The invention concerns a ventilation device for a motor vehicle.

The invention relates to the field of motor vehicles, and more particularly to the field of air circulation for cooling the engine and its equipment.

Motor vehicles, whether of the combustion or electric type, have to discharge the heat generated by their operation, and are equipped with heat exchangers for this purpose. A motor vehicle heat exchanger usually comprises tubes in which a heat transfer fluid, notably a liquid such as water, is designed to circulate, and heat exchange elements connected to these tubes, often designated by the term “fins” or “spacers”. The fins may be used to increase the exchange surface between the tubes and the ambient air.

However, in order to increase further the heat exchange between the heat transfer fluid and the ambient air, a ventilation device is commonly used in addition, to generate or increase an air flow directed toward the tubes and fins.

Such a ventilation device most commonly comprises a propeller fan, which has a number of drawbacks.

In the first place, the assembly formed by the propeller fan and its propulsion device occupies a considerable space.

Furthermore, the distribution of the air formed by the propeller, often placed in the center of the tube array, is not uniform over the whole surface of the heat exchanger. In particular, certain regions of the heat exchanger, such as the ends of the heat transfer tubes and the corners of the heat exchanger, are not reached, or only reached to a small extent, by the air flow ejected by the propeller.

Furthermore, when it is not found necessary to put the ventilation device into operation, notably when the heat exchange with the ambient air is sufficient to cool the heat transfer fluid, the blades of the propeller partially obstruct or “mask” the flow of the ambient air toward the tubes and fins. This limits the heat exchange between the ambient air, on the one hand, and the tube and fins, on the other hand.

Moreover, in this case, the engine friction is reduced less rapidly, thus increasing the fuel consumption of the vehicle and consequently the carbon dioxide emission.

One object of the invention is to provide a ventilation device for a heat exchanger that does not exhibit at least some of the drawbacks of the known ventilation devices for heat exchangers.

For this purpose, the invention proposes a ventilation device for a motor vehicle, comprising at least one manifold for distributing air to the tubes, at least one turbomachine being arranged in said at least one manifold, said at least one turbomachine comprising a cross-flow fan, said at least one manifold forming a volute of the cross-flow fan.

Thus, advantageously, the plurality of tubes from which air is ejected makes it possible to replace the conventional propeller placed in front of the heat transfer fluid circulation tubes of the heat exchanger, without suffering from any of the drawbacks mentioned above.

This is because, for an equal heat exchange capacity, the volume occupied by such a ventilation device is much smaller than a ventilation device using a propeller. Furthermore, the distribution of the ventilated air by the tubes is easier to control and can be made more uniform.

Additionally, because of the device according to the invention, the obstruction of the air flow toward the heat exchanger is limited. This is because the tubes of the ventilation device can advantageously be placed facing low heat exchange areas of the heat exchanger, called “dead areas”, such as the front faces of the tubes through which the heat transfer fluid passes, which are not in contact with the cooling fins. This cannot be done with a conventional propeller.

The invention also makes it possible to place the air ejection means that supply the air flow to the tubes of the ventilation device at a distance from the array of heat transfer fluid circulation tubes, thus providing greater freedom in the design of the heat exchanger.

According to another characteristic of the invention, the device comprises at least one manifold for distributing air to the tubes, at least one turbomachine being arranged in said at least one manifold, said at least one turbomachine comprising a cross-flow fan, said at least one manifold forming a volute of the cross-flow fan.

According to another characteristic of the invention, the volute comprises an air inlet into the manifold through which an air flow can be drawn by the cross-flow fan, and an air outlet through which the air flow drawn in can be distributed to the tubes, the tubes extending parallel to a longitudinal direction of the tubes, called the longitudinal direction, the cross-flow fan extending in a direction orthogonal to the longitudinal direction, called the intake direction, another direction, called the direction of advance, orthogonal to the longitudinal direction and the intake direction, coinciding with a direction of advance of the vehicle when the ventilation device is installed in the vehicle.

According to another characteristic of the invention, the air inlet comprises a first inlet wall at an angle of between 40° and 75°, preferably 58°, to said longitudinal direction.

According to another characteristic of the invention, one end of the first wall opposed to the air inlet is curved in a plane containing the longitudinal direction and the direction of advance, the length of this end being between 1 mm and 8 mm, and a minimum distance between said end and a disk delimited by the cross-flow fan in said plane is between 0.5 mm and 1.5 mm.

According to another characteristic of the invention, the air inlet comprises a second inlet wall comprising a rounded edge shaped so that its curvature in a plane containing the longitudinal direction and the direction of advance is an arc of a circle whose center is located on a concentric circle of a disk delimited by the cross-flow fan in said plane.

According to another characteristic of the invention, the device comprises a part forming a junction of the air inlet of the volute and air outlet of the volute, called the intermediate part, shaped to house the cross-flow fan.

According to another characteristic of the invention, said intermediate part comprises a wall, called the intermediate wall, curved along an arc of a circle in a plane containing the longitudinal direction and the direction of advance, said arc of a circle having a center distinct from the center of a disk delimited by the cross-flow fan in said plane.

According to another characteristic of the invention, a distance between the center of the intermediate wall and the center of the disk is smaller than or equal to the value of the radius of the disk.

According to another characteristic of the invention, a section of the intermediate part at an interface between the intermediate part and the air outlet is at an angle, preferably a non-zero angle, to the longitudinal direction, preferably within the range [0° 20], or, also preferably, within the range]0°, 20°].

According to another characteristic of the invention, the cross-flow fan is capable of creating an air flow with a flow rate of between 0 and 750 m3/h and a pressure of between 0 and 900 Pa. For this purpose, the cross-flow fan comprises a rotor whose rotation speed may be between 2000 r.p.m. and 13,000 r.p.m., preferably between 2500 r.p.m. and 9000 r.p.m.

For this purpose, one or more of the following characteristics, considered individually or in combination, may, notably, be provided:the rotor is formed of a plurality of stages of blades separated by reinforcing disks;the rotor has a blade height, defined as the sum of the heights of the different stages of blades, measured parallel to the axis of rotation of the rotor, of between 100 and 600 mm;each stage of blades has a height, measured parallel to the axis of rotation of the rotor, of between 16 and 33 mm;each reinforcing disk has a thickness, measured parallel to the axis of rotation of the rotor, of between 0.8 and 1.5 mm;each stage of blades comprises between 15 and 30 blades, preferably between 20 and 28 blades;the various blades of each stage of blades51are inscribed in a ring having an inside diameter Dint and an outside diameter Dext;the inside diameter is between 0 and 84 mm, preferably between 60 and 84 mm;the outside diameter is between 35 and 120 mm, preferably between 60 and 120 mm;each blade has a crescent-shaped cross section, the blades preferably being substantially cylindrical;a pitch angle γ of each blade, defined as the angle between the chord of the blade and axis connecting the axis of rotation of the rotor to the geometric center of the cross section of the blade53, is between 0 and 30°;an angle of flow at the leading edge of each blade, defined as the angle between the current line at the leading edge of the blade and the tangent to the outside diameter of the rotor, is between 0° and 40°, preferably between 10° and 20°;an angle of flow at the trailing edge of each blade, defined as the angle between the current line at the trailing edge of the blade and the tangent to the inside diameter of the rotor, is between 60° and 90°, preferably between 70° and 80°;the maximum thickness of the cross section of each blade is between 0.35 and 1.6 mm, preferably between 0.8 and 1.2 mm;the length of the chord of the cross section of each blade, connecting the leading edge to the trailing edge of the cross section of each blade, along a rectilinear segment, is between 6 and 8 mm;the rotor is formed of a plurality of portions, rolling bearings being placed between each portion; andthe rotor is formed of a number of portions that is less than 4.

