Lubrication system for a transmission unit with a reservoir chute and a scraper

Abstract

The invention relates to a transmission unit for a motor vehicle, comprising at least one differential with a differential mechanism and an input wheel ring gear (3) provided with a toothing (31) and providing a lubricating oil lifting function, the ring gear comprising a first rim flank (81) oriented towards the differential mechanism and a second rim flank oriented in the opposite direction, the transmission unit comprising a reservoir chute (9) arranged in a position at least partially above the axis (A3), and configured to receive oil lifted by the ring gear, the reservoir chute (9) comprising one or more flow openings, the reservoir chute (9) comprising a scraper (2) located near the first rim flank of the ring gear.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: Lubrication system for transmission unit with reservoir trough and scraper

[0003] The present invention relates to a lubrication system for a transmission unit in a motor vehicle. It is of interest to transmission units with a differential where oil is lifted by the rotation of the differential's input wheel.

[0004] The differential transmission unit in question may be part of a power unit that includes an electric machine and the differential transmission unit itself. An electrically driven oil pump may be present to supply the electric machine with pressurized oil, but its activation is selective and it does not operate continuously while the transmission is running.

[0005] [0 The differential transmission unit includes a reducer and a differential mechanism which require lubrication, in particular to lubricate the pinion teeth, bearings, seals, etc.

[0006] In the known art, a device is used to direct the oil lifted by the crown gear to the part of the differential mechanism containing the bevel, satellite, and planetary gears meshed together. This device takes the form of a scraper that catches some of the oil lifted by the crown gear. The oil caught by the scraper then falls by gravity into the heart of the differential mechanism.

[0007] Usually, the scraper appears as a shape directly from the casing that contains the transmission, which, once the differential is assembled, is located near the rim of the crown.

[0008]

[0006] It should be noted, however, that the scraper must be located in the immediate vicinity of the crown flange, typically with a clearance of approximately 1 millimeter, in order to effectively collect oil. This implies a significant geometric constraint on the design of the housing as well as on the manufacturing of the corresponding mold used to produce the housing casting. Furthermore, the scraper in question may require further machining to ensure the required tolerance range.

[0009] The inventors sought to reduce the aforementioned constraint on the geometry of the crankcase and endeavored to identify an oil scraping solution equivalent to that known in the prior art.

[0010] To this end, a transmission unit for a motor vehicle is proposed, comprising at least one differential with a differential mechanism and an input wheel ring having an axle, equipped with teeth and providing a lubricating oil lifting function, the ring comprising a first rim flange oriented towards the differential mechanism and a second rim flange oriented in the opposite direction, the transmission unit comprising: a reservoir trough arranged in a position at least partly above the axle, and configured to receive oil lifted by the ring, the reservoir trough comprising one or more flow openings characterized in that the reservoir trough comprises a scraper near the first rim flange of the ring.

[0011] Put another way, the scraper no longer comes from the housing that contains the differential but comes from an auxiliary part of the lubrication system, namely the reservoir chute, which forms a buffer reserve and is located in the upper zone, at least partly above the differential and generally above the intermediate reduction gear that attacks the differential.

[0012]

[0010] Thanks to these arrangements, the geometric constraints on the casing are reduced at this point, and its cost price and material cost can thus be reduced.

[0013]

[0011] The term "differential mechanism" here refers to a set of conical gears, namely at least two satellites and two planetary gears which perform the known differential function.

[0014] It is noticeable that the reservoir trough acts as an upper buffer reservoir, which, during operation, receives a large portion of the oil flow lifted by the differential ring gear above a certain rotational speed. The aim is to reduce the hydraulic drag caused by the ring gear splashing in order to improve overall vehicle performance, by lowering the oil level at the bottom of the sump due to the temporary storage of oil in the upper reservoir trough.

[0015] According to one embodiment, a clearance E2 is provided between a scraper edge and the first rim side of the crown, said clearance being between 0.5 mm and 1.5 mm.

[0016] The crown wheel rim is immersed in the oil reservoir at the bottom of the crankcase, where it becomes coated with a layer of oil on its teeth and flanks. This oil-coated rim then reaches the scraper, which traps some of the oil. The remaining oil, not scraped, flows into the reservoir formed by the oil filler neck.

[0017]

[0015] Depending on the rotational speed of the crown wheel, an oil bead can form on the radially inner part of the crown wheel rim flank or on the radially outer part of the crown wheel rim flank. In one embodiment, the scraping edge extends along the entire height of the crown wheel rim flank, so as to be able to capture an oil bead, whether it is on the inner or outer side of the crown wheel rim.

[0018]

[0016] The shape of the oil layer on the rim side depends on the balance between gravity, which tends to cause a drop to form on the radially inner side, and centrifugal force, which tends conversely to cause a drop to form on the radially outer side.

[0019]

[0017] According to one option, the clearance (E2) is constant along the height (H3) of the crown rim. The scraper edge is parallel to the rim flank, i.e., perpendicular to axis A3. For example, the clearance E2 may have an permissible tolerance of + / - 0.4 mm. The reservoir chute can be positioned quite precisely using indexers, including in the vicinity of the scraper, to maintain the prescribed tolerance.

[0020] In one embodiment, the scraper comprises a front wall with a vertically oriented groove. The groove helps to channel the oil, which is stopped by the scraping edge, towards the core of the differential.

[0021] In an optional design, a dispensing hole is provided in the trough above the channel to allow oil from the electric oil pump circuit to flow out. This dispensing hole allows oil to be delivered in configurations where oil lifting by the ring gear is not effective.

[0022] According to one embodiment, the scraper is formed integrally with the chute body.

[0023] This solution offers a good performance-to-cost ratio. The chute is formed like a molded plastic part; it can contain more or less complex shapes, and in this case, the scraper is molded from the same material as the rest of the chute.

[0024] According to one embodiment, the transmission unit includes an intermediate reducer gear, the chute extends above the intermediate reducer gear.

[0025] There is available space above the intermediate gear of the reducer to form the oil reservoir at this location.

[0026] The intermediate gear of the reducer is functionally interposed between the output pinion of the electric machine and the ring gear of the differential.

[0027] The intermediate gear of the reducer comprises a small pinion and a large pinion and rotates around an axis A2 which is offset from the crown gear axis

[0028] [0 According to one embodiment, the scraper is arranged near the top of the first rim flange of the crown. Thus the oil falls back by gravity near the vertical axis of rotation of the crown and the differential mechanism.

[0029] In one embodiment, the scraper is arranged in an end zone of a front chute arm. The front arm is located above the differential ring gear. The scraper is positioned laterally to the front arm relative to the ring gear's median plane.

[0030] The main reservoir of the chute is located above the intermediate reduction gear and therefore behind the top of the differential ring gear. The main chute body is extended forward by an arm which itself carries the scraper.

[0031]

[0031] According to one embodiment, the arm includes an opening facing downwards and an opening parallel to axis A2. One of these openings may, for example, lead to an oil supply channel above one or more points to be lubricated. During steady-state operation at a speed greater than or equal to 500 rpm, the reservoir chute stores up to 50% of the total quantity of oil present in the transmission unit housing.

[0032] [0 This reservoir gutter is spatially arranged opposite the oil lift area inside the transmission unit casing; it is a place where there is more space available and is also higher, which allows gravity flow from this reservoir gutter.

[0033] In one embodiment, at least one oil supply channel is also provided above one or more points to be lubricated. This supply channel can be shaped like a chute and can be fixed to the reservoir chute body.

[0034] In one embodiment, the crown gear teeth engage in a flat position with the intermediate gear's driving pinion, the driving pinion rotating on an axis (A2) parallel to the differential axis (A3). In another embodiment, the teeth are helical, which allows for minimal operating noise.

[0035]

[0036] In one embodiment, the reservoir chute includes a pumped circulating oil inlet. The pump fills the reservoir chute under certain operating conditions, such as very slow rotation or prolonged reverse movement, but these examples are not exhaustive.

[0036] According to one embodiment, in operation, in steady state, the decrease in the oil level at the bottom of the crankcase makes it possible to reduce the splashing and to reduce the hydraulic drag caused by the splashing of the ring in the oil present at the bottom of the crankcase.

[0037] The present invention also relates to an electric or hybrid vehicle, comprising at least one transmission unit as described above.

[0038] [0 The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which:

[0039] - [Fig.1] schematically illustrates an electric vehicle in top view with the electromotor unit mounted transversely;

[0040] - [Fig.2] illustrates a schematic cross-section of the electromotor unit according to a generally vertical cross-section, with the electrical machine compartment shown on the right and the transmission compartment shown on the left;

[0041] - [Fig.3] schematically illustrates a cross-sectional view of a transmission unit with the reservoir chute and the scraper according to the present invention, as indicated by arrow III in figure 2:

[0042] - [Fig.4] schematically illustrates in perspective in more detail the area of ​​the scraper formed in the reservoir chute;

[0043] - [Fig.5] illustrates in perspective view an example of an embodiment of the reservoir chute according to the present invention;

[0044] - [Fig.6] illustrates in top view the reservoir chute of figure 4;

[0045] - [Fig.7] shows in partial front view the geometric elements characteristic of the scraper function according to the present invention; - [Fig.8] illustrates two situations of oil layer present on the rotating differential ring.

[0046]

[0040] In the various figures, the same reference numerals designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale, in particular the gaps and intervals.

[0047] Figure 1 shows a top view of a VH vehicle. In the example shown, this vehicle includes an electric motor unit placed transversely in the front engine compartment, with an electric traction machine 1 located on the right side of the electric motor unit and a transmission TR located on the left side of the electric motor unit.

[0048] Of course, the arrangement could be reversed, with the machine on the left and the transmission on the right. Alternatively, the electric motor could interact with the vehicle's rear axle. The electric motor can be installed in conjunction with either a steering or non-steering axle.

[0049] In the figures, the vehicle and its electromotor unit are located with respect to an orthogonal coordinate system as follows: the vertical direction is noted Z, the horizontal direction called longitudinal is noted X, the horizontal direction called transverse is noted Y.

[0050] The TR transmission includes a RED reducer and a 7 differential. The lubrication system that equips the electric motor group will be discussed in the following paragraphs.

[0051] In the illustrated example, the electric motor 1 provides torque which enters the transmission, to be distributed to the two wheels of the axle via the differential 7. At the output of the TR transmission, there are two wheel shafts, one connected to the left wheel and the other connected to the right wheel of the vehicle (not shown).

[0052] Regarding the reducer, as known in itself and not described in detail, there is a double intermediate pinion 6 which is driven by an output pinion of the electric machine and which in turn drives the ring 3 of the differential.

[0053] The crown comprises a first rim side 81 oriented towards the differential mechanism and a second rim side 82 oriented in the opposite direction.

[0054] As can be seen in Figure 2, this intermediate gear 6 comprises a first pinion 61 of large diameter and a second pinion 62 of small diameter fixed to the first pinion. The second pinion 62 has teeth 63 permanently engaged with the teeth 31 of the differential ring gear 3.

[0055] The differential 7 comprises a ring gear 3 and a mechanism body 32 which contains the planetary and satellite gears (35, 36) as previously described. The ring gear 3 forms the input wheel of the differential. It should be noted that the ring gear has a parallel drive; it is not a bevel gear drive. The ring gear 3 has teeth 31. In the illustrated example, the teeth are helical; they are not parallel to the axis.

[0056] The rotor of the electric motor rotates around the axis A1. The rotor of the electric motor is rotationally fixed to a primary pinion permanently engaged with the large pinion 61 of the intermediate gear 6.

[0057] The ring gear 3 rotates about an axis labeled A3. The intermediate gear 6 rotates about an axis labeled A2. Axes A1, A2, and A3 are parallel. The electromotor unit comprises a main housing 4. The housing 4 delimits an internal space 4M that houses the electric machine (electrical machine compartment) and another internal space 4T that houses the transmission (transmission compartment). It is provided with a cover 42 on the machine side and a cover 41 on the transmission side. The housing 4 can be made in one piece or in several pieces assembled together.

[0058] The electric motor unit includes an oil pump 5, which is the driving element of a first lubrication circuit, labeled C1. The oil pump is electrically driven. The oil pump supplies pressurized oil to the core of the electric machine; circuit C1 is shown schematically in Figure 2. Furthermore, a heat exchanger, not shown in the figures, is provided on the first oil circuit C1. The oil pump is selectively controlled by a control unit, for example, according to the machine's cooling requirements.

[0059] [0 In addition, an oil lifting function is provided, obtained by rotating the teeth 31 of the ring 3. The oil lifting function is part of a second lubrication circuit marked C2, circuit C2 being schematically shown in figure 2.

[0060] Note that there is no specific pumping component in circuit C2.

[0061] In addition, the second lubrication circuit includes a trough 9, also called a reservoir trough, which can be described as a multi-function reservoir trough whose functions are discussed later.

[0062] When the electric oil pump 5 is operating, the oil level in the first oil reservoir VM in the electric machine compartment drops. The portion of oil delivered to the 4T transmission compartment flows into the reservoir trough 9, then trickles back into the transmission compartment, and finally returns to the first oil reservoir to be drawn back up by the pump.

[0063] In this configuration, the first lubrication circuit C1 prevails, the lifting function may be disprimed, but there is no adverse consequence, the delivery of oil being ensured by the first lubrication circuit C1 which supplies the reservoir chute 9 with oil dispensing and distribution orifices at the appropriate locations.

[0064] When the electric oil pump 5 is not in operation, the oil lifting function by the crown 3 is operational, the oil level in the second VT transmission-side oil reservoir may drop, but is partially replenished via the calibrated hole 8 from the first VM oil reservoir which is not being drawn by the pump.

[0065] A second lubrication circuit, C2, is established when the electric oil pump is not in operation, based on the lift produced by the rotation of the differential ring gear. The oil is sprayed into the reservoir trough 9.

[0066]

[0061] It is noted that in the two aforementioned operating modes, namely with the pump running or with the pump stopped, the oil level in which the ring 3 is immersed is substantially lower than the oil level at rest, which makes it possible to significantly reduce the hydraulic drag on the ring and the splashing in the lower area. The trough 9 forms a buffer oil reservoir; it accumulates a certain quantity of oil during lubrication operation.

[0067] Chute 9 is continuously supplied by the lift and / or the electric oil pump and simultaneously discharges oil onto the relevant parts through orifices. Chute 9 receives the oil lifted by the ring gear, which rotates at varying speeds.

[0068] The reservoir chute 9 is arranged in a position above the axis A3, and also above the axis A2 of the intermediate gear 6.

[0069] In the second lubrication circuit C2, there is no specific filter per se, but a magnet is planned to trap metallic particles that could circulate in the oil.

[0070]

[0066] A first oil reservoir VM is provided on the electrical machine side and a second oil reservoir VT on the transmission side. The first oil reservoir is connected to the second oil reservoir by a passage 18 in the lower part.

[0071] The reservoir chute 9 is formed as a molded plastic part. Thus, the reservoir chute 9 comprises complex shapes.

[0072] The reservoir chute 9 includes a main body 90 and a front arm 20. The main body 90 includes a bowl 91 which can hold a quantity of oil.

[0073] The main body extends over the differential ring gear and the large pinion 61 of the intermediate gear 6. As can be seen in Figures 6 and 7, the main body has a width W3 which corresponds substantially to the sum of the thickness of the ring gear and the thickness W6 of the large pinion 61 of the intermediate gear.

[0074]

[0070] The front arm 20 extends above the differential ring gear. The front arm 20 has a width W2 which substantially corresponds to the thickness of the ring gear.

[0075]

[0071] Advantageously, a scraper 2 is provided in the vicinity of the first rim flank 81. The scraper 2 includes a scraping edge 21 located near the first rim flank 81 of the crown with a clearance E2 which is discussed further.

[0076] In the illustrated example, scraper 2 is formed from the same material as the rest of the chute. The scraper could be formed as an add-on part attached to the body of the reservoir chute.

[0077] In the illustrated example, scraper 2 is arranged at the end of the front arm 20 of the chute, a lateral front arm. Scraper 2 is positioned laterally on the front arm relative to the median plane of the PM3 crown.

[0078] The scraper 2 comprises a front face in which a groove 25 is formed. The groove 25 has a vertical axis. The front face has a width W4 of a few mm, for example, 8 mm around.

[0079] In place of the aforementioned channel, a deflector of a different shape may be provided to direct the oil downwards.

[0080] The front lateral arm includes a downward-facing opening 27 and an opening 28 parallel to axis A3. The lateral opening 28 leads to a supply channel formed like a chute 16, which dispenses oil onto the ball bearing 17, located at a distance from the ring gear. The downward-facing dispensing hole 27 allows oil to flow from the electric oil pump circuit to the core of the differential.

[0081]

[0077] The reservoir chute 9 includes one or more flow openings. As can be seen in figures 5 and 6, there is a downward-opening orifice 93 which lubricates in particular the teeth of the rotor pinion.

[0082] Furthermore, laterally open ports 94, 96, 87, and 85 are provided to allow oil to flow towards the gear teeth and bearing 19 on the side opposite the machine. The cross-sectional areas of each port are adjusted according to the lubrication requirements of each position served.

[0083] The front arm 20 comprises two parallel cheeks 99 connected by a cross member 95.

[0084] The reservoir chute 9 includes an oil inlet 11 receiving pressurized oil from the first lubrication circuit C1.

[0085] The front arm 20 includes one or two indexers 88. This indexer is used to ensure precise positioning of the scraper edge relative to the rim sidewall 81.

[0086] The clearance E2 between the scraper edge 21 and the first rim sidewall 81 of the crown is between 0.5 mm and 1.5 mm.

[0087] An permissible range of + or - 0.4 mm around a target value of E2, for example 0.9 mm, can be provided.

[0088] Referring to Figure 8, the shape of the oil film on the rim sidewall depends on the balance between gravity, which tends to cause a droplet to form on the inner radial side, and centrifugal force, which tends conversely to cause a droplet to form on the outer radial side.

[0089]

[0086] Depending on the rotational speed of the crown, an oil bead can form on the radially inner part of the crown rim flank (example in Figure 8, right side) or on the radially outer part of the crown rim flank (example in Figure 8, left side). It can be seen that in both cases, the scraping edge 21 captures some of the oil carried along by the crown rim flank 81.

[0090] Advantageously, the scraping edge extends in height H4 over the entire height H3 of the side of the crown rim, in order to be able to capture an oil bulge, whether it is on the inside or outside side of the crown rim.

[0091] It should be noted here that the oil lift function is activated when the differential ring gear rotates in a direction corresponding to the vehicle's forward movement. It is worth noting that reverse vehicle sequences are generally very short and performed at low speeds, thus the lubrication requirement is much lower than in forward driving situations. Certain forward driving situations, such as going uphill and / or when towing a trailer, are the most critical with regard to lubrication requirements. It should also be noted that lubrication also performs a thermal function, cooling the transmission components, particularly the hottest areas, such as the bearings and the contact points between gear teeth.

Claims

DEMANDS 1. Transmission unit (TR) for a motor vehicle, comprising at least one differential (7) with a differential mechanism and an input wheel ring (3) having an axle (A3), provided with teeth (31) and providing a lubricating oil lifting function, the crown comprising a first rim flange (81) oriented towards the differential mechanism and a second rim flange (82) oriented in the opposite direction, the transmission unit comprising a reservoir chute (9) arranged in a position at least partly above the axis (A3), and configured to receive oil raised by the crown, the reservoir chute (9) comprising one or more flow openings (93,94,96) characterized in that the reservoir chute (9) includes a scraper (2) near the first rim side of the crown.

2. Transmission unit according to claim 1, in which a clearance (E2) is provided between a scraper edge and the first rim side (81) of the crown, said clearance being between 0.5 mm and 1.5 mm.

3. Transmission unit according to any one of claims 1 to 2, wherein the scraper (2) is formed integrally with the chute body (90).

4. Transmission unit according to any one of claims 1 to 3, wherein the transmission unit comprises an intermediate reduction gear (6), the chute extending above the intermediate reduction gear.

5. Transmission unit according to any one of claims 1 to 4, wherein the scraper is arranged at the top (81a) of the first rim side of the crown.

6. Transmission unit according to any one of claims 1 to 5, wherein the scraper (2) is arranged in an end area of ​​a front arm (20) of chute.

7. Transmission unit according to any one of claims 1 to 6, wherein there is further provided at least one oil supply conduit (16) above one or more points to be lubricated.

8. Transmission unit according to any one of claims 1 to 7, wherein the reservoir chute (9) includes a pumped circulating oil inlet (11).

9. Motor vehicle power unit comprising a housing (4), an electric machine (1) and a transmission unit (TR) according to any one of claims 1 to 8, the power unit comprising an electric oil pump (5), supplying a high-pressure lubrication circuit, configured at least to cool the electric machine and to deliver pressurized oil to the reservoir chute (9).

10. Electric or hybrid vehicle, comprising at least one transmission unit according to any one of claims 1 to 9.

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