Mass flow controller

Abstract

The invention relates to a mass flow controller (1) for providing a fluid mass flow, having a valve module (2) and having a measuring assembly (3), wherein at least two valve assemblies (72) are arranged in the valve module (2) between a supply connection (7) and an outlet connection (113) and wherein the measuring assembly (3) has an inlet connection (43) for connecting to the outlet connection (113) and a working connection (8) for connecting to a fluid consumer, wherein a working channel (42), in which a flow restrictor (201) is arranged, extends between the inlet connection (43) and the working connection (8), and wherein a pressure sensor assembly (61, 62) for determining a differential pressure across the flow restrictor (201) is associated with the working channel (42); and having a control device (75) which is electrically connected to the pressure sensor assembly (61, 62) and to the valve module (2) and which is designed to determine a fluid mass flow in the working channel (42) on the basis of sensor signals from the pressure sensor assembly (61, 62) and to control the valve assemblies (72) in a regulated manner.

Description

[0001] Mass flow controller

[0002] The invention relates to a mass flow controller for providing a fluid mass flow.

[0003] From US 101 656 684 B2 a fluid control device is known which makes it possible to establish a cable connection even when a plurality of fluid control devices are arranged next to one another. The fluid control device comprises fluid control units for controlling a flow rate or a pressure of a fluid, an electrical circuit board for sending and receiving a signal to and from the fluid control units, a housing for accommodating the fluid control units and the electrical circuit board, and a device-side connector arranged between the electrical circuit board and a cable electrically connected thereto. The fluid control device further comprises a connector board which is configured such that it can be mounted on the device-side connector.The connector board is attached to the electrical circuit board, with at least a part of the connector board being in surface contact with the electrical circuit board or overlapping the electrical circuit board with a space therebetween.

[0004] The object of the invention is to provide a mass flow controller that has a compact design. This object is achieved for a mass flow controller of the type mentioned above, which is designed to provide a fluid mass flow, with the following features: the mass flow controller comprises a valve module and a measuring arrangement, wherein the valve module has a supply connection for connection to a fluid source and an output connection for providing a fluid mass flow to the measuring arrangement, and in the valve module between the supply connection and the output connection at least two valve arrangements are arranged, each of which is designed to proportionally influence the fluid mass flow, and wherein the measuring arrangement has an inlet connection for connection to the outlet connection and a working connection for connection to a fluid consumer,wherein a working channel extends between the inlet connection and the working connection, in which a flow throttle is arranged and wherein a pressure sensor arrangement for determining a differential pressure across the flow throttle is assigned to the working channel, as well as with a control device which is electrically connected to the pressure sensor arrangement and to the valve module and which is designed to determine a fluid mass flow in the working channel based on sensor signals from the pressure sensor arrangement and for the controlled activation of the valve arrangements to maintain a setpoint for the fluid mass flow.,

[0005] The task of the valve assemblies accommodated in the valve module is to influence a fluid flow that can be provided by a fluid source, for example a compressed air source or a process gas source, at a supply connection of the valve module, in such a way that a desired fluid mass flow can be provided at a working connection of the mass flow controller. Preferably, the valve assemblies of the valve module are configured in such a way that a maximum fluid mass flow provided by the fluid source can be throttled to the fluid mass flow required at the working connection due to throttling effects that can be exerted on the fluid mass flow by the at least two valve assemblies arranged in the valve module. Particularly preferably, this throttling effect is individually and freely adjustable for each of the valve assemblies of the valve module.

[0006] The plurality of, in particular at least two, valve assemblies are each electrically connected to the control device and can each be adjusted between a closed position and an open position depending on electrical control signals from the control device. Each of the valve assemblies serves to influence a portion of the fluid mass flow in the working channel. It is preferably provided that each of the valve assemblies is used to influence an identical portion of the fluid mass flow. This can be achieved in that the valve assemblies of the valve module are of identical construction and are supplied with control signals from the control device in the same way.It is particularly preferred that each of the valve arrangements is controlled with an individual parameterization stored in the control device in order to always ensure that a valve cross-section that is as identical as possible is released for all valve arrangements.

[0007] By using a plurality of valve arrangements for a valve module it can be achieved in particular that the valve modules and thus the mass flow controller can be designed to be particularly compact in one of three spatial directions of a Cartesian coordinate system, which can be referred to, for example, as the width, length and height of the valve module. This compact design results from the fact that each of the valve arrangements has a small dimension in one of the spatial directions and the valve arrangements are arranged next to one another in another spatial direction. For example, the valve arrangements can each be cuboid-shaped, wherein they have a round, rectangular or square cross-section in a cross-sectional plane that is aligned transversely to a longest extension of the respective valve arrangement and are arranged next to one another in a spatial direction transversely to the longest extension in the valve module.

[0008] After the fluid mass flow exits the valve module at an outlet connection, starting from the supply connection of the valve module and after passing through at least two valve assemblies arranged in the valve module, it is supplied directly to an inlet connection of a measuring arrangement. Provision can be made for a mechanical separation between the valve module and the measuring arrangement, so that a seal is provided between the outlet connection and the inlet connection. Alternatively, the valve module and the measuring arrangement can also be implemented in a common assembly.

[0009] In addition to the input connection, the measuring arrangement also comprises a working connection which is designed for connection to a fluid consumer, wherein the fluid consumer can be, for example, a fluid actuator or a reactor vessel which has to be supplied with a predetermined fluid mass flow of a fluid in order to carry out a manufacturing process.

[0010] A working channel, also referred to as a measuring section, extends between the inlet port and the working port in the measuring arrangement. A flow restrictor is arranged in this working channel. This restrictor is designed to create a pressure drop between the inlet port and the working port that is dependent on the fluid mass flow. This allows a differential pressure measurement, which, using a suitable calculation model, can be used to determine the fluid mass flow flowing through the working channel.

[0011] The use of a flow throttle enables the generation of a significant pressure difference between a first measuring point arranged upstream of the flow throttle in the working channel and a second measuring point arranged downstream of the flow throttle in the working channel.

[0012] In order to determine the pressure drop across the flow restrictor, a pressure sensor arrangement is assigned to the working channel and is electrically connected to a control device. The pressure sensor arrangement can be used to determine a differential pressure across the flow restrictor. For this purpose, either a differential pressure signal generated directly by the pressure sensor arrangement is provided to the control device, or several discrete pressure signals are provided to the control device for further processing.

[0013] The task of the control device is to determine a differential pressure from the sensor signals of the pressure sensor arrangement and, using a mathematical model, to draw a conclusion from this differential pressure about the respective existing fluid mass flow in the working channel. The control device then compares the determined fluid mass flow with a predetermined (target) fluid mass flow. From any difference that may exist between the determined fluid mass flow and the predetermined fluid mass flow, one or more control signals for the valve module are generated in order to minimize the determined difference.The control signals provided by the control device are converted in the valve module in such a way that the throttling effect of the valve module is adapted to the required fluid mass flow, thereby ensuring a closed control loop for the fluid mass flow output by the mass flow controller at the working connection.

[0014] Advantageous further developments of the invention are the subject of the dependent claims.

[0015] It is expedient if the flow throttle is designed as a turbulence throttle which has at least two flow guide elements from the group: inlet plate with at least one inlet bore, throttle plate with at least one throttle bore, outlet plate with at least one outlet bore, which are arranged at a distance from one another in the working channel, wherein the at least one inlet bore, the at least one throttle bore and the at least one outlet bore are each arranged offset from one another in a spatial direction transverse to a central axis of the working channel.

[0016] A turbulence throttle enables a precisely predictable pressure drop for the fluid mass flow as it flows through the working channel, thus enabling precise differential pressure measurement. Furthermore, the turbulence throttle features a compact and cost-effective design compared to other throttle elements, particularly laminar flow elements.

[0017] The function of the turbulence throttle is based on the fact that the

[0018] Fluid mass flow is deflected several times, in particular at least twice, when passing through the turbulence throttle and thus experiences a multiple change in flow direction, whereby the desired significant pressure drop across the turbulence throttle can be achieved.

[0019] For this purpose, at least two, preferably three, flow-guiding elements are arranged in the turbulence throttle, each of which is penetrated by one or more recesses. The recesses of adjacently arranged flow-guiding elements are arranged and designed such that, in a projection plane oriented transversely to a main flow direction of the fluid mass flow, in particular transversely to a central axis of the outlet channel, there are no overlaps between the projections of the recesses of the adjacently arranged flow-guiding elements.

[0020] Depending on the design of the flow guide elements and the fluid pressure provided at the supply connection, the fluid flow flows through the recesses (inlet bore and / or throttle bore and / or outlet bore) of the flow guide elements (inlet plate and / or throttle plate and / or outlet plate) at a speed below the speed of sound (subcritical flow type) or at a speed above the speed of sound (supercritical flow type). A turbulence throttle operated in the subcritical flow type requires somewhat more installation space. In contrast, a turbulence throttle operated in the supercritical flow type can be built more compactly.Depending on the intended use of the mass flow controller, the turbulence throttle must be designed so that either a subcritical flow type or a supercritical flow type exists across the entire intended mass flow control range. Depending on the design of the turbulence throttle, it always has the same throttling properties regardless of the flow direction, so that a fluid source that can provide a negative pressure can be connected to the supply connection of the mass flow controller as an alternative to a fluid source that can provide a pressurized fluid. However, it may be necessary to adapt the valve module depending on the fluid source.

[0021] It is preferably provided that the at least one inlet bore, the at least one throttle bore and the at least one outlet bore are arranged offset from one another without overlap in a projection plane oriented transversely to the central axis. This ensures that each gas molecule of the fluid flow inevitably experiences the multiple deflection of the flow direction required to ensure high measurement accuracy for the differential pressure measurement. Due to the offset arrangement between the at least one inlet bore and the at least one throttle bore or between the at least one throttle bore and the at least one outlet bore, none of the gas molecules can pass the turbulence throttle on a flow path oriented parallel to the central axis of the working channel.

[0022] It is advantageous if the inlet plate has a plurality of inlet bores which are at a radial distance from the central axis and / or that the throttle bore of the throttle plate is aligned coaxially to the central axis and / or that the outlet plate has a plurality of outlet bores which are at a radial distance from the central axis. In a further development of the invention it is provided that a total cross section of the inlet bores is equal to or greater than a cross section of the throttle bore and / or that the cross section of the throttle bore is equal to or greater than the total cross section of the outlet bores. The total cross section is the cross section which results from adding up all the cross sections of the inlet bores or the outlet bores and which is related to the cross section of the, preferably single, throttle bore.If the total cross section of the inlet bores and / or the outlet bores is equal to the cross section of the throttle bore, a throttling effect of the turbulence throttle that is independent of the flow direction can be assumed, provided that the inlet plate has the same distance from the throttle plate as the outlet plate has from the throttle plate. If such independence of flow direction is not required, it can be provided that the total cross section of the inlet bores is larger than the cross section of the throttle bore. In addition or alternatively, it can be provided that the total cross section of the outlet bores is smaller than the cross section of the throttle bore. This reinforces the throttling effect of the turbulence throttle and thus increases the pressure difference for the same fluid flow compared to the flow direction-independent turbulence throttle.

[0023] In a further embodiment of the invention, the throttle plate is designed as a circular disk through which the throttle bore extends from a front circular surface to a rear circular surface, and a front annular collar extends in the axial direction from the front circular surface and is designed for surface contact with the inlet plate, and / or a rear annular collar extends in the axial direction from the rear circular surface and is designed for surface contact with the outlet plate. Thus, in addition to its throttling function, which is determined by the throttle bore and its arrangement relative to the inlet bores of the inlet plate and / or to the outlet bores of the outlet plate, the throttle plate has a further function, which lies in ensuring a predetermined distance between the inlet plate and / or the outlet plate.For this purpose, the throttle plate has a base body in the shape of a circular disk, which can also be described as a section of a circular cylinder with a centrally arranged throttle bore. Starting from a front circular surface of this base body, a front annular collar can extend in the axial direction, which is designed with an end face facing away from the base body for the inlet plate to bear against. Starting from a rear circular surface of this base body, a rear annular collar can extend in the axial direction, which is designed with an end face facing away from the base body for the outlet plate to bear against. Preferably, an inside diameter of the front annular collar and / or an inside diameter of the rear annular collar is selected such that there is no risk of the fluid flow being impaired between the inlet plate and the throttle plate or between the throttle plate and the outlet plate.

[0024] It is expedient if all inlet bores are designed with the same bore diameter, with the same angular pitch and with the same radial distance from the central axis on the inlet plate and / or if all outlet bores are designed with the same bore diameter, with the same angular pitch and with the same radial distance from the central axis on the outlet plate. This ensures a symmetrical division of the fluid flow provided at the supply connection through the inlet plate and / or the outlet plate with respect to the central axis of the working channel, whereby advantageous flow behavior for the fluid flow is established in the turbulence throttle. This results in a more stable curve for the pressure difference measurement compared to an asymmetrical division of the fluid flow provided at the supply connection.

[0025] It is preferably provided that an axial extension of the throttle bore along the central axis corresponds to 2 times to 10 times an axial extension of the inlet bore and / or 2 times to 10 times an axial extension of the outlet bore.

[0026] It is advantageous if the turbulence throttle comprises the inlet plate, the throttle plate, and the outlet plate, and if the inlet plate, the throttle plate, and the outlet plate are arranged in a throttle sleeve. This creates a self-contained assembly that can be manufactured, assembled, and tested independently of other components of the mass flow controller, thus achieving advantages in the manufacturing process for the mass flow controller.

[0027] In a further embodiment of the invention, the valve module is provided with a plurality of valve shafts which have extension axes aligned parallel to one another and which are each designed to accommodate a valve arrangement, wherein outlet openings of the valve shafts are arranged adjacent to the outlet connection and wherein the outlet connection opens into the working channel in the radial direction. It is assumed here that each of the valve arrangements has its own housing and can be tested for functionality before being installed in the respective valve shaft. It is further assumed that each of the valve arrangements seals off the respective valve shaft in the region of the outlet opening, so that, for example, all of the valve shafts can be pressurized together with the pressurized fluid provided at the supply connection.Preferably, one or more outlet openings are provided on the end faces of the valve assemblies, each of which protrudes from the valve shafts. The respective fluid flow portion released by the respective valve assembly flows out toward the outlet connection. Furthermore, the outlet connection opens radially into the working channel, which is preferably designed as a circular-cylindrical bore. This causes a flow deflection for the fluid flow at the transition from the valve module to the measuring assembly.

[0028] It is expedient for each valve arrangement to have at least one valve channel extending between the supply connection and the output connection, in which a valve seat and a piezoelectric bender are arranged, the piezoelectric bender carrying a sealing element that releases or closes the valve seat depending on a functional position of the piezoelectric bender. For example, the valve seat is formed on an inner surface of the valve channel as the mouth opening of a connecting bore that is fluidly connected to the respective output opening of the valve arrangement.The task of the piezo bender arranged in the valve channel with the sealing element attached to it is then to change the distance between the sealing element and the valve seat by changing its shape, in particular by changing its curvature, and thus to enable the valve seat to be opened partially or completely or closed as desired. For example, the piezo bender is designed as a combination of a metal strip and a piezoelectric coating applied thereto, wherein the expansion of the piezoelectric coating can be changed by changing the electrical voltage applied to the piezoelectric coating. This brings about the desired change in shape, in particular by changing its curvature, for the piezo bender.Preferably, the valve arrangement can be operated in the manner of a proportional valve with a freely selectable valve cross-section that can be predetermined by a corresponding electrical control voltage.

[0029] It is particularly preferred that a first and a second valve seat be arranged in the valve channel, and that each valve seat is assigned a piezo bender with a sealing element, so that the valve arrangement has a dual valve function. This dual valve function is preferably utilized in such a way that the two piezo bender are controlled by the control device, optionally with the aid of individual control parameters for each piezo bender, in such a way that they synchronously release the same opening cross-section of the valve seat.

[0030] It is preferably provided that the pressure sensor arrangement has a first pressure sensor, in particular a first absolute pressure sensor, which is connected to the working channel upstream of the turbulence throttle, and that the pressure sensor arrangement has a second pressure sensor, in particular a second absolute pressure sensor, which is connected to the working channel downstream of the turbulence throttle. By evaluating the sensor signals of the first pressure sensor and the second pressure sensor, the pressure drop across the turbulence throttle can be determined. If the two pressure sensors are designed as relative pressure sensors, an ambient pressure sensor designed as an absolute pressure sensor is additionally to be provided in order to enable a pressure level present in the working channel to be determined.Preferably, the first pressure sensor can be designed as a first absolute pressure sensor and the second pressure sensor as a second absolute pressure sensor, in which case the ambient pressure sensor can be dispensed with.

[0031] Furthermore, an absolute pressure level for the fluid mass flow in the working channel can be determined from the sensor signals. From this information, the control device can determine the current fluid mass flow in the working channel.

[0032] It is advantageous if the pressure sensor arrangement has an absolute pressure sensor which is connected to the working channel upstream of the turbulence throttle, and that the pressure sensor arrangement has a differential pressure sensor which is connected to a first differential pressure measuring point arranged upstream of the turbulence throttle in the working channel and to a second differential pressure measuring point arranged downstream of the turbulence throttle in the working channel. Such a pressure sensor arrangement can be implemented at lower cost than a pressure sensor arrangement with two absolute pressure sensors and can thus be used for the mass flow controller, in particular in price-sensitive applications.

[0033] It is expedient if the working channel has a quiet zone designed as a blind hole in a spatial direction parallel to the central axis, which is opposite to the main flow direction for the fluid flow. There is almost no fluid flow in this quiet zone, so that if the first absolute pressure sensor is arranged in this area an at least essentially, preferably complete, static pressure determination is possible. This increases the accuracy of the differential pressure determination across the flow restrictor. It is advantageous if the control device is provided with an interface for a supply of electrical energy and for communication with a communication network from the group: Modbus, IO-Link, EtherCat, Profibus, DeviceNet, Ethernet-IP, Profinet.This allows, on the one hand, an electrical supply to the mass flow controller and, on the other hand, communication between the mass flow controller and other members of a communication network according to one of the aforementioned communication protocols. Preferably, it is also possible to communicate with a data cloud.

[0034] An advantageous embodiment of the invention is shown in the drawing. Herein:

[0035] The invention is explained in more detail below using the attached drawing, which shows

[0036] Figure 1 is a perspective view of a mass flow controller,

[0037] Figure 2 is a perspective exploded view of central components of the mass flow controller according to Figure 1,

[0038] Figure 3 is a planar sectional view of the mass flow controller according to Figure 1,

[0039] Figure 4 is a schematic sectional view of a flow throttle designed as a turbulence throttle with an inlet plate, a throttle plate and an outlet plate, Figure 5 is a top view of the inlet plate according to the

[0040] Figure 1 , and

[0041] Figure 6 is a top view of the throttle plate according to Figure 1

[0042] Figure 7 is a detail view of a working channel of the mass flow controller, to which an absolute pressure sensor and a differential pressure sensor are assigned.

[0043] A mass flow controller 1 shown in Figure 1 is designed as an independent functional component for use in a fluid system (not shown). By way of example, the fluid system is a process gas supply used to carry out a manufacturing process for a product. Purely by way of example, the mass flow controller 1 is used to supply a predetermined mass flow of a process gas, for example nitrogen, into a working chamber (not shown) in order to treat products received therein according to a predetermined process specification.

[0044] To perform such a task, the mass flow controller 1 must be connected to a fluid source (not shown) and to a fluid consumer (not shown). Furthermore, the mass flow controller 1 requires electrical energy and, if necessary, control or communication signals regarding the fluid mass flow to be delivered by the mass flow controller 1.

[0045] In order to enable the mass flow controller 1 to be connected to the fluid source (not shown), a supply connection 7 is provided on a front side 21 of the mass flow controller 1, said supply connection being designed as a coupling for a fluid hose (not shown). Furthermore, in order to connect the mass flow controller 1 to a consumer (not shown), a working connection 8 is provided on a rear side 22 of the mass flow controller 1 opposite the front side 21, said working connection being designed as a coupling for a fluid hose (not shown). As will be described in more detail below, a fluid mass flow, which can be provided by the fluid source (not shown), is passed through the mass flow controller 1 to the working connection 8. In this case, it is provided that the fluid mass flow is influenced in the mass flow controller 1 in order to be able to provide a fluid mass flow at the working connection 8 in accordance with a predetermined setpoint.

[0046] By way of example, it is provided that a mounting plate 31 is fastened to an underside 24 of the mass flow controller 1, which enables convenient mounting of the mass flow controller 1 on a machine frame (not shown in detail).

[0047] As can also be seen from the illustration in Figure 1, the mass flow controller 1 has an electrical interface 4 on a top side 23, designed purely as an example as a 9-pin D-Sub connector. Electrical energy can be supplied to the mass flow controller 1 via the interface 4. Furthermore, the electrical interface 4 can be used for communication purposes between the mass flow controller 1 and a higher-level control system (not shown).

[0048] On the upper side 23, in addition to the electrical interface 4, a first status display 5 and a second status display 6 are arranged purely by way of example, which can be used for optical output of status information about a state of the mass flow controller 1 and are designed, for example, as light-emitting diodes.

[0049] On a right side surface 26 of the mass flow controller 1, a selector switch arrangement 10 is provided, which is designed purely as an example as a DIP switch arrangement and enables a configuration of the mass flow controller 1 by a user by selecting different switch positions.

[0050] The exploded view in Figure 2 focuses on the essential functional components of the mass flow controller 1 shown in Figure 1. These include: the valve module 2 and a measuring arrangement 3, which comprises a channel plate 11 and a sensor board 12.

[0051] The channel plate 11 is made purely by way of example from a metallic material, in particular aluminum, or from a plastic, and contains a supply channel 41, visible in Figure 3, and a working channel 42, also visible in Figure 3. Furthermore, the channel plate 11 has an inlet connection 43 on an upper side 52, which can be seen in the perspective view in Figure 2, from which an inlet channel 44, visible in Figure 3, extends and opens into the working channel 42. By way of example, the channel plate 11 is cuboid-shaped, with the supply connection 7 and the working connection 8 each being arranged on opposite end faces, which are part of the front side 21 and the rear side 22, respectively, of the mass flow controller 1.

[0052] On a left side surface 51 of the channel plate 11, which is preferably flat, two sensor bores 57, 58 are provided, which can be seen in Figure 3 and each open into the working channel 42. Furthermore, further, invisible threaded bores are provided on the left side surface 51, which enable pressure sensors 61, 62 to be sealed onto the channel plate 11. It is provided that the pressure sensors 61, 62, which form a pressure sensor arrangement, are arranged on an upper side of the sensor board 12 opposite the left side surface 51 and can be fastened to the left side surface 51 of the channel plate 11 with fastening screws 63, which pass through the sensor board 12. Purely by way of example, it is provided that the sensor board 12 comprises an electronic circuit (not shown in detail) which is designed for processing sensor signals from the pressure sensors 61, 62.Furthermore, it is provided that the sensor board 12 is electrically connected to the control board 75 in a manner not shown, for example via a cable connection or a flexible conductor arrangement, in order to be able to provide the sensor signals of the pressure sensors 61, 62 to the electronic control circuit on the control board 75. By way of example, it is assumed that the electronic control circuit on the control board 75 also contains the controller which, based on the sensor signals of the pressure sensors 61, 62, controls valve arrangements 72 arranged in the valve module 2.

[0053] Opposite the upper side 52 of the channel plate 11 is arranged the valve module 2, which comprises a valve housing 71 and a plurality of valve assemblies 72 accommodated in the valve housing 71, a collecting plate 73, a circuit board holder 74, a control board 75, an upper sealing element 76 and a lower sealing element 77.

[0054] The valve housing 71 has a cuboid shape, with a left screw guide 80 and a right screw guide 81 being attached to opposite narrow sides 78, 79 of the valve housing 71. Each of the two screw guides 80, 81 is secured by a fastening screw

[0055] 82, which are provided for fixing the valve housing 71 and the collecting plate 73 to the channel plate 11. The two sealing elements 76, 77 serve to seal between the valve housing 71, the collecting plate 73 and the channel plate 11.

[0056] Purely by way of example, it is provided that the valve housing 71 has a width extension 83 and a width extension

[0057] 83 has a substantially corresponding height extension 84 , while a depth extension 85 of the valve housing 71 has only a fraction , for example 20 percent , of the width extension 8 .

[0058] Starting from an underside 86 of the valve housing 71, five valve shafts 88, which can be seen purely by way of example in Figure 3, extend in the direction of the vertical extension 84. By way of example, it is provided that a cartridge-like valve arrangement 72 is accommodated in each of the valve shafts 88, which is described in more detail below in connection with Figure 3 and which can be inserted into the valve shaft 88 through an opening 90 of the respective valve shaft 88.

[0059] In an embodiment of the mass flow controller 1 not shown, it can be provided that in one or more of the valve shafts 88, only a placeholder is arranged instead of a valve arrangement 72, unless all possible valve arrangements 72 as shown in Figures 2 and 3 are required. A circuit board holder 74 is arranged opposite an upper side 87 of the valve housing 71, which is designed to receive the control circuit board 75.

[0060] The control board 75 is designed as a printed circuit board (PCB) and carries electrical and electronic components (not shown in detail) that form a control device for the mass flow controller 1. For example, in addition to passive electrical components (not shown), such as resistors and capacitors, one or more microcontrollers or microprocessors are also arranged on the control board 75, with the aid of which the control of the fluid mass flow described in more detail below can be carried out.

[0061] Since each of the valve assemblies 72 has, purely by way of example, two piezo bender 101 described in more detail below, the control board 75 is further equipped with high-voltage components (not shown) which are designed for the individual high-voltage supply, in particular with a direct voltage in the range from 250 volts to 500 volts, of each of the piezo bender 101 of the respective valve assembly 72. It is preferably provided that all piezo bender 101 of all valve assemblies 72 are controlled by the control device on the control board 75 in such a way that an at least substantially identical portion of the fluid mass flow to be provided at the working connection 8 flows through each of the valve assemblies 72. Deviating from the representation in Figure 3, it can also be provided that some or all of the valve arrangements 72 are each equipped with only one piezo bender 101.

[0062] In a minimal configuration of the mass flow controller 1 (not shown), either one valve arrangement with two piezo benders or two valve arrangements, each with one piezo bender, are provided, so that at least a double valve function is always provided.

[0063] As can be seen from the illustration in Figure 3, the piezo benders 101 of the valve arrangements 72 are electrically connected to the control board 75 via contact pins 105, which each pass through the board holder 74.

[0064] Furthermore, it can be seen from Figure 3 that each of the valve assemblies 72 has a valve channel 102 which is formed inside a cartridge housing 108 of the respective valve assembly 72, visible in the illustrations in Figures 2 and 3. The valve channels 102 of the valve assemblies 72 are in fluid communication with a feed channel 89 of the valve housing 71, which in turn is fluidly connected to the supply channel 41 via a branch channel 53 in the channel plate 11. Thus, all valve channels 102 of the valve assemblies 72 are equally subjected to a uniform fluid pressure provided at the supply connection 7.

[0065] As can be seen from the illustration in Figure 3, the two piezo benders 101 are arranged in a mirror image of one another in the respective cartridge housing 108. Furthermore, it is provided that the piezo benders 101 are pressed against bearing edges (not shown in detail) in the valve channel 102 by leaf springs 106, which are also accommodated in the valve channel 102. An arrangement of these bearing edges is adapted to the strip-shaped piezo benders 101 in such a way that the piezo benders 101 experience a change in curvature when a high electrical voltage is provided to the respectively associated contact pins 105. As a result, sealing elements 103 attached to the ends of mutually facing surfaces of the piezo benders 101 of the respective valve arrangement 72 can be lifted off from a respective oppositely arranged valve seat 104, as can be seen in particular from the detailed illustration in Figure 3.It should be noted that due to the sectional view, only a sealing element 103 of the right piezo bender 101 can be seen; the same applies to the valve seat 104, which is also only shown for the right piezo bender 101.

[0066] Extending from the respective valve seat 104 into the cartridge housing 108 is an outlet channel (not shown in detail), through which the respective portion of the fluid mass flow that has passed through the valve seat 104 can exit the cartridge housing 108. An outlet nozzle 111, visible in Figure 2, projects into this outlet channel and extends from an upper side 112 of the collecting plate 73, which is essentially designed as a plane-parallel plate, in the direction of the respective valve arrangement 72, and is sealingly connected to the outlet channel. As can be seen from the sectional view of Figure 3, the collecting plate 73 is provided on a bottom side 114 with a cuboid-shaped recess 113, which forms a collecting space for the proportional fluid mass flows that are provided by the respective valve arrangements 72 via the outlet channels and the associated outlet nozzles 111.

[0067] Starting from this recess 113, which can also be referred to as the output connection of the valve module 2, the fluid mass flow can flow into the inlet connection 43 of the channel plate 11 and from there is guided into the inlet channel 44. The inlet channel 44 has an inlet channel axis 46 which is aligned transversely to a central axis 45 of the working channel 42 and thus enters the inlet channel 44 in a radial direction. Since the working channel 42 extends in a straight line along the central axis 45 to the working connection 8, the fluid mass flow is deflected at a right angle parallel to the central axis 45 of the working channel 42 upon exiting the inlet channel 44 and can flow from there to the working connection 8. This determines a main flow direction which is symbolically shown in the working channel 42 and is aligned parallel to the central axis 45.

[0068] By way of example, it is provided that the working channel 42 extends counter to the main flow direction 47 over the inlet channel 44 along the central axis 45, whereby a section of the working channel 42 designed in the manner of a blind hole is formed, which section is referred to as the rest zone 48. Due to the above-described deflection of the fluid mass flow starting from the inlet connection 43 in the main flow direction 47 in the working channel 42, a fluid pressure can be determined in the rest zone 48, in which the fluid pressure has only small or even negligible dynamic components and predominantly or even entirely only static components. Accordingly, in the rest zone 48, a first sensor bore 57 is introduced into the working channel 42 transversely to the central axis 45, into which the first pressure sensor 61, which is attached to the control board 12, projects.A second sensor bore 58 is also introduced into the working channel 42 transversely to the central axis 45, the second sensor bore 58 being concealed in the illustration in Figure 3 by the turbulence throttle 201 described in more detail below and is therefore only shown in dashed lines. A second pressure sensor 62, which is also attached to the control board 12, projects into the second sensor bore 58. In order to enable reliable and precise differential pressure measurement in the working channel 42, the working channel 42 is provided with a flow throttle designed purely as an example as a turbulence throttle 201, which extends completely over the cross section of the working channel 42 and is arranged between the inlet channel 44 and the working connection 8.

[0069] The turbulence throttle 201, shown in more detail in Figure 4, is designed as an independent assembly that can be mounted independently of other components of the mass flow controller 1 and tested for its functionality. The turbulence throttle 201 comprises a tubular throttle sleeve 203, which is designed purely as an example, rotationally symmetrical to a central axis 202 and extends along the central axis 202.

[0070] An outer surface 204 of the throttle sleeve 203 is divided purely by way of example into three sections adjoining one another along the central axis 202, namely a first guide section 205, a sealing section 206 and a second guide section 207.

[0071] Here, the first guide section 205 has a first outer diameter 231, which essentially corresponds to an inner diameter of a first throttle section 49 in the working channel 42, which serves to receive the first guide section 205. For example, it can be provided that the first guide section 205 and the first throttle section 49 are provided with corresponding external and internal threads, respectively, so that the turbulence throttle 201 can be screwed into the working channel 42.The sealing section 206 arranged between the first guide section 205 and the second guide section 207 has a smaller outer diameter 233 than the two guide sections 205, 207 and, when the turbulence throttle 201 is mounted in the throttle section 49 of the working channel 42, forms with the throttle section 49 a first annular channel 54 in which a sealing ring 227 is arranged, which ensures that the throttle sleeve 203 is sealed against the throttle section 49. Furthermore, it is provided that the second guide section 207 has a similar or identical outer diameter 232 to that of the first guide section 205.Since the working channel 42 has a second throttle section 50 with a larger inner diameter adjacent to the throttle section 49 in the direction of the main flow direction 47, a second annular channel 55 is formed by the turbulence throttle 201 with the working channel 42, which is delimited by an annular collar 228 formed at the end of the throttle sleeve 203 and projecting outwards in the radial direction. The second pressure sensor 62 is arranged in this second annular channel 55, which, similar to the quiet zone 48, is arranged fluidically away from the main flow of the fluid mass flow.

[0072] A recess 208 of the throttle sleeve 203, which is designed purely as an example to be rotationally symmetrical to the central axis 202, can be divided into an inflow section 209, a holding section 210 and an outflow section 211. The inflow section 209 and the outflow section 211 have a larger diameter than the holding section 210. Purely as an example, it is provided that both the inflow section 209 and the outflow section 211 are each designed to be slightly conical, starting from the holding section 210, and widen to an inflow opening 212 or to an outflow opening 213. A plurality of flow guide elements are arranged in the inflow section 209, with which the desired turbulence throttling function can be brought about when a gaseous fluid flows through the turbulence throttle 201.Starting from the inlet opening 212, in the inlet section 209 there is an inlet plate 214, a throttle plate 215 directly adjacent thereto in the axial direction along the central axis 202 and an outlet plate directly adjacent to the throttle plate 215 in the axial direction along the central axis 202.

[0073] 216 is provided .

[0074] As can be seen from the illustration in Figure 5, the inlet plate 214 is circular disk-shaped and designed as a plane-parallel plate and has several inlet holes

[0075] 217, which are arranged purely by way of example on a common pitch circle 220 at a constant angular pitch relative to one another. For example, the inlet plate 214 can be made from a metal sheet that is provided with the inlet holes 217 by a laser cutting process or an etching process. Alternatively, the inlet plate can also be made from a plastic material, in particular by a plastic injection molding process.

[0076] It is preferably provided that the inlet plate 214 and the outlet plate 216 are of identical construction.

[0077] The throttle plate 215 has a considerably greater axial extent along the central axis 202 compared to the inlet plate 214 and the outlet plate 216. Functionally, the throttle plate 215 can be divided into a throttle disk 221 and an upstream spacer ring 222 and a downstream spacer ring 223. The throttle disk 221 is circular in shape and has an outer diameter (not designated) that is slightly smaller than an inner diameter (likewise not designated) of the inflow section 209. The throttle disk 221 is provided with precisely one throttle bore 218 that is arranged coaxially to the outer diameter of the throttle disk 221. Purely as an example, the throttle bore 218 is circular in shape.As can be seen from the illustration in Figure 4, the throttle plate 221 has an axial extension along the central axis 202 which corresponds approximately to seven times the axial extension of the inlet plate 214 or the outlet plate 216. On opposite axial end faces 224, 225, circular spacer rings 222, 223 protrude from the throttle plate 221 and serve as axial spacers for the inlet plate 214 or the outlet plate 216. The spacer rings 222 , 223 each have an undesignated inner diameter which is selected such that the inlet bores 217 of the inlet plate 214 and the outlet bores 219 of the outlet plate 216 are not covered .Rather, the spacer rings 222, 223 are provided exclusively for the spaced arrangement of the inlet plate 214 and the outlet plate 216 and have no significant contribution to the throttling effect of the turbulence throttle 201 described in more detail below.

[0078] The task of the holding section 210, which has a slightly smaller inner diameter than the subassembly comprising the inlet plate 214, the throttle plate 215 and the outlet plate 216, is solely to provide axial support for this subassembly and also has no significant contribution to the throttling effect of the turbulence throttle 201, which is described in more detail below.

[0079] The outflow section 211 has a substantially identical axial extension along the central axis as the inflow section 209 and serves to calm the fluid flow after passing the flow guide elements described above (inlet plate 214, throttle plate 215, outlet plate 216).

[0080] Furthermore, a radial bore 226 is formed in the outflow section 211, which ensures a fluid communication between the outflow section 211 and the second annular channel 55 described above and thus enables a fluid pressure prevailing in the outflow section 211 to be tapped for the purpose of pressure determination by the second pressure sensor 62.

[0081] As can be seen from the illustration in Figure 5, a projection 227 of the throttle bore 218 onto the inlet plate 214 has no overlaps with the inlet bores 217. This ensures that a fluid, in particular a compressed air stream or a process gas stream flowing through the turbulence throttle 201, experiences multiple deflections of its flow direction. This causes the desired turbulent flow in the turbulence throttle 201.The advantage of such a turbulent flow is that the compact design of the turbulence throttle 201 enables a differential pressure measurement in which a pressure value upstream or in front of the turbulence throttle 201, in particular in the area of ​​the inlet opening 212, can be significantly differentiated from a pressure value downstream or after the turbulence throttle 201, in particular at the radial bore 226, thereby enabling a precise differential pressure measurement. From this differential pressure measurement, the fluid mass flow through the turbulence throttle 201 can then be determined with high accuracy. In principle, the mass flow controller 1 is intended to be used to provide a fluid mass flow to a fluid consumer. In addition, the mass flow controller 1 can also be used as a pressure controller.

[0082] In the illustration in Figure 7, which shows a detail of the channel plate 11 with the working channel 42 formed therein, the only difference from the illustration in Figure 3 is that instead of the second absolute pressure sensor 62, a differential pressure sensor 66 is used, which is designed to determine the pressure difference across the turbulence throttle 201. For this purpose, the differential pressure sensor 66 has a first tap 67, which is provided for pressure determination immediately upstream of the turbulence throttle 201. Furthermore, the differential pressure sensor 66 has a second tap 68, which is designed to pressure determination in the second 55. The tap for the first absolute pressure sensor 61 takes place in the same way as in the illustration in Figure 3 in the rest zone 48. Deviating from the representation in Figure 7, the first tap 67 can also be arranged in the rest zone 48.

Claims

Claims 1. Mass flow controller (1) for providing a fluid mass flow, comprising a valve module (2) and a measuring arrangement (3), wherein the valve module (2) has a supply connection (7) for connection to a fluid source and an output connection (113) for providing a fluid mass flow to the measuring arrangement (3), and in the valve module (2) between the supply connection (7) and the output connection (113) at least two valve arrangements (72) are arranged, each of which is designed to proportionally influence the fluid mass flow, and wherein the measuring arrangement (3) has an inlet connection (43) for connection to the output connection (113) and a working connection (8) for connection to a fluid consumer, wherein a working channel (42) extends between the inlet connection (43) and the working connection (8), in which working channel a flow throttle (201) is arranged, and wherein the working channel (42 is assigned a pressure sensor arrangement (61,62) for determining a differential pressure across the flow restrictor (201), and with a control device (75) which is electrically connected to the pressure sensor arrangement (61, 62) and to the valve module (2) and which is designed to determine a fluid mass flow in the working channel (42) on the basis of sensor signals from the pressure sensor arrangement (61, 62) and for the controlled control of the valve arrangements (72) to maintain a setpoint for the fluid mass flow.

2. Mass flow controller (1) according to claim 1, characterized in that the flow throttle is designed as a turbulence throttle (201) which has at least two flow guide elements from the group: inlet plate (214) with at least one inlet bore (217), throttle plate (215) with at least one throttle bore (218), outlet plate (216) with at least one outlet bore (219), which are arranged at a distance from one another in the working channel (42), wherein the at least one inlet bore (217), the at least one throttle bore (218) and the at least one outlet bore (219) are each arranged offset from one another in a spatial direction transverse to a central axis (45) of the working channel (42).

3. Mass flow regulator (1) according to claim 2, characterized in that the at least one inlet bore (217), the at least one throttle bore (218) and the at least one outlet bore (219) are arranged offset from one another without overlap in a projection plane oriented transversely to the central axis (45).

4. Mass flow controller (1) according to claim 2, characterized in that the inlet plate (214) has a plurality of inlet bores (217) which are at a radial distance from the central axis (45) and / or that the throttle bore (218) of the throttle plate (215) is aligned coaxially to the central axis (45) and / or that the outlet plate (216) has a plurality of outlet bores (219) which are at a radial distance from the central axis (45).

5. Mass flow controller (1) according to claim 4, characterized in that a total cross section of the inlet bores (217) is equal to or greater than a cross section of the throttle bore (218) and / or that the cross section of the Throttle bore (218) is equal to or larger than the total cross section of the outlet bores (219).

6. Mass flow controller (1) according to one of claims 2 to 5, characterized in that the throttle plate (215) is designed as a circular disk (221) through which the throttle bore (218) extends from a front circular surface (224) to a rear circular surface (225), and in that a front annular collar (222) extends in the axial direction from the front circular surface (224) and is designed for flat contact with the inlet plate (214), and / or a rear annular collar (223) extends in the axial direction from the rear circular surface (225) and is designed for flat contact with the outlet plate (216).

7. Mass flow controller (1) according to one of claims 2 to 6, characterized in that all inlet bores (217) are formed with the same bore diameter, with the same angular pitch and with the same radial distance from the central axis (45) on the inlet plate (214) and / or that all outlet bores (219) are formed with the same bore diameter, with the same angular pitch and with the same radial distance from the central axis (45) on the outlet plate (216).

8. Mass flow regulator (1) according to one of claims 2 to 7, characterized in that an axial extension of the throttle bore (218) along the central axis (45) corresponds to 2 times to 10 times an axial extension of the inlet bore (217) and / or 2 times to 10 times an axial extension of the outlet bore (219).

9. Mass flow controller (1) according to one of claims 2 to 8, characterized in that the turbulence throttle (201) comprises the inlet plate (214), the throttle plate (215) and the outlet plate (216) and that the inlet plate (214), the throttle plate (215) and the outlet plate (216) are arranged in a throttle sleeve (203).

10. Mass flow controller (1) according to one of claims 1 to 9, characterized in that the valve module (2) has a plurality of valve shafts (88) which have extension axes aligned parallel to one another and which are each designed to receive a valve arrangement (72), wherein mouth openings (90) of the valve shafts (88) are arranged adjacent to the output connection (113) and wherein the output connection (113) opens into the working channel (42) in the radial direction.

11. Mass flow controller (1) according to one of claims 9 or 10, characterized in that each valve arrangement (72) has at least one valve channel (102) extending between the supply connection (7) and the output connection (113), in which a valve seat (104) and a piezo bender (101) are arranged, wherein the piezo bender (101) carries a sealing element (103) which opens or closes the valve seat (104) depending on a functional position of the piezo bender (101).

12. Mass flow controller (1) according to one of claims 1 to 11, characterized in that the pressure sensor arrangement (61, 62) has a first pressure sensor, in particular a first absolute pressure sensor (61), which is connected to the working channel (42) upstream of the flow throttle (201), in particular the turbulence throttle, and that the pressure sensor arrangement (61, 62) has a second pressure sensor, in particular a second absolute pressure sensor (62) which is connected to the working channel (42) downstream of the flow throttle (201), in particular the turbulence throttle.

13. Mass flow controller (1) according to one of claims 1 to 11, characterized in that the pressure sensor arrangement has a first absolute pressure sensor (61) which is connected to the working channel (42) upstream of the flow throttle (201), in particular the turbulence throttle, and in that the pressure sensor arrangement has a differential pressure sensor (66) which is connected to a first differential pressure measuring point (67) arranged upstream of the flow throttle (201) in the working channel (42) and to a second differential pressure measuring point (68) arranged downstream of the flow throttle (201), in particular the turbulence throttle, in the working channel (42).

14. Mass flow controller (1) according to one of claims 12 or 13, characterized in that the working channel (42) has a rest zone (48) designed as a blind hole in a spatial direction parallel to the central axis (45), which is opposite to a main flow direction (47) for the fluid flow, and that the first absolute pressure sensor (61) is arranged in the rest zone (48).

15. Mass flow controller (1) according to one of the preceding claims, characterized in that the control device (75) is provided with an interface (4) for a supply of electrical energy and for communication with a communication network from the group: Modbus, IO-Link, EtherCat, Profibus, DeviceNet, Ethernet-IP, Profinet.

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