DE102020131588A1 - Elastic transmission element for a tension shaft transmission, method - Google Patents

Abstract

The invention relates to an elastic transmission element for a stress wave transmission, the elastic transmission element having a strain gauge sensor arrangement for measuring mechanical expansion and/or compression, in particular shearing expansion and/or compression caused by a torque, characterized in that that the strain gauge sensor arrangement comprises at least a first strain gauge sensor and a second strain gauge sensor, wherein the first strain gauge sensor is locally angled clockwise to a local pole axis of the elastic transmission element, wherein the second strain gauge sensor locally counter to the Clockwise angled to a local polar axis of the elastic transmission element is formed

Description

The invention relates to an elastic transmission element for a stress wave transmission, the elastic transmission element having a strain gauge sensor arrangement for measuring mechanical expansion and/or compression, in particular shearing expansion and/or compression caused by a torque. The elastic transmission element is also referred to as a flexspline. Furthermore, the invention relates to a tension shaft transmission. Stress wave gears of this type are also referred to as harmonic drives, strain wave gears, sliding wedge gears or strain wave gears.

In the article by Hashimoto, M. et al.: "A joint torque sensing technique for robots with harmonic drives" in Proceedings of IEEE International Conference on Robotics and Automation, Issue 2, pages 1034-1039, April 1991 is a method for measuring of a torque in a tension shaft transmission. Strain gauges, which are arranged on an elastic transmission element of the stress wave drive, are used for the measurement.

the DE 10 2004 041 394 A1 shows a wave gear device with a torque detection mechanism including a plurality of strain gauges with resistance wire portions on a flexible external gear, which are electrically connected via lead wires.

the JP 2016-045055 A shows the use of a Wheatstone bridge with a strain gauge on a rotating shaft of a harmonic drive.

From the U.S. 6,840,118 B2 a torque measuring method for measuring a torque transmitted in a wave gear device is known. In the wave gear device, a flexible circular external gear partially meshes with a rigid internal gear. Multiple sets of strain gauges are attached to the surface of the flexible external gear.

It is an object of the present invention to be able to advantageously reduce interference when measuring a mechanical stress, in particular a shearing strain generated by a torque in a stress wave transmission, so that a precise and high-quality torque measurement is preferably made possible cost-effectively and as space-neutrally as possible.

The object is achieved according to the invention by an elastic transmission element for a stress wave transmission, the elastic transmission element having a strain gauge sensor arrangement for measuring mechanical expansion and/or compression, in particular shearing expansion and/or compression caused by a torque, characterized in that the strain gauge sensor arrangement comprises at least a first strain gauge sensor and a second strain gauge sensor, the first strain gauge sensor being formed locally at an angle clockwise to a local pole axis of the elastic transmission element, the second strain gauge sensor is locally angled counterclockwise to a local pole axis of the elastic transmission element.

With the help of the strain gauge sensors, shear strains, in particular in the front area and/or in the cylindrical part of the elastic transmission element, can be detected, which are generated by the torque.

According to the invention, it is possible for the angle of the strain gauge sensors to the local pole axis to be based in particular on the local angle between the strip or strips of a strain gauge sensor provided for measurement and the local pole axis, which extends from a central axis of the transmission element in radial Extends towards the outside relates.

According to the invention, it is conceivable that the strain gauge sensor arrangement or the strain gauge sensors are arranged on an outside (or face) of the face area, which faces away from a cylindrical part or a sleeve area of the elastic transmission element, as well as on an inner side of the end region, which faces towards the cylindrical part or the sleeve region of the elastic transmission element. The strain gauge sensors are each angled to the local pole axis of the elastic transmission element, so in particular they do not run parallel to the pole axis. The measuring directions of the strain gauge sensors thus preferably each extend locally in a direction that lies between the local polar axis and the local polar angle direction. It is alternatively possible that the strain gauge sensor arrangement or the strain gauge sensors are arranged on a cylindrical part of the elastic transmission element.

The fact that the first strain gauge sensor is angled locally in the polar angle direction clockwise to the polar axis and the second Strain gauge sensors is angled locally counterclockwise to the polar axis, unwanted interference signals can be advantageously eliminated by interconnecting the sensors. Such interference signals include, in particular, interference signals that change several times per revolution period of the non-circular wave generator of the voltage wave transmission, in particular periodically. For example, the spurious signals periodically change twice, three times, four times, five times, six times, etc. per revolution period of the non-circular wave generator. The interference signals are caused in particular by the local deformation that the elastic transmission element periodically experiences twice per revolution of the shaft generator through the non-circular disk of the shaft generator. The non-circular disc deforms the elastic transmission element as it rotates, which sometimes leads to significant interference signals in the output signals of the strain gauge sensors. In many applications, these spurious signals are of the same order of magnitude as the desired torque-induced signal from the strain gauge sensors, or may even be larger than the desired signal. Due to the arrangement of the strain gauge sensors according to the invention, such interference signals can be eliminated or at least significantly reduced in a particularly cost-effective manner. It is also possible to enable a space-saving and space-saving design by attaching the strain gauge sensors to the forehead area or to the cylindrical part of the elastic transmission element.

According to the invention, the “clockwise direction” preferably refers to a top view of the front area of the elastic transmission element, in particular to a top view of the strain gauge sensor arrangement.

The elastic transmission element according to the invention can form a torque-transmitting component of a stress wave transmission. Such a stress wave gear can also be referred to as a harmonic drive, strain wave gear, sliding wedge gear or strain wave gear. The elastic transmission element can also be referred to as a flexspline. The elastic transmission element is preferably designed to derive a torque to be transmitted by the tension shaft transmission. It is conceivable that the elastic transmission element is a stationary part or a moving part during operation of the stress wave transmission.

The elastic transmission element preferably has an external toothing which is designed to engage in an internal toothing of a rigid outer ring of the tension shaft transmission. The external toothing and the internal toothing have a difference in the number of teeth, which is two, for example.

Advantageous developments and configurations can be found in the dependent claims.

• -- dass die Dehnungsmessstreifen-Sensoren-Anordnung auf einem Stirnbereich des elastischen Übertragungselements angeordnet ist, insbesondere auf einer Stirnseite des Stirnbereichs, die von einem zylindrischen Teil des elastischen Übertragungselements abgewandt ist, oder auf einer Innenseite des Stirnbereichs, die zum zylindrischen Teil des elastischen Übertragungselements hingewandt ist, und/oder
• -- dass die Dehnungsmessstreifen-Sensoren-Anordnung auf einem zylindrischen Teil des elastischen Übertragungselements angeordnet ist. Bevorzugt ist dabei die Ausbildung der Dehnungsmessstreifen-Sensoren-Anordnung an dem Stirnbereich. Alternativ ist es jedoch auch denkbar, dass die Dehnungsmessstreifen-Sensoren-Anordnung auf einem zylindrischen Teil des elastischen Übertragungselements angebracht ist.

According to one embodiment of the present invention, it is conceivable

• -- that the strain gauge sensor arrangement is arranged on a front area of the elastic transmission element, in particular on a front side of the front area that faces away from a cylindrical part of the elastic transmission element, or on an inside of the front area that faces the cylindrical part of the elastic transmission element is directed, and/or
• -- that the strain gauge sensor arrangement is arranged on a cylindrical part of the elastic transmission element. The configuration of the strain gauge sensor arrangement on the forehead area is preferred. Alternatively, however, it is also conceivable that the strain gauge sensor arrangement is attached to a cylindrical part of the elastic transmission element.

• -- wobei die Gruppe von Dehnungsmessstreifen-Sensoren entweder als Halbbrücke ausgebildet ist, oder
• -- wobei die Gruppe von Dehnungsmessstreifen-Sensoren zusätzlich einen dritten und einen vierten Dehnungsmessstreifen-Sensor umfasst, wobei die Gruppe von Dehnungsmessstreifen-Sensoren als Vollbrücke ausgebildet ist, wobei der dritte Dehnungsmessstreifen-Sensor lokal im Uhrzeigersinn gewinkelt zu einer lokalen Polachse des elastischen Übertragungselements ausgebildet ist, wobei der vierte Dehnungsmessstreifen-Sensor lokal gegen den Uhrzeigersinn gewinkelt zu einer lokalen Polachse des elastischen Übertragungselements ausgebildet ist, wobei im Uhrzeigersinn insbesondere:
• -- der zweite Dehnungsmessstreifen-Sensor nach dem ersten Dehnungsmessstreifen-Sensor,
• -- der dritte Dehnungsmessstreifen-Sensor nach dem zweiten Dehnungsmessstreifen-Sensor und
• -- der vierte Dehnungsmessstreifen-Sensor nach dem dritten Dehnungsmessstreifen-Sensor angeordnet ist.

According to one embodiment of the present invention, it is conceivable that the strain gauge sensor arrangement comprises a group of strain gauge sensors, the group of strain gauge sensors comprising the first and the second strain gauge sensor,

• -- wherein the group of strain gauge sensors is designed either as a half-bridge, or
• -- wherein the group of strain gauge sensors additionally comprises a third and a fourth strain gauge sensor, wherein the group of strain gauge sensors is designed as a full bridge, wherein the third strain gauge sensor is locally angled clockwise to a local pole axis of the elastic transmission element is, wherein the fourth strain gauge sensor is formed locally at an angle counterclockwise to a local pole axis of the elastic transmission element, wherein clockwise in particular:
• -- the second strain gauge sensor after the first strain gauge sensor,
• -- the third strain gauge sensor after the second strain gauge sensor and
• -- the fourth strain gauge sensor is located after the third strain gauge sensor.

The group of strain gauge sensors is preferably evaluated as a pair of sensors in the sense of a half bridge or with four strain gauge sensors in the sense of a full bridge. It has been shown that a particularly efficient reduction in interference can be achieved by forming and interconnecting the group of strain gauge sensors as a full bridge. The strain gauge sensors of the group of strain gauge sensors are angled in the circumferential direction (of the elastic transmission element) alternately clockwise and counterclockwise to the local pole axis of the elastic transmission element. This results in a particularly advantageous elimination of interference signals. However, it is also conceivable that some or all of the strain gauge sensors are connected individually in the sense of quarter bridges.

It is preferably possible that the strain gauge sensors of the strain gauge sensor arrangement are each guided (curved) along a pitch circle.

According to one embodiment of the present invention, it is conceivable that the first strain gauge sensor is formed locally at an angle A to the local pole axis, with the second strain gauge sensor being formed locally at an angle -A to the local pole axis, with the third strain gauge preferably being formed sensor is formed locally at the angle A to the local pole axis, with the fourth strain gauge sensor preferably being formed locally at the angle -A to the local pole axis. The angle A or -A to the local pole axis relates in particular to the local angle between the strip or strips of a strain gauge sensor provided for measurement and the local pole axis, which extends radially outwards starting from a central axis of the transmission element extends. A positive angle A is present in particular when the strip or strips of a strain gauge sensor are angled clockwise relative to the local pole axis. A negative angle -A is present in particular when the strip or strips of a strain gauge sensor are angled counterclockwise to the local pole axis. The strain gauge sensors of the group of strain gauge sensors are thus particularly preferably formed alternately clockwise and counterclockwise in the circumferential direction and thus alternately with a positive angle A and negative angle −A relative to the local pole axis. This results in a particularly advantageous elimination of interference signals. The angle A and the angle -A have in particular the same amount, ie for example 45° and -45° (or 40° and -40°, etc.).

According to one embodiment of the present invention, it is conceivable that the angle A is between 1° and 89° inclusive, preferably between 15° and 75° inclusive, more preferably between 30° and 60° inclusive, particularly preferably 45°. In particular, the angle -A has the same magnitude as the angle A, but opposite sign (since it points counterclockwise from the local polar axis). The angle -A is accordingly preferably between -1° and -89° inclusive, preferably between -15° and -75° inclusive, more preferably between -30° and -60° inclusive, particularly preferably -45°.

According to one embodiment of the present invention, it is provided that the group of strain gauge sensors is arranged along a circular line running concentrically to the axis of the elastic transmission element. The strain gauge sensors thus advantageously all have the same radial distance from the central axis of the elastic transmission element and are arranged along a circular line. In this way, an advantageous elimination or reduction of the interference signals can be achieved. The circular line is in particular an imaginary circular line, which is preferably arranged on the front area (or alternatively on the cylindrical part) of the elastic transmission element.

According to one embodiment of the present invention, it is provided that the strain gauge sensors are each arranged with the same polar angle distances from one another over an angular range of the circular line over which the group of strain gauge sensors extends. The angular range can cover the entire circle, that is 360°, but it can also be smaller, for example 90°, 120° or 180°. It is therefore particularly conceivable that the group of strain gauge sensors only extends over part of the circle. One or more further groups of strain gauge sensors can be arranged along the circular line. By arranging the strain gauge sensors at equal polar angle distances, a particularly advantageous reduction in interference is possible.

According to one embodiment of the present invention, it is conceivable that the strain gauge sensor arrangement comprises a further group of strain gauge sensors, with the further group of strain gauge sensors being arranged in particular along the circular line, with the further group of strain gauge sensors being at least comprises a further first strain gauge sensor and a further second strain gauge sensor, the further first strain gauge sensor being angled locally clockwise to a local pole axis of the elastic transmission element, the further second strain gauge sensor being angled locally counterclockwise to a local pole axis of the elastic transmission element is formed. All strain gauge sensors arranged along the circular line are particularly preferred (i.e. both the strain gauge sensors of the group of strain gauge sensors and the strain gauge sensors of the further group of strain gauge sensors and any strain gauge sensors of further groups of strain gauges -sensors) arranged in equal polar angle distances to each other offset along a circular line. All strain gauge sensors preferably extend in the circumferential direction over circular segments of the same length of the circular line.

• -- dass die weitere Gruppe von Dehnungsmessstreifen-Sensoren als Halbbrücke ausgebildet ist, oder
• -- dass die weitere Gruppe von Dehnungsmessstreifen-Sensoren zusätzlich einen weiteren dritten und einen weiteren vierten Dehnungsmessstreifen-Sensor umfasst, wobei die weitere Gruppe von Dehnungsmessstreifen-Sensoren als Vollbrücke ausgebildet ist, wobei der weitere dritte Dehnungsmessstreifen-Sensor lokal im Uhrzeigersinn gewinkelt zu einer lokalen Polachse des elastischen Übertragungselements ausgebildet ist, wobei der weitere vierte Dehnungsmessstreifen-Sensor lokal gegen den Uhrzeigersinn gewinkelt zu einer lokalen Polachse des elastischen Übertragungselements ausgebildet ist. Es ist denkbar, dass im Uhrzeigersinn insbesondere:
• -- der weitere zweite Dehnungsmessstreifen-Sensor nach dem weiteren ersten Dehnungsmessstreifen-Sensor,
• -- der weitere dritte Dehnungsmessstreifen-Sensor nach dem weiteren zweiten Dehnungsmessstreifen-Sensor und
• -- der weitere vierte Dehnungsmessstreifen-Sensor nach dem weiteren dritten Dehnungsmessstreifen-Sensor angeordnet ist. Es ist alternativ jedoch auch möglich, dass im Uhrzeigersinn
• -- der weitere erste Dehnungsmessstreifen-Sensor nach dem weiteren zweiten Dehnungsmessstreifen-Sensor,
• -- der weitere vierte Dehnungsmessstreifen-Sensor nach dem weiteren ersten Dehnungsmessstreifen-Sensor und
• -- der weitere dritte Dehnungsmessstreifen-Sensor nach dem weiteren vierten Dehnungsmessstreifen-Sensor angeordnet ist.

According to one embodiment of the present invention, it is conceivable

• -- That the other group of strain gauge sensors is designed as a half-bridge, or
• -- that the further group of strain gauge sensors additionally comprises a further third and a further fourth strain gauge sensor, wherein the further group of strain gauge sensors is designed as a full bridge, wherein the further third strain gauge sensor is locally angled clockwise to a local one Pole axis of the elastic transmission element is formed, wherein the further fourth strain gauge sensor is formed locally angled counterclockwise to a local pole axis of the elastic transmission element. It is conceivable that clockwise in particular:
• -- the additional second strain gauge sensor after the additional first strain gauge sensor,
• -- the further third strain gauge sensor after the further second strain gauge sensor and
• - the further fourth strain gauge sensor is arranged after the further third strain gauge sensor. Alternatively, however, it is also possible that clockwise
• -- the additional first strain gauge sensor after the additional second strain gauge sensor,
• -- the further fourth strain gauge sensor after the further first strain gauge sensor and
• - the further third strain gauge sensor is arranged after the further fourth strain gauge sensor.

According to one embodiment of the present invention, it is conceivable that in addition to the group of strain gauge sensors and the further group of strain gauge sensors, one or more further groups of strain gauge sensors are present. It is conceivable, for example, that the strain gauge sensor arrangement comprises a total of two, three, four, five, six, seven, eight or more groups of strain gauge sensors, which are preferably connected as full bridges or alternatively as half bridges. The strain gauge sensors within a group of strain gauge sensors are each arranged along a circular line. All groups of strain gauge sensors are preferably arranged along the same circular line, that is to say at the same distance radius from a central axis of the elastic transmission element. All strain gauge sensors within a strain gauge sensor arrangement are angled in the circumferential direction alternately clockwise and counterclockwise to the local pole axis at their location, preferably alternately with a positive angle A and negative angle -A to the local pole axis. All strain gauge sensors preferably extend in the circumferential direction over circular segments of the same length of the circular line. At the same time, the strain gauge sensors are particularly preferably each guided (curved) along a pitch circle.

• -- wobei der Stirnbereich einen Flansch umfasst, der sich ausgehend von dem zylindrischen Teil radial nach außen erstreckt, und/oder
• -- wobei der Stirnbereich einen sich ausgehend von dem zylindrischen Teil radial nach innen erstreckenden Bereich umfasst. Der zylindrische Teil kann auch als Hülsenbereich verstanden werden und umfasst vorzugsweise eine Außenverzahnung.

According to one embodiment of the present invention, it is conceivable that the elastic transmission element comprises a cylindrical part and a front area,

• -- the end portion comprising a flange extending radially outwards from the cylindrical portion, and/or
• -- the end portion comprising a portion extending radially inward from the cylindrical portion. the cylindri cal part can also be understood as a sleeve area and preferably includes an external toothing.

A further object of the present invention is a tension shaft transmission, with a wave generator comprising a non-circular disk, a rigid outer ring and an elastic transmission element according to an embodiment of the present invention. The outer ring has, in particular, internal teeth which can interact with external teeth of the elastic transmission element. Furthermore, the system preferably includes readout and/or evaluation circuitry for reading out and/or evaluating the measurement signals of the strain gauge sensor arrangement. Stress shaft drives of this type can be used in a variety of ways, for example in joints in robotics.

Another object of the present invention is a method for measuring mechanical expansion and / or compression of an elastic transmission element according to an embodiment of the present invention, in particular shearing expansion and / or compression caused by a torque, the mechanical expansion and /or compressions are measured using the strain gauge sensor arrangement.

The features, embodiments and advantages that have already been described in connection with the elastic transmission element according to the invention or in connection with an embodiment of the elastic transmission element according to the invention can be used for the stress wave transmission according to the invention and the method for measuring mechanical expansion and/or compression .

• 1 eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 2 eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 3A eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 3B eine vergrößerte Darstellung eines Teilbereichs eines elastischen Übertragungselements gemäß der Ausführungsform der 3A.
• 4A eine schematische Darstellung einer Schaltung einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß einer Ausführungsform der vorliegenden Erfindung.
• 4B eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 4A.
• 4C eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 4A.
• 5A eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 5B eine schematische Darstellung einer Schaltung für eine Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 5A.
• 5C eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 5A.
• 6A eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 6B eine schematische Darstellung einer Schaltung für eine Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 6A.
• 6C eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 6A.
• 6D eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 6A.
• 7A eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 7B eine schematische Darstellung einer Schaltung für eine Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 7A.
• 8A eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 8B eine schematische Darstellung einer Schaltung für eine Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 8A.
• 9A eine schematische Darstellung eines elastisches Übertragungselements gemäß einer Ausführungsform der vorliegenden Erfindung.
• 9B eine schematische Darstellung einer Schaltung für eine Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 9A.
• 9C eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 9A.
• 9D eine schematische Darstellung von Signalen einer Dehnungsmessstreifen-Sensoren-Anordnung gemäß der 9A.

Further details and advantages of the invention are to be explained below with reference to the exemplary embodiments illustrated in the drawings. Herein shows:

• 1 a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 2 a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 3A a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 3B an enlarged view of a portion of an elastic transmission element according to the embodiment of FIG 3A .
• 4A a schematic representation of a circuit of a strain gauge sensor arrangement according to an embodiment of the present invention.
• 4B a schematic representation of signals of a strain gauge sensor arrangement according to FIG 4A .
• 4C a schematic representation of signals of a strain gauge sensor arrangement according to FIG 4A .
• 5A a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 5B a schematic representation of a circuit for a strain gauge sensor arrangement according to 5A .
• 5C a schematic representation of signals of a strain gauge sensor arrangement according to FIG 5A .
• 6A a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 6B a schematic representation of a circuit for a strain gauge sensor arrangement according to 6A .
• 6C a schematic representation of signals of a strain gauge sensor arrangement according to FIG 6A .
• 6D a schematic representation of signals of a strain gauge sensor arrangement according to FIG 6A .
• 7A a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 7B a schematic representation of a circuit for a strain gauge sensor arrangement according to 7A .
• 8A a schematic representation of an elastic transmission element according to an embodiment of the present invention.
• 8B a schematic representation of a circuit for a strain gauge sensor arrangement according to 8A .
• 9A a schematic representation of an elastic transmission element according to FIG an embodiment of the present invention.
• 9B a schematic representation of a circuit for a strain gauge sensor arrangement according to 9A .
• 9C a schematic representation of signals of a strain gauge sensor arrangement according to FIG 9A .
• 9D a schematic representation of signals of a strain gauge sensor arrangement according to FIG 9A .

In 1 1 is a schematic representation of an elastic transmission element 30 for a stress wave transmission according to an embodiment of the present invention. The elastic transmission element 30 comprises a cylindrical part 33 with external teeth 34 and an end region 31 adjoining the cylindrical part 33, which extends outwards from the cylindrical part 33 (away from the central axis 110) and is designed as a flange. Alternatively, it would be conceivable for the end region to extend inwards from the cylindrical part, ie in the direction of the central axis 110, or both inwards and outwards. A strain gauge sensor arrangement (not shown) is arranged on the forehead area. The strain gauge sensor arrangement can be formed on the end face 32 and/or on the side of the end region 31 pointing in the direction of the cylindrical part 33 . The central axis 110 describes an axial direction of the elastic transmission element 30.

In 2 is a schematic representation of an elastic transmission element 30 according to an embodiment of the present invention in a plan view of an end face 32 of the end region 31 of the elastic transmission element 30 is shown. A strain gauge sensor arrangement is formed on the forehead area 31 . The strain gauge sensor arrangement comprises a total of 16 strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, which are equidistant from the central Axis 110 are formed along a circular line 40 in the circumferential direction 101 . The strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 are each arranged with the same polar angle distances from one another over the entire circumference of the circular line 40 . In particular, the angular distance between two adjacent strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 is therefore 360°/16=22.5 °. Strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 can be connected as quarter bridges, half bridges or full bridges. The strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 are each alternately angled clockwise 102 and counterclockwise 102 to a local Pole axis 100 of the elastic transmission element 30 is formed. The strain gauge sensors 1, 3, 5, 7, 9, 11, 13, 15 are thus angled clockwise to the local pole axis 100 and the strain gauge sensors 2, 4, 6, 8, 10, 12, 14, 16 are angled counterclockwise to the local polar axis 100 . The strain gauge sensors 1, 3, 5, 7, 9, 11, 13, 15 thus each have a local angle A to the local pole axis 100 and the strain gauge sensors 2, 4, 6, 8, 10, 12, 14, 16 a local angle -A to the local polar axis 100. The angle A is in particular 45° and the angle -A is -45°. However, other angles are also possible.

In 3A is a schematic representation of an elastic transmission element 30 according to an embodiment of the present invention in a plan view of an end face 32 of the end region 31 of the elastic transmission element 30 is shown. In contrast to the one in the 2 In the embodiment shown, the strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 are connected to form groups. In particular, the strain gauge sensors 1, 2, 3, 4 are designed together as a group of strain gauge sensors and are connected as a full bridge. Correspondingly, the additional strain gauge sensors 5, 6, 7, 8 are designed as an additional group of strain gauge sensors and connected as a full bridge, the additional strain gauge sensors 9, 10, 11, 12 are configured as an additional group of strain gauge sensors and connected as a full bridge, as well as the other strain gauge sensors 13, 14, 15, 16 designed as yet another group of strain gauge sensors and connected as a full bridge. A total of four full bridges are therefore present. The outer contact pads of each group of strain gauge sensors are connected to the same electrical potential. For example, the contact pads 70, 71 of the group of strain gauge sensors 1, 2, 3, 4 are therefore at the same electrical potential.

The angular distances between the strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 along the circular line 40 are also in the embodiment according to FIG 3A 360°/16 = 22.5° each, so that the strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 are evenly distributed over the Circle line 40 are distributed.

A particularly advantageous reduction of interference signals can be achieved by the even distribution of the strain gauge sensors along the circular line, the connection as full bridges and the total number of four full bridges. Even interferences with higher orders, ie interferences whose period often fits into the period of the wave generator of the voltage wave transmission, can thus advantageously be eliminated or reduced.

In 3B is an enlarged view of the 3A around the area of the array of strain gauge sensors 1, 2, 3, 4 are shown. The group of strain gauge sensors 1, 2, 3, 4 designed as a full bridge comprises the first strain gauge sensor 1, the second strain gauge sensor 2, the third strain gauge sensor 3 and the fourth strain gauge sensor 4. The first and the third Strain gauge sensors 1, 3 are locally angled in a clockwise direction 102 at an angle A to the local pole axis 100 of the elastic transmission element 30. The second and fourth strain gauge sensors 2 , 4 are locally angled counterclockwise 102 at the angle -A to the local pole axis 100 of the elastic transmission element 30 . The alternating design of the strain gauge sensors 1, 2, 3, 4 with a positive angle A and a negative angle -A to the local pole axis 100 results in an advantageous suppression of interference. The further groups of strain gauge sensors are preferably each designed accordingly.

In 4A 1 is an electrical schematic for a strain gauge sensor assembly according to an embodiment of the present invention. It can be, for example, the strain gauge sensor arrangement according to 3A and 3B act. The strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 each have corresponding electrical resistances R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16 and are connected according to four full bridges with voltages Uout1, Uout2, Uout3, Uout4. The signals of the four full bridges are preferably added. It is conceivable to amplify the signals of the full bridges individually and then combine them, or to combine the signals and then amplify them. For the illustrated embodiment of the present invention, all odd-numbered disturbances, ie all disturbances whose period corresponds to 1/n of the period of the wave generator, where n is an odd natural number, are eliminated. Even additive even-numbered disturbances, ie disturbances whose period corresponds to 1/n of the period of the wave generator, where n is an even natural number, are eliminated. From n=6, however, even-numbered multiplicative interferences are no longer eliminated (exception: n=12, 14, 16, 18, 20, ...). A simulation of the signals S10, S20, S30, S40 of the four full bridges for a 6-period additive disturbance, i.e. a disturbance excitation whose period corresponds to 1/6 of the period of the wave generator, is in 4B shown. The signals S10, S20, S30, S40 of the individual full bridges are plotted against the angle K of the wave generator. The signal S10 is the signal from the group of strain gauge sensors 1, 2, 3, 4, the signal S20 is the signal from the other group of strain gauge sensors 5, 6, 7, 8, and the signal S30 is the signal from the other group of strain gauge sensors 9, 10, 11, 12, and the signal S40 the signal of the still further group of strain gauge sensors 13, 14, 15, 16. The sum signal S is the sum of the signals S10, S20, S30, S40 four full bridges. As can be seen, the periodic disturbances of the signals S10, S20, S30, S40 are eliminated in the sum signal S, so that the sum signal S does not depend on the angle K of the shaft generator. This enables a particularly advantageous elimination, even of interference with a comparatively high order or frequency. In 4C a simulation for an additive and multiplicative 6-period disturbance excitation is shown. In this case, too, the dependency on the shaft generator angle K and thus the interference signal in the sum signal S is greatly reduced in comparison to the individual signals S10, S20, S30, S40. However, a periodic disturbance remains in the sum signal S, which is caused in particular by the multiplicative 6-period disturbance excitation.

In 5A is a schematic representation of an elastic transmission element 30 according to an embodiment of the present invention in a plan view of an end face 32 of the end region 31 of the elastic transmission element 30 is shown. A strain gauge sensor arrangement is formed on the forehead area 31 and has a total of four strain gauge sensors 1 , 2 , 3 , 4 . The strain gauge sensors 1, 2, 3, 4 are arranged along a circular segment of 180° and connected together as a full bridge. The first and third strain gauge sensors 1, 3 are locally angled clockwise 102 at the angle A to the local pole axis 100 of the elastic transmission element 30, and the second and fourth strain gauge sensors 2, 4 are locally counterclockwise 102 with the Angle -A angled to the local pole axis 100 of the elastic transmission element 30 is formed. This angling to the local pole axis 100 is shown in the illustration by the first and third strain gauge sensors 1, 3 being shown as dots and the second and fourth strain gauge sensors 2, 4 as dashed lines are filled in. The strain gauge sensors are arranged along the circular segment at the same angular distance from one another, ie in particular offset by 180°/4=45°. In 5B FIG. 14 is an electrical schematic for the strain gauge sensor assembly of FIG 5A shown. A simulation of the signals S1, S2, S3, S4 of the four strain gauge sensors 1, 2, 3, 4 for a 2-period additive disturbance, i.e. a disturbance excitation whose period corresponds to 1/2 of the period of the wave generator, is in 5C shown. The signal S1 of the first strain gauge sensor 1, the signal S2 of the second strain gauge sensor 2, the signal S3 of the third strain gauge sensor 3 and the signal S4 of the fourth strain gauge sensor 4 are plotted against the angle K of the shaft generator. The sum signal S of the entire full bridge does not depend on the angle K of the wave generator for the additive 2-period interference. Thus, a disturbance that is important in practice can be eliminated.

In 6A is a schematic representation of an elastic transmission element 30 according to an embodiment of the present invention in a plan view of an end face 32 of the end region 31 of the elastic transmission element 30 is shown. A strain gauge sensor arrangement is formed on the forehead area 31 and has a total of eight strain gauge sensors 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . The strain gauge sensors 1, 2, 3, 4 form a group of strain gauge sensors that is connected as a full bridge, and the other strain gauge sensors 5, 6, 7, 8 form another group of strain gauge sensors that are also connected as a full bridge is connected. The first, third, additional first and additional third strain gauge sensors 1 , 3 , 5 , 7 are locally angled in a clockwise direction 102 at an angle A to the local pole axis 100 of the elastic transmission element 30 . The second, fourth, further second and further fourth strain gauge sensors 2 , 4 , 6 , 8 are locally angled counterclockwise 102 at the angle −A to the local pole axis 100 of the elastic transmission element 30 . Thus, the strain gauge sensors are always alternately formed with a positive angle A and a negative angle −A to the local pole axis 100 in the circumferential direction. The strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8 are each arranged offset from one another at the same angular distance on a circular line. In 6B FIG. 14 is an electrical schematic for the strain gauge sensor assembly of FIG 6A shown. A simulation of the signals of the strain gauge sensor arrangement according to the 6A and 6B for a 3-period additive and multiplicative disturbance, i.e. a disturbance excitation whose period corresponds to 1/3 of the period of the wave generator, is in 6C shown. The signal S10 of the full bridge formed by the strain gauge sensors 1, 2, 3, 4 and the signal S20 of the full bridge formed by the strain gauge sensors 5, 6, 7, 8 are shown. The sum signal S of the two signals S10 and S20 is not dependent on the angle K of the shaft generator. In 6D is a simulation of the signals of the strain gauge sensor arrangement according to the 6A and 6B for a 2-period additive and multiplicative disturbance, i.e. a disturbance excitation whose period corresponds to 1/2 of the period of the wave generator.

In the previously illustrated embodiments, the individual full bridges are preferably connected in such a way that a full bridge has its own amplification. In this way, for example, slight structural or electrical differences in the individual full bridges can be adjusted by appropriate selection of the gain of individual full bridges, in particular before the signals of the individual full bridges are added. A particularly advantageous result can thus be achieved by taking into account production fluctuations or changes over the lifetime of the component. In the 7A and 7B an alternative to this is shown. The one in the 7A The arrangement of the strain gauge sensors shown on the elastic transmission element 30 basically corresponds to that in FIG 6A arrangement shown. According to the in the 7B In the alternative circuit shown, however, the sum signal of the two full bridges is generated by connecting the full bridges in parallel, with amplification only taking place afterwards. As a result, it is possible for there to be only one measuring amplifier in total, and installation space and costs can thus be saved.

In 8A is a schematic representation of an elastic transmission element 30 according to an embodiment of the present invention in a plan view of an end face 32 of the end region 31 of the elastic transmission element 30 is shown. A strain gauge sensor arrangement is formed on the forehead area 31 and has a total of eight strain gauge sensors 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . The strain gauge sensors 1, 2, 3, 4 are connected as a full bridge and according to the 7A arranged on the forehead area 31 . In contrast to the arrangement according to the 7A However, the further first strain gauge sensor 5 of the further group of strain gauge sensors 5, 6, 7, 8, which is arranged in the circumferential direction behind the fourth strain gauge sensor 4, is angled locally counterclockwise 102 at the angle -A to the local pole axis 100 of the elastic transmission elements 30 formed. The same applies to the further, third strain gauge sensor 7. The further, second and further, fourth strain gauge sensors 6, 8, on the other hand, are locally angled clockwise 102 at the angle A to the local pole axis 100 of the elastic transmission element 30. Thus, the further group of strain gauge sensors 5, 6, 7, 8 is mirrored to the group of strain gauge sensors 1, 2, 3, 4 formed. In this variant, too, the strain gauge sensors within a group of strain gauge sensors (or within a full bridge) in the circumferential direction are always alternately locally angled clockwise and counterclockwise at angles A and -A to the local pole axis. An equivalent circuit for the embodiment of 8A is in the 8B shown.

In 9A is a schematic representation of an elastic transmission element 30 according to an embodiment of the present invention in a plan view of an end face 32 of the end region 31 of the elastic transmission element 30 is shown. The strain gauge sensor arrangement comprises a total of twelve strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. In particular, the strain gauge sensors 1, 2, 3, 4 are common designed as a group of strain gauge sensors and connected as a full bridge. Correspondingly, the additional strain gauge sensors 5, 6, 7, 8 are designed as an additional group of strain gauge sensors and are connected as a full bridge, and the additional strain gauge sensors 9, 10, 11, 12 are configured as an additional group of strain gauge sensors and wired as a full bridge. Each of the three groups of strain gauge sensors covers an angular range of 120°. The strain gauge sensors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 are angled in the circumferential direction alternately at a positive angle A and a negative angle -A to the local pole axis 100. In 9B FIG. 12 is a circuit diagram for the embodiment according to FIG 9A shown.

With the embodiment according to 9A and 9B it is possible to eliminate all odd-numbered disturbances, i.e. all disturbances whose period corresponds to 1/n of the period of the wave generator, where n is an odd natural number. Even additive even-numbered disturbances, ie disturbances whose period corresponds to 1/n of the period of the wave generator, where n is an even natural number, are eliminated. From n=4, however, even-numbered multiplicative interferences are no longer eliminated (exception: 10, 12, 14, 22, 24, 26, 34, 36, 38, ...). A simulation of the signals of the three full bridges according to 9A and 9B for a 4-period additive disturbance, i.e. a disturbance excitation whose period corresponds to 1/4 of the period of the wave generator, is in 9C shown. The signals S10, S20, S30 of the individual full bridges are plotted against the angle K of the wave generator. The signal S10 is the signal from the group of strain gauge sensors 1, 2, 3, 4, the signal S20 is the signal from the other group of strain gauge sensors 5, 6, 7, 8 and the signal S30 is the signal from the other group of strain gauge sensors 9, 10, 11, 12. The sum signal S is the sum of the signals S10, S20, S30 of the three full bridges. As can be seen, the periodic disturbances of the signals S10, S20, S30 are eliminated, so that the sum signal S does not depend on the angle K of the wave generator. This enables a particularly advantageous elimination, even of interference with a comparatively high order or frequency. In 9D a simulation for an additive and multiplicative 4-period disturbance excitation is shown. In this case, too, the interference signal in the sum signal S is reduced in comparison to the individual signals S10, S20, S30. However, a periodic disturbance remains in the sum signal S, which is caused in particular by the multiplicative 4-period disturbance excitation.

The n-periodic disturbances or disturbance excitations described above can in particular be associated with the periodicity of the non-circular disk of the wave generator, which deforms the elastic transmission element during operation of the shaft drive. In the first order, the non-circular disk typically deforms the elastic transmission element 30 at twice the frequency. The deformation of the elastic transmission element 30 thus runs through two periods per complete revolution of the non-circular disk of the wave generator. This causes a 2-period disturbance. In practice, however, particularly depending on the application and the precise configuration of the shaft drive, interference with an even higher frequency, ie n-periodic interference, where n is a natural number greater than 2, can also occur. Disturbances that are not merely additive but multiplicative are also conceivable. According to the invention, an advantageous reduction in the interference in the measurement signal of the strain gauge sensor arrangement can be achieved, as a result of which a better determination of a torque on the basis of the measurement signal or the measurement signals of the strain gauge sensor arrangement is made possible.

Reference List

1

first strain gauge sensor

2

second strain gauge sensor

3

third strain gauge sensor

4

fourth strain gauge sensor

5

another first strain gauge sensor

6

another second strain gauge sensor

7

another third strain gauge sensor

8th

another fourth strain gauge sensor

9, 10, 11, 12, 13, 14, 15, 16

other strain gauge sensors

30

elastic transmission element

31

forehead area

32

face

33

cylindrical part

34

external teeth

40

circle line

100

local polar axis

101

circumferential direction

102

clockwise

110

axis

K

Wave generator angle

R1-R16

Resistances of the corresponding strain gauge sensors

S1-S4

Strain gauge sensor signals

S10-S40

signals of the full bridges

Uout1-Uout4

tensions

U0

tension

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was 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.

Patent Literature Cited

• DE 102004041394 A1 [0003]
• JP 2016045055 A [0004]
• US 6840118 B2 [0005]

Claims (11)

Elastic transmission element (30) for a stress wave transmission, wherein the elastic transmission element (30) has a strain gauge sensor arrangement for measuring mechanical expansion and/or compression, in particular shearing expansion and/or compression caused by a torque, thereby characterized in that the strain gauge sensor arrangement comprises at least a first strain gauge sensor (1) and a second strain gauge sensor (2), the first strain gauge sensor (1) being locally angled clockwise (102) to a local polar axis ( 100) of the elastic transmission element (30), the second strain gauge sensor (2) being locally angled counterclockwise (102) to a local pole axis (100) of the elastic transmission element (30). Elastic transmission element (30) after claim 1 , -- wherein the strain gauge sensor arrangement is arranged on a front area (31) of the elastic transmission element (30), in particular on a front side (32) of the front area (31), which faces away from a cylindrical part (33) of the elastic transmission element or on an inner side of the end region (31), which faces the cylindrical part of the elastic transmission element (30), and/or -- the strain gauge sensor arrangement being on a cylindrical part (33) of the elastic transmission element (30) is arranged. Elastic transmission element (30) according to one of the preceding claims, wherein the strain gauge sensor arrangement comprises a group of strain gauge sensors, wherein the group of strain gauge sensors comprises the first and the second strain gauge sensor (1, 2), -- wherein the group of strain gauge sensors is designed either as a half-bridge, or -- the group of strain gauge sensors additionally comprises a third and a fourth strain gauge sensor (3, 4), the group of strain gauge sensors being designed as a full bridge, the third strain gauge sensor (3) rotating locally clockwise ( 102) angled to a local pole axis (100) of the elastic transmission element (30), wherein the fourth strain gauge sensor (4) is angled locally counterclockwise (102) to a local pole axis (100) of the elastic transmission element (30). where clockwise (102) specifically: -- the second strain gauge sensor (2) after the first strain gauge sensor (1), -- the third strain gauge sensor (3) after the second strain gauge sensor (2) and - The fourth strain gauge sensor (4) is arranged after the third strain gauge sensor (3). Elastic transmission element (30) according to one of the preceding claims, wherein the first strain gauge sensor (1) is formed locally at an angle A to the local pole axis (100), wherein the second strain gauge sensor (2) is formed locally at an angle -A to local pole axis (100), the third strain gauge sensor (3) preferably being formed locally at the angle A to the local pole axis (100), the fourth strain gauge sensor (4) preferably being formed locally at the angle -A to the local Pole axis (100) is formed. Elastic transmission element (30) after claim 4 , wherein the angle A is between 1° and 89° inclusive, preferably between 15° and 75° inclusive, more preferably between 30° and 60° inclusive, particularly preferably 45°. Elastic transmission element (30) according to one of the preceding claims, wherein the group of strain gauge sensors is arranged along a circular line (40) running concentrically to the axis (110) of the elastic transmission element (30). Elastic transmission element (30) after claim 6 , wherein the strain gauge sensors (1, 2, 3, 4) are each arranged with the same polar angle distances from one another over an angular range of the circular line (40) over which the group of strain gauge sensors extends. Elastic transmission element (30) according to one of the preceding claims, wherein the strain gauge sensor arrangement comprises a further group of strain gauge sensors, wherein the further group of strain gauge sensors is arranged in particular along the circular line (40), the further group of Strain gauge sensors comprises at least one further first strain gauge sensor (5) and one further second strain gauge sensor (6), wherein the further first strain gauge sensor (5) locally angled clockwise (102) to a loka len pole axis (100) of the elastic transmission element (30), wherein the further second strain gauge sensor (6) is formed locally at an anticlockwise (102) angle to a local pole axis (100) of the elastic transmission element (30). Elastic transmission element (30) after claim 8 , -- wherein the further group of strain gauge sensors is designed as a half-bridge, or -- wherein the further group of strain gauge sensors additionally comprises a further third and a further fourth strain gauge sensor (7, 8), wherein the further group of Strain gauge sensors is designed as a full bridge, the further third strain gauge sensor (7) being angled locally in a clockwise direction (102) to a local pole axis (100) of the elastic transmission element (30), the further fourth strain gauge sensor (8 ) is formed locally counterclockwise (102) angled to a local pole axis (100) of the elastic transmission element (30). Stress wave transmission, with a wave generator comprising a non-circular disc, a rigid outer ring and an elastic transmission element (30) according to any one of the preceding claims. Method for measuring mechanical expansion and/or compression of an elastic transmission element (30) according to one of Claims 1 until 9 , In particular shear strains and/or compressions caused by a torque, the mechanical strains and/or compressions being measured using the strain gauge sensor arrangement.

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