DE102013221623A1 - axial piston - Google Patents

Abstract

Axial piston machine (100) for pump and / or motor operation with a housing (10), a drive shaft (20) and a piston drum (40). The piston drum (40) is connected to the drive shaft (20). The drive shaft (20) is rotatably supported by a first bearing (21) and a second bearing (22) within the housing (10), wherein the first bearing (21) as a tapered roller bearing and the second bearing (22) is designed as a sliding bearing. The first bearing (21) can receive axial forces on the drive shaft (20) in a direction of force from the second bearing (22) to the first bearing (21). The drive shaft (20) is biased in this direction of force. On a housing end face (11) of the housing (10), which is turned on or off, a stop surface (12) is arranged which is in contact with a stop face (15a) of a drive wheel (20) arranged on the drive shaft (20). Abtriebrades (15) can interact.

Description

The invention relates to an axial piston machine according to the preamble of claim 1.

State of the art

Axial piston machines are hydrostatic pumps or motors which are based on the positive displacement principle and which compress hydraulic fluids or are driven by compressed fluids. The known axial piston machines have a plurality of working cylinders in a rotating piston drum and on a pivotable pivoting cradle kinematically guided working piston. The working piston are acted upon on the fluid side of the axial piston machine with a fluid pressure, wherein the resulting forces are absorbed on the opposite side of the working piston, in particular via a respective shoe, on the pivoting cradle.

• – Bei einer Axialkolbenpumpe wird die Kolbentrommel über eine Triebwelle durch ein Getriebe angetrieben und das Fluid in den Arbeitszylindern durch die Arbeitskolben gegen einen Hochdruckbereich verdichtet.
• – Bei einem Axialkolbenmotor wird den Arbeitszylindern unter Hochdruck stehendes Fluid zugeführt und so eine Drehbewegung der Kolbentrommel erzeugt und dadurch ein Drehmoment an der Triebwelle erzeugt.

An axial piston machine can be operated in both pump and motor mode:

• - In an axial piston pump, the piston drum is driven via a drive shaft through a transmission and the fluid in the working cylinders is compressed by the working piston against a high pressure area.
• - In an axial piston motor high pressure fluid is supplied to the working cylinders and thus generates a rotational movement of the piston drum and thereby generates a torque on the drive shaft.

From the EP 0 608 144 A2 Such an axial piston pump is known, the drive shaft is designed with a first bearing as a tapered roller bearing and a second bearing as a sliding bearing. In this case, the plain bearing has a bearing bottom as a thrust bearing, which serves as a stop surface for the drive shaft, when axial forces are introduced in one direction from the tapered roller bearing to the plain bearing.

However, the production of the known thrust bearing requires a high accuracy of fit between drive shaft and plain bearing. Due to the press-fitting process of the sliding bearing into the housing of the axial piston pump, disadvantageous deformations on the bearing bottom and subsequently additional wear can continue to occur.

The axial piston machine according to the invention has the advantage that an easy to be manufactured thrust bearing is used.

Disclosure of the invention

For this purpose, the axial piston according to the invention comprises a housing, a drive shaft and a piston drum, wherein the piston drum is connected to the drive shaft. The drive shaft is rotatably supported by a first bearing and a second bearing within the housing, wherein the first bearing is designed as a tapered roller bearing and the second bearing is designed as a sliding bearing. The first bearing can absorb axial forces on the drive shaft in a direction of force from the second bearing to the first bearing and the drive shaft is biased in this direction of force. An abutment surface is arranged on a housing end face of the housing facing the input or output, which abutment surface can co-operate with a contact surface, which is opposite the abutment surface, of a drive wheel or output wheel arranged on the drive shaft. As a result, the Axialkraftaufnahme is assigned in a simple manner to the arrival and driven wheel and can even be placed outside the housing, so that a good manageable adjustment and verification of the contact surfaces of the thrust bearing can be done.

In an advantageous embodiment of the axial piston machine according to the invention, the stop surface is formed on a steel disc arranged on the housing front side. As a result, stop surface and steel disc can be made of different materials and optimized accordingly adapted to the respective functions. For the steel disc, it is preferable to use a wear-resistant material which at the same time has good tribological properties on contact with the contact surface of the drive and driven wheel, especially a low coefficient of friction.

Advantageously, the housing is designed in two parts, with a drive or Abtriebsseitigem first housing part in which the first bearing is arranged, and a housing end side second housing part in which the second bearing is arranged. As a result, all functional parts of the axial piston machine can be arranged within the housing in a compact design.

In an advantageous embodiment, the biasing force is generated by a spring which is arranged between the drive shaft and the piston drum. As a result, on the one hand the drive shaft is biased against the designed as a tapered roller bearing first bearing and on the other hand, the piston drum against the housing. The operation of the tapered roller bearing requires an axial preload, through the use of the spring eliminates a costly alternative type of bias. During operation of the axial piston machine, it may come to lift the piston drum from the housing or from an interposed control disc and thus to increased leakage. The spring force on the piston drum counteracts this leakage advantageous.

In an advantageous development of the axial piston machine according to the invention, the second bearing consists of a composite material. By separating axial and radial bearing functions for the second bearing, the design of the second bearing designed as a slide bearing can be optimized for the radial bearing functions. An advantageous mixture of stiffness and tribological running properties is preferably achieved with a composite material.

Advantageously, the second bearing consists of a steel backing with sintered bronze and a cover layer of polyphenylene sulfide. The steel backing with sintered-on bronze contains a dimensionally stable, well-pressed outer steel shell and a deformable bronze core that can better adapt to any inhomogeneous load than a steel core. Furthermore, the polyphenylene sulfide can be applied well to the running surface of the slide bearing on the bronze layer. Polyphenylene sulfide has very good mechanical, thermal and chemical properties and is therefore particularly well suited as a sliding surface of the second bearing.

In an advantageous embodiment, the first bearing has a larger inner diameter than the second bearing. If the drive shaft is sealed to the housing on the shaft diameters of the first and second bearings, this results in a resulting hydraulic force from the second to the first bearing, because the pressure acting on the drive shaft in the axial piston machine is greater than the ambient pressure. The resulting hydraulic force acts in the direction of the spring force and thus supported the bias of the trained as a tapered roller bearing first bearing.

In a further advantageous embodiment, a shaft end is formed on the drive shaft housing end side, wherein the second bearing is arranged on the shaft end. As a result, the housing can be made closed at this end of the shaft. This eliminates a seal between the drive shaft and housing and in addition increases the advantageous resulting hydraulic force on the drive shaft in the direction of running as a tapered roller bearing first bearing.

Advantageously, the Lagergleitfläche the shaft end to a crown. As a result, the bearing properties are further improved with respect to the radial bearing of the designed as a sliding bearing second bearing. The crowning leads to a homogeneous contact pressure distribution and to avoid unwanted edge beams. The crowning can be performed either as an elliptical profile or with a constant radius.

In an advantageous embodiment, the crown of the bearing sliding surface is 5 microns to 30 microns, preferably 15 microns. A crown of at least 5 microns is required to effectively reduce the edge support of the contact pressure distribution. With a crown of more than 30 microns, the maximum contact pressure in the middle of the bearing surface increases too much, so that from this value, the crown is disadvantageous again.

drawings

1 shows schematically an axial piston machine according to the invention 100 in longitudinal section, with only the essential areas are shown.

2 shows the with II designated section of the 1 an embodiment.

description

1 shows an axial piston machine 100 in longitudinal section, with a housing 10 that consists of a first housing part 10a and a second housing part 10b consists. The two housing parts 10a and 10b are by a screw connection 19 braced together.

• – ein erstes Lager 21, das als Kegelrollenlager ausgeführt ist und im ersten Gehäuseteil 10a angeordnet ist und
• – ein zweites Lager 22, das als Gleitlager ausgeführt ist und im zweiten Gehäuseteil 10b angeordnet ist.

In the case 10 is a shoot 20 rotatably supported by two bearings:

• - a first camp 21 , which is designed as a tapered roller bearing and in the first housing part 10a is arranged and
• - a second camp 22 , which is designed as a sliding bearing and in the second housing part 10b is arranged.

The second camp 22 is at a shaft end 25 the drive shaft 20 arranged and acts with a storage area 25a of the shaft end 25 together.

A first circlip 26 fixes the inner ring of the tapered roller bearing first bearing 21 against a shoulder of the drive shaft 20 ,

The designed as a plain bearing second bearing 22 is in the second housing part 10b pressed. A second circlip 24 is in a groove of the second housing part 10b arranged and fixed in addition to the press connection, the second bearing 22 in the axial direction against a further shoulder of the second housing part 10b ,

With the drive shaft 20 is a piston drum 40 connected, for example via a tooth connection, so that the piston drum 40 synchronous with the drive shaft 20 rotates. The piston drum 40 acts on a face 41 in the axial direction with the second housing part 10b together. A feather 23 is between the drive shaft 20 and the piston barrel 40 biased. The spring pushes 23 the piston drum 40 to the face 41 and the shoot shaft 30 in the direction of the first camp 21 , This is the one hand, the piston drum 40 and on the other hand, the first camp 21 biased.

A pivoting cradle 30 is about a rotation axis 31 perpendicular to the drive shaft 20 stands, rotatably mounted. With the swivel cradle 30 are adjuster pistons 33 each connected by a ball joint, wherein the adjuster piston 33 in the second housing part 10b arranged adjuster cylinders 43 are guided. Advantageously, over the circumference of the drive shaft 20 distributes two adjuster pistons 33 arranged opposite. Through a stroke of a first piston adjustment 33 becomes the pivoting cradle 30 around the axis of rotation 31 tilted, the second adjuster piston 33 doing the same stroke in the opposite direction. I'm in the 1 shown state, the tilt angle α is more than 90 °. At rest or idle, the tilt angle is α = 90 °.

In the piston drum 40 are parallel to the drive shaft 20 working cylinder 45 trained, in which are working pistons 35 are located. One working cylinder each 45 and a working piston 35 limit a workspace 46 , The working cylinders 45 are circular and concentric around the drive shaft 20 arranged. Typically, the number of working cylinders 45 seven or nine working cylinders 45 that are even over the circumference within the piston drum 40 are distributed. To better illustrate the piston positions at the bottom and top dead center are in the 1 however, an even number of working cylinders 45 shown, so that in longitudinal section of the upper working piston 35a located at top dead center and the lower piston 35b at bottom dead center.

The working cylinders 45 Depending on hub and function are connected alternately both with a high pressure H and with a low pressure N. These are in the second housing part 10b connections 18 formed, which are connected to high pressure H or low pressure N. When using switching devices, the connections 18 also switchable with high pressure H or low pressure N are connected, for example, to switch between pump and engine operation.

In many embodiments of axial piston machines 100 will all connections 18 the working cylinder 45 in the second housing part 10b to two connections 18a and 18b summarized, wherein one is connected to high pressure H and one with low pressure N.

At every working cylinder 45 is a sliding shoe 36 arranged by means of a ball joint. The sliding shoes 36 lie on the swivel cradle 30 on and are by a device, not shown, on the pivoting cradle 30 held, so from the pivoting cradle 30 both tensile and compressive forces on the shoes 36 and thus on the working pistons 35 can be transmitted.

Drive or output side - depending on the type of operation, whether pump or motor operation - is the drive shaft 20 outside the case 10 with a drive wheel 15 , For example, connected via a toothing. In the case of a motor operation is thus a torque from the drive shaft 20 on the drive wheel 15 transferred, which is thus a driven wheel. In the case of a pump operation is thus a torque from the drive wheel 15 on the drive shaft 20 transferred, which thus serves as a drive wheel.

The task of the drive wheel 15 is the torque transmission from or to the drive shaft 20 , Depending on the type of connection to the drive shaft 20 However, axial forces can also be transmitted, for example with helical gearing. The designed as a plain bearing second bearing 22 can not absorb axial forces. The first bearing designed as a tapered roller bearing 21 can axial forces in the direction of the second bearing 22 to the first camp 21 take up. To axial forces in the direction of the first bearing 21 to the second camp 22 to record, has the drive wheel 15 a contact surface 15a on the housing side either with one on the housing 10 trained stop surface 12 on the housing front 11 interacts or - as in 1 shown - with a stop surface 12 on one on the case front 11 arranged steel disc 13 is trained.

The 2 shows the with II designated section of the 1 an embodiment in which that with the second bearing 22 cooperating shaft end 25 at his storage area 25a has a crown. For this purpose, the first diameter D ₁ at both edges of the bearing surface 25a smaller than the second diameter D ₂ in the middle of the bearing surface 25a , The crowning is defined by the difference between the two diameters D ₁ and D ₂ and is preferably between 5 μm and 30 μm. In this case, the crown can be viewed in cross-section with a constant radius, or - analogous to embodiments of cylindrical roller bearings - with elliptical cross sections on the bearing edges to achieve the most homogeneous contact pressure distribution without edge support over the entire bearing length.

The operation of the axial piston machine 100 is in pump mode as follows: The pivoting cradle 30 is by means of the adjuster piston 33 adjusted to a tilt angle α, which is greater than 90 °, so that in the 1 upper workspace 46a one has comparatively small volume and that in the 1 lower working space 46b a comparatively large volume; the upper working piston 35a is located at top dead center, the lower working piston 35b at bottom dead center, the remaining distributed over the circumference of the working piston 35 accordingly in intermediate positions. At the same time, the one in the 1 upper connection 18a connected to the high pressure H and the lower port 18b with the low pressure N. The drive shaft 20 gets from the drive wheel 15 driven, in this case, the drive wheel 15 So a drive wheel. Working fluid is from the lower piston 35b sucked in the bottom dead center position on the low pressure side N and by means of the rotating piston drum 40 moved to the top dead center and thereby in the decreasing working space 46 compacted by the sliding shoes 36 on a circular path of the pivoting cradle 30 slide off while keeping the working pistons 35 on their way from bottom to top dead center into the working cylinder 45 to press. At top dead center are the work spaces 46 with the high pressure connection 18a hydraulically connected, and so the working fluid supplied to the high pressure area H.

To change from pump to motor operation, either the tilt angle α is adjusted from> 90 ° to <90 °, or the high pressure and low pressure connections 18a and 18b exchanged. In the following, the engine operation becomes brief using the example of the exchanged connections 18 explains:
The upper connection 18a is connected to the low pressure N and the lower port 18b with the high pressure H. The tilt angle α is still greater than 90 °, so that the upper working space 46a a comparatively small volume and the lower working space 46b has a comparatively large volume; the upper working piston 35a is located at top dead center, the lower working piston 35b at bottom dead center.

working piston 35 due to the rotating piston drum 40 on the way from the top to the bottom dead center are, so from the working cylinders 45 move out, are connected to the high pressure H. The corresponding workrooms 46 expand, a lifting movement of the working piston located therein 35 is generated by the applied high pressure H. By the lifting movement of the working piston 35 becomes a rotation of the piston drum 40 and the drive shaft connected with it 20 triggered, so that the drive shaft 20 the drive wheel 15 can drive. In this case, the drive wheel 15 a driven wheel.

In the area of bottom dead center, the working pistons 35 via damping devices, not shown, successively connected to the low pressure N, so that the working fluid can relax without generating excessive pressure pulsations.

• – Das Radial hoch belastbare Kegelrollenlager ist räumlich nahe am Triebrad 15 angeordnet und damit nahe an der Querkrafteinleitung bzw. Querkraftableitung.
• – Durch die Querkraft auf das Kegelrollenlager wird eine Axialkraft in Richtung des Gleitlagers erzeugt, die über die Feder 23 auf die Kolbentrommel 40 wirkt. Dies wirkt einem Abheben der Kolbentrommel 40 vom zweiten Gehäuseteil 10b bzw. der dazwischen liegenden Steuerscheibe entgegen. Die Leckage aus den Arbeitsräumen 46 wird so minimiert.
• – Das Gleitlager erzielt durch seine vergleichsweise große Schmierfläche gute Schwingungs-, Stoß- und Geräuschdämpfungen.
• – Das Gleitlager kann durch die ballige Ausführung der Lagerfläche 25a des Wellenendes 25 so ausgeführt werden, dass eine möglichst homogene Kontaktpressungsverteilung vorliegt.
• – Hohe Axialkräfte in Richtung vom ersten Lager 21 zum zweiten Lager 22, die eine Festkörperreibung zwischen der Kolbentrommel 40 und dem zweiten Gehäuseteil 10b bzw. der dazwischen liegenden Steuerscheibe erzeugen würden, werden zwischen Antriebsrad 15 und der Anschlagfläche 12 der Gehäusestirnseite 11 übertragen.
• – Die Kombination stellt eine kostengünstige Lösung dar, speziell wenn Serienkegelrollenlager verwendet werden.

Due to the working principle of the axial piston machine 100 determine the design of the first camp 21 and second camp 22 significantly the durability and efficiency of the entire axial piston machine 100 , The advantages of the combination of tapered roller bearings and plain bearings are listed below:

• - The radial high-load tapered roller bearing is close to the drive wheel 15 arranged and thus close to the lateral force introduction or lateral force dissipation.
• - Due to the lateral force on the tapered roller bearing an axial force is generated in the direction of the sliding bearing, via the spring 23 on the piston drum 40 acts. This acts to lift the piston drum 40 from the second housing part 10b or the intermediate control disc. The leakage from the workrooms 46 is minimized.
• - The sliding bearing achieved by its comparatively large lubrication surface good vibration, shock and noise attenuation.
• - The plain bearing can by the spherical design of the bearing surface 25a of the shaft end 25 be executed so that the most homogeneous contact pressure distribution exists.
• - High axial forces in the direction of the first bearing 21 to the second camp 22 , which is a solid friction between the piston drum 40 and the second housing part 10b or the intervening control disc would generate between drive wheel 15 and the stop surface 12 the housing front 11 transfer.
• - The combination is a cost-effective solution, especially if series tapered roller bearings are used.

• – einfache Montage,
• – keine Deformation eines Lagerbodens aufgrund von Einpressprozessen,
• – einfache Wartung und Überprüfung der Lagergleitflächen (Anlauffläche 15a und Anschlagfläche 12),
• – kostengünstige Lösung,
• – großer Spielraum bei der Auswahl der Materialpaarung der Lagergleitflächen.

However, the combination of tapered roller and plain bearings requires additional axial bearing in one direction, advantageously by the contact between the thrust surface 15a of the drive wheel 15 and on the front of the case 11 arranged stop surface 12 is designed. This configuration of the axial bearing has the following advantages:

• - easy installation,
• No deformation of a storage floor due to press-in processes,
• - easy maintenance and inspection of the bearing sliding surfaces (contact surface 15a and stop surface 12 )
• - cost-effective solution,
• - great flexibility in the selection of the material pairing of the bearing sliding surfaces.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0608144 A2 [0004]

Claims (10)

Axial piston machine ( 100 ) for pump and / or motor operation with a housing ( 10 ), a drive shaft ( 20 ) and a piston drum ( 40 ), whereby the piston drum ( 40 ) with the drive shaft ( 20 ) and wherein the drive shaft ( 20 ) through a first warehouse ( 21 ) and a second warehouse ( 22 ) within the housing ( 10 ) rotatably mounted, wherein the first bearing ( 21 ) as a tapered roller bearing and the second bearing ( 22 ) is designed as a sliding bearing, wherein the first bearing ( 21 ) Axial forces on the drive shaft ( 20 ) in a direction of force from the second bearing ( 22 ) to the first camp ( 21 ) and the drive shaft ( 20 ) is biased in this direction of force. characterized in that on a side facing the input or output housing ( 11 ) of the housing ( 10 ) a stop surface ( 12 ) arranged with one of the stop surface ( 12 ) opposite contact surface ( 15a ) one on the drive shaft ( 20 ) arranged drive wheel or driven wheel ( 15 ) can work together. Axial piston machine ( 100 ) according to claim 1, characterized in that the stop surface ( 12 ) at one on the housing front side ( 11 ) arranged steel disc ( 13 ) is trained. Axial piston machine ( 100 ) according to claim 1 or 2, characterized in that the housing ( 10 ) is designed in two parts, with a drive or output-side first housing part ( 10a ), in which the first bearing ( 21 ) is arranged, and a housing-side second housing part ( 10b ), in which the second warehouse ( 22 ) is arranged. Axial piston machine ( 100 ) according to one of claims 1 to 3, characterized in that the biasing force by a spring ( 23 ) generated between the drive shaft ( 20 ) and piston drum ( 40 ) is arranged. Axial piston machine ( 100 ) according to one of the preceding claims, characterized in that the second bearing ( 22 ) consists of a composite material. Axial piston machine according to claim 5, characterized in that the second bearing ( 22 ) consists of a steel backing with sintered bronze and a top layer of polyphenylene sulfide. Axial piston machine ( 100 ) according to one of the preceding claims, characterized in that the first bearing ( 21 ) has a larger inner diameter than the second bearing ( 22 ). Axial piston machine ( 100 ) according to one of the preceding claims, characterized in that on the drive shaft ( 20 ) housing end a shaft end ( 25 ), the second bearing ( 22 ) at the shaft end ( 25 ) is arranged. Axial piston machine ( 100 ) according to claim 8, characterized in that the bearing sliding surface ( 25a ) of the shaft end ( 25 ) has a crown. Axial piston machine ( 100 ) according to claim 9, characterized in that the crown of the bearing sliding surface ( 25a ) Is 5 μm to 30 μm, preferably 15 μm.

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