DE102023100473B3 - Storage unit with integrated sensor - Google Patents

Abstract

Bearing unit (2) with a bearing (4) and at least one sensor (22), the sensor (22, 30, 34, 38) being integrated into the bearing (4), the sensor (22, 30, 34, 38) is designed to detect the output-side torque of an electrical machine or a mechanical transmission and/or to measure the transverse force and/or the tilting moment.

Description

The invention relates to a storage unit according to the preamble of claim 1.

The most important physical variables of an electrical machine include speed and torque. While the speed can in many cases be easily determined using the existing motor encoder (e.g. encoder, tachogenerator, resolver), the actual torque remains unknown. This torque can only be determined approximately by measuring the current and the torque constant. If a gearbox is also used, the result will be significantly distorted due to its efficiency. Significant differences in the torque to be determined arise between driving and braking operation. Vibrations on the transmission output cannot always be detected on the engine side.

If knowledge of the current torque is required in a specific application, a torque sensor can be used. However, the known torque sensors require considerable installation space and sometimes react sensitively to lateral forces (tilting moment). In addition, these sensors are cost-intensive and require considerable integration effort. Installing such sensors changes the topology of the application, which is why the meaningfulness is reduced by sensor integration. Additional specialist knowledge is required for successful implementation.

Bearings or pivot bearings are also particularly suitable for the rotary mounting of tension shaft gears, with the pivot bearing and the tension shaft gear forming a bearing unit, in particular a gear box. Such gearboxes are used in a variety of ways in many technological areas. In particular, such gearboxes are increasingly being used in robotics and prosthetics. A drive component designed as an elliptical wave generator deforms via a ball bearing a transmission component designed as an externally toothed flexspline, which is in engagement in the opposite regions of the large elliptical axis with an internally toothed wheel designed as a circular spline. As the wave generator rotates, the large ellipse axis and thus the tooth engagement area shifts.

Since the Flexspline of such a Harmonic Drive® transmission usually has two fewer teeth than the Circular Spline, there is a relative movement between the Flexspline and Circular Spline by one tooth during half a revolution of the wave generator and by two teeth during a whole revolution. When the circular spline is fixed, the flexspline as an output element rotates in the opposite direction to the drive. The circular spline can be arranged in a fixable manner in a bearing ring of the bearing or pivot bearing.

In order to realize a rotary movement between two components, such tension wave gears are placed on a rotary bearing ring on which they are rotatably mounted. On the one hand, the wheel of the tension shaft gear can be arranged in a rotationally fixed manner with respect to the pivot bearing ring, with rolling bodies then being arranged between pivot bearing surfaces of the pivot bearing ring and the transmission component, whereby the rotatability of the tension shaft gear relative to the pivot bearing ring is ensured. On the other hand, the transmission component of the tension shaft gear can also be arranged in a rotationally fixed manner with respect to the pivot bearing ring, with rolling bodies then being arranged between pivot bearing surfaces of the pivot bearing ring and the wheel, whereby the rotatability of the tension shaft gear with respect to the pivot bearing ring is also guaranteed.

From the DE 10 2017 130 433 A1 a bearing unit with a bearing and at least one sensor for detecting the absolute angular position or angular position of an electrical machine is known, in which the sensor and electronics for controlling the electrical machine are integrated into the bearing.

The DE 102020109 605 A1 describes a sensor bearing arrangement for supporting a rotatable machine element and for detecting a torque on this rotatable machine element. Such a torque acts on the machine element, resulting in a mechanical tension, which in turn acts on a magnetizable primary sensor and causes a change in the magnetic field, which is detected by a secondary sensor. A sensor housing of the torque sensor extends radially between the bearing housing and the rotatable machine element.

From the DE 10 2012 209 771 A1 a combination of a torque-transmitting drive shaft and a bearing arrangement supporting the drive shaft is known, the bearing arrangement having at least one integrated sensor device for detecting a torsion-related change in a magnetic field of a magnetized section provided on the drive shaft in the area of the bearing arrangement or connected to the drive shaft in a torque-proof manner.

The DE 10 2007 017 705 A1 discloses a shaft assembly with a rotatable shaft, which is stored in a rolling bearing. A torsion sensor is provided in an outer ring, which has a permanent magnetic ring and at least one magnetic field sensor attached to a fixed sensor carrier connected to the outer ring.

The invention is based on the object of providing an improved storage unit with a compact design and reduced complexity, which allows the determination of physical quantities.

This object is achieved according to the invention by the features of claim 1.

Advantageous embodiments of the invention are the subject of the subclaims.

The invention is based on the idea that the torque delivered by an electrical machine or a mechanical transmission is also transmitted via stationary components, such as the housing. The fixed outer ring of an output bearing is often the mechanical interface to the application and therefore also the torque support. If sensors for measuring the torque are integrated into this component, the so-called reaction torque can be measured. The prerequisite is that there is no further support of the torque through additional mechanical connections.

As has now been recognized, the problem according to the invention can be solved by integrating a torque sensor system into a bearing. Such an integration was recognized as possible without having to limit the bearing rigidity or service life too much. The challenge lies in measuring the component deformation and calculating the torque. The recesses represent local measuring points that are used to record the torque. However, the entire component is rigid and cannot be deformed. All known rotation sensors in bearing units measure the angular position, but this is a different physical quantity, so this challenge has not yet played a role in the prior art. The bearing is preferably designed as a pivot bearing.

Advantageously, the bearing has a bearing inner ring and a bearing outer ring, with the respective sensor being arranged in at least one sensor pocket formed in the bearing outer ring. In this embodiment, no additional installation space is necessary since the sensor is located directly in the component. Furthermore, no other components are necessary since the bearing ring is a component of the sensor and vice versa. The customer interface can remain unchanged compared to warehouses without a sensor.

The outer ring is preferably the outer ring of an output bearing, which in particular simultaneously represents the fixed mechanical customer interface.

In a preferred embodiment, at least two sensor pockets are provided, which are arranged offset from one another along the circumference of the bearing outer ring. In this way, greater measurement reliability can be achieved through multiple measuring points due to the larger amount of data. For small components, only small pockets can be created, in which only one strain gauge can be placed. This means that no bridge connection is possible if there is only one pocket. The strain gauges are advantageously connected using the bridge circuit. If the circuit is symmetrical, unwanted thermal expansions can be electrically compensated (half bridge and full bridge). A full bridge with four strain gauges (four pockets) has the largest output signal and the best compensation properties. The sensor pockets are particularly preferably arranged offset from one another by an angle of 90° or 180°. The stiffness of the component is locally minimized by milling pockets offset by 180°. The advantage of opposing sensor pockets is that errors cancel each other out through a spatially targeted arrangement of the measuring points. Parasitic forces transverse to the measuring direction have the same magnitude, but can be compensated for by opposite signs. For example, a tilting moment on a bearing creates tension on one side and pressure on the other side. The influence on the torque to be measured can be eliminated through targeted arrangement and interconnection.

Strain gauges (DMS) are advantageously fixed to the bottom of these depressions in order to measure the strain in the material. This allows torques, but also axial forces and tilting moments, to be recorded. The evaluation and calibration of the strain gauge is carried out using preferably external electronics, which is preferably arranged outside the warehouse due to the limited installation space available in the warehouse. According to the invention, the respective sensor pocket has a wall thickness on the inside of the bearing between 0.5 mm and 1 mm.

This local weakening of the material can in turn generate locally higher strains, which can then be better measured. This only slightly influences the rigidity of the entire component. The sensor Bags are advantageously all designed the same.

At least one cabling pocket is preferably arranged in the bearing outer ring. The sensor bag enables short electrical connections with low resistance values. It is also possible to use other types of electrical conductors from the cabling pocket onwards. There are usually different demands on the conductors within the bridge circuit than on the conductors between the bridge and the evaluation electronics.

The bearing outer ring and/or the bearing inner ring are advantageously made of steel.

In a preferred embodiment, a tension shaft gear is mounted in the bearing. This preferably applies to the storage of the output-side load of an electric machine (even without a gearbox), e.g. in a direct drive with a crossed roller or four-point bearing.

The tension wave gear advantageously has a drive component, an elastic transmission component provided with external teeth and a wheel provided with internal teeth, the transmission component being pluggable onto the drive component and thereby elliptically deformable by the drive component in such a way that the external teeth of the transmission component are in opposite areas large elliptical axis can be brought into engagement with the internal teeth of the wheel.

The wheel preferably forms the bearing outer ring. The bearing inner ring is preferably designed as a clutch wheel with an internal toothing which has the same number of teeth as the external toothing of the transmission component, the internal toothing of the clutch wheel engaging with the external toothing of the transmission component.

The advantages of the invention lie in particular in the fact that the storage unit provided enables a space-optimized measurement of physical variables. The storage unit can be used, for example, in robot axes, in special machine construction, in automation systems or in medical technology. By knowing the tilting moments, it is possible to carry out an online service life estimate of the bearings by relating the lateral forces and revolutions to the load capacity.

An exemplary embodiment of the invention is explained in more detail with reference to a drawing. All of the described and/or illustrated features, individually or in any sensible combination, form the subject matter of the present invention, regardless of their summary in the claims or their relationship.

• 1 eine Lagereinheit in einer bevorzugten Ausführungsform in einem seitlichen Schnitt,
• 2 die Lagereinheit gemäß 1 in einer Draufsicht,
• 3 die Lagereinheit gemäß 1 in einer perspektivischen Darstellung,
• 4 die Lagereinheit gemäß 1 in einem Ausschnitt und
• 5 die Lagereinheit gemäß 1 in einem weiteren Ausschnitt. Gleiche Teile sind in allen Figuren mit denselben Bezugszeichen versehen.

Some of them show schematically:

• 1 a storage unit in a preferred embodiment in a side section,
• 2 the storage unit according to 1 in a top view,
• 3 the storage unit according to 1 in a perspective view,
• 4 the storage unit according to 1 in a cutout and
• 5 the storage unit according to 1 in another excerpt. The same parts are given the same reference numbers in all figures.

The 1 shows a storage unit 2 in a side section. The bearing unit 2 comprises a bearing 4 with a bearing outer ring 6 and an inner bearing ring 10 rotatably arranged therein. Rolling bodies 14 run in a known manner between the two rings 6, 10 in a rolling body path 18 formed by the two rings 6, 10. The rolling bodies 14 are preferably designed as balls, so that the bearing 4 is designed in the manner of a ball bearing. In other alternative embodiments, the rolling elements 14 can also be designed as rollers or needles in various arrangements. The invention also includes further designs of the rolling elements and their arrangements.

The storage unit 2 is designed to enable torque measurement in a compact and robust design. For this purpose, a plurality of sensor pockets 20 are formed in the outer ring 6, the respective sensor pocket 20 each having at least one sensor 22 (see 2 and 4 ) can or does record. The ones in the 1 Sensor pocket 20 shown is designed to accommodate a torque sensor. For this purpose, according to the invention, the sensor pocket 20 has a sensor wall 24 facing the inner ring 10. The wall thickness of the sensor wall 24 is in particular 1 mm, 0.7 mm, or 0.5 mm.

The in 1 Sensor 22 shown is designed to detect the output-side load of an electrical machine or a mechanical transmission. Depending on the design, longitudinal or transverse forces can be measured. According to the invention, the thin sensor wall 24 has a wall thickness that can be deformed under load for the sensor application and deforms during operation of the machine or gearbox, so that the sensor 22 has a deformation due to the pressure voltage from which the torque or axial force can be calculated. The sensor technology used is based on the principle of the strain gauge (DMS). This sensor 22 changes its electrical resistance even with small deformations. The change in resistance is used as a measurement signal.

An arrow 8 indicates the direction in which forces are introduced into the bearing 4. Another arrow 12 indicates the support of the moments and forces. A cabling pocket 52 for the cabling 56 of one or more sensors 22 is formed in the outer ring 6. The storage unit 2 includes the bearing 4 and the respective sensor 22.

In 2 the storage unit 2 is shown in a top view. In addition to the in 1 shown sensor bag 20 with sensor 22 are in 2 three further sensor pockets 32, 36, 40 are shown, which are formed in the outer ring 6. A sensor 30 is arranged in the sensor bag 32, a sensor 34 is arranged in the sensor bag 36, and a sensor 38 is arranged in the sensor bag 40. The sensor 22 and the sensor 30, which are designed as torque sensors, are each designed to determine the change in circumferential direction/torsion. Opposite sensors 22, 30 are always advantageous for detecting torque or axial force. The two sensors 22, 30 are distributed over the circumference 60 of the outer ring 6 over an angle of 180 °. The two sensors 34, 38 are used to measure the axial direction or the tilting moment. The two sensors 34, 38 are also distributed over the circumference 60 of the outer ring 6 over an angle of 180°. In the embodiment shown, the sensor pockets for all sensors are of the same design with thin walls. In this version described, torque and axial force can be measured. In other preferred embodiments, it is also possible to equip all four pockets for torque or, conversely, only for axial force.

The 3 shows the inner ring 10 and the outer ring 6 in a perspective view with the sensor pocket 20 and a cabling pocket 52. The individual sensors are led to the cabling pocket in a star shape with two electrical conductors. From then on, the electrical connection to the evaluation electronics is implemented using 3- or 4-wire technology, depending on which bridge circuit is used and where the passive resistors are spatially located.

The 4 shows a section of the storage unit according to 1 with the sensor 22, which is arranged in the sensor pocket 24. In 5 the two rings 6, 10 are shown in detail in a section in which the cabling 56 of the sensor or sensors is shown.

Claims (8)

Storage unit (2) with a bearing (4) and at least one sensor (22), the sensor (22, 30, 34, 38) being integrated into the bearing (4), characterized in that the sensor (22, 30, 34, 38) is designed to detect the output-side torque of an electrical machine or a mechanical transmission and/or to measure the transverse force and/or the tilting moment, the bearing (4) having an inner bearing ring (10) and an outer bearing ring (6), and wherein the respective sensor (22, 30, 34, 38) is arranged in at least one sensor pocket (20, 32, 36, 40) formed in the bearing outer ring (6), and wherein the respective sensor pocket (20) is one of the inner ring (10) facing sensor wall (24), and wherein the thin sensor wall (24) has a wall thickness that can be deformed under load for the sensor application and deforms during operation of the machine or the transmission, and wherein the respective sensor pocket (20, 32, 36, 40 ) has a wall thickness on the inside of the bearing between 0.5 mm and 1 mm, and at least two sensor pockets (20, 32; 36, 40) are provided, which are arranged offset from one another along the circumference of the bearing outer ring (6). Storage unit (2). Claim 1 , wherein the sensor pockets (20, 32, 36, 40) are arranged offset from one another by an angle of 90° or 180°. Bearing unit (2) according to one of the preceding claims, wherein at least one cabling pocket (52) is arranged in the bearing outer ring (6). Bearing unit (2) according to one of the preceding claims, wherein the bearing outer ring (6) and/or the bearing inner ring (10) is made of steel. Bearing unit (2) according to one of the preceding claims, wherein a tension shaft gear is mounted in the bearing (4). Storage unit (2). Claim 5 , wherein the tension wave gear has a drive component, an elastic transmission component provided with external teeth and a wheel provided with internal teeth, the transmission component being pluggable onto the drive component and thereby elliptically deformable by the drive component in such a way that the external teeth of the transmission component are in opposite ones Areas of a large elliptical axis can be brought into engagement with the internal teeth of the wheel. Storage unit (2). Claim 6 , whereby the wheel forms the bearing outer ring (6). Storage unit (2). Claim 7 , wherein the bearing inner ring (10) is designed as a clutch wheel with internal teeth which have the same number of teeth as the external teeth of the transmission component, and wherein the internal teeth of the clutch wheel engage with the external teeth of the transmission component.

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