JPH07305903A - Controller for freezer - Google Patents

Abstract

PURPOSE:To rapidly establish a stable state after starting by detecting fresh air temperature just before starting of a compressor, and when the fresh air temperature is judged to be lower than a preset value fully opening a hot gas bypass side for the degree of opening of a three-way valve to start the compressor for pressure control. CONSTITUTION:Prior to starting of operation of a compressor 1, fresh air temperature is detected with a fresh air temperature sensor 9 and is compared with a preset value. When the fresh air temperature is smaller than the preset value, it is judged that high pressure is not raised because of greater condensation capability in ordinary control, and a refrigerant does not flow because a pressure difference is not obtained across an expansion valve 3 and hence low pressure side pressure is excessively lowered. Accordingly, a controller 13 sends a signal to a three-way valve 5 such that it fully opens a hot gas bypass circuit whereby discharge gas from the compressor 1 is passed to the hot gas bypass circuit and is directed to directly flow into a liquid receptor 6 and push out liquid refrigerant for circulation of a refrigerant. Thereafter the controller 13 controls the degree of opening of the three-way valve 5 such that a freezing cycle is more stabilized than a numerical value obtained from a low pressure sensor 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to refrigeration cycle control of a refrigeration system using an air-cooled condenser that performs annual cooling operation, and more particularly to low temperature outside air operation and low temperature outside air start.

[0002]

2. Description of the Related Art In the prior art, a refrigeration cycle is provided with a hot gas bypass circuit having an electromagnetic valve interposed between
When the pressure drops, the solenoid valve is opened and the hot gas bypass circuit is activated to prevent the refrigerant temperature and pressure from dropping.

As a similar known example, there is JP-A-4-84072.

[0004]

Since the solenoid valve used in the above technique has only two values, open or closed, for example, at the time of cold start (the refrigerant is unevenly present in the refrigeration cycle). , The refrigerant gas temperature and pressure rise in the bypass circuit temporarily, but when the solenoid valve is closed, the bypass circuit becomes invalid, so the temperature and pressure drop sharply and the solenoid valve opens again. The cycle may become unstable and hunting may occur.

An object of the present invention is to control the refrigeration system so as to detect the state of the refrigeration cycle immediately before starting the compressor of the refrigeration cycle and, based on the detection result, make the refrigeration cycle into a stable state immediately after the compressor is started. To provide the device.

[0006]

A control device for a refrigerating apparatus according to the present invention has a structure described in each of the claims.

[0007]

Operation: Depending on whether the outside air temperature detected immediately before the start of the compressor is higher or lower than a preset value, the opening of each three-way valve is set to the opening during normal operation (hot gas bypass circuit). Fully close or slightly open) or the opening for low temperature operation (hot gas bypass circuit fully open) and then start the compressor. After the compressor is started, the three-way valve is controlled while detecting the pressure to reach the steady operation state.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a system diagram of the refrigerating apparatus of this embodiment. Compressor 1, condenser 2, expansion valve 3, evaporator 4, three-way valve whose opening can be controlled by electrical control means 5, liquid receiver 6, refrigerant pipe 7
The refrigerating cycle is constituted by the hot gas bypass circuit 8. Further, an outside air temperature sensor 9, a high pressure sensor 10, a low pressure sensor 11, a chilled water temperature sensor 12, and a controller 13 are attached to control the refrigeration cycle. The condenser 2 exchanges heat with the air, while the evaporator 4
Is designed to exchange heat with cold water 14.
4 is used to cool other objects to be cooled.

The refrigeration system uses the cold water temperature sensor 12 to cool the cold water 1
The temperature of 4 is detected, and the operation stop of the compressor 1 is controlled. When the compressor 1 is in operation, the controller 13 controls the opening degree of the three-way valve 5 and adjusts the hot gas bypass amount according to the values detected by the high pressure pressure sensor 10 and the low pressure pressure sensor 11 to stabilize the refrigeration cycle. Keep in a state.

By the way, when the refrigerating apparatus is started when the outside air temperature is low, the pressure of the refrigerating cycle is lower than that of the normal time. Therefore, when the compressor 1 is started as it is, the low pressure side of the compressor 1 becomes a vacuum state, and the operating state is out of specifications. Therefore, there is a possibility that the cold water 14 will freeze and the evaporator will be damaged due to a failure of the compressor or a sharp decrease in the temperature inside the evaporator 4. Therefore, in this embodiment, control is performed as follows.

That is, prior to the start of operation of the compressor 1 of the refrigeration system, the outside air temperature sensor 9 detects the outside air temperature and sends the detected temperature to the controller 13. The controller 13 compares the sent value with a preset value, and if the value is smaller than the set value, the outside air temperature is low and the condensation capacity is large under normal control, so the high pressure does not rise and the expansion valve 3 Since there is no pressure difference between before and after, the refrigerant does not flow, and as a result, it is determined that the low pressure side is in a refrigerant shortage state and the low pressure side pressure drops transiently.
In order to avoid this, the controller 13 transmits to the three-way valve 5 to fully open the hot gas bypass circuit, and after the compressor 1 is started, the discharge gas of the compressor 1 is passed to the hot gas bypass circuit.
By directly flowing into the liquid receiver 6 and pushing out the liquid refrigerant in the liquid receiver 6, the refrigerant is circulated to avoid a refrigerant shortage state.
Thereafter, the controller 13 controls the opening degree of the three-way valve 5 so that the refrigeration cycle becomes stable based on the values obtained from the high pressure pressure sensor 10 and the low pressure pressure sensor 11.

In performing the control, a high pressure sensor 10 and a low pressure sensor 11 are used instead of the outside air temperature sensor 9.
May be used.

[0013]

According to the present invention, the condition of the refrigeration cycle immediately before the compressor of the refrigeration system is detected, and the three-way valve is controlled according to the detection result to start the compressor. The transient pressure drop phenomenon that occurs during start-up does not occur, and a stable state can be achieved early after the start of the compressor. Moreover, since the pressure does not drop, the refrigeration cycle protection device does not operate and the compressor does not frequently start and stop.

Further, since the three-way valve used in the present invention is continuous control, unlike the on / off control of the solenoid valve, the stability of the refrigeration cycle is excellent even after the compressor is started.

[Brief description of drawings]

FIG. 1 is a system diagram of a refrigeration cycle according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Compressor, 2 ... Condenser, 3 ... Expansion valve, 4 ... Evaporator, 5
... 3-way valve, 6 ... Liquid receiver, 7 ... Refrigerant piping, 8 ... Bypass circuit, 9 ... Outside air temperature sensor, 10 ... High pressure sensor, 11
... low pressure sensor, 12 ... cold water temperature sensor, 13 ... controller, 14 ... cold water.

Claims (1)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, an expansion valve and an evaporator are sequentially connected by refrigerant pipes, and a hot gas bypass circuit connecting a discharge side of the compressor and an outlet side of the condenser. And an air-cooled type that has a three-way valve whose opening can be controlled by an electric means to open and close the hot gas bypass circuit, and which adjusts the amount of liquid refrigerant in the condenser to adjust the high pressure. In the refrigeration system, the outside air temperature is detected immediately before the start of the compressor, and when it is determined that the temperature is lower than a preset value, the opening degree of the three-way valve is fully opened on the hot gas bypass circuit side, and then the A control device for a refrigerating apparatus, which starts a compressor and performs pressure control.