DE102010035820A1 - Hydrostatic positive displacement engine has piston that is subjected to input tilting movement along transverse direction of raceway - Google Patents

Abstract

The engine has a cylindrical drum (2) which is provided with hole-shaped piston recess portion (3b) around a rotational axis. The piston is supported by rolling element (W) at stroke-producing raceway (6). The piston is tilted between rolling element and raceway, so as to support piston by hole-shaped piston recess of cylindrical drum. The piston in the region of rolling element is subjected to input tilting movement along transverse direction of raceway.

Description

The invention relates to a hydrostatic displacement machine with a cylinder drum arranged about a rotation axis, which is provided with at least one bore-shaped piston recess, in which a piston is arranged longitudinally displaceable, wherein the piston is supported by means of a roller-shaped rolling body on a thrust generating track.

In such positive displacement machines, for example single-stroke or multi-stroke axial piston machines or radial piston machines, it is known to support the piston forces resulting from the pressurization of the pistons by means of a roller-shaped rolling element on a thrust-producing track. The rolling element is in this case mounted in the piston by means of a sliding bearing.

From the DE 10 2005 058 323 A1 a generic displacement machine is known, which is designed as a multi-stroke axial piston machine, in which the pistons are supported by means of a respective roller-shaped rolling elements on the inclined in the direction of travel, huberzeugenden career. The pistons are guided longitudinally displaceable in a bore-shaped piston recesses of the cylinder drum with a relatively small clearance.

Due to manufacturing tolerances and due to resulting in the operation of the displacement engine from the engine forces occurring deformations of the components, for example on a non-rotatably connected to the cylinder drum drive shaft, or by external forces on the drive shaft, it may come to operating conditions in which a parallelism of the huberzeugenden career and the outer circumferential surface of the rolling element is not guaranteed and a misalignment between the roller-shaped rolling elements and the raceway occurs. However, this misalignment of the rolling body with respect to the thrust generating career leads to a reduction of the contact area in the rolling contact of the rolling body with the track and an uneven load distribution with high voltage spikes in the region of the remaining contact area and rolling contact of the rolling body on the track. This results in the contact area of the rolling element with the track high Hertzian pressure, which adversely affects the life of the pairing of rolling, which is formed by the rolling element and the track. In addition, the resulting from the misalignment of the rolling element reduction of the contact area between the rolling element and the raceway causes increased wear.

If between the rolling elements and the piston, a sliding bearing, such as a hydrostatically relieved sliding bearing is formed, the sliding bearing in a misalignment of the rolling element with respect to the track on a strong increase in the surface pressure, whereby the wear in the sliding bearing increases and its life decreases.

Because of these effects, such positive displacement machines are used only with pressures in the so-called medium pressure range in the range of about 200 to about 300 bar, while continuing to avoid high speeds. As a result, such a displacement machine has only a low power density and low wear resistance. Due to the limited life also the applications are limited.

The present invention has for its object to provide a positive displacement machine of the type mentioned, which has an increased power density and increased wear resistance.

This object is achieved in that the piston is mounted to compensate for a misalignment between the rolling elements and the raceway in the piston recess of the cylinder drum, that the piston in the region of the rolling body can perform a directed in the transverse direction of the career Ausgleichskippbewegung. The idea according to the invention therefore consists in compensating for a misalignment possibly occurring between manufacturing tolerances and component deformations between the roller body and the raceway by a targeted compensating movement of the respective piston in the corresponding piston recess in the form of a compensating tilting movement. The compensating tilting movement of the piston is in this case directed essentially in the transverse direction of the raceway. A compensating rocking movement in the transverse direction of the track is in this case a movement transversely to the track and thus transversely to the running direction of the piston along the track. In axial piston machines, this compensating rocking movement in the transverse direction of the track is a tilting movement of the piston in the radial direction of the axial piston machine. In a radial piston machine according to the invention, the compensatory tilting movement in the transverse direction is a tilting movement in the axial direction of the radial piston machine. The inventive compensatory tilting movement of the piston provided with the roller-shaped rolling element can thus be ensured that the rolling element is aligned with the outer lateral surface parallel to the raceway. As a result, line contact of the rolling element with the raceway is ensured even with manufacturing tolerances and component deformations, so that a high and optimal osculation between the rolling element and the raceway with a large contact area in the rolling contact is ensured. A misalignment of the rolling element on the track is thus compensated by the compensating tilting movement of the piston, so that the loads of the sliding bearing between the piston and the rolling elements and the loads in the rolling contact between the rolling elements and the raceway can be reduced. A resulting from manufacturing tolerances or component deformations inclined position of the rolling element on the raceway can thus be compensated by the invention Ausgleichskippbewegung of the piston, so that no adverse effects on the Hertzian pressure between the rolling elements and the raceway and in the region of the sliding bearing between the piston and the rolling elements arise. As a result, the displacement machine according to the invention can be operated without increasing the wear at higher pressures. In addition, the positive displacement machine according to the invention has a lower wear. Overall, a high power density with high wear resistance and thus a long service life is thus achieved in the positive displacement machine according to the invention.

According to a preferred embodiment of the invention, the piston is provided for generating the Ausgleichskippbewegung in the region of a Verdrängerraumes having a different shape of a cylindrical cross-sectional shape, wherein the piston dimensions of the cross-sectional shape in the circumferential direction of the track are greater than in the transverse direction of the track. With a deviating from the cylindrical shape cross-sectional shape in the region of the displacer can be achieved in a simple manner compensating rocking movement of the piston in the bore-shaped piston recess of the cylinder barrel. If the piston dimensions at this deviating from the cylindrical shape cross-sectional shape in the circumferential direction of the track and thus in the running direction of the rolling element along the track is greater than in the transverse direction of the track, can be achieved in a simple manner that in the circumferential direction of the raceway of the piston a little play in the Having bore-shaped piston recess. This can be avoided in a simple manner excessive tilting of the piston in the transmission of the torque-generating propulsive force in the piston recess. In the transverse direction of the track, a clearance between the piston and the piston recess is achieved by the reduced piston dimension, which allows the desired Ausgleichskippbewegung the piston.

According to an embodiment of the invention, the cross-sectional shape deviating from the cylindrical shape is formed by an ellipse, wherein the elliptical piston is arranged in the piston recess, that the main axis of the ellipse is arranged in the circumferential direction of the raceway and the minor axis of the ellipse is arranged in the transverse direction of the raceway , On the piston, such an ellipse can be easily manufactured. The ellipse is in this case arranged on the piston in such a way that the minor axis of the ellipse, in which the ellipse has the smallest extent, extends in the transverse direction of the raceway, so that a corresponding clearance and clearance is created, in order to compensate for the piston tilting in the piston recess to enable. The major axis of the ellipse, in which the ellipse has the largest extent, extends in the circumferential direction of the raceway, so that excessive tilting of the piston in the piston recess during the transmission of the propulsion force can be avoided.

According to an alternative embodiment of the invention, the deviating from the cylindrical shape cross-sectional shape of two oppositely arranged, in particular by 180 ° opposite, extensions, in particular circular segment-shaped extensions, formed on the cylindrical piston. With such a cross-sectional shape of the piston, wherein the piston is substantially cylindrical or circular in cross-section and provided on the outer circumference with two hump-like extensions, the desired deviating from the cylindrical shape cross-sectional shape can be produced with a simple manufacturing effort. The clearance and thus the play for the compensating tilting movement of the piston in the piston recess can already be made without any measure on the blank of the cylindrical piston. An exact machining, for example, a mechanical processing of the piston is only required in the region of the two extensions, which form the transmission areas for transmitting propulsive forces from the piston to the cylinder drum.

The piston provided with the extensions is in this case arranged in the piston recess such that the extensions are arranged in the circumferential direction of the raceway. In this way it is achieved that excessive tilting of the piston in the piston recess during the transmission of the driving force can be avoided and a clearance and thus a clearance is generated on the remaining, cylindrical cross-sectional shape of the piston to the compensating rocking movement of the piston in the transverse direction of the track achieve.

According to one embodiment of the invention, the piston is provided on the outer circumference with the cross-sectional shape deviating from the cylindrical shape. Between the outer periphery of the piston and the bore-shaped piston recess thus the desired clearance and clearance can be generated to allow the Ausgleichkippbewegung the piston in the piston recess. Such a training of the cylinder shape deviating cross-sectional shape on the outer circumference of the piston is particularly favorable in a positive displacement machine in which a supporting force occurring in operation of the positive displacement machine in the region of the displacement is transmitted directly from the piston to the piston recess.

Appropriately, in this case for sealing the displacement of the piston in the region of the deviating from the cylindrical shape cross-sectional shape with a sealing device, in particular a piston ring provided. In this way can be achieved in a simple manner, a sealing of the pressurized medium from the displacer to the housing interior of the displacement machine.

The piston is in this case provided for receiving the sealing device with the groove, wherein the groove bottom of the groove has a circular shape. Such a groove having a circular groove bottom can be easily manufactured on the piston provided on the outer periphery with the cross-sectional shape deviating from the cylinder shape to receive the sealing means.

In a direct support of the supporting force of the piston in the piston recess is unfavorable that the supporting force in the region of a main vertex of the major axis of the ellipse, where the ellipse has a small radius of curvature, or on the circular segment-shaped extensions, which also have a small radius of curvature is transmitted from the displacement-side portion of the piston to the cylinder drum. Due to the small radius of curvature at this contact area between the piston and the piston recess creates an unfavorable osculation. In addition, occurs in the direct support of the supporting force of the piston in the piston recess by the longitudinal movement of the piston in the piston recess wear on the main crests of the ellipse or the circular segment extensions on the outer circumference of the piston, by the axial relative movement of the main vertex or the extension is caused in the piston recess.

In order to avoid these effects, it is provided according to a preferred embodiment of the invention that for sealing the displacement of the piston with a sealing device, in particular a piston ring is provided, wherein the piston for receiving the sealing means is provided with a groove and the groove bottom of the groove is provided with the deviating from the cylindrical shape cross-sectional shape. The desired play and the clearance to allow the Ausgleichkippbewegung of the piston in the piston recess is thus achieved by the groove bottom of the seal receiving groove in the piston is provided with the deviating from the cylindrical shape cross-sectional shape. Such a configuration of the cross-sectional shape deviating from the cylindrical shape at the groove base of the groove receiving the sealing device enables an embodiment of the displacement machine in which a supporting force in the region of the displacement chamber is transferred indirectly from the piston to the piston recess with the interposition of the sealing device. The supporting force is in this case transmitted from the piston to the sealing device, which is supported on the piston recess. The region with the unfavorable osculation thus lies between the piston and the sealing device, these components performing no relative axial movement relative to one another during the longitudinal movement of the piston. In such an embodiment of the invention, a small diameter clearance can be selected between the sealing device and the piston recess, so that a high osculation is provided between the sealing device and the piston recess, whereby the supporting force can be transmitted to the cylinder drum with a low pressure. As a result, the wear of the piston longitudinal movement resulting axial movement, which occurs between the sealing device and the piston recess, can be kept low.

In such an embodiment of the invention, the piston can be formed substantially cylindrical in the region of the displacement on the outer circumference. As a result, an easily manufactured piston is made possible, since the outer circumference of the piston in the region of the displacement chamber can already be produced in the blank of the piston with a corresponding outer diameter reduced relative to the piston recess, so that only the piston with the cylinder shape in the displacement side end region deviating groove base provided groove for the sealing device must be incorporated.

According to an embodiment of the invention, the sealing device provided on the displacement chamber-side end region of the piston for sealing the displacement chamber can be designed as a circumferentially slotted sealing ring. With such a slotted sealing ring easy assembly of the sealing ring in the corresponding groove of the piston can be achieved.

In the case of a circumferentially slotted sealing ring, the required gap in the circumference of the sealing ring constitutes a leakage point at which leakage oil can escape from the displacement space into the housing interior of the displacement machine.

In order to avoid this possible leakage of a slotted sealing ring, the sealing device is designed as a circumferentially closed sealing ring according to a preferred embodiment of the invention.

The mountability of such a circumferentially closed sealing ring can be made possible in a simple manner, if according to an expedient embodiment of the invention, the displacement side portion of the piston formed as a groove bottom of the seal receiving groove and on the piston a securing device for axially securing the sealing ring is provided. The sealing device can thus be mounted on the corresponding, formed as a groove bottom of the displacement chamber side portion of the piston and secured by means of the securing device in the axial direction.

In an indirect support of the supporting force on the sealing ring in this case the displacement chamber side portion of the piston is provided with the deviating from the cylindrical shape cross-sectional shape and formed as a corresponding groove bottom for the sealing device.

An attachment of the securing device can be achieved in a simple manner when the piston is provided on the displacement side portion with a recess for receiving the securing device.

In such a puncture, for example, a securing device in the form of a retaining ring or a snap ring can be arranged. According to a preferred embodiment of the invention, the securing device is formed by two semicircular securing washers. Such semi-circular lock washers can be produced in a simple and cost-effective manner and can be inserted without the aid of a tool in the recess of the piston to achieve the axial securing of the closed sealing ring.

The rolling element for supporting the pistons on the thrust-producing track can be designed as a cylindrical roller or as a barrel roller or as a tapered roller in a positive-displacement machine according to the invention.

The displacement machine according to the invention may be designed as one-stroke or multi-stroke and operated as a pump or motor, wherein the displacement machine may be designed as a radial piston machine or as an axial piston machine.

The axial piston machine can be designed as a swashplate machine with a cylinder drum mounted rotatably about the rotation axis or as a swashplate machine with a raceway arranged so as to be rotatable about the rotation axis.

Further advantages and details of the invention will be explained in more detail with reference to the embodiments illustrated in the schematic figures. This shows

1 a displacement machine of the prior art in a longitudinal section

2 a section of the 1 in an enlarged view,

3 a first embodiment of a positive displacement machine according to the invention in a representation according to the 2

4 a section along the line AA the 3 .

5 a section along the line BB of 4 .

6 a section along the line CC the 4 .

7 a second embodiment of the invention in a section according to the 5 .

8th a third embodiment of the invention in a representation according to the 3 .

9 a section along the line AA the 8th .

10 a section along the line BB of 9 .

11 a section along the line CC the 9 .

12 A fourth embodiment of the invention in a representation according to the 3 respectively. 8th .

13 a section along the line AA the 12 .

14 a section along the line BB of 13 .

15 a section along the line CC the 13 and

16 a sixth embodiment of the invention in a section according to the 15 ,

In the 1 is a hydrostatic positive displacement machine 1 of the prior art shown in a longitudinal section, which is designed for example as a multi-stroke axial piston machine in swash plate design.

The displacement machine 1 has a cylinder drum rotatably mounted about a rotation axis D. 2 on, with several concentric with the axis of rotation D piston recesses arranged 3 is provided, in each of which a piston 4 is mounted longitudinally displaceable.

The pistons 4 are supported by means of a respective roller-shaped rolling element W on a particular multi-stroke, huberzeugenden career 6 off, on the front side of a housing-fixed Hubscheibe 7 is trained. The rolling element W is, for example, a roller designed as a cylindrical roller 8th formed, whose axis of rotation R is arranged perpendicular to the axis of rotation D.

The cylinder drum 2 is supported in the axial direction of the axial piston machine 1 opposite to the lifting disc 7 on a housing-fixed axial control surface 9 provided with kidney-shaped control slots, which has an inlet port 10 and an outlet port 11 the axial piston machine 1 form. The cylinder drum 2 is for each piston recess 3 with a connection channel 12 provided during a rotation of the cylinder drum 2 about the axis of rotation D, a compound of the piston recess 3 and the piston 4 formed Verdrängerraums V with the inlet port 10 and the outlet port 11 allows.

The cylinder drum 2 is further arranged with a concentric with the axis of rotation D drive shaft 13 rotatably connected, within the cylinder drum 2 in a housing 15 the axial piston machine 1 by means of appropriate bearings 16 . 17 is rotatably arranged. The connection between the cylinder drum 2 and the shoot shaft 13 For example, by means of a toothing 19 ,

For loading the cylinder drum 2 in the direction of the control surface 9 is a spring 14 intended.

At the positive displacement machine 1 are the rolling elements W, with which the pistons 4 at the track 6 supported in the corresponding piston 4 in a recess 18 held on the piston 4 at the runway 6 is incorporated facing front side. The recess 18 of the piston 4 encloses in this case the rolling elements W - as in conjunction with the 2 is clear - cage-like, being between the piston 4 and the outer circumference of the rolling body W preferably a sliding bearing G is formed. The sliding bearing G is formed in the illustrated embodiments as a hydrostatically relieved sliding bearing G. Corresponding side walls in the region of the recess 18 of the piston 4 serve in the illustrated embodiment of the positive displacement machine 1 for securing the rolling elements W in the radial direction of the displacement machine 1 along the axis of rotation R.

The hydrostatically relieved slide bearing G between the recess 18 of the piston 4 and the rolling element W can from at least one arranged in the recess pressure pocket 20 are formed, extending in the circumferential direction of the recess 18 extends and for hydrostatic discharge by means of a piston in the 4 arranged supply ducts 21 with a displacement V of the corresponding piston 4 communicates.

In the illustrated positive displacement machine 1 are the pistons 4 designed as a stepped piston, each having a first piston portion 4a and a second piston portion 4b have, wherein the first piston portion 4a in a first section 3a the piston recess 3 and the piston section 4b in a second section 3b the piston recess 3 is arranged. The two piston sections 4a . 4b are directly adjacent to each other on the piston 4 arranged. The piston recess 3 is step-shaped and formed for example by a stepped bore, at least in the section 3b has a circular cross-section.

The first piston section 4a and the first section 3a the piston recess 3 is opposite to the second piston portion 4b and the second section 3b the piston recess 3 enlarged in diameter or in cross section. The reduced in diameter or cross-section second section 3b the piston recess 3 form with the corresponding second piston portion 4b the pressurized displacer V. The enlarged in diameter or cross section first piston section 4a holds the rolling element W. The first piston section 4a and the first section 3a the piston recess 3 are the career path here 6 facing and in the front region of the axial piston machine 1 arranged. The second piston section 4b and the second section 3b the piston recess 3 is the control surface 9 facing and thus in the rear of the axial piston machine 1 arranged.

In the illustrated positive displacement machine 1 is designed as a stepped piston piston 4 with a small clearance in the stepped bore-shaped piston recess 3 the cylinder drum 2 arranged longitudinally displaceable. This can - as in the 2 is shown - as a result of manufacturing tolerances or component deformations during operation of the positive displacement machine 1 a misalignment α between the raceway 6 at the Hubscheibe 7 and the outer circumferential surface of the rolling element W occur and thus a parallelism of the rolling body W with the raceway 6 at the Hubscheibe 7 no longer be guaranteed. The misalignment α between the roller-shaped rolling elements W and the raceway 6 leads to the support of the pressure in the displacement V forthcoming forces on the Hubscheibe 7 to an uneven load distribution with high voltage spikes in the remaining rolling contact between the rolling element W and the raceway 6 , This results in high Hertzian pressure, which leads to a reduction in the life of the rolling mating, which of the raceway 6 and the rolling element W is formed lead. The misalignment α also leads to the surface pressures in the sliding bearing G between the piston 4 and the rolling element W has strong elevations, whereby at the sliding bearing G high wear and a low life occurs.

In the 3 is a positive displacement machine according to the invention 1 shown. In the 3 is just the area according to the 2 shown, wherein the remaining structure of the positive displacement machine according to the invention 1 with the in the 1 represented construction of the positive displacement machine of the prior art.

In the in the 3 to 7 illustrated embodiments of a positive displacement machine according to the invention 1 is the piston 4 on the outer circumference in the region of the second, displacement chamber-side section 4b with one of the cylindrical shape and in cross-section of the piston 4 seen with a deviating from the circular cross-sectional shape Q provided.

The deviating from the cylindrical shape cross-sectional shape Q in the region of the section 4b of the piston 4 is according to the in the 3 to 6 illustrated first embodiment of the invention is formed by an ellipse E.

The piston provided with the ellipse E 4 is here in the piston recess 3 arranged so secured against rotation, that the main axis HA of the ellipse E, in which the ellipse has the largest extent, in the circumferential direction of the raceway 6 is arranged. In the 4 Here is a section through the piston subcircuit of the cylinder drum 2 in the circumferential direction of the raceway 6 and thus in the running direction of the rolling elements W, in which the main axis HA of the ellipse E can be seen. The minor axis NA of the ellipse E, in which the ellipse E has the smallest extent, is arranged for this purpose in a vertical plane and is in the transverse direction of the raceway 6 is arranged. In the 3 is a longitudinal section of the axial piston machine shown, it being apparent that the ellipse E with the minor axis NA in the transverse direction of the track 6 and thus in the radial direction of the axial piston machine designed as a displacement machine 1 is arranged.

With this orientation of the ellipse E at the section 4b of the piston 4 is thus achieved that the piston dimensions of the piston 4 at the deviating from the cylindrical shape cross-sectional shape Q in the circumferential direction of the raceway 6 and thus in the running direction of the rolling elements W greater than in the transverse direction of the raceway 6 and thus in the radial direction of the axial piston machine designed as a displacement machine 1 is.

By the arrangement of the main axis HA of the ellipse E in the circumferential direction of the raceway 6 is achieved that the piston 4 - like in the 4 and the 5 it can be seen - with the outer circumference elliptical shaped piston section 4b in the circumferential direction of the raceway 6 only a slight play in the bore-shaped section 3b the piston recess 3 Has. By the arrangement of the minor axis NA of the ellipse E in the radial direction of the displacement machine 1 points the piston 4 - like in the 3 and the 5 it can be seen - in the radial direction of the displacement machine 1 with the outer circumference elliptical shaped piston section 4b a big game in the hole-shaped section 3b the piston recess 3 on. This will release the piston 4 achieved by the piston 4 a compensating tilting movement α 'in the piston recess 3 can perform. By this Ausgleichskippbewegung α ', the piston 4 with its piston longitudinal axis K with respect to the longitudinal axis L of the piston recess 3 tilt out of its axle center. The compensating rocking movement α 'of the piston 4 from its axial center causes the rolling elements W in the transverse direction of the raceway 6 and thus in the radial direction of the displacement machine 1 tilted, so that caused by component deformations or manufacturing tolerances misalignment α between the rolling body W and the raceway 6 is balanced and between the rolling element W and the raceway 6 a linear contact area is achieved in the rolling contact.

To seal the displacer V is the elliptical shaped section on the outer circumference 4b of the piston 4 with a sealing device 40 , For example, a piston ring provided. The piston 4 is to receive the sealing device 40 with the groove 41 provided, wherein the groove bottom 42 the groove 41 - as in particular from the 3 . 4 and 6 is apparent - has a circular shape.

When in the 7 illustrated second embodiment of the invention is deviating from the cylindrical shape cross-sectional shape Q in the area of the displacement-side section 4b of the piston 4 of two oppositely arranged extensions 45a . 45b , in particular circular segment-shaped extensions, on the otherwise cylindrical portion 4b of the piston 4 educated. In the 7 Here is a section according to the 5 through the displacement side section 4b of the piston 4 shown. The second embodiment according to the 7 otherwise corresponds to the construction of the piston 4 and the arrangement of the sealing device 40 in the 3 . 4 and 6 illustrated embodiment.

The two extensions 45a . 45b are in this case on the cylindrical portion 4b of the piston 4 molded that extensions 45a . 45b - Like the main axis HA of the ellipse E - in the circumferential direction of the track 6 are arranged so that between the remaining cylindrical portion 4b of the piston 4 and the bore-shaped piston recess 3b a clearance arises, the compensating rocking movement α 'of the piston 4 from its middle allows.

In the 4 are for the positive displacement machine according to the invention 1 the forces occurring during operation of the positive displacement machine according to the invention 1 when rolling the rolling element W along the track 6 at a force acting in the direction of the piston longitudinal axis K, resulting from the pressure in the displacement chamber V cylinder force F _z . The rolling element W supports the cylinder force F _z by means of a perpendicular to the raceway 6 acting normal force F _N , which is decomposed by the power decomposition in a force acting in the piston longitudinal direction piston force F _k and a lateral force F _q , the torque on the cylinder drum 2 causes. When dipping the centers or the roller axes R of the rolling elements W from the cylinder drum 2 arises due to the lateral force F _q a tilting moment on the piston 4 , which is supported by a pair of forces with supporting forces F _A and F _B. The supporting force F _A occurs here in the front region of the piston 4 between the section 4a the piston 4 and the section 3a the piston recess 3 on. The supporting force F _B occurs at the displacement-side end portion of the piston 4 between the portion provided with the cross section Q in the outer circumference 4b of the piston 4 and the bore-shaped section 3b the piston recess 3 on.

In the in the 3 to 7 illustrated two embodiments of the invention, the supporting force F _B directly from the piston 4 on the section 3b the piston recess 3 transfer.

Like from the 5 and 7 is apparent, the supporting force F _B at the region of the piston 4 on the piston recess 3b on which the main axis HA of the ellipse E is arranged or a hump-like extension 45a on the piston 4 is trained. The piston 4a indicates at these transmission areas due to the small radius of curvature in the region of the main vertex of the ellipse E or the small radius of curvature of the extension 45a an unfavorable osculation with the bore-shaped piston recess 3b on. In addition, occurs in the embodiments of the 3 to 7 with a direct support of the supporting force F _B at the transmission areas of the supporting force F _B during the longitudinal movement of the piston 4 in the piston recesses 3b a relative axial movement on these transmission areas. As a result, wear can occur at the transmission areas.

In the 8th to 16 Further embodiments of the invention are shown in which by an indirect support of the supporting force F _B possible wear on the transmission areas of the supporting force F _{B can} be avoided.

In contrast to the embodiment according to the 3 to 7 is in the embodiments according to the 8th to 16 the displacement-side end portion of the piston 4 and thus the section 4b of the piston 4 provided with a substantially cylindrical cross-section on the outer periphery and in the section 3b the bore-shaped piston recess 3 arranged with an appropriate game, as in particular in the 10 is apparent. To the Ausgleichskippbewegung α 'of the piston 4 to enable, is the groove bottom 42 the sealing device 40 , For example, a piston ring, receiving groove 41 provided with the deviating from the circular cross-sectional shape Q.

The deviating from the cylindrical shape cross-sectional shape Q at the bottom of the groove 42 of the piston 4 is according to the in the 8th to 11 represented third embodiment of the invention of an ellipse E is formed.

The embodiment according to the 8th to 11 is here with respect to the orientation of the ellipse E with the main axis HA and the minor axis NA at the bottom of the groove with the 3 to 6 identical, so that the main axis HA of the ellipse E in the circumferential direction of the raceway 6 and the minor axis NA of the ellipse in the transverse direction of the raceway 6 and thus in the radial direction of the displacement machine 1 is arranged. This orientation allows the Ausgleichskippbewegung α 'of the piston 4 from its center to a possible misalignment α of the rolling element W on the track 6 compensate.

Both 3 to 11 is the one in the groove 41 on the piston 4 used sealing device 40 as circumferentially slotted sealing ring 40a educated. At the radial gap 44 the slotted sealing ring 40a can in the sealing of the displacement V leakage oil through the gap of the sealing ring 40a into the housing interior of the positive displacement machine 1 escape.

To avoid this leakage, according to the in the 12 to 15 illustrated fourth embodiment of the invention, the sealing device 40 as circumferentially closed sealing ring 40b educated. To a mountability of the closed sealing ring 40b to allow, is the displacement-side section 4b of the piston 4 as groove bottom 42 the sealing device 40 receiving groove 41 educated. To secure the sealing device 40 in the axial direction is on the piston 4 a safety device 50 for axial securing of the sealing ring 40b intended.

The safety device 50 is - as in the 14 is shown - of two semicircular lock washers 51a . 51b formed in a groove-shaped recess 52 of the piston 4 who is at the section 4b of the piston 4 is arranged, are included.

The in the 12 to 15 illustrated embodiment corresponds to the in the 8th to 11 described embodiment in which the groove bottom 42 is provided with the ellipse E. In the in the 12 to 15 illustrated embodiment is thus the displacement side portion 4b of the piston 4 at its the Verdrängerraum V facing end portion as a groove bottom 42 formed, which is provided with the ellipse E.

A closed sealing ring 40b as a sealing device 40 Alternatively, in the in the 3 to 7 illustrated embodiments are used.

When in the 16 illustrated fifth embodiment of the invention is deviating from the cylindrical shape cross-sectional shape Q in the groove bottom 42 the sealing device 40 of two oppositely arranged extensions 45a . 45b , in particular circular segment-shaped extensions, on the otherwise cylindrical portion 4b of the piston 4 educated. The 16 is in terms of orientation and the arrangement of the two extensions 45a . 45b at the bottom of the groove with the 7 identical, so the two extensions 45a . 45b such on the groove bottom 42 of the piston 4 are formed, that the extensions 45a . 45b - Like the main axis HA of the ellipse E - in the circumferential direction of the track 6 are arranged.

The in the 16 illustrated embodiment may in this case instead of the elliptical groove bottom 42 in a positive displacement machine 1 according to the 8th to 11 with a slotted sealing ring or a positive displacement machine 1 according to the 12 to 15 be used with a closed seal.

In the in the 8th to 16 illustrated embodiments of the invention, the supporting force F _B on the displacement side portion 4b of the piston 4 - as in the 11 . 15 and 16 is clarified - indirectly from the piston 4 on the drill-shaped section 3b the piston recess 3 transfer. The support force F _B is in this case first on the sealing device 40 coming from a slotted sealing ring 40a or a closed seal 40b can be formed, transferred and from the sealing device 40 on the section 3b the piston recess 3b transfer. The transmission regions with the small radius of curvature in the region of a vertex of the main axis HA of the ellipse E or the small radius of curvature of the extension 45a , which have an unfavorable osculation, are here between the piston 4 and the sealing device 40 arranged, these components during the longitudinal movement of the piston in the piston recess 3 Do not perform relative axial movement to each other. The diameter clearance between the sealing device 40 and the section 3b the piston recess 3 can be chosen low, so that a high osculation between the sealing device 40 and the section 3b the piston recess 3 can be achieved. Thereby, a low pressure in the transmission of the supporting force F _B can be achieved and a low wear can be achieved.

According to the invention is distinguished by the deviating from the cylindrical shape cross-section Q of the piston 4 that of an ellipse E or the two extensions 45a . 45b can be formed, and thereby achievable Ausgleichskippbewegung α 'of the piston 4 achieved that a possible misalignment α of the roller-shaped rolling body W on the track 6 can be compensated, so that the parallelism of the outer circumferential surface of the rolling element W with the raceway 6 is guaranteed. As a result, in the displacement machine according to the invention 1 optimum osculation between the roller-shaped rolling elements W and the raceway 6 in the rolling contact and in the sliding bearing G between the rolling elements W and the piston 4 achieved and in the operation of the positive displacement machine 1 guaranteed. As a result, the maximum pressures and loads in the region of the rolling contact between the rolling elements W and the raceway 6 and in the region of the sliding bearing G between the piston 4 and the rolling element W are reduced, so that the displacement machine 1 operable at high pressures and at high speeds. In addition, the positive displacement machine according to the invention 1 a little wear and tear thus a high wear resistance, so that there is a long life. Overall, thus, the power density of the positive displacement machine 1 increased at the same time high life.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102005058323 A1 [0003]

Claims (22)

Hydrostatic displacement machine having a cylinder drum arranged about a rotation axis and provided with at least one bore-shaped piston recess in which a piston is arranged so as to be longitudinally displaceable, wherein the piston is supported by means of a roller-shaped rolling element on a thrust-generating raceway, characterized in that the piston ( 4 ) for compensating a misalignment (α) between the rolling body (W) and the raceway ( 6 ) in the bore-shaped piston recess ( 3 ) of the cylinder drum ( 2 ) is mounted, that the piston ( 4 ) in the region of the rolling body (W) a in the transverse direction of the track ( 6 ) directed compensating tilting movement (α ') can perform. Hydrostatic displacement machine according to claim 1, characterized in that the piston ( 4 ) is provided for generating the compensating tilting movement (α ') in the region of a displacement chamber (V) with a cross-sectional shape (Q) deviating from a cylindrical shape. Hydrostatic displacement machine according to claim 2, characterized in that the piston dimensions at the deviating from the cylindrical shape cross-sectional shape (Q) in the circumferential direction of the track ( 6 ) greater than in the transverse direction of the track ( 6 ) are. Hydrostatic displacement machine according to claim 2 or 3, characterized in that the deviating from the cylindrical shape cross-sectional shape (Q) of an ellipse (E) is formed, wherein the piston ( 4 ) in the piston recess ( 3 ) is arranged such that the main axis (HA) of the ellipse (E) in the circumferential direction of the track ( 6 ) is arranged and the minor axis (NA) of the ellipse (E) in the transverse direction of the track ( 6 ) is arranged. Hydrostatic displacement machine according to claim 2 or 3, characterized in that the deviating from the cylindrical shape cross-sectional shape (Q) of two oppositely disposed extensions ( 45a . 45b ), in particular circular segment-shaped extensions, on the cylindrical piston ( 4 ) is formed. Hydrostatic displacement machine according to claim 5, characterized in that the extension ( 45a . 45b ) provided pistons ( 4 ) in the piston recess ( 3 ) is arranged that the extensions ( 45a . 45b ) in the circumferential direction of the track ( 6 ) are arranged. Hydrostatic displacement machine according to one of claims 2 to 6, characterized in that the piston ( 4 ) is provided on the outer periphery with the deviating from the cylindrical shape cross-sectional shape (Q). Hydrostatic displacement machine according to claim 7, characterized in that for sealing the displacement chamber (V) of the piston ( 4 ) in the region of the cross-sectional shape (Q) deviating from the cylindrical shape with a sealing device ( 40 ), in particular a piston ring, is provided. Hydrostatic displacement machine according to claim 8, characterized in that the piston ( 4 ) for receiving the sealing device ( 40 ) with a groove ( 41 ), the groove bottom ( 42 ) of the groove ( 41 ) has a circular shape. Hydrostatic displacement machine according to one of claims 2 to 6, characterized in that for sealing the displacement chamber (V) of the piston ( 4 ) with a sealing device ( 40 ), in particular a piston ring, is provided, wherein the piston ( 4 ) for receiving the sealing device ( 40 ) with a groove ( 41 ) and the groove bottom ( 42 ) of the groove ( 41 ) is provided with the deviating from the cylindrical shape cross-sectional shape (Q). Hydrostatic displacement machine according to claim 10, characterized in that the piston ( 4 ) is substantially cylindrical in the region of the displacement chamber (V) on the outer circumference. Hydrostatic displacement machine according to one of claims 8 to 11, characterized in that the sealing device ( 40 ) as a circumferentially slotted sealing ring ( 40a ) is trained. Hydrostatic displacement machine according to one of claims 8 to 11, characterized in that the sealing device ( 40 ) as circumferentially closed sealing ring ( 40b ) is trained. Hydrostatic displacement machine according to claim 13, characterized in that the displacement side portion ( 4b ) of the piston ( 4 ) as groove bottom ( 42 ) of the sealing device ( 40 ) receiving groove ( 41 ) is formed and on the piston ( 4 ) a safety device ( 50 ) for axially securing the sealing ring ( 40b ) is provided. Hydrostatic displacement machine according to claim 14, characterized in that the displacement side portion ( 4b ) of the piston ( 4 ) is provided with the deviating from the cylindrical shape cross-sectional shape (Q). Hydrostatic displacement machine according to claim 14 or 15, characterized in that the piston ( 4 ) on the displacement side ( 4b ) with a puncture ( 52 ) for receiving the safety device ( 50 ) is provided. Hydrostatic displacement machine according to one of claims 14 to 16, characterized in that the securing device ( 50 ) of two semicircular lock washers ( 51a . 51b ) is formed. Hydrostatic displacement machine according to one of claims 1 to 17, characterized in that the rolling body (W) is designed as a cylindrical roller or barrel roller or tapered roller. Hydrostatic displacement machine according to one of claims 1 to 18, characterized in that the displacement machine ( 1 ) is designed in one stroke. Hydrostatic displacement machine according to one of claims 1 to 18, characterized in that the displacement machine ( 1 ) is designed to be multi-stroke. Hydrostatic displacement machine according to one of claims 1 to 20, characterized in that the displacement machine ( 1 ) is designed as a radial piston machine. Hydrostatic displacement machine according to one of claims 1 to 21, characterized in that the displacement machine ( 1 ) is designed as an axial piston machine.

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