JP2004360965A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device for controlling the degree of superheat of outlet refrigerant in an evaporator to be a preset value by using a tank incorporating a heat exchanger for heat exchange with the outlet refrigerant in the evaporator for adjusting the amount of the refrigerant filled in a cycle to control the degree of superheat of the outlet refrigerant in the evaporator. <P>SOLUTION: The tank 6 is arranged in a pipe 5 on the outlet side of the evaporator 4, and the heat exchanger 7 is arranged in the tank 6 for heat exchange between the outlet refrigerant in the evaporator 4 and refrigerant inside the tank 6. Besides, the inside of the tank 6 is communicated with an inlet portion of the evaporator 4 via a communication pipe 8. The saturation temperature of the refrigerant inside the tank 6 is higher by a temperature equivalent to a pressure difference between the inside of the tank 6 and an outlet portion of the evaporator 4 than the saturation temperature of the outlet refrigerant in the evaporator 4. As a result, the outlet refrigerant in the evaporator 4 has a degree of superheat equivalent to the saturation temperature difference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refrigeration cycle device that controls the degree of superheat of the evaporator outlet refrigerant by adjusting the amount of refrigerant charged in the cycle by a tank containing a heat exchanger that performs heat exchange with the evaporator outlet refrigerant, for example, It is suitable for use in a vehicle air conditioner.
[0002]
2. Description of the Related Art
In a conventional refrigeration cycle device, a receiver (liquid receiver) that separates gas and liquid of the refrigerant at the condenser outlet and stores the liquid refrigerant is disposed at the condenser outlet side, and the liquid refrigerant within the receiver is decompressed and expanded by an expansion valve. A typical method is to control the degree of opening of the expansion valve according to the degree of superheat of the refrigerant at the evaporator outlet, thereby controlling the flow rate of the circulating refrigerant in the cycle to control the degree of superheat within a predetermined range. .
[0003]
In this method, since the expansion valve needs to have a valve mechanism in which the valve opening is automatically adjusted in response to the degree of superheat of the evaporator outlet refrigerant, the expansion valve needs to have a complicated and precise configuration. The cost is high.
[0004]
Therefore, a method is known in which an accumulator that separates gas-liquid of the evaporator outlet refrigerant and stores the liquid refrigerant is disposed on the evaporator outlet side, and a gas refrigerant (saturated gas) separated by the accumulator is sucked into a compressor. I have. According to this method, the gas refrigerant separated by the accumulator can always be sucked into the compressor. Therefore, a simple fixed throttle such as a capillary tube or an orifice can be used as the decompression means.
[0005]
However, the accumulator needs to increase the tank volume because it is necessary to separate the gas-liquid of the low-pressure refrigerant having a much larger specific volume than the high-pressure refrigerant and store the liquid refrigerant. Therefore, when the refrigeration cycle equipment is mounted in a narrow space such as a vehicle engine room, the mountability of the accumulator is much worse than that of the receiver.
[0006]
Therefore, the present inventors studied another method shown in FIG. 6 as a method for controlling the degree of superheat of the refrigerant at the evaporator outlet. In the system shown in FIG. 6, a tank 6 is disposed in an outlet pipe 5 of an evaporator 4, and an outlet refrigerant of the evaporator 4 and a liquid refrigerant in the tank 6 are supplied to a lower liquid refrigerant area in the tank 6. A heat exchanger 7 for exchanging heat is arranged. One end of a communication pipe 8 ′ is connected to the bottom of the tank 6, and the other end of the communication pipe 8 ′ is connected to the outlet pipe 5 of the evaporator 4. Thus, the inside of the tank 6 communicates with the outlet of the evaporator 4 via the communication pipe 8 '.
[0007]
In this method, the liquid refrigerant is supplied from the tank 6 to the outlet of the evaporator 4 through the communication pipe 8 ′, whereby the amount of refrigerant charged in the cycle is adjusted to reduce the degree of superheat of the evaporator outlet refrigerant. It is controlled to almost zero. Here, the amount of refrigerant charged in the cycle means that the refrigerant is charged into a closed circuit composed of the compressor 1, the condenser 2, the pressure reducing device 3, the evaporator 4, and the compressor 1. It refers to the amount of circulating refrigerant, and does not include the amount of refrigerant in the tank 6 and the communication pipe 8 '.
[0008]
More specifically, the superheat control operation in the study example of FIG. 6 will be described. When the cooling load of the evaporator 4 increases and the superheat of the refrigerant at the evaporator outlet increases, the heat of the refrigerant at the evaporator outlet changes to the heat exchanger. At 7 the liquid refrigerant in the tank 6 is transmitted to evaporate the liquid refrigerant.
[0009]
As a result, the pressure in the tank 6 increases, and the liquid refrigerant in the tank 6 is supplied to the outlet of the evaporator 4 via the communication pipe 8 '. As a result, the amount of the charged refrigerant in the cycle is substantially increased, whereby the degree of superheat of the refrigerant at the evaporator outlet can be reduced to almost zero.
[0010]
However, conversely, when the cooling load suddenly decreases, for example, when the vehicle air conditioner switches from the outside air introduction mode to the inside air introduction mode and the evaporator intake air temperature sharply decreases, the evaporator 4 Since the liquid refrigerant cannot complete evaporation in the inside, the liquid refrigerant flows through the evaporator outlet pipe 5. Therefore, the refrigerant at the evaporator outlet shifts from the state of superheat: almost 0 to the gas-liquid two-phase state.
[0011]
On the other hand, since the pressure change in the tank 6 is a slow change based on heat exchange between the refrigerants in the heat exchanger 7, it cannot follow the rapid change in the refrigerant state described above. For this reason, when the cooling load suddenly decreases, the flow of the refrigerant from the evaporator outlet side into the tank 6 also becomes slow, so that most of the liquid refrigerant on the evaporator outlet side is sucked into the compressor 1. . As a result, a large amount of liquid refrigerant returns to the compressor 1 and adversely affects the durable life of the compressor 1.
[0012]
In particular, in the vehicle air conditioner, the rotational speed of the compressor 1, the temperature of the air sucked by the evaporator, the air volume, and the like frequently change suddenly due to changes in vehicle environmental conditions. Becomes remarkable.
[0013]
In view of the above, the present invention provides a refrigeration cycle apparatus that controls the degree of superheat of the evaporator outlet refrigerant by adjusting the amount of refrigerant charged in the cycle by a tank containing a heat exchanger that performs heat exchange with the evaporator outlet refrigerant. It is another object of the present invention to control the degree of superheat of the evaporator outlet refrigerant to a predetermined target value.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the invention, a compressor (1) for compressing and discharging a refrigerant, and a high-pressure side radiator (2) for radiating the refrigerant discharged from the compressor (1) are provided. A decompression device (3, 3a, 3b) for decompressing the refrigerant at the outlet of the high-pressure side radiator (2), and an evaporator (4) for evaporating the low-pressure refrigerant decompressed by the decompression device (3, 3a, 3b). A refrigerating cycle device for sucking the refrigerant having passed through the evaporator (4) into the compressor (1), including a tank (6) communicating with a portion having a higher pressure than the outlet of the evaporator (4); A heat exchanger (7) for exchanging heat between the refrigerant at the outlet of the evaporator (4) and the refrigerant inside the tank (6) is arranged inside the tank (6).
[0015]
According to this, the refrigerant saturation temperature inside the tank (6) is reduced by the temperature corresponding to the pressure difference between the pressure inside the tank (6) and the outlet of the evaporator (4). Higher than the saturation temperature.
[0016]
As a result, the refrigerant at the outlet of the evaporator (4) has a degree of superheating corresponding to the above-mentioned saturation temperature difference, so that the refrigerant in the tank (6) is thermally balanced. In other words, when the refrigerant enters and exits between the inside of the tank (6) and the communicating portion in the cycle so that this thermal balance is maintained, the refrigerant at the outlet of the evaporator (4) corresponds to the above-mentioned saturation temperature difference. Overheating.
[0017]
Therefore, even when the cooling heat load is rapidly reduced, a large amount of liquid refrigerant can be prevented from returning to the compressor 1 only by reducing the degree of superheat of the evaporator outlet refrigerant. Therefore, it is extremely advantageous from the viewpoint of ensuring the durable life of the compressor 1.
[0018]
According to a second aspect of the present invention, in the first aspect, the inside of the tank (6) is communicated with the inlet of the evaporator (4).
[0019]
Thus, the pressure inside the tank (6) can be made higher than the outlet of the evaporator (4) by the pressure loss in the refrigerant flow path of the evaporator (4). Therefore, the state of the outlet refrigerant of the evaporator (4) can be controlled so as to have a degree of superheat corresponding to the pressure loss of the refrigerant flow path of the evaporator (4).
[0020]
According to a third aspect of the present invention, in the first aspect, the inside of the tank (6) is communicated with an intermediate portion of the refrigerant flow path of the evaporator (4).
[0021]
As a result, the pressure inside the tank (6) is increased from the outlet of the evaporator (4) by the pressure loss between the intermediate portion of the refrigerant flow path of the evaporator (4) and the outlet of the evaporator (4). Can also be higher. Therefore, the state of the refrigerant at the outlet of the evaporator (4) can be controlled so as to have a degree of superheat corresponding to the pressure loss after the intermediate portion of the refrigerant flow path of the evaporator (4).
[0022]
As in the fourth aspect, in the first aspect, the inside of the tank (6) may be communicated with the upstream side of the pressure reducing device (3, 3a, 3b).
[0023]
In a refrigeration cycle device operated with a small height difference, the inside of the tank (6) is communicated with the upstream side (high pressure side) of the pressure reducing device (3, 3a, 3b). Also, it is possible to control the outlet refrigerant of the evaporator (4) to an appropriate superheat degree range.
[0024]
According to a fifth aspect of the present invention, in the first aspect, the pressure reducing device is constituted by two pressure reducing devices (3a, 3b) connected in series, and the inside of the tank (6) is connected to the two pressure reducing devices (3a, 3a, 3a, 3b). It may be communicated with the intermediate part of 3b).
[0025]
In addition, the code | symbol in the parenthesis of each said means shows the correspondence with the concrete means described in embodiment mentioned later.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
FIG. 1 shows a first embodiment, and shows a case where the present invention is applied to a refrigeration cycle device for vehicle air conditioning. The compressor 1 is rotationally driven by a vehicle engine (not shown) to compress and discharge the refrigerant. The high-pressure gas refrigerant discharged from the compressor 1 flows into the condenser 2, where it exchanges heat with outside air to be cooled and condensed.
[0027]
Here, the condenser 2 is a high-pressure side radiator that radiates heat of the high-pressure gaseous refrigerant, and is disposed at a location that is cooled by receiving the traveling wind generated by the traveling of the vehicle, specifically, at the forefront in the vehicle engine room. The air is cooled by the traveling wind and the air blown by a condenser cooling fan (not shown).
[0028]
The pressure reducing device 3 serves to reduce the pressure of the refrigerant that has passed through the condenser 2 to a low-pressure gas-liquid two-phase state. In this example, the pressure reducing device 3 includes a fixed restrictor such as a capillary tube or an orifice.
[0029]
The evaporator 4 absorbs the low-pressure refrigerant that has passed through the pressure reducing device 3 from the air blown by an air-conditioning blower (not shown) and evaporates the same. The evaporator 4 is arranged in a case of an air-conditioning indoor unit (not shown), and cool air cooled by the evaporator 4 is blown into the vehicle interior after being temperature-controlled by a heater core (not shown) as is well known. The outlet pipe 5 of the evaporator 4 is connected to the suction side of the compressor 1, and the gas refrigerant evaporated by the evaporator 4 is sucked into the compressor 1.
[0030]
Further, a tank 6 for controlling the degree of superheating of the refrigerant at the outlet of the evaporator 4 is disposed in the outlet pipe 5 of the evaporator 4. The tank 6 is formed of a metal such as aluminum into a vertically long cylindrical shape. Further, a heat exchanger 7 for exchanging heat between the outlet refrigerant of the evaporator 4 and the liquid refrigerant in the tank 6 is disposed in a liquid refrigerant region stored in a lower portion of the tank 6.
[0031]
Here, the heat exchanger 7 is integrally formed with the outlet pipe 5 of the evaporator 4 and has a refrigerant pipe 7a through which the outlet refrigerant of the evaporator 4 passes, and is formed on the outer periphery of the refrigerant pipe 7a to enlarge the heat transfer area. Fins 7b. In the example of FIG. 1, the fins 7b are formed by a plurality of plate fins formed in a disk shape on the outer periphery of the refrigerant pipe 7a.
[0032]
One end of the communication pipe 8 is connected to the lower liquid refrigerant area of the tank 6, more specifically, to the bottom of the tank 6, and the other end of the communication pipe 8 is connected to the inlet pipe 9 of the evaporator 4. Connected. Thus, the inside of the tank 6 communicates with the inlet of the evaporator 4 via the communication pipe 8.
[0033]
As is well known, the temperature of the evaporator 4 is controlled to a predetermined temperature or higher by controlling the capacity of the compressor 1, specifically, controlling the intermittent operation of the compressor 1 and controlling the discharge capacity of the compressor 1. Thereby, frost (frost formation) of the evaporator 4 is prevented.
[0034]
Next, the operation of the first embodiment in the above configuration will be described. When the compressor 1 is driven by the vehicle engine, the gas refrigerant discharged from the compressor 1 first radiates heat into cooling air (outside air) in the condenser 2 and condenses. Next, the condensed refrigerant is reduced in pressure by the pressure reducing device 3 to be in a low pressure state. Next, the low-pressure refrigerant absorbs heat from the air blown by an air-conditioning blower (not shown) in the evaporator 4 and evaporates. The gas refrigerant after the evaporation passes through the evaporator outlet pipe 5 and the refrigerant pipe 7a of the heat exchanger 7, is drawn into the compressor 1, and is compressed again.
[0035]
Next, the operation of controlling the degree of superheat of the refrigerant at the evaporator outlet based on the combination of the tank 6, the heat exchanger 7, and the communication pipe 8 will be specifically described. The basic operation of the superheat degree control is the same as that of the study example of FIG. 6. When the superheat degree of the refrigerant at the evaporator outlet becomes excessive, the liquid in the tank 6 is removed from the refrigerant at the evaporator outlet by the heat exchanger 7 in the tank 6. The refrigerant absorbs heat and the liquid refrigerant evaporates. As a result, the pressure in the tank 6 increases, and the liquid refrigerant in the tank 6 is pushed out to the inlet of the evaporator 4 through the communication pipe 8, so that the amount of refrigerant charged in the cycle substantially increases.
[0036]
As a result, the amount of refrigerant discharged to the condenser 2 side by the compressor 1 increases, the degree of supercooling of the refrigerant at the outlet of the condenser 2 and the high pressure of the cycle increase, and the pressure reducing device 3, specifically, the fixed throttle Increases the flow rate of the refrigerant that can flow. Thereby, the excessive degree of superheat of the refrigerant at the evaporator outlet can be reduced.
[0037]
Conversely, when the degree of superheat of the refrigerant at the evaporator outlet decreases, the amount of evaporation of the liquid refrigerant in the tank 6 decreases, and the pressure in the tank 6 decreases. Thereby, the refrigerant at the inlet of the evaporator 4 flows into the tank 6 through the communication pipe 8 and is stored in the tank 6. Therefore, the amount of refrigerant charged in the cycle is substantially reduced, and the cycle behavior opposite to the above occurs, thereby suppressing a decrease in the degree of superheat of the refrigerant at the evaporator outlet.
[0038]
In the present embodiment, since the inside of the tank 6 communicates with the inlet of the evaporator 4 through the communication pipe 8, the degree of superheat of the refrigerant at the evaporator outlet is reduced by the pressure loss ΔP of the refrigerant flow path in the evaporator 4. Can be controlled to be a predetermined value corresponding to. More specifically, since the inside of the tank 6 communicates with the inlet of the evaporator 4 through the communication pipe 8, the pressure inside the tank 6 becomes the same as the pressure at the inlet of the evaporator 4. This means that the pressure inside the tank 6 is higher than the pressure at the outlet of the evaporator 4 by the pressure loss ΔP in the refrigerant flow path in the evaporator 4. In other words, the pressure inside the tank 6 in the present embodiment is higher by the pressure loss ΔP than in the study example of FIG.
[0039]
Here, since the refrigerant inside the tank 6 is in a saturated state in which the saturated liquid and the saturated gas coexist, the refrigerant temperature inside the tank 6 becomes a saturation temperature corresponding to the pressure at the inlet of the evaporator 4. This saturation temperature is higher than the saturation temperature of the evaporator outlet refrigerant by a predetermined value corresponding to the pressure loss ΔP.
[0040]
Therefore, in order to heat and evaporate the liquid refrigerant inside the tank 6 by the evaporator outlet refrigerant, the evaporator outlet refrigerant rises to a temperature higher than its saturation temperature by a predetermined value corresponding to the pressure loss ΔP or more. That is, it is necessary to have a degree of superheat. This means that thermal balance between the evaporator outlet refrigerant and the refrigerant inside the tank 6 is performed so that the evaporator outlet refrigerant has a predetermined degree of superheat.
[0041]
Incidentally, the superheat degree of the evaporator outlet refrigerant corresponding to the pressure loss ΔP is a value determined by the physical properties of the refrigerant enclosed in the cycle. When HFC134a is used as the refrigerant, the pressure loss as shown by the solid line A in FIG. The degree of superheat SH can be uniquely determined according to ΔP.
[0042]
As described above, the state of the evaporator outlet refrigerant can be controlled so that the evaporator outlet refrigerant has a degree of superheat corresponding to the pressure loss ΔP of the evaporator 4. Even if the reduction of the amount of the filled refrigerant cannot be followed, only the degree of superheat of the refrigerant at the evaporator outlet is reduced, and a large amount of the liquid refrigerant returned to the compressor 1 can be prevented. Therefore, it is extremely advantageous from the viewpoint of ensuring the durability life of the compressor 1.
[0043]
In FIG. 2, the solid line B is the superheat degree SH of the evaporator outlet refrigerant in the study example of FIG. 6, and in the study example of FIG. 6, the superheat degree SH of the evaporator outlet refrigerant is always irrespective of the pressure loss ΔP. It is maintained at almost zero. For this reason, if a delay in following the decrease in the amount of charged refrigerant in the cycle occurs as described above when the cooling heat load is rapidly reduced, a large amount of liquid refrigerant returns to the compressor 1.
[0044]
(2nd Embodiment)
In the first embodiment, the inside of the tank 6 is communicated with the inlet of the evaporator 4 by a communication pipe 8, but in the second embodiment, as shown in FIG. In the middle of the refrigerant flow path.
[0045]
Therefore, according to the second embodiment, the pressure inside the tank 6 is higher than the pressure at the evaporator outlet by a pressure loss smaller than the pressure loss in the refrigerant flow path of the entire evaporator 4. As a result, the state of the refrigerant at the evaporator outlet can be controlled so as to have a superheat degree smaller than the superheat degree determined by the pressure loss of the refrigerant flow path of the entire evaporator 4.
[0046]
In other words, when the degree of superheat determined by the pressure loss of the refrigerant flow path of the entire evaporator 4 is larger than necessary, an appropriate degree of superheat can be set by employing the second embodiment.
[0047]
(Third embodiment)
In the first and second embodiments, the inside of the tank 6 is communicated with the inlet of the evaporator 4 or the intermediate portion of the refrigerant flow path of the evaporator 4 by the communication pipe 8, but in the third embodiment, it is shown in FIG. Thus, the inside of the tank 6 is communicated with the upstream side of the pressure reducing device 3, that is, the high pressure side of the cycle by the communication pipe 8.
[0048]
Therefore, the pressure inside the tank 6 becomes the pressure on the high pressure side of the cycle, and there is a concern that the degree of superheat of the refrigerant at the evaporator outlet becomes excessive. However, the refrigeration cycle apparatus for applications in which the cooling load (refrigerator load) is constantly small. For example, a refrigeration cycle device for a cold showcase placed indoors is operated in a state where the pressure difference between the high pressure side pressure and the low pressure side pressure is small. Therefore, in the refrigeration cycle device for such use, the superheat degree of the evaporator outlet refrigerant can be set to an appropriate range even if the inside of the tank 6 is communicated with the upstream side of the pressure reducing device 3 by the communication pipe 8.
[0049]
In addition, as a refrigeration cycle device for applications where the cooling load (refrigerator load) is constantly small, for example, there is a refrigeration cycle device of a refrigeration showcase installed inside a building.
[0050]
(Fourth embodiment)
FIG. 5 shows a fourth embodiment, in which the decompression device is a composite throttle composed of two decompression devices 3a and 3b connected in series, and the inside of the tank 6 is connected to the middle part of the two decompression devices 3a and 3b by a communication pipe 8. Is communicated with.
[0051]
(Other embodiments)
In each of the above embodiments, one end of the communication pipe 8 is connected to the bottom of the tank 6 so that the liquid refrigerant inside the tank 6 is pushed out to the communication pipe 8 side. One end of the communication pipe 8 may be connected to the refrigerant area.
[0052]
In order to quickly increase the amount of charged refrigerant in the cycle in accordance with an increase in the degree of superheat of the evaporator outlet refrigerant, the liquid refrigerant in the tank 6 should be pushed out to the communication pipe 8 side as in the above embodiments. However, due to the layout of the communication pipes 8, it may be difficult to connect one end of the communication pipe 8 to the bottom of the tank 6. In this case, one end of the communication pipe 8 is connected to the gas refrigerant area above the tank 6.
[0053]
Thus, when the degree of superheat of the refrigerant at the evaporator outlet rises, the gas refrigerant inside the tank 6 is supplied from the communication pipe 8 to the refrigerant circulation flow path in the cycle such as the inlet of the evaporator 4. Therefore, as compared with the case where the liquid refrigerant is pushed out to the communication pipe 8 side, the responsiveness of the increase in the amount of the charged refrigerant in the cycle when the degree of superheat increases is reduced, but basically the same operation as in each embodiment. The effect can be demonstrated.
[Brief description of the drawings]
FIG. 1 is a refrigeration cycle diagram showing a first embodiment of the present invention.
FIG. 2 is a graph for explaining the operation and effect of the first embodiment.
FIG. 3 is a refrigeration cycle diagram showing a second embodiment.
FIG. 4 is a refrigeration cycle diagram showing a third embodiment.
FIG. 5 is a refrigeration cycle diagram showing a fourth embodiment.
FIG. 6 is a refrigeration cycle diagram showing a study example of the present inventors.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Condenser (high-pressure side radiator), 3 ... Decompression device, 4 ... Evaporator,
5 outlet pipe, 6 tank, 7 heat exchanger, 8 communication pipe.

Claims (5)

A compressor (1) for compressing and discharging the refrigerant;
A high-pressure side radiator (2) for radiating the refrigerant discharged from the compressor (1);
A decompression device (3, 3a, 3b) for decompressing an outlet refrigerant of the high-pressure side radiator (2);
An evaporator (4) for evaporating the low-pressure refrigerant decompressed by the decompression device (3, 3a, 3b);
In the refrigeration cycle apparatus, the refrigerant that has passed through the evaporator (4) is sucked into the compressor (1).
A tank (6) communicating with a portion having a higher pressure than the outlet of the evaporator (4);
A refrigeration cycle apparatus, wherein a heat exchanger (7) for exchanging heat between an outlet refrigerant of the evaporator (4) and an internal refrigerant of the tank (6) is arranged inside the tank (6). . The refrigeration cycle apparatus according to claim 1, wherein the inside of the tank (6) communicates with an inlet of the evaporator (4). The refrigeration cycle apparatus according to claim 1, wherein the inside of the tank (6) communicates with an intermediate portion of a refrigerant flow path of the evaporator (4). The refrigeration cycle apparatus according to claim 1, wherein the inside of the tank (6) communicates with an upstream side of the pressure reducing device (3, 3a, 3b). The pressure reducing device is constituted by two pressure reducing devices (3a, 3b) connected in series,
The refrigeration cycle apparatus according to claim 1, wherein the inside of the tank (6) communicates with an intermediate portion between the two pressure reducing devices (3a, 3b).

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