JP4224915B2 - Air conditioner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air conditioner, and more particularly to an air conditioner provided with a current suppressing means for preventing breaker down and protecting the heat of electrical components.
[0002]
[Prior art]
A separate type air conditioner composed of an indoor unit and an outdoor unit is widely used because it can obtain cold air and hot air with relatively simple construction and can be operated individually. This separate type air conditioner includes a refrigerant circuit including a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, and an accumulator. An indoor heat exchanger is arrange | positioned in an indoor unit, and cools or heats by exchanging heat with a refrigerant | coolant and room air. The outdoor heat exchanger is disposed in the outdoor unit and evaporates or condenses the refrigerant by exchanging heat between the refrigerant and the outdoor air. The compressor, the four-way switching valve, and the expansion valve compress / condense refrigerant and perform cooling / heating.
[0003]
When the load of the air conditioner increases due to a sudden change in the room temperature during the operation of the air conditioner, the compressor current flowing through the compressor may become excessive. In such a case, the current flowing into the air conditioner may exceed the breaking current of the breaker, causing the breaker to be down, or an electrical component such as an inverter circuit that drives the compressor may be destroyed by heat generation.
[0004]
Conventionally, in such a case, the current flowing through the compressor is suppressed when the current flowing through the compressor exceeds a predetermined value in order to prevent a breaker down and to prevent damage to electrical components and the like due to heat generation.
[0005]
[Problems to be solved by the invention]
When the compressor current approaches the breaker cutoff current, it is necessary to quickly reduce the compressor current to prevent breaker down. It decreases rapidly and the compressor torque decreases. When the refrigerant is at a high pressure, the load on the compressor increases, and in the worst case, the compressor may stop. Conventionally, regardless of whether the outdoor temperature is low or high, the compressor current is reduced at a fast reduction rate, so the burden on the compressor is large and the life of the compressor may be shortened.
[0006]
An object of the present invention is to reduce the burden on the compressor when suppressing the compressor current in order to prevent breaker down or to protect the electrical components in the air conditioner.
[0007]
[Means for Solving the Problems]
An air conditioner according to a first aspect of the present invention is an air conditioner that adjusts a room temperature by controlling a current flowing through a compressor in a refrigerant circuit, and a current detection unit that detects an input current supplied to the air conditioner; Current suppression means. In the current suppression means, the control current set from the input current, the breaker protection current for preventing the breaker from being lowered and the thermal protection current for protecting the electrical components, and the rate changing current set smaller than the breaker protection current Are compared. When the input current is larger than the control current and the rate change current, the input current is decreased at a predetermined decrease rate. When the input current is larger than the control current and smaller than the rate change current, the input current is reduced at a speed slower than the predetermined reduction speed.
[0008]
The rate change current is a current value serving as a reference for determining whether or not there is a possibility that the breaker may be down. If the compressor current does not exceed the rate change current, there is no possibility of the breaker being down. Therefore, if the compressor current exceeds the control current and exceeds the rate change current, there is a risk of breaker down, and therefore it is necessary to quickly reduce the compressor current at a rapid reduction rate. On the other hand, if the compressor current exceeds the control current but does not exceed the rate change current, the compressor current may be reduced at a slower rate than the above.
[0009]
According to such an air conditioner, when the input current is larger than the control current and smaller than the rate change current, the input current can be lowered at a relatively slow rate, and the burden on the compressor can be reduced. it can.
The air conditioner according to a second aspect of the present invention is the air conditioner according to the first aspect, wherein the current detecting unit detects a compressor current flowing through the compressor. The current suppression means reduces the input current at a predetermined rate when the compressor current is greater than the control current and the rate change current, and reduces the input current when the compressor current is greater than the control current and less than the rate change current. The input current is reduced at a speed slower than a predetermined reduction speed.
[0010]
In this case, the current detection unit does not detect the input current but detects the compressor current. This is because only the compressor current changes significantly depending on the operating condition of the air conditioner in the input current, and other current values flowing through the fan motor and the like may be considered to be substantially constant. Therefore, if only the compressor current is detected and only the compressor current is suppressed, the entire input current can be suppressed.
[0011]
The air conditioner according to a third aspect of the present invention is the air conditioner according to the first or second aspect, wherein the control current is set to be lower as the outdoor temperature exceeds a predetermined temperature.
When the outdoor temperature is higher than a predetermined temperature, the control current is determined by the thermal protection current of the electrical component. The thermal protection current is a magnitude of a current allowed to flow through the electrical component, and becomes smaller as the ambient temperature where the electrical component is disposed is higher.
[0012]
In this case, by setting the control current to be lower as the outdoor temperature exceeds the predetermined temperature, the input current can be suppressed corresponding to the current allowed to flow through the electrical component.
The air conditioner according to a fourth aspect of the present invention is the air conditioner according to any one of the first to third aspects, wherein a plurality of rate change currents are set according to a difference between an input current or a compressor current and a control current.
[0013]
In this case, as the difference between the input current or compressor current and the control current becomes smaller, there is less risk of damage due to heat generation of the electrical components. Therefore, the lower the difference, the slower the rate of decrease of the input current or compressor current. Thus, the burden on the compressor is further reduced.
[0014]
Embodiment
〔overall structure〕
FIG. 1 is a block diagram showing a schematic configuration of an air conditioner in which an embodiment of the present invention is adopted.
This air conditioner includes a refrigerant circuit 1 configured by connecting a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, an accumulator, and the like in an annular shape, and driving the refrigerant circuit 1 The drive circuit 2, the frequency control means 3 for controlling the operating frequency of the compressor of the refrigerant circuit 1 via the drive circuit 2, and the output of the frequency control means 3 are restricted under the conditions described later to suppress the compressor current. Current suppression means 4 that performs the current detection, and a current detection unit 5 that detects the current flowing through the compressor of the refrigerant circuit 1.
[0015]
The configuration of the refrigerant circuit 2 is shown in FIG. The refrigerant circuit 2 is connected to a compressor 11, a four-way switching valve 12 connected to the discharge side of the compressor 11, an outdoor heat exchanger 13 connected to the four-way switching valve 12, and the outdoor heat exchanger 13. An expansion valve 14 that is an electric expansion valve, an indoor heat exchanger 15 connected to the expansion valve 14, and an accumulator that is connected to the suction side of the compressor 11 and prevents liquid refrigerant from entering the compressor 11. 16. The compressor 11, the four-way switching valve 12, the accumulator 16, the outdoor heat exchanger 13, and the expansion valve 14 are provided in the outdoor unit, and the indoor heat exchanger 15 is provided in the indoor unit.
[0016]
A drive circuit 2 for driving the refrigerant circuit 1 is shown in FIG. The drive circuit 2 mainly includes an A / D converter 22 and an inverter 23. The A / D converter 22 converts the voltage supplied from the commercial AC power supply 21 into a DC voltage. The inverter 23 converts the DC voltage into an AC voltage according to the signal from the frequency control means 3. The motor 24 of the compressor 11 is driven by the output voltage from the inverter 23 to form a refrigerant flow. Between the inverter 23 and the compressor 11, a current detection unit 5 for detecting a current flowing through the compressor 11 is disposed.
[0017]
The frequency control means 3 and the current suppression means 4 are configured by a control unit 31 formed of a microprocessor as shown in FIG. The control unit 31 is connected to the refrigerant circuit 1, the drive circuit 2, and the current detection unit 5. The control unit 31 is connected to a fan motor 32 for driving fans provided in the indoor unit and the outdoor unit. Furthermore, a receiving unit 33 for receiving an instruction transmitted from the remote controller is connected to the control unit 31. Connected to the control unit 31 is a target temperature setting unit 34 that sets a target temperature based on an instruction received by the reception unit 33. The target temperature setting unit 34 can be set as a predetermined area of a memory connected to the control unit 31. The controller 31 is connected to an indoor temperature detector 35 that is a temperature sensor that detects the indoor temperature, and an outdoor temperature detector 36 that is a temperature sensor that detects the temperature inside the case of the outdoor unit.
[0018]
In such an air conditioner, during the cooling operation, the four-way switching valve 12 is set to a solid line position, the expansion valve 14 is throttled to a predetermined opening degree, and the compressor 11 is started. The high-pressure refrigerant discharged from the compressor 11 is condensed by the outdoor heat exchanger 13 and then decompressed by the expansion valve 14. The decompressed low-pressure refrigerant evaporates in the indoor heat exchanger 15 and then returns to the compressor 11 via the four-way switching valve 12 and the accumulator 16. When the refrigerant evaporates in the indoor heat exchanger 15, the indoor air is deprived of heat by the refrigerant, and the indoor air deprived of this heat acts as cold air.
[0019]
During the heating operation, the four-way switching valve 12 is set to the dotted line position, the expansion valve 14 is throttled to a predetermined opening degree, and the compressor 11 is started. The high-pressure refrigerant discharged from the compressor 11 is condensed by the indoor heat exchanger 15 and then decompressed by the expansion valve 14. The decompressed low-pressure refrigerant evaporates in the outdoor heat exchanger 13 and then returns to the discharge side of the compressor 11 via the four-way switching valve 12 and the accumulator 13. When the refrigerant condenses in the indoor heat exchanger 15, heat is released to the indoor air, so that the indoor air that has absorbed this heat acts as warm air.
[0020]
[Current suppression means]
The operation control in such an air conditioner will be described with reference to FIG. In the figure, the horizontal axis represents the outdoor temperature, and the vertical axis represents the current value. A straight line parallel to the horizontal axis of the current value 15A is a breaker down line representing the breaking current of the breaker. When the compressor current exceeds this straight line, the breaker is down. A straight line that crosses the breaker down line at an outdoor temperature of 43 ° C. is a thermal protection line that represents a limit temperature at which the electrical component is destroyed by heat generation. If the compressor current exceeds this straight line, the electrical components may be destroyed by heat generation. Although there are many electrical components, the thermal protection line for the electrical components that are most easily destroyed should be used.
[0021]
A polygonal line that is stepped at an outdoor temperature of 43 ° C. or higher represents a control current at each outdoor temperature, and the compressor current is controlled so as not to exceed this value. The control current needs to be set in the area below the breaker down line and the thermal protection line. As shown in the figure, the outdoor temperature is set along the breaker down line when the outdoor temperature is 43 ° C or lower, and the outdoor temperature is 43 ° C or higher. In, it is set in steps along the heat protection line.
[0022]
A straight line parallel to the horizontal axis of the current value 14A represents a rate changing current. The rate change current is the magnitude of the compressor current that serves as a reference for determining whether or not there is a risk of breaker down. In other words, if the compressor current is less than the rate change current, there is no risk of the breaker going down, and if the compressor current exceeds the rate change current, the compressor current is reduced at a fast rate to prevent breaker down. Must be reduced.
[0023]
For example, if the compressor current rises to point A, B, or C, the compressor current exceeds the control current and also exceeds the rate change current, so the compressor has a fast rate of decline. The current needs to be reduced. However, if the compressor current rises to point D or E, the compressor current exceeds the control current but not the rate change current, so the compressor current is reduced at a slower rate than the above. It may be lowered. If the rate change current is not exceeded, there is no possibility of breaker down, and the compressor current may be reduced at a slower rate than when there is a possibility of breaker down. In this way, by reducing the compressor current at a slow reduction rate, the burden on the compressor can be reduced.
[0024]
FIG. 6 shows how the rotational speed of the compressor decreases when the compressor current is reduced at the two types of reduction speeds as described above. The horizontal axis is time, and the vertical axis is the number of rotations per second of the compressor.
In the figure, two types of stepped broken lines indicate how the rotational speed of the compressor decreases with time when there is a compressor current at points C and D in FIG. The target rotational speed of the compressor is the rotational speed corresponding to the control current in FIG. When the compressor current is at point C, there is a possibility of breaker down, so that it can be seen that the compressor current is reduced at a fast reduction rate, and the rotation speed of the compressor is also reduced at a fast rate. On the other hand, when the compressor current is at point D, there is no risk of breaker down, so the compressor current is reduced at a slower speed, and the rotational speed of the compressor is also reduced at a slower speed. I can see that
[0025]
In this way, when there is no possibility of breaker down and a slow reduction speed is acceptable, the burden on the compressor can be reduced by reducing the rotational speed of the compressor at a slow reduction speed.
(Operation control)
Next, with reference to the flowchart shown in FIG. 7, the current suppression control of this embodiment will be described.
[0026]
In step S1, it is determined whether or not a driving instruction signal is received from the remote controller. Here, when the instruction signal from the remote controller is received by the receiving unit 33, the target temperature included in the instruction signal or a preset standard target temperature is stored in the target temperature setting unit 34, and the process proceeds to step S2. Transition. In step S2, it is determined whether or not the instruction signal is an instruction for dry operation. If it is determined that the instruction signal is an instruction for dry operation, the process proceeds to step S3. In step S3, the operation is performed in one of the cooling operation, the heating operation, and the reheat dry mode depending on the room temperature.
[0027]
If it is determined in step S2 that the instruction signal does not instruct dry operation, the process proceeds to step S4. In step S4, it is determined whether or not the instruction signal is an instruction for cooling operation. When it is determined that the instruction signal is an instruction for cooling operation, the process proceeds to step S5. In step S5, a normal cooling operation is performed.
[0028]
If it is determined in step S4 that the instruction signal does not indicate cooling operation, the process proceeds to step S6. In step S6, it is determined whether or not the instruction signal is an instruction for heating operation. If it is determined that the instruction signal instructs heating operation, the process proceeds to step S7. In step S7, a normal heating operation is performed.
[0029]
In step S8, another process is executed, and the process proceeds to step S1.
In each operation mode of the air conditioner, based on the deviation between the detected target temperature DS at room temperature DI and the target temperature setting unit 34 detected by the indoor temperature detector 35, operation frequency of the compressor 11 is controlled Bring the room temperature closer to the target temperature. During operation, when the compressor current becomes equal to or higher than the control current described above, the compressor current is controlled by the current control means of this embodiment.
[0030]
FIG. 8 is a flowchart showing the control in steps S3, S5, and S7 of FIG.
In step S11, a temperature difference DI-DS between the room temperature DI and the target temperature DS is calculated. In order to reduce the temperature difference DI-DS, an operation frequency command is output to the compressor 11 in step 13 to be described later. Next, the process proceeds to step 12.
[0031]
In step S12, the magnitude of the compressor current detected by the current detector 5 and the control current is determined. If the compressor current is smaller than the control current, the process proceeds to step 13. In step S13, a frequency command is output to the drive circuit 2 based on the DI-DS calculated in step S11.
If the compressor current exceeds the control current in step S12, the process proceeds to step S14. In step S14, the magnitude of the compressor current and the rate change current is determined. If the compressor current exceeds the rate change current, the process proceeds to step 15. In step S15, a frequency command is output to the drive circuit 2 so as to decrease the compressor current at a predetermined decrease rate. If the compressor current is equal to or less than the rate change current in step S14, the process proceeds to step 16. In step S16, a frequency command is output to the drive circuit 2 so as to reduce the compressor current at a slower rate than in step S15.
[0032]
In this way, when the compressor current is smaller than the rate change current, that is, when there is no risk of breaker down, the compressor current is decreased at a slow decrease rate, and the rotation speed of the compressor is decreased at a slow decrease rate. . Thereby, the fall of the torque of a compressor can be prevented and the burden of a compressor can be reduced.
[Other Embodiments]
In the above embodiment, only the compressor current is detected and the compressor current is suppressed to prevent the breaker down and to protect the heat of the electrical components. However, in addition to the compressor current, the current of the fan motor and the like is also detected and compressed. The machine current may be suppressed. In this case, not only the compressor but also fluctuations in the current flowing through the other electrical components can be taken into account, so that the accuracy of the breaker down prevention and the electrical protection of the electrical components is increased.
[0033]
In the above embodiment, only one value of the rate change current is set, but a plurality of rate change current values may be set depending on the difference between the compressor current and the control current. In this case, as the compressor current approaches the control current, the rate of decrease in the compressor current may be slower. Therefore, setting a plurality of rate change currents further reduces the burden on the compressor.
[0034]
【The invention's effect】
According to the present invention, when suppressing the compressor current for preventing breaker down and protecting the electrical components, when there is no risk of breaker down, the compressor current is reduced at a slow decrease rate. Torque can be prevented from decreasing and the burden on the compressor can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an air conditioner in which an embodiment of the present invention is adopted.
FIG. 2 is a configuration diagram of the refrigerant circuit.
FIG. 3 is a configuration diagram of the drive circuit.
FIG. 4 is a control block diagram thereof.
FIG. 5 is a diagram showing a relationship between a control current and a rate change current.
FIG. 6 is a diagram showing a state of a decrease in the rotational speed of the compressor.
FIG. 7 is a control flowchart.
FIG. 8 is a control flowchart.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Refrigerant circuit 4 Current suppression means 5 Current detection part 11 Compressor

Claims (4)

In an air conditioner that adjusts the room temperature by controlling the current flowing through the compressor (11) in the refrigerant circuit (1),
A current detector (5) for detecting an input current supplied to the air conditioner; and a current suppressing means (4) for reducing the input current,
The current suppressing means (4) is configured such that the input current is set to be smaller than a breaker protection current and a control current set from a breaker protection current for preventing the breaker from going down and a thermal protection current for protecting the electrical components. The input current is decreased at a predetermined rate of decrease, and when the input current is greater than the control current and smaller than the rate change current, An air conditioner that reduces the input current at a speed slower than a reduction speed. The current detector (5) detects a compressor current flowing through the compressor (11),
When the compressor current is larger than the control current and the rate change current, the current suppression means (4) decreases the input current at a predetermined decrease rate, and the compressor current is less than the control current. If greater and less than the rate change current, the input current is reduced at a rate slower than the predetermined rate of decrease;
The air conditioner according to claim 1. The air conditioner according to claim 1 or 2, wherein the control current is set lower as the outdoor temperature is higher than a predetermined temperature. The air conditioner according to claim 1, wherein a plurality of the rate changing currents are set according to a difference between the input current or the compressor current and the control current.

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