EP1174617B1 - Hydrostatic axial piston machine - Google Patents

Description

The invention relates to a hydrostatic axial piston machine with a drum-shaped Cylinder block that is mounted on a drive or output shaft so that it cannot rotate and provided concentrically and parallel to the center line with cylinder bores is in which axially displaceable pistons are arranged, which are spherical Heads on a housing-fixed, preferably adjustable in their helix angle, Support the swashplate, with the swashplate opposite Cylinder openings such as kidney-shaped low-pressure and high-pressure control openings of a control body, between which there are reversing areas with additional holes.

When running the open or apertured sides of the cylinder bores via the located between the low pressure and high pressure control openings Reversal areas can lead to undesirable pressure and flow pulsations come with appropriate noise because the open cylinder sides closed suddenly at the changeover areas and at Abruptly be expelled with a high or low pressure, the deviates from the pressures prevailing in the cylinder openings.

To alleviate these pressure and flow pulsations, it is known to reduce the and inlet areas of the low pressure and high pressure control openings by notches or connect wedge-shaped transitions to the reversal areas as it is 13 and 14 can be seen. Furthermore, it is known the reversal areas connect through channels to the low pressure and high pressure control ports, as can be seen from FIGS. 15 and 16.

However, since the volumes that are decisive for the pressure build-up in the cylinder space, namely the dead volume plus the stroke volume, from the swivel angle of the Swashplate, the volumes to be added to build up pressure the pressure in the high pressure control port and the available one Time interval for pressure changeover and thus depend on the speed, is an optimal pressure reversal with a constant notch in the reversal area or with the reversing areas through channels with the low-pressure and high-pressure control openings connecting channels across the entire operating range not possible.

Basically, it is an effort to avoid undesirable pressure and flow pulsations when the open cylinder sides pass through the reversing areas to avoid that the reversing areas are provided with holes through which such an influence on the pressure prevailing in the cylinder openings takes place in the cylinders during the transition from the low pressure to the High-pressure control openings and vice versa a continuous pressure build-up or Pressure reduction sets. In a hydrostatic known from DE 198 18 721 A1 or U55634776 A machine is arranged in each of the reversing areas through which through pumping and / or loading or unloading devices the pressure in the cylinder increasing pressure or a pressure relieving this pressure is applied becomes. However, the known hydrostatic machine is expensive in that special pumping and / or relief devices must be provided.

The object of the invention is to provide a hydrostatic axial piston machine specified type to create, in which in the or the changeover areas located additional bores, which increase or decrease the pressure Influence the passage of the cylinder openings over the reversing areas, depending on of the operating conditions, namely the pressure, the speed and the Swivel angle of the swash plate are controlled. Furthermore, a hydrostatic Axial piston machine can be created that is simple and reliable Way even with changed operating conditions when running through the Cylinder openings over the reversal areas an undesirable sudden increase or prevent pressure drops in the cylinders.

According to the invention, this object is achieved by an axial piston machine according to claim 1. It is therefore provided that at least one Reversal area of the control body opens a hole through a line is connected to the high pressure side or the high pressure control opening, and that in the line a throttle controlled by the high pressure is arranged, which in the line opens a throttle opening corresponding to the high pressure. About Strokes the open cylinder side the bore, flows out of this under higher Oil under pressure in the cylinder opening, so that the pressure in the passage through the changeover range and a continuous in the cylinder Pressure increase until the open cylinder side enters the high pressure control opening he follows. Unwanted sudden pressure increases and changes in the flow are avoided.

The hole expediently opens into an area of the reversing area, which faces the high pressure control opening.

According to a preferred embodiment it is provided that at least one the low pressure control opening facing area of a reversing area of the Control body opens a hole through a line with the low pressure control opening is connected, and that in the line one controlled by the high pressure Throttle is arranged, which corresponds to the high pressure in the line Throttle opening releases. This configuration improves pressure compensation and leads in front of the inlet and the inlet of the open cylinder sides in the Low pressure control opening to a continuous, avoiding pressure surges Pressure reduction.

The two bores are expediently located in the reversing area Pass of each cylinder opening covered by this at the same time. Conveniently, point the two holes in the reversal area or areas equal distances to the low pressure and high pressure control openings.

Known solutions, for example those described with reference to FIGS. 13 to 16 Art have the disadvantage that they equalize the pressure increase or the pressure drop when the open cylinder sides pass through the reversing areas only for a specific mode of operation, for example a specific one Pressure, ensure the axial piston machine. The solution according to the invention In contrast, is characterized in that the holes in the reversing areas Form throttle openings through which one is controlled via the controlled throttle Pressure adjustment takes place, which is derived from the respective high pressure, so that the axial piston machine according to the invention even in different operating modes and in particular at different pressures a gentle pressure equalization or an adjustment of the pressure when passing through the open cylinder sides guaranteed over the reversal areas.

According to an inventive embodiment it is provided that the controlled throttle from a cylindrical bore in the control body or one in the Control body-held cylinder, in which or by a compression spring loaded piston is displaceably guided, the opposite of the compression spring Side acted on by the high pressure in the high pressure control opening is that in the cylinder bore or the cylinder at an axial distance from each other to the bore of the reversing area and to the high pressure control opening or lines leading to the low-pressure control opening and that the control piston according to its displacement of different sizes Throttle openings opposite the line leading to the reversing area releases. According to this embodiment of the invention, one of the high pressure or the high pressure side controlled throttle with a flow restricting cross section provided that is adapted to the respective high pressure and therefore in optimal Way to a continuous pressure increase or pressure drop in the Reversal areas leads through cylinder openings.

The line of the reversing area opening into the control cylinder can be through an axial groove with a changing cross section of the control piston with the the high-pressure control opening or the low-pressure control opening leading line be connected. The changing cross section is due to Adapted calculations or experiences of the respective axial piston machine.

According to another embodiment it is provided that the connection of the Control cylinder to the line leading to the reversing area from one Slit exists, which the control piston due to its displacement releases the high pressure on one side in different lengths. The approved length corresponds to the respective flow cross section of the controlled Throttle, which is adapted to the respective axial piston machine.

According to a preferred embodiment it is provided that the control piston acted upon on one side by at least two compression spring enclosing each other of which the springs following or following the first spring are successive corresponding to the displacement of the control piston in the direction of the springs are used, i.e. they use their force to load the control piston. With this configuration, an approximately hyperbolic spring characteristic can be created be the way the spool faces the increasing pressure on the High pressure side takes into account in a better way.

For example, increases with constant power and a smaller swivel angle the swash plate the pressure with a correspondingly reduced volume flow. To different operating conditions, for example the pressure change and the change in volume flow when the helix angle changes Taking into account swashplate must have a certain control characteristic with regard to the throttle opening which can be changed in cross section, which takes into account the special spring characteristics and spring characteristic. at a change in the helix angle of the swash plate changes the dead volume in the cylinder between the piston and the control body, so that changed conditions, which are controlled by the invention Throttle is taken into account. In addition to the high pressure, the Swivel angle of the swash plate changed, is also taking this change into account Throttle opening control required.

According to another embodiment of the invention it is provided that the control piston is shifted in the control cylinder by an actuator whose Travel from a control device, for example a computer, depending the high pressure, the speed and the swivel angle of the swash plate is determined. The values influencing the travel of the control piston, the for the respective axial piston machine from the variable high pressure, the variable speed and the variable swivel angle, can be stored in tables (ROM) in the memory unit of the computer, so that the computer according to the respectively measured high pressure, the respectively measured Speed and the respective swivel angle of the swash plate Control piston adjusted.

According to another embodiment of the invention it is provided that the control piston is designed as a stepped piston, the annular piston surface and the disk-shaped piston surface of the high pressure and another from one of the set helix angle of the swash plate speaking pressure are applied. The helix angle of the swashplate corresponding pressure can be, for example, from the pressure in one Derive the actuating cylinder that adjusts the swash plate and is proportional to the angle adjustment the swash plate is.

According to a further embodiment of the invention it is provided that the control piston is designed as a three-stage piston, through the two ring surfaces and the central disc-shaped piston surfaces each formed by Pressures applied to the high pressure in the high pressure control port, correspond to the helix angle of the swash plate and the speed. The the Pressure corresponding to the rotational speed can be achieved, for example, by one of the axial piston machines driven auxiliary pump are derived, the a speed proportional pressure generated.

According to a preferred embodiment, it is provided that the changeover areas opening holes formed by the holes of a constant throttle are. According to the invention, each inlet throttle has at least two throttle cross sections on, the one choke a constant choke in the control plate and the other choke or chokes near the control surface of the control body or housed in the control body itself are, the cross section or the cross sections of the controllable chokes controlled according to the operating conditions of the axial piston machine will or can be controlled that the pressure build-up and pressure reduction in the controlled Cylinder space takes the desired course.

In the described embodiments of the invention, it is possible that the high pressure side, i.e. the high pressure control openings, a certain volume of the pressure oil is removed, which is then missing from the flowing pressure medium. Missing pressure medium on the high pressure side can in turn lead to undesirable ones Cause pulsations. For this reason, another is preferred Embodiment of the invention provided that the controlled throttle Pressurized oil is supplied from an external pressurized oil source.

Fig. 1

eine Draufsicht auf die Steuerfläche des Steuerkörpers mit gestrichelt angedeuteter Stellung der Zylinderöffnungen in den Umsteuerbereichen,

Fig. 2

einen Schnitt durch den Steuerkörper sowie einen Zylinder längs der Linie II - II in Fig. 1 in schematischer Darstellung,

Fig. 3

eine der Fig. 2 entsprechende Darstellung, in der auch die der Niederdruck-Steueröffnung zugewandte Bohrung in dem Umsteuerbereich mit einer gesteuerten Drossel versehen ist,

Fig. 4, 4a und 4b

den Fig. 1 bis 3 entsprechende Darstellungen, in denen die jeweils beiden den beiden Umsteuerbereichen angeordneten Bohrungen mit gesteuerten Drosseln versehen sind,

Fig. 5

eine gesteuerte Drossel der aus Fig. 2 ersichtlichen Art in vergrößerter Darstellung,

Fig. 6

eine der Fig. 5 entsprechende Darstellung einer gesteuerten Drossel, bei der der Steuerkolben von einander einfassenden Druckfedern beaufschlagbar ist,

Fig. 7

eine der Fig. 6 entsprechende Darstellung, bei der der Steuerkolben von einer von einer Steuereinrichtung gesteuerten Stelleinrichtung verschiebbar ist,

Fig. 8

eine der Fig. 5 entsprechende Darstellung, bei der der Steuerkolben durch einen Stufenkolben verschiebbar ist,

Fig. 9

eine der Fig. 8 entsprechende Darstellung, bei der der Steuerkolben durch eine dreistufige Kolbenanordnung verschiebbar ist,

Fig. 10

eine der Fig. 1 entsprechende Darstellung, bei der der Bohrung in dem Umsteuerbereich über die gesteuerte Drossel von einer externen Druckquelle Drucköl zugeführt wird,

Fig. 11

eine der Fig. 1 entsprechende Darstellung, bei der die beiden Bohrungen des Umsteuerbereichs, die sich auf den der Niederdruck- und Hochdruck-Steueröffnungen zugewandten Seiten befinden, durch gesteuerte Drosseln gesteuerte sind,

Fig. 12

eine schematische Darstellung eines Steuerkörpers, bei der sämtliche Bohrungen der Umsteuerbereiche durch gesteuerte Drosseln gesteuert sind und die Bohrungen an eine externe Druckmittelquelle angeschlossen sind,

Fig. 13 bis 16

bekannte Ausführungen von Steuerkörpern.

Embodiments of the invention are explained below with reference to the drawing. In this shows

Fig. 1

2 shows a plan view of the control surface of the control body with the position of the cylinder openings in the reversing areas indicated by dashed lines,

Fig. 2

2 shows a section through the control body and a cylinder along the line II-II in FIG. 1 in a schematic illustration,

Fig. 3

2 shows a representation corresponding to FIG. 2, in which the bore facing the low-pressure control opening is also provided with a controlled throttle in the reversing area,

4, 4a and 4b

1 to 3 corresponding representations in which the two holes arranged in each of the two reversing areas are provided with controlled throttles,

Fig. 5

3 shows a controlled throttle of the type shown in FIG. 2 in an enlarged view,

Fig. 6

5 shows a representation of a controlled throttle, in which the control piston can be acted upon by compression springs which surround one another,

Fig. 7

6 shows a representation corresponding to FIG. 6, in which the control piston can be displaced by an actuating device controlled by a control device,

Fig. 8

5 shows a representation corresponding to FIG. 5, in which the control piston is displaceable by a stepped piston,

Fig. 9

8 shows a representation corresponding to FIG. 8, in which the control piston can be displaced by a three-stage piston arrangement,

Fig. 10

1 shows a representation corresponding to FIG. 1, in which pressure oil is supplied to the bore in the reversing area via the controlled throttle from an external pressure source,

Fig. 11

1, in which the two bores of the reversing area, which are located on the sides facing the low-pressure and high-pressure control openings, are controlled by controlled throttles,

Fig. 12

1 shows a schematic representation of a control body in which all the bores in the reversing areas are controlled by controlled throttles and the bores are connected to an external pressure medium source,

13 to 16

known designs of control bodies.

A control body 1 is shown schematically in FIGS. 1 and 2, of which in FIG. 1 only the control surface with the high pressure control opening 2 and the low pressure control opening 3 and those in the reversal areas between the low pressure and High-pressure control openings located throttle bores 4, 5 and 6, 7 shown are. The control surface of the control body is formed by the approximately oval Openings 8 of the cylinder 9 are swept over, which are shown in broken lines in FIG are.

The hydraulic connections of the low-pressure and high-pressure control openings 2, 3 are of a common type and are therefore not shown.

In the cylinders 9 it stands between the pistons 10 and those on the control surface of the control body 1 sliding openings 8 corresponding to the respective helix angle the swash plate a dead space 11, which in the control of throttle openings formed through bores 4 to 7 must be taken into account.

The throttle openings 4 to 7 have a constant cross section and form thus, as can be seen from FIG. 2, constant chokes.

To control the pressure media flowing through the constant throttles is a Controlled throttle 12 is provided, which will be described with reference to FIG. 5.

In a bore 15 of the control body 1 or in a control cylinder a special one connected to the control body 1 by lines A control piston 16 is arranged displaceably in the cylinder. This control piston is loaded by a compression spring 17 which between the bottom of the cylinder 15 and the side of the control piston 16 facing this is clamped. The opposite Side of the control piston is acted on by the high pressure, that is the pressure in the high-pressure control opening 2 of the control body 1 prevails. For this purpose, the side of the compression spring 17 opposite Cylinder via a line 18 and a branch line 19 with the high pressure control opening 2 connected. Of course, the high pressure could also be from be derived from another point of the axial piston machine. The control piston 16 is provided with an axially closed bore 20 at its ends, which communicates with radial bores or slots 21, 22. The radial Bore 21 is via line 18 and an annular space 23 with the pressure of Pressurized medium in the high pressure control opening 2. The hole or preferably the slot 22 communicates with an annular space 24, of which a line 25 to the throttle opening 5 in the control surface of the control body 1 leads. The piston 16 is in the cylinder bore 15 through the right piston surface acting high pressure shifted against the force of the compression spring 17, a control slot of different lengths according to the displacement path 22 is controlled, each of the length detected by the annular space 24 of the control slot.

In the exemplary embodiment according to FIG. 2, the control piston 16 has an axial one Provide slot that has a variable cross section, so that accordingly the displacement of the control piston with that leading to the throttle opening 5 Throttle cross-sections of different sizes can be opened.

To build up the pressure in the cylinder bores, volume from the high pressure control opening via the controlled throttle and the constant throttle in the Cylinder rooms of the cylinder bores. With the controlled throttle can the volume flowing into the control time can be influenced in such a way that the desired one Pressure curve in the cylinder bore is reached. Influencing the Throttle cross section can on the relationship between that in the control openings prevailing pressure and the open throttle cross section both over the compression spring and the shape of the throttle can be achieved.

In the exemplary embodiment according to FIG. 3, both the Throttle openings 5 constant cross-section on the low pressure and high pressure control openings 2, 3 facing sides with controlled throttles 12. The controlled throttles 12 are in both cases on their compression springs 17 opposite sides of the high pressure, which preferably in the form shown in dashed lines via lines from the high pressure control opening 2 is derived.

A special feature of the invention is to be seen in the fact that the preferably oval cylinder openings over the control surfaces of the control body the cylinder opening 8 covers both throttle openings 4, 5, so that it becomes one smoothing pressure equalization comes.

According to the embodiment of Figures 4, 4a and 4b it is provided that in two reversing areas, i.e. in the two areas between the low-pressure and high pressure control orifices throttle bores 5 are arranged via the controlled throttles 12 in connection with variable throttle openings stand so that an optimal pressure compensation when the cylinder openings overflow can take place via the reversing areas.

In the embodiment of FIG. 6, the control piston is a compression spring 30 acted on, which encloses a compression spring 31 of shorter length in the manner that this only on the control piston after a predetermined displacement 16 attacks and thereby changes the spring characteristic and a hyperbolic Course attacks.

7, a displacement device 33 is provided, which displaces the control piston 16 via a tappet 34, the displacement device 33 controlled by a control device, for example a computer which is a travel for the plunger 34 from the pressure of the high pressure side, the speed and the swivel angle are calculated. Conveniently, the path of the throttle piston is controlled by a proportional magnet, d. H. the positioning force of the magnet depends on the size of the electrical applied Tension. The relationship between tension and the compression spring - Travel made. This proportional magnet can be of any electrical Signals are controlled. This allows the pressure curve in the cylinder bore depending on different sizes, for example pressure, Swivel angle and speed can be influenced.

In the embodiment according to FIG. 8, the control piston 16 is a stepped piston executed, wherein the annular surface 36 of the stepped piston from the pressure of the high pressure side and the piston surface 37 of the piston with a smaller cross section of a liquid pressure is applied, which is the helix angle of the swash plate equivalent.

In the exemplary embodiment according to FIG. 9, the control piston 16 has three stages Piston formed, the annular surfaces 36 and 38 of the high pressure and one the pressure corresponding to the helix angle of the swash plate and the End face 39 of the piston section with the smallest cross section of a pressure is applied, which is proportional to the speed of the axial piston machine.

10 it is provided that the controlled Throttle 12 a pressure medium via line 40 from an external pressure medium source is fed.

Fig. 11 shows an embodiment in which both throttle openings in the Reversal area are controlled by controlled throttles, the oil supply the throttle opening 5 facing the high-pressure control opening 2 by a external pressure oil supply takes place.

In the exemplary embodiment according to FIG. 12, all of the holes are in the two Reversal areas provided with controlled throttles, the high-pressure side controlled throttles from an external pressure oil source with pressurized Medium are supplied. The supply of pressure oil from external pressure oil sources can be beneficial in certain cases. Firstly, through the external Pressure oil supply the pulsation in the high pressure control opening can be reduced and on the other hand, the higher pressure can supply the throttle system another desired pressure characteristic in the cylinder bores can be achieved.

13 and 14 show known control bodies in which the reversing areas with the adjacent low pressure and high pressure control openings connected by wedge-shaped narrowing slots or notches 50 are.

Known control bodies can also be seen from FIGS. 15 and 16, at which the low-pressure and high-pressure control openings with the throttle bores are connected directly by lines 51 in the reversal area.

Claims (9)

1. Hydrostatic axial-piston machine, with a drum-shaped cylinder block which is mounted fixedly in rotation on a drive or output shaft and is provided concentrically and parallel to its centre line with cylinder bores, in which are arranged axially displaceable pistons which are supported via spherical heads on a swashplate fixed with respect to the housing and preferably adjustable in its angle of inclination, the cylinder orifices (8) located opposite the swashplate sweeping over approximately kidney-shaped low-pressure and high-pressure control orifices (3, 2) of a control body (1), between which are located reversal regions with additional bores (4, 5, 6, 7), at least one reversal region of the control body (1) having issuing in it a bore (5; 7) which is connected by means of a line to the high-pressure side or the high-pressure control orifice (2), and the line having arranged in it a throttle (12) which is controlled by the high pressure and which opens in the line a throttle orifice corresponding to the high pressure, characterized in that the at least one reversal region has issuing in it a further bore (4; 6) which is connected by means of a line to the low-pressure control orifice (3), the line having arranged in it a throttle (12) which is likewise controlled by the high pressure and which opens in the line a throttle orifice corresponding to the high pressure, in that the cylinder orifices (8), when they pass over the reversal region of the control body (1), cover the two bores (4, 5; 6, 7), and in that the controlled throttles (12) assigned to the two bores consist in each case of a cylindrical bore (15) in the control body (1) or of a cylinder held together with the control body, in which cylindrical bore or in which cylinder is guided displaceably a control piston (16) which is loaded by a compression spring (17) and of which the side located opposite the compression spring (17; 30, 31) is acted upon by the high pressure, the cylindrical bore (15) or the cylinder having issuing into it, at an axial distance from one another, lines leading, on the one hand, to the respective bore (4, 5; 6, 7) of the reversal region and, on the other hand, to the high-pressure control orifice (2) or the low-pressure control orifice (3), and the control piston (16), according to its displacement, opening a throttle orifice having a differing size and corresponding to the high pressure with regard to the respective line leading to the reversal region.
2. Axial-piston machine according to Claim 1, characterized in that the bore (5; 7) connected to the high-pressure side or high-pressure control orifice issues in a region of the reversal region of the control body (1) which faces the high-pressure control orifice (2), and the further bore (4; 6) connected to the low-pressure control orifice (3) issues in a region of the reversal region of the control body (1) which faces the low-pressure control orifice (3).
3. Axial-piston machine according to either one of Claims 1 and 2, characterized in that that line of the reversal region which issues into the control cylinder (15) is connected by means of an axial groove of varying cross section of the control piston (16) to the line leading to the high-pressure control orifice or low-pressure control orifice.
4. Axial-piston machine according to one of Claims 1 to 3, characterized in that the connection of the control cylinder (15) to the line leading to the reversal region consists of a slot which the control piston (16) opens to a differing length according to its displacement on account of the high pressure exerting load on one side.
5. Axial-piston machine according to one of Claims 1 to 4, characterized in that the control piston (16) is acted upon on one side by at least two compression springs (30, 31) which frame one another and of which the spring or springs following the first spring come into use in succession according to the displacement of the control piston in the direction of the springs.
6. Axial-piston machine according to one of Claims 1 to 5, characterized in that the control piston (16) is designed as a step piston, the annular piston surface (36) of which and the disc-shaped piston surface (37) of which are acted upon, on the one hand, by the high pressure and, on the other hand, by a pressure corresponding to the set angle of inclination of the swashplate.
7. Axial-piston machine according to one of Claims 1 to 6, characterized in that the control piston (16) is designed as a three-step piston, of which the piston surfaces formed by the two annular surfaces (36, 38) and by the middle disc-shaped surface (39) are acted upon in each case by pressures which correspond to the high pressure in the high-pressure control orifice, to the angle of inclination of the swashplate and to the rotational speed.
8. Axial-piston machine according to one of Claims 1 to 7, characterized in that the bores (4, 5) issuing into the reversal regions are formed by the bores of a constant throttle.
9. Axial-piston machine according to one of Claims 1 to 8, characterized in that pressure oil from an external pressure-oil source is supplied to the controlled throttles (12).

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