CN116755316A - Hairspring, timepiece movement and timepiece - Google Patents

Abstract

The application aims to provide a hairspring, a movement for a clock and the clock. The hairspring of the application is characterized in that: the Nb-Mo alloy contains 5-14% Mo in at%. Alternatively, the hairspring of the application is characterized in that: the Nb-Mo alloy contains 5-14% Mo in at%, and the balance is composed of unavoidable impurities and Nb. Preferably, the region having a processed texture and having a <110> ||{001} degree of orientation in the cross section accounts for 30% or more of the total cross-sectional area.

Description

Hairspring, timepiece movement and timepiece

Technical Field

The present application relates to a hairspring, a movement for a timepiece and a timepiece.

Background

In a mechanical timepiece using a hairspring as a vibration source, it is known that the time accuracy changes due to external factors such as temperature, posture, vibration, etc., that is, the difference rate (the degree of clock lag, advance) changes.

For example, the precision of a mechanical timepiece depends on the stability of the natural frequency of the hairspring assembly oscillator. That is, when the temperature changes, the natural frequency of the component oscillator changes due to the thermal expansion of the balance spring and the change in young's modulus of the balance spring, and the precision of the timepiece is unstable.

In order to reduce the change in natural frequency due to temperature in a component oscillator of a mechanical timepiece, a niobium-based alloy having a low thermal expansion coefficient to which zirconium or molybdenum is added is known as a metallic material constituting a hairspring.

For example, patent document 1 below describes a technique for predicting the temperature characteristics of young's modulus of nb—mo alloy by computer simulation.

Patent document 2 below discloses a hairspring made of an nb—zr alloy, which contains 500 mass ppm or more of an oxygen-containing interstitial doping component and controls the amount of Zr-rich phase deposited to realize an arbitrary temperature characteristic.

[ Prior Art literature ]

[ patent literature ]

Patent document 1: european patent application publication No. 3663867 specification

Patent document 2: japanese patent laid-open No. 11-071625.

Disclosure of Invention

(problem to be solved by the application)

According to the technique described in patent document 1, in nb—mo alloys in which Mo is added to Nb in a range of 15% to 50%, it is expected that a temperature coefficient of a target young's modulus can be obtained.

However, in the technique described in patent document 1, the young's modulus is not measured by actually manufacturing a balance spring made of nb—mo alloy, but is estimated based on the result calculated by the first principle. Therefore, it is not clear whether or not the calculated value and the measured value actually used as a hairspring correspond to each other due to the influence of processing strain or the like, and there is a problem that the practicality is not clear.

According to the technique described in patent document 1, it is necessary to adjust the amount of residual strain in accordance with the processing rate and the heat treatment temperature of the nb—mo alloy, and further, it is necessary to adjust the <110> orientation degree of the crystal.

Therefore, it is considered that it is not easy to apply the nb—mo alloy to the hairspring and achieve the target temperature characteristic.

In addition, the technique described in patent document 2 requires precise control of the oxygen content of the alloy, and thus it is considered that the production of the alloy is not easy.

Accordingly, an object of the present application is to provide: by using a nb—mo alloy of a special composition which has not been known in the prior art, it is possible to adjust the temperature coefficient by taking into consideration actual processing without adjusting the temperature coefficient by oxygen concentration.

Another object of the present application is to provide a technique capable of eliminating a change in the difference rate with time which is considered to occur when the balance spring is made of the nb—mo alloy.

(means for solving the problems)

(1) The hairspring according to the present application is characterized in that: the Nb-Mo alloy contains 5-14% Mo in at% (atomic percentage).

In the case of an nb—mo alloy containing Mo in an amount of 5% or more and 14% or less in at%, since Mo is contained as the second element in an appropriate range, it is not necessary to adjust the temperature coefficient by the oxygen concentration, and by adjusting the Mo content, the processing texture and the residual strain amount, a hairspring in which the temperature coefficient is adjusted to a target low range can be obtained. That is, according to the hairspring of the present application, it is possible to provide a hairspring in which the temperature coefficient can be controlled within the target range while taking into consideration actual processing at the time of forming the hairspring without adjusting the oxygen concentration.

(2) The hairspring according to the present application is characterized in that: the Nb-Mo alloy contains 5-14% Mo in at%, and the balance is composed of unavoidable impurities and Nb.

If the nb—mo alloy contains Mo in an amount of 5% to 14% by at% and the balance is made up of unavoidable impurities and Nb, since Mo is contained as the second element in an appropriate range, it is not necessary to adjust the temperature coefficient by the oxygen concentration, and by adjusting the Mo content, the processing texture and the residual strain amount, a hairspring whose temperature coefficient is adjusted to a target low range can be obtained. That is, according to the hairspring of the present application, it is possible to provide a hairspring in which the temperature coefficient can be controlled within the target range while taking into consideration actual processing at the time of forming the hairspring without adjusting the oxygen concentration.

(3) In the hairspring according to one embodiment of the present application, it is preferable to have a processed texture, and the region having <110> ||{001} orientation degree in the cross section accounts for more than 30% of the total cross section.

The temperature coefficient can be adjusted by processing the texture, and in addition to the above-mentioned regulation of the Mo content, a processing texture having a <110> ||{001} degree of orientation is also generated, it is thereby possible to provide a balance spring capable of adjusting the temperature coefficient by taking into account actual processing when manufacturing the balance spring.

(4) In the hairspring according to one embodiment of the present application, the average KAM (Kernel Average Misorientation, kernel average difference in orientation) value is preferably 1.0 to 4.0.

It is possible to provide a hairspring whose temperature coefficient can be adjusted by averaging KAM values in addition to the Mo content and the processed texture described above.

(5) In the hairspring according to any one of (1) to (4) of the present application, it is preferable that the hairspring further comprises a base material and a first oxide film layer and a second oxide film layer covering the base material, wherein the base material is composed of the nb—mo alloy, the first oxide film layer contains Nb, mo, and O, and the second oxide film layer contains Nb and O.

Nb—mo alloy constituting the hairspring is naturally oxidized with time to easily form a passivation film in the atmosphere, and the difference rate is changed with time when used in the atmosphere with the lapse of time due to the influence thereof.

If the passivation film is formed by oxidation treatment, the difference rate is hardly changed with time. Therefore, if the timepiece is constituted by using the hairspring having the first oxide film layer and the second oxide film layer, it is possible to provide a timepiece with high accuracy.

(6) A timepiece movement according to an aspect of the application includes: a balance spring according to any one of (1) to (5); a pendulum shaft; a balance wheel; a balance spring mechanism.

In the case of the timepiece movement including the hairspring, the temperature coefficient of the hairspring can be adjusted to be within a small desired range, and the timepiece movement can be provided with a high precision and stability by making the natural frequency of the component oscillator uniform with a small variation in the difference.

In addition, in the case of a hairspring provided with the first oxide film layer and the second oxide film layer, it is possible to provide a stable timepiece movement in which the difference rate does not change with time.

(7) A timepiece according to an aspect of the application is characterized in that: the timepiece movement according to (6).

In the case of a timepiece including the timepiece movement, by providing the hairspring having a temperature coefficient in a desired range, it is possible to provide a timepiece with high accuracy in which the natural frequency of the component oscillator is uniform and the variation in the difference rate is small.

In addition, in the case of the timepiece movement having the hairspring including the first oxide film layer and the second oxide film layer, a stable timepiece in which the difference rate does not change with time can be provided.

(effects of the application)

A hairspring comprising an Nb-Mo alloy, wherein 5at% to 14at% Mo is added to Nb as a second element, whereby the temperature coefficient can be adjusted in consideration of actual processing such as wire drawing processing, and the temperature coefficient can be adjusted to a desired range by optimizing processing texture and residual strain amount.

The hairspring according to the present application has a feature that the degree of orientation of the processed texture is high, KAM values can be used in a wide range, and the hairspring can be easily manufactured without adjusting the temperature coefficient by the oxygen concentration.

The hairspring of the application has the following characteristics: the combination of the control of Mo content and processing texture and the control of KAM value and residual strain amount can be adjusted to an arbitrary temperature coefficient. In addition, by providing the hairspring having the first oxide film layer and the second oxide film layer, the difference ratio can be prevented from changing with time.

Therefore, the timepiece movement and timepiece using the hairspring of the application have the effect of providing a timepiece movement and timepiece with small time-dependent changes in the difference ratio and high accuracy.

Drawings

Fig. 1 is an external view showing a first embodiment of a timepiece according to the application.

Fig. 2 is a plan view of a timepiece movement provided in the timepiece of the first embodiment.

Fig. 3 is a plan view showing an example of a balance spring mechanism provided in the timepiece movement shown in fig. 2.

Fig. 4 is a cross-sectional view of the same balance spring mechanism.

Fig. 5 is a graph showing the temperature characteristics of the difference in balance springs made of Nb-9at% mo alloy.

Fig. 6 is a graph showing the temperature characteristics of the difference in balance springs made of Nb-11at% mo alloy.

Fig. 7 is a graph showing the temperature characteristic of the difference in balance spring composed of Nb-13at% mo alloy.

Fig. 8 is a graph showing the correlation between the temperature coefficients (C1, C2) and the Mo content in the hairspring made of nb—mo alloy.

Fig. 9 is a graph showing the correlation between the first temperature coefficient (C1), the second temperature coefficient (C2), and the third temperature coefficient (C3) and the Mo content in the hairspring made of nb—mo alloy.

FIG. 10 is a graph showing the relationship between the temperature coefficient of the difference rate and the average KAM value in a hairspring made of Nb-11at% Mo alloy.

Fig. 11 is a graph showing a relationship between a temperature coefficient and a Mo amount in a hairspring made of nb—mo alloy.

FIG. 12 is a graph showing the relationship between the temperature coefficient of the difference rate and the average KAM value in a hairspring made of Nb-9at%Mo alloy.

Fig. 13 is a graph showing the relationship between the temperature coefficient of the difference rate and the average KAM value in a hairspring made of Nb-10at% mo alloy.

FIG. 14 is a graph showing the relationship between the temperature coefficient of the difference rate and the average KAM value in a hairspring made of Nb-13at% Mo alloy.

Fig. 15 is a graph showing the relationship between the temperature coefficient of young's modulus of nb—mo alloy and the etching time of the test piece.

Fig. 16 is a drawing showing <110 in a hairspring made of Nb-Mo alloy a graph of the relation between the degree of orientation of || {001} and the etching time.

FIG. 17 is a view showing a cross section of a hairspring made of Nb-Mo alloy

Tissue analysis photographs of the region of <110> ||{001} orientation.

Fig. 18 shows the hairspring of fig. 17 after 24 seconds of etching the outer periphery thereof a photograph of a tissue analysis of the region in cross section showing the <110> ||{001} orientation.

FIG. 19 is a drawing showing that the outer peripheral portion of the hairspring sample obtained in the example was etched for 48 seconds a tissue analysis photograph of the region showing the <110> ||{001} orientation in the cross section after.

FIG. 20 is a drawing showing that the outer peripheral portion of the hairspring sample obtained in the example was etched for 72 seconds a tissue analysis photograph of the region showing the <110> ||{001} orientation in the cross section after.

Fig. 21 is <110 showing a hairspring made of Nb-Mo alloy a graph of the relation between the degree of orientation of ||{001} and the processing rate.

Fig. 22 is a cross-sectional view of a hairspring according to a second embodiment provided with an oxide film layer.

FIG. 23 is a view showing the outer part of a hairspring sample having an oxide film layer obtained in the example the cross section after etching of the periphery shows <110> ||in cross section. Tissue analysis photographs of {001} oriented regions.

Fig. 24 is a STEM bright field image showing a cross section of the hairspring provided with the oxide film layer obtained in the example.

Fig. 25 is a graph showing an example of the time-dependent change in the difference rate in the hairspring without the oxide film layer.

Fig. 26 is a graph showing an example of the time-dependent change in the difference rate in the hairspring having the oxide film layer.

Detailed Description

Hereinafter, embodiments according to the present application will be described with reference to the drawings. In the present embodiment, a mechanical timepiece is described as an example of a timepiece. In each drawing, the scale of each component is appropriately changed so that each component has a size that can be visually recognized.

< Structure of timepiece of the first embodiment >

In general, a mechanical body comprising a driving portion of a timepiece is referred to as a "movement". The movement is fitted with a dial and a hand, then put into a case to make a finished product, this state being called the "complete whole" of the timepiece. Of the two sides of the main board constituting the timepiece base plate, the side on which the glass of the case is located (the side on which the dial is located) is referred to as the "back side" of the movement. In addition, of the two sides of the main board, the side on which the case bottom cover of the case is located (the side opposite to the dial) is referred to as the "face side" of the movement.

As shown in fig. 1, the timepiece 1 of the first embodiment includes, in a case 3 composed of a case bottom cover and glass 2, not shown, the whole of the timepiece: movement (movement for timepiece according to the present application) 10; a dial 4 having a scale (time character) displaying at least information related to time; and a pointer including an hour hand 5at the time of display, a minute hand 6 displaying a minute, and a second hand 7 displaying a second.

As shown in fig. 2, the movement 10 has a main board 11 constituting a substrate. In fig. 2, for ease of viewing the drawings, the illustration of parts constituting the movement is omitted.

A stem guide hole 11a is formed in the main plate 11. A stem 12 connected to the crown 8 shown in fig. 1 is rotatably assembled in the stem guide hole 11a. The axial position of the stem 12 is determined by a switching device having a pull-out piece 13, a clutch lever 14, a clutch lever spring 15 and a pull-out piece compression spring 16. Further, a standing wheel 17 is rotatably provided at a guide shaft portion of the stem 12.

With the above-described configuration, when the stem 12 is rotated, the standing wheel 17 is rotated by the rotation of the clutch wheel, not shown. When the vertical wheel 17 rotates, the small steel wheel 20 and the large steel wheel 21 sequentially rotate, and a spring (power source), not shown, housed in the barrel wheel 22 is wound up. The cartridge wheel 22 is supported by a shaft between the main plate 11 and the cartridge clamp plate 23.

The second wheel 25, the third wheel 26, the fourth wheel 27, and the escape wheel 35 are pivotally supported between the main plate 11 and the train wheel bridge 24. Is configured such that the second wheel 25, the third wheel 26 and the fourth wheel 27 are rotated in sequence when the barrel wheel 22 is rotated by the restoring force of the spring. These case wheel 22, second wheel 25, third wheel 26 and fourth wheel 27 constitute a wheel train on the front side.

When the second wheel 25 rotates, a hollow shaft pinion, not shown, rotates based on the rotation, and the minute hand 6 shown in fig. 1 attached to the hollow shaft pinion displays "minute". When the hollow shaft pinion rotates, an unillustrated hour wheel rotates via an unillustrated straddle, and an hour hand 5 shown in fig. 1 attached to the hour wheel displays "hour". The second hand 7 shown in fig. 1 attached to the fourth wheel 27 displays "seconds" by the rotation of the fourth wheel 27.

An escapement/governor mechanism 30 for controlling rotation of the timepiece train is disposed on the front surface side of the movement 10.

The escapement/governor mechanism 30 includes: the escape wheel 35 engaged with the fourth wheel 27; an escapement fork 36 for regularly rotating the escapement wheel 35; balance spring mechanism 40. The following describes the structure of balance spring mechanism 40 in detail.

(Structure of balance spring mechanism)

As shown in fig. 3, the balance spring mechanism 40 includes a balance shaft 41, a balance 42, and a balance spring 43, and reciprocally rotates (rotates in a forward and backward direction) around a center axis O of the balance shaft 41 with a constant vibration cycle (a balance angle) by power of the balance spring 43.

In the present embodiment, a direction orthogonal to the central axis O of the pendulum shaft 41 may be referred to as a radial direction, and a direction around the central axis O in a plan view from the central axis O may be referred to as a circumferential direction.

The pendulum shaft 41 is made of metal such as brass, and is a rod-like member extending along the central axis O. A first tongue portion 41a and a second tongue portion 41b having a thin tip are formed at both ends of the pendulum shaft 41 in the axial direction.

The balance shaft 41 is pivotally supported between the main plate 11 and a balance spring mechanism clip, not shown, via the first and second tenon portions 41a and 41b. The substantially central portion of the balance 41 in the axial direction is fixed to a fitting hole 50 of the balance 42 by press fitting, for example. Thereby, the balance 41 and the balance 42 are fixed as one body.

An annular pendulum seat 44 is fitted coaxially with the center axis O to the pendulum shaft 41at a portion closer to the second tenon portion 41b than the balance 42. The pendulum seat 44 has a flange portion 44a protruding radially outward. A balance 45 for swinging the pallet fork 36 is fixed to the flange portion 44a.

Further, an annular collet 46 for fixing the balance spring 43 is fitted to the balance shaft 41 coaxially with the center axis O at a portion closer to the first tongue portion 41a than the balance 42.

Balance 42 includes: an annular edge portion 47 disposed coaxially with the center axis O and surrounding the pendulum shaft 41 from the radially outer side; and an arm portion 48 connecting the edge portion 47 and the pendulum shaft 41 in the radial direction.

The edge portion 47 is formed of metal such as brass. A plurality of arms 48 extend radially and are circumferentially spaced apart. In the illustrated example, 4 arm portions 48 are arranged at 90-degree intervals around the central axis O. However, the number, arrangement, and shape of the arm portions 48 are not limited to this case.

In each arm portion 48, the radially outer end portion is integrally connected to the inner peripheral portion of the edge portion 47, and the radially inner end portions are integrally connected to each other. Further, a fitting hole 50 disposed coaxially with the central axis O is formed in the connecting portion 49 integrally formed with the inner end portion of each arm portion 48. As described above, the pendulum shaft 41 is fixed in the fitting hole 50 by press fitting, for example.

Further, an adjustment screw (adjustment portion) 51 for adjusting the mass balance around the center axis O of the balance-spring mechanism 40 including the balance spring 43 and the balance-spring 42 is attached to the edge portion 47.

A plurality of these adjustment screws 51 are arranged at intervals in the circumferential direction, and are screwed to the edge portion 47 from the radially outer side, for example. By performing adjustment by removing one or more adjustment screws 51 or the like, the mass balance around the center axis O can be adjusted, and so-called unbalance (mass imbalance) can be reduced.

The adjusting portion for adjusting the mass balance is not limited to the adjusting screw 51, and for example, a film body that is easily cut may be formed on the surface (upper surface, lower surface, or outer peripheral surface) of the balance 42, and the film body may be used as the adjusting portion. In this case, by scraping off a part of the film body, the mass balance around the center axis O can be adjusted as well.

(Structure of hairspring)

The hairspring 43 includes: the inner end 61 is fixed to the hairspring body 60 of the balance staff 41 via the inner post 46; and a balance weight 65 and an auxiliary weight 66 mounted on balance spring body 60.

The hairspring body 60 is a thin plate spring made of nb—mo alloy described below, and is formed in a spiral shape when viewed in the axial direction of the balance staff 41.

Specifically, in a polar coordinate system having the center axis O as the origin, the hairspring body 60 is formed in a spiral shape along an archimedes curve. As a result, the hairspring body 60 is wound so as to be adjacent to each other at substantially equal intervals in the radial direction with a plurality of turns as viewed in the axial direction of the balance staff 41.

In the illustrated example, the hairspring body 60 is formed by winding out the connecting portion between the inner end portion 61 and the inner post 46 along the archimedes curve as the winding-out position, and has 14 turns, but the illustrated example is an example, and an appropriate number of turns may be selected according to the movement.

In the hairspring body 60, a part of the outermost peripheral portion (14 th turn) is radially outwardly distant via a modified portion 63, and an arc portion 64 formed to have a larger radius of curvature than the other portions is provided. The end of the circular arc portion 64 is an outer end 62 of the hairspring body 60, and is fixed to an outer post 67 attached via an outer post clip, not shown. Further, the outer piles 67 are shown by two-dot chain lines in the respective drawings.

Composition of hairspring "

The hairspring 43 of the present embodiment is composed of an Nb-Mo alloy containing Mo in an amount of 5% to 14% by at%. More specifically, hairspring 43 is composed of an Nb-Mo alloy containing Mo in an amount of 5% or more and 14% or less in at%, and the balance is composed of unavoidable impurities and Nb.

The nb—mo alloy constituting hairspring 43 preferably contains 9% to 13% Mo in at%, and most preferably contains 9.5% to 12% Mo.

Any element of oxygen, nitrogen, hydrogen, and carbon may be contained in the nb—mo alloy as an unavoidable impurity. The oxygen content as an unavoidable impurity is preferably 0.6at% or less, more preferably 0.41at% or less. The nitrogen content as an unavoidable impurity is preferably 0.05at% or less, more preferably 0.033at% or less. The hydrogen content as an unavoidable impurity is preferably 0.7at% or less, more preferably 0.46at% or less. The carbon content as an unavoidable impurity is preferably 0.5at% or less, more preferably 0.39at% or less.

In addition, in addition to these impurities, in the Nb-Mo alloy constituting hairspring 43, nb master alloy or Mo master alloy is used as a raw material when the Nb-Mo alloy is melted. When these master alloys are used as raw materials, as impurities derived from the raw materials, 0.007at% or less of iron (Fe), 0.05at% or less of tantalum (Ta), 0.0005at% or less of nickel (Ni), and 0.0008at% or less of tungsten (W) may be contained.

Further, in addition to the above elements, elements such as titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), hafnium (Hf), platinum (Pt), palladium (Pd), and silicon (Si) may be contained.

In the case of manufacturing a hairspring composed of the nb—mo alloy of the above composition, the alloy of the above composition is melted, and the obtained cast material is subjected to wire drawing processing to produce a wire rod having a desired thickness and cross-sectional shape.

In the case of wire drawing, it is preferable to perform intermediate heat treatment. For example, the wire rod is subjected to a wire drawing process for a necessary number of times, and then heated to about 950 ℃ to 1200 ℃ after the wire drawing process, whereby a wire rod having a target cross-sectional shape and a target wire diameter can be finally obtained. After the coil is processed to a target wire diameter, the coil is rolled to a target thickness, then formed into a target spring shape, and heat-treated at a temperature range of about 700 to 1000 ℃ for about several hours, whereby a hairspring having an increased <110> ||{001} orientation degree of the processed texture occupied in the cross-sectional area can be produced. In addition, when the heat treatment temperature is lower than 700 ℃, a shape crease as a spring cannot be imparted to the hairspring.

For example, a wire rod having a diameter of about 1.0mm may be subjected to drawing for a necessary number of times until a target wire diameter of 0.5mm, 0.3mm, 0.05mm, or the like is achieved.

Among the nb—mo alloys having the above composition, alloys having a composition containing Mo of 5% to 14% by at% have a worked texture formed by plastic working such as rolling or wire drawing.

As an example of the processing texture, when observing the cross section of hairspring 43, the area of the processing texture having the <110> ||{001} orientation degree is preferably made to occupy 30% or more of the entire cross section. Of course, the textured area may be a higher range or may be a 100% tissue of the entire cross-section.

In the Nb-Mo alloy of the above composition, the average KAM value is preferably in the range of 1.0 to 4.0. KAM values are measurement values that can be obtained by crystal orientation analysis based on an electron beam back scattering diffraction image (EBSD) method using a scanning electron microscope. The crystal orientation measuring device attached to a scanning electron microscope observes, for example, a range of 1000 μm×1000 μm so that tens of crystal grains are contained in a measuring region of a sample cross section. Then, in this observation range, KAM values, which are orientation differences between measurement points within the same crystal grain, are measured, and thus an average KAM value can be obtained. The average KAM value can be said to be an average of the orientation differences of the pixel of interest and the neighboring pixels within the observed image.

The Nb-Mo alloy of the above composition has a low and stable temperature coefficient.

The first temperature coefficient (C1) of the balance spring made of Nb-Mo alloy of the above composition can be calculated by the formula c1= (difference rate ₃₈ -difference rate ₈ )/(38-8)[s/d/℃]Preferably within + -2.0, more preferably within + -0.5.

The second temperature coefficient (C2) of the balance spring made of Nb-Mo alloy of the above composition can be calculated by the formula c2= (difference rate ₃₈ -difference rate ₂₃ )/(38-23)[s/d/℃]Preferably within + -2.0, more preferably within + -0.5.

The third temperature coefficient (C3) of the balance spring made of Nb-Mo alloy of the above composition can be calculated by the formula c3= (difference rate ₂₃ -difference rate ₈ )/(23-8)[s/d/℃]Preferably within + -2.0, more preferably within + -0.5.

Fig. 5 shows the temperature characteristics of the balance spring shown in fig. 3 and 4, which is made of Nb-9at% mo alloy.

Fig. 6 shows the temperature characteristics of the balance spring shown in fig. 3 and 4, which is made of Nb-11at% mo alloy.

Fig. 7 shows the temperature characteristics of the balance spring shown in fig. 3 and 4, which is made of Nb-13at% mo alloy.

In the temperature characteristic, the first temperature coefficient (C1) and the second temperature coefficient (C2) may be calculated as shown in table 1 below according to the relationships shown in fig. 5, 6, and 7 and the above calculation formulas. The calculation results of C1 and C2 of the Nb-10at% Mo alloy obtained by the same method are also shown in Table 1 below.

TABLE 1

	C1[s/d/℃]	C2[s/d/℃]
			Nb-9at% Mo alloy	-1.49	-1.68
Nb-10at% Mo alloy	0.34	0.49
			Nb-11at% Mo alloy	0.62	0.65
Nb-13at% Mo alloy	1.08	1.29

Fig. 8 shows Mo concentration dependence of temperature coefficients (C1, C2) in nb—mo alloy of respective compositions (Mo content: 9at%, 11at%, 13 at%) obtained in advance from the relationships shown in fig. 5 to 7.

As is clear from the results shown in Table 1 and FIG. 8, the first temperature coefficient and the second temperature coefficient may be within.+ -. 2.0 in the case of Nb-Mo alloy containing 9 to 13at% of Mo.

Fig. 9 shows Mo concentration dependence of temperature coefficients (C1, C2, C3) obtained as described above from test results of the samples having the compositions shown in fig. 5 to 7 and the samples having other compositions.

As is clear from the results shown in fig. 9, the nb—mo alloy constituting the hairspring 43 can suppress the temperature coefficient within the range of ±2.0[ s/d/°c ] by containing Mo of 9at% or more and 13at% or less. Further, it is found that the temperature coefficient can be suppressed within a range of.+ -. 0.8[ s/d/. Degree.C ] by containing 9.5at% to 12.5at% Mo in the Nb-Mo alloy.

Further, it is also found that, when only the temperature coefficients C1 and C2 are considered, the Nb-Mo alloy can be suppressed to within a temperature coefficient of + -0.5 [ s/d/. Degree.C ] by containing 9.5at% to 12.5at% of Mo.

FIG. 10 shows the results of examining the relationship between the temperature coefficient of the difference in Nb-11at% Mo alloy and the average KAM value.

As can be seen from the results shown in fig. 10, the temperature coefficient of the difference can be adjusted when the average KAM value is adjusted.

Fig. 11 is a graph showing the results of obtaining the Mo concentration dependence of the temperature coefficient in the range of 5 to 13at% of Mo content. The nb—mo alloy is known to have a temperature coefficient within ±4.0 when the Mo content is within a range of 5 to 13 at%.

FIG. 12 shows the relationship between the temperature coefficient of the difference in balance springs made of Nb-9at% Mo alloy and the average KAM value.

Fig. 13 shows the relationship between the temperature coefficient of the difference in the balance spring made of Nb-10at% mo alloy and the average KAM value, and fig. 14 shows the relationship between the temperature coefficient of the difference in the balance spring made of Nb-13at% mo alloy and the average KAM value.

By observing any of these graphs shown in fig. 10 to 14, it can be seen that the temperature coefficient of the difference can be adjusted when the average KAM value is adjusted, similarly to the Nb-11at% Mo alloy described above.

Fig. 15 shows the results of measuring the relationship between the etching time and the temperature coefficient of young's modulus (TCE) using a hydrofluoric acid-nitric acid mixed solution, with respect to a hairspring made of Nb-11at% mo alloy having the cross-sectional shapes shown in fig. 17 to 20.

The cross-sectional-shape hairspring shown in fig. 17 shows a cross-section in an unetched state, the cross-sectional-shape hairspring shown in fig. 18 shows a 24-second-etched cross-section, the cross-sectional-shape hairspring shown in fig. 19 shows a 48-second-etched cross-section, and the cross-sectional-shape hairspring shown in fig. 20 shows a 72-second-etched cross-section.

The hairspring shown in fig. 18 to 20 shows each sample section when the whole hairspring is immersed in an etching liquid, and the periphery is gradually removed and the hairspring is processed to be thin. As shown in fig. 15, a temperature coefficient of a lower young's modulus can be obtained in any sample.

Fig. 17 to 20 show results of investigating how the machined texture (< 110> || {001} oriented region) is generated in the cross section when the cross section of the hairspring is observed by EBSD analysis.

As shown in fig. 17, the central region of the hairspring presents dark and longitudinally long regions with a machined texture, which are regions in cross section with <110> ||{001} degree of orientation. It can be seen that the area occupied by the machined texture can be gradually increased as the etching proceeds to gradually remove the outer peripheral side of the hairspring.

Fig. 16 shows that there is <110> | in each hairspring sample shown in fig. 17 to 20. Area ratio of the region of the {001} orientation degree with respect to the total area of the cross section.

As shown in fig. 16, 60% of the total cross-sectional area in the sample of fig. 17 is the processed texture, 58% of the total cross-sectional area in the sample of fig. 18 is the processed texture, 63% of the total cross-sectional area in the sample of fig. 19 is the processed texture, and 68% of the total cross-sectional area in the sample of fig. 20 is the processed texture.

It follows that the area ratio of the processing texture relative to the total cross-sectional area of the balance spring can be adjusted by etching.

Fig. 21 shows the results of obtaining the <110> ||{001} orientation degree in the working ratio and the RD direction (rolling direction) in the case where the Nb-5at% mo alloy (MN 5), the Nb-7at% mo alloy (MN 7), and the Nb-13at% mo alloy (MN 13) were wire-drawn respectively.

In fig. 21, the degree of <110> ||{001} orientation in the RD direction does not significantly change until the processing rate is about 90%, but when the processing rate exceeds 90%, the degree of <110> || {001} orientation in the RD direction greatly increases. In particular, the <110> ||{001} orientation degree in the RD direction is 45 to 90% in the range of 95 to 99% of the processing rate.

As is clear from the results shown in fig. 21, when the nb—mo alloy is plastic worked, the degree of orientation of <110> ||{001} in the RD direction in the hairspring can be adjusted to 45 to 90% by setting the working ratio to the range of 95 to 99%.

That is, when the nb—mo alloy is subjected to plastic working, the degree of orientation of the worked texture can be adjusted by setting the working ratio to 95 to 99%, and the composition ratio can be set to correspond to the amount of residual strain introduced according to the working ratio.

In this way, in the case of the alloy described above, it is possible to provide a hairspring in which the temperature coefficient can be adjusted in consideration of actual processing, and in which KAM values can be adjusted to a desired range and the temperature coefficient can be adjusted to a desired range by optimizing processing texture and residual strain amount.

< Structure of timepiece of the second embodiment >

The basic structure of the timepiece of the second embodiment is the same as that of the timepiece of the first embodiment described above.

In the structure of the second embodiment, the difference from the structure of the first embodiment is in the structure of the hairspring. As shown in fig. 22, the hairspring of the second embodiment has: a substrate 100; a first oxide film layer 101 covering the outer peripheral surface of the substrate 100; and a second oxide film layer 102 covering the outer peripheral surface of the first oxide film layer 101.

The substrate 100 is composed of the nb—mo alloy described previously. The first oxide film layer 101 contains or is composed of Mo, nb, and O. For example, the first oxide film layer 101 may be formed of Mo oxide and Nb oxide. Alternatively, the Nb oxide layer may be formed of an oxide film layer in which Mo oxide is mixed.

The first oxide film layer 101 is formed of a film of metal oxide. As an example, nb—mo alloy is formed by anodic oxidation or thermal oxidation in an oxygen mixed gas atmosphere. The coating layer 101 is formed of a mixture of Nb oxide film and Mo oxide film. In addition, the first oxide film layer 101 may contain an electrolyte component, and for example, when the anodic oxidation treatment is performed in a phosphoric acid aqueous solution, the film layer 101 may contain phosphate ions or the like.

The second oxide film layer 102 is formed of a film of metal oxide. The Nb-Mo alloy is formed by anodic oxidation or thermal oxidation under the atmosphere of oxygen mixed gas. The second oxide film layer 102 is formed of an Nb oxide film. In addition, the second coating layer 102 may contain an electrolyte component, for example, phosphate ions or the like when the anodic oxidation treatment is performed in a phosphoric acid aqueous solution.

Further, as an example, the boundaries of the first oxide film layer 101 and the second oxide film layer 102 may be clearly distinguished, or may have a continuous structure in which a gradient of concentration forming a gradient of the element contained therein is formed at the boundaries of the respective layers.

The total film thickness of the first film layer 101 and the second film layer 102 is, for example, 10 to 300nm.

If the total film thickness is within the above range, the change with time of the difference rate due to natural oxidation of the hairspring can be suppressed. Even in the above range, an oxide film layer exhibiting a highly decorative interference color can be produced when the total film thickness is 140 to 250 nm.

The method for forming the oxide film layer may be any one of an anodic oxidation method and a thermal oxidation method in an oxygen mixed gas atmosphere.

"Forming oxide film layer by anodic oxidation"

An example of the anodic oxidation method is a method in which a hairspring made of nb—mo alloy is immersed in a 1% phosphoric acid aqueous solution and a voltage is applied at a weak current.

As an example, the applied voltage is slowly increased to about 65V, and when about 65V is reached, the process is continued until the amount of current is no longer changed. By this treatment, an oxide film layer of about 160nm can be formed on the hairspring, and the oxide film layer thus obtained has a bluish violet color.

The electrolyte for the anodic oxidation treatment may be sulfuric acid, ammonia water or the like, in addition to phosphoric acid.

The applied voltage may be any value, but it is preferable to consider a balance among film thickness, aesthetic appearance, and operation safety. Among them, it is preferable to perform the anodic oxidation treatment under an applied voltage of 30 to 35V or 60 to 75V to present a color tone considered to have a high-quality feel in the mechanical wristwatch, that is, an interference color of blue or violet.

In the samples produced by the same composition, the same processing rate, and the same heat treatment, the thicker the oxide film thickness, that is, the higher the applied voltage, the greater the barrier effect against oxygen in the atmosphere, and therefore the greater the effect of suppressing the variation of the difference rate with time. Further, the thicker the oxide film thickness is, the smaller the temperature coefficient of young's modulus is. The reason why the temperature coefficient of Young's modulus becomes smaller is as follows.

As shown in an IPF diagram based on SEM-EBSD analysis of fig. 23, the crystal orientation in the RD section of the balance spring made of Nb-Mo alloy was oriented at <110> at the center portion and the outermost surface, and at random at the center portion and the middle portion of the outermost surface. In the temperature range used as a timepiece, the temperature coefficient of young's modulus of metals and alloys is a negative value in many cases.

On the other hand, in the nb—mo alloy, as the <110> degree of orientation of the cross section becomes higher, the temperature coefficient of young's modulus becomes positive. Therefore, the temperature coefficient of young's modulus can be reduced by decreasing the <110> orientation degree by breaking the <110> orientation layer of the outermost surface of the hairspring by the anodizing treatment.

In view of the above, in order to simultaneously achieve three points of suppressing the change with time of the difference ratio, controlling the temperature coefficient of young's modulus, and improving the aesthetic appearance, it is preferable to set the composition, processing method/processing ratio, and conditions for fixing the heat treatment temperature of the spiral shape, to manufacture the hairspring so that the temperature coefficient of young's modulus becomes large in the state where the coating layer is not oxidized, and then to perform the anodic oxidation treatment at about 65V.

"formation of oxide film layer by thermal oxidation"

In order to produce a hairspring made of an nb—mo alloy having an oxide film layer by thermal oxidation, a heat treatment of 300 ℃ or higher is performed in a muffle furnace, for example. By this means, a thermally oxidized film can be formed on the hairspring.

The thickness of the oxide film layer depends on the temperature and time of the heat treatment, and for example, when the film is treated in air at 350 ℃ for 20 minutes, an oxide film layer of about 50nm is produced, and the oxide film layer exhibits a blue interference color.

The atmosphere gas for the heat treatment may be oxygen or a mixed gas containing oxygen and not corroding the alloy, and examples thereof include air, an oxygen-rare gas (Ar, etc.) mixed gas, and the like.

The heat treatment temperature and time for forming the oxide film layer by the thermal oxidation method may be determined according to the film thickness of the oxide film layer to be formed, and may be performed at a temperature of 300 to 700 ℃ for a time period of 1 minute to 12 hours.

The effect obtained by the thermal oxidation method is the same as in the case of anodic oxidation, the temperature coefficient of young's modulus can be controlled, and the beauty can be improved by interference colors.

The difference between the first coating layer 101 and the second coating layer 102 can be distinguished from the bright field image of a Scanning Transmission Electron Microscope (STEM) as shown in fig. 24.

In the bright field image of fig. 24, four layers, layer 200, layer 201, layer 202, and layer 203, are formed.

Layer 200 is a hairspring made of nb—mo alloy as a base material, and corresponds to base material 100 in fig. 22. The layers 201 and 202 are oxide film layers corresponding to the first film layer 101 and the second film layer 102, respectively. Layer 203 is an Au protective film coated for STEM observation.

In STEM bright field images, electrons are detected that are transmitted through the sample, so lighter elements appear brighter and heavier elements appear darker. If layer 201 and layer 202 are compared, layer 201 is seen to contain more multiple elements than layer 202 because layer 201 is slightly darker. Further, the element can be specified by combining an energy dispersive X-ray spectroscopy (EDX), and it is found that Nb, mo, and O are contained in the layer 201 (first film layer 101), and Nb and O are contained in the layer 202 (second film layer).

The same STEM observations were made regardless of whether the method of forming the oxide film layer was anodic oxidation or thermal oxidation.

"inhibition effect on variation of differential Rate over time"

In a mechanical timepiece movement using an untreated nb—mo alloy hairspring, as shown in fig. 25, the difference rate increases with the passage of time (the number of days elapsed), and the accuracy deviation after 250 days is about 13 seconds/day.

On the other hand, as shown in fig. 26, the mechanical timepiece movement using the nb—mo alloy hairspring having the oxidized film layer formed by the anodic oxidation method with a film thickness of 160nm according to the application hardly causes a deviation in accuracy due to the lapse of time after 80 days.

Thus, it was found that by forming the first coating layer 101 and the second coating layer 102 on the nb—mo alloy constituting the hairspring, it is possible to provide a hairspring in which the difference rate hardly changes with time. It is also known that a timepiece movement and a timepiece including the hairspring and having little variation in the difference rate can be provided.

(description of the reference numerals)

1a timepiece; 10 movement for timepiece; a 40 balance spring mechanism; 41 pendulum shaft; 42 balance wheel; 43 hairspring; 100 substrates; 101 a first oxide film layer; 102 a second oxide film layer.

Claims (11)

1. A hairspring characterized in that:

the Nb-Mo alloy contains 5-14% Mo in at%.

2. A hairspring characterized in that:

the Nb-Mo alloy contains 5-14% Mo in at%, and the balance is composed of unavoidable impurities and Nb.

3. A balance spring according to claim 1 or claim 2, wherein:

the region having a processed texture and having a <110> ||{001} degree of orientation in the cross section accounts for 30% or more of the total cross section.

4. A balance spring according to claim 1 or claim 2, wherein:

the average KAM value is 1.0 to 4.0.

5. A balance spring according to claim 3, wherein:

the average KAM value is 1.0 to 4.0.

6. A balance spring according to claim 1 or claim 2, wherein:

the substrate is composed of the Nb-Mo alloy, the first oxide film layer contains Nb, mo and O, and the second oxide film layer contains Nb and O.

7. A balance spring according to claim 3, wherein:

the substrate is composed of the Nb-Mo alloy, the first oxide film layer contains Nb, mo and O, and the second oxide film layer contains Nb and O.

8. A balance spring according to claim 4, wherein:

the substrate is composed of the Nb-Mo alloy, the first oxide film layer contains Nb, mo and O, and the second oxide film layer contains Nb and O.

9. A balance spring according to claim 5, wherein:

the substrate is composed of the Nb-Mo alloy, the first oxide film layer contains Nb, mo and O, and the second oxide film layer contains Nb and O.

10. A timepiece movement, comprising:

a balance spring as claimed in any one of claims 1 to 9; a pendulum shaft; a balance wheel; a balance spring mechanism.

11. A timepiece, characterized in that:

a timepiece movement having the structure of claim 10.