FR3117704A1 - Electronic assembly for a rotating electric machine - Google Patents

Abstract

The present invention proposes an X-axis electronic assembly for a rotating electrical machine, said assembly comprising an electrical system (2), a cooling circuit (3) comprising a body (30) forming a housing adapted to allow the circulation of a fluid cooling circuit (300), the electrical system (2) being mounted on the body (30), the cooling circuit (3) also comprising fins (4) projecting from the body (30) Figure for the abstract: Figure 3a

Description

Electronic assembly for a rotating electric machine

The invention relates in particular to an electronic assembly for a rotating electrical machine.

The invention finds a particularly advantageous application in the field of rotating electrical machines such as alternators, alternator-starters or even reversible machines or electric motors.

A rotating electrical machine comprises a mobile rotor rotating around an axis, a fixed stator and an electronic assembly which supplies electrical consumers from the electrical current generated by the stator, or also allows the battery to be recharged.

In operation, the temperature of the electronic assembly rises as well as the temperature at the level of the active parts which are the stator and the rotor. The cooling of the machine is necessary for its proper functioning. To this end, the subject of the present invention is therefore an X-axis electronic assembly for such a machine comprising an electrical system, a cooling circuit comprising a body forming a housing adapted to allow the circulation of a cooling fluid, the system electric being mounted on the body, the cooling circuit also comprising fins extending projecting from the body.

The invention therefore uses the cooling circuit of the electronic assembly to cool the flow of air entering the machine. The air flow thus cooled beforehand in contact with the fins circulates at a lower temperature in the machine.

According to one embodiment, the body extends between the fins and the electrical system.

According to one embodiment, the body comprises a plate and at least one tube for the circulation of the cooling fluid, the fins extending from the tube.

According to one embodiment, at least one fin partially surrounds the tube, extending in a plane substantially transverse to a direction of extension of the tube.

According to one embodiment, the fins extend radially with respect to the axis X.

According to one embodiment, two adjacent fins are separated by an angle of between 3° and 20° and advantageously between 5° and 10°.

According to one embodiment, the fins extend axially along the X axis.

According to one embodiment, the fins are integral with the body.

According to one embodiment, at least one fin has a thickness of between 1mm and 3mm and advantageously between 1.8mm and 2mm transversely to its extension plane.

The present invention also relates to a rotating electrical machine comprising a box comprising at least one flange housing active parts of the machine, an electronic assembly mounted on the flange, the fins being arranged between the electrical system and said flange, the fins s extending next to the flange.

. The rotating electrical machine can advantageously form an alternator, an alternator-starter, a reversible machine or an electric motor.

The present invention may be better understood on reading the detailed description which follows, non-limiting examples of implementation of the invention and examination of the appended drawings.

There represents, schematically and partially, a sectional view of a rotating electrical machine and illustrates the air flows entering the machine.

There illustrates the stacking of the electronic assembly on the flange, in the presence of fins.

There schematically represents the rear face of the cooling circuit provided with fins in a first embodiment

There schematically represents the rear face of the cooling circuit provided with fins in a second embodiment

Identical, similar or analogous elements retain the same references from one figure to another. It will also be noted that the various figures are not necessarily on the same scale. In addition, the embodiments which are described below are in no way limiting. It is possible in particular to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described.

There represents an example of a compact and polyphase rotating electrical machine 10, in particular for a vehicle such as a motor vehicle or a drone. This machine 10 transforms mechanical energy into electrical energy, in alternator mode, and can operate in motor mode to transform electrical energy into mechanical energy. This rotating electrical machine 10 is, for example, an alternator, an alternator-starter, a reversible machine or an electric motor.

In this example, the machine 10 comprises a box 11 on which an electronic assembly is mounted. Inside this box 11, it further comprises a shaft 13, a rotor 12 integral in rotation with the shaft 13 and a stator 15 surrounding the rotor 12. The rotational movement of the rotor 12 takes place around an X axis. In the rest of the description, the axial direction corresponds to the X axis, passing through the shaft 13 at its center, while the radial orientations correspond to concurrent planes, and in particular perpendicular, to the axis X. For radial directions, the inner denomination corresponding to an element oriented towards the axis, or closer to the axis with respect to a second element, the outer denomination designating a distance from the axis.

In this example, the box 11 comprises a front flange 16 and a rear flange 17 which are assembled together. These flanges 16, 17 are hollow in shape and each carry, centrally, a bearing coupled to a respective ball bearing 18, 19 for the rotational mounting of the shaft 13. In addition, the housing 11 comprises fastening means ( not shown) allowing the mounting of the rotary electrical machine 10 in the vehicle.

A drive member such as a pulley 20 can be fixed on a front end of the shaft 13. This member makes it possible to transmit the rotational movement to the shaft or to the shaft to transmit its rotational movement to the belt. In the remainder of the description, the denominations front/rear refer to this member. Thus a front face is a face oriented in the direction of the organ while a rear face is a face oriented in the opposite direction of said organ.

The rear end of the shaft 13 carries, here, slip rings 21 belonging to a commutator 22. A brush holder (not shown) comprises brushes arranged so as to rub on the slip rings 21. The brush holder is connected to electronic assembly 1.

The front flange 16 and the rear flange 17 may comprise axial and radial openings for the passage of an air flow in order to allow the cooling of the active parts of the machine 10 by circulation of air generated by the rotation of a front fan 25 arranged on a front axial face of the rotor 12 and a rear fan 26 arranged on a rear axial face of said rotor.

In general, the air is sucked in by axial openings (not visible in the figure), then circulates in the casing passing in particular through the winding of the stator, and is expelled by radial openings 171 of the flange shown in .

The recirculation of the hot air which leaves the machine through the radial openings 171, and which would re-enter through the axial openings under the effect of the fan, is notably limited by a shutter 170 illustrated in . The shutter makes it possible to close the openings of the flange in particular as close as possible to the phase outlets in order to limit this recirculation of hot air.

In this example, the rotor 12 is a claw rotor comprising two pole wheels. Each pole wheel is made up of a plate oriented transversely, a plurality of claws forming magnetic poles and a cylindrical core. The rotor has a coil 35 wound around the core. For example, the collector rings 21 belonging to the collector 22 are connected by wire connections to said coil 35. The rotor 12 can also include magnetic elements, such as permanent magnets, interposed between two adjacent claws. Alternatively, the rotor can be formed from a stack of laminations housing permanent magnets forming the magnetic poles.

In this exemplary embodiment, the stator 15 comprises a body 27 formed from a stack of laminations provided with notches, equipped with notch insulation for mounting an electric winding 28. The winding passes through the notches of the body 27 and form a front bun and a rear bun on either side of the body of the stator. Furthermore, the winding 28 is formed of one or more phases comprising at least one electrical conductor. Each phase has one end forming a phase output which is electrically connected to an electronic assembly such as a voltage converter.

The electronic assembly 1 illustrated in includes an electrical system connected between an electrical power source and the active parts of the machine to convert between DC voltage and phase outputs.

The electrical system 2 first comprises a positive bus bar and a negative bus bar intended to be connected to the electrical power source to receive the DC voltage, the positive bus bar receiving a high electrical potential and the negative bus bar receiving a low electrical potential.

The electrical system 2 further comprises at least one power module comprising one or more phase busbars intended to be respectively connected to one or more phases of the electric machine, to supply their respective phase voltages.

The electrical system 2 also comprises a support box on which is fixed a control module. The control module is typically a control card.

The electronic assembly 1 also includes a cooling circuit 3 for cooling the electrical system 2. The body of the cooling circuit 30 includes a plate 31 on which the power modules are mounted. The heat exchange between the plate 31 and the power module is achieved for example by means of a contact, direct or by means of a thermally conductive paste. The body 30 of the cooling circuit also comprises a tube 32 in thermal contact with the plate and in which a cooling fluid 300 circulates.

Thus the calories to be evacuated are transferred from the electrical system to the plate then evacuated for the most part to the cooling fluid 300. The cooling fluid typically circulates at a temperature of 70° to 90°.

The tube 32 is for example arranged in a groove, duct or channel of the plate 31 and held integral with the plate by overmolding or brazing or gluing or inserted by pressure into the housing. The body 30 of the cooling circuit is advantageously made of metal. The plate 31 typically has a circular shape of substantially the same outer dimension (perimeter) as the electrical system 2. The tube 32 is for example arranged along the periphery of the plate. The tube 32 is for example arranged on two thirds of the circumference of the plate. It extends between a fluid inlet 301 and a fluid outlet 302.

The fins 4 extend projecting from the tube 32 as illustrated in . Each fin 4 extends in its plane of extension which is substantially transverse to the direction of extension of the tube 32. In its plane of extension the fin 4 partially surrounds the tube 32, over at least a portion of the surface of the tube which is not in contact with the plate, called the free surface of the tube 32. The fins 4 thus extend radially with respect to the axis of the machine.

A fin 4 has for example a rounded U-shape at its section closest to the tube 32, and has a U-shape with projecting edges at its section furthest from the tube.

The arrangement and shape of the fins 4 are in particular dependent on the other elements of the machine, arranged close to the cooling circuit 3, and on the space available. The angular arrangement of the fins 4 is for example irregular with tube portions 32 at which the fins 4 are angularly closer together and other tube portions 32 where the fins 4 are angularly further apart. In the same way, in their extension plane, certain fins 4 may not extend over the entire circumference of the free portion of the tube, but over only one part. By defining the axial height of a fin 4 as its axial height between its end closest to the plate 31 and its so-called free end farthest from the plate 31, adjacent fins 4 may have different axial heights. A fin 4 may also have a variable axial height in its extension plane.

Two adjacent fins 4 will typically be separated by an angle of between 3° and 20°. The fins 4 are for example separated by an angle of the order of 5° for fins with a thickness of the order of 1.8 mm, as illustrated in . As a variant in the case illustrated in , the fins 4 are a little further apart, at an angle of the order of 10° for a fin thickness of the order of 2 mm. Other fin thicknesses combined with other angles could be envisaged without departing from the scope of the invention.

Alternatively the fins may extend parallel to each other, projecting from the body.

When the machine is assembled as shown in , the electronic assembly is mounted on the rear flange 17, a space separating the rear flange 17 from the electronic assembly 1 is in particular necessary to allow the entry of the air flow aimed at circulating as close as possible to the electronic assembly and through the machine to cool it. The fins of the cooling circuit 3 extend into this space. The space can advantageously have an axial height of between 8mm and 20mm and advantageously of the order of 14mm

A fin 4 typically has a height along the X axis adapted so that the free end of the fin is sufficiently close to the facing flange, to have the largest possible fin surface. A clearance must however be respected between the flange 17 and the free end of the fin 4, to absorb the tolerances of the side chain of the assembly. The fin advantageously has a height of the order of 7mm to 19mm and advantageously of the order of 13mm for a space of axial height of 14mm, so that the free end of the fin is therefore in axial proximity to the bearing but not in contact with the bearing.

The fins 4 in thermal contact with the coolant maintained at a temperature of the order of 70°-90° are thus maintained at a temperature of the same order. In contact with the fins 4, the incoming air flow is thus cooled before circulating at the level of the active parts of the machine to be cooled and in particular at the level of the bun. For ambient air at 120°C, the air flow typically enters the housing at approximately 140° in the absence of fins, i.e. heated by approximately 20°C. In the presence of fins, the ambient air initially at 120°C enters the housing at only 125°C typically, i.e. it has been heated by only 5°C. In contact with the fins, the heating of the air circulating near the electronic assembly was therefore significantly limited. The heating of the air entering the crankcase has been reduced by 75%. Such an improvement corresponds to a reduction in the temperature of the air entering the crankcase by 15°C.

Such a cooling circuit 3 provided with fins can be obtained directly by molding, the fins 4 thus being integral with the tube. The manufacturing cost is thus limited.

As a variant, the cooling circuit 3 comprises a plate in which a cavity is provided for the circulation of the cooling fluid 300. As a further variant, the cooling circuit 3 comprising the cavity for the cooling liquid is obtained by molding in a sand core or printing 3D.

The present invention finds applications in particular in the field of electronic assemblies for alternators or reversible machines, but it could also be applied to any type of rotating machine.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the present invention, which would not be departed from by replacing the various elements with any other equivalents.

Claims (10)

X-axis electronic assembly (1) for rotating electric machine
said set comprising

• an electrical system (2)
• a cooling circuit (3) comprising a body (30) forming a housing adapted to allow the circulation of a cooling fluid (300)

the electrical system (2) being mounted on the body (30),
the cooling circuit (3) also comprising fins (4) projecting from the body (30). Electronic assembly (1) according to Claim 1, in which the body (30) extends between the fins (4) and the electrical system. Electronic assembly (1) according to Claim 2, in which the body (30) comprises a plate (31) and at least one tube (32) for the circulation of the cooling fluid (300), the fins (4) extending from the tube (32). Electronic assembly (1) according to Claim 3, in which at least one fin (4) partially surrounds the tube (32) by extending in a plane substantially transverse to a direction of extension of the tube. Electronic assembly (1) according to any one of the preceding claims, in which the fins (4) extend radially with respect to the X axis. Electronic assembly (1) according to Claim 5, in which two adjacent fins (4) are separated by an angle of between 3° and 20° and advantageously between 5° and 10°. Electronic assembly (1) according to any one of the preceding claims, in which the fins (4) extend axially along the X axis. Electronic assembly (1) according to any one of the preceding claims, in which the fins (4) are integral with the body (30). Electronic assembly (1) according to any one of the preceding claims, in which at least one fin (4) has, transversely to its plane of extension, a thickness of between 1mm and 3mm and advantageously between 1.8mm and 2mm. Rotating electric machine comprising
a box (11) comprising at least one flange (17) housing the active parts of the machine
an electronic assembly (1) according to any one of claims 1 to 9 mounted on the flange (17),
the fins (4) being arranged between the electrical system (2) and said flange (17), the fins (4) extending opposite the flange (17).