WO2014079409A2

WO2014079409A2 - Torque measuring device and method for measuring a torque

Info

Publication number: WO2014079409A2
Application number: PCT/DE2013/000698
Authority: WO
Inventors: Herbert Meuter; Oliver Jandousek; Volker Clarenbach
Original assignee: GIF Gesellschaft für Industrieforschung mbH
Priority date: 2012-11-26
Filing date: 2013-11-26
Publication date: 2014-05-30
Also published as: DE112013005644A5; DE102012022982A1; WO2014079409A3

Abstract

The invention relates to a torque measuring device, comprising a stator, a rotor, a torque measuring pickup provided on the rotor, a signal generation device for generating a switching signal from the torque measurement signal, at least one primary coil provided on the stator, which primary coil can be energized by alternating current from a supply volatage source, at least one secondary coil provided on the rotor for supplying energy to the torque measuring pickup and the signal generation device, wherein the secondary coil voltage is induced by the primary coil, energized by the supply voltage source, in the secondary coil, at least one modulation apparatus provided on the rotor for modulating the coil current in the secondary coil, and at least one evaluation device provided on the stator, which evaluation device is designed to detect the coil current modulation induced by the modulation of the coil current of the secondary coil in the primary coil. The invention also relates to a method for measuring a torque.

Description

Torque measuring device and method for measuring a torque

[01] The invention relates to a torque measuring device and a method for measuring a torque.

[02] A stator and a rotor having torque measuring devices are known. The rotor is rotatably mounted on the torque transmitting device for measuring the respective torque, wherein the torque applied to the rotor is measured by means of a torque sensor provided on the rotor. The measured torque measurement signal is usually converted into a frequency or digital signal and then transferred without contact to a provided on the stator signal-receiving device, which is at least partially disposed around the rotor.

The contactless transmission takes place for example in a known from WO 2009/062481 AI solution by driving a provided on the rotor light emitting diode by a frequency-modulated signal by means of the measuring signal and receiving the provided by the control frequency-modulated light signal by means of a signal-receiving device in the form a photoelectric cell provided on the rotor. In the solution known from DE 10 2004 015 771 B4, the non-contact transmission of the frequency-modulated signal to the stator takes place inductively or by inductive coupling. All known solutions have in common that for the production of complex components provided or specially manufactured, accompanied by a high production cost and high production costs.

[04] The invention is therefore based on the object to provide a torque measuring device which is much cheaper to produce compared to the known solutions, and to provide a method for measuring a torque which is feasible compared to the known solutions with significantly lower cost.

CONFIRMATION COPY This object is achieved with a torque measuring device having the features of claim 1 and with a method for measuring a torque with the features of claim 9.

[06] The torque measuring device according to the invention has a torque measuring transducer provided on the rotor for measuring a torque acting on the rotor and for outputting a torque measuring signal. Furthermore, the torque measuring device according to the invention comprises a signal generating device for generating a switching signal from the torque measurement signal, at least one provided on the stator primary coil, which can be powered by a supply voltage source with alternating current, at least one provided on the rotor secondary coil, which is used to power the torque sensor and the signal generating means is provided by a secondary coil voltage of the secondary coil, wherein the secondary coil voltage is induced by the supplied by the supply voltage source primary coil in the secondary coil, at least one provided on the rotor modulation device for modulating the coil current in the secondary coil, said Modulation device for modulating the coil current in accordance with the switching signal from this can be controlled, and at least one provided on the stator evaluation, which is set by the da s modulating the coil current of the secondary coil in the primary coil induced coil current modulation to detect.

[07] The operation of the device according to the invention is based on modulating the coil current in the secondary coil according to the switching signal by means of the modulation device and detecting the current induced by modulating the coil current of the secondary coil in the primary coil coil current modulation by means of the evaluation. The modulation of the coil current in the secondary coil or the coil current modulation in the primary coil depends on the time characteristic of the torque measurement signal since the switching signal or modulation signal generated by the signal generation input is also dependent on the temporal progression of the signal Torque measuring signal depends. This mode of operation thus makes it possible, by means of a modulation of the coil current in the secondary coil, which can be carried out in a simple and practical manner, to store the information contained in the torque measurement signal on the coil Rotor acting or transmitted torque without contact to the stator or to transmit the evaluation unit. The particularly necessary for the realization of this transmission signal generating device and modulation device can be advantageously constructed and formed in a simple and practical manner, for example, from inexpensive electronic components, along with a significant reduction in manufacturing costs and manufacturing costs over the known solutions.

[08] The stator is preferably arranged at least in sections or entirely around the rotor.

[09] In a practical embodiment of the torque measuring device according to the invention, the torque measuring signal is an analog torque measuring signal or the torque measuring transducer is set up to output the measuring result as an analog torque measuring signal. Preferably, in this practical embodiment, the signal generating device is adapted to generate from the analog torque measurement signal dependent on the temporal waveform of the analog torque measurement signal switching signal or modulation signal, the switching signal or modulation signal preferably a through the analog torque measurement signal frequency-modulated carrier signal or preferably a pulse width modulated by the analog torque measurement signal carrier signal. Due to the intended frequency modulation or pulse width modulation, distortions due to amplitude changes, which can occur due to environmental influences, can advantageously be avoided during transmission.

[10] In the above practical embodiment, the signal generator may also include a digital-to-analog converter for converting the analog torque measurement signal into a temporal waveform-dependent digital switching signal. Even by digitizing the analog torque measurement signal, adulterations due to amplitude changes during transmission, which can occur as a result of environmental influences, can advantageously be avoided.

[1 1] In a preferred embodiment, the modulation device comprises a switching device provided on the rotor for short-circuiting the secondary coil, which can be controlled by the switching signal for time-sequential short-circuiting of the secondary coil is, wherein the evaluation device is adapted to detect the induced by the temporally successive short-circuiting in the primary coil coil current modulation. The modulation of the coil current of the secondary coil by short-circuiting by means of a switching device provided on the rotor can be realized in a very simple and practical manner by means of one or more electronic components, such as in particular by means of a transistor.

For measuring or detecting the torque transmitted by a shaft, the rotor may preferably be designed in the form of a flange which can be fastened rotationally fixed on a shaft.

[13] Due to the simple and inexpensive construction of the inventive torque measuring device set forth above, this is particularly suitable for torque measurement or torque detection of rotatable parts on devices that are used in everyday life - ie in particular for such devices, in a large variety are produced and in which a cost-optimized production is in the foreground. The torque measuring device according to the invention for torque measurement or torque detection on a pedal of a bicycle or for torque measurement or torque detection in the region of the pedals of a bicycle can particularly preferably be provided.

[14] The method according to the invention for measuring a torque comprises the following steps: (A) measuring a torque acting on a rotor, (B) generating a switching signal dependent on the time profile or the time profile of the measured torque, (C) modulating a coil current in a secondary coil according to the switching signal, and (D) detecting the coil current modulation induced by modulating the coil current of the secondary coil in a primary coil.

[15] By naming the steps with the letters A to D no exclusive binding to a chronological order is pursued. The letters serve only for naming or marking the steps. In particular, the method according to the invention can be carried out in such a way that steps A to D are carried out at the same time or substantially simultaneously. [16] The method according to the invention can be carried out in particular using the torque measuring device according to the invention. As can be seen from the above for the torque measuring device according to the invention, the method according to the invention can be carried out in comparison to the known solutions with significantly lower cost usage. In particular, step C of the method according to the invention can be realized in a very simple and practical manner by means of a modulation device provided on the rotor.

[17] In a practical embodiment of the method according to the invention, a signal is generated from the coil current modulation detected in step D, from which the time profile of the measured torque can be provided by multiplication by a constant factor. Since the coil current modulation in the primary coil-as a result of the dependence of the switching signal on the time profile of the measured torque or the time waveform of the measured torque-depends on the time profile of the measured torque, advantageously a signal can be generated by conversion or signal processing from which the time profile of the measured torque can be provided by multiplication by a constant factor.

[18] Preferably, the signal generation of the switching signal by the signal generating device is ratiometric, so that only a measurement of the change of the torque measurement signal is determined. Changes can be determined in terms of construction and energy with little effort, and consequently according to the task mentioned above.

[19] A simple determination of changes in the torque measurement signal takes place in particular if it is permitted that a reference voltage of the signal generation device varies with the secondary coil voltage. In particular, it is then possible to dispense with highly complex smoothing mechanisms, since corresponding fluctuations in the voltage for determining the torque measurement signal are subject to the same fluctuations, so that overall the structural and energy costs can be limited to a minimum, as to corresponding smoothing or calibrating Measures that compensate for such voltage fluctuations can be dispensed with. A high signal yield and therefore a structurally simple structure, which can dispense with complex signal generation processes and amplifier systems, takes place when the primary coil is energized with alternating current between 40 kHz and 200 kHz or is energized. At these frequencies, there is a sufficient range of the signal even under adverse system conditions, so that reliable signal transmission can take place. Also, such a frequency already carries enough energy to provide the rotor reliable, without the range of the corresponding signal transmission would be too low, which is to be feared at higher frequencies. On the other hand, the above-mentioned frequency band allows a sufficiently fast frequency, to which then a signal still with sufficient signal density, for example between 100 Hz and 900 Hz.

As a frequency which is impressed on the primary coil, in particular frequencies above 40 kHz or more than 60 kHz and in particular more than 75 kHz have proven successful in practice, as a result, a sufficient signal density and a good energy density can be ensured. On the other hand, in particular frequencies below 200 kHz or below 150 kHz or below 90 kHz are advantageous because they still allow a sufficient range with reasonably simple handling of the frequencies.

[23] It is understood that the features of the solutions presented above or in the claims can be used both individually and jointly, the latter correspondingly resulting in an accumulation of the advantages of the corresponding features.

[24] Further advantages, objects and characteristics of the present invention will be explained with reference to the following description of attached drawings. 1 shows a sectional view of an embodiment of a torque measuring device according to the invention, and

Fig. 2 is a very schematic representation of the embodiment;

3 shows by way of example the signal course at the transmitter under a load modulation of the supply voltage; and

Fig. 4 corresponding to the waveform at the receiver with the decoded raw signal. [25] The exemplary embodiment of a torque measuring device 10 according to the invention shown in a sectional view in FIG. 1 has a stator 12 and a rotor 14. For measuring or detecting the torque transmitted by a shaft, the rotor 14 is designed in the form of a flange 14 which can be fastened on a shaft so as to be fixed against rotation or on a shaft. On the rotor 14, a torque transducer 16 is provided with strain gauges 18. With the strain gauges 18, a distortion of the formed in the form of a flange rotor 14, which is proportional to the acting or transmitted torque, are detected.

The fixed stator 12 is arranged in sections around the rotor 14. On the stator 12, a primary coil 20 is provided which can be supplied with current from a supply voltage source (not shown in FIG. 1). On the rotor 14, a secondary coil 22 is provided. An electronics 24 also provided on the rotor 14 includes, inter alia, a signal generating device for generating a switching signal from the torque measuring signal of the torque sensor and a modulation device for modulating the coil current in the secondary coil (not shown in detail in FIG. 1), wherein the modulation device for modulating the coil current according to the switching signal from this is controllable.

[27] With reference to FIG. 2, which shows a very schematic representation of the embodiment, the structure of the torque measuring device according to the invention will be explained in more detail below. [28] The torque transducer 16 provided on the rotor 14 for measuring a torque applied to the rotor 14 and for outputting an analog torque measurement signal comprises a strain gauge bridge 26.

[29] The signal generator 28 for generating a switching signal from the analog torque measurement signal includes an amplifier 30 and a controller 32. The controller 32 has a pulse width modulation function and is configured after amplification of the analog torque measurement signal by the amplifier 30 to generate from the amplified torque measurement signal dependent on the temporal waveform of the analog torque measurement signal switching signal, wherein the switching signal in the form of a pulse width-modulated by the analog torque measurement signal carrier signal is trained. A typical frequency of this carrier signal is for example in a frequency band between 100 Hz and 900 Hz. This ensures a sufficient signal density, without affecting the other transmission parameters, in particular without the power supply of the rotor 14. Alternatively, the controller 32 may also have a frequency modulation function and be configured to generate, after amplification of the analog torque measurement signal by the amplifier 30 from the amplified torque measurement signal, a switching signal that is frequency modulated in the form of a frequency modulated by the analog torque measurement signal Carrier signal is formed. A further alternative may provide that the controller 32 comprises a digital-to-analog converter provided for converting the analog torque measurement signal amplified by the amplifier 30 into a timing signal-dependent digital switching signal.

[31] The primary coil 20 provided on the stator 12 can be supplied with alternating current from a supply voltage source 34, the supply voltage source 34 having a controller 36 and a transistor 38 serving as switching means 38 for providing the corresponding AC voltage in the desired AC voltage frequency. typically eg at about 40 kHz to 200 kHz, preferably at about 80 kHz, may be - is controlled by the controller 36.

[32] The secondary coil 22 provided on the rotor 14 is provided for energizing the torque transducer 16 and the signal generator 28 by a secondary coil voltage of the secondary coil 22, the secondary coil voltage being from the primary coil 20 energized by the supply voltage source 34 in the secondary coil 22 is induced. For smoothing and rectifying the secondary coil voltage, an electronic device 40 with smoothing function and rectifying function is also provided.

[33] The modulation device 42 provided on the rotor 14 for modulating the coil current in the secondary coil 22 is controllable for modulating this coil current according to the switching signal thereof. The likewise supplied by the secondary coil voltage of the secondary coil 22 with energy modulation device 42 comprises a switching Device in the form of a transistor 44 for shorting the secondary coil 22, which is the the switching signal for temporally successive short-circuiting of the secondary coil 22 can be controlled.

[34] The signal generating device 28 is ratiometric in this embodiment, whereby only measured in the strain gauge bridge 26 voltage changes are measured in proportion. These measurements make it possible, in particular, to determine the ratio independently of any voltage fluctuations of the secondary coil voltage, without requiring any additional metrological effort. In particular, in this embodiment, the reference voltage of the amplifier 30 and the controller 32, which are both part of the signal generating device 28, equated the voltage supply of the strain gauge bridge 26, so that a ratiometric measurement can be performed directly and without further electronic aids. Due to the ratiometric measurement, the measurement result provided by the controller 32 is independent of any voltage voltages, since the voltage ratios of the voltage fluctuations provided by the strain gauge bridge 26 as a measurement fluctuate equally.

[35] The rectifying function of the above electronic device 40 in this embodiment makes it possible to drive the transistor 44 to short-circuit the secondary coil 22, which operates only when the current is rectified. The electronic device 40 further comprises - not shown - capacitors and diodes to the short-circuiting of the secondary coil 22 through the transistor 44 in its possibly damaging effect on the controller 32 and the amplifier 30 of the signal-generating device 28 and in his possibly Damaging effect on the torque transducer 16 to weaken advantageous. [36] An evaluation device 46 provided on the stator 12 is arranged to detect the coil current modulation induced by modulating the coil current of the secondary coil 22 in the primary coil 20, ie the coil current modulation induced by the temporally successive short-circuiting in the primary coil 20 , To avoid the short-circuit To separate in the primary coil 20 induced coil current modulation of higher-frequency components, the evaluation device 46 has a low-pass filter (not shown in detail).

The embodiment of the torque measuring device 10 according to the invention shown in FIGS. 1 and 2 can accordingly be used in particular for carrying out an embodiment of a method according to the invention for measuring a torque, which comprises the following steps:

(A) measuring the torque acting on the rotor 14,

(B) generating a dependent of the time course of the measured torque switching signal by the signal generating means 28, (C) modulating a coil current in the secondary coil 22 according to the switching signal by the modulation device 42, and

(D) detecting the current induced by modulating the coil current of the secondary coil 22 in the primary coil 20 coil current modulation by the evaluation device 46. For example, as exemplified in Figures 3 and 4, by between two measuring points 48 and 50 of Signal transmission on the transmitter side, ie on the rotor side, is measured (see Figure 3), a torque measurement signal corresponding to the supply voltage of about 80kHz with 250 Hz to 450 Hz transmitted accordingly, for example, at a measuring point 52 measured to ground (see Figure 4 above) and correspondingly decoded (see Fig. 4 below). In this way, a reliable evaluation succeeds in particular with minimal structural and energy costs.

LIST OF REFERENCE NUMBERS

10 torque measuring device

12 stators

14 rotor

16 torque transducers

18 strain gauges

20 primary coil

22 secondary coil

24 electronics

26 Strain gauge bridge

28 signal generating device

30 amplifiers

32 controllers

34 supply voltage source

36 controllers

38 transistor

40 electronic device

42 modulation device

44 transistor

46 E nputing

48 Measuring point signal course transmitter

50 measuring point signal course transmitter

52 Measuring point signal course receiver

Claims

Torque measuring device (10), with

- a stator (12),

- a rotor (14),

- a torque sensor (16) provided on the rotor (14) for measuring a torque acting on the rotor (14) and for outputting a torque measurement signal,

- a signal generating device (28) for generating a switching signal from the torque measurement signal,

- at least one primary coil (20) provided on the stator (12), which can be supplied with alternating current from a supply voltage source (34),

- at least one secondary coil (22) provided on the rotor (14), which is provided for supplying energy to the torque measuring sensor (16) and the signal generating device (28) by a secondary coil voltage of the secondary coil (22), the secondary coil voltage of the primary coil (20) energized by the supply voltage source (34) is induced in the secondary coil (22),

- at least one modulation device (42) provided on the rotor (14) for modulating the coil current in the secondary coil (22), the modulation device (42) being controllable by the latter for modulating the coil current according to the switching signal,

- At least one evaluation device (46) provided on the stator (12), which is set up to detect the coil current modulation induced by modulating the coil current of the secondary coil (22) in the primary coil (20).

2. Torque measuring device (10) according to claim 1, characterized in that the signal generating device (28) generates a switching signal ratiometrically from the torque measuring signal.

Torque measuring device (10) according to claim 2, characterized in that a reference voltage of the signal generating device (28) fluctuates with the secondary coil voltage.

Torque measuring device (10) according to one of the preceding claims, characterized in that the primary coil (20) can be energized by the supply voltage source (34) with alternating current between 40 kHz and 200 kHz.

Torque measuring device (10) according to one of the preceding claims, characterized in that the torque measurement signal is an analog torque measurement signal.

Torque measuring device (10) according to claim 5, characterized in that the signal generating device (28) is set up to generate from the analog torque measurement signal a switching signal which is dependent on the time signal curve of the analog torque measurement signal.

Torque measuring device (10) according to claim 6, characterized in that the signal generating device 828) has a digital-to-analog converter for converting the analog torque measuring signal into a digital switching signal that is dependent on the time signal curve.

Torque measuring device (10) according to claim 6, characterized in that the switching signal is a carrier signal frequency modulated by the analog torque measurement signal.

Torque measuring device (10) according to claim 6, characterized in that the switching signal is a carrier signal pulse width modulated by the analog torque measurement signal.

Torque measuring device (10) according to one of the preceding claims, characterized in that the modulation device (42) comprises a switching device (44) provided on the rotor (14) for short-circuiting the secondary coil (22), which is supplied by the switching signal for successive short-circuiting the secondary coil (22) can be controlled, the evaluation device (46) being set up to detect the coil current modulation induced by the successive short-circuiting in the primary coil (20).

Torque measuring device (10) according to one of the preceding claims, characterized in that the rotor (14) is designed in the form of a flange which can be fastened to a shaft in a rotationally fixed manner.

Method for measuring a torque, comprising the following steps:

(A) Measuring a rotor

(14) acting torque,

(B) generating a switching signal that is dependent on the time course of the measured torque,

(C) modulating a coil current in a secondary coil (22) according to the switching signal, and

(D) detecting the coil current modulation induced by modulating the coil current of the secondary coil (22) in a primary coil (20).

Method according to claim 12, characterized in that a signal is generated from the coil current modulation detected in step (D), from which the time course of the measured torque can be provided by multiplication by a constant factor.

Method according to claim 12 or 13, characterized in that the switching signal is generated ratiometrically, in particular using a reference voltage that fluctuates with a secondary coil voltage.

15. The method according to any one of claims 12 to 14, characterized in that the primary coil (20) is energized with alternating current between 40 kHz and 200 kHz.