EP2249033B1 - Equalization of the supply flow of oscillating pressure pumps - Google Patents

Description

The invention relates to a method for equalizing the flow rate in oscillating positive displacement pumps according to the preamble of claim 1.

The invention also relates to an apparatus for carrying out this method according to the preamble of claim 5.

When operating oscillating positive displacement pumps, it is desirable for fundamental considerations to achieve a largely constant flow rate. This is true even if only because otherwise adverse effects occur in the pressure or delivery line. These consist e.g. in that at each pressure stroke, a pressure pulsation arises in the delivery line, which can adversely affect the lines of the entire system and therefore by means of separate pulsation damper and the like. Must be suppressed or prevented.

Therefore, in order to achieve a substantially constant flow in oscillating displacement pumps, it is already known, for example, not to build pumps as a single pump, but at least as Provide triple pump with even eccentric offset. Due to the superimposition of the flow rates, the pulsation of the flow decreases as the number of cylinders increases. However, this is not sufficient in many cases, so that additional measures for pulsation damping are necessary. However, this requires a considerable design effort.

It is also known (cf. DE 198 49 785 C1 ), to the desired flow adjustment of the oscillating positive displacement pump to use their drive shaft itself, in such a way that a transition from the rotational movement of the drive shaft in a pivoting movement or vice versa, to provide various desired flow settings. Such a method has been well proven in practice. However, it is not yet possible to achieve a continuously constant or even flow of the total fluid to be pumped, since still during the - although short - suction stroke of the pump is no promotion, which interrupts the otherwise achieved constancy of the flow.

The DE 41 30 295 A1 discloses a pumping device with two parallel piston pumps, each having its own drive. The two piston pumps are operated via a common control device in such a way that the most constant possible delivery flow is achieved. The drive of each of the piston pumps via its own synchronous motor, which translates the rotational movement of the output shaft of the synchronous motor in a translation of a piston rod of the respective piston pump via a threaded spindle.

The DE 198 49 785 C1 discloses a method for adjusting the flow rate in oscillating displacement pumps whose drive is effected by means of a drive motor via a shaft and a crank gear. Up to three characteristics of the pump are controlled by means of the drive motor: the stroke frequency, the stroke length and the flow characteristic, Why the drive motor is variable both in its speed and in its direction of rotation.

The invention is therefore based on the object, the method of the generic type to eliminate the disadvantages described in such a way that it makes it possible to achieve a largely uniform or constant flow rate by means of simple constructive means with reasonable economic effort.

In addition, an apparatus for performing this method is to be created, which is easy to operate.

This object is achieved by the method according to the invention by the features of claim 1. Advantageous embodiments thereof are described in the further claims.

The features of the inventively created device will become apparent from claim 5. Advantageous embodiments thereof are set forth in the further claims.

The inventive method for equalizing the flow in oscillating displacement pumps is based on the essential idea that the generation of the fluid flow in a delivery line by means of at least two oscillating displacement, whose drive motors are controlled so that the total flow generated in the delivery line largely uniform or constant is.

According to the invention, it is further provided that the displacement pumps are operated in a composite with each other without mechanical coupling.

It is within the scope of the invention that the positive displacement pumps are operated so electronically synchronized that a nearly pulsation-free uniform flow (volume flow) is generated in the common delivery line.

According to the invention, the method according to the invention is operated in such a way that the speed of the drive motor of each displacement pump is changed in such a way that the superposed flow rates of the positive displacement pumps produce a substantially constant total flow rate.

In this case, the shaft of the drive motor of each positive displacement pump to achieve the constant characteristic of the total flow rate performs an adapted rotational movement.

The inventive device for carrying out the aforementioned method is provided with at least two oscillating displacement pumps, the pressure lines are connected to superimpose the individual flow rates to a common feed line and each having a drive motor without mechanical coupling in electronic synchronization to achieve a largely uniform or constant sum flow are operable.

Advantageously, the drive of each displacement pump is a highly dynamic drive. This may be a servo motor, preferably a permanent-magnet three-phase synchronous servo motor.

It is within the scope of the invention that the displacement pumps are diaphragm pumps.

With the invention, it is thus possible to prevent the pressure pulsation in the common delivery line without pulsation damper and at the same time a largely constant flow rate due to the deliberately carried out superimposition of the flow rates of two individual pumps to reach. This is done by exact electronic synchronization of the mechanically uncoupled positive displacement pump.

Finally, in order to check whether the desired constant characteristic of the delivery flow is achieved, various methods are already known (US Pat. DE 35 46 189 C2 ), which consist, for example, in that the pressure curve in the pump cylinder is measured by means of pressure sensors, whereupon the actually conveyed volume flow of the pump is then calculated from the detected measured values via the kinematic law of motion of the pump piston.

Fig. 1

schematisch die Anordnung von zwei mechanisch nicht gekoppelten oszillierenden Verdrängerpumpen zur Vergleichmäßigung des Gesamtförderstroms;

Fig. 2 a-d

verschiedene Diagramme von Pumpenmesswerten, aufgetragen über der Zeit t, zur Verdeutlichung der Erzielung einer konstanten Fluidgeschwindigkeit und damit eines gleichmäßigen Förderstroms, bei einem Fördergrad der Pumpen von insgesamt 100%, sowie

Fig. 3 a-c

verschiedene Diagramme von entsprechenden Pumpenmesswerten, aufgetragen über der Zeit t, bei einem reduzierten Pumpenfördergrad von ca. 90%.

The invention is explained in more detail below in the form of an embodiment with reference to the drawings. These show in:

Fig. 1

schematically the arrangement of two mechanically uncoupled oscillating displacement to equalize the total flow rate;

Fig. 2 ad

various diagrams of pump readings, plotted against time t, to illustrate the achievement of a constant fluid velocity and thus a uniform flow rate, with a pump delivery of 100%, as well as

Fig. 3 ac

various diagrams of corresponding pump readings, plotted over time t, with a reduced pumping rate of about 90%.

How out Fig. 1 The drawing shows, for performing the method according to the invention in the illustrated embodiment, two oscillating positive displacement pumps in the form of diaphragm pumps 1, 2 are provided, the pressure lines 3, 4 are connected to a common feed line 5.

The mechanically uncoupled diaphragm pumps 1, 2 each have a drive motor 6 and 7, which is designed as a highly dynamic drive. This is preferably a servo motor, in particular a permanent-magnet three-phase synchronous servo motor.

The drive motors 6, 7 of the two diaphragm pumps 1, 2 are operated by exact electronic synchronization such that a substantially uniform or constant sum flow in the common delivery line 5 can be achieved.

This procedure, which is operated by the method not covered by the invention, is illustrated by the individual diagrams in FIG Fig. 2a-d shown, in which the pump delivery is 100% each. In this case, for the sake of simplicity, only the pressure stroke of each diaphragm pump 1, 2 is shown, wherein the respective left half of the diagrams represent the respective measured value course during the pressure stroke of the diaphragm pump 1, while the corresponding right half of the diagram shows the measured value course in dashed form during the pressure stroke of the diaphragm pump 2.

Diagram 2a shows the course of the piston travel over the time t for both diaphragm pumps 1, 2. Since this is a linear course due to the special operation of the drive motors 6, 7 of the two diaphragm pumps 1, 2, the result is as follows Fig. 2b can be seen, a constant piston speed.

This is not least caused by the fact that the angular velocity of the eccentric shafts of the respective diaphragm pumps 1, 2, plotted over the time t, the course according to Fig. 2c in each case has a high initial and final speed with constant course between these two basic values.

Finally the diagram shows according to Fig. 2d clearly that yourself due to the illustrated mode of operation, a constant fluid velocity, plotted against the time t, results. This immediately results in a constant flow in the delivery line 5.

The diagrams according to Fig. 3a-c show different measurements of the diaphragm pump 1 (solid line) and the diaphragm pump 2 (dashed line), respectively apply over time t, the diaphragm pumps 1, 2 each have only a reduced flow rate of about 90%. Here the diagram shows according to Fig. 3a the fluid velocity applied over time t without compensation of the loss due to the "dead compression path hK" occurring at the beginning of the pressure stroke.

This loss of value is compensated according to the invention, so that then a representation of the fluid velocity over time t according to Fig. 3b results, in which the degree of delivery is compensated. For this purpose, the "dead compression path hK" occurring at the beginning of the compression stroke must be known or automatically determined. A corresponding method for this purpose is for example from the DE 35 46 189 C2 known.

As for this Fig. 3c can be seen, the pump piston is brought after completion of the suction stroke in the position hK before the actual delivery stroke begins. The piston travel then starts at hK, ie the fluid is displaced immediately in the pressure stroke.

• aus einer Ansaugphase, in der das Fluid in eine Pumpenkammer angesaugt wird,
• einer Kompressionsphase, in der das angesaugte Fluid auf Förderdruck gebracht wird,
• einer Förderphase, in der ein Teil des komprimierten Fluids aus der Pumpenkammer ausgestoßen wird, und
• schließlich einer Dekompressions- bzw. Expansionsphase, in der das in der Pumpenkammer verbliebene Fluid wieder auf Ansaugdruck gebracht wird. Hierbei benötigt jede oszillierende Verdrängerpumpe für die Kompression des Fluids vom Saugdruck auf den Förderdruck einen bestimmten geringen Kolbenweg, den sog. toten Kompressionsweg hK, der in der Kompressionszeit zurückgelegt wird.

To understand the concept of "dead compression path hK" is based on the known fact that each oscillating positive displacement pump has a delivery cycle. This one exists

• from a suction phase, in which the fluid is sucked into a pump chamber,
• a compression phase in which the sucked fluid is brought to delivery pressure,
• a delivery phase in which a portion of the compressed fluid is expelled from the pumping chamber, and
• finally, a decompression or expansion phase in which the fluid remaining in the pump chamber is returned to suction pressure. In this case, each oscillating positive displacement pump for the compression of the fluid from the suction pressure to the delivery pressure requires a certain small piston travel, the so-called dead compression travel hK, which is covered in the compression time.

With regard to features not explained in detail above, reference is expressly made expressly to the claims and the drawings.

Claims (7)

1. Method for equalisation of the supply flow of oscillating positive-displacement pumps, the driving of which takes place by means of a drive motor (6, 7) via a rotating eccentric shaft wherein the creation of the fluid supply flow in a supply line (5) is achieved by means of at least two oscillating positive-displacement pumps, wherein the positive-displacement pumps carry out a displacement cycle with a suction stroke and a pressure stroke wherein the pressure stroke comprises a compression phase in which a fluid drawn in by the suction pressure of a preceding suction stroke is compressed to the supply pressure, and a supply phase in which part of the compressed fluid is expelled, characterised in that the drive motors (6, 7) thereof are controlled such that the overall supply flow generated in the supply line (5) is largely even and/or constant in that the angular speed of the eccentric shafts of each of the drive motors (6, 7) is varied within the supply phase of the pressure stroke such that an essentially constant piston speed of the associated positive-displacement pump results, wherein compensation of the inactive compression movement (hK) covered in the compression phase takes place in that at the end of the pressure stroke of one positive-displacement pump, the other positive-displacement pump begins the supply phase.
2. Method according to claim 1, characterised in that the positive-displacement pumps are driven interconnected with one another without any mechanical coupling.
3. Method according to claim 1 or 2, characterised in that the positive-displacement pumps are operated electronically synchronised such that an almost pulse-free even supply flow (volume flow) is generated in the common supply line (5).
4. Method according to one of the preceding claims, characterised in that the inactive compression movement (hK) is automatically determined.
5. Device for carrying out a method according to one of the preceding claims having at least two oscillating displacement pumps which carry out a displacement cycle with a suction stroke and a pressure stroke wherein the pressure stroke comprises a compression phase in which a fluid drawn in by the suction pressure of a preceding suction stroke is compressed to the supply pressure, and a supply phase in which part of the compressed fluid is expelled, the pressure lines (3, 4) of said pumps being connected to a common supply line (5) for overlaying the individual supply flows and each pump having a drive motor (6, 7) with an eccentric shaft, characterised in that the drive motors (6, 7) can be operated without mechanical coupling in electronic synchronisation to achieve a largely even and/or constant overall supply flow in that the angular speed of the eccentric shafts of each of the drive motors (6, 7) is varied within the supply phase of a pressure stroke such that an essentially constant piston speed of the associated positive-displacement pump results, wherein compensation of the inactive compression movement (hK) covered in the compression phase takes place in that at the end of the pressure stroke of one positive-displacement pump, the other positive-displacement pump begins the supply phase.
6. Device according to claim 5, characterised in that the drive motor (6, 7) of each oscillating displacement pump (1, 2) is a highly dynamic drive, in particular a servomotor, preferably a permanent-field three-phase synchronous servomotor.
7. Device according to claim 5 or 6, characterised in that the oscillating displacement pumps are diaphragm pumps (1, 2).

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