Electric machine cooled by dielectric heat transfer fluid

Abstract

The invention relates to an electric machine for an electric or hybrid vehicle, comprising: a cooling system suitable for spraying a dielectric heat transfer fluid onto the active components of the machine; a reservoir (OT) for collecting the fluid that flows under the action of gravity through an orifice (TR) in a wall separating the active components from the reservoir (OT); the machine is characterized in that it comprises a flap, attached to the wall at the orifice (TR) and suitable for closing the orifice (TR), an elastic device suitable for opening the flap under the action of the gravity of the liquid, and a non-return device suitable for keeping the flap closed when the force exerted on the fluid in the reservoir (OT) causes the liquid to abut against the flap.

Description

[0001] The present invention relates generally to the fields of electronics and motor vehicles and more particularly to electric machines for electric or hybrid motor vehicles.

[0002] Electric machines for electric or hybrid vehicles, particularly electric or hybrid vehicle motors that provide torque to the drivetrain of such vehicles, require high performance cooling systems.

[0003] Known cooling systems for electric motors, such as that described in document CN 201355790, are used to cool at least a portion of the active components of the electric motor using an oil-type dielectric heat transfer liquid. The cooling circuit injects the liquid into the upper part of the motor stator, the liquid flows under gravity towards the lower part of the stator and is collected in a reservoir via holes located in the bottom part of the motor.

[0004] This cooling system has disadvantages in certain motor architectures on electric or hybrid vehicles. In fact, when such a vehicle is moving, with such a system, when the vehicle is accelerating, braking or turning, the liquid will move in the oil reservoir so that the liquid will move back upwards through the holes in the bottom part of the motor and will flood part of the air gap between the rotor and the stator. This will cause a loss of performance of the motor and emulsification of the liquid, which will compromise good cooling of the motor and good lubrication of the bearings of the rotor shaft.

[0005] One of the objects of the present invention is to remedy at least some of the shortcomings of the prior art by providing an electric machine for an electric or hybrid vehicle, cooled by a dielectric heat transfer cooling liquid, which does not experience performance loss due to vehicle steering, acceleration or braking.

[0006] To this end, the invention proposes an electric machine for an electric or hybrid motor vehicle, the electric machine comprising: a housing capable of protecting the active components of the electric machine; a cooling system comprising means for spraying a dielectric heat transfer cooling liquid onto at least a portion of the active components; a reservoir capable of collecting, under the action of gravity, the cooling liquid flowing through at least one orifice of a wall separating the active components from the reservoir, the machine being characterized in that it comprises a flap, an elastic device and a non-return device, the flap being fixed to the wall at the level of the at least one orifice and capable of closing the at least one orifice, the elastic device being capable of opening the flap under the action of the gravity of the cooling liquid, the non-return device being capable of keeping the flap closed when a force exerted on the cooling liquid in the reservoir causes the liquid to press against the flap.

[0007] By means of the present invention, the cooling liquid does not rise back up into the housing to flood the rotor and create an emulsion. This protects the performance of the machine.

[0008] According to an advantageous characteristic of the invention, the flap, the elastic means and the non-return means consist of a single membrane made of elastic material, which is attached to one side of the at least one orifice and in which, in the orifice in which the flap is made, the edge of the fixed part of the membrane covers the edge of the flap, the edge of the flap forming a downward slope towards the reservoir.

[0009] This embodiment of the invention has the advantage of being cost-effective and easy to manufacture.

[0010] The membrane is preferably made of silicone, which has the advantage of being able to withstand high temperatures and having deformation as a mechanical property.

[0011] Advantageously, the membrane comprises concave outer edges which can be fastened to the edges of the at least one orifice by elasticity. This makes the membrane easy to install, since it only has to be clamped to the wall at the level of the flow orifice for the cooling liquid. Moreover, such installation does not require modification of the existing housing of the prior art electric machine.

[0012] Alternatively, the flap is arranged below the wall and has dimensions greater than those of the orifice, the non-return means comprising a return spring fixed to a pivot connection connecting the flap to the wall. This alternative has the advantage that it can be used for oil flow orifices of large dimensions, in this alternative embodiment the flap being rigid.

[0013] Advantageously, in this alternative, the flap is fixed to a frame by means of the pivot connection, the frame being fixed to the wall by means of clips on the edge of the aperture.This makes it possible to benefit from the invention without modifying an existing casing of a prior art electric machine.

[0014] Preferably, the flap and the frame are made of plastic material, which has the advantage that production is cost-effective.

[0015] Other features and advantages will become apparent upon reading the preferred embodiments described with reference to the accompanying drawings, in which:

[0016] - Figure 1 An electric machine according to the invention is depicted,

[0017] - Figure 2 Describes in detail Figure 1 The bottom part of the electric machine,

[0018] - Figure 3 The membrane used in the bottom part is depicted in cross section,

[0019] - Figure 4A view that vividly depicts the film,

[0020] -and Figure 5 A variant embodiment of the invention in the bottom part of the electric machine according to the invention is described in detail.

[0021] According to a preferred embodiment of the present invention, Figure 1 The electric machine ME according to the invention shown comprises a casing CA protecting the active parts of the machine, such as its stator STA and rotor ROT. The electric machine ME is intended to provide torque to the wheels of an electric or hybrid vehicle and therefore requires a high performance cooling system.

[0022] To this end, the electric machine notably comprises a cooling circuit OC capable of circulating oil from an oil reservoir OT to the active parts of the electric machine ME, in this case to the rotor bundle. At the outlet of the oil circuit OC, the oil is sprayed on either side of the rotor bundle of the electric machine ME facing the electric machine ME, through nozzles fixed in the planar walls of the casing CA. Other nozzles at the outlet of the oil circuit OC spray the oil on the bearings RO of the rotor shaft, which are fixed in receptacles of each planar wall of the casing CA, on either side of the electric machine ME.

[0023] The oil sprayed by these various nozzles flows, under the effect of gravity, to the bottom part of the electric machine ME and then enters the oil reservoir OT through the holes TR located in the lower wall of the casing CA. A pump OP positioned on the cooling circuit OC extracts the oil from the oil reservoir OT and returns the extracted oil to the active parts of the electric machine ME. In this embodiment of the invention, three flow orifices TR are regularly distributed on the lower wall of the casing CA, but in a variant, a single central flow orifice TR is used, which reduces the risk of oil rising back upwards.

[0024] To prevent the oil from rising back into the air gap of the electric machine ME, Figure 2 The membrane MB is shown closing the orifice TR while allowing the oil to flow through the membrane MB. Figure 3 and Figure 4One of these membranes MB is shown in detail, made of a flexible material, such as silicone or any equivalent material that can withstand temperatures between -40°C (degrees Celsius) and 120°C. This membrane comprises a flexible flap V that sags towards the oil reservoir OT under the weight of the oil flowing out of the active components of the electric machine ME. The flap V is made by making a cut in the membrane MB or by being molded simultaneously with the membrane MB. The cross section of the flap is inclined in the vertical direction relative to the electric machine ME, that is to say in the direction of flow of the oil during normal operation. The edges of the flap V thus form a slope that allows the oil to flow into the reservoir, but when the oil from the oil reservoir OT is pressed against the membrane MB, these edges rest fixedly on the corresponding edges of the rest of the membrane MB, which prevents the oil from rising upwards back into the air gap. As a variant, the edges of the flap V are not made as regular slopes, but form a more irregular descent to the reservoir OT, for example a stepped descent. The membrane MB further comprises rail-shaped edges, by means of which it can be clamped to the edges of the wall of the housing CA at the orifice TR.

[0025] according to Figure 5 An alternative embodiment is shown, in which a plastic frame is clamped to the edge of the orifice TR. A rigid flap V2, also made of plastic, is fixed to the edge of the frame located in the reservoir by means of a pivot connection LP. The plastic used for flap V2 and frame can withstand temperatures between -40°C and 120°C. An adjustable return spring is used to keep flap V2 in contact with the frame. The spring is coiled around a central rod that connects flap and frame by means of a hinge connection.

[0026] Thus, when the vehicle is travelling at a constant speed on a straight road, when this oil flows out of the active parts of the machine ME, the return spring allows the flap V2 to open and allows the oil to enter the reservoir OT. The dimensions of the flap V2 are greater than those of the orifice TR, so that, in the event of a turn or sudden acceleration / deceleration, the oil contained in the reservoir OT is pressed against the flap V2, which is fixed by the edge of the wall of the casing CA and prevents the oil from rising back up into the air gap.

[0027] Of course, other variant embodiments of the invention are conceivable, for example, dielectric heat transfer cooling liquids other than oil may be used.

Claims

1. An electric machine (ME) for an electric or hybrid motor vehicle, the electric machine comprising: a casing (CA) capable of protecting active components (ROT, STAT) of the electric machine (ME); A cooling system comprising means for spraying a dielectric heat transfer cooling liquid onto at least a portion of the active component; a reservoir (OT) capable of collecting, under the action of gravity, the cooling liquid flowing through at least one orifice (TR) of a wall separating the active component and the reservoir (OT), the machine (ME) being characterized in that it comprises a flap (V, V2) fixed to the wall at the level of the at least one orifice (TR) and capable of closing the at least one orifice (TR), an elastic device capable of opening the flap (V, V2) under the action of the gravity of the cooling liquid, the non-return device capable of keeping the flap (V, V2) closed when a force exerted on the cooling liquid in the reservoir (OT) causes the liquid to press against the flap (V, V2), Therein, the flap (V), the elastic means and the non-return means consist of a single membrane (MB) made of elastic material, which is attached on either side of the at least one orifice (TR), and in the orifice where the flap (V) is made, the edge of the fixed part of the membrane (MB) covers the edge of the flap (V), and the edge of the flap (V) forms a downward slope towards the reservoir (OT).

2. An electric machine (ME) according to claim 1, characterized in that The membrane (MB) is made of silicone.

3. An electric machine (ME) according to claim 1 or 2, characterized in that The membrane (MB) comprises concave outer edges capable of being fastened elastically to the edges of the at least one orifice (TR).

4. An electric machine (ME) for an electric or hybrid motor vehicle, the electric machine comprising: a casing (CA) capable of protecting active components (ROT, STAT) of the electric machine (ME); A cooling system comprising means for spraying a dielectric heat transfer cooling liquid onto at least a portion of the active component; a reservoir (OT) capable of collecting, under the action of gravity, the cooling liquid flowing through at least one orifice (TR) of a wall separating the active component and the reservoir (OT), the machine (ME) being characterized in that it comprises a flap (V, V2) fixed to the wall at the level of the at least one orifice (TR) and capable of closing the at least one orifice (TR), an elastic device capable of opening the flap (V, V2) under the action of gravity of the cooling liquid and a non-return device. , V2), the non-return device being capable of keeping the flap (V, V2) closed when a force exerted on the cooling liquid in the reservoir (OT) causes the liquid to press against the flap (V, V2), wherein the flap (V2) is arranged below the wall and has dimensions greater than the dimensions of the orifice (TR), the non-return device comprising a return spring fixed to a pivot connection (LP) connecting the flap (V2) to the wall, wherein the flap (V2) is fixed to a frame via the pivot connection (LP), and the frame is fixed to the wall via a clip on the edge of the orifice (TR).

5. An electric machine (ME) according to claim 4, characterised in that The flap (V2) and the frame are made of plastic material.

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