Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04G—ELECTRONIC TIME-PIECES
  • G04G21/00—Input or output devices integrated in time-pieces
  • G04G21/08—Touch switches specially adapted for time-pieces
• • G—PHYSICS
  • G04—HOROLOGY
  • G04C—ELECTROMECHANICAL CLOCKS OR WATCHES
  • G04C3/00—Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means
  • G04C3/001—Electromechanical switches for setting or display
  • G04C3/007—Electromechanical contact-making and breaking devices acting as pulse generators for setting
• • G—PHYSICS
  • G04—HOROLOGY
  • G04C—ELECTROMECHANICAL CLOCKS OR WATCHES
  • G04C3/00—Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means
  • G04C3/14—Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means incorporating a stepping motor

Definitions

• the present invention relates to a timepiece, in particular a watch, comprising a rotary mobile and an electric capacitive detection device for detecting positions and / or movements of said mobile, in which the detection device comprises at least one capacitive sensor, having a fixed part provided with one or more fixed electrodes and a mobile part provided with an electrically conductive rotor driven by said mobile, and electronic detection means which are sensitive to variations in the capacity of said sensor.
• the invention applies particularly, but not exclusively, to the control of functions such as the manual correction of the time or the date in an electronic watch by means of the traditional control rod equipped with an outer crown.
• the detection of the rotational and translational movements of this rod is essentially based on electromechanical switches actuated by an arrangement of cams integral with the rod, these cams acting on flexible contact strips which will touch fixed contacts generally provided on a printed circuit which includes other components of the timepiece.
• the main difficulty lies in the reliability of closing the electrical contact, which requires very precise positioning of each contact strip relative to the corresponding cam and relative to the corresponding fixed contact. It is therefore necessary to carry out functional tests and possibly adjustments during the assembly of each timepiece. These operations are costly and considerably hamper the automation of the assembly of watches. Similar problems arise with electrical contacts intended to detect particular positions of a mobile, for example the "zero" position of a chronograph hand or of a date indicator.
• pulses are generated from variations in the capacitive coupling produced by the rotor electrode between different electrodes of the stator, thanks to variations in the overlap area between the rotor and each fixed electrode, while the thickness of the dielectric between the electrodes remains constant.
• the rotor must be mounted with sufficient precision and stability so that the distance between the electrodes, that is to say the thickness of the dielectric, remains constant.
• the present invention aims to avoid the drawbacks of the prior art by creating a reliable contactless detection device, usable in a timepiece such as a watch, which can be produced and assembled at low cost and which can apply advantageously to correct the time or date or the detection of a particular position of a rotary mobile.
• each fixed electrode is arranged opposite a peripheral surface of the rotor, said surface comprising teeth arranged to pass close to each electrode. fixed during rotation of the rotor.
• the detection device acts essentially by variation of the capacitance by virtue of the variation in distance between the toothed peripheral surface of the rotor and each fixed electrode.
• a device By its nature, such a device can be produced in a form which is both compact and consumes little electrical energy, which is very suitable for use in a watch.
• capacitive sensors can be produced without great complication which make it possible to detect a fairly large number of successive angular positions, for example eight or twelve positions per revolution.
• the fixed part of the capacitive sensor comprises a pair of fixed electrodes and the rotor is arranged to influence the electric field between the fixed electrodes by its rotational position.
• the rotor can be kept at a fixed potential, its teeth being arranged to screen in the electric field between the fixed electrodes.
• these two fixed electrodes are coplanar on a substrate and are separated from each other by an interval, the axis of the rotor being arranged opposite said interval and parallel to the fixed electrodes.
• the substrate can advantageously be part of a printed circuit element of the timepiece, that is to say that an element is thus used which already exists in an electronic or electromechanical timepiece movement.
• the rotor in order to maintain a constant spacing between the rotor and the fixed electrodes, it can be provided that the rotor is integral with the mobile, which comprises a support cylinder which bears by sliding against a dielectric layer disposed on the substrate and / or on the fixed electrodes. This avoids any adjustment of the sensor when mounting the mobile.
• the fixed electrodes form two respective opposite spaced plates and the rotor is arranged between them, its axis of rotation being parallel to this. Thanks to the toothed shape of the peripheral surface of the rotor, the variation in capacitance between the electrodes is due in this case to the thickness modulation of the dielectric.
• the fixed electrodes can be on the same printed circuit substrate, for example on two opposite edges of an opening in the substrate.
• the rotor can be isolated and serve as a transmitter of an electrical signal between the two fixed electrodes. The rotor is then at a floating potential.
• the rotor is a mobile electrode connected to the detection means and the teeth of which, during its rotation, pass alternately opposite one or the other of the fixed electrodes.
• the rotor thus forms a third electrode for injecting a signal into the two capacitors which it forms respectively with the two fixed electrodes.
• the fixed part of the capacitive sensor comprises an annular stator provided with internal teeth forming a fixed electrode and in that the rotor is placed inside the stator, its teeth forming a movable electrode in look of the stator teeth.
• electrodes are thus obtained having a relatively large surface and a small distance between these surfaces, therefore a fairly high capacity.
• the stator can be internally coated with a thin dielectric layer against which the rotor is capable of pressing while sliding, which ensures the centering of the rotor in the stator.
• the contactless detection device can also indicate the direction of rotation of the mobile, the detection device preferably comprises two of said capacitive sensors, which are angularly offset so as to provide respective output signals which are in quadrature during the rotation of the mobile.
• FIG. 1 schematically represents a first embodiment of the invention, more particularly a device for non-contact detection of the positions of a rotary mobile, this device comprising a capacitive sensor
• FIG. 2 is a view similar to FIG. 1, illustrating another position of the mobile
• FIG. 3 is a diagrammatic view in cross section of a capacitive sensor used in the present invention, along line III-III of Figure 4
• Figure 4 is a schematic side view of a device comprising two capacitive sensors associated with a rotary and sliding mobile
• - Figure 5 is a view in schematic section of another embodiment of a capacitive sensor
• FIG. 1 schematically represents a first embodiment of the invention, more particularly a device for non-contact detection of the positions of a rotary mobile, this device comprising a capacitive sensor
• FIG. 2 is a view similar to FIG. 1, illustrating another position of the mobile
• FIG. 3 is a diagrammatic view in cross section of a capacitive sensor used in the present invention, along line III-III of Figure
• FIG. 6 is an equivalent electrical diagram of the cap Figure 5 is a schematic sectional view of another embodiment of a capacitive sensor
• Figure 8 is an equivalent electrical diagram of the sensor of Figure 7
• FIG. 9 is a schematic sectional view of another embodiment of a capacitive sensor
• FIG. 10 schematically represents yet another embodiment of the invention, where the control rod of a watch is associated with two cylindrical capacitive sensors
• FIG. 11 is a cross-sectional view of one of the sensors of FIG. 10
• FIG. 12 represents electrical signals obtained in the device of FIGS. 10 and 11 during the rotation of the mobile.
• the mobile whose positions it is a question of detecting is a rod 1 which can be, for example, the time control rod of a watch or of another piece. of watchmaking. However, this mobile could be another part of a timepiece movement, for example a shaft carrying a seconds, minutes or hours hand, or a hand of a chronograph counter.
• the rod 1 is associated with a device for detecting its angular positions which comprises a capacitive sensor 2 and electronic detection means 3 using the signal from the sensor on an output line 4.
• the sensor 2 comprises a movable part, constituted by a rotor 5 fixed coaxially on the rod 1, and a fixed part consisting essentially of two fixed electrodes 6 and 7 which, in this case, are coplanar and applied to the underside of an insulating substrate 8 parallel to the axis of the rotor 5.
• This can advantageously be a printed circuit board such as exists in most electronic or electromechanical watches, this card usually being parallel to the watch dial and to the control rod.
• a voltage source 9 is connected in series between the ground 10 and the first electrode 6 to apply to it a pulsed voltage Ue.
• the second electrode 7 is connected to line 4 to deliver a output signal which depends on the capacity between the two electrodes 6 and 7.
• the rotor 5 is a conductive part, preferably metallic, in the shape of a star, its peripheral surface having in this case four teeth 11 to 14 regularly spaced angularly. Preferably, it is connected to ground 10 by means of the rod 1.
• the rotor is opposite the gap 15 separating the electrodes 6 and 7 and its teeth pass a short distance from the electrodes. The presence and position of the rotor thus influences the electric field 16 and therefore the capacitive coupling between the electrodes.
• the capacity of the sensor 2 varies periodically and the output signal on the line 4 passes through a minimum in the position of FIG. 1, where the rotor forms a screen in the electric field, and by a maximum in the position of FIG. 2, where the rotor practically does not screen.
• the sensor output signal is applied to the negative input of an amplifier 16 connected in parallel to an integration capacitor 17 of capacitance Ci.
• Each pulse of this signal represents the passage of one of the teeth 11 to 14 in front of the electrodes, therefore a step of rotation of the rod 1, this step being a quarter turn in the present example.
• the signal Us is used in a processing circuit 19 which controls the desired function in known manner, for example setting the time or setting the date of the watch.
• FIG. 3 illustrates an advantageous embodiment of the capacitive sensor 2, in order to maintain a determined distance and as small as possible between the teeth of the rotor 5 and the electrodes 6 and 7, so that the variations in capacitance of the sensor during the movements of rod 1 are as high as possible and can therefore be detected easily.
• a thin dielectric layer 20 is applied to at least part of the electrodes 6 and 7 and to the gap 15 between them.
• This layer can be formed for example of a resin film having a thickness of a few micrometers. This thickness is obviously exaggerated in the drawing.
• the rod 1 carries a support cylinder 21 placed at a sufficient distance from the rotor 5 so as not to influence the capacitance between the electrodes.
• the rod 1 is placed relative to the substrate 8 so that its cylinder 21 bears lightly against the layer 20, which also extends on the substrate opposite the cylinder.
• the end surfaces of the teeth 11 to 14 of the rotor 5 can be cylindrical and have the same radius as the cylinder 21, so that their distance from the electrodes 6 and 7 is practically equal to the thickness of the dielectric layer 20.
• FIG. 4 illustrates an embodiment comprising, next to the capacitive sensor 2, a second similar capacitive sensor 22 in order to be able to detect the direction of rotation of the rod 1.
• the sensor 22 comprises a rotor 25 fixed on the rod 1 and a pair of electrodes 26 and 27 identical to electrodes 6 and 7 and applied to the substrate 8 next to these. These electrodes are also covered by the dielectric layer 20.
• the rotor 25 is identical to the rotor 5, but angularly offset by a quarter of the pitch of the teeth, that is to say a sixteenth of a turn in this case, so that the output signals of sensor 22 are in quadrature with those of sensor 2. Signals of this kind are described below with reference to FIG. 12.
• control rod 1 of the watch can slide axially between at least two positions, one of which is a positioning position. at the time, shown in solid lines in Figure 4.
• the other axial position of the rod is a neutral position, shown in broken lines, where the rod 1 must be able to rotate without correcting the time of the watch.
• the rotor 25 of the sensor 22 is then located opposite the electrodes 6 and 7 of the sensor 2, so that the sensor 2 is active, while the sensor 22 is inactive.
• the processing circuits 19 detect this fact when the rod 1 rotates and they do not trigger any action.
• FIGS. 5 and 6 illustrate another embodiment of a capacitive sensor which can be used in place of each of the sensors 2 and 22 described above.
• This sensor 30 comprises two fixed electrodes disposed on a common insulating substrate 33 and connected to respective terminals A and B. Each electrode 31, 32 extends in particular on opposite edges of an opening 34 of the substrate 33 to each form a plate electrode 35, 36.
• the axis 37 of the rotary rod 1 extends in the middle of the opening 34, in the median plane of the substrate, so that the rotor 5 fixed on the rod 1 is substantially at the same distance from each of the electrodes 31 and 32.
• the rotor 5 has an even number of teeth, it is electrically isolated and is at a floating potential, to serve as a passive transmitter of an electrical signal between the two electrodes.
• the equivalent diagram in FIG. 6 shows that the capacity of the sensor 30 is equal to the placing in series of the variable capacities C1 and C2 situated respectively between the electrode 31 and the rotor 5 and between the rotor 5 and the electrode 32.
• the capacitances C1 and C2 vary together by variation of the distances and therefore of the dielectric intervals between the conducting rotor and the electrodes when the rod 1 rotates. If necessary, the rod 1 can be guided by the insulating substrate 33. Of course, it can be associated with two sensors 30 delivering quadrature signals which also make it possible to indicate the direction of rotation of the rod by a method analogous to that described with reference to Figure 4.
• FIGS 7 and 8 illustrate a capacitive sensor 40 in which there are the same elements 31 to 37 as in the sensor 30, but with a different rotor 41 which constitutes a mobile electrode connected to a terminal D by a flexible blade 42 which rubs on a collar 43 of the rotor 41.
• This comprises an odd number of teeth, for example three teeth 44, 45 and 46, which have equal angular intervals and therefore pass alternately in front of one or the other of the electrodes 31 and 32
• Terminal D is used for injecting an electrical signal on the mobile electrode formed by rotor 41, the output signals being collected on terminals A and B.
• Another advantage of the sensor 40 is that its resolution for one revolution of the rotor is twice the number of teeth. For example, a resolution of ten steps per revolution would be obtained with only five teeth.
• FIG. 9 illustrates a capacitive sensor 50 comprising the same elements 31 to 37 and 41 to 43 as the sensor 40 described above, but in this case the rotor 41 has only two teeth 44 and 45 arranged asymmetrically, their angular distance being for example 135 °.
• the signals collected at terminals A and B follow one another in a different order depending on whether the rod 1 rotates in one direction or in the other. Therefore, the detection means can determine both angular positions and the direction of rotation of the rod 1 by means of the single sensor 50.
• the control rod 1 of a watch 51 has a conventional outer crown 52 and it is rotatably and slidingly supported in the case 53 of the watch and in a fixed part 54 of the watch movement.
• the rod 1 is equipped with two coaxial cylindrical capacitive sensors 55 and 56 arranged to deliver quadrature output signals, as in the example of the Figure 4.
• Each sensor 55, 56 has a rotor 57, 58 made in one piece with the rod 1 and an annular stator 59, 60 arranged coaxially around the rotor (when the rod 1 occupies the axial position shown in Figure 10) and attached to the inside of the watch.
• Figure 11 is a schematic sectional view of the sensor 55, on an enlarged scale.
• the generally cylindrical outer surface of the metal rotor 57 is striated with axial grooves 62 which define between them, for example eight regularly spaced outer teeth 63.
• the metal stator 59 is internally striated by the same number of axial grooves not referenced, defining between them eight interior teeth 64 regularly spaced and having substantially the same width as the teeth 63 of the rotor.
• the stator 59 is coated internally with a layer 65 of dielectric material, this layer being as thin as possible on teeth 64 in order to increase the capacity of the sensor.
• the stator is also provided with a longitudinal slot 66 in order to be able to be applied by elasticity against the periphery of the rotor.
• the stator 59 has for example two opposite ears 67 engaging with a small clearance in recesses (not shown) inside the watch.
• the circumferential width of the teeth 63 and 64 is preferably slightly less than that of the grooves of the rotor and the stator. During rotation, the capacity goes through a maximum when the teeth 63 and 64 are located opposite one another and through a minimum when the grooves 62 of the rotor are located opposite the teeth 64 of the stator.
• FIG. 12 represents, as a function of the angle ⁇ of rotation of the rod 1, the variation of the capacitance Cl of the sensor 55 and of the capacitance C2 of the sensor 56. These two signals are in quadrature if, by example, the teeth 63 of the two rotors 57 and 58 are mutually aligned while the teeth 64 of the stator 60 are offset by a quarter of their pitch, that is to say 1/32 of a turn, relative to those of the stator 59 in the direction of rotation (arrow F) of the rod 1.
• FIG. 12 also shows the square pulses of voltage Us1 and Us2 which are obtained for each sensor as described with reference to the figure 1 and which allow the detection means to indicate the number of steps and the direction of rotation of the rod 1.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Electromechanical Clocks (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)
• Electric Clocks (AREA)

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Publications (1)

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Family Applications (1)

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Citations (10)

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• 1997
  • 1997-02-17 FR FR9701813A patent/FR2759792B1/fr not_active Expired - Lifetime
• 1998
  • 1998-02-16 JP JP53519798A patent/JP2001524206A/ja active Pending
  • 1998-02-16 US US09/367,535 patent/US6252825B1/en not_active Expired - Lifetime
  • 1998-02-16 CN CN98802602.3A patent/CN1119724C/zh not_active Expired - Fee Related
  • 1998-02-16 DE DE69817536T patent/DE69817536T8/de active Active
  • 1998-02-16 EP EP98901919A patent/EP0960361B1/fr not_active Expired - Lifetime
  • 1998-02-16 WO PCT/CH1998/000057 patent/WO1998036332A1/fr not_active Ceased
  • 1998-02-17 TW TW087102178A patent/TW342472B/zh not_active IP Right Cessation

Patent Citations (10)

Non-Patent Citations (3)

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