Rotational damper

An electric rotational damper includes a generator which including a stator and a rotor; a damper housing having a housing attachment, wherein the stator is connected with the damper housing, and wherein the housing attachment and the stator in fixed rotative relationship with the damper housing; a transmission connecting a coupling lever with the rotor of the transmission of the rotational damper; a housing part connected with and co-rotating with the transmission, wherein the housing part is in surrounding relationship with the rotor, and wherein the housing attachment is in surrounding relationship with the housing part; and a centrifugal brake arranged between the housing part and the housing attachment.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2013 004 956.3, filed Mar. 22, 2013, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a rotational damper with a housing-fixed stator, a rotor and a transmission, which connects an coupling lever with the rotor of the transmission of the rotational damper.

WO 2011/042085 A1 relates to an electric damper for damping relative movements between a first and a second mass, including a generator which is driven by the movement of the mass, and which is characterized in that the generator is integrated into a transmission, wherein a first transmission element which forms a stator is caused by the masses to rotate, which causes rotation of a second transmission element which forms a rotor and is coupled with the first transmission element in a directly or indirectly transmitted manner, wherein means for generating a magnetic field are provided either on the first or on the second transmission element. The transmission is a planetary transmission with a ring gear which forms the first transmission element, planetary gears which mesh with the ring gear, and with a sun gear which interacts with the planetary gears.

FIG. 1of the present specification exemplary shows the course of the damping force of a conventional hydraulic damper, for example according to WO 2011/042085 A1, in traction and compression direction. The moment that can maximally be provided by a generator operated in the generator mode is the tilting moment. This also at the same time limits the maximally provided damping force. Curve x ofFIG. 1shows the course of the damping force of an electric damper. As soon as the tilting moment in the generator is exceeded, the damping force significantly decreases. The generator therefore has to be configured so that the damping forces, which occur during normal operation, are below the tilting moment of the generator. However, for exceptional situations (for example when the vehicle drives over a bump with high speed) the high damping force of a hydraulic damper has to be provided also with an electric damper. Increasing the tilting moment by configuring the generator accordingly inevitably leads to a very large and heavy generator.

Exceptional situations in which the maximal damping forces are required are encountered rather infrequently during operation of the vehicle. It is therefore not useful to dimension the generator in accordance with these maximal forces. Therefore electric dampers were developed in which the generator is merely configured in accordance with the damping forces occurring during normal driving operation. The high damping forces required for exceptional situations are generated by additional means which are activated via centrifugal force and are not activated at damper speeds below the trigger speed.

Thus DE 198 46 275 A1 relates to a system for roll stabilization of vehicles, in particular motor vehicles, in which actuators are provided, which have at least one sensor for detecting a roll parameter and at least one swivel drive which is arranged between halves of the front and/or rear chassis stabilizer, which actuators cause a pre-tensioning of the stabilizer halves for reducing or suppressing the roll movement and in case of rolling generate a counter moment on the vehicle superstructure depending on starting signals of the sensor. The swivel actuator is an electromechanical swivel actuator and means for blocking the pivoting of the stabilizer halves relative to each other are provided. The blocking means have a brake which opens electromagnetically or closes electromagnetically, and which in each swivel actuator is arranged between a respective swivel motor and a reduction gear of the swivel motor.

DE 10 2009 018 889 A1 relates to a roll stabilizer of a motor vehicle with an actuator which is arranged between two stabilizer sections and whose rotor is actuatable for a rotation of the stabilizer sections, wherein a braking device which acts on the rotor is characterized in that the braking device is configured as centrifugal brake which transfers a friction between the rotor and a stator. When the rotor is formed by a motor shaft of an electric motor, radially displaceable centrifugal bodies of the centrifugal brake are connected with the motor shaft. The centrifugal bodies and the stator are configured as friction partners for each other. The stator has a housing which receives the centrifugal bodies. The centrifugal bodies can be displaced radially outwardly against a spring element.

In electric dampers according to the state of the art the centrifugal brake, if provided, is integrated in the damper itself between the rotor and the stator of the generator. Consequently, the forces occurring in an exceptional situation are still introduced into the rotor/stator.

It would therefore be desirable and advantageous to provide an electric damper in which the generator in the exceptional situation is completely bridged.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an electric rotational damper includes a generator which includes a stator and a rotor; a damper housing having a housing attachment, wherein the stator is connected with the damper housing, and wherein the housing attachment and the stator are in fixed rotative relationship with the damper housing; a coupling lever; a transmission connecting the coupling lever with the rotor of the transmission of the rotational damper; a housing part connected with and co-rotating with the transmission, wherein the housing part is in surrounding relationship with the rotor, and wherein the attachment is in surrounding relationship with the housing part; and a centrifugal brake arranged between the housing part and the housing attachment.

The generator of the electric damper can be configured small, light and efficient without being subjected to the high damping forces occurring in exceptional situations. Further, during an exceptional situation, i.e., when the damping force exceeds the tilting moment of the electric damper, the generator, which is formed by the stator and the rotor, is completely bridged because the force introduction between the damper housing on the superstructure and the housing part which is directly connected with the coupling lever occurs through centrifugal force coupling.

According to another advantageous feature of the invention, the co-rotating housing part can be rotatably supported on the stator by rotary bearings. Because the stator itself is mounted directly on and in rotative fixed relationship with the damper housing, this results in a stable and advantageous support of the co-rotating housing part on the stator.

According to another advantageous feature of the invention the centrifugal brake can include a tension spring which is connected with the housing part and a friction element with a mass m which is impinged by the tension spring, which friction element is moved as a result of the centrifugal force in the direction toward a housing-fixed friction surface on the housing attachment, wherein advantageously the tension spring and the mass of the friction element are dimensioned so that the centrifugal brake is activated when a required damping force exceeds the tilting moment provided by the generator. In this advantageous way, the action of the centrifugal brake can be adjusted to the respective application.

According to another advantageous feature of the invention, the housing attachment can form the friction surface of the centrifugal brake, thereby obviating the requirement for additional parts for providing the friction surface or for individual friction surfaces.

According to another advantageous feature of the invention, the friction element can be fastened on the housing part via a carrier element and a hinge. This advantageously results in a secure arrangement of the centrifugal brake in the electric damper, which requires little constriction effort.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawing, and in particular toFIG. 2, there is shown the functioning diagram of an electric rotational damper2with an electric generator4. A coupling lever6of the rotational damper2is rigidly connected with a ring gear8of a planetary transmission10via housing part24. Planetary gears12are connected with a damper housing14, which in turn is connected with a vehicle superstructure16. A sun gear18of the planetary transmission10is directly connected with a rotor20of the electric generator4. A housing-fixed stator22of the electric generator4is surrounded by a housing part24, which is connected with the ring gear8. The co-rotating housing part24is rotatably supported on the stator22by rotary bearings26.

Between the co-rotating housing part24and the attachment36a centrifugal brake is arranged, which in the exemplary embodiment is formed by a friction element30and a tension spring28. The friction element30with a mass m is arranged on the housing part24via the tension spring28. The friction element30is mounted pivotably on the housing part24via the carrier element32and the hinge34. When the housing part24rotates sufficiently fast as a result of the activation by the coupling lever6, the friction element30is pushed against the housing-fixed friction surfaces on a housing attachment36, which is connected with the damper housing14in rotative fixed relationship, and the described damping force is generated due to friction. The housing attachment36itself forms the friction surface of the centrifugal brake. The trigger speed, i.e., the rotational speed at which the friction element30is effectively pushed against the friction surface on the housing attachment36, can be adjusted via the mass m of the friction element30and the spring stiffness of the tension spring28.

Thus, the tension spring28and the mass of the friction element30are dimensioned so that the centrifugal brake is activated when the required damping force exceeds the tilting moment provided by the generator4.

FIG. 3shows the course of the damping force of a hydraulic damper, an electric damper and a friction element in traction and compression direction. The course of the damping force by the friction element30shows that the centrifugal brake becomes active exactly at the point of the force profile at which the damping force exceeds the tilting moment provided by the generator, so that a sufficient damping force is also available when exceeding the tilting moment.

FIG. 4shows exemplary how the rotational damper2can be mounted in an axle with push rod steering. As part of a motor vehicle a wheel40with a wheel carrier42is shown on which a push rod44is arranged which is connected with a lever element46. The lever element46is supported for pivoting about a pivot axis D, wherein the damper2is located at the site of the rotation axis D. The damper2can also be directly integrated in the rotary suspension of one or both transverse control arms48. When the wheel40springs in or out, the lever element46is moved via the push rod44, so that it rotates about the rotation axis D, whereby the damper2is activated and can perform the described damper function.