Patent Description:
A fan unit is adjusted so as to meet a required volume of air and not to cause surging even when various ducts having different resistances are connected thereto. For example, in <CIT>, pressure on an outlet side of a fan is detected for a predetermined time, and if the fluctuation amount of the pressure is greater than or equal to a predetermined amount, it is determined that the fan is in a surging region. The document <CIT> is directed to a ventilator configured to reach a predetermined air volume rapidly at the time of start-up and maintaining such volume constant during operation.

However, the pressure fluctuation amount that causes surging varies greatly depending on a rotation speed of the fan. Therefore, even if the pressure fluctuation amount is greater than or equal to the predetermined amount, the fan is not necessarily in a surging state, and the reliability of determination of occurrence or non-occurrence of surging is not high.

There is accordingly an object of the present invention to enhance the reliability of determination of occurrence or non-occurrence of surging.

A fan unit according to a first aspect is a fan unit connected to a predetermined unit through a duct, and includes a fan with a variable rotation speed, a casing, a first acquisition unit, a second acquisition unit, and a control unit. The casing has an intake port and a blow-out port, and houses the fan. The first acquisition unit acquires front-rear differential pressure that is a difference in air pressure between the intake port and the blow-out port of the casing. The second acquisition unit acquires a volume of air or a wind speed of the fan. The control unit determines whether or not surging by the fan occurs on the basis of the volume of air or the wind speed and the front-rear differential pressure.

In a case where the fan unit is connected to another fan unit through the duct, the front-rear differential pressure may change due to a change in volume of air of the another fan unit and the like, and the normally operating fan unit may enter the surging state. Alternatively, the duct resistance changes by changing the volume of air, so that the surging state may be caused.

Whether or not surging occurs depends on the front-rear differential pressure. Therefore, by determining occurrence or non-occurrence of surging on the basis of the front-rear differential pressure, the fan unit can detect and avoid surging with higher accuracy than when determining by using the pressure on the outlet side of the fan.

In the fan unit of the first aspect, the control unit stores in advance a first relational expression that derives an allowable upper limit value of the front-rear differential pressure with respect to the volume of air of the fan. The control unit further determines whether or not surging by the fan occurs by comparing the allowable upper limit value of the front-rear differential pressure calculated on the basis of the volume of air acquired by the second acquisition unit and the first relational expression with the front-rear differential pressure acquired by the first acquisition unit.

The control unit determines occurrence or non-occurrence of surging by a simple means of comparing the acquired front-rear differential pressure with the allowable upper limit value of the front-rear differential pressure without newly providing a dedicated sensor in the fan unit.

A fan unit according to a second aspect is the fan unit according to the first aspect, and the first relational expression is expressed by a curve passing through extreme values on curves expressing a relation between the volume of air of the fan and the front-rear differential pressure that are measured for each rotation speed of the fan.

In the fan unit, the first relational expression can be obtained only by measuring at least three extreme values on the curves expressing the relation between the volume of air of the fan and the front-rear differential pressure that are measured for each rotation speed of the fan, making it easy to adapt to each model.

A fan unit according to a third aspect is the fan unit according to any one of the first to second aspects, and when determining that surging by the fan occurs, the control unit increases the rotation speed of the fan.

An air treatment system according to a fourth aspect includes an air treatment unit and the fan unit according to any one of the first to third aspects. The air treatment unit performs a predetermined treatment to air. The fan unit is connected to the air treatment unit through a duct. The control unit includes a first control unit provided in the air treatment unit, and a second control unit provided in the fan unit. When determining that surging occurs, the second control unit transmits a first signal to the first control unit. When receiving the first signal, the first control unit determines a volume of air of the fan unit that eliminates the surging and transmits the volume of air to the second control unit as an air volume target value. The second control unit controls a rotation speed of the fan unit on the basis of the air volume target value.

Even if surging is avoided by, for example, increasing the rotation speed by using the fan unit alone, there is a possibility that another fan unit connected through the duct causes surging due to a change in front-rear differential pressure in the another fan unit. Furthermore, the air volume target value cannot be set irrespective of a total volume of air required for an air treatment target space.

In the air treatment system, the air treatment unit can determine the air volume target value for the fan unit for avoiding surging in consideration of the total volume of air required for the air treatment target space, so that the reliability of surging elimination is high.

<FIG> is a configuration diagram of an air treatment system <NUM> equipped with fan units according to an embodiment of the present invention.

The air treatment system <NUM> in <FIG> includes a first unit <NUM>, a plurality of second units <NUM>, a duct <NUM>, and a controller <NUM>. In the present application, for convenience of description, the fan units are referred to as the second units.

The first unit <NUM> includes a first fan <NUM>. Each second unit <NUM> includes a second fan <NUM>. Each second fan <NUM> supplies air from the second unit <NUM> to a target space <NUM>.

The target space <NUM> is, for example, a room in a building. The room is a space where the movement of air is restricted by a floor, a ceiling, and walls, for example. The plurality of second units <NUM> are installed with respect to one or a plurality of target spaces <NUM>.

In <FIG>, the air treatment system <NUM> including two second units <NUM> installed with respect to one target space <NUM> is illustrated as a typical example of the air treatment system <NUM> including a plurality of second units <NUM>.

The number of second units <NUM> may also be three or more, and is set appropriately. The number of target spaces <NUM> in which the second units <NUM> are installed may be two or more.

The duct <NUM> distributes first air SA delivered from the first unit <NUM> by the first fan <NUM> to the plurality of second units <NUM>. The duct <NUM> includes a main pipe <NUM> and branch pipes <NUM> branched off the main pipe <NUM>.

<FIG> illustrates a case where the main pipe <NUM> is disposed outside the first unit <NUM>, but the main pipe <NUM> may also be disposed inside the first unit <NUM>, and may also be disposed to extend from the inside of the first unit <NUM> to the outside of the first unit <NUM>.

The case where the main pipe <NUM> is disposed inside the first unit <NUM> also includes a case where a portion of a casing <NUM> of the first unit <NUM> functions as the main pipe <NUM>. <FIG> illustrates an example in which the main pipe <NUM> has an inlet 41a connected to the first unit <NUM>.

The first fan <NUM> is disposed inside the first unit <NUM>. Here, it is configured that all of the air blown out from the first fan <NUM> flows into the duct <NUM>.

The main pipe <NUM> of the duct <NUM> also has an outlet 41b connected to inlets 42a of the branch pipes <NUM>. The configuration for branching the main pipe <NUM> into the branch pipes <NUM> may be a configuration using a branch chamber.

Each second unit <NUM> includes a casing <NUM> having an intake port 33a and a blow-out port 33b. The branch pipes <NUM> have a plurality of outlets 42b connected to intake ports 33a of the plurality of second units <NUM>.

Each second unit <NUM> is connected to the target space <NUM> through a ventilation path <NUM>. The ventilation path <NUM> has an inlet 81a connected to the blow-out port 33b of the second unit <NUM>. Each second fan <NUM> produces an air flow from the outlet 42b of the duct <NUM> toward the inlet 81a of the ventilation path <NUM>, inside the second unit <NUM>. Therefore, each second fan <NUM> is suctioning the first air SA from the outlet 42b of the branch pipe <NUM>.

Each second fan <NUM> can change front-rear differential pressure that is a difference in air pressure between the intake port 33a and the blow-out port 33b of the corresponding second unit <NUM> by changing a rotation speed of a motor. Assuming that the static pressure in the duct <NUM> is constant, each second fan <NUM> can increase the front-rear differential pressure in the corresponding second unit <NUM> by increasing the rotation speed.

If the front-rear differential pressure in the second unit <NUM> increases, the volume of the first air SA flowing through the ventilation path <NUM> increases. This change in volume of flowing air changes the supplied air volume that is blown out from an outlet 81b of each ventilation path <NUM> into the target space <NUM>.

The controller <NUM> includes a first controller <NUM> and a plurality of second controllers <NUM>. The first controller <NUM> and the plurality of second controllers <NUM> are connected to each other.

The first controller <NUM> controls the rotation speed of a fan motor 21b of the first fan <NUM>. If the rotation speed of the first fan <NUM> increases, a volume of air sent by the first fan <NUM> increases.

One second controller <NUM> is provided with respect to each second unit <NUM>. Each second controller <NUM> controls a volume of air of the corresponding second fan <NUM>. Each second controller <NUM> stores an air volume target value received from the first controller <NUM>.

If the supplied air volume is insufficient with respect to the air volume target value, each second controller <NUM> increases the rotation speed of the second fan <NUM>. Conversely, if the supplied air volume is excessive with respect to the air volume target value, the second controller <NUM> reduces the rotation speed of the second fan <NUM>.

The controller <NUM> obtains information about the volume of air supplied to the target space <NUM> by a plurality of the second fans <NUM>. The information about the volume of air includes, for example, a necessary volume of air to be supplied into the target space <NUM> per second or per minute.

Each second controller <NUM> outputs the information about the volume of air to the first controller <NUM>. The first controller <NUM> determines the output required from the first fan <NUM> on the basis of the obtained information about the volume of air.

The first unit <NUM> includes the first fan <NUM>, a heat exchanger <NUM>, a first air volume detector <NUM>, a temperature sensor <NUM>, and a water volume adjustment valve <NUM>.

The heat exchanger <NUM> is supplied with, for example, cold water or hot water as a heat medium from a heat source unit <NUM>. For example, the heat medium supplied to the heat exchanger <NUM> may be something other than cold water or hot water, such as brine.

Examples of the first air volume detector <NUM> include an air volume sensor, a wind speed sensor, or a differential pressure sensor. In the embodiment, the first air volume detector <NUM> detects a volume of air sent by the first fan <NUM>.

The first air volume detector <NUM> is connected to the first controller <NUM>. The first air volume detector <NUM> transmits the value of the volume of air detected by the first air volume detector <NUM> to the first controller <NUM>.

The volume of air detected by the first air volume detector <NUM> is the volume of air flowing through the main pipe <NUM> of the duct <NUM>, and is also a total volume of air supplied from the plurality of second units <NUM> to the target space <NUM>.

The temperature sensor <NUM> detects the temperature of the first air SA sent from the first fan <NUM> to the duct <NUM>. The temperature sensor <NUM> is connected to the first controller <NUM>. The temperature sensor <NUM> inputs the detected value to the first controller <NUM>.

The first unit <NUM> is connected to the target space <NUM> through a ventilation path <NUM>. Second air RA passing through the ventilation path <NUM> and returning from the target space <NUM> is sent out by the first fan <NUM> to the duct <NUM> through the heat exchanger <NUM>.

The second air RA returning from the target space <NUM> is the air that existed inside the target space <NUM>. When passing through the heat exchanger <NUM>, the returning second air RA exchanges heat with the cold water or the hot water flowing through the heat exchanger <NUM> to become conditioned air.

The water volume adjustment valve <NUM> adjusts the amount of heat imparted to the first air SA that exchanges heat in the heat exchanger <NUM> and is sent out to the duct <NUM>. An opening degree of the water volume adjustment valve <NUM> is controlled by the first controller <NUM>. If the opening degree of the water volume adjustment valve <NUM> is increased, the volume of water flowing through the heat exchanger <NUM> increases, so that the amount of heat to be exchanged between the heat exchanger <NUM> and the first air SA per unit time increases. Conversely, if the opening degree of the water volume adjustment valve <NUM> is decreased, the volume of water flowing through the heat exchanger <NUM> decreases, so that the amount of heat to be exchanged between the heat exchanger <NUM> and the first air SA per unit time decreases.

The second unit <NUM> includes the second fan <NUM>, a fan motor 31b that rotates the second fan <NUM>, and a second air volume detector <NUM>.

Each fan motor 31b is connected to a corresponding one of the second controllers <NUM>, and sends the rotation speed to the second controller <NUM>. Each second air volume detector <NUM> is connected to a corresponding one of the second controllers <NUM>.

Examples of the second air volume detector <NUM> include an air volume sensor, a wind speed sensor, or a differential pressure sensor. In the embodiment, the second air volume detector <NUM> detects a volume of air sent by the second fan <NUM>.

The second air volume detector <NUM> inputs the detected value of the volume of air to the second controller <NUM>. The volume of air detected by the second air volume detector <NUM> is the volume of air flowing through the ventilation path <NUM>, and is also the volume of air supplied from each second unit <NUM> to the target space <NUM>.

A plurality of remote sensors <NUM> function as temperature sensors. Each remote sensor <NUM> is configured to transmit data indicating the temperature of the second air RAin the target space <NUM> to a corresponding second controller <NUM>.

<FIG> is a block diagram for describing the configuration of the controller <NUM>. The controller <NUM> in <FIG> includes the first controller <NUM> and the plurality of second controllers <NUM>. The first controller <NUM> and the plurality of second controllers <NUM> are connected to each other.

The first controller <NUM> includes a processor 51a and a memory 51b. The processor 51a reads an air volume control program for the first fan <NUM> stored in the memory 51b, and outputs necessary commands to the first fan <NUM> and each second controller <NUM>.

The memory 51b stores detected values of the first air volume detector <NUM> and the temperature sensor <NUM> as needed in addition to the air volume control program for the first fan <NUM>.

The processor 51a reads the detected values of the first air volume detector <NUM> and the temperature sensor <NUM> stored in the memory 51b, and calculates an air volume target value for the first fan <NUM> (a total of target air volume to be supplied to the target space <NUM>).

The above description is an example and the present disclosure is not limited to the above content of description.

Each second controller <NUM> includes a processor 52a and a memory 52b. The processor 52a reads an air volume control program for the second fan <NUM> stored in the memory 52b, and outputs necessary commands to the second fan <NUM>.

The memory 52b stores the air volume target value output from the first controller <NUM> and a detected value of the second air volume detector <NUM> as needed in addition to the air volume control program for the second fan <NUM>.

The processor 52a reads the air volume target value and the detected value of the second air volume detector <NUM> stored in the memory 52b, and calculates a rotation speed target value of the second fan <NUM>.

The above description is an example and the present invention is not limited to the above content of description.

Each second controller <NUM> receives a temperature measurement value of the target space <NUM> from a corresponding one of the remote sensors <NUM> connected thereto. Each second controller <NUM> holds data indicating a set temperature as a temperature set value.

Each second controller <NUM> transmits the temperature set value and the temperature measurement value to the first controller <NUM>. The first controller <NUM> determines an air volume target value for each second unit <NUM> on the basis of the temperature set value and the temperature measurement value. The first controller <NUM> transmits the value of the air volume target value to each second controller <NUM>.

The first controller <NUM> determines the air volume target value for each second fan <NUM> according to the total of the target air volume to be supplied to the target space <NUM>, and transmits the air volume target value to each second controller <NUM>. Each second controller <NUM> adjusts the rotation speed of the second fan <NUM> in the corresponding second unit <NUM>. The rotation speeds of the plurality of second fans <NUM> are adjusted independently from each other.

Each second controller <NUM> controls the rotation speed of the corresponding second fan <NUM> so that the supplied air volume matches the air volume target value. The plurality of second controllers <NUM> control the rotation speeds of the plurality of second fans <NUM> independently from each other. If the volume of air detected by the second air volume detector <NUM> is small compared to the air volume target value, each second controller <NUM> increases the rotation speed of the corresponding second fan <NUM>. If the volume of air detected by the second air volume detector <NUM> is large compared to the air volume target value, each second controller <NUM> reduces the rotation speed of the corresponding second fan <NUM>.

Specific air volume control will be described in the section of "(<NUM>) Air volume control".

The length of the duct <NUM> connecting the first unit <NUM> and the second units <NUM> varies depending on the positions of the blow-out ports of the second units <NUM>, and also varies depending on a property in which the first unit <NUM> and the second units <NUM> are installed.

There is resistance (hereinafter, referred to as duct resistance) between the air flowing through the duct <NUM> and the inner surface of the duct <NUM>, and the static pressure of the air flowing through the duct <NUM> is reduced by friction. The longer the duct <NUM>, the larger the duct resistance.

<FIG> is a graph indicating a relation between a volume of air and the duct resistance using the duct length as a parameter. In <FIG>, the duct resistance changes nonlinearly with respect to the volume of air flowing through the duct <NUM>. Accordingly, the volume of air is not proportional to the rotation speed of the fan. Therefore, the rotation speed for achieving the value of the target air volume cannot be calculated proportionally.

The difference between the static pressure at the blow-out port and the static pressure at the intake port of the second unit <NUM> is referred to as front-rear differential pressure of the second unit <NUM>.

<FIG> is a graph indicating results of measuring an air volume change amount when the rotation speed of the fan motor 31b is changed by <NUM> (r/m) while changing the front-rear differential pressure of the second unit <NUM>. The rotation speed of the fan motor 31b before the change is <NUM> (r/m).

In <FIG>, when the volume of air is changed to adjust the temperature, the duct resistance fluctuates, so that the front-rear differential pressure of the second unit <NUM> changes. Since the volume of air that changes when the rotation speed of the fan is changed by <NUM> (r/m) varies depending on the situation (front-rear differential pressure) at that time, adjustment is difficult. Therefore, the target air volume may not be reached unless the rotation speed of the fan is adjusted in consideration of the change in duct resistance.

For example, as illustrated in <FIG>, even when the volume of air is changed from <NUM> (m<NUM>/min) to <NUM> (m<NUM>/min), the required rotation speed change amount of the fan motor 31b varies even with the same air volume change amount as long as the duct resistance is different. This is because the duct resistance also changes depending on the change in volume of air. Therefore, an air volume adjustment function considering a change in duct resistance is required.

Furthermore, in the case where the branch pipes <NUM> branched off the main pipe <NUM> are connected to the respective second units <NUM> as illustrated in <FIG>, the front-rear differential pressure of one second unit <NUM> is affected by a change in volume of air of the other second unit <NUM> and air discharge pressure of the first unit <NUM>.

Furthermore, as illustrated in <FIG>, when the volume of air of the other second unit <NUM> or the air discharge pressure from the first unit <NUM> is changed and the front-rear differential pressure is increased to the dotted line in <FIG>, simply maintaining the rotation speed of the fan motor 31b leads to a decrease in the volume of air from <NUM> (m<NUM>/min) to <NUM> (m<NUM>/min). Therefore, the rotation speed of the fan motor 31b needs to be increased in order to maintain the initial volume of air <NUM> (m<NUM>/min).

On the other hand, when the front-rear differential pressure is decreased to a two-dot chain line in <FIG>, maintaining the rotation speed of the fan motor 31b leads to an increase in the volume of air from <NUM> (m<NUM>/min) to <NUM> (m<NUM>/min). Accordingly, the rotation speed of the fan motor 31b needs to be reduced in order to maintain the initial volume of air <NUM> (m<NUM>/min).

Therefore, the second unit <NUM> requires also an air volume maintaining function considering a change in front-rear differential pressure.

As described above, it has been found that the air volume control for one second unit <NUM> requires the air volume maintaining function considering the duct resistance, the volume of air of the other second unit <NUM>, and the air discharge pressure of the first unit <NUM>. However, the duct length varies depending on the property in which the first unit <NUM> and the second units <NUM> are installed or the installation position of the second units <NUM>, and the duct resistance also fluctuates depending on the duct length and the volume of air flowing through the duct. Therefore, it is difficult to convert the relation between the rotation speed and the volume of air of the fan motor <NUM>1b into data by conventional trial run adjustment.

In view of the above, the applicant focuses attention on the fact that the change in duct resistance appears as front-rear differential pressure, and has found that the rotation speed target value for the fan motor <NUM>1b or the rotation speed change amount of the fan motor 31b is calculated by a function using a variable obtained by acquiring information about the volume of air, a wind speed, or the front-rear differential pressure of the second unit <NUM>, in addition to the rotation speed and the value of the target air volume of the fan motor 31b.

This reduces the number of man-hours for a preliminary test, and eliminates the need for a trial run at the time of duct connection. An air volume control logic will be described below.

<FIG> is a graph indicating a relation between a wind speed V and a rotation speed N of the fan motor 31b using front-rear differential pressure ΔP as a parameter. In <FIG>, when the front-rear differential pressure ΔP is the same, the rotation speed N of the fan motor 31b can be expressed by a linear expression of the wind speed V by using a coefficient a and a constant term b.

As illustrated in <FIG>, when the front-rear differential pressure is constant, the equation (<NUM>) can be derived by performing a test for obtaining values of at least three points.

Furthermore, <FIG> is a graph indicating a relation between the front-rear differential pressure ΔP and the coefficient a and the constant term b derived from <FIG>. In <FIG>, the relation between the front-rear differential pressure ΔP and the coefficient a and the constant term b can be expressed by the following equations. <MAT> <MAT>.

From the above equations (<NUM>), (<NUM>), and (<NUM>), the relation among the rotation speed N, the wind speed V, and the front-rear differential pressure ΔP is expressed by the following equation.

From the equation (<NUM>), the following equation is further derived.

The equation (<NUM>) means that the front-rear differential pressure ΔP can be calculated by measuring the wind speed V when the fan motor 31b of the second fan <NUM> operates at the rotation speed N.

Therefore, the rotation speed N of the fan motor 31b, the wind speed V or volume of air Q of the second fan <NUM>, and the front-rear differential pressure ΔP are parameters having a relation in which, from the two values of them, the remaining one value is derived.

A calculus equation for calculating a rotation speed target value Ny can be derived from the above equation (<NUM>) and a theoretical formula of the fan. The relation among current front-rear differential pressure ΔPx, a current volume of air Qx, a front-rear differential pressure target value ΔPy, and an air volume target value Qy is expressed by an equation below from the theoretical formula of the fan.

From the above equations (<NUM>) and (<NUM>), the following equation holds.

Furthermore, since Vy = (Qy/Qx) × Vx, the following equation holds.

Hereinafter, the equation (<NUM>) is referred to as a first function.

Technical significance of the first function will be described with reference to <FIG> is a graph indicating a relation between the volume of air and the rotation speed of the fan motor 31b using the front-rear differential pressure ΔP as a parameter. In <FIG>, the change in duct resistance appears as a change in front-rear differential pressure ΔP.

For example, the rotation speed of the fan motor 31b for maintaining the volume of air <NUM> (m<NUM>/min) at the front-rear differential pressure <NUM> (Pa) is <NUM> (r/m). If the duct resistance is constant irrespective of the volume of air, when the volume of air is changed to <NUM> (m<NUM>/min), the rotation speed may be simply set to <NUM> (r/m).

However, the duct resistance changes by changing the volume of air. According to <FIG>, by changing the volume of air to <NUM> (m<NUM>/min), the front-rear differential pressure increases to <NUM> (Pa) due to the change in duct resistance. In order to maintain the volume of air <NUM> (m<NUM>/min) when the front-rear differential pressure is <NUM> (Pa), it is necessary to maintain the rotation speed of the fan motor 31b at <NUM> (r/m).

Therefore, the air volume adjustment function considering the change in duct resistance is required, and the rotation speed Ny in the first function (the above equation (<NUM>)) is the rotation speed considering the change in duct resistance.

When the air volume target value Qy, which is an instruction value of the volume of air from the first controller <NUM>, is changed, the second controller <NUM> calculates the rotation speed target value for the fan motor <NUM>1b of the second fan <NUM> by using the first function.

If the front-rear differential pressure ΔP does not fluctuate even after the rotation speed of the fan motor 31b reaches the rotation speed target value, the rotation speed is maintained. However, when the volume of air of the other second unit <NUM> or the air discharge pressure of the first unit <NUM> is changed, the front-rear differential pressure ΔP fluctuates.

<FIG> is a graph indicating a relation between the wind speed and the rotation speed of the fan motor 31b. In <FIG>, for example, the rotation speed of the fan motor 31b necessary to maintain the wind speed target value Vy at the front-rear differential pressure <NUM> (Pa) is <NUM> (r/m).

Here, when the front-rear differential pressure ΔP is increased to the dotted line in <FIG>, simply maintaining the rotation speed of the fan motor 31b at <NUM> (r/m) leads to a decrease in the wind speed to Vx, so that the volume of air becomes insufficient.

In order to maintain the air volume target value, it is necessary to return the wind speed from Vx to Vy, and it is necessary to increase the rotation speed of the fan motor 31b by <NUM> r/m to <NUM> (r/m).

The rotation speed change amount ΔN of the fan motor 31b is expressed by the following equation from the equations (<NUM>) and (<NUM>).

Hereinafter, the equation (<NUM>) is referred to as a second function.

The second function is used when calculating the rotation speed change amount when the air volume target value Qy is not changed but the rotation speed of the fan motor 31b needs to be changed due to the fluctuation of the front-rear differential pressure ΔP.

<FIG> is a flowchart of air volume control. The air volume control will be described below with reference to <FIG>.

First, in step S1, the second controller <NUM> determines whether or not the air volume target value Qy is received from the first controller <NUM>. When the second controller <NUM> receives the air volume target value Qy, the process proceeds to step S2. When the second controller <NUM> does not receive the air volume target value Qy, the process proceeds to step S6.

Next, in step S2, the second controller <NUM> calculates the wind speed target value Vy for achieving the air volume target value Qy.

Next, in step S3, the second controller <NUM> updates the wind speed target value Vy to the value calculated in step S2.

Next, in step S4, the second controller <NUM> calculates the rotation speed target value Ny for the fan motor 31b for achieving the wind speed target value Vy updated in step S3 using the first function.

Next, in step S5, the second controller <NUM> updates the rotation speed target value for the fan motor 31b to the value Ny calculated in step S4. After updating the rotation speed target value to Ny, the second controller <NUM> controls the rotation speed of the fan motor <NUM>1b to reach the target value.

Next, in step S6, the second controller <NUM> acquires a detected value of the second air volume detector <NUM> as a current wind speed Vx.

Next, in step S7, the second controller <NUM> calculates the difference between the wind speed target value Vy and the current wind speed Vx.

Next, in step S8, the second controller <NUM> calculates the front-rear differential pressure ΔP.

Next, in step S9, the second controller <NUM> calculates a coefficient a as a control parameter.

Next, in step S10, the second controller <NUM> calculates the rotation speed change amount ΔN by applying the difference between the wind speed target value Vy and the current wind speed Vx calculated in step S7 and the coefficient a calculated in step S9 to the second function.

Next, in step S11, the second controller <NUM> calculates the rotation speed target value Ny on the basis of the rotation speed change amount ΔN calculated in step S10.

Next, in step S12, the second controller <NUM> updates the rotation speed to the rotation speed target value Ny calculated in step S11. Then, the process by the second controller <NUM> returns to step S1.

As described above, when there is an instruction of the air volume target value from the first controller <NUM>, a first program from step S1 to step S5 is executed, but when there is no instruction of the air volume target value from the first controller <NUM>, a second program from step S6 to step S12 is executed.

The first program is for calculating the rotation speed target value by using the first function, and the second program is for calculating the rotation speed change amount by using the second function.

Furthermore, the rotation speed target value Ny can also be calculated by using the second function, and the second controller <NUM> can switch between the first program and the second program. Therefore, even when the second unit <NUM> acquires a new air volume target value Qy or a new wind speed target value Vy, the second unit <NUM> can control the rotation speed while calculating the rotation speed change amount ΔN by using the second function without using the first function.

<FIG> is a graph showing a relation between the volume of air Q and the front-rear differential pressure ΔP using the rotation speed N of the fan motor 31b of the second fan <NUM> as a parameter. In <FIG>, the horizontal axis represents the volume of air Q, and the vertical axis represents the front-rear differential pressure ΔP.

As understood from <FIG>, in the second unit <NUM>, when the volume of air Q changes in a state where the rotation speed N of the fan motor 31b of the second fan <NUM> is maintained constant, the front-rear differential pressure ΔP has one extreme value at which the front-rear differential pressure ΔP changes from rising to falling. Hereinafter, a point indicating the extreme value is referred to as an extreme value point.

The volume of air at the extreme value point countervails the resistance of the duct <NUM> connected to the second unit <NUM>. Accordingly, the resistance of the duct <NUM> decreases when the volume of air decreases from the extreme value point. Therefore, this time, the volume of air is increased and takes a value on the right side of the extreme value point. As a result, the resistance of the duct <NUM> increases and pushes the air back. A state where the behavior of the air is repeated in such a manner is referred to as surging.

The surging causes a periodic pressure fluctuation, which causes sound and vibration that adversely affect the equipment. Usually, the fan is used while avoiding such a volume of air and the vicinity of the volume of air. However, in the air treatment system <NUM> according to the embodiment, the front-rear differential pressure of one second unit <NUM> fluctuates due to an increase or decrease in discharge pressure of the first unit <NUM> and volume of air of the other second unit <NUM>. Accordingly, the front-rear differential pressure may unintentionally reach the extreme value illustrated in <FIG>.

<FIG> is a graph illustrating a curve passing through extreme value points of the respective rotation speeds illustrated in <FIG>. In <FIG>, surging occurs when the volume of air takes a value on the left side of the extreme value points. Therefore, surging does not occur when the combination of the volume of air and the front-rear differential pressure falls outside the region (hereinafter, referred to as surging occurrence region) surrounded by the vertical axis and the curve in <FIG>. The curve in <FIG> is expressed by the following equation. <MAT> "r" and "s" can be determined by experimental data.

Therefore, f(Qx) calculated by substituting the current volume of air Qx into the above equation (<NUM>) corresponds to the front-rear differential pressure that can cause surging when the volume of air is Qx.

If the current front-rear differential pressure ΔPx is within a surging occurrence region, ΔPx - f(Qx) ≥ <NUM>. On the other hand, if the current front-rear differential pressure ΔPx is outside the surging occurrence region, ΔPx - f(Qx) < <NUM>.

For example, when receiving an instruction signal of the air volume target value Qy from the first controller <NUM>, the second controller <NUM> calculates a front-rear differential pressure target value ΔPy by substituting the air volume target value Qy and the current front-rear differential pressure ΔPx and volume of air Qx into the equation (<NUM>): ΔPy/ΔPx = (Qy/Qx)<NUM>. Furthermore, the second controller <NUM> calculates f(Qy) by substituting the air volume target value Qy into the above equation (<NUM>).

If the front-rear differential pressure target value ΔPy is within the surging occurrence region, ΔPy - f(Qy) ≥ <NUM>. On the other hand, if the front-rear differential pressure target value ΔPy is outside the surging occurrence region, ΔPy - f(Qy) < <NUM>.

Therefore, whether or not the air volume target value Qy causes surging can be determined by whether or not ΔPy - f(Qy) ≥ <NUM>.

<FIG> is a flowchart of surging determination control in which the second controller <NUM> determines occurrence of surging and eliminates the surging. In <FIG>, the second controller <NUM> performs control processing from step S21 to step S28 in parallel with control processing from step S1 to step S12 in <FIG>.

In step S21, the second controller <NUM> acquires the current rotation speed Nx of the fan motor 31b.

Next, in step S22, the second controller <NUM> acquires a detected value of the second air volume detector <NUM> as the current wind speed Vx.

Next, in step S23, the second controller <NUM> calculates the current volume of air Qx. The volume of air Qx can be calculated from the wind speed Vx.

Next, in step S24, the second controller <NUM> calculates the current front-rear differential pressure ΔPx. The front-rear differential pressure ΔPx can be calculated by substituting the current rotation speed Nx and wind speed Vx into the equation (<NUM>).

Next, in step S25, the second controller <NUM> calculates f(Qx). "f(Qx)" can be calculated by substituting the volume of air Qx into the equation (<NUM>).

Next, in step S26, the second controller <NUM> determines whether or not ΔPx - f(Qx) ≥ <NUM>. When the second controller <NUM> determines that ΔPx - f(Qx) ≥ <NUM>, the process proceeds to step S27.

Here, the determination that "ΔPx - f(Qx) ≥ <NUM>" is the same as the confirmation of occurrence of surging.

On the other hand, when the second controller <NUM> determines that ΔPx - f(Qx) < <NUM>, the process returns to step S21 to continue the determination of the presence or absence of the occurrence of surging.

Next, in step S27, the second controller <NUM> increases the rotation speed of the fan motor 31b to C × Nx obtained by multiplying the current rotation speed Nx by a predetermined ratio C. The ratio C has an initial set value of <NUM>, but the setting can be changed on the user side.

Here, since it is determined that ΔPx - f(Qx) ≥ <NUM> and the occurrence of surging is confirmed in the preceding step S26, the second controller <NUM> gradually increases the rotation speed of the fan motor 31b to eliminate the surging.

Next, in step S28, the second controller <NUM> waits for a predetermined time, and the process returns to step S21. The purpose of waiting for a predetermined time is to secure a response time from when the rotation speed of the fan motor 31b is increased to when the wind speed changes. The initial set value of the predetermined time is one second, but the setting can be changed on the user side.

As described above, the second controller <NUM> repeats the routine from step S21 to step S28 described in <FIG> while the air treatment system <NUM> is operating. In this manner, the second controller <NUM> monitors whether or not ΔPx - f(Qx) ≥ <NUM>, and when ΔPx - f(Qx) ≥ <NUM>, determines that surging occurs, and increases the rotation speed of the fan motor 31b.

An advantage of the surging determination control is that the surging can be eliminated by the second controller <NUM> alone.

Furthermore, since the rotation speed of the fan motor 31b is gradually increased, it is possible to avoid a situation in which too much margin is taken for the rotation speed just in order to eliminate the surging.

In the control described in <FIG>, after confirming the occurrence of surging, the second controller <NUM> alone eliminates the surging. However, in a following modification, the second controller <NUM> eliminates the surging in cooperation with the first controller <NUM>.

<FIG> is a flowchart of surging determination control according to the modification. <FIG> differs from <FIG> in that steps S27 and S28 are replaced with steps 27x to S32x.

The second controller <NUM> performs control processing from step S21 to step S32x in <FIG> in parallel with the control processing from step S1 to step S12 in <FIG>.

Since steps S21 to S26 have already been described, step 27x and subsequent steps will be described here.

In step S27x, the second controller <NUM> notifies the first controller <NUM> that ΔPx - f(Qx) ≥ <NUM>. Specifically, the second controller <NUM> transmits a signal Sig1 set in advance and indicating that "ΔPx - f(Qx) ≥ <NUM>" to the first controller <NUM>.

Next, when receiving the signal from the second controller <NUM>, the first controller <NUM> determines that surging occurs or there is a possibility that surging may occur, and sets a new air volume target value Qy and instructs the second controller <NUM> in order to eliminate the surging.

When the first controller <NUM> sets a new air volume target value Qy, the first controller <NUM> may set the air volume target value Qy in consideration of the volume of air of the other fan unit and a total volume of air required for the target space <NUM>, which is an air treatment target.

In step S29x, the second controller <NUM> determines whether or not the air volume target value Qy is received from the first controller <NUM>. When the second controller <NUM> receives the air volume target value Qy, the process proceeds to step S30x.

Next, in step S30x, the second controller <NUM> calculates the front-rear differential pressure target value ΔPy. The front-rear differential pressure target value ΔPy can be calculated by substituting the air volume target value Qy and the current front-rear differential pressure ΔPx and volume of air Qx into the equation (<NUM>).

Next, in step S31x, the second controller <NUM> calculates f(Qy). "f(Qy)" can be calculated by substituting the air volume target value Qy into the equation (<NUM>).

Next, in step S32x, the second controller <NUM> determines whether or not ΔPy - f(Qy) ≥ <NUM>.

When determining that ΔPy - f(Qy) ≥ <NUM>, the second controller <NUM> determines that the surging cannot be eliminated, and the process returns to step S27x to notify the first controller <NUM> that ΔPy - f(Qy) ≥ <NUM>.

Specifically, the second controller <NUM> transmits a signal Sig2 set in advance and indicating that "ΔPy - f(Qy) ≥ <NUM>" to the first controller <NUM>. Here, the determination that "ΔPy - f(Qy) ≥ <NUM>" is the same as the possibility of occurrence of surging.

On the other hand, when the second controller <NUM> determines that ΔPy - f(Qy) < <NUM>, the process returns to step S21 to continue the determination of the presence or absence of the occurrence of surging.

When the air volume target value Qy is reset and transmitted to the second controller <NUM>, control processing from step S1 to step S12 in <FIG> is performed.

Thereafter, the second controller <NUM> repeats the routine from step S21 to step S32x described in <FIG> to monitor the presence or absence of the occurrence of surging.

(<NUM>-<NUM>)
Whether or not surging occurs depends on the front-rear differential pressure. Therefore, by determining occurrence or non-occurrence of surging on the basis of the front-rear differential pressure, the second unit <NUM> can detect and avoid surging with higher accuracy than when determining by using the pressure on the outlet side of the second fan <NUM>.

(<NUM>-<NUM>)
The second controller <NUM> determines occurrence or non-occurrence of surging by a simple means of comparing the current front-rear differential pressure ΔPx with an allowable upper limit value of the front-rear differential pressure at the current rotation speed Nx. Therefore, the second unit <NUM> does not need to be newly provided with a dedicated sensor.

(<NUM>-<NUM>)
In the second unit <NUM>, a relational expression: f(Q) = r × Q<NUM> + s × Q can be obtained only by measuring at least three extreme values on curves expressing a relation between the volume of air of the second fan and the front-rear differential pressure that are measured for each rotation speed of the second fan <NUM>, making it easy to adapt to each model.

(<NUM>-<NUM>)
In the second unit <NUM>, when determining that surging by the second fan <NUM> occurs, the second controller <NUM> increases the rotation speed of the second fan <NUM>. Since the second unit can alone increase the rotation speed, it is easy to avoid surging.

(<NUM>-<NUM>)
Even if surging is avoided by, for example, increasing the rotation speed by using one second unit <NUM> alone, there is a possibility that the other fan unit connected through the duct <NUM> causes surging due to a change in front-rear differential pressure in the other fan unit. Furthermore, the air volume target value Qy cannot be set irrespective of the total volume of air required for the target space <NUM>, which is an air treatment target. Therefore, in the air treatment system <NUM>, the first controller <NUM> determines the air volume target value Qy for the second unit <NUM> for avoiding surging in consideration of the total volume of air required for the target space <NUM>, which is an air treatment target. As a result, the reliability of surging elimination is high.

The first unit <NUM> includes the first fan <NUM> in the above embodiment, but the first unit <NUM> does not necessarily need the first fan <NUM>. The air volume control according to the present disclosure is also applicable to a second unit connected to a first unit not including a fan through a duct.

Specific examples will be described below.

(<NUM>-<NUM>)
<FIG> is a configuration diagram of an air treatment system <NUM> equipped with fan units according to another embodiment. The air treatment system <NUM> in <FIG> is disposed behind a ceiling of a floor of a building BL, and ventilates a room. The air treatment system <NUM> includes a first unit <NUM> as an air treatment unit, second units <NUM> as air supply fan units, and third units <NUM> as air exhaust fan units.

The air treatment system <NUM> further includes an outdoor air duct <NUM>, a supply air duct <NUM>, a return air duct <NUM>, and an exhaust air duct <NUM>. The outdoor air duct <NUM>, the supply air duct <NUM>, the return air duct <NUM>, and the exhaust air duct <NUM> are connected to the first unit <NUM>.

The outdoor air duct <NUM> constitutes an air flow path leading from an opening <NUM> leading to the outside of the building BL to the first unit <NUM>. The supply air duct <NUM> constitutes an air flow path leading from the first unit <NUM> to blow-out ports <NUM> provided in the room.

The return air duct <NUM> constitutes an air flow path leading from intake ports <NUM> provided in the room to the first unit <NUM>. The exhaust air duct <NUM> constitutes an air flow path leading from the first unit <NUM> to an opening <NUM> leading to the outside of the building BL.

The supply air duct <NUM> includes a single main duct <NUM> and a plurality of branch ducts <NUM> branched off the main duct <NUM> via a branch chamber <NUM>.

The return air duct <NUM> includes a single main duct <NUM> and a plurality of branch ducts <NUM> branched off the main duct <NUM> via a branch chamber <NUM>.

The first unit <NUM> removes dust in air passing through the unit, changes temperature of the air, changes humidity of the air, and removes predetermined chemical composition and a predetermined pathogen in the air.

The second units <NUM> are connected to the supply air duct <NUM>. The third units <NUM> are connected to the corresponding return air duct <NUM>.

In the air treatment system <NUM>, the first unit <NUM> does not include any fan, so that the second units <NUM> and the third units <NUM> generate a flow of air in the first unit <NUM>.

Therefore, a change in front-rear differential pressure of one second unit <NUM> is mainly caused by changes in volume of air of fans of other second units <NUM>. Furthermore, a change in front-rear differential pressure of one third unit <NUM> is mainly caused by a change in volume of air of a fan of the other third unit <NUM>.

In the air treatment system <NUM>, the "front-rear differential pressure" is introduced as a variable of the calculation formula for the rotation speed target value similarly to the above embodiment. Accordingly, it is possible to reflect the change in duct resistance that changes from moment to moment in the calculation of the air volume target value, and to shorten the response time of the output value (volume of air) to the input value (rotation speed).

Furthermore, in the air treatment system <NUM>, whether or not surging occurs depends on the front-rear differential pressure. A second controller <NUM> in the second unit <NUM> or a third controller <NUM> in the third unit <NUM> determines occurrence or non-occurrence of surging by a simple means of comparing the current front-rear differential pressure with the allowable upper limit value of the front-rear differential pressure at the current rotation speed. Therefore, the air treatment system <NUM> does not need to be newly provided with a dedicated sensor just to detect the occurrence of surging.

(<NUM>-<NUM>)
<FIG> is a configuration diagram of an air treatment system <NUM> equipped with fan units according to still another embodiment. The air treatment system <NUM> in <FIG> is disposed behind a ceiling of a floor of a building.

The air treatment system <NUM> differs from the air treatment system <NUM> in <FIG> in that the first unit does not include a first fan, and other configurations are the same as those of the air treatment system <NUM> in <FIG>. Therefore, components same as those of the air treatment system <NUM> in <FIG> will be denoted by the same reference signs and description thereof is omitted.

A utilization-side heat exchanger <NUM> of a first unit <NUM> is supplied with heat energy required for heat exchange from the heat source unit <NUM>. The first unit <NUM> generates conditioned air through heat exchange in the utilization-side heat exchanger <NUM>.

The first unit <NUM> is connected to the duct <NUM>. The duct <NUM> includes the main pipe <NUM> and the branch pipes <NUM>. The main pipe <NUM> has one end connected to the first unit <NUM>. The main pipe <NUM> has the other end branched and connected to a plurality of branch pipes <NUM>. Each branch pipe <NUM> has a terminal end connected to one second unit <NUM>.

Each second unit <NUM> includes a second fan <NUM>. The second fan <NUM> rotates to suck the conditioned air generated in the first unit <NUM> into the second unit <NUM> through the duct <NUM>, and then supplies the conditioned air to the target space <NUM>.

A fan motor 31a of each second fan <NUM> is configured to change the rotation speed individually. Each fan motor 31a changes the rotation speed individually to change the supply air volume of the corresponding second unit <NUM> individually.

In the air treatment system <NUM>, the first unit <NUM> does not include any fan, so that the second units <NUM> generate a flow of air in the first unit <NUM>.

Therefore, the change in front-rear differential pressure of one second unit <NUM> is mainly caused by a change in volume of air of the second fan <NUM> of the other second unit <NUM>. However, since the "front-rear differential pressure" is introduced as a variable of the calculation formula for the rotation speed target value, it is possible to reflect the change in duct resistance that changes from moment to moment in the calculation of the air volume target value, and to shorten the response time of the output value (volume of air) to the input value (rotation speed).

Furthermore, in the air treatment system <NUM>, whether or not surging occurs depends on the front-rear differential pressure. The second controller <NUM> in the second unit <NUM> determines occurrence or non-occurrence of surging by a simple means of comparing the current front-rear differential pressure with the allowable upper limit value of the front-rear differential pressure at the current rotation speed. Therefore, the air treatment system <NUM> does not need to be newly provided with a dedicated sensor just to detect the occurrence of surging.

(<NUM>-<NUM>)
In the above embodiment and modifications, the front-rear differential pressure is calculated on the basis of the wind speed or the volume of air acquired from the second air volume detector <NUM>. However, the front-rear differential pressure value may be calculated from sensor values of pressure sensors respectively disposed at the intake port and the blow-out port of the second unit, and the wind speed value may be obtained from the front-rear differential pressure and the rotation speed.

(<NUM>-<NUM>)
In <FIG>, changes in wind speed of a fan when the rotation speed of a fan motor is changed are observed at five front-rear differential pressures. This is utilized as data for deriving a relational expression of the rotation speed, the wind speed, and the front-rear differential pressure, but does not necessarily require data for five front-rear differential pressures, and the relational expression can be derived if there is data for at least three front-rear differential pressures.

Claim 1:
A fan unit (<NUM>) connectable to a predetermined unit through a duct, the fan unit (<NUM>) comprising:
a fan (<NUM>) with a variable rotation speed;
a casing (<NUM>) that has an intake port and a blow-out port and houses the fan;
a first acquisition unit that acquires front-rear differential pressure (ΔPx) that is a difference in air pressure between the intake port and the blow-out port of the casing (<NUM>);
a second acquisition unit (<NUM>) that acquires a volume of air (Qx) or a wind speed (Vx) of the fan (<NUM>); and
a control unit (<NUM>);
is characterized in that
the control unit (<NUM>) is configured to store in advance a first relational expression that derives an allowable upper limit value of the front-rear differential pressure with respect to the volume of air of the fan (<NUM>), and
the control unit (<NUM>) is further configured to determine whether or not surging by the fan (<NUM>) occurs by comparing the allowable upper limit value of the front-rear differential pressure calculated on the basis of the volume of air (Qx) acquired by the second acquisition unit (<NUM>) and the first relational expression with the front-rear differential pressure (ΔPx) acquired by the first acquisition unit.