JPH0533737Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention relates to a refrigeration system suitable for cooling or frozen storage of foods and other items, and in particular, controls the rotation speed of a compressor to adjust and control the refrigeration capacity. Regarding possible refrigeration equipment.

[Technical background of the invention and its problems]

In general, this type of refrigeration system configures a closed refrigeration cycle by sequentially connecting a compressor 1, a condenser 2, a liquid receiver 3, an expansion mechanism 4, and an evaporator 5. , food is now stored chilled or frozen.

Some refrigeration cycles use a thermostatic expansion valve as the expansion mechanism 5. This temperature-type expansion valve is an expansion valve whose opening degree changes according to the refrigerant outlet temperature of the evaporator 5, and is adjusted so that the expansion valve opening degree increases as the outlet temperature of the evaporator 5 rises. be done.
That is, as the refrigeration load of the refrigeration cycle increases, the outlet temperature of the evaporator 5 increases, the expansion valve opening increases, the refrigerant flow rate increases, and as a result, the second
As shown in the figure, the suction pressure of the compressor 1 increases.

However, when the temperature-type expansion valve 4 is used to control the refrigerating capacity of the refrigeration system, the evaporation temperature changes in accordance with changes in the refrigeration load, so the humidity and temperature of the cooled material change. For this reason, there was a problem that it was not suitable for cooling or freezing articles that required constant temperature and constant humidity storage.

[Purpose of invention]

This idea takes the above points into consideration, and by detecting the suction pressure of the compressor and controlling the rotation speed of the compressor so that the suction pressure is constant, the evaporation temperature in the evaporator is kept constant, and the product is Constant temperature/humidity cooling,
The purpose is to provide a refrigeration device suitable for refrigeration.

[Summary of the idea]

In order to achieve the above-mentioned object, the refrigeration system according to the present invention adjusts the power supply frequency using a frequency converter and controls the rotation speed of the compressor. and a capacity control means for controlling the operation of the frequency converter so that the suction pressure is constant according to the output from the pressure detection means, and the power supply frequency from the frequency converter is adjusted and controlled by the capacity control means. This is what I did.

[Example of idea]

Hereinafter, embodiments of the refrigeration system according to this invention will be described with reference to the accompanying drawings.

FIG. 3 shows a refrigeration system according to this invention, which includes a compressor 10, a condenser 11,
Liquid receiver 12, temperature type expansion valve 1 as an expansion mechanism
3. A closed refrigeration cycle 15 for refrigerant circulation is constructed by sequentially connecting the evaporators 14. The refrigerant flowing in the refrigeration cycle 15 is subjected to an evaporation action in the evaporator 14, and this evaporation action absorbs heat to cool or freeze the article.

A pressure detector 16 is installed on the suction side of the compressor 10 of the refrigeration cycle 15 to detect the suction pressure of the refrigerant, and the pressure of the compressor 10 detected by the pressure detector 16 is
The suction pressure is output from a pressure transmitter 17 to a capacity control means 19 via an amplifier 18. The pressure detector 16 and pressure transmitter 17
The pressure detection means 20 is configured by the above.

The capacity control means 19 has a logic operation circuit 21 to which a suction pressure detection signal of the compressor 10 is input. A preset pressure signal is inputted from the pressure setting circuit 22 to this logical calculation circuit 21, and the two pressure signals are compared and calculated here. Further, a frequency setting signal is inputted from the frequency setting circuit 23 to the logic operation circuit 21, and the pressure difference signal subjected to the comparison calculation is set to a frequency signal corresponding to this pressure difference. The frequency converter 25 is outputted to control the operation of the frequency converter 25.

The frequency converter 25 converts the power frequency from the commercial power source 26 and controls the motor rotation speed of the compressor 10, and the discharge pressure is adjusted by controlling the rotation speed of the compressor 10. The suction pressure of the compressor 10 is adjusted and controlled to be maintained at a set pressure.

Next, the operation of this invention will be explained.

When the refrigeration load of the refrigeration equipment increases, the expansion valve 13
The opening degree of the valve increases, the refrigerant flow rate increases, and the suction pressure of the compressor 10 increases as shown in FIG. At this time, the increased suction pressure is detected by pressure detector 1.
6, the detection signal is input to the logic operation circuit 21, where it is compared with a preset set pressure, the degree of pressure increase with respect to the set pressure is calculated, and a calibration frequency signal corresponding to this degree of pressure increase is generated. The signal is output to the frequency converter 25, and the frequency converter 25 is controlled to increase the frequency so that the power supply frequency corresponds to the degree of pressure increase. This frequency conversion increases the rotational speed of the compressor 10 and increases the refrigerating capacity, thereby preventing the refrigerant evaporation pressure in the evaporator 14 from increasing.

Furthermore, when the refrigeration load of the refrigeration system decreases, the valve opening of the thermostatic expansion valve 13 decreases, and the suction pressure of the compressor 10 decreases, but this decrease in suction pressure is detected by the pressure detection means 20. The capacity control means 19 is operated in accordance with the pressure detection signal to control the operation of the frequency converter 25. This frequency converter 2
5, the power supply frequency is converted to reduce the motor rotation speed of the compressor 10, thereby reducing the refrigerating capacity. This prevents the suction pressure of the compressor 10 from decreasing.

In this way, this invention reduces the evaporation pressure from the evaporator 14 by controlling the operation so that the suction pressure of the compressor 10 is always equal to the set pressure regardless of fluctuations in the refrigeration load of the refrigeration cycle 15. This is to stabilize the evaporation temperature and prevent fluctuations in the evaporation temperature.

In general, in the case of refrigeration equipment that cools and freezes goods, compared to air conditioners, the evaporator 14 and condensing unit (condenser side unit) are located farther apart, and the refrigeration cycle has many refrigerant pipes. A branched multi-branch cycle or the like is installed, which is advantageous when it is difficult to control refrigeration load fluctuations on the evaporator 14 side.

In one embodiment of this invention, an example has been described in which a temperature-type expansion valve is used as the expansion mechanism, but a capillary tube may be used instead of this expansion valve.

[Effect of idea]

As described above, the refrigeration system according to this invention includes a pressure detection means for detecting the suction pressure of the compressor and an output from this pressure detection means.
If the suction pressure is higher than the set pressure, the frequency will be increased according to the degree of pressure increase relative to the set pressure, and if it is lower than the set pressure, the frequency will be lowered according to the degree of pressure relative to the set pressure. It has a capacity control means for controlling the operation of the frequency converter so that the pressure is constant, and the power supply frequency from the frequency converter is adjusted and controlled by this capacity control means, regardless of fluctuations in the refrigeration load of the refrigeration cycle. First, the evaporation pressure of the refrigerant from the evaporator can be kept constant, and as a result, the evaporation temperature of the evaporator can be kept constant at all times.

Therefore, in the case of a refrigeration system that generally consists of an outdoor unit equipped with a compressor and a condenser, and an indoor unit such as a show case equipped with an evaporator for cooling or frozen storage of food and other items, Since the operation of the refrigeration cycle can be controlled only by the outdoor unit, it is also suitable for equipment that cools or freezes and stores food and other items, each with different capacities depending on the load conditions and capacity of the installation location. It can be easily applied and is suitable for constant temperature/humidity cooling and refrigeration of articles.

In addition, since the evaporation temperature in the evaporator is controlled by detecting the suction pressure of the compressor, the control response characteristics are excellent, and the rotation speed of the compressor can be controlled quickly and reliably according to the refrigeration load. This has the effect that efficient operation control can be performed at all times.

[Brief description of the drawings]

Fig. 1 is a refrigeration cycle diagram showing a conventional refrigeration system, Fig. 2 is a graph showing the relationship between the refrigeration load of the refrigeration cycle and the suction pressure of the compressor, and Fig. 3 is an example of the refrigeration system according to this invention. FIG. 10... Compressor, 11... Condenser, 13... Temperature expansion valve, 14... Evaporator, 15... Refrigeration cycle, 16... Pressure calibrator, 17... Pressure transmitter, 19... Capacity Control means, 20...Pressure detection means, 21...Logic operation circuit, 22...Pressure setting circuit, 25...Frequency converter, 26...Commercial power supply.

Claims (1)

[Scope of utility model registration request] A refrigeration system that connects a compressor, condenser, expansion mechanism, and evaporator for load cooling in sequence to form a refrigeration cycle for refrigerant circulation, and also uses a frequency converter to adjust the power frequency and control the rotation speed of the compressor. The device includes a pressure detection means having a compressor suction pressure detector and a detected pressure signal transmitter, and receives a signal from the pressure detection means, compares it with a preset pressure, and calculates the suction pressure at the set pressure. If the pressure is higher than the set pressure, the frequency will be increased according to the degree of pressure increase relative to the set pressure, and if the pressure is lower than the set pressure, the frequency will be set so that the frequency is lowered according to the degree of pressure rise relative to the set pressure, so that the suction pressure remains constant. A refrigeration system characterized by comprising: a capacity control means for outputting a frequency setting signal for optimizing the compressor; and a frequency converter for adjusting and controlling the power supply frequency to the compressor based on the output signal from the capacity control means. .