Hydrostatic axial piston machine

Details Hydrostatic axial piston machine Hydrostatic axial piston machine

2001-07-18

2004-05-18

Freay, Charles G. (Department: 3746)

Motors: expansible chamber type

Three or more cylinders arranged in parallel radial or...

Cylinders parallel to rotation axis

C091S505000, C092S057000, C417S269000, C417S270000

Reexamination Certificate

active

06736048

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a hydrostatic axial piston machine having a drum-like cylinder block which is fixedly supported against rotation on a driving shaft or an output shaft and is provided with cylinder boreholes concentrically and parallel to its center line in which axially displaceable pistons are arranged which are supported via spherical heads on a slanting disk which is fixed with respect to the housing and preferably adjustable in its slanting angle, with the cylinder openings opposite the slanting disk sweeping over roughly kidney-shaped low pressure and high pressure control openings of a control body between which reversing regions with additional boreholes are located.
Unwanted pressure and conveyor flow pulsations with a corresponding noise development can occur on the running of the open sides of the cylinder boreholes, or the sides of the cylinder boreholes provided with openings, over the reversing regions located between the low pressure and high pressure control openings, because the open cylinder sides are closed abruptly on running onto the reversing regions and, on running off, are abruptly exposed to a high or low pressure which differs from the pressures prevailing in the cylinder openings.
To alleviate these pressure and conveyor flow pulsations, it is known to connect the run-out and run-in regions of the low pressure and high pressure control openings to the reversing regions by notches or wedge-shaped transitions such as can be seen in
FIGS. 13 and 14
. It is furthermore known to connect the reversing regions to the low pressure and high pressure control openings by passages such as can be seen in
FIGS. 15 and 16
.
Since, however, the volumes decisive for the pressure build-up in the cylinder space, namely the dead volume plus the stroke volume, depend on the swivel angle of the slanting disk, the necessary volumes to be supplied for the pressure build-up on the pressure in the high pressure control opening and on the available time interval for the pressure reversing and thus on the speed, an optimum pressure reversing is not possible over the whole operating range with a constant notch between the run-out and run-in regions and the reversing region or with passages connecting the reversing regions to the low pressure and high pressure control openings by passages.
It is generally desired to avoid unwanted pressure and conveyor flow pulsations on the passing of the open cylinder sides over the reversing regions, by the reversing regions being provided with boreholes via which an influencing of the pressure prevailing in the cylinder openings takes place such that a continuous pressure build-up or reduction is assumed in the cylinders on the transition from the low pressure to the high pressure control openings and vice versa. In a hydrostatic machine known from DE 198 18 721 A1, one borehole is respectively disposed in the reversing regions via which a pressure increasing the pressure in the cylinders or a pressure relieving this pressure is applied by pumping and/or loading or load relieving devices. The known hydrostatic machine is, however, complex in that special pumping and/or load relieving devices have to be provided.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a hydrostatic axial piston machine of the kind first mentioned in which the additional boreholes located in the reversing region(s), which influence the pressure increase or the pressure drop on the passing of the cylinder openings over the reversing regions, are controlled in dependence on the operation states, namely the pressure, the speed and the swivel angle of the slanting disk. Furthermore, a hydrostatic axial piston machine should be provided in which an unwanted abrupt increase or drop in the pressure in the cylinders should be avoided in a simple and reliable way even with changed operating conditions on the passing of the cylinder openings over the reversing regions.
This object is solved in accordance with the invention by a borehole, which is connected to the high pressure side or the high pressure control opening by a line, opening at least in one reversing region of the control body and by a restrictor controlled by the high pressure being disposed in the line which releases a restrictor opening corresponding to the high pressure in the line. If the open cylinder side sweeps over the borehole, oil under higher pressure flows from this into the cylinder opening so that the pressure in this increased on passing the reversing region and a continuous pressure increase takes place in the cylinder until the open cylinder side runs into the high pressure control opening. Unwanted abrupt pressure increases and changes to the conveyor flow are thereby avoided.
The borehole appropriately opens in a region of the reversing region which is facing the high pressure control opening.
In accordance with a preferred embodiment, it is planned that, at least in a region of the reversing region of the control body facing the low pressure control opening, a borehole opens which is connected to the low pressure control opening by a line and that a restrictor controlled by the high pressure is disposed in the line, which releases a restrictor opening corresponding to the high pressure in the line. This aspect improves the pressure compensation and results in a continuous pressure drop avoiding abrupt pressure changes prior to and during the running of the open cylinder sides into the low pressure control opening.
The two boreholes in the reversing region are appropriately simultaneously covered by the respective cylinder opening on the passing of each of them. The two boreholes appropriately have respectively equal distances to the low pressure and high pressure control openings in the reversing region(s).
Known solutions, for example of the kind described with reference to
FIGS. 13
to
16
, have the disadvantage that these only ensure an evening of the pressure increase or of the pressure drop on the passing of the open cylinder sides over the reversing regions for a certain operating mode, for example a certain pressure, of the axial piston machine. The solution of the invention is characterized, in contrast to this, by the boreholes in the reversing regions forming restrictor openings by which a pressure approximation takes place via the controlled restrictor which is carried off from the respective high pressure so that the axial piston machine of the invention also ensures a gentle pressure compensation or an adaptation of the pressure on the passing of the open cylinder sides over the reversing regions with different operating modes and in particular with different pressures.
In accordance with an inventive aspect, it is provided that the controlled restrictor consists of a cylindrical borehole in the control body or a cylinder held in the control body in which borehole or which cylinder a control piston loaded by a compression spring is displaceably guided whose side opposite the compression spring is exposed to the high pressure in the high pressure control opening, that lines open into the cylinder borehole or the cylinder at an axial distance to one another, which lines lead to the borehole of the reversing region and to the high pressure control opening or to the low pressure control opening, and that, corresponding to its displacement, the control piston releases differently sized restrictor openings with respect to the line leading to the reversing region. In accordance with this aspect of the invention, a restrictor controlled by the high pressure or the high pressure side is provided with a cross-section restricting the flow which is matched to the respective high pressure and therefore results in an optimum manner in a continuous pressure increase or pressure drop in the cylinder openings passing the reversing regions.
The line of the reversing region opening into the control cylinder can be connected to the line leading to the high pressure control opening or the low pressure control opening respectively by an axial

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