Connection structure for capillary tube

Abstract

To provide a connection structure of a capillary tube capable of simplifying connection work of the capillary tube while surely preventing deposition of sludge in the capillary tube, and contributing to cost reduction of a refrigerating device including the capillary tube by preventing increase of the number of components.SOLUTION: A primary pressure reducing part is formed between a base end part 17 of the outlet pipe 11 and a pressure reducing pipe part 18 formed on the downstream side of the base end part 17 and having a pipe inside diameter D3 smaller than that of the base end part 17. A secondary pressure reducing part is formed between the outlet pipe 11 and a pipe tip 14 related to the upstream end of the inlet pipe 13. A clearance between an outer surface of an inlet pipe 13 of the capillary tube 4 inserted into the outlet pipe 11 via a tip opening of the tip part 20 and an inner surface of the tip part 20 is sealed by brazing. The pipe tip 14 of the inlet pipe 13 is positioned on the upstream side of the tip part 20 and on the downstream side of the base end part 17.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a connection structure for connecting a capillary tube to an outlet pipe arranged downstream of a compressor. [Background technology]

[0002] Refrigeration oil circulates in the refrigerant circuit of a refrigeration system along with the refrigerant to lubricate the compressor. This refrigeration oil, along with impurities in the refrigerant, tends to precipitate as sludge in the expansion section where the refrigerant pressure suddenly drops, i.e., where the high-pressure liquid refrigerant is decompressed and adiabatically expanded. This sludge tends to adhere as solid matter to the inner surface of the capillary tube inlet. When sludge precipitates at the capillary tube inlet, the adhered sludge narrows the inner diameter of the capillary tube, reducing the amount of refrigerant that can flow into the tube and reducing the refrigeration capacity of the refrigeration system. Furthermore, the adhered sludge may clog the capillary tube, potentially causing it to become clogged. To prevent problems caused by sludge precipitation due to refrigeration oil, for example, the refrigeration system described in Patent Document 1 intentionally precipitates sludge upstream of the main capillary tube to prevent sludge from precipitating in the tube.

[0003] Specifically, the expansion section in the refrigeration device of Patent Document 1 is composed of a main capillary tube (hereinafter referred to as the "main capillary") and a sub-capillary tube (hereinafter referred to as the "sub-capillary") that is provided upstream of the main capillary and that primarily reduces the pressure of the liquid refrigerant. The outer diameter of the sub-capillary is the same as that of the main capillary, and its refrigerant inlet end is connected to the filter dryer, while its refrigerant outlet end is connected to the main capillary via a connecting pipe. The connecting pipe is a straight pipe whose inner diameter is approximately the same as the outer diameters of both capillaries, and both capillaries are connected with their opposing tube ends spaced apart. With this configuration, the liquid refrigerant is primarily reduced in pressure by the sub-capillary, and refrigerating machine oil can be actively precipitated as sludge at the inlet portion of the sub-capillary (primary pressure reduction section), thereby preventing sludge from precipitating in the subsequent main capillary (secondary pressure reduction section). The inner diameter of the sub-capillary is set larger than that of the main capillary, so that even if sludge is deposited in the sub-capillary, problems such as a decrease in the amount of refrigerant flowing into the sub-capillary due to sludge deposition or clogging of the sub-capillary are unlikely to occur. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-85334 Summary of the Invention [Problem to be solved by the invention]

[0005] In a typical refrigeration system in which the expansion section is composed of only one capillary tube, a refrigerant circuit can be constructed simply by brazing the capillary tube to the connecting pipe upstream of the capillary tube. However, in a refrigeration system in which the expansion section is composed of three components, namely, a sub-capillary, a connecting pipe, and a main capillary, as in Patent Document 1, it is necessary to braze the sub-capillary to the connecting pipe and then braze the connecting pipe to the main capillary. This inevitably increases the number of components compared to a typical refrigeration system. Furthermore, the brazing process requires more time and effort, which inevitably leads to an increase in the overall cost of the system.

[0006] The present invention has been made in view of the above problems, and its object is to provide a capillary tube connection structure that has two pressure reduction sections, i.e., a primary pressure reduction section and a secondary pressure reduction section, and can reliably prevent sludge from depositing in the capillary tube, yet simplifies the capillary tube connection work, and prevents an increase in the number of parts, thereby contributing to the cost reduction of refrigeration equipment that includes capillary tubes. [Means for solving the problem]

[0007] The present invention relates to a connection structure for connecting an outlet pipe 11 arranged downstream of a compressor 1 and an inlet pipe 13 arranged upstream of a capillary tube 4. The outlet pipe 11 has a base end 17 formed at its upstream end, a pressure reduction pipe section 18 formed downstream of the base end 17 and having a smaller inner diameter D3 than the base end 17, a central section 19 formed downstream of the pressure reduction pipe section 18 and having a larger inner diameter D4 than the pressure reduction pipe section 18, and a tip section 20 formed downstream of the central section 19 and having a smaller inner diameter D5 than the central section 19. The inlet pipe 13 is a straight pipe with a uniform outer diameter D1. A primary pressure reduction zone is formed between the base end 17 and the pressure reduction pipe section 18, and a secondary pressure reduction zone is formed between the outlet pipe 11 and a pipe tip 14 associated with the upstream end of the inlet pipe 13. The inner diameter D5 of the tip portion 20 is set larger than the outer diameter D1 of the inlet pipe 13, and the outer surface of the inlet pipe 13 inserted into the outlet pipe 11 through the tip opening of the tip portion 20 is sealed to the inner surface of the tip portion 20 by brazing. The tip 14 of the inlet pipe 13 is located upstream of the tip portion 20 and downstream of the base end 17.

[0008] The decompression tube portion 18 and the tip portion 20 are formed by drawing.

[0009] An inner diameter D3 of the decompression pipe section is set to be larger than an outer diameter D1 of the inlet pipe 13. A pipe tip 14 of the inlet pipe 13 is located inside the decompression pipe section .

[0010] The base end portion 17 and the decompression tube portion 18 are connected via a reduced diameter portion 21 whose inner diameter gradually decreases from the upstream side to the downstream side. [Effects of the Invention]

[0011] In the present invention, the inlet pipe 13 of the capillary tube 4 is inserted into the outlet pipe 11 from the tip opening of the tip portion 20, and then the outer surface of the inlet pipe 13 is brazed to the inner surface of the tip portion 20 to connect the inlet pipe 13 of the capillary tube 4 to the outlet pipe 11 of the compressor 1, thereby constructing a connection structure. Furthermore, in the present invention, the outlet pipe 11 includes a base end 17 formed at the upstream end and a pressure reduction pipe section 18 formed downstream of the base end 17 and having a smaller inner diameter D3 than the base end 17. This allows a primary pressure reduction zone to be formed between the base end 17 and the pressure reduction pipe section 18. Furthermore, in the present invention, the inlet pipe 13 is a straight pipe with a uniform outer diameter D1, the inner diameter D5 of the tip portion 20 is set larger than the outer diameter D1 of the inlet pipe 13, and the tip 14 of the inlet pipe 13 is located downstream of the base end 17. This allows a secondary pressure reduction zone to be formed between the outlet pipe 11 and the tip 14 of the upstream end of the inlet pipe 13. As described above, in the present invention, a capillary tube connection structure including a primary pressure reduction section and a secondary pressure reduction section can be constructed by simply brazing one location. This significantly reduces the labor and time required for brazing compared to the connection structure of Patent Document 1, which requires brazing at two locations. By reducing the number of brazing locations from two to one, the probability of poor brazing can be reduced, resulting in a more reliable connection structure. Since the connection structure is comprised of two components, the outlet tube 11 and the inlet tube 13, and therefore the number of components can be reduced compared to the connection structure of Patent Document 1, which requires three components, this reduces the cost of the connection structure and contributes to lowering the cost of refrigeration equipment including capillary tubes.

[0012] A central section 19 having a larger inner diameter D4 than the vacuum section 18 is formed downstream of the outlet tube 11, and a tip section 20 having a smaller inner diameter D5 than the central section 19 is formed downstream of the central section 19. Furthermore, the tip section 14 of the inlet tube 13 is positioned upstream of the tip section 20. This reliably prevents the outer periphery of the tip section 14 of the inlet tube 13 from contacting the inner surface of the tip section 20. Even if an excess amount of brazing filler metal is supplied during the brazing operation between the tip section 20 and the inlet tube 13, the brazing filler metal flowing upstream from the tip section 20 due to capillary action can be stopped at the boundary between the tip section 20 and the central section 19, reliably preventing the brazing filler metal from reaching the tip section 14 of the inlet tube 13. Therefore, the present invention provides a capillary tube connection structure having a primary pressure reduction section and a secondary pressure reduction section, yet with a simple structure, can prevent the tip section 14 of the capillary tube 4 from being blocked by the brazing filler metal.

[0013] When the vacuum pipe section 18 and the tip section 20 are formed by drawing, it is possible to easily and inexpensively obtain the outlet pipe 11 in which the vacuum pipe section 18 and the tip section 20 are integrally formed, compared to a configuration in which an outlet pipe having a vacuum pipe section and a tip section is formed by joining pipe bodies of different diameters.In this respect, too, it is possible to suppress an increase in the cost of the connection structure and contribute to the reduction of the cost of refrigeration equipment including capillary tubes.

[0014] The inner diameter D3 of the pressure reduction pipe section 18 is set larger than the outer diameter D1 of the inlet pipe 13. When the pipe tip 14 of the inlet pipe 13 is located within the pressure reduction pipe section 18, the liquid refrigerant is reduced in pressure in the primary pressure reduction section formed between the base end 17 and the pressure reduction pipe section 18, and then can be further reduced in pressure in the secondary pressure reduction section formed between the pressure reduction pipe section 18 and the pipe tip 14 of the inlet pipe 13 without any subsequent increase in pressure. This allows the liquid refrigerant to be smoothly reduced in pressure and adiabatically expanded, allowing the refrigeration system to operate efficiently.

[0015] If the base end 17 and the pressure reduction pipe section 18 are connected via a reduced diameter section 21 whose inner diameter gradually decreases from the upstream side to the downstream side, the flow path cross section on the upstream side of the pressure reduction pipe section 18 is gradually reduced, thereby preventing turbulence from occurring in the liquid refrigerant flowing from the base end 17 into the pressure reduction pipe section 18. This makes it possible to prevent sludge deposited on the inner surface of the inlet part of the pressure reduction pipe section 18 from peeling off due to turbulence and reaching the capillary tube 4 on the downstream side. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view showing an expansion section of a refrigeration device according to a first embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 2 is a cross-sectional view of a main part of the refrigeration device. [Figure 4] FIG. 5 is a cross-sectional view showing an expansion section of a refrigeration device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1 to 3 show a first embodiment in which a capillary tube connection structure according to the present invention is applied to a refrigeration device mounted in a refrigerator such as a showcase or a refrigerator. In Fig. 2, the refrigeration device R includes a compressor 1 that compresses a gaseous refrigerant, a condenser 2 that liquefies the high-pressure gaseous refrigerant delivered from the compressor 1, a capillary tube 4 that reduces the pressure of the high-pressure liquid refrigerant delivered from the condenser 2 to cause adiabatic expansion, and an evaporator 5 that evaporates the low-pressure liquid refrigerant delivered from the capillary tube 4 at a low temperature.

[0018] The compressor 1, condenser 2, capillary tube 4, and evaporator 5 are connected in this order by connecting pipes 6, and a looped refrigerant circuit is formed by these devices and connecting pipes 6. The connecting pipes 6, which run from the compressor 1 via the condenser 2 to the capillary tube 4, are high-pressure side pipes through which high-pressure refrigerant (gaseous or liquid) flows, while the connecting pipes 6, which run from the capillary tube 4 to the compressor 1 via the evaporator 5, are low-pressure side pipes through which low-pressure refrigerant (gaseous or liquid) flows. A dryer 7 is provided on the high-pressure side connecting pipes 6 between the condenser 2 and the capillary tube 4 to remove moisture from the refrigerant. An accumulator 8 is provided on the low-pressure side connecting pipes 6 between the evaporator 5 and the compressor 1 to send only gaseous refrigerant to the compressor 1 side.

[0019] The evaporator 5 that constitutes the refrigeration unit R is installed inside the refrigerator and cools the inside of the refrigerator by exchanging heat with the air inside the refrigerator. The other devices that make up the refrigeration unit R are installed in a machine room or the like located outside the refrigerator. In Figure 2, reference numeral 2A denotes a cooling fan that cools the compressor 1 and condenser 2, and reference numeral 5A denotes a circulation fan that sends the air inside the refrigerator toward the evaporator 5.

[0020] As shown in Figure 2, the capillary tube 4 is connected to an outlet pipe 11 located downstream of the compressor 1. The capillary tube 4 is made of a single circular tube, and is composed of a spirally wound tube 12 and an inlet pipe 13, which is a straight tube located upstream of the wound tube 12. The wound tube 12 is used to ensure the pipe length required to reduce the pressure of the liquid refrigerant to an appropriate level. The inlet pipe 13 is made of a thin copper tube with an outer diameter D1 and an inner diameter D2 (see Figure 1).

[0021] The outlet pipe 11 is connected to the downstream side of the dryer 7, and the connection structure between the outlet pipe 11 and the inlet pipe 13 of the capillary tube 4 forms a refrigerant circuit for that portion. As shown in Fig. 1, the outlet pipe 11 includes a base end 17 formed at the upstream end, a pressure reduction pipe section 18 formed downstream of the base end 17 and having a smaller pipe inner diameter D3 than the base end 17, a central section 19 formed downstream of the pressure reduction pipe section 18 and having a larger pipe inner diameter D4 than the pressure reduction pipe section 18, and a tip end 20 formed downstream of the central section 19 and having a smaller pipe inner diameter D5 than the central section 19. The pipe inner diameter D6 of the base end 17 is set to be the same as the pipe inner diameter D4 of the central section 19.

[0022] The base end 17 and the decompression tube section 18 are connected via a first reduced diameter section 21 whose inner diameter gradually decreases from the upstream side to the downstream side, and the first reduced diameter section 21 reduces the pipe inner diameter D6 of the base end 17 to the pipe inner diameter D3 of the decompression tube section 18. The decompression tube section 18 and the central section 19 are connected via an expanded diameter section 22 whose inner diameter gradually increases from the upstream side to the downstream side, and the expanded diameter section 22 expands the pipe inner diameter D3 of the decompression tube section 18 to the pipe inner diameter D4 of the central section 19. The central section 19 and the tip section 20 are connected via a second reduced diameter section 23 whose inner diameter gradually decreases from the upstream side to the downstream side, and the second reduced diameter section 23 reduces the pipe inner diameter D4 of the central section 19 to the pipe inner diameter D5 of the tip section 20.

[0023] The vacuum tube section 18 and the tip section 20 formed in the outlet tube 11 are formed by swaging (drawing). Specifically, a blank made of a copper tube having an inner diameter D6 that matches the inner diameter D6 of the base end 17 is prepared, and the blank's intermediate section in the elongation direction and tip section are swaged to reduce the tube wall of the blank so that the inner diameter of the intermediate section of the blank becomes the inner diameter D3 of the vacuum tube section 18 and the inner diameter of the tip section of the blank becomes the inner diameter D5 of the tip section 20. This results in the outlet tube 11, which is integrally formed with the base end 17, vacuum tube section 18, central section 19, tip section 20, and expanded / contracted diameter sections 21-23. The vacuum tube section 18 is drawn so that its inner diameter D3 is slightly larger than the outer diameter D1 of the capillary tube 4, and the tip section 20 is drawn so that its inner diameter D5 is slightly larger than the outer diameter D1 of the inlet tube 13 (see FIG. 3).

[0024] As shown in Figure 3, the outlet pipe 11 and the capillary tube 4 are joined by brazing the outer surface of the inlet pipe 13 inserted into the outlet pipe 11 through the tip opening of the tip portion 20 to the inner surface of the tip portion 20. The position of the tip 14 of the inlet pipe 13 relative to the outlet pipe 11 is upstream of the tip portion 20 and downstream of the base end 17. In this embodiment, the inlet pipe 13 is inserted from the tip opening of the tip portion 20 until the tip 14 is positioned within the decompression pipe portion 18, and in this state the inner surface of the tip portion 20 and the outer surface of the inlet pipe 13 are sealed with a seal 24 by brazing. It is preferable that the tip 14 of the inlet pipe 13 be positioned downstream of the center of the decompression pipe portion 18 in the extension direction.

[0025] When connecting the outlet pipe 11 and the capillary tube 4, the inside of the outlet pipe 11, which is made of copper, cannot be visually inspected, so the positioning of the outlet pipe 11 and the inlet pipe 13 is first performed. Specifically, the distance from the desired position inside the outlet pipe 11 for the tip of the inlet pipe 13, that is, from a position downstream of the center of the pressure reducing pipe section 18, to the tip of the tip section 20 (the end of the outlet pipe 11), is measured with a ruler or the like, and based on this measurement, a mark is made on the inlet pipe 13 at the measured position beyond the tip section 14. Next, the inlet pipe 13 is inserted through the tip opening of the tip section 20, and with the tip of the tip section 20 aligned with the marking, the outlet pipe 11 and the capillary tube 4 are temporarily fixed and positioned. Next, while the two (outlet pipe 11 and capillary tube 4) are temporarily fixed, the overlapping portion of the inner surface of tip portion 20 and the outer surface of inlet pipe 13 is heated with a torch and brazing material is supplied to braze the inner surface of tip portion 20 to the outer surface of inlet pipe 13. As a result, the outer surface of inlet pipe 13 and the inner surface of tip portion 20 are sealed with brazing seal 24, and outlet pipe 11 and capillary tube 4 are connected.

[0026] In Figure 1, the liquid refrigerant that has passed through the dryer 7 first flows through the base end portion 17 of the outlet pipe 11 and flows into the pressure reduction pipe section 18 via the first reduced diameter section 21. At this time, as the inner diameter of the refrigerant circuit decreases from the pipe inner diameter D6 to the pipe inner diameter D3, the pressure of the liquid refrigerant decreases and the liquid refrigerant undergoes adiabatic expansion (primary pressure reduction). Next, the liquid refrigerant that has been primarily reduced in pressure and flows through the pressure reduction pipe section 18 flows into the inlet pipe 13. At this time, as the inner diameter of the refrigerant circuit decreases from the pipe inner diameter D3 to the pipe inner diameter D2, the pressure of the liquid refrigerant further decreases and the liquid refrigerant undergoes adiabatic expansion (secondary pressure reduction).

[0027] As described above, the connected outlet pipe 11 and capillary tube 4 constitute an expansion section of the refrigeration apparatus, and the liquid refrigerant is adiabatically expanded as its pressure is reduced in a primary pressure reduction section formed between the base end 17 and the pressure reduction pipe section 18, and in a secondary pressure reduction section formed between the pressure reduction pipe section 18 (outlet pipe 11) and the pipe tip 14 associated with the upstream end of the inlet pipe 13. The liquid refrigerant adiabatically expanded in this expansion section reaches the downstream evaporator 5 and cools the evaporator 5. Note that, due to the dimensional relationship between the outer diameter D1 of the inlet pipe 13 and the inner diameter D3 of the pressure reduction pipe section 18, a small gap is formed between the outer peripheral surface of the inlet pipe 13 and the inner peripheral surface of the pressure reduction pipe section 18. However, when the central section 19 is filled with refrigerant, almost no refrigerant flows back and forth between the pressure reduction pipe section 18 and the central section 19 via this gap.

[0028] According to the above-described configuration, by primarily reducing the pressure of the liquid refrigerant in the primary pressure reduction section upstream of the capillary tube 4, the refrigeration oil circulating through the refrigerant circuit together with the refrigerant can be actively precipitated as sludge at the inlet of the pressure reduction pipe section 18. This makes it possible to minimize the precipitation of sludge at the inlet of the inlet pipe 13 (capillary tube 4) when the liquid refrigerant is secondarily reduced in pressure, that is, when the liquid refrigerant flows into the inlet pipe 13 and is reduced in pressure. The cross section of the pressure reduction pipe section 18 is sufficiently larger than the cross section of the inlet pipe 13, so that the amount of refrigerant flowing into the pressure reduction pipe section 18 due to the sludge precipitated in the pressure reduction pipe section 18 can be reduced or clogging can be suppressed.

[0029] As described above, in this embodiment, the inlet pipe 13 of the capillary tube 4 is inserted into the outlet pipe 11 from the tip opening of the tip portion 20, and then the outer surface of the inlet pipe 13 is brazed to the inner surface of the tip portion 20 simply to connect the inlet pipe 13 of the capillary tube 4 to the outlet pipe 11 of the compressor 1, thereby constructing a connection structure. The outlet pipe 11 includes the base end 17 formed at the upstream end and the pressure reduction pipe section 18 formed downstream of the base end 17 and having a smaller inner diameter D3 than the base end 17. This allows a primary pressure reduction zone to be formed between the base end 17 and the pressure reduction pipe section 18. Furthermore, the inlet pipe 13 is a straight pipe with a uniform outer diameter D1, the inner diameter D5 of the tip portion 20 is set to be larger than the outer diameter D1 of the inlet pipe 13, and the tip 14 of the inlet pipe 13 is located downstream of the base end 17. This allows a secondary pressure reduction zone to be formed between the outlet pipe 11 and the tip 14 of the upstream end of the inlet pipe 13. As described above, in this embodiment, a capillary tube connection structure including a primary pressure reduction section and a secondary pressure reduction section can be constructed by simply brazing one location. This significantly reduces the labor and time required for brazing compared to conventional connection structures that required brazing at two locations. By reducing the number of brazing locations from two to one, the probability of poor brazing can be reduced, resulting in a more reliable connection structure. Since the present invention is composed of two components, the outlet tube 11 and the inlet tube 13, the number of components can be reduced compared to conventional connection structures that required three components. This reduces the cost of the connection structure and contributes to lowering the cost of refrigeration equipment that includes capillary tubes.

[0030] A central section 19 having a larger inner diameter D4 than the vacuum section 18 is formed downstream of the outlet tube 11, and a tip section 20 having a smaller inner diameter D5 than the central section 19 is formed downstream of the central section 19. Furthermore, the tip section 14 of the inlet tube 13 is positioned upstream of the tip section 20. This reliably prevents the outer periphery of the tip section 14 of the inlet tube 13 from contacting the inner surface of the tip section 20. Even if an excess amount of brazing filler metal is supplied during the brazing operation between the tip section 20 and the inlet tube 13, the brazing filler metal flowing upstream from the tip section 20 due to capillary action can be stopped at the boundary between the tip section 20 and the central section 19, reliably preventing the brazing filler metal from reaching the tip section 14 of the inlet tube 13. Therefore, this embodiment provides a capillary tube connection structure having a primary pressure reduction section and a secondary pressure reduction section, yet has a simple structure that prevents the tip section 14 of the capillary tube 4 from being blocked by the brazing filler metal.

[0031] Since the vacuum pipe section 18 and the tip section 20 are formed by drawing, it is possible to easily and inexpensively obtain the outlet pipe 11 in which the vacuum pipe section 18 and the tip section 20 are integrally formed, compared to a configuration in which an outlet pipe having a vacuum pipe section and a tip section is formed by joining pipe bodies of different diameters.In this respect, too, it is possible to suppress an increase in the cost of the connection structure and contribute to the reduction of the cost of refrigeration equipment including capillary tubes.

[0032] Since the pipe tip 14 of the inlet pipe 13 is located within the pressure reduction pipe section 18, the liquid refrigerant is reduced in pressure in the primary pressure reduction section formed between the base end 17 and the pressure reduction pipe section 18, and then can be further reduced in pressure in the secondary pressure reduction section formed between the pressure reduction pipe section 18 and the pipe tip 14 of the inlet pipe 13 without any subsequent increase in pressure. This allows the liquid refrigerant to be smoothly reduced in pressure and adiabatically expanded, allowing the refrigeration system to operate efficiently.

[0033] Since the base end 17 and the decompression pipe section 18 are connected via the first reduced diameter section 21, the inner diameter of which gradually decreases from the upstream side to the downstream side, the flow path cross section on the upstream side of the decompression pipe section 18 is gradually reduced, thereby preventing turbulence from occurring in the liquid refrigerant flowing from the base end 17 into the decompression pipe section 18. This prevents sludge deposited on the inner surface of the inlet part of the decompression pipe section 18 from peeling off due to turbulence and reaching the capillary tube 4 on the downstream side.

[0034] Second Embodiment Figure 4 shows a second embodiment of the capillary tube connection structure according to the present invention. Similar to the first embodiment, this embodiment is applicable to a refrigeration device installed in a refrigerator or showcase. This embodiment differs from the first embodiment in that the pipe tip 14 of the inlet pipe 13 does not reach the pressure reduction pipe section 18, but passes through the tip section 20 and is positioned at the central section 19. When connecting the outlet pipe 11 and the inlet pipe 13, the distance from the midpoint of the central section 19 to the tip of the tip section 20 (the end of the outlet pipe 11) is measured and marked with a ruler or the like. The outlet pipe 11 and the inlet pipe 13 are then connected using the same procedure as in the first embodiment. In this embodiment, a primary pressure reduction section is formed between the base end 17 and the pressure reduction pipe section 18, and a secondary pressure reduction section is formed between the central section 19 (outlet pipe 11) and the pipe tip 14 at the upstream end of the inlet pipe 13. The liquid refrigerant undergoes a stepwise pressure reduction in both pressure reduction sections, resulting in adiabatic expansion. The rest is the same as in the first embodiment, so the same configurations, structures, and members are denoted by the same reference numerals and the description thereof will be omitted.

[0035] According to the above-described configuration, even if an excess amount of brazing material is supplied during the brazing operation between the tip portion 20 and the inlet pipe 13, the brazing material moving upstream from the tip portion 20 due to capillary action can be stopped at the boundary between the tip portion 20 and the central portion 19, thereby reliably preventing the brazing material from reaching the pipe tip 14 of the inlet pipe 13.

[0036] In addition to the above embodiment, when the high-pressure side connecting pipe 6 is not provided with a dryer 7 or the like, the connecting pipe 6 connected to the refrigerant outlet of the condenser 2 can be used as the outlet pipe 11. The expanded / contracted diameter portions 21-23 of the outlet pipe 11 can be omitted. The pipe inner diameter D6 of the base end portion 17 and the pipe inner diameter D4 of the central portion 19 may be different dimensions. [Explanation of symbols]

[0037] 1 Compressor 4 capillary tubes 11 Outlet pipe 13 Inlet pipe 17 Proximal end 18 Pressure reducing tube section 19 Central part 20 Tip 21 Reduced diameter part (first reduced diameter part) D1 Inlet pipe outer diameter D3 Inner diameter of pressure reducing pipe D4 Central pipe inner diameter D5 Tip pipe inner diameter

Claims

1. A connection structure for connecting an outlet pipe (11) arranged downstream of a compressor (1) and an inlet pipe (13) arranged upstream of a capillary tube (4), The outlet pipe (11) has a base end (17) formed at the upstream end, a pressure reduction pipe section (18) formed downstream of the base end (17) and having a pipe inner diameter (D3) smaller than that of the base end (17), a central section (19) formed downstream of the pressure reduction pipe section (18) and having a pipe inner diameter (D4) larger than that of the pressure reduction pipe section (18), and a tip end section (20) formed downstream of the central section (19) and having a pipe inner diameter (D5) smaller than that of the central section (19), The inlet pipe (13) is a straight pipe having a uniform outer diameter (D1), A primary pressure reduction section is formed between the base end (17) and the pressure reduction pipe section (18), and a secondary pressure reduction section is formed between the outlet pipe (11) and a pipe tip (14) associated with the upstream end of the inlet pipe (13), The inner diameter (D5) of the tip portion (20) is set larger than the outer diameter (D1) of the inlet pipe (13), and the outer surface of the inlet pipe (13) inserted into the outlet pipe (11) through the tip opening of the tip portion (20) is sealed between the inner surface of the tip portion (20) and the outer surface of the inlet pipe (13). A capillary tube connection structure characterized in that the pipe tip (14) of the inlet pipe (13) is located upstream of the tip end (20) and downstream of the base end (17).

2. 2. A capillary tube connection structure according to claim 1, wherein the pressure reducing tube portion (18) and the tip portion (20) are formed by drawing.

3. The inner diameter (D3) of the decompression pipe section (18) is set to be larger than the outer diameter (D1) of the inlet pipe (13), 2. A capillary tube connection structure according to claim 1, wherein the tip (14) of the inlet pipe (13) is located within the pressure reducing pipe section (18).

4. 4. A capillary tube connection structure according to claim 1, wherein the base end (17) and the pressure reduction tube section (18) are connected via a reduced diameter section (21) whose inner diameter gradually decreases from the upstream side to the downstream side.

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