Method for thermally connecting a heat pipe to the inner wall of a shaft bore of a rotor

Abstract

The invention relates to a method for thermally connecting a heat pipe (10) to the inner wall (20) of a shaft bore (8) of a rotor (4) of a rotating dynamo-electric machine (1) by means of the following steps: - a shaft (6) of the rotor (4) is provided with a shaft bore (8), in particular a blind bore or a through-bore, - the heat pipe (10), which has a closed casing (11), is thermally connected to the inner wall (20) of the shaft bore (8) by means of forming, characterised in that, after the heat pipe (10) has been inserted into the shaft bore (8), the casing (11) of the heat pipe (10) is axially upset.

Description

[0001] Description

[0002] Method for thermally connecting a heat pipe to the inner wall of a shaft bore of a rotor

[0003] The invention relates to a method for thermally connecting a heat pipe to the inner wall of a shaft bore of a rotor of a rotary dynamoelectric machine, a rotor equipped therewith whose shaft is provided with a heat pipe, the manufacture of such a rotor, as well as a rotary dynamoelectric machine with such a rotor.

[0004] Rotary dynamoelectric machines typically cool their rotors with a cooling airflow generated by an axial fan. However, if the rotor's heat load is higher, as in asynchronous machines, such a cooling airflow alone is insufficient for rotor cooling. In these cases, hollow shafts are used, containing a cooling medium that conducts the rotor's heat axially outwards through the shaft.

[0005] Furthermore, in the case of permanent magnet synchronous machines, specified temperature limits must be observed for the permanent magnets positioned on or in the rotor in order to avoid irreversible demagnetization of the permanent magnets.

[0006] For example, DE 10 2009 051 114 A1 discloses an electric machine, including a rotor, wherein the rotor has a hollow shaft and wherein a closed cavity is formed by means of the hollow shaft, wherein the closed cavity is intended to hold a refrigerant, and wherein a three-dimensional transport structure is provided in the closed cavity for transporting the refrigerant. The heat generated is thus transferred axially to the outside via this transport structure and cooled there by means of a cooling airflow.

[0007] Heat pipes are also placed inside a shaft to cool rotors. For this purpose, a shaft bore with a slightly larger diameter than the heat pipe is machined, allowing for easy installation by simply inserting the heat pipe.

[0008] A disadvantage of this design is that a gap between the wall of the heat pipe and the inside of the shaft bore results in a poor thermal connection between the heat pipe and the shaft bore. This gap can be up to several tenths of a millimeter wide.

[0009] To minimize this disadvantage, thermal pastes or greases are used when inserting heat pipes into shaft bores.

[0010] However, reliably filling this entire gap with thermal paste is comparatively complex.

[0011] Furthermore, the thermal conductivity of these pastes is at a low level of approximately 1-6 W / mK, which reduces the efficiency of the heat pipe and thus the cooling efficiency.

[0012] JP S58 72884 A discloses a method for thermally joining a heat pipe to the inner wall of a shaft bore of a rotor of a dynamoelectric rotary machine, wherein the thin heat pipe is designed in bellows form, the maximum outer diameter of which is smaller than the inner diameter of a cylindrical opening, and wherein the heat pipe is inserted into the cylindrical opening and subsequently a high-temperature joining process is carried out by changing the volume of the heat pipe.

[0013] JP S58 93520 A discloses a similar method for thermally joining a heat pipe to the inner wall of a hollow shaft, wherein the heat pipe is inserted into a hollow shaft and the inner wall of the hollow shaft and the heat pipe have a diameter difference sufficient for the joining process. The heat pipe is pressed through a die from one end, thereby generating an impulsive high static hydraulic pressure in the fluid contained in the heat pipe to expand the heat pipe over the entire inner surface of the container.

[0014] JP S57 186950 A discloses a dynamoelectric rotary machine with a heat pipe in the rotor shaft, wherein the shaft bore is designed such that it has a conical section at its end for fixing the heat pipe. Furthermore, the ends of the heat pipe are shaped to have a spherical surface, and the end on one side of this surface is bonded under pressure to the conical section of the shaft bore. An adhesive is filled into the gap between the heat pipe and the shaft bore to fix the heat pipe in place.

[0015] Based on this, the invention aims to reliably position a heat pipe within the shaft of a rotor with a constant and comparatively high heat transfer rate. Such a rotor is intended to increase the efficiency of asynchronous and permanent magnet synchronous machines.

[0016] The problem posed is solved by the features of the independent claims. Advantageous embodiments of the invention can be found in the dependent claims.

[0017] According to the invention, the thermal connection of a heat pipe to the shaft of a rotor of a dynamo-electric machine is improved, in particular the efficiency of asynchronous machines and permanent magnet synchronous machines with such a rotor is increased, whereby the use of a thermal paste between heat pipe and shaft can be dispensed with.

[0018] Depending on the design of the heatpipe's condenser zone, the rotor laminations are either rotationally fixed to the shaft before or after the heatpipe is inserted into the shaft bore, e.g. by shrink-fitting.

[0019] Ideally, the heat pipe is only inserted into the finished dynamoelectric machine, i.e., when the dynamoelectric machine is completely assembled with rotor and bearing shields.

[0020] For the compressed heatpipe variant, which will be described in more detail later, the capacitor zone can also be constructed separately (hub part and fan). This simplifies the "mounting" of the bearing on the ventilation side.

[0021] The heat pipe has a closed shell, with at least one evaporation zone and one condenser zone, which are connected by a transport zone.

[0022] In the inventive method, the heat pipe is inserted into a bore in the shaft of a rotor of a dynamoelectric rotary machine. This shaft bore can be designed as a central blind hole or as a through hole. Preferably, the shaft is subjected to machining, such as drilling.

[0023] The evaporation zone of the heat pipe has approximately the axial length of the rotor's laminated core in order to absorb the heat generated there during the operation of the dynamo-electric rotary machine.

[0024] A microscale structure, at least in the condenser zone, i.e., within the shell of the heat pipe, can improve the cooling effects.

[0025] A thermally conductive connection should therefore be sought from the inside of the shaft bore to the evaporator zone and from the condenser zone to a cooling structure, in particular a fan.

[0026] In the inventive method, the heat pipe with its closed shell, in particular the evaporator zone, is thermally connected to the inside of the shaft bore by means of forming.

[0027] A relatively thin-walled tube made of relatively soft metal forms the base material for the production of the heat pipe's shell, which is therefore easily deformable without much force being applied.

[0028] Preferably, soft-annealed copper with a Brinell hardness in the range of 35-40 HB (H035) is used.

[0029] The heat pipe is manufactured with a slightly smaller diameter than the shaft bore to facilitate easy axial insertion into the bore. To simplify the forming process, the heat pipe is designed with an axial excess length relative to the axial installation depth in the bore.

[0030] After inserting and positioning the heat pipe in the shaft bore, it is compressed axially. This is possible because the outer shell is easily deformable due to its low hardness. With axial compression, the outer diameter of the shell increases, resulting in direct, highly thermally conductive contact between the inner wall / inside of the shaft bore and the heat pipe shell. This compression process leads to almost complete axial contact between the shell, particularly between the evaporator zone and the inner wall of the shaft bore.

[0031] Axial compression can be achieved by targeted pressure or blows to the protruding end face of the heat pipe casing.

[0032] Furthermore, a cone can be formed on the capacitor side through the axial compression process, e.g. also by sliding on a correspondingly conical fan hub.

[0033] The outer diameter of the heat pipe and the cone of the heat pipe in at least sections of the capacitor zone are therefore only formed when the shaft is assembled with the fan.

[0034] Even existing heat pipes – with a classic "thick" shell – can be prepared for this insertion process by soft annealing before axial insertion. Soft annealing at temperatures between 400 and 600 °C also achieves shell hardness values ​​in the range of 35–40 HB.

[0035] However, when the heat pipe is axially compressed and the associated, at least partially, but rather predominantly, increase in the diameter of the shell, there is a risk that the capillary structure on the inner wall of the heat pipe shell will break off.

[0036] Therefore, this design of the heat pipe eliminates the need for a capillary structure, particularly in the transport zone. The rotational speed of the rotor takes over the function of this capillary structure during operation of the dynamo-electric machine. The rotor's rotation propels the cooling medium radially outwards, distributing it as a uniform film axially from the condenser zone to the evaporator zone. Thus, capillaries are not strictly necessary to maintain the circulation within the heat pipe.

[0037] In one embodiment, the cross-section of the heat pipe is not circular, but rather shaped in such a way that a deformation occurs during axial insertion into the shaft bore, which on the one hand enables axial insertion with low force and on the other hand increases the contact area between the shell and the inner wall of the shaft bore.

[0038] In this process, an interference fit exists in at least one plane before the heat pipe is axially inserted into the shaft bore. Viewed comprehensively, this results in a section-by-section interference fit.

[0039] A preferred design for this cross-section of the heat pipe's shell can be, for example, an elliptical or cloverleaf shape, which results in a relatively large contact area with the shaft bore at an angle of approximately 300° due to the deformation during insertion.

[0040] During operation of the dynamo-electric machine, under the centrifugal force of the shaft, stable contact between the heat pipe and the inner wall of the shaft bore is maintained, and may even be strengthened. These heat pipes are generally designed as follows: At least one end face of the heat pipe is slightly conical, so that the geometry facilitates the axial insertion of the heat pipe into the shaft bore and / or the positioning of the fans on the condenser zone. At least the condenser zone has a microscale structure within the casing, which is thermally connected to a wall of the casing in the area of ​​the condenser zone. The microscale structure can be rib-like, conical, and / or porous. Additionally or optionally, the condenser zone has an internal taper that widens, in particular, towards the evaporator zone.A cooler on the condenser zone is designed as a fan, which is thermally connected to the condenser zone.

[0041] The advantages of this thermal connection of the heat pipes to the inner wall of the shaft bore according to the invention:

[0042] The use of thermal paste and its complex application are unnecessary. This simplifies the assembly process and ultimately leads to improved efficiency of the dynamo-electric machine. A capillary structure, particularly as a transport zone, is therefore not required.

[0043] Due to the inventive design of the shaft, no change in efficiency occurs due to aging of the materials, such as the thermal paste.

[0044] This technique is particularly useful for asynchronous motors, as the rotor's laminations reach high temperatures, and improved cooling can increase efficiency. The rotor laminations are rotationally fixed to the shaft, ensuring good thermal conductivity between the laminations and the shaft.

[0045] Using them in the rotors of synchronous motors has the advantage that the embedded permanent magnets are only exposed to reduced temperatures.

[0046] Thus, according to the invention, a rotor with a heat pipe in the shaft is now provided, wherein the rotor exhibits increased efficiency due to the improved heat absorption in the evaporation zone. This also has a beneficial effect on the efficiency and compactness of the respective dynamoelectric machines.

[0047] The cooler surrounding the condenser zone is designed specifically as a fan with high thermal conductivity, which is thermally well coupled to the condenser zone. This, together with the airflow generated by the fan during operation of the dynamo-electric machine, results in efficient cooling of the condenser zone and thus improved cooling of the respective rotor.

[0048] The fan is preferably made of a material with good thermal conductivity, such as aluminum, copper or aluminum alloys or copper alloys.

[0049] The invention and advantageous embodiments of the invention are presented by means of exemplary embodiments, showing:

[0050] FIG 1 shows a principal longitudinal section through a dynamoelectric rotary machine,

[0051] FIG 2 shows a basic structure of a heat pipe, FIG 3-6 shows a basic representation of the positioning of the heat pipes in a shaft bore.

[0052] It should be noted that terms such as "axial," "radial," "tangential," etc., refer to the axis 7 used in the respective figure or in the described example. In other words, the directions axial, radial, and tangential always refer to an axis 7 of the rotor 4 and thus to the corresponding axis of symmetry of the stator 2. "Axial" describes a direction parallel to the axis 7, "radial" describes a direction orthogonal to the axis 7, either towards or away from it, and "tangential" is a direction that is circular around the axis 7 at a constant radial distance and with a constant axial position. The expression "circumferential" is synonymous with "tangential."

[0053] With regard to a surface, e.g. a cross-sectional area, the terms "axial", "radial", "tangential", etc. describe the orientation of the normal vector of the surface, i.e. the vector that is perpendicular to the surface in question.

[0054] The term "coaxial components," e.g., coaxial components such as rotor 4 and stator 2, refers here to components that have the same normal vectors, meaning that the planes defined by the coaxial components are parallel to each other. Furthermore, the term implies that the centers of coaxial components lie on the same axis of rotation or symmetry. However, these centers may be located at different axial positions on this axis, and the planes in question may therefore have a distance greater than zero from each other. The term does not necessarily require that coaxial components have the same radius.The term "complementary," in the context of two components that are complementary to each other, means that their external forms are designed such that one component can preferably be completely enclosed within its complementary component, so that the inner surface of one component and the outer surface of the other ideally touch without gaps or across their entire surface. Consequently, in the case of two complementary objects, the external form of one object is determined by the external form of the other. The term "complementary" could be replaced by the term "inverse."

[0055] For the sake of clarity, in some cases where components are present multiple times, not all components shown in the figures are provided with reference symbols.

[0056] The same reference symbols have the same meaning in the figures.

[0057] The descriptions in the general section as well as in the specific figure descriptions can be combined as desired. Likewise, the individual features of the respective embodiments mentioned therein can also be combined without altering the essence of the invention.

[0058] FIG. 1 shows a rotary dynamoelectric machine 1 comprising a stator 2 and a rotor 4. In this embodiment, the rotor 4 is a squirrel-cage rotor, but it could also be a rotor equipped with permanent magnets, a rotor of a reluctance machine, or a rotor with a winding system. Through electromagnetic interaction across an air gap 9, a current-energized winding system 3 sets the rotor 4 into rotation about an axis 7. The reluctance rotor 3 is arranged coaxially with the stator 2. The laminations of the rotor 4 are stacked as a laminated core and rotated and thermally connected to a shaft 6, in this case a shaft 6 with a bore 8.

[0059] The rotor 4 is rotationally fixed to the shaft 6, which is designed as a hollow shaft and is supported in bearings not shown. A rotationally fixed connection is understood to be a torque-transmitting connection, such as a shrink fit, a keyway connection, or another shaft-hub connection between the lamination stack of the rotor 4 and the shaft 6, which in any case provides a comparatively good thermally conductive transition from the lamination stack of the rotor to the shaft 6.

[0060] The housing of the electric machine 1 (not shown in detail) has axially extending cooling fins that guide a cooling airflow generated by a fan 12 along the housing. For reasons of contact protection and / or to guide the generated cooling airflow, the fan 12 is housed in a fan hood.

[0061] In this embodiment, the shaft 6 is provided with a central axial recess in the shaft bore 8. According to FIG. 2, the heat pipe 10 arranged in the shaft bore 8 has an evaporation zone 17 in the axial region of the rotor 4. A transport zone 18 adjoins this axially, transitioning into a condenser zone 19. The axial extent of the evaporation zone 17 of the hollow shaft 6 corresponds at least to the axial extent of the laminated core of the rotor 4.

[0062] In this version, the shaft 6 has a central shaft bore 8, but it is also conceivable that there are several axially parallel bores, which are then supplied with a corresponding number of heat pipes and lead into a correspondingly designed capacitor zone 19.

[0063] In the condenser zone 19, the cooling medium circulating in the heat pipe 10, e.g., an evaporating liquid, is recooled. It is crucial that good thermal transfer exists between the laminated core and the shaft 6, as well as between the inner wall 20 of the shaft bore 8 and the heat pipe wall, i.e., a shell 11. Furthermore, efficient recooling of the evaporating liquid in the condenser zone 19 must be ensured for good cooling efficiency of the dynamo-electric machine I.

[0064] In the evaporation zone 17, a cooling medium is evaporated by absorbing heat upon heat input 14 from the rotor 4 and then cooled back down in the condenser zone 19 by releasing heat 15. Particularly in the transport zone 18, suitable packing materials can improve the transport of the evaporated and / or cooled cooling medium in the heat pipe 10.

[0065] The Heatpipe 10 uses a relatively thin-walled tube made of soft metal as the base material for its casing II. Preferably, annealed copper with a Brinell hardness in the range of 35-40 HB is used as the base material.

[0066] Thus, it is possible to reshape the body without applying significant force.

[0067] In addition, the heat pipe 10 is provided with an axial interference in its axial length with respect to the axial length of the shaft bore 8.

[0068] The heat pipe 10 is initially manufactured with a slightly smaller diameter than the shaft bore 8 to facilitate easy insertion of the heat pipe 10 into the shaft bore 8. After insertion into the shaft bore 8, the heat pipe 10 is axially compressed.

[0069] This is possible because the outer shell 11 of the heatpipe 10 is easily deformable due to its low hardness. During compression, the outer shell 11 expands radially – thus increasing the outer diameter of the heatpipe 10, resulting in direct, large-area, and highly thermally conductive contact between the two components: shaft 6 / heatpipe 10 – more precisely, the inner wall 20 of the shaft bore 8 and the outer shell 11 of the heatpipe 10.

[0070] The axial compression can be achieved by defined, predetermined pressure and / or defined blows to the protruding end face of the heat pipe 10, for example by applying a thermally conductive fan 12 to this end face.

[0071] This makes it possible, in a simple manner, to form a cone 13 on at least an axial section of the capacitor zone 19 by sliding on a correspondingly shaped conical fan hub.

[0072] The outer diameters of the casing 11 of the heatpipe 10 and the cone 13 of the heatpipe 10 are thus only formed during the assembly of the shaft 6, especially with the fan 12.

[0073] It is also possible to adapt existing heat pipes 10 for this method by soft annealing. Soft annealing these heat pipes 10 at temperatures between 400 and 600 °C also achieves sheath hardness values ​​of 35-40 HB, which are suitable for the method described above and lead to the desired result.

[0074] However, when axially compressing the heatpipe 10 and thereby at least partially increasing the diameter of the shell 11 of the heatpipe 10, there is a risk that the capillary structure on the inner wall of the shell 11 will break off.

[0075] Therefore, for this design of the heat pipe 10, the capillary structure in the heat pipe 10 can be omitted from the outset. The function of the capillary structure in these heat pipes 10, e.g., the transport function of the recooled cooling medium, is taken over by the rotor speed during operation of the dynamo-electric machine 1. Through the rotation of the rotor 4, the cooling medium of the heat pipe 10 is flung radially outwards and spreads as a uniform film in the axial direction from the condenser zone 19 to the evaporator zone 17. Thus, capillaries are not necessarily required for the transport of the cooling medium.

[0076] In a further embodiment according to FIGS. 3 to 4, the cross-section of the heatpipe 10 is not circular, but rather shaped in such a way that when the heatpipe 10 is axially inserted into the shaft bore 8, a deformation occurs which on the one hand enables insertion with low force and on the other hand increases the contact area.

[0077] In this case, before joining according to FIG. 3, there is an excess in at least one plane, so, viewed comprehensively, there is an excess in sections.

[0078] A preferred cross-sectional design of the heat pipe 10 can be, for example, an elliptical or cloverleaf shape according to FIG. 3 or FIG. 5, whereby, due to the deformation during axial insertion into the shaft bore 8, a relatively large contact area with the inside of the shaft bore 8 at an angle of approximately 300° or more is achieved when viewed from all sides. During operation of the dynamo-electric machine 1, under centrifugal force, stable contact is maintained between the heat pipe 10 and the shaft 6, in particular between the sleeve 11 and the inner wall 20 of the shaft bore 8.

[0079] Ideally, at least one end face of the heatpipe 10 is slightly conical in the area of ​​the condensation zone 19 and / or the evaporation zone 17, so that this geometry facilitates the insertion of the heatpipe 10 into the shaft bore 8.

[0080] This optimal thermal connection of the heat pipe 10 to the shaft 6 results in an increase in efficiency for asynchronous motors and synchronous motors through improved cooling.

[0081] This eliminates the need for the complex positioning of thermal pastes in the wave bore 8 and monitoring for their aging. Simple heat pipes 10 can be used, which do not require a capillary structure.

[0082] Such dynamoelectric machines 1 are used, particularly in industrial environments, as drives for fans, pumps, compressors, etc., since sufficient cooling of the rotor 4 is now achieved even without forced ventilation, regardless of its design. Forced ventilation leads to insufficient cooling, especially of the rotor 4, in the case of highly dusty air and / or alternating operation of the motor with downtime.

Claims

Patent claims 1. Method for thermally connecting a heat pipe ( 10 ) to the inner wall ( 20 ) of a shaft bore ( 8 ) of a rotor ( 4 ) of a dynamoelectric rotary machine ( 1 ) by the following steps: - a shaft ( 6 ) of the rotor ( 4 ) is provided with a shaft bore ( 8 ), in particular a blind bore or through bore, - the heat pipe ( 10 ) which has a closed shell ( 11 ) is thermally connected to the inner wall ( 20 ) of the shaft bore ( 8 ) by means of forming , characterized by the fact that after the heatpipe ( 10 ) is inserted into the shaft bore ( 8 ) the sheath ( 11 ) of the heatpipe ( 10 ) is axially compressed .

2. Method for thermally connecting a heat pipe (10) to the inner wall (20) of a shaft bore (8) of a rotor (4) of a dynamoelectric rotary machine (1) according to claim 1, characterized in that the shell (11) of the heat pipe (10) consists of a closed thin-walled tube made of comparatively soft metal l in order to be formed.

3. Method for thermally connecting a heat pipe (10) to the inner wall (20) of a shaft bore (8) of a rotor (4) of a dynamoelectric rotary machine (1) according to claim 1 or 2 , characterized by this , that the heat pipe ( 10 ), in particular its shell ( 11 ), is annealed in order to be reshaped.

4. Method for thermally connecting a heat pipe (10) to the inner wall (20) of a shaft bore (8) of a rotor (4) of a dynamoelectric rotary machine (1) according to claim 2 or 3 , characterized by this , that the sheath ( 11 ) of the heatpipe ( 10 ) is preferably made of soft-annealed copper with a Brinell hardness in the range of 35-40 HB .

5. Method for thermally connecting a heat pipe ( 10 ) to the inner wall ( 20 ) of a shaft bore ( 8 ) of a rotor ( 4 ) of a dynamoelectric rotary machine ( 1 ), characterized in that the heat pipe ( 10 ) is designed with an axial interference or an axial interference and a smaller diameter than the shaft bore ( 8 ) with respect to the immersion depth in the shaft bore ( 8 ).

6. Method for thermally connecting a heat pipe (10) to the inner wall (20) of a shaft bore (8) of a rotor (4) of a dynamoelectric rotary machine (1) according to claim 1, characterized in that the axial compression of the sheath (11) of the heat pipe (10) is carried out by predeterminable pressure or blows on the protruding end face of the sheath (11) of the heat pipe (10).

7. Method for thermally connecting a heat pipe ( 10 ) to the inner wall ( 20 ) of a shaft bore ( 8 ) of a rotor ( 4 ) of a dynamoelectric rotary machine ( 1 ), characterized in that axially sliding a correspondingly conical hub of a fan ( 12 ) allows a cone ( 13 ) to be formed at least section by section on the capacitor zone ( 19 ).

8. Method for thermally connecting a heat pipe ( 10 ) to the inner wall ( 20 ) of a shaft bore ( 8 ) of a rotor ( 4 )19 a dynamoelectric rotary machine (1) according to claim 1, characterized in that the shell (119) of the heat pipe (10) has a cross-sectional shape different from the cross-section of the shaft bore (8), wherein the heat pipe (10) is in particular not circular, so that before axial insertion an excess of the shell (11) of the heat pipe (10) is present in at least one plane, such that when the heat pipe (10) is axially inserted into the bore a deformation occurs which on the one hand enables axial insertion with low force and on the other hand an increase of the contact area between shell (11) and inner wall (20) of the bore is achieved.

9. Method for thermally connecting a heat pipe (10) to the inner wall (20) of a shaft bore (8) of a rotor (4) of a dynamoelectric rotary machine (1), according to claim 8, characterized in that the shell (11) has an elliptical or cloverleaf shape in cross-section, whereby the deformation of the shell (11) during axial insertion results in a comparatively large contact area with the inner wall (20) of the bore at an angle of approximately 300° circumferentially.

10. Rotor (4) with a shaft (6), wherein the shaft (6) has a shaft bore (8) in which a heat pipe (10) having a closed sheath (11) is thermally connected to the inner wall (20) of the shaft bore (8) by forming according to any one of claims 1 to 9, wherein at least one evaporation zone (8) of the heat pipe (10) is arranged in the region of a laminated core or other magnetic flux-conducting element of the rotor (4).

11. Dynamoelectric machine ( 1 ) with a stator ( 2 ) and a rotor ( 5 ) according to claim 10 and a cooler on the condenser zone ( 19 ) .

12. Dynamoelectric machine ( 1 ) according to claim 11 , characterized in that the cooler is designed as a self-contained fan .

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