Electricity: electrical systems and devices – Safety and protection of systems and devices – Motor protective condition responsive circuits
Patent
1995-01-03
1997-05-06
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Motor protective condition responsive circuits
361 24, H02H 504
Patent
active
056277105
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on an electric motor drive system with an overload protector for the motor. Electric motor drive systems often contain an overload protector to avoid irreparable thermal damage to the electric motor, which could occur in case of a suddenly occurring force on a component that is to be moved or if obstacles appear in its path.
A protector against thermal overload can be implemented, for example, by means of a temperature sensor which is thermally coupled to the motor winding, with the switching contact of the temperature sensor being disposed in the motor circuit. Another possibility of implementing an overload protector is the monitoring of the speed of the electric motor or of the speed of gear elements. An overload is assumed when a predetermined minimum speed is not reached.
SUMMARY OF THE INVENTION
It is the object of the invention to propose an electric motor drive system having an overload protector, such a motor being particularly suitable for use in an adjustment system that responds to an input for predetermining a desired position of a movable component.
The task is solved by providing a drive system which is characterized in that an input for predetermining a desired position of a movable component is provided, in that a change of the desired position to a resting position takes place when an overload detector emits an overload signal, and in that the motor can only be switched off by means of a switch-off signal after the resting position has been reached.
The electric motor drive system according to the invention offers the advantage that the component which is movable by the motor can move to a predeterminable resting position after the overload protector has responded and that the electric motor can only be switched off once the resting position has been reached. This measure prevents the occurrence of possible subsequent damage. The electric motor drive system according to the invention is suited for use with adjustment systems which are arranged, in particular, in motor vehicles. Examples of such adjustment systems in motor vehicles are a sliding roof/lift-up roof, a seat adjustment, a mirror adjustment, a window lifter or the like. Following the response of the overload protector in these electric motor drive systems, it is ensured that, for example, the sliding roof/lift-up roof or, for example, the window is placed into the closed position.
In a first embodiment it is provided that the overload protector evaluates a speed of the motor.
In another embodiment it is provided that the overload protector responds to the motor temperature. A first alternative provides for the use of a temperature sensor. A second alternative provides for the detection of the electric resistance of the armature winding during a motor operating break, this resistance being temperature-dependent. A particularly advantageous alternative provides that during the on period of the electric motor its power loss or a quantity that is proportional to the latter is calculated and integrated on the basis of measured motor data and that the result of the integration is compared to a predetermined threshold value. The advantage of the last alternative is that, for the detection of the overload case, no sensors are used but only motor data and operating data which are known anyway.
Further advantageous modifications and improvements of the electric motor drive system according to the invention will be apparent from the description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block circuit diagram of an electric motor drive system according to the invention, FIG. 2 illustrates a signal course within an overload protector of the electric motor drive system, and FIG. 3 shows a block circuit diagram of an embodiment of an overload protector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows an electric motor 10 which drives a movable component, not shown in detail, within an electric motor drive system. The electric motor 10 is connected to a fina
REFERENCES:
patent: 4345288 (1982-08-01), Kampf et al.
patent: 5105132 (1992-04-01), Sakamoto et al.
patent: 5323287 (1994-06-01), Peter
patent: 5373205 (1994-12-01), Busick et al.
Gaffin Jeffrey A.
Leja Ronald W.
Robert & Bosch GmbH
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