Reduction gear of a hybrid powertain

Abstract

The invention relates to a reduction gear comprising an outer casing (100) which houses shafts and pinions of the gearbox and which comprises a cooling and lubricating circuit adapted to project a lubricating fluid onto said shafts and pinions. According to the invention, the reduction gear further comprises an electric machine (200) which comprises an output shaft (201), adapted to be coupled to one of said shafts, and which is cooled and lubricated by said lubricating fluid thanks to a pump mechanically driven by this electric machine.

Description

DESCRIPTION TITLE OF THE INVENTION: HYBRID POWERTRAIN SPEED REDUCER TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates generally to the hybridization of powertrains.

[0002] It relates more particularly to a speed reducer (typically a gearbox) comprising an external casing which houses at least one shaft and one pinion and which comprises a cooling and lubrication circuit adapted to project a lubricating fluid onto said shaft and pinion.

[0003] It also relates to a motor vehicle comprising a powertrain which comprises an internal combustion engine and such a speed reducer. STATE OF THE ART

[0004] To move forward, a motor vehicle is equipped with a powertrain. This powertrain can have very varied architectures.

[0005] For example, it may include an internal combustion engine, a clutch, a gearbox, and a differential that distributes the torque from the gearbox to the vehicle's two drive wheels. A water cooling system, including a main heat exchanger located at the front of the vehicle (the "radiator"), then cools the internal combustion engine to prevent it from overheating.

[0006] Currently, in the interests of environmental protection, these powertrains are increasingly being equipped with electric machines. Such an electric machine can, in motor mode, assist the internal combustion engine in propelling the motor vehicle or even replace it in certain operating phases, or, in generator mode, recover mechanical energy to transform it into electrical energy to be stored in a battery.

[0007] The electric machine is then generally positioned near the internal combustion engine or the radiator, so that it can take advantage of the water circuit to be cooled.

[0008] The major disadvantage of this solution is that it is bulky and restrictive in the sense that the electric machine must be located in the path of the water circuit and the latter must be sized to effectively cool not only the internal combustion engine, but also the electric machine, whatever their speeds. PRESENTATION OF THE INVENTION

[0009] In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes to incorporate the electric machine with its cooling and lubrication system into the gearbox.

[0010] More particularly, the invention provides a speed reducer as defined in the introduction, in which the following are also provided: - an electric machine which comprises an output shaft coupled to said at least one shaft of the reducer, and - a pump which is operated by the electric machine and which is adapted to cool and lubricate the electric machine using said lubricating fluid.

[0011] Thus, thanks to the invention, the speed reducer components and the electric machine are lubricated and cooled by the same volume of lubricant, which makes it possible to reduce the overall size of the assembly.

[0012] Furthermore, thanks to the invention, the lubrication and cooling of the electric machine are ensured by this electric machine, which drives the pump. It is thus possible to provide a fluid flow adjusted to the speed of the electric machine to ensure lubrication and cooling that are always suitable, neither too low nor too high (which would reduce efficiency unnecessarily).

[0013] This advantage is particularly interesting when the motor vehicle is stationary and the electric machine is starting. In this configuration, the electric machine can be lubricated and cooled, even if the internal combustion engine remains stationary.

[0014] Thanks to the invention, it is possible to house the speed reducer components and the electric machine in the same housing. The installation of the electric machine in the speed reducer housing is therefore less restrictive, particularly because the system for cooling it is more compact than a water cooling system.

[0015] Other advantageous and non-limiting characteristics of the speed reducer according to the invention, taken individually or in all technically possible combinations, are the following: - the electric machine and the pump are housed in said external casing; - a speed reduction means is provided, one input of which is coupled to the output shaft of the electric machine and one output of which is coupled to said pump; - the speed reduction means has a reduction ratio of less than 1 / 2; - the external casing delimits three separate chambers, including a first chamber which houses the electric machine, a second chamber which houses the speed reduction means and a third chamber which houses the pump; - sealing means are provided between at least the second and third chambers; - the electric machine, the speed reduction means and the pump have a common axis of rotation; - the speed reduction means and / or the pump comprises a drive shaft which is located in alignment with the output shaft of the electrical machine and which has an internal longitudinal conduit through which the lubricating fluid circulates; - the output shaft of the electric machine has, over at least part of its length, an internal longitudinal conduit through which the lubricating fluid circulates; - the output shaft of the electric machine has at least one radial opening allowing the lubricating fluid circulating in the internal longitudinal conduit to be ejected from the output shaft.

[0016] The invention also provides a motor vehicle comprising a powertrain which comprises an internal combustion engine and a speed reducer as mentioned above.

[0017] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. DETAILED DESCRIPTION OF THE INVENTION

[0018] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0019] On the attached drawings:

[0020] [Fig. 1] is a schematic view of a gearbox according to the invention;

[0021] [Fig. 2] is a view of a portion of the gearbox housing of Fig. 1, on the left of which is shown an electric machine coupled to a speed reduction means and a pump;

[0022] [Fig. 3] is a sectional view of the portion of the casing of Figure 2, showing the electric machine, the speed reduction means and the pump;

[0023] [Fig. 4] is an exploded view of a first part of the gearbox of Fig. 1;

[0024] [Fig. 5] is an exploded view of a second part of the gearbox of Fig. 1, in which the part of Fig. 4 is shown in the assembled position;

[0025] [Fig. 6] is a view similar to that of Figure 3, in which the path of the oil is shown.

[0026] Figure 1 shows a speed reducer of a group powertrain. This is more precisely a 10-speed gearbox, but alternatively, it could be a simpler reducer (single-speed or even dual-speed).

[0027] The powertrain is preferably designed to be installed in a motor vehicle. This motor vehicle can take various forms. For example, it could be a truck, a motorcycle, an airplane, a boat, etc. However, it is preferably a car.

[0028] This powertrain is called a hybrid. It then comprises an internal combustion engine (not shown) and an electric machine 200.

[0029] Conventionally, the internal combustion engine has a crankshaft which is coupled to the gearbox 10, possibly via a clutch.

[0030] The electric machine 200 can have a motor function (its torque being added to that developed by the internal combustion engine), or an alternator function (its torque being subtracted from that developed by the internal combustion engine), or both depending on the conditions encountered.

[0031] This 200 electric machine is coupled here to the rest of the powertrain at the 10-speed gearbox. We are therefore talking about a hybridized 10-speed gearbox.

[0032] As shown in Figure 1, in a conventional manner, the gearbox comprises an external casing 100 which houses shafts 20, 30 and pinions 40, 50 in order to offer several gearbox ratios. This gearbox could come in different forms: manual gearbox, robotic gearbox, automatic gearbox, etc.

[0033] Typically, it may comprise two shafts 20, 30 provided with facing pinions 40, 50 of different diameters which mesh with each other, the pinions 50 of one of the shafts 30 being for example mounted loose on this shaft (i.e. being left free to rotate on this shaft) while the others are mounted fixed on the other shaft 20. In order to change a gear ratio, such a gearbox 10 uses coupling devices (known as a sliding gear) designed to couple one of the loose pinions 50 with the shaft 30 so as to equalize their rotation speeds.

[0034] Such a gearbox 10 also houses a main lubrication and cooling circuit 60, which takes a lubricating fluid such as oil from the bottom of the housing 100 to eject it at various locations requiring lubrication and cooling.

[0035] This part of the gearbox 10 will not be described in more detail here since it is well known.

[0036] The casing 100 of this gearbox delimits a main chamber which houses the aforementioned shafts 20, 30 and pinions 40, 50.

[0037] Here, this casing 100 has a protrusion so as to be able to house in particular the electric machine 200.

[0038] This growth is shown in more detail on the right side of the figure. 2.

[0039] This protrusion comprises several parts, so as to facilitate the assembly of the entire hybrid gearbox. It is here formed of four parts 110, 120, 130, 140 which are fixed together so as to house the electric machine 200 as well as a speed reduction means 300 and an oil pump 400 (these three elements 200, 300, 400 being shown in detail on the left part of figure 2).

[0040] The idea here is therefore that the casing 100 houses not only the electric machine 200, but also an oil pump 400 specifically and exclusively designed to cool and lubricate the electric machine 200. The speed reduction means 300 is then employed so that the electric machine 200 can mechanically actuate the oil pump 400 at an ideal speed to ensure this cooling and lubrication.

[0041] It will be noted that this speed is non-zero as soon as the electric machine 200 begins to rotate. The oil pump 400 being in constant engagement with the electric machine 200 via the speed reduction means 300, its speed will depend on that of the electric machine 200, so that the oil flow rate used to cool and lubricate the electric machine 200 will be a function of the speed of this electric machine (here a linear function).

[0042] According to the invention, the oil used for this purpose will be the same as that used to cool and lubricate the other components of the gearbox. Thus, here, this oil will be taken from the bottom of the casing 100.

[0043] The electric machine 200, the speed reduction means 300 and the oil pump 400 are here successively stacked on the same axis (called rotation axis A1), so as to have a reduced footprint.

[0044] For simplification, in the remainder of this presentation, the terms “right” and “left” will be used taking into account the orientation of the three elements 200, 300, 400 in the different figures, the electrical machine 200 therefore being located to the left of the speed reduction means 300, which is itself located to the left of the oil pump 400.

[0045] At this point, we can describe in more detail the three elements 200, 300, 400.

[0046] As shown in Figures 2 and 3, the electrical machine 200 conventionally comprises a rotor 230, for example a permanent magnet rotor or a wound rotor, and a stator 220 located around the rotor 230 and comprising electrical coils making it possible to establish a rotating magnetic field suitable for rotating the rotor.

[0047] The rotor 230 is equipped with an output shaft 201 which is therefore adapted to rotate around the axis of rotation A1. For this, this output shaft 201 is equipped with two ball bearings engaged in openings provided in two flanges 210, 211 fixed to the stator 220, on either side of it. These two flanges are here held in position by bolts.

[0048] It can be seen in Figure 3 that the left end of the output shaft 201 is solid and that it carries a fixed pinion 240. This is a pinion enabling this output shaft 201 to be coupled with one of the shafts 20 of the gearbox 10.

[0049] It is observed that the right end of this shaft is hollow. A longitudinal bore 201A is in fact provided which extends over the major part of this shaft, along the axis of rotation A1. This longitudinal bore 201A therefore opens onto the side of the oil pump 400. As will become clear in the remainder of this presentation, it allows the oil to enter the interior of the electrical machine 200. To exit this longitudinal bore 201A, two series of radial openings 201B are provided here, located near the two ball bearings and which allow the oil to be ejected towards them and towards the windings of the stator 220 in order to cool the entire electrical machine 200 and lubricate it.

[0050] As shown in Figure 4, the electrical machine 200 is fixed to a first part 110 of the casing 100 by screws 111, here four in number. It is also observed that two centering pins 112 are used to best adjust the position of the electrical machine 200 relative to this first part 110 of the casing 100.

[0051] As shown in this figure 4, a second part 120 of the casing 100 is then screwed onto this first part 110 to enclose the electrical machine 200. This enclosure is of course not complete, since openings are provided so that the oil emerging in the electrical machine 200 can flow by gravity towards the bottom of the casing, via openings provided for this purpose.

[0052] The first and second parts 110, 120 of the casing 100 together delimit a space for the electric machine 200, which is part of the first chamber (which, it is recalled, houses the shafts and pinions of the gearbox). Thus, the oil flowing by gravity into this space will naturally drain towards the bottom of the casing 100, that is to say towards the bottom of the first chamber 200A delimited by the casing 100.

[0053] The first part 110 of the casing 100 comprises a main wall that is substantially planar and orthogonal to the axis of rotation A1, with a flange-shaped rim for fixing it to the second part 120 of the casing 100. This second part comprises a curved side wall around the electric machine 200, which is open on the side of the first part 110 of the casing but which is closed on the opposite side by a substantially planar wall in the center of which is provided an opening 121 for the passage of the right end of the output shaft 201 of the electric machine 200.

[0054] The sealing at this opening 121 is here ensured by a seal 122, preferably of the lip seal type to withstand the high rotation speeds of the output shaft 201. This seal is fixed in the opening 121 so that its lip rests on the output shaft.

[0055] The speed reduction means 300 is directly coupled to this output shaft, without any member interposing between the two.

[0056] This means of speed reduction 300 could come in many different forms.

[0057] In all cases, it is designed to offer a reduction ratio of less than 1 / 2, the value of which allows the oil pump 400 to be operated at a speed adapted to that of the electric machine 200. Typically, this reduction ratio may be between 1 / 8 and 1 / 10.

[0058] Preferably, this speed reduction means 300 is of the epicyclic gear train type. Preferably also, its input and output axes are coaxial.

[0059] In this case, as clearly shown in Figure 4, this speed reduction means comprises a fixed crown 340, a central planetary pinion 310, and a planet carrier 320 equipped with at least one satellite pinion 330 meshing with the central pinion 310 and the fixed crown 340.

[0060] The fixed crown 340 is here forcibly engaged in a bore provided in the second part 120 of the casing 100. This bore is here made hollow in the right side of this second part 120 of the casing 100, so that its bottom is formed by the wall in which the opening 121 for the passage of the output shaft 201 of the electric machine is located. This fixed crown 340 has an external face adjusted to the shape of the bore, and an internal face having straight teeth regularly distributed around the axis of rotation A1.

[0061] The central pinion 310 is mounted on the right end of the output shaft 201 of the electrical machine 200. It is fixedly mounted relative to this output shaft 201, for example by force-fitting or via a splined connection coupled to an axial stop (here a circlip 311). Other connection means could of course be used.

[0062] The planet carrier 320 here comprises a shaft (called “drive shaft 301”), a left end of which is fixed to a flange, here in the form of a cross, each branch of which extends radially relative to the axis of rotation A1. Each of the ends of these branches has a shaft on which a satellite pinion 330 is freely pivotally mounted, around an axis parallel to the axis of rotation A1.

[0063] Thus, when the central pinion 310 pivots, the satellite pinions 330 rotate around the periphery of the fixed crown 340, which forces the drive shaft 301 to rotate around the axis of rotation A1 at a speed lower than but dependent on that of the output shaft 201 of the electric machine 200.

[0064] As shown in Figure 3, the speed reduction means 300 is provided for be housed in a second chamber 300A delimited by the casing 100, which may optionally be sealed relative to the first chamber 200A.

[0065] For this, as shown in figure 5, the casing 100 comprises a third tubular part 130 of which a left end is attached against the second part 120 of the casing and a right end of which is closed by a flat wall.

[0066] This wall is pierced with a central opening 131 for the passage of the drive shaft 301.

[0067] The sealing at this opening 131 is here ensured by a seal 132, preferably of the lip seal type to withstand the high rotation speeds of the drive shaft 301. This seal is fixed in the opening 131 so that its lip rests on the drive shaft 301.

[0068] The drive shaft 301 is then mounted to rotate freely in this third part 130 of the casing 100, around the axis of rotation A1, thanks to a ball bearing 133 which is engaged in a housing provided in this third part 130, next to the opening 131.

[0069] It will be noted that the static seal provided between the second and third parts 120, 130 of the casing 100 is achieved by means of a flat seal 134. Their fixing is ensured by screwing.

[0070] It will be noted in Figure 5 that the third part 130 of the casing is equipped on each of its two faces with two centering pins 136 to allow precise adjustment of the different parts of the casing 100 to each other, which guarantees a perfect adjustment between the axis of the output shaft 201 and the axis of the drive shaft 301.

[0071] As shown in Figure 3, the drive shaft 301 is hollow. A longitudinal bore 301A is provided which extends over the entire length of this shaft, along the axis of rotation A1. This longitudinal bore 301A therefore opens onto the side of the oil pump 400 and onto the side of the electric machine 200. As will become clear in the remainder of this description, it allows the oil to enter the interior of the electric machine 200. It is here connected to the output shaft 201 by a cannula 500 which is shrunk into the output shaft 201 (so that it is fixed there) and which pivots freely relative to the drive shaft 301.

[0072] As shown in Figures 3 and 5, the oil pump 400 is then installed to the right of the third part 130 of the casing 100, in a chamber 400A which is sealed and which is delimited by the third and fourth parts 130, 140 of the casing 100.

[0073] This oil pump 400 is installed directly on the drive shaft 131, which makes it possible to restrict its size. It is therefore centered on the axis of rotation A1.

[0074] Different types of pumps could be used. Typically, one could use a vane pump or a crescent internal gear pump.

[0075] However, here the choice of a volumetric pump with eccentric rotor was retained.

[0076] This type of pump has a flow rate which depends directly on the rotation speed of the drive shaft 301, which is perfectly suited to the needs of the electric machine 200.

[0077] As shown in Figure 5, it comprises a toothed wheel 420 having a central opening through which it is fixedly mounted on the drive shaft 301. This mounting could be achieved by force or by shrink fitting. However, here, it has been chosen to use a key which is locked in grooves provided in the drive shaft 301 and in the central opening of the toothed wheel 420. The right end of the drive shaft 301 is threaded so that a nut 421 can be screwed thereto to lock the toothed wheel 420.

[0078] In the same way as in the second part 120 of the casing 100, a bore is provided in the third part 130 of the casing 100. This bore is here made hollow in the right side of this third part 130 of the casing 100, so that its bottom is formed by the wall in which the opening 131 for the passage of the drive shaft 301 is located.

[0079] The pump then has an eccentric crown 410 with internal teeth which is placed inside this bore.

[0080] So, when the gear wheel 420 rotates, it drives the eccentric ring gear 410, which pumps oil from one side of the bore and returns it to the opposite side.

[0081] Two coaxial bores 137, 138 are then provided opposite each other, in the edge of the bore. One of these bores 137 is here tapped, so that a connection can be screwed into it, which makes it possible to connect this bore to the bottom of the casing 100, where the oil is drawn.

[0082] The outer end of the other bore 137 is closed by a first plug. This bore is connected to a conduit provided in a hollow in the third and fourth parts 130, 140 of the casing 100, to conduct the oil from this bore to the right end of the drive shaft 301.

[0083] The fourth part 140 of the casing 100 is adapted to bear against the third part 130 to enclose the pump 400. For this purpose, it has a disc shape, with four pierced ears allowing the passage of screws which pass through the third part of the casing 100 and are screwed into the second part 120.

[0084] A flat gasket 145 is used to ensure static sealing between these two parts 130, 140 of the casing.

[0085] As clearly shown in Figure 5, the fourth part 140 of the casing 100 has a projecting bulge on its external face, which extends in length radially relative to to the axis of rotation A1. This bulge internally delimits a radial conduit 142 which makes it possible to bring the oil coming from the pump 400 into an orifice provided longitudinally in the cover, along the axis of rotation A1. This orifice is connected to the inside of the drive shaft 301 by a cannula 501 which is shrunk into the casing and which can pivot freely relative to this shaft.

[0086] In Figure 6, the path taken by the oil is shown. It can be seen that the oil arrives through the first bore 137 and passes through the pump 400 to open into the second bore 138. An intermediate conduit 141 then allows it to circulate (parallel to the axis of rotation A1) towards the radial conduit 142 which is provided in the fourth part 140 of the casing 100. Thus, the oil can reach the axial orifice in order to pass into the drive shaft 301 then into the output shaft 201 to open into the electrical machine 200.

[0087] Here, the first bore 137, the intermediate duct 141 and the radial duct 142 are made by drilling, which explains the use of plugs 139, 149 placed at their outlet to the outside. Alternatively, they could be made differently, for example during the casing casting step, or they could be replaced by external ducts in order to guide the flow of oil from the discharge zone of the pump to the oil return axis.

[0088] The operation of gearbox 10 is then as follows.

[0089] When the output shaft 201 of the electric machine 200 is subjected to a rotational speed Q1, it drives via the speed reduction means 300 the drive shaft 301 at a reduced rotational speed Q2, adapted to the operation of the oil pump 400.

[0090] Driven in rotation, the toothed wheel 420 will give the eccentric crown 410 an eccentric circular movement which will create a suction on the side of the bore 137 and a discharge on the opposite side.

[0091] Thanks to the internal conduits in the casing 100, a flow of oil will then be brought axially along the two shafts 201, 301 (the cannulas ensuring the seal between the casing 100 and the drive shaft 301 and between the drive shaft and the output shaft 201). Finally, the radial holes provided in the shaft 201 will supply oil to the active parts and the bearings of the electrical machine 200.

[0092] Thanks to the rotation speed of the electric machine 200 and these radial holes, the oil is in fact naturally projected towards these different components. It then falls directly back into the bottom of the casing 100, by trickling along the walls of the casing.

[0093] The oil flow rate used to lubricate and cool the electric machine can reach a maximum value which is greater than 2 L / min, and which is here of the order of 6 L / min when The electric machine reaches a rotation speed of 18,000 rpm.

[0094] At this stage, it may be noted that the oil supply circuit of the oil pump 400 will preferably include a non-return valve type valve (not shown) in order to prevent the oil pump 400 from planing (the latter being above the oil level of the gearbox). It could also include a heat exchanger in order to cool the oil.

[0095] It may also be noted that the lubrication of the speed reduction means may be carried out in several ways. Lifetime lubrication may be used, by enclosing a lubricant in the chamber 300A at the time of assembly of the gearbox. Alternatively, a filler plug could be provided in the housing to allow a lubricant to be added to this chamber 300A and to be drained as needed. As a further alternative, orifices could be provided in the wall separating the chambers 200A, 300A, so that the oil from the electric machine can be sprayed onto the speed reduction means 300.

[0096] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

[0097] In particular, it could be provided that the oil lubricating the components of the gearbox and the electric machine 100 is stored not in the bottom of the casing, but in a dedicated oil tank located outside the casing, under the latter.

Claims

DEMANDS

1. Speed ​​reducer (10) comprising an external housing (100) which accommodates at least one shaft (20, 30) and one pinion (40, 50) and which comprises a cooling and lubrication circuit (60) adapted to spray a lubricating fluid onto said shaft (20, 30) and / or said pinion (40, 50), characterized in that it also comprises: - an electrical machine (200) which includes an output shaft (201) coupled to said at least one shaft (20, 30), and - a pump (400) which is driven by the electric machine (200) and which is adapted to cool and lubricate the electric machine (200) using said lubricating fluid.

2. Speed ​​reducer (10) according to claim 1, wherein the electric machine (200) and the pump (400) are housed in said external casing (100).

3. Speed ​​reducer (10) according to any one of claims 1 and 2, wherein a speed reduction means (300) is provided, having an input coupled to the output shaft (201) of the electric machine (200) and having an output coupled to said pump (400).

4. Speed ​​reducer (10) according to claim 3, wherein the speed reduction means (300) has a reduction ratio of less than 1 / 2.

5. Speed ​​reducer (10) according to claim 3 or 4, in which the external casing (100) delimits three separate chambers, including a first chamber (200A) which houses the electric machine (200), a second chamber (300A) which houses the speed reduction means (300) and a third chamber (400A) which houses the pump (400), and in which sealing means are provided between at least the second and third chambers (300A, 400A).

6. Speed ​​reducer (10) according to any one of claims 3 to 5, wherein the electric machine (200), the speed reduction means (300) and the pump (400) have a common axis of rotation (A1).

7. Speed ​​reducer (10) according to any one of claims 3 to 6, wherein the speed reduction means (300) and / or the pump (400) comprises a drive shaft (301) which is located in alignment with the output shaft (201) of the electric machine (200) and which has an internal longitudinal conduit (301A) through which the lubricating fluid flows.

8. A speed reducer (10) according to any one of claims 1 to 7, wherein the output shaft (201) of the electric machine (200) has, over at least a portion of its length, an internal longitudinal conduit (201A) through which the lubricating fluid flows.

9. A speed reducer (10) according to claim 8, wherein the output shaft (201) of the electric machine (200) has at least one radial opening (201B) allowing the lubricating fluid flowing in the internal longitudinal conduit (201A) to be ejected from the output shaft (201).

10. Motor vehicle comprising a powertrain which includes an internal combustion engine and a speed reducer (10), characterized in that the speed reducer (10) conforms to one of the preceding claims.

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