Compressor control system and compressor control method

Abstract

Provided are a compressor control system capable of achieving energy saving, and a compressor control method. This compressor control system comprises: a compressor for compressing gas; a sequencing control panel; and a pressure gauge for measuring a terminal pressure of a piping system that is connected to the compressor. A packaged compressor has a measurement unit, a determination unit, a setting unit, a control unit, and the compressor. The sequencing control panel has a measurement unit and an analog output unit. The sequencing control panel sends a first pressure that is received at the measurement unit from the pressure gauge, to the measurement unit through the analog output unit in the form of an analog signal. In the packaged compressor, the measurement unit sends the received analog signal to the determination unit as a pressure, the determination unit determines a relationship between the pressure and a threshold value which is stored in advance in the setting unit, and the control unit carries out compression control by controlling the compressor on the basis of the determination result derived by the determination unit.

Description

Compressor control system and compressor control method

[0001] The present disclosure relates to a compressor control system and a compressor control method for delivering compressed air using a compressor.

[0002] In compressor control systems that use compressors to supply compressed air to air tools, air blowers, air guns, etc., it is known to perform so-called rotation speed control to maintain the compressed air pressure within a certain range within the system. Patent Document 1 (JP 2010-24845 A) describes a method of detecting the pressure of each discharge air system, calculating the fluctuation in the pressure difference from the compressor outlet to each terminal, and operating the compressed air production equipment at a minimum pressure setting or discharge air volume.

[0003] JP 2010-24845 A

[0004] One method for detecting the compressed air pressure in a compressor control system is to use a pressure gauge installed inside the compressor. However, this method does not allow for the determination of the compressed air pressure at the end of the compressor control system (the load equipment side). To address this issue, it is conceivable to set the pressure inside the compressor (source pressure) higher in order to prevent the compressed air pressure at the end from falling below the required pressure. This results in increased energy consumption by the compressor control system.

[0005] The technology described in the present disclosure aims to provide a compressor control system and a compressor control method that can achieve energy savings.

[0006] A brief summary of a representative embodiment of the present invention will be given below.

[0007] A compressor control system according to one embodiment includes a first package compressor that compresses gas, a unit control panel, and a first pressure gauge that measures an end pressure of a piping system connected to the first package compressor. Here, the first package compressor includes a first measurement unit, a first determination unit, a first setting unit, a control unit, and a compressor, and the unit control panel includes a second measurement unit and an analog output unit. The unit control panel transmits a first pressure received from the first pressure gauge by the second measurement unit to the first measurement unit from the analog output unit. In the first package compressor, the first measurement unit transmits the received analog signal as a pressure to the first determination unit, and the first determination unit determines a relationship between the pressure and a threshold value pre-stored in the first setting unit. The control unit controls the compressor based on the determination result of the first determination unit to perform compression control.

[0008] A method of controlling a compressor according to one embodiment includes the steps of: (a) operating a first package compressor having a first measuring unit, a first determining unit, a first setting unit, a control unit, and a compressor, the first package compressor sending compressed gas to a piping system; (b) after step (a), receiving a pressure measured by a first pressure gauge connected to an end of the piping system with a second measuring unit in a number control panel, and transmitting an analog signal as a control pressure from the analog output unit in the number control panel to the first measuring unit; and (c) within the first package compressor, transmitting the analog signal received by the first measuring unit as a pressure to the first determining unit, the first determining unit determining the relationship between the pressure and a threshold value pre-stored in the first setting unit, and the control unit controlling the compressor based on the determination result, thereby performing compression control.

[0009] The effects obtained by the representative inventions disclosed in this application will be briefly explained as follows.

[0010] According to the present disclosure, it is possible to provide a compressor control system and a compressor control method that can achieve energy savings.

[0011] FIG. 1 is a schematic diagram showing a compressor control system according to an embodiment. FIG. 2 is a schematic diagram showing a compressor control system according to an embodiment. FIG. 3 is a flow diagram showing the operation of a number of units control panel according to an embodiment. FIG. 4 is a flow diagram showing the operation of a compressor after a signal is output from the number of units control panel according to an embodiment. FIG. 5 is a graph showing an image of pressure control by the compressor control system. FIG. 6 is a flow diagram showing the operation of a number of units control panel according to a first modified example of the embodiment. FIG. 7 is a flow diagram showing the operation of a number of units control panel according to a second modified example of the embodiment. FIG. 8 is a schematic diagram showing a compressor control system according to a third modified example of the embodiment. FIG. 9 is a schematic diagram showing a compressor control system according to a fourth modified example of the embodiment. FIG. 10 is a schematic diagram showing a compressor control system according to a fifth modified example of the embodiment.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. Furthermore, in the following embodiments, explanations of identical or similar parts will not be repeated unless specifically required. Furthermore, in the drawings for explaining the embodiments, hatching may be used even in plan views or perspective views to make the configuration easier to understand. Furthermore, in the drawings for explaining the embodiments, hatching may be omitted in cross-sectional views to make the configuration easier to understand.

[0013] In this application, "pressure" refers to the pressure of gas inside a tank or pipe after being compressed by a compressor in a compressor control system and before being discharged from a discharge port provided in a load facility. Also, in this application, pressure and pressure value have the same meaning. In the examples, air is compressed and discharged, but the gas to be compressed may be a gas other than air (e.g., nitrogen gas).

[0014] The details of the embodiment will be described below.

[0015] (Embodiment) Fig. 1 shows a schematic diagram of a compressor control system according to this embodiment. As shown in Fig. 1, the system has a unit control panel 20 and package compressors 30 and 31. The unit control panel 20 is connected to each of the package compressors 30 and 31. The unit control panel 20 may control a plurality of package compressors as shown in Fig. 1, or may control a single package compressor.

[0016] The package compressor 30 has a constant-speed compressor housed within a housing. The compressor 10 (see FIGS. 8 and 9 ) includes an air end that compresses air using power, a motor that operates at a constant speed, and a switch that supplies and cuts off power to the motor. The package compressor 31 has a variable-speed compressor housed within a housing. The compressor 11 (see FIG. 2 ) includes an air end that compresses air using power, a controller (e.g., an inverter) that controls the rotation speed, and a motor whose rotation speed can be adjusted by the controller. These motors are used to drive the air end. In one embodiment, each of the package compressors 30 and 31 has an air tank built into the housing. However, compressors with air tanks located outside the package may also be used. In FIG. 1 , only the package compressors 30 and 31 are connected to the unit control panel 20, but more package compressors may be connected to the unit control panel 20. In this embodiment, of the package compressors connected to the unit count control panel 20, only one package compressor is controlled in rotation speed at the same timing, and the remaining package compressors are controlled at a constant speed even if they are variable speed compressors, but the scope of application of the present invention is not limited to this.

[0017] The air tank is connected to a pipe 9, which is an air flow path extending to the outside of each of the package compressors 30 and 31. The pipe 9 branches out toward multiple terminals (downstream) to form a piping system. Compressed air (compressed gas) is discharged from each of the package compressors 30 and 31 to the pipe 9. Multiple flow meters Q for measuring the flow rate of the compressed air and multiple pressure gauges Pm for measuring the pressure of the compressed air are provided along the pipe 9. In FIG. 1 , the pressure gauges Pm are hatched. Multiple or single load equipment 25, 26, 27, and 28 are provided near the terminals of the piping system relative to the package compressors 30 and 31. Many of the pressure gauges Pm are located downstream of the load equipment. The load equipment 25, 26, 27, and 28 are each a different type of appliance that uses the compressed air discharged from the package compressors 30 and 31 as power. In this manner, in this embodiment, a plurality of load devices and pressure gauges are provided at the terminal side of the piping system extending from the package compressor (compressor). The terminal pressure values ​​measured by each of the plurality of pressure gauges Pm are transmitted to the unit control panel 20 via wire or wirelessly.

[0018] FIG. 2 is a schematic diagram of a compressor control system according to this embodiment. FIG. 2 shows, as an example, the package compressor 31 and air tank 8 of FIG. 1 , as well as the number control panel 20 and piping 9 external to the package compressor 31. The compressor 11 and air tank 8 are interconnected by piping 7. The pressure of the air in the piping 7 within the package compressor 31 is measured by a pressure gauge PS0 provided in the piping 7. That is, the pressure gauge PS0 is provided in the piping 7 upstream of the air tank 8. In the present application, the pressure measured anywhere from the piping within the package compressor to the air tank external to the package compressor is referred to as the source pressure. This source pressure naturally includes the pressure in the air tank within the package compressor and the pressure in the piping to the air tank external to the package compressor. Although not shown in FIG. 2 , if a pressure gauge is provided in the air tank 8, the pressure measured by that pressure gauge is the source pressure. The pressure measured by any other pressure gauge, i.e., a pressure gauge provided in a piping downstream of the air tank, is referred to as the terminal pressure.

[0019] The package compressor 31 includes a measuring unit 1, a determining unit 2, a setting unit 3, a control unit 4, and a compressor 11. The measuring unit 1 is connected to the determining unit 2, and the setting unit 3 is connected to the determining unit 2. The control unit 4 is connected to the compressor 11. The compressor 11 includes a controller CTL, an air end (air compression device) AE, and a motor M that operates the air end AE, and compresses air and sends it out through a pipe 7 to an air tank 8. Within the package compressor 31, a pressure gauge PS0 is provided on the pipe 7. Compressed air is sent out from the air tank 8 through a pipe 9, at the end of which pressure gauges PS1 to PSn are provided. Of the pressure gauges PS1 to PSn, only pressure gauges PS1 and PSn are shown in FIG. 2 .

[0020] As described above, the unit count control panel 20 is installed separately from the package compressors 30, 31 including the compressors. The unit count control panel 20 includes a measurement unit m0, a measurement unit mn, a determination unit 12, a setting unit 13, a calculation unit 14, and an analog output unit 15. The measurement units m0, mn are each connected to the determination unit 12, and the setting unit 13 is connected to the determination unit 12 and the calculation unit 14. The calculation unit 14 is connected to the analog output unit 15.

[0021] The information (source pressure) measured by the pressure gauge PS0 is sent to the measuring unit m0, and the information (terminal pressure) measured by the pressure gauge PSn is sent to the measuring unit mn. These pressure values ​​may be transmitted by wire or wirelessly. The analog output unit 15 transmits an analog signal (pressure value, control pressure) to the measuring unit 1 in the package compressor 31.

[0022] <Explanation of Operation> Next, the operation of the unit count control panel 20 in the compressor control method of this embodiment will be described. The control method performed by the unit count control panel 20 in this embodiment is referred to as the transparent mode. Figure 3 shows a flow chart of the operation of the unit count control panel 20 when the transparent mode is used in this embodiment.

[0023] As shown in FIG. 3 , after processing is initiated, the setting unit 13 is set to the permeable mode (step S1 in FIG. 3 ). Next, the pressure gauge PSn is used to measure the terminal pressure Pn (step S2 in FIG. 3 ). Next, the determination unit 12 associates the terminal pressure Pn with the permeable mode (step S3 in FIG. 3 ). As a result, the determination unit 12 recognizes that the terminal pressure Pn sent from the measurement unit mn is to be used in the permeable mode. The determination unit 12 determines the mode in which the compressor control system is to be operated. Modes other than the permeable mode will be described later in Modifications 2 and 3, but these modes can be changed to other modes during operation of the compressor control system. The determination unit 12 also determines which pressure value is the lowest among the pressure values ​​sent from each measurement unit and sends the determined lowest pressure value to the analog output unit 15 via the calculation unit 14. The determination unit 12 may select a pressure value based on other criteria rather than determining the smallest pressure value among multiple pressure values.

[0024] Next, the analog output unit 15 outputs an analog signal to the package compressor 31 as the control pressure P (=terminal pressure Pn) (step S4 in FIG. 3). In the permeation mode, no calculation is performed by the calculation unit 14 between steps S3 and S4. In other words, if the permeation mode is the only mode used in the compressor control system, the calculation unit 14 may be omitted. The control pressure referred to in this application is the pressure value to be controlled, and means the pressure value used for pressure control in the compressor control system.

[0025] This analog signal may be transmitted wirelessly or via a wire. Even when the unit control panel 20 and the package compressor 31 are connected via a wire and a plurality of pieces of terminal pressure information are transmitted from a plurality of pressure gauges PS0 to the unit control panel 20, only one signal is output from the unit control panel 20, so that the package compressor 31 only needs to have one signal receiving port.

[0026] Upon receiving the analog signal, the package compressor 31 recognizes that its own source pressure is Pn and controls the rotation speed as follows: In reality, the source pressure of the package compressor 31 is P0 measured by a pressure gauge PS0, but in this embodiment of FIG. 3, this value is not used for control.

[0027] Next, the operation of the package compressor 31 that receives the analog signal will be described with reference to FIG. 4 . FIG. 4 is a flow chart showing the operation of the package compressor 31 after the analog signal is output from the unit count control panel 20 in step S4 of FIG. 3 according to this embodiment. The analog signal output from the unit count control panel 20 is received and measured by the measurement unit 1 in the package compressor 31 (step S5 of FIG. 4 ). Next, the determination unit 2 determines the relationship (magnitude relationship) between a value (threshold) pre-stored in the setting unit 3 and the measurement value measured in step S5 (step S6 of FIG. 4 ). The value (threshold) pre-stored in the setting unit 3 is, for example, the lower and upper limits of a pressure threshold band that serves as a reference for rotation speed control. The relationship here refers to a state in which the measurement value (pressure value) is within the range from the lower limit to the upper limit of the pressure threshold band, exceeds the upper limit, or is below the lower limit. Specifically, the determination unit 2 determines the difference between the measurement value and each of the lower and upper limits of the pressure threshold band.

[0028] Next, the control unit 4 transmits a rotation speed control signal to the compressor 11 based on the determination made in step S6, thereby controlling the rotation speed of the compressor 11 (step S7 in FIG. 4). That is, the controller CTL of the compressor 11 controls the speed of the motor M in accordance with the control signal, thereby controlling the operation of the air end AE. If the measured value is within the range from the lower limit to the upper limit of the pressure threshold band, the frequency of the rotation speed control signal sent from the control unit 4 to the compressor 11 is not changed. If the measured value exceeds the upper limit of the pressure threshold band, the control unit 4 reduces the frequency of the rotation speed control signal sent to the compressor 11, thereby slowing down the rotation of the motor M. If the measured value is below the lower limit of the pressure threshold band, the control unit 4 increases the frequency of the rotation speed control signal sent to the compressor 11, thereby speeding up the rotation of the motor M. In this way, the pressure of the air discharged from the piping 7 to the outside of the package compressor 31 is controlled to remain within the pressure threshold band as much as possible.

[0029] <Effects of the Present Embodiment> FIG. 5 is a graph showing the relationship between compressed air pressure and time in the compressor control systems of the comparative example and the present embodiment. The horizontal axis of the graph in FIG. 5 represents time, and the vertical axis represents pressure. In FIG. 5, the source pressure measured by a pressure gauge installed in the package compressor before the introduction of the compressor control system of the comparative example is shown by a relatively thin solid line in graph 1A, and the terminal pressure measured by a pressure gauge installed at the end of the package compressor before the introduction of the compressor control system of the comparative example is shown by a relatively thin dashed-dotted line in graph 1B. Also in FIG. 5, the source pressure measured by a pressure gauge PS0 installed in the compressor of the present embodiment is shown by a relatively thick solid line in graph 2A, and the terminal pressure measured by a pressure gauge PSn installed at the end of the compressor of the present embodiment is shown by a relatively thick dashed-dotted line in graph 2B. Both the left and right vertical axes in FIG. 5 represent pressure, with the values ​​at the bottom of each vertical axis being the same and the values ​​at the top of each vertical axis being the same.

[0030] The vertical axis on the right side of Figure 5 is scaled to indicate values ​​of LLL1, LL1, L1, H1, HH1, and HHH1, in ascending order of pressure. These values ​​serve as a guideline for pressure control before the introduction of the compressor control system of the comparative example. The vertical axis on the left side of Figure 5 is scaled to indicate values ​​of LLL2, LL2, L2, H2, HH2, and HHH2, in descending order of pressure. These values ​​serve as a guideline for pressure control in the compressor control system of this embodiment. In Figure 5, the required pressure for the terminal load equipment is indicated by a two-dot chain line near pressures LLL1 and LLL2.

[0031] In a comparative example in which rotation speed is controlled by feedback of the source pressure, pressure control is performed so that the source pressure falls within a pressure threshold band between pressure L1 and pressure H1. In contrast, in this embodiment in which rotation speed is controlled by feedback of the end pressure, pressure control is performed so that the end pressure falls within a pressure threshold band between pressure L2 and pressure H2. Here, when the end pressure falls below pressure L2, the rotation of motor M is increased by speeding up. When the end pressure falls below pressure LL2, the rotation of motor M is increased more rapidly with high output to increase the pressure. When the end pressure falls below pressure LLL2, the rotation of motor M is increased more rapidly than when the end pressure falls below pressure LL2. Furthermore, when the end pressure exceeds pressure H2, the rotation of motor M is slowed down to decrease the pressure. When the end pressure exceeds pressure HH2, the rotation of motor M is slowed down more rapidly to decrease the pressure. When the end pressure exceeds pressure HHH2, the rotation of motor M is slowed down more rapidly to decrease the pressure. When the end pressure exceeds pressure HHH2, the rotation of motor M is slowed down more rapidly than when the end pressure exceeds pressure HH2 to decrease the pressure.

[0032] In this embodiment, instead of measuring only the source pressure, the terminal pressure is constantly measured and the terminal pressure is fed back to control the operation of the compressor. Therefore, compared to when the rotation speed is controlled by measuring the source pressure without measuring the terminal pressure, the compressor control system can be operated at a pressure closer to the required pressure of the terminal load equipment. In other words, as shown in Figure 5, compared to graphs 1A and 1B of the comparative example, graphs 2A and 2B of this embodiment move at lower values ​​closer to the required pressure of the terminal load equipment, thereby achieving energy savings.

[0033] Furthermore, in this embodiment, since the end pressure is measured, fine pressure control is possible, and therefore the width of the pressure threshold band between pressure L2 and pressure H2 (between the upper and lower limits of the pressure threshold band) can be narrower than the width of the pressure threshold band between pressure L1 and pressure H1, enabling further energy savings.

[0034] The measuring unit 1 shown in FIG. 2 recognizes the received analog signal as the discharge pressure of the package compressor 31 (the source pressure measured by the pressure gauge PS0) and operates accordingly. Therefore, any type of compressor that measures source pressure and controls pressure can be used in the compressor control system of this embodiment. In other words, one of the main features of this embodiment is that a unit control panel 20 is provided, a single analog signal is sent from the unit control panel 20 to the package compressor 31, and the analog signal is recognized as the discharge pressure of the package compressor 31 and operated accordingly. This applies whether a single pressure value is sent to the unit control panel 20 or multiple pressure values ​​are sent. Therefore, even when pressure control is performed by collecting multiple pressure values ​​from multiple terminal pressure gauges, there is no need to prepare a unit control panel corresponding to the measurement of such multiple pressures. In other words, there is no need to prepare a unit control panel with multiple measuring units and signal receiving ports corresponding to multiple pressure gauges. This allows for energy savings at low cost.

[0035] Furthermore, even if the unit control panel 20 receives multiple pressure values ​​from each pressure gauge, the package compressor 31 receives only one analog signal from the unit control panel 20, and therefore, unlike the comparative example, the unit control panel 20 does not need to perform complex control such as PID control.

[0036] Furthermore, the operation of the package compressor 31 may be controlled not only by the terminal pressure but also based on the source pressure within the package compressor 31. To enable such control switching, in this embodiment, not only the terminal pressure measured by the pressure gauge PSn but also the source pressure measured by the pressure gauge PS0 is transmitted to the unit count control panel 20. This allows the rotation speed to be controlled even when the package compressor 31 is operated independently.

[0037] As described above, the compressor control system of this embodiment measures the terminal pressure and controls the pressure, thereby realizing energy savings for the entire system. Furthermore, the compressor control system of this embodiment uses a multiple-unit control panel to transmit the results of measurements at multiple terminal pressures to the package compressor as a single analog signal, and the package compressor controls the pressure based on this analog signal, preventing the control of the entire system from becoming complicated.

[0038] <Modification 1> The operation mode of the unit control panel 20 may be a pressure difference correction mode, which performs more stable rotation speed control by taking into account the average value of the pressure difference as described below, instead of the transmission mode described above.

[0039] The operation of the unit control panel 20 in the compressor control method of Modification 1 will be described below. The control method performed by the unit control panel 20 in this modification is referred to as the pressure difference correction mode. Figure 6 shows a flow chart of the operation of the unit control panel 20 when the pressure difference correction mode is used in this embodiment.

[0040] As shown in FIG. 6 , after processing begins, the setting unit 13 is set to the pressure difference correction mode (step S11 in FIG. 6 ). Next, the pressure gauge PS0 is used to measure the base pressure P0 (step S12 in FIG. 6 ). Next, the pressure gauge PSn is used to measure the terminal pressure Pn (step S13 in FIG. 6 ). The order of steps S12 and S13 may be reversed, or they may be performed simultaneously. Next, the determination unit 12 associates the base pressure P0 and the terminal pressure Pn with the pressure difference correction mode (step S14 in FIG. 6 ). This allows the determination unit 12 to recognize that the base pressure P0 and the terminal pressure Pn sent from the measurement units m0 and mn are to be used in the pressure difference correction mode. Next, the calculation unit 14 calculates the average pressure difference ΔP(TYP) = P0 - Pn over a certain interval (step S15 in FIG. 6 ). In other words, the pressure difference ΔP in the section between the position of the pipe to which pressure gauge PS0 is connected and the position of the pipe to which pressure gauge PSn is connected is calculated multiple times within a specified time period, and these are averaged to calculate ΔP (TYP).

[0041] Next, the analog output unit 15 outputs the control pressure P as an analog signal to the package compressor 31 (step S16 in FIG. 6). The control pressure P is calculated by the calculation unit 14 as P=P0-ΔP(TYP) or P=Pn+ΔP(TYP). Either of these methods may be used to calculate the control pressure P.

[0042] Thereafter, the package compressor 31 performs steps S5 to S7 described with reference to FIG. 4 to control the rotation speed based on the control pressure P.

[0043] In this modification, the package compressor does not operate instantaneously by measuring the instantaneous end pressure Pn, but performs correction control based on the average value ΔP (TYP) of the pressure difference over a certain interval. In other words, the package compressor does not increase or decrease the pressure by a large fluctuation range over a short period of time, but the pressure controlled by the package compressor is controlled to fluctuate by a small fluctuation range over a predetermined time, allowing for relatively stable control.

[0044] <Variation 2> The operation mode of the number control panel 20 may be a pressure time difference correction mode in addition to the pressure difference correction mode, in which predictive control is performed taking into account the transmission time difference between P0 and Pn as described below, thereby achieving more accurate rotation speed control.

[0045] The operation of the number of units control panel 20 in the compressor control method of Modification 2 will be described below. The control method performed by the number of units control panel 20 in this modification is referred to as the pressure time difference correction mode. Figure 7 shows a flow chart of the operation of the number of units control panel 20 when the pressure time difference correction mode is used in this embodiment.

[0046] As shown in FIG. 7 , after processing is started, the setting unit 13 is set to the pressure-time difference correction mode (step S21 in FIG. 7 ). Next, the source pressure P0 is measured using the pressure gauge PS0 (step S22 in FIG. 7 ). Next, the terminal pressure Pn is measured using the pressure gauge PSn (step S23 in FIG. 7 ). The order of steps S22 and S23 may be reversed, or they may be performed simultaneously. Next, the determination unit 12 associates the source pressure P0 and the terminal pressure Pn with the pressure-time difference correction mode (step S24 in FIG. 7 ). As a result, the determination unit 12 recognizes that the source pressure P0 and the terminal pressure Pn sent from the measurement units m0 and mn will be used in the pressure-time difference correction mode.

[0047] Next, the calculation unit 14 calculates the transmission time difference ΔT (TYP) between P0 and Pn (step S25 in FIG. 7). Referring to the graph shown in FIG. 5, the source pressure graph 2A and the end pressure graph 2B appear to fluctuate at exactly the same timing, but in reality, they fluctuate with a slight time difference. For example, when the source pressure reaches its peak, the end pressure also reaches its peak a short time later. In other words, a time difference (transmission time difference ΔT) occurs in the transmission of pressure between the pressure gauge PS0 and the pressure gauge PSn. In step S25, the calculation unit 14 calculates the transmission time difference ΔT between the time when P0 reaches its peak and the time when Pn reaches its peak multiple times, and calculates the transmission time difference ΔT (TYP), which is the average value of these ΔTs. Note that the peak referred to here refers to both a crest and a trough.

[0048] Next, the calculation unit 14 calculates the average pressure difference ΔP' (TYP) = P0 - Pn over a certain interval, taking into account the transmission time difference ΔT (step S26 in FIG. 7). That is, the calculation unit 14 calculates multiple pressure differences ΔP over the interval between the position of the pipe connected to the pressure gauge PSn and the position of the pipe connected to the terminal pressure Pn within a predetermined time period, and calculates the average of these ΔP (TYP). ΔP' calculated taking into account the transmission time difference ΔT is a prediction of the terminal pressure Pn ΔT after the measurement of the source pressure P0, or a prediction of the source pressure P0 ΔT after the measurement of the terminal pressure Pn.

[0049] Next, the analog output unit 15 outputs the control pressure P as an analog signal to the package compressor 31 (step S27 in FIG. 7). The calculation unit 14 calculates the control pressure P by P=P0-ΔP'(TYP) or P=Pn+ΔP'(TYP). Either of these methods may be used to calculate the control pressure P.

[0050] Thereafter, the package compressor 31 performs steps S5 to S7 described with reference to FIG. 4 to control the rotation speed based on the control pressure P.

[0051] In this modification, as in the first modification, the control pressure P is calculated based on the average value ΔP (TYP) of the pressure difference over a certain period, and therefore has the characteristics of a pressure time difference correction mode, enabling relatively stable control. In addition, predictive control is performed taking into account the transmission time difference ΔT, so the range of fluctuation in pressure during rotation speed control is small, enabling more stable control. Here, calculating ΔP' by predicting the terminal pressure Pn after ΔT from the base pressure P0 in step S26 enables more accurate control in response to changes in the amount of compressed air supplied. Furthermore, calculating ΔP' by predicting the base pressure P0 after ΔT from the terminal pressure Pn in step S26 enables more accurate control in response to changes in the amount of compressed air used.

[0052] <Modification 3> A case where the terminal pressures measured by a plurality of pressure gauges are grouped will be described. Fig. 8 is a schematic diagram showing a compressor control system according to this modification. The compressor control system shown in Fig. 8 differs from the compressor control system shown in Fig. 2 in the following ways.

[0053] In this modification, the pipe 9 branches into multiple branches downstream of the air tank 8, and pressure gauges PS3 to PSn are provided at the ends of each of the multiple branches. Furthermore, pressure gauge PS1 is provided on the pipe 9 closer to the air tank 8 than the downstream side (end) of the pipe 9. Furthermore, pressure gauge PS2 is provided on the pipe 9 downstream of pressure gauge PS1 and upstream of the point where the pipe 9 branches into multiple branches. In this modification, for example, pressure gauges PS4 and PS5 belong to group A, and pressure gauges PS2 and PS3 belong to group B. That is, the pressure gauges are arranged from the first pressure gauge PS1 to the nth pressure gauge PSn, where n is a positive natural number. Group A includes the load equipment near pressure gauges PS4 and PS5, and group B includes the load equipment near pressure gauges PS2 and PS3. However, it is not necessary for some of these pressure gauges to have no load equipment near them. It should be noted that although the pressure gauges PS1 and PS2 shown in FIG. 8 are located on the upstream side compared to the pressure gauges PS3 to PSn, the pressures measured by these two pressure gauges PS1 and PS2 are end pressures.

[0054] The unit control panel 20 includes a measuring unit m0 that receives pressure values ​​from the pressure gauge PS0 and multiple measuring units m1 to mn that receive pressure values ​​from the pressure gauges PS1 to PSn. In other words, the unit control panel 20 includes a total of n+1 measuring units, including the measuring unit m0 and n measuring units m1 to mn. The unit control panel 20 also includes a grouping determining unit 12a instead of the determining unit 12, and a load / unload control output unit 16 in addition to the analog output unit 15. While FIG. 8 illustrates the compressor 11 and the load / unload operation unit 6 within the package compressor 31, in reality, the package compressor 31 (variable speed compressor) equipped with the compressor 11 and the package compressor 30 (fixed speed compressor) equipped with the load / unload operation unit 6 are provided separately (see FIG. 9). These are the differences between the configuration of the compressor control system shown in FIG. 8 and the configuration of the compressor control system shown in FIG. 2.

[0055] In this embodiment, the loading / unloading unit 6 is built into the package compressor 30 shown in Fig. 1, but the present invention is not limited to this. A variable speed machine (package compressor 31) may have a loading / unloading unit, or a fixed speed machine (package compressor 30) may be a package compressor without a loading / unloading unit.

[0056] Furthermore, the load / unload control output unit 16 of the unit count control panel 20 may be equipped with a control that measures the elapsed time since the start of unload operation and stops the compressor 10 or 11 itself if the elapsed time is equal to or greater than a predetermined time. During unload operation, compressed air is not generated, but the motor M itself is driven and consumes power. Therefore, if the unload operation time is equal to or greater than a predetermined time, power consumption can be reduced by cutting off power to the motor M to stop the compressor 10 or 11 itself. Of course, this determination may be made by the control unit 4 in the package compressor 30 or 31, rather than by the unit count control panel 20.

[0057] In group A, if the pressures measured by pressure gauges PS4 and PS5 fall below L2, LL2, or LLL2, pressure control is performed under an OR condition, and if they exceed H2, HH2, or HHH2, control is also performed under an OR condition. That is, for example, if one of the pressures measured by pressure gauges PS4 and PS5 in group A falls below L2, the control unit 4 increases the rotation speed of motor M to boost the pressure. Also, in group B, if the pressures measured by pressure gauges PS2 and PS3 fall below L2, LL2, or LLL2, pressure control is performed under an OR condition, and if they exceed H2, HH2, or HHH2, control is also performed under an OR condition. That is, for example, if one of the pressures measured by pressure gauges PS2 and PS3 in group B falls below L2, the control unit 4 increases the rotation speed of motor M to boost the pressure. When the load equipment of Group A and Group B is used at the same time, for example, when the pressure measured by either the pressure gauge of Group A or the pressure gauge of Group B exceeds a threshold value such as H2 or falls below a threshold value such as L2, the compressor 11 will decrease or increase the pressure at the instruction of the control unit 4.

[0058] When group A and group B operate simultaneously, differences in pressure may occur between the groups because the pressure of group B is measured at a position closer to the package compressor 31 (upstream side) than that of group A. In this case, pressure control is performed so that the pressures of group A and group B fall within different pressure threshold bands. In other words, the target pressures H2 and L2 of group A and the target pressures H2 and L2 of group B may be different values.

[0059] Furthermore, the load equipment of groups A and B is not operated at the same time, and the operation timing (time period) may differ. For example, if group A is not operated, there is no need to ensure that the pressures at the pressure gauges PS4 and PS5 of group A maintain the pressure required for the terminal load equipment. Therefore, in this case, pressure control is performed to maintain the target pressure (pressure threshold band) of group B. In other words, the calculation unit 14 outputs information on the pressure of group B to the package compressor 31 as an analog signal.

[0060] Furthermore, the types of load equipment in Group A and Group B may differ. In this case, the target pressure (pressure threshold band) or the required pressure for the terminal load equipment may differ between Group A and Group B. For example, if the pressure value in Group B is lower than the pressure value in Group A, the pressure value in Group A may be below the lower limit (L2) of the target pressure threshold band, while the pressure value in Group B may be above the lower limit (L2) of the target pressure threshold band. In such a case, pressure control is performed to increase the pressure in Group A so that it falls within the pressure threshold band. In other words, the calculation unit 14 outputs information about the pressure in Group A, which is outside the pressure threshold band, to the package compressor 31 as an analog signal.

[0061] In this modification, the setting unit 13 stores pressure control thresholds (H2, L2, etc.) for each group, and the setting unit 13 associates each group with a target pressure (pressure threshold band) and a required pressure for terminal load equipment. The grouping determination unit 12a determines which group a pressure value sent from each of the measurement units m1 to mn belongs to. The grouping determination unit 12a also determines whether the group to which the pressure value belongs is a group that currently requires pressure control, i.e., whether the group is using load equipment. If the received pressure value is a pressure value for a group that requires pressure control, the grouping determination unit 12a sends information about the pressure value to the calculation unit 14. If the received pressure value is a pressure value for a group that does not require pressure control, the grouping determination unit 12a does not send information about the pressure value to the calculation unit 14. The grouping determination unit 12a also determines which pressure value is the lowest among the pressure values ​​sent from each of the measurement units m1 to mn, and transmits the pressure value determined to be the lowest to the calculation unit 14. That is, based on the storage of the setting unit 13, the grouping determination unit 12a transmits to the calculation unit 14 the pressure values ​​of the groups for which the need for pressure value control is greater.

[0062] In the transmission mode, the calculation unit 14 does not perform any calculation, and transmits the pressure value received from the grouping determination unit 12a as the control pressure to the package compressor 31 via the analog output unit 15. In the pressure difference correction mode or the time difference correction mode, the calculation unit 14 performs the calculations described in the first and second modifications, and transmits the control pressure P calculated as a result to the package compressor 31 via the analog output unit 15.

[0063] Furthermore, when controlling the operation of the constant speed machine, the calculation unit 14 sends a control signal to the load / unload operation unit 6 via the load / unload control output unit 16. The constant speed machine controls the amount of compressed air produced by turning on / off a switch that supplies power to the motor in response to the received control signal, stopping / rotating the motor, and thereby controlling the pressure. Alternatively, the constant speed machine controls the amount of compressed air produced by switching the air end suction valve open / closed in response to the received control signal, thereby controlling the pressure.

[0064] In this embodiment, the load / unload operation refers to switching between opening and closing the suction valve of the air end. During load operation, the suction valve is closed to generate compressed air, and during unload operation, the suction valve is opened to allow the motor to rotate but not generate compressed air.

[0065] The details of the loading / unloading operation are not limited to this, and for example, the operation may be to open / close the discharge valve instead of the suction valve.

[0066] Furthermore, the present invention is not limited to adopting only one of the switch and the load / unload operation, and naturally includes a configuration in which pressure is controlled by controlling both of them together.

[0067] <Modification 4> As shown in FIG. 9, a plurality of package compressors 31a, 30a, and 30b may be connected to one unit control panel 20. The package compressor 31a is a variable speed compressor equipped with a compressor 11, similar to the package compressor 31 shown in FIG. 2. The package compressors 30a and 30b are fixed speed compressors equipped with a compressor 10 and a load / unload operation unit 6. The compressor 10 is equipped with a motor M and an air end AE. Unlike the compressor 11, the compressor 10 is equipped with a switch OC instead of a controller CTL. The unit control panel 20 has a structure similar to that shown in FIG. 2. Each of the package compressors 31a, 30a, and 30b is connected to the same piping system, similar to that shown in FIG. 1. The piping system may have the structure shown in FIG. 2 or may be divided into groups as described in Modification 3.

[0068] When the compressor control system is in operation, an analog signal is sent from an analog output unit provided in the unit count control panel 20 to the measurement unit 1 of each of the package compressors 31a, 30a, and 30b. As a result, the package compressor 31a, which is a variable speed compressor, functions in the same manner as the package compressor 31 described with reference to FIG. 2 and controls the rotation speed. In response to this, the package compressors 30a and 30b receive the analog signal via the measurement unit 1, and the determination unit 2 determines the relationship between a value (threshold) pre-stored in the setting unit 3 and the measurement value measured in step S5. Based on this determination, the control unit 4 sends a control signal to the compressor 10 and the load / unload operation unit 6 to perform the load / unload operation. In other words, the control signal switches between the load operation and the unload operation of the package compressors 30a and 30b, thereby controlling the pressure.

[0069] Even if any one of the package compressors 31 a, 30 a, and 30 b has a different output from the other compressors, the same analog signal is transmitted to each of the package compressors 31 a, 30 a, and 30 b from the unit control panel 20. For example, each of the package compressors 30 a, 30 b that has received the analog signal transmits a different control signal to its own compressor 10 and loading / unloading operation unit 6 in the control unit 4 according to the output, thereby performing pressure control.

[0070] In this modified example, there is no need to prepare multiple unit control panels depending on the type of compressor, and there is no need to send different analog signals from the unit control panel depending on the type of compressor, so the configuration of the unit control panel can be simplified.

[0071] <Modification 5> As shown in Fig. 10 , the package compressor 31 may have a built-in unit control panel 20. In this modification, the package compressor 31 is a variable speed machine, and the unit control panel 20 built into the package compressor 31 outputs an analog signal not only to the measurement unit 1 inside the package compressor 31 but also to the measurement units 1 of the package compressors 30c and 30d, which are fixed speed machines installed outside the main package compressor 31. In this case, too, the measurement unit m0 measures the pressure (source pressure) of the pressure gauge inside the package compressor 31, and the measurement unit mn measures the pressure (terminal pressure) of the terminal pressure gauge outside the package compressor 31. In this way, information on one or more terminal pressures is measured by the unit control panel 20 inside the package compressor 31, and an analog signal is transmitted from the analog output unit 15, thereby enabling pressure control by the package compressors 31, 30c, and 30d.

[0072] In this modification, by incorporating the function of a unit control panel into the compressor, an inexpensive compressor control system can be realized.

[0073] Even if a sub-compressor is not connected to the main package compressor 31, the same effects as those of the compressor control system described with reference to FIGS. 1 to 5 can be obtained.

[0074] The present invention has been specifically described above based on the embodiments, but it goes without saying that the present disclosure is not limited to the above embodiments and can be modified in various ways without departing from the spirit of the present invention. For example, the compressor to which the analog signal is sent from the unit control panel can be any type of compressor. In other words, the compressor can be, for example, a reciprocating compressor, a screw compressor, a scroll compressor, or a turbo compressor.

[0075] The present invention can be widely used in compressor control systems and compressor control methods.

[0076] 1, m0, m1, mn Measuring unit 2, 12 Determination unit 3, 13 Setting unit 4 Control unit 6 Load / unload operation unit 7, 9 Piping 8 Air tank 10, 11 Compressor 12a Grouping determination unit 14 Calculation unit 15 Analog output unit 16 Unload control output unit 20 Number control panel 30, 30a, 30b, 30c, 30d, 31 Package compressor AE Air end CTL Controller M Motor OC Switch Pm, PS0, PS1, PS2, PS3, PS4, PS5, PSn Pressure gauge Q Flow meter

Claims

1. A compressor control system comprising: a first package compressor that compresses gas; a unit control panel; and a first pressure gauge that measures the end pressure of a piping system connected to the first package compressor; wherein the first package compressor has a first measurement unit, a first judgment unit, a first setting unit, a control unit, and a compressor; the unit control panel has a second measurement unit and an analog output unit; the unit control panel receives a first pressure from the first pressure gauge via the second measurement unit and transmits it as an analog signal from the analog output unit to the first measurement unit; in the first package compressor, the first measurement unit transmits the received analog signal as a pressure to the first judgment unit, the first judgment unit judges the relationship between the pressure and a threshold value pre-stored in the first setting unit, and the control unit controls the compressor based on the judgment result of the first judgment unit, thereby performing compression control.

2. A compressor control system according to claim 1, further comprising: a second pressure gauge provided inside the first package compressor; and a calculation unit and a third measurement unit provided in the unit control panel, wherein the unit control panel receives the first pressure from the first pressure gauge at the second measurement unit and receives the second pressure from the second pressure gauge at the third measurement unit, the calculation unit calculates an average value of pressure differences in the section between the second pressure gauge and the first pressure gauge, and calculates a control pressure using the difference between the second pressure and the average value or the sum of the first pressure and the average value, and the analog output unit transmits the first pressure or the control pressure as the analog signal.

3. A compressor control system according to claim 2, wherein, when the first pressure is Pn and the second pressure is P0, the calculation unit calculates the average value ΔP(TYP) of the pressure difference in the section between the second pressure gauge and the first pressure gauge using the formula ΔP(TYP) = P0 - Pn, calculates the control pressure P using the formula P = P0 - ΔP(TYP) or P = Pn + ΔP(TYP), and transmits the control pressure P as the analog signal from the analog output unit to the first measurement unit.

4. A compressor control system according to claim 1, further comprising: a second pressure gauge provided inside the first package compressor; and a calculation unit and a third measurement unit provided in the unit control panel, wherein the unit control panel receives the first pressure from the first pressure gauge at the second measurement unit and receives the second pressure from the second pressure gauge at the third measurement unit, and the calculation unit calculates a pressure transmission time difference between the second pressure gauge and the first pressure gauge, and calculates an average value of pressure differences in a section between the second pressure gauge and the first pressure gauge from the difference between the second pressure and the first pressure, using the second pressure and the first pressure after the transmission time difference from the time of measurement of the second pressure, or the first pressure and the second pressure after the transmission time difference from the time of measurement of the first pressure, a control pressure is calculated as a difference between the second pressure and the average value, or a sum of the first pressure and the average value, and the control pressure is transmitted as the analog signal from the analog output unit to the first measurement unit in place of the first pressure.

5. A compressor control system according to claim 4, wherein, when the first pressure is Pn and the second pressure is P0, the calculation unit calculates the pressure transmission time difference ΔT between the second pressure gauge and the first pressure gauge, calculates the average value ΔP' (TYP) of the pressure difference in the section between the second pressure gauge and the first pressure gauge using the equation ΔP' (TYP) = P0 - Pn, using the second pressure P0 and the first pressure Pn after the transmission time difference ΔT from the time the second pressure P0 was measured, or the first pressure Pn and the second pressure P0 after the transmission time difference ΔT from the time the first pressure Pn was measured, and calculates the control pressure P using the equation P = P0 - ΔP' (TYP) or the equation P = Pn + ΔP' (TYP), and transmits the control pressure P from the analog output unit to the first measurement unit as the analog signal.

6. A compressor control system as described in claim 1, wherein a plurality of the first pressure gauges are provided, the number control panel has a second determination unit and a plurality of the second measurement units that receive each of the plurality of pressures transmitted from the plurality of first pressure gauges, the second determination unit determines the smallest pressure among the plurality of pressures transmitted from the plurality of second measurement units, and the analog output unit transmits the pressure determined to be smallest by the second determination unit to the first measurement unit as the analog signal.

7. A compressor control system as claimed in claim 1, wherein a plurality of the first pressure gauges are provided, the unit control panel has a second determination unit, a second setting unit, and a plurality of the second measurement units that receive each of the plurality of pressures transmitted from the plurality of first pressure gauges, the plurality of first pressure gauges are divided into a plurality of groups, the second setting unit stores in advance which group each of the plurality of pressures transmitted from the plurality of first pressure gauges belongs to, the second determination unit determines which pressure in the group is in greater need of pressure control based on the storage of the second setting unit, and the analog output unit transmits the pressure that the second determination unit determines to be in the group in greater need of control to the first measurement unit as the analog signal.

8. A compressor control system according to claim 1, wherein the number control panel is connected to one or more second package compressors in addition to the first package compressor.

9. A method for controlling a compressor, comprising: (a) operating a first package compressor having a first measuring unit, a first judging unit, a first setting unit, a control unit, and a compressor, and sending compressed gas to a piping system; (b) after step (a), receiving a first pressure measured by a first pressure gauge connected to the end of the piping system by a second measuring unit in a number control panel, and transmitting the first pressure measured by a first pressure gauge connected to the end of the piping system to the first measuring unit from an analog output unit in the number control panel; (c) within the first package compressor, transmitting the analog signal received by the first measuring unit as pressure to the first judging unit, the first judging unit judging the relationship between the pressure and a threshold value pre-stored in the first setting unit, and the control unit controlling the compressor based on the judgment result of the first judging unit, thereby performing compression control.

10. A compressor control method according to claim 9, further comprising: a second pressure gauge provided inside the first package compressor; and a calculation unit and a third measurement unit provided in the unit control panel, wherein step (b) comprises: (b1) after step (a), receiving the first pressure measured by the first pressure gauge with the second measurement unit, and receiving the second pressure measured by the second pressure gauge with the third measurement unit; (b2) the calculation unit calculates an average value of pressure differences in the section between the second pressure gauge and the first pressure gauge, and calculates a control pressure using the difference between the second pressure and the average value, or the sum of the first pressure and the average value; and the analog output unit transmits the first pressure or the control pressure as the analog signal to the first measurement unit.

11. A compressor control method according to claim 10, wherein, when the first pressure is Pn and the second pressure is P0, in step (b2), the calculation unit calculates the average value ΔP(TYP) of the pressure difference in the section between the second pressure gauge and the first pressure gauge using the formula ΔP(TYP) = P0 - Pn, and calculates the control pressure P using the formula P = P0 - ΔP(TYP) or P = Pn + ΔP(TYP), and transmits it as the analog signal from the analog output unit to the first measurement unit.

12. A compressor control method according to claim 9, further comprising: a second pressure gauge provided inside the first package compressor; and a calculation unit and a third measurement unit provided in the unit control panel, wherein step (b) comprises: (b3) after step (a), receiving the first pressure measured by the first pressure gauge with the second measurement unit, and receiving the second pressure measured by the second pressure gauge with the third measurement unit; (b4) the calculation unit calculates a pressure transmission time difference between the second pressure gauge and the first pressure gauge, and calculates an average value of pressure differences in the section between the second pressure gauge and the first pressure gauge by using the second pressure and the first pressure after the transmission time difference from the time of measurement of the second pressure, or the first pressure and the second pressure after the transmission time difference from the time of measurement of the first pressure, as a difference between the second pressure and the first pressure; and calculating a control pressure using the difference between the second pressure and the average value, or the sum of the first pressure and the average value. a step of the analog output unit transmitting the control pressure, instead of the first pressure, as the analog signal to the first measurement unit.

13. A compressor control method according to claim 12, wherein, when the first pressure is Pn and the second pressure is P0, in step (b4), the calculation unit calculates the pressure transmission time difference ΔT between the second pressure gauge and the first pressure gauge, calculates the average value ΔP' (TYP) of the pressure difference in the section between the second pressure gauge and the first pressure gauge using the equation ΔP' (TYP) = P0 - Pn, using the second pressure P0 and the first pressure Pn after the transmission time difference ΔT from the time the second pressure P0 was measured, or the first pressure Pn and the second pressure P0 after the transmission time difference ΔT from the time the first pressure Pn was measured, and calculates the control pressure P using the equation P = P0 - ΔP' (TYP) or the equation P = Pn + ΔP' (TYP), and transmits the control pressure P from the analog output unit to the first measurement unit as the analog signal.

14. A method for controlling a compressor as described in claim 9, wherein a plurality of the first pressure gauges are provided, the unit control panel has a second determination unit and a plurality of the second measurement units, and the (b) step comprises: (b5) a step of receiving, by a plurality of the second measurement units, each of the plurality of pressures measured by the plurality of the first pressure gauges; (b6) a step of the second determination unit determining the smallest pressure among the plurality of pressures transmitted from the plurality of the second measurement units; and (b7) a step of the analog output unit transmitting, by the analog signal, the pressure determined to be the smallest by the second determination unit in the (b6) step to the first measurement unit.

15. A method for controlling a compressor as defined in claim 9, wherein a plurality of the first pressure gauges are provided, the unit control panel has a second determination unit, a second setting unit, and a plurality of the second measurement units that receive each of the plurality of pressures transmitted from the plurality of first pressure gauges, the plurality of first pressure gauges being divided into a plurality of groups, and (a0) before step (a), the second setting unit further has a step of storing to which group each of the plurality of pressures transmitted from the plurality of first pressure gauges belongs, and the step (b) has the following steps: (b8) a step of receiving, by the plurality of second measurement units, each of the plurality of pressures measured by the plurality of first pressure gauges, (b9) a step of the second determination unit determining, based on the storage in step (a) by the second setting unit, a pressure in a group that is in greater need of pressure control, and (b10) a step of the analog output unit transmitting, as the analog signal, the pressure that the second determination unit has determined in step (b9) to be a pressure in a group that is in greater need of control.

16. A compressor control method according to claim 9, wherein the unit control panel is connected to one or more second package compressors in addition to the first package compressor.

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