DE102010034638A1 - Torquemeter - Google Patents

Abstract

Torque measuring shaft, which on the one hand enables high measuring sensitivity with a large bandwidth and on the other hand is designed to be gentle on the material with at least two measuring ranges, a first measuring range with high sensitivity and low torsional rigidity and a second measuring range with low sensitivity and high torsional rigidity.

Description

The invention relates to a torque measuring shaft.

From the EP 1 074 826 B1 and the DE 40 09 286 A1 torque measuring shafts are known, which have cylindrical shaft sections, in which pocket-shaped recesses or membranes are incorporated and wherein strain gauges (DMS) are applied for measuring a voltage proportional to the applied torque in this membrane. Torque shafts according to this prior art usually have a defined linear measuring range and are designed for a specific maximum torque applied to the torque measuring shaft. A disadvantageous side effect of a torque measuring shaft designed for a large measuring range was the fact that in the range of very small torques to be measured, the resolution of the electrical or electronic signal generated via the strain gauge is very small.

In order to provide a sufficiently high resolution of the measuring signal even in a small measuring range, torque measuring shafts, for example from the DE 10 2007 005 894 A1 known, which have recesses in the cylindrical part of the torque measuring shaft, through which membranes with different, preferably two, wall thicknesses are formed. As a result, in each case sensors with different sensitivities are available in accordance with the applied torque and the angle of rotation associated therewith. The disadvantage of such torque measuring waves is the fact that, at high angles of rotation, the thinner and more sensitive diaphragms are likewise further loaded when the load or the applied torque is further increased. Thus, the membranes set aside for small measuring ranges can be subjected to an excessive load, whereby these membranes may already be plastically stretched and a reproducible measurement of the applied torque is no longer possible.

It is therefore an object of the present invention to provide a torque measuring shaft, which on the one hand enables a high measuring sensitivity with a large bandwidth and on the other hand is designed to be gentle on the material.

As a solution, a torque measuring shaft is proposed, which is characterized by at least two measuring ranges, a first measuring range with a high sensitivity and a low torsional stiffness and a second measuring range with a low sensitivity and a high torsional stiffness.

The advantage of this proposed torque measuring shaft is that the torque measuring shaft has two measuring ranges with different torsional stiffnesses, whereby the torsion angle occurring at the torque measuring shaft is limited and thus the first measuring range with the high sensitivity is no longer loaded unduly high.

Thus, the means for detecting the torque, which may consist of resiliently active elements or membranes, are designed for the respectively intended measuring range. The design can then be such that the resilient elements can each have linear characteristics and are not claimed in a non-linear or plastic range.

Also already known torque measuring shafts have resilient elements that allow under torque movement, which then ultimately lead to a proportional to the torque measurement signal. These spring-acting elements will ultimately have non-linear characteristics, which - at least before a break - rise sharply. However, the measuring ranges of such torque measuring shafts are designed for such small rotational angles that these regions of the resilient elements are not reached. In this respect, in the present context of a linear characteristic and a corresponding linear behavior is spoken if within the desired measurement accuracy, a linear relationship between torque and measurement signal can be assumed, which can then be used for example by a corresponding equation for interpolation purposes.

The loads occurring in the two measuring areas on the resilient elements extend proportionally, preferably linearly proportional, to a torque applied to the torque measuring shaft. Since the applied torque to the torque measuring shaft generates a torque angle or torsion angle proportional to this torque, it is further proposed that the torque measuring shaft is characterized by means for increasing the rotational stiffness when a defined rotational angle is exceeded. Advantageously, by this measure, on the one hand, the first measuring range can be delimited to the second measuring range by using a defined angle of rotation for the delimitation, and on the other hand, the rotational stiffness is increased from this defined angle of rotation to the extent that the means for measuring the torque in the first measuring range is not be subjected to an unduly high load.

In order to increase the torsional stiffness of the torque measuring shaft from a defined angle of rotation in the simplest possible way, it is therefore further proposed that the rotational stiffness increasing means comprise a stop. By an appropriately aligned stop the entire measuring range can be divided into two measuring ranges, wherein preferably the first measuring range has a linear characteristic and the second measuring range has a linear characteristic and thus the entire measuring range has an overall characteristic with partially linear dependencies.

Alternatively or cumulatively to a stop, it is proposed that the torsional stiffness increasing means comprise a plant. A system as a torsional stiffness enhancer has the advantage that the change in the overall characteristic of the torque shaft may have a steady course, wherein the dependence of the rotational angle of the applied torque no longer necessarily have to have a linear course. For example, the profile of the angle of rotation of the applied torque in a range of smaller torques can have a high sensitivity and thus a high rotational angle change as a function of the torque change and in a second measuring range for higher torques have a smaller rotational angle change in response to the torque change. In this respect, it is understood in the present context that the term "two measuring ranges with different torsional stiffness" in the present context does not necessarily have to provide a discontinuous transition between the two measuring ranges, as will usually be the case in a stop.

Cumulatively or alternatively, the invention proposes a torque measuring shaft, which is characterized by at least one arranged between two flanges spring element with an effective spring length and means for changing the spring length as a function of the rotation angle to provide different measuring ranges.

This solution has the advantage that the rotation angle of the torque measuring shaft, in contrast to the above solution or other known solutions is no longer dependent only on the torsional stiffness of the torque measuring shaft, but that of the torque-dependent rotation angle of the torque measuring shaft is a function of the free spring length of Can be spring element, in which case the spring stiffness of this spring element can remain substantially constant over the entire measuring range. In this context, it is understood that the change of the spring length can be made depending on the specific requirements substantially continuously or even at certain points discontinuous.

In particular, a torque measuring shaft is accordingly proposed, which is characterized in that the spring length is shortened with increasing rotation angle. This has the advantage that the rotation angle change in a measurement range with low torque has a higher sensitivity to a torque change and that the rotation angle change in a measurement range with higher torque has a lower sensitivity to a torque increase.

It is understood that the spring stiffness need not remain constant over the length of the spring. It is also possible, for example, the use of a spring with variable torsional or bending stiffness as a function of the free spring length.

The object of the present invention is also achieved by a torque measuring shaft, which is characterized by a centrally disposed between two flanges and a measuring rod by a radially outside the measuring rod between the flanges effective spring arrangement.

As a result, a torque measuring shaft can advantageously be provided in which the means for measuring the angle of rotation are provided independently of the means for generating a torque-rotational angle characteristic. In this case, it is no longer necessary in particular to provide different membranes for different measuring ranges, since only measuring transducers, for example strain gauges, are required for the entire measuring range on the measuring rod used. Due to the separate spring arrangement, the torque / rotation angle characteristic curve can be selected such that the transducers can operate optimally. Here, the radially inwardly provided arrangement of the measuring rod has the advantage that the load on the transducers on the one hand by small Verdrehlängen caused by the small radius on which the transducers must be effective, and on the other hand by low centrifugal forces, also due to the small radius, can be minimized.

To provide a constructed according to this principle torque measuring shaft is further proposed that the spring assembly comprises at least two axially aligned spring elements. This implements the advantage that the spring elements used can be distributed uniformly on the circumference, so that by the torsion of the torque measuring shaft no skewed bend outside the axis of symmetry, at the Torque measuring shaft itself, can arise, and so that the spring elements can be used by their axial alignment as a bending springs with a linear in a large range spring characteristic. In contrast, torque measuring shafts according to the prior art generally use a cylindrical tube which is subjected to torsion.

In this context, it should be mentioned that the measuring rod itself also influences the torque / rotation angle characteristic or is resiliently effective in a correspondingly restoring manner. However, this influence can be determined as desired by the suitable choice of the springs and by the relatively small radius of the measuring rod.

Furthermore, this torque measuring shaft may have a circumferential direction with at least one spring element arranged system. In this way, advantageously, the axially aligned spring rest against the system such that by means of the system, the free spring length of the spring, instead of the bending or torsional stiffness of the spring, is changed.

In particular, beam springs can be used as spring elements. This embodiment offers the further advantage that in a torque measuring shaft with axially arranged spring elements, which are pronounced as bar springs, preferably uniaxial tensile or compressive stresses occur instead of possibly multiaxial stresses. In this way, the mechanical characteristic of the torque measuring shaft can be favorably influenced, which in turn increases the accuracy of the torque measuring shaft as a whole, since electronic adjustment parameters no longer have to be used to the same extent as in torque measuring shafts according to the prior art.

Preferably, the beam spring is radially wider than in the circumferential direction. This has the advantage that the torque measuring shaft can be designed very rigid in total constant torsional stiffness.

According to a further aspect of the invention, alternatively or cumulatively, a torque measuring shaft is proposed, which is characterized by two flanges, which are arranged rotatable within the intended measuring range by more than 0.5 ° against each other.

This has the advantage that the large angle of rotation enables both a good resolution and a large measuring range, in particular if the characteristic curve of the torque measuring shaft increases sharply at larger angles of rotation, thus in particular also leaves the linear characteristic range. By a degressive embodiment of the characteristic, a high resolution can be achieved in a lower measuring range by means of a large gradient and higher torques can be measured in an upper measuring range, in which the further rotation of the shaft is limited due to a smaller gradient of the characteristic.

It is understood that the features of the solutions described above or in the claims can optionally also be combined in order to implement the advantages in a cumulative manner.

Further advantages, objects and features of the present invention will be explained with reference to the following description of exemplary embodiments, which are shown in particular in the appended drawing. In the drawing show:

1 a first torque measuring shaft in a schematic view in which a first measuring rod is more sensitive and is bridged from a certain angle of rotation, by stops over the entire spring length is shortened;

2 a second torque measuring shaft in a schematic view in which a first measuring rod is more sensitive and is bridged from a certain angle of rotation by stops the entire spring length is shortened;

3 a spring characteristic (torque angle of rotation) of the measuring rods of the second torque measuring shaft;

4 a third torque measuring shaft in a schematic view in which a dipstick is more sensitive than a measuring sleeve and is bridged from a certain angle of rotation, by stops the entire spring length is shortened;

5 a spring characteristic (torque rotation angle) of the measuring rod and the measuring sleeve of the third torque measuring shaft;

6 a fourth torque measuring shaft in a schematic view in which a centrally arranged measuring rod and externally arranged, first provided at a certain angle of rotation via stops effective spring rods;

7 a spring characteristic (torque rotation angle) of the fourth torque measuring shaft;

8th a fifth torque measuring shaft in a schematic view, in which a centrally arranged measuring rod and externally arranged, above a certain angle of rotation via stops impacted spring bars are provided which run against equipment;

9 a spring characteristic (torque rotation angle) of the fifth torque measurement shaft;

10 a sixth torque measuring shaft in a schematic view in which a centrally arranged measuring rod and externally arranged round spring rods are provided, which run against systems which are already arranged very close to the spring bars.

1 shows a torque measuring shaft 10 with a flange 11 and a flange 12 by means of which the torque measuring shaft 10 can be integrated in an existing drive train. The torque measuring shaft shown 10 also has an intermediate flange 15 and another intermediate flange 16 , which divides the overall arrangement into two sections. In a first portion of the torque measuring shaft 10 , between the flange 11 and the intermediate flange 16 , is a first dipstick 13 arranged. This first dipstick 13 has a much smaller diameter than that in the second portion of the torque measuring shaft 10 located second dipstick 14 , Due to the smaller diameter of the first measuring rod 13 is therefore a higher sensitivity to torque on the first dipstick 13 present, whereby preferably small torques with high resolution can be measured on this dipstick. Furthermore, there are between the flange 11 and the intermediate flange 16 the attacks 17 and 18 which rest upon reaching a defined angle of rotation to each other, so that a rotation of the first measuring rod 13 is prevented in a further increase of the torque and thus the first portion of the torque measuring shaft 10 between the flange 11 and the intermediate flange 16 a much higher, preferably infinitely high, torsional rigidity than the second region of the torque measuring shaft 10 between the flange 12 and the intermediate flange 15 having.

The second part of the torque measuring shaft 10 between the flange 12 and the intermediate flange 15 points through the second dipstick 14 , which has a much larger diameter than the dipstick 13 has, one opposite the first dipstick 13 much higher torsional stiffness. Due to this higher torsional rigidity of the second measuring rod 14 is the second part of the torque measuring shaft 10 suitable for measuring high torques at a low resolution. The second part of the torque measuring shaft 10 between the flange 12 and the intermediate flange 15 thus has a linear over the entire measurement range characteristic curve, by means of which the rotation angle is related to the applied torque.

2 shows a torque measuring shaft 20 as another embodiment with a flange 21 and a flange 22 , by means of which the torque measuring shaft 20 can be inserted in an existing drive train. Between the flanges 21 and 22 In turn, there are two dipsticks, a first dipstick 23 and a second dipstick 24 , which merge into each other and thus represent two series-connected torsion springs. Furthermore, the torque measuring shaft 20 or the second dipstick 24 an intermediate piece 26 on, which in turn with an intermediate flange 25 connected is. The flange 21 includes several attacks 27 to which the intermediate flange 25 can apply, provided that a corresponding angle of rotation between the flanges 21 and 22 the torque measuring shaft 20 is present.

Similar to the torque measuring shaft 10 be at the Drehmonentmesswelle 20 at an applied torque, the measuring rods 23 and 24 twisted in linear dependence on the applied torque. Here's the dipstick 23 a much smaller diameter than the dipstick 24 , causing the dipstick 23 has a much greater sensitivity to an applied torque, and the dipstick 23 can be used for small torques at a very high measurement resolution. If there is a rotation of the torque measuring shaft 20 due to a higher applied torque, beats the intermediate flange 25 at the stop 27 , thereby further rotating the first measuring rod 23 is prevented and the entire applied torque only on the second dipstick 24 is directed. High torques are in this range over the second dipstick 24 recorded and fed to a corresponding measuring device. Also this torque measuring shaft 20 can be formed such that the characteristics of the individual measuring rods, the first measuring rod 23 and the second dipstick 24 , Sectional linear or proportional to the applied torque are executed.

3 shows a characteristic for a torque measuring shaft after the 1 and 2 , Herein the twist angle α is plotted against the applied torque T. As also clear herein, the first dipstick has 23 a characteristic divided into two sections 23A in which the first section has a very high gradient, ie a high sensitivity to an applied torque, and a gradient of 0 in a second partial section. It becomes clear that the first dipstick 23 is not further loaded from a certain applied torque and thus the measuring device located on this dipstick no Overloading is subjected. The dipstick 24 has in contrast a characteristic curve 24A Although, which has a much lower slope, so also a much lower sensitivity to torque, but is just hereby suitable for the measurement of high torques. The characteristic 24A of the second measuring rod 24 runs steadily and linearly over the entire measuring range.

The torque measuring shafts 10 . 20 then have correspondingly an overall characteristic in which the characteristics 23A and 24A are superimposed additively.

4 shows a torque measuring shaft 30 with a flange 31 and a flange 32 , by means of which the torque measuring shaft 30 can be integrated into an existing drive train. The flange 31 is operatively connected to a measuring sleeve 34 , which in turn attacks 37 and by means of this in the second flange 32 empties. With the stop 37 is still an intermediate piece 36 connected, which at its the stop 37 opposite end an intermediate flange 35 having. Also, the torque measuring shaft has 30 a dipstick 33 on which the intermediate flange 35 and the flange 32 operatively couples. The dipstick 33 is, similar to the previous embodiments, intended to have a low on the torque measuring shaft 30 to measure applied torque over the rotation angle caused by this torque. The dipstick 33 is also over the flange 35 and the intermediate piece 36 in series with the measuring sleeve 34 connected. Now reach that on the torque measuring shaft 30 applied torque a defined value, the stopper strikes 37 on the flange 32 on, causing the dipstick 33 is bridged and the applied torque only via the measuring sleeve 30 is transmitted. Thus, the torque measuring shaft shown in this figure 30 also two measuring ranges, wherein a first measuring range has a characteristic curve with a high gradient for low torques at a high measuring resolution and a second measuring range has a characteristic curve with a low gradient, thus also a lower sensitivity, for high torques.

The dependencies of the rotation angle of the measuring rod 33 and the measuring sleeve 34 opposite to the torque measuring shaft 30 applied torque, that shows in 5 illustrated diagram. Here again is the characteristic 33A the dipstick 33 assigned, in which a first region with a high sensitivity to torque and a second region with a non-increasing angle of rotation can be seen. This makes it clear that the dipstick 33 is preferably used for a measurement of low applied torques. The measuring range for high torques is determined by the measuring sleeve 34 assigned characteristic 34A shown. The characteristic 34A has in contrast to the characteristic 33A an up to certain torques lower but overall steady slope, which is linear over the entire measuring range. The measuring sleeve 34 Thus, similarly to the above-explained embodiments, it has a large torque measuring range at a low resolution, in which both partial characteristics are also used here 33A and 33B be superimposed additively.

Another torque measuring shaft 40 is in 6 represented, which in turn a flange 41 and a flange 42 has, by means of which the torque measuring shaft 40 can be integrated into an existing drive train. In contrast to the embodiments explained above, the torque measuring shaft includes 40 just a single central dipstick 43 , The central dipstick 43 connects directly the flange 41 with the flange 42 and thus measures the entire on the torque measuring shaft 40 applied torque. The torque measuring shaft 40 moreover has spring bars arranged axially relative to the torque measuring shaft 48 on. The spring bars 48 are radially outward on the torque measuring shaft 40 arranged and each have a stop 47 on which in the flange 42 intervention. Upon reaching a limit torque and an associated rotation angle beat the attacks 47 on the flange 42 , which causes an increase in the torsional rigidity of the torque measuring shaft 40 comes. Due to the torsional stiffness increase, the torque measuring shaft 40 less sensitive to torque, causing a further rotation of the torque measuring shaft and the central measuring rod 43 is difficult. This again results in a division of the measuring range into two partial regions, a first partial region for low torques with a high resolution and a second partial region for high torques with a low resolution. A particularly noteworthy advantage of this embodiment is the fact that only one measuring device is required for both torque measuring ranges, since both measuring ranges are detected by the decoupling of the measuring device from the device for increasing the rotational stiffness by means of a measuring device.

7 shows an example of a characteristic 40A the torque measuring shaft 40 , Herein again, a first portion is visible in which the slope, so the sensitivity of the torque measuring shaft to torque is very high and a second portion in which the sensitivity is lower because of the small slope. It is noticeable here that the entire measuring range by a characteristic can be mapped, since in the torque measuring shaft 40 only one transducer is used. Thus, no device for superimposing or evaluating two individual measured values is required. Likewise, for the same reason, the possibility of erroneous measurement is reduced, since a shift or drift of the measured value and a calibration of the torque measuring shaft necessary for this purpose 40 only required at a measuring device.

Another embodiment of a torque measuring shaft shows 8th in which the torque measuring shaft 50 with the flange 51 and flange 52 is shown, by means of which the torque measuring shaft can be integrated into an existing drive train. Between the flange 51 and the flange 52 In turn, there is a central dipstick 53 which the flange 52 and the flange 51 Actively connects and the entire on the torque measuring shaft 50 applied torque detected. Also this torque measuring shaft 50 has axial and parallel to the central dipstick 53 arranged spring bars 58 which also between the flange 51 and the flange 52 are arranged on and on the torque measuring shaft 50 applied torque torsional resistance. The acting as a beam spring spring rods 58 bend under an applied torque and start with increasing deformation at the plant 59 to rest. Due to the gradual concern with the system 59 experience the spring bars 58 a shortening of their effective spring length, which leads to a stiffening of the torque measuring shaft 50 comes. The increasing with increasing applied torque stiffening of the torque measuring shaft 50 has a degressive rotation angle torque characteristic of the torque measuring shaft 50 result. Because the spring bars 58 in a relaxed state a small distance to the plants 59 exhibit, form these plants 59 first attacks in the moment in which it comes to a first contact. The relatively small distance and the low angle at which this contact takes place require that the slope at this point changes only slightly discontinuous.

9 shows a diagram with a characteristic 50A the torque measuring shaft 50 , It becomes clear that with a very small applied torque T, the characteristic of the torque measuring shaft 50 has a high slope and by means of this a high resolution of the rotation angle α is possible. With increasing applied torque T, the sensitivity of the torque measuring shaft gradually decreases due to the falling slope of the characteristic 50A , The degressive change of the characteristic curve 50A Thus, in contrast to the previous embodiments, a continuous characteristic result.

10 shows a further embodiment of a torque measuring shaft according to the invention. The shown torque measuring shaft 50 has, as the embodiments described above, a flange 61 and a flange 62 for integration of the torque measuring shaft 60 in a drive train. Between the two flanges 61 and 62 is the central measuring rod 63 arranged to measure an applied torque. The dipstick 63 , the spring bars 68 as well as the plant body 69B are arranged axially to the axis of rotation of the torque measuring shaft. The spring bars 68 , which in a radially outer region of the torque measuring shaft 60 are arranged, deform under a tangential to the axis of the torque measuring shaft 60 acting force and cause by their resistance to bending of the torque measuring shaft 60 assigned characteristic.

By resulting from the applied torque deformation of the spring rods, these begin to the plants 69 , which on an outer surface of the plant body 69B are arranged to create. This results in a shortening of the free spring length of the spring rods 68 and consequently a stiffening of the entire torque measuring shaft 60 , whereby the in 9 shown characteristic results.

LIST OF REFERENCE NUMBERS

10

Torquemeter

11

flange

12

flange

13

first dipstick

14

second dipstick

15

Wafer

16

Wafer

17

attack

18

attack

20

Torquemeter

21

flange

22

flange

23

first dipstick

23A

Characteristic of the first dipstick 13 . 23

24

second dipstick

24A

Characteristic of the second dipstick 14 . 24

25

Wafer

26

connecting piece

27

attack

30

Torquemeter

31

flange

32

flange

33

dipstick

33A

Characteristic of the dipstick 33

34

measuring sleeve

34A

Characteristic of the measuring sleeve 34

35

Wafer

36

connecting piece

37

attack

40

Torquemeter

40A

Characteristic of the torque measuring shaft 40

41

flange

42

flange

43

central dipstick

47

attack

48

spring bar

50

Torquemeter

50A

Characteristic of the torque measuring shaft 50

51

flange

52

flange

53

central dipstick (dashed line)

57

Stop (numbered as an example)

58

spring bar

59

Annex (numbered as an example)

60

Torquemeter

61

flange

62

flange

63

central dipstick

68

Spring bar (numbered as an example)

69

Annex (numbered as an example)

69B

Investment body (numbered as an example)

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

• EP 1074826 B1 [0002]
• DE 4009286 A1 [0002]
• DE 102007005894 A1 [0003]

Claims (12)

Torque measuring shaft, characterized by at least two measuring ranges, a first measuring range with a high sensitivity and a low torsional stiffness and a second measuring range with a low sensitivity and a high torsional stiffness. Torque measuring shaft according to claim 1, characterized by means for increasing the rotational stiffness when a defined angle of rotation is exceeded. Torque measuring shaft according to claim 2, characterized in that the means for increasing the rotational stiffness comprise a stop. Torque measuring shaft according to claim 2 or 3, characterized in that the means for increasing the torsional rigidity comprise a plant. Torque measuring shaft according to one of the preceding claims, characterized by at least one arranged between two flanges spring element with an effective spring length and means for changing the spring length in dependence on the rotation angle. Torque measuring shaft according to claim 5, characterized in that the spring length is shortened with increasing angle of rotation. Torque measuring shaft, in particular according to one of the preceding claims, characterized by a centrally disposed between two flanges and a measuring rod by means of a radially outside the measuring rod between the flanges effective spring arrangement. Torque measuring shaft according to claim 7, characterized in that the spring arrangement comprises at least two axially aligned spring elements. Torque measuring shaft according to claim 7 or 8, characterized by an arrangement arranged in the circumferential direction next to at least one spring element. Torque measuring shaft according to one of claims 5 to 9, characterized by beam springs as spring elements. Torque measuring shaft according to claim 10, characterized in that the beam spring is radially wider than in the circumferential direction. Torque measuring shaft, in particular according to one of the preceding claims, characterized by two flanges, which are arranged within the intended measuring range by more than 0.5 ° against each other rotatable.

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