Electro-hydraulic drive system

Abstract

The present invention relates to an electro-hydraulic drive system having an electric motor (10) and a fluid pump (12) drivable by the electric motor (10) via an output shaft (14), wherein the output shaft has a rotor (16), the rotor is rotatably guided within a stator (18), the stator is surrounded by a housing (22) of the electric motor (10), and the fluid pump has a pump housing (24). According to the invention, in order to reduce noise emission, a damping block (26) is inserted between the electric motor housing (22) and the pump housing (24), the damping block is made of a metallic material with a solid structure, and is penetrated by the output shaft (14), the output shaft being guided within a bearing location (28) in the damping block (26), completely surrounded by the damping block (26), and the bearing shell thereof being directly supported by the damping block.

Description

Technical Field

[0001] The present invention relates to an electro-hydraulic drive system having an electric motor and a fluid pump, wherein the fluid pump can be driven by the electric motor via an output shaft, has a rotor, the rotor is rotatably guided within a stator, the stator is surrounded by a housing of the electric motor, and the fluid pump has a pump housing.

Background Art

[0002] European Patent Application Publication No. 2921703 (Patent Document 1) discloses, as such a drive system, a motor-pump unit having an electric motor and a reversible internal gear machine, the motor-pump unit having a housing divided into several parts, inside which an externally toothed pinion and an internally toothed hollow wheel are arranged. A gap is formed between the above-described gears, and several divided filling pieces are arranged therein, the filling pieces having a plurality of radially movable radial seal segments, and a radial gap is formed between them. An axially movable axial seal plate is arranged between the axial end face of the gear and the housing part of the housing, the radial-axial seal plate having a seal plate control groove open towards the end face of the gear, which can supply pressure means, the seal plate control groove being open towards the radial gap and directly facing it. The pinion segment and / or the hollow wheel segment have a laterally extending radial seal segment control passage, which can supply pressure means, the radial seal segment control passage being open towards the radial gap and directly communicating into the radial gap.

[0003] The so-called switch to e-mobility is accelerating, and furthermore, the internal combustion engine is being replaced by an electric synchronous motor, and both the hydrostatic drive for the traction drive of the machine tool and the drive for the attached working hydraulic machine are driven by such a synchronous motor. The internal combustion engine has hitherto been the main factor regarding the noise generation of vehicles, but by switching to electric drive components, fluid pumps or hydraulic pumps are now becoming decisive factors for the noise level of vehicles incorporating this type of drive system. Therefore, the electric drive operates with low noise as mentioned, but now, mounting components such as fluid pumps are causing troublesome noise.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Based on this prior art, the problem of the present invention is to provide an electro-hydraulic drive system with low noise for all its components. This problem is solved by a drive system having the features of claim 1 as a whole.

Means for Solving the Problems

[0006] According to the part showing the features of claim 1, in order to reduce noise emission, a damping block is inserted between the electric motor housing and the pump housing. The damping block is made of a metal material with a solid structure, and the output shaft passes through the damping block. The output shaft is guided within a bearing location in the damping block, completely surrounded by the damping block, and directly supported by the damping block by its bearing shell. In this way, a continuous and significant reduction in the noise level for the entire drive system is obtained. The mentioned damping block, which is appropriately solid and especially made of steel material, is an effective radial and axial noise countermeasure for reducing noise. Such an arrangement fully meets the special noise requirements for a drive system with a synchronous motor and, to that extent, is a substitute for the noisy internal combustion engine as the first noise attenuation. In particular, a part of the bearing noise in the driving of the output shaft is directly introduced into the damping block. Surprisingly for an average person skilled in the art in this field of drive systems, by the solution means of the drive system according to the present invention, a drive with almost no noise emission is achieved. In particular, for noise reduction, a metal material is used instead of an ordinary general elastomer material such as rubber.

[0007] Furthermore, since effective isolation is performed by the damping block between the hydraulic part and the electrical part of the drive system, a fluid separation is performed between the hydraulic unit and the electrical unit. Here, when using hydraulic drive means within the framework of driving a fluid pump, to some extent, dirt and water components always occur in the drive fluid. Therefore, by the above-mentioned separation, a short-circuit-free drive for the electric motor is achieved in each case. Furthermore, by separating the hydraulic and the electrical, the cooling is improved for each of these components.

[0008] Furthermore, for the drive system as a whole having an electric motor and a fluid pump as its components, a modular structure is obtained, so that this drive system can be easily adapted to changing output requirements, for example when a larger stroke volume is required. Then, even in such cases, a damping block provides a noise level that is acceptable and above for the entire drive system. In particular, the damping block can be used as a standardized base component, to which various types of electric motors and fluid pumps can be connected on opposite sides of the damping block. This is something unseen in the prior art.

[0009] In a preferred embodiment of the electro-hydraulic drive system, it has been shown to be preferable if the damping block forms a prism that extends towards the surroundings, preferably in the shape of a hexagonal prism, particularly preferably in the shape of an octagonal prism. Such prism formation results in a number of refractive edges, and the noise generated during driving can be refracted appropriately at these refractive edges, which clearly reduces the noise emission.

[0010] In another particularly preferred embodiment of the electro-hydraulic drive system according to the present invention, the output shaft has a coupling location for connecting the drive shaft of the fluid pump at one of its free end regions, and this coupling location is surrounded by the damping block, and the bearing location for the output shaft and the coupling location for the drive shaft of the fluid pump are formed in this damping block at the opposite end face of the damping block. By having the coupling location housed within the damping block, vibrations that can also result in noise emission during shaft driving are appropriately damped.

[0011] In another preferred embodiment of the electro-hydraulic drive system according to the present invention, the damping block is penetrated by individual fluid guides, which are used for the supply and discharge of a fluid such as a hydraulic medium or a cooling medium, and the fluid provides a damping effect when flowing through the damping block. In addition to the additional damping effect, a short route for the supply and discharge of the hydraulic medium and / or the cooling medium is formed in this way, and it has been clarified that this is energetically preferable for the drive system as a whole.

[0012] From a vibration technology perspective, and thus to ensure noise reduction, it has been clarified that it is preferable that, when viewed in the direction of the output shaft, the total axial length of the damping block substantially corresponds to the total axial length of the pump housing of the fluid pump.

[0013] In another preferred embodiment of the electro-hydraulic drive system, the output shaft is supported via additional bearing locations, and the bearing locations are accommodated within the cover portion of the electric motor in the terminal region on the side opposite to one bearing location, and the cover portion seals the electric motor on the side opposite to the damping block. In that case, it is preferable that one of the bearing locations for the output shaft is integrated within the shield-shaped cover portion of the electric motor housing, and the other bearing location is integrated within the end formed by the damping block. In this way, the longitudinal and lateral forces applied to the output shaft of the electric motor are reliably absorbed by the individual bearing locations. In this case, here, for reliable support and a certain "floating mounting system", only two bearing locations in total are sufficient. Such an arrangement of bearing locations, having one bearing location within the damping block and an additional bearing location within the shield-shaped cover portion, shields each bearing location from the surroundings, and also ensures a low-noise drive for the fluid pump via the output shaft of the electric motor within the region of the bearing location. In particular, by supporting the cylindrical drum of the pump within the point of application of the applied force, the bending vibration of the output shaft is avoided.

[0014] The end wall of the electric motor housing and the end wall of the pump housing are both flush with and adjacent to opposite end faces of the damping block. As a result, when vibrations occur, they are introduced into the damping block from both sides. Insofar as the damping block occupies a central position for the entire drive system as a damping material, it has been shown to be particularly advantageous. Additionally, a mounting aid located centrally is obtained in order to securely assemble the entire drive system together with various components via the damping block.

[0015] For good damping action, it has further been shown to be preferable if the outer diameter of the electric motor housing is selected to be larger than the outer diameter of the pump housing. As a result, good support is achieved for the pump via the electric motor housing, which damps in this regard even when it is being driven.

[0016] In another particularly preferred embodiment of the electro-hydraulic drive system, the damping block tapers conically in the direction of the receiving portion within the housing of the electric motor at the bearing location, and the damping block, together with the adjacent wall portion of the electric motor, defines a funnel-shaped acoustic chamber. Assisted by the funnel-shaped acoustic chamber, sound waves that may occur are attenuated in a desired manner, thereby preventing noise generation.

[0017] In another preferred embodiment of the electro-hydraulic drive system, the damping block is formed in a stand structure, and the housing of the electric motor and the pump housing are connected to opposite sides of the stand thus formed. In this way, within a roughly configured frame, the drive system according to the invention can be inserted later into almost any hydraulic working machine, and even if vibrations that generate noise in the drive system occur, they can be dissipated as desired through the base portion of the stand as a whole to a base such as the base portion of the machine.

[0018] For an electro-hydraulic drive system, preferably, in reverse drive, the fluid pump can be used as a hydraulic motor, in which case the hydraulic motor performs the work of an electric motor that generates current in generator drive. In this way, four-quadrant drive is achievable, so the pump takes on the hydraulic motor function and the synchronous motor acts as a generator that generates current. In that case, it is particularly effective if the drive system is integrated into one unit from its component design to realize the two drive possibilities mentioned, whereby various applications can be covered by one component unit when driving a mobile working machine.

[0019] The fluid pump is preferably a swashplate machine, and its individual delivery pistons are supported on a fixed swashplate at one end thereof. The individual delivery pistons are guided axially in the piston chambers of the housing part that is rotatably interlocked using an output shaft, parallel to the longitudinal axis of the output shaft, in order to perform the pump movement from different piston positions in a successive order with respect to each other. The use of a swashplate machine or an axial piston machine has been proven to be functionally reliable. This is because the individual delivery pistons are guided without friction in the fluid of the associated piston chambers of the pump housing part for their respective axial pump movement. However, external gear pumps and internal gear pumps are also easily used as fluid pumps, and they tend to generate less noise during operation in principle despite the tooth meshing.

[0020] The housing part having the individual piston chambers and the accommodated delivery pistons is preferably biased in the direction of the swashplate using a tensioning device in the form of a compression spring. The error during the drive of the fluid pump is compensated by the mentioned tensioning device, and the tensioning device is used in particular to ensure contact of the cylinder drum with the control liquid level at each drive position of the pump in the chamber in a pressureless drive.

[0021] Alternatively, instead of an integral output shaft, the output shaft and the independent drive shaft of the fluid pump can be coupled to each other via a coupling such as a splined shaft tooth cut. In that way, easy assembly of the entire drive system becomes possible, and the fluid pump, together with its drive shaft, can be removed for maintenance or repair purposes in a simple manner by pulling it out from the damping block and the output shaft guided therein. In this way, it is also freely possible to replace an old fluid pump with a new one.

[0022] Preferably, the output shaft is led out through a through-opening axially arranged in the free end face of the pump housing, and a coupling piece is supported at its free end, and the coupling piece is led out of the pump housing and is preferably formed as a further splined shaft tooth cut and is used for the attachment of third-party components such as a further fluid pump. As long as it is used, the pump output for the drive system within the framework of the entire transfer concept can be further enhanced in a quiet manner by connecting a plurality of fluid pumps together.

[0023] Hereinafter, the electro-hydraulic drive system according to the present invention will be described in detail with reference to the embodiments shown in the drawings.

Brief Description of the Drawings

[0024]

Figure 1

Modes for Carrying Out the Invention

[0025] The electro-hydraulic drive system shown in the figure generally has an electric motor 10 and a fluid pump 12, and the fluid pump can be driven by the electric motor 10 via an output shaft 14. The output shaft 14 has a rotor 16, and the rotor is rotatably guided within a stator 18 having coil windings 20, such that the rotor is common to the electric motor 10. The stator 18 or the coil windings 20 are surrounded by a cylindrical housing 22 of the electric motor 10.

[0026] To reduce various types of noise generation, a solid metal damping block 26 is inserted between the electric motor housing 22 and the pump housing 24. The damping block is completely penetrated by the output shaft 14, and the output shaft is guided within a bearing location 28 within the damping block 26. The damping block 26 is formed substantially in a hollow cylindrical shape to allow the output shaft 14 to pass through. As is further apparent from the figure, the overall axial length of the damping block 26, viewed in the direction of the longitudinal axis 30 of the output shaft 14, is approximately equal to the overall axial length of the pump housing 24 in the same orientation as the longitudinal axis 30. In particular, the electric motor housing 22, the pump housing 24, and the damping block 26 are arranged concentrically with respect to the longitudinal axis 30. In particular, the hollow damping block 26 forms a prism having a number of refractive edges around its perimeter.

[0027] The end wall 32 of the electric motor housing 22 and the end wall 34 of the pump housing 24 are both flush with and adjacent to the end faces 36 or 38 on opposite sides of the damping block 26. For this purpose, a reduced-diameter step portion 40 is formed on the end wall 36 of the damping block 26, and at this location, the step portion is gripped by the cylindrical end region of the electric motor housing 22. Further, a peripheral wall extension 42 protruding in the direction of the rotor 16 is formed within this end face 36, and the peripheral wall extension houses the bearing location 28. On the other hand, the flat end wall 34 of the pump housing 34 is in flat contact with the opposite end wall 38 of the damping block 26 and is firmly arranged in a removable manner, for example, fixedly screwed. To that extent, the damping block 26 forms a kind of bearing shield or connection plate for the entire device.

[0028] It has been made clear that it is preferable to select the outer diameter of the electric motor housing 22 to be larger than the outer diameter of the pump housing 24 so that vibrations are preferably applied with a corresponding damping effect, and in that case, the outer diameter of the damping block 26 is located between the above-mentioned outer diameters.

[0029] The rear side of the output shaft 14 is supported via a further bearing location 44, and the bearing location is housed in the end region on the opposite side of one bearing location 28 within the shield-shaped cover portion 46 of the electric motor 10, and the cover portion also seals the electric motor 10 airtight against the surroundings on the side opposite to the damping block 26.

[0030] The circumferential wall extension 42 is formed to taper and extend in a conical shape in the direction of the longitudinal axis 30 of the output shaft 14, and together with the portions of the adjacent coil windings 20, defines a funnel-shaped acoustic chamber 48, which is suitable for guiding acoustic emissions from the fluid pump 12 towards the central receiving chamber 50 for the output shaft 14 in case there is any. The receiving chamber is a space 50 sound-insulated from the surroundings by the housing 22 and the stator 18. In that case, it is also an advantage that the central receiving chamber 50 communicates towards its other end into a further acoustic chamber 52 having a conical shape and a spatial "capacity" similar to that of the first acoustic chamber 48, as it provides a further possibility of attenuation with respect to the sound waves that can be "accumulated" in the central receiving chamber 50.

[0031] As further shown in the figure, this further acoustic chamber 52 widens towards a hollow cylindrical cover portion 56 having a further bearing location 44. The cover portion 46 is firmly but removably coupled to the surrounding jacket of the housing 22 as shown, and on the outer wall side has two access locations for the electrical connection 54 in the form of two supply conductors between the coil winding 20 and a current supply source not shown in detail.

[0032] Furthermore, in the line-of-sight direction of looking at the figure, the lower side of the damping block 26 has a stand device 56 that projects downward in a web-like manner. Using this stand device, it is possible to install or fix the entire drive system on the base side via the damping block 26 to a third-party component (not shown) such as a mechanical part. Also in this way, noise emission based on vibration is reduced and effectively conducted to the mechanical part connected via the stand device 56. As shown in the figure, the damping block 26 can be penetrated by a passage or opening 58 used for the supply and discharge of the pump fluid of the fluid pump 12, and the pump fluid, usually in the form of a hydraulic medium, also provides a damping effect when flowing through the damping block 26. Also in this way, although not shown in detail itself, coolant can be supplied to the electric motor during the driving of the electric motor 10. Similarly in this way, a coolant supply for the fluid pump 12 would also be possible. The stand component 56 forms a certain kind of interface for supporting the pump 12 and the electric motor 10, so it is clear that a balanced installation is obtained and it is also effective regarding the suppression of sound emission.

[0033] The structure of the fluid pump 12 will be described in detail below. In this embodiment, the fluid pump is configured as a so-called swash plate machine. Such a fluid pump can be demonstrated in a number of structural forms in the prior art, such as, for example, the specification of German Patent Application Publication No. 102013008678. Therefore, the fluid pump 12 will only be described in general terms to the extent necessary for understanding the present invention. The axial piston pump with the swash plate structure shown in the figure has a swash plate 60, which is fixedly arranged in the pump housing 24 and is held in place by at least one cylindrical pin 62. In this embodiment, unlike in the specification of German Patent Application Publication No. 102013008678, the swash plate 60 is immovable, so that a certain type of fixed displacement pump as the fluid pump 12 with a constant delivery volume is realized. Further, the fluid pump 12 has a cylindrical pump housing portion 64, which is non-rotatably coupled to the output shaft 14 by a spline shaft teeth 66 and can be rotationally driven by this output shaft. And such a jacket surface is rotatably guided in the pump housing 24 along a third bearing location 71.

[0034] As shown by the cutting plane located above the longitudinal axis 30 in the figure, individual piston chambers 68 are formed within the housing portion 64, and individual transfer pistons 70 associated therewith are guided to be longitudinally movable therein. In the figure, for simplicity, only one piston chamber 68 having an associated transfer piston 70 is shown, and in this case, a plurality of transfer pistons 70 of this kind are concentrically distributed around the longitudinal axis 30 at equal intervals from each other around the output shaft 14. Due to the swash plate 60 being in an inclined position, the illustrated transfer piston 70 is in its lowest fluid discharge transfer position, and on the side disposed diametrically opposite to the longitudinal axis 30 of the output shaft 14, the transfer piston within the housing portion 64 is accommodated in its highest position, and the maximum possible transfer volume of the fluid pump 12 occurs in the associated piston chamber 68 of that transfer piston. As shown for the upper transfer piston 70, in the lowest position, the fluid amount thus accommodated is pushed out again from the pump housing portion 64 for supply to a hydraulic consumption device (not shown in detail, such as a working cylinder) during pump drive.

[0035] Each transfer piston 70 that sucks up and discharges fluid is connected to appropriate fluid supply conduits and fluid discharge conduits by respective piston bases of each piston chamber 68, and they are omitted in the figure for simplicity and clarity. In addition to fluid supply and fluid discharge through the passage 58 in the damping block 26, it is also possible to attach appropriate conduits, if necessary, via the exposed outer end face of the pump housing 24 and thus connect the pump 12 to a supply circuit (not shown).

[0036] With the assistance of the mentioned splined shaft tooth cut 66, the pump housing part 64 is guided to be movable coaxially with respect to the longitudinal axis 30 on the output shaft 14, and with the assistance of an energy storage device in the form of a compression spring 72, the individual transfer pistons 70 of the housing part 64 are biased in the direction of the swash plate 72 via an additional abutting sleeve 74. At this time, one free end of the compression spring 72 is supported on the abutting sleeve 74 in the direction of the swash plate 60, and the other free end is supported in the housing-side accommodation chamber of the pump housing part 64 facing the splined shaft tooth cut 66.

[0037] The output shaft 14 shown in the figure is integrally formed, and one of its free ends communicates into a further splined shaft tooth cut 76. At the terminal side, the integral output shaft 14, which is led out from the pump housing 24 beyond the axially arranged access opening 77, is guided through two bearing locations 28 and 44, and these bearing locations are held in place by retaining rings in the normal way and can be composed of bearings of a normal structure, such as ball bearings. However, it is also possible to replace the individual bearing locations with bearing bushes, not shown in detail, having good sliding characteristics. When a further splined tooth cut 76 of the output shaft 14 projects beyond the front terminal wall of the pump housing 24, a seal 78 is formed at this location by the constriction in the swash plate 60. However, in an embodiment not shown in detail, only one fluid pump 12 can be used to omit the protruding part having the above-mentioned further splined tooth cut 76, and in that case, it would be necessary to provide a sealing cover on the end face of the pump housing 24 that is exposed outward to seal it.

[0038] By means of the drive system according to the invention shown in the figures, so-called reverse drive or four-quadrant drive is furthermore possible, in which the fluid pump 12 acts as a hydraulic motor, in which case the output shaft 14 driven from the side of the fluid pump 12 generates a changing electric field in the stator 18 via its rotor 16, so that at that time the electric motor 10 generates a current in generator drive, and that current is output in the normal way via the electrical connection 54 to an electrical consumer (not shown). Instead of the fluid pump 12 with swashplate structure, it is also possible to use a fluid pump, not shown in detail, for example in the form of an internal gear machine and / or an external gear machine. However, ultimately, in this solution, the transfer piston 70 is guided inside the piston chamber 68 and is enclosed therein to that extent, which serves to reduce noise.

[0039] The converted electro-hydraulic output is obtained from the possible leakage oil volume flow in addition to the drive speed and the pressure in the fluid discharge working conduit not shown in detail, the leakage oil volume flow being derived from the pump housing 24 via at least one separate leakage oil connection end 80, which leakage oil connection ends are sealed by plugs before the start of drive, as shown in each case in the figure display. All components used in the drive system are preferably constructed with a solid structure, which particularly applies to the solid damping block 26, so that a very rigid structure results in quiet behavior during drive. If necessary, other measures can be taken to reduce noise, for example using additional damping inserts (not shown) in the housings 22 and 24.

Claims

1. An electrohydraulic drive system comprising an electric motor (10) and a fluid pump (12) driveable by the electric motor (10) via an output shaft (14), wherein the output shaft has a rotor (16), the rotor is rotatably guided within a stator (18), the stator is surrounded by a housing (22) of the electric motor (10), and the fluid pump has a pump housing (24), characterized in that, in order to reduce noise emission, a damping block (26) is inserted between the housing (22) of the electric motor and the pump housing (24), the damping block is a solid structure made of a metal material, the output shaft (14) passes through the damping block, the output shaft is guided within a bearing location (28) within the damping block (26), is completely surrounded by the damping block (26), and the bearing shell of the output shaft is directly supported by the damping block.

2. The electrohydraulic drive system according to claim 1, characterized in that the damping block (26) forms a prism with respect to its surroundings, preferably in the shape of a hexagonal prism, more preferably in the shape of an octagonal prism.

3. The output shaft (14) has a coupling portion at one end of its terminal region for connecting the drive shaft of the fluid pump (12), the coupling portion is surrounded by the damping block (26), and the bearing portion (28) for the output shaft (14) and the coupling portion for the drive shaft of the fluid pump (12) are inserted into the damping block (26) at opposite end faces of the damping block (26). The electrohydraulic drive system according to any one of claims 1 to 2.

4. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that the damping block (26) is penetrated by individual fluid guides (58), the fluid guides are used for supplying and discharging fluids such as hydraulic media or cooling media, and have a damping effect when the fluid flows through the damping block (26).

5. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that, when viewed in the direction of the output shaft (14), the total axial length of the damping block (26) substantially corresponds to the total axial length of the pump housing (24) of the fluid pump (12).

6. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that the output shaft (14) is supported via a further bearing location (44), the further bearing location (44) is housed within a cover portion (46) of the electric motor (10) in the terminal region opposite to the bearing location (28), and the cover portion seals the electric motor (10) on the side opposite to the damping block (26).

7. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that the end wall (32) of the housing (22) of the electric motor and the end wall (34) of the pump housing (24) are both attached to opposite end faces (36, 38) of the damping block (26) on the same plane.

8. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that the outer diameter of the housing (22) of the electric motor is selected to be larger than the outer diameter of the pump housing (24).

9. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that the damping block (26) tapers conically at the bearing location (28) in the direction of the housing portion of the electric motor (10) within the housing (22), and together with the adjacent conical wall portion of the electric motor (10) of the damping block, defines a funnel-shaped acoustic chamber (48).

10. The electrohydraulic drive system according to any one of claims 1 to 2, characterized in that the damping block (26) is manufactured in a stand structure, and the housing (22) and pump housing (24) of the electric motor (10) are connected to the stand (56) formed in this manner on opposite sides.

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