Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
2002-08-02
2004-03-23
Ro, Bentsu (Department: 2834)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S286000, C318S432000, C318S437000
Reexamination Certificate
active
06710562
ABSTRACT:
FIELD OF INVENTION
The invention relates to a synchronous motor with an electronic control device for adjusting devices in motor vehicles, in particular for adjusting devices with trap protection and/or limitation of excess force, and to a method of controlling the motor-drive unit of the adjusting device. The drive unit according to the invention may be used particularly advantageously in conjunction with an electrically operated window regulator or a sliding roof.
BACKGROUND
A generic electronically controlled drive unit is known from EP 0 482 040 B1. It consists of a permanently excited DC motor in the form of a bar-wound armature motor which forms a structural unit with a gear and an electronic control unit. A tongue-like projection of the control unit has, at its free end, means for making electric contact with the motor and Hall-effect sensors associated with a ring magnet arranged on the motor shaft. The adjusted position of the windowpane as well as the adjustment rate can be determined from the sensor signals. If an object is trapped in the closing window gap, the resistance to adjustment increases so the interval between the succeeding signals increases. If a previously defined extent of change in speed is exceeded, the drive is stopped and the windowpane reversed.
A corresponding method of trap protection for controlling a window regulator drive is described in DE 30 34 118 C2. In that patent, the distance covered is determined electronically during the opening and closing process and the opening distance is compared with the respectively covered closing distance during the closing process. The adjustment range of the windowpane is divided into three ranges. In a first range between completely opened and about half opened, the electronic trap protection remains switched off; when a blocked state occurs, the motor is switched off after exceeding a predetermined time limit. In the following second range which ends just before the seal of the window frame, the trap protection is activated. Measured values dependent on the speed or velocity of the unit are determined here and compared with a limit based on the initial measured value. If the limit is exceeded, the controller momentarily changes over the drive and then switches it off. The trap protection is deactivated again when the closure range is reached as the windowpane could not otherwise be completely closed owing to the additional resistance of the seal.
An inadmissibly high trapping force could occur during entrapment owing to the system-dependent motor characteristic which leads to an increase in the torque during a reduction in the motor speed.
To detect entrapment, an adjusting path of the motor shaft carrying the ring magnets which is sufficient for detecting at least one further signal period after the beginning of the entrapment, the signal period being compared with the value for the preceding signal period, is required so an adjustment path of at least two signal periods must be guaranteed. Under undesirable circumstances, in particular when a hard object (for example a head) is trapped, the situation where even the maximum torque is achieved can be a considerable and may not be prevented.
SUMMARY
It is accordingly the object of the invention to provide a drive unit for adjusting devices in motor vehicles and to develop a method of controlling the drive unit which are capable of ensuring simple and reliable operation of the adjustment members. In particular, reliable detection of the trap protection and adherence to predetermined limits for the permitted trapping force are to be guaranteed even during speed control for achieving a constant adjustment speed of the adjustment member which is independent of load. In addition, a reliable approach to stop positions should be possible, without additionally distorting the adjustment system with considerable excess forces.
A sealing element which subdivides the motor into a dry space comprising the electric and electronic components and a wet space, is accordingly arranged between the stator and the rotor of the motor drive unit constructed as a synchronous motor. The conditions for the use of inexpensive designs of dry space for the electric components are therefore met. In addition, the best conditions are provided owing to the use of a synchronous motor with its system-specific properties for fulfilling the specific requirements of adjusting devices in motor vehicles. This applies, in particular, to the attainment of a constant speed of adjustment of an adjustment member as the adjustment force requirements change over the adjustment path (for example owing to varying coefficients of friction) and with respect to the compliance with comparatively low trapping forces, particularly if malfunctioning of the trap protection (for example due to vibrations or impacts during travel) is to be avoided.
To guarantee suitable starting conditions, a synchronous motor with at least two windings is used to produce at least two pairs of poles of the rotating field of which the motor speed may be controlled to a constant value via the frequency of the rotating field. The torque proposed for the adjustment movement of the adjustment member is provided via the setting of the load angle &dgr; which is defined as phase displacement between the exciting field and the rotating field of the motor.
Preferably, the stator of the synchronous motor forms a prefabricated, pre-testable unit with the electronic control device and the connectors and optionally with the sensor device. A mechanical carrier comprises interconnecting elements which, for producing a mechanical connection to the stator, engage in the interstices thereof. To protect the electric parts of the stator from moisture, the carrier may be pot-shaped in construction so the stator is at least partially surrounded by the carrier in such a way that the carrier can act as a partition between a wet and a dry space. In this embodiment, the partition extends in the air gap between stator and rotor.
A further method of connecting the stator to the carrier and protecting it from wetness is to fasten the stator on the carrier by encapsulating the stator with a plastics material. If the carrier also consists of plastics material, the stator can be injection moulded into it. To avoid power losses, it is necessary to keep the air gap between stator and rotor as small as possible. Encapsulation of the stator which is as thin-walled as possible should therefore be provided.
The invention is particularly suitable for use in window regulators or sliding roofs, particularly if the body compartment in which the drive unit is arranged has separate wet and dry spaces. Trap protection can be detected simply and particularly reliably. as an adjustment movement of the adjustment member is not required for this purpose. Analysis of the load-dependent phase displacement between the exciting field of the rotor and the rotating field of the stator guarantees, at all times, a reliable measurement which, in conjunction with other measured values such as the adjustment position, adjustment speed and historic measured values, allows complex evaluation. If a specific excess force or maximum trapping force is predetermined, the exceeding of this force can be reliably avoided by adjusting the operating point of the synchronous motor to such a load angle &dgr;
B
before the load angle &dgr;
K
of the breakdown torque that the increase in torque &Dgr;M between the two load angles &dgr;
B
, &dgr;
K
at the adjustment member (for example windowpane) leads, to the maximum extent, to attainment of a predetermined excess or trapping force.
It is mentioned at this point that the drive according to the invention can also be used to operate seat adjusters. Similarly to window regulators, seat adjusters may be equipped with trap protection to avoid injury. As the conditions for adjusting a vehicle seat depend not only on the operating temperature, the degree of aging, the contamination etc., but also on the weight of the user, it is advisable to adjust each seat q
Kalb Roland
Kinnell Craig
Brose Fahrzeugteile GmbH & Co. KG
Christie Parker & Hale LLP
Ro Bentsu
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