INTERNAL GEAR MACHINE

Description

[0001] The invention relates to an internal gear machine for reversing operation with the features mentioned in the preamble of claim 1.

[0002] Internal gear machines of this type are known. WO 2018 / 172059 A1, EP 1 110 000 B1, and DE 43 38 875 C2 each disclose internal gear machines for reversing operation, in which an externally toothed pinion and an internally toothed ring gear are arranged in a meshing manner within a housing cavity. The rotational axes of the internal pinion and the ring gear are arranged parallel and spaced apart from one another, so that they are eccentric to one another. A filler piece is arranged in a crescent-shaped cavity resulting between the pinion and the ring gear. The housing cavity is further axially delimited. The housing has fluid connections that communicate with pressure pockets provided in the housing.

[0003] Such reversible internal gear units can thus be used as pumps in both directions of rotation of the driven pinion. Furthermore, so-called four-quadrant operation is also possible, meaning that by applying fluid to one of the pressure ports of the internal gear unit, it can also be operated as a hydraulic motor. In this case, reversible operation is also possible.

[0004] Internal gear machines for high-pressure applications have a so-called hydrostatic ring gear bearing. Due to the design-related ring gear clearance, leakage of the pumped medium, usually oil, such as hydraulic oil, can occur. During a zero crossing when changing the force direction of the ring gear, i.e., switching the pumping direction or switching the drive direction, both sides of the bearing can be pressurized simultaneously. This is also possible with external pressurization in multi-range operation, i.e., an inlet pressure acts at the pump inlet. This leads to increased leakage in the ring gear bearing, since the ring gear can only seal one side of the ring gear bearing.

[0005] The invention is based on the object of creating an internal gear machine of the generic type in which leakage in the ring gear bearing during the zero crossing or when pressurization is applied on both sides is minimized in a simple manner.

[0006] According to the invention, this object is achieved by an internal gear machine having the features recited in claim 1. By arranging a switching valve in each connection between the pressure pocket and the pressure connection, i.e., in both connections between the pressure pocket and the pressure connection on each bearing side, which opens or closes the connection depending on the pressure, it is advantageously possible to control the internal gear machine such that only one pressure pocket is pressurized at a time. This makes it very advantageous to switch the hydrostatic ring gear bearing into a hydrodynamic ring gear bearing. Leakage between the two pressure sides, particularly during a zero crossing or when pressurization is applied on both sides, can thus be avoided, since pressurization of the ring gear bearing on both sides is avoided.

[0007] In a preferred embodiment of the invention, the switching valves are hydraulically spring-loaded two-position valves. This allows the switching function between the hydrostatic ring gear bearing and the hydrodynamic ring gear bearing to be easily integrated into the internal gear machine.

[0008] In a further preferred embodiment of the invention, a spring side of a first switching valve is connected to a second pressure connection of the internal gear unit, and a spring side of a second switching valve is connected to a first pressure connection of the internal gear unit. This mutual pressure connection ensures that the connection between the pressure pocket and the pressure connection can be opened or closed simply and reliably via the pressure applied to the other pressure connection. Switching between the hydrostatic ring gear bearing and the hydrodynamic ring gear bearing is thus particularly simple.

[0009] Furthermore, a preferred embodiment of the invention provides for the switching sides of the switching valves to be connected to the respective pressure port of the internal gear unit assigned to the switching valve. Thus, by providing appropriate control channels in the housing, the pressure difference between the two pressure ports in the internal gear unit can be easily applied to the switching valves arranged in the connections between the pressure pockets and the pressure port.

[0010] Furthermore, a preferred embodiment of the invention provides for the opening pressure of the switching valves to be adjustable by preloading the switching springs of the switching valves. This allows the opening pressure to be easily achieved by dimensioning the switching springs, which thus determine the differential pressure between the pressure ports at which the switching valves close or open.

[0011] Finally, in a further preferred embodiment of the invention, the opening pressure of the switching valves is <30 bar, in particular <20 bar. This allows the ring gear bearings to switch from a hydrostatic to a hydrodynamic state very sensitively and quickly. The internal gear unit can thus operate without significant leakage, even at high pressures applied to the pressure connections, for example, >300 bar.

[0012] According to a further preferred embodiment (not shown), the switching valves can also be controlled electromagnetically. The pressures applied to the internal gear unit are then converted by a control unit into control signals that serve to control the corresponding switching solenoids of the switching valves.

[0013] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0014] The invention is explained in more detail below in an exemplary embodiment with reference to the accompanying drawings. They show: Figure 1 shows a sectional view of an internal gear machine, Figures 2 and 3 show a sectional view of the internal gear machine according to section line II and section line II-II in Figure 1 , Figure 4 is an enlarged view of a switching valve, and Figure 5 is a schematic diagram of the internal gear machine according to the invention.

[0015] Figure 1 shows a sectional view of an internal gear machine, designated overall by 10. The internal gear machine 10 is designed for so-called reversing operation, meaning it can be operated as a pump in both directions of rotation. The internal gear machine 10 can also be operated in so-called four-quadrant operation.

[0016] The internal gear machine 10 has a housing 12 within which a cavity 14 is formed. An externally toothed pinion 16 and an internally toothed ring gear 18 are arranged in the cavity 14. The pinion 16 is arranged for rotation about a longitudinal axis 20, and the ring gear 18 is arranged for rotation about a longitudinal axis 22. The longitudinal axes 20 and 22 thus form axes of rotation for the pinion 16 and the ring gear 18, respectively. The axes of rotation are arranged parallel and spaced apart from one another. The pinion 16 and the ring gear 18 are arranged such that their external and internal teeth mesh with each other, respectively.

[0017] A filler piece 26 is arranged within a crescent-shaped free space 24 formed between pinion 16 and ring gear 18. The filler piece 26 has two filler pieces 28 and 30, respectively, arranged on either side of a stop pin 32. These filler pieces 28 and 30 each consist of inner sealing segments 34 and outer sealing segments 36. The gap between inner sealing segments 32 and outer sealing segments 34 is sealed by sealing rollers 38.

[0018] The housing 12 also contains pressure pockets 40 and 42, each of which is connected to a pressure port 44 and a pressure port 46 of the internal gear machine 10. The pressure pockets 40 and 42, and thus the pressure ports 44 and 46, are connected to the cavity 14 via the control geometries 48 and 50.

[0019] The structure and mode of operation of such an internal gear machine 10 are well known to those skilled in the art, so a more detailed description is omitted here. Reference is also made, for example, to the prior art cited at the beginning.

[0020] In the Figures 2 and 3 sectional views are shown in a step section through several planes through the internal gear machine 10 along the section lines II and II-II respectively.

[0021] Based on the Figures 2 and 3It becomes clear that the housing 12 is constructed in three parts and consists of a housing ring 52 and a flange cover 54 or connection cover 56. The housing ring 52 encloses the cavity 14, in which the pinion 16 and ring gear 18, as well as the filler piece 26, are arranged. The pinion 16 is connected to a shaft 58, which is guided sealingly through the flange cover 54 and acts as the input shaft or output shaft in the internal gear machine, depending on the operating mode. The shaft 58 is preferably hydrodynamically mounted by bearing bushes 59.

[0022] An axial sealing of the cavity 14 is achieved by axial pressure plates 57, which are arranged in the axial direction between the ring gear 18 and the connection cover 56 or flange cover 54.

[0023] In Figure 2It becomes clear that a switching valve 60 assigned to the pressure pocket 42 and a switching valve 62 assigned to the pressure pocket 40 are integrated within the housing 12. In the example shown, the switching valves 60 and 62 are provided within the housing ring 52.

[0024] The switching valves 60 and 62 are hydraulically spring-loaded two-position valves.

[0025] The switching valves 60 and 62 comprise a control piston 68 and 70, respectively, which can be displaced within a cavity against the force of a spring element 64 and 66, respectively.

[0026] The spring side of the control piston 68 of the switching valve 60 is connected to the pressure port 44 and thus to the fluid port via a connection 72. On its switching side, the switching valve 60 is connected to the pressure port 46 via a connection 74. This connection is made via a further connection 76, which connects the switching valve 60 to the displacement chamber 78 associated with the pressure pocket 42 and thus also to the pressure port 46 of the internal gear machine 10. A further connection 77 connects the switching valve 62 to the pressure pocket 42.

[0027] In a completely analogous manner, the spring side of the switching valve 62 is connected to the pressure port 46 via a connection 80. The switching side of the switching valve 62 is connected to the pressure port 44 via a connection 82. The switching valve 62 is connected via a connection 84 to a displacement chamber 86 of the internal gear machine 10 associated with the pressure port 44. Another connection 85 connects the switching valve 62 to the pressure pocket 40.

[0028] Based on the enlarged view of the switching valve 60 in Figure 4 It becomes clear that the control piston 68 is guided within an interior space 90, displaceably sealing against the force of the spring element 64. On the spring side, the connection 72 and, on the opposite switching side, the connection 74 open into the interior space 90. Furthermore, the connection 77 opens into the interior space 90, which is sealed by the control piston 68 in the illustration shown.

[0029] Basically, if the pressure at connection 74 exceeds the pressure at connection 72 plus the pressure force of spring 64, the control piston 68 is moved as shown in Figure 4 to the right in the plane of the paper. This creates a continuous connection between the connections 74 and 77 via passages 92 within the control piston 68. The switching valve 60 thus switches from its Figure 4 shown locked position into the open position. There is then a continuous connection between the pressure pocket 42 and the pressure connection 46 and thus the displacement chamber 78.

[0030] Based on the Figure 5 The schematic representation of the internal gear machine 10 shown illustrates the overall function of the arrangement of the additional switching valves 60 and 62 provided according to the invention.

[0031] Each pressure pocket is assigned a switching valve, here the switching valve 62 is assigned to the pressure pocket 40 and the switching valve 60 is assigned to the pressure pocket 42. The respective spring side of the switching valves 60 and 62 is connected here via the connection 72 and 80 to the respective opposite displacement chamber 86 and 78.

[0032] The switching side of the switching valves 60 and 62 is connected to the displacement chamber 78 and 86 on the same side via the connections 74 / 76 and connections 82 / 84, respectively.

[0033] The preload of the springs corresponds to an opening pressure of approximately 20 bar.

[0034] Both switching valves 60 and 62 are in Figure 5shown in their closed position. In this case, there is a pressure difference between the pressures present in the displacement chambers 86 and 78, respectively, which is smaller than the opening pressure of the switching valves 60 and 62, respectively, which is approximately 20 bar, for example. The two pressure pockets 42 and 40 are therefore not supplied with pressure due to the closed position of the switching valves 60 and 62. The ring gear 18 is thus hydrodynamically mounted.

[0035] If the pressure difference between the displacement chambers 78 and 86 increases above the opening pressure of the switching valve 60 or the switching valve 62, the respective switching valve 60 or 62 is switched to its open position. In this case, a connection is created between the respective displacement chamber 78 and the switching pocket 42, or between the displacement chamber 86 and the switching pocket 40. This means that the switching pocket 42 or the switching pocket 40 is subjected to the higher displacement pressure present in the associated displacement chamber 78 or 86, respectively. At this moment, the ring gear 18 is hydrostatically mounted. Reference symbol

[0036] 10Internal gear machine 12Housing 14Cavity 16Pinion 18Ring gear 20Longitudinal axis 22Longitudinal axis 24Sickle-shaped free space 26Filling piece 28Filling piece part 30Filling piece part 32Stop pin 34Inner sealing segment 36Outer sealing segment 38Sealing roller 40Pressure pocket 42Pressure pocket 44Fluid connection 46Fluid connection 48Control geometry 50Control geometry 52Housing ring 54Flange cover 56Connection cover 57Axial pressure plate 58Shaft 59Bearing bush 60Switching valve 62Switching valve 64Spring element 66Spring element 68Control piston 70Control piston 72Connection 74Connection 76Connection 77Connection 78Displacement chamber 80Connection 82Connection 84Connection 85Connection 86Displacement chamber 90Interior 92Passages

Claims

1. An internal gear machine (10) for reverse operation, having a housing (12) with a cavity (14), an externally toothed pinion (16) and an internally toothed ring gear (18) being arranged within said cavity (14) which engage with each other and whose rotation axes (20, 22) run in parallel and spaced apart from each other, the cavity (14) of the housing (12) being axially limited, a first pressure pocket (40) and a second pressure pocket (42) being located in the housing (12) which are connected to the cavity (14), the first pressure pocket (40) being connected to a first pressure port (44) and the second pressure pocket (42) being connected to a second pressure port (46) of the internal gear machine (10), characterized in that a first switching valve (62) is arranged in the connection between the first pressure pocket (40) and the first pressure port (44) and a second switching valve (60) is arranged in the connection between the second pressure pocket (42) and the second pressure port (46) and the first pressure port (44) is connected to a first displacement chamber (86) and the second pressure port (46) is connected to a second displacement chamber (78) of the internal gear machine (10).

2. The internal gear machine (10) according to Claim 1, characterized in that the switching valves (60, 62) are hydraulically spring-loaded two-position valves.

3. The internal gear machine (10) according to any one of the preceding claims, characterized in that a spring side of the second switching valve (60) is connected to the pressure port (44) of the internal gear machine (10).

4. The internal gear machine (10) according to any one of the preceding claims, characterized in that a spring side of the first switching valve (62) is connected to the pressure port (46) of the internal gear machine (10).

5. The internal gear machine (10) according to any one of the preceding claims, characterized in that the switching sides of the switching valves (60, 62) are connected to the pressure port (46, 44) of the internal gear machine (10) associated with the respective switching valve (60, 62).

6. The internal gear machine (10) according to any one of the preceding claims, characterized in that an opening pressure of the switching valves (60, 62) is adjustable via a biasing of a switching spring (64, 66) of the switching valves (60, 62).

7. The internal gear machine (10) according to Claim 6, characterized in that the opening pressure of the switching valves is <30 bar, in particular <20 bar.