DE1403747A1 - Pump with variable delivery rate and constant pressure - Google Patents

Description

Pump with variable flow rate and constant pressure

The invention relates to an adjusting piston which is used to regulate the stroke volume and the delivery rate of a pump, its setting by a control slide arranged in the inflow of the pressure medium to the pressure side of the actuating piston takes place, a corner connection being provided between the pressure side of the actuating piston and the low pressure is.

jJie!, rfindung is based on a known pump in which • The pump delivery rate is controlled by an actuating piston and a control slide is provided to control it npalt serves as a connection between the setting piston and the pressure side of the pump. The control slide moves depending on the pump delivery pressure, so that the control gap is opened more or less, which is an ent

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'-rt.' S ■ "*"> · 2 ^No. -1 Sau 3 of the amendment ··. v. 4. '->

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speaking displacement of the actuating piston has the consequence, so that Mur keeping the pump delivery pressure constant The delivery rate of the pump is increased or decreased accordingly.

In these known pumps, however, vibrations occur during control, which lead to an unstable mode of operation to lead. This is due to the fact that a shift of the control slide depending on the position of the Control spool often does not have the intended effect, i.e. the control spool has a dead gear, that on the actuating piston frictional resistances act, and that between the movement of the actuating piston and that of the control slide a certain delay occurs due to the compressibility of the pressure medium.

The invention is therefore based on the object of the vibrations that lead to fluctuations in the pump delivery pressure and / or delays in response to avoid.

A pressure control valve is already known (German Patent Specification 886 99o) that in the lead to a

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Burner nozzle is installed between this and the feed pump. The connection between the pump pressure side and the burner producing valve needle is controlled by a plunger, which is also used to Control of the overflow line is used. The reflux in the overflow line is controlled in such a way that the feed pressure of the burner is kept at the correct value will. TJm to avoid fluctuations in the feed pressure when the valve is around an equilibrium position oscillates, grooves are changeable in the plunger between the supply line and the overflow line Cross-section provided, which represent a corner connection, so that by the constant overflow of pressure medium into the overflow line through the corner connection Fluctuations in the feed pressure are suppressed. However, through the known pressure control valve not regulated the pump. In this respect, the invention is of a different nature, there there the vibrations when controlling a pump are to be avoided and therefore the pressure medium of the pump outlet side flows through the control gap of the control slide to the setting piston.

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The object described above is according to the invention in a pump actuating piston of the type described at the beginning solved by the fact that the control slide is caused by the amount of pressure flowing out through the leakage connection is set in such a way that the outflowing quantity always passes through the control gap of the control slide Pressure medium flowing into the pressure side of the actuating piston is replaced.

/ This means that so much pressure medium flows through the leakage connection on the corset pressure side, see that a control gap is set on the control slide through which always as much pressure medium reaches the actuating piston as flows out through the leakage connection. Through the leakage connection on the one hand and the control gap on the other hand, the control slide is thus an equilibrium position of the control spool causes the control spool to be easier and better at pressure changes in the control pressure responds, so that vibrations and oversized travel ranges that give rise to vibrations are avoided. Not only does the pressure medium flowing out through the leakage connection flow through the control gap, but also that required to adjust the control piston of the pumps to change the delivery rate

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Pressure medium control quantity.

In an expedient embodiment of the invention, the Le clever "binding through one in the control slide or in the Control slide housing provided bore, bevel, annular groove, bypass channel or the like. Be formed.

On the other hand, in an expedient embodiment of the invention, the leakage connection can also be made by one of the two Throttle opening connecting sides of the actuating piston may be formed.

The invention is explained in more detail below using an axial piston pump. The drawings show:

3? Ig. 1 an axial piston pump in section,

. 2 shows the enlarged control slide according to Pig. I,

3? Ig. 5 another embodiment of the actuating piston,

4 another embodiment of the control slide with a bevel,

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5 shows a further embodiment of the control slide with an annular groove,

6 shows a further embodiment of the control slide with a bypass channel, and

7 shows a section along the line 7-7 of FIG. 6,

The drawings show a pressure balanced axial piston pump that works as known, but one ! Corner connection between the pressure chamber of an actuating piston for the swashplate and the low pressure chamber of the pump has, which vibrations in the pump as a result of the idle path present in a control slide, the Friction between the actuating piston and the swash plate and the compressibility of the fluid reduced.

The housing 2o is provided with an inlet opening 22 and an outlet opening 24. In the housing 2o is a Shaft 26 rotatably arranged on which an annular cylinder block 28 is attached. In this cylinder block are seven equally spaced cylinders 3o. intended. Each cylinder 3o is provided with a channel 32

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see the one formed in the housing 2o kidney-shaped Opening 34 can be connected to the inlet opening 22. The channel 32 is also kidney-shaped Opening 36 can be connected to the outlet opening 24.

On a ball joint firmly connected to the shaft -26 is a swash plate 4o pivotable, but mounted cteh-proof. The swash plate 4o runs with the ball joint 38 and the shaft 26 together, but is able to about the center point of the joint ball transversely to the shaft 26. tumble. On one side of the disk 4o, seven sliding disks 41 provided with ball sockets 42 are arranged, in which balls 44 are mounted in order to provide an all-round rotary movement. Each ball 44 is on a piston 46 attached, the pistons reciprocate in a respective cylinder 3o.

In the housing 2o there is formed a cylinder 5o which extends in the longitudinal direction and in which an actuating piston 52 is located reciprocated, the projection 54 of which acts on the swash plate 4o, about its angle about an axis transverse to the To adjust the shaft 26 and thus the stroke of the piston 46 in the cylinders 3o. In the housing 2o is diametrically opposite from the cylinder 5o a cylinder 56 arranged in which

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a. Counterforce piston 58 is arranged to be movable to and fro, the piston 58 acting on a head 53 which is pressed by a peder 6o against the swash plate 4o in order to press it against the projection 54. For guiding of fluid pressure to move the actuating piston 52 against the swash plate 4o, in a space formed in the housing 2o axial Z3 ^r linder 64 is a sleeve 62 inserted and arranged in the sleeve to execute a reciprocating motion of a spool 66th The ; Pig. 2 shows an enlarged schematic representation of the control slide 66 without the sleeve 62. The control slide 66 is moved in one direction by a compression spring 68 and in the other direction by the pump pressure applied to the end 70 and a shoulder 72. An axial channel 74 and a transverse slot 76 which intersects the channel 74 are formed in the control slide 66. When the spool 66 moves to the right under the pressure of the spring 68, the slot 76 communicates with an annular channel 78 in the sleeve 62, which in turn communicates with the actuating piston 52 via a channel 80. In the When the position of the control slide 66 is shifted to the right, the fluid located in the line 8o flows through the channel 74

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the slot 76 to a discharge opening 82 of the sleeve, with the result that the one directed against the adjusting cage 52 Pressure decreases and the angle of the swash plate 4o increased, which increases the pump performance. When the control piston 66 is moved to the left until the Shoulder 72 has been moved past the edge of the annular tube 78, the fluid is removed from the pump outlet pumped into the line 8o, whereby the pressure acting on the actuating piston 52 increases and the angle of the swash plate 4o is decreased. This pump is therefore a constant pressure pump because when the pressure drops in the Outlet port 24> what by opening a valve 88 in an outlet line 9o would cause the control slide 66 to be moved to the right by the spring 68, so that the fluid flows through the line 8o to the reservoir of the pump and thereby the pressure against the piston 52 is reduced, the angle of the swash plate 4o is increased and the delivery rate of the pump is increased. When the amount of fluid pumped has been increased sufficiently, the delivery pressure of the pump will be restored rise and the spool 66 moves to the left against the force of the spring 68 until the shoulder 72 moves from of the annular groove 78 and the pumped fluid is pumped into the line 8o, around the

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To reduce the angle of the swash plate 4o. There is also a channel 97 is provided which connects the outlet opening with the Cylinder 56 connects so that the delivery pressure during the pressure movement of the counterforce piston 58 against the swash plate 4o participates in a supportive manner.

The previously described axial piston pump with constant fluid pressure is known. The pumps of this type were previously subject to vibrations that were due to various causes and led to instability the pump. Most often, instability is caused by the Shoulder 72 has a tendency to move a certain amount from the annular opening 78 to the right when If the control slide 66 is in the neutral position, when the pressure in the outlet opening 24 increases Idling occurs in the control slide movement, which is due to the fact that the control slide 66 is must first move to the left by the aforementioned amount before * between the line 8o and the outlet opening a Connection is established. As a result of this idling, the delivery pressure tends to increase to a greater level build up as needed or desired, and

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therefore "the actuating piston 52 moves too far to the right, so that a correction is required in order to move the actuating piston 52 back into the position in which the required Delivery pressure is reached. The control slide 66 then closes or moves to the right until the Line 8o communicates with the G-housing container or the drainage opening 82 via the annular groove 78. this causes unnecessary oscillation of the spool 66 and fluctuations in the pump delivery pressure.

This instability is compensated by the arrangement of a small Leäcleitung 94 (Pig. 1 and 2) in the control slide 66 between the line 80 and the outlet 82 of the housing container. Since a certain amount of fluid flows constantly through the leakage line 94 to the housing outlet 82, the pressure in the line 8o is somewhat lower than it should normally be, so that the delivery rate of the pump is slightly increased. This leads to an increase in the pressure acting on the end of the control slide 66 until a gap is formed between the shoulder 72 and the annular hat 78, which allows a sufficient amount of the pumped fluid to flow off into the line 8o to compensate for this opening 94 to create lost fluid. In this way, an increase always results of ^x 'to a örderdruckes

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essentially instantaneous increase in pressure in of the line 80 and a corresponding movement of the piston 52. Excessive pressure increases are reduced because the idle or the overlap comes in port case.

Another cause of instability or vibration the pump is due to the fact that the Movement of the swash plate by the pistons 52 and 58 and their movement in the journal bearings a certain amount Frictional resistance is opposed. This slows down • the movement of the actuating piston 52, and it is therefore necessary to that the spool 66 is revealed, too after the required pressure has been reached is. The delivery pressure changes while the valve is open, causing excessive pressure increases and vibrations leads. By providing a sufficient leakage passage between the control pressure line 80 and the Fluid reservoir of the pump, the pump becomes less sensitive to small pressure fluctuations, since a slight increase in the pressure in the line 80 only leads to a greater part of the fluid flowing through the leakage connection 94 without that a control movement of the actuating piston 52 takes place. Therefore, if the leakage passage is large enough that the

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Pump against errors caused by the frictional force arise between the actuating piston 52 and the swash plate, becomes insensitive, no vibrations arise.

Another error arises in the known pumps due to the compressibility of the fluid. Since that Fluid in the control line 80 is compressible, exists between an increase in the delivery pressure and the movement of the actuating piston 52 a certain delay. 'During this time the delivery pressure builds up to a value which is larger than the desired one, resulting in a movement of the actuating piston 52 in the opposite direction leads so that the pressure is lowered and thereby ^ undesirable Vibrations are caused. This can also be avoided by using the leakage connection 94, since any increase in pressure due to compressibility of the fluid only causes a larger amount of fluid to flow through the corner connection 94.

The passage of the corner connection 94 is therefore so large that slight deviations in the pressure in the control line: Go from the precisely erroneous Puaipenfor derdruck not a movement of the valve piston 52, but an increased or reduced flow through the connection

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caused. While this is to a very small extent the pressure tolerance of the desired delivery pressure, it eliminates unwanted vibrations.

FIGS. 3 and 7 show further possibilities for the formation of the leakage passage. The Pig. 3 shows an enlarged view of the actuating piston 52, in the front end of which a small opening has been formed in order to establish a connection between the pressure chamber of the actuating piston 52 and a spring pressure chamber, for example the container outlet 82. Figure 4 shows a shoulder Io2 of the web of the control slide 66 between the channels So and 76, which is beveled so that there is a slight leakage path between the channel 8o and the container drain 82. Figure 5 is a view similar to Figure 4, except that the bevel Io2 is through an annular hat Io4 on the web of the spool valve 66 has been replaced in order to provide the leakage path between the actuating piston 52 and the container outlet 82. Figures 6 and 7 show a leakage path between the delivery pressure channel 24 and the container outlet 82, which goes through one on each Side of the mouth of the line Bo provided throttle passage is formed, which heru the passage of the fluid around the control slide 66 Allow m when he is in the neutral position.

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The cross-section of the required leakage passage changes directly with the given pumping conditions Desired control pressure in line 80, the desired pump output, the fluid passage of the control slide, namely the flow into the control line 80 for each time required to open the control slide Pressure change and the volume of pressurized fluid in the control pressure circuit, and changes inversely to the leakage coefficient of the pump, the total module of the fluid and the area of the actuating piston 52.

Although the invention has been described and illustrated with reference to particular areas of use, the basic ideas find application in many other areas.

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Claims (2)

Claims For regulating the stroke volume and the delivery rate of a Actuating piston serving for the pump, the setting of which is carried out by an in-flow of the pressure medium to the pressure side of the Control slide arranged on the control piston takes place, with a corner connection between the pressure side of the control piston and low pressure is provided, characterized in that through the Pressure medium quantity of the control slide (66) is set so that the outflowing quantity is always through the control gap (72,78) of the control slide » pressure medium flowing in on the pressure side of the control piston (52) is replaced. 2. Device according to claim 1, characterized dadurah, that the corner connection is made by an in the control slide (66) or the bore (94), bevel (lo2), annular groove (lo4), bypass channel (lo6, Io8) or the like. Is formed. - 2 - 903810/0002 original; ^ ~ 07 ~ d Ulilüi lUfcjbi ι (Mi .; § l Au «, j. No. 1 sau 3 du Amendmentao ··. V. 4,9. | 9 (> / 3, device according to claim 1, characterized in that the leakage connection through one of the "two sides throttle opening (loo) is formed.