JPS60175970A - Refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vapor compression type refrigeration system in which operating conditions vary widely.

[Prior art]

Conventionally, a vapor compression type refrigeration system has been generally used, which is equipped with a refrigeration cycle having a compressor, a condenser, a throttling device, and an evaporator. The compressor sucks in the refrigerant gas, which compresses it and sends it to the condenser.
As the specific volume of refrigerant gas drawn into the compressor becomes smaller, the amount of refrigerant circulated increases. The specific volume of the suction refrigerant gas decreases as the suction pressure of the compressor increases.

Therefore, as the suction pressure increases, the amount of refrigerant circulation increases. Further, the required power of the electric motor that drives the compressor (hereinafter referred to as required power) increases in proportion to the amount of refrigerant circulation.

There is a proportional relationship between the amount of refrigerant circulation and the refrigeration capacity. As shown in FIG. 1, a steam compression type refrigeration system has a characteristic that its refrigeration capacity and required power increase in proportion to the suction pressure of the compressor.

By the way, 1. For example, in a freezing device for quick freezing.

The temperature and quality of the freezing chamber fluctuate significantly between the start of operation and the completion of freezing. Therefore, the evaporation temperature of the refrigerant in the refrigeration system also varies significantly. Considering the case where the evaporation temperature is high, the refrigerating capacity and required power are large. Therefore, a large capacity motor is required to drive the compressor.

Also, a condenser with large capacity is required.

Furthermore, the mechanical strength of a refrigeration system is an example of the discharge of a compressor.
The strength of the suction valve, crankshaft, connecting rod, etc. must also be high. When a refrigeration system that satisfies these conditions is operated, as cooling progresses and the evaporation temperature of the refrigerant decreases, the suction pressure decreases because the evaporation temperature and suction pressure are in a proportional relationship. In this state, the refrigerating capacity decreases and the required power decreases, so the compressor, electric motor, and condenser are under light load and do not exert their full potential. Therefore, the time required for freezing is correspondingly longer. Furthermore, the efficiency of electric motors decreases when the load becomes light, so the coefficient of performance also decreases. Another problem is that when using the same refrigeration equipment, the
In the Hz region, there was a drawback that the refrigeration capacity decreased.

[Summary of the Invention] This invention attempts to solve the above-mentioned conventional drawbacks, and by controlling the rotation speed of the electric motor that drives the compressor based on the suction pressure of the compressor, it is possible to solve the problem of large load fluctuations. It is an object of the present invention to provide a refrigeration device whose refrigeration capacity can be improved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In Figure 2, 1 is a compressor that compresses refrigerant gas, 2 is a condenser, 3 is an expansion valve that is a throttling device, and 4 is an evaporator, and these are connected in a closed loop via a pipe. This makes up the refrigeration cycle. 5 is an inverter that changes the frequency of the commercial power source and outputs it; 6 is a control unit that controls the inverter 5 according to the output of a pressure detection device 7 that detects the suction pressure of the compressor 1; the inverter 5 and the control unit 6;
These constitute a rotation speed control device for an electric motor (not shown) provided in the compressor 1. 8 is an electromagnetic contactor, and 9 is an overcurrent relay for protecting the motor, which is connected between the inverter 5 and the motor of the compressor 1 via the electromagnetic contactor 8.

The operation of the refrigeration system according to the embodiment configured as described above will be explained. When a power switch (not shown) is turned on, the electromagnetic contactor 8 closes and the output of the inverter 5 is supplied to the electric motor of the compressor 1, thereby driving the compressor 1. By this-
Cooling is performed by evaporating the refrigerant liquid in the evaporator 4. As the cooling progresses, the evaporation temperature of the refrigerant in the evaporator 4 decreases,
The suction pressure of the refrigerant gas in the compressor 1 decreases. The pressure detection device 7 detects this decrease in suction pressure, and the pressure detection signal given to the control section 6 decreases. The control unit 6 compares the pressure detection signal with a reference value, and controls the output frequency of the inverter 5 to become higher as the pressure detection signal becomes lower than the reference value. Therefore, as the suction pressure decreases, the output frequency of the inverter 5 increases.
, the rotation speed of the electric motor of the compressor 1 increases. That is, the decrease in the refrigerant circulation amount i due to the increase in the specific volume of the suction refrigerant gas accompanying the decrease in the suction pressure can be compensated for by increasing the rotational speed of the electric motor of the compressor 1, thereby suppressing a decrease in the refrigerating capacity.

The operating characteristics of the refrigeration system of this embodiment are shown by the solid line in FIG. 3, and the broken line in FIG. 3 shows the operating characteristics of the conventional refrigeration system for reference.

Note that the output frequency of the inverter 5 in this embodiment is adjusted to be high within a range that does not exceed the upper limit of the capacity of the compressor and its electric motor, so the compressor and electric motor will not be overloaded. do not have.

In addition, if defrosting is performed in the middle of cooling with the refrigeration equipment, the room temperature will rise significantly compared to the product temperature, so the product temperature and room temperature will not necessarily match. However, in order to prevent overload operation when the low pressure side pressure becomes extremely high, if a suction pressure adjustment valve is installed, the room temperature and the compressor suction pressure will not match, but the required power of the compressor and the suction The pressure relationship is always consistent. Therefore, control that detects suction pressure as in this example is superior to control that detects product temperature or room temperature.

〔Effect of the invention〕

As explained above, the refrigeration system of the present invention detects the suction pressure of one compressor using a pressure detection device, and when the detected pressure is high, the rotation speed of the electric motor that drives the compressor is reduced, and the detected pressure is When the rotation speed of the motor is low, the rotation speed of the motor is controlled to be increased by the rotation speed control device, so as cooling progresses and the suction pressure of the compressor decreases, the rotation speed of the compressor increases, and the refrigeration capacity is reduced. Decrease can be suppressed. This improves the refrigerating capacity in the low suction pressure range of the compressor, that is, in the low evaporation temperature range of the evaporator.

Therefore, when the refrigeration apparatus of the present invention is used for rapid freezing, the time required for freezing can be shortened. Furthermore, the refrigeration system of the present invention is highly efficient because the compressor, condenser, etc. always exhibit nearly 100% of their capacity no matter what the operating conditions are. Furthermore, in the refrigeration system of the present invention, the rotation speed of the electric motor of one compressor is determined by the suction pressure regardless of the frequency of the commercial power supply, so the decrease in capacity in the 15QHz area is eliminated, and even in this area, the same as in the 60Hz area. The effect of gaining abilities is obtained.

[Brief explanation of drawings]

FIG. 1 is an operating characteristic diagram of a conventional refrigeration system, FIG. 2 is a block diagram of a refrigeration system according to an embodiment of the present invention, and FIG. 3 is an operational characteristic diagram of the refrigeration system shown in FIG. 1...Compressor-2...Condenser-3...Expansion valve, 4
...Evaporator, ...Inverter 6...Control unit, 7
...Pressure detection device. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) 1st [Figure 2 Figure 3 Rii, So-

Claims (1)

[Claims] In a refrigeration system equipped with a refrigeration cycle having a compressor, a condenser, a throttling device, and an evaporator, a pressure detection device detects the suction pressure of the compressor, and if the detected pressure of this detection device is high, the compressor 1. A refrigeration system comprising a rotation speed control device that reduces the rotation speed of an electric motor that drives the refrigeration system and increases the rotation speed of the electric motor when the detected pressure is low.