Valve plate with hydraulic passageways for axial piston pumps

Information

  • Patent Grant
  • 6361285
  • Patent Number
    6,361,285
  • Date Filed
    Tuesday, December 21, 1999
    25 years ago
  • Date Issued
    Tuesday, March 26, 2002
    22 years ago
Abstract
An axial piston pump of the swash-plate variety having a rotating cylinder block and pistons movable in a longitudinal direction within bores formed in the block, and having a reversing capacitance for reducing pressure pulsations. For the further reduction of such pulsations, one or more channels, each having an associated discharge opening, are formed into a web of the valve plate of the pump to sequentially couple the reversing capacitance into fluid communication with the cylinder bores passing across the web.
Description




CROSS-REFERENCE TO RELATED APPLICATION




This application claims priority to German Application No. DE 198 59 328.7, filed Dec. 22, 1998, the disclosure of which is incorporated herein by reference.




BACKGROUND OF THE INVENTION




The present invention relates to an axial piston pump of a swash plate variety having a driven rotating cylinder block or drum and a large number of cylinder bores arranged radially therein, each of the bores being separated within the cylinder drum by a web of cylinder drum material. Pistons are arranged in each of the cylinder bores to be reciprocatingly movable in an axial, linear direction relative to the rotation of the cylinder drum between, at the end of a de-compression stroke, a bottom dead center position and, at the end of a compression stroke, a top dead center position. A valve plate having a low pressure connection port and a high pressure connection port also is provided, with the low and high pressure connection ports being separated in the valve plate by a web of valve plate material. The rotation of the cylinder drum causes the cylinder bores to be aligned in alternating fashion with the low-pressure connection port and the high-pressure connection port. Concurrently, the cylinder bores sweep past the web in the valve plate separating the low and high pressure connection ports, whereupon a reversing capacitance in fluid communication with the sweeping cylinder bore via at least one channel is supplied through the valve plate to mitigate the effects of a pressure pulsation.




The structure and operation of axial piston pumps of the type herein involved is described in further detail in the publication “Measures For The Reduction Of High-Pressure-Side Pulsations Of Hydrostatic Swash Plate Units” by Marcus Jarchow, Dissertation 1997, Aachen Institute of Technology, Verlag Mainz, Aachen, and in the following U.S. Pat. Nos.: 3,250,227; 3,667,867; 3,774,505; 4,037,521; 4,212,596; 4,366,627; and 5,123,815. The Jarchow publication deals in particular with the problem of high-pressure-side pulsations, and sets forth a solution which involves a reversing capacitance. In this regard, in order to avoid compression oil flows when each individual cylinder bore of the cylinder block is aligned with the high-pressure connection port, it is necessary to adjust the pressure forming in the cylinder bore through the compression movement of the piston to the pressure prevailing on the high-pressure side of the control base in its high-pressure connection port. Through the use of a reversing capacitance, this adjustment is effected by admitting compression oil under high pressure into the cylinder bore. This reversing capacitance is formed in the control base via a channel in communication with the cylinder bores of the rotating cylinder block and, respectively, via an additional channel with the high-pressure connection port.




It has been observed, however, that the undesirable high-pressure-side pulsations continue to occur in attenuated form even with the use of a reversing capacitance. In this regard, the clearing of the channel extending from the reversing capacitance through the web between each of the cylinder bores results in an abrupt pressurization of the cylinder bore as the compression oil is admitted under high pressure from the reversing capacitance. An object of the present invention therefore is to further reduce the development of pulsations in an axial piston pump, and to ensure a less abrupt alignment of the cylinder bore with the high-pressure connection port.




BROAD STATEMENT OF THE INVENTION




Broadly, the present invention is directed to the provision of one or more channels, each having an associated discharge opening, which are formed in the web of the valve plate to couple the reversing capacitance in fluid communication sequentially with each of the cylinder bores passing across the web.




According to one exemplary embodiment of the invention, at least two such channels are provided which are arranged on an arc defined by the low and high pressure connection ports. Optionally, the discharge openings and their associated channels may have the same or different diameters.




According to another exemplary embodiment of the invention, particularly if two channels are provided, the discharge openings of the channels are connected with each other via a recess formed in the web of the valve plate, such recess surrounding the discharge openings.




For a further improvement of a positioning of the cylinder bores the discharge openings of the channels extending from the reversing capacitance to each of the cylinder bores via the web formed on the valve plate are equipped with adjoining guide-in notches and/or guide-out notches. In one exemplary embodiment, the first discharge opening relative to the direction of rotation of the cylinder block is provided with a longer guide-in notch and a shorter guide-out notch adjoining the discharge opening. In addition, in the case of two channels being formed through the valve plate web, the second discharge opening relative to the direction of rotation of the cylinder block is provided with a shorter guide-in notch and a longer guide-out notch. Similarly, if a recess is formed surrounding the discharge openings of the two channels, this recess may be provided with a guide-in notch and/or a guide-out notch.




The present invention, accordingly, comprises the apparatus and method possessing the construction, combination of elements, and arrangement of parts and steps which are exemplified in the detailed disclosure to follow. Advantages of the invention includes an axial piston pump construction which reduces undesirable high-pressure-side pulsations. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.











BRIEF DESCRIPTION OF THE DRAWINGS




For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:





FIG. 1

shows a swash plate-type axial piston pump in a generally schematic representation;





FIG. 2

shows the reversal of one of the pistons of the pump of

FIG. 1

while occluded by a supplied reversing capacitance;





FIG. 3

is a top view of the fixed valve plate of the pump of

FIG. 1

showing an arrangement of the discharge openings of the channels provided to couple the cylinder bores into fluid communication with the reversing capacitance;





FIG. 4

shows an alternative embodiment of the discharge opening arrangement of

FIG.3

; and





FIG. 5

shows another alternative embodiment of the discharge opening arrangements of FIGS.


3


and


4


.











The drawings will be described further in connection with the following Detailed Description of the Invention.




DETAILED DESCRIPTION OF THE INVENTION




An important element of the axial piston pump construction shown in

FIG. 1

is a cylinder block or drum


10


which will be readily understood to be rotatable by a drive (not shown) coupled to the drum via a shaft


9


. Cylinder bores


11


are spaced-apart radially in the outer area of the cylinder block, with a piston


12


being received with each of the bores


11


to be reciprocatingly movable in a linear, axial direction. A ball,


13


, of each of the pistons


12


is supported on one face of cylinder block


10


within the socket


14


of a guide shoe


15


disposed outside of cylinder block


10


. Guide shoe


15


bears upon a rotationally stationary swash plate


16


such that the rotation of cylinder block


10


in relation to the swash plate


16


can be converted into a linear motion of the pistons


12


in cylinder bores


11


, which motion is directed axially relative to the axis of rotation of block


10


.




A valve plate


20


is arranged fixedly on the face of cylinder block


10


opposite swash plate


16


. High pressure connection ports, commonly referenced at


18


, are formed to extend along an arc over a portion of the circumference of the valve plate


20


, with corresponding low pressure connection ports, referenced at


19


in the views of

FIGS. 2-5

, also being formed in the control plate for the low-pressure range. As may be seen with additional reference to

FIGS. 2-5

, connection ports


18


and


19


are separated a web


26


, of material in valve plate


20


(FIG.


2


).




A transition of the connection of cylinder bore


11


with low-pressure connection port


19


and high pressure connection port


18


is shown schematically in

FIG. 2

, such reversal being effected by means of a reversing capacitance. For this purpose, a reversing capacitance


23


is formed in connection plate


17


from which the two channels commonly referenced at


24


extend to the face of cylinder block


11


and empty into a corresponding discharge opening, commonly referenced at


27


in each of the views of

FIGS. 3-5

. A resistance,


25


, each is provided in each of the channels


24


.




Looking next to

FIG. 2

, the control sequence of the pump of

FIG. 1

is illustrated with reference to three cylinder bores


11


and their associated pistons


12


which are adjacently-arranged in cylinder block


10


. Each of the cylinder bores


11


is separated from an adjacent bore by a web, commonly referenced at


21


, of the cylinder block material. In the left-most illustration, the cylinder bore


11


communicates with low-pressure connection port


19


, with piston


12


still moving in the direction of its bottom dead center position such that oil is suctioned from the low-pressure connection port


19


. Continuing with the center illustration of

FIG. 2

, piston


12


is now moved to its bottom dead center position


22


wherein the discharge opening


27


of channel


24


is occluded by web


21


. As the rotation of cylinder block


10


continues, the discharge opening


27


of channels


24


is unblocked, and the pressure in the cylinder bore


11


is increased with the incipient piston stroke via the supply of compression oil from reversing capacitance


23


. Concluding with the right-most, the cylinder bore


11


is now in communication with the high-pressure connection port


18


as the compression stroke of piston


12


proceeds in the direction of its top dead center position. However, the pressure in bore


11


previously has been increased to such an extent that during the connection of the bore


11


to the high-pressure connection port


18


, the pressure surge and consequently the pulsation in rotating cylinder block


10


is correspondingly reduced.




An arrangement according to the present invention of two or more channels


24


is next revealed in the several views of

FIGS. 3-5

. As may be seen in

FIG. 3

, two discharge openings


27


of two corresponding channels


24


(

FIG. 2

) can be arranged in web


26


of valve plate


20


. Web


26


separates low-pressure connection port


19


and high-pressure connection port


18


, with channels


24


being arranged on the partial arc defined by connection ports


18


and


19


.




With reference now to

FIG. 4

, discharge openings


27


may be seen to be provided with correspondingly-arranged guide-in notches


28


and guide-out notches


30


, respectively, the first discharge opening


27


being provided with a guide-in notch


28


having a longer extension and a shorter guide-out notch


30


in the direction of rotation of cylinder block


10


from low-pressure connection port


19


to high-pressure connection port


18


. In turn, the second discharge opening


27


located forwardly in the direction of rotation first has a shorter guide-in notch


28


and a longer guide-out notch


30


directed towards high-pressure connection port


18


. These guide-in and guide-out notches


28


and


30


are each variable in number, shape, position and size and can thus be designed appropriately to optimize the reversing process.




Another exemplary embodiment of the invention is shown in

FIG. 5

wherein the discharge openings


27


of two channels


24


are in communication with each other via a surrounding recess


27


to effect a still further graduation of the activation characteristics. Preferably, recess


29


may be designed to be kidney or oblong-shaped and to be arranged on the arc defined by connection ports


18


and


19


. Additionally, guide-in and guide-out notches may be provided at the beginning and ending portions of recess


29


.




Although not shown in greater detail, it will be appreciated that discharge openings


27


and channels


24


may be configured as having the same or different diameters. Discharge openings


27


and their adjoining channels


24


also may have variable diameters, and further may be arranged in varied angular positions relative to each other.




As it is anticipated that certain changes may be made in the present invention without departing from the precepts herein involved, it is intended that all matter contained in the foregoing description shall be interpreted as illustrative and not in a limiting sense. All references cited herein are expressly incorporated by reference.



Claims
  • 1. An axial piston pump of a swash-plate variety comprising:a cylinder block rotatable in a first radial direction about a central axis and having a plurality of cylinder bores formed therein about said central axis for angular displacement with the rotation of said cylinder, each of said bores being spaced-apart in said first radial direction from an adjacent one of said bores and extending in an axial direction generally parallel to said central axis from a first end opening to a second end opening; a piston received in a corresponding one of each of said bores for sequentially reciprocating linear motion therein responsive to the rotation of said cylinder bock, each said piston being movable in said corresponding one of said bores in a first said axial direction towards the first end of said bore defining a suction stroke of said piston, and in an opposite, second said axial direction towards the second end of said bore defining a compression stroke of said piston; a source of fluid pressure for providing a fluid capacitance to each of said pistons; a valve plate aligned coaxially with said cylinder block as positioned over the second end openings of said bores, said valve plate having a low pressure connection port disposed at a first angular position relative to the rotation of said cylinder block and a high pressure connection port disposed at a second angular position spaced-apart radially from said low pressure connection port by a web of said valve plate; a first channel formed in said valve plate web intermediate said low and said high pressure connection port, said first channel extending axially through said valve plate between a first inlet opening coupled in fluid communication with said source of said fluid pressure, and a first discharge opening selectively couplable in fluid communication with the second end openings of said bores; a second channel formed in said valve plate web intermediate said low and said high pressure connection port, said second channel being radially spaced-apart from said first channel and extending axially through said valve plate between a second inlet opening coupled in fluid communication with said source of said fluid pressure, and a second discharge opening selectively couplable in fluid communication with the second end openings of said bores; a first guide notch formed into said valve plate web about said first discharge opening and elongated in a second radial direction opposite said first radial direction; and a second guide notch formed into said valve plate web about said second discharge opening and elongated in said first radial direction; whereby the second end openings of said bores are sequentially registered in fluid communication with said low pressure connection port during the suction stroke of each said piston, and with said high pressure connection port during the compression stroke of each said piston; and whereby the second end openings of said bores additionally are sequentially registered in fluid communication with the first discharge opening of said first channel and with the second discharge opening of said second channel to supply said fluid pressure to each said piston as said bores pass along said web of said valve plate.
  • 2. The piston pump of claim 1 further comprising a connection plate aligned coaxially with said valve plate as disposed opposite said cylinder block, said connection plate having a chamber containing said source of said fluid pressure and having a conduit formed therein, said conduit extending axially in said connection plate from a first end coupled in fluid communication with said chamber to a second end coupled in fluid communication with the first inlet end of said valve plate first channel.
  • 3. The piston pump of claim 1 wherein said low and said high pressure connection port and the first and the second discharge opening of, respectively, said first and said second channel are aligned in said valve plate along a common arc relative to said central axis.
  • 4. The piston pump of claim 1 wherein said first and said second channel are of equal diameters.
  • 5. The piston pump of claim 1 wherein said first and said second channels are of different diameters.
  • 6. An axial piston pump of a swash-plate variety comprising:a cylinder block rotatable in a first radial direction about a central axis and having a plurality of cylinder bores formed therein about said central axis for angular displacement with the rotation of said cylinder, each of said bores being spaced-apart in said first radial direction from an adjacent one of said bores and extending in an axial direction generally parallel to said central axis from a first end opening to a second end opening; a piston received in a corresponding one of each of said bores for sequentially reciprocating linear motion therein responsive to the rotation of said cylinder bock, each said piston being movable in said corresponding one of said bores in a first said axial direction towards the first end of said bore defining a suction stroke of said piston, and in an opposite, second said axial direction towards the second end of said bore defining a compression stroke of said piston; a source of fluid pressure for providing a fluid capacitance to each of said pistons; a valve plate aligned coaxially with said cylinder block as positioned over the second end openings of said bores, said valve plate having a low pressure connection port disposed at a first angular position relative to the rotation of said cylinder block and a high pressure connection port disposed at a second angular position spaced-apart radially from said low pressure connection port by a web of said valve plate; a first channel formed in said valve plate web intermediate said low and said high pressure connection port, said first channel extending axially through said valve plate between a first inlet opening coupled in fluid communication with said source of said fluid pressure, and a first discharge opening selectively couplable in fluid communication with the second end openings of said bores; a second channel formed in said valve plate web intermediate said low and said high pressure connection port, said second channel being radially spaced-apart from said first channel and extending axially through said valve plate between a second inlet opening coupled in fluid communication with said source of said fluid pressure, and a second discharge opening selectively couplable in fluid communication with the second end openings of said bores; and a recess formed into said valve plate web, said recess surrounding and connecting said first and said second discharge opening; whereby the second end openings of said bores are sequentially registered in fluid communication with said low pressure connection port during the suction stroke of each said piston, and with said high pressure connection port during the compression stroke of each said piston; and whereby the second end openings of said bores additionally are sequentially registered in fluid communication with the first discharge opening of said first channel and with the second discharge opening of said second channel to supply said fluid pressure to each said piston as said bores pass along said web of said valve plate.
  • 7. The piston pump of claim 6 further comprising a connection plate aligned coaxially with said valve plate as disposed opposite said cylinder block, said connection plate having a chamber containing said source of said fluid pressure and having a conduit formed therein, said conduit extending axially in said connection plate from a first end coupled in fluid communication with said chamber to a second end coupled in fluid communication with the first inlet end of said valve plate first channel.
  • 8. The piston pump of claim 6 wherein said low and said high pressure connection port and the first and the second discharge opening of, respectively, said first and said second channel are aligned in said valve plate along a common arc relative to said central axis.
  • 9. The piston pump of claim 6 wherein said first and said second channel are of equal diameters.
  • 10. The piston pump of claim 6 wherein said first and said second channels are of different diameters.
  • 11. The piston pump of claim 6 wherein said recess has a beginning portion and an ending portion, said beginning portion being configured as a first guide notch elongated in a second radial direction opposite said first radial direction, and said ending portion being configured as a second guide notch elongated in said first radial direction.
Priority Claims (1)
Number Date Country Kind
198 59 328 Dec 1998 DE
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