EP3991275A1

EP3991275A1 - Plastic bearing for a rotating electric machine

Info

Publication number: EP3991275A1
Application number: EP20734420.1A
Authority: EP
Inventors: Pierre Faverolle; Khadija El Baraka; Svetislav JUGOVIC; Othmane OUAZZANI JAMIL
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2019-06-27
Filing date: 2020-06-29
Publication date: 2022-05-04
Also published as: US20220352784A1; CN114026771A; KR20220025740A; FR3098049A1; FR3098049B1; WO2020260715A1

Abstract

The invention relates to a bearing for a rotating electric machine, comprising a plastic body and at least one electrical conductor that is non-removably attached to the plastic body.

Description

Title of the invention: Plastic bearing for machine

rotating electric

[1] The present invention relates to a plastic bearing for an electric machine

rotating.

[2] In a manner known per se, rotating electrical machines comprise a stator and a rotor secured to a shaft. The rotor may be integral with a driving and / or driven shaft and may belong to a rotating electric machine in the form of an alternator, an electric motor, or a reversible machine capable of operating in both modes.

[3] The stator is mounted in a housing configured to rotate the shaft on bearings by means of bearings. The rotor comprises a body formed by a stack of metal sheets held in the form of a bundle by means of a suitable fixing system. The rotor has poles formed for example by permanent magnets housed in cavities formed in the magnetic mass of the rotor. Alternatively, in a so-called “salient” pole architecture, the poles are formed by coils wound around the arms of the rotor. Alternatively, the rotor will be formed of two pole wheels comprising claws.

[4] Furthermore, the stator comprises a body consisting of a stack of sheets

thin forming a crown, the inner face of which is provided with notches open inwards to receive phase windings. These windings pass through the notches in the body of the stator and form buns projecting on either side of the body of the stator. The phase windings are obtained for example from a continuous wire of round or square section covered with enamel or from conductive elements in the form of pins connected together by welding.

[5] The constraints, in particular imposed by the antipollution standards, require limiting the mass in particular of the machine on the vehicle. But such machines are heavy, in particular due to the metal mass of the housing bearings.

[6] The machine housing supports a number of functional devices.

One of the functional devices is the interconnector, that is to say the part ensuring the connection between the phase windings of the stator of the machine and a power electronics. The casing also supports a certain number of sensors such as for example the temperature or position sensor.

[7] Document FR3065338 describes for example the integration of a position sensor on the front bearing.

[8] The installation of these devices on the housing requires additional assembly steps in particular, which involves a cost.

[9] According to the invention, the bearing for a rotary electrical machine comprises a plastic body and at least one electrical conductor non-removable attached to the plastic body.

[10] Thanks to the invention, the obtained plastic bearing is lighter, which reduces the overall mass of the machine. Furthermore, such a bearing in which the various functions are for example molded directly during the molding of the body of the bearing is less expensive to manufacture. The manufacturing process is particularly simplified since the number of manufacturing steps is limited.

[1 1] According to other characteristics taken alone or in combination:

- the electrical conductor is a trace at least partially molded in the bearing;

- the electrical conductor is a trace on the surface of the bearing;

- the trace is intended to connect at least a first winding end with a terminal for connection to the power electronics of the machine or two second winding ends between them, or a first point connected to an element which is at the potential of the ground of the control electronics at a second point connected to an element which is at the potential of the ground of the engine control;

In this case, the neutral bar of the stator winding is directly integrated into the body of the bearing, which makes it possible in particular to strengthen the mechanical strength of the the neutral bar, to simplify the manufacturing process, and to ensure good electrical insulation.

- the trace is intended to connect a first winding end with a connection pad to the power electronics of the machine or two second winding ends between them, the body comprising a molded wall surrounding the at least one connection;

- the body also includes a probe of a device for detecting

current positioned next to at least one trace.

The term “opposite” will be understood to mean that the probe is close to the trace at a distance allowing a measurement by Hall effect of the current flowing in the trace. The distance between the probe and the trace will typically be of the order of 1 5mm.

- the body includes a probe of a thermal unit;

- the body also includes at least one probe of a rotor position sensor;

- at least one guide channel suitable for guiding at least one electrical connector is molded in the body of the bearing.

[12] The invention also relates to a rotating electrical machine comprising a polyphase stator surrounding a rotor mounted on a shaft extending along an axis X corresponding to the axis of rotation of the rotor and at least one bearing comprising a bearing housing for rotational mounting of the shaft, and such a bearing.

[13] The invention will be better understood from reading the following description and examining the accompanying figures. These figures are given only by way of illustration but in no way limit the invention.

[14] Brief description of the drawings:

[15] [Figure 1] is a longitudinal sectional view of a rotary electrical machine according to the present invention;

[16] [Figure 2] is a perspective view of the machine showing the interface box on the bearing surface;

[17] [Figure 3] is a perspective view of a machine bearing

including traces; [18] [Figure 4] is a perspective view of a bearing comprising a probe of a current sensing device;

[19] [Figure 5a] is a sectional view of part of the machine equipped with a thermal detection unit;

[20] [Figure 5b] is a perspective view of the thermal unit of

detection fitted to the machine;

[21] [Figure 6a] is a top view of a bearing equipped with a

rotor position;

[22] [Figure 6b] is a perspective view of part of the bearing bearing the

position sensor.

[23] Identical, similar or analogous elements keep the same

reference from one figure to another.

[24] In the remainder of the description, a "front" element means an element located on the drive side and a "rear" element means an element located on the opposite side.

[25] The description will be given in the case of a machine architecture where the front and rear bearings are plastic bearings, each bearing incorporating certain functions.

[26] Figure 1 shows a rotating electrical machine 10 comprising a polyphase stator 11 surrounding a rotor 14 mounted on a shaft 13 extending along an axis X corresponding to the axis of rotation of the rotor 14.

[27] In the remainder of the description, the axial, radial,

exterior and interior refer to the X axis passing through the shaft 13 at its center. The axial direction corresponds to the X axis while the radial orientations correspond to concurrent planes, and in particular perpendicular, to the X axis. the radial directions, the exterior or interior denominations are assessed with respect to the same X axis, the interior denomination

corresponding to an element oriented towards the axis, or closer to the axis with respect to a second element, the external name designating a

distance from the axis. [28] The stator 11 surrounds the rotor 14 with the presence of an air gap between the inner periphery of the stator and the outer periphery of the rotor 14. The stator 1 1 is mounted in a housing provided with a front bearing 17 and a rear bearing 18, the two bearings each being arranged at an axial end of the stator.

[29] The bearings 17, 18 are assembled together by means of screws called tie rods intended to cooperate with threaded holes made in projecting lugs of the bearings 17, 18 so that the stator is mounted tight between the two bearings 17, 18 .

[30] At least one of the two bearings 17 is plastic. The other bearing 18 is for example metallic, for example aluminum. Alternatively, the other bearing 18 is also made of plastic. Each bearing 17, 18 is easily obtained by molding. In the remainder of the description, the two bearings will be considered to be made of plastic.

[31] Each bearing comprises a body formed by a transverse flange 171, 181 and by a skirt 172, 182. The transverse flange 171, 181 extends in a plane perpendicular to the axis X1 of the bearing intended to be merged with the X axis of the machine. The annular skirt 172, 182 comes from the outer periphery of the flange and has an axial orientation with respect to the axis X1. At least one of the bearings has a bearing housing 15 for guiding the shaft in rotation.

[32] This electric machine 10 may for example be intended to be

coupled to a gearbox belonging to a motor vehicle traction chain. The electric machine 10 is able to operate in an alternator mode in order in particular to supply energy to the battery and to the on-board network of the vehicle, and in an engine mode, not only for starting the thermal engine of the vehicle, but also to participate in the traction of the vehicle alone or in combination with the heat engine. The power of the machine 10 may be between 10kW and 50kW.

Alternatively, the electric machine 10 could be installed on an axle of the motor vehicle, in particular a rear axle.

[33] More precisely, the rotor 14 comprises a body in the form of a bundle of sheets. Permanent magnets are implanted in cavities in the body. In the example shown, the magnets are implanted in a V-shaped configuration. Alternatively, the magnets are implanted radially inside the cavities, the opposite sides of two adjacent magnets being of the same polarity. This is then a flow concentration configuration. The magnets may be of rare earth or ferrite depending on the applications and the desired power of the machine 10.

[34] Furthermore, the stator comprises a body consisting of a bundle of sheets and a coil 24. The body is formed by a stack of sheets of sheets independent of each other and held in the form of a package by means of a suitable fixing system. The body is provided with teeth defining two by two notches for mounting the stator winding.

[35] The coil 24 comprises a set of phase windings passing through the notches and forming buns 25 and extending projecting on either side of the stator body 1 1. The phase windings are obtained here from conductive elements in the form of pins, the ends of which are interconnected for example by welding. Alternatively, the phase windings could be obtained from one or more continuous wires.

[36] The phase windings may have, for example, a three-phase or double three-phase star or delta configuration. These windings are intended to be connected to the power part of the electronic module. The electronic module comprises the power part with the power bridge integrating power elements, such as MOSFET type transistors, as well as an electronic control circuit for several detectors.

[37] As illustrated in Figure 2, an interface box 40 intended to be connected to the electronic module is secured to the surface of the front bearing 17. The box 40 comprises pads 41 of conductive material molded by their base in the bearing plastic. A wall 42 surrounding the studs advantageously extends from the surface of the bearing transversely to the surface of the bearing. The wall, for example, is made integral with the plastic bearing. The wall 42 allows the cooperation of the box 40 with the connection box of the electronic module and ensures the seal. [38] As illustrated in Figure 3, conductors 43 connect in particular first ends 240 of said coil 24 to the connection pads 41 of the interface box 40. The conductors 43 are fixed in a non-removable manner to the plastic bearing.

[39] The conductors 43 are advantageously traces at least partially molded in the bearing. As a variant, the conductors are traces obtained by painting or plastronics on the surface of the plastic bearing. The traces made by plastronics will be in particular the traces making it possible to connect masses between them, and therefore in which a weak current circulates. A first winding end 240 is for example welded to a trace.

[40] As a variant, the first end of the winding 240 is screwed to the track. The trace 43 is also advantageously welded to the stud 41.

[41] As can be seen in Figure 3, the traces 43 therefore make it possible to ensure an electrical connection of each phase output with a pad 41 adapted to connect it to the aforementioned power electronic module, and neutral outputs between they. In the three-phase case, three traces 43 therefore connect

respectively each of the first coil ends corresponding to a phase 240, with one pad 41 per phase. Other traces 44 also make it possible to establish the electrical connections of the second coil ends 241 corresponding to the neutral outputs between them. In the three-phase case, two other traces 44 make it possible to establish the electrical connections of the second coil ends 241 between them.

[42] Openings 45 are provided in particular in the transverse flange of the front bearing 171 in order to bring out the stator winding ends to be connected to the traces 43, 44. An opening 45 allows for example to bring out the two winding ends 240, 241 of a phase and neutral

corresponding in the case of a star coupling.

[43] As illustrated in Figure 2, the opening 45 is for example surrounded by a wall 46 adapted to protect the ends of the son coming out of this opening, thus forming a housing 47. The wall 46 is for example integral. with the transverse flange of the plastic bearing, that is to say that the wall 46 is formed integrally with the flange. The walls are advantageously directly molded during the molding of the bearing.

[44] In the case of an oil-cooled machine in particular, the uninsulated winding ends must be protected against the ingress of oil. In this case, the housings 47 are advantageously filled with resin in order to protect the winding ends. As a variant, a single opening 45 can be provided for all the winding outlets of a three-phase system for example, the wall 46 surrounding this opening and resin which can be used to fill the housing thus formed so as to protect the winding ends. . As a variant, each housing thus formed by the wall may be closed by a cover, mounted in a sealed manner on said wall 46.

[45] Traces may also be provided to interconnect a first point connected to an element which is at the ground potential of the control electronics to a second point connected to an element which is at the ground potential of the engine control. The ground potential of the control electronics is recovered at one of the phase pads 41 of the interface box. The ground potential of the engine control is recovered at the level of fixing holes 190 of the crankcase to the vehicle. The mass is for example in this case that of the 12V.

[46] The bearing 17 comprises a probe 51 of a current detection device 50, illustrated in FIG. 4, allowing a measurement of a current flowing in the power trace. The probe is therefore at least partially molded in the body of the plastic bearing. The probe 51 is for example a magnetic field probe. The magnetic field probe may be a Hall effect probe which has the advantage of being compact, consuming little power, and providing a signal that is insensitive to noise. In the embodiment of FIG. 4, the probe 51 is mounted opposite the power trace. More precisely, the probe is positioned opposite a portion of the trace.

[47] As can be clearly seen in FIGS. 4, a ferromagnetic shield 52 makes it possible to reduce the magnetic disturbances liable to influence the measurement made by the probe. The ferromagnetic shield 52 is formed by a U-shaped part having a bottom wall 521 from which two end walls 522 issue. The bottom wall 521 has a face in contact with the face of the trace opposite to that carrying the probe 51. The walls d 'end 522 extend on either side of the probe 51. The end walls 522 extend substantially perpendicular to the bottom 521 and to the portion of the trace carrying the probe. The width of the U of the shield 52

corresponding to the distance between the end walls 522 is substantially equal to the width of the power trace.

[48] The probe 51 is associated with a connector 53 provided with a plurality of connection pins. Two of the pins are intended for supplying the probe 51, and at least one pin is intended for transporting a signal relating to the measurement performed by the probe.

[49] The probe 51 and the connector 53 are mounted on an integrated circuit 54 which is pressed against the portion of the power trace. The integrated circuit can be rigid or flexible. The connector 53 is connected to the control electronics control unit, via a connection cable as illustrated in FIG. 4. As a variant, the connector is connected to the control electronics, for example by overmolded tracks ( not shown).

[50] As illustrated in Figure 4, trace 43 as well as at least part of the

shield 52 and the integrated circuit 54 are overmolded in the plastic bearing, delimiting a cavity in which the probe 51 is located. In order to avoid the

penetration of dust, liquid, or other dirt in the measurement zone, the cavity is hermetically closed by a cover. As a variant, the cavity is filled with a resin-type material.

[51] Furthermore, in order to protect the electrical machine in the event of overheating, this machine is fitted with a thermal detection unit 70, illustrated in FIG. 5a. This unit is intended to be connected via at least one conductor 73 to a thermal protection circuit (not shown) configured to reduce or cut off the power supply to the machine upon detection of overheating.

[52] More specifically, a temperature sensor 71 (visible in particular in FIG. 5b) is used which is integral with an elastic support 72 for fixing to the front bearing 17 of the rotary electrical machine. The temperature probe 71 will in particular be a thermistor encapsulated in glass. The fixing support 72 will in particular be a flexible portion such as a compressible sheath. The sheath will for example be a silicone sheath. As a variant, it will be a rubber or resin sheath with elastic properties. The probe 71 opens at both ends of the sheath.

[53] Part of the sheath is overmolded in the front plastic bearing 17, so that the two ends of the probe emerge on either side of the wall of the plastic bearing. In one embodiment, the elastic sheath is pre-molded around the periphery of an opening in the bearing and then the temperature probe is inserted into the sheath. As a variant, the probe is integrated beforehand in the compressible sheath then the whole is molded in the bearing.

[54] The conductors 73, for example wires, connected to the end of the probe 71 are guided along the surface of the front bearing 17. In a preferred embodiment, connection tabs 74 allow the wires to be connected. to the thermal protection circuit. The conductive tabs 74 are for example traces on the surface of the front bearing 17. The ends of the wires are connected to the conductive tabs 74, in particular by soldering. Resin is advantageously used to cover the junction between the conductive tabs 74 and the wires 73, to prevent them from being damaged.

[55] The sheath 72 protrudes towards the winding chignon 25, and is intended to come into local contact with the relevant chignon 25 of the stator winding. The sheath is made of a material resistant to the heat transmitted by the bun 25 of the winding. It ensures a large thermal transfer between the probe 71 and the bun 25 concerned of the winding. This sheath is electrically insulating. The internal face of this sheath has a larger area of contact with the chignon than that of direct contact between the probe 71 and the chignon 25 as visible in FIG. 5b. The sheath provides sealing and electrical insulation of the probe 71 and of the end of the connector (s) 73, which can be stripped. The probe 71 is in contact with the winding chignon 25 by the spring effect of the support 72.

[56] Alternatively, in the case where the plastic material is not electrically

conductive, the probe can be partially molded directly into the bearing plastic, in particular for measuring the ambient temperature of the machine. In this case, the probe is not encapsulated in a conductive sheath. The probe extends between two ends, the side wall of the probe being molded into the plastic bearing, the probe therefore opening out on either side of the transverse flange of the plastic bearing.

[57] As illustrated in Figure 6a, the rear bearing 18 also comprises

including probes 61 of a rotor position sensor 60. The position sensor detects in particular the angular position of the rotor. The position sensor is in particular of the axial reading type.

[58] This sensor 60, visible in FIG. 6b, comprises a target washer 65 mounted around the shaft 13. The washer 65 extends in a plane perpendicular to the axis of rotation X of the rotor.

[59] The magnetic field measurement probes 61 are arranged to provide a measurement of the magnetic field generated by the target washer 65 along the direction of the axis of rotation X of the rotor. In this case, three probes are used

61 angularly offset from each other on a regular basis. The probes 61 are advantageously Hall effect type probes. As a variant, the probes 61 are eddy current probes.

[60] The magnetic field measurement probes 61 are mounted on the surface of a printed circuit 62, as shown in FIG. 6b. The printed circuit 62 is mounted on a support 63. The support 63, for example of plastic, is integral with the stator 1 1 so that the probes 61 are opposite the target washer 65.

[61] The probes 61 are connected to a control unit for the control electronics, for example by wire connectors 65 going from the printed circuit

62 towards electronics. The support 63 on which the printed circuit 62 is mounted is molded into the plastic bearing 18 so that the probes 61 are released facing the washer, the wire connectors 65 emerging from the bearing to the electronics. As a variant, the connectors 65 to the control electronics are partly molded tracks in the bearing (not shown).

[62] Thus, in operation, the rotation of the rotor causes the magnetic field received by the various probes 61 to vary. These probes 61 transmit to the control unit electrical signals which are a function of the field levels. magnetic receipts. The control unit processes these signals to deduce the speed as well as the position of the rotor.

[63] The integration of the position sensor 60 in the rear plastic bearing 18 makes it possible to reduce the number of parts, to improve and simplify the fixing of said position sensor on the machine and allows the non-rotation of the sensor during all thermal variations.

[64] In a preferred embodiment, the transverse flange of the rear bearing 181 may in particular include at least one guide channel 64 adapted to guide at least one electrical connector 65 connecting the probes 61 to the control unit, as illustrated in figure 6a. The guide channel 64 is for example delimited by two beads of plastic material molded during the molding of the bearing at the level of the transverse flange 181 and potentially extending onto the annular skirt 182 for guiding.

[65] Of course, the above description has been given by way of example.

only and does not limit the field of the invention from which one would not depart by replacing the various elements with any other equivalent.

[66] In addition, the different characteristics, variants, and / or forms of

embodiments of the present invention may be associated with each other in various combinations, as long as they are not incompatible or mutually exclusive.

[67] This description could in particular be applied to a machine of the claw rotor type in which, for example, the pinion will be replaced by a pulley.

Claims

1. Bearing (17, 18) for a rotary electrical machine comprising a body (170, 180) of plastic material and at least one electrical conductor fixed in a non-removable manner to the plastic body (170, 180).

2. Bearing according to claim 1 wherein the electrical conductor is a trace at least partially molded in the bearing (17, 18).

3. Bearing according to claim 1 wherein the electrical conductor is a trace on the surface of the bearing (17, 18).

4. Bearing according to any one of claims 2 to 3 wherein the trace (43, 44, 80) is intended to connect:

- at least one first winding end (240) with a terminal for connection to the power electronics of the machine (41) or two second winding ends (241) between them,

- or a first point connected to an element which is at the potential of the ground of the control electronics to a second point connected to an element which is at the potential of the ground of the engine control.

5. Bearing according to claim 4 wherein the trace is intended to connect a first winding end (240) with a connection pad to the power electronics (41) of the machine or two second winding ends (241) between them, the body (170, 180) comprising a molded wall (42) surrounding the at least one connection pad (41).

6. Bearing according to any one of the preceding claims, the body of which also comprises a probe (51) of a current detection device (50) positioned opposite at least one trace.

7. Bearing according to any one of the preceding claims, the body of which comprises a probe (71) of a thermal unit (70).

8. Bearing according to any one of the preceding claims, the body of which also comprises at least one probe (61) of a rotor position sensor (60).

9. A bearing according to any preceding claim in the body of which is molded at least one guide channel (64) adapted to guide at least one electrical connector (65).

10. Rotating electric machine comprising a polyphase stator (11) surrounding a rotor mounted on a shaft (13) extending along an axis X corresponding to the axis of rotation of the rotor and at least one bearing (17, 18) comprising a bearing housing (15) for rotatably mounting the shaft (13), the bearing (17, 18) being according to any one of claims 1 to 9.