EP0960361B1 - Wheel work part comprising a capacitive sensing device - Google Patents

Description

The present invention relates to a part horological, in particular a watch, comprising a mobile rotary and an electrical device capacitive sensing to detect positions and / or movements of said mobile, in which the detection device comprises at least one capacitive sensor having a fixed part provided at least two fixed electrodes and part mobile with electrically conductive rotor driven by said mobile and arranged to influence the electric field between the fixed electrodes by its rotational position, and means detection electronics that are sensitive to variations in the capacity of said sensor, both fixed electrodes being arranged on a substrate and separated from each other by an interval.

The invention is particularly applicable, but not exclusively, when ordering functions such as manual time correction or the date in an electronic watch using the traditional control rod fitted with a outer crown. Usually the detection rotational and translational movements of this stem is essentially based on electromechanical switches actuated by a arrangement of cams integral with the rod, these cams acting on contact slats flexible that will touch fixed contacts generally provided on a printed circuit which includes other component parts watchmaking.

For the manufacture and assembly of these switches, the main difficulty lies in the reliability of closing the electrical contact, which requires very precise positioning of each contact strip with respect to the cam corresponding and relative to the fixed contact corresponding. It is therefore necessary to perform functional tests and possibly adjustments during assembly of each part watchmaking. These operations are costly and considerably hamper the automation of assembly of watches.

Similar problems arise with electrical contacts for detecting particular positions of a mobile, for example the "zero" position of a chronograph hand or a date indicator.

It would therefore be desirable to replace the switches mentioned above by devices contactless, suitable for use in watches.

In patent application DE 3934158 A1, it a usable pulse generator is described to control an electronic clock in a domestic appliance, this corresponding generator roughly like a capacitive sensor indicated in the preamble above. A shaped rotor disc, rotatable about a perpendicular axis to the disc, carries a flat electrode having two diametrically opposite sectors, opposite a flat stator with several fixed electrodes having a particular arrangement and connected to electronic detection circuits. A thin dielectric is placed between the stator and the rotor. When the rotor turns, pulses are generated from variations in coupling capacitive produced by the rotor electrode between different stator electrodes, 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.

Such a construction is far too much bulky for industrial applications horological, in particular in watches. Else apart, the rotor must be mounted with precision and sufficient stability for the distance between the electrodes, i.e. the thickness of the dielectric, remains constant.

In the publication Patent Abstracts of Japan flight. 007, no. 270 (P-240) relating to the request for patent JP 58-150865A, a detector is described rotational capacitive with two electrodes fixed annular superimposed and provided with teeth interior, and a rotary electrode mounted on an insulating disc with teeth exterior high enough to face the teeth of the two fixed electrodes at the same time. We detect the rotation of the disc by variations of capacity between the two fixed electrodes. Such a construction, intended to detect the rotation of a motor, is too bulky to be usable in a watch.

The object of the present invention is to avoid disadvantages of the prior art by creating a reliable contactless detection device, usable in a timepiece such as watch, can be made and mounted at a low cost and can be applied advantageously to the correction of time or date or on detection of a particular position of a mobile rotary.

To this end, according to a first aspect of the invention there is provided a timepiece as defined in claim 1.

Thus, the detection device acts essentially by varying capacity thanks to the variation in distance between the surface toothed device of the rotor and each electrode fixed. By its nature, such a device is achievable in a space-saving form and consuming little electrical energy, which suitable for use in a watch. Of more, we can achieve without great complication capacitive sensors that detect a quite a lot of angular positions successive, for example eight or twelve positions per turn.

The rotor can be kept at a potential fixed, its teeth being arranged to screen in the electric field between the electrodes fixed.

As the two fixed electrodes are coplanar on a substrate, this substrate can advantageously be part of an element to printed circuits of the timepiece, i.e. that we use an element that exists already in an electronic watch movement or electromechanical.

In order to maintain a constant spacing between the rotor and the fixed electrodes, we can provide that the rotor is integral with the mobile, which has a support cylinder which rests in sliding against a dielectric layer arranged on the substrate and / or on the fixed electrodes. This avoids any adjustment of the sensor when mounting the mobile.

According to a second aspect of the invention, it is provided a timepiece as defined in claim 2.

Thanks to the toothed shape of the surface rotor device, capacity variation between the electrodes is due in this case to the thickness modulation of the dielectric. In this arrangement also, the fixed electrodes can be find on the same printed circuit substrate, for example on two opposite edges of an opening of the substrate. The rotor can be isolated and used as transmitter of an electrical signal between the two fixed electrodes. The rotor is then at a potential floating.

Another advantageous embodiment of the sensor with a pair of fixed electrodes consists of the rotor being an electrode mobile connected to the detection means and whose teeth, during its rotation, pass alternately opposite one or other of the fixed electrodes. The rotor thus forms a third electrode for signal injection in the two capacitors it forms respectively with the two fixed electrodes.

So that the detection device without contact can also indicate the direction of rotation of the mobile, the detection device includes preferably two of said capacitive sensors, which are offset angularly so as to provide respective output signals which are quadrature during the rotation of the mobile.

• la figure 1 représente schématiquement une première forme de réalisation de l'invention, plus particulièrement un dispositif de détection sans contact des positions d'un mobile rotatif, ce dispositif comportant un capteur capacitif,
• la figure 2 est une vue analogue à la figure 1, illustrant une autre position du mobile,
• la figure 3 est une vue schématique en coupe transversale d'un capteur capacitif utilisé dans la présent invention, suivant la ligne III-III de la figure 4,
• la figure 4 est une vue latérale schématique d'un dispositif comportant deux capteurs capacitifs associés à un mobile rotatif et coulissant,
• la figure 5 est une vue en coupe schématique d'une autre forme de réalisation d'un capteur capacitif,
• la figure 6 est un schéma électrique équivalent du capteur de la figure 5,
• la figure 7 est une vue en coupe schématique d'une autre forme de réalisation d'un capteur capacitif,
• la figure 8 est un schéma électrique équivalent du capteur de la figure 7,
• la figure 9 est une vue en coupe schématique d'une autre forme de réalisation d'un capteur capacitif, et
• la figure 10 représente des signaux électriques obtenus dans le dispositif des la figures 4 au cours de la rotation du mobile.

Other characteristics and advantages of the present invention will appear in the following description of various exemplary embodiments, with reference to the appended drawings, in which:

• 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 schematic cross-sectional view of a capacitive sensor used in the present invention, along the line III-III of FIG. 4,
• FIG. 4 is a schematic side view of a device comprising two capacitive sensors associated with a rotary and sliding mobile,
• FIG. 5 is a schematic sectional view of another embodiment of a capacitive sensor,
• FIG. 6 is an equivalent electrical diagram of the sensor of FIG. 5,
• FIG. 7 is a schematic sectional view of another embodiment of a capacitive sensor,
• FIG. 8 is an equivalent electrical diagram of the sensor of FIG. 7,
• FIG. 9 is a schematic sectional view of another embodiment of a capacitive sensor, and
• FIG. 10 represents electrical signals obtained in the device of FIGS. 4 during the rotation of the mobile.

In the example of Figures 1 and 2, the mobile which it is a question of detecting positions is a rod 1 which can be for example the rod of time setting command for a watch or another timepiece. However, this mobile could be another piece of a movement of watchmaking, for example a tree bearing a second, minute or hour hand, or a chronograph counter hand.

The rod 1 is associated with a device for detection of its angular positions which includes a capacitive sensor 2 and electronic means detection 3 using the signal from the sensor on an output line 4. The sensor 2 comprises a mobile part, constituted by a fixed rotor 5 coaxially on the rod 1, and a fixed part essentially consisting of two electrodes fixed 6 and 7 which, in this case, are coplanar and applied to the underside an insulating substrate 8 parallel to the axis of the rotor 5. This can advantageously be a card to printed circuits as there are in the most electronic watches or electromechanical, this card usually being parallel to the watch face and to the ordered. A voltage source 9 is connected in series between ground 10 and first electrode 6 to apply a pulsed voltage Ue thereto. The second electrode 7 is connected to line 4 to deliver an output signal which depends on the capacity between the two electrodes 6 and 7.

The rotor 5 is a conductive part, of preferably metallic, star-shaped, its peripheral surface presenting in this case four teeth 11 to 14 regularly spaced angularly. Preferably, it is connected to the mass 10 via rod 1. The rotor is located in front of the interval 15 between the electrodes 6 and 7 and its teeth go to low distance from the electrodes. Presence and position of the rotor thus influences the electric field 16 and therefore the capacitive coupling between the electrodes. At during rotation of the rod 1, the capacity of the sensor 2 varies periodically and the signal exit on line 4 goes through a minimum in the position of Figure 1, where the rotor forms a screen in the electric field, and by a maximum in the position of figure 2, where the rotor does practically no screen.

In the detection means 3, the signal sensor output is applied to the negative input an amplifier 16 connected in parallel to a integration capacitor 17 of capacity Ci. On obtains at output 18 of amplifier 16 a square pulse voltage signal Us = (Cv / Ci) · Ue, where Cv is the capacitance between two electrodes 6 and 7. Each pulse of this signal represents the passage of one of teeth 11 to 14 in front of the electrodes, so a step of rotation of rod 1, this step being a quarter turn in this example. The Us signal is used in a processing circuit 19 which controls so known the desired function, for example setting the time or date of the watch.

Figure 3 illustrates an embodiment advantage of the capacitive sensor 2, in order to maintain a determined distance and also small as possible between the teeth of rotor 5 and the electrodes 6 and 7, so that variations in sensor capacity during rod movements 1 are as high as possible and can therefore be detected easily. A thin layer dielectric 20 is applied to at least one part of electrodes 6 and 7 and on interval 15 separating them. This layer can be formed by example of a resin film having a thickness of a few micrometers. This thickness is obviously exaggerated in the drawing. Otherwise, the rod 1 carries a support cylinder 21 placed at a sufficient distance from rotor 5 so as not to influence the capacitance between the electrodes. The rod 1 is placed relative to substrate 8 of so that its cylinder 21 rests slightly against layer 20, which also extends over the substrate in front of the cylinder. The surfaces end of teeth 11 to 14 of rotor 5 can be cylindrical and have the same radius as the cylinder 21, so that their distance to electrodes 6 and 7 is practically equal to the thickness of the dielectric layer 20.

The advantages of such an arrangement do not not just about signal quality obtained: as it positively determines the distance between the rod 1 and the substrate 8, it allows easy mounting of sensor 2 avoiding any setting. In particular, when the rod 1 is the control rod of a watch, it is set place after the printed circuit substrate 8. This can be held resiliently so as to press lightly against the cylinder 21 of the stem.

Figure 4 illustrates an embodiment comprising, next to the capacitive sensor 2, a second similar capacitive sensor 22 in order to ability to detect direction of rotation of 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 to side of these. These electrodes are also covered by the dielectric layer 20. The rotor 25 is identical to rotor 5, but offset angularly of a quarter of the pitch of the teeth, or a sixteenth of a turn in this case, so that the output signals from sensor 22 are in quadrature with those of sensor 2. Signals from these kinds are described later with reference to the figure 10. As usual, the control rod 1 of the watch can slide axially between at minus two positions, one of which is a position time setting, shown in solid lines in Figure 4. The other axial position of the rod is a neutral position, shown in lines interrupted, where the rod 1 must be able to rotate without correct the time of the watch. The rotor 25 of sensor 22 is then located opposite the electrodes 6 and 7 of sensor 2, so that sensor 2 is active, while the sensor 22 is inactive. The processing circuits 19 detect this fact when rod 1 turns and they do not engage any action. If, on the contrary, the two sensors 2 and 22 provide quadrature signals, circuits 19 make a time correction the extent of which is determined by the number of steps indicated by sensor 2, and direction by order of succession of signals from sensors 2 and 22.

Figures 5 and 6 illustrate another form of a capacitive sensor usable at the place of each of the sensors 2 and 22 described above. This sensor 30 has two electrodes fixtures arranged on a common insulating substrate 33 and connected to respective terminals A and B. Each electrode 31, 32 extends in particular over opposite edges of an opening 34 of the substrate 33 to each form an electrode plate 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, of so that the rotor 5 fixed on the rod 1 is roughly the same distance from each of electrodes 31 and 32. In this case, the rotor 5 has an even number of teeth, it is isolated electrically and stands at a potential floating, to serve as a passive transmitter of a electrical signal between the two electrodes. The equivalent diagram in Figure 6 shows that the sensor capacity 30 is equal to the serialization variable capacities C1 and C2 located respectively between the electrode 31 and the rotor 5 and between the rotor 5 and the electrode 32. The capacities C1 and C2 vary together by variation distances and therefore dielectric intervals between the conducting rotor and the electrodes when rod 1 rotates. If necessary, rod 1 can be guided by the insulating substrate 33. Of course, it can be associated with two sensors 30 delivering quadrature signals that allow also indicate the direction of rotation of the rod by a method analogous to that described with reference to Figure 4.

Figures 7 and 8 illustrate a sensor capacitive 40 in which we find the same elements 31 to 37 than in sensor 30, but with a different rotor 41 which constitutes an electrode mobile connected to a terminal D by a flexible blade 42 which rubs on a collar 43 of the rotor 41. The latter has 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 other of the electrodes 31 and 32. Thus, the capacity C1 is maximum when capacity C2 is minimum. The terminal D is used for signal injection electric on the mobile electrode constituted by the rotor 41, the output signals being collected on terminals A and B. It is thus possible to measure from a precisely a differential capacitance between A and B, eliminating the stray capacitances between the different conductors and the mass, which are often much higher than C1 and C2. A another advantage of sensor 40 is that its resolution for one revolution of the rotor is double the number teeth. For example, a resolution of ten steps per revolution would be obtained with only five teeth.

FIG. 9 illustrates a capacitive sensor 50 with the same elements 31 to 37 and 41 to 43 that the sensor 40 described above, but in this case the rotor 41 has only two teeth 44 and 45 asymmetrically arranged, their distance angular being for example 135 °. The result that the signals collected at terminals A and B are succeed in a different order depending on whether the rod 1 turns in one direction or the other. So the detection means can determine both angular positions and the direction of rotation of the rod 1 by means of the single sensor 50.

Note that it is possible to obtain the same result with a rotor having teeth diametrically opposite, if the two plates electrodes 35 and 36 are not diametrically opposite with respect to the axis 37 of the rotor.

The top diagram in Figure 10 represents, as a function of the angle α of rotation of the rod 1, the variation of the capacity C1 of the sensor 2 and the capacity C2 of sensor 22 shown in Figure 4. These two signals are in squaring if, for example, teeth 11 to 14 of two rotors 5 and 25 are mutually in the direction of rotation of the rod 1. Also shown in figure 10 the square voltage pulses Us1 and Us2 which are obtained for each sensor as described with reference to Figure 1 and which allow the detection means to indicate the number of steps and the direction of rotation of the rod 1.

The examples described above demonstrate that the present invention allows to install in a small timepiece, like a watch, a contactless detection device which advantageously replaces the rotation detection with electrical contacts, thanks to to its simplicity and reliability.

Claims (12)

1. Timepiece including a rotating member (1) and an electric capacitive detection device for detecting positions and/or movements of said rotating member, wherein the detection device includes at least one capacitive sensor (2, 22), having a fixed portion provided with a pair of fixed electrodes (6, 7; 26, 27) and a mobile portion provided with an electrically conductive rotor (5, 25) driven by said rotating member and arranged to influence the electric field between the fixed electrodes by its position of rotation, and electronic detection means (3) which are sensitive to variations in said sensor's capacitance, the two fixed electrodes (6, 7; 26, 27) being coplanar on a substrate (8) and separated from each other by a gap (15),
      characterized in that the rotor (5, 25) axis is disposed opposite said gap and parallel to the plane of the fixed electrodes, and in that each fixed electrode (6, 7, 26, 27) is disposed opposite a peripheral surface of the rotor (5, 25), said surface including teeth (11-14) arranged to pass close to each fixed electrode during rotation of the rotor.
2. Timepiece including a rotating member (1) and an electric capacitive detection device for detecting positions and/or movements of said rotating member, wherein the detection device includes at least one capacitive sensor (30, 40), having a fixed portion provided with at least two fixed electrodes (31, 32) and a mobile portion provided with an electrically conductive rotor (5, 41) driven by said rotating member and arranged to influence the electric field between the fixed electrodes by its position of rotation, and electronic detection means (3) which are sensitive to variations in said sensor's capacitance, the two fixed electrodes (31, 32) being disposed on a substrate (33) and separated from each other by a gap,
      characterized in that the fixed electrodes form two respective spaced opposite electrode plates (35, 36) separated by said gap, in that the rotor (5, 25, 41) is disposed within said gap, its axis of rotation (37) being parallel to said plates, and in that each of said fixed electrode plates (35, 36) is disposed opposite a peripheral surface of the rotor, said surface including teeth (11-14, 44-46) arranged to pass close to each electrode plate during rotation of the rotor.
3. Timepiece according to claim 1, characterized in that the rotor (5) is held at a fixed potential and in that its teeth (11-14) are arranged to form a shield in the electric field between the fixed electrodes.
4. Timepiece according to claim 1 or 2, characterized in that said teeth (11-14, 44-46) are distributed with a constant angular pitch about the rotor.
5. Timepiece according to claim 2, characterized in that the substrate (33) is planar and has an opening (34) wherein the rotor is located, said electrode plates (35, 36) extending on opposite edges of said opening.
6. Timepiece according to claim 1 or 2, characterized in that the substrate (8, 33) forms part of a printed circuit element of the timepiece.
7. Timepiece according to claim 1, characterized in that the rotor (5, 25) is attached to the rotating member (1), which includes a support cylinder (21) which slidingly abuts against a dielectric layer (20) disposed on the substrate and/or on the fixed electrodes.
8. Timepiece according to claim 2, characterized in that the rotor (5) is insulated and acts as transmitter of an electric signal between the two fixed electrodes.
9. Timepiece according to claim 1 or 2, characterized in that the rotor (41) is a mobile electrode connected to the detection means and whose teeth (44, 45, 46) pass alternately opposite one or other of the fixed electrodes during its rotation.
10. Timepiece according to claim 1 or 2, characterized in that the detection device includes two of said capacitive sensors (2, 22), which are offset angularly so as to provide respective output signals which are in quadrature during the rotation of the rotating member.
11. Timepiece according to claim 1 or 2, characterized in that the rotating member (1) is a control stem having at least two axial positions, namely a time-setting position in which the capacitive sensor (22) is active and at least one other position in which said sensor is inactive.
12. Timepiece according to claim 1 or 2, characterized in that the rotating member (1) is an indicator element having a reference position which is detected by the detection device.

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