Tandem pump with main flood and dry swamp flood

Description

[0001] The invention relates to a tandem pump for an electric axle of a motor vehicle, with a dry sump flood through which hydraulic fluid can be conveyed from a gearbox chamber to a hydraulic chamber, and a main flood through which hydraulic fluid can be conveyed from the hydraulic chamber to a hydraulic consumer.

[0002] Tandem pumps are already known from the prior art in which a dry sump functionality / dry sump flooding is integrated into one pump for supplying hydraulic consumers.

[0003] Tandem pumps are already known from documents DE 20 2019 107 293 U1, DE 10 2019 201 863 B3 and DE 10 2016 104 416 A1, DE 10 2011 079 822 A1.

[0004] However, the state of the art always has the disadvantage that strict installation space requirements exist for the design of the tandem pump, so that known tandem pumps do not fit into the available installation space in the axial or radial direction.

[0005] The object of the invention is therefore to avoid or at least mitigate the disadvantages of the prior art. In particular, a tandem pump is to be provided in which a dry sump function / dry sump flooding is integrated into a pump for supplying hydraulic consumers, and which simultaneously meets the installation space requirements. In addition, the dry sump flooding of the tandem pump should be able to draw in a certain amount of air without generating any acoustic disturbances or allowing air to pass from the dry sump side to the main flood side.

[0006] The problem is solved by a tandem pump with the features of claim 1. Advantageous further developments are the subject of the dependent claims.

[0007] Accordingly, the invention relates to a tandem pump for an electric axle of a motor vehicle, comprising a dry sump flow through which hydraulic fluid can be pumped from a transmission compartment to a hydraulic compartment, and a main flow through which hydraulic fluid can be pumped from the hydraulic compartment to a hydraulic consumer, wherein the dry sump flow and the main flow are formed by pump types with different flow directions. This means that, in a device of this type, this problem is solved, particularly according to the invention, by the fact that the dry sump flow and the main flow are formed by pump types with different flow directions. In other words, the inventive solution consists in using two pump types whose flow directions can be optimally positioned within the available installation space.

[0008] According to a preferred embodiment, the dry sump flow can be formed by a pump type with an axial flow direction, and the main flow by a pump type with a radial flow direction. Particularly with such a selection of pump types for the respective flow, the connections of the tandem pump can be arranged so that the tandem pump fits into the given installation space. Alternatively, depending on the available installation space, it may be advantageous if the dry sump flow is formed by a pump type with a radial flow direction and the main flow by a pump type with an axial flow direction.

[0009] According to a preferred embodiment, the dry sump and the main sump can each have separate inlets. Such separate inlets are essential if fluid is to be drawn from two different reservoirs / tanks. This allows the dry sump to advantageously draw hydraulic fluid from the gearbox compartment and the main sump to draw hydraulic fluid from the hydraulic compartment.

[0010] According to a preferred embodiment, the dry sump flood and the main flood can be formed by pump types with different form factors. In particular, by choosing coaxial and axially parallel form factors for the two pump types, an ideal arrangement of the hydraulic connections and screw points of the housing components of the tandem pump can advantageously be achieved.

[0011] The dry sump flood system is formed by a gerotor pump. A gerotor pump is a positive displacement pump. It has an inner and an outer rotor. The inner rotor has n teeth (at least two), while the outer rotor has n+1 teeth. One axis of the inner rotor is offset from the axis of the outer rotor, and both rotors rotate around their respective axes. Thus, the driving and driven rotors are eccentrically positioned relative to each other. Since gerotor pumps are radially space-saving compared to external gear pumps, this design prevents a radial increase in the size of the tandem pump. Another advantage of using a gerotor pump for dry sump flooding is that gerotor pumps retain their full functionality even with minimal contamination and air ingress, which is particularly important for the conditions encountered when operating in a dry sump flood system.

[0012] The main flow is generated by an external gear pump. An external gear pump is a positive displacement pump. The external gear pump has two identical gears that mesh with each other. One of the two gears is driven by a motor, and the other gear is driven by the driven gear. Because external gear pumps are axially space-saving compared to gerotor pumps, this design prevents an axial increase in the size of the tandem pump.

[0013] The dry sump flood and the main flood are mechanically coupled, establishing a defined ratio between them. This means that the different displacement volumes allow for adjusting the ratio between the two floods to meet the varying requirements of each. Furthermore, the mechanical coupling simplifies the drive mechanism for the tandem pump.

[0014] The dry sump pump and the main pump can be driven by a single motor. This means that only one motor is required to drive both the dry sump pump and the main pump, resulting in a particularly cost-effective and space-saving tandem pump.

[0015] According to the invention, the main sump has a driving gear that can be driven by the motor and a driven gear that can be driven by the driving gear. According to the invention, the dry sump has a rotor that can be driven by the driven gear of the main sump. This has the advantage that an axially parallel arrangement of the dry sump is enabled with respect to the driving gear and thus to the motor. At the same time, it ensures that the main sump and the dry sump can be driven by the common motor.

[0016] The dry sump drain is arranged parallel to the engine's axis. This has the advantage that the connections (of the main drain) can be positioned radially further inwards compared to a coaxial arrangement of the dry sump drain to the engine. This allows the main drain (with its connections) to be designed particularly compactly.

[0017] According to a preferred embodiment, the tandem pump can have a radial shaft seal that separates the dry sump and the main pumping circuits. This advantageously ensures that no leakage occurs between the two circuits and that no air can enter the main pumping circuit from the dry sump.

[0018] In other words, the invention relates to a tandem pump with dry sump flooding.

[0019] Dual-flow pumps, in which the flow is realized from a hydraulic reservoir, or in particular dual-flow pumps in which a dry sump function / dry sump flood is integrated into the pump for supplying hydraulic consumers, are already generally known. In such a tandem pump, i.e., a pump with a dry sump flood and a main flood that draws from two reservoirs / tanks, the dry sump flood / dry sump pump is intended to draw fluid from the gearbox compartment and deliver it to a hydraulic compartment, while the main flood is intended to draw fluid from the hydraulic compartment and supply the hydraulic consumers. Due to the foaming of the oil in the gearbox compartment, it is necessary that the dry sump flood be able to draw in a certain amount of air without producing any unusual noises.Furthermore, it is necessary to prevent leakage between the two sumps to prevent air from flowing from the dry sump side to the main sump. Additionally, the seal between the hydraulic pump housing components should be particularly economical, utilizing the screw clamping force, which requires the screws to be positioned at defined intervals. In tandem pumps, the positioning of the screws is crucial for simultaneously sealing both sumps.

[0020] According to the invention, two (different) pump types are used, which can be optimally positioned in terms of their flow direction within the available installation space. In particular, a combination of an external gear pump and a gerotor pump allows for separate flow directions for the water or different flow directions (radial / axial), which is necessary for drawing water from different reservoirs. This enables the pump connections to be positioned so that the pump fits within the given installation space. In other words, the use of two pump types with different form factors ("coaxial" and "axis-parallel") allows for an ideal arrangement of the hydraulic connections and the screw connections of the housings. Furthermore, these pump types are advantageous due to their low cost per unit and their ease of industrialization.In contrast, a combination of two external gear pumps would result in a radial increase in size, since the axially parallel design of an external gear pump used as a dry sump pump would necessitate the radial outward relocation of the main pump's connections. Furthermore, a combination of two gerotor pumps would result in an axial increase in size, as axial flow is required, necessitating an axial increase in installation space by the height of the inlet channel. The gerotor pump is particularly advantageous due to its simple installation and is ideal for use as a dry sump pump, as it can handle low levels of contamination and air ingress. The pump streams are mechanically coupled as a tandem pump, so that the different displacement volumes establish a defined ratio between the two streams to meet the varying requirements of the main and dry sump pumps.Furthermore, only one drive motor is required. The gerotor pump is driven by a coupling with the driven wheel of the external gear pump, which allows the gerotor pump to be positioned axially parallel to the motor. This, in turn, allows the hydraulic connections of the underlying external gear pump to be arranged in the most compact way. In contrast to a coaxial arrangement of the gerotor pump to the motor, the connections can thus be positioned radially further inwards. A radial shaft seal can also preferably be used between the sumps to prevent air from entering the main sump from the dry sump.

[0021] The invention is explained below with the aid of drawings. These show: Fig. 1 a longitudinal section view of a tandem pump with a dry sump flood and a main flood, Fig. 2a perspective view of the tandem pump, where the housing of the tandem pump is not shown, Figs. 3 to 6 Perspective views of the tandem pump, illustrating the oil flow of the dry sump flood and the oil flow of the main flood, as well as the installation space required for the tandem pump, and Fig. 7 a schematic sectional view of an arrangement of an inlet and an outlet.

[0022] The figures are purely schematic and serve solely to illustrate the invention. The same elements are identified by the same reference symbols.

[0023] Figures 1 to 6Figure 1 shows an embodiment of a tandem pump 1 according to the invention. The tandem pump 1 is used, in particular, in an electric axle of a motor vehicle to supply one or more hydraulic consumers with hydraulic fluid. The tandem pump 1 has a dry sump 2 through which hydraulic fluid can be pumped from a transmission compartment (not shown) to a hydraulic chamber (not shown). The tandem pump 1 also has a main sump 3 through which hydraulic fluid can be pumped from the hydraulic chamber (not shown) to the hydraulic consumer(s) (not shown).

[0024] According to the invention, the dry sump flood 2 and the main flood 3 are formed by pump types with different flow directions. In particular, in the illustrated embodiment, the dry sump flood 2 is formed by a pump type with an axial flow direction, preferably by a gerotor pump 4, and the main flood 3 is formed by a pump type with a radial flow direction, preferably by an external gear pump 5.

[0025] In particular, the dry swamp flood 2 and the main flood 3 can each have a separate inflow. As especially in Figs. 2 and 3As can be seen, the main flow 3 has a suction-side connection 6 and a pressure-side connection 7, through which the hydraulic fluid can be supplied to or discharged from the main flow 3. The suction-side connection 6 can be connected to or is connected to the hydraulic chamber, and the pressure-side connection 7 can be connected to or is connected to the hydraulic consumer(s). The drawn-in hydraulic fluid is introduced into the external gear pump 5 via the suction-side connection 6, pumped by the external gear pump 5, and discharged via the pressure-side connection 7. As can be seen in particular in Figs. 2 and 4As can be seen, the dry sump 2 has a suction-side connection 8 and a pressure-side connection 9, through which the hydraulic fluid can be supplied to and discharged from the dry sump 2. The suction-side connection 8 can be connected to, or is connected to, the gearbox compartment, and the pressure-side connection 9 can be connected to, or is connected to, the hydraulic compartment. The drawn-in hydraulic fluid is introduced into the gerotor pump 4 via the suction-side connection 8, pumped by the gerotor pump 4, and discharged via the pressure-side connection 9.

[0026] The gerotor pump 4 is a positive displacement pump and has an inner rotor 10 and an outer rotor 11. The inner rotor 10 has n teeth (here six teeth), while the outer rotor 11 has n+1 teeth (here seven teeth). One axis of the inner rotor 10 is offset (parallel to) the axis of the outer rotor 11, and both rotors 10, 11 rotate about their respective axes. Thus, the driving and driven rotors 10, 11 are arranged eccentrically to each other.

[0027] The external gear pump 5 is a positive displacement pump and has two identical gears 12, 13 that mesh with each other. A first gear 12 of the two gears 12, 13 is driven by a motor 14, and a second gear 13 of the two gears 12, 13 is driven by the first (driven) gear 12. In the illustrated embodiment, the motor 14 is designed as an electric motor.

[0028] The dry sump flood 2 and the main flood 3 are mechanically coupled, establishing a defined ratio between them. Both the dry sump flood 2 and the main flood 3 are driven by a common motor, in this case, motor 14.

[0029] The driving rotor of the two rotors 10, 11 of the gerotor pump 4 is coupled to the second (driven) gear 13, so that the motor 14 drives the external gear pump 5 (or the first gear 12), and the external gear pump 5 (or the second gear 13) drives the gerotor pump 4.

[0030] The dry sump flood 2 is arranged parallel to the axis of the motor 14, i.e. to a rotational axis of the motor 14.

[0031] Furthermore, the tandem pump 1 can have a radial shaft seal 15 that separates the dry sump 2 and the main sump 3 from each other. In the illustrated embodiment, the radial shaft seal 15 is arranged on an intermediate shaft between the second gear 13 of the external gear pump 5 and the rotor 10 of the gerotor pump 2.

[0032] Especially in Fig. 5 It can be seen that the external gear pump 5 is located at the top and is designed with radial flow to minimize axial installation space. In particular, in Fig. 6 It can be seen that the gerotor pump 4 is designed with axial flow in order to maintain radial installation space and to avoid a collision (or a radial outward displacement) of the connections 6, 7 of the external gear pump 5. Fig. 7The figure schematically shows the necessary design of an inlet 16 and an outlet 17 of gerotor pumps in general. A radial flow is not possible with this type of pump due to its inherent design. Reference symbol list

[0033] 1 Tandem pump 2 Dry sump 3 Main sump 4 Gerotor pump 5 External gear pump 6 Suction-side connection 7 Pressure-side connection 8 Suction-side connection 9 Pressure-side connection 10 Internal rotor 11 External rotor 12 First gear 13 Second gear 14 Motor 15 Radial shaft seal 16 Inlet 17 Outlet

Claims

1. A tandem pump (1) for an electric axle of a motor vehicle, having a dry sump flow (2), via which hydraulic fluid can be delivered from a transmission chamber into a hydraulic chamber, and a main flow (3), via which hydraulic fluid can be delivered from the hydraulic chamber to a hydraulic consumer, wherein the dry sump flow (2) and the main flow (3) are formed by types of pump having different inflow directions, wherein the dry sump flow (2) is formed by a gerotor pump (4) and the main flow (3) is formed by an external gear pump (5), wherein the dry sump flow (2) and the main flow (3) can be driven via a common motor (14), characterised in that the gerotor pump (4) is driven by a coupling with the driven wheel of the external gear pump (5), and the dry sump flow (2) is arranged axially parallel to the motor (14).

2. The tandem pump (1) according to claim 1, characterised in that the dry sump flow (2) is formed by a type of pump with an axial inflow direction and the main flow (3) is formed by a type of pump with a radial inflow direction.

3. The tandem pump (1) according to claim 1 or 2, characterised in that the dry sump flow (2) and the main flow (3) each have a separate inflow.

4. The tandem pump (1) according to any one of claims 1 to 3, characterized in that the dry sump flow (2) and the main flow (3) are formed by types of pump with different form factors.

5. The tandem pump (1) according to any one of claims 1 to 5, characterized in that the dry sump flow (2) and the main flow (3) are mechanically coupled to one another, so that a defined ratio between the main flow (3) and the dry sump flow (2) is set.

6. The tandem pump (1) according to claim 7, characterized in that the main flow (3) has a driving gear (12) that can be driven by the motor (14) and a driven gear (13) that can be driven by the driving gear (12), wherein the dry sump flow (2) has a rotor (10, 11) that can be driven by the driven gear (13) of the main flow (3).

7. The tandem pump (1) according to any one of claims 1 to 9, characterized in that the tandem pump (1) has a radial shaft seal (15) that separates the dry sump flow (2) and the main flow (3) from one another.