JP2504451B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air conditioner, and in particular, in a duct terminal, for example, a VAV (variable air volume) unit adjusts a required air volume, and a blower rotates according to the required air volume. The present invention relates to an air conditioner that controls the number.

(Prior Art) It is generally known that "surging" occurs in a blower used in an air conditioner. Blower surging means that when the volume of air handled falls below a certain limit, air in the normal flow direction does not fill the flow path between the blades of the impeller, causing a stall condition or backflow of air. It means that the air flow pulsates and becomes unstable. When such surging occurs in the blower, noise and vibration increase, and in extreme cases, the bearing of the impeller or the impeller or the blade itself is damaged.

(Problems to be Solved by the Invention) Conventionally, in particular, an air conditioner using a VAV unit, as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-41842, which is a co-pending application of the present applicant. In the above, there was no effective device for preventing the surging of the blower as described above.

For example, Japanese Patent Application Laid-Open No. 56-56998, which was published on May 19, 1981, discloses that, in surging control of a compressor, a pulsation of a detection parameter such as a gas discharge flow rate at a compressor outlet is detected. , A technique for determining whether or not the compressor is in the surging range is disclosed.

However, this conventional technique cannot be applied to an air conditioner. This is because it is very difficult for the blower used in the air conditioner to accurately detect the pulsation of the parameter.

Therefore, a main object of the present invention is to provide a novel air conditioner that can effectively prevent surging of a blower.

(Means for Solving the Problems) Briefly, the present invention has a blower having a suction port and a discharge port, and a main duct connected to the discharge port of the blower,
A plurality of branch ducts branched from the main duct, and air flow rate adjusting means provided in each of the plurality of branch ducts for adjusting the air flow rate of the branch ducts and controlling the rotation speed of the blower according to the state of the air flow rate adjusting means In an air conditioner equipped with a rotation speed control means for, a surging determining means for comparing the surging air volume of the blower with the actual air volume flowing in the main duct to determine that the blower is in the surging area, and surging of the surging determining means An air conditioner characterized by comprising a rotation speed sudden decrease means for rapidly decreasing the rotation speed of the blower by the rotation speed control means according to the determination.

(Operation) In the surging determination, for example, it is determined whether or not the blower is in the surging region by comparing the actual air volume that can be detected by the wind speed sensor provided in the main duct with the surging air volume of the blower. If it is determined that the surging region is in the surging region, the surging determination signal is given to the rotational speed abrupt decreasing means. The rotation speed rapid decrease means rapidly increases the response speed so that the rotation speed control means can decrease the rotation speed of the blower more rapidly than in the normal control state. Accordingly, in the surging area, the rotation speed of the blower is rapidly decelerated, the actual air volume exceeds the surging air volume, and the blower immediately leaves the surging area.

(Effect of the Invention) According to the present invention, even if no special adding means is used,
With a simple configuration, it is possible to effectively prevent the surging of the blower. Since it is determined whether or not the blower is in the surging range by comparing the surging air volume of the blower with the actual air volume, the surging determination can be made accurately.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. For example, a blower 10 such as a sirocco fan has a suction port and a discharge port. The blower 10 includes an impeller (not shown) driven by a blower motor 12. The blower motor 12 drives its impeller, and the rotation speed of the impeller is controlled by a rotation speed control means such as an inverter 14.

A main duct 16 is connected to the discharge port of the blower 10, and a plurality of branch ducts 18, 18, ...
Is connected. Each of the branch ducts 18, 18, ... Has a damper (not shown) as an air volume adjusting means.
VAV units 20, 20, ... Are provided.

The frequency of the above-mentioned inverter 14 is controlled based on the opening degree of the VAV unit 20 provided in this branch duct 18. That is, the amount of air blown from the blower 10 to the main duct 16 is
It is controlled according to the opening degree of the VAV units 20, 20, ....
This has been disclosed in detail in the above-cited Japanese Patent Laid-Open No. 61-41842, and therefore, the description of the air volume adjustment itself of the blower 10 according to the opening degree of the VAV unit 20 will not be given here. Omit it.

The main duct 16 is provided with a wind speed sensor 22 for detecting the amount of air flowing through the main duct 16. As this wind speed sensor 22, a Karman vortex wind speed sensor as disclosed in Japanese Patent Laid-Open No. 61-41842 may also be used.

The system is further provided with a surging prevention and motor control circuit 24. A signal from the wind speed sensor 22 is given to the surging prevention and motor control circuit 24. The surging prevention and motor control circuit 24 simply puts, based on the frequency of the inverter 14, the amount of air entering the surging region at the rotation speed of the blower 10 at that time (may be simply referred to as “surging air amount” in this specification). ) And the amount of air blown from the blower 10 (actual airflow), the blower 10
Is in the surging region, and if it is in the surging region, the response speed of the rotation speed of the motor 12 by the inverter 14 is changed so that the rotation speed is rapidly reduced.

Referring to FIG. 2, the horizontal axis shows the air volume, and the vertical axis shows the static pressure of the blower. The curve A is a surging line determined by the type of the blower 10, the left side thereof is a surging area, and the right side thereof is an area where no surging occurs. Curve B is the resistance curve of the air flow path, which varies depending on the opening of the VAV units 20, 20, ... (Fig. 1), but the control of each VAV unit 20, 20 ,. In this state, the opening is fixed. A curve C is a characteristic curve at a predetermined rotation speed N ₀ of the blower 10, and a curve D
Indicates a characteristic curve at the rotational speed N. An intersection E between the curve A and the curve C is a surging point at a predetermined rotation speed N ₀ , Q ₀ is a surging air volume at the rotation speed N ₀ , and P is a blower static pressure at that time.

An intersection G between the curve B and the curve C indicates an operating point at a predetermined rotation speed N ₀ when the resistance of the air blowing path is the curve B, the air volume is Q ₁ , and the blower static pressure is P ₁ .

Therefore, the curve A when the number of rotations of the blower 10 becomes N
The intersection F of the curve D and the curve D, that is, the air volume Q ′ of the surging pump and the blower static pressure P ′ at the rotation speed N are given by the equation (1).

Further, the intersection point H between the curve B and the curve D, that is, the rotation speed N
In the case where the resistance of the air blowing path at the point B is the curve B, the air volume Q _{2 at} the operating point and the blower static pressure P ₂ are given by the equation (2).

Equations (1) and (2) are formulas that can be applied to any blower.

Referring to FIG. 3, surging prevention and motor control circuit
24 will be described in detail.

Each damper opening detection circuit 26 is an output shaft of a motor (not shown) or a damper of the VAV unit 20 (FIG. 1).
Includes a first contact 28 which is connected to the shaft of a corresponding damper and is turned on when the opening of the corresponding damper reaches a predetermined amount of less than 100%, for example, 90% or more, and the first contact 28 includes, for example, 20 kΩ. A first resistance component R ₁ having such a resistance value, in this embodiment a fixed resistor, is connected. In addition, the damper opening detection circuit
26 further includes a second contact 30 that is turned on when the opening of the corresponding damper is substantially 100%. And, the series connection of the first contact 28 and the first resistor R ₁ and the second contact
30 is connected in parallel, and each parallel connection is substantially connected in parallel. One end of the plurality of parallel connections is the control unit 32.
Connected to the input terminal of the reception controller 34 included in the above, and connected to a constant DC voltage source (for example, 5 V) via a resistance component having a resistance value of, for example, 5 kΩ, a fixed resistor R ₂ in the embodiment. To be done. Further, the other end of the plurality of parallel connections is connected to a reference voltage such as ground.

The receiving circuit 34 receives the voltage signal from the other end of the plurality of parallel connections described above from its input terminal. Such a voltage signal is
It is given to the level discriminator 36 via the receiving circuit 34. The level discriminator 36 discriminates the level of the voltage supplied from the receiving circuit 34 with a constant hysteresis characteristic. That is, the level discriminator 36 outputs the first signal when the input voltage is equal to or lower than the first predetermined value such as 0.1V, and outputs the second signal when the input voltage is equal to or higher than the second predetermined value such as 4.5V. Output a signal. When the voltage is between 0.1 and 4.5 V, neither the first nor the second signal is output from the level discriminator 36.

More specifically, as described above, when the damper opening is less than 100% and 90% or more, the first contact 28 is closed, so that the voltage of 5V is divided by the resistors R ₂ and R ₁ and received. Given to circuit 34. If there are many dampers that are less than 100% and 90% or more, 5V will be stepped down gradually, resulting in 0.1V overall.
It becomes the following. On the other hand, when the number of VAV units 20 in which the damper opening has become substantially 100% increases, the second contact is closed, so that no voltage drop occurs and the voltage becomes 4.5 V or more as a whole. Therefore, the output of the first signal means that the capacity of the blower is large, and the output of the second signal means that the capacity of the blower is small. To that end, the first signal acts to reduce the capacity of the blower and the second signal acts to increase the capacity of the blower.

The first signal from the level discriminator 36 via the first normally closed contact 38b1 of the relay 38, to the flow loading circuit 40 is given as the signal U _L, the second signal, the second relay 38 Is given as a signal D _L via the normally closed contact 38b2 of.

The floating circuit 40 is for "floating control" of the inverter 14 for driving the blower drive motor 12 (FIG. 1). When one signal _UL is high level, the floating circuit 40
Increase the oscillation frequency of 14. Then, when the other signal D _L is at the high level, the oscillation frequency of the inverter 14 is reduced at a constant speed. When both signals U _L and D _L are at low level, this floating circuit 40
The oscillation frequency of the inverter 14 is maintained as it is.

For example, a DC voltage signal corresponding to the frequency of the inverter 14 from the floating circuit 40 is applied to the Q'calculation circuit 42. The Q'calculation circuit 42 determines the fan rotation speed N at that time.
To obtain the data or the signal. In addition, the Q'calculation circuit 42
Are supplied with data or signals corresponding to the surging air volume Q ₀ at the above-described predetermined rotation speed N ₀ from a constant circuit (not shown). Then, in the Q'calculation circuit 42,
On the surge line, Q '= Q ₀ × (N /
The surging air volume Q ′ is obtained from N ₀ ).

Data or a signal corresponding to the surging air volume Q ′ from the Q ′ calculation circuit 42 is given to the Q / Q ′ calculation circuit 44.

On the other hand, the signal from the wind speed sensor 22 is given to the Q calculation circuit 46, and this Q calculation circuit 46 includes a wind speed sensor reception circuit. Therefore, a voltage signal corresponding to the wind speed is obtained from the wind speed sensor receiving circuit. The wind speed obtained by the wind speed sensor 22 and the air volume have a constant relationship, and therefore the Q calculation circuit 46 outputs table data or a signal of the actual air volume Q according to the relationship. The data or signal representing the actual air flow rate Q is given to the other input of the Q / Q 'calculation circuit 44 described above.

The Q / Q 'calculation circuit 44 performs division (= Q / Q') for determining which of the actual air flow Q and the air flow Q'on the surge line is larger. The result is given to the comparison circuit 48.

In the comparison circuit 48, whether Q / Q 'calculated in the Q / Q' calculation circuit 44 is "1" or less, that is, Q '
Judge whether or not> Q. When a signal is output from the comparison circuit 48, Q '> Q (Q / Q'1)
Therefore, since the blower 10 is in the surging area, a bias signal is given to the above-mentioned relay 38, and
Signal D _H is supplied to floating circuit 40.

The aforementioned signal _UL is given by the floating circuit 40 as a signal for increasing the oscillation frequency of the inverter 14 at a constant response speed, and the signal _DL is the floating circuit.
It is given by 40 as a signal for reducing the oscillation frequency of the inverter 14 at a constant response speed. Then, the above-mentioned signal D _H is given by the floating circuit 40 as a signal for reducing the oscillation frequency of the inverter 14 at a faster response speed.

In operation, relay 38 remains de-energized when no signal is output by comparison circuit 48, ie, when blower 10 is not in the surging region. Therefore, its normally closed contacts 38b1 and 38b2 are both on. Therefore, in that state, the floating circuit 40
Controls inverter 14 in response only to signals U _L and D _L. That is, in this state, the frequency of the inverter 14, that is, the rotation speed of the blower 10 is the line U _L or the line shown in FIG.
VAV unit 2 with a relatively slow response speed according to D _L
It is controlled according to the opening degree of 0. The details of such control are similar to those described in, for example, co-pending application No. 60-134288 of the applicant's application, and here, in order to avoid complication, , The description is omitted.

For example, the VA included in the branch duct 18 in FIG.
Suppose most of the V units 20 are closed at once. Then, the required air volume Q ₁ required for the system is reduced, and the inverter 14 is controlled according to the required air volume Q ₁ to reduce the air flow rate from the blower 10, but this control is relatively gentle. Response speed eg 10
~ 15 minutes. Controlling hunting occurs when the loop is set so that the response can be performed too rapidly, and therefore the response speed is generally set to that level. However, the fully closed state of the VAV unit 20 is achieved within a relatively short time, for example, within 2 minutes, and if no control is performed during that time, surging occurs as described above.

More specifically, when most of the VAV units 20 suddenly become fully closed, the required air volume Q _{1 of the} entire system becomes small, and therefore the actual air volume Q of the main duct 16 from the blower 10 also becomes small. On the other hand, since the frequency of the inverter 14 is not completely controlled yet, the blower 10 is operated at the rotation speed before the fully closed state of the VAV unit 20 which received the closing command. Therefore, in the VAV unit 20 which is not receiving the closing command, the static pressure of the inlet is increased and the damper is squeezed, and the resistance curve temporarily becomes I as shown in FIG. From O ₀ to O, the surging air volume Q ′ at the rotational speed N becomes larger than the actual air volume Q.

In such a state, the division result "Q / Q '" in the Q / Q' operation circuit 44 becomes smaller than "1", and therefore the comparison circuit 48 outputs a signal.

In response to the output from comparator circuit 48, relay 38 is energized, normally closed contacts 38b1 and 38b2 are both turned off, and signal D _H
Are supplied to the floating circuit 40.

In the floating circuit 40, in response to the signal D _H , the fourth
As indicated by the line _DH in the figure, the oscillation frequency of the inverter 14 is sharply reduced. When the oscillation frequency of the inverter 14 suddenly decreases, the rotation speed of the blower motor 12 or the blower 10 decreases.

By such control of the inverter 14, the rotation speed of the blower 10 is drastically reduced, the static pressure at the inlet of the operating VAV unit 20 is also reduced, and the damper is opened.
A low target resistance curve B as shown in FIG. 5 results and the actual air flow Q
Becomes larger than the surging air volume Q ', the operating point shifts from O to O ₁ and exits the surging area as shown in FIG. After that, the rotation speed of the blower 10 is further reduced at the normal response speed, and the actual air volume Q shifts from the operating point O ₁ to the target air volume initially set, that is, the operating point O ₂ shown in FIG. Then, the normal operation state is entered with the rotation speed reduced.

Explaining the above with the passage of time, if a large number of VAV units 20 are suddenly closed at the fifth operating point O ₀ and the operation is started, at this time, the control (response) speed of the blower 10 is still slow. Therefore, for example, the operating point enters the surging area after 4 minutes (point O in FIG. 5). Therefore, when the response speed is rapidly increased in order to escape from the surging area, the operating point shifts to the O ₁ point in FIG. 5 after 5 minutes, and escapes from the surging area. At that time, since the actual air volume becomes larger than the surging air volume, the normal response speed is restored, and the target operating point O ₂ is reached after 6 minutes, for example.

FIG. 6 is a circuit diagram showing a preferred circuit example of the embodiment shown in FIG. Although not shown from the blower rotation speed calculation circuit,
The control command signal to the inverter 14 is output as a voltage according to the blower rotation speed. The voltage representing this rotation speed N is Q ′.
It is given to the arithmetic circuit 42.

The Q'calculation circuit 42 includes an operational amplifier 42a, and has a rotation speed N.
Is applied to the (-) terminal of the operational amplifier 42a. A predetermined voltage determined by the resistors 42b and 42c is applied to the (+) terminal of the operational amplifier 42a. A feedback resistor 42d is connected between the (-) terminal and the output terminal of the operational amplifier 42a. Therefore, this operational amplifier 42a
Is configured as an inverting amplifier as a whole. The resistors 42b to 42d described above act as an input circuit for the constants Q ₀ and N ₀ in FIG. Therefore, the output of the Q'calculation circuit 42, that is, the output of the operational amplifier 42a is output as a signal representing the surging air volume Q'in which the input voltage signal is inverted.

On the other hand, a voltage signal according to the wind speed of the main duct 16 is given from the wind speed sensor receiving circuit that receives the signal from the wind speed sensor 22. This voltage signal is output as a voltage signal representing the actual air volume Q by the converter 46a included in the Q calculation circuit 46. That is, in the Q operation circuit 46, the converter 46
By a, the voltage signal from the wind speed sensor 22 is converted into a voltage signal of the actual air flow Q having a predetermined proportional relationship.

Then, a voltage signal V _Q corresponding to the Q 'surging air quantity Q from the arithmetic circuit 42', the voltage signal V _Q corresponding to the actual air volume Q from Q calculation circuit 46 'and is, Q / Q' the arithmetic circuit 44 It is given to each of the resistors 44a and 44b constituting the resistor. The Q / Q 'arithmetic circuit 44 is configured as an averaging circuit in this embodiment,
Based on the voltage signals V _Q and V _Q , (V _Q + V _Q ′) / 2 = V
Performs _{Q / Q} 'calculation. The voltage V _{Q / Q} ′ from the Q / Q ′ operation circuit 44 is applied to the (−) terminal of the operation amplifier 48 a included in the comparison circuit 48. A constant voltage determined by the resistors 48b and 48c is applied to the (+) terminal of the operational amplifier 48a. That is, the operational amplifier 48a of the comparison circuit 48 determines whether the input voltage VQ _{/ Q} 'is smaller than a constant voltage.

Each of the above-mentioned embodiments is constructed by using a discrete circuit as shown in FIG. 6, for example. However, it goes without saying that the present invention may be controlled by a microcomputer or a program for executing the present invention.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a graph for explaining the resistance curve of the blower path where the surging area of the blower and the VAV unit are stable at each opening, where the horizontal axis is the air volume and the vertical axis is the static pressure of the blower. Shown respectively. FIG. 3 is a block diagram showing an example of a surging prevention and motor control circuit in the embodiment of FIG. FIG. 4 is a graph for explaining the operation of changing the response speed. FIG. 5 is a graph for explaining the escape from the surging area. FIG. 6 is a circuit diagram showing a concrete circuit example of the embodiment shown in FIG. In the figure, 10 is a blower, 14 is an inverter, 16 is a main duct, 18 is a branch duct, 20 is a terminal VAV unit, 22 is a wind speed sensor, and 24 is a surging prevention and motor control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Shinozaki 28, Hiraide Industrial Park, Utsunomiya City Kubota Train Co., Ltd., Tochigi Plant (56) References JP 61-41842 (JP, A) JP 56- 56998 (JP, A)

Claims (4)

(57) [Claims] 1. A blower having a suction port and a discharge port, a main duct connected to the discharge port of the blower, a plurality of branch ducts branched from the main duct, and provided in each of the plurality of branch ducts. In an air conditioner comprising an air volume adjusting means for adjusting the air volume of the branch duct, and a rotation speed control means for controlling the rotation speed of the blower according to the state of the air volume adjusting means, in which the surging air volume of the blower and the A surging determination means for determining that the blower is in a surging range by comparing with the actual air volume flowing in the main duct, and a sudden decrease in the rotation speed of the blower by the rotation speed control means according to the surging judgment of the surging determination means. An air conditioner, characterized in that it comprises means for rapidly reducing the number of revolutions. 2. The surging determining means obtains a surging air volume (Q ') at an actual rotation speed of the blower based on a preset predetermined rotation speed of the blower and a predetermined surging air volume, and the actual air flow rate. Means for obtaining (Q), the surging air volume (Q ') and the actual air volume (Q)
An air conditioner according to claim 1 including means for comparing with. 3. The air volume adjusting means includes a damper provided in each branch duct for adjusting an air volume passing therethrough, and further for increasing the capacity of the blower in relation to the opening of the damper. A control signal output unit that outputs a first signal or a second signal for reducing the capacity of the blower is provided, and the rotation speed control unit rotates the motor of the blower according to the first signal or the second signal. The air conditioner according to claim 1 or 2, further comprising a motor control unit that increases or decreases the speed at a predetermined speed. 4. The rotation speed sudden decrease means provides a third signal for rapidly decreasing the rotation speed of the motor to the motor control means in response to the surging judgment of the surging judgment means. The air conditioner according to the third aspect.