ELECTRIC DRIVE UNIT FOR A MOTOR VEHICLE

Description

[0001] The invention relates to an electric drive unit for a motor vehicle, comprising an electric drive, a gearbox downstream of the electric drive in the direction of power flow and arranged in a gearbox housing, means for circulating coolant in the interior of the gearbox housing, and a rotatably arranged input or output shaft of the gearbox, wherein the gearbox housing is composed of a housing shell surrounding a central axis in an annular manner and an end wall, and wherein the end wall extends radially outwards from an opening for the input or output shaft to a connection area in which the end wall and the housing shell are connected to each other.

[0002] Such an electric drive unit serves as the propulsion system for a vehicle. It is preferably used as part of an electric drive axle for a commercial vehicle. In this type of vehicle axle, a multi-stage transmission is connected downstream of the electric drive, which is positioned close to the vehicle's center for optimal weight distribution. The transmission, either alone or together with the electric drive, is housed in a casing consisting of a housing shell enclosing the interior of the transmission, including the transmission components, and a front wall closing off the interior at the end. The housing shell is predominantly annular in shape. The front wall extends essentially radially and has a central opening through which the transmission input shaft or output shaft passes.

[0003] A drive system for an electrically powered vehicle is known from US patent 5,443,130 A.

[0004] To cool the transmission components, coolant is circulated within the transmission housing in a closed loop, ensuring that the coolant flows through as many mechanically stressed areas of the transmission as possible, including the rolling bearings for the rotating transmission components. Preferably, a transmission oil serves as the coolant, thus lubricating the transmission components and dissipating heat.

[0005] Especially when the gearbox is a planetary gear system, the gearbox oil rotates rapidly on the inside of the housing. This rotation creates an annular oil sump around the inside of the gearbox housing. In the case of injection lubrication, this hinders the optimal lubrication process. Oil extraction is particularly difficult because, due to the aforementioned rotation, the oil flows past the designated oil drain at high velocity instead of completely entering it.

[0006] The invention is based on the objective of improving the flow conditions, particularly in those areas of the gearbox housing where the coolant is drawn off or extracted from the gearbox housing during circulation, by means of constructive measures.

[0007] To solve this problem, an electric drive unit with the features of claim 1 is proposed.

[0008] An additional annular chamber, connected to the interior of the gearbox housing only via individual openings, serves to calm the coolant flowing or rotating at high speed in other areas of the gearbox housing. The annular chamber acts as a calming zone for the coolant. This annular calming zone is preferably arranged over a large diameter. The annular calming zone is open to the interior on certain circumferential sections, namely in the area of ​​the individual openings, so that coolant, and in particular gearbox oil, can flow into the annular chamber through these openings and be calmed there.In contrast, on other circumferential sections, the annular chamber is essentially closed off from the gearbox interior, so that no significant coolant exchange takes place in these areas and the fluid, and especially its flow, can settle in these regions of the annular chamber. As a result of this smoother flow, oil extraction and drainage are significantly improved, particularly when space in the extraction area is already limited.

[0009] According to a preferred embodiment of the annular calming zone, it is advantageous if the openings alternate with circumferential sections without openings. For example, the number of openings and the number of circumferential sections without openings in the annular chamber can each be six to ten.

[0010] Regarding the annular chamber serving as a calming zone, it is proposed that the wall of the annular chamber be formed partly by the housing shell and partly by the end wall, the end wall being a partition between the gearbox and the electric motor of the drive unit.

[0011] In order for the annular chamber to be arranged on a large diameter, it is proposed that the diameter of the annular chamber be larger than the largest diameter that the inside of the housing shell has outside the area of ​​the annular chamber.

[0012] Furthermore, it is proposed that the annular chamber is bounded towards the interior by an inner chamber wall, and towards the outside of the housing shell by an outer chamber wall, with the openings and the openingless circumferential sections being located in or on the inner chamber wall.

[0013] According to a particularly advantageous embodiment from a manufacturing perspective, the inner chamber wall is shaped like a crenellation, with the crenellations forming the circumferential sections without openings, and the circumferential areas between the crenellations forming the openings. Preferably, the axial extent of the openings, i.e., their extent in the direction of the axis, is less than the axial length of the annular chamber.

[0014] Regarding the cross-sectional geometry of the annular chamber, it is further proposed that the length of the annular chamber in the axial direction is greater than the maximum width of the annular chamber, measured between the inner and outer chamber walls.

[0015] Preferably, bores or channels are provided in the housing shell, extending from the annular chamber to the outer surface of the housing shell. These bores or channels can serve various functions and purposes in connection with the coolant flow. For example, the outer ends of the bores or channels can be threaded to accommodate a vent valve, a vent filter, a measuring plug for detecting the coolant level, a magnetically operated metal chip catcher, or a temperature sensor. One of the bores or channels, preferably located at the lowest point of the annular chamber, serves to drain the transmission oil into a collector located below.

[0016] Since the functions associated with the bores or channels sometimes require more space, a further embodiment proposes that the housing shell around the annular chamber be designed as a flange radially extended compared to the rest of the housing shell, and that the bores or channels extend through the flange to its outer surface. The additional volume associated with the radially extended flange is thus used to gain space for sufficiently large bores or channels, as well as space for the technical purposes assigned to these bores or channels.

[0017] Additionally, the flange can serve as a bolted connection between the gearbox housing and, for example, the directly adjacent motor housing of the electric drive. For this purpose, it is advantageous if the flange is provided with axial openings distributed around its circumference for receiving screws or bolts, e.g., bolts as rigid connecting elements between the gearbox housing and the motor housing.

[0018] To achieve particularly favorable flow conditions in the calming zone, it is proposed that the end wall be provided with a collar extending into the annular chamber, and that the transition between the radially extending part of the end wall and the collar be formed as a radius. Preferably, the radius of this radius is between 25% and 75% of the maximum width of the annular chamber, measured between the inner and outer chamber walls.

[0019] The wall of the annular chamber, insofar as the wall is formed by the housing shell, is a U-shaped wall of a groove open towards the end wall.

[0020] The groove, open towards the end wall, allows for the formation of a flange extending into the annular chamber on the end wall. This flange abuts one of the groove walls, preferably the radially outer wall. In this configuration, the groove not only serves to stabilize the coolant flow but also acts as a centering element, ensuring precise alignment of the end wall with the housing shell in the connection area. This alignment is further enhanced if the flange or centering collar formed on the end wall, with at least one annular seal interposed, abuts the corresponding wall of the groove, thus achieving a liquid-tight connection between the end wall and the housing shell in the connection area.

[0021] Preferably, the seal is inserted into a sealing groove formed in the collar or centering collar. In one embodiment of the electric drive unit, it is proposed that the transmission is a planetary gear whose ring gear is the toothed inner surface of the housing. The toothing is designed as helical teeth such that the coolant collected in the teeth is transported towards the longitudinal section of the housing containing the openings.

[0022] Further advantages and details of the electric drive axle for a commercial vehicle will become apparent from the following description of an exemplary embodiment shown in the drawing. Specifically, we will show... Fig. 1 : an electric drive axle for a commercial vehicle with a multi-stage gearbox in the design of a double planetary gearbox, a gearbox housing to accommodate the gearbox, a motor housing attached to it, and an axle housing also attached to the gearbox housing; Fig. 2 : a perspective partial section of the gearbox housing, together with a planetary gear carrier of the gearbox; Fig. 3 : a perspective partial section of the gearbox housing, together with an end wall arranged between the gearbox housing and the engine housing; Fig. 3a : an enlarged detail section of the connection area from Fig. 3 ; Fig. 4 : a longitudinal section through parts of the gearbox and through the front wall, but without the gearbox housing; Fig. 5 : another perspective view of the gearbox housing from a different angle; Fig. 6 : a side view of the gearbox housing; and Fig. 7 : a section through the gearbox housing according to the in Fig. 6 designated section plane VII - VII.

[0023] The Fig. 1 Figure 1 shows one half of an electric drive axle for a motor vehicle. The depicted half of the axle serves to drive a motor rotatably mounted on a steering knuckle 1, in Fig. 1 The vehicle wheel 2, shown with a dashed line on the left edge, is shown with a dashed line. The similarly designed second half of the drive axle is located symmetrically on the other side of the wheel shown with a dashed line. Fig. 1 The registered vehicle center plane M, and carries the respective vehicle wheel on the opposite side of the vehicle. The electric drive axle is, in its entirety, a rigid axle extending from one side of the vehicle to the other.

[0024] For each side of the vehicle, and thus for the drive of the respective vehicle wheel 2, an electric drive 5, in particular an electric motor, is provided near the vehicle's central plane M. A gearbox 6, here in the form of a two-stage planetary gearbox, is connected downstream of each electric motor towards the outside of the vehicle.

[0025] The two electric drives are located in a common motor housing 3, which can be one or more parts. Each gearbox 6 is located in a gearbox housing 4, which is flanged to the motor housing 3.

[0026] The gearbox housing 4 comprises, among other things, a substantially cylindrical housing shell 11, whose inner surface 7 surrounds the gearbox elements of the gearbox 6 in a ring-like manner, and an end wall 12 that is integral with the housing shell 11. The end wall 12 is predominantly closed, but leaves a gearbox opening 12a in its center, through which the gearbox output shaft 18 of the gearbox 6, rotating on the central axis of rotation A, passes.

[0027] The gearbox housing 4 is also provided with an end wall 13 at its other end, which, however, is a separate component. This end wall 13 and the housing shell 11 are connected to each other in a fluid-tight manner within a circular connecting area 14.

[0028] At its center, the end wall 13 is provided with an opening 17 through which the input shaft 19 of the gearbox passes. This input shaft 19 of the gearbox can also be the motor output shaft, and it also rotates on axis A. .

[0029] The end wall 13 extends radially outwards from the opening 17 for the transmission input shaft 19 to the connection area 14, where the end wall 13 and the housing shell 11 are fluid-tightly connected. The transmission output shaft 18, which extends from the other end wall 12, can be rotatably connected, preferably via a splined connection, to a drive shaft that leads to and drives the vehicle wheel 2. The drive shaft rotates in a tubular axle housing 15 of the drive unit, which also extends along the central axle A. The axle housing 15 is attached to the end wall 12 by means of a flange 16.

[0030] The axle housing 15 is fitted with the steering knuckle 1 at its outer end. The brake caliper bracket of the vehicle brake, preferably a disc brake caliper bracket, is also attached to the axle housing 15. Axle guidance elements, such as a trailing arm and, if applicable, a lateral control arm of the vehicle axle, are also attached to the axle housing 15.

[0031] To attach the axle housing 15 to the gearbox housing 4, the axle housing 15 is provided at its inner end with a radially widened flange 16. The flange 16 is rigidly bolted to the end wall 12 of the gearbox housing 4 by means of several bolts.

[0032] The connection between the motor housing 3, which accommodates the electric drive 5, and the gearbox housing 4 is also made by means of screw connections, for which purpose the respective ends of these housing parts are designed as radial flanges 25, 26, which are firmly connected to each other by means of screws which pass through axial openings 27 in the flange 26 of the gearbox housing 4.

[0033] The gearbox housing 4 not only serves as a housing but is also itself part of the planetary gear system. On the inner surface 7 of the housing shell 11, a helical gear 30a of the first gear stage is arranged around the axis of rotation A, and axially offset, a helical gear 30b of the second gear stage is arranged around the axis of rotation A. Each of the two helical gears 30a, 30b therefore forms the ring gear of the respective planetary gear system. The orientation or helical position of the teeth of the helical gear 30b is opposite to that of the teeth of the first helical gear 30a. The planet gears of the two gear stages of the planetary gear system mesh with these helical gears.

[0034] The remaining gear elements of the planetary gears are arranged in a planet carrier rotating on axis A, which is inserted into the gearbox housing 4 as a pre-assembled gear carrier 17c. The central element of the gear carrier 17c is the gearbox output shaft 18, which rotates on axis A and protrudes from the gearbox opening 12a of the gearbox housing 4, which is also centrally located.

[0035] The cooling of the gearbox 6 and its partially heavily loaded teeth, pinions, and bearings is achieved by means of a cooling fluid circulated by a pump. The cooling fluid is preferably a gear oil, so that the fluid both lubricates the gearbox components and dissipates heat.

[0036] Due to its planetary gear design, cooling and lubricating fluid is flung outwards from the planet gears against the helical gears 30a, 30b by centrifugal forces. The cooling fluid therefore collects on the inner surface 7 of the housing shell 11, and a pronounced rotation of the fluid occurs along this inner surface 7. The fluid must be collected and returned to the cooling and lubrication process by transporting it back to more central areas of the gearbox, such as the rolling bearings of the gearbox input shaft 19 and the gearbox output shaft 18.

[0037] The inclined position of both gears 30a, 30b creates a scooping action on the coolant directed towards the end wall 13 during active recirculating cooling, combined with a rotation of the gear oil along the inside 7. Only during passive sump cooling is the orientation of gear 30b reversed, so that a scooping action directed towards the end wall 12 then also occurs.

[0038] As a result of the rotation of the transmission oil on the inside 7 of the transmission housing, a rapidly flowing oil sump forms there, which, unless additional measures as described below are taken, would impede the ideal lubrication and cooling process. This is because the resulting flow would make it difficult to extract the transmission oil necessary for circulation if the transmission oil were to flow past the existing oil drain at high velocity instead of entering it completely.

[0039] The solution to this problem consists of providing an annular chamber 33, preferably circular in shape, around the axis A, which extends circumferentially along the connection area 14 where the end wall 13 is attached to the housing shell 11. Importantly, the annular chamber 33 is connected to the interior 7 of the gearbox housing only via individual openings 40. The openings 40 are evenly distributed around the inner circumference of the annular chamber 33.

[0040] The annular chamber 33 serves to calm the coolant, which flows at high speed in other areas of the gearbox housing and rotates strongly, especially along the inner wall. For the coolant, the annular chamber 33 therefore functions as a calming zone, which is only open to the interior 7 on certain circumferential sections, namely in the area of ​​the individual openings 40, so that the coolant or gearbox oil flows into the annular chamber 33 through these openings 40 and is calmed there.

[0041] In contrast, on other circumferential sections, the annular chamber 33 is essentially closed off from the gearbox interior 7, so that no significant fluid exchange takes place on these other circumferential sections and the fluid flow can stabilize along these areas of the annular chamber 33 that are closed off from the gearbox interior. This stabilization of the flow leads to improved oil suction or drainage, which occurs directly from the annular chamber 33, e.g., through a channel opening into the annular chamber 33 at its lowest point, through which the fluid can flow downwards to a collector.

[0042] To ensure that the annular chamber 33 forms the calming zone, the openings 40 alternate with circumferential sections 41 without openings in the circumferential direction of the annular chamber. The number of openings 40 and the number of circumferential sections 41 without openings is equal; in the embodiment shown, there are six openings 40 and, correspondingly, six circumferential sections 41 without openings around the circumference.

[0043] The diameter of the ring chamber 33 is larger than the largest diameter that the inside 7 of the case shell 11 has outside the area of ​​the ring chamber 33.

[0044] By extending the annular chamber 33 along the connecting area 14 where the end wall 13 is attached to the housing shell 11, the wall of the annular chamber 33 is formed partly by the housing shell 11 and partly by the end wall 13.

[0045] The annular chamber 33 is bounded on the interior side 7 by an inner chamber wall 44 and on the exterior side of the housing shell 11 by an outer chamber wall 45. The openings 40 and the circumferential sections 41 without openings are located in or on the inner chamber wall 44. In a manufacturingly simple manner, the inner chamber wall 44 is shaped like a crenellation, with crenellations extending parallel to the central axis A forming the circumferential sections 41 without openings, and the circumferential sections between the crenellations forming the openings 40. Both the crenellations and the circumferential sections 41 arranged between them are rectangular when viewed radially from the inner chamber wall 44.

[0046] The wall of the annular chamber 33, insofar as this wall is formed by the housing shell 11 and not by the end wall 13, is a U-shaped wall circumferentially around axis A in the form of a groove open towards the end wall 13. The length of this groove and the length of the annular chamber 33 in the direction of axis A is greater than the maximum width of the annular chamber 33, measured between the inner chamber wall 44 and the outer chamber wall 45.

[0047] The axial extent of the openings 40, i.e. their extent in the direction of axis A, is less than the axial length of the annular chamber 33.

[0048] The circumferential sections 41 without openings extend axially so far in the direction of the end wall 13 that they either touch the inside 13a of the end wall 13, or only a small gap remains here through which no or essentially no fluid exchange is possible.

[0049] The end wall 13 separates the gearbox 6 from the electric drive 5. On its side facing the gearbox 6, the end wall 13 is provided with a collar 50 extending perpendicular to the main extent of the end wall 13, which serves, among other things, as a centering collar. The collar 50 is an integral part of the end wall 13. It is of such axial length that it extends into the annular chamber 33. For centering purposes, the outer surface of the collar 50 rests radially against the outer chamber wall 45 with a seal 51 interposed. In the exemplary embodiment, the axial length of the circumferential centering collar is approximately half the axial extent of the annular chamber 33.

[0050] Since the connection area 14 must be liquid-tight, the collar 50 rests radially against the chamber wall 45 with the annular seal 51 interposed. The seal 51 is inserted into a sealing groove on the outside of the collar 50. Fig. 3aThe transition between the inner surface 13a of the end wall 13, extending transversely to the central axis A, and the inner surface 50a of the collar 50 is formed as a curve 52, and preferably as a 90° curve with a radius R of the curve 52 that is between 25% and 75% of the maximum width of the annular chamber 33 between the inner 44 and the outer 45 chamber wall. Forming the transition as a curve 52 results in improved flow guidance at the annular chamber 33.

[0051] Several radially extending bores and channels 60 lead from the annular chamber 33 to the outside of the housing shell 11 and in particular to the outside of the flange 26 of the gearbox housing, since the flange 26 is arranged around the annular chamber 33.

[0052] One of the radial bores or channels 60 is an oil drain through which the gear oil, which has accumulated and settled in the annular chamber 33, can drain downwards to a collector. For this reason, this bore or channel is located at the lowest point of the flange 26.

[0053] Further bores or channels 60 can serve various functions and purposes in connection with the coolant routing. For example, they can accommodate a vent valve, a vent filter, a measuring plug for detecting the coolant level in the transmission, a magnetically operated catcher for metal shavings accumulated in the fluid, or a temperature sensor for measuring the oil temperature.

[0054] Since the bores or channels 60 are not located in the rather thin-walled part of the gearbox housing, but rather in the area of ​​the radially expanded flange 26 of the gearbox housing, there is sufficient space here for such additional functional components. For example, the outer ends of the bores or channels 60 can be provided with a thread into which the respective functional component is screwed from the outside.

[0055] The bores or channels 60 are located on those circumferential sections of the flange 26 where it does not have any of the axial openings 27. Reference numeral list 1 Steering knuckle 2 Vehicle wheel 3 Motor housing 4 Gearbox housing 5 Electric drive 6 Gearbox 7 Inside 1 1 Housing shell 12 End wall 12a Gearbox opening 13 End wall 13a Inside end wall 14 Connection area 15 Axle housing 16 Flange 17 Opening 17c Gearbox carrier 18 Gearbox output shaft 19 Gearbox input shaft 25 Flange 26 Flange 27 Axial opening 30a Helical gear 30b Helical gear 33 Annular chamber 40 Opening 41 Openingless circumferential section 44 Inner chamber wall 45 Outer chamber wall 50 Collar, centering collar 50a Inside collar 51 Seal 52 Rounding 60 Bore, channel A Axle, axis of rotation M Vehicle centerline R Radius

Claims

1. Electric drive unit for a motor vehicle, comprising an electric drive (5), a gearbox (6) downstream of the electric drive (5) in the direction of power flow and arranged in a gearbox housing (4), means for circulating cooling fluid in the interior (7) of the gearbox housing (4), and a rotatably arranged input or output shaft (19, 18) of the gearbox (6), the gearbox housing (4) consisting of a housing casing (11) annularly surrounding a central axis (A) and an end wall (13), and characterized in that the end wall (13) extends radially outward from an opening (17) for the input or output shaft (19, 18) to a connection region (14) in which the end wall (13) and the housing casing (11) are connected to one another, an annular chamber (33) which extends in the circumferential direction along the connection region (14) and is connected to the interior (7) via individual openings (40).

2. Electric drive unit according to claim 1, characterized in that the openings (40) are evenly distributed around the inner circumference of the annular chamber (33).

3. Electric drive unit according to claim 1 or claim 2, characterized in that the openings (40) alternate with circumferential portions (41) without openings in the circumferential direction.

4. Electric drive unit according to claim 3, characterized in that the number of openings (40) and of circumferential portions (41) without openings is six to ten in each case.

5. Electric drive unit according to any of the preceding claims, characterized in that the wall of the annular chamber (33) is formed partly by the housing casing (11) and partly by the end wall (13).

6. Electric drive unit according to any of the preceding claims, characterized in that the annular chamber (33) surrounds the central axis (A) in a circular shape, and in that the diameter of the annular chamber (33) is larger than the largest diameter that the inside (7) of the housing casing (11) has outside the region of the annular chamber (33).

7. Electric drive unit according to any of claims 2 - 6, characterized in that the annular chamber (33) is bounded toward the interior (7) by an inner chamber wall (44) and toward the outside of the housing casing (11) by an outer chamber wall (45), the openings (40) and the circumferential portions (41) without openings being located in or on the inner chamber wall (44).

8. Electric drive unit according to claim 7, characterized in that the inner chamber wall (44) is designed in a crenelated shape, the crenelations forming the circumferential portions (41) without openings.

9. Electric drive unit according to claim 7 or claim 8, characterized in that the length of the annular chamber (33) in the axial direction is greater than the maximum width of the annular chamber (33) between the inner chamber wall (44) and the outer chamber wall (45).

10. Electric drive unit according to any of claims 7 - 9, characterized by bores or channels (60) in the housing casing (11) leading from the annular chamber (33) to the outside of the housing casing (11).

11. Electric drive unit according to claim 10, characterized in that the housing casing (11) is formed around the annular chamber (33) as a flange (26) which is radially expanded with respect to the rest of the housing casing, and in that the bores or channels (60) extend through the flange (26) to its outside.

12. Electric drive unit according to claim 11, characterized in that the flange (26) is provided with axial openings (27), distributed around its circumference, for receiving screws or bolts.

13. Electric drive unit according to any of claims 7 - 12, characterized in that the end wall (13) is provided with a collar (50) which extends into the annular chamber (33), and in that the transition between the radially extending part of the end wall (13) and the collar (50) is formed as a rounded portion (52), the radius (R) of the rounded portion (52) preferably being between 25% and 75% of the maximum width of the annular chamber (33) between the inner chamber wall (44) and the outer chamber wall (45).

14. Electric drive unit according to claim 5, characterized in that the wall of the annular chamber (33), insofar as it is formed by the housing casing (11), is a U-shaped wall of a groove which is open toward the end wall (13).

15. Electric drive unit according to claim 14, characterized in that the end wall (13) is provided with a collar (50) which extends into the annular chamber (33) and abuts one of the walls of the groove, preferably the radially outer wall of the groove.

16. Electric drive unit according to claim 15, characterized in that the collar (50) abuts the wall of the groove with at least one annular seal (51) in between.

17. Electric drive unit according to claim 16, characterized in that the seal (51) is inserted into a sealing groove which is formed in the collar (50).

18. Electric drive unit according to any of the preceding claims, characterized in that the gearbox (6) is a planetary gearbox, the ring gear of which is the inner side of the housing casing (11) provided with teeth (30a), the teeth (30a) being designed as helical teeth in such a way that the cooling fluid accumulated in the teeth is transported in the direction of the longitudinal portion of the housing casing (11) having the openings (40).