Pipe connecting structure

A pipe connecting structure including a male flange block combined with a first pipe and a female flange block combined with a second pipe, which is fastened to the male flange block by a fastener, where a protrusion having a hole that communicates with the first pipe is formed through the male flange block, and an insert portion into which the protrusion is inserted is formed through the female flange block, and a sealing member to closely contact with the end face of the protrusion is seated on the bottom inside the insert portion, and the sealing member includes an inner sealing part of soft metal and an outer sealing part of rubber tightly fitted around the outer circumference of the inner sealing part. Therefore joints between pipes, a heat exchanger and a pipe, or two components can bear high pressures in a refrigerating cycle system using a CO2 refrigerant, air tightness can be maintained under low and high temperatures without changes in quality and shape of a sealing members, and it is possible to prevent and minimize leakage of the refrigerant by preventing permeation of CO2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pipe connecting structure, particularly a pipe connecting structure that connects two pipes with improved air tightness.

2. Description of the Related Art

In general, two pipes in refrigerating cycle systems for a vehicle are connected by flange blocks as shown inFIG. 1.

In detail, a flange connecting structure has a male flange block4of a peanut shaped cross section combined with a first pipe2and a female flange block8of a peanut shaped cross section combined with a second pipe6that are fastened by a bolt10. The male flange block4has a protrusion4ahaving a hole communicating with the first pipe2and the female flange block8has an insert portion8ato which the protrusion4ais inserted. A rubber sealing member12(O-ring) is fitted around the protrusion4afor sealing. The bolt10is fixedly inserted in a hole8bof the female flange block8through a through hole4bof the male flange block4.

In recent years, refrigerating cycle systems using an environmentally friendly natural refrigerant of Carbon dioxide (CO2) have increased because Freon gas causes environmental pollution.

A refrigerating cycle using CO2refrigerant as a heat exchange medium is a supercritical refrigerating cycle with internal pressure exceeding a critical pressure, so that the internal pressure is a lot larger (generally, about 7 to 9 times) than refrigerating cycle systems, in the related art, using a Freon-series refrigerant. The internal temperature of the system ranges from −40° C. to 180° C.

Rubber sealing members (O-ring) used in pipe flanges of the refrigerating cycle system for vehicles in the related art cannot bear the high pressure in the refrigerating cycle system using CO2refrigerant. Sealing members of ethylene-based (ACM) rubber is relatively high in density, so that they are short in elasticity at a cold region under extremely low temperature. Therefore, when the sealing members receive an outer shock, they cannot sufficiently absorb the shock, so that they are distorted or gaps are created, and thus, the refrigerant correspondingly leaks out. Further, as for sealing members of propylene-based (EPDM) rubber, permeation is caused by CO2refrigerant's characteristics, so that the refrigerant leaks out regardless of the environments.

The present invention is designed to overcome the above problems, it is an object of the invention to provide a pipe connecting structure that bears high pressure, keeps air tightness without changes in quality or deformation of a sealing member at low and high temperatures, and prevents leakage of a refrigerant by preventing permeation of CO2in a refrigerating cycle system using CO2refrigerant.

SUMMARY OF THE INVENTION

A pipe connecting structure for a refrigerating cycle system for a vehicle according to an embodiment of the invention includes a male flange block combined with a first pipe and a female flange block combined with a second pipe, which is fastened to the male flange block by fastening means, in which a protrusion having a hole that communicates with the first pipe is formed through the male flange block, and an insert portion into which the protrusion is inserted is formed through the female flange block, and a sealing member to get a close contact with the end face of the protrusion is seated on the bottom inside the insert portion, and the sealing member includes an inner sealing part of soft metal and an outer sealing part of rubber tightly fitted around the outer circumference of the inner sealing part.

The male flange block includes a protrusion with a hole that communicates with the first pipe, the female flange block has an insert portion into which the protrusion is inserted, and the sealing member is fitted around the outside of the protrusion, and the sealing member includes an outer sealing part of soft metal and an inner sealing part of rubber closely contacting the inside of the outer sealing part.

The male flange block includes a protrusion with a hole that communicates with the first pipe, the female flange block has an insert portion into which the protrusion is inserted, and the sealing member is fitted around the outside of the protrusion. Further, a receiving groove to receive the sealing member is formed around the root end of the protrusion, the sealing member includes an inner sealing part of soft metal and an outer sealing part of rubber closely contacting the outer circumference of the inner sealing part, and a circumferential prominence to press the inner sealing part is formed around the edge of the entrance of the insert portion of the female flange block.

The male flange block includes a protrusion with a hole that communicates with the first pipe, the female flange block has an insert portion into which the protrusion is inserted, and the sealing member is fitted around the outside of the protrusion. A step to receive and seat the sealing member is formed on an outer circumference of the end of the protrusion, and the sealing member includes an inner sealing part of soft metal and an outer sealing part of rubber entirely wrapping around the outside of the inner sealing part.

A pipe connecting structure for a refrigerating cycle system according to an embodiment of the invention includes first and second pipes that are connected and arranged to allow a refrigerant to circulate in the refrigerating cycle, and connecting means that connects the first pipes to a second pipe. The connecting means includes: a male flange block that includes a first pipe-combining hole to fit the first pipe; a first combining protrusion that protrudes from a surface of the male flange block in communication with the first pipe-combining hole; a second combining protrusion that protrudes from the end face of the first combining protrusion and has a first seating face inside the second combining protrusion; a sealing member that is fitted around the outside of the second combining protrusion and seated in the first seating face inside the second combining protrusion; a female flange block that has a second pipe-combining hole bored from one side to insert the second pipe, a first protrusion-combining hole bored from the other side in communication with the second pipe-combining hole to insert the first combining protrusion, a second protrusion-combining groove formed around the edge inside the first protrusion-combining hole to insert the second combining protrusion, and a second seating face formed inside along the second protrusion-combining groove to seat a side of the sealing member; and fastening means that fastens the male flange block and the female flange block.

In other words, the male flange block and the female flange block are combined by inserting the first and second combining protrusions, in the first protrusion-combining hole and the second protrusion-combining hole, respectively, and the hardness is increased at the joints accordingly. Further, the sealing member is fitted around the second combining protrusion and provides double sealing inside and outside the first and second pipe-combining holes. Therefore, the air tightness is increased at the joints after assembling.

A pipe connecting structure for an air conditioner for a vehicle according to another embodiment of the invention includes a male flange block combined with a first pipe and a female flange block combined with a second pipe, which is fastened to the male flange block by a bolt. The male flange block has a protrusion that communicates with the first pipe and the female flange block has an insert portion into which the protrusion is inserted. A primary sealer is provided at the middle of the protrusion for primary sealing and a secondary sealer is provided at the root end of the protrusion for secondary sealing. A fixing pin is inserted into the male flange block and the female flange block so that the protrusion is accurately inserted into the insert portion and provides convenience in working.

The primary sealer is a rubber ring and the secondary sealer is a ring including a metal sealing part and a rubber sealing part combined with the metal sealing part.

The protruding length of the protrusion of the male flange block ranges from 12 to 18 mm and the thickness of the male flange block and the bolt-fastening length (the distance between the centers of the protrusion and the bolt) ranges from 14 to 16 mm.

The fastening torque for the male flange block and the female flange block ranges from 10 to 14 Nm.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2 to 4show a pipe connecting structure according to a first embodiment of the invention. As shown in the figures, the pipe connecting structure is assembled by fastening a rectangular shaped male flange block24combined with a first pipe22and a rectangular shaped female flange block28combined with a second pipe26, with fastening means of a stud bolt30and a nut32.

The male flange block24has a protrusion24ahaving a hole H1that communicates with the first pipe22and the female flange block28has an insert portion28ato which the protrusion24ais inserted. A sealing member34to get a closecontact with the end face24bof the protrusion24ais seated on the bottom28binside the insert portion28a. A fixing pin36is inserted into the male and female flange blocks24,28so that the protrusion24ais accurately inserted into the insert portion28a. The second pipe26communicates with a hole H2in the insert portion28a.

The stud bolt30passes via a through hole24eof the male flange block24and a through hole28eof the female flange block28and fixed by the nut32. A nut at the opposite side is not shown in the present embodiment.

Holes24c,28cto which the fixing pin36is inserted are formed through the male flange block24and the female flange block28, respectively. The hole24cis a through hole and the hole28cis closed at one side.

As shown inFIG. 5, the sealing member34is an integral unit formed by closely combining an inner sealing part34aof soft metal with an outer sealing part34bof rubber around the outer circumference of the inner sealing part34a. The inner sealing part34ais made of soft metal, such as aluminum, white wax, or tin alloy, and the outer sealing part34bis made of propylene-based or nitrol-based rubber with high elasticity and air tightness. The outer sealing part34bhas a diamond-shape cross section with one corner cut and the outer sealing part34bis adhered to the inner sealing part34aby a bond to reinforce the combination.

The outer sealing part34bhas a larger thickness t1in the range of 1.2 to 2 times larger than a thickness t2of the inner sealing part34ato allow the sealing member34to keep air tightness as it is pressed by the bottom28bof the insert portion28aand the end face24bof the protrusion24a.

As shown inFIGS. 6 and 7, beads24b-1,28b-1having a triangular cross section are circumferentially formed on the end face24bof the protrusion24aand the bottom28bof the insert portion28ato keep air tightness by pressing the inner sealing part34a. The beads24b-1,28b-1may have a circular or polygonal cross section.

A seating groove28dis circumferentially formed along the edge of the bottom inside the insert portion28ato which the outer sealing part34binsertedly mounted.

FIG. 8illustrates the keeping of air tightness by pressing the outer sealing part34bof the sealing member34with the bottom28dof the insert portion28aand the end face24bof the protrusion24a, and by pressing the inner sealing part34aof the sealing member34with the beads24b-1,28b-1.

As shown inFIG. 3, in the male flange block, a step24dis formed at one side (which is toward the hole28cof the female flange block28) of the hole24cto which the fixing pin is inserted to uniformly distribute fastening force to the sealing member34that is pressed when the male and female flange blocks24,28are fastened by the bolt. The step24dhas a height equal to or smaller than the thickness of the inner sealing part34aof the sealing member34.

FIGS. 9A and 9Bshow modifications for the sealing member shown inFIG. 5. As for sealing members134,234according to the present modification, a prominence and a depression to fit each other are formed on the combining surfaces of inner sealing parts134a,234aof soft metal and outer sealing parts134b,234bof rubber to increase the combining force. The other configurations are the same as the sealing member34ofFIG. 5.

Referring toFIG. 10, instead of the fixing pin ofFIG. 4, a step124cis formed at the male flange block124and a counter step128cthat is fitted to the step124cis formed at the female flange block128. The steps124c,128callow accurate assembly of the male flange block124and the female flange block128.

Referring toFIG. 11, instead of the fixing pin ofFIG. 4, a prominence224cis formed at the male flange block224and a counter depression228cthat is fitted to the prominence224cis formed at the female flange block228. The prominence224cand counter depression228callow accurate assembly of the male flange block224and the female flange block228.

Referring toFIGS. 12 and 13, instead of forming the beads on the male and female flange blocks as shown inFIG. 3, beads are formed at a sealing member. As shown in the figures, in a sealing member334including an inner sealing member334aof soft metal and an outer sealing member334bof rubber, beads334a-1,334a-2that are pressed by the end face of a protrusion324aand the bottom of an insert portion328aare formed on both sides of the inner sealing part334ato keep air tightness.

Referring toFIG. 14, engraved beads to fit the beads formed on the male and female flange blocks ofFIG. 3are formed on a sealing member. As shown inFIG. 14, in a sealing member434including an inner sealing part434aof soft metal and an outer sealing part434bof rubber, engraved beads434a-1,434a-2are formed on both sides of the inner sealing part434ato fit the beads24b-1formed on the end face24bof the protrusion24aand to fit the beads28b-1formed on the bottom28bof the insert portion28a. Air tightness is kept by closely fitting the beads24b-1,28b-1in the engraved beads434a-1,434a-2.

FIG. 15shows a pipe connecting structure according to a second embodiment on the invention. As shown inFIG. 15, a male flange block524has a protrusion524awith a hole H1communicating with the first pipe (shown inFIG. 4), a female flange block528has a insert portion528ato which the protrusion524ais inserted, and a sealing member534is fitted around the outside of the protrusion524a. A receiving groove524eto receive the sealing member534is formed around the root end of the protrusion524.

The sealing member534includes an inner sealing part534aof soft metal and an outer sealing part534bclosely contacting the outer circumference of the inner sealing part534a. The detailed structure and quality of material of the sealing member534are the same as the sealing member34in the first embodiment. The receiving groove524ehas a depth d2equal to or smaller than the thickness t2of the inner sealing part534ato closely press the sealing member inserted in the receiving groove524e.

A circumferential prominence528dthat presses the inner sealing part534ais formed around the edge of the entrance of the insert portion528aof the female flange block528.

Beads524e-1,528d-1having triangular cross sections are circumferentially formed on the bottom inside the receiving groove524eand on the circumferential prominence528dto keep air tightness, respectively. The beads524e-1,528d-1may have a circular cross section or a polygonal cross section.

FIG. 16is a detailed view for the E-part ofFIG. 15andFIG. 17is an assembly view ofFIG. 15. The other configurations in the second embodiment are the same as in the first embodiment and detailed descriptions for them are not provided.

FIG. 18shows a pipe connecting structure according to a third embodiment of the invention. As shown inFIG. 18, a male flange block624has a protrusion624awith a hole H1communicating to the first pipe (shown inFIG. 4), a female flange block628has an insert portion628ato which the protrusion624ais inserted, and a sealing member634is fitted around the outside of the protrusion624a.

As shown inFIG. 19, the sealing member19includes an outer sealing part634aof soft metal and an inner sealing part634bclosely contacting the inside of the outer sealing part634a. The outer sealing part634ais made of soft metal, such as aluminum, white wax, or tin alloy, and the inner sealing part634bis made of propylene-based or nitrol-based rubber having high elasticity and air tightness. A prominence and a depression to fit each other are formed on the combining surfaces of the outer sealing part634aof soft metal and the inner sealing part634bof rubber to increase the combining force.

The inner diameter Di of the inner sealing part634bof rubber is set smaller than the outer diameter Do of the protrusion624ato increase air tightness of the sealing member634fitted around the outer circumference of the protrusion624a.

Beads628fhaving a triangular cross section are circumferentially formed around the edge (on the combining surface) of the entrance of the insert portion628aof the female flange block628to keep air tightness by pressing a side of the sealing member634. Beads624fhaving a triangular cross section are formed around the root end (on the combining surface) of the protrusion624aof the male flange block624to keep air tightness by pressing the other side of the sealing member634. The beads628f,624fmay have a circular cross section or a polygonal cross section.

FIG. 20is an assembly view ofFIG. 18andFIG. 21is a detailed view for F-part ofFIG. 20. The other configurations in the third embodiment are the same as in the first embodiment and the detailed descriptions for them are not provided.

FIG. 22shows a pipe connecting structure according to a fourth embodiment of the invention. As shown inFIG. 22, a male flange block724has a protrusion724awith a hole H1communicating to a first pipe22, a female flange block728has an insert portion728ato which the protrusion724ais inserted, and a sealing member734is fitted around the outside of the protrusion724a. A step734eto seat the received sealing member734is formed around the end of the protrusion734e.

As shown inFIG. 23, the sealing member734includes an inner sealing part734aof soft metal and an outer sealing part734bof rubber entirely wrapping around the outside of the inner sealing part734a. The inner sealing part734ais made of soft metal, such as aluminum, white wax, or tin alloy, and the outer sealing part is made of propylene-based or nitrol-based rubber having high elasticity and air tightness.

The inner sealing part734aaccording to the present (fourth) embodiment is a ring having the same cross section as a plate that is wide in the thickness direction of the sealing member734. However, as shown inFIG. 24A, the sealing member734-1may include a ring-shaped inner sealing part734a-1having the same cross section as a plate that is wide in the width direction of a sealing member734-1and an outer sealing part734b-1wrapping around the inner sealing734a-1. Alternatively, as shown inFIG. 24B, the sealing member734-2may include a ring-shaped inner sealing part734a-2having a circular cross section and an outer sealing part734b-2wrapping around the inner sealing part734a-2. The inner sealing part may be a ring having a variety of cross sections, such as plate, rectangle, polygon, or circle.

The other configurations in the fourth embodiment are the same as in the first embodiment and detailed descriptions for them are not provided.

FIG. 25shows a pipe connecting structure according to a fifth embodiment of the invention. Referring toFIG. 25, for example, first and second pipes801,802allowing a refrigerant to circulate are connected and arranged by connecting means including a male flange block803and a female flange block804.

The male flange block803of the connecting means, as shown inFIGS. 25 and 26, has a first pipe-combining hole803ato fit an end of the first pipe801at one side of the male flange block803and a first fastening hole803bto fasten a bolt841(described below) at the other side of the male flange block803.

The male flange block803has a first combining protrusion810on the combining surface to combine with the female flange block804. The first combining protrusion810protrudes in communication with the first pipe-combining hole803a.

The first pipe-combining hole803ais bored at the center of the first-combining protrusion810and a second combining protrusion820protrudes from the end face of the first combining protrusion810at a predetermined interval around the first pipe-combining hole803a.

A first seating face823to seat an inner sealing part832of a sealing member830(described low) is formed between the second combining protrusion820and the first pipe-combining hole803a.

Sealing beads824protrude from the first seating face823and allow the inner sealing part832of the sealing member830to be seated. The sealing beads824may be formed in a variety of cross sections such as a triangle, circle, or polygon.

The second combining protrusion820has a plurality of vertical combining grooves821that is formed perpendicular to the end face at predetermined intervals and a plurality of horizontal combining grooves822may be formed in communication with the vertical combining grooves821in a predetermined horizontal length at predetermined intervals along the outer circumference of the second combining protrusion820.

When only the vertical combining grooves821are formed through the second combining protrusion820, the inner diameter of an O-ring831of the sealing member830is set smaller than the outer diameter of the second combining protrusion820to tightly fit, or holding prominences821aare formed at the end of the second combining protrusion820to hold the O-ring831.

Alternatively, when the vertical combining grooves821and the horizontal combining grooves822are formed through the second combining protrusion820, the sealing member830is combined with the second combining protrusion820by inserting wings833(described later) into the vertical grooves821and then rotating the O-ring831to insert the wings into the horizontal combining grooves822.

The sealing member830is fixedly combined with the second combining protrusion820by setting the inner diameter of the O-ring831of the sealing member830to 0.8 times of the outer diameter of the second combining protrusion820, in order to use an elasticity of the O-ring831.

To reinforce the combining force of the sealing member830, the holding prominences821ato hold the sealing member830protrude radially outside at the end of the second combining protrusion820and prevent the sealing member830from coming off.

The holding prominences821amay protrude around the outer circumference at the end of the second combining protrusion820at predetermined intervals or may circumferentially protrude, and has a smaller thickness than the thickness t1of the O-ring831, so that it maintains the function of the O-ring831and prevents separation.

The female flange block804is formed in the corresponding shape to the male flange block803and has the second pipe-combining hole804abored at the position corresponding to the first pipe-combining hole803a.

In the female flange block804, a first protrusion-combining hole804bto insert the first combining protrusion810is formed on the combining surface to combine with the male flange block803, and the first protrusion-combining hole is in communication with the second pipe-combining hole804a.

The second pipe-combining hole804ais bored at the center of the first protrusion-combining hole804band second protrusion-combining grooves804care formed at predetermined intervals around the second pipe-combining hole804ato insert the end of the second combining protrusion820.

A second seating face804dto seat a side of the inner sealing part832of the sealing member830is formed between the second protrusion-combining groove804cand the second pipe-combining hole804aand sealing beads824are formed on the second seating face804d.

The female flange block804has a second fastening hole804ecorresponding to a first fastening hole803band is combined with the male flange block by a fastening bolt841through the first and second fastening holes803b,804e.

The first fastening hole803bor the second fastening hole804ehave a thread inside, respectively, to fasten the bolt.

Pin holes803c,804fare respectively formed on the combining surfaces of the male flange block803and the female flange block804to combine the blocks by inserting a fixing pin850.

The fixing pin850guides the combining position of the male flange block803and the female flange block804so as to combine them at an accurate position.

The sealing member830is fitted around the second combining protrusion820, and the sealing member830, as shown inFIGS. 28 and 29, includes the O-ring831surrounding the outside of the second combining protrusion820for sealing and the inner sealing part832having a through hole832acommunicating with the first and second pipe-combining holes803a,804a. The inner sealing part832is provided inside the O-ring831and seated on the first seating face823inside the second combining protrusion820.

In the sealing member830, the O-ring831and inner sealing part832may be integrally formed. The wings833, which protrude at predetermined intervals along the outer circumference of the inner sealing part832and maintain the space between the inner sealing part832and the O-ring831with the ends of the wings fixed to the inside of the O-ring831, may be formed.

The O-ring831has a circular ring shape having an inner diameter not larger than the outer diameter of the second combining protrusion820and is fitted around the outside of the second combining protrusion820.

The O-ring831is made of rubber of synthetic rubber, preferably ethylene-base rubber (EPDN), fluorine-based rubber (FKM), or nitrol-based rubber (H-NBR) having high cold resistance and air tightness.

The inner sealing part832has a circular plate shape with a through hole832aat the center and is fixed to the inside the O-ring831such that spaces D1to fit the second combining protrusion820are formed between the outside of the inner sealing part832and the inside of the O-ring831.

The inner sealing part832is made of soft metal, such as tin alloy, soft aluminum, white wax, or fluorine resin, or Teflon-series resin.

In detail, the inner sealing part832is made of a softer material than the male flange block803or the female flange block804. If the same material is used, the inner sealing part832may be given different hardness through heat treatment and change of process, or it may be made of a resin.

The inner sealing part832has wings833integrally protruding from the outer circumference at predetermined intervals and the wings833are fixedly inserted in the O-ring.

Parts of the outside of the wings833are covered by the O-ring831to reinforce the combining force.

The number of the wings833depends on the number of the vertical combining grooves821in the second combining protrusion820, and have the width and thickness capable of being inserted in and combined with the vertical combining grooves821and horizontal combining grooves822.

The space D1between the O-ring831and the inner sealing part832is set in 1 to 2 times thicker than the thickness D2of the second combining protrusion820to facilitate to fit the second combining protrusion820into the sealing member830without deteriorating the air tightness.

FIG. 35shows the most suitable cross-sectional thickness ratio t1/t2to a fracture pressure.

As shown inFIG. 35, the O-ring831preferably has a thickness t11.0 to 2.0 times of the thickness t2of the inner sealing part832, which allows main sealing by the inner sealing part832and secondary sealing by pressing the O-ring to be uniform. As the cross-sectional thickness t1of the O-ring increases, the secondary sealing effect increases, while it adversely affects the function of the main sealing part (i.e. the inner sealing part832), assembling and the structure. Further, as the cross-sectional thickness t1of the O-ring decreases, the main sealing is improved, but the secondary sealing deteriorates. As a result, the inner sealing part may corrode due to corrosive materials permeating from the outside.

Further, the cross-sectional thickness ratio t1/t2affects the assembling and the flange size of the male and female flange blocks. Accordingly, as the cross-sectional thickness ratio increases (t1>t2), the assembling becomes difficult and the male flange block should be increased in size.

On the other hand, fastening means840to fasten the male flange block803and the female flange block804is a bolt841that is threaded-fastened in the first and second fastening holes803b,804e.

Returning toFIG. 26, a step860protrudes from one side end on the combining surface of the male flange block803to reinforce the combining force of the bolt841so that it serves as a lever to uniformly transmit the combining force of the bolt841.

It is preferable to assemble the male flange block803and female flange block804such that a space H1smaller than the height H2of the step860is formed therebetween.

The height H2of the step860depends on a bolt-fastening distance G between the centers of the pipes and bolt841.

The bolt-fastening distance G of the bolt841, as shown inFIG. 36, preferably ranges from 13 mm to 16 mm. As the distance becomes larger, the intensity of the fracture pressure is rapidly decreased.

As shown inFIG. 37, it is preferable to basically set the height H2of the step860in the range of 0.3 to 1.5 mm where the intensity of the fracture pressure is highest.

The less the bolt-fastening distance G, the higher the fracture pressure, and when the step860is excessively high, the fracture pressure decreases.

The step860uniformly transmits the fastening force of the bolt841by serving as a lever in assembling the male flange block803and female flange block804, and maintains the fastening force such that it prevents a high-pressured refrigerant flowing from leaking out due to decrease of the fastening force and bears high pressures.

The assembly of the male flange block803and the female flange block804having the configurations as described above is now described in detail below.

The first and second pipes801,802are inserted into the first and second pipe-combining holes803a,804aof the male flange block803and the female flange block804, respectively, and then fixed in the first and second pipe-combining holes803a,804aby welding or brazing.

When the sealing member830is combined with the second combining-protrusion820by inserting the wings833into the vertical combining grooves821, the O-ring831combines with outside of the second combining protrusion820and the inner sealing part832combines with inside the second combining protrusion820.

The sealing member830is fixedly combined with the second combining-protrusion820by inserting the wings833in the vertical grooves821and then rotating it to insert the wings833into the horizontal combining-grooves822.

In other words, the sealing member830is fixedly combined with the second combining-protrusion820by fitting the second combining-protrusion820into the spaces between the O-ring831and the inner sealing part832.

Since the inner sealing part832is made of a resin or soft metal with a predetermined rigidity, the sealing member830primarily seals the joint against the refrigerant flowing through the first and second pipe holes803a,804aunder high pressure of the refrigerant. Further, the O-ring831surrounds the outside of the second combining-protrusion820to carry out secondary sealing.

When the sealing member830is combined with the second combining-protrusion820and seated on the first seating face823, a bead mark is left on the inner sealing part832by the sealing beads824, so that the bead mark should be accurately positioned on the sealing beads824to keep air tightness in reassembling.

The bead mark allows accurate location for reassembling the sealing member830, and the workability in reassembling and air tightness after reassembling to be maintained.

After being combined with the sealing member830as described above, the second combining-protrusion820is inserted into the second protrusion-combining groove804cwhile the first combining protrusion810is inserted into the first combining hole804b, so that the male flange block803and female flange block804is combined.

The fixing pin850that is inserted into the pin holes803c,804fof the male flange block803and the female flange block804guides the combining position of the blocks to facilitate a combining work.

As described above, after the male flange block803is combined with the female flange block804, the first and second pipes801,802are completely connected by threaded-fastening the bolt841into the first and second fastening holes803b,804e. Because the fastening force uniformly acts on the male flange block803and female flange block804, the pipe connecting structure comes to have durability and air tightness under high pressures.

On the other hand, as shown inFIG. 34, the pipe connecting structure may have two male flange blocks, a female flange block, a sealing member, and fastening means.

According to the above configuration, a sub-male flange block803-2is seated on a groove803dof a male flange block803-1, a female flange block804-1is connected with the male flange block803-1, pipes are connected, and then they are fastened by a bolt841.

FIGS. 38 and 39show a sixth embodiment of the invention. Referring toFIGS. 38 and 39, a rectangular shaped male flange block924connected with a first pipe922and a rectangular shaped female flange block928connected with a second pipe926are fastened by a bolt930.

The male flange block924has a protrusion924ahaving a hole that communicates with the first pipe922and the female flange block928has an insert portion928ato which the protrusion924ais inserted. A primary sealer932is provided at the middle outside the protrusion924afor primary sealing and a secondary sealer934is provided at the root end of the protrusion924afor secondary sealing. A fixing pin936is inserted into the male flange block924and the female flange block928so that the protrusion924ais accurately inserted into the insert portion928a. The second pipe926communicates with the insert portion928a.

The bolt930is fixedly inserted in a hole928bof the female flange block928via a through hole924bof the male flange block924. Holes924c,928cto fit the fixing pin936are respectively formed through the male flange block924and the female flange block928.

The primary sealer932is a rubber ring that bears high temperatures of a CO2refrigerant and compressor oil and fitted in a circumferential groove924dformed at the middle outside the protrusion924a. The secondary sealer934is an integral ring with a metal sealing part934aand a rubber sealing part934bfitted inside the metal sealing part934a. The portion of the male flange block924where the hole924cto insert the fixing pin is formed protrudes to the same level with the thickness of the metal sealing part934aof the secondary sealer934and closely contacts with the combining surface of the female flange block928.FIG. 39shows the rubber sealing part934bof the secondary sealer934that is not closely pressed yet by assembling.

The rubber sealing part934bis made of rubber with high cold resistance against low temperatures, flexibility, and air tightness. The metal sealing part934aprevents the rubber sealing part934bfrom deforming. The rubber sealing part934bis 1.05 to 2 times thicker than the metal sealing part934ato keep air tightness by close-pressing.

InFIGS. 38 and 39, a reference character D represents the distance between the centers of the protrusion924aand the bolt930(hereafter, called ‘bolt-fastening distance’), E represents the thickness of the male flange block924(including the thickness of the secondary sealer), and F represents the protruding length of the protrusion924a(except for the thickness of the secondary sealer).

The male flange block924and female flange block928are rectangular shaped blocks. Therefore, when the combining areas are the same, the fracture pressure reaches the maximum. The double sealing structure having the primary sealer932and the secondary sealer934minimizes leakage and increases the fracture pressure, and the fixing pin936allows accurate insertion of the protrusion924aof the male flange block924with the primary and secondary sealers932,934into the insert portion928aof the female flange block928to uniformly distribute pressure to the primary and secondary sealers, to thereby increase air tightness.

The pipe connecting structure according to the embodiment of the invention changes in the fracture pressure according to the thickness of the male flange block, the bolt-fastening distance, the distance between centers of the protrusion and bolt, the protruding length of the protrusion of the male flange block (inserting depth in the insert portion), and the fastening torque of the bolt.

FIG. 40shows a graph for changes in the fracture pressure to the fastening torque of the bolt for samples of pipe connecting structures according to the invention, where fastening torque of 4 Nm, 6 Nm, 8 Nm, 10 Nm, 12 Nm, 14 Nm, 16 Nm was applied to the samples having male flange block thicknesses E of 8 mm (sample 1), 10 mm (sample 2), 12 mm (sample 3), 14 mm (sample 4), and 16 mm (sample 5), respectively. As shown inFIG. 40, it can be seen that a stagnant section where the fracture pressure stops increasing appears from 8 Nm to 12 Nm fastening torque, which implies that even though the thickness of the male flange block continuously increases, the fracture pressure does not increase at above a specific torque. In other words, suitable assembling torque exists for the thicknesses of the male flange block.

Considering the result in the graph, it is preferable to set the fastening torque within 10 to 14 Nm for the embodiment.

FIG. 41shows a graph for changes in the fracture pressure when 10 Nm fastening torque was applied, for each sample, where the male flange block thicknesses E of 8 mm, 10 mm, 12 mm, 14 mm, and 16 mm were given to the samples and the bolt-fastening distances D of 12 mm, 14 mm, 16 mm, 18 mm, and 20 mm were given to each of the samples. As shown in the graph, the maximum fracture pressure appears at 12 mm bolt-fastening distance, and it can be seen that as the bolt-fastening distance decreases, the fracture pressure increases.

Considering the result from the graph, it is preferable to set the thickness of the male flange block and the bolt-fastening distance within 12 to 16 mm for the embodiment.

FIG. 42shows a graph for changes in the fracture pressure, where samples having the protruding length F of the protrusion of the male flange block of 9 mm, 12 mm, 14 mm, 16 mm, 18 mm, and 20 mm were provided, and the thickness of the male flange block of 14 mm and the bolt-fastening distance of 14 mm were given to each of the samples. As seen from the graph, the fracture pressure rapidly increases at the protruding length of the protrusion of the male flange block from 9 mm to 14 mm and a gentle fracture curve appears in the section from 14 mm to 20 mm. The result seen from the graph implies that even though the protruding length of the protrusion of the male flange block continuously increases, the fracture pressure does not increase at above a specific protruding length.

Because the weight increases according to increase of the protruding length, a suitable extent in increase of the protruding length for the increasing amount of the fracture pressure exists.

Considering the result from the graph, it is preferable to set the protruding length of the protrusion of the male flange block in the embodiment within 12 to 18 mm for a double sealing structure, but it may be reduced for an integral sealing member of metal and rubber.

According to a pipe connecting structure of the invention, when pipes, a heat exchanger and a pipe, or two members are connected in a refrigerating cycle system using a CO2refrigerant, the connecting structure can bear high pressures, air tightness can be maintained under low and high temperatures without changes in quality and shape of sealing members, and it is possible to prevent and minimize leakage of the refrigerant by preventing permeation of CO2.

Further, it is easy to assemble and reassemble a male flange block, female flange block, and sealing member, and thus, convenience and efficiency in application is improved. Particularly, durability and air tightness can be maintained in reassembling.

Further, thickness of a male flange block, a bolt-fastening distance, a fastening torque, and a protruding length of a protrusion can be optimized.