Electricity: motive power systems – Open-loop stepping motor control systems
Patent
1992-07-27
1994-04-19
Shoop, Jr., William M.
Electricity: motive power systems
Open-loop stepping motor control systems
318685, H02P 800
Patent
active
053049101
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for controlling the electrical power supply of a stepping motor, more particularly, to such a device designed for a stepping motor whose stator comprises a plurality of p ed in series with an electrical energy source and a transistor for controlling the electrical power supply of that phase, the power supply of the phases being sequentially and cyclically controlled in order to make the rotor of the motor turn step by step. The invention also relates to a stepping motor equipped with such a device.
When all the phases of such a stepping motor stop being supplied, its rotor stops turning and should normally stop in the last commanded position. This is the case in particular if the motor shaft is not subject to any torque of external origin, or if this torque is less than the "rest moment" of the stepping motor. This rest moment, due to a reluctance effect, corresponds to the torque which has to be applied to the motor shaft in order to make it turn continuously in the absence of any excitation of the windings and of any other torque of external origin on this shaft.
If the torque of external origin is greater than the rest moment, the accidental or deliberate cutting of f of the power supply of the phases of the stator is followed by a rotation of the rotor up to a position which is defined, for example, by a stop.
At the present time the use of a stepping motor is envisaged for controlling an actuator such as the butterfly valve adjusting the intake of air for an internal combustion engine driving a motor vehicle.
In this respect, there is known from the French Patent Application No 8806363 of the 11th May 1988, lodged in the name of BENDIX ELECTRONICS SA, a device for controlling the air intake butterfly valve of an internal combustion engine which comprises an electric motor whose stator is mechanically coupled to an accelerator pedal while the rotor of this motor is connected to the butterfly valve by a friction coupling device. An excitation of the motor causes a rotation of the rotor with respect to the stator, which allows the reduction, by a predetermined angle, of the opening of the butterfly valve in order to adjust the speed of the vehicle or, in detecting the imminence of a skidding of the wheels, to avoid this skidding by reducing the driving torque supplied to these wheels.
When it is envisaged, as in the abovementioned Patent Application, to correct the position of the butterfly valve using a motor, it is observed that in the case of the failure of the motor, an external torque applied to the butterfly valve could modify, possibly in an erratic manner, the position of the latter. Such a torque could result, for example, from turbulence in the air intake manifold. The erratic variations in the position of the butterfly valve which are observed are therefore capable of seriously affecting the stability of the engine speed. In such a situation, it is desirable that the butterfly valve should remain in the position adjusted at the moment of the failure, its controls then being able to be provided conventionally by the accelerator pedal of the vehicle by means of the mechanical coupling of this pedal with the stator of the motor, as described for example in the abovementioned Patent Application.
In order to achieve this result, it is possible to consider inserting a friction coupling device between the butterfly valve and a fixed reference surface. This friction coupling device is dimensioned in order to introduce a friction torque greater than the interfering torque which could be applied to the butterfly valve in the case of a failure of the motor, and less than the torque supplied by this motor when the latter is functioning normally. This solution is not without disadvantage. In fact, the motor must overcome an additional "dry" frictional torque each time it is actuated and must therefore be oversized in consequence.
A second solution consists in inserting an electromagnetically controlled friction clutch between the butterfly valve and a fixed referen
REFERENCES:
patent: 4730164 (1988-03-01), Daido et al.
patent: 4868478 (1989-09-01), Hedlund et al.
patent: 5034674 (1991-07-01), Sato
patent: 5103151 (1992-04-01), Kondo et al.
Loncle Jean-Pierre
Pournain Michel A.
Greenberg Laurence A.
Lerner Herbert L.
Masih Karen
Shoop Jr. William M.
Siemens Aktiengesellschaft
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