Patent Application
20070281813
The invention is explained in more detail below with reference to an enclosed drawing. The sole figure shows very schematically a tensioning and vibration-damping device constructed according to the invention for a belt drive.
The tensioning and vibration-damping device for a belt drive with means 1 for conveying rotary motion, which can be an endless chain or an endless belt, essentially comprises a tension-roller carrier 2, which can pivot in this case on one end in a slide bushing 4 connected rigidly to a support component 3 and which, on the other end, supports a rotating tension roller 5.
The support component 3 can be formed, for example, by a base plate that can be fixed to a support chassis component of a motor vehicle, by the mentioned chassis component itself, by a crankcase or transmission gearbox, or by any other suitable support component. For guaranteeing a constant tension of the means 1 for conveying rotary motion, the tension roller 5 is brought into active connection with the means 1 for conveying rotary motion, in that the tension-roller carrier 2 together with the tension roller 5 is pressed with a certain pre-tensioning force against the means 1 for conveying rotary motion. For applying the force, in the present case a known piezoelectric structure 6 is provided, which is supported on one end on the support component 3 and on the other end on the tension-roller carrier 2.
Piezoelectric structures 6 or piezoelectric actuators, for example, in the form of piezoelectric ceramics, are suitable for this purpose and are deformed by an electric voltage. Accordingly, they allow extremely precise movements that are associated, incidentally, with very high forces to be generated through deformation, when a voltage is applied.
In the present case, the piezoelectric structure 6 is formed by a known piezoelectric linear actuator. It is also possible, however, and recognized accordingly by the invention to use a piezoelectric stack composed of several piezoelectric linear actuators connected in series as a function of the desired travel of the piezoelectric structure 6.
Due to the recognition that a piezoelectric structure 6 or a piezoelectric actuator can be lengthened or shortened by approximately 1% of its overall length through the application of a voltage, the desired number of piezoelectric actuators to be combined to form a piezoelectric stack can be determined relatively easily.
As the sole figure further shows, there is at least one vibration sensor 7, which is connected electrically via a control and regulation circuit with an electronic controller and regulator 8 to the piezoelectric structure 6 for triggering this structure. The power supply for the piezoelectric structure 6 and for the vibration sensor 7 can be realized here externally via, for example, the onboard network of a motor vehicle.
Likewise, the vibration sensor 7 can also be connected wirelessly to the controller and regulator 8, for example, by radio (not shown in more detail). In this case, in particular, an electrical accumulator allocated directly to the vibration sensor 7 is provided.
As a function of the vibrations generated in the belt drive by the operation of this belt drive and detected by the at least one vibration sensor 7, a force for compensating or damping these vibrations can be generated by the piezoelectric structure 6 and guided via the tension-roller carrier 2 and the tension roller 5 to the means 1 for conveying rotary motion, as a result of which vibration damping can be realized by the piezoelectric structure 6 for a suitably selected frequency and amplitude of the force action.
Here, it does not involve passive damping of the vibrations as in conventional friction or hydraulic systems, but instead active damping, such that the piezoelectric structure 6, in the form of an actuator or a stack of actuators, can be controlled actively against vibration so that no disruptive vibrations with greater amplitude are produced. Thus, for example, known “fluttering” of the means 1 for conveying rotary motion, e.g., a belt, is prevented. Smooth running and special protection of the means 1 for conveying rotary motion are the result.
The damping effect by the device according to the invention can be adjusted independent of external parameters such as temperature and speed of the means for conveying rotary motion. Because the vibration amplitudes of the tension-roller carrier 2 can be held to a very low level, the slide bushing 4 wears to a much lower degree than in conventional devices. Detectable sagging of the belt, in particular, which currently is a limiting factor in many cases for the service life of the means for conveying rotary motion, can be reduced very strongly.
Also, with respect to conventional friction linings for damping vibrations, disadvantageous stick-slip effects positioned there are, in principle, prevented.
The vibration sensor 7 is arranged in the present case directly on the tension-roller carrier 2. Certainly other components of the belt drive can also be used for fixing the vibration sensor 7 if these are excited to vibrate by the operation of the belt drive.
Thus, the one or more vibration sensors 7 can also be constructed as a piezoelectric structure, for example, as a vibration sensor 7 with a seismic mass and can be integrated on the mentioned tension-roller carrier 2 or another vibrating component of the belt drive or also in the optionally used piezoelectric stack.
It is further possible that a piezoelectric actuator (linear actuator) is constructed so that this actuator functions both as an actuator and also as a vibration sensor.
Also, a piezoelectric structure 6, whether it is an actuator and/or a vibration sensor, can be constructed to be self powered with respect to the necessary power supply, in that an electric voltage, which can be made available, in turn, to other piezoelectric actuators or vibration sensors, is generated, for example, through the deformation of the piezoelectric ceramics due to the vibrational excitation of these ceramics.
As is to be further taken from the sole figure, based on the above properties of the piezoelectric structure 6 in the form of a single linear actuator or a piezoelectric stack, this structure can be arranged very close to the rotational axis 9 of the tension-roller carrier 2 that can pivot on the support component 3, whereby savings in installation space are to be noted.
The distance “s” between the rotational axis 9 of the tension-roller carrier 2 and the frictional contact point 10 of the piezoelectric structure 6 on the tension-roller carrier 2 thus can be minimized as a function of the maximum possible travel of the piezoelectric structure 6 and the maximum necessary travel of the tension roller 5 of the tension-roller carrier 2.
As was already explained farther above, the invention is not limited to chain drives, which conventionally require relatively small correcting movements or travels of the allocated tension elements, but instead also comprises belt drives, in which the correcting movements can be increased proportionally.
In order also to be able to effectively implement such correcting movements in the sense of the invention, it can be specified to arrange the piezoelectric structure 6 in the form of one or more actuators combined to form a piezoelectric stack in series with a conventional tensioning element that can be actuated mechanically or hydraulically not shown in more detail. This means that, as an example, a spring-loaded linear tensioner is combined with a piezoelectric structure 6 or with a piezoelectric actuator or a piezoelectric stack, whereby large correcting paths are implemented by the mentioned linear tensioner that can be actuated mechanically or hydraulically, while the damping of the vibrations in question is performed essentially by means of the piezoelectric structure 6.
Finally, there is also the possibility of using the measurement signals prepared by the vibration sensor 7 for detecting the current wear state of the belt drive, in that a comparison of these measurement signals is performed against reference values that are stored, for example, in an electronic memory of the controller and regulator 8.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102006019879.4 | Apr 2006 | DE | national |
