Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
2000-04-24
2001-11-20
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
Reexamination Certificate
active
06318187
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an apparatus for torque measurement on rotating torque shafts, in particular in motors having a torque shaft, in which optical response signals are generated in an axially offset manner at least at two points on the torque shaft by radiating light onto the rotating torque shaft, an azimuthal offset over and above a rotary movement is determined for evaluating the signals, and at least one light source and an associated device for generating and evaluating the response signals are provided.
In practice, it is required to detect the torque output by machines. With electric machines, it should be possible to perform the measurement, in particular, inside the motor housing. However, it is also necessary to be able to determine the torque accurately in the case of the use of machines in industrial plants, for example electric motors for driving rolling mills, with the aim there being to perform the measurement outside the motor.
The torque of rotating machines is frequently measured by torque measuring shafts which are mounted between the motor and the driven machine. In that case, the torque measuring shaft includes a spindle, the torsion of which is detected through a strain gauge, for example. The signal transmission is performed in that case through sliprings or telemetric methods.
It has already been proposed to determine the torque through micromechanically produced capacitors which are fitted on the torque shaft and have a capacitance that is varied by the torsion. However, that also requires telemetric signal transmission. In addition, it is also possible to use configurations with surface wave filters for torsion measurement, which is described, for example, in German Published, Non-Prosecuted Patent Application DE 195 32 601 A1.
Furthermore, German Patent DE 44 28 362 C2 proposes a method for contactless detection of the movement, in particular the rotary movement, of a machine part. To be specific, a pulsed light beam is directed onto a measuring point at which markings having a defined length that are disposed on the machine part sequentially in the direction of movement thereof pass by, and light reflected by the markings is detected and evaluated. That method develops a method previously known from UK Patent Application GB 2 093 991 A in such a way that the light beam is pulsed at a prescribed frequency and focused in such a way that upon striking the markings it generates a sequence of light points which can be counted in a simple way. It is also possible in that case to measure torque through the use of a twofold, axially offset measurement. The pulsed light beam is advantageously generated by a laser. In addition, UK Patent Application GB 2 093 992 A likewise discloses a method which operates with pulsed lasers and in which irradiation is performed in an axially offset manner at two points on the rotating shaft and the torque is determined by defining a temporal reference point for the axial offset of the response signals. That method has proved not to be functional in practice.
U.S. Pat. No. 2,586,540 discloses a torsion meter in which the shaft is optically scanned. However, German Published, Non-Prosecuted Patent Application 30 11 700 discloses an apparatus for load-dependent measurement of the torque of a torque shaft in which the torque shaft is irradiated with light in an axially offset manner and subareas which reflect radiation supply torque-dependent response signals with the twisting of the torque shaft.
In addition, German Published, Non-Prosecuted Patent Application DE 195 23 756 A1 discloses a sensor which detects the force or the torque on a working machine. The sensor is constructed as an optoelectric sensor that generates at least one light path in the case of which the quantity of light transmitted through the light path, or the magnitude and variation thereof, are a function of the force of the torque on the machine.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an apparatus for torque measurement on rotating torque shafts, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known manifold devices of this general type and which provides a practical apparatus for torque measurement that, in particular, is to be able to be used in electric machines.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for torque measurement of a rotating torque shaft of a machine, in particular motors which have a torque shaft, comprising at least two axially offset reflector systems disposed at the torque shaft; each of the reflector systems having a respective light source, the light sources generating axially offset optical response signals at least at two points of the torque shaft by radiating light onto the rotating torque shaft; each of the reflector systems having an individual concave mirror associated with a respective one of the light sources; and each of the reflector systems having an evaluation device associated with a respective one of the concave mirrors, the evaluation devices generating and evaluating the response signals by determining an azimuthal offset beyond a rotary movement.
In accordance with another feature of the invention, the concave mirror of each of the reflector systems is one of a prescribed number of similar concave mirrors concentric with the torque shaft. In accordance with a further feature of the invention, there is provided a reflection disk connected to the torque shaft and having a periphery, and the concave mirrors are fitted near the periphery of the reflection disk. In accordance with an added feature of the invention, the torque shaft has a periphery, and the concave mirrors are fitted at the periphery of the torque shaft.
In accordance with an additional feature of the invention, the light source is a continuously emitting laser. In accordance with yet another feature of the invention, the light source is a light-emitting diode.
In accordance with yet a further feature of the invention, there are provided optical elements for beam focusing which are disposed between the light source and the concave mirrors.
In accordance with yet an added feature of the invention, there is provided a device for optically separating irradiated and reflected light beams.
In accordance with yet an additional feature of the invention, there is provided an optical receiver for evaluating a reflected light beam. In accordance with again another feature of the invention, the receiver is a double photodiode. In accordance with again a further feature of the invention, the double photodiode has two diode halves, and a comparator determines an exact triggering instant when the light signal is equally strong on both of the diode halves.
In accordance with a concomitant feature of the invention, the light source is an optical transmitter, the evaluation device has a receiver, and a scanning system including the optical transmitter and the receiver is accommodated in end shields of a machine.
Mirror configurations for detecting torsion have certainly already been proposed in German Patent No. 880 510. The shaft therein is partially surface-ground for that purpose.
In addition to a device for generating response signals, the apparatus for torque measurement according to the invention includes a device for detection and evaluation. The device for generating the response signals includes at least two mutually axially offset reflector systems on the torque shaft of the machine, which in each case have individual concave mirrors. Each reflector system is formed from a prescribed number of similar concave mirrors which are either fitted on a disk, connected to the torque shaft, as a reflecting disk, or are fitted, for example, on the rotor of the motor in such a way that they lie on a circle concentrically surrounding the axis of the torque shaft.
The novel apparatus is accurate and safe against overloading. It is possible to measure acceleration and braking torques
Griepentrog Gerd
Lins Gunter
Maier Reinhard
Greenberg Laurence A.
Lerner Herbert L.
Noori Max
Siemens Aktiengesellschaft
Stemer Werner H.
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