Gerotor pump and motor-pump unit

Abstract

The invention relates to a gerotor pump (1) for pumping a fluid from an inlet pump chamber connected to an inlet (2) to an outlet pump chamber of the gerotor pump (1) connected to an outlet (3), comprising a rotatable outer rotor (4); a rotatable inner rotor (5) which is arranged radially inside the outer rotor (4); a housing (8) with a housing cover (6) and a housing base (7) between which the outer rotor (4) and the inner rotor (5) are arranged; and at least one compensation plate (9, 10, 11) which is arranged axially between the outer rotor (4) and the inner rotor (5) and the housing cover (6) or the housing base (7), wherein the at least one compensation plate (9, 10, 11) is axially spaced from the outer rotor (4) and the inner rotor (5) by preload in the rest state of the gerotor pump (1).

Description

[0001] The invention relates to a gerotor pump for conveying a fluid and a motor-pump unit comprising the gerotor pump.

[0002] Conventional gerotor pumps, also known as "gear ring pumps" or "Eaton pumps," have a rotating outer rotor and a rotating inner rotor, with the inner rotor arranged radially inside the outer rotor. The inner rotor is typically driven by a motor. The inner rotor is designed as a gear and the outer rotor as a toothed ring, with the inner and outer rotors having different axes of rotation. As a result, the outer rotor rotates eccentrically on the outer teeth of the inner rotor. Due to the changing volumes between the tooth gaps between the inner and outer rotors, pressure zones, also called pumping chambers, form through which the fluid is pumped.

[0003] "Fundamentals of Designing Hydraulic Gear Machines" by Jaroslaw Stryczek (ISBN: 978-83-01-21226-1) and "Axial clearance compensation in the gerotor pump" by Jaroslaw Stryczek and Slawomir Bednarczyk from "the 19th International Conference on Hydraulics and Pneumatics, Prague, September 29 - October 1, 2008" describe conventional axial compensation in gerotor pumps using compensation plates.

[0004] However, conventional gerotor pumps have the disadvantage that manufacturing tolerances lead to a so-called axial gap between the inner and outer rotors and the housing, especially a housing cover or housing base. Such an axial gap causes internal leakage ("internal leakage") of the pumped fluid, which reduces the pump's efficiency. The aforementioned conventional compensation plates also have the disadvantage that, when the pump is at rest, the compensation plates rest against active parts, i.e., the inner and outer rotors, with a certain force, which slows the rotors when the pump starts up. This is also referred to as "normally closed." As a result, the pump requires an increased starting torque and thus higher power.Furthermore, the conventionally compensated axial gap causes a sharp drop in pump efficiency, especially at lower temperatures, because the fluid to be pumped generally has a higher viscosity at lower temperatures. Pump wear, particularly due to friction between the rotors and the compensation plates, is also disadvantageous.

[0005] It is an object of the invention to provide a gerotor pump which can reduce an axial gap and at the same time has a high efficiency and low wear in the low pressure range.

[0006] This problem is solved by the features of the independent claim. The subclaims contain advantageous embodiments of the invention.

[0007] This object is achieved in particular by a gerotor pump according to claim 1. The gerotor pump is designed and suitable for conveying a fluid from an inlet pumping chamber connected to an inlet to an outlet pumping chamber of the gerotor pump connected to an outlet. The gerotor pump has a rotatable outer rotor and a rotatable inner rotor. The inner rotor is arranged radially inside the outer rotor. The gerotor pump also has a housing with a housing cover and a housing base. The outer rotor and the inner rotor are arranged between the housing cover and the housing base. Furthermore, the gerotor pump has at least one compensation plate, which is arranged axially between the outer rotor and inner rotor and the housing cover or the housing base.For example, the gerotor pump has at least one compensation plate arranged axially between the outer rotor and inner rotor and the housing cover, and / or at least one compensation plate arranged axially between the outer rotor and inner rotor and the housing base. In the resting state of the gerotor pump, the at least one compensation plate is axially spaced from the outer rotor and the inner rotor by preload.

[0008] By preloading the at least one compensation plate to keep it spaced from the outer and inner rotors when the gerotor pump is at rest, wear on the pump can be reduced and the pump's efficiency improved, even in low pressure ranges. This is also referred to as "normally open."

[0009] In the following explanations, terms such as "the rotors" are to be understood as collectively referring to "inner rotor and outer rotor." Furthermore, above and below, an element that is, for example, "arranged between the inner rotor and outer rotor and the housing (cover / base)" is to be understood as an element that is arranged between the housing (cover / base) and the inner rotor and / or between the housing (cover / base) and the outer rotor, particularly with respect to the axial direction.

[0010] In an advantageous embodiment, the gerotor pump has, as the at least one compensation plate, an upper compensation plate and / or a lower compensation plate. The upper compensation plate is arranged axially between the outer rotor and inner rotor and the housing cover. The lower compensation plate is arranged axially between the outer rotor and inner rotor and the housing base. Preferably, the gerotor pump has only the upper compensation plate. Alternatively, the gerotor pump has only the lower compensation plate. Further alternatively, the gerotor pump has both the upper compensation plate and the lower compensation plate.

[0011] In an advantageous embodiment of the invention, the gerotor pump has at least one spring element that preloads the upper compensation plate axially relative to the housing cover and / or that preloads the lower compensation plate axially relative to the housing base. This preloads the at least one compensation plate such that, in the resting state of the gerotor pump, it is axially spaced from the outer rotor and the inner rotor ("normally open").

[0012] The spring element is preferably a helical spring. Advantageously, the at least one compensation plate has at least one retaining structure for the respective spring element. For example, the at least one compensation plate has at least one recess ("spring element recess") for the at least one spring element as a helical spring, in which one end of the helical spring is received. Alternatively or additionally, the compensation plate has a retaining lug as a retaining structure, which can receive and clamp one end of a leaf spring. This enables the at least one spring element to be held radially by the compensation plate.

[0013] In an advantageous embodiment, in which the gerotor pump has the upper compensation plate and the lower compensation plate, the at least one spring element is arranged axially between the upper and lower compensation plates. In other words, the spring element is clamped axially between the upper and lower compensation plates and preloads them in the axial direction. The spring element extends axially from the upper to the lower compensation plate and is preferably in direct contact with both.

[0014] Advantageously, the at least one compensation plate has at least one inlet through-bore that is fluidically connected to the inlet. Furthermore, the at least one compensation plate has at least one outlet through-bore that is fluidically connected to the outlet. This allows pressure equalization between a housing side and a rotor side of the compensation plate. Consequently, the manufacturing tolerances of the gerotor pump can also be expanded, simplifying production.

[0015] In an advantageous embodiment, the at least one compensation plate has at least one first groove, which runs on a housing cover-side end face or on a housing base-side end face of the compensation plate at least along a circumference of the compensation plate. This aforementioned groove advantageously promotes pressure equalization between the housing side and the rotor side of the compensation plate. The aforementioned pressure equalization advantageously reduces or minimizes an axial compressive force acting on the compensation plate.

[0016] Advantageously, the upper compensation plate has the first groove on the housing cover-side end face. Further advantageously, the lower compensation plate has the first groove on the housing base-side end face. Alternatively or additionally, the lower compensation plate has a first groove on the housing cover-side end face and / or the upper compensation plate has a first groove on the housing base-side end face. In an exemplary case in which at least one of the compensation plates has first grooves on both of its end faces (housing base side / housing cover side), these can be fluidly connected to one another by an axial groove.

[0017] Advantageously, the at least one groove is formed radially from the circumference to the radial center of the compensation plate in at least one radial section of the compensation plate(s). In other words, the groove advantageously runs from the circumference to the radial center of the compensation plate in at least one radial section of the compensation plate. This advantageously enables the fluid that enters the aforementioned groove of the compensation plate to reach a shaft and thus back to the inner rotor or the outer rotor. The respective groove(s) can also each run in several radial sections of the corresponding compensation plate(s) to the radial center thereof, for example, at opposite radial sections with respect to the radial center.

[0018] In an advantageous embodiment of the gerotor pump, it comprises the upper compensation plate and the lower compensation plate, with the first groove of the upper compensation plate running on the housing cover-side end face and the first groove of the lower compensation plate running on the housing base-side end face. In other words, both the upper and lower compensation plates have the first groove on their housing-side end faces, in contrast to their rotor-side end faces.

[0019] The first groove has the particular advantage of reducing the gap between the compensation plate and the housing (housing base or housing cover) through the aforementioned pressure equalization, even at high fluid back pressures. Furthermore, fluid leakage can be directed back to the rotors.

[0020] Advantageously, the at least one compensation plate has at least one pumping chamber groove. The respective pumping chamber groove runs on a rotor-side end face of the respective compensation plate and, together with gaps between the inner rotor and outer rotor, defines the inlet pumping chamber or the outlet pumping chamber. Advantageously, the respective compensation plate has a first pumping chamber groove for the inlet pumping chamber and a second pumping chamber groove for the outlet pumping chamber. Advantageously, each of the compensation plates has the aforementioned first and the aforementioned second pumping chamber groove.

[0021] Further advantageously, the gerotor pump has at least one compensation seal. The at least one compensation seal is arranged on a housing cover-side or a housing base-side end face of the at least one compensation plate. The respective compensation seal encloses a compensation surface that is axially opposite the pump chamber groove. An area enclosed by the pump chamber groove is smaller than the aforementioned compensation surface. Due to the different (directly) opposing surface sizes, to which fluid reaches the same pressure through the inlet / outlet through-bores, a directed force is created that counteracts the preload and presses the compensation plate(s) toward the rotor side, thereby reducing the axial gap during pump operation.

[0022] In particular, the pump chamber groove generates a pressure surface that can be larger than the pump chamber groove during pump operation. In such a case, the pressure surface generated by the pump chamber groove is preferably smaller than the aforementioned compensation surface. In other words, the aforementioned compensation surface is at least larger than the pump chamber groove, preferably larger than the pressure surface generated by the pump chamber groove.

[0023] The compensation seal encloses in particular the inlet through-bore(s) or the outlet through-bore(s).

[0024] In one example of a gerotor pump, the gerotor pump has four such compensation seals, namely two on the upper compensation plate and two on the lower compensation plate. Each of these compensation seals is axially opposite a pumping chamber groove of the respective compensation plate. Because the area enclosed by the pumping chamber groove or its generated pressure area is smaller than the compensation area of ​​the compensation seal, a directed force is created that reduces the distance between the at least one compensation plate and the outer rotor or the inner rotor. This reduces the axial gap during pump operation, especially at higher pressures, thereby increasing efficiency. When the pump is shut down to its idle state, the directed force weakens, so that the "normally open" state reappears. In other words, the axial gap is reduced by hydraulic pressure.

[0025] The invention also relates to a motor-pump unit. The motor-pump unit comprises a gerotor pump according to one of the above preferred embodiments. Furthermore, the motor-pump unit comprises a motor, which is preferably connected to the inner rotor and is configured to rotate the inner rotor to operate the gerotor pump. The motor is mechanically connected to the inner rotor, in particular by means of a shaft. The motor-pump unit has increased efficiency and low wear. Alternatively, the motor is connected to the outer rotor of the gerotor pump and operates it.

[0026] The gerotor pump and motor pump unit according to the present invention also have the following advantages: The (volumetric) efficiency is increased, wear is reduced, the starting torque is reduced, the pump operation is more efficient at lower temperatures or higher fluid viscosity, and the power requirement is reduced. Furthermore, the gerotor can be operated at higher pressures. A widening of the manufacturing tolerances is also possible.

[0027] Further details, advantages, and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawings. It shows: Fig. 1 a schematic cross-sectional view of a gerotor pump according to an embodiment of the present invention; Fig. 2 a perspective view of a compensation plate of the gerotor pump according to the embodiment of the present invention; Fig. 3 a schematic sectional view of the gerotor pump according to the embodiment of the present invention; and Fig. 4 a schematic block diagram of a motor pump unit according to another embodiment of the present invention.

[0028] Figure 1 shows a schematic cross-sectional view of a gerotor pump 1 according to a first embodiment of the present invention.

[0029] The gerotor pump 1 is arranged and designed to convey a fluid from an inlet pump chamber connected to an inlet 2 to an outlet pump chamber of the gerotor pump 1 connected to an outlet 3.

[0030] In Figure 1 Arrows 28 show the exemplary fluid flow for explanation. The gerotor pump 1 has a rotatable outer rotor 4 and a rotatable inner rotor 5, wherein the inner rotor 5 is arranged radially inside the outer rotor 4. A radial direction 26 is in Figure 1The inner rotor 5 is connected to a shaft 25, which drives the inner rotor 5 during operation of the pump 1. A rest state is defined as no torque applied by the shaft 25.

[0031] Furthermore, the gerotor pump 1 has a housing 8 with a housing cover 6 and a housing base 7, wherein the inner rotor 5 and the outer rotor 4 are arranged axially between the housing cover 7 and the housing base 7. In Figure 1 an axial direction 27 is shown.

[0032] In the present embodiment, the gerotor pump 1 has two compensation plates 9. The gerotor pump 1 has an upper compensation plate 10 between the outer rotor 4 and inner rotor 5 and the housing cover 6, as well as a lower compensation plate 11 between the outer rotor 4 and inner rotor 5 and the housing base 7. However, the gerotor pump 1 of the present invention is not limited to this, but can have only the upper compensation plate 10 or only the lower compensation plate 11.

[0033] The compensation plates 10, 11 are preloaded by spring elements 12, in this case coil springs. The upper compensation plate 10 is preloaded toward the housing cover 6, and the lower compensation plate 11 is preloaded toward the housing base 7. In an exemplary case in which only one of the compensation plates 10, 11 is present, the spring element 12 rests against the correspondingly opposite housing cover 6 or housing base 7.

[0034] The spring elements 12 cause the compensation plates 10, 11 to be axially spaced from the outer rotor 4 and the inner rotor 5 when the gerotor pump 1 is at rest due to the preload of the spring elements 12. This reduces the friction between the compensation plates 10, 11 and the rotors 4, 5, so that the gerotor pump 1 requires a low starting torque.

[0035] The spring elements 12 create the aforementioned axial distance between the compensation plates 10, 11 (or the respective compensation plate 10, 11 from the opposite housing base 7 or housing cover 6), particularly when the gerotor pump 1 is at rest. During operation of the gerotor pump 1, particularly at higher pressures, the compensation plates 10, 11 are pressed toward each other by the pressurized fluid. In other words, during operation of the gerotor pump 1, the upper compensation plate 10 is pressed toward the housing base 7 and / or the lower compensation plate 11 is pressed toward the housing cover 6. This is explained below.

[0036] Figure 2 shows a perspective view of a compensation plate 9 of the gerotor pump 1 according to the present embodiment. Figure 2shows in particular the upper compensation plate 10, wherein the following explanations can alternatively or additionally describe the lower compensation plate 11 (in particular reversed with respect to the axial direction 27). Furthermore, the preceding and following explanations relate to a recuperation gerotor pump which can be operated bidirectionally. However, the invention can equally be applied to a unidirectional gerotor pump. In this case, the axial compensation is preferably carried out only on one side of the high-pressure side or the low-pressure side, in particular only on the high-pressure side. In other words, only the left half of the Figure 1 The gerotor pump 1 shown in the drawing can have the described structures, while the right half (low pressure side or tank pressure side) can be designed according to a conventional gerotor pump. Figure 2The illustrated compensation plate 10 can also be approximately halved in its circumference. In other words, instead of the illustrated 360° configuration (circular), the compensation plate 10 can encompass approximately 160° or more, preferably approximately 180° or more, more preferably 190° or more, preferably no more than 270° (partially circular). Of course, a geometric shape other than circular can also be selected, depending on the requirements.

[0037] As from Figure 2 As can be seen, the compensation plate 10 has an end face 16. With reference to the upper compensation plate 10, the end face 16 is a housing cover-side end face 16 (compare Figure 1 ). The compensation plate 10 has a groove 15, which runs on the housing cover-side end face 16 along a circumference 18 of the compensation plate 10. As a comparison of the Figure 2 with the Figure 1shows the lower compensation plate 11 has the first groove 15 on a housing bottom-side end face 17. As further Figure 2 The groove 15 in a radial section 19 of the compensation plate 10 runs radially from the circumference 18 to the radial center 20 of the compensation plate 10. Figure 1 The shaft 25 shown extends through the radial center 20 of the compensation plate 10.

[0038] This allows pressurized fluid that enters an area between the upper compensation plate 10 and the housing cover 6 or between the lower compensation plate 11 and the housing base 7 to flow back to the shaft 25 and thus back to the inner rotor 5 or outer rotor 4. The radial center 20 of the compensation plate 10 can accommodate the shaft 25 with a clearance fit, allowing fluid to flow through the radial center 20 (radially) between the shaft 25 and the compensation plate 10 in the axial direction 27.

[0039] Furthermore, in the present embodiment, the compensation plate 10 has two inlet through-bores 13, which are fluidly connected to the inlet 2. Furthermore, the compensation plate 10 has two outlet through-bores 14, which are fluidly connected to the outlet 3.

[0040] One in Figure 2 The recess 29 shown in the compensation plate 10 is designed to receive a locking pin (not shown) which prevents the compensation plate 10 from rotating during operation of the pump 1.

[0041] In Figure 2 Also shown are spring element recesses 40, each of which accommodates a spring element 12.

[0042] The compensation plate(s) 10 (upper and / or lower) may also have several of the above-described grooves 15, for example, one on each of the end faces 16, 17 of the compensation plate(s) 10. In such an exemplary case, the two grooves 15 may be fluidly connected by at least one axially extending groove of the compensation plate(s) 10. This advantageously allows pressure equalization between both sides of the compensation plate(s) 10 to be achieved, so that axial compressive forces on them are reduced or minimized.

[0043] In Figure 1 the inlet through-holes 13 and the outlet through-holes 14 are shown in dashed lines for the upper compensation plate 10.

[0044] Figure 3 shows a schematic sectional view of the gerotor pump 1 according to the present embodiment. The sectional view of the Figure 3shows in particular a plan view along the axial direction 27 with transparent housing cover 6.

[0045] As from the Figure 3 As can be seen, the gerotor pump 1 according to the present embodiment has a pumping chamber groove 21 for the inlet pumping chamber and a pumping chamber groove 21 for the outlet pumping chamber. These pumping chamber grooves 21 are formed in the rotor-side end face 22 of the compensation plate 10 (shown in dashed lines). The lower compensation plate 11 can also have these pumping chamber grooves 21. The pumping chamber grooves 21, together with gaps between the inner rotor 5 and the outer rotor 4, define the inlet pumping chamber and the outlet pumping chamber (respectively).

[0046] As the cross-section of the Figure 1 shows these pump chamber grooves 21 are arranged axially opposite, in particular axially directly opposite, compensation seals 23 (or their enclosed surfaces). The compensation seals 23, which in Figure 3, include compensation surfaces axially opposite the corresponding pumping chamber grooves 21. The compensation surface, enclosed by the compensation seal 23, and the pumping chamber groove 21 are fluidly connected through the corresponding inlet through-bores 13 or outlet through-bores 14.

[0047] The pressurised fluid flows from the inlet pumping chamber (from the corresponding pumping chamber groove 21) through the inlet through-bore 13 into a compensation chamber 30 enclosed by the compensation seal 23 in the housing cover 6 or in the housing base 7. This is in Figure 1 shown.

[0048] As a comparison of the Figure 1 with the Figure 3As shown, the compensation area enclosed by the compensation seal 23 is larger than the area enclosed by the pump chamber groove 21. Since the fluid in the pump chamber groove 21 has the same pressure as the fluid in the compensation space 30, and the compensation area is larger than the area enclosed by the pump chamber groove 21, the pressurized fluid exerts a greater force on the compensation area than on the pump chamber groove 21 (P = F / A; F = P*A). This results in a total force that counteracts the preload by the spring elements 12.

[0049] In other words, during operation of the pump 1, the compensation plates 10, 11 are pressed axially toward the inner rotor 5 and the outer rotor 4, reducing the axial gap at higher pressures. This increases the efficiency of the gerotor pump 1 for higher pressures. At lower pressures, the preload of the compensation plates 10, 11 reduces viscous friction and thus also reduces the starting torque of the gerotor pump 1. These advantages are achieved in particular by appropriately adapting the compensation surface.

[0050] Figure 4 shows a schematic block diagram of a motor pump unit 100 according to an embodiment of the present invention.

[0051] The motor pump unit 100 comprises a motor 101 and a gerotor pump 1 according to the present invention. The motor 101 is configured to rotate the inner rotor 5 to operate the gerotor pump 1. The motor 101 is connected to the shaft 25 (see also Figure 1 ) is mechanically connected to the inner rotor 5. The motor pump unit 100 has a particularly good efficiency and a particularly long service life.

[0052] In addition to the above written description of the invention, reference is hereby explicitly made to the graphic representation of the invention in the figures for the purpose of supplementary disclosure. Reference sign list

[0053] 1 Gerotor pump 2 Inlet 3 Outlet 4 Outer rotor 5 Inner rotor 6 Casing cover 7 Casing base 8 Casing 9 Compensation plate 10 Upper compensation plate 11 Lower compensation plate 12 Spring element 13 Inlet through-bore 14 Outlet through-bore 15 Groove 17 End face 18 Circumference 19 Radial section 20 Radial center 21 Pump chamber groove 22 Rotor-side end face 23 Compensation seal 25 Shaft 26 Radial direction 27 Axial direction 28 Fluid flow 29 Recess 30 Compensation chamber 40 Spring element recess

Claims

1. A gerotor pump (1) for conveying a fluid from an inlet pumping chamber connected to an inlet (2) to an outlet pumping chamber of the gerotor pump (1) connected to an outlet (3), comprising: a rotatable outer rotor (4); a rotatable inner rotor (5) arranged radially inside the outer rotor (4); a housing (8) with a housing cover (6) and a housing base (7), between which the outer rotor (4) and the inner rotor (5) are arranged; and at least one compensation plate (9, 10, 11), each of which is arranged axially between the outer rotor (4) and the inner rotor (5) and the housing cover (6) or the housing base (7), wherein the at least one compensation plate (9, 10, 11) is axially spaced from the outer rotor (4) and the inner rotor (5) by prestressing when the gerotor pump (1) is at rest.

2. Gerotor pump (1) according to claim 1, comprising, as the at least one compensation plate (9, 10, 11), an upper compensation plate (10) which is arranged axially between the outer rotor (4) and inner rotor (5) and the housing cover (6), and / or a lower compensation plate (11) which is arranged axially between the outer rotor (4) and inner rotor (5) and the housing base (7).

3. Gerotor pump (1) according to claim 2, comprising at least one spring element (12) which prestresses the upper compensation plate (10) axially relative to the housing cover (6) and / or which prestresses the lower compensation plate (11) axially relative to the housing base (7).

4. Gerotor pump (1) according to claim 3, comprising the upper compensation plate (10) and the lower compensation plate (11), wherein the at least one spring element (12) is arranged axially between the upper and the lower compensation plate (10, 11).

5. Gerotor pump (1) according to one of the preceding claims, wherein the at least one compensation plate (9, 10, 11) has at least one inlet through-bore (13) which is fluidly connected to the inlet (2) and at least one outlet through-bore (14) which is fluidly connected to the outlet (3).

6. Gerotor pump (1) according to one of the preceding claims, wherein the at least one compensation plate (9, 10, 11) has at least one first groove (15) which runs on a housing cover-side end face (16) or a housing base-side end face (17) at least along a circumference (18) of the compensation plate (9, 10, 11).

7. Gerotor pump (1) according to claim 6, wherein the at least one first groove (15) in at least one radial section (19) of the compensation plate (9, 10, 11) extends radially from the circumference (18) to the radial center (20) of the compensation plate (9, 10, 11).

8. Gerotor pump (1) according to one of the preceding claims, wherein the at least one compensation plate (9, 10, 11) has at least one pumping chamber groove (21) which runs on a rotor-side end face (22) and which, together with spaces between the inner rotor (5) and the outer rotor (4), defines the inlet pumping chamber or the outlet pumping chamber.

9. Gerotor pump (1) according to claim 8, comprising at least one compensation seal (23) which is arranged on a housing cover-side or a housing base-side end face (16, 17) of the at least one compensation plate (9) and encloses a compensation surface which is axially opposite the pump chamber groove (21), wherein an area enclosed by the pump chamber groove (21) is smaller than the compensation surface.

10. A motor-pump unit (100) comprising: a gerotor pump (1) according to one of the preceding claims; and a motor (101) connected to the inner rotor (5) and configured to rotate the inner rotor (5) to operate the gerotor pump (1).

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