Patent Description:
In a mechanical timepiece, it is important that a balance with a hairspring has a vibrating period set within a predetermined specified value. This is because, when the vibrating period deviates from the specified value, the rate (timepiece delay, degree of advancement) of the mechanical timepiece changes. As a method for adjusting the rate, generally, a method for adjusting the length (effective length) of a hairspring with an inner end fixed to a balance staff of the balance with a hairspring and an outer end fixed to a stud using a regulator is known.

The metal hairspring has a spiral part along an Archimedes curve, and an outer end curve portion that is spaced to an outer side in a radial direction from an outer end portion of the spiral part via a reformed portion and extends with a certain curvature (for example, refer to <CIT>). The outer end curve portion is engaged with the stud that fixes the outer end of the hairspring, the regulator that adjusts the effective length of the hairspring, and the like.

There is a case where the hairspring is plastically deformed when an impact is applied to cause contact with other components or self-contact, and the isochronism of vibrating period and rate is disturbed. In particular, in a case where the reformed portion has a small bending point with a curvature, stress is likely to concentrate when an impact is applied to the hairspring, and there is a possibility of plastic deformation.

In the technique described in <CIT>, in order to improve the resistance against permanent deformation of the hairspring, heat treatment is applied to an outer end region of the hairspring to remove internal stress.

However, in the technique described in <CIT>, the manufacturing cost increases due to the addition of heat treatment when manufacturing the hairspring. Therefore, there is a problem in that deformation due to stress concentration is suppressed while suppressing an increase in manufacturing cost of the hairspring.

Document <CIT> discloses a spiral spring having a flexible part body bent in a plane perpendicular to a central axis and made of a composite material.

It is an aspect of the present application to provide a hairspring, a balance with a hairspring, a timepiece movement, and a timepiece in which deformation due to stress concentration is suppressed while suppressing an increase in manufacturing cost.

According to another aspect of the present application, there is provided a hairspring according to claim <NUM>.

According to the application, by forming the reformed portion including the first bent portion and the second bent portion, for example, by performing bending processing or the like with respect to a part of a spiral thin plate spring, it is possible to provide the outer end curve portion spaced to the outer side in the radial direction from the main body portion in an outermost circumferential portion of the hairspring as a part engaged with a regulator or the like. In such a configuration, since at least one of the first bent portion and the second bent portion is curved, compared to a case where the first bent portion and the second bent portion are bent, it is possible to suppress stress concentration generated in the reformed portion. Therefore, it is possible to provide a hairspring in which deformation due to stress concentration is suppressed while suppressing an increase in manufacturing cost due to addition of heat treatment or the like.

According to embodiments, the stress generated in at least one curved portion of the first bent portion and the second bent portion can be dispersed substantially evenly in a curved range with a certain curvature. Therefore, the deformation of the hairspring due to stress concentration can be more reliably suppressed.

According to embodiments, stress concentration can be suppressed in both the first bent portion and the second bent portion. Therefore, the deformation of the hairspring due to stress concentration can be more reliably suppressed.

In the hairspring, the first bent portion and the second bent portion may be connected to each other.

According to the application, since the entire reformed portion is a curved bent portion, the stress generated in the reformed portion can be dispersed to the entire reformed portion. Therefore, the deformation of the hairspring due to stress concentration can be more reliably suppressed.

According to the application, there is provided a balance with a hairspring according to claim <NUM>.

According to the application, since the hairspring is provided that suppresses deformation due to stress concentration while suppressing an increase in manufacturing cost, a high-quality balance with a hairspring can be provided at a low cost with less variation in rate due to deformation of the hairspring.

According to the application, there is provided a timepiece movement according to claim <NUM>.

According to the application, there is provided a timepiece according to claim <NUM>.

According to the application, since a high-quality and inexpensive balance with a hairspring with less variation in rate is provided, a high-quality timepiece movement and timepiece with little time error can be provided at low cost.

According to the application, it is possible to provide a hairspring in which deformation due to stress concentration is suppressed while suppressing an increase in manufacturing cost.

Embodiments, of which the first to fourth embodiments are described by way of background to the present invention and do not fall within the scope of the claimed invention, and of which the fifth and sixth embodiments are embodiments of the present invention, will now be described by way of further example only and with reference to the accompanying drawings, in which:.

Hereinafter, embodiments of the invention will be described with reference to the drawings. In addition, in the following description, the same reference numerals will be given to configurations having the same or similar functions. In addition, there is a case where overlapping description of the configurations is omitted.

<FIG> is an external view of a timepiece according to a first embodiment.

As illustrated in <FIG>, a timepiece <NUM> of the embodiment includes a movement <NUM> (timepiece movement), a dial <NUM> having a scale that indicates at least information regarding time, and an hour hand <NUM> that indicates the hour, a minute hand <NUM> that indicates the minute, and a second hand <NUM> that indicates the second, within a timepiece case <NUM> including a case back lid (not illustrated) and a glass <NUM>.

<FIG> is a plan view of a movement according to the first embodiment.

As illustrated in <FIG>, a movement <NUM> has a main plate <NUM> that configures a board. A winding stem guide hole 11a is formed on the main plate <NUM>. A winding stem <NUM> coupled to a crown <NUM> illustrated in <FIG> is rotatably incorporated in the winding stem guide hole 11a. The position of the winding stem <NUM> in a shaft direction is determined by a switching device having a setting lever <NUM>, a yoke <NUM>, a yoke spring <NUM>, and a setting lever jumper <NUM>. In addition, a winding pinion <NUM> is rotatably provided in a guide shaft portion of the winding stem <NUM>.

Under such a configuration, when the winding stem <NUM> is rotated, the winding pinion <NUM> is rotated through the rotation of a clutch wheel (not illustrated). When the winding pinion <NUM> rotates, a crown wheel <NUM> and a ratchet wheel <NUM> rotate in order, and a hairspring (not illustrated) accommodated in a movement barrel <NUM> is wound up. In addition, the movement barrel <NUM> is pivotally supported between the main plate <NUM> and a barrel bridge <NUM>.

A center wheel & pinion <NUM>, a third wheel & pinion <NUM>, a second wheel & pinion <NUM>, and an escape wheel & pinion <NUM> are pivotally supported between the main plate <NUM> and a train wheel bridge <NUM>. When the movement barrel <NUM> is rotated by a restoring force of the hairspring, the center wheel & pinion <NUM>, the third wheel & pinion <NUM>, and the second wheel & pinion <NUM> are configured to be rotated in order. The movement barrel <NUM>, the center wheel & pinion <NUM>, the third wheel & pinion <NUM>, and the second wheel & pinion <NUM> configure a front train wheel.

When the center wheel & pinion <NUM> rotates, a cannon pinion (not illustrated) rotates based on the rotation, and the minute hand <NUM> (refer to <FIG>) attached to the cannon pinion displays "minute". In addition, when the cannon pinion rotates, an hour wheel (not illustrated) rotates via a minute wheel (not illustrated), and the hour hand <NUM> (refer to <FIG>) attached to the hour wheel displays "hour". Further, when the second wheel & pinion <NUM> rotates, the second hand <NUM> (refer to <FIG>) attached to the second wheel & pinion <NUM> displays "second".

On the front side of the movement <NUM>, an escapement & speed adjustment mechanism <NUM> for controlling the rotation of the front train wheel are disposed. The escapement & speed adjustment mechanism <NUM> includes the escape wheel & pinion <NUM> that meshes with the second wheel & pinion <NUM>, a pallet fork <NUM> that makes the escape wheel & pinion <NUM> escape and rotate regularly, and a balance with a hairspring <NUM>. Hereinafter, the structure of the balance with a hairspring <NUM> will be described in detail.

<FIG> is a plan view of the balance with a hairspring according to the first embodiment. <FIG> is a sectional view taken along line IV-IV of <FIG>.

As illustrated in <FIG> and <FIG>, the balance with a hairspring <NUM> includes a balance staff <NUM>, a balance wheel <NUM>, and a hairspring <NUM>. The balance with a hairspring <NUM> uses the power of the hairspring <NUM> to reciprocate (rotate forwardly and rearwardly) around a central axis O of the balance staff <NUM> with a certain vibrating period (oscillation angle). In the embodiment, a direction along the central axis O of the balance staff <NUM> is referred to as a shaft direction, a direction orthogonal to the central axis O and extending radially from the central axis O is referred to as a radial direction, and a direction around the central axis O in a plan view when viewed from the shaft direction is referred to as a circumferential direction.

The balance staff <NUM> is formed of a metal material, such as brass, for example, and is a rod-like member that extends along the central axis O. A tapered first tenon 41a and a second tenon 41b are formed at both ends of the balance staff <NUM> in the shaft direction. The balance staff <NUM> is pivotally supported between the main plate <NUM> and a balance bridge (not illustrated) via the first tenon 41a and the second tenon 41b. The balance staff <NUM> has a substantially center part in the shaft direction fixed into a fitting hole 49a (which will be described later) of the balance wheel <NUM> by, for example, press-fitting. Accordingly, the balance staff <NUM> and the balance wheel <NUM> are fixed integrally.

An annular double roller <NUM> is externally fitted to the balance staff <NUM> coaxially to the central axis O at a part positioned closer to the second tenon 41b than the balance wheel <NUM>. The double roller <NUM> has a flange portion 44a that projects to the outer side in the radial direction. An impulse pin <NUM> for swinging the pallet fork <NUM> is fixed to the flange portion 44a. Furthermore, an annular collet <NUM> for fixing the hairspring <NUM> is externally fitted to the balance staff <NUM> at a part positioned closer to the first tenon 41a than the balance wheel <NUM>.

The balance wheel <NUM> includes an annular rim portion <NUM> that surrounds the balance staff <NUM> from the outer side in the radial direction, and an arm portion <NUM> that couples the rim portion <NUM> and the balance staff <NUM> to each other in the radial direction. The rim portion <NUM> is disposed coaxially to the central axis O. The rim portion <NUM> is formed of a metal material, such as brass. A plurality of arm portions <NUM> extend in the radial direction and are arranged at intervals in the circumferential direction. In the example illustrated in the drawing, four arm portions <NUM> are arranged at intervals of <NUM> degrees around the central axis O. However, the number, arrangement, and shape of the arm portions <NUM> are not limited to this case.

The outer end portions of each arm portion <NUM> in the radial direction are integrally coupled to the inner circumferential portion of the rim portion <NUM>. The inner end portions of each arm portion <NUM> in the radial direction are connected to each other and integrated. In a coupling portion <NUM> in which the inner end portions of each arm portion <NUM> are integrated with each other, the fitting hole 49a coaxial to the central axis O is formed. As described above, the balance staff <NUM> is fixed into the fitting hole 49a by, for example, press-fitting.

The hairspring <NUM> is a thin plate spring formed of a metal material. The hairspring <NUM> is made of, for example, iron or nickel. The hairspring <NUM> is formed in a spiral shape within a surface perpendicular to the central axis O. The inner end portion of the hairspring <NUM> is fixed to the balance staff <NUM> via the collet <NUM>. A part of the outermost circumferential portion of the hairspring <NUM> is spaced to the outer side in the radial direction via a reformed portion <NUM> which will be described later, and the radius of curvature is formed to be larger than that of the part positioned at the inner circumference of the reformed portion <NUM>. The outer end portion of the hairspring <NUM> is fixed to a stud <NUM> attached via a stud holder (not illustrated).

<FIG> is a plan view of the hairspring according to the first embodiment.

As illustrated in <FIG>, the hairspring <NUM> includes a main body portion <NUM> that extends along an Archimedes curve when viewed from the shaft direction around the central axis O, an outer end curve portion <NUM> that extends along the circumferential direction on the outer side of the main body portion <NUM> in the radial direction, and the reformed portion <NUM> that connects the main body portion <NUM> and the outer end curve portion <NUM> to each other.

The main body portion <NUM> is wound with a plurality of turns adjacent to each other at substantially equal intervals in the radial direction when viewed from the shaft direction. In the example illustrated in the drawing, using an inner end portion 51a as an unwinding position, unwinding proceeds along the Archimedes curve with the central axis O as a polar coordinate origin when viewed from the shaft direction, and the main body portion <NUM> is formed with <NUM> windings. The inner end portion 51a of the main body portion <NUM> is an inner end portion of the hairspring <NUM>. Hereinafter, among the circumferential directions, a direction in which the main body portion <NUM> extends from the inner end portion 51a is referred to as an unwinding direction of the main body portion <NUM>.

The outer end curve portion <NUM> is the outermost circumferential portion of the hairspring <NUM>. The outer end curve portion <NUM> extends around the central axis O with a certain curvature. The outer end curve portion <NUM> is formed in an arc shape having a radius of curvature larger than that of the main body portion <NUM>. The "radius of curvature" in each portion of the hairspring <NUM> is a reciprocal number of the curvature of a concave surface at a target part. A first end portion 53a of the outer end curve portion <NUM> is an outer end portion of the hairspring <NUM>. A second end portion 53b of the outer end curve portion <NUM> is provided at a position deviated from the outer end portion 51b of the main body portion <NUM> by a predetermined angle in the unwinding direction of the main body portion <NUM>.

The reformed portion <NUM> connects the outer end portion 51b of the main body portion <NUM> and the second end portion 53b of the outer end curve portion <NUM> to each other. The reformed portion <NUM> extends from the outer end portion 51b of the main body portion <NUM> to the outer side in the radial direction and in the unwinding direction of the main body portion <NUM>, and is coupled to the second end portion 53b of the outer end curve portion <NUM>. The reformed portion <NUM> includes a first bent portion <NUM> that is bent outward in the radial direction from a tangent line T of the Archimedes curve in a first connection portion 55a with the main body portion <NUM>, and a second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in a second connection portion 55b with the outer end curve portion <NUM>. At least one of the first bent portion <NUM> and the second bent portion <NUM> is curved. In the embodiment, only the first bent portion <NUM> of the first bent portion <NUM> and the second bent portion <NUM> is curved. In other words, the first bent portion <NUM> is curved and the second bent portion <NUM> is bent. The first bent portion <NUM> is curved with a certain curvature. The radius of curvature of the first bent portion <NUM> is larger than the thickness of the hairspring <NUM> at the reformed portion <NUM>. The first bent portion <NUM> is smoothly connected to the main body portion <NUM> when viewed from the shaft direction. In addition, "smooth connection" means connection in a state where a gradient of the tangent line is continuous without being curved. The first bent portion <NUM> and the second bent portion <NUM> are connected to each other.

When describing the dimensions and angles of each part in the hairspring <NUM> of the embodiment in detail, the original shape of the hairspring <NUM> will be described. The original shape of the hairspring <NUM> is not deformed by the reformed portion <NUM> and the entire hairspring <NUM> has a shape that extends along the Archimedes curve. In other words, the original shape of the hairspring <NUM> is a shape in which the part that configures the reformed portion <NUM> and the outer end curve portion <NUM> in the hairspring <NUM> further extends along the Archimedes curve from the outer end portion 51b of the main body portion <NUM> as illustrated by a two-dot chain line A in the drawing.

An inner diameter of the outermost circumferential portion of the original shape of the hairspring <NUM> is defined as a time diameter D on a virtual straight line L that passes through the central axis O and the outer end portion of the original shape of the hairspring <NUM> when viewed from the shaft direction. In a case where the time diameter D satisfies <NUM> ≤ D ≤ <NUM>, the radius of curvature R of the outer end curve portion <NUM> satisfies <NUM> ≤ R-(D/<NUM>) ≤ <NUM>, and a center angle θ on the central axis O between both ends of the reformed portion <NUM> satisfies <NUM>° ≤ θ ≤ <NUM>°, it is desirable that a radius of curvature R1 of the first bent portion <NUM> satisfies <NUM> ≤ R1 ≤ <NUM>. Furthermore, it is more desirable that the radius of curvature R1 of the first bent portion <NUM> satisfies <NUM> ≤ R1 ≤ <NUM>. Accordingly, the maximum value of the stress generated in the first bent portion <NUM> can be relaxed by <NUM>% or more.

As described above, the hairspring <NUM> of the embodiment includes the reformed portion <NUM> that connects the main body portion <NUM> and the outer end curve portion <NUM> to each other. The reformed portion <NUM> includes the first bent portion <NUM> that is bent outward in the radial direction from the tangent line T of the Archimedes curve in the first connection portion 55a with the main body portion <NUM>, and the second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in the second connection portion 55b with the outer end curve portion <NUM>. The first bent portion <NUM> is curved.

According to the configuration, by forming the reformed portion <NUM> including the first bent portion <NUM> and the second bent portion <NUM>, for example, by performing bending processing or the like with respect to a part of a spiral thin plate spring (original shape of the hairspring <NUM>), it is possible to provide the outer end curve portion <NUM> spaced to the outer side in the radial direction from the main body portion <NUM> at the outermost circumferential portion of the hairspring <NUM> as a part engaged with the regulator or the like. In such a configuration, since the first bent portion <NUM> is curved, compared to a case where the first bent portion and the second bent portion are bent (but not curved), it is possible to suppress stress concentration generated in the reformed portion <NUM>. Therefore, it is possible to provide the hairspring <NUM> in which deformation due to stress concentration is suppressed while suppressing an increase in manufacturing cost due to addition of heat treatment or the like.

In the embodiment, the outer end curve portion <NUM> is spaced from the main body portion <NUM> by the reformed portion <NUM> having the first bent portion <NUM> and the second bent portion <NUM>. The hairspring having such a shape is formed, for example, by reforming the thin plate spring by plastic deformation. Here, in the hairspring that does not have the first bent portion that is bent outward in the radial direction from the tangent line of the Archimedes curve, a bending amount (angle) when the outer end curve portion is spaced from the main body portion is minute. Therefore, the thin plate spring cannot be sufficiently plastically deformed, and there is a possibility that the position accuracy of the outer end curve portion deteriorates. According to the embodiment, since the first bent portion <NUM> and the second bent portion <NUM> are provided, it is possible to easily reform the thin plate spring by plastic deformation when forming the hairspring <NUM>, and it is possible to improve the accuracy of the position and shape of the outer end curve portion <NUM>.

In addition, the first bent portion <NUM> is curved with a certain curvature.

According to the configuration, the stress generated in the first bent portion <NUM> can be dispersed substantially evenly in a curved range with a certain curvature. Therefore, the deformation of the hairspring <NUM> due to stress concentration can be more reliably suppressed.

Here, the effectiveness of stress relaxation by providing the hairspring with a bent portion curved with a certain curvature will be described.

<FIG> is a graph illustrating a relationship between a radius of curvature and a stress relaxation rate of a bent portion, where the bent portion curved with a certain curvature is provided at a part of the hairspring. In <FIG>, the horizontal axis indicates the radius of curvature of the bent portion. The longitudinal axis indicates a reduction rate of the maximum value of the stress in a case where the radius of curvature of the bent portion is <NUM> as the stress relaxation rate. The results illustrated in <FIG> are the results in a case where the width of the hairspring is <NUM> and the thickness of the hairspring is <NUM>.

As illustrated in <FIG>, it is possible to confirm that the relaxation rate of the stress increases as the radius of curvature of the bent portion increases. Therefore, in the embodiment, it has been confirmed that the stress concentration generated in the reformed portion <NUM> can be suppressed by curving the first bent portion <NUM> with a certain curvature.

Furthermore, according to the balance with a hairspring <NUM> of the embodiment, since the above-described hairspring <NUM> is provided, the high-quality and inexpensive balance with a hairspring <NUM> with less variation in rate due to deformation of the hairspring <NUM> can be obtained.

Furthermore, according to the movement <NUM> and the timepiece <NUM> of the embodiment, since the above-described balance with a hairspring <NUM> is provided, the high-quality movement <NUM> and timepiece <NUM> with little time error can be obtained.

Next, a second embodiment will be described with reference to <FIG>. The second embodiment is different from the first embodiment in that a reformed portion <NUM> includes a straight portion <NUM> between a first bent portion <NUM> and a second bent portion <NUM>. In addition, the configuration other than that described below is the same as that of the first embodiment.

<FIG> is a plan view of the hairspring according to the second embodiment.

As illustrated in <FIG>, the reformed portion <NUM> includes a first bent portion <NUM> that is bent outward in the radial direction from the tangent line T of the Archimedes curve in a first connection portion 155a with the main body portion <NUM>, a second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in a second connection portion 155b with the outer end curve portion <NUM>, and a straight portion <NUM> that connects the first bent portion <NUM> and the second bent portion <NUM> to each other. In the embodiment, only the first bent portion <NUM> of the first bent portion <NUM> and the second bent portion <NUM> is curved. The first bent portion <NUM> is curved with a certain curvature. The straight portion <NUM> extends linearly when viewed from the shaft direction. The straight portion <NUM> extends from the outer end portion of the first bent portion <NUM> to the outer side in the radial direction and in the unwinding direction of the main body portion <NUM>, and is coupled to the second bent portion <NUM>. The straight portion <NUM> is smoothly connected to the first bent portion <NUM> when viewed from the shaft direction. In addition, it is desirable that the time diameter D, the radius of curvature R of the outer end curve portion <NUM>, the center angle θ between both ends of the reformed portion <NUM>, and the radius of curvature R1 of the first bent portion <NUM> satisfy the same conditions as those in the first embodiment.

As described above, since the hairspring <NUM> according to the embodiment includes the first bent portion <NUM> curved with a certain curvature, the same operational effects as those of the hairspring <NUM> according to the first embodiment can be achieved.

Next, a third embodiment will be described with reference to <FIG>. The third embodiment is different from the first embodiment in that a first bent portion <NUM> is bent and a second bent portion <NUM> is curved. In addition, the configuration other than that described below is the same as that of the first embodiment.

<FIG> is a plan view of the hairspring according to the third embodiment.

As illustrated in <FIG>, a reformed portion <NUM> includes the first bent portion <NUM> that is bent outward in the radial direction from the tangent line T of the Archimedes curve in a first connection portion 255a with the main body portion <NUM>, and the second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in a second connection portion 255b with the outer end curve portion <NUM>. In the embodiment, only the second bent portion <NUM> of the first bent portion <NUM> and the second bent portion <NUM> is curved. The second bent portion <NUM> is curved with a certain curvature. The second bent portion <NUM> is smoothly connected to the outer end curve portion <NUM> when viewed from the shaft direction. The first bent portion <NUM> and the second bent portion <NUM> are connected to each other. In a case where the time diameter D, the radius of curvature R of the outer end curve portion <NUM>, and the center angle θ between both ends of the reformed portion <NUM> satisfy the same conditions as those in the above-described first embodiment, it is desirable that a radius of curvature R2 of the second bent portion <NUM> satisfies <NUM> ≤ R2 ≤ <NUM>. Furthermore, it is more desirable that the radius of curvature R2 of the second bent portion <NUM> satisfies <NUM> ≤ R2 ≤ <NUM>. Accordingly, the maximum value of the stress generated in the second bent portion <NUM> can be relaxed by <NUM>% or more.

As described above, since the hairspring <NUM> according to the embodiment includes the second bent portion <NUM> curved with a certain curvature, the same operational effects as those of the hairspring <NUM> according to the first embodiment can be achieved.

Next, a fourth embodiment will be described with reference to <FIG>. The fourth embodiment is different from the third embodiment in that a reformed portion <NUM> includes a straight portion <NUM> between a first bent portion <NUM> and a second bent portion <NUM>. In addition, the configuration other than that described below is the same as that of the third embodiment.

<FIG> is a plan view of the hairspring according to the fourth embodiment.

As illustrated in <FIG>, the reformed portion <NUM> includes the first bent portion <NUM> that is bent outward in the radial direction from the tangent line T of the Archimedes curve in a first connection portion 355a with the main body portion <NUM>, the second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in a second connection portion 355b with the outer end curve portion <NUM>, and the straight portion <NUM> that connects the first bent portion <NUM> and the second bent portion <NUM> to each other. In the embodiment, only the second bent portion <NUM> of the first bent portion <NUM> and the second bent portion <NUM> is curved. The second bent portion <NUM> is curved with a certain curvature. The straight portion <NUM> extends linearly when viewed from the shaft direction. The straight portion <NUM> extends from the inner end portion of the second bent portion <NUM> to the inner side in the radial direction and in a direction opposite to the unwinding direction of the main body portion <NUM> in the circumferential direction, and is coupled to the first bent portion <NUM>. The straight portion <NUM> is smoothly connected to the second bent portion <NUM> when viewed from the shaft direction. In addition, it is desirable that the time diameter D, the radius of curvature R of the outer end curve portion <NUM>, the center angle θ between both ends of the reformed portion <NUM>, and the radius of curvature R2 of the second bent portion <NUM> satisfy the same conditions as those in the third embodiment.

As described above, since the hairspring <NUM> according to the embodiment includes the second bent portion <NUM> curved with a certain curvature, the same operational effects as those of the hairspring <NUM> according to the third embodiment can be achieved.

Next, a fifth embodiment will be described with reference to <FIG>. The fifth embodiment is different from the first embodiment in that both a first bent portion <NUM> and a second bent portion <NUM> are curved. In addition, the configuration other than that described below is the same as that of the first embodiment.

<FIG> is a plan view of the hairspring according to the fifth embodiment.

As illustrated in <FIG>, a reformed portion <NUM> includes the first bent portion <NUM> that is bent outward in the radial direction from the tangent line T of the Archimedes curve in a first connection portion 455a with the main body portion <NUM>, and the second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in a second connection portion 455b with the outer end curve portion <NUM>. In the embodiment, both the first bent portion <NUM> and the second bent portion <NUM> are curved. Each of the first bent portion <NUM> and the second bent portion <NUM> is curved with a certain curvature. The first bent portion <NUM> is smoothly connected to the main body portion <NUM> when viewed from the shaft direction. The second bent portion <NUM> is smoothly connected to the outer end curve portion <NUM> when viewed from the shaft direction. The first bent portion <NUM> and the second bent portion <NUM> are smoothly connected to each other. For example, the radius of curvature of the first bent portion <NUM> is larger than the radius of curvature of the second bent portion.

In a case where the time diameter D, the radius of curvature R of the outer end curve portion <NUM>, and the center angle θ between both ends of the reformed portion <NUM> satisfy the same conditions as those in the above-described first embodiment, it is desirable that the radius of curvature R1 of the first bent portion <NUM> satisfies <NUM> ≤ R1 ≤ <NUM> and the radius of curvature R2 of the second bent portion <NUM> satisfies <NUM> ≤ R2 ≤ <NUM>. Furthermore, it is more desirable that the radius of curvature R1 of the first bent portion <NUM> satisfies <NUM> ≤ R1 ≤ <NUM> and the radius of curvature R2 of the second bent portion <NUM> satisfies <NUM> ≤ R2 ≤ <NUM>. Accordingly, the maximum value of the stress generated in each of the first bent portion <NUM> and the second bent portion <NUM> can be relaxed by <NUM>% or more.

As described above, in the embodiment, both the first bent portion <NUM> and the second bent portion <NUM> are respectively curved with a certain curvature. According to the configuration, stress concentration can be suppressed in both the first bent portion <NUM> and the second bent portion <NUM>. Therefore, the deformation of the hairspring <NUM> due to stress concentration can be more reliably suppressed.

In addition, the first bent portion <NUM> and the second bent portion <NUM> are connected to each other.

According to the configuration, since the entire reformed portion <NUM> is a curved bent portion, the stress generated in the reformed portion <NUM> can be dispersed to the entire reformed portion <NUM>. Therefore, the deformation of the hairspring <NUM> due to stress concentration can be more reliably suppressed.

Next, a sixth embodiment will be described with reference to <FIG>. The sixth embodiment is different from the fifth embodiment in that a reformed portion <NUM> includes a straight portion <NUM> between a first bent portion <NUM> and a second bent portion <NUM>. In addition, the configuration other than that described below is the same as that of the fifth embodiment.

<FIG> is a plan view of the hairspring according to the sixth embodiment.

As illustrated in <FIG>, the reformed portion <NUM> includes the first bent portion <NUM> that is bent outward in the radial direction from the tangent line T of the Archimedes curve in a first connection portion 555a with the main body portion <NUM>, the second bent portion <NUM> that is bent inward in the radial direction from the outer end curve portion <NUM> in a second connection portion 555b with the outer end curve portion <NUM>, and the straight portion <NUM> that connects the first bent portion <NUM> and the second bent portion <NUM> to each other. In the embodiment, both the first bent portion <NUM> and the second bent portion <NUM> are curved. Each of the first bent portion <NUM> and the second bent portion <NUM> is curved with a certain curvature. The straight portion <NUM> extends linearly when viewed from the shaft direction. The straight portion <NUM> extends from the outer end portion of the first bent portion <NUM> to the outer side in the radial direction and in the unwinding direction of the main body portion <NUM>, and is coupled to the inner end portion of the second bent portion <NUM>. The straight portion <NUM> is smoothly connected to each of the first bent portion <NUM> and the second bent portion <NUM> when viewed from the shaft direction. In addition, it is desirable that the time diameter D, the radius of curvature R of the outer end curve portion <NUM>, the center angle θ between both ends of the reformed portion <NUM>, the radius of curvature R1 of the first bent portion <NUM>, and the radius of curvature R2 of the second bent portion <NUM> satisfy the same conditions as those in the fifth embodiment.

As described above, in the embodiment, since both the first bent portion <NUM> and the second bent portion <NUM> are respectively curved with a certain curvature, similar to the fifth embodiment, it is possible to more reliably suppress the deformation of the hairspring <NUM> due to stress concentration.

In addition, the invention is not limited to the above-described embodiments described with reference to the drawings, and various modification examples can be considered within the technical scope.

For example, in the above-described embodiments, the outer end curve portion <NUM> extends around the central axis O with a certain curvature, but the invention is not limited thereto. The outer end curve portion may extend along the circumferential direction, and only the curvature may slightly change at a part. The outer end portion may extend in an Archimedes curve, or have some other fixed or varying curvature.

In addition, in the embodiments, although the first bent portion <NUM> and the second bent portion <NUM> are formed by plastic deformation, the method for forming the hairspring is not specifically limited. For example, the hairspring may be formed by a micro electro mechanical systems (MEMS) technique, such as electroforming.

Claim 1:
A hairspring (<NUM>) comprising:
a main body portion (<NUM>) that extends around a central axis (O) along an Archimedes curve;
an outer end curve portion (<NUM>) that extends around the central axis (O) on an outer side in a radial direction from the main body portion (<NUM>); and
a reformed portion (<NUM>) that connects the main body portion (<NUM>) and the outer end curve portion (<NUM>) to each other includes a first bent portion (<NUM>) that is bent outward in the radial direction from a tangent line (T) of the Archimedes curve in a first connection portion (455a) with the main body portion, and a second bent portion (<NUM>) bent inward in the radial direction from the outer end curve portion in a second connection portion (455b) with the outer end curve portion, and in which both of the first bent portion and the second bent portion are curved,
characterized in that, where an inner diameter of the outermost circumferential portion of an original shape of the hairspring (<NUM>) is defined as a time diameter (D) on a virtual straight line (L) that passes through the central axis (O) and the outer end portion of the original shape of the hairspring (<NUM>) when viewed from the shaft direction, the time diameter (D) satisfies <NUM> ≤ D ≤ <NUM>, the radius of curvature (R) of the outer end curve portion (<NUM>) satisfies <NUM> ≤ R-(D/<NUM>) ≤ <NUM>, and a center angle (θ) on the central axis (O) between both ends of the reformed portion (<NUM>) satisfies <NUM>° ≤ θ ≤ <NUM>°, the radius of curvature (R1) of the first bent portion (<NUM>) satisfies <NUM> ≤ R1 ≤ <NUM> and the radius of curvature (R2) of the second bent portion (<NUM>) satisfies <NUM> ≤ R2 ≤ <NUM>,
the original shape of the hairspring (<NUM>) being the shape of the hairspring (<NUM>) when not deformed by the reformed portion (<NUM>) with the entire hairspring (<NUM>) having a shape that extends along the Archimedes curve.