REDUCER FOR A ROTATING ELECTRIC MACHINE WITH IMPROVED SEALING

Abstract

The invention relates to a gearbox (10) for a rotating electrical machine comprising: - a housing (11) having a bore (16) allowing the inlet of coolant, - a hollow primary shaft (12) having a bore (20) passing axially through the primary shaft (12), - a bearing (13) arranged radially between an outer periphery of the primary shaft (12) and the housing (11), - a bearing screw (15) ensuring axial retention of the bearing (13), said bearing screw (15) having a recess (24) passing axially through the bearing screw (15), said bearing screw (15) being fixed to one end of the hollow primary shaft (12), the coolant inlet opening opposite the recess (24) of said bearing screw (15), and - a sealing segment (30) interposed radially between the bearing screw (15) and the housing (11). Figure 1

Description

Title of the invention: REDUCER FOR A ROTATING ELECTRIC MACHINE WITH IMPROVED SEALING

[0001] The present invention relates to a reducer for a rotating electrical machine with improved sealing. The invention finds a particularly advantageous application with rotating electrical machines used with electric or hybrid type motor vehicles such as cars, trucks, construction machinery, buses, or tractors.

[0002] In a manner known per se, an electric or hybrid type motor vehicle comprises a rotating electrical machine mounted on a set of wheels, in particular the front set of wheels. A speed reducer makes it possible to make the high rotational speed of the rotating electrical machine compatible with the rotational speed of the wheels.

[0003] A rotating electrical machine of the synchronous type comprises a wound stator and a rotor equipped with permanent magnets. Conventionally, these permanent magnets are rare earth magnets which have the disadvantage of being heavy.

[0004] To reduce the mass of the rotor, it is possible to replace the rare earth magnets with permanent magnets having a very low Curie temperature, in particular less than 150°C. In order to comply with this thermal constraint, it is necessary to cool the rotor magnets with a high calorific value coolant, such as oil. The main difficulty in conveying the oil into the rotor is to ensure dynamic sealing between the gearbox housing and an oil inlet located in the rotor axis. Indeed, if the sealing is not carried out correctly, a significant part of the oil flow will leak at this interface without contributing to the cooling of the permanent magnets. This generates an energy loss in the oil circuit and therefore an unnecessary demand for excessive energy from the oil pump, which degrades the overall efficiency of the powertrain.

[0005] The invention aims to effectively resolve this drawback by proposing a reducer for a rotating electrical machine comprising: - a casing with a hole allowing the inlet of coolant, - a hollow primary shaft comprising a bore passing axially through the primary shaft from one side to the other, - a bearing arranged radially between an external periphery of the primary shaft and the casing, - a rolling screw ensuring axial support of the bearing, said rolling screw comprising a hollow passing axially through the rolling screw from one end to the other part, said bearing screw being fixed to one end of the hollow primary shaft, the coolant inlet passage opening opposite the hollow of said bearing screw, and - a sealing segment interposed radially between the bearing screw and the casing.

[0006] The invention thus makes it possible to ensure dynamic sealing compatible with the speed of the rotating electrical machine which can be 15000 rpm without generating friction. In particular, the invention makes it possible to reduce the leakage at the interface between the oil inlet and the casing and therefore to limit the flow rate of coolant required from the oil pump. This limits the energy consumption of the oil pump while improving the flow rate of coolant circulating inside the rotor. The invention also makes it possible to improve the efficiency of the electric motor by reducing the temperature of the magnets and the rotor via control of the flow rate of the coolant.

[0007] According to one embodiment of the invention, the sealing segment is arranged inside a groove made in an external periphery of the rolling screw, said sealing segment bearing against the casing.

[0008] According to one embodiment of the invention, there is radial clearance between a bottom of the groove and the sealing segment.

[0009] According to one embodiment of the invention, an axial width of the groove is greater than an axial width of the sealing segment so as to create an axial clearance between at least one side wall of the groove and the sealing segment.

[0010] According to one embodiment of the invention, the bearing is held axially between a shoulder of the primary shaft and a collar of the bearing screw.

[0011] According to one embodiment of the invention, the sealing segment is made of a metallic material.

[0012] According to one embodiment of the invention, the coolant is oil.

[0013] The invention also relates to an assembly comprising a reducer as previously defined and a rotating electrical machine comprising a stator and a rotor mounted on a rotor shaft.

[0014] According to one embodiment of the invention, the primary shaft and the rotor shaft are coaxial with respect to each other.

[0015] The invention further relates to a motor vehicle comprising an assembly as previously defined.

[0016] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.

[0017] [Fig. 1] is a partial longitudinal sectional view of a reducer according to the invention;

[0018] [Fig.2] is a partial detailed sectional view of a sealing segment according to the invention arranged inside a groove made in the rolling screw;

[0019] [Fig.3] is a front view of a sealing segment according to the present invention.

[0020] Identical, similar, or analogous elements retain the same reference from one figure to another.

[0021] [Fig.l] shows a reducer 10 for a rotating electrical machine comprising a casing 11, a hollow primary shaft 12 rotatably mounted relative to the casing 11 by means of a bearing 13, in particular a ball bearing, and a rolling screw 15 ensuring axial retention of the bearing 13. The reducer 10 has an axis X corresponding to the axis of the primary shaft 12, the rolling screw 15 and the casing 11 mounted coaxially.

[0022] More precisely, the casing 11 comprises a bore 16 allowing an inlet of coolant. Preferably, the coolant is a coolant with a high calorific value, such as oil. The casing 11 comprises a transverse flange 17 comprising a housing 14 intended to receive a rolling screw 15 described in more detail below. The transverse flange 17 of the casing 11 is extended by an annular portion 18 of axial orientation relative to the axis X.

[0023] Furthermore, the hollow primary shaft 12 comprises a bore 20 passing axially through the primary shaft 12 from one side to the other. The primary shaft 12 carries a pinion 21 which can be attached and fixed to the primary shaft 12 or be in one piece with the primary shaft 12. This pinion 21 is intended to mesh with a pinion of a secondary shaft (not shown). The primary shaft 12 of the reducer 10 being coaxial with the rotor shaft, there is no dynamic sealing between these two shafts which rotate at the same speed.

[0024] The bearing 13 is arranged radially between an external periphery of the primary shaft 12 and the casing 11. In this case, the bearing 13 is arranged radially between an external periphery of the primary shaft 12 and an internal periphery of the annular portion 18 of the casing 11. This bearing 13 makes it possible to ensure rotational guidance of the primary shaft 12 relative to the casing 11.

[0025] The rolling screw 15 is a hollow screw comprising a hollow 24 passing right through the rolling screw 15. The rolling screw 15 is fixed to one end of the hollow primary shaft 12. The coolant inlet bore 16 opens opposite the hollow 24 of the rolling screw 15. The coolant inlet bore 16 preferably opens at the X axis.

[0026] In this case, the rolling screw 15 has a threaded annular portion 25 cooperating with an internal thread of corresponding shape made in the hollow primary shaft 12. The rolling screw 15 also comprises a collar 26, so that a ring of the bearing 13 is held axially between a shoulder 27 of the hollow primary shaft 12 and the collar 26 of the rolling screw 15. For this purpose, the collar 26 extends radially relative to the axis X. The rolling screw 15 also comprises an annular portion 28 arranged inside the housing 14 of the casing 11. The threaded annular portion 25 has a diameter smaller than the annular portion 28 arranged inside the housing 14.

[0027] A sealing segment 30 is interposed radially between the rolling screw 15 and the casing 11. The sealing segment 30 is arranged inside a groove 31 made in an external periphery of the rolling screw 15. In the example shown, the groove 31 is made in the external periphery of the annular portion 28. The sealing segment 30 bears against the casing 11. The sealing segment 30 has the shape of a split ring, as shown in [Fig. 3]. The split ring extends in a radial plane relative to the axis X. Preferably, the sealing segment 30 is made of a metallic material to withstand high speed stresses. The sealing segment 30 is mounted compressed radially inside the groove 31 so as to guarantee radial contact between the sealing segment 30 and the casing 11.

[0028] As can be seen in [Fig.2], there is a radial clearance J1 between a bottom of the groove 31 and the sealing segment 30. In other words, an internal diameter of the sealing segment 30 is greater than the diameter of the bottom of the groove 31. The sealing segment 30 is therefore not in contact with the bottom of the groove 31.

[0029] Furthermore, an axial width of the groove 31 is greater than an axial width of the sealing segment 30 so as to create an axial clearance J2 between at least one side wall of the groove 31 and the sealing segment 30. The axial clearance J2 between the sealing segment 30 and the groove 31 is small, for example of the order of 0.1 mm, in order to guarantee the dynamic sealing function. By "of the order of" is meant a variation of plus or minus 10% around the indicated value.

[0030] The clearances J1 and J2 are guaranteed hot and cold, taking into account differential thermal expansions to guarantee the absence of rotation of the sealing segment 30 relative to the casing 11.

[0031] This sealing segment 30 thus creates a labyrinth for the passage of the cooling liquid due to, on the one hand, the contact between the segment and the casing 11 of the reducer 10 via a calibration of the sealing segment 30 and, on the other hand, the low axial clearance J2 between the sealing segment 30 and the groove 31 of the rolling screw 15.

[0032] The cooling liquid coming from the supply bore 16 can thus flow mainly axially inside the hollow 24 of the bearing screw 15 then inside the bore 20 of the primary shaft 12 which is coaxial with respect to the hollow 24 of the bearing screw 15. The cooling liquid can then penetrate inside a bore 20 made inside the rotor in order to evacuate calories from the latter so as to maintain a temperature compatible with the permanent magnets.

[0033] The axial clearance J2 and the radial force ensured by the calibration of the sealing segment 30 ga also ensure that the sealing segment 30 remains fixed relative to the reduction gear 10 casing 11. The absence of axial force and the radial clearance J1 of the sealing segment 30 with the bottom of the groove 31 also make it possible to limit the friction between the sealing segment 30 and the groove 31.

Claims

Claims

1. Reducer (10) for a rotating electrical machine characterized in that it comprises: - a casing (11) comprising a bore (16) allowing a coolant inlet, - a hollow primary shaft (12) comprising a bore (20) passing axially through the primary shaft (12) from one side to the other, - a bearing (13) arranged radially between an external periphery of the primary shaft (12) and the casing (11), - a bearing screw (15) ensuring axial retention of the bearing (13), said bearing screw (15) comprising a hollow (24) passing axially through the bearing screw (15) from one side to the other, said bearing screw (15) being fixed to one end of the hollow primary shaft (12), the coolant inlet passage opening opposite the hollow (24) of said bearing screw (15), and - a sealing segment (30) interposed radially between the bearing screw (15) and the casing (11).

2. Reducer according to claim 1, characterized in that the sealing segment (30) is arranged inside a groove (31) made in an external periphery of the rolling screw (15), said sealing segment (30) bearing against the casing (11).

3. Reducer according to claim 2, characterized in that there is a radial clearance (Jl) between a bottom of the groove (31) and the sealing segment (30).

4. Reducer according to claim 2 or 3, characterized in that an axial width of the groove (31) is greater than an axial width of the sealing segment (30) so as to create an axial clearance (J2) between at least one side wall of the groove (31) and the sealing segment (30).

5. Reducer according to any one of claims 1 to 4, characterized in that the bearing (13) is held axially between a shoulder of the primary shaft (12) and a collar (26) of the bearing screw (15).

6. Reducer according to any one of claims 1 to 5, characterized in that the sealing segment (30) is made of a metallic material.

7. Reducer according to any one of claims 1 to 6, characterized in that the cooling liquid is oil.

8. Assembly comprising a reducer (10) as defined according to one any of the preceding claims and a rotating electrical machine comprising a stator and a rotor mounted on a rotor shaft.

9. Assembly according to claim 8, characterized in that the primary shaft (12) and the rotor shaft are coaxial with respect to each other.

10. A motor vehicle comprising an assembly according to claim 8 or 9.

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