JPH05113253A - Capacity control method of refrigerating device - Google Patents

Abstract

PURPOSE:To provide a capacity control method of a refrigerating device wherein a stable capacity control can be performed and reliability is high and fluctuation width of refrigeration capacity is small in a refrigerating device provided with a capacity control line which also serves as a relief line and has a line open-and- close means. CONSTITUTION:A capacity control method of a refrigerating device includes a capacity control line 5 which also serves as a relief line and has a solenoid valve 6 therein, wherein degree of opening of the solenoid valve 6 is controlled to a predetermined opening corresponding to a set temperature (target temperature) of a space or matter subjected to the temperature control of the refrigerating device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacity control method for a refrigeration system, and more particularly to a capacity control method for a refrigeration system provided with a capacity control circuit which also functions as a relief circuit and has circuit opening / closing means.

[0002]

2. Description of the Related Art A refrigerating device having a circuit control means and a capacity control circuit which also serves as a relief circuit is used in various fields. A typical example thereof will be described with reference to FIG. The refrigerating apparatus shown in FIGS. 4A and 4B is
Used in environmental test equipment such as incubators and thermo-hygrostats for investigating the characteristics and effects of various products and materials in certain temperature or humidity environments It has been done.

FIG. 1A shows a unitary refrigeration system. In this device, a refrigerant is compressed by a compressor 1 and then condensed by passing through a condenser 2, and then passes through an expansion mechanism 3 such as a capillary tube and an electronic expansion valve to be expanded while being expanded. After the heat is exchanged there, it is circulated so as to return to the compressor 1 again. On the other hand, a relief circuit / capacity control circuit 5 is provided in a bypass shape between the compressor discharge side and the suction side, and this circuit 5 includes an electromagnetic valve 6, a relief tank 7, and an expansion mechanism 8 such as a capillary tube. ing.

When functioning as a relief circuit, as described above, when the refrigerant pressure on the compressor discharge side reaches a predetermined abnormal pressure while the refrigeration system is operating, the high pressure switch 50 detects this. The solenoid valve 6 is opened based on the detected value. The evaporator 4 together with the heater 9 is installed in a test tank of an environmental testing device. While the evaporator 4 cools the inside of the test tank, the heater 9 is turned on in response to the heating heater signal from the temperature controller 10 to heat the inside of the test tank.
In this way, the test tank is controlled to the installation temperature (target temperature) by both cooling and heating, but the heater signal is output intermittently, and the solenoid valve 6 in the capacity control circuit is opened and closed in synchronization with this. Signal is output. That is, when the heater signal is output, the solenoid valve 6 is opened, and when the heater signal is off, the valve 6 is closed. Thus, when the heater is on, the refrigeration system is capacity controlled.

FIG. 4B shows a binary refrigeration system. In this device, 1A, 1B are compressors, 2A are condensers, 2B are cascade condensers, 3A, 3
B indicates an expansion mechanism and 4B indicates an evaporator. 5B shows a relief circuit and capacity control circuit. In this circuit, 6B is a solenoid valve, 7B is a relief tank, and 8B is an expansion mechanism. Further, 50B is a high pressure switch. In the figure, the refrigeration circuit on the right side may be provided with the relief circuit / capacity control circuit 5A as shown by the broken line, but it is not provided in this example. The evaporator 4B is installed in the test tank of the environmental testing device together with the heater 9 and is used for temperature control.

Also in this binary refrigeration system, the heater 9 is turned on and off based on the heater heater signal from the temperature controller 10, and in synchronization with this, the opening / closing signal of the solenoid valve 6B is also output, and the heater 9 is turned on. When it is on, the valve 6B is opened, when the heater 9 is off, the valve 6B is closed, and when the heater is on, the capacity of the refrigeration system is controlled.

[0007]

However, according to the conventional capacity control method for a refrigerating apparatus, the heating life of the heater is considered to be a major factor that determines the reliability of control because the mechanical life of the solenoid valve in the capacity control circuit is a major factor. Since the solenoid valve frequently opens and closes in synchronization with the output, there is a problem that the mechanical life of the solenoid valve is short.

At present, the mechanical life of a general solenoid valve is 500,000 times / rated, and even the long-life one has a mechanical life of 5 million times / rated. For example, in a device such as an environmental test device, such a capacity control method is adopted, and it is assumed that the solenoid valve in the capacity control circuit is turned on once every 5 seconds, and the annual equipment operation rate is halved for 1 year. Therefore, the life is only about 1.6 years even if the long life of 5 million times / rated is used.

Therefore, it is difficult to adopt such capacity control of the refrigerating apparatus in an apparatus such as an environmental test apparatus which is continuously operated for a relatively long time. Further, according to the conventional capacity control method, during low temperature control that requires the maximum refrigerating capacity, the fluctuation range of the refrigerating capacity becomes large due to the opening / closing operation of the solenoid valve in the capacity control circuit. There is a problem that the temperature (humidity) degree adjustment range becomes large.

Therefore, the present invention is a capacity control method for a refrigerating apparatus provided with a capacity control circuit having a circuit opening / closing means, which also functions as a relief circuit, and is capable of performing more stable capacity control than in the prior art and having high reliability. Another object of the present invention is to provide a method in which the fluctuation range of the refrigerating capacity is small.

[0011]

According to the above-mentioned object, the present invention provides a capacity control method for a refrigerating apparatus which is provided with a capacity control circuit which also functions as a relief circuit and which has a circuit opening / closing means. The present invention provides a capacity control method for a refrigerating apparatus, characterized in that the refrigerating apparatus is controlled to a predetermined opening degree according to a set temperature (target temperature) of a space or an object used for temperature control. ..

The opening / closing means of the capacity control circuit may be a single solenoid valve capable of controlling the opening to either fully closed or fully opened.
Alternatively, a plurality of solenoid valves having different opening degrees at full opening are connected in parallel, and one or more solenoid valves are fully opened or fully closed according to the set temperature (target temperature). Alternatively, it may be an automatic valve that is automatically adjusted to an opening degree according to the set temperature, that is, any opening valve that can obtain a predetermined opening degree according to the set temperature may be used as the entire opening / closing means.

In order to make the capacity control circuit function as a relief circuit, if abnormal pressure occurs in the refrigeration circuit,
It is assumed that the opening / closing means as a whole can obtain an opening degree capable of avoiding abnormal pressure.

[0014]

According to the method of the present invention, the circuit opening / closing means in the capacity control circuit is set in advance according to the set temperature (target temperature) of the space or object in which the refrigerating apparatus is subjected to temperature control during operation of the refrigerating apparatus. When the opening is fixed and is open, a part of the refrigerant flows into the capacity control circuit to perform the capacity control.

When an abnormal pressure is generated in the refrigeration circuit, the circuit opening / closing means is opened preferentially to the opening for avoiding this abnormal pressure.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a refrigeration system for carrying out the method according to the invention. This refrigeration system has the same hardware configuration as the refrigeration system shown in FIG. The same parts as those of the conventional device are designated by the same reference numerals. The evaporator 4 is installed in the test tank of the environmental testing device together with the heater 9.

In this apparatus, however, the heater 9 is turned on / off based on the heater signal from the temperature controller 10, but the solenoid valve 6 in the relief circuit / capacity control circuit 5 is the solenoid valve and the compressor. It is maintained in a fully open or fully closed state based on an instruction from the control unit 100. That is, the control unit 100 is configured as follows.

As shown in FIG. 1 (B), the set temperature in the test tank, which is notified from the temperature controller 10 for controlling the heater 9, is a temperature T1 lower than 0 ° C. and a temperature T2 higher than 0 ° C. In the range below, where the refrigerating capacity is relatively small, an instruction to open the solenoid valve 6 is issued, and an instruction to close the solenoid valve 6 when the set temperature is lower than T1. When it is high, the compressor 1 is stopped and the OFF signal is kept applied to the solenoid valve 6.

According to the refrigerating apparatus described above, the method of the present invention is carried out as follows. That is, when the set temperature in the test tank is T2 or less, the compressor 1 is operated and the refrigerator is operated. When the set temperature is in the range of T1 or more and T2 or less, the solenoid valve 6 in the capacity control circuit 5 is opened, whereby a part of the refrigerant flows into the capacity control circuit, and the capacity control is performed. Moreover, this capacity control is performed while the solenoid valve 6 is fixed in the open state, so that the mechanical life of the solenoid valve is extended by that amount, stable capacity control is performed for a long time, and the fluctuation range of the refrigerating capacity is increased. As a result, the width of temperature control in the test tank is also suppressed to be small.

When the set temperature is lower than T1, the solenoid valve 6 is closed based on the instruction from the control unit 100. Therefore, the refrigerant does not flow into the capacity control circuit, and the refrigerating apparatus can fully exert its capacity and contribute to the temperature control of the test tank. Also in this case, since the solenoid valve 6 is fixed in the closed state, the mechanical life of the solenoid valve is extended by that much, the refrigeration system operation is stable for a long time, the fluctuation range of the refrigeration capacity is suppressed to a small extent, and The temperature control width in the test tank is also suppressed to a small level.

When the set temperature is higher than T2, the compressor 1 is stopped based on the instruction from the control unit 100, and the operation of the refrigeration system is stopped accordingly. Further, the OFF signal is still applied to the solenoid valve 6. Therefore, in the case where the solenoid valve 6 is a normally open solenoid valve, the solenoid valve 6 is fixed in an open state, and in the case of a normally closed solenoid valve, it is fixed in a closed state. FIG. 2 shows another example of the refrigerating apparatus for carrying out the present invention. This refrigerating device is a binary refrigerating device and is substantially the same in hardware configuration as the refrigerating device shown in FIG. 4B, and the same parts are designated by the same reference numerals.

Also in this refrigeration system, the evaporator 4B is installed in the test tank of the environmental testing system together with the heater 9. Then, the heater 9 is turned on / off based on an instruction from the temperature controller 10, but the opening / closing of the solenoid valve 6B in the capacity control circuit 5B is performed based on an instruction from the compressor and a control unit 100 that controls the solenoid valve. Is done. Control unit 1
00 is the control unit 1 in the refrigerating apparatus shown in FIG.
The configuration is substantially the same as 00. Therefore, the method of the present invention performed in this refrigerating apparatus is also the same as the method of the present invention described with reference to FIG.

In both of the refrigerating apparatus of FIGS. 1 and 2, if the refrigerant pressure in the refrigerating circuit becomes abnormally high,
The high-pressure pressure switches 50 and 50B provided on the refrigerant discharge side of the compressors 1 and 1B are activated, and the control unit 100 causes the relief circuits 5 and 5B based on the abnormal pressure detection by the pressure switches.
Open the solenoid valves 6 and 6B inside to avoid a dangerous state. Thus, the opening of the solenoid valves 6 and 6B when the circuits 5 and 5B function as a relief circuit is preferentially performed regardless of the opening and closing of the solenoid valves for the capacity control.

Here, in the constant temperature bath shown in FIG. 3 using the refrigerating apparatus including the relief circuit and the capacity control circuit shown in FIGS. 2 and 4B, the conventional method and the method of the present invention are used as the capacity control method. When the error of the temperature inside the constant temperature bath with respect to the set temperature was investigated using, the following results were obtained. As can be seen from this result, according to the method of the present invention, it is possible to suppress the temperature adjustment range of the constant temperature bath to a small degree and obtain a desired temperature with high accuracy.

The "maximum fluctuation range with respect to the set temperature" shown below is that after the temperature in the tank reaches the set temperature and is sufficiently stable (about 1 hour in this example), the temperature is measured for about 30 minutes, Maximum temperature T (> set temperature) and minimum temperature t in the meantime
The half value (T−t) / 2 of the difference of (<set temperature) is represented by a width of ±. Maximum fluctuation range with respect to set temperature Constant temperature chamber Capacity control of the present invention Capacity control Conventional capacity control When using the method When using the method However, T1 = -18 ° C, T2 = 50 ° C + 50 ° C ± 0.06 ° C (valve 6B open) ± 0.13 ° C 0 ° C ± 0.05 ° C (valve 6B open) ± 0.18 ° C -40 ° C ± 0.09 ° C (valve 6B closed) ± 0.33 ° C -70 ° C ± 0.06 ° C (valve 6B closed) ± 0.51 ° C + 180 ° C ± 0.11 ° C (compressor stopped) ± 0.17 ° C Regarding conditions such as the dimensions of the constant temperature bath shown in FIG. 3, the capacity of the heater 9 and the freezing capacity of the refrigerating device Was as follows:

Details of constant temperature chamber of FIG. 3 Outer dimensions: width 940 × height 637 × depth 533 (m
m) Tank dimensions: width 406 x height 305 x depth 280 (m
m) Insulation layer: Glass wool (thickness 100 mm) Refrigeration system: Dual refrigeration system Compressor 400W each Rated refrigeration capacity 1500BTU / Hr (378Kcal / Hr) Relief tank capacity Present method 0.76 liter Conventional method 2.21 liter heater Capacity 500W Circulating air volume in the tank: 4m ³ / min or more Temperature control: PID control Temperature measurement: Position Tank central measuring tool Thermocouple (steel diameter 0.3mm) with a 5mm diameter steel ball at the tip Sample in the tank, shelf board None

[0027]

As described above, according to the present invention, there is provided a capacity control method for a refrigerating apparatus having a capacity control circuit which has a circuit opening / closing means and which also functions as a relief circuit. It is possible to provide a highly reliable method with a small fluctuation range of the refrigerating capacity.

[Brief description of drawings]

FIG. 1A is a circuit diagram of a unitary refrigerating apparatus for carrying out the method of the present invention, and FIG. 1B is an opening / closing state of a solenoid valve in a capacity control circuit in the refrigerating apparatus shown in FIG. It is a figure which shows the relationship between the set temperature in an environmental test apparatus test tank.

FIG. 2 is a circuit diagram of a binary refrigeration system for carrying out the method of the present invention.

FIG. 3 is a schematic cross-sectional view of a constant temperature bath used in an experiment for knowing the effect of the method of the present invention.

FIG. 4 (A) is a diagram for explaining a conventional method in a single refrigeration system, and FIG. 4 (B) is a diagram for explaining a conventional method in a dual refrigeration system.

[Explanation of symbols]

 1, 1A, 1B Compressor 2, 2A Condenser 3, 3A, 3B Expansion mechanism 4, 4B Evaporator 2B Cascade condenser 5, 5B Relief circuit and capacity control circuit 6, 6B Solenoid valve 7, 7B Relief tank 8, 8B Expansion Mechanism 50, 50B High pressure switch 9 Heating heater 10 Temperature controller 100 Valve control unit

Claims (1)

[Claims] 1. A method for controlling the capacity of a refrigerating apparatus that includes a capacity control circuit that also functions as a relief circuit and that has circuit opening / closing means, wherein the circuit opening / closing means of the capacity control circuit is used for temperature control of the refrigeration apparatus. A method for controlling the capacity of a refrigerating apparatus, comprising controlling the opening to a predetermined degree according to a set temperature of a space or an object to be cooled.