JP2013164025A - System for controlling number of compressors - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for controlling the number of compressors, capable of producing a compressed air in a manner quickly following a use load of the compressed air with a simple structure.SOLUTION: A system for controlling the number of compressors comprises: a plurality of compressor 2; a receiver tank 3 to which compressed air from the compressor 2 is supplied and which feeds the compressed air to a compressed air using apparatus; a pressure sensor 4 installed on the receiver tank 3; and an operating number controller 5 changing the number of operating compressors 2 on the basis of a detection pressure of the pressure sensor 4. An operating number reducing pressure as a boundary value whether to reduce the number of operating compressors by the operating number controller 5 is set to be lower as the number of operating compressors is larger. Each compressor 2 is subjected to capacity control so that a discharge pressure is maintained between an upper limit pressure and a lower limit pressure. The operating number controller 5, in which the upper limit pressure and the lower limit pressure of the compressor 2 are input as set values in advance, performs a control by determining the operating number reducing pressure C on the basis of the set values of the operating compressors 2.

Description

  The present invention relates to a compressor number control system that includes a plurality of air compressors and changes the number of operating compressors according to the use load of compressed air.

  Conventionally, as disclosed in the following Patent Document 1, it has been proposed to change a pressure threshold value for increasing or decreasing the number of operating compressors based on a pressure and a rate of change thereof. In the invention described in Patent Document 1, all the compressors are on / off controlled (paragraph number 0029 and the like).

JP 2007-120497 A (claims, paragraph numbers 0140-0155, FIGS. 15 and 16)

  However, even if the pressure change rate is considered, the number of compressors in operation is not considered. In addition, the plurality of compressors are simply on / off controlled. In this case, the compressed air cannot be manufactured by quickly following the usage load of the compressed air.

  The problem to be solved by the present invention is to provide a compressor number control system capable of producing compressed air by controlling the number of operating units with a simple configuration and quickly following the usage load of the compressed air. There is.

  The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is directed to a plurality of compressors, compressed air supplied from these compressors, and compressed air to a device using compressed air. A pressure sensor for detecting the pressure of compressed air, and a unit controller for changing the number of operating compressors based on the detected pressure of the pressure sensor. The number reduction pressure as a boundary value of whether to decrease or not is set so as to decrease as the number of operating units increases, and each compressor has a capacity so as to maintain the discharge pressure between the upper limit pressure and the lower limit pressure. And the upper limit pressure and the lower limit pressure of each of the compressors are previously input as set values, and the number controller obtains the number reduction pressure based on the set values of the compressors in operation. The pressure Detection pressure of the capacitors is compressor units control system characterized by stopping one compressor and in operation becomes more the number reduced Pressure.

According to the first aspect of the present invention, the pressure for reducing the number of vehicles as a boundary value for determining whether or not to decrease the number of operating vehicles is set so as to decrease as the number of operating vehicles increases. As the number of operating compressors increases, the contribution rate per unit for maintaining the target pressure decreases, and the pressure fluctuation can be suppressed. Therefore, the pressure for reducing the number of units can be lowered as the number of operating units increases. In other words, one compressor is usually stopped when the pressure for reducing the number of units is higher than that, and one compressor is started when the pressure for increasing the number of units is lower, but the pressure for decreasing the number is lowered as the number of operating units increases. The pressure fluctuation range can be suppressed.
In addition, each compressor is capacity-controlled so that the discharge pressure is maintained between the upper limit pressure and the lower limit pressure, but the upper limit pressure and the lower limit pressure are set in the unit controller, and the setting of the compressor during operation is set. Based on the value, the pressure for reducing the number of units is obtained and controlled. Therefore, the upper limit pressures of the compressors do not need to be the same or the lower limit pressures do not have to be the same, and even if they are within the allowable range, the allowable range can be increased. Furthermore, it is not always necessary to adjust the capacity adjustment range of each compressor to be within the same or within the allowable range, and the actual upper limit pressure and lower limit pressure of each compressor can be set in the unit controller to simplify the operation. Highly accurate unit control is possible.

The invention according to claim 2 calculates an average upper limit pressure as an average value of the upper limit pressure and an average lower limit pressure as an average value of the lower limit pressures of the compressor in operation, and the number reduction pressure is The compressor number control system according to claim 1, wherein the compressor number control system is set by the following formula based on the number of operating units.
Number reduction pressure = {(average upper limit pressure-average lower limit pressure) / number of operating units} + average lower limit pressure

  According to the invention described in claim 2, in addition to the average upper limit pressure and the average lower limit pressure of the compressor in operation, the number-decreasing pressure can be obtained from the number of operating units, and can be easily controlled.

In the invention according to claim 3, when compressors having different discharge capacities are included, for each compressor in operation, the specific number as a value obtained by dividing the discharge capacity of the compressor by the discharge capacity of the next scheduled stop machine For the compressors in operation, obtain the sum of the values obtained by multiplying the upper limit pressure of each compressor by its specific number of units, and calculate the average upper limit pressure as a value obtained by dividing this by the sum of the number of specific units. As for the compressors, the total lower limit pressure of each compressor is obtained by multiplying the specific number of units, and the average lower limit pressure is obtained as a value obtained by dividing this by the total number of specific units. 3. The compressor number control system according to claim 2, wherein the compressor number control system is set according to the following equation based on the total number of compressors in operation.
Number reduction pressure = {(Average upper limit pressure-Average lower limit pressure) / (Total number of compressors in operation)} + Average lower limit pressure

  According to the third aspect of the present invention, even when compressors having different discharge capacities are included, the ratio that is a value obtained by dividing the discharge capacities of the compressors in operation with the next scheduled stoppage as a reference discharge capacity Using the concept of the number of units, the pressure for decreasing the number of units can be obtained and controlled.

  Furthermore, the invention according to claim 4 is characterized in that the number of operating compressors is decreased after a set time has elapsed in a state where the pressure detected by the pressure sensor is equal to or higher than the pressure for decreasing the number of units. The compressor number control system according to any one of items 3 to 3.

  According to the fourth aspect of the present invention, since the number of operating compressors is decreased after the set time is maintained while the pressure detected by the pressure sensor is equal to or higher than the pressure for decreasing the number of compressors, the compressors are excessively stopped one after another. Can be prevented.

  According to the present invention, it is possible to manufacture compressed air by controlling in consideration of the number of operating units with a simple configuration and quickly following the usage load of the compressed air.

It is the schematic which shows one Example of the compressor number control system of this invention. It is a figure which shows an example of the number control method by the compressor number control system of FIG. 1, and has shown the discharge pressure of each compressor during a driving | operation, the pressure in a receiver tank, and a driving | operation number increase / decrease table. In the compressor number control system of FIG. 1, it is a figure which shows an example of the setting screen of the touch screen of a number controller. In the compressor number control system of FIG. 1, it is a figure which shows the other example of the setting screen of the touch screen of a number controller.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing an embodiment of a compressor number control system according to the present invention. The compressor number control system 1 according to the present embodiment detects a plurality of compressors 2, 2,..., A receiver tank 3 to which compressed air is supplied from the compressor 2, and a pressure in the receiver tank 3. A pressure sensor 4 and a number controller 5 for controlling the compressors 2 based on the pressure detected by the pressure sensor 4 are provided.

  Each compressor 2 is an electric air compressor, and the compressor body is driven by a motor to suck, compress, and discharge outside air. Compressed air from each compressor 2 is sent to one or a plurality of various compressed air utilization devices (not shown) via a common receiver tank 3.

  Each compressor 2 is not particularly limited in its configuration, such as a screw type, a turbo type, or a reciprocating type, but typically has the same configuration as each other. Each compressor 2 typically has the same discharge capacity.

  Each compressor 2 of a present Example is comprised so that capacity | capacitance control is possible. Here, the capacity can be controlled mechanically by itself. Although the specific configuration of the capacity control is not particularly limited, in this embodiment, the capacity control is performed by adjusting the opening of a capacity adjustment valve (not shown) provided on the suction side of the compressor 2.

  A capacity | capacitance adjustment valve adjusts an opening degree by itself so that the pressure of the discharge side of the compressor 2 may be maintained as desired. In other words, as the pressure on the discharge side of the compressor 2 increases, the capacity adjustment valve reduces the suction amount by reducing the opening, thereby reducing the discharge amount while the compressor 2 reduces the discharge amount. As the pressure on the side decreases, the capacity adjustment valve increases the opening to increase the intake amount, thereby causing the compressor 2 to increase the discharge amount.

  More specifically, in FIG. 2, the capacity adjustment valve adjusts the opening so as to maintain the pressure on the discharge side of the compressor 2 between the lower limit pressure PL and the upper limit pressure PH. In this case, the capacity adjustment valve is fully opened when the pressure on the discharge side of the compressor 2 is lower than the lower limit pressure PL, and is fully closed when the pressure is higher than the upper limit pressure PH. Further, the opening degree is proportionally reduced between the lower limit pressure PL and the upper limit pressure PH as it goes from the lower limit pressure PL to the upper limit pressure PH. Thus, the pressure range between the lower limit pressure PL and the upper limit pressure PH is the control range of the capacity adjustment valve. That is, each compressor 2 has a linear characteristic in which the discharge pressure and the discharge flow rate are inversely proportional to each other within a specified adjustment range PL to PH by the capacity adjustment valve. In other words, the discharge pressure and the load factor of the compressor 2 are linear functions. If the pressure on the discharge side of the compressor 2 exceeds a predetermined stop pressure PS, the compressor 2 is forcibly stopped.

  Each compressor 2 of the present embodiment is typically capacity-controlled even when a plurality of compressors 2 are operated at the same time. Therefore, it is not necessary for each compressor 2 to have a full load lock function for maintaining full load operation.

  The receiver tank 3 is a hollow container that is supplied with compressed air from each compressor 2 and supplies compressed air to one or a plurality of compressed air using devices. A pressure sensor 4 is provided so that the pressure in the receiver tank 3 can be detected.

  The number controller 5 is connected to each compressor 2 and the pressure sensor 4, and controls each compressor 2 based on the pressure detected by the pressure sensor 4. In this embodiment, the presence or absence of operation of each compressor 2 (that is, change of the number of operating units) is switched. A specific control method is as follows.

  FIG. 2 is a diagram showing an example of the number control method by the compressor number control system 1 of the present embodiment. The discharge pressure of each compressor 2 during operation and the pressure in the receiver tank 3 (that is, the pressure sensor 4) Detection pressure) and the number of operating units increase and decrease table.

  As shown in the form of a table in the center of FIG. 2, the operation number increase / decrease table is divided into a start table for increasing the operation number and a stop table for reducing the operation number as shown in a bar graph on the right side of FIG. Divided. The start-up table shows how to start the compressor 2 based on the pressure P in the receiver tank 3 and the rate of change ΔP, in other words, how to increase the number of operating units. On the other hand, the stop table shows how to stop the compressor 2 on the basis of the pressure P in the receiver tank 3 and the number of units currently in operation, in other words, how to reduce the number of units in operation. . These controls are performed based on the detected pressure P of the pressure sensor 4 and the pressure change rate ΔP at predetermined intervals. In the present embodiment, an average value for a predetermined number of times (for example, 20 times) of the calculation cycle of the CPU of the number controller 5 is used as the detected pressure P, and the most recent predetermined time (for example, the latest 20 seconds) is used as the pressure change rate ΔP. ) Average value is used.

  The pressure change rate ΔP is a fluctuating pressure per predetermined time. When the pressure change rate ΔP is negative, the pressure in the receiver tank 3 tends to decrease, and when the pressure change rate ΔP is positive, the pressure in the receiver tank 3 tends to increase. When the amount of compressed air used by the device using compressed air is larger than the amount of compressed air discharged by the compressor 2, the pressure in the receiver tank 3 decreases, and conversely, the amount of compressed air discharged by the compressor 2 is When the amount of compressed air used is greater than the amount of compressed air used by the device using compressed air, the pressure in the receiver tank 3 increases.

  Due to the pressure loss of the piping from the compressor 2 to the receiver tank 3, the pressure in the receiver tank 3 is slightly lower than the discharge pressure of the compressor 2. Therefore, the pressures PL1 and PL2 in the receiver tank 3 correspond to the discharge pressures PL1 ′ and PL2 ′ of the compressor 2, respectively, as shown by a broken line having a slight inclination in FIG. In the case of the compressor number control system 1 of this embodiment, as is apparent from the stop table, when the pressure in the receiver tank 3 becomes the upper limit pressure PH of the control range of the capacity adjustment valve, all the compressors 2 are Since the air flow rate is stopped, the compressor discharge pressure and the receiver tank pressure are the same with respect to the upper limit pressure PH.

  The number controller 5 compares the detected pressure of the pressure sensor 4 with a preset pressure value, and increases or decreases the number of operating compressors 2. At this time, the pressure value for increasing the number of operating units is set to be different based on the pressure change rate ΔP of the detected pressure P of the pressure sensor 4 as shown in the startup table. In other words, the number controller 5 starts one compressor 2 when the detected pressure P of the pressure sensor 4 is equal to or less than the number-increasing pressure A, but increases the number as a boundary value of whether to increase the number of operating units. The pressure A is set so as to increase gradually as the pressure change rate ΔP increases to the negative side.

  When the number of operating units is to be increased, the unit controller 5 is configured such that, when the detected pressure P of the pressure sensor 4 is maintained at a level equal to or lower than the number increasing pressure A, the compressor 2 is started, but in a region where the pressure change rate ΔP is equal to or less than the set value (−ΔP1) (that is, ΔP ≦ −ΔP1), if the detected pressure P of the pressure sensor 4 is equal to or less than the immediate increase pressure B, One more unit is activated without waiting for the elapse of a predetermined time. The immediate increase pressure B is preferably set to a higher pressure as the absolute value of the pressure change rate ΔP is larger.

  On the other hand, as shown in the stop table, the pressure value for decreasing the number of operating units is set to be different based on the number of operating compressors 2 that are currently operating. That is, the number controller 5 stops one compressor 2 when the detected pressure P of the pressure sensor 4 is equal to or higher than the number reduction pressure C, but the number controller 5 serves as a boundary value for determining whether or not to reduce the number of operating units. The pressure C is set so as to gradually decrease as the number of operating units increases.

  The pressure C for reducing the number of units should be determined in consideration of the load factor of each compressor 2. That is, when the load factor is 0% when stopped (above the upper limit pressure PH) and the load factor is 100% when full load (lower limit pressure PL or less), the load factor per compressor 2 in operation is If it becomes below the stop load factor calculated | required by a type | formula, one in operation will be stopped.

  The number controller 5 calculates the pressure C for reducing the number of units based on the number of units in operation by the following formula in order to stop one unit at a stop load factor according to the number of units in operation, and reduces the number of units operated accordingly based on this formula. Let

  This Formula 2 can be rewritten as follows using the Formula 1.

  In this way, the pressure C for decreasing the number can be defined according to the number of operating units. Note that the upper limit pressure PH and the lower limit pressure PL in the formulas 2 and 3 are compressor discharge pressures that define the control range of the capacity adjustment valve as described above, but the actual stop control is performed in the receiver tank in this embodiment. 3 is performed based on the detected pressure of the pressure sensor 4 provided in 3, it is preferable to use a value corrected in consideration of the pressure loss between the compressor 2 and the receiver tank 3. However, as described above, the upper limit pressure PH is the same as the compressor discharge pressure and the receiver tank pressure. Therefore, it is preferable to use the value converted into the receiver tank pressure for the lower limit pressure PL. Alternatively, the number-decreasing pressure C derived from Equation 2 and Equation 3 is strictly a compressor discharge pressure, and is preferably controlled by converting it into a receiver tank pressure.

  Hereinafter, specific control will be described with reference to FIG. The second lower limit pressure PL2 is set lower than the first lower limit pressure PL1, and the first lower limit pressure PL1 and the second lower limit pressure PL2 are set lower than the control range lower limit PL of the capacity adjustment valve. The first set value ΔP1 and the second set value ΔP2 are set in consideration of the discharge capacity during full load operation for one compressor.

(1) Increase control of the number of operating units of the compressor 2 (1-1) When the absolute value of the pressure change rate ΔP is less than the first set value ΔP1. Specifically, when -ΔP1 <ΔP <+ ΔP1.
When the detected pressure P of the pressure sensor 4 is equal to or lower than the second lower limit pressure PL2 as the pressure A for increasing the number of units, one unit is activated. As a result, the pressure normally exceeds the second lower limit pressure PL2, but if the use load of compressed air continues to increase during this time, the pressure may remain below the second lower limit pressure PL2. In that case, every time the predetermined continuous activation prevention time elapses, one compressor 2 is activated. That is, when the detected pressure P of the pressure sensor 4 remains in the “one unit start” region in FIG. 2, as long as there is a compressor 2 that is stopped, one unit is started each time the continuous start prevention time elapses.

(1-2) A case where the absolute value of the pressure change rate ΔP is equal to or greater than the first set value ΔP1 but less than the second set value ΔP2. Specifically, when -ΔP2 <ΔP ≦ −ΔP1.
When the detected pressure P of the pressure sensor 4 is equal to or lower than the first lower limit pressure PL1 as the number increase pressure A, one unit is activated. In this case as well, if the first lower limit pressure PL1 or less is maintained even if one unit is activated, one unit is activated every time a predetermined continuous activation prevention time elapses, but the second lower limit pressure PL2 as the immediately increasing pressure B If it becomes below, another one is started, without waiting for progress of continuous starting prevention time.

  That is, in FIG. 2, if one unit is started by entering the “one unit start” region and still remains in that region, it remains 1 every continuous start prevention time as long as there is a compressor 2 being stopped. The compressor 2 is started one by one. In the meantime, if the “one more unit activation” area is entered, one unit is activated even if the continuous activation prevention time has not elapsed.

(1-3) The absolute value of the pressure change rate ΔP is equal to or greater than the second set value ΔP2. Specifically, when ΔP ≦ −ΔP2.
When the pressure in the receiver tank 3 drops (when the pressure change rate ΔP is negative, that is, ΔP ≦ −ΔP2), the detection pressure P of the pressure sensor 4 is the upper limit of the control range of the capacity adjustment valve as the pressure A for increasing the number of units. Even if it is below the value PH, in other words, within the control range PL to PH of the capacity adjustment valve, one unit is activated. Also in this case, when the control range PL to PH of the capacity adjusting valve is maintained even if one unit is started, one unit is started every time a predetermined continuous start prevention time elapses. If the pressure falls below the lower limit pressure PL1, another unit is activated without waiting for the continuous activation prevention time to elapse.

  That is, even if one unit is started by entering the “one unit start” area in FIG. 2 and still remains in that region, as long as there is a compressor 2 that is stopped, one unit for each continuous start prevention time The compressor 2 is started one by one. In the meantime, if the “one more unit activation” area is entered, one unit is activated even if the continuous activation prevention time has not elapsed.

(2) Reduction control of the number of operating compressors 2 When the air pressure is monitored by the pressure sensor 4 and, for example, two units are operating, one unit stops when the load factor per unit becomes 50% or less. When three units are operating, one unit is stopped when the load factor per unit is 67% or less. When four units are operating, the unit load rate is 75% or less. In this case, the number of operating compressors 2 is reduced in consideration of the stop load factor according to Equation 1 as described above.

  Thereby, when only one unit is operated, the load factor is operated at 0 to 100%, and when two units are operated, the load factor per unit is operated at 50 to 100%. In the case of operating three units, the operation is performed with a higher load as the number of units increases, such as operation with a load factor of 67 to 100% per unit.

  In order to perform the control based on the pressure, it is only necessary to stop one unit if the pressure is not less than the number-decreasing pressure C corresponding to the number of operating units determined by the above-described Formula 3 (or Formula 2). For example, when two units are operating, when “{(upper limit pressure PH−lower limit pressure PL) / 2)} + lower limit pressure PL” or more, one compressor 2 is stopped. In addition, when operating three units, when “{(upper limit pressure PH−lower limit pressure PL) / 3} + lower limit pressure PL” or more, one compressor 2 is stopped so that one compressor is stopped. The number-decreasing pressure C is set according to Equation 3 based on the number.

  Here, it is preferable to reduce the number of operating compressors 2 after the set time continues for a state in which the pressure P detected by the pressure sensor 4 is equal to or higher than the pressure C for reducing the number of units. As a result, it takes a specified time to stop the next one after stopping one, and there is no risk of stopping one after another.

  When operating multiple units at the same time, if only one unit is capacity controlled and the others are operated at full load, the capacity adjustment is performed with only one unit, so if the air usage decreases rapidly, the receiver tank There is a possibility that the pressure in 3 will rise excessively. However, according to the configuration of this embodiment, even when a plurality of compressors 2 are operated, the capacity is controlled for all, so even if the amount of air used is drastically reduced, the capacity control of the plurality of compressors 2 is performed. By the functions acting in parallel, it is possible to prevent the pressure in the receiver tank 3 from rising excessively. Even if the air usage suddenly disappears at all, the air pressure does not rise excessively.

  In the case of operating a plurality of units simultaneously, if only one unit is capacity-controlled and the others are operated at full load, each compressor 2 needs a full load lock function for holding at full load operation. However, this function is not normally provided in the compressor 2, and the compressor 2 needs to be modified. However, according to the system 1 of the present embodiment, each compressor 2 does not need a full load lock function, so that it is not necessary to modify each compressor 2.

  Further, when the pressure C for decreasing the number is lowered in accordance with the increase in the number of operating units, the load factor of each operating compressor 2 increases as described above. In other words, each compressor 2 operates on the side where the discharge pressure is low. Will do. In general, the compressor 2 is more efficient as it operates at a lower discharge pressure. Therefore, the operation efficiency can be improved by lowering the pressure C for decreasing the number of units.

  By the way, in the said Example, the capacity | capacitance adjustment valve of each compressor 2 demonstrated the example in which the upper limit pressure PH was mutually set and the lower limit pressure PL was mutually set. However, it is difficult to set the upper limit pressures PH and lower limit pressures PL of the capacity adjustment valves of the compressors 2 to be the same, and even if they are within an allowable range (for example, within 10 kPa), they are skilled in work. It takes time. If all the compressors 2 cannot be set to the same capacity adjustment range, the load factors of the individual compressors 2 vary.

  Therefore, the number controller 5 receives the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 as preset values, respectively, and reduces the number of units based on the set value of the compressor 2 in operation. When the pressure C is obtained and the detected pressure of the pressure sensor 4 is equal to or higher than the pressure C for reducing the number of units, the number of operating compressors 2 is preferably decreased. In other words, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are set in the number controller 5, and the number controller 5 uses this set value to stop the operation number of the compressors 2 from being reduced. It is preferable to calculate the number reduction pressure C to be a load factor, and to stop one compressor 2 when the number reduction pressure C is exceeded. Here, the upper limit pressure PHi indicates the upper limit pressure of the capacity adjustment valve of the i-th unit among the plurality of compressors 2, and the lower limit pressure PLi indicates the lower limit pressure of the capacity adjustment valve of the i-th unit.

  More specifically, first, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are obtained in advance by a test. For example, each compressor 2 is operated one by one, and the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are determined from the relationship between the pressure on the discharge side of the compressor 2 and the load current of the compressor 2. Can be requested.

  Then, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 obtained in this way are input to the unit controller 5 and set. For example, FIG. 3 is a diagram showing an example of the setting screen of the touch screen of the number controller 5, and as shown in this figure, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are shown. Set to the number controller 5. In this example, the compressor number control system 1 shows an example including five compressors 2 from No. 1 to No. 5, but it goes without saying that the number of compressors 2 can be changed as appropriate. Yes.

  Now, it is assumed that the discharge capacity (discharge air amount at the time of rating) of each compressor 2 is the same. In addition, it is assumed that m compressors 2 are operating from the n-th unit. That is, it is assumed that from the n-th unit to the (n + m-1) -th unit is operating. Note that n and m are positive integers (any one of 1, 2, 3,...).

  In this case, the number controller 5 obtains the number-decrease pressure C based on the set value (PHi, PLi) of the compressor 2 in operation, and the detected pressure of the pressure sensor 4 is equal to or higher than the number-decrease pressure C. Then, one compressor 2 in operation is stopped. That is, for the compressor 2 in operation, an average upper limit pressure as an average value of the upper limit pressure and an average lower limit pressure as an average value of the lower limit pressure are obtained, and the mathematical formula is calculated using these average upper limit pressure and average lower limit pressure. 3, the pressure C for decreasing the number of units is obtained. When the pressure detected by the pressure sensor 4 becomes equal to or higher than the pressure C for decreasing the number of units, one compressor 2 in operation is stopped.

  More specifically, the number controller 5 calculates the average upper limit pressure by the following formula 4 and the average lower limit pressure by the following formula 5 for the compressor 2 in operation. Furthermore, the number controller 5 obtains the pressure C for decreasing the number by the following formula 6, and when the detected pressure of the pressure sensor 4 becomes equal to or higher than the pressure C for decreasing the number, one compressor 2 in operation is stopped.

  In such a configuration, the upper limit pressures PHi of the capacity adjustment valves of the compressors 2 do not have to be the same as each other, and the lower limit pressures PLi do not have to be the same as each other. Can be greatly increased. Furthermore, it is not always necessary to adjust the capacity adjustment ranges of the compressors 2 so that they are within the same range or within an allowable range. That is, the actual upper limit pressure PHi and the lower limit pressure PLi of the capacity adjusting valve of each compressor 2 may be set in the number controller 5, thereby enabling simple and accurate number control.

  For example, if the total load factor for 5 units becomes 4/5 (ie 80%) or less during operation of 5 units, the number of units operated will be reduced to 4, but the capacity adjustment valve of the compressor 2 that is operating By using the actual upper limit pressure PHi and the lower limit pressure PLi, the number reduction pressure C corresponding to an overall load factor of 80% is calculated, so that accurate number control is possible. Here, the total load factor is that the upper limit pressures PHi and the lower limit pressures PLi of the compressors 2 in operation are different from each other, in other words, the load factors of the compressors 2 are different from each other. This means the load factor when viewed in the entirety of all the compressors 2 in operation.

  As in the above-described embodiment, the operation of the compressor 2 of the next scheduled machine to be stopped should be stopped after a set time has elapsed while the pressure detected by the pressure sensor 4 is equal to or greater than the pressure C for decreasing the number of units. . Here, the control for decreasing the number of operating compressors 2 has been described, but the control for increasing the number of operating compressors is the same as in the above-described embodiment, and thus the description thereof is omitted.

  Further, here, the capacity of each compressor 2 is controlled between the upper limit pressure PHi and the lower limit pressure PLi by the capacity adjustment valve, and the upper limit pressure PHi and the lower limit pressure PLi of each compressor 2 are set in the unit controller 5. However, as long as the upper limit pressure PHi and the lower limit pressure PLi are set and operated, the capacity of each compressor 2 is not necessarily controlled by the capacity adjustment valve. Even in that case, the upper limit pressure PHi and the lower limit pressure PLi of each compressor 2 can be set in the number controller 5 and the number control can be performed in the same manner as described above.

  In the above description, the discharge capacities of the compressors 2 are the same. However, when the compressors 2 having different discharge capacities are included, the following control may be performed.

  Also in this case, first, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are checked in advance. Then, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are input to the number controller 5 and set. Furthermore, the discharge capacity of each compressor 2 is also input to the number controller 5 and set.

  For example, FIG. 4 is a diagram showing another example of the setting screen of the touch screen of the number controller 5, but as shown in this figure, the upper limit pressure PHi and the lower limit pressure PLi of the capacity adjustment valve of each compressor 2 are shown. In addition, the discharge capacity is set in the number controller 5. In this example, the compressor number control system 1 shows an example including five compressors 2 from No. 1 to No. 5, but it goes without saying that the number of compressors 2 can be changed as appropriate. Yes. In this example, the first and second machines have a discharge capacity that is twice that of the third and fifth machines. For example, Unit 1 and Unit 2 are 75 kW compressors, and Units 3 to 5 are 37 kW compressors.

  Assume that m compressors 2 are operating from the n-th unit. That is, it is assumed that from the n-th unit to the (n + m-1) -th unit is operating. In this case, the number controller 5 uses the following formula 7 to calculate the specific number Ni as a value obtained by dividing the discharge capacity of the compressor 2 by the discharge capacity of the next scheduled stop machine for each compressor 2 in operation. Ask. Since the total sum of the specific number Ni corresponds to the actual number of operating units, the stop load factor can be obtained using Equation 1 above.

  For example, when the No. 2 (75 kW machine) and No. 3 (37 kW machine) are in operation and the compressor to be stopped next (the next scheduled stop machine) is No. 3, the ratio of No. 3 is 1, and the No. 2 machine The specific number of units is 2, and the total number of specific units is 3. Therefore, the No. 3 machine scheduled for the next stop will be stopped if its load falls to 2/3 (load factor 67%) or less based on Formula 1 (where the number of operating units is equivalent to the sum of the ratios). The

  In addition, when the No. 2 (75 kW) and No. 3 (37 kW) machines are in operation and the next compressor to be stopped (next scheduled stop) is No. 2, the ratio of No. 2 is 1, and No. 3 The specific number of units is 0.5, and the total number of specific units is 1.5. Therefore, the second scheduled stop machine will be stopped if its load falls to 1/3 (load factor 33%) or less based on the above formula 1 (where the number of operating units is equivalent to the sum of the ratios). The

  In order to perform pressure control more simply, the following formula 8 is used to calculate the sum of values obtained by multiplying the upper limit pressure PHi by the specific number Ni for the compressor 2 in operation, and this is divided by the sum of the specific number Ni. The average upper limit pressure is obtained as a value. Further, according to the following formula 9, for the compressor 2 in operation, the sum of values obtained by multiplying the lower limit pressure PLi by the specific number Ni is obtained, and the average lower limit pressure is obtained by dividing this by the sum of the specific number Ni. . In addition to the average upper limit pressure and the average lower limit pressure obtained in this way, the number C of pressure reduction can be obtained by the following formula 10 based on the total number of the specific number of compressors 2 in operation. Then, the number controller 5 may stop the operation of the next scheduled stop machine when the detected pressure of the pressure sensor 4 becomes equal to or higher than the pressure C for decreasing the number.

  The number-of-compressor control system 1 of the present invention is not limited to the configuration of the above-described embodiments (including modifications), and can be changed as appropriate. In particular, the capacity control method of each compressor 2 is not limited to the capacity adjustment valve provided on the suction side of the compressor 2 as in the above-described embodiment, and other conventionally known configurations may be employed. In particular, the control for increasing the number of operating compressors 2 is not limited to the configuration of the above embodiment, and various conventionally known ones can be used.

  Furthermore, in the said Example, although the compressed air from each compressor 2 was sent to the apparatus using compressed air via the receiver tank 3, and the pressure sensor 4 was provided in the receiver tank 3, in addition to the receiver tank 3, each compression The pressure sensor 4 may be provided at a location where the compressed air is supplied from the machine 2 or a location where the compressed air is sent to the device using the compressed air.

DESCRIPTION OF SYMBOLS 1 Compressor number control system 2 Compressor 3 Receiver tank 4 Pressure sensor 5 Number controller A Number of units increase pressure B Immediate increase pressure C Number of units decrease pressure

Claims (4)

Multiple compressors,
A pressure sensor for detecting the pressure of the compressed air, which is provided at a location where the compressed air is supplied from these compressors and the compressed air is sent to the device using the compressed air;
A number controller for changing the number of operating compressors based on the pressure detected by the pressure sensor,
The pressure for reducing the number of vehicles as a boundary value whether or not to reduce the number of operating units by the number controller is set so as to decrease as the number of operating units increases,
Each of the compressors is capacity-controlled so as to maintain the discharge pressure between an upper limit pressure and a lower limit pressure,
In the number controller, an upper limit pressure and a lower limit pressure of each compressor are input in advance as set values, respectively, and the pressure for reducing the number of units is obtained based on the set value of the compressor in operation. A compressor number control system, wherein one operating compressor is stopped when the detected pressure of the sensor exceeds the number reduction pressure. For the compressor in operation, obtain an average upper limit pressure as an average value of the upper limit pressure and an average lower limit pressure as an average value of the lower limit pressure,
The compressor number control system according to claim 1, wherein the pressure for decreasing the number of units is set by the following equation based on the number of operating units.
Number reduction pressure = {(average upper limit pressure-average lower limit pressure) / number of operating units} + average lower limit pressure When compressors with different discharge capacities are included, for each compressor in operation, find the specific number of units as the value obtained by dividing the discharge capacity of the compressor by the discharge capacity of the next scheduled shutdown machine,
For the compressor in operation, obtain the sum of the values obtained by multiplying the upper limit pressure of each compressor by its specific number, and obtain the average upper limit pressure as a value obtained by dividing this by the sum of the specific number of units,
For the compressors in operation, obtain the sum of the values obtained by multiplying the lower limit pressure of each compressor by its specific number of units, and obtain the average lower limit pressure as a value obtained by dividing this by the total number of specific units,
The compressor number control system according to claim 2, wherein the pressure for decreasing the number of units is set by the following equation based on a total number of specific units of compressors in operation.
Number reduction pressure = {(Average upper limit pressure-Average lower limit pressure) / (Total number of compressors in operation)} + Average lower limit pressure The compressor according to any one of claims 1 to 3, wherein the number of operating compressors is decreased after a set time has continued for a state in which the pressure detected by the pressure sensor is equal to or greater than the pressure for decreasing the number of units. Unit control system.

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