JPS628702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air conditioner that operates continuously under a wide range of temperature conditions, and in particular is equipped with a mechanism for preventing overload on cycle components under high temperature outside air conditions. The present invention relates to the air conditioner.

In recent years, there has been a strong demand for improved livability, and air-cooling systems used in extremely hot regions or vehicles, such as the air-cooled cooling system disclosed in Japanese Patent Application Laid-Open No. 50-54948, have become increasingly popular when the outside temperature is 50-50°C. There is a growing demand for continuous operation of air conditioners even when the temperature rises to 60℃.

On the other hand, for example, in conventional air conditioners in which a compressor, condenser, expansion means, and evaporator are connected in sequence, when the outside air temperature rises abnormally, the condensing pressure or temperature rises abnormally, causing the compression It has been difficult to meet the above-mentioned requirements because of fatal adverse effects on the operation of the air conditioner, such as destruction of air conditioner valves, deterioration of the refrigerant, and insulation breakdown of the compressor motor coil. Therefore, for example, in the above-mentioned air conditioner using refrigerant R-22, the maximum outside air temperature at which it can be operated is approximately 45°C, and if the temperature exceeds this, continuous operation of the air conditioner is impossible and operation must be stopped. It used to stop. From the principle of air conditioning equipment,
In order to enable the air conditioner to operate even under such abnormally high temperatures, it is sufficient to make the heat dissipation area of the condenser sufficiently large, but when considering the frequency of operation under such abnormally high temperatures, This cannot be said to be a realistic solution in terms of equipment installation space or economic efficiency.

Therefore, in order to meet this demand, considering the frequency of use under abnormally high temperatures, it is better to maintain the durability of the component equipment and improve livability by not stopping the operation of the air conditioner, even if it sacrifices some cooling capacity. An air conditioner equipped with a compressor overload prevention mechanism using a so-called liquid bypass system has been proposed for the air conditioner as shown in FIG. 1. .

The air conditioner shown in the figure is capable of continuous operation even under particularly high-temperature outside air conditions, and consists of a compressor 1, an air-cooled condenser 2, a main circuit expansion means 3, and an evaporator 4 connected in sequence. The main circuit A is connected from the outlet of the condenser 2 to the compressor 1 so as to bypass the evaporator 4.
(referred to as a first bypass circuit B). The bypass circuit B is provided with a circuit opening/closing means 5, a circuit expansion means 6, and a refrigerant heat exchanger 7, and the opening/closing means 5 opens and closes according to the condensing pressure of the air conditioner, for example. The refrigerant heat exchanger 7 condenses the bypass refrigerant which has been intermittently expanded by the expansion means 6 to a low temperature and low pressure. The structure is such that the high-temperature, high-pressure refrigerant at the outlet of the container 2 is placed in a heat exchange relationship.

In such an air conditioner, when the air conditioner is operated under normal temperature conditions, cold is generated in the evaporator 4 by a well-known function to perform the desired cooling, and of course the first bypass circuit is occluded. However, as described above, if the temperature of the outside air used to cool the condenser 2 rises abnormally, heat dissipation in the condenser 2 becomes insufficient. Therefore, due to the self-controllability of the air conditioner, the condensing temperature, that is, the condensing pressure increases so that the temperature difference with the outside air becomes larger. When this pressure (approximately equal to the discharge pressure of the compressor 1) exceeds a limit value determined for the durability of the compressor, the opening/closing means 5 is opened and a portion of the refrigerant in the main circuit A flows into the bypass circuit B. This refrigerant is expanded into a low-temperature, low-pressure refrigerant by an expansion means 6 in the same circuit, and sent to a refrigerant heat exchanger 7. Here, the high-temperature, high-pressure refrigerant in the main circuit A is cooled, and the refrigerant itself is heated and sucked into the compressor 1.

At this time, the flow rate of refrigerant supplied to the evaporator 4 of the main circuit A decreases, so the amount of heat absorbed in the evaporator 4 decreases, and the required amount of heat radiation in the condenser 2 decreases. In addition, since the high temperature refrigerant in the main circuit A is cooled by the low temperature refrigerant in the bypass circuit B in the refrigerant heat exchanger 7, the temperature of the condensate becomes low.

Due to these two effects, even if the outside air temperature rises abnormally, the condensing pressure (temperature) can be kept below a predetermined limit value. As the outside air temperature further rises, the flow rate flowing into the bypass circuit B increases due to the action of the circuit opening/closing means 5, and the amount of refrigerant sent to the evaporator 4 decreases accordingly, so that the condensing pressure does not exceed the limit value. .

In this way, the air conditioner can operate continuously even under outside air conditions that are higher than the conventional temperature limit.

Incidentally, one of the problems with this type of air conditioner is that when the bypass circuit B is opened, the temperature of the gas discharged from the compressor 1 may rise abnormally. This phenomenon will be explained using FIG. 2 as follows.

This figure shows the changes in the discharge pressure of the compressor 1 and the gas temperature with respect to the cooling air temperature of the condenser 2 in the air conditioner shown in FIG. 1 above, using the cooling load of the evaporator 4 as a parameter. . As shown in the figure, the discharge pressure of the compressor 1 is controlled to be below the limit value regardless of the magnitude of the cooling load, but as the cooling load increases, the discharge gas temperature of the compressor 1 is controlled to be above the limit value. This means that there exists an area where

Generally, in the case of an air conditioner using refrigerant R-22, the discharge gas temperature limit value is 120 to 130°C. If this value is exceeded, deterioration of the refrigerant, deterioration of the compressor lubricating oil, or in the case of a compressor with a built-in motor, an abnormal rise in the motor coil temperature, etc. will occur.
Causes serious adverse effects on air conditioner operation.

The present invention has been made in view of the above points, and an object of the present invention is to provide an air conditioner equipped with a compressor overload prevention mechanism using the liquid bypass method, in which the compressor is compressed when the bypass circuit is opened. It is an object of the present invention to provide the air conditioner which suppresses a rise in discharge gas temperature and has more excellent durability.

The present invention has the following drawbacks of the above-mentioned air conditioner:
The degree of superheating of the refrigerant at the outlet of the evaporator 4 increases as the amount of refrigerant flowing into the evaporator 4 decreases, and the degree of superheating of the refrigerant on the low-pressure side of the bypass circuit in the refrigerant heat exchanger 7 increases when the bypass flow rate decreases. We have experimentally confirmed that this is caused by an increase in the suction refrigerant temperature, and as a way to prevent this increase in suction refrigerant temperature, we have the compressor 1 suck in low-temperature refrigerant with high humidity, thereby reducing the discharge gas temperature. This prevents the increase.

This point will be explained in more detail as follows. As shown in FIG. 1, when the bypass circuit B is open, the compressor 1 transfers the refrigerant that exerts a cooling effect and absorbs heat in the evaporator 4 of the main circuit A and the refrigerant heat exchanger of the bypass circuit B. At step 7, the refrigerant in which the refrigerant that has absorbed heat from the high-temperature refrigerant in the main circuit A is merged and mixed is sucked. When the bypass circuit B is open, the amount of refrigerant flowing into the evaporator 4 decreases relative to the cooling load of the evaporator 4 as described above, so the degree of superheating of the refrigerant at the outlet of the evaporator 4 increases.
The degree of overheating increases as the cooling load increases.

On the other hand, the amount of heat exchanged in the refrigerant heat exchanger 7 is such that the required bypass amount flows when the air conditioner is operated at the highest outside temperature, and the liquid returns to the compressor 1 (refrigerant with high humidity is compressed). It is necessary to determine the heat transfer area of the heat exchanger 7 so that the heat exchanger 7 has a value that does not cause the phenomenon of suction into the heat exchanger 1. This is because, as is well known, the return of liquid to the compressor causes inconvenient effects on the operation of the compressor, such as dilution of the compressor lubricating oil and destruction of the valves of the compressor due to liquid compression.It is important to avoid this phenomenon. This is an essential requirement for air conditioner design.
In addition, in reality, the refrigerant at the outlet of the refrigeration heat exchanger 7 is
Depending on the degree of superheat at the outlet of the evaporator 4, a slightly damp state may be allowed.

Therefore, in an operating situation where the outside temperature is higher than the conventional limit outside temperature but below the maximum outside temperature that can be predicted, the flow rate flowing into the bypass circuit B is small, and therefore the refrigerant at the low pressure side outlet of the refrigerant heat exchanger 7 is The degree of superheating has become quite high. in this way,
In a region where the enthalpy of the refrigerant at the low-pressure side outlet of the refrigerant heat exchanger 7 is higher than the enthalpy of the refrigerant at the outlet of the evaporator 4, the refrigerant temperature sucked into the compressor 1 is lower than the refrigerant temperature at the outlet of the evaporator 4. This will induce an increase in the discharge gas temperature.

In order to prevent this discharge gas temperature from rising,
It is necessary to lower the temperature of the refrigerant sucked into the compressor 1 by some method.

The first consideration is to lower the temperature of the refrigerant at the outlet of the evaporator 4. For this purpose, it is necessary to supply the evaporator 4 with more refrigerant than the cooling load of the evaporator 4, but this impairs the overload prevention function of this system. In other words, by doing this, the amount of heat absorbed by the evaporator 4 increases, and the amount of heat absorbed by the condenser 2 increases.
This increases the amount of heat dissipation required, making it difficult to maintain the condensing pressure below the limit value.

Another method is to make the opening/closing means of the bypass circuit B capable of changing the degree of opening according to changes in the temperature of the discharged gas. Compared to the case of changing the flow rate according to the pressure change shown in Figure 1, this method means that the bypass flow rate is further increased in the outside air condition region in question, and the degree of decrease in cooling capacity is reduced. In addition, the bypass flow rate decreases at the maximum outside temperature, and although the temperature can be maintained below the limit value, the pressure limit may be exceeded.
Furthermore, control based on the temperature detection method generally has a slow response and has problems such as not being able to adequately respond to pressure changes.

Therefore, when taking into account the frequency of excessive cooling loads, the system shown in Fig. 1 may include, if necessary, sucking refrigerant with an enthalpy smaller than the enthalpy of the refrigerant at the 4th outlet of the evaporator into the refrigerant sucked into the compressor. In other words, the best solution is to introduce a low-temperature refrigerant that does not absorb heat or has high humidity into the low-pressure piping of the compressor to lower the intake gas temperature, thereby preventing the discharge gas temperature from rising. preferable.

Hereinafter, the present invention will be explained in more detail using a specific embodiment shown in FIG.

First, to explain the embodiment shown in FIG. 3, a main circuit A is constructed by sequentially connecting a compressor 1, an air-cooled condenser 2, an expansion means 3, and an evaporator 4. A portion of the refrigerant in the main circuit A is bypassed from the outlet of the condenser 2 to the inlet of the compressor 1 through the expansion means 6 and the refrigerant heat exchanger 7, so as to bypass the evaporator 4 of the main circuit A. A second bypass circuit C is arranged in parallel between the first bypass circuit B, the expansion means 6 of the circuit B, and the refrigerant heat exchanger 7 so as to bypass the expansion means 6 of the circuit B. A circuit opening/closing means 11 is disposed in the middle of the second bypass circuit C and is activated by detecting a change in the temperature of the gas discharged from the compressor 1. This opening/closing means 11 includes a fluid introduction part 11a branched and joined to a pipe 8 connecting the outlet of the expansion means 6 and the refrigerant heat exchanger inlet, and a fluid introduction part 11a whose tip is connected to the low pressure side outlet of the refrigerant heat exchanger 7. The derivation section 11b and both of these 11a and 11b
an opening 11 that separates the
a housing member 11e composed of a seat material 11d having a diameter of 1.c; a valve body 11f that forms a gap (not shown) through which fluid can flow by relatively changing the positional relationship with the seat material 11d; A spring 11g that presses against the valve body 11f, an adjustment mechanism 11h for changing the strength of the spring 11g, one end of which is fixed to the casing member 11e, and a spring 11i inside the casing member 11e. A flexible member such as a bellows frame 11j configured to be isolated from the inside, a rod 11k having one end fixed to this and the other end pressed against the valve body 11f, and the inside of the bellows frame 11j and the conduit 11.
1, and has a temperature sensing end 112 inside which has a medium, such as a gas or a liquid, for converting a temperature change into a pressure change. This temperature detection end 112 is installed in the discharge pipe 10 of the compressor 1 so as to detect the temperature of the discharge gas of the compressor 1. Further, when the detection end 112 detects a temperature equal to or higher than a preset temperature, the valve body 11f separates from the seat member 11d, and the spring 11
The strengths of g and 11i are set respectively.

In an air conditioner with such a configuration,
The functions of the air conditioner under normal temperature conditions and conditions in which the cooling air in the condenser 2 becomes high, the condensing pressure exceeds a predetermined value, and the first bypass circuit B functions are as explained in Fig. 1 above. Since they are the same, they will be omitted here.

Now, when the first bypass circuit B is open and the cooling load of the evaporator 4 of the main circuit A increases, the discharge gas temperature of the compressor 1 increases as explained in FIG. 2 above. , will eventually exceed this limit value. In such a case, the temperature sensing end 112 of the opening/closing means 11 of the second bypass circuit C detects this abnormality as an internal pressure change, and transmits it to the bellow flamm 11j via the conduit 111. The bellow frame 11j then expands, and the rod 11k fixed thereto acts on the valve body 11f in the opening direction.
As a result, the inlet portion 11a and the outlet portion 11b communicate with each other, and the humid, low-temperature, low-pressure refrigerant coming out of the expansion means 6 bypasses the refrigerant heat exchanger 7 and enters the first
This results in lowering the temperature of the refrigerant in the bypass circuit B and thus the refrigerant sucked into the compressor 1. Therefore, the discharge gas temperature of the compressor 1 will decrease.
This action continues until the temperature detection end 112 detects a temperature below the discharge gas temperature limit value, and the greater the degree to which the discharge gas temperature exceeds the limit value, the more the humidity flowing through the second bypass circuit C increases. The amount of low-temperature refrigerant with high temperature increases.

In addition, as the opening/closing means 11, an energizing circuit is activated by a thermoswitch that detects the discharge gas temperature.
A solenoid valve that can be turned on and off may be used, but this method requires a complicated control circuit, and since the flow rate is almost constant when open, hunting is likely to occur. As shown in the figure, it is preferable to use means that allows the flow rate flowing into the second bypass circuit C to be changed continuously in accordance with the magnitude of the discharge gas temperature. Furthermore, in the embodiment, the first
The low-temperature, low-pressure refrigerant is bypassed from the downstream side of the expansion means 6 of the first bypass circuit B, but the opening/closing means 11 is also provided with an expansion function, and It goes without saying that the same effect can be obtained by bypassing the high-temperature, high-pressure refrigerant from upstream of the opening/closing means 11.
It is necessary to use one with a high allowable pressure.

As explained above, according to the present invention, a low-temperature, low-pressure refrigerant with high humidity can be mixed into the compressor suction gas as necessary at the time of overload to lower the gas temperature. Since the present invention has the effect of preventing an abnormal rise in the temperature of the compressor discharge gas, it is possible to provide an air conditioner with an overload prevention mechanism that is more durable.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional air conditioner equipped with a mechanism to prevent overload under high-temperature outside air conditions.
The figure is a characteristic diagram of the discharge pressure and discharge gas temperature of the compressor to explain the problems in the air conditioner of Figure 1, and Figure 3 is a system showing an embodiment of the air conditioner according to the present invention. It is a diagram. A... Main circuit, B... First bypass circuit, C
...Second bypass circuit, 1...Compressor, 2...
Condenser, 3... Main circuit expansion means, 4... Evaporator,
5...first bypass circuit opening/closing means, 6...first
bypass circuit expansion means, 7...refrigerant heat exchanger,
11...Second bypass circuit opening/closing means.

Claims (1)

[Claims] 1. In a refrigeration cycle formed by sequentially connecting a compressor, an air-cooled condenser, a main circuit expansion means, and an evaporator, a first bypass circuit is provided between the upstream side of the main circuit expansion means and the upstream side of the compressor. A first bypass circuit is formed by sequentially arranging an opening/closing means, a first bypass circuit expansion means, and a refrigerant heat exchanger adjacent to the downstream side of the air-cooled condenser from the upstream side of the main circuit expansion means. In the harmonizing device, a second bypass circuit operates to bypass the refrigerant of the refrigerant heat exchanger when refrigerant flows through the first bypass circuit and a refrigerant temperature downstream of the compressor rises above a predetermined value. An air conditioner characterized in that a bypass circuit opening/closing means is disposed between the upstream side of the compressor and the main circuit expansion means.