GB2108648A - Heat exchanger - Google Patents

Abstract

A heat-exchanging core (1), has an end cover member (5, 6) mounted on the opposite end portions to define a chamber (8, 9) for receiving one of first and second fluids which are allowed to pass through the core for mutual heat-exchanging. Assembly (130) for sealingly mounting the end cover member (5, 6) on the core (1) includes a mounting member (131) secured to the core (1) and having a channel section (133) for receiving a peripheral attaching portion (22) on the end cover member (5, 6) upon a resilient sealing member (138) disposed on the bottom wall (137) of the channel section (133). A staking member (141) engages with an outer surface of the channel section (133) and is staked against a surface section (26) of the attaching portion. The inner surface (139) of the bottom wall (137) of the mounting member (131) is maintained in such condition that it is subjected to a compressive stress, after the staking of the staking member (141). <IMAGE>

Description

SPECIFICATION Heat exchanger The present invention relates to an improvement in a heat exchanger comprising a heat-exchanging core made of a metal and end cover members made of a resin and respectively mounted on the opposite end portions of the core by means of a staking working. Particularly, the present invention is suitably applicable to a radiator for use in motor vehicles, for example.

Description of the Prior Art In a heat exchanger of the kind referred to above, a heat-exchanging core allows first and second fluids to pass through the core to cause the heat-exchanging to be performed between the first and second fluids. Each of end cover members is mounted on and cooperates with the associated end portion of the core to define a chamber for receiving therein one of the first and second fluids. The end cover member is provided at a peripheral edge thereof with a peripheral attaching portion.

A sealingly mounting assembly for sealingly mounting the end cover member on the end portion of the core includes a mounting member which has an inner peripheral edge thereof secured to the core and a peripheral channel section spaced outwardly from the core.

The channel section has opposed side walls and a bottom wall extending therebetween, which walls have their respective inner surfaces cooperating with each other to define an open channel for receiving therein the peripheral attaching portion on the end cover member. A resilient sealing member is disposed between the inner surface of the bottom wall of the channel section and a first surface area of the peripheral attaching portion on the end cover member received in the open channel, which first surface area is faced to the inner surface of the bottom wall of the channel section. A staking member engages with an outer surface of the channel section and is staked against a second surface area of the peripheral attaching portion on the end cover member opposite to the first surface area thereof.

With the arrangement of the prior art heat exchanger, the fluid received within the chamber penetrates into a gap or interface between the resilient sealing member and the inner surface of the bottom wall of the channel section on the mounting member. If the fluid received within the chamber is inferior in quality, the inferior fluid penetrated into the gap or interface causes cracking to occur in the inner surface of the bottom wall of the channel section on the mounting member, along the crystal intergranular from the inner surface in the direction of the thickness of the bottom wall. This decreases the service life of the heat exchanger. The inventors of the present application have found the fact that such cracking is a stress corrosion cracking.The term "stress corrosion cracking" means a cracking caused to occur by the interaction of a chemical action called "corrosion" and a physical action called "stress". The reason why such stress corrosion cracking occurs will be described later in detail.

According to the present invention, there is provided a heat exchanger comprising a heatexchanging core made of a metal for aliowing first and second fluids to pass through the core to cause the heat-exchanging to be performed between the first and second fluids; an end cover member associated with each of the opposite end portions of the core, the end cover member being mounted on and cooperating with the end portion of the core to define a chamber for receiving therein one of the first and second fluids, the end cover member being provided at a peripheral edge thereof with a peripheral attaching portion; a sealingly mounting assembly for sealingly mounting the end cover member on the end portion of the core, the sealingly mounting assembly including a mounting member having an inner peripheral edge thereof secured to the core and a peripheral channel section spaced outwardly from the core, the channel section having opposed side walls and a bottom wall extending therebetween which walls have their respective inner surfaces cooperating with each other to define an open channel for receiving therein the peripheral attaching portion on the end cover member, a resilient sealing member disposed between the inner surface of the bottom wall of the channel section and a first surface area of the peripheral attaching portion on the end cover member received in the open channel, the first surface area of the peripheral attaching portion being faced to the inner surface of the bottom wall of the channel section, and a staking member engaging with an outer surface of the channel section and staked against a second surface area of the peripheral attaching portion on the end cover member opposite to the first surface area thereof such that a compressive strain is developed in the inner surface of the bottom wall of the channel section of the mounting member, to fixedly mount the peripheral attaching portion on the end cover member within the channel section of the mounting member; and the inner surface of the bottom wall of the channel section of the mounting member being maintained in such condition that the inner surface of the bottom wall is subjected to a compressive stress, after the peripheral attaching portion is fixedly mounted within the channel section of the mounting member by the staking member.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a front elevational view, partially broken away, of a heat exchanger or radiator in accordance with an embodiment of the present invention; Fig. 2 is a fragmentally enlarged cross-sectional view similar to that taken along the line VIl-Vil of Fig. 1, showing a mounting structure of the prior art heat exchanger; Fig. 3 is a front elevational view of a staking member shown in Fig. 2; Fig. 4 is a cross-sectional view taken along the line IV-IV of Fig. 3; Figs. 5a-5d are fragmentally cross-sectionai views showing successive staking steps of forming the prior art mounting structure shown in Fig. 2;; Fig. 6 is a graph showing a strain developed in a bottom wall of a mounting member during the staking working with the strain developed in the prior art mounting structure indicated by the solid line and the strain developed in a mounting structure of a heat exchanger in accordance with the embodiment of the present invention indicated by the broken line; Fig. 7 is a fragmentally enlarged cross-sectional view taken along the line VIl-VIl of Fig. 1, showing the mounting structure of the heat exchanger in accordance with the embodiment of the present invention; Fig. 8 is a front elevational view of a staking member shown in Fig. 7; Fig. 9 is a cross-sectional view taken along the line IX-IX of Fig. 8:: Fig. 10 is a graph showing the relation between the stress applied to the bottom wall of the mounting member and the value of (H - h); and Fig. 11 is a fragmentally enlarged crosssectional view showing a staking die assembly used in staking the staking member against a peripheral attaching portion of an end cover member in accordance with the embodiment of the present invention.

Referring to Fig. 1 there is shown an heat exchanger, and more particularly a radiator for use in motor vehicles, for example, in accordance with the embodiment of the present invention. The heat exchanger comprises a heat-exchanging core 1 which includes a plurality of tubes 3 made of brass and extending in parallel and substantially equidistantly spaced relation to each other, and corrugated fines 4 made of copper. Each of the corrugated fines 4 is disposed between each pair of adjacent tubes 3 and has crests and roots secured to one and the other of the adjacent two tubes 3, respectively.

End cover members 5 and 6 made of a resin are respectively mounted on the opposite end portions of the core 1 in a fluid-tight manner by means of sealingly mounting assemblies which are not shown in Fig. 1, but will be described later.

The end cover member 5 and 6 respectively cooperate with the opposite end portions of the core 1 to define inlet and outlet chambers 8 and 9 which are communicated with each other by means of the tubes 3. The end cover member 5 has formed integrally therewith a short pipe section 11 defining an opening through which a cooling liquid or water is replenished into the inlet chamber 8. The opening of the pipe section 11 is normally closed by a cap 12. The end cover member 5 has further formed integrally therewith a fitting pipe section 13 to which a pipe is adapted to be connected for introducing into the inlet chamber 8 the cooling liquid after cooling an instrument to be cooled, such as an internal combustion engine for motor vehicles, for example.The cooling liquid flows from the inlet chamber 8 to the outlet chamber 9 through the tubes 3 and is cooled by a fluid or air passing through the core 1 in contact with the corrugated fins 4 and the outer peripheral surfaces of the tubes 3. The other end cover member 6 has formed integrally therewith a fitting pipe section 14 to which a pipe is adapted to be connected for delivering the cooled cooling liquid from the outlet chamber 9 to cool the instrument to be cooled.

The reason why the stress corrosion cracking described previously in "Description of the Prior Art" occurs will be discussed in more detailed manner with reference to Fig. 2 which is a crosssectional view similar to that taken along the line VIl-VIl of Fig.1, showing the mounting structure of the prior art heat exchanger. In Fig. 2, the same reference characters are applied to parts and members common in function to those shown in Fig. 1. In addition, although the following description will be directed only to the connection between the end cover member 5 and the core 1, it is to be understood that the same is equally appiicable to the connection between the end cover member 6 and the core 1, because the end cover member 6 is substantially identical in structure with the end cover member 5.

Accordingly, the description regarding the connection between the end cover member 6 and the core 1 will be omitted for simplification.

As shown in Fig. 2, the end cover member 5 has a body 21 and an peripheral attaching portion or peripheral bead 22 integrally connected to the entire peripheral edge of the body 21 by a peripheral web portion 23. The bead 22 has a parallelogrammic cross-sectional shape and has parallel peripheral inner and outer surfaces 24 and 25, and parallel peripheral top and bottom surfaces 26 and 27. The end cover member 5 is mounted on the end portion of the core 1 in a fluid-tight manner by means of a sealingly mounting assembly generally designated by the reference character 30 and peripherally continuously extending along the bead 22 on the end cover member 5. The mounting assembly 30 includes a mounting member 31 formed of a brass plate having a thickness of at most 1.2 mm. The mounting member 31 has a flange 32 secured to the core 1 by means of soldering, brazing or the like, a channel section 33 and a connecting web section 34 extending between and integrally connecting the flange 32 and the channel section 33 to each other. The channel section 33 includes substantially parallel peripheral inner and outer side walls 35 and 36 and a bottom wall 37 extending therebetween, which walls 35, 36 and 37 cooperate with each other to define an open channel having a generally U-shaped crosssection for receiving therein the bead 22 on the end cover member 5.A peripherally continuously extending resilient sealing member 38 made of a rubber such as nitrile-butadiene rubber and having a circular cross-section in its original shape is disposed between the bottom surface 27 of the bead 22 and an inner surface 39 of the bottom wall 37 of the channel section 33 on the mounting member 31. The sealingly mounting assembly 30 further includes a staking member 41 formed of an iron alloy plate or steel plate having a thickness of at most 1.2 mm. The staking member 41 has a generally L-shaped cross-section, at best shown in Fig. 4, before the staking member 41 is staked as shown in Fig. 2.More particularly, the staking member 41 has peripheral inner and outer side walls 42 and 43 and a bottom wall 44 which are integral with each other and engage with respective inner surfaces of the inner, outer and bottom walls 35, 36 and 37 of the channel section 33 on the mounting member 31, respectively. As shown in Fig. 3, the outer side wall 43 of the staking member 41 has formed in integrally therewith a plurality of projections 45 which extend from a free edge of the outer side wall 43 in aligned relation thereto, before the staking member 41 is staked.The projections 45 are bent and staked against the top surface 26 of the bead 22 on the end cover member 5 as a fulcrum of the free edge of the outer side wall 36 of the channel section 33 by means of a staking die assembly similar to that shown in Fig. 11 with the sealing member 38 compressively deformed between the bead 22 and the bottom wall 37 of the channel section 33 on the mounting member 31 so that the end cover member 5 is sealingly mounted on the core 1, as shown in Fig. 2. It should be noted in Fig. 2 that the height h of the outer side wall 36 from the inner surface 39 of the bottom wall 37 of the channel section 33 is equal to the staking height H or the distance from the inner surface 39 of the bottom wall 37 of the channel section 33 to the top surface 26 of the bead 22 on the end cover member 5.

With the arrangement shown in Fig. 2, the cooling liquid within the inlet chamber 8 penetrates into a gap or interface between the inner surface of the inner side wall 35 of the channel section 33 and the inner surface 24 of the bead 22 and flows into a chamber 46 defined by the bottom surface 27 of the bead 22, inner surface of the inner side wall 35, inner surface 39 of the bottom wall 37 and a surface section of the compressively deformed sealing member 35. The cooling liquid within the chamber 46 then penetrates into a gap or interface 47 between the inner surface 39 of the bottom wall 37 of the channel section 33 and the surface section of the deformed sealing member 38 in contact therewith. Thus, the interface 47 between the deformed sealing member 38 and the bottom wall 37 of the channel section 33 is placed in a corrosion environment.More particularly, corrosion components contained in the cooling liquid penetrated into the interface 47 are difficult to be diffused, and in addition thereto, the passive state coating or oxide coating on the surface of the mounting member 31 made of brass tends to maintain its passive state and consumes oxygen in the penetrated cooling liquid. This causes the oxygen concentration in the liquid in the interface 47 to be differed from that of the cooling liquid within the inlet chamber 8, whereby an oxygen concentration cell is formed and the interface 47 becomes an anode. The oxygen concentration cell causes a pH value of the liquid in the interface 47 to be decreased, thereby to present a very severe corrosion environment at the interface 47.

Moreover, as described previously with reference to Fig. 2, since the height h of the outer side wall 36 of the channel section 33 is equal to the staking height H, the bending load applied to the projections 45 of the staking member 41 when the projections 45 are bent against the top surface 26 of the bead 22 on the end cover member 5 is transmitted through the outer side wall 36 to the bottom wall 37 of the channel section 33, thereby to place the bottom wall 37 in a tensile stress condition. The tensile stress remains in the bottom wall 37 even after the completion of the staking working.

It is clear that such conditions cause the stress corrosion cracking to easily occur in the bottom wall 37 of the channel section 33 on the mounting member 31. This fact or phenomenon has been found for the first time by the inventors of the present application, and the inventors have conducted several kinds of experiments and reached the present invention. Upon the experiments, it has been also confirmed that the use of the normal water much containing components such as ammonia or the like as the cooling liquid causes the cracking life to be considerably deteriorated.

The mechanism as to why such corrosion cracking occurs will be discussed in detail with reference to Figs. 5a-5d and Fig. 6. Fig. 5a indicates a step in which the bead 22 on the end cover member 5 is received in the channel section 33 of the mounting member 31 with the resilient sealing member 38 disposed between the bead 22 and the bottom wall 37 of the channel section 33 and the staking member 41 is engaged with the outer peripheral surface of the channel section 33. In the step shown in Fig. 5a, it is of course that no strain is developed in the bottom wall 37 of the channel section 33, because the staking working is not yet performed with respect to the projections 45 on the staking member 41. The step shown in Fig. 5a corresponds to the section a-b in Fig. 6.As the staking working is initiated using a staking die assembly similar to that shown in Fig. 11, a staking load indicated by the arrow F, and inclined relative to a line perpendicular to the top surface 26 of the bead 22 is applied to the projections 45 on the staking member 41 as shown in Fig. 5b, and the outer side wall 36 of the channel section 33 is deformed under the force substantially parallel to the outer surface 25 of the bead 22 while being pressed against the outer surface 25, thereby to cause a compressive strain to be developed in the bottom wall 37 of the channel section 33. The step shown in Fig. 5b corresponds to the section b-c in Fig. 6.The maximum compressive strain developed during the step shown in Fig. 5b is indicated by "Eo" in Fig. 6. As the staking working further proceeds, the staking load is gradually changed in its direction from the inclined direction F1 to the direction perpendicular to the top surface 26 of the bead 22, and the load perpendicular to the top surface 26 indicated by the arrow F2 in Fig. 5e is transmitted to the bottom wall 37 through the outer side wall 36 of the channel section 33.

Since the inner and outer side walls 35 and 36 of the channel section 33 are restrained by the staking member 41, the bottom wall 37 is deformed such that a central portion of the bottom wall 37 is displaced toward the sealing member 38, i.e., the bottom wall 37 is buckled as shown in Fig. 5c. This causes a tensile strain E1 to be developed in the inner surface 39 of the bottom wall 37. The change in strain from the step shown in Fig. 5b to the step shown in Fig. 5e corresponds to the section c-din Fig. 6. The staking load F2 is maintained applied to the projections 45 for a predetermined time duration which corresponds to the section d-e in Fig. 6.After the completion of the staking working, the staking load F2 is released at the point e in Fig. 6 as shown in Fig. 5d, and the projections 45 are slightly returned to their original positions under the spring-bake action. Accordingly, the tensile strain E1 in the inner surface 39 of the bottom wall 37 is reduced to a level E2, which corresponds to the section e-f in Fig. 6.The tensile strain E2 includes a plastic deformation strain E3. If the staking member 41 placed in the condition shown in Fig. 5d were removed from the mounting member 31 to release the restrain thereof from the staking member 41, the bottom wall 37 would be returned toward its original position by the amount of resilient strain (E2 - E3). The resilient strain (E2 - E3) iS the strain which participates in the stress corrosion cracking. It will be understood from the foregoing and from Fig. 6 that the tensile strain is developed in the inner surface 39 of the bottom wall 37 of the channel section 33 on the mounting member 31 in the prior art mounting structure (H-h =0).

A mounting structure of the heat exchanger or radiator for motor vehicles, for example, in accordance with the embodiment of the present invention will now be described with reference to Figs. 7-11 and Fig. 6. In the mounting structure in the present invention, the same reference characters are applied to parts and members common in function to those of the prior art mounting structure shown in Fig. 2, but the reference characters used to show the mounting structure in the present invention are added "100" to distinguish the present invention from the prior art. In addition, the description regarding such common parts and members will be simplified to avoid duplication.

Referring to Figs. 7-9, a sealingly mounting assembly generally designated by the reference character 130 used in the present invention comprises a mounting member 131 formed of a brass plate having a thickness of at most 1.2 mm, and preferably about 0.6 mm. The mounting member 1 31 has a flange 132, a channel section 133 and a connecting web section 134. The channel section 1 33 includes inner, outer and bottom walls 135, 136 and 137. A resilient sealing member 1 38 made of a rubber such as ethylene-propylene rubber is disposed between the bottom surface 27 of the peripheral bead 22 on the end cover member 5 and an inner surface 139 of the bottom wall 137 of the channel section 133 on the mounting member 131.The sealingly mounting assembly 1 30 further includes a staking member 141 formed of an iron alloy plate or steel plate having a thickness of at most 1.2 mm, and preferably about 0.8 mm.

The staking member 141 has a generally L-shaped cross-section, as shown in Fig. 9, before the staking working of the staking member 141.

The staking member 141 has integral inner, outer and bottom walls 142, 143 and 144. As shown in Fig. 8, the outer wall 143 of the staking member 141 has formed integrally therewith a plurality of projections 145 each having a width w1 with a gap having a width w2 defined between each pair of adjacent projections 145. In the present invention, the dimensions of the widths w, and w2 are determined as follows: w1 = (0.5 to 0.9) x W w2=(0.1 toOS) x W W = w1 + w2 The dimensions of w1 ad w2 are determined dependent upon the quality of the cross-sectional configuration of the staking member 141 after having been staked, and an accuracy of the staking high H or accuracy of the staking working by a staking die assembly 1 50 shown in Fig. 11.

For example, in the actual products in accordance with the embodiment of the present invention, w is approximately 7 mm, and w2 is approximately 3 mm.

The staking working by means of the staking die assembly 1 50 will be briefly described with reference to Fig. 11. The staking die assembly 1 50 comprises a die 151 which includes a stationary die section 1 52 having formed integrally therewith an upstanding abutment 1 53 and a movable die section 1 54 movable along the stationary die section toward and away from the abutment 1 53 thereof, and a staking punch 1 56 movable toward and away from the die 151. The staking punch 1 56 has in its cross-sectional configuration a first planar surface section 1 57 substantially parallel to the abutment 153, a second pianar surface section 1 58 substantially perpendicular to the first planar surface section 1 57 and a curved surface section 1 59 extending between the first and second planar surface sections 1 57 and 1 58. At the outset, with the staking punch 1 56 moved away from the die 1 51 , the L-shaped staking member 141 shown in Fig. 8 is received within a recess defined by the stationary die section 1 52 and the movable die section 1 54. Then, the channel section 133 of the mounting member 131 with the bead 22 on the end cover member 5 received in the channel section 1 33 and with the sealing member 138 disposed between the bead 22 and the bottom wall 137 of the channel section 1 33 is fitted into the L-shaped staking member 141. Then, the staking punch 1 56 is moved toward the die 151 and the curved surface 1 59 of the punch 1 56 is caused to abut against the free edges of the projections 145 on the outer wall 143 of the staking member so that the projections 145 are slightly bent along the curved surface section 156, as shown by the chain-anddot line.As the punch 1 56 is further moved toward the die 151, the projections 145 are further bent along the curved surface section 1 59 and the edges of the projections 145 approach the second planar surface section 1 58 as shown by the broken line. Finally, the projections 145 are pressed or staked against the top surface 26 of the bead 22 by the second planar surface section 1 58 of the punch 1 58 are shown by the solid line.

Thus, the staking working by means of the staking die assembly 1 50 is completed and the mounting structure shown in Fig. 7 is formed.

It will be clearly seen from Fig. 7, the height h of the outer side wall 1 36 from the inner surface 1 39 of the bottom wall of the channel section 1 33 is lower than the staking height H or the distance from the inner surface 139 of the bottom wall 137 to the top surface 26 of the bead 22. The inventors of the present application have found the fact that if the heights h and H satisfy the relation (H - h) > = 0.5 mm, a pattern of strain developed in the inner surface 1 39 of the bottom wall 137 of the mounting member 131 follows the broken line shown in Fig. 6.The reason for this is that the staking load perpendicular to the top surface 26 of the bead 22 applied to the projections 145 of the staking member 141 during the staking working by means of the staking die assembly 1 50 is not transmitted to the bottom wall 137 through the outer side wall 136 of the mounting member 131, and the strain developed in the inner surface 139 of the bottom wall 137 becomes only the compressive strain E4 as shown in Fig, 6. For the same reason as that described with reference to Fig, 2, as the staking load is released, the projections 145 tend to return toward their original positions, and the compressive strain E4 is reduced to a level E5 shown in Fig. 6. The compressive strain E, includes a plastic deformation strain E6.

Accordingly, after the completion of the staking working, the inner surface 139 of the bottom wall 1 37 is subjected to the resilient compressive strain (Es - E8). The resilient compressive strain (E5 - E6) can be converted to a stress S, using the following equation: 6 = E (56) where E is a module of longitudinal elasticity.

Fig. 10 is a graph showing the experimental results, in which the abscissa indicates the value of (H - h) and the ordinate indicates the stress b.

As will be clearly seen from Fig. 10, if the relation (H - h) ~ 0.5 mm is satisfied, the stress ö developed in the inner surface 139 of the bottom wall 1 37 becomes a compressive stress and is stabilized. Thus, the occurrence of the stress corrosion cracking is remarkably restrained and the life of the bottom wall 1 39 is considerably prolonged.

In the actual application of the present invention to the products, the assembling ability or performance is improved, if the bottom surface 27 of the bead 22 is located inwardly from the free edge of the outer side wall 136 of the mounting member 131, prior to the performing of the staking working, in consideration of the variations in dimension due to the longitudinal warp of the end cover member 5, meandering and partial separation of the sealing member 138 within the channel section 133, longitudinal warp of the mounting member 131 due to thermal strain developed upon the bonding of the mounting member to the core 1 by means of soldering, brazing or the like, and the like. In view of this, it is preferable to set the maximum upper limit of the value (H - h) to approximately 2-3 mm.For example, the value of H may be approximately 7.2 mm, and the value of h may be approximately 6.3 mm.

The experiments conducted on the mounting structure in the present invention based on the actual market use reveal that if no stress is developed in the inner surface 1 39 of the bottom wall 137, the life of the stress corrosion cracking is made ten (1 0) times as compared with the prior art mounting structure, and if the stress developed in the inner surface 139 of the bottom wall 137 is the compressive stress, the life of the stress corrosion cracking is made five (5) to six (6) times as compared with the prior art mounting structure.

However, since the external load such as internal pressure, heat or the like in addition to the stress developed upon the staking working is applied as an actual load to the inner surface of the bottom wall of the channel section, the products in accordance with the present invention may have the life of the stress corrosion cracking above twice that of the prior art mounting structure.

Claims (14)

1. A heat exchanger comprising: a heat-exchanging core made of a metal for allowing first and second fluids to pass through said core to cause the heat-exchanging to be performed between the first and second fluids; an end cover member associated with each of the opposite end portions of said core, said end cover member being mounted on and cooperating with the end portion of said core to define a chamber for receiving therein one of the first and second fluids, said end cover member being provided at a peripheral edge thereof with a peripheral attaching portion;; a sealingly mounting assembly for sealingly mounting said end cover member on the end portion of said core, said sealingly mounting assembly including a mounting member having an inner peripheral edge thereof secured to said core and a peripheral channel section spaced outwardly from said core, said channel section having opposed side walls and a bottom wall extending therebetween which walls have their respective inner surfaces cooperating with each other to define an open channel for receiving therein said peripheral attaching portion of said end cover member, a resilient sealing member disposed between the inner surface of said bottom wall of said channel section and a first surface area of said peripheral attaching portion on said end cover member received in said open channel, said first surface area of said peripheral attaching portion being faced to the inner surface of said bottom wall of said channel section, and a staking member engaging with an outer surface of said channel section and staked against a second surface area of said peripheral attaching portion on said end cover member opposite to said first surface area thereof such that a compressive strain is developed in the inner surface of said bottom wall of said channel section on said mounting member, to fixedly mount said peripheral attaching portion on said end cover member within said channel section of said mounting member; and the inner surface of said bottom wall of said channel section on said mounting member being maintained in such condition that the inner surface of said bottom wall is subjected to a compressive stress, after said peripheral attaching portion is fixedly mounted within said channel section of said mounting member by said staking member.

2. A heat exchanger as defined in Claim 1, wherein a height (h) of an outer one of said side walls, remote from said core, of said channel section on said mounting member from the inner surface of said bottom wall thereof is less than a staking height (H) from the inner surface of said bottom wall to said second surface area of said peripheral attaching portion on said end cover member against which said staking member is staked, by a predetermined distance.

3. A heat exchanger as defined in Claim 2, wherein said heights (h) and (H) have a difference therebetween at least equal to approximately 0.5 mm.

4. A heat exchanger as defined in Claim 3, wherein said heights (h) and (H) have a difference therebetween less than approximately 3 mm.

5. A heat exchanger as defined in any one of Claims 1-4, wherein said staking member has side walls and a bottom wall respectively engaging with the outer surfaces of said side walls and said bottom wall of said channel section on said mounting member, and a plurality of projections extending from a free edge of an outer one of said side walls of said staking member engaging with said outer side wall of said channel section on said mounting member, said projections being spaced from each other with a gap defined between each pair of adjacent projections, said projections being bent and staked against said second surface area of said peripheral attaching portion on said end cover member.

6. A heat exchanger as defined in Claim 5, wherein each of said projections has a width (w1) and each of said gaps has a width (w2) as measured along the free edge of said outer side wall of said staking member, said widths (w1) and (w2) satisfying the following relations: w1 = (0.5 to 0.9) x W w2=(0.1 to 0.5) xW W = w1 + w2.

7. A heat exchanger as defined in Claim 6, wherein said projections are bent and staked against said second surface area of said peripheral attaching portion on said end cover member by means of a staking die assembly, said staking die assembly including a die defining therein a peripheral recess for receiving therein an assembly of said staking member, said channel section on said mounting member and said peripheral attaching portion on said end cover member, and a staking punch having thereon a staking surface, one of said die and said staking punch being movable toward apd away from the other to cause said projections to abut against said staking surface on said staking punch to bend and stake said projections against said second surface area of said peripheral attaching portion on said end cover member.

8. A heat exchanger as defined in Claim 7, wherein said peripheral attaching portion on said end cover member is comprised of a bead having a generally rectangular cross-section and connected to the peripheral edge of said end cover member in integral relation thereto.

9. A heat exchanger as defined in Claim 8, wherein said end cover member is made of a resin.

10. A heat exchanger as defined in Claim 9, wherein said mounting member is formed of a brass plate.

11. A heat exchanger as defined in Claim 10, wherein said staking member is formed of an iron alloy plate.

12. A heat exchanger as defined in Claim 11, wherein said resilient sealing member is made of ethylene-propylene rubber.

13. A heat exchanger as defined in Claim 12, wherein said core comprises a plurality of spaced tubes made of brass and a corrugated fin made of copper and disposed between each pair of adjacent tubes, said chambers respectively defined by said end cover members respectively mounted on the opposite end portions of said core being communicated with each other by said tubes.

14. A heat exchanger substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 7 to 11 of the accompanying drawings.