CH711795A2 - Electronic device for the detection and compensation of shocks. - Google Patents

Abstract

The present invention relates to an electronic device (1), in particular for a timepiece, comprising a computing unit (5) capable of generating a signal representative of a physical quantity, of a motor (4) driving a device display, said motor comprising a rotor in a magnetic circuit, two terminals, positive and negative, by which the calculation unit controls it, the electronic device further comprising at least one shock detection circuit connected between the calculation and an engine terminal for detecting an external shock applied to the engine, said motor having a first stable equilibrium position placed at a reference angular position and a second stable equilibrium position positioned 180 degrees from the first stable angular position, for each direction of rotation, a limit angular position from which it is no longer possible to bring the rotor of the motor r in an anterior angular position, the calculation unit using an algorithm that, after an impact, makes it possible to detect the direction of rotation of the rotor by analyzing an induced voltage detected by said shock detection circuit and order the sending of a blocking pulse having a reverse polarity of that of the induced voltage.

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an electronic device comprising a computing unit capable of generating a signal representative of a physical quantity, of a motor driving a display device, said motor comprising two terminals, positive and negative, by which the computing unit controls, the electronic device further comprising at least one shock detection circuit connected between the computing unit and the motor terminals for the detection of an external shock applied to the motor.

BACKGROUND

There are known timepieces comprising a housing in which an electromechanical clockwork movement is arranged. Such a movement is clocked by a quartz oscillator system. For the display of time indications such as time and second, needles are mounted on motors to be rotated. The engines used are Lavet type motors also called stepper motors. In these motors, a magnetized rotor of cylindrical shape creates a radial magnetic field in the air gap of a magnetic circuit on which is wound a coil whose terminals are connected to a control circuit, generally an integrated circuit, providing pulses of current, each pulse advancing the rotor one step. The coil consists of a very fine wire wound on a hollow insulating tube containing inside a part of the magnetic circuit.

These engines located in the watch suffer shocks may come from falls of the watch or violent movement of the user. These shocks are then likely to disrupt the operation of the engines. These disturbances consist of an uncontrolled displacement of the rotor or rotors due to their inertia causing the jump of at least one step.

Therefore, the hourly indications provided by the needles may no longer be accurate.

To remedy this, there are shock detection systems. For this, an electronic device is responsible for measuring the voltage induced by the motor during impact. Indeed, under the effect of displacement (rotation) of the rotor, an induced voltage is generated. This induced voltage is detected by a detection circuit which compares this induced voltage with a predetermined threshold. If the voltage is greater than said threshold, the detection circuit deduces that a shock has occurred and transmits the information to a control unit.

In response to this shock, the control unit sends to said engine a blocking pulse used to block the rotation of the rotor due to impact.

However, the blocking pulse must allow to lock the rotor in a well-defined position so that no error position of the needle does occur.

SUMMARY OF THE INVENTION

The invention aims to overcome the disadvantages of the prior art by proposing to provide a shock detection device of an engine for detecting a shock more quickly and more accurately.

For this purpose, the present invention relates to an electronic device comprising a calculation unit capable of generating a signal representative of a physical quantity, of a motor driving a display device, said motor comprising a rotor in a circuit magnetic, two terminals, positive and negative, by which the calculation unit controls it, the electronic device further comprising two shock detection circuits, each shock detection circuit being connected between the computing unit and a terminal of the engine for detecting an external shock applied to the engine, said engine having a first stable equilibrium position placed at a reference angular position and a second stable equilibrium position positioned 180 degrees from the first stable angular position, for each direction of rotation, a limit angular position from which it is no longer possible to return the rotor of the m in an anterior angular position, the calculation unit using an algorithm that, following an impact, makes it possible to detect the direction of rotation of the rotor by analyzing an induced voltage detected by said shock detection circuit and to order the sending of a blocking pulse having a reverse polarity of that of the induced voltage, characterized in that the blocking pulse has a maximum duration of 58.5ms for stopping the rotation of the rotor due to an impact and returning it to an angular position predetermined before the limit angular position is reached.

In a first advantageous embodiment, the blocking pulse has a hashing rate ranging from 25% to 100%.

In a second advantageous embodiment, the blocking pulse comprises at least a first and a second distinct temporal phase, each phase may have a distinct hash rate.

In a third advantageous embodiment, the second phase has a duration greater than the first phase.

In a fourth advantageous embodiment, the second phase has a duration two times greater than the first phase.

In a fifth advantageous embodiment, the shock detection circuit comprises a selection portion adapted to allow adjustment of the detection sensitivity.

In another advantageous embodiment, the selection portion allows a sensitivity range of 50 to 600 millivolts.

In another advantageous embodiment, the motor is arranged so that the stable equilibrium position of the rotor is positioned at an angle of 90 degrees with respect to the main axis of the magnetic flux generated by the coil, the position limiting angle is, for each direction of rotation, 270 degrees relative to the reference position.

In another advantageous embodiment, the motor is arranged so that the stable equilibrium position of the rotor is positioned at an angle of at least 30 degrees with respect to the main axis of the magnetic flux generated by the coil. stable, the limit angular position being, for each direction of rotation, at least 120 degrees relative to the reference position.

In another advantageous embodiment, the blocking pulse is sent to the motor via one or the other of its connection terminals.

BRIEF DESCRIPTION OF THE FIGURES

The objects, advantages and features of the invention will appear more clearly in the following detailed description of at least one embodiment of the invention given solely by way of non-limiting example and illustrated by the accompanying drawings in which: :

Fig. 1 represents a general diagram of the electronic device according to the invention;

Figs. 2 and 3 show detailed views of a shock detection circuit according to the invention;

Fig. 4 to 6 show schematically an engine according to the invention;

Fig. 7 shows operating diagrams of the electronic device according to the invention.

DETAILED DESCRIPTION

The present invention proceeds from the general idea of providing a shock detection device of an engine for detecting a shock more quickly and more accurately.

In FIG. 1 is a schematic view of an electronic movement. This movement or electronic device 1 comprises a control module 2 clocked by a quartz oscillator system 3. For the display of time indications such as time and second, needles are mounted on motors 4 to be rotated. The motors used are Lavet motors also called stepper motors and comprise two connection terminals Mot1, Mot2. In these motors, a magnetized rotor 4a of cylindrical shape creates a radial magnetic field in the air gap of a magnetic circuit 4b on which is wound a coil whose terminals are connected to the control module, generally an integrated circuit, providing pulses of current in a terminal order, each pulse advancing the rotor one step. The coil consists of a very fine wire wound on a hollow insulating tube containing inside a part of the magnetic circuit. Such a motor also comprises two stable equilibrium positions 4c as shown in FIG. 4. This control module 2 generally comprises a computing unit 5. The whole is powered by a power supply unit 8 such as a battery or a battery. This power supply unit supplies a supply voltage Vdd. A mass Vss is also planned.

Such a motor comprises two stable equilibrium positions, that is to say two positions in which the rotor is naturally placed in case of power failure.

The control module 2, visible in FIG. 3, further comprises a detection unit 6 comprising at least one shock detection circuit 7. This shock detection circuit 7 is used to determine whether an impact has occurred. Thus, if a shock is detected, the control module 2 can act accordingly and send a lock pulse to prevent the rotor from rotating. The shock detection circuit is placed at the output of at least one of the motor terminals. In the following description, the example of a shock detection circuit 7 connected to the negative terminal Motor Mot2 will be taken. At each motor terminal Mot1, Mot2, a voltage Vmot is measured. At each terminal Mot1, Mot2, a motor buffer is arranged, these motor buffers comprise a flip-flop B1, B2 and two different type of transistors connected in series, the gates of these transistors being connected to the flip-flop as shown in FIG. 3. These buffers are used to pass either positive or negative current through the motor coil to rotate it.

In FIG. 2, it can be seen that the shock detection circuit 7 can comprise a selection part 71 connected directly to the motor 2 Mot 2 terminal. This selection part 71 has an output connected to a comparison part 72. This comparison part 72 is connected to the computing unit 5 so as to provide the signal indicating whether a shock is detected or not.

The selection part comprises a series of resistor Ri connected in series associated with a selector 71a in the form of a multi-position switch. This selector 71a has an output V1 and a plurality of selection points pi, each being associated with a resistor Ri. The selector 71a further comprises a flip-flop 71b for connecting the output of the selector with one of the selection points pi. This flip-flop 71b then makes it possible to modify the sensitivity of the shock detector in order to detect more or less large induced voltages and therefore more or less strong shocks. According to the invention, the resistance series Ri is calculated to have a sensitivity ranging from 50 to 600 millivolts. The output of the selector 71a is the voltage V1 which is connected to the comparison part 72. This comparison part 72 comprises a comparator 72b whose positive input is connected to the output of the selector 71a and whose negative input is at a reference voltage Vref of 50mV (not shown). This comparator 72b provides an output Sh_out2. The resistance chain Ri is controlled by the transistor T which makes it possible to activate the shock detector. Advantageously according to the invention, each Mot1, Mot2 terminal of the Lavet motor is provided with a shock detection circuit 7 so that it can be associated with a management algorithm that makes it possible, during an impact, to manage the rotor 4a as visible in fig. 3.

In a first step, the control module 2 is programmed to detect the direction of rotation of the shock. For this, the two shock detection circuits 7 are used. Each shock detection circuit 7 is connected to an engine terminal so that during an impact, the rotor rotates causing a voltage induced in the shock detection circuits 7. These shock detection circuits 7 send information to the module 2 indicating that a shock has occurred. According to the order in which the information comes, it is easy to detect the rotation of the rotor. As only the positive induced voltages are detected by one or the other detector, it is possible to deduce the direction of rotation of the rotor.

Indeed, the control module 2 is provided with a program allowing it to interpret the information sent by the shock detection circuit 7. For this, this program defines the direction of rotation of the shock depending on the triggering shock detection circuits 7.

During an impact, there is rotation of the rotor 4a, an induced voltage appears so that if this induced voltage is positive then the rotor 4a rotates in the direction of clockwise whereas if the induced voltage is negative then the rotor 4a rotates in the opposite direction of that of the clockwise. Of course, this shock detection is done when the rotor is initially in a stable equilibrium positions 4c as shown in FIG. 4.

Following this detection of the direction of rotation of the shock, it is then possible to apply a shock compensation protocol so as to cancel the effects of said shock. Indeed, the present invention advantageously proposes a compensation protocol for canceling or limiting as much as possible the effects of the shock.

This compensation protocol consists of the application to the motor, by the control unit 2, a blocking signal. This blocking signal is a signal that counteracts the rotation of the rotor 4a during an impact.

This blocking signal is a pulse sent to at least one of the connection terminals of the motor 4 in order to act on the rotor. This pulse is defined as allowing an action contrary to that of the impact on the rotor 4a. Thus, if the rotor is subjected to a shock causing its rotation in the direction of clockwise then the blocking signal is a pulse whose signal is able to drive the rotor in a direction of rotation opposite to that of the needles of a shows and vice versa.

Advantageously according to the invention, the blocking signal, that is to say the blocking pulse is configured to bring the rotor in a desired position. Indeed, the rotor 4a driven by the shock implies that the apparatus associated with said engine is driven, this apparatus consists of cogs driving the needles. Therefore, it appears a change in the position of the needles and therefore the occurrence of an error in the display of the time information.

Therefore, the blocking pulse is configured to not only block the rotation of the rotor following the shock but also to ensure that the rotor returns to its initial stable position when the shock is completed and the blocking pulse is stopped.

This objective of bringing the rotor 4a to a desired position at the moment of impact involves a sub-objective to be achieved. Indeed, in this type of motor, it is known an angular position of the rotor 4a called the point of no return is defined as being the angular position beyond which the rotor can no longer be returned to the initial position.

Indeed, during the rotation of the rotor, it acquires a speed and therefore a moment of inertia. Therefore, if it reaches a certain angular position, it becomes physically impossible to return the rotor 4a to the desired position. This limiting angular position depends on the arrangement of the engine. Indeed, each motor comprises at least two cells 4d or positioning notches. These cells 4d are arranged in an angular position and define the stable equilibrium positions of the rotor. However, the limit angular position depends on the position of these cells 4d with respect to the direction of the main magnetic flux generated by the coil. Thus, in the case where the two cells are arranged at 90 degrees, as shown in FIG. 5, the limit angular position is 270 degrees, that is to say the angular position of one of the cells. In the case where the cells are arranged at 45 degrees as shown in FIG. 6, the limit angular position is 135 degrees.

Claims (10)

According to the invention, the locking pulse is arranged to allow, in case of shock, the return of the rotor in a desired position without the latter does not exceed a limit angular position. As such, the blocking pulse is a pulse provided with a plurality of phases. This plurality of phases makes it possible to modify the characteristics of the blocking pulse. In the present case, the blocking pulse comprises two phases, a first phase Ph1 can be a so-called intense phase that is to say during which the intensity of the retaining torque is maximum and a second phase Ph2 in which the retaining torque is less intense. To vary the intensity of the retaining torque created by the pulse, it is expected to vary the hash ratio that is to say the duty cycle of the pulse. Depending on the hashing rate, the pulse is more or less intense so that the effect on the rotor is more or less sensitive. According to the invention, it is expected that this hash rate varies from 25% to 100%. Therefore, it may be advantageous to have a first phase of the blocking pulse having a high hash ratio and a second phase having a lower hash rate. Moreover, it may be expected to have phases of different durations. For example, the first phase Ph1 will be short but with a high hashing rate while the second phase Ph2 will have a longer duration but a lower hash rate. In a preferred example, the second phase will have a duration equal to twice the duration of the first phase. The first phase here will have a maximum duration of 19.5 milliseconds. In this case, the total duration of the blocking pulse will be at most 58.5 milliseconds as shown in fig. 7. Thus, the sending of the blocking pulse, the polarity of which is the opposite of that of the rotation of the rotor 4a, makes it possible to stop the rotation of the rotor and to bring it back to the desired position. Once in this desired position, the rotor is naturally directed to the initial stable equilibrium position when the pulse is stopped. However, it is advantageously provided a variant in which this displacement to a stable equilibrium position is detected. For this, the shock detection circuits are set to have maximum sensitivity. For this, the flip-flop 71b is switched to act on the resistance series Ri and to select the lowest sensitivity, here 50mV. This low sensitivity makes it possible to measure the voltage induced following the very small displacement of the rotor when it is in a stable equilibrium position. According to the sign, positive or negative, of this induced voltage, it then becomes possible to know towards which positions of stable equilibrium, the rotor is gone. Therefore, the computing unit 5 can take this information into account for the time information. It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to the various embodiments of the invention described in the present description without departing from the scope of the invention. claims An electronic device (1) comprising a computing unit (5) capable of generating a signal representative of a physical quantity, a motor (4) driving a display device, said motor comprising a rotor (4a) in a magnetic circuit (4b), two terminals (Mot1, Mot2) by which the computing unit controls it, the electronic device further comprising two shock detection circuits (7), each shock detection circuit being connected between the calculation unit and a motor terminal for detecting an external shock applied to the motor, said motor having a first stable equilibrium position at a reference angular position and a second stable equilibrium position at 180 degrees from the first stable angular position, for each direction of rotation, a limit angular position from which it is no longer possible to return the motor rotor to an angular position ant higher, the calculation unit using an algorithm, following a shock, to detect the direction of rotation of the rotor by analyzing an induced voltage detected by said shock detection circuit and order the sending of a blocking pulse having a polarity inverse to that of the induced voltage, characterized in that the blocking pulse has a maximum duration of 58.5ms for stopping the rotation of the rotor due to an impact and returning it to a predetermined angular position before the position angular limit is reached. 2. Electronic device according to claim 1, characterized in that the blocking pulse has a hashing rate ranging from 25% to 100%. 3. Electronic device according to claim 2, characterized in that the blocking pulse comprises at least a first (Ph1) and a second (Ph2) distinct time phase, each phase may have a distinct hash rate. 4. Electronic device according to claim 3, characterized in that the second phase has a duration greater than the first phase. 5. Electronic device according to claim 4, characterized in that the second phase has a duration two times greater than the first phase. 6. Electronic device according to one of the preceding claims, characterized in that the shock detection circuit (7) comprises a selection portion (71) adapted to allow adjustment of the detection sensitivity. 7. Electronic device according to claim 6, characterized in that the selection portion allows a sensitivity range from 50 to 600 millivolts. 8. Electronic device according to one of the preceding claims, characterized in that the electronic device comprises two shock detection circuits. Electronic device according to one of the preceding claims, characterized in that the motor (4) is arranged in such a way that the stable equilibrium positions of the rotor when no current flows in the coil are placed at an angle. 30 to 90 degrees to the axis of the main flux generated by the coil in the magnetic circuit when it is traversed by a current 10. Electronic device according to one of the preceding claims, characterized in that the blocking pulse is sent to the motor (4) via one or other of its connection terminals.