Shaft drive

Abstract

Wave gear (21), comprising a flexible ring element (2) with external teeth (3) and a rigid ring element (4) with internal teeth (5), the flexible ring element (2) being locally radially deformable around its circumference by a wave generator (1) with a non-circular outer circumferential surface, wherein the external teeth (3) of the flexible ring element (2) are at least partially engaged with the internal teeth (5) of the rigid ring element (4) for the transmission of a torque at at least one tooth engagement area (8), wherein the wave generator (1) comprises a non-circular first inner ring (9) which projects at least partially into the flexible ring element (2) and is rotationally fixed to a shaft (10), the wave gear (21) further comprising a first bearing element (11), comprising a second inner ring (12) and at least a first outer ring (13a), wherein the second inner ring (12) is attached to the rigid ring element (4),and wherein the respective outer ring (13a) is attached to the flexible ring element (2), wherein a gear cover (14) is further provided which is attached to a substantially radially extending section (2a) of the flexible ring element (2), wherein at least one opening (15) is formed in the gear cover (14) in which a diaphragm (16) is arranged for compensating for gas pressure and / or temperature differences between an interior (17) of the wave gear (21) and an environment (18) of the wave gear (21), wherein the gear cover (14) is configured to accommodate a torque sensor and / or a printed circuit board, wherein the torque sensor and / or the printed circuit board (33) is arranged in a sensor receptacle (14a) of the gear cover (14) which is sealed against the remaining interior (17) of the wave gear (21).

Description

[0001] The invention relates to a strain wave gear for a robot. Furthermore, the invention relates to a robot with such a strain wave gear.

[0002] DE 11 2012 000 058 T5 discloses a wave gear comprising a fixed, internally toothed gear, a flexible, externally toothed gear arranged within the fixed, internally toothed gear, and a wave generator. The wave generator causes the flexible, externally toothed gear to bend into an elliptical shape and partially mesh with the fixed, internally toothed gear. Furthermore, the wave generator causes the meshing positions of the two gears to move circumferentially. The flexible, externally toothed gear has a cylindrical drum portion with an open edge at one end and capable of radial flexion.The cylindrical drum portion has an external gear forming portion in which the external gear is formed, and a pressed portion that is pressed in the radial direction by the wave generator to cause the external gear forming portion to bend into an elliptical shape. The external gear forming portion and the pressed portion are formed in different portions of the cylindrical drum portion in the direction of the central axis of the flexible external gear. The wave generator is disposed outside the cylindrical drum portion and configured to press the pressed portion in the radial direction from the outside to the inside, causing the pressed portion to bend into an elliptical shape.

[0003] DD 2 57 670 A1 describes a device for pressure equalization in a gear housing with a multi-chamber system, in particular for harmonic drive units in a vertical installation position with a cup-shaped elastic wheel open at the top, wherein a pressure and lubricant equalizing bypass line is arranged between the chambers and to the outside environment.

[0004] DE 10 2007 031 850 A1 describes a drive device for windshield wiper systems with a motor housing attached to a gear housing. An opening with a membrane is provided in the gear housing to allow pressure equalization during temperature fluctuations.

[0005] The object of the present invention is to further develop a strain wave gear, in particular to improve the service life of wear parts of the strain wave gear. This object is achieved according to a first aspect of the invention by the subject matter of patent claim 1 and according to a second aspect of the invention by the subject matter of patent claim 4. Preferred embodiments can be found in the dependent claims, the description, and the figures.

[0006] A wave gear comprises a flexible ring element with external teeth, which can be locally radially deformed circumferentially by a wave generator with a non-circular outer circumferential surface, and a rigid ring element with internal teeth, wherein the external teeth of the flexible ring element are at least partially in meshing engagement with the internal teeth of the rigid ring element for transmitting a torque at at least one tooth engagement region, wherein the wave generator comprises a non-circular first inner ring which projects at least partially into the flexible ring element and is connected in a rotationally fixed manner to a shaft, the wave gear further comprising a first bearing element, comprising a second inner ring and at least one first outer ring, wherein the second inner ring is fastened to the rigid ring element, and wherein the respective outer ring is fastened to the flexible ring element, wherein a gear cover is further provided,which is attached to a substantially radially extending portion of the flexible ring element. For example, the wave generator, and thus also the first inner ring, have an elliptical or oval cross-sectional shape. The gear cover preferably covers the flexible ring element from the input side.

[0007] According to a first aspect of the invention, at least one opening is formed on the gear cover, on which a membrane is arranged to compensate for gas pressure and / or temperature differences between an interior of the wave gear and an environment of the wave gear.

[0008] The respective opening connects the interior of the strain wave gear with the external environment of the gear. The opening is to be understood as a recess or bore, with the diaphragm completely covering the associated opening. The respective opening extends essentially in the axial direction through the respective component on which it is formed. The interior of the strain wave gear described here is spatially separated from the external environment of the strain wave gear, with the interior only being pneumatically and / or thermally connected to the environment of the strain wave gear, in particular the outside atmosphere, via the respective diaphragm arranged at the associated opening. "Pneumatically connected" in this context means that pressure equalization between two spaces is possible via the respective diaphragm. "Thermally connected" in this context means that temperature equalization between two spaces is possible via the respective diaphragm.At the same time, the respective membrane separates the interior of the strain wave gear from the external environment of the strain wave gear, so that neither liquid nor solid substances can pass from one area to the other.

[0009] When switching from speed to torque, the strain wave gear dissipates heat to increase its internal temperature. Furthermore, the strain wave gear's internal pressure increases. A small portion of the heat is dissipated through the housing or the contact surface of each part. The remaining portion of the heat is dissipated through the respective diaphragm and the associated aperture. This prevents an unwanted increase in the strain wave gear's internal pressure, which would in turn place additional strain on the strain wave gear's seals and bearings. In other words, the respective diaphragm positively influences the durability of the strain wave gear's seals and bearings.

[0010] The membrane suppresses a rise in temperature and / or pressure in the lubrication of the relatively movable and / or rotatable components within the interior of the strain wave gear. The membrane also separates the liquid and / or solid media within the interior from the surrounding environment. In other words, it prevents the penetration and / or inflow of foreign substances from the outside into the interior of the strain wave gear. Conversely, the membrane is designed to prevent substances from the interior of the strain wave gear, especially oil or grease, from escaping through the respective opening.

[0011] According to one embodiment, the respective opening and the membrane are designed and arranged in such a way that a temperature and / or pressure increase in a lubricant chamber is suppressed. In other words, a temperature and / or pressure equalization between the interior and the environment of the strain wave gear takes place via the respective membrane. In this case, the interior is to be understood as the space inside the strain wave gear in which parts of the strain wave gear that are rotatable relative to one another are arranged and mounted and supported via respective bearings so that they can rotate relative to one another. The interior of the strain wave gear is therefore to be understood as a lubrication chamber in which the aforementioned bearings of the strain wave gear are supplied with lubricant, in particular lubricating grease. In other words, the interior in this case is a space filled with lubricant.

[0012] The membrane is a membrane filter, preferably made of an aluminum ceramic, for example, comprising aluminum oxide and silicon oxide. The membrane has an undetermined number of micropores, the pore size of the narrowly distributed pores preferably being substantially between 0.1 and 50 µm. The membrane is designed such that the pores do not deform due to temperature and / or pressure. Furthermore, the membrane is heat-resistant and mechanically stable. Furthermore, the membrane is chemically resistant.

[0013] The wave generator, also called a “wave generator,” is operatively connected to the shaft, wherein the shaft is preferably driven in rotation at least indirectly by an electric machine in order to set the wave generator in rotation. For example, the wave generator, in particular the first inner ring, has an elliptical or oval cross-sectional shape. The first inner ring and the shaft are preferably two separate components, wherein the first inner ring is pressed onto the shaft, for example, to create a rotationally fixed connection. The shaft can also be connected to the first inner ring in a rotationally fixed manner via driving teeth. Alternatively, it is conceivable to design the first inner ring and the shaft in one piece. The wave generator forms the drive of the wave gear and, in the case of a two-part design of the shaft and the first inner ring, is preferably integrated into the flexible orelastically deformable ring element is pressed in. The shaft can be designed as a hollow shaft or a solid shaft.

[0014] The flexible ring element, also called a "flexspline," is a high-strength, torsionally rigid sleeve element. It is designed to be flexible enough to accommodate the wave generator at least partially axially, and is thus locally deformable depending on the external shape of the wave generator. The wave generator is rotatable relative to the flexible ring element or is slidably mounted within it. Thus, the flexible ring element assumes the non-circular shape of the wave generator and deforms elastically in a substantially radial direction, analogous to the direction of rotation of the wave generator. In other words, the wave generator is set into a rotational movement during operation of the wave gear, which causes the flexible ring element to undergo circumferential deformation.

[0015] Preferably, the external toothing of the flexible ring element for transmitting a torque is in two symmetrically opposite tooth engagement areas, relative to the rotation axis of the wave generator, at least partially in tooth engagement with the internal toothing of the rigid ring element.

[0016] Preferably, a plurality of rolling elements are arranged spaced apart from one another between an outer circumferential surface of the inner ring and an inner circumferential surface of the flexible ring element. In other words, the elastic ring element is an outer ring, with the rolling elements rolling spatially between the inner ring and the outer ring. Alternatively, the wave generator can have an additional outer ring arranged radially between the rolling elements and the flexible ring element. During assembly, the outer ring of the wave generator in this case rests against the inner circumferential surface of the flexible ring element. This simplifies handling of the wave generator and assembly.

[0017] The rigid ring element, also called a "circular spline," is a torsionally rigid, rigid ring whose internal toothing has more teeth than the external toothing of the flexible ring element. The rotation of the wave generator causes a permanent, circumferential tooth engagement between the flexible ring element and the rigid ring element. In other words, the opposing tooth engagement areas move continuously around the axis of rotation of the wave generator, or in the circumferential direction, during the rotation of the wave generator. Since the flexible ring element has fewer teeth than the rigid ring element, rotation of the wave generator causes a relative movement of the flexible ring element to the rigid ring element. This causes the rolling elements to roll between the inner ring and the flexible ring element or the outer ring of the wave generator.

[0018] During operation, the wave generator rotates, causing the first inner ring of the wave generator to rotate relative to the flexible ring element or the outer ring of the wave generator, which is separately and non-rotatably accommodated within it. The flexible ring element deforms elastically in accordance with the direction and speed of rotation of the wave generator. In other words, during operation of the wave gear, the wave generator is set in a rotational motion, which causes the flexible ring element to undergo circumferential deformation. The first inner ring and the flexible ring element, or, if present, the outer ring of the wave generator, form a second bearing element of the wave gear.

[0019] The shaft is preferably configured to be rotatably mounted relative to a robot arm segment, in particular an output flange, via a third bearing element. The shaft can be configured, at least in sections, as a hollow shaft or as a solid shaft, with the third bearing element being arranged radially within the shaft. In contrast to the first and second bearing elements, the third bearing element is preferably a floating bearing and enables rotation of the shaft relative to another part, in particular a robot arm segment or an output flange.

[0020] Preferably, the diaphragm is integrally bonded to the gear cover. The diaphragm is preferably glued to an inner surface of the gear cover facing the interior. This improves the sealing effect of the diaphragm and effectively protects the interior of the strain wave gear from external influences, particularly unwanted solid and / or liquid substances. The integral bond between the diaphragm and the associated component can be achieved using a double-sided coated tape.

[0021] According to a further embodiment, the interior space is divided into different segments: the space filled with lubricant, i.e., a lubrication area, and at least one further segment sealed from the lubrication area. The further segment can be provided to accommodate at least part of the strain wave gear's electronics. In this case, the membrane additionally suppresses a temperature and / or pressure increase in the components or elements arranged in the further interior segment.

[0022] In this sense, the gear cover is designed to accommodate a torque sensor and / or a circuit board. The torque sensor and / or the circuit board are arranged in a sensor receptacle of the gear cover, which is sealed from the rest of the interior of the strain wave gear. Thus, the interior of the strain wave gear is divided into a section that accommodates the lubricant and a section that accommodates the strain wave gear's electronic components, with the two sections being sealed from each other.

[0023] The torque sensor mounted on the strain wave gear has a circuit board or printed circuit board. This is located inside the strain wave gear, here on the gear cover. As already mentioned, the temperature and pressure in the strain wave gear rise, especially during gear shifting. Since the sensor and, if applicable, the circuit board are also located inside the strain wave gear, the temperature of these parts also rises and they are subjected to pressure. The circuit board of the torque sensor consists of electronic components that are affected by temperature changes, which in turn can negatively impact the operation and / or service life of the circuit board components.

[0024] In this design, a small portion of the heat is dissipated to the outside through the housing or the contact surface of each component. The remaining portion of the heat is dissipated to the outside through the respective diaphragm and the corresponding aperture. This prevents an unwanted increase in the internal pressure of the strain wave gear, which would in turn cause additional stress on the seals and bearings of the strain wave gear. In other words, the durability of the torque sensor and / or the circuit board is positively influenced by the respective diaphragm.

[0025] A recess or depression can be provided on the gear cover, which serves as a sensor receptacle and into which at least the circuit board of the torque sensor is accommodated. The sensor receptacle is also formed in the interior of the strain wave gear, in particular on the inside of the gear cover. The sensor receptacle is sealed from the interior of the strain wave gear, which is designed as a lubrication chamber.

[0026] In this sense, at least one seal is arranged radially between the gear cover and the flexible ring element to seal the sensor receptacle from the rest of the interior of the strain wave gear. The sealing element is preferably a lip seal.

[0027] Wiring of the torque sensor and / or the circuit board can be arranged, attached and, if necessary, passed through the gearbox cover.

[0028] According to a second aspect of the invention, at least one opening is formed on at least the second inner ring of the first bearing element, at which opening a membrane is arranged to compensate for gas pressure and / or temperature differences between an interior of the strain wave gear and an environment of the strain wave gear. In particular, the opening extends axially through the second inner ring, the rigid ring element and any output elements arranged thereon. An output element can, for example, be a slowly rotating output flange. In this case, it may be necessary to provide a plurality of openings on the rotating element in order to achieve the desired temperature and / or pressure compensation. Furthermore, reference is made to the explanations relating to the first aspect of the invention, particularly with regard to the function and effects of the membrane at the associated opening.

[0029] Such an arrangement of the respective opening is particularly suitable if the part of the interior of the strain wave gear that receives the lubricant is not connected to the gear cover.

[0030] In this exemplary embodiment, the membrane is preferably connected to the second inner ring in a materially bonded manner. The membrane is preferably glued to an inner surface of the second inner ring facing the interior.

[0031] For all embodiments, the first bearing element is preferably a crossed roller bearing, comprising the second inner ring, the first outer ring, and a second outer ring arranged axially adjacent to the first outer ring. A plurality of rollers are arranged at a distance from one another between the second inner ring and the first outer ring. A plurality of rollers are also arranged at a distance from one another between the second inner ring and the second outer ring. Crossed roller bearings are advantageous for moment loads and loads from all directions, including axial and radial directions. The rollers of the two rows of rolling elements are arranged in an X-arrangement.

[0032] The invention also relates to a robot comprising a strain wave gear according to the invention according to the first aspect of the invention or the second aspect of the invention. In particular, the strain wave gear according to the invention is arranged in a joint for a robot arm and acts at least indirectly between two robot arm segments.

[0033] Further measures improving the invention are described in more detail below together with the description of three preferred embodiments of the invention with reference to the figures, wherein identical or similar components are provided with the same reference numerals. Fig. 1 a simplified schematic representation of a partially shown robot with a wave gear according to the invention according to a first embodiment, Fig. 2 a schematic longitudinal section of the wave gear according to the invention according to Fig. 1, Fig. 3 a schematic partial longitudinal section of the wave gear according to the invention according to Fig. 1 and Fig. 2, Fig. 4 a schematic longitudinal sectional view of the wave gear according to the invention according to a second embodiment, Fig. 5 a schematic partial longitudinal section of the wave gear according to the invention according to Fig. 4, Fig. 6 a highly schematic representation of an opening on a gear cover of the wave gear according to the invention, and Fig. 7 a schematic partial longitudinal sectional view of the wave gear according to the invention according to a third embodiment.

[0034] Fig. Figure 1 shows a section of a robot 20. A joint 23 is arranged between a first robot arm segment 22a and a second robot arm segment 22b, which connects the two robot arm segments 22a, 22b in an articulated manner. To change the position of the two robot arm segments 22a, 22b relative to each other, the robot 20 has a drive unit 24 comprising an electric motor 25 and a strain wave gear 21 according to the invention.

[0035] According to the Fig. 2 to 5 and Fig. 7, a wave gear 21 according to the invention according to a first embodiment comprises a flexible ring element 2 with an external toothing 3, which can be deformed in the radial direction by a wave generator 1, and a rigid ring element 4 with an internal toothing 5, wherein the external toothing 3 of the flexible ring element 2 meshes with the internal toothing 5 of the rigid ring element 4 for transmitting a torque at two opposite tooth engagement regions 8.

[0036] The strain wave gear 21 has a first bearing element 11, which is designed as a crossed roller bearing. The first bearing element 11 comprises a second inner ring 12, a first outer ring 13a, and a second outer ring 13b arranged axially adjacent to the first outer ring 13a. A respective rolling element row with a plurality of rolling elements 28 is arranged between the second inner ring 12 and the respective outer ring 13a, 13b. The second inner ring 12 is fastened to the rigid ring element 4, with the outer rings 13a, 13b being fastened to a radially extending section 2a of the flexible ring element 2.

[0037] The wave generator 1 further comprises a non-circular second bearing element 26, which is arranged radially between the flexible ring element 2 and a shaft 10 of the wave gear 21. The second bearing element 26 comprises a first inner ring 9, which is arranged in a rotationally fixed manner on an outer circumferential surface 27 of the shaft 10, and a third outer ring 29, which is arranged radially within a flexible ring element 2 of the wave gear 21. The wave generator 1 can be set into a rotational movement via the shaft 10 by an electric motor (not shown here).

[0038] The first inner ring 9 and the third outer ring 29 of the non-circular, in particular elliptical, second bearing element 26 have, in this case, an elliptical outer geometry, for example, wherein the outer peripheral surface of the third outer ring 29 comes into rotationally fixed contact with an inner peripheral surface of the flexible ring element 2. Before assembly of the second bearing element 26, the third outer ring 29 has a substantially round outer geometry, which, however, is elastically deformed into the elliptical outer geometry during assembly depending on the outer geometry of the first inner ring 9. The second bearing element 26 is pressed into the flexible ring element 2, so that the wave generator 1 with the second bearing element 26 protrudes into the flexible ring element 2. The flexible ring element 2 thereby assumes the elliptical outer shape of the wave generator 1.During operation of the wave gear 21, the wave generator 1 is set into a rotational movement via the shaft 10, whereby the third outer ring 29 and the flexible ring element 2 are locally radially deformed. In other words, the rotation of the wave generator 1 about its rotation axis 7 causes the flexible ring element 2 and the third outer ring 29 to be circumferentially deformed.

[0039] Since the flexible ring element 2 adapts to the elliptical shape of the wave generator 1, the flexible ring element 2, with its external toothing 3, only meshes with the internal toothing 5 of the rigid ring element 4 at the respective tooth engagement area 8. The rigid ring element 4 is understood here as a ring gear.

[0040] The wave gear 21 further comprises a gear cover 14 which is fastened to the substantially radially extending section 2a of the flexible ring element 2 on the input side, i.e. on a side of the substantially radially extending section 2a opposite the outer rings 13a, 13b of the first bearing element 11.

[0041] According to the Fig. 3 and Fig. 5, an axial opening 15 is formed on the gear cover 14, at which a membrane 16 is arranged. The membrane is designed, on the one hand, to compensate for gas pressure and temperature differences between an interior space 17 of the strain wave gear and an environment 18 of the strain wave gear. Furthermore, the membrane 16 is provided to prevent substances, in particular lubricant, from escaping from the strain wave gear 21 and to prevent substances, in particular dirt and / or moisture, from entering the strain wave gear 21.

[0042] As in Fig. 6, the membrane 16 is integrally connected to the gear cover 14. The membrane 16 has a band 16a coated on both sides with an adhesive, which is arranged between a membrane body 16b and the gear cover 14. The band 16a ensures that the gas pressure reduction and the dissipation of excess heat, i.e. the gas pressure and temperature equalization, occur exclusively via the membrane body 16b. During operation of the strain wave gear 21, there is an increase in temperature and an increase in the internal pressure in the interior 17 of the strain wave gear 21. This is partially absorbed and dissipated via a housing (not shown here). The remaining, substantial portion of the additional heat is dissipated via the membrane 16 and the opening 15 into the environment 18 of the strain wave gear 21. The opening also provides pressure equalization between the interior 17 and the environment 18, or the outside atmosphere.

[0043] According to the first embodiment according to Fig. 2 and Fig. 3, the interior 17 of the strain wave gear 21 is to be understood as the lubrication area of ​​the strain wave gear 21. The interior 17 is within the dashed line 30 according to Fig. 3, and in the present case comprises the two rows of rolling elements with the rolling elements 28 of the first bearing element 11, the second bearing element 26 and a third bearing element 31, which rotatably supports the shaft 10 relative to an output flange 32, and a fourth bearing element 6, which rotatably supports the shaft 10 relative to the gear cover 14.

[0044] According to the second embodiment according to Fig. 4 and Fig. 5, the interior 17 of the strain wave gear 21 is divided into two areas, in contrast to the first embodiment, firstly into the lubrication area analogous to the first embodiment and an electronics receptacle area, here designed as a sensor receptacle 14a on the gear cover 14. Fig. Figure 5 shows the sensor receptacle 14a using the dashed line 30. A circuit board 33 for a torque sensor is arranged within the sensor receptacle 14a. The sensor receptacle 14a is sealed from the lubrication area by a seal 19 designed as a lip seal, wherein the seal 19 is arranged radially between an axial section 14b of the gear cover 14 and the flexible ring element 2. Thus, the sensor receptacle 14a of the gear cover 14 is sealed from the remaining interior 17 of the strain wave gear 21, here the part of the interior 17 designed as a lubrication area. For further details, please refer to the above explanations.

[0045] The wave gear 21 according to the third embodiment according to Fig. 7 is essentially identical to the second embodiment according to the Fig. 4 and Fig.5. The difference here is that the sensor receptacle 14a is fluidically and spatially separated from the interior 17 of the strain wave gear 21, which is designed as a lubrication area, analogous to the first exemplary embodiment. The dashed line 30 schematically surrounds the interior 17 of the strain wave gear 21 forming the lubrication area. Due to this spatial separation, an opening 15 is formed on the second inner ring 12 of the first bearing element 11, on which a diaphragm 16 is arranged, via which the gas pressure and temperature equalization takes place, analogous to the previous embodiments, between the interior 17 of the strain wave gear 21 and the surrounding area 18 of the strain wave gear 21. The diaphragm 16 is integrally connected to the second inner ring 12. Due to the present structural design, the opening 15 extends axially through the second inner ring 12, the rigid ring element 4, and the output flange 32.Since the rigid ring element 4 and the output flange 32 are slowly rotating components, they can have additional openings (not shown here) distributed over the circumference to ensure sufficient heat dissipation and pressure equalization. This exemplary embodiment is intended to clarify that the respective opening 15 can also be arranged on components of the strain wave gear 21 other than the gear cover 14. In any case, a membrane 16 is provided at the respective opening 15, regardless of its position, to prevent an exchange of substances between the interior 17 and the environment, as well as to realize heat dissipation to the environment 18 and pressure equalization between the interior 17 and the environment 18. List of reference symbols 1 wave generator 2 Flexible ring element 2a Radially extending section 3 External gearing 4 Rigid ring element 5 Internal gearing 6 Fourth bearing element 7 Rotation axis 8 Tooth engagement area 9 First inner ring or inner ring of the second bearing element 10 Wave 11 First bearing element 12 Second inner ring of the first bearing element 13a, 13b Outer ring of the first bearing element 14 Gearbox cover 14a Sensor mount of the gearbox cover 14b Axial section of the gearbox cover 15 Breakthrough 16 Membran 17 Interior 18 Surroundings 19 Seal 20 robots 21 wave gears 22a, 22b Robot arm segment 23 Joint 24 drive unit 25 electric motor 26 Second bearing element 27 Outer peripheral surface of the shaft 28 rolling elements of the first bearing element 29 Third outer ring of the second bearing element 30 Dashed line 31 Third bearing element 32 Output flange 33 circuit board

Claims

[1] Wave gear (21), comprising a flexible ring element (2) with external teeth (3) that can be locally radially deformed circumferentially by a wave generator (1) with a non-circular outer circumferential surface, and a rigid ring element (4) with internal teeth (5), wherein the external teeth (3) of the flexible ring element (2) are at least partially in meshing engagement with the internal teeth (5) of the rigid ring element (4) for transmitting a torque at at least one tooth engagement region (8), wherein the wave generator (1) comprises a non-circular first inner ring (9) that projects at least partially into the flexible ring element (2) and is connected in a rotationally fixed manner to a shaft (10), the wave gear (21) further comprising a first bearing element (11) comprising a second inner ring (12) and at least one first outer ring (13a), wherein the second inner ring (12) is fastened to the rigid ring element (4),and wherein the respective outer ring (13a) is fastened to the flexible ring element (2), wherein a gear cover (14) is further provided, which is fastened to a substantially radially extending section (2a) of the flexible ring element (2), wherein at least one opening (15) is formed on the gear cover (14), at which opening a membrane (16) is arranged to compensate for gas pressure and / or temperature differences between an interior space (17) of the harmonic gear (21) and an environment (18) of the harmonic gear (21), wherein the gear cover (14) is designed to accommodate a torque sensor and / or a printed circuit board, wherein the torque sensor and / or the printed circuit board (33) is arranged in a sensor receptacle (14a) of the gear cover (14), which is sealed off from the remaining interior space (17) of the harmonic gear (21). [2] Wave gear (21) according to claim 1, characterized bythat the membrane (16) is integrally connected to the gear cover (14). [3] Wave gear (21) according to claim 1 or 2, characterized by that at least one seal (19) is arranged radially between the gear cover (14) and the flexible ring element (2) for sealing the sensor receptacle (14a) from the remaining interior space (17) of the harmonic gear (21). [4] Wave gear (21), comprising a flexible ring element (2) with external teeth (3) that can be locally radially deformed circumferentially by a wave generator (1) with a non-circular outer circumferential surface (6), and a rigid ring element (4) with internal teeth (5), wherein the external teeth (3) of the flexible ring element (2) are at least partially in meshing engagement with the internal teeth (5) of the rigid ring element (4) for transmitting a torque at at least one tooth engagement region (8), wherein the wave generator (1) comprises a non-circular first inner ring (9) that projects at least partially into the flexible ring element (2) and is connected in a rotationally fixed manner to a shaft (10), the wave gear (21) further comprising a first bearing element (11) comprising a second inner ring (12) and at least one first outer ring (13a), wherein the second inner ring (12) is fastened to the rigid ring element (4),and wherein the respective outer ring (13a) is fastened to the flexible ring element (2), wherein a gear cover (14) is further provided which is fastened to a substantially radially extending portion (2a) of the flexible ring element (2), , characterized by that at least one opening (15) is formed at least on the second inner ring (12) of the first bearing element (11), on which opening a membrane (16) is arranged to compensate for gas pressure and / or temperature differences between an interior space (17) of the wave gear (21) and an environment (18) of the wave gear (21). [5] Wave gear (21) according to claim 4, characterized by that the membrane (16) is integrally connected to the second inner ring (12). [6] Wave gear (21) according to one of the preceding claims, characterized bythat the first bearing element (11) is a crossed roller bearing, comprising the second inner ring (12), the first outer ring (13a) and a second outer ring (13b) arranged axially adjacent to the first outer ring (13a). [7] Robot (20) comprising a wave gear (21) according to one of the preceding claims.

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