System comprising an electric machine and a hydraulic unit, and electric machine and hydraulic unit

Abstract

The invention relates to a system comprising an electric machine (10) and a hydraulic unit (20), wherein the electric machine (10) has a first shaft (11) and the hydraulic unit (20) has a second shaft (21), the first shaft (11) and the second shaft (21) are connected to each other to form a shaft-hub connection, the shaft-hub connection has a central recess (29), and the shaft-hub connection is fluidically connected to the inside of the hydraulic unit (20) for lubrication.

Description

Technical Field

[0001] This application relates to a system comprising a motor having a first shaft and a hydraulic unit having a second shaft. This application also relates to a hydraulic unit and a motor for such a system. Background Technology

[0002] The motor is typically configured as an electric motor and connected to a hydraulic unit configured as a pump. The motor includes a stator and a rotor, the rotor being connected to or forming a shaft. However, the hydraulic unit can also be configured to drive the motor as a generator.

[0003] To transmit torque between the shaft of the motor (first shaft) and the shaft of the hydraulic unit (second shaft), it is known to use a so-called bell box, which connects the motor and the hydraulic unit to each other, and within the bell box, a drive shaft connects the first and second shafts. The bell box and drive shaft have the advantage that the motor and hydraulic unit can be aligned to a certain extent during assembly, thereby compensating for manufacturing errors, particularly in the bearings of the first shaft of the motor and the second shaft of the hydraulic unit. However, a disadvantage is that the overall system length (along the direction of shaft extension) is substantially increased by the bell box and drive shaft. Furthermore, a large number of components, with corresponding assembly costs, are necessary to constitute the complete system.

[0004] To construct a more compact system requiring fewer components, it is known to directly insert the first shaft of the motor and the second shaft of the hydraulic unit into each other, thus forming an active and direct shaft-hub connection. Such a more compact system is known, for example, from patent publication DE102016225196A1. Therein, the shaft-hub connection is lubricated by means of hydraulic fluid transmitted by the hydraulic unit. For this purpose, a leakage oil passage extending axially along the pump shaft is proposed, extending along the entire length of the pump shaft. Hydraulic fluid from the pump's pressurized transmission chamber, passing through the bearing of the pump head into the leakage oil passage within the hydraulic unit, can thus enter the end of the leakage oil passage, which is located at the front end of the pump shaft within the hydraulic unit. Leakage oil flowing through the central leakage oil passage exits from the leakage oil passage at the shaft-hub connection and flows along and lubricates the shaft-hub connection. To facilitate this leakage oil flow, a drain is proposed, through which the leakage oil is drained after lubricating the shaft-hub connection. Therefore, a separate drainage section is required, which must be formed between the motor and the hydraulic unit or within the motor. Consequently, equipment compatibility with the motor or with adapters located between the motor and the hydraulic unit is essential. Summary of the Invention

[0005] Therefore, the purpose of this application is to provide a system including a motor and a hydraulic unit, and a motor and a hydraulic unit, thereby further integrating the leakage oil drainage section into the hydraulic unit.

[0006] This objective is achieved by a system, motor, and intermediate shaft having the features of the respective independent claims. Advantageous further modifications of the system, hydraulic unit, motor, and intermediate shaft are pointed out in the dependent claims and the specification, wherein the various features of the advantageous further modifications can be combined with each other in a technically meaningful manner. In particular, the features described with reference to the system can be applied to the hydraulic unit or motor, and vice versa.

[0007] This objective is achieved, in particular, by a system comprising a motor and a hydraulic unit, wherein the motor comprises a first shaft, and the hydraulic unit comprises a second shaft, wherein the first and second shafts are connected to each other to form a preferably active locking shaft-hub connection, the shaft-hub connection comprising a central recess and the shaft-hub connection being fluidly connected (capable of transmitting fluid) to the interior of the hydraulic unit for lubrication, wherein the central recess is adjacent to at least one transverse channel extending from the central recess to the outer periphery of the shaft-hub connection.

[0008] This objective is also achieved by a hydraulic unit, wherein the shaft of the hydraulic unit has a central recess and at least one transverse channel, and the at least one transverse channel extends from the central recess to the outer periphery of the shaft.

[0009] This objective is also achieved by an electric motor, wherein the motor shaft has a central recess and at least one transverse channel, wherein the at least one transverse channel extends from the central recess to the outer periphery of the shaft.

[0010] This objective is also achieved by an intermediate shaft for connecting the first and second shafts of such a system, wherein the intermediate shaft has a central recess and at least one transverse channel extending from the central recess to the outer periphery of the intermediate shaft.

[0011] This application will now be discussed with reference to the system. However, the described embodiments also explicitly relate to a separate hydraulic unit, a separate motor, and a separate intermediate shaft.

[0012] In one embodiment of the system, the first and second shafts are directly inserted into each other to form a shaft-hub connection. In this case, the first or second shaft includes a central recess, wherein at least one lateral channel extends from the central recess to the outer periphery of the respective shaft. Preferably, the central recess and at least one lateral channel are formed in the second shaft of the hydraulic unit.

[0013] The first and second shafts can be directly inserted into each other to form a shaft-hub connection, thus eliminating the need for other components (such as a clock housing and a drive / intermediate shaft) to connect the motor shaft to the hydraulic unit shaft.

[0014] In an alternative embodiment, the first shaft and the second shaft may be indirectly connected via an intermediate shaft. In this case, the shaft-hub connection includes an intermediate shaft for connecting the first shaft and the second shaft, wherein a central recess and at least one lateral channel may be formed in the intermediate shaft.

[0015] Preferably, a plurality of (at least two, preferably at least four, particularly preferably no more than eight) transverse channels adjoin the central recess, each extending particularly linearly from the central recess to the outer periphery of the shaft. At least one transverse channel may extend strictly radially and thus at a right angle relative to the longitudinal axis of the shaft. However, it is also possible for at least one transverse channel to be arranged at a different angle relative to the longitudinal axis of the shaft. For example, the transverse channels may be formed by holes.

[0016] This application is based on the discovery that fluid located in at least one transverse channel (particularly leaking oil from the leaking oil chamber of the hydraulic unit) is subjected to centrifugal force during system operation, and the fluid can be transferred from the central recess to the chamber around the outer periphery of the shaft, wherein the fluid can be drawn in by the negative pressure formed in the recess, resulting in a predetermined specific direction of fluid transfer.

[0017] In other words, this application provides, based on its basic concept, a first shaft of a motor, a second shaft of a hydraulic unit, or an intermediate shaft having a transverse channel extending radially outward to deliver leaking oil along the shaft-hub connection. Thus, the leaking oil can be specifically transported to lubricate the contact points between the shafts, and can be specifically circulated back into the leaking oil chamber of the hydraulic unit. Therefore, no additional drainage section is required for the leaking oil.

[0018] In one embodiment, the hydraulic unit may be configured to include a leakage oil chamber. The leakage oil chamber is specifically a chamber within the hydraulic unit into which hydraulic oil enters during operation from a pressurized transmission chamber of the hydraulic unit. For example, hydraulic fluid enters along a bearing of a component that transmits pressurized hydraulic fluid. In this case, a central recess may be provided in the (second) shaft or intermediate shaft of the hydraulic unit, wherein at least one lateral channel extends from the central recess to the leakage oil chamber. The recess is preferably formed in the (second) shaft of the hydraulic unit as an axial channel and extends from at least one lateral channel through the second shaft to the direct shaft-hub connection. Alternatively, the central recess may be formed in the intermediate shaft as an axial channel and extends from at least one lateral channel through the intermediate shaft to the front end of the intermediate shaft. The axial channel extending axially along the shaft thus has an inlet at the front end toward the motor, through which leakage oil (after lubricating the shaft-hub connection) can enter the axial channel. Therefore, the axial channel does not extend completely through the second shaft or through the intermediate shaft. Therefore, the axial channel will be considered as a blind hole extending from the front end through the shaft to at least one lateral channel.

[0019] In an alternative embodiment, the (first) shaft of the motor may be configured to have a recess adjacent to at least one transverse channel. In this case, the recess is arranged specifically to directly abut a housing for the (second) shaft of the hydraulic unit or for an intermediate shaft. In this embodiment, leaking oil that has flowed along the contact point of the shaft-hub connection is transferred through the (first) shaft of the motor into a chamber surrounding the shaft.

[0020] Preferably, in this embodiment, it is feasible to provide a separate drain for leaked oil transmitted through at least one transverse channel of the first shaft of the motor.

[0021] It is also preferably configured such that at least one transverse channel terminates at a point on the outer periphery of the shaft that does not overlap with another shaft in the connected state. The at least one transverse channel is therefore arranged axially offset relative to the shaft-hub connection in one of the shafts. This ensures that leaking oil can be transferred from the leaking oil chamber within the hydraulic unit along the shaft-hub connection arranged outside the housing of the hydraulic unit.

[0022] In one embodiment, the shaft-hub connection is preferably configured such that the shaft-hub connection is fluidly connected to a leakage oil chamber within the hydraulic unit outside the second shaft via at least one passage. The first passage or a first set of such passages is configured such that leakage oil flows from the leakage oil chamber within the hydraulic unit to the shaft-hub connection.

[0023] This first passage can be implemented, for example, by mounting the (second) shaft of the hydraulic unit in a direction toward the shaft-hub connection without a shaft seal within the housing of the hydraulic unit. In this case, leaking oil flows from the leaking oil chamber along the surface of the (second) shaft through the housing of the hydraulic unit in the direction of the shaft-hub connection. In the case of the first embodiment described above (according to which the central recess and at least one transverse channel are formed in the (second) shaft or intermediate shaft of the hydraulic unit), the fluid that has already come from the leaking oil chamber (after it has flowed along the contact point of the shaft-hub connection) enters the axial channel in the second shaft (or intermediate shaft). In the second embodiment described above (according to which the central recess and at least one transverse channel are formed in the (first) shaft of the motor), the fluid that has come from the leaking oil chamber along the second shaft is transferred to the chamber surrounding the first shaft.

[0024] The passage for fluid connection between the leakage oil chamber and the shaft-hub connection within the hydraulic unit can additionally or alternatively be formed by at least one, preferably multiple, openings (particularly formed as recesses and preferably as holes) located adjacent to the second shaft in the housing or housing component (e.g., in a cap or bearing) of the hydraulic unit. In the case of the first embodiment described above, leakage oil can flow from the leakage oil chamber through at least one opening in the housing to the shaft-hub connection and then into an axial channel in the second shaft or intermediate shaft. In the case of the second embodiment described above, leakage oil transmitted through at least one lateral channel can flow back into the leakage oil chamber through an opening. In this connection configuration, it is preferable that the front end face of the first shaft is sealed relative to the hydraulic unit, so that leakage oil can flow from the leakage oil chamber within the hydraulic unit along the outside of the shaft and along the shaft-hub connection to a recess in the (first) shaft of the motor, and from there be transmitted back through at least one lateral channel to an opening in the housing (the opening being radially outwardly offset relative to the sealed end face of the shaft) into the leakage oil chamber.

[0025] Preferably, at least one opening can be closed, and preferably has internal threads for this purpose. Thus, in the conveying state, the opening can be closed, for example, by a screw. In this case, the opening can be closed until just before the hydraulic unit is attached to the motor / shortly before the hydraulic unit is attached to the electrode.

[0026] In a preferred embodiment, the shaft-hub connection has a spline connection, wherein the spline connection includes at least one pin with an external tooth structure and at least one housing with an internal tooth structure.

[0027] Preferably, a pin with an external tooth structure can be formed on the first shaft of the motor, in which case a housing with an internal tooth structure is preferably provided on the front end of the second shaft of the hydraulic unit.

[0028] Alternatively, a pin with an external tooth structure can preferably be formed on the (second) shaft of the hydraulic unit, in which case a housing with an internal tooth structure is preferably provided on the front end of the (first) shaft of the motor.

[0029] In even further embodiments, the first shaft of the motor and the second shaft of the hydraulic unit may each have a housing (preferably with an internal tooth structure) on their front ends, wherein if the first shaft is connected to the second shaft via an intermediate shaft, the intermediate shaft forms two pins, each pin having an external tooth structure for insertion into the corresponding housing.

[0030] In order to secure the motor to the hydraulic unit, the motor housing and the hydraulic unit housing can be connected to each other in a suitable manner (e.g., by appropriate threaded connection) for example by forming at least one flange or cap.

[0031] The first shaft is mounted in the motor, specifically by means of two bearings. The second shaft is mounted in the hydraulic unit, specifically by means of two bearings. In particular, if a pin with an external tooth structure is formed on the second shaft of the hydraulic unit, the pin extends beyond one of the bearings and beyond the housing of the hydraulic unit in the direction of the motor.

[0032] When implementing the system specifically, severe wear has been found in the internal and external gear structures of the spline connection. This severe wear is due to the forces acting on the shaft within the hydraulic unit during operation, which can cause the pins extending beyond the bearings to deflect from their neutral position and thus fail to maintain their stationary position / alignment within the motor housing. Another cause of severe wear could be errors in the motor or hydraulic unit, where the pins within the housing do not occupy the desired position / alignment when the motor is connected to the hydraulic unit.

[0033] It has been shown that, in order to reduce wear and other factors in the spline connection, a specific ratio range between the pitch circle diameter on the pin and the length of the external tooth structure is advantageous.

[0034] Therefore, the external tooth structure of the pin (which may be formed on the first shaft of the motor, the second shaft of the hydraulic unit, or the intermediate shaft) has an external tooth structure length and a pitch circle diameter. The external tooth structure length is the length of the tooth in the direction of extension of the shaft. It is now preferred that the ratio of the pitch circle diameter to the external tooth structure length is less than 1.2, particularly preferably less than 1.1, and quite particularly preferably less than 1.05. On the other hand, the ratio of the pitch circle diameter to the external tooth structure length should be at least 0.8, preferably at least 0.9, and particularly preferably at least 0.95. In a particularly preferred embodiment, the ratio of the pitch circle diameter to the external tooth structure length is between 0.95 and 1.05, and particularly preferably equal to 1. The invention alone, as seen in this ratio between the pitch circle diameter and the external tooth structure length, can be claimed independently of the above-described scheme for a system including a motor and a hydraulic unit.

[0035] Therefore, the independent invention can be seen in the hydraulic unit, the shaft of which has a pin, the pin having an external tooth structure, wherein the external tooth structure has an external tooth structure length and a pitch circle diameter, the ratio between them (i.e., the ratio of the pitch circle diameter to the external tooth structure length) being within the aforementioned range.

[0036] As shown, in order to reduce wear on the spline connection, the external tooth structure can be alternatively or additionally configured to have an error level of 0.7. This error level is defined herein in the 1996 standard ZNSI B92.1.

[0037] Therefore, a hydraulic unit is also proposed as an independent invention, the hydraulic unit having a shaft having a pin having an external tooth structure, wherein the external tooth structure has an error of 0.7 level.

[0038] The ratio of pitch circle diameter to external tooth structure length as described above (especially the error level of the internal tooth structure) has the effect of minimizing wear on the spline connection.

[0039] The hydraulic unit is preferably implemented as a swash plate unit, which can operate as a pump or a motor. In the swash plate unit, the deflection of the pin extending beyond the housing during operation is particularly large due to the force acting on the shaft in the swash plate pump. The pin of the swash plate pump shaft extending beyond the housing of the swash plate pump is thus immediately and directly inserted into the corresponding housing of the motor. Alternatively, the hydraulic unit, which can operate as a pump or motor, can function as an angled piston unit, a gear unit, a rotary vane unit, or a helical shaft unit.

[0040] The spline connection is preferably a type of spline in which narrowed teeth of an external tooth structure engage in an internal tooth structure. Such a spline is defined, for example, in ANSI B92.1 of 1996. Attached Figure Description

[0041] This application and the background art are hereby explained with reference to the accompanying drawings as examples. The drawings schematically illustrate...

[0042] Figure 1 A perspective view of the hydraulic unit is shown;

[0043] Figure 2 The connection area of ​​the electrical unit is shown;

[0044] Figure 3 The second shaft of the hydraulic unit is shown;

[0045] Figure 4 A cross-sectional view of a region through a schematic embodiment of the system is shown;

[0046] Figure 5 A cross-sectional view of a region through another illustrative embodiment of the system is shown; and

[0047] Figure 6 A cross-sectional view of a region through an even more illustrative embodiment of the system is shown. Detailed Implementation

[0048] like Figure 1 The hydraulic unit 20 shown and configured as a swivel pump includes a housing 26 having a cap 27. A shaft 21 is mounted within the housing 26, extending beyond the cap 27 by a pin 22. The pin 22 has an external tooth structure 23, having an external tooth structure length 24 and a pitch circle diameter 25. The shaft 21 with the pin 22 is also... Figure 3 It is shown as a single component.

[0049] Figure 2 A motor 10 is shown, its connection area being connected to a hydraulic unit 20. The shaft 11 of the motor 10 has a housing 12, which has an internal gear structure 13.

[0050] The pin 22 of the shaft 21 of the hydraulic unit 20 is inserted into the housing 12 of the motor 10 to form a system. The shaft 11 of the motor 10 is thus directly connected to the shaft 21 of the electro-hydraulic unit 20, forming an active locking shaft-hub connection. Therefore, no additional components are required to connect the shafts 21 and 22 of the motor 10 and the hydraulic unit 20 to each other.

[0051] In order for the bearing error deviations of shafts 11 and 21 to be compensated, the ratio of the pitch circle diameter 25 to the external tooth structure length 24 can be between 0.8 and 1.2, and preferably between 0.95 and 1.05. For the same reason, the internal tooth structure 13 has an error level of 0.7.

[0052] Figure 4 and 5The regions of the system including electrode 10 and hydraulic unit 20 are shown separately. Thus, the ends of hydraulic unit 20 facing motor 10 and the ends of hydraulic unit 20 facing motor 10 are shown. In all illustrative embodiments, it can be seen that hydraulic unit 20 has a housing 26, which may include a cap 27 as a component. A leakage oil chamber 28 is formed within the housing 26, into which hydraulic fluid can flow from the delivery chamber of the hydraulic unit along a corresponding bearing (not shown) of the pump head. Additionally, a leakage oil outlet 32 ​​may be provided, from which leakage oil can exit from the leakage oil chamber 28.

[0053] Additionally, as can be seen from the above-described housing 12, the pin 22 of the second shaft 21 of the hydraulic unit 20 is inserted into the housing at one end of the first shaft 11.

[0054] exist Figure 4 In the illustrated embodiment, a central recess 29, configured as an axial channel, is formed in the second shaft 21 of the hydraulic unit 20. This axial channel recess 29 is abutted by two transverse channels 30, which extend radially to the outer periphery 31. The transverse channels 30 thus extend from the ends of the recess 29 into the leakage oil chamber 28. The recess 29 terminates on the end face of the second shaft 21 on a side facing the motor 10.

[0055] In such Figure 5 In the schematic embodiment shown, a recess 29 is formed in the first shaft 11 of the motor 10, adjacent to a housing 12 for the pin 22. Starting from the recess 29, two transverse channels 30 extend to the outer periphery 31 of the first shaft 11.

[0056] In two illustrative embodiments, passage 33 is formed along the outer peripheral surface or through the bearing of the second shaft 21 of the hydraulic unit 20, through which leaking oil can flow from the leaking oil chamber 28 under suitable pressure conditions. Figure 5 An illustrative embodiment provides a separate leaking oil outlet 32 ​​in the motor 10, which is fluidly connected to a recess 29 in the first shaft 11 via a transverse channel 30.

[0057] During operation, the first shaft 11 and the second shaft 21 rotate about their longitudinal axes. As a result, leaking oil located in the transverse channel 30 is transported outward by centrifugal force, and negative pressure is formed in the recess 29.

[0058] In such Figure 4In the illustrated embodiment, this also results in a negative pressure forming in the region of the reservoir 12, causing leaking oil to flow from the leaking oil chamber 28 through the passage 33 and along the coupling point between the pin 22 and the reservoir 12. Thus, the coupling point between the pin 22 and the reservoir 12 is permanently lubricated. The leaking oil then enters the recess 29, which is formed as an axial channel, and flows back into the leaking oil chamber 28 through the transverse channel 31.

[0059] In such Figure 5 In the illustrative embodiment shown, the rotation of shafts 11 and 21 also results in a negative pressure forming in the recess 29 due to the centrifugal force acting on the leaking oil within the leaking oil chamber 30. This causes the leaking oil (hydraulic fluid) to flow along the outside of the second shaft 21 through the first passage 33 and along the coupling point between the housing 12 and the pin 22, thereby lubricating the coupling point. The fluid transmitted through the transverse passage 30 flows to the separate leaking oil outlet 32 ​​of the motor 10.

[0060] Figure 6 An area of ​​another embodiment of a system including a motor 10 and a hydraulic unit 20 is shown, the hydraulic unit 20 being, for example, a gear pump. The differences from the embodiments described above will be described in detail below.

[0061] In this embodiment, the first shaft 11 of the motor 10 is indirectly connected to the second shaft 21 of the hydraulic unit 20. The first shaft 11 is connected to the second shaft 21 via an intermediate shaft 40, one end of which (having an external tooth structure) is inserted into a housing 12 of the first shaft 11 and the other end (also having an external tooth structure) is inserted into a housing formed in the second shaft 21. Therefore, the intermediate shaft 40 connects the first shaft 11 and the second shaft 21 in a manner that prevents torque (or prevents relative rotation), thereby transmitting the rotational motion of the first shaft 11 to the rotational motion of the second shaft 21. Thus, a shaft-hub connection is formed between the first shaft 11 and the second shaft 21.

[0062] The intermediate shaft 40 has a central recess 29 extending from the end face of the intermediate shaft 40 toward the first shaft 11 to a transverse channel 30 extending radially outward toward the outer periphery of the intermediate shaft 40. Within the housing 26 of the hydraulic unit 20, a leakage oil chamber 28 is formed, surrounding the outer periphery of the intermediate shaft 40 in the area discharged through the transverse channel 30.

[0063] During operation, the centrifugal force acting on the leaking oil in the transverse channel 30 generates negative pressure in the central recess 29, causing the leaking oil from the leaking oil chamber 28 to flow along the outer periphery of the intermediate shaft 40 into the housing 12 of the first shaft 11 and from there into the central recess 29. The leaking oil in the central recess 29 is discharged back into the leaking oil chamber 28 through the transverse channel 30. Therefore, the active locking connection between the first shaft 11 and the intermediate shaft 40 is lubricated by the leaking oil.

[0064] To improve the flow of leaking oil along the outer circumference of the shaft, the teeth in the external or internal gear structure of the shaft-hub connection may be omitted.

[0065] Therefore, a compact system including a motor and hydraulic unit is provided, which can operate with low maintenance.

[0066] List of reference numerals

[0067] 10 motors

[0068] 11 First Axis

[0069] 12 seats

[0070] 13 Internal tooth structure

[0071] 20 Hydraulic Units

[0072] 21 Second Axis

[0073] 22 sales

[0074] 23 External tooth structure

[0075] 24. External tooth structure length

[0076] 25 pitch circle diameter

[0077] 26. Shell

[0078] 27 blocks

[0079] 28. Leaking oil chamber

[0080] 29 recess

[0081] 30 Horizontal Channels

[0082] 31 Periphery

[0083] 32. Oil spill outlet

[0084] 33 access

[0085] 40 intermediate shaft

Claims

1. A system comprising: Motor (10), wherein the motor (10) includes a first shaft (11), and A hydraulic unit (20), wherein the hydraulic unit (20) includes a second shaft (21), wherein The first shaft (11) and the second shaft (21) are connected to each other to form a shaft-hub connection. The shaft-hub connection includes a central recess (29), and The shaft-hub connection is fluidly connected to the interior of the hydraulic unit (20) for lubrication. Its features are, The central recess (29) is adjacent to at least one transverse channel (30), wherein the at least one transverse channel (30) extends from the central recess (29) to the outer periphery (31) of the shaft-hub connection, wherein the fluid located in the at least one transverse channel is subjected to centrifugal force during the operation of the system, and the fluid is transferred from the central recess to the leakage oil chamber around the outer periphery of the shaft, wherein the fluid is drawn in by the negative pressure formed in the recess, thereby the specific direction of fluid transmission is predetermined.

2. The system according to claim 1, characterized in that, The first shaft (11) and the second shaft (21) are inserted into each other to form the shaft-hub connection.

3. The system according to claim 2, characterized in that, The first shaft (11) and / or the second shaft (21) include the central recess (29), wherein the at least one transverse channel (30) extends from the central recess (29) to the outer periphery (31) of the shaft.

4. The system according to claim 2 or 3, characterized in that, The central recess (29) and the at least one transverse channel (30) are provided in the second axis (21).

5. The system according to claim 1, characterized in that, The shaft-hub connection includes an intermediate shaft (40) for connecting the first shaft (11) and the second shaft (21), wherein the central recess (29) and the at least one transverse channel (30) are formed in the intermediate shaft (40).

6. The system according to any one of claims 1 to 3, characterized in that, The hydraulic unit (20) includes a leakage oil chamber (28), wherein at least one transverse channel (30) extends from the central recess (29) to the leakage oil chamber (28).

7. The system according to claim 6, characterized in that, The central recess (29) extends as an axial channel from the at least one transverse channel (30) through the second shaft (21) to the shaft-hub connection.

8. The system according to claim 5, characterized in that, The central recess (29) extends as an axial channel from the at least one transverse channel (30) through the intermediate shaft (40) to the front end of the intermediate shaft (40) facing the first shaft (11).

9. The system according to any one of claims 1 to 3, characterized in that, The first shaft (11) has a housing (12) for the second shaft (21), and wherein a central recess (29) formed in the first shaft (11) is adjacent to the housing (12), and wherein at least one transverse channel (30) is formed in the first shaft (11).

10. The system according to claim 9, characterized in that, The front end face of the first shaft (11) is sealed relative to the hydraulic unit (20).

11. The system according to any one of claims 1 to 3, characterized in that, The at least one transverse channel (30) terminates at a point on the outer periphery (31) of the shaft that does not overlap with another shaft in the connected state.

12. The system according to any one of claims 1 to 3, characterized in that, The shaft-hub connection is fluidly connected to the leakage oil chamber (28) of the hydraulic unit (20) outside the second shaft (21) via at least one passage (33).

13. The system according to claim 12, characterized in that, The second shaft (21) is installed in the housing (26) of the hydraulic unit (20) without shaft seal to form a passage (33) in the direction toward the shaft-hub connection.

14. The system according to claim 12, characterized in that, The hydraulic unit (20) has a housing (26) surrounding the second shaft (21), and at least one opening is formed in the housing to form a passage.

15. The system according to claim 14, characterized in that, The at least one opening can be closed.

16. The system according to any one of claims 1 to 3, characterized in that, The hydraulic unit (20) is a swivel plate unit, an angled piston unit, a gear pump unit, a rotary vane unit, or a spiral shaft unit.

17. The system according to claim 15, characterized in that, The at least one opening has an internal thread.

18. The system according to claim 4, characterized in that, The central recess (29) extends as an axial channel from the at least one transverse channel (30) through the second axis (21) to the front end of the second axis (21) facing the first axis (11).

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