Patent Publication Number: US-11654508-B2

Title: Method for producing liquid-cooled jacket

Description:
This application is a National Stage Application of PCT/JP2018/027337, filed Jul. 20, 2018, which claims benefit of priority to Japanese Patent Application No. 2017-185941, filed Sep. 27, 2017, which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
     TECHNICAL FIELD 
     The present invention relates to a method for producing a liquid-cooled jacket. 
     BACKGROUND ART 
     A rotary tool used for friction stir joining, including a shoulder portion and a stir pin suspended from the shoulder portion, is known. The rotary tool is also used in manufacturing a liquid-cooled jacket composed of a jacket body and a sealing body. The rotary tool is used for friction stir joining in which a lower end surface of the shoulder portion is pushed onto a metal member. By pressing the shoulder portion onto the metal member, the plastically fluidized material can be pressed to prevent the generation of burrs. However, if the height position of the joining changes, a defect is likely to occur, and there is a problem that a lot of burrs are generated the concave groove increases in size. 
     Alternatively, a friction stir joining method of joining two metal members by using a rotary tool equipped with a stir pin and the method including a main joining step in which the rotating stir pin is inserted an abutted portion of the metal members and the friction stir joining is performed with only the stir pin coming in contact with a metal members, is known (Patent Document 1). According to the prior art, since a spiral groove is engraved in the outer circumferential surface of the stir pin and friction stir joining is performed under the condition that the base-end portion is exposed while contacting only the stir pin with the member to be joined, the occurrence of defects is prevented even if the height position of the joining changes, and a load in the friction stir device is reduced. However, since the plastically fluidized material is not pressed by the shoulder portion, there is a problem that the concave groove in the surface of the metal members is widened and the joined surface increases roughness. In addition, there is a problem that a bulging portion (a portion where the surface of the metal members bulges as compared with that before joining) is formed next to the concave groove. 
     Additionally, Patent Document 2 describes a rotary tool including a shoulder portion and a stir pin suspended from the shoulder portion. Tapered surfaces are formed on outer circumferential surfaces of the shoulder portion and the stir pin, respectively. A spiral groove in a planar view is formed on the tapered surface of the shoulder portion. The cross-sectional shape of the groove is semicircular. By providing the tapered surface, stable joining is performed even if the thickness of the metal members or the height position of joining changes. In addition, when the plastically fluidized material enters the groove, the flow of the plastically fluidized material is controlled to form a suitable plasticized area. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Publication No. 2013-39613 
         Patent Document 2: Japanese Patent No. 4210148 
       
    
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, in the prior art of Patent Document 2, since the plastically fluidized material intrudes into the groove of the tapered surface, there is a problem that the groove does not function. In addition, when the plastically fluidized material enters the groove, the plastically fluidized material is frictionally stirred with the plastically fluidized material adhered to the groove, so that there is a problem that the metal members to be joined and the adhered material rub against each other to deteriorate the joining quality. Furthermore, there is a problem that the surfaces of the joined metal members increase in roughness, burrs increase, and the concave groove in the surface of the metal members also increases in size. 
     From such a point of view, it is an object of the present invention to provide a method for manufacturing a liquid-cooled jacket which to allow for reducing the size of the concave groove in the surface of the metal members and reducing the joined surface in roughness. 
     Means for Solving the Problems 
     In order to solve such problems, the present invention (the first invention of the present application) is a method for manufacturing a liquid-cooled jacket configured with: a jacket body having a bottom portion, a peripheral wall portion rising from a peripheral edge of the bottom portion and a support column rising from the bottom portion; and a sealing body provided with a hole in which a tip-end of the support column is inserted and sealing an opening of the jacket body, wherein the jacket body and the sealing body are joined by friction stirring, the method including: 
     a preparation step of forming a peripheral wall step portion having a step bottom surface and a step side surface rising from the step bottom surface on an inner peripheral edge of the peripheral wall portion, a support column end surface of the support column at the same height position as a peripheral wall end surface of the peripheral wall portion, and a support column step portion having a step bottom surface and a step side surface rising from the step bottom on an outer periphery of a tip-end of the support column; 
     a placing step of placing the sealing body on the jacket body; 
     a first main joining step of performing friction stirring by moving a rotary tool around along a first abutted portion where the step side surface of the peripheral wall step portion and the outer peripheral side surface of the sealing body abut each other; and 
     a second main joining step of performing friction stirring by moving the rotary tool around along a second abutted portion where the step side surface of the support column step portion is abutted against a hole wall of the hole, wherein 
     the rotary tool is a main joining rotary tool for friction stirring having a base-end-side pin and a tip-end-side pin, 
     a taper angle of the base-end-side pin is greater than a taper angle of the tip-end-side pin and a stairs-like pin step portion is formed in an outer circumferential surface of the base-end-side pin and 
     friction stirring is performed in the first main joining step and the second main joining step under the condition that the tip-end-side pin and the base-end-side pin come in contact with the jacket body and the sealing body. 
     In addition, the present invention (the second invention of the present application) is a method for manufacturing a liquid-cooled jacket configured with: a jacket body having a bottom portion, a peripheral wall portion rising from a peripheral edge of the bottom portion and a support column rising from the bottom portion; and a sealing body sealing an opening of the jacket body, wherein the jacket body and the sealing body are joined by friction stirring, the method including: 
     a preparation step of forming a peripheral wall step portion having a step bottom surface and a step side surface rising from the step bottom surface on an inner peripheral edge of the peripheral wall portion, and a support column end surface of the support column at the same height position as the step bottom surface of the peripheral wall step portion; 
     a placing step of placing the sealing body on the jacket body; 
     a first main joining step of performing friction stirring by moving a rotary tool around along a first abutted portion where the step side surface of the peripheral wall step portion is abutted against the outer peripheral side surface of the sealing body; and 
     a second main joining step of performing friction stirring, by moving the rotary tool, to an overlapping portion where the support column end surface of the support column and a back surface of the sealing body are overlapped, wherein 
     the rotary tool is a main joining rotary tool for friction stirring having a base-end-side pin and a tip-end-side pin, 
     a taper angle of the base-end-side pin is greater than a taper angle of the tip-end-side pin and a stairs-like pin step portion is formed in an outer circumferential surface of the base-end-side pin, while 
     friction stirring is performed in the first main joining step under the condition that the tip-end-side pin and the base-end-side pin come in contact with the jacket body and the sealing body; and 
     friction stirring is performed in the second main joining step under the condition that the tip-end-side pin comes in contact with either both the jacket body and the sealing body or only the sealing body and the base-end-side pin comes in contact with the sealing body. 
     According to either one of the joining methods, since the sealing body is pressed by the outer circumferential surface of the base-end-side pin having a large taper angle, the concave groove in the joining surface is reduced in size and a bulging portion formed next to the concave groove is eliminated or reduced in size. Since the stairs-like step portion is shallow and has a wide exit angle, the plastically fluidized material less likely adheres to the outer circumferential surface of the base-end-side pin even when the sealing body is pressed by the base-end-side pin. As a result, the joined surface is reduced in roughness, and the joining quality is suitably stabilized. In addition, it is easily inserted to a deep position by having a tip-end-side pin. 
     Additionally, it is preferable in the preparation step to form the jacket body by die casting to have the bottom portion formed to be convex toward the front surface of the jacket body, and to form the sealing body formed to be convex toward a front surface thereof. 
     Although heat shrinkage may occur in the plasticized area due to the heat input by friction stir joining and the sealing body of the liquid-cooled jacket may be deformed so as to be concave inward, the liquid-cooled jacket is made flat according to this manufacturing method by making the jacket body and the sealing body convex toward the front surface in advance and utilizing heat contraction. 
     Furthermore, it is preferable that the deformation amount of the jacket body is measured in advance, and the friction stirring is carried out while the insertion depth of the rotary tool being adjusted to the deformation amount in the first main joining step and the second main joining step. 
     According to this manufacturing method, even when friction stir joining is carried out with the jacket body and the sealing body being curved in a convex shape, the length and the width of the plasticized area formed in the liquid-cooled jacket is made constant. 
     Furthermore, in the first invention of the present application, it is preferable to include a provisional joining step of provisionally joining at least one of the first abutted portion and the second abutted portion prior to the first main joining step and the second main joining step. 
     Additionally, in the second invention of the present application, it is preferable to include a provisional joining step of provisionally joining the first abutted portion prior to the first main joining step. 
     According to this manufacturing method, performing the provisional joining prevents abutted portion from coming apart in the first main joining step and the second main joining step. 
     In addition, in the first main joining step and the second main joining step, it is preferable to dispose a cooling plate in which a cooling medium flows, on the back surface of the bottom portion and then to perform friction stirring while the jacket body and the sealing body being cooled by the cooling plate. 
     According to this manufacturing method, since the frictional heat is reduced to a low level, the deformation of the liquid-cooled jacket due to the thermal contraction is reduced. 
     In addition, it is preferable that the front surface of the cooling plate comes in surface contact with the back surface of the bottom portion. According to this manufacturing method, the cooling efficiency is enhanced. 
     Furthermore, it is preferable that the cooling plate has a cooling flow passage in which the cooling medium flows, and the cooling flow passage has a planar shape to follow a moving trajectory of the rotary tool in the first main joining step. 
     According to this manufacturing method, since the portion to be frictionally stirred is intensively cooled, the cooling efficiency is further enhanced. 
     In addition, it is preferable that the cooling flow passage in which the cooling medium flows is composed of a cooling pipe embedded in the cooling plate. According to this manufacturing method, the cooling medium is easily managed. 
     Furthermore, in the first main joining step and the second main joining step, it is preferable to carry out the friction stirring while flowing a cooling medium in a hollow portion composed of the jacket body and the sealing body to cool the jacket body and the sealing body. 
     According to this manufacturing method, since the frictional heat is suppressed to a low level, the deformation of the liquid-cooled jacket due to the thermal contraction is reduced. In addition, cooling may be performed using the jacket body itself without using a cooling plate or the like. 
     Effects of the Invention 
     According to the method for manufacturing a liquid-cooled jacket of the present invention, the groove on the surfaces of the metal members is reduced in size and the joined surface is reduced in roughness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a main joining rotary tool according to an embodiment of the present invention. 
         FIG.  2    is a schematic cross section in a joining operation of the main joining rotary tool. 
         FIG.  3    is an expanded sectional view of the main joining rotary tool. 
         FIG.  4    is a side view of a provisional joining rotary tool according to an embodiment of the present invention. 
         FIG.  5    is a schematic cross section of a provisional joining rotary tool in a joining operation. 
         FIG.  6    is a perspective view of a liquid-cooled jacket according to a first embodiment of the present invention. 
         FIG.  7    is an disassembled perspective view of a liquid-cooled jacket according to the first embodiment of the present invention. 
         FIG.  8    is a cross-sectional view taken along a line I-I in  FIG.  6   . 
         FIG.  9    is a cross-sectional view of the liquid-cooled jacket before the placing step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  10    is a cross-sectional view of the liquid-cooled jacket after the placing step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  11    is a plan view of the liquid-cooled jacket in the provisional joining step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  12    is a plan view of the liquid-cooled jacket in the first main joining step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  13    is a cross-sectional view of the liquid-cooled jacket in the first main joining step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  14    is a plan view of the liquid-cooled jacket in the second main joining step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  15    is a cross-sectional view taken along a line II-II of  FIG.  14    showing the second main joining step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  16    is a cross-sectional view of the liquid-cooled jacket in the drilling process of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  17    is a cross-sectional view of the liquid-cooled jacket in the mounting step of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  18    is a conceptual view of a conventional shoulder-less rotary tool. 
         FIG.  19    is a conceptual view of a conventional rotary tool. 
         FIG.  20    is a perspective view of the liquid-cooled jacket in a first modification of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  21    is a perspective view of a table in the second modification of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  22    is a perspective view of the liquid-cooled jacket in the second modification of the method for manufacturing the liquid-cooled jacket fixed to a table according to the first embodiment. 
         FIG.  23    is a disassembled perspective view of the liquid-cooled jacket in the third modification of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  24    is a perspective view of the liquid-cooled jacket and the sealing body fixed to a table in the third modification of the method for manufacturing the liquid-cooled jacket according to the first embodiment. 
         FIG.  25    is a disassembled perspective view of a liquid-cooled jacket according to the second embodiment. 
         FIG.  26    is a cross-sectional view of the liquid-cooled jacket according to the second embodiment. 
         FIG.  27    is a cross-sectional view of the liquid-cooled jacket before the placing step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  28    is a cross-sectional view of the liquid-cooled jacket after the placing step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  29    is a plan view of the liquid-cooled jacket in the provisional joining step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  30    is a plan view of the liquid-cooled jacket in the first main joining step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  31    is a cross-sectional view of the liquid-cooled jacket in  FIG.  30    in the first main joining step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  32    is a plan view of the liquid-cooled jacket in the second main joining step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  33    is a cross-sectional view taken along a line III-III in  FIG.  32    showing the liquid-cooled jacket in second main joining step of the method for manufacturing the liquid-cooled jacket according to the second embodiment second. 
         FIG.  34    is a cross-sectional view of the liquid-cooled jacket in the drilling step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  35    is a cross-sectional view of the liquid-cooled jacket in the placing step of the method for manufacturing the liquid-cooled jacket according to the second embodiment. 
         FIG.  36    is a cross-sectional view of the first modification of the main joining rotary tool. 
         FIG.  37    is a cross-sectional view of the second modification of the main joining rotary tool. 
         FIG.  38    is a cross-sectional view of the third modification of the main joining rotary tool. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     A liquid-cooled jacket and a method for manufacturing the liquid-cooled jacket according to the first embodiment of the present invention will be described in details with reference to the drawings. First, a main joining rotary tool and a provisional joining rotary tool used in the present embodiment will be described. 
     As shown in  FIG.  1   , the main joining rotary tool F is a tool used for friction stir joining. The main joining rotary tool F is formed of a tool steel, for example. The main joining rotary tool F is mainly composed of a base portion F 1 , a base-end-side pin F 2 , and a tip-end-side pin F 3 . The base portion F 1  has a cylindrical shape and is a portion connected to a main shaft of a friction stirring device. The rotation axis of the main joining rotary tool F may be inclined with respect to the vertical direction, but in the present embodiment, it coincides with the vertical direction. In addition, a plane perpendicular to the vertical direction is defined as a horizontal plane. 
     The base-end-side pin F 2  is formed continuously to the base portion F 1  and is tapered toward the tip. The base-end-side pin F 2  has a truncated cone shape. The taper angle A 1  of the base-end-side pin F 2  may be set as appropriate, but is set to fall in a range of 135 to 160°, for example. When the taper angle A 1  is less than 135° or exceeds 160°, joined surface increases roughness after friction stirring. The taper angle A 1  is larger than the taper angle A 2  of the tip-end-side pin F 3  described below. As shown in  FIG.  3   , a stairs-like pin step portion  30  is formed on the outer circumferential surface of the base-end-side pin F 2  over the entire height direction. The pin step portion  30  is formed in a spiral shape clockwise or counterclockwise. That is, the pin step portion  30  has a spiral shape in a planar view and a step shape in a side view. In the present embodiment, the pin step portion  30  is set counterclockwise from the base-end side toward the tip-end side in order to rotate the rotary tool clockwise. 
     Note that in the case of the main joining rotary tool F being rotated counterclockwise, it is preferable to set the pin step portion  30  clockwise from the base-end side to the tip-end side. Thereby, since a plastically fluidized material is directed toward the tip-end by the pin step portion  30 , metal overflowing to the outside of the joined metal members is reduced. The pin step portion  30  is composed of step bottom surfaces  30   a  and step side surfaces  30   b . A distance Z 1  (horizontal distance) between apexes  30   c  of the adjacent pin step portions  30  is appropriately set according to the step angle C 1  and the height Y 1  of the step side surface  30   b  described below. 
     The height Y 1  of the step side surface  30   b  may be set as appropriate, and is set to, fall in a range of 0.1 to 0.4 mm, for example. The joined surface increases roughness when the height Y 1  is less than 0.1 mm. On the other hand, when the height Y 1  exceeds 0.4 mm, the joined surface tends to increase in roughness, and the number of effective step portions (the number of pin step portions  30  in contact with the joined metal members) decreases. 
     The step angle C 1  formed by the step bottom surface  30   a  and the step side surface  30   b  may be set as appropriate, and is set fall in a range of 85 to 120°, for example. The step bottom surface  30   a  is parallel to the horizontal plane in the present embodiment. The step bottom surface  30   a  may be inclined within a range of −5° to 15° with respect to the horizontal plane from the rotation axis of the tool toward the outer circumferential direction (minus means downward with respect to the horizontal plane, and plus means upward with respect to the horizontal plane). The distance Z 1 , the height Y 1  of the step side surface  30   b , the step angle C 1  and the angle of the step bottom surface  30   a  with respect to the horizontal plane are set as appropriate so that the plastically fluidized material is pushed out without staying in and adhering to the inside of the pin step portion  30  at the time of friction stirring, and that the plastically fluidized material is pressed by the step bottom surface  30   a  to reduce the joined surface in roughness. 
     The tip-end-side pin F 3  is formed continuously to the base-end-side pin F 2 . The tip-end-side pin F 3  has a truncated cone shape. The tip of the tip-end-side pin F 3  has a flat surface. The taper angle A 2  of the tip-end-side pin F 3  is smaller than the taper angle of the base-end-side pin F 2 . A spiral groove  31  is engraved on the outer circumferential surface of the tip-end-side pin F 3 . The spiral groove  31  may be either clockwise or counterclockwise. However, in the present embodiment, the spiral groove  31  is engraved counterclockwise from the base end toward the tip end in order to cause the main joining rotary tool F to be rotated clockwise. 
     Note that in the case of the main joining rotary tool F being rotated counterclockwise, the spiral groove  31  is preferably formed clockwise from the base end toward the tip end. Thereby, since the plastically fluidized material is directed toward the tip end by the spiral groove  31 , the metal overflowing to the outside of the joined metal members is reduced. The spiral groove  31  is composed of a spiral bottom surface  31   a  and a spiral side surface  31   b . The distance (horizontal distance) between the apexes  31   c  of the adjacent spiral grooves  31  is set to a length Z 2 . The height of the spiral side surface  31   b  is set to a height Y 2 . The spiral angle C 2  formed by the spiral bottom surface  31   a  and the spiral side surface  31   b  falls in a range of 45 to 90°, for example. The spiral groove  31  works to raise the frictional heat by contacting the joined metal members and direct the plastically fluidized material toward the tip end. 
     As shown in  FIG.  2   , when the friction stir joining is performed using the main joining rotary tool F, the friction stir joining is performed while the surface of the joined metal members (a jacket body  2  and a sealing body  3  described below) being pressed by the outer circumferential surface of the base-end-side pin F 2  of the main joining rotary tool F. The insertion depth of the main joining rotary tool F is set so that at least a part of the base-end-side pin F 2  is in contact with the surface of the joined metal members. In the moving trajectory of the main joining rotary tool F, a plasticized area W 1  (or a plasticized area W 2 ) is formed because the metal subjected to friction stirring hardens. 
     As shown in  FIG.  4   , a provisional joining rotary tool G is composed of a shoulder portion G 1  and a stir pin G 2 . The provisional joining rotary tool G is formed of a tool steel, for example. The shoulder portion G 1  is a portion which is connected to the main shaft of the friction stir device as shown in  FIG.  5    and which presses the plasticized metal. The shoulder G 1  has a cylindrical shape. The lower end surface of the shoulder portion G 1  is concave to prevent the fluidized metal from flowing out to the outside. 
     The stir pin G 2  is suspended from the shoulder portion G 1  and is coaxial with the shoulder portion G 1 . The stir pin G 2  is tapered as being smaller diameter with the increasing distance from the shoulder portion G 1 . A spiral groove G 3  is engraved in the outer circumferential surface of the stir pin G 2 . 
     As shown in  FIG.  5   , when friction stir joining is performed using the provisional joining rotary tool G, the provisional joining rotary tool G is moved while the rotated stir pin G 2  and the lower end surface of the shoulder portion G 1  being inserted into the joined metal members. A plasticized area W is formed on the moving trajectory of the provisional joining rotary tool G because the metal subjected to friction stirring hardens. 
     Next, the liquid-cooled jacket of the present embodiment will be described. As shown in  FIG.  6   , the liquid-cooled jacket  1  according to the present embodiment is composed of a jacket body  2  and a sealing body  3 , and has a rectangular parallelepiped shape. The jacket body  2  and the sealing body  3  are integrated by friction stir joining. The liquid-cooled jacket  1  has a hollow portion formed therein so that a heat transport fluid such as water may flow in the hollow portion. The liquid-cooled jacket  1  allows the heat transport fluid to flow through the hollow portion, for example, to cool the heating element mounted to the liquid-cooled jacket  1 . 
     As shown in  FIG.  7   , the jacket body  2  is a box-like body whose upper side is opened. The jacket body  2  is configured to include a bottom portion  10 , a peripheral wall portion  11 , and a plurality of support columns  12 . The jacket body  2  is appropriately selected from metals which can be frictionally stirred such as aluminum, aluminum alloy, copper, copper alloy, titanium, titanium alloy, magnesium and magnesium alloy. The jacket body  2  is formed of an aluminum alloy of the same material type as the sealing body  3  in the present embodiment, but an aluminum alloy cast material (for example, JIS AC4C, ADC12 or the like) may be used. 
     The bottom portion  10  has a rectangular plate shape in a planar view. The peripheral wall portion  11  rises from the periphery of the bottom portion  10 , and has a rectangular frame shape in a planar view. The peripheral wall portion  11  is composed of wall portions  11 A,  11 B,  11 C, and  11 D having the same thickness. The wall portions  11 A and  11 B are short side portions and face each other. In addition, the wall portions  11 C and  11 D are long side portions and face each other. A recess  13  is formed inside the bottom portion  10  and the peripheral wall portion  11 . 
     A peripheral wall step portion  14  is formed in the peripheral wall end surface  11   a  which as an end surface of the circumferential wall portion  11  along the inner peripheral edge of the peripheral wall portion  11  of the jacket body  2 . The peripheral wall step portion  14  is composed of a step bottom surface  14   a  and a step side surface  14   b  rising from the step bottom surface  14   a . The step bottom surface  14   a  is formed at a position one step lower than the circumferential wall end surface  11   a.    
     The support column  12  rises from the bottom portion  10  and has a columnar shape. The number of the support columns  12  may be any number as long as being one or more, but in the present embodiment, four support columns are formed. The shapes of the support columns  12  are all the same. The support column  12  is composed of a large diameter portion  15  and a small diameter portion  16  protruding from the tip of the large diameter portion  15 . Both the large diameter portion  15  and the small diameter portion  16  have a cylindrical shape. A support column step portion  17  is formed with the step between the large diameter portion  15  and the small diameter portion  16 . 
     The support column step portion  17  is composed of a step bottom surface  17   a  and a step side surface  17   b  rising from the step bottom surface  17   a . A support column end surface  16   a  is formed on the end surface of the small diameter portion  16 . The step bottom surface  17   a  is formed at the same height as the step bottom surface  14   a  of the peripheral wall step portion  14 . Furthermore, the support column end surface  16   a  is formed at the same height position as the peripheral wall end surface  11   a.    
     The sealing body  3  is a plate-like member which is rectangular in a planar view and seals the opening of the jacket body  2 . In the present embodiment, the sealing body  3  is formed of an aluminum alloy of the same material type as the jacket body  2 , but a wrought aluminum alloy material (for example, JIS A1050, A1100, A6063 etc.) may be used. The sealing body  3  is formed in a size to be placed on the peripheral wall step portion  14  with substantially no gap. The plate thickness of the sealing body  3  is substantially equal to the height of the step side surface  14   b . The sealing body  3  is formed with four holes  19  corresponding to the support columns  12 . The hole  19  has a circular shape in a planar view, and the small diameter portion  16  is inserted therein. 
     As shown in  FIG.  8   , the jacket body  2  is joined by friction stirring and integrated with the sealing body  3  as the liquid-cooled jacket  1 . The liquid-cooled jacket  1  has a first abutted portion J 1  in which the step side surface  14   b  of the peripheral wall step portion  14  is abutted against the outer peripheral side surface  3   c  of the sealing body  3 , and four second abutted portion J 2  in which the step side surfaces  17   b  of the support column step portion  17  are abutted against the hole walls  19   a  of the holes  19 , respectively joined by friction stirring. A plasticized area W 1  is formed in the first abutted portion J 1 , and a plasticized area W 2  is formed in the second abutted portion J 2 . The liquid-cooled jacket has a hollow portion formed therein, in which a heat transport fluid for transporting heat to the outside flows. 
     Next, a method for manufacturing a liquid-cooled jacket (a method for manufacturing a liquid-cooled jacket with a heating elements) according to the first embodiment will be described. In the method for manufacturing a liquid-cooled jacket, a preparation step, a placing step, a fixing step, a provisional joining step, a first main joining step, a second main joining step, a drilling step, a burr removing step and a mounting step are performed. 
     The preparation step is a step of forming the jacket body  2  and the sealing body  3  as shown in  FIG.  7   . The jacket body  2  is formed by die casting, for example. 
     The placing step is a step of placing the sealing body  3  on the jacket body  2  while the holes  19  of the sealing body  3  having the small diameter portions  16  of the support column  12  through the hole  19  of the sealing body  3  as shown in  FIGS.  9  and  10   . The back surface  3   b  of the sealing body  3  comes in surface contact with the step bottom surface  14   a  of the peripheral wall step portion  14  and the step bottom surface  17   a  of the support column step portion  17 , respectively. In the placing step, the step side surface  14   b  of the peripheral wall step portion  14  is abutted against the outer peripheral side surface  3   c  of the sealing body  3  to form the first abutted portion J 1 . The first abutted portion J 1  has a rectangular shape in a planar view. Furthermore, in the placing step, the step side surface  17   b  of the support column step portion  17  is abutted against the hole wall  19   a  of the hole  19  to form the second abutted portion J 2 . The second abutted portion J 2  has a circular shape in a planar view. 
     In the fixing step, the jacket body  2  and the sealing body  3  are fixed to a table (not shown). The jacket body  2  and the sealing body  3  are immovably restrained to the table by a fixing jig such as a clamp. 
     The provisional joining step is a step of provisional joining the jacket body  2  with the sealing body  3 , as shown in  FIG.  11   . In the provisional joining step, friction stir joining is performed to the abutted portion J 1  by using the provisional joining rotary tool G. A plasticized area W is formed on the moving trajectory of the provisional joining rotary tool G. The provisional joining may be performed continuously or may be performed on and off as shown in  FIG.  11   . Since the provisional joining rotary tool G is compact, the thermal deformation of the jacket body  2  and the sealing body  3  in the provisional joining is reduced. 
     As shown in  FIGS.  12  and  13   , the first main joining step is a step of performing friction stir joining to the first abutted portion J 1  by using the main joining rotary tool F. In the first main joining step, the main joining rotary tool F rotated clockwise is inserted into an arbitrary start position s 1  on the first abutted portion J 1 , and the main joining rotary tool F is moved clockwise along the first abutted portion J 1 . That is, the main joining rotary tool F is moved around clockwise along the periphery of the sealing body  3 . A plasticized area W 1  is formed on the moving trajectory of the main joining rotary tool F. 
     In the first main joining step, as shown in  FIG.  13   , friction stirring is performed under the condition that the tip-end-side pin F 3  and the base-end-side pin F 2  come in contact with the peripheral wall portion  11  of the jacket body  2  and the sealing body  3 . In the first main joining step, friction stir joining is performed while the peripheral wall end surface  11   a  of the peripheral wall portion  11  and the front surface  3   a  of the sealing body  3  being pressed by the outer peripheral surface of the base-end-side pin F 2  of the main joining tool F. The insertion depth of the main joining rotary tool F is set so that at least the plasticized area W 1  reaches the step bottom surface  14   a , and at least a part of the base-end-side pin F 2  comes in contact with the peripheral wall end surface  11   a  of the peripheral wall portion  11  and the front surface  3   a  of the sealing body  3 . In the present embodiment, the insertion depth is set so that the tip of the tip-end-side pin F 3  does not reach the step bottom surface  14   a  of the peripheral wall step portion  14  and that the central portion in the height direction of the outer circumferential surface of the base-end-side pin F 2 , or around, is in contact with the peripheral wall end surface  11   a  of the peripheral wall portion  11  and the front surface  3   a  of the sealing body  3 . Then, the main joining rotary tool F is moved so as to trace the first abutted portion J 1  with the height position kept constant. 
     In the case of the main joining rotary tool F being moved clockwise around the sealing body  3  as in the present embodiment, it is preferable to rotate the main joining rotary tool F clockwise. On the other hand, in the case of the main joining rotary tool F being moved counterclockwise around the sealing body  3 , it is preferable to rotate the main joining rotary tool F counterclockwise. 
     When the main joining rotary tool F is rotated clockwise, there is a possibility that a joining defect may occur on the left in the moving direction. When the main joining rotary tool F is rotated counterclockwise, there is a possibility that a joining defect may occur on the right in the moving direction. When such a joining defect is formed in the sealing body  3  having a thin plate thickness, water tightness and air tightness may be reduced. However, by setting the moving direction and the rotating direction of the main joining rotary tool F as described above the defect is formed on a side close to the jacket body  2  with a relatively large thickness and at a position away from the hollow portion of the liquid-cooled jacket  1 , even if a joining defect associated with friction stir joining is formed, to prevent the decrease of water tightness and air tightness. 
     As shown in  FIG.  12   , the main joining rotary tool F is moved around along the first abutted portion J 1 , and then is moved to pass the start position s 1 . Then, the main joining rotary tool F is moved to the end position e 1  set on the peripheral wall end surface  11   a  of the wall portion  11 A, while being deviated to the outer side. When the main joining rotary tool F reaches the end position e 1 , the main joining rotary tool F is moved upward to separate the main joining rotary tool F from the wall portion  11 A. 
     When a removal trace remains on the peripheral wall end surface  11   a  of the wall portion  11 A after the main joining rotary tool F is separated from the wall portion  11 A, a repair step of repairing the removal trace may be performed. In the repair step, overlay welding is performed, for example, to fill the weld metal in the removal trace for repair. This makes the peripheral wall end surface  11   a  flat. 
     Note that in the case where the main joining rotary tool F is separated from the peripheral wall  11 , the main joining rotary tool F may be gradually moved upward while moving the main joining rotary tool F on the peripheral wall end surface  11   a  of the peripheral wall portion  11 , for example, so that the insertion depth of the main joining rotary tool F is gradually reduced. By doing so, it is possible to prevent the removal trace after the first main joining step from remaining on the peripheral wall end surface  11   a  or to make the removal trace small. 
     The second main joining step is a step of performing friction stir joining to the respective second abutted portion J 2  by using the main joining rotary tool F, as shown in  FIGS.  14  and  15   . In the second main joining step, the main joining rotary tool F rotated clockwise is inserted into an arbitrary start position s 2  of the second abutted portion J 2 , and the main joining rotary tool F is moved counterclockwise along the second abutted portion J 2 . With the second main joining step, a plasticized area W 2  is formed in the second abutted portion J 2 . 
     In the second main joining step, as shown in  FIG.  15   , friction stirring is performed with the tip-end-side pin F 3  and the base-end-side pin F 2  brought in contact with the support columns  12  of the jacket body  2  and the sealing body  3 . In the second main joining step, the friction stir joining is performed while the support column end surface  16   a  of the support column  12  and the front surface  3   a  of the sealing body  3  being pressed by the outer circumferential surface of the base-end-side pin F 2  of the main joining rotary tool F. The insertion depth of the main joining rotary tool F is set so that at least the plasticized area W 2  reaches the step bottom surface  17   a , and that at least a part of the base-end-side pin F 2  comes in contact with the support column end surface  16   a  of the support column  12  and the front surface  3   a  of the sealing body  3 . In the present embodiment, the insertion depth is set so that the tip of the tip-end-side pin F 3  does not reach the step bottom surface  17   a  of the support column step portion  17  and that the center portion in the height direction of the outer peripheral surface of the base-end-side pin F 2 , or around, comes in contact with the support column end surface  16   a  of the support column  12  and the front surface  3   a  of the sealing body  3 . Then, the main joining rotary tool F is moved so as to trace the second abutted portion J 2  with the height position kept constant. 
     Note that the insertion depth of the main joining rotary tool F may not necessarily be constant. For example, the insertion depth may be changed between the first main joining step and the second main joining step. In addition, the insertion depth of the main joining rotary tool F may be set so that the tip of the tip-end-side pin F 3  comes in contact with the step bottom surface  14   a  of the peripheral wall step portion  14  and the step bottom surface  17   a  of the support column step portion  17 . At this time, the plastically fluidized material needs to be prevented from flowing out to the inside of the liquid-cooled jacket  1 . 
     In the second main joining step, in the case of the main joining rotary tool F being moved counterclockwise with respect to the support column  12  as in the present embodiment, it is preferable to rotate the main joining rotary tool F clockwise. On the other hand, in the case of the main joining rotary tool F being moved clockwise with respect to the support column  12 , it is preferable to rotate the main joining rotary tool F counterclockwise. By setting the moving direction and the rotating direction of the main joining rotary tool F as described above, a joining defect due to friction stir joining, even if formed, is formed on the side close to the support column  12 , having a relatively large thickness, and at a position away from the hollow portion of the liquid-cooled jacket  1 , to allow for preventing the decrease in water tightness and air tightness. 
     As shown in  FIG.  14   , the main joining rotary tool F is moved around along the second abutted portion J 2 , and further moved to pass through the starting position s 2 . Then, the main joining rotary tool F is moved to the end position e 2  set on the second abutted portion J 2 . Once the end position e 2  is reached, the main joining rotary tool F is moved upward to separate the main joining rotary tool F from the second abutted portion J 2 . 
     When a removal trace remains in the second abutted portion J 2  after the main joining rotary tool F is separated from the second abutted portion J 2 , a repair step of repairing the removal trace may be performed. In the repair step, overlay welding may be performed to fill the weld metal in the removal trace to repair it, for example. This makes the front surface  3   a  of the sealing body  3  and the support column end surface  16   a  of the support column  12  flat. 
     Note that when the main joining rotary tool F is separated from the second abutted portion J 2 , the main joining rotary tool F may be moved toward the center of the support column  12  for separation on the support column  12 . Furthermore, in the case of separating the main joining rotary tool F from the second abutted portion J 2 , the main joining rotary tool F may be gradually moved upward while moving the main joining rotary tool F on the second abutted portion J 2  or the support column end surface  16   a , for example, so that the insertion depth of the main joining rotary tool F is gradually reduced. By doing so, the removal trace after the second main joining step is prevented from remaining on the front surface  3   a  of the sealing body  3  and the support column end surface  16  of the support column  12 , or is reduced in size. 
     The drilling step is a step of forming fixing holes X for mounting the heating elements H in respective support columns  12  as shown in  FIG.  16   . The fixing hole X is formed so as to penetrate a part of the plasticized area W 2  to reach the support column  12 . 
     In the burr removing step, the burrs exposed on the surfaces of the jacket body  2  and the sealing body  3  with the first main joining step, the second main joining step, and the drilling step, are removed. This allows for finishing the surfaces of the jacket body  2  and the sealing body  3  clean. 
     The mounting step is a step of mounting the heating element H by means of the mounting member M as shown in  FIG.  17   . When the heating element H is mounted, the through hole formed in the flange H 1  of the heating element H is communicated with the fixing hole X and the heating element H is fixed by the mounting member M such as a screw. The mounting member M is inserted to reach the support column  12 . 
     Note that the fixing hole X is formed on the sealing body  3  side in the present embodiment to mount the heating element H to the sealing body  3  side in the present embodiment, but the fixing hole X reaching the support column  12  may be formed in the bottom portion  10  to mount the heating element H the bottom portion  10 . The heating element H may be mounted to at least one of the sealing body  3  and the bottom portion  10 . Moreover, although the fixing hole X is formed in the present embodiment, the heating element H may be fixed with the mounting member M without forming the fixing hole X. 
     Next, the advantageous effects of the present embodiment will be described. 
     As shown in  FIG.  18   , since the conventional shoulder-less main joining rotary tool  100  does not press the surface of the metal members  110  to be joined by the shoulder portion, there is a problem that the concave groove (the concave groove made with the surface of the joined metal members and the surface of the plasticized area) increases in size and the joined surface increases in roughness. In addition, there is a problem that a bulging portion (a portion where the surfaces of the joined metal members expand as compared with those before joining) is generated to the recessed groove. Alternatively, when the taper angle β of the main joining rotary tool  101  is larger than the taper angle α of the shoulder-less main joining rotary tool  100  as in the case of the main joining rotary tool  101  in  FIG.  19   , the surface of the joined metal members  110  may be pressed compared to the shoulder-less main joining rotary tool  100 , so the recessed groove is reduced in size and the bulging portion is reduced in size. However, since the downward plastic flow increases, a kissing bond is likely to be formed under the plasticized area. 
     In contrast, according to the method for manufacturing a liquid-cooled jacket of the present embodiment, the main joining rotary tool F comprises a base-end-side pin F 2  and a tip-end-side pin F 3  whose taper angle is smaller than the taper angle A 1  of the base-end-side pin F 2 . This facilitates inserting, the main joining rotary tool F can be easily inserted into the jacket body  2  and the sealing body  3 . In addition, since the taper angle A 2  of the tip-end-side pin F 3  is small, the main joining rotary tool F can be easily inserted to a deep position of the jacket body  2  and the sealing body  3 . In addition, since the taper angle A 2  of the tip-end-side pin F 3  is small, the downward plastic flow can be prevented as compared with the main joining rotary tool  101 . For this reason, forming a kissing bond in the lower part of the plasticized areas W 1 , W 2  is prevented. On the other hand, since the taper angle A 1  of the base-end-side pin F 2  is large, stable joining can be performed as compared with the conventional rotary tool even if the thickness of the jacket body  2  and the sealing body  3  and the height position of joining are changed. 
     In addition, since the plastically fluidized material is pressed by the outer peripheral surface of the base-end-side pin F 2 , the recessed groove generated on the joined surface is reduced in size and the bulging portion generated next to the recessed groove is eliminated or become smaller. Furthermore, since the stairs-like pin step portion  30  is shallow and has an exit angle, the plastically fluidized material is easily pushed out to the outside of the pin step portion  30  while the plastically fluidized material is pressed by the step bottom surface  30   a . Then, even though the plastically fluidized material is pressed by the base-end-side pin F 2 , the plastically fluidized material less likely adheres to the outer circumferential surface of the base-end-side pin F 2 . Therefore, the joined surface is reduced in roughness, and joining quality is stabilized suitably. 
     Moreover, since the sealing body  3  is supported by the support column  12  and the sealing body  3  is joined with and the support column  12  by the friction stirring, the deformation resistance of the liquid-cooled jacket  1  is enhanced. Furthermore, according to the present embodiment, since the support column  12  is disposed in the hollow portion in the liquid-cooled jacket  1 , the heat transport fluid also comes in contact with the outer circumferential surface of the support column  12 . Therefore, the heat transferred from the heating element H to the support column  12  via the mounting member M is efficiently discharged. That is, the heat leaking through the mounting member M, which fixes the heating element H to the liquid-cooled jacket  1 , is prevented. Furthermore, since the support columns  12 , to which the heating element H is fixed, are disposed inside the jacket body  2 , the liquid-cooled jacket  1  may be reduced in size. 
     Furthermore, according to the method for manufacturing a liquid-cooled jacket according to the present embodiment, since only the tip-end-side pin F 3  and the base-end-side pin F 2  are inserted into the jacket body  2  and the sealing body  3 , the load applied to the friction stir device is reduced as compared with such a case that the shoulder portion of the rotary tool is pushed into, and the operability of the main joining rotary tool F is also improved. Moreover, since the load applied to the friction stir device is reduced, the deep positions of the first abutted portion J 1  and the second abutted portion J 2  are joined with no large load applied to the friction stir device. 
     In addition, when the main joining rotary tool F is pulled out on the sealing body  3  having a relatively small thickness, it is difficult to repair the removal trace, or the pulling-out operation is not stable and consequently generates a defect in the sealing body  3 . However, according to the method for manufacturing a liquid-cooled jacket of the present embodiment, the main joining rotary tool F is pulled out on the peripheral wall portion  11  or the support column  12  having a larger thickness than the sealing body  3 , and such problems are solved. 
     Furthermore, according to the method for manufacturing a liquid-cooled jacket of the present embodiment, the provisional joining step before the first main joining step is performed, and therefore the first abutted portion J 1  and the second abutted portion J 2  are each prevented from coming apart when performing the first main joining step and the second main joining step. 
     Furthermore, since the support column  12  (support column end surface  16   a ) is exposed on the surface  3   a  of the sealing body  3  in the present embodiment, the drilling step of drilling the fixing hole X and the mounting step of mounting the heating element H are easily performed. Moreover, since the support column  12  is brought into direct contact with the heating element H, the cooling efficiency is further enhanced. 
     Hereinabove, although the method for manufacturing the liquid-cooled jacket of the first embodiment of the present invention has been described, appropriate design change is possible within the scope of the present invention. For example, the main joining step is performed in the order of the first abutted portion J 1  and the second abutted portion J 2  in the present embodiment, but the second abutted portion J 2  may be joined first by friction stirring. In addition, the cooling medium may be flown into the jacket body  2  to perform the friction stir joining, while the jacket body  2  and the sealing body  3  being cooled, in the first main joining step and the second main joining step. This keeps the frictional heat at a low level, to reduce the deformation of the liquid-cooled jacket  1  caused by the thermal contraction. Moreover, according to such a method, cooling may be performed using the jacket body  2  and the sealing body  3  themselves without separately using a cooling plate, a cooling means, etc. 
     In addition, although the flat cross-sectional shape of the support column  12  is circular in the present embodiment, it may be of an oval or another polygon. 
     In addition, although provisional joining is performed using the provisional joining rotary tool G in the first embodiment, provisional joining may be performed using the main joining rotary tool F. This eliminates time and effort of replacing the rotary tool. Furthermore, the provisional joining step may be performed on at least one of the first abutted portion J 1  and the second abutted portion J 2 . Moreover, the provisional joining step may be performed by welding. 
     First Modification 
     Next, a method for manufacturing the liquid-cooled jacket according to a first modification of the first embodiment will be described. As shown in  FIG.  20   , the first modification is different from the first embodiment in that the provisional joining step, the first main joining step, and the second main joining step are performed using a cooling plate. The first modification will be described focusing on differences from the first embodiment. 
     As shown in  FIG.  20   , the jacket body  2  is fixed to the table K in the fixing step in the first modification. The table K is configured with a basal plate K 1  having a rectangular parallelepiped shape, clamps K 3  formed at four corners of the basal plate K 1 , and a cooling pipe WP arranged inside the basal plate K 1 . The table K is a member which restrains the jacket body  2  so as to be immovable and functions as a “cooling plate” in the claims. 
     The cooling pipe WP is a tubular member embedded inside the basal plate K 1 . Inside the cooling pipe WP, a cooling medium for cooling the basal plate K 1  flows. The arrangement position of the cooling pipe WP, that is, the shape of the cooling flow passage through which the cooling medium flows is not particularly limited, but in the first modification, is in a planar shape along the moving trajectory of the main joining rotary tool Fin the first main joining step. That is, the cooling pipe WP is arranged so that the cooling pipe WP substantially overlaps the first abutted portion J 1 . 
     In the provisional joining step, the first main joining step and the second main joining step of the first modification, after the jacket body  2  is fixed to the table K, friction stir joining is performed with a cooling medium flowed through the cooling pipe WP. This keeps the frictional heat during the friction stirring at a low level to reduce the deformation of the liquid-cooled jacket  1  resulting from heat contraction. Furthermore, since the cooling flow passage overlaps in a planar view with the first abutted portion J 1  (the moving trajectory of the provisional joining rotary tool G and the main joining rotary tool F) in the first modification, it is possible to intensively cool the portion where frictional heat is generated. This enhances the cooling efficiency. Furthermore, since the cooling pipe WP is disposed to circulate the cooling medium, the management of the cooling medium is easy. Moreover, since the table K (cooling plate) and the jacket body  2  are in surface contact with each other, the cooling efficiency is enhanced. 
     Note that friction stir joining may be performed with the jacket body  2  and the sealing body  3  being cooled by using a table K (cooling plate), and also with a cooling medium being flowed inside of the jacket body  2 . 
     Second Modification 
     Next, a method for manufacturing a liquid-cooled jacket according to a second modification of the first embodiment will be described. As shown in  FIGS.  21  and  22   , the second modification is different from the first embodiment in that the first main joining step and the second main joining step are performed with the front surface of the jacket body  2  and the front surface  3   a  of the sealing body  3  curved so as to be convex upward. The second modification will be described focusing on differences from the first embodiment. 
     As shown in  FIG.  21   , a table KA is used in the second modification. The table KA is configured with a basal plate KA 1  in the form of a rectangular parallelepiped, a spacer KA 2  formed at the center of the basal plate KA 1 , and clamps KA 3  formed at the four corners of the basal plate KA 1 . The spacer KA 2  may be integral with or separate from the basal plate KA 1 . 
     In the fixing step of the second modification, the jacket body  2  and the sealing body  3  integrated in the provisional joining step are fixed to the table KA by the clamps KA 3 . As shown in  FIG.  22   , when the jacket body  2  and the sealing body  3  are fixed to the table KA, the bottom  10  of the jacket body  2 , the peripheral wall end surface  11   a  and the front surface  3   a  of the sealing body  3  are curved so as to be convex upward. More specifically, those described are curved so that the first side  21  of the wall portion  11 A, the second side  22  of the wall portion  11 B, the third side  23  of the wall portion  11 C, and the fourth side  24  of the wall portion  11 D of the jacket body  2  exhibit curved lines. 
     In the first main joining step and the second main joining step of the second modification, friction stir joining is performed using the main joining rotary tool F. In the first main joining step and the second main joining step, an amount of deformation of at least one of the jacket body  2  and the sealing body  3  is measured, and the friction stir joining is performed while the insertion depth of the tip-end-side pin F 3  of the main joining rotary tool F being adjusted according to the amount of deformation. That is, the main joining rotary tool F is moved so that the moving trajectory thereof of exhibits a curved line along the curved surface of the circumferential wall end surface  11   a  of the jacket body  2  and the front surface  3   a  of the sealing body  3 . This makes the depths and widths of the plasticized areas W 1  and W 2  constant. 
     Thermal contraction may occur in the plasticized areas W 1  and W 2  due to the heat input from the friction stir joining to deform portions, closer to the sealing body  3 , of the liquid-cooled jacket  1  in a concave shape. However, according to the first main joining step and the second main joining step of the second modification, since the jacket body  2  and the sealing body  3  are fixed in a convex upward shape in advance so that tensile stress acts on the peripheral wall end surface  11   a  and the front surface  3   a , the liquid-cooled jacket  1  is made flat by way of thermal contraction after friction stir joining. In addition, when the main joining step is performed with the conventional rotary tool, there is a problem that if the jacket body  2  and the sealing body  3  are warped in a convex shape, the shoulder portion of the rotary tool has in contact with the jacket body  2  and the sealing body  3  and the operability is bad. However, according to the second modification, since the shoulder portion does not exist in the main joining rotary tool F, even when the jacket body  2  and the sealing body  3  are warped in a convex shape, the operability of the main joining rotary tool F is good. 
     An amount of deformation of each of the jacket body  2  and the sealing body  3  may be measured by using a well-known height detection device. In addition, the first main joining step and the second main joining step may be performed while an amount of deformation of the jacket body  2  and the sealing body  3  being detected, for example, using a friction stir device equipped with a detection device for detecting the height from the table KA to at least one of the jacket body  2  and the sealing body  3 . 
     Furthermore, the jacket body  2  and the sealing body  3  are curved in the second modification so that all of the sides from the first side  21  to the fourth side  24  exhibit curved lines, but the present invention is not limited thereto. For example, the first side  21  and the second side  22  may exhibit straight, while the third side  23  and the fourth side  24  may exhibit curved lines. Also, for example, the first side  21  and the second side  22  may exhibit curved lines, and the third side  23  and the fourth side  24  may exhibit straight lines. 
     Furthermore, the height position of the tip-end-side pin F 3  of the main joining rotary tool F is changed according to the amount of deformation of the jacket body  2  or the sealing body  3  in the second modification. However, the main joining step may be performed with the height of the tip-end-side pin F 3  of the main joining rotary tool F with respect to the table KA kept constant. 
     In addition, the spacer KA 2  may have any shape as long as the front surfaces of the jacket body  2  and the sealing body  3  are fixed so as to be convex. Furthermore, the spacer KA 2  may be omitted as long as the front surfaces of the jacket body  2  and the sealing body  3  are fixed so as to be convex. In addition, the main joining rotary tool F may be attached to a robot arm having a spindle unit or the like at its tip, for example. According to this configuration, the rotation axis of the main joining rotary tool F is easily changed to have various inclination angles. 
     Third Modification 
     Next, a method for manufacturing the liquid-cooled jacket according to the third modification of the first embodiment will be described. As shown in  FIG.  23   , the third modification is different from the first embodiment in that the jacket body  2  and the sealing body  3  are formed in advance so as to be convexly curved toward the front surfaces thereof in the preparation step. The third modification will be described focusing on differences from the first embodiment. 
     In the preparation step according to the third modification, the jacket body  2  and the sealing body  3  are formed by die casting so as to be convexly curved toward the front surfaces thereof. This makes the jacket body  2  formed so that the bottom portion  10  and the peripheral wall portion  11  are convex toward the front surfaces thereof, respectively. Moreover, the front surface  3   a  of the sealing body  3  is formed so as to be convex. 
     As shown in  FIG.  24   , when the fixing step is performed in the third modification, the jacket body  2  and the sealing body  3  provisional joined are fixed to the table KB. The table KB is configured with a basal plate KB 1  having a rectangular parallelepiped shape, a spacer KB 2  arranged at the center of the basal plate KB 1 , clamps KB 3  formed at four corners of the basal plate KB 1 , and a cooling pipe WP embedded inside the basal plate KB 1 . The table KB is a member that restrains the jacket body  2  so as to be immovable and functions as a “cooling plate” in the claims. 
     The spacer KB 2  is composed of a curved surface KB 2   a  which is curved to be convex upward, and elevated surfaces KB 2   b  and KB 2   b  which are formed at both ends of the curved surface KB 2   a  and rise from the basal plate KB 1 . The first side Ka and the second side Kb of the spacer KB 2  exhibit curved lines, and the third side Kc and the fourth side Kd exhibit straight lines. 
     The cooling pipe WP is a tubular member embedded inside the basal plate KB 1 . A cooling medium for cooling the basal plate KB 1  flows in the cooling pipe WP. The position of disposing the cooling pipe WP, that is, the shape of the cooling flow passage in which the cooling medium flows is not particularly limited. In the third modification, the passage has a planar shape along the moving trajectory of the main joining rotary tool F in the first main joining step. That is, the cooling pipe WP substantially overlaps with the first abutted portion J 1  substantially overlap. 
     In the fixing step of the third modification, the jacket body  2  integrated with the sealing body  3  by the provisional joining are fixed to the table KB by the clamps KB 3 . More specifically, those described are fixed to the table KB so that the back surface of the bottom portion  10  of the jacket body  2  comes in surface contact with the curved surface KB 2   a . The jacket body  2 , when fixed to the table KB, is curved so that the first side  21  of the wall portion  11 A and the second side  22  of the wall portion  11 B of the jacket body  2  exhibit curved lines, while the third side  23  of the wall portion  11 C and the fourth side  24  of the wall portion  11 D exhibit straight lines. 
     In the first main joining step and the second main joining step of the third modification, friction stir joining is respectively performed on the first abutted portion J 1  and the second abutted portion J 2  using the main joining rotary tool F. In the first main joining step and the second main joining step, an amount of deformation of at least one of the jacket body  2  and the sealing body  3  is measured, and the friction stir joining is performed while the insertion depth of the tip-end-side pin F 3  of the main joining rotary tool F being adjusted to the amount of deformation. That is, the main joining rotary tool F is moved so that the moving trajectory thereof exhibits a curved line or a straight line along the peripheral wall end surface  11   a  of the jacket body  2  and the front surface  3   a  of the sealing body  3 . This makes the depth and width of the plasticized area W 1  constant. 
     Thermal contraction may occur in the plasticized areas W 1  and W 2  due to the heat input from the friction stir joining, to deform portions, close to the sealing body  3 , of the liquid-cooled jacket  1  in a concave shape. However, according to the first main joining step and the second main joining step of the third modification, since the jacket body  2  and the sealing body  3  are formed to be convex in advance, the liquid-cooled jacket  1  is made flat by way of thermal contraction after friction stir joining. 
     Furthermore, the curved surface KB 2   a  of the spacer KB 2  comes in surface contact with the concave back surface of the bottom portion  10  of the jacket body  2  in the third modification. This allows for performing friction stir joining is performed while the jacket body  2  and the sealing body  3  being cooled more effectively. Since the frictional heat in the friction stir joining is kept at a low level, the deformation of the liquid-cooled jacket  1  caused by the thermal contraction is reduced. This allows, in the preparation step, the jacket body  2  and the sealing body  3  are formed in a convex shape for reducing the curvature of the jacket body  2  and the sealing body  3 . 
     An amount of deformation of each of the jacket body  2  and the sealing body  3  may be measured by using a well-known height detection device. In addition, the main joining step may be performed while an amount of deformation of the jacket body  2  and the sealing body  3  being detected, for example, using a friction stir device equipped with a detection device for detecting the height from the table KB to at least one of the jacket body  2  and the sealing body  3 . 
     Moreover, although the jacket body  2  and the sealing body  3  are curved in the third modification, so that the first side  21  and the second side  22  exhibit curved lines in the third modification, the present invention is not limited thereto. For example, the spacer KB 2  having a spherical surface may be formed, and the back surface of the bottom portion  10  of the jacket body  2  may come in surface contact with the spherical surface. In this case, when the jacket body  2  is fixed to the table KB, all of the first side  21  to the fourth side  24  exhibit curved lines. 
     In addition, the height position of the tip-end-side pin F 3  of the main joining rotary tool F is changed according to the amount of deformation of the jacket body  2  or the sealing body  3  in the third modification. However, the main joining step may be performed with the height of the tip-end-side pin F 3  of the main joining rotary tool F with respect to the table KB kept constant. 
     Second Embodiment 
     Next, a method for manufacturing a liquid-cooled jacket according to a second embodiment of the present invention will be described. As shown in  FIG.  25   , the second embodiment is different from the first embodiment in that the support column  12  does not have any support column step portion formed. The method for manufacturing a liquid-cooled jacket according to the second embodiment will be described focusing on differences from the first embodiment. 
     A liquid-cooled jacket  1 A according to the second embodiment is composed of a jacket body  2 A and a sealing body  3 A. The jacket body  2 A is a box-like body whose upper side is open. The jacket body  2 A includes the bottom portion  10 , the peripheral wall portion  11 , and a plurality of the support columns  12 . The jacket body  2 A is appropriately selected from metals which may be frictionally stirred such as aluminum, aluminum alloy, copper, copper alloy, titanium, titanium alloy, magnesium and magnesium alloy. In the present embodiment, the jacket body  2 A is formed of an aluminum alloy of the same material type as the sealing body  3 A, but an aluminum alloy cast material (for example, JIS AC4C, ADC12 or the like) may be used. The bottom portion  10  has a rectangular shape in a planar view. The peripheral wall portion  11  is composed of the wall portions  11 A,  11 B,  11 C, and  11 D having the same plate thickness. 
     The peripheral wall step portion  14  is formed on the peripheral wall end surface  11   a  of the circumferential wall portion  11 , along the circumferential edge of the opening of the jacket body  2 A. The peripheral wall step portion  14  is composed of the step bottom surface  14   a  and the step side surface  14   b  rising from the step bottom surface  14   a . The step bottom surface  14   a  is formed at a position one step lower than the circumferential wall end surface  11   a.    
     The support column  12  rises from the bottom portion  10  and has a cylindrical shape. The number of the support columns  12  may be any number as long as being one or more, but in the present embodiment, four support columns are formed. The shapes of the support columns  12  are all the same. The support column end surface  12   a  as an end surface of the support column  12  is formed at the same height position as the step bottom surface  14   a  of the peripheral wall step portion  14 . 
     The sealing body  3 A is a plate-like member having a rectangular shape in a planar view. In the present embodiment, the material of the sealing body  3 A is formed of an aluminum alloy of the same material type as the jacket body  2 A, but a wrought aluminum alloy material (for example, JIS A1050, A1100, A6063 etc.) may be used. The sealing body  3 A is formed in a size to be placed on the peripheral wall step portion  14  with substantially no gap. The plate thickness of the sealing body  3 A is substantially equal to the height of the step side surface  14   b.    
     As shown in  FIG.  26   , the jacket body  2 A is joined by friction stirring and integrated with the sealing body  3 A as the liquid-cooled jacket  1 A. The liquid-cooled jacket  1 A has the first abutted portion J 1  in which the step side surface  14   b  (see  FIG.  25   ) of the peripheral wall step portion  14  is abutted against the outer peripheral side surface  3   c  of the sealing body  3 A are abutted, and the four overlapping portions J 3  in which the back surface  3   b  of the sealing body  3 A and the support column end surfaces  12   a  of the support columns  12  are overlapped with each other, respectively joined by friction stirring. The plasticized area W 1  is formed in the first abutted portion J 1 , and a plasticized area W 2  is formed in the overlapping portion J 3 . The liquid-cooled jacket  1 A has a hollow portion formed therein, in which a heat transport fluid for transporting heat to the outside flows. 
     Next, a method for manufacturing a liquid-cooled jacket (a method for manufacturing a liquid-cooled jacket with heating elements) according to a second embodiment will be described. In the method for manufacturing a liquid-cooled jacket, a preparation step, a placing step, a fixing step, a provisional joining step, a first main joining step, a second main joining step, a drilling step, a burr removing step and a mounting step are performed. 
     The preparation step is a step of forming the jacket body  2 A and the sealing body  3 A, as shown in  FIG.  25   . The jacket body  2 A is formed by die casting, for example. 
     The placing step is a step of placing the sealing body  3 A on the jacket body  2 A, as shown in  FIGS.  27  and  28   . The back surface  3   b  of the sealing body  3 A comes in surface contact with the step bottom surface  14   a  of the peripheral wall step portion  14  and the support column end surface  12   a  of the support column  12 , respectively. In the placing step, the step side surface  14   b  of the peripheral wall step portion  14  is abutted against the outer peripheral side surface  3   c  of the sealing body  3 A to form the first abutted portion J 1 . The first abutted portion J 1  has a rectangular shape in a planar view. Furthermore, in the placing step, the back surface  3   b  of the sealing body  3 A is overlapped with the support column end surface  12   a  of the support column  12  to form the overlapping portion J 3 . The overlapping portion J 3  has a circular shape in a planar view. 
     In the fixing step, the jacket body  2 A is fixed to a table (not shown). The jacket body  2 A is immovably restrained to the table by a fixing jig such as a clamp. 
     The provisional joining step is a step of provisional joining the jacket body  2 A with the sealing body  3 A, as shown in  FIG.  29   . The provisional joining step is the same as that of the first embodiment, and thus the description thereof is omitted. 
     The first main joining step is a step of performing friction stir joining to the first abutted portion J 1  by using the main joining rotary tool F, as shown in  FIGS.  30  and  31   . The first main joining step is the same as that of the first embodiment, and thus the description thereof is omitted. 
     The second main joining step is a step of performing friction stir joining to the respective overlapping portions J 3  by using the main joining rotary tool F, as shown in  FIGS.  32  and  33   . In the second main joining step, the main joining rotary tool F rotated clockwise is inserted from the front surface  3   a  of the sealing body  3 A into the start position s 2 , and the main joining rotary tool F is moved counterclockwise along the outer circumferential edge of the support column  12 . With the second main joining step, a plasticized area W 2  is formed in the overlapping portion J 3 . 
     In the second main joining step, friction stirring is performed with the tip-end-side pin F 3  brought in contact with only the sealing body  3 A, and with the base-end-side pin F 2  brought in contact with the sealing body  3 A, as shown in  FIG.  33   . In the second main joining step, friction stir joining is performed while the surface  3   a  of the sealing body  3 A being pressed by the outer circumferential surface of the base-end-side pin F 2  of the main joining rotary tool F. The insertion depth of the main joining rotary tool F is set so that at least the plasticized area W 2  reaches the support column end surface  12   a , and that at least a part of the base-end-side pin F 2  comes in contact with the surface  3   a  of the sealing body  3 . In the present embodiment, the insertion depth is set so that the tip of the tip-end-side pin F 3  does not reach the support column end surface  12   a  and that the central portion in the height direction of the outer circumferential surface of the base-end-side pin F 2  or around comes in contact with the surface  3   a  of the sealing body  3 . Then, the main joining rotary tool F is moved circularly in a planar view with the height position kept constant. 
     Note that the insertion depth of the main joining rotary tool F may not be necessarily constant. For example, the insertion depth may be changed between the first main joining step and the second main joining step. In addition, the insertion depth of the main joining rotary tool F may be set so that the tip of the tip-end-side pin F 3  reaches the support column end surface  12   a  of the support column  12 , that is, the tip-end-side pin F 3  comes in contact with both the jacket body  2 A and the sealing body  3 A. At this time, the plastically fluidized material needs to be prevented from flowing out to the inside of the liquid-cooled jacket  1 A. 
     In the second main joining step, in the case of the main joining rotary tool F being moved counterclockwise with respect to the support column  12  as in the present embodiment, it is preferable to rotate the main joining rotary tool F clockwise. On the other hand, in the case of the main joining rotary tool F being moved clockwise with respect to the support column  12 , it is preferable to rotate the main joining rotary tool F counterclockwise. By setting the moving direction and the rotating direction of the main joining rotary tool F as described above, a joining defect due to friction stir joining, even if formed, is formed on the side closer to the support column  12 , having a relatively large thickness, and at a position away from the hollow portion of the liquid-cooled jacket  1 A, to allow for the decrease in water tightness and airtightness preventing. 
     As shown in  FIG.  32   , the main joining rotary tool F is moved around along the overlapping portion J 3 , and further moved to pass through the starting position s 2 . Then, the main joining rotary tool F is moved to the end position e 2  set on the sealing body  3 A, and when the main joining rotary tool F reaches ending position e 2 , the main joining rotary tool F is moved upward to separate the main joining rotary tool F from the sealing body  3 A. 
     If a removal trace remains in the sealing body  3 A after the main joining rotary tool F is separated from the overlapping portion J 3 , a repair step may be performed to repair the removal trace. In the repair step, for example, overlay welding may be performed to fill the weld metal in the removal trace for repair, for example. This makes front surface  3   a  of the sealing body  3 A becomes flat. 
     Note that when the main joining rotary tool F is separated from the sealing body  3 A, the main joining rotary tool F may be moved toward the center of the support column  12  for separation on the sealing body  3 A. Alternatively, when the main joining rotary tool F is separated from the sealing body  3 A, the main joining rotary tool F may be gradually moved upward while the main joining rotary tool F being moved on the sealing body  3 A, for example, so that the insertion depth of the main joining rotary tool F is gradually reduced. By doing so, the removal trace after the second main joining step is prevented from remaining on the sealing body  3 A, or is reduced in size. 
     The drilling step is a step of forming a fixing holes X which communicates the sealing body  3 A with the support column  12  and is for fixing the heating element H, as shown in  FIG.  34   . The fixing hole X is formed so as to penetrate a part of the plasticized area W 2  to reach the support column  12 . 
     In the burr removing step, the burrs exposed on the surfaces of the jacket body  2 A and the sealing body  3 A with the first main joining step, the second main joining step, and the drilling step, are removed. This allows for finishing the surfaces of the jacket body  2 A and the sealing body  3 A clean. 
     The mounting step is a step of mounting the heating element H by means of the mounting member M, as shown in  FIG.  35   . When the heating element H is mounted, the through hole formed in the flange H 1  of the heating element H and the fixing hole X are communicated with each other and the heating element is fixed by the mounting member M such as a screw. The mounting member M is inserted to reach the support column  12 . 
     Note that, the fixing hole X is formed on the sealing body  3 A side in the present embodiment to fix the heating element H to the sealing body  3 A. However, the heating element H may be fixed to the bottom portion  10  by forming a hole in the bottom portion  10  to communicate with the bottom portion  10  and the support column  12 . The heating element H may be mounted to at least one of the sealing body  3 A and the bottom portion  10 . Moreover, although the fixing hole X is formed in the present embodiment, the heating element H may be fixed with the mounting member M without forming the fixing hole X. 
     Substantially the same advantageous effects as with the first embodiment may be also obtained by the method for manufacturing a liquid-cooled jacket described above. In the first embodiment, the second abutted portion J 2  (see  FIG.  12   ) is exposed on the sealing body  3 , but the abutted portion is not exposed in the second embodiment. However, the sealing body  3  is joined with the support column  12  by performing a friction stir joining in which the overlapping portion J 3  is friction stirred the sealing body  3 A downward. Furthermore, having no holes in the sealing body  3 A and forming no support column step portions in the support column  12 , facilitate producing a liquid-cooled jacket in the second embodiment. 
     In addition, according to the method for manufacturing a liquid-cooled jacket of the present embodiment, the tip-end-side pin F 3  is inserted into either the jacket body  2 A and the sealing body  3 A or only the sealing body  3 A and the base-end-side pin F 2  is inserted into the sealing body  3 A and therefore the load applied to the friction stir device is reduced as compared with the case where the shoulder portion of the rotary tool is pushed in, and the operability of the main joining rotary tool F is also improved. In addition, since the load applied to the friction stir device is reduced, the deep position in the first abutted portion J 1  is joined without large load applied to the friction stir device, and the overlapping portion J 3  located at a deep position is joined. 
     Furthermore, in the second main joining step, the water tightness and the airtightness is improved by performing a friction stir joining in which the inside of the outer circumferential edge of the support column  12  is friction stir joined one or more rounds in the second main joining step of the present embodiment. Note that in the moving route of the main joining rotary tool F in the second main joining step, the main joining rotary tool F does not have to be moved one or more rounds with respect to the support column  12 . The moving route may be set so that the plastically fluidized material does not flow out to the inside of the liquid-cooled jacket  1 A and at least a part of the overlapping portion J 3  is friction stir joined. 
     Although the second embodiment of the present invention has been described above, design may be changed as appropriate within the scope of the present invention. For example, in the second embodiment, the liquid-cooled jacket  1 A may be manufactured by employing the manufacturing methods of the first to third modifications described above. 
     Although the embodiments and modifications of the present invention have been described above, design may be changed as appropriate. For example, fins may be formed on at least one of the jacket body and the sealing body. In addition, the main joining rotary tool F may be moved two rounds along the first abutted portion J 1 . In addition, the rotary tools used in the first main joining step and the second main joining step may be different from each other. Moreover, although the present invention is applied to the method for manufacturing the liquid-cooled jacket having the heating element H attached thereto in the embodiments, the present invention may be also applied to the method for manufacturing the liquid-cooled jacket without attaching heating element H thereto. In this case, the drilling step and the mounting step are omitted. 
     The design of the main joining rotary tool F of the present invention may be changed as appropriate.  FIG.  36    is a side view of the first modification of the main joining rotary tool of the present invention. As shown in  FIG.  36   , in a main joining rotary tool Fa according to the first modification, a step angle C 1  between the step bottom surface  30   a  and the step side surface  30   b  of the pin step portion  30  is 85°. The step bottom surface  30   a  is parallel to the horizontal plane. In this way, the step bottom surface  30   a  is parallel to the horizontal plane, and the step angle C 1  may be an acute angle within a range in which the plastically fluidized material is pushed out without staying in and adhering to the pin step portion  30  during friction stirring. 
       FIG.  37    is a side view of the second modification of the main joining rotary tool of the present invention. As shown in  FIG.  37   , in the case of a main joining rotary tool Fb according to the second modification, the step angle C 1  of the pin step portion  30  is 115°. The step bottom surface  30   a  is parallel to the horizontal plane. In this way, the step bottom surface  30   a  is parallel to the horizontal plane, and the step angle C 1  may be an obtuse angle within a range of allowing for functioning as the pin step portion  30 . 
       FIG.  38    is a side view of the third modification of the main joining rotary tool of the present invention. As shown in  FIG.  38   , in the case of a main joining rotary tool Fc according to the third modification, the step bottom surface  30   a  is inclined 10° upward with respect to the horizontal plane at an angle of, radially outward from the rotation axis of the tool. The step side surface  30   b  is parallel to the vertical plane. In this way, the step bottom surface  30   a  may be formed so as to be inclined upward to the horizontal plane in, radically outward from the rotation axis of the tool, as long as the plastically fluidized material is pressed during the friction stirring. The same advantageous effects as those of the present embodiment are also achieved by the first to third modifications of the rotary tool for the main joining described above. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1  liquid-cooled jacket 
               1 A liquid-cooled jacket 
               2  jacket body 
               2 A jacket body 
               3  sealing body 
               3 A sealing body 
               3   a  front surface 
               3   b  back surface 
               3   c  outer peripheral side surface 
               10  bottom portion 
               11  peripheral wall portion 
               11 A wall portion 
               11 B wall portion 
               11 C wall portion 
               11 D wall portion 
               11   a  peripheral wall end surface 
               12  support column 
               12   a  support column end surface 
               13  recess 
               14  peripheral wall step portion 
               14   a  step bottom surface 
               14   b  step side surface 
               16   a  support column end surface 
               17  support column step portion 
               17   a  step bottom surface 
               17   b  step side surface 
             F main joining rotary tool (rotary tool) 
             Fa main joining rotary tool 
             Fb main joining rotary tool 
             Fc main joining rotary tool 
             F 1  base portion 
             F 2  base-end-side pin 
             F 3  tip-end-side pin 
               30  pin step portion 
               30   a  step bottom surface 
               30   b  step side surface 
               31  spiral groove 
             A 1  taper angle (of a base-end-side pin) 
             A 2  taper angle 
             C 1  step angle 
             C 2  spiral angle 
             Z 1  distance (to a base-end-side pin) 
             Z 2  distance 
             Y 1  height (at a step side surface) 
             Y 2  height 
             G provisional joining rotary tool 
             J 1  first abutted portion 
             J 2  second abutted portion 
             J 3  overlapping portion 
             K table (cooling plate) 
             M fastening member 
             W 1  plasticized area 
             W 2  plasticized area 
             WP cooling pipe