DE102017124587A1 - Electric motor and method for sealing a terminal of the electric motor - Google Patents

Abstract

The invention provides an electric motor with a stator and a terminal of the stator, wherein the stator is encapsulated with a thermosetting material, whereby a molded body is formed. The terminal, for example a terminal pin, projects outwardly from the injection body in a first direction. A sealing cap made of a thermoplastic material surrounds the terminal and adjoins the injection body. The sealing cap is designed such that a pressure on the sealing cap, which acts in the first direction, presses the sealing cap against the injection body.

Description

FIELD OF THE INVENTION

The invention relates to the sealing of the terminals of an electric motor. The electric motor is used in particular for driving a pump, for example a pump for circulating coolant in a motor vehicle.

BACKGROUND OF THE INVENTION

Coolant pumps in a motor vehicle, which are driven by an electric motor, are usually constructed so that the output shaft of the electric motor and an impeller for circulating the coolant lie on a common axis. A mechanical seal can seal the shaft of the coolant pump to the outside. In operation, however, cooling fluid can penetrate into the rotor space of the electric motor. Within the electric motor, the stator, stator terminals and electronics are sealed to prevent coolant from penetrating to live parts. The seal can be realized for example by encapsulation of the corresponding engine parts.

The seal must be resistant to coolant and withstand high temperature fluctuations and pressures. In coolant systems of motor vehicles e.g. As a rule, temperature fluctuations of the order of magnitude of -40 ° C. to approx. + 125 ° C. and pressures of up to 3 bar occur. Accordingly, there is a need for pump drive systems that are rated for at least these temperature ranges and pressures and can withstand, for example, operating temperature variations in the range of -40 ° C to +180 ° C and an operating pressure of up to 10 bar.

The seal must ensure, during operation of the electric motor, that high media tightness is ensured on all parts enclosed by the seal at all expected operating temperatures and pressures. The penetration of liquid and gases, such as coolant, to live parts also along any existing capillary gaps must be safely prevented.

It is therefore an object of the invention to provide an electric motor and a method for its sealing, which allow reliable sealing of current-carrying parts of the electric motor against the rotor.

SUMMARY OF THE INVENTION

This object is achieved by an electric motor according to claim 1 and by a method according to claim 14. Embodiments of the invention are specified in the dependent claims.

The invention provides an electric motor with a stator and a terminal of the stator, wherein the stator is encapsulated with a thermosetting material, whereby a molded body is formed. The terminal, for example a terminal pin, projects outwardly from the injection body in a first direction. A sealing cap made of a thermoplastic material surrounds the terminal and adjoins the injection body. The sealing cap is designed such that a pressure on the sealing cap, which acts in the first direction, presses the sealing cap against the injection body. The electric motor may also have a plurality of terminals, for example, three or four terminals and a corresponding number of sealing caps. When the invention is described below with reference to a terminal and a sealing cap, it will be understood that corresponding arrangements can also be provided at further terminals.

The encapsulation of the stator with the thermosetting material creates a high media density, because the temperature coefficients of metal and thermosetting plastic are similar and their expansion behavior thus runs largely the same even at high temperature fluctuations. For example, there is glass fiber reinforced epoxy resin having a coefficient of thermal expansion of the order of 18 ppm / K (at 20 to 105 ° C, in accordance with standard ISO 11359-2). The coefficient of thermal expansion of the sheet materials used for the stator is compared to the order of 12 ppm / K, that is of the same order of magnitude. Furthermore Duroplast adheres well to metal. The spray of the thermoset material can thus provide a good seal against metal.

Duroplast has at the processing temperatures that occur during injection molding, a very low viscosity, especially at conventional injection molding temperatures of about 280 ° C to 300 ° C and injection pressures of about 500 to 800 bar. It is therefore expedient to seal the connecting pins of the electric motor or other parts which protrude outwardly from the injection-molded body, separately. Due to manufacturing tolerances, namely gaps can be formed between the pins and the injection molding tool, the thermoset then during processing even at very small gap widths, for example> 15 microns, can flow into the column. Thus, without separate sealing of the pins, there is the danger that the thermoset will leak out of the tool due to tolerance variations through a gap between the pin and the injection molding tool. To prevent this, the sealing cap is applied to the connecting pin. The A sealing cap also has the purpose of positioning and fixing the connection pins during the injection molding process and of ensuring the media tightness of the injection body where terminals emerge from the injection body.

The sealing cap is made of a thermoplastic material and can be pressed or sprayed onto the terminals. Basically, a variety of thermoplastic materials in question, for example, acrylonitrile-butadiene-styrene (ABS), polyamides (PA), polylactate (PLA), polymethylmethacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyetheretherketone (PEEK), polybutylene terephthalate (PBT) or polyphenylene sulfide (PPS) or a combination thereof. The thermoplastic material should, at least for a short time, be resistant to high temperatures and withstand high pressures in order to withstand the high temperatures and pressures encountered in processing the thermoset without damage. When processing thermosetting plastic, pressures of up to 800 bar and temperatures of up to 300 ° C can occur, as mentioned above. Since thermoplastic material has a coefficient of thermal expansion which is about a factor compared to thermoset or metal 10 to 20 is greater, the total sealing of the stator should not be done with thermoplastic material. For the sealing of the terminal, it is quite suitable. Particularly suitable as a thermoplastic material is, for example, PBT, PA and PPS.

The flat surface of the sealing cap serves to seal the terminals in the injection molding tool. In order to ensure the media density of the injection body in the region of the sealing cap during operation of the electric motor, this is designed so that a pressure on the sealing cap, which acts in the direction of the exiting terminal, presses the sealing cap against the injection body. Thus, if an existing in the electric motor medium, for example by capillary, at an interface of the injection body penetrates to the sealing cap and presses against the sealing cap, this is pressed due to the design of the invention against the injection molding and thus acts as a kind of check valve, which the overall system seals. The penetrating through the gap fluid builds up a pressure that is used with the special shape of the sealing cap to press the sealing cap against the thermoset molding.

According to the invention, a first interface portion is formed between the sealing cap and the injection body, which extends perpendicular or obliquely to the first direction, in particular at an angle between 30 ° and 120 ° to the first direction. Preferably, the first interface portion is perpendicular or approximately perpendicular to the first direction.

In one embodiment, a slot insulation is applied to the stator, and the sealing cap is engaged with the groove insulation, in particular positively connected to position the sealing cap in the injection mold and to fix. For this purpose, the slot insulation may have a projection extended in the first direction, and the sealing cap may have a recess into which the projection engages. The reverse configuration is also possible, that is to say a projection on the sealing cap and a recess on the slot insulation, which engage in one another. Other complementary forms for supporting the sealing cap on the slot insulation are possible, for example, interlocking steps, teeth or the like.

Gaps may be formed between the sealing cap and the slot insulation and between the sealing cap and the injection body, which form a creepage path for fluid, wherein the leakage path extends at least partially in the first direction, and between the sealing cap and the slot insulation and / or between the sealing cap and forming a second interface portion extending perpendicular or oblique to the first direction, such that a fluid entering the gap exerts pressure in the first direction against the second interface portion, such that the sealing cap abuts against the first interface portion the syringe body is pressed. The gap may represent a capillary gap for the fluid, which has, for example, a gap width of approximately 15 μm or in the range of 15 μm to 100 μm, in particular in the range of 15 μm to 50 μm or of 15 μm to 25 μm. The second interface portion may be perpendicular or approximately perpendicular to the first direction.

The electric motor may be used as a pump motor for conveying a fluid, e.g. for circulating a coolant for an internal combustion engine of a motor vehicle. The fluid may be under pressure, for example under a pressure of up to 10 bar or about 10 bar.

The invention also provides a method of sealing a terminal coupled to a stator of an electric motor. First, a sealing cap made of a thermoplastic material is applied to the terminal, for example sprayed or a preform is pressed on. The stator with the terminal and the sealing cap sitting thereon is placed in an injection mold and overmolded with a thermosetting material, whereby a molded body is formed, the terminal projecting outwardly of the molding in a first direction, and the nozzle Sealing cap adjacent to the injection body. An interface between the sealing cap and the syringe body is designed such that a pressure on the sealing cap, which acts in the first direction, presses the sealing cap against the interface, so that a gap existing between the sealing cap and the syringe body is reduced or closed. The interface preferably comprises a first interface portion that is perpendicular or approximately perpendicular or oblique, and at least not parallel to the first direction. Further, a second interface portion may be provided which is parallel or substantially parallel to the first interface portion.

The stator can be provided with a slot insulation prior to encapsulation, with the sealing cap being brought into engagement with the slot insulation when it is applied to the terminal.

list of figures

• 1 zeigt eine Längsschnittdarstellung durch einen Teil eines Elektromotors gemäß einem Beispiel, wobei der Stator im Bereich des Statorjoches angeschnitten ist;
• 2 zeigt einen vergrößerten Ausschnitt aus der Darstellung der 1, in dem in 1 mit X gekennzeichneten Bereich;
• 3 zeigt eine Querschnittdarstellung durch einen Teil des Elektromotors, wobei die Schnittebene der 1 durch die Linie A-A dargestellt ist.

The invention is explained below by way of example with further details with reference to the drawings.

• 1 shows a longitudinal sectional view through a part of an electric motor according to an example, wherein the stator is cut in the region of the stator yoke;
• 2 shows an enlarged section of the representation of 1 in which 1 X marked area;
• 3 shows a cross-sectional view through a part of the electric motor, wherein the sectional plane of the 1 represented by the line AA.

DETAILED DESCRIPTION OF THE INVENTION

In the longitudinal section of the 1 and 2 is a part of a stator 10 shown, which is composed of a stack of sheets. A cross-sectional view of the stator 10 is in 3 to see. The stator 10 can be made from individual laminations with a Statorjoch 10 ' and stator teeth 10 '' be built, which are punched and packaged into a stack. The stator has a stator insulation or slot insulation 12 on, which is applied to the wall surfaces of the stator and the stator teeth 10 ' and the stator yoke 10 '' of stator windings 14 separates and electrically isolated. The slot insulation 12 can be sprayed or prefabricated and inserted into the stator slots. In the example shown is the slot insulation 12 in the axial direction on both sides of the stator 10 and forms a receptacle for a pin 16 of the stator, which is an example of a stator terminal. The pin 16 is in his foot area 16 ' with one end 14 ' the stator winding 14 coupled. In this example, a clamp press fit is between the pin 16 and the end of the stator winding 14 intended. In the example shown, the slot insulation 12 provided only within the stator, wherein the inner circumference of the stator yoke has no corresponding insulation. The slot insulation 12 may be made of a polyester material or a polymeric material, for example based on PA.

The stator 12 is in a syringe body 18 embedded the stator 12 surrounds and embeds on its outer periphery. In addition, it may be provided in other embodiments that the stator 12 also encapsulated on its inner circumference and thus completely from the Sprtizkörper 18 surrounded and embedded in these. The injection body 18 is made of a thermoset, for example, a glass fiber reinforced epoxy resin, which adheres well to the metal of the stator and has a similar coefficient of thermal expansion. By "similar coefficient of thermal expansion" is meant, for example, a thermal expansion coefficient which does not deviate from the coefficient of thermal expansion of the stator material by more than <15 ppm / K.

As in 1 shown, both on the outer circumference of the stator 10 as well as on the outer circumference of the slot insulation 12 Projections and recesses 20 be formed with the corresponding projections and recesses in the injection molded body 18 engage in the manner of a toothing to a particularly intimate connection between the injection molding 18 and the stator 10 or the slot insulation 12 to achieve. The teeth in the area of the projections and recesses 20 acts like a labyrinth seal. In addition, between the stator 10 and the injection body 18 and / or between the slot insulation 12 and the injection body 18 seals 22 be introduced, with the in the 1 and 2 shown sealing rings 22 are exemplary and more or fewer sealing rings can be provided at different positions.

The injection body 18 can, as in 1 shown to be designed so that it not only the stator 10 isolated, but that other functional parts are formed, for example, a connector housing 24 , a flange and / or tabs 26 for mounting the electric motor, an electronics room 28 with a holder 30 for receiving a control board (not shown). The injection body 18 separates and isolates the stator 10 and the rotor (not shown) from the electronics compartment 28 , The rotor (not shown) is in the interior of the stator in the example shown 10 arranged circumferentially, wherein the rotor space 32 in 3 is illustrated. The rotor space 32 is just like the stator 10 from the electronics room 28 through the injection body 18 , in particular its end wall 18 ' isolated and electrically isolated.

The rotor (not shown) has a drive shaft (not shown) via which the rotational movement of the electric motor can be transmitted, for example, to an impeller of a pump or to another unit to be driven.

How best in 2 It can be seen at the electronics room 28 facing end face of the slot insulation 12 a lead 12 ' trained, with a sealing cap 36 is engaged. The sealing cap 36 Can be made of a thermoplastic material and placed on the pin 16 be pressed or sprayed on. In the example shown, it has a recess 36 ' on top of that with the lead 12 ' the slot insulation 12 engaged to the sealing cap 36 to position and fix. Between the sealing cap 36 and the injection body 18 For example, an interface is formed with a plurality of steps or steps, which in the example shown at least a first interface portion 40 and at least a second interface portion 42 include. In the example shown, the interface portions extend 40 . 42 perpendicular or approximately perpendicular to the direction in which the pin 16 from the injection body 18 exit. Unlike shown, however, the interface portions may also extend obliquely to this direction, for example at an angle between 30 ° and 120 °. The first interface section 40 is the front end of the injection molding 18 to which the pin 16 exit, facing (referred to herein as first direction), and the second interface section 42 is the stator 10 facing. The two interface sections 40 . 42 thus point in opposite directions.

The described relative shape of sealing cap 36 and syringes 18 has the effect of having a fluid which is in a gap between the sealing cap 36 and the injection body 18 penetrates or creeps, along this gap to the second interface 42 penetrates and there a pressure P against the sealing cap 36 in the first direction exerts and thus the sealing cap 36 against the first interface 40 suppressed. At the first interface 40 this creates a back pressure P ' who has the sealing cap 36 against the injection body 18 sealed and prevents further penetration of the fluid. The creepage distance of the fluid is in 2 through a chain of arrows K indicated. Due to the different thermal expansion coefficients of the materials of the sealing cap 36 and the injection body 18 At least the formation of a capillary gap can not be reliably prevented. By the shaping of sealing cap 36 and syringes 18 However, a seal between the two can be created, which operates in the manner of a check valve and closes the gap, as soon as the penetration of the fluid, a corresponding pressure in the gap or against the second interface portion 42 is built. In some embodiments, the pin may 16 itself with an insulating material, such as epoxy resin, be jacketed, so it does not have to be sealed separately.

In one application example, the electric motor is used for driving a pump, for example a pump for circulating a coolant of a motor vehicle. The injection body 18 in conjunction with the sealing cap 36 In this application, the media density between the stator 12 , the terminals 16 and the electronics in the electronics room 28 for sure. The media tightness is ensured at all occurring in this application temperature and pressure, as explained in the introduction.

The electric motor can be made by first the slot insulation 12 on the stator 10 applied, for example, sprayed or inserted into the grooves. The stator windings 14 be on the stator 10 applied. One pin each 16 comes with every end 14 ' a stator winding 14 connected, and the sealing cap 36 is on the pin 16 postponed. Alternatively, a pin 16 with a pre-molded or applied sealing cap 36 be used. The sealing cap 36 and the slot insulation 12 are engaged, the projection 12 ' the slot insulation 12 into the recess 36 ' the sealing cap 36 can intervene. Other positive connection are possible, for example with a projection on the sealing cap 36 which fits into a corresponding recess in the slot insulation 12 engages, or with adjoining surfaces and / or steps.

The stator 10 , with the slot insulation 12 and the stator windings 14 , Pin (s) 16 and sealing cap (s) 36 is inserted into an injection mold with a mold cavity corresponding to the shape of the injection molding 18 brought in. The tool is closed, and a thermosetting material for molding the molding 18 is introduced into the mold cavity. The sealing cap 36 is in the mold cavity using the slot insulation 12 positioned and fixed during the injection molding process. The flat surface or end face 36 '' of the sealing cap 36 During the injection molding process, the pin (s) 16 Seal in the injection mold. To the injection body 18 Further functional elements, such as a flange, tabs, a connector housing, etc., can be molded.

LIST OF REFERENCE NUMBERS

10

stator

10 '

stator yoke

10 ''

stator tooth

12

slot insulation

12 '

Projection of the slot insulation

14

stator windings

14 '

End of the stator windings

16

Pin, terminal

16 '

Foot area of the terminal pin

18

spray body

18 '

End wall of the injection body

20

Projections and recesses

22

seals

24

plug housing

26

tabs

28

electronics compartment

30

holder

32

rotor chamber

36

sealing cap

36 '

Recess of the sealing cap

36 ''

Flat surface, end face of the sealing cap

40

first interface section

42

second interface section

P

print

P '

backpressure

K

creepage

Claims (16)

Electric motor with a stator (10) and a terminal (16) of the stator (10), wherein the stator (10) is encapsulated with a thermosetting material, whereby a syringe body (18) is formed, wherein the terminal (16) from the injection body (18) projecting outwardly in a first direction, and having a sealing cap (36) of a thermoplastic material surrounding the terminal (16) and adjacent to the syringe body (18), the sealing cap (36) being shaped such that a pressure on the sealing cap (36), which acts in the first direction, presses the sealing cap (36) against the injection body (18). Electric motor after Claim 1 wherein between the sealing cap (36) and the injection body (18), a first interface portion (40) is formed, which is perpendicular or oblique to the first direction, in particular at an angle between 30 ° and 120 ° to the first direction. Electric motor after Claim 2 wherein the first interface portion (40) is perpendicular or approximately perpendicular to the first direction. Electric motor according to one of the preceding claims, wherein on the stator (10) has a slot insulation (12) is applied and the sealing cap (36) with the slot insulation (12) is engaged, in particular positively connected. Electric motor after Claim 4 wherein the groove insulation (12) has a projection (12 ') extending in the first direction and the sealing cap (36) has a recess into which the projection (12') engages; and / or wherein the sealing cap (36) has a projection extending in the first direction and the slot insulation (12) has a recess into which the projection engages. Electric motor after Claim 2 and Claim 4 or 5 in that a gap is formed between the sealing cap (36) and the slot insulation (12) and between the sealing cap (36) and the injection body (18), which forms a leakage path for a fluid, the leakage path extending at least partially in the first direction , and wherein between the sealing cap (36) and the groove insulation (12) and / or between the sealing cap (36) and the injection body (18) a second interface portion (42) is formed, which is perpendicular or oblique to the first direction, so in that a fluid which penetrates into the gap exerts a pressure in the first direction against the second interface section (42), so that the sealing cap (36) is pressed against the injection body (18) at the first interface section (40). Electric motor after Claim 6 wherein the second interface portion (42) is perpendicular or approximately perpendicular to the first direction. Electric motor after Claim 6 or Claim 7 wherein the gap has a gap width of about 15 μm or in the range of 15 μm to 100 μm, in particular in the range of 15 μm to 50 μm or of 15 μm to 25 μm. Electric motor according to one of the preceding claims, wherein the sealing cap (36) is pressed or sprayed onto the terminal (16). Electric motor according to one of the preceding claims, wherein between the sealing cap (36) and the injection body (18) a check valve function is formed. Electric motor according to one of the preceding claims, wherein the thermosetting material of the injection molded body (18) comprises an epoxy resin, in particular a glass fiber reinforced epoxy resin, or a polyurethane or a polyester resin, or phenol or melamine. Electric motor according to one of the preceding claims, wherein the thermoplastic material the sealing cap (36) acrylonitrile-butadiene-styrene (ABS), polyamides (PA), polylactate (PLA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyetheretherketone (PEEK) or polyphenylene sulfide (PPS) or a combination thereof. Use of the electric motor according to one of the preceding claims as a pump motor for conveying a fluid at a pressure of up to 10 bar or at about 10 bar. A method of sealing a terminal (16) coupled to a stator (10) of an electric motor, comprising: Applying a sealing cap (36) of a thermoplastic material to the terminal (16); Injecting the stator (10) of the electric motor with a thermosetting material and thereby forming a molded body (18), wherein the terminal (16) protrudes outwardly of the injection body (18) in a first direction and the sealing cap (36) to the injection body ( 18) adjacent, wherein an interface between the sealing cap (36) and the syringe body (18) is designed such that a pressure on the sealing cap (36) acting in the first direction presses the sealing cap (36) against the interface, such that a between the Sealing cap (36) and the injection body (18) existing gap is reduced or closed. Method according to Claim 14 wherein the interface comprises a first interface portion (40) that is perpendicular or approximately perpendicular or oblique to the first direction. Method according to Claim 14 or 15 in that the stator (10) is provided with a slot insulation (12) before encapsulation, and wherein the sealing cap (36) is brought into engagement with the slot insulation (12) when applied to the terminal (16).

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