INTERNALLY LUBRICATED TRANSMISSION MECHANISM AND ASSOCIATED ELECTRIC PROPULSION ASSEMBLY

Abstract

A transmission mechanism (M) with internal lubrication comprising: - a casing (40a, 40b) comprising a base (42) and a circumferential rim (43) delimiting an internal volume capable of receiving a lubricating fluid; - at least one transmission shaft (10, 20, 30) comprising a pinion with teeth which is rotatable relative to the casing around an axis of rotation (X1, X2, X3); - a guide bearing (100a, 200a, 300a) supporting the transmission shaft relative to the casing which comprises rolling elements, the guide bearing being inserted into a cylindrical housing (41) arranged in the base of the casing, and - a reservoir (90a, 90b) for retaining lubricating fluid arranged inside the casing, the reservoir forms a first space (E1) which surrounds the transmission shaft. (Abstract Figure: 1)

Description

Title of the invention: INTERNALLY LUBRICATED TRANSMISSION MECHANISM AND ASSOCIATED ELECTRIC PROPULSION ASSEMBLY TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the internal lubrication, for example by splashing, of a transmission mechanism, and in particular of a speed reduction mechanism. More specifically, the invention relates to the rise in temperature of the lubricating fluid within the speed reduction mechanism between the start-up of the motorized vehicle and the achievement of a stabilized temperature, the time necessary to obtain this stabilized temperature being reduced. The motorized vehicle may be an electrically powered vehicle, a thermally powered vehicle or even a hybrid vehicle. STATE OF THE PRIOR ART

[0002] To lubricate the components of a transmission mechanism, and in particular the rotating guide bearings and gears of such a mechanism, it is known to arrange the rotating mobile components of the mechanism inside a casing containing oil, but without the mobile components, for example a transmission shaft supporting pinions, being completely immersed in the oil. It is then the movement of the transmission mechanism which, by splashing, stirs the oil and projects it throughout the entire interior volume of the casing, to ensure the desired lubrication of the entire mechanism, including the non-immersed parts.

[0003] When the electric or hybrid vehicle is started, the transmission mechanism, all of its components and the lubricating fluid contained in the mechanism casing are at room temperature. The guide bearings supporting the rotating mobile components, for example of the ball bearing type, are lubricated and are generally crossed by the flow of lubricating fluid. By being set in rotation, the guide bearings heat up and the dissipated calories are evacuated by the lubricating fluid which also rises in temperature. However, after being evacuated from the guide bearing, the fluid is projected into the casing and in particular onto the internal walls of the casing which are still at room temperature. Contact with the casing delays the rise in temperature of the lubricating fluid.The thermal inertia of the internal walls of the casing constituting the speed reduction mechanism therefore slows down the rise in temperature of the lubricating fluid, for example lubricating oil.

[0004] For example, the thermal inertia of a speed reduction mechanism as illustrated for example in document JP2011214658 A2 is very high, so that it is necessary to wait several tens of minutes for the temperature of the lubricating oil to reach stable conditions. This means that for short usage cycles of the electric or hybrid vehicle, the temperature of the oil may never be stabilized and may potentially remain in conditions below the optimal usage conditions. During this transient phase, the internal timing of the guide bearings will not be respected due to the erratic rise in temperature of the various internal components of the transmission mechanism during this transient phase. This transient temperature rise phase must be as short as possible to quickly obtain the correct axial timing of the guide bearings and thus improve their reliability. Statement of the invention

[0005] The invention aims to remedy the drawbacks of the state of the art and to propose a transmission mechanism having reduced internal thermal inertia.

[0006] To do this, according to a first aspect of the invention, a transmission mechanism with internal lubrication is proposed, comprising:

[0007] - a casing comprising a base and a circumferential rim delimiting a volume internally capable of receiving a lubricating fluid;

[0008] - at least one transmission shaft comprising a pinion with teeth, said shaft transmission being rotatable relative to the casing around an axis of rotation of the transmission shaft; and

[0009] - a lubricating fluid retention reservoir disposed inside the housing, the reservoir forms a first space which surrounds the transmission shaft and which comprises closing valves capable of maintaining the lubricating fluid in the reservoir when the closing valves are in a closed position, and capable of discharging the lubricating fluid outside the reservoir when the closing valves are in an open position, and the thermal conductivity of the lubricating fluid retention reservoir is lower than the thermal conductivity of the casing.

[0010] The thermal conductivity of the lubricating fluid holding tank is at least twice as low as the thermal conductivity of the casing, for example three times as low as the thermal conductivity of the casing.

[0011] The unit of measurement for thermal conductivity is Watt per meter-kelvin (W / m K). The higher the thermal conductivity, the more heat-conducting the material is; the lower the thermal conductivity, the more insulating the material is.

[0012] The lubricating fluid retaining tank makes it possible to thermally insulate the interior of the transmission mechanism housing from the lubricating fluid temporarily, long enough to allow the lubricating fluid to reach its optimum operating temperature. This solution therefore aims to reduce the thermal inertia of the transmission mechanism without increasing the overall volume of the transmission mechanism.

[0013] Advantageously, the volume measured in cubic meters contained in the first space may be greater than or equal to 60% of the internal volume of the casing, for example greater than or equal to 80%. This limits the quantity of lubricating fluid in contact with the casing, in particular when starting the electric or hybrid vehicle. To achieve such a ratio, the shape of the lubricating fluid retention reservoir matches the shapes of the internal volume of the casing as closely as possible while leaving a substantially constant dimensional clearance between the reservoir and the casing.

[0014] Preferably, the lubricating fluid retaining reservoir may comprise a wall delimiting the first space, a second space is formed between the external surface of the wall of the reservoir and the internal surface of the casing formed by the base and the circumferential rim, this second space being capable of containing a portion of the lubricating fluid when the closing valves are in the open position.

[0015] Advantageously, the transmission mechanism may comprise at least one guide bearing supporting the transmission shaft relative to the casing which comprises rolling elements, the guide bearing being inserted into a cylindrical housing arranged in the base of the casing, the lubricating fluid retention reservoir comprises at least one orifice which communicates directly or indirectly with the cylindrical housing, the orifice being capable of conveying fluid independently of the opening or closing of the closing valves. In this way, the lubricating fluid passes through the guide bearing(s) which heat up as they rotate. By heating the guide bearings, the dissipated calories are evacuated by the lubricating fluid which rises in temperature.

[0016] Preferably, the transmission mechanism may comprise a collector for receiving and distributing lubricating fluid housed in the first space, said collector comprising at least a bottom, an outer periphery and a fluid supply pipe coming from the bottom or the outer periphery, said fluid supply pipe passing through the orifice of the reservoir.

[0017] Advantageously, the collector for receiving and distributing lubricating fluid can be arranged above the transmission shaft, between the axis of rotation of the transmission shaft and the wall of the reservoir when the transmission mechanism is in a reference operational position. In this way, the collector acts as a container and occupies a central position within the first space, which allows it to receive all the projections of lubricant coming from the pinion of the transmission shaft. The lubricant can fall back directly or indi- directly into the collector.

[0018] According to one embodiment of the invention, the transmission mechanism may comprise at least one guide bearing supporting the transmission shaft relative to the casing which comprises rolling elements, the guide bearing being inserted into a cylindrical housing arranged in the base of the casing, the casing comprises at least one fluid conveying channel communicating the first space with the bottom of the cylindrical housing, the fluid conveying channel being capable of conveying fluid independently of the opening or closing of the closing valves. In this way, the lubricating fluid passes through the guide bearing(s) which heat up as they rotate. By heating the guide bearings, the dissipated calories are evacuated by the lubricating fluid which rises in temperature.

[0019] Preferably, the lubricating fluid retaining reservoir may comprise at least one through hole through which the at least one transmission shaft passes. The through hole may comprise a cylindrical surface portion which serves as a centering surface of the lubricating fluid retaining reservoir on the casing.

[0020] Advantageously, the lubricating fluid retention reservoir may comprise two passage holes crossed by the transmission shaft, the two ends of the transmission shaft passing through the reservoir.

[0021] Preferably, the lubricating fluid retaining reservoir may comprise two half-reservoirs forming the first space, the two half-reservoirs being assembled by fitting one into the other.

[0022] Advantageously, each half-reservoir can be nested in the internal volume of the casing.

[0023] According to one embodiment of the invention, the casing may be composed of a main casing and a closing casing bearing on the main casing, at a joint plane to seal the internal volume of the casing. For example, the two half-reservoirs may be fitted together in a plane parallel to the joint plane of the casing. This facilitates assembly of the transmission mechanism. In this way, the half-reservoir may be housed inside the internal volume of the main casing and the shapes of the half-reservoir may be nested in the internal volume of the main casing.

[0024] According to one embodiment of the invention, the closing valves can be controlled as a function of the temperature of the lubricating fluid.

[0025] According to one embodiment of the invention, the closing valves can be controlled according to a time delay linked to the rotation of the transmission shaft.

[0026] Preferably, at least one of the closing flaps may comprise a flap adjustable capable of diverting the lubricating fluid to bring a portion of the lubricating fluid from the first space to the second space when the latter is in an open position. Conversely, at least one of the closing valves may comprise an adjustable flap capable of diverting the lubricating fluid to bring a portion of the lubricating fluid from the second space to the first space when the latter is in an open position.

[0027] Advantageously, the closing flap may comprise a fixing zone and a hinge arranged between the adjustable flap and the fixing zone.

[0028] According to a variant of the invention, the free end of the adjustable flap can rest on the casing when the closing valve is in the open position.

[0029] According to a variant of the invention, the adjustable flap can be made from a single material with the wall of the tank.

[0030] According to a variant of the invention, the closing valve can be fixed, respectively riveted or heat-welded or glued, to the wall of the tank, the hinge being arranged between the adjustable flap and the fixing zone respectively supporting the rivet, or the welding point, or the glue point.

[0031] According to a variant of the invention, the hinge may comprise a metal rod acting as a pivot between the adjustable flap and the wall of the tank or the fixing zone.

[0032] According to a variant of the invention, the closing valve may comprise a bimetallic device made in the form of two superimposed elastic blades of unequally expandable materials, the two elastic blades forming the fixing zone, the hinge and the adjustable flap. Under the effect of a temperature variation, the bimetallic device curves allowing the adjustable flap to be opened or closed. One of the elastic blades may be constituted by the wall of the lubricating fluid retention tank.

[0033] For example, the closing valve may comprise a bimetallic device produced in the form of an elastic blade attached to the wall of the tank, the elastic blade being made of a material that is unequally expandable relative to the material of the tank. Advantageously, the elastic blade may be superimposed on the fixing zone, the hinge and the adjustable flap.

[0034] According to a variant of the invention, the closing valve may be a valve having a linear opening and closing movement.

[0035] According to a variant of the invention, the closing valve may be a solenoid valve controlled by an electronic device.

[0036] Preferably, the transmission mechanism may comprise an additional thermal insulation device integral in rotation with the transmission shaft and which at least partially covers axially and / or radially the parts free of toothing of the transmission shaft, the thermal conductivity of the additional thermal insulation device being at least twice lower than the thermal conductivity of the transmission shaft, for example three times lower than the thermal conductivity of the transmission shaft.

[0037] Alternatively, the additional thermal insulation device may be a surface coating applied to the rough machined surfaces of the transmission shaft.

[0038] Alternatively, the additional thermal insulation device may be a plate partially having a sheath shape extending axially along the axis of rotation and which surrounds a cylindrical portion of the transmission shaft.

[0039] Preferably, the transmission shaft may comprise rough machined surfaces and machined surfaces in contact with the guide bearing and / or splined surfaces in contact with a pinion, the rough machined surfaces being partly covered by the additional thermal insulation device. This solution aims to reduce the thermal inertia of the transmission shaft without increasing the overall volume of the transmission mechanism.

[0040] Preferably, the housing may contain a lubricating fluid, for example oil, reaching an oil level plane at rest when the transmission mechanism is in a reference operational position.

[0041] According to a variant of the invention, the transmission mechanism may comprise, housed in the casing, a first transmission shaft guided in rotation about a first axis of rotation by a first guide bearing and integral in rotation with at least one drive pinion, a second transmission shaft guided in rotation about a second axis of rotation by a second guide bearing and integral in rotation with at least one intermediate pinion, and a third transmission shaft guided in rotation about a third axis of rotation by a third guide bearing and integral in rotation with at least one driven pinion, the first transmission shaft, the second transmission shaft and the third transmission shaft being contained in the first space formed by the reservoir.

[0042] Advantageously, the lubricating fluid retention reservoir can be crossed by at least two transmission shafts chosen from among the first, the second and the third transmission shaft.

[0043] For example, the first transmission shaft, the second transmission shaft and the third transmission shaft are parallel to each other.

[0044] Advantageously, the third transmission shaft may be a differential body obtained by casting, comprising machined surfaces in contact with the third guide bearing, in contact with satellite gears arranged inside the differential body or in contact with a toothed crown acting as a receiving pinion, the additional thermal insulation device re- axially and / or radially covering all or part of the rough machining surfaces.

[0045] Preferably, the transmission mechanism may comprise one or more gears establishing a fixed speed ratio between the driving pinion and the receiving pinion, this speed ratio being greater than one.

[0046] According to another aspect of the invention, it relates to an electric propulsion assembly comprising an electric motor and a transmission mechanism incorporating all or part of the characteristics mentioned above, the first transmission shaft constituting an output shaft of the electric motor or being integral in rotation with a drive shaft of the electric motor.

[0047] Advantageously, a stator of the electric motor can be fixed to the casing.

[0048] Preferably, the casing may be composed of a main casing supporting the electrical machine and a closing casing bearing on the main casing, the main casing supporting a first half-reservoir and the closing casing supporting a second half-reservoir.

[0049] This solution therefore aims to reduce the internal thermal inertia of the transmission mechanism without increasing the overall volume of the electric propulsion assembly.

[0050] The invention is more particularly applicable to a reduction transmission mechanism, and in particular to a speed reducer with a fixed ratio or with two reduction ratios, to a reducer with parallel shafts or to a speed reducer of the coaxial type comprising an epicyclic gear train, in which the axis of rotation of the electric motor is concentric with the output shaft of the epicyclic gear train. BRIEF DESCRIPTION OF THE FIGURES

[0051] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures.

[0052] [Fig.l] [Fig.l] illustrates a section of the transmission mechanism according to a first embodiment of the invention.

[0053] [Fig.2] [Fig.2] illustrates a front view of the interior of the transmission mechanism of [Fig.l].

[0054] [Fig.3] [Fig.3] illustrates a detailed view of the transmission mechanism of [Fig.l].

[0055] [Fig.4] [Fig.4] illustrates a view of the transmission mechanism along a substantially vertical section plane, the transmission mechanism being in the reference operational position.

[0056] [Fig.5] [Fig.5] illustrates an isometric view of a half-tank according to the first embodiment of the invention.

[0057] [Fig.6] [Fig.6] illustrates a detailed view of a closing valve of the transmission mechanism according to the first embodiment of the invention.

[0058] [Fig.7] [Fig.7] illustrates a detailed view of a closing valve of the transmission mechanism according to a second embodiment of the invention.

[0059] [Fig.8] [Fig.8] illustrates a detailed view of a closing valve of the transmission mechanism according to a third embodiment of the invention.

[0060] [Fig.9] [Fig.9] illustrates a sectional view of the transmission mechanism according to a fourth embodiment of the invention, the transmission mechanism being in the reference operational position.

[0061] [Fig. 10] [Fig. 10] illustrates a partial view of a transmission mechanism according to a fifth embodiment of the invention.

[0062] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of embodiments

[0063] Figures 1 to 6 illustrate an electric propulsion assembly 1, comprising an electric machine 60 and a transmission mechanism M according to a first embodiment of the invention. In this example, the transmission mechanism M is a speed reduction mechanism transmitting the torque from the electric machine 60 to the wheels of the electric or hybrid vehicle.

[0064] The electrical machine 60 may be, for example, an induction electric motor, comprising a rotor 62 and a stator 61, electrically powered with three-phase alternating current by accumulator batteries via a current converter (not shown in [Fig.l]). The electrical machine may be of another type, for example axial flux.

[0065] The electrical machine 60 is held on a casing 40a, 40b. The casing is generally composed of a main casing 40a supporting the electrical machine 60 and a closing casing 40b bearing on the main casing 40a, at a joint plane 48, to seal a cavity delimited by the main casing 40a and the closing casing 40b. The main casing 40a comprises a base 42 and a circumferential rim 43 delimiting an internal volume capable of receiving a lubricating fluid.

[0066] The electric machine 60 rotates a first transmission shaft 10 which penetrates the main casing 40a. The first transmission shaft 10 constitutes an input shaft of the transmission mechanism M, which also comprises a second transmission shaft 20, and a third transmission shaft 30 which constitutes an output shaft of the transmission mechanism M.

[0067] The second transmission shaft 20 which constitutes an intermediate shaft of the transmission mechanism M is parallel to the input shaft 10 and the output shaft 30 of the transmission mechanism M. At the output of the speed reducer, the third transmission shaft 30 is a differential which is used to transmit and distribute a torque from the electric machine 60, not shown, to two wheel shafts 2, 3 of an axle of a motor vehicle

[0068] As illustrated in [Fig.l], the input shaft 10 is aligned with the motor shaft 63 of the electrical machine 60 relative to the casing 40a, 40b, and carries at least one toothed wheel, here called motor pinion 11, linked in rotation to the transmission shaft. The input shaft 10 is guided by two guide bearings 100a, 100b in rotation so as to rotate about a first axis of rotation XI relative to the casing 40a, 40b.

[0069] The guide bearing 100a which supports the first transmission shaft 10 relative to the casing comprises in particular rolling elements 103, in this case rolling balls. The guide bearing 100a is inserted into a cylindrical housing 41 provided in the closing casing 40b.

[0070] To lubricate the various components of the transmission mechanism M, the casing 40a, 40b contains lubricating fluid, for example oil. The guide bearings and the pinions of the transmission shafts are partially immersed in the oil. It is then the movement of the transmission mechanism which, by splashing, stirs the oil and projects it throughout the entire interior volume of the casing, to ensure the desired lubrication of the entire mechanism, including the non-immersed parts.

[0071] The output shaft 30 carries in joint rotation at least one driven pinion 31. The output shaft 30 further comprises a fixed connection in rotation with a planet carrier of a differential 32, or constitutes the planet carrier of the differential 32. The differential 32 can be open or with limited slip, depending on the desired properties. The output shaft 30 is guided by two guide bearings 300a, 300b in rotation so as to rotate around a third axis of rotation X3 relative to the casing 40a, 40b.

[0072] Like the input shaft 10 and the output shaft 30, the intermediate shaft 20 is guided by several guide bearings 200a, 200b in rotation about a second axis of rotation X2, and carries two intermediate pinions 21, 22 in joint rotation, the first intermediate pinion 21 forming a first speed reduction gear with the driving pinion 11 of the input shaft 10, and the second intermediate pinion 22 forming a second speed reduction gear with the receiving pinion 31 of the output shaft 30.

[0073] The first, second and third rotation axes XI, X2, X3 are parallel to each other. The first rotation axis XI and the third rotation axis X3 are located in a reference plane P of the transmission mechanism M. As illustrated in [Fig.2], the second rotation axis X2 is located outside the reference plane P.

[0074] The motor pinion 11 has a diameter and a number of teeth smaller than the diameter and the number of teeth of the intermediate pinion 21 of the intermediate shaft 20 forming the first speed reduction gear. Similarly, the second intermediate pinion 22 of the intermediate shaft 20 forming the second speed reduction gear has a diameter and a number of teeth smaller than the diameter and the number of teeth of the receiving pinion 31 of the output shaft 30. The transmission mechanism M is therefore reducing and without changing ratio.

[0075] For the remainder of the description, a reference operational position of the transmission mechanism M is defined as being the three-dimensional orientation in which the transmission mechanism M is installed in a vehicle horizontally. In this reference operational position, the second axis of rotation X2 is located above the reference plane P. In the remainder of this description, unless otherwise stated, the invention will be described in a reference operational position.

[0076] The objective of the invention is to reduce the internal thermal inertia of the transmission mechanism. For this purpose, the transmission mechanism M comprises a lubricating fluid retaining reservoir 90 arranged inside the casing 40a, 40b which forms a first space E1 surrounding the first transmission shaft 10, the second transmission shaft 20 and the third transmission shaft 30. The lubricating fluid retaining reservoir 90 is traversed by the first, second and third transmission shafts. The ends of the transmission shafts pass through the lubricating fluid retaining reservoir 90.

[0077] The lubricating fluid retaining reservoir 90 comprises two half-reservoirs 90a, 90b forming the first space E1. In order to form a substantially closed first space E1, a first half-reservoir 90a and a second half-reservoir 90b are assembled by fitting one into the other. The fitting of the two half-reservoirs 90a, 90b is carried out in a plane parallel to the joint plane 48 of the casing.

[0078] As illustrated in Figures 2 and 3, the first half-tank 90a is housed inside the internal volume of the main casing 40a and the shapes of the first half-tank 90a are nested in the internal volume of the main casing. The first half-tank 90a is for example fixed directly to the main casing 40a using fixing screws. Similarly, the second half-tank 90b is nested in the closing casing 40b.

[0079] The lubricating fluid retaining reservoir comprises a wall 93 delimiting the first space E1. A second space E2 is formed between the external surface of the wall 93 of the reservoir and the internal surface of the casing 40a, 40b formed by the base 42 and the circumferential rim 43. The volume measured in cubic meters contained in the first space E1 is greater than or equal to 70% of the internal volume of the casing 40a, 40b. The first half-reservoir 90a comprises a rib 98 which diverts the flow of lubricating oil near the external diameter of the driven pinion 31, the rib 98 being made of the same material as the wall 93.

[0080] As illustrated in [Fig.5], the lubricating fluid retaining reservoir 90 comprises closing valves 110 capable of retaining the lubricating fluid in the reservoir when the closing valves are in a closed position and of discharging the lubricating fluid out of the reservoir when the closing valves are in an open position. The lubricating fluid retaining reservoir 90 comprises two through holes 97 through which the first, second and third transmission shafts 10, 20, 30 pass. The through holes 97 each comprise a portion of cylindrical surface which serves as a centering surface of the lubricating fluid retaining reservoir on the casing.

[0081] In this first embodiment of the invention, the casing 40a, 40b is made of aluminum and the lubricating fluid retention reservoir 90 is made of plastic, for example polyamide.

[0082] The thermal conductivity of the lubricating fluid holding tank is lower than the thermal conductivity of the casing. The thermal conductivity K2 of the material constituting the casing 40a, 40b made of aluminum is approximately 185 W / m K while the thermal conductivity K1 of the lubricating fluid holding tank 90 is approximately 1 W / m K.

[0083] When starting the electric or hybrid vehicle, the transmission mechanism M, all of its components and the lubricating fluid contained in the casing are at ambient temperature. The lubricating fluid still at rest fills the lower part of the first space E1 and the lower part of the second space E2. The closing valves 110 are in a closed position.

[0084] When the transmission shafts are rotated, the oil contained in the first space E1 is stirred and begins to lubricate the guide bearings through which the flow of lubricating fluid generally passes. By rotating them, the guide bearings heat up and the dissipated calories are evacuated by the lubricating fluid which also rises in temperature. Since the closing valves 110 are in a closed position, the lubricating oil is projected into the lubricating fluid retention reservoir 90 and in particular onto the wall 93 which begins to rise in temperature. At this stage, the lubricating oil remains contained in the first space E1.

[0085] Since the thermal conductivity K1 of the lubricating fluid retention reservoir 90 is lower than the thermal conductivity K2 of the casing, the lubricating fluid retained within the first space E1 is not cooled by the cold surfaces of the casing 40a, 40b. The gain is effective when the thermal conductivity K1 of the thermal insulation device is at least twice lower than the thermal conductivity K2 of the transmission shaft. The greater the difference in thermal conductivity, the faster the temperature rise of the lubricating oil.

[0086] When the temperature of the lubricating oil reaches a sufficient threshold value, for example 70 degrees, the closing valves 110 change position to reach the open position. In this case, the closing valves are controlled as a function of the temperature of the lubricating fluid. The lubricating oil can then penetrate into the second space E2 and come into contact with the casing 40a, 40b.

[0087] As illustrated in [Fig.5], one of the closing valves 110 comprises an orientable flap 111 capable of diverting the lubricating fluid to bring a portion of the lubricating fluid from the first space E1 to the second space E2 when the latter is in the open position. Also, another closing valve 110 comprises an orientable flap 111 capable of diverting the lubricating fluid to bring a portion of the lubricating fluid from the second space E2 to the first space E1 when the latter is in the open position. The lubricating fluid follows a path going from the first space E1 to the second space E2 to then return to the first space E1.The passage of the oil within the first space El makes it possible to lubricate all the components of the transmission mechanism M and the passage of the oil in the second space E2 makes it possible to maintain the lubricating oil at the optimum stabilized temperature in terms of efficiency thanks to the dissipation of calories through the aluminum of the casing.

[0088] According to a variant of the invention, the closing valves can be controlled according to a time delay linked to the rotation of the transmission shaft.

[0089] Thanks to its thermal conductivity Kl of approximately 16 W / m K, stainless steel could be used for the manufacture of the lubricating fluid retention tank 90.

[0090] The path of the lubricating oil within the lubricating fluid retaining reservoir 90 will now be described. Figures 3 and 4 illustrate the transmission mechanism M in a partial and simplified front view showing the third transmission shaft 30 guided in rotation by means of the guide bearing 300b, and in the reference operational position.

[0091] The guide bearing 300b comprises a rotating inner ring, an outer ring that does not rotate relative to the main casing 40a, and rolling elements 303 arranged between the two rings. The guide bearing 300b is inserted into a cylindrical housing 41 provided in the base of the casing. The lubricating fluid retaining reservoir 90 comprises at least one orifice 95 that communicates indirectly with the cylindrical housing 41, the orifice making it possible to convey fluid independently of the opening or closing of the closing valves. In this way, the lubricating fluid passes through the guide bearing(s), which heat up as they rotate. By heating the guide bearings, the dissipated heat is evacuated by the lubricating fluid, which heats up.

[0092] In operation, the casing 40a, 40b is filled with lubricating oil up to a prescribed limit which corresponds to an oil level plane at rest, this oil level plane at rest being horizontal when the transmission mechanism is in the reference operational position.

[0093] A portion of the reference plane P of the transmission mechanism M, delimited by the first transmission shaft 10 and the third transmission shaft 30, is located above the oil level plane at rest.

[0094] A collector 80 for receiving and distributing lubricating fluid is arranged between the first transmission shaft 10 and the third transmission shaft 30. The collector 80 for receiving and distributing lubricating fluid is housed in the first space E1. The collector 80 retains a portion of the oil sprayed by the elements of the transmission mechanism which splash in the oil.

[0095] The collector 80 has at least one upper opening 82, located above the oil level plane at rest, a bottom 84, an outer periphery 85 and a fluid supply line 81 coming from the bottom 84 or from the outer periphery 85. The fluid supply line 81 passes through the orifice 95 of the reservoir. It is thus possible to precisely bring a flow of lubricating oil into an upper zone of the reservoir 90.

[0096] The collector 80 makes it possible to provide a dynamic oil level as a function of the rotation speed of the input shaft 10, and more precisely, to reduce the oil level in the bottom of the reservoir 90 when the speed increases, by retaining a portion of the oil sprayed by the elements of the transmission mechanism which splash in the oil.

[0097] At rest, that is to say when stopped, the collector 80 located above the oil level plane at rest is empty, and the oil level corresponds to the oil level plane at rest. The maximum oil level varies only slightly when the transmission mechanism M operates at very low speed. This is explained by a low-speed rotation of the driven pinion 31, the driven pinion 31 being the largest toothed wheel of the transmission mechanism M and therefore the wheel most capable of projecting the oil through the reservoir 90.

[0098] The higher the rotation of the transmission shafts, the more oil will be projected through the reservoir 90 by the rotation of the gears. When the oil is projected into the reservoir, it falls back • on a mechanical part such as a pinion or a bearing; and / or • in the bottom of the tank where the oil rests; and / or • in the collector 80 for receiving and distributing lubricating fluid shown in [Fig.4].

[0099] The oil collected by the collector 80 is then partly directed into a groove 45 formed in the main casing 40a in order to be routed into the guide bearing 300b as illustrated by arrows in [Fig.4]. The groove 45 opens into the upper part of the cylindrical housing 41 of the guide bearing 300b. The fluid supply line 81 opens into the groove 45 by passing through the orifice 95 of the reservoir 90.

[0100] A flow of lubricating oil is therefore conveyed towards the guide bearing 300b to a space available between the bottom 41a of the cylindrical housing 41 and the rear face of the guide bearing 300b. By gravity, the lubricating fluid descends along the groove 45, then enters the cavity formed by the cylindrical housing of the main casing 40a before exiting through the guide bearing 300b. The lubricating fluid then falls back into the first space E1.

[0101] The structure of the closing valve will now be described. As illustrated in [Fig.6], the closing valve 110 comprises a fixing zone 112, a hinge 113 arranged between the adjustable flap 111 and the fixing zone. In this example, the adjustable flap 111 is made in one piece with the wall of the tank. The rotational movement of the adjustable flap 111 is made around the hinge and tends to make the adjustable flap enter inside the first space E1.

[0102] The closing valve 110 comprises a bimetallic device produced in the form of an elastic blade 117 attached to the wall 93 of the tank. The elastic blade 117 is made of a material that is unequally expandable relative to the material of the tank. The elastic blade is superimposed on the fixing zone 112, the hinge 113 and the adjustable flap 111. Under the effect of a variation in temperature, the bimetallic device curves, allowing the adjustable flap to be opened or closed.

[0103] According to another variant of the invention not shown, the rotational movement of the adjustable flap 111 may tend to cause the adjustable flap to return inside the second space E2. In this case, the free end of the adjustable flap may be supported on the casing when the closing valve is in the open position.

[0104] A second embodiment of the invention will now be described with reference to [Fig.7], which differs from the first embodiment by the hinge 113 comprising a metal rod acting as a pivot between the adjustable flap 111 and the wall 93 of the tank or the fixing zone 112. The fixing zone 112 supports the metal rod. The actuation of the adjustable flap can be assisted by an external actuator which orients the adjustable flap between the open position and the closed position.

[0105] We will now describe with reference to [Fig.8], a third embodiment of the invention, which differs from the first embodiment by the method of fixing the adjustable flap. In this third embodiment, the closing valve 110 is fixed to the wall of the tank by a rivet 114.

[0106] The closing valve 110 comprises a bimetallic device produced in the form of two superimposed elastic blades of unequally expandable materials, the two elastic blades forming the fixing zone 112, the hinge 113 and the adjustable shutter 111. Under the effect of a variation in temperature, the bimetallic device curves allowing the opening or closing of the adjustable shutter.

[0107] According to a variant of the invention, the closing valve can be heat-sealed or glued to the wall of the tank, the hinge being arranged between the adjustable flap and the fixing zone supporting the welding point or the glue point.

[0108] According to a variant of the invention, the closing flap may be a valve having a linear opening and closing movement, the valve being electromechanically controlled.

[0109] According to a variant of the invention, the closing valve may be a solenoid valve controlled by an electronic device.

[0110] We will now describe with reference to [Fig.9], a fourth embodiment of the invention, which differs from the first embodiment in that the casing 40a, 40b comprises a fluid conveying channel 47 connecting the first space E1 with the bottom 41a of the cylindrical housing 41. This fluid conveying channel 47 makes it possible to convey lubricating fluid into the guide bearing independently of the opening or closing of the closing valves.

[0111] The oil collected by the collector 80 is partly directed towards the fluid conveying channel 47 formed in the main casing 40a in order to be conveyed into the guide bearing 300b as illustrated by arrows in [Fig.9]. The fluid conveying channel 47 opens into the upper part of the cylindrical housing 41 of the guide bearing 300b.

[0112] A flow of lubricating oil is therefore conveyed towards the guide bearing 300b to a space available between the bottom 41a of the cylindrical housing 41 and the rear face of the guide bearing 300b. By gravity, the lubricating fluid descends along the wall 93, then enters the fluid conveying channel 47 to reach the bottom 41a of the cylindrical housing 41. After passing through the guide bearing 300b, the lubricating fluid falls back into the first space E1.

[0113] We will now describe with reference to [Fig. 10], a fifth embodiment of the invention, which differs from the first embodiment by the use of an additional thermal insulation device 70 having the objective of further reducing the internal thermal inertia of the transmission mechanism.

[0114] For this purpose, the transmission mechanism M comprises an additional thermal insulation device 70 which at least partially axially covers tooth-free parts of the third transmission shaft 30.

[0115] The additional thermal insulation device 70 is here a surface coating applied to the rough machined surfaces of the third transmission shaft 30. The third transmission shaft 30 is a differential body 32 obtained by casting, comprising machined surfaces 32a in contact with the third guide bearing 300a, 300b, in contact with satellite gears 35 arranged inside the differential body or in contact with a toothed crown acting as a receiving pinion 31, the additional thermal insulation device axially and radially covering all of the rough machined surfaces.

[0116] The surface coating is applied directly to the rough casting of the differential housing 32 and to the rough forging of the driven pinion body 31. During the machining operations, the surface coating is removed from all of the machined surfaces but remains present on all of the rough machining surfaces. The machined surfaces 32a are, for example, the bearing surfaces of the guide bearings, the splines, the teeth, the drill holes, the bearing surfaces of the satellite gears 35 or the bearing surfaces of the driven pinion 31.

[0117] The surface coating is, for example, a water-based reactive prepolymer paint. This coating can, for example, be applied by electrostatic powder coating.

[0118] Alternatively, the surface coating may be Teflon-based or a ceramic coating.

[0119] The advantage of the surface coating is that it is possible to avoid the complexity of the shapes of the transmission shaft and, in this case, the shapes of the differential housing 32. The thermal conductivity K3 of the surface coating is at least three times lower than the thermal conductivity K4 of the transmission shaft. For example, the thermal conductivity of the transmission shaft made of steel is 50 W / m K. In comparison, the thermal conductivity of the surface coating is less than 2 W / m K. Given the difference in thermal conductivity, the lubricating fluid projected into the first space El and in particular onto the rotating part is not cooled when the thermal, electric or hybrid vehicle is started.

[0120] Naturally, the examples shown in the figures and discussed above are given for illustrative purposes only and are not limiting. It is explicitly provided that the different embodiments illustrated can be combined with each other to propose others.

[0121] According to a variant not illustrated, the transmission mechanism M is of the coaxial type comprising an epicyclic gear train, in which the axis of rotation of the electric motor is concentric with the output shaft of the epicyclic gear train.

[0122] The transmission mechanism M described above is a reduction mechanism with a constant speed ratio to an intermediate shaft, but the invention is also intended to be applied to mechanisms with several intermediate shafts, or without an intermediate shaft, to mechanisms with several speed ratios, and / or to mechanisms canisms whose ratio of input speed to output speed is less than 1.

[0123] The transmission mechanism M described above is a speed reducer mechanism with internal splash lubrication, but the invention is also intended to be applied to a speed reducer mechanism with internal lubrication under pressure in which the oil is directed via pipes or hoses to the main points of the reducer to be lubricated. The oil then falls by gravity into the bottom of the casing. In this other example, a mechanical or electrical pump can be used to bring the fluid under pressure into the pipes or hoses.

Claims

Claims

1. Transmission mechanism (M) with internal lubrication, comprising: - a casing (40a, 40b) comprising at least one base (42) and a circumferential rim (43) delimiting an internal volume capable of receiving a lubricating fluid; - at least one transmission shaft (10, 20, 30) comprising a pinion (11, 21, 22, 31) with teeth, said transmission shaft being movable in rotation relative to the casing around an axis of rotation (XI, X2, X3) of the transmission shaft;and - a reservoir (90, 90a, 90b) for retaining lubricating fluid arranged inside the casing, the reservoir forms a first space (El) which surrounds the transmission shaft and which comprises closing valves (110) capable of maintaining the lubricating fluid in the reservoir when the closing valves (110) are in a closed position, and capable of discharging the lubricating fluid outside the reservoir when the closing valves (110) are in an open position, and the thermal conductivity (Kl) of the lubricating fluid retaining reservoir is lower than the thermal conductivity (K2) of the casing.;

2. Transmission mechanism (M) according to the preceding claim, in which the volume measured in cubic meters contained in the first space (El) is greater than or equal to 60% of the internal volume of the casing, for example greater than or equal to 80%.

3. Transmission mechanism (M) according to one of the preceding claims, in which the reservoir (90, 90a, 90b) for retaining lubricating fluid comprises a wall (93) delimiting the first space (El), a second space (E2) is formed between the external surface of the wall (93) of the reservoir and the internal surface of the casing (40a, 40b) formed by the base (42) and the circumferential rim (43), this second space (E2) is capable of containing a portion of the lubricating fluid when the closing valves (110) are in the open position.

4. Transmission mechanism (M) according to one of the preceding claims, in which the lubricating fluid retaining reservoir (90a, 90b) comprises at least one passage hole (97) crossed by the at least one transmission shaft (10, 20, 30).

5. Transmission mechanism (M) according to one of the preceding claims, in which the reservoir (90, 90a, 90b) for retaining lubricating fluid comprises two half-reservoirs (90a, 90b) forming the first space (El), the two half-tanks (90a, 90b) being assembled by fitting one into the other.

6. Transmission mechanism (M) according to one of the preceding claims, in which the closing valves (110) are controlled as a function of the temperature of the lubricating fluid.

7. Transmission mechanism (M) according to one of the preceding claims, in which at least one of the closing valves (110) comprises an adjustable flap (111) capable of diverting the lubricating fluid to bring a portion of the lubricating fluid from the first space (El) to the second space (E2) when the latter is in an open position.

8. Transmission mechanism (M) according to one of the preceding claims, in which at least one of the closing valves (110) comprises an adjustable flap (111) capable of diverting the lubricating fluid to bring a portion of the lubricating fluid from the second space (E2) to the first space (El) when the latter is in an open position.

9. Transmission mechanism (M) according to claim 7 or 8, wherein the closing flap (110) comprises a fixing zone (112) and a hinge (113) arranged between the adjustable flap (111) and the fixing zone.

10. Transmission mechanism (M) according to the preceding claim, in which the closing valve (110) comprises a bimetallic device produced in the form of two superimposed elastic blades of unequally expandable materials, the two elastic blades forming the fixing zone (112), the hinge (113) and the adjustable flap (111).

11. Transmission mechanism (M) according to one of the preceding claims, comprising at least one guide bearing (100a, 200a, 300a) supporting the transmission shaft relative to the casing (40a, 40b) which comprises rolling elements (103, 203, 303), the guide bearing being inserted into a cylindrical housing (41) arranged in the base (42) of the casing, the reservoir (90, 90a, 90b) for retaining lubricating fluid comprises at least one orifice (95) which communicates directly or indirectly with the cylindrical housing (41), the orifice (95) being capable of conveying fluid independently of the opening or closing of the closing valves.

12. Transmission mechanism (M) according to the preceding claim, comprising a collector (80) for receiving and distributing fluid. lubrication housed in the first space (El), said collector comprising at least a bottom (84), an outer periphery (85) and a fluid supply pipe (81) coming from the bottom or the outer periphery, said fluid supply pipe (81) passes through the orifice (95) of the reservoir.

13. Transmission mechanism (M) according to one of claims 1 to 10, comprising at least one guide bearing (100a, 200a, 300a) supporting the transmission shaft relative to the casing (40a, 40b) which comprises rolling elements (103, 203, 303), the guide bearing being inserted into a cylindrical housing (41) arranged in the base (42) of the casing, the casing comprises at least one fluid conveying channel (47) communicating the first space (El) with the bottom of the cylindrical housing (41), the fluid conveying channel (47) being capable of conveying fluid independently of the opening or closing of the closing valves.

14. Transmission mechanism (M) according to one of the preceding claims, comprising an additional thermal insulation device (70) integral in rotation with the transmission shaft (100, 200, 300) and which at least partially axially and / or radially covers the tooth-free parts of the transmission shaft, the thermal conductivity (K3) of the additional thermal insulation device (70) being at least twice lower than the thermal conductivity (K4) of the transmission shaft, for example three times lower than the thermal conductivity of the transmission shaft.

15. Transmission mechanism (M) according to one of the preceding claims, characterized in that the casing (40a, 40b) contains a lubricating fluid, for example oil, reaching an oil level plane at rest (14) when the transmission mechanism (M) is in a reference operational position.

16. Transmission mechanism (M) according to one of the preceding claims, further comprising, housed in the casing (40a, 40b), a first transmission shaft (10) guided in rotation about a first axis of rotation (X1) by a first guide bearing (100a, 100b) and rotationally fixed to at least one drive pinion (11), a second transmission shaft (20) guided in rotation about a second axis of rotation (X2) by a second guide bearing (200a, 200b) and rotationally fixed to at least one intermediate pinion (21, 22), and a third transmission shaft (30) guided in rotation about a third axis of rotation (X3) by a third guide bearing (300a, 300b) and rotationally secured to at least one driven pinion (31), the first transmission shaft (10), the second transmission shaft (20) and the third transmission shaft (30) are contained in the first space (El) formed by the reservoir.

17. Electric propulsion assembly (1) comprising an electric motor (60) and a transmission mechanism (M) according to any one of the preceding claims, the first transmission shaft (10) constituting an output shaft of the electric motor (60) or being rotationally integral with a drive shaft (63) of the electric motor.

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