Valve device and method for regulating the pressure of a fluid

Abstract

The invention relates to a valve device and a method for regulating the pressure of a fluid. A valve device with a proportional valve is provided, wherein compliance with a certain setpoint or minimum pressure in a volume connectable to the valve device is ensured. The valve device (1) forms the core of the invention, and comprises a proportional valve (2), the proportional valve having an orifice cross section that is continuously variable via an actuator, a sensor device for detecting a valve output pressure, a digital control device, and a switching valve (3) arranged in parallel with the proportional valve (2), wherein the orifice cross section of the switching valve is smaller than the maximum orifice cross section of the proportional valve (2), and wherein the control device is programmed to automatically calculate the maximum achievable working pressure of the proportional valve (2) at the maximum orifice size according to the currently given valve output pressure and the current position of the actuator during operation, and to additionally open the switching valve (3) when the calculated maximum achievable working pressure is below a predetermined setpoint working pressure by a deviation value that can be determined.

Description

Technical Field

[0001] The present invention relates to a valve device and a method for regulating the pressure of a fluid. Background Art

[0002] In the prior art of fluid technology control or regulation systems, it is often necessary to comply with and ensure a specific rated or minimum pressure in the connected volume that may be variable over time in an application-specific manner, for example, in order to ensure sufficient reaction speed and / or closing force of the tool (laser cutting, welding gun control), for the spatially error-free shaping of the container flask when the container is blow-molded from the parison or for the sufficiently fast refilling of the tank (Tank) or storage. In order to achieve such precise pneumatic control or regulation tasks, proportional valves with variable orifice cross sections are often used in the prior art. However, in this case, in principle, the maximum manufacturable orifice cross section of a suitable proportional valve may prove insufficient in a specific application to ensure a specific rated or minimum pressure with respect to a specific special system state (for example, the final blow molding of the container or the rapid refilling of the tank). This is especially applicable when an open volume, such as a cutting nozzle or a perforated plate, is pressure-loaded with a process gas during laser cutting or when sufficient cooling air flow is provided after the final blow molding of the glass bottle. In the context of efficient system design and the desired universal use of components, in this case, the parallel arrangement of an additional switching valve (“booster”) for such system states may be preferable to a higher-performance design of the proportional valve. This system configuration has the additional advantage that the increase in the maximum system performance is not affected by the control or regulation accuracy burden in the performance range of the proportional valve. However, in this case, the task of effective functional integration of the additional switching valve is posed.

[0003] WO 2013 / 135838 A1 discloses a valve device for stretch blow molding containers, in which, in addition to a proportional valve, a switching valve or a plurality of switching valves are additionally provided for applying an increased pressure level to the molded part. To operate the valve, WO 2013 / 135838 A1 proposes a time-based control device or a control device that is dependent on the position of a stretch rod; in addition, the proportional valve is disclosed to be switched off when a pressure threshold value in the molded part is reached. No device is disclosed for determining in advance the maximum achievable working pressure level with the proportional valve or for detecting in advance that a nominal or minimum pressure has not been exceeded. In addition, it is relatively complex in terms of design to provide and integrate a sensor system that is sufficiently suitable in an application-specific manner for detecting the actual pressure in the expanded molded part.

[0004] EP 0 666 792 B1 discloses a pressure control and / or regulating device for a fluid medium to be supplied to an injection mold in addition to a plastic melt, wherein a plurality of parallel flow paths leading from a pressure intensifier to an injection system are provided, and each of the flow paths is equipped with a medium inflow control valve. The medium inflow control valve may be a proportional valve. The medium inflow control valve may be controlled by a PID regulator and a logic circuit so as to switch to blocking or flow according to a pressure gradient detected by a pressure sensor in the cavity of the injection mold. A device for determining in advance the maximum achievable working pressure level using a proportional valve or for identifying in advance that a rated or minimum pressure has not been exceeded is not disclosed. In addition, providing and integrating a sensor system suitable for detecting the actual pressure in the cavity of the injection mold in an application-specific manner is relatively complex in construction.

[0005] DE 10 2010 035 747 A1, DE 27 51 743 C2 and US Pat. No. 5,329,965 A disclose valve devices having a plurality of electrically actuated individual valves connected in parallel, which are arranged in a control circuit. The disclosed valve devices are relatively complex in design. No device is disclosed for determining in advance the maximum achievable operating pressure level with a proportional valve or for detecting in advance that a nominal or minimum pressure has not been exceeded. Summary of the invention

[0006] The object of the present invention is to provide a valve device for regulating the pressure of a fluid using a proportional valve, wherein compliance with a specific setpoint or minimum pressure in a volume connectable to the valve device is ensured by constructively simple measures and wherein the disadvantages of the prior art are avoided.

[0007] This object is achieved according to the invention by a valve device for regulating the pressure of a fluid according to claim 1 and a method for regulating the pressure of a fluid according to claim 6. Advantageous developments of the invention are described in the dependent claims.

[0008] A valve device for regulating the pressure of a fluid forms the core of the invention, the valve device having a proportional valve with an orifice cross section that is continuously variable by an actuator, a sensor device for detecting the valve output pressure, a digital control device and a switching valve arranged in parallel with the proportional valve, wherein the orifice cross section of the switching valve is smaller than the maximum orifice cross section of the proportional valve, wherein the control device is set up in programming technology to automatically calculate the maximum achievable working pressure of the proportional valve with the maximum orifice size of the proportional valve according to the currently given valve output pressure and the current position of the actuator during operation, and additionally open the switching valve when the calculated maximum achievable working pressure is below a predetermined setpoint working pressure by a deviation value that can be determined. This calculation is based on a model mapping of the fluid technology application system on the working side of the proportional valve. For this purpose, the control device is set up in programming technology to include instructions, which are used to map a suitable technical calculation model corresponding to the corresponding application system and constructed according to the general laws of fluid mechanics. In this case, the calculation model can be approximately simplified. In the simplest application case, the working pressure corresponds to the detected valve output pressure in the calculation model. In the simplest application case, the deviation value can be "0", whereby the switching valve is opened as soon as the calculated maximum achievable operating pressure does not exceed the predefinable setpoint operating pressure. In order to make the switching behavior dynamic, a deviation value greater than but not equal to 0 is determined, whereby the switching behavior is shifted forward in time, i.e. the switching valve is opened even before the predefinable setpoint operating pressure is exceeded by the maximum achievable operating pressure.

[0009] The invention has recognized that within the scope of an efficient system design of a valve arrangement with a proportional valve, compliance with a specific setpoint or minimum pressure in a volume connectable to the valve arrangement can be ensured in a structurally simple manner if the maximum achievable operating pressure is calculated during operation depending on the respective current system state and, depending on the calculation, a switching valve arranged in parallel with the proportional valve is additionally opened in the event of a detected imminent under-exceeding of the setpoint or minimum pressure. A correspondingly configured valve arrangement furthermore enables efficient and precise pressure regulation in the connected volume in a structurally simple manner, with compliance with a specific setpoint or minimum pressure, in particular at the open volume.

[0010] Depending on the pneumatic application, in order to increase the accuracy of the calculation result when calculating the maximum achievable working pressure, the aerodynamic resistance (flow resistance) of the further line path (Leitungsführung) from the valve outlet to the line end on the working side of the valve device is additionally taken into account. Within the scope of the technical calculation model, this variable can be considered approximately as a constant to be determined, for example.

[0011] In order to further increase the accuracy of the calculation result when calculating the maximum achievable working pressure, the outflow characteristic of the line end on the working side of the valve device is additionally taken into account. Depending on the fluid technology application, this can be, for example, an orifice plate or a nozzle, the outflow characteristic of which can be taken into account, for example, approximately as a constant to be determined within the scope of the technical calculation model.

[0012] The accuracy of the calculation result can be further improved when calculating the maximum achievable working pressure by additionally taking into account the supply pressure drop that occurs with an increase in the orifice cross section of the proportional valve, that is, in this case the pressure drop that occurs in the section between the supply source and the valve inlet.

[0013] In order to stabilize the control behavior of the valve arrangement, the switching hysteresis is taken into account when determining the opening time of the switching valve.

[0014] A method for regulating the pressure of a fluid by means of a valve device constitutes another core of the present invention, the valve device comprising a proportional valve having an orifice cross section that is continuously variable by means of an actuator and a sensor device for detecting a valve output pressure; a digital regulating device and a switching valve arranged in parallel with the proportional valve, wherein the orifice cross section of the switching valve is smaller than the maximum orifice cross section of the proportional valve, wherein the digital regulating device automatically calculates during operation the maximum achievable working pressure of the proportional valve using the maximum orifice size of the proportional valve according to the currently given valve output pressure and the current position of the actuator and compares it with a predeterminable rated working pressure, and when the calculated maximum achievable working pressure is below a deviation value that can be determined by the predeterminable rated working pressure, a setting amount is generated for additionally opening the switching valve.

[0015] In order to increase the accuracy of the calculation result, the aerodynamic resistance (flow resistance) of the further line path from the valve outlet to the line end is additionally taken into account when calculating the maximum achievable operating pressure.

[0016] In order to further improve the accuracy of the calculation results, the outflow characteristics of the pipeline end are additionally taken into account when calculating the maximum achievable working pressure. Depending on the fluid technology application, this can be, for example, an orifice plate or a nozzle, the outflow characteristics of which can be taken into account, for example, approximately as a constant to be determined within the scope of the technical calculation model.

[0017] A further increase in the accuracy of the calculation result when calculating the maximum achievable operating pressure is achieved by additionally taking into account the supply pressure drop that occurs with an increase in the opening cross section of the proportional valve when calculating the maximum achievable operating pressure.

[0018] In order to stabilize the control behavior of the valve arrangement, the switching hysteresis is taken into account when determining the opening time of the switching valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other advantages of the present invention are described in more detail below together with the description of the preferred embodiments of the present invention according to the figures. Among them:

[0020] Figure 1 An equivalent circuit diagram of a pneumatic valve device is shown;

[0021] Figure 2 Show according to Figure 1 The electrical equivalent circuit diagram of the valve device;

[0022] Figure 3 A diagram is shown to illustrate the composition of the air quantity released by the valve device. DETAILED DESCRIPTION

[0023] Figure 1 1 shows a simplified pneumatic equivalent circuit diagram of a valve device 1. The valve device 1 comprises a proportional valve 2, a switching valve 3 and a microcontroller 4. The important functional components of the valve device 1 are constructed in a common housing symbolically represented by a dotted frame. The valve device 1 is connected to a volume V (at Figure 1 (not shown in more detail), the volume V is an open volume, such as a processing head of a laser cutting device. For this purpose, the working line 5 opens into the volume V at its line end, wherein in accordance with Figure 1In the embodiment of the invention, the line end of the working line 5 is configured as an open orifice plate, which describes a sudden cross-sectional constriction at the line end. The proportional valve 2 is configured as a 3 / 3-way proportional valve. In its rest position in the no-flow state, the proportional valve 2 adopts its blocked intermediate position (NC), in which the working line 5 is blocked. In order to load the working line 5, the proportional valve 2 can be switched to a first switching position by the proportional magnet 7a against the spring load of the mechanical return spring 8b, in which the proportional valve connects the working line 5 to the compressed air supply device 9 with a variable valve opening cross section. In order to exhaust the working line 5, the proportional valve 2 can be switched to a second switching position by the proportional magnet 7b against the spring load of the mechanical return spring 8a, in which the proportional valve connects the working line 5 to the exhaust line 10 with a variable valve opening cross section. The electrical control of the proportional magnets 7a and 7b is carried out by a microcontroller 4 integrated into the housing of the valve device 1, which serves as a digital control device of the valve device 1. The microcontroller 4 is designed as a "single board computer (SBC)", in which all electronic components required for operation (CPU, memory, input and output interfaces, A / D converter, DMA controller, etc.) are combined on a single printed circuit board. The microcontroller 4 receives a continuous electrical signal from the pressure sensor 11, which represents the respective current valve output pressure at the proportional valve 2. The microcontroller 4 is also designed with a data communication interface 12, which can be used to communicate with a higher-level programmable logic device controller (SPS, in Figure 1 The microcontroller 4 receives the dynamically predeterminable nominal operating pressure from the programmable logic device controller during operation. The microcontroller 4 is programmed to automatically calculate the respective maximum achievable working pressure at the maximum bore size of the proportional valve from the currently specified valve output pressure and the current position of the actuator of the proportional valve 2 known to it from the current control state during operation and compare it with the respectively predetermined setpoint pressure. Furthermore, the microcontroller 4 is programmed to automatically calculate the respective maximum achievable working pressure at the maximum bore size of the proportional valve from the currently specified valve output pressure and the current position of the actuator of the proportional valve 2 known to it from the current control state and compare it with the respectively predetermined setpoint pressure. The switching valve 3 is additionally opened at a predeterminable deviation value in that the microcontroller controls the switching magnet 13. The switching valve 3 is arranged in a bypass line 14 extending between the compressed air supply device 9 and the working line 5 and blocks the bypass line in its static position in a no-flow state. In its switching position, an additional orifice cross section between the compressed air supply device 9 and the working line 5 is opened by the switching valve 3. The cross-sectional constriction 15 in the bypass line 14 is used to symbolically represent the following feature: the switchable line cross section of the bypass line 14 is smaller than the maximum hole size of the proportional valve 2. In practice, this can be achieved not only by the nominal width of the switching valve 3, the cross section of the bypass line 14 or the orifice plate or the throttle valve. The condition that the switchable line cross section of the bypass line 14 is smaller than the maximum hole size of the proportional valve 2 must be met so that the regulated combined air volume can be increased in a seamless manner.

[0024] Figure 2 Show according to Figure 1 The electrical equivalent circuit diagram of the valve device 1 is used to illustrate the parameters to be taken into account when configuring a suitable technical calculation model. On the input side, the pneumatic application system is loaded with supply pressure by the compressed air supply device 9. The air flow is subject to an aerodynamic resistance R2 until it enters the valve device 1, which is characterized by the cross section and the properties of the corresponding pipeline path. The valve device 1 is supplied with compressed air at a pressure p1 on the supply side. From the valve device 1, the compressed air is supplied as a mass flow with a pressure p2 set by the valve device 1. The air flow is subject to a further aerodynamic resistance R1 up to the end of the line, which is characterized by the cross section and properties of the corresponding further line path. The air flow finally passes through the end of the pipe configured as an orifice plate 6, wherein the outflow characteristic of the orifice plate 6 can be characterized by the conductance G and causes the loading of the volume V, which is Figure 2 The electrical equivalent circuit diagram shows capacitor C.

[0025] based on Figure 2 The electrical equivalent circuit diagram of the following represents a suitable technical calculation model: The air flow introduced into the working line 5 through the valve device 1 can generally be described as the mass flow :

[0026]

[0027] in

[0028] - outflow function,

[0029] -General functional relationship of proportional valve 1,

[0030] - General functional relationship of the switching valve 3,

[0031] - variable orifice cross section of proportional valves,

[0032] - the switching state of the switching valve,

[0033] - the orifice cross section of the switching valve,

[0034] - universal gas constant,

[0035] -temperature.

[0036] For a constant working volume V (= Figure 2 The capacitor C in the equivalent circuit diagram of It can be described as follows:

[0037]

[0038] The variables c1 and c2 can be approximately determined as constants for the corresponding pneumatic application system.

[0039] In order to be able to achieve a predeterminable setpoint operating pressure p with the valve device 1 CMD , the conditions must be met . It follows that if:

[0040]

[0041] If applicable, the switching valve 3 can be always opened, wherein the variable c3 can be approximately determined as a constant for the corresponding pneumatic application.

[0042] In order to be able to increase the adjusted combined regulated air quantity of the proportional valve 2 and the switching valve 3 in a seamless manner, the following condition must also be met, namely that the switchable line cross section of the bypass line 14 is smaller than the maximum bore size of the proportional valve 2 :

[0043] .

[0044] As the flow through proportional valve 2 increases, the supply pressure This can be simplified as follows:

[0045] .

[0046] In the case of a closed switching valve 3, with u=0, the mass flow introduced into the working line 5 is The equation is changed as follows:

[0047] .

[0048] On this basis, a suitable calculation algorithm for the maximum achievable working pressure of the proportional valve 2 at the maximum hole size can be derived as follows:

[0049] From the use of pressure increase The equations shown for and the mass flow introduced into the working line 5 when the switching valve 3 is closed, taking into account the supply pressure drop The calculable pressure increase is simplified in :

[0050] ,

[0051] The maximum achievable working pressure can be determined as follows:

[0052] .

[0053] The above equation can be discretized as follows:

[0054] .

[0055] The results of the above calculations are continuously accumulated in the buffer memory during operation. Based on the buffer data collection, the parameters required for operating the switching valve 3 for estimating the maximum achievable working pressure are: and Continuously as an optimization task at runtime:

[0056]

[0057] is solved, where Not only the data accumulation but also the optimization calculations are performed as background processes at runtime.

[0058] Taking the calculation basis shown above as a starting point, the switching time for opening the switching valve 3 is defined by

[0059] .

[0060] Taking this as a starting point, the following switching rules can actually be formulated to further improve the switching behavior:

[0061] In order to make the switching behavior dynamic, we first introduce the general parameters , using the general parameters, the switching behavior is shifted forward in time by an additional predeterminable deviation value>0, i.e. the switching valve is already opened before the predeterminable nominal operating pressure is exceeded by the maximum achievable operating pressure:

[0062]

[0063] It can be done by introducing additional parameters and The switching hysteresis of the valve device 1 is avoided by the following switching rule which stabilizes the switching behavior, which is caused by frequent switching on and off:

[0064]

[0065] parameter is an additional minimum rated value, under which the switching valve is shut off and the rated pressure p CMD Only regulated via proportional valve 2.

[0066] Figure 3 The valve device 1 is shown as a function of the predeterminable setpoint operating pressure p CMD Graph of the regulated air flow, wherein the abscissa axis shows the increasing preset value p CMD The ordinate axis shows the amount of air released from the valve device into the working side of the pneumatic application system. Straight line A shows that as the preset value p CMD Increases the total air volume introduced by the valve device into the working side of the pneumatic application system. CMD The total air volume A is composed of the partial air volume B released by the proportional valve 2 and the partial air volume C additionally released by the switching valve 3 from the time when the switching valve 3 is opened to the switching time point T. The total air volume A released by the valve device is the same as the partial air volume B released by the proportional valve 2 until the switching time point T, so the graph B first extends from the coordinate origin to the switching time point T in the same way as the straight line A, that is, it coincides with the straight line. With the opening of the switching valve 3, the supply pressure Decreases, so the partial air quantity B released by the proportional valve 2 also decreases from this time point. Since the partial air quantity C released by the switching valve 3 increases suddenly from this time point, the combined total air quantity A released by the valve device 1 continues to increase linearly.

[0067] Reference numerals list

[0068] 1 Valve device

[0069] 2 Proportional valve

[0070] 3 Switching valve

[0071] 4 Microcontroller

[0072] 5 Working pipeline

[0073] 6-well plate

[0074] 7a, 7b Proportional magnet

[0075] 8a, 8b Return spring

[0076] 9 Compressed air supply device

[0077] 10 Exhaust pipe

[0078] 11. Pressure sensor

[0079] 12 Data communication interface

[0080] 13 Switching magnets

[0081] 14 Bypass line

[0082] 15 Cross-sectional contraction.

Claims

1. A valve device (1) for regulating the pressure of a fluid, the valve device comprising a proportional valve (2), the proportional valve having an orifice cross section which is continuously variable via an actuator, a sensor device for detecting the valve output pressure; a digital regulating device and a switching valve (3) arranged in parallel with the proportional valve (2), wherein the orifice cross section of the switching valve (3) is smaller than the maximum orifice cross section of the proportional valve (2), characterized in that: The regulating device is programmed to automatically calculate during operation the maximum achievable working pressure of the proportional valve using the maximum bore size of the proportional valve (2) based on the currently specified valve output pressure and the current position of the actuator, and to additionally open the switching valve (3) when the calculated maximum achievable working pressure falls below a predeterminable setpoint working pressure by a deviation value.

2. The valve device (1) according to claim 1, characterized in that When calculating the maximum achievable working pressure, the aerodynamic resistance of the further line path from the valve outlet to the line end on the working side of the valve device (1) is additionally taken into account.

3. The valve device (1) according to claim 1 or 2, characterized in that When calculating the maximum achievable working pressure, the outflow characteristics of the line end on the working side of the valve device (1) are additionally taken into account.

4. The valve device (1) according to any one of claims 1 to 3, characterized in that When calculating the maximum achievable operating pressure, the supply pressure drop occurring with an increase in the opening cross section of the proportional valve (2) is additionally taken into account.

5. The valve device (1) according to any one of claims 1 to 4, characterized in that In order to stabilize the control behavior, the switching hysteresis is taken into account when determining the opening time of the switching valve (3).

6. A method for regulating the pressure of a fluid by means of a valve device (1), the valve device comprising a proportional valve (2), the proportional valve having an orifice cross section which is continuously variable by means of an actuator and a sensor device for detecting the valve output pressure; a digital regulating device and a switching valve (3) arranged in parallel with the proportional valve (2), wherein the orifice cross section of the switching valve (3) is smaller than the maximum orifice cross section of the proportional valve (2), characterized in that: The digital regulating device automatically calculates the maximum achievable working pressure of the proportional valve (2) based on the currently given valve output pressure and the current position of the actuator during operation and compares it with a predeterminable rated working pressure, and generates a control quantity for additionally opening the switching valve (3) when the calculated maximum achievable working pressure is below a deviation value that can be determined from the predeterminable rated working pressure.

7. The method according to claim 6, characterized in that When calculating the maximum achievable working pressure, the aerodynamic resistance of the further line path from the valve outlet to the line end on the working side of the valve device (1) is additionally taken into account.

8. The method according to claim 6 or 7, characterized in that: When calculating the maximum achievable working pressure, the outflow characteristics of the line end on the working side of the valve device (1) are additionally taken into account.

9. The method according to any one of claims 6 to 8, characterized in that The supply pressure drop that occurs with an increase in the opening cross section of the proportional valve is additionally taken into account when calculating the maximum achievable operating pressure.

10. The method according to any one of claims 6 to 9, characterized in that In order to stabilize the control behavior, the switching hysteresis is taken into account when determining the opening time of the switching valve.

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