Device for transmitting power between coaxial input and output shafts

Abstract

The invention relates to a device (14) for transmitting power between coaxial input (20) and output (22) shafts, said device (14) comprising: - a casing (16), - an input pinion (24), able to rotate and intended to be coaxially connected to said input shaft (20), - an output pinion (26), able to rotate and intended to be coaxially connected to said output shaft (22), said device (14) being configured for transmission of power between the input pinion (24) and the output pinion (26), - one or more guide bearings (52, 54), called mobile bearings, interposed kinematically between said input pinion (24) and said output pinion (26).

Description

[0001] DESCRIPTION

[0002] TITLE: DEVICE FOR TRANSMITTING POWER BETWEEN COAXIAL INPUT AND OUTPUT SHAFTS

[0003] Technical field of the invention

[0004] The invention relates to a power transmission device between coaxial input and output shafts, and to an electric vehicle powertrain comprising such a power transmission device.

[0005] Technical background

[0006] Single gearboxes are widely used in the automotive industry for electric vehicle powertrains. There are two main types.

[0007] According to a first known configuration, reducers with three parallel shafts are known, i.e. with three shafts and two center distances. Such a configuration makes it possible to have a reducer with reduced axial length, but at the expense of its transverse size, due to a juxtaposition of the radial dimensions of the pinions, also called pinion masks.

[0008] According to a second known configuration, reducers with coaxial input and output shafts are known, which, unlike reducers with three parallel shafts, allow for a reducer with reduced transverse dimensions, since the input and output shafts are coaxial and consequently the masks of the input and output pinions are superimposed. However, in this type of reducer, the reduction in transverse dimensions is achieved at the expense of axial dimensions. In particular, a reducer with coaxial shafts generally comprises a coaxial input shaft and output shaft, each carrying an associated input pinion and output pinion, which are both connected by a parallel shaft carrying a double pinion or two pinions.

[0009] This design requires rigorous rotational guidance of the input and output gears. Generally, these gears are guided in rotation relative to a gearbox housing by means of bearings at each of their ends. Such an assembly therefore implies a cumulative axial length of all the input and output gears which is partly dependent on the axial length of the four bearings which carry them.

[0010] Furthermore, the mounting of the pinions in the main casing of the reducer involves the use of a spacer housed in this main casing for the mounting of the two central bearings, which, on the one hand, tends to further increase the axial size of the reducer and, on the other hand, complicates its manufacture, since machining for the mounting of this spacer in the main casing is then necessary.

[0011] There is therefore a need for a new arrangement of a power transmission device between coaxial input and output shafts, aimed at providing an axial space saving for this device.

[0012] Summary of the invention

[0013] The invention meets this need by proposing a new transmission device arrangement in which bearings are no longer mounted in a spacer attached to the main casing, but are kinematically interposed between the input pinion and the output pinion. For this purpose, the invention proposes a power transmission device between coaxial input and output shafts, said device comprising:

[0014] - a casing,

[0015] - an input pinion, movable in rotation and intended to be coaxially connected to said input shaft,

[0016] - an output pinion, movable in rotation and intended to be coaxially connected to said output shaft, said device being configured for power transmission between the input pinion and the output pinion,

[0017] - one or more guide bearings, called mobile, kinematically interposed between said input pinion and said output pinion.

[0018] The interposition of the movable guide bearing(s) between the input and output pinions makes it possible to dispense with a spacer supporting this or these bearings, resulting in a gain in axial space, reduced machining, and a correspondingly reduced mass of the power transmission device.

[0019] Furthermore, since the direction of rotation of the input and output gears is, where appropriate, identical, the differential speed between the inner and outer rings of the moving bearings is limited, which makes it possible to use bearings subject to reduced stresses, and therefore of reduced size.

[0020] According to another characteristic of the invention, a first end of said input pinion extends inside said output pinion and the or at least one of said movable guide bearings is interposed between said first end and said output pinion.

[0021] Such an arrangement of the movable guide bearing(s) makes it possible to further improve the axial compactness of the power transmission device.

[0022] According to another characteristic of the invention, the output pinion comprises a toothing and the or at least one of said movable guide bearings is located axially in line with said toothing. The arrangement of the movable bearing(s) in line with the toothing makes it possible to limit the phenomena of swiveling and therefore of skewing of the toothing, in particular in the case of a helical definition of the toothing.

[0023] According to other characteristics of the invention:

[0024] - there are two of said mobile guide bearings,

[0025] - the two movable guide bearings are located axially in line with the teeth,

[0026] - the two movable guide bearings are axially distant from each other,

[0027] - the output pinion has a bore into which the first end of the input pinion extends,

[0028] - the two movable guide bearings are received in the bore,

[0029] - the device comprises one or more guide bearings, called fixed, carrying the input pinion and / or the output pinion in the casing,

[0030] - the fixed guide bearing(s) are rigidly connected to the casing,

[0031] - a first of the fixed guide bearings is mounted at a second end of the input pinion, opposite said first end,

[0032] - a second of the fixed bearings is mounted at one end of the output pinion opposite the input pinion,

[0033] - the device further comprises a gear train, kinematically interposed between the input and output pinions for the transmission of power between them,

[0034] - the gear train comprises an intermediate pinion, mounted to rotate in the housing and parallel to the input and output pinions,

[0035] - the intermediate pinion meshes respectively with the input and output pinions. According to another characteristic of the invention, to limit the axial movements of the output pinion, the latter is guided by the second fixed bearing, preferably produced in the form of a rolling bearing, an inner ring of which is tightened, for example by shrink fitting, and an outer ring of which is housed in an attached casing. The outer ring is rigidly connected to this attached casing by fixing screw, a circlip or any other connecting element. The same may possibly apply to the input pinion, via the first fixed bearing, provided similarly.

[0036] This arrangement makes it possible to have no relative axial displacement between the input and output gears, and to have mutual guidance between the coaxial input and output shafts which are coupled to these gears.

[0037] The invention also relates to an electric vehicle powertrain, comprising an assembly formed of an electric machine and a transmission device of the type described above.

[0038] The invention thus makes it possible to have a particularly compact electric vehicle powertrain.

[0039] According to other powertrain characteristics:

[0040] - the electric machine comprises a rotor connected in rotation to the input shaft,

[0041] - the input shaft extends coaxially into the input pinion,

[0042] - the input shaft extends inside a bore of the input gear,

[0043] - said group comprises a key connecting the input shaft and the input pinion,

[0044] - the output shaft extends coaxially in the output pinion, the output shaft extends coaxially in the input shaft, - the electrical machine comprises a stator housed in a casing attached and fixed to the casing of the power transmission device, the group comprises two assemblies, located symmetrically on either side of a median plane, the casing of said transmission devices of each of said assemblies being common.

[0045] Brief description of the figures

[0046] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0047] [Fig. 1] Figure 1 is a schematic axial sectional view of an electric vehicle powertrain according to the invention;

[0048] [Fig. 2] Figure 2 is a schematic axial sectional view of an arrangement of input and output gears of a power transmission device according to the state of the art.

[0049] Detailed description of the invention

[0050] Figure 1 shows a powertrain 10 of an electric vehicle according to the invention.

[0051] The powertrain 10 comprises at least one assembly formed of an electric machine 12 and a transmission device 14.

[0052] In Figure 1, a powertrain 10 is shown comprising two assemblies formed of two electric machines 12 and two power transmission devices 14 distributed on either side of a median plane of symmetry P, but it will be understood that this arrangement is not limiting of the invention and that the latter could be applied to a powertrain comprising only such an electric machine 12 and such a power transmission device 14.

[0053] The power transmission device 14 comprises a casing 16. The casing 16 is here common to the two power transmission devices 14 of each of the assemblies.

[0054] The electrical machine 12 comprises a stator 15, housed in a casing 18 of this electrical machine, and a rotor 17. In the illustrated embodiment, the casing 18 of the electrical machine 12 is attached and / or fixed to the casing 16 of the associated power transmission device 14.

[0055] The power transmission device 14 is kinematically arranged between an input shaft 20 which is here linked to the rotor 17 and driven in rotation by the electric machine 12, and an output shaft 22, coaxial with the input shaft 20, which is here intended to drive, directly or indirectly, at least one associated wheel of the vehicle in which the powertrain 10 is installed.

[0056] More particularly, the power transmission device 14 comprises an input pinion 24, movable in rotation, which is coaxially connected to the input shaft 20, and an output pinion 26, also movable in rotation, which is coaxially connected to the output shaft 22.

[0057] The power transmission device 14 is configured to provide power transmission between the input pinion 24 and the output pinion 26, and for this purpose, it advantageously comprises a gear train 28 which is kinematically interposed between the input 24 and output 26 pinions, with which it meshes.

[0058] This gear train 28 comprises, for example, a gearbox, an epicyclic gear train, or as is the case here, be reduced to its simplest expression in the form of an intermediate pinion 30, which is rotatably mounted in the casing 16 parallel to the input 24 and output 26 pinions, and which meshes with each of these. According to the illustrated embodiment, the intermediate pinion 30 comprises two toothed wheels carried by a common shaft 32 rotatably mounted in the casing 16, namely a toothed wheel 34 which meshes with the input pinion 24 and a toothed wheel 36 which meshes with the output pinion 26.

[0059] The power transmission device 14 makes it possible to transmit the power from the electrical machine 12 to the output shaft 22. The input shaft 20 also extends coaxially in the input pinion 24.

[0060] The input pinion 24 comprises in particular a bore 42 inside which extends the input shaft 20, which is connected to this bore 42 for example by means of a key 40 or, alternatively, by means of a set of splines. Thus, the input pinion 24 is connected to the input shaft 20.

[0061] The output shaft 26, on the one hand, extends coaxially in the output pinion 26. On the other hand, it extends coaxially inside the input shaft 24 and it passes through the casing 16 of the power transmission device 14 and a casing 18 of the electric machine 12 from which it projects for its coupling to the wheels of the vehicle.

[0062] Conventionally, as illustrated in the detailed view of FIG. 2, the input 24 and output 26 gears of such a power transmission device 14 are axially juxtaposed in the casing 16 of the power unit 10 and they are all guided by means of fixed guide bearings. Thus, the input gear 24 is guided in rotation at its ends by a first fixed bearing 44 and by a second fixed bearing 46. Similarly, the output gear 26 is guided at its ends by a third fixed bearing 48 and by a fourth fixed bearing 50.

[0063] This design is entirely satisfactory in terms of guiding the input 24 and output 26 pinions, but nevertheless has some drawbacks. In fact, the input 24 and output 26 pinions are axially juxtaposed, so that their axial size corresponds substantially to the cumulative length of said pinions 24, 26. Furthermore, for obvious assembly reasons, it is not possible to mount the four bearings 44, 46, 48, 50 directly in the casing 16 and therefore the assembly of the bearings, in particular the second and third bearings 46, 48, requires the assembly in the casing 16 of an attached housing or a spacer (not shown) making it possible to hold these bearings. This configuration further increases the axial size of the casing 16 since the second and third bearings 46, 48 cannot be placed next to each other within the spacer.In addition, mounting the spacer in the housing 16 requires additional machining which increases the manufacturing cost of the housing 16.

[0064] As illustrated in Figure 1, the invention remedies this problem by proposing a new arrangement of the transmission device 14 in which the second and third bearings 46, 48 are no longer mounted in a spacer, but in which, as illustrated in Figure 1, at least one guide bearing 52, 54, called a mobile bearing, is kinematically interposed between the input pinion 24 and the output pinion 26.

[0065] This configuration is particularly advantageous, because it makes it possible to dispense with a spacer ensuring the maintenance of the second and third bearings, the movable guide bearing(s) 52 and 54 now being interposed between the input 24 and output 26 pinions.

[0066] Furthermore, unlike the known configuration of the prior art, due to their kinematic interposition between the input 24 and output 26 pinions, the movable guide bearing(s) 52 and 54 have the advantage of seeing the relative speed between the inner and outer rings of said bearings substantially reduced, at least in cases where the input 24 and output 26 pinions are both rotating in the same direction of rotation. Compared to the known configuration of the prior art shown in FIG. 2, it is therefore possible to provide one or more bearings 52, 54 that are less expensive, since they are less subject to high rotation speeds.

[0067] According to a first embodiment, not illustrated, a single movable guide bearing is interposed between the input pinion 24 and the output pinion 26, depending on the type of bearings used. Thus, a single movable guide bearing consisting for example of a roller bearing is kinematically interposed between the input pinion 24 and the output pinion 26. However, as illustrated in FIG. 1, in the preferred embodiment of the invention, two movable guide bearings 52, 54 are interposed between the input pinion 24 and the output pinion 26. Thus, the input pinion 24 is guided by the first fixed bearing 44 and by the second movable guide bearing 52, while the output pinion 26 is guided by the third movable guide bearing 54 and by the fourth fixed bearing 50.

[0068] Advantageously, for the sake of additional axial compactness, a first end 56 of the input pinion 24 extends inside the output pinion 26. Each of the movable guide bearings 52, 54 is interposed between this first end 56 and the output pinion 26. More particularly, the output pinion 26 comprises a bore 58 in which the first end 56 of the input pinion 24 extends. The two movable guide bearings 52, 54 are received in the bore 58.

[0069] The output pinion 26 advantageously comprises a toothing 60 for its meshing. Preferably, the second and / or third movable guide bearings 52 and 54 are located axially in line with this toothing 60. This configuration makes it possible to limit the swiveling phenomena of the bearings 52 and 54 and consequently to limit the misalignment of the output pinion 26 in order to avoid the toothing being skewed while ensuring uniform contact pressure over its entire toothing. The swiveling phenomenon is furthermore minimized as the two movable guide bearings 52, 54 are axially spaced from each other by a distance d, as shown in FIG. 1.

[0070] The first bearing 44 and / or the fourth bearing 50 are mounted directly in the casing 16, to which they are rigidly connected, for example by means of a fixing screw, a holding element, a circlip, or any other connecting element.

[0071] Advantageously, still to limit the swiveling phenomena and ensure the maintenance of a uniform contact pressure on the teeth of the input pinion 24, the first of the fixed guide bearings, that is to say the first bearing 44, is mounted at a second end 62 of the input pinion 24, which is opposite the first end 56. The inner ring of this first bearing 44 is for example fixed to the input pinion 24 by shrink fitting.

[0072] In the same way, the second of the fixed bearings, that is to say the fourth bearing 50, is mounted at one end 64 of the output pinion 26 which is opposite the input pinion 24. The inner ring of this fourth bearing 44 is for example fixed to the output pinion 26 by shrink fitting.

[0073] The invention therefore advantageously makes it possible to propose an electric motor vehicle powertrain of increased compactness and reduced mass. The invention also makes it possible to reduce production costs.

Claims

CLAIMS 1. Device (14) for transmitting power between coaxial input (20) and output (22) shafts, said device (14) comprising: - a casing (16), - an input pinion (24), movable in rotation and intended to be coaxially connected to said input shaft (20), - an output pinion (26), movable in rotation and intended to be coaxially connected to said output shaft (22), said device (14) being configured for power transmission between the input pinion (24) and the output pinion (26), - one or more guide bearings (52, 54), called mobile, kinematically interposed between said input pinion (24) and said output pinion (26).

2. Power transmission device (14) according to the preceding claim, in which a first end (56) of said input pinion (24) extends inside said output pinion (26) and in which the or at least one of the movable guide bearings (52, 54) is interposed between said first end (56) and said output pinion (26).

3. Power transmission device (14) according to the preceding claim, in which the output pinion (26) comprises a bore (58) in which the first end (56) of said input pinion (24) extends.

4. Power transmission device (14) according to one of claims 2 or 3, wherein said device comprises one or more guide bearings (44, 50), called fixed, carrying said input pinion (24) and / or said output pinion (26) in said casing (16).

5. Power transmission device (14) according to the preceding claim, in which a first (44) of the fixed guide bearings is mounted at a second end (62) of the input pinion (24), opposite said first end (56).

6. Power transmission device (14) according to the preceding claim, in which a second (50) of the fixed bearings is mounted at an end (64) of the output pinion opposite the input pinion (24).

7. Power transmission device (14) according to any one of the preceding claims, wherein said output pinion (26) comprises a toothing (60) and the or at least one of the movable guide bearings (52, 54) is located axially in line with said toothing (60).

8. Power transmission device (14) according to any one of the preceding claims, wherein said movable guide bearings (52, 54) are two in number.

9. Power transmission device (14) according to the preceding claim, in which the two movable guide bearings (52, 54) are axially distant from each other.

10. Powertrain (10) of an electric vehicle, comprising an assembly formed of an electric machine (12) and a transmission device (14) according to any one of the preceding claims. 1 1. Powertrain (10) according to the preceding claim, wherein said output shaft (22) extends coaxially in said input shaft (20).

12. Powertrain (10) according to one of claims 10 or 11, wherein said electrical machine (12) comprises a stator (15) housed in a casing (18) attached and fixed to the casing (16) of said power transmission device (14).

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