JPH06281234A - Refrigerating cycle apparatus - Google Patents

Abstract

PURPOSE:To rapidly converge a degree of superheat to a set value and afford stable operation at all times by correcting opening degree control values for electronic expansion valves in a manner to make the same decreasing when a decreasing variation of a maximum value of a difference between the set value and the degree of overheat is not more than a set value and this is successively satisfied a predetermined times. CONSTITUTION:A difference between a set value and a degree of super heat, and a maximum value of the difference are successively detected. When a variation detected is not more than a set value, for example, 2 deg.C and a maximum value at that time is not less than a predetermined value, for example, 1 deg.C, a gain G is decreased a predetermined value, for example, 0.3 at a point of time when a number of times reaches a set value, for example 2. An opening degree control value for electronic expansion valves 11, 21 is corrected to be decreased, and a flow rate of a refrigerant flowing to an evaporator becomes small in variation. Therefore, an amplitude variation of the degree of overheat is suppressed, and the degree of overheat can be made to rapidly tend to the set value. Accordingly, it is possible to perform stable operation at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle device used in an air conditioner.

[0002]

2. Description of the Related Art Air conditioners include compressors, outdoor heat exchangers,
A decompressor and an indoor heat exchanger are connected to form a refrigeration cycle, and the refrigerant discharged from the compressor is allowed to flow in the order of the outdoor heat exchanger, the decompressor, and the indoor heat exchanger, whereby the outdoor heat exchanger is condensed. , The indoor heat exchanger is made to function as an evaporator, and the cooling operation is executed. In a heat pump type refrigeration cycle configured by connecting a compressor, a four-way valve, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger, by switching the four-way valve, the flow of refrigerant can be made opposite to that during cooling operation. The indoor heat exchanger can function as a condenser and the outdoor heat exchanger can function as an evaporator to perform heating operation.

When the compressor is of variable capacity type, the air conditioning load based on the room temperature is detected and the capacity of the compressor is controlled in accordance with the air conditioning load, so that the optimum cooling capacity corresponding to the air conditioning load and Heating capacity is obtained.

However, in this capacity control, the flow rate of the refrigerant changes with the capacity change, so that the degree of superheat of the refrigerant in the evaporator changes. This superheat degree must be maintained at a constant value in order to ensure stable operation. Therefore, an electronic expansion valve is used as the pressure reducer, and the opening degree of the electronic expansion valve is controlled so that the degree of superheat is maintained at a constant value (= set value).

An example of an air conditioner that employs such superheat control is disclosed in Japanese Patent Laid-Open No. 60-263065. By the way, there are feedback control and fuzzy control as specific methods of superheat control. In the feedback control example, the degree of superheat in the refrigeration cycle is detected and fed back to the PID control unit. PI
In the D control unit, the manipulated variable of the opening degree for the electronic expansion valve is calculated and calculated from the deviation between the degree of superheat and the set value. The opening degree of the electronic expansion valve is adjusted by this operation amount.

[0006]

When the opening degree of the electronic expansion valve is adjusted, first, the flow rate of the refrigerant to the indoor heat exchanger changes, which appears as a change in superheat degree. That is, there is a time delay from the opening adjustment to the change in superheat degree. Due to the influence of this time delay, the degree of superheat does not immediately converge to the set value, but rather converges while repeating amplitude fluctuations around the set value.

Although the amplitude fluctuation of the superheat degree is absorbed to some extent by the feedback control and the fuzzy control, if the fluctuation of the air conditioning load is large, it may not be easily converged. Depending on the load conditions, instead of converging, it may diffuse in the opposite direction, or may become stable at a distance from the set value. Basically, constants such as PID and fuzzy control are set, but it is extremely difficult to set sufficient constants for refrigeration cycles with extremely large load fluctuations.

The present invention takes the above circumstances into consideration,
It is an object of the present invention to provide a refrigeration cycle apparatus capable of quickly converging the degree of superheat to a set value and always performing stable operation.

[0009]

A refrigeration cycle apparatus according to claim 1 comprises a refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are connected, and the degree of superheat of the refrigerant in the evaporator is set to a set value. In the one that controls the opening degree of the electronic expansion valve so that the maximum value of the difference between the set value and the superheat degree is sequentially detected, and the maximum value detected by the first detection means Second detecting means for detecting the amount of change in the decreasing direction,
A determination unit that determines whether the amount of change detected by the second detection unit is less than or equal to a set value and the maximum value detected by the first detection unit is greater than or equal to a predetermined value, and the determination of this determination unit is predetermined. And a correction means for correcting the opening control value for the electronic expansion valve in a decreasing direction when the number of times is continuously satisfied.

The refrigeration cycle apparatus of claim 2 is a compressor,
A condenser, an electronic expansion valve, and a refrigeration cycle in which an evaporator is connected, and the opening degree of the electronic expansion valve is controlled so that the superheat degree of the refrigerant in the evaporator becomes a set value. The difference between and the maximum value of the difference
A detection means; a second detection means for detecting a change amount of the maximum value detected by the first detection means in a decreasing direction; and a change amount detected by the second detection means that is less than or equal to a set value and the first detection Means for determining whether or not the maximum value detected by the means is a predetermined value or more, and an opening control value for the electronic expansion valve when the determination by the first determination means is satisfied a predetermined number of times in succession And a second determining means for determining whether or not the difference detected by the first detecting means has continued for a certain period of time.
Second correction means for correcting the opening control value for the electronic expansion valve in the increasing direction when the judgment of the judgment means is satisfied.

The refrigeration cycle apparatus of claim 3 is the same as that of claim 2
In the refrigeration cycle apparatus, when the operating frequency of the compressor changes, a superheat degree change amount that is a difference between a maximum value detected by the first detection means and a difference detected a predetermined time after the detection is detected. 3 detection means, prediction means for predicting the time until the superheat degree reaches the set value from the difference detected by the superheat degree change amount and the first detection means, and electronic expansion when the predicted time is a predetermined value or more A third correction means is provided for correcting the opening control value for the valve in the increasing direction and for decreasing the opening control value in the decreasing direction when it is less than or equal to a predetermined value.

[0012]

In the refrigeration cycle apparatus of the first aspect, the maximum value of the difference between the set value and the degree of superheat is sequentially detected, and the change amount in the decreasing direction of the maximum value is detected. It is determined whether the amount of change is less than or equal to the set value and the maximum value at that time is greater than or equal to the predetermined value. When this determination is continuously satisfied a predetermined number of times, the opening control value for the electronic expansion valve is corrected in the decreasing direction.

In the refrigeration cycle apparatus of the second aspect, the difference between the set value and the degree of superheat and the maximum value thereof are sequentially detected, and the amount of change in the decreasing direction of the maximum value is also detected.
It is determined whether the amount of change is less than or equal to the set value and the maximum value at that time is greater than or equal to the predetermined value. When this determination is satisfied a predetermined number of times in succession, the opening control value for the electronic expansion valve is corrected in the decreasing direction. On the other hand, it is determined whether the detected difference is equal to or more than a predetermined value for a certain period of time. When this determination is satisfied, the opening control value for the electronic expansion valve is corrected in the increasing direction.

In the refrigeration cycle apparatus of claim 3, in addition to the operation of the refrigeration cycle apparatus of claim 2, when the operating frequency of the compressor changes, the maximum value detected and the difference detected a predetermined time after the detection. The amount of change in superheat which is the difference between From this change amount of superheat degree and the difference (difference between the set value and the superheat degree) detected at the beginning, the time until the superheat degree reaches the set value is predicted. When the predicted time is equal to or greater than the predetermined value, the opening control value for the electronic expansion valve is corrected in the increasing direction. When the predicted time is less than or equal to the predetermined value, the opening control value for the electronic expansion valve is corrected in the decreasing direction.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, A is an outdoor unit,
B ₁ and B ₂ are indoor units, and the following refrigeration cycle is configured in these units.

An outdoor heat exchanger 3 is connected to a discharge port of the compressor 1 via a four-way valve 2, and a liquid side main pipe W is connected to the outdoor heat exchanger 3. The liquid side main pipes W are liquid side branch pipes W ₁ and W _2.
The liquid side branch pipes W ₁ and W ₂ are connected to the indoor heat exchangers 12 and 22.

The liquid side branch pipes W ₁ and W ₂ are provided with electronic expansion valves 11 and 21 which are pressure reducing means. The electronic expansion valves 11 and 21 are pulse motor valves (PMV) whose opening continuously changes according to the number of drive pulses supplied. Hereinafter, the electronic expansion valve is referred to as PMV.

A gas side branch pipe G is attached to the indoor heat exchangers 12 and 22.
₁ , G ₂ are connected. The gas side branch pipes G ₁ and G ₂ are gathered together in the gas side main pipe G, and the gas side main pipe G is connected to the suction port of the compressor 1 via the four-way valve 2.

An outdoor fan 4 is provided near the outdoor heat exchanger 3. One end of a defrosting bypass 5 is connected to a pipe between the discharge port of the compressor 1 and the four-way valve 2, and the other end of the bypass 5 is connected to the liquid side main pipe W. Two-way valve 6 on bypass 5
Is provided. The heat exchanger temperature sensor 7 is attached to the outdoor heat exchanger 3.
Is installed. A refrigerant temperature sensor 8 is attached to a pipe between the four-way valve 2 and the suction port of the compressor 1.

Indoor fans 13, 23 are provided near the indoor heat exchangers 12, 22. A heat exchanger temperature sensor 14 is attached to the indoor heat exchanger 12. A heat exchanger temperature sensor 24 is attached to the indoor heat exchanger 22. Gas side branch pipe G
_A refrigerant temperature sensor 15 is attached to 1. Gas side branch pipe G
_Second refrigerant temperature sensor 25 is attached to.

The control circuit is shown in FIG. Commercial AC power supply 30
The outdoor control unit 40 of the outdoor unit A is connected to the. The outdoor control unit 40 includes a microcomputer and its peripheral circuits. PMV1 is added to the outdoor control unit 40.
1, 21, two-way valve 6, four-way valve 2, outdoor fan motor 4
M, the refrigerant temperature sensors 7, 8, 15, 25, and the inverter circuit 41 are connected.

The inverter circuit 41 rectifies the voltage of the power supply 30, converts it into a voltage of a frequency and level according to a command from the outdoor control section 40, and outputs it. This output becomes drive power for the compressor motor 1M.

The indoor units B ₁ and B ₂ each include an indoor control section 50. The indoor control unit 50 includes a microcomputer and its peripheral circuits. This indoor control unit 5
0, the indoor temperature sensor 51, the heat exchanger temperature sensor 14
(And 24), remote control type operation device (hereinafter, abbreviated as remote controller) 52, indoor fan motor 13
M (and 23M) are connected.

The indoor control unit 50 and the outdoor control unit 40 are connected by a power supply line ACL and a serial signal line SL for data transfer, respectively. Each indoor control unit 50 includes the following functional means.

[1] A means for notifying the outdoor control section 40 of the operating conditions (including the set temperature Ts) by the operation of the remote controller 52 by a serial signal synchronized with the power supply voltage. [2] Temperature Ta detected by the indoor temperature sensor 51 and the remote controller 5
A means for detecting a difference from the set temperature Ts set in 2 as an air conditioning load and notifying the outdoor control unit 40 of the required capacity (frequency value) corresponding to the air conditioning load by a serial signal synchronized with the power supply voltage.

[3] Heat exchanger temperature sensor 14 (and 2
A means for notifying the outdoor control unit 40 of the detected temperature Tc of 4) and the detected temperature Ta of the indoor temperature sensor 51 by a serial signal synchronized with the power supply voltage.

The outdoor control section 40 has the following functional means. [1] The four-way valve 2, the outdoor heat exchanger 3, the PMVs 11 and 21, the indoor heat exchangers 12 and 2 are used for the refrigerant discharged from the compressor 1 based on the cooling operation mode command from each outdoor control unit 50.
2. Means for returning to the compressor 1 through the four-way valve 2 to execute the cooling operation.

[2] The four-way valve 2 is switched based on the heating operation mode command from each outdoor control unit 50, and the refrigerant discharged from the compressor 1 is transferred to the four-way valve 2, the indoor heat exchangers 12, 22, P.
Means for returning to the compressor 1 through the MVs 11 and 21, the outdoor heat exchanger 3, and the four-way valve 2 to execute heating operation.

[3] A means for controlling the operating frequency F of the compressor 1 (= the output frequency of the inverter circuit 41) during the cooling and heating operations according to the sum of the required capacities from the indoor control units 50.

[4] During cooling operation, the temperature Tg detected by the refrigerant temperature sensor 15 and the temperature Tc detected by the heat exchanger temperature sensor 14
(= Tg−Tc) is detected as the degree of superheat (superheat) SH of the refrigerant in the indoor heat exchanger 12, and the detected temperature Tg of the refrigerant temperature sensor 25 and the detected temperature Tc of the heat exchanger temperature sensor 24 are detected. Of the refrigerant in the indoor heat exchanger 22
Means to detect as SH.

[5] Each superheat degree SH detected during cooling operation
A means for controlling the opening of the PMVs 11 and 21 so that the value becomes the set value SHs. [6] Temperature T detected by the heat exchanger temperature sensor 7 during heating operation
e and the temperature Ts detected by the refrigerant temperature sensor 8 (= Ts-
Means for detecting Te) as the superheat degree SH of the refrigerant in the outdoor heat exchanger 3.

[7] A means for controlling the opening degree of the PMVs 11 and 21 so that the detected superheat degree SH becomes the set value SHs during the heating operation. [8] A means for periodically performing the defrosting operation on the outdoor heat exchanger 3 by opening the two-way valve 6 during the heating operation. Two-way valve 6
When is opened, the high temperature refrigerant discharged from the compressor 1 is injected into the outdoor heat exchanger 3.

[9] Set value SHs during cooling and heating operation
And a superheat degree difference ΔSH and a maximum value ΔSHmax thereof are sequentially detected. Maximum value ΔSH detected here
The latest value of max is stored as ΔSHmax (n), and the previous value is stored as ΔSHmax (n-1).

[10] Maximum value Δ detected by the first detecting means
Second detection means for detecting the amount of change in the SHmax decreasing direction. The amount of change in the decreasing direction is the difference between the two when ΔSHmax (n-1)> ΔSHmax (n) (= ΔSHmax (n-1) -ΔSHmax (n)).

[11] A state in which the amount of change detected by the second detecting means is less than a set value (for example, 2 ° C.) and the maximum value ΔSHmax detected by the first detecting means is over a predetermined value (for example, 1 ° C.). First determining means for determining whether or not

[12] When the judgment of the first judging means is satisfied a predetermined number of times (for example, twice) in succession, the PMV 11,
First correction means for correcting the opening control value for 21 in a decreasing direction.

[13] Second determining means for determining whether or not the difference ΔSH detected by the first detecting means is kept at a predetermined value (eg, 1 ° C.) or more for a certain period of time (eg, 5 minutes). [14] When the determination by the second determining means is satisfied, PMV1
2nd for correcting the opening control values for 1, 21 in the increasing direction
Correction means.

Next, the operation will be described. Each remote controller 52
When the cooling operation mode is set, the refrigerant discharged from the compressor 1 flows in the direction of the solid line arrow in FIG. 1, the outdoor heat exchanger 3 functions as a condenser, and the indoor heat exchangers 12 and 22 function as evaporators. As a result, the cooling operation is executed.

During this cooling operation, the operating frequency F of the compressor 1
(= Output frequency of the inverter circuit 41) is controlled according to the total required capacity of the indoor units B ₁ and B ₂ . At the same time, the superheat degrees SH of the refrigerant in the indoor heat exchangers 12 and 22 are respectively detected, and the opening degrees of the PMVs 11 and 21 are controlled so that the superheat degrees SH become set values SHs, respectively.

When the heating operation mode is set by each remote controller 52, the four-way valve 2 is switched and the refrigerant discharged from the compressor 1 flows in the direction of the broken line arrow in FIG.
2 functions as a condenser, and the outdoor heat exchanger 3 functions as an evaporator.
As a result, the heating operation is executed.

During this heating operation, the operating frequency F of the compressor 1
Is controlled in accordance with the total required capacity of the indoor units B ₁ and B ₂ . At the same time, the degree of superheat SH of the refrigerant in the outdoor heat exchanger 3
Is detected and the superheat degree SH reaches the set value SHs, P
The opening degrees of the MVs 11 and 21 are controlled. By this opening degree control, an appropriate amount of refrigerant flows through the indoor heat exchangers 12 and 22, respectively.

By the way, the superheat degree control during the cooling and heating operations is executed by the feedback control shown in FIG. That is, the superheat degree SH in the refrigeration cycle is detected and fed back to the PID control unit. PI
The set value SHs is taken in the D control unit, and the set value SHs
From the deviation between SHs and the degree of superheat SH, the operation amount (the number of drive pulses) for the PMVs 11 and 21 is calculated. The gain G is corrected with respect to this operation amount, and the opening degree control of the PMVs 11 and 21 is executed according to the corrected operation amount.

The detected superheat degree SH is supplied to the gain G determination section, where the convergence state of the superheat degree SH with respect to the set value SHs is monitored, and the gain G is set based on the convergence state.

Here, how the superheat degree SH is monitored and the gain G is actually set will be described with reference to FIGS. 4, 5 and 6. When the number of operating indoor units B ₁ and B ₂ changes at the start of operation, PMV1
ΔSH in the memory when 1, 2 is setting the initial opening or during defrosting operation (steps 101, 102, 103, 104)
max (n), ΔSHmax (n-1), the number of times count N, and the time count t are cleared, and the gain G is "1".
Is set to (step 105). This gain G = "1"
Corresponds to no correction, and the operation amount determined by the PID control unit is used as it is for opening control.

By the way, when the opening degree of the PMVs 11 and 21 is adjusted, first, the flow rate of the refrigerant to the evaporator changes, which appears as a change in the superheat degree SH. That is, there is a time delay from the opening adjustment to the change in superheat degree. Due to the influence of this time delay, the superheat degree SH does not immediately converge to the set value, but it converges while repeating the amplitude fluctuations around the set value SHs. The amplitude fluctuation of the superheat degree SH may be absorbed to some extent by PID control or the like, but may not be easily converged if the fluctuation of the air conditioning load is large. Depending on the load conditions, instead of converging, it may diffuse in the opposite direction, or may become stable at a distance from the set value.

After the start of operation, when the number of operating indoor units B ₁ and B ₂ does not change, PMVs 11 and 21 are not in the initial opening setting, and are not in defrosting operation (steps 101, 101).
102, 103, 104), the superheat degree SH in the evaporator, the difference ΔSH between the set value SHs and the superheat degree SH, and the maximum value ΔSHmax of the difference ΔSH are sequentially detected (step 106). At the same time, the flag H is set to "0" (step 107).

It is determined whether the difference ΔSH is a predetermined value or more, for example, 1 ° C. or more (step 108). If the difference ΔSH is 1 ° C. or more (YES in step 108) and there is no change in the operating frequency F (NO in step 110), based on the flag H being “0” (NO in step 113), the time The count t is started (step 114).

When the difference ΔSH is less than 1 ° C (step 10
8 NO) and flag H are set to "1" (step 10)
9). When the operating frequency F changes (YES in step 110), ΔSHmax (n) and ΔSHmax (n- in the memory
1) and the count N are cleared (step 111) and the flag H is set to "1" (step 105). In this case, the time count t is cleared (step 115) on the basis of the flag H being "1" (YES in step 113).

The time count t is compared with a constant time t ₁ for example 5 minutes (step 116). When the time count t reaches 5 minutes, that is, when the difference ΔSH between the set value SHs and the degree of superheat SH is 1 ° C or more for 5 minutes (YES in step 115), the gain G is a predetermined value, for example, "0.2". Is increased (step 116). The gain G set in this way corrects the number of drive pulses for the PMVs 11 and 21 (step 128).

That is, depending on the load conditions, the superheat degree SH may be stable for 5 minutes or more while maintaining a value higher than the set value SHs by 1 ° C. or more or a value lower by 1 ° C. or more. In this case, the gain G is increased. When the gain G increases, the opening control values for the PMVs 11 and 21 are corrected in the increasing direction, and the change in the refrigerant flow rate to the evaporator increases. As a result, unnecessary stabilization of the superheat degree SH is released, and the superheat degree SH can quickly converge to the set value SHs.

On the other hand, the superheat degree SH converges while repeating the amplitude fluctuation up and down about the set value SHs. In this case, each time the difference ΔSH is on the positive side (+ side) (step 11
8 YES), the maximum value of the difference ΔSH ΔSHmax is the latest ΔSHmax
It is updated and stored as (n) (step 119).

When the difference ΔSH falls from the positive side to the negative side (YES in step 120), ΔSHmax (n) is the previous ΔSH.
It is updated and stored as max (n-1) (step 121). When the superheat SH converges toward the set value SHs, the maximum value ΔSH
max changes in the decreasing direction. Therefore, the previous ΔSHma
Between x (n-1) and the latest ΔSHmax (n), ΔSHmax (n-1)>
The relationship of ΔSHmax (n) occurs, and the difference (= ΔSHmax (n-1) −ΔSHma
x (n)) is detected as the amount of change in the decreasing direction.

It is determined whether the detected change amount is a set value, for example, 2 ° C. or less, and the maximum value ΔSHmax at that time is at a predetermined value, for example, 1 ° C. or more. this is,
This is for monitoring the situation where the amplitude fluctuation of the superheat degree SH converges toward the set value HSs.

When the variation is as small as 2 ° C. or less and the maximum value ΔSHmax is 1 ° C. or more, that is, when the above determination is satisfied, it is determined that hunting is present (step 122).
YES). The amount of change is 2 ° C or more, or the maximum value Δ
When SHmax is 1 ° C or less, that is, when the above determination is not satisfied, it is determined that there is no hunting (step 122).
NO).

With hunting, count N
Is counted up (step 123). When there is no hunting, the count N is cleared (step 124).

When the number of times N reaches the set value N _1, for example, twice (YES in step 125), the number of times N is cleared (step 126) and the gain G is decreased by a predetermined value, for example, "0.3" (step). 127). The gain G set in this way corrects the number of drive pulses for the PMVs 11 and 21 (step 128).

That is, although the amplitude fluctuation of the superheat degree SH is absorbed to some extent by PID control or the like, if the air conditioning load fluctuation is large, it may not be easily converged. Although there is some unavoidable side to this convergence delay, if it is extended too much, it adversely affects driving. Therefore, the gain G is reduced when convergence is delayed or spread.

When the gain G is reduced, the opening control values for the PMVs 11 and 21 are corrected in a decreasing direction, and the change in the refrigerant flow rate to the evaporator is reduced. As a result, the amplitude fluctuation of the superheat degree SH is suppressed, and the superheat degree SH can be quickly converged to the set value SHs. Therefore, stable operation can always be performed.

A second embodiment of the present invention will be described.
When the opening control values for the PMVs 11 and 21 are corrected, the operating frequency F may change. In this case, there is a risk that the convergence of the superheat degree SHs will eventually be delayed due to the change in the operating frequency F, although the correction has been made. This is the second to deal with this
This is an example.

As the functional means of the outdoor control section 40, the following [15] to [17] are provided in addition to the above [1] to [14]. [15] When the operating frequency F of the compressor 1 changes, the superheat degree change amount, which is the difference between the maximum value ΔSHmax detected by the first detection means and the difference ΔSH detected a predetermined time t ₃ after the detection, Third detecting means for detecting.

[16] Detected superheat change amount and first
From the difference ΔSH detected by the detection means, the degree of superheat SH is the set value SH
Prediction means for predicting the time t ₄ until reaching s. [17] PMV1 when the estimated time t ₄ is equal to or greater than the predetermined value t _up
Third correction means for correcting the opening control values for the Nos. 1 and 21 in the increasing direction and correcting the opening control values for the PMVs 11 and 21 in the decreasing direction when the predicted time t ₄ is equal to or less than the predetermined value t _dw .

The other structure is the same as that of the first embodiment. As an operation peculiar to the second embodiment, FIG. 7, FIG.
As shown in the flowcharts of FIGS. 9 and 10, step
Step 112a and step 112b are added between 112 and step 113, and step 131 to step 139 are added between step 121 and step 122. Further, the time count t ₂ is cleared in step 105. Other functions are the same as those in the first embodiment.

That is, when the operating frequency F has changed (YES in step 110), the flag H ₂ is set to "1" (step 112a) and the time count t ₂ is cleared (step 112b).

When the difference ΔSH falls from the positive side to the negative side (YES in step 120), if the flag H ₂ is "1" (YES in step 131), there is a change in the operating frequency F. If it is determined that the time is t, the time count t ₂ is started (step 132).

When the time count t ₂ reaches a predetermined time t ₃ , the latest maximum value ΔSHmax stored in step 121 is stored.
Difference between (n-1) and current difference ΔSH (= ΔSHmax (n) −ΔSH)
Is detected as the superheat change amount. Then, as shown in the following equation, the ratio between the current difference ΔSH and the superheat change amount is obtained, and the predetermined time t ₃ is added to the ratio, so that the difference ΔSH
There from the start of falling (from the start of the time count t _2), the time until the degree of superheat SH reaches the set value SHs t ₄
Is predicted (step 134).

FIG. 11 shows the relationship between t ₄ = ΔSH / (ΔSHmax (n−1) −ΔSH) + t ₃ change in superheat degree SH and the predicted time t ₄ . The predicted time t ₄ is compared with a predetermined value t _up, for example, 5 minutes (step 135).

When the predicted time t ₄ is longer than the predetermined value t _up (YES in step 135), the gain G is increased by a predetermined value, for example, "0.2" (step 136). When the gain G increases, the opening control values for the PMVs 11 and 21 are corrected in the increasing direction, and the change in the refrigerant flow rate to the evaporator increases. As a result, the superheat degree SH quickly reaches the set value SHs.

Further, the estimated time t ₄ is compared with a predetermined value t _dw, for example, 1 minute (step 137). If the predicted time t ₄ is shorter than the predetermined value t _dw (YES in step 137), there is a fear that the degree of superheat SH will repeat amplitude variation around the set value SHs. Therefore, in this case, the gain G is reduced by a predetermined value, for example, "0.3" (step 138). When the gain G decreases, the opening control values for the PMVs 11 and 21 are corrected in the decreasing direction, and the change in the refrigerant flow rate to the evaporator becomes small. This prevents the superheat SH from fluctuating in amplitude around the set value SHs.
It quickly converges to s. In each of the above-described embodiments, the application to the air conditioner has been described, but the present invention can be applied to other devices as long as the device has a refrigeration cycle.

[0069]

As described above, according to the present invention, the refrigeration cycle apparatus of claim 1 successively detects the maximum value of the difference between the set value and the degree of superheat, and detects the maximum value in the decreasing direction. When the amount of change is detected, it is determined whether the amount of change is less than or equal to a set value and the maximum value at that time is greater than or equal to a predetermined value. Since the opening control value is corrected in the decreasing direction, the degree of superheat can be quickly converged to the set value, and stable operation can always be performed.

According to another aspect of the refrigeration cycle apparatus of the present invention, the difference between the set value and the degree of superheat and its maximum value are sequentially detected, and the change amount of the maximum value in the decreasing direction is detected. It is determined whether or not the maximum value detected below is a predetermined value or more, and when the determination is continuously satisfied for a predetermined number of times, the opening control value for the electronic expansion valve is corrected in a decreasing direction, Further, it is determined whether or not the detected difference has continued for a certain period of time over a predetermined value, and when the determination is satisfied, the opening control value for the electronic expansion valve is corrected in the increasing direction. It can be quickly converged to the set value, and stable operation is always possible.

The refrigeration cycle apparatus of claim 3 is the same as that of claim 2
In addition to the configuration of the refrigeration cycle device, when the operating frequency of the compressor changes, the amount of change in the degree of superheat, which is the difference between the maximum value detected and the difference detected a predetermined time after the detection, is detected. Degree change amount and the difference detected at the beginning (difference between set value and superheat degree), predict the time until the superheat degree reaches the set value. The opening control value is corrected in the increasing direction, and when the predicted time is less than the predetermined value, the opening control value for the electronic expansion valve is corrected in the decreasing direction, so that the degree of superheat is quickly converged to the set value. It is possible, and stable operation is always possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refrigeration cycle according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a control circuit in the first embodiment.

FIG. 2 is a block diagram for explaining feedback control in the first embodiment.

FIG. 4 is a diagram showing a change in a difference ΔSH between a superheat degree SH and a set value SHs in the first embodiment.

FIG. 5 is a flow chart for explaining the operation of the first embodiment.

FIG. 6 is a flowchart for explaining the operation of the first embodiment.

FIG. 7 is a flow chart for explaining the operation of the second embodiment of the present invention.

FIG. 8 is a flowchart for explaining the operation of the second embodiment.

FIG. 9 is a flowchart for explaining the operation of the second embodiment.

FIG. 10 is a flowchart for explaining the operation of the second embodiment.

FIG. 11 is a diagram showing the relationship between changes in superheat degree SH and predicted time t ₄ in the second embodiment.

[Explanation of symbols]

A ... outdoor unit, B _1, B ₂ ... indoor unit, 1 ... variable capacity compressor, 2 ... four-way valve, 3 ... outdoor heat exchanger, 11,
21 ... PMV, 12, 22 ... Indoor heat exchanger, 7, 14,
24 ... Heat exchanger temperature sensor, 8, 15, 25 ... Refrigerant temperature sensor, 40 ... Outdoor control unit, 50 ... Indoor control unit.

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[Procedure amendment]

[Submission date] December 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refrigeration cycle according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a control circuit in the first embodiment.

FIG. 3 is a block diagram for explaining feedback control in the first embodiment.

FIG. 4 is a diagram showing a change in a difference ΔSH between a superheat degree SH and a set value SHs in the first embodiment.

FIG. 5 is a flow chart for explaining the operation of the first embodiment.

FIG. 6 is a flowchart for explaining the operation of the first embodiment.

FIG. 7 is a flow chart for explaining the operation of the second embodiment of the present invention.

FIG. 8 is a flowchart for explaining the operation of the second embodiment.

FIG. 9 is a flowchart for explaining the operation of the second embodiment.

FIG. 10 is a flowchart for explaining the operation of the second embodiment.

FIG. 11 is a diagram showing the relationship between changes in superheat degree SH and predicted time t ₄ in the second embodiment.

[Reference Numerals] A ... outdoor unit, B _1, B ₂ ... indoor unit, 1 ... variable capacity compressor, 2 ... four-way valve, 3 ... outdoor heat exchanger, 11,
21 ... PMV, 12, 22 ... Indoor heat exchanger, 7, 14,
24 ... Heat exchanger temperature sensor, 8, 15, 25 ... Refrigerant temperature sensor, 40 ... Outdoor control unit, 50 ... Indoor control unit.

Claims (3)

[Claims] 1. A refrigeration cycle including a refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are connected, and the opening of the electronic expansion valve is controlled so that the degree of superheat of the refrigerant in the evaporator becomes a set value. In the device, first detection means for sequentially detecting a maximum value of the difference between the set value and the superheat degree, and second detection means for detecting a change amount of the maximum value detected by the first detection means in a decreasing direction. Means for determining whether or not the amount of change detected by the second detecting means is equal to or less than a set value and the maximum value detected by the first detecting means is equal to or more than a predetermined value, and the determining means. And a correction unit that corrects the opening degree control value for the electronic expansion valve in a decreasing direction when the determination of is satisfied a predetermined number of times consecutively. 2. A refrigeration cycle including a refrigeration cycle in which a compressor, a condenser, an electronic expansion valve, and an evaporator are connected, and the opening of the electronic expansion valve is controlled so that the degree of superheat of the refrigerant in the evaporator becomes a set value. In the apparatus, a first detection unit that sequentially detects a difference between the set value and the superheat degree and a maximum value thereof, and a second detection unit that detects a change amount of the maximum value detected by the first detection unit in a decreasing direction. Detecting means; first determining means for determining whether or not the amount of change detected by the second detecting means is equal to or less than a set value and the maximum value detected by the first detecting means is equal to or more than a predetermined value. When the determination of the first determination means is satisfied a predetermined number of times in succession, the difference detected by the first correction means and the first correction means for correcting the opening control value for the electronic expansion valve in a decreasing direction is predetermined. Judgment whether or not the state above the value continued for a certain time Refrigeration cycle apparatus, comprising: a second determination means for controlling the electronic expansion valve; and a second correction means for correcting the opening control value for the electronic expansion valve in an increasing direction when the determination of the second determination means is satisfied. . 3. The refrigeration cycle apparatus according to claim 2, wherein when the operating frequency of the compressor changes, the first
Third detecting means for detecting a superheat change amount, which is a difference between the maximum value detected by the detecting means and a difference detected after a predetermined time from the detection, and the superheat change amount and the first detecting means. Prediction means for predicting the time until the superheat reaches the set value from the difference, and when the predicted time is a predetermined value or more, the opening control value for the electronic expansion valve is corrected in the increasing direction, and the predicted time And a third correction means for correcting the opening control value for the electronic expansion valve in a decreasing direction when is less than or equal to a predetermined value.