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

Abstract

Proposed is an electric traction system (40) that has an electric machine, 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 by means of an electric oil pump (19) and via oil spray from components of the transmission, and 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), characterized in that the oil reservoir (2) comprises two separate oil stores which are situated geodetically above all axes of rotation of the shafts of the electric traction system, wherein an oil chamber (117) and an oil sump (109) are provided.

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 an intermediate shaft spur gear in combination with a suitable, as

[0006] The 2024P00063WQ oil guide system utilizes an effective housing. This results in a limited delivery 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. During passive lubrication of 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 discharged by the pump is supplied, comprise a tank that has a passage to the

[0010] 2024P00063WO The supply of the coolant moved upwards by the rotation of the rotating element to the parts to be cooled forms 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] To adequately lubricate the differential, the oil level in the differential area must be raised, which leads to an increase in churning losses.

[0012] The amount of oil in the differential can be reduced to decrease hydrodynamic losses. However, this necessitates the use of additional oil lines for differential lubrication.

[0013] 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, whereby the lubrication of the differential via the oil reservoir is always ensured.

[0014] Description of the invention

[0015] 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 comprises two separate oil accumulators which are geodesically positioned above all axes of rotation of the shafts of the

[0016] 2024P00063WQ electric traction system, including an oil chamber and an oil collection tray.

[0017] The oil reservoir has a tank inlet from the differential gear and the oil collection tray has a tank inlet from the differential gear.

[0018] The tank inlet of the differential gear extends beyond a differential spur gear by a distance in the horizontal direction beyond the axis of rotation.

[0019] The tank inlet from the differential gear for the oil collection pan is located directly below the tank inlet for the oil chamber between the differential spur gear and an intermediate shaft gear.

[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] 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] 2024P00063WQ Description of the figures

[0026] Figure 1 shows a schematic representation of a combined active and passive cooling lubricant circuit for an electric traction drive,

[0027] Figure 2 shows a schematic representation of an electric drive system,

[0028] Figure 3 shows a schematic representation of a modified oil reservoir,

[0029] Figures 4 and 5 show a schematic representation of the first part of the oil reservoir according to the invention.

[0030] Figures 6 and 7 show a schematic representation of the second part of the oil reservoir according to the invention.

[0031] Figure 8 shows the installation situation of the oil reservoir.

[0032] Figure 2 shows a traction drive 40 with an electric machine, 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.

[0033] 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 in

[0034] In this example, the flap valve 5a integrated in oil reservoir 2 (part number 2024P00063WQ) is in its 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 fill levels of different heights in the different chambers 20a, 20b, and 20c.

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

[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 passive cooling / lubricating oil points 7 with cooling / lubricating oil.

[0038] 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] 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 e.g.

[0042] The hydraulic resistance control (2024P00063WQ) is provided by the electrically driven oil pump 19 via orifices. In this operating state, the pressure-side oil lines, consisting of oil bores, rotor lance, etc., and the oil reservoir 2 are completely filled with oil, which automatically lowers the oil level in the oil sump 8 and consequently prevents unnecessary splashing of the gears.

[0043] 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 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.

[0044] A change between active operation with dry sump or pressure circulation lubrication and passive operation with splash lubrication can be automatically effected, 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.

[0045] In operating conditions where active cooling of the electric motor is advantageous or required for thermal reasons, the active cooling lubrication circuit is operated via

[0046] The electrically driven oil pump (part number 2024P00063WQ) maintains a low pre-charge pressure in oil reservoir 2, depending on the oil pump speed and oil temperature. This offers advantages in supplying the transmission components with oil as needed during longitudinal and lateral acceleration, particularly in sporty, dynamic driving, and at varying vehicle inclinations. Additionally, the oil pump speed control allows for adjusting the flow rate, thereby delivering a higher oil flow to individual components during operating conditions with increased cooling / lubricating oil requirements. Furthermore, in this operating state, any heat exchanger present in the system's supply line is circulated by the entire coolant flow, and the pressure tank is filled with cooled oil.

[0047] 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.

[0048] One 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.

[0049] 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 sprayed oil enters the oil reservoir 2, which is directly connected to the housing 41 of the traction drive.

[0050] 2024P00063WQ In Figures 4 and 5, the oil reservoir 2 is shown in detail with a first part of tank 100 and a connected second part of tank 200 according to Figures 6 and 7.

[0051] The first part of the tank 100 has a first 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.

[0052] 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 slows down any oil flung off the tank oil inlet 104 and directs it into the interior of the oil reservoir.

[0053] 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.

[0054] The oil scraper edge 114 prevents the oil entering via the tank oil inlet 104 from immediately escaping through the overflow.

[0055] The first part of the tank 100 has a separate oil storage unit in the form of an oil collection tray 109, which is filled via a third tank inlet 106'.

[0056] 2024P00063WQ 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.

[0057] The two oil lines under 107 and 108 are fed by the oil collection tray 109, which has an oil drain 110.

[0058] Thus, the oil reservoir 2 forms two separate oil storage units: the larger volume in the oil chamber 117 and the smaller volume in the oil collection tray 109.

[0059] Figures 6 and 7 show the second part of tank 200, which together with the first part of tank 100 forms a closed shape and encloses the two oil reservoirs.

[0060] 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.

[0061] The oil reservoir 2 is filled either by the oil pump, which is fluidically connected to the tank inlet 104 via an oil line, or by the pumping action of the differential spur gear 12, which pumps oil into the tank by its own rotation.

[0062] The main flow of oil, which is flung off by the rotation of the differential spur gear 12, flows through the tank inlet channel 106 into the oil reservoir. The secondary flow of oil pumped by the differential spur gear 12 is collected through the tank inlet 106' of the oil collection pan 109 and directed towards the differential via the oil lines under 107 and 108.

[0063] The arrangement of the two tank inlets 106, 106' into the oil reservoir 2 is implemented such that a large proportion of the oil supplied by the differential spur gear 12,

[0064] 2024P00063WQ is collected. The main flow of oil supplied by the differential spur gear 12 is received by the tank inlet 106.

[0065] The tank inlet 106 of the main channel projects beyond the differential spur gear 12 by a distance d in the horizontal direction H beyond the axis of rotation D, as shown in Figure 8. The tank inlet 106' of the oil collection pan 109 lies directly below the main channel between the differential spur gear 12 and the intermediate shaft gear 13.

[0066] 2024P00063WQ Reference number

[0067] 1 Cooling lubricant circuit

[0068] 2 oil reservoirs

[0069] 2' pressure tank

[0070] 2" high tank

[0071] 3 Pressure line from oil pump

[0072] 4 Oil collection channel

[0073] 5 valve

[0074] 6 Outlet

[0075] 7 cooling / lubricating oil points

[0076] 8 Oil sump

[0077] 9 gear

[0078] 10 Oil piping system

[0079] 11 Spray oil

[0080] 12 Differential spur gear

[0081] 13 Intermediate shaft gear

[0082] 14 Rotor shaft gear

[0083] 15 Differential housing spur gear

[0084] 16 Housing Intermediate shaft gear

[0085] 19 Oil pump

[0086] 20a, 20b, 20c chambers

[0087] 33 Opening for passive filling

[0088] 40 electric traction system

[0089] 41 cases

[0090] 100 first part of the tank

[0091] 2024P00063WO 200 second part of the tank

[0092] 103 Overflow edge at the outlet

[0093] 104 Tank oil inlet

[0094] 105 Overflow edge at the inlet

[0095] 106 Tank inlet from the differential gear

[0096] 106' third tank inlet

[0097] 107 Oil line to differential

[0098] 108 Oil line to side shaft bearing and seal

[0099] 109 Drip tray

[0100] 110 Outlet drip tray

[0101] 111 Outlet to the warehouse

[0102] 112 Tank outlet to overflow

[0103] 113 Tank outlet to gearbox sump

[0104] 114 Oil rebound area / oil scraper edge

[0105] 115 Outer contour top

[0106] 116 Outer contour below

[0107] 117 Oil room

[0108] 2024P00063WO

Claims

Claims 1. Electric traction system (40) with an electric machine and a gearbox and with 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 means of splash 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) comprises two separate oil accumulators which are geodesically located above all axes of rotation of the shafts of the electric traction system, wherein an oil chamber (117) and an oil collection pan (109) are provided.

2. Electric traction system (40) according to claim 1 , characterized in that the oil reservoir (2) for the oil chamber (117) has a tank inlet from the differential gear (106) and for the oil collection tray (109) has a tank inlet from the differential gear (106').

3. Electric traction system (40) according to claim 2, characterized in that the tank inlet (106) of the differential gear projects beyond a differential spur gear (12) by a distance (d) in the horizontal direction (H) beyond the axis of rotation (D).

4. Electric traction system (40) according to claim 2 or 3, characterized in that the tank inlet (106') from the differential gear for the oil collection pan (109) is located directly below the tank inlet (106) for the oil space (117) between the differential spur gear (12) and an intermediate shaft gear (13).

5. Electric traction system (40) according to one of the preceding claims, characterized in that the oil reservoir (2) oil lines 2024P00063WQ (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). 2024P00063WQ

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