Clock movement provided with a generator and a circuit for regulating the rotation frequency of the generator

Abstract

The invention relates to a watch movement, which is provided with a generator and a circuit for regulating the rotation frequency of the generator, the regulating circuit being arranged to detect the zero crossing of an induced voltage (2) generated in a stator by a rotating rotor and to generate a first braking pulse (44), the first braking pulse (44) being triggered after the zero crossing and each ending before the induced voltage reaches a peak value, preferably before the rectified induced voltage reaches a supply voltage provided by a supply capacitor. In addition, the regulating circuit is arranged to further generate second braking pulses (50), each of which appears after detecting the end of a charging period of the supply capacitor during which the induced voltage (2) reaches a peak value and each ends before the induced voltage passes zero.

Description

Technical Field

[0001] The invention relates to the field of timepiece movements provided with a generator and a circuit for regulating the rotation frequency of the generator.

[0002] More specifically, the invention relates to a watch movement comprising a barrel, an analog time display mechanism driven by at least one barrel, and a regulator module for the operation of the analog display mechanism. The regulator module comprises a continuously rotating generator and a circuit for regulating the angular velocity or equivalently the rotational frequency of the generator, that is to say its rotor. More specifically, the regulating circuit is arranged to be able to regulate the average rotational frequency of the rotor, which is also driven by the at least one barrel and kinematically connected to the analog display mechanism, so that the regulator module can regulate its operation. In addition, the generator is intended to be a source of electrical energy for a power supply circuit for the regulating circuit. Background Art

[0003] A watch movement of the type mentioned in the technical field is described in document EP 935 177, which refers to document CH 686 332. As indicated in this document, as long as the barrel intended to drive the watch movement, i.e. at least the time display mechanism and the generator, has a winding rate corresponding to the normal operating range of the watch movement (including the indicators associated therewith), the generator will rotate too fast without braking, that is to say its rotor rotates freely at a speed greater than the set speed - or in an equivalent manner, at a frequency greater than the set frequency. The regulating circuit is associated with a quartz oscillator, which allows the set frequency to be determined with the accuracy characteristic of a quartz oscillator. The regulating circuit includes a measuring circuit that allows the measurement of the rotation of the rotor over time and thus detects the drift of the average rotation frequency of the generator relative to the set frequency determined by the quartz oscillator. The regulating circuit is then arranged to be able to generate a braking pulse of the rotor by temporarily reducing the impedance at the terminals of at least one coil of the generator when the drift of the average rotation frequency is greater than a given positive value in order to correct this drift. In addition, the regulation circuit is arranged to detect the zero crossing of the induced AC voltage generated by the rotating rotor in the at least one coil, and to generate braking pulses respectively triggered after detecting the zero crossing of the induced AC voltage (hereinafter referred to as "induced voltage").

[0004] Figure 1A graph of the voltage induced at the two terminals of the stator of a generator of the type considered here is shown. The sinusoidal curve 2 (partially represented in dashed lines) corresponds to the voltage induced at the terminals of the stator formed by at least one coil when the permanent magnet rotor of the generator rotates substantially at a set angular velocity. The digital signal 4 represents the control signal of a switch arranged between the terminals of the stator, the state "1" indicating the closure (on) of the switch, which produces a short circuit of the at least one coil. Each short circuit causes the voltage at the terminals of the stator (represented by curve 6) to drop substantially to zero. Each temporary closure of the switch generates a braking pulse on the generator, thereby allowing its rotation speed to be limited so that it can be maintained on average at the set angular velocity.

[0005] from Figure 1 As can be seen in , each braking pulse is triggered quickly upon detection of a zero crossing of the induced voltage, and the duration of each braking pulse is arranged so that it ends just after the zero crossing used to trigger the braking pulse and before the induced voltage reaches a peak value. Preferably, the duration of each braking pulse is arranged so that it ends before the rectified induced voltage reaches the value of the supply voltage of the power supply capacity intended to be recharged by the generator. Therefore, each braking pulse has a maximum duration T1, which allows to ensure that the generator can fulfill its function as a source of electrical energy for the regulation module in the normal operation of the watch movement, and to this end recharge the power supply capacity in each half cycle of the induced voltage signal. Therefore, a single braking pulse with a limited duration, for example at most one sixth of the period T0 of the signal (T1=T0 / 6), is provided in each half cycle of the induced voltage signal after the zero crossing of the induced voltage signal. Although the braking pulses can be applied to the generator at a frequency equal to twice the frequency of the induced voltage signal, the braking power is limited. A consequence of this fact is that the normal operating range of a watch movement is limited, since the torque continuously applied to the generator must be limited so that the useful portion of the mechanical power used to drive it, which is available when the rotor is accelerating, is always less than the maximum braking power. Since a watch movement is usually provided with an internal mechanical energy source, i.e. it comprises one or more barrels, the limited braking power results in a limited power reserve. Summary of the invention

[0006] The object of the present invention is to overcome the above-mentioned problems by proposing a timepiece movement of the above-mentioned type which allows a wider operating range of the torque that can be provided by the barrel and therefore a greater power reserve.

[0007] To this end, the invention relates to a timepiece movement comprising a barrel, an analog time display mechanism and a regulator module for regulating the operation of the analog display mechanism, the regulator module comprising a continuously rotating generator formed by a rotor with permanent magnets rotated by the barrel and comprising at least one coil forming a stator connected to a regulation circuit arranged to be able to regulate the average rotation frequency of the rotor. The timepiece movement then comprises a power supply circuit connected to said coil and intended to supply power to the regulation circuit, the power supply circuit comprising a rectifier for rectifying an induced alternating voltage and a supply capacitor recharged by the voltage induced via the rectifier during charging cycles, said induced voltage reaching a peak value during each charging cycle. In addition, the regulating circuit is arranged to measure the rotation of the rotor over time, thereby detecting a drift of the average rotation frequency of the generator relative to a set frequency determined by an electronic oscillator associated with the regulating circuit, and / or a change in the rotation frequency, and to generate a braking pulse of the rotor by temporarily reducing the impedance at the terminals of the at least one coil, thereby braking the rotor according to the drift and / or the change to adjust the rotation speed of the generator and thus the operation of the analog display mechanism. The regulating circuit is arranged to detect the zero crossing of the induced alternating voltage generated in the at least one coil by the rotating rotor and to generate a first braking pulse, each first braking pulse being triggered after the detection of the zero crossing of the induced voltage, the duration of each first braking pulse being arranged so that it ends after the zero crossing for triggering the first braking pulse and before the induced alternating voltage reaches a peak value. According to the invention, the regulating circuit is arranged to further generate a second braking pulse, each second braking pulse being triggered after the detection of the end of one of the charging cycles of the supply capacitor, and each second braking pulse having a duration arranged for each second braking pulse to end before the zero crossing of the induced alternating voltage.

[0008] In a preferred variant, each first braking pulse is arranged so that it ends before the absolute value of the induced alternating voltage reaches the supply voltage value of the supply capacitor intended for supplying the regulating circuit. The charging cycle of the supply capacitor is both a cycle of direct recharging of this supply capacitor and a cycle of recharging an additional capacitor incorporated in the rectifier, which temporarily stores the electrical energy generated by the generator, which is then transferred to the supply capacitor, in particular in the second half of the cycle of the induced voltage.

[0009] Thanks to the characteristics of the invention, the braking power of the generator can be increased by means of the generation of second braking pulses, without interfering with the recharging of the supply capacitor by the generator and without hindering the detection of the zero crossing of the induced voltage signal, thus allowing the number of rotor revolutions to be counted so as to be able to determine the almost instantaneous frequency of the generator and its average frequency over time, thus being able to ensure a high-precision indication of the current time through the regulation of the generator speed when the watch movement is continuously running. In a preferred embodiment, the invention allows the generation of two first braking pulses and two second braking pulses in each period of the voltage signal induced in the stator of the generator by the rotating rotor to brake the generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will be described in more detail below using the accompanying drawings, given by way of non-limiting examples, in which:

[0011] - Already described Figure 1 shows the voltage induced in at least one coil of the stator of a clock-type generator and the voltage at the terminals of said at least one coil when the rotation speed of the generator is regulated with a maximum braking power according to the prior art by braking pulses via a short circuit of said at least one coil, each braking pulse occurring in the first half of each half-period of the induced voltage signal;

[0012] - Figure 2 shows the voltage induced at the terminals of the stator of a clock-type generator and the voltage between these terminals when the rotation speed of the generator is regulated according to the invention with a braking power increased by means of braking pulses via a short circuit forming at least one coil of the stator, each braking pulse occurring in the second half of a half-period of the induced voltage signal;

[0013] - Figure 3 A first embodiment of a timepiece movement according to the invention is shown schematically and partially. DETAILED DESCRIPTION

[0014] refer to Figure 2 and 3 , a first embodiment of a timepiece movement 12 according to the invention will be described. In general, the timepiece movement 12 comprises a barrel 14, an analog time display mechanism 16 arranged to be able to drive a current time indicator (not shown), and a regulator module for regulating the operation of the analog display mechanism, the regulator module comprising a continuously rotating generator 18 and a regulating circuit 20. The generator is formed in a known manner by a rotor with permanent magnets rotated by the barrel and a stator comprising at least one coil connected to a regulating circuit, the regulating circuit being arranged to be able to regulate the average rotation frequency of the rotor. Figure 3In the variant shown, the generator comprises one or more “wafer” type coils (in the shape of a flat disk with a circular or other external contour, for example a trapezoidal contour). In the case of a plurality of coils, the coils are connected in series or in parallel so that the stator has two terminals 22 and 24 .

[0015] The watch movement comprises a power supply circuit 26 connected to the stator and intended to supply the regulating circuit. This power supply circuit comprises: a "half-wave" rectifier for rectifying the induced alternating voltage generated by the rotation of the rotor in the coils of the stator, the rectifier being formed by an active diode / switching tube 30; and a power supply capacitor 32 charged by the induced voltage via the active diode. It should be noted that the rectifier may further comprise a booster. Thus, the rectifier receives at its input a voltage U corresponding to the voltage at the terminals of the stator. B , and provides a rectified voltage U corresponding to the rectified induced voltage to the active diode at the output terminal G (In the absence of a short circuit between the terminals of the stator). The active diode 30 is formed by a transistor 34 and a comparator 36, the output of which controls the transistor, and is arranged by construction so that when the input voltage U G Greater than the output voltage U A Add a predetermined threshold voltage U S (U G >U A +U S ), so when the active diode is turned on, the voltage drop across the transistor is greater than the threshold voltage. A is the supply voltage provided by the supply capacitor 32. The threshold voltage U S For example, it has a value between 10 and 20 mV. This threshold voltage is obtained by the asymmetric structure of the comparator 34 (known in the art).

[0016] The regulating circuit is arranged to be able to measure the rotation of the rotor over time and thus detect a drift of the average rotation frequency of the generator relative to a set frequency determined by an electronic oscillator associated with the regulating circuit, and / or a variation of the rotation frequency, and to be able to generate a braking pulse of the rotor by temporarily reducing the impedance at the terminals of the stator, thereby braking the rotor according to the measured drift and / or the detected variation, in order to regulate the rotation speed of the generator 18 and thus the operation of the analog display means 16. The measurement of the rotor rotation can advantageously be performed in a known manner by detecting the zero crossing of the induced voltage signal 2 at the stator terminals (see Figure 2 ). Circuits and oscillators of electronic type (usually quartz oscillators) for measuring the rotation of a rotor are known and are used in Figure 32 , 24 of the stator, which is controlled by a control unit 40 which closes the switch during different time intervals in order to generate the braking pulses by short-circuiting. The control unit 40 is part of the regulating circuit and it supplies a digital control signal 42 to the switch 38 as a function of various regulating parameters characteristic of the planned regulating method. Thus, the control circuit 40 generates more or less braking pulses, in particular as a function of changes detected over time in the rotation of the rotor and / or of drifts measured.

[0017] As stated above, the object of the invention is to allow increasing the braking power of the generator without compromising its function of supplying the regulating circuit and without hindering the detection of the zero crossing of the induced voltage in the stator of the generator, which detection can be used to measure the rotation of the rotor and can also be used to generate a first braking pulse in a known manner, the first braking pulse corresponding to the first control pulse 44 that generates the first braking pulse, the first braking pulse being triggered after the detection of the zero crossing of the induced voltage signal.

[0018] When the switch is turned on / on, Figure 2 The voltage U at the terminals of the stator represented by curve 46 is B becomes essentially zero, and the induced voltage can no longer be measured. Therefore, the duration T1 of each first control pulse 44 is arranged so that the first braking pulse generated thereby ends after the zero crossing for triggering the first braking pulse and before the induced voltage reaches a peak value, that is, within the first half of the half cycle of the induced voltage signal 2. Preferably, the duration T1 has the following maximum value, that is, the maximum value ensures that each first braking pulse is terminated when the induced voltage reaches a supply voltage U equal to the supply voltage U provided for the regulating circuit. A Ends before the value of Figure 2 ) to allow for an optimal charging period of the supply capacitor, i.e. as long as possible. The recharging of the supply capacitor by the generator is respectively expressed as a voltage signal U at the stator output terminal. B Neutralizes the voltage signal U at the output of the rectifier 28 G A substantially flat region is generated in the , which corresponds to the charging period of the supply capacitor during which the active diode is turned on / conducting. The induced voltage and the rectified induced voltage reach a peak value and a maximum value, respectively, in each charging period.

[0019] According to the invention, the regulating circuit 20 is arranged to be able to generate, in addition to the first braking pulse, a second braking pulse by temporarily reducing the impedance at the terminals of the stator, the second braking pulse corresponding to the second control pulse 50 generating the second braking pulse, the reduction of the impedance being achieved by closing the switch 38 to short-circuit these terminals as for the first braking pulse. The second braking pulses each occur after the induced voltage has crossed a peak value, i.e. in the second half of a half-cycle of the induced voltage signal, and each ends before the induced voltage crosses zero according to this peak value. More specifically, it is envisaged that each second braking pulse occurs after the end of a charging cycle of the supply capacitor 32, so as not to limit this charging cycle and thus not to reduce the efficiency of the generator in recharging the supply capacitor. To this end, the regulating circuit 20 comprises a detection circuit 48 allowing the detection of charging cycles during which the active diode 30 is switched on / conducting and the supply capacitor is thus recharged, and more specifically the end of these charging cycles.

[0020] The detection circuit 48 provides the control unit 40 with a digital detection signal S indicating the state of the active diode 30. D The control unit 40 manages the impedance at the terminals of the stator, and is arranged so that as long as the signal S D With a transition indicating the end of one of the charging cycles, the second braking pulse can be triggered by the rising edge of the second control pulse 50. Thus, the rising edge of each second pulse 50 of the control signal 42 generating the second braking pulse advantageously follows almost immediately after the detection of the end of one of the charging cycles during which the supply capacitor is recharged.

[0021] The detection circuit 48 comprises an amplifier and an inverter 52 which receives at its input the output signal of the comparator 36 which is supplied to the transistor 34 of the active diode 30. It should be noted that the transistor 34 is manufactured in P-type MOS technology (PMOS). Therefore, when the output signal of the comparator is in the "low" state, the transistor is conducting. When the comparator receives the rectified voltage U of the generator at its negative terminal, the comparator 36 is turned on. G And receives the supply voltage U at its positive terminal A In the case of U G >U A +U S, its state is "low" and the transistor is turned on. Thus, during each charging cycle in which the generator recharges the power source 32, the comparator 36 supplies a "low" signal, and when this charging cycle is over, the output signal of the comparator switches from the "low" state to the "high" state, and the analog signal 54 at the output of the inverting amplifier 52 switches from the "high" state to the "low" state. The detection circuit 48 further comprises an analog-to-digital converter 56 (A / D converter), in particular of the "Schmitt trigger" type with hysteresis, arranged after the inverting amplifier. This A / D converter supplies a digital detection signal S to the control unit 40. D , thereby allowing the control unit 40 to receive information on the end of each charging cycle of the power supply capacitor by detecting changes in the value of the signal SD.

[0022] In the shown variant of the detection circuit, when the signal S D The value of switches from the value "1" to the value "0" (signal S D The charging cycle ends when the falling edge of the signal S D The transition between the value "0" and the value "1" (rising edge) of indicates the moment of the end of the charging cycle. As described above, as long as the control unit detects the end of the charging cycle, and if the regulation method requires a second braking pulse at this time, the control unit generates a second control pulse 50, the rising edge of which (the case where the control pulse is given by the value "1" of the control signal 42) occurs almost simultaneously with the detected end of the charging cycle. The duration T2 of each second control pulse 50 is arranged so that the generated second braking pulse ends before the induced voltage reaches the value zero, so that the second braking pulse is within the second half of the half cycle of the induced voltage signal 2 (see Figure 2 ). It should be noted that Figure 2 Only the induced voltage 2 in the stator and the voltage U at the terminals of the stator of the generator 18 are shown. B and three control pulses which generate three braking pulses within this period, namely two first braking pulses and one second braking pulse, the second braking pulse appearing in the positive half-period of the induced voltage, as allowed by the above-mentioned first embodiment with a "half-wave" rectifier.

[0023] It should be noted that in the context of the first embodiment, as long as the sign of the induced voltage is known after each zero crossing of the induced voltage, it is possible to increase the duration of the braking pulses occurring in the negative half-cycle of the induced voltage, thereby significantly increasing the braking power by means of third braking pulses, each of which starts before the moment when the induced voltage crosses an extremely negative value and ends after this moment. The duration of the third braking pulse is in particular greater than one quarter of the period of the induced voltage. However, according to the technology used and the electronic circuit provided, the recharging of the capacitor by the generator requires recharging of the capacitor in each half-cycle of the induced voltage. For this purpose, a second preferred embodiment of the invention is envisaged (not shown), in which a "full-wave" rectifier is arranged, which is formed in a known manner by two active diodes, advantageously an active PMOS diode that becomes conductive in the positive half-cycle and an active NMOS diode that is conductive in the negative half-cycle of the induced voltage. At the terminals 22 of the generator and the transmission voltage U A The positive terminal of the power supply capacitor V DD A PMOS diode (also used in the first embodiment) is also arranged between the Figure 3 The detection circuit 48 is shown in FIG. 4. The NMOS diode is arranged between the terminal 22 of the generator and the negative terminal V of the supply capacitor. SS The NMOS diode is arranged in the rectifier so that G Less than negative U S (That is to say, U G <-U S ) is turned on. In addition, between the terminal 24 of the generator and the terminal V of the power supply capacitor 32 DD An additional capacitor (of which the value is usually slightly less than half of the supply capacitance) is arranged between the two electrodes. This additional capacitor is charged during the positive half-cycle of the conduction of the PMOS diode and discharged during the negative half-cycle of the conduction of the NMOS diode, and the energy transfer to the supply capacitance occurs only once per cycle of the induced voltage, but the energy transferred is approximately equal to twice the energy transferred in the first embodiment. A second detection circuit is provided, which is similar to the first detection circuit associated with the active PMOS diode. This second detection circuit is arranged to provide a detection signal to the control unit, thereby enabling it to detect when the charging cycle of the supply capacitance ends, that is to say when the active NMOS diode switches from the conducting state to the non-conducting state, during the negative half-cycle of the induced voltage, thereby allowing the second braking pulse according to the invention to be generated also in these negative half-cycles.

[0024] It should be noted that the invention allows the speed of the generator 18 to be adjusted within a wide range of torques applied to the rotor of the generator, which range is roughly within the torque used for the normal operation of the watch movement to the maximum torque that still allows the operation of the display mechanism 16 to be adjusted by the adjustment module according to the invention. When the torque is minimum, that is to say theoretically no braking pulses are needed to keep the rotation of the generator at the set speed in stable conditions, in practice no more regulation is performed, so that in practice the torque used for the normal operation of the watch movement is slightly greater than such minimum torque. In a second embodiment, when the torque is maximum, the regulation of the angular speed of the generator rotor requires the generation of a first braking pulse and a second braking pulse in each half cycle of the induced voltage, each of which has a corresponding maximum duration. Between these two extreme values ​​of torque, there are several possible options for regulating the average frequency of the generator. In particular, it can be started by reducing the duration of the first braking pulse and / or the second braking pulse. It can also be started by periodically eliminating / suppressing the first braking pulse and / or the second braking pulse. In a specific variant in which the number of second braking pulses per unit time first gradually decreases as the torque decreases from its maximum value, an intermediate torque is reached at a specific moment for which only the first braking pulses are required in stable operation of the generator. As the torque continues to decrease, the duration and / or frequency of the first braking pulses then decreases. It can thus be understood that several variants of the regulation method can be considered within the context of the invention.

[0025] The central point of the invention concerns the arrangement of the regulation module so that, if necessary, a first braking pulse and a second braking pulse can be generated in each positive half-cycle (first embodiment) or in each half-cycle (second embodiment) of the voltage induced between the terminals of the stator of the generator, without interfering with the function of the generator's power supply to recharge the power supply circuit of the regulation circuit, and without hindering the detection of the successive zero crossings of the induced voltage signal, the detection for measuring the angular velocity of the rotor and therefore its frequency (revolutions per second), and the detection for triggering the first braking pulse, optionally with a small time phase shift.

Claims

1. A watch movement (12) comprising a barrel (14), an analog time display mechanism (16) and a regulating module for regulating the operation of the analog time display mechanism, the regulating module comprising a continuously rotating generator (18) and a regulating circuit (20), the generator being formed by a rotor having a permanent magnet driven to rotate by the barrel and comprising at least one coil forming a stator, the at least one coil being connected to the regulating circuit, the regulating circuit being arranged to be able to regulate the average rotation frequency of the rotor; the watch movement comprising a power supply circuit (26) connected to the at least one coil and intended to power the regulating circuit, the power supply circuit comprising a rectifier (28) for rectifying an induced AC voltage and a power supply capacitor (32) which is recharged by a voltage induced by the rectifier during a charging cycle, the induced voltage reaching a peak value in each charging cycle; the regulating circuit being arranged to be able to measure the The invention relates to a device for controlling the rotation of the generator with respect to the rotation of the rotor over time and thus being able to detect a drift of the average rotation frequency of the generator relative to a set frequency determined by an electronic oscillator associated with the regulating circuit, and / or a change in the rotation frequency, and being able to generate a braking pulse of the rotor by temporarily reducing the impedance at the terminals of the at least one coil, thereby braking the rotor in accordance with the drift and / or the change to adjust the rotation speed of the generator and thus adjust the operation of the analog time display mechanism; the regulating circuit is arranged to be able to detect the zero crossing of the induced AC voltage generated in the at least one coil by the rotating rotor and to generate a first braking pulse (44), each of the first braking pulses (44) being triggered after the zero crossing of the induced voltage is detected, the duration (T1) of each first braking pulse being arranged so that it ends after the zero crossing for triggering the first braking pulse and before the induced AC voltage reaches a peak value; characterized in that The regulating circuit is arranged to further generate second braking pulses (50), each of which is triggered after detecting the end of one of the charging cycles of the supply capacitor and has a duration (T2) arranged for each second braking pulse to end before the induced AC voltage passes through zero.

2. The watch movement according to claim 1, characterized in that: Each first braking pulse is provided so that the absolute value of the induced AC voltage is equal to the supply voltage (U A ) ends before.

3. The watch movement according to claim 1 or 2, characterized in that: The rectifier (28) comprises at least one active diode (30) formed by a transistor (34) and a comparator (36), the output of the comparator controlling the transistor, the active diode being arranged by construction to G ) is greater than the output voltage (U A ) plus a predetermined threshold voltage (U S ), and when the active diode is turned on, the voltage drop across the transistor is greater than the predetermined threshold voltage.

4. The watch movement according to claim 3, characterized in that: The regulation circuit comprises a detection circuit (48) for detecting a charging period during which the active diode conducts and the generator recharges the supply capacitor, the detection circuit providing a digital detection signal (S) about the state of the active diode to a control unit (40). D ), the control unit (40) managing the impedance at the terminals of the at least one coil, the control unit being arranged to trigger a second braking pulse (50) as soon as the digital detection signal has a transition indicating the end of one of the charging cycles.

5. The watch movement according to claim 4, characterized in that: The regulating circuit comprises a switch (38) between the terminals of the at least one coil, which switch is controlled by the control unit (40), which closes the switch during different time intervals (T1, T2) in order to generate a braking pulse by short-circuiting.

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