Flow control device and method, and chiller

Abstract

A flow control device according to an embodiment of the present invention includes: a flow meter that repeatedly generates a pulse signal in accordance with flow of fluid discharged from a fluid machine by driving of a brushless motor or an alternating-current motor, and forms the pulse signal in such a manner that a pulse width of the pulse signal is inversely proportional to a flow rate of the fluid; an FV conversion section that frequency / voltage-converts the pulse signal to generate a voltage value corresponding to the pulse signal; and a controller that changes a frequency of a driving input voltage for driving the brushless motor or the alternating-current motor in accordance with a difference between a converted flow rate of the fluid based on the voltage value generated by the FV conversion section and a target flow rate set in advance.

Description

Technical Field

[0001] The present invention relates to a flow control device and method for controlling the flow rate of fluid discharged from fluid machinery such as pumps or blowers, and a cooler equipped with the flow control device. Background Technology

[0002] Previously known flow control devices (JP4569324B) include a flow meter that detects the flow rate of liquid discharged from a pump and a controller that controls the pump drive based on the difference between the flow meter's detected value and the target flow rate.

[0003] In such flow control devices, impeller flow meters are sometimes used as flow meters. Impeller flow meters repeatedly generate pulse signals based on the flow of liquid. The greater the liquid flow rate, the smaller the pulse width of the generated pulse signal; that is, the period becomes shorter and the frequency becomes higher. Therefore, in an impeller flow meter, the greater the flow rate of the liquid being measured, the more pulse signals are generated within a certain period.

[0004] When the controller described above uses a CPU, the CPU acquires the potential level of the pulse input wave, which is composed of pulse signals repeatedly generated by the impeller flowmeter, at a predetermined sampling period. It can determine the current flow rate by judging whether the potential level of the pulse signal is high or low. That is, for example, the pulse width of the pulse signal can be determined based on the time interval between adjacent low-level detection points sandwiched between regions of continuously high potential levels, thereby determining the current flow rate. In this case, the smaller the pulse width, the larger the flow rate can be determined. Summary of the Invention

[0005] The technical problem that the invention aims to solve

[0006] To date, the inventors of this case have applied flow control devices, which, as described above, sample pulse signals from impeller-type flow meters via a CPU, to numerous systems. However, in such systems, it is extremely rare for flow control to become unstable.

[0007] The inventors conducted in-depth research and determined that the aforementioned phenomenon was caused by a missed detection of the pulse signal. A typical CPU (a so-called single-core CPU) suspends other processing while performing one process. Therefore, the CPU essentially suspends pulse signal sampling while performing a process different from the pulse signal sampling process. When determining the pulse width, the CPU needs to continuously perform sampling to cover the entire pulse width. However, there are situations where sampling cannot be performed immediately if other processing is in progress. Furthermore, there are situations where proper sampling cannot be performed if other processing is interspersed within the sampling process. In such cases, a missed detection may occur.

[0008] The aforementioned detection omissions can be eliminated through measures such as using high-performance CPUs, multiple CPUs, or dual-core CPUs. However, these measures all lead to increased hardware costs and complexity. Furthermore, using multiple CPUs or dual-core CPUs can also complicate software processing.

[0009] Furthermore, while PID control is generally used in flow control, executing PID control via the CPU increases the CPU's processing load, raising concerns about reduced responsiveness. Using a CPU with high processing power can achieve good responsiveness, but this results in high hardware resource costs. Additionally, it is difficult to create software for CPU-executed PID control. On the other hand, while PID controllers applicable to various fields are available on the market, they also suffer from the same high hardware resource costs and increased device footprint. For example, to increase the implementation flexibility of high-processing operations like PID control, it is desirable to simplify processing methods different from PID control, such as sampling processing, and to reduce the high cost and complexity of hardware resources used for these different processes.

[0010] The present invention was made in view of the above-mentioned situation, and its object is to provide a flow control device and method, as well as a cooler, that can appropriately implement flow control through simplified hardware resources and software processing.

[0011] Solution to the above technical problems

[0012] One embodiment of the flow control device of the present invention comprises: a flow meter that repeatedly generates pulse signals based on the flow of fluid discharged from a fluid machine driven by a brushless motor or an AC motor, wherein the pulse signal is formed inversely proportional to the flow rate of the fluid; an FV conversion unit that performs frequency-to-voltage conversion on the pulse signal to generate a voltage value corresponding to the pulse signal; and a controller that changes the frequency of the drive input voltage for driving the brushless motor or AC motor based on the difference between the converted flow rate of the fluid calculated based on the voltage value generated by the FV conversion unit and a preset target flow rate.

[0013] In the flow control device of the present invention, by performing frequency-to-voltage conversion on the pulse signal generated by the flow meter by the FV conversion unit, the pulse signal repeatedly generated according to the flow of fluid can be converted into a continuous physical quantity (analog signal) consisting of voltage values. Thus, the controller can, for example, determine the voltage value indicating the flow rate and the flow rate of the fluid discharged from the fluid machinery by sampling at any given time. This reduces the load on signal processing and suppresses flow detection omissions in the controller, thereby enabling appropriate flow control based on flow detection. Therefore, flow control can be appropriately implemented with simplified hardware resources and software processing.

[0014] Alternatively, the FV conversion unit generates a voltage value for a pulse signal, calculates a reference voltage value by a moving average of multiple voltage values, and the controller calculates the converted flow rate based on the reference voltage value.

[0015] In this case, even if the voltage value generated by the FV converter may contain a value with low reliability, the information sampled by the controller becomes a reference voltage value calculated by a moving average of multiple voltage values. Therefore, the reliability of the information used to determine the flow rate can be improved, and the reliability of the determined flow rate can be improved.

[0016] Alternatively, the FV conversion unit may calculate the reference voltage value by a moving average of 40 to 80 voltage values.

[0017] Alternatively, the FV conversion unit may convert the pulse signal generated by the flow meter into a frequency / voltage signal at a rate of 10 to 120 pulses per second.

[0018] In this case, the reliability of the reference voltage value, which serves as the information sampled by the controller, can be effectively improved.

[0019] Alternatively, the controller maintains an adjustment frequency table, which records the relationship between multiple difference ranges and multiple adjustment frequencies determined respectively for the multiple difference ranges. The multiple difference ranges are determined by their respective lower and upper limits based on the range of the absolute value of the difference between the converted flow rate and the target flow rate. Based on the difference between the converted flow rate and the target flow rate and the adjustment frequency table, the controller determines the adjustment frequency corresponding to the difference between the converted flow rate and the target flow rate from the multiple adjustment frequencies, and outputs an instruction to add or subtract the determined adjustment frequency to the frequency of the drive input voltage when the adjustment frequency is determined, thereby changing the frequency of the drive input voltage.

[0020] In this case, a simple frequency adjustment table can be used to control a brushless motor or AC motor to bring the fluid flow rate close to the target flow rate. Since flow control can be implemented without complex logic operations, it is possible to effectively simplify the processing of hardware resources and software.

[0021] Alternatively, the controller may first perform a pre-adjustment action by adding or subtracting the adjustment frequency (Δf) once. If, after adding or subtracting the adjustment frequency (Δf) once, the sign of the difference between the fluid flow rate and the target flow rate is not reversed or disappears relative to the difference between the converted flow rate and the target flow rate when the adjustment frequency (Δf) was determined (i.e., the difference at frequency determination), then the controller may further add or subtract the adjustment frequency (Δf) once or repeatedly until the sign of the difference between the fluid flow rate and the target flow rate is reversed or disappears relative to the difference at frequency determination when the adjustment frequency (Δf) was determined.

[0022] After the pre-stage adjustment action, if the difference between the fluid flow rate and the target flow rate has not disappeared, the following post-stage adjustment action is performed: n fine-tuning unit processes are performed until the fluid flow rate matches the target flow rate. In the fine-tuning unit process, the drive input voltage is added to or subtracted by a fine-tuning frequency (Δfn) smaller than the adjustment frequency (Δf) used in the pre-stage adjustment action once or repeatedly.

[0023] In this case, it is also possible that, in the case of performing the fine-tuning unit process multiple times (n≥2), the fine-tuning frequency (Δfn) used in the fine-tuning unit process is set to be smaller than the fine-tuning frequency (Δfn) used in the previous fine-tuning unit process.

[0024] Alternatively, the preceding adjustment action can be defined as the 0th fine-tuning unit process.

[0025] In the nth fine-tuning unit processing within the subsequent adjustment action,

[0026] If the fluid flow rate calculated after the (n-1)th fine-tuning unit processing exceeds the target flow rate, an action is performed to subtract the fine-tuning frequency (Δfn) from the frequency of the drive input voltage after the (n-1)th fine-tuning unit processing once or repeatedly until the sign of the difference between the fluid flow rate and the target flow rate turns negative or the difference between the fluid flow rate and the target flow rate disappears.

[0027] If the flow rate of the fluid calculated after the (n-1)th fine-tuning unit processing is lower than the target flow rate, the fine-tuning frequency (Δfn) is added once or repeatedly to the frequency of the drive input voltage after the (n-1)th fine-tuning unit processing until the sign of the difference between the fluid flow rate and the target flow rate turns positive or the difference between the fluid flow rate and the target flow rate disappears.

[0028] Alternatively, if the difference between the fluid flow rate and the target flow rate does not disappear after the nth fine-tuning unit processing, the controller may perform the next fine-tuning unit processing in the subsequent adjustment action.

[0029] Alternatively, the fine-tuning frequency (Δfn) used in the nth fine-tuning unit process can be set to the value obtained by dividing the adjustment frequency (Δf) used in the previous adjustment action by 2 to the power of n.

[0030] In this case, a brushless motor or AC motor can be controlled to gradually bring the fluid flow rate closer to the target flow rate without complex logic calculations. Specifically, in the case of multiple fine-tuning unit processes, by simply deriving the fine-tuning frequency (Δfn) used in the fine-tuning unit process according to a simple rule that it becomes smaller than the previous one, the computational load on the amount of data used to gradually bring the fluid flow rate closer to the target flow rate can be effectively suppressed.

[0031] In particular, when the fine-tuning frequency used in the nth fine-tuning unit is determined by dividing the initially determined adjustment frequency by a power of 2, the computational load on the amount of fluid flow to gradually approach the target flow rate can be effectively suppressed. Furthermore, the reduced responsiveness to the target flow rate and the load on the fluid machinery that may result from large flow rate fluctuations can be suppressed.

[0032] Alternatively, the adjustment frequency (Δf) may be set such that the absolute value of the change in fluid flow rate increased or decreased by adding or subtracting the adjustment frequency (Δf) to the frequency of the drive input voltage is less than the lower limit of the differential range corresponding to the adjustment frequency (Δf).

[0033] In this case, it is possible to suppress the reduced responsiveness to the target traffic that may result from large fluctuations in the adjusted traffic.

[0034] Alternatively, the upper limit value can be set to be smaller than twice the lower limit value, and the adjustment frequency (Δf) can be set such that the absolute value of the change in fluid flow rate increased or decreased by adding or subtracting the adjustment frequency (Δf) to the frequency of the drive input voltage is greater than half the upper limit value of the differential range corresponding to the adjustment frequency (Δf).

[0035] In this case, it is possible to suppress the reduced responsiveness to the target traffic caused by excessively small traffic adjustments.

[0036] Alternatively, the controller may use a single-core CPU to perform the following processes: acquiring the voltage value, calculating the flow rate of the fluid based on the voltage value, determining the difference between the calculated flow rate and the target flow rate, and changing the frequency of the drive input voltage.

[0037] In this case, appropriate flow control can be implemented while avoiding high costs through streamlined hardware resources.

[0038] Furthermore, one embodiment of the flow control method of the present invention includes the following steps: a pulse signal acquisition step, wherein a pulse signal is repeatedly generated from a flowmeter that generates the pulse signal based on the flow of fluid discharged from a fluid machine driven by a brushless motor or an AC motor, and the pulse signal is generated in such a way that the pulse width of the pulse signal is inversely proportional to the flow rate of the fluid; an FV conversion step, wherein the pulse signal is frequency-to-voltage converted to generate a voltage value corresponding to the pulse signal; and a control step, wherein the frequency of the drive input voltage used to drive the brushless motor or the AC motor is changed based on the difference between the converted flow rate of the fluid calculated based on the voltage value generated by the FV conversion step and a preset target flow rate.

[0039] Furthermore, one embodiment of the present invention provides a cooler that includes the flow control device and a liquid flow device for circulating cooled liquid, wherein the flow rate of the liquid is controlled by the flow control device.

[0040] Invention Effects

[0041] According to the present invention, flow control can be appropriately implemented through streamlined hardware resources and software processing. Attached Figure Description

[0042] Figure 1 This is a diagram showing a schematic configuration of a cooler equipped with a flow control device according to an embodiment of the present invention.

[0043] Figure 2 This is a block diagram illustrating the functional configuration of a flow control device according to an embodiment of the present invention.

[0044] Figure 3 This diagram illustrates the pulse signal generated by the flow meter of the flow control device according to an embodiment of the present invention, and the frequency / voltage conversion achieved by the FV conversion unit of the flow control device.

[0045] Figure 4 This is a diagram that conceptually illustrates an example of an adjustment frequency table maintained by a controller in a flow control device according to an embodiment of the present invention.

[0046] Figure 5 This is a graph showing the state of flow rate changes when flow control is performed by a flow control device according to an embodiment of the present invention.

[0047] Figure 6 This is a flowchart illustrating an example of the operation of flow control performed by a flow control device according to an embodiment of the present invention. Detailed Implementation

[0048] Hereinafter, a cooler 1 equipped with a flow control device 100 according to an embodiment of the present invention will be described. Figure 1 This is a diagram showing the general structure of cooler 1.

[0049] like Figure 1 As shown, the cooler 1 includes a pump 10, an upstream flow path 20 connected to the suction port of the pump 10, a downstream flow path 30 connected to the discharge port of the pump 10, and a flow control device 100.

[0050] Pump 10 has a pump body 11 that houses the impeller within a housing and a motor 12 that rotates the impeller.

[0051] The cooler 1 uses the motor 12 to rotate the impeller of the pump body 11, which draws liquid from the upstream flow path 20 into the pump 10 and discharges it to the downstream flow path 30. The liquid flowing into the downstream flow path 30 is cooled by the heat exchanger 40 and then supplied from the outlet of the downstream flow path 30 to a temperature control object (not shown).

[0052] In this embodiment, the liquid supplied from the outlet of the downstream flow path 30 to the temperature control target flows into the upstream flow path 20 after passing through the temperature control target, and is drawn back into the pump 10. That is, the cooler 1 is configured to circulate the liquid.

[0053] The cooler 1 is not limited to the circulation type described above, but can also be configured as a discharge type. For example, a discharge type cooler is configured to sequentially draw in liquid supplied to the temperature control object from the liquid source, so that the liquid supplied to the temperature control object does not circulate back to the liquid source.

[0054] In the cooler 1 of this embodiment, brine is used as the circulating liquid, but the liquid is not particularly limited.

[0055] Motor 12 is electrically connected to drive circuit 60 and is driven by the drive input voltage supplied from drive circuit 60. In this embodiment, motor 12 is a brushless DC motor, and its rotational speed increases proportionally to the frequency of the drive input voltage supplied from drive circuit 60. Specifically, motor 12 in this embodiment is a three-phase brushless DC motor, but the number of phases of motor 12 is not particularly limited.

[0056] The drive circuit 60 has the function of changing the frequency of the drive input voltage according to the command from the flow control device 100. The flow control device 100 adjusts the rotational speed of the motor 12 by changing the frequency of the drive input voltage, thereby controlling the flow rate of the liquid discharged from the pump 10. Alternatively, the motor 12 can also be an AC motor, in which case the rotational speed increases proportionally to the frequency of the supplied drive input voltage. When the motor 12 is an AC motor, the drive circuit 60 is configured as an inverter.

[0057] The flow control device 100 includes a flow meter 110 disposed in the downstream flow path 30, an FV conversion unit 120 electrically connected to the flow meter 110, and a controller 130 electrically connected to the FV conversion unit 120 and the drive circuit 60. Figure 2 This is a block diagram illustrating the functional configuration of the flow control device 100. Hereinafter, refer to... Figure 1 and Figure 2 The details of each part of the flow control device 100 are explained.

[0058] The flow meter 110 repeatedly generates pulse signals based on the flow of liquid discharged from the pump 10, forming pulse signals in such a way that the pulse width of the generated pulse signal is inversely proportional to the flow rate of the liquid. For the pulse signals generated by the flow meter 110, the greater the flow rate of the liquid, the smaller the pulse width and period, and the greater the frequency.

[0059] The flow meter 110 shown in the diagram is an impeller-type flow meter, but it could also be a paddle-type flow meter, etc. Furthermore, such as... Figure 1 As shown, in this embodiment, the flow meter 110 is disposed between the outlet of the downstream flow path 30 and the heat exchanger 40, but the placement of the flow meter 110 is not particularly limited.

[0060] The FV conversion unit 120 performs frequency-to-voltage conversion (hereinafter referred to as FV conversion) on the pulse signal generated by the flow meter 110, generating a voltage value corresponding to the pulse signal generated by the flow meter 110. In detail, the FV conversion unit 120 converts the pulse signal repeatedly generated by the flow meter 110 into a continuous physical quantity (analog signal) composed of voltage values.

[0061] The FV converter 120 generates a voltage value for a pulse signal, and the voltage value generated by the FV converter 120 increases proportionally to the frequency of the pulse signal generated by the flow meter 110.

[0062] Furthermore, in this embodiment, the FV conversion unit 120 calculates a reference voltage value based on a moving average of the generated multiple voltage values. This reference voltage value is preferably calculated using a moving average of 40 to 80 voltage values; more specifically, it is preferable to calculate the reference voltage value based on a moving average of 40 to 80 voltage values ​​with a period of 1 to 4 seconds. In this case, the FV conversion unit 120 preferably performs FV conversion on the pulse signal generated by the flow meter 110 at a rate of 10 to 120 pulses per second, for example. To achieve such a high-speed FV conversion, it is preferable to determine the specifications of the flow meter 110 by enabling the flow meter 110 to output a pulse signal at a frequency of 10 Hz to 120 Hz according to the flow rate of the liquid.

[0063] Various configurations have been proposed for the FV conversion unit 120 in the past, but in this embodiment, since the FV conversion unit 120 only receives rectangular pulses from the flow meter 110, it may not have functions such as sinusoidal FV conversion. Therefore, the FV conversion unit 120 is a relatively small component capable of performing the minimum required FV conversion, and it is particularly preferable to be constructed from a single-chip IC. Using such a small FV conversion unit is advantageous in terms of space utilization.

[0064] Figure 3 This diagram illustrates the pulse signal generated by the flow meter 110 and the frequency / voltage conversion performed by the FV conversion unit 120. Figure 3 The diagram shows three graphs arranged vertically, with the horizontal axis representing time (t) and the vertical axis representing voltage (V). The upper graph shows the pulse signal generated by the flow meter 110 based on the elapsed time of liquid flow. The middle graph shows the voltage value generated by the FV converter 120 after converting the pulse signal generated by the flow meter 110 into an FV value. The lower graph shows the reference voltage value calculated by moving average of multiple voltage values ​​generated by the FV converter 120.

[0065] exist Figure 3 In the upper-level chart, the range shown by L indicates the range where the liquid flow rate is relatively small, the range shown by H indicates the range where the fluid flow rate is greater than the liquid flow rate in range L, and the range shown by M indicates the range where the liquid flow rate is greater than the liquid flow rate in range L and less than the liquid flow rate in range H.

[0066] from Figure 3 As shown in the upper-level chart, the pulse width (period) of the pulse signal generated in range H is smaller than the pulse width (period) of the pulse signals generated in ranges L and M. Furthermore, the pulse width (period) of the pulse signal generated in range M is smaller than the pulse width (period) of the pulse signal generated in range L. Additionally, Figure 3 The pulse signals represented by the ranges L, H, and M in the upper-level chart are shown in fewer numbers than they actually are for the sake of simplicity.

[0067] Figure 3 The middle layer diagram shows the voltage values ​​of the pulse signals in the ranges L, H, and M when the FV conversion unit 120 performs FV conversion. The voltage value corresponding to the pulse signal in range H is greater than the voltage values ​​corresponding to the pulse signals in other ranges L and M. Furthermore, the voltage value corresponding to the pulse signal in range M is greater than the voltage value corresponding to the pulse signal in range L.

[0068] Here, in Figure 3 In the middle layer of the graph, among the series of voltage values ​​corresponding to the pulse signals of each range L, H, and M, there are voltage values ​​that are very likely to be noise components. Therefore, the FV conversion unit 120 in this embodiment calculates the reference voltage by means of a moving average.

[0069] Figure 3 The lower-level chart shows the reference voltage value calculated by the FV conversion unit 120 through a moving average. The reference voltage value in the chart shifts smoothly, suppressing the generation of voltage values ​​that are likely to be noise components.

[0070] As an example, the FV conversion unit 120 can also calculate a reference voltage value based on the latest voltage value and a moving average of the voltage values ​​detected at several points prior to the latest voltage value. Specifically, when using... Figure 3 When calculating the reference voltage value for point P in the middle layer of the chart, it can be calculated based on the moving average of the voltage values ​​detected at several points between point P and the period x preceding point P. Figure 3 The reference voltage value is located at point P' in the lower layer of the graph. In this embodiment, the controller 130 samples the reference voltage value, calculates the liquid flow rate based on the reference voltage value, and then performs flow control. That is, in this embodiment, the situation where the controller 130 samples the noise component of the voltage value and performs flow control based on that is avoided, thus improving the stability of the flow control.

[0071] Next, the controller 130 will be described. The controller 130 changes the frequency of the drive input voltage used to drive the motor 12 based on the difference between the liquid's converted flow rate (based on the voltage value generated by the FV converter 120) and a preset target flow rate.

[0072] The controller 130 can also be configured as a computer with a CPU, ROM, etc. In this case, various processes are performed according to the program stored in the ROM, such as voltage value acquisition processing, liquid flow rate conversion processing based on voltage value, determination processing of the difference between the converted flow rate and the target flow rate, and frequency change processing of the drive input voltage based on the difference. In particular, as will be clearly understood in the following description, by implementing such various processes in a simplified manner, appropriate control can be implemented even when using a single-core CPU. Therefore, it becomes easier to simplify the use of hardware resources based on a single-core CPU, for example. However, the form of the CPU is not particularly limited. Furthermore, the controller 130 can also be configured as other processors or circuits (such as FPGA (Field Programmable Gate Array)).

[0073] like Figure 2 As shown, the controller 130 has a flow conversion unit 131, a table holding unit 132, an adjustment frequency determination unit 133, and an adjustment frequency output unit 134 as functional components.

[0074] The flow conversion unit 131 samples the voltage value generated by the FV conversion unit 120, which in this embodiment is a reference voltage value, and calculates the converted flow rate, i.e., the current flow rate of the liquid, based on the reference voltage value. The larger the reference voltage value, the larger the converted flow rate calculated by the flow conversion unit 131 becomes.

[0075] The table holding unit 132 holds an adjustment frequency table Ta, which records the relationship between multiple difference ranges and multiple adjustment frequencies determined respectively for these multiple difference ranges. The multiple difference ranges are determined by their respective lower and upper limits, which are the ranges to which the absolute value of the difference between the converted flow rate calculated by the flow conversion unit 131 and the target flow rate belongs. That is, the adjustment frequency table Ta records the relationship between multiple difference ranges used to classify the degree of difference between the converted flow rate calculated by the flow conversion unit 131 and the target flow rate into multiple stages, and the multiple adjustment frequencies determined respectively for each of the multiple difference ranges. The lower and upper limits of the multiple difference ranges are different from each other.

[0076] The target flow rate, which is compared with the converted flow rate calculated by the flow rate conversion unit 131, is input by the user to the controller 130. In this embodiment, the input target flow rate is sent to the adjustment frequency determination unit 133 and the adjustment frequency output unit 134, and is held by the adjustment frequency determination unit 133 and the adjustment frequency output unit 134 respectively.

[0077] The frequency adjustment determination unit 133 determines the difference between the converted flow rate calculated by the flow rate conversion unit 131 and the target flow rate, and based on the difference and the frequency adjustment table Ta held by the table holding unit 132, determines the adjustment frequency corresponding to the determined difference from a plurality of adjustment frequencies recorded in the frequency adjustment table Ta.

[0078] The adjustment frequency determined by the adjustment frequency determination unit 133 is sent to the adjustment frequency output unit 134. The adjustment frequency output unit 134 outputs a command to the drive circuit 60 to add or subtract the adjustment frequency sent from the adjustment frequency determination unit 133 to the frequency of the drive input voltage when the adjustment frequency is determined. As a result, the frequency of the drive input voltage input to the motor 12 by the drive circuit 60 is changed.

[0079] Figure 4 This is a conceptual diagram illustrating the adjustment frequency table Ta held by the table holding unit 132. Figure 4 The diagram illustrates a portion of the relationship between the differential range and the adjustment frequency. Specifically, it shows the relationship between the differential range determined by the lower limit D1 and the upper limit D2 and its corresponding adjustment frequency Δf1; the differential range determined by the lower limit D2 and the upper limit D3 and its corresponding adjustment frequency Δf2; the differential range determined by the lower limit D3 and the upper limit D4 and its corresponding adjustment frequency Δf3; and the differential range determined by the lower limit D4 and the upper limit D5 and its corresponding adjustment frequency Δf4.

[0080] In the adjustment frequency table Ta, multiple adjustment frequency values ​​are set such that the larger the difference Δd between the converted flow rate calculated by the flow conversion unit 131 and the target flow rate, the larger the flow rate adjusted by the adjustment frequency. Therefore, in Figure 4 In this case, the relationship Δf1<Δf2<Δf3<Δf4 holds true.

[0081] After determining the difference Δd between the converted flow rate calculated by the flow rate conversion unit 131 and the target flow rate, the frequency adjustment determination unit 133 determines the adjustment frequency by referring to the adjustment frequency table Ta to change the frequency of the current drive input voltage. Then, the adjustment frequency output unit 134 generates an instruction (voltage signal) to add or subtract the adjustment frequency sent from the adjustment frequency determination unit 133 to the frequency of the drive input voltage when the adjustment frequency is determined, and outputs the instruction to the drive circuit 60. Here, when the sign of the difference Δd between the converted flow rate and the target flow rate when the adjustment frequency is determined is negative, an instruction to add the adjustment frequency is generated and output; when the sign of the difference Δd is positive, an instruction to subtract the adjustment frequency is generated and output.

[0082] For clarity of explanation, the adjustment frequency determined by the adjustment frequency determination unit 133 will be referred to as "adjustment frequency (Δf)" and the operation of the adjustment frequency output unit 134 in this embodiment will be explained in detail.

[0083] In this embodiment, the frequency adjustment output unit 134 first performs a pre-stage adjustment operation, which adds or subtracts the adjustment frequency (Δf) once or repeatedly when determining the frequency of the drive input voltage determined by the frequency adjustment determination unit 133. After the pre-stage adjustment operation, if the difference between the liquid flow rate and the target flow rate has not disappeared, a post-stage adjustment operation is performed.

[0084] In the pre-adjustment operation, the adjustment frequency output unit 134 first outputs a command to add or subtract the adjustment frequency (Δf) from the frequency of the drive input voltage at which the adjustment frequency (Δf) is determined once. Then, it operates as follows: if the sign of the difference between the liquid flow rate and the target flow rate relative to the difference between the converted flow rate and the target flow rate at the time of determining the adjustment frequency (Δf) (hereinafter referred to as the frequency determination time difference) has not reversed or disappeared, the drive input voltage after the first addition or subtraction of the adjustment frequency (Δf) is further added or subtracted once or repeatedly until the sign of the difference between the liquid flow rate and the target flow rate relative to the aforementioned frequency determination time difference, which serves as the difference at the time of determining the adjustment frequency (Δf), reverses or disappears. In addition, in the pre-adjustment operation, the flow conversion unit 131 appropriately samples the reference voltage value and converts it into a converted flow rate, and the adjustment frequency output unit 134 refers to the converted flow rate as needed.

[0085] In this embodiment, the adjustment frequency (Δf) is set such that the absolute value of the increase or decrease in liquid flow rate when the frequency of the drive input voltage is added to or subtracted from the adjustment frequency (Δf) is less than the lower limit of the difference range corresponding to the adjustment frequency (Δf). Therefore, in this embodiment, the difference between the liquid flow rate and the target flow rate is not substantially eliminated by the addition or subtraction of the adjustment frequency (Δf) in the first adjustment operation. This setting of the adjustment frequency (Δf) is implemented to suppress the possible decrease in responsiveness to the target flow rate due to large changes in the adjusted flow rate.

[0086] More specifically, the upper limit of the differential range determined by the adjustment frequency table Ta is set to be smaller than twice the lower limit. Furthermore, the adjustment frequency (Δf) is set such that the absolute value of the change in liquid flow rate resulting from adding or subtracting this adjustment frequency (Δf) to the frequency of the drive input voltage is greater than half the upper limit of the differential range corresponding to that adjustment frequency (Δf). In other words, in Figure 4In the example, the relationship D2 / 2 < the flow rate change caused by the adjustment frequency (Δf1) < D1 holds. In this case, it is possible to suppress a decrease in responsiveness to the target flow rate due to an excessively small adjusted flow rate.

[0087] Then, after the above-described pre-stage adjustment operation, when the difference between the flow rate of the liquid and the target flow rate does not disappear, the adjustment frequency output unit 134 performs a post-stage adjustment operation. In the post-stage adjustment operation, the adjustment frequency output unit 134 performs the following post-stage adjustment operation: performs n fine adjustment unit processes until the flow rate of the liquid coincides with the target flow rate. In the fine adjustment unit process, it operates in such a way that the drive input voltage is increased or decreased by one or repeatedly by a fine adjustment frequency (Δfn) smaller than the adjustment frequency (Δf) used in the pre-stage adjustment operation. Also, when performing multiple (n ≥ 2) fine adjustment unit processes, the fine adjustment frequency (Δfn) used in the fine adjustment unit process can be set to be smaller than the fine adjustment frequency (Δfn) used in the previous fine adjustment unit process. In addition, the above "n" is, of course, an integer.

[0088] More specifically, when defining the pre-stage adjustment operation as the 0th fine adjustment unit process, in the nth fine adjustment unit process in the post-stage adjustment operation, when the flow rate of the liquid calculated after the (n - 1)th fine adjustment unit process exceeds the target flow rate (liquid flow rate > target flow rate), perform an operation to subtract the fine adjustment frequency (Δfn) from the frequency of the drive input voltage after the (n - 1)th fine adjustment unit process by one or repeatedly until the sign of the difference between the liquid flow rate and the target flow rate turns negative or the difference between the liquid flow rate and the target flow rate disappears. That is, the adjustment frequency output unit 134 outputs an instruction (voltage signal) for subtracting the fine adjustment frequency (Δfn) to the drive circuit 60 by one or repeatedly until the sign of the difference between the liquid flow rate and the target flow rate turns negative or the difference between the liquid flow rate and the target flow rate disappears.

[0089] On the other hand, in the nth fine adjustment unit process when the flow rate of the liquid calculated after the (n - 1)th fine adjustment unit process is lower than the target flow rate (liquid flow rate < target flow rate), perform an operation to add the fine adjustment frequency (Δfn) to the frequency of the drive input voltage after the (n - 1)th fine adjustment unit process by one or repeatedly until the sign of the difference between the liquid flow rate and the target flow rate turns positive or the difference between the liquid flow rate and the target flow rate disappears. That is, the adjustment frequency output unit 134 outputs an instruction (voltage signal) for adding the fine adjustment frequency (Δfn) to the drive circuit 60 by one or repeatedly until the sign of the difference between the liquid flow rate and the target flow rate turns positive or the difference between the liquid flow rate and the target flow rate disappears.

[0090] Then, if the difference between the liquid flow rate and the target flow rate does not disappear after the nth fine-tuning unit processing as described above, the adjustment frequency output unit 134 performs the next fine-tuning unit processing in the subsequent adjustment operation. Similarly, in the subsequent adjustment operation, the flow conversion unit 131 appropriately samples the reference voltage value and converts it into a converted flow rate, and the adjustment frequency output unit 134 refers to the converted flow rate as needed. Furthermore, the concepts of the difference between the liquid flow rate and the target flow rate not disappearing and the concepts of the liquid flow rate being consistent with the target flow rate include not only the case where the liquid flow rate and the target flow rate are completely consistent, but also the concept of being considered consistent. The benchmark for being considered consistent can be appropriately determined by the user based on the flow rate of the liquid being processed, etc.

[0091] Furthermore, in this embodiment, when the fine-tuning unit process is performed multiple times (n≥2) as described above, the fine-tuning frequency (Δfn) used in the fine-tuning unit process is set to be less than the fine-tuning frequency (Δfn) used in the previous fine-tuning unit process. This allows the liquid flow rate to gradually approach the target flow rate. More specifically, in this embodiment, the fine-tuning frequency (Δfn) used in the nth (n≥1) fine-tuning unit process is set to the value obtained by dividing the adjustment frequency (Δf) used in the previous adjustment action by 2 raised to the power of n. In this case, the fine-tuning frequency (Δfn) can be determined through a simple process.

[0092] Figure 5 The state of flow change when flow control is performed by flow control device 100 is shown. More specifically, the state of the pre-stage adjustment operation and the subsequent post-stage adjustment operation described above are shown. Figure 5 The horizontal axis in the chart represents time (t), and the vertical axis represents flow rate (L / min).

[0093] exist Figure 5 In the example, the difference (Δd) between the converted flow rate and the target flow rate calculated by the flow conversion unit 131 is included in the calculation by the flow conversion unit 131. Figure 4 The adjustment frequency is determined by the lower limit D1 and the upper limit D2 in the adjustment frequency table Ta shown. Therefore, the adjustment frequency determination unit 133 determines the adjustment frequency (Δf1) as the adjustment frequency corresponding to the difference (Δd).

[0094] Then, if the liquid flow rate before the pre-adjustment is lower than the target flow rate TL (liquid flow rate < target flow rate TL), the adjustment frequency (Δf1) is added twice during the pre-adjustment. Furthermore, the sign (negative) of the difference between the liquid flow rate and the target flow rate TL is reversed relative to the difference (Δd) when the adjustment frequency (Δf1) is determined.

[0095] Furthermore, since the difference between the liquid flow rate and the target flow rate TL does not disappear after the initial adjustment, a subsequent adjustment is performed. In this subsequent adjustment, the fine-tuning frequency (Δfn1) is subtracted twice during the first fine-tuning unit processing. The fine-tuning frequency (Δfn1) in the first fine-tuning unit processing becomes the adjustment frequency (Δf1) / 2. And since the difference between the liquid flow rate and the target flow rate TL does not disappear after the first fine-tuning unit processing, a second fine-tuning unit processing is performed. Then, in the second fine-tuning unit processing, the fine-tuning frequency (Δfn2) is added twice. The fine-tuning frequency (Δfn2) in the second fine-tuning unit processing becomes the adjustment frequency (Δf1) / 2. 2 Furthermore, since the difference between the liquid flow rate and the target flow rate TL did not disappear after the second fine-tuning unit process, a third fine-tuning unit process is performed. Then, in the third fine-tuning unit process, two subtractions of the fine-tuning frequency (Δfn3) are performed. The fine-tuning frequency (Δfn3) in the third fine-tuning unit process becomes the adjustment frequency (Δf1) / 2. 3 As mentioned above, the liquid flow rate gradually approaches the target flow rate TL.

[0096] Figure 6 This is a flowchart illustrating an example of the operation of flow control performed by the flow control device 100. Hereinafter, refer to... Figure 6 An example of the flow control operation performed by the flow control device 100 will be described.

[0097] Figure 6 The process can be initiated, for example, by the occurrence of a flow control start event. This flow control start event can occur periodically or when the difference between the liquid flow rate and the target flow rate exceeds a certain value.

[0098] In this example, firstly, the flow conversion unit 131 samples the voltage value (in this embodiment, the reference voltage value) generated by the FV conversion unit 120 in step S1, and then in step S2, it converts the reference voltage value into a converted flow rate.

[0099] Next, in step S3, the frequency determination unit 133 determines the difference between the converted flow rate calculated by the flow rate conversion unit 131 and the target flow rate. Then, in step S4, the frequency determination unit 133 determines the adjustment frequency corresponding to the determined difference from a plurality of adjustment frequencies recorded in the adjustment frequency table Ta, based on the determined difference and the adjustment frequency table Ta held by the table holding unit 132.

[0100] Then, in step S5, the frequency adjustment output unit 134 outputs an instruction (adjustment frequency instruction) to the drive circuit 60 to add or subtract the adjustment frequency once when the adjustment frequency determined by the frequency adjustment determination unit 133 is determined. As a result, the frequency of the drive input voltage input to the motor 12 by the drive circuit 60 is changed, and the flow rate of the liquid discharged by the pump 10 is changed.

[0101] Then, in step S6, the frequency adjustment output unit 134 determines whether the sign of the difference between the liquid flow rate and the target flow rate after the first addition or subtraction of the adjustment frequency is reversed relative to the sign of the difference when the adjustment frequency was determined in step S4 (the difference when the frequency was determined). In step S6, if the difference is not reversed, the frequency adjustment output unit 134 determines in step S7 whether there is a difference between the current fluid flow rate and the target flow rate. If a difference is determined to exist in step S7, the frequency adjustment output unit 134 returns to step S5 and outputs a command to the drive circuit 60 to perform another addition or subtraction of the adjustment frequency. If a difference is determined to not exist in step S7, since the liquid flow rate is consistent with the target flow rate, the flow control operation ends.

[0102] The process of adding or subtracting the adjustment frequency in step S5 is repeated until the sign of the difference is reversed in step S6 or the difference is determined to be non-existent in step S7. That is, the processes in steps S5 to S7 correspond to the above-described pre-stage adjustment actions.

[0103] On the other hand, in step S6, if the sign of the difference between the liquid flow rate and the target flow rate is reversed relative to the sign of the difference when the adjustment frequency was determined in step S4, the process proceeds to step S8. In step S8, the adjustment frequency output unit 134 outputs an instruction (adjustment frequency instruction) to the drive circuit 60 to add or subtract the fine-tuning frequency once to the frequency of the drive input voltage after the previous adjustment operation. That is, the first fine-tuning unit processing in the subsequent adjustment operation is performed. As described above, the fine-tuning frequency in the first fine-tuning unit processing is set to the value obtained by dividing the adjustment frequency used in the previous adjustment operation by 2 to the power of 1.

[0104] Then, in step S9, the frequency output unit 134 determines whether the sign of the difference between the current liquid flow rate and the target flow rate is reversed relative to the sign of the difference when the difference was reversed in step S6. If it is determined in step S9 that the difference has not been reversed, the frequency output unit 134 determines in step S10 whether there is a difference between the current fluid flow rate and the target flow rate. If it is determined in step S10 that there is a difference, the frequency output unit 134 returns to step S8 and outputs a command to the drive circuit 60 to further add or subtract the fine-tuning frequency once. If it is determined in step S10 that there is no difference, since the liquid flow rate is consistent with the target flow rate, the flow control operation ends.

[0105] The process of adding or subtracting the fine-tuning frequency in step S8 is repeated until the sign of the difference is reversed in step S9 or the difference is determined not to exist in step S10.

[0106] Then, in step S9, if the sign of the difference between the liquid flow rate and the target flow rate is reversed relative to the difference in step S6, the process moves to step S11 to perform the second fine-tuning unit processing in the subsequent adjustment action.

[0107] In step S11, the frequency adjustment output unit 134 outputs a command (frequency adjustment command) to the drive circuit 60 to add or subtract a fine-tuning frequency once to the frequency of the drive input voltage. As described above, the fine-tuning frequency in this second fine-tuning unit process is set to the value obtained by dividing the adjustment frequency used in the previous adjustment operation by 2 to the power of 2.

[0108] Then, in step S12, the frequency output unit 134 determines whether the sign of the difference between the current liquid flow rate and the target flow rate is reversed relative to the sign of the difference between the liquid flow rate and the target flow rate when the difference was reversed in step S9. If it is determined in step S12 that the difference has not been reversed, the frequency output unit 134 determines in step S13 whether there is a difference between the current liquid flow rate and the target flow rate. If it is determined in step S13 that a difference exists, the frequency output unit 134 returns to step S11 and outputs a command to the drive circuit 60 to further add or subtract the fine-tuning frequency once. If it is determined in step S13 that there is no difference, since the liquid flow rate is consistent with the target flow rate, the flow control operation ends.

[0109] The process of adding or subtracting the fine-tuning frequency in step S11 is repeated until the sign of the difference is inverted in step S12 or the absence of a difference is determined in step S13. Then, in step S12, if the sign of the difference is inverted, the fine-tuning frequency is updated to half the value used in step S11 in step S14, and the process returns to step S8. In step S8, the drive circuit 60 is output with an instruction (adjustment frequency instruction) to add or subtract the fine-tuning frequency updated in step S14 once to the frequency of the drive input voltage. The processes of steps S8 to S14 correspond to the subsequent adjustment operation.

[0110] In addition, the above explanation Figure 6 The illustrated procedure is merely an example, and the invention is not limited to this. Figure 6 The actions shown.

[0111] The flow control device 100 of this embodiment described above includes a flow meter 110, an FV converter 120, and a controller 130. The flow meter 110 repeatedly generates pulse signals based on the flow of liquid discharged from the pump 10 (a fluid machine) driven by a motor 12 (a brushless motor), forming pulse signals such that the pulse width of the generated pulse signal is inversely proportional to the liquid flow rate. The FV converter 120 performs frequency-to-voltage conversion on the pulse signals generated by the flow meter 110, generating a voltage value corresponding to the pulse signal. The controller 130 changes the frequency of the drive input voltage used to drive the motor 12 based on the difference between the converted flow rate of the liquid calculated based on the voltage value generated by the FV converter 120 and a preset target flow rate.

[0112] In other words, if described using a flow control process, this embodiment includes a pulse signal acquisition step, an FV conversion step, and a control step that changes the frequency of the drive input voltage. In the pulse signal acquisition step, a pulse signal is acquired from the flow meter 110. In the FV conversion step, the pulse signal acquired in the pulse signal acquisition step is frequency-to-voltage converted to generate a voltage value corresponding to the pulse signal. In the control step, the frequency of the drive input voltage of the motor 12 is changed based on the difference between the converted flow rate of the liquid calculated from the voltage value generated in the FV conversion step and a preset target flow rate.

[0113] In this embodiment, by performing frequency-to-voltage conversion on the pulse signal generated by the flow meter 110 using the FV conversion unit 120, the pulse signal repeatedly generated according to the flow of fluid can be converted into a continuous physical quantity (analog signal) consisting of voltage values. Therefore, the controller 130 can, for example, determine the voltage value indicating the flow rate and the flow rate of the liquid discharged from the pump 10 by sampling at any given time. This reduces the load on signal processing and prevents flow detection omissions in the controller 130, enabling appropriate flow control based on flow detection. Thus, flow control can be appropriately implemented with simplified hardware resources and software processing.

[0114] The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above, and various modifications can be made to the above embodiments. For example, the flow control device 100 of the above embodiments is applied to the flow control of liquid discharged by pump 10, but the flow control device 100 can also be applied to the flow control of gas discharged by blower, etc.

Claims

1. A flow control device, characterized in that, have: The flow meter repeatedly generates pulse signals based on the flow of liquid discharged from the pump driven by a brushless motor or an AC motor, and the pulse signal is formed in such a way that the pulse width of the pulse signal is inversely proportional to the flow rate of the liquid. The FV conversion unit performs frequency-to-voltage conversion on the pulse signal to generate a voltage value corresponding to the pulse signal; The controller, based on the difference between the calculated flow rate of the liquid (based on the voltage value generated by the FV converter) and a preset target flow rate, changes the frequency of the drive input voltage used to drive the brushless motor or AC motor. The controller maintains an adjustment frequency table, which records the relationship between multiple difference ranges and multiple adjustment frequencies determined respectively for each of the multiple difference ranges. The multiple difference ranges are determined by their respective lower and upper limits, based on the absolute value of the difference between the converted flow rate and the target flow rate. Based on the difference between the calculated flow rate and the target flow rate and the adjustment frequency table, the controller determines the adjustment frequency corresponding to the difference between the calculated flow rate and the target flow rate from among the plurality of adjustment frequencies, and outputs an instruction to add or subtract the determined adjustment frequency to the frequency of the drive input voltage at the time the adjustment frequency was determined, thereby changing the frequency of the drive input voltage. The adjustment frequency is set such that the absolute value of the change in liquid flow rate increased or decreased when the frequency of the drive input voltage is added to or subtracted from the adjustment frequency is less than the lower limit of the differential range corresponding to the adjustment frequency.

2. The flow control device as described in claim 1, characterized in that, The FV converter generates a voltage value for one pulse signal and calculates a reference voltage value by a moving average of multiple voltage values. The controller calculates the converted flow rate based on the reference voltage value.

3. The flow control device as described in claim 2, characterized in that, The FV conversion unit calculates the reference voltage value by a moving average of 40 to 80 voltage values.

4. The flow control device as described in claim 3, characterized in that, The FV conversion unit converts the pulse signal generated by the flow meter into a frequency / voltage at a rate of 10 to 120 pulses per second.

5. The flow control device as described in claim 1, characterized in that, The controller first performs a pre-adjustment action by adding or subtracting the adjustment frequency once. If, after adding or subtracting the adjustment frequency once, the sign of the difference between the liquid flow rate and the target flow rate, relative to the difference between the converted flow rate and the target flow rate when the adjustment frequency was determined (i.e., the difference when the frequency was determined), does not reverse or disappear, the controller further adds or subtracts the adjustment frequency once or repeatedly until the sign of the difference between the liquid flow rate and the target flow rate, relative to the difference when the frequency was determined, reverses or disappears. After the initial adjustment, if the difference between the liquid flow rate and the target flow rate has not disappeared, the subsequent adjustment is performed as follows: n fine-tuning unit processes are performed until the liquid flow rate matches the target flow rate. In the fine-tuning unit process, the drive input voltage is adjusted by adding or subtracting a fine-tuning frequency smaller than the adjustment frequency used in the initial adjustment. When performing the fine-tuning unit process multiple times (n≥2), the fine-tuning frequency used in the fine-tuning unit process is set to be smaller than the fine-tuning frequency used in the previous fine-tuning unit process.

6. The flow control device as described in claim 5, characterized in that, When the preceding adjustment action is defined as the 0th fine-tuning unit process, In the nth fine-tuning unit processing within the subsequent adjustment action, If the liquid flow rate calculated after the (n-1)th fine-tuning unit processing exceeds the target flow rate, an action is performed to subtract the fine-tuning frequency from the frequency of the drive input voltage after the (n-1)th fine-tuning unit processing once or repeatedly, until the sign of the difference between the liquid flow rate and the target flow rate turns negative or the difference between the liquid flow rate and the target flow rate disappears. If the calculated flow rate of the liquid after the (n-1)th fine-tuning unit processing is lower than the target flow rate, the frequency of the drive input voltage after the (n-1)th fine-tuning unit processing is increased once or repeatedly by the fine-tuning frequency until the sign of the difference between the liquid flow rate and the target flow rate turns positive or the difference between the liquid flow rate and the target flow rate disappears. If the difference between the liquid flow rate and the target flow rate does not disappear after the nth fine-tuning unit processing, the controller will perform the next fine-tuning unit processing in the subsequent adjustment action.

7. The flow control device as described in claim 5, characterized in that, The fine-tuning frequency used in the nth fine-tuning unit process is set to the value obtained by dividing the adjustment frequency used in the previous adjustment action by 2 to the power of n.

8. The flow control device as described in claim 1, characterized in that, The upper limit value is set to be smaller than the value obtained by doubling the lower limit value. The adjustment frequency is set such that the absolute value of the change in liquid flow rate increased or decreased by adding or subtracting the adjustment frequency to the frequency of the drive input voltage is greater than half the upper limit of the differential range corresponding to the adjustment frequency.

9. The flow control device as described in claim 1, characterized in that, The controller uses a single-core CPU to acquire the voltage value, calculate the flow rate of the liquid based on the voltage value, determine the difference between the calculated flow rate and the target flow rate, and change the frequency of the drive input voltage.

10. A flow control method, characterized in that, have: The pulse signal acquisition process involves acquiring the pulse signal from a flow meter that repeatedly generates pulse signals based on the flow of liquid discharged from the pump driven by a brushless motor or an AC motor, and forms the pulse signal in such a way that the pulse width of the pulse signal is inversely proportional to the flow rate of the liquid. The FV conversion process performs frequency / voltage conversion on the pulse signal to generate a voltage value corresponding to the pulse signal; The control process, based on the difference between the calculated flow rate of the liquid (based on the voltage value generated by the FV conversion process) and a preset target flow rate, changes the frequency of the drive input voltage used to drive the brushless motor or AC motor. In the control process, based on the difference between the calculated flow rate and the target flow rate and an adjustment frequency table, an adjustment frequency corresponding to the difference between the calculated flow rate and the target flow rate is determined from multiple adjustment frequencies. An instruction is output to add or subtract the determined adjustment frequency from the frequency of the drive input voltage at the time the adjustment frequency is determined, thereby changing the frequency of the drive input voltage. The adjustment frequency table records the relationship between multiple difference ranges and multiple adjustment frequencies determined corresponding to the multiple difference ranges. The multiple difference ranges are determined by the range to which the absolute value of the difference between the converted flow rate and the target flow rate belongs, through their respective lower and upper limits. The adjustment frequency is set such that the absolute value of the change in liquid flow rate increased or decreased when the frequency of the drive input voltage is added to or subtracted from the adjustment frequency is less than the lower limit of the differential range corresponding to the adjustment frequency.

11. A cooler, characterized in that, have: The flow control device according to claim 1; and A liquid flow device that allows cooled liquid to circulate. The flow rate of the liquid is controlled by the flow control device.

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