JP2001147048A - Superheat extent controller for refrigeration circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superheat extent controller for refrigerating circuit which enables an air conditioner to comfortably conduct air conditioning by increasing the capacity of the refrigeration circuit of the air conditioner, when the refrigeration by means of the circuit becomes insufficient due to rise in the outside air temperature, idling of the air conditioner, etc. SOLUTION: A vapor compression type air conditioner using a CO2 refrigerant, is constituted by connecting a compressor, a gas cooler, an expansion valve, and an evaporator in this order through pipeline, and is divided into high- and low-pressure sides. The high-pressure side of the air conditioner is composed of the compressor, gas cooler, and expansion valve and operated at the critical pressure and the low-pressure side is composed of the expansion valve and evaporator. A superheat extent controller for the refrigeration circuit of the air conditioner makes up for the insufficient capacity of the refrigeration circuit by increasing degree of superheat of the refrigerant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for a vapor compression cycle such as a refrigerator, an air conditioning unit, and a heat pump using a refrigerant, for example, carbon dioxide or the like, operating on a high pressure side in a closed circuit under supercritical conditions. In particular, the present invention relates to a control device capable of improving the performance of such a device.

[0002]

2. Description of the Related Art As shown in FIG. 11, a conventional air conditioner includes a compressor (compressor) 51, a condenser 52, a throttle means (expansion valve) 53, and a pipe 55a, 55b, 55c, 55d. Evaporator (evaporator) 54
It has. The components are connected in a closed circuit, in which a refrigerant is circulated. Normally, these devices are operated below the critical pressure, with refrigerants R-12, R-134
a, R-22 and the like are used.

The path from the compressor 51 to the expansion valve 53 is as follows:
The path from the evaporator 52 to the compressor 51 is a region where the pressure is relatively low. On the other hand, in the following description, the former is called the high pressure side and the latter is called the low pressure side. The pressure on the high pressure side of this refrigeration circuit is 10-20 k
g / cm ² (0.98 MPa to 1.96 MPa). In the description in this specification, the word "idling" appears, but this term is used for a vehicle air conditioner.

The operation of a CO ₂ cycle using CO ₂ as a refrigerant is in principle the same as the operation of a conventional vapor compressor refrigeration cycle using Freon.

However, CO₂Critical temperature is 31 ° C.
Critical temperature of the next CFC (for example, 112 for R12)
℃), and in summer, etc., CO on the radiator side₂temperature
Is CO ₂Higher than the critical temperature. Supercritical operation
Then, the part that was said to be the condenser 52 is
It is a critical gas and does not condense. Therefore, the condenser 5
2 is called a radiator (gas cooler).

[0006] The pressure corresponding to the critical temperature is 75.3 kg.
/ Cm ² (7.38 MPa) and usually 100 kg / cm ^{2 to} 170 kg / cm depending on the temperature of the outside air.
It is operated at a high pressure of ² (9.8 to 16.7 MPa).

[0007] Considering the case where the degree of superheating is taken with a conventionally used refrigerant, in the case of CFCs, in addition to the improvement of the coefficient of performance,
The purpose is to protect the liquid refrigerant from flowing to the compressor. However, on the other hand, if the degree of superheat is taken, the temperature of the refrigerant discharged from the compressor will increase, which may cause deterioration of the lubricating oil.

Therefore, in the conventional refrigerant, the degree of superheat (SH) is determined by balancing the discharge temperature, the coefficient of performance (COP), the protection of the compressor and the purpose.

[0009]

When CO ₂ is used as the refrigerant, the vehicle is stopped at a low rotation speed of the compressor as compared with the conventional refrigerant, and only the fan is used for cooling. It is known that the refrigeration capacity during idling is low. This is the present inventors, as shown in FIG. 12, it was confirmed the phenomenon conducted an experiment under the same conditions with a conventional refrigerant R134a and CO _2.

FIG. 12 is a diagram used for explaining a verification experiment in which the degree of superheat is controlled. Referring to FIG. 12, a case where the degree of superheat is controlled to, for example, 10K will be considered. As shown in FIG. 12, it is assumed that the operation was performed at an evaporating temperature of 0 ° C. at a medium speed. When the engine speed drops due to idling, the speed of the compressor directly connected to the engine also drops, so the refrigerant circulation amount in the refrigeration circuit drops.

As a result, the amount of the refrigerant flowing through the evaporator 54 decreases, so that the refrigerant evaporates inside the evaporator 54 faster than before. For this reason, the refrigerant is warmed more downstream than the evaporator 54 in the refrigeration circuit.
This equates to an increase in superheat.

In order to control the degree of superheat, the expansion valve 53 attempts to open and close the valve opening to adjust it. That is, as shown in FIG. 12, at the time of idling, the valve operates slightly in the direction in which the valve is opened to allow the refrigerant to flow. Until now, the throttle was released, the low pressure side pressure increased, the superheat decreased, and
It becomes K. As the valve opens, the high pressure drops.

On the other hand, when the engine speed increases,
The rotation speed of the compressor also increases, and the refrigerant circulation amount also increases. As a result, the amount of refrigerant flowing through the evaporator 54 also increases, so that the degree of superheat decreases. Then, the expansion valve works in the direction of reducing the valve opening this time, and reduces the flow rate. As a result, the pressure on the low pressure side decreases and the pressure on the high pressure side increases.

[0014] This phenomenon is particularly caused when the outside air is high other than at the time of idling. At the time of idling, the vehicle stops, so that there is no front wind at the time of running, and only the fan is cooled. For this reason, the heat radiation capability of the gas cooler 52 shown in FIG. 11 decreases, and the outlet temperature of the gas cooler 52 increases.

In a CO ₂ refrigerant operated in a range exceeding the critical point, the high pressure and the temperature do not change independently. Therefore, even if the high pressure is the same, if the temperature changes, the state of the refrigerant greatly changes.

This is represented by the fact that the operation normally performed in the cycle 61 of B is changed to the cycle 62 of A as shown in FIG. In other words, the point C corresponding to the gas cooler outlet is normally operated at 35 ° C., but rises to 40 ° C. during idling, and as a result, the cycle changes from B to A. Since the refrigerating capacity of the evaporator is represented by the enthalpy difference Δh, going from cycle B to A means reducing Δh ₂ to Δh ₁ , which leads to a decrease in the refrigerating capacity. this is,
The same is true when the outside air temperature rises.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a refrigeration circuit control device capable of increasing the capacity at the time of insufficient refrigeration such as an increase in the outside air temperature or idling and performing comfortable air conditioning. .

[0018]

According to the present invention, CO _{2 is used.}
Using a refrigerant, a compressor, a gas cooler, an expansion valve, and an evaporator are connected in this order by piping, and the section from the compressor to the expansion valve is on the high pressure side, and the section from the expansion valve to the compressor is on the low pressure side, A superheat control apparatus for a refrigeration circuit of a refrigeration circuit of a vapor compression type air conditioner in which a high pressure side is operated at a critical pressure, wherein a superheat degree is compensated for by increasing the degree of superheat. .

Further, according to the present invention, in the superheat degree control device for the refrigeration circuit, the detection of whether or not the capacity is insufficient is performed by:
A superheat control device for a refrigeration circuit, wherein the control is performed based on the outlet temperature of the gas cooler, is obtained.

According to the present invention, in any one of the superheat degree control devices for a refrigeration circuit, the superheat degree is controlled by the expansion valve. Can be

According to the present invention, in the superheat degree control device for a refrigeration circuit, the expansion valve comprises an electronically controlled expansion valve or a mechanical expansion valve. Is obtained.

Further, according to the present invention, in any one of the superheat degree control devices for the refrigeration circuit, the superheat degree is a superheat degree at an outlet of the evaporator, and the expansion based on an outlet temperature of the evaporator. A superheat degree control device for a refrigeration circuit, characterized in that the valve opening degree of the valve is controlled.

Further, according to the present invention, in any one of the above-described superheat degree control apparatuses for a refrigerating circuit, when the discharge temperature reaches a temperature that causes deterioration of oil or other possible problems, a signal is sent to reduce the degree of superheat. , A superheat control device for a refrigeration circuit, characterized by comprising discharge temperature protection means for controlling the temperature of the refrigeration circuit.

Further, according to the present invention, there is provided a superheat degree control device for a refrigeration circuit, characterized in that in any one of the superheat degree control devices for a refrigeration circuit, control is performed to keep the pressure on the low pressure side constant. Can be

Further, according to the present invention, in any one of the superheat degree control devices for the refrigeration circuit, the compressor comprises a variable capacity compressor, and the superheat degree control device for the refrigeration circuit is obtained.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a supercritical refrigeration circuit of an air conditioner according to a first embodiment of the present invention. Referring to FIG. 1, a refrigeration circuit 10 according to a first embodiment of the present invention includes a compressor 51, a gas cooler (gas cooler) 52, an expansion valve 3, and an evaporator 54 connected to a pipe 55.
a, 55b, 55c, and 55d.

In the first embodiment of the present invention,
A first sensor 2 for detecting the temperature and pressure at the outlet of the gas cooler 52 as a control device; a second sensor 4 for detecting pressure and temperature at the outlet of the evaporator 54;
And a third sensor 1 for detecting the temperature of the outlet of the third sensor. The detection outputs of the first to third sensors 2, 4, 1 are:
The opening of the expansion valve 3 is adjusted according to these detection outputs as input to the control circuit 5.

Here, as described above, the present inventor
In O _2, largely take refrigerating capacity superheat as compared with the conventional refrigerant, that the coefficient of performance increases are confirmed by experiments. By utilizing this, when the capacity is insufficient, the control for increasing the degree of superheat is performed.

Specifically, the control circuit 5 according to the first embodiment of the present invention roughly grasps the current state of the refrigerant based on the outputs of the first and second sensors. When the outlet temperature of the gas cooler 52 rises due to idling or the like, if the pressure is sufficiently high, there is no problem, but the refrigeration capacity shortage is detected from data input in advance,
The feedback is made to the expansion valve 3. That is, control is performed to narrow down the expansion valve 3 and increase the degree of superheat.

The third sensor is provided for stopping the operation of the expansion valve 3 when the discharge temperature of the compressor 51 exceeds a certain limit value, for example, the temperature immediately before the deterioration of the lubricating oil. It is a safety device.

FIG. 2 is a flowchart showing the operation of the control device of FIG. As shown in FIG. 2, the temperature at the outlet of the gas cooler 52 is detected by the first sensor 2 (Step S1). Next, the outlet pressure of the gas cooler becomes the first pressure.
(Step S2). Next, the temperature at the outlet of the evaporator 54 is detected by the second sensor 4 (step S3). Next, the pressure at the outlet of the evaporator 54 is detected by the second sensor 4 (Step S4). On the basis of these detection outputs, the control circuit 5
Calculates the refrigerating capacity and determines whether or not it is smaller than a preset target value (step S5). In this case, if the calculated refrigerating capacity is equal to or more than the target value, the process returns to step S1.

On the other hand, if the calculated refrigerating capacity is smaller than the target value, the control circuit 5 controls the expansion valve to be throttled (step S6).

Next, the discharge temperature of the compressor is measured by the third sensor 1.
(Step S7). In this case, if the discharge temperature is equal to or higher than the predetermined upper limit, the process returns to step S1 again. On the other hand, if the discharge temperature is higher than the upper limit, the control circuit controls the expansion valve 3 to open (step S9). The above operation is repeated.

Next, the control of the refrigeration circuit according to the second embodiment of the present invention will be described more specifically.

FIGS. 3 to 7 are views for explaining the control in which the pressure on the low pressure side is kept constant.

As shown in FIG. 4, under the same conditions,
Towards CO ₂ than R134a refrigerant according to the prior art, a large compressor speed dependent ratio of refrigerating capacity.

In the second embodiment of the present invention, pressure control is performed instead of superheat control. At any rotation speed, the evaporation pressure is about 35 kg / cm ² (3.43 MPa, 0
° C). However, the degree of superheat during normal operation is set so as to be a desired degree of superheat.

That is, in the example of FIG. 3, the superheat degree at the medium speed is set to 10K, and the evaporation pressure is changed to about 35 kg / cm ² (3.43 MPa, 0 ° C.) even when the rotation speed is changed.
It is controlled so that

Experiments have confirmed that the use of such an expansion valve 3 results in a cycle as shown in FIG.

That is, as shown by the curve 43 in FIG. 5, in the prior art, the dependence of the degree of superheat on the rotation speed is hardly observed, but as shown by the curve 44 in FIG. When the engine is operated at a superheat degree of 10K at a medium speed, the superheat degree (SH) increases as the rotational speed decreases. Conversely, if the rotation speed increases, the degree of superheat (SH) decreases. As a result, the effect of increasing the degree of superheating during idling, which is the object of the present invention, can be obtained.

As shown in FIG. 6, when the low pressure constant control is performed, the refrigerating capacity depends on the number of revolutions of the compressor. Less than the one (curve 45). As shown in FIG. 7, when the constant low pressure control is performed, the COP (coefficient of performance) according to the related art has a small variation as indicated by a line 48, while the COP (coefficient of performance) according to the present invention has a medium level. At the rotation speed (about 1200 rpm).

It is considered that the expansion valve 3 only needs to have a fixed opening degree. However, unless the pressure is kept constant, a desirable effect cannot be obtained. In the embodiment, the one whose opening is adjusted is used.

Further, as shown in FIG. 5, when the rotation speed becomes higher and higher, the degree of superheat becomes zero, and the liquid refrigerant returns to the compressor and may be damaged by the liquid compression. When such a danger is considered, it is preferable to use a variable displacement compressor in which the internal volume of the compressor changes.

FIG. 8 is a sectional view showing an example of an expansion valve as a control device of a refrigeration circuit according to a second embodiment of the present invention. Referring to FIG. 8, the expansion valve 3 includes valve housings 3a and 3a.
b, a valve member including a valve body 11a, a valve rod 11b, and a support member 11c for supporting the valve rod 11b; a ring-shaped spring support portion 15 provided in a space inside the housing 3b; A coil spring 16 provided between the spring support portion 15 and the support member 11c to urge the valve member to move upward; and a coil spring 16 provided to contact the support member 11c.
The diaphragm 17 includes a coil spring 19 provided to urge the diaphragm 17 downward. The space outside the valve seat 13 is connected to a gas cooler (gas cooler) 52 via a pipe 3c.
The internal space 14 is connected to an evaporator (evaporator) 54.

When the pressure in the internal space 14 increases, the diaphragm 17 is pushed upward by overcoming the drag of the spring 19. For this reason, since the valve is closed, the pressure at the inlet of the evaporator 54 can be controlled to a predetermined pressure or less. For this reason, the spring 19 is 35 kg / cm
² (3.43 MPa) or more.

FIGS. 9A and 9B are diagrams showing another example of the expansion valve of FIG. 8, wherein FIG. 9A shows a state in which the diameter of the pipe is reduced, and FIG. Indicates a state where has become larger. Referring to FIGS. 9 (a) and 9 (b), this type of valve is called a wax pellet type, and is made of metal,
For example, a rubber boot 25 is placed in a capsule 23 made of a brass cup, and a wax 24 made of paraffin-like plastic is put between the capsule 23 and the rubber boot 25. Have been exposed to A stainless steel tapered rod-shaped piston 27 is inserted into the rubber boot 25, and a stepped portion made of brass is attached to the capsule, and is urged upward by a spring 26.

Here, in the state shown in FIG. 9A, the temperature of the expanding liquid drops. That is, when the low pressure side pressure decreases, the wax 24 contracts, the rubber boot 25 expands, and the taper piston 27 is inserted into the boot 25.

However, since the piston 27 is fixed and cannot move, the capsule 23 moves upward and is moved upward by the spring 26 to reach the state shown in FIG. 9B.

On the other hand, in the state shown in FIG. 9B, when the temperature after expansion increases, the wax 24 expands and the rubber boot 2 expands.
5 is compressed, and the taper piston 27 is pushed out. However, since the piston 27 is fixed and cannot move, the capsule 23 is pushed out and the spring 2
Compress 6 and descend. This is a method of detecting the temperature and controlling the low pressure to be constant.

It should be noted that, even when the capsule 23 descends, a gap is formed between the capsule 23 and the wall of the pipe.

FIGS. 10A and 10B show another example of the expansion valve of FIG. FIG. 10 (a)
As shown in FIG. 10B, the expansion valve 30 is
0a, a valve member housed in the housing 30a, a support member 32 for supporting the valve member, and a lid member 34c made of a heat insulating material such as urethane foam for sealing the upper portion of the housing 30a. The valve member includes a valve body 31a, a rod 31b,
And a support portion 31c provided at one end of the rod 31b. One surface of the support portion 31c is
a, and a liquid or wax 34b having the same effect as the refrigerant used in the refrigeration circuit is sealed between the diaphragm and the lid member 34c. One end of the support portion 31c is in contact with one surface of the diaphragm 34a, and urges the valve body 31a upward so as to push up the diaphragm 34a, that is, to raise the valve body 31a. A coil spring 33 is provided between the support member 32 and the diaphragm 34a. Case 3
The two ports 30b and 30c provided on the port 0a
As in the case of, they are connected to the gas cooler 52 and the evaporator 54, respectively.

In the state of FIG. 10 (a), when the temperature drops after expansion, that is, when the pressure drops, the wax 34b sealed in the upper part of the housing 30a contracts, and the diaphragm 31a is pushed upward by the action of the spring 31c. . Then, as shown in FIG. 10B, the gap between the hole 35 of the valve seat and the valve body 31a increases, and the pressure of the fluid discharged from the port 30b increases.

On the other hand, in the state shown in FIG.
After the expansion, when the refrigerant temperature rises, that is, when the pressure rises, the wax 34b sealed in the upper part of the housing 30a expands,
The diaphragm 34a is deformed so as to be convex downward,
Push down the valve member. Therefore, as shown in FIG. 10 (b), the valve member rises, the gap between the valve body 31a and the hole 35 widens, and the pressure of the fluid to be discharged again drops. That is, similarly to FIG. 9, this is a constant control of the low pressure.

In the embodiment of the present invention described above, a hermetic electric compressor can be used as the compressor, but of course, a favorable result can be obtained with a conventional open type compressor.

[0056]

As described above, according to the present invention,
In particular, it is possible to provide a control device for a refrigeration circuit that can improve the capacity shortage during idling.

Further, according to the present invention, there is a method of controlling the capacity of the refrigerant as a capacity control method. However, the capacity can be easily increased by a simple structure without a complicated component required in such a case. A control device for a refrigeration circuit that can be controlled can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a supercritical refrigeration circuit of an air conditioner according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the control device of FIG.

FIG. 3 is a diagram which is used for describing control in which the pressure on the low pressure side is kept constant.

FIG. 4 is a diagram which is used for describing control in which the pressure on the low pressure side is kept constant.

FIG. 5 is a diagram which is used for describing control in which the pressure on the low pressure side is kept constant.

FIG. 6 is a diagram which is used for describing control in which the pressure on the low pressure side is kept constant.

FIG. 7 is a diagram which is used for describing control in which the pressure on the low pressure side is kept constant.

FIG. 8 is a cross-sectional view illustrating an example of an expansion valve as a control device of a refrigeration circuit according to a second embodiment of the present invention.

9 is a sectional view showing another example of the expansion valve of FIG. 8,
(A) shows a state where the diameter of the pipe is reduced, and (b) shows a state where the diameter of the pipe is increased.

FIGS. 10 (a) and (b) are cross-sectional views showing another example of the expansion valve of FIG. 8;

FIG. 11 is a diagram schematically showing a refrigeration circuit of an air conditioner according to the related art.

FIG. 12 is a diagram that is used for describing a verification experiment in which the degree of superheat is controlled.

FIG. 13 is a diagram showing a method for controlling so as to obtain a large degree of superheat in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 3rd sensor 2 1st sensor 3 Expansion valve 3a, 3b Valve housing 3c Piping 4 2nd sensor 5 Control circuit 10 Refrigeration circuit 11a Valve main body 11b Valve rod 11c Support member 13 Valve seat part 14 Internal space 15 Spring Supporting part 16 Coil spring 17 Diaphragm 19 Coil spring 23 Capsule 24 Wax 25 Rubber boot 26 Spring 27 Piston 30 Expansion valve 30a Housing 30b, 30c Port 31a Valve body 31b Rod 31c Supporting part 32 Supporting member 33 Coil spring 34 Capping member 34a Diaphragm 34a Diaphragm Member 51 Compressor (compressor) 52 Condenser (gas cooler) 53 Throttling means (expansion valve) 54 Evaporator (evaporator) 55a, 55b, 55c, 55d Piping

Claims (8)

[Claims] 1. A compressor, a gas cooler using CO ₂ refrigerant,
An expansion valve and an evaporator are connected in this order by piping, a high pressure side from the compressor to the expansion valve, a low pressure side from the expansion valve to the compressor, and a vapor compression in which the high pressure side is operated at a critical pressure. A superheat degree control device for a refrigeration circuit of a refrigeration circuit of a type air conditioner, wherein the superheat degree is compensated for by increasing the degree of superheat. 2. A superheat degree control system for a refrigeration circuit according to claim 1, wherein the detection of whether or not the capacity is insufficient is performed based on an outlet temperature of the gas cooler. Control device. 3. The superheat control device for a refrigeration circuit according to claim 1, wherein the control of the superheat is performed by the expansion valve. 4. The superheat control apparatus for a refrigeration circuit according to claim 3, wherein said expansion valve comprises an electronically controlled expansion valve or a mechanical expansion valve. 5. The superheat control device for a refrigeration circuit according to claim 1, wherein the superheat is a superheat at an outlet of the evaporator, and is based on an outlet temperature of the evaporator. Controlling the degree of opening of the expansion valve by controlling the degree of superheating of the refrigeration circuit. 6. A superheat control apparatus for a refrigeration circuit according to claim 1, wherein a signal is sent when the discharge temperature reaches a temperature at which oil deterioration or other possible troubles occur. A superheat degree control device for a refrigeration circuit, comprising discharge temperature protection means for controlling so as to lower the temperature. 7. The superheat control apparatus for a refrigeration circuit according to claim 1, wherein control is performed to keep the pressure on the low-pressure side constant. apparatus. 8. The superheat control apparatus for a refrigeration circuit according to claim 1, wherein said compressor comprises a variable capacity compressor.