Arrangement for detecting jamming situations in electric drives

Details Arrangement for detecting jamming situations in electric drives Arrangement for detecting jamming situations in electric drives

1998-07-16

2001-05-29

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Impedance, admittance or other quantities representative of...

Lumped type parameters

C324S545000, C318S434000, C318S455000

Reexamination Certificate

active

06239610

ABSTRACT:

FIELD OF THE INVENTION
The present invention (jamming) related to on an arrangement for detecting pinching situations in electric drives provided mainly for window and sunroof opening devices of motor vehicles.
BACKGROUND INFORMATION
In a conventional circuit arrangement described in German Patent Application No. 28 20 330 C2, a motor is provided, which is controlled by a switching unit in turn influenced by a motor monitor. The motor monitor derives a reset signal from a certain static motor current value and, in addition, detects, at least occasionally, a reset signal from a certain variation of the motor current over time. In this conventional arrangement, static and dynamic monitoring is performed, whereby the motor is switched off or its direction of rotation is reversed in the event of a sudden change in torque or increase in current due, for example, to the window pane hitting an obstacle, even if the instantaneous current is relatively low. The motor, however, is switched off or its direction of rotation is reversed even if, in the event of a gradual increase in the current to a value close to short-circuit current, a rapid further increase is no longer possible. In this case, therefore, two criteria are analyzed to detect a pinching (jamming) situation: the static motor current and the variation of the motor current over time.
In general, methods of monitoring the rotation speed to limit the force and prevent pinching jamming in displacement drives such as window and sunroof motors in motor vehicles, detecting gradual or abrupt changes in the rotation speed determined, for example, using Hall sensors, and deriving the required motor control signals therefrom, are also known.
SUMMARY OF THE INVENTION
The arrangement according to the present invention uses a different, advantageous approach. In the arrangement according to the present invention, the voltage induced in the motor armature is used to detect pinching (jamming) situations and to protect against pinching, (jamming) said voltage being determined from the voltage across the motor terminals and the current flowing in the motor armature.
In an embodiment of the present invention, the induced voltage is determined as the difference between the voltage across the motor terminals and the product of the armature current and armature resistance. According to another version of this embodiment, the armature resistance is determined periodically, in particular, at each new motor run.
According to another embodiment of the present invention, the armature resistance is determined from the voltage across the motor terminals and the blocking current of the motor. In yet another embodiment, the blocking current is determined by extrapolation of the armature current measured at a given point in time.
In a another embodiment of the present invention for simply and reliably implementing the invention, the current flowing in the armature is measured using a shunt resistor and digitized by means of an analog-digital converter after optional amplification.
In another embodiment of the present invention, the current signal determined from the current flowing in the armature is determined with the help of an integrator controlled by a microcontroller with adjustable, computed integration periods.
According to another embodiment of the present invention, the current signal determined from the current flowing in the armature is integrated over a plurality of commutation periods, in particular over 3 to 5 commutation periods.
In another embodiment of the present invention, the integration of the current signal determined from the current flowing through the armature is aborted when a threshold value is reached, the value determined is digitized and stored, the integration is resumed, and this procedure is continued until the entire adjusted and predefined integration period has elapsed.
According to another embodiment of the present invention, in order to trigger the pinching (jamming) protection, the current flowing in the armature is determined, which for actual triggering must be greater than a value composed of:
a determined value of the armature current,
a correction value taking into account the change in the supply voltage over the time period of averaging, and
a triggering value according to the following equation:
I
Armature
>
I
Armature
_
+
U
B
n
-
U
B
n
-
1
R
Armature
+
I
S
In another embodiment of the present invention, the measured armature current values are stored in a memory, in particular, in a ring memory, and the oldest measured value is overwritten with the current measured value.


REFERENCES:
patent: 4473856 (1984-09-01), Takahashi
patent: 4532567 (1985-07-01), Kade
patent: 4725765 (1988-02-01), Miller
patent: 4952854 (1990-08-01), Periou et al.
patent: 5773945 (1998-06-01), Kim, I
patent: 5801503 (1998-09-01), Kim, II
patent: 28 20 330 (1979-11-01), None
patent: 0 328 838 (1989-08-01), None

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