JPH11201568A - Supercritical refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the breakdown of a compressor, in a CO2 cycle which has an internal heat exchanger. SOLUTION: When the temperature of CO2 on the discharge side of a compressor comes a specified temperature or over, CO2 having flown out of an accumulator 500 is circulated to the compressor 100, bypassing an internal heat exchanger 600. Hereby, the heat exchange between high-pressure CO2 and low-pressure CO2 stops, and the refrigerant temperature can be lowered in the refrigerant passage leading to the discharge side from the suction side of the compressor 100, so the breakdown of the compressor 100 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the pressure in the radiator relates steam compressor refrigeration cycle exceeds the critical pressure of the refrigerant (supercritical refrigerating cycle), carbon dioxide (hereinafter, referred to as CO _2.) This is effective when applied to a supercritical refrigeration cycle (hereinafter, referred to as a CO ₂ cycle) using as a refrigerant.

[0002]

_2. Description of the Related Art The operation of a CO ₂ cycle is, in principle,
This is the same as the operation of a conventional vapor compression refrigeration cycle using Freon. That is, as shown by ABCDA in FIG. 23 (CO ₂ Mollier diagram), the compressor 1
To compress the CO ₂ in the gas phase (AB), and cool the CO ₂ in the supercritical state at a high temperature and a high pressure by the radiator 2 (B-B).
C).

Then, the pressure is reduced by the pressure control valve 3 (C
-D), CO in gas-liquid two-phase state _TwoIs evaporated (D
-A), the latent heat of evaporation is removed from an external fluid such as air, and
Cool the body. Note that CO_TwoIs the saturated liquid pressure (line
When the pressure falls below the pressure at the intersection of the partial liquid CD and the saturated liquid line SL).
, The phase changes to a gas-liquid two-phase state.
If it slowly changes to the state of_TwoIs supercritical
The state changes from the state to the gas-liquid two-phase state through the liquid state.

Incidentally, the supercritical state means that the density is equal to the liquid density.
While almost equivalent, CO_TwoMolecules run as if they were in the gas phase
It refers to the state of movement. However, CO_TwoHas a critical temperature of about 31
° C and the critical temperature of conventional fluorocarbon (for example, 11 for R12)
2 ℃), so in summer, etc., CO on the radiator side
_TwoTemperature is CO_TwoBecomes higher than the critical point temperature. One
In other words, CO _TwoDoes not condense (line
The minute BC does not cross the saturated liquid line).

[0005] The state of the radiator outlet side (C point) is determined by the discharge pressure of the compressor and the CO ₂ temperature at the radiator outlet side, CO ₂ temperature at the radiator outlet side, the radiator Is determined according to the heat radiation capacity and the outside air temperature. Since the outside air temperature cannot be controlled, the CO ₂ temperature at the radiator outlet side cannot be substantially controlled. Therefore, the state of the radiator outlet side (point C) can be controlled by controlling the compressor discharge pressure (radiator outlet side pressure). In other words, when the outside air temperature is high, such as in summer,
To ensure sufficient cooling capacity (enthalpy difference)
As shown by EFGHE in FIG. 14, it is necessary to increase the pressure on the radiator outlet side.

However, in order to increase the pressure on the outlet side of the radiator, the discharge pressure of the compressor must be increased as described above, so that the compression work of the compressor 1 (the enthalpy change ΔL in the compression process) increases. I do. Therefore, the evaporation process (D
If the increase in the enthalpy change ΔL in the compression process (AB) is larger than the increase in the enthalpy change Δi in −A), the coefficient of performance of the CO ₂ cycle (COP = Δi / Δ)
L) worsens.

Therefore, for example, CO ₂ at the exit side of the radiator ₂
When the relationship between the CO ₂ pressure at the outlet of the radiator 2 and the coefficient of performance is estimated using FIG. 23 at a temperature of 40 ° C., the coefficient of performance at the pressure P ₁ (about 10 MPa) is obtained as shown by the solid line in FIG. Is the largest. Similarly, CO at the radiator outlet side
_{2 When the} temperature is 35 ° C., the coefficient of performance becomes the maximum at the pressure P ₂ (about 9.0 MPa), as shown by the broken line in FIG.

As described above, CO _{2 at the} radiator outlet side
Calculating the temperature and the pressure at which the coefficient of performance is the maximum, and drawing the result on FIG. 23, the thick solid line η _max (hereinafter,
Called the optimal control line. ). Therefore,
To operate the CO ₂ cycle efficiently, it is necessary to control the radiator outlet pressure and the radiator outlet CO ₂ temperature as indicated by the optimal control line η _max .

Incidentally, the above-mentioned optimal control line η _max is obtained by setting the pressure on the evaporator side to about 3.5 MPa (corresponding to the evaporator temperature of 0 ° C.), and the degree of supercooling (subcooling) in the condensation region (region below the critical pressure) Is calculated to be about 3 ° C. FIG. 25 is a graph in which the optimal control line η _max is drawn in the Cartesian coordinates where the CO ₂ temperature on the radiator outlet side and the pressure on the radiator outlet side are variables. As is apparent from FIG. It is necessary to raise the pressure on the radiator outlet side in accordance with the rise in the CO ₂ temperature on the outlet side of the radiator.

The present inventors have already filed Japanese Patent Application No. 8-11248 as a pressure control device for controlling the pressure on the outlet side of the radiator ₂ in the CO ₂ cycle.

[0011]

By the way, the inventors have found that CO ₂ flowing out of the evaporator (hereinafter, this CO ₂ is referred to as low-pressure CO ₂ ) and CO ₂ flowing out of the radiator (hereinafter, this CO ₂ ). ₂ is called high-pressure CO ₂ ) to reduce the enthalpy of CO ₂ on the inlet side of the evaporator, increase the enthalpy difference between the inlet and outlet of the evaporator, and improve the refrigeration capacity of the CO ₂ cycle. While studying the CO ₂ cycle to be performed (see A′-B′-CD in FIG. 26), it was found that the following problem might occur.

Namely, in the CO ₂ cycle, since the low-pressure CO ₂ and the high-pressure CO ₂ heat exchanger, A-B-C-the CO ₂ cycle (Figure 26 without heat exchange between both CO ₂
Unlike D), the low-pressure CO ₂ has a predetermined heating degree of 0 ° C. or more. On the other hand, since the pressure control device controls the pressure at the radiator outlet side based on the CO ₂ temperature at the radiator outlet side, the pressure control device reduces the heat load on the evaporator and reduces the pressure inside the evaporator. Even when the low-pressure CO ₂ temperature decreases, the pressure at the radiator outlet side is not immediately reduced in conjunction with this, and the pressure at the radiator outlet side is controlled based on the CO ₂ temperature at the radiator outlet side at that time. .

For this reason, if the CO ₂ temperature on the radiator outlet side does not change, the pressure on the radiator outlet side does not change. Therefore, as shown in FIG. 26, when the heat load on the evaporator becomes small, in the passage of CO ₂ leading to the discharge side of the suction side of the compressor CO ₂ temperature rises. And CO
_{(2) When the} temperature rises, an oil film breakage is caused in the sliding portion of the compressor, which causes a problem that the compressor is damaged.

Incidentally, CO at the radiator inlet side_TwoTemperature rises
Then, the CO at the radiator outlet side_TwoAs the temperature also rises, the pressure
Force control device is low pressure CO_TwoDo not work immediately with temperature
The heat load on the evaporator is small.
The pressure controller increases the pressure at the radiator outlet
You. Therefore, the heat load in the evaporator decreases and the CO2 _Two
The temperature may rise.

SUMMARY OF THE INVENTION In view of the above, the present invention prevents a compressor from being damaged in a supercritical refrigeration cycle having a pressure control device for controlling a pressure at a radiator outlet based on a temperature at a radiator outlet. The purpose is to:

[0016]

The present invention uses the following technical means to achieve the above object. Claim 1
In the invention described in Item 3, when the refrigerant temperature at a predetermined position of the refrigerant passage from the inflow side of the evaporator (400) to the inlet side of the radiator (200) becomes equal to or higher than the predetermined temperature, the gas-liquid separation device (500) ) Is transferred to the heat exchanger (600).
And a refrigerant bypass means (700) for bypassing and flowing through the compressor (100).

[0017] This makes it possible to lower the refrigerant temperature on the suction side of the compressor (100) as compared with the case where the refrigerant is sucked into the compressor (100) via the heat exchanger (600). The refrigerant temperature in the refrigerant passage from the suction side to the discharge side of (100) can be lowered, and damage to the compressor (100) can be prevented. According to the invention described in claim 4, when the refrigerant temperature at a predetermined position in the refrigerant passage from the discharge side of the compressor (100) to the pressure on the inflow side of the pressure control device (300) becomes equal to or higher than the predetermined temperature, The heat exchange in the exchanger (600) is stopped.

Thus, the refrigerant temperature at the suction side of the compressor (100) can be reduced, as in the first aspect of the present invention, so that the refrigerant passage from the suction side to the discharge side of the compressor (100). In this case, the refrigerant temperature can be lowered, and damage to the compressor (100) can be prevented. In the invention described in claim 5, the pressure control device (30
The heat exchange in the heat exchanger (600) is stopped when the refrigerant temperature at a predetermined position of the refrigerant passage from the outlet side of (0) to the suction side of the compressor (100) becomes equal to or lower than the predetermined temperature. I do.

Thus, the refrigerant temperature at the suction side of the compressor (100) can be reduced, as in the first aspect of the present invention, and thus the refrigerant passage from the suction side to the discharge side of the compressor (100). In this case, the refrigerant temperature can be lowered, and damage to the compressor (100) can be prevented. In the invention according to claim 6, the refrigerant pressure at a predetermined position of the refrigerant passage from the discharge side of the compressor (100) to the inflow side of the pressure control device (300) is determined by the pressure control device (3).
00), the heat exchange in the heat exchanger (600) is performed when the pressure difference between the refrigerant pressure at a predetermined position in the refrigerant passage from the outlet side of the compressor (100) to the suction side of the compressor (100) becomes equal to or higher than the predetermined pressure difference. It is characterized by stopping.

Thus, the refrigerant temperature on the suction side of the compressor (100) can be reduced, as in the first aspect of the present invention, so that the refrigerant passage from the suction side to the discharge side of the compressor (100). In this case, the refrigerant temperature can be lowered, and damage to the compressor (100) can be prevented. In the invention according to claim 7, the pressure control device (30
Heat exchange in the heat exchanger (600) is stopped when the refrigerant pressure at a predetermined position in the refrigerant passage from the outlet side of (0) to the suction side of the compressor (100) becomes equal to or lower than the predetermined pressure. And

Thus, the refrigerant temperature at the suction side of the compressor (100) can be reduced, as in the first aspect of the present invention, so that the refrigerant passage extending from the suction side to the discharge side of the compressor (100). In this case, the refrigerant temperature can be lowered, and damage to the compressor (100) can be prevented. Incidentally, the reference numerals in parentheses of the respective means are examples showing the correspondence with specific means described in the embodiment described later.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG.
CO pertaining to state_TwoCycle applied to vehicle air conditioner
100 is the driving force from the vehicle driving engine.
CO in the gas phase_TwoCompressor. 200 is
CO compressed by the compressor 100_TwoHeat exchange with the outside air
Is a radiator (gas cooler) for cooling
CO at radiator 2 outlet side _TwoRadiator 200 out according to temperature
Pressure control valve (pressure control device)
You. It should be noted that the pressure control valve 300 is provided at the outlet side of the radiator 200.
It controls the power and doubles as a pressure reducer._TwoIs
The low-temperature low-pressure gas-liquid 2 is depressurized by the pressure control valve 300.
CO in phase state_TwoBecomes

[0023] 400, an evaporator forming the air cooling means in the cabin at (heat absorber), CO ₂ in the gas-liquid two-phase state is the evaporator 40
At the time of vaporization (evaporation) within 0, the latent heat of evaporation is taken from the air in the vehicle interior to cool the air in the vehicle interior. An accumulator 500 separates CO ₂ in a gaseous state and CO ₂ in a liquid state, causes a gaseous refrigerant to flow toward the suction side of the compressor 100, and temporarily stores CO ₂ in a liquid state. (Gas-liquid separation device).

600 flows out of the accumulator 500
Drawn into the compressor 100 _TwoAnd the radiator 200
CO leaked from_TwoInternal heat exchanger that exchanges heat with
710 is the C flowing out of the accumulator 500
O_TwoBypasses the internal heat exchanger 600 to the compressor 100
Solenoid valve (valve valve) that opens and closes the bypass passage 720 that circulates
Stage).

As shown in FIG. 2, the internal heat exchanger 600 is provided with a spiral CO ₂ channel opposed thereto, and 601 is a high-pressure inlet connected to the radiator 200 side. , 602 are high-pressure outlets connected to the pressure control valve 300 side, 603 is a low-pressure inlet connected to the accumulator 500 side, and 604 is a low-pressure outlet connected to the compressor 100 side.

Reference numeral 711 denotes a thermistor type temperature sensor (temperature detector) for detecting the CO ₂ temperature on the discharge side of the compressor 100.
The detection signal of the temperature sensor 711 is input to the comparison device 712. The comparison device 712 determines that the CO ₂ temperature corresponding to the detection signal of the temperature sensor 711 is equal to the predetermined temperature T.
When it is determined that the temperature is higher than (120 ° C. in the present embodiment), a signal is issued to a control device 713 that controls opening and closing of the solenoid valve 710.

The control device 713 controls the comparison device 71
When the signal from 2 is input, the solenoid valve 710 is opened,
When no signal is input, the solenoid valve 710 is closed. Hereinafter, 710 to 713 and 720 are collectively referred to as refrigerant bypass means. The predetermined temperature T is not limited to 120 ° C., and should be appropriately selected in consideration of the wear resistance of the compressor 100 and the heat resistance of the lubricating oil.

Reference numeral 800 denotes a relief valve that bypasses the pressure control valve 300 and allows CO ₂ to flow when the pressure on the outlet side of the radiator 200 abnormally rises due to a failure of the pressure control valve 300 or the like. Next, the structure of the pressure control valve 300 will be described with reference to FIG. Reference numeral 301 denotes a casing for forming a part of the CO ₂ flow path 6a from the radiator 2 to the evaporator 400, and for accommodating an element case 315 described later, and 301a is an inflow port 301b connected to the radiator 2 side. Reference numeral 301c denotes a casing body having an outlet 301d connected to the evaporator 4 side.

The casing 301 is provided with a partition wall 302 for partitioning the CO ₂ flow path 6a into an upstream space 301e and a downstream space 301f.
Is formed with a valve port 303 for communicating the upstream space 301e and the downstream space 301f. And valve 3
03 is a needle-shaped needle valve element (hereinafter abbreviated as a valve element) 3
The valve body 303 and a later-described diaphragm 306 are displaced from the neutral state toward the valve body 303 (the other end in the thickness direction of the diaphragm 306) from the neutral state in response to the displacement of the diaphragm 306. The opening of the valve port 303 (the amount of displacement of the valve body 304 based on the state in which the valve port 303 is closed) is maximized when the valve port 303 is closed and displaced toward one end in the thickness direction. It is configured.

A sealed space (gas sealing chamber) 305 is formed in the upstream space 301e. The sealed space 305 is made of a stainless steel material which is deformed and displaced in accordance with a pressure difference between the inside and the outside of the sealed space 305. It is formed of a thin film diaphragm (displacement member) 306 and a diaphragm upper support member (formation member) 307 disposed at one end in the thickness direction of the diaphragm 306.

On the other hand, a diaphragm lower support member (holding member) 308 for holding and fixing the diaphragm 306 together with a diaphragm upper support member (hereinafter abbreviated as upper support member) 307 is disposed on the other end side in the thickness direction of the diaphragm 306. Of the diaphragm lower support member (hereinafter, abbreviated as “lower support member”) 308, a deformation accelerating portion (displacement member deforming portion) 3 formed on the diaphragm 306.
As shown in FIGS. 4 and 5, a concave portion (holding member deforming portion) 308a formed in a shape along the deformation accelerating portion 306a is formed in a portion corresponding to 06a.

The deformation accelerating portion 306a is obtained by deforming a part of the radially outer side of the diaphragm 306 into a wavy shape so that the diaphragm 306 is deformed and displaced substantially in proportion to the pressure difference between the inside and outside of the sealed space 305. It is to make. The diaphragm 30 of the lower support member 308
6, a lower flat portion (holding member flat surface) that is substantially flush with a surface 304a of the valve body 304 that contacts the diaphragm 306 when the valve port 303 is closed by the valve body 304. Part) 308b is formed.

As shown in FIG. 3, one end of the diaphragm 306 in the thickness direction (in the closed space 305) is connected to the valve body 304 through the diaphragm
A first coil spring (first elastic member) 309 for applying an elastic force in a direction to close the valve is provided. On the other hand, the other end of the diaphragm 306 in the thickness direction is provided with a valve port 303 for the valve element 304. A second coil spring (second elastic member) 310 for applying an elastic force in an opening direction is provided.

Reference numeral 311 denotes a plate (rigid body) also serving as a spring seat of the first coil spring 309.
Reference numeral 11 is made of a metal having a predetermined thickness so as to have higher rigidity than the diaphragm 306. And
As shown in FIGS. 4 and 5, the plate 311 includes a stepped portion (stopper portion) 307a formed on the upper support member 307.
, Restricting the displacement of the diaphragm 306 toward one end side in the thickness direction (closed space 305 side) of a predetermined value or more.

When the plate 311 and the stepped portion 307a come into contact with each other, the surface 31 of the plate 311 which comes into contact with the diaphragm 306 is contacted with the upper support member 307.
An upper flat portion (formed member flat portion) 307b which is substantially flush with 1a is formed. Incidentally, the inner wall of the cylindrical portion 307c of the upper support member 307 is
Nine guides are also used.

The plate 311 and the valve element 304
Are pressed toward the diaphragm 306 by the two coil springs 309 and 310, so that the plate 311, the valve body 304 and the diaphragm 306 are integrally displaced (operated) while being in contact with each other. by the way,
In FIG. 3, reference numeral 312 denotes an adjusting screw (elastic force adjusting mechanism) that adjusts the elastic force applied to the valve body 304 by the second coil spring 310 and also serves as a plate of the second coil spring 310. Reference numeral 312 is screwed to a female screw 302a formed in the partition wall 302. Incidentally, the initial load (elastic force in a state where the valve port 303 is closed) by the two coil springs 309 and 310 is changed by the diaphragm 30.
6 is about 1 MPa in terms of pressure.

Reference numeral 313 denotes an upper support member 307 extending inside and outside of the closed space 305, and C
This is a sealing tube (penetrating member) for sealing O ₂ , and the sealing tube 313 is made of a material such as copper having a higher thermal conductivity than the stainless steel upper support member 307. The lower support member 308 is also made of stainless steel. The sealing tube 313 has a volume of about 600 kg / m ^{3 with} respect to the inner volume of the closed space 305 when the valve port 303 is closed.
After sealing at an end density, the end is closed by joining means such as welding.

Reference numeral 314 denotes the partition 302 to the sealing tube 3.
13 is a conical spring that fixes the element case 315 made of the casing 13 into the casing main body 301c.
This is an O-ring that seals a gap between the O-ring and Oc. 6A is a view of the element case 315 as viewed from the direction of arrow A, and FIG. 6B is a view of the element case 315 as viewed from the direction of arrow B. As is clear from FIG. The side surface of the partition wall 302 communicates with the upstream space 301e.

Next, the pressure control valve 300 according to this embodiment
The operation of will be described. About 600 kg in the closed space 305
Since CO ₂ is sealed with / m ^3, the closed space 305
The internal pressure and the temperature change along the isopycnic line of 600 kg / m ³ shown in FIG. Therefore, for example, when the temperature inside the closed space 305 is 20 ° C., the internal pressure is about 5.8.
MPa. The valve body 304 has a closed space 305.
And the initial load of both coil springs 309 and 310 are acting at the same time, so that the acting pressure is about 6.8M
Pa.

Therefore, when the pressure in the upstream space 301e on the radiator 2 side is 6.8 MPa or less, the valve port 3
03 is closed by the valve 304, and when the pressure of the upstream space 301e exceeds 6.8 MPa, the valve port 303 is closed.
Opens. Similarly, for example, when the temperature in the closed space 12 is 40
7, the internal pressure of the closed space 305 is about 9.
7 MPa, and the acting force acting on the valve body 304 is about 1
0.7 MPa. Therefore, the upstream space 301e
Is less than 10.7 MPa, the valve port 303 is closed by the valve 304 and the upstream space 301
When the pressure of e exceeds 10.7 MPa, the valve port 303 opens.

Next, the operation of the CO ₂ cycle will be described with reference to FIG. Here, for example, the outlet side temperature of the radiator 200 is 40 ° C., and the radiator 200 outlet pressure is 10.7MP.
a, the pressure control valve 300 is closed as described above, so that the compressor 100
The CO ₂ stored inside is sucked and discharged toward the radiator 200. As a result, the outlet pressure of the radiator 200 increases (b′−c ′ → b ″ −c ″).

When the outlet pressure of the radiator 200 finally exceeds 10.7 MPa (BC), the pressure control valve 300
Is opened, so that CO ₂ changes in phase from a gas phase state to a gas-liquid two-phase state while reducing the pressure, and flows into the evaporator 400 (C-D). And it evaporates in the evaporator 400 (DA).
After cooling the air, the air is returned to the accumulator 500 again. At this time, the pressure on the outlet side of the radiator 200 decreases again, so the pressure control valve 300 closes again.

That is, this CO_TwoThe cycle is pressure controlled
By closing the control valve 300, the outlet side of the radiator 200
After increasing the pressure to a predetermined pressure, CO 2_TwoDecompress, steam
It emits and cools the air. Next, the present embodiment
The features of CO according to the present embodiment_TwoThe cycle is
With the refrigerant bypass means 700, the compressor 10
0 discharge side (entrance side of radiator 200) CO_TwoPredetermined temperature
When the temperature becomes equal to or higher than T, the accumulator 500
Outflowed CO_TwoTo bypass the internal heat exchanger 600
And low pressure CO_TwoAnd high pressure CO_TwoHeat exchange takes place between
, The CO on the suction side of the compressor 100_Two(Low pressure CO_Two)heating
The temperature becomes 0 ° C. Therefore, it passes through the internal heat exchanger 600.
Low-pressure CO
_TwoSince the temperature can be lowered, the compressor 100
CO from suction side to discharge side_TwoCO in the passage_TwoWarm
The compressor 100 can be reduced,
Can be prevented.

Further, since the accumulator 500 is provided, it is possible to prevent the liquid phase CO _{2 from} being sucked into the compressor 100. As a result, it is possible to prevent the compressor 100 from being damaged by liquid compression. (Second Embodiment) In the above-described embodiment, the refrigerant bypass means 700 is constituted by an electric device such as the electromagnetic valve 710 and the temperature sensor 730. However, in the present embodiment, as shown in FIGS. The bypass unit 700 is configured mechanically.

That is, as shown in FIG. 9, a spring (elastic body) 732 for applying an elastic force to the valve element 731 in a direction to close the bypass path 720 is disposed on one side of the valve element 731 for opening and closing the bypass path 720. At the same time, a temperature-sensitive cylinder portion 733 in which a fluid such as isobutane is sealed at a predetermined density is provided on the other side, and a pressure for opening the bypass passage 720 is applied to the valve body 731.

Therefore, CO ₂ on the discharge side of the compressor 100
When the pressure in the temperature-sensitive cylinder portion 733 rises as the temperature rises, the valve body 731 operates by the pressure and the bypass passage 720 is opened. On the other hand, CO ₂ on the compressor 100 discharge side
When the pressure in the temperature sensing tube portion 733 decreases as the temperature decreases, the bypass passage 720 is closed by the elastic force of the spring 732.

(Third Embodiment) In the above embodiment, C
Although the bypass passage 720 is opened and closed by detecting the O ₂ temperature electrically or mechanically, as described in the section of “Problems to be Solved by the Invention”, the present embodiment employs the low pressure CO ₂ Is the temperature of the low-pressure CO ₂ (CO ₂ on the discharge side of the compressor 100)
Temperature).

That is, as shown in FIG.
00 between the outlet side of the compressor 100 and the suction side of the compressor 100.
Pressure sensor (pressure detecting means) 74 for detecting the pressure of ₂
1, and a comparison device 742 that issues a signal to the control device 713 when the pressure detected by the pressure sensor 741 becomes equal to or lower than the predetermined pressure P. The predetermined pressure P is
The pressure corresponds to the predetermined temperature T in the first and second embodiments, and is about 6 MPa in the present embodiment.

Thus, when the pressure of the low-pressure CO ₂ becomes equal to or lower than the predetermined pressure P, the CO ₂ flowing out of the accumulator 500 is bypassed to the internal heat exchanger 600 as in the first and second embodiments. CO on the suction side of the compressor 100
₂ (Low pressure CO ₂ ) The heating degree becomes 0 ° C. Therefore, the low-pressure CO ₂ temperature can be reduced as compared with the case where the CO ₂ is sucked into the compressor 100 via the internal heat exchanger 600, so that the CO ₂ passage from the suction side to the discharge side of the compressor 100 is reduced. The CO ₂ temperature can be reduced, and damage to the compressor 100 can be prevented.

(Fourth Embodiment) In the third embodiment, the refrigerant bypass means 700 is configured by electrically detecting the pressure on the suction side of the compressor 100 with the pressure sensor 741. As shown in FIGS. 11 and 12, a refrigerant bypass unit 700 that mechanically operates with respect to the pressure on the suction side of the compressor 100 is employed.

That is, as shown in FIG. 12, a spring (elastic body) 752 for applying an elastic force to open the bypass passage 720 to the valve body 751 is arranged on one side of the valve body 751 for opening and closing the bypass passage 720. At the same time, a force for closing the bypass passage 720 is applied to the valve 751 on the other side.
, The pressure on the suction side of the compressor 100 is guided.

As a result, when the pressure on the suction side of the compressor 100 decreases as the heat load decreases, the valve 751 operates by the elastic force of the spring 752, and the bypass passage 720 is opened. When the pressure on the side rises, the bypass passage 720 is closed by the pressure. (Fifth Embodiment) The above-described embodiments, by opening and closing the bypass passage 720 to the CO ₂ flowing out of the accumulator 500 to bypass the internal heat exchanger 600 to flow through the compressor 100, the low-pressure CO ₂ and the high-pressure CO _Although it was controlled whether or not to perform heat exchange with ₂ , this embodiment,
As shown in FIG. 14, CO ₂ flowing out of the radiator 200
By opening and closing the bypass passage 740 for bypassing the internal heat exchanger 600 and flowing to the pressure control valve 300 with the solenoid valve 750, it is determined whether or not to perform heat exchange between the low-pressure CO ₂ and the high-pressure CO _2. It is configured to control.

That is, as in the first embodiment, when the CO ₂ temperature on the discharge side of the compressor 100 (the inlet side of the radiator 200) becomes equal to or higher than the predetermined temperature T, the solenoid valve 750 is opened and the radiator 200 is opened. CO ₂ flowing out of the internal heat exchanger 600
Is bypassed to flow through the pressure control valve 300 and the low-pressure CO ₂
The heat exchange between and high pressure CO ₂ is stopped. Thus, it is possible to reduce the low-pressure CO ₂ temperature, can reduce the CO ₂ temperature at the passage of CO ₂ leading to the discharge side of the suction side of the compressor 100, compressor 100
Can be prevented beforehand.

(Sixth Embodiment) This embodiment relates to a compressor 1
In the CO ₂ passage from the suction side to the discharge side
And when the O ₂ temperature increases, for example, as when the cool-down (rapid cooling operation), high pressure of the low pressure CO _2, focusing on that is when the pressure difference between the low-pressure CO ₂ and the high-pressure CO ₂ is small (ABC- of FIG. 7)
D). At the time of cool down (rapid cooling operation), the outside air temperature can be generally regarded as substantially constant.
The O ₂ pressure can also be considered to be substantially constant.

At the time of cooling down, a large refrigeration capacity is required.
It is better to cause heat exchange between O ₂ and high-pressure CO ₂ . On the other hand, the pressure of the low-pressure CO ₂ is decreased been cabin temperature is lowered, when the pressure difference between the low-pressure CO ₂ and the high-pressure CO ₂ has been increased, in addition to not requiring a large cooling capacity,
Since the temperature of the refrigerant discharged from the compressor 100 increases as compared with the time of the cool down (see EFG in FIG. 7), it is better to stop the heat exchange between the low-pressure CO ₂ and the high-pressure CO ₂ .

Therefore, in the present embodiment, as shown in FIG. 15, the discharge side pressure (= high pressure CO ₂ pressure) of the compressor 100 and the suction side pressure (= low pressure CO ₂ pressure) of the compressor 100 are different. A bypass means 760 for mechanically opening and closing the bypass passage 720 by a differential pressure is provided. Here, as shown in FIG. 16, the bypass unit 760 is provided on one side of the valve body 761 that opens and closes the bypass passage 720 with a spring (elastic body) that applies an elastic force in the direction to close the bypass passage 720 to the valve body 761. In addition to the arrangement of the compressor 762, the compressor 100 is operated so that the outlet side pressure of the accumulator 500 (the suction side pressure of the compressor 100) acts on the other side and a force for opening the bypass passage 720 acts on the valve body 761.
Discharge pressure.

At this time, the differential pressure between the discharge side pressure (= high pressure CO ₂ pressure) of the compressor 100 and the suction side pressure (= low pressure CO ₂ pressure) of the compressor 100 becomes 6 MPa or more. The setting is such that the bypass passage 720 is opened when the vehicle is turned on. Accordingly, CO ₂ temperature at the passage of CO ₂ leading to the discharge side of the suction side of the compressor 100 can be lowered, damage to the compressor 100 can be prevented.

(Seventh Embodiment) This embodiment, like the sixth embodiment, is configured to control whether or not to heat-exchange both CO ₂ based on the pressure difference between the low-pressure CO ₂ and the high-pressure CO _2. It was done. That is, in this embodiment, as shown in Figure 17, the CO ₂ inlet side of the pressure control valve 300 pressure (=
A bypass means 780 is provided for mechanically opening and closing the bypass passage 740 by a differential pressure between the pressure of the high pressure CO ₂ (pressure of the high pressure CO ₂ ) and the pressure at the CO ₂ outlet side of the pressure control valve 300 (= pressure of the low pressure CO ₂ ).

Here, as shown in FIG. 18, the bypass means 780 is a valve body 781 for opening and closing the bypass passage 720.
A spring (elastic body) 782 for applying an elastic force in the direction of closing the bypass passage 720 to the valve body 781 is disposed on one side of the valve, and the pressure at the CO ₂ outlet side of the pressure control valve 300 (= low pressure CO ₂ Pressure) is applied, and the discharge side pressure of the compressor 100 is guided to the other side to apply a force for opening the bypass passage 720 to the valve body 771.

At this time, the spring 762 is
The pressure difference between the pressure on the CO ₂ inlet side of 0 (= high-pressure CO ₂ pressure) and the pressure on the CO ₂ outlet side of the pressure control valve 300 (= low-pressure CO ₂ pressure) became 6 MPa or more. Sometimes, the bypass passage 720 is set to open. (Eighth Embodiment) In the present embodiment, as described at the beginning of the sixth embodiment, the pressure of the low-pressure CO ₂ is higher at the time of cool-down and the like than when the temperature in the vehicle compartment decreases. It was done using.

That is, in this embodiment, as shown in FIG. 19, the bypass means 7 for opening and closing the bypass passage 720 is provided.
A spring (elastic body) 782 for applying an elastic force in the direction of opening the bypass passage 720 to the valve body 781 is provided on one side of the valve body 781 of the valve 80, and a force for closing the bypass passage 720 is provided on the other side. Is applied to the valve body 781 to guide the pressure on the outlet side of the accumulator 500.

Here, the spring 782 is connected to the accumulator 5
The bypass passage 720 is set to open when the outflow pressure (pressure of the low-pressure CO ₂ ) of 00 becomes a predetermined pressure (4 MPa in this embodiment) or lower. (Ninth Embodiment) This embodiment is similar to the eighth embodiment by utilizing the fact that the pressure of the low-pressure CO ₂ is higher at the time of cool down and the like when the temperature in the vehicle compartment is lowered. It is a thing.

That is, in this embodiment, as shown in FIG. 21, the bypass means 7 for opening and closing the bypass passage 740 is provided.
A spring (elastic body) 792 for applying an elastic force in the direction of opening the bypass passage 740 to the valve body 791 is provided on one side of the valve body 791 of the 90, and a force for closing the bypass passage 740 on the other side. Is applied to the valve element 791 to guide the pressure on the outlet side of the pressure control device 300.

Here, the spring 792 is connected to the pressure control device 30.
The setting is such that the bypass passage 740 is opened when the outflow pressure of 0 (the pressure of the low-pressure CO ₂ ) becomes equal to or lower than a predetermined pressure (4 MPa in this embodiment). By the way, the present invention is not limited to the use of a supercritical refrigeration cycle using CO ₂ , for example, a vapor compression refrigeration cycle using a refrigerant used in a supercritical region such as ethylene, ethane, and nitrogen oxide. Can also be applied.

In the above embodiment, the pressure control valve 3
Although 00 is mechanically configured, an electrical pressure control valve may be configured by a pressure sensor, an electric open / close valve, and the like.
Further, the structure of the internal heat exchanger 600 is not limited to a spiral shape as shown in FIG. 2, and may be formed in a double cylindrical shape as shown in FIG. In addition, the first and second
In the embodiment, the valve means such as the electromagnetic valve is opened and closed based on the CO ₂ temperature on the discharge side of the compressor 100. However, the position for detecting the CO ₂ temperature is not limited to this, Any position may be used as long as it is a predetermined position of the refrigerant passage from the side to the inlet side of the radiator 200. However, the predetermined temperature needs to be set appropriately according to the detection position.

[0066] Further, the 8,9 embodiments have a low pressure CO ₂ and the high-pressure CO ₂ controls whether or not to heat exchange on the basis of the pressure of the low pressure CO _2, CO ₂ pressure, CO ₂ temperature correlation Because of the relationship, when the temperature of the low-pressure CO ₂ becomes equal to or lower than a predetermined temperature (for example, a CO ₂ temperature corresponding to 4 MPa of CO ₂ ), the heat exchange between the low-pressure CO ₂ and the high-pressure CO ₂ may be stopped. Good.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a supercritical refrigeration cycle according to a first embodiment.

FIG. 2 is an explanatory diagram of an internal heat exchanger.

FIG. 3 is a sectional view of a pressure control valve.

FIG. 4 is an enlarged view of a diaphragm portion showing a valve open state.

FIG. 5 is an enlarged view of a diaphragm portion showing a valve closed state.

6 (a) is a view as viewed from an arrow A in FIG. 3, and FIG. 6 (b) is a view as viewed from an arrow B in FIG. 3 (a).

FIG. 7 is a Mollier diagram of CO ₂ .

FIG. 8 is a schematic diagram of a supercritical refrigeration cycle according to a second embodiment.

FIG. 9 is a schematic view of a pressure control valve according to a second embodiment.

FIG. 10 is a schematic diagram of a supercritical refrigeration cycle according to a third embodiment.

FIG. 11 is a schematic diagram of a supercritical refrigeration cycle according to a third embodiment.

FIG. 12 is a schematic diagram of a pressure control valve according to a fourth embodiment.

FIG. 13 is a drawing showing a modification of the internal heat exchanger.

FIG. 14 is a schematic diagram of a supercritical refrigeration cycle according to a fifth embodiment.

FIG. 15 is a schematic diagram of a supercritical refrigeration cycle according to a sixth embodiment.

FIG. 16 is an enlarged view of a bypass unit according to the sixth embodiment.

FIG. 17 is a schematic diagram of a supercritical refrigeration cycle according to a seventh embodiment.

FIG. 18 is an enlarged view of a bypass unit according to the seventh embodiment.

FIG. 19 is a schematic diagram of a supercritical refrigeration cycle according to an eighth embodiment.

FIG. 20 is an enlarged view of a bypass unit according to the eighth embodiment.

FIG. 21 is a schematic diagram of a supercritical refrigeration cycle according to a ninth embodiment.

FIG. 22 is an enlarged view of a bypass unit according to a ninth embodiment.

FIG. 23 is a Mollier diagram of CO ₂ .

FIG. 24 is a graph showing the relationship between the radiator outlet pressure and the coefficient of performance (COP).

FIG. 25 is a graph showing the relationship between the CO ₂ temperature at the radiator outlet and the target radiator outlet pressure.

FIG. 26 is a Mollier diagram of CO ₂ .

[Explanation of symbols]

100: compressor, 200: radiator, 300: pressure control valve (pressure control device) 400: evaporator, 500: accumulator (gas-liquid separator), 600: internal heat exchanger, 700: refrigerant bypass means.

Claims (7)

[Claims] A compressor (100) for compressing a refrigerant; a radiator (200) for cooling a refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant; A pressure controller (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200); An evaporator (400) for evaporating the refrigerant depressurized by the pressure control device (300); separating the refrigerant flowing out of the evaporator (400) into a gaseous refrigerant and a liquid-phase refrigerant; A gas-liquid separator (500) that flows toward the suction side of the compressor (100); a refrigerant that flows out of the gas-liquid separator (500) and is sucked into the compressor (100); Container (200)
Heat exchanger that exchanges heat with the refrigerant flowing out of the
0) and the radiator (20) from the inflow side of the evaporator (400).
When the refrigerant temperature at a predetermined position of the refrigerant passage reaching the inlet side of 0) becomes equal to or higher than a predetermined temperature, the refrigerant flowing out of the gas-liquid separation device (500) is transferred to the heat exchanger (600).
And a refrigerant bypass means (700) for bypassing and flowing through the compressor (100). 2. The refrigerant bypass unit (700) includes a bypass passage (70) that allows the refrigerant flowing out of the gas-liquid separator (500) to bypass the heat exchanger (600) and flow to the compressor (100). 720) and valve means (71) for opening and closing the bypass passage (720).
0) and a valve control means (711-713) for detecting the temperature of the refrigerant discharged from the compressor (100) and opening the valve means (710) when the detected temperature becomes equal to or higher than a predetermined temperature.
The supercritical refrigeration cycle according to claim 1, characterized by comprising: 3. The refrigerant bypass means (700) includes a bypass passage (70) for allowing the refrigerant flowing out of the gas-liquid separator (500) to bypass the heat exchanger (600) and flow to the compressor (100). 720) and valve means (71) for opening and closing the bypass passage (720).
0) and a valve control means (741 to 743) for detecting the pressure of the refrigerant drawn into the compressor (100) and opening the valve means (710) when the detected pressure becomes equal to or lower than a predetermined pressure.
The supercritical refrigeration cycle according to claim 1, characterized by comprising: 4. A compressor (100) for compressing a refrigerant, a radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant, A pressure controller (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200); An evaporator (400) for evaporating the refrigerant depressurized by the pressure control device (300); separating the refrigerant flowing out of the evaporator (400) into a gaseous refrigerant and a liquid-phase refrigerant; A gas-liquid separator (500) that flows toward the suction side of the compressor (100); a refrigerant that flows out of the gas-liquid separator (500) and is sucked into the compressor (100); Container (200)
Heat exchanger that exchanges heat with the refrigerant flowing out of the
0), wherein when a refrigerant temperature at a predetermined position in a refrigerant passage from a discharge side of the compressor (100) to an inflow side of the pressure control device (300) becomes equal to or higher than a predetermined temperature, the heat exchanger A supercritical refrigeration cycle, wherein the heat exchange in (600) is stopped. 5. A compressor (100) for compressing a refrigerant, a radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant, A pressure controller (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200); An evaporator (400) for evaporating the refrigerant depressurized by the pressure control device (300); separating the refrigerant flowing out of the evaporator (400) into a gaseous refrigerant and a liquid-phase refrigerant; A gas-liquid separation device (500) that flows out toward the suction side of the compressor (100); a refrigerant that flows out of the gas-liquid separation device (500) and is sucked into the compressor (100); Container (200)
Heat exchanger that exchanges heat with the refrigerant flowing out of the
0), wherein when a refrigerant temperature at a predetermined position of a refrigerant passage from an outlet side of the pressure control device (300) to a suction side of the compressor (100) becomes equal to or lower than a predetermined temperature, the heat exchanger A supercritical refrigeration cycle, wherein the heat exchange in (600) is stopped. 6. A compressor (100) for compressing a refrigerant, a radiator (200) for cooling a refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant, A pressure controller (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200); An evaporator (400) for evaporating the refrigerant depressurized by the pressure control device (300); separating the refrigerant flowing out of the evaporator (400) into a gaseous refrigerant and a liquid-phase refrigerant; A gas-liquid separation device (500) that flows out toward the suction side of the compressor (100); a refrigerant that flows out of the gas-liquid separation device (500) and is sucked into the compressor (100); Container (200)
Heat exchanger that exchanges heat with the refrigerant flowing out of the
0), and a refrigerant pressure at a predetermined position of a refrigerant passage from a discharge side of the compressor (100) to an inflow side of the pressure control device (300), and the refrigerant pressure from an outlet side of the pressure control device (300). The heat exchange in the heat exchanger (600) is stopped when a pressure difference between the refrigerant pressure at a predetermined position in the refrigerant passage reaching the suction side of the compressor (100) and the refrigerant pressure becomes equal to or higher than the predetermined pressure difference. And a supercritical refrigeration cycle. 7. A compressor (100) for compressing a refrigerant, a radiator (200) for cooling the refrigerant discharged from the compressor (100) and having an internal pressure exceeding a critical pressure of the refrigerant, A pressure controller (300) for reducing the pressure of the refrigerant flowing out of the radiator (200) and controlling the refrigerant pressure at the outlet of the radiator (200) based on the temperature of the refrigerant at the outlet of the radiator (200); An evaporator (400) for evaporating the refrigerant depressurized by the pressure control device (300); separating the refrigerant flowing out of the evaporator (400) into a gaseous refrigerant and a liquid-phase refrigerant; A gas-liquid separation device (500) that flows out toward the suction side of the compressor (100); a refrigerant that flows out of the gas-liquid separation device (500) and is sucked into the compressor (100); Container (200)
Heat exchanger that exchanges heat with the refrigerant flowing out of the
0), wherein when the refrigerant pressure at a predetermined position in the refrigerant passage from the outlet side of the pressure control device (300) to the suction side of the compressor (100) becomes equal to or lower than a predetermined pressure, the heat exchange is performed. A supercritical refrigeration cycle characterized by stopping heat exchange in a vessel (600).