JPH04124558A - Refrigerating plant - Google Patents

Abstract

PURPOSE:To make it possible to operate a refrigerating plant without driving a low pressure cut-of device by opening a solenoid valve installed on the way of mounting a bypass line which connect a discharge side of a compressor with its suction side for a fixed time simultaneously when the compressor starts and to open when the suction pressure of said compressor is lower than a specified pressure and bypassing a part of discharged gas of the compressor into the suction side. CONSTITUTION:When a pressure drops at a specified temperature or below, it is necessary to introduce a part of refrigerant gas discharged from a compressor 1 by opening a setting time solenoid valve 7 for a time relay 13 resultant from the closing of a low pressure cut-off device 11, and maintain the suction pressure which exceeds a specified value. This construction does not halt the compressor 1 by driving the low pressure cut-off device 10. Under this condition, the compressor 1 is arranged to operate for a specified time. The refrigerant gas whose heating value is increased by the drive of the compressor 1 is introduced into a condenser 2 so as to increase the condensation pressure and the internal pressure of a liquid receiver while the refrigerant is introduced into a vaporizer 5 so as to maintain a required suction pressure. A bypass solenoid valve 7 is arranged to be closed by opening the low pressure cut-off device 11 after the specific time by the time limit relay 13 when a contact point 13B is opened or the suction pressure rises at a pressure higher than the specified value after having started the compressor 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a refrigeration system, and particularly to a refrigeration system that is improved so that it can operate stably when the refrigeration system is installed in a low-temperature environment. Regarding equipment.

[Conventional technology]

As described in Japanese Patent Application Laid-Open No. 63-17356, the conventional device controls the opening of an electric expansion valve as a means of preventing the suction pressure from dropping below a certain value, but the control is complicated and requires a microcomputer. control is required.

It was also expensive in terms of cost.

[Problem to be solved by the invention]

Conventional technology does not take into consideration the operating conditions when the condenser and liquid receiver are installed in a location lower than the temperature inside the refrigerator where the evaporator is installed. When the machine starts, the pressure inside the receiver and the pressure inside the evaporator are reversed, so it is difficult for the refrigerant in the receiver to flow through the expansion valve to the evaporator, so the refrigerant suction capacity of the compressor is As a result, the suction pressure drops abnormally, causing the compressor to stop due to the activation of a low-pressure protection shut-off device, and a situation where cooling operation is impossible. Conventional countermeasures have been to short-circuit the low-pressure cutoff device and install a heater, etc. to the liquid receiver to increase the pressure inside the liquid receiver while the refrigeration equipment is stopped, but this also poses a problem in terms of reliability. This resulted in unnecessary electricity consumption.

An object of the present invention is to ensure the minimum suction pressure necessary for compressor operation, regardless of the environment and temperature conditions in which each component of the refrigeration system is installed.

[Means to solve the problem]

In order to achieve the above object, the present invention prevents an abnormal drop in suction pressure by bypassing a part of the discharge gas from the compressor to the compressor suction side for a certain period of time immediately after starting the compressor, and By sending discharge gas into the refrigerant, the pressure inside the condenser and liquid receiver is gradually increased to ensure a differential pressure with the evaporator, making it easier for the refrigerant to flow and maintaining stable operating conditions. This is what I did.

[Effect]

In the refrigeration system of this invention, the bypass piping connecting the discharge side and the suction side of the compressor is installed so that when the solenoid valve installed in the middle is activated, the suction pressure of the compressor is below the specified pressure for a certain period of time at the same time as the compressor is started. Open to bypass some percentage of the compressor discharge gas to the suction side. As a result, the compressor suction pressure can be maintained at a constant pressure or higher even if the amount of refrigerant sucked in is smaller than that of the evaporator, so that operation can be performed without activating the low-pressure pressure cutoff device.

In addition, as the compressor operates, the remaining discharged gas is introduced into the condenser, so the pressure in the condenser and receiver is gradually increased to ensure the necessary differential pressure across the expansion valve. This allows the refrigerant to be smoothly introduced into the evaporator, making the suction pressure stable and at the specified evaporation pressure.

In addition, the solenoid valve in the middle of the bypass pipe is closed after a certain period of time.

Alternatively, it is possible to return to the normal refrigeration cycle by closing it when the suction pressure is secured above the specified pressure and completing the bypass of the discharged gas.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, compressor 1. Condenser 2. Receiver 3° expansion valve 4. The evaporator 5 constitutes a basic refrigeration cycle.

Further, a solenoid valve 7 is provided between the discharge side and the suction side of the compressor 1, and they are connected by a bypass pipe 8 having a resistance for controlling the flow rate to some extent. In addition, a solenoid valve 6 is provided in front of the expansion valve 4.
At the same time, on the suction side of the compressor 1, a low pressure cutoff device 10 that opens when the pressure falls below the set pressure and a low pressure cutoff device 11 that closes when the pressure falls below the set pressure are installed. With this structure, as shown in the control circuit of Fig. 2, during normal cooling operation, the refrigerated J! The temperature inside the refrigerator is controlled by opening and closing the solenoid valve 6 installed in front of the expansion valve 4 by the refrigerator temperature controller 9 installed in the refrigerator 12. Every time the regulator 9 closes, the solenoid valve 6 opens.
When the refrigerant is introduced into the evaporator 5 and the suction pressure rises, the low pressure cutoff device 10 reaches a set pressure or higher and closes, thereby energizing the compressor electromagnetic contactor IA and starting operation. When the temperature controller 9 is stopped, the electromagnetic valve 6 closes to cut off the flow of refrigerant into the evaporator 5, thereby recovering the refrigerant and lowering the suction pressure.
When the pressure becomes lower than the set pressure and opens, the compressor 1 stops.

With this control, if the condenser 2 and receiver 3 are installed at a temperature lower than the internal temperature of the refrigerator 12 where the evaporator 5 is installed, the temperature controller 9 may Even if the solenoid valve 6 opens in response to the operation command, immediately after operation, the internal pressure of the liquid receiver 3 and the evaporator 5 will change between the expansion valve 4 and the evaporator 5.
The internal pressure of the evaporator 5 may be reversed, making it difficult for the refrigerant to flow into the evaporator 5 as expected, and the compressor attempts to suck in the refrigerant at a constant capacity, resulting in an abnormal drop in suction pressure. In the refrigeration system of the present invention, when the pressure drops below the specified pressure, the low pressure cutoff device 11 is closed and the time relay 13 is activated.
By opening the solenoid valve 7 for the set time, a part of the refrigerant gas discharged from the compressor 1 is introduced into the suction side of the compressor 1, making it possible to maintain the suction pressure above a certain pressure.
The compressor 1 is not stopped due to the operation of the low pressure cutoff device 1o. By operating the compressor 1 for a certain period of time in this state, the refrigerant gas to which the amount of heat associated with the operation of the compressor has been added is introduced into the condenser 2, and the condensation pressure and receiver internal pressure can be gradually increased. The refrigerant can be introduced into the evaporator 5, the necessary suction pressure can be secured, and stable operation can be achieved.

The bypass solenoid valve 7 is connected to the time-limited relay 1 after the compressor 1 is started.
3, after opening at the specified time, contact 13B is opened.

Alternatively, when the suction pressure rises above a certain pressure, the low pressure cutoff device 11 opens and closes to stop bypassing the discharged gas and return to the normal operation cycle.

〔Effect of the invention〕

According to the present invention, the condenser and liquid receiver of the refrigeration system are installed in an environmental condition at a temperature lower than the temperature condition inside the refrigerator where the evaporator is installed, and even when the operation is stopped for a long time, the condenser and liquid receiver are connected to the compressor suction side. By bypassing the discharged gas, the suction pressure can be maintained above a certain level, allowing stable operation. Also,
Since there is no need to short-circuit the low voltage cut-off device, safety and reliability can be ensured, and since there is no need to install a heater or the like, unnecessary voltage is not consumed and it is economical.

[Brief explanation of drawings]

FIG. 1 is a refrigeration cycle system diagram showing an embodiment of the present invention.
FIG. 2 is a control circuit diagram of the present invention.

Claims (1)

[Scope of Claims] 1. In a refrigeration system including a compressor, a condenser, a liquid receiver, an expansion valve, and an evaporator, the discharge pipe and suction pipe of the compressor are connected by a bypass pipe having a solenoid valve in the middle. Conclusion If the suction pressure is less than the specified suction pressure for a certain period of time immediately after starting the compressor, the solenoid valve is opened and the discharge gas is partially bypassed to the suction side. A refrigeration system characterized by being operable and ensuring a minimum required suction pressure.