Rotating resonator with flexure bearing maintained by a detached lever escapement

Abstract

Timepiece regulator comprising a detached lever escapement mechanism, and a resonator with a quality factor Q including an inertia element including an impulse pin cooperating with a fork of the lever, subjected to the return force of two flexible strips attached to the plate, defining a virtual pivot having a main axis (DP), the lever pivoting about a secondary axis (DS), and the lift angle (β) of the resonator, during which the impulse pin is in contact with the fork, is less than 10°, and the ratio I.sub.B/I.sub.A between the inertia I.sub.B of the inertia element with respect to the main axis (DP) and the inertia I.sub.A of the lever with respect to the secondary axis (DS) is greater than 2Q.Math.α.sup.2/(0.1.Math.π.Math.β.sup.2), where α is the lift angle of the lever corresponding to the maximum angular travel of the fork.

Claims

1. A timepiece regulating mechanism, comprising, arranged on a main plate; a resonator mechanism with a quality factor, the quality factor being associated with losses of energy and disruptions of rate; and an escapement mechanism which is subjected to a torque of driver comprised in a movement, said resonator mechanism comprising an inertia element arranged to oscillate with respect to said plate, said inertia element being subjected to an action of elastic return means directly or indirectly attached to said plate, and said inertia element being arranged to cooperate indirectly with an escape wheel set comprised in said escapement mechanism, wherein said resonator mechanism is a resonator with a virtual pivot rotating about a main axis, with a flexure bearing including at least two flexible strips, and including an impulse pin integral with said inertia element, said escapement mechanism includes a lever pivoting about a secondary axis and including a lever fork arranged to cooperate with said impulse pin, and is a detached escapement mechanism, wherein, during an operating cycle, said resonator mechanism has at least one phase of freedom in which said impulse pin is at a distance from said lever fork, a lift angle of the resonator, during which said impulse pin is in contact with said lever fork, is less than 10°, and said impulse pin is configured to be removed from said lever fork when said impulse pin travels through a half of the lift angle of the resonator, which has a non-zero degree.

2. The regulating mechanism according to claim 1, wherein an inertia I.sub.B of said inertia element with respect to said main axis on the one hand, and an inertia I.sub.A of said lever with respect to said secondary axis on the other hand, are such that a ratio I.sub.B/I.sub.A is greater than than 2Q.Math.α.sup.2/(0.1.Math.π.Math.β.sup.2), where Q is the quality factor, α is a lift angle of the lever which corresponds to the maximum angular travel range of said lever fork, and β is the lift angle of the resonator.

3. The regulating mechanism according to claim 1, wherein said overall lift angle of the resonator is less than twice an angle of amplitude by which said inertia element deviates furthest, in only one direction of motion, from a rest position.

4. The regulating mechanism according to claim 1, wherein the angle of amplitude, by which said inertia element deviates furthest from a rest position, is comprised between 5° and 40°.

5. The regulating mechanism according to claim 1, wherein, during each vibration, in the contact phase, said impulse pin penetrates said lever fork with the depth of travel greater than 100 micrometres, and in the unlocking phase, said impulse pin remains at the distance from said lever fork with the safety distance greater than 25 micrometres, and said impulse pin and said lever fork are dimensioned such that a width of said lever fork is greater than (P+S)/sin(α/2+β/2), said depth of travel (P) and said safety distance (S) being measured radially with respect to said main axis, where a is a lift angle of the lever which corresponds to the maximum angular travel range of said lever fork, and 13 is the lift angle of the resonator.

6. The regulating mechanism according to claim 1, wherein said lever is in a single layer of silicon, placed on a metal arbor pivoted with respect to said plate.

7. The regulating mechanism according to claim 1, wherein said escape wheel set is an escape wheel which is perforated to minimize an inertia with respect to its axis of pivoting.

8. The regulating mechanism according to claim 1, wherein said lever is perforated to minimize said inertia with respect to said secondary axis.

9. The regulating mechanism according to claim 1, wherein said lever is symmetrical with respect to said secondary axis.

10. The regulating mechanism according to claim 1, wherein the largest dimension of said inertia element is greater than half the largest dimension of said plate.

11. The regulating mechanism according to claim 1, wherein said main axis, said secondary axis and the axis of pivoting of said escape wheel set, are arranged to be centered at a right angle whose apex is on said secondary axis within a plane defined perpendicular to three axes.

12. The regulating mechanism according to claim 1, wherein said flexure bearing includes two flexible strips which are crossed in projection onto a plane perpendicular to said main axis, at said virtual pivot defining said main axis, and located in two parallel planes that are at distinct levels.

13. The regulating mechanism according to claim 12, wherein said two flexible strips, in projection onto a plane perpendicular to said main axis, form therebetween an angle comprised between 59.5° and 69.5°, and intersect at between 10.75% and 14.75% of their length, such that said resonator mechanism has a deliberate isochronism error which is an additive inverse of a loss error at the escapement of said escapement mechanism.

14. The regulating mechanism according to claim 12, wherein said two flexible strips are identical and are positioned in symmetry.

15. The regulating mechanism according to claim 12, wherein each said flexible strip forms part of a one-piece assembly in one piece with means thereof for alignment and attachment to said plate or to an intermediate elastic suspension strip attached to said plate and arranged to allow a displacement of said flexure bearing and of said inertia element in the direction of said main axis.

16. The regulating mechanism according to claim 1, wherein at least said resonator mechanism is attached to an intermediate, elastic suspension strip attached to said plate and arranged to allow a displacement of said resonator mechanism in the direction of said main axis, and said plate includes at least one shock absorber stop at least in the direction of said main axis, arranged to cooperate with stiff elements of said inertia element.

17. The regulating mechanism according to claim 1, wherein said inertia element includes inertia blocks for adjusting rate and unbalance.

18. The regulating mechanism according to claim 1, wherein said impulse pin is in one-piece with a said flexible strip.

19. The regulating mechanism according to claim 1, wherein said lever includes bearing surfaces arranged to cooperate in abutment with teeth comprised in said escape wheel set and to limit an angular travel of said lever.

20. The regulating mechanism according to claim 1, wherein said flexure bearing is made of oxidized silicon to compensate for effects of temperature on the rate of said regulating mechanism.

21. A timepiece movement including driver and the regulating mechanism according to claim 1, wherein said escapement mechanism is subjected to the torque of said drive means.

22. A watch including the timepiece movement according to claim 21.

23. The regulating mechanism according to claim 1, wherein said impulse pin is configured to be removed from said lever form when said impulse pin travels through a half of the lift angle of the resonator, which is between 5 degrees and 10 degrees.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which:

(2) FIG. 1 includes a double graph including, on the same abscissa, the ratio between the inertia of the inertia element of the resonator and the inertia of the lever, and which shows, on the ordinate, for a particular example mechanism, on the one hand, in the positive portion in the top graph, the rate of efficiency of the regulator in %, and in the negative portion in the bottom graph, the losing rate in seconds per day; these top and bottom graphs are drawn for a same given escapement geometry, with specific values of the quality factor, angle of lift of the lever and operating amplitude.

(3) FIG. 2 represents a schematic, partial, perspective view of a timepiece movement, with a main plate carrying a regulating mechanism according to the invention, comprising a resonator with a flexure bearing with two flexible strips arranged on two parallel levels and crossed in projection, attached to the plate by means of an elastic element, this resonator comprising an extensive inertia element, shaped like the letter omega, and whose central portion, carried by the two flexible strips, carries an impulse pin arranged to cooperate with a symmetrical lever, (whose pivoting on the plate by means of a metal arbor is not represented), which in turn cooperates with a conventional escape wheel.

(4) FIG. 3 represents a plan view of the regulating mechanism of FIG. 2, arranged on the plate of the movement.

(5) FIG. 4 represents a plan view of the detail of the regulating mechanism of FIG. 2.

(6) FIG. 5 represents a partially exploded perspective view of the regulating mechanism of FIG. 2.

(7) FIG. 6 represents a plan view of a detail of the area of cooperation between the impulse pin of the inertia element of the resonator, and the lever fork, represented in a stop position on a banking pin.

(8) FIG. 7 represents a plan view of the lever of the mechanism of FIG. 2, shaped like the horns of Watusi cattle.

(9) FIG. 8 represents a plan view of the flexure bearing of the mechanism of FIG. 2.

(10) FIG. 9 represents a plan view of a particular embodiment of one level of the flexure bearing of the mechanism of FIG. 2.

(11) FIG. 10 represents a side view of the regulating mechanism of FIG. 2.

(12) FIG. 11 represents, in perspective, a detail of the regulating mechanism of FIG. 2, showing the shock absorber stops on its plate.

(13) FIGS. 12 to 14 are graphs comprising, on the abscissa, the torque applied to the escape wheel set, and on the ordinate, respectively the amplitude measured in degrees in FIG. 12, the loss in seconds per day in FIG. 13, and the efficiency of the regulator in % in FIG. 14.

(14) FIG. 15 is a block diagram which represents a watch comprising a movement with drive means and a regulating mechanism according to the invention.

(15) FIGS. 16 to 19 represent plan views of the kinematic stages, already symbolised by FIG. 6, as regards the impulse pin, the lever fork of FIG. 7, and the escape wheel set formed here by a conventional escape wheel:

(16) FIG. 16: locking of the escape wheel on the entry pallet, supplementary arc of the resonator;

(17) FIG. 17: unlocking:

(18) FIG. 18: start of impulse;

(19) FIG. 19: locking of the escape wheel on the exit pallet, supplementary arc of the resonator, and safety function.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(20) The invention combines a resonator having a rotary flexure bearing, to increase the power reserve and precision, with an optimised lever escapement to maintain acceptable dynamic losses and to limit the chronometric effect of the unlocking phase.

(21) The invention therefore concerns a timepiece regulating mechanism 300, comprising, arranged on a main plate 1, a resonator mechanism 100 with a quality factor Q and an escapement mechanism 200, which is subjected to the torque of drive means 400, comprised in a movement 500.

(22) This resonator mechanism 100 includes an inertia element 2 which is arranged to oscillate with respect to plate 1. This inertia element 2 is subjected to the action of elastic return means 3 directly or indirectly secured to plate 1. Inertia element 2 is arranged to cooperate indirectly with an escape wheel set 4, particularly an escape wheel, which is comprised in escapement mechanism 200 and pivots about an escapement axis DE.

(23) According to the invention, resonator mechanism 100 is a resonator with a virtual pivot rotating about a main axis DP, with a flexure bearing including at least two flexible strips 5, and includes an impulse pin 6 integral with inertia element 2. Escapement mechanism 200 includes a lever 7, which pivots about a secondary axis DS and includes a lever fork 8 arranged to cooperate with impulse pin 6, and is thus a detached escapement mechanism: during its operating cycle, resonator mechanism 100 has at least one phase of freedom in which impulse pin 6 is at a distance from lever fork 8. The lift angle β of the resonator, during which impulse pin 6 is in contact with lever fork 8, is less than 10°.

(24) Taking a specific escapement geometry and a specific operating amplitude, in particular 8°, it is possible with dynamic multi-body simulations (i.e. relating to a set of several components, each of which is assigned a particular mass and inertia distribution) to evaluate the efficiency and loss of this escapement mechanism as a function of the inertia ratio between the inertia of the inertia element and the inertia of the lever, which cannot be established using normal kinematic simulations. As seen in FIG. 1, it is observed that, under the simulation conditions, there is a threshold of good efficiency, higher than 35%, and of low loss, less than 8 seconds per day, where the inertia of the inertia element, particularly of a balance, is 10000 times greater than the inertia of the lever.

(25) The analytical model of the system thus showed that, if one wishes to limit dynamic losses, a particular condition links the inertia of the lever, the inertia of the inertia element, the resonator quality factor, and the angles of lift of the lever and of the inertia element: for a dynamic loss coefficient ε, the inertia I.sub.B of all the inertia elements 2 with respect to main axis DP, on the one hand, and the inertia I.sub.A of lever 7 with respect to secondary axis DS on the other hand, are such that the ratio I.sub.B/I.sub.A is greater than 2Q.Math.α.sup.2/(0.1.Math.π.Math.β.sup.2), where α is the lift angle of the lever which corresponds to the maximum angular travel of lever fork 8.

(26) More particularly, if one wishes to limit dynamic losses to a factor ε=10%, the inertia I.sub.B of inertia element 2 with respect to main axis DP on the one hand, and the inertia I.sub.A of lever 7 with respect to secondary axis DS on the other hand, are such that the ratio I.sub.B/I.sub.A is greater than 2Q.Math.α.sup.2/(0.1.Math.π.Math.β.sup.2), where α is the lift angle of the lever which corresponds to the maximum angular travel of lever fork 8.

(27) More particularly, the lift angle β of the resonator, which is an overall angle, taken from both sides of the rest position, is less than twice the angle of amplitude by which inertia element 2 deviates furthest, in only one direction of motion, from a rest position.

(28) More particularly, the angle of amplitude by which inertia element 2 deviates furthest from a rest position, is comprised between 5° and 40°.

(29) More particularly, during each vibration, in a contact phase, impulse pin 6 penetrates lever fork 8 with a depth of travel P greater than 100 micrometres, and in an unlocking phase, impulse pin 6 remains at a distance from lever fork 8 with a safety distance S greater than 25 micrometres.

(30) Impulse pin 6 and lever fork 8 are dimensioned such that the width L of lever fork 8 is greater than (P+S)/sin(α/2+β/2), depth of travel P and safety distance S being measured radially with respect to main axis DP.

(31) The useful width L1 of impulse pin 6, seen in FIG. 6, is slightly smaller than width L of lever fork 8, and, more particularly, less than or equal to 98% of L. Impulse pin 6 is advantageously tapered behind its useful width surface L1, the pin can, in particular, have a prismatic shape of triangular cross-section as suggested in the Figure, or similar.

(32) Thus, by design, the invention defines a new impulse pin/fork layout which has a very particular characteristic, wherein the horns of the fork are further apart, and the pin is wider than in a known type of Swiss lever mechanism with a normal angle of lift of 50°.

(33) Thus, by substantially enlarging the lever fork in comparison to the usual proportions, it is also possible to design a Swiss lever escapement with a very small angle of lift, for example on the order of 10°.

(34) More particularly, lever 7 is in a single layer of silicon, placed on a metal arbor pivoted with respect to plate 1.

(35) More particularly, escape wheel set 4 is a silicon escape wheel.

(36) More particularly, escape wheel set 4 is an escape wheel that is perforated to minimise its inertia with respect to its axis of pivoting DE.

(37) More particularly, lever 7 is perforated to minimise its inertia I.sub.A with respect to secondary axis DS.

(38) Preferably, lever 7 is symmetrical with respect to secondary axis DS, in order to avoid any unbalance, and to avoid unwanted torque in the event of linear impact.

(39) FIG. 7 shows the two horns 81 and 82 arranged to cooperate with impulse pin 6, pallets 72 and 73 arranged to cooperate with teeth of escape wheel set 4, and horn-like elements 80 and pallet-like elements 70 whose only role is to achieve perfect balancing.

(40) More particularly, the largest dimension of inertia element 2 is greater than half the largest dimension of plate 1.

(41) More particularly, the eccentricity E2 of pin 6 with respect to the axis of the balance, and the eccentricity E7 of the horn of fork 8 with respect to the axis of lever 7, are comprised between 40% and 60% of the distance of centres E between the axis of lever 7 and the balance axis. More particularly, eccentricity E2 is comprised between 55% and 60% of distance of centres E, and eccentricity E7 is comprised between 40% and 45% of distance of centres E. More particularly, the area of interference between pin 6 and fork 8 extends over 5% to 10% of distance of centres E.

(42) More particularly, main axis DP, secondary axis DS and the axis of pivoting of escape wheel set 4 are arranged to be centred at a right angle, whose apex is on secondary axis DS.

(43) More particularly, the flexure bearing includes two flexible strips 5 which are crossed in projection onto a plane perpendicular to main axis DP, at a virtual pivot defining main axis DP, and located on two parallel and distinct levels. FIGS. 16 to 19 illustrate the kinematics and show that suitable depths of travel P and safety distances S are obtained by this combined design, wherein pin 6 is very far away from the balance axis and lever 7 has a particular shape, especially with an enlarged fork. More particularly still, the two flexible strips 5, in projection onto a plane perpendicular to main axis DP, form therebetween an angle comprised between 59.5° and 69.5°, and intersect at between 10.75% and 14.75% of their length, such that resonator mechanism 100 has a deliberate isochronism error which is the additive inverse of the loss error at the escapement of escapement mechanism 200.

(44) The resonator thus has an anisochronism curve which compensates for the loss caused by the escapement. This means that the detached resonator is designed with an isochronism error which is the additive inverse of the error caused by the lever escapement. The design of the resonator therefore compensates for the loss at the escapement.

(45) More particularly, the two flexible strips 5 are identical and are positioned in symmetry. More particularly still, each flexible strip 5 forms part of a one-piece assembly 50, in one piece with its first means of alignment 52A, 52B, and of attachment 54 to plate 1, or, advantageously and as seen in FIG. 10, of attachment to an intermediate elastic suspension strip 9 attached to plate 1, and which is arranged to allow a displacement of the flexure bearing and of inertia element 2 in the direction of main axis DP.

(46) In the non-limiting variant illustrated in the Figures, the first alignment means are a first V-shaped portion 52A and a first flat portion 52B, and the first attachment means include at least a first bore 54. A first press strip 53 presses on the first attachment means. Likewise, one-piece assembly 50 includes, for attachment thereof to inertia element 2, second alignment means which are a second V-shaped portion 56A and a second flat portion 56B and the second attachment means include at least a second bore 58. A second press strip 57 presses on the second attachment means.

(47) Flexure bearing 3 with crossed strips 5 is advantageously formed of two identical, silicon, one-piece assemblies 50, assembled in symmetry to form the crossing of the strips, and aligned precisely with respect to each other by means of the integrated alignment means and auxiliary means, such as pins and screws, which are not represented in the Figures.

(48) Thus, more particularly, at least resonator mechanism 100 is attached to an intermediate elastic suspension strip 9 attached to plate 1 and arranged to allow a displacement of resonator mechanism 100 in the direction of main axis DP, and plate 1 includes at least one shock absorber stop 11, 12, at least in the direction of main axis DP, and preferably at least two such shock absorber stops 11, 12, which are arranged to cooperate with stiff elements of inertia element 2, for example flanges 21 or 22 added during assembly of the inertia element to flexure bearing 3 comprising strips 5.

(49) The elastic suspension strip 9, or a similar device, allows displacements of the entire resonator 100 substantially in the direction defined by virtual axis of rotation DP of the bearing. The object of this device is to avoid strips 5 breaking in the event of transverse impact in direction DP.

(50) FIG. 11 illustrates the presence of shock absorber stops limiting the travel of inertia element 2 in three directions in case of impact but located at a sufficient distance for the inertia element not to touch the stops under the effect of gravity. For example, flange 21 or 22 includes a bore 211 and a face 212, able to cooperate respectively in a shock absorber stop arrangement with a trunnion 121 and a complementary surface 122 on stop 21 or 22.

(51) More particularly, inertia element 2 includes inertia blocks 20 for adjusting rate and unbalance.

(52) More particularly, impulse pin 6 is in one-piece with a flexible strip 5, or more particularly, a one-piece assembly 50 as illustrated in the Figures.

(53) More particularly, lever 7 includes bearing surfaces arranged to cooperate in abutment with teeth comprised in escape wheel set 4 and to limit the angular travel of lever 7. These bearing surfaces limit the angular travel of the lever, as solid banking would do. The angular travel of lever 78 can also be limited in a conventional manner by banking pins 700.

(54) More particularly, flexure bearing 3 is made of oxidised silicon to compensate for the effects of temperature on the rate of regulating mechanism 300.

(55) The invention also concerns a timepiece movement 500 comprising drive means 400, and such a regulating mechanism 300, whose escapement mechanism 200 is subjected to the torque of these drive means 400.

(56) The overbanking prevention function is thus advantageously performed by the combination of edge 60, in the form of an arc of a circle, of impulse pin 6, and by the corresponding surface 810, 820, of the horn 81, 82 concerned: this horn plays the usual part of a guard pin, and the periphery of the impulse pin plays the part of the safety roller.”

(57) The graphs of FIGS. 12 to 14 set out a series of results from simulations in which Q=2000, I.sub.B=26550 mg.mm.sup.2, the frequency is 20 Hz, the escape wheel set has 20 teeth, more particularly the lift angle α of the lever is 14°, and the lift angle β of the resonator is 10°.

(58) The invention also concerns a watch 1000, more particularly a mechanical watch, including such a movement 500, and/or such a regulating mechanism 300.

(59) In short, the present invention makes it possible to increase the power reserve and precision of current mechanical watches. For a given movement size, the autonomy of the watch can be quadrupled, and the regulating power of the watch can be doubled. This means that the invention provides a gain of a factor 8 in the performance of the movement.