Stator components of electrical machines

Abstract

The stator member (4') of an electric machine includes a resin structure (13'), a stator unit (8') having a plurality of coils at least partially embedded in the resin structure, an electronic control device, and a plurality of metallic conductor elements (12'), the coils being connected to the electronic control device via the conductor elements, with portions of the extensions of the conductor elements embedded in the resin structure (13'). The resin structure (13') is manufactured from a thermoplastic resin by injection molding and is overmolded onto a pre-assembled assembly consisting of the stator unit (8') and the conductor elements (12') connected to the coils of the stator unit. The resin structure (13') forms a flange (28) adjacent to the free end (19') of each of the corresponding metallic conductor elements (12') protruding from the resin structure and assigned to contact the electronic control device, completely surrounding the metallic conductor element and exposed and projecting from other portions of the resin structure. The sealing between the resin structure (13') and the metallic conductor element (12') is achieved without the use of a separate sealant, but only by contact between the thermoplastic resin of the resin structure (13') and the corresponding metallic conductor element (12'). In the part of the metallic conductor element (12') that penetrates the corresponding collar (28), a microstructure in the form of a groove (31) is provided around the periphery of the conductor element, which is set on the surface using laser engraving and filled with ribs made of the thermoplastic resin of the resin structure (13').

Description

[Technical Field]

[0001] The present invention relates to a stator member for an electric machine, in particular an electric motor, comprising a resin structure, a stator unit having a plurality of coils at least partially embedded in the resin structure, an electronic control device and a plurality of metallic conductor elements, the coils being connected to the electronic control device via the conductor elements. [Background technology]

[0002] Stator elements of the above-mentioned type are known, for example from Chinese Patent Application Publication No. 105656221 (A). They are useful for a variety of applications, for example as part of an electric motor for a motor-pump unit (which serves to propel a liquid medium). In order to make the motor-pump unit very compact and relatively simple in construction, the motor rotor and the pump rotor are often installed in a common space, so that the motor rotor operates "wet", i.e. the medium to be propelled flows through and contacts it.

[0003] In particular, when dealing with aggressive media (fuel, automatic transmission fluid, etc.), it is absolutely necessary to prevent the media from reaching the electronic control unit, otherwise the electronic control unit would be irreparably damaged in a very short time. With a view to hermetically separating the electronic control unit from the internal space of the stator member (which houses the rotor of the electric machine), there is a requirement that the conductor elements connecting the coil to the electronic control unit must protrude from the plastic structure in order to make contact with the electronic control unit. Experiments have shown that there is a great risk of the medium penetrating along the surface of the conductor elements to the electronic control unit; therefore, there is a rather serious risk of damage.

[0004] Various methods have been proposed and implemented to prevent damage to electronic control devices. First, there is direct protection of the electronic control device, in particular by molding it over with a thermosetting resin (especially an epoxy resin). On the other hand, there are proposals for improved sealing of metallic conductor elements to the resin structure. One method for this purpose is to mold the resin structure (manufactured from a thermoplastic resin by injection molding) into a small bowl at each point where the conductor elements protrude from the resin structure for contact with the electronic control device. These small bowls are then filled with a special sealant (potting compound) that has very good adhesive properties both to the material of the conductor elements and to the resin of the resin structure. However, this method entails significant costs. A second method in this regard is to injection-mold the resin structure from a thermosetting resin optimized for adhesion to the metal of the conductor elements, characterized by a significantly lower processing viscosity and a lower coefficient of thermal expansion or shrinkage than thermoplastic resins. This involves significant restrictions on the shape of the resin structure (due to the significantly more difficult processing of thermosetting resins compared to thermoplastic resins during injection molding), which in turn forces compromises on other requirements, and this is also because the choice of material is significantly restricted by the need to sacrifice optimization of the resin structure in other respects (e.g., other important material properties, cost, surface properties, thermal expansion properties, etc.).

[0005] To date, no solution has been found that satisfies the requirements of practical importance or that gives satisfactory results in the demanding test methods common in the automotive industry, such as combined tests carried out after repeated thermal shock treatment. The stator elements of the electric machines described above (compared to other applications with resin structures overmolded around metal conductor elements or other metal inserts) make it difficult to solve the sealing problem between the metal conductor elements and the resin structure, and no definitive solution is known, since lack of sealing is observed even in expensively manufactured stator elements. Possible reasons include the fact that (even the smallest) imbalances of the rotating parts that can occur during the operation of the electric machine create wobble and vibrations that can promote the delamination of the resin structure from the metal conductor elements. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 105656221(A) Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above-mentioned prior art and the problems associated therewith, it is an object of the present invention to provide a stator element of the type mentioned at the beginning, which is characterized by a combination of very favorable properties both in production (e.g., a wide range of material choices, high freedom of design, low production costs) and in operation (e.g., good protection against damage to electronic control units), such that, unlike conventional parts, the stator element should also be able to withstand the latest and most demanding test methods employed in the automotive industry, in particular a combined test carried out after repeated thermal shock treatments (e.g., 600 temperature cycles, each consisting of 90 minutes of heating at 90°C and cooling to -40°C within 30 seconds). [Means for solving the problem]

[0008] The above problem can be solved by the following features of the stator member in addition to those mentioned at the beginning: a metallic conductor element is embedded in the resin structure along a part of its longitudinal extension between the corresponding coil and the contact terminal of the electronic control device, and a free end portion assigned to the contact terminal of the electronic control device protrudes from the resin structure; a resin structure is manufactured from a thermoplastic resin by injection molding and is overmolded onto a pre-assembled assembly consisting of a stator unit and conductor elements connected to the coils of the stator unit; the resin structure forms flanges adjacent to the free ends of the corresponding metal conductor elements, completely surrounding the periphery of each metal conductor element and protruding from other portions of the resin structure; The sealing between the resin structure and the metallic conductor element is performed solely by contact between the thermoplastic resin of the resin structure and the corresponding metallic conductor element without using a separate sealant; in the part of the metallic conductor element that penetrates the corresponding collar, a microstructure in the form of a groove is provided around the periphery of the conductor element, which is set on the surface using laser engraving and filled with the thermoplastic resin of the resin structure; This is resolved by combining each feature.

[0009] By implementing the combination of the aforementioned features, stator members can be manufactured that are adaptable to practical requirements to a previously unimaginable degree. Some of the significant relationships that contribute to the unique performance of the stator members of the present invention include: The resin structure, which includes an exposed, protruding collar adjacent to the free end of each corresponding metal conductor element (in contact with the electronic control device), and which completely surrounds the corresponding metal conductor element (i.e., protruding from the remainder of the resin structure, i.e., without being connected to the resin structure via beams, bridges, ribs, etc.), provides flexibility within the corresponding region of the resin structure, allowing the resin structure to deform to accommodate the enclosed conductor element. Therefore, the resin structure can accommodate thermal expansion (in multiple directions) of the conductor element in the region of the collar, as well as (minor) re-deformation of the conductor element due to deformation of the conductor element caused by mounting of the electronic control device (due to manufacturing tolerances) and / or vibrations caused by imbalances in the rotating parts of the electric machine. Furthermore, the resin structure can also accommodate (fine) deformations of the conductor element caused by shaking in the area of the flange surrounding the conductor element. All of the above also applies to resin structures injection-molded from common thermoplastic resins (with characteristic material properties, including damping). This is extremely effective in substantially reducing the pressure generated between the conductor element and the resin structure during assembly and operation. This also significantly reduces the tendency for (long-term) delamination. In combination with a unique method for improving the adhesive properties of the thermoplastic resin to the metallic conductor element, this method achieves a permanent sealing of the interface between the conductor element and the resin structure without additional measures (in the flange area, anyway). This therefore prevents media from penetrating along the surface of the conductor element and causing damage to the electronic control unit.In this regard, the possibility of producing resin structures by injection molding from thermoplastic resins (which are less difficult to process than thermosetting resin materials) even offers the advantageous side effect of allowing for significantly increased design freedom in terms of the structural details of the resin structure, thereby enabling significant improvements in functionality (as well as processability).Thermoplastic resins, due to their characteristic material properties, are particularly well suited for the implementation of the present invention, including polybutylene terephthalate (PBT), high-density polyethylene (HDPE), and polyphenylene sulfide (PPS), as well as mixtures containing PBT, HDPE, or PPS (particularly as the main component, i.e., more than 50%).

[0010] The above-mentioned preferred feature is particularly pronounced when (according to the first preferred additional configuration) the collar has a wall thickness that is at least largely uniform (except for a possible distal taper (see below)). A "uniform" wall thickness in this case exists when the collar wall thickness does not vary substantially in either the longitudinal or circumferential direction, but excludes any technically necessary reductions in wall thickness over the length of the collar (e.g., reductions in wall thickness over the draft angle required for removal from the mold). In this case, it is highly preferred that the wall thickness of the collar in the thickest region is not more than 50%, more preferably not more than 25%, and even more preferably not more than 15% of the wall thickness of the collar in the thinnest region.

[0011] Not only the uniformity of the flange wall thickness but also the wall thickness itself has an effect. This is because the aforementioned flange deformability depends on the wall thickness in combination with the material properties of the thermoplastic resin of the resin structure. For example, in a stator member having a resin structure made of PBT applied to a typical 240-watt BLDC motor, the flange wall thickness is preferably 1.0 to 1.6 mm. For a flat metal conductor element with a rectangular cross section and a side length ratio of at least 3:1 (e.g., 5.5 mm x 0.8 mm), a valid relationship can also be defined between the cross section of the conductor element and the flange wall thickness. That is, the flange wall thickness is preferably 1.4 to 1.9 times the value of the smaller side length.

[0012] According to another preferred additional feature of the present invention, for a permanent and effective sealing between the conductor element and the resin structure, it is highly preferred that the microstructured grooves on the surface of the corresponding conductor element are oriented substantially perpendicular to the longitudinal direction of the metal conductor element. Such a groove orientation has the advantage that, in the event of (micro) deformations of the conductor element, which occur most frequently in typical applications (see above), the grooves are expected to provide a protective effect, particularly against the risk of delamination of the thermoplastic resin structure from the metal conductor element caused by such deformation. Similarly, the configuration of the collars of the thermoplastic resin structure, in which each collar terminates with a tapered portion distally toward the free end of the corresponding metal conductor element, offers a particularly effective advantage in significantly reducing the tendency toward harmful delamination phenomena. If the tapered portion is formed conically, it is preferred that the apex angle or cone angle be 70° to 120°. It is particularly preferred that the apex angle or cone angle be 80° to 110°.

[0013] Furthermore, microstructures with grooves having a depth of 10 μm to 100 μm and / or a width of 3 μm to 50 μm have proven to be very effective, with a preferred ratio between the width and depth of the grooves being 0.6 to 1.5, particularly preferably 0.8 to 1.2. The spacing between the grooves also influences the adhesion of the thermoplastic resin structure to the metallic conductor element. It is preferred that the spacing between two adjacent grooves is at least as large as the width of the grooves.

[0014] The combination and synergy of the above-mentioned features (substantially uniform collar wall thickness, orientation of the microstructured grooves substantially perpendicular to the longitudinal direction of the corresponding metallic conductor element, and formation of microstructured grooves with a depth of 10 μm to 100 μm and / or a width of 3 μm to 50 μm) allows for the production of stator elements with properties previously unattainable, since the uniquely achievable physico-chemical connection of each collar to the conductor element penetrating it allows the corresponding stator element to meet the most stringent requirements for the protection of electronic control units (in particular without the need for additional measures such as additional sealing), even when the collar is made of a thermoplastic resin material. In combination with other construction features, an effective micromechanical interlock (MMI) effectively prevents any delamination of the collar from the corresponding conductive element, thus preventing the large differential shrinkage between thermoplastic and metal during manufacturing from having a detrimental effect on the hermetic protection of the electronic control unit, as well as compatibility with rigorous inspection and test methods (see above).

[0015] According to yet another preferred additional feature of the present invention, the conductor element has at least one hole in the area of the flange of the resin structure, which is filled with the thermoplastic resin of the resin structure. This naturally applies to conductor elements with a significantly flat cross-section, with one dimension at least three times larger than the orthogonal dimension (e.g., 5.5 mm x 0.8 mm). Such a hole is highly effective in two respects: it creates a resistance to heat conduction, thereby preventing heat conducted into the conductor element during soldering of the electronic control device to the conductor element from heating the conductor element (especially in the area of the microstructure) in a manner that would damage the intimate bond between the resin structure and the conductor element. Furthermore, a "bridge" of thermoplastic resin extending through the at least one hole provides an additional effective protection against the risk of delamination of the thermoplastic resin from the surface of the metallic conductor element between the two sides.

[0016] Similarly, in order to minimize the heat load on the conductor elements during soldering of the electronic control device, according to a further additional feature of the invention, the conductor elements are preferably forked at their ends (by notches). Such a forked conductor element configuration also effectively reduces jamming that may occur during installation of the electronic control device.

[0017] As described above, the surface treatment, i.e., microstructuring, of the conductor element, which functions to synergize the collar of the thermoplastic resin structure and improve the adhesive properties of the thermoplastic resin to the metallic conductor element, is important for achieving a favorable effect. Even in this case, it is understood that the relationship between the collar and the microstructure, defined by the relative spatial arrangement of the collar and the conductor element, cannot be ignored. Therefore, according to yet another preferred additional configuration of the present invention, it is highly effective that the length of each of the portions of the metallic conductor element that are provided with the microstructure is at least 50%, preferably 65%, of the exposed length of the collar parallel to the longitudinal direction of the corresponding metallic conductor element, where "exposed length" can be understood to mean the extension of the collar protruding from the rest of the resin structure. It is also highly effective that at least 80%, preferably at least 90%, of the length of each of the portions of the metallic conductor element that are provided with the microstructure is located within the collar area. It is particularly preferred that the entire length of each of the portions of the metallic conductor element that are provided with the microstructure is located within the collar area, i.e., 100%.

[0018] The exposed length of the collar (measured parallel to the longitudinal direction of the relevant conductor element) has a predetermined relationship to the dimensions of the conductor element: for flat conductor elements having a rectangular cross section with a side ratio of at least 3:1, the exposed length of the collar is preferably 0.7 to 1.0 times, particularly preferably 0.8 to 0.9 times, the longer of the two dimensions transverse to the longitudinal direction of the metallic conductor element.

[0019] The relationship between the electronic control device and the various deformation pressures acting on the conductor elements (particularly vibrations that may occur during installation and operation of the electronic control device while in contact with the conductor elements) has already been mentioned above. In view of this relationship, the advantages achievable by the present invention are particularly effective in stator members in which the electronic control device, i.e., the substrate attached thereto, is directly fixed to a resin structure via one or more connection points. In this case, it is also preferable to house the electronic control device in a space partitioned by a thermoplastic resin structure and a cover material that is connected to the resin structure and encloses the electronic control device.

[0020] The present invention will now be described in detail with reference to a number of preferred embodiments thereof as illustrated in the accompanying drawings. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a longitudinal section of an electric machine configured as an electric motor according to the prior art; [Figure 2] 2 is a three-dimensional view of a stator member of the electric motor of FIG. 1. [Figure 3] 3 is an explanatory diagram showing a detail A of the stator member of FIG. 2. FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a further enlarged detail of the stator member of FIGS. 2 and 3; [Figure 5] FIG. 2 is a three-dimensional view showing a stator member according to the present invention. [Figure 6] 6 is an explanatory diagram showing a detail B of the stator member of FIG. 5. FIG. [Figure 7] FIG. 7 is a cross-sectional view showing a further enlarged detail of the stator member of FIGS. 5 and 6; DETAILED DESCRIPTION OF THE INVENTION

[0022] The electric motor shown in FIG. 1 includes a stator 1 and a rotor 3 rotatably supported about an axis X using two roller bearings 2 therein. The stator 1 includes a built-in stator member 4, an electronic control unit 5, a cover member 6, and a bearing cap 7. The stator member 4 further includes a stator unit 8 having a pole piece 9 with a coil support 10 arranged about the axis X and a coil 11 mounted on the coil support, a metal conductor element (pin) 12 in contact with the coil, and a resin structure 13, the resin structure being injection-molded onto a pre-assembled component group consisting of the stator unit 8 and the conductor element 12. The rotor 3 includes a rotor shaft 14 and a rotor armature 15 mounted on the rotor shaft.

[0023] The electronic control device 5 (housed in a hollow 16 formed between the resin structure 13 and the lid 6) comprises a circuit board 17 on which an electronic component E is mounted. The board is mounted on a rod 18 which is part of the resin structure 13. The conductor elements 12 are embedded in the resin structure 13 only over a portion of their length; in each case, the free ends 19 of the conductor elements protrude from said resin structure and penetrate through said free ends into openings 20 in the respective circuit board 17 to make contact with the electronic control device 5. The same applies to the neutral pin 21.

[0024] In the region of the three conductor elements 12 and the neutral pin 21, each resin structure 13 is configured in the form of a socket 22. Each socket 22 is connected to a central region 23 of the resin structure 13 via a reinforcing rib 24. Each socket 22 is configured as a bowl member 25 surrounding the corresponding conductor element 12 or neutral pin 21 at its tip end, and has a central, generally pyramidal or roof-shaped protrusion 26 disposed therein. The bowl member 25 is filled with a sealant (potting compound) 27 (shown only in Figures 1 and 4) (before the electronic control device 5 is installed).

[0025] Electric motors having stator members of the configuration shown in Figures 2 to 4 are well known (e.g., as drive motors for the oil pump of a Tesla Model 3) and further details are not necessary for understanding the present invention, so a further detailed description will be omitted.

[0026] The stator member 4' configured according to the present invention and shown in Figures 5 to 7 is similar in basic structural features to the technology shown in Figures 2 to 4. Therefore, in the following description, a full description will be omitted and only important differences will be described.

[0027] A particularly notable and important difference is that in the resin structure 13' (injection molded from PBT), the conductor elements 12' are not formed as thick-walled sockets that are also connected to the central region 23' of the resin structure via reinforcing ribs. Rather, each conductor element 12' is surrounded (again, only along a portion of its length) by a relatively thin collar 28 that protrudes from the rest of the resin structure 13' along its entire periphery. In this case, the collar 28 has at least a substantially uniform wall thickness W. For a conductor element having a cross section of 5.5 mm by 0.8 mm, the surrounding collar 28 has an average wall thickness W of approximately 1.3 mm, resulting in an exposed length L1 of approximately 4.5 mm. The collar 28 terminates distally in a tapered portion 29 toward the free end 19' of the corresponding metal conductor element 12'.

[0028] The metal conductor element 12' has a microstructure 30 (shown very diagrammatically and not to scale) in the form of grooves 31, approximately 50 μm deep and 10 μm wide, formed in the surface by laser engraving, in the portion of the metal conductor element 12' that penetrates into the corresponding collar 28. The grooves are parallel to each other and oriented perpendicular to the longitudinal direction of the corresponding metal conductor element 12'. The spacing between adjacent grooves 31 is approximately 20 μm. The length L2 of each metal conductor element 12' that includes the microstructure 30 is approximately 3.5 mm, i.e., approximately 75% of the exposed length L1 of the collar 28; the portion of the metal conductor element 12' that includes the microstructure 30 is then located entirely within the collar 28. The neutral pin 21' is formed in a similar manner to the conductor element 12'.

[0029] Each conductor element 12' has three interstices 32 and 33 extending therethrough. The first interstices 32 (formed in the form of an oblong oval) are located in the portion of each conductor element 12' where the element has the microstructure 30 on its surface. The two (substantially circular) interstices 33 (visible in FIG. 6 by appropriately cutting through the resin structure of the tapered portion 29) are located in the region of the corresponding conductor element 12' that is shielded by the distal tapered portion 29 of the collar 28. A thermoplastic resin "bridge" 34 extends through each of the three interstices 32 or 33, connecting the collar 28 or tapered portion 29 regions on opposite sides of the conductor element 12'.

[0030] Furthermore, it can be seen that the terminal end 19' (which serves to contact the electronic control device) of the conductor element 12' is configured in a fork shape with a terminal notch 35, unlike the prior art shown in Figures 1 to 4.

[0031] The stator member 4' is characterized by excellent sealing performance between the metallic conductor elements 12' and the PBT resin structures 13' that fit over the conductor elements (via the ribs 36 that align with and fill the grooves 31), along with very good long-term rigidity and a very low tendency to delaminate. That is, the sealing between the resin structures 13' and the metallic conductor elements 12' is achieved solely by contact between the PBT thermoplastic resin of the resin structures 13' and the corresponding metallic conductor elements 12'; no separate sealant (e.g., potting material used in the prior art) is required.

Claims

1. A stator member (4') for an electric motor, which is an electric machine, comprising: a resin structure (13'); a stator unit (8') having a plurality of coils (11) at least partially embedded in the resin structure; an electronic control device (5); and a plurality of metallic conductor elements (12'), the coils (11) being connected to the electronic control device (5) via the conductor elements, the metallic conductor elements (12') being embedded in the resin structure (13') with a portion of their longitudinal extension between the corresponding coil (11) and a contact terminal of the electronic control device (5), and a free end portion (19') assigned to the contact terminal of the electronic control device (5) protruding from the resin structure: a resin structure (13') is produced from a thermoplastic resin by injection molding and is overmolded onto a pre-assembled assembly consisting of a stator unit (8') and conductor elements (12') connected to the coils (11) of the stator unit; The resin structure (13') is adjacent to the free end portion (19') of the corresponding metal conductor element (12'), and forms a flange portion (28) that completely surrounds the corresponding metal conductor element (12') and protrudes from other portions of the resin structure, The sealing between the resin structure (13') and the metallic conductor element (12') is performed solely by contact between the thermoplastic resin of the resin structure (13') and the corresponding metallic conductor element (12') without using a separate sealant; A stator element characterized in that in the part of the metallic conductor element (12') that penetrates the corresponding collar (28), a microstructure (30) in the form of a groove (31) is provided around the periphery of the conductor element, the groove (31) being set on the surface by means of laser engraving and filled with ribs (36) made of thermoplastic resin of the resin structure (13'), A stator member characterized in that the distance between two adjacent grooves (31) is at least as large as the width of the grooves (31).

2. 2. A stator element according to claim 1, characterized in that the grooves (31) are oriented substantially perpendicular to the longitudinal direction of the corresponding metallic conductor element (12').

3. 3. A stator member according to claim 1 or 2, characterized in that the grooves (31) are formed with a depth of 10 μm to 100 μm.

4. 4. A stator member according to claim 1, wherein the grooves (31) are formed with a width of 3 μm to 50 μm.

5. 5. A stator member according to claim 1, wherein the ratio between the width and the depth of the grooves (31) is between 0.6 and 1.

5.

6. 6. A stator member according to any one of claims 1 to 5, characterized in that the length (L2) of the portion having the microstructure (30) is at least 50% of the exposed length (L1) of the flange portion (28) parallel to the longitudinal direction of the corresponding metallic conductor element (12').

7. 7. A stator member according to claim 1, wherein at least 80% of the length (L2) of the portion of the metallic conductor element (12') having the microstructure (30) is located within the region of the flange (28).

8. 8. A stator member according to claim 1, characterized in that, in the case of a conductor element (12') having a rectangular cross section, the exposed length (L1) of the flange portion (28) parallel to the longitudinal direction of the corresponding conductor element (12') is 0.7 to 1.0 times larger than the longer of the two dimensions transverse to the longitudinal direction of the metallic conductor element (12').

9. 9. A stator element according to claim 1, wherein the collar (28) terminates in a tapered portion (29) on the distal side in the direction of the free end (19') of the corresponding metallic conductor element (12').

10. A stator member according to any one of the preceding claims, characterized in that the collar (28) has a wall thickness (W) that is uniform.

11. 11. A stator element according to claim 1, characterized in that the conductor element (12') comprises at least one lacuna (32, 33) in the area of the coating by the collar (28) of the resin structure (13') and in the area of the surface microstructure (30), both of which are filled with thermoplastic resin of the resin structure (13').

12. 12. A stator element according to any one of claims 1 to 11, characterized in that the free end portions (19') of the conductor elements (12') are formed in a fork shape by having notches (35) on the distal side.

13. 13. A stator member according to claim 1, wherein the electronic control device (5) is fixed on the resin structure (13') and is shielded by a cover (6) connected to the resin structure.

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