JP4112869B2 - Method and apparatus for controlling the number of operating air compressors - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for controlling the number of operating air compressors for controlling the number of operating air compressors that send compressed air to an air tank based on the state of compressed air sent from an air tank to a load.
[0002]
[Prior art]
FIG. 9 shows an instrumentation diagram of a conventional air compressor operation number control system. In the figure, 1-1 to 1-4 are air compressors that generate compressed air, 2 is an air tank into which compressed air from the air compressors 1-1 to 1-4 is fed, and 3 is an air tank 2 A pressure transmitter that measures the pressure P, 4 is a header, and 5 ′ is an air compressor operation number control device.
[0003]
In this system, the compressed air sent out from the air compressors 1-1 to 1-4 is stored in the air tank 2. The air tank 2 supplies the compressed air stored in the tank to the load via the header 4. For example, the compressed air stored in the air tank 2 is supplied for power for buildings and for instruments.
[0004]
During the supply of compressed air to the load, the pressure transmitter 3 measures the pressure P in the air tank 2 and sends the measured pressure Ppv to the air compressor operation number control device 5 ′. The air compressor operation number control device 5 ′ controls the operation number of the air compressors 1-1 to 1-4 so that the measured pressure Ppv from the pressure transmitter 3 falls within a preset allowable range. That is, as shown in FIG. 10, an allowable range PS having an upper limit value of PH and a lower limit value of PL is defined, and the number of operating air compressors 1-1 to 1-4 is controlled so that PL ≦ Ppv ≦ PH. To do.
[0005]
There are three operating states of the air compressor 1 (1-1 to 1-4): “load state”, “unload state”, and “stop state”, and the air compressor 1 is sending out compressed air. The state is called the load state, the state where the air compressor 1 is operated but the compressed air is not sent out is called the unload state, and the state where the air compressor 1 is not operated is called the stop state.
[0006]
When the measured pressure Ppv from the pressure transmitter 3 becomes PH <Ppv, the air compressor operation number control device 5 ′ puts one of the loaded air compressors 1 into an unloaded state, and a predetermined time has elapsed. After that, stop. When the measured pressure Ppv from the pressure transmitter 3 becomes Ppv <PL, any one of the air compressors 1 that are not in the loaded state is replaced with the air compressor 1 that is in the unloaded state. The load state is given priority over 1. For example, when the air compressors 1-1 and 1-2 are loaded, the air compressor 1-3 is unloaded, and the air compressor 1-4 is stopped, the stopped air compressor 1-4 Instead, the air compressor 1-3 in the unloaded state is set to the loaded state.
[0007]
[Problems to be solved by the invention]
However, according to such a method for controlling the number of operating air compressors, as described below, the pressure lower limit value PLL (PLL <PL ) It might be the following. When the pressure in the air tank 2 is equal to or lower than the lower pressure limit PLL, the stability on the load side is lost, and as a result, control and measurement using compressed air cannot be performed well.
[0008]
The mechanism by which the pressure in the air tank 2 is equal to or lower than the lower pressure limit PLL will be described. The air compressor 1 has a time delay from the start to the load state due to star / delta start or the like. When the measured pressure Ppv becomes Ppv <PL, any one of the air compressors 1 that are not in the loaded state is put into the loaded state with priority given to the air compressor 1 that is in the unloaded state. When there is no air compressor 1, the stopped air compressor 1 is set to the load state. However, when the air compressor 1 in the stopped state is delayed until it enters the load state, and the consumption of compressed air increases rapidly during this time, the pressure in the air tank 2 further decreases, Below the lower and lower limit PLL.
[0009]
As one method for preventing the pressure in the air tank 2 from becoming lower than the lower pressure limit PLL, it is conceivable to set the allowable range PS higher. That is, even if the consumption amount of compressed air increases rapidly until the lower limit value PL of the allowable range PS is set higher than the lower pressure limit PLL, and the stopped air compressor 1 enters the load state. It is conceivable that the pressure in the air tank 2 does not become lower than the lower pressure limit PLL. However, in this method, since the allowable range PS is set higher, the operation becomes excessive and the energy cost increases.
[0010]
As another method for preventing the pressure in the air tank 2 from becoming lower than the lower pressure limit PLL, it is considered that the standby air compressor 1 is not in a stopped state but always in an unloaded state. It is done. In this way, since the time until the load state is reached is short, the allowable range PS can be set lower. However, even in such a method, since the air compressor 1 is always in the unloaded state instead of the stopped state, the operation becomes excessive and the energy cost increases.
[0011]
The present invention has been made to solve such a problem, and the object of the present invention is to supply compressed air with a stable pressure that does not fall below the lower limit of the pressure even when there is a load fluctuation. An object of the present invention is to provide a method and apparatus for controlling the number of operating air compressors that can reduce the energy cost without causing excessive operation.
[0012]
[Means for Solving the Problems]
In order to achieve such an object, the present invention (invention according to claim 1 or claim 4) measures the flow rate of the compressed air to the load sent from the air tank, and the measured flow rate of the compressed air is previously measured. When the nearest increase flow rate that has been set is reached, one of the air compressors that are not in the loaded state is given priority to the air compressor that is in the unloaded state, while the previous measured flow rate Calculate the flow rate change of compressed air to the load sent from the air tank from the current value and the current value, and the time from the flow rate change of compressed air to this load until the current flow rate reaches the nearest step flow rate Calculated as the arrival time, and if this stage increase point arrival time is shorter than the preset rise time from the stopped state of the air compressor, assuming that there is no unloaded air compressor, In a stopped state It is obtained by any one of the air compressor to the unloaded state.
[0013]
According to this invention, the flow rate of the compressed air to the load sent out from the air tank is measured, the change in the flow rate of the compressed air is obtained from the previous value and the current value of this measured flow rate, and the flow rate of the compressed air to this load The time from the change until the current flow rate reaches the nearest step increase flow rate is calculated as the step increase point arrival time t.
Then, the calculated increase point arrival time t is compared with a preset rise time t0 from the stopped state of the air compressor, and t is shorter than t0, and the unloaded air compressor is 1 If there is no stand, any one of the air compressors in a stopped state is activated and brought into an unloaded state.
In other words, any one of the stopped air compressors is started early and brought into an unload state so that the measured flow rate reaches the nearest increased flow rate and can immediately shift to the load state.
It should be noted that the air compressor is not in a state where unloading is completed (unload completion state) immediately after startup. In the present invention, the way to the unload completion state is included in the unload state as one form thereof. Hereinafter, the way to the unload state is referred to as an unload state.
In the unloading state or in the unloading completion state, when the measured flow rate reaches the preset preset flow rate, the air compression is in the unloading state (in the unloading state or unloading completion state) The machine is loaded.
[0014]
In the present invention, when the pressure in the air tank is measured and the measured pressure is equal to or lower than a preset pressure lower limit value, any one of the air compressors not in the loaded state is in the unloaded state. The compressor may be preferentially placed in the load state (invention according to claim 2 or claim 5).
According to the present invention, when the pressure in the air tank becomes equal to or lower than the preset pressure lower limit value, any one of the air compressors that are not in the loaded state is brought into the loaded state. At this time, if there is an air compressor in the unloaded state, the air compressor in the unloaded state is preferentially placed in the loaded state.
[0015]
In the present invention, the flow rate of compressed air to the load sent from the air tank is measured, the pressure in the air tank is measured, and the measured pressure in the air tank is equal to or higher than a preset pressure lower limit value, When the measured flow rate of compressed air to the load falls below the preset step-down flow rate, or when the measured pressure in the air tank exceeds the preset pressure upper limit, Any one of the air compressors may be in an unloaded state, and may be stopped after a predetermined time has passed (invention according to claim 3 or claim 6).
According to the present invention, when the pressure in the air tank is equal to or higher than the pressure lower limit value, when the flow rate of the compressed air to the load is equal to or less than the nearest step-down flow rate, any one of the loaded air compressors is unloaded. The loaded state is set, and after a predetermined time has elapsed, the stopped state is set. Further, when the pressure of the compressed air in the air tank becomes equal to or higher than the pressure upper limit value, any one of the air compressors in the loaded state is unloaded, and is stopped after a predetermined time has elapsed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an instrumentation diagram showing an example of an air compressor operation number control system used for implementing an air compressor operation number control method according to the present invention. In the figure, the same reference numerals as those in FIG. 9 denote the same or equivalent components, and the description thereof is omitted.
[0017]
In this embodiment, a flow meter 6 is provided in the air flow path between the air tank 2 and the header 4, the flow rate F of compressed air to the load sent out from the air tank 2 is measured, and the measured flow rate Fpv is used as the air. The data is sent to the compressor operation number control device 5.
[0018]
FIG. 2 shows an outline of an internal configuration of an air compressor operation number control device (hereinafter simply referred to as a control device) 5. The control device 5 includes a CPU 5-1, a ROM 5-2, a RAM 5-3, and interfaces 5-4 to 5-6. The measured pressure Ppv from the pressure transmitter 3 is given to the CPU 5-1 through the interface 5-4, and the measured flow rate Fpv from the flow meter 6 is given through the interface 5-5. The CPU 5-1 executes processing while accessing the RAM 5-3 according to the program stored in the ROM 5-2 based on the input measured pressure Ppv and measured flow rate Fpv, and the air compressors 1-1 to 1-4. Make a control command to
[0019]
In ROM5-2, in addition to the above-described program, as step-up flow rates SPU1, SPU2, SPU3 used as threshold values in the control operation at the time of step-up described later, and as threshold values in control operation at the time of step-down. The step-down flow rates SPD1, SPD2, and SPD3 used are set.
[0020]
In the present embodiment, the discharge / air amounts of the air compressors 1-1 to 1-4 are all the same, and the increased flow rate SPU1 is set equal to the discharge / air amount of one air compressor 1. The increased flow rate SPU2 is set equal to the discharge / air amount for two air compressors 1, and the increased flow rate SPU3 is set equal to the discharge / air amount for three air compressors 1. To do. Further, the step-down flow rate SPD1 is set as a flow rate value lower than the step-up flow rate SPU1 by a predetermined value DIF1, and the step-down flow rate SPD2 is set as a flow rate value lower than the step-up flow rate SPU2 by a predetermined value DIF2, and the step-down flow rate SPD3. Is assumed to be set as a flow rate value lower than the increased flow rate SPU3 by a predetermined value DIF3.
[0021]
FIG. 3 shows the relationship between the increased flow rates SPU1, SPU2, SPU3 and the decreased flow rates SPD1, SPD2, SPD3 and the number N of operating air compressors. In this embodiment, DIF1 = DIF2 = DIF3.
[0022]
Further, in the ROM 5-2, a pressure lower limit value PL and a pressure upper limit value PH for the measured pressure Ppv are set, and the pressure lower limit value PL is set close to the pressure lower limit value PLL (see FIG. 4). That is, in the present embodiment, the allowable pressure range PS in the air tank 2 is set low.
[0023]
Further, in the present embodiment, the predetermined value P with respect to the pressure lower limit value PL. _DIF1 A pressure value PLH when the air compressor 1 with the higher point is increased by turning off the increase request with hysteresis (maintenance is maintained) is set to a predetermined value P with respect to the pressure upper limit PH. _DIF2 The pressure value PHL is determined when the air compressor 1 having a step reduced by a lower point is provided with hysteresis and the step reduction request is turned off (maintenance is maintained).
[0024]
[Control action when increasing steps]
The CPU 5-1 reads the measured pressure Ppv from the pressure transmitter 3 and the measured flow rate Fpv from the flow meter 6 every 0.2 seconds (steps 5A1, 5B1, and 5C1 shown in FIG. 5), and steps 5A1 to 5A7, Steps 5B1 to 5B4 and steps 5C1 to 5C4 are executed in parallel.
[0025]
[Number control by flow rate (1): Load prediction control]
Load prediction control is performed by the processing of steps 5A1 to 5A7. In this load predictive control, the measured flow rate Fpv is read (step 5A1), and when the read number of the measured flow rate Fpv reaches a predetermined number (5 in this example) (YES in step 5A2), the process proceeds to step 5A3.
[0026]
In step 5A3, the flow rate change ΔF of the compressed air from the air tank 2 to the load is obtained from the five measured flow rates Fpv1 to Fpv5 read this time and the last measured flow rate Fpv0 read last time. Then, from this flow rate change ΔF, a time until the current flow rate F reaches the nearest step-up flow rate SPUn is obtained as a step-up point arrival time t (step 5A4).
[0027]
An example of change in the flow rate F of compressed air from the air tank 2 to the load is shown in FIG. In FIG. 6, it is assumed that the measurement point of the last measured flow rate Fpv0 read last time is T0, and the measurement point of the last measured flow rate Fpv5 read this time is T5. In this case, the CPU 5-1 reads the measured flow rate Fpv from the flow meter 6 every 0.2 seconds from T0 to T5. That is, as shown in FIG. 7, f0 is measured flow rate Fpv0 at point T0, f1 is measured flow rate Fpv1 at point T1, f2 is measured flow rate Fpv2 at point T2, f3 is measured flow rate Fpv3 at point T3, T4 At the point, f4 is read as the measured flow rate Fpv4, and at the point T5, f5 is read as the measured flow rate Fpv5.
[0028]
The CPU 5-1 calculates the flow rate change ΔF for ΔT = 1 sec from T0 to T5 by the following equation (1).
ΔF = {(f1−f0) + (f2−f1) + (f3−f2) + (f4−f3) + (f5−f4)} / (0.2) / 5 (1)
[0029]
Then, the CPU 5-1 calculates the time (increase point arrival time) t until reaching the nearest increased flow rate SPUn (in the example of FIG. 6, SPUn = SPU 1) t from this calculated flow rate change ΔF, t = ( Calculated as SPUn−f5) / ΔF.
[0030]
Next, the CPU 5-1 compares the calculated increase point arrival time t with a preset rise time (time from the stop state to the load state) t0 of the air compressor 1 (step 5A5). When the step increasing point arrival time t is shorter than the rise time t0 (0 ≦ t ≦ t0), it is confirmed that there is no air compressor 1 in an unloaded state (YES in step 5A6) and stopped. Any one of the air compressors 1 in the state is brought into an unloaded state (step 5A7).
[0031]
For example, if the nearest step-up flow rate is SPU1, the air compressor 1-1 is in a loaded state, and the air compressors 1-2 to 1-4 are in a stopped state, the air compressor 1-2 is started and unloaded. State. As a result, the air compressor 1-2 in the stopped state is started early and brought into the unloaded state so that the measured flow rate Fpv can be immediately shifted to the loaded state at the point where it is predicted that the increased flow rate SPU1 will be reached. . Note that the air compressor 1 does not reach the unload completion state immediately after activation. In this embodiment, the way to the unload completion state is included in the unload state as one form. The way to the unload state is called an unload state.
[0032]
[Number control by flow rate (2): Number control by using the nearest step-up flow rate SPUn as a threshold value]
The number control using the nearest step-up flow rate SPUn as a threshold value is performed by the processing of steps 5B1 to 5B4. In this number control, the measured flow rate Fpv is read every 0.2 sec (step 5B1), and this measured flow rate Fpv is compared with the nearest increased flow rate SPUn (step 5B2).
[0033]
When the measured flow rate Fpv becomes equal to or greater than the nearest increased flow rate SPUn (YES in step 5B2), the soft timer starts counting in step 5B3, and the measured flow rate Fpv exceeds the nearest increased flow rate SPUn due to the time-up of this soft timer. After confirming that the state has continued for a predetermined time or longer (YES in step 5B3), any one of the air compressors 1 that are not in the loaded state is preferentially placed in the loaded state with the air compressor 1 in the unloaded state. (Step 5B4).
[0034]
For example, according to the predicted load control, the air compressor 1-1 is in the loaded state, the air compressor 1-2 is in the unloaded state (the unloading state or the unloading complete state), the air compressors 1-3, If 1-4 is in the stopped state, the air compressor 1-2 in the unloaded state is set to the loaded state.
[0035]
In the example of FIG. 6, the increase point arrival time t is calculated at the point T5, the point reaching the increase step flow rate SPU1 is predicted as TA, and the unload completion state is reached when the TA point is reached. The air compressor 1-2 is activated. Therefore, when the flow rate F of the compressed air from the air tank 2 changes as predicted and reaches the increased flow rate SPU1 at the TA point, the empty compressor 1-2 in the unload completed state is immediately put into the load state. . The time from the unload completion state to the load completion state is very short, and even if the consumption of compressed air suddenly increases during the transition of the empty compressor 1-2 from the unload completion state to the load completion state, The pressure in the air tank 2 does not drop significantly.
[0036]
Further, after the point T5, when the flow rate F of the compressed air from the air tank 2 suddenly increases contrary to the prediction (FIG. 6 shows this state), the TA point predicted to reach the increased flow rate SPU1. If the measured flow rate Fpv exceeds the step-up flow rate SPU1 at the TB point before the time point, and the step-up arrival time t up to the TB point is calculated to be shorter than the preset rise time t0 of the air compressor 1, Immediately the air compressor 1-2 is activated. When the point TB is reached, the air compressor 1-2 is still in an unloading state, and there is a slight time delay until the loading completion state is reached. However, this time delay is shorter than the time delay from the stop state to the load completion state, and the air compressor 1-2 is immediately loaded. For this reason, the pressure in the air tank 2 does not drop significantly during the transition of the air compressor 1-2 from the unloading state to the loading completion state.
[0037]
As described above, in the present embodiment, any one of the air compressors 1 that are in a stopped state by the predictive load control is activated early to be in an unloaded state (an unloading state or an unloading completed state) Since the uncompressed air compressor 1 is immediately loaded when the measured flow rate Fpv exceeds the nearest step-up flow rate SPUn, even if the load fluctuates during step-up, The pressure does not drop greatly. As a result, even if there is a load fluctuation without setting the allowable pressure range PS of the compressed air from the air tank 2 to a high level and without always leaving the standby compressor 1 unloaded. It becomes possible to supply compressed air having a stable pressure that does not fall below the lower pressure limit PLL.
[0038]
[Unit control by pressure: Unit control with lower limit of pressure PL as threshold value]
The number control using the pressure lower limit value PL as a threshold value is performed by the processing of steps 5C1 to 5C4. In this number control, the measured pressure Ppv is read every 0.2 sec (step 5C1), and the measured pressure Ppv is compared with a preset pressure lower limit PL (step 5C2).
[0039]
When the measured pressure Ppv becomes lower than the pressure lower limit value PL (YES in step 5C2), the time measurement of the soft timer is started in step 5C3, and the state where the measured pressure Ppv is lower than the lower pressure limit PL is reached for a predetermined time by the time-up of this soft timer. After confirming the above (YES in step 5C3), any one of the air compressors 1 that are not in the loaded state is preferentially put in the loaded state with the air compressor 1 in the unloaded state (step 5C4). .
[0040]
For example, according to the previous predicted load control, the air compressors 1-1 and 1-2 are loaded, the air compressor 1-3 is unloaded, the air compressor 1-4 is stopped, and the measured flow rate Fpv Has not yet reached the nearest step-up flow SPU2. In such a state, when the load increases rapidly and the measured pressure Ppv becomes equal to or lower than the pressure lower limit value PL, the air compressor 1-3 in the unloaded state even if the measured flow rate Fpv does not reach the increased flow rate SPU2. Is loaded.
[0041]
That is, if the measured pressure Ppv is equal to or lower than the pressure lower limit PL at the point TC shown in FIG. 4, the air compressor 1-3 in the unloaded state is loaded even if the measured flow rate Fpv does not reach the increased flow rate SPU2. State. In this case, the air compressor 1-3 is in an unloading state or in an unloading completed state, and is immediately loaded, so that the pressure in the air tank 2 does not drop greatly.
[0042]
In addition, even if the measurement pressure Ppv rises by setting the air compressor 1-3 to the load state and exceeds the pressure value PLH when turning off the stage increase request (maintenance is maintained) (point TD shown in FIG. 4). The CPU 5-1 continues to operate the air compressor 1-3 in the loaded state.
[0043]
[Control action during step reduction]
The CPU 5-1 reads the measured flow rate Fpv from the flow meter 6 every 0.2 seconds (step 801 shown in FIG. 8), and compares the read measured flow rate Fpv with the nearest reduced flow rate SPDn (step 802). ). When the measured flow rate Fpv becomes equal to or less than the nearest reduced flow rate SPDn (YES in step 802), the timing of the soft timer is started in step 803, and the measured flow rate Fpv falls below the nearest reduced flow rate SPDn due to the time-up of this soft timer. After confirming that the state has continued for a predetermined time or longer (YES in step 803), the process proceeds to step 807.
[0044]
On the other hand, the CPU 5-1 reads the measured pressure Ppv from the pressure transmitter 3 every 0.2 seconds (step 804), and checks whether the measured pressure Ppv is equal to or higher than the pressure lower limit value PL (step 805). . If the measured pressure Ppv is equal to or higher than the pressure lower limit PL (YES in step 805), the soft timer is started in step 806, and the state where the measured pressure Ppv is equal to or higher than the lower pressure limit PL is predetermined by the time-up of the soft timer. After confirming that it has continued for more than the time (YES in step 806), the process proceeds to step 807.
[0045]
In step 807, AND of “YES in step 803” and “YES in step 806” is performed, that is, the state where the measured flow rate Fpv is equal to or less than the nearest step-down flow rate SPDn continues for a predetermined time and the measured pressure Ppv is It is confirmed that the state of being equal to or greater than the pressure lower limit PL has continued for a predetermined time or longer (YES in Step 807), and any one of the air compressors 1 in the loaded state is set to the unloaded state (Step 808). Then, in step 809, the time of the soft timer is started, and after confirming that a predetermined time has elapsed due to the time-up of the soft timer (YES in step 809), the air compressor 1 that has been unloaded in step 808 is set. A stop state is set (step 810).
[0046]
Further, the CPU 5-1 reads the measured pressure Ppv from the pressure transmitter 3 every 0.2 seconds (step 804), and checks whether or not the measured pressure Ppv is equal to or higher than the pressure upper limit PH (step 811). . If the measured pressure Ppv is equal to or higher than the pressure upper limit PH (YES in step 811: TE point shown in FIG. 4), the time measurement of the soft timer is started in step 812. After confirming that the state of the value PH or more has continued for a predetermined time or longer (YES in step 812), the process proceeds to step 808.
[0047]
The operation after step 808 is as described above, and any one of the air compressors 1 in the loaded state is set in the unloaded state (step 808), and after a predetermined time has elapsed (YES in step 809), The air compressor 1 thus made is brought into a stopped state (step 810).
[0048]
In the above-described embodiment, it is confirmed in steps 5B3 and 5C3 shown in FIG. 5 and YES in steps 803, 806, and 812 shown in FIG. However, it may be possible to immediately proceed to the next step without confirming that it has continued for a predetermined time.
In the above-described embodiment, the time from the stop state of the air compressor 1 to the load state (load completion state) has been used as the rising time t0. However, from the stop state of the air compressor 1 to the unload state The time until it reaches (unload completion state) may be used as the rising time t0.
Needless to say, the air compressor is more effective even with an inverter.
[0049]
【The invention's effect】
As is apparent from the above description, according to the present invention, any one of the air compressors in the stopped state can be immediately shifted to the load state at the point where the measured flow rate is predicted to reach the nearest increased flow rate. One is started early and unloaded, and the air compressor in this unloaded state is immediately loaded when the measured flow exceeds the nearest increased flow, so the load is increased when the load is increased. Even if there is a fluctuation, the pressure in the air tank does not drop greatly. As a result, the pressure lower limit value is maintained even if there is a load fluctuation without setting the allowable pressure range of the compressed air from the air tank to a high level and without always leaving the standby air compressor unloaded. It is possible to supply compressed air with a stable pressure that does not fall below.
[Brief description of the drawings]
FIG. 1 is an instrumentation diagram showing an example of an air compressor operation number control system used to implement an air compressor operation number control method according to the present invention.
FIG. 2 is a block configuration diagram showing an outline of an internal configuration of an air compressor operation number control device in the air compressor operation number control system.
FIG. 3 is a diagram showing a relationship between increased flow rates (SPU1, SPU2, SPU3) and reduced flow rates (SPD1, SPD2, SPD3) and the number of operating air compressors (N).
FIG. 4 shows the setting state of the pressure lower limit value PL and the pressure upper limit value PH and when the step increase request determined by providing hysteresis to the pressure lower limit value PL and the pressure upper limit value PH is turned off (maintenance is maintained). It is a figure which shows the setting condition of the pressure value PHL at the time of turning OFF the pressure value PLH and the reduction | decrease request | requirement (current condition maintenance).
FIG. 5 is a flowchart showing a control operation at the time of increasing the number of CPUs in the air compressor operation number control device.
FIG. 6 is a diagram showing an example of a change in the flow rate of compressed air from an air tank to a load.
FIG. 7 is a diagram showing a measured flow rate Fpv that is read every 0.2 sec from T0 to T5.
FIG. 8 is a flowchart showing a control operation when the CPU is stepped down in the air compressor operation number control device.
FIG. 9 is an instrumentation diagram showing an example of a conventional air compressor operation number control system.
FIG. 10 is a diagram showing a setting state of a pressure lower limit value PL and a pressure upper limit value PH in a conventional air compressor operation number control system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 (1-1 to 1-4) ... Air compressor, 2 ... Air tank, 3 ... Pressure transmitter, 4 ... Header, 5 ... Air compressor operation number control apparatus, 5-1 ... CPU, 5-2 ... ROM, 5-3 ... RAM, 5-4 to 5-6 ... interface, 6 ... flow meter, PL ... pressure lower limit, PH ... pressure upper limit, PS ... allowable range, PLL ... lower pressure lower limit, PHH ... pressure Upper and upper limit values, SPU1, SPU2, SPU3 ... step-up flow, SPD1, SPD2, SPD3 ... step-down flow, t ... step-up point arrival time.

Claims (6)

A plurality of air compressors for generating compressed air; and an air tank for storing the compressed air sent from these air compressors, and the air compressor based on the state of the compressed air sent from the air tank to a load In the air compressor operation number control method for controlling the operation number of
When the flow rate of compressed air to the load sent out from the air tank is measured, and the measured flow rate of the compressed air reaches the preset step-up flow rate, air that is not in a load state that is sending compressed air While any one of the compressors is in a loaded state in preference to an air compressor in an unloaded state that is in operation but not sending out compressed air over an air compressor that is in a stopped state,
The change in the flow rate of the compressed air to the load sent from the air tank is determined from the previous value and the current value of the measured flow rate, and the time from the flow rate change of the compressed air until the current flow rate reaches the nearest increased flow rate is determined. When the increase point arrival time is calculated and is shorter than the preset rise time from the air compressor stop state, there is no unloaded air compressor. As a premise, one of the air compressors in a stopped state among the plurality of air compressors is set to an unloaded state. In the air compressor operation number control method according to claim 1,
When the pressure in the air tank is measured and the measured pressure falls below a preset pressure lower limit value, any one of the plurality of air compressors that are not in a loaded state is unloaded. A method of controlling the number of operating air compressors, wherein an air compressor in a loaded state is preferentially placed in a loaded state. In the air compressor operation number control method according to claim 1,
Measure the flow rate of compressed air to the load sent out from the air tank, measure the pressure in the air tank, in a state where the measured pressure in the air tank is equal to or higher than a preset pressure lower limit value, When the measured flow rate of compressed air to the load is equal to or less than a preset step-down flow rate, or when the measured pressure in the air tank is equal to or greater than a preset pressure upper limit value, the plurality of A method for controlling the number of operating air compressors, wherein any one of the air compressors in a loaded state is set to an unloaded state and stopped after a predetermined time has elapsed. Attached to a system including a plurality of air compressors that generate compressed air and an air tank in which compressed air sent from these air compressors is stored, and based on the state of compressed air sent from the air tank to a load In the air compressor operation number control device for controlling the operation number of the air compressor,
A flow rate measuring means for measuring the flow rate of compressed air to the load delivered from the air tank;
When the measured flow rate of the flow rate measuring means reaches the preset step-up flow rate set in advance, any one of the air compressors that are not in a loaded state that is sending out compressed air is being operated but compressed. A stage increasing means for preferentially setting the air compressor in an unloaded state in which air is not sent out to a loaded state over the air compressor in a stopped state;
The flow rate change of the compressed air is obtained from the previous value and the current value of the measured flow rate, and the time from the flow rate change of the compressed air until the current flow rate reaches the nearest step increase flow rate is calculated as the step increase point arrival time. In the case where the time for reaching the increased stage point is shorter than the preset rise time from the stopped state of the air compressor, the plurality of air compressions are performed on the premise that there is no air compression in the unloaded state. An apparatus for controlling the number of operating air compressors, comprising: unloading means for unloading any one of the air compressors in a stopped state among the compressors. In the air compressor operation number control device according to claim 4,
Pressure measuring means for measuring the pressure in the air tank;
When the measured pressure of the pressure measuring unit is equal to or lower than a preset pressure lower limit value, one of the plurality of air compressors is in an unloaded state. And a unit for controlling the number of operating air compressors. In the air compressor operation number control device according to claim 4,
Pressure measuring means for measuring the pressure in the air tank;
In a state where the measured pressure in the air tank by the pressure measuring means is equal to or higher than the preset pressure lower limit value, the measured flow rate of the compressed air to the load by the flow rate measuring means is equal to or smaller than the preset nearest stepped flow rate. If any one of the plurality of air compressors, the first stage degrading means to put any one of the air compressors in a loaded state into an unloaded state, and to stop after a predetermined time,
When the measured pressure in the air tank by the pressure measuring unit is equal to or higher than a preset pressure upper limit value, any one of the plurality of air compressors in the loaded state is unloaded. And an air compressor operation number control device comprising: second step-down means for stopping after a predetermined time has elapsed.

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