JPS62116880A - 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 (a) Industrial Application Field The present invention relates to a refrigeration system that is used in super showcases, large refrigerators, etc., and whose capacity can be changed according to the load inside the refrigerator by controlling the rotation speed of the compressor, etc. In particular, the present invention relates to a refrigeration system that requires high accuracy in controlling the temperature inside the refrigerator.

(B) Conventional technology Conventionally, this type of refrigeration equipment has been described in Japanese Patent Publication No. 60-23261 or Japanese Patent Application Laid-open No. 58-205057, and as shown in FIG. 8, a frequency variable device 21 such as an inverter, etc. It is composed of a compressor 22 whose capacity is controlled by a compressor 22, a condenser 23, an evaporator 24, and a temperature-type expansion valve 25 connected to the inlet side of the evaporator. And compressor, 22 low pressure.

The frequency variable device 21 inputs the detected signal of the pressure sensor 26 via the controller 27 and outputs a frequency command suitable for the load to the compressor 22. The frequency variable device 21 controls the capacity of the refrigeration system, while also detecting the temperature inside the refrigerator. When the temperature detected by the temperature sensor 28 is higher than the preset upper limit temperature, the compressor continues to operate, and when it is lower than the preset lower limit temperature, the compressor is stopped. This allows the internal temperature to be maintained constant.

(c) Problems to be Solved by the Invention However, according to the above configuration, when the load inside the refrigerator becomes small and the frequency command of the frequency variable device 210 reaches the lower limit frequency, when the load decreases further, the compressor 22 stops. If the temperature inside the refrigerator exceeds the preset upper or lower limit temperature, the compressor will repeatedly start and stop, causing the temperature inside the refrigerator to rise or fall rapidly and fluctuate greatly. There's a problem. In addition, in order to suppress fluctuations in the temperature inside the refrigerator, the lower limit frequency of the frequency variable device 21 may be continuously controlled down to OHZ, or the differential between the upper limit temperature and the lower limit temperature described above may be set small. In the former case, the frequency variable device 21
There is a limit to the frequency range that can be controlled by compressor 2, and continuous control up to Oh cannot actually be performed.
There are problems in that the compressor is frequently started and stopped, and the control parts of the compressor are easily damaged and power consumption increases. For this reason, in a refrigeration system having such a configuration, it is difficult to perform highly accurate temperature control such as controlling the internal temperature within a range of, for example, ±0.5 to 1°C.

The present invention was developed in view of these points, and it prevents the compressor from stopping when the refrigeration equipment is under a light load, suppresses changes in the ambient temperature of the evaporator, and controls the temperature inside the refrigerator with high precision and little fluctuation. The purpose is to

B) Means for Solving the Problems The present invention is composed of a compressor, a condenser, an evaporator, etc. whose capacity can be changed by a variable frequency device such as an inverter.
In the refrigeration system, the frequency of the frequency variable device is changed based on a signal from a pressure sensor provided on the low pressure side of the compressor.

An electric expansion valve that operates based on a signal from a temperature sensor that detects the ambient temperature of the evaporator is provided on the inlet side of the evaporator, and a bypass pipe that communicates the low pressure side and the high pressure side of the compressor is provided, When the frequency variable device reaches the lower limit frequency, the lower limit frequency is held and the bypass pipe is opened.

(e) Effect The refrigeration system of the present invention has the above-described configuration, and the temperature sensor detects the ambient temperature of the evaporator that is closest to the temperature inside the refrigerator.
The degree of throttling of the electric expansion valve can be adjusted according to the difference between the detected temperature and the preset temperature, while the load inside the refrigerator becomes lighter and the low pressure of the compressor decreases, lowering the frequency of the frequency variable device to the lower limit. Even if the frequency drops below the frequency, this lower limit frequency can be maintained and the compressor can be prevented from stopping.
Even during such light loads, the temperature inside the refrigerator can be continuously controlled using the temperature sensor and the electric expansion valve, and the differential with the preset temperature can be kept small, so the temperature inside the refrigerator can be controlled with little fluctuation. This allows for highly precise control. Furthermore, when the frequency variable device reaches the lower limit frequency.

Since the bypass pipe is opened to increase the low pressure, it is possible to prevent the low pressure from falling below a predetermined value, such as the set value of the pressure switch for starting and stopping the compressor, and when the low pressure decreases. This also prevents vacuum operation and compressor shutdown.

(f) Example Embodiments of the present invention will be described below based on the drawings.

1 is a pressure sensor installed on the low pressure side of the compressor 3, and the device is composed of a compressor 3 whose capacity is varied by a frequency variable device 2 such as an inverter, a condenser 4, an electric expansion valve 5, and an evaporator 6. be.

8 is a controller that compares the pressure value detected by the pressure sensor 7 with a preset pressure value (consisting of a cut-in value and a cut-out value) and outputs a signal to the frequency variable device. This controller sends a signal to the frequency variable device 2 to reduce the frequency when the pressure value detected by the pressure sensor 7 becomes below a preset cut-out value, and when the detected pressure value becomes above the cut-in value. Then, send a signal to the frequency variable device 2 to increase the frequency, and when the detected pressure value is between the cut-out value and the cut-in value, keep the frequency of the frequency variable device as it is. The variable frequency device 2 controls the rotation speed of the compressor 3 in the range from the upper limit frequency to the lower limit frequency of the device based on a signal from the controller. Further, this frequency variable device is provided with a function to maintain the lower limit frequency when a frequency lowering signal is output from the controller 8 and reaches the lower limit frequency of the device. A bypass pipe 9 communicates the low pressure side and the high pressure side of the compressor 3 and has a normally closed solenoid valve 10. The bypass pipe 9 is opened only when the solenoid valve 10 is opened by a signal output from the variable frequency device 2 when the frequency of the variable frequency device 2 reaches the lower limit frequency.

11 is a temperature sensor that detects the ambient temperature (blowing temperature or suction temperature) of the evaporator. Reference numeral 12 denotes a valve controller that compares the temperature detected by the temperature sensor 11 with a preset temperature and outputs a signal of a magnitude corresponding to the difference to the electric expansion valve 5.

When the temperature detected by the temperature sensor 11 falls below a preset temperature, this valve controller sends a signal to the electric expansion valve 5 to reduce the opening degree according to the degree to which the temperature detected by the temperature sensor 11 falls below a preset temperature. When the temperature exceeds the set temperature, a signal is sent to the electrically operated expansion valve 5 to increase the opening degree according to the extent to which the temperature has exceeded the set temperature.

In the refrigeration system configured as described above, the seventh operation will be explained based on FIGS. 2 to 7. First, when the load in the refrigerator is relatively large and is within the control range of the frequency variable device 20 (f, ~ft in FIG. 5), the pressure value detected by the pressure sensor 7 is set in the controller 8 for a When the frequency falls below the out value (for example, at point 34 in FIG. 4), the controller sends a signal to the frequency variable device 2 to lower the frequency, and the compressor 3 decreases its rotation speed, while the pressure value detected by the pressure sensor 7 When exceeds the cut-in value (for example, point 02 in Figure 2), the controller issues a signal to the variable frequency device 2 to increase the frequency, and the compressor 3 increases its rotation speed, which is the capacity control operation according to the load. will be carried out. At this time, the electric expansion valve 5 is automatically adjusted by the valve controller 12 to a throttle amount according to the ambient temperature of the evaporator 6, and the ambient temperature of the evaporator is kept constant as shown in FIG. kept within control. For example, when the temperature detected by the temperature sensor 11 is lower than the set temperature of the valve controller 12 (point 02 in FIG. 2), the opening degree of the electric expansion valve 5 is decreased (point 02 in FIG. 2). point) If a signal is issued from the valve controller 12 and the detected temperature exceeds the set temperature (point 7 in Figure 2),
A signal is issued from the valve controller 12 to increase the opening degree of the electric expansion valve 5 (point 1 in FIG. 3). Next, if the load in the refrigerator becomes smaller and the frequency of the frequency variable device 20 reaches the lower limit frequency f1, and the load decreases further, the frequency variable device 2 changes the frequency to the lower limit frequency f, as shown in the flowchart of FIG. will be maintained as is. In this state, the evaporator 6 is operated by the temperature sensor 11 and the electric expansion valve 5.
Temperature control is performed. For example, if the frequency variable device 2 is maintained at the lower limit frequency f in such a light load state (the fifth
(point C5 in the figure), the low pressure of the compressor 3 and the ambient temperature of the evaporator 6 begin to drop (point 04 in figure 4, point 02 in figure 2), but the opening degree of the electric expansion valve 50 (point C5 in FIG. 3), the ambient temperature of the evaporator is maintained within a constant control range as shown in FIG. 2. On the other hand, when the variable frequency device 2 is maintained at the lower limit frequency, a signal is sent from the device to the solenoid valve 10, and the solenoid valve 10 is opened. As a result, the bypass pipe 9 is opened and the hot gas discharged from the compressor is supplied to the low pressure side, thereby preventing the low pressure from decreasing. For example, the low pressure starts to rise as shown after point 02 in Figure 2, and the compressor 3
A pressure cage inch (not shown) for starting and stopping the compressor is activated to prevent the compressor from stopping or running under vacuum.

In this way, the refrigeration system of this embodiment controls the ambient temperature of the evaporator, which is easily affected by changes in the internal load, to be within a certain control range, and Even if the frequency drops below the lower limit frequency of the variable device, the device can be maintained at the lower limit frequency and the compressor can continue to operate, and the temperature of the evaporator can still be controlled.
As shown in Fig. 6, it is possible to accurately maintain the temperature inside the refrigerator within a control range, regardless of the magnitude of the load.

In addition, a bypass pipe that opens when the frequency variable device reaches the lower limit frequency prevents a drop in low pressure during light loads, and prevents the pressure cusp inch for starting and stopping the compressor from operating. This prevents the compressor from stopping.

(G) Effects of the Invention As described above, the present invention is composed of a compressor, a condenser, an evaporator, etc. whose capacity is changed by a variable frequency device such as an inverter, and a pressure sensor provided on the low pressure side of the compressor. In the refrigeration system, the frequency of the frequency variable device is changed based on a signal from the evaporator, and an electric expansion device is provided on the inlet side of the evaporator and operates based on a signal from a temperature sensor that detects the ambient temperature of the evaporator. While providing a valve, a bypass pipe is provided to communicate the low pressure side of the compressor and the high pressure 9III,
When the frequency variable device reaches the lower limit frequency, this lower limit frequency is maintained and the bypass pipe is opened. It can be controlled according to changes in the ambient temperature of the chamber, and even if the load in the chamber becomes lighter than the lower limit frequency of the variable frequency device, the device can be maintained at the lower limit frequency and the compressor can be prevented from stopping. Even under such light loads, the temperature inside the refrigerator can be controlled continuously using the temperature sensor and the electric expansion valve, making it possible to control the temperature inside the refrigerator with high precision and little fluctuation. Furthermore, the bypass pipe that opens when the frequency variable device reaches the lower limit frequency can prevent a drop in low pressure during such light loads, and prevents the pressure switch for starting and stopping the compressor from operating. This prevents the compressor from stopping.

[Brief explanation of drawings]

Figures 1 to 7 show embodiments of the present invention, Figure 1 is a refrigerant circuit diagram of a refrigeration system, Figure 2 is a time chart showing changes in the ambient temperature of the evaporator, and Figure 3 is an electric expansion valve. Fig. 4 is a time chart showing changes in the low pressure, Fig. 5 is a time chart showing changes in the frequency of the variable frequency device, and Fig. 6 is a time chart showing changes in the temperature inside the refrigerator. 7 is a flowchart showing a control example of a variable frequency device, and FIG. 8 is a refrigerant circuit diagram of a refrigeration system showing a conventional example. 1... Refrigeration device, 2... Frequency variable device, 3.
... Compressor, 4... Condenser, 6... Electric expansion valve, 6... Evaporator, 7... Pressure sensor, 9...
- Bypass pipe, 10... Solenoid valve, 11... Temperature sensor. Applicant Sanyo Electric Co., Ltd. and one other representative Patent attorney Masao Sano Figure 4 Figure 5 Figure 6 WJ Figure 7

Claims (1)

[Claims] (1) It consists of a compressor, condenser, evaporator, etc. whose capacity is changed by a frequency variable device such as an inverter, and the frequency variable device is changed based on a signal from a pressure sensor installed on the low pressure side of the compressor. In a refrigeration system that changes the frequency, an electric expansion valve that operates based on a signal from a temperature sensor that detects the ambient temperature of the evaporator is provided on the inlet side of the evaporator, and an electric expansion valve that operates based on a signal from a temperature sensor that detects the ambient temperature of the evaporator is provided on the inlet side of the evaporator. A refrigeration system comprising a bypass pipe communicating with a high pressure side, and configured to hold the lower limit frequency and open the bypass pipe when a variable frequency device reaches a lower limit frequency.