WO2015058896A1

WO2015058896A1 - Axial piston machine

Info

Publication number: WO2015058896A1
Application number: PCT/EP2014/069172
Authority: WO
Inventors: Matthias Greiner
Original assignee: Robert Bosch Gmbh
Priority date: 2013-10-24
Filing date: 2014-09-09
Publication date: 2015-04-30
Also published as: CN105683561B; DE102013221623A1; CN105683561A

Abstract

An axial piston machine (100) for operation as a pump and/or motor, having 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 mounted rotatably within the housing (10) by means of a first bearing (21) and a second bearing (22), wherein the first bearing (21) is in the form of a tapered-roller bearing and the second bearing (22) is in the form of a plain bearing. The first bearing (21) can absorb axial forces on the drive shaft (20) in a force direction from the second bearing (22) toward the first bearing (21). The drive shaft (20) is preloaded in said force direction. On a housing face side (11), facing toward the drive input and/or output, of the housing (10), there is arranged an abutment surface (12) which can interact with a run-on surface (15a), facing the abutment surface (12), of a drive input or drive output wheel (15) arranged on the drive shaft (20).

Description

description

title

axial piston

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 well-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 on the opposite side of the working piston, in particular via a respective sliding shoe on the pivoting cradle

be recorded.

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 gear and compressed the fluid in the working cylinders by the working piston against a high pressure area.

In an axial piston motor, the working cylinders are supplied under high pressure fluid and thus generates a rotational movement of the piston drum and thereby generates a torque on the drive shaft. Such an axial piston pump is known from EP 0 608 144 A2, the drive shaft of which is designed as a tapered roller bearing with a first bearing and as a sliding bearing with a second bearing. In this case, the slide 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

Fitting accuracy between drive shaft and plain bearing. Due to the

Pressing operation of the sliding bearing into the housing of the axial piston pump can continue to lead to disadvantageous deformations on the bearing base and then to additional wear.

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. This is the result

Axialkraftaufnahme easily associated with 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 according to the invention, the stop surface is arranged on a on the housing front side

Steel disc formed. 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 output side 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. This allows for a compact design all

functionally necessary parts of the axial piston are arranged within the housing.

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 be arranged to lift the piston drum from the housing or from therebetween

Control disc come and thus 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 one

Inner diameter as 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

Tapered roller bearing trained 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

Camp.

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 avoidance

unwanted edge support. 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 5 μηη to 30 μηη, preferably 15 μηη. A crown of at least 5 μηη is

required to effectively reduce the edge support of the contact pressure distribution. With a crown of more than 30 μηη the maximum increases

Contact pressure in the middle of the bearing sliding surface too strong, so starting from this

Value the crown again becomes disadvantageous.

drawings

Fig.l shows schematically an axial piston machine 100 according to the invention in the

Longitudinal section, with only the essential areas are shown.

Fig.2 shows the designated II section of Fig.l one

Embodiment.

Description Fig.l shows an axial piston machine 100 in longitudinal section, with a housing

10, which consists of a first housing part 10a and a second housing part 10b. The two housing parts 10a and 10b are clamped together by a screw 19. In the housing 10, a drive shaft 20 is rotatably supported by two bearings:

- A first bearing 21, which is designed as a tapered roller bearing and in the first

Housing part 10 a is arranged and

- A second bearing 22, which is designed as a sliding bearing and is disposed in the second housing part 10 b. The second bearing 22 is arranged on a shaft end 25 of the drive shaft 20 and cooperates with a bearing surface 25 a of the shaft end 25.

A first securing ring 26 fixes the inner ring of the first bearing 21 designed as a tapered roller bearing against a shoulder of the drive shaft 20. The designed as a slide bearing second bearing 22 is pressed into the second housing part 10 b. A second securing ring 24 is arranged in a groove of the second housing part 10b and fixes the second bearing 22 in the axial direction against a further shoulder of the second housing part 10b in addition to the press connection. With the drive shaft 20, a piston drum 40 is connected, for example via a

Tooth connection, so that the piston drum 40 rotates synchronously with the drive shaft 20. The piston drum 40 cooperates on an end face 41 in the axial direction with the second housing part 10b. A spring 23 is biased between the drive shaft 20 and the piston drum 40. In this case, the spring 23 presses the piston drum 40 against the end face 41 and the drive shaft 30 in the direction of the first bearing 21. As a result, on the one hand the piston drum 40 and on the other the first bearing 21 is biased.

A pivoting cradle 30 is rotatably mounted about an axis of rotation 31 which is perpendicular to the drive shaft 20. With the pivoting cradle 30 Verstellerkolben 33 are each connected by a ball joint, the Verstellerkolben 33 are guided in the second housing part 10b arranged adjusting cylinders 43. Advantageously, over the

Scope of the drive shaft 20 distributed two Verstellerkolben 33 opposite

arranged. By a stroke of a first Verstellerkolbens 33, the pivoting cradle 30 is tilted about the axis of rotation 31, the second Verstellerkolben 33 performs the same stroke in the opposite direction. In the state shown in Fig.l the tilt angle α is more than 90 °. At rest or idle, the tilt angle is α =

90 °.

In the piston drum 40 20 working cylinder 45 are formed parallel to the drive shaft, in which working piston 35 are located. Depending on a working cylinder 45 and a piston 35 define a working space 46. The working cylinder 45 are circular and

arranged concentrically about the drive shaft 20. Typically, the number of

Working cylinder 45 seven or nine working cylinder 45, which are evenly distributed over the circumference within the piston drum 40. For a better illustration of the piston positions in the lower and upper dead center, however, an even number of working cylinders 45 are shown in FIG. 1, so that in longitudinal section the upper working piston 35a is at top dead center and the lower working piston 35b is at bottom dead center.

The working cylinder 45 are hub and function-dependent alternately connected to both a high pressure H and a low pressure N. These are in the second Housing part 10 b terminals 18 are formed, which are connected to high pressure H or low pressure N. When using switching devices, the terminals 18 can also be switchably connected to high pressure H or low pressure N, for example to switch between pump and motor operation. In many embodiments of axial piston machines 100, all the ports 18 of the power cylinders 45 in the second housing part 10b are combined into two ports 18a and 18b, one connected to high pressure H and one connected to low pressure N.

At each working cylinder 45, a sliding shoe 36 is arranged by means of a ball joint. The sliding blocks 36 rest on the pivoting cradle 30 and are held by a device, not shown, on the pivoting cradle 30, so that of the

Schwenkwiege 30 both tensile and compressive forces on the shoes 36 and thus can be transmitted to the piston 35.

Drive or Abtriebsseitig - depending on the type of operation, whether pump or engine operation - the drive shaft 20 is outside the housing 10 with a drive wheel 15, for example, connected via a toothing. In the case of engine operation becomes so

Transmit torque from the drive shaft 20 to the drive wheel 15, which is thus a driven wheel. In the case of a pump operation, a torque is thus transmitted from the drive wheel 15 to the drive shaft 20, 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. However, depending on the type of connection to the drive shaft 20 can also

Axial forces are transmitted, for example, in a helical toothing. The designed as a sliding bearing second bearing 22 can not absorb axial forces. The designed as a tapered roller bearing first bearing 21 can absorb axial forces in the direction of the second bearing 22 to the first bearing 21. To axial forces in the direction of the first bearing

21 to accommodate the second bearing 22, the drive wheel 15 has a contact surface 15 a, the housing side formed either with a housing 10 on the

Stop surface 12 cooperates on the housing end face 11 or - as in Fig.l

shown - with a stop surface 12 which is formed on a arranged on the housing end face 11 steel disc 13.

FIG. 2 shows the section II of FIG. 1 of an embodiment in which the shaft end 25 cooperating with the second bearing 22 has a crown on its bearing surface 25a. For this purpose, the first diameter Di 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 diameters Di and D ₂ and is preferably between 5 μm and 30 μm. It can the

Viewed crown in cross-section with a constant radius, or also - in analogy to embodiments of cylindrical roller bearings - with elliptical

Cross-sections at the edges of the warehouse, as homogeneous as possible

Contact pressure distribution without edge beams over the entire length of the bearing to achieve.

The mode of operation of the axial piston machine 100 in pump operation is as follows: The pivoting cradle 30 is adjusted by means of the adjusting piston 33 to a tilting angle α which is greater than 90 °, so that the upper working space 46a in FIG

comparatively small volume and the lower working space 46b in FIG. 1 has a comparatively large volume; the upper piston 35a is located at top dead center, the lower piston 35b at bottom dead center, the remaining distributed over the circumference of the working piston 35 corresponding to intermediate positions. At the same time, the upper port 18a in FIG. 1 is connected to the high pressure H and the lower port 18b is connected to the low pressure N. The drive shaft 20 is driven by the drive wheel 15, in which case the drive wheel 15 is a drive wheel. Working fluid is sucked from the lower piston 35b in the bottom dead center position on the low pressure side N and moved by means of the rotating piston drum 40 in the top dead center and thereby compressed in the decreasing working space 46 by the

Sliding shoes 36 slide on a circular path of the pivoting cradle 30 and thereby press the working piston 35 on its way from the bottom to top dead center in the working cylinder 45. At top dead center, the work spaces 46 with the

High pressure port 18 a hydraulically connected, and so the working fluid the

High-pressure area H supplied.

To switch from pump to engine operation, either the tilt angle α is adjusted from> 90 ° to <90 °, or high-pressure and low-pressure connections 18a and 18b are exchanged. In the following, the engine operation is briefly explained using the example of the exchanged connections 18: The upper connection 18a is connected to the low pressure N and the lower one to the lower connection 18a

Port 18b with the high pressure H. The tilt angle α is still greater than 90 °, so that the upper working chamber 46a has a comparatively small volume and the lower working chamber 46b has a comparatively large volume; the upper piston 35a is at top dead center, the lower piston 35b at bottom dead center. Working piston 35, which are due to the rotating piston drum 40 on the way from the top to the bottom dead center, so move out of the working cylinders 45 are connected to the high pressure H. The corresponding working chambers 46 expand, a lifting movement of the working pistons 35 located therein is generated by the applied high pressure H. By the lifting movement of the working piston 35, a rotation of the piston drum 40 and the drive shaft 20 connected to it is triggered, so that the drive shaft 20 can drive the drive wheel 15. In this case, the drive wheel 15 is a driven wheel.

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

Due to the principle of operation of the axial piston machine 100, the design of the first bearing 21 and the second bearing 22 decisively determine 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 spatially arranged close to the drive wheel 15 and thus close to the lateral force introduction or lateral force dissipation.

Due to the transverse force on the tapered roller bearing an axial force is generated in the direction of the sliding bearing, which acts on the piston drum 40 via the spring 23. This counteracts a lifting of the piston drum 40 from the second housing part 10b or the intermediate control disc. The leakage from the work spaces 46 is minimized.

The plain bearing achieved by its comparatively large lubrication surface good

Vibration, shock and noise attenuation.

The sliding bearing can by the crowned design of the bearing surface 25 a of the

Shaft end 25 are executed so that a homogeneous as possible

Contact pressure distribution is present.

High axial forces in the direction from the first bearing 21 to the second bearing 22, which would generate a solid friction between the piston drum 40 and the second housing part 10b or the intermediate control disc are transmitted between the drive wheel 15 and the stop surface 12 of the housing end face 11. The combination provides a cost-effective solution, especially when used in series tapered roller bearings.

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

simple assembly, 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.

Claims

claims

An axial piston machine (100) for pump and / or motor operation with a housing (10), a drive shaft (20) and a piston drum (40), wherein the piston drum (40) is connected to the drive shaft (20) and wherein the Drive shaft (20) through a first bearing (21) and a second bearing

(22) is rotatably mounted 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, wherein the first bearing (21) axial forces on the drive shaft (20) in one Force direction from the second bearing (22) to the first bearing (21) can receive and the drive shaft (20) is biased in this direction of force. characterized in that on a facing to the input or output housing front side (11) of the

Housing (10) a stop surface (12) is arranged, which can cooperate with one of the stop surface (12) opposite thrust surface (15a) arranged on the drive shaft (20) driving wheel or driven wheel (15).

2. axial piston machine (100) according to claim 1, characterized in that the stop surface (12) on one on the housing end face (11)

arranged steel disc (13) is formed.

3. axial piston machine (100) according to claim 1 or 2, characterized

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 end side second

Housing part (10b), in which the second bearing (22) is arranged.

4. axial piston machine (100) according to one of claims 1 to 3, characterized in that the biasing force by a spring (23) is generated, which is arranged between the drive shaft (20) and piston drum (40).

5. axial piston machine (100) according to one of the preceding claims, characterized in that the second bearing (22) consists of a

Composite material exists.

6. axial piston machine according to claim 5, characterized in that the second bearing (22) consists of a steel backing with sintered bronze and a cover layer of polyphenylene sulfide.

7. axial piston machine (100) according to any one of the preceding claims, characterized in that the first bearing (21) has a larger

Inner diameter has as the second bearing (22).

8. axial piston machine (100) according to any one of the preceding claims, characterized in that on the drive shaft (20) housing end a shaft end (25) is formed, wherein the second bearing (22) on the shaft end (25) is arranged.

9. axial piston machine (100) according to claim 8, characterized in that the Lagergleitfläche (25a) of the shaft end (25) has a crown.

10. axial piston machine (100) according to claim 9, characterized in that the crown of the Lagergleitfläche (25a) 5 μηη to 30 μηη, preferably 15 μηη.