Electric traction drive with specially designed oil reservoir and method for operating an electric traction system

Abstract

Electric traction system (40) with an electric machine and a transmission and with a common cooling lubricant circuit (1), wherein an oil sump (8) and at least one oil reservoir (2) are installed and the oil reservoir (2) can be filled both with an electric oil pump (19) and via spray oil through components of the transmission, wherein the oil reservoir (2) acts as a raised tank and the at least one outlet of the oil reservoir (2) is connected to cooling / lubricating oil points (7), characterized in that the oil reservoir (2) is at least a two-part tank, the outer contour of which at the bottom (116) adapts to the outer contours of gearwheels of the traction system (40) and the outer contour of which at the top (115) follows the course of the housing (41) of the electric traction system (40).

Description

[0001] The invention relates to an electric traction drive with a specially designed oil reservoir and a method for operating an electric traction system. State of the art

[0002] Partially or fully oil-cooled electric machines are used in powerful electric drives with high energy density. The rotor shaft and / or the stator of the electric machine are cooled with oil. In fully oil-cooled electric machines, the cooling oil requirement of the rotor shaft and stator varies depending on the respective operating point, particularly due to the copper, iron, and electromagnetic losses that occur in the machine. Therefore, to ensure maximum thermal availability and minimize power losses, the partial volume flows to the rotor shaft and stator must be distributed according to demand. Conventional electric traction drives, which are equipped with an electrically operated oil pump, use the oil produced by the positive displacement pump - usually in the form of a gear ring or rotary pump.Gerotor pumps generally provide the flow rate exclusively for the on-demand cooling of temperature-critical active components such as the stator and / or rotor of the electric drive motor. The electrically driven oil pump is switched on and off as needed and / or operated with speed control.

[0003] The cooling and lubrication of transmission components is generally passive, utilizing the pumping action of a differential spur gear or an intermediate shaft spur gear in combination with a suitable housing that acts as an oil guide. This results in a limited pumping action that is dependent on the vehicle speed or gear speed, and associated hydrodynamic losses, which are highly dependent on the speed and oil temperature. Splashing losses occur with passive lubrication of transmission components such as gears, rolling bearings, and radial shaft seals.

[0004] WO 2021 / 005186 A1 shows a transmission. In addition to the gears of the transmission, the transmission has a multi-chamber system. The multi-chamber system is located adjacent to individual gears of the transmission. The multi-chamber system is located next to a gear stage, in the immediate vicinity of the gear stage, in order to store lubricant or transmission oil in the vicinity of the gear stage. The reservoir formed by the multi-chamber system is located in close proximity to at least one gear stage. The multi-chamber system stores a certain amount of lubricant during operation of the transmission and only releases this amount back into the (re)circulation after some time. The rotation of the gears can be used to separate the lubricant using centrifugal force. The separated lubricant reaches at least part of the multi-chamber system, into a first receiving chamber, which can be, for example, a reservoir chamber.A recirculation path leads from chamber to chamber.

[0005] From JP 2009-250415 A, a cooling mechanism is known that is capable of increasing the amount of cooling liquid supplied to a part to be cooled when the rotational speed of a rotating element is low. The cooling mechanism comprises a pump driven by a power transmitted through the rotating element, which sucks and discharges the cooling liquid into a cooling liquid pocket; and the parts to be cooled, to which the cooling liquid discharged by the pump is supplied, comprise a tank that forms a passage for supplying the cooling liquid moved upward by the rotation of the rotating element to the parts to be cooled, provides a passage for supplying the cooling liquid discharged by the pump and the cooling liquid moved upward by the rotating element to the parts to be cooled, and retains the cooling liquid once.

[0006] Further examples are described in the documents US 2019 / 0 249 765 A1, DE 10 2021 206 607 B3, DE 10 2021 213 491 A1 and DE 20 2023 002 785 U1.

[0007] The problem is that in an eDrive system, oil from the tank often cannot be distributed in the transmission during longitudinal and transverse inclinations as well as during longitudinal and transverse acceleration.

[0008] The object of the invention is to provide an oil reservoir for a combined active and passive cooling lubricant circuit for an electric traction drive, whereby the filling behavior of the oil reservoir is optimized regardless of the inclination of the vehicle and at the same time a fail-safe lubrication system is ensured. Description of the invention

[0009] The problem is solved with an electric traction system with an electric machine and a transmission and with a common cooling lubricant circuit, wherein an oil sump and at least one oil reservoir are installed and the oil reservoir can be filled both with an electric oil pump and via spray oil through components of the transmission, wherein the oil reservoir acts as a high tank and the at least one outlet of the oil reservoir is connected to cooling / lubricating oil points, wherein the oil reservoir is at least a two-part component, the outer contour of which at the bottom adapts to the outer contours of gears of the traction system and the outer contour of which at the top follows the course of the housing of the electric traction system, wherein the oil reservoir has a tank inlet from the differential gear, which extends into the oil reservoir as far as an overflow edge at the inlet.

[0010] The combination of an active dry sump lubrication system with a fully functional passive splash oil lubrication system, in conjunction with a suitable operating strategy of the electric oil pump, leads to an increase in energy efficiency at the overall system level, an increase in the thermal availability and performance of the drive system, a fail-safe lubrication concept, since the passive cooling lubricant circuit is automatically activated when the electric oil pump is inactive, and enables the implementation of new functions, e.g. active preconditioning / post-cooling during standstill.

[0011] The oil reservoir has a tank inlet from the differential gear that extends into the oil reservoir to an overflow edge at the inlet.

[0012] The overflow edge at the inlet extends to a horizontal position corresponding to the center of a rotor shaft gear.

[0013] This provides a cost-effective solution to ensure that oil is delivered to the lubrication-relevant transmission components during inclination and acceleration.

[0014] The oil reservoir has a tank outlet for overflow, which extends from an overflow edge at the outlet to the outer contour of the oil reservoir and opens into a tank outlet to the transmission sump.

[0015] The oil reservoir has oil lines to the sideshaft bearing and seal and differential, as well as an outlet to a bearing.

[0016] The oil pump is directly connected to cooling / lubricating oil points under pressure, whereby the other cooling / lubricating oil points are also subjected to either the pressure of the oil pump or the geodetic pressure of the oil reservoir.

[0017] A single valve is attached to one inlet of the oil reservoir.

[0018] The valve is designed as a 2 / 2-way valve and is a hydraulic shuttle valve with a valve ball as a sealing element or a flap valve.

[0019] The object is also achieved with a method for operating an electric traction system with an electric machine and a transmission and with a common cooling lubricant circuit, wherein in operating states in which active cooling of the electric machine is advantageous or required for thermal reasons, the active cooling lubricant circuit is maintained via the electrically operated oil pump and a passive cooling / lubrication circuit is automatically activated in operating states in which active operation of the electric oil pump is not or not absolutely necessary for thermal reasons, as well as in the event of failure of the electric oil pump.

[0020] The method for operating an electric traction system is designed in such a way that the oil reservoir contains oil for passive cooling and lubrication even at inclination angles of up to + / - 45 degrees. Description of the characters Fig. 1 shows a schematic representation of a combined active and passive cooling lubricant circuit for an electric traction drive, Fig. 2 shows a schematic representation of an electric drive system, Fig. 3 shows a schematic representation of an adapted oil reservoir, Fig. 4 and Fig. 5 shows a schematic representation of the first part of the oil reservoir according to the invention, Fig. 6 and Fig. 7 shows a schematic representation of the second part of the oil reservoir according to the invention, Fig. 8 and Fig. 9 show sectional views through the oil reservoir at different vehicle inclinations,

[0021] According to Fig. 2, a traction drive 40 with an electric machine is assumed, of which only a rotor shaft gear 14 is shown in the sectional view. Other components of the electric machine, such as the stator, are not shown. The rotor shaft gear 14 meshes with an intermediate shaft gear 13, which is surrounded by a housing 16. The intermediate shaft gear 13, in turn, meshes with a differential spur gear 12, which rotates in a housing 15. The two housings are connected to an oil sump 8 and an oil reservoir 2, which is located geodetically above all axes of rotation of the aforementioned shafts. The housings are located in or form a housing 41 of the traction drive 40.

[0022] Fig. Figure 2 shows a schematic representation of the drive with an exemplary oil reservoir 2, which is divided into several chambers 20a, 20b, 20c. The flap valve 5a integrated in the oil reservoir 2 in this example is in a first operating state and allows the reservoir to be filled up to the maximum fill level h. max in all three chambers 20a, 20b, and 20c, which have different heights h1, h2, and h3. The chambers are separated from each other by partition walls and can thus have fill levels of different heights in the different chambers 20a, 20b, and 20c.

[0023] Fig. 1 shows a cooling lubricant circuit that supplies cooling oil to active cooling / lubricating oil points 7' via an electrically driven oil pump 19. A connection parallel to the active cooling / lubricating oil points 7' is connected to a valve 5 mounted at the inlet of an oil reservoir 2 near the upper limit of the oil reservoir.

[0024] Spray oil 11 is sprayed through the rotating gears of a transmission with differential in the direction of the circular arrow and is collected by an oil guide device 10 and an oil collecting trough 4 and directed into the oil reservoir 2. On the underside of the oil reservoir 2 there is at least one outlet 6, which supplies passive cooling / lubricating oil points 7 with cooling / lubricating oil.

[0025] The oil reservoir 2 has a geodetic height hmax.

[0026] The oil reservoir 2 arranged in the gearbox at the corresponding position acts - depending on the operating state of the electrically operated oil pump - as a pressure tank or as a high tank.

[0027] Depending on the vehicle operating mode, the most efficient state for the current operating mode can always be selected by using an appropriate operating strategy for the electric oil pump.

[0028] If the oil pump 19 is active, the oil reservoir 2 is actively filled via the entire delivery volume flow, or via a partial volume flow, which is provided, for example, via hydraulic resistance control using orifices from the electrically driven oil pump 19. The pressure-side oil lines consisting of oil bores, rotor lance, etc., and the oil reservoir 2 are completely filled with oil in this operating state, which automatically lowers the oil sump level in the oil sump 8 and consequently prevents unnecessary splashing of the gears.

[0029] If the oil pump 19 is inactive, the oil reservoir 2 is passively filled via at least one of the spur gears used as oil delivery gears, the differential spur gear 12 and the intermediate shaft spur gear 13, by thrown-off spray oil 11. The pressure-side lines such as oil bores, rotor lance, etc. run empty in this operating state (p=0), which automatically increases the oil sump level in the oil sump 8 and subsequently achieves the passive pumping effect by immersing the differential spur gear 12 in the oil sump 8. The pressure p provided at the outlet of the oil reservoir 2 is composed of density * gravitational acceleration * height h and is a geodetic pressure. A geodetic pressure describes the pressure at the lower end of the fluid column, which is created by the fluid's own weight.

[0030] A change between active operation with dry sump or forced circulation lubrication and passive operation with splash oil lubrication can, for example, be effected automatically by a flap valve 5a integrated in the oil reservoir 2 and designed as a 2 / 2-way valve. Depending on the operating state of the electric oil pump 19, the connection from a pressure line of the oil pump 19 to the oil reservoir 2 and the connection from an inlet opening of the oil reservoir 2 to the oil reservoir 2 is closed or opened.

[0031] In operating conditions where active cooling of the electric motor is advantageous or required for thermal reasons, the active cooling-lubricating circuit is maintained via the electrically operated oil pump. A low preload pressure is established in oil reservoir 2, depending on the oil pump speed and oil temperature. This leads to advantages in the demand-based oil supply to the transmission components during longitudinal and lateral acceleration, particularly during sporty, dynamic vehicle operation, as well as during varying vehicle inclinations. In addition, the oil pump speed control can be used to control the delivery volume flow, thereby delivering a higher oil volume flow to the individual consumers at operating points with increased cooling / lubricating oil requirements.In addition, in this operating state, any heat exchanger present in the system is flowed through by the entire coolant flow and the pressure tank is filled with cooled oil.

[0032] The passive cooling / lubrication circuit is automatically activated in operating conditions in which active operation of the electric oil pump is not or not absolutely necessary for thermal reasons, as well as in the event of a failure of the electric oil pump.

[0033] An embodiment according to the invention uses a special shape of the oil reservoir 2, which allows a reliable oil supply to the components of the electric traction drive 40 even at large inclines of up to 45 degrees.

[0034] Fig. 3 shows the installation location of the oil reservoir 2 above the rotor shaft gear 14 and the intermediate shaft gear 13. On the left side of the Fig. 3, an opening 33 is provided for the passive filling of the oil reservoir 2. This is where the spray oil enters the oil reservoir 2. The oil reservoir is directly connected to the housing 41 of the traction drive.

[0035] In Fig. 4 and Fig. 5, the oil reservoir 2 is shown in detail with a first part of the tank 100 and a second part of the tank 200 connected thereto according to Fig. 6 and Fig. 7.

[0036] The first part of the tank 100 has a tank inlet 106 coming from the differential gear. This tank inlet 106 runs above the intermediate shaft gear 13 and its shape is adapted to the contour of the intermediate shaft gear. The tank inlet 106 forms a channel that is formed by the outer skin 115 of the first part of the tank 101 and an overflow edge 105 inside the oil reservoir 2. The overflow edge 105 at the inlet extends to or beyond the axial center of the rotor shaft gear 14. In the example shown, the overflow edge 105 extends a distance a beyond the center of the rotor shaft gear 14. The overflow edge at the inlet 105 is formed by the lower outer wall 116 of the first part of the tank 100. This extends into the interior of the component and is bent inward in a narrow U-shape.

[0037] Furthermore, the oil reservoir has a tank oil inlet 104, which is supplied with oil by an oil pump if necessary. An oil scraper edge 114 is located on the outer skin 115 of the first part of the tank 100, which slows down any oil thrown off the tank oil inlet 104 and directs it into the interior of the oil reservoir.

[0038] On the output side, the first part of the tank 100 has a tank outlet 113 leading to the transmission sump 8. An overflow edge 103 is also present at the outlet on the output side. This edge extends into the interior of the oil reservoir 2 and forms a tank outlet 112 for overflow.

[0039] The oil scraper edge 114 prevents the oil entering via the tank oil inlet 104 from immediately escaping via the overflow.

[0040] From the oil reservoir 2 there are further outlets, such as the outlet for lubricating the bearings 111, an oil line 107 to the differential and an oil line 108 to the sideshaft bearing and the seal.

[0041] The two oil lines under 107 and 108 are fed by an oil collecting pan 109, which has an oil drain 110.

[0042] In the Fig. 6 and Fig. 7 shows the second part of the tank 200, which together with the first part of the tank 100 forms a closed shape.

[0043] The overflow edges 105 and 103 are extended horizontally along the arrow h so that when the vehicle is tilted, sufficient oil remains in the oil reservoir 2 and the consumers, such as bearings, gears, sealing rings and differential, are supplied with oil.

[0044] Fig. Figure 8 shows a first tilt state. By extending the overflow edge 105 of the inlet of the tank inlet 106 for spray oil of the differential gear, oil can be pumped to the lubrication-relevant transmission components even at transmission tilts of α<45°. The oil level is adjusted such that the openings from the tank to the lubrication channels are below the oil level. When tilted, the tank can be filled with oil from the oil sump 8 either by means of the differential gear or the oil pump 19.

[0045] Fig.Figure 9 shows a second tilt condition. By extending the edge 103 of the overflow horizontally, oil can be pumped to the lubrication-relevant transmission components even at transmission tilts of α<45°. The oil level is adjusted so that the openings from the reservoir to the lubrication channels are below the oil level. When tilted, the reservoir can be filled with oil from the sump either via a differential gear or an oil pump. Reference symbol 1 cooling lubricant circuit 2 oil reservoir 2' pressure tank 2'' high tank 3 Pressure line from oil pump 4 Oil collecting trough 5 Valve 6 Outlet 7 cooling / lubricating oil points 8 Oil sump 9 gear 10 Oil guide device 11 Spray oil 12 Differential spur gear 13 Intermediate shaft gear 14 Rotor shaft gear 15 Housing differential spur gear 16 Intermediate shaft gear housing 19 Oil pump 20a, 20b, 20c chambers 33 Opening for passive filling 40 electric traction system 41 housings 100 first part of the tank 200 second part of the tank 103 Overflow edge at the outlet 104 Tank oil inlet 105 Overflow edge at the inlet 106 Tank inlet from the differential gear 107 Oil line to the differential 108 Oil line to sideshaft bearing and seal 109 drip tray 110 Outlet collecting tray 111 Outlet to the warehouse 112 Tank outlet to overflow 113 Tank outlet to the transmission sump 114 Oil rebound area / oil scraper edge 115 Outer contour above 116 Outer contour below

Claims

[1] An electric traction system (40) comprising an electric machine and a transmission and a common cooling lubricant circuit (1), wherein an oil sump (8) and at least one oil reservoir (2) are installed, and the oil reservoir (2) can be filled both with an electric oil pump (19) and via spray oil through components of the transmission, wherein the oil reservoir (2) acts as a raised tank and the at least one outlet of the oil reservoir (2) is connected to cooling / lubricating oil points (7), wherein the oil reservoir (2) is a tank comprising at least two parts, comprising a first part of the tank (100) and a second part of the tank (200), the outer contour of which at the bottom (116) adapts to the outer contours of gears of the traction system (40) and the outer contour of which at the top (115) follows the profile of the housing (41) of the electric traction system (40), characterized bythat the oil reservoir (2) has a tank inlet from the differential gear (106) which extends into the oil reservoir (2) up to an overflow edge at an inlet (105). [2] Electric traction system (40) according to claim 1, characterized by that the overflow edge at the inlet (105) extends to a horizontal position corresponding to the center of a rotor shaft gear (14). [3] Electric traction system (40) according to one of the preceding claims, characterized by that the oil reservoir (2) has an overflow (112) as a tank outlet (103), which extends from an overflow edge at the tank outlet (103) to the outer contour of the oil reservoir (2) and opens into a tank outlet (113) to the transmission sump. [4] Electric traction system (40) according to one of the preceding claims, characterized bythat the oil reservoir (2) has oil lines (107, 108) to the sideshaft bearing and seal and differential, as well as at least one outlet to a bearing (111). [5] Electric traction system (40) according to one of the preceding claims, characterized by that the oil pump (19) is directly connected to cooling / lubricating oil points (7') under pressure (p1), wherein the further cooling / lubricating oil points (7) are either also connected to the pressure (p1) of the oil pump (19) or to the geodetic pressure (p g ) of the oil reservoir. [6] Electric traction system (40) according to one of the preceding claims, characterized by that a single valve (5, 5a) is attached to an inlet of the oil reservoir (2). [7] Electric traction system (40) according to claim 6, characterized by that the valve (5, 5a) is designed as a 2 / 2-way valve and is a hydraulic shuttle valve with a valve ball as a sealing element or a flap valve (5a). [8] Method for operating an electric traction system (40) with an electric machine and a transmission and with a common cooling lubricant circuit (1) according to one of claims 1 to 7, wherein in operating states in which active cooling of the electric machine is advantageous or required for thermal reasons, the active cooling lubricant circuit is maintained via the electrically operated oil pump (19) and a passive cooling / lubrication circuit is automatically activated in operating states in which active operation of the electric oil pump (19) is not or not absolutely necessary for thermal reasons, as well as in the event of failure of the electric oil pump (19). [9] Method for operating an electric traction system (40) according to claim 8, wherein oil for passive cooling and lubrication is present in the oil reservoir (2) even at inclination angles of up to + / -45°.

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