Clockwork oscillating weights and clocks

Abstract

The present invention provides a watch rotor and a watch that can be plated uniformly while maintaining the strength of the rotor. [Solution] The watch rotor comprises a tungsten sintered body mainly composed of tungsten and a plating layer formed on the surface of the tungsten sintered body, wherein each tungsten particle of the tungsten sintered body has a maximum diameter of 50 μm or less and has a polycrystalline structure containing multiple crystal grains. The watch is characterized by comprising a watch rotor.

Description

Technical Field

[0001] The present invention relates to a rotating weight for a clock and a clock having the rotating weight for a clock.

Background Art

[0002] Patent Document 1 discloses a clock incorporating a rotating weight for a clock used for power generation or winding a spring. The manufacturing process for manufacturing the rotating weight for a clock disclosed in Patent Document 1 includes a blank forming process and a secondary processing process. In the blank forming process, a compound mainly composed of heavy metal powder such as tungsten is molded and sintered to form a rotating weight blank in which a rotating weight body part and a rotating heavy weight part are integrated. In the secondary processing process, the appearance of the surface of the rotating weight for a clock is improved by performing surface processing on the rotating weight blank by machining.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to further enhance the ornamentality of the rotating weight for a clock, it is conceivable to apply plating to the surface of the rotating weight for a clock. However, even when plating is applied to the surface of the rotating weight for a clock, the ornamentality may be reduced, such as unevenness occurring. For this reason, there is a demand for a rotating weight for a clock and a clock that can apply plating uniformly while maintaining the strength of the rotating weight for a clock.

Means for Solving the Problems

[0005] The clock rotor of the present disclosure comprises a tungsten sintered body mainly composed of tungsten and a plating layer formed on the surface of the tungsten sintered body, wherein the tungsten particles of the tungsten sintered body have a maximum diameter of 50 μm or less and have a polycrystalline structure containing a plurality of crystal grains.

[0006] The clock of this disclosure is characterized by comprising a clock rotor. [Brief explanation of the drawing]

[0007] [Figure 1] This is a front view showing a clock using a clock rotor according to the first embodiment. [Figure 2] This is a rear view showing a clock using a clock rotor according to the first embodiment. [Figure 3] This is a perspective view showing the rotor for a clock according to the first embodiment. [Figure 4] This is an enlarged cross-sectional view showing the main part of the rotor for a watch according to the first embodiment. [Figure 5] This is a flowchart showing the manufacturing process for a watch rotor according to the first embodiment. [Figure 6] This is a photograph showing a cross-section of the tungsten sintered body that constitutes the rotor for a watch in the first embodiment. [Figure 7] This is a photograph showing a magnified cross-section of the tungsten sintered body in Figure 6. [Figure 8] This is a photograph showing a cross-section of a conventional tungsten sintered body. [Figure 9] This is a photograph showing a magnified cross-section of the tungsten sintered body in Figure 8. [Figure 10] This is a perspective view showing the rotor for a clock according to the second embodiment. [Figure 11] This figure shows the conditions and evaluation results for the examples and comparative examples. [Modes for carrying out the invention]

[0008] [First Embodiment] The clock 1 according to the first embodiment will be described below with reference to the drawings. Figure 1 is a front view of watch 1, and Figure 2 is a rear view of watch 1. Watch 1 in this embodiment is a wristwatch worn on the user's wrist and comprises a cylindrical outer case 2, with a dial 3 positioned on the inner circumference of the outer case 2. Of the two openings in the outer case 2, the opening on the front side is covered with a cover glass, and the opening on the back side is covered with a case back 9. The case back 9 consists of a ring-shaped frame 9A and a case back glass 9B attached to the frame 9A. The outer case 2 houses a movement 10 powered by a mainspring (not shown), and also contains a watch rotor 20 that constitutes an automatic winding mechanism for winding the mainspring. The watch movement 10, which includes the mainspring and watch rotor 20, is a typical movement with a base plate and gear train bridge 14, so its description is omitted. The outer case 2, cover glass, and case back 9 constitute the exterior components of the watch 1, sealing the internal space that houses the movement 10. A crown 7 is provided on the side of the outer case 2.

[0009] As shown in Figures 1 and 2, the watch 1 includes an hour hand 4, a minute hand 5, and a second hand 6 that indicate the time, as well as a first power reserve hand 33 and a second power reserve hand 34. The dial 3 is provided with a calendar window 3A, through which the date wheel 8 can be seen. The dial 3 is provided with a fan-shaped first scale section 31, which is indicated by the first power reserve hand 33. The gear train bridge 14 is provided with a fan-shaped second scale section 32, which is indicated by the second power reserve hand 34. The second scale section 32 and the second power reserve hand 34 are visible through the case back glass 9B of the case back 9. The power reserve hands 33 and 34 indicate the remaining winding amount of the mainspring by pointing to the scales 31 and 32. In this embodiment, the watch 1 has scales 31 and 32 and power reserve hands 33 and 34 on the front and back sides respectively, but the scales and power reserve hands may be provided on only one side.

[0010] As shown in FIGS. 3 and 4, the rotating weight 20 for a watch includes a rotating weight main body 21 made of a tungsten sintered body having tungsten as a main component, and a plating layer 25 formed on the surface of the rotating weight main body 21 which is a tungsten sintered body. Since tungsten has a high specific gravity, it is suitable as a material for the rotating weight 20 for a watch. As shown in FIG. 3, the rotating weight main body 21 includes a rotating weight body portion 22 and a rotating heavy weight portion 23. The rotating weight body portion 22 includes a central shaft portion 220 and two connecting portions 225. The central shaft portion 220 is formed in a substantially ring shape, and a rotation center hole 221 is formed at the center of the plane. A ball bearing 15 serving as a rotating shaft portion is provided on the wheel train receiver 14. This ball bearing 15 is fitted into the rotation center hole 221, and the central shaft portion 220 is rotatably supported with respect to the wheel train receiver 14 by the ball bearing 15. That is, the inner ring of the ball bearing 15 is attached to the wheel train receiver 14, and the central shaft portion 220 is fixed to the outer ring that rotates via balls with respect to this inner ring. Further, a gear is also formed on the outer ring, and the winding wheel train of the spring is engaged with this gear. Each connecting portion 225 extends from the central shaft portion 220 and connects the central shaft portion 220 and the rotating heavy weight portion 23.

[0011] The rotating heavy weight portion 23 is disposed on the outer peripheral side of the rotating weight body portion 22, and its outer periphery is formed in an arc shape centered on the rotation axis of the rotating weight 20 for a watch. Both ends of the rotating heavy weight portion 23 are connected to the respective connecting portions 225. As shown in FIG. 4, the rotating heavy weight portion 23 is formed to be thicker than the rotating weight body portion 22, and is further formed to be thicker stepwise toward the outer peripheral side. Therefore, the rotating weight 20 for a watch is configured such that the amount of weight imbalance is large and it rotates easily by moving the arm wearing the watch 1.

[0012] A through hole 24 is formed between the respective connecting portions 225 of the rotating weight body portion 22. The through hole 24 is partitioned and formed by the central shaft portion 220 of the rotating weight body portion 22, the two connecting portions 225, and the rotating heavy weight portion 23.

[0013] As described above, the rotating weight body 21 is integrally manufactured from a tungsten sintered body mainly composed of tungsten. A plating layer 25 is laminated on the surface of the rotating weight body 21. The plating material constituting the plating layer 25 is a metal material such as copper, nickel, gold, silver, platinum, etc. The plating layer 25 is formed on the entire surface of the rotary weight 20 for a watch by wet plating.

[0014] Next, the manufacturing method of the rotary weight 20 for a watch will be described with reference to the flowchart of FIG. 5. First, a raw material preparation step S1 of preparing the powder that becomes the raw material of the rotary weight 20 for a watch is executed. The powder prepared as the raw material of the rotary weight 20 for a watch is a powder of W (tungsten) as the main raw material and powders of Ni (nickel), Cu (copper), Fe (iron), Co (cobalt), etc. as binder materials. Further, as the tungsten powder, a high-purity powder with a purity of 99.9% is used. Next, a kneading step S2 of mixing each powder at a predetermined mass ratio, adding a resin binder, and kneading using a kneader is executed. The mass ratio of each powder can be set as appropriate. For example, nickel may be 3.0% by mass, copper may be 1.5% by mass, and tungsten may be the remaining 95.5% by mass, etc. It is sufficient to set tungsten, which is the main raw material, to about 95.5% by mass.

[0015] Next, a molding step S3 of obtaining a molded body from the material kneaded in the kneading step S2 by injection molding, unidirectional pressing, or the like is executed. Next, a degreasing step S4 of gasifying and removing the resin binder by heating the molded body to around 1000°C in a vacuum atmosphere or in a state where argon gas is injected into the vacuum atmosphere is executed. Next, the molded body is heated in a vacuum atmosphere or in a vacuum atmosphere with hydrogen gas injected to perform the main sintering process, and a sintering process S5 is carried out to produce a tungsten sintered body with a relative density of 99% or more as a blank for a watch rotor 20. In this sintering process S5, the sintering temperature and sintering time are adjusted in order to suppress the size of the tungsten particles and to create a polycrystalline structure. Specifically, the sintering temperature is set to a predetermined temperature in the range of 1300°C or higher and 1380°C or lower, and the sintering time is adjusted to a predetermined time in the range of 60 to 70 minutes. On the other hand, conventionally, tungsten raw material powder with a purity of about 98-99% was used, and the sintering process was carried out by setting the sintering temperature to 1380°C or higher and the sintering time to 60-70 minutes, or by setting the sintering temperature to 1380°C or lower and the sintering time to 100 minutes or more. In other words, when the sintering time was shortened, the sintering temperature was increased, and when the sintering temperature was lowered, the sintering time was increased.

[0016] Figures 6 to 9 are photographs showing cross-sections of tungsten sintered bodies. Figure 6 is a photograph showing a cross-section of the tungsten sintered body 50 of the first embodiment, and Figure 7 is a magnified photograph of the cross-section of the tungsten sintered body 50. Figure 8 is a photograph showing a cross-section of a conventional tungsten sintered body 60, and Figure 9 is a magnified photograph of the cross-section of the tungsten sintered body 60. In this embodiment, by using tungsten raw material powder with a purity of 99.9%, both a reduction in sintering temperature and a reduction in sintering time were achieved. As a result, as shown in Figure 6, the size of the tungsten particles 51 in the tungsten sintered body 50 is 10 to 50 μm, meaning the maximum diameter is 50 μm or less. As shown in Figure 6, the tungsten sintered body 50 is composed of multiple tungsten particles 51, and each tungsten particle 51 is bonded to other adjacent tungsten particles 51. In this case, as shown in Figure 7, the crystalline state of each tungsten particle 51 is a polycrystalline structure containing multiple crystal grains 52. A crystal grain 52 is a crystalline structure in which atoms are arranged regularly, and it represents a mass (unit) where the arrangement of crystal structures is uniform, and the crystal orientation within a single crystal grain 52 is the same. Therefore, at the bonding portions between adjacent tungsten particles 51, each crystal grain 52 is bonded to the others, and the bonding surface is zigzag. When stress is applied to the bonding surface of the tungsten particle 51, the bonding surface is not cut in a straight line but in a zigzag pattern, thus increasing toughness. As a result, the bonding state of the tungsten particles 51 can be strengthened, and the strength of the tungsten sintered body 50 can be improved. Furthermore, the gaps between the tungsten particles 51 are binder portions 53 composed of nickel, copper, iron, etc., added as binder materials. Since the maximum diameter of the tungsten particles 51 is set to 50 μm or less, the volume of the gaps between the tungsten particles 51, i.e., the binder portions 53, can also be made small. This prevents cracks from forming between the tungsten particles 51 and the binder portions 53, and in this respect as well, the strength of the tungsten sintered body 50 can be improved.

[0017] On the other hand, in conventional tungsten sintered bodies 60, the purity of the tungsten raw material powder was sometimes around 98.0-99.0%, so the sintering temperature in the sintering process S5 was increased or the sintering time was extended. As a result, as shown in Figure 8, the tungsten particles 61 grew, and their size became larger than that of the tungsten particles 51 in Figure 6. Also, as shown in Figure 9, the crystal grains within the tungsten particles 61 became single crystals, and the crystal structure of each tungsten particle 61 became a single crystal structure. Therefore, at the bonding areas between adjacent tungsten particles 61, the single crystal structure of the tungsten particles 61 bonded together, resulting in a linear bonding surface. When stress is applied to the bonding surface of the tungsten particles 61, the bonding surface is cut linearly, resulting in a decrease in bonding strength compared to the bonding state between tungsten particles 51. As a result, the strength of the tungsten sintered body 60 is lower than that of the tungsten sintered body 50. Furthermore, the gaps between the tungsten particles 61 are also binder portions 63 made of nickel, copper, iron, etc. Because the maximum diameter of the tungsten particles 61 is larger than that of the tungsten particles 51, the volume of the gaps between the tungsten particles 61, i.e., the binder portions 63, also increases, making it easier for cracks to form between the tungsten particles 61 and the binder portions 63. In this respect as well, the strength of the tungsten sintered body 60 is lower than that of the tungsten sintered body 50.

[0018] Next, as shown in Figure 5, a processing step S6 is performed to shape a blank product made of a tungsten sintered body 50, in which polycrystalline tungsten particles 51 are bonded together, into a component shape for a watch rotor 20 by cutting and polishing. Next, a plating process S7 is performed to form a plating layer 25 of a thin metallic film for decoration on the surface of the watch rotor 20 by wet plating such as electroplating. The metal used as the plating material is, for example, nickel, copper, gold, silver, or platinum, and the plating layer 25 is formed on the entire surface of the watch rotor 20. In the tungsten sintered body 50, the tungsten particles 51 have a polycrystalline structure containing various crystal grains 52. As a result, the tungsten sintered body 50 as a whole is electrically uniform, and a plating layer 25 can be formed on the entire surface of the tungsten sintered body 50 by electroplating. That is, because each crystal grain 52 has a different crystal orientation, the electrical resistance value varies, and the thickness of the plating layer 25 on the surface of each crystal grain 52 also varies. However, since the size of each crystal grain 52 is small, about 1 to 5 μm, the variation in each tungsten particle 51 and the plating layer 25 on the surface of the tungsten sintered body 50 is negligible, and the thickness dimension of the plating layer 25 on the entire tungsten sintered body 50 is approximately uniform, thereby enhancing the decorative properties of the plating layer 25. Furthermore, the tungsten content in the rotor body 21 integrally formed from the tungsten sintered body 50 is 90% by mass or more. Because it contains a large amount of tungsten, which has a high specific gravity, the weight of the watch rotor 20 can be increased.

[0019] On the other hand, in conventional tungsten sintered bodies 60, the tungsten particles 61 have a single-crystal structure, resulting in an electrically non-uniform state for the tungsten sintered body 60 as a whole. Even if a plating layer is formed on the binder portion 63 by electroplating, the plating layer may not be formed on the tungsten particles 61, making it impossible to form a plating layer over the entire surface of the tungsten sintered body 60. In other words, since the tungsten particles 61 are single crystals and each tungsten particle 61 has a different crystal orientation, the electrical resistance also varies from tungsten particle 61 to tungsten particle 61. This can lead to variations in the thickness of the plating layer on the surface of each tungsten particle 61, or uneven plating, making it difficult to enhance the decorative properties of the plating layer.

[0020] The rotor 20 for the watch manufactured through the above process is incorporated into the movement 10, and the watch 1 can be manufactured by incorporating this movement 10 into the outer case 2.

[0021] [Effects of the First Embodiment] The watch rotor 20 comprises a rotor body 21 made of a tungsten sintered body 50 mainly composed of tungsten, and a plating layer 25 formed on the surface of the rotor body 21. Each tungsten particle 51 of the tungsten sintered body 50 has a maximum diameter of 50 μm or less and has a polycrystalline structure containing multiple crystal grains 52, thereby increasing the strength of the watch rotor 20. As a result, the toughness required for a watch rotor 20 can be ensured, making the watch rotor 20 less likely to break when the watch 1 is dropped. Furthermore, by giving the tungsten particles 51 a polycrystalline structure, a plating layer 25 can be formed over the entire surface of the watch rotor 20. This prevents uneven plating and other defects from occurring on the surface of the watch rotor 20, thus preventing a decrease in appearance. A uniform plating layer 25 can be formed over the entire surface of the watch rotor 20, improving the aesthetic appeal of the watch rotor 20. Moreover, since the plating layer 25 functions as a protective film, corrosion of the watch rotor 20 can be prevented.

[0022] Because the strength of the watch rotor 20 can be increased, the connecting portion 225 of the rotor body 22 can be made thinner. This enhances the aesthetic appeal of the watch rotor 20. In addition, the size of the through hole 24 formed between the connecting portions 225 can be increased, allowing the second scale portion 32, the second power reserve hand 34, and other watch components such as the mainspring, escape wheel, and lever, which are located on the back side of the watch rotor 20, to be easily visible from the case back 9 side.

[0023] Since the rotor body 21 is integrally formed from a rotor body portion 22 and a rotating weight portion 23 made of a tungsten sintered body 50, a plating layer 25 can be formed over the entire rotor body 21 in a single plating process S7, reducing the work efficiency and cost of the plating process S7. Furthermore, because the entire rotor body 21 is made of the same material, the appearance, such as color, can be unified by forming the plating layer 25, improving the design of the watch rotor 20. Furthermore, since the rotor body 21, which is integrally formed from a tungsten sintered body 50, has a tungsten content of 90% by mass or more, the weight of the watch rotor 20 can be increased compared to, for example, a case where only the rotating weight portion 23 is made of a tungsten sintered body and the rotor body portion 22 is made of a metal such as stainless steel, and the winding efficiency of the mainspring can also be improved.

[0024] [Second Embodiment] Next, the clock rotor 40 according to the second embodiment will be described with reference to Figure 10. The watch rotor 40 comprises a rotor body 41 and a plating layer 45. The rotor body 41 comprises a rotor body 42 made of stainless steel or the like, and a rotating weight 43 made of a tungsten sintered body. The rotor portion 42 is formed in a thin, roughly fan-shaped plate form and comprises a central shaft portion 420, three connecting portions 425, and a roughly arc-shaped outer edge portion 427. The central shaft portion 420 has a rotating center hole 421 into which the shafts of the gears of the winding gear train that winds the mainspring are fitted. The connecting portions 425 extend from the central shaft portion 420 and connect the central shaft portion 420 to the outer edge portion 427. Through holes 44 are formed between each connecting portion 425 of the rotor portion 42. Each through hole 44 is demarcated by the central axis portion 420, the connecting portion 425, and the outer edge portion 427 of the rotor portion 42.

[0025] The rotating weight portion 43 is positioned on the outer circumference of the rotating weight portion 42, and its outer circumference is formed in an arc shape centered on the rotation axis of the watch rotor 40. The rotating weight portion 43 comprises a thin flange portion 431 and a weight body portion 432 which is formed to be thicker than the rotating weight portion 42. Therefore, the watch rotor 40 is configured to have a large weight imbalance, and to rotate easily when the arm wearing the watch 1 is moved.

[0026] The rotating weight portion 43 is manufactured from a tungsten sintered body 50, which is mainly composed of tungsten, similar to the first embodiment. The outer edge portion 427 of the rotating weight portion 42 and the flange portion 431 of the rotating weight portion 43 are overlapped and connected and fixed with fastening members 46 such as screws or rivets. The outer edge portion 427 and the flange portion 431 may also be connected with an adhesive or the like. Furthermore, a plating layer 45 is laminated on the surface of the watch rotor 40, which is composed of a rotor body 42 and a rotating weight 43. The plating material constituting the plating layer 45 is a metal material such as copper, nickel, gold, silver, or platinum, as in the first embodiment. The plating layer 45 is formed on the entire surface of the watch rotor 40 by wet plating. In this case, the plating process may be carried out after connecting the rotor body 42 and the rotating weight 43, but since the rotor body 42 and the rotating weight 43 are made of different materials, they may be plated separately and then connected and fixed.

[0027] [Effects of the second embodiment] The clock rotor 40 of the second embodiment can achieve the same effects as the clock rotor 20 of the first embodiment. Since the rotor portion 42 is made of a metal plate such as stainless steel, rotor portions 42 of various designs can be manufactured inexpensively. The rotating weight portion 43 is made of a tungsten sintered body 50 with a high specific gravity, which can improve the winding efficiency of the mainspring by the watch rotor portion 40. Furthermore, since the rotor body 42 and the rotating weight 43 are constructed as separate components, the design variations of the watch rotor 40 can be easily increased. In other words, by combining multiple types of rotor body 42 with different numbers and shapes of connecting parts 425 and through holes 44 with a common rotating weight 43, watch rotors 40 with different designs can be manufactured easily and at low cost.

[0028] [Differentiation] The shape of the watch rotors 20 and 40 is not limited to the above embodiments. For example, the number of connecting parts 225 and 425 is not limited to each of the above embodiments; there may be one, three, or four. Also, the rotor body parts 22 and 42 are not limited to those having through holes 24 and 44; they may be flat plates without through holes. If the rotor body part does not have through holes, it will be less likely to crack, allowing for a smaller thickness and thus reducing manufacturing costs. In the watch rotor 40, the rotor body 42 was made of a metal plate material such as stainless steel, and the rotating weight portion 43 was made of a tungsten sintered body 50. However, the rotor body 42 may also be made of a tungsten sintered body 50, and the rotor body 42 and the rotating weight portion 43 may be connected by a fastening member 46. In other words, the watch rotor only needs to have at least the rotating weight portion made of a tungsten sintered body 50.

[0029] The watch rotors 20 and 40 are not limited to being used for winding the mainspring of a mechanical watch, but may also be used to drive the rotor of a generator in a watch that incorporates a generator. Furthermore, in an electronically controlled mechanical watch that drives the rotor of a generator with a mainspring while simultaneously regulating the rotational speed of the generator rotor, the watch rotors 20 and 40 may be used for winding the mainspring. In addition, although the watch rotors 20 and 40 in the above embodiment are formed to be about half the size of the case back 9, a micro-rotor (watch rotor) about half the size of the watch rotor 20 may also be used. If a watch rotor made of tungsten, which has a high specific gravity, is used as a micro-rotor, winding efficiency can be ensured even if the size of the watch rotor is small.

[0030] [Examples] Next, the examples and comparative examples of this disclosure will be described with reference to Figure 11. Figure 11 shows the manufacturing conditions, manufacturing results, and evaluation results for Examples 1 to 5 and Comparative Examples 1 to 6. Examples 1-5 and Comparative Examples 1-6 were prepared by mixing the metal material powders shown in the raw materials column of Figure 11 in the mass percentages listed in the raw materials column. In the raw materials column, "Bal" in the mass percentage column for tungsten (W) represents the remainder. For example, in Example 1, nickel (Ni) is 3 mass%, and copper (Cu) is 1.5 mass%, so the remainder, tungsten (W), is 100-(3+1.5)=95.5 mass%. Similarly, the mass percentage of tungsten (W) is 95.5 mass% in Examples 2-4, 95.6 mass% in Example 5, 95.5 mass% in Comparative Examples 1, 2, 4-6, and 96.0 mass% in Comparative Example 3.

[0031] As shown in Figure 11, in Examples 1 to 5, the size of the sintered tungsten particles 51 was 10 to 50 μm, the maximum diameter was 50 μm or less, and the crystalline state of the tungsten particles 51 was polycrystalline. Furthermore, the strength evaluation by drop test was rated "A" or "B", and the plating evaluation, which was visually evaluated for uniform appearance, was rated "A" or "B". On the other hand, in Comparative Examples 1 to 6, the purity of the tungsten raw material powder, the sintering temperature in sintering process S5, or the sintering time differ from Examples 1 to 5. As a result, the size of the sintered tungsten particles 61 is 35 to 120 μm, the maximum diameter is 50 μm or more, and the crystalline state of the tungsten particles 61 is single crystal. Furthermore, the strength evaluation by drop test is "B" or "C", and the plating evaluation is "C". Here, a strength evaluation of "C" indicates that the necessary strength for a watch rotor 20 is not secured and it is prone to cracking, a strength evaluation of "B" indicates that the necessary strength for a watch rotor 20 is secured, and a strength evaluation of "A" indicates that even higher strength than "B" is achieved. In addition, a plating evaluation of "C" indicates that the plating layer 25 is not formed on the entire surface of the watch rotor 20 and there are plating inconsistencies, "B" indicates that there may be slight plating inconsistencies, but the plating layer 25 is formed on the entire surface of the watch rotor 20 and the necessary appearance for a watch rotor 20 is obtained, and a plating evaluation of "A" indicates that a uniform plating layer 25 is formed on the entire surface of the watch rotor 20 and high aesthetic appeal is obtained.

[0032] As shown in the examples and comparative examples in Figure 11, it was found that when the purity of the tungsten raw material powder is lower than 99.9% (e.g., 98%, 99%), or when the sintering temperature in the sintering process S5 is high (1400°C or higher), or when the sintering time is long (100 minutes or more), the size of the tungsten particles 61 increases, resulting in a single-crystal state, which can easily lead to reduced strength and uneven plating. On the other hand, by increasing the purity of the tungsten raw material powder to 99.9%, lowering the sintering temperature in the sintering process S5 to 1330-1380°C, and shortening the sintering time to 60-70 minutes, it was confirmed that the size of the tungsten particles 51 could be suppressed, allowing for a polycrystalline state, thereby improving strength and enabling the uniform formation of the plating layer 25. In particular, Examples 1-3 and 5, in which the maximum diameter of the tungsten particles 51 was 40 μm or less, received an "A" rating for the uniform appearance of the plating layer 25 compared to Example 4, in which the maximum diameter was 50 μm or less, confirming that the aesthetic appeal could be further improved.

[0033] [Summary of this disclosure] The clock rotor of the present disclosure comprises a tungsten sintered body mainly composed of tungsten and a plating layer formed on the surface of the tungsten sintered body, wherein the tungsten particles of the tungsten sintered body have a maximum diameter of 50 μm or less and have a polycrystalline structure containing a plurality of crystal grains. According to this disclosure, the bonding strength between tungsten particles in the tungsten sintered body can be increased, making it less likely for cracks to occur between the tungsten particles and the binder. This ensures the necessary strength and toughness for a watch rotor, and makes the rotor less likely to break even if the watch is dropped. Furthermore, a uniform plating layer can be formed on the entire surface of the watch rotor, improving the aesthetic appeal of the watch rotor and preventing corrosion.

[0034] In the clock rotor of the present disclosure, it is preferable that the maximum diameter of the tungsten particles is 40 μm or less. According to this disclosure, since the maximum diameter of the tungsten particles is reduced to 40 μm or less, the uniformity of the plating layer can be further improved, and the design of the watch rotor can be enhanced.

[0035] In the clock rotor according to the present disclosure, it is preferable that the tungsten sintered body comprises a rotor body portion having a rotating central hole and a rotating weight portion disposed on the outer circumference side of the rotor body portion and integrally formed with the rotor body portion. According to this disclosure, since the rotor and rotating weight are integrally formed from a tungsten sintered body, the plating layer can be formed over the entire structure in a single plating process. Therefore, the number of plating processes can be reduced compared to when the rotor and rotating weight are formed separately, and costs can also be reduced.

[0036] In the clock rotor of the present disclosure, the rotor body comprises a central shaft portion in which the rotational center hole is formed, and a plurality of connecting portions connecting the central shaft portion and the rotational weight portion, and through holes may be formed between the connecting portions. According to this disclosure, a through hole can be formed in the rotor portion, thereby enhancing the decorative aspect of the watch rotor. Furthermore, when a see-through case back with a glass case back and a power reserve indicator visible from the case back side are provided, the power reserve indicator can also be seen through the through hole in the rotor portion, thereby improving visibility.

[0037] In the clock rotor of the present disclosure, the tungsten content of the tungsten sintered body is preferably 90% by mass or more. According to this disclosure, by making the tungsten sintered body, in which the rotor and rotating weight are integrally formed, have a tungsten content of 90% by mass or more, the weight of the watch rotor can be increased, and the winding efficiency can be improved.

[0038] The clock of this disclosure is characterized by comprising a clock rotor. According to this disclosure, by incorporating the aforementioned watch rotor, the necessary strength and toughness for a watch rotor can be ensured, and the watch rotor can be made less likely to break even if the watch is dropped. Furthermore, since a uniform plating layer can be formed on the entire surface of the watch rotor, the aesthetic appearance of the watch rotor can be improved and corrosion can be prevented. [Explanation of Symbols]

[0039] 1... Clock, 20... Clock rotor, 21... Rotor body, 22... Rotor body section, 23... Rotating weight section, 24... Through hole, 25... Plating layer, 40... Clock rotor, 41... Rotor body, 42... Rotor body section, 43... Rotating weight section, 44... Through hole, 45... Plating layer, 46... Fastening member, 50... Tungsten sintered body, 51... Tungsten particles, 52... Crystal grains, 53... Binder section, 220... Central shaft section, 221... Rotating central hole, 225... Connecting section, 420... Central shaft section, 421... Rotating central hole, 425... Connecting section, 427... Outer edge section, 431... Flange section, 432... Weight body section.

Claims

1. A watch rotor comprising a tungsten sintered body mainly composed of tungsten, and a plating layer formed on the surface of the tungsten sintered body, The tungsten particles in the tungsten sintered body have a maximum diameter of 50 μm or less and a polycrystalline structure containing multiple crystal grains. A clockwork rotor characterized by the following features.

2. In the clock rotor according to claim 1, The maximum diameter of the tungsten particles is 40 μm or less. A clockwork rotor characterized by the following features.

3. In the clock rotor according to claim 1, The tungsten sintered body is A rotating weight section having a central hole for rotation, The rotating weight portion is provided with a rotating counterweight portion that is positioned on the outer circumference of the rotating weight portion and is formed integrally with the rotating weight portion. A clockwork rotor characterized by the following features.

4. In the clock rotor according to claim 3, The rotating weight portion comprises a central shaft portion in which the rotating center hole is formed, and a plurality of connecting portions that connect the central shaft portion and the rotating weight portion. Through holes are formed between the aforementioned connecting portions. A clockwork rotor characterized by the following features.

5. In the clock rotor according to claim 3, The tungsten content of the tungsten sintered body is 90% by mass or more. A clockwork rotor characterized by the following features.

6. A clock comprising a clock rotor as described in any one of claims 1 to 5.

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