Measuring apparatus for measuring the temperature of a stator winding

Abstract

The invention relates to a measuring apparatus for measuring the temperature of a measuring surface (14) associated with the stator winding of a stator of an electric motor, having a measurement sensor holder (21) axially movable relative to a housing part (15) of the measuring apparatus and mounted in spring-loaded manner by means of a spring element (22) preferably configured as a spiral spring, which measurement sensor holder can be arranged on the measuring surface (14) and has a measurement sensor (28) for measuring the temperature of the measuring surface (14), wherein the measurement sensor holder (21) has an end portion (26) arranged outside the housing part (15) or movable out of the housing part (15), which can be brought into contact with the measuring surface (14) for temperature measurement.

Description

[0001] Measuring device for measuring the temperature of a stator winding

[0002] The present invention relates to a measuring device for measuring the temperature of a measuring surface associated with the stator winding of a stator of an electric motor. The invention further relates to an electric motor having such a measuring device.

[0003] Particularly in high-performance operation of electric motors, it is often necessary to monitor the heat development of stator windings using temperature sensors with measuring probes. In this context, one known method, for example with stators with hairpin windings, is to leave a stator or hairpin protruding from the winding and measure its temperature in order to draw conclusions about the stator winding temperature. This approach is relatively inflexible because the location of the protruding stator pin is fixed in the electric motor, and the position and design of the measuring device must be adapted accordingly. Furthermore, it can be challenging to position the measuring device's measuring probe safely and reliably despite possible positional tolerances of the stator pin.

[0004] Based on this, it is the object of the present invention to further develop the measuring device and the electric motor mentioned above.

[0005] This object is achieved by a measuring device having the features of claim 1 and an electric motor having the features of claim 16.

[0006] A measuring device according to the invention accordingly comprises a housing part and a sensor holder, which is axially movable relative to the housing part and has a sensor for measuring the temperature of the measuring surface, in particular a resistance sensor (in particular an NTC sensor) which is spring-mounted by means of a spring element preferably designed as a spiral spring. The sensor holder has an end section arranged outside the housing part or at least movable out of the housing part, which can be brought into contact with the measuring surface for temperature measurement. Such a measuring device allows different types of measuring surfaces of the stator to be used and to be contacted in a simple and reliable manner for temperature measurement.

[0007] For example, a screw head of a stator screw could be used as a measuring surface. This screw head can reach the same or at least approximately the same temperature as the stator winding itself during operation of the electric motor or during heating of the stator winding, thus allowing conclusions to be drawn about its temperature. This screw head, or the measuring surface it forms, could then be brought into contact with the measuring device for the measurement.

[0008] The spring-loaded mounting of the sensor holder can then serve to ensure secure contact between the measuring surface and the sensor holder. This applies in particular if the spring element is designed and / or operatively connected to the movable sensor holder in such a way that it can be converted into a preloaded or more strongly preloaded state by moving the movable sensor holder towards the interior of the housing part, in particular its end section, in which the spring element subsequently exerts a restoring force on the movable sensor holder acting in the opposite direction. When the movable sensor holder then contacts the measuring surface with the appropriately preloaded spring element, the corresponding restoring force of the spring element ensures that the sensor holder is pressed against the measuring surface with a pressure force corresponding to the restoring force and is held securely there.

[0009] As for the housing part, it can have an interior space, preferably formed as a hollow space (filled with potting compound or unfilled), in which the spring element is arranged and / or in which at least one section of the sensor holder is arranged, in particular a section of the sensor holder that is supported on the spring element. In this case, the spring element and / or the at least one section of the sensor holder would be securely protected from external influences in the interior space.

[0010] The spring element can be supported in the interior of the housing part, directly or indirectly, on a wall of the housing part that defines the interior, for example, on a wall formed by a cover part of the housing part. This can be achieved via a spacer located between this wall and the spring element, which may be separate, i.e., removable from the housing part, preferably made of plastic or another electrically insulating material. Preferably, this spacer rests against the spring element and / or is positively and / or frictionally connected to the spring element.

[0011] As far as the sensor is concerned, as already mentioned, it is preferably designed as an NTC sensor.

[0012] Further preferably, the measuring sensor is assigned to the end section of the measuring sensor holder, in particular arranged in or on it, so that when the end section is or will be arranged on the measuring surface, it is also located as close as possible to the measuring surface.

[0013] Irrespective of this, the measuring sensor can preferably be arranged inside the movable measuring sensor holder for protection against harmful external influences, for example in an interior space thereof designed as a cavity (possibly filled with casting compound or also unfilled), which in turn is also preferably arranged on or in the end section of the movable measuring sensor holder.

[0014] For the contact with the measuring surface, the end section of the movable sensor holder has a contact side which can be placed on the measuring surface for temperature measurement, in particular a contact side of a contact wall of the sensor holder which preferably delimits the interior of the sensor holder, preferably made of a heat-conducting material, in particular a material with a thermal conductivity of at least 1 W / mK, preferably of at least 6 W / mK, particularly preferably of at least 8 W / mK.

[0015] The high thermal conductivity then ensures good heat transfer from the system side or the system wall to the measuring sensor, which is preferably arranged directly adjacent to the system wall, in particular inside or in the interior of the sensor holder. It can also be provided that the measuring sensor touches or contacts the system wall (possibly from the inside or interior of the sensor) and / or is thermally connected to it by means of a thermally conductive material with a thermal conductivity of at least 1 W / mK, preferably of at least 6 W / mK, particularly preferably of at least 8 W / mK.

[0016] As far as the axial mobility of the sensor holder relative to the housing part is concerned, the movable sensor holder can have a guide section for this purpose with a particularly cylindrical surface which is slidably guided on an opposite, particularly also cylindrical, surface of a bearing section of the housing part.

[0017] The movable sensor holder can further be radially sealed with respect to the housing part, in particular by means of (at least) one O-ring, preferably in such a way that no medium can penetrate from the outside into the interior of the housing part along the sealed area.

[0018] In particular, the opposing surfaces of the guide section of the movable sensor holder and the bearing section of the housing part can be radially sealed against each other, preferably by means of an O-ring which extends radially in a or the sealing gap between the opposing surfaces.

[0019] The measuring device can further comprise a radial seal, preferably arranged circumferentially on a particularly radially circumferential outer side of the housing part, for sealing a circumferential sealing gap. In particular, a circumferential sealing gap formed between the housing part and a housing wall surface of a housing wall of the electric motor, which defines a preferably round through-opening in which the housing part can be arranged. The radial seal arranged on an outer side of the housing part preferably faces the outside environment. The radial seal is preferably arranged on an outer side of the housing part such that the preferably circumferential sealing gap is sealed off from the outside environment. As far as the housing part of the measuring device and / or the sensor holder are concerned, these can preferably consist of or be made of plastic.

[0020] Further preferably, a power or control line can be led from the measuring sensor of the measuring sensor holder to a contact area of ​​the measuring device having at least one electrical connection contact, which electrically connects the electrical connection contact and the measuring sensor, via which the measuring sensor is supplied with power or, if necessary, is controlled.

[0021] Further preferably, the spring element is supported in the interior of the housing part, directly or indirectly, on a wall of the housing part that defines the interior. The spring element can be supported by a spacer located between the wall and the spring element, preferably a spacer that bears against the spring element and / or is positively and / or frictionally connected to the spring element.

[0022] The sensor holder preferably comprises a thermal coupler, wherein the thermal coupler is preferably arranged in the end section such that the thermal coupler contacts the measuring surface during the measurement. The thermal coupler is preferably made of metal, more preferably of aluminum or an aluminum alloy. The thermal coupler enables faster transport of thermal energy from the surface of the measuring surface to be measured to the sensor, thereby shortening the time until a measurement is available at the sensor, also known as the response time.

[0023] The sensor holder preferably comprises a potting element arranged in contact with the heat coupler. The potting element preferably surrounds the sensor in such a way that the sensor surrounded by the potting element is held in position by the potting element. For this purpose, the potting element is arranged in the interior of the sensor holder. Furthermore, the potting element ensures consistently firm, secure, and complete contact with the entire outer surface of the sensor. The material for the potting element is further preferably an epoxy resin.

[0024] Further preferably, the expansion coefficients of the heat coupler, the encapsulation element, and the sensor holder are selected such that the expansion coefficients are close to one another. This has the advantage of preventing the formation of capillaries during thermal expansion. As already described above, the sensor holder is preferably made of plastic.

[0025] In a preferred embodiment, the sensor holder and the end section have a one-piece construction. In a further preferred embodiment, the sensor holder, the encapsulating element, the end section, and the heat coupler have a one-piece construction. The one-piece construction can be designed such that the individual components are made from the materials already described above and are connected to one another as a single piece. The one-piece construction ensures constant, reliable, and consistent contact with the measuring surface and transmits events occurring on the measuring surface, such as temperature fluctuations, to the sensor.

[0026] In a further preferred embodiment, the heat coupler comprises a three-dimensionally structured surface having depressions with dimensions in the nanometer or micrometer range. The depressions preferably have undercuts. The three-dimensional structure can be introduced by a surface treatment of the heat coupler. The structure is preferably introduced by a chemical etching process of the surface. A three-dimensionally structured surface, which preferably has undercuts with depressions with dimensions in the nanometer or micrometer range, can be used to create a plurality of positive connections with a part adjacent to the heat coupler, for example the potting element arranged in contact with the heat coupler or the sensor holder sealing against the heat coupler.

[0027] Furthermore, the invention relates to an electric motor according to the invention with a stator, a stator winding and a measuring surface that is thermally conductively connected to the stator winding such that the temperature of the measuring surface allows conclusions to be drawn about the temperature of the stator winding, wherein the electric motor has a measuring device for measuring the temperature of the stator winding, wherein the measuring device has a measuring sensor holder that is axially movable relative to a housing part of the measuring device and spring-mounted by means of a spring element that is preferably designed as a spiral spring, said sensor holder having a measuring sensor for measuring the temperature of the measuring surface and having an end section arranged outside the housing part that is brought into contact with the measuring surface for temperature measurement. The electric motor can have the measuring device in one of the preferred embodiments described above.

[0028] Further features of the present invention emerge from the appended patent claims, the following description of a preferred embodiment of the invention and from the appended drawings.

[0029] It shows:

[0030] Fig. 1 is a schematic oblique view of a part of a housing wall of a housing of an electric motor according to the invention, which has a stator with a measuring surface associated therewith, the temperature of which is to be measured,

[0031] Fig. 2 shows the representation from Fig. 1, but with the measuring device according to the invention, also shown in an oblique view, arranged in a through opening of the housing wall,

[0032] Fig. 3 shows a cross section through the measuring device of the embodiment according to Fig. 2.

[0033] Fig. 4 shows a cross section through the measuring device of an alternative embodiment.

[0034] The measuring device 10 according to the invention serves to measure the temperature of a stator or the corresponding stator winding of an electric motor 11. Most of the components, etc., known per se, of both the electric motor 11 and its stator are not shown.

[0035] As an example, a section of a housing wall 12 of the housing of the electric motor 11 is shown. Only a screw 13 of the stator is shown, which is thermally conductively connected to the stator or to the stator winding thereof. The front side of the screw 13 facing the measuring device 10 (at the screw head) forms a measuring surface 14, the temperature of which is measured in order to draw conclusions about the temperature of the stator winding.

[0036] The screw 13 or the measuring surface 14 thereof is located in the interior 19 of the electric motor 11 arranged on one side of the housing wall 12 or in the interior 19 of the housing of the electric motor 11. On the other side of the housing wall 12 is the external environment 20 or the external space.

[0037] The measuring device 10 for measuring the temperature of the measuring surface 14 comprises a housing part 15 which extends through a through opening 16 of the housing wall 12 and is held or fastened therein by a central section in the present case.

[0038] A radial seal 18 sealing the sealing gap 31 is arranged in a sealing gap 17 formed between the circumferential housing wall surface of the housing wall 12, which defines the through-opening 16, and the opposite outer side of the central section of the second housing part 15. This seal serves to protect the exterior space from, for example, oil mist, which could otherwise possibly penetrate from the interior space 19 of the housing of the electric motor 12 into the exterior space, or, more generally, to protect against harmful medium transfer between the exterior space 20 and the interior space 19 of the housing of the electric motor 11.

[0039] The measuring device 10 further comprises a measuring sensor holder 21 which is axially movable relative to the housing part 15 at least in sections in an interior space 15a of the housing part 15 and which in turn has a measuring sensor 28 arranged in an interior space 21a of the measuring sensor holder 21.

[0040] The sensor holder 21 is resiliently mounted in the interior 15a of the housing part 15 by means of a spring element 22, in this case designed as a spiral spring. For this purpose, a rear, in particular disc-shaped, contact piece of the sensor holder 21 is supported on a spacer 34 arranged in the interior 15a.

[0041] This in turn rests against or is supported on a cover part 32 of the housing part 15, which closes the interior 15a of the housing part 15 on its side facing the outside environment.

[0042] The cover part 32 can be connected in a materially bonded and / or media-tight manner (for example by means of laser welding) to one or more walls of the housing part 15 delimiting the interior space 15a.

[0043] As can also be seen, a front, in this case (hollow) cylindrical section 24 of the sensor holder 21 extends coaxially thereto within a hollow cylindrical end piece 23 of the housing part 15.

[0044] In a front region of the housing part 15, the section 24 extends through a through-opening 25 in the housing part 15 and finally protrudes therefrom with an end section 26, so that in the present case it protrudes a few mm or possibly a few cm relative to the front side of the housing part 15 which has the through-opening 25 and faces the measuring surface 14.

[0045] In order to effect the axial mobility of the sensor holder 21 relative to the housing part 15, the section 24 of the sensor holder 21 forms a guide section which has a cylindrical surface (outside of the section 24) which is slidably guided on the opposite, in this case also cylindrical surface (inside of the end piece 23) of the end piece 23 of the housing part 15 forming a bearing section.

[0046] The opposing surfaces of the section 24 of the movable sensor holder and the end piece 23 of the housing part 15 are radially sealed against each other by means of O-rings 27 which extend radially in the corresponding sealing gap between the opposing surfaces.

[0047] The end section 26 of the sensor holder 21 contacts the measuring surface 14 during the measurement. In the present case, the end section 26 has, for this purpose, a contact wall 29 with a contact side 29a (in this case running transversely axially), which is or is in contact with the measuring surface 14. The sensor 28 is arranged at a short distance from the contact wall 29 in the interior space 21a of the sensor holder 21, which in this section is filled with a potting compound, this potting compound corresponding to the potting element 36 shown in Fig. 4. In order to enable good heat transfer, both the potting compound and the contact wall 29 can be made of a material with good thermal conductivity, for example a highly thermally conductive plastic.

[0048] As can also be seen, a power line 31 is guided from the measuring sensor 28 of the measuring sensor holder 21 through the interior 15 a of the housing part 15 and through a (transverse axial) wall of the cover part 32 to a contact area of ​​the measuring device 10 having at least one electrical connection contact 30, which power line connects this electrical connection contact 30 and the measuring sensor 28 to one another and via which the measuring sensor 28 is or can be supplied with power (from the external environment 20).

[0049] For this purpose, power lines can be led to the connection contact 30 through an externally accessible connection opening of a connection channel 33 of the cover part 32 of the housing part 15.

[0050] As already indicated, the spring-loaded mounting of the sensor holder 21 by means of the spring element 22 described above serves in particular to ensure secure contact between the measuring surface 14 and the sensor holder 21.

[0051] For this purpose, as will be apparent to a person skilled in the art, the spring element 22 is operatively connected to the sensor holder 21 in such a way that it is transferred into a pre-tensioned or a more strongly pre-tensioned state by movement of the sensor holder 21 in the direction of the housing part interior, in which the spring element 22 then subsequently exerts a restoring force on the sensor holder 21 acting in the opposite direction.

[0052] If the measuring device 10 together with the sensor holder 21 is now mounted on the

[0053] Measuring device 10 is moved against the measuring surface 14, so that the contact side 29a of the sensor holder 21 exerts a corresponding counterforce on the sensor holder 21 directed into the interior of the housing part 15, so that the sensor holder

[0054] 21 is then moved toward the interior of the housing, and when the measuring device 10 is then held or mounted / fastened in this position, the spring element 22 is accordingly pre-tensioned (or further pre-tensioned if it is already pre-tensioned due to other measures). The corresponding restoring force of the spring element

[0055] 22 then ensures that the sensor holder 21 is pressed against the measuring surface 14 with a pressure or contact force corresponding to the restoring force and is held securely there.

[0056] The embodiment shown in Fig. 4 differs from the embodiment described in Fig. 3 in that the end section 26 has a thermal coupler 35. The thermal coupler 35 is arranged in contact with the potting element 36. The thermal coupler 35 has a contact side 29a facing the measuring surface, which is in contact with and in contact with the measuring surface 14 for temperature measurement. The thermal coupler 35 is arranged in a sealing manner on the sensor holder 21. The potting element 36 is arranged in the interior of the sensor holder 21a and surrounds the sensor 28, so that the sensor 28 is held in position.

[0057] 10 Measuring device

[0058] 11 Electric motor

[0059] 12 Electric motor housing wall

[0060] 13 Screw

[0061] 14 Measuring area

[0062] 15 Housing part

[0063] 15 a Interior housing part

[0064] 16 Through-opening electric motor housing wall

[0065] 17 Sealing gap

[0066] 18 Radial seal

[0067] 19 Interior electric motor housing

[0068] 20 Outdoor environment

[0069] 21 probe holder

[0070] 21 a Interior sensor holder

[0071] 22 Spring element

[0072] 23 hollow cylindrical end piece housing part

[0073] 24 hollow cylindrical section sensor holder

[0074] 25 Through opening housing part

[0075] 26 final section

[0076] 27 O-ring

[0077] 28 sensors

[0078] 29 system wall

[0079] 29 a Investment page

[0080] 30 connection contact

[0081] 31 power line

[0082] 32 cover part

[0083] 33 connecting channel

[0084] 34 spacer

[0085] 35 heat couplers

[0086] 36 Casting element

Claims

Patent claims 1. A measuring device for measuring the temperature of a measuring surface (14) associated with the stator winding of a stator of an electric motor, comprising a measuring sensor holder (21) which is axially movable relative to a housing part (15) of the measuring device and spring-mounted by means of a spring element (22) preferably designed as a spiral spring, which can be arranged on the measuring surface (14) and has a measuring sensor (28) for measuring the temperature of the measuring surface (14), wherein the measuring sensor holder (21) has an end section (26) which is arranged outside the housing part (15) or can be moved out of the housing part (15) and which can be brought into contact with the measuring surface (14) for the temperature measurement.

2. Measuring device according to claim 1, characterized in that the housing part (15) has an interior space preferably designed as a cavity in which the spring element (22) is arranged and / or in which at least one section of the sensor holder (21) is arranged.

3. Measuring device according to claim 1 or 2, characterized in that the measuring sensor (28) is arranged in the interior of the movable measuring sensor holder (21), preferably in an interior space of the movable measuring sensor holder (21) designed as a cavity, and / or on or in the end section (26) of the movable measuring sensor holder (21).

4. Measuring device according to one or more of the preceding claims, characterized in that the end section (26) of the movable sensor holder (21) has a contact side which can be placed against the measuring surface (14) for temperature measurement, in particular a contact side of a contact wall which preferably delimits the interior or the interior of the sensor holder (21), preferably made of a heat-conducting material, in particular a material with a thermal conductivity of at least 1 W / mK, preferably of at least 6 W / mK, particularly preferably of at least 8 W / mK.

5. Measuring device according to one or more of the preceding claims, characterized in that the spring element (22) is moved by movement of the movable measuring sensor holder (21), in particular its end section (26), can be converted into a prestressed or a more strongly prestressed state in the direction of the housing part interior, in which the spring element (22) exerts a restoring force acting in the opposite direction on the movable sensor holder (21).

6. Measuring device according to one or more of the preceding claims, characterized in that for the axial mobility of the movable sensor holder (21) relative to the housing part (15), a guide section of the movable sensor holder (21) has a particularly cylindrical surface which is slidably guided on an opposite, particularly likewise cylindrical surface of a bearing section of the housing part (15).

7. Measuring device according to one or more of the preceding claims, characterized in that the movable sensor holder (21) is radially sealed with respect to the housing part (15), in particular by means of an O-ring, preferably in such a way that no medium can penetrate into the interior of the housing part (15) from the outside along the sealed area.

8. Measuring device according to claim 6 or 7, characterized in that the opposing surfaces of the guide section of the movable sensor holder (21) and the bearing section of the housing part (15) are radially sealed against each other, in particular by means of an O-ring which extends radially in a sealing gap between the opposing surfaces.

9. Measuring device according to one or more of the preceding claims, characterized in that the measuring device has a radial seal, preferably arranged circumferentially on an outer side of the housing part (15), for sealing a circumferential sealing gap, in particular a circumferential sealing gap between the housing part (15) and a housing wall surface of a housing wall of the electric motor, which delimits a preferably round through-opening in which the housing part (15) can be arranged.

10. Measuring device according to one or more of the preceding claims, characterized in that the housing part (15) of the measuring device and / or the sensor holder (21) is made of plastic.

11. Measuring device according to one or more of the preceding claims, characterized in that a power or control line electrically connecting the connection contact and the measuring sensor (28) is guided from the measuring sensor (28) of the measuring sensor holder (21) to a contact area of ​​the measuring device having at least one electrical connection contact.

12. Measuring device according to one or more of the preceding claims, characterized in that the spring element (22) in the interior of the housing part (15) is supported directly or indirectly on a wall of the housing part (15) delimiting the interior, optionally via a spacer located between the wall and the spring element (22), preferably a spacer lying on the spring element (22) and / or positively and / or frictionally connected to the spring element (22).

13. Measuring device according to one or more of the preceding claims, characterized in that the sensor holder (21) comprises a heat coupler (35), wherein the heat coupler (35) is associated with the end portion (26).

14. Measuring device according to claim 13, characterized in that the sensor holder (21) comprises a potting element (36) arranged in contact with the heat coupler (35), wherein the potting element (36) surrounds the sensor (28).

15. Measuring device according to claim 13 or claim 14, characterized in that the heat coupler (35) comprises a three-dimensionally structured surface having depressions with dimensions in the nanometer or micrometer range.

16. Electric motor with a stator, a stator winding and a measuring surface (14) connected to the stator winding in a heat-conducting manner such that the temperature of the measuring surface (14) allows conclusions to be drawn about the temperature of the stator winding, characterized in that that the electric motor has a measuring device for measuring the temperature of the stator winding, in particular according to one or more of the preceding claims, which has a measuring sensor holder (21) which is axially movable relative to a housing part (15) of the measuring device and spring-mounted by means of a spring element (22) preferably designed as a spiral spring, which has a measuring sensor (28) for measuring the temperature of the measuring surface (14) and has an end section (26) arranged outside the housing part (15) which is brought into contact with the measuring surface (14) for the temperature measurement.

17. Electric motor according to claim 16, characterized in that the electric motor has a housing part (15) with a housing wall in which there is a through opening in which the housing part (15) of the measuring device is arranged with at least one section, wherein in a sealing gap between the housing part (15) of the measuring device for measuring the temperature on the one hand and the housing wall surface of the housing wall of the housing part (15) of the electric motor which delimits the through opening on the other hand a radial seal is arranged which seals the sealing gap.

18. Electric motor according to one or more of the preceding claims 16 to 17, characterized by one or more features of claims 1 to 15.

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