Oil pump for transmission of electric vehicle

Abstract

The invention relates to a transmission device of an electric vehicle. The transmission device is provided with an oil pan; an oil reservoir disposed in the oil pan, wherein a gear of the transmission is disposed above a level of the oil reservoir; the invention relates to an oil pump, which is mechanically driven by means of a transmission shaft, and is characterized in that the oil pump has a pump plunger guided in a pump housing, an eccentric wheel driven by the transmission shaft for generating a vertical movement between the pump housing and the pump plunger, and a non-return valve, and in that the suction end of the pump is mounted in an articulated manner in an oil pan.

Description

Background Art

[0001] To drive a motor vehicle, an electric motor is used to provide an alternative to an internal combustion engine that requires petroleum fuel.

[0002] The article "Hochintegrativ und Flexibel ElektrischeAntriebseinheit für E-Fahrzeuge" by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold in the journal ATZ, Volume 113, May 2011, pages 360 to 365, provides a clear description of such an electric drive device. In the article, a drive unit (electromechanical axle powertrain) for a vehicle axle is described, which drive unit includes an electric motor that is arranged concentrically and coaxially with a bevel gear differential, wherein a switchable two-speed planetary gear set is arranged in the power path between the electric motor and the bevel gear differential, and the two-speed planetary gear set is also positioned coaxially with the electric motor or the bevel gear differential. The drive unit is constructed very compactly and due to the switchable two-speed planetary gear set allows a good compromise between climbing ability, acceleration and energy consumption.

[0003] An alternative to the bevel gear differential is a spur gear differential.

[0004] Instead of the coaxial and concentric arrangement of the electric motor and the differential, an axially parallel arrangement is considered, wherein the motor shaft of the electric motor is axially parallel to the output shaft of the differential and is arranged spaced apart from the output shaft of the differential. In the example of the above coaxial and concentric arrangement, the motor shaft is flush with the output shaft of the differential, wherein the output shaft passes through the motor shaft.

[0005] In the example of the above article, the electromechanical axle powertrain can be implemented in two speeds with a switchable planetary gear train or, in a simpler manner, only have one gear (single-gear). The transmission (reduction transmission / reducer) downstream of the electric motor (E-Motor) in the power path reduces the common high output speed of the electric motor and increases the torque introduced into the differential.

[0006] In a commonly used transmission in an electric drive vehicle, such as in an electric axle, lubricated parts are supplied by means of an oil mist or by distributing oil through the teeth in the transmission. A reserve container can also be provided in the upper region of the transmission housing, and then the cooling oil and / or lubricating oil drips from the reserve container onto the lubricated parts. The cooling oil and / or lubricating oil is conveyed to the mentioned reserve container by means of the teeth and possibly a guide plate. This has the disadvantage that splash losses occur due to one or more gears of the transmission stage or differential constantly being immersed in the transmission oil, and these splash losses reduce efficiency. Due to splashing, oil foaming may also occur, so that in order to reliably supply oil, a higher oil quantity must be maintained in order to be able to reliably convey the oil.

[0007] A transmission with immersion lubrication is known from German Offenlegungsschrift DE 37 19 096 A1. In this transmission, the lower gears are in immersion lubrication, and thus the intermediate gears meshing with the lower gears are also supplied with oil.

[0008] German Offenlegungsschrift DE 10 2021 103 667 A1 relates to a transmission of an electrically operable powertrain of a motor vehicle, wherein the transmission has a first transmission section which is arranged in a first transmission space, wherein the first transmission section has a rotatably supported first gear and a rotatably supported second gear meshing with the first gear, and wherein the transmission space includes an oil sump filled with hydraulic fluid. The first gear engages into the oil sump such that the first gear transports the hydraulic fluid from the oil sump by rotation during the operation of the electrically operable powertrain and distributes it in the transmission space, wherein the first gear is partially surrounded in the circumferential direction, such as radially on both sides, by a separate first fluid guiding element which can be inserted into the transmission space, such that the first gear rotates partially in a channel-shaped section of the first fluid guiding element configured in such a way. The second gear is partially surrounded in the circumferential direction by a separate second fluid guiding element which can be inserted into the transmission space. Summary of the Invention

[0009] The object of the present invention is to avoid the mentioned disadvantages and to provide an improved supply to the parts to be cooled and / or lubricated in the transmission of an electric drive vehicle.

[0010] This object is achieved by means of a transmission of an electric vehicle having the features of claim 1 and having an oil pump mechanically driven by a transmission shaft, and an electric vehicle drive device having the features of claim 10.

[0011] The transmission of an electric vehicle has: an oil sump; an oil reserve arranged in the oil sump, wherein the gears of the transmission are arranged above the level of the oil reserve; an oil pump mechanically driven by a transmission shaft, characterized in that the oil pump has a pump plunger guided in a pump housing, an eccentric driven by the transmission shaft, and a check valve, the eccentric being used to generate an up-and-down movement between the pump housing and the pump plunger, and wherein the suction end of the pump is articulated and supported in the oil sump. Thus, the transmission is arranged "dry", in such a way that the transmission has an oil sump or an oil reserve space in the transmission housing. Thus, the gears of the differential or the gear stage do not run in the oil reserve. In this way, splash losses are excluded. For supplying the lubrication sites, a simple mechanical oil pump is provided, which is cost-effective and supplies oil to the lubrication sites and / or the cooling sites in a targeted manner. Here, the pump plunger denotes a tubular member that sinks into a tubular section of the pump housing (or vice versa), thus forming a common internal volume, and thus the pump plunger has an axial through-hole. Due to the eccentric connection of the pump housing to the drive shaft and the axially fixed but articulated connection of the suction end to the oil sump, during operation, i.e., when driving the pump, the internal volume changes. The resulting up-and-down movement of the pump housing causes a volume change and, in cooperation with the check valve, causes oil to be sucked from the oil sump and conveyed out of the pump through an oil passage. Such a pump is not only very cost-effective, but also very narrow in construction, i.e., it occupies a small structural space, so that it can be simply used in different types of transmissions without major adaptation. The efficiency of the transmission can be significantly increased in such a way that no splash losses occur. Since the oil does not foam, all lubrication sites and / or cooling sites are also reliably supplied with oil.

[0012] Advantageous embodiments are claimed in the dependent claims and are elaborated in detail below.

[0013] In an improvement of the present invention, the eccentric has an oil passage, and the shaft has an oil hole for leading away the conveyed oil from the pump. Such an oil hole can lead to an outflow opening from which the oil conveyed from the oil sump flows out.

[0014] Advantageously, the lubrication and / or cooling of the transmission is carried out directly by means of the oil flowing out of the outflow opening of the oil hole. In this way, a particularly simple and cost-effective feasibility of lubricating or cooling lubrication sites, such as meshing gears, directly with the oil dripping or flowing from above is achieved.

[0015] However, in an improved embodiment of the present invention, it is also feasible that, in order to lubricate and / or cool the transmission, oil is guided to the cooling or lubricating part by means of an oil pipeline arranged at the outflow opening of the oil hole. Thereby, it is feasible to more precisely convey the target to the cooling / lubricating part, and the cooling / lubricating part is not adjacent to the oil pump or the cooling / lubricating part is at a higher level than the outflow opening of the pump. Therefore, a pressure circulation lubrication can be shown.

[0016] Preferably, a control groove is provided between the eccentric wheel and the pump housing for closing the oil passage during the suction process. This ensures that during the suction process, a negative pressure is applied at the suction end of the pump in the oil sump, and it is not sucked from the transmission space or the pressure side.

[0017] Particularly advantageously, the suction end of the pump is formed by a check valve. In this way, a hinged but axially fixed connection to the oil sump can be achieved in a simple manner, such that the check valve has a profile at its end facing the oil sump, and the profile engages in a mating profile arranged at the oil sump in a pivotally hinged but fixed manner in the direction of the longitudinal axis of the pump plunger. The pump plunger can, for example, be pushed into the mating profile of the oil sump and then be held in place axially by the pump plunger. Alternatively, this connection can also be achieved by means of a snap connection.

[0018] It is also feasible that a plurality of oil pumps are provided. The plurality of oil pumps can be driven by the same or different transmission shafts. Therefore, the volume of oil that can be conveyed can be increased several times. In order to compensate for pressure pulsations, the eccentric wheels of the individual oil pumps can be arranged torsionally relative to each other such that multiple working strokes are carried out per revolution of the drive shaft. Description of the Drawings

[0019] The present invention will be described in detail below with the aid of the drawings. The drawings show:

[0020] Figure 1 A side view of a transmission of an electric vehicle, the transmission having an oil pump mechanically driven by a transmission shaft

[0021] Figure 2 Showing Figure 1 A 90° rotated view of the transmission in

[0022] Figures 3a to 3c A schematic cross-sectional view of the oil pump in multiple working stages. Detailed Description of the Embodiment

[0023] The drawings are only schematic and are only used to understand the present invention. The drawings are illustrative of the principle and are not suitable as a structural drawing. The same elements are provided with the same reference numerals.

[0024] In Figure 1 a part of the transmission 1 is schematically shown, wherein the transmission housing is not shown. Four gears 2, 3, 4, 5 are arranged such that the gears 2 and 3 and the gears 4 and 5 respectively form a transmission stage. The gears 3 and 4 are fastened to a common intermediate shaft 6. The gear 5 drives a differential 20, which in turn drives two drive wheels (not shown). Below the gears 2, 3, 4, 5 there is an oil sump 8, which is filled with oil (not shown) and is arranged such that the gear 5 does not dip into the oil sump. For conveying an oil volume for lubrication purposes and / or cooling purposes, a mechanically driven oil pump 9 is provided, which is driven by means of the intermediate shaft 6. It can be clearly seen that the oil pump 9 is very narrowly constructed and can also be inserted into other transmissions without great difficulty.

[0025] Figure 2 Shows Figure 1 a view of the transmission in rotated counterclockwise by 90°, i.e., the following view, in which the oil pump 9 is visible in front of the gears. As already mentioned, the drive of the oil pump 9 is achieved by means of the intermediate shaft 6, with an eccentric 7 interposed therebetween in order to generate an up-and-down movement between the pump housing 10 and the pump plunger 11. The end of the oil pump 9 that dips into the oil sump 8, i.e., the suction end, is formed by a check valve 13, which is pivotally but axially fixed in the oil sump 8.

[0026] By means of Figure 3a , Figure 3b and Figure 3c the mechanical oil pump 9 and its mode of operation are elaborated in detail. Figure 3a , Figure 3b and Figure 3c show the same oil pump 9 in different working positions or functional positions, and the drive of the oil pump is carried out in the clockwise direction.

[0027] First, it should be based on Figure 3aThe illustration shows the oil pump 9 in detail. As already mentioned, the oil pump 9 consists of a driven pump housing 10, which is composed of a cylindrical upper part and a pipe part connected to the upper part. The hollow space of the upper part is connected to the hollow space of the pipe part so that the oil to be transported can pass through. When driven by an eccentric wheel 7 driven by an intermediate shaft, the pump housing moves up and down, and the pump plunger 11 is axially movable and supported in the pump housing in a sealed manner relative to the surrounding environment. The pump plunger 11 is connected at its end facing the oil sump 8 to a check valve 13, which in turn is hingedly but axially fixed to its valve housing 14 in the oil sump 8. Thus, the up and down movement of the pump housing 10 results in an increase and decrease in the internal space formed by the tubular part of the pump housing and the hole 12 of the pump plunger 11. Therefore, a negative pressure is generated when the internal space increases, which is greater than the spring force of the spring 16 that presses the valve ball 15 tightly against the valve housing 14. Thus, the check valve 13 opens, and oil can be sucked from the oil sump 8 and transported into the pump housing 10. When the maximum stroke of the eccentric wheel 7 is reached, the suction phase ends and the pressure phase begins with a downward movement in which the internal space decreases. Here, due to the increased pressure and the spring force of the spring 16, the check valve 13 closes and the oil flows via the oil passage 18 and the oil hole 17 of the intermediate shaft 6 to the parts to be lubricated or cooled in the transmission 1. In addition, a control groove 19 is provided in the pump housing 10 such that the connection between the internal space of the pump housing 10 and the oil passage 18 is closed during the suction phase and released during the pressure phase.

[0028] In Figure 3b the end of the suction phase and the start of the pressure phase are shown, so the eccentric wheel reaches its highest position and the common internal space of the pump housing 10 and the pump plunger 11 reaches its maximum value. When the eccentric wheel 7 continues to rotate, the internal space decreases, the check valve 13 closes, and the connection between the oil passage 18 and the oil hole 17 is released by means of the control groove 19, so that the oil can flow out through the oil hole 17.

[0029] When the eccentric wheel 7 continues to rotate, the pressure phase stops with the discharge of oil until the Figure 3c lowest position shown in Figure 3a is reached. The connection between the control groove 19 and the oil passage 18 is closed again, and a new suction phase starts as the Figure 3a eccentric wheel 7 continues to rotate in the clockwise direction as shown in

[0030] List of reference numerals

[0031] 1 Transmission

[0032] 2 Gear

[0033] 3 Gear

[0034] 4 Gear

[0035] 5 Gear

[0036] 6 Intermediate Shaft

[0037] 7 Eccentric Wheel

[0038] 8 Oil Sump

[0039] 9 Oil Pump

[0040] 10 Pump Housing

[0041] 11 Pump Plunger

[0042] 12 Hole

[0043] 13 Check Valve

[0044] 14 Valve Housing

[0045] 15 Valve Ball

[0046] 16 Valve Spring

[0047] 17 Oil Hole

[0048] 18 Oil Passage

[0049] 19 Control Groove

[0050] 20 Differential

Claims

1. A transmission device (1) for an electric vehicle, the transmission device having: an oil sump (8); an oil reserve provided in the oil sump (8), wherein gears (2, 3, 4, 5) of the transmission device (1) are provided above the liquid level of the oil reserve; an oil pump (9) mechanically driven by a transmission shaft (6), characterized in that, The oil pump (9) has a pump plunger (11) guided in a pump housing (10), an eccentric (7) driven by the transmission shaft (6), and a check valve (13). The eccentric is used to generate an up-and-down movement between the pump housing (10) and the pump plunger (11), and the suction end of the pump (9) is pivotally supported in the oil sump (8).

2. The transmission device (1) for an electric vehicle according to claim 1, characterized in that, The eccentric (7) has an oil passage (18), and the shaft (6) has an oil hole (17) for leading away the oil delivered by the pump (9).

3. The transmission device (1) for an electric vehicle according to claim 2, characterized in that, The lubrication and / or cooling of the transmission (1) is directly carried out by means of the oil flowing out of the outflow opening of the oil hole (17).

4. The transmission device (1) for an electric vehicle according to claim 3, characterized in that, For lubricating and / or cooling the transmission (1), the oil is guided to the cooling or lubricating part by means of an oil pipeline arranged at the outflow opening of the oil hole (17).

5. The transmission device (1) for an electric vehicle according to any one of claims 2 to 4, characterized in that, A control groove (19) is provided between the eccentric (7) and the pump housing (10) for closing the oil passage (18) during the suction process.

6. The transmission device (1) for an electric vehicle according to claim 1, characterized in that, The suction end of the pump (9) is formed by the check valve (13).

7. The transmission device (1) for an electric vehicle according to claim 6, characterized in that, The check valve (13) has a profile at its end facing the oil sump (8), and the profile engages in a mating profile arranged at the oil sump (8) in a pivotally hinged but fixed manner in the direction of the longitudinal axis of the pump plunger (11).

8. The transmission device (1) for an electric vehicle according to any one of the above claims, characterized in that, A plurality of oil pumps (9) are provided, and the plurality of oil pumps are driven by the same or different transmission shafts.

9. The transmission device (1) for an electric vehicle according to claim 8, characterized in that, The eccentrics (7) of the plurality of oil pumps (9) are arranged in reverse.

10. An electric vehicle drive device, in particular an electric axle, the electric vehicle drive device having a transmission device (1) according to any one of claims 1 to 9.

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