JPS62196555A - 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 is a refrigerator that is used in super showcases, large refrigerators, etc., and whose capacity can be changed according to the load inside the refrigerator, such as by controlling the rotation speed of the compressor. This patent relates to a refrigeration system that requires high precision in controlling the internal temperature.

(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. 9, a frequency variable device 27 such as an inverter, It consists of a compressor 28 whose capacity is controlled by a compressor 28, a condenser 29, an evaporator 30, and a temperature-type expansion valve 31 provided on the inlet side of the evaporator. The capacity of the refrigeration system is controlled by the frequency variable device 27 which inputs a signal from the pressure sensor 32 that detects the low pressure of the compressor 28 via the controller 33 and outputs a frequency command suitable for the load to the compressor 28. On the other hand, when the temperature detected by the temperature sensor 34 that detects the internal temperature is higher than the preset upper limit temperature, the compressor 28 is allowed to continue operating, and when it is lower than the preset lower limit temperature, the compressor 28 is stopped. The internal temperature of the refrigerator can be kept constant by using temperature control.

(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 270 reaches the lower limit frequency, if the load decreases further, the compressor 28 stops. what you end up doing,
When the temperature inside the refrigerator exceeds the preset upper and lower temperature limits, the compressor repeatedly starts and stops, which causes the problem that the temperature inside the refrigerator suddenly rises or falls, resulting in fluctuations. In addition, in order to suppress fluctuations in the temperature inside the refrigerator, the lower limit frequency of the frequency variable device 27 can 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, there is a limit to the frequency range that the frequency variable device 27 can control, and in reality, continuous control up to OHz cannot be performed (in the latter case, the compressor starts and stops frequently and the compressor There is a problem that the control parts of the refrigerator are easily damaged (or the power consumption increases).For these reasons, in a refrigeration system with such a configuration, the internal temperature must be kept within the range of ±0.5 to 1℃, for example. It has been difficult to achieve highly accurate temperature control with a simple structure.

The present invention has been made in view of the above points, and is designed to prevent the compressor from stopping when the refrigeration equipment is under a light load, and to suppress changes in the ambient temperature of the evaporator to reduce fluctuations in the temperature inside the refrigerator. The purpose is to control with high precision.

B) Means for Solving the Problems The present invention is composed of a compressor, a condenser, a pressure reducing device, an evaporator, etc. whose capacity can be changed by a variable frequency device such as an inverter, and is 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 a pressure sensor that operates based on a signal from a temperature sensor that detects the ambient temperature of the evaporator on the outlet side of the evaporator. A motorized valve is provided with electric power, a bypass pipe is provided that communicates the low pressure side and the high pressure side of the compressor, and when the frequency variable device reaches the lower limit frequency, this lower limit frequency is maintained and the bypass pipe is opened. It is.

(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 amount of refrigerant circulation can be controlled by adjusting the throttle of the electric valve according to the difference between the detected temperature and the preset temperature, while the load inside the refrigerator is lightened and the low pressure of the compressor is lowered, making the frequency variable. Even if the frequency of the device falls below the lower limit frequency, this lower limit frequency can be maintained to prevent the compressor from stopping, and the temperature inside the refrigerator can be controlled using the temperature sensor and electric valve even during such light loads. It is possible to perform this continuously and to keep the differential with the preset temperature small, making it possible to control the temperature inside the refrigerator with little fluctuation and with high precision.

Furthermore, when the frequency variable device reaches the lower limit frequency,
Since the bypass pipe is opened and the high pressure gas is guided to low pressure gJJJK 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. 5&1. ing.

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

1 is a compressor 3 whose capacity is varied by a variable frequency device 2 such as an inverter, a condenser 4, an evaporator 5, and a temperature-type expansion whose opening degree is adjusted by a temperature-sensing tube 6 that senses the refrigerant temperature at the outlet of this evaporator. This is a pressure sensor equipped with a device consisting of a valve 7. A controller 9 compares the pressure value detected by the pressure sensor 8 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 2. This controller sends a signal to the frequency variable device 2 to reduce the frequency when the pressure value detected by the pressure sensor 8 becomes less than a preset cut-out value, and when the detected pressure value becomes equal to or greater than the cut-in value. Then, a signal is sent 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, the frequency of the frequency variable device is maintained as it is. The frequency converter W2 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 the signal from the controller 9. The frequency variable device 2 also has a function of maintaining the lower limit frequency when the lower limit frequency of the device is reached, even if a frequency reduction signal is output from the controller 9. A bypass pipe 10 communicates the low pressure side and the high pressure side of the compressor 3 and has a normally closed solenoid valve 11 and a capacity adjustment valve 12. When the frequency of the frequency variable device 20 reaches the lower limit frequency, the solenoid valve 11 is opened by a signal issued from the device, and the bypass pipe is opened. The capacity adjustment valve 1 has an operation setting higher than a lower limit value (a value set to stop the compressor when the low pressure falls below this level).
The opening degree is adjusted by 2. Reference numeral 13 denotes an electric valve provided on the outlet side of the evaporator 5. 14 is the ambient temperature of the evaporator (
This is a temperature sensor that detects the air outlet temperature or suction temperature. Reference numeral 15 denotes a valve controller that compares the temperature detected by the temperature sensor 14 with a preset temperature and outputs a signal of a magnitude corresponding to the difference to the electric valve 13. When the temperature detected by the temperature sensor 14 falls below a preset temperature, this valve controller sends a signal to the motor-operated valve 13 to reduce the opening degree according to the degree to which the temperature detected by the temperature sensor 14 falls below a preset temperature. When the temperature exceeds the temperature, a signal is sent to the electric valve 13 to increase the opening degree according to the degree of the temperature exceeded.

The operation of the refrigeration system configured as described above will be explained based on FIGS. 2 to 7. First, when the load in the refrigerator is relatively large and within the control range of the variable frequency device 2 (f1 to fz in FIG. When the output value falls below the out value (for example, at point C4 in FIG. 4), a signal is sent from the controller to the frequency variable device 2 to lower the frequency, and the compressor 3 decreases its rotation speed, while the pressure detected by the pressure sensor 8 decreases. When the value exceeds the cut-in value (for example, point 02 in Fig. 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 according to the load. Driving takes place. At this time,
The motor-operated valve 13 is automatically adjusted to the throttle amount according to the ambient temperature of the evaporator 5 by the valve controller 15, and the amount of refrigerant circulated in the refrigeration cycle is controlled by adjusting the opening of this motor-operated valve. The ambient temperature of the vessel 5 is maintained within a certain control range as shown in FIG. For example, temperature sensor 1
When the detected temperature of 4 is lower than the set temperature of the valve controller 15 (point C6 in FIG. 2), the valve controller 15 decreases the opening degree of the electric valve 13 (point C3 in FIG. 3). If the detected temperature exceeds the set temperature (0 in Figure 2), a signal is output from
2 points) VC should be set so as to increase the opening degree of the electric valve 13 (
(8 points in FIG. 3) A signal is output from the valve controller 15. Thereby, the amount of refrigerant circulated in the freezing cycle can be controlled according to the ambient temperature of the evaporator 5, and the ambient temperature of the evaporator can be kept close to the target set temperature.

Next, when the load in the refrigerator becomes smaller and the frequency of the frequency variable device 20 reaches the lower limit frequency f, K, if 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 temperature of the evaporator 5 is controlled by the temperature sensor 14 and the electric valve IHC. For example, when the frequency variable device 2 maintains the lower limit frequency f, K in such a light load state (point C6 in Fig. 5), the low pressure of the compressor 3 and the ambient temperature of the evaporator 5 start to decrease (
04 point in FIG. 4, 02 point in FIG.
(Point C8 in FIG. 3) Therefore, the amount of refrigerant circulated in the refrigeration cycle is reduced and the ambient temperature of the evaporator 5 is maintained within a certain range as shown in FIG. On the other hand, when the frequency variable device 2 is maintained at the lower limit frequency, a signal is sent from the device to the solenoid valve 11, which opens and sets the pressure switch (not shown) for starting and stopping the compressor 30. The capacity regulating valve 12 with the higher operating setting is activated. As a result, bypass pipe 1
0 is opened with an opening degree corresponding to the drop in the low pressure pressure, and an appropriate amount of hot gas discharged from the compressor 3 is supplied to the low pressure side to prevent the low pressure pressure from dropping and the compressor 3 from stopping due to this. There is. For example, the low pressure starts to rise as shown from point d4 in Figure 4, and the pressure switch is activated, causing the compressor
I'm setting it to 5 so I won't stop it.

In this way, the refrigeration system of this embodiment controls the ambient temperature of the evaporator 5, which is easily affected by changes in the internal load, to be within a certain control range; Even if the frequency becomes lower than the lower limit frequency of the frequency variable device 2, the device can be maintained at the lower limit frequency and the compressor 3 can be continuously operated, and the temperature of the evaporator 5 can be continuously controlled. As shown in Figure 2, it is possible to accurately (focus) the temperature inside the refrigerator within a control range regardless of the magnitude of the load. 10, it is possible to prevent a drop in the low pressure during light loads, and it is possible to prevent the compressor 3 from stopping by preventing the pressure switch for starting and stopping the compressor from operating. Since it is installed on the outlet side of the container 5, it is possible to control the flow rate of the refrigerant in the gas state.For example, when installing a VCt valve on the inlet side of the evaporator, that is, when controlling the flow rate of the refrigerant in the liquid state, it is possible to control the flow rate of the refrigerant in the gas state. The throttling mechanism of the valve itself does not require much precision, and an inexpensive electric valve can be used.

Further, FIG. 8 shows another embodiment, in which a defrosting circuit using hot gas is added to the refrigerant circuit of FIG. 1. In this case, during normal cooling operation, the temperature control of the evaporator is performed in the same manner as in the embodiment shown in FIG. 1, but during defrosting operation, the above-mentioned temperature control is discontinued. That is, by switching the three-way valve 16, the gas discharged from the compressor 17 flows to the evaporator 19 via the hot gas bypass pipe 18, and defrosting operation is performed. Regardless of the size, the upper limit frequency is forcibly set by the controller 21,
The compressor 17 is operated at maximum capacity.

At this time, the electric valve 22 is fully opened by the valve controller 240 command regardless of the signal from the temperature sensor 23, and the bypass pipe 25 is also opened by opening the solenoid valve 26, so that the low pressure immediately after the start of defrosting is opened. drop, which causes the compressor 1
Activation of the 7-start/stop pressure switch is also prevented. That is, at the time of defrosting, the temperature control of the evaporator 19 is interrupted as described above so that defrosting can be carried out smoothly.

(G) Effects of the Invention As described above, the present invention is composed of a compressor, a condenser, a pressure reducing device, an evaporator, etc. whose capacity is changed by a variable frequency device VC such as an inverter, and the low pressure side of the compressor is In the refrigeration system t, the frequency of the frequency variable device is changed based on a signal from a pressure sensor provided at A bypass pipe is provided that communicates the low pressure side and the high pressure side of the compressor, and when the frequency variable device reaches the lower limit frequency, this lower limit frequency is maintained and the bypass pipe is opened. With this configuration, the electric valve can be controlled according to the ambient temperature of the evaporator, which is easily affected by load fluctuations, and the load inside the refrigerator can be reduced to below the lower limit frequency of the frequency variable device. It is also possible to maintain the device at the lower limit frequency to prevent the compressor from stopping, and even during such light loads, the temperature inside the refrigerator can be continuously controlled using the temperature sensor and electric valve.
It becomes possible to control the temperature inside the refrigerator with high precision and little fluctuation. 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 switch for starting and stopping the compressor from operating. Compressor stoppage can be prevented. Furthermore, by providing the motorized valve on the outlet side of the evaporator, the motorized valve only needs to control the flow rate of the gaseous refrigerant.
Compared to the case of controlling the flow rate of liquid refrigerant, the throttle mechanism of the electric valve itself does not require much precision (and an inexpensive electric valve can be used).

[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 evaporator suction temperature, and Figure 3 is the operation of an electric valve. Fig. 4 is a time chart showing changes in 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 internal temperature (solid line, ...This embodiment, broken line...Conventional example),
FIG. 7 is a flowchart showing an example of control of the frequency variable device, FIG. 8 is a refrigerant circuit diagram of a refrigeration system showing another embodiment, and FIG. 9 is a refrigerant circuit diagram of a refrigeration system showing a conventional example. 1... Refrigeration device, 2... Frequency variable device, 3.
... Compressor, 4... Condenser, 5... Evaporator,
7... Expansion valve, 8... Pressure sensor, 10...
Bypass pipe, 13...Electric valve, 14...Temperature sensor. Applicant Sanyo Electric Co., Ltd. and one other agent Patent attorney Shizuo Sano Figure 8

Claims (1)

[Claims] (1) It is composed of a compressor, a condenser, a pressure reducing device, an evaporator, etc. whose capacity is changed by a variable frequency device such as an inverter, and the frequency is determined 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 of a variable device, an electric valve that operates based on a signal from a temperature sensor that detects the ambient temperature of the evaporator is provided on the outlet side of the evaporator, and an electric valve is provided on the low pressure side of the compressor. A refrigeration system comprising: a bypass pipe that communicates with a high-pressure side; and when a variable frequency device reaches a lower limit frequency, the lower limit frequency is maintained and the bypass pipe is opened.