Patent Application
20200325936
This application claims priority under 35 U.S.C. § 119 to patent application no. DE 10 2019 205 142.1, filed on Apr. 10, 2019 in Germany, the disclosure of which is incorporated herein by reference in its entirety.
The disclosure relates to a hydrostatic axial piston machine of swashplate design with through drive, i.e. with a drive shaft which may be coupled on either side.
In axial piston machines of swashplate design, it is usual that the drive shaft thereof is mounted on either side in the housing via one respective rolling bearing. In this case, the drive shaft generally only protrudes from the housing on the side of its swashplate and has a coupling means at that point, for example a feather key groove. For example, in the case of an axial piston pump the shaft of an electric motor may be coupled fixedly in terms of rotation onto this drive shaft end, in order to drive the axial piston pump in this manner. The opposing drive shaft end in this case is entirely received in the housing or in the connecting plate thereof.
It is also known to design the second drive shaft end, which may also be denoted as the end on the distributor plate side, with a coupling means for a shaft of a further machine, for which purpose the drive shaft also penetrates the housing in a sealed manner on a second side. Such axial piston machines are able to be used in many different ways.
The publication “Axial piston variable pump A10VO, A10VSO, A10VSNO, series 32, instruction manual RD92714-01-B” of the Applicant of April 2018 discloses such axial piston machines.
A drawback with the last-mentioned axial piston machines is that the second shaft end is designed to be thinner than the first shaft end and thus is able to transmit less torque at the second shaft end than at the first shaft end.
Moreover, the second shaft end has a weakening relative to deflection and torque due to an undercut which is configured on the internal periphery of an annular bearing surface. This annular bearing surface serves as a radial bearing portion for the rolling bearing at that point, so that the drive shaft may be supported via the annular bearing surface and via the rolling bearing on the housing and/or on the connecting plate thereof.
Relative thereto the object of the disclosure is to provide an axial piston machine with through drive, the drive shaft thereof being able to transmit a greater torque on its second side relative to the prior art.
This object is achieved by an axial piston machine having the features disclosed herein.
The disclosed hydrostatic axial piston machine has a drive shaft, wherein, on the one hand, a non-rotating swashplate is arranged and, on the other hand, a cylinder drum is coupled fixedly in terms of rotation on an external periphery of a central region of the drive shaft. Pistons which are coupled to the swashplate are guided in the cylinder drum. A compression spring is arranged between the drive shaft, in particular the central region, and the cylinder drum, via which compression spring the cylinder drum is clamped against a distributor plate. A first rolling bearing and a first coupling device are provided on an end portion of the drive shaft on the swashplate side, whilst a second rolling bearing and a second coupling device are provided on an end portion of the drive shaft on the distributor plate side. An annular bearing surface is formed on the drive shaft, in particular between the central region and the end portion on the distributor plate side, by which bearing surface the drive shaft is supported via a ring or via a sleeve on the second rolling bearing. A shaft shoulder is formed between the annular bearing surface and the second rolling bearing, said shaft shoulder producing a reduction in the diameter of the drive shaft, viewed in the direction from the central region to the end portion on the distributor plate side. According to the disclosure, this shaft shoulder has the shape of a concave rounded portion, the radius thereof being significantly larger than that of the undercut of the prior art. Moreover, the rounded portion on the drive shaft is located further radially outwardly than the undercut of the prior art. Moreover, according to the disclosure, the annular bearing surface is arranged in the interior of the compression spring and the rounded portion is arranged in the interior of the sleeve or the ring. Thus the notch effect of the undercut is eliminated and the end portion of the drive shaft on the distributor plate side may be designed to be thicker than in the prior art. The torque which may be transmitted via the end portion of the drive shaft on the distributor plate side is increased thereby.
In the case of an axial piston pump this increased torque is a drive torque which is introduced by a motor via the second coupling device into the axial piston pump and has to be transmitted from the drive shaft to the cylinder drum. In the case of an axial piston motor, the increased torque is an output torque which has to be transmitted from the cylinder drum via the drive shaft to the second coupling device.
Preferably, the second rolling bearing is a conical rolling bearing, the sleeve or the ring being supported on the internal bearing race thereof.
It is particularly preferred if the end portion on the distributor plate side continuously or tangentially transitions into the rounded portion. Then preferably a circular cylindrical portion, which is encompassed by the second rolling bearing, continuously or tangentially transitions into the rounded portion.
If the ring or the sleeve has an external diameter which corresponds to the internal diameter of the compression spring, the ring or the sleeve may be an internal bearing portion for the compression spring—in particular for its end portion on the distributor plate side. Thus the drive shaft may have a maximum thickness and absorb and/or transmit a further increased torque on the end portion on the distributor plate side.
Alternatively or additionally, it is preferred if a preferably circular cylindrical portion of the drive shaft extends from the annular bearing surface in the direction of the central region of the drive shaft, the external diameter of said circular cylindrical portion corresponding to the internal diameter of the compression spring. Thus this portion may be an internal bearing portion for the compression spring—in particular for its end portion on the distributor plate side. Also in this embodiment the drive shaft may have a maximum thickness and absorb and/or transmit a further increased torque on the end portion on the distributor plate side.
In a first exemplary embodiment, a preferably circular cylindrical bearing portion for the sleeve is formed between the annular bearing surface and the rounded portion on the drive shaft, the sleeve being radially retained by said circular cylindrical bearing portion. In this case, the sleeve extends axially from the annular bearing surface via the bearing portion and via the rounded portion to the second rolling bearing.
Preferably, an undercut is formed between the annular bearing surface and the bearing portion of the first exemplary embodiment. Thus the undercut of the prior art which weakens the drive shaft is advantageously displaced into a region of larger diameter of the drive shaft since the bearing portion is located further radially outward than the circular cylindrical portion which is encompassed by the second rolling bearing.
In a second exemplary embodiment, just one reduction in diameter in the form of just one rounded portion is configured between the annular bearing surface and the second rolling bearing.
If the rounded portion continuously or tangentially transitions into the annular bearing surface, the drive shaft may absorb and/or transmit a further increased torque on the end portion on the distributor plate side.
In order to provide space for the rounded portion, and at the same time to permit a flat axial bearing portion of the sleeve relative to the annular bearing surface and a radial bearing portion over the entire periphery relative to the drive shaft, in particular relative to the end portion on the distributor plate side, it is preferred if the sleeve or the ring has a conical internal casing portion which is arranged on the external periphery of the rounded portion.
The axial piston machine may be an axial piston pump which is adjustable in terms of its swept volume.
A plurality of exemplary embodiments of the axial piston pump according to the disclosure are shown in the figures. In the figures:
The drive shaft has a central region 6, a cylinder drum 8 being coupled fixedly in terms of rotation thereto. In the cylinder drum 8, pistons 10 which are radially guided and uniformly distributed over the periphery are received in the respective cylinders 11, said cylinders being supported and guided on a swashplate 12. By adjusting the angle of the swashplate 12 a swept volume of the pistons 10 and thus of the axial piston machine may be altered.
A distributor plate 14 is arranged on a side of the cylinder drum 8 opposing the swashplate 12, wherein the cylinder drum 8 is clamped thereagainst via a compression spring 16.
During operation of the axial piston machine the cylinders 11 extend with their ports via respective kidney-shaped through-recesses 18 which are connected, on the one hand, to a high pressure connection and, on the other hand, to a low pressure connection of the connecting plate of the housing 1 of the axial piston machine.
Starting from the central region 6 of the drive shaft, an end portion 20 on the swashplate side extends through the first conical rolling bearing 2 and through the housing 1 and has a first coupling device 22 which is formed by a feather key groove.
On the other side (to the right in
According to the disclosure, an increase in the mechanical strength of the end portion 24 of the drive shaft on the distributor plate side, which may only be used when the housing cover 28 is removed from the connecting plate of the housing 1 so that the second coupling device 27 is accessible and is subjected to torque, is described hereinafter.
The second conical rolling bearing 4 is arranged on the external periphery of the end portion 24 of the drive shaft on the distributor plate side, said second conical rolling bearing being supported with its external ring on the connecting plate of the housing 1.
A concave rounded portion 30 is formed on the external periphery of the drive shaft. Viewed from the end portion 24 in the direction of the central region 6 of the drive shaft (from right to left in
Moreover, viewed from the end portion 24 on the distributor plate side in the direction of the central region 6 of the drive shaft, the annular bearing surface 38 is followed by a relatively short circular cylindrical bearing portion 40 for the compression spring 16. An external diameter of the bearing portion 40 has the same diameter as an external casing 42 of the sleeve 34. This external casing 42 of the sleeve 34 may also serve as a bearing portion for the compression spring 16.
Via the compression spring 16 and via a locking ring or an adjusting washer 44, which is inserted into an internal periphery of the cylinder drum 8, this cylinder drum is axially clamped (to the right in
According to the disclosure, reductions in diameter and, in particular, an undercut are not provided between the central region 6 and the end portion 24 of the drive shaft, the internal diameter thereof being smaller than the diameter of the end portion 24. Thus the drive shaft with its end portion 24 is provided with a greater strength and via the second coupling device 27 provided on the end portion 24 may transmit a greater torque relative to the prior art.
In contrast to
In the second exemplary embodiment according to
Also deviating from the first exemplary embodiment according to
Disclosed is a hydrostatic axial piston machine, the drive shaft thereof penetrating a housing 1 on either side. In this case, the mechanically weaker of the two shaft ends 24 is strengthened by an undercut (of the prior art) being eliminated, said undercut defining the minimum diameter of the shaft end 24 and thus of the entire drive shaft. Instead, the strength of the relevant shaft end 24 is increased by a displacement of a circular bearing surface 38 for a rolling bearing 4 radially outwardly and away from the rolling bearing 4. In this case, the circular bearing surface is displaced below a compression spring 16 which clamps the cylinder drum 8 against a distributor plate 14. The resulting spacing between the circular bearing surface 38 and the rolling bearing 4 remaining in place is bridged by a sleeve 34 or by a ring 134. A concave rounded shaft shoulder 30 is simply formed below the sleeve 34 and/or the ring 134.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 205 142.1 | Apr 2019 | DE | national |
