Electric motor, in particular brushless direct current motor

Abstract

The invention relates to an electric motor (1), having a printed circuit board (7) with leadthroughs (7b) in which plug-in contacts (19) sit, which plug-in contacts are contacted on a circuit-board side (7c) at a first soldering point (29) and are guided on the opposite circuit-board side (7d) by a receiving socket (22a) formed by a plastic encapsulation (22), the receiving socket having a recess (30) surrounding the respective plug-in contact (19) for forming a second soldering point (31).

Description

[0001] Page 1

[0002] 2024 481 WO

[0003] Description

[0004] Electric motor, especially brushless DC motor

[0005] The invention relates to an electric motor, in particular a brushless DC motor, comprising motor electronics with a printed circuit board and a number of plug contacts which are contacted or can be contacted at a solder joint on one side of the printed circuit board.

[0006] Such an electric motor, in particular a brushless direct current (BLDC) motor, also known as an electronically commutated electric motor, is typically a synchronous motor that uses direct current (DC) to generate mechanical energy by rotating a rotor. As an electric (three-phase) machine, this type of motor usually has a stator equipped with the rotating field or stator winding, which is arranged coaxially with a rotor containing one or more permanent magnets, spaced apart by an annular gap or air gap. During operation, the stator winding generates a rotating magnetic field, which causes a torque to be applied to the permanently excited rotor.

[0007] Depending on the number of phases, such an electric motor typically has several wires or connecting leads running from the stator or the rotating field or stator winding to the motor electronics or a printed circuit board. The motor electronics (Electronic Control Unit, ECU) of such a BLDC electric motor includes a converter (inverter) that converts direct current (DC), for example, from a vehicle's electrical system, into alternating currents with phase shifts. In the case of a three-phase electric motor, phase currents that are 120° out of phase with each other are generated, which are then used to power the stator or rotating field winding (see page 2).In such an electric motor, the motor electronics are typically arranged in an electronics compartment formed by a motor carrier to which the electric motor is attached and sealed with an electronics cover that is sealed against the motor carrier.

[0008] If the phase connections leading from the motor electronics to the stator or rotating field winding are designed as rod-shaped plug or connector contacts, these may be overmolded with plastic or guided through receptacles formed by the plastic overmolding. If the plastic of overmolded plug contacts is in direct contact during soldering in the area of ​​plated-through holes or panel openings of a printed circuit board, especially in the area of ​​a metallized hole in an electronic circuit carrier, the solder joints are often only partially formed. Particularly if the solder penetration through the respective panel opening is insufficient due to outgassing on only one side or a missing solder meniscus, the robustness of the (soldered) connection can be adversely affected.

[0009] The invention is based on the objective of providing a particularly suitable electric motor, especially as a fan drive for a fan module of a motor vehicle. Preferably, a reliable solder joint or solder connection should be achieved on a printed circuit board, particularly one with through-holes, of motor electronics via a plug connector with a plastic overmolding.

[0010] The problem is solved according to the invention by the features of claim 1. Advantageous embodiments and further developments are the subject of the dependent claims.

[0011] The electric motor is intended, in particular, for driving a motor vehicle component and preferably a radiator fan motor to drive the impeller of a radiator fan. A brushless, electronically commutated direct current (BLDC) motor is especially preferred. Page 3

[0012] The electric motor features motor electronics with a circuit carrier hereinafter referred to as a printed circuit board (PCB). The PCB, or circuit carrier, has a number of through-holes or openings. Suitablely, each through-hole in the PCB is provided with a metal layer or via a plated-through hole on its inner wall. Plug connectors are inserted into these through-holes and are connected, or can be connected, to a first solder joint on one side of the PCB, in particular in the form of a solder meniscus formed by the solder. Each plug connector is guided through a receptacle formed by a plastic overmolding on the opposite side of the PCB from the first solder joint.In other words, the plastic overmolding forms hollow cylindrical sockets in which the plug contacts, especially those with an electronics-side or board-side connection end, fit with their electronics-side connection ends.

[0013] The socket has a recess surrounding the respective plug contact, open towards the circuit board, for the formation of a second solder joint. The recess is suitably shaped like a bead surrounding the plug contact in the area of ​​the socket. The recess can, for example, be cylindrical. Advantageously, the recess surrounding the respective plug contact, particularly annular, in the socket formed by the plastic overmolding, is funnel-shaped to form a conical solder meniscus at the second solder joint. In other words, a bead-like recess is provided in the socket, surrounding the plug contact.

[0014] In an advantageous embodiment, the recess of the receiving socket surrounding the respective plug contact has a degassing opening. This ensures that degassing can occur during the soldering process, thus preventing or at least reducing the formation of cavities or inclusions (voids). Page 4

[0015] Preferably, the plastic overmolding is triangular in shape, with each corner forming a receiving socket for one of the plug contacts. The plastic overmolding suitably features a number of, preferably two, connecting pins that engage in corresponding connecting openings in the circuit board. This enables centering or positioning, and in particular prevents rotation, of the plastic overmolding relative to the circuit board of the motor electronics. The plastic overmolding suitably forms a fixing element, particularly a plate-like one, for the plug contacts.

[0016] According to a suitable embodiment of the electric motor, it has a motor carrier with an electronics compartment in which the motor electronics or the circuit board are arranged. The respective plug contact is guided through a seal that is inserted or can be inserted into a through-opening in the motor carrier. The seal is suitably conical or wedge-shaped in longitudinal section. Preferably, the seal has a number of circumferential sealing ribs on its outer circumference.

[0017] The electric motor advantageously features a stator with a stator or rotating field winding and a rotor surrounding the stator as an external rotor, with a cup-shaped rotor housing containing permanent magnets arranged on its inner walls, as well as the motor carrier with the electronics compartment housing the motor electronics. Plug contacts connected to or contactable with the stator or rotating field winding are routed into this compartment as phase leads via through-holes provided in the motor carrier. Seals, preferably elastomer or rubber seals, are inserted into these through-holes on the carrier side, enclosing the plug contacts like a sealing sleeve. Advantageously, a recess adapted to the outer contour of the plastic overmolding, which acts as a fixing element, is provided in the motor carrier within the electronics compartment, ensuring that the plastic overmolding is securely positioned within this recess.

[0018] The electronics, which are intended in particular for an electric motor of the type mentioned, and are preferably also generally suitable as electronics for other applications, and which constitute an independent invention (page 5), have a printed circuit board with a number of feedthroughs in which plug contacts are inserted, which are contacted or can be contacted at a first solder joint on one side of the printed circuit board, wherein the plug contacts are guided on the opposite side of the board by a receiving socket made of plastic, in particular as a plastic overmolding, and wherein the receiving socket has a recess surrounding the respective plug contact, in particular in a ring shape and open to the printed circuit board, in particular in a groove-like manner, for forming a second solder joint.

[0019] The advantages achieved with the invention consist in particular of the fact that by ensuring the formation of a solder joint on a plug or connector contact that is in contact with a printed circuit board via a plastic overmolding, the robustness of a (soldered) connection is increased, especially by providing the possibility of forming a solder meniscus. Furthermore, the robustness can be increased by providing a controlled opening in the plastic overmolding to allow outgassing. In particular, this can advantageously reduce or minimize the number of inclusions (voids) in the respective solder joint.

[0020] In a through-hole plating system, the solder penetration or fill level in a metallized hole or through-hole plating of the printed circuit board is increased. This results in greater robustness of the respective (solder) connection, especially with regard to aging.

[0021] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. The drawing shows:

[0022] Fig. 1 shows a sectional view of a multi-phase electric motor with a motor carrier containing motor electronics arranged in an electronics compartment, the three phase lines of which, in the exemplary embodiment, are designed as plug contacts with a plastic overmolding and sealed against the motor carrier, page 6

[0023] Fig. 2 shows a perspective view of the motor carrier with the motor electronics circuit board seated in the electronics compartment and with recesses in the plastic mounting socket for the plug contacts.

[0024] Fig. 3 shows in a perspective view the arrangement of the plug contacts that are embedded in or penetrate the receiving sockets of the plastic overmolding and with the surrounding recesses with outgassing openings opening from them,

[0025] Fig. 4 shows a partial perspective view of the arrangement mounted against the circuit board according to Fig. 3 with the plastic overmolding receiving bushings resting on the underside of the board, and

[0026] Fig. 5 shows a schematic sectional view of a plug contact passing through the plated through-hole of the circuit board with a solder meniscus formed on both sides of the board, in particular also in the recess of the receiving socket.

[0027] Corresponding parts are marked with the same reference symbols in all figures.

[0028] Figure 1 shows an electric motor 1, which is designed as a brushless DC motor (BLDC) with an external rotor. The electric motor 1 has a stator 2 designed as a laminated core with a number of stator teeth (not specified) which are wound with a three-phase rotating field winding (stator winding) 3. The electric motor 1 also has a rotor 4 and a motor mount 5.

[0029] With reference also to Figure 2, the motor mount 5 has an electronics compartment 6 in which a circuit board 7 of a motor electronics unit 8, populated with unspecified electronic components, is located. The electronics compartment 6 is closed and sealed with an electronics cover 9. The motor mount 5 is designed for mounting and securing the electric motor 1 at a desired installation location, preferably as a mechanical fastening interface to a vehicle part, for example, a radiator fan drive on a fan shroud. For this purpose, the motor mount 5 has, for example, circumferentially projecting screw or flange tabs 10.

[0030] The rotor 4 is rotatably mounted on a stationary rotor shaft 11, which forms the axis of rotation for the rotor 4's rotational movement. The rotor shaft 11 is positively and non-positively engaged, and in particular rotationally fixed, in a support bushing 12 of the motor carrier 5. The rotor 4 has a cup-shaped rotor housing 13, which is, for example, a deep-drawn part made of sheet steel. The rotor housing 13 has a housing base 14 and a hollow cylindrical housing wall 15. Arc-shaped permanent magnets 16 of a magnet arrangement are bonded to the inner wall or inner surface of the tubular or hollow cylindrical housing wall 15. A bearing seat 17 for receiving two axially spaced rolling bearings 18 is provided in the housing base 14, by means of which the rotor 4 is rotatably mounted on the rotor shaft 11.The rotor 4 is, for example, non-rotatably coupled to a fan hub of a fan wheel by means of the rotor housing 13, in particular via the housing base 14, for example by being screwed to it.

[0031] The motor electronics 8 are electrically connected to the rotating field winding 3 of the stator 2 via phase-forming plug contacts 19. In the exemplary embodiment of the three-phase electric motor 1, the three plug contacts 19 extend through the stator 2 to near the bottom of the housing 14. A rotating field-side or stator-side connection end 19a of each plug contact 19 is electrically connected to a corresponding phase contact 20 of the rotating field winding 3.

[0032] Each plug contact 19 is guided through a seal 21. Each plug contact 19 is guided with a connection end 19b associated with the motor electronics 8 into a connection or socket 22a of a plastic overmolding 22. This arrangement of the plug contacts 19 embedded in the plastic overmolding 22, which forms a plate-like fixing element, is screwed to or onto the motor carrier 5 by means of a single fastening screw 23. The seal 21 of each plug contact 19 sits in a preferably conical or tapered through-opening 24 on the carrier side of the motor carrier 5 within the electronics compartment 6. The seal 21 is conical or wedge-shaped in longitudinal section, with a sealing tip that extends into the corresponding through-opening 24 of the motor carrier 5. The seals 21 have a number of circumferential sealing ribs 21a on their outer circumference, which are shown in Fig.4 are comparatively clearly recognizable.

[0033] Figure 2 shows a top view of the motor mount 5 without the electronics cover 9, looking into the electronics compartment 6 at the motor electronics 8 and its populated circuit board 7. The motor electronics 8 are electrically connected via a terminal 25, through which a DC voltage, in particular from a vehicle electrical system, is supplied, so that the motor electronics 8 are supplied with a direct current (DC). During operation of the electric motor 1, this DC is converted by means of an inverter, in particular a bridge circuit with semiconductor switches preferably connected in a B6 bridge, into three phase-shifted phase currents, which are used to energize the rotating field winding 3 of the stator 2 via the plug contacts 19.

[0034] As can be seen in Figure 3 in conjunction with Figure 4, the plastic overmolding 22 is triangular, with each of its corner regions forming one of the receiving or plug sockets 22a for the associated plug contact 19. The plastic overmolding 22 has two joining pins 22b which engage in corresponding joining openings 7a of the circuit board 7. This enables advantageous centering, positioning, and / or rotational locking of the plastic overmolding 22 relative to the circuit board 7 of the motor electronics 8. The plastic overmolding 22 has a finger-shaped support leg 22c designed as a compensating extension. This is a design element for compensating extension, so that a uniform and efficient seal of all seals (phase seals) 21 is achieved. A recess adapted to the outer contour of the plastic overmolding 22 can also be formed in the motor carrier 5 within the electronics compartment 6. Page 9

[0035] The plug contacts 19, together with the plastic overmolding 22, are attached to the circuit board 7 of the motor electronics 8 in a corresponding arrangement, so that the latter can be inserted into the electronics compartment 6. The plug contacts 19, together with their seals 21, extend through the corresponding through-holes 24 on the carrier side, into which the seals 21 are either already inserted or are inserted together with the plug contacts 19. In the assembled state, in which the plug contacts 19 are in contact with the rotating field winding 3 of the stator 2, the motor electronics 8, housed in the electronics compartment 6, and the connection contact 25 are attached to the motor carrier 5, in particular by screws.

[0036] With reference also to Figure 5, the circuit board 7 of the motor electronics 8 has a number of feedthroughs or plate openings 7b. Each feedthrough 7b of the circuit board 7 is provided on its inner wall with a via 26 in the form of a metal layer, for example made of copper. The via 26 is electrically connected to conductor tracks 27 on both sides 7c, 7d of the circuit board 7 or is formed as a single unit. The inner diameter of the plate openings 7b or of the particularly sleeve-shaped via 26 is at least slightly larger than the outer diameter of the respective plug contact 19.

[0037] As schematically illustrated in Figure 5, the plug contact 19 in the plate openings 7b or within the via 26 is surrounded by solder 28. On the plate side 7c that faces away from the arrangement of plug contact 19 and plastic overmolding 22 or the corresponding receiving or plug socket 22a, or which, in the assembled state, faces the electronics compartment cover 9, a conical solder meniscus 29a is visible at a first solder joint 29 between the plug contact 19 and the circuit board 7 or the conductor track 27 therein, which is produced during a soldering process.

[0038] As can be seen relatively clearly in Figures 3 and 5, the receiving or plug socket 22a, formed by the plastic overmolding 22 and penetrated by the respective plug contact 19 (page 10), has a recess 30 surrounding the respective plug contact 19. This bead-like and ring-shaped recess 30 is open towards the circuit board 7 or the corresponding board side 7d. A second solder joint 31 is formed in the recess 30 by the soldering process in which the solder 28, during contact between the plug contact 19 and the via 26 of the circuit board 7, reaches the board side 7d opposite board side 7c and there, in particular forming a conical solder meniscus 29b, enters the recess(s) 30.

[0039] The recess 30 surrounding the respective plug contact 19 in the receiving socket 22a formed by the plastic overmolding 22 advantageously features a degassing opening 32. This ensures that degassing occurs during the soldering process and that the formation of cavities or inclusions 33 indicated in Figure 5 is prevented or significantly reduced.

[0040] In summary, the invention relates to an electric motor 1, comprising a circuit board 7 with feedthroughs 7b for plug contacts 19, which are contacted on one side of the board 7c at a first solder point 29 and are guided on the opposite side of the board 7d through a receiving socket 22a formed by a plastic overmolding 22, which has a recess 30 surrounding the respective plug contact 19 for forming a second solder point 31.

[0041] The claimed invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived by a person skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. In particular, all individual features described in connection with the various embodiments can also be combined in other ways within the scope of the disclosed claims without departing from the subject matter of the claimed invention. Page 11

[0042] Reference symbol list

[0043] 1 electric motor

[0044] 2 Stator

[0045] 3 Rotating field / stator winding

[0046] 4 Rotor

[0047] 5 engine mounts

[0048] 6 Electronic compartment

[0049] 7 printed circuit board

[0050] 7a Joining opening

[0051] 7b Routing / Plate opening

[0052] 7c, 7d plate side

[0053] 8 Motor electronics

[0054] 9 Electronic covers

[0055] 10 screw / flange straps

[0056] 11 Rotor axis

[0057] 12 Carrier socket

[0058] 13 Rotor housings

[0059] 14 Case base

[0060] 15 Housing wall

[0061] 16 permanent magnets

[0062] 17 bearing seat

[0063] 18 rolling bearings

[0064] 19 Plug contact / phase wire

[0065] 20 phase contacts

[0066] 21 Seal

[0067] 21a Sealing rib

[0068] 22 Plastic overmolding / Fixing element

[0069] 22a Mounting / plug socket

[0070] 22b Joining pin

[0071] 22c Support leg

[0072] 23 Fastening screw

[0073] 24 Carrier-side through-opening Page 12

[0074] 25 connection contacts

[0075] 26 Through-hole plating

[0076] 27 conductor track

[0077] 28 Soldering medium 29 First solder joint

[0078] 29a, 29b Lotminiskus

[0079] 30 In-depth study

[0080] 31 second solder joint

[0081] 32 Degassing opening 33 Cavity / Inclusion

Claims

Page 13 Claims 1. Electric motor (1), in particular a cooling fan motor, comprising motor electronics (8) with a printed circuit board (7) with a number of feedthroughs (7b) in which plug contacts (19) are inserted, which are contacted or can be contacted on a side (7c) of the printed circuit board (7) at a first solder point (29), - wherein the plug contacts (19) on the side (7d) of the circuit board (7) opposite the first solder point (29) are guided through a receiving socket (22a) formed by a plastic overmolding (22), and - wherein the receiving socket (22a) has a recess (30) surrounding the respective plug contact (19), in particular in a ring shape, and open to the circuit board (7) to form a second solder joint (31).

2. Electric motor (1 ) according to claim 1 , characterized in that the recess (30) of the receiving socket (22a) surrounding the respective plug contact (19) is funnel-shaped to form a conical solder mini-discus (29b) at the second solder joint (31).

3. Electric motor (1) according to claim 1 or 2, characterized in that the recess (30) of the receiving socket (22a) surrounding the respective plug contact (19) has a degassing opening (32).

4. Electric motor (1) according to one of claims 1 to 3, characterized by a triangular plastic overmolding (22) in the corner areas of which a receiving socket (22a) for one of the plug contacts (19) is formed.

5. Electric motor (1) according to one of claims 1 to 4, characterized in that, Page 14 shows that the respective through-hole (7b) of the circuit board (7) for the plug contact (19) is provided with a through-hole (26) on the inner wall side.

6. Electric motor (1) according to one of claims 1 to 5, characterized in that the circuit board (7) of the motor electronics (8) is arranged in an electronics compartment (6) of a motor carrier (5), wherein the respective plug contact (19) is guided over a seal (21) that is inserted or can be inserted in a through-opening (24) of the motor carrier (5).

7. Electric motor (1 ) according to claim 6, characterized in that the seal (21) is conical or wedge-shaped in longitudinal section.

8. Electric motor (1 ) according to claim 6 or 7, characterized in that the seal (21) has a number of circumferential sealing ribs (21a) on its outer circumference.

9. Electric motor (1) according to one of claims 1 to 8, characterized in that the plastic overmolding (22) has a number of, preferably two, joining pins (22b) which engage in corresponding joining openings of the circuit board (7).

10. Electric motor (1) according to one of claims 1 to 9, characterized by a stator (2) having a stator or rotating field winding (3) and a rotor (4) surrounding it as an external rotor with a pot-shaped rotor housing (13) with permanent magnets (16) arranged on the inner wall.

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