel &amp; pinion  128 , the escape wheel &amp; pinion  130  are supported so as to be rotatable with respect to the main plate  102  and a train wheel bridge  162 . That is, the upper shaft portion  124   a  of the center wheel &amp; pinion  124 , the upper shaft portion  126   a  of the third wheel &amp; pinion  126 , the upper shaft portion  128   a  of the second wheel &amp; pinion  128 , and the upper shaft portion  130   a  of the escape wheel &amp; pinion  130  are supported so as to be rotatable with respect to the train wheel bridge  162 . Further, the lower shaft portion  124   b  of the center wheel &amp; pinion  124 , the lower shaft portion  126   b  of the third wheel &amp; pinion  126 , the lower shaft portion  128   b  of the second wheel &amp; pinion  128 , and the lower shaft portion  130   b  of the escape wheel &amp; pinion  130  are supported so as to be rotatable with respect to the main plate  102 . 
     The pallet fork  142  is supported so as to be rotatable with respect to the main plate  102  and the pallet bridge  164 . That is, an upper shaft portion  142   a  of the pallet fork  142  is supported so as to be rotatable with respect to a pallet bridge  164 . A lower shaft portion  142   b  of the pallet fork  142  is supported so as to be rotatable with respect to the main plate  102 . 
     Lubricating oil is applied to a bearing portion of the barrel bridge  160  rotatably supporting the upper shaft portion  120   a  of the barrel arbor  120   f , to a bearing portion of the train wheel bridge  162  rotatably supporting the upper shaft portion  124   a  of the center wheel &amp; pinion  124 , to a bearing portion of the train wheel bridge  162  rotatably supporting the upper shaft portion  126   a  of the third wheel &amp; pinion  126 , to a bearing portion of the train wheel bridge  162  rotatably supporting the upper shaft portion  128   a  of the second wheel &amp; pinion  128 , to a bearing portion of the train wheel bridge  162  rotatably supporting the upper shaft portion  130   a  of the escape wheel &amp; pinion  130 , and to a bearing portion of the pallet bridge  164  rotatably supporting the upper shaft portion  142   a  of the pallet fork  142 . Further, lubricating oil is applied to a bearing portion of the main plate  102  rotatably supporting the lower shaft portion  120   b  of the barrel arbor  120   f , to a bearing portion of the main plate  102  rotatably supporting the lower shaft portion  124   b  of the center wheel &amp; pinion  124 , to a bearing portion of the main plate  102  rotatably supporting the lower shaft portion  126   b  of the third wheel &amp; pinion  126 , to a bearing portion of the main plate  102  rotatably supporting the lower shaft portion  128   b  of the second wheel &amp; pinion  128 , to a bearing portion of the main plate  102  rotatably supporting the lower shaft portion  130   b  of the escape wheel &amp; pinion  130 , and to a bearing portion of the main plate  102  rotatably supporting the lower shaft portion  142   b  of the pallet fork  142 . It is desirable for this lubricating oil to be a precision instrument oil, and, in particular, a so-called timepiece oil 
     In order to enhance the lubricating oil performance, it is desirable for each of the bearing portions of the main plate  102 , the bearing portion of the barrel bridge  160 , and the bearing portion of the train wheel bridge  162  to be provided with a conical, cylindrical, or truncated-cone-shaped oil sump portion. When the oil sump portion is provided, it is possible to effectively prevent diffusion of oil due to the surface tension of the lubricating oil. The main plate  102 , the barrel bridge  160 , the train wheel bridge  162 , and the pallet bridge  164  may be formed of a metal such as brass or a resin such as polycarbonate. 
     (Structure of the Balance with Hairspring) 
     Next, the structure of the balance with hairspring of this embodiment will be described. 
     As shown in  FIG. 3 , the balance with hairspring  140  is equipped with a balance staff  140   a  and a hairspring  140   c.    
     The hairspring  140   c  is a volute (spiral) thin plate bearing of a plurality of turns. The inner end portion of the hairspring  140   c  is fixed to a collet  140   d  fixed to the balance staff  140   a , and the outer end portion of the hairspring  140   c  is fixed in position by screw fastening via a stud  170   a  mounted to a stud support  170  rotatably mounted to the balance bridge  167 . A bearing  180  is fixed to the balance bridge (support member)  167  via the outer peripheral portion of a frame member  166 . A regulator  168  is rotatably mounted to the balance bridge  167 . Further, the balance with hairspring  140  is supported so as to be rotatable with respect to the main plate  102  and the balance bridge  167 . 
     Here, the balance with hairspring  140  is rotatable around a center axis C, and has thin shaft portions  144  and  145  at both ends of a shaft member  143 . The lower shaft portion  144  is supported so as to be rotatable with respect to the main plate  102 , and the upper shaft portion  145  is supported so as to be rotatable with respect to the bearing  180 . 
     The bearing  180  is equipped with a bearing member  181  provided on the side of the shaft portion  145  constituting one end portion of the shaft member  143  rotating around the center axis C and adapted to regulate axial and radial movement of the shaft member  143 , an elastic member  182  exerting an axial urging force F with respect to the bearing member  181 , and the frame member  166  containing the bearing member  181 . 
     As shown in  FIGS. 4 through 6 , the bearing member  181  is of unitary construction and formed in a substantially cylindrical configuration, and at a central portion on one surface  181   a  supporting the shaft portion  145 , there is formed an insertion hole (blind bore)  183  into which the shaft portion  145  is inserted. Formed at the bottom portion of the insertion hole  183  is a tapered portion tapered forwards. Further, the forward end of the shaft portion  145  is formed in a substantially spherical configuration, and the forward end of the shaft portion  145  can abut the tapered portion of the insertion hole  183 . That is, the forward end of the shaft portion  145  and the tapered portion of the insertion hole  183  are in line contact with each other in the peripheral direction; in this state, axial and radial movement of the shaft portion  145  is regulated. 
     An elastic member  182  consists of a plate spring member formed, for example, of metal. The elastic member  182  is equipped with an inner ring portion  185  formed so as to be capable of being forced into and fixed to an outer peripheral surface  181   b  of the bearing member  181 , and a plurality of spring portions  186  extending radially outwards from the inner ring portion  185 . In this embodiment, three spring portions  186  are formed at substantially equal peripheral intervals. As shown in  FIG. 3 , the elastic member  182  is arranged so as to be curved in the initial state; however, this should not be construed restrictively; it is also possible for the elastic member to be arranged so as to be flat in the initial state. 
     The frame member  166  is formed in a substantially cylindrical configuration, and has a through-hole  187  capable of containing the bearing member  181  and the elastic member  182 . Further, one surface  166   a  of the frame member  166  has a plurality of (three in this embodiment) cutout portions  188  in conformity with the configuration of the spring portions  186  so as to allow insertion of the forward ends of the spring portions  186  of the elastic member  182 . Further, the inner peripheral surface  166   b  of the frame member  166  has, over the entire periphery, a groove portion  189  with which the forward ends of the spring portions  186  are fit-engaged for support in the peripheral direction. The cutout portions  188  and the groove portions  189  are connected with each other. That is, by inserting the forward ends of the spring portions  186  in conformity with the positions of the cutout portions  188 , the forward ends of the spring portions  186  can be arranged in the groove portion  189 , and, in this state, the elastic member  182  is rotated in the peripheral direction with respect to the frame member  166  to support and fix the forward ends of the spring portions  186  in the groove portion  189 , whereby the spring portions  186  of the elastic member  182  can be supported by and fixed to the frame member  166 . Furthermore, an outer peripheral surface  166   c  of the frame member  166  is forced into an inner peripheral surface of the balance bridge  167  for fixation. 
     Here, the elastic member  182  has an urging force F urging the bearing member  181  in the direction of the shaft portion  145  (the shaft member  143 ). This urging force F brings the bearing member  181  into contact with the shaft portion  145 , and allows the shaft portion  145  (the shaft member  143 ) to rotate around the center axis C. If the urging force F is too large, although it is possible to bring the bearing member  181  and the shaft portion  145  into contact with each other, the energy loss due to the rotation of the shaft portion  145  increases, resulting in deterioration in time indication accuracy. On the other hand, if the urging force F is too small, although the energy loss due to the rotation of the shaft portion  145  is small, the fluctuation in the shaft position when a strong impact is applied to the bearing  180  increases, resulting in deterioration in time indication accuracy. Thus, the elastic member  182  adopted is one having an appropriate urging force F. 
     According to this embodiment, the bearing  180  can impart an appropriate pressurization to the shaft portion  145  (the shaft member  143 ), so that it is possible to rotate the shaft portion  145  (the shaft member  143 ) around the center axis C, with no space formed between the shaft portion  145  and the bearing member  181 . Thus, even if the attitude of the bearing  180  is changed or an impact is applied thereto, it is possible to suppress fluctuation in the position of the shaft member  143 . As a result, it is possible to suppress fluctuation in the torque transmitted from the movement barrel  120  to the balance with hairspring  140 , and to suppress fluctuation in the oscillation angle and the rate of the balance with hairspring  140 , making it possible to achieve an improvement in terms of the time indication accuracy of a portable timepiece such as a wristwatch or a pocket watch. 
     Further, by constructing the bearing  180  as described above, it is possible to easily support and fix in position the elastic member  182  between the bearing member  181  and the frame member  166 , making it possible to exert the urging force F between the bearing member  181  and the frame member  166  due to the spring portions  186 . Further, since the frame member  166  is supported by and fixed to the balance bridge  167 , the bearing member  181  strives to move in the urging direction with respect to the frame member  166 . Thus, by urging the spring portion  186  toward the shaft portion  145  (the shaft member  143 ), it is possible to reliably urge the bearing member  181  in the direction of the shaft member, making it possible to bring the bearing member  181  and the shaft portion  145  into contact with each other. As a result, it is possible to suppress fluctuation in the position of the shaft member  143 , thereby achieving an improvement in terms of the time indication accuracy of the timepiece. 
     Further, since the elastic member  182  is detachable with respect to the frame member  166 , the elastic member  182  can be easily removed from the frame member  166  when performing maintenance on the bearing  180 , making it possible to perform maintenance individually on each member. Thus, it is possible to achieve an improvement in terms of maintenance efficiency. 
     The present invention is not restricted to the above-described embodiment but covers various modifications of the above embodiment made without departing from the gist of the present invention. That is, the specific configuration, construction, etc. of the above embodiment are only given by way of example, and allow modifications as appropriate. 
     For example, as shown in  FIGS. 7 and 8 , it is also possible to arrange a substantially cylindrical guide member  203  in a space portion formed between the frame member  166  and the bearing member  181 . The guide member  203  is formed in a size allowing it to be forced into and fixed to the inner peripheral surface  166   b  of the frame member  166 , and is formed such that the bearing member  181  can be arranged inside a through-hole  204  of the guide member  203 . Due to this construction, even if the bearing member  181  strives to move in the radial direction, the radial movement can be regulated by the guide member  203 . In this connection, it is desirable for a slight gap to be formed between the inner peripheral surface of the guide member  203  and the outer peripheral surface of the bearing member  181 . On the other hand, it is also possible for the inner peripheral surface of the guide member to be fixed to the outer peripheral surface of the bearing member  181  so as to form a gap between the outer peripheral surface of the guide member and the inner peripheral surface of the frame member  166 , regulating the moving direction of the bearing member  181 . 
     Further, as shown in  FIGS. 9 through 11 , it is also possible to provide, on the opposite side of the shaft portion  145  (the shaft member  143 ) via the bearing member  181 , a stopper member  205  regulating the axial displacement amount of the bearing member  181 . Due to the arrangement of the stopper member  205 , when the attitude of the timepiece is changed or an impact is applied thereto, the bearing member  181  hits the stopper member  205 , whereby it is possible to regulate its axial displacement. As a result, it is possible to suppress axial positional fluctuation of the shaft member  143 , making it possible to improve the time indication accuracy of the timepiece. The stopper member  205  is fixed, for example, to the frame member  166  while forming an axial gap between itself and the bearing member  181 . To fix the stopper member to the frame member  166 , there are formed, for example, lock portions  206  at both ends of the stopper member  205 , and the lock portions  206  are locked to the groove portion  189  of the frame member  166 . Due to this construction, it is possible to arrange the stopper member  205  without affecting the urging force F for urging from the bearing member  181  toward the shaft member. 
     Further, as shown in  FIGS. 12 through 14 , it is also possible to adopt, as an elastic member  282 , one equipped with an outer ring portion  285  forced into the inner peripheral surface  166   b  of the frame member  166  for fixation, and a plurality of spring portions  286  extending radially inwards from the outer ring portion  285 . In this case, cutout portions  288  allowing insertion of the forward ends of the spring portions  286  of the elastic member  282  are formed in one surface  281   a  of a bearing member  281  in conformity with the configuration of the spring portions  286 . Further, in the outer peripheral surface  281   b  of the bearing member  281 , there is formed, over the entire periphery, a groove portion  289  supporting the forward ends of the spring portions  286  in the peripheral direction through fit-engagement. And, the cutout portions  288  and the groove portion  289  are connected with each other. That is, by mating the forward ends of the spring portions  286  with the positions of the cutout portions  288  and inserting them, it is possible to arrange the forward ends of the spring portions  286  in the groove portion  289 , and, in this state, the elastic member  282  is rotated in the peripheral direction with respect to the bearing member  281  to support and fix the forward ends of the spring portions  286  in the groove portion  289 , whereby it is possible to support and fix in position the elastic member  282  in the bearing member  281 . Due to this construction, when performing maintenance on the bearing  280 , the elastic member  282  can be easily removed from the bearing member  281 , and it is possible to perform maintenance individually on each member. Thus, it is possible to achieve an improvement in terms of maintenance efficiency. 
     Further, while in the above embodiment the elastic member  182  is arranged between the frame member  166  and the bearing member  181  and urging is effected from the bearing member  181  toward the shaft portion  145  (the shaft member) with the appropriate urging force F, it is also possible to provide a pressurization adjustment mechanism capable of adjusting this urging force F. By providing the pressurization adjustment mechanism, even in the case of bearings and shaft members with individual difference, it is possible to adjust pressurization for each individual bearing and shaft member, making it possible to easily set the urging force F to a proper force capable of rotating the shaft member around the center axis C while always holding the bearing member  181  and the shaft portion  145  (the shaft member) in contact with each other. Thus, it is possible to adjust the energy loss and wear amount in the bearing to a substantially fixed level. 
     As an example of the pressurization adjustment mechanism, there is formed, as shown, for example, in  FIGS. 15 and 16 , a screw portion  201  between the outer peripheral surface  166   c  of the frame member  166  and the inner peripheral surface of the balance bridge  167 . By thus forming the screw portion  201 , the degree to which the frame member  166  is threadedly engaged with the balance bridge  167  is adjusted, whereby it is possible to easily adjust the urging force F with which urging is effected from the bearing member  181  toward the shaft portion  145  (the shaft member  143 ). Further, due to the above-described screw structure between the outer peripheral surface  166   c  of the frame member  166  and the inner peripheral surface of the balance bridge  167 , the frame member  166 , the elastic member  182 , and the bearing member  181  are collectively detachable with respect to the balance bridge  167 , so that it is possible to form the frame member  166 , the elastic member  182 , and the bearing member  181  integrally while maintaining the maintenance efficiency. 
     Further, as another example of the pressurization adjustment mechanism, it is also possible, as shown, for example, in  FIGS. 17 and 18 , a plurality of spring support recesses  207  in an inner peripheral surface  266   b  of a frame member  266  at axially deviated positions. Due to this construction, the positions at which the spring portions  186  of the elastic member  182  are supported are selected from a plurality of spring support recesses  207  formed at axially deviated positions, whereby it is possible to easily adjust the urging force F with which urging is effected from the bearing member  181  toward the shaft portion  145  (the shaft member  143 ). As shown in  FIG. 18 , when forming the spring support recesses  207 , the frame member  266  is formed so as to be capable of being axially divided at the positions of the spring support recesses  207 . That is, in the state in which the frame member  266  is divided, the forward ends of the spring portions  186  of the elastic member  182  are arranged in the spring support recesses  207  at desired positions, and, in this state, the frame member  266  is integrated, whereby the positions of the spring portions  186  can be easily adjusted, making it possible to easily adjust the urging force F of the spring portions  186 . 
     Further, as still another example of the pressurization adjustment mechanism, it is also possible, as shown, for example, in  FIG. 19 , to spirally form a spring support groove portion  209  in the inner peripheral surface  266   b  of the frame member  266 . Due to this construction, through movement of the forward ends of the spring portions  186  of the elastic member  182  along the spring support groove portion  209 , it is possible to easily adjust the urging force F with which urging is effected from the bearing member  181  toward the shaft portion  145  (the shaft member  143 ). That is, when forming the spring support groove portion  209 , by rotating the elastic member  182  around the center axis C along the spring support groove portion  209 , the positions of the forward ends of the spring portions  186  can be adjusted, that is, the urging force F of the spring portions  186  can be easily adjusted. 
     Further, while in the above embodiment the bearing member  181 , the elastic member  182 , the frame member  166 , the guide member  203 , and the stopper member  205  are formed as separate components, it is also possible to form a part of these components integrally. For example, it is also possible to form the bearing member  181  and the elastic member  182  integrally, or form the elastic member  182  and the frame member  166  integrally, or form the frame member  166  and the stopper member  205  integrally, or form the bearing member  181  and the stopper member  205  integrally, or form the bearing member  181  and the guide member  203  integrally, or form the frame member  166  and the guide member  203  integrally. In such a construction, it is possible to reduce the number of components, and achieve an improvement in terms of the production efficiency at the time of production and of the maintenance efficiency at the time of maintenance. 
     Further, it is also possible to adopt a construction in which the guide member  203 , the stopper member  205 , and the pressurization adjustment mechanism are combined with each other. 
     Further, while the above embodiment adopts a plate spring member as the elastic member, it is also possible to adopt, as shown in  FIG. 20 , a construction in which a coil spring  382  is arranged between the bearing member  181  and the frame member  166 . 
     Further, while in the above-described embodiment the bearing  180  is provided on the shaft portion  145  side, it is also possible to arrange the bearing  180  on the shaft portion  144  side. 
     Further, while the above-described embodiment adopts the bearing  180  constructed as described above as the bearing arranged in the balance with hairspring  140 , it is also possible to adopt the bearing  180  as described above, apart from the balance with hairspring  140 , as the bearing of the movement barrel  120 , of the center wheel &amp; pinion  124 , of the third wheel &amp; pinion  126 , of the second wheel &amp; pinion  128 , of the escape wheel &amp; pinion  130 , and of the pallet fork  142 . By thus providing the bearing  180  at each of these portions, it is possible to rotate a shaft member around an axis with no space formed between the shaft member and the bearing member. Thus, even if the attitude of the timepiece bearing is changed or an impact is applied thereto, it is possible to suppress fluctuation in the position of the shaft member. As a result, it is possible to suppress fluctuation in torque, so that it is possible to achieve an improvement in terms of the time indication accuracy of the timepiece. Further, since the construction easily allows division into the individual components, it is possible to easily perform maintenance on each component, making it possible to achieve an improvement in terms of maintenance efficiency.