Patent Publication Number: US-2006000587-A1

Title: Side plate with reduced warp for heat exchanger and heat exchanger using the same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a side plate, for a heat exchanger, formed by bending so as to have a U-shaped section and a heat exchanger using the same, and is preferably applicable to, for example, a condenser for vehicle air conditioning.  
      2. Description of the Related Art  
      In a conventional condenser for vehicle air conditioning, a side plate formed by bending so as to have a U-shaped section is arranged at the end of a core section composed of flat tubes and corrugated fins. Specifically, the side plate is joined by brazing to the corrugated fin at the outermost side of the core section and to the end of a header tank and serves to reinforce the core section and protect the corrugated fin, etc.  
      The side plate described above is, as shown in  FIG. 5 , a long and narrow member having a U-shaped section formed by a bottom section  21  and bent sections  22  and  23  on both sides thereof, and its length dimension L ranges between approximately 250 mm and 850 mm in accordance with the specifications of the condenser.  
      Being such a long and narrow member, a phenomenon occurs that the side plate warps arch-wise in the lengthwise direction when the side plate is formed by bending a plate-like aluminum material using a press die so as to have a U-shaped section. This is because a residual stress state of the material is unbalanced. The reference letter “a” in  FIG. 5  indicates the arch-like warp.  
      The cause of the occurrence of the warp a in the lengthwise direction of the side plate can be explained using  FIG. 6 . When forming the bent sections  22  and  23  by bending, a contracted (compressive) region A is formed in the inner part of the bent section and a stretched (tensile) region B is formed in the outer part of the bent section.  
      As the contracted (compressive) region A in the inner part of the bent section and the stretched (tensile) region B in the outer part in the bent section exist concurrently, if the distortion of the side plate in the lengthwise direction is observed, a stretched distortion C occurs in the inner part of the bent section and a contracted distortion D occurs in the outer part of the bent section. As a result, the side plate is brought into an unbalanced stress state, under stress, because of the coexistence of the contraction and stretch. Therefore, a phenomenon occurs that the side plate warps arch-wise in the lengthwise direction.  
      The inventors of the present invention have also confirmed that the arch-like warp a reaches 5.6 mm when the length L=814 mm.  
      If such a large warp a occurs, it becomes difficult to assemble the ends of the side plate in the lengthwise direction to the ends of the header tanks in the core assembling process before integrally brazing a condenser. Further when integrally brazing a condenser, a gap is produced between the side plate and the corrugated fin owing to the warp a, and poor joinability of the corrugated fin results.  
      Therefore, the inventors of the present invention have examined countermeasures such as so-called “forming in a holding state” in which pressure is applied to the bent sections  22  and  23  of the side plate in the direction of its height h, a countermeasure in which the back pressure to be applied to the bottom section  21  of the side plate is increased, etc. However, as pressure must be applied to an area to be pressed of a wide range across the entire length of the side plate in the lengthwise direction in any of these countermeasures, a high pressure is required and a large press machine is required. Because of this, the facility cost is raised and, therefore, these countermeasures are not practical.  
     SUMMARY OF THE INVENTION  
      The above-mentioned points being taken into account, the object of the present invention is to reduce a warp of a side plate in the lengthwise direction with a simple pressed form without the need to increase a press machine in size.  
      In order to attain the above-mentioned object, a side plate for a heat exchanger according to a first aspect of the present invention is characterized by being arranged at the end of a core section ( 13 ) composed of tubes ( 11 ) and fins ( 12 ), and having a long and narrow shape with a U-shaped section comprising a bottom section ( 21 ) and bent sections ( 22 ,  23 ) formed by bending both ends of the bottom section in the width direction thereof, and in that a plurality of recesses ( 24 ) extending in the width direction are formed by pressing the bottom section ( 21 ) at predetermined intervals (c).  
      According to this aspect, by forming the plurality of recesses ( 24 ) on the side plate bottom section ( 21 ) by pressing, a contracted region can be formed not only in the inner part of the bent section of the side plate but also in the outer part of the bent section.  
      Due to this, it is possible to bring the side plate into a balanced stress state, under no stress, and, as a result, the warp of the side plate in the lengthwise direction can be reduced.  
      Further, the recesses ( 24 ) can be formed only by partly pressing the bottom section ( 21 ) at the predetermined intervals (c), and as it is not necessary to apply a high pressure to the entire bottom section ( 21 ), the press machine can be prevented from becoming large in size.  
      In a side plate for a heat exchanger in a second aspect of the present invention according to the first aspect, the recesses ( 24 ) can be formed on the inner surface of the bottom section ( 21 ).  
      In a side plate for a heat exchanger in a third aspect of the present invention according to the first aspect, the recesses ( 24 ) may be formed on the outer surface of the bottom section ( 21 ).  
      In a side plate for a heat exchanger in a fourth aspect of the present invention according to any one of the first to third aspects, if the recesses ( 24 ) are formed into a shape having an arc-like section, the recesses ( 24 ) can be formed smoothly and the pressure to be applied for forming the recesses ( 24 ) can be reduced.  
      In a side plate for a heat exchanger in a fifth aspect of the present invention according to any one of the first to fourth aspects, the recesses ( 24 ) can be formed at the same time that the bent sections ( 22 ,  23 ) are formed by bending.  
      In a side plate for a heat exchanger in a sixth aspect of the present invention according to any one of the first to fourth aspects, the recesses ( 24 ) may be formed after the bent sections ( 22 ,  23 ) are formed by bending.  
      A heat exchanger in a seventh aspect of the present invention is characterized by comprising a core section ( 13 ) including of tubes ( 11 ) and fins ( 12 ) and side plates ( 19 ,  20 ) arranged on the ends of the core section ( 13 ), and in that the heat exchanger comprises the side plates ( 19 ,  20 ) for a heat exchanger in any one of the first to sixth aspects.  
      Due to this, it is possible to provide a heat exchanger capable of exhibiting the function and effect in the first to seventh aspects described above.  
      A heat exchanger in an eighth aspect of the present invention according to the seventh aspect is characterized in that header tanks ( 14 ,  15 ) with which the ends of the tubes ( 11 ) are communicated respectively are arranged on both ends of the tubes ( 11 ) in the lengthwise direction, the fins ( 12 ) are corrugated fins ( 12 ), and the tubes ( 11 ), the corrugated fins ( 12 ), and the header tanks ( 14 ,  15 ) are integrally joined by brazing and at the same time, the side plates ( 19 ,  20 ) are integrally joined by brazing to the corrugate fins ( 12 ) located on the ends of the core section ( 13 ) and to the ends of the header tanks ( 14 ,  15 ).  
      According to this aspect, in the heat exchanger assembled by brazing, the distance between the side plates ( 19 ,  20 ) and the corrugated fins ( 12 ) is reduced by reducing the warp of the side plates ( 19 ,  20 ) and thereby the joinability can be ensured and, at the same time, the workability in assembling the side plates ( 19 ,  20 ) to the ends of the header tanks ( 14 ,  15 ) can be improved.  
      The symbols in the parenthesis attached to each means described above indicate a correspondence with a specific means in the embodiments to be described later.  
      The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In the drawings:  
       FIG. 1  is a perspective view showing a general configuration of a condenser to which the present invention is applied.  
       FIG. 2A  is partly broken perspective view showing a side plate according to a first embodiment of the present invention.  
       FIG. 2B  is an essential part sectional view of the side plate in the lengthwise direction.  
       FIG. 2C  is an essential part sectional view of the side plate in the width direction.  
       FIG. 3  is a diagram for explaining a function of reducing the warp of the side plate according to the first embodiment.  
       FIG. 4  is a partly broken perspective view showing a side plate according to a second embodiment of the present invention.  
       FIG. 5  is a perspective view showing a side plate according to the prior art.  
       FIG. 6  is a diagram for explaining the cause of the occurrence of the warp of the side plate according to the prior art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
      The present embodiment relates to a condenser for vehicle air conditioning and, first of all, an outline of the condenser for vehicle air conditioning is explained by referring to  FIG. 1 . As is widely known, a condenser  10  is connected to the discharge side of a refrigerant of a compressor in a refrigerating cycle and cools and condenses the gas refrigerant discharged from the compressor with the outside air.  
      The condenser  10  has a core section  13  comprising a plurality of flat tubes  11  extending in the horizontal direction and a plurality of corrugated fins  12 , and on both the right end and the left end of the core section  13 , header tanks  14  and  15  having a substantially cylindrical shape and extending in the vertical direction are arranged, and both ends of the flat tubes  11  are communicated with the inside of the header tanks  14  and  15 .  
      At the upper part of the header tank  14  on one side, an inlet join  16  through which a discharged gas refrigerant, from a compressor, flows in, is connected and at the lower part of the header tank  15  on the other side, an outlet join  17  through which a refrigerant condensed and cooled in the core section  13  flows out, is connected.  
      The condenser  10  in the present embodiment forms a condensation section  13   a  for condensing a gas refrigerant at the upper part of the core section  13  and a cooling section  13   b  for cooling a liquid refrigerant after condensation at the lower part of the core section  13 . Then, a receiver  18  is integrally formed with the header tank  14  on the one side, the refrigerant at the outlet of the condensation section  13   a  is introduced into the inside of the receiver  18 , the refrigerant is separated into gas and liquid in the receiver  18 , and only the liquid refrigerant is caused to flow into the cooling section  13   b.    
      On the other hand, side plates  19  and  20  are arranged on both the upper end and the lower end of the core section  13 . The side plates  19  and  20  have a long and narrow shape extending in the horizontal direction on both the upper end and the lower end of the core section  13  and are formed by bending so as to have a U-shaped section.  
      Both ends of the side plate  19  in the lengthwise direction on the upper side are joined to the top ends of both the header tanks  14  and  15 . The U-shaped bottom section of the side plate  19  on the upper side comes into contact with and is joined to the corrugated fin  12  at the uppermost part of the core section  13 .  
      Both ends of the side plate  20  in the lengthwise direction on the lower side are joined to the bottom ends of both the header tanks  14  and  15 . The U-shaped bottom section of the side plate  20  on the lower side comes into contact with and is joined to the corrugated fin  12  at the lowermost part of the core section  13 . A plurality of mounting holes  19   a  and  20   a  are bored in the side plates  19  and  20  and the condenser  10  is mounted to the body of a vehicle using the mounting holes  19   a  and  20   a , and means such as screw fixing.  
      The constituent members  11 ,  12 , and  14  to  20  of the condenser shown in  FIG. 1  are formed of aluminum alloy and are assembled into a structure shown in  FIG. 1 , and the assembled body is brought into a heating oven while being held with a jig. The assembled body is heated to a temperature higher than the melting point of the brazing material in the heating oven and each member is integrally brazed into a single unit.  
      Because of this, in order to smoothly carry out assembling of the condenser before the brazing process and ensure excellent brazing properties, it is important to keep the arch-like warp a (refer to  FIG. 6  described above) of the side plates  19  and  20  in the lengthwise direction as small as possible.  
      Countermeasures to reduce the arch-like warp a in the present embodiment are explained based on  FIGS. 2A and 2B .  FIG. 2A  is a partly broken perspective view of the side plates  19  and  20 ,  FIG. 2B  is an essential part sectional view of the side plates  19  and  20  in the lengthwise direction, and  FIG. 2C  is an essential part sectional view of the side plates  19  and  20  in the width direction (direction perpendicular to the lengthwise direction).  
      The side plates  19  and  20  each have a U-shaped section formed by the bottom section  21  and the bent sections  22  and  23  located on both the right end and the left end of the bottom section  21  in the width direction. The material of the side plates  19  and  20  is a bare aluminum material with no clad brazing material. JIS (Japanese Industrial Standard)-A 3003 is used in the present embodiment, and its thickness t is, for example, 1.6 mm.  
      A plurality of recesses  24  having a minuscule depth b of the bottom section  21  are parallel formed on the U-shaped inner surface at constant intervals c across the entire length of the side plates  19  and  20  in the lengthwise direction. The recess  24  has a long and narrow shape extending in the width direction of the bottom section  21  and its section has an arc shape (R-shape) with a predetermined radius as shown in  FIG. 2B . The depth is, for example, as minuscule as 0.04 mm. The width d of the recess  24  is, for example, 1.5 mm.  
      The length f of the recess  24  is 8 mm. Here, the width dimension e of the bottom section  21  is, for example, 12.8 mm and, therefore, the length f of the recess  24  occupies 60% or more of the width dimension e of the bottom section  21 .  
      On each of both ends of the recess  24  in the lengthwise direction, a slope surface  24   a  is formed so that both ends of the recess  24  in the lengthwise direction are smoothly connected to the inner surface of the bottom section  21 . Here, the angle θ between the slope surface  24   a  and the line vertical to the bottom section  21  is, for example, 75°.  
      The formation of the above-mentioned recesses  24  can be carried out together with the formation of the side plates  19  and  20  by bending. In other words, protrusions (rib-shaped) each having an arc-like section for partly pressing the bottom section  21  at the constant intervals c are formed in advance in a press die for forming by bending a plate-like aluminum material into a side plate comprising the bottom section  21  and the bent sections  22  and  23  and having a U-shaped section. Due to this, it is possible to form the U-shaped section by bending using the press die and simultaneously to form a number of recesses  24  by pressing.  
      The reason why it is possible to reduce the warp of the side plates  19  and  20  by forming the recesses  24  by pressing is explained below. As shown in  FIG. 3 , it is possible to produce a contraction stress E by forming the recesses  24  by pressing and thereby, a contraction region F is formed also in the outer part of the bent section.  
      In other words, the stretched (tensile) region B in the outer part of the bent section in  FIG. 6  is changed to the contracted region F in the present embodiment, that is, both the regions in the inner part and in the outer part of the bent section are the contracted (compressive) regions A and F and a balanced stress state, under no stress, is established.  
      As a result, it is possible to reduce the arch-like warp of the side plate in the lengthwise direction by producing a stretched distortion both in the inner part and in the outer part of the bent section in the lengthwise direction of the side plate and at the same time, bringing the stretched distortions in the inner part and in the outer part of the bent section into a balanced state.  
      The inventors of the present invention measured the magnitude of the arch-like warp a while changing the interval c between the recesses  24  based on the above-mentioned design example with the total length L=814 mm, and obtained the following results.  
      Interval c=40 mm . . . warp a=2.6 mm  
      Interval c=30 mm . . . warp a=1.5 mm  
      Interval c=20 mm . . . warp a=0.3 mm  
      As described above, it has been found that the warp a=5.6 mm in the conventional example shown in  FIG. 5  can be more than halved by setting the interval c between the recesses  24  to a value equal to or less than 40 mm.  
      From the results discussed above, it will be understood that the smaller the interval c, the more the warp a can be reduced. However, if the interval c is reduced excessively, the contracted region F in the outer part of the bent section becomes dominant over the contracted region A in the inner part of the bent section and the side plates.  19  and  20  warp in the opposite direction of the warp a shown in  FIG. 5 . Therefore, in the present embodiment, it is preferable to set the lower limit of the interval c to around 20 mm.  
      According to a study by the inventors of the present invention, it is possible to form the recesses  24  after forming the side plates  19  and  20  by bending. It has been confirmed that the arch-like warp a can be similarly reduced in this manner.  
      On the other hand, if the formation of the recesses  24  on a plate-like aluminum material is carried out before the formation of the side plates  19  and  20  by bending, a phenomenon occurs in that, due to the residual stress accompanying the formation of the recesses  24 , the plate-like aluminum material warps in the opposite direction of the warp a in  FIG. 5 . The occurrence of the warp makes it difficult to insert the plate-like aluminum material into the press die. Therefore, it is not preferable to carry out the formation of the recesses  24  before the formation of the side plates  19  and  20  by bending.  
     Second Embodiment  
      Although the recesses  24  are formed on the inner surface of the bottom section  21  of the side plates  19  and  20  having a U shaped section in the first embodiment, the recesses  24  are formed on the outer surface of the bottom section  21  in the second embodiment as shown in  FIG. 4 .  
      It has been confirmed that even if the recesses  24  are formed on the outer surface of the bottom section  21  as described above, the warp a can be reduced as in the first embodiment.  
      However, as is seen from  FIG. 1 , the corrugated fin  12  is joined by brazing to the outer surface of the bottom section  21  of the side plates  19  and  20  and, therefore, the formation of the recesses  24  on the outer surface deteriorates the joinability (brazing properties) between the side plates  19  and  20  and the corrugated fin  12 . Therefore, from the viewpoint of the joinability, the first embodiment is preferable to the second embodiment.  
     Other Embodiments  
      In the above mentioned embodiments, although the shape of the section of the recess  24  is an arc, it is also possible to obtain the same effect to reduce the arch like warp a even if the shape of the section of the recess  24  is formed into a trapezoidal shape. However, as a trapezoidal shape is formed of combined flat surfaces, the pressure to be applied for forming the recesses by pressing is increased compared to the case of an arc shape.  
      In the above mentioned embodiments, although the interval c between the recesses  24  is constant across the entire area of the bottom section  21  in the lengthwise direction, it may be possible to change the interval c between the recesses  24  in the lengthwise direction of the bottom section  21  as the need arises.  
      In the above mentioned embodiments, examples are shown in which the present invention is applied to the side plates  19  and  20  in a condenser in a refrigerating cycle, however, the present invention can be similarly applied to a heat exchanger such as a radiator because side plates having a U shaped section are mounted on a heat exchanger such as a radiator for cooling the cooling water for a vehicle engine.  
      While the invention has been described by reference to specific embodiments chosen for the purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention.