EP0239820B1 - Mechanical-to-electrical energy converter - Google Patents

Abstract

1. A mechanical-to-electrical energy converter which comprises : - an electrical energy generator (2; 30; 50) having a rotor (3) and means (6, 7; 40, 41, 7) for generating said electrical energy in response to rotation of said rotor (3) ; - means (8) for storing at least temporarily said electrical energy ; - a mechanical energy source (1) connected mechanically to said rotor (3) and able to generate a mechanical driving torque for driving said rotor (3) at a first speed greater than a predetermined set speed in the absence of any other influence ; - means (21, 22; 22'; 22"; 54, 55) for generating a periodic reference signal having a period equal to the ratio between a predetermined angle of rotation of said rotor (3) and said set speed ; - means (23 to 28; 23, 24', 25', 26 to 29; 23, 24", 25", 26, 27, 28"; 56, 59) for generating a control signal having a first and a second state ; and - means (11; 11') for electrically braking said rotor (3) able to respond to said first state of the control signal to cause the application to said rotor (3) of a braking torque opposed to said mechanical driving torque and imposing on said rotor (3) a second speed lower on average than said set speed and able to respond to said second state of the control signal to stop said application to the rotor (3) of said braking torque ; characterized in that said means (23 to 28; 23, 24', 25', 26 to 29; 23, 24", 25", 26, 27, 28"; 56, 59) for generating a control signal include means (23, 56) for putting said control signal into one of said states at each one of a plurality of first instants that follow each other periodically with a period equal to that of said reference signal, and means (24 to 28; 24', 25', 26 to 29; 24", 25", 26, 27, 28"; 59) for putting said control signal into the other of said states at second instants, each separated from the immediately preceding first instant by a time interval having a duration less than said reference signal period.

Description

The present invention relates to a converter of mechanical energy into electrical energy.

The cells and batteries used to power portable devices, such as electronic timepieces, cameras or radio receivers, have many disadvantages. In particular, their lifespan is limited, which requires them to be replaced more or less frequently, and their sealing is often not perfect, which can cause damage to the devices they supply.

It has been proposed to replace these cells and batteries with converters comprising a rotary generator of electrical energy driven in rotation by a source of mechanical energy.

Patent CH-B-597,636, for example, describes an electronic timepiece supplied with electrical energy by such a converter. In this converter, the mechanical energy source is constituted by a barrel spring of the type, well known, of those which drive mechanical timepieces of small volume, which is connected to a manual or automatic winding device.

The electric power generator described in this patent CH-B-597,636 comprises six permanent magnets fixed to a rotor driven in rotation by the spring, by means of a gear train. It also comprises a fixed coil, arranged near the rotor, so that the displacement of the permanent magnets relative to this coil induces in the latter an alternating voltage.

The converter also comprises a rectifier circuit which transforms the alternating voltage produced by the coil in response to the rotation of the magnets into a rectified voltage, and a storage and filtering capacitor which temporarily stores the electric energy produced by the generator and the restores in the form of a substantially continuous voltage.

The timepiece described in this patent CH-B-597,636 further includes time display hands which are also connected to the spring by at least part of the gear train connecting this spring to the generator rotor. .

The average speed of rotation of the needles, which must of course have a well-determined value, is controlled by an electronic circuit for adjusting the average speed of rotation of the generator rotor.

This adjustment circuit is supplied by the substantially continuous voltage present at the terminals of the storage capacitor mentioned above. It comprises electrical braking means connected in parallel with the storage capacitor, and a circuit for controlling these braking means. The latter consist of a braking resistor and an electronic switch connected in series with each other.

The braking means control circuit includes a source delivering a reference signal having a well-determined frequency.

The source of the reference signal is constituted by a quartz oscillator connected to the input of a frequency divider circuit whose output delivers the reference signal in the form of pulses.

The control circuit further comprises a reversible counter, or up-down counter, whose down-counting input receives the reference signal and whose down-counting input receives a measurement signal having a frequency equal to the frequency of the alternating voltage produced by the coil, and therefore proportional to the speed of rotation of the rotor.

The reversible counter produces a signal which closes the switch connected in series with the braking resistor when its content is greater than zero, and which opens this switch otherwise.

The various elements of the gear train are dimensioned so that if the rotor was continuously rotating at a speed such that the frequency of the measurement signal is equal to that of the reference signal, the time display hands would rotate at their normal speed, i.e. one revolution every twelve hours for the hour hand, one revolution per hour for the minute hand and, if necessary, one revolution per minute for the second hand .

This rotational speed of the rotor will be called the reference speed Vc in the rest of this description.

The elements of the converter are also dimensioned so that if the switch is open, that is to say if the braking resistor is not connected to the terminals of the storage capacitor, the rotor is accelerated to a speed greater than this reference speed Vc in response to the motor torque applied to it by the spring via the gear train.

The elements of the converter are also dimensioned so that, if the switch is closed, and the braking resistor is therefore connected in parallel with the storage capacitor, the rotor is braked to a speed which is, on average, lower than the speed Vc in response to the electric braking torque caused by the connection of the braking resistor in parallel with the storage capacitor.

It is easy to see that, under these conditions, the instantaneous speed of the rotor oscillates on either side of this set speed Vc.

When the content of the reversible counter is less than zero, the switch is open and the rotor is accelerated. When its speed becomes greater than the setpoint speed Vc, the frequency of the measurement signal becomes greater than the frequency of the reference signal. The reversible counter is therefore incremented faster than it is decremented, and its content increases. When this content becomes greater than zero, the reversible counter closes the switch in series with the braking resistor. From this moment, the rotor is therefore braked, and its speed decreases.

When this speed becomes lower than the set speed Vc, the frequency of the measurement signal becomes lower than that of the reference signal. The reversible counter is therefore decremented faster than it is incremented, and its content decreases. When this content drops below zero, the reversible counter opens the switch again. From this moment, the rotor is therefore no longer braked, its speed increases, and the process described above begins again.

If it is measured over a sufficiently long time, the average speed of the rotor is therefore well equal to the set speed Vc.

The generator rotor described above has the serious drawback of having a large inertia, which makes it very sensitive to shocks of all kinds that the timepiece can undergo. In addition, the coil of this generator does not have a core, which complicates and increases its production and prevents it from being given a high number of turns.

To avoid these drawbacks, it is possible to replace the generator described above with that described in Japanese patent application JP-A-52-85 851, which lends itself much better to use in a timepiece. .

This generator resembles stepper motors as they are commonly used in electronic timepieces. It comprises a rotor comprising a single bipolar magnet which is magnetically coupled to a coil by a stator.

As in stepper motors, the stator of this generator has two pole shoes almost completely surrounding the rotor and ending, each, a pole piece whose other end is connected to one of the ends of the coil core. The pole shoes are separated by air gaps arranged symmetrically with respect to the axis of the rotor.

On the other hand, this stator does not include the notches, or other means, which, in the motors, are used to create a positioning torque for the rotor.

In a converter such as that just described, the losses by mechanical friction of the various moving parts between them and their bearings are directly proportional to the set speed Vc of the rotor. In addition, the hysteresis and eddy current losses in the generator stator, when the latter has one, are respectively proportional to this set speed Vc and to its square.

It is therefore imperative to choose for this reference speed Vc a value as low as possible, so that the efficiency of the converter is as high as possible, and that its autonomy, that is to say the time during which it can operate without the spring which supplies it with mechanical energy having to be wound up, is as long as possible.

In the converter described by patent CH-B-597,636, the braking resistor remains engaged as long as the content of the up-down counter is greater than zero. It can therefore occur that the rotor is braked without interruption for a fairly long time, especially if an angular shock previously strongly accelerated it.

The instants of engagement and initiation of the braking resistor also occur practically randomly with respect to the angular position of the rotor. It can therefore happen, during several consecutive turns of the rotor, that the alternating voltage produced by the generator coil is close to zero between each of these triggering instants and the next engagement instant, and that this generator therefore does not provide any electric energy.

To prevent the supply voltage of the electronic circuits from decreasing too much in such cases, it is necessary to size the converter so that the generator continues to supply the electrical energy consumed by these circuits even when the rotor is braked.

The rotational speed of the rotor when it is braked should therefore not be chosen too low, because otherwise the number of turns of the generator coil should be very high for the above condition to be fulfilled. This coil would then have a space incompatible with the space available in a timepiece of small volume. Or if the diameter of its wire is chosen small enough so that this space is not too large, the technical difficulties of its manufacture, and therefore its cost price, would become very high.

It is well known that the voltage supplied by the coil depends not only on the number of turns of the latter and the speed of rotation of the rotor, but also on the number of poles of the permanent magnet and the amount of magnetic flux produced by this magnet and going through the coil. This last quantity is generally called "coupled flow".

It would therefore theoretically be possible to increase these last two factors, or at least one of them, to increase the voltage produced by a coil having a relatively small number of turns in response to the voltage of a rotor rotating at an equally low speed.

These increases are not practically achievable, however. On the one hand, permanent multipolar magnets are difficult to produce, and therefore expensive. In addition, for a given material and volume, the product of the flux coupled by the number of pairs of poles of the magnet decreases when this number of pairs of poles increases.

On the other hand, the increase in the coupled flux requires a reduction in the width of the air gap separating the permanent magnet from the stator which surrounds it or the use of a magnet having a higher coercive field. These modifications lead to a tightening of the tolerances which can be accepted for the manufacture of the stator and the magnet, and therefore an increase in their cost price. In addition, these modifications also lead to an increase in the residual positioning torque of the rotor and of the friction of its axis in its bearings, this torque and this friction being caused by the inaccuracies which still exist in the dimensions and the actual relative positions of the magnet and stator. Finally, these modifications lead to an increase in losses of magnetic origin in the stator.

Still in order to be able to use a coil having a number of turns which is not too high and to be able to choose a low value for the rotation speed of the rotor, it would also theoretically be possible to use a voltage multiplier rectifier to rectify the voltage produced by the coil. However, such rectifiers include a large number of capacitors, which are bulky elements. In practice, it is possible to use, in a device such as that which has been described above, only simple rectifiers or, at most, so-called "voltage doublers" rectifiers.

It follows from the above that the rotational speed of the rotational generator of a converter such as that described by patent CH-B-597,636 when it is braked must be chosen at a relatively high value. The setpoint speed Vc of this rotor, which must of course be greater than the latter, cannot therefore be chosen at an arbitrarily low value.

As the efficiency of the converter is higher the lower this set speed Vc, the latter is chosen as close as possible to the speed of the generator rotor when it is braked. It follows that the elements of the converter must be dimensioned so that the speed of the generator rotor when it is not braked is also close to the set speed Vc. The variations in the instantaneous speed of the rotor around the set speed Vc are therefore small.

Theoretical considerations, which will not be reproduced here, confirmed by practical tests, have shown that the setpoint speed Vc above cannot be less than 8 to 10 revolutions per second if the generator coil must have a compatible volume with the volume available in a timepiece such as a wristwatch, and if the diameter of the wire of this spool must be compatible with the requirements of mass production and low cost price.

These same considerations and these same tests show that, for such a reference speed, the efficiency and the autonomy of the converter are insufficient for it to be able to be used practically in a timepiece of small volume.

The converter described by patent CH-B-597,636 has yet another drawback, due to the fact that the braking means of the rotor are connected directly in parallel with the storage capacitor of the electrical energy supplied by the generator.

When the switch in series with the braking resistor is closed, the storage capacitor therefore discharges into this resistor, and part of the energy dissipated in the braking resistor is supplied by the storage capacitor. The braking of the rotor is therefore less effective than if the energy dissipated in the braking resistor was supplied only by the generator. In addition, the overall efficiency of the converter is reduced by the fact that the energy coming from the storage capacitor which is dissipated in the braking resistor is lost for the supply of the circuits for which it was intended.

The object of the present invention is to provide a converter of the type described above, but which does not have the disadvantages thereof, that is to say a converter in which the set speed of the generator rotor can be chosen at a low value so that the efficiency and the autonomy of this converter are great, in which the number of turns of the coil of this generator is however low enough so that this coil can be manufactured in a volume and at a low price, and in which the generator provides in all circumstances, with safety, a sufficient amount of energy so that the voltage across the storage capacitor remains permanently high enough for the electronic circuits powered by this voltage work properly.

This object is achieved by the claimed converter.

• - la figure 1 représente schématiquement une forme d'exécution du convertisseur selon l'invention;
• - les figures 2a et 2b sont des diagrammes permettant d'expliquer le fonctionnement du convertisseur de la figure 1;
• - la figure 3 repésente schématiquement la variation du facteur de couplage entre le rotor et la bobine du générateur des figures 1 et 7, ou les bobines du générateur de la figure 5.
• - la figure 4 représente le schéma d'une variante du circuit de commande des moyens de freinage de la figure 1;
• - la figure 5 représente schématiquement une autre forme d'exécution du convertisseur selon l'invention;
• - la figure 6 représente le schéma d'une variante du circuit de commande des moyens de freinage de la figure 5;
• - la figure 7 représente schématiquement une autre forme d'exécution du convertisseur selon l'invention;
• - la figure 8 représente schématiquement les couples exercés sur le rotor du générateur de la figure 7; et
• - la figure 9 est un diagramme permettant d'expliquer le fonctionnement du convertisseur de la figure 7.

The present invention will now be described with the aid of the drawing in which:

• - Figure 1 schematically shows an embodiment of the converter according to the invention;
• - Figures 2a and 2b are diagrams to explain the operation of the converter of Figure 1;
• FIG. 3 schematically represents the variation of the coupling factor between the rotor and the generator coil of FIGS. 1 and 7, or the generator coils of FIG. 5.
• - Figure 4 shows the diagram of a variant of the control circuit of the braking means of Figure 1;
• - Figure 5 shows schematically another embodiment of the converter according to the invention;
• - Figure 6 shows the diagram of a variant of the control circuit of the braking means of Figure 5;
• - Figure 7 schematically shows another embodiment of the converter according to the invention;
• - Figure 8 shows schematically the torques exerted on the rotor of the generator of Figure 7; and
• FIG. 9 is a diagram making it possible to explain the operation of the converter of FIG. 7.

The mechanical energy to electrical energy converter shown in FIG. 1 is intended to equip a timepiece.

It comprises a mechanical energy source 1 constituted by a barrel spring which has only been shown schematically because it is of the same kind as those which are used in mechanical timepieces and which are well known. This spring is coupled to a manual or automatic winding mechanism which has not been shown because it can be similar to any of the many mechanisms of this kind which are well known in watchmaking.

The converter of FIG. 1 also comprises an electrical energy generator 2, similar to that which is described by the patent application JP-A-5,285,851 already mentioned.

This generator 2, which is shown diagrammatically, resembles stepper motors as they are commonly used in electronic timepieces. Like these motors, it comprises a rotor 3 comprising a permanent bipolar magnet 3a having an axis of magnetization substantially perpendicular to the axis of rotation 3b of the rotor 3. To avoid unnecessarily complicating the drawing, the rotor 3 has not been shown in detail in the figures where it is simply symbolized by the magnet 3a.

The rotor 3, and therefore the magnet 3a, are rotated around the axis 3b by the spring 1, by means of a gear train 4 symbolized by a dashed line.

The generator 2 also includes a stator 5 which magnetically couples the magnet 3a to a coil 6.

As in some stepper motors, the stator 5 has two air gaps 5a and 5b arranged symmetrically with respect to the axis 3b of the rotor 3 and which separate from one another two pole shoes each terminating a pole piece, the other end is connected to one of the ends of the core of the coil 6. The air gaps 5a and 5b can moreover be replaced by metal parts forming only one piece with the rest of the stator and the dimensions of which are such that they have a very high reluctance.

By cons, the stator 5 does not include any means such as notches in the wall of the pole shoes, which are intended, in stepper motors, to create a positioning torque of the rotor.

The converter further comprises a rectifier circuit 7 which transforms the alternating voltage produced by the coil 6 in response to the rotation of the magnet 3a into a rectified voltage, and a storage capacitor 8 which filters this rectified voltage and which temporarily stores the electrical energy produced by the converter.

The rectifier 7 has not been shown in detail, since it may be similar to any of the rectifiers which are well known to specialists. It can be, for example, a simple bridge rectifier, or a voltage doubler rectifier. In the latter case, the capacitor 8 can advantageously consist of the two capacitors which are an integral part of this kind of rectifier.

The electronic circuits of the converter of FIG. 1, which will be described below, are supplied by the substantially direct voltage present at the terminals of the capacitor 8, by connections which have not been shown.

It is obvious that neither terminal 8a nor terminal 8b of capacitor 8 is at the same electrical potential as terminal 6a or terminal 6b of the coil 6.

In the rest of this description, it will be accepted by way of nonlimiting example that the potential of terminal 6a of coil 6 is the reference potential of the converter or, in other words, that this terminal 6a is connected to the mass of the converter. It will also be accepted that the rectifier 7 is arranged so that the voltage present at the terminals 8a and 8b of the capacitor 8 is substantially symmetrical with respect to this reference potential, the potentials of the terminals 8a and 8b being respectively negative and positive with respect to this benchmark potential.

Similarly, in the description of the logic circuits which will follow, the points whose potential will be substantially equal to that of terminal 8a or terminal 8b will be described respectively as being in logic state "0" and in state logic "1".

The timepiece equipped with the converter of FIG. 1 further comprises hands 9 for displaying the time. It may also include a calendar mechanism, or other ancillary mechanisms.

The needles 9 and, where appropriate, the annex mechanism, are also connected to the spring 1 and to the rotor 3 by at least part of the gear train 4.

The average speed of rotation of the needles 9, which must of course have a well-determined value, is controlled by a circuit 10 for adjusting the speed of rotation of the rotor 3.

This adjustment circuit 10 comprises electrical braking means 11 of the rotor 3 and a control circuit 12 of these braking means 11.

In this example, these braking means 11 comprise a braking resistor 13 and an electronic switch 14 constituted by a transmission door which is blocked or conductive depending on whether its control electrode 14a is respectively in the logic "0" or " 1 ".

These braking means 11 are connected directly to the terminals of the coil 6 and not to the terminals of the capacitor 8 for storing electrical energy as in the converter described by patent CH-B-597,636 mentioned above.

In the example of FIG. 1 and in the examples which will be described below with the aid of FIGS. 4, 5 and 6, the reference speed Vc of the rotor 3 has been fixed, by way of nonlimiting example, at 4 rotations per second, and the elements of the device, in particular the gear train 4, have been dimensioned so that the hands 9 of the timepiece rotate at their normal speed when the speed of rotation of the rotor 3 is equal to this set speed Vc.

In the converter of FIG. 1, the control circuit 12 of the braking means 11 includes a quartz oscillator 21 which delivers a signal in the form of pulses having a frequency of 32,768 Hz.

The output of this oscillator 21 is connected to the input of a counter 22 composed of thirteen flip-flops connected in cascade to each other in a conventional manner. These thirteen flip-flops have not been shown separately.

This counter 22 therefore has a counting capacity of 81 92, that is to say that its content, which is represented by the binary number formed by the logic states "0" and "1 of the direct outputs of its thirteen flip- flops, varies periodically and cyclically, when expressed in decimal notation, from 0 to 8191.

The output 22a of the counter 22 is constituted by the inverse output, generally designated by Q, of the last of the thirteen flip-flops of this counter 22. This output 22a therefore delivers a signal having a frequency of 4 Hz or, in other words , a period of 250 milliseconds.

This signal goes from state "0" to state "1" each time the content of counter 22 goes from its maximum value 8191 to its minimum value 0, and returns to state "0" 125 milliseconds later. .

It will be made clear by the following description that the frequency of this signal determines the average speed of rotation of the rotor 3, and that this value of 4 Hz is that which gives this average speed a value equal to the chosen set value. , or 4 revolutions per second.

The signal produced by the output 22a of the counter 22 will be called the reference signal in the following description.

The output 22a of the counter 22 is connected to the clock input Ck of a flip-flop 23. This flip-flop 23 is of type T, so that its outputs Q and cr change state each time the reference signal goes from logic state "0" to logic state "1", provided that its reset input R is in state "0" at this time. When this input R is in logic state "1", the outputs Q and Q of the flip-flop 23 are respectively in the state "0" and "1", independently of the state of the input Ck. This last state of the flip-flop 23 will be designated as its rest state.

The outputs Q of the thirteen flip-flops which make up the counter 22, of which only the first, Q1, and the last, Q13, have been represented, are connected to the first thirteen inputs of a binary digital comparator 24 of which, again, only the first and the last were represented. These first inputs will be designated overall as the inputs A of the comparator 24.

The comparator 24 furthermore comprises second inputs, also thirteen in number, which will be designated, overall, as being its inputs B. Again, only the first and the last of the inputs B have been shown. The comparator 24 also includes an output 24a which is normally in the logic state “0” and which takes the state “1” when the binary numbers represented respectively by the logic states of the inputs A and B are equal. This output 24a is connected to the reset input R of the flip-flop 23.

The inputs B of the comparator 24 are connected to the outputs Q of thirteen flip-flops which are part of a reversible counter 25. These flip-flops have not been shown separately, and only the outputs of the first, Q1, and of the last , Q13, of these flip-flops have been shown.

Since the reversible counter 25 has the same number of flip-flops as the counter 22, the counting capacities of these two counters are therefore equal.

The counter 25 is arranged, in a well-known manner, so that its content is increased by one unit each time its counting input C changes from state "0" to state "1", and this content is decreased by one each time its down counting input D goes from state "0" to state "1".

The inputs C and D of this counter 25 are respectively connected to the outputs of two AND gates 26 and 27.

The first inputs of these gates 26 and 27 are connected together to the output of a formatter circuit 28, and their second inputs are respectively connected to the outputs Q and Q flip-flop 23.

This exit Q of the flip-flop 23 is also connected to the control electrode 14a of the transmission door 14.

The forming circuit 28 is arranged so that its output delivers a pulse each time the voltage of its input, which is connected to terminal 6b of the coil 6, passes through zero from its negative values to its positive values. It comprises, for example, an amplifier 28.1 with high gain and high input impedance, a capacitor 28.2 and a resistor 28.3 connected to each other as shown.

The operation of the converter of FIG. 1 will be described with the aid of FIGS. 2a and 2b in which the diagrams designated by 22a, Q23 and 28a respectively represent the logic states of the signals measured at the output 22a of the counter 22, at the output Q of the flip-flop 23 and at the outlet 28a of the formatter 28, and the diagrams designated by V and X schematically represent the speed of the rotor 3 and, respectively, its angular position as a function of time.

This angular position is identified by the angular position of the magnetization axis of the magnet 3a, and the origin of the angles X is chosen arbitrarily at the position through which this rotor 3 passes when, in the absence of any current by the coil 6, the voltage of the terminal 6b of the latter goes through zero increasing or, in other words, from its negative values to its positive values.

This position, which will be called the zero position of the rotor 3 in the following description, is one of those where the magnetization axis of the magnet 3a is perpendicular to the right joining the middle of the two air gaps 5a and 5b . It practically corresponds to the position through which the rotor 3 passes when the formatter 28 delivers a pulse.

In the description which follows, the instants when the reference signal goes from state "0" to state "1 will be designated by the reference t0. This reference will sometimes be supplemented by a serial number making it possible to distinguish the different instants t0 from one another.

It will be made clear later on in this description that if the rotor 3 making each of its turns at a constant average speed equal to the set speed Vc, it would pass through its zero position at each instant t0. In reality, the average speed of the rotor 3 during each of its turns is always slightly higher or slightly lower than the set speed Vc. It follows that, at each instant t0, the rotor 3 is slightly ahead or behind with respect to its zero position. As will also be made clear later on in this description, this advance or delay is detected by the gates 26 and 27 which together form a circuit for comparing the actual angular position of the rotor 3 at each instant t0 and its position zero.

The description of the operation of the converter in FIG. 1 begins at time t0, designated by t01.

It will be assumed, for example, that the rotor 3 has already passed through its zero position at this instant tO 1, and therefore has started a revolution, which will be called arbitrarily the first revolution, just before this instant t01. The trainer 28 therefore delivered a pulse also just before this instant t01, and the content of the counter 25 took a value N other than zero and its maximum value in response to this pulse.

It will be shown subsequently that just before each of the instants t0 and therefore also just before the instant t01, the flip-flop 23 is in its rest state, and its output Q is therefore in the state "1". The transmission door 14 is therefore conductive, and the rotor 3 is braked by the resistor 13 which is connected in parallel with the coil 6. The speed V of the rotor 3 is therefore low.

It should be noted that when the rotor 3 is braked, its speed V is not constant, since the braking torque applied to it depends in particular on the flux magnetic of the magnet 3a passing through the coil 6, which itself depends on the angular position of the rotor 3. To simplify Figures 2a and 2b, it is the average speed of the rotor 3 while it is braked which has been shown with reference V1.

As mentioned above, the reference signal goes from state "0" to state "1" at time t01.

At this instant t01, the flip-flop 23 therefore takes the state where its outputs Q and Q are respectively in state "1" and in state "0". This latter state “0” causes the transmission door 14 to block. The rotor 3 is therefore no longer braked by the resistor 13, and its speed V increases rapidly to take a high value.

The speed V of the rotor 3 is also not constant when this rotor 3 is not braked. This speed depends in particular on the current supplied by the coil 6 to the capacitor 8. However, as long as the no-load voltage output of the rectifier 7, that is to say the voltage which would be measured at its terminals if the latter were not not connected to the capacitor 8 or to the rest of the circuit, is less than the voltage across the capacitor 8, the coil 6 does not supply any current, and the rotor 3 is therefore not subjected to any electrical braking. By cons, as soon as the no-load output voltage of the rectifier 7 becomes greater than the voltage across the capacitor 8, the coil 6 begins to supply a current which charges this capacitor 8. The rotor 3 is therefore subjected to a braking torque due to the supply of this current. The latter is also not constant either because it depends, among other things, on the speed of rotation of the rotor 3 and the angular position of the latter. Still to simplify the drawing, it is the average speed of the rotor 3 when it is not braked which is represented in FIGS. 2a and 2b with the reference V2.

At each time t0, and therefore at time t01, the content of the counter 22 goes from its maximum value to zero.

After the instant t01, the content of the counter 22 increases regularly, starting from its zero value, in response to the pulses supplied by the oscillator 21.

At an instant designated by t11, the content of counter 22 becomes equal to the number N contained in counter 25.

The binary numbers applied to the inputs A and B of the comparator 24 then being equal, the output 24a of this comparator 24 goes to state "1", which returns the flip-flop 23 to its rest state.

The exit Q of this flip-flop 23 therefore returns to the state "1", which again makes the transmission door 14 conductive. The rotor 3 is again braked by the resistor 13, and its speed V returns to a low value.

It can be seen that the time T1 separating the instants t01 and t11, which is the time during which the rotor 3 is not braked, is proportional to the number N contained in the counter 25 at this instant t11.

The passage of the reference signal from state "1" to state "0", 125 milliseconds after time t01, has no influence on the circuit which remains in the last state described above until that one of the following two cases occurs.

In the first case, which is illustrated in FIG. 2a, the reference signal returns to the state "1", at an instant t02, before the rotor 3 has completed its first turn. The rotor 3 is therefore late.

As described above, this change to state “1” of the reference signal causes the transmission door 14. The rotor 3 not to be braked since this instant t02, it very quickly ends its first round, and begins a second round, at an instant t21 posterior to the instant t02 and very close to it.

The output Q of the flip-flop 23 being in the state “1 from time t02, the comparison circuit formed by the gates 26 and 27 delivers a comparison signal in the form of a pulse which appears at the output of gate 26 in response to the pulse delivered by trainer 28 at time t21. The output of the gate 26 being connected to the input C of the counter 25, the content of the latter therefore takes the value (N + 1) at this time t21, in response to this comparison signal.

At time t02, the content of counter 22 goes from its maximum value to zero. After this instant t02, as after the instant t01, this content increases regularly in response to the pulses produced by the oscillator 21.

When the content of the counter 22 reaches a value equal to the value (N + 1 at an instant t12, the output of the comparator 24 again changes to the state "1". As at instantt11, the output Q of the flip flop 23 therefore returns to the state "1" at this instant t12, which makes the conduction door 14 again conductive and therefore causes the braking of the rotor 3 by the resistor 13.

As during its first turn, the rotor 3 continues to rotate at low speed after the instant t12.

It should be noted that, in this case, the time T2 which separates the instants t02 and t12, that is to say the time during which the rotor 3 is not braked, is longer than the time T1 mentioned above. above. Indeed, this time T2 is proportional to the number (N + 1) contained in the counter 25 at time t12, a number which is obviously greater than the number N which determined the duration of the time T1.

The second of the cases which may arise at the end of the first turn of the rotor 3 is illustrated by FIG. 2b in which the left part also corresponds to this first turn and will not be described again.

In this second case, the rotor 3 ends its first turn at an instant t21 'situated before the instant t02' where the reference signal goes from the state "0" to the state "1". He is therefore ahead.

The output Q of the flip-flop 23 still being in the state "1" at the instant t21 ', the comparison signal has, in this case, the form of a pulse which appears at the output of the gate 27 in response to the impulse supplied at this time t21 'by the trainer 28. The output of gate 27 being connected to input D of counter 25, the content of this counter takes a value (N-1) in response to this comparison signal.

When the reference signal returns to the state "1", at the instant t02 ', the braking of the rotor 3 is suppressed and this rotor 3 takes a high speed until an instant t12' where the value of the content of the counter 22 becomes equal to this value (N-1).

As in the other cases described above, the rotor 3 is braked from this instant t12 'and then continues to rotate at low speed.

We see that, in this case, the time T2 'which separates the instants t02' and t12 'and during which the rotor is not braked is shorter than the time T1 mentioned above, since it is proportional to the number (N-1) contained in the counter 25 at time t12 ', a number which is obviously less than the number N.

In summary, it can be seen that the content of the counter 25 is incremented or decremented depending on whether the comparison signal between the real angular position of the rotor 3 at each instant t0 and its zero position shows that it is late or early.

It is clear that one or the other of the two cases described above occurs at the end of each period of the reference signal, but not necessarily alternately. It is indeed possible that at two or more successive times t0, the rotor 3 is always early or, on the contrary, always late. The number contained in the counter 25 is then respectively decreased or increased each time.

It is obvious that during each of the periods of the reference signal, the average speed Vt of the rotor 3 depends directly on the time during which it is not braked and therefore rotates at a high speed, time which is proportional to the number contained in the counter 25. All other things being equal, an increase or decrease in this number therefore causes an increase or, respectively, a decrease in this average speed Vt.

If, at an instant t0, the rotor 3 is late, its average speed Vt during the period of the reference signal which begins at this instant t0 is therefore increased compared to its average speed during the previous period. This increase in the average speed has the consequence that, all other things remaining equal, the rotor 3 will probably have an advance at the next instant t0 or, at least, its delay will have decreased.

A similar reasoning can be made in the case where, at an instant t0, the rotor 3 is ahead. In this case, at the next instant t0, the rotor will probably be late or, at least, its advance will have decreased.

It can therefore be seen that, during the operation of the converter, the real angular position of the rotor 3 at each t0 oscillates on either side of its zero position. The average angular position of the rotor 3 at times t0, measured over a fairly long time, is therefore identical to its zero position.

It follows that the average speed of the rotor 3, also measured over a fairly long time, is equal to the set speed Vc. This equality is maintained, independently of the variations in the motor torque exerted by the spring 1 via the gear train 4, provided of course that this spring 1 is not completely disarmed, and independently of the possible variations in mechanical friction and / or electrical and magnetic losses in the converter.

In summary, it can be seen that the circuit 10 adjusts the average speed of the rotor 3 during each period of the reference signal as a function of the result of a comparison, carried out just before or just after the start of this period, between the actual position of the rotor 3 and the position it would occupy if it were to rotate continuously at the set speed Vc.

This periodic regulation is carried out thanks to the fact that the circuit 12 systematically opens the switch 14 in series with the braking resistor 13 at the start of each period of the reference signal, which allows the rotor 3 to rotate at a speed greater than the setpoint speed Vc, and closes this switch after a time which is always less than the period of the reference signal and which depends on the result of the above comparison, which causes the braking of the rotor 3 to a speed which is on average less than the set speed Vc.

In the example of FIG. 1, the period of the reference signal is equal to the time that the rotor 3 would take to make exactly one revolution, that is 360 °, if it rotated at the set speed Vc. This period of the reference signal is obviously also equal to the period that the voltage supplied by the coil 6 would have if the rotor 3 rotated at the set speed Vc.

It follows from the above that the angle traveled by the rotor when it is not braked remains approximately constant regardless of the mechanical torque applied to it. Indeed, if this torque is high, the speed of the rotor when it is not braked is relatively high, but the time during which this rotor turns at this speed is relatively short. On the contrary, if this torque is low, this speed of the rotor is relatively low, but the time during which the rotor turns at this speed is relatively long.

This property is retained regardless of the difference between the speed of the rotor when it is braked, or when it is not, with the set speed Vc.

The fact that, in the converter of FIG. 1, the switch 14 is systematically opened at the start of each reference period guarantees that the rotor 3 never performs, whatever the circumstances, several consecutive turns, or even a single full turn, being braked. At each of its turns, the rotor 3 rotates for a more or less long time without being braked and therefore at a speed greater than the set speed Vc.

Theoretical considerations verified by practical tests have shown that all the electrical energy consumed by the various electronic circuits of the converter of FIG. 1 during the duration of a period of the reference signal can be supplied by the generator 2 during the part of this period when the rotor 3 is not braked.

It is therefore possible to dispense with the supply of electrical energy by the generator 2 when the rotor 3 is braked, since the latter is never braked without interruption during a complete revolution or several consecutive revolutions.

The components of the converter, and in particular the braking resistor 13, can therefore be dimensioned so that the speed 3 when it is braked is much lower than in the known converter described by patent CH-B-597,636. The value minimum of the braking resistor 13 is limited only by the fact that the voltage across the terminals of the coil 6 must have a sufficient value for the formatter 28 to function correctly even when the transmission door 14 is conductive. Ultimately, it is possible to replace the braking resistor 13 with a short circuit, and to design the formatter 28 so that the low voltage remaining at the terminals of the transmission door 14 when the latter is conductive is sufficient for it to work properly.

In practice, the speed of the rotor 3 when it is braked can be chosen at a value as low as about 1 revolution per second.

The fact that the speed of the rotor 3 when it is braked can be very low makes it possible to choose for the reference speed Vc a value much lower than in the known converter described above, while being however still clearly different from this. speed of rotor 3 when braked.

In the example of FIG. 1, the set speed Vc is four revolutions per second, whereas it cannot be less than eight to ten revolutions per second in the known converter, as has been explained above.

It follows that the efficiency of the converter of Figure 1, and therefore its autonomy, are significantly increased compared to those of a known converter using comparable components.

The fact that the reference speed Vc is chosen at a value clearly different from the speed of the rotor 3 when it is braked makes it possible to choose a fairly high value for the speed of this rotor 3 when it is not braked.

It follows that the number of turns of the coil 6 can be low enough so that its volume is compatible with the space available in a timepiece such as a wristwatch, that its manufacture poses no particular problem, and that its cost price is therefore low.

Similarly, the internal resistance of the coil 6 being lower than in the known converter described above, the Joule losses in this coil 6 are also lower, which further improves the efficiency of the converter.

Finally, the DC voltage necessary for the operation of the various electronic circuits can be easily obtained by using a simple rectifier, or possibly a voltage doubling rectifier, to rectify the AC voltage supplied by the coil 6.

In summary, in the converter of FIG. 1, the systematic triggering of the braking resistor 13 at the start of each period of the reference signal supplied by the counter 22 has the consequence that the set speed of the generator rotor can be chosen at a significantly lower value than in the known converter described above. All other things being equal, the efficiency and the autonomy of the converter of FIG. 1 are therefore clearly superior to those of the known converter.

The systematic and periodic triggering of the braking resistor 13 also has the consequence that the DC voltage necessary for the operation of the electronic circuits of the converter and, where appropriate, of the auxiliary circuits, can be obtained using a generator whose the coil has a sufficiently low number of turns so that its manufacture and its assembly in a timepiece of small volume do not pose any problem.

Theoretical calculations confirmed by practical tests have shown that, in the converter of FIG. 1, the rotor 3 traverses at high speed an angle of 200 ° to 300 ° approximately at each of its turns, the rest of this turn being of course traveled at low speed.

It is well known that the instantaneous value of the voltage across the terminals of the coil 6 depends, in particular, on the product of the instantaneous values of the speed of rotation of the rotor 3 and on a term generally called the magnetic coupling factor between the magnet 3a. and coil 6.

The coupling factor, which will be designated by C1 in the rest of this description, is equal to the partial derivative, with respect to the angle X defined above, of the product of the flux of the magnet 3a passing through the coil 6 by the number of turns of this coil 6. It has a substantially sinusoidal variation as a function of the angle X, with maximum values, one positive and the other negative, corresponding to the positions of the rotor 3 for which the angle X is 90 ° and 270 °. This variation is shown schematically in Figure 3.

In addition, the generator 2 can only supply electrical energy to the capacitor 8 when the no-load voltage at the output of the rectifier 7, that is to say the voltage which would be measured at its terminals if these do not were not connected to capacitor 8 and to the rest of the circuit, becomes greater than the voltage across capacitor 8.

It follows from the above that, immediately after each instant t0, the generator 2 does not supply any electrical energy to the capacitor 8, the instantaneous speed of the rotor 3 and the coupling factor C both having a relatively low value at this moment. The generator 2 therefore operates “empty”, and the speed of the rotor 3 increases very rapidly.

However, since the rotor 3 travels at least 200 ° at high speed, the product of the instantaneous speed of the rotor 3 and the coupling factor C1 necessarily reaches a value at each revolution of the rotor such that the generator 2 begins to supply electrical energy to capacitor 8.

This supply of electrical energy causes, in a well known manner, a certain braking of the rotor 3 whose instantaneous speed decreases slightly.

This instantaneous speed remains however sufficient for the electrical energy to continue to be supplied to the capacitor 8 until the coupling factor C1 reaches a value such that this supply is no longer possible, or until the circuit of control 12 causes braking of the rotor 3 by making the transmission door 14 conductive.

In both cases, no more energy is supplied to the capacitor 8 until the next instant t0, where the process described above begins again.

The rectifier 7, like all rectifiers, allows the transfer of electrical energy from the coil 6 to the capacitor 8, but prevents the transfer of this energy in the opposite direction. The fact that, in the converter of FIG. 1, the braking means 11 are connected directly to the terminals of the coil 6 therefore has the further advantage that the capacitor 8 cannot discharge into the braking resistor 13 when the transmission door 14 is conductive. The electrical energy stored in the capacitor 8 can therefore in no case be dissipated in the braking resistor 13, which has the consequence, all other things being equal, of further increasing the efficiency of the converter of FIG. 1 and therefore its autonomy compared to those of the converter described in patent CH-B-597,636.

FIG. 4 represents the diagram of a control circuit 12 ′ of the braking means 11 of the converter of FIG. 1, which is a variant of the circuit 12 of this FIG. 1.

In this circuit 12 ', the counters 22 and 25 of the circuit 12 are replaced by other counters 22' and 25 'each comprising fifteen flip-flops. The counting capacity of these counters 22 'and 25' is therefore equal to 32,768, and the period of the reference signal produced by the output 22'a of the counter 22 'is equal to 1 second.

The circuit 12 'includes a comparator 24' similar to the comparator 24 of the circuit 12 but comprising fifteen first inputs A and fifteen second inputs B connected respectively to the fifteen outputs Q of the flip-flops of the counters 22 'and 25'.

In addition, a counter 29 comprising two flip-flops is interposed between the output of the trainer 28 and the first inputs of the doors 26 and 27. The counting capacity of this counter 29 is 4.

The operation of the converter comprising this control circuit 12 'is as follows:

As with circuit 12, the passage of the reference signal to the state "1 causes the flip-flop 23 to switch to the state where its output Q is in the logic state" 0 ", and therefore the blocking of the transmission door 14 which was previously conductive.

The braking of the rotor 3 is therefore eliminated, and the latter begins to rotate at high speed.

When the content of the counter 22 'becomes equal to the content of the counter 25', the output 24'a of the comparator 24 'goes to state “1”. The output Q of the flip-flop 23 is therefore reset to the state "1", the transmission door 14 becomes conductive again and the rotor 3 is braked again. It then continues to rotate at low speed until the reference signal changes to state "1".

The pulses produced by the trainer 28 each time that the rotor 3 passes through its zero position are counted by the counter 29. The output of the latter therefore changes to state “1” each time the rotor 3 has made four turns.

If this output of the counter 29 changes to the state "1" while the output Q of the flip-flop 23 is in the state "0", which means that the rotor 3 is ahead with respect to the position that it would occupy if it rotated at a speed equal to the set speed Vc, the content of the counter 25 'is reduced by one unit in response to the comparison signal supplied, in this case, by the output of gate 27. The duration during which the rotor 3 will rotate at high speed during the next reference signal period will therefore be shorter than during the previous period, and its average speed will therefore be lower.

If, on the other hand, this output of the counter 29 passes to the state “1 after the output Q of the flip-flop 23 has passed to the state“ 1 ”, which means that the rotor 3 is late with respect to the position it would occupy if it rotated at the set speed Vc, the content of the counter 25 'is increased by one unit in response to the comparison signal supplied, in this case, by the output of door 26. The duration during which the rotor 3 will rotate at high speed during the next reference signal period will therefore be longer than during the previous period, and its average speed will be higher.

Theoretical calculations confirmed by practical tests have shown that, with such a circuit 12 ′, the content of the counter 25 ′, which determines the time during which the rotor 3 rotates at high speed, stabilizes at a value such that this rotor 3 does about three laps at high speed, and therefore about one lap at low speed.

This circuit 12 ′ therefore also performs periodic regulation of the speed of rotation of the rotor 3. As in the case of FIG. 1, the regulation of the average speed of the rotor 3 is made during each period of the reference signal as a function of a comparison, made at the start of this period, between the actual angular position of the rotor and the position it would occupy if it rotated at the set speed Vc. However, in this case of FIG. 4, the period of the reference signal corresponds to the time that the rotor 3 would take to make four turns, that is 1440 °, if it turned at an average speed equal to the set speed Vc.

It is obvious that the principle of regulation described with the aid of FIG. 4 can be applied whatever the values chosen for the angle traveled by the rotor 3 between two successive comparison signals and for the reference speed Vc. This angle is generally equal to k-360 ¹ , and the factor k can be in principle arbitrary. For obvious reasons of simplicity, we will choose for k an integer value equal to or greater than 1. It will be shown later, in the description of FIG. 5, that we can choose for the factor k a value equal to 0 , 5.

Whatever the value chosen for this factor k, that is to say whatever the value of the angle traveled by the rotor between two successive comparison signals, it is of course necessary that the period of the reference signal is equal to the ratio between this angle and the chosen target speed.

It is also obvious that the advantages of the converter according to the invention as they have been described in relation to the embodiment of FIG. 1, and which are brought about by the fact that the braking resistor of the rotor is triggered periodically , are found unchanged in the other embodiments described above, even if in the latter the rotor 3 can, in certain cases, make more than one revolution at low speed.

The symbol Vt has been used in the description of FIG. 1 to designate the real average speed of the rotor 3 while it makes, roughly, the only revolution which it must make during each period of the reference signal. This same symbol Vt will be used in the remainder of this description to designate, in general, the real average speed of the rotor 3 pen during a period of the reference signal, whatever the number of turns it makes, roughly, during this period.

As has already been mentioned above, the mechanical and magnetic losses in mechanical energy to electrical energy converters of the kind which have been described depend directly on the set speed Vc chosen or on its square. It is therefore desirable to choose this speed Vc as low as possible to reduce these losses and increase the efficiency of the converter.

However, the control circuit must be able to maintain in all circumstances the average speed Vt of the rotor 3 at a value close to the chosen reference speed Vc.

This speed Vt naturally depends, among other things, on the average speed of the rotor 3 during the periods when it is braked, the average speed which is designated by the reference V1 in in FIG. 2.

To be able to choose a low speed Vc, this average speed V1 must therefore also be low. It is clear that the lowest average speed V1 that can be reached is that at which the rotor 3 rotates when the terminals of the coil 6 are short-circuited.

However, the instantaneous speed of the rotor 3 when it is braked is not constant. This instantaneous speed depends on the magnetic coupling factor C1 between the magnet 3a and the coil 6, which was mentioned above, and therefore the variation as a function of the angular position X of the rotor 3 is shown diagrammatically in FIG. 3.

It is obvious that, all other things remaining equal, the instantaneous speed of the rotor 3 increases when the latter approaches, during the periods when it is braked, positions where the coupling factor C1 is zero, and that this instantaneous speed decreases again when the rotor 3 moves away from these positions.

The value of the average speed V1 of the rotor 3 while it is braked is influenced unfavorably by these increases in its instantaneous speed, which consequently imposes a lower limit on the value which can be chosen for the reference speed Vc.

The converter shown in Figure 5 overcomes this drawback. Like the converter of FIG. 1, it is intended to equip a timepiece, and it comprises a spring 1 driving, via a gear train 4, the rotor 3 of an energy generator electric which is designated, in this case, by the reference 30, and hands 9 for displaying the time.

The spring 1, the gear train 4 and the needles 9 have not been shown in this figure 5. The rotor 3 is identical to that of the generator 2 in FIG. 1 and, like the latter, it is symbolized by l magnet 3a which is part of it.

The generator 30, which is represented diagrammatically, has a structure which makes it resemble the motor described in patent US-A-4 371 821. Like this motor, the generator 30 comprises a stator 31 comprising three pole pieces 32, 33 and 34 .

The first ends of these pole pieces 32, 33 and 34 are separated from each other by air gaps 35, 36 and 37 and delimit a substantially cylindrical space in which the permanent magnet 3a of the rotor 3 is disposed.

The second end of the pole piece 32 is connected to the second end of the pole piece 33 by a frame 38 and to the pole piece 34 by a frame 39. Two coils 40 and 41 are respectively arranged on the frames 38 and 39.

Unlike the engine mentioned above, the generator 30 in FIG. 5 does not have any means for positioning the rotor 3.

The converter of FIG. 5 comprises a rectifier 7, similar to that of FIG. 1, the input of which is connected to the terminals 40a and 40b of the coil 40 and the output of which is connected to a storage and filtering capacitor 8, also similar to that in Figure 1.

The speed of rotation of the rotor 3 of the generator 30 is regulated by a circuit which includes braking means 11 'and a control circuit 12 of these braking means 11' which is identical, in this example, to circuit 12 in the figure 1 and which has therefore not been shown in detail again. The input and output of this circuit 12, designated by 12a and by 12b in FIG. 5, correspond respectively to the input of the forming circuit 28 and to the output Q of the flip-flop 23 of FIG. 1.

The braking means 11 ′ comprise a resistor 13 and a transmission door 14 connected, in series with each other, to the terminals 40a and 40b of the coil 40. This resistor 13 and this door 14 are similar to those of Figure 1.

The braking means 11 'further include a transmission door 42 connected directly to the terminals 41 a and 41 b of the coil 41. The control electrode 42a of this door 42 is connected, like the control electrode 14a of the gate 14, at the output 12b of the control circuit 12.

Terminal 41a of coil 41 is connected to terminal 40a of coil 40, the potential of which is taken as the reference potential of the circuit. The transmission door 42 therefore responds as the transmission door 14 to the signal produced by the control circuit 12. When this signal is in the logic state "0", these two doors 14 and 42 are blocked, and when it is in logic state "1", they are conductive.

Finally, the input 12a of the control circuit 12 is connected to the terminal 40b of the coil 40.

The coil 40 therefore plays the same role as the coil 6 of the converter of FIG. 1. It provides in particular the electrical energy intended to supply the circuit 12 and the other possible circuits, and the voltage present at its terminal 40b is used by this circuit 12 to determine the instants when the rotor 3 passes through its zero position.

The magnetic coupling factor of the magnet 3a with the coil 40 has a variation as a function of the angular position of the rotor 3 which is, at least as a first approximation, identical to that of the coupling factor C1 in the case of FIG. 1 In a generator such as that which has been represented in FIG. 5, the angular positions where this coupling factor is zero are close to those where the direction of the axis of magnetization of the magnet 3a makes an angle of 60 ° approximately with the straight line passing through the middle of the air gap 35 and through the axis of rotation of the rotor 3. One of these two positions is the zero position of the rotor 3 defined above.

The magnet 3a is obviously also magnetically coupled to the coil 41. The coupling factor C2 of this magnet 3a and of this coil 41 has a variation similar to that of the factor C1, but with zero values which are close to the angular positions of the rotor 3 where the direction of the magnetization axis of the magnet 3a makes an angle of approximately 60 ° with the straight line passing through the middle of the air gap 36 and through the axis of rotation of the rotor 3.

The offset of the curves representing the variation of the coupling factors C1 and C2 with respect to each other obviously depends on the relative angular position of the air gaps 35, 36 and 37. Figure 3, where the curve representing the variation of the factor C2 coupling has also been drawn, represents a case where this offset is approximately 60 °.

The operation of the device in FIG. 5 is identical to that of the device in FIG. 1 and will therefore not be described again here.

It should however be noted that the two transmission doors 14 and 42 are conductive or blocked at the same time, since they are controlled by the same signal.

It follows that when this signal is in the logic state "0", that is to say during the periods when the rotor 3 is not braked, the coil 41 is in open circuit and does not influence the rotation of this rotor 3.

On the other hand, when the control signal supplied by the circuit 12 is in the state "1", that is to say during the periods when the rotor 3 is braked, the coil 41 is practically short-circuited by the transmission door 42. Since the coupling factor C2 of this coil 41 and of the magnet 3a has a high value when the coupling factor C 1 of the coil 40 and of this magnet 3a has a low value, this coil 41 ensures effective braking of the rotor 3 when the coil 40 is unable to do so.

The rotor 3a is therefore effectively braked whatever its angular position, and its instantaneous speed, when it is braked, no longer exhibits the significant variations which it exhibited in the case of FIG. 1.

Thanks to this characteristic, which is due to the fact that the generator 30 is provided with two coils 40 and 41 whose coupling factors with the magnet 3a are offset from the angular position of the rotor 3, the set speed Vc can therefore be chosen to an even lower value than in the case of FIG. 1, which correspondingly reduces the mechanical and magnetic losses in the converter and therefore increases its efficiency.

The counting capacity of the counters 22 and 25 as well as, if necessary, the frequency of the signal supplied by the oscillator 21 must of course be adapted to the chosen target speed.

It should be noted that the control circuit 12 ′ in FIG. 4 can also be used in a converter equipped with the generator 30 in FIG. 5. This variant will not be described here.

FIG. 6 represents the diagram of a control circuit 12 "of the braking means 11 which can be used in place of the circuit 12 in the converter of FIG. 5.

In this 12 "circuit, the counters 22 and 25 of circuit 12 are replaced by 22" and 25 "counters each comprising twelve flip-flops. The counting capacity of these 22" and 25 "counters is therefore only 4096 The comparator 24 of circuit 12 is of course replaced by a comparator 24 "having twelve first and twelve second inputs, also designated respectively by A and B. In addition, the formatter 28 of circuit 12 is replaced by a formator 28" whose output delivers a pulse each time the voltage across the coil 40 passes through zero in one direction or the other, that is to say twice per revolution of the rotor 3.

The trainer 28 "comprises, in this example, an amplifier 28.1, a capacitor 28.2 and a resistor 28.3 similar to the elements bearing the same references in FIG. 1, an inverter 28.4 a second capacitor 28.5, a second resistor 28.6 and an OR gate 28.7 All of these are connected to each other as shown.

The other components of circuit 12 "are similar to the components of circuit 12 having the same references.

The operation of the converter equipped with this 12 "control circuit is comparable to that of the converter in FIG. 5 and will not be described in detail. It should simply be noted that the period of the reference signal produced by output 22" a of the counter 22 "is only 125 milliseconds, and it corresponds to the time it would take rotor 3 to make a U-turn, or 180 °, if its average speed during this U-turn was equal to the set speed Vc , which was also set at four revolutions per second in this example.

In addition, the period of the reference signal corresponding to about half a turn of the rotor 3, and the coupling factor C1 between the magnet 3a and the coil 40 reaching a high value during the part of this period when the rotor 3 n is not braked, the generator 30 supplies electrical energy to each half-turn of the rotor 3.

The braking of the rotor 3 during the part of the period of the reference signal where it must be braked is however effective since the coupling factor C2 of the magnet 3a with the coil 41 reaches a high value during this part of this period. As in the converter of FIG. 5, the reference speed Vc of the rotor 3 could therefore be chosen at a lower value than four revolutions per second. It would of course be necessary, in such a case, to adapt the various components of the converter accordingly, in particular the oscillator 21 and / or the counter 22 "so that the period of the reference signal has a value corresponding to the chosen reference speed.

It is obvious that, in the converter of FIG. 5 and in its variant described above, the coil 41 could be connected to the input of a rectifier, similar to rectifier 7, the output of which would also be connected to the capacitor of storage 8. In this embodiment, which has not been shown, the coil 41 would therefore also supply electrical energy to the capacitor 8.

It is also obvious that the coils 40 and 41 could be connected in series, at least when the rotor 3 is not braked. The means necessary to this connection will not be described here because their realization is within the reach of the skilled person.

In such a case, the voltage applied to the rectifier 7 would obviously be higher than in the case of FIG. 5, which would improve the efficiency of this rectifier 7, and therefore of the converter thus modified.

In the converters described above, the average speed Vt of the rotor 3 during a period of the reference signal starting at an instant t0 is adjusted by modifying by a fixed duration, at this instant t0, the time T2 or T2 'during which the rotor 3 will not be braked during this period, the direction of this modification being determined by the direction of the difference between the actual angular position of the rotor 3 at this time t0 and its zero position.

In other words, the average speed Vt of the rotor 3 during each period of the reference signal is simply adjusted as a function of the direction of the difference between the average speed Vt during the previous period and the reference speed Vc.

This adjustment mode has the advantage of being particularly simple to implement. However, depending on the type of converter in which it is used, and in particular according to the mechanical characteristics of the various moving elements of this converter and the electrical and magnetic characteristics of its generator 2, this mode of adjustment is not always the best. adapted.

In particular, if the modification of time T2 or T2 'made at each instant t0 is small, as in the examples described where it is equal to a period of the signal produced by the oscillator 21, that is to say approximately 30.5 microseconds, the speed of the adjustment, that is to say the speed with which the average speed Vt is brought back to a value close to the speed of reference Vc after having deviated considerably from it for any reason, can also be low.

It is obviously possible to increase the speed of this adjustment by increasing the variation imposed at time T2 or T2 'at each instant t0.

According to the characteristics of the converter mentioned above, this increase in the speed of adjustment can however cause instability of the speed Vt which can start to oscillate with a relatively large amplitude around the reference speed Vc.

Many other modes for adjusting the average speed Vt can be used and the choice of the one which is best suited to a particular type of converter obviously depends on the characteristics of the latter.

Among all these adjustment modes, one can mention that which consists in determining, at each instant t0, the direction of the difference between the real angular position of the rotor 3 and its zero position, as well as the direction of the variation of the value. of this deviation from the value it had at the previous time t0, and to modify the time T2 or T2 'as a function of these two pieces of information.

This adjustment mode can advantageously be implemented in practically any type of converter because the influence of each of the pieces of information that it uses on the value of the modification imposed at time T2 or T2 'can be adapted as a function of the characteristics of the converter so as to ensure great speed in adjusting the speed Vt while virtually eliminating any risk of excessive oscillation of this speed Vt around the set speed Vc.

The means necessary for the implementation of such an adjustment mode, or of another adjustment mode which would be better suited in this particular case or another, will not be described here since their constitution depends on the characteristics of the converter mentioned. above and their realization is also within the reach of the skilled person.

In all the embodiments of the converter according to the invention which have just been described, the mean speed of the rotor is regulated by adjusting, during each period of the reference signal, the duration during which it rotates at a speed higher than the setpoint speed as a function of the more or less direct measurement, made at the start of this period, of its average speed during the preceding period of the reference signal. It is obvious that this regulation can also be ensured by adjusting, during each period of the reference signal, the duration during which the rotor turns at a speed lower than the set speed according to the same comparison. Embodiments of converters according to the invention making use of this possibility have not been shown because they are easily deduced from those which have been described above.

It should also be noted that, in all the embodiments of the converter according to the invention which have just been described, the counter 25, 25 'or 25 "which determines the duration of the time T2 or T2' can be designed so its content automatically takes on a predetermined value at the moment when, after switching on the converter, the voltage across the terminals of the capacitor 8 reaches a value sufficient for the electronic circuits which it supplies to function properly. This predetermined value may be equal, for example, half the maximum value that the contents of this 25, 25 'or 25 "counter can take.

This arrangement, which will not be described in more detail since its production is within the reach of the specialist, makes it possible to significantly reduce the time necessary for the average speed of the rotor 3 to stabilize at the set speed when the converter is restarted. after a stop.

In all the converters which have been described above, the rotor 3 rotates continuously, sometimes at high speed, sometimes at low speed. The setpoint speed Vc cannot therefore be chosen at an arbitrarily low value. In practice, the minimum value that can be chosen is around two to three revolutions per second.

FIG. 7 represents the diagram of a converter in which the reference speed Vc of the rotor 3 can be chosen at a value practically as low as desired. In the example of this figure 7, this value was chosen at 0.5 revolutions per second.

The converter of FIG. 7 comprises, like those which have been described above, a source of mechanical energy constituted by a barrel spring, which is similar to those of the preceding converters and which has therefore not been shown.

This barrel spring is connected, via a gear train, also not shown, to the rotor 3 of a generator 50. This rotor 3 is also similar to the rotors of the generators of the previous converters, and like those Ci, it is symbolized by the permanent magnet 3a which is part of it.

The generator 50 differs from the generator 2 in FIG. 1 only by the presence of two notches 51 and 52 which are formed in the wall of the pole shoes which surround the magnet 3a and which are diametrically opposite one another.

It is well known that the presence of these notches 51 and 52 has the effect of creating a torque, generally called positioning torque, which is exerted on the rotor 3 and which has a substantially sinusoidal variation as a function of the angular position of the rotor. 3, with a period equal to 180 °, that is to say a half-turn of the rotor 3. This positioning torque has been shown in FIG. 8 with the reference CP.

By convention, the torque CP tends to rotate the rotor 3 in the increasing direction of the angle X when it is represented as positive in FIG. 8, and in the decreasing direction of the angle X when it is represented as negative. The same convention will be used for the representation of the other couples which will be described later.

In the absence of any other influence, the torque CP therefore tends to bring or maintain the rotor 3 in one or the other of two stable equilibrium positions, which are designated by CP1 and CP2 in FIG. 8.

These positions CP1 and CP2 are those for which the magnetization axis of the magnet 3a of the rotor 3 has a direction substantially perpendicular to the straight line joining the middle of the notches 51 and 52. In the example of FIG. 7, the straight line joining the middle of the notches 51 and 52 makes an angle of 10 ° with the straight line taken as the origin of the angles X. As in the example of FIG. 1, this straight line taken as the origin of the angles X is perpendicular to the straight line joining the middle of air gaps 5a and 5b.

In the absence of any other influence, the two stable equilibrium positions CP1 and CP2 of the rotor 3 are therefore those where the magnetization axis of the magnet 3a makes an angle of 80 ° with the origin of the angles X and an angle of 90 ° with the straight line joining the middle of the notches 51 and 52.

However, in the converter of FIG. 7, the rotor 3 is also subjected to the mechanical motor torque transmitted by the gear train 4 which connects it to the spring 1. The various components of the converter are chosen so that the maximum value of this mechanical torque is less than the maximum value of the positioning torque CP.

An arbitrary value of the mechanical torque has been represented in FIG. 8 with the reference CM.

In the absence of any other influence, the rotor 3 is therefore subjected to a resulting torque equal to the sum of the mechanical torque CM and the torque CP. This resulting torque has also been represented in FIG. 8 with the reference CR.

Like that of the torque CP, the variation of the torque CR is periodic, with a period equal to 180 °. Since, in addition, the maximum value of the mechanical torque CM is less than the maximum value of the torque CP, the torque CR has, on one revolution of the rotor, four zero values, two of which, separated by an angle of 180 °, correspond to positions d stable equilibrium and the other two, also separated by an angle of 180 °, correspond to unstable equilibrium positions of the rotor 3. In FIG. 8, the two stable equilibrium positions have been designated by P1 and P2 and the two positions of unstable equilibrium have been designated by P3 and P4.

The converter of FIG. 7 comprises braking means 11, a rectifier 7 and a capacitor 8 similar to those of FIG. 1 and which will not be described again here.

The converter of FIG. 7 also includes a circuit 53 for controlling the braking means 11. This circuit 53 includes an oscillator 54 which delivers a signal in the form of pulses having a frequency of 32,768 Hz for example.

The output of the oscillator 54 is connected to the input of a counter 55 composed of fifteen flip-flops which have not been shown separately. These fifteen flip-flops are connected to each other in a cascade in a conventional manner, so that the counting capacity of the counter 55 is equal to 32,768.

The counter 55 has an output 55a constituted by the inverse output of the fifteenth of the above flip-flops and which therefore delivers a signal having a period of 1 second. This output 55a is connected to the clock inputs Ck of three flip-flops 56, 57 and 58, all three of type T.

The counter 55 further comprises outputs 55b, 55c and 55d which are constituted by the direct outputs of its fifth, seventh and eighth flip-flops. These outputs 55b, 55c and 55d therefore deliver signals having frequencies of 2048 Hz, 256 Hz and 128 Hz respectively.

The outputs 55b, 55c and 55d of the counter 55 are connected to the inputs of an AND gate 59 whose output is connected to the reset input R of the flip-flop 56.

The outputs 55b and 55c of the counter 55 are connected to the inputs of another AND gate 60 whose output is connected to the reset input R of the flip-flop 58.

The output Q of the flip-flop 56 is connected to the control electrode 14a of the transmission door 14.

The outputs Q of the flip-flops 57 and 58 are connected to the inputs of a NAND gate 61 whose output is connected to the control electrode of a P-type MOS transistor designated by Tr1.

The output Q of the flip-flop 58 is further connected to an input of an AND gate 62 having a second input connected to the output Q of the flip-flop 57. The output of the gate 62 is connected to the control electrode an N-type MOS transistor designated by Tr2.

The drains of the transistor Tr1 and Tr2 are connected, together, to the terminal 6b of the coil 6 and their sources are connected respectively to the terminals 8b and 8a of the capacitor 8. The connections of these sources with these terminals have not been shown. As in the case of FIG. 1, these terminals 8a and 8b respectively constitute the negative and positive terminals of the supply of the circuit.

The operation of the converter of FIG. 7 will be described with the aid of FIGS. 8, already mentioned, and 9 which represents the logic states measured at some points of the circuit 53.

The output 55a of the counter 55 delivers a signal having a period of 1 second which will later be shown to constitute a reference signal comparable to the reference signals described above. The instants when this signal 55a goes to state "1" will be designated by t0, as above.

It will be made evident from this description that, just before each instant t0, the rotor 3 is stopped in one or other of its stable equilibrium positions P1 and P2, and the output Q of the flip-flop 56 is in state "1". The transmission door 14 is therefore conductive, and the braking resistor 13 is connected in parallel with the coil 6. If, in this situation, the rotor 3 is subjected to an angular acceleration due, for example, to a shock, it is therefore braked by the torque CR and by the torque due to the current induced by the displacement of the rotor and flowing in this resistor 13, and brought back to its equilibrium position by the torque CR.

Also just before each instant t0, the output Q of the flip-flop 58 is in the state "0". The outputs of the gates 61 and 62 are therefore respectively in the state "1" and in the state "0", and the two transistors Tr1 and Tr2 are blocked.

It will be assumed that, before the instant t0 at which this description begins, which will be designated by t01, the rotor 3 is stopped in the position P1.

It will also be admitted that, always before time t01, the output Q of the flip-flop 57 is in the state "0".

Finally, it will be admitted that the coil 6 is shaped and arranged on the stator 5 so that when its terminal 6b is connected to the positive pole of the power supply, in a manner which will be described later, it creates a magnetic field which causes the rotation of the rotor 3 in the positive direction of the angle X when this rotor 3 is in its stable equilibrium position P1. Similarly, when the terminal 6b of the coil 6 is connected to the negative pole of the power supply, the magnetic field created by this coil 6 causes the rotation of the rotor 3 also in the positive direction of the angle X, but when this rotor 3 is in its stable equilibrium position P2.

At instantt01, the output 55a of the counter 55 goes to state "1". At the same instant, the outputs 55b, 55c and 55d of this counter 55 pass to the state "0". The inputs R of the flip-flops 56 and 58 therefore pass to the "O" state. The Q output of the flip-flop 56 therefore goes to the "O" state, which blocks the transmission gate 14, and the Q outputs of the flip-flop 57 and 58 go to the "1" state.

The blocking of the transmission door 14 is not sufficient to cause the rotation of the rotor 3, since the latter is only subjected to the torque CR which tends to maintain it in the position P1.

At the same time as the transmission gate 14 is blocked, the transistor Tr1 is made conductive by the state "0" which appears at the output of the gate 61. The terminal 6b of the coil 6 is therefore connected to the positive pole of the power supply to the circuit, and a current begins to flow in this coil 6, in the direction of arrow 1. The magnetic field produced by this current causes the rotor to rotate in the increasing direction of the angle X.

The generator 50 therefore operates, immediately after time t01, like a motor.

At an istantt31 located, in this example, 2.2, milliseconds after time t01, the output 55b of the counter 55 goes to state "1". The output 55c of the counter 55 being already at "1" at this instant, the output of the gate 60 also changes to the state "1". The flip-flop 58 therefore switches to the state where its output Q is in the state "0".

The transistor Tr is therefore blocked by the state "1" which appears at the output of the gate 61, and the current flowing in the coil 6 is interrupted.

The characteristics of the generator 50 and the duration of the time T3 separating the instants t01 and t31 have been chosen so that the rotor 3 is close to its unstable equilibrium position P3 at the instant t31 and that, if there is n has not reached this position P3 at this time, its kinetic energy is sufficient for it to reach and exceed it.

After the rotor 3 has exceeded the position P3, it is rotated, still in the increasing direction of the angle X, by the torque CR which is then positive.

This situation lasts for a time T4, up to an instant t41 situated, in the present example, approximately 6 milliseconds after the instant t01, or, which amounts to the same thing, approximately 3.8 milliseconds after the instant t31. At this instant t41, the output 55b of the counter 55 goes to state "1" while the outputs 55c and 55d of this counter 55 are already in state "1". The output of gate 59 therefore also goes to state "1", which puts the output back Q flip-flop 56 also in state "1". The transmission door 14 therefore becomes conductive, and the resistor 13 is connected to the terminals of the coil 6.

The rotor 3, which is at this instant t41 in an intermediate position Pf1 situated between its unstable equilibrium point P3 and its stable equilibrium point P2, is therefore braked, and its speed decreases sharply. It continues to rotate at slow speed in response to the torque CR which decreases and which is canceled when the rotor 3 reaches its second stable equilibrium position P2. The rotor 3 therefore stops in this position P2, after having made some oscillations around it.

The same process is repeated at the following instant t02, with the only difference that the flip-flop 57 switches this time to the state where its output Q is at state "0" and its output Q at state " 1 ". It is therefore the transistor Tr2 which becomes conductive in response to the state "1" applied to its control electrode by the output of the gate 62.

The terminal 6b of the coil 6 is therefore connected, this time, to the negative pole of the power supply, and a current begins to flow in this coil 6, in the opposite direction to the arrow 1. As the rotor is in the position P2 at time t02, the field produced by this current causes the rotor 3 to rotate again in the direction of the increasing angle X. The generator 50 therefore functions again as a motor.

As above, the output of gate 60 goes to state "1" after a time T3, at a time situated approximately 2.2 milliseconds after time t02 and designated by t32. The output Q of the flip-flop 58 therefore returns to the “0” state, which causes the transistor Tr2 to block.

Also as above, the rotor 3 continues its rotation under the influence of its kinetic energy and the torque CR for a time T4, until the output of the gate 59 changes to the state "1", at a moment designated by t42 and located approximately 3.8 milliseconds after time t32 when the rotor 3 is in an intermediate position Pf2 located between its positions P4 and P1.

From this instant t42, the transmission door 14 is conductive and the rotor 3 is braked. The rotor 3 continues to rotate at low speed until it again reaches the stable equilibrium position P1 where it stops until the next instant t0. The process described above of course starts again at each instant t0.

It can be seen that the average speed of rotation of the rotor 3 is indeed equal to the set speed Vc which has been chosen, ie in this example 0.5 revolutions per second. In addition, as in the other embodiments described above, the period of the reference signal is equal to the ratio between a predetermined angle of rotation of the rotor, 180 °, and the reference speed Vc. The factor k mentioned above is therefore equal to 0.5, as in the case of FIG. 5.

The mechanical and magnetic losses in the converter of FIG. 7, which are dependent on this reference speed Vc, are therefore even lower than in the converters of FIGS. 1 and 5.

We also see that this average speed is independent of the time actually taken by the rotor 3 to turn around, provided of course that this time is not greater than the period of the reference signal produced by the output 55a of the counter 55 .

If this condition is fulfilled, which is almost always the case, the average speed of the rotor 3 only depends on the period of the reference signal. In a timepiece without a second hand, it would therefore be possible to choose a value even lower than 0.5 revolutions per second for this average speed.

It should however be noted that the capacity of the storage capacitor 8 must be all the greater when this average speed is low. This capacitor 8 must in fact supply the various electronic elements throughout the time which separates two supplies of electrical energy by the generator 50, without the voltage at its terminals varying too much.

The volume of a capacitor being proportional to its capacity, it may prove impossible to choose a very low value for the reference speed Vc, the capacitor 8 then necessary being too bulky to enter a timepiece such that, for example, a wristwatch.

As appears from the description which has just been made, each half-turn of the rotor 3 is broken down into three phases:

During the first phase, which begins at each instant t0 and which ends after a time T3, that is to say approximately 2.2 milliseconds in this example, the generator 50 operates as a stepping motor. It receives from the storage capacitor 8 a certain amount of electrical energy, which it transforms, with a certain efficiency, into mechanical energy which it uses to rotate its rotor from its position P1 or P2, to its position P3 or , respectively, P4. The magnitude of this mechanical energy is proportional to the area of each of the zones Z1 delimited by the X axis and the negative part of the curve CR in FIG. 8.

During the second phase, which begins at the end of the first and which lasts for a time T4, that is to say approximately 3.8 milliseconds in this example, the rotor 3 of the generator 50 rotates at high speed under the influence of the torque CR. The generator 50 therefore produces a certain amount of electrical energy, like the generators 2 and 30 of FIGS. 1 and 5. This amount of energy produced is substantially proportional to the surface of each of the zones Z2 delimited by the X axis and the positive part of the CR curve in Figure 8, between points P3 and Pf1 1 or P4 and Pf2.

Theoretical considerations which will not be reproduced here, confirmed by practical tests, show that it is possible to size the various components of the converter so that the difference between the amount of electrical energy produced during the second phase and the amount of the electrical energy consumed during the first phase is sufficient for the electronic circuits of the converter of FIG. 7 to function correctly until the spring 1 is almost completely disarmed.

During the third phase, which begins approximately 6 milliseconds after each instant t0 in the present example and which lasts until the rotor 3 stops in one of its stable equilibrium positions P1 and P2, the generator 50 still produces a certain amount of electrical energy, but this energy is dissipated in the resistor 13, which causes braking of the rotor 3. The rotor 3 then remains stationary until the time t0 following when the process described above start again.

It is obvious that when the converter of FIG. 7 stops working because the spring 1 is relaxed, the capacitor 8 discharges and the voltage across its terminals becomes zero.

When the spring 1 is wound up, after such a stop, the converter does not start to operate again if adequate means are not provided for this purpose, since the mechanical motor torque applied by the spring 1 to the rotor 3 via the train 4 is less than the positioning torque created by the notches 51 and 52, and that no more electrical energy is available in the capacitor 8 to overcome this positioning torque.

The means required to restart the converter can be mechanical in nature. They can for example be constituted by a clutch responding to a rapid rotation of a control rod, such as the time-setting rod of the watch, for connecting this control rod to the rotor 3.

These means can also be of an electrical nature. They can for example be constituted by a photoelectric cell connected in parallel with the capacitor 8 and capable of charging the latter when it receives a sufficient quantity of light.

Such a cell has been represented in FIG. 7, in dotted lines, with the reference 63.

In the converters described above, the rotor of the generator has a single permanent magnet having only one pair of magnetic poles. The voltage produced by this generator therefore has a full period for each revolution of the rotor. In addition, the period of the reference signal is equal to the ratio between a predetermined angle of rotation of the rotor and the set speed Vc, this predetermined angle being equal to k · 360 ° with preferably, k equal to 0.5 or to a whole number equal to or greater than 1.

It is obvious that in all the embodiments of the converter according to the invention described above, the permanent magnet of the generator rotor can comprise not one but p pairs of magnetic poles, with p integer. In such a case, which has not been shown, the voltage produced by the generator therefore has p periods per revolution of the rotor. The predetermined angle mentioned above is then obviously equal to k · 360 ° / p, the period of the reference signal always having to be equal to the ratio between this predetermined angle and the set speed.

The same considerations can be made if the generator rotor does not have a single permanent magnet but, like the generator rotor described in patent CH-B-597,636 mentioned above, a plurality of magnets arranged at the periphery of 'a rotating disc. In such a case, the number p above is obviously equal to half the number of these magnets.

A generator according to the invention may also not include a stator for magnetically coupling its magnet (s) to its coil (s).

It should also be noted that, in all the converters according to the invention which have been described above, the capacitor 8 for storing electrical energy can be replaced without difficulty by a rechargeable accumulator.

Claims (8)

1. A mechanical-to-electrical energy converter which comprises:

- an electrical energy generator (2; 30; 50) having a rotor (3) and means (6, 7; 40,41,7) for generating said electrical energy in response to rotation of said rotor (3);

- means (8) for storing at least temporarily said electrical energy;

- a mechanical energy source (1) connected mechanically to said rotor (3) and able to generate a mechanical driving torque for driving said rotor (3) at a first speed greater than a predetermined set speed in the absence of any other influence;

- means (21, 22; 22'; 22"; 54, 55) for generating a periodic reference signal having a period equal to the ratio between a predetermined angle of rotation of said rotor (3) and said set speed;

- means (23 to 28; 23, 24', 25', 26 to 29; 23, 24", 25", 26, 27, 28"; 56, 59) forgenerating a control signal having a first and a second state; and

- means (11; 11') for electrically braking said rotor (3) able to respond to said first state of the control signal to cause the application to said rotor (3) of a braking torque opposed to said mechanical driving torque and imposing on said rotor (3) a second speed lower on average than said set speed and able to respond to said second state of the control signal to stop said application to the rotor (3) of said braking torque;

characterized in that said means (23 to 28; 23, 24', 25', 26 to 29; 23, 24", 25", 26, 27, 28"; 56, 59) for generating a control signal include means (23, 56) for putting said control signal into one of said states at each one of a plurality of first instants that follow each other periodically with a period equal to that of said reference signal, and means (24 to 28;24', 25',26 to 29; 24", 25", 26, 27, 28"; 59) for putting said control signal into the other of said states at second instants, each separated from the immediately preceding first instant by a time interval having a duration less than said reference signal period.

2. A converter as in claim 1, characterized in that said means (24 to 28; 24', 25', 26 to 29; 24" 25", 26, 27, 28") for putting the control signal into its other state include means (26 to 28; 26 to 29; 26, 27, 28") for generating a comparison signal between the real position of said rotor (3) at each first instant and the position it would be in if it were to rotate at said set speed, and means (24, 25; 24', 25'; 24", 25") for adjusting the duration of the time interval that immediately follows each first instant in response to said comparison signal.

3. A converter as in claim 1, characterized in that said means (56) for putting the control signal into one of its states at each first instant sets the control signal into its second state at each first instant, said time interval has a predetermined fixed value, said generator (50) further has means (51, 52) for subjecting said rotor (3) to a positioning torque having a maximum value greater than said mechanical driving torque, and said converter further comprises means (Tr1, Tr2) for applying temporarily to said rotor (3), from each said first instant, an electrical driving torque having the same direction as said mechanical driving torque, the sum of said two driving torques being greater than said positioning torque.

4. A converter as in claim 1, 2 or 3, characterized in that said breaking means (11; 11') are separated from said storage means (8) by at least one unidirectional component (7) enabling the transfer of said electrical energy from said generator (2; 30; 50) to said storage means (8) and prohibiting the transfer of said energy from said storage means (8) to said braking means (11; 11').

5. A converter as in claim 1, 2 or 3, characterized in that said rotor (3) includes a permanent magnet (3a) which has at least one pair of magnetic poles defining a magnetization axis and which is rotatably driven with said rotor around an axis of rotation (3b) substantially perpendicular to said magnetization axis, and in that said means for generating said electrical energy include a coil (6; 40) coupled magnetically to said permanent magnet (3a).

6. A converter as in claim 5, characterized in that said means for generating the electrical energy further include a rectifying circuit (7) positioned between said coil (6; 40) and said storage means (8), and in that said braking means (11; 11 are connected between said coil (6; 40) and said rectifying circuit (7).

7. A converter as in claim 5, characterized in that said generator (30) has a second coil (41) coupled magnetically to said permanent magnet (3a) and in that said converter further comprises second means (42)forelectrically braking said rotor (3) that are connected to said second coil (41) and that are also able to respond to said first state of the control signal to cause a braking torque to be applied to said rotor (3).

8. A converter as in claim 5, characterized in that said predetermined angle is equal to k-360°/p, where k is equal to 0.5 or to an integer equal to or greater than 1 and where p is equal to the number of pairs of poles in said permanent magnet (3a).

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