Method for manufacturing a stator and electric motor

Abstract

A method for manufacturing a stator (12) for an electric motor (10) of a fluid pump is described. In a first process step, a stator core (12) is provided which is equipped with several windings (20). The stator core (12) is inserted into a mold (46) such that a portion of the stator core (16) is supported against an inner wall of the mold (46) in such a way that the remaining portion of the stator core (16) maintains a defined distance from the inner wall of the mold (46). Subsequently, the stator core (16) is overmolded with plastic in the mold (46) such that the plastic overmolding forms a stator housing (18), whereby the portion of the stator core (16) that is supported in the mold (46) remains free of plastic. Furthermore, an electric motor (10) for a fluid pump is described.

Description

[0001] The invention relates to a method for manufacturing a stator for an electric motor of a fluid pump and an electric motor for a fluid pump.

[0002] Fluid pumps are used, for example, in motor vehicles to provide a flow of fluid that can be used to cool or lubricate various components. For instance, fluid pumps are designed to pump coolant for battery cooling, transmission oil, lubricating oil, or other fluids.

[0003] Such fluid pumps feature an electric motor with a rotor and a stator, the rotor being coupled to an impeller or similar fluid conveying element. The rotor can be cooled by a partial flow of the pumped medium. However, the electrical components on the stator, as well as a circuit board, must be protected from contact with the medium. For this purpose, the stator of the electric motor in a fluid pump is housed in a casing, which increases manufacturing complexity and space requirements. Furthermore, there is the challenge of reliably sealing such casings to prevent moisture ingress.

[0004] It is therefore an object of the invention to provide a stator optimized with regard to installation space requirements and fluid tightness.

[0005] This problem is solved according to the invention by a method for manufacturing a stator for an electric motor of a fluid pump, in which, in a first process step, a stator core is provided which is equipped with several windings. The stator core is inserted into a mold such that a portion of the stator core is supported against an inner wall of the mold in such a way that the remaining portion of the stator core has a defined distance to the inner wall of the mold. Subsequently, the stator core is overmolded with plastic in the mold such that the plastic overmolding forms a stator housing, whereby the portion with which the stator core is supported in the mold remains free of plastic.

[0006] The stator housing, formed by overmolding, achieves a compact design. Furthermore, such a stator exhibits high resistance to various media. In particular, it is not necessary to equip the stator housing with a cover, thus eliminating the need for complex sealing.

[0007] By supporting the stator core with a portion of it in such a way that the remaining area maintains a defined distance from the inner wall of the mold, it is ensured that the stator core is uniformly overmolded, meaning that the plastic housing has a defined thickness everywhere except in the area left unsupported. The distance between the stator core and the inner wall of the mold, or the thickness of the plastic housing, does not necessarily have to be uniform but can vary. The crucial point is that a certain minimum distance is maintained.

[0008] The defined support of the stator core prevents the formation of areas with very thin walls due to undefined core positioning – areas where the plastic forms only a thin skin. Areas with such thin walls in the stator housing could become compromised over the lifespan of the plastic housing, for example, through abrasion, dissolution by an aggressive medium, or material fatigue.

[0009] According to the invention, the position of the exposed section is chosen such that the stator housing is particularly robust and the stator core, especially the electronic components, are reliably protected from moisture. Ideally, the path from the exposed section to the electronic components of the stator core, more precisely to a printed circuit board, is as long as possible.

[0010] According to one aspect, the stator core is provided with a coil carrier to which at least one radially projecting support element is molded. The stator core is held in the mold by this support element. More precisely, the support element is clamped between two mold halves when the mold is closed. After the stator core is overmolded, only the ends of the support elements are exposed, while the stator core and windings are completely encased in plastic. This provides particularly good protection for the stator core. Specifically, the stator core is largely encased in plastic.

[0011] According to an alternative embodiment, the stator core is supported, for example, along its inner wall within the mold. This allows for a particularly large support area. The stator core is centered within the mold, with frictional support on its inner surface. Consequently, the inner surface of the stator core remains free of plastic. This is advantageous with regard to the air gap to the rotor. Specifically, a particularly small air gap can be achieved. The exposed area on the stator core poses no problem in oil applications.

[0012] According to a further alternative embodiment, the stator core is supported along its outer wall in the mold. As with support along the inner wall, this achieves large-area support and centering of the stator core. However, with support along the outer wall, the inner wall of the stator core is covered with plastic. This is advantageous when the stator is used in water pumps, as the plastic applied to the inner wall protects the stator core from corrosion, resulting in particularly high media compatibility.

[0013] The stator core can rest against the inside of the mold with an end face facing away from a connection side. This positions the stator core axially within the mold. Such axial contact is advantageous when the stator core is supported along an inner or outer wall of the mold, as described above. In this case, the supported area at the axial end face abuts directly against the supported inner or outer wall.

[0014] According to one aspect, the stator core comprises electrical contact elements attached to it, particularly to the coil carrier, with the stator core being additionally held in place by these electrical contact elements within the mold. This provides additional axial fixation of the stator core, preventing it from being lifted by the pressure of the liquid plastic during overmolding. This risk exists, for example, if the stator core is supported in the mold solely by the inner or outer wall. Furthermore, the electrical contact elements, which are typically pressed into plastic parts on the stator core, are also fixed during overmolding. This also ensures that certain areas of the contact elements remain free from plastic overmolding, allowing for electrical contact.

[0015] The stator can comprise a printed circuit board. The control electronics for controlling an electric motor containing the stator can be located on the circuit board.

[0016] The circuit board is supported, for example, by a separate holder on the stator core, particularly on the coil former. The circuit board is thus also completely encapsulated in plastic, which protects it from moisture and mechanical damage and allows heat from the electrical components to be efficiently dissipated. Furthermore, encapsulating the circuit board contributes to a compact design, as no screws are required to secure it.

[0017] The holder serves to stabilize the circuit board before and during overmolding.

[0018] The holder can be loosely placed on the stator core.

[0019] Alternatively, the circuit board can be supported solely by the contact elements. This type of support reduces manufacturing costs, as only the existing elements are used for support.

[0020] The contact elements protrude a short distance through the circuit board or are pressed into it to establish the electrical contact.

[0021] An injection channel is arranged, for example, such that the plastic is injected into the mold from a side facing the circuit board. For instance, the injection channel is located on the top side of the mold or in a lateral area near the top.

[0022] This allows the plastic to flow onto the circuit board from above during overmolding, preventing the circuit board from being lifted by the plastic before the mold is completely filled with plastic.

[0023] According to one aspect, the stator core is overmolded using a low-pressure injection molding process, specifically a thermoset overmolding. Low-pressure injection molding reduces the risk of damage to delicate electronic components, making it particularly well-suited for overmolding the printed circuit board. The thermoset plastic used is typically relatively low in viscosity, allowing all parts to be completely overmolded and even thin gaps to be sealed. Furthermore, due to its low viscosity, the injected material exerts minimal shear force on components in its flow path.

[0024] When overmolding the stator core, at least one mounting tab and / or a groove for receiving a seal can be formed in the stator housing. This eliminates subsequent machining steps such as milling a groove or creating mounting points in the stator housing, which also contributes to lower manufacturing costs for the stator.

[0025] The problem is further solved according to the invention by an electric motor for a fluid pump, comprising a stator manufactured by a method according to the invention and a rotor mounted concentrically to rotate with respect to the stator. Due to the stator housing formed by overmolding the stator core, such an electric motor has a particularly compact design and is also easy to assemble, as fewer individual parts need to be handled.

[0026] Further advantages and features of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. The drawings show: - Fig. 1 an electric motor according to the invention in a side view, - Fig. 2 a sectional view of the electric motor made of Fig. 1, - Fig. 3 a stator of the electric motor from the Fig. 1 and Fig. 2, - Fig. 4 the stator Fig. 3 with an attached circuit board, - Fig. 5 a holder to stabilize the circuit board, - Fig. 6 a sectional view of the stator according to the Fig. 1 and Fig. 2 in a tool shape, - Fig. 7 an alternative stator for an electric motor according to the Fig. 1 and Fig. 2, - Fig. 8 another alternative stator for an electric motor according to the Fig. 1 and Fig. 2, - Fig. 9 another alternative stator for an electric motor according to the Fig. 1 and Fig. 2, and - Fig. 10 A top view of a stator housing.

[0027] The Fig. 1 and Fig. Figure 2 shows an electric motor 10 with a stator 12 and a rotor 14 mounted concentrically to the stator 12. The electric motor 10 is intended, for example, to drive a fluid pump.

[0028] The stator 12 is formed by overmolding a stator core 16. Specifically, a stator housing 18 is formed by overmolding the stator core 16.

[0029] The individual components of the stator 12 and a method for manufacturing a stator 12 are described with reference to the following figures.

[0030] Fig. Figure 3 shows the stator core 16, which is equipped with several windings 20.

[0031] Furthermore, the stator core 16 is provided with a coil carrier 22. Two radially projecting support elements 24 are integrally formed on the coil carrier 22; their function will be explained in detail below.

[0032] The stator core 16 comprises electrical contact elements 26, 28, which are attached to the stator core 16, more precisely to the coil carrier 22. Specifically, the electrical contact elements 26, 28 are pressed into the coil carrier 22, which is made of, for example, plastic.

[0033] A first group of contact elements 26 forms connector pins that serve for the electrical contact of the electric motor 10. A second group of contact elements 28 provides the electrical connection between a printed circuit board 30, which is in Fig. 4 is shown, and the windings 20.

[0034] The circuit board 30 is placed on the stator core 16, with the ends of the contact elements 26, 28 engaging in the circuit board 30 in such a way that an electrical connection is established.

[0035] In order to be able to mount the circuit board 30 in a defined position, the contact elements 26, 28 have insertion sections 32 at their ends facing the circuit board 30 and widened central sections 34 relative to the insertion sections 32, which serve on the one hand as a stop for the circuit board 30 and on the other hand give the contact elements 26, 28 the required stability.

[0036] Optionally, a separate holder 36 can be provided for additional support of the circuit board 30, which is supported on the stator core 16, more precisely on the coil carrier 22.

[0037] The holder 36 is loosely placed on the stator core 16 before the circuit board 30 is attached.

[0038] In Fig. Figure 5 shows the holder 36 separately. In the exemplary embodiment, the holder 36 is a one-piece injection-molded part.

[0039] The holder 36 has a support ring 38 from which four support arms 40 extend. This gives the holder 36 an X-shape.

[0040] Alignment pins 42 are molded onto the free ends of the support arms 40.

[0041] The alignment pins 42 are stepped to provide an axial contact surface for the printed circuit board 30.

[0042] As in Fig. As can be seen in Figure 4, the circuit board 30 has complementary recesses 44 for the alignment pins 42, into which the alignment pins 42 engage, so that the circuit board 30 is correctly aligned by means of the holder 36 and is also axially supported.

[0043] Fig. Figure 6 shows the stator core 16 in a tool shape 46.

[0044] The tool shape 46 has a first tool half 48 and a second tool half 50 as well as a slide for forming a plug connector 52 (see Fig. 1) However, the slider is due to the in Fig. The orientation of the tool shape 46 shown in section 6 is not visible.

[0045] In the tool mold 46, the stator core 16 is overmolded with plastic in such a way that the plastic overmolding forms the stator housing 18.

[0046] Before overmolding, the stator core 16 is placed in a cavity of the mold 46 in such a way that the stator core 16 is supported with a partial area against an inner wall of the mold 46 in such a way that the stator core 16 has a defined distance to the inner wall of the mold 46 in the remaining area.

[0047] In the exemplary embodiment according to Fig. 6 the stator core 16 is held in the tool shape 46 by means of the support elements 24, namely by the support elements 24 being taken in between the tool halves 48, 50.

[0048] In this way, the stator core 16, as described in Fig. As can be seen in Figure 6, it is firmly fixed in both the axial and radial directions.

[0049] For example, during overmolding, the plastic is injected into the mold 46 from a side facing the circuit board 30. For this purpose, in the exemplary embodiment, a injection channel 55 is provided in the mold half 48, the outlet of which is directed towards the circuit board 30. However, it is also conceivable that the plastic is injected into the mold from the side or from a side facing away from the circuit board.

[0050] The overmolding of the stator core 16 is carried out, for example, in a low-pressure injection molding process, in particular by thermoset overmolding.

[0051] In Fig. Figure 6 shows the stator core 16 in the tool mold 46 already in an overmolded state, thus completing a stator 12 with a stator housing 18. In this state, only the support elements 24 are exposed; the remaining part of the stator core 16 is completely encased in plastic.

[0052] Fig. Figure 7 shows a stator 12, which was also manufactured by a method as described above.

[0053] Unlike the one in Fig. The stator core 16 shown in section 6 was the one in Fig. The stator 12 shown in Figure 7 is manufactured by not only holding the stator core 16 at the support elements 24 during overmolding in the mold 46, but also by supporting it along its inner wall 54 in the mold 46. This is the case with the stator shown in Figure 7. Fig. Figure 7 illustrated stator 12 based on the exposed inner wall 54.

[0054] In this embodiment, the support elements 24 can optionally be omitted, so that the stator core 16 is only supported along its inner wall 54 in the tool mold 46 during overmolding.

[0055] Fig. Figure 8 shows another embodiment of the stator 12.

[0056] The in Fig. The stator 12 shown in Figure 8 was manufactured by supporting the stator core 16 along its outer wall 56 in the mold 46 during overmolding.

[0057] This is in Fig. 8 can be seen from the exposed area on the outer wall 56. In the illustrated embodiment, the exposed area is arranged adjacent to an end face facing away from the circuit board 30.

[0058] The in the Fig. 7 and Fig. The 8 stators 12 shown have in common that, in addition to the support of the stator core 16 along the inner wall 54 or along the outer wall 56, the stator core 16 was in contact with the inside of the tool shape 46 with an end face 58 facing away from a connection side of the stator 12.

[0059] This is in the Fig. 7 and Fig. 8 can be seen from the fact that the exposed area is not only present on the inner wall 54 or on the outer wall 56 of the stator core 16, but the stator core 16 is also partially exposed in the area of ​​the axial end face 58.

[0060] Fig. Figure 9 shows a stator 12 according to a further embodiment.

[0061] At the in Fig. Figure 9 illustrates that a groove 60 for receiving a seal is provided on one end face of the stator 12 in the stator housing 18. The groove 60 was formed during the overmolding of the stator core 16.

[0062] A corresponding 60 mm groove can be used in all of the [unclear] Fig. 6, Fig. 7 to Fig. 8 illustrated stators 12 may be present.

[0063] Fig. Figure 10 shows a stator 12, on whose stator housing 18 mounting tabs 62 are integrally molded. The mounting tabs 62 were also formed during the overmolding of the stator core 16.

[0064] Such screw-on tabs 62 can be used on all of the ones in the Fig. 6, Fig. 7 to Fig. 8 illustrated stators 12 may also be present.

Claims

[1] Method for manufacturing a stator (12) for an electric motor (10) of a fluid pump, comprising the following steps: - a stator core (12) is provided which is equipped with several windings (20), - the stator core (12) is inserted into a tool mold (46) such that the stator core (16) is supported with a partial area against an inner wall of the tool mold (46) in such a way that the stator core (16) has a defined distance to the inner wall of the tool mold (46) in the remaining area, and - Subsequently, the stator core (16) is overmolded with plastic in the tool mold (46) in such a way that the plastic overmolding forms a stator housing (18), whereby the part area with which the stator core (16) is supported in the tool mold (46) remains free of plastic. [2] Method according to claim 1, characterized by, that the stator core (16) is provided with a coil carrier (22) to which at least one radially projecting support element (24) is integrally formed, wherein the stator core (16) is held in the tool shape (46) by means of the support element (24). [3] Method according to claim 1, characterized by , that the stator core (16) is supported along its inner wall (54) in the tool shape (46). [4] Method according to claim 1, characterized by , that the stator core (16) is supported along its outer wall (56) in the tool shape (46). [5] Method according to claim 3 or 4, characterized by , that the stator core (16) with an end face of the stator core (16) facing away from a connection side is in contact with the inside of the tool shape (46). [6] Method according to any one of the preceding claims, characterized by, that the stator core (16) comprises electrical contact elements (26, 28) which are attached to the stator core (16), in particular to the coil carrier (22), wherein the stator core (16) is additionally held on the electrical contact elements (26, 28) in the tool shape (46). [7] Method according to any one of the preceding claims, characterized by , that the stator (12) comprises a circuit board (30). [8] Method according to claim 7, characterized by , that the circuit board (30) is supported on the stator core (16), in particular on the coil carrier (22), via a separate holder (36). [9] Method according to claim 7 or 8, characterized by , that a injection channel (55) is arranged such that the plastic is injected into the mold (46) from a side facing the circuit board (30). [10] Method according to any one of the preceding claims, characterized by, that the overmolding of the stator core (16) is carried out in a low-pressure injection molding process, in particular by thermoset overmolding. [11] Method according to any one of the preceding claims, characterized by , that when overmolding the stator core (16) in the stator housing (18) at least one screw-on tab (62) and / or a groove (60) for receiving a seal is formed. [12] Electric motor (10) for a fluid pump, comprising a stator (12) manufactured by a method according to one of the preceding claims and a rotor (14) mounted concentrically to the stator (12) so as to be rotatable.

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