Classifications

• • 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
  • G04C3/143—Means to reduce power consumption by reducing pulse width or amplitude and related problems, e.g. detection of unwanted or missing step
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
  • H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices

Definitions

• the object of the present invention is a control device for a stepping motor.
• stepping motors are supplied with open loop, that is to say that the supply only supplies the motor with electric voltage pulses by an associated control circuit with a source of energy, so that this motor develops mechanical torque likely to cause a certain load.
• the energy delivered by said source is approximately the same for each voltage pulse.
• the duration of the pulses and their voltage level are constant.
• the voltage pulses are chosen so that the motor develops a mechanical torque high enough to guarantee the drive of this load.
• the torque required to drive the load can, however, vary widely.
• the energy delivered by the source must be high enough so that the torque developed by the motor at each pulse it receives is greater than the greatest resistance that it can happen. responsible for opposing his training.
• This energy is however far too high in all cases, the most numerous, where the resistance opposed by the load is lower. This therefore results in excessive consumption of electrical energy.
• This is inconvenient in certain applications, in particular when the overall dimensions of the assembly ble of a device with an energy source must be reduced and when, in addition, this device must operate autonomously and absolutely reliably for a relatively long time, as in the case of medical devices implementable in the human body.
• the drawback of feeding the stepping motor in open loop therefore lies in the excessively high electrical energy consumption, necessitated by the fact that the motor must drive its charge in a safe manner during each pulse received. .
• the engine consumes as little power and torque it develops citca ⁇ lunch, s r just to drive the load in majo ⁇ rity of cases, does not guarantee this training every impetus of this first type.
• Those of the second type have a high energy level, either that their duration is long or that the level of their tension is high.
• the motor consumes a lot of electrical energy, but it then develops a mechanical torque which guarantees the drive of the load.
• the position detector does not cause any reaction from the control circuit. On the other hand, if the load is not driven following one of these pulses of the first type, the position detector causes the control circuit to react, which then immediately sends to the motor a pulse of the second type, called pulse of correction.
• the servo device which thus closes the feed loop of the stepping motor therefore makes it possible to reduce the consumption of electrical energy of the motor while absolutely guaranteeing the load drive.
• the known servo devices are not, however, satisfactory. Most of them only ensure the drive of the load after each pulse of the first type, thanks to that of the second type which follows it, if necessary, but they do not guarantee the running accuracy of the load.
• the displacements that the latter can perform in the absence of a pulse, in the interval between two pulses for example when the engine is shocked at that time, as can happen in a quartz watch with analog display completely escape the position detector of the servo device. It should therefore be checked not only that the motor drives its load well when it is desired, but also that the load is not driven when it is not desired.
• the present invention aims to create a servo device which makes it possible to actuate a stepper motor while consuming reduced electrical energy while guaranteeing, as desired, the drive of the load or the precision of this last market.
• Fig. 1 is a perspective view of this embodiment.
• OM Fig. 2 is a sectional view.
• Fig. 3 is a block diagram of a device guaranteeing the entrainment of the load.
• Fig. 4 is a block diagram of a device guaranteeing the running accuracy of the load.
• Figs. 1 and 2 show a servo device, the position detector of which is associated with a Lavet type motor, which performs two steps per revolution.
• This motor is composed of a magnetic rotor 1, a stator 2 and a wound core 3.
• a voltage pulse in the motor coil produces a 180 ° rotation of the rotor 1, which transmits this movement by a pinion (not shown), which is integral with it, to a gear train (not shown).
• the position detector of the servo device is composed of an electret 4, a fixed electrode 5 and a detection circuit 6.
• an electret is an element made of a material which retains an electrical polarization even in the absence of an electric field. In other words, it is the electric analog of a permanent magnet.
• Such elements are already used industrially, in particular in miniature microphones.
• the electret 4 is fixed to the rotor 1. As for the electrode 5, it is arranged so that the electret 4 stops opposite its end each revolution of the rotor 1.
• the detection circuit 6 is sensitive to the presence of the electret 4 opposite the electrode 5 and it delivers voltage signals to the control circuit, which indicate to it whether the motor has stalled or not, depending on the influence of the electret 4 on the electrode 5. If the control circuit receives a signal indicating that the motor has not taken its step, it sends to the motor a significantly stronger correction pulse, which advances it by one step.
• FIG. 3 illustrates the application of the servo control device intended to guarantee the drive of the load.
• This figure represents the control circuit 7, the electric power source 8, the motor 9 and the servo device 10, which is summarized as position detector comprising the electret 4, which is associated with the motor 9, the electrode 5 and the detection circuit 6.
• the broken lines indicate the line by which the detection circuit 6 sends its voltage signals to the control circuit 7 to indicate if the engine has stalled or not.
• the position detector could comprise only a single electrode; but it would then be necessary to distribute N / 2 electrets at the periphery of the rotor.
• the rotor could also carry only one electret; it would then be necessary to have N / 2 electrodes around the rotor.
• the rotor is not the only mobile with which the positio detector can be associated. The latter could be applied to any mobile gear train driven by the stepping motor.
• the position detector of the control device according to the invention is advantageously associated to the mobile carrying the second hand 11
• the position detector of the control device is advantageously associated to the mobile carrying the second hand 11
• the servo device further comprises a time base 13, which simultaneously controls the control circuit 7 and a counter 14 modulo "60", ie the number N of steps per revolution of the mobile with which the position detector 15 is associated .
• a discriminator 16 receives particular information, on the one hand, from the position detector 15, when the electret is opposite the electrode, and, on the other hand, from the counter 14, when the latter reaches "60 ". If it receives these two pieces of information at the same time, it does not react; but if that of the counter 14 reaches it before that of the position detector 15, that is to say if the needle 11 is late, it informs the control circuit 7 in such a way by the line 17 in broken lines, let the latter send the engine a train of rapid pulses, to catch up with the needle 11.
• the particular information from the position detector 15 reaches it before that from the counter 14, that is to say if the needle 11 is ahead, it forms the control circuit 7 in such a way that the latter suspends its normal pulses to the motor, the time to compensate for the advance of the needle 11.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Control Of Stepping Motors (AREA)
• Electromechanical Clocks (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=4278150

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Country Status (3)

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Family Cites Families (5)

• 1983
  • 1983-08-22 CH CH454983A patent/CH654170GA3/fr unknown
• 1984
  • 1984-08-22 WO PCT/CH1984/000133 patent/WO1985001130A1/fr unknown
  • 1984-08-22 EP EP84903049A patent/EP0153934A1/fr not_active Withdrawn

Non-Patent Citations (1)

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