Patent Grant
11385598
The present invention concerns a portable object of small dimensions such as a timepiece, comprising a rotating control stem for controlling at least one electronic or mechanical function of the portable object. More specifically, the invention concerns such a portable object wherein actuation of the rotating control stem is detected by measuring magnetic induction by means of two inductive sensors.
The present invention concerns portable objects of small dimensions, such as wristwatches, that comprise a rotating control stem, the actuation of which controls a mechanical or electronic function of the portable object in which the rotating control stem is arranged.
To properly perform the mechanical or electronic function concerned, it must be possible to detect the actuation of the rotating control stem. Among various possible solutions, one consists in measuring the variation in magnetic induction produced by the rotation of a magnet integral with the control stem. To detect this variation in magnetic induction, it is possible to use a magnetic sensor such as a Hall effect sensor which is capable of measuring the value of magnetic induction of the environment in which it is located.
A recurrent problem that arises in the field of detecting the rotation of a control stem by measuring magnetic induction is that of knowing precisely how far and in which direction the control stem is rotated. To overcome this problem, systems have already been proposed that include a pair of magnetic sensors such as magnetoresistors or Hall-effect sensors. In these known systems, the magnetic sensors detect the variation in magnetic induction produced by the rotation of the magnet integral with the control stem in two orthogonal directions in space.
One drawback of such systems lies in the fact that, since the magnetic sensors measure variations in magnetic induction in two orthogonal directions, it is not possible to subtract from the measuring signal produced by the magnetic sensors the effects due to magnetic disturbances outside the portable object when these magnetic disturbances are directed along the axis of measurement of only one of the two magnetic sensors. Indeed, in that case, the other magnetic sensor does not sense the external magnetic disturbance, so the influence of this magnetic disturbance on the two measuring signals is not symmetrical and therefore cannot be eliminated. It is therefore necessary to provide the portable object with an electromagnetic shield, which is particularly cumbersome and costly. Other solutions are known but more particularly intended for measuring the Earth's magnetic field. In such applications, the magnetic sensor or sensors exhibit high sensitivity since the Earth's magnetic field to be measured is very low, typically on the order of 20 to 60 μT. However, these magnetic sensors cannot usually measure magnetic induction in excess of 5 mT, whereas the values associated with magnets of small dimensions frequently reach 100 mT.
It is an object of the present invention to overcome the aforementioned problems, in addition to others, by providing a portable object comprising a rotating stem for controlling at least one mechanical or electronic function of the portable object, the actuation of the rotating stem being detected in a reliable and reproducible manner by means of inductive sensors.
To this end, the present invention concerns a portable object comprising a control stem, the actuation of which in rotation can control at least one electronic or mechanical function of the portable object, a magnetized ring being driven in rotation by the rotating control stem, the rotation of the control stem and the position of the latter being detected by two inductive sensors arranged to be sensitive to a variation in magnetic induction produced by rotation of the magnetized ring in only two directions in space, which are parallel to each other.
According to other embodiments of the invention which form the subject of the dependent claims:
An ‘inductive sensor’ means a sensor that transforms a magnetic field passing therethrough into electric voltage due to the phenomenon of induction defined by Lenz's law and Faraday's law. By way of example, this may be a Hall effect sensor or a magnetoresistance component of the AMR (anisotropic magnetoresistance), GMR (giant magnetoresistance) or TMR (tunneling magnetoresistance) type.
As a result of these features, the present invention provides a portable object in which detection of the rotation of a control stem controlling at least one mechanical or electronic function of the portable object is obtained by measuring the variation in magnetic induction caused by rotation of a magnet driven by the control stem by means of two inductive sensors. These two inductive sensors are arranged to be sensitive to a variation in magnetic induction in only one direction in space. It is clear that the magnetic induction produced by the environment in which the portable object is located is added to the magnetic induction produced by the magnetized ring. By teaching that the pair of inductive sensors are arranged so that the sensors exhibit sensitivity to magnetic induction in only a single direction, the present invention makes it possible, via a suitable signal processing treatment, to completely eliminate from the measurement result the influence of the magnetic induction of the environment in which the portable object is located. In fact, as a result of these measures, the case where magnetic disturbances produced by the environment in which the portable object is located are directed along the axis of measurement of only one of the two inductive sensors cannot occur. Consequently, the case where one of the two inductive sensors does not sense the external magnetic disturbance is precluded, so that the influence of the external magnetic disturbance on the measurement signals is the same for both inductive sensors and can therefore be eliminated. It is consequently unnecessary to magnetically shield the portable object to avoid the influence of magnetic induction outside the portable object, which saves space. This is very advantageous in the case of a portable object of small dimensions in which the available space is necessarily very limited. The lack of shielding also simplifies the manufacture of the portable object and thus ensures better reliability and a lower cost price.
The invention also concerns a method for detecting a position of a control stem, the actuation of which in rotation controls an electronic or mechanical function of a portable object provided with the control stem, a magnetized ring being driven in rotation by the control stem, the rotation of the control stem and the position of the latter being detected by two inductive sensors arranged to be sensitive to a variation in magnetic induction produced by rotation of the magnetized ring in only one direction in space, the method comprising the step which consists in calculating the arctangent function of the ratio between the signals produced by each of the inductive sensors to determine the direction of rotation and the position of the control stem.
As a result of these features, it is possible, regardless of the direction of rotation of the control stem, to determine the absolute position of the control stem, i.e. it is possible at any time to know the angular position of the stem. The resolution of the position detection measurement of the control stem is thus high and reproducible from one object to another, even in the case of large scale production.
Other features and advantages of the present invention will appear more clearly from the following detailed description of an example embodiment of a portable object according to the invention, this example being given purely by way of non-limiting illustration with reference to the annexed drawing, in which:
The present invention proceeds from the general inventive idea which consists in detecting the rotation of a control stem mounted in a portable object of small dimensions, such as a timepiece, in a reliable and reproducible manner from one portable object to another, particularly in the case of mass production. To overcome this problem, it is proposed to drive a magnetized ring in rotation via the control stem and to detect the variation in magnetic induction caused by rotation of the ring by means of a pair of inductive sensors. These two inductive sensors are arranged to be sensitive each to fluctuations in magnetic induction in only one direction in space. Consequently, the influence of magnetic induction outside the portable object is the same on the measuring signals of both inductive sensors, so that, via a suitable signal processing process, it is possible to completely eliminate from the measurement result the influence of the magnetic induction of the environment in which the portable object is located.
The invention also concerns a method for detecting the position and the direction of rotation of a rotating control stem which consists in calculating the arctangent function of the ratio between the signals produced by two inductive sensors arranged to be sensitive to fluctuations in magnetic induction in two directions in space parallel to each other. Since the magnetic induction of the environment in which the portable object is located only exercises an influence on the sensing elements of the two inductive sensors in one direction in space, calculating the arctangent function of the ratio between the signals produced by these two inductive sensors can eliminate the signal component due to the influence of magnetic induction outside the portable object.
In all that follows, the back-to-front direction is a rectilinear direction which extends horizontally along longitudinal axis of symmetry X-X of the control stem from the external actuation crown towards the interior of the portable object equipped with the control device, parallel to a plane in which a back of the portable object extends. Thus, the control stem will be pushed from back to front, and will be pulled from front to back. Further, the vertical direction is a direction that extends perpendicularly to the plane in which the control stem extends.
At a rear end 6, which will be located outside the portable object once the latter is equipped with a control device 1, control stem 4 will receive an actuation crown 8 (see
At a front end 10, which will be located inside control device 1 once the latter is assembled, control stem 4 has, for example, a square section 12 and receives in succession a magnetic assembly 14 and a smooth bearing 16.
Magnetic assembly 14 includes a magnetized ring 18 and a support ring 20, on which magnetized ring 18 is fixed, typically by adhesive bonding (see
Smooth bearing 16 defines (see
It is noted that the square hole 26 provided in first section 22a of support ring 20 is extended towards the front of control device 1 by an annular hole 30 whose second internal diameter D4 is fitted onto third external diameter D5 of smooth bearing 16. Support ring 20 is thus fitted for free rotation on smooth bearing 16 and moves into axial abutment against smooth bearing 16, which ensures the perfect axial alignment of these two components and makes it possible to correct any problems of concentricity that may be caused by a sliding pinion type coupling.
It is observed that, for axial immobilization thereof, smooth bearing 16 is provided on its outer surface with a circular collar 32 which projects into a first groove 34a and into a second groove 34b, respectively arranged in lower frame 2 (see
It is important to note that the magnetic assembly 14 and smooth bearing 16 described above are indicated purely for illustrative purposes. Indeed, smooth bearing 16, for example made of steel or brass, is arranged to prevent control stem 4, for example made of steel, rubbing against lower and upper frames 2 and 36, and causing wear of the plastic material of which these two lower and upper frames 2 and 36 are typically made. However, in a simplified embodiment, it is possible to envisage not using such a smooth bearing 16 and arranging for control stem 4 to be directly carried by lower frame 2.
Likewise, magnetized ring 18, and support ring 20 on which magnetized ring 18 is fixed, are intended for the case where rotation of control stem 4 is detected by a local variation in the magnetic field induced by the pivoting of magnetized ring 18. It is, however, entirely possible to envisage replacing magnetic assembly 14, for example with a sliding pinion which, according to its position, will for example control the winding of a mainspring or the time-setting of a watch equipped with control device 1.
It is also important to note that the example of control stem 4 provided on one part of its length with a square section is given purely for illustrative purposes. Indeed, in order to drive magnetic assembly 14 in rotation, control stem 4 may have any type of section other than a circular section, for example triangular or oval.
Lower frame 2 and upper frame 36, the combined assembly of which defines the external geometry of control device 1 are, for example, of generally parallelepiped shape. Lower frame 2 forms a cradle which receives control stem 4. To this end (see
Lower frame 2 further includes, towards the back, a second receiving surface 40, whose semicircular profile is centred on longitudinal axis of symmetry X-X of control stem 4, but whose diameter is greater than that of control stem 4. It is important to understand that control stem 4 only rests on second receiving surface 40 at the stage when the assembled control device 1 is tested prior to being integrated in the portable object. At this assembly stage, control stem 4 is inserted into control device 1 for test purposes and extends horizontally, supported and axially guided by smooth bearing 16 at its front end 10 and via second receiving surface 40 at its rear end 6. However, once control device 1 is integrated in the portable object, control stem 4 passes through a hole 42 provided in case middle 48 of the portable object in which it is guided and supported (see
Third and fourth clearance surfaces 44a and 46a of semicircular profile are also provided in lower frame 2 and complementary clearance surfaces 44b and 46b (see
As visible in
As visible in
Two apertures 70 exhibiting an approximately rectangular contour are provided in guide arms 62 of position indexing plate 58 (see in particular
The two apertures 70 provided in guide arms 62 are intended to receive the two ends 78 of a positioning spring 80 (see
It was mentioned above that position indexing plate 58 is coupled in translation to control stem 4, but that it is free with respect to control stem 4 in the vertical direction z. It is thus necessary to take steps to prevent position indexing plate 58 disengaging from control stem 4 in normal conditions of use, for example under the effect of gravity. To this end (see
Displacement limiting spring 88 includes a substantially rectilinear central portion 90 from the ends of which extend two pairs of elastic arms 92 and 94. These elastic arms 92 and 94 extend on either side of central portion 90 of displacement limiting spring 88, upwardly away from the horizontal plane in which central portion 90 extends. As these elastic arms 92 and 94 are compressed when upper frame 36 is joined to lower frame 2, they impart elasticity to displacement limiting spring 88 along vertical direction z. Between the pairs of elastic arms 92 and 94 there is also provided one pair, and preferably two pairs, of stiff lugs 96 which extend perpendicularly downwards on either side of central portion 90 of displacement limiting spring 88. These stiff lugs 96 which move into abutment on lower frame 2 when upper frame 36 is placed on lower frame 2, ensure that a minimum space is provided between position indexing plate 58 and displacement limiting spring 88 in normal operating conditions of control device 1.
Displacement limiting spring 88 guarantees the dismantability of control device 1. Indeed, in the absence of displacement limiting spring 88, position indexing plate 58 would have to be integral with control stem 4 and, consequently, control stem 4 could no longer be dismantled. If control stem 4 cannot be dismantled, the movement of the timepiece equipped with control device 1 cannot be dismantled either, which is inconceivable, particularly in the case of an expensive timepiece. Thus, when control device 1, formed by joining lower and upper frames 2 and 36, is mounted inside the portable object and control stem 4 is inserted into control device 1 from outside the portable object, control stem 4 slightly lifts position indexing plate 58 against the elastic force of displacement limiting spring 88. If control stem 4 continues to be pushed forwards, there comes a moment when position indexing plate 58 drops into groove 56 under the effect of gravity. Control stem 4 and position indexing plate 58 are then coupled in translation.
A disassembly plate 98 is provided to allow disassembly of control stem 4 (see
From its stable rest position T1, control stem 4 can be pushed forwards into an unstable position T0 or pulled out into a stable position T2. These three positions T0, T1 and T2 of control stem 4 are indexed by cooperation between position indexing plate 58 and positioning spring 80. More precisely (see
When they reach a transition point 116, ends 78 of arms 86 engage on a second ramp profile 118 which extends first ramp profile 114 with a second slope β lower than first slope α of first ramp profile 114. At the instant that ends 78 of arms 86 of positioning spring 80 cross transition point 116 and engage on second ramp profile 118, the force required from the user to continue moving control stem 4 drops sharply and the user feels a click indicating the transition of control stem 4 between position T1 and position T0. As they follow second ramp profile 118, arms 86 of positioning spring 80 continue to move slightly away from their rest position and tend to try to move towards each other again under the effect of their elastic return force opposing the thrust force exerted by the user on control stem 4. As soon as the user releases pressure on control stem 4, arms 86 of positioning spring 80 will spontaneously return down first ramp profile 114 and their ends 78 will again lodge inside first recesses 74a of the two apertures 70 provided in guide arms 62 of position indexing plate 58. Control stem 4 is thus automatically returned from its unstable position T0 to its first stable position T1.
First and second contact springs 120a and 120b are arranged compressed inside a first and a second cavity 122a and 122b provided in lower frame 2. These first and second contact springs 120a and 120b could be helical contact springs, strip-springs or other springs. The two cavities 122a, 122b preferably, but not necessarily, extend horizontally. Because the two contact springs 120a, 120b are installed in the compressed state, their positioning precision is dependent on the manufacturing tolerance of lower frame 2. The manufacturing precision of lower frame 2 is higher than the manufacturing precision of these first and second contact springs 120a, 120b. Consequently, the precision with which position T0 of control stem 4 is detected is high.
As visible in
First and second contact springs 120a, 120b are of the same length. However, preferably, first cavity 122a will be, for example, longer than second cavity 122b, in particular to take account of tolerance problems (the difference in length between the two cavities 122a, 122b is several tenths of a millimetre). Thus, when control stem 4 is pushed forwards into position T0, finger 66a of position indexing plate 58, which is lined up with first contact spring 120a housed inside the first, longest cavity 122a, will come into contact with and start to compress first contact spring 120a. Control stem 4 will continue to move forward and second finger 66b of position indexing plate 58 will come into contact with second contact spring 120b housed inside the second, shortest cavity 122b. At that moment, position indexing plate 58 will be in contact with first and second contact springs 120a, 120b and the electric current will flow through position indexing plate 58, which allows the closure of the electrical contact between the first two contact springs 120a, 120b to be detected. It is noted that fingers 66a, 66b of position indexing plate 58 move into abutment contact with first and second contact springs 120a, 120b. There is thus no friction or wear when control stem 4 is pushed forwards into position T0 and closes the circuit between first and second contact springs 120a, 120b. It is also noted that, the difference in length of first and second cavities 122a and 122b ensures that closure of the electrical contact and entry of the corresponding command into the portable object equipped with control device 1 occur only after a click is felt.
When the two fingers 66a, 66b of position indexing plate 58 are in contact with first and second contact springs 120a, 120b, first contact spring 120a housed inside first, longest cavity 122a is in a compressed state. Consequently, when the user releases pressure on control stem 4, this first contact spring 120a relaxes and forces control stem 4 to return from its unstable pushed-in position T0 to its first stable position T1. The first and second contact springs 120a, 120b thus act simultaneously as electrical contact parts and elastic return means for control stem 4 in its first stable position T1.
From first stable position T1, it is possible to pull control stem 4 backwards into a second stable position T2 (see
It will be noted that, in the case of stable position T2, fingers 66a, 66b of position indexing plate 58 also come into abutment contact with third and fourth contact springs 130a, 130b, thereby avoiding any risk of wear from friction. Further, third and fourth contact springs 130a, 130b are capable of bending when fingers 66a, 66b of position indexing plate 58 collide therewith, and therefore of absorbing any lack of precision in the positioning of position indexing plate 58.
Preferably, but not necessarily, third and fourth contact springs 130a, 130b are arranged to work in flexion (see
In
The free portion 144 of flexible printed circuit sheet 128 is connected to the rest of flexible printed circuit sheet 128 by two strips 152, which allow free portion 144 to be folded around the assembly of upper frame 36 and lower frame 2, and then folded down against lower face 112 of lower frame 2, so that inductive sensors 150 penetrate two housings 156 arranged in lower surface 112 of lower frame 2. Thus positioned inside their housings 156, inductive sensors 150 are precisely located under magnetized ring 18, which ensures reliable detection of the direction of rotation of control stem 4.
Once free portion 144 of flexible printed circuit sheet 128 has been folded down against lower frame 2 (see
Control stem 4 is carried by lower frame 2 which acts as a cradle. Likewise, the two inductive sensors 150 are disposed inside two housings 156 provided in said lower frame 2, and are pressed against the bottom of these housings 156 by one or two elastic fingers 160 (see
Inductive sensor or sensors 150 each include a sensing element 154 which, in a simplified manner, takes the form of a parallelepiped element sensitive to fluctuations in magnetic induction in a direction S perpendicular to the large side of the parallelepiped (see
In the case where a single inductive sensor 150 is provided (see
Owing to the phase shift δ between the sinusoidal measurement signals sin(x) and sin(x+δ) produced by the two inductive sensors 150, when the arctangent function of the ratio between these two measurement signals is calculated, a straight line is obtained. Consequently, it is possible, from a rotary motion of control stem 4, to obtain a linear response from the system formed by control stem 4, magnetized ring 18 and the two inductive sensors 150. This linearization of the rotation of control stem 4 advantageously permits absolute detection of the position of control stem 4. In other words, it is possible at any time to know the direction of rotation and the position of control stem 4. Further, owing to phase shift δ, there is constantly a situation where, when sinusoidal measurement signal sin (x) produced by one of the two inductive sensors 150 varies slightly, the other sinusoidal signal sin(x+δ) varies more sharply and vice versa, such that the ratio between these two signals always gives precise information about the rotation of control stem 4.
It was mentioned above that inductive sensors 150 were preferably oriented such that their sensing element only detects fluctuations in magnetic induction along the vertical axis z. This component of magnetic induction is the sum of inductions along axis z generated by magnetized ring 18 and by the magnetic field outside the portable object. However, given that inductive sensors 150 are very close to each other, the influence exercised thereon by the external magnetic field is substantially the same for both inductive sensors 150. Consequently, calculating the ratio between the two sinusoidal signals sin(x) and sin(x+δ) eliminates the component of magnetic induction due to the magnetic field outside the portable object. The response of the system formed by control stem 4, magnetized ring 18 and inductive sensors 150 is thus totally independent of the external magnetic field, and it is not necessary to take steps to magnetically shield the portable object. Likewise, the response of the system is independent of temperature insofar as the temperature has the same effect on both inductive sensors.
It goes without saying that the present invention is not limited to the embodiment that has just been described and that various simple modifications and variants can be envisaged by those skilled in the art without departing from the scope of the invention as defined by the annexed claims. In particular, the magnetized ring concerned here is preferably a bipolar ring but it may also be a multipolar magnetized ring. The dimensions of the magnetized ring could also be extended so that it corresponds to a hollow cylinder.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16202478 | Dec 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/075415 | 10/5/2017 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/103914 | 6/14/2018 | WO | A |
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| Number | Date | Country |
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| 1 930 794 | Jun 2008 | EP |
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| Entry |
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| Number | Date | Country | |
|---|---|---|---|
| 20190171166 A1 | Jun 2019 | US |
