JPH11237091A - Multi-room split type air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-room split type air conditioner for operating with a high efficiency and a high power factor by suitably switching a PWM type and a PAM type. SOLUTION: A PWM type control for controlling an output frequency F of an inverter 51 according to a change of a duty ratio of an output voltage of the inverter 51 by confirming the duty ratio of the inverter 51 and fixing the output voltage of the inverter 15 to a set value until the ratio becomes a maximum (100%) is executed. After the ratio becomes the maximum, a PAM type control for controlling the frequency F of the inverter 51 according to the change of a level of the output voltage of the inverter 51 to the set value or more is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-room air conditioner having an inverter for outputting drive power to a compressor and controlling the output frequency of the inverter in accordance with the required capacity of a plurality of air-conditioned rooms.

[0002]

2. Description of the Related Art In a multi-room air conditioner provided with a compressor and an inverter for supplying drive power to the compressor, the air conditioning load in each room is detected, and the operation of the compressor is performed in accordance with the sum of these air conditioning loads. The frequency, that is, the output frequency of the inverter, is determined.

As a means for controlling the operation frequency, a PWM method for controlling the operation frequency by changing the duty ratio of the output voltage of the inverter is well known.

[0004] In recent years, in compressors equipped with a DC motor,
For the purpose of improving the efficiency, a driving method in which the PWM method is combined with the PAM method has been adopted. PAM
The method is a method of controlling the operation frequency by changing the level of the output voltage of the inverter.

[0005] For example, as shown in FIG. 5, when the operating frequency F is lower than the set value Fa, the control of the PWM system is executed.
In the case of “a” or more, the control of the PAM system is executed.

[0006]

As described above, switching between the PWM system and the PAM system in accordance with the required value of the operating frequency F requires a switch to the PAM system depending on the environment such as temperature conditions and installation conditions. Switching may occur too early or too late, causing a problem that the efficiency and the power factor deteriorate.

[0007] In a multi-room air conditioner, the operating frequency fluctuates relatively frequently due to the air-conditioning load fluctuation in each room. Under such circumstances, the switching between the PWM system and the PAM system becomes frequent, and the above-mentioned problems are more and more caused.

[0008] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide an excellent multi-room air conditioner capable of appropriately switching between a PWM system and a PAM system and performing high-efficiency, high-power-factor operation.

[0009]

Means for Solving the Problems First Invention (Claim 1)
The multi-room air conditioner comprises: first control means for fixing the output voltage of the inverter to a set value and controlling the output frequency of the inverter by changing the duty ratio of the output voltage; A second control means for controlling the output frequency of the inverter by a level change equal to or more than a value, and a control of the first control means until the duty ratio of the output voltage of the inverter by the first control means is maximized. After the duty ratio becomes maximum, the second
And third control means for executing control of the control means.

[0010] A multi-room air conditioner according to a second aspect of the present invention is characterized in that the output voltage of the inverter is fixed at a set value and the output frequency of the inverter is controlled by changing the duty ratio of the output voltage. Control means; second control means for controlling the output frequency of the inverter by a level change of the output voltage of the inverter equal to or greater than the set value; and control of the first control means until the input current to the inverter reaches a predetermined value. And a third control means for executing the control of the second control means after the input current reaches a predetermined value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, A is an outdoor unit, and B1,
B2 and B3 are indoor units, and these units constitute the next refrigeration cycle.

An outdoor heat exchanger 3 is connected to a discharge port of the compressor 1 through a four-way valve 2, and the outdoor heat exchanger 3 is connected to a liquid side pipe W.
Is connected. The liquid side pipe W is branched into liquid side pipes W1, W2, W3, and the liquid side pipes are connected to the indoor heat exchangers 12, 22, 32, respectively.
Is connected.

The liquid-side branch pipes W1, W2 and W3 are provided with electric expansion valves 11, 21 and 31 as flow control valves. These electric expansion valves are pulse motor valves (PMV) whose opening changes in accordance with the number of supplied drive pulses.

Gas side pipes G1, G2, and G3 are connected to the indoor heat exchangers 12, 22, and 32, and the gas side branch pipes G1, G
Refrigerant temperature sensors 16, 25, 35 are attached to 2, G3. Each gas side pipe is connected to a gas side pipe G, and the gas side pipe G is connected to a suction port of the compressor 1 via the four-way valve 2.

An outdoor fan 4 is provided near the outdoor heat exchanger 3, and a heat exchanger temperature sensor 5 is attached to the outdoor heat exchanger 3. Indoor fans 13, 23, and 33 are provided near the indoor heat exchangers 12, 22, and 32, respectively.
2, 22, 32, heat exchanger temperature sensors 14, 24, 34
Are attached respectively.

FIG. 1 shows a control circuit.

The outdoor control unit 50 of the outdoor unit A is connected to the commercial AC power supply 40. The outdoor control unit 50 includes a four-way valve 2, an outdoor fan motor 4M, a heat exchanger temperature sensor 5, electric expansion valves 11, 21, 31, and a refrigerant temperature sensor 1.
6, 26, 36, inverter circuit 51, current sensor 52
Is connected.

The inverter circuit 51 rectifies the voltage of the power supply 40, converts the rectified voltage into a voltage having a frequency corresponding to a command from the outdoor control unit 50, and outputs the voltage. This output is the compressor motor 1M
Is supplied as driving power. The current sensor is attached to a connection line between the power supply 40 and the inverter circuit 51.

Each of the indoor units B1, B2 and B3 has an indoor control unit 60. The indoor controller 60 includes an indoor temperature sensor 15 (25, 35), a heat exchanger temperature sensor 1
4 (24, 34), indoor fan motor 13M (23M,
32M), and a remote control device (hereinafter, simply referred to as a remote controller) 61 is connected.

The indoor control unit 60 and the outdoor control unit 5
0 are connected by a power supply line ACL and a data transfer serial signal line SL, respectively.

Each of the indoor control units 60 has the following main functions [1] to [3].

[1] Operating conditions (including set temperature Ts) by operation of remote controller 61, heat exchanger temperature sensors 14 and 2
Means for informing the outdoor unit A of the detected temperatures 4 and 34 by a serial signal synchronized with the power supply voltage.

[2] Set temperature Ts set by remote controller 61 and detected temperature T of indoor temperature sensor 15 (25, 35)
a means for detecting a difference ΔT from T.a (= Ts−Ta) as an air conditioning load and informing the outdoor unit A of a required capacity (required output frequency value) corresponding to the air conditioning load ΔT by a serial signal.

[3] Heat exchanger temperature sensor 14 (24, 3
4) Means for notifying the outdoor unit A of the detected temperature Ti by a serial signal.

The outdoor controller 50 has the following [1] to [7] as main functional means.

[1] Based on the cooling operation mode command from each indoor unit, the refrigerant discharged from the compressor 1 is supplied to the four-way valve 2, the outdoor heat exchanger 3, the electric expansion valves 11, 21, 31, and the indoor heat exchanger. 12, 22, 32, means for returning to the compressor 1 through the four-way valve 2 and performing a cooling operation.

[2] The four-way valve 2 is switched based on a heating operation mode command from each indoor unit, and the refrigerant discharged from the compressor 1 is supplied to the four-way valve 2 and the indoor heat exchangers 12, 22, 3
2. Means for returning to the compressor 1 through the electric expansion valves 11, 21, 31, the outdoor heat exchanger 3, and the four-way valve 2, and performing a heating operation.

[3] During the cooling operation, the refrigerant temperature sensor 16
26, 36 and the detected temperatures Ti of the heat exchanger temperature sensors 14, 24, 34 notified from the indoor unit.
Difference (= Tg-Ti) from the indoor heat exchanger (evaporator) 1
Superheat degree detecting means for detecting the degree of superheat SH (superheat amount) of the refrigerant at 2, 22, and 32, respectively.

[4] Electric expansion valves 11 and 12 so that each superheat degree SH detected by the superheat degree detection means becomes a set value SHs.
Means for controlling the opening degrees Q of the first and the 31st, respectively.

[5] A first PWM type control in which the output voltage of the inverter circuit 51 is fixed at a set value which is an optimum value, and the output frequency F of the inverter circuit 51 is controlled by changing the duty ratio of the output voltage. means.

[6] Second control means of the PAM system for controlling the output frequency F of the inverter circuit 51 by a level change of the output voltage of the inverter circuit 51 above the set value.

[7] The control of the first control means is executed until the duty ratio of the output voltage of the inverter circuit 51 by the first control means reaches the maximum (100%). (2) Third control for executing the control of the control means
Control means.

Next, the operation of the above configuration will be described with reference to the flowchart of FIG.

The output frequency (hereinafter referred to as the operating frequency) F of the inverter circuit 51 is calculated and obtained according to the required capacity in each room, and the inverter circuit 51 is driven to obtain the operating frequency F.

In consideration of this driving, the duty ratio of the output voltage of the inverter circuit 51 is checked, and the output voltage of the inverter circuit 51 is fixed at a set value until the duty ratio reaches the maximum (100%). The control of the PWM method for controlling the output frequency F of the inverter circuit 51 by the change of the duty ratio of the voltage is executed.

After the duty ratio becomes maximum, the output voltage F of the inverter circuit 51 is controlled by the level change of the output voltage of the inverter circuit 51 above the set value.
The control of the AM system is executed.

As described above, by setting the output voltage of the inverter circuit 51 to the set value which is the optimum value,
Switching between the PWM system and the PAM system is possible at the point where the efficiency and the power factor are the best.

Since the duty ratio is essentially indispensable for the control of the PWM system, it is not necessary to provide a special sensor, and an increase in cost can be avoided.

In the above embodiment, the switching between the PWM system and the PAM system is performed based on the duty ratio. However, attention is paid to the fact that there is a current sensor 52 used for overcurrent protection and the like. Until the detection current (input current to the inverter circuit 51) I reaches the predetermined value Ia, P
The control of the WM method may be executed, and the control of the PAM method may be executed after the detection current I reaches the predetermined value Ia.

Also in this case, since the current sensor 52 is a component originally provided, an increase in cost can be avoided.

In the above embodiment, the indoor unit has three
Although the case of a single unit has been described as an example, the present invention can be similarly implemented when the number of indoor units is two or four or more.

[0043]

As described above, according to the present invention, the first control means for fixing the output voltage of the inverter to the set value and controlling the output frequency of the inverter by changing the duty ratio of the output voltage, A second control means for controlling the output frequency of the inverter by a level change of the output voltage of the inverter not less than the set value, and a control of the first control means until the duty ratio of the output voltage of the inverter by the first control means becomes maximum. And the third control means for executing the control of the second control means after the duty ratio is maximized. Therefore, it is possible to appropriately switch between the PWM method and the PAM method to achieve high efficiency and high power factor. An excellent multi-room air conditioner that can be operated can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a refrigeration cycle of the embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a flowchart for explaining the operation of a modification of the embodiment.

FIG. 5 is a flowchart for explaining a conventional driving method.

[Explanation of symbols]

A: outdoor unit, B1, B2, B3: indoor unit,
DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... 4-way valve, 3 ... Outdoor heat exchanger, 11 and 12
1, 31 ... electric expansion valve (flow regulating valve), 12, 22, 3
2: indoor heat exchanger, 14, 24, 34: heat exchanger temperature sensor, 15, 25, 35: indoor temperature sensor, 16, 2
6, 36 ... refrigerant temperature sensor, 50 ... outdoor control unit, 51 ...
Inverter circuit, 52: current sensor, 60: indoor control unit.

Claims (2)

[Claims] 1. A multi-room air conditioner including a plurality of indoor units and an inverter for outputting drive power to a compressor, wherein an output voltage of the inverter is fixed at a set value, and an output voltage of the First control means for controlling the output frequency of the inverter by changing the duty ratio; second control means for controlling the output frequency of the inverter by changing the level of the output voltage of the inverter equal to or higher than the set value; and the first control means A third control unit that executes control of the first control unit until the duty ratio of the output voltage of the inverter becomes maximum, and executes control of the second control unit after the duty ratio becomes maximum. A multi-room air conditioner characterized by comprising: 2. A multi-room air conditioner comprising a plurality of indoor units and an inverter for outputting drive power to a compressor, wherein the output voltage of the inverter is fixed at a set value, and the output voltage of First control means for controlling the output frequency of the inverter by changing the duty ratio; second control means for controlling the output frequency of the inverter by changing the level of the output voltage of the inverter equal to or higher than the set value; input to the inverter And a third control unit that executes control of the first control unit until the current reaches a predetermined value, and executes control of the second control unit after the input current reaches a predetermined value. Features A multi-room air conditioner.