Electric traction drive and method for operating traction drive

Abstract

The invention relates to an electric traction system (40) having an electric machine and a transmission and a common cooling lubricant circuit (1), in which an oil sump (8) and at least one oil reservoir (2) are mounted, and the oil reservoir (2) can be filled both by means of an electric oil pump (19) and by means of injection oil through components of the transmission, wherein the oil reservoir acts as a pressure tank (2 ') or a high-level tank (2' '), and wherein the oil pump (19) is directly connected to the cooling / lubricating oil point (7') under pressure (p1), and at least one outlet (6) of the oil reservoir (2) is connected to a further cooling / lubricating oil point (7), and wherein the further cooling / lubricating oil point (7) is either likewise acted upon by the pressure (p1) of the oil pump (19), or loading with the geographical location pressure (pg) of the storage. The invention also relates to a method for operating an electric traction system.

Description

Technical Field

[0001] The invention relates to an electric traction drive having an active and a passive cooling / lubricant circuit.

[0002] The invention also relates to a method for operating a traction drive. Background Art

[0003] Oil-cooled electric motors are partially or completely used in high-power electric drives with high energy density. In this case, the rotor shaft and / or stator of the electric motor are cooled by means of oil. In completely oil-cooled electric motors, the cooling oil demand of the rotor shaft and stator varies - depending on the respective operating point - especially due to the copper, iron and electromagnetic losses occurring in the machine. Therefore, in order to achieve the highest thermal availability and minimize power loss, it is necessary to distribute part of the volume flow to the rotor shaft and stator as required. Conventional electric traction drives equipped with an electrically operated oil pump use the delivery volume flow provided by a positive displacement pump - usually in the embodiment as a gear ring pump or a cycloidal rotor pump - usually only for cooling temperature-sensitive active components such as the stator and / or rotor of the electric drive machine as required. For this purpose, the electrically operated oil pump is switched on and off as required and / or operated in a speed-regulated manner.

[0004] Known solutions use passive, pressure- or temperature-controlled valves, as described in DE 10 2017 101 826 A1. The use of active, electrically actuable switching valves or proportional valves is also possible, but is usually avoided for cost reasons.

[0005] The cooling and lubrication of transmission components usually takes place passively, wherein for this purpose the conveying effect of the differential spur gears or the intermediate shaft spur gears is used in combination with a suitable housing that acts as an oil guide. This is associated with a limited conveying effect that is dependent on the vehicle speed or the gear speed and the fluid dynamic losses that are associated therewith, which are highly dependent on the speed and the oil temperature. When passively lubricating transmission components such as gears, rolling bearings, radial shaft sealing rings, churning losses occur.

[0006] WO 2021 / 005 186A1 shows a transmission. In addition to the gears of the transmission, the transmission also has a multi-chamber system. The multi-chamber system is adjacent to the individual gears of the transmission. The multi-chamber system is positioned next to the gear stage directly adjacent to the gear stage in order to maintain lubricant or transmission oil adjacent to the transmission stage. The reservoir formed by the multi-chamber system is locally located near at least one transmission stage. The multi-chamber system stores a certain amount of lubricant during the operation of the transmission and only returns the amount to the (re)circulation after a period of time. The rotation of the gears can be used to separate the lubricant using centrifugal force. The separated lubricant at least partially enters the multi-chamber system, into the first receiving chamber, which is, for example, a storage chamber.

[0007] The recirculation path leads from chamber to chamber. However, there is no active lubrication of the powertrain or transmission via the oil pump.

[0008] A cooling mechanism capable of increasing the amount of cooling liquid delivered to a component to be cooled when the rotation speed of a rotating element is low is known from JP 2009-250 415 A. The cooling mechanism comprises: a pump that is driven by a force transmitted via the rotating element and discharges and sucks cooling liquid into a cooling liquid bag; and a component to be cooled to which the cooling liquid discharged from the pump is delivered, the cooling mechanism comprising a tank that forms a passage for delivering the cooling liquid moved upward by the rotation of the rotating element to the component to be cooled, provides a passage for delivering the cooling liquid discharged from the pump and the cooling liquid moved upward by the rotating element to the component to be cooled, and retains the primary cooling liquid.

[0009] US2020 / 0 271 194A1 describes a vehicle drive device comprising: a rotating electric machine; a force transmission mechanism that transmits a rotational driving force between the rotating electric machine and a plurality of wheels; a housing that accommodates the force transmission mechanism and at least a portion of the rotating electric machine; and a hydraulic pump.

[0010] In DE 10 2022 202 272 A1, a transmission device includes: a motor; a transmission having a plurality of gears; a first shaft; and a bearing that supports the first shaft and transmits power of the motor; a housing that accommodates the transmission and holds the bearing at the inner side; oil collected in a lower region in the interior of the housing; a collecting container that is disposed in the interior of the housing and is open upward; an oil passage through which oil flows; and an oil pump disposed in the oil passage. The oil passage has a first path that connects the oil pump and the collecting container and a lifting path for lifting oil by rotation of the gears so as to guide the lifted oil to the collecting container. The collecting container has an inflow section for supplying oil to the transmission or the bearing. Summary of the invention

[0011] The object of the present invention is to realize a combined active and passive cooling lubricant circuit for an electric traction drive and a corresponding method for operating an oil pump, by means of which the efficiency and / or thermal availability of the electric traction drive is optimized as a function of the vehicle operating mode and a fail-safe lubrication system is simultaneously ensured.

[0012] The object is achieved by means of an electric traction system, which has an electric motor and a transmission and a common cooling lubricant circuit, in which an oil sump and at least one oil reservoir are installed, and the oil reservoir can be filled not only by means of an electric oil pump but also by injection oil through components of the transmission, wherein the oil reservoir acts as a pressure oil tank or a high-level oil tank, and wherein the oil pump is directly connected to a cooling / lubricating oil point under pressure, and at least one outlet of the oil reservoir is connected to a further cooling / lubricating oil point, wherein the further cooling / lubricating oil point is either also loaded with the pressure of the oil pump or with the geographical position pressure of the oil reservoir ( Druck) loaded.

[0013] In active pump operation, the combination of active and passive transmission lubrication can achieve a reduction in churning losses in the transmission and an increase in the thermal availability of the system in conjunction with an operating strategy optimized with regard to efficiency and / or thermal availability.

[0014] In an advantageous embodiment, the oil reservoir is formed from individual chambers which are separated from one another by partition walls of different heights.

[0015] Advantageously, the oil reservoir can be filled by an oil pump via a single valve.

[0016] The valve can be designed as a 2 / 2-way valve and can be a hydraulic switching valve or a flap valve with a valve ball as a sealing element.

[0017] As a result, a cost-effective implementation is possible since, apart from the simple flap valve, no additional components are required.

[0018] A simple construction is possible in that the flap valve is accommodated in an oil reservoir, wherein the oil reservoir is formed from two housing parts which are connected to one another and serve as bearing elements for a bearing pin of a valve flap of the flap valve.

[0019] In a simple construction, the valve flap with the bearing pin is a one-piece component having a sealing surface and a connection to the bearing pin via a taper.

[0020] The object is also achieved by means of a method for operating an electric traction system having an electric motor and a transmission and a common cooling-lubricant circuit, wherein, in operating states in which active cooling of the electric motor is advantageous or required for thermal reasons, the active cooling-lubricant circuit is maintained via an electrically driven oil pump, whereas in operating states in which active operation of the electric oil pump is not required or is not absolutely necessary for thermal reasons and in the event of a failure of the electric oil pump, a passive cooling / lubrication circuit is automatically activated.

[0021] The method is carried out in such a way that a low preload pressure is established in the oil reservoir as a function of the oil pump rotational speed and the oil temperature.

[0022] Depending on the current driving state, the oil pump operation strategy is used to select between actively providing the transmission cooling lubricating oil flow or passively providing the transmission cooling lubricating oil flow. In addition, when the oil pump is not working, the fail-safety of the transmission lubrication is ensured by automatically activating the passive cooling lubrication circuit.

[0023] The combination of active dry sump lubrication with complete passive oil injection lubrication in conjunction with a suitable operating strategy for the electric oil pump leads to increased energy efficiency at the overall system level, increased 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 not operating, and the combination enables new functions, such as active pre-conditioning / secondary cooling when stationary. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a combined active and passive cooling lubricant circuit for an electric traction drive according to the invention is shown,

[0025] Figure 2 Show according to Figure 1 Schematic diagram of the cooling and lubrication circuit with the oil pump working.

[0026] Figure 3 Show according to Figure 1 Schematic diagram of the cooling and lubrication circuit when the oil pump is not working.

[0027] Figure 4 A schematic diagram of a cooling lubrication circuit according to the invention with a multi-chamber fluid reservoir having an integrated flap valve is shown in a first operating state.

[0028] Figure 5 A schematic diagram of a cooling lubrication circuit according to the invention with a multi-chamber fluid reservoir with an integrated flap valve is shown in a second operating state.

[0029] Figure 6Show according to Figure 5 A cross-sectional view of a multi-chamber fluid reservoir,

[0030] Figure 7 Show according to Figures 4 to 6 A cross-sectional view of an exemplary embodiment of a fluid reservoir with an integrated valve,

[0031] Figure 8 A flow chart showing, by way of example, a possible operating strategy for operating a cooling lubricant circuit according to the invention,

[0032] Figures 9 to 15 An embodiment of a cooling lubrication circuit using a flap valve is shown. DETAILED DESCRIPTION

[0033] according to Figure 5 The starting point is a drive device with an electric motor, from which a rotor shaft gear 14 is shown in a sectional view. Other parts of the electric motor, 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. These two housings are connected to an oil pan 8 and an oil reservoir 2, which are located above the geographical position of all the rotation axes of the shafts mentioned above.

[0034] Figure 1 A cooling lubricant circuit is shown which conducts cooling oil via an electrically driven oil pump 19 to an active cooling / lubricating oil point 7 ′.

[0035] The connection parallel to the active cooling / lubricating oil point 7 ′ is connected to a valve 5 which is arranged at the inlet of the oil reservoir 2 close to the upper boundary of the oil reservoir.

[0036] The injection oil 11 is injected in the direction of the circular arrow through the rotating gear of the transmission with differential, and is collected by the oil guide device 10 and the oil collecting groove 4 and guided into the oil reservoir 2. At least one outlet 6 is located on the bottom side of the oil reservoir 2, which outlet is charged with cooling / lubricating oil to the passive cooling / lubricating oil point 7.

[0037] Oil storage 2 has a geographical location height hmax.

[0038] The oil reservoir 2 arranged at a corresponding position in the transmission acts—depending on the operating state of the electrically operated oil pump—as a pressure oil tank 2 ′ or as a header tank 2 ″.

[0039] Figure 2 Show according to Figure 1Schematic diagram of a cooling and lubrication circuit of the embodiment of the invention with the oil pump 19 in operation. The reservoir 2 as a pressure oil tank 2' is filled with cooling / lubricating oil via a valve 5. Subsequently, the pressure p1 generated by the oil pump is provided to the cooling / lubricating oil point 7 at the outlet 6. Active filling with a low preload pressure, for example of the order of 20 mBar, allows cooling / lubrication even when there is no injection oil.

[0040] Figure 3 Show according to Figure 1 Schematic diagram of the cooling lubrication circuit of FIG. 1 when the oil pump 19 is not working, but the transmission device that moves the injection oil 11 toward the reservoir is working. Passive, pressure-free filling is carried out here.

[0041] Depending on the vehicle operating mode, the state that is most effective for the current operating mode can always be selected by a corresponding operating strategy of the electric oil pump.

[0042] If the oil pump 19 is operating, 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 by means of a baffle by the electrically driven oil pump 19. In this operating state, the pressure-side oil lines formed by oil holes, rotor nozzles, etc. and the oil reservoir 2 are completely filled with oil, whereby a lowering of the oil sump level in the oil sump 8 is automatically achieved, thereby preventing unnecessary stirring of the gears.

[0043] If the oil pump 19 is not working, the oil reservoir 2 is filled passively by the ejected injection oil 11 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. In this operating state, the pressure-side lines such as oil holes, rotor nozzles, etc. run empty (p=0), which automatically increases the oil sump level in the oil sump 8, so that a passive delivery effect is achieved by sinking the differential spur gear 12 into the oil sump. The pressure p provided at the outlet of the oil reservoir is composed of density*gravitational acceleration*height h and is the geodetic pressure. The geodetic pressure describes the pressure at the lower end of the fluid column, which is generated by the dead weight of the fluid.

[0044] The switch between active operation with dry sump or pressure circulation lubrication and passive operation with oil injection lubrication is automatically carried out by means of a flap valve 5a which is integrated in the oil reservoir 2 and is designed as a 2 / 2-way valve. Depending on the operating state of the electric oil pump 19, the connection from the pressure line of the oil pump 19 to the oil reservoir 2 and the connection from the inlet opening of the oil reservoir 2 to the oil reservoir 2 are closed or released.

[0045] Figure 4The schematic diagram of a cooling lubrication circuit 1 according to the invention is shown, which has an oil reservoir 2 divided into a plurality of chambers 20a, 20b, 20c. The flap valve 5a integrated in the oil reservoir is in a first operating state and allows the reservoir to be filled up to a maximum filling height h1, h2 and h3 in all three chambers 20a, 20b and 20c having different structural heights h1, h2 and h3. max The chambers are separated from one another by partition walls.

[0046] Figure 5 The schematic diagram shows the cooling lubrication circuit 1 according to the invention in a second operating state, in which the fluid levels in the different chambers 20 a , 20 b and 20 c each have different heights.

[0047] Figure 6 Show according to Figure 5 Sectional view of the chamber of the oil reservoir 2 along the line AA. The small location height h1 is used for lubrication of the differential.

[0048] Figure 7 Show Figure 5 The oil level shows a height h3 and serves for cooling / lubricating the rotor shaft 14 .

[0049] By implementing the oil reservoir 2 as a multi-chamber system, when the electric oil pump 19 is not working or fails, cooling / lubricating oil can be supplied to critical cooling / lubricating points in the transmission in a targeted manner, dependent on / independent of the vehicle speed or the wheel set speed level. For this purpose, an associated chamber 20a, 20b, 20c is provided in the oil reservoir 2 for each component to be supplied with cooling lubricant or for a group of components to be supplied with cooling lubricant. In addition to the geographical height of the chamber inflow area, the chamber volume and the geographical height h1, h2, h3 and the cross section of the outlet opening 6 are used as structural parameters for coordinating the partial volume flow of the components to be supplied with cooling lubricant.

[0050] Figure 8 By way of example, a flow chart of a possible operating strategy for operating a cooling lubricant circuit according to the invention is shown.

[0051] Step S1 starts with the presence of an electric traction system 40. In step S2, it is queried whether active cooling of the electric machine is required. In step S3, it is queried whether cooling of the transmission is required. In step S4, it is queried whether lubrication of the transmission is required.

[0052] If one of the queries of steps S2, S3 and S4 is answered with "yes", the pumping speed of the electric oil pump 19 is calculated in step S6. In step S7, the electric oil pump 19 is activated and switched on at the required rotational speed n>0 rpm. As a result, active cooling and lubrication of the transmission and the electric motor are activated in S8.

[0053] If the queries of steps S2, S3 and S4 have a negative result, it is determined in step S5 whether the vehicle speed is sufficient to provide a sufficient passive oil flow. To this end, it is queried whether v 车辆 ≥v 极限 , that is, whether the vehicle speed is greater than the limit speed.

[0054] If the query is positive, the electric oil pump 19 is deactivated in step S9 and the result of step S10 is passive cooling and lubrication of the transmission and the electric machine.

[0055] In operating states in which active cooling of the electric machine is advantageous or required for thermal reasons, an active cooling lubrication circuit is maintained via an electrically operated oil pump. Depending on the oil pump speed and the oil temperature, a low preload pressure occurs in the oil reservoir 2. This leads to advantages in the case of longitudinal and transverse acceleration, in particular in the dynamic operation of the vehicle and in the case of different inclinations of the vehicle, when the transmission components are supplied with oil in a demand-oriented manner. In addition, the delivery volume flow can be controlled via the speed regulation of the oil pump, and thus a higher oil volume flow can be delivered to the individual consumers at operating points with increased requirements for the cooling / lubricating oil demand. In addition, in this operating state, a heat exchanger that may be present on the system side is flowed through in advance by the entire cooling lubricant flow, and the pressure oil tank is filled with cooled oil.

[0056] In operating states in which active operation of the electric oil pump is not necessary or absolutely necessary for thermal reasons, and in the event of failure of the electric oil pump, the passive cooling / lubrication circuit is automatically activated. The heat exchanger present on the system side is not flowed through.

[0057] An embodiment without valves is also optionally possible. In active pump operation, the fluid reservoir is filled via the oil pump, but is not actively preloaded.

[0058] Different valve embodiments are possible. For example, the valve can also be embodied as a simple hydraulic switching valve with a (plastic) valve ball as a sealing element.

[0059] One specific implementation uses Figures 9 to 15 The valve 5 a and the specific shape of the oil reservoir 2 are shown in FIG.

[0060] Fig. 9The oil reservoir 2 with the flap valve is shown in the installed position above the differential spur gear 12 and the countershaft gear 13. Fig. 9 An opening 33 for passively filling the oil reservoir 2 is provided on the left side of the . Here, the injection oil enters the oil reservoir 2.

[0061] exist Fig.10 , the oil reservoir 2 is shown in detail, which has a first housing half 22 and a second housing half 23 connected to the first housing half. A sleeve 24 is arranged on the housing half, which surrounds the fastening screw 25. An opening 30 for active filling by means of an oil pump 19 is arranged in the middle area. Different outlet openings 32', 32" and 32'" perform different lubrication and cooling tasks.

[0062] exist Fig.12 It can be seen in Fig.11 AA in FIG. In addition to the sleeve 24 with the fastening screw 25, the valve flap 26 with its sealing surface 27 can be seen. The valve flap 26 is mounted on a bearing pin 28, which rotates about the rotation axis 29 of the valve flap 26. The flap valve is a float valve and closes as the oil level in the oil reservoir 2 rises.

[0063] Fig.15 The valve flap 26 is shown in detail. The valve flap 26 is seated on a bearing pin 28 connected via a tapered section 34 and extending outwards on both sides of the tapered section. The component is designed in one piece.

[0064] Reference numerals list

[0065] 1 Cooling lubricant circuit

[0066] 2 Oil reservoir

[0067] 2' Pressure Oil Tank

[0068] 2” high level fuel tank

[0069] 3 Oil pump pressure line

[0070] 4 Oil collecting groove

[0071] 5 valves

[0072] 6 Exit

[0073] 7 Cooling / lubricating oil area

[0074] 8 Oil sump

[0075] 9 Gear

[0076] 10 Oil guide device

[0077] 11. Injection oil

[0078] 12 Differential spur gear

[0079] 13 Intermediate shaft gear

[0080] 14 Rotor shaft gear

[0081] 15 Differential spur gear housing

[0082] 16 Intermediate shaft gear housing

[0083] 17 Oil reservoir for intermediate gear

[0084] 18 Oil reservoir for rotor shaft gear

[0085] 19 Oil pump

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

[0087] 22 First housing half

[0088] 23 Second shell half

[0089] 24 Sleeve

[0090] 25 Fastening bolts

[0091] 26 Valve

[0092] 27 Sealing surface

[0093] 28 Support pin

[0094] 29 Axis of rotation of valve

[0095] 30 Opening for active filling via oil pump

[0096] 31 Overflow channel

[0097] 32', 32", 32"' outlet opening

[0098] 34 Taper

[0099] 33 Opening for passive filling

[0100] 40 Electric traction system

Claims

1. An electric traction system (40) having an electric motor 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 not only by means of an electric oil pump (19) but also by injection oil through components of the transmission, wherein the oil reservoir acts as a pressure oil tank (2') or a high-level oil tank (2"), and wherein the oil pump (19) is directly connected to a cooling / lubricating oil point (7') under pressure (p1), and at least one outlet (6) of the oil reservoir (2) is connected to a further cooling / lubricating oil point (7), wherein the further cooling / lubricating oil point (7) is either also charged with the pressure (p1) of the oil pump (19) or with the local pressure (p1) of the oil reservoir. g )load.

2. The electric traction system (40) according to claim 1, characterized in that: The oil reservoir (2) is composed of chambers (20a, 20b, 20c) separated from each other by partition walls of different heights.

3. The electric traction system (40) according to claim 1 or 2, characterized in that: A single valve (5, 5a) is arranged at the inlet of the oil reservoir (2).

4. The electric traction system (40) according to claim 3, characterized in that: The valve (5, 5a) is designed as a 2 / 2-way valve and is a hydraulic switching valve or a flap valve (5a) having a valve ball as a sealing element.

5. The electric traction system (40) according to claim 4, characterized in that: The flap valve (5a) is installed in the oil reservoir, wherein the oil reservoir (2) is composed of two housing parts which are connected to one another and serve as bearing elements for a bearing pin of a valve flap (26) of the flap valve.

6. The electric traction system (40) according to claim 5, characterized in that The valve flap (26) with the bearing pin (28) is a one-piece component having a sealing surface (27) and a connection to the bearing pin (28) via a taper (34).

7. A method for operating an electric traction system (40) according to any one of claims 1 to 5, the electric traction system having an electric machine and a transmission and a common cooling lubricant circuit (1), wherein: In operating states in which active cooling of the electric motor is advantageous or required for thermal reasons, an active cooling-lubrication circuit is maintained via the electrically operated oil pump, whereas in operating states in which active operation of the electric oil pump is not required or is not absolutely necessary for thermal reasons, and in the event of a failure of the electric oil pump, a passive cooling / lubrication circuit is automatically activated.

8. The method for operating an electric traction system (40) according to claim 7, wherein a low preload pressure occurs in the oil reservoir (2) as a function of the oil pump speed and the oil temperature.

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