JPH0510183Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a control device for a refrigeration system that adjusts cooling capacity by causing discharge gas from a compressor to flow into an evaporator.

(Prior Art) A system diagram of a conventional refrigeration system is shown in FIG.

In FIG. 10, 1 is a compressor, 2 is a condenser,
3 is a bypass circuit, 4 is an evaporator, 5 is a hot gas control valve installed in the bypass circuit 3, 8 is a sensor that detects the temperature of the air blown out from the evaporator 4, that is, the temperature to be controlled, and 9 is a control device, 10 is a temperature setting device, 51a, 51b are electromagnetic on-off valves, 52
is a temperature-type expansion valve, 53 is a temperature-sensitive cylinder, 54 is a pressure equalization pipe,
55 indicates a capillary.

When a large cooling capacity is required, such as during pull-down, the control device 9 issues an operating command to the compressor 1, and also commands the electromagnetic on-off valve 51a to open, and the electromagnetic on-off valve 51b.
A close command is issued to the hot gas control valve 5, and a close command is issued to the hot gas control valve 5.
The refrigeration equipment begins operating at full capacity.

During full capacity operation, the refrigerant gas discharged from the compressor 1 releases heat to the outside air in the condenser 2, condenses and liquefies, and then passes through the electromagnetic on-off valve 51a to the thermostatic expansion valve 52.
to go into. This temperature-type expansion valve 52 is connected to the refrigerant temperature at the outlet of the evaporator 4 detected by a temperature-sensing tube 53 and a pressure-equalizing tube 54.
The degree of superheating of the refrigerant at the outlet of the evaporator 4 is detected from the pressure of the refrigerant at the outlet of the evaporator 4, which is introduced through The ability of the evaporator 4 is maximized by adjusting the amount. The refrigerant whose pressure is reduced by the thermostatic expansion valve 52 enters the evaporator 4, where it evaporates by cooling the air, and returns to the compressor 1 in this state.

When the temperature of the air blown out from the evaporator 4 drops to near the set temperature Ts set in the temperature setting device 10 as a result of full capacity operation, the control device 9 commands capacity control operation. The control device 9 adjusts the opening degree of the hot gas control valve 5 so that the temperature of the blown air detected by the blown air temperature sensor 8 becomes the set temperature Ts set in the temperature setting device 10. Then, a part of the refrigerant gas (hot gas) discharged from the compressor 1 flows into the evaporator 4 through the bypass circuit 3 and the hot gas control valve 5, and the flow rate of this hot gas is changed by the hot gas control valve 5. This controls the cooling capacity of the refrigeration system.

During this capacity control operation, at normal outside temperature, the electromagnetic on-off valve 51a is open and the electromagnetic on-off valve 51b is closed, as in the full capacity operation. However, when the cooling load becomes smaller due to a drop in outside air temperature or the like, the control device 9 closes the electromagnetic on-off valve 51a and opens the electromagnetic on-off valve 51b. As a result, the liquid refrigerant is switched to be throttled by the capillary 55. The flow resistance of this capillary 55 is selected such that the flow rate of the liquid refrigerant flowing through it is considerably smaller than the maximum flow rate of the liquid refrigerant flowing past the expansion valve 52.

Therefore, the cooling capacity control range during the capacity control operation is as shown in FIG.
When it is being throttled by the capillary 55, it is between the solid line A, which shows the capacity when the hot gas control valve 5 is fully closed, and the solid line B, which is showing the capacity when it is fully open. It is between the broken line C indicating the capacity when closed and the broken line D indicating the capacity when fully opened.

The temporal change in the temperature of the blown air in this refrigeration system will be explained with reference to FIG.

When the refrigeration system is operated at full capacity, the temperature of the blown air gradually decreases and reaches point a on the temperature Th, which is set slightly higher than the set temperature Ts.
The control device 9 commands capacity control operation and starts adjusting the opening degree of the hot gas control valve 5. At this time, the electromagnetic on-off valve 51a is open and the electromagnetic on-off valve 51b is closed, as in the case of full capacity operation.

If the cooling load during this capacity control operation is point E in FIG. By balancing, the blowing air temperature is adjusted to the set temperature Ts as shown by the solid line b in Figure 11.
can be gradually stabilized.

However, when the outside temperature is low, the cooling load is the first
In the case of point F in FIG. 2, the cooling capacity of the refrigeration system remains at point G even if the hot gas control valve 5 is fully open. Since point 0 is larger than point 0 of the cooling load, the temperature of the outlet air is indicated by the dotted line in Figure 11.
The temperature decreases as shown by C′, so this is the set temperature.
It cannot be stabilized to Ts.

However, when the blowing air temperature reaches a point e above a temperature Tl that is slightly lower than the set temperature Ts, the control device 9 issues a command to close the electromagnetic on-off valve 51a and open the electromagnetic on-off valve 51b, and causes the liquid refrigerant to flow into the capillary. 55, the cooling capacity control range of the refrigeration system will be between H and D, as shown in Fig. 12, so the cooling capacity of the refrigeration system and the cooling load are balanced, and the blowing air temperature is adjusted. As shown by line c in FIG. 11, the temperature can be stabilized at the set temperature Ts.
In addition, in this operating state, when the temperature of the blown air increases due to an increase in the cooling load and reaches point f above the temperature Th, the electromagnetic on-off valve 51a is opened again, the electromagnetic on-off valve 51b is closed, and the liquid refrigerant is If the temperature type expansion valve 52 is used to throttle the temperature, the temperature of the blown air will be reduced to the line shown in Figure 11.
It is possible to prevent the temperature from rising as indicated by d' and stabilize the temperature at the set temperature as indicated by line d.

(Problem to be solved by the invention) In the above conventional refrigeration system, the temperature type expansion valve 5
2 and a capillary 55, as well as electromagnetic on-off valves 51a and 51b for switching these, there is a problem that not only these costs increase, but also the refrigerant circuit becomes complicated, which increases assembly costs and assembly space.

(Means for Solving the Problems) The present invention was proposed to solve the above problems, and its gist is to provide refrigeration using a compressor, a condenser, an electric expansion valve, and an evaporator. In a refrigeration system comprising a hot gas bypass circuit that constitutes a cycle and has a hot gas control valve that guides discharged gas from a compressor to an evaporator, when the temperature deviation between the temperature to be controlled and the set temperature is greater than or equal to a predetermined value, a first control system that fully closes the hot gas control valve and adjusts the opening of the electric expansion valve so that the degree of superheating of the refrigerant at the outlet of the evaporator becomes a constant value; a second control system that adjusts the opening of the hot gas control valve according to temperature deviation; and when the opening of the hot gas control valve adjusted by the second control system exceeds a predetermined range; A control device for a refrigeration system is characterized by comprising a third control system that adjusts the opening degree of the electric expansion valve so as to change the control target value of the degree of superheat of the refrigerant and increase or decrease the cooling capacity.

(Function) Since the present invention has the above configuration, when the temperature deviation between the temperature to be controlled and the set temperature is greater than a predetermined value, the refrigerant at the outlet of the evaporator is turned off with the hot gas control valve fully closed. The refrigeration system is operated at full capacity by adjusting the opening degree of the electric expansion valve so that the degree of superheat becomes a constant value. When the temperature deviation is within a predetermined value, the refrigeration system is operated under capacity control by adjusting the opening degree of the hot gas control valve according to the temperature deviation. When the opening degree of the hot gas control valve exceeds a predetermined range during this capacity control operation, the control target for the refrigerant superheat degree is changed,
In addition, the capacity of the refrigeration system is controlled by adjusting the opening degree of the electric expansion valve.

(Example) A system diagram of a refrigeration system according to the present invention is shown in FIG.

An electric expansion valve 30 for reducing the pressure by throttling the liquid refrigerant condensed in the condenser 2 in the refrigerant pipe connecting the condenser 2 and the evaporator 4 and controlling the flow rate thereof.
is interposed, and this electric expansion valve 30 is connected to a control device 31.
Controlled by instructions from. The pressure of the refrigerant at the outlet of the evaporator 4 is detected by a pressure sensor 6, and the temperature of the refrigerant at the outlet of the evaporator 4 is detected by a temperature sensor 7. The detected values of the pressure sensor 6 and temperature sensor 7 are input to the control device 31. The rest of the structure is the same as the conventional one shown in FIG. 10, and corresponding members are given the same reference numerals.

A control block diagram of this refrigeration system is shown in FIG. 2, and a control flowchart is shown in FIG. 3. The degree of superheat detection means 11 detects the degree of superheat at the outlet of the evaporator 4 based on detection signals from the temperature sensor 7 and the pressure sensor 6. The degree of superheat detected by this degree of superheat detection means 11 (hereinafter referred to as detection SH) is input to the degree of superheat comparison means, and here the degree of superheat detected by the degree of superheat determination means 16 (hereinafter referred to as target
(referred to as SH), and the deviation between the two is detected. This deviation is input to the expansion valve opening determining means 13, which determines the opening of the electric expansion valve 30 based on the deviation, and this opening is input to the control means 18.

The set temperature Ts set by the temperature setting device 10 and the blowing air temperature detected by the blowing air temperature sensor 8 are input to the temperature deviation detection means 14, where the temperature deviation ΔT (blowing air temperature - set temperature Ts) is detected. be done. This temperature deviation ΔT is input to the target superheat degree determining means 16 and also to the hot gas control valve opening determining means 15, which determines the opening degree of the hot gas control valve 5 based on the temperature deviation ΔT. Control means 18 and target superheat degree determination means 16
is input. The target superheat degree determining means 16 determines whether or not to change the target SH according to the opening determined by the hot gas control valve opening determining means 15 and the temperature deviation ΔT detected by the temperature deviation detecting means 14, and determines whether or not to change the target SH.
Determine SH. The timer 17 is for informing whether a predetermined time has elapsed since the previous change when the target superheat degree determining means 16 changes the target SH, and the timer 17 informs the target superheat degree determining means 16 of whether a predetermined time has elapsed since the previous change. It is set by the command from.

As shown in FIG. 3, the target superheat degree determining means 16 first determines whether or not the timer has timed up based on the output from the timer means 17. If the time has elapsed, it is determined whether the opening degree of the hot gas control valve 5 determined by the hot gas control valve opening degree determining means 15 is above, within, or below a predetermined range. If the opening degree of the hot gas control valve 5 is above the predetermined range, the target SH has not reached the upper limit SH, and the temperature deviation ΔT is smaller than the predetermined value, the target SH is increased by a predetermined amount, and the timing means 17 is increased. Set the timer. If the opening degree of the hot gas control valve 5 is within a predetermined range, the target SH remains unchanged. When the opening degree of the hot gas control valve 5 is below the specified range, the target SH
has not reached the lower limit SH and the temperature deviation ΔT is larger than a predetermined value, the target SH is decreased by a predetermined amount and the timer of the timer 17 is set. Note that the upper limit SH is selected to be a value that can prevent overheating of the compressor 1 due to an insufficient amount of refrigerant circulation, and the lower limit SH is set to a value that can prevent liquid from returning to the compressor due to an excessive amount of refrigerant circulation. On the other hand, if the target SH has reached the upper limit SH or lower limit SH,
The target SH is not made larger or smaller, respectively, and the target SH is fixed at the upper limit SH or the lower limit SH, respectively. Further, if each of the above judgment conditions is not met, the target SH is not changed and the previous target SH is maintained. Control means 18
receives the outputs of the expansion valve opening determination means 13, the hot gas control valve opening determination means 15, etc., and operates the electric expansion valve 3.
0 and the drive means 21 of the hot gas control valve 5, and the operation command means 1 of the compressor 1.
Issue an ON-OFF command to 9. The electric expansion valve driving means 20 and the hot gas control valve driving means 21 each operate the electric expansion valve 3 based on the output of the control means 18.
0, the hot gas control valve 5 is driven to the desired opening degree. The compressor operation command means 19 controls the refrigerating capacity by turning the compressor 1 ON and OFF based on the output of the control means 18.

When the refrigeration system is operating at full capacity, the control device 31 issues an operating command to the compressor 1 and also issues a fully close command to the hot gas control valve 5. The electric expansion valve 30 has a target that the degree of superheat of the refrigerant at the outlet of the evaporator 4 is constant.
The opening is adjusted so that it becomes SH. This target SH is selected to be a value that allows the evaporator 4 to exhibit its maximum capacity, and is set to about 5 degrees Celsius in a normal refrigeration system.

When the temperature of the blown air that has passed through the evaporator 4 falls to near the set temperature Ts set in the temperature setting device 10 and the cooling load becomes smaller, capacity control operation is performed and the blown air temperature sensor 8 detects the temperature. The opening degree of the hot gas control valve 5 is adjusted so that the temperature of the blown air becomes the set temperature Ts.

The control range of the cooling capacity will be explained with reference to FIG.

When the hot gas control valve 5 is fully closed, the cooling capacity changes as shown by line P as the degree of superheat increases (that is, the opening degree of the electric expansion valve 30 decreases), and when the hot gas control valve 5 is fully opened, the cooling capacity changes as shown by the P line. In this state, the cooling capacity changes as shown by the Q line as the degree of superheating increases. Therefore, the opening degree of the electric expansion valve 30 is adjusted to
When the detected SH at the outlet of the refrigeration system is controlled so that it is at a constant and appropriate degree of superheating, the electric expansion valve 30 is almost fully opened during hot gas bypass operation, allowing the liquid refrigerant to flow to the maximum extent, so that the cooling capacity of the refrigeration system can be varied. The range is a range O controlled by adjusting the opening of the hot gas control valve 5. However, if the degree of superheating is increased by decreasing the opening degree of the electric expansion valve 30, the variable range of the cooling capacity will be reduced by the hot gas control valve 5.
The P line indicates the capacity when fully closed, and the Q line indicates the capacity when fully open.
The range R is between the lines, and can accommodate a wide range of cooling loads. In other words, since it is possible to narrow down the opening of the electric expansion valve 30 to a smaller opening between lines A and D in FIG. 12, it is possible to continuously and finely control the cooling capacity even smaller than line D. .

FIG. 5 is a diagram showing temporal changes in the opening degree of the hot gas control valve 5 and the temperature of the blown air when the target SH is changed by controlling the opening degree of the electric expansion valve 30 during capacity control operation. When the target SH is kept constant as shown by line C, as the cooling load decreases, the opening degree of the hot gas control valve 5 increases as shown by line B, and even if the hot gas control valve 5 is fully opened, Note that when the cooling capacity is large, the cooling capacity of the refrigeration system and the cooling load are not balanced, and the temperature of the blown air decreases as shown by line A, making it impossible to maintain the set temperature Ts.

However, the opening degree of the hot gas control valve 5 is not the predetermined opening degree.
becomes larger than OH, and the blowing air temperature reaches the set temperature.
When the temperature drops below the point TL, which is slightly lower than Ts, the target SH is gradually made larger than the appropriate superheat degree C (that is, the opening degree of the electric expansion valve 30 is made smaller) as shown by line C'. Then, the cooling capacity gradually decreases, and the opening degree of the hot gas control valve 5 balances with the cooling load at an appropriate opening degree as shown by line B', and as a result, the blowing air temperature is set as shown by line A'. temperature
Ts can be maintained.

Next, contrary to the above, when the cooling load is large, the opening degree of the hot gas control valve 5 becomes smaller than the opening degree OL, which is slightly smaller than the above-mentioned OH, and the blowing air temperature reaches a point TH or higher, which is slightly higher than the set temperature Ts. If it rises, the target SH is gradually increased as shown by line F (that is, the opening degree of the electric expansion valve 30 is increased).
As the cooling capacity increases, the opening degree of the hot gas control valve 5 gradually decreases as shown by line E, and the cooling load is balanced at an appropriate opening degree, and as a result, the blowing air temperature becomes as shown by line D. The set temperature Ts can be maintained again as shown.

A second embodiment of the invention is shown in FIGS. 6 and 7.

In the first embodiment, in order to increase or decrease the cooling capacity during capacity control operation, the target SH is changed by a predetermined amount every predetermined period of time, but instead of changing the opening degree of the electric expansion valve 30 to the current opening. A similar effect can be obtained by changing the amount by a predetermined amount at predetermined time intervals.

In FIG. 6, 22 is superheat degree comparison determining means;
23 is an electric expansion valve control method switching means, 24 is an electric expansion valve opening determining means, and 25 is an electric expansion valve opening increasing/decreasing means. The rest is the same as that shown in FIG. 2, and corresponding members are given the same reference numerals.

As shown in FIG. 7, when the opening degree of the hot gas control valve 5 exceeds the predetermined range, the detected
has not been reached and the temperature deviation ΔT is smaller than a predetermined value, the opening degree of the electric expansion valve 30 is reduced by a predetermined amount, and the timer of the timer 17 is set. When the opening degree of the hot gas control valve 5 is within a predetermined range, the opening degree of the electric expansion valve 30 is maintained as before. If the opening degree of the hot gas control valve 5 is below the predetermined range, the detected SH has not reached the lower limit SH,
And when the temperature deviation ΔT is larger than the predetermined value,
The opening degree of the electric expansion valve 30 is increased by a predetermined amount, and the timer of the timing means 17 is set. Furthermore, if the detected SH has reached the upper limit SH or the lower limit SH, the opening degree of the electric expansion valve 30 is not made smaller or larger, but the target SH is set to the upper limit SH or the lower limit SH, and the electric expansion is performed. Controls the valve 30.

In the first and second embodiments described above, both the opening degree of the hot gas control valve 5 and the blowing air temperature are compared with preset conditions as a means of detecting the cooling load during capacity control operation. It is also possible to compare only one of them. Furthermore, the control of the electric expansion valve 30 during the capacity control operation gradually changes the target SH or the opening degree of the electric expansion valve 30 according to the cooling load, from the optimum superheat degree constant value control during the full capacity operation. As a simple method, the target SH can be set to a value considerably larger than the optimum degree of superheating so that the opening degree corresponds to the capillary of the conventional system, or the opening degree of the electric expansion valve 30 can be set to a value corresponding to the degree of superheating. It may be fixed at the opening degree. As a result, the capacity control range can be expanded compared to when only optimum superheat degree constant value control is performed.

A third embodiment of the invention is shown in FIGS. 8 and 9.

In this third embodiment, in order to detect the cooling load during capacity control operation, the temperature deviation ΔT' (outside air temperature - set temperature) is compared with a preset condition. As shown in FIG. 8, the outside air temperature detected by the outside air temperature sensor 26 and the set temperature set by the temperature setting device 10 are input to the cooling load determination means 29, and if the temperature deviation ΔT' between the two is smaller than a predetermined value, For example, assuming that the cooling load is small, a switching signal to high superheat degree control is issued to reduce the cooling capacity. The superheat degree comparison means 27 detects the target SH (usually the same optimal superheat value as during full capacity operation, or a high superheat value if there is a high superheat degree control command from the cooling load determination means 29) and the superheat degree detection means 11. The deviation from the target SH is detected and outputted to the electric expansion valve opening determining means 28. Other functions are similar to those shown in FIG. 2. In this way, although it is necessary to provide the outside air temperature sensor 26, the outside air temperature, the cooling load, and the cooling capacity control range of the refrigeration system can be known in advance, and the blowing air temperature can be adjusted to the set temperature during normal capacity control operation. It can be converged quickly. Further, in this third embodiment, the target SH is switched to a high degree of superheat when the cooling load is small, but the opening degree of the conductive expansion valve 30 may be changed to correspond to the degree of superheat. Furthermore, in preparation for the problem that there is no cooling load balance point within the cooling capacity control range during high superheat control regardless of outside temperature conditions, and the outlet air temperature rises, the temperature deviation ΔT (outlet air temperature - set temperature) is calculated. ) becomes larger than a predetermined value, a function may be added that returns the target SH to the same degree of superheating (optimum degree of superheating) as during full capacity operation.

In all of the above explanations, the temperature of the outlet air of the evaporator 4 is detected as the air temperature to be controlled, but it goes without saying that the intake air temperature of the inlet of the evaporator 4 may also be detected. Nor.

(Effect of the invention) The control device of the invention fully closes the hot gas control valve when the temperature deviation between the temperature to be controlled and the set temperature is equal to or higher than a predetermined value, and also controls the electric expansion valve to control the refrigerant at the outlet of the evaporator. a first control system that adjusts the opening of the hot gas control valve so that the degree of superheating becomes a constant value; and a second control system that adjusts the opening of the hot gas control valve according to the temperature deviation when the temperature deviation is within a predetermined value. , when the opening degree of the hot gas control valve whose opening degree is adjusted by the second control system exceeds a predetermined range, the control target value of the refrigerant superheat degree is changed, and the electric expansion valve is controlled to increase or decrease the cooling capacity. Since it is equipped with a third control system that adjusts the opening, when the temperature deviation between the temperature to be controlled and the set temperature is greater than a predetermined value, the opening of the electromagnetic on-off valve is adjusted with the hot gas control valve fully closed. The refrigeration system is operated at full capacity by adjusting the degree of superheat of the refrigerant at the outlet of the evaporator to a constant value. When the temperature deviation is within a predetermined value, the capacity of the refrigeration system is controlled by adjusting the opening degree of the hot gas control valve according to the temperature deviation. When the opening degree of the hot gas control valve exceeds a predetermined range during this capacity control operation, the control target for the refrigerant superheat degree is changed and the opening degree of the electromagnetic on-off valve is adjusted to increase the capacity of the refrigeration system. control.

As a result, the capacity control range is expanded, and in particular, the capacity can be continuously controlled even when the load is small, and precise temperature control becomes possible. In addition, since the flow rate of liquid refrigerant can be suppressed to the necessary minimum during capacity control, input to the compressor can be reduced. Furthermore, since there is no need to switch the aperture as in the conventional case, the refrigerant circuit can be simplified and its cost can be reduced.

[Brief explanation of the drawing]

Figures 1 to 5 show one embodiment of the present invention; Figure 1 is a system diagram of the refrigeration system, Figure 2 is a control block diagram, Figure 3 is a control flowchart, and Figure 4 is a diagram of the degree of superheating. FIG. 5 is a diagram showing the relationship with cooling capacity, and FIG. 5 is a diagram showing temporal changes in target superheat degree, hot gas control valve opening degree, and blowing air temperature during capacity control operation. 6 and 7 show a second embodiment of the present invention, with FIG. 6 being a control block diagram and FIG. 7 being a control flowchart. 8 and 9 show a third embodiment of the present invention, with FIG. 8 being a control block diagram and FIG. 9 being a control flowchart. 10th
Figures 1 to 12 show an example of a conventional refrigeration system, Figure 10 is a system diagram, Figure 11 is a diagram showing temporal changes in outlet air temperature, and Figure 12 is a diagram showing cooling load and cooling with respect to outside air temperature. It is a line diagram showing changes in ability. Compressor...1, Condenser...2, Electric expansion valve...
30. Evaporator...4. Hot gas bypass circuit...
...3. Hot gas control valve...5. Temperature deviation detection means...14. Superheat degree comparison means...11. Electric expansion valve opening degree determination means 13, 24, 28.

Claims (1)

[Scope of utility model registration request] In a refrigeration system comprising a refrigeration cycle including a compressor, a condenser, an electric expansion valve, and an evaporator, and a hot gas bypass circuit having a hot gas control valve that guides discharged gas from the compressor to the evaporator, the temperature to be controlled is and a set temperature, the hot gas control valve is fully closed, and the opening of the electric expansion valve is adjusted so that the degree of superheating of the refrigerant at the outlet of the evaporator becomes a constant value. a control system; a second control system that adjusts the opening of the hot gas control valve according to the temperature deviation when the temperature deviation is within a predetermined value; and the hot gas whose opening is adjusted by the second control system. A third control system that changes the control target value of the refrigerant superheat degree and adjusts the opening degree of the electric expansion valve to increase or decrease the cooling capacity when the opening degree of the control valve exceeds a predetermined range. Characteristic control device for refrigeration equipment.