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AssigneesHitachi, Ltd., Hitachi Construction Machinery Co., Ltd.
InventorsYoshimichi Akasaka, Ichiro Nakamura, Ken Ichiryu, Eiji Kometani, Yasuharu Gotoh
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A thrust hydrostatic bearing device for use in an axial piston machine includes a bearing sleeve fitted into a housing cover for rotatably supporting a drive shaft through a bearing and having a plurality of hydrostatic pads. The hydrostatic pads are disposed at locations which are symmetrical with respect to an axis lying in a cross-section taken perpendicular to the drive shaft, and these pads increase the performance and durability of the thrust hydrostatic bearing device for use in an axial piston machine.
A thrust hydrostatic bearing device for use in an axial piston machine including a housing cover, a cylinder block having a plurality of cylinder holes, and pistons movable back and forth in corresponding cylinder holes and fixed to piston rods rotatably engaged with a disc portion of a drive shaft of said axial piston machine, said pistons being mounted such that they are inclined with respect to said drive shaft, hydrostatic pads disposed at locations at which the equation e.sub.L .multidot..theta..sub.L =e.sub.R .multidot..theta..sub.R is satisfied, where axes each other and to the axis of a bearing sleeve fixed into said housing cover for rotatably supporting said drive shaft through a bearing are called the x-axis and y-axis, e.sub.L is the difference between the x-coordinate e.sub.O of the mean point of application of the piston reaction forces and the x-coordinate E.sub.L of the centers of a number of said hydrostatic pads disposed on the side of points of application of said reaction forces, e.sub.R is the sum of the x-coordinate e.sub.O of the mean point of application of the piston reaction forces and the x-coordinates E.sub.R of the centers of a number of said hydrostatic pads disposed on the side at which said reaction forces are not applied, .theta..sub.L is the angle between the center of each of said hydrostatic pads disposed on said side of points of application of said reaction forces and the x-axis, and .theta..sub.R is the angle between the center of each of said hydrostatic pads disposed on said side at which said reaction forces are not applied and the y-axis.
A thrust hydrostatic bearing device for use in an axial piston machine including a housing cover, a cylinder block having a plurality of cylinder holes, and pistons movable back and forth in corresponding cylinder holes and fixed to piston rods rotatably engaged with a disc portion of a drive shaft of said axial piston machine, said pistons being mounted such that they are inclined with respect to said drive shaft, a bearing sleeve being fitted into said housing cover for rotatably supporting said drive shaft through a bearing is provided with hydrostatic pads which are capable of leading static pressures, some of said hydrostatic pads being positioned at the side of said bearing sleeve at which the resultant force of piston reaction forces is applied and others of said hydrostatic pads being positioned at the side thereof at which said resultant force is not applied, in such a manner that the equation F.sub.p .gtoreq.W.gtoreq.F.sub.s holds, where F.sub.p is said resultant force of said piston reaction forces, W is the load capacity of the surface of guiding the pads' static pressures, and F.sub.s is the rod thrust acting against said pads.
A thrust hydrostatic bearing device for use in an axial piston machine including a housing cover, a cylinder block having a plurality of cylinder holes, and pistons movable back and forth in corresponding cylinder holes and fixed to piston rods rotatably engaged with a disc portion of a drive shaft of said axial piston machine, said pistons being mounted such that they are inclined with respect to said drive shaft, a bearing sleeve being fitted into said housing cover for rotatably supporting said drive shaft through a bearing and having three hydrostatic pads, said three hydrostatic pads being disposed on said bearing sleeve at locations at which the equation W.sub.L .multidot.E.sub.L =W.sub.R .multidot.E.sub.R is satisfied, where axes perpendicular to each other and to the axis of said bearing sleeve are the x-axis and y-axis, W.sub.L is the sum of load capacities of two of said hydrostatic pads that are disposed at the side of the points of application of the resultant force of the piston reaction forces, W.sub.R is the load capacity of the remaining hydrostatic pad that is disposed on the side at which said piston reaction forces are not applied, E.sub.L is the distance between the x-coordinate of the mean point of application of said resultant force of said piston reaction forces and the x-coordinate of the point at which a line passing through the centers of said two hydrostatic pads intersects the x-axis, and E.sub.R is the distance between the x-coordinate off the mean point of application of said resultant force of said piston reaction forces and the x-coordinate of the center of the hydrostatic pad disposed on the side at which said piston reaction forces are not applied.
A thrust hydrostatic bearing device for use in an axial piston machine including a casing, a cylinder block having a plurality of cylinder holes, and pistons movable back and forth in corresponding cylinder holes and fixed to piston rods rotatably engaged with a disc portion of a drive shaft of said axial piston machine, said pistons being mounted such that they are inclined with respect to said drive shaft, means for adjusting in synchronism with the angle of inclination of said cylinder block a restricted area formed by an oil groove communicating with a discharge port of a port plate having one end surface in slidable contact with said cylinder block and another end surface in slidable contact with said casing, as well as an oil groove provided in a seal land for a discharge port in an arcuate, inclined sliding surface of said casing, said bearing device further including an oil passage for communicating an adjusted discharge pressure of said axial piston machine to an end face of a hydrostatic pad at a side of a rod provided in a thick wall portion of said casing thereby rotatably supporting said disc portion of said drive shaft.
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Details of hydrostatic bearings independent of fluid supply or direction of load: of bearing pads
Swash plates: bearings for swash plates or driving axles
Engines or pumps
Shafts
Term ended 24 Aug 2007 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates to a ben axis type axial piston machine. More particularly, the present invention pertains to a thrust-radial hydrostatic bearing support type, bent axis type axial piston machine which is suitable for use at high pressures. Still more particularly, the present invention is concerned with a thrust hydrostatic bearing device for use in an axial piston machine which is suitable for carrying out a method of supporting the axial components of piston reaction force loads, relative to a driving shaft, as well as moment loads caused by these axial components.
Known devices of the type described above are designed to support thrust loads by the provision of a hydrostatic shoe for each piston. Such a device is disclosed in, for example, the specification of Japanese Patent Laid-Open No. 131776/1984.
In this piston machine, the number of pistons associated with the discharge pressure varies between certain values and is in accordance with the total number of pistons. For example, if a total of nine pistons is provided, the number of pistons associated with the discharge pressure varies between five and four. Therefore, the resultant force of the piston reaction force loads varies with the number of pistons located in the discharge pressure area and in proportion to the rotational speed of a driving shaft, the path of the point of application thereof generally being described as a figure eight. Due to this dynamic behavior of the piston reaction forces, not only thrust loads but also moment loads act on a drive disc of a driving shaft which supports a plurality of piston rods, the moment loads being supported by hydrostatic shoes. In this case, the moment loads also act on the hydrostatic shoes located in the suction pressure area.
FIG. 1 is a cross-sectional view of a thrust hydrostatic bearing device for use in a thrust-radial hydrostatic bearing support type and bent axis type axial piston machine, illustrating an embodiment of the present invention;
FIG. 2 is a cross-section taken along the line II--II of FIG. 1;
FIG. 3 illustrates the action of piston reaction forces on a drive disc in the axial piston machine of FIG. 2;
A first embodiment of the present invention will hereinunder be described in detail with reference to FIGS. 1 and 2.
An axial piston machine includes a housing cover 1, a cylinder block 3 having a plurality of cylinder holes 2, and pistons 5 movable back and forth within a corresponding cylinder holes 2 and fixed to piston rods 4. The piston rods 4 are pivotally supported within a drive disc 6B which, together with a shaft 6A connected to an operation input shaft (not shown) of the axial piston machine, forms a drive shaft body 6. While no input is being applied to the shaft 6A of the axial piston machine, the shaft 6A and the drive disc 6B are in engagement with each other at a spline shaft connecting section 7, with a certain gap maintained therebetween in the radial direction. Bearings 9 are disposed between the outer periphery of the shaft 6A and a bearing sleeve 8 to rotatably support the shaft 6A. The cylinder block 3 is rotatably mounted through a spherical universal joint or a center rod (both not shown), and is supported on a head cover 12 by a center shaft 10 through a port plate 11 having working medium suction ports 11A and discharge ports 11B. The head cover 12 has suction ports 12A and discharge ports 12B which are made to communicate with the suction ports 11A and the discharge ports 11B on the port plate 11. The spherical universal point is provided with a spherical bearing (neither of which is shown), and is pivotally supported within the drive disc 6B.
A device (not shown) for adjusting and changing the angle of inclination of the cylinder block 3 acts on a yoke (not shown). The stroke of the pistons 5 disposed in the cylinder holes 2 is changed by changing the inclination angle of the cylinder block 3. The drive disc 6B and the shaft 6A are connected by the spline shaft portion 7, and the shaft 6A acts as an input shaft in conformity with the method of operation of the axial piston machine.