OSCILLATOR FOR CLOCK MOVEMENT

Description

[0001] The invention relates to an oscillator for a watch movement. The invention also relates to a watch movement and a timepiece comprising such an oscillator.

[0002] The accuracy of mechanical watches depends on the stability of the oscillator's frequency, which consists of a balance wheel and a balance spring. However, this frequency is disrupted if the watch is exposed to a magnetic field, resulting in a difference in rate before and after magnetization. This difference can be negative or positive. Regardless of its sign, this difference is called the "residual rate effect" or "residual rate" and is measurable according to the NIHS 90-10 standard. This standard aims to certify wristwatches exhibiting good chronometric performance after exposure to a magnetic field of 4.8 kA / m (60 G). However, the wearer of the watch may encounter magnetic fields of much higher intensities in their daily life, on the order of 32 kA / m (400 G). It is therefore important to minimize this effect for fields of such intensity.

[0003] The vast majority of balance springs are made from Fe-Ni alloys (Nivarox® alloy, for example), whose elastic moduli depend on the state of magnetization. Recent developments have led to the creation of self-compensating balance springs made from paramagnetic materials (Nb-Zr-O alloy, Parachrom® alloy, for example) or diamagnetic materials (silicon coated with a layer of SiO2, for example), which significantly reduce the residual effect for magnetic fields exceeding 4.8 kA / m, as shown in the diagram. figure 1 However, a residual effect remains, particularly for a magnetic field with an intensity significantly greater than 4.8 kA / m, for example 32 kA / m.

[0004] In general, the structure of a balance wheel assembled within an oscillator is as represented by the NIHS 34-01 standard. figure 3 This illustrates such an assembled balance wheel structure. The balance wheel hub is directly attached to the balance staff, for example, by riveting. Its position and seating are ensured by a bearing surface defined by the diameter of a flange on the staff, also called the balance wheel seating diameter according to the terminology of NIHS 34-01. A plate, generally machined from CuBe2, on which a pin is mounted, is pressed onto a portion of the staff whose diameter is substantially smaller than that of the balance wheel seating, independently of the balance wheel hub on the other side of the flange. The ferrule, intended to hold the balance spring, is pressed onto the other side of the flange onto a portion of the staff whose diameter is also substantially smaller than that of the balance wheel seating, as illustrated in figure 2 Such a balance wheel structure has become a benchmark due to its robustness and the resulting simplicity of assembly. This type of assembled balance wheel structure is particularly relevant to any oscillator equipped with a paramagnetic or diamagnetic balance spring. For example, patent CH700032 discloses an oscillator with at least two balance springs, for instance made of silicon, mounted on a balance staff as described above. This oscillator, due to the properties of the material chosen for the balance spring, reduces the residual effect for a magnetic field of approximately 4.8 kA / m, but does not minimize it for a magnetic field significantly higher than 4.8 kA / m, for example, 32 kA / m.

[0005] Document FR1427115 discloses an oscillating assembly for a watch movement comprising a cylindrical shaft fitted with pivots, a ferrule for fixing the balance spring, a cannon with two projections forming the small and large escapement plate and a collar intended to receive the balance wheel.

[0006] The aim of the invention is to provide an oscillator that overcomes the aforementioned drawbacks and improves upon known prior art oscillators. In particular, the invention proposes an oscillator that minimizes, or even eliminates, the residual effect, negative or positive, of magnetic fields that the wearer of the watch is likely to encounter in their daily life, especially magnetic fields exceeding, or even significantly exceeding, 4.8 kA / m, for example, 32 kA / m.

[0007] According to a first aspect, objects of the invention are defined by the following propositions.

[0008] An oscillator according to the invention is defined by claim 1.

[0009] An embodiment of an oscillator is defined by dependent claim 2.

[0010] A watch movement according to the invention is defined by claim 3.

[0011] A timepiece according to the invention is defined by claim 4.

[0012] The attached drawings represent, by way of example, three embodiments of an oscillator according to the invention. There figure 1 is a graph showing the residual rate M of different movements depending on the magnetic field B to which these movements are subjected. Curve 1 illustrates the residual rate M of a movement with an oscillator having a magnetic spiral (Nivarox®). Curve 2 illustrates the residual rate M of a movement with an oscillator having a paramagnetic spiral (Parachrom®). Finally, curve 3 illustrates the residual rate M of a movement with an oscillator having a diamagnetic spiral (Silicon coated with a layer of SiO2). figure 2 is a view of a known oscillator from the prior art. figure 3 is a detailed view of an assembled balance wheel structure of the oscillator of the figure 2 . THE figures 4 And 5 These are views of a first variant of a first embodiment of an oscillator according to the invention. figure 6 represents a second variant of a first embodiment of an oscillator according to the invention. figure 7 represents a third variant of a first embodiment of an oscillator according to the invention. figure 8 is a view of a variant of a second embodiment of an oscillator. The figure 9 is a view of a first variant of a third embodiment of an oscillator. The figure 10 is a view of a second variant of a third embodiment of an oscillator. The figure 11 is a view of a third variant of a third embodiment of an oscillator. The figure 12 is a table showing the residual path of a motion subjected to a given magnetic field as a function of the material of a balance shaft of a known state-of-the-art oscillator as represented in figures 2 And 3 It also shows the residual steps of oscillators implemented in a first and second mode. figure 13 This graph shows, for comparison, the residual rate M of four movements as a function of the magnetic field B to which they were subjected: a first movement comprising an oscillator made according to the first variant of the first embodiment of the invention, and three movements comprising an oscillator made according to the prior art. Curve 1 illustrates the residual rate M of a movement with an oscillator equipped with an assembled balance wheel, having a balance staff with a flange, which is associated with a Nivarox® balance spring. Curve 2 illustrates the residual rate M of a movement with an oscillator equipped with an assembled balance wheel, having a balance staff without a flange, which is associated with a Nivarox® balance spring. Curve 3 illustrates the residual rate M of a movement with an oscillator equipped with an assembled balance wheel, having a balance staff with a flange, which is associated with a paramagnetic balance spring.Finally, curve 4 illustrates the residual rate M of a movement equipped with an oscillator implemented according to the first variant of the first embodiment of the invention. The . figure 14 is a graph showing, for comparison purposes, the residual step M of two movements as a function of the magnetic field B to which they were subjected, a first movement comprising an oscillator made according to the first variant of the third embodiment of the invention (curve 1 of the graph) and the second movement comprising an oscillator made according to the prior art and equipped with a Nivarox ® type spiral (curve 2 of the graph).

[0013] The applicant noted that the geometry of the balance staff has a surprising influence on the residual effect. More specifically, following various studies conducted by the applicant, it was observed that minimizing, or even eliminating, the portion with the largest diameter, called the balance staff seat according to the terminology of NIHS 34-01, or commonly referred to as the "flange," minimizes the residual effect in the same way as a balance staff made of a paramagnetic material such as CuBe2, as shown in the table of the figure 12 It is then observed that combining a paramagnetic or diamagnetic balance spring with a balance wheel assembled with a flanged balance staff according to the prior art does not produce the same effects as combining a paramagnetic or diamagnetic balance spring with a balance staff assembled according to the invention. More specifically, combining a paramagnetic or diamagnetic balance spring with a balance wheel assembled with a balance staff according to the invention makes it possible, for a magnetic field of 32 kA / m (400G), to considerably minimize, or even eliminate, the residual rate, the parasitic torque disturbing the restoring torque of the balance spring then being due to the presence of the magnetic components surrounding the oscillator.

[0014] Referring to the graph of the figure 13 It is observed that adding a paramagnetic balance spring to an assembled balance wheel with a collared balance staff allows, for a magnetic field B of 32 kA / m (400G), a reduction in residual rate M by approximately a factor of 2 compared to the same assembled balance wheel with a Nivarox® type balance spring. Surprisingly, it is noted that adding a paramagnetic balance spring to an assembled balance wheel with a collarless balance staff, as proposed in the first variant of the first embodiment of the invention, allows, for a magnetic field of 32 kA / m (400G), a reduction in residual rate by approximately a factor of 12 compared to the same assembled balance wheel with a Nivarox® type balance spring.It is also noted that the oscillator of the first embodiment of the invention, for a magnetic field of 32 kA / m (400G), allows for a very significant reduction in residual rate, by approximately a factor of 17, compared to an assembled balance wheel that includes a flanged arbor and is combined with a Nivarox®-type balance spring. In particular, as shown in Figure 1. figure 13 For magnetic fields between 15 and 32 kA / m, a synergistic effect has been observed between the paramagnetic or diamagnetic spiral and the geometry of the axis, in relation to the magnetic phenomenon. Indeed, the combined effect of the change in the spiral's material and the modification of the axis's geometry exceeds the sum of the individual effects of the spiral's material change and the modification of the axis's geometry. Referring to the graph of the figure 14 , we note surprisingly that combining a diamagnetic spiral with an assembled balance wheel equipped with a balance staff whose maximum diameter is minimized, as proposed in the first variant of the third embodiment, allows, for a magnetic field B of 32 kA / m (400G), a very significant reduction in the residual rate M, by about a factor of 35, compared to an assembled balance wheel which has a flanged staff and which is combined with a Nivarox ® type spiral.

[0015] Thus, the invention relates to an oscillator comprising a balance spring made of a paramagnetic or diamagnetic material and a balance wheel assembled within this oscillator. The balance wheel includes a steel shaft with a minimized maximum diameter, on which are mounted a balance wheel, a plate, and the ferrule of the balance spring. In one scenario, the ferrule may be attached to the balance spring. In this case, it is preferably made of a copper alloy such as brass or CuBe2, or alternatively, stainless steel. In a second scenario, the ferrule may be manufactured along with the balance spring, for example, when the balance spring is made of silicon. In this case, the ferrule is also made of silicon. The shaft is made of steel to withstand the mechanical stresses to which the oscillator is subjected.The balance wheel and the balance wheel are machined from a paramagnetic or diamagnetic material, for example, a copper alloy such as CuBe2 or brass, silicon, or nickel-phosphorus. Preferably, the maximum diameter Dmax of the shaft is less than 3.5, or even 2.5, or even twice the minimum diameter D1 of the shaft on which one of the oscillator elements is mounted. Even more preferably, the maximum diameter Dmax of the shaft is less than 2, or even 1.8, or even 1.6, or even 1.3 times the maximum diameter D2 of the shaft on which one of the oscillator elements is mounted. Thus, the residual effect is greatly minimized because the parasitic torque disturbing the balance spring's restoring torque is then primarily due to the presence of the magnetic components surrounding the oscillator.Of course, the minimization of the residual effect can be further increased by making the components which are located near the oscillator according to the invention, for example the components of the escapement such as the anchor or the anchor wheel, out of paramagnetic or diamagnetic materials.

[0016] According to a first embodiment of the invention, the smallest diameter D1 of the portion of the shaft on which an oscillator element (chosen from the group: ferrule, plate, balance wheel) is mounted has a value Dmax that corresponds to the largest diameter of the shaft. Furthermore, the largest diameter D2 of the portion of the shaft on which an oscillator element is mounted also has a value that corresponds to the largest diameter Dmax of the shaft. Thus, in this first embodiment, Dmax = D1 = D2.

[0017] According to a second embodiment, the largest diameter D2 of the portion of the shaft on which an oscillator element is mounted also corresponds to the diameter Dmax but differs from the smallest diameter D1 of the portion of the shaft on which an oscillator element is mounted. Thus, in this second embodiment, Dmax = D2 > D1.

[0018] According to a third embodiment, the largest diameter D2 of the portion of the shaft on which an oscillator element is mounted differs from the largest diameter of the shaft Dmax, but may be greater than or equal to the smallest diameter D1 of the portion of the shaft on which an oscillator element is mounted. Thus, in this third embodiment, Dmax > D2 ≥ D1

[0019] A first variant of the first embodiment of the oscillator according to the invention is described below with reference to figures 4 And 5The oscillator 10 comprises a balance spring 11 made of paramagnetic or diamagnetic material and an assembled balance wheel 12 comprising a shaft 13 on which are mounted a balance wheel 14, a plate 15, and the ferrule 16 of said balance spring. In this first variant, the balance wheel 14 is fixed to the shaft 13 via the plate 15. The latter is attached, for example by pressing, to a portion 135 and covers the shaft 13 to a height H. The diameter of this portion 135 is equal to the maximum diameter Dmax. The balance wheel 14 is attached to the plate 14, for example by riveting, onto a bearing surface 131 formed on the plate. The ferrule is mounted directly onto the shaft. It can be fixed there, for example, by pressing. The ferrule is mounted on a portion 136 of the shaft whose diameter is equal to the maximum diameter Dmax of the shaft.In this first variant of the first embodiment, the smallest diameter D1 of the portion of the shaft on which an element (chosen from the group: ferrule, plate, balance wheel) is mounted corresponds to the value Dmax, which is equal to the largest diameter of the shaft. Furthermore, the largest diameter D2 of the portion of the shaft on which an element is mounted also has a value that coincides with that of the largest diameter of the shaft. Thus, in this first variant of the first embodiment, Dmax = D1 = D2. This value is on the order of 0.5 mm in the design illustrated by the figures. figures 4 And 5 .

[0020] Measurements were taken for magnetic fields at different intensity levels in order to compare the residual path of the first variant of the first embodiment of the oscillator with those of known prior art oscillators. As shown in the figure 13 , that the average residual rate of a movement equipped with the first variant of the first embodiment of the oscillator, for a magnetic field of 32 kA / m, is on the order of 2 s / d (curve 4 of the graph), i.e. a decrease of about a factor 12 compared to that of a movement equipped with a known oscillator fitted with a Nivarox ®< balance spring and a balance staff without a collar (curve 2 of the graph). It is also observed that the average residual rate of a movement with an oscillator equipped with an assembled balance wheel, fitted with a flanged balance staff, which is associated with a paramagnetic balance spring, for a magnetic field of 32 kA / m, is on the order of 15 s / d (curve 3 of the graph), i.e. a decrease of about a factor of 2 compared to that of a movement with the same assembled balance wheel which is associated with a Nivarox ®< balance spring.Thus, we observe that combining a paramagnetic spiral with an assembled balance wheel equipped with a collarless axis produces an unexpected effect on the residual rate of a movement, namely, its clear minimization, or even its cancellation, for a magnetic field of 32kA / m (400G).

[0021] Furthermore, this factor is likely to increase by minimizing the number of magnetic components surrounding the oscillator within the movement under consideration.

[0022] A second variant of the first oscillator embodiment is described below with reference to the figure 6 In this second variant, elements identical to or having the same function as the elements of the first variant have a "2" in the tens digit instead of a "1" and the same units digit. Parts or portions of these elements also have a "2" in the hundreds digit instead of the "1" of equivalent parts or portions of the elements in the first variant and the same tens digit. As in the first variant of the first embodiment, Dmax = D1 = D2. This value is approximately 0.3 mm in the design illustrated by the figure 4 This second variant differs from the first variant in that the plate 25 covers the shaft along virtually its entire length and / or in that the ferrule 26 is fixed to the shaft via the plate. In other words, the ferrule 26 is fixed, for example by pressing, onto the plate 25.

[0023] Measurements show that this modification has very little impact on minimizing the residual effect. Regardless of the variant considered, the average residual step, for a magnetic field of 32 kA / m, is 2 s / day, representing a reduction by a factor of 8 compared to that of a movement with a known state-of-the-art design as illustrated in figures 2 And 3 and equipped with a paramagnetic spiral.

[0024] According to the first two variants of the first embodiment, the balance wheel is attached to the shaft via the balance plate. Compared to the usual structure known in the prior art, the shaft flange is thus eliminated, and the balance plate-wheel assembly can be directly attached to the shaft, for example, by pressing. Alternatively, according to a third variant of the first embodiment, the balance wheel is directly attached to a portion of the shaft whose diameter is equal to the diameters of the portions onto which the balance plate and the ferrule are attached. Thus, the balance wheel can be attached to the shaft independently of the balance plate.

[0025] In this third variant of the first embodiment illustrated by the figure 7 The elements identical to, or having the same function as, the elements of the first variant of the first embodiment have a "3" in the first digit (tens or hundreds) instead of a "1" and have the same second digit (units or tens). The balance wheel 34 is fixed to a portion 334 independently of the plate 35, which is attached to a portion 335. To achieve this, the hub of the balance wheel 34 has a sufficient overall height H, in particular equal to or substantially equal to the height of the portion 334, so as to guarantee adequate support and torque for the balance wheel. The ferrule is fixed to a portion 336, for example by pressing. The diameter of each of the portions 334, 335, and 336 is equal to the maximum diameter Dmax of the shaft. Thus, as in the first two variants, Dmax = D1 = D2. This value is on the order of 0.4 mm in the design illustrated by the figure 7 The measurements show that the average residual rate of a movement equipped with an oscillator made according to this third variant, for a magnetic field of 32kA / m, is equivalent to that of a movement equipped with an oscillator made according to one of the first two variants, namely about 2 s / j.

[0026] The second embodiment differs from the first embodiment in that the value of the largest shaft diameter Dmax does not coincide with that of the minimum shaft diameter D1 on which one of the elements chosen from the group—ferrule, plate, balance wheel—is mounted. In other words, Dmax = D2 > D1. A variant of the second oscillator embodiment is described below with reference to the figure 8 In this second embodiment, the elements identical to, or having the same function as, the elements of the first variant of the first embodiment have a "4" in the first digit (tens or hundreds) instead of a "1" and have the same second digit (units or tens). In this embodiment, the ferrule 46 is attached to the shaft 43 at a portion 436, for example by pressing. The plate 45 is, for example, pressed against a portion 435. The diameter of this portion is equal to the minimum diameter D1 of the shaft on which an element is mounted. The balance wheel 44, for its part, is directly mounted on the shaft 43 at a portion 434, for example by pressing, regardless of the location of the plate 45.To achieve this, the balance wheel hub 44 has a sufficient overall height H, in particular equal to or substantially equal to the height of the portion 434, so as to guarantee adequate support and holding torque for the balance wheel. The diameter of this portion 434 is equal to the maximum diameter D2 of the shaft on which an element is mounted. It also corresponds to the diameter Dmax. Thus, in this embodiment, Dmax = D2 > D1. Preferably, the maximum diameter Dmax of the shaft is less than 3.5, or even 2.5, or even twice the minimum diameter D1 of the shaft on which one of the elements is mounted. In the example illustrated by the... figure 8 D1 is on the order of 0.4 mm, D2 and therefore Dmax are on the order of 0.8 mm. Thus, Dmax is less than approximately 2.5 times the diameter D1.

[0027] Measurements were carried out for a magnetic field of 32 kA / m in order to compare the residual step of this variant of the second embodiment of the oscillator with that of a known prior art oscillator as illustrated in figures 2 And 3 , both equipped with a paramagnetic spiral. The table of the figure 12 shows that the average residual step, for a magnetic field of this intensity, is on the order of 2 s / d, i.e. a decrease of about a factor of 8 compared to that of a movement with a known oscillator and equipped with a paramagnetic or diamagnetic spiral.

[0028] The third embodiment differs from the second embodiment in that the value of the largest diameter of the shaft Dmax does not coincide with that of the maximum diameter D2 of the shaft on which one of the elements chosen from the group ferrule, plate, balance wheel is mounted. Thus, Dmax>D2≥D1.

[0029] A first variant of the third oscillator embodiment is described below with reference to the figure 9 In this first variant of the third embodiment, the elements identical or having the same function as the elements of the first variant of the first embodiment have a "5" in the first digit (tens or hundreds) instead of a "1" and have the same second digit (units or tens). The ferrule 56 is mounted directly onto the shaft 53 at a portion 536, for example by pressing. The plate 55 is also mounted directly onto the shaft 53. It is, for example, pressed against the shaft 53 at a portion 535. The diameter of this portion is equal to the minimum diameter D1 of the shaft on which an element is mounted. The rocker arm is attached to the shaft at a portion 534, for example by pressing.To achieve this, the balance wheel hub 54 has a sufficient overall height H, in particular equal to or substantially equal to the height of the portion 534, so as to guarantee adequate support and holding torque for the balance wheel. The diameter of this portion 534 is equal to the maximum diameter D2 of the shaft on which an element is mounted. In this first variant of the third embodiment, a shaft portion 533 has a diameter Dmax greater than diameters D1 and D2. Thus, this portion has shoulders against which the balance wheel and / or the ferrule can bear when fixed to the shaft. In this way, the position of the balance wheel and that of the ferrule can be precisely defined.

[0030] In this first variant of the third embodiment, Dmax > D2 > D1, and the maximum diameter Dmax of the shaft is less than 3.5, or even 2.5, or even 2 times the minimum diameter D1 of the shaft on which one of the elements is mounted, and / or the maximum diameter Dmax of the shaft is less than 2, 1.8, or even 1.6, or even 1.3 times the maximum diameter D2 of the shaft on which one of the elements is mounted. In the example illustrated by the figure 9 D1 is approximately 0.3 mm, D2 is approximately 0.8 mm, and Dmax is approximately 1 mm. Thus, Dmax is less than approximately 3.5 times the diameter D1, and Dmax is less than approximately 1.3 times the diameter D2. Within a known state-of-the-art design as represented in figures 2 And 3within which Dmax > D2 > D1, D1 is approximately 0.3 mm, D2 is approximately 0.8 mm, and Dmax is approximately 1.4 mm. Dmax is then more than 4.5 times the diameter D1, and Dmax is more than 1.6 times the diameter D2. It can therefore be seen that the largest diameter of the shaft, Dmax, is greatly minimized compared to the largest diameter, Dmax, of a shaft equipping a known state-of-the-art oscillator. Thus, the residual effect is minimized because the parasitic torque disturbing the spring's restoring torque is then primarily due to the presence of the magnetic components surrounding the oscillator. figure 14 This shows the residual rate of the first variant of the third embodiment of the oscillator compared to that of a known oscillator which includes a balance staff with a flange and is equipped with a Nivarox® type balance spring. It is observed that the average residual rate, for a magnetic field of 32kA / m, is on the order of 1 s / day, representing a very significant decrease by a factor of 35 compared to that of a movement equipped with the aforementioned oscillator.

[0031] A second variant of the third oscillator embodiment is described below with reference to the figure 10 In this second variant of the third embodiment, the elements identical to, or having the same function as, the elements of the first variant of the first embodiment have a "6" in the first digit (tens or hundreds) instead of a "1" and have the same second digit (units or tens). As in the first variant of the third embodiment, Dmax > D2 > D1. This second variant differs from the first variant in that the balance wheel 64 is fixed to the shaft 63 via the plate 65. The latter is attached, for example by pressing, onto a portion 635 and covers the shaft 63 to a height H1. The diameter of this portion 635 is equal to the minimum diameter D1 of the shaft on which an oscillator element is mounted. The balance wheel is mounted against the plate, for example by pressing.To achieve this, the balance wheel hub 64 has a sufficient overall height H2, in particular equal to or substantially equal to the height of the portion 654 of the plate 65, so as to guarantee adequate support and holding torque for the balance wheel. The ferrule is fixed to a portion 636 of the shaft 63, for example by pressing. The diameter of this portion 635 is equal to the maximum diameter D2 of the shaft on which an oscillator element is mounted. In this second variant of the third embodiment, a portion of the shaft 633 has a diameter Dmax greater than diameters D1 and D2. Thus, this portion has shoulders against which the plate and / or the ferrule can bear when fixed to the shaft. In this way, the position of the balance wheel and that of the ferrule can be precisely defined.In this second variant of the third embodiment, Dmax > D2 > D1, and the maximum diameter Dmax of the shaft is less than 3.5, or even 2.5, or even 2 times the minimum diameter D1 of the shaft on which one of the elements is mounted, and / or the maximum diameter Dmax of the shaft is less than 2, 1.8, or even 1.6, or even 1.3 times the maximum diameter D2 of the shaft on which one of the elements is mounted. In the example illustrated by the... figure 10 D1 is approximately 0.4 mm, D2 is approximately 0.5 mm, and Dmax is approximately 0.7 mm. Therefore, Dmax is less than approximately twice the diameter D1, and Dmax is less than approximately 1.6 times the diameter D2. In this way, the maximum diameter Dmax of the shaft is also greatly minimized.

[0032] A third variant of the third embodiment differs from the first two variants in that the value of the maximum diameter D2 of the shaft on which an oscillator element is mounted is equal to that of the minimum diameter D1 on which an oscillator element is mounted. This variant is described below with reference to the figure 11 The elements identical to, or having the same function as, the elements of the first variant of the first embodiment have a "7" in the first digit (tens or hundreds) instead of a "1" and have the same second digit (units or tens). As in the second variant of the third embodiment, the balance wheel 74 is fixed to the shaft 73 by means of the plate 75. The latter is attached, for example by pressing, to a portion 735 and covers the shaft 73 to a height H1. The diameter of this portion 735 is equal to the minimum diameter D1 of the shaft on which an oscillator element is mounted. The diameter of this portion 735 also corresponds to the maximum diameter D2 of the shaft on which an oscillator element is mounted. The balance wheel is mounted against the plate, for example by pressing.To achieve this, the balance wheel hub 74 has a sufficient overall height H2, in particular equal to or substantially equal to the height of the portion 754 of the plate 75, so as to guarantee adequate support and holding torque for the balance wheel. The ferrule is fixed to a portion 736 of the shaft 73, for example by pressing. The diameter of this portion 736 corresponds to the maximum diameter D2 of the shaft on which an oscillator element is mounted, and also to the minimum diameter D1 of the shaft on which an oscillator element is mounted. Thus, D1 = D2. In this third variant, a portion of the shaft 733 has a diameter Dmax greater than diameters D1 and D2. Thus, this portion has shoulders against which the plate and / or the ferrule can bear when fixed to the shaft. In this way, the position of the balance wheel and that of the ferrule can be precisely defined.In this third variant, Dmax > D1 = D2, and the maximum diameter Dmax of the shaft is less than 3.5, or even 2.5, or even 2 times the minimum diameter D1 of the shaft on which one of the elements is mounted, and the maximum diameter Dmax of the shaft is less than 2, 1.8, or even 1.6, or even 1.3 times the maximum diameter D2 of the shaft on which one of the elements is mounted. In the example illustrated by the... figure 11 D1 and D2 are on the order of 0.4 mm, and Dmax is on the order of 0.7 mm. Thus, Dmax is less than approximately twice the diameter D1, and Dmax is less than approximately twice the diameter D2. In this way, the maximum diameter Dmax of the shaft is also greatly minimized.

[0033] In the third embodiment, Dmax is preferably the diameter of a seat in contact with which one element, or even two elements (plate, balance wheel, ferrule), can be driven onto the axis.

[0034] Regardless of the embodiment, when a first element, for example the balance wheel, is not mounted directly on the shaft but is mounted on a second element, itself mounted directly on the shaft at a first portion of the shaft having a first diameter, the diameter of the shaft on which the first element is mounted is considered to be the first diameter. Of course, regardless of the embodiment considered, all the elements chosen from the group—ferrule, plate, balance wheel—can be arranged on one of the three diameters D1, D2, Dmax.

[0035] In the various embodiments, the diameter Dmax is preferably less than 1.1 mm, or even less than 1 mm, or even less than 0.9 mm.

[0036] The oscillator according to the invention, equipped with a paramagnetic (Nb-Zr-O alloy, Parachrom® for example) or diamagnetic (particularly silicon coated with a layer of SiO2) balance spring, is distinguished by its balance staff made of free-cutting steel whose geometry has been modified to minimize the residual effect. The balance wheel and the plate are machined from a paramagnetic or diamagnetic material, for example, a copper alloy such as CuBe2 or brass, silicon, or nickel-phosphorus. The plate, depending on the embodiment considered, is preferably adapted to allow the assembly of the balance wheel.

[0037] In this document, "a first element attached to a second element" means that the first element is fixed to the second element.

[0038] In this document, "assembled balance wheel" means an assembly comprising or consisting of a balance shaft, a balance wheel, a plate and a ferrule, the balance wheel, the plate and the ferrule being mounted on the balance shaft.

[0039] In this document, "axis" and "tree" refer to the same element.

[0040] In this document, the ratios of residual step values ​​are given in absolute value.

[0041] The graphs of figures 1 , 13 And 14 are carried out to scale, so that values, including residual step values, can be deduced by measurement on the graph.

Claims

1. An oscillator (10; 20; 30; 40; 50; 60; 70) comprising a balance spring (11; 21; 31; 41; 51; 61; 71) made of a paramagnetic or diamagnetic material and an assembled balance (12; 22; 32; 42; 52; 62; 72) comprising a shaft (13; 23; 33; 43; 53; 63; 73) made of steel and on which the following elements are mounted: a balance (14; 24; 34; 44; 54; 64; 74), a roller (15; 25; 35; 45; 55; 65; 75) and a collet (16; 26; 36; 46; 56; 66; 76) secured to said balance spring (11; 21; 31; 41; 51; 61; 71), in which the maximum diameter (Dmax) of the shaft is equal to the minimum diameter (D1) of the shaft on which one of the elements is mounted and equal to the maximum diameter (D2) of the shaft on which one of the elements is mounted, the minimum diameter (D1) of the shaft on which one of the elements is mounted being of the order of 0.5 mm or of the order of 0.4 mm or of the order of 0.3 mm.

2. The oscillator as claimed in claim 1, characterized in that the balance shaft is made of profile turning steel.

3. A clock movement comprising an oscillator (10; 20; 30; 40; 50; 60; 70) as claimed in one of the preceding claims.

4. A timepiece comprising a clock movement as claimed in the preceding claim or an oscillator (10; 20; 30; 40; 50; 60; 70) as claimed in one of claims 1 and 2.