Fluid conveying system

Abstract

Fluid conveying device (1) with a backing pump (2) and a main pump (3) fluidically connected to the backing pump (2), wherein the backing pump (2) can be driven via a backing pump input shaft (8) and the main pump (3) via a main pump input shaft (9) and the backing pump input shaft (8) and the main pump input shaft (9) are mechanically coupled to a common drive shaft (7) of the fluid conveying device (1), wherein the backing pump (2) is designed as an uncompensated gear pump or as a centrifugal pump, characterized in that the main pump (3) is designed as a compensated internal gear pump, wherein the backing pump (2) has a higher limiting speed and a larger pump volume than the main pump (3).

Description

[0001] The invention relates to a fluid conveying device with a backing pump and a main pump fluidically connected to the backing pump, wherein the backing pump can be driven via a backing pump input shaft and the main pump via a main pump input shaft, and the backing pump input shaft and the main pump input shaft are mechanically coupled to a common drive shaft of the fluid conveying device, wherein the backing pump is designed as an uncompensated gear pump or as a centrifugal pump.

[0002] For example, the prior art is known from publication DE 10 2007 032 103 A1. This relates to a pump unit with a main pump and a charging pump with an adjustable delivery volume. A lifting ring is provided for adjusting the delivery volume of the charging pump. The lifting ring is subjected to an actuating force that depends on the inlet pressure of the main pump.

[0003] Furthermore, German patent application DE 103 52 029 A1 discloses a positive displacement pump with a pre-charging device, comprising the following: a housing with an inlet and an outlet for a fluid to be pumped, a displacement chamber contained in the housing into which the inlet and outlet open, a displacement element housed in the displacement chamber which performs a pumping motion by which fluid is conveyed from the inlet to the outlet, increasing its pressure, a drive shaft whose rotational motion causes the pumping motion of the displacement element, and a pre-charging device that conveys the fluid through the inlet. The pre-charging device is a centrifugal pump with at least one impeller driven by the drive shaft.

[0004] The object of the invention is to propose a fluid conveying device which has advantages over known fluid conveying devices, in particular achieving a high conveying capacity with high efficiency.

[0005] According to the invention, this is achieved with a fluid conveying device having the features of claim 1. It is provided that the main pump is designed as a compensated internal gear pump, wherein the backing pump has a higher limiting speed and a larger pump volume than the main pump.

[0006] The fluid handling system is used to transfer a fluid, such as a liquid or a gas. For this purpose, the system comprises a backing pump and a main pump, with the main pump being fluidically connected to the backing pump. This means that the fluid is first fed to the backing pump, which then transfers it to the main pump. The fluid pumped by the backing pump is thus made available to the main pump, which transfers the fluid further, for example, towards a fluid outlet of the system, which can also be referred to as the system's fluid outlet.

[0007] Each pump has an input shaft through which it is driven: the backing pump via its backing pump input shaft and the main pump via its main pump input shaft. The backing pump also has two gears for fluid transfer: the backing pump pinion and the backing pump ring gear. The backing pump pinion has external teeth, and the backing pump ring gear has internal teeth. The external and internal teeth mesh with each other in certain areas. The backing pump pinion and the backing pump ring gear are designed for fluid transfer and are therefore configured to work together when the backing pump input shaft rotates to transfer the fluid, meshing with each other in the process.

[0008] The pre-pump pinion is coupled to the pre-pump input shaft, preferably rigidly and / or permanently. The pre-pump pinion is preferably arranged on the pre-pump input shaft so that it always rotates at the same speed as the pre-pump input shaft during operation. The pre-pump input shaft is coupled to the common drive shaft, preferably again rigidly and / or permanently. For example, the pre-pump input shaft and the common drive shaft are formed as a single piece, so that the pre-pump input shaft is formed from the drive shaft and / or vice versa. In this case, the pre-pump can be driven directly and immediately via the drive shaft.

[0009] Similarly, the main pump has a main pump pinion and a main pump ring gear. The main pump pinion has external teeth, and the main pump ring gear has internal teeth. The external and internal teeth mesh with each other in certain areas. The main pump pinion and the main pump ring gear are designed for fluid transport and are configured to work together when the main pump input shaft rotates to pump the fluid, meshing or meshing with each other in the process.

[0010] It can be provided that the main pump input shaft is coupled to the common drive shaft in a drive-related manner, analogous to the pre-pump input shaft, preferably rigidly and / or permanently. For example, the pump input shaft and the common drive shaft are formed as a single piece, such that the main pump input shaft is formed from the drive shaft and / or vice versa. In this respect, the main pump can be driven directly and immediately via the drive shaft. It is particularly preferred that both the pre-pump input shaft and the main pump input shaft are formed from the common drive shaft. In other words, the pre-pump input shaft and the main pump input shaft are formed as a single piece and / or from a single material, so that together they form the drive shaft. Accordingly, the pre-pump input shaft and the main pump input shaft are arranged coaxially with each other.In such a design, the pre-pump and the main pump are always operated at the same speed.

[0011] Alternatively, the main pump can be driven indirectly via the drive shaft. In this case, the main pump is connected to the drive shaft via the booster pump, so that when the drive shaft rotates, the main pump is driven via the booster pump. Preferably, the booster pump pinion and the booster pump ring gear are connected to each other. This means that the booster pump pinion is designed and configured to drive the booster pump ring gear, so that when the booster pump input shaft rotates, both the booster pump pinion and the booster pump ring gear rotate.

[0012] The pre-pump ring gear is now connected to the main pump input shaft via a connecting shaft. In other words, the main pump is connected to the pre-pump ring gear so that, preferably, rotation of the pre-pump ring gear also results in rotation of the main pump input shaft. The main pump input shaft and the connecting shaft can be separate components or formed as a single unit. In the latter case, the main pump input shaft forms the connecting shaft and / or vice versa. For example, the pre-pump ring gear is rotatably mounted by means of the connecting shaft and / or the main pump input shaft.

[0013] This means that in this embodiment, the fluid transfer system is designed such that the input shaft of the backing pump is directly and immediately coupled to the drive shaft. The input shaft of the main pump, on the other hand, is only indirectly coupled to the drive shaft via the connecting shaft and / or the backing pump. This design of the fluid transfer system has the advantage that the rotational speeds of the backing pump and the main pump, or rather their respective input shafts, are in a fixed relationship to one another, so that, for example, a specific ratio exists between the rotational speeds and the two pumps are operated at different speeds. This results in very good coordination between the backing pump and the main pump during operation of the fluid transfer system.

[0014] In every case—that is, regardless of how the backing pump and the main pump are connected to the drive shaft—the backing pump is an uncompensated gear pump or a centrifugal pump, and the main pump is a compensated internal gear pump. In one embodiment, both pumps, i.e., both the backing pump and the main pump, are gear pumps, with the backing pump preferably being an internal gear pump or an external gear pump, and the main pump an internal gear pump. The main pump is axially and / or radially compensated. In another embodiment, the backing pump is a centrifugal pump and the main pump an internal gear pump. Again, the main pump is axially and / or radially compensated. It is possible for the main pump to be axially compensated and radially uncompensated, axially uncompensated and radially compensated, or both axially and radially compensated.Axial compensation means that, viewed in the axial direction with respect to the respective internal gear pump, an axial disk is arranged between the pinion and the ring gear of the internal gear pump.

[0015] The axial disk is displaceable with minimal play in the axial direction. During operation of the respective gear pump or internal gear pump, it is forced axially towards the pinion and the ring gear and preferably bears against them at least temporarily, and in particular continuously. It is especially preferred that such an axial disk is located on opposite sides of the pinion and the ring gear in the axial direction. For example, the axial disks are arranged between the pinion and the ring gear on one side and a machine housing of the main pump on the other, i.e., on the end faces of the pinion and the ring gear. While the following description refers only to one axial disk, the statements are always applicable to each of the multiple axial disks, where applicable.

[0016] The axial disk is preferably mounted in the machine housing in a rotationally fixed manner. On its side facing away from the pinion and ring gear, and thus towards the machine housing, it can have a pressure field, for example, in the form of a recess in the axial disk. This pressure field can be pressurized with fluid via a fluid channel formed in the machine housing. For example, the pressure field is fluid-connected to a pressure side of the gear pump or internal gear pump via the fluid channel. During operation of the gear pump or internal gear pump, the pressure field is pressurized via the fluid channel, and the axial disk is accordingly forced axially towards the pinion and ring gear, in particular against them.

[0017] In addition to or as an alternative to axial compensation, radial compensation is provided for the internal gear pump. The internal gear pump has a filler piece which, viewed radially with respect to the pinion's axis of rotation, is arranged between the pinion and the ring gear. The filler piece serves to fluidically separate a pressure side from a suction side of the internal gear pump, or a pressure chamber from a suction chamber, which are also formed radially between the pinion and the ring gear. In the case of radial compensation, the filler piece is designed in multiple parts and has a first filler piece section that rests against the pinion and a second filler piece section that rests against the ring gear.The two filling element parts are movable relative to each other in a radial direction and are designed such that the first filling element part is pressed radially inwards against the pinion and the second filling element part is pressed radially outwards against the ring gear. This ensures excellent sealing between the pressure chamber and the suction chamber throughout the operating time of the internal gear pump.

[0018] For example, a pressure chamber located radially between the first and second filling element sections is fluidically connected to the pressure side of the internal gear pump, so that the pressure chamber is pressurized during operation of the internal gear pump. Due to this pressurization, the two filling element sections are subjected to radial forces, causing the first filling element section to be forced towards the pinion and the second filling element section to be forced towards the ring gear. Therefore, it is preferably provided that the axial and / or radial compensation of the internal gear pump is dependent on the pressure on the pressure side of the internal gear pump. The sealing effect achieved by means of the axial disk and / or the filling element is thus greater the higher the pressure on the pressure side of the internal gear pump.

[0019] As explained above, the main pump can be designed with axial compensation, radial compensation, or both. The backing pump, designed as a gear pump, is partially uncompensated, i.e., either axially uncompensated or radially uncompensated. It is particularly preferred that it be both axially and radially uncompensated. For example, the backing pump does not have the same level of compensation as the main pump. Thus, if the main pump is axially compensated and radially uncompensated, the backing pump is axially uncompensated and radially compensated. Conversely, if the main pump is axially uncompensated and radially compensated, the backing pump is axially and radially uncompensated. And if the main pump is axially and radially compensated, the backing pump is axially and radially uncompensated.In the case of a backing pump designed as an external gear pump, a first gear replaces the pinion, and a second gear replaces the ring gear. This second gear meshes with the first gear to pump the fluid. The centrifugal pump can be designed as a radial pump, diagonal pump, side-channel pump, peripheral pump, or axial pump. With such a design of the fluid pumping system, very high rotational speeds can be achieved, at least of the backing pump, but preferably also of the main pump, so that the entire fluid pumping system is designed for extremely high fluid flow rates.

[0020] A further embodiment of the invention provides that the backing pump, designed as an internal gear pump, has a backing pump pinion and a backing pump ring gear, and the main pump has a main pump pinion and a main pump ring gear, wherein the backing pump pinion and the main pump pinion are arranged coaxially and the backing pump ring gear and the main pump ring gear are arranged offset from each other. The embodiments for the main pump are, of course, also applicable to the backing pump designed as a centrifugal pump. The backing pump pinion is rotatably mounted about a backing pump pinion axis, the backing pump ring gear about a backing pump ring gear axis, the main pump pinion about a main pump pinion axis, and the main pump ring gear about a main pump ring gear axis. The axes of rotation of the pinion and the ring gear of both the backing pump and the main pump are arranged offset from each other, so that their axes of rotation are spaced apart and parallel to each other.A preferred design of the fluid conveying device is one in which the backing pump pinion and the main pump pinion are arranged coaxially, so that their axes of rotation coincide or are identical. The backing pump ring gear and the main pump ring gear, on the other hand, are arranged offset from each other, so that the axis of rotation of the backing pump ring gear and the axis of rotation of the main pump ring gear are parallel and spaced apart. This enables a particularly advantageous fluid flow between the backing pump and the main pump.

[0021] Alternatively, the pilot pump pinion and the main pump pinion can, of course, be arranged coaxially, as can the pilot pump ring gear and the main pump ring gear. In this case, the pilot pump pinion axis and the main pump pinion axis coincide. This also applies to the pilot pump ring gear axis and the main pump ring gear axis. In any case, the pilot pump pinion and the main pump pinion can have identical dimensions in the radial direction. It is particularly preferred that the pilot pump pinion and the main pump pinion are of identical construction. The pilot pump ring gear and the main pump ring gear additionally or alternatively have identical dimensions in the radial direction. It is particularly preferred that they are of identical construction.The dimensions of the pinions refer to their outer circumference, and the dimensions of the ring gears refer to their inner circumference. In other words, the dimensions of the pinions and ring gears correspond to the respective pitch circle diameter of the corresponding gear teeth, i.e., the outer teeth of the pinions and the inner teeth of the ring gears.

[0022] It is particularly preferred that the teeth of the pre-pump pinion and the main pump pinion and / or the teeth of the pre-pump ring gear and the main pump ring gear are arranged offset from each other in the circumferential direction, for example by half a tooth spacing. This prevents pulsations in the fluid conveying device.

[0023] According to the invention, the backing pump has a higher maximum speed and a larger pump volume than the main pump. Due to the at least partial or complete absence of compensation in the backing pump, it is suitable for higher maximum speeds than the compensated main pump. This design of the fluid delivery system ensures that the main pump is always optimally supplied with fluid by the backing pump. Additionally, the backing pump has a larger pump volume compared to the main pump. The pump volume can also be referred to as the geometric delivery volume. This, in turn, describes the delivery volume of the respective pump during one revolution of the respective input shaft, i.e., the backing pump input shaft for the backing pump and the main pump input shaft for the main pump. The geometric delivery volume neglects tolerances, clearances, and deformations that may occur during operation of the respective pump.The larger pump volume of the pre-pump enables a consistently reliable supply of fluid to the main pump.

[0024] In a further embodiment of the invention, the backing pump and the main pump are arranged in a common machine housing. This offers the advantage of simple and cost-effective manufacturing of the fluid pumping device. For example, the machine housing is designed such that the backing pump pinion and the backing pump ring gear are inserted into the machine housing from one side and the main pump pinion and the main pump ring gear from the other side during assembly of the fluid pumping device. A partition is arranged in the machine housing to separate the backing pump and the main pump from each other, at least partially, in terms of fluid flow. In any case, the backing pump and the main pump are preferably arranged adjacent to each other in the axial direction, and in particular spaced apart from each other, i.e., without overlap in the axial direction, within the machine housing.

[0025] A further preferred embodiment of the invention provides that a suction chamber of the backing pump, designed as an internal gear pump, extends over a larger angular range than a suction chamber of the main pump, and / or that a pressure chamber of the backing pump extends over at least the same angular range as a pressure chamber of the main pump. In cross-section, the suction chamber and the pressure chamber are located radially between the pinion and the ring gear of the respective pump. In other words, the suction chamber and the pressure chamber are each bounded radially inwards by the pinion and radially outwards by the ring gear. The pinion and the ring gear of the respective pump are designed such that they convey fluid located in the suction chamber towards the pressure chamber.

[0026] For example, the fluid is supplied to the suction chamber in an axial and / or radial direction. For axial fluid supply, at least one inlet channel is provided in the machine housing. For radial supply, the respective ring gear has at least one recess that opens into the suction chamber, at least temporarily. The fluid can be extracted from the pressure chamber in an axial and / or radial direction. For axial extraction, an outlet channel is provided in the machine housing. For radial extraction, the ring gear has a recess that is in flow communication with the pressure chamber, at least temporarily. A flow connection between the pressure chamber and the outlet channel or an outlet of the fluid conveying device is thus established, at least temporarily, via this recess.

[0027] In cross-section, the suction chamber of the backing pump extends over a larger angular range than the suction chamber of the main pump. This is achieved primarily through a different design of the filling element, which is smaller in the circumferential direction for the backing pump than for the main pump. The larger extension of the backing pump's suction chamber allows for a higher rotational speed because the greater distance available for filling the suction chamber with fluid reduces the backing pump's tendency to cavitate. The larger dimensions of the suction chamber also reduce the fluid flow velocity required to fill it. The angular range over which the backing pump's suction chamber extends is particularly preferred to be at least 25%, at least 50%, at least 75%, or at least 100% larger than the angular range over which the main pump's suction chamber extends.

[0028] Additionally or alternatively, the pressure chamber of the backing pump has a cross-sectional area at least as large as that of the main pump, thus extending over at least the same angular range. Of course, it is also possible for the pressure chamber of the backing pump to extend over a larger angular range than that of the main pump. Preferably, the angular range over which the pressure chamber of the backing pump extends is at least 10%, at least 20%, or at least 25% larger than that of the main pump. This enables the high rotational speed of the backing pump described above.

[0029] A further embodiment of the invention provides that the suction chamber and the pressure chamber of the backing pump are directly connected to each other via a bypass valve. The bypass valve is designed such that it establishes a flow connection between the pressure chamber and the suction chamber when a certain pressure difference between them is exceeded, and otherwise interrupts it. The bypass valve thus serves as a pressure relief valve, which opens when a certain pressure difference between the pressure chamber and the suction chamber is reached or exceeded, allowing the pressure present in the pressure chamber to be released towards the suction chamber. The bypass valve closes as soon as the pressure difference between the pressure chamber and the suction chamber falls below the specified pressure difference again. The bypass valve can be integrated into the machine housing or arranged outside of the machine housing.The overflow valve prevents the pressure from being exceeded and / or cavitation from occurring in the backing pump, thus ensuring a reliable supply of fluid to the main pump at all times.

[0030] In a further embodiment of the invention, the angular range over which the suction chamber of the backing pump, designed as an internal gear pump, extends in the circumferential direction is at least 180°, at least 190°, at least 200°, at least 210°, at least 220°, or at least 225°. Such a circumferential extension of the suction chamber ensures reliable filling of the suction chamber even at high rotational speeds of the backing pump.

[0031] A further development of the invention provides that in the backing pump, designed as an internal gear pump, a backing pump filler piece is arranged between the backing pump pinion and the backing pump ring gear, and in the main pump, a main pump filler piece is arranged between the main pump pinion and the main pump ring gear. The backing pump filler piece has a smaller angular extent in the circumferential direction with respect to an axis of rotation of the backing pump pinion than the main pump filler piece in the circumferential direction with respect to an axis of rotation of the main pump pinion. As already explained, the respective filler piece serves to fluidically separate the pressure chamber from the suction chamber. For this purpose, the filler piece seals against the respective pinion on one side and the respective ring gear on the other, in a radial direction or in cross-section.To achieve the largest possible circumferential extent of the suction chamber for the backing pump, the backing pump filler piece is designed with a smaller angular extent in the circumferential direction than the main pump filler piece. The angular extent of each filler piece is defined as the angle relative to the respective pinion axis of rotation. This described design of the filler pieces ensures reliable filling of the backing pump's suction chamber at high speeds.

[0032] A preferred further embodiment of the invention provides that the pre-pump filling piece, the pre-pump pinion, and the pre-pump ring gear are arranged and / or designed such that the sealing effect between the pre-pump filling piece and the pre-pump pinion and / or the sealing effect between the pre-pump filling piece and the pre-pump ring gear is greater on a side of the pre-pump filling piece facing the pressure chamber than on a side of the pre-pump filling piece facing the suction chamber. In cross-section, the pre-pump filling piece seals against the pre-pump pinion on one side and the pre-pump ring gear on the other. Viewed circumferentially, the sealing effect between the pre-pump filling piece and the pre-pump pinion is greater on the side facing the pressure chamber than on the side facing the suction chamber. In particular, the sealing effect decreases circumferentially from the pressure chamber towards the suction chamber, and especially continuously.

[0033] Additionally or alternatively, this applies to the sealing effect between the pre-pump filling piece and the pre-pump ring gear. The sealing effect is greater the higher the contact pressure of the pre-pump filling piece against the pre-pump pinion or the pre-pump ring gear. Ultimately, this means that the contact pressure of the pre-pump filling piece against the pre-pump pinion or the pre-pump ring gear is greater on the side of the pre-pump filling piece facing the pressure chamber than on the side facing the suction chamber, or that the contact pressure decreases, preferably continuously, from the side facing the pressure chamber towards the side facing the suction chamber. This, in turn, allows for a particularly large design of the pre-pump's suction chamber with the advantages already described.

[0034] In a further embodiment of the invention, it can be provided that, prior to commissioning, the pre-pump pinion is designed with an oversize dimension relative to the pre-pump filling piece and / or the pre-pump ring gear is designed with an undersize dimension relative to the pre-pump filling piece, so that during the initial run-in period, a run-in wear occurs, resulting in a backlash-free fit. In other words, the pre-pump pinion or the pre-pump ring gear is designed with an interference fit relative to the pre-pump filling piece, or conversely, the pre-pump filling piece is designed with an interference fit relative to the pre-pump pinion and / or the pre-pump ring gear. During commissioning of the fluid conveying device, the run-in wear occurs, which wears down the pre-pump pinion, the pre-pump ring gear, and / or the pre-pump filling piece to such an extent that a backlash-free fit is subsequently achieved, resulting in a particularly high sealing effect.Preferably, the pre-pump filling piece is made of a softer material than the pre-pump pinion and the pre-pump ring gear, so that essentially only the pre-pump filling piece is worn away during the running-in period. Due to the backlash-free fit that exists after running in, a particularly good seal is achieved between the pressure chamber and the suction chamber of the pre-pump, which in turn leads to high achievable pressures.

[0035] Another embodiment of the invention provides that the centrifugal pump has an impeller, wherein the diameter of the impeller is at most 125% of the outer diameter of the main pump's internal gear. The impeller is designed and configured for conveying the fluid. At its largest radial point, it has a diameter that is at most 125% of the outer diameter of the main pump's internal gear. The outer diameter describes the outer diameter of the main pump's internal gear at its largest radial point. Preferably, the diameter of the impeller corresponds to, or is exactly the same as, the outer diameter of the main pump's internal gear. However, it is also possible for the diameter of the impeller to be at most 90%, at most 80%, or at most 75% of the outer diameter of the main pump's internal gear, or generally smaller. In this way, a compact design of the fluid conveying device is achieved.

[0036] Finally, in a further embodiment of the invention, the impeller of the centrifugal pump can be arranged coaxially with the main pump pinion. The impeller of the centrifugal pump can be driven via the backing pump input shaft; in particular, it is rigidly and / or permanently connected to it, for example, it is formed integrally with the backing pump input shaft. According to the foregoing, the backing pump input shaft, to which the impeller of the centrifugal pump is coaxial, and the main pump input shaft, to which the main pump pinion is coaxial, can be formed integrally and / or of a single material. In this case, the impeller of the centrifugal pump and the main pump pinion are preferably mounted on the same shaft, namely the drive shaft of the fluid pumping device. This enables a particularly advantageous coupling of the backing pump and the main pump.

[0037] It is particularly preferred that the diameter of the impeller of the centrifugal pump and / or the number of impeller blades, the pressure achievable by the centrifugal pump, and / or the fluid flow rate achievable by the centrifugal pump are selected such that cavitation-free operation of the main pump is ensured. For this purpose, the impeller of the centrifugal pump is preferably designed accordingly.

[0038] The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawing, without limiting the invention. The drawing shows: Fig. 1 A schematic longitudinal section view through a fluid conveying device with a backing pump and a main pump, Fig. 2 a schematic cross-sectional view through the fluid conveying device, Fig. 3 a schematic cross-sectional view through the fluid conveying device in the area of ​​the backing pump, as well as Fig. 4 A schematic longitudinal section view through the fluid conveying device in a further embodiment.

[0039] The Fig. Figure 1 shows a schematic longitudinal section through a fluid pumping device 1, which includes a backing pump 2 and a main pump 3 fluidically connected to the backing pump 2. The fluid pumping device 1 has a fluid inlet 4 and a fluid outlet 5 and is designed to pump fluid from the fluid inlet 4 towards the fluid outlet 5. The backing pump 2 is directly connected to the fluid inlet 4, but only indirectly, via the main pump 3, to the fluid outlet 5. Conversely, the main pump 3 is only indirectly connected to the fluid inlet 4 via the backing pump 2, but directly, fluidically, to the fluid outlet 5. This means that the fluid supplied at the fluid inlet 4 is pumped by the backing pump 2 towards the main pump 3 and then pumped by the main pump 3 towards the fluid outlet 5, where it is subsequently available.

[0040] The backing pump 2 and the main pump 3 are arranged in a common machine housing 6, or pump housing, on which both the fluid inlet 4 and the fluid outlet 5 are formed. A drive shaft 7 is rotatably mounted in the machine housing 6, by means of which a backing pump input shaft 8 and a main pump input shaft 9 can be driven. In the embodiment shown here, the backing pump input shaft 8 and the main pump input shaft 9 are formed in one piece and / or of the same material. The drive shaft 7 is preferably non-rotatably coupled to the backing pump input shaft 8 and the main pump input shaft 9 by means of a positive-locking connection, for example a gear connection. The backing pump 2 has a backing pump pinion 10 and a backing pump ring gear 11 and is designed as an internal gear pump.The pre-pump pinion 10 has an external toothing 12 which meshes in certain areas with an internal toothing 13 of the pre-pump ring gear 11 for pumping the fluid. In the embodiment shown here, the pre-pump pinion 10 is connected to the pre-pump input shaft 8 via a toothed connection, preventing rotation but allowing axial movement. However, it is also possible for the pre-pump pinion 10 to be formed integrally with the pre-pump input shaft 8 and / or made of the same material. Alternatively, the pre-pump 2 can be an external gear pump or a centrifugal pump.

[0041] The main pump 3 has a main pump pinion 14 and a main pump ring gear 15. The main pump pinion 14 has external teeth 16 which, viewed circumferentially, mesh only partially with internal teeth 17 of the main pump ring gear 15. In the backing pump 2, a suction chamber 18 is located radially between the backing pump pinion 10 and the backing pump ring gear 11. This also applies to a pressure chamber 19. The suction chamber 18 is directly connected to the fluid inlet 4, and the backing pump 2 is designed such that the fluid can flow into the suction chamber 18 from both sides in the axial direction. Accordingly, there is a flow connection from the fluid inlet 4 to both sides of the suction chamber 18.The pressure chamber 19 is fluidically connected to the main pump 3 via a flow channel 20 formed in the machine housing 6, namely to a suction chamber 21 of the main pump, which is located in a radial direction between the main pump pinion 14 and the main pump ring gear 15.

[0042] The main pump 3 is designed such that the flow channel 20 is fluidically connected to the suction chamber 21 on both sides in the axial direction, allowing fluid to flow from the flow channel 20 into the suction chamber 21 of the main pump 3 on both sides in the axial direction. Additionally, recesses 22 are formed in the main pump's internal gear 15, providing an additional flow connection between the flow channel 20 and the suction chamber 21. The main pump 3 also has a pressure chamber 23, located radially between the main pump pinion and the main pump's internal gear 15. The pressure chamber 23 is fluidly connected to the fluid outlet 5 via the recesses 22, preferably exclusively. This means that fluid present in the pressure chamber 23 can only exit the pressure chamber 23 towards the fluid outlet 5 via at least one of the recesses 22.

[0043] In the embodiment shown here, the main pump 3 is at least axially compensated, i.e., it has an axial compensation 24. For this purpose, an axial disk 25 is arranged on both sides of the main pump pinion 14 and the main pump ring gear 15, viewed in the axial direction. During operation of the main pump 3, these disks are forced towards the main pump pinion 14 and the main pump ring gear 15 and seal against the end faces of the main pump pinion 14 and the main pump ring gear 15. For this purpose, the axial disks 25 are pressurized with pressure from the pressure chamber 23 of the main pump 3. For example, an opening 26 is formed in the axial disks 25 for this purpose, through which the pressure chamber 23 is in flow communication with a pressure field 27 located on the side of the axial disk facing away from the pressure chamber 23.

[0044] The Fig. Figure 2 shows a schematic cross-sectional view of the fluid conveying device 1, showing the pilot pump pinion 10, the pilot pump ring gear 11, the main pump pinion 14, and the main pump ring gear 15. The pilot pump pinion 10 is rotatably mounted about a pilot pump pinion axis 28, the pilot pump ring gear 11 about a pilot pump ring gear axis 29, the main pump pinion 14 about a main pump pinion axis 30, and the main pump ring gear 15 about a main pump ring gear axis 31. It can be seen that the pilot pump pinion axis 28 and the main pump pinion axis 30 are identical, so that the pilot pump pinion 10 and the main pump pinion 14 are arranged coaxially with each other. The pilot pump ring gear axis 29 is arranged parallel to and spaced apart from the pilot pump pinion axis 28, and the main pump ring gear axis 31 is arranged parallel to and spaced apart from the main pump pinion axis 30.

[0045] In the embodiment of the fluid conveying device 1 shown here, the main pump ring gear axis 31 and the pilot pump ring gear axis 29 are arranged on opposite sides of the pilot pump pinion axis 28. In other words, the pilot pump pinion axis 28, the pilot pump ring gear axis 29, the main pump pinion axis 30, and the main pump ring gear axis 31 lie on an imaginary straight line, with the pilot pump ring gear axis 29 and the main pump ring gear axis 31 being arranged on opposite sides of the pilot pump pinion axis 28 and preferably having the same distance a from it. As shown here, it can be provided that the teeth of the pilot pump pinion 10 and the teeth of the main pump pinion 14 are arranged circumferentially offset from each other, i.e., not overlapping or aligned with each other when viewed axially.This effectively prevents pulsations. For example, an offset of half a tooth spacing is provided, so that each tooth of the pilot pump pinion 10 lies centrally between two teeth of the main pump pinion 14, and vice versa. However, any other circumferential offset can also be selected.

[0046] The Fig. Figure 3 shows a schematic cross-sectional view of the fluid conveying device 1 in the area of ​​the backing pump 2. The backing pump input shaft 8, the backing pump pinion 10, and the backing pump ring gear 11, which are arranged in the machine housing 6, are visible. A backing pump filler piece 32 is arranged between the backing pump pinion 10 and the backing pump ring gear 11 to fluidically separate the suction chamber 18 from the pressure chamber 19. This filler piece 32 is shown here in two different positions. It can be seen that the backing pump filler piece 32 has a comparatively small circumferential extent or angular extent. Accordingly, the angular range α over which the suction chamber 18 extends circumferentially is very large for both arrangements of the backing pump filler piece 32 and is at least 150°, preferably at least 180° or more than 180°. This ensures particularly rapid filling of the suction chamber 18 with fluid.

[0047] The figures described clearly show that the backing pump 2 is uncompensated and, in the embodiment shown here, has neither axial nor radial compensation. The main pump, on the other hand, is compensated and, in the embodiment shown here, has at least axial compensation 24. Additionally or alternatively, the main pump 3 can be equipped with radial compensation. The described design of the fluid delivery system 1 enables a particularly high rotational speed, especially of the backing pump 2. This ensures a reliable supply of fluid to the main pump 3, so that the fluid delivery system 1 as a whole achieves a high delivery pressure or a large pressure ratio between the pressure at the fluid outlet 5 and the pressure at the fluid inlet 4.

[0048] The Fig.Figure 4 shows a schematic longitudinal section of the fluid conveying device 1 in a further embodiment. This corresponds in essential parts to the fluid conveying device 1 described so far, so reference is made to the corresponding descriptions and only the differences are discussed below. These differences lie in the fact that the backing pump 2 is not designed as an internal gear pump, but as a centrifugal pump. The backing pump 2, designed as a centrifugal pump, has an impeller 33, which in the embodiment shown here is a radial pump impeller. Accordingly, the centrifugal pump is designed as a radial pump. The impeller 33 has a diameter D1, which in the embodiment shown here corresponds to an outer diameter D2 of the main pump ring gear 15. In any case, however, the diameter D1 of the impeller 33 corresponds to at most 125% of the outer diameter D2 of the main pump ring gear 15.It can be seen that the impeller 33 of the backing pump 2 is arranged coaxially with the main pump pinion 14. This results in a particularly compact design of the fluid conveying device 1. REFERENCE MARK LIST 1 Fluid conveying device 2 Pre-pump 3 Main pump 4 Fluid inlet 5 Fluid outlet 6 machine housings 7 Drive shaft 8 Pre-pump input shaft 9 Main pump input shaft 10 Pre-pump gears 11 Pre-pump ring gear 12 External teeth 13 Internal teeth 14 Main pump pinion 15 Main pump ring gear 16 External teeth 17 Internal teeth 18 Suction chamber 19 Pressure chamber 20 Flow channel 21 Suction chamber 22 Exclusion 23 Pressure chamber 24 Compensation 25 Axial disc 26 Breakthrough 27 Print field 28 Pre-pump pinion axis 29 Pre-pump ring gear pivot axis 30 Main pump pinion rotation axis 31 Main pump ring gear rotation axis 32 Pre-pump filling piece 33 Wheel

Claims

[1] Fluid conveying device (1) comprising a backing pump (2) and a main pump (3) fluidically connected to the backing pump (2), wherein the backing pump (2) can be driven via a backing pump input shaft (8) and the main pump (3) can be driven via a main pump input shaft (9) and the backing pump input shaft (8) and the main pump input shaft (9) are mechanically coupled to a common drive shaft (7) of the fluid conveying device (1), wherein the backing pump (2) is designed as an uncompensated gear pump or as a centrifugal pump, characterized by , that the main pump (3) is designed as a compensated internal gear pump, wherein the pilot pump (2) has a higher limiting speed and a larger pump volume than the main pump (3). [2] Fluid conveying device (1) according to claim 1, characterized by, that the pre-pump (2) designed as an internal gear pump has a pre-pump pinion (10) and a pre-pump ring gear (11) and the main pump (3) has a main pump pinion (14) and a main pump ring gear (15), wherein the pre-pump pinion (10) and the main pump pinion (14) are arranged coaxially and the pre-pump ring gear (11) and the main pump ring gear (15) are arranged offset from each other. [3] Fluid conveying device (1) according to one of the preceding claims, characterized by , that the pre-pump (2) and the main pump (3) are arranged in a common machine housing (6). [4] Fluid conveying device (1) according to any one of the preceding claims, characterized by, that a suction chamber (18) of the pre-pump (2) designed as an internal gear pump extends over a larger angular range (α) than a suction chamber (21) of the main pump (3), and / or that a pressure chamber (19) of the pre-pump (2) extends over at least the same angular range as a pressure chamber (23) of the main pump (3). [5] Fluid conveying device (1) according to claim 4, characterized by , that the suction chamber (18) and the pressure chamber (19) of the pre-pump (2) are directly connected to each other via a bypass valve in terms of flow technology. [6] Fluid conveying device (1) according to claim 4 or 5, characterized by , that the angular range (α) over which the suction chamber (18) of the pre-pump (2) designed as an internal gear pump extends in the circumferential direction is at least 180°, at least 190°, at least 200°, at least 210°, at least 220° or at least 225°. [7] Fluid conveying device (1) according to any of the preceding claims, characterized by, that in the pre-pump (2) designed as an internal gear pump a pre-pump filling piece (32) is arranged between the pre-pump pinion (10) and the pre-pump ring gear (11) and in the main pump (3) a main pump filling piece is arranged between the main pump pinion (14) and the main pump ring gear (15), wherein the pre-pump filling piece (32) has a smaller angular extent in the circumferential direction with respect to an axis of rotation (28) of the pre-pump pinion (10) than the main pump filling piece in the circumferential direction with respect to an axis of rotation (30) of the main pump pinion (14). [8] Fluid conveying device (1) according to claim 7 in combination with claim 2, characterized by, that the pre-pump filling piece (32), the pre-pump pinion (10) and the pre-pump ring gear (11) are arranged and / or designed such that a sealing effect between the pre-pump filling piece (32) and the pre-pump pinion (10) and / or a sealing effect between the pre-pump filling piece (32) and the pre-pump ring gear (11) is greater on a side of the pre-pump filling piece (32) facing the pressure chamber (19) than on a side of the pre-pump filling piece (32) facing the suction chamber (18). [9] Fluid conveying device (1) according to claim 7 or 8, each in combination with claim 2, characterized by , that prior to commissioning the pre-pump pinion (10) is designed with an oversize dimension with respect to the pre-pump filling piece (32) and / or the pre-pump ring gear (11) is designed with an undersize dimension with respect to the pre-pump filling piece (32), so that during a running-in period a running-in wear occurs, by which a backlash-free fit is achieved. [10] Fluid conveying device (1) according to claim 1, characterized by , that the centrifugal pump has an impeller (33) wherein a diameter (D1) of the impeller (33) has at most 125% of an outer diameter (D2) of the main pump ring gear (15). [11] Fluid conveying device (1) according to claim 10, characterized by , that the impeller (33) of the centrifugal pump is arranged coaxially to the main pump pinion (14).

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