Thermal decoupling of sensors and active components on motors with optical sensors

Abstract

The invention relates to an electric machine (1) having a shaft (5) which is connected in a torque-proof manner to a rotor (9), wherein the shaft (5) has an encoder (13) at one end (NDE) and can be mechanically coupled to a working machine at the other end (DE), wherein the rotor (9) interacts electromagnetically via an air gap (12) with a stator (8) having a winding system (7), in turn rotating the shaft (5), wherein the encoder (13) is arranged in an encoder housing (14) which is thermally decoupled from the machine components directly following axially from the electric machine (1) by means of a shaped seal (16).

Description

Technical Field

[0001] The present invention relates to an electric motor having an encoder, wherein the encoder housing or encoder cover of the electric motor is thermally decoupled from the electric motor. Background Technology

[0002] In permanent magnet excitation motors, such as servo motors, the circuit board of the encoder on its non-driving end (NDE) is equipped with sensor components and their electronics. The circuit board is only allowed to operate within a predetermined, structurally specific temperature limit.

[0003] Otherwise, the encoder components will suffer irreversible damage or even be destroyed, which will significantly limit the operation of the electric machine and thus affect the working process.

[0004] Due to heat generation in the winding system of the electric motor, losses in the encoder, and losses generated by the components on the encoder circuit board, the overall limit temperature of the encoder circuit board will be reached. Even when these limit temperatures are reached, for a large number of electric motors, the winding temperature is still below the temperature allowed by the insulation system of the winding system.

[0005] Therefore, the use of this electric motor is limited by the extreme temperatures reached by the circuit board components, rather than by the allowable heat utilization of the winding system's insulation system. Furthermore, this necessitates the use of more active materials in the electric motor to reduce the temperature generated in the encoder.

[0006] In addition, electric motors, such as servo motors, must also meet protection ratings such as IP64, IP65 or IP67 as required.

[0007] Therefore, this also applies to the sealing positions between the bearing cover and the insulating gasket, as well as between the insulating gasket and the encoder housing or encoder cover.

[0008] Therefore, it is necessary to thermally decouple the electric motor and / or certain components of the electric motor relative to the encoder. This is achieved by means of insulating gaskets, which are bonded and / or screwed to predetermined locations on the electric motor housing or bearing caps.

[0009] This aims to prevent heat flow, especially from the winding system of the electric motor, through the housing and bearing cover, to the encoder components. To further meet the required level of protection, O-rings are installed at the interfaces between the housing or bearing cover and the insulating gasket, and at the interfaces between the insulating gasket and the encoder. For the sealing seats of these O-rings, high requirements are placed on the machined surfaces of the sealing mating parts involved in the sealing, such as the housing or bearing cover and the insulating gasket.

[0010] Due to the high radial load caused by the compressed O-ring and the locally thin wall thickness of the insulating gasket, the insulating gasket may occasionally break, which could lead to a failure of the protection level of the electric machine. However, this relatively high radial compression is required to meet the protection level.

[0011] Similarly, electric motors, such as servo motors, must also meet predetermined electromagnetic compatibility requirements. Summary of the Invention

[0012] Therefore, the object of the present invention is to create an electric motor that particularly avoids the aforementioned disadvantages and allows for a relatively high utilization rate of its active components, even when an encoder is installed. Furthermore, relatively high loads on the insulating gaskets should be avoided.

[0013] The proposed objective is achieved according to the invention through the features of the independent claims.

[0014] The advantageous configurations of the present invention are the subject of the dependent claims.

[0015] According to the present invention, an electric machine is provided having a shaft connected to a rotor in a torsion-resistant manner, wherein the shaft has an encoder at one end (NDE) and is mechanically coupled to a working machine at the other end (DE), and wherein the rotor interacts electromagnetically with a stator having a winding system via an air gap, thereby causing the shaft to rotate. The encoder is arranged in an encoder housing, which is at least thermally decoupled from the machine parts that directly follow the electric motor in the axial direction by means of a shaped seal.

[0016] Here, encoder should be understood as all types of encoders, especially optical encoders or rotary transformers.

[0017] An encoder housing should generally be understood as a cover used to conceal the space containing the encoder—that is, the encoder cavity—and is also a non-drive end enclosure element. This can be a cover or a housing having at least one axially extending flange.

[0018] Furthermore, the molded seal provides a sealing effect in this area to meet the corresponding predetermined protection level. Additionally, the molded seal also supports electromagnetic shielding to meet the predetermined electromagnetic compatibility requirements of electric machinery.

[0019] The shaped seal in the sense of this invention should be understood in particular as a static, releasable contact seal that generates a pressure seal by an external, here axial, force.

[0020] Molded seals exhibit relatively high resilience under pressure and temperature to ensure long-term protection requirements. Advantageously, a long-term operating temperature of approximately 120-125°C should be set. Sufficient manufacturing precision is desired to ensure the sealing performance of the molded seal in its installed state. Furthermore, molded seals are resistant to industrial environments, such as those encountered when used in machine tools and robots. Advantageously, molded seals are silicone-free, as this avoids the potential risk of volatiles emitted during the operation of electric machinery, which could affect encoder functionality.

[0021] The molded seal can be made of, for example, FKM (fluororubber), EPDM (ethylene propylene diene monomer) or NBR (nitrile butadiene rubber).

[0022] Here, an encoder should be understood as a sensor used to detect changes in position or angle, capable of detecting angular changes and rotation direction, and equipped with corresponding evaluation electronics. These encoders can be self-supporting bearings or coupled to a shaft without their own bearings.

[0023] The encoder housing or encoder cover has a flange that almost completely surrounds the outer radial circumference and extends axially toward the motor.

[0024] The shaped seal located on the encoder cover and on the radial and axial inner side of the flange is ideally designed so that the sprayed water does not directly impact the sealing surface, but must first undergo at least one deflection.

[0025] The reliable contact required to meet electromagnetic compatibility requirements between the encoder housing or encoder cover and machine components, such as the housing of an electric motor or a bearing cover, is ideally ensured by a protrusion located in the flange region at the radially outer edge of the encoder housing or encoder cover. Thus, the encoder housing or encoder cover is also detachably secured to the machine component, such as a bearing cover, by a predetermined number of fastening bolts.

[0026] The molded seal according to the invention is disposed in the force diversion section, thereby greatly avoiding loads caused by pressure and temperature during operation. Furthermore, this force diversion section prevents bending loads on the connecting components (machine parts and encoder housing), thereby ensuring the guaranteed tightening of bolts.

[0027] Therefore, the encoder housing or encoder cover will not bend when screwed on, and the internal shaped seal is circumferentially defined and uniformly pressed between the machine part and the encoder housing or encoder cover, thereby particularly meeting the protection level and electromagnetic compatibility requirements.

[0028] At the outer circumference, that is, between the circumferentially distributed screw positions, i.e., between the protrusions, the outer flange of the encoder housing or encoder cover is axially recessed relative to the machine component to form a defined gap between the machine component, such as a bearing cover, and the encoder housing. As a result, heat transfer from the machine component to the encoder housing is further significantly reduced.

[0029] The embodiments of the present invention have the following advantages: The encoder cover or encoder housing has a relatively large outer surface, and thus forms a large surface area, which is used to dissipate the heat of the encoder or encoder cavity into the environment.

[0030] This avoids the complex structure and fault sensitivity of the past, such as the occasional breakage of the insulating gasket between the machine parts and the encoder cover or encoder housing due to the high mechanical load of the insulating gasket.

[0031] The molded seal and its positioning according to the present invention achieve functional integration, thereby achieving more functions with fewer parts, for example, eliminating the need for two O-rings. Furthermore, this reduces the number of interfaces requiring sealing compared to conventional embodiments.

[0032] Because the shaped seal is particularly planar, machining of the encoder cover can be eliminated. One embodiment of the invention specifies that the shaped seal is substantially constructed as a disc or annular shape. Therefore, the shaped seal can be constructed non-uniformly in radial and / or axial extension to adapt to the contours of adjacent encoder components and / or machine components. Thus, the shaped seal can compensate for geometric irregularities according to the specific configuration of the mating parts, such as encoder components and / or machine components.

[0033] Furthermore, the encoder, and in particular the encoder circuit board, is optionally connected to the inside of the encoder cover, for example, made of die-cast aluminum, by means of thermal paste, to conduct heat loss generated on the circuit board and in the encoder's optional self-contained bearing support from the circuit board to the encoder cover, and then dissipate it into the environment through the outer surface of the encoder cover and / or optional heat sinks. For this purpose, the encoder cover must be correspondingly cooler than the circuit board, or must be thermally decoupled from the motor housing to achieve a sufficient temperature gradient required for the desired heat transfer in the encoder region.

[0034] The predetermined contact surface formed by the protrusion, that is, between the machine component and the encoder cover or encoder housing, should preferably be kept as small as possible, because otherwise, heat flow from the machine component, such as the bearing cover, to the encoder cover would be avoided.

[0035] To secure the encoder housing or encoder cover to the machine component, at least two fixing points are required. Four fixing points constitute a preferred and sufficient implementation in this respect. However, the number of protrusions should be optimized in terms of electromagnetic compatibility requirements, heat transfer, and sealing, as these protrusions also constitute thermal bridges between the machine component and the encoder housing or encoder cover.

[0036] By using molded seals and their arrangement between the machine parts and the encoder housing, protection levels can now be met in a simple way, up to the so-called IP codes (IP = International Protection) IPX5 (water jet protection), even IPX7 (protection against short-term immersion), and especially up to IP68 (complete dust protection and protection against short-term immersion). Furthermore, the protrusions not only secure the encoder housing to the machine parts, such as bearing covers, but also meet electromagnetic compatibility requirements, such as grounding functionality. Attached Figure Description

[0037] The invention and other advantageous configurations thereof will now be described in more detail with the aid of embodiments shown in principle, wherein: Figure 1 A longitudinal sectional view of an electric machine shown in principle is presented; Figure 2 A detailed view of the area of ​​the shaped seal is shown; Figure 3 An exemplary fixing of the encoder housing and machine parts is shown; Figure 4 A detailed diagram of the gap is shown; Figure 5 A three-dimensional detailed view of the encoder housing and bearing cover is shown. Detailed Implementation

[0038] It should be noted that terms such as "axial," "radial," and "tangential" refer to the axis 6 as used in the corresponding figures or examples described. In other words, the directions axial, radial, and tangential always refer to the axis 6 of the rotor 9, and consequently, the corresponding axis of symmetry of the stator 8. Here, "axial" describes a direction parallel to axis 6, "radial" describes a direction orthogonal to axis 6, toward or away from axis 6, and "tangential" is a circumferentially oriented direction about axis 6 at a constant radial distance from axis 6 and at a constant axial position. The expression "circumferential" is equivalent to "tangential."

[0039] Regarding a surface, such as a cross-section, terms such as "axial," "radial," and "tangential" describe the orientation of the normal vector of that surface, that is, the orientation of the vector perpendicular to the relevant surface.

[0040] Here, the term "coaxial component," such as rotor 9 and stator 8, should be understood as components having the same normal vector; that is, the planes defined by the coaxial components are parallel to each other. Furthermore, this description should also include the fact that the center points of the coaxial components lie on the same axis of rotation or axis of symmetry. However, these center points can, if necessary, be located at different axial positions on that axis, and the planes can therefore have a distance greater than zero from each other. This description does not necessarily require the coaxial components to have the same radius.

[0041] When the term "complementary" is associated with two complementary components, it means that their external shapes are implemented such that one component is preferably able to be completely arranged within its complementary component, so that the inner surface of one component is in ideal, gapless, or complete contact with the outer surface of the other component. Therefore, in the case of two complementary objects, the external shape of one object is determined by the external shape of the other object. The term "complementary" can be replaced by the term "opposite."

[0042] For clarity, in the accompanying drawings, where parts are present multiple times, not all shown parts are usually labeled with reference numerals.

[0043] The described embodiments can be combined arbitrarily. Similarly, individual features of the various embodiments can also be combined without departing from the spirit of the invention.

[0044] Figure 1 A schematic longitudinal sectional view of the electric machine 1 is shown. In this example, a stator 8 is arranged in a housing 2, the stator having a winding system 7 arranged in slots that extend substantially axially. The housing 2 is supported on a shaft 5 by means of a bearing 4 via a bearing cover 3.

[0045] Alternatively, a so-called cup-shaped housing can be conceived, wherein the housing 2 and the bearing cover 3 on the DE side form an integral component, which has a shaft through-hole.

[0046] A rotor 9 is provided, which is spaced apart from the stator 8 by an air gap 12, and has, for example, permanent magnets (not shown further). Optionally, the laminated iron cores 10, 11 of both the stator 8 and the rotor 9 have axially extending cooling channels to achieve a closed internal cooling circuit within the housing 2. When the winding system 7 of the stator 8 is powered, the shaft 5 rotates about the axis 6 due to its electromagnetic interaction with the rotor 9. This rotation generates a drive (torque) on the DE side of the electric motor 1 to the working machine (not shown further).

[0047] On the NDE side, encoder 13 is attached to the axial extension of shaft 5.

[0048] The encoder 13 in the sense of the present invention should be understood in particular as a sensor for detecting position and / or angle changes, capable of detecting angle changes and rotation direction of shaft 5, and equipped with corresponding evaluation electronics arranged on a circuit board of the encoder 13.

[0049] Here, these encoders 13 can be coupled to the shaft 5 with their own bearings or cantilever, or they can be coupled directly to the shaft. Similarly, it is also conceivable that the encoders 13 are mechanically coupled via a coupling (not shown further).

[0050] These encoders 13 are designed in particular as optical encoders 13 with code disks, or constructed as rotary transformers.

[0051] The winding system 7 of the electric motor 1, particularly the stator 8, is powered via one or more plugs 15, and the signal of the encoder 13 is transmitted to the converter (not shown further), the plugs preferably being attached to the bearing cover 3.

[0052] The housing 2 of the electric motor and / or the encoder housing 14 or encoder cover is preferably manufactured by a casting process. Here, die casting of aluminum, gray cast iron, plastic, and composite materials are preferred materials. The machine parts and the encoder housing 14 or encoder cover can also be produced by additive manufacturing (AM).

[0053] The encoder housing 14 or encoder cover is mechanically connected to a machine component of the electric machine 1, such as housing 2 or bearing cover 3. This machine component is made of metal, particularly by die casting. The machine component and / or encoder housing 14 are made, for example, of aluminum or an aluminum alloy.

[0054] One embodiment of the invention specifies that the shaped seal 16 is implemented substantially in a disc-shaped or annular manner. The shaped seal 16 can be implemented non-uniformly in radial and / or axial expansion to adapt to the contours of adjacent encoder components and / or machine components. Therefore, the shaped seal 16 can compensate for geometric irregularities according to the specific configuration of the mating parts, such as encoder components and / or machine components.

[0055] The molded seal 16 is made of a sealing material, such as silicone, FKM (fluororubber), EPDM (ethylene propylene diene monomer rubber), NBR (nitrile butadiene rubber), TPE (thermoplastic polyurethane), TPU, or a two-component injection seal.

[0056] The molded seal 16, especially in conjunction with the embodiments described in this invention, advantageously achieves extensive thermal decoupling between the machine component and the encoder housing 14 adjacent to the machine component, resulting in a relatively large temperature gradient between the machine component and the encoder housing 14.

[0057] This avoids overheating of the encoder 13 or its sensor components and electronics. This is particularly advantageous if the electric motor 1 is implemented as a servo motor, because the active components of a servo motor typically become very hot during operation.

[0058] One embodiment of the invention specifies that the shaped seal 16 itself and / or the adjacent sealing surfaces of the machine parts and / or encoder covers are respectively implemented with at least one labyrinthine circumferentially extending profile or structure 22 to achieve the desired level of protection. Here, the profile can also be implemented as a step or groove in a simple configuration.

[0059] The sealing surfaces on the machine parts and / or encoder housing 14 and / or shaped seal 16 are at least partially provided with labyrinthine circumferentially extending structures 22 or recesses, which improve the sealing effect and form a form-fit connection between the machine parts and encoder housing 14.

[0060] At the same time, the molded seal 16 prevents liquid from entering the electric motor 1. Such liquids are, for example, spray water or lubricants, which the electric motor 1, located in or on a cutting machine (e.g., a milling machine), would be exposed to.

[0061] By using the molded seal 16 and its arrangement between the machine parts and the encoder housing 14, it is now possible to meet protection levels in a simple way, up to the so-called IP code (IP = International Protection) IPX5 (water jet protection), even IPX7 (short-term immersion protection), and especially up to IP68 (complete dust protection and short-term immersion protection).

[0062] Shaft 5 has a section that is torsionally connected to rotor 9. Encoder 13 is specifically positioned on the section of shaft 5 facing the NDE side. Shaft 5 is supported at this location. Furthermore, encoder 13 can also be supported by its own bearing or cantilever support at this location.

[0063] On the DE side, shaft 5 extends outward from the machine housing, namely housing 2 and encoder housing 14, and can be mechanically coupled to the working machine there.

[0064] Figure 2 A plug 15 positioned on the bearing cover 3 is shown as an example. The encoder housing 14 abuts the bearing cover 3 via a shaped seal 16 in the direction toward the NDE side.

[0065] Due to the flange 21, the encoder housing 14 has a relatively large outer surface, and thus forms a large surface area for dissipating the heat of the encoder 13 into the environment.

[0066] This avoids the previous complex and at least occasionally faulty structure, which could cause the insulating gasket between the machine parts and the encoder housing 14 to break.

[0067] The molded seal 16 according to the invention and its positioning on the bearing cover 3 and encoder housing 14 achieve functional integration, thereby achieving more functionality with fewer parts, for example, eliminating the need for two O-rings. Furthermore, this reduces the number of interfaces requiring sealing compared to conventional embodiments.

[0068] Since the formed seal 16 is planar, the cutting process of the encoder housing 14 can be eliminated.

[0069] The bearing cap 3 and / or the shaped seal 16 and / or the encoder housing 14 have at least one labyrinthine or groove-shaped circumferentially extending structure 22 or profile.

[0070] Thus, gas and liquid intrusion into the motor 1 is further prevented at the mounting location of the motor. Therefore, the molded seal 16 and its arrangement according to the invention between the bearing cover 3 and the encoder housing 14 meet the so-called IP code (IP = International Protection) IPX5 (water jet protection), even IPX7 (protection against short-term immersion), and especially even IP68 (complete dust protection and protection against short-term immersion).

[0071] Furthermore, the encoder circuit board is at least partially bonded to the inside of the encoder housing 14, which is made of die-cast aluminum, by means of thermal paste to conduct heat loss generated on the circuit board and in the optional self-supporting bearing portion of the encoder 13, for example, from the circuit board to the encoder housing 14. Here, the heat is dissipated to the environment via the outer surface through heat sinks 20 arranged inside and / or outside the encoder housing 14.

[0072] Therefore, the encoder housing 14 must be correspondingly cooler than the circuit board, or it must be thermally decoupled from the housing of the motor 1 in order to achieve the sufficient temperature gradient required for the desired heat transfer in the encoder 13 region.

[0073] Thermal management of encoder 13 or encoder cavity is specified herein, wherein heat flow from electric motor 1 is substantially avoided by the shaped seal 16, while heat generated in encoder 13 can be dissipated relatively easily by thermal paste and / or heat sink 20.

[0074] Figure 3 An exemplary connection between the encoder housing 14 and the bearing cover 3 via protrusions 18 is shown. A plurality of protrusions 18, at least two protrusions 18, are arranged circumferentially on the encoder housing 14.

[0075] The predetermined contact surface 23 formed by the protrusions 18, i.e., between the bearing cover 3 and the encoder housing 14, should preferably be kept as small as possible to minimize heat flow from the bearing cover 3 to the encoder housing 14. In addition to securing the encoder housing 14 to machine components, such as the bearing cover 3, these protrusions 18 are also necessary to meet electromagnetic compatibility requirements, such as grounding functionality.

[0076] The molded seal 16 is provided in the force diversion section to largely avoid loads caused by pressure and temperature during operation. In addition, the force diversion section prevents the bearing cover 3 and the encoder housing 14 from being subjected to bending loads, thereby ensuring the limited tightening of the bolts 19.

[0077] Therefore, the encoder cover will not bend when screwed on, and the internal shaped seal 16 is circumferentially defined and simultaneously pressed between the bearing cover 3 and the encoder cover, thereby meeting the above protection level requirements for a long period of time.

[0078] At the outer circumference of the encoder housing 14, that is, between the screw positions distributed around the circumference, the outer flange 21 is axially retracted to form a defined gap 17 between the bearing cover 3 and the encoder housing 14, thereby minimizing heat transfer from the bearing cover 3 to the encoder housing 14 as much as possible.

[0079] Figure 4 exist Figure 2 The detailed drawing shows the extension of gap 17, which, when viewed circumferentially, is interrupted only by protrusion 18.

[0080] Figure 5 The encoder housing 14 is shown in a partial perspective view. This housing is directly connected to the bearing cover 3 or its contact surface 23 via protrusions 18. A shaped seal 16 is visible circumferentially between the protrusions 18. In these areas between the protrusions, the flanges 21 of the encoder housing 14 are axially recessed, forming a gap 17 relative to the bearing cover 3. Therefore, no heat input to the encoder cavity occurs at this location.

[0081] Reference number list

[0082] 1 Electric Machine

[0083] 2. Shell

[0084] 3. Bearing cover

[0085] 4 bearings

[0086] 5-axis

[0087] 6 axis lines

[0088] 7 Winding System

[0089] 8 Stator

[0090] 9 rotors

[0091] 10 Stator laminated iron core

[0092] 11. Rotor laminated iron core

[0093] 12 air gaps

[0094] 13 Encoders

[0095] 14 Encoder Housing

[0096] 15 plugs

[0097] 16 Molded Seals

[0098] 17. Gap between bearing cap and cover body

[0099] 18 Protruding parts

[0100] 19 Bolted connection

[0101] 20 heat sinks

[0102] 21 Flange

[0103] 22. Maze-like structure

[0104] 23. Contact surface.

Claims

1. An electric motor (1) having a shaft (5) connected to a rotor (9) in a torsion-resistant manner, wherein, The shaft (5) has an encoder (13) at one end (NDE) and is mechanically coupled to a working machine at the other end (DE). The rotor (9) interacts electromagnetically with the stator (8) having a winding system (7) via an air gap (12), thereby causing the shaft (5) to rotate. The encoder (13) is arranged in an encoder housing (14), which is thermally decoupled from the machine parts that directly follow the electric motor (1) in the axial direction by means of a shaped seal (16). Direct contact between the machine component and the encoder housing (14) is achieved only via a protrusion (18), and a predetermined gap (17) is provided between the machine component and the encoder housing (14). The shaped seal (16) is disposed in the force diversion section, such that there is a defined compression of the shaped seal (16) between the machine component and the encoder housing (14).

2. The electric machine (1) according to claim 1, characterized in that, The encoder housing (14) and the machine component are connected by means of bolts (19) via at least two protrusions (18), which are located on the outer circumference of the encoder housing and extend axially parallel from the encoder housing (14) toward the machine component.

3. The electric machine (1) according to any one of the preceding claims, characterized in that, The machine component is designed as the housing (2) or bearing cover (3) of the electric motor (1).

4. The electric machine (1) according to any one of the preceding claims, characterized in that, At least the encoder circuit board of the encoder (13) is thermally bonded to the encoder housing (14) by means of thermal paste.

5. The electric machine (1) according to any one of the preceding claims, characterized in that, The encoder housing has at least some heat sinks (20), especially vertically extending heat sinks (20).

6. The electric machine (1) according to any one of the preceding claims, characterized in that, The molded seal (16) is made of sealing material.

7. The electric machine (1) according to any one of the preceding claims, characterized in that, At least the shaped seal (16) has at least one labyrinthine or stepped profile extending circumferentially, and at least the shaped seal is form-fitted with the adjacent encoder housing (14) and / or machine parts.

8. The electric machine (1) according to any one of the preceding claims, characterized in that, The machine parts and / or the encoder housing (14) are made of aluminum or aluminum alloy, in particular.

9. The electric machine (1) according to any one of the preceding claims, characterized in that, The shaped seal (16) is implemented non-uniformly in the radial and / or axial extensions of the shaped seal to adapt to the contours of adjacent encoders and / or machine parts.

10. The electric machine (1) according to any one of the preceding claims, characterized in that, The shaped seal (16) is implemented as substantially circumferentially closed, especially annular.

11. The electric machine (1) according to any one of the preceding claims, characterized in that, The protrusion (18) not only secures the encoder housing (14) to the machine component, such as the bearing cover (3), but also meets electromagnetic compatibility requirements, such as grounding.

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