JPS60223964A - 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 refrigeration system, and more particularly to an improvement of a refrigeration system that uses an inverter to control the rotation of a compressor.

[Prior art]

A refrigeration system having an inverter controls the rotation of an electric motor that drives a refrigerant compressor by varying the power frequency. By controlling the rotational speed of the compressor in this way, the refrigerating capacity can be changed continuously.

FIG. 1 is a block diagram showing an example of a refrigeration system having an inverter that has been commonly used in the past, in which fi+ is a compressor that compresses refrigerant, (2) is a condenser, (3) is an expansion valve, ( 4) is an evaporator, which constitutes a refrigeration cycle by being connected to a closed loop via a pipe line. (5) is an inverter that outputs a variable frequency of the commercial power supply, and 1 and (6) are inverters that respond to the output signal of the pressure detector (7) that detects the refrigerant pressure on the low pressure side of the compressor (1). This is a control unit that controls (5). (8) is −F
An electromagnetic contactor (9) is provided in the power line connecting the inverter (5) and the compressor (1), and an overcurrent relay (9) is also provided in series with the power line.

In the conventional refrigeration system configured as described above, when the power switch (not shown) is turned on, the wL magnetic contactor (8)
When the inverter (5) is closed, the electric power output from the inverter (5) is supplied to the electric motor (not shown) of the compressor fil, and the compressor 1 is operated. When compressed refrigerant flows through the refrigeration cycle by operating the compressor (1), cooling is performed by the evaporator (4) as is well known.

Here, when the refrigeration load decreases, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, and the pressure detection section (7)
The level of the pressure detection signal outputted to the control unit (6) also decreases. The control unit (6) compares the pressure detection signal with the reference value, so if the pressure detection signal is lower than the reference value, the control unit (6) controls the inverter 15) so that the output frequency is lowered. The egg cooling power is lowered by controlling the rotation speed of the compressor (1) to lower the rotation speed of the compressor (1). When the cooling capacity is lowered in this way, the refrigerant pressure on the low pressure side of the refrigeration cycle increases and converges to the set pressure.

Further, when the cooling load is high, the refrigerant pressure on the low pressure side of the refrigeration cycle increases, and the pressure detection signal output from the pressure detection section (7) to the control section (6) increases accordingly.

As a result, the control unit (6) controls the inverter (6) to increase its output frequency, and increases the rotational speed of the compressor (υ), thereby increasing the cooling capacity.

Therefore, in a refrigeration system having such an inverter (5), it is possible to control the cooling capacity according to the cooling load, and it is possible to save power.

However, in the conventional refrigeration equipment described above, when the refrigerant pressure fluctuates greatly, or when the refrigerant pressure is higher than the refrigerant pressure to be converged, such as at the start of operation or during pulldown after defrosting, the inverter (5) Since the setting time of the output frequency is constant, it takes a long time to reach the target refrigerant pressure, which increases the temperature change of the cooled object and has the disadvantage that the freshness of the cooled object cannot be maintained. Ta.

[Summary of the invention]

This invention solves the conventional problems as described above, and detects the refrigerant pressure on the low pressure side and converges the refrigerant pressure to a predetermined value. By controlling the output time of the inverter output frequency according to the difference, the predetermined pressure can be quickly reached even when pressure fluctuations are large or the cooling load is large such as at the start of operation or after defrosting, and the An object of the present invention is to provide a refrigeration system that can reduce power consumption.

[Embodiments of the invention]

FIG. 2 is a block diagram showing an embodiment of a refrigeration system according to the present invention, and the same parts as in FIG. 1 are indicated using the same symbols. In the figure, al is a frequency setting section, which sets the inverter output frequency according to the pressure difference between the pressure production signal output from the pressure detection section (7) and the refrigerant pressure that is about to be converged. . Further, CI+) is a time setting section, which is set by the frequency setting section (10) according to the pressure difference between the pressure detection/signal outputted from the pressure detection section (7) and the refrigerant pressure to be converged. (2) is a frequency output circuit that outputs a frequency output signal to the above-mentioned inverter +6), and it outputs the frequency set by the frequency setting section (IQ) over the above-mentioned time. Setting unit q It is configured to output during the time set in the cram school.In other words, the time setting unit (11
), the output time of the inverter output frequency can be freely changed according to the pressure difference between the pressure detection signal output from the pressure detection section (7) and the refrigerant pressure to be converged. For example, if the pressure difference between the pressure detection signal output from the pressure detection section (7) and the refrigerant pressure to be converged is large, the output time of the inverter output frequency is set to 1 second, and the pressure detection signal output from the pressure detection section (7) is set to 1 second. When the pressure difference between the pressure detection signal output from the inverter and the refrigerant pressure to be converged is small, the output time of the inverter output frequency can be set to 6 seconds.

Moreover, since the refrigerant pressure in the operating state is constantly detected and compared with the refrigerant pressure to be converged, the output time changes from 1 second to 2 seconds to 5 seconds depending on the pressure difference. Converge the pressure. The detected refrigerant pressure until convergence does not change more than the refrigerant pressure to be converged, and quickly reaches the predetermined pressure. After reaching the predetermined pressure, the compressor (1) continues to operate at the frequency at which the predetermined pressure was reached.

〔Effect of the invention〕

As explained above, the refrigeration system according to the present invention constantly detects the pressure detection signal output from the pressure detection section and the refrigerant pressure to be converged, and outputs an inverter output frequency set according to the pressure difference. Since the time is determined,
Even in cases where pressure fluctuations are large or the cooling load is large, such as at the start of operation or after desizing, the predetermined pressure can be quickly reached, reducing the extinguishing force and reducing the temperature of the object to be cooled. It becomes constant and freshness is maintained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional refrigeration system, and FIG. 2 is a block diagram showing an embodiment of a refrigeration MN according to the present invention. 1 (1) - compressor, +21... condenser, (3) -
...expansion valve, +4)...evaporator, (6)...inverter, (6)...control section, (7)...pressure detection section,
IIQ...frequency setting section, C11...time setting section,
(2)...Frequency output circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] A refrigeration cycle configured by connecting a compressor, a condensing type, an expansion valve, and an evaporator in a closed loop, an inverter that varies the power frequency and supplies it to an electric motor that drives the compressor, and a low pressure of the refrigeration cycle. a pressure detection unit that detects the refrigerant pressure on the side and generates a pressure detection signal; and a frequency setting that sets the output frequency of the inverter so that the refrigerant pressure on the low pressure side converges to a predetermined set value according to the pressure detection signal. and a time setting section that controls the output time of the output frequency of the inverter according to the pressure difference between the pressure detection signal and the refrigerant pressure to be converged.