Electric powertrain with differential integrated into the wound rotor of the electric machine.

Abstract

Electric powertrain 1, comprising an oil-cooled electric machine 10 whose wound rotor 12 constructed on a tubular base 12a externally carries a stack of laminations and windings 12c and internally accommodates a torque-sharing differential mechanism 20 comprising a two-part housing 21, 22 containing a spherical differential mechanism with two or four satellites 24 and two planetary gears 23 called tail gears, extending axially, and at the end of which is cut a helical toothing 23c driving the satellites 42 of a reducer 40a, 40b lubricated by oil according to a network common to the cooling of the electric machine 10, characterized in that the parts 21, 22 of the housing, integral in rotation with the wound rotor 12 have axial extensions 21a, 22a, one carries a bearing 35 for guiding the wound rotor 12 in the casing 50 as well as the rotor of the resolver 37,and the other a bearing 35 for guiding the wound rotor 12 in the cover 51 as well as the current supply device 100 of the wound rotor 12 consisting of a fixed element 130 in rotation, connected to an external electric current supply, of two support elements 110 and complementary 120 driven in rotation by the rotor, connected to the coils 12c of the latter and of two intercalated transmitter discs 150a, 150b ensuring the transmission of the current from the fixed element 130 in rotation to the support elements 110 and complementary 120 rotating. Figure for the abstract: Fig.5,

Description

Title of the invention: Electric powertrain with differential integrated into the wound rotor of the electric machine. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a powertrain comprising a radial magnetic flux electric machine with a centrally wound rotor, carried by a housing containing a spherical type epicyclic gear train, similar to that of the differential of an automobile gearbox, distributing the torque of the electric machine to two lateral reducers with epicyclic gear train. STATE OF THE ART

[0002] Publications disclosing an electric machine with a hollow rotor shaft and containing a differential are relatively numerous when the rotor has permanent magnets.

[0003] Among these publications, we can cite document EP3644479. The torque of the motor is shared equally and addressed to two epicyclic gear reducers arranged at each end of the motor.

[0004] Publications disclosing an electric machine with a hollow rotor shaft and containing a differential are rather rare when the rotor is equipped with coils.

[0005] Among these, document CH55838(1912) discloses a powertrain for an electric vehicle where the entire differential and transmission mechanism, without a reducer, is arranged in a tubular body around which the rotor winding is located. The winding power supply device, which is not very detailed, comprises a collector mounted on the outer diameter of this tubular body, i.e. on a large diameter. This is acceptable because the rotational speed is equal to the average of the wheel speeds of a slow vehicle from the beginning of the twentieth century.

[0005] Publication DE4334590 (1995) also discloses a powertrain for an electric vehicle where the entire differential and transmission mechanism, without a reducer, is arranged in a tubular body around which the rotor winding is located. In the figures of this document the device for supplying the rotor coils does not appear.

[0006] The problem with wound rotor machines is precisely the supply of electric current to the coils.

[0007] the power supply of the rotor coils of an electrical machine uses a device comprising two friction contacts between rotating elements, rings generally made of copper also called collectors, carried by an insulating ring arranged on the rotor shaft, connected to the rotor coils and fixed elements, the brushes, also called "carbons" because of the high proportion of carbon, carried by an insulating structure fixed to the casing of the electric machine.

[0008] The current supply to the coils has constraints: - the need to create a sealed chamber because the wear of the brushes releases dust; - wear of the brushes may require maintenance; - collector rings must be of a small diameter in order to limit the tangential speed of contact with the brushes.

[0009] This last feature requires us to associate a conventional reducer with a remote differential with the motor. The small diameter rings do not, in fact, allow the association of the electric machine with a coaxial reducer, advantageous in packaging, because one of the transmission shafts, whose diameter is of the order of 25 to 30 mm, passes through the hollow shaft of the rotor. However, the external diameter of the collector rings is of the same order of magnitude as that of the transmission shaft.

[0010] Integrating the differential into the rotor further increases the axial compactness of the powertrain. The rotor must be designed differently on a tubular base inside which is fixed a housing enclosing a spherical differential mechanism and externally carrying a stack of laminations and magnets as disclosed in publication US5759128.

[0011] In this publication, the powertrain not being equipped with a reducer, the differential housing has axial extensions for guiding the axes of the transmission tulips. These extensions are integral in rotation with the rotor and one of the two could then accommodate a current supply device on a diameter much smaller than the tubular base of the rotor if the latter is wound.

[0012] The outer diameter of the housing extensions is of the order of magnitude of the tubular base of a hollow rotor allowing passage to a transmission shaft for a coaxial type reducer. The current supply device in both situations can then be of the same nature. PRESENTATION OF THE INVENTION

[0013] the subject of this invention is an electric powertrain, comprising a motor whose wound rotor accommodates a torque sharing differential, a planetary gear reducer at each end of the motor, and a device for supplying electric current transmitted by rolling bodies arranged between fixed tracks connected to a power supply external to the motor and rotating tracks secured to the rotor.

[0014] According to a first characteristic, the tubular base of the rotor externally carries a stack of sheets and windings and internally a two-part housing. containing a spherical mechanism with two or four satellites and two planetary gears called tail gears, extending axially, and at the end of which is cut a toothing driving the satellites of a reducer.

[0015] According to a second characteristic, the two parts of the differential housing each have an axial extension surrounding the tail of a sun gear up to the toothing zone, each carrying a rotor support bearing, the first arranged in the motor casing and the second in the cover closing the casing.

[0016] According to a third characteristic, one of the extensions of the housing rotates a device for supplying electric current to the rotor coils.

[0017] According to other characteristics, the power supply device is composed of a central annular element made of insulating material framed by two crown-shaped plates made of conductive material, each having a tab connected by a conductive wire to a connector arranged in the wall of the motor cover and this central element is blocked in rotation by a pin planted in the motor cover.

[0018] The fixed rotating annular assembly of the current supply device is framed by two annular elements made of insulating material, carried by one of the axial extensions of the differential housing, therefore rotating, each carrying a crown-shaped plate made of conductive material, with a tongue connected by a conductive wire to the rotor coils.

[0019] Between the crown-shaped plates carried by the non-rotating central annular element and the rotating crown-shaped plates carried by the two framing elements are interposed two identical annular discs made of insulating material into which are inserted a large quantity of cylindrical rollers, made of conductive material, of diameter greater than the thickness of the disc, ensuring the transmission of the electric current from the non-rotating plates to the rotating plates. DETAILED DESCRIPTION OF THE INVENTION

[0020] These characteristics, aims and advantages of the present invention will appear on reading the detailed description which follows and with regard to the appended drawings given as non-limiting examples and in which:

[0021] [Fig. 1] is a sectional view of the powertrain consisting of a wound rotor electric machine incorporating a differential and two epicyclic gear reducers arranged at both ends of the electric machine.

[0022] [Fig.2] is a sectional view of the wound rotor.

[0023] [Fig.3] is a sectional view of the powertrain, electric machine and re separate drivers.

[0024] [Fig.4] is a sectional view of the device for supplying the wound rotor with electric current.

[0025] [Fig.5] is a sectional view of the powertrain disclosing the re circuit internal oil cooling in the engine and lubrication of the reducers.

[0026] The power unit 1, shown in section in [Fig.l] comprises an electric machine 10 of the radial magnetic flux type composed of a stator 11 and a wound rotor 12, arranged in a casing 50 closed by a cover 51. This machine 10 is positioned at the center of the power unit and is framed by two identical reducers 40a and 40b, each receiving from the motor an equal torque distributed by the differential mechanism 20 of the spherical type arranged at the center of the rotor.

[0027] A device 100 for supplying electric current to the rotor coils, the particularity of which is to have multiple electrical contacts by cylindrical roller bearings, is connected to an external power supply (not shown) via the connector 101 carried by the cover 51.

[0028] The wound rotor 12, shown in section in [Fig.2] is constructed on a tubular base 12a. On the outside it is surrounded by the active parts, i.e. the stack of sheets 12b and the coils 12c. The stack 12b and the tubular base 12a are integral in rotation by notches and 12al, bearing axially on the shoulder 12a2 and axially blocked at the other end by the hoop 12a3.

[0029] In its internal part, the tubular base 12a accommodates the differential mechanism 20. This cylindrical mechanism is composed of two housings 21 and 22.

[0030] The housing 21 is centered in the tubular base 12a. It rests on the internal shoulder 12a4 and is secured in rotation by pins 31. It is secured axially and a second time in rotation by the screws 30.

[0031] The housing 22 closes the housing 21 on which it is centered. It is secured axially and in rotation by the screws 32.

[0032] The closed volume constituted by the housings 21, 22 contains the differential mechanism constituted by two planetary gears 23 with bevel gears 23a provided with axial extensions 23b, commonly called tails, of different lengths for each, ending in a helical gear 23c which acts as a planetary gear for the lateral reducers 40a, 40b.

[0033] The helix angle of this toothing 23c will be chosen so that it produces an axial force which opposes that generated in the bevel teeth 23a, 24a. Consequently, the bearing force on the needle thrust bearing 33 is reduced and the resultant of the axial forces in the helical teeth 23c is zero.

[0034] Between each body of the planets 23 carrying the conical toothing 23a, and the supports on the housings 21, 22 are interposed needle stops 33 securing the device against seizure in the event of low oil supply.

[0035] Each planetary tail 23 is grooved longitudinally in the extension of each tooth of the helical toothing 23c. These very fine grooves 23d allow by capillary effect the oil projected laterally in contact with the teeth to reach the pinions of the differential mechanism and their bearing faces.

[0036] To facilitate the circulation of the oil, a set of evacuation and pressure balancing conduits is provided. The first part of the set of conduits is a radial bore 21b, which opens into a first axial bore 21c extended by an axial bore 22b.

[0037] This partially spherical volume also contains four satellites 24, two guided by the axis 25 and the other two by the half-axes 26 supported in the center of the differential mechanism 20 by the ring 27 surrounding the first axis 25.

[0038] Each satellite 24 has a conical toothing 24a cooperating with the conical toothing 23a. A cup 28 made of a material that is not very sensitive to seizure or of sheet metal covered with Teflon is interposed between each satellite and its spherical support in the housing 21. A ring 29 made of a material that is not very sensitive to seizure or of sheet metal covered with Teflon is interposed between each satellite and its axis 25, and half-axes 26.

[0039] The axial extension 21a of the housing 21 carries the electric current supply device 100. It rests on the shoulder 21d, driven by the grooves 21e and axially blocked by the bearing 35 for guiding the rotor in the cover 51, retained by the stop ring 36.

[0040] The axial extension 22a of the housing 22 carries the rotor of the resolver 37 and the second bearing 35 for guiding the rotor in the casing 50.

[0041] The power unit 1 is shown in section in [Fig. 3], electric machine 10 and separate reducers 40a, 40b. The two reducers, simple epicyclic gear trains, are identical. The train consists of a cylindrical sun gear, with helical teeth 23c at the end of the axial extension 23b of the sun gear 23 of the differential mechanism 20, a planet carrier body 41, three satellites 42, conventionally guided on needles and an axle held at its two ends by the body of the planet carrier 41 and a reinforcing plate 43, a crown 44 fixed in rotation mounted crimped one in the casing 50 of the electric machine and the other in the cover 51.

[0042] The movement and torque of the electric machine enters through the helical teeth 23c at the end of the axial extension 23b of the planetary gear 23 and exits through the splines 41a of the hub of the planet carrier 4L

[0043] The epicyclic gear train is contained in a casing 46 made watertight by the cover 48 obstructing the hub of the planet carrier 41 and the dynamic seal 49 arranged near the bearing 45 of the planet carrier guide in the casing 46.

[0044] [Fig.4] is a sectional view of the current supply device 100. It comprises a first support element 110, made of insulating material, for the other elements making up this device.

[0045] It is carried by the axial extension 21a, resting on the shoulder 21d, driven in rotation by the splines 21e and stopped in translation by the bearing 35 retained by the stop ring 36.

[0046] On this support element 110 is fixed, for example by gluing, a crown-shaped plate 111 made of conductive material, preferably copper or copper alloy.

[0047] On the support element 110 is mounted a complementary element 120, having the same function, also made of insulating material and driven in rotation by the grooves 110a.

[0048] The support element 110 and the complementary element 120, integral in rotation, frame a fixed element in rotation 130, made of insulating material.

[0049] The fixed element 130 in the form of a crown, is centered on the support element 110, has a protrusion 130a which cooperates with a pin 160, for locking in rotation, planted in the cover 51 of the electric machine.

[0050] On the complementary element 120 is attached a crown-shaped plate 121 made of conductive material, preferably copper or copper alloy.

[0051] The fixed element 130, made of insulating material, carries on either side the crown-shaped plates 131 and 132 made of conductive material.

[0052] Between the crown-shaped plates 111, 131 on the one hand and 121, 132 on the other hand are interposed identical transmitter discs 150a and 150b, the first 150a centered by its external diameter in the support element 110, the second 150b centered by its external diameter in the complementary element 120, free to rotate.

[0053] These two transmitting discs 150a, 150b are similar to those of the needle thrust bearings, but play a very different role. They are composed of an annular disc 151 made of insulating material which has, on two concentric circles, a large quantity of rectangular openings in which are inserted rollers 152, cylindrical and all identical, made of conductive material, copper or copper alloy, with a diameter greater than the thickness of the annular disc 151.

[0054] These rollers are subjected to a very low axial load which ensures the contact of the largest possible proportion of rollers 152 with on the one hand the crown-shaped plates 111, 131 (transmitter disc 150a) and on the other hand the crown-shaped plates 121, 132 (transmitter disc 150b) in order to transmit the current from the fixed element 130, connected to an external electrical supply, to the support element 110 and the complementary element 120 in rotation, connected to the rotor coils.

[0055] The choice of a very large number of rollers 152 is the way of splitting the electric current and limiting it, for each contact, to a low intensity electric level reducing the risks of electric arcing and damage.

[0056] The crown-shaped plates 111, 121 have tabs 111a and 121a for connection with the rotor coils.

[0057] The crown-shaped plates 131, 132 carried by the fixed element 130 have each a tab 13la, 132a for connection with an external current supply device (not shown) via the connector 101.

[0058] The complementary element 120, the fixed element 130, as well as the transmitting discs 150a, 150b are pressed against each other and against the support element 110 by a spring of the corrugated washer type 125, mounted in a circular groove 120b of the complementary element 40, put under tension by the washer 126 held by the stop ring 127 engaged in a groove of the support element 110.

[0059] [Fig.5] shows a section of the engine cooling and gearbox lubrication network.

[0060] This network has only one supply orifice 200, opening onto a supply conduit 201 of the watering ramp 210 of the stator 11 of the electrical machine 10, and onto an opposite conduit 202 towards the conduit 203 for the lubrication of the reducer 40b.

[0061] The watering ramp 210 has several holes 211, 212 for watering the entire stator (winding coils) and stack of sheets.

[0062] the end of the watering ramp 210 carried by the casing 50 feeds the conduit 204, towards the conduit 205 in the reducer 40a for its lubrication.

[0063] In the wall of the cover 51 is provided a passage 220 allowing the excess lubricating oil from the reducer 40b to be evacuated towards the compartment of the electric machine 10 and prevents the oil from exceeding the level 221.

[0064] In the wall of the casing 50 is provided a passage 230 allowing the excess lubricating oil from the reducer 40a to be evacuated towards the compartment of the electric machine 10 and prevents the oil from exceeding the level 231.

[0065] A single orifice 240 allows the oil to be evacuated to an external network (not shown) comprising a pump, a filter with magnet and an oil / air exchanger.

Claims

Claims

1. Electric powertrain (1), comprising an oil-cooled electric machine (10) whose wound rotor (12) constructed on a tubular base (12a) externally carries a stack of sheets and windings (12c) and internally accommodates a torque-sharing differential mechanism (20) comprising a two-part housing (21), (22) containing a spherical differential mechanism with two or four satellites (24) and two planetary gears (23) called tail gears, extending axially, and at the end of which is cut a helical toothing (23c) driving the satellites (42) of a reducer (40a), (40b) lubricated by oil according to a network common to the cooling of the electric machine (10), characterized in that the parts (21), (22) of the housing integral in rotation with the rotor (12) have axial extensions (2la), (22a), one carries a bearing (35) for guiding the wound rotor (12) in the housing (50) as well as the resolver rotor (37),and the other a bearing (35) for guiding the wound rotor (12) in the cover (51) as well as the current supply device (100) of the wound rotor (12) consisting of a fixed element (130) in rotation, connected to an external electric current supply, of two support elements (110) and complementary (120) driven in rotation by the rotor, connected to the coils (12c) of the latter and of two interposed transmitter discs (150a), (150b) ensuring the transmission of the current from the fixed element (130) in rotation to the rotating support elements (110) and complementary (120).,

2. Electric powertrain (1) according to claim 1 characterized in that the part (21) of the housing carries the satellite axes (25) and half-axes (26), is centered in the tubular base (12a) and fixed thereto.

3. Electric powertrain (1) according to claim 1 characterized in that the part (22) of the housing is centered and fixed to the housing (21).

4. Electric powertrain (1) according to claim 1 characterized in that a cooling and lubrication network comprises only one supply orifice (200).

5. Electric powertrain (1) according to claim 4 characterized in that the end of a watering ramp (210) carried by the casing (50), supplies a conduit (204), which in turn supplies a conduit (205) for the lubrication of the reducer (40a).

6. Electric powertrain (1) according to claim 4 characterized in that the supply orifice (200) also supplies a conduit (202), opposite the conduit (201), which in turn supplies a conduit (203) for the lubrication of the reducer (40b).

7. Electric powertrain (1) according to claims 1 or 4 characterized in that passages (220), (230) in the walls of the casing (50) and the cover (51) evacuate the excess oil towards the compartment containing the electric machine (10).

8. Electric powertrain (1) according to claims 6 or 7 characterized in that the cooling and lubrication network comprises only one discharge orifice (240) towards an external network (not shown) comprising a pump, a filter and an exchanger.

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