Electric motor equipped with an electronic circuit

Abstract

The invention relates to an electric motor (30), comprising: - a rotor (10) which comprises: • a shaft (12) which is mounted so as to be able to rotate about an axis (X); • a lamination stack (14) which is mounted coaxially on the shaft (12), the lamination stack (14) comprising a plurality of internal cavities; • a plurality of permanent magnets (16) which are housed inside the internal cavities of the lamination stack (14); and • at least one flange (17, 19) which is mounted axially on the shaft (12); - a stator (36) which surrounds the rotor (10); - at least one sensor (43) which is configured to measure a physical quantity; and - an electronic circuit (44) which is electrically connected to the at least one sensor (43), wherein the electronic circuit (44) is rigidly connected to a housing (20) which is attached to the stator (36), the housing (20) being provided with at least one internal fluid-circulation channel (22) inside which a cooling fluid can circulate, the at least one internal fluid-circulation channel (22) being separated from the electronic circuit (44) by an electrically insulating wall (220), the electrically insulating wall (220) being configured to allow a heat exchange between the cooling fluid and the electronic circuit (44).

Description

[0001] ELECTRIC MOTOR EQUIPPED WITH AN ELECTRONIC CIRCUIT

[0002] The present invention relates to an electric motor equipped with an electronic circuit.

[0003] Generally speaking, current electric motors comprise a rotor secured to a shaft and a stator which surrounds the rotor. The stator is mounted in a casing which comprises bearings for the rotational mounting of the shaft. The rotor comprises a body formed by a stack of laminations or claw poles held in the form of a packet by means of a suitable fastening system. The rotor body comprises internal cavities housing permanent magnets. The stator comprises a body constituted by a stack of laminations forming a crown, the inner face of which is provided with teeth delimiting two by two a plurality of notches open towards the interior of the stator body and intended to receive phase windings. These phase windings pass through the notches of the stator body and form buns projecting on either side of the stator body.The phase windings may, for example, consist of a plurality of U-shaped conductor segments, the free ends of two adjacent segments being connected together by welding.

[0004] In the rotor, the lamination pack is axially sandwiched between a front flange and a rear flange mounted coaxially to the shaft. Each flange has the overall shape of a disc extending in a radial plane perpendicular to the axis of the shaft. Each flange has a central hole for coaxial mounting on the shaft and several through holes intended to receive bolts passing axially through the entire lamination pack, the screws being secured to the flanges by means of nuts. The front and rear flanges are generally made of a non-magnetic, heat-conducting material, for example a metal.

[0005] Powering and controlling the electric motor requires the integration of a rotation angle measuring device to determine the position of the electric motor shaft. Generally, these rotation angle measuring devices include a target fixed to one of the rotor flanges and a sensor carried by the motor housing. However, arranged in this way, the sensor is in a position relatively far from the target, which can affect the accuracy of the angle measurement. This solution is, however, preferred because installing such sensors in a region of the motor that is close to the rotor is not easy to achieve, due to the fact that they need to be connected to an electronic circuit to ensure their correct operation and to allow downstream processing of the data measured by these sensors. To avoid disturbances caused by movement and the risk of malfunction, the electronic circuit cannot be arranged on the rotor.It is therefore necessary to position the electronic circuit at the stator level. This positioning of the electronic circuit at the stator level, however, poses several problems. On the one hand, it does not always allow a simple connection, for example by wire, between the sensor and the electronic circuit. On the other hand, due to the relatively high temperature of the rotor and the stator during operation of the motor, the electronic circuit can be subject to significant heating which can ultimately lead to its rapid deterioration. This problem is obviously not specific to position sensors. It also applies to the installation of any type of sensor at the stator level of an electric motor.

[0006] The present invention aims to propose a solution which responds to the aforementioned problems.

[0007] To this end, the present invention relates to an electric motor comprising:

[0008] - a rotor comprising:

[0009] • a shaft mounted to rotate around an axis,

[0010] • a sheet metal pack mounted coaxially on the shaft, said sheet metal pack comprising a plurality of internal cavities,

[0011] • a plurality of permanent magnets housed inside the internal cavities of the sheet metal pack,

[0012] • at least one flange mounted axially on the shaft,

[0013] - a stator surrounding the rotor,

[0014] - at least one sensor configured to measure a physical quantity,

[0015] - an electronic circuit electrically connected to said at least one sensor, characterized in that said electronic circuit is integral with a housing fixed to the stator, said housing being provided with at least one internal fluid circulation channel inside which a cooling fluid can circulate, said at least one internal fluid circulation channel being separated from the electronic circuit by an electrically insulating wall, said electrically insulating wall being configured to allow a heat exchange between the cooling fluid and the electronic circuit.

[0016] Thus configured, the motor of the invention will make it possible to better evacuate the heat generated by the electronic circuit, due to the passage of a cooling fluid inside an internal channel circulating inside a housing fixed on the stator, the heat transfers between the electronic circuit and the cooling fluid being advantageously promoted due to the fact that the internal channel is separated from the electronic circuit by a wall having high thermal conductivity.

[0017] The engine of the invention may also include one or more of the following characteristics:

[0018] - the electronic circuit is integrated into a plate which is embedded in the housing.

[0019] - the plate comprises a first support and a second support, the first support integrating said at least one sensor and the second support comprising electrical connection terminals intended to be connected to a control unit of the electric motor.

[0020] - the housing comprises a first part incorporating the electronic circuit and a second part, said first and second parts being connected to each other, preferably by welding, said first part being provided with at least one hollow zone, and said second part completely covering said at least one hollow zone, such that said at least one internal fluid circulation channel is partially formed by said at least one hollow zone and by a portion of the second part which covers said at least one hollow zone.

[0021] - the first and second parts are each provided with a central opening of circular shape, said central opening having a diameter substantially equal to or slightly greater than that of an end portion of the rotor shaft.

[0022] - the first part is provided with a window through which a portion of the electronic circuit is visible.

[0023] - the first part has a central zone, of annular shape, and a peripheral zone, of annular shape, the central and peripheral zones being connected by at least two intermediate segments, oriented radially, and the second part having a central zone, of annular shape, intended to come opposite the central zone of the first part, and two radial branches intended to come opposite said at least two intermediate segments of the first part.

[0024] - said at least one internal fluid circulation channel has a first section, extending inside one of the intermediate segments, and a second section, extending inside another of the intermediate segments, the first section and the second section opening inside a central section, said central section forming an internal cavity between the central zone of the first part and the central zone of the second part.

[0025] - the central zone of the first part is provided with a series of protrusions configured to increase the contact surface between the fluid circulating inside said at least one internal channel and said electrically insulating wall.

[0026] - the electronic circuit is configured to transmit signals using contactless communication technology.

[0027] - contactless communication technology is chosen from induction and NFC.

[0028] - said at least one sensor is configured to measure a physical quantity chosen from temperature, humidity, position and vibration. - the rotor supports at least one target, said at least one sensor being able to interact with said at least one target to determine the angular position of the rotor.

[0029] - said at least one target is formed at least partially from a metallic material and said at least one sensor comprises one or more coils capable of interacting with said at least one target.

[0030] - the wall (electrically insulating) has a thermal conductivity of between 0.3 and 15 W / mK.

[0031] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of non-limiting example, and made with reference to the appended drawings in which: [Fig. 1] is a perspective view of an electric motor according to a particular embodiment of the invention.

[0032] [Fig. 2] is an axial view of the electric motor shown in Fig. 1 with the rear bearing removed.

[0033] [Fig. 3] is a sectional view of the electric motor of Figure 1 along the section plane P shown in Figure 2.

[0034] [Fig. 4] is an axial view of a set of inductive position sensors that can be fitted to the motor of Figure 1.

[0035] [Fig. 5] is a perspective view of the electronics support housing equipping the motor of Figure 1.

[0036] [Fig. 6] is an exploded perspective view of the electronics support housing shown in Fig. 5.

[0037] In the figures and in the rest of the description, the same references represent identical or similar elements. In addition, the different elements are not represented to scale so as to favor the clarity of the figures.

[0038] With reference to figures 1 to 3, an electric motor is shown according to a particular embodiment of the invention.

[0039] This electric motor 30 comprises in particular a two-part casing housing a rotor 10 integral in rotation with a rotor shaft 12 and an annular stator 36 which surrounds the rotor 10 coaxially with the rotor shaft 12. The casing consists in particular of a front bearing 32 and a rear bearing 34 connected to each other by means of screws 31. The bearings 32, 34 are hollow in shape and each centrally carry a ball bearing respectively 33 and 35 for the rotational mounting of the rotor shaft 12. The rotor shaft 12 is rotatably mounted around an axis X.

[0040] As illustrated in Figure 2, buns 37 project axially on either side of the stator lamination pack 36. The rotor 10 comprises a body formed by a lamination pack 14, for example, formed from a ferromagnetic material, in particular steel, the lamination pack 14 being mounted coaxially on the rotor shaft 12. The lamination pack 14 is formed from an axial stack of laminations which extend in a radial plane perpendicular to the axis of the rotor shaft 12. The rotor shaft 12 may for example be force-fitted inside a central opening of the lamination pack 14 so as to connect the rotor body 10 to the rotor shaft 12 in rotation.

[0041] The sheet metal pack 14 includes a plurality of internal cavities within which a plurality of permanent magnets 16 are housed.

[0042] The sheet metal stack 14 is axially sandwiched between a front flange 17 and a rear flange 19. The flanges 17 and 19 each have the shape of a disc extending in a radial plane perpendicular to the axis X of the rotor shaft 12. The flanges 17, 19 have a central orifice for coaxial mounting on the shaft 12. These flanges 17, 19 ensure balancing of the rotor 10 while allowing good retention of the permanent magnets 16 inside their internal cavity. Balancing can be carried out by adding or removing material from these flanges 17, 19. The removal of material can be carried out by machining, while the addition of material can be carried out by implanting elements in openings provided for this purpose and distributed along the circumference of the flange 17, 19.

[0043] The rear flange 19 also incorporates one or more electrically conductive targets 46. Each target 46 may, for example, be in the form of a metal plate, having an external shape similar to a fan blade, the targets being separated from each other by an empty angular space. The plate may be made of any type of metal, such as aluminum, steel, or a printed circuit board with a printed copper layer. However, it is conceivable to use other types of targets, such as wire loops or passive resonant circuits made up of inductors and capacitors.

[0044] These targets 46 will be able to interact with one or more inductive position sensors 43 secured to a plastic housing 20 fixed to the stator 36. These inductive position sensors implement a magnetless technology, using the physical principles of eddy currents or inductive coupling to detect the position of a target which moves above a set of coils, composed for example of a transmitter coil and two receiver coils, in particular a sine receiver coil and a cosine receiver coil.

[0045] In a practical implementation of the three coils, one transmitter coil and two receiver coils are typically provided as copper traces on a printed circuit board (PCB).

[0046] They are arranged in such a way that the transmitter coil induces a secondary voltage in both receiver coils, which depends on the position of the target above the receiver coils. Therefore, the inductive sensor includes or is connected to an oscillator that generates a radio frequency signal, which is applied to the transmitter coil to create a high-frequency magnetic field. This high-frequency magnetic field is picked up by the receiver coils, specifically the sinusoidal receiver coil and the cosine receiver coil. Depending on the position of the conductive target above the coils, the secondary voltage picked up by the receiver coils changes in amplitude, making it possible to determine the position of the target by analyzing this effect. For example, the target position is calculated by the arctangent of the sine signal divided by the cosine signal.The calculation is performed by a processing unit, which is connected to the position sensor or is an integral part of the position sensor.

[0047] In particular, as shown in Figure 4, each of the sensors 43 may comprise a transmitter coil 432 and two pairs of receiver coils 433, 434 which are formed in the form of copper tracks on a support 41 of the printed circuit board (PCB) type. The support 41 is integrated in a plate 40, which is embedded in the housing 20 and which extends in a plane perpendicular to the longitudinal axis X of the shaft 12, being axially aligned with the rotor 10.

[0048] The plate 40 is formed, on the one hand, of the annular-shaped support 41 and, on the other hand, of a rectangular-shaped segment 42 supporting electrical connection wires (not shown) connected to each of the coils 432, 433 and 434 and to electrical connection terminals 45 intended to be connected to a control unit of the electric motor.

[0049] The plate 40 further comprises an electronic circuit 44, which is arranged on the support 41 and / or on the segment 42 and which is connected to each of the receiving coils 433, 434. The electronic circuit 44 may be configured to emit signals by means of a contactless communication technology, such as for example induction or NFC. This electronic circuit 44 will be responsible for processing the secondary voltage captured by the receiving coils 433, 434, which will change in amplitude depending on the position of the conductive target. This processing will thus make it possible to determine the angular position of the target.

[0050] Thus configured, the sensor(s) 43 will make it possible to detect the angular position of the rotor 10. The sensors 43 will advantageously be axially aligned with the targets 46 carried by the rear flange 19. The axial distance separating the sensors 43 from the targets 46 will be as small as possible so as to improve the accuracy of the angle measurements. It will be particularly advantageous to position the sensors 43 at a maximum distance of 5 mm from the targets 46 so as to obtain the most accurate angle measurement possible. As described above, this short distance may, however, generate significant heating of the sensors 43 and the associated electronic circuit 44, which, in the long term, will lead to a malfunction of said sensors.To avoid these malfunctions, the solution of the invention consists in passing a cooling fluid, such as glycolated water for example, inside the plastic housing 20 so that it absorbs part of the heat released by the sensors 43 and the electronic circuit 44. This cooling fluid may in particular be supplied from outside the electric motor via a fluid inlet pipe 38 arranged at the outer periphery of the front bearing 32 and opening, inside the casing, onto an internal fluid circulation channel formed inside the housing 20, said internal channel communicating with a fluid outlet pipe 39 arranged at the outer periphery of the front bearing 32. During its passage in the internal channel of the housing 20, the fluid may thus cool the sensors 43 and the electronic circuit 44.

[0051] The solution of the invention is obviously not limited to the embodiment described above. In particular, in other embodiments of the invention, it will be possible to use, instead of inductive position sensors, Hall effect sensors capable of interacting with magnetic targets carried by the rotor to determine the angular position of the rotor.

[0052] In other embodiments of the invention, the sensor(s) 43 may be used to measure another physical quantity, such as temperature, humidity or vibration in a specific area of ​​the electric motor. Therefore, the sensor(s) 43 may be arranged on the element of the motor whose physical quantity is to be measured, such as the rotor 10 for example. The electronic circuit 44 will however remain positioned on a support secured to the housing 20.

[0053] With reference to Figures 5 and 6, a possible embodiment of the housing 20 is shown. In this embodiment, the housing 20 is formed of a first part 21 and a second part 23, said first and second parts 21, 23 being connected to each other, preferably by welding. These first and second parts 21, 23 are each provided with a central opening 215, 235 of circular shape. These central openings 215, 235 have a diameter slightly greater than that of one end 123 of the shaft 12 of the rotor 10 so as to allow the housing 20 to be fixed to the stator 36. The plate 40 supporting the electronic circuit 44 is embedded in the first part 21. In an advantageous embodiment of the invention, the plate 40 may be overmolded with the first part 21.

[0054] The first part 21 of the housing 20 has a central ring 211 and a peripheral ring 212, said rings 212, 212 being connected by three intermediate segments 213a, 213b, 213c, oriented radially and spaced at 120° from each other. The peripheral ring 212 may be fixed, by any conceivable means, to a peripheral wall of the stator 36. In addition, the peripheral ring 212 is provided with tabs 214 projecting from the lower edge of said peripheral ring 212 and intended to engage in corresponding hollow shapes of the stator 36, as shown in FIG. 3. These tabs 214 serve as an anti-rotation device for this peripheral ring. The central ring 211 is provided with a hollow zone 216 in which a series of axially oriented protuberances 217 are provided. In the housing 20, this hollow zone 216 is covered by a central zone 231, of annular shape, of the second part 23.

[0055] The support 41 which carries the sensors 43 is completely embedded inside the central ring 211. It is therefore advantageous for this central ring 211 to be arranged at a short distance in the axial direction from the rear flange 19 supporting the targets 46, so as to improve the accuracy of the measurements made by the sensors 43. This distance will preferably be between 1 mm and 3 mm. For this purpose, the central ring 211 is offset axially towards the inside of the top zone of an end portion 213e of each of the intermediate segments 213a, which, when the housing 20 is mounted in the motor 30, surrounds the coils 37 of the stator 36, as illustrated in FIG. 3.

[0056] One of the intermediate segments 213c is provided with a rectangular window 213d through which the rectangular segment 42 supporting the electrical connection terminals 45 is visible.

[0057] The other two intermediate segments 213a and 213b are each provided with two parallel ribs 218i, 218j oriented axially, thus forming two radially oriented hollow zones 219a, 219b. As shown in FIG. 6, these hollow zones 219a, 219b communicate with the hollow zone 216. In the housing 20, these hollow zones 219a, 219b are covered respectively by two radial branches 232a, 232b of the second part 23 which extend radially from the central zone 231.

[0058] Thus, as shown in Figure 3, when the second part 23 is fixed to the first part 21, an internal channel 22 is formed inside the housing 20, said internal channel 22 being delimited, on one side, by a portion of the external side wall of the first part 21, which surrounds the hollow zones 216, 219a, 219b, and, on the other side, by a portion of the internal side wall of the second part 23, which covers said hollow zones 216, 219a, 219b. As illustrated in FIG. 2, this internal channel 22 has a first section 221, extending inside the intermediate segment 213a, and a second section 223, extending inside the intermediate segment 213b, the first section 221 and the second section 223 opening inside a central section 222, said central section 222 forming an internal cavity between the central zone 211 of the first part 21 and the central zone 231 of the second part 23.The first section 221 communicates fluidically with a fluid inlet channel 24 formed through the fluid inlet tubing 38 and the second section 223 communicates fluidically with a fluid outlet channel 25 formed through the fluid outlet tubing 39. Thus, a cooling fluid, supplied from the fluid inlet channel 24, will be able to circulate inside the housing 20 through the internal channel 22 and exit through the fluid outlet channel 25. During its passage in the housing 20, this cooling fluid will be in contact with a wall 220 (shown in FIG. 3) separating the internal channel 22 from the electronic circuit 44. During this contact, the cooling fluid will be able to absorb part of the heat released by the electronic circuit 44. The contact surface between the cooling fluid and said wall 220 will be advantageously increased by the protuberances 217 formed at the central zone 216 of the first part 21.Optimal cooling of the electronic circuit 44 will be obtained by appropriately choosing the material constituting the wall 220 and its thickness. In particular, it will be advantageous to choose this constituent material from styrenic polymers, such as polystyrene or acrylonitrile butadiene styrene (ABS), polyamides, such as PA6, PA66, or polyphthalamide, poly(phenylene sulfide) (PPS), polysulfones, and composite materials reinforced with mineral fillers such as glass fibers. This constituent material must have a high resistivity, in particular between 1x10. 10 Qm and 1x10 16Dm, so as to make the wall 220 electrically insulating. Furthermore, this constituent material must also have a high thermal conductivity, in particular between 0.3 and 15 W / mK, so as to allow a heat exchange between the cooling fluid circulating inside the internal channel 22 and the electronic circuit 44 which is embedded inside the wall 220. The thickness of the wall 220 will advantageously be between 0.25 mm and 2 mm to ensure an optimal heat exchange between the cooling fluid and the electronic circuit 44.

[0059] The invention is obviously not limited to the embodiment as described above. In particular, the invention may include certain modifications compared to this embodiment, provided that these modifications are covered by the set of claims provided below.

Claims

CLAIMS 1. Electric motor (30) comprising: - a rotor (10) comprising: • a shaft (12) mounted to rotate around an axis (X), • a pack of sheets (14) mounted coaxially on the shaft (12), said pack of sheets (14) comprising a plurality of internal cavities, • a plurality of permanent magnets (16) housed inside the internal cavities of the sheet metal pack (14), • at least one flange (17, 19) mounted axially on the shaft (12), - a stator (36) surrounding the rotor (10), - at least one sensor (43) configured to measure a physical quantity, - an electronic circuit (44) electrically connected to said at least one sensor (43), characterized in that said electronic circuit (44) is integral with a housing (20) fixed to the stator (36), said housing (20) being provided with at least one internal fluid circulation channel (22) inside which a cooling fluid can circulate, said at least one internal fluid circulation channel (22) being separated from the electronic circuit (44) by an electrically insulating wall (220), said electrically insulating wall (220) being configured to allow a heat exchange between the cooling fluid and the electronic circuit (44).

2. Electric motor (30) according to claim 1, characterized in that the electronic circuit (44) is integrated in a plate (40) which is embedded in the housing (20).

3. Electric motor (30) according to claim 2, characterized in that the plate (40) comprises a first support (41) and a second support (42), the first support (41) integrating said at least one sensor (43) and the second support (42) comprising electrical connection terminals (45) intended to be connected to a control unit of the electric motor (30).

4. Electric motor (30) according to one of the preceding claims, characterized in that the housing (20) comprises a first part (21) incorporating the electronic circuit (44) and a second part (23), said first and second parts (21, 23) being connected to each other, preferably by welding, said first part (21) being provided with at least one hollow zone (216, 219a, 219b), and in that said second part (23) completely covers said at least one hollow zone (216, 219a, 219b), such that said at least one internal fluid circulation channel (22) is partially formed by said at least one hollow zone (216, 219a, 219b) and by a portion of the second part (23) which covers said at least one hollow zone (216, 219a, 219b).

5. Electric motor (30) according to claim 4, characterized in that the first and second parts (21, 23) are each provided with a central opening (215, 235) of circular shape, said central opening (215, 235) having a diameter substantially equal to or slightly greater than that of an end portion (123) of the shaft (12) of the rotor (10).

6. Electric motor (30) according to claim 4 or 5, characterized in that the first part (21) is provided with a window (213d) through which a portion (45) of the electronic circuit (44) is visible.

7. Electric motor (30) according to one of claims 4 to 6, characterized in that the first part (21) has a central zone (211), of annular shape, and a peripheral zone (212), of annular shape, the central and peripheral zones (211, 212) being connected by at least two intermediate segments (213a, 213b), oriented radially, and in that the second part (23) has a central zone (231), of annular shape, intended to come opposite the central zone (211) of the first part (21), and two radial branches (232a, 232b) intended to come opposite said at least two intermediate segments (213a, 213b) of the first part (21).

8. Electric motor (30) according to claim 7, characterized in that said at least one internal fluid circulation channel (22) has a first section (221), extending inside one of the intermediate segments (213a), and a second section (223), extending inside another of the intermediate segments (213b), the first section (221) and the second section (223) opening inside a central section (222), said central section (222) forming an internal cavity between the central zone (211) of the first part (21) and the central zone (231) of the second part (23).

9. Electric motor (30) according to claim 8, characterized in that the central zone (211) of the first part (21) is provided with a series of protrusions (217) configured to increase the contact surface between the fluid circulating inside said at least one internal channel (22) and said electrically insulating wall (220).

10. Electric motor (30) according to one of the preceding claims, characterized in that the electronic circuit (44) is configured to emit signals by means of contactless communication technology.

11. Electric motor (30) according to claim 10, characterized in that the contactless communication technology is chosen from induction and NFC.

12. Electric motor (30) according to one of the preceding claims, characterized in that said at least one sensor (43) is configured to measure a physical quantity chosen from temperature, humidity, position and vibration.

13. Electric motor (30) according to claim 12, characterized in that the rotor (10) supports at least one target (46), said at least one sensor (43) being able to interact with said at least one target (46) to determine the angular position of the rotor (10).

14. Electric motor (30) according to claim 13, characterized in that said at least one target (46) is formed at least partially from a metallic material and said at least one sensor (43) comprises one or more coils (432, 433, 434) capable of interacting with said at least one target (46).

15. Electric motor (30) according to one of the preceding claims, characterized in that the electrically insulating wall (220) has a thermal conductivity of between 0.3 and 15 W / mK.

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