DE102016125837A1 - Drive device for a fluid pump - Google Patents

Abstract

The invention relates to a drive device for a fluid pump with a conveyor, which is designed to promote a delivery volume in each revolution, and a method for operating a fluid pump.

Description

The invention relates to a drive device for a fluid pump with a conveyor, which is designed to promote a delivery volume in each revolution, and a method for operating a fluid pump. The drive device comprises a drive motor for driving the conveyor at a speed.

Methods are known in which the energy efficiency of variable speed pumps is improved. The speed of the drive can be specified as a manipulated variable. The control is done on the pump itself. Also, to determine the speed, external sensors, e.g. for determining the volume flow or the delivery pressure, used.

These sensors are relatively expensive to manufacture and maintain.

It is therefore an object of the invention to improve a drive device of the type mentioned, a system with a drive device and a fluid pump and a method for operating a fluid pump to the effect that energy is saved in a simple and cost-effective manner.

The solution of this object is achieved by the drive device, the system and the method of the independent claims.

The fluid pump may in particular be an axial piston pump or a radial piston pump. The fluid pump may preferably be designed as an adjustment or control pump, i. the delivery volume can be varied. Basically, however, the use of a constant displacement pump is conceivable.

According to the invention, the drive device comprises a frequency converter. While conventional pump arrangements are often operated by asynchronous motors operated directly on the grid, in the present case a frequency converter is connected upstream of the drive motor.

The term frequency converter is to be understood broadly and includes any type of variable-speed actuators.

The drive device comprises a control device which is designed to determine a desired rotational speed without external sensors, that is to say without a sensor, wherein the nominal rotational speed corresponds to a rotational speed optimized to the overall efficiency of the drive device and the fluid pump.

In contrast to conventional pump arrangements, according to the invention, the overall efficiency is considered, that is from the energy supply at the entrance to the hydraulic power, e.g. Pressure and flow rate provided at the outlet. The pressure can preferably always be maintained. In contrast to conventional pump arrangements, the pressure is thus not adapted in particular.

The term desired speed is to be understood broadly and includes, for example, a desired speed range. The setpoint speed, that is to say the speed at which the overall efficiency is high and energy is thus saved, can be determined without external sensors, such as sensors for determining the volumetric flow, the delivery pressure or the swivel angle. Costs can be saved here both during manufacture and during maintenance.

The control device then controls the pump, in particular with the specific setpoint speed. So it is effectively cut the possibility of the fluid pump in the control range to achieve high efficiency. The percentage energy savings is thus high, for example, in hydraulic presses or individual units.

Further developments of the invention can be found in the dependent claims, the description and the accompanying drawings.

According to one embodiment, the desired speed can be determined only on the basis of technical data of the drive motor, the frequency converter and / or the fluid pump. Alternatively or additionally, the desired speed is stored in a memory.

The desired speed is therefore calculated in particular exclusively on the basis of technical data or determined on the basis of a stored in a memory record. For example, measurements of the volume flow, the delivery pressure or the swivel angle are not provided for the calculation of the target speed, but in principle additionally conceivable.

According to a further embodiment, the technical data comprises the output power of the drive motor, the operating pressure of the fluid pump, the delivery volume of the fluid pump, the actual speed from the frequency converter and / or the torque from the frequency converter being regulated.

In order to obtain the best overall efficiency in the respective part-load range, the optimum target speed can be calculated in each case by creating a control algorithm in the control device.

In particular, in this case, the pivot angle is almost full even in the partial load range, i. at least 80%, preferably at least 90%, more preferably at least 95%, swung out. This can be kept in the best possible operating point.

In addition to the technical data of the fluid pump, in particular the operating pressure, for example, the actual speed values provided by the frequency converter can be used to calculate the setpoint speed.

The target speed is in particular proportional to the output power of the drive motor, preferably the power at the shaft, and the overall efficiency. Furthermore, the target speed is inversely proportional to the operating pressure and the delivery volume of the fluid pump per revolution.

This results in particular the following calculation approach: $$\begin{array}{l}\text{Target speed ~ power at the shaft * 600}\text{.000 * Overall efficiency /}\\ \text{operating pressure * delivery volume of the fluid pump per revolution)}\text{,}\end{array}$$

The speed can be automatically adjusted by the control device for each part load range. Thus, the speed can e.g. can be reduced in order to optimally deflect a Torkelscheibe or a slip ring of a fluid pump and to improve the overall efficiency.

This leads to a significant increase in efficiency and thus to a significant increase in the energy efficiency of the entire system of a hydraulic supply.

According to a further embodiment, the drive motor is designed as a reluctance motor or as a synchronous servo motor. Basically, e.g. Also be provided a DC, three-phase or asynchronous motor.

By using a reluctance or synchronous servomotor in conjunction with a frequency converter instead of an asynchronous motor operating directly on the grid, it is possible to increase the overall efficiency at the rated operating point of up to approximately 6%, depending on the optimization of the frequency converter. In addition, in such an arrangement of reluctance or synchronous servomotor, frequency converter and axial or radial piston pump, the starting current and the reactive power required by the network are substantially reduced. For a system of reluctance or synchronous servomotor, frequency converter and axial or radial piston pump is also independently claimed protection.

According to a further embodiment, the frequency converter has the control device. While conventional fluid pumps regulate themselves, the control device is not disposed in the fluid pump. Even existing fluid pumps can be retrofitted in a simple manner, since only one frequency converter must be connected in series with a corresponding control device. Alternatively, the control device may also be designed as a separate component.

According to a further embodiment, the control device is designed to determine a setpoint speed for each part-load range. The speed can thus be adjusted automatically for each part load range, whereby the best overall efficiency is achieved for the respective part load range.

According to a further embodiment, the control device comprises a memory or has access to a memory in which a data record is stored. Preferably, the data set can be stored, for example, in the form of a table, a polygonal draft or a characteristic field. The data set includes target speeds as a function of torque from the frequency converter being regulated.

To create the data set, e.g. the start and the end are measured or determined empirically. For example, the system can be operated with a minimum speed and an excessive speed. Interpolated between the measured or empirically determined data.

The control device selects from the data set the torque from the frequency converter to which is regulated, and determined in the record the corresponding target speed at which the fluid pump is to be operated.

The invention also relates to a system with a drive device according to the invention and a fluid pump. On the one hand existing fluid pumps can be retrofitted with a drive device and on the other hand new complete systems can be produced.

According to one embodiment, the fluid pump is designed as an axial piston pump or radial piston pump.

Furthermore, the invention relates to a method for operating a fluid pump with a drive device according to the invention, in which without external sensors, so sensorless, a target speed is determined, the target speed corresponds to an optimized on the overall efficiency of the drive device and the fluid pump speed.

In particular, the fluid pump is then operated at the corresponding desired speed. Thus, in the partial load range of the fluid pump by determining the load profile, the speed can be reduced so far that the pivot angle of the fluid pump is operated at the maximum amount conveyed in the optimum tilt angle. This can be achieved, for example, by a fixed set speed, e.g. 950 revolutions per minute. Already at this point, the overall efficiency can be increased by around 9% at this operating point.

In addition to this manual reduction of the speed, the speed can also be adjusted automatically. Thus, the speed can be adjusted accordingly to automatically obtain the best overall efficiency in each partial load range. In this case, a control algorithm can be used. This increases the overall efficiency by around 10%.

All embodiments of the device and of the system described here are in particular designed to be operated according to the method described here. Furthermore, all embodiments of the device or of the system described here, as well as all embodiments of the method described here, can each be combined with one another, in particular also detached from the specific embodiment in connection with which they are mentioned.

• 1 eine schematische Darstellung einer Ausführungsform eines erfindungsgemäßen Systems,
• 2 den Wirkungsgradverlauf in Abhängigkeit vom Volumenstrom bei einem erfindungsgemäßen System,
• 3 den Wirkungsgradverlauf in Abhängigkeit vom Volumenstrom bei einem erfindungsgemäßen System bei optimierter, manueller Drehzahlanpassung, und
• 4 den Wirkungsgradverlauf in Abhängigkeit vom Volumenstrom bei einem erfindungsgemäßen System bei optimierter, automatisierter Drehzahlanpassung.

The invention will now be described by way of example with reference to the drawings. Show it:

• 1 a schematic representation of an embodiment of a system according to the invention,
• 2 the efficiency curve as a function of the volume flow in a system according to the invention,
• 3 the efficiency curve as a function of the volume flow in a system according to the invention with optimized, manual speed adjustment, and
• 4 the efficiency curve as a function of the volume flow in a system according to the invention with optimized, automated speed adjustment.

First, it should be noted that the illustrated embodiments are merely exemplary in nature. The features of one embodiment may also be arbitrarily combined with features of another embodiment.

1 shows a fluid pump 10 , For example, an axial piston or radial piston pump, and a drive motor 12 , For example, a reluctance or synchronous servomotor, which the fluid pump 10 drives at a certain speed.

The speed at which the fluid pump 10 is controlled, is basically arbitrary. This can for example be in the range of 300 to 3,000 revolutions per minute, in particular 500 to 1,500 revolutions per minute.

About a frequency converter 14 which is a control device 16 includes, a desired speed can be determined. The drive motor 12 can be operated at the desired speed to achieve overall efficiency η to increase the arrangement.

In 2 is the overall efficiency η depending on the volume flow V shown in liters per minute. The curve A shows the course of a conventional arrangement with an asynchronous motor, which is operated directly from the grid, ie without frequency converter 14 ,

The highest efficiency η This occurs only at relatively high volume flows of about 95% of their nominal volume. fluid pumps 10 However, they are usually operated with volume flows between about 20 and 80% of their nominal volume.

By using an arrangement with an axial piston or radial piston pump 10 , a reluctance or synchronous servo motor 12 and a frequency converter 14 can depending on the optimization of the frequency converter 14 a significant increase in overall efficiency η can be achieved, as can be seen by the curve S. Also in the normal operating range with volume flows between about 20 and 80% of their nominal volume is a significant increase in the overall efficiency η seen.

The overall efficiency η can increase by up to 6% compared to a conventional arrangement.

In 3 is the overall efficiency η depending on the volume flow V shown in liters per minute. As a reference again are the curves A and S shown.

In the partial load range of the fluid pump 10 can be reduced by determining the load profile, the speed so far that the pivot angle of the fluid pump 10 operated at the maximum amount conveyed in the optimum swing angle. This can be achieved for example by a set target speed, for example, 950 revolutions per minute. Already this allows the overall efficiency at this operating point η increase by about 9%.

The curves shown represent the course for different setpoint speeds. This is how the curve represents S500 a target speed of 500 revolutions per minute. The total effect wheel η is significantly increased, especially at low flow rates. S600 corresponds to a target speed of 600 revolutions per minute, S700 a target speed of 700 revolutions per minute, S800 a target speed of 800 revolutions per minute, S900 a target speed of 900 revolutions per minute and S1000 a target speed of 1,000 revolutions per minute.

The higher the setpoint speed, the further to the right, ie in the direction of higher volume flows V , shifts the maximum overall efficiency η ,

In 4 is the overall efficiency η depending on the volume flow V shown in liters per minute. As a reference again are the curves A and S shown.

The curve R corresponds to the course of the overall efficiency η wherein the desired speed is automatically determined using a control algorithm in the control device 16 is determined.

In addition to the technical data of the fluid pump, in particular the operating pressure, for example, the actual speed values provided by the frequency converter can be used to calculate the setpoint speed. By contrast, data from external sensors are not used to determine the respective setpoint speed.

The target speed is in particular proportional to the output power of the drive motor 12 and the overall efficiency η , Furthermore, the target speed is inversely proportional to the operating pressure and the delivery volume of the fluid pump 10 per revolution.

kann die Steuerungsvorrichtung 16 für jeden Teillastbereich die optimale Soll-Drehzahl bestimmen und für den entsprechenden Volumenstrom V automatisch anpassen.According to the calculation approach $$\begin{array}{l}\text{Target speed ~ power at the shaft * 600}\text{.000 * Overall efficiency /}\\ \text{operating pressure * delivery volume of the fluid pump per revolution)}\end{array}$$

can the control device 16 determine the optimum setpoint speed for each partial load range and for the corresponding volume flow V automatically adjust.

This leads to a considerable improvement in the overall efficiency throughout the partial load range η , Thus, increases of about 10% can be achieved.

LIST OF REFERENCE NUMBERS

10

Fluid pump, axial piston pump, radial piston pump

12

Drive motor, reluctance motor, synchronous servo motor

14

frequency converter

16

control device

η

Overall efficiency

V

flow

A

Course with asynchronous motor without frequency converter

S

Course with synchronous servo motor with frequency converter

S500

Course at nominal speed of 500 revolutions per minute

S600

Course at target speed of 600 revolutions per minute

S700

Course at target speed of 700 revolutions per minute

S800

Course at nominal speed of 800 revolutions per minute

S900

Course at nominal speed of 900 revolutions per minute

S1000

Course at target speed of 1000 revolutions per minute

R

Course with automatic adjustment of the setpoint speed

Claims (10)

Driving device for a fluid pump (10), in particular axial piston pump or radial piston pump, with a conveyor, which is designed to convey a delivery volume at each revolution, comprising a drive motor (12) for driving the conveyor at a speed, a frequency converter (14), and a control device (16) which is designed to determine a setpoint speed without external sensors, wherein the setpoint speed corresponds to a speed optimized for the overall efficiency of the drive device and of the fluid pump (10). Drive device after Claim 1 , characterized in that the target rotational speed is determinable only on the basis of technical data of the drive motor (12), the frequency converter (14) and / or the fluid pump (10) and / or stored in a memory. Drive device after Claim 2 , characterized in that the technical data, the output power of the drive motor (12), the operating pressure of the fluid pump (10), the delivery volume of the fluid pump (10), the actual speed of the frequency converter (14) and / or the torque from the frequency converter (14), which is regulated. Drive device according to one of the preceding claims, characterized in that the drive motor (12) is designed as a reluctance motor or as a synchronous servo motor. Drive device according to one of the preceding claims, characterized in that the frequency converter (14) has the control device (16). Drive device according to one of the preceding claims, characterized in that the control device (16) is adapted to determine a target speed for each partial load range. Drive device according to one of the preceding claims, characterized in that the control device (16) comprises a memory or access to a memory in which a data set, in particular traverse, is deposited, which target rotational speeds in dependence on torques from the frequency converter (14 ), which is regulated. System with a drive device according to one of the preceding claims and a fluid pump (10) with a conveyor, which is designed to convey a delivery volume with each rotation. System after Claim 8 , characterized in that the fluid pump (10) is designed as an axial piston pump or radial piston pump. Method for operating a fluid pump (10) with a drive device according to one of the Claims 1 to 7 in which a setpoint speed is determined without external sensors, the setpoint speed corresponding to a speed optimized for the overall efficiency of the drive device and the fluid pump (10).

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