Motorized fan unit, in particular for a motor vehicle

Abstract

The invention relates to a motorized fan unit (1) comprising a fan wheel (3), a motor (5) for driving the fan wheel (3), a motor support (7) comprising a plastic bearing carrier (13) defining at least a first housing (15) and a second housing (17), and corresponding bearings (9A, 9B) mounted around a rotor shaft (51) and inside the housings (15, 17) and comprising a respective inner ring (91) and a respective outer ring (93). According to the invention, the outer rings (93) of the bearings (9A, 9B) are mounted tightly in the housings (15, 17), and at least one housing (15, 17) has at least one stress relief zone (25).

Description

Description Title of the invention: Motor-fan unit, particularly for a motor vehicle Technical field

[0001] The present invention relates to the field of vehicles, particularly motor vehicles. The invention relates more particularly to a motor-fan unit. The invention can be applied, for example, to heating, ventilation and / or air conditioning installations for vehicles, particularly motor vehicles, and comprising such a motor-fan unit. Technical background

[0002] Vehicles, particularly motor vehicles, are commonly equipped with a system, for example heating, ventilation and / or air conditioning, which creates an airflow in the passenger compartment. Such a system also makes it possible to manage the temperature and distribution of the airflow created within the passenger compartment. Such a system includes, among other things, a fan, particularly a blower type, comprising a fan wheel rotated by a drive motor, particularly an electric motor. The electric motor may in particular be electronically commutated, controlled by a control module.

[0003] An electronically commutated electric motor, or brushless direct current motor (also known as "brushless"), comprises a rotor and stator assembly, each of these components carrying electromagnetic elements whose interaction generates the movement of the rotor relative to the stator, and thus the movement of the fan wheel.

[0004] The electric motor is assembled in the installation, for example heating, ventilation and / or air conditioning, by means of a motor support which comprises a base or a structure, generally annular, allowing the electric motor, more precisely the stator, to be fixed. The motor support further comprises a bearing holder fixed to the structure or the base, and forming a support for at least one, for example two bearings. For this purpose, the bearing holder has housings in which the corresponding bearings are positioned.

[0005] Bearings are typically tightly mounted around the motor rotor shaft. The rotor shaft and inner rings are therefore rotationally fixed, while the outer rings are slidingly mounted in the corresponding housings. These housings are traditionally cylindrical in shape with a smooth internal surface.

[0006] However, when the engine is running, such an assembly generates friction that can be amplified at the contact areas of the bearing holder with the outer rings. This is problematic when the bearing holder is made of plastic material, which is more fragile than a metal bearing holder, made of aluminum for example. The stresses generated when inserting the bearings over the entire internal surface of the housings can cause cracks and this further weakens the bearing holder. This can result in premature wear of the contact areas of the bearing holder with the bearings, when the bearing holder is made of plastic material.

[0007] The invention aims to limit the stresses exerted on the housings during the insertion of the bearings. The invention also aims to secure the forceful insertion of the bearing(s) into the corresponding housings of the bearing holder. Summary of the invention

[0008] To this end, the invention relates to a motor-fan unit, in particular for a motor vehicle, the motor-fan unit comprising a fan wheel, a brushless motor for driving the fan wheel, a motor support comprising a bearing holder made at least partly of plastic material and defining at least a first housing and a second housing, and corresponding bearings mounted around a rotor shaft of the drive motor and mounted inside the housings, the bearings comprising a respective inner ring and an outer ring.

[0009] According to the invention, the outer rings of the bearings are force-fitted, tightly fitted, in the housings. At least one housing has at least one stress relief zone.

[0010] The stress release or relaxation zones provide a certain flexibility to the bearing holder at the housing level and allow the stresses generated during insertion of the bearing(s) into the corresponding housing to be released, which could weaken the plastic bearing holder and cause cracks or premature wear.

[0011] The motor-fan unit may further include one or more of the following characteristics described below, taken separately or in combination.

[0012] The housings are advantageously of a shape complementary to that of the bearings. For example, they have a general annular shape.

[0013] Advantageously, the stress relief zone is more flexible than the rest of the housing.

[0014] The at least one dwelling may have at least three stress relief zones, for example regularly distributed.

[0015] The stress relief zone may have a deformation and / or a reduced thickness compared to the rest of the housing. Alternatively, the stress relief zone may be made of a softer material than the rest of the housing.

[0016] The deformation is for example chosen from a semi-circular shape, a wave shape, an accordion shape, a rectangular shape, a triangular shape, a curved shape, a convex shape, a concave shape.

[0017] According to one embodiment, the stress relief zone is curved or convex with convexity oriented towards the outside of the housing. The stress relief zone is in particular curved or convex in the direction of a force applied from the inside to the outside of the housing during insertion of the corresponding bearing.

[0018] Both dwellings may have at least one respective stress relief zone.

[0019] The stress relief zones of the two housings are, for example, aligned along a central axis of the bearing holder.

[0020] Alternatively, the stress relief zones of the two housings may not be axially aligned.

[0021] The stress relief zones of the first housing may be identical to the stress relief zones of the second housing.

[0022] Alternatively, the stress relief zones of the first housing may be different from the stress relief zones of the second housing.

[0023] The bearing holder may comprise a base fixed to a structure of the engine support and comprising the second housing.

[0024] The bearing carrier may comprise a tubular tower around the central axis of the bearing carrier, extending axially from the base and terminating in the first housing opposite the second housing along the central axis.

[0025] Stress relief zones may extend axially from the base to the opposite end of the tower.

[0026] The base may be stiffer than the end of the tower opposite the base.

[0027] In another aspect, the housings may have an inner wall provided with a predefined number of radial support reliefs shaped to establish contact with the corresponding bearing.

[0028] The radial support reliefs of the first housing are different from the radial support reliefs of the second housing.

[0029] Contact can be linear or surface.

[0030] According to one embodiment, the radial support reliefs of the first housing define support surfaces against the corresponding bearing that are larger than the radial support reliefs of the second housing.

[0031] The radial support reliefs of the first housing can be shaped to establish surface contact with the corresponding bearing.

[0032] The radial support reliefs of the first housing are, for example, included in a hypothetical cylindrical shape surrounding the corresponding bearing.

[0033] The radial support reliefs of the second housing may be shaped to establish a linear contact or a surface contact with the corresponding bearing. In the latter case, the surface contact may be less than a surface contact established between the radial support reliefs of the first housing and the corresponding bearing.

[0034] The first housing can be arranged on an upper part of the bearing holder facing the fan wheel when the motor-fan unit is assembled.

[0035] The second housing may be arranged on a lower portion of the bearing holder opposite the upper portion along a central axis of the bearing holder which coincides with the axis of the rotor shaft. The lower portion is oriented towards a structure of the engine support such as a ring or a base of the engine support fixed to a deflector when the motor-fan unit is assembled.

[0036] At least one housing may have at least three radial support reliefs, regularly distributed at 120° from each other.

[0037] Radial support reliefs are for example made by ribs.

[0038] According to one embodiment, the rotor shaft is mounted freely inside the inner rings of the bearings.

[0039] The motor-fan unit may be intended in particular for a heating, ventilation and / or air conditioning installation of a motor vehicle. Brief description of the drawings

[0040] Other advantages and characteristics of the invention will appear more clearly on reading the following description given by way of illustrative and non-limiting example, and the appended drawings among which:

[0041] [Fig. 1] is a perspective view of one embodiment of a motor-fan unit.

[0042] [Fig. 2] is an exploded view of the motor-fan assembly of Figure 1.

[0043] [Fig. 3A] is a perspective view of an upper part of a bearing holder of the motor-fan unit of figures 1 and 2 receiving a first bearing.

[0044] [Fig. 3B] is a perspective view of a lower part of a bearing holder of the motor-fan unit of Figures 1 and 2 receiving a second bearing.

[0045] [Fig. 4A] is a perspective view of the upper portion of the bearing carrier of Figure 3A with the first bearing removed.

[0046] [Fig. 4B] is a perspective view of the lower portion of the bearing carrier of Figure 3B with the second bearing removed.

[0047] In these figures, identical elements have the same reference numbers.

[0048] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments, without departing from the scope of the invention, as defined by the claims.

[0049] In the description, certain elements may be indexed, for example first element or second element. In this case, it is a simple indexing to differentiate and name close but not identical elements. This indexing does not imply a priority of one element over another and such names can easily be interchanged without departing from the scope of the present invention. This indexing also does not imply an order in time. Detailed description

[0050] Figures 1 and 2 illustrate a motor-fan unit 1, in particular for a vehicle such as a motor vehicle. It may in particular be a motor-fan unit 1 for a heating, ventilation and / or air conditioning installation for a vehicle, in particular a motor vehicle.

[0051] The motor-fan unit 1 (or ventilation device) comprises in particular a fan wheel 3, an electric motor 5, and a support 7 for the motor 5, hereinafter called motor support 7.

[0052] The fan wheel 3, in particular of the blower type, rotates around an axis of rotation A. The motor 5 is intended to drive the fan wheel 3 in rotation around its axis A.

[0053] It may in particular be a brushless motor 5. The motor 5 comprises a rotor 5A and a stator part 5B. The rotor 5A is for example an external rotor. The rotor 5A may have a cup shape fixed to a rotor shaft 51. The fan wheel 3 may be fixed directly to the rotor shaft 51. The rotor 5A may comprise magnets for example fixed on an internal face of the cup. The stator part 5B may be internal, that is to say arranged inside the rotor 5A. The stator part 5B comprises a stator and for example at least one stator winding, in particular three stator windings. The magnets of the rotor 5A may be arranged radially outside relative to the stator windings. The term radially is understood to mean relative to the axis of rotation A.

[0054] At least one bearing 9A, 9B is intended to be mounted around the rotor shaft 51. In particular, a first bearing 9A and a second bearing 9B are provided. Each bearing 9A, 9B comprises an inner ring 91 and an outer ring 93. The rotor shaft 51 can be mounted free, sliding, inside the inner rings 91 of the bearings 9A, 9B.

[0055] The engine support 7 is intended to allow the motor-fan unit 1 to be fixed in the vehicle, in particular an automobile.

[0056] The engine mount 7 may comprise a base 71 allowing the engine 5 to be fixed. For example, the base 71 has an annular shape or a ring shape. The base 71 may comprise a decoupling element such as an elastomeric material. The elastomeric material is for example polystyrene-b-poly(ethylene-butylene)-b-polystyrene or SEBS. Such a decoupling element makes it possible to limit the transmission of vibrations generated by the engine 5 and / or the fan wheel 3 in the vehicle and / or external stresses towards the engine 5 and / or the fan wheel 3.

[0057] The base 71 may be intended to be fixed to the engine 5. The base 71 may also be intended to be fixed, directly or indirectly, to a structural element of the vehicle, for example a vehicle heating, ventilation and / or air conditioning system. In the example illustrated, the engine support 7 comprises a peripheral air deflector 73 to which the base 71 is fixed. The air deflector 73 may be intended to be fixed to the vehicle.

[0058] The engine support 7 advantageously carries a control module 11 of the engine 5. In particular, the base 71 can carry the control module 11. The control module 11 can comprise an electronic card (not visible in the figures) and at least one connector electrically connected to the electronic card for the electrical supply of the electronic card and, consequently, of the engine, when it is connected to an electrical harness in particular of the vehicle. In particular, when the electronic card is powered, the stator windings can create a magnetic field causing the rotation of the rotor and consequently of the fan wheel 3. A cover 12 can be fixed on the engine support 7, in particular the base 71, so as to cover the control module 11.

[0059] Furthermore, a support part such as a bearing holder 13 may be attached to the base 71 and / or to the air deflector 73.

[0060] The bearing holder 13 may have an upper part 13A and a lower part 13B opposite each other along a central axis of the bearing part 13 intended to coincide with the axis of rotation A in the mounted state of the engine support with the engine. The terms lower and upper are defined with reference to the orientation of FIG. 1.

[0061] The upper part 13A of the bearing holder 13 is oriented towards the fan wheel 3 when the motor-fan unit 1 is assembled.

[0062] The lower part 13B can be oriented towards a structure of the engine support 7, such as the base 71, when the motor-fan unit 1 is assembled.

[0063] The bearing holder 13 is made at least partly of plastic material. According to a particular embodiment, the plastic material may be reinforced with glass fibers. According to one example, the plastic material may be a thermoplastic, in particular of the polyester type, such as polybutylene terephthalate, with for example 30% glass fiber reinforcement (known under the name PBT GF30).

[0064] The bearing holder 13 defines at least a first housing 15 and a second housing 17 (visible in FIGS. 3 A and 3B). The first housing 15 is for example arranged on the upper part 13A of the bearing holder 13. The second housing 17 is for example arranged on the lower part 13B of the bearing holder 13.

[0065] The housings 15, 17 are configured to receive the corresponding first and second bearings 9A, 9B. More specifically, the first bearing 9A can be mounted in the first housing 15. The second bearing 9B can be mounted in the second housing 17.

[0066] In particular, during assembly, the outer rings 93 of the bearings 9A, 9B are force-fitted inside the housings 15, 17. The bearings 9A, 9B can be inserted with the same force into the housings 15, 17 on both sides of the bearing holder 13, without distinction of the flexibility or rigidity of the bearing holder 13 at the housings 15, 17.

[0067] Due to this forceful insertion of the outer rings 93 of the bearings 9A, 9B into the bearing holder 13 and the rotor shaft 51 slidably mounted inside the bearings 9A, 9B, in operation, the bearings 9A, 9B do not move while the rotor shaft 51 moves through the inner rings 91 of the bearings 9A, 9B.

[0068] The housings 15, 17 defined by the bearing holder 13 are of a shape complementary to that of the bearings 9A, 9B. The housings 15, 17 have, for example, a general annular or crown shape.

[0069] At least one or both of the housings 15, 17 may be shaped so as to allow the stresses generated by the insertion of a bearing 9A, 9B into the corresponding housing 15, 17 to be released.

[0070] For this purpose, at least one housing 15, 17 may have at least one stress relief zone 25 (FIGS. 4A, 4B). This may in particular be an area of ​​the housing 15, 17 which is more flexible than the rest of the housing 15, 17. This allows the bearing holder 13 to open, or deform, slightly at the level of the housing 15, 17 to allow the insertion of the corresponding bearing 9A, 9B and limit the forces required.

[0071] Such a zone 25 may have a deformation. The deformation is for example chosen from a semi-circular shape, a wave shape, an accordion shape, a rectangular shape, a triangular shape, a curved shape, a convex shape, a concave shape.

[0072] For example, the stress relief zone 25 is a domed or convex shape with convexity oriented towards the outside of the housing 15, 17. The stress relief zone 25 is in particular domed or convex in the direction of a force applied from the inside to the outside of the housing 15, 17 during insertion of the corresponding bearing 9A, 9B.

[0073] Alternatively or additionally, a stress relief zone 25 may have a reduced thickness compared to the rest of the housing 15, 17.

[0074] According to yet another variation, a more flexible material than the material used for the remainder of the housing 15, 17 may be used to provide the flexibility necessary for stress relief.

[0075] The two housings 15, 17 may each have at least one respective stress relief zone 25.

[0076] When the two housings 15, 17 have one or more stress relief zones 25, they may be identical or on the contrary different between the two housings 15, 17.

[0077] According to an exemplary embodiment, the stress relief zones 25 can extend axially, that is to say along the central axis of the bearing holder 13 coinciding with the axis of rotation A.

[0078] Also, when the two housings 15, 17 have one or more stress relief zones 25, they can be aligned along the central axis of the bearing holder 13 coinciding with the axis of rotation A.

[0079] Alternatively, the stress relief zones 25 of the two housings 15, 17 may not be axially aligned.

[0080] According to a particular embodiment, the housing 15, 17 may have at least three stress relief zones 25. They are preferably regularly distributed at 120°. In the example illustrated, each of the two housings 15, 17 has three stress relief zones 25. Of course, this is not limiting.

[0081] Furthermore, the internal wall of the housings 15, 17 may be provided with a predefined number of radial support reliefs 151, 171. These radial support reliefs 151, 171 are shaped so as to establish contact with the corresponding first 9A or second 9B bearing. The contact may be linear or surface.

[0082] The first housing 15 and the second housing 17 may or may not have the same number of radial support reliefs 151, 171.

[0083] At least one of the housings 15, 17 may have at least three radial support reliefs 151, 171. These three radial support reliefs 151, 171 are preferably regularly distributed at 120° from one another. Of course, this is not limiting; it may, for example, be envisaged to increase the number of radial support reliefs 151, 171 to improve the coaxial position of the bearings 9A, 9B in the housings 15, 17 and make the assembly even more secure.

[0084] Each radial support relief 151, 171 can define at least one support or contact surface against the corresponding first 9A or second 9B bearing. The radial support reliefs 151 of the first housing 15 define, for example, support surfaces against the first bearing 9A. The radial support reliefs 171 of the second housing 17 define, for example, support surfaces against the second bearing 9B. The radial support reliefs 151, 171 are better visible in FIGS. 4A and 4B.

[0085] Furthermore, the radial support reliefs 151 of the first housing 15 are different from the radial support reliefs 171 of the second housing 17.

[0086] The radial support reliefs 151 of the first housing 15 may be of different shapes compared to the radial support reliefs 171 of the second housing 17. In particular, the radial support reliefs 151 of the first housing 15 can define support surfaces which are larger than the support surfaces defined by the radial support reliefs 171 of the second housing 17.

[0087] According to an embodiment of the first housing 15 illustrated in FIGS. 3 A and 4A, the radial support reliefs 151 are shaped to establish surface contact with the first bearing 9A.

[0088] To do this, the radial support reliefs 151 are, for example, included in a hypothetical cylindrical shape surrounding the first bearing 9A.

[0089] The radial support reliefs 151 may, for example, have a contact surface with a rectangular or triangular outline. They may also be prismatic in shape.

[0090] According to an embodiment of the second housing 17 illustrated in FIGS. 3B and 4B, the radial support reliefs 171 are shaped to establish linear contact with the second bearing 9B. The radial support reliefs 171 may for example have a rounded contact surface to establish linear contact with the second bearing 9B. In particular, the radial support reliefs 171 may be of circular or semi-circular shape making it possible to establish linear contact with the bearing 9B.

[0091] According to a variant not shown, the radial support reliefs 171 could be shaped to establish surface contact with the second bearing 9B. When the radial support reliefs 151, 171 of the two housings 15, 17 are shaped to establish surface contacts with the corresponding bearing 9A, 9B, the surface contact established between the radial support reliefs 171 of the second housing 17 and the second bearing 9B may be less significant than the surface contact established between the radial support reliefs 151 of the first housing 15 and the first bearing 9A.

[0092] Furthermore, the radial support reliefs 151 of the first housing 15 and / or the radial support reliefs 171 of the second housing 17 may be produced by ribs.

[0093] The radial support reliefs 151 such as ribs of the first housing 15 may optionally be axially aligned with the radial support reliefs 171 such as ribs of the second housing 17. Alternatively, the radial support reliefs 151, 171 of the first housing 15 and of the second housing 17 may be arranged independently, so that the radial support reliefs 171 of the second housing 17 are not necessarily axially aligned with the radial support reliefs 151 of the first housing 15.

[0094] In addition, the bearing carrier 13 may comprise a base 131 and a tower or chimney 133.

[0095] The tower 133 may be tubular in shape around the central axis of the bearing part 13 coinciding with the axis of rotation A. This tower 133 extends for example axially from the base 131. The tower 133 may end with the first housing 15. In other words, the first housing 15 is located at one end of the tower 133.

[0096] The tower 133 has an internal surface delimiting a cavity. This cavity allows the first bearing 9A to be received. At this end, the internal surface of the tower 133 therefore faces the first bearing 9A when the latter is received in the first housing 15.

[0097] The tower 133 may comprise one or more external stiffening fins 19 visible in FIGS. 3 A and 4A. The fins 19 are said to be external because they are provided on an external surface of the tower 133 which is opposite the internal surface of the tower 133.

[0098] Such fins 19 may extend axially from the base 131 along the tower 133. The fins 19 may terminate at a non-zero distance d from the end of the tower 133 which is opposite the base 131.

[0099] The base 131, for its part, includes in particular the second housing 17 (visible in figures 3B and 4B) with its radial support reliefs 171. The first housing is arranged at the end of the tower 133 opposite this second housing 17.

[0100] The base 131 can be fixed to a structure of the engine support, such as the base and / or the deflector previously described. For this purpose, the base 131 can comprise a predefined number of fixing points 21, such as bosses, screw points. Thus, when assembling the engine support, the second bearing 9B is trapped between the base 131 of the bearing holder 13 and the base or the deflector of the engine support.

[0101] The base 131 may also comprise one or more reinforcing elements 23 surrounding the second housing 17. This may for example be one or more low walls which are arranged so as to go around the base 131. The low walls may extend between the fixing points 21 as shown in FIG. 4B, for example forming arcs of a circle around the base 131.

[0102] According to one embodiment, the base 131 may be more rigid than the end of the tower 133 which is free, not fixed to a structure, opposite the base 131. The points of fixing 21 such as bosses, and / or the reinforcing elements 23 make it possible to further stiffen the base 131.

[0103] The free end of the tower 133 is in this case more flexible than the base 131, in particular due to the height of the tower 133. In addition, at its free end, the tower 133 may have a smaller thickness than at the base 131.

[0104] One or more stress relief zones 25 may be provided at least on the side of the base 131 which is more rigid than the end of the tower 133. Thus at least the second housing 17 may have such stress relief zones 25. The first housing 15 may also have such stress relief zones 25. In the example illustrated, both housings 15, 17 have stress relief zones 25.

[0105] According to an exemplary embodiment, the stress relief zones 25 may extend axially from the base 131 to the opposite end of the tower 133.

[0106] Furthermore, due to the greater rigidity on the side of the base 131, the radial support reliefs 171 of the second housing 17, when they are provided, can be shaped to establish a linear or point (or even surface) contact. On the other hand, on the side of the more flexible end of the tower 133 (Figures 3A, 4A), the radial support reliefs 151, when they are provided, are preferably shaped to establish a greater surface contact in order to prevent in particular the first bearing 9A from coming out of the first housing 15 during operation in the event of possible vibrations for example.

[0107] This makes it possible to obtain a larger friction zone between the first bearing 9A and the first housing 15 (compared to the second housing 17) and makes it possible to limit, for example, outward deformation of the first housing 15 during insertion of the first bearing 9A. Thus, the assembly of the bearings 9A, 9B in the two housings 15, 17 can be homogenized, for example, with the same force on the sides (base 131 and end of the tower 133) so as not to require modification of an assembly tool depending on the side, for example.

[0108] Furthermore, with reference to Figures 3A to 4B, when the first 9A, respectively second 9B, bearing is inserted into the first 15, respectively second 17, housing, the contact surface is therefore reduced compared to the solutions of the prior art whose housings are defined by smooth cylinders. According to the embodiment described, the radial support reliefs 151, 171 define one or more small contact sections with the corresponding bearing 9A, 9B. The stresses generated by the insertion of a bearing 9A, 9B into the corresponding housing 15, 17 are concentrated at the level of the radial support reliefs 151, 171 and the stress release zones 25 allow these stresses to be released.

[0109] Thus, during a step of a method of assembling the motor-fan unit 1 as described previously with reference to all of the figures, the outer rings 93 of the bearings 9A, 9B can be inserted by force into the housings 15, 17 on both sides of the bearing holder 13 made of plastic material.

[0110] The bearings can be inserted with the same force into the housings 15, 17 on both sides of the bearing holder 13, without distinction of the flexibility or rigidity of the bearing holder 13 at the housings 15, 17. This allows homogeneity of the assembly step on both sides without modifying the assembly tool. [OR I] The stresses generated during the forced insertion of one or more bearings 9A, 9B are released thanks to the flexibility of stress relaxation zones 25 of the housing(s) 15, 17.

[0112] The forceful insertion of the bearings 9A, 9B is advantageously secured thanks to the presence of the respective radial support reliefs 151, 171 on the internal surfaces of the housings 15, 17.

[0113] Preferably, a more substantial contact, in particular surface contact, is established between the first bearing 9A and the radial support reliefs 151 of the first housing 15 on the side of the free end of the tower 133 of the bearing holder 13, while on the side of the more rigid base 131 of the bearing holder 13, the contact may be less between the second bearing 9B and the radial support reliefs 171 of the second housing 17. Thus, the bearings 9A, 9B, even at the free end of the tower 133, remain stable for example in the event of vibrations.

[0114] During another step of the assembly process of the motor-fan unit 1, the rotor shaft 51 of the motor 5 is slidably mounted in the inner rings 91 of the bearings 9A, 9B.

Claims

Claims

1. Motor-fan unit (1) in particular for a motor vehicle, the motor-fan unit (1) comprising a fan wheel (3), a brushless motor (5) for driving the fan wheel (3), a motor support (7) comprising a bearing holder (13) made at least partly of plastic material and defining at least a first housing (15) and a second housing (17), and corresponding bearings (9A, 9B) mounted around a rotor shaft (51) of the drive motor (5) and mounted inside the housings (15, 17), the bearings (9A, 9B) comprising a respective inner ring (91) and outer ring (93), characterized in that: the outer rings (93) of the bearings (9A, 9B) are mounted tightly in the housings (15, 17), and in that at least one housing (15, 17) has at least one zone of release of constraints (25).

2. Motor-fan unit (1) according to the preceding claim, in which the housing (15, 17) has at least three regularly distributed stress relief zones (25).

3. Motor-fan unit (1) according to one of the preceding claims, in which the stress relief zone (25) has a deformation and / or a reduced thickness compared to the rest of the housing (15, 17).

4. Motor-fan unit (1) according to the preceding claim, in which the deformation is chosen from a semi-circular shape, a wave shape, an accordion shape, a rectangular shape, a triangular shape, a curved shape, a convex shape, a concave shape.

5. Motor-fan unit (1) according to one of the preceding claims, in which the two housings (15, 17) have at least one respective stress relief zone (25), and in which the stress relief zones (25) of the two housings (15, 17) are aligned along a central axis of the bearing holder (13).

6. Motor-fan unit (1) according to the preceding claim, in which the bearing holder (13) comprises: a base (131) fixed on a structure of the motor support and comprising the second housing (17), and a tower (133) of tubular shape around the central axis, extending axially from the base (131) and ending with the first housing (15) opposite the second housing (17) along the central axis, the stress relief zones (25) extending axially from the base (131) to the opposite end of the tower (133).

7. Motor-fan unit (1) according to one of the preceding claims, in which the housings (15, 17) have an internal wall provided with a predefined number of radial support reliefs (151, 171) shaped to establish contact with the corresponding bearing (9A, 9B), the radial support reliefs (151) of the first housing (15) being different from the radial support reliefs (171) of the second housing (17).

8. Motor-fan unit (1) according to the preceding claim, in which: the radial support reliefs (151) of the first housing (15) are shaped to establish surface contact with the corresponding bearing (9 A), and the radial support reliefs (171) of the second housing (17) are shaped to establish linear contact or surface contact with the corresponding bearing (9B).

9. Motor-fan unit (1) according to one of the preceding claims, in which the radial support reliefs (151, 171) are produced by ribs.

10. Motor-fan unit (1) according to one of the preceding claims, in which the rotor shaft (51) is mounted freely inside the inner rings (91) of the bearings (9 A, 9B).

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