DE102009042310A1 - Arrangement for determining torque of driving shaft of e.g. wind turbine, of cement mill, has evaluation unit determining predetermined torque acting on shaft under observation of predetermined torsion rigidity of shaft - Google Patents

Abstract

The arrangement has a pivot bearing (2) including an outer ring (3) and an inner ring (5), and a solid measurer (8) fixed on a shaft (1) or the outer ring and comprised of a frame fixed angle sensor (7). The sensor supplies an angle signal that depends upon time basis of a rotation angle of the shaft, to an evaluation unit. The evaluation unit determines torque dependent regulation of the shaft under utilization of the angle signal and the time basis and predetermined torque acting on the shaft under observation of predetermined torsion rigidity of the shaft. An independent claim is also included for a method for determining torque of a shaft.

Description

Field of the invention

The present invention relates to an arrangement for determining torque on a shaft which is mounted in at least one rotary bearing, which has a frame-fixed bearing part and a shaft-fixed bearing part. The invention also relates to a method for determining torque on a shaft.

Especially in the field of large torque transmission, there is a need to capture as accurately as possible the torques acting on a shaft in the drive or driven line. The knowledge of these torques is required both for the protection of the shaft and the units coupled thereto against overloading, as well as for the improvement of the control of corresponding machine units, taking into account the torques actually occurring. For example, in the operation of wind turbines (wind turbines) it is desirable to introduce the torque occurring at the main shaft as a control variable in the control loop in order to optimize the operating conditions of the coupled generator. The torque acting on the shaft can be subject to considerable fluctuations in this case by the change in the wind force, so that an increase in the efficiency of the wind turbine would be possible if the torque can be provided as a real-time controlled variable.

In other applications, the detection of the torque occurring at a shaft is of particular importance, especially when an overuse of shafts, bearings or gears in heavy industrial applications (for example, cement mills, marine propulsion and the like) should be excluded.

From the prior art it is known to determine torques in the drive or driven train on a shaft with the aid of strain gauges.

In addition, it is for example from the DE 690 10 378 T2 It is known to detect an angular displacement between a drive shaft and an output shaft and to deduce therefrom an acting torque. The torque detecting device described therein uses a capacitor-mounted capacitor and a solenoid coil wound on the shaft and forming a resonant circuit with the capacitor. In addition, a position-adjustable, non-ferromagnetic metal core element is provided, which is rotatably connected to the shaft and is arranged opposite a sensor coil. In the case of an angular displacement, an inductance change occurs in the sensor coil, which is evaluated as a measure of the torque occurring. This measurement setup is complicated and requires the arrangement of numerous elements on the shaft, so that the torque can only be determined at positions that are remote from the torque transmitting gear stages and bearings. Due to this spatial distance, there are already deviations between the measured torque and the torque occurring at the points of interest, which are due in part to the limited torsional rigidity in the shaft train. For the high-precision determination of a torque and its consideration in real time within a plant control such measuring arrangements are therefore not suitable.

From the DE 11 2004 001 038 T5 For example, a non-contact rotary displacement optical sensor device for use with a torque transmitting mechanism is known. For this purpose, a rotatable and compressible bending element is connected to a drive end and a driven end. At the bending element, a pattern of reflective and non-reflective lines is arranged, which is illuminated by a light source. A detector device receives a phase-shifted by a field mask light signal for evaluating the rotational displacement.

The object of the present invention is thus to provide an arrangement and a method for determining torque on a shaft, which allows the real torques or torque forces in the main drive train, for example wind turbines or comparable installations where high torques can occur with a high dynamic to determine. In particular, it should allow the invention to detect the torque in input or output strands in real time and derive therefrom a control variable, which is provided for the control of the system. For a high control accuracy, the invention should also make it possible to at least greatly reduce or completely eliminate the influence of torsional stiffness on the accuracy in the determination of the torque.

The solution of this problem is achieved by an arrangement according to the appended claim 1 and a method according to the appended claim 7.

The inventive arrangement for determining torque on a shaft is characterized in particular by the fact that a material measure is attached to the shaft or a shaft-fixed bearing part, wherein at least one frame-fixed angle sensor is arranged to the material measure to capture or query and based on a time base to provide angle signals to an evaluation unit, which are dependent on the rotation angle of the shaft. Using the angle signals and the time base, the evaluation unit first determines the torque-dependent speed change of the shaft and, with further consideration of a predetermined torsional rigidity of the shaft, determines the torque acting on the shaft.

The material measure, which can be formed for example by a line scale engraved on the shaft surface, by applied surface sections with different reflectance, by regions with different magnetic sensitivity or comparable elements, can be attached in the immediate vicinity of a gear stage or a shaft section to be observed, that is, at positions in which a torque-related torsion of the shaft can be measured very precisely, since at these points other force influences, which can also lead to a torsion or bending of the shaft, are kept small. Such sites can be found in particular within Wellenstützlagern or in the immediate vicinity.

The angle sensor can be integrated, for example, in a frame-fixed bearing ring of a bearing or laterally attached to this.

It is particularly advantageous to provide a plurality of arrangements according to the invention on a shaft in order to determine the torque at different portions of the shaft. Thus, actual torque values are available in different shaft sections, from which torsional vibrations can be determined over the shaft path. This allows, for example, in wind turbines the targeted control and regulation of a load application to reduce load fluctuations. Ultimately, this serves to optimize the efficiency of such an energy system, since load peak fluctuations can be compensated. The invention further enables the reduction of load stresses on shafts that need to transmit high torques. This reduces the wear of the corresponding components and increases the life of the entire system. Likewise, the invention can be used to monitor particularly stressed sections of corresponding waves to detect impending damage in time and to stop the plant if necessary, before it comes, for example, to a wave break, which can result in the destruction of an entire system.

A modified embodiment of the invention is characterized in that the material measure not directly on the shaft but the shaft-fixed bearing ring of the pivot bearing, which is preferably a roller bearing, is mounted. The determination of torque assumes, of course, that no slip between the shaft and the shaft-fixed bearing ring occurs. This embodiment allows the direct integration of the arrangement according to the invention in a rolling bearing, which reduces the assembly effort and at the same time ensures that the torque is determined directly at the shaft support point.

The above-mentioned problem is further solved by a method according to claim 7.

It is essential for the method according to the invention that the angle of rotation of the shaft is determined by an angle sensor, from which the speed change of the shaft is determined, and the torque acting on the shaft is subsequently determined by using the predetermined torsional rigidity of the shaft. The rotation angle determination is carried out in particular by scanning (preferably non-contact) of the material measure and using a time base in order to calculate the rotational speed of the shaft or its change.

For example, starting from an initially constant rotational speed, a change in rotational speed can already be detected during a single revolution of the shaft, which results from a torsion of the shaft. The evaluation unit uses a known value of the torsional stiffness of the shaft, which was previously stored in a memory, for determining the torque. Assuming that a speed change occurs due to an introduced torque, the magnitude of the torque introduced can be inferred from knowledge of the torsional rigidity from the speed change measured by the angle sensor. The corresponding mathematical relationships and usable calculation algorithms are known to the person skilled in the art, so that they need not be explained in more detail here.

Further advantages, details and developments of the present invention will become apparent from the following description of a preferred embodiment, with reference to the drawings. Show it:

1 a sectional view of an inventive arrangement for determining torque on a shaft;

2 a perspective view of a shaft bearing with an integrated therein arrangement for torque determination.

1 shows in a longitudinal sectional view of a preferred embodiment of an arrangement for torque determination on a shaft 1 in a pivot bearing 2 is stored. The pivot bearing 2 is formed in the illustrated embodiment as a double-row roller bearing and has a frame-fixed outer ring 3 , Rolling elements 4 and a shaft-tight inner ring 5 , rotatably on the shaft 1 is appropriate. The outer ring 3 is in a machine frame 6 attached. Also fixed to the frame is an angle sensor 7 provided in the machine frame 6 and / or on the outer ring 3 can be appropriate and suitable for a material measure 8th is chosen on the shaft 1 is arranged and twisted with this. In modified embodiments, the material measure 8th also on the inner ring 5 be mounted on the pivot bearing.

It is expedient if both the material measure and the angle sensor are integrated into the bearing housing in order to be as close as possible to the pivot bearing 2 to be arranged. In this immediate vicinity of the pivot bearing occur essentially only torsors on the shaft, which depend on the introduced torque. Disturbance variables that would lead to a falsification of the measured value and, for example, can result from a vibration of the shaft, are minimized as far as possible in the immediate vicinity of the bearing.

The angle sensor 7 gropes the material measure 8th continuously, so that a rotation angle can be determined continuously. If a torsion occurs on the shaft, this leads to an angle change, which can also be regarded as a short-term speed change in the area of the material measure. This shift of the angle of rotation can be derived taking into account a time base from the observation of the material measure. That by the material measure 8th and the angle sensor 7 formed angle measuring system can fall back on different measuring methods and work, for example, optically, magnetoresistive or inductive.

The angle sensor 7 for example, transmits the recorded measured values via a connecting cable 9 to an evaluation unit 10 ( 2 ) further. The evaluation unit uses a stored, predetermined torsional rigidity of the shaft for determining the torque, which can be determined from the design features of the shaft used. The evaluation unit first determines the occurring angular displacement or the speed change from the sensor signals. Using the torsional stiffness, the torque occurring in the area of the material measure can then be determined.

2 shows a modified embodiment of the arrangement according to the invention in a perspective view. The location of the wave 1 is only by its axis line 1' symbolizes. In this embodiment, the material measure in the pivot bearing 2 integrated while two angle sensors 7 . 7 ' are arranged radially outside the pivot bearing to scan the material measure. The two angle sensors 7 . 7 ' are diametrically opposed so that they provide a 180 ° offset angle of rotation signal. If the resolution is sufficiently high, the changed angle of rotation or a speed change due to a torsion of the shaft can be determined from the phase offset of the two angle signals. This in turn allows the torque to be determined taking into account the torsional rigidity of the shaft.

The design of the material measure is versatile possible, depending on the applied measuring principle and accuracy requirements. According to a further developed embodiment, the material measure may include at least one reference mark, which is detected by the angle sensor and can be defined as a rotation angle zero point. Based on the reference mark, for example, the angle sensor can be used to determine when the shaft has completed a complete turn and what time was required for this.

The evaluation unit preferably supplies corresponding data to a controller in order, for example, to be able to react to a torque change by changing the drive current, setting an excitation current, initiating braking forces or the like.

LIST OF REFERENCE NUMBERS

1

wave

2

pivot bearing

3

outer ring

4

rolling elements

5

inner ring

6

machine frame

7

angle sensor

8th

Measuring standard

9

connecting cable

10

evaluation

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 69010378 T2 [0005]
• DE 112004001038 T5 [0006]

Claims (9)

Arrangement for determining the torque on a shaft ( 1 ), which in at least one pivot bearing ( 2 ), which is a frame-fixed bearing part ( 3 ) and a shaft-fixed bearing part ( 5 ), characterized in that a material measure ( 8th ) on the shaft ( 1 ) or the shaft-fixed bearing part ( 5 ) that the dimensional standard ( 8th ) of at least one frame-fixed angle sensor ( 7 ) is detected, based on a time base of the rotational angle of the shaft dependent angle signals to an evaluation unit ( 10 ) using the angle signals and the time base first the torque-dependent speed change of the shaft and therefrom, taking into account a predetermined torsional rigidity of the shaft on the shaft ( 1 ) acting torque determined. Arrangement according to claim 1, characterized in that the pivot bearing ( 2 ) is a rolling bearing and the material measure ( 8th ) on the shaft-fixed bearing ring ( 3 ) is attached. Arrangement according to claim 1 or 2, characterized in that a plurality of angle sensors ( 7 . 7 ' ) at different angular positions relative to the circumference of the shaft ( 2 ) are arranged. Arrangement according to one of claims 1 to 3, characterized in that a plurality of material measures ( 8th ) with associated angle sensors ( 7 ) axially spaced on the shaft ( 1 ), preferably in close proximity to pivot bearings ( 2 ). Arrangement according to one of claims 1 to 4, characterized in that the shaft ( 1 ) is the drive shaft of a wind turbine, a generator or a motor and that the evaluation unit ( 10 ) for determining the torque continues to use the default values for controlling the speed. Arrangement according to one of claims 1 to 5, characterized in that the material measure ( 8th ) comprises a reference mark provided by the angle sensor ( 7 ) and detected by the evaluation unit ( 10 ) can be assigned to a zero angular position. Method for determining torque on a shaft ( 1 ), which in at least one pivot bearing ( 2 ), which is a frame-fixed bearing part ( 3 ) and a shaft-fixed bearing part ( 5 ), comprises the following steps: determining the angle of rotation of the shaft ( 1 ) based on a time base with an angle sensor; Determination of a torque-dependent speed change of the shaft ( 1 ) from the determined angle of rotation and time base; - Determination of the wave ( 1 ) acting torque from the determined speed change and a predetermined torsional stiffness of the shaft. A method according to claim 7, characterized in that the angle of rotation in the immediate vicinity of one or more pivot bearing ( 2 ) the wave ( 1 ) is determined. A method according to claim 7 or 8, characterized in that for determining the angle of rotation of the angle sensor ( 7 ) a material measure ( 8th ), which is at the shaft ( 1 ) or a shaft-fixed bearing part ( 5 ) of the pivot bearing ( 2 ) is attached.

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