JPH03225161A - Liquid injection device of freezing cycle in thermostatic device - Google Patents

Abstract

PURPOSE:To enable a disturbance of a freezing cycle caused by a liquid injection to be reduced by a method wherein a liquid injection refrigerant passage is arranged to be connected to a refrigerant passage branched from a refrigerant passage between a condensor and a pressure reducing mechanism, passing through an oil cooler of a pressure device and an electrical expansion valve and between an evaporator and a suction side of a compressor. CONSTITUTION:A branch pipe is arranged between a condensor 2 and a pressure reducing mechanism 3 and then the branch pipe is connected to an inlet pipe of an oil cooler 1a of a compressor. An outlet pipe of the oil cooler 1a is connected through an electronic expansion valve 5 to the branch pipe arranged between an evaporator 4 and a suction of the compressor 1. A temperature sensor 8 detects a temperature in a thermostatic chamber, a temperature sensor 9 detects a temperature outside the thermostatic chamber, a temperature sensor 10 detects a temperature of discharged gas of the compressor and a temperature sensor 11 detects an oil temperature of the compressor. A micro-computer 12 takes each of the temperatures detected by the sensors 8 to 11, calculates these temperature signals and outputs a proper pulse-like signal of a degree of opening to the electronic expansion valve 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid injection and oil cooler mechanism of a refrigeration cycle of a constant temperature device.

[Prior art] In a constant temperature device that uses a refrigeration cycle, the temperature inside the constant temperature chamber (hereinafter simply referred to as room temperature or room temperature) is 150°C.
Since the temperature ranges over a wide range from -70°C, it occurs when the refrigerator is operated in a state where the indoor temperature is high. Therefore, in this case, the refrigerant that returns from the evaporator is a superheated gas with approximately the same temperature as the room temperature, and therefore the temperature of the discharge gas and oil of the compressor becomes high and may not meet the specifications of the compressor. obtain. Therefore, liquid injection is necessary to prevent this. Additionally, hermetic compressors are equipped with an oil cooler mechanism to release heat from the motor.

In conventional thermostats, the liquid injection circuit and oil cooler mechanism exist as separate mechanisms. The liquid injection circuit is composed of a capillary tube and a solenoid valve, and the solenoid valve is generally opened and closed by detecting the temperature of the compressor discharge gas. Furthermore, when it is desired to change the amount of liquid injection, a method is adopted in which a plurality of capillary tubes with different aperture amounts are switched.

The oil cooler mechanism has a structure in which the condenser refrigerant pipe is directly connected to the oil cooler artificial pipe midway through the condenser, and returns to the condenser again from the oil cooler outlet pipe. Therefore, all the refrigerant flowing through the condenser passes through the oil cooler.

An example of a related device of this type is Utility Model Application No. 63-132252.

[Problems to be Solved by the Invention] Liquid injection in the prior art is performed by opening and closing an electromagnetic valve, so there is a problem in that the refrigeration cycle is suddenly disturbed, and this disturbance causes disturbances in indoor temperature control. Further, in a constant temperature device, the temperature range in the operating room is wide ranging from 170°C to 150°C, so the appropriate amount of liquid injection differs depending on the size of the operating room, but there was a problem that this was not satisfied with the conventional technology.

Further, the operating ambient temperature of the constant temperature device (temperature outside the constant temperature room) is wide ranging from 0°C to 40°C. However, in the oil cooler mechanism of a conventional constant temperature device with an air-cooled condenser, the amount of refrigerant passing through the oil cooler is constant, so when the ambient temperature of the device is low, the amount of refrigerant passing through the oil cooler does not reach the appropriate amount. There was a problem in that the oil temperature became excessive in comparison and the oil temperature fell below the compressor specification value.

The present invention has been made in order to solve the problems of the prior art, and its purpose is to: (i) set the amount of night injection and the amount of refrigerant passing through the oil cooler to appropriate amounts;
The purpose is to eliminate the above-mentioned problems on the refrigeration cycle and oil temperature, suppress disturbances in the refrigeration cycle, and prevent disturbances in indoor temperature control of a constant temperature device.

[Means for Solving the Problems] The present invention provides a liquid injection device in a constant temperature device having the features described in each claim.

[Function] The opening degree of the electronic expansion valve is controlled to optimize the amount of refrigerant for liquid injection: (1) The opening degree is set in advance according to the temperature inside the thermostatic chamber and the ambient temperature. or (2) when the temperature of the discharged gas exceeds a predetermined limit, continuous control, such as Pl[) control, is performed in accordance with the temperature.

There are two ways.

The opening degree of the electronic expansion valve is controlled to optimize the amount of refrigerant passing through the oil cooler: (1) The opening degree is set in advance according to the temperature inside the thermostatic chamber and the ambient temperature of the device. or (2) when the oil temperature exceeds a predetermined limit, continuous control, such as PID control, is performed according to the temperature.

There are two ways.

During operation when the oil temperature is low, the discharge gas temperature is also low, so the amount of liquid injection will not run out.

[Example] An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a diagram showing a partial schematic cross section of a constant temperature chamber of a constant temperature device, a refrigeration cycle system of the constant temperature device, and human output of signals to a microcomputer according to an embodiment of the present invention.

An evaporator 4 that cools the air in the room, a heater 6 that heats the air in the room, and a blower 7 that circulates the air in the room are arranged in a constant temperature room separated by a heat insulating material 13.

The temperature inside the constant temperature room (hereinafter abbreviated as vehicle interior temperature or room temperature) is detected by a temperature sensor 8. The evaporator 4 is
A completely hermetic compressor 1, a condenser 2, and a pressure reducing mechanism 3 constitute one refrigeration cycle. In this embodiment, a branch pipe is provided between the condenser 2 and the pressure reducing mechanism 3, and this branch pipe is connected to the inlet pipe of the oil cooler 1a of the compressor. The outlet pipe of the oil cooler 1a is connected to a branch pipe provided between the evaporator 4 and the suction side of the hermetic compressor 1 via an electronic expansion valve 5. Temperature sensor 9 detects the temperature outside the constant temperature room, temperature sensor 10 detects the compressor discharge gas temperature, and temperature sensor 11 detects the oil temperature of the compressor. Each temperature detected by the temperature sensors 8 to 11 is taken into the control microcomputer 12. The control microcomputer 12 calculates these temperature signals and outputs an appropriate pulse-shaped opening signal to the electronic expansion valve 5.

Next, control of liquid injection and oil cooler according to this embodiment will be explained.

As mentioned in the [Prior Art] section, when using a constant temperature device, there are times when the refrigerator is operated at a high indoor temperature.
Since the refrigerant that returns from the evaporator 4 is a superheated gas with a temperature almost the same as room temperature, the discharge gas temperature and oil temperature of the hermetic compressor 1 may become high, and the compressor specification range may not be met. Ru. Therefore, liquid injection is necessary to prevent this, but since the room temperature disturbance allowed by a constant temperature device is ±05°C to ±0.3°C as required by the market, it is not permissible to disturb the refrigeration cycle by night injection. Not done. Furthermore, the temperature range of the room temperature of the constant temperature device is wide, and the enthalpy of the refrigerant returned from the evaporator 4 differs depending on the room temperature, so injecting a fixed amount of liquid as in the prior art will result in excess or deficiency. For the above two reasons, it is necessary to control the amount of liquid injected in the constant temperature device to an appropriate amount to bring the discharge gas temperature within the specification range.

Further, the ambient temperature at which the constant temperature device can be operated is within a wide range of 0°C to 40°C. Therefore, if the refrigerant flow rate through the oil cooler is constant, such as in the oil cooler mechanism of a conventional constant temperature device with an air-cooled condenser, when the ambient temperature of the device is low, the refrigerant flow rate through the oil cooler will be lower than the appropriate value. This will cause the oil temperature to drop below the compressor specifications. Therefore, the flow rate of refrigerant flowing through the oil cooler mechanism also needs to be appropriately controlled so as to keep the oil temperature in the compressor within the specified range.

This embodiment appropriately controls the liquid injection and the refrigerant flow rate passing through the oil cooler as described above.
This will be explained below.

Figure 3 (illustrated is the electronic expansion valve 5 which is controlled according to the detected indoor temperature when the ambient temperature of the device is 20°C)
2 shows the degree of opening of the compressor 1 and the accompanying changes in the discharge gas temperature and oil temperature of the compressor 1. In the figure, the solid line graph corresponds to the present embodiment, and the dashed line graph (indicated as Conventional A and Conventional S) corresponds to the conventional technique.

In this embodiment, the opening degree of the electronic expansion valve 5 is controlled to change in a predetermined stepwise manner according to the indoor temperature as shown in the figure, and as a result, the discharge gas temperature and oil temperature are changed as shown by the solid line in the figure. Changes to The amount of liquid injection, i.e.
In this embodiment, the appropriate value of the refrigerant flow rate passing through the oil cooler a is obtained by the expansion valve opening degree shown by the solid line in the section of the room temperature from 20°C to 40°C in Fig. 3 (#). shall be taken as a thing. If the expansion valve opening, that is, the liquid injection amount remains constant regardless of the indoor temperature, as shown by the broken line in conventional a, the discharge gas temperature and oil temperature will exceed the upper limit of the specification value when the indoor temperature is around 50°C.

In addition, in the area where the indoor temperature is 60 to 80°C, the discharge gas temperature,
It is assumed that the appropriate amount of liquid infusion for which the oil temperature satisfies the specifications can be obtained at the expansion valve opening degree shown by the solid line in the relevant section in FIG. 3 (7). If the expansion valve opening degree, that is, the amount of liquid injection were constant as shown by the broken line in the conventional case, the oil temperature would fall below the lower limit of the specification when the room temperature was around 30°C. However, such a situation does not occur in this embodiment because the opening degree of the expansion valve 5 is changed stepwise according to the room temperature as shown in the figure.

Figure 3 (J) shows how the opening degree of the expansion valve 5 is controlled according to the detected ambient temperature when the indoor temperature is 20°C, and the accompanying changes in oil temperature and discharge gas temperature. The meanings of the solid lines and broken lines are the same as in the case of FIG. 3 (6). If conventional C
Assuming that the expansion valve opening is constant regardless of the ambient temperature, as shown by the broken line, when the ambient temperature drops below 20°C, the temperature of the refrigerant passing through the oil cooler drops and the ambient temperature drops to 10°C.
℃ or below, the oil temperature cannot satisfy the specified lower limit value, but in this embodiment, the opening degree of the expansion valve 5 is controlled as shown by the solid line according to the ambient temperature, so this situation does not occur.

The above is the electronic expansion valve 5 in advance depending on the indoor temperature and ambient temperature.
This is an example of a control method that determines the opening degree of the valve.

Another embodiment regarding the opening control of the electronic expansion valve 5 will be described below with reference to FIGS. 4 and 5.

FIG. 4 shows an example in which the opening degree of the expansion valve 5 is controlled according to the temperature of the discharge gas from the compressor. The discharge gas temperature increases due to reasons such as an increase in indoor temperature or an increase in ambient temperature. Assume now that the upper limit of the specification range for the discharge gas temperature of the compressor is 130°C.

If the opening degree of the expansion valve 5 is not controlled, the discharge gas temperature will exceed the upper limit of the specification range. Therefore, in this example, the control temperature is set at 120°C, and the discharge gas temperature is set at 120°C.
When the temperature becomes 3 degrees lower than the above temperature, the opening degree of the electronic expansion valve 5 is PID-controlled to maintain the discharge gas temperature at 120°C. When the discharge gas temperature becomes 3 degrees or more lower than 120° C., the opening degree of the electronic expansion valve 5 is returned to the standard opening degree again. Such control allows the discharge gas temperature to always satisfy the upper specification limit of the compressor.

FIG. 5(a) shows an example in which the opening degree of the electronic expansion valve 5 is controlled based on the detected oil temperature so that the oil temperature does not exceed the upper limit of specifications. Similar to the discharge gas temperature, the oil temperature also increases due to reasons such as an increase in room temperature or an increase in ambient temperature. Assume that the upper specification limit for the oil temperature of the compressor is 90°C. If the opening degree of the electronic expansion valve 5 is not controlled, the oil temperature will exceed the upper limit of the specification range.

Therefore, in this embodiment, 80°C is set as the control temperature, and when the oil temperature becomes 3 degrees lower than 80°C, the opening degree of the electronic expansion valve 5 is PID controlled to maintain the oil temperature at 80°C. do. When the oil temperature becomes 3 degrees or more lower than 80° C., the opening degree of the electronic expansion valve 5 is returned to the standard opening degree again. This control allows the oil temperature to satisfy the upper limit of the compressor specifications.

FIG. 5(b) shows an example in which the opening degree of the electronic expansion valve 5 is controlled based on the detected oil temperature so that the oil temperature does not fall below the lower limit of the specification. If the opening degree of the electronic expansion valve 5 is not controlled, a phenomenon occurs in which the oil temperature falls below the lower limit of the specification value of the compressor due to a decrease in room temperature and ambient temperature. Therefore, in this embodiment, the control temperature is set at 20°C with respect to the lower limit of 10°C, and the oil temperature is set at 20°C.
When the temperature becomes 3 degrees higher than ℃, the opening degree of the electronic expansion valve 5 is controlled by PID to maintain the oil temperature at 20℃.

If the oil temperature becomes 3 degrees or more higher than 20°C, the opening degree will be returned to the standard opening degree. Thereby, the oil temperature can be controlled so as to satisfy the lower limit of the compressor specifications.

As described above, in order to maintain the discharge gas temperature or oil temperature of the compressor within the specification range, the opening degree of the electronic expansion valve 5 is controlled according to the detected value of the indoor temperature, ambient temperature, discharge gas temperature, or oil temperature. Although the above control methods have been described, the constant temperature device may adopt any one of these methods, or a combination of two or more methods, if necessary. The control microcomputer 12 is caused to perform such control.

FIG. 2 shows an example that is different from the first section in that the liquid injection refrigerant is introduced into the suction side of the compressor via the electronic expansion valve 5 without an oil cooler. Since compressor oil is also cooled by liquid injection, the above-described control can be applied in this example as well.

[Effects of the Invention] According to the present invention, it is possible to reduce disturbances in the refrigeration cycle caused by liquid injection, so that the disturbances in the temperature inside the thermostatic chamber during liquid injection can be reduced, for example, from ±0.5 to ±
It can be made as low as 0.3℃.

Furthermore, the amount of liquid injectidine can be controlled to an appropriate amount over a wide range of constant temperature chamber temperatures, and the discharge gas temperature does not exceed the specification limit.

Furthermore, when the ambient temperature is low, the flow rate of refrigerant for cooling the oil can be reduced, which has the effect of preventing a drop in oil temperature.

Furthermore, by obtaining an appropriate amount of liquid injection and oil cooling, there is no wasted bypass refrigerant, and there is an effect of minimizing a decrease in refrigerating capacity.

Further, by integrating the liquid injection circuit and the oil cooler mechanism, reliability is increased, and an inexpensive and highly reliable refrigeration cycle can be provided.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams showing the configuration of an embodiment of the constant temperature device of the present invention, and FIGS. FIG. 4 is a diagram showing the change in discharge gas temperature and oil temperature; FIG. 4 is a diagram showing another control method of the constant temperature device according to the embodiment of the present invention; FIG. 5 is a diagram showing the relationship between discharge gas temperature and expansion valve opening; Figures (a) and (b) show a control method for a constant temperature device according to an embodiment of the present invention, and are diagrams showing the relationship between oil temperature and expansion valve opening degree. 1... Compressor, 2... Condenser, 3... Pressure reduction mechanism,
4... Evaporator, 5... Electronic expansion valve, 6... Heater, 7... Air blower, 8... Room temperature sensor, 9... Device ambient temperature sensor, 10... Discharge gas Temperature sensor, 11... Oil temperature sensor, 12... Control microcomputer, 13.°° insulation material, 1a.
・Oil cooler. Figure 1: Microcomputer Figure 2: How to enter and exit the microcomputer Figure 3: Indoor 5 degrees ('C) Ambient temperature ('C) Figure 4: Time course Figure 5 (α)

Claims (1)

[Claims] 1. A refrigeration cycle is provided in which the refrigerant discharged from the compressor passes through a condenser, a pressure reducing mechanism, and an evaporator in this order and returns to the compressor, and the evaporator is used as a cooler in a constant temperature room. In the thermostat installed, a liquid injection system branches from the refrigerant path between the condenser and pressure reduction mechanism and connects to the refrigerant path between the evaporator and the suction side of the compressor via an electronic expansion valve with variable opening. A refrigeration cycle in a constant temperature device, characterized in that a refrigerant path is provided and control means is provided for controlling the opening degree of the electronic expansion valve so as to maintain the compressor discharge gas temperature and/or the compressor oil temperature within the specification range. liquid injection device. 2. A constant temperature device equipped with a refrigeration cycle in which the refrigerant discharged from the compressor passes through a condenser, a pressure reducing mechanism, and an evaporator in this order and returns to the compressor, and the evaporator is installed as a cooler in a constant temperature room. , the liquid injection branched from the refrigerant path between the condenser and the pressure reduction mechanism and connected to the refrigerant path between the evaporator and the suction side of the compressor via the compressor's oil cooler and an electronic expansion valve with variable opening. A refrigeration cycle in a constant temperature device, characterized in that a refrigerant path is provided and control means is provided for controlling the opening degree of the electronic expansion valve so as to maintain the compressor discharge gas temperature and/or the compressor oil temperature within the specification range. liquid injection device. 3. The control means includes a thermostatic chamber internal temperature sensor, an ambient temperature sensor, and a controller that controls the opening degree of the electronic expansion valve so that the opening degree is predetermined as a function of the temperatures detected by these sensors. according to claim 1 or 2, consisting of
Liquid injection device for refrigeration cycle in constant temperature equipment. 4. The control means controls the compressor discharge gas temperature sensor and/or the compressor oil temperature sensor so that when the detected temperature of one or both of these sensors deviates from the respective predetermined limit temperatures, the deviation is corrected. 3. A liquid injection device for a refrigeration cycle in a constant temperature device according to claim 1, further comprising a controller that continuously controls the opening degree of an electronic expansion valve.