FR3125116A1 - Cooling circuit of a voltage converter, equipped with fins - Google Patents

Abstract

The present invention proposes a cooling circuit for an electronic component, in particular for a voltage converter, comprising a cooling channel in which a cooling fluid flows, the channel comprising an internal surface in contact with the cooling fluid, and at least a member projecting from the inner surface, said member defining a first fin and at least one second fin intersecting the first fin. Figure for abstract: Fig.3

Description

Cooling circuit of a voltage converter, equipped with fins

The present invention relates to the cooling of electronic components of the electric motor of a motor vehicle, such as the components of a voltage converter.

A rotating electrical machine comprises a mobile rotor in rotation around an axis and a fixed wound stator. The stator winding is connected to the voltage converter. In alternator mode, when the rotor is rotating, it induces a magnetic field in the stator which the voltage converter transforms into electric current in order to supply the electrical consumers of the vehicle and recharge the battery. In motor mode, the stator is electrically powered and induces a magnetic field driving the rotor in rotation, for example to start the heat engine.

The voltage converter, housed in an electronic housing, comprises a power stage making it possible to receive or supply an electrical power signal to the electrical phases of the winding. The power stage includes at least one power module having a power terminal arranged to be electrically connected to a phase output to form a phase connection. The power module forms a voltage rectifier bridge to transform the alternating voltage generated by the phases of the stator into a direct voltage and/or, conversely, to transform a direct voltage into an alternating voltage to supply the phases of the stator. The voltage converter also comprises a control stage comprising a control module allowing the control of the power module(s) as well as regulating, in the case of a wound rotor, - the current injected via the brush holder into the rotor and to interface with an external computer of the vehicle.

During operation of the machine, the temperature of the power module rises, the value of this rise in this temperature being linked to the dimensioning of the module. The excessive increase in temperature will cause significant damage to electronic components.

To limit these thermal effects, it is known to use a cooling circuit for the electronic housing. The cooling circuit is advantageously arranged under the power module and comprises a channel in which a cooling fluid circulates, the fluid entering through an inlet of said fluid and exiting through a fluid outlet.

The channel is delimited by a wall whose internal surface is in contact with the cooling fluid and an external surface is in contact with the electronics to be cooled. The wall thus ensures by thermal conduction the transfer of calories from the heating of the electronics to the cooling fluid which by its circulation evacuates them outside the system.

However, the efficiency of this calorie exchange at the interface between the fluid and the wall can be limited, thus penalizing the cooling of the electronic components, the latter thus not being cooled optimally.

The object of the present invention is therefore to overcome this drawback of the device of the prior art by proposing a more efficient cooling circuit.

For this, the present invention proposes a cooling circuit for an electronic component, in particular for a voltage converter, comprising a cooling channel in which a cooling fluid flows, the channel comprising an internal surface in contact with the cooling fluid, and at least one element projecting from the inner surface, said element defining a first fin and at least a second fin intersecting the first fin.

The first and second fins increase the heat exchange surface between the cooling fluid and the channel wall. Cooling is thus improved.

According to one embodiment of the invention, the first fin comprises a median plane and the second fin comprises a median plane, the median planes forming an acute angle greater than 10° around a straight line of intersection between said two planes. This is the angular limit to allow depowdering.

According to one embodiment, the channel extends along an X axis in an X, Y, Z frame, the line of intersection between said two planes extending along the X axis, the Y and Z axes being perpendicular to the X axis and secant between them, the median plane of the first fin extending in the X, Y plane and the median plane of the second fin extending in the X, Z plane. The fins thus arranged in the flow allow a better compromise between the increase of the exchange surface and the limitation of the pressure drop.

According to one embodiment, the Y and Z axes are mutually perpendicular, the median plane of the first fin being transverse to the Z axis and the median plane of the second fin being transverse to the Y axis. Such a configuration allows to minimize load loss.

According to one embodiment, at least one of the fins has a thickness defined in a direction transverse to the median plane, which increases along the axis X between a rear edge of the fin and a front edge of the fin.

According to one embodiment, the rear end and/or the front end is rounded.

According to one embodiment, the first fin extends along the Y axis between an upper end and a lower end, the upper and lower ends of the first fin being integral with the internal surface of the channel. Such a configuration makes it possible to maximize the exchange surface.

According to one embodiment, the element comprises two second fins, the distance d2 between the two second fins being between 1.5mm and 4.5mm and being advantageously 3mm.

The invention also relates to a voltage converter comprising an electronic housing containing electronic components, and provided with such a cooling circuit.

The invention also relates to the method of manufacturing such a cooling circuit by additive manufacturing. Indeed, for reasons of demoulding axis to be respected, the molding only makes it possible to provide in the channel fins parallel to each other and perpendicular to the internal surface from which they extend. On the other hand, additive manufacturing makes it possible to obtain elements extending from the internal surface of the channel, formed of intersecting fins, according to the object of the invention. These elements, at least, are obtained by additive manufacturing.

As a variant, the cooling circuit is obtained entirely by additive manufacturing.

There is a schematic representation of an electronics housing with cooling circuit.

There is a top view of a cooling channel provided with elements according to the invention.

There is a schematic representation of a channel portion comprising elements according to the invention illustrating the median planes of the fins.

There is a schematic representation of a channel portion comprising elements according to the invention illustrating the X, Y, Z marker.

There is a schematic representation of a cross-sectional view of a first fin.

There is a schematic representation of a channel element whose first fin extends to the wall of the channel by its two ends.

There is a sectional view of a simplified distribution of first fins according to the invention.

There is a schematic representation of the additive manufacturing device.

In the remainder of the description, an axis X which may be curvilinear and axes Y and Z perpendicular to X and intersecting with each other will be considered.

There illustrates part of a voltage converter 70 comprising an electronic housing 60 with a cooling circuit 500 according to the invention.

The electronic housing 60 includes the switching elements of the power module and the electronic components of the control module making it possible to control the switching elements.

The cooling circuit 500 is in contact with the electronic housing 60, so as to allow the cooling of the electronic components and more particularly of the electronic components of the power module.

The cooling circuit 500 comprises a channel 5 formed in the body of the circuit. The cooling circuit 500 comprises for example a circular channel. As a variant, the cooling circuit comprises a channel in the shape of a parallelepiped or any shape compatible with the operation of the cooling circuit.

The cooling circuit is for example made of aluminum, traversed by a cooling fluid. The cooling fluid is for example water or a water-glycol mixture.

The channel 5 comprises at least two interfaces towards the outside, the fluid entering through one interface and leaving through the other, the channel extending substantially tubular around the axis X between the two interfaces, as illustrated in . Channel wall 502 includes an inner surface 50 against which fluid flows.

As a first approximation, in the tubular channel along the X axis, the fluid flow is along the X axis, i.e. the fluid flows transversely to a plane perpendicular to the X axis.

In the remainder of the description, an element 3 illustrated in which protrudes from the internal surface of the channel 50. The element 3 comprises a first fin 1 which protrudes from the internal surface of the channel and a second fin 2 which intersects the first fin 1.

Each fin of element 3 advantageously extends in an extension plane, a thickness of the fin in a direction transverse to the extension plane being less than the dimensions of the fin in the extension plane. A typical fin thickness may be 2mm for a fin 8mm high in its extension plane.

The fin advantageously extends around a median plane illustrated in . Such a plane intersects the fin in the middle of its thickness so that the fin is substantially symmetrical with respect to this plane (P).

The median planes P1 of the first fin and P2 of the second fin intersect along a straight line advantageously extending along the axis X of flow of the cooling fluid, that is to say that the fins extend in the flow of fluid in the channel. The pressure drop is thus minimized.

The median planes form an acute angle greater than 10° around the X axis, so as to facilitate the depowdering step which will be described later in the additive manufacturing process for the cooling circuit. Advantageously, the median planes are transverse, i.e. they form a right angle around the X axis.

The first and the second fin of an element advantageously have the same extension along the X axis.

Considering the reference X, Y, Z defined above, the median plane of the first fin P1 thus extends in the plane X, Y and the median plane of the second fin P2 extends in the plane X, Z, as illustrated at .

The Y axis advantageously extends perpendicular to the internal surface of the channel, as illustrated in . The first fin is thus transverse to the surface of the channel. The Y axis secant to the Z axis is advantageously perpendicular to the Z axis, the median planes of the first and second fins thus being perpendicular to each other.

We will describe here a geometry of the first fin of median plane P1 according to (X, Y). The description will be transposed without difficulty to the second fin of median plane P2 according to (X, Z).

In an advantageous embodiment, in any plane transverse to the Y axis and intersecting the first fin, the section of the fin has a thickness transverse to the median plane P1 which increases along the X axis.

The section of the fin in one of these section planes, illustrated in extends by widening along X between two rounded edges, the rear edge 13 and the front edge 14, the fluid flowing in contact with the fin from the rear edge towards the front edge. The thickness of the fin between the edges increases from 0.2mm at the rear edge to 1.5mm at the front edge.

The profiled fin thus makes it possible to limit the pressure drop while increasing the exchange surface of the cooling fluid with the surface of the channel, the fins increasing the internal exchange surface of the channel.

The fin extends in particular along Y between a lower axial end 10 and an upper axial end 11. In an advantageous embodiment, the first fin is integral with the wall of the channel by its upper and lower axial ends as illustrated in .

Such a fin height, which can be obtained by additive manufacturing, makes it possible to increase the liquid exchange surface in the channel as much as possible to improve cooling.

As a variant, an element can advantageously comprise several second fins 2, 2' intersecting the first fin 1 as illustrated in . The median plane of the second fin P2' also includes the axis X. The median planes of the two second fins 2, 2' can for example be parallel. As a variant, the median planes of the second fins P2 and P2' are secant. The angle between the median plane P1 and the median plane P2' is also an acute angle comprised between 10° and 90°.

The distance d2 between two second fins of an element 3 illustrated in is defined as being the distance between the lines of intersection of the median planes P2 and P2' with the median plane P1 of the same element. The distance d2 is between 1.5mm and 4.5mm and is advantageously of the order of 3mm, for a channel of height H along the axis Y of between 6mm and 12mm.

Consider the simplified case illustrated in of a channel comprising a plurality of identical elements 3 extending from a flat surface of the internal surface of the channel 50. In this simplified case, the first fins 1 extend in particular perpendicular to the surface and parallel to each other. others and are aligned along the X and Z axes as shown in .

Such a simplification does not limit the general character of the claims and of the description which also cover the case where the internal surface of the channel is not flat in the case of a channel with a circular section, and the case where although the surface from which the elements extend are flat, the first fins and the second fins respectively of two elements are not parallel and possibly where the elements 3 are different from each other. The description of the simple case can be transposed without difficulty to these other cases.

The invention aims in particular to increase as much as possible the number of fins to increase the exchange surface while limiting the pressure drop for the flow of the cooling fluid in the channel. The invention relates in particular to regular fin distributions in order to limit the pressure drop. Thus in the simplified case illustrated in , by defining the distance d1 as the distance between the adjacent planes of two adjacent first fins along the Z axis, in any section plane perpendicular to the Y axis, as shown in , the distance d1 between two first fins is advantageously between 2mm and 4mm and more particularly of the order of 2.5mm for a channel of height h along the Z axis of between 10mm and 20mm. The distance d1' along X between two adjacent first fins 1 along X is advantageously of the order of 1 mm to 2 mm, in particular to prevent the fluid flow lines from being disturbed near the edges of the fins.

In a first alternative to the method of manufacturing the cooling circuit 500, illustrated in this one is built by additive manufacturing. The cooling circuit is produced by adding successive layers, from a digital model resulting from computer-aided design, using a metal powder tank 101 used to draw the material to be deposited therein.

The additive manufacturing process of the cooling circuit is illustrated in the . It includes the steps described below.

In a chamber under controlled atmosphere 110 (i.e. under neutral gas such as Argon, where pressure and temperature are also regulated)

- the scraper roller 102 deposits a 60 micrometer powder bed in the manufacturing plate 103

- the laser 104 guided by the galvanometric head 105 fuses the grains where the material of the desired part is required

- the plate of the supply tank 106 rises by 60 micrometers

- the manufacturing plate 103 descends by 60 micrometers

- roller 102 deposits the next layer of powder and so on

- once the circuit is finished, the tank 107 containing the circuit and the powder is removed,

- powder is powdered with a brush, or with compressed air to remove approximately 60 to 80% of the volume which constitutes the unmelted powder (which can be reused 3 times)

- and we keep the remaining 10% (approximately) which constitute the finished circuit,

- then using heat treatments and surface treatments, the circuit is finalized. An oven stress relief treatment is desirable to relieve the level of stress inside the circuit due to thermal gradients during the process.

The depowdering process imposes an angle greater than 10° between the median planes P1 and P2 and the minimum distances d1 and d2. For depowdering, the angle between the median planes will even advantageously be greater than 20°.

This manufacturing method makes it possible in particular to manufacture a cooling circuit provided with first fins being integral with the channel by their two ends and with fins which intersect according to the invention.

In a variant not shown, the cooling circuit 500 is formed of two complementary parts, the elements 3 being manufactured by additive manufacturing on a first part forming for example the bottom of the channel, a second part then being assembled with the first part to form the circuit .

The scope of the present invention is not limited to the details given above and allows embodiments in many other specific forms without departing from the scope of the invention. Therefore, the present embodiments should be considered by way of illustration, and can be modified without departing from the scope defined by the claims.

Claims (11)

Cooling circuit for an electronic component, in particular for a voltage converter, comprising a cooling channel (5) in which a cooling fluid flows, the channel (5) comprising an internal surface (50) in contact with the cooling fluid , and at least one element (3) projecting from the inner surface (50), said element defining a first fin (1) and at least a second fin (2) intersecting the first fin (1). Cooling circuit according to Claim 1, in which the first fin (1) comprises a median plane (P1) and the second fin (2) comprises a median plane (P2), the median planes (P1) and (P2) forming an angle acute greater than 10° around a line of intersection (I) between the said two planes. Cooling circuit according to Claim 2, in which the channel (5) extends along an axis X in a frame (X, Y, Z), the line of intersection (I) between the said two planes extending along the axis X, the axes Y and Z being perpendicular to the axis X and intersecting with each other, the median plane (P1) of the first fin extending in the plane (X, Y) and the median plane (P2) of the second fin extending in the plane (X, Z). Cooling circuit according to Claim 3, in which the Y and Z axes are mutually perpendicular, the median plane (P1) of the first fin being transverse to the Z axis and the median plane (P2) of the second fin being transverse to the Y axis. Cooling circuit according to either of Claims 3 and 4, in which at least one of the fins (1,2) has a thickness defined in a direction transverse to the median plane (P1, P2), which increases along the axis X between a rear edge of the fin (13) and a front edge of the fin (14). Cooling circuit according to Claim 5, in which the rear end (13) and/or the front end (14) is rounded. Cooling circuit according to one of Claims 3 to 6, in which the first fin (1) extends along the Y axis between an upper end (11) and a lower end (10), the upper ends (11) and bottom (10) of the first fin (1) being integral with the inner surface of the channel (50). Cooling circuit according to any one of the preceding claims, in which the element (3) comprises two second fins (2, 2'), the distance d2 between the two second fins (2, 2') being between 1.5 mm and 4.5mm and being advantageously 3mm. Voltage converter (70) comprising an electronic housing (60) containing electronic components, and a cooling circuit (500) of the electronic housing (60) according to any one of claims 1 to 8. Method of manufacturing a cooling circuit according to any one of Claims 1 to 8, in which at least the elements (3) are obtained by additive manufacturing. Process for manufacturing a cooling circuit according to claim 10, entirely obtained by additive manufacturing.