Patent Publication Number: US-6701824-B2

Title: Axial piston machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an axial piston machine with a swashplate and a cylinder block provided with a torque transmission member rotationally mounted by a bearing system which is located radially between the cylinder block and a housing. 
     2. Background Information 
     A similar axial piston machine of the prior art is described in DE 198 54 415 A1. In contrast to conventional axial piston machines that utilize the swashplate construction, it does not have a drive shaft on which the cylinder block is mounted. Rather, the cylinder block has an “external bearing system”. The feed and discharge of hydraulic fluid to and from the cylinder bores that are worked into the cylinder block takes place through channels in the swashplate, the slippers and the work pistons. The control surface is therefore located on the swashplate. On account of the relatively large diameter of the control surface, a high degree of manufacturing accuracy is required to keep leak losses low, and that makes the manufacturing process correspondingly complex, time-consuming and expensive. 
     The object of the invention is to make available an axial piston machine of the type described above which is compact and has an improved hydraulic supply system. 
     SUMMARY OF THE INVENTION 
     This object is accomplished by the invention, in which the cylinder block and the swashplate are penetrated centrally by two plain conduits which are coaxial to each other, are connected on the swashplate-side ends to hydraulic fluid supply channels, and emerge at the cylinder-block-side ends in a control body which has a control surface that interacts with the cylinder block. 
     The teaching of the invention is accordingly to use the space made available inside the axial piston machine by the elimination of the drive shaft for the supply of hydraulic fluid to the cylinder bores. It thereby becomes possible to make available, in the vicinity of the cylinder block, a control surface which has small dimensions and extremely low oil leakage losses, and therefore, offers advantages in terms of the simplification of the manufacturing processes required. 
     To minimize the dimensions of the axial piston machine of the invention, the invention teaches that the control body is located inside the cylinder block. 
     The plain conduits are appropriately supported in a swashplate mounting and in the cylinder block. 
     The rotating cylinder block can be stopped by a brake, in particular a spring-loaded, multiple-disc brake, which can be located radially between the cylinder block and the housing. 
     In that case, it is advantageous for reasons of space if the brake is located axially between two tapered roller bearings of the bearing system, in particular two conical roller bearings in an O-arrangement. 
     In one particularly advantageous configuration of the invention, the bearing system can absorb the forces generated by the drive system as well as external forces. Therefore no separate bearing is required to absorb the external forces, such as for example, the wheel forces. 
     The axial piston machine of the invention can therefore be advantageously realized in the form of a wheel motor. The wheel motor in question has direct drive, i.e., it drives a wheel without a reducing transmission. 
     For the application described above, it is advantageous if a rim driver flange is shaped onto the cylinder block. It thereby becomes possible to minimize the number of components that have to be assembled. 
     The same advantage can be achieved by a configuration in which a rim centering device is shaped onto the cylinder block. 
     BRIEF DESCRIPTION OF THE DRAWING 
     Additional advantages and details of the invention are explained in greater detail below with reference to the exemplary embodiment of the invention which is schematically illustrated in the accompanying drawing. The drawing shows an axial piston machine that employs the swashplate construction and is realized in the form of a wheel motor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A cylinder block  2  is mounted in a housing  1  by a system of external bearings consisting of two tapered roller bearings (in this case, conical roller bearings in an  0 -arrangement)  3  and  4 . In other words, the tapered roller bearings  3  and  4  are located radially between the cylinder block  2  and the housing  1 . The bearing system at least partly absorbs the forces generated by the drive mechanism, as well as the external forces (wheel forces). 
     Worked into the cylinder block  2  are concentric cylinder bores  5 , in each of which there is a work piston  6  which is supported by a slipper  7  on a swashplate  8 , which in this exemplary embodiment is adjustable. The swashplate  8  is pivotably mounted in a swashplate mounting  9  in which there are supply channels  10   a ,  10   b  (indicated in broken lines) for the hydraulic fluid. Of course, it is also possible to realize the axial piston machine with a constant intake volume. 
     Radially between the cylinder block  2  and the housing  1  and axially between the two tapered roller bearings  3  and  4  of the bearing system there is a brake  11  which is a wet, spring-loaded, multiple-disc brake  11 . Shaped onto the cylinder block  2  are a rim centering device  2   a  and a rim driver flange  2   b  (torque drive or torque transmission member). 
     Both the cylinder block  2  and the swashplate  8  are penetrated centrally by two plain conduits  12  and  13  which are coaxial to each other and are supported in the cylinder block  2  and on the swashplate side in the swashplate mounting  9 . To absorb forces in the axial direction, the inner plain conduit  12  is connected to the swashplate mounting  9  in an area A by a threaded connection. An axially movable control body  14  which is located inside the cylinder block  2  and is supported on the inner plain conduit  12  in the axial direction (by a threaded connection B between the plain conduit  12  and a retaining bolt H in a support body S), has a control surface E. Channels in the cylinder block  2  lead from the surface of the cylinder block  2  which faces the control surface E to the cylinder bores  5 . A central boring  15  of the inner plain conduit  12  is connected to the hydraulic fluid supply channel  10   b , while the hydraulic fluid supply channel  10   a  is in communication with an annular channel  16  formed between the inner plain conduit  12  and the outer plain conduit  13 . The central boring  15  and the annular channel  16  emerge in the control body  14  in connecting channels to the control surface E. 
     Having described the details of the illustrated embodiment, it will be apparent that various modifications may be made without departing from the spirit and scope of the present invention. The scope of the present invention should be defined by the appended claims and equivalents thereto.