JP7637488B2 - Eccentric valve device and control method thereof - Google Patents

Description

The present invention relates to an eccentric valve device and a control method thereof.

Conventionally, piping systems that make up production processes in factories and the like incorporate valve devices to control the flow of various gases, liquids, powders, and mixtures of these (hereinafter collectively referred to as fluids). The flow path in the piping is blocked or opened by opening and closing the valve of the valve device. For example, a valve device with an automatic operation function can open and close the valve without manual operation.

In general, a valve device with an automatic operation function includes a substantially cylindrical valve box having an opening that communicates with a flow path, a ring-shaped seat member attached around the opening inside the valve box, a valve body that is rotatably mounted inside the valve box and blocks the flow path when pressed against the seat member, a valve drive unit that rotates the valve body, and a control unit that controls the drive of the valve drive unit.

There are various types of valves known for use in valve devices, including double eccentric valves and single eccentric valves such as ball valves. Double eccentric valves have an eccentric structure in which the axis of rotation of the valve body is eccentric with respect to the axis of the seat member, and the valve body and seat member are not in contact when the flow path is open, and only come into contact near the position where the valve body closes the flow path (see Patent Document 1). On the other hand, in ball valves, the valve body and seat member are always in contact, and the valve body opens and closes when pressed against the seat member.

JP 2015-48856 A

When an eccentric valve is in the fully closed state, the valve disc crushes the seat member, and the contact surface of the valve disc with the seat member receives a repulsive force. As a result, the two come into close contact and the flow of fluid is blocked. However, even in the fully closed state, so-called seat leakage may occur, in which fluid flows from upstream to downstream between the valve disc and the seat member. Seat leakage is undesirable because it changes the amount of fluid flowing as a material and may have a negative effect on product quality. Therefore, it is required to keep the amount of fluid leakage within an acceptable range when the valve disc is fully closed.

Generally, there are two types of seat leakage: one that occurs when a foreign object gets caught between the seat member and the valve body, and one that occurs when the seat member becomes worn or worn out. The former type of seat leakage occurs when a solid foreign object adheres to the contact surface between the valve body and the seat member, and is often a temporary leak unless the seat member is permanently damaged. On the other hand, the latter type of seat leakage occurs when the seat member deteriorates over time, and once a leak occurs, it will continue to occur, which may have a negative impact on, for example, product quality.

In addition, since sheet leakage due to wear and tear is an event that occurs inside the valve device, it is difficult to immediately detect its occurrence from the outside. In particular, valve devices equipped with automatic operation functions are often installed in narrow places, remote locations, or special atmospheric environments where manual inspection is not possible. For this reason, sheet leakage is often discovered some time after it occurs, which may result in energy loss, resource loss, and reduced yield. For example, one possible method for detecting sheet leakage is to install various sensors such as a flow sensor or a vibration sensor and detect it based on the output from the sensors. However, this method has problems such as the expense of installing the sensors and the difficulty of setting a threshold value for determining the occurrence of sheet leakage. Therefore, it is desirable to be able to easily detect sheet leakage due to wear and tear immediately after it occurs and to predict it in advance.

In addition, it is desirable for a valve device to be able to immediately shut off the flow path when a request to shut off the flow path occurs. However, it takes a certain amount of time for the valve disc to change from a fully open to a fully closed state, and the flow of fluid after a shutoff request is made is wasted in the production process. For this reason, it is desirable for the opening and closing time of the valve disc to be short.

The present invention has been made in consideration of the above circumstances, and aims to provide an eccentric valve device and a control method thereof that can reliably detect or predict seat leakage even with short opening and closing times in eccentric valves, including double eccentric valves.

The eccentric valve device of the present invention is an eccentric valve device that controls the blocking or opening of a flow path in a pipe, and the eccentric valve device includes a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body that is rotatably provided in the valve box and blocks the flow path by being pressed against the seat member, a valve drive unit that rotates the valve body, and a control unit that controls the drive of the valve drive unit, and the valve body is structured so that it does not contact the seat member in the fully open state and contacts the seat member in the fully closed state, and the control unit is characterized in that it includes a speed control unit that changes the rotation speed of the valve body in the process of rotating from the fully open state to the fully closed state, and a leak determination unit that determines the presence or absence of a leak between the seat member and the valve body based on the drive parameters of the valve drive unit. Here, "determining the presence or absence of a leak" includes determining whether a leak has actually occurred, as well as determining whether there is a sign of a leak.

In the present invention, it is preferable that the speed control unit rotates the valve body from a fully open state at a first speed, and then changes the rotation speed to a second speed slower than the first speed to rotate the valve body to a fully closed state.

In the present invention, it is preferable that the speed control unit rotates the valve body from a predetermined position where the valve body is close to the seat member to a fully closed state at a second speed. Here, the "predetermined position close to the seat member" is a position where the valve body does not contact the seat member, and where the gap between the valve body and the seat member can be narrowed to increase the flow rate of the fluid to a level where foreign matter adhering to the valve body and the seat member can be blown away.

Moreover, in the present invention, it is more preferable that the control unit has a torque calculation unit that calculates the drive torque of the valve drive unit based on the drive parameters, and the leak determination unit determines that a leak has occurred between the seat member and the valve body when the drive torque is smaller than a predetermined threshold value while the valve body is rotating at the second speed.

Moreover, in the present invention, it is more preferable that the time required for the valve body to change from a fully open state to a fully closed state is within 3.0 seconds.

In addition, in the present invention, the valve drive unit may be an electric motor that can rotate the valve body by inertia even after the current supply is stopped.

The control method of the eccentric valve device of the present invention is a control method of an eccentric valve device that controls the blocking or opening of a flow path in a pipe, the eccentric valve device comprising a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body that is rotatably provided in the valve box and blocks the flow path when pressed against the seat member, and a valve drive unit that rotates the valve body, the valve body being structured so that it does not contact the seat member in a fully open state and contacts the seat member in a fully closed state, the control method is characterized by comprising a step of rotating the valve body at a first speed in the process of rotating the valve body from a fully open state to a fully closed state, and a step of determining the presence or absence of leakage between the seat member and the valve body based on the drive parameters of the valve drive unit while rotating the valve body at a second speed slower than the first speed.

By configuring the eccentric valve device and control method of the present invention in this way, it is possible to reliably detect or predict seat leakage even with short opening and closing times.

1 is an explanatory diagram showing a schematic configuration of an entire eccentric valve device according to the present invention; FIG. 2 is an enlarged cross-sectional view of the valve mechanism portion of FIG. 1 . FIG. 4 is a cross-sectional view showing a valve body in a fully open state. FIG. 4 is a cross-sectional view showing a valve body in a fully closed state. FIG. 13 is a diagram showing a change in shaft torque when the valve body transitions from a fully closed state to a fully closed state. FIG. 13 is a diagram showing a change in shaft torque when the valve body transitions from a fully closed state to a fully closed state. FIG. 13 is a diagram showing a change in shaft torque when the valve body transitions from a fully closed state to a fully closed state. 4 is a graph showing a ratio of the shaft torque at the timing when the power supply to the motor is stopped to the peak value of the shaft torque. FIG. 2 is a block diagram of an eccentric valve device according to the present invention. 11A and 11B are diagrams illustrating an example of a position where the rotation speed of the valve body is switched. FIG. 13 is a diagram showing changes in driving torque of a new sheet member and a worn sheet member. FIG. 13 is a diagram showing changes in driving torque of a new sheet member and a worn sheet member. 10 is a flowchart showing a processing procedure for detecting a sheet leakage. FIG. 11 is a diagram showing a relationship between a calculated driving torque and a threshold value. 6 is an example of a timing chart when a valve body transitions from a fully open state to a fully closed state. 13 is another example of a timing chart when the valve body transitions from a fully open state to a fully closed state.

Figure 1 is an explanatory diagram showing the overall schematic configuration of the eccentric valve device according to the present invention, and Figure 2 is an enlarged cross-sectional view of the valve mechanism of Figure 1. Note that Figure 1 shows a cross-sectional view of a portion of the eccentric valve device. The eccentric valve device 1 shown in Figure 1 is a device that is placed midway through a flow path in a pipe through which a fluid flows, and controls the blocking and/or opening of the flow path.

As shown in FIG. 1, the eccentric valve device 1 includes a valve mechanism 2 having a valve body 22, a valve drive unit 3 that drives the valve mechanism 2, and a control unit 4 that controls the drive of the valve drive unit 3. The valve mechanism 2 and the valve drive unit 3 are connected by a valve rod 35, and the drive of the valve drive unit 3 can be transmitted to the valve mechanism 2. The eccentric valve device 1 has the function of being able to hold the attitude of the valve body 22 in a fully open position, a fully closed position, or any other position (for example, a position immediately before being fully closed).

The control unit 4 is mainly composed of a microcomputer including a well-known CPU, ROM, RAM, etc. Note that in Figs. 1 and 9, for convenience, the control unit 4 is shown separately from the valve drive unit 3, but the valve drive unit 3 also has a built-in microcomputer, and all or part of the functions of the control unit 4 described below may be provided by the microcomputer in the valve drive unit 3.

The valve mechanism 2 comprises a substantially cylindrical valve box 21, a valve element 22 rotatably provided within the valve box 21, a ring-shaped seat member 23 attached within the valve box 21, and a support member 24 that supports the seat member 23. The valve mechanism 2 is installed midway through a fluid piping, and pipes (not shown) are connected to the upstream and downstream sides of the valve box 21. The fluid flows in the direction of the arrow in FIG. 1. By rotating the valve element 22 in the valve mechanism 2, the flow path within the valve box 21 is blocked or opened, and the flow of fluid from the upstream side to the downstream side can be blocked or opened.

As shown in FIG. 2, the valve box 21 has an opening 211 that connects the upstream flow path and the downstream flow path. Around the opening 211, a step 214 is formed that protrudes radially inward so that the inner circumferential surface of the valve box 21 has a reduced diameter, and a seat member 23 is attached to the step 214. The seat member 23 is supported by a support member 24 inserted from the upstream end of the valve box 21. The upper part of the valve box 21 is formed with a mounting hole 212 that penetrates the inner circumferential surface and the outer circumferential surface and into which the valve rod 35 is inserted. The mounting hole 212 is formed in a direction perpendicular to the axial direction of the valve box 21, and the valve rod 35 is rotatably inserted. In addition, a pin groove 213 into which the pin 25 fits is formed in the lower part of the valve box 21.

In the valve box 21, the valve body 22 is connected to the end of the valve rod 35, and the valve body 22 rotates as the valve rod 35 rotates. The rotation axis of the valve rod 35 and the rotation axis of the valve body 22 are aligned. Note that Figure 2 shows the fully closed state in which the valve body 22 blocks the opening 211.

The valve body 22 has a substantially disk-shaped valve portion 221 and support portions 222 and 223. The upstream end face of the valve portion 221 forms a sealing surface, and is formed by a flat surface at the center of the disk and a curved surface at the periphery of the disk. The curved surface is formed in a convex shape toward the upstream side. The support portion 222 is connected to the valve rod 35, and the support portion 223 is connected to the pin 25. The valve body 22 is formed from a metal material such as stainless steel, a resin material, or the like.

The seat member 23 has a hollow circular seat ring 231 and a rubber ring 232. The surface of the seat ring 231 facing the valve body 22 constitutes a sealing surface. A groove is formed on the back side of the sealing surface of the seat ring 231, and the rubber ring 232 is fitted into the groove. The seat ring 231 is made of a resin such as polytetrafluoroethylene resin. This resin may be mixed with a fibrous reinforcing material such as carbon fiber or glass fiber. In addition, the rubber ring 232 may be made of fluororubber such as tetrafluoroethylene-perfluoromethylvinylether rubber (FFKM) or nitrile butadiene rubber (NBR). In the fully closed state as shown in FIG. 2, the valve portion 221 of the valve body 22 is pressed against the seat member 23, so that the sealing surface of the valve body 22 is in close contact with the sealing surface of the valve body 22.

Next, the operation of the valve mechanism 2 will be described with reference to Figures 3 and 4. Figures 3 and 4 are partial cross-sectional views of the valve mechanism in Figure 2, viewed from the valve stem side. As shown in each figure, the valve body 22 has a double eccentric structure. Specifically, the rotation axis O of the valve body 22 is eccentric by a distance Y with respect to the axis of the seat ring 231, and the rotation axis O of the valve body 22 is eccentric by a distance X with respect to the sealing surface of the seat ring 231.

Figure 3 shows the fully open state of the valve body 22, with the valve portion 221 of the valve body 22 facing a direction perpendicular to the flow path. At this time, the valve body 22 is not in contact with the sheet member 23. From this fully open state, the valve body 22 rotates so that the valve portion 221 faces the upstream side of the flow path. The valve body 22 rotates at a rotation angle θ of 0 to 90 degrees, with the fully open state being 0 degrees and the fully closed state being 90 degrees. Figure 4 shows the fully closed state of the valve body 22, with the valve portion 221 of the valve body 22 facing the upstream direction of the flow path. The flow path is blocked by the valve body 22 coming into close contact with the sheet member 23. The opening and closing speed of the valve body 22 can be set appropriately, and generally, the time required from the fully open state to the fully closed state is 1 second or more.

In the fully closed state of FIG. 4, the seat member 23 is elastically deformed by being pressed against the valve body 22. The amount of deformation (deformation margin) of the seat member 23 is generally about 1/500 to 1/1000 of the cross-sectional width of the seat member 23. In the case of an eccentric valve, the seat member is repeatedly deformed every time the valve body opens and closes. The seat member is scraped or worn down (permanent set) in approximately proportion to the number of times the valve body opens and closes, and the amount of deformation (repulsive force) of the seat member decreases, which may ultimately result in seat leakage. The present invention uses the drive parameters of the valve drive unit to detect or predict the decrease in the repulsive force of the seat member over time as seat leakage.

First, the shaft torque transition when the valve body is closed will be described. Figure 5 shows the shaft torque transition, motor current transition, and brake state as the valve body rotates from a fully open state (0 seconds) to a fully closed state (8 seconds). During the valve closing operation, the valve drive unit rotates the output shaft by energizing the motor unit, thereby rotating the valve body. Then, at a predetermined timing, the motor unit is de-energized and the brake is activated at the same time, bringing the valve body into a fully closed state. The valve drive unit is, for example, an electric motor (such as a brushless motor) that rotates the valve body by inertial force even after de-energization. In this case, the timing of de-energization and brake activation is set according to the rotation speed of the valve body so that the seat member is not subjected to excessive load due to inertial force.

In Figure 5, the shaft torque (dashed line) is a value detected by a torque sensor attached to the output shaft of the motor. The torque sensor has a strain gauge and generates a detection signal corresponding to the shaft torque generated on the output shaft of the motor. The motor current (dotted line) is the motor current calculated, for example, from the voltage value between shunt resistors in the motor circuit. Note that in Figure 5, the motor current gradually decreases after the brake is activated, that is, after the current to the motor is cut off, but this is due to the influence of the measurement method, and in reality, the current becomes zero immediately after the current is cut off. Note that the brake state (solid line) indicates the brake activation states of off and on.

Figure 5 shows the case where the time required for the valve disc to go from the fully open state to the fully closed state (opening/closing time) is 8.0 seconds. In this test, the rotation speed of the valve disc is maintained constant by energizing the motor unit. As shown in Figure 5, the shaft torque is almost constant from the start of the valve disc closing operation until 7 seconds before, and then begins to increase around 7 seconds, and continues to increase until it reaches 8 seconds when the valve disc is in the fully closed state. This shaft torque transition is based on the operation in which the valve disc contacts the seat member as the valve opening operation progresses and further pushes the seat member. Also, in Figure 5, the motor current shows a temporary increase immediately after the start, but then shows a transition in which it increases from just before the fully closed state, similar to the shaft torque transition. In other words, the motor current can be said to reflect the driving torque of the valve disc during the valve closing operation, and it is thought that this can be used to detect and predict seat leakage.

In the example of Figure 5, if the shaft torque at the peak (8.0 seconds) is taken as 100%, the proportion of shaft torque at the time the brakes are applied is approximately 100%. In other words, in this case, the motor section is energized until the valve body is almost fully closed. Therefore, it is possible to detect seat leakage, etc., by using the motor current for the entire section in which the valve body is pressing the seat member.

Next, Fig. 6 and Fig. 7 show examples of shaft torque transitions etc. when the opening and closing time of the valve disc is made shorter than 8.0 seconds. Fig. 6(a) shows the case of 4.0 seconds, Fig. 6(b) shows 3.0 seconds, Fig. 7(a) shows 2.0 seconds, and Fig. 7(b) shows 1.0 seconds.

As shown in Figures 6 and 7, the shorter the opening and closing time, the earlier the timing of braking with respect to the target time (for example, when the opening and closing time is 4.0 seconds, the time 4.0 seconds after the start of the valve closing operation) becomes. In other words, the shorter the opening and closing time, the earlier the timing of stopping the motor's current. This is because the shorter the opening and closing time of the valve body, the faster the valve body's rotation speed becomes, and the longer the valve body moves by inertia after the current is stopped. For example, when the opening and closing time is 8.0 seconds, the current is 99.4% when the opening and closing time is 4.0 seconds, the current is 99.3% when the opening and closing time is 3.0 seconds, the current is 97.8% when the opening and closing time is 2.0 seconds, and the current is 91.8% when the opening and closing time is 1.0 seconds. As shown in Figures 6 and 7, the earlier the timing of stopping the current to the motor, the shorter the section in which the driving parameters can be measured becomes compared to the entire section (100%).

Figure 8 is a graph showing the ratio of the shaft torque at the timing when the motor is deenergized to the peak value of the shaft torque. Since the change in the shaft torque reflects the change in the drive torque while the motor is energized, the graph in Figure 8 shows the ratio of the drive parameter that can be measured to the peak value. As shown in Figure 8, when the opening and closing time is 8.0 seconds, the measurable drive parameter is about 100%, whereas when the opening and closing time is 4.0 seconds, it is about 94%, when the opening and closing time is 3.0 seconds, it is about 92%, when the opening and closing time is 2.0 seconds, it is about 81%, and when the opening and closing time is 1.0 seconds, it is about 35%. In other words, when the opening and closing time is 4.0 seconds or less, the supply of power to the motor is stopped before the shaft torque reaches the peak value, so the drive parameter cannot be measured in the entire section until the shaft torque reaches the peak value.

In contrast, the eccentric valve device of the present invention is characterized by having a speed control section that changes the rotation speed of the valve disc as it rotates from a fully open state to a fully closed state, and a leakage determination section that determines the presence or absence of leakage between the seat member and the valve disc based on the drive parameters of the valve drive section. Specifically, a period in which the speed control section rotates the valve disc quickly is combined with a subsequent period in which the valve disc rotates slowly. This makes it possible to shorten the overall opening and closing time while bringing the timing of stopping the power supply to the motor as close as possible to the fully closed state, in other words, bringing the section in which the drive parameters can be measured as close as possible to the entire section, making it possible to adequately determine an increase in drive torque using the drive parameters.

Figure 9 is a block diagram showing an example of an eccentric valve device according to the present invention. The eccentric valve device 1 includes a valve mechanism unit 2, a valve drive unit 3, and a control unit 4, and the specific configuration of the valve mechanism unit 2 is as described above. The eccentric valve device 1 also includes sensors 51, 52, and 53 for detecting drive parameters, and each sensor is connected to the control unit 4. The detection results of each sensor are input to the control unit 4 at any time, and are configured to be continuously detected and stored during opening and closing operations. The control unit 4 also has various calculation functions. In the present invention, the drive parameters are parameters that indicate the drive state of the valve drive unit 3, and include, for example, the motor rotation speed, motor current value, motor voltage value, drive torque, and rotation angle θ of the motor unit 33. In the present invention, the drive parameters of the valve drive unit 3 are used to detect sheet leakage, so that separate sensors such as a torque sensor, flow rate sensor, and vibration sensor are not essential, and sheet leakage can be detected by a simple means of monitoring the motor rotation speed and current value.

The valve drive unit 3 includes a power supply circuit unit 31, a motor circuit unit 32, a motor unit 33, a reducer (gear box) 34, a valve rod 35, and a current sensor 53. The motor circuit unit 32 is connected to the power supply circuit unit 31, and adjusts the current flowing to the motor unit 33 based on a control signal from the control unit 4. The motor unit 33 is made of a brushless motor, and rotates the output shaft based on the current flowing from the motor circuit unit 32. In the configuration of FIG. 1, the rotational speed of the output shaft is reduced by the reducer 34 to rotate the valve rod 35.

In FIG. 9, the control unit 4 has a speed control unit 41, a torque calculation unit 42, and a leakage determination unit 43. The processing in each unit is mainly executed when the valve body transitions from a fully open state to a fully closed state.

The speed control unit 41 changes the rotation speed of the valve disc at a predetermined timing as the valve disc rotates from a fully open state to a fully closed state. Specifically, after rotating the valve disc from a fully open state at a first speed, the rotation speed is changed to a second speed slower than the first speed to rotate the valve disc to the fully closed state. The second speed is set to, for example, 1/8 to 1/3 of the first speed. Here, the timing of switching from the first speed to the second speed is based on, for example, that the valve disc has rotated to a predetermined position. The position determination unit in the control unit 4 determines that the valve disc has rotated to the predetermined position based on the rotation angle detected by an angle sensor 52 such as an encoder.

The above-mentioned predetermined position is preferably a predetermined position close to the seat member. The predetermined position close to the seat member is, for example, as shown in FIG. 10, a position where the valve body 22 does not contact the seat member 23, where the gap between the valve body 22 and the seat member 23 is narrowed, and the flow rate of the fluid can be increased to a degree that blows away foreign matter adhering to the valve body 22 and the seat member 23. In this case, when the rotation angle θ becomes, for example, 60 degrees or 70 degrees, the first speed is switched to the second speed. By switching at a predetermined position close to the seat member, the frictional force generated by the subsequent contact between the valve part 221 and the seat ring 231 becomes a pure frictional force that is not affected by foreign matter, so that a decrease in sealing performance due to sagging or wear can be detected separately from a decrease in sealing performance due to the ingress of foreign matter.

9, a torque calculation unit 42 calculates the drive torque of the valve drive unit 3 based on drive parameters such as the rotation speed of the motor unit 33 detected by a rotation sensor 51 and the motor current value detected by a current sensor 53. The drive torque can be calculated according to a known method. For example, the drive torque can be calculated by the following formula (1). Note that the coefficients in the following formula (1) are values that can be obtained by experiment.
Driving torque = coefficient × motor current value / motor rotation speed (1)

The leak determination unit 43 determines whether or not there is a leak between the seat member 23 and the valve body 22 based on the drive parameters of the valve drive unit 3. For example, in the configuration of FIG. 9, the seat leak is determined based on the drive torque calculated by the torque calculation unit 42 and a predetermined threshold value.

Figure 11 shows the transition of the drive torque calculated from the drive parameters using a new seat member and a worn seat member. Figure 11 shows the case where the opening and closing time is 8.0 seconds, and the differential pressure, which is the pressure difference between the upstream flow path and the downstream flow path, is zero. Note that the drive torque in the figure is a value calculated using the above formula (1) without using a torque sensor.

As shown in FIG. 11, a new seat member and a worn seat member behave in a similar manner, but the drive torque value during the period when the drive torque increases is smaller for the worn seat member. When the seat member becomes worn or worn, the repulsive force of the seat member when the valve is closed decreases, which is thought to result in a smaller drive torque than normal. Based on this result, the leak determination unit 43 shown in FIG. 9 determines that a seat leak has occurred when the calculated drive torque is smaller than a predetermined threshold value. The predetermined threshold value can be set based on a correlation between the amount of seat leakage and the drive torque that has been obtained in advance through experiments.

On the other hand, if the fluid contains solid foreign matter such as powder or slurry, there is a risk of seat leakage due to the foreign matter getting caught. In the case of a foreign matter getting caught, the valve closing operation becomes an overload, and it is thought that the drive torque will be larger than normal. Therefore, by determining that a seat leakage has occurred when the calculated drive torque is smaller than a predetermined threshold value, it is possible to distinguish and detect seat leakage due to settling or wear, rather than seat leakage due to a foreign matter getting caught.

Next, Figure 12 shows the relationship between drive torque and differential pressure. Figure 12(a) shows the results of examining the differential pressure using a new seat member, and Figure 12(b) shows the results of examining the differential pressure using a worn seat member. As shown in each figure, the drive torque tended to be higher as the differential pressure increased. As such, since the drive torque when the valve is closed changes depending on the differential pressure, when using a threshold value to determine seat leakage, it is preferable to set the threshold value according to the differential pressure. Note that when comparing cases where the differential pressure is the same, the drive torque was lower for worn items than for new items.

As another method of determination by the leak determination unit 43, a method of determining that a seat leak has occurred when the difference between the calculated drive torque and a past value (for example, the drive torque calculated the previous time the valve was closed) is equal to or greater than a certain value. For example, the average value of the past 100 times is used as the past value.

In the configuration of FIG. 9, sheet leakage is determined based on the drive torque calculated by the torque calculation unit 42, but leakage determination may be performed based on a drive parameter other than the drive torque. For example, since the motor current value is approximately correlated with the drive torque of the motor unit 33, the motor current value can be used directly for leakage determination.

Next, we will explain the process by the control unit 4 to detect sheet leakage during the valve closing operation. This detection process is performed repeatedly at predetermined time intervals.

Figure 13 is a flowchart showing the processing procedure for sheet leakage detection. The process from start to end in Figure 13 is repeated at predetermined time intervals. First, in step S11, it is determined whether or not a command to close the valve (close command) has been input from a higher-level control device or the like. If step S11 is Yes, the process proceeds to step S12, and if step S11 is No, the process is temporarily terminated.

In step S12, it is determined whether the switching flag is off. As described below, the switching flag is turned on after the valve body 22, which rotates at the first speed, rotates to a predetermined position. If step S12 is Yes, the process proceeds to step S13, where the motor unit 33 is driven. The valve body 22 rotates at the first speed toward the fully closed state by driving the motor unit 33. In step S14, drive parameters related to the drive of the motor unit 33 are acquired. Specifically, the motor current value and the motor rotation speed are acquired. In the following step S15, the drive torque is calculated based on the acquired motor current value and motor rotation speed.

In step S16, it is determined whether the drive torque is within the normal range. Specifically, it is determined whether the drive torque calculated in step S15 is between a predetermined upper threshold and a lower threshold. These thresholds are appropriately set according to the type and flow rate of the fluid flowing through the flow path. As shown in FIG. 11, the drive torque is generally stable at a low value until it exceeds the rotation angle at which the valve body 22 contacts the seat member (for example, the rotation angle θ is 60 degrees). Therefore, if the drive torque suddenly increases to or exceeds the predetermined upper threshold, it is considered that an abnormality such as a foreign object being caught has occurred. If it is determined that the drive torque is not within the normal range (if step S16 is No), the process proceeds to step S26 and error processing is performed. As error processing, an alarm is issued or an alarm lamp is turned on. Note that as error processing, the drive of the motor unit may be stopped to interrupt the valve closing operation.

If step S16 is Yes, proceed to step S17 to determine whether the valve body 22 has rotated to a predetermined position. Specifically, it is determined whether the rotation angle θ detected by the angle sensor 52 has reached a predetermined angle. If the valve body 22 has not reached the predetermined position (if step S17 is No), this process is temporarily terminated. Note that in FIG. 13, if step S17 is No, a loop may be provided to repeatedly execute the processes of steps S13 to S17.

When the closing operation of the valve body 22 progresses further and the valve body rotates to a predetermined position (step S17: Yes), the switching flag is turned on (step S18) and this process is temporarily terminated.

When the switching flag is turned on and step S12 is negative, the process proceeds to step S19, where the valve body 22 is rotated at the second speed. This switches the rotation speed from the first speed to the second speed. In the following step S20, it is determined whether the valve body is in the fully closed position. Specifically, it is determined whether the rotation angle θ detected by the angle sensor 52 is 90 degrees. If step S20 is negative, the drive parameters are acquired (step S23), and the drive torque is calculated (step S24). The processes of steps S23 and S24 are the same as those of steps S14 and S15.

In step S25, it is determined whether the driving torque is within the normal range. Specifically, this is determined based on the driving torque calculated in step S24 and the predetermined upper and lower thresholds. Here, the relationship between the calculated value and each threshold is shown in FIG. 14. As shown in FIG. 14, the upper threshold is set higher than the driving torque in normal conditions (e.g., at the time of shipment), and the lower threshold is set lower than the driving torque in normal conditions. The setting of each threshold is not particularly limited, but the upper threshold is set, for example, 10% higher and the lower threshold is set, for example, 10% lower than the driving torque in normal conditions. In step S25 of FIG. 13, for example, it is determined whether the driving torque calculated at each rotation angle falls between the predetermined upper and lower thresholds at that rotation angle. If it is determined that the driving torque is outside the range between the two thresholds (if step S25 is No), proceed to step S26 and execute error processing.

If it is determined that the drive torque is within the normal range (if step S25 is Yes), this process is temporarily terminated. Then, if the valve closing operation continues while the drive torque remains within the normal range, the valve body 22 reaches the fully closed position, and step S20 is positive, the drive of the motor unit 33 is stopped (step S21), the switching flag is turned off (step S22), and the series of processes is terminated. Note that the part that executes the processes of steps S13 and S19 corresponds to the speed control unit, the part that executes the process of step S17 corresponds to the position determination unit, the part that executes the process of step S24 corresponds to the torque calculation unit, and the part that executes the process of step S25 corresponds to the leak determination unit.

Figure 13 shows the processing in the control unit 4 during the valve closing operation, but the control method of the present invention is not limited to this. For example, the predetermined position determined in step S17 may be variable depending on the flow rate, viscosity, temperature, etc. of the fluid.

In FIG. 13, in the leak determination in step S25, it is determined whether the calculated drive torque is between an upper threshold value and a lower threshold value, but this is not limited to this. For example, the leak determination may be performed using only a threshold value that is set lower than the normal drive torque. As described above, when the sheet member becomes worn or worn, it is considered that the drive torque becomes smaller than normal. Therefore, if the drive torque falls below this threshold value, it can be determined that a sheet leak has occurred.

In addition, in FIG. 13, sheet leakage is determined based on the drive torque while the valve body is rotated at the second speed. In other words, a configuration is shown in which the occurrence of sheet leakage is detected by the eccentric valve device 1, but sheet leakage can also be predicted using a similar configuration. In this case, for example, the lower limit threshold used in step S25 can be set higher than in the case of sheet leakage detection to determine the stage immediately before sheet leakage occurs (signs of sheet leakage). The timing of sheet leakage can be predicted based on the determination result. It is also possible to determine the timing of sheet leakage from the transition of the drive torque calculated at any time. As a result, it becomes possible to detect the occurrence of sheet leakage in advance and issue an alarm.

Figure 15 is a timing chart showing the flow when the valve body 22 transitions from a fully open state to a fully closed state. When a command to close the valve body is issued at time t1 in the fully open state, the motor unit starts and the valve closing operation begins at a first speed V1. As time passes, the rotation angle θ increases. At this time, the drive torque is stable at a low value. When the valve body rotates to a predetermined position at time t2, the rotation speed of the valve body 22 is switched to a second speed V2. The valve opening operation continues, and the drive torque increases as the seat member and the valve body come into contact. When the valve body reaches a fully closed state at time t3, the motor unit stops and the valve closing operation is completed. Between time t2 and time t3, seat leakage is determined at any time based on the drive torque. Note that the time required from time t1 to time t3 corresponds to the opening and closing time.

In the present invention, the manner in which the rotation speed of the valve body is changed by the speed control unit is not limited to the manner shown in FIG. 15. For example, as shown in FIG. 16(a), a period in which the rotation of the valve body is temporarily stopped (time t5 to time t6) may be provided between the period in which the valve body is rotated at the first speed V1 (time t4 to time t5) and the period in which the valve body is rotated at the second speed V2 (time t6 to time t7). In this case, when the valve body rotates to a predetermined position, the motor unit stops at time t5 and the valve closing operation is temporarily stopped. After the temporary stop time has elapsed, the motor unit starts up and the valve closing operation is resumed at the second speed V2 (time t6). The time for which the valve body is temporarily stopped can be set appropriately. In addition, it is preferable that the position at which the valve body is temporarily stopped is a predetermined position close to the seat member.

Also, as shown in FIG. 16(b), a period (time t9 to time t10) in which the valve body is rotated at a third speed V3 slower than the first speed V1 and faster than the second speed V2 may be provided between the period (time t8 to time t9) in which the valve body is rotated at the first speed V1 and the period (time t10 to time t11) in which the valve body is rotated at the second speed V2. In this case, the time for which the valve body is rotated at the third speed V3 can be set appropriately. Furthermore, a period in which the valve body is rotated at another speed may be added to the embodiment of FIG. 16(b).

In the above embodiment, a double eccentric valve was described as an eccentric valve device according to the present invention, but the present invention can also be applied to eccentric valves that exhibit a change in drive torque similar to that of a double eccentric valve when the valve is opened or closed.

The eccentric valve device of the present invention is capable of detecting or predicting seat leakage due to sagging or wear while shortening the opening and closing time in eccentric valves, including double eccentric valves, installed in the production process piping of a production plant, allowing for safe and efficient maintenance and reducing overall losses in the production process. It is also possible to replace the valve before seat leakage occurs, contributing to stable operation of the equipment and reducing the work involved in equipment maintenance.

1: Eccentric valve device 2: Valve mechanism 21: Valve box 211: Opening 212: Mounting hole 213: Pin groove 214: Step 22: Valve body 221: Valve section 222: Support section 223: Support section 23: Seat member 231: Seat ring 232: Rubber ring 24: Support member 25: Pin 3: Valve drive section 31: Power supply circuit section 32: Motor circuit section 33: Motor section 34: Reducer 35: Valve rod 4: Control section 41: Speed control section 42: Torque calculation section 43: Leak determination section 51: Rotation sensor 52: Angle sensor 53: Current sensor

Claims (5)

An eccentric valve device for controlling blocking or opening of a flow path in a pipe,
The eccentric valve device includes a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body rotatably provided in the valve box and configured to block the flow path by being pressed against the seat member, a valve drive unit that rotates the valve body, and a control unit that controls the drive of the valve drive unit,
The valve body is structured so as not to come into contact with the seat member in a fully open state, and to come into contact with the seat member in a fully closed state,
the control unit includes a speed control unit that changes a rotation speed of the valve element during a process of the valve element rotating from the fully open state to the fully closed state, and a leakage determination unit that determines the presence or absence of leakage between the seat member and the valve element based on a drive parameter of the valve drive unit ,
the speed control unit rotates the valve body from the fully open state at a first speed, and then changes the rotation speed to a second speed slower than the first speed to rotate the valve body to the fully closed state, and rotates the valve body at the second speed from a predetermined position where the valve body is close to the seat member to the fully closed state, the predetermined position being a position where the valve body does not contact the seat member and where a gap between the valve body and the seat member can be narrowed to increase the flow rate of the fluid . the control unit has a torque calculation unit that calculates a drive torque of the valve drive unit based on a motor current value and a motor rotation speed of the electric motor that is the valve drive unit, as the drive parameters;
2. The eccentric valve device according to claim 1, wherein the leakage determination unit determines that a leakage has occurred between the seat member and the valve body when the drive torque is smaller than a predetermined threshold value while the valve body is rotating at the second speed. 3. The eccentric valve device according to claim 1 , wherein a time required for the valve body to change from the fully open state to the fully closed state is within 3.0 seconds. 4. The eccentric valve device according to claim 1 , wherein the valve drive unit is an electric motor that is capable of rotating the valve body by inertia even after the supply of current thereto is stopped. A method for controlling an eccentric valve device that controls blocking or opening of a flow path in a pipe, comprising:
The eccentric valve device includes a substantially cylindrical valve box having an opening communicating with the flow path, a ring-shaped seat member attached around the opening in the valve box, a valve body rotatably provided in the valve box and configured to block the flow path by being pressed against the seat member, and a valve drive unit configured to rotate the valve body.
The valve body is structured so as not to come into contact with the seat member in a fully open state, and to come into contact with the seat member in a fully closed state,
The control method includes a step of rotating the valve disc at a first speed during a process in which the valve disc rotates from the fully open state to the fully closed state, and a step of determining the presence or absence of leakage between the seat member and the valve disc based on a drive parameter of the valve drive unit while the valve disc is rotated at a second speed slower than the first speed,
a step of rotating the valve body from the fully open state at a first speed, changing the rotation speed to a second speed slower than the first speed to rotate the valve body to the fully closed state, and rotating the valve body at the second speed from a predetermined position where the valve body is close to the seat member to the fully closed state, wherein the predetermined position is a position where the valve body does not contact the seat member and where a gap between the valve body and the seat member can be narrowed to increase a flow rate of the fluid .

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