JPH109719A - Pressure reducing device for freezing cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure reducing device in which a pressure at an outlet port of a radiator is automatically controlled in response to a required freezing capability. SOLUTION: A valve body 35 of a pressure reducing device 3 controls degree of opening of a valve port 24 in response to a pressure within an evaporator 4 in such a way that a pressure difference between a pressure in a space 32a at an inlet port 32 side and a pressure in a space 33a at a flowing outlet port 33 side may become a predetermined pressure difference ΔP (5.5 to 7MPa in the case that refrigerant is CO2 ). When such an arrangement as above, when a thermal load of the evaporator 4 is increased, a repressor at the outlet port of a radiator 2 is increased and in turn when the thermal load of the evaporator 4 is decreased, a pressure at the outlet port of the radiator 2 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pressure control valve for controlling the radiator outlet-side pressure of the vapor compression refrigeration cycle, the steam using a refrigerant in a supercritical range, such as carbon dioxide (CO ₂₎ compression It is suitable for use in a type refrigeration cycle.

[0002]

2. Description of the Related Art In recent years, as one of measures against defluorocarbon of a refrigerant used in a vapor compression type refrigeration cycle, for example,
As described in JP-18602, carbon dioxide (C
O ₂ ) (hereinafter referred to as CO ₂ )
Abbreviated as ₂ cycles. ) Has been proposed.

The operation of this CO ₂ cycle is in principle the same as the operation of a conventional vapor compression refrigeration cycle using chlorofluorocarbon. That is, as shown by A-B-C-D- A in FIG. 6 (CO ₂ Mollier chart), compressing the CO ₂ in the vapor phase by a compressor (A-B), the gas of the high temperature and high pressure The CO ₂ in the phase is cooled by a radiator (gas cooler) (B-C). Then, the pressure was reduced by a pressure reducer (C-
D), evaporating CO ₂ in a gas-liquid two-phase state (D-
A), the external fluid is cooled by removing latent heat of vaporization from an external fluid such as air. Note that CO ₂ changes into a gas-liquid two-phase state when the pressure falls below the saturated liquid pressure (the pressure at the intersection of the line segment CD and the saturated liquid line SL).

However, CO_TwoCritical temperature is about 31 ° C.
Critical temperature of the coming Freon (eg, 112 ° C for R12)
In summer, etc., the CO on the radiator side is lower_Twotemperature
Is CO_TwoBecomes higher than the critical point temperature. That is,
CO at the radiator outlet side _TwoDoes not condense (line BC
Does not intersect with the saturated liquid line). In addition, the radiator outlet side (C
Point) indicates the compressor discharge pressure and C at the radiator outlet side.
O_TwoAnd CO at the radiator outlet side_Two
The temperature is determined by the heat dissipation capacity of the radiator and the outside air temperature.
You. And since the outside air temperature cannot be controlled,
CO at radiator outlet side_TwoTemperature is substantially controlled
Can not.

[0005] Therefore, the state of the radiator outlet side (point C) can be controlled by controlling the discharge pressure of the compressor (radiator outlet side pressure). That is, when the outside air temperature is high in summer or the like, in order to secure a sufficient cooling capacity (enthalpy difference), as shown by EFGHE in FIG. Need to be higher.

[0006]

Incidentally, in order to control the pressure at the radiator outlet side, the above-mentioned publication describes that the opening of the pressure reducer is manually controlled according to the required refrigerating capacity. is there. However, in this means, there is no problem as long as it is a test for confirming whether or not the refrigeration capacity can be controlled by controlling the pressure on the radiator outlet side.
In an actual use situation, the required refrigeration capacity changes every moment. Therefore, means such as controlling the opening of the decompressor by manual operation requires a CO that exhibits a sufficient refrigeration capacity.
₂ cycles cannot be provided.

[0007] In view of the above, it is an object of the present invention to provide a pressure reducing device that controls the pressure at the radiator outlet side in accordance with the required refrigerating capacity.

[0008]

The present invention uses the following technical means to achieve the above object. Claim 1
In the invention described in Item 4, the valve body (35) of the refrigeration cycle decompression device (3) that decompresses the refrigerant flowing out of the radiator (2).
Is the space (32a) on the side of the inlet (32) and the outlet (3
The opening of the valve port (34) is controlled according to the pressure in the evaporator (4) so that the pressure difference with the space (33a) on the 3) side becomes a predetermined pressure difference (ΔP).

Thus, as described later, when the heat load of the evaporator (4) increases, the opening of the valve port (34) is reduced, while the heat load of the evaporator (4) decreases. At this time, the opening of the valve port (34) is increased.
For this reason, when the heat load of the evaporator (4) increases, the outlet pressure of the radiator (2) increases, while the evaporator (4) increases.
When the heat load of the radiator (2) decreases, the outlet pressure of the radiator (2) decreases. Therefore, the pressure on the outlet side of the radiator (2) of the vapor compression refrigeration cycle in which the pressure in the radiator (4) exceeds the critical pressure of the refrigerant can be controlled.

[0010] Here, "pressure in the evaporator (4)"
Does not mean the pressure in the evaporator (4) in a strict sense, but a part of the vapor compression refrigeration cycle diagram shown on the Mollier diagram that shows the pressure in the evaporator (4). Show the whole. That is, the "pressure in the evaporator (4)" indicates the pressure from the outlet side of the refrigeration cycle pressure reducing device (3) to the suction port side of the compressor.

According to the second aspect of the present invention, the valve body (35)
Is arranged in the space on the outlet (33) side, and is formed by an elastic member (36) that generates elastic force.
2) It is characterized by being pressed toward the space on the side. Thereby, as described later, the pressure reduced by the refrigeration cycle pressure reducing device (3), that is, the pressure difference (Δ
P) can be adjusted by adjusting the elastic force of the elastic member (36). Therefore, as compared with the electric control means for adjusting the opening degree of the valve port (34) using a pressure sensor, a proportional control electromagnetic valve or the like, the refrigeration cycle depressurizing device 3 is used.
Can be simplified, and an increase in the manufacturing cost of the pressure reducing device 3 can be prevented.

[0012] In the third aspect of the present invention, carbon dioxide is used as the refrigerant, and the predetermined pressure difference (ΔP) is:
It is 5.5 to 7 MPa. According to a fourth aspect of the present invention, there is provided a vapor compression refrigeration cycle having the pressure reducing device (3) according to any one of the first to third aspects. In addition, the code | symbol in the parenthesis of each said means shows the correspondence with the concrete means of embodiment mentioned later.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; (First Embodiment) FIG. 1 shows a CO using a pressure reducing device for a refrigeration cycle (hereinafter abbreviated as a pressure reducing device) 3 according to the present embodiment.
_Two cycles are applied to an air conditioner for vehicles.
Is a compressor that obtains driving force from an engine (not shown) to compress CO ₂ in a gaseous state. Reference numeral 2 denotes a radiator (gas cooler) that cools the CO ₂ compressed by the compressor 1 by exchanging heat with the outside air or the like, and depressurizes the high-pressure (about 12 MPa) CO ₂ flowing out of the radiator 2. This is a decompression device.

The pressure reducing device 3 serves as a pressure reducing means and also has a function of controlling the outlet pressure of the radiator 2 as will be described later.
₂ flows into an evaporator 4 described later in a gas-liquid two-phase state. Reference numeral 4 denotes an evaporator (heat absorber) which serves as a cooling means for air blown into the vehicle interior. When CO ₂ in a gas-liquid two-phase state is vaporized (evaporated) in the evaporator 4, latent heat of evaporation is generated from the air in the vehicle interior. Steal and cool the cabin air. 5 separates CO ₂ in a gaseous state from CO _{2 in} a liquid state,
_An accumulator that temporarily stores ₂ . In addition,
Reference numerals 6 and 7 are cooling fans for promoting heat exchange between the radiator 2 and the evaporator 4.

The compressor 1, the radiator 2, the pressure reducing device 3, the evaporator 4, and the accumulator 5 are connected by pipes to form a closed circuit. The radiator 2 is arranged in front of the vehicle in order to make the temperature difference between the CO 2 inside the radiator ₂ and the outside air as large as possible. Next, the pressure reducing device 3 will be described in detail (see FIG. 2).

Reference numeral 31 denotes an inlet 32 communicating with the radiator 2.
And a housing made of a metal such as stainless steel or brass having an outlet 33 communicating with the evaporator 4. A space 32 a on the inlet 32 side and a space 33 a on the outlet 33 side are formed in the housing 31. A valve port 34 for communication is formed. In the space 33a, a valve body 35 for adjusting the opening degree of the valve port 34 is provided. The valve body 35 is formed by a metal coil spring (elastic member) 36 to the inlet 32.
Side space 32a.

The housing 31 is a housing 31
(A lid portion) 31a of which the outlet 33 is formed
(A bottom portion) 31b where the inflow port 32 is formed
And a main part 31c having a cylindrical shape. The bottom part 31b and the main part 31c are integrally formed, and the lid part 31a stores the valve body 35 and the coil spring 36 in the housing 31. It is connected to the housing 31 by connecting means such as welding or screw connection.

A guide skirt 37 guides the movement of the valve body 35 in the housing 31. The cylindrical outer surface 37a of the guide skirt 37 contacts the inner wall 31d of the housing 31, Valve body 3
5 is guided. Furthermore, guide skirt 3
7, a plurality of holes 37b forming a flow path of CO ₂ are formed in the vicinity of the valve body 35.

Next, the operation of the pressure reducing device 3 will be described. As is clear from FIG. 2, on the inflow port 32 side of the valve body 35,
Since the acting force F ₁ due to the pressure on the outlet side of the radiator 2 acts, the valve body 35 is pressed to the outlet 33 side. On the other hand, the outflow port 33 side, since the acting force F ₂ acting by the elastic force of the evaporator 2 of the inlet pressure and the coil spring 36, the valve body 3
5 is pressed toward the inlet 32.

That is, when the acting force F ₂ is larger than the acting force F ₁ , the valve body 35 moves so that the opening of the valve port 34 becomes smaller, and the acting force F ₁ is larger than the acting force F _2. In this case, the valve element 35 moves so that the opening of the valve port 34 increases (see FIG. 2B). Therefore, the valve element 35
Stops at a position where the acting force F ₁ and the acting force F ₂ are balanced (or a position in contact with the valve port 34).
The opening degree of 4 is determined by the elastic force exerted on the valve body 35 by the coil spring 36. That is, the pressure difference ΔP between the two spaces 32a and 33a corresponds to the elastic force exerted on the valve body 35 by the coil spring 36.

Since the movement amount (lift amount) of the valve body 35 is small, the change in the elastic force exerted on the valve body 35 by the coil spring 36 can be almost neglected.
The pressure difference ΔP between a and 33a is substantially constant. In addition,
In the present embodiment, the opening degree of the valve port 34 indicates a distance t between the valve port 34 and the valve body 35.

Next, the operation of the CO ₂ cycle according to this embodiment will be described. FIG. 3 is a Mollier diagram showing the operation of the CO ₂ cycle according to the present embodiment. In FIG. 3, a dashed-dotted line diagram A shows a case where the refrigerating capacity (heat load) is small.
A solid line diagram B shows a case where the heat load is large. For example, when the room temperature is high in summer or the like, the temperature of the air cooled by the evaporator 4 also increases, so that the temperature in the evaporator 4 increases and the pressure in the evaporator 4, that is, CO ₂
Evaporating pressure rises.

[0023] Therefore, the greater the applied force F _2, as described above, since the opening degree of the valve port 34 is reduced, the radiator 2
The pressure on the outlet side rises (the state of the diagram B). Therefore, as shown in FIG. 3, since the specific enthalpy difference between the outlet and the inlet of the evaporator 4 increases (h ₁ > h ₂ ), the refrigeration capacity increases. On the other hand, when the indoor temperature is low such as in spring or autumn, the temperature of the air cooled by the evaporator 4 is also low.
As the temperature in the evaporator 4 decreases, the pressure in the evaporator 4, that is, the evaporation pressure of CO ₂ decreases.

[0024] Therefore, the smaller the applied force F _2, as described above, since the opening degree of the valve port 34 is increased, the radiator 2
, The pressure on the outlet side decreases (state of the diagram A). Therefore, as shown in FIG. 3, the difference in specific enthalpy between the outlet and the inlet of the evaporator 4 is reduced, and the refrigeration capacity is reduced. Next, the pressure difference ΔP will be described.

When the temperature in the evaporator 4 is below the freezing point (0 ° C. or less), frost is generated in the evaporator 4 and the refrigeration capacity of the evaporator 4 is reduced. It is desirable to raise it. However, if the temperature inside the evaporator 4 is increased unnecessarily, there arises a problem that the air blown into the vehicle compartment cannot be sufficiently cooled. Then, the inventors conducted various tests and examinations, and found that the maximum temperature in the evaporator 4 was about 17 ° C. and the pressure in the evaporator 4 (evaporation pressure of CO ₂ ) was about 3.5 to 5.5. It was concluded that 5 MPa (hereinafter referred to as low pressure side pressure) was appropriate. Then, the inventors tried the following study in order to determine the outlet pressure of the radiator 2 (hereinafter, referred to as high pressure side pressure) based on the low pressure side pressure.

That is, the graph of FIG. 4 shows the result of calculating the coefficient of performance (COP) of the CO ₂ cycle with respect to the high pressure side pressure while the low pressure side pressure is constant (3.5 MPa). As is apparent from the results, when the high pressure side pressure is 9 MPa or less and 12.5 MPa or more, the COP is extremely deteriorated. Therefore, it is desirable to keep the high pressure side pressure at 9 to 12.5 MPa. That is, the pressure difference ΔP is preferably set to 5.5 to 7 MPa.

The coefficient of performance (COP) is a value obtained by dividing the enthalpy difference (refrigeration capacity) between the outlet and the inlet of the evaporator 4 by the compression work of the compressor 1, as is well known. The efficiency was 65%. Here, for example, when the pressure difference ΔP is 6.0 MPa and the low pressure side pressure is 3.5 MPa (about 0 ° C. in the evaporator 4), the high pressure side pressure is 9.5 MPa. Therefore, the specific enthalpy difference between the outlet and the inlet of the evaporator 4 is about 111 kJ / kg, and the CO ₂ density at the inlet of the compressor 1 is about 96.3 kg / m ³ (see FIG. 6).

When the heat load increases and the low pressure side pressure rises to 5 MPa, the high pressure side pressure becomes 11M.
Pa (at about 13 ° C. in the evaporator 4). Therefore, the specific enthalpy difference between the outlet and the inlet of the evaporator 4 is about 121.5 kJ / kg, and the CO 1
_{(2) The} density is about 151.5 kg / m ³ (see FIG. 6).
Therefore, the low pressure side pressure is from 3.5MPa to 5MPa.
By increasing to a, the refrigerating capacity of the evaporator 4 becomes about 1.7 times.

As described above, according to this embodiment, simple means such as adjusting the opening of the valve port 34 so that the pressure difference ΔP between the high pressure side pressure and the low pressure side pressure becomes a predetermined value. Thus, the CO ₂ cycle can be controlled. The pressure difference ΔP is determined by the coil spring 3 in the pressure reducing device 3.
6, the structure of the decompression device 3 is simplified and the decompression device 3 is simpler than an electric control means for adjusting the opening of the valve port 34 by using a pressure sensor, a proportional control solenoid valve or the like. 3 can prevent an increase in manufacturing cost.

(Second Embodiment) In this embodiment, the valve 35
The elastic force acting on the coil spring 36 is adjustable. This will be described below with reference to FIG. 40 is provided on one end side of the coil spring 36 and applies the elastic force of the coil spring 36 to the needle-shaped valve
Reference numeral 41 denotes a second pressing plate which is disposed on the other end of the coil spring 36 and adjusts the elastic force of the coil spring 36. This second holding plate 41
Is formed with a female screw portion 41a, and a male screw portion 42a formed on an adjusting shaft 42 for moving the second pressing plate 41 in the axial direction of the coil spring 36 is screwed to the female screw portion 41a.

Therefore, the second pressing plate 41 moves in the axial direction of the coil spring 36 in conjunction with the rotation of the adjusting shaft 42, so that the elastic force acting on the valve body 35 can be adjusted. Reference numeral 43 denotes a key for preventing the second pressing plate 41 from co-rotating with the adjustment shaft 42, and reference numeral 44 denotes a nitrile rubber O-ring serving as a seal member for sealing a gap between the adjustment shaft 42 and the housing 31. is there.

Incidentally, the CO ₂ cycle has a higher high-pressure side pressure (approximately 8 times) than that of a normal vapor compression refrigeration cycle using chlorofluorocarbons. Is desirably disposed on the outlet 33 side after decompression as described above. by the way,
In the above-described embodiment, the pressure difference ΔP is mechanically controlled using the coil spring 36.
The present invention can be implemented by using an electric actuator that detects the internal pressure and that can adjust the valve opening based on the detected value, such as a proportional control solenoid valve.

Since the pressure and the temperature have a relationship as shown by the isotherm in the Mollier diagram, a temperature sensor may be used instead of the pressure sensor. In this case, the pressure sensor may detect the pressure at the outlet side or the inlet side of the evaporator 4 or at any location in the evaporator 4. However, when pressure is detected at the outlet side of the evaporator 4 when the pressure loss in the evaporator 4 is large, it is necessary to compensate for the pressure loss. Similarly, when a temperature sensor is used, it is necessary to consider a temperature change between the inlet side and the outlet side of the evaporator 4.

In the above-described embodiment, the valve body 35 has C
Although the pressure of CO ₂ circulating in the O ₂ cycle was directly applied, the pressure inside the evaporator 4 or at the outlet side or the inlet side of the evaporator 4 was taken out by a thin tube or the like, and the valve body 35 was opened via a diaphragm or the like. It may be activated. In addition, the use of the pressure reducing device 3 according to the present invention is not limited to a vapor compression refrigeration cycle using CO ₂ , and for example, a refrigerant used in a supercritical region such as ethylene, ethane, or nitrogen oxide is used. It can also be applied to a vapor compression refrigeration cycle.

Further, even if the accumulator 5 is eliminated, a vapor compression refrigeration cycle can be implemented.
In this case, the refrigerant remaining in the evaporator 4 is sucked, and the same operation as in the CO ₂ cycle having the accumulator 5 can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a CO ₂ cycle according to a first embodiment.

FIG. 2 is a cross-sectional view of the pressure reducing device according to the first embodiment.

FIG. 3 is a Mollier diagram for explaining a CO ₂ cycle according to the first embodiment.

FIG. 4 is a graph showing a relationship between a high pressure side pressure and a coefficient of performance (COP).

FIG. 5 is a sectional view of a pressure reducing device according to a second embodiment.

FIG. 6 is a Mollier diagram for explaining a CO ₂ cycle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Heat radiator, 3 ... Decompression device, 4 ... Evaporator,
5 Accumulator, 31 Housing, 32 Inflow port, 33 Outflow port, 34 Valve port, 35 Valve body, 36 Coil spring (elastic member).

Claims (4)

[Claims] 1. A vapor compression type having a radiator (2) for cooling a refrigerant and an evaporator (4) for evaporating the refrigerant, wherein a pressure in the radiator (2) exceeds a critical pressure of the refrigerant. A decompression device (3) for a refrigeration cycle, applied to a refrigeration cycle, for decompressing the refrigerant flowing out of the radiator (2) and flowing the depressurized refrigerant toward the evaporator (4). A housing (31) formed with an inlet (32) communicating with the vessel (2) and an outlet (33) communicating with the evaporator (4); Entrance (3
A valve port (34) for communicating the space (32a) on the 2) side with the space (33a) on the outlet (33) side; and a valve body (35) for adjusting the opening of the valve port (34). The valve body (35) is provided in accordance with the pressure in the evaporator (4) such that a pressure difference between the two spaces (32a, 33a) becomes a predetermined pressure difference (ΔP). (34) The pressure reducing device for a refrigeration cycle, wherein the opening degree is controlled. 2. The valve body (35) is connected to the outlet (3).
3) A pressure reducing device for a refrigeration cycle, which is disposed in the space on the side and is pressed toward the space on the inlet (32) side by an elastic member (36) generating an elastic force. 3. The pressure reducing device for a refrigeration cycle according to claim 1, wherein the refrigerant is carbon dioxide, and the predetermined pressure difference (ΔP) is 5.5 to 7 MPa. 4. A compressor (1) for compressing a refrigerant, a radiator (2) for cooling the refrigerant compressed by the compressor (1), and a decompressor for the refrigerant. A vapor compression refrigeration cycle comprising: the pressure reducing device (3) according to any one of the above, and an evaporator (4) that evaporates the refrigerant depressurized by the pressure reducing device (3).