Stator assembly for an electric motor, electric motor and method for assembling a stator assembly

Abstract

Stator assembly (1, 15) for an electric motor, comprising an outer housing (2) with an opening in which a stator core (4) with a stator coil (5) is received, wherein radially projecting busbar terminals (8, 17) are arranged near an axial end of the stator coil (5), wherein a fluid deflection ring (6, 20) is arranged at a position which is axially further inward than the busbar terminals (8, 17), wherein the busbar terminals (8, 17) extend radially further outward than an inner circumference of the fluid deflection ring (6, 20), wherein the fluid deflection ring (6, 20) comprises at least two ring segments (9, 12, 16, 19) which are designed to be joined together. Furthermore, a method for assembling a stator assembly (1, 15) is proposed.

Description

The invention relates to a stator assembly for an electric motor having an outer housing with an opening in which a stator package with a stator coil is accommodated, wherein radially protruding busbar connections are arranged in the vicinity of an axial end of the stator coil.Electric machines are increasingly used in electric or hybrid vehicles. The electric machine is mainly used as an electric motor for driving a wheel or an axle of the vehicle.The electric motor is usually mechanically coupled to a transmission for speed adaptation. In addition, the electric motor is electrically connected to an inverter which generates an AC voltage, in particular a polyphase AC voltage, for operating the electric machine from a DC voltage which is provided by a battery.The stator of an electric machine includes a stator core and stator windings. The laminated rotor core consists of axially stacked laminated rotor laminations. Some of the rotor laminations have recesses that form pockets for magnets. When a current is applied to the stator windings, a rotating electric field is generated, causing the rotor to rotate.When a stator assembly is assembled, a stator stack having a stator coil is inserted into an outer case. The stator pack is provided with radially protruding bus bar terminals in the vicinity of an axial end of the stator coil. A liquid cooled stator is provided with a liquid diverting ring on an axial side to obtain sufficient back pressure for a cooling liquid. However, a liquid diverting ring cannot be mounted due to the protruding bus bar terminals being an obstacle.The invention is therefore based on the problem of assembling a stator assembly comprising a stator coil with radially protruding bus bar terminals in the vicinity of an axial end of the stator coil and a fluid diverting ring.This problem is solved by a stator having the features of claim 1.According to the invention, a liquid diverting ring is arranged at a position axially further inward than the busbar terminals, the busbar terminals extending further radially outward than an inner periphery of the liquid diverting ring, the liquid diverting ring comprising at least two ring segments configured to be joined together.The invention is based on the idea that a liquid diverting ring can be mounted after a stator coil has been inserted into an outer housing, with the proviso that the ring comprises at least two separate ring segments which can be joined together after the insertion into the outer housing. Dividing the liquid diverting ring into two or more ring segments allows them to be separately inserted and joined together axially further inward than the protruding bus bar terminals.The ring segments for the stator assembly according to the invention are preferably provided with positive connections, which enables the joining of the at least two ring segments.A form-fit connection comprises a ring segment with an undercut and a further ring segment with a corresponding counterform. Such a form-fit connection has the advantage that the ring segments can be connected without additional connecting elements such as screws, rivets, adhesive or the like.According to a preferred embodiment of the invention, the ring segment with the undercut is formed in a T-shape and the other ring segment is formed in a corresponding negative T-shape. Such shapes can be produced without problems. They have a similar shape to a puzzle piece.In the stator assembly according to the invention, it is assumed that a ring segment is provided with a radial inner projection which is designed to abut against a projection of the outer housing when the liquid deflecting ring is rotated in the circumferential direction. The radial inner projection ensures that both ring segments assume a predefined position in the assembled state.Preferably, the liquid deflecting ring is secured with a retaining ring, a snap ring, a locking ring or a retaining ring, which is each inserted into a circumferential groove of the outer housing. Each of these rings holds the liquid diverting ring in position and prevents it from moving.In the invention, it is particularly preferred that the liquid diverting ring comprises spray holes which are arranged along its inner circumference in the circumferential direction. Through the spray holes, cooling liquid is sprayed onto the stator coil, so that heat is dissipated from the stator coil.The fluid diverting ring of the stator assembly of the invention may be provided with radial struts on one or both surfaces.The liquid deflecting ring preferably comprises holes for fastening elements, in particular for screws. The fastening elements make it possible to clamp the liquid deflection ring in the axial direction.The invention further relates to an electric motor comprising a stator assembly as described and a rotor accommodated in the stator stack.In addition, the invention relates to a method for assembling a stator assembly, comprising the steps of: inserting a stator package having a stator coil into an opening of an outer housing, wherein radially protruding bus bar terminals are arranged in the vicinity of an axial end of the stator coil; inserting a first ring segment of a liquid diverting ring in the axial direction to a position which is located axially further inward than the bus bar terminals at a circumferential position, wherein the first ring segment does not contact the bus bar terminals; rotating the first ring segment in the circumferential direction until bus bar terminals are no longer present in a gap between the two ends of the first ring segment; and inserting a second ring segment and assembling it with the first ring segment to form a closed liquid diverting ring.The invention will be explained with reference to the drawings by way of a preferred example. The drawings are schematic representations and show: FIG. 1 shows a perspective view of a stator assembly according to the invention; FIG. 2 shows a view of the stator assembly from FIG. 1 along the axial direction; FIG. 3 shows the stator assembly with rotated first ring segment; FIG. 4 shows the stator assembly after assembly; FIG. 5 is a perspective view of a liquid diverting ring; FIG. 6 shows a second embodiment of an inventive stator assembly; FIG. 7 shows a detail of a first ring segment; FIG. 8 shows the stator assembly from FIG. 6 with the first ring segment rotated; FIG. 9 shows the stator assembly with a retaining ring; and FIG. 10 shows the stator assembly with a securing ring.FIG. 1 is a perspective view showing a stator assembly 1 for an electric motor having an outer casing 2 that is cup-shaped. The outer housing 2 comprises an opening 3, in which a stator package 4 with a stator coil 5 is accommodated. The stator package 4 is designed as a hollow cylinder which is provided with stator coils 5 at both axial ends.The stator assembly 1 is provided with a cooling device whereby cooling liquid is supplied through an inlet (not shown). The cooling liquid is conducted through the stator assembly 1 and dissipates heat from the stator stack 4 until it leaves the stator assembly 1 through an outlet (not shown). A liquid diverting ring 6 is positioned on the outer axial side of the stator stack 4 and fixed with screws 7. Inside the outer housing 2, cooling liquid is sprayed against the liquid deflecting ring 6. On its inner periphery, the liquid diverting ring 6 is provided with through holes through which cooling liquid is sprayed onto the stator coil 5.FIG. 2 is a view of the stator assembly of FIG. 1 taken approximately along the axial direction. The stator core 4 is provided with radially protruding bus bar terminals 8 disposed at the axial end of the stator core 4 in the vicinity of the open end of the outer casing 2 at approximately the same axial position as the stator coil 5. During assembly of the stator assembly 1, the problem arises that a conventional liquid diverting ring cannot be mounted, since the busbar connections 8 project radially outwards, while the liquid diverting ring has to be positioned axially further inwards.In order to avoid this problem, the liquid deflecting ring 6 comprises a first ring segment 9 and a second ring segment, which will be explained in the following. The first ring segment 9 is provided with positive connections 10 at both ends. Each interlocking connection 10 comprises an undercut which can be joined to a corresponding counterform of the second ring segment. In this embodiment, the positive connection 10 is formed in a T-shape.When the stator assembly 1 is assembled, the stator core 4 with the stator coil 5 is inserted into the opening 3 of the outer case 2. Subsequently, the first ring segment 9 of the liquid diverting ring 6 is introduced in the axial direction of the outer housing 2 and positioned axially further inward than the busbar connections 8. The first ring segment 9 is then rotated in the circumferential direction, so that the first ring segment 9 does not contact the busbar connections 8. A rotation of the first ring segment 9 is possible since it is positioned axially further inward than the busbar connections 8.The next step of the assembly process is illustrated in Figure 3. As can be seen, the first ring segment 9 has been rotated in the circumferential direction approximately 90° in the clockwise direction, as indicated by the arrow. In this state, the bus bar terminals 8 are no longer present in a gap 11 between the two ends of the first ring segment 9. A second ring segment 12 can then be inserted and joined to the first ring segment 9.FIG. 4 shows the final state after the attachment of the second ring segment 12. Both positive connections 10 are joined together like puzzle pieces which are firmly seated against one another. The liquid diverting ring 6, which comprises the first ring segment 9 and the second ring segment 12, is secured by screws 7, as shown in FIG. 1. A rotor may then be inserted into the stator assembly 1 to form an electric motor.In FIG. 5, the liquid diverting ring 6 is illustrated as comprising the first ring segment 9 and the second ring segment 12. Both ring segments 9, 12 comprise radial struts 13 on both sides. Spray holes 14 are arranged along the inner periphery of the ring segments 9, 12. The function of the liquid diverting ring 6 is to obtain a back pressure to a certain extent for cooling liquid which is supplied to the outer housing 2 under pressure, so that it sprays against the inner surface of the liquid diverting ring 6. Cooling liquid injected from the spray holes 14 is sprayed onto the stator coil 5. Thus, heat is dissipated from the stator coil 5.FIG. 6 shows a second embodiment of a stator assembly 15 having a similar structure to the stator assembly 1. Therefore, identical components will not be explained in detail again. According to the first embodiment, the stator assembly 15 comprises the outer housing 2, in which the stator package 4 with the stator coil 5 is accommodated. A first ring segment 16 of a liquid deflection ring is inserted into the opening of the outer housing 2. A gap is formed between the two ends of the first ring segment 16 in the circumferential direction. The first ring segment 16 is positioned in the circumferential direction so as not to contact the bus bar terminals 17. The first ring segment 16 is provided with an inner projection. When the first ring segment 16 is rotated clockwise, the inner protrusion abuts a protrusion of the outer housing 2 such that the first ring segment 16 is located at a predetermined position.FIG. 7 shows a detail of the first ring segment 16 with the projection 18 on the inner side. Spray holes 14 are arranged in two rows in the circumferential direction of the first ring segment 16.FIG. 8 shows the stator assembly 15 after the first ring segment 16 has been rotated to such an extent that its projection 18 bears against the outer housing 2. In this state, a second ring segment 19 is connected to the first ring segment 16 as in the first embodiment. For simplification, the positive connections of the two ring segments 16, 19 are not shown in FIG. 8. The joined ring segments 16, 19 form a liquid deflection ring 20.FIG. 9 shows the stator assembly 15 after a retaining ring 21 has been attached for the radial securing of the liquid deflecting ring 20. The retainer ring 21 is received in a circumferential groove in the vicinity of the opening of the outer casing 2. The retaining ring 21 serves as a barrier for the liquid diverting ring 20 which is thus held in place.Figure 10 shows an alternative embodiment in which a circlip 22 is used. The retaining ring 22 is an elastic spring ring which is partially received in the circumferential groove in the outer housing 2.List of reference characters1 Stator assembly 2 Outer housing 3 Opening 4 Stator package 5 Stator coil 6 Liquid deflection ring 7 Screw 8 Busbar connections 9 First ring segment 10 Positive connection 11 Gap 12 Second ring segment 13 Strut 14 Spray hole 15 Stator assembly 16 First ring segment 17 Busbar connections 18 Projection 19 Second ring segment 20 Liquid deflection ring 21 Retaining ring 22 Retaining ring

Claims

A stator assembly (1, 15) for an electric motor having an outer casing (2) with an opening in which a stator pack (4) with a stator coil (5) is received, wherein radially protruding bus bar terminals (8, 17) are arranged in the vicinity of an axial end of the stator coil (5), characterized in that a liquid diverting ring (6, 20) is arranged at a position that is axially further inward than the bus bar terminals (8, 17), wherein the bus bar terminals (8, 17) extend further radially outward than an inner periphery of the liquid diverting ring (6, 20), wherein the liquid diverting ring (6, 20) comprises at least two ring segments (9, 12, 16, 19) configured to be joined together.Stator assembly according to Claim 1, wherein the ring segments (9, 12, 16, 19) are provided with positive connections (10).Stator assembly according to claim 1 or 2, wherein a positive connection (10) comprises a ring segment (9) with an undercut and a further ring segment (12) with a corresponding counterform.The stator assembly according to claim 3, wherein the ring segment (9) is formed with the undercut in a T-shape and the other ring segment (12) is formed in a corresponding negative T-shape.A stator assembly according to any preceding claim, wherein a ring segment (16) is provided with a radially inner protrusion (18) adapted to abut a protrusion of the outer housing (2) when the liquid diverting ring (20) is rotated in a circumferential direction.A stator assembly according to any preceding claim, wherein the liquid diverting ring (6, 20) is secured by a retaining ring (21), a snap ring, a locking ring or a locking ring (22) inserted into a circumferential groove of the outer housing (2).A stator assembly according to any preceding claim, wherein the liquid diverting ring (6, 20) comprises spray holes (14) arranged in a circumferential direction along its inner periphery.A stator assembly according to any preceding claim, wherein the liquid diverting ring (6) comprises radial struts (13) on one or both surfaces.Stator assembly according to any one of the preceding claims, wherein the liquid diverting ring (6) comprises holes for fastening elements, in particular for screws (7).An electric motor comprising a stator assembly (1, 15) according to any one of claims 1 to 9 and a rotor accommodated in the stator stack (4).Method for assembling a stator assembly (1, 15) comprising the steps of: - inserting a stator stack (4) with a stator coil (5) into an opening of an outer housing (2), wherein radially protruding bus bar terminals (8) are arranged in the vicinity of an axial end of the stator coil (5), - inserting a first ring segment (9, 16) of a liquid diverting ring (6, 20) in the axial direction to a position which is axially further inward than the bus bar terminals (8) at a circumferential position, wherein the first ring segment (9, 16) does not contact the bus bar terminals (8), - rotating the first ring segment (9, 16) in a circumferential direction until there are no bus bar terminals (8) any longer present in a gap (11) between the two ends of the first ring segment (9, 16), and - inserting a second ring segment (12, 12, 19) and joining it to the first ring segment (9, 16) to form a closed liquid deflecting ring (6, 20).

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