Mechanical-electric energy converter and watch part comprising this energy converter

A mechanical-electric energy converter comprising a wheel for transmitting energy which rotates at a low speed. The teeth of the driving wheel shift the rotor of the generator from its position of equilibrium, causing it to oscillate around the wheel. This converter can produce high angular velocities without a speed-increasing gear train.

The present invention has for its object a converter of mechanical energy 
into electrical energy and the timepieces using these converters. 
Portable electric apparatus, as well as electronic quartz timepieces, use 
essentially, as an energy source, batteries or accumulators. The principal 
drawback of these latter is their limited lifetime. It is for this reason 
of interest to replace these electrical energy sources by a mechanical 
energy source and a converter for mechanical energy into electrical 
energy. 
Converters for mechanical energy into electrical energy are known. European 
patent application 0 665 478 discloses an electronic watch comprising a 
toothed wheel (4) secured to an oscillating mass (8). The toothed wheel 
drives several rotors disposed at the periphery of a plate. In 
International patent application PCT 89/06833, there is described an 
electronic watch comprising an oscillating mass coupled with the rotor of 
a generator through a speed multiplying gear train. 
The energy converters described in these mentioned patent applications have 
in common the following drawbacks: 
to obtain sufficient speed of rotation of the rotor of the generator, there 
must be a substantial speed multiplication, which gives rise to 
consumption space and increase in the cost of the converter. 
the high speed multiplying ratio introduces important friction losses, 
which results in decrease of the overall output of the converter. 
The object of the present invention is to overcome the mentioned drawbacks 
by providing a new type of converter as defined in claim 1.

FIG. 1 shows a first embodiment of the converter according to the 
invention. This converter has a toothed wheel 11 turning under the 
influence of a mechanical energy source, either an oscillating mass, or a 
coil spring. The toothed wheel 11 drives the pinion 12, secured to the 
rotor 13, of an electromagnetic generator. This rotor, constituted by a 
permanent cylindrical magnet, is disposed in an air gap of substantially 
cylindrical shape, provided in a stator of ferro-nickel material. The flux 
generated by the rotor is coupled with the winding 15 of the generator. On 
the cylindrical surface of the stator air gap, there are provided two 
semicircular openings 16a and 16b to give the rotor a magnetic reluctance 
couple. 
FIG. 2 shows the respective positions of the rotor of the generator as a 
function of that of the toothed wheel 11. At the time t=T1, the pinion of 
the rotor of the generator is located between the teeth 1 and 2 of the 
toothed wheel, the latter exerting no couple on the rotor. The rotor, 
under the influence of the magnetic reluctance couple, is located on the 
axis R. At time t=T2, the toothed wheel 11, turning in the clockwise 
direction, drives the pinion of the rotor of the generator and spaces it 
by an angle .alpha.0 relative to its initial position. At time t=T3, the 
tooth 2 of the toothed rotor being no longer in engagement with the pinion 
of the rotor of the generator, the rotor disengages and oscillates about 
its rest position, which is to say the axis R, under the influence of the 
magnetic reluctance couple. Given the very low inertia of the rotor, this 
latter can attain very high angular speeds (an angular speed exceeding 600 
rad/sec). The high frequency oscillating movement of the rotor permits 
obtaining, at the terminals of the winding 15 of the generator, a high 
level induced voltage. 
The interest of this arrangement resides in the fact that the electrical 
energy supplied by the generator depends on the speed of oscillation of 
the rotor 13 when it is freed from the pinion 12. Because during its free 
oscillations of the rotor it is disengaged from the pinion 12, its speed 
of oscillation is a function only of its inertia and of the magnetic 
reluctance couple. There can thus be obtained high angular speeds of 
oscillation of the rotor, permitting in turn the creation by induction in 
the winding 15 of a high voltage, which voltage can reach several Volts 
whilst in present generators, a voltage only a fraction of a Volt can be 
achieved. 
Thus, an original characteristic of the converter of mechanical energy into 
electrical energy, resides in the fact that the production of electrical 
energy is obtained when the rotor is free and not when it is mechanically 
engaged with an oscillating mass or a coil spring as is the case with 
prior designs. 
When the winding 15 of the generator is connected to a load, the 
oscillating movement of the rotor is quickly damped under the influence of 
the load current. Because of this, at time t=T4, the rotor has the same 
relationship to the toothed wheel 11 as at time t=T1. 
It will be seen that the mechanical-electrical converter according to the 
invention permits obtaining a high instantaneous speed of the rotor of the 
generator from a low mean speed of the toothed wheel and without a speed 
multiplying gear train. Moreover, during the mechanical-electrical 
conversion, the generator is subject only to its own mechanical losses, 
the rotor being free, which permits obtaining a high overall output. 
FIG. 3 shows a second embodiment of the converter according to the 
invention. In this figure, the toothed wheel 31 simultaneously engages the 
rotors 33a and 33b thanks to the pinions 32a, respectively 32b. The 
respective rest positions of the rotors are offset such that the variation 
of the total reaction couple on the wheel 31 will be minimal. 
FIG. 4 shows a first example of use of the converter according to the 
invention. In this example, the coil spring 40 supplies the mechanical 
energy to the converter through the transmission wheel 41; the voltage 
induced at the terminals of the winding 45 of the converter is rectified 
and multiplied by means of the rectifier 46. The transformed electrical 
energy is then stored in capacitances C1 and C2. This energy can be used 
by an electrical apparatus shown in the form of a load resistance Rc. 
FIG. 5 shows a second embodiment of the converter according to the 
invention. It is here a case of an electronic timepiece whose energy 
source is of mechanical origin. The energy source 50, comprised by a coil 
spring, distributes the mechanical energy through wheels 51. Display means 
52, generally formed by hands, are mechanically connected to the wheels 
51. The wheels 51 also drive the converter 53, which supplies electrical 
energy to the rectifier 54, which stores this energy in the capacitance C. 
This stored energy serves to supply the control member 56 and speed 
measuring means 55. The electromagnetic brake 57, whose braking couple is 
adjusted by the control member 56 as a function of the mean speed of 
rotation of the wheels, permits adjusting this latter. 
FIG. 6 shows an embodiment of the electromagnetic brake. This brake is 
constituted by a magnetic circuit 61 of ferromagnetic material, a 
permanent magnet rotor 62 of cylindrical shape, a winding 63 coupled with 
the flux created by the rotor 62. 
The terminals of the winding 63 are connected with a braking resistance 
network 64. The effective value of the braking resistance can be adjusted 
by switches controlled by control signals from the bloc 65, which permits 
modifying the braking couple exerted on the rotor 62. 
FIG. 7 shows an embodiment of the mean speed of rotation measuring device 
of the transmission wheels of the converter according to the invention. 
This device comprises a measuring circuit 71 of the voltage at the 
terminals of the generators; this voltage, varying greatly during each 
disengagement of the pinion of the rotor from the generator according to 
the associated explanations in FIGS. 2a, 2b, 2c and 2d, is supplied to the 
input of the comparison circuit 72 which compares it with a reference 
voltage Uref. The output of the circuit 72 delivers a logic signal of 
level 1 or 0 accordingly as the measured voltage is greater than or less 
than the reference voltage. This logic signal permits a counter 73 to 
determine the duration between two disengagements of the rotor pinion, 
which is to say the inverse of the mean angular speed of the transmission 
wheels, by counting the number of clock pulses between two successive 
passages of the logic signal from level 0 to level 1. The time base 74, 
comprising a quartz oscillator, shaping and dividing circuits, supplies 
the clock signal CK to the counter 73. This time base is supplied with 
electrical energy by the capacitance C of the bloc 54 of FIG. 5. So as to 
save the electrical energy stored in the capacitance C, the time base 74 
is not permanently supplied but only during the phase of measuring the 
mean speed of rotation, the control of supply of the time base being 
ensured by the switch 17. 
The third embodiment of the converter shown in FIG. 8 comprises a toothed 
wheel 61 driven mechanically by a coil spring or an eccentric mass and 
engaging with the pinions 62a, 62b of two rotors 63a, 63b disposed in a 
same stator 64 comprising two legs 64a, 64b about which are wound the 
windings 65a, 65b. 
Here again, the drive of the rotor 63 by the toothed wheel 61 does not take 
place simultaneously, the teeth of the pinions 62a, 62b being in rest 
position disposed parallel but engaging with the teeth of the wheel 61 in 
different angular positions of this wheel.