Electricity: motive power systems – Automatic and/or with time-delay means
Reexamination Certificate
2000-12-08
2002-09-24
Fletcher, Marlon T. (Department: 2837)
Electricity: motive power systems
Automatic and/or with time-delay means
C318S286000, C318S280000, C318S467000
Reexamination Certificate
active
06456027
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a closing device having a safety for the following purpose: When a closing element that moves across an opening closes the opening, the safety function keeps objects that may be located in the opening from being trapped and damaged.
BACKGROUND INFORMATION
An important area of applications for closing devices of this kind is, for example, the side windows or roof windows of motor vehicles in the case of which a window pane or, respectively, sunroof is moved with the help of an electric drive motor.
Per the legal regulations, closing devices of this kind for vehicle windows are to have a trapping protection function that is designed to, to as great an extent as possible, keep users from being injured if they trap body parts. This protection function is achieved by limiting the closing force exerted by the closing device to 100 N.
As a general rule, this is achieved via, for example, closing devices in which the speed of the closing element, the torque exerted by its drive motor, or a force acting on the closing element in the opposite direction to its movement is detected, the closing movement being reversed if changes in these detected values indicate that an object may be trapped in the opening.
It has become clear that simply limiting the closing force to a maximum of 100 N does not provide adequate protection against injuries to the user if, for example, his or her hand or individual fingers accidentally become trapped. Therefore efforts have been made to develop closing devices having trap protection that exert a lower maximum force. However, problems arise if the closing devices are exposed to vibration during operation, in particular if they are used as closing devices for the window panes or sunroof of a motor vehicle. These vibrations cause parameters such as motor torque and counterforce, which are monitored by the closing device in order to limit the closing force, to fluctuate temporarily. The lower the predefined maximum closing force of the closing device, the easier it is for the parameter that is being monitored to exceed a limit value for which the closing device detects that the maximum closing force has been exceeded and thereupon interrupts or reverses the closing movement. For example, with a device of this kind it may be impossible to close the side window of the motor vehicle when the vehicle is driving across uneven terrain.
In order to tackle this problem, German Published Patent Application No. 4020351 proposes a closing device to which a sensor element supplies measured signals resulting from acceleration forces exerted on the vehicle body in the vertical direction. The accelerations measured this sensor element are offset against the monitored parameters of the closing device, which are measured simultaneously so that the disruptive influence of these accelerations can be suppressed.
It is true that this technology ensures that the closing device functions more reliably even if the closing force limit values are lower than the 100 N permitted by law; however, for various reasons it is not totally satisfactory.
One problem is that as a general rule the mechanical structure of the closing device is not absolutely rigid, so that as a result of external vibrations the closing element or its drive mechanism may start to vibrate, and as a result force peaks greater than the closing force limit values may be detected at the drive motor even after the external vibration has already decayed. The known device cannot compensate for reverberation of this kind, so that undesired reversing may still occur as a result of vibration during the closing movement.
Another problem is that frictional resistance arising when the closing element moves up and down its guideway or arising in the drive mechanism of the guideway element can also cause the parameter that is monitored to exceed the limit value at which the closing device detects that the closing force limit value has been exceeded. If, for example, the parameter that is being monitored is the torque exerted by the drive motor of a window raiser, it is clear that this will increase not only if an object has been trapped between the window pane and its frame but also if there is frictional resistance that keeps the window pane from moving freely up and down its guideway. Such frictional resistances may increase during the operating life of a closing device due to wear and tear; in addition, for design-related reasons they may have different values at different points in the closing movement. In the case of the known closing device, the only way to take this into account is to ensure that the chosen closing force limit value is not too low and in particular to ensure that when one defines the limit value a safety margin is calculated in to reflect the possibility that with increasing age the closing device will start to encounter greater frictional resistance.
SUMMARY OF THE INVENTION
In the case of the present invention, a closing device, in particular for the window or sunroof of a motor vehicle which allows one to choose a sufficiently low closing force limit value is provided, the closing movement being interrupted, or reversed if the limit value is exceeded, so that there is no absolutely no risk of injury if a body part becomes trapped in the opening to be closed. Because the closing force limit value can be varied, this limit value can be calculated very precisely for normal operating conditions, without the need for a safety margin for taking into account uneven distribution of frictional forces across the range of closing movement or due to aging of the closing device. Because the device varies the limit value based on force exerted on the closing element that has been measured at an earlier point in time, it can filter out vibrations to which the closing element is exposed, a separate sensor for this purpose being unnecessary. By choosing a suitable time period during which a variation in the limit value lasts, the device can be rendered insensitive to reverberation phenomena in the closing element following external vibration or, respectively, in the drive mechanism used to transfer the closing force of a motor to the closing element, which can cause the force to be exerted by the motor to fluctuate.
Preferably the force limit value is varied in such a way that if the sensor which detects the force exerted on the closing element in the direction opposite to closing detects an abrupt decrease in this force, the control circuit increases the lit value for a limited time period or for a limited stretch of the closing element's path. This is based on the realization that an abrupt decrease in the force is generally due to the fact that the object on which the closing device is mounted is being accelerated downwards and that an upward acceleration will follow immediately once the object's downward movement comes to an end. In the case of a motor vehicle, this situation occurs, for example, when the vehicle drives off a curbstone or into a recess such as a pothole. The upward acceleration causes the force in the direction opposite to the closing movement to increase but is not due to trapping of an object and is therefore ignored by the closing device according to the present invention by the limit value being increased at the point in time when this force arises.
Herein, in particular, the control circuit may detect the length of a time period or length of stretch of the closing element's path during which the decrease in the force lasts. It is reasonable to anticipate that the acceleration in the opposite direction will be roughly of the same absolute value and will last for roughly the same time; therefore it is useful if the time period or the length of stretch of the path during which limit value is increased is chosen to be exactly equal to, or better still, given that there may be vibration phenomena, greater than the length that has been detected.
It is useful if the amount by which the limit value is increased as a result of a downw
Fletcher Marlon T.
Kenyon & Kenyon
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