Device comprising a housing receiving a magnetic core in C around a conductive bar

Abstract

The invention relates to a device comprising a C-shaped magnetic core (5), a conductive bar (1), the C-shaped magnetic core (5) being installed around said conductive bar, a part forming a housing (7) comprising a bottom (8) and a side wall (9) defining a volume for receiving the housing (10) in which the C-shaped magnetic core (5) is received, said part forming a well in an air gap (6) of the C-shaped magnetic core (5) adapted to receive a current sensor. The housing (7) comprises elements for centering the C-shaped magnetic core (5) in a transverse plane, parallel to the bottom (8) of the housing. The device comprises in the housing (7) a resin or an adhesive in which the C-shaped magnetic core (5) is at least partly included. The bottom (8) of the housing (7) comprises pads on which the C-shaped magnetic core (5) is supported. The conductive bar (1) passes through the bottom (8) and is in direct contact with the resin or the adhesive.figure for the abstract: figure 1.

Description

Title of the invention: Device comprising a housing receiving a magnetic core in C around a conductive bar TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of electrical connection between an inverter and an electrical machine whose operation is controlled by this inverter.

[0002] It relates more particularly to the means allowing measurement of the current in this electrical connection, and to the assembly of these means.

[0003] The invention is described below in the context of an inverter powering and controlling an electric traction motor in a motor vehicle, which is the preferred application of the invention. The present invention is nevertheless applicable to any assembly comprising an inverter and an electric machine electrically powered by this inverter. STATE OF THE ART

[0004] Electric or hybrid vehicles are generally equipped with one or more inverters making it possible in particular to generate alternating voltages adapted to the operation of an electric traction motor, synchronous or asynchronous, from a direct voltage source, such as an electric battery.

[0005] An inverter comprises power modules, forming a “power stage”, and comprising electronic switches whose openings and closings are controlled appropriately by a control module, in order to supply the phases (for example the three phases) of an electrical machine.

[0006] The electrical connection between an inverter and an electric motor, making it possible to establish an electrical connection between the power stage of the inverter and phases of the electric motor, is generally made using conductive bars, generally designated by the English term "busbars" or by the expression "bus bar".

[0007] These busbars, which correspond to thick conductors, generally made of copper, which are used to transmit electrical power with low resistance and minimal losses, are hereinafter referred to as "conductive bar".

[0008] It is important to be able to measure the current flowing in these conductive bars.

[0009] Current measurements can in particular be used to provide feedback to the inverter, allowing the power outputs to be precisely adjusted and the speed and torque of the electrical machine to be controlled more efficiently. In addition, the current measurements provided are important for system supervision and protection. For example, they can be used to detect overload situations or possible malfunctions of the electrical machine.

[0010] It is known to carry out a measurement of the current in a conductive bar using an assembly comprising a magnetic core in C and a Hall effect sensor.

[0011] The expression "C-shaped magnetic core" designates a component made of a magnetic material which has a "C"-shaped geometry. It is also more simply called "C-core" or, more often, "C-core" according to the English expression commonly used in the field. In the remainder of this document, these expressions are synonymous.

[0012] Thus, to measure the current in a conductive bar, a C-core is used in conjunction with a current sensor, in this case a Hall effect type sensor. The C-core serves to concentrate the magnetic field created by the current flowing through the conductive bar, thereby improving the measurement accuracy. Thanks to the open shape of the magnetic C-core, the current sensor can be installed in the air gap (the open part of the C-core). The C-core protects the sensor from external magnetic interference, improving the reliability and accuracy of the measurements.

[0013] There are different types of C-shaped magnetic cores on the market, which differ in the choice of material from which they are made or their manufacturing process. The C-shaped magnetic core can be laminated or wound. A laminated C-shaped magnetic core consists of multiple layers of insulated magnetic material stacked to form the C-shaped core, while a wound C-shaped magnetic core is made from a single strip of magnetic material to create a continuous magnetic core that is more efficient at high frequencies.

[0014] Depending on the application considered, the C-cores can be held in position in different ways: they can be glued with a resin, held by overmolding, or held by a mechanical fixing (clipping, screws, etc.).

[0015] When the C-shaped magnetic core is of the laminated type, it is possible to hold the layers together mechanically, for example with punches, and / or to carry out a surface treatment on it. When it is of the wound type, it cannot be coated or overmolded, and therefore cannot be protected against corrosion. However, a wound and untreated C-shaped magnetic core makes it possible to obtain the best magnetic characteristics. But these cores, generally made of Iron-Silicon, are very sensitive to corrosion.

[0016] Regardless of the C-shaped magnetic core technology considered, there is generally a need to ensure its mechanical strength, its protection, and its positioning as precisely as possible when it is in place around a conductive bar. Also, the C-shaped magnetic core must be placed as close as possible to the conductive bar.

[0017] For example, document JP2013140140 discloses a substantially annular housing for receiving a C-core. This housing comprises an outer wall and a internal wall, and it includes elements projecting from the external walls of the housing, towards the inside of it. These elements ensure the centering of the C-core in the transverse plane of the housing. The C-core is immobilized there by resin, and the electrically conductive bar passes through the opening formed by the internal wall.

[0018] Nevertheless, the proposed assembly can still be improved, in order to ensure in particular better efficiency of the current sensor and in order to guarantee perfectly repeatable positioning and better protection of the magnetic core in C. Furthermore, the implementation of the magnetic core in C must be simple and industrializable, if possible automatable. Statement of the invention

[0019] The present invention is thus developed in the above context and tends to improve the assembly of a system comprising a C-shaped magnetic core and a conductive bar, in order to carry out a measurement of the current in the conductive bar.

[0020] For this purpose, the invention relates to a device comprising a C-shaped magnetic core, a conductive bar, the C-shaped magnetic core being installed around said conductive bar, a part forming a housing comprising a bottom and a side wall defining a receiving volume of the housing in which the C-shaped magnetic core is received, said part forming a well in an air gap of the C-shaped magnetic core adapted to receive a current sensor. The housing comprises elements for centering the C-shaped magnetic core in a transverse plane, parallel to the bottom of the housing. The device further comprises in the housing a hardened resin or glue in which the C-shaped magnetic core is at least partly included. The bottom of the housing comprises pads on which the C-shaped magnetic core rests. The conductive bar, which passes through the bottom, is in direct contact with the resin or glue.

[0021] The device thus proposed within the framework of the present invention allows the positioning and maintenance of a C-shaped core with respect to a conductive bar, according to a precise and repeatable position with respect to the conductive bar. In particular, the distance separating the outer edge of the conductive bar and the inner edge of the C-core is preferably substantially constant all around said conductive bar and may be between 0.5 mm and 3 mm, and preferably between 1 mm and 2 mm. This makes it possible to avoid early saturation of the C-core at a high current, to better concentrate the magnetic field, and to reduce the volume of the C-core. Indeed, this distance is a compromise between the mechanical considerations according to which it is appropriate to minimize this distance and the electronic considerations according to which it is necessary to leave a sufficient distance to guarantee electrical insulation.The magnetic field created by the current passing through the bar is thus perfectly predictable, and the current measurement which will be carried out using a sensor adapted to this level will be very . precise.

[0022] Furthermore, the studs present on the bottom of the housing, in addition to guaranteeing the position and alignment of the C-core in the depth of the housing, make it possible to guarantee that the liquid resin or glue can circulate in the liquid state all around the C-core. Thanks to this good flow, the risk of air bubbles included in the resin or glue is limited, and the time required for the inclusion of the C-core in the resin or glue is reduced. The resin or glue absorbs thermal deformations (of the conductive bar and the housing) which would impact the quality of the measurement.

[0023] In certain embodiments, the core being totally enclosed, without air, it is effectively protected, in particular from corrosion, by the resin or the glue. This allows, in certain preferred embodiments, to use a wound C-shaped core.

[0024] Furthermore, the conductive bar being in direct contact with the resin or the glue, this means that, the conductive bar passing through the bottom of the housing, the housing does not have a wall surrounding the conductive bar between the conductive bar and the magnetic core in C. This allows greater proximity between the conductive bar and the magnetic core in C. Finally, the current measurement produced by the sensor is repeatable and stable.

[0025] The centering elements may comprise two median walls internal to the housing which form said well, the C-shaped magnetic core comprising two air gap surfaces parallel to each other, each air gap surface being in contact with one of the median walls.

[0026] The device may further comprise a Hall effect sensor, the Hall effect sensor being positioned in the well of the housing, said well being formed between said middle walls.

[0027] The well may have a flared entrance, with entrance walls in the well forming an angle of between 30° and 90°, for example 60°.

[0028] The centering elements may comprise reliefs projecting into the receiving volume of the housing, perpendicular to the bottom, the reliefs being in contact with an interior surface of the C-core.

[0029] The plots can advantageously be three in number.

[0030] The part forming the housing may be made of plastic material, preferably polyphenylene sulfide.

[0031] The part forming the housing may be an overmolding on the conductive bar.

[0032] The magnetic core at C may be a wound type core.

[0033] The device may comprise three conductive bars, three housings and three C-shaped magnetic cores.

[0034] The invention also relates to an assembly comprising an inverter, a motor electric, and a device as described above, in which each conductive bar connects a power module of the inverter to a phase of the electric motor.

[0035] The invention relates to a motor vehicle comprising an assembly as described above, in which the electric motor is configured to provide all or part of the traction of the vehicle. BRIEF DESCRIPTION OF THE FIGURES

[0036] Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the present invention, with reference to the appended drawings, in which: • [Fig.l] is a schematic perspective view of a device according to one embodiment of the invention; • [Fig.2] is a schematic front view of a C-shaped magnetic core housing that can be used in a device according to the present invention; • [Fig.3] is a schematic view of a section of the housing of [Fig.2]; • [Fig.4] is a schematic view of the housing of figures 2 and 3 with a C-shaped magnetic core installed in the housing; • [Fig.5] is a schematic sectional view of the device of [Fig.l]. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present description is given as a non-limiting example of embodiment.

[0038] [Fig. 1] represents a device according to an embodiment of the invention, in the context of a set of conductive bars intended to connect an inverter to an electrical machine. In this case, the set comprises three conductive bars 1. Each conductive bar 1 comprises a first end 2 intended to be connected, for example welded, to an output conductive bar of a power module of an inverter. Each conductive bar 1 also comprises a second end 3, intended to be connected, for example by a screw, to a phase of an electric motor.

[0039] In the example shown here, an overmolding 4 is formed around the conductive bars 1, in particular to hold them in position, protect them, and insulate them. The overmolding 4 can be made of various plastic materials. It can for example be made of polyphenylene sulfide, also designated by the acronym PPS (from the English “polyphenylene sulfide”).

[0040] This material allows the formation of complex shapes, with very thin thicknesses.

[0041] It is important to be able to determine the current flowing in each of the phases of the motor, therefore in each of the conductive bars 1. The measurement of the current is made in the following manner. A magnetic core in C, referenced 5, also called C-core 5, is positioned around the conductive bar 1. According to various embodiments, the shape of C can be completely rounded or can have straight branches, arranged in a “C”. The C-core 5 makes it possible to concentrate the magnetic field created by the current passing through the conductive bar. A sensor, generally a Hall effect sensor, is used to measure the current. The C-core 5 has a general shape of C, as its name indicates. The two ends of the “C” are separated by an air gap 6. The Hall effect sensor is placed in the air gap of the C-core 5, which allows precise and reliable measurement of the current in the conductive bar thus equipped.

[0042] The C-core and the sensor are advantageously positioned at the output of the inverter, that is to say close to the first end 2 of the conductive bar.

[0043] According to the present invention, each C-core is installed in a housing 7. The housing 7 is, in the example shown, formed in a single piece with the overmolding 4.

[0044] The housing 7 is described in more detail with reference to Figures 2, 3 and 4.

[0045] The housing 7 comprises a bottom 8 and a side wall 9. The side wall 9 is sen possibly perpendicular to the bottom 8. A receiving volume 10 is thus formed for the C-Core 5, which is surrounded by the side wall 9. The housing is advantageously configured so that the C-core 5 is received in the housing with a substantially constant clearance J between the external surface 11 of the C-core 5 and the side wall 9 of the housing 7. In the example shown here, and as can be seen in [Fig.4], the side wall 9 nevertheless forms at least one (here two) concavities 12 facilitating the introduction of a liquid resin into the housing 7.

[0046] The C-Core 5 may alternatively be at least partly included in an adhesive, for example a silicone or acrylate adhesive. In the remainder of this description, it is assumed that the C-Core 5 is included, in whole or in part, in a resin, but the description applies, mutatis mutandis, with an adhesive.

[0047] The bottom 8 of the housing 7 comprises studs 13. A stud 13 corresponds to a local protrusion, projecting into the receiving volume 10. The studs can have various shapes. They can be conical, truncated, prismatic, cylindrical, half-sphere, etc.

[0048] The pads thus each form a small, quasi-point-like support surface for the C-core 5. The pads are preferably at least three in number. Three pads form an isostatic support for the C-core in the housing 7. This has several advantages. First of all, the precise orientation of the C-core is better controlled and repeatable with such support on point-like pads, in particular on three pads, than if the support of the C-core in the housing were made plane on plane. In addition, the use of pads as a reference is simpler and more repeatable, during the manufacture of the housing by molding or overmolding, than the use of a large reference surface (which should be perfectly flat and perfectly oriented). Finally, the pads 13 create a space E (visible in [Fig.5]) between the bottom 8 and the magnetic core at C 5.

[0049] This space E allows a liquid resin to circulate between the bottom 8 and the C-core 5. Thus, thanks to the clearance J and the space E, it is possible to completely submerge the C-core 5 in a resin, in order to immobilize and protect it, while limiting the risk of residual air bubbles being present in the resin.

[0050] While the pad 13 guarantees the position of the C-core 5, [Fig.3] illustrates how it is proposed, in the example shown, to ensure the position of the C-core 5 in a transverse plane, parallel to the bottom 8 of the housing 7.

[0051] Centering elements are provided in the housing 7 to serve as a reference and to cooperate mechanically with the C-shaped core 5, and to ensure its positioning (this is called centering) in the transverse plane. In the preferred example shown, the centering means comprise two middle walls 14. The C-core 5 comprises, on either side of its air gap 6, two air gap surfaces 15 which are parallel to each other. Each air gap surface 15 is in contact with a middle wall 14 when the C-core is placed in the housing 7. This guarantees the position of the C-core in the housing in the direction perpendicular to the air gap surfaces 15 and to the middle walls 14.

[0052] Furthermore, reliefs 16 are formed projecting from the bottom 8, and are configured to be in contact with the inner surface 17 of the C-core 5 when the C-core 5 is in place in the housing 7, as shown in [Fig. 4]. The reliefs 16 are in particular configured to ensure the centering of the C-core 5 in the housing in the direction parallel to the air gap surfaces 15 and to the middle walls 14.

[0053] Furthermore, the middle walls 14 form between them a well 18 adapted to receive a Hall effect sensor. The Hall effect sensor can for example be glued into the well. Since the middle walls 14 can be very thin, in particular when the housing is made of PPS or other plastic material with similar properties, the Hall effect sensor is positioned very close to the magnetic core at C.

[0054] In order to facilitate the introduction of the sensor into the well 18, the well 18 may have a flared inlet, for example chamfered. For example, the inlet walls in the well may form an angle [3 of between 30° and 90°, for example 60° or approximately 60°. The term “approximately” is interpreted as designating the corresponding value plus or minus 10%. The current sensor (typically the Hall effect sensor) is generally soldered onto the PCB board, and is relatively long, which leads to certain dispersions in the positioning of its end to be introduced into the well, this angle allows a certain recentering of the sensor. This facilitates the automation of the implementation sensor position in well 18.

[0055] According to another aspect of the present invention, and contrary to what is generally observed in known systems, there is no wall in the housing 7 which surrounds the conductive bar 1 in contact or in the immediate vicinity thereof, that is to say no wall which would be formed around the conductive bar 1 between the latter and the magnetic core in C. This is made possible on the one hand thanks to the very precise centering of the C-core 5, this centering being obtained as described above. In addition, the circulation of a liquid resin being guaranteed around the C-core by the pads 13 and the clearance J, the presence of resin between the conductive bar 1 and the inner surface 17 of the C-core is ensured, which guarantees good insulation between the C-core 5 and the conductive bar 1.In other words, with the possible exception of the area of ​​the well 18 (between the middle walls 14) and the areas which include the reliefs 16, the conductive bar is in direct contact with the resin which fills the housing 7 and in which the magnetic core in C is included, in whole or in part.

[0056] This absence of a wall also makes it possible to obtain a very close proximity between the conductive bar 1 and the magnetic core in C 5, which improves the concentration of the magnetic field formed by the current flowing in the conductive bar. Thanks to this close proximity, the measurement of the current carried out by the Hall effect sensor installed in the well 18 is precise and reliable.

[0057] This is also visible in [Fig. 5], which is a sectional view, at the level of the housings of the device of [Fig. 1], in the plane of the conductive bars 1. The sectional plane AA of [Fig. 5] is also shown in [Fig. 1]. We can see in [Fig. 5], in particular, the space E formed between the bottom 8 and the clearance J allowing the C-core 5 to be embedded in a resin R which completely fills the housing 7. At the level of the opening of the housing 7, a cover 19 can be added, in particular before the resin hardens, in order to close the housing 7. This cover can in particular be glued by the resin R.

[0058] Thus, a device according to the invention can be obtained in the following manner. First of all, the housing 7 is formed. It can advantageously be formed with the overmolding 4 of the conductive bar(s) 1. The conductive bar 1 passes through the bottom 8 of the housing 7. The C-shaped magnetic core 5 is placed in the housing. Its position in depth and its orientation in a plane parallel to the bottom 8 are guaranteed by the support on the pads 13. Its centering is ensured by the contact of the air gap surfaces 15 on the middle walls 14, and by the cooperation between the inner surface 17 of the C-core and the reliefs 16.

[0059] Once the C-core is in position, liquid resin is introduced into the housing 7 through the concavities 12. In particular, one or more delivery nozzles are introduced into the concavity(ies) 12, and fill the housing 7 with liquid resin. The C-core 5 is, in the example shown, completely enclosed in the resin, without any residual air bubbles. The cover 19 is put in place. The resin hardens, which permanently holds and protects the C-core, and insulates it from the busbar. This also fixes the cover 19. Finally, the Hall effect sensor is inserted into the well 18, where it is fixed. It can, for example, be glued.

[0060] The housing configuration proposed in the invention can finally be used on several applications (for example on a range of electric motors) by simply changing the thickness of the magnetic core in C.

[0061] The present invention thus proposes a device allowing precise and automated positioning of a C-shaped magnetic core around a conductive bar, in order to allow precise and reliable measurement of the current with a suitable sensor, in particular a Hall effect sensor. The means developed in the invention which allow the positioning and centering of the C-shaped magnetic core are configured to also allow easy circulation of a liquid resin in the housing, all around the C-shaped core, so that it can be included in the resin without air bubbles and in a short time, which is industrially interesting. The present invention also makes it possible not to provide a wall around the conductive bar, between said conductive bar and the C-shaped magnetic core. This reduces the distance between the conductive bar and the C-shaped magnetic core, which improves the concentration of the magnetic field by the C-shaped core.

[0062] In a device comprising several housings and several C-cores, the dispersions of position and orientation between the C-cores are limited.

[0063] Nomenclature: • 1: Conductor bars • 2: First end of each conductive bar • 3: Second end of each conductive bar • 4: Overmolding • 5: Magnetic C-core, also called C-core • 6: Air gap • 7: Housing • 8: Background • 9: Side wall • 10: Reception volume • 11: External surface of the C-core • 12: Concavity • 13: Plot • 14: Median wall • 15: Air gap surface 16: Relief 17: Inner surface of the C-core 18: Well 19: Hood

Claims

Claims

1. Device comprising: a C-shaped magnetic core (5), a conductive bar (1), the C-shaped magnetic core (5) being installed around said conductive bar, a part forming a housing (7) comprising a bottom (8) and a side wall (9) defining a volume for receiving the housing (10) in which the C-shaped magnetic core (5) is received, said part forming a well (18) in an air gap (6) of the C-shaped magnetic core (5) adapted to receive a current sensor, the housing (7) comprising elements for centering the C-shaped magnetic core (5) in a transverse plane, parallel to the bottom (8) of the housing;the device further comprising in the housing (7) a resin or an adhesive in which the magnetic core in C (5) is at least partly included, the device being characterized in that the bottom (8) of the housing (7) comprises pads (13) on which the magnetic core in C (5) is supported, and in that the conductive bar (1), which passes through the bottom (8), is in direct contact with the resin or the adhesive.;

2. Device according to claim 1, in which the centering elements comprise two median walls (14) internal to the housing (7) and forming said well (18), the C-shaped magnetic core (5) comprising two air gap surfaces (15) parallel to each other, each air gap surface (15) being in contact with one of the median walls (14).

3. A device according to claim 2, further comprising a Hall effect sensor, the Hall effect sensor being positioned in the well (18) of the housing (7), said well (18) being formed between said middle walls (14).

4. Device according to claim 3, in which the well (18) has a flared entrance, entrance walls in the well forming an angle (|3) of between 30° and 90°, for example 60°.

5. Device according to any one of the preceding claims, in which the centering elements comprise reliefs (16) projecting into the receiving volume of the housing (10), perpendicular to the bottom (8), the reliefs (16) being in contact with an interior surface (17) of the C-core.

6. Device according to any one of the preceding claims, in which the pads (13) are three in number.

7. Device according to any one of the preceding claims, in which the part forming the housing (7) is made of plastic material, preferably polyphenylene sulfide.

8. Device according to any one of the preceding claims, in which the part forming the housing (7) is an overmolding (4) on the conductive bar (1).

9. A device according to any preceding claim, wherein the C-shaped magnetic core (5) is a wound-type core.

10. Device according to one of the preceding claims, which comprises three conductive bars (1), three housings (7) and three C-shaped magnetic cores (5).

11. An assembly comprising an inverter, an electric motor, and a device according to claim 10, in which each conductive bar (1) connects a power module of the inverter to a phase of the electric motor.

12. A motor vehicle comprising an assembly according to claim 11, in which the electric motor is configured to provide all or part of the traction of the vehicle.

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