This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2013 222 602.0, filed on Nov. 7, 2013 in Germany, the disclosure of which is incorporated herein by reference in its entirety.
The disclosure relates to a hydrostatic axial piston machine.
The known types of hydrostatic axial piston machines include not only the classic type of machine with an integral rotating cylinder drum but also a type of machine in which the cylinders are arranged in revolving cylinder sleeves. The different displacer chambers are therefore formed in individual cylinder sleeves, which are articulated on a common rotor via respective ball joints, on the one hand, and into which respective spherical or ball-shaped pistons are inserted, on the other hand, said pistons being secured on a common piston disk. By setting the piston disk obliquely to the rotor or setting the rotor obliquely to the piston disk, the desired stroke motion of the pistons in the cylinder sleeves is produced as the cylinder sleeves revolve with the rotor and with the piston disk. In this case, the rotor or the piston disk is secured on a drive shaft or is formed integrally therewith, wherein the drive shaft serves as an output shaft in the case of an axial piston motor and as an input shaft in the case of an axial piston pump. Axial piston machines of this kind require a driving device in order to synchronize the rotary motion of the rotor and of the piston disk despite the fact of their being set obliquely to one another.
Printed publication DE 10 2007 011 441 A1 discloses a double hydrostatic axial piston machine having two groups of individual cylinder sleeves, in which toothing, a torsionally stiff bellows and a constant velocity rolling bearing clutch are shown as a driving device.
Printed publication DE 10 2012 222 850 A1 shows a hydrostatic axial piston machine with individual cylinder sleeves, wherein a driving pin inserted transversely into the drive shaft is proposed as a driving device, said pin engaging in slots in a collar on an obliquely set rotor disk. A Cardan joint and a constant velocity joint are furthermore proposed as a driving device.
In DE 10 2012 222 743 A1, a hydrostatic axial piston machine is disclosed with individual cylinder sleeves, the obliquely set cylinder end of which is articulated by means of a Cardan joint on the drive shaft.
The disadvantage with hydrostatic axial piston machines of this kind is that there is a rigid coupling between the rotor and the piston disk in the direction of the drive shaft, and therefore these components cannot be pushed apart by a mechanical force (e.g. by a preloading spring).
Given this situation, it is the underlying object of the disclosure to provide a hydrostatic axial piston machine having individual cylinder sleeves, in which this disadvantage is eliminated.
The object is achieved by a hydrostatic axial piston machine having the features of the disclosure.
The hydrostatic axial piston machine has a drive shaft and a plurality of cylinder sleeves, in which a spherical or ball-shaped section, on the one hand, and a spherical or ball-shaped piston, on the other hand, are inserted in order to delimit a respective displacer chamber. The sections are secured on a rotor, while the pistons are secured on a piston disk or piston drum. Depending on the embodiment, the piston disk and the rotor can be tilted relative to one another in a variable-displacement machine, or the piston disk and the rotor are tilted relative to one another in a constant-displacement machine. The rotor and the piston disk are furthermore coupled to one another for conjoint rotation by means of a driving device. This coupling can also be implemented indirectly by means of a drive shaft of the machine. According to the disclosure, a sliding joint axial with respect to a drive shaft is arranged between the rotor and the piston disk. This ensures decoupling and axial mobility of the piston disk relative to the rotor.
The axial sliding joint can have a key and a groove or toothing, for example.
The driving device can be arranged inside or outside a pitch circle of the sections and pistons. At the outer circumference of the pitch circle, the circumferential forces to be transmitted are lower, and therefore the driving device can have comparatively small individual elements (e.g. journals). In this case, the drive shaft can be continuous.
To support an axial preloading force, which is required between the piston disk and the rotor, a pressure sleeve can be arranged on (e.g. pushed onto) the outer circumference of the drive shaft, said sleeve having on its outer circumference a spherical shape against which the piston disk or the rotor rests.
In a preferred principle of the axial piston machine according to the disclosure, the rotor is arranged perpendicularly to the drive shaft and is connected to the latter for conjoint rotation or is formed integrally therewith, while the piston disk can be tilted or is tilted relative to the drive shaft.
The piston disk can be provided with a bushing-type extension, which is part of the driving device or which is used to articulate the driving device thereon.
In an illustrative embodiment which is simple in terms of device design, the driving device has a joint having just one transverse axis. According to a first variant, two journals are arranged along the transverse axis, said journals being inserted into two mutually opposite axial slotted holes or grooves in such a way as to be pivotable and slidable. According to a second variant, a continuous pin is arranged along the transverse axis, said pin being inserted into two mutually opposite axial slotted holes or grooves in such a way as to be pivotable and slidable.
In a Cardan-like illustrative embodiment, the driving device has two joints having respective transverse axes, wherein the two transverse axes are set at 90 degrees to one another. According to a first variant, two journals are in this case arranged along each transverse axis, said journals being inserted into two mutually opposite axial slotted holes or grooves in such a way as to be pivotable and slidable. In this case, the two transverse axes can intersect, i.e. form a cross. According to a second variant, a continuous pin is arranged along each transverse axis, said pin being inserted into two mutually opposite axial slotted holes or grooves.
To reduce frictional losses, laterally flattened sliding blocks or sliding bushings can be placed on end sections of the two or four journals or on the pin or pins, said sliding blocks being pivotable or rotatable relative to the journal or to the pin or pins about the transverse axis and being inserted in a sliding manner into the slotted holes or grooves.
In another illustrative embodiment, the driving device has at least one Cardan joint known per se from the prior art, the central part of which has two transverse axes, which intersect and are perpendicular to one another and along each of which two journals inserted pivotably into holes extend.
In a development of the Cardan joint, the central part thereof can be an intermediate sleeve which is annular, for example, which is arranged between an outer circumference of the drive shaft of or the rotor and an inner circumference of the piston disk or the bushing-type extension thereof. In this case, the intermediate sleeve can be connected in an articulated manner to the rotor by means of two mutually opposite inner journals and can be connected in an articulated manner to the piston disk by means of two mutually opposite outer journals, for example.
Particularly in the case of relatively large tilting angles of the piston disk, it is preferred if the driving device has a central bushing, which, on the one hand, is articulated on the drive shaft or on the rotor and, on the other hand, is articulated on the piston disk or the bushing-type extension thereof. This enables the central bushing to adopt a tilt relative to the drive shaft corresponding to half the tilt of the piston disk.
In this arrangement, the two articulations can be embodied by respective Cardan joints with intermediate sleeves as described above, for example.
The central bushing can also be articulated on the drive shaft or on the rotor by means of two rotary-sliding connectors and can be articulated on the piston disk or the extension thereof by means of two rotary-sliding connectors offset by 90 degrees relative to said rotary-sliding connectors. The rotary-sliding connectors each have a sliding block which is guided in an axial slotted hole or an axial groove, and they each have a journal which is inserted pivotably into a hole.
In another preferred illustrative embodiment, the driving device is formed by a plurality of radially inward-directed projections, e.g. webs, which are each arranged on a cylinder sleeve and which remain engaged in axial grooves of the piston disk or of the extension thereof during revolution or can be engaged therein during revolution in order in this way to transmit the torque. In this illustrative embodiment, no additional components are required for the driving device.
In another preferred illustrative embodiment, the driving device has a constant velocity joint or homokinetic joint, which has a plurality of balls, wherein each ball is guided in a first and a second groove.
In this case, the balls can be guided in a cage, thereby making possible pairs of grooves which are not capable alone of determining the position of the common ball thereof.
In another preferred illustrative embodiment, the driving device has at least two balls or spherical segments distributed over the circumference, which are each guided along a first straight track set obliquely to the drive shaft (or to the rotor) and along a second straight track set obliquely to a longitudinal axis of the piston disk. In an embodiment as a bipot joint, two mutually opposite balls or spherical segments are provided.
In this case, a pin can be provided, which extends along the first track. According to a first variant, the ball or spherical segment is secured on the pin, and the pin can be moved along the first track. According to a second variant, the pin is secured on the drive shaft or on the rotor, while the ball or spherical segment can be moved along the pin and hence along the first track.
As an alternative, it is also possible for each ball to be guided along the first track and along the second track by two grooves in each case.
The driving device can be a tripot joint having three spherical segments, which are each guided so as to be movable on one of three radial journals of the drive shaft or of the rotor, said radial journals being distributed uniformly over the circumference, and which are each guided so as to be movable in two mutually opposite axial grooves of the piston disk.
It is also possible to provide two tripot joints of this kind, of which a first tripot joint connects the drive shaft or the rotor in an articulated manner to the central bushing, and wherein the second tripot joint connects the central bushing in an articulated manner to the piston disk.
In another preferred illustrative embodiment which is simple in terms of device design, the driving device is formed by the spherical or ball-shaped sections inserted in the cylinder sleeves and by the cylinder sleeves and by necks of the pistons. The necks are preferably of tapered shape for this purpose.
In another illustrative embodiment, the driving device has a plurality of recesses, which are distributed over the circumference of the rotor, for example, and into which corresponding pins, which are secured on the piston disk, for example, engage during revolution.
In another illustrative embodiment, the driving device has a curved toothing, which is formed on the drive shaft or on the rotor, on the one hand, and on the piston disk, on the other hand. In the case of a constant-displacement machine, the toothing can be of tapered configuration.
The driving device can also have a flexible element or an element which can be bent according to the tilt of the drum disk. This element can be a bellows, for example.
Various illustrative embodiments of a hydrostatic axial piston machine according to the disclosure are described in detail below with reference to the figures.
In the drawings:
During revolution of the drive shaft 1 with the rotor 2, the piston disk 14 and with the cylinder sleeves 6, the pistons 8 perform a stroke motion relative to the respective cylinder sleeve 6. In this case, the spherical pistons 8 are inserted pivotably in the respective cylinder sleeves 6. The piston disk 14 is pushed in the direction of the rotor 2 (to the left in
By means of an axial sliding joint according to the disclosure, which is designed as a groove-key arrangement 16 between the rotor 2 and the drive shaft 1 in the first illustrative embodiment according to
Driving is accomplished by means of the displacer unit having the three contact partners: spherical segment 4, cylinder sleeve 6 and neck 12. In this case, the necks 12 are configured in such a way that, at one of the pistons 8, there is always surface contact between the neck 12 thereof and the associated cylinder sleeve 6, via which the torque is transmitted. The driving piston 8 changes during one revolution of the illustrative embodiment shown in
The piston disk 114 is driven by means of flattened outer regions of the sliding blocks 126, which are in contact with one of two contact surfaces of the slotted holes 122. As an alternative, the pin can also be secured in the rotor instead of in the drive shaft. Moreover, the pin can be introduced into the piston disk or into the extension and the contact surfaces can be introduced into the rotor. As a supplement to the second illustrative embodiment according to
In the third illustrative embodiment and in the fourth illustrative embodiment, axial decoupling is ensured by introducing a groove-key arrangement 16 according to
Since the shape of the grooves 236, 237 does not unambiguously determine the position of the associated balls 234 in the fifth illustrative embodiment according to
According to another basic variant, the driving device is formed by a plurality of pots, the balls 244 of which each run on two obliquely set straight tracks.
In the illustrative embodiment according to
A disclosure is made of a hydrostatic axial piston machine having a drive shaft and having a plurality of cylinder sleeves, in which a spherical or ball-shaped section, on the one hand, and a spherical or ball-shaped piston, on the other hand, are inserted in order to delimit a respective displacer chamber. The sections are secured on a rotor, while the pistons are secured on a piston disk or piston drum. Depending on the embodiment, the piston disk can be tilted at different pivoting angles relative to the rotor in a variable-displacement machine, or the piston disk is tilted continuously relative to the rotor in a constant-displacement machine. The rotor and the piston disk are coupled to one another for conjoint rotation by means of a driving device. This coupling can also be implemented indirectly by means of a drive shaft of the machine. A sliding joint axial with respect to a drive shaft is arranged between the rotor and the piston disk.
Number | Date | Country | Kind |
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10 2013 222 602.0 | Nov 2013 | DE | national |