JPH0130075B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention has a temperature control function that maintains the quality of frozen products by increasing the temperature inside the freezer as much as possible.
In particular, the present invention relates to the configuration of a refrigeration system suitable for marine refrigerated containers.

(Prior art) Refrigeration equipment for marine refrigerated containers is different from general land-based refrigeration equipment because it is used under conditions where the outside air temperature fluctuates over a wide range, for example from 50°C to -40°C. In particular, when operating in an extremely low temperature range such as -40℃ outside air temperature, special operation control as described below is performed to prevent liquid from returning to the compressor. It is necessary to do this, and this is known in the art.

That is, in a known refrigeration cycle consisting of a compressor, a condenser, a pressure reducer, such as an expansion valve, and an evaporator, a liquid pipe (referring to both high-pressure and low-pressure liquid pipes) connects the outlet of the condenser and the inlet of the evaporator. A liquid-side solenoid valve is installed in the middle of the refrigeration process, and a pressure detector is installed in the low-pressure gas pipe to detect low pressure and pressure. Prior to interrupting the operation, the liquid side solenoid valve is closed while the compressor is still running, and the refrigerant on the low pressure side is sucked in and sent to the condenser side, maintaining the low pressure side in a diluted gas state close to vacuum. The pressure sensor detects a low limit pressure and operates to stop the compressor, and this is called pump-down operation.

By performing pump-down operation in this way, it is possible to eliminate the inconvenience of liquid refrigerant being sucked in when the compressor is restarted, but when the outside temperature is in the extremely low range, the pressure in the low-pressure gas pipe may For example, when CFC R-12 is used as a refrigerant, the pressure of 400 mm of mercury (-50°C) is maintained for a long time and the compressor can be started, for example, 0.2 kg/cm ² As a result, it takes a long time for the refrigeration system to rise to a certain temperature, and as a result, the operation interruption time of the refrigeration equipment becomes considerably longer than in the normal case.

However, in order to average the temperature of the atmosphere inside the freezer, the blower device, which consists of a fan directly connected to the motor, continues to operate.
The heat generated by the motor becomes a heat load and the temperature inside the refrigerator gradually rises.The temperature inside the refrigerator becomes higher than the set temperature and the compressor does not restart even though refrigeration operation is required. As a result, the range of temperature changes inside the freezer becomes large, which leads to problems that adversely affect the quality of stored products.

(Problems to be Solved by the Invention) Therefore, as disclosed in Japanese Utility Model Application Publication No. 55-172779, except for a part of the fans, the other fans are stopped in conjunction with the compressor. There is a system that starts and stops the fans in the refrigerator intermittently, but this can achieve the purpose of reducing the heat load and suppressing the rise in temperature inside the refrigerator, but the heat load still exists. This cannot be said to be a perfect solution, since an increase in temperature is unavoidable, and since the average circulating air volume is considerably reduced, there is a risk that the temperature inside the refrigerator will become uneven.

In view of these problems, the present invention has been made to provide a refrigeration system that can eliminate the drawbacks of conventional systems, and the present invention has been developed to provide a refrigeration system that can eliminate the drawbacks of conventional systems. The feature is that the operation of the freezer is continued for a permissible limit, and the rest is completely stopped, thereby eliminating heat load, thereby contributing to maintaining a stable temperature inside the freezer and realizing energy savings.

(Means for Solving the Problems) As is clear from FIG. 1 showing its configuration, the present invention has a compressor 1, a condenser 2, a pressure reducer 3, and an evaporator 4 for cooling the inside of the freezer. A refrigeration cycle, a liquid side electromagnetic valve 5 which is interposed in a liquid pipe of the refrigeration cycle and can open and close the pipe, and a blower device 6 which is attached to the evaporator 4 and is energized by a motor.
, solenoid valve control means 7 , and low pressure detection means 15
, compressor control means 8, and blower control means 9 constitute a refrigeration system.

The solenoid valve control means 7 is configured to detect the internal temperature of the freezer and open/close the liquid side solenoid valve 5 so as to control the temperature to a set temperature.

The low pressure detection means 15 has a two-stage set value of a set pressure and a lower limit pressure, and detects the low pressure of the refrigeration cycle and detects when the detected pressure reaches the set pressure due to an increase. The configuration is such that the first output is generated during the period from when the pressure decreases to the limit pressure, and the second output is generated during the period from when the limit pressure is reached due to the decrease until the pressure rises to the set pressure.

On the other hand, the compressor control means 8 generates a drive output for driving the compressor 1 by the first output generated after the liquid side solenoid valve 5 is opened by the operation of the solenoid valve control means 7. The compressor 1 is configured to generate a stop output for stopping the compressor 1 during pump-down operation by the second output generated after the liquid side solenoid valve 5 is closed.

Further, the blower control means 9 calculates the logical product of the condition under which the compressor control means 8 is issuing a stop output and the condition under which the solenoid valve control means 7 opens the liquid side solenoid valve 5. Therefore, it has a configuration in which the blower device 6 is forcibly stopped at the front.

(Function) The present invention uses the liquid-side solenoid valve 5, the solenoid valve control means 7 to switch to the valve-closing output, and the compressor control means 8 to switch to the stop output when the refrigeration operation is automatically stopped. Since the pump down operation is performed, liquid compression at the time of restart is prevented.

Furthermore, the present invention operates the air blower 6 while the compressor 1 is forced to stop until a low pressure and force condition that allows restarting is reached when the outside temperature drops, and the air blower 6 is operated until the temperature inside the refrigerator rises from the set temperature. The internal temperature distribution is averaged, and if there is a risk of the internal temperature rising, the blower device 6 is completely stopped to eliminate the heat load, making it possible to maintain stable internal temperature and reduce power consumption. be.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a circuit diagram of a refrigeration system used in marine refrigerated containers, in which 1 is a compressor;
2 is an air-cooled condenser having a blower 13; 3 is a pressure reducer, such as an expansion valve; 4 is an evaporator for cooling the freezer 10; 12 is an accumulator;
A known refrigeration cycle is formed by connecting each of these devices to a cycle in the order described.

Reference numeral 6 denotes a blower device attached to the evaporator to circulate cold air into the freezer, and includes a motor 6.
Two fans 6A directly connected to AM and 6BM,
6B.

Reference numeral 5 designates a liquid-side solenoid valve that is installed in the liquid pipe of the refrigeration cycle, in the middle of a high-pressure liquid pipe that connects the condenser 2 outlet and the expansion valve 3 inlet, and is capable of opening and closing this liquid pipe. .

On the other hand, 14 is a temperature detection sensor provided on the air suction side of the evaporator 4, and is designed to measure the atmospheric temperature in the freezer 10 as a representative of the temperature of the suction air.

Reference numeral 15 denotes a low-pressure force switch as a low-pressure pressure detection means in which a pressure sensitive part is branch-connected to the suction pipe connected to the suction port of the compressor 1. The output contact (corresponding to the stop output) that opened when the set pressure of 0.2Kg/cm ² (temperature conversion: -21℃) was reached in the process of increasing the low pressure force.
is closed (corresponding to the drive output), and a low pressure force descends in this closed state to reach the limit pressure of 400 mercury columns.
mm (-50℃ in terms of temperature), and operates to open the output contact that is currently closed when the pressure reaches the limit pressure.The electrical signal caused by the opening and closing of this output contact is The signal is input to the controller 11 as a control signal.

The temperature detection signal from the sensor 14 is inputted to the controller 11 as a control signal in the same way as the low-pressure force switch 15, and the temperature control section in the controller 11 receives the temperature detection signal from the sensor 14. For example, when the internal temperature of the freezer 10 rises and reaches -17°C, which is the upper limit of the set temperature, the L level output (corresponding to the valve closing output) is changed to the H level output (corresponding to the valve opening output). Equivalent to)
, and hold this H level output until just before the temperature inside the refrigerator drops and reaches the lower limit of the set temperature of -18℃, and when this lower limit is reached, the H level output is
The level output is switched to the L level output, and it is formed into a so-called flip-flop circuit.
Furthermore, the temperature control section is equipped with a switching circuit separate from the flip-flop circuit, and when the internal temperature rises beyond the upper limit (-17°C) and reaches a slightly higher limit temperature, for example -16°C, It was formed so that the H level output that was emitted was switched to an L level output.

An outline of the electric control circuit that controls the operation of the refrigeration system, including the controller 11, is shown in FIG.
The motor 13M has a coil 17c and a normally open contact 17a.
The motors 6AM, 6BM of each of the fans 6A, 6B are driven by the closing of a main magnetic switch 17 having a coil 18AC, a first magnetic switch 18A having a coil 18AC, a first magnetic switch 18A having a coil 18BC, and a first magnetic switch 18A having a coil 18AC.
It is actuated by closing the second magnetic switch 18B having a .

The coil 17c is connected to the output terminal of the controller 11 via the output contact of the low pressure force switch 15 in series, while the coil 18AC, the coil 18BC and the solenoid 5S of the liquid side solenoid valve 5 are connected to the output terminal of the controller 11, respectively. connected to the output terminal.

In addition, in Fig. 3, 16 is the operation switch, 17a
is used as an auxiliary contact for indirectly transmitting the operating state of the output contact of the low-pressure force switch 15 to the controller 11, and 19 indicates a step-down type transformer.

Next, Figures 2 and 3 and controller 1
The operation control of the refrigeration system will be explained based on the flowchart of FIG. 4 showing the operation mode of No. 1.

With the operation switch 16 turned on, the low pressure and force switch 15 closes the output contact (low pressure and force
When it is 0.2Kg/cm2 or ^more . ), and freezer 10
The temperature inside is higher than -17℃ and controller 11
If the internal temperature control section emits an H level output,
The main magnet switch 17 is turned on by closing the output contact, and the solenoid 5S is energized by the H level output, and the liquid side solenoid valve 5 is opened.

In this way, the compressor 1 and the blower 13 are driven, and the two fans 6A and 6B are also driven at the same time, so that the refrigeration system enters steady operation and the temperature inside the refrigerator decreases (step (a)).

The temperature control section checks the temperature (step (B)), and when the intake air temperature (IT) falls to the lower limit of the set temperature (ST = -18°C), the H level output changes. Since it switches to L level output,
Close the liquid side solenoid valve 5 (step (c)).

This step (c) corresponds to the operation of the electromagnetic valve control means 7.

In this way, the compressor 1 performs a pump-down operation in which the low-pressure refrigerant is sucked, compressed, and sent to the condenser 2 side, so that the low-pressure force gradually decreases, and the compressor 1
When the suction side becomes a lean gas state and the low pressure force reaches the limit pressure of 400 mm of mercury, the low pressure force switch 15
Since the output contact of the compressor 1 is opened (step (d)), the compressor 1 is stopped (step (e)).

Therefore, the pump down operation is completed and the liquid side solenoid valve 5
is closed and the refrigeration system stops with the low pressure maintained at the critical pressure, but the fans 6A and 6B remain driven to equalize the temperature distribution of the air inside the refrigerator.

Note that step (d) corresponds to the operation of the low pressure detection means 15, and step (e) corresponds to the operation of the compressor control means 8, respectively.

The temperature control section of the controller 11 checks the temperature (step (F)), and the suction air temperature (IT) reaches the upper limit of the set temperature (S.T + 1°C = -17°C).
℃), the L level output is switched to the H level output, so the liquid side solenoid valve 5 is opened (step (T)).

This step corresponds to the operation of the electromagnetic valve control means 7.

Next, it is checked whether the output contact of the low-pressure force switch 15 has switched to closing due to the pressure increase (step (ch)), and if it has switched to closing, the compressor 1 is driven. Then, the system returns to the initial steady operation and starts the refrigeration movement again (step (a)).

Compressor 1 in this step (ch) and step (a)
The driving corresponds to the operation of the compressor control means 8.

On the other hand, if the outside air temperature has dropped extremely to around -40°C and the low pressure remains low, the temperature control section will check the inside temperature (step (re)). ), the suction air temperature (IT)
is higher than the set temperature rise value (S.T+
2°C = -16°C), the compressor 1 is stopped and both the fans 6A and 6B are kept running; however, if the temperature has reached the limit temperature, the fans 6A, Stop 6B (step (N)).

In this way, the temperature inside the refrigerator increases due to the heat load caused by the operation of fans 6A and 6B, and under conditions where the outside air temperature is extremely low and there is no heat penetration, and the compressor 1 does not restart, fan 6A , 6B, the refrigerating load can be eliminated and the temperature rise can be suppressed.

Note that steps (ch) to (n) correspond to the operation of the blower control means 9.

Thereafter, when the check in step (ch) is repeated and the output contact of the low-pressure force switch 15 is closed, the compressor 1 is driven, and at the same time both fans 6A,
6B is driven to return to normal operation (step
(stomach)).

In the embodiment described above, the check of the limit temperature (-16°C) in the blower control means 9 is detected by a temperature detection sensor. In this embodiment, a timer is used as a transmitter for checking the temperature limit instead of the sensor.

To explain the control mode in this embodiment, steps (A) to (G) are the same as in the above-mentioned embodiment, and in step (T), the liquid side solenoid valve
The timer is activated in response to the opening of the timer (step).

By the way, the set time limit of the timer is determined at the time of designing the refrigeration system, and is based on the lowest outside temperature in the area where the refrigeration system is operated and the freezer 10.
The time required for the temperature inside the refrigerator to rise by 1°C from the temperature (-17°C) when the liquid side solenoid valve 5 is opened is calculated based on the conditions such as the insulation performance of the refrigerator wall and the heat load of the fans 6A and 6B. This is then used as the time limit for setting the timer.

After the timer has started counting, the state of the output contact of the low-pressure force switch 15 is checked (step (H)), and if it has been switched to closing, the timer is reset and activated (step (W)). ) and at the same time,
The compressor 1 is driven to return to the initial steady operation (step (a)).

On the other hand, if the outside temperature is extremely low and the low pressure remains low, the current state is maintained until the timer counts up, and the timer counts up (step (wa)). Therefore, both fans 6A and 6B are stopped (step (N)).

Thereafter, when the check in step (ch) is repeated and the output contact of the low-pressure force switch 15 is closed, the compressor 1 is driven and at the same time the fans 6A, 6
B is driven and normal operation is returned (step (a)).

It is also possible to form the above-mentioned timer with an electronic timer circuit and have an automatic adjustment function that uses the outside air temperature as a parameter and lengthens the set time period when the outside air temperature is low, and shortens it when the outside air temperature is high. Either the timed type or the variable setting timed type may be selected at any time.

In the embodiment described above, as a forced stop condition for the blower device 6 in the blower device control means 9, the inside of the refrigerator rises to a limit temperature slightly higher than the set temperature upper limit value for opening the liquid side solenoid valve 5. However, the present invention may be such that the forced stop of the blower device 6 is linked to the opening of the liquid-side solenoid valve 5, and in this case, as a matter of course, The compressor control means 8 generates a drive output to drive the compressor 1, and at the same time, the blower device 6 is driven.

(Effects of the Invention) As is clear from the above description, the present invention has the following effects:
If the temperature of the freezer rises above the set temperature while the compressor 1 is forced to stop until the pressure and force conditions are low enough to restart it when the outside air temperature drops, the air blower that was being operated will be turned off. Since the device 6 is completely stopped, it is possible to maintain a stable temperature inside the refrigerator by dissipating the heat load that causes the temperature to rise, and it is also possible to reduce running costs, and to maintain the quality of stored items in the refrigerator and improve operation. This will have the effect of killing two birds with one stone and improving the economy.

Furthermore, in the present invention, in a conventional refrigeration system that enables pump-down control, it is only necessary to electrically connect the blower device 6 to a detector that detects the temperature inside the refrigerator, so the cost required for improvement is low. It is great because it is rich in general-purpose value.

[Brief explanation of drawings]

FIG. 1 is a block diagram clearly showing the configuration of the present invention, FIG. 2 is a device circuit diagram according to an embodiment of the present invention, FIG. 3 is an electric circuit diagram, and FIGS.
The figure is a flowchart showing the operation control mode in each embodiment of the present invention. 1...Compressor, 2...Condenser, 3...Compressor,
4...Evaporator, 5...Liquid side solenoid valve, 6...Blower device, 7...Solenoid valve control means, 8...Compressor control means, 9...Blower device control means, 15...Low pressure detection means.

Claims (1)

[Scope of Claims] 1. A refrigeration cycle having a compressor 1, a condenser 2, a pressure reducer 3, and an evaporator 4 for a freezer, and a liquid interposed in a liquid pipe of the refrigeration cycle and capable of opening and closing the pipe. a side solenoid valve 5; a blower device 6 attached to the evaporator 4 and energized by a motor; and a blower device 6 that detects the internal temperature of the freezer and controls the liquid side solenoid valve 5 to control the temperature to a set temperature. It has a solenoid valve control means 7 for opening and closing, and a two-stage set value of a set pressure and a lower limit pressure, and detects the low pressure of the refrigeration cycle and the detected pressure reaches the set pressure by rising. a low-pressure pressure detection means 15 that generates a first output from the time the pressure reaches the limit pressure until the pressure decreases to the limit pressure, and generates a second output from the time the pressure reaches the limit pressure due to lowering until the pressure rises to the set pressure; A driving output for driving the compressor 1 is generated by the first output generated after the liquid side solenoid valve 5 is opened by the operation of the solenoid valve control means 7; said second occurring after
compressor control means 8 that generates a stop output that stops the compressor 1 during pump-down operation according to the output;
The above condition is determined by the logical product of the condition in which the compressor control means 8 is generating a stop output and the condition in which the solenoid valve control means 7 is in operation to open the liquid side solenoid valve 5. A refrigeration system comprising a blower control means 9 for forcibly stopping the blower 6 completely.