POWER UNIT AND MOBILITY MACHINE COMPRISING SUCH A POWER UNIT

Abstract

The motor unit comprises: - an electrical machine comprising a stator (104) and a rotor; - an inverter (110) for controlling the stator (104); - an output shaft; - a gear system between the rotor and the output shaft; - a housing in which at least the stator (104) and the gear system extend, the housing containing oil (124) extending over a bottom (126) of the housing (112), a wheel (118D) of the gear system, called a projection wheel, being designed to, during its rotation, drive and project the oil from the bottom (126) of the housing (112) onto an element to be cooled (116); - a retention basin (138) designed to receive the projected oil (124); and - an oil return path (124) overflowing from the retention basin (138) towards the bottom (126) of the housing (112). The stator (104) and / or a heat sink (112) of the inverter (110) extend at least partly into the retention basin (138) to bathe in the retained oil (124).Figure for abstract: Fig. 3.

Description

Title of the invention: MOTOR UNIT AND MOBILITY MACHINE COMPRISING SUCH A MOTOR UNIT Technical field of the invention

[0001] The present invention relates to a power unit and a mobility device comprising such a power unit.

[0002] A mobility device is, for example, a motorized land vehicle, a train, an aircraft or a drone. A motorized land vehicle is, for example, a motor vehicle, a motorcycle, a motorized bicycle or a motorized wheelchair. Technological background

[0003] The PCT international application published under number WO 2018 150128 A1, describes a motor group comprising: - an electrical machine comprising a stator and a rotor; - a stator control inverter; - an output shaft; - a gear system between the rotor and the output shaft; and - a housing in which at least the stator and the gear system extend, the housing containing oil extending over a bottom of the housing, a wheel of the gear system, called a projection wheel, being designed to, upon rotation, drive and project the oil from the bottom of the housing onto cooling fins of the inverter.

[0004] Thus, the inverter is cooled passively, without requiring an oil circulation pump. However, this solution has the disadvantage that at low speed of the electric machine, the oil projections are less significant and may not be sufficient to effectively cool the inverter.

[0005] Furthermore, the PCT international application published under number WO 2022 201590 Al proposes spraying oil onto the stator to cool it, and providing a retention basin to receive the sprayed oil. The retention basin is placed next to a rotor bearing, so that this bearing is bathed in the retained oil. This ensures that the bearing is always lubricated, even after the electric machine has not been used for a long period. However, this prior art does not provide a solution to the problem of cooling the inverter at low speed of the electric machine.

[0006] It may thus be desirable to provide a motor unit which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention

[0007] A motor group is therefore proposed comprising: - an electrical machine comprising a stator and a rotor; - a stator control inverter; - an output shaft; - a gear system between the rotor and the output shaft; - a housing in which at least the stator and the gear system extend, the housing containing oil extending over a bottom of the housing; - a part, called a projection part, designed to be driven in rotation by the gear system and, during its rotation, to drive and project the oil from the bottom of the housing onto an element to be cooled; - a retention basin designed to receive the projected oil; and - a return path for the oil overflowing from the retention basin to the bottom of the housing; characterized in that the stator and / or a heat sink of the inverter extend at least partly into the retention basin to bathe in the retained oil.

[0008] Thus, thanks to the invention, the stator and / or the inverter are always sufficiently cooled, even at low speed of the electric machine, thanks to the retained oil in which they are bathed.

[0009] The invention may further comprise one or more of the following optional features, in any technically possible combination.

[0010] Optionally, the projection part is a wheel of the gear system, called a projection wheel, designed, during its rotation, to drive and project the oil from the bottom of the housing onto the element to be cooled.

[0011] Also optionally, the projection wheel is the largest wheel in the gear system.

[0012] Also optionally, the heat sink comprises a body against which the inverter is pressed and projections of the body of the heat sink, these projections being designed to bathe in the retained oil.

[0013] Also optionally, the projections of the heat sink comprise fins extending in an oil projection direction so that the projected oil flows between the fins.

[0014] Also optionally, the element to be cooled comprises the heat sink and / or the stator.

[0015] Also optionally, at least a portion of the stator is located on the return path so that oil overflowing from the retention basin flows onto the stator.

[0016] Also optionally, the motor unit further comprises, on the return path, a device for limiting a flow rate of the oil on the stator, comprising: - a buffer basin designed to receive the oil overflowing from the retention basin; and - pipes arranged in the bottom of the buffer basin and designed to conduct the oil from the buffer basin to the stator.

[0017] Also optionally, the gear system is a reducer.

[0018] A mobility device is also proposed comprising: - a movement system, comprising for example one or more drive wheels; and a motor unit according to the invention, used as a powertrain unit for driving the movement system. Brief description of the figures

[0019] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which: - [Fig. 1] is an exploded view of an example of an engine group in which the invention is implemented, - [Fig.2] is a sectional view of the engine unit of [Fig.l], and - [Fig.3] is another sectional view of the engine unit of [Fig.l]. Detailed description of the invention

[0020] With reference to [Fig.l], an example of a motor group 100 in which the invention is implemented will now be described.

[0021] The engine group 100 is for example designed to equip a mobility device comprising a movement system, for example one or more drive wheels. The engine group 100 can then be used as a powertrain for driving the movement system.

[0022] Thus, the motor group 100 firstly comprises an electrical machine 102 provided with a stator 104 and a rotor 106 movable relative to the stator around a motor axis AM. The electrical machine 102 is designed to operate as a motor and / or as a generator. The electrical machine 102 further comprises a motor shaft 108 extending over the motor axis AM and fixed to the rotor 106 to rotate with the latter.

[0023] The motor group 100 further comprises an inverter 110 for controlling the stator 104. More precisely, the inverter 110 is designed to control the stator 104 so that the latter generates a rotating magnetic field, under the effect of which the rotor 106 is designed to rotate around the axis of rotation AM.

[0024] To cool the inverter 110, the motor unit 100 further comprises a heat sink 112 comprising a body 114 against which the inverter 110 is pressed, and projections 116 projecting from the body 114 of the heat sink 112. These pro ejections 116 may be pins or fins. In the latter case, the fins preferably extend in a direction of projection of the oil 124, as in the example illustrated, so that the projected oil 124 rushes between the fins and better evacuates the heat.

[0025] The motor group 100 further comprises a gear system 118 coupled to the rotor 106 in order to be driven by the latter. The gear system 118 comprises successive wheels 118A-D meshing with each other, the first wheel 118A of the succession being for example integral with the motor shaft 108. For example, the gear system 118 is a reduction gear, so that the last wheel 118D of the succession rotates at a lower speed, for example at least 5 times lower, for example still at least 8 times lower, for example still at least 10 times lower, than that of the first wheel 118A of the succession.

[0026] The motor unit 100 further comprises an output shaft 120 designed to be coupled to the gear system 118, and more precisely to the last wheel 118D of the gear system 118, in order to drive the movement system of the mobility device. For example, the output shaft 120 is integral with the last wheel 118D to rotate with the latter.

[0027] The motor unit 100 further comprises a housing 122 in which at least the stator 104 and the gear system 110 extend. The housing 122 is adapted to contain oil 124 extending over a bottom 126 of the housing 122.

[0028] For example, the housing 122 comprises an upper cover 122A in which the inverter 110 extends and which has a lower opening 128 closed by the body 114 of the heat sink 112. The housing 122 further comprises a lower tank 122B having a first compartment 130 for receiving the electric machine 102 and a second compartment 132 for receiving the gear system 118. These two compartments 130, 132 communicate with each other. The tank 122B further has an upper opening 134 opening onto the first compartment 130.

[0029] A wheel of the gear system 110, called the projection wheel, is designed, during its rotation, to drive and project the oil 124 from the bottom 126 of the housing 122. Preferably, this is the largest wheel of the gear system 118. Indeed, the largest wheel is generally the one which is always immersed in the oil 124 from the bottom 126 of the housing 122. This is the wheel 118D in the illustrated example. To promote the driving of the oil 124, the housing 122, and in particular the tank 122B, has a curved wall 136 following the curvature of the projection wheel 118D.

[0030] The oil 124 is for example sprayed onto the cooling fins 116. For this, as in the example illustrated, the spray wheel 118D is designed to spray the oil 124 into the upper opening of the tank 122 where the cooling fins 116. In this case, the curved wall 136 preferably extends from the bottom 126 to the upper opening 134 of the tank 122B.

[0031] The motor unit 100 further comprises a retention basin 138 designed to receive the sprayed oil 124. For example, as in the illustrated example, the motor unit 100 comprises a tray 140, at least a portion of which forms the retention basin 138. The tray 140 extends into the upper opening 134 of the tank 122B. The cooling fins 116 of the inverter 110 then extend at least partially into the retention basin 138 to bathe in the retained oil 124. The retention basin 138 has no bottom discharge to allow the oil 124 to accumulate. The evacuation takes place at a certain height, by overflowing over a wall of the retention basin 138 (as in the example illustrated) or through an opening made in a wall of the retention basin 138.

[0032] The engine group 100 comprises a path 142 for returning the oil 124 overflowing from the retention basin 138, towards the bottom 114 of the housing 112.

[0033] Preferably, as in the illustrated example, at least a portion of the stator 104 is located on the return path 142, for example under the retention basin 138, to receive the oil 124 overflowing from the retention basin 138.

[0034] With reference to [Fig. 2], the motor unit 100 further comprises, on the return path 142, a device 202 for limiting a flow rate of the oil on the stator 104. This flow rate limiting device 202 comprises a buffer basin 204 designed to receive the oil 124 overflowing from the retention basin 138. The flow rate limiting device 202 further comprises conduits 206 (in [Fig. 2], for the sake of clarity only some are identified by the reference 206), arranged in a bottom 208 of the buffer basin 204 and designed to conduct the oil 124 from the buffer basin 204 to the stator 104. Thus, it is possible to limit the flow rate of oil 124 reaching the rotor 104, while ensuring that the oil 124 is well distributed over the stator 104. 104.

[0035] With reference to [Fig. 3], in operation, the rotor 106 rotates, which causes the projection wheel 118D to rotate. The latter is in contact with the oil 124 present at the bottom 126 of the housing 112 and, by its rotation, drives and lifts the oil 124 to project it onto the cooling fins 116 to cool the inverter 110. The projected oil 124 then falls back into the retention basin 138 where it accumulates, so that the cooling fins 116 bathe in the accumulated oil 124. When the accumulated oil 124 reaches a certain level (that of [Fig.2]), it overflows from the retention basin 138 to flow into the buffer basin 204 from which the oil 124 emerges through the pipes 206 to reach the stator 104. The output flow rate of the oil 124 is limited by the pipes 206. Thus, when the projection of oil 124 on the cooling fins 116 is significant, the buffer basin has tendency to fill up, whereas when the projection is low, the buffer basin tends to empty. This makes it possible to ensure a relatively constant flow of oil 124 on the stator 104, independently of the level of oil projection and therefore of the speed of the electrical machine 102. The oil 124 passing over the stator 104 then joins the compartment 132 of the gear system 118, by the fact that the compartments 130, 132 are in communication, to return to the bottom 126 of the housing 112.

[0036] In conclusion, it appears clearly that a motor group such as that described previously makes it possible to evacuate the heat from the cooling fins, without requiring a pump and even when the electric machine is running at low speed.

[0037] It will also be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in light of the teaching which has just been disclosed to them.

[0038] In particular, the retention basin could be located under the stator, so that it is the latter which bathes in the oil accumulated in the retention basin. It could even be envisaged that the inverter is placed lower so that both the heat sink and the stator bathe in the oil accumulated in the retention basin. Furthermore, the element cooled by the oil splashes could be the stator, instead of or in addition to the heat sink, or even another element than the stator and the heat sink.

[0039] In the detailed presentation of the invention which is made above, the terms used must not be interpreted as limiting the invention to the embodiments set out in the present description, but must be interpreted to include all equivalents whose prediction is within the reach of those skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Claims

1. Motor group (100) comprising: - an electrical machine (102) comprising a stator (104) and a rotor (106); - an inverter (110) for controlling the stator (104); - an output shaft (120); - a gear system (118) between the rotor (106) and the output shaft (120); - a housing (112) in which at least the stator (104) and the gear system (118) extend, the housing (112) containing oil (124) extending over a bottom (126) of the housing (112); - a part (118D), called a projection part, designed to be rotated by the gear system (118) and, during its rotation, to drive and project the oil (124) from the bottom (126) of the housing (112) onto an element to be cooled; - a retention basin (138) designed to receive the projected oil (124); and - a return path (142) for the oil (124) overflowing from the retention basin (138) towards the bottom (126) of the housing (112);characterized in that the stator (104) and / or a heat sink (112) of the inverter (110) extend at least partly into the retention basin (138) to bathe in the retained oil (124).;

2. Engine group (100) according to claim 1, in which the projection part is a wheel (118D) of the gear system (118), called projection wheel, designed, during its rotation, to drive and project the oil (124) from the bottom (126) of the housing (112) onto the element to be cooled.

3. The power unit (100) of claim 2, wherein the projection wheel (118D) is the largest wheel of the gear system (118).

4. A motor unit (100) according to any one of claims 1 to 3, wherein the heat sink (112) comprises a body (114) against which the inverter (110) is pressed and projections (116) of the body (114) of the heat sink (112), these projections (116) being designed to bathe in the retained oil (124).

5. The engine unit (100) of claim 4, wherein the projections (116) of the heat sink (112) comprise fins extending in a direction of projection of the oil (124) so that the projected oil (124) flows between the fins.

6. Motor group (100) according to any one of claims 1 to 5, wherein the element to be cooled comprises the heat sink (112) and / or the stator (104).

7. A power unit (100) according to any one of claims 1 to 6, wherein at least a portion of the stator (104) is located in the return path (142) for oil (124) overflowing from the retention basin (138) to flow over the stator (104).

8. Motor group (100) according to claim 7, further comprising, on the return path (142), a device (202) for limiting a flow rate of the oil (124) on the stator (104), comprising: - a buffer basin (204) designed to receive the oil (124) overflowing from the retention basin (138); and - conduits (206) arranged in a bottom (208) of the buffer basin (204) and designed to conduct the oil (124) from the buffer basin (204) to the stator (104).

9. A power unit (100) according to any one of claims 1 to 8, wherein the gear system (118) is a reduction gear.

10. Mobility device comprising: - a movement system, comprising for example one or more drive wheels; and - a motor unit (100) according to any one of claims 1 to 9, used as a powertrain unit for driving the movement system.

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