Device comprising a housing for a C-shaped magnetic core and a cover

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 (1). The device comprises a housing (7) comprising a bottom (8) and a side wall (9) defining a receiving volume (10) in which the C-shaped magnetic core (5) is received, a resin (11) or an adhesive being in the housing (7). The C-shaped magnetic core (5) is at least partially included therein. A cover (12) closes an open face of the housing (7) opposite the bottom (8), the cover (12) comprising a closing plate comprising an inner face opposite the housing (7), and an outer face, the closing plate comprising an elongated orifice crossed by the conduction bar (1).The cover is fixed by adhesion with resin or glue and it comprises at least two pins (16) projecting from the inner face of the closing plate, which extend between the magnetic core in C (5) and the side wall of the housing (7), and which are at least partly included in the resin (11) or glue. figure for the abstract: figure 5.

Description

Title of the invention: Device comprising a housing for a C-shaped magnetic core and a cover 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 solutions making it possible to place a magnetic core in C around such an electrical connection, in order to allow measurement of the current in this connection.

[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] The 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 the supervision and protection of the system. For example, they allow the detection of 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 "magnetic C-core" designates a component made of a material magnetic core that 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, which improves 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] 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.

[0015] Whatever 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.

[0016] Thus, it is known to arrange the magnetic core in C in a housing which can be formed in various ways around a conductive bar.

[0017] The C-shaped magnetic core can be held in position in different ways: it can be glued with a resin, held by an overmolding, or held by a mechanical fixing (clipping, screw, etc.).

[0018] While a resin may provide mechanical protection for the magnetic core, a resin may tend to retain particles that come into contact with it, and in particular metal particles that could disrupt the operation of the magnetic core. Such particles may be generated, for example, when the conductive bar is welded, for example to another conductive bar, close to the magnetic core. The use of a cover to protect the magnetic core and, more generally, the interior of the housing in which it is installed is therefore advisable.

[0019] Document EP2546660 discloses a current sensor system for a three-phase assembly. The system is arranged in a housing closed by a cover. The housing and the cover thus contain three magnetic cores.

[0020] Document EP3086130 relates to an electric current sensor, which comprises a magnetic core positioned in a housing covered by a covering portion. The covering portion is fixed to the housing by snap-fastening, welding or gluing.

[0021] Nevertheless, the known systems can be improved, in particular with regard to the reliability of their fixing and their simplicity of implementation. In particular, the installation and fixing of the cover must advantageously be automated. Statement of the invention

[0022] 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.

[0023] To this end, 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, and a housing comprising a bottom and a side wall defining a receiving volume in which the C-shaped magnetic core is received. A resin or an adhesive is in the housing and the C-shaped magnetic core is at least partially included therein. A cover closes an open face of the housing opposite the bottom, the cover comprising a closing plate comprising an inner face opposite the housing, and an outer face, the closing plate comprising an elongated orifice crossed by the conduction bar.The cover is fixed by adhesion with resin or glue and it has at least two pins projecting from the inner face of the closing plate, which extend between the magnetic core at C and the side wall of the housing, and which are at least partly included in the resin or glue.

[0024] The device thus proposed allows simple and reliable fixing of a cover on a magnetic core housing in C, when the core is included, in whole or in part, in a resin or glue. Since the fixing is achieved by the resin, only precise removal and pressing of the cover on the open face of the housing are necessary to close the housing, which can be automated. The pins located on the inside of the cover ensure reliable fixing of the cover by inclusion in the resin. In addition, these pins being interposed between the magnetic core and the side wall of the housing, they can participate in the centering of the magnetic core in the housing, or at least ensure that the magnetic core is correctly centered. Since the resin is generally not transparent, a visual check of the centering of the core is no longer possible when it is embedded (totally included) in the resin, and these elements allowing to mechanically guarantee a certain quality of the centering are important, because the position of the magnetic core cannot be visually checked after this core has been resinated.

[0025] The cover may comprise at least one hole, distinct from said elongated orifice, formed through the closing plate and allowing air to pass through.

[0026] The cover may have on its inner face a rib facing or in contact with a surface of the magnetic core at C.

[0027] The rib of the hood may be in the resin.

[0028] The inner face may have a higher average roughness than the outer face.

[0029] The hood may include at least one ear projecting beyond the side wall of the housing.

[0030] The hood may, for example, have one or two axes of symmetry.

[0031] Each pawn may have a height, measured perpendicular to the inner face, greater than 3 mm, for example 4 mm.

[0032] Each pawn may have a cross-section.

[0033] Each pawn can have a shape of revolution and a cross-section whose diameter is greater than or equal to 1.5 mm over the entire height of the pin.

[0034] The cover may be made of plastic material.

[0035] The hood may comprise a metal sheet covered with an insulating coating.

[0036] The invention also relates to an assembly comprising three devices as described above, the three housings of which are formed from a single piece.

[0037] In such an assembly, the cover can be configured to close the three housings.

[0038] The invention also relates to a system comprising an inverter, a motor electrical, and an assembly as described above, in which each conductive bar connects a power module of the inverter to a phase of the electric motor.

[0039] The invention finally relates to a motor vehicle comprising such a system and in which the electric motor is configured to provide all or part of the traction. of the vehicle. BRIEF DESCRIPTION OF THE FIGURES

[0040] 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 an assembly conforming to one embodiment of the invention; • [Fig.2] is a schematic view of a hood which can be used in one embodiment of the invention; • [Fig.3] is a three-dimensional schematic view of the cover of [Fig.2]; • [Fig.4] is a side view of the hood of Figures 2 and 3; • [Fig.5] illustrates, in a schematic sectional view, a device in accordance with one embodiment of the invention; • [Fig.6] illustrates, in a three-dimensional schematic view, a system in accordance with one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0041] The present description is given as a non-limiting example of embodiment.

[0042] [Fig. 1] represents an assembly 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 assembly 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.

[0043] 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”).

[0044] This material allows the formation of complex shapes, with very thin thicknesses.

[0045] Alternatively, the cover 12 may be formed from a metal sheet; for example a steel sheet, bearing an insulating coating (e.g. plastic material). This embodiment provides a magnetic shielding effect which can secure the current measurement.

[0046] 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 carried out in the following manner. A magnetic core in C, referenced 5 (and better visible in [Fig.3]), also called C-core 5, is positioned around the conductive bar 1. The C-core 5 allows the magnetic field created by the current passing through the conductive bar to be concentrated. A sensor, generally a Hall effect sensor, is used to measure the current.

[0047] 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.

[0048] 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. The housing 7 is intended to accommodate the C-core 5 and forms a well 6 for receiving the current sensor.

[0049] The housing 7 comprises a base 8 (see [Fig.5]) and a side wall 9. The side wall 9 is substantially perpendicular to the base 8. A receiving volume 10 is thus formed for the C-Core 5, which is surrounded by the side wall 9.

[0050] The C-core 5 is included, at least partially, in a resin 11. The resin generally corresponds to the material generally designated by the English term "potting", which can correspond to a polyurethane, epoxy or silicone resin. We also speak of encapsulation or resination. The C-Core 5 can 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.

[0051] The resin is introduced into the housing 7 in liquid or pasty form, then polymerizes around the magnetic core at C.

[0052] A device according to the present invention comprises a cover 12, which closes the open face of the housing 7 which is opposite the bottom 8. The cover 12 is shown in [Fig.l] detached from the rest of the device,

[0053] The cover 12 comprises a closing plate 13, which is a substantially flat element which is sized to allow the housing 7 to be closed.

[0054] The cover 12 (in particular the closing plate 13) has an outer face 14 and an inner face 15. The notions of “outer” and “inner” are understood with respect to the housing 7, once the cover 12 is in position to close the housing. In other words, the inner face 15 faces the bottom 8 of the housing 7.

[0055] From a structural point of view, and as can be seen in particular in Figures 2, 3 and 4, the hood has the following characteristics, in the embodiment shown.

[0056] The cover comprises pins 16, here two in number, which protrude from the inner face 15. As can be seen in [Fig.5], the pins 16 are included in the resin 11. This inclusion, total or partial, of the pins 16, creates a solid fixing of the cover 12 in the resin 11, and therefore a solid fixing of the cover 12 with respect to the housing 7. In addition, the pins taking up a certain space in the housing 7, the quantity of resin necessary to completely fill the receiving volume 10 is reduced, which reduces the quantity of resin to be polymerized and therefore the polymerization time.

[0057] The pins 16 advantageously have a height (measured perpendicular to the outer face 14, greater than or equal to 3 mm, for example of the order of 4 mm.

[0058] When the pins 16 have a shape of revolution, the smallest diameter of the cross-section of the pin is advantageously greater than or equal to 1.5 mm, for example of the order of 2 mm. The smallest diameter of the pin may in particular be of the order of the thickness of the closing plate 13.

[0059] The pins 16 can have various shapes, and be for example cylindrical or truncated conical. They can have a cross-shaped cross-section, which increases the contact surface with the resin.

[0060] The pins 16 may be solid or hollow, and may have, for example, an annular cross-section.

[0061] The housing 13 may have, simply by way of example, a depth of between 7 and 14 mm, for example of the order of 11 mm. The cover 12 is placed on the open face of the housing 7 while the housing 7 is filled with resin 11 in the liquid state. In order to prevent air bubbles from being trapped in the housing, in particular between the surface of the resin 11 and the cover 12, when the cover is placed in place, the latter comprises at least one hole 17 allowing the passage of air (in addition to an elongated orifice 18 through which the conductive bar 1 passes). The hole(s) 17, by allowing the passage of air, promote the polymerization of the resin. The cover advantageously comprises several holes 17, for example six holes as in the example shown, which are distributed over the surface of the closing plate 13.The holes 17 are small in size, in order to allow air to pass easily without constituting a large opening for the passage of resin or particles towards the resin. Circular holes 17 with a diameter of between 1 mm and 3 mm can for example be used.

[0062] The cover 12 further comprises on its inner face 15 at least one rib 19. The rib 19 is a protrusion on the inner face 15 which, once the cover is in position on the open face of the housing 7, is opposite or in contact with a flat surface of the C-core 5. This rib 19 (or these ribs), can partly take up the geometry of the C-core, and makes it possible to ensure the correct insertion of the C-core 5 into the housing 7. If the C-core were, for example, to lift during the introduction of the resin 11 in liquid form into the housing 7, then the rib 19 would correct the insertion of the C-core 5 when the cover 12 is put into position, to bring the C-core 5 back into a correct position.

[0063] Furthermore, the pins 16 are housed between the C-core 5 and the side wall 9 when the cover 5 is put into position. This can ensure correct centering of the C-core. This centering function generally complements other centering elements, in order to correct any excessive decentering of the C-core 5 when the cover 12 is put into position.

[0064] Generally, the cover 12 is fixed by the resin 11 alone. As explained above, the pins 16 play an important role in this fixing, by being included in the resin 11. Furthermore, the rib 19 can also be in the resin, and participate in the fixing of the cover 12. Finally, the resin can in certain embodiments be in contact with the inner face 15, to which it adheres. In this case, the inner face 15 can have a coarse roughness which helps with the adhesion, that is to say the bonding, of the resin. Typically, the average roughness Ra can be of the order of Ra = 3. The inner face may have been treated by a plasma treatment. The purpose of the plasma treatment is to obtain a high surface tension, which guarantees good adhesion of the resin. A surface tension of around 50mN / m can thus be obtained, compared to 32mN / m with a PPS type plastic cover in the absence of this treatment.

[0065] The cover 12 may also comprise one or more lugs 20. An lug 20 is a protrusion which projects laterally from the general outline of the closure plate 13, so as to project laterally from the side wall 9. The lug(s) 20, which in the example shown are four in number, provide a grip making it possible to check that the cover 12 is properly fixed by carrying out a tear-off test, by applying traction at the level of an lug 20.

[0066] The cover 12 advantageously comprises an axis of symmetry, or even two axes of symmetry. In the example shown, the cover 12 comprises a first axis of symmetry A, in the direction of its length, and a second axis of symmetry B, perpendicular to the axis A.

[0067] A symmetrical part, in particular with two axes of symmetry, is simpler to use with an automaton allowing it to be put into position. Indeed, it can be put into place without worrying about its orientation. More precisely, as long as the inner face 15 is correctly positioned towards the inside of the housing 7, and the cover 12 is correctly centered and aligned, it can be positioned indifferently according to the two possible orientations. Furthermore, the centering and alignment of the cover 12 can be obtained in fact by the introduction of the conductive bar into the elongated orifice 18. For this, the elongated orifice 18 has a shape which corresponds, to within a functional clearance, to the cross section of the conductive bar 1.

[0068] [Fig. 6] shows a system according to one embodiment of the invention. This system comprises an inverter 21, and each conductive bar 1 of the device is connected to a phase of an electric motor. An output conductive bar 22 of a power module 23 of the inverter 21 is connected to the first end 2 of the conductive bar 1.

[0069] The connection to be made is thus in the immediate vicinity of the magnetic core in C present in the housing 7. This connection can advantageously be made by a weld 24. During welding, a very high temperature is generated at the weld. In addition, small metal particles can be projected in particular towards the housing 7. During storage and transport of the parts, they can also come into contact with dust and various particles. This is also the case, more generally, throughout the lifetime (from production to the end of use) of the device. The cover 12 forms effective protection for the contents of the housing 7, i.e. the resin and the magnetic core in C, against these phenomena.

[0070] The present invention thus proposes a device allowing effective protection of a C-shaped core, and ultimately greater reliability of the current measurements carried out thanks to this adapted core and sensor. The cover used to close the housing is fixed very simply, by the resin in which the magnetic C-shaped core is at least partly included. For this, the cover is placed on the open face of the housing while the liquid resin has just been introduced. The fixing is ensured by inclusion in the resin of pins carried by the cover, and, if necessary, adhesion to other parts of the cover. This simple fixing is automatable. The configuration of the cover can allow very simple installation.

[0071] The invention finds a preferential application in the connection between an inverter and an electric traction motor of a motor vehicle.

[0072] Nomenclature: • 1: Conductor bar • 2: First end of a conductive bar • 3: Second end of a conductive bar • 4: Overmolding • 5: Magnetic C-core, also called C-core • 6: Well • 7: Housing • 8: Background • 9: Side wall • 10: Reception volume • 11: Resin • 12: Hood • 13: Closing plate • 14: Exterior face : Inner face : Pawn : Hole : Elongated orifice : Rib : Ear : Inverter : Output conductor bar : Power module : Welding

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 (1), a housing (7) comprising a bottom (8) and a side wall (9) defining a receiving volume (10) in which the C-shaped magnetic core (5) is received, a resin (11) or an adhesive in the housing (7) and in which the C-shaped magnetic core (5) is at least partially included, and a cover (12) closing an open face of the housing (7) opposite the bottom (8), the cover (12) comprising a closing plate (13) comprising an inner face (15) opposite the housing (7), and an outer face (14), the closing plate (13) comprising an elongated orifice (18) crossed by the conduction bar (1),the device being characterized in that the cover (12) is fixed by adhesion with the resin (11) or the glue and in that it comprises at least two pins (16) projecting from the inner face (15) of the closing plate (13), which extend between the magnetic core in C (5) and the side wall (9) of the housing (7), and which are at least partly included in the resin (11) or the glue.,

2. Device according to claim 1, in which the cover (12) comprises at least one hole (17), distinct from said elongated orifice (18), formed through the closing plate (13) and allowing air to pass through.

3. Device according to claim 1 or claim 2, in which the cover (12) comprises on its inner face (15) a rib (19) facing or in contact with a surface of the C-shaped magnetic core (5).

4. A device according to claim 3, wherein the rib (19) is in the resin (11).

5. Device according to one of the preceding claims, in which the inner face (15) has a roughness greater than that of the outer face (14).

6. Device according to one of the preceding claims, in which the cover (12) comprises at least one ear (20) projecting beyond the side wall (9) of the housing (7).

7. Device according to one of the preceding claims, in which the cover (12) has one or two axes of symmetry.

8. Device according to one of the preceding claims, in which each pawn has a height, measured perpendicular to the inner face, greater than 3mm, for example 4mm.

9. Device according to claim 8, in which each pin has a cross-section.

10. Device according to claim 8, in which each pin has a shape of revolution and a cross-section having a diameter greater than or equal to 1.5 mm over the entire height of the pin.

11. Device according to one of the preceding claims, in which the cover (12) is made of plastic material.

12. Device according to one of claims 1 to 9, in which the cover (12) comprises a metal sheet covered with an insulating coating.

13. An assembly comprising three devices according to any one of the preceding claims, in which the three housings (7) are formed from a single piece and in which the cover (12) is configured to close the three housings (7).

14. System comprising an inverter (21), an electric motor, and an assembly according to claim 13, in which each conductive bar (1) connects a power module (23) of the inverter (21) to a phase of the electric motor.

15. Motor vehicle comprising a system according to claim 14, in which the electric motor is configured to provide all or part of the traction of the vehicle.

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