Method for determining correction value for control device for control valve
Patent Information
- Application Number
- JP2024140892
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-08-23
- Filing Date
- 2024-08-22
- Publication Date
- 2025-03-07
Smart Images
Figure 2025031667000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for determining correction values for a control device for a control valve, and further to a method for controlling the position of a closing mechanism of the control valve using the correction values thus determined.
[0002] Control valves are used in particular in so-called vacuum technology to control the flow of fluid through a chamber. That is, by means of the control valve, the amount of fluid flowing through the chamber per unit of time can be set. Corresponding control valves are known in the prior art through well-known prior use. These control valves have a closing mechanism and an actuator for this closing mechanism. The respective position of the closing mechanism is determined by means of an encoder. The control device uses the encoder value output by the encoder as information about which position the closing mechanism is currently in. If the closing mechanism is in a minimum flow position, only a corresponding minimum amount of fluid flows through the flow opening. In this minimum flow position, the closing mechanism can completely close the flow opening, so that in this case there is no flow rate corresponding to a minimum flow rate. However, in the minimum flow position, a certain minimum flow rate may still be possible. If it is desired to flow more fluid through the chamber, the closing mechanism is moved by means of the actuator to a corresponding further open position, in which case exactly correspondingly more fluid flows through the chamber per unit of time.
[0003] The encoder values represent the respective positions of the closing mechanism. In the ideal case, in the minimum flow position the encoder value is equal to 0. In practice, however, this is not the case when the control valve is started up or when the control valve has to be maintained or when part or the entire control valve has to be replaced. That is to say, the encoder usually outputs another value, and not necessarily the value 0, in the minimum flow position.
[0004] It is therefore an object of the present invention to provide a method for determining correction values, which allows to solve this problem.
[0005] For this purpose, according to the invention, a method as claimed in claim 1 is proposed.
[0006] The present invention therefore provides a method for determining a correction value for a control device for a control valve, in which the control valve controls the fluid flow through a chamber, a closing mechanism of the control valve is arranged in different positions relative to a flow opening for the fluid flow by the control device using an actuator of the control valve, in particular an encoder for the control valve is provided, each position of the closing mechanism corresponds to an encoder value of the encoder, a pressure sensor measures pressure values, in particular representative of the fluid in the chamber, at the different positions of the closing mechanism, the control device identifies the position of the closing mechanism as a minimum flow position of the closing mechanism, in which the maximum of the pressure values is measured, and determines the correction value from the encoder value at which the minimum flow position is identified.
[0007] The encoder value at which the minimum flow position is identified can be specified as a correction value, for example, where the correction value is equal to the encoder value at which the minimum flow position is identified, however, the encoder value at which the minimum flow position is identified and the correction value may have another mathematical relationship to each other.
[0008] The basic idea of the invention is therefore to measure the pressure at various positions of the closing mechanism by means of a pressure sensor and to reproduce the respective positions of the closing mechanism by means of the respective encoder values. The minimum flow position of the closing mechanism, which may also be called the maximum closing position of the closing mechanism, is identified as the position at which the pressure value reaches its maximum value. In this case, a correction value is determined from the encoder value output by the encoder at the minimum flow position. The correction value may also be called an offset.
[0009] The method according to the invention is therefore a kind of calibration process, which is preferably carried out at least once at the start of operation, at the restart of operation or after maintenance or replacement of parts of the control valve or the entire device, in particular of parts of the actuator or the encoder. In this case, during the implementation of the method, it is determined which encoder value is output by the encoder in the minimum flow position of the closing mechanism. In the ideal case, the encoder value is equal to 0 in the minimum flow position. In this case, the correction value can also be set equal to 0. However, as a rule, in the minimum flow position of the closing mechanism, another encoder value is output by the encoder, from which the correction value can be determined in the subsequent operation of the control valve, in a manner that will be further described below.
[0010] The closing mechanism is the part of the control valve that is used to completely or partially close or open the flow opening. The closing mechanism can basically be shaped in various ways. However, in a preferred embodiment, the closing mechanism is a plate-like closing mechanism, which can also be called a closing plate or a valve plate.
[0011] The flow openings, which are correspondingly largely closed or opened by the closing mechanism depending on the position of the closing mechanism, may be located on the housing of the control valve. However, it is also possible for the flow openings to be located, for example, on the chamber wall of the chamber or in a fluid line connected to the chamber. In the minimum flow position, the closing mechanism may completely seal or close the flow openings, but may still allow a certain flow rate or a minimum flow rate. This can be configured by the skilled person according to what the skilled person requires for the respective use case. In any case, the minimum flow position may also be referred to as the maximum closing position of the closing mechanism.
[0012] The actuator of the control valve, which can move the opening mechanism to various positions relative to the flow opening, can be configured, for example, as an electric servomotor. However, it can also be a pneumatic drive, a hydraulic drive or a separately shaped motor drive. Mixtures of these drive forms, which are known per se, are also possible.
[0013] The encoder, however, does not have to be a direct part of the control valve, and in particular not a direct part of the actuator. The encoder can, for example, be integrated in or attached to the actuator, or can otherwise determine and reproduce the respective position of the closing mechanism. The encoder can, however, be analog, but also a digital encoder that measures in steps, i.e. in encoder steps. Correspondingly, in the case of a digital embodiment, these encoder values can be a sequence of integers. However, in an analog measuring encoder, the encoder values can also reproduce the respective position of the closing mechanism as rational numbers, i.e. with a decimal place. What is preferably determined in any case is that the respective position of the closing mechanism corresponds to exactly one encoder value of the encoder. The encoder can also be called a measurement value generator or, in the case of a rotary encoder, a rotary encoder. Correspondingly, the encoder values can be called measurement value generator values or rotary encoder values.
[0014] The fluid flow through the chamber, controlled by means of a control valve, may be a pure gas flow, but also a pure liquid flow or a mixture thereof.
[0015] The pressure value measured by the pressure sensor is preferably a pressure value representative of the fluid in the chamber. This pressure value can be measured directly in the chamber, but also in a line connected to the chamber, or at another suitable point. Preferably, the pressure value represents the current pressure in the chamber in any case.
[0016] When carrying out the method, the position of the closing mechanism should at least be the key quantity that mainly influences the respective pressure value, i.e. the pressure value should clearly correlate with the respective position of the closing mechanism or be influenced by the closing mechanism. In other words, the position of the closing mechanism should be a clearly identifiable key influence quantity on the pressure measured by the pressure sensor. A preferred embodiment of the method according to the invention specifies that the position of the closing mechanism during the execution of the method according to the invention for determining the correction value is the only influence quantity on the pressure measured by the pressure sensor. In this sense, it is preferably specified that the chamber is continuously circulated with fluid during the entire method, and the change in the position of the closing mechanism is the only quantity that changes during the method and influences the fluid flow.
[0017] The control device receives the encoder values from the encoder and the pressure values from the pressure sensor. Typically, the control device is primarily used to control the actuator to move the closing mechanism to the respective desired position depending on a set value, i.e. the respective desired position of the closing mechanism, taking into account the encoder values. However, in the method according to the invention, the control device is used precisely to carry out the method according to the invention and thus also to determine the correction values. The control device may be directly a part of the control valve. However, this control device may also be an external control device that is precisely connected to the control valve and the pressure sensor.
[0018] It is preferably specified that during the method according to the invention for determining the correction value, a pump is used to draw fluid through the flow control valve, the chamber and the flow opening. The control valve is preferably located between the pump and the chamber. The control valve may, for example, be arranged in a fluid line extending between the pump and the chamber or directly between the pump and the chamber.
[0019] Basically, one execution of the method according to the invention for determining the correction value can be considered sufficient. However, in particular if the closing mechanism has a certain amount of play or is a digital encoder that outputs only integer encoder values, it may be appropriate to execute the method for determining the correction value once when opening the control valve and once when closing the control valve. In a preferred variant of the invention, the method is determined by executing it a first time and then a second time, passing the position of the closing mechanism in a first direction and passing the position of the closing mechanism in a second direction opposite to the first direction, determining a first correction value and a second correction value, and determining the correction value based on the first and second correction values. In this case, determining the correction value based on two correction values, i.e. the first and the second correction value, can therefore also be said to be the final correction value taken into account during the operation of the control valve, as will be explained further below. To calculate this final correction value, for example, an average value can be calculated from the first and the second correction values. However, it is also conceivable to simply use the smaller or larger of the two correction values mentioned here as the final correction value.If the method according to the invention operates with a digital encoder whose encoder values are always integers, the final correction value thus calculated can also be rounded up or down accordingly to the nearest integer.
[0020] Basically, in the method according to the invention for determining the correction value, it is possible to cycle through all possible positions of the closing mechanism to ensure that the minimum flow position and the corresponding encoder value are found. However, as a rule, there is sufficient prior information, so that the skilled person only needs to cycle through the range of positions of the closing mechanism that is to be determined in advance, so that the minimum flow position is also included. Such prior information can be, for example, the encoder value at the minimum flow position of a previously used control valve when replacing a control valve or a part of a control valve. However, it is also possible for the control valve to have an initial position that is preset by a stop or in another way, and starting from this initial position of the closing mechanism when carrying out the method, the closing mechanism can be arranged in different positions relative to the flow opening for the fluid flow. The initial position that is preset in another way can be, for example, a marked position instead of a stop on the housing of the control valve, etc.
[0021] The method according to the invention for determining the correction value can be used for control valves of various configurations. The control valve can be, for example, a so-called butterfly valve, i.e. in other words a butterfly valve. It can be specified that the closing mechanism is a valve plate which can be pivoted by an actuator about a pivot axis which runs along the valve plate, the valve plate projecting beyond the pivot axis on opposite sides of the pivot axis. In so-called butterfly valves, it can also be said that the pivot axis runs in the plane of the valve plate, the concept of the plane of the valve plate naturally representing a certain simplification due to the spatial extent of the valve plate.
[0022] However, the control valve for carrying out the method according to the invention for determining the correction value can also be, for example, a shuttle valve. It can also be specified that the closing mechanism is a valve plate which can be pivoted by an actuator around a pivot axis which runs parallel to the normal of the valve plate. In shuttle valves, the pivot axis usually runs laterally to the edge of the valve plate. The valve plate can be connected to the pivot axis via a pivot arm. However, the bearing of the pivot axis can also be arranged directly on the edge of the valve plate.
[0023] In the control valves in the form of butterfly valves and shuttle valves mentioned so far, the different positions of the closing mechanism are always different angular positions. This does not necessarily have to be the case either. The method according to the invention for determining the correction value can also be used, for example, in valves in which the closing mechanism is supported, in particular linearly, so that it can slide. That is to say, in such control valves, the closing mechanism is moved back and forth between different positions which close the flow opening to a certain extent. For this purpose, the closing mechanism can be supported, for example, on a guide, in particular a linear guide or the like.
[0024] Once the correction values have been determined, they can then be used during the already described operation of the control valve, or in other words during the normal operation of the control valve, in which the fluid flow through the flow opening is correspondingly adjusted via the corresponding position of the closing mechanism. This operation, or in other words the normal operation, of the control valve is performed in a method according to the invention for controlling the position of a closing mechanism of a control valve by means of a control device, which is configured to determine the position of the respective actuation control object of the closing mechanism by taking into account the correction values determined by the above-described method according to the invention. Such a method can be referred to as a method for controlling the position of a control valve, in particular if no other controlled quantities can be taken into account apart from the pure setting of the desired position of the closing mechanism.
[0025] That is to say, in this method, during operation or normal operation of the control valve, the minimum flow position is preferably an end position which is not passed through, in contrast to the method according to the invention for determining a correction value, and it is preferably specified in this operation or normal operation of the control valve that the closing mechanism is only moved to positions where the respective encoder value is equal to or greater than the correction value or where the respective encoder value is equal to or less than the correction value.
[0026] Further features and details of preferred embodiments of the method according to the invention are explained by way of example below on the basis of examples. [Brief description of the drawings]
[0027] [Figure 1] FIG. 1 shows a schematic representation of an apparatus with a chamber and a control valve in which the method according to the invention can be carried out. [Diagram 2] 1 is a schematic longitudinal section through a control valve in the form of a butterfly valve in which the method according to the invention can be carried out; [Diagram 3] FIG. 3 shows a schematic cross-section through the control valve of FIG. 2 in the region of the closing mechanism. [Figure 4] FIG. 13 shows pressure versus encoder value for the case where no correction is required. [Diagram 5] 5 is a diagram showing the position of the closing mechanism at an encoder value of 0 in FIG. 4. FIG. [Figure 6] 5 is a diagram showing the position of the closing mechanism at the encoder value 10 in FIG. 4. FIG. [Figure 7] FIG. 5 shows an example of a view similar to FIG. 4 in which correction is required. [Figure 8] 8 is a diagram showing the position of the closing mechanism at an encoder value of 2 in FIG. 7. FIG. [Figure 9] FIG. 8 is a diagram showing the position of the closing mechanism at encoder value 4 in FIG. 7. [Figure 10] FIG. 8 is a diagram showing the position of the closing mechanism at the encoder value 12 in FIG. 7. [Figure 11]FIG. 4 is a diagram showing pressure versus encoder value to explain the method according to the invention for determining correction values; [Figure 12] 12 is a diagram showing the position of the closing mechanism of the control valve when the encoder value is 0 in FIG. 11. FIG. [Figure 13] 12 is a diagram showing the position of the closing mechanism at encoder value 4 in FIG. 11. FIG. [Figure 14] 12 is a diagram showing the position of the closing mechanism at an encoder value of 8 in FIG. 11. FIG. [Figure 15] 4 shows pressure versus encoder value for a second variant of the method according to the invention for determining correction values; FIG. [Figure 16] FIG. 2 is a schematic diagram of a control valve in the form of a shuttle valve. [Figure 17] FIG. 13 is another schematic diagram of a control valve in the form of a shuttle valve. [Figure 18] FIG. 13 is yet another schematic diagram of a control valve in the form of a shuttle valve. [Figure 19] FIG. 1 is a schematic diagram of a control valve with a movably supported closure mechanism. [Figure 20] FIG. 13 is another schematic diagram of a control valve with a movably supported closure mechanism. [Figure 21] FIG. 11 is yet another schematic diagram of a control valve with a movably supported closure mechanism. [Figure 22] FIG. 13 is a diagram of pressure values versus encoder values to illustrate how correction values are used to control the position of a closing mechanism of a control valve. [Figure 23] 23 is an explanatory diagram of the position of the closing mechanism at the encoder value 4 in FIG. 22. FIG. [Figure 24] 23 is an explanatory diagram of the position of the closing mechanism at the encoder value 14 in FIG. 22.
[0028] In Fig. 1, a schematic diagram of an apparatus is shown in which both the method according to the invention for determining the correction value K and the method according to the invention for controlling the position of the closing mechanism 3 of a control valve 1 can be implemented. The apparatus includes a chamber 2, which can be, for example, a process chamber, a transfer chamber or another chamber. Overall, the apparatus is preferably used in the field of vacuum technology, although this does not necessarily have to be the case. The same applies to the method according to the invention. Vacuum technology is particularly understood to refer to operation at pressure levels below 0.001 mbar (millibar) or below 0.1 Pascal. However, vacuum technology can also refer to operation at pressures below standard pressure, i.e. below 1 bar.
[0029] Here, in this embodiment, the control valve 1 is arranged in a fluid line 17 between the chamber 2 and the pump 9. The actuator 5 serves to adjust the closing mechanism 3 of the control valve 1. The actuator 5 is driven and controlled by the control device 4, which is also connected for this purpose to a pressure sensor 8 for determining a pressure value P, which in this embodiment represents the pressure in the chamber 2. Via the flow control valve 10 and the corresponding fluid line 17, a fluid, in particular a gas, can flow into the chamber 2. The negative pressure required for this is generated by the pump 9, which in this embodiment is a suction pump 9, by means of which the fluid, in particular a gas, is sucked through the flow control valve 10, the chamber 2 and the flow opening 6 of the control valve 1. For the sake of completeness, it is noted that a pressure sensor 8 can also be arranged in the fluid line 17 between the chamber 2 and the control valve 1 in order to measure the pressure value P, which in this embodiment represents the pressure in the chamber 2. Other arrangements of the pressure sensor 8 are also possible in principle.
[0030] In FIG. 2, a schematic longitudinal section of a control valve 1 in the form of a so-called butterfly valve, or in other words a butterfly valve, is shown. The closing mechanism 3 is in this embodiment a valve plate, which can be pivoted by means of an actuator 5 about a pivot axis 13 extending along the valve plate. The valve plate always projects beyond the pivot axis 13 on opposite sides of the pivot axis 13. Such so-called butterfly valves are known per se and do not require further description. In the minimum flow position shown in FIGS. 2 and 3, or in other words the maximum closing position, the closing mechanism 3, i.e. in this embodiment the valve plate, is arranged at the flow opening 6 in such a way that it closes the flow opening 6 to the maximum, i.e. in other words only a minimum flow rate of the fluid is possible. Depending on the embodiment of the control valve 1, the closing mechanism 3 can completely close or seal the flow opening 6 in the minimum flow position, so that the fluid flow is equal to zero. However, control valves 1 are also conceivable in which in the minimum flow position a certain minimum value of the fluid flow through the flow opening 6 is still barely permitted.
[0031] In this embodiment of the control valve 1, the flow opening 6 is located in the valve housing 16 of the control valve 1. However, this does not necessarily have to be the case, as explained at the beginning. It is also possible for the flow opening 6 to be located directly in the chamber wall of the chamber 2 or in a separate housing, for example in a fluid line 17.
[0032] To pivot the valve plate or the closing mechanism 3 about a pivot axis 13, the control valve 1 is provided with an actuator 5 which is correspondingly driven and controlled by a control device 4. In this embodiment, the actuator 5 can be, for example, an electric motor, but can also be another suitable actuator 5 which is known per se in the prior art.
[0033] In the longitudinal section according to Fig. 2, the encoder 7 is also visible, which determines the respective position of the closing mechanism 3 and transfers it to the control device 4. The encoder 7 has direct access to the pivot axis 13, which is rotated by the actuator 5, and thus determines its position. Here, in this example, the encoder 7 is shown as an auxiliary part, which is connected to the actuator 5. Naturally, the encoder 7 may also be integrated directly into the actuator 5. However, it is also possible to use an encoder 7 for determining the position of the closing mechanism 3, which is completely separate from the actuator 5 or even from the control valve 1.
[0034] 3 further shows a schematic representation of a stopper 15 which may optionally, but need not necessarily, be provided. When the closing mechanism 3 is pivoted so as to come into contact with the stopper 15, it reaches a defined initial position.
[0035] 4 to 10 are used to explain the problems of the prior art that are to be solved by the present invention.
[0036] In Fig. 4, the pressure values P measured by the pressure sensor 8 for various positions of the control valve 1 are plotted against the encoder values E output by the encoder 7 in the respective positions. Additionally, the figure also shows the actual angle W, i.e. the actual position of the closing mechanism 3. Here, an angle of 0.0° corresponds to the minimum flow position shown in Fig. 5. An angle W equal to 9.0° corresponds to the position of the closing mechanism 3 of the control valve 1 shown in Fig. 6. Fig. 4 shows the ideal situation in which the encoder outputs the encoder value 0 when the closing mechanism 3 is in the minimum flow position, i.e. in other words in the maximum closing position. In this position, the pressure value P is maximum.
[0037] However, as already explained at the beginning, this ideal state shown on the basis of Figs. 4 to 6 often does not correspond to reality. Either at the start of operation of the device or after replacement of the control valve 1 or the encoder 7 or the actuator 5 or their components, the encoder 7 may no longer output the encoder value 0 in the minimum flow position, but some other encoder value. An example of this is shown in Fig. 7. In this figure too, the pressure value P measured by the pressure sensor 8 is plotted against the encoder value E output by the encoder 7 in the respective position of the closing mechanism 3. In addition, in this figure too, the angle W, i.e. the position, in which the closing mechanism 3 is actually located at the respective encoder value E is also plotted. This angle W is always measured relative to the minimum flow position, as in Fig. 4.
[0038] In the embodiment shown in FIG. 7, which is freely selected here, the maximum value Pmax of the pressure P measured by the pressure sensor 8 is not at the encoder value 0, as is truly desired, but at the encoder value 4. That is to say, in this embodiment, the minimum flow position at which the maximum value Pmax of the pressure value P is measured corresponds to the encoder value 4 and not to the encoder value 0, as is also achieved in the ideal case shown in FIG. 4. FIG. 8 shows the position of the closing mechanism 3 at the encoder value 2 in FIG. 7. FIG. 9 shows the minimum flow position of the closing mechanism 3, which is achieved exactly at the encoder value 4 in the embodiment shown in FIG. 7. FIG. 10 shows the position of the closing mechanism 3 at the encoder value 12 in FIG. 7.
[0039] 7 to 10, that the minimum flow position is not reached at the encoder value 0 but at another encoder value, as in this example, namely at the encoder value 4, would not be taken into account, leading to error positions when controlling the position of the closing mechanism 3 by means of the control device 4. In these error positions, the closing mechanism 3 would be set to an angle W or a position different from that truly intended by the control device 4.
[0040] In order to be able to correct this possible error, a method according to the invention is proposed for determining a correction value K for a control device 4 for a control valve 1, by means of which the fluid flow through a chamber 2 is controlled, a closing mechanism 3 of the control valve 1 is arranged by the control device 4 using an actuator 5 of the control valve 1 in different positions relative to a flow opening 6 for the fluid flow, in particular an encoder 7 of the control valve 1, each position of the closing mechanism 3 corresponds to an encoder value E of the encoder 7, at different positions of the closing mechanism 3 a pressure sensor 8 measures a pressure value P, in particular representative of the fluid in the chamber 2, the control device 4 measures a maximum value Pmax of the pressure values P, a position of the closing mechanism 3 is identified as a minimum flow position of the closing mechanism 3 and a correction value K is determined from the encoder value E at which the minimum flow position is identified.
[0041] Based on Figs. 11 to 14, a first variant of carrying out the method is shown. In Fig. 11, the pressure values P measured by the pressure sensor 8 are also plotted against the encoder values E output by the encoder 7 at various positions of the closing mechanism 3. The solid line in Fig. 11 shows the continuous change of the pressure value P with the change in the position of the closing mechanism 3 from a relatively small encoder value to the maximum value Pmax of the pressure value P in the range of encoder values 4 and the subsequent decrease of the pressure value P to even larger encoder values. The crosses written in Fig. 11 show the measured values when the pressure P is not measured continuously but only at exactly certain encoder values, for example when only integer encoder values are output by the digital encoder 7. In Fig. 12, the position of the closing mechanism at the encoder value 0 in Fig. 11 is shown. In Fig. 13, the position of the closing mechanism 3 in the minimum flow position at the encoder value 4 in Fig. 11 is shown, and in Fig. 14, the position of the closing mechanism 3 at the encoder value 8 in Fig. 11 is illustrated. It can be clearly seen that in the exemplary implementation of the method according to the invention for determining the correction value K in Fig. 11, the maximum value Pmax of the pressure value P is identified in the encoder value 4. In this embodiment of the method according to the invention, this encoder value 4 is then determined as the correction value K.
[0042] If an encoder 7 is used which does not only output integer encoder values E, but which outputs the encoder values E continuously, as shown by the solid curve in FIG. 11, it may possibly be noticed that the actual maximum value Pmax is not exactly at the encoder value 4, but somewhat beside it, as is also the case in FIG. 11. In order to detect this, or to be able to detect and possibly take into account also the possibly existing play in the closing mechanism 3, it is also possible, as already explained at the beginning, to carry out the method according to the invention for determining the correction value K twice, i.e. it is possible to determine by carrying out the method a first time and then a second time, passing the position of the closing mechanism 3 in the first direction 11 and passing the position of the closing mechanism 3 in the second direction 12 opposite to the first direction 11, determining a first correction value K1 and a second correction value K2 and determining the correction value K on the basis of the first correction value K1 and the second correction value K2.
[0043] This embodiment is shown in FIG. 15. In this embodiment, the invention is carried out a first time in the direction 11, i.e. from a smaller encoder value to a larger encoder value E, and a second time in the second direction 12 from a larger encoder value E to a smaller encoder value E. In FIG. 15, the pressure values P determined during the implementation of the method in the first direction 11 are indicated by the symbol x. The pressure values P shown as circles are determined during the implementation of the method in the second direction 12. During the first implementation of the method, a correction value K1 is obtained. During the second implementation of the method, a correction value K2 is obtained from the respective position of the maximum value Pmax of the measured pressure value P. If this is compared with the solid curve, which represents the successive pressure measurements, it can be seen that both the encoder values E determined as correction values K1 and K2 deviate somewhat from the actual maximum value Pmax of the pressure value P. On the basis of the first correction value K1 and the second correction value K2, various options are available for determining the common correction value K. For example, an average value formation is possible. It may be decided to continue to use the smaller or larger of the two values as correction value K. If the control device 4 and the encoder 7 only work with integer encoder values E, it is also possible to round the correction value K up or down to an integer. Possible residual errors can be accepted as correct in any case. Also in the example shown in FIG. 15, the correction value finally determined will correspond to the encoder value 4.
[0044] When carrying out the method according to the invention for determining the correction value K, it is preferably specified in any case, as already explained at the beginning, that during the entire method, the chamber 2 is continuously circulated with fluid, and that the change in the position of the closing mechanism 3 is the only quantity which changes during the method and influences the fluid flow. It is preferably further specified that during the method, the pump 9 is used to draw fluid through the regulating valve 10, the chamber 2 and the circulating opening 6, and it is preferably specified that the control valve 1 is arranged between the pump 9 and the chamber 2.
[0045] In the previously described variants of the method according to the invention for determining the correction value K, a butterfly valve or in other words a butterfly valve, as shown in FIGS. 2 and 3, respectively, was used as the control valve 1. However, the method according to the invention for determining the correction value K is not limited to this valve type. Exemplarily selected alternative embodiments of the control valve 1 which can be used in the method according to the invention are shown in a largely schematic manner and by way of example in FIGS. 16 to 21. In FIGS. 16 to 18, a so-called shuttle valve is shown in a largely schematic manner. In this case too, the closing mechanism 3 is a valve plate. This valve plate is pivoted by an actuator 5, which is not explicitly shown in FIGS. 16 to 18, about a pivot axis 13 which, in the case of a shuttle valve, runs parallel to the normal 14 of the valve plate. This pivot axis 13 usually runs at the edge of the valve plate or laterally of the valve plate. In addition, a stop 15 is also shown in FIGS. 16 to 18. Such shuttle valves are known, so there is no need to further describe or illustrate them in detail. Different positions of the closing mechanism 3 are also different angular positions in this valve type, which are then each associated with a corresponding encoder value E. FIG. 16 shows by way of example a position of the closing mechanism 3 on one side of the minimum flow position. FIG. 17 shows the minimum flow position, and FIG. 18 shows the position on the other side of the minimum flow position. The method according to the invention for determining the correction value K can be carried out with such a control valve 1 in the same way as already explained above, as in the case of the butterfly valve shown in FIGS. 2 and 3. Here too, it is determined that the control device 4 identifies the position of the closing mechanism 3 at which the maximum value Pmax of the pressure value P is measured as the minimum flow position of the closing mechanism 3 and determines as the correction value K the encoder value at which the minimum flow position is identified.
[0046] In the control valve 1 shown diagrammatically in Fig. 19 to Fig. 21, the closing mechanism 3 is again a valve plate. However, this valve plate is not pivotable in this valve type, but is slidably supported by an actuator 5. In the embodiment shown here, the movement of the closing mechanism 3 along a linear guide 18 is performed by means of an actuator 5, which is also not shown in the figures. Such sliding door type control valves 1 are known per se and likewise do not need to be described further. With these control valves too, the method according to the invention for determining the correction value K can be carried out, in which case the different positions of the closing mechanism 3 are not necessarily different angular positions, but are preferably positions arranged along a rectilinear axis.
[0047] FIG. 19 also shows, by way of example, how the closing mechanism 3 can be initially positioned on one side of the minimum flow position when implementing the method according to the invention for determining the correction value K.
[0048] In FIG. 20, the minimum flow position is again shown. In FIG. 21, the closing mechanism 3 is shown in a position already moved beyond the minimum flow position. However, even in such a variant of the control valve 1, it is not necessary to provide corresponding stops 15. If these stops 15 are provided, it is provided by the method according to the invention for determining the correction value K that the method is started in an initial position of the closing mechanism 3, in which the closing mechanism 3 is located at the stops 15. However, this does not necessarily have to be the case, as explained at the beginning. In all embodiments, the stops 15 can also be omitted. In the absence of the stops 15, for example, it is also possible to cycle through all possible positions of the closing mechanism 3 when carrying out the method according to the invention. However, it is usually sufficient for the user of the method according to the invention to cycle through a certain range of positions, in which the minimum flow position is estimated.
[0049] After the correction values K have been determined according to the invention in the manner described, the correction values K can subsequently be used for the operation or normal operation of the control valve 1. This is a method according to the invention for controlling the position of the closing mechanism 3 of the control valve 1 by means of a control device 4, which determines the position of the respective drive control object of the closing mechanism 3 taking into account the correction values K determined according to the invention. Such a method is illustrated on the basis of the diagram in FIG. 22, in which the pressure values P measured by the pressure sensor 8 are also plotted against the encoder values E.
[0050] Also shown is the actual angle W that the closing mechanism 3 assumes in the first exemplary embodiment relative to the minimum flow position. To set the minimum flow position, in this method according to the invention, the control device 4 controls the closing mechanism 3 not with an encoder value E equal to 0, but with an encoder value E equal to 4, and this encoder value E is determined precisely on the basis of the correction value K. In the exemplary embodiment shown in FIG. 22, the correction value K is equal to 4. FIG. 23 shows the minimum flow position of the closing mechanism 3 when the encoder value E is equal to 4. FIG. 24 shows, by way of example, the position of the closing mechanism 3 when the encoder value E is equal to 14. In normal operation of the control valve 1, which is shown by way of example with reference to FIG. 22, the closing mechanism 3 is preferably only moved to positions in which the respective encoder value E is equal to or greater than the correction value K. Alternatively, it is also conceivable that the respective encoder value E is equal to or less than the correction value K. Finally, this simply means that only the position of the closing mechanism 3 is set on one side of the minimum flow position, and not circulating between positions on both sides of the minimum flow position, as in the case of implementing the method for determining the correction value. [Explanation of symbols]
[0051] 1. Control valve 2 Chamber 3 Closing mechanism 4. Control device 5 Actuators 6 Flow opening 7 Encoders 8. Pressure Sensors 9. Pump 10. Flow Control Valve 11 1st direction 12 Second direction 13 Swivel Axis 14 Normal 15 Stopper 16 Valve housing 17 Fluid line 18 Linear guide E Encoder Value P Pressure value Pmax Maximum value K correction value K1 First correction value K2 Second correction value W Angle
Claims
1. 1. A method for determining a correction value (K) for a control device (4) for a control valve (1), by means of which a fluid flow through a chamber (2) is controlled, a closing mechanism (3) of the control valve (1) is arranged by the control device (4) using an actuator (5) of the control valve (1) in different positions relative to a flow opening (6) for the fluid flow, in particular an encoder (7) for the control valve (1), each position of the closing mechanism (3) corresponding to an encoder value (E) of the encoder (7), measuring by a pressure sensor (8) at different positions of the closing mechanism (3), in particular a pressure value (P) representative of a fluid in the chamber (2), the control device (4) measuring a maximum value (Pmax) of the pressure value (P), identifying a position of the closing mechanism (3) as a minimum flow position of the closing mechanism (3) and determining the correction value (K) from the encoder value (E) at which the minimum flow position is identified.
2. 2. The method of claim 1, wherein the fluid is continuously passed through the chamber (2) during the entire method, and the change in position of the closing mechanism (3) is the only quantity that changes during the method to affect the fluid flow.
3. 3. The method according to claim 1 or 2, characterized in that during the implementation of the method, a pump (9) is used to draw the fluid through a flow control valve (10), the chamber (2) and the flow opening (6), preferably the control valve (1) being specified to be arranged between the pump (9) and the chamber (2).
4. 4. The method according to claim 1, further comprising the steps of: performing the method a first time and a second time, passing the position of the closing mechanism (3) in a first direction (11) in the first time and passing the position of the closing mechanism (3) in a second direction (12) opposite to the first direction (11); determining a first correction value (K1) in the first time and a second correction value (K2) in the second time; and determining the correction value (K) based on the first correction value (K1) and the second correction value (K2).
5. 5. The method according to claim 1, wherein the closing mechanism (3) is a valve plate, the valve plate being pivotable by the actuator (5) about a pivot axis (13) extending along the valve plate, the valve plate protruding beyond the pivot axis (13) on opposite sides of the pivot axis (13).
6. 5. The method according to claim 1, wherein the closing mechanism (3) is a valve plate, the valve plate being pivotable by the actuator (5) about a pivot axis (13) extending parallel to a normal (14) of the valve plate.
7. 5. The method according to claim 1, wherein the closing mechanism (3) is supported by the actuator (5) in a preferably linearly slidable manner.
8. 8. The method according to claim 1, wherein the control valve (1) has an initial position that is preset by a stop (15) or in another way, and, starting from the initial position of the closing mechanism (3), different positions of the closing mechanism (3) are placed relative to the flow opening (6) for the fluid flow when carrying out the method.
9. 9. A method for controlling a position of a closing mechanism (3) of a control valve (1) by means of a control device (4), the method comprising determining the position of a respective controlled object of the closing mechanism (3) by means of the control device (4) taking into account a correction value (X) determined by the method according to any one of claims 1 to 8.