Diaphragm pump, assembly and method for conveying a fluid, and associated control unit

Abstract

It is proposed that, in an assembly (1) and a method for conveying a fluid (2), a positive displacement pump (3), in particular a diaphragm pump (16), having an adjustable stroke amplitude (h) is used, and that the stroke amplitude (h) of the positive displacement pump (3) can be controlled by a control unit (6). A stroke frequency (f) of the positive displacement pump (3) can be controllable in such a way that it lies outside a hydraulic resonant frequency of the assembly (1). The stroke amplitude (h) of the positive displacement pump (3) can be controlled as a function of a measured flow parameter (cf. figure 1).

Description

[0001] Diaphragm pump and arrangement and method for conveying a fluid and associated control unit

[0002] The invention relates to a diaphragm pump comprising a lifting element with adjustable stroke amplitude. Such

[0003] Diaphragm pumps are well known in practice.

[0004] The invention further relates to an arrangement for conveying a fluid. The arrangement comprises a positive displacement pump. The arrangement further comprises a hydraulic storage element and a line. The invention further relates to a method for conveying a fluid by means of such an arrangement. Such arrangements and methods are known in practice.

[0005] The positive displacement pump is preferably a diaphragm pump. The positive displacement pump is preferably designed to pump a liquid, such as water.

[0006] The invention further relates to a method for determining a hydraulic resonance frequency of an arrangement for conveying a fluid.

[0007] The invention further relates to a control unit with which an arrangement for conveying a fluid can be controlled.

[0008] Periodic suction and pressure phases in positive displacement pumps lead to pressure and volume flow pulsations. These can be reduced by the hydraulic storage element. The applicant has discovered that the pulsations are frequency-dependent. It has discovered that in many applications the storage element and the line lead to a hydraulic resonance frequency occurring at which the pressure and volume flow pulsations reach a maximum. In practice, positive displacement pumps are usually controlled by rotary motors and eccentric drives with a fixed stroke. To adjust the delivery rate, it is usual to adjust the speed and thus the pump frequency. This means that when the frequency is changed, the resonance frequency is passed through, so that high pulsations occur.

[0009] The invention is based on the object of improving the conveyance of fluids. In particular, it is intended to enable consistent fluid conveyance and reduce energy consumption. This is preferably achieved by reducing pressure and volume flow pulsations.

[0010] To achieve this object, the invention proposes the features of claim 1. In particular, the invention proposes that a diaphragm pump of the type described above has a backlash-free linear drive designed as a direct drive for driving the lifting element.

[0011] A backlash-free drive can be characterized by the fact that the lifting element moves without any play. In particular, in a direct drive, the lifting element is firmly attached to a diaphragm of the diaphragm pump.

[0012] The lack of backlash is particularly advantageous for small stroke amplitudes and high frequencies. Any backlash in the drive limits the minimum stroke at which the pump can be operated. This is not critical for the current applications of diaphragm pumps. However, the inventors have recognized that a backlash-free, direct linear drive can significantly expand the application possibilities of pulsation-damped pumps, as the pump can then be operated at high frequencies and small stroke amplitudes. This also permits operation in which the delivery rate can be varied over a very wide range while still being precise. In particular, resonance frequencies can be avoided.

[0013] A linear drive only permits translational movements, not rotational ones. Thus, the stroke amplitude of the lifting element can be controlled with particular precision and variability.

[0014] A direct drive offers the advantage of eliminating the need for a gear mechanism, and thus eliminating backlash in the lifting movement of the lifting element. This allows the lifting element to be controlled quickly and precisely. Furthermore, using a direct drive can ensure a long service life for the diaphragm pump, as there is no wear on the gear components.

[0015] Furthermore, the diaphragm pump has a hydraulic storage element and a control unit with which the stroke amplitude of the stroke element can be controlled.

[0016] The hydraulic storage element can have two chambers that are separated from one another by a separating layer - for example an elastomer plate or a diaphragm. One chamber can be in contact with a fluid to be pumped. The other chamber can be under atmospheric air pressure or a different pressure. Furthermore, the other chamber can have a spring element that supports the separating layer. By means of such a hydraulic storage element, any pressure and volume flow pulsations generated by the diaphragm pump can be balanced out, so that more uniform flow conditions prevail in the line. The storage element can therefore also be referred to as a pulsation damper. The diaphragm pump preferably has a line that is connected to the diaphragm pump. The hydraulic storage element is particularly preferably arranged in the line.

[0017] The controllability of the stroke amplitude makes it possible to set the desired flow rate and / or pressure by changing the stroke amplitude. This means that the diaphragm pump can be operated continuously at a high stroke frequency, preferably at a stroke frequency of more than 20 Hz, 30 Hz, 50 Hz, 100 Hz, 200 Hz or even more than 500 Hz or in an interval between the frequencies mentioned and at least 500 Hz, for example in an interval of at least between 50 Hz and 500 Hz. This enables a compact and space-saving design of the diaphragm pump. In addition, operation at high stroke frequencies can minimize pressure and / or volume flow pulsations.

[0018] A sensor, for example a pressure sensor and / or a volume flow sensor, can be connected to the control unit so that the stroke amplitude can be controlled depending on a measured value.

[0019] In the control unit, a flow parameter—for example, a pressure or a volume flow—can be set, with the stroke amplitude being adjustable as a function of the flow parameter. In particular, the diaphragm pump has an interface connected to the control unit, via which the flow parameter or a parameter convertible into the flow parameter can be read in as an input value. The flow parameter can also be entered via a user interface.

[0020] In an advantageous embodiment, the linear drive can be designed as an electromagnetic drive. This allows the linear drive to be precisely controlled.

[0021] The linear drive is preferably designed as an electrodynamic drive. The structure of an electrodynamic drive consists of a rigid coil armature and a mobile rotor which has permanent magnets, or in the reverse arrangement of a rigid permanent magnet armature and a mobile rotor which has coils. If an electric current flows through the coils and is perpendicular to the magnetic field, then a force perpendicular to the electric current and to the magnetic field is generated (Lorentz force). This force causes either the coil to move in the case of a fixed permanent magnet armature or the permanent magnet armature in the case of a fixed coil. If the current direction is reversed, the direction of the force is also reversed. The electrodynamic drive is preferably pole piece-free on the coil side. The aforementioned coils are preferably passed through by magnetic fields of alternating directions with alternating winding directions.The Lorentz force can then act directly between the magnetic fields of the permanent magnets and the coils.

[0022] Since the force buildup of an electrodynamic drive is proportional and very direct, i.e., without any time lag, to the applied current, such a drive can control the diaphragm pump very precisely and with high responsiveness. Furthermore, an electrodynamic drive can enable the diaphragm pump to operate at high stroke frequencies.

[0023] In a further advantageous embodiment, it can be provided that the hydraulic storage element is arranged on a suction side or on a pressure side of a pump chamber of the diaphragm pump. In a further advantageous embodiment, it can be provided that the diaphragm pump has a pump housing which encloses the hydraulic storage element and the lifting element. The pump housing can also enclose other or all components of the diaphragm pump, such as the drive, the diaphragm, valves, valve chambers and / or a pump chamber. The pump housing can in particular completely enclose the diaphragm pump. A common pump housing can lead to a particularly compact design and thus avoids line-related functional impairments of the hydraulic storage element.

[0024] In a further advantageous embodiment, a channel can be formed between a chamber of the hydraulic storage element and a valve chamber of the diaphragm pump. The channel preferably opens directly and / or freely into the chamber. Such a configuration can be provided for one, several, or all hydraulic storage elements. This can, optionally in combination with a common pump housing, lead to a particularly compact design with minimal line-related influences, since the channels can be made very short.

[0025] Alternatively, the hydraulic storage element of the diaphragm pump can also be arranged outside a pump housing and connected to the pump chambers via a line section.

[0026] In a further advantageous embodiment, it can be provided that the hydraulic storage element is arranged on the suction side, and that the diaphragm pump has a further hydraulic storage element arranged on the pressure side. This allows pressure and volume flow pulsations to be compensated on both the suction side and the pressure side of the diaphragm pump. The further hydraulic storage element can be designed like the first hydraulic storage element.

[0027] In a further advantageous embodiment, it can be provided that the diaphragm pump has two pump chambers each delimited by a diaphragm, wherein the two diaphragms are connected to one another via the lifting element.

[0028] This design eliminates the need for additional bearing elements for the lifting element, as the lifting element is adequately supported by the two membranes.

[0029] The described double-headed design of the diaphragm pump can be more robust against drifts in a linear drive and can keep the rotor's center position stable. Thus, a shift in the rotor's center position during a half-stroke can be compensated for by the subsequent half-stroke. This reduces the requirement for active control of the rotor's position. Correction of the rotor's center position is also unnecessary. A position sensor for determining the rotor's position is also unnecessary.

[0030] The fact that the two diaphragms are connected to one another via the lifting element also ensures that the two pump chambers can be operated alternately. A lifting movement of the lifting element means that fluid can be sucked into one of the pump chambers while fluid is expelled from the other pump chamber. This means that the two pump chambers can be operated without interfering with each other. This design means that the pump chambers are always in different phases: while the first pump chamber is in the suction phase, i.e. the intake process, the second pump chamber is in the pressure phase, i.e. the discharge process, and vice versa. This allows the flow conditions on the suction and pressure sides of the diaphragm pump to be stabilized.

[0031] The diaphragm pump preferably has a hydraulic storage element on the suction side and a hydraulic storage element on the pressure side, which are each connected to the two pump chambers. Thus, a hydraulic storage element common to both pump chambers is connected to the suction side of the two pump chambers. A hydraulic storage element common to both pump chambers is also connected to the pressure side of the pump chambers. In this way, there is no need to provide two separate hydraulic storage elements for each of the two pump chambers. This makes it possible to reduce the installation space of the diaphragm pump.

[0032] The described double-headed diaphragm pump can thus have one, two, three, four or more hydraulic storage elements.

[0033] In a further advantageous embodiment, the diaphragm pump can be provided with at least four hydraulic storage elements, two of the hydraulic storage elements being arranged on each suction side of the pump chambers and two of the hydraulic storage elements being arranged on each pressure side of the pump chambers. Thus, a hydraulic storage element is arranged on each suction and pressure side of each pump chamber. This allows pressure and volume flow pulsations to be reduced even more effectively.

[0034] To achieve the stated object, it can be provided that the previously described diaphragm pump and the described variants are used in an arrangement which comprises the diaphragm pump and a line which is connected to the diaphragm pump.

[0035] Alternatively or additionally, to achieve the stated object, the features of the first independent claim directed to an arrangement for conveying a fluid are provided according to the invention. In particular, in an arrangement of the type described at the outset, it is proposed according to the invention that a stroke amplitude of the positive displacement pump is adjustable. The positive displacement pump is preferably designed as a diaphragm pump. This can be designed in particular as described above or further below; in this case, the said hydraulic storage element of the arrangement and the hydraulic storage element of the diaphragm pump preferably coincide, i.e. are the same component. The arrangement further comprises a control unit which is connected to the positive displacement pump.It is further provided that the stroke amplitude of the positive displacement pump is controllable by the control unit and that the control unit is set up in such a way that a stroke frequency of the positive displacement pump lies outside a hydraulic resonance frequency of the arrangement.

[0036] The line can connect the positive displacement pump to a fluid reservoir on the suction side. The line can also connect the positive displacement pump to the same or a different fluid reservoir or a fluid consumer on the pressure side. Thus, the positive displacement pump can pump a fluid from a first fluid reservoir to a second fluid reservoir via the line. Instead of a different, second fluid reservoir, the line can also be returned to the first fluid reservoir.

[0037] One or more hydraulic storage elements can be arranged in the line. Preferably, a hydraulic storage element can be placed on the suction side of the positive-displacement pump. Furthermore, a hydraulic storage element can preferably be placed on the pressure side of the positive-displacement pump.

[0038] The hydraulic resonance frequency corresponds to the frequency at which the pressure and / or volume flow pulsations occurring in the pumped fluid are at their maximum. The hydraulic resonance frequency can be determined empirically or calculated. The hydraulic resonance frequency approximately corresponds to a stroke frequency of the positive displacement pump at which the pressure and / or volume flow pulsations occurring in the pumped fluid are at their maximum.

[0039] It has been shown that, starting from a standstill, pressure pulsations in the aforementioned arrangements can initially increase with increasing frequency and reach a maximum at the hydraulic resonance frequency. If the frequency increases further, the pressure pulsations can decrease again until a constant value is reached—in this range, the pressure pulsations are therefore no longer dependent on the frequency.

[0040] Flow rate pulsations can also increase with increasing frequency and can reach a maximum value at the hydraulic resonance frequency. As the stroke frequency increases further, the flow rate pulsations can decrease again.

[0041] Consequently, it may be advantageous to avoid the hydraulic resonance frequency when selecting the stroke frequency, as this allows for consistent fluid delivery with reduced pulsations in the pressure and / or flow rate of the fluid.

[0042] The adjustability and controllability of the displacement pump's stroke amplitude has the advantage that the flow rate and / or fluid pressure can be flexibly adjusted even if adjusting the stroke frequency would otherwise result in the hydraulic resonance maximum being reached. Therefore, any desired values ​​for the pressure and / or fluid flow can be achieved without the risk of the stroke frequency entering the range of the hydraulic resonance frequency.

[0043] The fact that the stroke frequency lies outside the hydraulic resonance frequency preferably means that the stroke frequency is below 90% of the resonance frequency or above 110% of the resonance frequency. Particularly preferably, the lower limit is 80% and the upper limit is 125% of the resonance frequency. Even more preferably, the lower limit is 70% and the upper limit is 140% of the resonance frequency.

[0044] In an advantageous embodiment, the control unit can be configured in one operating mode so that the stroke frequency is constant. This prevents frequency-dependent changes in the pressure and / or volume flow pulsations, and the fluid can be pumped continuously.

[0045] In this case, the stroke frequency can be adjusted but kept constant. Alternatively, the control unit can be configured so that the stroke frequency is fixed. This ensures that the stroke frequency has an optimal value that minimizes pressure and / or volume flow pulsations.

[0046] Alternatively or additionally, the control unit can be configured so that the stroke frequency is above the hydraulic resonance frequency. "Above" preferably means above 110%, particularly preferably above 120%, and most particularly preferably above 140% of the resonance frequency. If the stroke frequency is above the resonance frequency, high delivery rates can be achieved with low pulsations.

[0047] In a further advantageous embodiment, it can be provided that the control unit is set up in such a way that in an operating mode, in particular a further operating mode, a minimum value of the stroke frequency is not undercut.

[0048] The minimum value can be a value above the hydraulic resonance frequency. This value can preferably be 110%, 120%, or 140% of the hydraulic resonance frequency. This ensures that the stroke frequency lies outside the hydraulic resonance frequency and that pressure and flow rate pulsations are particularly small.

[0049] Preferably, the control unit is configured such that when a delivery rate of the fluid is reduced, the stroke amplitude is first reduced and the stroke frequency is only reduced when a minimum value of the stroke amplitude is reached.

[0050] In this way, the delivery rate can be varied by controlling both the stroke frequency and the stroke amplitude. This is advantageous, for example, when the desired delivery rate is so low that it cannot be achieved at high stroke frequencies by controlling only the stroke amplitude. At the same time, however, specifying the minimum value ensures that the stroke frequency remains above the hydraulic resonance frequency.

[0051] Alternatively or additionally, to achieve the stated object, the features of the second independent claim directed to an arrangement for conveying a fluid are provided according to the invention. In particular, to achieve the stated object, in an arrangement of the type described at the outset, it is proposed according to the invention that a stroke amplitude of the positive displacement pump is adjustable. The positive displacement pump is preferably designed as a diaphragm pump. This can be designed in particular as described above or further below; in this case, the said hydraulic storage element of the arrangement and the hydraulic storage element of the diaphragm pump preferably coincide, i.e. are the same component. The arrangement further comprises a control unit which is connected to the positive displacement pump. In addition, the arrangement comprises a sensor for measuring a flow parameter of the fluid.In addition, it is provided that the stroke amplitude of the positive displacement pump can be controlled by the control unit depending on the flow parameter measured by the sensor.

[0052] In this way, the measured flow parameter can, for example, be adjusted to specified target values. The controllability of the stroke amplitude offers the advantage that control of the stroke frequency is not necessary and that this can be essentially constant and / or outside a resonant frequency of the arrangement, preferably at a high value. This allows pulsations in the pressure and / or volume flow of the fluid to be reduced to a minimum.

[0053] In an advantageous embodiment, it can be provided that the flow parameter is a pressure and / or a flow rate. The pressure and / or the flow rate at the position of the sensor can thus be adjusted by controlling the stroke amplitude of the positive displacement pump. In a further advantageous embodiment, it can be provided that the sensor is designed and arranged in such a way that a deflection of a separating layer of the hydraulic storage element can be measured by it and that a pressure, for example the pressure already mentioned, can be determined from the measured deflection, in particular by the control unit.

[0054] This offers the advantage that a pressure sensor can be installed directly in the hydraulic storage element. This saves space, as no pressure sensor needs to be installed in the line, and the low pulsations in the storage element allow for precise pressure measurement.

[0055] In a further advantageous embodiment, it can be provided that a stroke frequency of the positive displacement pump, for example the stroke frequency already mentioned, can be controlled by the control unit as a function of the flow parameter measured by the sensor.

[0056] This means that the positive displacement pump can be controlled not only via the stroke amplitude but also via the stroke frequency.

[0057] The advantage of this is the greater flexibility in control. In particular, it allows for particularly high and particularly low flow parameters that cannot be achieved by controlling the stroke amplitude alone.

[0058] In a further advantageous embodiment, the line can be provided with an orifice to increase flow resistance. The orifices support the damping effect of the hydraulic storage element in order to reduce the pressure and volume flow pulsations generated by the positive displacement pump. Furthermore, the orifices can be used effectively to influence the resonance behavior of the hydraulic system. Furthermore, the installation of an orifice can reduce the resonance frequency of the hydraulic system, so that a larger stroke frequency range above the resonance frequency is available for the operation of the positive displacement pump.

[0059] The orifice plate can be arranged on the suction side of the positive displacement pump. The orifice plate is preferably positioned so that the hydraulic storage element is located between the positive displacement pump and the orifice plate. This reduces pressure and volume flow pulsations on the suction side of the positive displacement pump.

[0060] Alternatively or additionally, the orifice plate can be arranged on a pressure side of the positive displacement pump. The orifice plate is preferably arranged so that the hydraulic storage element is located between the positive displacement pump and the orifice plate. This has the advantage that the fluid pumped by the positive displacement pump first flows into the hydraulic storage element because the flow resistance for this is lower than the flow resistance that would exist if the fluid flowed through the orifice plate directly into the line. In this way, pressure and volume flow pulsations on the pressure side of the positive displacement pump can be reduced.

[0061] In a further advantageous embodiment, it can be provided that the hydraulic storage element is arranged on a suction side of the positive displacement pump, and that the arrangement comprises a further hydraulic storage element arranged on a pressure side of the positive displacement pump. This allows pressure and volume flow pulsations to be reduced on both the pressure and suction sides.

[0062] In a further advantageous embodiment, it can be provided that the stroke amplitude is controllable by at least a factor of 10, preferably by at least a factor of 20, 50, or 100. This offers particularly high flexibility in controlling the arrangement, in particular when setting a specific pressure and / or a specific flow rate.

[0063] In a further advantageous embodiment, the control unit can be configured such that a stroke frequency, for example the stroke frequency already mentioned, is between 0.7 and 1.4 times, preferably between 0.8 and 1.2 times, particularly preferably between 0.9 and 1.1 times, a mechanical resonance frequency of the positive displacement pump. For example, the stroke frequency can correspond to the mechanical resonance frequency of the positive displacement pump.

[0064] The lifting element of a positive displacement pump can be mounted, for example, by leaf springs or, in the case of a diaphragm pump, by the pump diaphragm. The mechanical resonance frequency of the respective pump is thus the resonance frequency of the system, which is composed in particular of the oscillating lifting element and the element that supports the lifting element, for example, the pump diaphragm and / or the leaf springs.

[0065] It can be particularly advantageous from an energy perspective to set the stroke frequency close to the mechanical resonance frequency, as this allows the positive displacement pump to operate in the case of mechanical resonance. In this way, a maximum proportion of the electrical energy used to drive the stroke element can be transferred to the pumping of the fluid. This can result in a reduced

[0066] This can result in energy consumption of the positive displacement pump. Preferably, the stroke frequency is kept constant. This allows the energy consumption of the respective pump to be kept at a consistently low level.

[0067] In a further advantageous embodiment, the positive displacement pump can be provided with a linear drive. This means that the positive displacement pump has no rotary drive, and that only translational movements can be performed by the drive of the diaphragm pump. By avoiding rotating parts in the drive, the drive can respond more quickly to control signals from the control unit. Linear drives are particularly well suited for applications in which a stroke amplitude needs to be adjustable and controlled.

[0068] Preferably, the linear drive is an electromagnetic drive. An electromagnetic drive means that a stroke element of the positive displacement pump is moved by electromagnetic induction rather than by a gear. This allows for easier adjustment of the stroke amplitude and stroke frequency.

[0069] Alternatively or additionally, a positive displacement pump drive, especially the linear drive, is a direct drive. Using a direct drive eliminates the need for gears and thus eliminates backlash in the stroke movement, allowing the drive to respond even faster to control signals from the control unit. Furthermore, this minimizes maintenance requirements and ensures a long service life for the positive displacement pump, as wear on gear components is eliminated.

[0070] In a further advantageous embodiment, it can be provided that a stroke position of the positive displacement pump can be detected by a position sensor and that the position sensor is connected to the control unit.

[0071] The stroke position corresponds to the current position of the stroke element. The position sensor can be used to detect the current stroke amplitude. For example, the position sensor can be used to check whether a setpoint for the stroke amplitude specified by the control unit is actually being implemented.

[0072] In a further advantageous embodiment, it can be provided that the positive displacement pump can be operated with a head clearance which, in addition to the conveyance of liquid, also enables the conveyance of a gaseous medium, and that the stroke amplitude can be adjusted to the head clearance using the control unit. Alternatively or additionally, it can be provided that a zero position of the lifting element can be adjusted to the head clearance using the control unit. When conveying gaseous media, it is particularly advantageous to keep the head clearance as small as possible and thus the compression ratio as large as possible. This can be achieved by the stroke amplitude assuming a maximum value and / or by the zero position of the lifting element and thus the neutral position, i.e. the zero line, of the lifting movement being shifted towards the head.

[0073] In an advantageous embodiment, it can be provided that the control unit is set up to control the arrangement in such a way that a method as described below is carried out.

[0074] With the arrangements described above, methods for conveying a fluid can be carried out, wherein the stroke amplitude and / or a stroke frequency of the positive displacement pump is controlled. To achieve the stated object, the features of a first independent claim directed to a method for conveying a fluid are provided according to the invention. In particular, to achieve the stated object, in a method of the type described at the outset, the invention proposes that a stroke amplitude of the positive displacement pump be adjustable. Furthermore, it is provided that the stroke amplitude of the positive displacement pump is controlled and that a stroke frequency of the positive displacement pump is kept outside a hydraulic resonance frequency of the arrangement.

[0075] By keeping the stroke frequency outside the hydraulic resonance frequency, pressure and flow pulsations can be reduced, allowing the fluid to be pumped under consistent flow conditions. By controlling the stroke amplitude, the fluid flow conditions can be flexibly adjusted. The energy consumption of the positive displacement pump can also be reduced, as no unnecessary energy is used to generate pressure and flow pulsations.

[0076] What is meant by "off-resonance frequency" has already been described in connection with the arrangement. Since the method can be carried out in particular with the arrangement described above, the definitions and further developments of the arrangement also apply accordingly to the described methods.

[0077] Alternatively or additionally, the features of the second independent claim directed to a method for conveying a fluid are provided according to the invention to achieve the stated object. In particular, to achieve the stated object, in a method of the type described above, the invention proposes that a stroke amplitude of the positive displacement pump be adjustable. Furthermore, it is provided that a flow parameter of the fluid is measured, and that the stroke amplitude of the positive displacement pump is controlled as a function of the measured flow parameter.

[0078] The advantage here is that adjusting the flow parameter does not require a change in the stroke frequency, since the adjustment can be achieved by controlling the stroke amplitude. This allows the stroke frequency to be kept at a high value, which can even be above the hydraulic resonance frequency, so that pressure and volume flow pulsations can be reduced to a minimum.

[0079] In an advantageous embodiment, it can be provided that a stroke frequency, for example the stroke frequency already mentioned, of the positive displacement pump is controlled as a function of the measured flow parameter. This provides, in addition to controlling the stroke amplitude, a further degree of freedom with which the flow parameter can be adjusted.

[0080] In a further advantageous embodiment, it can be provided that the stroke amplitude is set to a maximum value until the positive displacement pump is filled with liquid, and that the stroke amplitude is then variably controlled.

[0081] This is particularly advantageous when starting up the positive displacement pump or when initializing a delivery process. During the start-up process there is often no liquid in the line or in the positive displacement pump. These are filled with air or another gas. The positive displacement pump must therefore first suck in the liquid. To do this the positive displacement pump must pump gas. To pump gases it is advantageous if the stroke amplitude is at its maximum. This results in a smaller dead volume in a pump chamber and a higher compression ratio. This means larger quantities of gas can be pumped. In addition it is the only way to create a sufficiently large vacuum to suck the liquid into the pump through the suction-side line.As soon as the liquid has been sucked in, i.e. has reached the positive displacement pump and has filled the pump chamber, the stroke amplitude can be reduced again and controlled in such a way that, for example, a desired flow parameter is set.

[0082] In a further advantageous embodiment, it can be provided that a setpoint value for the flow parameter is specified and compared with a measured value of the flow parameter, and that the stroke amplitude is controlled depending on the comparison result. Preferably, this adjusts the measured value to the setpoint value.

[0083] This allows the flow conditions of the fluid to be adapted to the corresponding requirements.

[0084] In a further advantageous embodiment, a control variable for the stroke amplitude can be updated in intervals, with the time steps being selected depending on the stroke frequency. This allows control signals to be taken into account particularly quickly by the positive displacement pump.

[0085] Preferably, the time steps are proportional to the current inverse of the stroke frequency. The inverse of the stroke frequency can be referred to as the stroke period. Thus, a new manipulated variable of the stroke amplitude can be specified for each stroke period or for any number of stroke periods, allowing the pressure or flow of the fluid to be adjusted particularly quickly and precisely to current measured values.

[0086] In a further advantageous embodiment, it can be provided that the hydraulic storage element is arranged on a suction side of the positive displacement pump, and that the arrangement has a further hydraulic storage element arranged on a pressure side of the positive displacement pump. This embodiment can make it possible to reduce pressure and volume flow pulsations on both the suction side and the pressure side.

[0087] Alternatively or additionally, to achieve the stated object, the features of the independent claim directed to a method for determining a hydraulic resonance frequency of an arrangement as described above are provided according to the invention. In particular, to achieve the stated object, in a method for determining a hydraulic resonance frequency of the type described above, the invention proposes that a range of stroke frequencies of the positive displacement pump be traversed, with a measured value of the flow parameter being recorded for each stroke frequency.

[0088] As previously described, the hydraulic resonance frequency can be approximated by the stroke frequency at which the largest pulsations in pressure and / or flow rate are measured. By determining the hydraulic resonance frequency in this way, it can be taken into account in the control system and avoided during operation of the system.

[0089] Alternatively or additionally, the features of the independent claim directed to a control unit are provided to achieve the object mentioned at the outset. In particular, it is thus proposed according to the invention that a control unit is set up to control an arrangement as described above in such a way that a

[0090] A method for conveying a fluid or for determining a hydraulic resonance frequency is carried out. This control unit enables the advantages described above to be realized.

[0091] The invention will now be described in more detail with reference to exemplary embodiments, but is not limited to these exemplary embodiments. Further variants of the invention and exemplary embodiments arise from combining the features of individual or multiple claims with one another and / or with individual or multiple features of the exemplary embodiments and / or the previously described variants of inventive devices and methods.

[0092] It shows

[0093] Fig. 1 shows an arrangement for conveying a fluid, wherein the measured flow parameter is a pressure,

[0094] Fig. 2 shows a modification of the arrangement, wherein several pressure sensors are arranged at different positions,

[0095] Fig. 3 shows a modification of the arrangement, where the measured flow parameter is a flow rate,

[0096] Fig. 4 shows a modification of the arrangement, wherein several flow sensors are arranged at different positions,

[0097] Fig. 5 is an electrical equivalent circuit diagram for the hydraulic arrangement shown in Fig. 1,

[0098] Fig. 6 shows a diaphragm pump according to the invention, Fig. 7 shows a diaphragm pump according to the invention with two pump combs,

[0099] Fig. 8 shows another diaphragm pump according to the invention with two pump combs,

[0100] Fig. 9 shows a further diaphragm pump according to the invention with two pump chambers and only two hydraulic storage elements.

[0101] In Fig. 1, the arrangement 1 comprises a positive displacement pump 3 which is equipped with a linear drive M. The positive displacement pump is designed as a diaphragm pump 16. The linear drive M is a direct drive with which a lifting element 17 can be driven. For better control of the positive displacement pump 3, a position sensor 10 is provided, by means of which the current stroke amplitude h of the positive displacement pump 3 can be detected.

[0102] The positive displacement pump 3 is connected by a line 5 on its suction side 11 to a first fluid reservoir 13, from which the fluid 2 is pumped out. On the pressure side 12, the positive displacement pump 3 is connected by a line 5 to a second fluid reservoir 14, into which the fluid 2 is pumped. The fluid 2 is a liquid.

[0103] Furthermore, a hydraulic storage element 4 and an orifice 8 are arranged in the line 5 on both sides 11, 12 of the positive displacement pump 3. The hydraulic storage element 4 has two chambers which are separated from one another by a separating layer 9.

[0104] The production rate Q p The displacement pump 3 exhibits a pulsation, since the displacement pump 3 undergoes a suction process and a discharge process per stroke period. As a result, the delivery rate Q p not continuous, but pulsating. The hydraulic storage elements 4 determine the flow rate Q p balanced so that the incoming flow Q u and the outgoing flow Q d have reduced pressure and volume flow pulsations.

[0105] The orifices 8 increase the flow resistance in the line 5. The orifice 8 positioned on the pressure side 12 ensures that the fluid 2 does not flow directly toward the second fluid reservoir 14 and thus bypass the hydraulic storage element 4. The flow resistance created by the orifice 8 makes it easier for the fluid 2 to first flow into the hydraulic storage element 4, which compensates for the pressure and volume flow pulsations. The effectiveness of the hydraulic storage element 4 is thus supported by the orifice 8.

[0106] The situation is similar on the suction side 11. The orifice plate 8 increases the flow resistance of the fluid 2 in the line 5. The positive displacement pump 3 therefore sucks in a larger proportion of the fluid 2 from the suction-side hydraulic storage element 4 and a smaller proportion from the line 5 upstream of the orifice plate 8. The flow conditions in the line 5 upstream of the orifice plate 8 are therefore more balanced, since the pressure and volume flow pulsations generated by the positive displacement pump are balanced out by the hydraulic storage element 4. The orifice plate 8 supports the work of the hydraulic storage element 4.

[0107] On the pressure side 12 of the displacement pump 3, a sensor 7 is arranged, with which a pressure p m can be measured. The measured pressure p m is sent to a control unit 6, in which the measured value is compared with a target pressure p ref is compared. Based on the comparison result, the control unit 6 of the positive displacement pump 3 specifies new manipulated variables for the stroke amplitude h and the stroke frequency f. The manipulated variables are recalculated with each period Δt. The period Δt corresponds to the stroke period - i.e. the inverse of the stroke frequency f - of the positive displacement pump 3, so that a new stroke amplitude h and a new stroke frequency f are specified for each new stroke period.

[0108] The described arrangement has a hydraulic resonance frequency. The hydraulic resonance frequency can either be calculated or determined empirically. For empirical determination, the available stroke frequencies f of the positive displacement pump 3 can be run through in a test run. For each stroke frequency f, measured values ​​for the pressure p are recorded by means of the sensor 7. mrecorded. These measured values ​​are recorded. By evaluating these measured values, the hydraulic resonance frequency can be identified as the stroke frequency f at which the largest pressure pulsations were measured.

[0109] For the subsequent operation of the arrangement 1, the control unit 6 is set up so that the stroke frequency f is always above the hydraulic resonance frequency. For setting the desired pressure p ref is primarily used to control the stroke amplitude h . However, in order to have the greatest possible flexibility when controlling arrangement 1, the stroke frequency f is also controlled, but in a range that lies above the hydraulic resonance frequency . A minimum value is specified for the stroke frequency f . When this minimum value is reached, the stroke frequency f is no longer reduced and from this point onwards control is carried out exclusively via the stroke amplitude h, which can be controlled by a factor of 100 and thus covers a very large range of deliverable pressure and / or flow.

[0110] The stroke frequency f is also kept in a range close to the mechanical resonance frequency of the positive displacement pump 3, which is designed as a diaphragm pump 16. Thus, the energy required to pump the fluid 2 is minimal.

[0111] However, before the positive displacement pump 3 can pump the fluid 2, which is a liquid, from the first fluid reservoir 13 into the second fluid reservoir 14, the positive displacement pump 3 must be operated in gas mode. This is necessary because, when the arrangement 1 is started up, the line 5 is not yet filled with the liquid fluid 2, but with a gas—in this case, air. The liquid fluid 2 must therefore first be sucked in from the first fluid reservoir 13.

[0112] For this purpose, the positive displacement pump 3 is operated at a maximum stroke amplitude h . This is advantageous for compressible media such as air, since the head clearance in the positive displacement pump 3 is minimal in this case. Alternatively or additionally, the neutral position of the stroke movement can be adjusted so that the head clearance is minimal. This provides a maximum stroke volume and thus a large vacuum for conveying the air and for sucking in the liquid fluid 2 . As soon as the liquid fluid 2 has been sucked in, the stroke amplitude h is variably controlled so that the desired pressure p m sets .

[0113] Figs. 2 to 4 show variants of the embodiment of Fig. 1. The respective arrangement 1 has the same basic configuration as described above and can be operated in a similar manner. Fig. 2 shows a variant of the arrangement 1 in which four possible positions for sensors 7 for detecting a pressure p m can be seen .

[0114] Two possible positions for sensors 7 are on the suction side 11 of the positive displacement pump 3 . This means that the pressure p m of the fluid 2 before entering the displacement pump 3, whereby the pressure p m can also be regulated in this range. In particular, the pressure p mbelow a maximum value and / or above a minimum value. The first of these positions for a sensor 7 is provided in front of the orifice 8. The second position is arranged in the suction-side hydraulic storage element 4 and measures the deflection of the separating layer 9 - the pressure p present in the hydraulic storage element 4 can then be determined via the measured deflection. m Alternatively, a regular pressure sensor can be installed in the hydraulic storage element 4.

[0115] Analogously, two further possible positions for sensors 7 are provided on the pressure side 12 of the positive displacement pump 3 - one position in the pressure-side hydraulic storage element 4 and one position behind the pressure-side orifice 8 .

[0116] Depending on the desired mode of operation, one or more sensors 7 can be placed at one or more positions.

[0117] The embodiment in Fig. 3 is similar to that in Fig. 1, however, the sensor 7 does not measure a pressure p m , but a flow Q m measured. The measured value is sent to the control unit 6, which compares it with a given reference value Q re f is compared. Based on the comparison result, updated control variables for the stroke amplitude h and the stroke frequency f are specified for the positive displacement pump 3 in magazines At.

[0118] This arrangement 1 is particularly suitable when a certain target flow Q re f is to be provided by the positive displacement pump 3 .

[0119] In Fig. 4, a variant of the embodiment of Fig. 3 can be seen. Here, a further installation position for a sensor 7 is provided in order to measure the flow Q m also on the suction side 11 of the positive displacement pump 3. This allows the flow Q mcan also be controlled on the suction side 11. A sensor 7 can be arranged at one of the two installation positions. Alternatively, two sensors 7 can be used, whereby leaks in the line 5 can be detected, for example, if the flow Q m on the suction side 11 is greater than the flow Q m on printed page 12 .

[0120] Fig. 5 shows an electrical equivalent circuit for the hydraulic arrangement shown in Fig. 1. In order to describe the behavior of a hydraulic system mathematically, the system can also be represented with an electrical diagram and the usual elements (resistance, capacitance, inductance, current source). Since the arrangement shown in Fig. 1 is symmetrical, only the pressure side is shown in Fig. 5.

[0121] The hydraulic and electrical symbols in Fig. 1 and Fig. 5 represent individual components of the system. A hydraulic line 5 corresponds to a series circuit of an electrical resistance (Rd) and an inductance (Ld). An orifice plate 8 corresponds to a resistance (Ro). A hydraulic storage element 4 corresponds to a capacitance (Ca). A reservoir with a connection below the liquid level corresponds to a mass 15. A

[0122] Displacement pump 3 corresponds to a power source (Ap ).

[0123] This analogy to electrical engineering shows that a hydraulic system has a certain resonance behavior, which depends on the capacity of the storage elements, the resistance of the lines and, if applicable, the orifices and other hydraulic elements as well as their wiring.

[0124] Based on this analogy, an electrical engineer is able to determine the resonance behavior of the hydraulic system from an equivalent circuit diagram developed in this way, as shown, for example, in Fig. 5. The information thus determined, in particular regarding resonance frequencies, can then be used according to the invention to control the positive displacement pump by controlling the stroke amplitude and, if necessary, also the stroke frequency in such a way that resonance frequencies are avoided.

[0125] Figure 6 shows a diaphragm pump 16 according to the invention, which can be integrated into an arrangement 1 for conveying a fluid 2 and which has a pumping chamber 19. The pumping chamber 19 is delimited by a diaphragm 18. The diaphragm 18 is connected to a lifting element 17.

[0126] Figure 6 also shows the coil windings 20 of the linear drive of the diaphragm pump 16. In this exemplary embodiment, the linear drive consists of a rigid coil armature and a mobile rotor, the lifting element 17, which has permanent magnets. When electrical current flows through the coil windings 20, the lifting element 17 is set in motion, causing a suction or discharge process in the pump chamber 19, depending on the direction of impact of the lifting element 17.

[0127] The diaphragm pump 16 comprises two hydraulic storage elements 4. These are connected via lines 5 to the suction valve 21 and the pressure valve 22 of the diaphragm pump 16. These lines 5 are short channels 27 which connect a valve chamber 26 of the diaphragm pump 16 and a chamber 25 of the hydraulic storage element 4. The channels 27 open directly and freely into the respective chamber 25. The diaphragm pump 16 has a pump housing 28 which comprises, among other things, the hydraulic storage elements 4, the lifting element 17, the diaphragm 18 and the linear drive M.

[0128] The suction valve 21 and the pressure valve 22 are in turn connected to the pump chamber 19 via lines 5.

[0129] The hydraulic storage elements 4 each have a separating layer 9, which in this example is an elastomer plate. In this example, the hydraulic storage elements 4 have only one chamber 25, which is in contact with the fluid 2 to be pumped. The other chamber of the respective hydraulic storage element 4 is omitted, since the hydraulic storage elements 4 shown operate with atmospheric air pressure. Thus, the respective separating layer 9 only separates the chamber 25 of the hydraulic storage element 4, in which the fluid 2 is located, from the environment.

[0130] On the suction side 11 of the diaphragm pump 16, an orifice plate 8 is arranged at an inlet 23 of the diaphragm pump 16 in front of the hydraulic storage element 4. This improves the damping behavior of the suction-side hydraulic storage element 4.

[0131] On the pressure side 12, an orifice 8 is also arranged at an outlet 24 of the diaphragm pump behind the hydraulic storage element 4. This also influences the damping behavior of the pressure-side hydraulic

[0132] Memory element 4 improved.

[0133] Figure 7 shows a variant of a diaphragm pump 16 according to the invention, which can be integrated into an arrangement 1 for conveying a fluid 2 and which has two pumping chambers 19, 19'. These pumping chambers 19, 19' are each delimited by a diaphragm 18, 18'.

[0134] The two diaphragms 18, 18' are connected to each other via a lifting element 17. This couples the pump chambers 19, 19' to each other. This means that when one of the pump chambers 19, 19' is in a suction process or suction phase, the other of the pump chambers 19, 19' is in an expulsion process or pressure phase.

[0135] In the view shown in Figure 7, the lifting element 17 of the diaphragm pump 16, which is a positive displacement pump 3, is in a rest position. For this reason, the pump chambers 19, 19' are of equal volume here.

[0136] Figure 7 also shows the coil windings 20 of the linear drive. In this embodiment, the linear drive consists of a rigid coil armature and a mobile rotor, the lifting element 17, which has permanent magnets. When electrical current flows through the coil windings 20, the lifting element 17 is set in motion, causing suction or discharge processes to occur in the pump chambers 19, 19', each with a phase shift.

[0137] In this exemplary embodiment, the diaphragm pump 16 comprises four hydraulic storage elements 4. These are connected via lines 5 to the suction valves 21 and the pressure valves 22 of the diaphragm pump 16, which in turn are connected via lines 5 to the pump chambers 19, 19'. In addition, the hydraulic storage elements 4 are connected via lines 5 to the inlet 23 and outlet 24 of the diaphragm pump 16. These lines 5 are short channels 27 which connect a valve chamber 26 of the diaphragm pump 16 and a chamber 25 of the hydraulic storage element 4. The channels 27 open directly and freely into the respective chamber 25. The diaphragm pump 16 has a pump housing 28 which comprises, among other things, the hydraulic storage elements 4, the lifting element 17, the diaphragm 18 and the linear drive M.

[0138] The hydraulic storage elements 4 each have a separating layer 9, which in this example is an elastomer plate. In this example, the hydraulic storage elements have only one chamber, which is in contact with the fluid 2 to be pumped. The other chamber of the respective hydraulic storage element 4 is omitted, since the hydraulic storage elements 4 shown operate with atmospheric air pressure. Thus, the respective separating layer 9 only separates the chamber of the hydraulic storage element 4, in which the fluid 2 is located, from the environment.

[0139] On the suction side 11 of the diaphragm pump 16, an orifice plate 8 is arranged in the lines 5, in front of each inlet opening of the hydraulic storage elements 4. This improves the damping behavior of the hydraulic storage elements 4.

[0140] On the pressure side 12, an orifice plate 8 is also arranged in the line 5 at an outlet opening of the hydraulic storage elements 4. This also

[0141] Damping behavior of the pressure-side hydraulic

[0142] Storage elements 4 improved. Figure 8 shows a diaphragm pump 16 according to the invention, which can be integrated into an arrangement 1 for conveying a fluid 2 and whose structure is similar to that of the diaphragm pump 16 from Figure 7. The only difference is that the orifices 8 are not arranged in front of the inlet and outlet openings of the hydraulic storage elements 4, as is the case in Figure 7.

[0143] Instead, an orifice plate 8 is arranged at the inlet 23 of the diaphragm pump 16 and at the outlet 24 of the diaphragm pump. This allows the two hydraulic storage elements 4 on the suction side 11 to be connected via a line 5 to form one large hydraulic storage element. On the pressure side 12, the two hydraulic storage elements 4 can also be connected via a line 5. This can have a beneficial effect on the damping behavior of the hydraulic storage elements 4.

[0144] The diaphragm pump 16 according to the invention shown in Figure 9 can be integrated into an arrangement 1 for conveying a fluid 2. The structure of the diaphragm pump 16 is similar to that of the diaphragm pump 16 shown in Figure 7. The only difference is that the diaphragm pump 16 has only two hydraulic storage elements 4 instead of four.

[0145] One of the hydraulic storage elements 4 is arranged on the suction side 11 of the diaphragm pump 16. Unlike in the exemplary embodiment according to Fig. 8, in which the separating layer 9 of the hydraulic storage element 4 is arranged on a transverse side of the diaphragm pump 16, in the exemplary embodiment shown in Fig. 9 the separating layer 9 is arranged on a longitudinal side of the diaphragm pump 16. A «transverse side» is a side of the diaphragm pump 16 which forms a closure of the diaphragm pump 16 in the stroke direction. A «longitudinal side» is a side which is located to the side of the stroke element 17. The separating layer 9 is divided into two sections, wherein the sections are preferably spatially separated from one another in the middle by the inlet 23 of the diaphragm pump 16. The fluid 2 thus reaches the suction-side hydraulic storage element 4 via the inlet 23 and via an orifice plate 8.

[0146] The other hydraulic storage element 4 is arranged on the pressure side 12 of the diaphragm pump 16. Here, too, the outlet 24 of the diaphragm pump 16 is preferably located centrally between two sections of the separating layer 9 of the pressure-side hydraulic storage element 4. The separating layer 9 is arranged on a transverse side of the diaphragm pump 16, which is opposite the transverse side on which the separating layer 9 of the suction-side hydraulic storage element 4 is arranged. A baffle 8 is also arranged at the outlet 24.

[0147] The hydraulic storage elements 4 are each connected via lines 5 to both pump chambers 19, 19'.

[0148] By providing only two hydraulic storage elements 4, a particularly compact design of the diaphragm pump 16 can be achieved.

[0149] It is proposed that, in an arrangement 1 and a method for conveying a fluid 2, a positive displacement pump 3, in particular a diaphragm pump 16, with an adjustable stroke amplitude h be used, and that the stroke amplitude h of the positive displacement pump 3 be controllable by a control unit 6. A stroke frequency f of the positive displacement pump 3 can be controllable such that it lies outside a hydraulic resonance frequency of the arrangement 1. The stroke amplitude h of the positive displacement pump 3 can be controlled as a function of a measured flow parameter. / List of reference symbols List of reference symbols

[0150] 1 arrangement

[0151] 2 Fluid

[0152] 3 positive displacement pump

[0153] 4 hydraulic storage element

[0154] 5 Management

[0155] 6 Control unit

[0156] 7 Sensor

[0157] 8 aperture

[0158] 9 Separating layer (of 4)

[0159] 10 Position sensor

[0160] 11 Suction side (of 3)

[0161] 12 printed pages (of 3)

[0162] 13 first fluid reservoir

[0163] 14 second fluid reservoir

[0164] 15 Mass

[0165] 16 Diaphragm pump

[0166] 17 Lifting element

[0167] 18 membranes (of 16)

[0168] 19 pump combs (of 16)

[0169] 20 coil windings (of 16)

[0170] 21 Suction valve

[0171] 22 Pressure valve

[0172] 23 entrances (of 16)

[0173] 24 Exit from (of 16 )

[0174] 25 chambers

[0175] 26 Valve chamber

[0176] 27 Channel

[0177] 28 Pump housing h Stroke amplitude f Stroke frequency

[0178] M Linear drive p m Pressure (measured) p re f Target pressure Q d escaping flow (from 3)

[0179] Q m Flow (measured)

[0180] Q p Production rate (out of 3)

[0181] Q re f Target flow Q u incoming flow (in 3)

[0182] At Magazine

[0183] / Claims

Claims

Claims 1. Diaphragm pump (16) comprising a lifting element (17) with adjustable stroke amplitude (h), a backlash-free linear drive (M) designed as a direct drive for driving the lifting element (17), a hydraulic storage element (4) and a control unit (6) with which the stroke amplitude (h) of the lifting element (17) can be controlled.

2. Diaphragm pump (16) according to the preceding claim, characterized in that the linear drive (M) is designed as an electromagnetic drive, in particular as an electrodynamic drive.

3. Diaphragm pump (16) according to one of the preceding claims, characterized in that the hydraulic storage element (4) is arranged on a suction side (11) or on a pressure side (12) of a pump chamber (20, 20') of the diaphragm pump (16).

4. Diaphragm pump (16) according to one of the preceding claims, characterized in that the diaphragm pump (16) has a pump housing (28) which encloses the hydraulic storage element (4) and the lifting element (17).

5. Diaphragm pump (16) according to one of the preceding claims, characterized in that a channel (27) is formed between a chamber (25) of the hydraulic storage element (4) and a valve chamber (26) of the diaphragm pump (16), in particular wherein the channel (27) opens directly and / or without a connection into the chamber (25).

6. Diaphragm pump (16) according to one of the preceding claims, characterized in that the hydraulic storage element (4) is arranged on the suction side and that the Diaphragm pump (16) another hydraulic Storage element (4) which is arranged on the pressure side.

7. Diaphragm pump (16) according to one of the preceding claims, characterized in that the diaphragm pump (16) has two pump chambers (19, 19') each delimited by a diaphragm (18, 18'), wherein the two diaphragms (18, 18') are connected to one another via the lifting element (17).

8. Diaphragm pump (16) according to one of the preceding claims, characterized in that the diaphragm pump (16) has at least four hydraulic storage elements (4), two of the hydraulic storage elements (4) being arranged on a suction side (11) of the pump chambers (19, 19') and two of the hydraulic storage elements (4) being arranged on a pressure side (12) of the pump chambers (19, 19').

9. Arrangement (1) for conveying a fluid (2), comprising - a displacement pump (3), in particular a diaphragm pump (16), which is preferably designed according to one of the preceding claims, with adjustable stroke amplitude (h) - a hydraulic storage element (4), - a line (5) and - a control unit (6) which is connected to the positive displacement pump (3), characterized in that the stroke amplitude (h) of the positive displacement pump (3) can be controlled by the control unit (6) and that the control unit (6) is set up such that a stroke frequency (f) of the positive displacement pump (3) lies outside a hydraulic resonance frequency of the arrangement.

10. Arrangement (1) according to the preceding claim, characterized in that the control unit (6) is set up in an operating mode so that the stroke frequency (f) is constant or that the stroke frequency (f) is unchangeable and / or that the stroke frequency (f) is above the hydraulic resonance frequency.

11. Arrangement (1) according to one of the preceding claims, characterized in that the control unit (6) is set up in such a way that in an operating mode a minimum value of the stroke frequency (f) is not undercut, in particular wherein when a delivery rate of the fluid (2) is reduced, first the stroke amplitude (h) is reduced and that only when a minimum value of the stroke amplitude (h) is reached is the stroke frequency (f) reduced.

12. Arrangement (1) for conveying a fluid (2), in particular according to one of the preceding claims, comprising - a positive displacement pump (3), in particular a diaphragm pump (16), which is preferably designed according to one of claims 1 to 8, with adjustable stroke amplitude (h), - a hydraulic storage element (4), - a line (5) , - a sensor (7) for measuring a flow parameter of the fluid (2) and - a control unit (6) which is connected to the displacement pump (3) and the sensor (7), characterized in that the stroke amplitude (h) of the displacement pump (3) can be controlled by the control unit (6) as a function of the flow parameter measured by the sensor (7).

13. Arrangement (1) according to the preceding claim, characterized in that the flow parameter is a pressure (p m ) and / or a flow (Q m ).

14. Arrangement (1) according to one of the two preceding claims, characterized in that the sensor (7) is so is designed and arranged such that a deflection of a separating layer (9) of the hydraulic storage element (4) can be measured by this (7) and that from the measured deflection, in particular by the control unit (6), a pressure or the pressure (p m ) can be determined.

15. Arrangement (1) according to one of the preceding claims, characterized in that one or the stroke frequency (f) of the positive displacement pump (3) can be controlled by the control unit (6) as a function of one or the flow parameter measured by one or the sensor (7).

16. Arrangement (1) according to one of the preceding claims, characterized in that the line (5) has an orifice (8) to increase a flow resistance.

17. Arrangement (1) according to one of the preceding claims, characterized in that the hydraulic storage element (4) is arranged on a suction side (11) of the displacement pump (3) and that the arrangement (1) has a further hydraulic storage element (4) which is arranged on a pressure side (12) of the positive displacement pump (3).

18. Arrangement (1) according to one of the preceding claims, characterized in that the stroke amplitude (h) is controllable by at least a factor of 10, preferably by at least a factor of 100.

19. Arrangement (1) according to one of the preceding claims, characterized in that the control unit (6) is set up so that a or the stroke frequency (f) is between 0.7 and 1.4 times a mechanical resonance frequency of the positive displacement pump (3), in particular wherein the stroke frequency (f) is kept constant becomes .

20. Arrangement (1) according to one of the preceding claims, characterized in that the positive displacement pump has a linear drive (M), in particular wherein the linear drive (M) is an electromagnetic drive and / or a direct drive.

21. Arrangement (1) according to one of the preceding claims, characterized in that a stroke position of the positive displacement pump (3) can be detected by a position sensor (10) and that the position sensor (10) is connected to the control unit (6).

22. Arrangement (1) according to one of the preceding claims, characterized in that the positive displacement pump (3) can be operated with a head clearance which, in addition to the conveyance of liquid, also enables the conveyance of a gaseous medium, and in that the stroke amplitude (h) and / or a neutral position of the lifting element (17) can be adjusted to the head clearance by means of the control unit (6).

23. Arrangement (1) according to one of the preceding claims, characterized in that the control unit (6) is arranged to control the arrangement (1) such that a method according to one of the subsequent method claims is carried out.

24. Method for conveying a fluid (2) by means of an arrangement (1), in particular according to one of the preceding claims, comprising - a positive displacement pump (3), in particular a diaphragm pump (16), which is preferably designed according to one of claims 1 to 8, with adjustable stroke amplitude (h), - a hydraulic storage element (4) and - a line (5), characterized in that the stroke amplitude (h) of the positive displacement pump (3) is controlled, in particular wherein a stroke frequency (f) of the positive displacement pump (3) is kept outside a hydraulic resonance frequency of the arrangement.

25. Method for conveying a fluid (2) by means of an arrangement (1), in particular according to one of the preceding claims directed to an arrangement, comprising - a positive displacement pump (3), in particular a diaphragm pump (16), which is preferably designed according to one of claims 1 to 8, with adjustable stroke amplitude (h), - a hydraulic storage element (4) and - a line (5), characterized in that a flow parameter of the fluid is measured and that the stroke amplitude (h) of the positive displacement pump (3) is controlled as a function of the measured flow parameter.

26. Method according to the preceding claim, characterized in that one or the stroke frequency (f) of the positive displacement pump (3) is controlled as a function of the measured flow parameter.

27. Method according to one of the preceding method claims, characterized in that the stroke amplitude (h) is set to a maximum value until the positive displacement pump (3) is filled with liquid, and that the stroke amplitude (h) is then variably controlled.

28. Method according to one of the preceding method claims, characterized in that a target value (p ref, Qref) is specified for the flow parameter and is compared with a measured value of the flow parameter and that the stroke amplitude (h) is determined as a function of a comparison result, in particular whereby the measured value is adjusted to the target value.

29. Method according to one of the preceding method claims, characterized in that a control variable of the stroke amplitude (h) is updated in time steps (At), wherein the time steps (At) are selected as a function of the stroke frequency (f), in particular wherein the time steps (At) are proportional to the respective current inverse of the stroke frequency (f).

30. Method according to one of the preceding method claims, characterized in that the hydraulic storage element (4) is arranged on a suction side (11) of the positive displacement pump (3) and that the arrangement (1) has a further hydraulic storage element (4) which is arranged on a pressure side (12) of the positive displacement pump (3).

31. Method for determining a hydraulic resonance frequency of an arrangement (1) according to one of the preceding claims, characterized in that a range of stroke frequencies (f) of the positive displacement pump (3) is traversed, wherein a measured value of the flow parameter is recorded for each stroke frequency (f).

32. Control unit (6) which is arranged to control a diaphragm pump (16) according to one of claims 1 or 2 and / or a To control the arrangement (1) according to one of the preceding claims 3 to 16 in such a way that a method according to one of the preceding method claims is carried out. / Summary

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