Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-06-07
2001-04-10
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S156000, C188S072700, C188S072800
Reexamination Certificate
active
06213256
ABSTRACT:
PRIOR ART
The invention relates to an electromechanical wheel brake device for a motor vehicle.
A wheel brake device of this kind has been disclosed by WO 96/03301. The known wheel brake device is embodied as a disk brake. It has a brake caliper embodied as a floating caliper, in which two friction brake linings are disposed on both sides of a brake disk as a brake body, which can be set into rotation between them. In order to press one of the two frictional brake linings against the one side of the brake disk, the known wheel brake device has a screw link actuator whose threaded nut can be driven to rotate by an electric motor and whose threaded spindle can be pressed against the one frictional brake lining. The other frictional brake lining is pressed against the other side of the brake disk in a known manner by means of reaction forces, which occur when the one frictional brake lining is applied and are transmitted to the other frictional brake lining by the floating caliper.
In order to restore the known wheel brake device in the event of a malfunction, i.e. upon failure of a set of control electronics or upon failure of the electric motor or its power supply, the known wheel brake device has a restoring spring in the form of a spiral spring, which is supported against the brake caliper and engages the threaded spindle. This spiral spring is stressed upon actuation of the wheel brake device and releases the wheel brake device after the end of a braking procedure by rotating the threaded spindle back. The known wheel brake device has the disadvantage that its restoring spring is stressed with each brake actuation, for which energy is required, which reduces the efficiency of the known wheel brake device. Moreover, during actuation of the wheel brake device, its electric motor must additionally exert the spring force of the restoring spring and must maintain this during braking; correspondingly, the electric motor must be embodied as more powerful. A further disadvantage is that the restoring spring always moves the wheel brake device into its completely reset initial position so that an air play between the frictional brake linings and the brake disk becomes greater with increasing wear of the frictional brake linings. This extends an advancing path and lengthens an advancing time until the frictional brake linings come into contact with the brake disk. Likewise, the spring force of the restoring spring, which must be overcome for the braking, rises with increasing wear of the frictional brake linings, which further impairs the efficiency of the wheel brake device and requires a sufficiently powerful and durable electric motor.
ADVANTAGES OF THE INVENTION
The electromechanical wheel brake device according to the invention, has a self locking-free screw link actuator whose threaded spindle, by means of pressure on the threaded spindle in the axial direction, can be set into rotation in relation to the spindle nut and therefore can be moved axially. Furthermore, according to the invention, both the spindle nut and the threaded spindle are supported in a rotatable fashion so that a force pressing the frictional brake lining against the brake body during braking, exerts a force in the axial direction on the threaded spindle, sets the threaded spindle into rotation in the spindle nut and thus produces a restoring of the wheel brake device until the frictional brake linings rest against the brake body with a pressing force that produces a residual brake force, which permits the brake body to rotate virtually freely. This assures the release of the wheel brake device to an acceptable residual brake force in the event of a malfunction. For actuation of the wheel brake device, it has a releasable rotation prevention device which prevents a rotation of the threaded spindle and permits its translatory motion in the axial direction through a rotational driving of the spindle nut. The brake is released through the rotational drive of the spindle nut in the opposite direction so that an air play between the frictional brake lining and the brake body can be adjusted. A release of the rotation prevention device of the threaded spindle is provided only for the event of a malfunction.
According to the invention, it is likewise possible to rotationally drive the threaded spindle instead of the spindle nut and to press the frictional brake lining against the brake body with the spindle nut instead of with the threaded spindle. In this instance, the rotation prevention device engages the spindle nut.
The wheel brake device has an advantage that its rotation prevention device, which permits a release of the wheel brake device without the electric motor in the event of a failure, does not influence the efficiency and function of the wheel brake device. Another advantage is that the air play between the frictional brake lining and the brake body with the electric motor can always be adjusted to the same value independent of a wear of the frictional brake lining, so that the advancing path and the advancing time remain the same.
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patent: 5829557 (1998-11-01), Halasy-Wimmer et al.
patent: 5931268 (1999-08-01), Kingston et al.
Greigg Edwin E.
Greigg Ronald E.
Kramer Devon
Oberleitner Robert J.
Robert & Bosch GmbH
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