HYDRAULIC COMPACT AXLE THAT INCLUDES SEVERAL TUBULAR COMPONENTS

Description

[0001] The invention relates to a hydraulic compact axle according to the preamble of claim 1.

[0002] In the context of the present patent application, a hydraulic compact axle is understood to be a self-contained assembly comprising a complete hydraulic circuit with a pump and an actuator, with a motor being provided to drive the pump.

[0003] It is known to design such a compact axle so that its external shape resembles a conventional hydraulic differential cylinder. Reference is made, for example, to US 11118610 B2. The compact axle shown there has the disadvantage of being difficult to assemble because many components must be incorporated into a long, slender outer tube. Furthermore, the compact axle can only be adapted to customer requirements with considerable effort. Even adjusting the stroke length involves considerable effort. Customer-specific valve assembly is hardly economically feasible.

[0004] DE 10 2008 025 054 B4 discloses a hydraulic system in which this problem was solved by designing the pump assembly, the motor assembly, and the volume compensation assembly as separate assemblies that can be attached to one another. However, the hydraulic system shown there is typically not designed as a compact axle because the actuator assembly is not permanently attached directly to the rest of the assembly. If this is exceptionally the case, the actuator assembly is arranged laterally next to the other assemblies for static reasons, so that the actuator assembly alone transmits the hydraulic forces, while the other assemblies are held force-free. Consequently, such a compact axle does not have the external shape of a conventional hydraulic differential cylinder.

[0005] DE 10 2007 023 412 A1 discloses a hydraulic compact axle comprising an actuator assembly, a pump assembly, a motor assembly, and a volume compensation assembly, each arranged concentrically with respect to a longitudinal axis. The volume compensation assembly comprises a pot-shaped tank valve block housing, which is fitted over the pump assembly to define the reservoir. The corresponding connection cannot transmit large forces along the longitudinal axis. The connection also cannot seal off high pressures in the reservoir, so the reservoir volume must be designed to be large.

[0006] US 2457467 A discloses another hydraulic compact axle in which the reservoir of the volume compensation assembly is located between the pump assembly and the actuator assembly. A pressure accumulator with a diaphragm cannot be provided there, which is why the corresponding pressure accumulator is positioned perpendicular to the longitudinal axis away from the remaining actuator. The actuator therefore does not have the external shape of a conventional hydraulic differential cylinder.

[0007] Another hydraulic compact axle is known from FR 2641340 A, in which the space around the electrical components of the motor assembly is used as an oil reservoir. This prevents the oil reservoir from being pressurized, so it must have a large volume. This contradicts the basic idea of a compact axle.

[0008] An advantage of the present invention is that the corresponding compact axle has the external shape of a conventional hydraulic differential cylinder, yet is easy to install. The compact axle can still absorb and transmit the hydraulic forces occurring during operation without excessive deformation, even leading to the breakage of individual components or leaks.

[0009] According to claim 1, it is proposed that the actuator assembly, the pump assembly, the motor assembly and the volume compensation assembly are each designed as a separate, preferably as a separately pre-assembled, assembly, wherein said assemblies are arranged in a row along the longitudinal axis, wherein they are fastened to one another exclusively in pairs at the end, wherein the actuator assembly is arranged at one end of said row.

[0010] The actuator assembly can be designed as a hydraulic cylinder or a hydraulic motor. The hydraulic cylinder can be designed as a differential or a double-action cylinder. The double-action cylinder can be unfolded or single- or multiply folded. A single-fold double-action cylinder is known, for example, from DE 10 2012 012 142 A1. A folded, in particular a double-fold double-action cylinder has the advantage that, on the one hand, it can be fastened to the adjacent assembly in accordance with the invention, in particular with a threaded screw connection, while, on the other hand, it is easily controllable, particularly when the direction of movement of the piston rod changes frequently. Such a double-action cylinder has an air space whose volume changes when the piston rod moves. This air space can be in permanent air exchange connection with the outside environment, for example via a sintered metal filter or via large windows in a dirt wiper.The actuator assembly can be provided with a mechanical override, allowing it to be moved by a means other than the motor assembly, for example, by hand. If the actuator assembly is designed as a hydraulic motor, it can be provided with a torque support, for which purpose the pivot pins explained below can be used, for example.

[0011] The pump assembly can comprise a single pump that is connected to the actuator in a closed hydraulic circuit. A fluid chamber of the volume compensation assembly is preferably in fluid communication with the hydraulic circuit such that the closed hydraulic circuit is always completely filled with pressurized fluid, whereby no excess pressure develops there that could lead to damage to the hydraulic compact axis. The pump assembly can comprise two pumps connected in series, with the fluid chamber of the volume compensation assembly being connected between the two pumps, whereby the flow rates of the two pumps can preferably be adjusted differently. In particular, when using a differential cylinder, the different fluid flows on the two cylinder sides can be compensated in this way.The respective delivery ratio can be fixed, as is known from DE 10 2010 020 690 B4. It can be adjustable during operation, for example, to compensate for pressure-dependent leaks. The pump can be designed as an internal gear pump, an external gear pump, an axial piston pump, a radial piston pump, or a vane pump.

[0012] The volume compensation assembly is preferably structurally similar to a hydraulic accumulator. The filling pressure of the volume compensation assembly is, for example, between 5 and 30 bar, with the high pressure of the hydraulic circuit being, for example, 200 bar. The stated filling pressure is therefore considerably lower than the stated working pressure. Accordingly, the volume compensation assembly stores hardly any hydraulic energy, so that despite the structural similarity, it cannot be considered a hydraulic accumulator. It functions more like a tank that can be arranged in any direction with respect to gravity.

[0013] The pump assembly may comprise at least one hydraulic valve, wherein at least some of the valves may be combined into a separately pre-assembled valve assembly. The valve assembly may, in particular, comprise at least one check valve, at least one pressure relief valve, at least one load-holding valve, and / or at least one overflow valve.

[0014] The motor assembly preferably comprises an electric motor. The electric motor can be designed as a synchronous motor, an asynchronous motor, or a DC motor. The speed of the electric motor is preferably highly dynamically adjustable using an associated regulating or control device, so that the movable component of the actuator assembly can be significantly accelerated or decelerated. The electric motor is preferably connected to the above-described at least one pump of the pump assembly for rotary drive.

[0015] The motor assembly can comprise a control device with which the respective electric motor is electrically controlled. In particular, a motor controller and, if desired, a setpoint generator can be provided. The control device can be mounted inside the compact axis or on the outside of the compact axis, although mixed forms are also conceivable. The control device can comprise a rotary encoder with which the rotational position and / or the rotational speed of the motor can be measured. The control device can comprise a pressure sensor with which the pressure of the volume compensation assembly can be measured, in particular the pressure in the respective liquid space or in the respective gas space. The control device can comprise a temperature sensor with which the temperature of the hydraulic fluid in the hydraulic compact axis can be measured.The control device can comprise a replaceable battery and / or operating elements, such as buttons or rotary controls, and / or a display. The currents flowing in the motor assembly during operation can be used to measure forces, torques, or other loads acting on the compact axis. All of the above-mentioned measured variables can be transmitted externally via a data interface and are preferably used not only within the compact axis. Wired or wireless data interfaces can be used as data interfaces. Wired data interfaces include, for example, a CAN bus or Ethernet. Wireless data interfaces include, for example, Wi-Fi, Bluetooth, LTE, or 5G-NR. Such data interfaces can be used to control the movement of the compact axis using a smartphone or tablet computer with an operating app.If the actuator assembly is designed as a hydraulic cylinder, a linear displacement sensor may be provided which directly measures the position of the movable part or piston rod, preferably being connected to the control device.

[0016] The hydraulic compact axis is preferably operated with a hydraulic fluid, which is preferably hydraulic oil. A gas chamber of the volume compensation assembly is preferably filled with a gas that can preferably be pressurized to a pressure higher than the ambient pressure. The gas is, for example, nitrogen.

[0017] It is intended that the aforementioned assemblies are arranged in a row along the longitudinal axis in the order of actuator assembly, pump assembly, motor assembly and volume compensation assembly.

[0018] The claimed arrangement has the advantage that the hydraulic fluid in the fluid chamber of the volume compensation assembly flushes the electric motor and thus provides improved cooling.

[0019] It is intended that all of the aforementioned assemblies are screwed together in pairs via a threaded screw connection, wherein the threaded screw connection each comprises an internal and an external thread, which are formed concentrically to the longitudinal axis and are screwed together. This makes it possible to achieve a particularly strong and rigid connection between the aforementioned assemblies. The connection can, as explained below, be designed such that it is leak-free even when the hydraulic fluid is applied from the inside at high pressure. This leak-free connection is also maintained when the compact axis is exposed to external forces, in particular the transverse forces explained below.

[0020] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0021] It can be provided that a centering device is arranged directly adjacent to at least one threaded screw connection, preferably to all threaded screw connections, wherein the centering device comprises two circular-cylindrical surfaces that are concentric with the longitudinal axis and bear against one another. With the centering device, a more precise relative alignment of the two components involved can be achieved than would be the case with the threaded screw connection alone. The proposed centering device requires little installation space in the radial direction. The wall thickness of the relevant tubular components can therefore be kept small.

[0022] It can be provided that a diameter of the circular cylindrical surfaces is preferably smaller than an inner diameter of the associated internal thread, with the centering device being arranged at the longitudinal end of the component of the threaded screw connection with the external thread. With regard to a possible leakage flow path of the hydraulic fluid from the interior of the compact axis via the threaded screw connection to the external environment, the centering device is arranged within the threaded screw connection, where it is preferably also used for sealing. During assembly of the threaded screw connection, damage to the centering device and the aforementioned seal is reliably prevented.

[0023] It can be provided that a static seal is arranged in the centering area, which preferably comprises a sealing ring arranged concentrically to the longitudinal axis. The sealing groove, which accommodates the sealing ring, is preferably arranged on the component with the external thread of the threaded connection. The circular-cylindrical surface on the other component preferably directly forms a sealing surface.

[0024] It can be provided that at least one of the mentioned assemblies, preferably all of the mentioned assemblies, are each provided with tool engagement means, in particular with at least one wrench flat, wherein the tool engagement means are designed such that the respective threaded screw connection can be tightened and / or loosened. The ideally circular-cylindrical outer shape of the compact axis offers only a small engagement surface for a screwing tool. This deficiency can be remedied with the proposed tool engagement means.

[0025] It can be provided that the component of the threaded screw connection with the external thread has a longitudinal end face oriented perpendicular to the longitudinal axis, which is clamped via the respective threaded screw connection with an adapted mating surface on the other component of the threaded screw connection. This allows the length of the centering in the direction of the longitudinal axis to be short, while the two components of the threaded screw connection are nevertheless securely aligned with regard to relative tilting. The longitudinal end face is preferably flat. At least one spacer ring can be arranged between the longitudinal end face and the mating surface in order to achieve a predetermined, defined relative rotational position of the two components.

[0026] It can be provided that the pump assembly comprises a first tubular component which is concentric with respect to the longitudinal axis and which is a component of at least one associated threaded screw connection, wherein at least one displacement chamber of a respective pump which has a variable volume is completely delimited by a separately pre-assembled first subassembly, wherein the first subassembly is received in the first tubular component so as to be rotatable with respect to the longitudinal axis, wherein the first subassembly is secured with respect to rotation about the longitudinal axis to a further component which is firmly connected to the first tubular component. The first subassembly is preferably used identically in many variants of the hydraulic compact axle. It is one of the most expensive components of the hydraulic compact axle because high hydraulic efficiency requires high manufacturing precision.The additional component is preferably a valve block of the valve assembly described above, with the one-piece valve block housing several valves connected to fluid channels defined by the valve block. The valve block is typically designed differently for each variant of the hydraulic compact axis. The proposed design optimally implements the cost-saving principle of "little variation in the expensive first subassembly and much variation in the cost-effective valve assembly."

[0027] It can be provided that the volume compensation assembly completely encloses a gas space, sealing an immediately adjacent tubular component at the front in a liquid-tight manner. The volume compensation assembly preferably comprises a force introduction means. The threaded screw connection proposed above enables reliable force transmission and securely seals the liquid space of the volume compensation assembly. The force introduction means can be designed as a ball joint or as a pair of pivot pins, wherein the preferably circular-cylindrical pivot pins are arranged concentrically to a common pivot axis.

[0028] It can be provided that the hydraulic compact axle comprises a first and a second force introduction means, wherein the first force introduction means is arranged on a movable component of the actuator assembly, wherein the second force introduction means is arranged at a distance from the first force introduction means in the direction of the longitudinal axis, wherein at least the second force introduction means comprises a pair of pivot pins which are arranged concentrically to a common pivot axis on opposite sides of the longitudinal axis, wherein the pivot axis is aligned perpendicular to the longitudinal axis. A ball joint can also be considered as the force introduction means, in particular for the first force introduction means. The aforementioned pivot pins have the advantage, in contrast, that they can absorb an acceleration torque of the electric motor, so that the compact axle does not execute a pivoting movement about the longitudinal axis during acceleration and braking.Preferably, the pivot axis intersects the longitudinal axis. The pivot axis can also intersect the longitudinal axis at a distance. It is conceivable that the second force introduction means is arranged at the end of the hydraulic compact axle opposite the first force introduction means in the direction of the longitudinal axis.

[0029] It can be provided that the pivot axis and the longitudinal axis intersect or cross near a center of mass of the hydraulic compact axis, preferably in the area of the pump assembly, most preferably in the area of a valve assembly that is a component of the pump assembly. This arrangement is advantageous when the compact axis as a whole is subjected to accelerated movement. This can result in transverse forces acting on the compact axis that are spatially distributed. The proposed arrangement of the pivot pins minimizes the resulting bending moments. The preferred arrangement of the assemblies in a row means that the center of mass is usually near the valve assembly. The corresponding valve block is particularly suitable for attaching the pivot pins to it, as this is a very massive component.

[0030] It can be provided that the motor assembly, the volume compensation assembly, the actuator assembly and / or the pump assembly is each provided with a plurality of cooling fins on its outer circumferential surface, wherein the cooling fins are preferably spaced apart from one another by intermediate spaces, wherein the intermediate spaces are most preferably open to the outside environment. Ideally, such cooling fins are dispensed with, since a hydraulic differential cylinder does not have cooling fins. In many hydraulic applications, for example in excavators, such cooling fins are easily damaged. Nevertheless, it may be necessary to provide cooling measures to prevent overheating of the compact axle. The proposed arrangement of the cooling fins is then particularly advantageous because clogging of the aforementioned intermediate spaces with dirt and the like is reliably prevented. This would greatly reduce the cooling effect.

[0031] The cooling fins can be components of a cooling device that uses heat pipes for heat transfer. The heat pipes are connected, for example, to the coils of the electric motor and / or to an integrated circuit of the control device, for example via a cooling plate, in order to efficiently dissipate the heat generated there to the environment. It is conceivable that the cooling effect of the cooling fins could be enhanced by means of a fan, wherein the fan is electrically driven, for example. The cooling fins are preferably arranged in one piece on an associated tubular component.

[0032] The actuator assembly can be designed as a hydraulic cylinder, with the average outer diameter of the actuator assembly being smaller than the average outer diameter of the remaining assemblies. This design deviates from the desired ideal of the "external shape of the hydraulic differential cylinder." However, this external shape can often result in significant cost savings by making the actuator assembly no larger than necessary for the desired forces.

[0033] If the compact axle is operated at low temperatures, for example in winter, it may be necessary to heat the oil. This can be achieved, for example, by pumping hydraulic fluid through the circuit using the overflow valves mentioned above without the compact axle, in particular the moving component of the actuator assembly, moving. It is also conceivable that the electric motor is supplied with reactive electrical power, which only heats the motor windings but does not produce any torque. It goes without saying that a hydraulic fluid is preferably used that always has the desired viscosity at the temperatures encountered during operation. However, such hydraulic fluids are very expensive if they are to be used at very low temperatures.

[0034] The hydraulic compact axle can be designed to supply additional hydraulic consumers and / or to be supplied by at least one additional pump. It is understood that hydraulically self-sufficient operation is preferred.

[0035] The hydraulic compact axis can be equipped with a load-holding mechanism that holds the movable component of the actuator assembly in place when the electric motor is not energized. This can be achieved, for example, by means of load-holding valves, which are preferably part of the pump assembly, in particular the valve assembly. The load can be held by means of a clamp, for example, by clamping a movable piston rod of the actuator assembly to a tubular component that is part of the actuator assembly.

[0036] The hydraulic compact axle can be controlled by an operating element designed as an operating lever or joystick. The operating lever can be equipped with a force feedback system that provides the user with haptic feedback about the force acting on the moving component of the actuator assembly. This force can be determined, for example, by measuring the current flowing in the electric motor.

[0037] The hydraulic compact axis according to the invention can replace hydraulic cylinders or rotary or swivel drives in any known machine, namely: on an excavator, for example on the bucket, boom and / or stick or slewing gear on an agricultural tractor, for example on the lifting gear and / or front loader on a telehandler, for example on the telescopic arm for retracting and extending or for raising and lowering on a forklift truck, for example for raising and lowering the lifting fork on a skid loader on a wheel loader on a dumper, for example for raising and lowering the loading trough on a scissor lift, for example for raising and lowering the lifting platform on a tunnel boring machine, for example for propulsion on a wind turbine, for example for rotor blade adjustment to open or close sliding doors, for example on ships on a bulldozer, for example for raising and lowering the dozer blade and for other alignment on a motion platform,which is designed, for example, according to the principle of a hexapod in an aircraft tractor in the steering of a vehicle, for example for the corresponding pivoting of the wheels in an active landing gear, for example in a tilting train or in a wagon steering mechanism in a retarder (switches) in machines for plastics molding, for example using the blow molding or injection molding process in a machine for pressing, sintering, flowing, ceramic production or powder pressing in a recycling machine, for example a shredder or a waste compactor in a welding machine in a machine for riveting, clinching, punching or nibbling in a bending machine in a machine for rolling components, for example for adjusting the position of the rollers during handling or moving workpieces within a production line,in particular between the various production stations in a machine for producing food in a machine for testing components in an actuator, for example for adjusting the pitch of a wing or a rotor blade, for adjusting a valve or for adjusting a hospital bed in a clamping device, for example for adjusting the clamping jaws,

[0038] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0039] The invention is explained in more detail below with reference to the accompanying drawings. It shows: Fig. 1 shows a perspective view of a hydraulic compact axle according to the invention; Fig. 2 shows a longitudinal section of a threaded screw connection; Fig. 3 shows a longitudinal section of a pump assembly according to a first embodiment and the adjacent actuator or motor assembly; Fig. 4 shows a longitudinal section of a pump assembly according to a second embodiment and the adjacent actuator or motor assembly; Fig. 5 shows a longitudinal section of the volume compensation assembly and the adjacent motor assembly.

[0040] Fig. 1 shows a perspective view of a hydraulic compact axle 10 according to the invention. The outer shape of the compact axle 10 is selected so that it can replace a conventional hydraulic differential cylinder, with the second force introduction means 12' being provided for this purpose. Accordingly, the outer shape is approximately circular-cylindrical over its entire length.

[0041] The compact axis 10 is composed of an actuator assembly 40, a pump assembly 50, a motor assembly 80, and a volume compensation assembly 90. These are arranged in a row along the longitudinal axis 13 in the order mentioned, with each assembly being fastened to one another in pairs exclusively at the end face. This division into separate assemblies, which can preferably be pre-assembled separately from one another, is advantageous because it significantly simplifies the assembly of the compact axis. The corresponding fastenings are designed to transmit the forces occurring during operation while requiring as little space as possible. The forces generated hydraulically by the actuator assembly 40 occur first. The actuator assembly 40 is designed in the manner of a folded synchronous cylinder, with the corresponding movable component 41 being movable in the direction of the longitudinal axis 13 in the manner of a piston rod.Accordingly, the hydraulic forces are directed in the direction of the longitudinal axis 13.

[0042] Furthermore, attention should be drawn to the acceleration forces that occur during operation, for example, when the compact axle 10 is accelerated or decelerated as a whole. This can happen, for example, when the compact axle is mounted on the bucket of an excavator, whereby the handle of the excavator arm is accelerated sharply. In such cases, considerable inertial forces directed transversely to the longitudinal axis can act on the compact axle 10 in a spatially distributed manner. The fixed connections of the aforementioned assemblies 40, 50, 80, 90 are therefore designed such that the resulting bending moments can be transmitted rigidly and without risk of breakage. Threaded screw connections 20, which are explained in more detail below, have proven particularly advantageous.

[0043] In applications in which the transverse forces explained above occur to a significant extent, the second force introduction means 12 are preferably used, which are designed in the form of two circular cylindrical pivot pins 15 which are arranged concentrically to a common pivot axis 14 on opposite sides of the longitudinal axis 13.

[0044] The first force introduction means 11, which is arranged at the outermost end of the movable component 41 of the actuator assembly 40, comprises a ball joint in this case, which cannot transmit any torque. The pivot pins 15, in contrast, can support the acceleration torque of the electric motor in the motor assembly 80. Furthermore, the intersection point between the longitudinal axis 13 and the pivot axis 14 can be arranged very close to the center of mass 17 of the compact axis 10. This minimizes the bending moments at the threaded connections 20 caused by the transverse forces explained above.

[0045] The second force introduction means 12' preferably also comprises a ball joint. It is arranged on the volume compensation assembly 90 and thus at the end of the compact axle 10 opposite the longitudinal axis 13 relative to the first force introduction means 11. The second force introduction means 12' is preferably used in applications where maximum external similarity to a conventional hydraulic differential cylinder is paramount.

[0046] The aforementioned assemblies 40, 50, 80, 90 can each comprise at least one subassembly, which in turn can preferably be pre-assembled separately. In the present case, the pump assembly 50 comprises two subassemblies, namely the first subassembly (No. 56 in Fig. 3 and 4) and the valve assembly 70. The valve assembly 70 comprises a valve block 71 in which at least one hydraulic valve is accommodated. The pivot pins 15 are preferably attached to the valve block 71 or formed integrally therewith.

[0047] The desired approximately circular-cylindrical outer shape results in hardly any suitable access points for screwing tools for tightening and loosening the threaded screw connections 20. Therefore, tool access means 16 in the form of wrench flats were arranged at various locations on the outside of the compact axis 10.

[0048] The actuator assembly 40 comprises a fourth tubular component 46, on which Fig. 1 At the left end, a guide 42 for the movable component 41 is arranged, which simultaneously forms a hydraulic seal. In the present case, the fourth tubular component 46 is designed largely over its entire length as a circular-cylindrical tube with respect to the longitudinal axis 13, with deviations occurring, for example, in the area of the threaded connection 20 and in the area of the guide 42. In the context of the present application, the term "tubular component" is intended to encompass any component that extends along an axis, surrounding this axis in a ring such that it has a hollow space inside, the hollow space being open at both opposite ends in the direction of the axis. In particular, such tubes are intended to be covered which are provided with cooling fins (No. 88 in Fig. 3 and 4). Although such cooling fins are undesirable in many applications of the compact axis because they can be easily damaged, they are sometimes necessary to prevent overheating of the compact axis 10.

[0049] Attention should also be drawn to the electrical connection 18 of the compact axle 10, which is preferably arranged on the motor assembly 80. A special feature of the present compact axle 10 is that, apart from this one electrical connection 18, no further connections are required, in particular no hydraulic connections.

[0050] Fig. 2 shows a longitudinal section of a threaded screw connection 20. All threaded screw connections 20 of the present compact axis are preferably designed essentially according to this basic pattern.

[0051] A threaded screw connection 20 comprises a first and a second component 101; 102, each of which is formed in one piece. The first component 101 is provided with the internal thread 21, wherein it is tubular in the sense explained above. The second component 102 is provided with the external thread 22. It can be tubular, wherein in the case of the valve block (No. 71 in Fig. 1 ) is designed as a compact component.

[0052] The internal thread 21 and the external thread 22 are screwed together. The alignment accuracy achievable in this way is often insufficient for the two assemblies assigned to the threaded screw connection 20 to interact reliably at this interface. Therefore, the threaded screw connection 20 comprises a centering device 24. The centering device 24 comprises a circular-cylindrical surface 23 on the first and second components 101; 102 with respect to the longitudinal axis, wherein the two circular-cylindrical surfaces 23 are adapted to one another essentially without play. This achieves alignment transverse to the longitudinal axis. The diameter of the circular-cylindrical surfaces 23 is slightly smaller than the internal diameter of the internal thread 21. Furthermore, the circular-cylindrical surface 23 is arranged at the very end of the second component 102 with the external thread 22.

[0053] The second component 102 with the external thread 22 has a flat longitudinal end face 27 oriented perpendicular to the longitudinal axis, wherein it is arranged at the outermost end of the second component 102. This longitudinal end face 27 bears at least indirectly against a matched counter surface 28 inside the first component 101. As a result, the first and second components 101; 102 are aligned with respect to mutual tilting such that their central axes coincide exactly with the longitudinal axis.

[0054] Furthermore, attention should be drawn to the static seal 25. Depending on where on the compact axis the threaded screw connection 20 is arranged, a very considerable hydraulic pressure can be present on its inside. For example, a pressure of 200 bar can be present inside the actuator assembly or inside the pump assembly. For example, a pressure of 30 bar can be present inside the volume compensation assembly. The circular cylindrical surfaces 23 already mentioned are used for sealing. The circular cylindrical surface 23 on the second component 102 serves directly as the sealing surface. In the circular cylindrical surface 23 on the first component 101, a groove is provided that is circular in shape with respect to the longitudinal axis and in which a sealing ring 26 is received, wherein the sealing ring 26 is designed, for example, as an O-ring. With this arrangement, there is a low risk of the sealing ring 26 being damaged during assembly of the threaded screw connection 20.This risk of damage is further minimized with the chamfer 29 in the area of the longitudinal end face 27 of the second component 102.

[0055] Fig. 3 shows a longitudinal section of a pump assembly 50 according to a first embodiment and the adjacent actuator or motor assembly 40; 80. In Fig. 3 A total of three threaded screw connections 20 can be seen, all of which are designed according to the basic pattern explained above, namely between the fourth tubular component 46 and the valve block 71, between the valve block 71 and the first tubular component 55 and between the first tubular component 55 and the second tubular component 82.

[0056] The actual pump 51 is designed as an internal gear pump, being formed entirely by a separate first subassembly 56, which is rotatably received in the first tubular component 55 relative to the longitudinal axis 13, and is secured against rotation by at least one cylindrical pin 58 on the valve block 71. This ensures that the hydraulic channels in the valve block 71 and in the first subassembly 56 are aligned.

[0057] The first subassembly 56 comprises a pot-shaped main body 60 in which the internal gear 52 of the internal gear pump is rotatably received, being rotatably mounted hydrostatically and / or hydrodynamically by means of the pressure fluid. Fig. 3 At the bottom, the external gear 53 of the internal gear pump meshes with the internal gear 52. The corresponding tooth contact separates the two pressure chambers 57 from one another in a fluid-tight manner. On the side opposite the longitudinal axis 13, a comparable seal is achieved by means of a filler piece 59, which in this case is formed integrally with the main body 60. For the purpose of increasing the maximum delivery pressure, separate filler pieces can be provided, which can be formed in multiple pieces if desired. The present internal gear pump is designed to be 4-quadrant capable, which is why the filler piece 59 is designed to be symmetrical with respect to a plane containing the longitudinal axis 13. The bore 61 in the shaft of the external gear 53 permanently guides the pressure in the fluid chamber of the volume compensation assembly. Furthermore, reference should be made to the cover 62 of the first subassembly 56, which, among other things,forms the control kidneys of the internal gear pump, and also supports the external gear 53 together with the main body 60 so as to be rotatable with respect to the longitudinal axis 13.

[0058] The valve block 71 in this case takes the two Fig. 3 visible pressure relief valves 72, which each limit the pressure in the associated first 43 or second pressure chamber 44 upwards. The pressure in the first pressure chamber 43 allows the movable part 41 to extend in the direction of the longitudinal axis 13. The pressure in the second pressure chamber allows the movable part 41 to retract in the direction of the longitudinal axis 13. The actuator assembly 40 is designed as a synchronous cylinder, so that the hydraulically effective areas of the first and second pressure chambers 43; 44 are identical. Tolerance-related deviations from this ideal and / or temperature fluctuations can, however, lead to an undesirable increase in the pressure in the currently closed hydraulic circuit. This pressure increase is limited upwards by the pressure relief valves 72. A suction valve can be assigned to each of the first and second pressure chambers 43; 44.A suction valve is a check valve that only allows fluid flow from the fluid chamber of the volume compensation assembly to the respective pressure chamber 43; 44. The suction valves can each be part of an associated pressure relief valve 72. They can also be designed as separate valves, which are, for example, screwed into the main body 60 of the first subassembly 56.

[0059] The valve assembly 70 is equipped with valves depending on the specific application of the compact axis. The present valve block 71 has the advantage of offering comparatively large installation space for valves. It can easily be extended in the direction of the longitudinal axis to provide more installation space for valves. Furthermore, the valves described with reference to Fig. 1 The pivot pins explained above can be easily attached to the outside of the valve block 71, ensuring safe force transmission to the adjacent assemblies.

[0060] It should also be noted that the air space 45 of the actuator assembly 40 changes its volume when the movable component moves. Since the piston 47 is in Fig. 3 When the valve is in its retracted end position, the air space has a volume of zero at the point marked 45. The air space is preferably permanently connected to the ambient air via at least one duct, which duct may be provided with a sintered filter to prevent the ingress of dirt.

[0061] The second tubular component 82 of the motor assembly 80 is firmly connected, for example, by adhesive bonding, to the stator 84 of the electric motor. The second tubular component 82 may be provided with cooling fins 88 on its outer circumferential surface, which dissipate the waste heat generated in the coil windings of the stator 84 to the environment.

[0062] The motor shaft 81 of the electric motor is provided with two pivot bearings 86 (see also Fig. 5 ) is rotatably mounted relative to the longitudinal axis 13. The pivot bearings 86 are designed as radial ball bearings in this case. The bore 89 inside the motor shaft 81 carries the pressure in the fluid chamber of the volume compensation assembly. The motor shaft 81 is connected to the external gear 53 via a separate coupling 104 for rotary drive. The corresponding coupling engagement can be easily established during assembly of the associated threaded screw connection 20. The rotor 85 of the electric motor, which in this case comprises several permanent magnets, is firmly connected to the motor shaft 81, for example, by adhesive bonding.

[0063] Fig. 4 shows a longitudinal section of a pump assembly 50' according to a second embodiment and the adjacent actuator and motor assembly 40; 80. The actuator and motor assembly 40; 80 are identical to Fig. 3 The pump assembly 50' is identical to that in Fig. 3 Regarding the commonality in question, please refer to the comments on Fig. 3 In the Fig. 3 and 4 Identical or corresponding components are marked with the same reference numbers. It should also be noted that the rotational position of the cutting planes with respect to the longitudinal axis 13 in the Fig. 3 and 4 differ in such a way that the pressure relief valves 72 are visible in each case. As a result, the internal gear 52, the external gear 53, and the filler piece appear different, although they are actually identical in design.

[0064] The second embodiment 50' differs from the first embodiment of the pump assembly with regard to the arrangement of the pressure relief valves 72. These have the same hydraulic function as with reference to Fig. 3 However, they are arranged in the main body 60 of the first subassembly 56. This increases the overall length of the first subassembly 56. In order to achieve the highest possible number of identical parts in all variants of the compact axle, given the already large variety of possible variants, the design according to Fig. 3 preferred.

[0065] It should be noted that immediately to the right of the pressure relief valves 72 in Fig. 4 the pressure in the fluid chamber of the volume compensation assembly is applied. The electric motor is designed as a so-called oil-filled motor, whose entire interior is filled with hydraulic fluid. The hydraulic fluid is therefore selected so that it does not interfere with the function of the electric motor. In particular, it is electrically non-conductive.

[0066] Fig. 5 shows a longitudinal section of the volume compensation assembly 90 and the adjacent motor assembly 80. In Fig. 3 Firstly, two further threaded screw connections 20 can be seen, which are shown in the figure with reference to Fig. 2 are designed according to the basic principle explained. A threaded screw connection 20 is arranged between the second and third tubular components 82; 83 of the motor assembly 80. Another threaded screw connection 20 is arranged between the third tubular component 83 and the base body 95 of the volume compensation assembly 90.

[0067] In Fig. 5 The second rotary bearing 86, with which the motor shaft 81 is rotatably mounted, can be seen. A rotary encoder 87 is arranged in the area of this rotary bearing 86, with which the angle of rotation of the motor shaft 81 can be measured. The corresponding measured value is used to electronically control the currents in the stator 84. It should be noted that the aforementioned current control is also possible without the rotary encoder 87.

[0068] As already mentioned, the entire interior of the motor assembly 80 forms part of the fluid chamber 91 of the volume compensation assembly 90. In order for the pressure fluid to reach all areas of this interior, several bores 105 are provided, which enable a corresponding fluid exchange.

[0069] On the fourth tubular component is the Fig. 1 visible electrical connection (No. 18 in Fig. 1 ). This preferably has a defined orientation relative to the second force introduction means 12' in the form of a ball joint, specifically with regard to the rotational position with respect to the longitudinal axis 13. This can be achieved by providing a spacer between the longitudinal end face (No. 27 in Fig. 2 ) and the counter surface (No. 28 in Fig. 2 ) at least one spacer disc is installed, the thickness of which is selected during assembly so that the desired rotational position is achieved.

[0070] The gas chamber 92 of the volume compensation assembly 90 has a small volume in this case. This is due to the fact that the actuator assembly is designed as a double-acting cylinder, so that the total volume of hydraulic fluid in the actuator assembly is essentially constant regardless of the position of the movable component. In this case, the volume compensation assembly 90 only needs to compensate for volume changes in the hydraulic fluid, which may result, for example, from a temperature change or internal leaks. If the actuator assembly is designed as a differential cylinder, the gas chamber is preferably considerably larger.

[0071] In this case, the gas chamber 92 is fluid-tightly separated from the liquid chamber 91 by a membrane 93. The membrane 93, which is pot-shaped in this case, is made of an elastomer, for example, so that it can deform elastically to compensate for a change in the volume of the pressure fluid in the liquid chamber 91.

[0072] The gas chamber 92 is filled with a gas, which is preferably dry nitrogen. This gas can be supplied by means of a (in Fig. 5 (not visible) filling valve, which is housed in the base body 95. The membrane 93 is protected from damage by a substantially rigid perforated plate 94. The perforated plate 94 is designed as a flat plate of constant thickness, with a plurality of holes penetrating it in the direction of the longitudinal axis 13.

[0073] The membrane 93 with the perforated plate 94 is fixed using a separate clamping ring between the longitudinal end face (No. 27 in Fig. 2 ) and the counter surface (No. 28 in Fig. 2 ) to the associated threaded screw connection 20 and thus held firmly.

[0074] The one-piece base body 95 of the volume compensation assembly 90 is pot-shaped, tightly sealing the associated longitudinal end face of the third tubular component 83. A second force transmission means 12' is arranged on its end face facing outwards in the direction of the longitudinal axis 13, which is designed as a ball joint in the present case. However, it can also be in the form of pivot pins according to the Fig. 1 shown other second force introduction means (No. 12 in Fig. 1 ). It goes without saying that only one of the second force transmission means explained above is used to transmit forces. Reference symbol

[0075] 10 hydraulic compact axle 11 first force introduction means 12 second force introduction means (first embodiment) 12 second force introduction means (second embodiment) 13 longitudinal axis 14 pivot axis 15 pivot pin 16 tool engagement means 17 center of gravity 18 electrical connection 20Threaded screw connection 21Internal thread 22External thread 23Circular cylindrical surface 24Centering 25Static seal 26Sealing ring 27Longitudinal end face 28Counter face 29Chamfer 40 Actuator assembly 41 Moving component 42 Guide 43 First pressure chamber 44 Second pressure chamber 45 Air chamber 46 Fourth tubular component 47 Piston 50 Pump assembly (first embodiment) 50 Pump assembly (second embodiment) 51 Pump 52 Internal gear 53 External gear 54 Check valve 55 First tubular component 56 First subassembly 57 Displacement chamber 58 Cylindrical pin (anti-twist device) 59 Filler piece 60 Main body of the first subassembly 61 Bore 62 Cover 70Valve assembly 71Valve block (additional component) 72Pressure relief valve 80Motor assembly 81Motor shaft 82Second tubular component 83Third tubular component 84Stator 85Rotor 86Rotary bearing 87Rotary encoder 88Cooling fin 89Bore 90Volume compensation assembly 91Liquid chamber 92Gas chamber 93Diaphragm 94Perforated plate 95Base body 96Clamping ring 101first component 102second component 103gap 104coupling 105bore

Claims

1. Hydraulic compact axle (10) comprising an actuator assembly (40), a pump assembly (50; 50'), a motor assembly (80) and a volume compensation assembly (90), which are each arranged concentrically with respect to a longitudinal axis (13), wherein the actuator assembly (40), the pump assembly (50; 50'), the motor assembly (80) and the volume compensation assembly (90) are each embodied as a separate assembly, preferably as a separately preassemblable assembly, wherein said assemblies (40; 50; 50'; 80; 90) are arranged in a row along the longitudinal axis (13), wherein they are fastened to one another exclusively in pairs at their ends, wherein the actuator assembly (40) is arranged at one end of said row, characterized in that said assemblies (40; 50; 50'; 80; 90) are arranged in a row along the longitudinal axis (13) in the sequence: actuator assembly (40), pump assembly (50; 50'), motor assembly (80) and volume compensation assembly (90), wherein all of said assemblies (40; 50; 50'; 80; 90) are in each case screwed to one another in pairs via a threaded screw connection (20), wherein the threaded screw connection (20) in each case comprises an internal thread and an external thread (21; 22), which are formed concentrically with the longitudinal axis (13), wherein they are screwed to one another.

2. Hydraulic compact axle (10) according to Claim 1, wherein a centring means (24) is in each case arranged directly adjacent to the at least one threaded screw connection (20), preferably to all the threaded screw connections (20), wherein the centring means (24) in each case comprises two circular-cylindrical surfaces (23), which are formed concentrically with the longitudinal axis (13), wherein they bear against one another.

3. Hydraulic compact axle (10) according to Claim 2, wherein a diameter of the circular-cylindrical surfaces (23) is preferably smaller than an internal diameter of the associated internal thread (21), wherein the centring means (24) is arranged at the longitudinal end of the component (102) of the threaded screw connection (20) with the external thread (22).

4. Hydraulic compact axle (10) according to either of Claims 2 and 3, wherein a static seal (25) is arranged in the region of the centring means (24), said static seal preferably comprising a sealing ring (26), which is arranged concentrically with the longitudinal axis (13).

5. Hydraulic compact axle (10) according to one of the preceding claims, wherein at least one of said assemblies (40; 50; 50'; 80; 90), preferably all of said assemblies (40; 50; 50'; 80; 90), is / are each provided with tool engagement means (16), in particular with at least one flat, wherein the tool engagement means (16) are designed such that the respective threaded screw connection (20) can be tightened and / or released.

6. Hydraulic compact axle (10) according to one of the preceding claims, wherein the component (102) of the threaded screw connection (20) with the external thread (20) has a longitudinal end surface (27), which is oriented perpendicular to the longitudinal axis (13) and is clamped with an adapted mating surface (28) on the other component (101) of the threaded screw connection (20) by means of the respective threaded screw connection (20).

7. Hydraulic compact axle (10) according to one of the preceding claims, wherein the pump assembly (50; 50') comprises a first tubular component (55), which is concentric with respect to the longitudinal axis (13) and is a constituent part of at least one associated threaded screw connection (20), wherein at least one variable-volume displacement space (57) of a respective pump (51) is completely delimited by a separately preassemblable first subassembly (56), wherein the first subassembly (56) is received in the first tubular component (55) so as to be rotatable with respect to the longitudinal axis (13), wherein the first subassembly (56) is secured, with respect to rotation about the longitudinal axis (13), to a further component (71), which is fixedly connected to the first tubular component (55).

8. Hydraulic compact axle (10) according to one of the preceding claims, wherein the volume compensation assembly (90) completely delimits a gas space (92), wherein it closes the end of a directly adjacent tubular component (83) in a liquid-tight manner, wherein the volume compensation assembly (90) preferably comprises a force-introducing means (12').

9. Hydraulic compact axle (10) according to one of the preceding claims, wherein the hydraulic compact axle (10) comprises a first and a second force-introducing means (11; 12; 12'), wherein the first force-introducing means (11) is arranged on a movable component (41) of the actuator assembly (40), wherein the second force-introducing means (12; 12') is arranged so as to be spaced apart from the first force-introducing means (11) in the direction of the longitudinal axis (13), wherein at least the second force-introducing means comprises a pair of pivot pins (15), which are arranged concentrically with a common pivot axis (14) on opposite sides of the longitudinal axis (13), wherein the pivot axis (14) is oriented perpendicular to the longitudinal axis (13).

10. Hydraulic compact axle (10) according to Claim 9, wherein the pivot axis (14) and the longitudinal axis (13) intersect or cross in the vicinity of a centre of mass (17) of the hydraulic compact axle (10), preferably in the region of the pump assembly (50; 50'), most preferably in the region of a valve assembly, which is a constituent part of the pump assembly (50; 50').

11. Hydraulic compact axle (10) according to one of the preceding claims, wherein the motor assembly (80), the volume compensation assembly (90), the actuator assembly (40) and / or the pump assembly (50; 50') are each provided with a plurality of cooling fins (88) on their external circumferential surface, wherein the cooling fins (88) are preferably spaced apart from one another via interspaces, wherein the interspaces are most preferably open towards the external surroundings.

12. Hydraulic compact axle (10) according to one of the preceding claims, wherein the actuator assembly (40) is designed as a hydraulic cylinder, wherein an average external diameter of the actuator assembly (40) is smaller than an average external diameter of the remaining assemblies (50; 50', 80; 90).