FR2721456A1 - Device for implementing an electric motor, in particular a stepper motor for detecting an overload or a blocking state of the electric motor. - Google Patents

Abstract

Device for implementing an electric motor, in particular an actuating stepping motor making it possible to detect an overload or a blocked state of the electric motor, by using a quantity characteristic of the current. Device characterized in that the determination of the characteristic quantity takes place within a time interval (TI) which begins at a first instant (T1) after the starting instant (T0), the electric motor being switched on. underway at the starting instant (T0) starting from a state at least practically cut off from the current this period ends at a second predetermined instant (T2) before reaching the stationary level of the motor current (40, 41 ).

Description

"Device for implementing an electric motor, in particular a

  stepper motor for detecting an overload or blocking state of the electric motor. "State of the art: The invention relates to a device for implementing an electric motor comprising means for detecting the current flowing through the electric motor and an operating circuit that exploits at least one characteristic quantity of the current, compares it. at a threshold and in case

  exceeding the threshold, emits an overload signal.

  According to DE 28 20 330, there is a known

  circuit for an electric lip actuator (or motor)

  window, provided with an anti-pinch means. A circuit of exploitation

  tation detects the current flowing through an electric motor, as well as the variation of intensity related to time. The two characteristic quantities of the current flowing through the electric motor are added and compared to a predetermined threshold. After exceeding a threshold, the electric motor is reversed, for example, to release the pinched object, if necessary, by a window. The operating circuit comprises several capacitors which, in combination with other components, each realize a low-pass filter. The removal of high components

  frequency of signals when determining the magnitudes of

  The features make it possible not only to eliminate

  genomes, parasites, but also the detection of the

  start-up, when the motor is calling an im-

  bearing representing a multiple of the intensity of the current

the engine in steady state.

  EP-A 0 116 904 discloses a device

  of a component of an air-conditioning system

  of a motor vehicle. The shutter is operated by a stepper motor. We make sure that the shutter actuated by the

  stepper motor reaches the end stops mechanically

  first and foremost at the beginning of a functioning phase.

  The control unit sends the stepping motor a maximum number of steps sufficient to reach one of the end stops of the shutter independently.

  from the predetermined position of the shutter. Moreover,

  other adjustment of the flap against each of the mechanical stops

  end-of-run engines, the stepper motor receives more

  necessary steps, others not in the sense of moving

  component, so that the component reaches each position

  end of the race, safely thanks to this number

  not compensating for any loss of step

step-by-step engine.

  The object of the present invention is to create a

  positive implementation of an electric motor

  With simple means, it is possible to detect an overload or a state of blockage of the electric motor, in particular a

step-by-step engine.

  For this purpose, the invention relates to a device

  of the type defined above, characterized in that the determination

  nation of the characteristic magnitude occurs within a time interval that begins at a first instant after the start time, the electric motor (10) being started at the start time from a state at least virtually cut off current this period

  ends at a second predetermined time before reaching

  the stationary level of the motor current.

Advantages of the invention:

  The device according to the invention has the advantage

  than by determining at least one characteristic magnitude

  of the motor, in particular the current passing through the stepping motor, it is possible to detect a state of overload by

example a blocking state.

  According to a first embodiment, it is pre-

  as determining at least one characteristic quantity takes place within an interval, starting a predetermined time after starting the electric motor,

  starting from a state at least approximately without

  rant, and ending before reaching the stationary

  motor current. This means makes it possible to detect an overload or blocking state as soon as the electric motor is turned on. The device according to the invention is thus particularly suitable for stepper motors receiving switching pulses, separated to predetermine the number of steps and the current starting to pass in the motor, at least approximately, each

  times from the powerless state. A state of function

  comparable situation may occur in the case of an engine

  dc powered by a clock feed

  CEE. In the case of such a clocked operation, it is

  intended to switch a predetermined operating voltage

  for a predetermined pulse duration on the DC motor, and then cut again for a predetermined pulse duration. At the same time the relationship between

  the duration of the impulse and the pause between two impulse

  frequency can be variable. The condition of a correct operation of the device according to the invention for the clocked supply of the DC motor is that the current flowing through the DC motor

  is at least appreciably nil during impulse breaks.

  sions. According to another embodiment of the device

  of the invention, it is intended that at least one

  The characteristic is predetermined at a fixed moment

  after the starting of the electric motor, in particular

  both of the state at least virtually zero, and before the

  motor current reaches its stationary level.

  The devices according to the invention are particularly suitable for detecting end stops of

  course that can be achieved by an adjustment device or

  driven by an electric motor.

  According to other advantageous features of

  invention as the first characteristic magnitude of the

  to exploit, is for example the amplitude of the current in the interval or at a certain moment. A realization

  advantageously provides as a characteristic quantity, the value

  the intensity or the maximum difference between the

  tensity occurring within a predetermined range.

  Another development of this means is to report the variation of intensity to time. The relation as a function of time corresponds to the derivative in time

  the intensity that can be achieved both in the inter-

  valle (report of a difference) and at a predetermined moment

mined (differential quotient.

  Another advantageous development of the first mode

  realization that the interval starts simultaneously

  with the start of the electric motor. This means ensures the detection of the characteristic quantity without

  delay, simultaneously with the start of the electric motor.

cudgel.

  An advantageous development foresees that the

  detected characteristic is compared with a pre-

  determined, which is for example enslaved and in case of displacement of the threshold, this results in the detection

  an overload or a blocking state that will be reported.

  The blocking state can for example serve to detect the end stop, mechanical, already described for a means

  driven by an electric motor.

  Drawings: The present invention will be described hereinafter in more detail with the aid of the accompanying drawings, in which: - Figure 1 is a block diagram of a device

  according to the invention for the implementation of an electric motor.

  cudgel; FIGS. 2 and 3 each show a curve of current as a function of time in the device according to

  the invention shown in FIG.

  FIG. 1 shows an electric motor 10 which uses a drive means or actuator 11. The drive means 11 comprises mechanical end stops 12, 13. The electric motor 10 is connected to a power stage. 18 by four feed lines 14- 17. The power stage 18 is energized

  electrical supply lines 19, 20.

  A control circuit 21 provides signals of

  command 22 at the power stage 18 and a signal of de-

  switching 23 to an operating circuit 24. The control circuit 21 also receives an external control signal

  as well as an overload signal 26 provided by the circuit

cooked operating 24.

  The power supply lines 14-17 are provided with an intensity detector 27 which detects the current passing through the supply lines 14-17 and transmits the information to a circuit 28 forming the average value of

  this parameter; this circuit belongs to the circuit of exploitation

  24. The circuit 28 giving the average value of the parameter

  it provides a parameter signal 29 to a comparator 30 comparing the signal 29 to a predetermined threshold to output the overload signal 26 as a function of the result of the comparison. The start signal 23 is applied to a clock 32 belonging to the operating circuit 24. This clock comprises a delay means 33. The clock 32 supplies an activation signal 34 to the circuit 28 forming the

average of the parameter.

  Figure 2 shows the intensities I detected by

  the current detector 27 as a function of time t. A first

  first saw-tooth current 40, occurs when

  the drive means 11 operates without overload.

  A second intensity 41 occurs by means of drive 11 overload. The intensities 40, 41 begin to pass each time after a start time T0. At the end of a predetermined pulse duration TD, the intensities 41 drop back to zero. After a break

  predetermined pulse Tp, the shape of the current

  farts. At a first moment T1 begins an interval of

  predetermined TI time ending at a second time T2.

  FIG. 3 shows the same intensities 40, 41 as a function of time t as in FIG. 2. Instead of the interval TI of FIG. 2, FIG.

  delay Tv starting at start time To and al-

  up to a moment of TA detection.

  The device according to the invention, represented in FIG. 1, operates as follows:

  The electric motor 10 actuates the means of

  11 as two end stops 12, 13. As an electric motor 10, there is for example a current motor

  continuously excited by a permanent magnet or preferably

  a stepper motor. A bipolar stepper motor requires as shown in Figure 1 at least four feeder lines 14-17. The energy required for the electric motor 10 is supplied by the power stage 18 which receives it from a source of energy that is not represented by means of the supply lines 19, 20. The direction of rotation and, if appropriate the power of the motor are fixed by the control circuit 21 as a function of external control signals 25. This information is transmitted to the power stage 18 via the control signals.

order 22.

  The current 40, 41 passing through the electric motor 10 is detected by a current detector 27. In the case of a stepper motor with more than two energy supply lines 14-17, it is sufficient to detect the current 40 , 41

  in a chosen feed line 14.

  As a current detector 27, it is possible, for example,

  use a shunt resistor, one can also detect

  a voltage drop on a component of the output stage. The current is preferably detected by its magnetic field. As an appropriate element for this detection,

  we have the Hall effect detectors, the magneto-

  sisters or for example inductive current clamps.

  The current detected by the current detector 27

  is transmitted for its exploitation to a circuit of exploitation

  24 which detects in the circuit 28 the average of

  meter at least a certain magnitude characteristic of the current 40, 41. The resulting characteristic magnitude signal 29 is compared in a comparator 30 to a

  predetermined threshold 31. Depending on the outcome of the

  reason, the comparator 30 provides the overload signal 26

to the control circuit 21.

  The overload signal 26 signals that an overload condition has occurred in the drive means 11. Such an overload condition occurs for example by the blocking of the electric motor 10 or the drive means 11. This blockage occurs in particular on one of the limit stops 12, 13. The overload signal 26 thus indicates that one has arrived against one of the end stops

12, 13.

  In the case of the electric motor 10 in the form of a stepping motor, the control circuit 21 can determine by itself the number of steps required to reach one of the two end stops 12 in a directed manner,

  13 and performs in this manner a calibration. The purpose of the

  librage is to associate for a predetermined position of the drive means 11, between the two stops 12 and 13, a predetermined number of steps to provide. This means allows calibration not only during the first start-up but also later, any use. This makes it possible to take into account and to compensate for the dispersion related to mass production of the drive means 11, to variations due to aging, variations in elasticity as a function of temperature as well as time-dependent mechanical play. In particular, the device according to the invention is suitable for implementing the electric motor 10 for its application to a motor vehicle

  exposed to extremely harsh environmental conditions.

  An example of training means 11 is that of the shutter

  an air-conditioning system of a motor vehicle

  bile. According to the invention, it is intended to determine the characteristic quantity as a function of time. The command in time is provided by the time generator 32 which comprises a timing means 33. The sequences

  will be described in more detail below.

  afterwards using intensity curves I as a function of

  times shown in Figures 2 and 3.

  According to a first embodiment of the

  According to the invention, it is intended to determine the characteristic quantity in the time interval TI shown in FIG. 2, which starts at the predetermined time T1 after the start of the electric motor 10 with respect to the instant To start; this interval ends at a

  second moment T2. It is important that the electric motor

  that at least 10 be practically cut off from the current to the

  both start To and that the time interval TI ends at the second time T2 before the motor current

  does not reach its stationary level. Such means guarantee

  We only use the start-up phase to determine the characteristic quantity. The start-up phase can be considerably shorter than the duration of the TD pulse.

  An overload condition results in a different route.

  40, 41. While the case without

  charge corresponds to the intensity curve 40, in the case

  of the intensity curve 41, we are in the presence of

  charge. As a suitable characteristic quantity, for example, the current amplitude that occurs in the TI interval can be used and is output as a magnitude signal.

  29. Another characteristic variable,

  property is the variation of intensity in the TI interval. The variation of current is determined by distributing

  the time interval TI in a predetermined number of inter-

  elementary periods of time in which the difference in intensity between the beginning and the

  end of the elementary interval and add up.

  Another characteristic variable is the variation

  intensity throughout the entire TI interval

duration of this TI interval.

  It is also possible to replace a difference quotient, at least approximately by the slope of the intensity 40, 41 constituting a differential quotient. AT

  from several different quotients obtained in the

  time interval, for example, you can select the

  maximum value and send it as a signal of large

  29. Another characteristic quantity is the mean value in time, the intensity 40, 41

during the time interval TI.

  During the tests carried out with an electric motor 10 constituted by a stepper motor, it was found that in case of overload, there is a rapid rise of the current. Thus higher intensities are encountered than at a previous time, after the start time To in case of overload, compared to the situation without

  overload. The TI interval can be adapted experimentally

  such data. The electric motor 10 is

  energized during the pulse duration TD, then it is cut off. The motor 40, 41 always returns to the value

  zero after the pulse duration TD, during the pulse pause.

  Tp. It should be noted that the impulse break

  tional Tp is long enough for the current

  (intensity) 40, 41 may decrease at least approximately

  to zero. Timed operation of a DC motor, for which there is no

  current interval between the different pulse durations

  TD reduces the security of state detection

overload.

  The first instant T1 which corresponds to the beginning of the time interval TI may coincide with the instant of

TO boot.

  FIG. 3 shows another embodiment of the device according to the invention for implementing the

  electric motor 10; in this case, instead of

  time interval TI shown in FIG. 2, current detection 40, 41 is used at the detection time TA

  predetermined. The detection time TA is separated from a re-

  late TV predetermined from start time To; this delay time is set by the delay circuit 33 of the clock 32. This embodiment is particularly suitable when

  the characteristic quantity chosen is the instantaneous value

  where the intensity of the intensity 40, 41 or the

  holds differential at the point of detection TA.

  The first and second times T1, T2 shown in FIGS. 2 and 3, which set the time interval TI as well as the TV delay time and the detection time TA are

  determined each time by the clock 32 of the circuit of ex-

  24 as the start signal, the starting signal 23 corresponding to the start time TO is used. The circuit of

  timer 33 of clock 32 provides either time

  be the start time To and the first time T1 is the delay between the start time To and the instant of

TA detection.

Claims (9)

R E V E N D I C A T I ONS   1) Device for implementing an electric motor comprising means for detecting the current   passing through the electric motor and a circuit of   which uses at least one characteristic magnitude of the current, compares it with a threshold and, if the threshold is exceeded, transmits an overload signal, characterized in that the determination of the characteristic quantity takes place within a time interval (TI) that   starts at a first moment (T1) after the moment of de-   the electric motor (10) is started at the starting moment (TO) starting from a state at least substantially cut off from the current this period ends at a   second predetermined time (T2) before reaching the   stationary calf of the motor current (40, 41).   2) Device for implementing an electric motor comprising means for detecting a current   passing through the electric motor and a circuit of   which processes at least one characteristic magnitude of the current, compares it with a threshold and, if the threshold is exceeded, outputs an overload signal, characterized in that the characteristic quantity is determined at a   fixed detection time (TA) following a   time (Tv), the start time (To), and for which the electric motor (10) starting from at least approximately cut off state of the current, is started, this time being before the current of the motor (40,   41) reaches its stationary level.   3) Device according to claim 1, characterized   rised in that the first moment (T1) corresponds to the so much start (To).   4) Device according to claim 1, characterized   characterized in that the characteristic quantity is the average value in time and / or the amplitude and / or the intensity variation and / or the maximum intensity difference and / or at least one difference quotient of the current and the time to   inside the time interval (TI).    Device according to claim 2, characterized in that the characteristic quantity and the instantaneous intensity (40, 41) and / or the differential quotient is the ratio of the intensity (40, 41) and the time (t). just now detection (TA).   6) Device according to claim 1 or 2,   characterized in that the overload signal (26) is a   10 blocking signal which corresponds to the blocking of a medium   drive (11) actuated by the electric motor (10).   7) Device according to claim 6, characterized   in that the blocking signal indicates that the drive means (10) has come against an end stop of race (12, 13).   8) Device according to claim 1 or 2,   characterized in that the electric motor (10) is an engine step by step.   9) Device according to claim 1 or 2,   characterized by its application to a climatic installation   of a motor vehicle, the electric motor (10) actuating a flap which in operation reaches   minus one limit stop (12, 13).