Oil-cooled electric machine

Abstract

The invention relates to an electric machine comprising: - a rotor (ROT) immersed in a dielectric cooling liquid, - a casing (CAR) comprising at least one bearing housing (LP) which houses a rolling bearing (RB) at the end of the rotation axis (AT) of the rotor (ROT), characterized in that said bearing housing (LP) comprises a receptacle (REC) capable of collecting the dielectric cooling liquid sprayed into the casing (CAR) by splash lubrication of said rotor (ROT), and in that said bearing housing (LP) comprises at least one duct which opens axially between the outer ring (BER) of said rolling bearing and an annular inner perimetric step (TRO) of said bearing housing (LP).

Description

Technical Field

[0001] This invention relates generally to the field of electrical engineering and more specifically to an electric motor cooled by a dielectric heat transfer liquid (such as oil). Background Technology

[0002] In oil-cooled sealed electric motors, dynamic seals are inserted around the shaft on both sides of the machine to ensure its sealing. The rolling bearings surrounding the machine's shaft also need to be lubricated. To cool the machine's driving components (i.e., the rotor and stator) and to lubricate the rolling bearings and seals with the same oil, a typically expensive oil circuit is created.

[0003] For example, in patent WO 2018206890, oil circulation pipes and injectors are positioned within the machine's housing to spray oil onto the machine's rolling bearings and active components. This type of cooling system requires pumps, oil filters, injectors, and circulation loops, which significantly increases the cost of the electric machine. Summary of the Invention

[0004] One of the objectives of this invention is to overcome at least some of the disadvantages of the prior art by providing an electric motor cooled by a dielectric liquid, which is cheaper while ensuring efficient cooling of the machine's active components and proper lubrication of the machine's rolling bearings and dynamic seals.

[0005] Therefore, the electric motor provided by the present invention has the following features:

[0006] - A rotor having a shaft, the lower portion of which is immersed in a dielectric coolant.

[0007] - A stator, fixed to the inner wall of the machine housing and surrounding the rotor, the housing having at least one generally cylindrical bearing housing receiving the end of the shaft via rolling bearings, the rolling bearings being held in place in the bearing housing by retaining rings fixed to the outer rings of the rolling bearings and by a circular shoulder of the shaft, the retaining rings being arranged to abut against the axial end surface of the bearing housing, and the inner rings of the rolling bearings being arranged to abut against the circular shoulder.

[0008] The bearing housing is characterized in that the upper corner portion of the generally cylindrical portion of the bearing housing has a receiver capable of collecting dielectric coolant sprayed into the housing by splashing from the rotor, and wherein the upper corner portion has at least one conduit radially passing through the generally cylindrical portion, the conduit being axially opened between the outer ring of the rolling bearing and the annular inner peripheral step of the bearing housing.

[0009] With this invention, the machine's active components are cooled by oil sprayed from the rotor as it rotates, and the machine's rolling bearings are similarly lubricated by oil sprayed from the rotor during operation. This eliminates the need for dedicated circulation piping, pumps, oil filters, and injectors for this cycle. As a result, the machine according to the invention is cheaper, more compact, and easier to manufacture compared to existing technologies.

[0010] Advantageously, in the machine according to the invention, the conduit opens into a space of at least 2 mm between the annular inner peripheral step of the bearing housing and the rolling bearing, and wherein the dynamic seal is disposed around the shaft within the space defined by the annular inner peripheral step. This space allows for proper circulation of oil around the rolling bearing and the dynamic seal.

[0011] Advantageously, the retaining ring has a notch located radially between the outer ring of the rolling bearing and the cylindrical inner surface of the bearing housing. This feature of the invention allows lubricating oil to flow towards the lower portion of the housing without flooding the space between the rolling bearing and the dynamic seal.

[0012] Advantageously, the cut is positioned at an angle closer to the horizontal plane containing the axis of the rotating shaft than to the vertical axis intersecting the axis of the rotating shaft. This allows a reserve of lubricating oil to be maintained at the rolling bearings when restarting the electric machine.

[0013] According to a variant of the invention, the receiver and the bearing housing of the outer casing are formed by a single, molded component. This variant allows for simpler assembly of the electric machine.

[0014] Preferably, the receiver is formed of a separate component axially positioned between the inner wall of the housing and the retaining ring, the component having an overflow channel forming the conduit and molded in a lower portion of the component, the lower portion of the component being inserted into a corresponding cutout formed in the generally cylindrical portion of the bearing housing. This embodiment of the invention allows for easier production of the housing wall, and the bearing housing of the machine according to the invention requires very few modifications in this embodiment compared to prior art bearing housings.

[0015] Advantageously, the receiver is formed from a separate component axially positioned between the inner wall of the housing and the retaining ring. This component has the form of a deformed crown-shaped segment, the outer periphery of which is axially offset relative to the inner periphery of the crown. The inner periphery of the crown is attached to the outer periphery of the crown via a corresponding annular segment. The outer periphery of the crown abuts against the retaining ring. The annular segment follows the surface of the upper corner portion of the generally cylindrical portion of the bearing housing. An overflow channel forming the conduit is molded into the annular segment and the inner periphery of the crown. The inner periphery of the crown inserts into a corresponding cutout formed in the generally cylindrical portion of the bearing housing. The component also has retaining elements in the form of walls extending radially and axially at the longitudinal ends of the annular segment. In this embodiment of the machine according to the invention, the receiver is easy to manufacture and easy to install onto the corresponding bearing housing.

[0016] Preferably, the receiver is made of plastic material. Therefore, it is easy to produce by molding and is inexpensive.

[0017] The present invention also relates to an electric vehicle or hybrid vehicle having an electric traction machine according to the invention, wherein the housing of the electric machine has a heat exchanger in its lower portion, the heat exchanger being combined with a network of coolant pipes connected to a cooling circuit that connects to other equipment of the vehicle (including a radiator located at the front of the vehicle), the coolant being ethylene glycol water. This heat exchanger allows for the cooling of the dielectric coolant located in the housing of the machine, particularly when the temperature of the dielectric coolant exceeds an upper temperature threshold.

[0018] Preferably, in the vehicle according to the invention, the dielectric coolant is oil, the electric motor is oil-tight and has an oil reservoir in the lower portion of the housing, in which a heating resistor is disposed, and the vehicle has means for activating the heating resistor when the temperature of the oil in the reservoir is below a lower lower threshold during the vehicle's start-up phase. This reheating of the oil during start-up allows the machine to operate normally in very cold weather, where the low-temperature oil cannot properly lubricate the rolling bearings and dynamic seals of the machine and causes significant viscous friction at the rotor.

[0019] Advantageously, in the vehicle according to the invention, the nominal speed of the electric motor is designed to not exceed 9000 rpm and it does not have an internal circuit for oil injection. This design allows the electric motor to maintain good efficiency, as oil friction at the rotor causes significant losses at very high speeds.

[0020] The electric vehicle or hybrid vehicle according to the invention has advantages similar to those of the electric machine according to the invention. Attached Figure Description

[0021] Other features and advantages will become clear from the preferred embodiments described with reference to the accompanying drawings, in which:

[0022] - Figure 1 A longitudinal section is shown of an electric motor cooled by a dielectric liquid according to the present invention in this preferred embodiment.

[0023] - Figure 2 The region of the rolling bearing of the electric motor according to the present preferred embodiment is shown. Figure 1 Enlarged image,

[0024] - Figure 3 The components of the forming receiver of the machine according to the invention in this preferred embodiment are shown.

[0025] -and Figure 4 The rotating shaft of the machine according to the invention in this preferred embodiment is shown, and the position of the component relative to other elements fixed to the shaft is shown. Detailed Implementation

[0026] according to Figure 1 The preferred embodiment of the invention shown indicates that the electric machine ME according to the invention has a sealed housing CAR, in which a stator STAT and a generally cylindrical hollow assembly (formed from a metal sheet with copper wire windings) are secured. The stator STAT is secured to the generally cylindrical inner wall of the housing CAR by screws or by interference fit. In this application, the term "generally" means "approximately," for example, the addition of a boss or hole compared to the form defined in this way, or a difference within the range of 10% compared to the orientation or position defined in this way.

[0027] The rotor ROT is housed in the stator STAT, which is an assembly of metal sheets and windings or magnets surrounding the shaft AT. The ends of the shaft AT are held in rolling bearings (especially ball bearings), which are mounted on the shaft AT and housed in a generally cylindrical bearing housing LP, formed within the generally flat walls of the outer casing CAR. Specifically, the ball bearings are housed within the cylindrical inner portion of the bearing housing.

[0028] exist Figure 1 In the enlarged view of the portion located in the area of ​​bearing housing LP, Figure 2As can be seen, the ball bearing RB, housed within the cylindrical inner portion of the bearing housing LP, has an outer ring BER and an inner ring BIR. The outer ring BER is fixed to the retaining ring BR at the axial end of the outer ring of the rolling bearing RB facing the rotor ROT. It should be noted that in this application, the axial direction refers to the rotation axis AX of the rotor ROT, and the radial and orthogonal directions are similarly defined relative to this axis AX.

[0029] In a known manner, the housing CAR is designed, for example, in two parts: a bottom wall into which the rotor ROT is inserted, and a cover that closes the housing CAR, the wall of which is... Figure 2 As can be seen, when the cover of the housing CAR is closed on the bottom wall of the housing CAR, the axial end surface SEA of the bearing housing LP, located on the rotor ROT side, presses against the retaining ring BR in the direction of the rotor ROT, thereby helping to apply pressure to the ball bearing RB. The axial end surface SEA extends in a plane orthogonal to the axis AX of the rotor ROT. The ball bearing RB is held in place on the shaft AT by a round shoulder EP, which applies a force in the opposite direction to that of the rotor ROT on the inner ring BIR of the ball bearing RB.

[0030] The lower portion of the rotor ROT is immersed in a dielectric coolant, which in this preferred embodiment is oil. The terms upper and lower, or top and bottom, refer in this application to the electric machine ME along its vertical axis V, which is oriented opposite to the direction of gravity. The oil level NO in the lower portion of the electric machine ME is located at the lower winding of the rotor ROT.

[0031] When the electric machine ME is running, the rotational motion of the rotor ROT delivers oil to the entire cylindrical surface of the rotor ROT, thereby cooling the rotor windings. Oil is also sprayed by the rotor ROT onto the cylindrical inner surface of the stator STAT, thus cooling the stator windings. During the fallback, the sprayed oil reaching the shaft AT of the rotor ROT only very lightly lubricates the ball bearings. Another portion of the sprayed oil is captured during the fallback in a receiver REC located on the upper surface of the bearing housing LP. A conduit through this upper portion of the bearing housing LP delivers the oil thus captured to the space between the ball bearing RB and the dynamic seal JD, which extends the wall of the housing CAR to seal the electric machine ME at the outlet of the shaft AT. The oil thus effectively lubricates both the ball bearing RB and the dynamic seal JD.

[0032] More specifically, the receiver REC is open in its upper portion, and its lower portion immediately follows the upper corner of the generally cylindrical portion of the bearing housing LP, except in the conduit region formed by the cutout EV in the bearing housing LP and opening between the outer ring BER of the ball bearing RB and the annular inner peripheral step TRO of the bearing housing LP. This space ESP between the step TRO and the outer ring BER of the ball bearing RB extends axially by at least 2 mm, and the ball bearing RB is not completely recessed into the bearing housing LP. This space ESP preferably extends axially by 4 mm to 6 mm.

[0033] The annular inner circumferential step TRO of the bearing housing LP defines a space within the wall of the housing CAR to accommodate the dynamic seal JD, which seals the axial end of the electric machine ME at the ball bearing RB.

[0034] In this preferred embodiment of the invention, the acceptor REC is Figure 3 The component shown is assembled onto the bearing housing LP, for example, by means of clamp fastening or screw screwing. This component, for example, made of molded plastic material, has the form of an axially deformed, flat, angular crown-shaped section. Specifically, the outer periphery PE of this crown-shaped section is axially offset relative to the inner periphery PI of this crown-shaped section. The walls of the outer periphery PE and the inner periphery PI of the receiver REC are connected by an annular surface SA, which follows the upper surface of the bearing housing LP on which it rests. The wall of the outer periphery PE presses against the retaining ring BR, and the wall of the inner periphery PI is inserted into a notch EV, which is radially formed in a generally cylindrical portion of the bearing housing LP. The receiver REC similarly has retaining elements ER that close the angular ends of the component, these angular elements extending radially along the circumferential outer wall PE and axially spanning the width of the annular surface SA. Therefore, the circumferential outer wall PE, the annular surface SA, the retaining element ER, and the wall of the housing CA (to which the receiver REC is held) form the walls of a reservoir for collecting the injected oil that falls back into the housing CAR by gravity. A radial conduit CAN, fabricated in the circumferential inner wall PI of the receiver REC, forms an overflow channel that allows oil to descend and lubricate the ball bearing RB and the dynamic seal JD.

[0035] Figure 4The diagram shows the position of the receiver REC relative to the ball bearing RB on the shaft AT and relative to the dynamic seal JD, without showing the housing CAR of the electric machine ME. The position sensor target CC is therefore located outside the housing CAR of the electric machine ME. A notch OR made in the retaining ring BR allows oil flowing between the dynamic seal JD and the ball bearing RB to overflow into the lower portion of the housing CAR. When the shaft AT is mounted in the electric machine ME, this notch OR is radially located between the outer ring of the ball bearing RB and the cylindrical inner wall of the bearing housing LP. To retain oil reserves, when the electric machine ME is stopped, the notch OR is angled in the space between the dynamic seal JD and the ball bearing RB, closer to the horizontal plane containing the axis AX of the shaft AT (which is therefore orthogonal to axis V) than to the vertical axis V passing through the axis AX of the shaft.

[0036] In addition, to facilitate proper lubrication and cooling of the electric machine (ME), a heating resistor is positioned in the lower portion of the housing (CAR). This heating resistor is connected to a circuit controlled by a computer connected to a temperature sensor. This temperature sensor reads the temperature of the oil or the ambient temperature. When the temperature reading is below a lower lower threshold, such as -10°C, the computer supplies power to the circuit connected to the heating resistor, which then heats the oil.

[0037] To cool the oil during operation of the electric machine ME so that it does not exceed the upper temperature threshold (e.g., 40°C), a heat exchanger ECH is incorporated into the housing CAR of the electric machine ME. This heat exchanger ECH is, for example, constructed from an ethylene glycol-water circuit machined into the lower part of the electric machine ME and connected to the cooling circuit.

[0038] Especially when the electric motor ME is the electric traction machine of an electric vehicle or a hybrid vehicle, the heat exchanger ECH is connected to the vehicle’s main cooling circuit, which cools the vehicle’s power electronics and is connected to the radiator located at the front of the vehicle.

[0039] Oil in direct contact with the rotor increases mechanical losses at high speeds. Preferably, the electric traction machine ME is therefore designed to operate nominally within a speed threshold range of up to 9000 rpm. This nominal maximum speed can be set slightly lower, for example, 8000 rpm. Thus, vehicles using the electric traction machine ME do not require an internal circuit specifically incorporating an oil pump for oil injection.

[0040] Although a single receiver REC is shown in this embodiment, as a variation, a receiver REC may be provided for each bearing housing of the electric machine ME. Other variations are also possible. For example, as a variation, the receiver REC and bearing housing are cast as a single component obtained by casting. In another variation, a single conduit CAN is molded within the component forming the receiver REC.

Claims

1. An electric motor (ME) having: - A rotor (ROT) having a rotating shaft (AT), the lower portion of which is immersed in a dielectric coolant (OIL). - A stator (STAT), fixed to the inner wall of the housing (CAR) of the electric machine (ME) and surrounding the rotor (ROT), the housing (CAR) having at least one generally cylindrical bearing housing (LP), which receives the end of the shaft (AT) via a rolling bearing (RB), the rolling bearing (RB) being held in place in the bearing housing (LP) on one hand by a retaining ring (BR) fixed to the outer ring (BER) of the rolling bearing (RB) and on the other hand by a circular shoulder (EP) of the shaft (AT), the retaining ring (BR) being arranged to abut against the axial end surface (SEA) of the bearing housing (LP), and the inner ring (BIR) of the rolling bearing being arranged to abut against the circular shoulder. Its features are, The upper corner portion of the generally cylindrical portion of the bearing housing (LP) has a receiver (REC) capable of collecting dielectric coolant (OIL) sprayed into the housing (CAR) by splashing from the rotor (ROT), and wherein the upper corner portion has at least one conduit (CAN) radially passing through the generally cylindrical portion, the conduit (CAN) opening axially between the outer ring (BER) of the rolling bearing and the annular inner peripheral step (TRO) of the bearing housing (LP). The receiver (REC) is formed by a separate component axially positioned between the inner wall of the housing (CAR) and the retaining ring (BR). The component has an overflow channel forming the conduit (CAN) and molded in the lower portion of the component. The lower portion of the component is inserted into a corresponding cutout (EV) formed in the generally cylindrical portion of the bearing housing (LP).

2. The electric machine (ME) as claimed in claim 1, wherein, The conduit (CAN) opens into a space (ESP) of at least 2 mm between the annular inner peripheral step (TRO) of the bearing housing (LP) and the rolling bearing (RB), and wherein the dynamic seal (JD) is disposed around the pivot (AT) in the space defined by the annular inner peripheral step (TRO).

3. The electric motor (ME) as described in claim 1 or 2, characterized in that, The retaining ring (BR) has a notch (OR) that is radially located between the outer ring (BER) of the rolling bearing (RB) and the cylindrical inner surface of the bearing housing (LP).

4. The electric machine (ME) as described in claim 3, characterized in that, The cut (OR) is positioned at an angle closer to the horizontal plane containing the axis (AX) of the pivot (AT) than the vertical axis (V) intersecting the axis of the pivot (AT).

5. The electric motor (ME) as described in claim 1 or 2, characterized in that, The component has the form of a deformed coronal segment, the outer periphery (PE) of which is axially offset relative to the inner periphery (PI) of which the inner periphery (PI) is attached to the outer periphery (PE) of which via a corresponding annular segment (SA). The outer periphery (PE) of which abuts against the retaining ring (BR), the annular segment (SA) following the surface of the upper corner portion of the generally cylindrical portion of the bearing housing (LP), an overflow channel forming the conduit (CAN) being molded into the annular segment (SA) and the inner periphery (PI) of which the inner periphery (PI) of the coronal segment is inserted into a corresponding cutout (EV) formed in the generally cylindrical portion of the bearing housing (LP). The component also has a retaining element (ER) in the form of a wall extending radially and axially at the longitudinal end of the annular segment (SA).

6. The electric machine (ME) as claimed in claim 1 or 2, wherein, The receiver (REC) is made of plastic material.

7. An electric vehicle or hybrid vehicle having an electric motor (ME) as described in any one of claims 1 to 6, wherein, The housing (CAR) of the electric motor (ME) has a heat exchanger (ECH) in its lower portion, which is combined with a network of coolant pipes connected to a cooling circuit that connects to other equipment of the vehicle, including a radiator located at the front of the vehicle, and the coolant is water glycol.

8. The electric vehicle or hybrid vehicle as described in claim 7, wherein, The dielectric coolant (OIL) is oil, the electric motor (ME) is oil-tight and has an oil reservoir in the lower portion of the housing (CA), in which a heating resistor is disposed, and the vehicle has a device for activating the heating resistor when the temperature of the oil in the reservoir is below a lower temperature threshold during the vehicle's start-up phase.

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