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

Abstract

An electric traction system (40) having an electric machine and a transmission and having 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 also by splash oil via components of the transmission, wherein the oil reservoir (2) acts as a high tank and the at least one outlet of the oil reservoir (2) is connected to cooling / lubricating oil points (7), characterised in that the oil reservoir (2) is an at least two-part tank which has a lower outer contour (116), which adapts to the outer contours of gear wheels of the traction system (40), and an upper outer contour (115), which follows the course of the housing (41) of the electric traction system (40).

Description

[0001] Electric traction drive with specially designed oil reservoir and method for operating an electric traction system

[0002] The invention relates to an electric traction drive with a specially designed oil reservoir and a method for operating an electric traction system.

[0003] State of the art

[0004] In high-performance electric drives with high energy density, partially or fully oil-cooled electric machines are used. 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 for the rotor shaft and stator varies depending on the operating point, particularly due to copper, iron, and electromagnetic losses occurring within the machine. Therefore, to achieve maximum thermal availability and minimize power losses, a demand-based distribution of the partial flow rates to the rotor shaft and stator is required. Conventional electric traction drives, equipped with an electrically driven oil pump, utilize the oil supplied by the positive displacement pump – usually in the form of a toothed ring or rotary valve – to achieve maximum thermal availability and minimize power losses.Gerotor pump – the supplied flow rate is generally used 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 at a controlled speed.

[0005] The cooling and lubrication of the transmission components is generally passive, relying on the pumping action of a differential spur gear or a

[0006] The 2024P00062WQ intermediate shaft spur gear is used in combination with a suitable housing that acts as an oil guide. This results in a limited pumping effect that depends on the vehicle speed and / or gear rotation speed, and consequently, hydrodynamic losses that are strongly dependent on rotational speed and oil temperature. When passively lubricating transmission components such as gears, rolling bearings, and radial shaft seals, churning losses occur.

[0007] WO 2021 / 005 186 A1 depicts a gearbox. In addition to the gearbox's gears, it features a multi-chamber system. This system is located adjacent to individual gears. It is situated next to a gear stage, in close proximity to that stage, to retain lubricant or gearbox oil near the gear stage. The reservoir formed by the multi-chamber system is located near at least one gear stage. During gearbox operation, the system stores a certain amount of lubricant and releases it back into circulation after a period of time. The rotation of the gears can be used to separate the lubricant using centrifugal force. At least some of the separated lubricant enters the multi-chamber system, specifically a first receiving chamber, which may be a reservoir chamber.

[0008] A recirculation path leads from chamber to chamber.

[0009] From JP 2009-250 415 A, a cooling mechanism is known that is capable of increasing the amount of coolant 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 force transmitted via the rotating element, which draws the coolant into and discharges it into a coolant reservoir; and the parts to be cooled, to which the coolant delivered by the pump is supplied.

[0010] 2024P00062WO coolant supplied, comprises a tank which forms a passage for supplying the coolant moved upwards by the rotation of the rotating element to the parts to be cooled, a passage for supplying the coolant delivered by the pump and the coolant moved upwards by the rotating element to the parts to be cooled and retains the coolant once.

[0011] The problem is that in an eDrive system, during longitudinal and lateral tilting as well as during longitudinal and lateral accelerations, oil from the tank often cannot be distributed in the gearbox.

[0012] The object of the invention is to create an oil reservoir for a combined active and passive cooling lubricant circuit for an electric traction drive, thereby optimizing the filling behavior of the oil reservoir regardless of the tilt of the vehicle and simultaneously ensuring a fail-safe lubrication system.

[0013] Description of the invention

[0014] The problem is solved with an electric traction system comprising an electric machine and a gearbox and a common coolant circuit, wherein an oil sump and at least one oil reservoir are installed and the oil reservoir can be filled both by an electric oil pump and via splash oil through components of the gearbox, wherein the oil reservoir acts as an elevated tank and the at least one outlet of the oil reservoir is connected to cooling / lubricating oil points, wherein the oil reservoir is a component of at least two parts, the outer contour of which at the bottom adapts to the outer contours of gears of the traction system and whose outer contour at the top follows the course of the housing of the electric traction system.

[0015] 2024P00062WQ The combination of active dry sump lubrication with full-fledged passive spray lubrication, in conjunction with a suitable operating strategy for 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 lubrication circuit is automatically activated when the electric oil pump is inactive, and enables the implementation of new functions, e.g., active preconditioning / postcooling at standstill.

[0016] The oil reservoir has a tank inlet from the differential gear, which extends into the oil reservoir up to an overflow edge at the inlet.

[0017] The overflow edge at the inlet extends to a horizontal position corresponding to the center point of a rotor shaft gear.

[0018] This provides a cost-effective solution to ensure that oil is delivered to the lubrication-relevant transmission components during inclines and accelerations.

[0019] The oil reservoir has a tank outlet to the overflow, which extends from an overflow edge at the outlet to the outer contour of the oil reservoir and leads into a tank outlet to the gearbox sump.

[0020] The oil reservoir has oil lines to the side shaft bearing and seal and differential, as well as an outlet to a bearing.

[0021] The oil pump is directly connected to pressurized cooling / lubricating oil points, with the other cooling / lubricating oil points either also subjected to the pressure of the oil pump or to the geodetic pressure of the oil reservoir.

[0022] A single valve is fitted at one inlet of the oil reservoir.

[0023] The valve is designed as a 2 / 2-way valve and is a hydraulic changeover valve with a valve ball as a sealing element or a flap valve.

[0024] 2024P00062WQ The problem is also solved by a method for operating an electric traction system with an electric machine and a gearbox and with a common cooling lubricant circuit, wherein in operating conditions where 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-lubricating circuit is automatically activated in operating conditions where active operation of the electric oil pump is not required or not absolutely necessary for thermal reasons, as well as in the event of failure of the electric oil pump.

[0025] The method for operating an electric traction system is designed in such a way that there is oil in the oil reservoir for passive cooling and lubrication even at inclination angles of up to + / - 45 degrees.

[0026] Description of the characters

[0027] Figure 1 shows a schematic representation of a combined active and passive cooling lubricant circuit for an electric traction drive,

[0028] Figure 2 shows a schematic representation of an electric drive system,

[0029] Figure 3 shows a schematic representation of a modified oil reservoir,

[0030] Figures 4 and 5 show a schematic representation of the first part of the oil reservoir according to the invention.

[0031] Figures 6 and 7 show a schematic representation of the second part of the oil reservoir according to the invention.

[0032] Figures 8 and 9 show cross-sectional views through the oil reservoir at different vehicle angles.

[0033] 2024P00062WQ According to Figure 2, a traction drive 40 with an electric machine is assumed, of which only a rotor shaft gear 14 is shown in the cross-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 geodesically located above all axes of rotation of the aforementioned shafts. The housings are located in or form a housing 41 of the traction drive 40.

[0034] Figure 2 shows a schematic representation of the drive with an exemplary oil reservoir 2, which is divided into several chambers 20a, 20b, and 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 to the maximum fill level hmax in all three chambers 20a, 20b, and 20c, which have different heights h1, h2, and h3. The chambers are separated from each other by partitions, thus allowing the fill levels in the different chambers 20a, 20b, and 20c to vary.

[0035] Figure 1 shows a cooling lubricant circuit which, via an electrically driven oil pump 19, carries cooling oil towards active cooling / lubricating oil points 7'.

[0036] A connection parallel to the active cooling / lubricating oil points 7' is connected to a valve 5 which is located at the inlet of an oil reservoir 2 near the upper boundary of the oil reservoir.

[0037] Sprayed oil 11 is sprayed by the rotating gears of a transmission with differential in the direction of the circular arrow and collected by an oil guide 10 and an oil collection 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 cooling / lubricating oil to passive cooling / lubricating oil points 7.

[0038] 2024P00062WQ Oil reservoir 2 has a geodetic height hmax.

[0039] The oil reservoir 2, located in the gearbox at the appropriate position, acts as a pressure tank or as an elevated tank, depending on the operating state of the electrically operated oil pump.

[0040] Depending on the vehicle's operating mode, the most efficient state for the current operating mode can always be selected by means of a corresponding operating strategy of the electric oil pump.

[0041] When oil pump 19 is active, oil reservoir 2 is actively filled via the entire delivery volume flow, or via a partial volume flow, which is provided, for example, by hydraulic resistance control using orifices from the electrically driven oil pump 19. In this operating state, the pressure-side oil lines, consisting of oil bores, rotor lance, etc., and oil reservoir 2 are completely filled with oil, which automatically lowers the oil level in oil sump 8 and consequently prevents unnecessary splashing of the gears.

[0042] 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 conveying gears, the differential spur gear 12 and the intermediate shaft spur gear 13, by means of splashed oil 11. The pressure-side lines, such as oil bores, rotor lance, etc., run dry in this operating state (p=0), which automatically results in an increase in the oil level in the oil sump 8. Consequently, the passive conveying effect is achieved by the differential spur gear 12 immersing itself in the oil sump 8. The pressure p provided at the outlet of the oil reservoir 2 is composed of density * acceleration due to gravity * height h and is a geodetic pressure. A geodetic pressure describes the pressure at the lower end of the fluid column, which is caused by the fluid's own weight.

[0043] 2024P00062WQ A change between active operation with dry sump or pressure circulation lubrication and passive operation with splash lubrication can be carried out automatically, for example, 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 are closed or opened.

[0044] In operating conditions where active cooling of the electric motor is advantageous or required for thermal reasons, the active cooling and lubrication circuit is maintained via the electrically driven oil pump. A low pre-charge pressure is established in oil reservoir 2, depending on the oil pump speed and the oil temperature. This offers advantages in supplying the transmission components with oil as needed during longitudinal and lateral acceleration, particularly during sporty and dynamic vehicle operation, as well as at varying vehicle inclinations. Additionally, the oil pump speed control allows the delivery volume flow to be regulated, thereby delivering a higher oil flow to the individual components during operating points with increased cooling and lubrication demands.In addition, in this operating state, any heat exchanger present in the system's supply line is flowed through by the entire coolant flow, and the pressure tank is filled with cooled oil.

[0045] The passive cooling / lubrication circuit is automatically activated in operating conditions where active operation of the electric oil pump is not required or not absolutely necessary for thermal reasons, as well as in the event of failure of the electric oil pump.

[0046] 2024P00062WQ An embodiment according to the invention uses a special form 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.

[0047] Figure 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 Figure 3, an opening 33 is provided for the passive filling of the oil reservoir 2. Here, the spray oil enters the oil reservoir 2, which is directly connected to the housing 41 of the traction drive.

[0048] Figures 4 and 5 show the oil reservoir 2 in detail with a first part of tank 100 and a connected second part of tank 200 according to Figures 6 and 7.

[0049] 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 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 point 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 wall extends into the interior of the component and is bent inwards in a tight U-shape.

[0050] Furthermore, the oil reservoir has a tank oil inlet 104, which may be supplied with oil by an oil pump. On the outer surface 115 of the first part of the tank 100 is an oil scraper edge 114, which

[0051] 2024P00062WQ slows down the flung-off oil from the tank oil inlet 104 and directs it into the interior of the oil reservoir.

[0052] On the outlet side, the first part of tank 100 has a tank outlet 113 leading to the transmission sump 8. Also on the outlet side, there is an overflow edge 103. This extends into the interior of oil reservoir 2 and forms a tank outlet 112 for overflow.

[0053] The oil scraper edge 114 prevents the oil entering via the tank oil inlet 104 from immediately escaping through the overflow.

[0054] From 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 side shaft bearing and to the seal.

[0055] The two oil lines under 107 and 108 are fed by an oil collection tray 109, which has an oil drain 110.

[0056] Figures 6 and 7 show the second part of tank 200, which together with the first part of tank 100 forms a closed shape.

[0057] The overhanging 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.

[0058] Figure 8 shows a first tilting state. By extending the overflow edge 105 of the inlet of the tank inlet 106, oil can be supplied to the lubrication-relevant transmission components even at transmission tilts of α < 45°. The oil level adjusts itself so 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 via the differential gear or the oil pump 19.

[0059] Figure 9 (2024P00062WQ) shows a second tilting condition. By horizontally extending the edge 103 of the overflow, oil can be supplied to the lubrication-relevant transmission components even at transmission tilts of α < 45°. The oil level adjusts itself so 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 sump either via the differential gear or an oil pump.

[0060] 2024P00062WQ Reference number

[0061] 1 Cooling lubricant circuit

[0062] 2 oil reservoirs

[0063] 2' pressure tank

[0064] 2" high tank

[0065] 3 Pressure line from oil pump

[0066] 4 Oil collection channel

[0067] 5 valve

[0068] 6 Outlet

[0069] 7 cooling / lubricating oil points

[0070] 8 Oil sump

[0071] 9 gear

[0072] 10 Oil piping system

[0073] 11 Spray oil

[0074] 12 Differential spur gear

[0075] 13 Intermediate shaft gear

[0076] 14 Rotor shaft gear

[0077] 15 Differential housing spur gear

[0078] 16 Housing Intermediate shaft gear

[0079] 19 Oil pump

[0080] 20a, 20b, 20c chambers

[0081] 33 Opening for passive filling

[0082] 40 electric traction system

[0083] 41 cases

[0084] 100 first part of the tank

[0085] 2024P00062WO 200 second part of the tank

[0086] 103 Overflow edge at the outlet

[0087] 104 Tank oil inlet

[0088] 105 Overflow edge at the inlet

[0089] 106 Tank inlet from the differential gear

[0090] 107 Oil line to differential

[0091] 108 Oil line to side shaft bearing and seal

[0092] 109 Drip tray

[0093] 110 Outlet drip tray

[0094] 111 Outlet to the warehouse

[0095] 112 Tank outlet to overflow

[0096] 113 Tank outlet to gearbox sump

[0097] 114 Oil rebound area / oil scraper edge

[0098] 115 Outer contour top

[0099] 116 Outer contour below

[0100] 2024P00062WO

Claims

Claims 1. Electric traction system (40) comprising an electric machine and a gearbox and a common coolant 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 by an electric oil pump (19) and by spray oil through components of the gearbox, wherein the oil reservoir (2) acts as an elevated 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 a tank comprising at least two parts, with a first part of the tank (100) and a second part of the tank (200), the outer contour at the bottom (116) of which adapts to the outer contours of gears of the traction system (40) and the outer contour at the top (115) of which follows the contour of the housing (41) of the electric traction system (40).

2. Electric traction system (40) according to claim 1, characterized in that 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 the inlet (105).

3. Electric traction system (40) according to claim 2, characterized in that the overflow edge at the inlet (105) extends to a horizontal position corresponding to the center point of a rotor shaft gear (14).

4. Electric traction system (40) according to one of the preceding claims, characterized in that the oil reservoir (2) has a tank outlet to the overflow (112) which extends from an overflow edge at the outlet (103) to the outer contour of the oil reservoir (2) and opens into a tank outlet to the transmission sump (113). 2024P00062WQ 5. Electric traction system (40) according to one of the preceding claims, characterized in that the oil reservoir (2) has oil lines (107, 108) to the side shaft bearing and seal and differential, and at least one outlet to a bearing (111).

6. Electric traction system (40) according to one of the preceding claims, characterized in 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.

7. Electric traction system (40) according to one of the preceding claims, characterized in that a single valve (5, 5a) is fitted at an inlet of the oil reservoir (2).

8. Electric traction system (40) according to claim 7, characterized in that the valve (5, 5a) is designed as a 2 / 2-way valve and is a hydraulic changeover valve with a valve ball as a sealing element or a flap valve (5a).

9. Method for operating an electric traction system (40) with an electric machine and a gearbox and with a common cooling lubricant circuit (1) according to any one of claims 1 to 8, wherein in operating conditions 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 / lubricating circuit is automatically activated in operating conditions in which active operation of the electric oil pump (19) is not required or not absolutely necessary for thermal reasons, as well as in the event of failure of the electric oil pump (19). 2024P00062WQ 10. Method for operating an electric traction system (40) according to claim 9, wherein the oil reservoir (2) also contains oil for passive cooling and lubrication at inclination angles of up to + / -45°. 2024P00062WO

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