JPH0221510B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an air conditioner equipped with a refrigerant flow rate control device that appropriately controls the amount of refrigerant circulated in a refrigeration cycle.

[Prior art] Normally, in a refrigeration cycle, the appropriate refrigerant flow rate varies depending on the evaporation temperature, and as the evaporation temperature increases, a larger refrigerant flow rate is required. If the refrigerant flow rate adjustment range is small and the evaporation temperature is high, the refrigerant flow rate becomes unstable and the degree of superheating of the refrigerant at the evaporator outlet becomes too large, causing the compressor temperature to rise and the evaporation temperature to rise. When it is low, the refrigerant flow rate becomes excessive and may cause liquid backflow in the compressor. Therefore, in order to solve these problems, a refrigeration cycle as shown in FIG. 1 can be considered. That is, in FIG. 1, 1 is a compressor, 2 is a condenser, and 3 is a pressure reducing device. As shown in FIG. Insert and turn. Then, the main constriction section 32 and the refrigerant flow passage 33 between the outer tube 31 and the main constriction section 32 are connected to each other.
The inlet pipes 35, 36 and the outlet pipe 3 are arranged in parallel.
7, the inlet pipes 35 and 36 are connected to the outlet of the condenser 2, the outlet pipe 37 is connected to the inlet of the evaporator described later, and the inlet pipe 36 is provided with an electric expansion valve 38. It is. Reference numeral 4 denotes an evaporator, which is sequentially connected to the devices 1 to 3 described above to form a refrigeration cycle. Therefore, the compressor 1 and the condenser 2 function in the same way as a normal refrigeration cycle, but in the pressure reducing device 3, the liquid refrigerant supplied from the condenser 2 flows through the main constriction section 32 and is depressurized. , is evaporated in the evaporator 4 and has a cooling effect. Also,
A part of the liquid refrigerant supplied from the condenser 2 is depressurized by the electric expansion valve 38 and evaporated within the refrigerant flow path 33 to cool the refrigerant flowing through the main throttle section 32. The refrigerant flow rate within 32 increases. In other words, 2 of the refrigerant generated within the main constriction section 32
This is because the gas content in the phase flow decreases as the amount of cooling increases, and the fluid resistance decreases. Therefore, by adjusting the opening degree of the electric expansion valve 38, the amount of cooling of the refrigerant flowing in the main constriction section 32 is changed, and the fluid resistance increases or decreases, so the flow rate of the refrigerant can be controlled. By detecting the temperature at the inlet and outlet of the evaporator 4 and controlling the electric expansion valve 38 so that the outlet temperature of the evaporator 4 is always slightly higher than the inlet temperature, the refrigerant is completely gasified at the evaporator 4 outlet. , the degree of superheating is slightly increased, and an appropriate flow rate of refrigerant can be constantly circulated within the refrigeration cycle. By the way, as shown in FIG. 3, the optimum refrigerant circulation amount changes depending on the refrigeration load. In FIG. 3, curve AB indicates the optimum refrigerant circulation amount for the refrigeration load.
The range enclosed by AB'B''A' indicates the circulation amount secured by the main throttle section 32. However, in the above-mentioned refrigeration cycle, the main throttle section 32
Since the liquid refrigerant from the condenser 2 is always flowing through the refrigerant, even if the electric expansion valve 38 is fully closed, the refrigerant circulation amount indicated by AA' is still flowing.
Therefore, the refrigerant circulation amount is controlled to the optimum amount in the range from point A to point B in FIG. 3, but furthermore, in the range from point A to point C where the refrigeration load is small,
There are problems with the optimal refrigerant circulation rate that cannot be controlled.

[Summary of the invention]

This invention was made in consideration of the above-mentioned circumstances, and aims to always obtain the optimum amount of refrigerant circulation even in an air conditioner in which the refrigeration load of the refrigeration cycle fluctuates widely.

[Embodiment of the Invention] An embodiment of the invention is shown in FIG. 4 below. In the figure, 1 is a compressor, 2 is a condenser, and 3 is a pressure reducing device, which has the same configuration as shown in FIG. 2, but an inlet pipe 3.
5 is provided with a solenoid valve 39. 4 is an evaporator, which is sequentially connected to these devices 1 to 3 to form a refrigeration cycle. In addition, an electric expansion valve 38
is controlled by a controller (not shown) which detects and calculates the heat medium temperatures of the condenser 2 and evaporator 4, and determines the applied voltage based on a signal output according to the calculated values. That is, the opening degree of the electric expansion valve 38 is determined by the applied voltage. Further, the solenoid valve 39 is closed when the heat medium temperature on the outlet side of the evaporator 4 is below a predetermined value, and is opened when the temperature is above a predetermined value.

Next, the operation will be explained based on FIGS. 4 and 5. The direction of refrigerant flow is indicated by solid arrows.
The case of normal load will be explained. In this case, the electromagnetic valve 39 is open because the temperature of the heat medium on the outlet side of the evaporator 4 is higher than the predetermined value. Refrigerant gas discharged from the compressor 1 is condensed and liquefied in a condenser 2 and guided to a pressure reducing device 3. In the pressure reducing device 3, the condenser 2
The liquid refrigerant supplied from the main throttle section 32 is depressurized and evaporated in the evaporator 4 to perform a cooling effect. Further, a part of the liquid refrigerant supplied from the condenser 2 is depressurized by the electric expansion valve 38 and evaporated in the refrigerant flow path 33 to cool the refrigerant flowing in the main constriction section 32. The flow rate of refrigerant in the throttle section 32 increases.

When the load is further reduced from the above state, the opening degree of the electric expansion valve 38 is further reduced. Therefore,
The amount of cooling of the refrigerant flowing through the main constriction section 32 decreases, and the flow rate of the refrigerant within the main constriction section 32 decreases. When the load further decreases and reaches just before point A' shown in Fig. 5, the opening degree of the solenoid valve 39 becomes fully closed.
The amount of cooling of the refrigerant flowing through the main constriction section 32 becomes 0, which is similar to complete capillary reach tube control. Furthermore, the load is further reduced, as shown in Fig. 5.
When the temperature drops below point A', the solenoid valve 39 closes and at the same time, the electric expansion valve 38 becomes open, and A-
The amount of refrigerant circulation indicated by A' is the same as that just before point A'. Furthermore, when the load decreases (for example, at point C' shown in FIG. 5), the opening degree of the electric expansion valve 38 decreases, allowing a circulating amount of refrigerant shown by C-C' to flow. In addition,
In FIG. 5, the area enclosed by CAA'C' indicates the amount of circulation ensured by the electric expansion valve 38.

〔Effect of the invention〕

With the above configuration, even in low-load operating conditions, the optimal refrigerant circulation amount can be ensured by opening and closing the solenoid valve and adjusting the opening of the electric expansion valve, allowing relatively simple control. This enables optimal control over a wide operating range and improves the reliability of the air conditioner.

[Brief explanation of drawings]

Figure 1 is a refrigeration cycle diagram showing a conventional example;
Figure 3 is a configuration diagram showing the configuration of a pressure reducing device, Figure 3 is a diagram showing the relationship between refrigeration load and optimal refrigerant circulation amount, which shows a conventional example, Figure 4 is a refrigeration cycle diagram showing an embodiment of the present invention, and Figure 5 The figure is a diagram showing the relationship between the refrigeration load and the optimum refrigerant circulation amount, showing one embodiment of the present invention. Further, in the figure, 1 is a compressor, 2 is a condenser, 3 is a pressure reducing device, 4 is an evaporator, 32 is a main throttle section, 38 is an electric expansion valve, and 39 is a solenoid valve. In addition, in the figure,
The same reference numerals indicate the same parts and corresponding parts.

Claims (1)

[Claims] 1. A solenoid valve and a main constriction section for reducing the pressure of the liquid refrigerant from the condenser flowing through the solenoid valve, and a main constriction section provided in parallel with the solenoid valve and the main constriction section, and a part of the liquid refrigerant from the condenser The main throttle section is cooled, and the refrigerant after cooling is adjusted to adjust the refrigerant flow rate in the bypass channel according to the operating state of the bypass channel and the refrigeration cycle arranged so that the cooled refrigerant merges with the refrigerant that has passed through the main throttle section. A refrigerant flow control device includes an electric expansion valve that changes the amount of cooling in the main throttle section, and when the refrigeration load of the refrigeration cycle is small, the solenoid valve is closed and the refrigerant flow rate is controlled only by the electric expansion valve. An air conditioning apparatus characterized in that when the refrigeration load of the refrigeration cycle is large, the solenoid valve is opened and the refrigerant flow rate is controlled by the solenoid valve and the electric expansion valve.