FR3134258A1 - Cooling fluid recovery device for electric machine - Google Patents

Abstract

The invention relates to a cooling fluid recovery device (10) for an electrical machine, which comprises: - a cooling fluid receiving wall (100) which is curved, and - a support (200) adapted to block the wall reception under the electric machine. Figure for abstract: Fig.5

Description

Cooling fluid recovery device for electric machine Technical field of the invention

The present invention generally relates to electrical machines.

It relates more particularly to a device for recovering cooling fluid from an electrical machine.

The invention finds a particularly advantageous application in motor vehicles with electric or hybrid propulsion.

State of the art

An electrical machine such as a motor generally includes a rotor pivotally mounted inside a stator. The stator has windings of electrical wires which generate a rotating magnetic field in order to turn the rotor.

Since electrical machines are not perfect, electrical losses occur and are dissipated mainly in the form of thermal energy, i.e. heat. It then turns out to be essential to dissipate this heat towards the outside of the electrical machine, otherwise the temperature of the electrical machine will exceed a threshold limit for the resistance of its materials.

For example, a varnish conventionally used in an electrical machine to provide electrical insulation of the windings reaches this threshold around 200°C. In practice, we then want to prevent the temperature on the surface of the stator from exceeding 140°C.

To do this, the electric machine is generally housed in a hermetic casing, and a cooling circuit is used in this casing in order to spray the stator with a cooling liquid such as oil.

Currently, the cooling of the stator is ensured by a circuit which includes a pump allowing the oil to be taken from the bottom of the crankcase and to bring it towards oil nozzles oriented towards the top of the stator and towards its ends (at the level buns formed by the coils).

At the points of impact of the oil, cooling is optimal. The power of the jet and the oil flow are in fact designed to ensure good heat exchange between the exterior surface of the stator and the oil, which allows heat to be evacuated from the stator. Then, the flow of oil on the sides of the stator allows the heat to be evacuated but in a less efficient and uneven manner. We understand in fact that the further the area to be cooled is from the point of impact of the oil jet, the hotter the oil flowing there and the less effective the cooling.

It is therefore necessary to provide a significant oil flow to properly cool the stator. But even so, the plaintiff noticed that a hot spot appeared in the lower part of the stator, where the oil cannot flow.

The performance of the electrical machine must then be limited to never exceed the temperature threshold in this zone.

Presentation of the invention

In order to remedy the aforementioned drawback of the state of the art, the present invention proposes a device making it possible to ensure the cooling of the stator in areas where it is currently not or only slightly cooled.

More particularly, according to the invention we propose a cooling fluid recovery device for an electric machine which comprises:
- a cooling fluid receiving wall which is curved, and
- a support suitable for blocking the receiving wall under the electric machine.

Thus, thanks to the invention, it is possible to recover part of the oil which flows onto the stator in order to fill the receiving wall, so that the underside of the stator bathes in the oil thus recovered and is therefore cooled.

From then on, it is no longer necessary to limit the performance of the electrical machine which can therefore be used to its full potential.

Other advantageous and non-limiting characteristics of the device according to the invention, taken individually or in all technically possible combinations, are as follows:
- the receiving wall is curved around a geometric axis;
- the receiving wall is curved with a substantially constant radius of curvature;
- the receiving wall is corrugated so as to form channels parallel to the geometric axis and whose ends are closed;
- the receiving wall includes at least one cooling fluid flow window;
- a window is provided in each of said channels;
- each window is offset relative to a median plane of the receiving wall which is orthogonal to said geometric axis;
- the support comprises a support part supporting the receiving wall, and elastically deformable legs which extend from the support part, on the side opposite the receiving wall;
- said legs extend in planes parallel to the geometric axis;
- at least two of said legs extend in planes inclined relative to each other at an angle greater than 30 degrees, and preferably equal to 60 degrees to plus or minus 10 degrees;
-the support includes a latching means suitable for clipping onto the electric machine.

The invention also proposes an electric machine comprising a stator housed in a casing, and a device as mentioned above, the support of which is adapted to rest on the casing to maintain the receiving wall under the stator.

Of course, the different characteristics, variants and embodiments of the invention can be associated with each other in various combinations as long as they are not incompatible or exclusive of each other.

Detailed description of the invention

The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

On the attached drawings:

is a schematic sectional view of an electrical machine according to the invention;

is a detailed view of zone II of the ;

is a sectional view according to plan AA of the ;

is a detailed view of zone IV of the ;

is a schematic perspective view of a recovery device according to the invention;

is a schematic perspective view of the device for recovering the , shown from a different angle.

On the , we have represented an electric machine. This is an electric motor 1 intended to be used in a motor vehicle with electric or hybrid propulsion, but alternatively it could be a motor used in another field or even an alternator.

As this figure clearly shows, this electric motor 1 comprises a rotor 30 which is adapted to rotate around an axis of rotation A1, and a stator 20 which is fixedly mounted in a casing 40.

The rotor 30 could be of any type (permanent magnet, wound, etc.).

The stator 20 is located around the rotor 30.

As clearly shown in the , this stator 20 comprises a frame 21 which delimits teeth 22 regularly distributed around the axis of rotation A1, and coils 23 of electric wire wound around these teeth 22. The number of teeth 22 and coils 23 is at least greater than three.

The frame 21 of the stator 20 here comprises a body of tubular shape, cylindrical of revolution around the axis of rotation A1, and its teeth 22 extend from the internal face of this body, towards the axis of rotation A1 . Alternatively, they could rise from the upper side of this body.

As shown in the , this frame 21 has two ends 21A, 21B designed to facilitate the winding of the spools of electrical wire around the teeth 22, one of them being further provided to allow the connection of the electrical wires to a power cable electric. We can say that the coils then form, at these ends 21A, 21B, “buns”. Of course, the type of winding of electrical wires might differ from this kind of winding with buns.

The casing 40 forms a hermetic chamber housing the stator 20 and the rotor 30.

This casing 40 could come in very different forms.

It will be noted here that in the embodiment illustrated in the figures, the casing 40 is shown in the position of use, that is to say with the orientation in which it will be used (the top of the image representing the upper part of the casing and the bottom of the image representing the lower part of the casing). In the following, we can therefore use the terms top and bottom, upper and lower, see right and left, relative to the orientation of the casing 40 illustrated on the .

Thus, the bottom of the casing 40 naturally forms a coolant storage tank.

It will be observed in Figures 1 and 3 that this casing 40 here comprises a side wall 41 which surrounds the stator 20, and two end walls 42 which close the two ends of the side wall 41 (at least one of these two end walls 42 having a passage opening for the rotor shaft 30).

We also observe that this casing 40 internally comprises an internal partition 43 which extends substantially horizontally, above the coolant level. In this case, the side wall 41 and this internal partition 43 forming a single piece from the foundry, the upper face 43A of this internal partition 43 is inclined relative to the axis of rotation A1 with a relief angle of about 1.5 degrees. This upper face 43A therefore has a slight slope, here towards the right on the .

We could predict that this upper face would be perfectly flat. However, here, as clearly shown in figs 3 and 4 in a plane orthogonal to the axis of rotation A1, it is slightly curved and is perforated by a light 44.

As clearly shown in the , the stator 20 is fixed in the casing 40 so that it extends at a distance from the side wall 41 of this casing 40 and at a distance from the upper face 43A of the internal partition 43.

As shown in Figures 1 and 2, the electric motor 1 also includes a cooling circuit 50.

This cooling circuit 50 comprises a pump 51 which is adapted to pump a cooling liquid (here oil) into the bottom of the casing 40 to bring it towards ejection nozzles 52. The cooling circuit 50 comprises for this oil pipes which are here delimited by channels provided in the different walls of the casing but which could alternatively be formed of hoses.

On the , three ejection nozzles 52 are shown located above the stator 20 and oriented so as to be able to project the oil onto the top of this stator 20. One of these nozzles 52 is located halfway along the stator 20, while the other two are located above the buns.

Once the oil has been projected onto the external surface of the stator 20 and onto the buns, it flows by gravity towards the bottom of the casing 40.

As clearly shown in Figures 1 and 2, to facilitate this flow at the level of the buns, the frame 21 of the stator has, near its ends 21A, 21B, openings 25 for oil passage. These openings 25 are located in two planes orthogonal to the axis of rotation A1 which pass respectively through the two buns. They are here distributed over restricted angular sectors around the axis of rotation A1, namely in the lower part and in the upper part of the stator 20 (see ).

Thanks to these openings 25, as shown in the detail view of the , the oil can flow down easily.

At this stage, we understand that if the oil projected on the top of the stator 20 allows the top of the stator 20 to be well cooled, the same is not true of the underside of this stator which the oil cannot reach.

The invention then proposes an oil recovery device 10, which allows a lower part of the stator 20 to be bathed in this oil in order to also cool it from below. This device is very schematically represented in Figures 1 and 2, in the form of a single part.

But in practice, as shown in Figures 3 to 6, this device 10 comprises two distinct elements, namely a receiving wall 100 making it possible to receive the oil flowing through the aforementioned openings 25, and a support 200 making it possible to block the receiving wall 100 under the stator 20.

As shown in the , the receiving wall 100 has the shape of a rectangular plate, with two longitudinal edges parallel to the axis of rotation A1 and two end edges.

As shown in the , the two end edges of the receiving wall 100 extend under the openings 25 provided in the frame 21 of the stator 20, so that the drops of oil flowing there are collected by the receiving wall 100 .

As clearly shown in Figures 4 to 6, the receiving wall 100 is curved around the axis of rotation A1. Here it has a constant radius of curvature, so that it extends along a portion of a cylinder. As a result, the two end edges of the receiving wall 100 have arc-shaped shapes.

The ends of this receiving wall 100 are preferably closed so that the oil does not escape through these ends.

This receiving wall 100 is also substantially profiled, that is to say that its profile in planes orthogonal to the axis of rotation A1 does not vary from one end to the other of this receiving wall 100.

This receiving wall 100 is intended to be installed under the stator 20 such that a non-zero distance separates this stator 20 and at least part of this receiving wall 100. Thanks to this non-zero distance, a space is provided between the stator and the receiving wall so that oil can flow through it.

For this, we could provide for this receiving wall 100 to be perfectly smooth in the sense that its profile forms an arc of a circle. In this eventuality, elements should be used to maintain the receiving wall at a reduced but not zero distance from the stator.

However, here, it is rather intended that the receiving wall 100 has reliefs which make it possible to maintain part of this wall at a distance from the stator 20.

In practice, this receiving wall 100 is corrugated with regular undulations over its entire width. Each undulation therefore delimits a hollow channel (seen from above) which extends over the entire length of the receiving wall 100 and which is delimited between two bulges.

The tops of the bulges are designed to rest against the external surface of the stator 20.

Each channel is capable of receiving oil to cool the underside of the stator 20.

Here, each ripple has dimensions such that the distance between two ripples (i.e. the “period” of the oscillations, their pitch) is 3 mm and the depths of the channels are equal to 0.5 mm.

Here, this receiving wall 100 is made of a thermally conductive material, preferably of a metallic material, for example aluminum alloy or stainless steel. It has a thickness of less than a millimeter, here of around 0.5 millimeters.

When the oil flows on this receiving wall 100, it is planned to guide it so as to ensure optimal cooling of the underside of the stator 20.

The canals partly ensure this guidance. As explained above, to ensure that oil does not escape from the channels through their ends, these ends are closed. For this, we can provide for a blade to be welded on each end edge of the receiving wall 100. Alternatively, we can provide for the support 200 to perform this function, thanks to edges plated on either side of the receiving wall 100.

However, so that the oil can escape from the channels, at least one window 130 is provided in the receiving wall 100.

In the embodiment illustrated in the figures, one is instead provided in each of said channels.

As shown in the , the centers of these windows 130 are located in the same plane P2 which is distinct from the median plane P1 of the receiving wall 100. Otherwise formulated, all the windows 130 extend at a non-zero distance from the centers of the channels. Indeed, the center of the underside of the stator 20 constitutes the zone which we wish to cool as efficiently as possible, so that we do not want the oil to escape from the receiving wall 100 at the height of this zone.

Here, these windows 130 are rectangular in shape and extend over a width corresponding to approximately half of a complete undulation of the receiving wall 100.

The oil which flows there then falls in particular on the internal partition 43, then flows towards the bottom of the casing 40 via the opening 44 provided in this partition (see ).

In order to block the receiving wall 100 bearing against the stator 20, the support 200 is interposed between this wall and the internal partition 43 of the casing 40.

This support 200 comprises a support part 210 on which the receiving wall 100 rests, and elastically deformable means, here in the form of tabs 220, which rest on the upper wall 43A of the internal partition 43 so as to block the receiving wall 100 against the stator 20.

The support part 210 could be in the form of a smooth wall, curved around the axis of rotation A1. However, here, as clearly shown in the , this support part 210 is formed of a succession of slats arced around the axis of rotation A1 and held at a distance from each other by the tabs 220. These slats have reduced widths, with the exception of the two end slats which have greater widths. Thanks to this shape, the support part 210 forms a sort of very perforated plate, promoting the cooling of the receiving wall 100.

The support part 210 preferably comprises means for blocking the receiving wall 100. In this case, these blocking means are formed by edges which border the four sides of the support part 210 and which come into contact with each other. position it on each side of the receiving wall 100 in order to lock it in position (except upwards, which allows it to be positioned on the support or removed from it).

As shown very schematically in the , the upper ends of the edges can optionally be folded inwards in order to completely block the receiving wall 100, even upwards.

As clearly shown in the , the tabs 220 extend from the lower face of the support part 210, that is to say on the side opposite the receiving wall 100.

These tabs 220 are designed to be elastically deformable so as to be able to deform during the assembly of the electric motor 1, so as to exert, once the assembly is complete, a pressing force of the receiving wall 100 against the stator 20, so that this wall best matches the shape of the stator in order to optimize thermal exchanges.

The legs thus have a reduced thickness which offers the desired flexibility. This thickness is here of the order of 0.5 to 2 mm (the support 200 being made of a plastic material such as ABS or polyamide PA6).

In practice, here, the flexibility of the legs and the flexibility of the undulations of the receiving wall 100 together ensure effective pressing of this wall against the stator 20.

As shown in the , the legs 220 extend over a height which can vary and which depends on the shape of the internal partition 43 on which they rest.

Here, eight legs are provided which each extend in a plane parallel to the axis of rotation A1, and which are regularly distributed on the underside of the support part 210. Thanks to this orientation, the legs 220 facilitate the installation of the device 10 in the casing 40 because they extend parallel to the direction of insertion of the device 10 in the casing 40 (from right to left on the ).

The legs 220 preferably extend over the entire length of this support part 210.

Among these eight legs 220, half of them extend in first planes parallel to each other, while the other half extends in planes parallel to each other but inclined relative to the first planes. The angle of inclination between these two sets of planes is at least equal to 30 degrees. Thanks to this inclination, the legs 220 are likely to bend elastically during assembly of the electric motor. This angle here is equal to 60 degrees, but it could be larger. However, it is preferably between 50 and 70 degrees.

The installation of the oil recovery device 10 in the casing 40 is done once the stator 20 has been fixed in this casing 40.

For this, the receiving wall 100 is placed in the support 200, then the entire device 10 is slid between the stator 20 and the internal partition 43 of the casing 40, here from right to left on the .

The slope formed by the upper face 43A of this internal partition 43, due to the relief angle, facilitates this installation in the sense that the insertion of the device 10 in the space allocated to it is initially done without effort. In fact, the thickness of the device on the side of its first end (the one on the left on the ) is less than the height between the internal partition 43 and the stator 20 on the right side.

On the other hand, due to the slope, this height is gradually reduced and the effort to push the device 10 towards its final position increases correspondingly. This effort makes it possible to deform the tabs 220 elastically as well as possibly the receiving wall 100, which, once the assembly is carried out, makes it possible to guarantee that the support 200 maintains the receiving wall 100 in contact with the stator 20.

We observe in Figures 5 and 6 that the support 200 includes stops 230 making it possible to block the engagement of the device 10 in the casing 40 when it has reached the desired final position. These stops 230 are here in the form of plates which extend on either side of the support part 210 of the support 200, at the height of its right end edge.

We also observe that these plates carry brackets 231. Each bracket 231 has a branch which rises from the plate, parallel to the axis of rotation A1 (and therefore to the direction of engagement of the device 10 in the casing 40), and a branch perpendicular to it shaped to facilitate the installation of the device 10 in the casing 40. This second branch in fact forms a support zone on which the user can press easily.

In order to ensure that once the device 10 is in place, it does not escape from the space allocated to it due in particular to the inclination of the slope formed by the top of the internal partition 43, Here there is provided a latching means 250 adapted to clip onto this internal partition 43.

As shown in the , this latching means 250 is in the form of a tab which extends from below the support part 210 of the support 200, near its right end edge and which is curved towards its left end edge.

This tab is shaped so as to disappear by curving towards the support part 210 of the support 200 when the device 10 slides along the internal partition 43, then to deploy in a cavity where it attaches once the device 10 is in place.

The present invention is in no way limited to the embodiments described and represented, but those skilled in the art will be able to make any variation conforming to the invention.

Claims (10)

Device (10) for recovering cooling fluid for an electric machine (1), characterized in that it comprises:
- a cooling fluid receiving wall (100) which is curved, and
- a support (200) adapted to block the receiving wall (100) under the electric machine (1). Device (10) according to claim 1, in which, the receiving wall (100) being curved around a geometric axis (A1), preferably with a constant radius of curvature, the receiving wall (100) is corrugated by so as to form channels which are parallel to the geometric axis (A1) and whose ends are closed. Device (10) according to one of claims 1 and 2, in which the receiving wall (100) comprises at least one window (130) for the flow of the cooling fluid. Device (10) according to claims 2 and 3, wherein a window (130) is provided in each of said channels. Device (10) according to one of claims 3 and 4, in which, the receiving wall (100) being curved around a geometric axis (A1), each window (130) is offset relative to a median plane ( P1) of the receiving wall (100) which is orthogonal to said geometric axis (A1). Device (10) according to one of claims 1 to 5, in which the support (200) comprises a support part (210) supporting the receiving wall (100), and elastically deformable tabs (220) which are extend from the support part (210), on the side opposite the receiving wall (100). Device (10) according to claim 6, wherein, the receiving wall (100) being curved around a geometric axis (A1), said tabs (220) extend in planes parallel to the geometric axis (A1 ). Device (10) according to one of claims 6 and 7, in which at least two of said legs (220) extend in planes inclined relative to each other at an angle greater than 30 degrees, and preferably equal to 60 degrees, plus or minus 10 degrees. Device (10) according to one of claims 1 to 8, in which the support (200) comprises a latching means (250) adapted to clip onto the electrical machine (1). Electric machine (1) comprising a stator (30) housed in a casing (40), characterized in that it comprises a device (10) according to one of claims 1 to 9, the support (200) of which is adapted to rest on the casing (40) to maintain the receiving wall (100) under the stator (30).