JPS60223965A - 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 outline of the invention] The present invention relates to a refrigeration system, and particularly relates 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 with an inverter that has been commonly used in the past, in which (1) is a compressor that compresses refrigerant, (2) is a condenser, and (3) is an expansion valve. , (4) are evaporators, which are connected in a closed loop via a pipe (c) to form a refrigeration cycle. (6) is an inverter that varies and outputs the frequency of the commercial power supply, and (6) is an inverter that outputs a variable frequency of the commercial power supply, and (6) is an inverter that changes the frequency of the commercial power supply according to the output signal of the pressure detection section (7) that detects the refrigerant pressure on the low pressure side of the compressor +1). (8) is a control unit that controls (5), and the wL electromagnetic contactor (9) is an overcurrent relay that is also installed in series with the power line that connects the inverter (5) and the compressor 10. It is.

In the conventional refrigeration system configured as described above, when a power switch (not shown) is turned on, the electromagnetic contactor (8) is closed and the electric power output from the inverter (6) is transferred to the electric motor of the compressor (1) (Fig. Not shown and supplied to 9, compressor +1>
is driven. When the compressed refrigerant flows through the refrigeration cycle due to the operation of the compressor fl), it is cooled by the evaporator (4) in a known manner.

Here, when the cooling load decreases, the refrigerant pressure on the low pressure side of the refrigeration cycle decreases, and the pressure detector (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. When the refrigerant is cooled by lowering the rotational speed of the compressor +1), 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 (0) increases accordingly.

As a result, the control unit (6) controls the inverter (5) to increase its output frequency, and increases the rotational speed of the compressor (1), thereby increasing the cooling capacity.

Therefore, in a refrigeration system having such an inverter, the cooling capacity can be controlled according to the cooling load, and power saving can be achieved.

However, in the above-mentioned conventional refrigeration equipment, the output frequency of the inverter (5) is continuously changed at a fixed frequency, for example, IH2 intervals, for a fixed period of time, for example, every 5 seconds. A situation occurs in which the pipe is operated at a frequency such that the entire west conduit enters a resonant state, causing cracks in the pipe (c) and ultimately causing the objects to be cooled to rot.

Moreover, the natural frequency of the pipe line ^ differs depending on the refrigeration equipment, so it is necessary to operate in such a way that it does not match the natural frequency of the pipe line (c) of any refrigeration equipment, so that the resonant state of the entire piping system is maintained. The problem is that it is extremely difficult to avoid.

[Summary of the invention]

This invention solves the conventional problems as mentioned above.
In addition to detecting the refrigerant pressure on the low-pressure side and converging the refrigerant pressure to a predetermined port, a resonant operation prohibition circuit that prohibits operation at the resonant frequency of the refrigerating cycle among the above-mentioned output frequencies is installed to prevent the refrigerating cycle from resonating. The purpose of the present invention is to provide a refrigeration system that can be operated in a normal state at all times by avoiding high frequencies.

[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, the moe has a resonance frequency setting section that is provided downstream of the control section (6) and can set an inverter output frequency range corresponding to the resonance frequency at the resonance frequency of the refrigeration cycle. That is, it has a function of arbitrarily setting a frequency that is not output among the output frequencies of the inverter (5).

Therefore, in the resonance operation prohibition circuit αQ, the inverter (
By setting the output frequency of the inverter 11+, which corresponds to the vibration frequency of the conduit (c) of the refrigeration cycle, as the non-output frequency among the output frequencies in step 5), existing refrigeration systems with unknown operating conditions and vibration systems can be used. In this case, the resonant frequency of the conduit (c) can be avoided, and the entire conduit (c) will not be in a resonant state, and the conduit (c) can always be operated in a normal state. That is, during cooling operation, if the cooling load becomes large and it is necessary to operate the compressor at the inverter output frequency corresponding to the resonance frequency, the control unit (6) changes the inverter output frequency to In2 every 6 seconds, for example. The rotation speed of the compressor (1) is gradually increased to control the rotation speed of the compressor (1), but when it reaches the innomata frequency range corresponding to the preset resonance frequency, the resonance operation prohibition circuit aO jumps over that frequency range and compresses at the 71st frequency. The compressor (1) is operated, and then the control unit (6) sequentially increases the rotation speed of the compressor (1) up to the frequency set by the control unit (6).Also, if the cooling load becomes small, the above Furthermore, if it is necessary to control the operation to the inverter output frequency corresponding to the resonant frequency, or if the cooling load increases or decreases, the inverter is operated at a frequency one step before reaching the resonant frequency range.

Therefore, the entire pipe ■ will not be in a resonant state,
There is no risk of cracks occurring in the pipe line (c), and there is no problem of rotting the object to be cooled.

〔Effect of the invention〕

As explained above, the refrigeration system according to the present invention is equipped with a resonance operation prohibition circuit that prohibits operation at an impark output frequency corresponding to the resonant frequency of the conduit of the refrigeration cycle among the output frequencies of the inverter. The system can be operated while avoiding the resonant frequency of the pipes, and the pipes can always be operated in a normal state without causing cracks in the pipes.

[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 the refrigeration system according to the present invention. (1)...Compressor, (2)? ...Condenser, (3)...
・Expansion valve, (4)...evaporator, inverter, (6)...control unit, (7)...pressure detection unit, OQ
...Frequency setting section. - In the figures, the same symbols indicate the same or equivalent parts. Agent Masuo Oiwa

Claims (2)

[Claims] (1) A refrigeration cycle configured by connecting a compressor, a condenser, an expansion valve, and an evaporator in a closed loop; an inverter that varies the power frequency and supplies the power to an electric motor that drives the compressor; A pressure detection unit that detects refrigerant pressure on the low pressure side of the refrigeration cycle and generates a pressure detection signal, and controls the inverter in accordance with the pressure detection signal to converge the refrigerant pressure on the low pressure side to a predetermined set value. A refrigeration system comprising: a control unit; and a resonance operation prohibition circuit that prohibits operation of the compressor at an inverter output frequency that corresponds to a resonance frequency of a conduit of the refrigeration cycle among the output frequencies of the inverter. (2) Claim 11) characterized in that the resonance operation prohibition circuit is provided with a resonance frequency setting section that can arbitrarily set the inverter output frequency corresponding to the resonance frequency of the conduit of the refrigeration cycle. Refrigeration equipment as described.