Electrohydraulic drive system

Abstract

The invention relates to an electrohydraulic drive system comprising an electric motor (10) and a fluid pump (12) that can be driven by the electric motor (10) via an output shaft (14) and has a rotor (16), which is rotatably guided in a stator (18) surrounded by a housing (22) of the electric motor (10), and a pump housing (24). The invention is characterized in that a damping block (26) is inserted between the electric motor housing (22) and the pump housing (24) in order to reduce noise emissions, said damping block being made of a metal material in a solid construction, and the output shaft (14) passes through the damping block, said output shaft being guided in the damping block (26) in a bearing point (28) which is completely surrounded by the damping block (26) and the bearing shell of which is directly supported against the damping block.

Description

[0001] Electro-hydraulic drive system

[0002] The invention relates to an electro-hydraulic drive system with an electric motor and with a fluid pump which can be driven by the electric motor via an output shaft, which has a rotor which is rotatably guided in a stator which is enclosed by a housing of the electric motor and which has a pump housing.

[0003] EP 2 921 703 A2 discloses a motor-pump unit as a drive system of this type, comprising an electric motor and a reversible internal gear machine having a multi-part housing in which an externally toothed pinion and an internally toothed ring gear are arranged. A free space is formed between said gears, in which a multi-part filler piece is arranged, comprising a plurality of radially movable radial sealing segments, between which a radial gap is formed. An axially movable axial sealing plate is arranged between axial end faces of the gears and a housing part of the housing. The sealing plate has a sealing plate control groove that is open toward the end faces of the gears and can be pressurized with pressure medium. The sealing plate control groove is open toward the radial gap and is located directly opposite it.The pinion segment and / or the ring gear segment have a transversely extending radial sealing segment control channel which can be pressurized with pressure medium and which is open towards the radial gap and which opens directly into the radial gap.

[0004] With the ongoing transition to so-called e-mobility, combustion engines are also being replaced by synchronous electric motors, with both the hydrostatic drives for the traction drive of a work machine and the drive for the associated working hydraulics being powered by synchronous motors. Combustion engines have previously been the dominant factor in terms of vehicle noise generation, but with the transition to electric drive components, fluid or hydraulic pumps are now increasingly becoming the determining factor in the noise level of vehicles in which such drive systems are installed. While an electric drive is therefore extremely quiet, the add-on components, such as fluid pumps, are now the ones that cause the disturbing noise.

[0005] Based on this prior art, the invention therefore seeks to create an electro-hydraulic drive system that operates quietly with all its components. This object is achieved by a drive system having the features of patent claim 1 in its entirety.

[0006] Because, according to the characterizing part of patent claim 1, a damping block is inserted between the electric motor housing and the pump housing to reduce noise emissions, which damping block is made of a solid metal material and is penetrated by the output shaft, which is guided in an eager point in the damping block, which is completely enclosed by the damping block and which is supported with its eager shell directly on the damping block, a significant, sustainable reduction in the noise level for the entire drive system is achieved.The damping block mentioned, which is correspondingly solid and consists in particular of a steel material, represents an effective radial and axial noise reduction measure, and this arrangement fully meets the specific noise requirements of drive systems with synchronous motors, which in this respect replace loud combustion engines as primary noise damping. In particular, a portion of the bearing noise during operation of the output shaft is introduced directly into the damping block. It will be surprising to an average person skilled in the art in the field of such drive systems that the drive system solution according to the invention achieves largely noise-emission-free operation, particularly since metal materials are used for noise damping instead of the otherwise conventional elastomer materials such as rubber.

[0007] Furthermore, the damping block effectively separates the hydraulic and electrical components of the drive system, achieving fluidic decoupling between the hydraulic and electrical units. Since a certain degree of contamination and water content always occur in the operating fluid when hydraulic equipment is used, in this case during operation of the fluid pump, this decoupling ensures short-circuit-proof operation for the electric motor in all cases. Furthermore, the separation of hydraulic and electrical components allows for improved cooling for each of these components.

[0008] Furthermore, a modular design for the drive system as a whole, with its components—electric motor and fluid pump—is achieved, allowing the drive system to be easily adapted to changing performance requirements, for example, when a larger displacement is needed. Even in this case, the damping block achieves a more than acceptable noise level for the entire drive system. In particular, the damping block can be used as a standardized basic component, to which various types of electric motors and fluid pumps can be connected on opposite sides of the damping block. This has no equivalent in the state of the art.

[0009] In a preferred embodiment of the electro-hydraulic drive system, it has proven advantageous for the damping block to span a prism toward the surroundings, preferably in the form of a six-sided prism, particularly preferably in the form of an eight-sided prism. This prismatic setup results in a multitude of refractive edges at which the noise generated during operation can be refracted accordingly, leading to a significant reduction in noise emissions.

[0010] In another particularly preferred embodiment of the electro-hydraulic drive system according to the invention, the output shaft has a coupling point at its one free end region for connecting a drive shaft of the fluid pump, which coupling point is enclosed by the damping block, and the bearing point for the output shaft and the coupling point of the drive shaft for the fluid pump are incorporated into the damping block on opposite end faces of the damping block. Because the coupling point is incorporated into the damping block, the vibrations occurring during operation of the shafts, which can also cause noise emissions, are correspondingly dampened.

[0011] In a further preferred embodiment of the electro-hydraulic drive system according to the invention, the damping block is provided with individual fluid guides that serve to supply and discharge fluid, such as a hydraulic or cooling medium, which exerts a damping effect as it flows through the damping block. In addition to the additional damping effect, this creates short paths for the supply and discharge of hydraulic and / or cooling media, which proves to be energetically advantageous for the drive system as a whole.

[0012] From a vibration-technical point of view and therefore low-noise, it has proven to be effective if the axial length of the damping block in the direction of the output shaft corresponds approximately to the axial length of a pump housing of the fluid pump.

[0013] In a further preferred embodiment of the electro-hydraulic drive system, the output shaft is supported by a further bearing point, which is accommodated at the opposite end region to the one bearing point in a cover part of the electric motor, which closes the electric motor on the side facing away from the damping block. Preferably, one of the bearing points for the output shaft is integrated into a shield-like cover part of the electric motor housing, and the other bearing point is located in the end part formed by the damping block. In this way, a secure absorption of longitudinal and transverse forces on the output shaft of the electric motor is achieved by means of the individual bearing points, whereby only two bearing points in total are sufficient for reliable support and a type of "flying bearing."This bearing arrangement, with one bearing in the damping block and another in the shield-like cover, shields each bearing from the environment, ensuring a low-noise drive for the fluid pump via the electric motor's output shaft, even in the area of ​​the bearings. In particular, bending vibrations of the output shaft are avoided by mounting the pump's cylinder drum at the point of application of the resulting force.

[0014] It has proven particularly advantageous that both an end wall of the electric motor housing and an end wall of the pump housing are flush with opposite ends of the damping block, ensuring that any vibrations are transmitted from both sides to the damping block, which thus occupies a central position for the overall drive system as a damping element. Furthermore, the damping block also provides a centrally located assembly aid for the secure assembly of the entire drive system with its various components.

[0015] For a good damping effect, it has also proven advantageous if the outer diameter of the electric motor housing is selected to be larger than the outer diameter of the pump housing, so that the pump, even during operation, is well supported by the damping electric motor housing.

[0016] In another particularly preferred embodiment of the electro-hydraulic drive system, the damping block tapers conically at the bearing point toward a receptacle in the electric motor housing, which, together with adjacent conical wall sections of the electric motor, defines a funnel-shaped sound chamber. Thanks to the funnel-shaped sound chamber, any sound waves can be dampened in a targeted manner, thus preventing noise emissions.

[0017] In a further preferred embodiment of the electro-hydraulic drive system, the damping block is designed as a stator, and the housing of the electric motor and the pump housing are connected to the stator formed in this way on opposite sides. In this way, the drive system according to the invention can be retrofitted, within a broad framework, to almost any hydraulic work machine, and any noise-generating vibrations of the drive system as a whole can be specifically diverted into the substructure, such as a machine bed or the like, via the stator base part. For the electro-hydraulic drive system, it can preferably be provided that in reversing operation, the fluid pump then serves as a hydraulic motor, which drives the electric motor to generate power in generator mode.In this way, 4-quadrant operation is possible, with the pump assuming a hydraulic motor function and the synchronous motor acting as a power generator. It is particularly advantageous if the drive system's component design allows both of these operating options to be combined into a single unit, allowing various applications in the operation of mobile machines to be covered with just one component.

[0018] The fluid pump is preferably a swash plate machine whose individual delivery pistons are supported at one end on a stationary swash plate, wherein the individual delivery pistons are guided in a successive sequence from different piston positions to perform a pumping movement in piston chambers of a housing part, which are rotatably carried by the output shaft, in axial travel directions parallel to the longitudinal axis of the output shaft. The use of a swash plate machine or axial piston machine has proven to be functionally reliable because the individual delivery pistons are guided with low friction for their respective axial pumping movement in the fluid of an associated piston chamber of a pump housing part. External and internal gear pumps can also be used as fluid pumps, however, they are generally less prone to noise emissions during operation despite the tooth engagement.

[0019] The housing section with the individual piston chambers and the delivery pistons accommodated therein can be preloaded toward the swash plate by means of an energy storage device, preferably in the form of a compression spring. This energy storage device allows tolerances during operation of the fluid pump to be compensated for, but in particular, it serves to ensure contact between the cylinder drum and the control plate during pressureless operation, in any position of the pump in the chamber.

[0020] Alternatively, instead of a one-piece output shaft, the output shaft and a separate drive shaft of the fluid pump can be coupled via a coupling, such as a splined shaft. This allows for simple assembly of the entire drive system, and the fluid pump, together with its drive shaft, can be easily removed from the damping block and the output shaft guided within it for maintenance or repair purposes by simply pulling it off. This also allows for a seamless replacement of an old fluid pump with a new one.

[0021] If the output shaft is preferably led out via an axially arranged through opening on the free end of the pump housing, and carries a coupling piece at its free end, which is led out of the pump housing, preferably designed as a further splined shaft toothing for coupling third components, such as a further fluid pump, the pump output for the drive system can be increased even further in a low-noise manner by interconnecting several fluid pumps within the framework of an overall pumping concept.

[0022] In the following, the electro-hydraulic drive system according to the invention is explained in more detail using an embodiment according to the drawing, wherein the only figure shows a longitudinal section through the essential components of such a drive system in a schematic representation.

[0023] The electro-hydraulic drive system shown in the figure comprises, as a whole, an electric motor 10 and a fluid pump 12, which can be driven by the electric motor 10 via an output shaft 14. The output shaft 14 has a rotor 16, which is rotatably guided in a stator 18 with a coil winding 20 in a manner typical for an electric motor 10. The stator 18 and the coil winding 20, respectively, are enclosed by a cylindrical housing 22 of the electric motor 10.

[0024] To reduce noise emissions of any kind, a solid, metallic damping block 26 is inserted between the electric motor housing 22 and a pump housing 24. The output shaft 14 passes completely through the damping block and is guided in a bearing 28 in the damping block 26. The damping block 26 is essentially hollow-cylindrical in design to allow the output shaft 14 to pass through. As can be seen from the figure, the axial length of the damping block 26, viewed in the direction of the longitudinal axis 30 of the output shaft 14, is approximately the same as the axial length of the pump housing 24 in the same alignment as the longitudinal axis 30. In particular, the electric motor housing 22, the pump housing 24, and the damping block 26 are arranged concentrically to the longitudinal axis 30. In particular, the hollow damping block 26 forms a prism with a plurality of refracting edges towards the environment.

[0025] Both an end wall 32 of the electric motor housing 22 and an end wall 34 of the pump housing 24 are flush with opposite end faces 36 and 38 of the damping block 26, respectively. For this purpose, a step 40 of reduced diameter is provided on the end wall 36 of the damping block 26, which at this point is overlapped by the cylindrical end region of the electric motor housing 22. Furthermore, a circumferential wall extension 42 is provided in the corresponding end face 36, which projects in the direction of the rotor 16 and accommodates the bearing point 28. The flat end wall 34 of the pump housing 34, on the other hand, is fixedly arranged flat on the opposite end face 38 of the damping block 26 in a detachable manner, for example, by being firmly screwed. In this respect, the damping block 26 forms a type of bearing plate or connecting plate for the entire device.For a favorable vibration introduction with a corresponding damping effect, it has proven advantageous to select the outer diameter of the electric motor housing 22 larger than the outer diameter of the pump housing 24, wherein the outer diameter of the damping block 26 lies between the aforementioned outer diameters.

[0026] The output shaft 14 is mounted at the rear via a further bearing point 44, which is received at the opposite end region to the one bearing point 28 in a shield-like cover part 46 of the electric motor 10, which hermetically seals this electric motor 10 from the environment on its side facing away from the damping block 26.

[0027] The wall extension 42 is tapered in the direction of the longitudinal axis 30 of the output shaft 14 and, together with adjacent parts of the coil winding 20, defines a funnel-shaped sound chamber 48 suitable for diverting any sound emissions from the fluid pump 12 toward a central receiving chamber 50 for the output shaft 14; a chamber 50 that is sound-insulated from the environment by the housing 22 and the stator 18. It is also advantageous that the central receiving chamber 50 opens toward its other end into another sound chamber 52 of comparable conicity and spatial "capacity" to the first sound chamber 48, which provides a further dampening option with regard to possible "accumulated" sound waves in the central receiving chamber 50.

[0028] As the figure further shows, this additional sound chamber 52 expands in the direction of the hollow-cylindrical cover part 56 with the additional bearing point 44. The cover part 46 is, as shown, firmly but detachably connected to the circumferential shell of the housing 22 and has two through-holes on the outer wall side for the electrical connection 54 in the form of two supply lines between the coil winding 20 and a power supply source (not shown in detail). Furthermore, as viewed in the direction of the figure, the underside of the damping block 26 has a web-like, downwardly projecting stand device 56, by means of which it is possible to support or fasten the drive system as a whole via the damping block 26 to a third component (not shown), such as a machine part, at the base.In this way, vibration-related noise emissions can also be effectively diverted with a dampening effect via the stator device 56 into an adjacent machine part. As shown, the damping block 26 can be penetrated by passages or openings 58, which serve to supply and discharge pump fluid from the fluid pump 12, which usually in the form of a hydraulic medium also exerts a dampening effect when flowing through the damping block 26. Also, although not shown in detail, cooling fluid can be supplied to the electric motor 10 during operation. Likewise, a coolant supply for the fluid pump 12 would be possible in this way. Since the stator component 56 forms a type of bearing interface for the pump 12 and the electric motor 10, a balanced mounting is achieved, which also proves advantageous with regard to the suppression of noise emissions.

[0029] The structure of the fluid pump 12, which in the present embodiment is designed as a so-called swash plate machine, will now be explained in more detail. Such fluid pumps can be found in a variety of designs in the prior art, for example in DE 10 2013 008 678 A1, so that the fluid pump 12 will only be described in broad outline, insofar as this is necessary for understanding the invention. The axial piston pump in swash plate design shown in the figure has a swash plate 60 which is stationary in the pump housing 24 and is held in position by means of at least one cylindrical pin 62. Since in the present embodiment the swash plate 60 is not movable, unlike in DE 10 2013 008 678 A1, a type of constant displacement pump is realized as the fluid pump 12 with a constant delivery volume.Furthermore, the fluid pump 12 has a cylindrical pump housing part 64, which is rotationally connected to the output shaft 14 by means of a spline 66 and is rotatably driven by the output shaft. The corresponding outer surface is rotatably guided along a third bearing point 71 in the pump housing 24.

[0030] As the sectional plane above the longitudinal axis 30 in the figure shows, individual piston chambers 68 are introduced into the housing part 64, in which individual associated delivery pistons 70 are guided so as to be longitudinally movable. For the sake of simplicity, only one piston chamber 68 with an associated delivery piston 70 is shown in the figure, with several such delivery pistons 70 being distributed concentrically around the longitudinal axis 30 at equal distances from one another around the output shaft 14. Due to the inclined position of the swash plate 60, the delivery piston 70 shown is in its lowest fluid-discharging delivery position, whereas on the side arranged diametrically opposite the longitudinal axis 30 of the output shaft 14, a delivery piston is accommodated in the housing part 64 in its uppermost position, in which the maximum possible delivery volume of the fluid pump 12 is established in the associated piston chamber 68.In the lowest position, as shown for the upper delivery piston 70, the amount of fluid absorbed in this way is pushed out again during pumping operation from the pump housing part 64 to supply a hydraulic consumer not shown in detail, such as a working cylinder.

[0031] The respective fluid-intake and fluid-discharge delivery pistons 70 are connected by their respective piston heads of each piston chamber 68 to corresponding fluid supply and discharge lines, which have been omitted from the figure for simplicity and clarity. In addition to fluid supply and discharge via the passages 58 in the damping block 26, it is also possible to attach corresponding lines via the exposed outer end face of the pump housing 24, if necessary, and thus connect the pump 12 to a supply circuit (not shown).

[0032] Thanks to the aforementioned splined shaft toothing 66, the pump housing part 64 is guided coaxially to the longitudinal axis 30 on the output shaft 14, and thanks to an energy accumulator in the form of a compression spring 72, the housing part 64 with its individual delivery pistons 70 is preloaded in the direction of the swash plate 72 via an additional contact sleeve 74. The compression spring 72 is supported with one free end on the contact sleeve 74 in the direction of the swash plate 60, and with its other free end on a housing-side receiving space of the pump housing part 64, which faces the splined shaft toothing 66.

[0033] The output shaft 14 according to the figure is formed in one piece and terminates at one of its free ends in a further spline 76. The one-piece output shaft 14, which extends out of the pump housing 24 at its end via an axially arranged through-opening 77, is guided over the two bearing points 28 and 44, which are held in position in the usual way by means of retaining rings and which can consist of bearings of a conventional design, such as a ball bearing. However, it is also possible to replace an individual bearing point with a bearing bush (not shown in detail) with good sliding properties. If the output shaft 14 with its further spline 76 projects beyond the end wall of the pump housing 24, a seal 78 is formed at this point by a constriction in the swash plate 60.In an embodiment not shown in detail, however, the described projection with the further spline toothing 76 can also be dispensed with when only one fluid pump 12 is used, and in this respect the pump housing 24 would have to be provided with a cover plate in a sealing manner on its end face which is freely facing outwards.

[0034] With the drive system according to the invention shown in the figure, a so-called reversing or four-quadrant operation is also possible, in which the fluid pump 12 functions as a hydraulic motor and the output shaft 14, which is then driven by the fluid pump 12, generates a changing electric field via its rotor 16 in the stator 18, so that the electric motor 10 now generates electrical current in generator mode, which can be delivered to an electrical consumer (not shown) in the usual way via the electrical connection 54. Instead of a fluid pump 12 in swash plate design, another fluid pump, not shown in detail, can also be used, for example in the form of an internal and / or external gear machine. Ultimately, however, in the present solution, the delivery pistons 70 are guided within the piston chambers 68 and are thus encapsulated therein, which contributes to noise reduction.

[0035] The converted electro-hydraulic power results from the drive speed and the pressure in the fluid-discharging working line (not shown in detail), plus a possible leakage oil volume flow, which is discharged from the pump housing 24 via at least one separate leakage oil connection 80, which is closed by a plug before commissioning, as shown in the figure. All components used in the drive system are designed, preferably in a solid construction, this particularly applies to the solid damping block 26, so that low-noise operation is achieved due to the very rigid construction. If necessary, further measures can be taken to reduce noise, for example the use of additional damping inserts (not shown) in the housings 22 and 24.

Claims

Patent claims Electro-hydraulic drive system with an electric motor (10) and with a fluid pump (12) which can be driven by the electric motor (10) via an output shaft (14), which has a rotor (16) which is rotatably guided in a stator (18) which is enclosed by a housing (22) of the electric motor (10) and which has a pump housing (24), characterized in that in order to reduce noise emissions between the electric motor housing (22) and the pump housing (24) a damping block (26) is inserted, which is formed in a solid construction from a metal material and through which the output shaft (14) passes, which is guided in a bearing point (28) in the damping block (26), which is completely enclosed by the damping block (26) and which is supported with its bearing shell directly on the damping block.Electro-hydraulic drive system according to claim 1, characterized in that the damping block (26) forms a prism with respect to the surroundings, preferably in the form of a six-sided prism, particularly preferably in the form of an eight-sided prism. Electro-hydraulic drive system according to one of the preceding claims, characterized in that the output shaft (14) has, at its one free end region, a coupling point for connecting a drive shaft of the fluid pump (12), which coupling point is enclosed by the damping block (26), and that the bearing point (28) for the output shaft (14) and the coupling point of the drive shaft for the fluid pump (12) are incorporated into the damping block (26) on opposite end faces of the latter. Electro-hydraulic drive system according to one of the preceding claims, characterized in that the damping block (26). is penetrated by individual fluid guides (58) which serve for the supply and removal of fluid, such as a hydraulic or cooling medium, which exert a damping effect when flowing through the damping block (26).

5. Electro-hydraulic drive system according to one of the preceding claims, characterized in that the axial length of the damping block (26) seen in the direction of the output shaft (14) corresponds approximately to the axial length of a pump housing (24) of the fluid pump (12).

6. Electro-hydraulic drive system according to one of the preceding claims, characterized in that the output shaft (14) is mounted via a further bearing point (44) which is received at the opposite end region to the one bearing point (28) in a cover part (46) of the electric motor (10) which closes the electric motor (10) on its side facing away from the damping block (26).

7. Electro-hydraulic drive system according to one of the preceding claims, characterized in that both an end wall (32) of the electric motor housing (22) and an end wall (34) of the pump housing (24) are flush with opposite end faces (36, 38) of the damping block (26).

8. Electro-hydraulic drive system according to one of the preceding claims, characterized in that the outer diameter of the electric motor housing (22) is selected to be larger than the outer diameter of the pump housing (24).

9. Electro-hydraulic drive system according to one of the preceding Claims, characterized in that the damping block (26) at the bearing point (28) in the direction of a receptacle in the housing (22) of the electric motor (10), which, together with adjacent conical wall parts of the electric motor (10), defines a funnel-shaped sound chamber (48).

10. Electro-hydraulic drive system according to one of the preceding Claims, characterized in that the damping block (26) is designed in a stator construction and that the housing (22) of the electric motor (10) and the pump housing (24) are connected to the stator (56) formed in this way on opposite sides.

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