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United States Patent Application	20110138996
Kind Code	A1
Maric-Colic; Njegos	June 16, 2011

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Foreign Application Data

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Date	Code	Application Number
Dec 15, 2009	DE	10 2009 058 332.7

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Claims

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1. An axial piston machine of an inclined axis design, comprising: a housing (6); a cylinder drum (50) disposed in said housing (6), said cylinder drum including a plurality of cylinder bores (54) open toward a drive shaft (42), said drive shaft (42) being rotatably supported in the housing (6); a piston (56) hingedly connected to the drive shaft (42), wherein said piston (56) is adapted to be axially displaceably guided in each of the cylinder bores (54) and includes a central journal bore (70) that extends approximately coaxially to a longitudinal axis thereof; a central journal (66) hingedly connected to the drive shaft (42), wherein said central journal (66) is inserted in said central journal bore (70) and rotatably supports the cylinder drum (50) using a central journal section (71); a spring (72) disposed in the central journal bore (70); a control disk (74) operatively connected to the cylinder bores (54) and bearing against the housing, wherein said spring (72) is adapted to bear against the central journal (66) and load the cylinder drum (50) against the control disk (74); and a recess (108) having a retaining element (110), said recess being formed in the central journal section (71) of the central journal (66) in such a manner that the retaining element (110) is connected in a non-positive manner to the central journal bore (70).

2. The axial piston machine according to claim 1, wherein the recess in the central journal (66) is an annular groove (108), and the retaining element is an O-ring (110).

3. The axial piston machine according to claim 1, wherein the retaining element (110) is disposed on the central journal (66) and the spring (72) has a spring stiffness, such that the retaining element (110), together with the central journal (66), cannot be moved out of the central journal bore (70) by a spring force of the spring (72) in an uninstalled state of the cylinder drum (50).

4. The axial piston machine according to claim 1, wherein the axial piston machine is a constant unit having a fixed pivot angle.

5. The axial piston machine according to claim 1, wherein the axial piston machine is an adjusting unit having an adjustable pivot angle.

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Description

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CROSS-REFERENCE

[0001] The invention described and claimed hereinbelow is also described in DE 102009058332.7, filed Dec. 15, 2009. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d).

BACKGROUND OF THE INVENTION

[0002] The invention relates to an axial piston machine.

[0003] An axial piston machine of that type is disclosed in DE 101 19 36 C1, in which a plurality of pistons are guided in an axially displaceable manner in cylinder bores of a cylinder drum. The cylinder drum is supported in a housing of the axial piston machine in a manner that allows it to swivel about a pivot axis that extends transversely to the rotational axis thereof. The pistons are supported on a drive shaft that is rotatably supported in the housing. A central journal that is used to support the cylinder drum and, similar to the pistons, is supported on the drive shaft is inserted in a gliding manner in a stepped bore of the cylinder drum, approximately coaxially to the longitudinal axis of the cylinder drum. The central journal includes, on its side facing away from the drive shaft, a blind hole into which a compression spring is inserted, the compression spring bearing against a hole base of the blind hole and loading the cylinder drum against a control disk.

[0004] The disadvantage of this solution is the extremely complex installation and deinstallation of the cylinder drum together with the central journal and the compression spring of the axial piston machine since it must be ensured that the cylinder drum and the central journal are not driven apart by the spring forces of the compression spring.

[0005] To solve this problem, an annular recess can be formed in the outer circumference of the central journal and in an inner jacket surface of the central journal bore, into which a common snap ring is placed. The snap ring would prevent the compression spring from driving the central journal and the cylinder drum apart. This solution has the disadvantage, however, that it requires a great deal of device complexity. Furthermore, it prevents the central journal from being removed from the cylinder drum.

SUMMARY OF THE INVENTION

[0006] In contrast, the object of the invention is to create an axial piston machine that is easily assembled and disassembled, and that can be manufactured cost-effectively.

[0007] According to the invention, an axial piston machine of an inclined axis design includes a housing in which a cylinder drum is disposed. A plurality of cylinder bores, which are open toward a drive shaft which is rotatably supported in the housing, is formed in the aforementioned cylinder drum; a piston which is hingedly connected to the drive shaft is axially displaceably guided in each of the cylinder bores. The cylinder drum also includes a central journal bore that extends approximately coaxially to its longitudinal axis. Inserted therein is a central journal which is hingedly connected to the drive shaft and is used to rotatably support the cylinder drum using a section of the central journal. Furthermore, a spring is disposed in the bore of the central journal. The spring bears against the central journal and loads the cylinder journal against a control disk which bears against the housing; the control disk can be used to connect the cylinder bores to a high-pressure channel or a low-pressure channel. Advantageously, a recess having a retaining element is formed in the central journal section of the central journal in a manner such that the central journal is connected via the retaining element in a non-positive manner to the central journal bore.

[0008] This solution has the advantage that the cylinder drum can be installed and removed together with the spring and the central journal as one unit. Without this recess with the retaining element, the central journal could be accelerated via the spring in the axial direction and separated from the cylinder drum upon removal. To prevent this, a strong counterforce would have to be applied if this recess and the retaining element were not present. The retaining element therefore facilitates safe installation and removal with a minimum of device complexity.

[0009] Advantageously, the recess in the central journal is a simple annular groove, and the retaining element is an O-ring that is inserted into this annular groove. An annular groove of that type is cost-effective to manufacture, and the O-ring is likewise a cost-effective, conventional component.

[0010] The annular retaining element is disposed on the central journal in a manner such that, and the spring is designed in a manner such that the retaining element remains in the central journal bore of the cylinder drum when the spring is in the substantially unloaded state.

[0011] The axial piston machine is designed e.g. as a constant unit having a fixed pivot angle, or as an adjusting unit having an adjustable pivot angle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A preferred embodiment of the invention is explained in the following in greater detail with reference to schematic drawings. They show:

[0013] FIG. 1 a longitudinal sectional view of an axial piston machine according to one embodiment; and

[0014] FIG. 2 an enlarged section of the axial piston machine depicted in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] FIG. 1 shows, in a longitudinal sectional view, an axial piston machine 4 according to one embodiment. It is a displacement machine of an inclined axis design, which can be used as a hydraulic motor and a hydraulic pump.

[0016] Axial piston machine 4 is accommodated in a pot-shaped housing section 38 of a housing 6, which is closed by a housing cover 40. A drive shaft 42 is rotatably supported using at least one journal bearing in housing cover 40, and drive shaft 42 extends outwardly through housing cover 40. The journal bearing is composed of two roller bearings 44, 46 disposed in the shape of an "o" in housing cover 40.

[0017] In a cavity 48 of housing section 38, a cylinder drum 50 that is axially opposite drive shaft 42 is supported such that it can rotate about drum axis 52 thereof. Cylinder drum 50 comprises a plurality of cylinder bores 54, which are distributed on a partial circle, are open toward drive shaft 42, and in which pistons 56 are supported in an axially displaceable manner. Pistons 56 are axially supported on a drive shaft flange 58 of drive shaft 42. Pistons 56 are hingedly supported, each with a spherical piston head 60, in a spherical cap 62 of drive shaft flange 58. Piston heads 60 are axially held by a retaining device 64 which extends behind piston heads 60 and is fastened to drive shaft flange 58, and which is formed e.g. by a screwed-on perforated plate.

[0018] Cylinder drum 50 is supported on a central journal 66 which is disposed coaxially to cylinder drum 50 and which--similar to piston 56--is hingedly held using a spherical central journal head 68 in one of the spherical caps 62 by retaining device 64. Central journal 66 is inserted via a central journal section 71 in a central journal bore or stepped bore 70 of cylinder drum 50, which extends approximately coaxially to drum axis 52. A spring or compression spring 72 is disposed in stepped bore 70, bears against a side of central journal 66 facing away from drive shaft 42, and loads cylinder drum 50 against a control disk 74. The end faces of cylinder drum 50 and control disk 74, which face one another, bear against one another via guide surfaces 76 and 78. Guide surface 76 of cylinder drum 50 is concave, while guide surface 78 of control disk 74 is convex. Cylinder bores 54 are connected by channel sections, which extend through cylinder drum 50 and control disk 74, to pressure-medium supply lines or pressure-medium discharge lines which extend approximately in a left--as shown in FIG. 1--housing section 80 of housing 6. The design of the channel sections is known per se and will therefore not be described in greater detail. Control disk 74 is securely connected to housing section 38 and is oriented using a centering bolt.

[0019] FIG. 2 mainly shows, in an enlarged sectional view and in sections, cylinder drum 50 together with central journal 66, one of the pistons 56, and compression spring 72 depicted in FIG. 1. Central journal section 71 of central journal 66, which is inserted into stepped bore 70 of cylinder drum 50, is designed substantially in the shape of a circular cylinder. Adjacent thereto is a centrally-located central journal section 94 which extends conically toward central journal head 68, and on the end of which central journal head 68 is formed. A blind hole 98 is formed in central journal 66 approximately coaxially to longitudinal axis 96 thereof, on the side facing away from central journal head 68. Compression spring 72 is disposed in blind hole 98, compression spring 72 being loaded between a base surface 100 of the blind hole and an annular disk 102. Annular disk 102 bears against a contact shoulder 104 of stepped bore 70 of cylinder drum 50. Compression spring 72 therefore does not have direct contact with cylinder drum 50.

[0020] Blind hole 98 extends through central journal section 71 along approximately 2/3 the length of central journal section 71; central journal section 71 is inserted substantially entirely into stepped bore 70. An annular groove 108, into which a retaining element or O-ring 110 is inserted, is formed on the remaining section of central journal section 71 of central journal 66. O-ring 110 bears against an inner wall of stepped bore 70, at least in sections, in a non-positive manner.

[0021] In the installed state of axial piston machine 4, cylinder drum 50, together with central journal 66 and compression spring 72, is supported between drive shaft 42, which is supported on housing cover 40, and control disk 74. When axial piston machine 4 is assembled or disassembled, housing cover 40 is released, thereby eliminating the supporting effect for drive shaft 42. In this state, cylinder drum 50 and central journal 66 are prevented from being driven apart by the spring forces of compression spring 72 via the non-positive connection between stepped bore 70 and central journal 66 by O-ring 110. Cylinder drum 50 and central journal 66 therefore form a unit that can be easily installed in and removed from the axial piston machine. Furthermore, central journal 66 can also be removed from cylinder drum 50, e.g. to perform maintenance work, simply by overcoming the retaining forces of the non-positive connection between O-ring 110 and stepped bore 70.

[0022] The spring force and the spring travel of compression spring 72 are designed such that compression spring 72 is released during installation and removal of cylinder drum 50 only to the extent that O-ring 110 is still disposed in stepped bore 70. Compared to the related art, compression spring 70 is preferably designed with high spring stiffness, thereby resulting in strong spring forces with minimal spring travel.

[0023] A continuous channel 112 is formed approximately coaxially in central journal 66 next to blind hole 98, and has a pressure-medium connection with leakage channels, which are not depicted, and are formed in left--as shown in FIG. 1--housing section 80 of housing 6, the pressure-medium connection being established via blind hole 98, a continuous port 114 in annular disk 102, a step 116 of stepped bore 70, and control disk 74. Furthermore, channel 112 is connected, on sides of drive shaft 42, to cavity 48 of housing 6 via connecting channels 120 formed in drive shaft 42, see FIG. 1.

[0024] It is feasible for annular groove 108 to not be formed in central journal 66, but rather in stepped bore 70, and for O-ring 110 to then be disposed in stepped bore 70.

[0025] For completeness, it is noted that axial piston machine 4 can also be formed in a separate housing, of course, without axial piston machine 2 shown in FIG. 1.

[0026] Disclosed herein is an axial piston machine of an inclined axis design comprising a housing in which a cylinder drum is disposed. The cylinder drum is rotatably supported on a central journal which is hingedly connected to a drive shaft. The central journal is inserted, in an axially displaceable manner, in a central journal bore formed in the cylinder drum which extends approximately coaxially to the longitudinal axis of the cylinder drum. A compression spring is disposed in central journal bore which bears against an end face facing away from the drive shaft, and loads the cylinder drum against a control disk. A radial groove is formed in central journal, in which an O-ring is accommodated, by way of which the central journal is held in a non-positive manner in the central journal bore when the axial piston machine is assembled and disassembled.

[0027] It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

[0028] While the invention has been illustrated and described as embodied in an axial piston machine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

[0029] Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

LIST OF REFERENCE CHARACTERS

[0030] 1 Engine [0031] 2 Axial piston machine [0032] 4 Axial piston machine [0033] 6 Housing [0034] 38 Housing section [0035] 40 Housing cover [0036] 42 Drive shaft [0037] 44 Roller bearing [0038] 46 Roller bearing [0039] 48 Cavity [0040] 50 Cylinder drum [0041] 52 Drum axis [0042] 54 Cylinder bore [0043] 56 Piston [0044] 58 Drive shaft flange [0045] 60 Piston head [0046] 62 Spherical cap [0047] 64 Retaining device [0048] 66 Central journal [0049] 68 Central journal head [0050] 70 Stepped bore [0051] 71 Central journal section [0052] 72 Compression spring [0053] 74 Control disk [0054] 76 Guide surface [0055] 78 Guide surface [0056] 80 Housing section [0057] 92 Central journal section [0058] 94 Central journal section [0059] 96 Longitudinal axis [0060] 98 Blind hole [0061] 100 Base surface [0062] 102 Annular disk [0063] 104 Contact shoulder [0064] 106 Annular end face [0065] 108 Annular groove [0066] 110 O-ring [0067] 112 Lubricating oil bore [0068] 114 Port [0069] 116 Step [0070] 120 Connecting channels

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