Patent Publication Number: US-6340055-B1

Title: Heat exchanger having multi-hole structured tube

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of Japanese Patent Applications No. 11-145323 filed on May 25, 1999, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to heat exchangers suitable for a radiator, an evaporator, or the like in a refrigerating cycle. 
     2. Description of the Related Art 
     JP-A-1-351783 proposes a heat exchanger in which, as shown in FIG. 15A, notch portions  211   a  indicated with slant lines are provided at both long-side end portions of a tube  211  to reduce a size of the heat exchanger in a direction parallel to an air flow direction. 
     On the other hand, as shown in FIG. 15B, a tube  211 , which is generally used at a high internal pressure state for a heat exchanger such as a condensers a radiator, or a heat exchanger of a super critical refrigerating cycle, adopts a multi-hole structure having several passage holes  211   b  arranged in the cross-sectional long-side direction thereof, thereby improving a withstand pressure of the tube  211 . The super critical refrigerating cycle uses refrigerant such as carbon dioxide, ethylene, ethane, or nitrogen oxide, a pressure of which exceeds a super critical pressure. 
     SUMMARY OF THE INVENTION 
     However, it has been revealed by the inventors that the following problems were liable to occur when the structure proposed in JP-A-11-351783 was applied to the tube  211  having the multi-hole structure. Specifically, the passage holes  211   b  are formed at the same time when the tube  211  is formed by extrusion molding or the like. If the notch portions  211   a  are formed on the tube  211  by cutting after the passage holes  211   b  are formed, as shown in FIG. 16A, the cut surface is liable to be crushed at a vicinal region of the passage holes  211   b . When the cut surface is crushed to form a crushed portion  160  and the tube  211  is inserted into a header tank with the crushed portion  160 , the crushed portion  160  forms a space between the tube  211  and the header tank, and the space induces joining failure (welding failure) therebetween readily. Further, if the tube  211  has manufacture variations when it is formed and it is cut, as shown in FIG. 16B, one of the passage holes  211   b  may be cut. The cut hole  211   b  forms a space (gap), which can induce the joining failure between the tube  211  and the header tank readily. 
     The present invention has been made in view of the above problems. An object of the present invention is to prevent joining failure between a multi-hole structured tube and a header tank in a heat exchanger. 
     According to the present invention, a tube for a heat exchanger has an end portion in a longitudinal direction thereof. The end portion is formed by a cut surface, which extends in the longitudinal direction of the tube and defines an end portion width, which is smaller than a tube width at a portion of the tube other than the end portion. The end portion width and the tube width are perpendicular to the longitudinal direction and parallel to a cross-sectional long side direction of the tube. The tube has a plurality of passage holes arranged in the cross-sectional long side direction within the end portion width, and a hole of the passage holes disposed most adjacently to the cut surface defines a specific distance δ 0  from the cut surface. 
     Accordingly, the hole and the cut surface can be prevented from being crushed when the cut surface is formed. When the end portion of the tube is inserted into a header tank, no gap is produced between the tube and the header tank, thereby preventing joining failure between the tube and the header tank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings, in which; 
     FIG. 1 is a perspective view showing a heat exchanger in a first preferred embodiment of the present invention; 
     FIG. 2 is a cross-sectional view showing a joining portion between a header and a tube in the first embodiment; 
     FIG. 3 is an exploded perspective view showing the header and the tube; 
     FIG. 4 is a front view showing a separator; 
     FIG. 5 is a front view showing a cap; 
     FIG. 6A is a front view showing a longitudinal direction end portion of the tube in the first embodiment; 
     FIG. 6B is a plan view showing the longitudinal direction end portion of the tube in a direction indicated by arrow VIB in FIG. 6A; 
     FIG. 7 is a cross-sectional view showing a core portion of the heat exchanger in the first embodiment; 
     FIG. 8 is a cross-sectional view showing a core portion of a heat exchanger as a comparative example; 
     FIG. 9A is a front view showing a longitudinal direction end portion of a tube in a second preferred embodiment; 
     FIG. 9B is a plan view showing the longitudinal direction end portion of the tube, in a direction indicated by arrow IXB in FIG. 9A; 
     FIG. 10A is a front view showing a longitudinal direction end portion of a modified tube in the second embodiment; 
     FIG. 10B is a plan view showing the longitudinal direction end portion of the tube in a direction indicated by arrow XB in FIG. 10A; 
     FIG. 11A is a front view showing a longitudinal direction end portion of a tube in a third preferred embodiment; 
     FIG. 11B is a plan view showing the longitudinal direction end portion of the tube in a direction indicated by arrow XIB in FIG. 11A; 
     FIG. 12A is a front view showing a longitudinal direction end portion of a tube in a modified embodiment of the present invention; 
     FIG. 12B is a plan view showing the longitudinal direction end portion of the tube in a direction indicated by arrow XIIB in FIG. 12A; 
     FIG. 13 is a cross-sectional view showing a core portion of a heat exchanger in another modified embodiment of the present invention; 
     FIG. 14A is a front view showing a longitudinal direction end portion of a tube in another modified embodiment of the present invention; 
     FIG. 14B is a plan view showing the longitudinal direction end portion of the tube in a direction indicated by arrow XIVB in FIG. 14A; 
     FIG. 15A is a front view showing a longitudinal direction end portion of a tube according to a prior art; 
     FIG. 15B is a plan view showing the longitudinal direction end portion of the tube in a direction indicated by arrow XVB in FIG. 15A; and 
     FIGS. 16A and 16B are enlarged cross-sectional views partially showing a tube for explaining conventional problems. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (First Embodiment) 
     In a first preferred embodiment of the present invention, a heat exchanger according to the present invention is adopted to an evaporator  100  of a super critical refrigerating cycle using carbon dioxide as refrigerant. 
     Referring to FIG. 1, the evaporator  100  has several flat tubes  111  extending in a vertical direction in which refrigerant (fluid) flows. The tubes  111  are formed from aluminum members by extrusion molding. Aluminum corrugated fins  112  are respectively disposed between and joined to adjacent two of the tubes  111 , thereby increasing a radiation area for facilitating heat exchange between refrigerant and air. Both front and back surfaces of each of the corrugated fins  112  are clad with brazing filler metal. The fins  112  and the tubers  111  are integrated with one another by brazing, thereby forming a core portion  110  of the evaporator  100 . 
     Side plates  113  for reinforcement are brazed to the fins  112  by the brazing filler metal coated on the fins  112  at both ends of the core portion  110  in a lamination direction of the tubes  111 . Header tanks (herebelow, referred to as header)  120  are joined to the tubes  111  at upper and lower ends in the longitudinal direction of the tubes  111 . The headers  120  extend in a direction perpendicular to the longitudinal direction of the tube  111  and communicate with the respective tubes  111 . In FIG. 1, the lower side header  120  is to distribute refrigerant into the respective tubes  111 , and the upper side header  120  is to collect refrigerant discharged from the tubes  111 . The evaporator  100  has two joint blocks  131 ,  132 . The joint block  131  is connected to a pressure reducing valve side (not shown), and the joint block  132  is connected to a compressor side (not shown) in the super critical refrigerating cycle. 
     As shown in FIGS. 2 and 3, each of the headers  120  is composed of a first plate  121  having first insertion holes  121   a  into which the flat tubes  111  are respectively inserted, and a second plate  122  joined to the first plate  121  to form a passage in which refrigerant flows. The second plate  122  integrally has an inner pillar member  123 , which extends in the longitudinal direction of the header  120  and protrudes toward the side of the first plate  121 . A front end portion of the inner pillar member  123  is joined to the inner wall of the first plate  121 , so that the inner walls of the plates  121  and  122  are connected to each other via the inner pillar member  123 . The inner pillar member  123  divides the inner space of the tube  120  into first and second spaces  120   a  and  120   b , respectively extending in the longitudinal direction of the header  120 . 
     In the present embodiment, the front end portion of the inner pillar member  123  at a side of the first plate  1221  is partially cut by milling, thereby forming communication passages  123   a . The communication passages  123   a  are, as shown in FIG. 2, provided correspondingly to the first insertion holes  121   a . The inner pillar member  123  has across-section, a width W of which increases as it approaches either one of the inner walls of the plates  121  and  122 . The cross-section of the inner pillar member  123  is arched so that each of the spaces  120   a  and  120   b  has a generally circular cross-section. The width W of the inner pillar member  123  is a dimension in a direction parallel to a longer radial direction of the flat (elliptic) header  120 . 
     The first plate  121  is formed from an aluminum member (A3003 system) by pressing, and the second plate  122  is formed from an aluminum member (A3003 system) by extrusion. Front and back surfaces of each of the plates  121 ,  122  are clad with brazing filler metal, and the plates  121 ,  122  having the inner pillar member  123 , the tubes  111 , and the side plates  113  are integrally brazed to one another by the brazing filler metal. 
     Referring back to FIG. 1, a separator  130  is disposed within the header  120  to divide the first and second spaces  120   a ,  120   b  into several spaces in the longitudinal direction of the header  120 . Refrigerant flows in the core portion  110  with an S-like shape due to the separator  130 . As shown in FIG. 4, the separator  130  is composed of first and second disk portions  131 ,  132 , a connecting portion  133  connecting the disk portions  131 ,  132  therebetween, and a protruding portion  134  protruding from the connecting portion  133  toward the side of the first plate  121 . The portions  131 - 134  are integrally formed from an A3003 system aluminum plate member by pressing. 
     On the other hand, as shown in FIG. 3, the first plate  121  has a second insertion hole  121   b  for receiving the protruding portion  134  therein. The separator  130  is brazed to the inner walls of the plates  121 ,  122  and the inner pillar member  123  in the sate where the protruding portion  134  is inserted into the second insertion hole  121   b.    
     Referring back again to FIG. 1, aluminum header caps  140  are brazed to the header  120  to close respective ends of the first and second spaces  120   a ,  120   b  in the longitudinal direction of the header  120 . As shown in FIG. 5, each of the caps  140  has columnar protruding portions  141  for being inserted into the first and second spaces  120   a ,  120   b , and each protruding portion  141  has a generally spherical surface portion  142  at a front end thereof. The caps  140  are also brazed to the header  120  (both the plates  121 ,  122 ) by brazing filler metal sprayed on the caps  140 . 
     Next, the structure of the tube  111  will be explained below. 
     As shown in FIG. 2, the tubes  111  has a maximum cross-sectional long side dimension (tube width T W0 ), which is larger than inner wall width T W1  and is equal to or smaller than outer wall width T W2  of the header  120 . As shown in FIG. 6A, the tube  111  has a longitudinal end portion, both cross-sectional long side ends of which are cut to form notch portions  111   a  as indicated by slant lines in the figure, and the longitudinal end portion is inserted into the header  120 . 
     Incidentally, the inner wall width T W1  of the header  120  is a maximum dimension defined by the inner wall of the header  120  in a direction parallel to the cross-sectional long side of the tube  111 , i.e., parallel to an air flow direction. The outer wall width T W2  of the header  120  is a maximum dimension defined by the outer wall of the header in the direction parallel to the cross-sectional long side of the tube  111 , i.e., parallel to the air flow direction. 
     On the other hand, as shown in FIG. 6B, several passage holes  111   b  each having a circular shape in cross-section are provided in the tube  111  to extend in the longitudinal direction of the tube  111 . The passage holes  111   b  are arranged in the cross-sectional long side direction of the tube  111  within a dimension (end portion width) L, which is smaller than the inner wall width T W1  of the header  120 . The dimension L is a dimension of a portion of the tube  111 , which is to be inserted into the first insertion hole  121   a . Therefore, the dimension L is determined in consideration of manufacture tolerances (variations) of the tube  111 , the first plate  121 , the first insertion hole  121   a , and the notch portions  111   a.    
     A distance δ 0  between one of the passage holes  111   b  disposed at the end in the long side direction of the tube  11  and the cut surfaces S of one of the notch portions  111   a  is the sum of dimensions δ 1 , δ 2 , and δ 3 . The dimension δ 1  is a dimension required for preventing the passage holes  111   b  from being crushed when the notch portions  111   a  are formed, i.e., when the both ends of the tubes  111  are removed by cutting to form the notch portions  111   a . The dimension δ 2  is a dimensional tolerance between two passage holes  111   b , i.e., a positional tolerance of a pillar portion having a length  111   c  and provided between the two passage holes  111   b . The dimension δ 3  is a positional cut tolerance (positional variation amount) of the cut surfaces S. Incidentally, the length  111   c  is a pitch of the passage holes  111   b , and the distance δ 0  is larger than the pitch  111   c.    
     As shown in FIG. 7, one of the cross-sectional long side ends of the tube  111 , which is disposed at the air flow downstream side, is tapered as a tapered portion  151 , a thickness of which is decreased as it approaches the front end (air flow downstream side) thereof. Accordingly, the tapered portion  151  of the tube  111  forms gaps  150  at both sides thereof with the fins  112  not to contact the fins  112 . 
     Because of this, the cross-sectional long side end of the tube  111  at the air flow downstream side has a curve Rr, which is smaller than a curve Rf at the air flow upstream side. Each of the gaps  150  has a dimension L 2  parallel to the cross-sectional long side direction of the tube  111 , and the dimension L 2  is larger than a half (=Rf) of the thickness h of the tube  111 . The thickness h of the tube  111  is a length of the tube in a cross-sectional short side direction of the tube  111 , and is approximately twice of the curve Rf at the air flow upstream side in the present embodiment. Incidentally, in FIG. 7, reference numerals  112   a  denotes louvers, which hare formed by partially cutting and bending the fin  112  to prevent a temperature boundary layer from being produced between the fin  112  and air. 
     Next, features of the present invention will be explained below. 
     The passage holes  111   b  are arranged in the cross-sectional long-side direction within the dimension L, which is smaller than the inner wall width T W1  of the header  120 . Therefore, the tube  111  of the present embodiment has portions corresponding to the notch portions  111   a  where no passage holes  111   b  are formed at the cross-sectional long side end portions. The passage holes  111   b  are prevented from being provided in the vicinity of the cut surfaces S. 
     Therefore, when the cross-sectional long side end portions of the tube  111  are removed by cutting to form the notch portions  111   a , the cut surfaces S are prevented form being crushed or sagged. In addition, the passage holes  111   b  are securely prevented from being cut when the notch portions  111   a  are formed. As a result, when the tube  111  is inserted into the first insertion hole  121   a , no gap is produced between the tube  111  and the first plate  121 . Therefore, joining failure (welding failure) does not occur between the tube  111  and the header  120 . 
     Thus, according to the present embodiment, the joining failure (welding failure) is prevented from occurring between the tube  111  and the header  120  while preventing an increase in manufacture cost of the tube  111  (evaporator  100 ). In addition, the tube  111  has the notch portions  111   a . Therefore, the effects described above can be achieved while maintaining a sufficient heat exchange capacity of the evaporator  100 . 
     As described above referring to FIG. 7, the gaps  150  are formed at the cross-sectional long side and air flow downstream side end of the tube  111 . Condensed water condensed on the surfaces of the fin  112  and the tube  111  gathers in the gaps  150  by a surface tension thereof (capillary phenomenon by the gaps  150 ) and flows downwardly along the tube  111 . As a result, the drainage property of condensed water is improved. Further, because the thickness of the tapered portion  151  is decreased as it approaches the front end thereof at the air flow downstream side, each of the gaps  150  has a wedge shape sharpened with an acute angle at the air flow upstream side thereof. This makes it secure to gather and drain condensed water. 
     When the passage holes  111   b  are formed entirely in the cross-sectional long side direction of the tube  111  as a conventional manner, as shown in FIG. 8, some of the passage holes  111   b  provided at the tapered portion  151  are crushed. Because of this, teeth used at the extrusion processing of the tube  111  are thinned to be broken readily. As opposed to this, according to the present embodiment, any of the passage holes  111   b  are not formed at the tapered portion  151 . Therefore, the teeth used at the extrusion processing need not be thinned, thereby preventing the damage to the teeth. 
     (Second Embodiment) 
     In the first embodiment, the tube  111  has no hole extending in the longitudinal direction of the tube  111 , at the cross-sectional long side ends with respect to the cut surfaces S. In a second preferred embodiment, as shown in FIG. 9A, holes  111   b  arranged in the cross-sectional long side direction of the tube  111  include holes provided at the cross-sectional long side ends with respect to the cut surfaces S. In this case, as shown in FIG. 9B, a pitch  111   c  of the passage holes  111   b  is increased to a pitch P at portions corresponding to the cut surfaces S as compared to the other portions. More specifically, a half of the pitch P is larger than the pitch  111   c , so that the distance of one of the passage holes  111   b , which is provided most adjacently to one of the cut surfaces S from the one of the cut surfaces S is set to be larger than the pitch  111   c . In this embodiment, only the holes  111   b  provided between the cut surfaces S function as passage holes in which refrigerant flows. 
     In the tube  111  according to the present embodiment, any of the holes  111   b  are not provided in the vicinity of the cut surfaces S. Therefore,the cut surfaces S are prevented from being sagged or deformed when the cross-sectional long side end portions of the tube  111  are removed by cutting. Incidentally, as shown in FIGS. 10A and 10B, each shape of the holes  111   b  provided at the cross-sectional long side ends with respect to the cut surfaces S is not limited to a circular shape, but may be other shapes. 
     (Third Embodiment) 
     In the first embodiment, the cut surface S is provided between the passage holes  111   b  and the tapered portion  151 . However, as shown in FIGS. 11A and 11B, the cut surface S may be provide by cutting a part of the tapered portion  151  in a thickness direction of the tube  111 . Accordingly, a cut length of the cut surface S can be decreased, resulting in decrease in man-hour of the step for forming the notch portions  111   a . This further results in decreased manufacture cost of the tube  111 . Here the cut length of the cut surface S is a dimension of the cut surface S in the thickness direction of the tube  111 . 
     In the embodiments described above, the present invention is applied to the evaporator, but is not limited to that. The present invention can be applied to other heat exchangers such as a radiator for a super critical refrigerating cycle and a condenser for a refrigerating cycle. The tubes  111  may be disposed to extend in a horizontal direction. Also, in the embodiments described above, although the tube width T W0  is set to be less than the outer wall width T W2  of the header  120 , the tube width T W0  may be set to be larger than the outer wall width T W2  of the header  120 . 
     In the third embodiment, although the tapered portions  151  are formed at the both ends in the cross-sectional long side direction of the tube  111 , the tapered portions  151  may be formed at only one of the ends of the tube  111 . In the embodiments described above, the notch portions  111   a  are provided at the both ends in the cross-sectional long side direction of the tube  111 . However, as shown in FIGS. 12A and 12B, the notch portion  111   a  may be provided at only one of the ends of the tube  111 . The shape of each passage hole  111   b  is not limited to a circle in cross section, but may be other shapes such as a rectangle shown in FIG. 13, a polygon, or an elliptic shape. 
     In the first and second embodiments, the tapered portion(s)  151  is formed at the cross-sectional long side end(s) of the tube  111 . However, as shown in FIGS. 14A and 14B, the tube  111  can dispense with the tapered portion  151 . Further, as shown in FIG. 7, the tapered surface of the tapered portion  151  is flat and extends linearly in cross section in the first and third embodiments. However, the tapered surface may be curved in cross section. It is apparent that one of the embodiments described above can be combined with another one of the embodiments appropriately. 
     While the present invention has been shown and described with reference to the foregoing preferred embodiments, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.