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

Abstract

The invention relates to a device comprising a magnetic core C (5), a conductive bar (1), the magnetic core C (5) being installed around said conductive bar, a part forming a housing (7) having a base (8) and a side wall (9) defining a receiving volume for the housing (10) in which the magnetic core C (5) is received, said part forming a well in an air gap (6) of the magnetic core C (5) adapted to receive a current sensor. The housing (7) has centering elements for the magnetic core C (5) in a transverse plane parallel to the base (8) of the housing. The device includes within the housing (7) a resin or an adhesive in which the magnetic core C (5) is at least partially embedded. The base (8) of the housing (7) has pads on which the magnetic core C (5) rests. The conductive bar (1) passes through the base (8) and is in direct contact with the resin or adhesive.Figure for the abbreviation: 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 enabling a 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 electrical machine powered by that inverter. STATE OF THE ART

[0004] Electric or hybrid vehicles are generally equipped with one or more inverters which allow, in particular, the generation of 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 appropriately controlled 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, allowing an electrical connection to be established between the power stage of the inverter and the phases of the electric motor, is generally made using conductive bars, generally referred to by the English term "busbars" or by the expression "bus bar".

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

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

[0009] Current measurements can be used, in particular, to provide feedback to the inverter, allowing for precise adjustment of the power outputs and more effective control of the speed and torque of the electric machine. Furthermore, the current measurements provided are important for system monitoring and protection. They allow, for example, the detection of overload situations or possible malfunctions of the electrical machine.

[0010] It is known to perform 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 term "C-core" refers to a component made of a magnetic material that has a "C"-shaped geometry. It is also more simply called a "C-core" or, more often, "C-core," according to the English expression commonly used in the field. In the remainder of this document, these terms 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 sensor. The C-core serves to concentrate the magnetic field created by the current flowing through the conductive bar, thereby improving the accuracy of the measurement. 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 against external magnetic interference, improving the reliability and accuracy of the measurements.

[0013] Various types of C-shaped magnetic cores are available on the market, differing in the material used in their construction or their manufacturing process. In particular, a C-shaped magnetic core can be laminated or wound. A laminated C-shaped magnetic core consists of multiple layers of an insulated magnetic material stacked to form the C-shape of the 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 an overmolding, or held by a mechanical fixing (clip, screw, etc.).

[0015] When the magnetic core in C is of the laminated type, it is possible to hold the layers together mechanically, for example with punches, and / or to apply a surface treatment. 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 magnetic core in C provides the best magnetic characteristics. But these cores, generally made of iron-silicon, are very susceptible to corrosion.

[0016] Regardless of the magnetic core technology used, there is generally a need to ensure its mechanical strength, protection, and the most precise positioning possible when it is in place around a conductive bar. Therefore, the magnetic core must be positioned 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 The internal wall has protruding elements extending from the external walls of the housing towards its interior. These elements ensure the centering of the C-core in the transverse plane of the housing. The C-core is held in place by resin, and the electrical conductor bar passes through the opening formed by the internal wall.

[0018] Nevertheless, the proposed assembly can still be improved, in particular to ensure better efficiency of the current sensor and 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. Description 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 magnetic core in C and a conducting bar, in order to carry out a measurement of the current in the conducting bar.

[0020] To this end, the invention relates to a device comprising a magnetic core C, a conductive bar, the magnetic core C being installed around said conductive bar, a part forming a housing having a base and a side wall defining a receiving volume for the housing in which the magnetic core C is received, said part forming a well in an air gap of the magnetic core C adapted to receive a current sensor. The housing includes centering elements for the magnetic core C in a transverse plane parallel to the base of the housing. The device further includes within the housing a hardened resin or adhesive in which the magnetic core C is at least partially embedded. The base of the housing includes pads on which the magnetic core C rests. The conductive bar, which passes through the base, is in direct contact with the resin or adhesive.

[0021] The device thus proposed within the framework of the present invention allows for the placement and maintenance of a C-shaped core relative to a conductive bar, in 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 around the entire circumference of said conductive bar and can be between 0.5 mm and 3 mm, and preferably between 1 mm and 2 mm. This makes it possible to avoid premature 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 mechanical considerations, according to which this distance should be minimized, and electronic considerations, according to which a sufficient distance must be left 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 accurate. precise.

[0022] Furthermore, the lugs on the bottom of the housing, in addition to ensuring the position and alignment of the C-core within the housing, guarantee that the liquid resin or adhesive can circulate in a liquid state all around the C-core. Thanks to this efficient flow, the risk of air bubbles being trapped in the resin or adhesive is limited, and the time required for the C-core to be embedded in the resin or adhesive is reduced. The resin or adhesive absorbs thermal deformations (of the conductive bar and the housing) that would otherwise affect the measurement quality.

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

[0024] Furthermore, since the conductive bar is in direct contact with the resin or glue, this means that, with 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 for 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 include two internal median walls of the housing which form said well, the magnetic core in C having two parallel air gap surfaces, each air gap surface being in contact with one of the median walls.

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

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

[0028] The centering elements may include protruding reliefs in 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 may advantageously be three in number.

[0030] The part forming the housing can be made of plastic material, preferably phenylene polysulfide.

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

[0032] The magnetic core in C can be a wound-type core.

[0033] The device may include three conductive bars, three housings and three magnetic cores in C.

[0034] The invention also relates to an assembly comprising an inverter, a motor electric, and a device such 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, purposes and particular features of the present invention will become apparent from the following non-limiting description of at least one particular embodiment of the devices and methods of the present invention, with reference to the accompanying drawings, in which: • Fig. 1 is a schematic perspective view of a device conforming to an 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 in [Fig.2]; • [Fig. 4] is a schematic view of the housing in Figures 2 and 3 with a magnetic core in C installed in the housing; • [Fig.5] is a schematic cross-sectional view of the device in [Fig.1]. DETAILED DESCRIPTION OF THE INVENTION

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

[0038] Figure 1 shows a device according to an embodiment of the invention, within 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 has a first end 2 intended to be connected, for example by welding, to an output conductive bar of a power module of an inverter. Each conductive bar 1 also has 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, notably to hold them in position, protect them, and insulate them. The overmolding 4 can be made of various plastic materials. For example, it can be made of polyphenylene sulfide, also known 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 phase of the motor, therefore in each of the conductive bars 1. The current measurement is implemented as follows. A magnetic core in the shape of a C, referenced as 5, also called C-core 5, is positioned around the conductive bar 1. In various embodiments, the C-core can be completely rounded or may have straight arms arranged in a "C" shape. The C-core 5 concentrates the magnetic field created by the current flowing through the conductive bar. A sensor, usually a Hall effect sensor, is used to measure the current. The C-core 5 has a general C-shape, 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 for a 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 near 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 one piece with the overmolding 4.

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

[0045] The housing 7 comprises a base 8 and a side wall 9. The side wall 9 is sen 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) concavity 12 facilitating the introduction of a liquid resin into the housing 7.

[0046] The C-Core 5 can alternatively be at least partially embedded 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 embedded, in whole or in part, in a resin, but the description applies, mutatis mutandis, to an adhesive.

[0047] The base 8 of the housing 7 has 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, frustoconical, prismatic, cylindrical, hemispherical, etc.

[0048] The pads thus each form a small, almost point-like bearing surface for the C-core 5. Preferably, there are at least three pads. Three pads provide isostatic support for the C-core in the housing 7. This offers several advantages. First, the precise orientation of the C-core is better controlled and repeatable with such support on point pads, particularly on three pads, than if the C-core were supported in the housing on a plane-by-plane basis. Furthermore, using pads as a reference is simpler and more repeatable during the manufacturing of the housing by molding or overmolding, using a large reference surface (which should be perfectly flat and perfectly oriented). Finally, the studs 13 create a space E (visible in [Fig. 5]) between the base 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 immerse the C-core 5 in a resin, in order to immobilize and protect it, limiting the risk of residual air bubbles being present in the resin.

[0050] While the plot 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 (referred to as centering) in the transverse plane. In the preferred example shown, the centering means comprise two median walls 14. The C-core 5 has, on either side of its air gap 6, two parallel air gap surfaces 15. Each air gap surface 15 is in contact with a median wall 14 when the C-core is placed in the housing 7. This ensures the position of the C-core in the housing in the direction perpendicular to the air gap surfaces 15 and the median 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 specifically configured to ensure the centering of the C-core 5 in the housing in the direction parallel to the gap surfaces 15 and the median walls 14.

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

[0054] To facilitate the insertion of the sensor into well 18, well 18 may have a flared, for example chamfered, inlet. For example, the inlet walls of the well may form an angle [3] between 30° and 90°, for example 60° or approximately 60°. The term "approximately" is interpreted as denoting the corresponding value plus or minus 10%. The current sensor (typically the Hall effect sensor) is generally soldered onto the PCB and is relatively long, which leads to some variation in the positioning of its end to be inserted into the well; this angle allows for some recentering of the sensor. This facilitates the automation of the setup. sensor placement 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 surrounding the conductive bar 1 in contact with it or in its immediate vicinity, that is to say, no wall formed around the conductive bar 1 between it and the magnetic core C. This is made possible, on the one hand, by the very precise centering of the C-core 5, this centering being achieved as described above. Furthermore, since the circulation of a liquid resin is ensured around the C-core by the pads 13 and the gap 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 well area 18 (between the median walls 14) and the areas which have 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 allows for very close proximity between the conductive bar 1 and the magnetic core at 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 current measurement performed by the Hall effect sensor installed in well 18 is precise and reliable.

[0057] This is also visible in [Fig. 5], which is a cross-sectional view of the housings of the device in [Fig. 1], in the plane of the conductor bars 1. The sectional plane AA of [Fig. 5] is also shown in [Fig. 1]. In [Fig. 5], one can see, in particular, the space E formed between the base 8 and the gap J, which allows the C-core 5 to be embedded in a resin R that completely fills the housing 7. A cover 19 can be attached to the opening of the housing 7, particularly before the resin hardens, in order to close the housing 7. This cover can, in particular, be bonded with the resin R.

[0058] Thus, a device according to the invention can be obtained in the following manner. First, the housing 7 is formed. It can advantageously be formed by overmolding 4 of the conductive bar(s) 1. The conductive bar 1 passes through the bottom 8 of the housing 7. The magnetic core C 5 is placed in the housing. Its depth and orientation in a plane parallel to the bottom 8 are ensured by the support on the pads 13. Its centering is ensured by the contact of the air gap surfaces 15 on the median walls 14, and by the interaction between the inner surface 17 of the C-core and the raised features 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 or concavities 12, and fill the housing 7 with liquid resin. In the example shown, the C-core 5 is completely embedded in the resin, without any residual air bubbles. The cover 19 is then put in place. The resin hardens, permanently securing and protecting the C-core and isolating it from the conductive bar. This also secures the cover 19. Finally, the Hall effect sensor is inserted into the well 18, where it is fixed. It can, for example, be glued in place.

[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 for the precise and automated placement of a C-shaped magnetic core around a conductive bar, in order to enable accurate and reliable current measurement with a suitable sensor, in particular a Hall effect sensor. The means developed in the invention that allow the positioning and centering of the C-shaped magnetic core are configured to also allow easy circulation of a liquid resin within the housing, all around the C-shaped core, so that it can be embedded in the resin without air bubbles and in a short time, which is industrially advantageous. The present invention also eliminates the need for 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, thereby improving the concentration of the magnetic field by the C-shaped core.

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

[0063] Nomenclature: • 1: Conductive bars • 2: First end of each conductor bar • 3: Second end of each conductor bar • 4: Overmolding • 5: Magnetic C-core • 6: Interference • 7: Accommodation • 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 area 16: Relief 17: Interior surface of the C-core 18: Well 19: Hood

Claims

Demands

1. Device comprising: a magnetic core in C (5), a conductive bar (1), the magnetic core in C (5) being installed around said conductive bar, a part forming a housing (7) having a bottom (8) and a side wall (9) defining a receiving volume of the housing (10) in which the magnetic core in C (5) is received, said part forming a well (18) in an air gap (6) of the magnetic core in C (5) adapted to receive a current sensor, the housing (7) having centering elements of the magnetic core in C (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 C (5) is at least partially included, the device being characterized in that the bottom (8) of the housing (7) has studs (13) on which the magnetic core C (5) rests, 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, wherein the centering elements comprise two median walls (14) internal to the housing (7) and forming said well (18), the magnetic core in C (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. 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 median walls (14).

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

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

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

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

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

9. Device according to any one of the preceding claims, wherein the magnetic core at C (5) is a wound-type core.

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

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

12. Motor vehicle comprising an assembly according to claim 11, wherein the electric motor is configured to provide all or part of the vehicle's traction.

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