Method for manufacturing a stator of an axial flux machine

Abstract

The invention relates to a method for manufacturing a stator (STAT) of an axial flux motor, comprising the following steps: - cutting slots on lateral portions (PL1) of a strip of metal sheets (RU), - cutting recesses (EV) on opposite lateral portions (PL2) of the strip to form a coolant circulation channel (CA), - winding the strip in a radial stack, cutting the recesses (EV) by double perforation symmetrical about a line orthogonal to the length of the strip (RU), cutting the recesses (EV) on a first radial periphery of the stator winding at a distance from a radial section (SR) of the stator passing through this line, until these recesses meet on the opposite radial periphery of the stator winding in the radial section, thereby forming a V-shaped channel (CA), the channel meeting at the ends of the branches of the V during the winding step.

Description

[0001] This invention relates generally to the fields of electrical engineering and mechanics, and more specifically to the manufacture of stators for axial flux motors.

[0002] The stator of an electric motor consists of teeth, typically made of magnets, with copper wire wound around them. When the motor operates, the copper wire generates heat due to the Joule effect, which must be dissipated. Additionally, magnetic flux generates eddy currents and hysteresis losses in the stator's steel structure, which must also be dissipated.

[0003] The stator of an axial flux motor is typically cooled using a cooling plate that is attached to the stator yoke, more specifically to an annular planar portion of the stator's steel structure, in a direction opposite to the toothed portion of the stator. This cooling plate includes channels that allow coolant (e.g., oil) to circulate. However, adding this specific cooling structure increases the space required for the manufactured machine and the material cost. Furthermore, ensuring good surface contact and thermal conductivity between the cooling plate and the stator yoke is challenging.

[0004] Reference FR 2999359 proposes integrating this cooling structure into the motor housing. However, this solution is complex to implement and cannot guarantee good heat conduction between the cooling channels and the stator yoke.

[0005] Document US 9006953 discloses a stator for an axial flux motor, which is manufactured by winding a metal sheet with recesses to form radial through channels. Tubes are needed to pass through these recesses, particularly at the inner radial periphery of the stator, to form cooling circuits. Therefore, heat conduction between the tubes and the metal sheet is suboptimal, and the space occupied by the tubes at the inner periphery of the stator is undesirable. The assembly of this stator and its cost are also suboptimal.

[0006] One of the objectives of this invention is to overcome at least some of the shortcomings of the prior art by providing a method for manufacturing a stator for an axial flux motor, thereby allowing for satisfactory cooling of the stator in a fast and inexpensive manner.

[0007] Therefore, the present invention proposes a method for manufacturing a stator of an axial flux motor, the method comprising the following steps:

[0008] - To perforate magnetic metal strips, the perforation step includes:

[0009] - Cut the material on the first lateral portion of the strip to leave grooves in the strip designed to form stator teeth.

[0010] - Recesses are cut into the second lateral portion of the strip opposite to the first lateral portion of the strip. These recesses are designed to form coolant circulation channels.

[0011] -The metal strips are wound in a radially stacked manner.

[0012] The feature is that, during the cutting of the material between the two grooves of the strip, these recesses are cut out by double perforations symmetrical with respect to a line parallel to the axial axis of symmetry included between the two grooves. These recesses are cut to be positioned on both sides of a radial section of the winding stator passing through the line, so that they are spaced apart from each other from a first radial peripheral portion of the stator until they converge on the radial section at a second radial peripheral portion of the stator opposite to the first radial peripheral portion, thus forming the channel, which is V-shaped and converges at the ends of the branches of the V-shape during the winding step.

[0013] With the aid of this invention, the stator's cooling channels form a sawtooth loop at the stator's axial periphery opposite to the toothed axial periphery of the stator. Coolant (e.g., oil) can therefore circulate directly on the stator metal sheets within this loop, thus improving cooling efficiency compared to the prior art. There are no additional pipes in the stator for oil circulation, thereby limiting the space occupied by the cooling system. Furthermore, advantageously, the channels are generated as quickly as in the prior art US 9006953, because in this invention, preferably, the perforations and slots forming the recesses of these channels are also implemented as a single operation.

[0014] According to an advantageous feature of the method according to the invention, the channel is open at the branch of the V-shape and / or at the point of the V-shape on the first radial peripheral portion or the second radial peripheral portion of the stator.

[0015] This feature allows for the same cutting of all the teeth of the stator, which is easier to achieve than simply opening the channels that open outward at the inlet or outlet of the coolant circuit, which serves as the interface between the stator and the heat exchanger, at the first or second radial periphery of the stator.

[0016] According to another advantageous feature of the invention, the first radial peripheral portion of the stator is an inner peripheral portion of the stator, and the second radial peripheral portion of the stator is an outer peripheral portion of the stator.

[0017] This embodiment of the invention is simpler than the embodiment with a V-shaped branch pointing to the outer radial periphery of the stator.

[0018] According to another advantageous feature of the invention, the parallel lines correspond to an axial axis of symmetry included between the two grooves. Therefore, this axial axis of symmetry can serve as a reference for perforating the recess, making the perforation process easier to control.

[0019] Advantageously, when the channel is open outward at at least one radial periphery of the stator, the method for manufacturing a stator according to the invention further includes the step of applying a seal to the first radial periphery portion and / or the second radial periphery portion of the stator at those openings of the channel that are not used as inlets or outlets for the coolant.

[0020] Further advantageously, when the recess opens outward at the axial periphery of the stator, the method for manufacturing a stator according to the invention further includes the step of closing the channel at the axial periphery by fastening an annular plate to the axial periphery.

[0021] Finally, the present invention also relates to a stator manufactured by the method according to the invention.

[0022] Other features and advantages will become clear from a study of the preferred embodiments described with reference to the accompanying drawings, in which:

[0023] - Figure 1 The steps of the manufacturing method according to the present invention in this preferred embodiment are shown.

[0024] - Figure 2a This illustrates a perforation step in a first portion of a metal strip, according to the manufacturing method of the invention, prior to core actuation, in this preferred embodiment of the invention. This first portion forms the inner radial periphery of the manufactured stator yoke.

[0025] - Figure 2b It shows Figure 2a The drilling process following core actuation.

[0026] - Figure 2c It shows Figure 2b The perforation step occurring immediately after the core disengages from the joint.

[0027] - Figure 2d The perforation step is shown on the second portion of the metal strip just before core actuation, which forms the inner annular portion of the manufactured stator yoke.

[0028] - Figure 2e It shows Figure 2d The drilling process following core actuation.

[0029] - Figure 2f It shows Figure 2e The perforation step occurring immediately after the core disengages from the joint.

[0030] - Figure 2gThe perforation step is shown on the final portion of the metal strip just before core actuation, which forms the outer radial periphery of the manufactured stator yoke.

[0031] - Figure 2h It shows Figure 2g The drilling process following core actuation.

[0032] - Figure 2i It shows Figure 2h The perforation step occurring immediately after the core disengages from the joint.

[0033] - Figure 3 A stator manufactured according to the invention in this preferred embodiment is shown.

[0034] - Figure 4 The diagram shows two parts of the yoke of a stator manufactured according to two different embodiments of the present invention.

[0035] -and Figure 5 The diagram shows the yoke portion and the closing plate portion of a stator manufactured according to a preferred embodiment of the invention.

[0036] according to Figure 1 The preferred embodiment of the present invention shown includes steps E1 to E4 in the method for manufacturing a stator of an axial flux motor according to the present invention.

[0037] like Figures 2a to 2i Step E1 shown is the perforation of the magnetic metal strip RU. The strip RU is made, for example, of, but not necessarily of, grain-oriented steel. In the latter case, the grains are preferably oriented along the winding direction of the metal strip so as to guide the magnetic flux in the stator yoke CS in an angular direction during motor operation. It should be noted that the step of winding the metal strip to form the stator yoke will be described further below.

[0038] The perforation step E1 includes two sub-steps performed simultaneously:

[0039] - Sub-step E11: Cut out the grooves CR, which will form the teeth DE of the stator yoke CS.

[0040] - and sub-step E12: cut out recesses EV, which will form cooling channels CA located at the axial periphery PAR opposite to the toothed axial periphery PAD of the stator yoke CS.

[0041] Step E1 uses: a mold MO, on which a strip RU travels in the travel direction DEF; and a core MA, which is actuated on the strip RU at regular time intervals in the perforation direction PO. The core MA includes: a first portion MA1, which cuts a groove CR on a first lateral portion PL1 of the strip RU; and a second portion MA2, which cuts a recess on a lateral portion PL2 of the strip RU opposite to the lateral portion PL1 of the strip RU.

[0042] More specifically, the second part MA2 of the core includes two punches that are symmetrically spaced apart from each other with respect to the longitudinal axis of the first part MA1 of the core. Therefore, for each cut of material between the two formed grooves CR, two recesses are created symmetrically spaced apart from each other with respect to the longitudinal axis of symmetry ASC of the two grooves.

[0043] exist Figures 2a to 2c In these figures, we can see the horizontally cut strips RU, marked by circular lines LC, forming the inner periphery of the stator yoke CS after winding. In one application of the core MA, the piercing step creates a recess wider than the width of the punch of the second part MA2 of the core by overlapping with a recess previously created during that piercing step, resulting in a recess having the width of the punch of the second part MA2 of the core. Specifically, because the width of the stator teeth DE is narrower at the inner periphery PRI of the stator yoke CS than at its outer periphery PRE, the distance between the punches of the second part MA2 of the core comprises the width of several slots. These wide recesses correspond to the junction of the two cooling channels CA at the inner periphery PRI of the stator yoke CS. These recesses are symmetrically spaced relative to the radial section SR of the stator yoke CS passing through the axial axis of symmetry ASC.

[0044] like Figures 2d to 2f As shown by the circular line LC, during the horizontal cutting strip RU of the metal sheet radially positioned at the center of the stator yoke CS, the cutting groove ratio is... Figures 2a to 2c Wider in the middle. In one application of the core MA, the piercing step creates two recesses, each with the width of the punch of the second part MA2 of the core MA. These recesses correspond to two separate cooling channels CA, which converge at the inner periphery PRI of the stator yoke CS.

[0045] like Figures 2g to 2i As shown by the circular line LC, during the horizontal cutting of the strip RU by the metal sheet located at the outer periphery of the stator yoke CS, the cutting groove ratio is... Figures 2d to 2fWider than the width of the punch in the second part of the core MA. In one application of the core MA, the piercing step again creates a recess wider than the width of the punch in the second part of the core MA2 by overlapping with the recess previously created during this piercing step, and creates a recess with the width of the punch in the second part of the core MA2. These recesses correspond to two separate cooling channels CA, which converge at the outer periphery PRE of the stator yoke CS.

[0046] Then step E2 is the winding of the strip RU, during which the metal sheets of the strip RU are radially stacked on themselves to form the stator yoke CS.

[0047] Step E3 involves placing an annular plate PLA on the axial periphery PAR of the stator yoke CS of the pre-manufactured stator STAT to axially seal the cooling channel CA, as shown below. Figure 3 As shown. The PLA plate is, for example, tightened onto the stator yoke CS by screws VIS. Figure 3 In the diagram, channel CA is schematically shown as appearing on a portion of the stator STAT if the board PLA is transparent.

[0048] Finally, step E4 involves applying seals JO to the inner radial periphery PRI and outer radial periphery PRE of the stator STAT to radially close the channels CA at the ends of the channels that are not used as inlets EN or outlets SO of the oil circuit contained in the stator yoke CS. These inlets and outlets are then connected to pipes of a cooling circuit outside the stator STAT, which includes a heat exchanger.

[0049] It should be noted that the setting of the channel CA at the axial periphery PAR of the stator yoke CS is actually independent of the angular position of the tooth DE. In the variant, the recess EV can therefore be stamped symmetrically on both sides of a line parallel to the axial symmetry line ASC but deviating from any desired angular position.

[0050] Figure 4 The portion of the stator yoke CS corresponding to the stator teeth is shown on the left in a variant of the main embodiment of the invention. In this main variant, the end of the channel CA is radially outwardly open. In the variant, the channel CA can, of course, be produced without being outwardly open. The sealing of the channel CA inside the stator yoke is ensured, for example, by varnish, adhesive, or coating. This seal need not be perfect, as oil is typically used as a coolant; the key is that the flow of liquid is mostly properly guided within the channel CA.

[0051] Figure 4The right side shows an embodiment variant of the invention, in which the channel CA is axially closed in the stator yoke CS. To implement this variant, a punch in the second portion MA2 of the core MA creates a hole in the second lateral portion PL2 of the strip RU, the hole not opening outward toward the outside of the strip RU.

[0052] at last, Figure 5 The diagram shows the portion of the stator yoke CS corresponding to the stator tooth DE, and the corresponding portion of the plate PLA, which is screwed to or bonded to the stator yoke CS in a variant of the main embodiment of the invention. The stator yoke CS can, of course, be manufactured in segments by stacking cut metal sheets for each stator tooth, but this manufacturing operation offers far fewer advantages than the metal sheet winding method used in this invention.

Claims

1. A method for manufacturing a stator (STAT) for an axial flux motor, the method comprising the following steps: - For perforation (E1) of magnetic metal strip (RU), the perforation step includes: - Cut (E11) material on the first lateral portion (PL1) of the strip to leave grooves (CR) on the strip designed to form stator teeth (DE). - Recesses (EV) are cut (E12) on the second lateral portion (PL2) of the strip (RU) opposite to the first lateral portion (PL1) of the strip (RU). These recesses are designed to form coolant circulation channels (CA). - The metal strip (RU) is wound in a radial stack (E2) manner. The feature is that, during the cutting (E11) of the material between the two grooves of the strip (RU), these recesses (EV) are cut (E12) by double perforations symmetrical with respect to a line parallel to the axial axis of symmetry (ASC) included between the two grooves. These recesses (EV) are cut to be positioned on both sides of the radial section (SR) through the wire of the winding stator (STAT) so that they are spaced apart from each other from a first radial peripheral portion of the stator (STAT) until they converge on the radial section (SR) at a second radial peripheral portion of the stator (STAT) opposite to the first radial peripheral portion, thus forming the channel (CA), which is V-shaped and converges at the ends of the branches of the V-shape during the winding step (E2).

2. The method for manufacturing a stator (STAT) of an axial flux motor as described in claim 1, characterized in that, The channel (CA) is open at the branch of the V-shape and / or at the point of the V-shape on the first radial peripheral portion or the second radial peripheral portion of the stator (STAT).

3. The method for manufacturing a stator (STAT) of an axial flux motor as described in claim 1 or 2, characterized in that, The first radial peripheral portion of the stator is the inner peripheral portion (PRI) of the stator (STAT), and the second radial peripheral portion of the stator is the outer peripheral portion (PRE) of the stator (STAT).

4. The method for manufacturing a stator (STAT) of an axial flux motor as described in any one of claims 1 to 3, characterized in that, The parallel lines correspond to the axial symmetry axis (ASC) included between the two slots.

5. The method for manufacturing a stator (STAT) of an axial flux motor as claimed in any one of claims 2 to 4, the method further comprising step (E4): applying a seal to the first radial peripheral portion and / or the second radial peripheral portion of the stator (STAT) at those openings of the channel (CA) that are not used as inlets (EN) or outlets (SO) for the coolant.

6. The method for manufacturing a stator (STAT) of an axial flux motor as described in any one of claims 1 to 5, characterized in that, The recess (EV) opens outward at the axial periphery (PAR) of the stator (STAT), and the method further includes the step (E3): closing the channel (CA) at the axial periphery (PAR) by fastening an annular plate (PLA) to the axial periphery (PAR).

7. A stator (STAT) manufactured by the method described in any one of claims 1 to 6.

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