JP4256217B2 - Heat transfer tube - Google Patents

Description

[0001]
[Industrial application fields]
  The present invention relates to a cooling medium such as cooling water, cooling air, a refrigerant for a car air conditioner, or other refrigerant liquid in a heat exchanger such as a multi-tube heat exchanger such as an EGR gas cooling device or a radiator built-in oil cooler. Heat transfer for various uses, such as those used for heat exchange with EGR gas, combustion exhaust gas containing soot, etc.On the tubeIt is related.
[0002]
[Prior art]
[Patent Document 1]
      JP-A-11-108578
[Patent Document 2]
      JP 2000-179410 A
[Patent Document 3]
      JP 2001-227413 A
[Patent Document 4]
      JP 2002-295987 A
[0003]
  Conventionally, in an automobile engine or the like, an EGR system in which a part of exhaust gas is extracted from the exhaust gas system, returned to the engine intake system, and added to the mixture or intake air has been used for gasoline engines and diesel engines. . EGR systems, especially cooled EGR systems with a high EGR rate for diesel engines, reduce NOx in exhaust gas, prevent fuel consumption deterioration and prevent deterioration of EGR valve function and durability due to excessive temperature rise. Therefore, an EGR gas cooling device that cools the heated EGR gas with a cooling medium such as cooling water, cooling air, a car air conditioner refrigerant, or other refrigerant liquid is provided.
[0004]
  And as this EGR gas cooling device, as shown in the conventional invention of the said patent document 1-patent document 4, etc., the several small diameter heat exchanger tube which can distribute | circulate an EGR gas is arrange | positioned inside, and this heat exchanger tube is outside. There exist some which perform heat exchange with EGR gas and a cooling medium via a heat exchanger tube by circulating cooling media, such as cooling water, cooling air, and a refrigerant liquid.
[0005]
  The heat transfer tube used in the EGR gas cooling apparatus as described above is often a metal tube with a smooth inner peripheral surface. However, in such a heat transfer tube, most of the EGR gas is high-speed around the axial center of the heat transfer tube. Heat is conducted only from the EGR gas flowing through the heat transfer tube and passing through the inner peripheral surface side of the heat transfer tube, and heat exchange with the cooling medium is difficult to be performed. In order to improve this heat exchange performance, in the conventional inventions of Patent Documents 1 and 2, a flat plate is spirally formed in a metal tube provided with a protrusion protruding inwardly in a spiral or annular shape. A fin member is inserted and disposed to form a heat transfer tube. Moreover, in patent document 3, the flat fin member is integrally protruded in the raw tube, and the heat exchanger tube is formed. In Patent Document 4, a helical fin member having an outer diameter substantially the same as the inner diameter of the raw tube is inserted and arranged in the raw tube, and then a protrusion protruding inwardly is provided on the raw tube. A heat pipe is formed.
[0006]
  In this way, by arranging a helically twisted fin member in the element tube or by projecting a flat fin member integrally, the heat transfer area of the heat transfer tube is increased and the inner surface of the heat transfer tube flows. In addition to the EGR gas, the heat of the EGR gas flowing in the vicinity of the center of the shaft is transmitted to the fin member to increase the efficiency of heat conduction from the EGR gas to the heat transfer tube. Furthermore, the flow of the EGR gas in the heat transfer tube is turbulent by the fin member, the flow distance of the EGR gas in the heat transfer tube is lengthened, the contact time between the heat transfer tube and the EGR gas is lengthened, and the boundary layer is peeled off Thus, the heat exchange efficiency between the EGR gas and the cooling medium via the heat transfer tube is to be increased.
[0007]
[Problems to be solved by the invention]
  However, in the prior arts of Patent Documents 1 and 2, the contact between the fin member and the raw pipe is an intermittent point contact between both side edges of the fin member and the protruding portion of the inner peripheral surface of the raw pipe. Therefore, the contact area between the fin member and the raw tube is small, and even if the fin member receives the heat of the EGR gas, the heat transfer from the fin member to the raw tube is not sufficiently performed, and the outer periphery of the EGR gas and the heat transfer tube There was a limit to increasing the efficiency of heat exchange with the flowing cooling medium. Also, if the helical pitch is reduced and the amount of fin members is increased, the heat transfer area increases, but the pressure resistance to the fluid flowing in the heat transfer tube increases, and a predetermined amount of fluid cannot flow. As a result, the heat exchange performance of the heat transfer tube may not be improved.
[0008]
  On the other hand, in patent document 3, since the raw pipe and the flat fin member are provided integrally, the raw pipe and the plate fin are in surface contact for the plate thickness of the plate fin. Also in Patent Document 4, by forming the outer diameter of the spiral fin member with substantially the same dimension as the inner diameter of the element tube, the element tube and the fin member can be brought into surface contact with the plate thickness of the fin member. Yes. Therefore, in patent documents 3 and 4, compared with the point contact of patent documents 1 and 2, thermal conductivity with an element pipe and a fin member becomes high.
[0009]
  However, in any case of Patent Documents 1 to 4, since the fin member is simply connected to the base tube by surface contact or intermittent point contact, the fixing property of the fin member is poor, the vibration of the heat transfer tube, the fluid flow pressure, etc. Therefore, there is a possibility that the fin member may be shaken or deformed, and further cracked due to distortion, and the heat exchange function and durability of the heat transfer tube may be impaired.
[0010]
  The present invention is intended to solve the above-described problems, and enhances the thermal conductivity between the fin member inserted and arranged in the elementary tube of the heat transfer tube and the fluid flowing inside and outside the heat transfer tube. Efficient heat exchange to transfer heatTubeThe heat exchange performance is improved. In addition, the fixing of the fin member in the raw tube is improved, and it is possible to suppress blurring and deformation of the fin member, as well as cracks due to distortion, etc.TubeIt is possible to improve durability and maintain excellent heat exchange performance. Moreover, the heat exchanger tube excellent in this heat exchange performance and durability is easily formed.
[0011]
[Means for Solving the Problems]
  In order to solve the above-described problems, the present invention provides a first fin and the other fin in which one piece and the other piece are arranged in a crossing direction through a bent portion in a metal tube. Insert and arrange thisThe one fin and the other fin are formed so that the length of the one piece is longer than 50% of the inner diameter of the base tube and shorter than 75%, and the one piece of the one fin and the one piece of the other fin are in surface contact with each other. In addition, the length of the other piece is shorter than 50% of the inner diameter of the raw tube and longer than 25%, and the inside of the raw tube is divided into four in the tube axis direction.The one end of the one fin and the other piece of the other fin are brought into contact with the inner peripheral surface of the raw tube, and the one fin and the other fin are brought into contact with each other at least in the bent portion direction.Withis there.
[0012]
  In addition, the second invention,One fin and the other fin, in which one piece and the other piece are arranged in the crossing direction, are inserted and arranged in a metal tube, and one piece and the other of the one fin and the other fin are inserted. The tip of the piece is brought into contact with the inner peripheral surface of the raw tube, and a stopper is provided on at least a part of the outer surface of the one piece and the other piece. In a state where the one fin and the other fin are brought into contact with each other at least in the bent portion directionIt is.
[0013]
  In addition, the one piece and / or the other piece is formed so that the tip side is bent so as to correspond to a part of the inner peripheral surface of the raw tube, and this close contact surface is formed on the inner peripheral surface of the raw tube. It may be possible to adhere by surface contact.
[0014]
  Further, the one piece and / or the other piece may be provided with a protrusion that is long in the tube axis direction and has a V-shaped or U-shaped cross-sectional shape in the circumferential direction of the raw tube.
[0015]
  The element tube may be provided with at least one spiral groove protruding inward of the element tube with one fin and the other fin disposed therein.
[0016]
  Further, the close contact surface provided on the one piece and / or the other piece may have a forming width in the circumferential direction of the raw tube of 5% or more and 20% or less of the circumferential length of the inner peripheral surface of the raw tube.
[0017]
  The one piece and the other piece may be twisted in the circumferential direction around the tube axis.
[0018]
  Further, the one piece and / or the other piece may be provided with a plurality of embossed protrusions having a certain length.
[0019]
[Action]
  The present invention is configured as described above.1 and / or second inventionIn the heat transfer tube of the invention, the one fin and the other fin made of a metal material are arranged in a metal base tube excellent in heat conductivity, so that the heat transfer area of the heat transfer tube can be increased. Further, the one fin and the other fin are in surface contact with the inner peripheral surface of the raw tube at least in the area of the plate thickness at four positions on the tip side of each one piece and the other piece. Compared with the contact at the location, the contact area between the raw tube and the one fin and the other fin is increased, and the thermal conductivity can be improved. Further, as compared with the conventional spiral fin member, the pressure resistance to the fluid is not excessively increased, and a fluid having a predetermined flow rate can be smoothly flowed. Therefore, the heat absorption characteristics and heat dissipation characteristics of the heat transfer tube are improved, and heat exchange between the internal and external fluids via the heat transfer tube can be performed efficiently, and a heat transfer tube excellent in heat exchange performance can be obtained.
[0020]
  In the heat transfer tube manufacturing process of the present invention, after the one fin and the other fin are inserted and disposed in the raw tube, the raw tube and the one fin and the other fin are connected and fixed by brazing, welding, or the like. . In the present invention, when the one fin and the other fin are inserted into the raw tube, the tip side of the one piece and the other piece comes into contact with the inner peripheral surface of the raw tube, and the one fin and the other fin are at least in the direction of the bent portion. Since it is formed with dimension matching so that it touches partly, alignment between one fin and the other fin is completed just by inserting it into the raw tube, and one fin and the other fin are separated apart during the insertion process Without causing any misalignment or misalignment, and stable insertion work is possible.
[0021]
  Even after the insertion into the raw tube, the stability of the one fin and the other fin in the raw tube is good, and there is no occurrence of positional displacement or dropping from the raw tube. Therefore, it is possible to efficiently perform brazing and welding work between the raw pipe and the one fin and the other fin in the next process. In addition, this brazing and welding increases the contact area between the fin and the one fin and the other fin and the element pipe and metallurgical contact, and the one fin and the other fin are fixed in the element pipe. In addition to this, both thermal conductivities can be further improved.
[0022]
  In addition, since the heat transfer tube is fixed, even if the fluid flow pressure or vibration of the heat transfer tube acts on the one fin and the other fin when the heat transfer tube is used, the one fin and the other fin are in contact with each other. And the ends of the one piece and the other piece are supported by abutting against the inner peripheral surface of the raw tube. Therefore, blurring and deformation of the one fin and the other fin are suppressed, the durability of the heat transfer tube is improved, and the excellent heat exchange performance can be maintained for a long time.
[0023]
  Also, install a heat transfer tube as described above.FeverThe exchanger can be used for any heat exchanger that performs heat exchange, such as an automobile engine, other internal combustion engines, and air conditioning. For example, by forming an EGR gas cooling device for an engine and other multi-tube heat exchangers, the EGR gas can be efficiently cooled. Therefore, in an EGR system, particularly a cooled EGR system with a high EGR rate of a diesel engine, NOx in the exhaust gas can be reduced and fuel consumption can also be prevented from deteriorating. In addition, it is possible to prevent an excessive increase in temperature and to surely prevent the EGR valve from deteriorating and functioning.
[0024]
  Also, heat transfer pipes may be installed in a built-in oil cooler to a radiator that circulates high-temperature oil inside and cools with engine cooling water, and performs excellent heat exchange, heat transfer characteristics and durability High oil cooler can be obtained.
[0025]
【Example】
  The following is an EGR gas cooling device for an automotive cooled EGR system.The heat transfer tubes of the first and second inventions of the present applicationThe incorporated embodiment will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a heat transfer tube according to the first embodiment, in which one end L-shaped fin and the other fin provided with one piece and the other piece are inserted and disposed in a substantially cross-shaped form in the raw tube. Moreover, the circular through-hole is provided in the one piece and the other piece. FIG. 2 is an end view of FIG. FIG. 3 is an enlarged perspective view of one piece of the second embodiment. A U-shaped raised portion is provided on one piece to form a through hole and irregularities.
[0026]
  FIG. 4 is an enlarged perspective view of one piece of the third embodiment. A louver portion is provided on one piece to form through holes and irregularities. FIG. 5 is an enlarged perspective view of one piece of the fourth embodiment, and a rectangular through hole is provided in the one piece. FIG. 6 is a perspective view of the heat transfer tube of the fifth embodiment. In the state where one fin and the other fin are inserted and arranged, a spiral groove projecting inward is provided on the outer periphery of the base tube. 7 is a cross-sectional view of the heat transfer tube of FIG. 6 along the line AA.
[0027]
  Further, FIG. 8 is an end view of the heat transfer tube of the sixth embodiment, provided on the tip end side of the one piece and the other piece with a close contact surface to be brought into surface contact with the inner peripheral surface of the raw tube, A protrusion having a U-shaped cross section in the circumferential direction of the base tube is provided. FIG. 9 is an end view of the heat transfer tube of the seventh embodiment. As in the sixth embodiment, the one piece and the other piece are provided with close contact surfaces and ridges. It is also wide. FIG. 10 is an end view of the heat transfer tube of the eighth embodiment, in which the contact surface and the ridge between the one piece and the other piece are formed so as to face each other. FIG. 11 is an end view of the heat transfer tube of the ninth embodiment. As in the eighth embodiment, the one piece and the other piece are provided with close contact surfaces and ridges. It is also wide.
[0028]
  Also figure12 isFirst10 fruitsFIG. 6 is a cross-sectional view in the circumferential direction of the heat transfer tube of the example, with a stopper projecting from the outer surface of one piece of one fin and the other fin, and the other piece of the mating fin abutting against the stopper. Figure13Figure12It is a perspective view which shows the engagement state of the stopper of one fin and the other fin. Also figure14 isFirst11 fruitsIn the perspective view of the one fin and the other fin of the embodiment, the one fin and the other fin are twisted in the circumferential direction. Figure15 isThe second12 fruitsIn the perspective view of the one fin and the other fin of the embodiment, a plurality of embossed protrusions having a fixed length in the inclined direction with respect to the tube axis are provided in the same direction on the one piece and the other piece. . Figure16 isFirst13 fruitsIn the perspective view of the one fin and the other fin of the embodiment, the embossed projections of the one piece and the other piece are provided in different directions. Figure17It is the schematic of the EGR gas cooling device using the heat exchanger tube of this invention.
[0029]
  First,First in the first invention of the present applicationFIG. 1, FIG. 2, FIG.To 17More specifically, (1) is a heat transfer tube, and the inside of the thin metal tube (2) through which EGR gas can flow is elongated in the tube axis direction and the end face shape is substantially L. The metal-made one fin (3) and the other fin (4) are inserted and arranged symmetrically in a point-symmetric manner so that the end surface has a substantially cross shape.
[0030]
  Moreover, the said pipe | tube (2), one fin (3), and the other fin (4) can obtain the heat exchanger tube (1) which is excellent in heat conductivity by using copper, aluminum, brass, stainless steel, etc. it can. Stainless steel or the like is excellent not only in thermal conductivity but also in corrosion resistance against EGR gas and the like. In addition, the raw tube (2) and the one fin (3) and the other fin (4) may be formed of the same metal in consideration of the purpose of use and cost, or may be formed of different metals. Also good. In addition, in order to further improve the reliability of corrosion resistance, the metal material as described above is subjected to a single-layer plating treatment of zinc, copper, tin, tin-zinc alloy, nickel, zinc-nickel alloy, etc., and chromate as necessary. A coating or the like may be applied, or two or more layers of plating may be performed, such as plating the outer surface of the metal material with nickel and further plating a zinc-nickel alloy on the outer peripheral surface of the nickel.
[0031]
  In addition, the heat conductivity with the one fin (3) and the other fin (4) and the element pipe (2) and the fixing property of the one fin (3) and the other fin (4) in the element pipe (2) are considered. Thus, it is preferable that the plate thickness of the plate member forming the one fin (3) and the other fin (4) is 1% or more and 15% or less of the inner diameter of the raw tube (2). If the plate thickness is thinner than 1% of the inner diameter of the raw tube (2), the thermal conductivity and the fixing property between the one fin (3), the other fin (4) and the raw tube (2) may be reduced. There is. Further, if the plate thickness is thicker than 15% of the inner diameter of the raw pipe (2), the occupied volume of the one fin (3) and the other fin (4) in the raw pipe (2) increases, and the EGR gas flow space Therefore, a predetermined amount of EGR gas cannot be flowed, and the heat exchange performance of the heat transfer tube (1) may be reduced.
[0032]
  In this embodiment, the plate member is formed with a plate thickness of 3% of the inner diameter of the blank tube (2). Specifically, the inner diameter d of the blank tube (2) shown in FIG. The other fin (4) has a plate thickness t of 0.3 mm. A plate member having such a thickness is bent at approximately 90 °, and provided with one piece (6) and the other piece (7) through a bent portion (5), and one fin having an L-shaped end surface. (3) and the other fin (4) are formed.
[0033]
  Further, the one fin (3) and the other fin (4) are formed in the same shape and the same size, thereby improving productivity. The length of each one piece (6) is longer than 50% of the inner diameter of the blank tube (2) and shorter than 75%, so that the one piece (6) of the one fin (3). And one piece (6) of the other fin (4) can be brought into surface contact with each other in the raw pipe (2). The other piece (7) has a length shorter than 50% of the inner diameter of the base tube (2) and longer than 25%. Specifically, as shown in FIG. 2, the formation length a of the one piece (6) is 6.0 mm, which is 60% of the inner diameter of the raw tube (2), and the formation length b of the other piece (7) is 4 .9 mm is 49% of the inner diameter of the tube (2). By adopting such dimensions, at the time of insertion and placement into the raw tube (2), the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4) are in the axial center portion ( 8) In the state of surface contact via 8), the tip of each of the one piece (6) and the other piece (7) of the one fin (3) and the other fin (4) is brought into contact with the inner peripheral surface of the raw tube (2). It becomes possible to contact.
[0034]
  Further, by arranging the one fin (3) and the other fin (4), the inside of the raw pipe (2) is divided into four in the tube axis direction, and as shown in FIG. 3) between the first inner space (10) between the one piece (6) and the other piece (7), and between the one piece (6) of the one fin (3) and the other piece (7) of the other fin (4). The second internal space (11), the third internal space (12) between the other piece (7) and one piece (6) of the other fin (4), and the one piece (6) and one of the other fin (4) A fourth internal space (13) between the other pieces (7) of the fin (3) is formed. The one fin (3) and the other fin (4) are adjacent to each other by opening circular through holes (14) at a plurality of locations on the one piece (6) and the other piece (7). The internal spaces (10), (11), (12), and (13) communicate with each other to allow EGR gas to enter and exit.
[0035]
  Then, in order to form the heat transfer tube (1) by inserting and arranging the one fin (3) and the other fin (4) in the base tube (2) as described above, one piece of the one fin (3) ( 6) Insert the one fin (3) and the other fin (4) into the raw tube (2) while bringing the bent part (5) side of the one piece (6) of the other fin (4) into surface contact with each other. To do. Since the one fin (3) and the other fin (4) are formed as described above, each one piece (6) and the other piece (7) of the one fin (3) and the other fin (4) are formed. The tip of the tube abuts on the inner peripheral surface of the raw tube (2), and the movement of the one fin (3) or the other fin (4) in the direction of the tip is prevented, and the one piece (6) of each other is in surface contact. Thus, the movement toward the inside of the raw tube (2) is also prevented. Therefore, the positioning of the one fin (3) and the other fin (4) is ensured, and the one fin (3) and the other fin (4) are separated apart in the insertion process into the raw tube (2). There is no position shift or the like, and a stable insertion operation up to the insertion completion position is possible. Therefore, the working efficiency is improved and the alignment of the one fin (3) and the other fin (4) is completed only by performing the insertion work.
[0036]
  When the above insertion and arrangement are completed, as shown in FIG. 1, the L-shaped one fin (3) and the other fin (4) are in the raw tube (2) with the one piece (6) in surface contact with each other. The end face shape is arranged in a substantially cross shape. Further, the tip ends of the one piece (6) and the other piece (7) are in surface contact with the inner peripheral surface of the element pipe (2), and the one fin (3) and the other fin (4) in the element pipe (2). And the heat conduction between the raw tube (2) and the one fin (3) and the other fin (4) is performed well through a contact area equivalent to four times the plate thickness. It will be.
[0037]
  Next, the tip edges of the one piece (6) and the other piece (7) of the one fin (3) and the other fin (4) and the inner peripheral surface of the raw pipe (2) are brazed. By this brazing, the one piece (6) and the other piece (7) and the inner peripheral surface of the raw pipe (2) are securely brought into close contact with the fillet (9) of the brazing material, and as shown in FIG. The width of the fillet (9) of the material makes a wide surface contact and metallurgical contact. The sex can be further enhanced. Further, the contact portion between the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4) may be brazed, and the one fin (3) and the other fin (4) As a result, the fixing property can be further improved and fretting can be prevented. In order to release the distortion due to thermal expansion, it is not necessary to braze the contact portion between the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4).
[0038]
  Further, at the time of brazing, a brazing material is plated on at least the tip edges of the one fin (3) and the other fin (4) in advance before insertion into the raw tube (2). When the contact surface of the one piece (6) is brazed, a brazing material is plated on the outer surface of the bent portion (5). The brazing material may be plated on the entire surface of the one fin (3) and the other fin (4) because it is easy to work. Alternatively, the brazing material may be plated on the inner peripheral surface of the base tube (2). You may do it. Also, a brazing material is clad on the plate member, which is a material for forming the one fin (3) and the other fin (4), and this clad material is processed to form one fin (3) and the other fin (4). Also good.
[0039]
  In addition, the one fin (3) and the other fin (4) in which a binder for adhering a brazing material is applied to the front edge of the one fin (3) and the other fin (4) and the outer surface of the bent portion (5) After insertion in (2), a powdery brazing material may be supplied into the raw tube (2). As another method, the one fin (3) and the other fin (4) supplied with brazing paste at the tip edges of the one piece (6) and the other piece (7) may be inserted into the raw tube (2). Then, after inserting the one fin (3) and the other fin (4) into the raw pipe (2), the brazing material paste may be supplied into the raw pipe (2). And it may braze at the time of manufacture of a heat exchanger tube (1), or may braze after attaching a heat exchanger tube (1) to the below-mentioned EGR gas cooling device (20).
[0040]
  And the EGR gas cooling device (20) assembled with the heat transfer tube (1) as described above is shown in FIG.To 17As shown, a pair of tube sheets (22) are connected to both ends of a cylindrical trunk tube (21) so that the inside can be sealed. And between the pair of tube sheets (22), a plurality of heat transfer tubes (1) of the present embodiment are connected and arranged through the tube sheet (22). Further, a bonnet (26) provided with an EGR gas inlet (24) and outlet (25) is connected to both ends of the trunk pipe (21).
[0041]
  Furthermore, the outer periphery of the trunk tube (21) is partitioned by a pair of tube sheets (22) by providing an inlet (27) and an outlet (28) for a cooling medium such as engine cooling water and cooling air. A cooling part (23) through which a cooling medium can flow is used in the airtight space. Further, a plurality of support plates (30) are joined and disposed in the cooling section (23), and the heat transfer tube (1) is inserted into the insertion hole (29) provided in the support plate (30). The heat transfer tube (1) is stably supported as a baffle plate, and the flow of the cooling medium flowing in the cooling unit (23) is meandered.
[0042]
  In the EGR gas cooling device (20), when high-temperature EGR gas is introduced into the trunk tube (21) from the introduction port (24), a plurality of the EGR gases are arranged in the trunk tube (21). It flows into (1). In the cooling part (23) in which the heat transfer tube (1) is arranged, a cooling medium such as engine cooling water is circulated in advance to the outside of the heat transfer tube (1). Heat exchange is performed between the EGR gas and the cooling medium.
[0043]
  The heat transfer tube (1) of the present invention increases the contact frequency with the EGR gas by increasing the heat transfer area by providing the one fin (3) and the other fin (4). Furthermore, by bringing the tip edges of the one piece (6) and the other piece (7) into contact with the inner peripheral surface of the raw tube (2), the one fin (3) and the other fin (4) are compared with the conventional one. The contact area with the base tube (2) increases, and the thermal conductivity of each other improves.
[0044]
  Further, EGR gas passes through the one fin (3) and the other fin (4) in the four internal spaces (10) (11) (12) (13) divided by the one fin (3) and the other fin (4). ) Is dispersed while flowing in contact with the inner and outer surfaces of the pipe, so that uneven flow is prevented, and not only the heat of the EGR gas on the inner peripheral surface side of the element tube (2) but also the heat of the EGR gas flowing near the center. In addition, heat can be efficiently transferred to the one fin (3) and the other fin (4).
[0045]
  Further, in the present embodiment, a through hole (14) is provided in one piece (6) and the other piece (7). For this reason, the EGR gas flows through the first through fourth inner spaces (10), (11), (12), and (13) through the through holes (14) and flows to the flow destination. Causes fluidization. By this turbulent flow, the flow distance of EGR gas in the heat transfer tube (1) becomes longer, and the contact time with the inner peripheral surface of the elementary tube (2) and the surfaces of the one fin (3) and the other fin (4). The EGR gas is agitated, and not only a part of the EGR gas but the entire EGR gas repeatedly comes into contact with the element pipe (2) and the one fin (3) and the other fin (4). Heat transfer to 3) and the other fin (4) is further promoted.
[0046]
  Then, the heat of the EGR gas received by the one fin (3) and the other fin (4) is efficiently transferred to the inner surface of the raw tube (2) by excellent thermal conductivity, and then the raw tube (2 The heat is dissipated to the cooling medium flowing on the outer periphery via the outer surface of). Therefore, the entire EGR gas is uniformly cooled without unevenness, and an excellent cooling effect on the EGR gas can be obtained.
[0047]
  The EGR gas thus well cooled flows out of the EGR gas cooling device (20) through the outlet port (25) and is returned to the intake manifold side. Accordingly, it is possible to prevent the EGR valve from being heated to high temperature and obtain the excellent functionality and durability of the EGR valve, and to reduce the temperature of the intake air, so that NOx can be reduced and good fuel consumption can be achieved. In addition, the turbulent flow of EGR gas in the heat transfer tube (1) promotes the separation of soot mixed in the EGR gas and prevents it from becoming a large lump. Cooling performance due to clogging, etc. It is possible to prevent deterioration and engine trouble.
[0048]
  Next, the durability of the heat transfer tube (1) against vibration of the heat transfer tube (1) and the flow pressure of EGR gas in the heat transfer tube (1) will be described. First, when an outward movement force of the raw tube (2) acts on the one fin (3) or the other fin (4), each one piece of the one fin (3) and the other fin (4) ( 6) and / or the tip of the other piece (7) abuts against the inner peripheral surface of the raw tube (2), so that the outward movement is prevented.
[0049]
  Moreover, if the case where the moving force to the inside of the raw tube (2) is applied to the one fin (3) and the other fin (4), the one fin (3) and the other fin (4) are When a moving force in the direction of the axial center (8) acts, the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4) abut each other by surface contact, Movement in the axial center (8) direction is prevented. Next, the movement force in the direction parallel to the one piece (6), that is, the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4) in the mutual sliding direction acts. In this case, the fourth inner space (13) and the second inner space (11) to which the one fin (3), the other fin (4) is moved are the circles of the other one piece (6) and the raw tube (2). The space surrounded by the arc-shaped inner peripheral surface is narrower than the formation height of the other piece (7). Therefore, in the state where the bent portion (5) side of the one piece (6) is supported by the other one piece (6), the tip edge of the other piece (7) is tapered to the inner peripheral surface of the element pipe (2). The one fin (3) and the other fin (4) are prevented from moving in the sliding direction with respect to each other.
[0050]
  As described above, when the vibration of the heat transfer tube (1), the flow pressure of EGR gas, or the like is applied, the movement in each direction is prevented, thereby fixing the one fin (3) and the other fin (4). As a result, it is possible to satisfactorily prevent blurring and deformation. Therefore, the durability of the heat transfer tube (1) and the EGR gas cooling device (20) assembled with the heat transfer tube (1) can be improved.
[0051]
  In the first embodiment, a circular through hole (14) is opened in one piece (6) and the other piece (7). In the second embodiment, as shown in FIG. (6) and the other piece (7) are provided with a raised portion (15) that opens in a U-shape on the inflow side of the EGR gas so that the surface of the one piece (6) and the other piece (7) is uneven (16) And the opening of the raised portion (15) serves as a through hole (14). FIG. 3 shows an enlarged perspective view of the one piece (6) provided with the raised portion (15). In FIG. 3 and FIGS. 4 and 5 showing the third and fourth embodiments described below, only an enlarged perspective view of one piece (6) is shown, but the other piece (7) is also shown. The one piece (6) has the same configuration.
[0052]
  In another different third embodiment, as shown in FIG. 4, the one piece (6) and the other piece (7) are provided with a louver portion (17) inclined in a taper shape in the tube axis direction. Concave and convex portions (16) are provided on the surfaces of (6) and the other piece (7), and a through hole (14) is opened. In a further different fourth embodiment, as shown in FIG. 5, a rectangular through hole (14) is opened in one piece (6) and the other piece (7). As another different embodiment, the through hole (14) may be opened in a shape such as an ellipse, an oval, a triangle, a pentagon, and other polygons.
[0053]
  In the heat transfer tube (1) in which the one fin (3) and the other fin (4) are inserted and disposed as in the second to fourth embodiments, excellent heat conductivity is obtained and the EGR gas penetrates. Since the fluid flows while passing through the holes (14) or being guided by the irregularities (16) and the edge portion increases, the turbulent flow of EGR gas and the stirring action are further promoted. As a result, the heat transfer efficiency between the EGR gas and the heat transfer tube (1) can be improved by peeling the boundary layer, and the heat transfer tube (1) having excellent heat exchange performance can be obtained. Moreover, these through holes (14), raised portions (15), irregularities (16), louvered portions (17), etc. can be easily performed by pressing or the like, and the manufacturing cost and productivity of the heat transfer tube (1) are improved. Will not be affected.
[0054]
  Further, in the fifth embodiment shown in FIGS. 6 and 7, the substantially fin-shaped one fin (3) and the other fin (4) having the same shape as that of the first embodiment are arranged with the one piece (6) facing each other. It is inserted and arranged in the raw pipe (2) in contact. In the first embodiment, the inner and outer surfaces of the raw tube (2) are smooth without any irregularities, but in the fifth embodiment, the one fin (3) and the other fin (4) are inserted. By pressing the wall surface of the raw tube (2) from the outside in a spiral shape, as shown in FIGS. 6 and 7, the outer surface of the raw tube (2) is moved inwardly from the outer side of the raw tube (2). One protruding spiral groove (18) is provided. In the fifth embodiment, only one spiral groove (18) is provided. However, as another different embodiment, two or more spiral grooves (18) may be provided on the outer periphery of the base tube (2). good.
[0055]
  By providing such a spiral groove (18), as shown in FIG. 7, the inner circumferential surface of the spiral groove (18) protruding inward presses the tip of one piece (6) or the other piece (7). Since the one fin (3) and the other fin (4) are clamped and fixed while being deformed, the fixability of the one fin (3) and the other fin (4) in the base tube (2) is further improved, and the heat transfer tube ( The durability of 1) is increased. Furthermore, at the position where the spiral groove (18) is formed, the inner peripheral surface of the blank tube (2) and the surfaces of the one piece (6) and the other piece (7) are in partial surface contact with each other. The thermal conductivity between (3) and the other fin (4) and the raw tube (2) can be further increased.
[0056]
  Further, in the sixth embodiment shown in FIG. 8, as in the above embodiments, the one fin (3) and the other fin (4) whose end face shape is substantially L-shaped, and the one piece (6) of each other are faced. It is placed in contact with the base tube (2) in a cruciform shape. Then, in the counterclockwise direction, the space between the one piece (6) and the other piece (7) of the one fin (3) is defined as a first internal space (10), and the one piece (6) and the other fin of the one fin (3) are arranged. Between the other piece (7) of (4) is the second internal space (11), and between the other piece (7) and one piece (6) of the other fin (4) is the third inner space (12), and the other fin A space between one piece (6) of (4) and the other piece (7) of one fin (3) is defined as a fourth internal space (13).
[0057]
  Moreover, in each said Example, although the front-end edge of one piece (6) and the other piece (7) is stuck to the inner peripheral surface of a raw pipe (2), in a 6th Example, one piece (6) Further, the close contact surface (31) is formed by bending the tip side of the other piece (7) in a counterclockwise direction so as to correspond to a part of the inner peripheral surface of the base tube (2). Then, when the one fin (3) and the other fin (4) are inserted into the raw pipe (2), the close contact surface (31) is brought into close contact with the inner peripheral surface of the raw pipe (2) by surface contact. ing.
[0058]
  By closely contacting the close contact surface (31) to the inner peripheral surface of the raw pipe (2), heat transfer between the one fin (3) and the other fin (4) and the raw pipe (2) can be further improved. In addition, the fixing property between the one fin (3) and the other fin (4) in the raw tube (2) is improved, and the durability of the heat transfer tube (1) is also increased.
[0059]
  In addition, it is preferable that the said contact surface (31) makes the formation width of the circumferential direction of a raw tube (2) into 5 to 20% of the circumferential length of the inner peripheral surface of a raw tube (2). . Even if the formation width of the contact surface (31) is less than 5% of the circumferential length of the blank tube (2), the tips of the one piece (6) and the other piece (7) without providing the contact surface (31) The thermal conductivity and fixability are not so different from those in the case where they are closely fixed with a contact area corresponding to the thickness of the edge. Moreover, even if the formation width of the contact surface (31) is larger than 20% of the circumferential length of the blank tube (2), there is no difference in the heat transfer effect. Furthermore, the close contact surface (31) abuts against the adjacent one piece (6) or the other piece (7) and curves, making it impossible to make contact with the inner peripheral surface of the raw tube (2), or wasting metal material. May occur.
[0060]
  Further, when the heat transfer tube (1) is constantly exposed to the high heat of the EGR gas, the one fin (3) and the other fin (4) are likely to undergo thermal expansion, but the one piece (6) and the other piece (7). It is possible to absorb some thermal expansion, for example, by bending slightly. However, since the tips of the one piece (6) and the other piece (7) are fixed to the inner peripheral surface of the element pipe (2) by brazing, if the thermal expansion becomes excessive, the one piece (6) The distortion with the other piece (7) cannot be missed, the one piece (6) and the other piece (7) are cracked, and this crack may cause a crack in the base tube (2). There is.
[0061]
  In order to eliminate the problem due to the excessive thermal expansion, in the sixth embodiment, as shown in FIG. 8, the one fin (3) and the other fin (4) are formed of one piece (6) and the other piece (7). Each is provided with a long ridge (32) projecting in the direction of the other surface from the one surface side in the tube axis direction. This protrusion (32) has a U-shaped cross section in the circumferential direction of the pipe (2), and as shown in FIG. 8, it protrudes all counterclockwise when installed in the pipe (2). It is formed to do. By providing the protrusion (32) in this way, even if thermal expansion occurs in the one piece (6) and the other piece (7), the protrusion (32) contracts inward to absorb the thermal expansion. As a result, the distortion of the one piece (6) and the other piece (7) can be suppressed, and the occurrence of cracks can be prevented.
[0062]
  Moreover, it is preferable that the protrusion (32) has a formation height that is not less than the plate thickness of the one fin (3) and the other fin (4) and not more than 25% of the inner diameter of the raw tube (2). If the height of the protrusion (32) is smaller than the plate thickness, the thermal expansion of the one piece (6) and the other piece (7) by the protrusion (32) is not effectively performed. . On the contrary, even if it is larger than 25% of the inner diameter of the raw tube (2), the thermal expansion absorbability is not improved any more, resulting in wasted material.
[0063]
  In addition, the one piece (6) and the other piece (7) are provided with a contact surface (31) to the inner peripheral surface of the base tube (2) and a ridge (32) for absorbing thermal expansion. FIGS. 9 to 11 show seventh to ninth embodiments having different configurations. First, in the seventh embodiment shown in FIG. 9, as in the sixth embodiment, an adhesion surface (31) is provided in the counterclockwise direction at the tips of the one piece (6) and the other piece (7). The U-shaped ridge (32) is also projected in the counterclockwise direction. The width of the ridge (32) is wider than that of the sixth embodiment, so that the thermal expansion absorption force is increased. It is increasing.
[0064]
  Further, in the eighth embodiment shown in FIG. 10, the contact surface (31) of the one piece (6) and the protrusion (32) are projected in the clockwise direction, and the contact surface (31 of the other piece (7)). ) And the ridge (32) are provided in a counterclockwise direction so that the contact surface (31) and the ridge (32) are placed inside the one piece (6) and the other piece (7). Oppositely arranged. By arranging the contact surface (31) and the protrusion (32) inside the one fin (3) and the other fin (4) in this way, the contact surface (31) is not bulky, and the raw tube (2) It becomes easy to store and transport the one fin (3) and the other fin (4) before being disposed on the front.
[0065]
  Further, in the ninth embodiment shown in FIG. 11, as in the eighth embodiment, the contact surface (31) and the protrusion (32) of the one piece (6) are projected in the clockwise direction, and the other piece (7 ) Are closely projecting in the counterclockwise direction, but the width of the protrusion (32) is wider than that of the eighth embodiment, and thermal expansion is achieved. Increases the absorption capacity.
[0066]
  In the first to ninth embodiments, the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4) are brought into surface contact.,oneThe fixing property between the one fin (3) and the other fin (4) is improved, and the blurring or deformation of the one fin (3) and the other fin (4) can be prevented. On the contraryThe tenth fruit which is the second invention of the present applicationIn the embodiment, as in the first to ninth embodiments, not only the one piece (6) of the one fin (3) and the one piece (6) of the other fin (4) are brought into surface contact, but also the one fin (3). A plurality of stoppers (34) are provided on the outer surface of the one piece (6) of (3) and the one piece (6) of the other fin (4). . This stopper (34)13As shown, a part of one piece (6) is formed by bulging, and by engaging the other piece (7) of the other side with this stopper (34), one fin (3) and the other fin (4 ) Can be prevented from moving in the sliding direction of the one piece (6).
[0067]
  Also figure14Show other different number11 fruitsIn the embodiment, the one fin (3) and the other fin (4) formed in the same shape as in the first embodiment are further twisted in the circumferential direction around the tube axis. Due to the formation of the twist, the first to fourth inner spaces (10), (11), (12), and (13) meander, and the turbulent flow and stirring action of the EGR gas are promoted, and the boundary layer is separated from the EGR gas. The efficiency of heat conduction with the heat pipe (1) can be improved, and soot accumulation can be suppressed.
[0068]
  Also figureTo 15Show first12 fruitsExamples and figures16Show first13 fruitsIn the embodiment, embossed protrusions (35) having a fixed length in the inclined direction with respect to the tube axis are formed on each one piece (6) and the other piece (7) of the one fin (3) and the other fin (4). ) Are projected. By projecting the projection (35), a plurality of projections (36) and recesses (37) are formed on both surfaces of the one piece (6) and the other piece (7). These protrusions (35) are arranged in an inclined direction such that the end portion on the inflow side of EGR gas is located in the central axis direction and the end portion on the outflow side is located outward, and one piece (6 ) And the other piece (7) are alternately projected in the tube axis direction so as not to be arranged on the same circumference.
[0069]
  Also,First12 fruitsIn the example, figureTo 15As shown, the protrusion (35) of the one piece (6) and the protrusion (35) of the other piece (7) are each provided in a counterclockwise direction.. on the other handThe second13 fruitsIn the example, figure16As shown, the projection (35) of one piece (6) is projected in the counterclockwise direction, but the projection (35) of the other piece (7) is projected in the clockwise direction, and the projections ( 36) and the recess (37) are formed to face each other. Further, the embossed protrusion (35) is not necessarily provided on both the one piece (6) and the other piece (7), and may be formed in an embossed shape with a certain length.15,Figure16It is not limited to the shape as shown. It should be noted that the embossed protrusion (35) does not necessarily have to be inclined with respect to the tube axis, and may be provided in parallel to the tube axis or at another angle.
[0070]
  Above12,First13 fruitsIn the heat transfer tube (1) in which the protrusion (35) is provided on the one piece (6) and the other piece (7) of the one fin (3) and the other fin (4) as in the embodiment, the heat transfer area is increased. And a protrusion (36) having a fixed length formed on both surfaces of one piece (6) and the other piece (7) of the one fin (3) and the other fin (4) and a recess ( Since the EGR gas flows along 37), the effect of promoting the turbulent flow of EGR gas and the stirring action is high. As a result, it is possible to improve the heat conduction efficiency between the EGR gas and the heat transfer tube (1) by separating the boundary layer, and to suppress soot accumulation and the like.
[0071]
  The fifth to fifth10 fruitsIn the embodiment, as in the first to fourth embodiments, the through holes (14) are formed in the one piece (6) and the other piece (7) of the one fin (3) and the other fin (4). A raised portion (15), unevenness (16), louver portion (17), and the like may be provided. Further, only one kind of these may be provided, or a plurality of kinds may be appropriately combined, and the through hole (14) and the unevenness (16) may be provided in the one piece (6) and the other piece (7). The second12,First13 fruitsAs in the embodiment, the one piece (6) and / or the other piece (7) are provided with a plurality of embossed protrusions (35) of a certain length in parallel or inclined direction or other angle with respect to the tube axis. May be.
[0072]
  Also, first to first9th fruitExample, No.11-First13 fruitsIn the example,10 fruitsAs in the embodiment, a stopper (34) may be provided on one piece (6) and the other piece (7) of the one fin (3) and the other fin (4). Also, the first to fifth embodiments, the first11-First13 fruitsIn the examples, 6th to 4th10 fruitsAs in the embodiment, a U-shaped or V-shaped protrusion (32) may be formed on the one piece (6) or the other piece (7). Furthermore, the first to fifth embodiments, the first11-First13 fruitsIn the examples, 6th to 4th10 fruitsAs in the example, the tip end side of the one piece (6) and the other piece (7) is bent so as to correspond to a part of the inner peripheral surface of the base pipe (2) to form a close contact surface (31). The contact surface (31) may be brought into surface contact with the inner peripheral surface of the raw tube (2).
[0073]
  Also, first to first10 fruitsExample, No.12,First13 fruitsIn the example,11 fruitsAs in the embodiment, the one fin (3) and the other fin (4) may be twisted in the circumferential direction around the tube axis. Also, the first to fourth embodiments, the sixth to the fourth13 fruitsIn the embodiment, as in the fifth embodiment, at least one spiral groove (18) may be provided on the outer peripheral surface of the element pipe (2).
[0074]
  In each of the above embodiments, the one fin (3) and the other fin (4) are formed in the same shape and are in surface contact with each other at the shaft center (8). It is not necessary to form one fin (3) and the other fin (4) in different shapes and sizes, and in the raw tube (2), they face each other at a position different from the axial center portion (8). You may make it contact.
[0075]
  In each of the above embodiments, the EGR gas cooling device (20) is described as being assembled with the heat transfer tube (1) of the present invention. However, the heat transfer tube of the present invention is applied to another different multi-tube heat exchanger. A heat tube (1) may be used, and excellent heat exchange performance can be obtained. In addition, the heat transfer tube of the present invention (1) is installed in a built-in oil cooler for a radiator in which high-temperature oil such as engine oil, mission oil, ATF, and power steering oil is circulated inside and cooled with engine coolant. ) Can also be assembled. And through the heat transfer pipe (1) having a large heat transfer area and high heat conductivity of the present invention, the engine cooling water flowing in the heat transfer pipe (1) and the oil to be cooled flowing in the outside of the heat transfer pipe (1) Heat exchange with the oil is promoted, and the oil to be cooled can be cooled uniformly and efficiently.
[0076]
【The invention's effect】
  The present invention is configured as described above, and the one fin and the other fin provided with one piece and the other piece in the crossing direction are inserted and disposed in a metal base tube excellent in thermal conductivity. The heat transfer area of the heat transfer tube can be increased, and furthermore, the thermal conductivity between the one fin and the other fin and the base tube can be increased. Further, the arrangement of the one fin and the other fin divides the internal space of the heat transfer tube into a plurality of parts, and prevents the uneven flow of the fluid, and the fluid that flows near the center of the heat transfer tube through the one fin and the other fin Exchange of heat with is promoted. Therefore, heat exchange between the fluids flowing inside and outside the heat transfer tube can be performed efficiently, and a heat transfer tube with high heat exchange performance can be obtained.
[0077]
  Furthermore, since the tips of the one piece and the other piece are in contact with the inner peripheral surface of the raw tube and the one fin and the other fin are in contact with each other at least partly, the fixing property of the one fin and the other fin in the raw tube This prevents vibration and deformation of the one fin and the other fin due to vibration of the heat transfer tube, fluid flow pressure, etc., as well as fretting the one fin and the other fin, and the wall surface of the raw tube where they are in contact. The heat exchange can be performed smoothly and the durability of the heat transfer tube is improved.
[0078]
  In addition, the heat transfer tube having excellent heat exchange performance as described above, without requiring complicated alignment and dimensional adjustment, etc., by simply inserting the fin and the other fin into contact with each other, When the alignment is completed, it is possible to easily form a heat transfer tube by preventing misalignment or dropping from the raw tube. And by using this heat transfer tube excellent in heat exchange performance for a multi-tube heat exchanger, a radiator built-in oil cooler, etc., a product with high heat transfer characteristics and durability can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a heat transfer tube according to a first embodiment of the present invention.
FIG. 2 is an end view of FIG.
FIG. 3 is an enlarged perspective view of one piece of a second embodiment.
FIG. 4 is an enlarged perspective view of one piece of a third embodiment.
FIG. 5 is an enlarged perspective view of one piece of a fourth embodiment.
FIG. 6 is a perspective view showing a heat transfer tube of a fifth embodiment.
7 is a cross-sectional view of the heat transfer tube of FIG. 6 along the line AA.
FIG. 8 is an end view showing a heat transfer tube of a sixth embodiment.
FIG. 9 is an end view showing a heat transfer tube of a seventh embodiment.
FIG. 10 is an end view showing a heat transfer tube of an eighth embodiment.
FIG. 11 is an end view showing a heat transfer tube of a ninth embodiment.
FIG.Sectional drawing of the circumferential direction which shows the heat exchanger tube of 10th Example.
FIG. 13The expansion perspective view of only the one fin and other fin of 10th Example.
FIG. 14The perspective view of only one fin and the other fin of 11th Example.
FIG. 15The perspective view of only one fin and the other fin of 12th Example.
FIG. 16The perspective view of only one fin and the other fin of 13th Example.
FIG. 17The partial notch top view of the EGR gas cooling device which assembled | attached the heat exchanger tube of 1st invention of this application, and 2nd invention.
[Explanation of symbols]
  2 Elementary tube
  3 One fin
  4 Other fin
  5 bent part
  6 One piece
  7 The other piece
18 Spiral groove
31 Contact surface
32 ridges
33 Contact piece
34 Stopper
35 protrusions

Claims (8)

One fin and the other fin, in which one piece and the other piece are arranged in a crossing direction, are inserted and arranged in a metal tube, and the one fin and the other fin are arranged in one piece. The forming length is longer than 50% of the inner diameter of the base tube and shorter than 75%, and the one piece of the one fin and the one piece of the other fin are brought into surface contact with each other, and the forming length of the other piece is set. The inner tube is shorter than 50% and longer than 25%, and the inside of the tube is divided into four in the direction of the tube axis. The heat transfer tube is characterized in that the one fin and the other fin are brought into contact with each other in at least a part in the bent portion direction. One fin and the other fin, in which one piece and the other piece are arranged in the crossing direction, are inserted and arranged in a metal tube, and one piece and the other of the one fin and the other fin are inserted. The tip of the piece is brought into contact with the inner peripheral surface of the raw tube, and a stopper is provided on at least a part of the outer surface of the one piece and the other piece, and the other piece or one piece of the mating fin is brought into contact with the stopper. In this state, the one fin and the other fin are brought into contact with each other in at least a part in the direction of the bent portion. The one piece and / or the other piece forms a close contact surface by bending the tip side corresponding to a part of the inner peripheral surface of the raw tube, and this close contact surface is in surface contact with the inner peripheral surface of the raw tube. The heat transfer tube according to claim 1, wherein the heat transfer tube can be closely attached . The one piece and / or the other piece is provided with a protrusion that is long in the tube axis direction and has a V-shaped or U-shaped cross section in the circumferential direction of the raw tube. Heat transfer tube. 5. The raw tube is provided with at least one spiral groove protruding inward of the raw tube with one fin and the other fin disposed therein. Heat transfer tube. The close contact surface provided on the one piece and / or the other piece is characterized in that the formation width in the circumferential direction of the raw tube is 5% or more and 20% or less of the circumferential length of the inner peripheral surface of the raw tube. The heat transfer tube according to claim 3. The heat transfer tube according to claim 1, 2, 3, 4, 5 or 6, wherein the one piece and the other piece are twisted in the circumferential direction about the tube axis. The heat transfer tube according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the one piece and / or the other piece are provided with a plurality of embossed protrusions having a fixed length.

Images