JPH07229655A - Refrigerant flow rate controller for vapor compression type refrigerator - Google Patents

Abstract

PURPOSE:To so control a refrigerant flow rate to branched refrigerant tubes that refrigerant states of outlets of the tubes become equivalent by controlling switching degree of an expansion valve for the tubes based on a mean value and unevenness of discharge refrigerant temperatures of the respective tubes. CONSTITUTION:A controller 201 stores refrigerant temperatures detected by indoor branch tube temperature detecting means 102 as branch refrigerant tube temperatures in a temperature data memory 203 at the time of cooling, and stores refrigerant temperatures detected by outdoor branch tube temperature detecting means 104 as branch tube refrigerant tube outlet temperatures in the memory 203 at the time of heating. A branch refrigerant state calculator 204 calculates a mean value and a dispersion value of the respective outlet temperatures based on the data stored in the memory 203. The controller 201 controls switching degrees of branch tube expansion valves 101, 103 based on this calculated result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor compression refrigerator having an evaporator in which a plurality of refrigerant pipes are branched, and more particularly to control of a refrigerant flow rate of the branched refrigerant pipes.

[0002]

2. Description of the Related Art Conventionally, in a vapor compression refrigerator used for indoor air conditioning, the indoor temperature is controlled to a set temperature,
At this time, the refrigerant flow rate is controlled in order to maximize the cooling capacity of the refrigerator itself and to keep the refrigerant state inside the refrigerator stable. For example, in the case of cooling, the refrigerator absorbs heat from the room into the refrigerant inside the evaporator and releases the heat from the condenser to the outside, and the compressor is operated when the room temperature is higher than the set temperature. When the indoor temperature becomes lower than the set temperature, the compressor operation is stopped and the indoor and outdoor heat exchange is stopped.

As a means for controlling the refrigerant flow rate of the refrigerator, the opening / closing degree of an electronic expansion valve provided between the evaporator and the condenser is controlled. There are various control methods for this purpose, such as superheat degree control in which the degree of opening and closing of the electronic expansion valve is controlled so that the degree of superheat at the evaporator outlet converges to a control target value. Hereinafter, the vapor compression refrigerator in which the conventional superheat degree control is performed will be specifically described below.

FIG. 6 shows a conceptual diagram of a refrigerant circuit of a vapor compression refrigerator. 1 is an indoor heat exchanger, 2 is an outdoor heat exchanger, 3
Is a compressor, 4 is an electronic expansion valve, and the electronic expansion valve 4 is electrically driven by, for example, a stepping motor, and its opening / closing degree can be adjusted. Reference numeral 5 is an outdoor unit, and 6 is an indoor unit. A solid line 7 inside the outdoor unit 5 and the indoor unit 6 shows a refrigerant pipe through which the refrigerant moves, and a dotted line 8 is for connecting the outdoor unit 5 and the indoor unit 6 in the refrigerant pipe. Shows piping. Reference numeral 9 is a four-way valve that switches the connection of the compressor 3 connected to the indoor heat exchanger 1 and the outdoor heat exchanger 2 via the refrigerant pipe 7 according to the operating state. Therefore, during the cooling operation by switching the four-way valve 9, the indoor heat exchanger 1 to the four-way valve 9, the compressor 3, the four-way valve 9, the outdoor heat exchanger 2
Are connected so that the refrigerant flows in that order, and during heating operation,
The four-way valve 9, the compressor 3, the four-way valve 9 and the indoor heat exchanger 1 are connected in this order from the outdoor heat exchanger 2 so that the refrigerant flows. Here, this figure shows the case of the cooling operation, and the refrigerant flows in the direction of the arrow in the drawing in the pipe.

Then, during the cooling operation, the indoor heat exchanger 1
As an evaporator and the outdoor heat exchanger 2 as a condenser, and vice versa during heating operation. Reference numeral 10 is a first temperature detecting means including a thermistor provided on the refrigerant inflow side of the indoor heat exchanger 1 that operates as an evaporator during the cooling operation, and 11 is provided on the refrigerant discharge side of the indoor heat exchanger 1 during the cooling operation. The second temperature detecting means consisting of a thermistor, 12 is the third temperature detecting means consisting of a thermistor provided on the refrigerant inflow side of the outdoor heat exchanger 2 that operates as an evaporator during the heating operation, and 13 is the outdoor heat during the heating operation. The fourth temperature detecting means is a thermistor provided on the refrigerant discharge side of the exchanger 2.

Therefore, during the cooling operation, the superheat degree of the refrigerant at the outlet of the indoor heat exchanger 1 which operates as an evaporator is calculated by the first and second temperature detecting means 10 and 11. Generally, the degree of superheat refers to the temperature rise from the saturated vapor temperature of the refrigerant,
During normal operation, the refrigerant temperature on the refrigerant inflow side of the evaporator has a value that is approximately a constant temperature lower than the saturated steam temperature.Therefore, the refrigerant temperature before and after the evaporator is detected, and the overheat at the evaporator outlet is detected based on the temperature difference. The degree is calculated. Similarly, during heating operation, the superheat degree of the refrigerant at the outlet of the outdoor heat exchanger 2 that operates as an evaporator is calculated by the third and fourth temperature detecting means 12 and 13.

FIG. 7 shows an ideal refrigerant temperature change diagram inside the evaporator. Here, the horizontal axis indicates the distance from the refrigerant inlet of the refrigerant pipe arranged inside the evaporator, and the vertical axis indicates the temperature of the refrigerant located at that distance. As can be seen from the figure, the refrigerant temperature gradually rises as the refrigerant takes away heat from the outside air and moves away from the refrigerant inlet (a in the figure).
Region), after passing through the state where the refrigerant temperature does not change (region b in the figure), the refrigerant temperature rises again to the refrigerant discharge port of the evaporator (region c in the figure).

That is, in the area a in the figure, the temperature of the refrigerant rises in the liquid state, and when it reaches the saturated vapor temperature under that pressure, the temperature does not rise as shown in the area b in the figure, and Is evaporated into a gas, and a refrigerant in a gas state and a liquid state are mixed to form a gas-liquid two-phase state. When all the refrigerant is in the gas state, the refrigerant temperature rises again as shown in the area c in the figure. Here, when the refrigerant discharge temperature at the outlet of the evaporator is higher than the saturated vapor temperature, that is, the refrigerant is completely in the gaseous state at the outlet of the evaporator, it is generally said that the degree of superheat is taken.

In superheat control, the control target is that the superheat at the evaporator outlet maximizes the refrigerating capacity of the refrigerator itself and keeps the refrigerant state inside the refrigerator most stable. Electronic expansion valve 4 so that it converges to the value
The degree of opening and closing is controlled to perform the heat exchange operation by circulating the refrigerant.

Further, in the conventional vapor compression refrigerator, in order to increase the surface area of the pipe exposed to the outside air and improve the heat exchange efficiency between the outside air and the refrigerant, only one evaporator is provided before and after the evaporator. The refrigerant pipe is internally branched into a plurality of refrigerant pipes, and the individual refrigerant pipes are arranged in a zigzag manner. FIG. 8 is a schematic structural diagram of the inside of the indoor heat exchanger 1 that operates as an evaporator during the cooling operation. In FIG. 8, the refrigerant pipe 7 that was one at the refrigerant inlet 72 of the indoor heat exchanger 1 during the cooling operation is divided into four refrigerant pipes 71, and another refrigerant pipe 7 is provided at the refrigerant outlet 73. It shows the case where the configuration is returned to.

[0011]

In the conventional vapor compression refrigerator, regardless of whether the evaporator is branched inside or outside, the degree of superheat depends on the refrigerant temperature difference before and after the evaporator. Is detected, and the opening / closing degree of the electronic expansion valve 4 is controlled so that the degree of superheat thereof becomes a control target value.

Therefore, when the inside of the evaporator is branched into a plurality of refrigerant pipes 71 (hereinafter abbreviated as branched refrigerant pipes), all the refrigerant pipes 71 are uniformly superheated at their respective outlets. However, in some cases, one of the plurality of branch refrigerant pipes 71 is not superheated, that is, the refrigerant at the outlet of the branch refrigerant pipe 71 may be in a gas-liquid two-phase state. there were. Therefore, effective heat exchange is not performed in the evaporator, and there is a possibility that the design capacity of the refrigerator cannot be effectively used.

Further, in order to solve this problem, conventionally, all the branched refrigerant pipes 71 were adjusted at the time of manufacturing so as to have a uniform degree of superheat. However, since there are variations in individual products at the time of manufacturing, the Could not solve the above problem.

Therefore, when the inside of the evaporator is branched into a plurality of branch refrigerant pipes, the degree of superheat before and after the evaporator is controlled to the control target value by the control of the electronic expansion valve. However, the refrigerant states at the outlets of the branch refrigerant pipes inside the evaporator are different, and as a result, the design capacity of the refrigerator has not been effectively utilized.

The present invention has been made in view of the above circumstances, and in a vapor compression refrigerator having an evaporator whose inside is branched into a plurality of refrigerant pipes, a refrigerant at each branch refrigerant pipe outlet An object of the present invention is to provide a vapor compression refrigerator in which the refrigerant flow rate to each branch refrigerant pipe is controlled so that the states are equalized and the design capacity of the refrigerator is effectively utilized.

[0016]

DISCLOSURE OF THE INVENTION The present invention relates to a vapor compression refrigerator in which the inside of an evaporator is branched into a plurality of branch refrigerant pipes. Branch pipe temperature detection means for detecting the refrigerant temperature, branch pipe expansion valve provided on the refrigerant inflow side of each branch refrigerant pipe, the degree of opening and closing is adjustable, and the temperature detected by each branch pipe temperature detection means Based on, the average value of the discharge refrigerant temperature of each branch refrigerant pipe within a predetermined time, and the branch refrigerant state calculation means for calculating the variation, and the discharge refrigerant temperature of each branch refrigerant pipe obtained by the branch refrigerant state calculation unit A control means for controlling the opening / closing degree of each branch pipe expansion valve based on the average value and the variation.

Also, an electronic expansion valve whose degree of opening and closing can be adjusted,
The refrigerant inflow side and the discharge side of the evaporator are respectively provided with temperature detecting means, and superheat degree calculating means for calculating the superheat degree of the evaporator outlet based on the temperature detected by the temperature detecting means, Based on the degree of superheat obtained by the degree calculation means, while controlling the opening and closing degree of the electronic expansion valve, the average value of the discharge refrigerant temperature of each branch refrigerant pipe obtained by the branch refrigerant state calculation unit, and based on the variation The degree of opening and closing of each branch pipe expansion valve may be controlled.

Further, the degree of opening / closing of each expansion valve for branch pipes is controlled after the variation of the degree of superheat within a predetermined time is within a certain range by controlling the degree of opening / closing of the electronic expansion valve by the control means. Good.

The control of the degree of opening / closing of the expansion valve for each branch pipe may be performed after the variation in the degree of superheat falls within the range of 1 to 3 ° C.

In addition, the control means may be executed after a predetermined time has elapsed after the vapor compression refrigerator is started.

[0021]

According to the present invention, since the opening / closing degree of each branch pipe expansion valve is controlled based on the average value of the discharge refrigerant temperature of each branch refrigerant pipe and the variation, the refrigerant state at each branch refrigerant pipe outlet is uniform. The refrigerant flow rate to each branch refrigerant pipe is controlled so that

Further, when the opening / closing degree of the electronic expansion valve is controlled on the basis of the superheat degree at the outlet of the evaporator and the opening / closing degree of the expansion valve for each branch pipe is controlled, it is effective in the evaporator by controlling the superheat degree. Heat exchange takes place.

Further, by controlling the opening / closing degree of the electronic expansion valve,
When the degree of opening / closing of each expansion valve for each branch pipe is controlled after the variation in the degree of superheat within a predetermined time is within a certain range, after stabilizing the refrigerant flow rate control of the evaporator by the degree of superheat control, The degree of opening / closing of the expansion valve for each branch pipe is controlled.

In addition, when the opening / closing degree control of the electronic expansion valve and the opening / closing degree control of each branch pipe expansion valve are controlled after a lapse of a predetermined time after starting the operation of the vapor compression refrigerator, the state of the circulating refrigerant. Is stabilized, the refrigerant flow rate control is performed.

[0025]

EXAMPLE A vapor compression refrigerator according to the present invention will be described below.
An embodiment will be described with reference to the drawings. The conceptual diagram of the refrigerant circuit of the vapor compression refrigerator has the same configuration as that of the conventional example (FIG. 6) described above.

FIG. 1 is a schematic structural diagram of the inside of the indoor heat exchanger 1 which operates as an evaporator during the cooling operation. The same components as those in the conventional example (FIG. 8) described above are designated by the same reference numerals.

Reference numeral 101 is provided at each refrigerant inlet of each of the four branch refrigerant pipes 71 when operating as an evaporator, and the opening / closing degree is electrically adjusted by a stepping motor to adjust the refrigerant flow rate of each branch refrigerant pipe 71. The indoor branch pipe expansion valve for changing the temperature of the branch refrigerant pipe, and the indoor branch pipe temperature detection means 102, which is provided at each refrigerant discharge port of the branch refrigerant pipe 71 and includes a thermistor for detecting the temperature of the discharged refrigerant. Therefore, each of the four branch refrigerant pipes 71 is detected by the four indoor branch pipe temperature detecting means 102.
The temperature of the discharged refrigerant is detected, and the degree of superheat at the outlet of each branch refrigerant pipe 71 during the cooling operation can be calculated based on the temperature difference from the first temperature detecting means 10.

Further, as shown in FIG. 2, the outdoor heat exchanger 2 which operates as an evaporator during the heating operation also has an expansion valve 103 for the outdoor branch pipe and an expansion valve 103 for the outdoor branch pipe therein, like the indoor heat exchanger 1. The outdoor branch pipe temperature detecting means 104 is provided in each of the four branch refrigerant pipes 74. Therefore, the degree of superheat at the outlet of each branch refrigerant pipe 74 during the heating operation can be calculated based on the temperature difference between the four outdoor branch pipe temperature detecting means 104 and the third temperature detecting means 12.

FIG. 3 is a schematic block diagram for controlling the refrigerant flow rate according to the present invention.

In the figure, 201 is supplied with the refrigerant temperature detected by the first to fourth temperature detecting means 10 to 13, the indoor branch pipe temperature detecting means 102, and the outdoor branch pipe temperature detecting means 104, which will be described later. To control the degree of opening / closing of the electronic expansion valve 4, the indoor branch piping expansion valve 101, and the outdoor branch piping expansion valve 103 based on the superheat degree at the evaporator outlet and the refrigerant temperature at each branch refrigerant piping outlet It is a department.

Reference numeral 202 denotes every predetermined time (every 10 seconds in this embodiment)
A timing signal generator for outputting a timing signal to the control unit 201, 203 is a branch refrigerant detected in the indoor branch pipe temperature detecting means 102, or the outdoor branch pipe temperature detecting means 104 in accordance with a command from the control unit 201. This is a temperature data storage unit that stores temperature data for a certain time (5 minutes in the present embodiment) of the pipe outlet temperature.

In accordance with a command from the control unit 201, reference numeral 204 denotes each branched refrigerant based on the detected temperature data Tij (i = 1 to 4, j = 1 to 30) for the past 5 minutes stored in the temperature data storage unit 203. It is a branch refrigerant state calculation unit that calculates an average value Mi and a dispersion value Di of the pipe outlet temperature Tij.

Reference numeral 205 designates a first to a first instruction in accordance with a command from the control unit 201.
A superheat degree calculating means for calculating the superheat degree at the evaporator outlet based on the refrigerant temperature detected by the fourth temperature detecting means 10 to 13, 206
Is a superheat degree data storage unit for storing superheat degree data for a certain time (5 minutes in this embodiment) of the superheat degree calculated by the superheat degree calculating means 205.

Reference numeral 207 is a ROM connected to the control unit 201, and the control unit 201 is based on a program stored in the ROM 207, and the electronic expansion valve 4, the indoor branch pipe expansion valve 101, and the outdoor branch pipe expansion valve 103. Etc. are controlled.

Here, the electronic expansion valve 4, the expansion valve 101 for indoor branch piping, and the expansion valve 103 for outdoor branch piping are controlled by the control unit 201.
The degree of opening and closing can be adjusted individually by the control pulse from, and in the present embodiment, the degree of opening and closing in the completely closed state is 0,
The degree of opening and closing in the fully open state is 200, and the degree of opening and closing between them is 200.
It is controlled by the value divided into steps, and the initial value is 10
It is set to 0 steps.

Further, the control unit 201 determines whether it is during the cooling operation or the heating operation, and based on the input signal from the timing signal generation unit 202, it is detected by the temperature detecting means 102 for each indoor branch pipe during the cooling operation. The stored refrigerant temperature is stored in the temperature data storage unit 203 as each branch refrigerant pipe outlet temperature Tij, and during the heating operation, each outdoor branch pipe temperature detecting means 10
The refrigerant temperature detected in 4 is stored in the temperature data storage unit 203 as each branch refrigerant pipe outlet temperature Tij.

The branch refrigerant state calculation unit 204 calculates the average value Mi and the dispersion value Di of each branch refrigerant pipe outlet temperature Tij on the basis of the data stored in the temperature data storage unit 203 according to the following formula. It is calculated. Therefore, the refrigerant state at the outlet temperature of each branch refrigerant pipe is thus detected.

[0038]

[Equation 1]

Here, the refrigerant state detection based on the average value Mi and the dispersion value Di of each branch refrigerant pipe outlet temperature Tij will be described.

As described above, at the outlet of the branch refrigerant pipe of the evaporator, the refrigerant is in the gas-liquid two-phase state shown in FIG. 7 (region b in the figure),
Alternatively, although it is in a gas state (region c in the drawing), if the refrigerant at each branch refrigerant pipe outlet is in a gas state, the refrigerant states at all branch refrigerant pipe outlets are detected from the average value Mi of each branch refrigerant pipe outlet temperature Tij. Therefore, it is possible to grasp the refrigerant flow rate state of each branch refrigerant pipe.

On the other hand, the refrigerant at the outlet of each branch refrigerant pipe is gas-liquid 2
In the case of the phase state, as shown in the area of FIG. 7b, the refrigerant temperature at the outlet of the branch refrigerant pipe hardly changes, so it is not known from the refrigerant temperature which refrigerant flow amount of the branch refrigerant pipe is high or low. .

However, in the gas-liquid two-phase state, the greater the mixing ratio of the liquid in the refrigerant, the greater the variation of the refrigerant temperature, that is, the dispersion value. It is considered that this is because the liquid particles in the refrigerant have a larger temperature variation than the gas particles.

Therefore, in the case of the gas-liquid two-phase state, as the mixing ratio of the liquid in the refrigerant becomes smaller, that is, as the refrigerant state shifts to the right in the region of FIG. 7b, the dispersion value of each branch refrigerant pipe outlet temperature Tij. Since Di becomes small, it becomes possible to detect the state of the refrigerant flow rate from the dispersion value Di at each branch refrigerant pipe outlet.

Next, the operation of the refrigerant flow rate control of the present invention having the above configuration will be described with reference to the main routine of FIG. 4 and the subroutine of FIG.

In FIG. 4, first, it is judged whether the refrigerator is currently set to the cooling operation or the heating operation, and the operation of the refrigerator is started in the set operation mode (S).
1).

When the refrigerator is in the cooling operation, the indoor heat exchanger 1 which operates as an evaporator is targeted for temperature detection, and when the refrigerator is in heating operation, the outdoor heat exchanger 2 which operates as an evaporator is targeted for temperature detection ( Step S3) and then the next step S5.
In the following steps, the case of the cooling operation in which the indoor heat exchanger 1 is the temperature detection target will be described.

In step S5, the timing signal generator 202 that outputs a timing signal at 10-second intervals is started, and in step S7, the timing signal generator 20 is started.
60 new timing signals from 2 are input, that is, 1
0 minutes have passed, judge whether or not to proceed.

In step S7, the refrigerator 10
After operating for a minute, the next step is
This is because the refrigerant flow rate control is not performed immediately after the operation of the refrigerator in which the refrigerant state is unstable is started. As a result, more accurate refrigerant flow rate control becomes possible.

In the next step S9, the first and second temperature detections are performed.
Based on the temperature detected by the output means 10 and 11,
Generator superheat SH (SH = t₂−t₁， T₁First temperature detecting means 10
Temperature detected by t₂Temperature detected by the second temperature detecting means 11
Degree) and calculate the target superheat SH _T(In this embodiment, SH_T4
Deviation (set to ℃) e (= SH_T−SH)
It During the heating operation, the outdoor heat exchanger 2 serves as an evaporator.
Since it operates by₀Is the third and fourth temperature
Temperature difference t detected by the detection means 12 and 13_Four−t₃(T₃; Third temperature
Temperature detected by the detection means 12, t_FourThe fourth temperature detecting means 13
Detected temperature).

Next, the deviation e is set as the deviation e ₀ (S1
1), it is determined whether or not three new timing signals have been input from the timing signal generation unit 202, that is, whether 30 seconds have elapsed, and the process proceeds to the next (S13).

Then, in the next step S15, the degree of superheat of the evaporator is controlled, and the process proceeds to step S17. In this step S15, specifically, in the same manner as in step S9, based on the detected temperatures detected by the first and second temperature detecting means 10 and 11, the current superheat degree SH of the evaporator and the target The deviation e from the degree of superheat SH _T is obtained, and the valve operation amount dv of the electronic expansion valve 4 is determined based on the variation de (= e−e ₀ ) between the deviation e ₀ and the current deviation e. The electronic expansion valve 4 is driven by the valve operation amount dv. Here, the valve operation amount dv is calculated according to the following rule.

When the deviation e is positive, the valve operation amount dv = -1
To set the opening degree of the electronic expansion valve 4 to be small, and when the deviation e is negative, the valve operation amount dv is set to 1 to increase the opening degree of the electronic expansion valve 4.

When the deviation e is positive and the change amount de is negative, or when the deviation e is negative and the change amount de is positive, that is, when the superheat degree SH changes in the direction of convergence to the target superheat degree SH _T. , The valve operation amount dv is set to 0, and the opening / closing degree of the electronic expansion valve 4 is not changed.

Then, in the next step S17, the superheat degree SH
Is stored in the superheat degree data storage unit 205 as superheat degree data, and the process proceeds to the next step S19.

In step S19, the superheat degree data storage unit 20
Whether 5 has stored the superheat data for the past 5 minutes,
That is, it is determined whether or not the past ten superheat data have been stored. If YES, the process proceeds to the next step S21, and if NO, the process returns to step S11.

In the next step S21, the superheat degree data for the past 5 minutes stored in the superheat degree data storage unit 205 is read out and the variation thereof is equal to or more than a certain value (3 ° C. in this embodiment).
If YES, the process returns to step S11, and if NO, the process proceeds to step S23, where each branch refrigerant pipe Li (i = 1) inside the evaporator to be described later.
The refrigerant flow rate adjustment subroutine of 4) is executed. still,
The variation setting value in this case may be any other value as long as it is within the range of 1 to 3 ° C.

Here, the reason why the refrigerant flow rate of each branch refrigerant pipe Li is adjusted only when the temporal change of the superheat data of the evaporator is within a predetermined range is that the degree of opening / closing of the electronic expansion valve 4 is controlled. As a stable state of the refrigerant flow rate control of the evaporator by
This is because the refrigerant flow rate of each branch refrigerant pipe Li inside the evaporator is adjusted and the refrigerant state at each branch refrigerant pipe outlet is uniformly controlled quickly and accurately.

Then, in the next step S25, the superheat degree control of the evaporator is performed in the same manner as in step S15, and the process proceeds to step S27.

In step S27, it is determined whether or not an instruction to stop the operation of the refrigerator is input. If YES, the operation of the refrigerator is stopped, and if NO, the process proceeds to step S29.

In step S29, the timing signal generator
It is judged whether or not 12 new timing signals have been input from 202, that is, whether or not 2 minutes have elapsed, and the process returns to step S25,
The superheat degree control of the evaporator is performed again.

Next, the contents of the refrigerant flow rate adjustment subroutine executed in step S23 will be described with reference to FIG.

First, the temperature detecting means 102 for the indoor branch pipe is provided for each timing signal input from the timing signal generator 202.
Therefore, the temperature Tij (i = 1) of the refrigerant discharged from each branch refrigerant pipe Li
˜4, j = 1 to 30) is detected, and the detected temperature data for a fixed time (5 minutes in this embodiment) is stored in the temperature data storage unit 203 (S101).

Next, the detected temperature data Tij stored in the temperature data storage unit 203 is read out, and the average value M of the discharge refrigerant temperature of each branch refrigerant pipe Li is read by the branch refrigerant state calculation unit 204.
i and the variance value Di are calculated, and the result is stored in the temperature data storage unit 203 (S103).

Then, in the next step S105, whether the variation of the average value Mi of each branch refrigerant pipe Li is within a predetermined range (1 ° C. in this embodiment), that is, the discharge refrigerant of each branch refrigerant pipe Li is It is determined whether the gas-liquid two-phase state is present. If YES, the process proceeds to step S107, and if NO, the process proceeds to step S113.

In step S107, it is determined whether the dispersion value Di of each branch refrigerant pipe Li is within a predetermined range (1 in this embodiment), that is, the refrigerant state of the discharge refrigerant of each branch refrigerant pipe Li is equal. If YES, the process returns to the main routine (step S25) shown in FIG. 4, and if NO, the process proceeds to step S109.

In step S109, the branch refrigerant pipe Li having the second smallest dispersion value Di is replaced with the standard branch refrigerant pipe Li _0.
Then, the process proceeds to step S111.

In step S111, the valve operation amount dv ₁ of each indoor branch pipe expansion valve 101 provided in the three branch refrigerant pipes other than the standard branch refrigerant pipes is determined, and the determined valve operation amount dv ₁ is determined. By driving the expansion valve 101 for each branch pipe by ₁
Return to step S101.

Here, the valve operation amount dv ₁ is set to the valve operation amount dv ₁ = -1 when the dispersion value Di is larger than the standard dispersion value Di ₀ , and the opening / closing degree of each indoor branch pipe expansion valve 101 is set. Is made small, and when it is small, the valve operation amount dv ₁ = 1 is set, and the opening / closing degree of each indoor branch pipe expansion valve 101 is increased.

On the other hand, in step S113, the branch refrigerant pipe Li having the second largest average value Mi is set as the standard branch refrigerant pipe Li _0, and the process proceeds to step S115.

In step S115, the valve operation amount dv ₂ of each indoor branch pipe expansion valve 101 provided in the three branch refrigerant pipes other than the standard branch refrigerant pipes is determined, and the determined valve operation amount dv is determined. By driving the expansion valve 101 for each indoor branch pipe by ₂
Return to step S101.

[0071] Here, the valve operating amount dv ₂ set on the valve operation amount dv ₂ = -1 if the average value Mi is less than the standard average value Mi _0, the opening degree of the indoor branch piping expansion valve 101 Make it smaller,
If it is larger, the valve operation amount dv ₂ is set to 1 to increase the opening / closing degree of each indoor branch pipe expansion valve 101.

By performing the above operation, the refrigerant flow rate to each branch refrigerant pipe is controlled so that the refrigerant state at each branch refrigerant pipe outlet inside the evaporator becomes uniform, and all the branch refrigerant pipe outlets are controlled. Will be controlled so that the degree of superheat can be taken evenly.

In the above embodiment, the vapor compression refrigerator in which the superheat degree is controlled has been described. However, in the case where other refrigerant flow rate control is performed, for example, at the outlet of the four-way valve 9 in FIG. The present invention can also be applied to a vapor compression refrigerator in which the four-way valve outlet temperature control for adjusting the opening / closing degree of the electronic expansion valve 4 is performed so that the refrigerant temperature becomes the target temperature.

[0074]

As described above, according to the present invention, since the opening / closing degree of each expansion valve for each branch pipe is controlled based on the average value of the discharge refrigerant temperature of each branch refrigerant pipe and the variation, each branch refrigerant pipe outlet The flow rate of the refrigerant to each branch refrigerant pipe is controlled so that the refrigerant state is uniform, and the design capacity of the refrigerator can be effectively utilized.

Further, by controlling the degree of opening / closing of the electronic expansion valve based on the degree of superheat at the outlet of the evaporator and by controlling the degree of opening / closing of each branch pipe expansion valve, effective heat in the evaporator is controlled by superheat control. It becomes possible to exchange.

Further, by controlling the opening / closing degree of the electronic expansion valve,
After the variation of the superheat degree within a predetermined time is within a certain range, by performing the opening / closing degree control of each branch pipe expansion valve, after stabilizing the refrigerant flow rate control of the evaporator by the superheat degree control, The degree of opening and closing of each branch pipe expansion valve is controlled, and the refrigerant state at each branch refrigerant pipe outlet can be quickly and accurately controlled uniformly.

In addition, the state of the circulating refrigerant is stabilized by controlling the opening / closing degree of the electronic expansion valve and the opening / closing degree of each branch pipe expansion valve after a lapse of a predetermined time after starting the operation of the vapor compression refrigerator. After this, the refrigerant flow rate control is performed, and accurate refrigerant flow rate control becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of the inside of an indoor heat exchanger that operates as an evaporator of a vapor compression refrigerator of the present invention.

FIG. 2 is a schematic structural diagram of the inside of an outdoor heat exchanger that operates as an evaporator of a vapor compression refrigerator of the present invention.

FIG. 3 is a schematic block diagram for performing a refrigerant flow rate control of the present invention.

FIG. 4 is a main routine for explaining the operation of the refrigerant flow rate control of the present invention.

5 is a subroutine for explaining the operation of adjusting the refrigerant flow rate of each branch refrigerant pipe inside the evaporator of FIG. 3 embodiment.

FIG. 6 is a conceptual diagram of a refrigerant circuit of a vapor compression refrigerator.

FIG. 7 is an ideal refrigerant temperature change diagram inside the evaporator.

FIG. 8 is a schematic structural diagram of the interior of an indoor heat exchanger that operates as an evaporator of a conventional vapor compression refrigerator.

[Explanation of symbols]

 1 Indoor heat exchanger 2 Outdoor heat exchanger 3 Compressor 4 Electronic expansion valve 5 Outdoor unit 6 Indoor unit 7 Refrigerant pipe 8 Piping 9 Four-way valve 10 First temperature detecting means 11 Second temperature detecting means 12 Third temperature detecting means 13 Fourth temperature detecting means 101 Expansion valve for indoor branch piping 102 Temperature detecting means for indoor branch piping 103 Expansion valve for outdoor branch piping 104 Temperature detecting means for outdoor branch piping 201 Control section 202 Timing signal generating section 203 Temperature data storage section 204 Branch Refrigerant state calculation unit 205 Superheat degree calculation means 206 Superheat degree data storage unit 207 ROM

Claims (5)

[Claims] 1. A vapor compression refrigerator in which a compressor, a condenser, and an evaporator whose inside is branched into a plurality of branch refrigerant pipes are connected by a refrigerant pipe, wherein the refrigerant of each branch refrigerant pipe is Branch pipe temperature detection means respectively provided on the discharge side, for detecting the discharge refrigerant temperature, branch pipe expansion valves respectively provided on the refrigerant inflow side of each of the branch refrigerant pipes, the degree of opening and closing of which is adjustable, Based on the temperature detected by the branch pipe temperature detecting means, a branch refrigerant state calculating means for calculating the average value of the discharge refrigerant temperature of each of the branch refrigerant pipes within a predetermined time and the variation, and the branch refrigerant state calculating part. Based on the average value of the discharge refrigerant temperature of each branch refrigerant pipe obtained, and based on the variation, control means for controlling the opening and closing degree of each expansion valve for each branch pipe, vapor compression, characterized in that Freezing Flow control device for machine. 2. A vapor compression system in which a compressor, a condenser, an electronic expansion valve whose degree of opening and closing is adjustable, and an evaporator whose inside is branched into a plurality of branched refrigerant pipes are connected by a refrigerant pipe. In the refrigerator, temperature detecting means respectively provided on the refrigerant inflow side and the discharge side of the evaporator, and superheat degree calculating means for calculating the superheat degree at the evaporator outlet based on the temperature detected by the temperature detecting means. A branch pipe temperature detection means for detecting the discharge refrigerant temperature, respectively provided on the refrigerant discharge side of each of the branch refrigerant pipes, respectively provided on the refrigerant inflow side of each of the branch refrigerant pipes, the degree of opening and closing is adjustable Branch pipe expansion valve, based on the temperature detected by the temperature detecting means for each branch pipe, the average value of the discharge refrigerant temperature of each branch refrigerant pipe within a predetermined time, and a branch refrigerant state calculation unit for calculating the variation And the superheat calculation Based on the degree of superheat obtained by means, while controlling the degree of opening and closing of the electronic expansion valve, the average value of the discharge refrigerant temperature of each branch refrigerant pipe obtained by the branch refrigerant state calculation unit, and based on the variation And a control means for controlling the degree of opening / closing of each of the branch pipe expansion valves, respectively, and a refrigerant flow rate control device for a vapor compression refrigerator. 3. The control means controls the degree of opening / closing of the expansion valve for each branch pipe after the variation of the degree of superheat within a predetermined time is within a certain range by controlling the degree of opening / closing of the electronic expansion valve. The refrigerant flow rate control device for a vapor compression refrigerator according to claim 1 or 2, characterized in that. 4. The expansion valve for each branch pipe after the variation of the degree of superheat within a predetermined time is within a range of 1 to 3 ° C. by controlling the opening / closing degree of the electronic expansion valve. 4. The refrigerant flow rate control device for a vapor compression refrigerator according to claim 3, wherein the opening / closing degree control is performed. 5. The refrigerant flow rate control device for a vapor compression refrigerator according to claim 1, wherein the control means starts the operation of the vapor compression refrigerator and executes the operation after a predetermined time has elapsed.