HK1240335A1 - Timepiece comprising a wheel set with a determinable angular position - Google Patents

Description

Timepiece comprising a wheel set with a determinable angular position

Technical Field

The invention concerns the technical field of timepieces comprising a timepiece movement provided with an analogue display mechanism and at least one wheel set rotating integrally with a rotation indicator of the analogue display mechanism.

Background

In order to determine the angular position of such a wheel set, it is known from EP patent 0952426 to provide the wheel set with a surface layer made of a special material and a through hole located in an intermediate region between the axis of rotation of the wheel set and its periphery. When the wheel set is in the reference position, a proximity sensor stationary with respect to the wheel set is positioned directly above or below the aperture. The sensor is capable of sensing the particular material and providing a measurement signal that is dependent on changes in the vicinity of the material. Thus, the measurement signal has a particular shape, e.g. a spike, when the hole passes over the sensor.

In order to determine the angular position of the wheel set, it is proposed to perform a step-wise rotation of the wheel set by means of a stepping motor, while recording the measurement signal. The above-mentioned spike thus indicates that the wheel set passes its reference position. Once the reference position has been determined in the graph representing the measurement signal, it is possible to easily deduce therefrom the angular position of the wheel set corresponding to another point on the graph, in particular the initial angular position of the wheel set, i.e. its position before starting rotation.

EP patent 0952426 proposes the use of inductive or capacitive sensors, but at the same time indicates that capacitive sensors are more sensitive to the environment and to disturbances caused by manufacturing and assembly tolerances than inductive sensors. The capacitive sensor is affected in particular by the axial play between the wheel set and the sensor along the axis of rotation of the wheel set. The larger the axial gap, the wider the spike: the accuracy of the determination of the angular reference position is thus directly influenced by the axial play.

Disclosure of Invention

One purpose of the present invention is to overcome the above drawbacks by proposing a solution for determining the angular position of a wheel set by means of a capacitive sensor, the accuracy of which is not affected by variations in the axial clearance between the wheel set and the sensor.

To this end, the invention relates to a timepiece comprising:

-a timepiece movement provided with an analogue display mechanism and at least one wheel set rotating integrally with a rotation indicator of said analogue display mechanism, said wheel set comprising an electrically conductive plate extending substantially orthogonally to the axis of rotation of said wheel set and pierced with at least one hole,

-detection means for detecting a reference angular position of said hole, comprising at least one set of planar electrodes comprising a first electrode, a second electrode and a common electrode arranged in a plane parallel to said wheel set, said common electrode being arranged along a portion of said first electrode and a portion of said second electrode,

the aperture at least partially:

-above or below the first electrode in a position referred to as a first unbalance position,

-above or below the first and second electrodes at a position called equilibrium position,

-above or below the second electrode in a position referred to as second unbalanced position.

The first electrode and the common electrode form a first capacitor having a capacitance of C1, and the second electrode and the common electrode form a second capacitor having a capacitance of C2. By using a stepping motor which causes the wheel set to perform a full stepping turn and generating a representation as a function of the number of stepsThe measuring circuit of measuring a signal of (1), obtaining a curve having a maximum value and a minimum value. A minimum value is observed when the aperture is in the first unbalanced position; a maximum value is observed when the aperture is in the second unbalanced position; the curve has a zero value when the aperture is in the equilibrium position.

Since the maxima and minima are characterized by a particular angular position of the wheel set, when the maxima and minima have been identified on the graph representing the measurement signal, an angular position of the wheel set corresponding to another point on the graph can be inferred. In particular, it is possible to deduce therefrom the initial angular position of the wheel set, i.e. its position before starting the rotation, which is the position to be sought.

The use of differential capacitance measurements, rather than a single capacitance measurement as in the prior art, allows the shape of the curve to be independent of the axial clearance between the wheel set and the electrode. Therefore, even when the axial gap is large, the maximum value and the minimum value can be accurately identified on the curve. In addition, the identification of two characteristic positions of the wheel set on the curve, instead of a single position as in the prior art, makes the determination of the angular position of the wheel set more reliable.

In addition, it should be noted that "planar electrode" refers to a conductive portion that extends significantly in at least two directions on one plane, as opposed to a rod-shaped electrode.

In addition, the wheel set plate may comprise a plurality of apertures and the detection means may comprise a plurality of sets of electrodes of the type described above. In this case, each hole is arranged opposite a first and a second electrode of a set of electrodes, in a specific position of the wheel set.

Furthermore, the timepiece may include one or more of the following features in any technically possible combination.

In one non-limiting embodiment, all three electrodes have substantially the same area. This configuration results in a significant imbalance (dissequibrium) between capacitance C1 and capacitance C2, and thus a large absolute value of the magnitude of the maximum and minimum values of the curve. Additionally, it should be noted that in some configurations of the electrode, the curve has a step (step) between the peak corresponding to the maximum and the valley corresponding to the minimum. A step means a segment with a decreasing slope on both sides of the segment. The configuration just described allows the length of the step to be minimized.

In one non-limiting embodiment, the aperture is at least partially above or below the common electrode in the first unbalanced position, the equalized position, and the second unbalanced position. This configuration makes it possible to obtain particularly pronounced peaks and valleys.

In one non-limiting embodiment, all three electrodes are located above or below the aperture in the equilibrium position. The hole in the wheel set can therefore be smaller than the full electrode. This configuration makes it possible to remove any step between the peaks and valleys of the curve.

In one non-limiting embodiment, the common electrode comprises two planar half-electrodes (halfellectrodes) electrically connected to each other, the half-electrodes being arranged on both sides of the assembly formed by the first and second electrodes.

In one non-limiting embodiment, the common electrode comprises two planar half-electrodes electrically connected to each other, the two half-electrodes being arranged between the first and second electrodes.

In one non-limiting embodiment, the first electrode and the second electrode are arranged side by side, and the common electrode extends substantially in a shape along the annular portions of the first and second electrodes. This configuration makes it possible to use first and second electrodes having a large surface area, for example, first and second electrodes whose total surface area is substantially the surface area of the pores. The large surface area of the first and second electrodes results in large absolute values of the amplitudes of the maxima and minima on the curve.

The invention also relates to a method for determining the angular position of a wheel set of a timepiece movement of a timepiece as described above, comprising:

-stepwise rotation of the wheel set, for example by means of a stepping motor,

measuring, simultaneously with the rotation, as a function of the number of steps of the rotationWhere C1 is the capacitance of the capacitor formed by the first electrode and the common electrode, and C2 is the capacitance of the capacitor formed by the second electrode and the common electrodeThe capacitance of the capacitor formed by the poles,

-detecting a maximum and a minimum on a curve representing the measurement results,

determining the angular position of the wheel set by means of the maximum and minimum values detected.

Drawings

Further characteristics and advantages will emerge clearly from the description that follows, given by way of non-limiting illustration with reference to the accompanying drawings, in which:

fig. 1 shows, in a first embodiment of the invention, a detection device for detecting the angular position of a rotating wheel set of a timepiece movement of a timepiece, superimposed over said wheel set.

Fig. 2a shows the detection device of fig. 1 with the rotating wheel set in a first angular position occupied during the completion of one complete rotation of said wheel set starting from the initial angular position.

Fig. 2b shows the measurement curves obtained step by step during the rotation of the wheel set in a state corresponding to the position of the wheel set in fig. 2 a.

Fig. 3a shows the detection device of fig. 1 with the rotating wheel set in a second angular position, referred to as the first unbalanced position, which it occupies during the completion of one complete rotation of said wheel set starting from the initial angular position.

Fig. 3b shows the measurement curve in a state corresponding to the position of the wheel set in fig. 3 a.

Fig. 4a shows the detection device of fig. 1, the rotating wheel set being in a third angular position, called equilibrium position, occupied during the completion of one complete rotation of said wheel set starting from the initial angular position.

Fig. 4b shows the measurement curve in a state corresponding to the position of the wheel set in fig. 4 a.

Fig. 5a shows the detection device of fig. 1 with the rotating wheel set in a fourth angular position, referred to as the second unbalanced position, which is occupied during the completion of one complete rotation of said wheel set starting from the initial angular position.

Fig. 5b shows the measurement curve in a state corresponding to the position of the wheel set in fig. 5 a.

Fig. 6a shows the detection device of fig. 1, the rotating wheel set being in a fifth angular position occupied during the completion of one complete rotation of said wheel set starting from the initial angular position.

Fig. 6b shows the measurement curve in a state corresponding to the position of the wheel set in fig. 6 a.

Fig. 7a shows the detection device of fig. 1, the rotating wheel set returning to the initial angular position after one complete rotation of said wheel set.

Fig. 7b shows the measurement curve in a state corresponding to the position of the wheel set in fig. 7 a.

Fig. 8 shows one such device according to a second embodiment of the invention.

Fig. 9 shows one such device according to a third embodiment of the invention.

Fig. 10 shows one such device according to a fourth embodiment of the invention.

Fig. 11 shows one such device according to a fifth embodiment of the invention.

Detailed Description

The invention relates to a timepiece comprising a timepiece movement. This timepiece movement comprises a wheel set MB in the form of a disc, which also comprises a spindle defining a geometric axis of rotation. The timepiece movement is associated with an analogue display mechanism comprising a rotary indicator (not shown) fixedly mounted on the arbour. The indicator may be used to indicate hours, minutes, seconds or any other information used for analog display.

Wheel set MB includes a conductive plate PT extending substantially orthogonal to the axis of rotation of wheel set MB. Said plate PT is pierced with through holes OV in the form of annular portions, arranged on an intermediate zone between the periphery of the plate PT and a central hole provided for the passage of the mandrel. The vias OV extend, for example, over 120 degrees.

Opposite the wheel set MB, a plate PA, for example in the form of a semicircular disk, is positioned above or below the wheel set MB. Plate PA extends substantially parallel to plate PT of wheel set MB and orthogonal to the axis of rotation of wheel set MB. Advantageously, the board PA is a Printed Circuit Board (PCB) on which three planar electrodes are printed. Unlike the wheel set, the plate PA is fixed: the wheel set is thus able to rotate relative to the plate PA.

The plate PA includes a set of electrodes. The set of electrodes comprises three planar electrodes, referred to as first electrode E1, second electrode E2 and common electrode Em. The three electrodes E1, E2, Em take the form of annular portions. The common electrode Em is disposed along a portion of the first electrode E1 and a portion of the second electrode E2 to form a first capacitor having a capacitance C1 with the first electrode E1 and a second capacitor having a capacitance C2 with the second electrode E2. The capacitances C1, C2 depend on the angular position of wheel set MB with respect to electrodes E1, E2, Em, due to the presence of holes OV in plate PT. In particular, the capacitance C1 or respectively C2 is greatest when the aperture OV is located above the first electrode E1 and the common electrode Em or above the second electrode E2 and the common electrode Em, respectively, because the transfer of charge from one electrode to the other is no longer facilitated by the presence of the conductive material of the plate PT.

Fig. 1 shows a first configuration of these electrodes E1, E2, Em on the plate PA. In this configuration, the three electrodes E1, E2, Em have substantially the same surface area, with the common electrode Em being arranged between the first electrode E1 and the second electrode E2. In addition, the total surface area of electrodes E1, E2, Em is substantially the same as the surface area of well OV. In the embodiment shown in fig. 1, the apertures OV extend through 120 degrees and each electrode extends through 120/3 x 0.98 x 38 degrees (these angular features are of course not limiting). There is thus an angular position of wheel set MB with respect to plate PA (shown in fig. 4 a): the three electrodes are completely opposite to the aperture OV and the aperture OV is completely opposite to the electrodes E1, E2, Em.

In order to determine the initial angular position of wheel set MB, which in the non-limiting example presented below is the angular position of fig. 1, it is proposed to make wheel set MB perform one complete step-wise rotation about its axis of rotation. This rotation is achieved by a stepper motor (not shown). The stepper motor is, for example, a bipolar "Lavet" type motor. The transmission (not shown) from the motor to the wheel set is preferably formed by a reduction train. An electronic measuring circuit, for example comprising a microcontroller, is arranged for measuring as a function of the number of steps applied to wheel set MBIs used to generate a measurement curve CB.

Fig. 2a, 3a, 4a, 5a, 6a and 7a show the successive angular positions of wheel set MB with respect to plate PA during a complete rotation of said wheel set MB starting from the position of fig. 1. In the position of fig. 2a, only first electrode E1 is opposite aperture OV of wheel set MB. In the position of fig. 3a, the first electrode E1 and the common electrode Em are positioned opposite the aperture OV. In the position of fig. 4a, all three electrodes E1, E2, Em are opposite the hole. In the position of fig. 5a, the common electrode Em and the second electrode E2 are opposite the aperture. In the position of fig. 6a, only the second electrode E2 is opposite the aperture OV. Finally, in the position of fig. 7a, wheel set MB returns to its initial position, none of the three electrodes E1, E2, Em being opposite aperture OV.

Fig. 2b, 3b, 4b, 5b, 6b and 7b show representations of the instants corresponding to the positions occupied by wheel set MB in fig. 2a, 3a, 4a, 5a, 6a and 7a, as a function of the number of steps N applied to wheel set MBThe measurement curve CB of (a).

From the wheel set, as shown in figure 2bThe initial position of MB to the position of fig. 2a, the measurement curve CB has a zero value. Then, as shown in fig. 3b, between the position of fig. 2a and the position of fig. 3a,the value of (c) is decreased. Curve CB reaches a minimum value if and only if both electrode E1 and common electrode Em are opposite aperture OV.

As shown in fig. 4b, between the position of fig. 3a and the position of fig. 4a, the values of the curve CB increase until they return to a zero value. Then, as shown in fig. 5b, between the position of fig. 4a and the position of fig. 5a,the value of (a) increases. Curve CB reaches a maximum if and only if both electrode E2 and common electrode Em are opposite aperture OV.

Then, as shown in fig. 6b, between the position of fig. 5a and the position of fig. 6a, the value of curve CB decreases and returns to a zero value. Finally, until wheel set MB returns to its initial angular position, curve CB has a value of zero.

The curve CB is then used to calculate the two characteristic positions of the wheel set MB. In a first characteristic position corresponding to the position of fig. 3a, the curve CB has a minimum value; in a second characteristic position, corresponding to the position of fig. 5a, the curve CB has a maximum. Since the number of steps to reach the position corresponding to the minimum value and the position corresponding to the maximum value can be determined from curve CB, the initial position of wheel set MB can be easily inferred therefrom.

Configurations different from those of electrodes E1, E2, Em on plate PA and/or of apertures OV on plate PT proposed with reference to fig. 1 are possible.

In the configuration of fig. 8, electrodes E1, E2, Em are similar to the electrode of fig. 1, but aperture OV extends only over 80 degrees (naturally, this angular aperture is not limiting). There is therefore no angular position of such wheel set MB: all three electrodes are opposite the aperture OV. This configuration avoids the step observed in fig. 7b between the peak corresponding to the maximum and the valley corresponding to the minimum.

In the configuration of fig. 9, the three electrodes E1, E2, Em do not have the same surface area: the first electrode E1 and the second electrode E2 have the same surface area, but the common electrode Em has a larger surface area. In the embodiment shown in fig. 9, the first electrode E1 and the second electrode E2 extend through 10 degrees, while the common electrode Em extends through 18 degrees (naturally, these angular features are not limiting). However, the aperture OV extends over 120 degrees: the surface area of the pores OV is therefore much greater than the sum of the surface areas of the electrodes E1, E2, Em.

In the configuration of fig. 10, the first electrode E1 and the second electrode E2 are side by side, the common electrode Em being formed by two electrically connected half-electrodes (the connection is not shown). The half electrodes are disposed on both sides of the assembly formed by the first electrode E1 and the second electrode E2. It should be noted that alternatively, two half-electrodes may be arranged between the first electrode E1 and the second electrode E2.

In the configuration of fig. 11, the first electrode E1 and the second electrode E2 are side by side, the common electrode Em being arranged along the outer portions of the electrodes E1 and E2. In addition, the total surface area of first electrode E1 and second electrode E2 is substantially equal to the surface area of aperture OV. There is therefore no angular position: the common electrode Em is opposite to the aperture OV. This configuration allows increasing the surface area of the first electrode E1 and the second electrode E2, thereby increasing the amplitude of the peaks and valleys of the measurement curve CB. In addition, this configuration avoids the step between the peak corresponding to the maximum and the valley corresponding to the minimum observed in fig. 7 b.

Of course, the present invention is not limited to the illustrated examples, but can have various variations and modifications apparent to those skilled in the art. For example, wheel set MB may be pierced with K apertures OV, K ≧ 2, and plate PA may include K sets of three electrodes like those set forth above. This will allow larger absolute peak and valley magnitudes of the measurement curve.

Claims (8)

1. A timepiece, comprising:

-a timepiece movement provided with an analogue display mechanism and at least one wheel set (MB) rotating integrally with a rotation indicator of said analogue display mechanism, said wheel set (MB) comprising a conductive Plate (PT) extending substantially orthogonally to the axis of rotation of said wheel set (MB) and pierced with at least one hole (OV),

-detection means for detecting a reference angular position of the hole (OV), comprising at least one set of planar electrodes comprising a first electrode (E1), a second electrode (E2) and a common electrode (Em) arranged in a plane parallel to the wheel set (MB), the common electrode (Em) being arranged along a portion of the first electrode (E1) and a portion of the second electrode (E2),

the aperture (OV) at least partially:

-above or below the first electrode (E1) in a position referred to as first unbalanced position,

-above or below the first electrode (E1) and the second electrode (E2) in a position called equilibrium position,

-above or below the second electrode (E2) in a position referred to as second unbalanced position.

2. Timepiece according to claim 1, wherein all three electrodes (E1, E2, Em) have substantially the same area.

3. Timepiece according to claim 2, wherein in the first unbalanced position, the equilibrium position and the second unbalanced position, the aperture (OV) is at least partially above or below the common electrode (Em).

4. Timepiece according to claim 3, wherein in the equilibrium position, the three electrodes (E1, E2, Em) are located completely above or below the aperture (OV).

5. Timepiece according to claim 1, characterised in that the common electrode (Em) comprises two planar half-electrodes (Em1, Em2) electrically connected to each other, the half-electrodes (Em1, Em2) being arranged on either side of the assembly formed by the first electrode (E1) and the second electrode (E2).

6. Timepiece according to claim 1, wherein the common electrode (Em) comprises two planar half-electrodes (Em1, Em2) electrically connected to each other, the half-electrodes (Em1, Em2) being arranged between the first electrode (E1) and the second electrode (E2).

7. Timepiece according to claim 1, wherein the first electrode (E1) and the second electrode (E2) are arranged side by side, the common electrode (Em) extending substantially in the shape of a ring portion along the first electrode (E1) and the second electrode (E2).

8. Method for determining the angular position of a wheel set (MB) of a timepiece movement of a timepiece according to claim 1, comprising:

-rotating the wheel set (MB) stepwise,

-measuring, simultaneously with said rotation, as a function of the number of steps of the rotationWherein C1 is the capacitance of the capacitor formed by the first electrode (E1) and the common electrode (Em), C2 is the capacitance of the capacitor formed by the second electrode (E2) and the common electrode (Em),

-detecting a maximum and a minimum on a Curve (CB) representing the measurement results,

-determining the angular position of the wheel set (MB) by means of the maximum and minimum values detected.