Patent Publication Number: US-10787988-B2

Title: Internal combustion engine

Description:
This application is the U.S. national phase of International Application No. PCT/JP2018/004883 filed 13 Feb. 2018, which designated the U.S. and claims priority to JP Patent Application No. 2017-028006 filed 17 Feb. 2017, the entire contents of each of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a heat retention material cartridge used as a heat retention material for a heat retention tool disposed in contact with groove-like cooling water passage-side wall surfaces of cylinder bore walls of a cylinder block of an internal combustion engine, and also relates to a cylinder bore wall heat retention tool including the same, and an internal combustion engine and an automotive vehicle provided with the them. 
     BACKGROUND ART 
     In the internal combustion engine, because of its structure causing fuel to explode at the top dead center of a piston in the bore and pushing down the piston by the explosion, the upper side of each cylinder bore wall has a higher temperature and the lower side has a lower temperature. Therefore, a difference arises in thermal deformation amount between the upper and lower sides of the cylinder bore wall. The upper side expands largely while the expansion of the lower side is smaller. 
     As a result, the frictional resistance between the piston and the cylinder bore wall increases, and this becomes a factor degrading fuel consumption. Therefore, it is required to reduce the difference in thermal deformation amount between the upper and lower sides of the cylinder bore wall. 
     Therefore, to make wall temperatures of respective cylinder bore walls uniform, it has been attempted to control the cooling efficiency by the cooling water on the upper and lower sides of the cylinder bore wall by installing a spacer in a groove-like cooling water passage to adjust the flow of cooling water in the groove-like cooling water passage. For example, Patent Literature 1 discloses an internal combustion engine cooling heat-transfer medium passage partition member, which is a passage partition member for partitioning a groove-like cooling heat-transfer medium passage into a plurality of passages when disposed in the groove-like cooling heat-transfer medium passage formed in a cylinder block of an internal combustion engine, including a passage division member formed to have a height not reaching the depth of the groove-like cooling heat-transfer medium passage and serving as a wall portion for dividing the groove-like cooling heat-transfer medium passage into a bore-side passage and an anti-bore-side passage, and a flexible lip member formed from the passage division member in a direction toward an opening portion of the groove-like cooling heat-transfer medium passage, and having a tip edge portion formed of a flexible material so as to extend beyond one inner surface of the groove-like cooling heat-transfer medium passage, so that the tip edge portion comes into contact with the inner surface by its own deflection restoration force, at an intermediate position in the depth direction of the groove-like cooling heat-transfer medium passage after completion of the insertion into the groove-like cooling heat-transfer medium passage, for separation into the bore-side passage and the anti-bore-side passage. 
     However, according to internal combustion engine cooling heat-transfer medium passage partition member disclosed in Patent Literature 1, since wall temperatures of cylinder bore walls can be made uniform to some extent, the difference in the thermal deformation amount between the upper and lower sides of the cylinder bore wall can be reduced. However, in recent years, it is required to further reduce the difference in the thermal deformation amount between the upper and lower sides of the cylinder bore wall. 
     Therefore, in recent years, wall temperatures of cylinder bore walls are made uniform by using a heat retention tool for active heat retention of a cylinder bore-side wall surface in a middle lower region of the groove-like cooling water passage of a cylinder block. Further, to attain effective heat retention of the cylinder bore-side wall surface in the middle lower region of the groove-like cooling water passage, the adhesion of the heat retention tool to the cylinder bore-side wall surface in the middle lower region of the groove-like cooling water passage is required to be high. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     Japanese Patent Laid-Open No. 2008-31939 (Claims) 
     SUMMARY OF INVENTION 
     Technical Problem 
     From such background, the applicant has developed a cylinder bore wall heat retention tool that is a heat retention tool installed in a groove-like cooling water passage of a cylinder block of an internal combustion engine having cylinder bores for heat retention of bore walls of one side half or a part of the one side of bore walls of all the cylinder bores, including a heat retention portion being arc-shaped when viewed from above for heat retention of a cylinder bore-side wall surface of the groove-like cooling water passage, and a support portion having a shape along the shape of the groove-like cooling water passage at an installation position of the heat retention tool for fixing the heat retention portion, wherein the heat retention portion includes a rubber member coming into contact with the cylinder bore-side wall surface of the groove-like cooling water passage and covering the cylinder bore-side wall surface of the groove-like cooling water passage, a back-side pressing member provided on the back side of the rubber member for pressing the rubber member entirely from the back side toward the cylinder bore-side wall surface of the groove-like cooling water passage, and an elastic member for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage so that the back-side pressing member presses the rubber member, wherein the heat retention portion is fixed to the support portion only at or near the center in the circular arc direction, and previously filed applications (Japanese Patent Application No. 2015-221931 and Japanese Patent Application No. 2015-221932). 
     In the cylinder bore wall heat retention tool according to these patent applications, used as a heat retention material is the heat retention portion (heat retention material cartridge) having the rubber member coming into contact with the cylinder bore-side wall surface of the groove-like cooling water passage and covering the cylinder bore-side wall surface of the groove-like cooling water passage, the back-side pressing member provided on the back side of the rubber member for pressing the rubber member entirely from the back side toward the cylinder bore-side wall surface of the groove-like cooling water passage, and the elastic member for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage so that the back-side pressing member presses the rubber member. 
       FIG. 27  illustrates an example of the heat retention portion. In  FIG. 27 , a heat retention portion  55  includes a rubber member  51 , a back-side pressing member (not illustrated) provided on the back side of the rubber member for pressing the rubber member  51  entirely from the back side toward a cylinder bore wall surface of a groove-like cooling water passage, a front-side abutting plate  50  provided on the contact surface side of the rubber member  51  and having a rectangular opening, and an elastic member (not illustrated) for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage so that the back-side pressing member presses the rubber member  51 . In the heat retention portion  55 , bendable portions  531   a  formed at an upper end of an elastic member attached member (not illustrated) to which the elastic member is attached, bendable portions  531   b  formed at a lower end thereof, a bendable portion  532   a  formed at a right end thereof, and a bendable portion  532   b  formed at a left end thereof are bent toward the front-side abutting plate  50 , so that the back-side pressing member, the rubber member  51 , and the front-side abutting plate  50  are sandwiched between the bendable portions and the elastic member attached member. 
     There is no problem if the rubber member of the heat retention portion  55  is solid rubber or the like. However, in the case of using a rubber material such as a thermosensitive expansion rubber that largely expands in the groove-like cooling water passage, if the thermosensitive expansion rubber expands when installed and heated in the groove-like cooling water passage, the expanded thermosensitive expansion rubber may protrude from an upper or lower side of the heat retention portion  55  and then the flow of cooling water may break off the thermosensitive expansion rubber at the protrusion portion. 
     Accordingly, the present invention intends to provide a heat retention material cartridge capable of preventing the expanded thermosensitive expansion rubber from protruding from the upper or lower side of the heat retention material cartridge even when it thermo-sensitively expands in the groove-like cooling water passage, in the case of using the thermosensitive expansion rubber as the rubber member of the heat retention material cartridge. 
     Solution to Problem 
     The above-mentioned problem can be solved by the present invention described below. That is, present invention (1) is a heat retention material cartridge fixed to a base member of a heat retention tool of a cylinder bore&#39;s bore wall for heat retention of the cylinder bore wall, which includes 
     a thermosensitive expansion rubber coming into contact with a cylinder bore-side wall surface of a groove-like cooling water passage and covering the cylinder bore-side wall surface of the groove-like cooling water passage, 
     a back-side pressing member being arc-shaped when viewed from above, and provided on a back side of the thermosensitive expansion rubber for pressing the thermosensitive expansion rubber entirely from the back side toward the cylinder bore-side wall surface of the groove-like cooling water passage, 
     a front-side abutting plate provided on a contact surface of the thermosensitive expansion rubber, having an arc-shaped when viewed from above and having an rectangular opening when viewed from the front side, and cooperative with the back-side pressing member for sandwiching an outer edge portion of the thermosensitive expansion rubber, and 
     an elastic member attached member to which an elastic member is attached, being arc-shaped when viewed from above, and provided on a back side of the back-side pressing member for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage so that the back-side pressing member presses the thermosensitive expansion rubber, 
     wherein 
     bendable portions are formed at an upper end, a lower end, a right end, and a left end of the elastic member attached member, and the bendable portions are bent toward the front-side abutting plate, so that the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are sandwiched between the bendable portions and the elastic member attached member, 
     there is a portion where an outer end is not sandwiched by the bendable portions at least at an upper-side portion and a lower-side portion of the front-side abutting plate, a convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the upper-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the upper-side portion of the front-side abutting plate, and a convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the lower-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the lower-side portion of the front-side abutting plate, and 
     the outer edge portion of the thermosensitive expansion rubber is formed in such a manner that the outer end of the thermosensitive expansion rubber is positioned inside an apex of the convex portion, at the portion of the front-side abutting plate where the convex portion is formed. 
     Further, present invention (2) is a heat retention material cartridge fixed to a base member of a heat retention tool of a cylinder bore&#39;s bore wall for heat retention of the cylinder bore wall, which includes 
     a thermosensitive expansion rubber coming into contact with a cylinder bore-side wall surface of a groove-like cooling water passage and covering the cylinder bore-side wall surface of the groove-like cooling water passage, 
     a back-side pressing member being arc-shaped when viewed from above, and provided on a back side of the thermosensitive expansion rubber for pressing the thermosensitive expansion rubber entirely from the back side toward the cylinder bore-side wall surface of the groove-like cooling water passage, 
     a front-side abutting plate provided on a contact surface of the thermosensitive expansion rubber, having an arc-shape when viewed from above and having an rectangular opening when viewed from the front side, and cooperative with the back-side pressing member for sandwiching an outer edge portion of the thermosensitive expansion rubber, and 
     an elastic member attached to the back-side pressing member for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage so that the back-side pressing member presses the thermosensitive expansion rubber, 
     wherein 
     bendable portions are formed at an upper end, a lower end, a right end, and a left end of the back side pressing member, and the bendable portions are bent toward the front-side abutting plate, so that the thermosensitive expansion rubber and the front-side abutting plate are sandwiched between the bendable portions and the back-side pressing member, 
     there is a portion where an outer end is not sandwiched by the bendable portions at least at an upper-side portion and a lower-side portion of the front-side abutting plate, a convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the upper-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the upper-side portion of the front-side abutting plate, and a convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the lower-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the lower-side portion of the front-side abutting plate, and 
     the outer edge portion of the thermosensitive expansion rubber is formed in such a manner that the outer end of the thermosensitive expansion rubber is positioned inside an apex of the convex portion, at the portion of the front-side abutting plate where the convex portion is formed. 
     Further, present invention (3) provides a cylinder bore wall heat retention tool that is a heat retention tool installed in a groove-like cooling water passage of a cylinder block of an internal combustion engine having cylinder bores for heat retention of bore walls of the cylinder bores, having the heat retention material cartridge of any one of (1) or (2), and a metal-made or synthetic resin-made support member having a shape along the shape of the groove-like cooling water passage at the installation position of the heat retention tool, to which the heat retention material cartridge is fixed, 
     wherein the heat retention material cartridge is fixed to the support member only at or near the center in the circular arc direction. 
     Further, present invention (4) provides an internal combustion engine in which the cylinder bore wall heat retention tool of (3) is installed. 
     Further, present invention (5) provides an automotive vehicle having the internal combustion engine of (4). 
     Advantageous Effects of Invention 
     According to the present invention, in the case of using the thermosensitive expansion rubber as a rubber member of the heat retention material cartridge, it is possible to provide the heat retention material cartridge capable of preventing the expanded thermosensitive expansion rubber from protruding from the upper or lower side of the heat retention material cartridge even when it thermo-sensitively expands in the groove-like cooling water passage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic plan view illustrating an embodied example of a cylinder block on which a cylinder bore wall heat retention tool according to the present invention is installed. 
         FIG. 2  is a cross-sectional view taken along a line x-x in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating the cylinder block illustrated in  FIG. 1 . 
         FIG. 4  is a schematic plan view illustrating an embodied example of the cylinder block on which the cylinder bore wall heat retention tool according to the present invention is installed. 
         FIG. 5  is a schematic perspective view illustrating how the embodied example of a heat retention material cartridge according to the present invention is manufactured. 
         FIG. 6  is a schematic front view illustrating the embodied example (heat retention material cartridge  35 ) of the heat retention material cartridge according to the present invention. 
         FIG. 7  is a view illustrating how the heat retention material cartridge  35  illustrated in  FIG. 6  is fixed to a support member  34 . 
         FIG. 8  is a schematic perspective view illustrating an embodied example (cylinder bore wall heat retention tool  36 ) of the cylinder bore wall heat retention tool according to the present invention. 
         FIG. 9  is a view illustrating a cylinder bore wall heat retention tool  36  viewed from above. 
         FIG. 10  is a view illustrating the cylinder bore wall heat retention tool  36  in  FIG. 8  viewed from the side, as viewed from the front side (contact surface side of a thermosensitive expansion rubber  31 ). 
         FIG. 11  is a view illustrating the cylinder bore wall heat retention tool  36  in  FIG. 8  viewed from the side, as viewed from the back side. 
         FIG. 12  is end views taken along lines X-X and Y-Y of  FIGS. 10 and 11 . 
         FIG. 13  is a view illustrating portions  303  of a front-side abutting plate  30 , which are sandwiched at the outer end thereof by bendable portions, viewed from the front side. 
         FIG. 14  is a view illustrating portions  304  of the front-side abutting plate  30 , which are not sandwiched at the outer end thereof by the bendable portions, viewed from the front side. 
         FIG. 15  is a view illustrating a thermosensitive expansion rubber  31  in the heat retention material cartridge  35 . 
         FIG. 16  is an enlarged view illustrating an upper side of the cylinder bore wall heat retention tool  36  in  FIG. 12  (Y-Y). 
         FIG. 17  is an enlarged view illustrating an upper side of the cylinder bore wall heat retention tool  36  in  FIG. 12  (X-X). 
         FIG. 18  is a schematic view illustrating how the cylinder bore wall heat retention tool  36  is installed on a cylinder block  11  illustrated in  FIG. 1 . 
         FIG. 19  is a schematic view illustrating the state of the cylinder bore wall heat retention tool  36  installed on the cylinder block  11  illustrated in  FIG. 1 . 
         FIG. 20  is end views illustrating the state of the thermosensitive expansion rubber  31  expanding in a groove-like cooling water passage  14 . 
         FIG. 21  is a view illustrating how the heat retention material cartridge comes into contact with a bore wall. 
         FIG. 22  is a schematic view illustrating a manufacturing procedure of an elastic member attached member. 
         FIG. 23  is a schematic front view illustrating an embodied example of the heat retention material cartridge according to the present invention. 
         FIG. 24  is a schematic perspective view illustrating a back-side pressing member to which an elastic member is attached. 
         FIG. 25  is a schematic perspective view illustrating an embodied example of the cylinder bore wall heat retention tool according to the present invention. 
         FIG. 26  is a schematic perspective view illustrating an embodied example of the cylinder bore wall heat retention tool according to the present invention. 
         FIG. 27  is a schematic front view illustrating a conventional heat retention material cartridge. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A cylinder bore wall heat retention tool according to the present invention and an internal combustion engine according to the present invention will be described with reference to  FIGS. 1 to 21 .  FIGS. 1 to 4  each illustrate an embodied example of a cylinder block on which the cylinder bore wall heat retention tool according to the present invention is installed.  FIGS. 1 and 4  are schematic plan views illustrating the cylinder block on which the cylinder bore wall heat retention tool according to the present invention is installed.  FIG. 2  is a cross-sectional view taken along a line x-x in  FIG. 1 .  FIG. 3  is a perspective view illustrating the cylinder block illustrated in  FIG. 1 .  FIG. 5  is a schematic perspective view illustrating how an embodied example of a heat retention material cartridge according to the present invention is manufactured.  FIG. 6  is a schematic front view illustrating the embodied example of the heat retention material cartridge (heat retention material cartridge  35 ) according to the present invention.  FIG. 7  is a view illustrating how the heat retention material cartridge  35  illustrated in  FIG. 6  is fixed to a support member  34 .  FIG. 8  is a schematic perspective view illustrating an embodied example of the cylinder bore wall heat retention tool (cylinder bore wall heat retention tool  36 ) according to the present invention, in which (A) is a view viewed from the front on the upper diagonal side, and (B) is a view viewed form the back on the upper diagonal side.  FIG. 9  is a view illustrating the cylinder bore wall heat retention tool  36  viewed from above. In  FIG. 9 , of the heat retention material cartridges  35  fixed to the cylinder bore wall heat retention tool  36 , a right-end heat retention material cartridge is illustrated separately for each constituent member.  FIG. 10  is a view illustrating the cylinder bore wall heat retention tool  36  in  FIG. 8  viewed from the side, as viewed from the front side (contact surface side of a thermosensitive expansion rubber  31 ).  FIG. 11  is a view illustrating the cylinder bore wall heat retention tool  36  in  FIG. 8  viewed from the side, as viewed from the back side.  FIG. 12  is end views taken along lines X-X and Y-Y in  FIGS. 10 and 11 .  FIG. 13  is a view illustrating portions  303  of a front-side abutting plate  30 , which are sandwiched at the outer end thereof by bendable portions, viewed from the front side, in which (A) is a view illustrating the portions of the front-side abutting plate  30  sandwiched at the outer end thereof by the bendable portions, and (B) is a view illustrating only the front-side abutting plate  30 .  FIG. 14  is a view illustrating portions  304  of the front-side abutting plate  30 , which are not sandwiched at the outer end thereof by the bendable portions, viewed from the front side, in which (A) is a view illustrating the portions of the front-side abutting plate  30 , which are not sandwiched at the outer end thereof by the bendable portions, and (B) is a view illustrating only the front-side abutting plate  30 .  FIG. 15  is a view illustrating the thermosensitive expansion rubber  31  in the heat retention material cartridge  35 , as viewed from the front side, in which (A) is a view illustrating the contour of the thermosensitive expansion rubber  31  installed in the heat retention material cartridge  35 , and (B) is a view illustrating only the thermosensitive expansion rubber  31 .  FIG. 16  is an enlarged view illustrating an upper side of the cylinder bore wall heat retention tool  36  in  FIG. 12  (Y-Y).  FIG. 17  is an enlarged view illustrating an upper side of the cylinder bore wall heat retention tool  36  in  FIG. 12  (X-X).  FIG. 18  is a schematic view illustrating how the cylinder bore wall heat retention tool  36  is installed on a cylinder block  11  illustrated in  FIG. 1 .  FIG. 19  is a schematic view illustrating the state of the cylinder bore wall heat retention tool  36  installed on the cylinder block  11  illustrated in  FIG. 1 .  FIG. 20  is end views illustrating the state of the thermosensitive expansion rubber  31  expanded in a groove-like cooling water passage  14 , in which (X-X) is an end view taken along a line X-X in  FIG. 19  and (Y-Y) is an end view taken along a line Y-Y in  FIG. 19 .  FIG. 21  is a view illustrating how the heat retention material cartridge comes into contact with a bore wall. 
     As illustrated in  FIGS. 1 to 3 , bores  12  for causing pistons to move up and down and the groove-like cooling water passage  14  for causing cooling water to flow are formed in the open-deck-type cylinder block  11  of an internal combustion engine to be mounted on a vehicle, on which the cylinder bore wall heat retention tool is installed. A wall partitioning the bores  12  and the groove-like cooling water passage  14  is a cylinder bore wall  13 . Further, a cooling water supply port  15  for supplying cooling water to the groove-like cooling water passage  11  and a cooling water discharge port  16  for discharging the cooling water from the groove-like cooling water passage  11  are formed in the cylinder block  11 . 
     Two or more bores  12  are formed in series in the cylinder block  11 . Therefore, the bores  12  include end bores  12   a   1  and  12   a   2  neighboring to one bore and intermediate bores  12   b   1  and  12   b   2  interposed between two bores (the cylinder block includes only two end bores when the number of bores of the cylinder block is two). Among the bores aligned in series, the end bores  12   a   1  and  12   a   2  are bores positioned at both ends, and the intermediate bores  12   b   1  and  12   b   2  are bores disposed between the end bore  12   a   1  positioned at one end and the end bore  12   a   2  positioned at the other end. Since a wall between the end bore  12   a   1  and the intermediate bore  12   b   1 , a wall between the intermediate bore  12   b   1  and the intermediate bore  12   b   2 , and a wall between the intermediate bore  12   b   2  and the end bore  12   a   2  (i.e., inter-bore walls  191 ) are portions sandwiched between two bores, heat is transferred from two cylinder bores. Therefore, the wall temperature becomes higher than the other walls. Accordingly, the temperature is highest in the vicinity of the inter-bore wall  191  on a cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 . Therefore, on the cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 , the temperature at a boundary  192  of the bore wall of each cylinder bore and the vicinity thereof becomes highest. 
     Further, in the present invention, among the wall surfaces of the groove-like cooling water passage  14 , the wall surface on the cylinder bore  13  side are described as the cylinder bore-side wall surfaces  17  of the groove-like cooling water passage. Among the wall surfaces of the groove-like cooling water passage  14 , the wall surfaces on the side opposite to the cylinder bore-side wall surfaces  17  of the groove-like cooling water passage are described as wall surfaces  18 . 
     Further, in the present invention, one side half refers to half at one side when the cylinder block is vertically divided into two in a direction in which the cylinder bores are aligned. Accordingly, in the present invention, one side half bore wall of the bore walls of all the cylinder bores refer to bore walls at one side half when all the cylinder bore walls are vertically divided into two in the direction in which the cylinder bores are aligned. For example, in  FIG. 4 , the direction in which the cylinder bores are aligned is a Z-Z direction, and each bore wall of one side half when vertically divided into two along the line Z-Z constitutes the one side half bore wall of the bore walls of all the cylinder bores. This is, in  FIG. 4 , one side half bore wall on a side indicated by  20   a  with respect to the line Z-Z is a bore wall  21   a  of one side half of the bore walls of all the cylinder bores, and one side half bore wall on a side indicated by  20   b  with respect to the line Z-Z is a bore wall  21   b  of the other side half of the bore walls of all the cylinder bores. Further, one side of all the cylinder bore walls refers to either the one side half bore wall  21   a  or the one side half bore wall  21   b , and a part on one side refers to a part of the one side half bore wall  21   a  or a part of the one side half bore wall  21   b.    
     Further, in the present invention, the bore wall of each cylinder bore refers to each bore wall portion corresponding to each cylinder bore, and in  FIG. 4 , the range indicated by a two-directional arrow  22   a   1  is a bore wall  23   a   1  of the cylinder bore  12   a   1 . The range indicated by a two-directional arrow  22   b   1  is a bore wall  23   b   1  of the cylinder bore  12   b   1 . The range indicated by a two-directional arrow  22   b   2  is a bore wall  23   b   2  of the cylinder bore  12   b   2 . The range indicated by a two-directional arrow  22   a   2  is a bore wall  23   a   2  of the cylinder bore  12   a   2 . The range indicated by a two-directional arrow  22   b   3  is a bore wall  23   b   3  of the cylinder bore  12   b   1 . The range indicated by a two-directional arrow  22   b   4  is a bore wall  23   b   4  of the cylinder bore  12   b   2 . In other words, the bore wall  23   a   1  of the cylinder bore  12   a   1 , the bore wall  23   b   1  of the cylinder bore  12   b   1 , the bore wall  23   b   2  of the cylinder bore  12   b   2 , the bore wall  23   a   2  of cylinder bore  12   a   2 , the bore wall  23   b   3  of the cylinder bore  12   b   1 , and the bore wall  23   b   4  of the cylinder bore  12   b   2  are bore walls of respective cylinder bores. 
     As illustrated in  FIG. 5 , the heat retention material cartridge  35  includes an elastic member attached member  33  to which a metal plate spring  39  is attached and being arc-shaped when viewed from above, a back-side pressing member  32  being arc-shaped when viewed from above, the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  being arc-shaped when viewed from above, which are sequentially overlapped. In manufacturing, as illustrated in  FIG. 6 , bendable portions  331   a  formed at an upper end of the elastic member attached member  33 , bendable portions  331   b  formed at a lower end of the elastic member attached member  33 , a bendable portion  332   a  formed at a right end of the elastic member attached member  33 , and a bendable portion  332   b  formed at a left end of the elastic member attached member  33  are bent toward the front-side abutting plate  30 , so that the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  are sandwiched between the bendable portions  331   a ,  331   b ,  332   a , and  332   b  and the elastic member attached member  33 , thereby fixing these members. 
     Then, as illustrated in  FIG. 7 , each heat retention material cartridge  35  is fixed to each bore portion of the support member  34  formed into the shape along the groove-like cooling water passage  14  in which the cylinder bore wall heat retention tool  36  is installed, that is, the shape including plural arcs that are continuous when viewed from above. The fixing of the heat retention material cartridge  35  to the support member  34  is performed by bending bendable portions  37  formed at the upper and lower ends of the elastic member attached member  33  toward the support member  34  so that the support member  34  is sandwiched between the bendable portions  37  and the elastic member attached member  33 , thereby fixing the heat retention material cartridge  35  to the support member  34 . 
     The cylinder bore wall heat retention tool  36  illustrated in  FIG. 8  is a heat retention tool for heat retention of the one side half bore wall  21   b  (the side indicated by  20   b ) in  FIG. 4 . A cooling water flow partition member  38  is attached to the cylinder bore wall heat retention tool  36 . The cooling water flow partition member  38  is a member for partitioning the cooling water supply port  15  and the cooling water discharge port  16  in such a manner that, in the cylinder block  11  illustrated in  FIG. 4 , cooling water supplied from the cooling water supply port  15  to the groove-like cooling water passage  14  initially flows in the groove-like cooling water passage  14  of one side half on the side indicated by  20   b  toward the end opposite to the position of the cooling water supply port  15 , without being directly discharged from the neighboring cooling water discharge port  16 , and when it reaches the end of the groove-like cooling water passage  14  of one side half on the side indicated by  20   b  opposite to the position of the cooling water supply port  15 , turns and enters into the groove-like cooling water passage  14  of one side half of the side indicated by  20   a , subsequently, flows in the groove-like cooling water passage  14  of one side half of the side indicated by  20   a  toward the cooling water discharge port  16 , and is finally discharged from the cooling water discharge port  16 . Although the cylinder block illustrated in  FIG. 4  is configured in such a manner that the cooling water having flowed to the end of the groove-like cooling water passage  14  of one side half of the side indicated by  20   a  is discharged from the cooling water discharge port  16  formed at the side of the cylinder block  11 , the cylinder block may be configured, for example, to cause the cooling water having flowed in the groove-like cooling water passage  14  of one side half of the side indicated by  20   a  from one end to the other end to flow into the cooling water passage formed in the cylinder head, without being discharged from the side of the cylinder block. 
     As illustrated in  FIGS. 8 to 11 , the cylinder bore wall heat retention tool  36  is a heat retention tool for heat retention of the one side half bore wall  21   b  of the cylinder block  11  illustrated in  FIG. 4 . The one side half bore wall  21   b  of the cylinder block  11  is constituted by bore walls of four cylinder bores of the bore wall  23   a   1  of the cylinder bore  12   a   1 , the bore wall  23   b   3  of the cylinder bore  12   b   1 , the bore wall  23   b   4  of the cylinder bore  12   b   2 , and the bore wall  23   a   2  of the cylinder bore  12   a   2 . The cylinder bore wall heat retention tool  36  is provided with the heat retention material cartridge for heat retention of the bore wall of each of the four cylinder bores. Therefore, the cylinder bore wall heat retention tool  36  is provided with four heat retention material cartridges  35 . 
     The heat retention material cartridges  35  are fixed to the cylinder bore wall heat retention tool  36  in such a manner that the cylinder bore-side wall surface face a contact surface  26  of the thermosensitive expansion rubber  31  so that the contact surface  26  of the thermosensitive expansion rubber  31  can be brought into contact with the cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 . Further, on the back side of the cylinder bore wall heat retention portion  36 , the metal plate spring  39  attached to the heat retention material cartridge  35  protrudes through an opening  42  of the support member  34  toward the side opposite to the thermosensitive expansion rubber  31 . Then, when the thermosensitive expansion rubber  31  expands in the groove-like cooling water passage, a protruding tip end  27  of the metal plate spring  39  comes into contact with the wall surface  18  on the side opposite to the cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 . 
     The heat retention material cartridge  35  fixed to the cylinder bore wall heat retention portion  36 , as illustrated in  FIG. 5 , is constituted by the front-side abutting plate  30 , the thermosensitive expansion rubber member  31 , the back-side pressing member  32 , and the elastic member attached member  33 . 
     The thermosensitive expansion rubber  31  is a member thermo-sensitively expanding in the groove-like cooling water passage, directly coming into contact with a bore wall  22  of each cylinder bore, and covering the heat retention portion of the bore wall  22 , for heat retention of the bore wall  22  of each cylinder bore. Further, the back-side pressing member  32  is arc-shaped when viewed from above and has a shape along the back side of the thermosensitive expansion rubber  31  (the surface on the side opposite to the contact surface  26 ), so that the thermosensitive expansion rubber  31  can be entirely pressed from the back side of the thermosensitive expansion rubber  31 . Further, the metal plate spring  39  that is an elastic member being arc-shaped when viewed from above and having a shape along the back side of the back-side pressing member  32  (the surface on the side opposite to the thermosensitive expansion rubber  31 ) is attached to the elastic member attached member  33 . The metal plate spring  39  is a vertically long rectangular metal plate and has one end in the longitudinal direction connected to the elastic member attached member  33 . The metal plate spring  39  is attached to the elastic member attached member  33  in such a manner that the tip end  27  is separated from the metal plate spring attachment member  33  and is bent from the elastic member attached member  33  at another end  28  connected to the metal plate spring attachment member  33 . The front-side abutting plate  30  has an opening  301  being arc-shaped when viewed from above and rectangular when viewed from the front side. Then, when the bendable portions  331   a  formed at the upper end of the elastic member attached member  33 , the bendable portions  331   b  formed at the lower end of the elastic member attached member  33 , the bendable portion  332   a  formed at the right end of the elastic member attached member  33 , and the bendable portion  332   b  formed at the left end of the elastic member attached member  33  are bent toward the front-side abutting plate  30 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  are sandwiched between the elastic member attached member  33  and the bendable portions  331   a ,  331   b ,  332   a , and  332   b , thereby fixing these members. The thermosensitive expansion rubber  31  has a surface on the side opposite to the back-side pressing member  32 , which serves as the contact surface  26  coming into contact with the cylinder bore-side wall surface  17  of the groove-like cooling water passage. 
     As illustrated in  FIGS. 13 and 14 , the front-side abutting plate  30  includes portions  303  sandwiched at the outer end thereof by the bendable portions and the portions  304  not sandwiched by the bendable portions. In the heat retention material cartridge  35 , an upper-side portion  308   a  of the front-side abutting plate  30  includes portions  303   a  sandwiched at the outer end thereof by the bendable portions  331   a , a lower-side portion  308   b  of the front-side abutting plate  30  includes portions  303   b  sandwiched at the outer end thereof by the bendable portions  331   b , a right-side portion of the front-side abutting plate  30  includes a portion  303   c  sandwiched at the outer end thereof by the bendable portion  332   a , and a left-side portion of the front-side abutting plate  30  includes a portion  303   d  sandwiched at the outer end thereof by the bendable portion  332   b . Further, in the heat retention material cartridge  35 , the upper-side portion  308   a  of the front-side abutting plate  30  includes portions  304   a  not sandwiched at the outer end thereof by the bendable portions  331   a , and the lower-side portion  308   b  of the front-side abutting plate  30  includes portions  304   b  not sandwiched at the outer end thereof by the bendable portions  331   b . In  FIG. 13 , dotted lines indicate the portions of the front-side abutting plate  30  sandwiched at the outer end thereof by the bendable portions. Further, in  FIG. 14 , dotted lines indicate the portions of the front-side abutting plate  30  not sandwiched at the outer end thereof by the bendable portions. 
     Convex portions are formed in portions of the front-side abutting plate  30  not sandwiched at the outer end thereof by the bendable portions. That is, convex portions  302   a  extending in the longitudinal direction of the upper-side portion  308   a  of the front-side abutting plate  30  are formed in the portions  304   a  where the upper-side portion  308   a  is not sandwiched at the outer end thereof by the bendable portions  331   a , of the front-side abutting plate  30 . Further, convex portions  302   b  extending in the longitudinal direction of the lower-side portion of the front-side abutting plate  30  are formed in the portions  304   b  where the lower-side portion  308   b  of the front-side abutting plate  30  is not sandwiched at the outer end thereof by the bendable portions  331   b.    
     As illustrated in  FIGS. 15 to 17 , the outer edge portion of the thermosensitive expansion rubber  31  is formed in such a manner that positions corresponding to the portions of the front-side abutting plate  30  not sandwiched by the bendable portions are cut out. Therefore, in the portions of the front-side abutting plate  30  where the convex portions  302   a  and  302   b  are formed, outer ends  312   a  and  312   b  of the thermosensitive expansion rubber  31  are positioned inside apexes  309   a  and  309   b  of the convex portions  302   a  and  302   b . In  FIG. 15(A) , a dotted line indicates the contour of the thermosensitive expansion rubber  31 . In  FIG. 15(B) , a dotted line (reference numeral  319 ) indicates the contour of the rectangular thermosensitive expansion rubber before being cut out. Further, the thermosensitive expansion rubber  31  is not cut out at positions corresponding to the portions of the front-side abutting plate  30  sandwiched by the bendable portions. At the portions  303   a  and  303   b  of the front-side abutting plate  30  sandwiched by the bendable portions, outer ends  313   a  and  313   b  of the thermosensitive expansion rubber  31  are positioned outside the apex positions of the convex portions  302   a  and  302   b.    
     The support member  34  to which the heat retention material cartridge  35  is fixed is formed in a shape in which four circular arcs are continuous when viewed from above, and the shape of the support member  34  is a shape along one side half of the groove-like cooling water passage  14 . Further, the support member  34  has the opening  42  so that the metal plate spring  39  attached to the heat retention material cartridge  35  can pass through the support member  34 , from the back side of the cylinder bore wall heat retention tool  36 , and protrude toward the wall surface  18  on the side opposite to the cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 . 
     The support member  34  is a member to which the heat retention material cartridge  35  is fixed, and plays a role in determining the position of the heat retention material cartridge  35  so that the position of the heat retention material cartridge  35  does not shift in the groove-like cooling water passage  14 . The support member  34  is a metal plate or a molded body of a synthetic resin. 
     In the cylinder bore wall heat retention tool  36 , the heat retention material cartridge  35  is fixed to the support member  34  only at or near the center in the circular arc direction when viewed from above (at or near the center of the arc-shaped heat retention material cartridge  35  when the heat retention material cartridge  35  is viewed from above). The X-X end view of  FIG. 12  is an end view taken along the center of the heat retention material cartridge  35 . In the X-X end view, it is illustrated that the upper and lower ends of the elastic member attached member  33  are fixed to the support member  34  by the bendable portions  37 . On the other hand, the Y-Y end view of  FIG. 12  is an end view taken along a position adjacent to the edge of the heat retention material cartridge  35 . In the Y-Y end view, it is illustrated that the elastic member attached member  33  is not fixed to the support member  34 . 
     The cylinder bore wall heat retention tool  36  is installed, for example, in the groove-like cooling water passage  14  of the cylinder block  11  illustrated in  FIG. 1 . As illustrated in  FIG. 18 , the cylinder bore wall heat retention tool  36  is inserted into the groove-like cooling water passage  14  of the cylinder block  11 . Then, as illustrated in  FIG. 19 , the cylinder bore wall heat retention tool  36  is installed in the groove-like cooling water passage  14 . 
     After the cylinder bore wall heat retention tool  36  is installed in the groove-like cooling water passage  14  of the cylinder block  11 , when the internal combustion engine is driven, the thermosensitive expansion rubber  31  is heated and thermo-sensitively expands. Then, as illustrated in  FIG. 20 , the thermosensitive expansion rubber  31  expands toward the cylinder bore-side wall surface  17  through the opening  301  formed in the inner portion of the front-side abutting plate  30 , and the contact surface  26  comes into contact with the cylinder bore-side wall surface  17 . Even after the contact surface  26  has contacted the cylinder bore-side wall surface  17 , the thermosensitive expansion rubber  31  continues to expand until it reaches an opened state. Therefore, the tip end  27  of the metal plate spring  39  is subjected to a force directing toward the elastic member attached member  33 . As a result, since the metal plate spring  39  deforms in such a manner that the tip end  27  approaches the elastic member attached member  33 , the metal plate spring  39  generates an elastic force for returning to the original position. Then, by this elastic force, the elastic member attached member  33  is pushed toward the cylinder bore-side wall surface  17  of the groove-like cooling water passage. As a result, by the back-side pressing member  32  pushed by the elastic member attached member  33 , the thermosensitive expansion rubber  31  is pressed against the cylinder bore-side wall surface  17  of the groove-like cooling water passage. That is, when the cylinder bore wall heat retention tool  36  is installed in the groove-like cooling water passage  14  and the thermosensitive expansion rubber  31  is heated and thermo-sensitively expands, the metal plate spring  39  deforms and the elastic force generated to restore from the deformation urges the back-side pressing member  32  in such a way as to press the thermosensitive expansion rubber  31  against the cylinder bore-side wall surface  17  of the groove-like cooling water passage. Thus, the thermosensitive expansion rubber  31  of the heat retention material cartridge  35  of the cylinder bore wall heat retention tool  36  comes into contact with the bore wall surfaces of respective cylinder bores constituting one side half wall surface  17   b  of the entire cylinder bore-side wall surface  17  of the groove-like cooling water passage. 
     At this time, in the cylinder bore wall heat retention tool  36 , since the heat retention material cartridge  35  is fixed to the support member  34  only at or near the center in the circular arc direction when the heat retention material cartridge  35  is viewed from above, when the metal plate spring  39  urges the elastic member attached member  33  and the back-side pressing member  32  of the heat retention material cartridge  35 , the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  can deform independently of the support member  34 . This will be described with reference to  FIG. 21 . In the manufacturing of the cylinder bore wall heat retention tool, the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  are processed so that their curvatures match the curvatures of the wall surfaces of the bore walls of respective cylinder bores with which the thermosensitive expansion rubber comes into contact. However, in fact, processing errors occur with respect to design values in any of the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , the front-side abutting plate  30 , and the wall surfaces of the bore walls of the respective cylinder bores. Then, when the curvatures of the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  become smaller than the curvatures of the wall surfaces of the bore walls of the respective cylinder bores due to processing errors of these members or the wall surfaces of the bore walls of the respective cylinder bores, if the heat retention material cartridge is entirely fixed to the support member (for example, fixed to the support member at a total of three positions near the center and both ends in the circular arc direction when the heat retention portion is viewed from above), the thermosensitive expansion rubber can come into contact with bore walls  23  of the respective cylinder bores at the portion near the center in the circular arc direction but cannot contact the bore walls at the portion adjacent to the edge, when urged by the metal plate spring, as illustrated in  FIG. 21(A) . On the other hand, when the curvatures of the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  become smaller than the curvatures of the wall surfaces of the bore walls of the respective cylinder bores, if the heat retention material cartridge  35  according to the present invention is fixed to the support member  34  only at or near the center in the circular arc direction when the heat retention material cartridge  35  is viewed from above, the portion of the heat retention material cartridge  35  adjacent to the edge is separated from the support member  34  and can deform toward the bore walls  23  of the respective cylinder bores when urged by the metal plate spring  39 , as illustrated in  FIG. 21(B) . Therefore, the thermosensitive expansion rubber  31  can come into contact with the bore walls  23  of the respective cylinder bores not only at the portion near the center but also at the portion adjacent to the edge in the circular arc direction. Because of this, in the cylinder bore wall heat retention tool  36 , even if the curvatures of the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  are different from the curvatures of the wall surfaces of the bore walls  23  of the respective cylinder bores due to processing errors, the thermosensitive expansion rubber  31  can be surely brought into contact with the wall surfaces of the bore walls of the respective cylinder bores. Therefore, the adhesion of the thermosensitive expansion rubber  31  to the wall surfaces of the bore walls  23  of the respective cylinder bores (the cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 ) is enhanced. 
     Further, when the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are larger than the curvatures of the bore walls of the respective cylinder bores, if the heat retention material cartridge is entirely fixed to the support member, the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate do not change. Therefore, there is a possibility that a gap may be formed between the thermosensitive expansion rubber and the bore walls in the vicinity of the center in the circular arc direction when viewed from above. On the other hand, in the cylinder bore wall heat retention tool  36 , even if the curvatures of the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  are larger than the curvatures of the bore walls  23  of the respective cylinder bores, since the heat retention material cartridge  35  is fixed to the support member  34  only at or near the center in the circular arc direction, the heat retention material cartridge  35  is pushed by the elastic member  39  from the back side at or near the center in the circular arc direction, and the portions of the heat retention material cartridge  35  other than the center or portions near the center in the circular arc direction deform in such a manner that the heat retention material cartridge  35  opens outward at the portions adjacent to both ends in the circular arc direction, independently of the support member  34 . Therefore, the thermosensitive expansion rubber  31  can come into contact with the bore walls  23  of the respective cylinder bores not only at or near the center but also at the portions adjacent to the edges in the circular arc direction. Because of this, in the cylinder bore wall heat retention tool  36 , even if the curvatures of the elastic member attached member  33 , the back-side pressing member  32 , the thermosensitive expansion rubber  31 , and the front-side abutting plate  30  are different from the curvatures of the wall surfaces of the bore walls  23  of the respective cylinder bores due to processing errors, the thermosensitive expansion rubber  31  can be surely brought into contact with the wall surfaces of the bore walls of the respective cylinder bores. Therefore, the adhesion of the thermosensitive expansion rubber  31  to the wall surfaces of the bore walls  23  of the respective cylinder bores (the cylinder bore-side wall surface  17  of the groove-like cooling water passage  14 ) is enhanced. 
     Although  FIG. 21(A)  illustrates large gaps formed between the contact surface of the heat retention material cartridge and the thermosensitive expansion rubber at both ends thereof entirely for the purpose of explaining the effects of the present invention, such large processing errors do not occur in practice. However, in fact, due to processing errors, small gaps may occur, or the contact surface of the rubber member and the bore wall may be partly separated. 
     In the heat retention material cartridge  35 , as illustrated in  FIG. 16 , since the bendable portions  331   a  ( 331   b ,  332   a ,  332   b ) are present in the portions  303   a  ( 303   b ,  303   c ,  303   d ) of the front-side abutting plate  30  sandwiched at the outer end thereof by the bendable portions  331   a  ( 331   b ,  332   a ,  332   b ) in such a way as to cover the outer end  313   a  ( 313   b ,  313   c ,  313   d ) of the thermosensitive expansion rubber  31 , the outer edge portion of the thermosensitive expansion rubber  31  does not protrude from the heat retention material cartridge  35  even when the thermosensitive expansion rubber  31  expands. Further, since the bendable portions  331   a  ( 331   b ,  332   a ,  332   b ) are present in such a way as to cover the outer end  313   a  ( 313   b ,  313   c ,  313   d ) of the thermosensitive expansion rubber  31 , it is insensitive to the flow of cooling water. Therefore, the problem of breakage of the thermosensitive expansion rubber  31  by the cooling water does not occur. 
     In the heat retention material cartridge  35 , as illustrated in  FIG. 17 , in the portions  304   a  of the front-side abutting plate  30  not sandwiched at the outer end thereof by the bendable portions  331   a , the convex portions  302   a  extending in the longitudinal direction of the upper-side portion  308   a  of the front-side abutting plate  30  are present in such a way as to protrude toward the back-side pressing member  32  at the position outside the outer end  312   a  of the thermosensitive expansion rubber  31 . Therefore, even when the thermosensitive expansion rubber  31  expands, the outer edge portion of the thermosensitive expansion rubber  31  cannot easily protrude from the heat retention material cartridge  35 . Further, since the convex portions  302   a  are present outside the outer end  312   a  of the thermosensitive expansion rubber  31 , even when the cooling water flows into a gap  48  between the back-side pressing member  32  and the front-side abutting plate  30 , the flow velocity of the cooling water flowing toward the outer end  312   a  of the thermosensitive expansion rubber  31  becomes very slow due to the presence of the convex portions  302   a . Therefore, the problem of breakage of the thermosensitive expansion rubber  31  by the cooling water does not occur. 
     The heat retention material cartridge according to a first aspect of the present invention is a heat retention material cartridge fixed to a base member of a heat retention tool of a cylinder bore&#39;s bore wall for heat retention of the cylinder bore wall, which includes 
     the thermosensitive expansion rubber coming into contact with the cylinder bore-side wall surface of the groove-like cooling water passage and covering the cylinder bore-side wall surface of the groove-like cooling water passage, 
     the back-side pressing member being arc-shaped when viewed from above, and provided on the back side of the thermosensitive expansion rubber for pressing the thermosensitive expansion rubber entirely from the back side toward the cylinder bore-side wall surface of the groove-like cooling water passage, 
     the front-side abutting plate provided on the contact surface of the thermosensitive expansion rubber, having an arc-shape when viewed from above and having an rectangular opening when viewed from the front side, and cooperative with the back-side pressing member for sandwiching the outer edge portion of the thermosensitive expansion rubber, and 
     the elastic member attached member to which the elastic member is attached, being arc-shaped when viewed from above, and provided on the back side of the back-side pressing member for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage so that the back-side pressing member presses the thermosensitive expansion rubber, 
     wherein 
     the bendable portions are formed at the upper end, the lower end, the right end, and the left end of the elastic member attached member, and the bendable portions are bent toward the front-side abutting plate, so that the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are sandwiched between the bendable portions and the elastic member attached member, 
     there is the portion where the outer end is not sandwiched by the bendable portions at least at the upper-side portion and the lower-side portion of the front-side abutting plate, the convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the upper-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the upper-side portion of the front-side abutting plate, and the convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the lower-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the lower-side portion of the front-side abutting plate, and 
     the outer edge portion of the thermosensitive expansion rubber is formed in such a manner that the outer end of the thermosensitive expansion rubber is positioned inside the apex of the convex portion, at the portion of the front-side abutting plate where the convex portion is formed. 
     The heat retention material cartridge according to the first aspect of the present invention is the heat retention material cartridge fixed to the base member of the cylinder bore wall heat retention tool for heat retention of the cylinder bore wall. The first heat retention material cartridge according to the present invention has the elastic member attached member to which the elastic member is attached and being arc-shaped when viewed from above, the back-side pressing member being arc-shaped when viewed from above, the thermosensitive expansion rubber thermo-sensitively expanding in the groove-like cooling water passage, having the contact surface coming into contact with the cylinder bore-side wall surface of the groove-like cooling water passage, and covering the cylinder bore wall, and the front-side abutting plate being arc-shaped when viewed from above, which are sequentially overlapped. The bendable portions formed at the upper end of the elastic member attached member, the bendable portions formed at the lower end of the elastic member attached member, the bendable portion formed at the right end of the elastic member attached member, and the bendable portion formed at the left end of the elastic member attached member are bent toward the front-side abutting plate, so that the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are sandwiched between the elastic member attached member and the bendable portion, thereby fixing these members to the elastic member attached member. In the present invention, the upper end, the lower end, the right end, and the left end of the heat retention material cartridge are the upper end, the lower end, the right end, and the left end, respectively, when viewed from the front side, in other words, from the contact surface side of the thermosensitive expansion rubber. 
     The heat retention material cartridge according to the first aspect of the present invention is fixed to each bore portion of the support member formed into the shape along the groove-like cooling water passage in which the cylinder bore wall heat retention tool is installed, that is, the shape including plural arcs that are continuous when viewed from above. In fixing the heat retention material cartridge according to the first aspect of the present invention to the support member, the bendable portions formed at the upper and lower ends of the elastic member attached member are bent toward the support member, and the support member is sandwiched between the bendable portions and the elastic member attached member. As a result, the heat retention material cartridge according to the first aspect of the present invention is fixed to the support member. In the present invention, each bore portion of the support member refers to the portion of the support member the bore wall side of each cylinder bore and corresponds to one arc shape forming the support member when viewed from above. 
     The thermosensitive expansion rubber relating to the heat retention material cartridge according to the first aspect of the present invention is the member for thermo-sensitively expanding in the groove-like cooling water passage, so that the contact surface directly contacts the bore walls of the respective cylinder bores to cover the bore wall heat retention portion, for heat retention of the bore walls of the respective cylinder bores. A surface of the thermosensitive expansion rubber on the side opposite to the back-side pressing member is the contact surface that contacts the cylinder bore wall of the groove-like cooling water passage. 
     The thermosensitive expansion rubber is a composite obtained by impregnating and compressing a base foam material with a thermoplastic material having a melting point lower than that of the base foam material, and is a material capable of maintaining the compression state by a cured product of the thermoplastic material present at least in its surface layer at normal temperature and releasing the compression state when the cured product of the thermoplastic material is softened by heating. The thermosensitive expansion rubber is, for example, a thermosensitive expansion rubber described in Japanese Patent Laid-Open No. 2004-143262. When the material of the rubber member is the thermosensitive expansion rubber, the cylinder bore wall heat retention tool according to the present invention is installed in the groove-like cooling water passage, and heat is applied to the thermosensitive expansion rubber, thereby causing the thermosensitive expansion rubber to expand and deform into a predetermined shape. 
     Base foam materials for the thermosensitive expansion rubber include various polymer materials, such as rubber, elastomer, thermoplastic resin, thermosetting resin. Specifically, the materials include natural rubber, various synthetic rubbers such as chloropropylene rubber, styrene butadiene rubber, nitrile butadiene rubber, ethylene-propylene-diene ternary copolymer, silicone rubber, fluorine rubber, and acrylic rubber, various elastomers such as soft urethane, hard urethane, and various thermosetting resins such as phenol resin, and melamine resin. 
     Thermoplastic materials with any one of the glass transition point, melting point, and softening temperature of less than 120° C. are preferable for the thermosensitive expansion rubber. The thermoplastic materials for the thermosensitive expansion rubber include thermoplastic resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic ester, styrene butadiene copolymer, chlorinated polyethylene, polyvinylidene fluoride, ethylene vinyl acetate copolymer, ethylene vinyl acetate vinyl chloride acrylic acid ester copolymer, ethylene vinyl acetate acrylic acid ester copolymer, ethylene vinyl acetate vinyl chloride copolymer, nylon, acrylonitrile butadiene copolymer, polyacrylonitrile, polyvinyl chloride, polychloroprene, polybutadiene, thermoplastic polyimide, polyacetal, polyphenylene sulfide, polycarbonate, and thermoplastic polyurethane, and various thermoplastic compounds such as low-melting point glass frit, starch, solder, and wax. 
     The back-side pressing member relating to the heat retention material cartridge according to the first aspect of the present invention is arc-shaped when viewed from above, has the shape along the back side of the thermosensitive expansion rubber (the surface on the side opposite to the contact surface side) so that the entire thermosensitive expansion rubber can be pressed from the back side of the thermosensitive expansion rubber, and has the shape covering the entire back side or substantially the entire back side of the thermosensitive expansion rubber. The material of the back-side pressing member can be appropriately selected if it can deform in such a way as to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage when pushed from the back side by the elastic member. Metal plates of stainless steel, aluminum alloy, and the like are preferable. The thickness of the back-side pressing member can be appropriately selected if it can deform in such a way as to press the rubber member toward the cylinder bore-side wall surface of the groove-like cooling water passage when pressed from the back side by the elastic member. 
     The elastic member attached member relating to the heat retention material cartridge according to the first aspect of the present invention is arc-shaped when viewed from above, and the elastic member is attached. Further, the bendable portions are formed at the upper, lower, right, and left ends of the elastic member attached member. The elastic member is the elastic urging member that enables the back-side pressing member to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage, when the cylinder bore wall heat retention tool fixed to the heat retention material cartridge according to the first aspect of the present invention is installed in the groove-like cooling water passage, and the thermosensitive expansion rubber expands and elastically deforms. 
     When the heat retention material cartridge according to the first aspect of the present invention is viewed from above, two or more elastic members are attached in the circular arc direction of the heat retention material cartridge according to the first aspect of the present invention. In the case where the attachment place for the elastic member is only one, the elastic member is attached to the heat retention material cartridge according to the first aspect of the present invention at or near the center in the circular arc direction in order to press the heat retention tool entirely. However, in this case, since the heat retention material cartridge according to the first aspect of the present invention is fixed to the support member at or near the center, the heat retention material cartridge according to the first aspect of the present invention is pressed together with the support member. Therefore, in the heat retention material cartridge according to the first aspect of the present invention, independently of the support member, the portion adjacent to the edge of the heat retention material cartridge according to the first aspect of the present invention is not separated from the support member and does not deform in such a way as to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage. Because of this, the elastic members need to be attached at least at two places in total, at one place near one end and at the other place near the other end, of the heat retention material cartridge according to the first aspect of the present invention, so that the portions adjacent to both edges of the heat retention material cartridge according to the first aspect of the present invention are separated and deform in such a way as to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage, independently of the support member. Further, it is preferable that the elastic members are attached at three positions in total, at one place at or near the center in the circular arc direction of the heat retention material cartridge according to the first aspect of the present invention, at one place near one end and at another place near the other end of the heat retention material cartridge according to the first aspect of the present invention, so that the heat retention material cartridge according to the first aspect of the present invention is entirely pressed and the portions adjacent to both edges of the heat retention material cartridge according to the first aspect of the present invention are pressed independently of the support member. Further, to enhance the adhesion of the thermosensitive expansion rubber of the heat retention material cartridge according to the first aspect of the present invention to the cylinder bore-side wall surface of the groove-like cooling water passage, the elastic members can be attached at four portions or more in the circular arc direction. 
     The form of the elastic member is not particularly limited, and examples thereof include a plate-like elastic member, a coil-like elastic member, a leaf spring, a torsion spring, and elastic rubber. The material of the elastic member is not particularly limited, but stainless steel (SUS), aluminum alloy and the like are preferable because of excellent LLC resistance and high strength. As the elastic member, a metal elastic member such as a metal plate spring, a coil spring, a leaf spring, or a torsion spring, is preferable. 
     Among the bendable portions formed on the elastic member attached member, the bendable portions formed at the right and left ends can be formed over the whole of the up-and-down direction of the right or left side of the elastic member attached member, like the embodied example illustrated in  FIG. 6 , or can be formed partly at the right end or the left end of the elastic member attached member in the up-and-down direction, like the embodied example illustrated in  FIG. 23 . In the case where the bendable portions are partly formed at the right end or the left end of the elastic member attached member, convex portions are formed at portions of the front-side abutting plate not sandwiched at the outer end thereof by the bendable portions. In an exemplary heat retention material cartridge  35   a  illustrated in  FIG. 23 , a convex portion  302   c  extending in the longitudinal direction of the right-side portion of a front-side abutting plate  30   a  is formed at a portion not sandwiched at the outer end thereof by bendable portions  332   c , of the right-side portion of the front-side abutting plate  30   a . Further, a convex portion  302   d  extending in the longitudinal direction of the left-side portion of the front-side abutting plate  30   a  is formed at a portion not sandwiched at the outer end thereof by bendable portions  332   d , of the left-side portion of the front-side abutting plate  30   a.    
     Since the bendable portions at the right and left ends of the elastic member attached member are linearly bendable, they can be bent properly even when they are formed over the entire right or left end of the elastic member attached member in the up-and-down direction, like the embodied example illustrated in  FIG. 6 . Forming the bendable portions at the right and left ends of the elastic member attached member over the entire right or left end of the elastic member attached member in the up-and-down direction so as to sandwich the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate entirely at the right or left side thereof in the up-and-down direction is preferable in that cooling water can be prevented from strongly flowing from the right or left side of the heat retention material cartridge according to the first aspect of the present invention between the back-side pressing member and the front-side abutting plate. 
     The upper and lower ends of the heat retention material cartridge according to the first aspect of the present invention are arc-shaped when viewed from above. Therefore, if the bendable portions formed at the upper and lower ends of the elastic member attached member are excessively long in width, the bendable portions cannot be bent properly, and further the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate cannot be fixed properly. Therefore, the bendable portions formed at the upper and lower ends of the elastic member attached member can be appropriately selected in width, in a range in which normal bending is feasible and normal fixing of the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate is feasible. The number of the bendable portions formed at the upper and lower ends of the elastic member attached member is two or more in the circular arc direction of the heat retention material cartridge according to the first aspect of the present invention, when the heat retention material cartridge according to the present invention is viewed from above. 
     The bendable portions for fixing the heat retention material cartridge according to the present invention are formed at or near the center in the circular arc direction of the upper and lower ends of the elastic member attached member. The bendable portions formed at the upper and lower ends of the elastic member attached member can be appropriately selected in width, in a range in which normal bending is feasible and fixing to the support member is feasible. 
     As illustrated in  FIG. 22 , the manufacturing procedure of the elastic member attached member  33  includes preparing a metal plate  43 , punching out the metal plate  43  along dotted lines indicated in  FIG. 22(A)  to form the metal plate spring  39 , the bendable portions  331   a ,  331   b ,  332   a , and  332   b , and the bendable portions  37 , as illustrated in  FIG. 22(B) , thereby manufacturing a metal plate punched product  45 . Further, the manufacturing procedure includes forming the entire metal plate punched product  45  into an arc shape, and bending the metal plate spring  39  toward the back side to manufacture the elastic member attached member  33 . In manufacturing the support member  34 , a metal plate is shaped or a synthetic resin is injection-molded to obtain the support member  34 . 
     The front-side abutting plate relating to the heat retention material cartridge according to the first aspect of the present invention is arc-shaped when viewed from above and has the substantially rectangular opening formed inside when viewed from the front side. In the heat retention material cartridge according to the first aspect of the present invention, the outer edge portion of the thermosensitive expansion rubber is sandwiched between the back-side pressing member and the front-side abutting plate so that the thermosensitive expansion rubber is fixed. 
     The front-side abutting plate has the portions sandwiched at the outer end thereof by the bendable portions, and the portions not sandwiched at the outer end thereof by the bendable portions. In the heat retention material cartridge, the front-side abutting plate has the portions not sandwiched at the outer end thereof by the bendable portions at least at the upper- and lower-side portions. Further, the heat retention material cartridge according to the first aspect of the present invention may include or not include the portions not sandwiched at the outer end thereof by the bendable portions at the right- and left-side portions of the front-side abutting plate. In other words, in the heat retention material cartridge according to the first aspect of the present invention, the right- and left-side portions of the front-side abutting plate may be entirely or partly sandwiched by the bendable portions at the outer end in the up-and-down direction. 
     The convex portions being convex toward the back-side pressing member are formed at the portions of the front-side abutting plate not sandwiched at the outer end thereof by the bendable portions. That is, the convex portions extending in the longitudinal direction of the upper-side portion of the front-side abutting plate are formed at the portions not sandwiched at the outer end thereof by the bendable portions, of the upper-side portion of the front-side abutting plate. The convex portions extending in the longitudinal direction of the lower-side portion of the front-side abutting plate are formed at the portions not sandwiched at the outer end thereof by the bendable portions, of the lower-side portion of the front-side abutting plate. Further, if there is any portion not sandwiched at the outer end thereof by the bendable portions in the right-side portion of the front-side abutting plate, the convex portion extending in the longitudinal direction of the right-side portion of the front-side abutting plate is formed in the right-side portion of the front abutting plate not sandwiched at the outer end thereof by the bendable portions. Further, if there is any portion not sandwiched at the outer end thereof by the bendable portions in the left-side portion of the front-side abutting plate, the convex portion extending in the longitudinal direction of the left-side portion of the front-side abutting plate is formed in the left-side portion of the front abutting plate not sandwiched at the outer end thereof by the bendable portions. 
     Further, in the heat retention material cartridge according to the first aspect of the present invention, at the portions of the front abutting plate where the convex portions are formed, the outer edge portion of the thermosensitive expansion rubber is formed so that the outer end of the thermosensitive expansion rubber is positioned inside the apex of the convex portion of the front abutting plate. In the portions of the front-side abutting plate where no convex portion is formed, namely, in the portions of the front-side abutting plate where the outer end is sandwiched by the bendable portions, it is preferable that the outer end of the thermosensitive expansion rubber is positioned inside the bendable portions. 
     The heat retention material cartridge according to a second aspect of the present invention is the heat retention material cartridge fixed to the base member of the heat retention tool of the cylinder bore&#39;s bore wall for heat retention of the cylinder bore wall, which includes 
     the thermosensitive expansion rubber coming into contact with the cylinder bore-side wall surface of the groove-like cooling water passage and covering the cylinder bore-side wall surface of the groove-like cooling water passage, 
     the back-side pressing member being arc-shaped when viewed from above, and provided on the back side of the thermosensitive expansion rubber for pressing the thermosensitive expansion rubber entirely from the back side toward the cylinder bore-side wall surface of the groove-like cooling water passage, 
     the front-side abutting plate provided on the contact surface of the thermosensitive expansion rubber, having an arc-shape when viewed from above and having an rectangular opening when viewed from the front side, and cooperative with the back-side pressing member for sandwiching an outer edge portion of the thermosensitive expansion rubber, and 
     the elastic member attached to the back-side pressing member for urging toward the cylinder bore-side wall surface of the groove-like cooling water passage, so that the back-side pressing member presses the thermosensitive expansion rubber, 
     wherein 
     the bendable portions are formed at the upper end, the lower end, the right end, and the left end of the back-side pressing, and the bendable portions are bent toward the front-side abutting plate, so that the thermosensitive expansion rubber and the front-side abutting plate are sandwiched between the bendable portions and the back-side pressing member, 
     there is a portion where the outer end is not sandwiched by the bendable portions at least at the upper-side portion and the lower-side portion of the front-side abutting plate, a convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the upper-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the upper-side portion of the front-side abutting plate, and a convex portion being convex toward the back-side pressing member and extending in the longitudinal direction of the lower-side portion of the front-side abutting plate is formed in the portion where the outer end is not sandwiched by the bendable portions at the lower-side portion of the front-side abutting plate, and 
     the outer edge portion of the thermosensitive expansion rubber is formed in such a manner that the outer end of the thermosensitive expansion rubber is positioned inside the apex of the convex portion, at the portion of the front-side abutting plate where the convex portion is formed. 
     The heat retention material cartridge according to the second aspect of the present invention and the heat retention material cartridge according to the first aspect of the present invention are mainly different in that the elastic member attached member is provided in the heat retention material cartridge according to the first aspect of the present invention and the elastic member is attached to the elastic member attached member, meanwhile the elastic member attached member is not provided in the heat retention material cartridge according to the second aspect of the present invention and the elastic member is attached to the back-side pressing member. Therefore, regarding points common to the heat retention material cartridge according to the second aspect of the present invention and the heat retention material cartridge according to the first aspect of the present invention, the description of the heat retention material cartridge according to the first aspect of the present invention will be referred to and detailed description will be omitted. 
     The heat retention material cartridge according to the second aspect of the present invention is the heat retention material cartridge fixed to the base member of the cylinder bore wall heat retention tool for heat retention of the cylinder bore wall. The heat retention material cartridge according to the second aspect of the present invention has the back-side pressing member to which the elastic member is attached and being arc-shaped when viewed from above, the thermosensitive expansion rubber thermo-sensitively expanding in the groove-like cooling water passage, having the contact surface coming into contact with the cylinder bore wall of the groove-like cooling water passage, and covering the cylinder bore wall, and the front-side abutting plate being arc-shaped when viewed from above, which are sequentially overlapped. The bendable portions formed at the upper end of the back-side pressing member, the bendable portions formed at the lower end of the back-side pressing member, the bendable portion formed at the right end of the back-side pressing member, and the bendable portion formed at the left end of the back-side pressing member are bent toward the front-side abutting plate, so that the thermosensitive expansion rubber and the front-side abutting plate are sandwiched between the bendable portions and the back-side pressing member, thereby fixing these members to the back-side pressing member. 
     The heat retention material cartridge according to the second aspect of the present invention is fixed to each bore portion of the support member formed into the shape along the groove-like cooling water passage in which the cylinder bore wall heat retention tool is installed, that is, the shape including plural arcs that are continuous when viewed from above. In fixing the heat retention material cartridge according to the second aspect of the present invention to the support member, the bendable portions formed at the upper and lower ends of the back-side pressing member are bent toward the support member, and the support member is sandwiched between the bendable portions and the back-side pressing member. As a result, the heat retention material cartridge according to the second aspect of the present invention is fixed to the support member. 
     The thermosensitive expansion rubber relating to the heat retention material cartridge according to the second aspect of the present invention is similar to the heat retention material cartridge according to the first aspect of the present invention. 
     The back-side pressing member relating to the heat retention material cartridge according to the first aspect of the present invention is arc-shaped when viewed from above, has the shape along the back side of the thermosensitive expansion rubber (the surface on the side opposite to the contact surface side) so that entire thermosensitive expansion rubber can be pressed from the back side of the thermosensitive expansion rubber, and has the shape covering the entire back side or substantially the entire back side of the thermosensitive expansion rubber. The material of the back-side pressing member can be appropriately selected if it can deform in such a way as to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage when pushed from the back side by the elastic member. Metal plates of stainless steel, aluminum alloy, and the like are preferable. The thickness of the back-side pressing member can be appropriately selected if it can deform in such a way as to press the rubber member toward the cylinder bore-side wall surface of the groove-like cooling water passage when pressed from the back side by the elastic member. 
     Further, the elastic member is attached to the back-side pressing member relating to the heat retention material cartridge according to the second aspect of the present invention. Further, the bendable portions are formed at the upper, lower, right, and left ends of the back-side pressing member relating to the heat retention material cartridge according to the second aspect of the present invention. The elastic member is the elastic urging member that enables the back-side pressing member to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage, when the cylinder bore wall heat retention tool fixed to the heat retention material cartridge according to the second aspect of the present invention is installed in the groove-like cooling water passage, and the thermosensitive expansion rubber expands and elastically deforms. 
     When the heat retention material cartridge according to the second aspect of the present invention is viewed from above, two or more elastic members are attached in the circular arc direction of the heat retention material cartridge according to the second aspect of the present invention. In the case where the attachment place for the elastic member is only one, the elastic member is attached to the heat retention material cartridge according to the second aspect of the present invention at or near the center in the circular arc direction in order to press the heat retention tool entirely. However, in this case, since the heat retention material cartridge according to the second aspect of the present invention is fixed to the support member at or near the center, the heat retention material cartridge according to the second aspect of the present invention is pressed together with the support member. Therefore, in the heat retention material cartridge according to the second aspect of the present invention, independently of the support member, the portion adjacent to the edge of the heat retention material cartridge according to the second aspect of the present invention is not separated from the support member and does not deform in such a way as to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage. Because of this, the elastic members need to be attached at least at two places in total, at one place near one end at the other place near the other end, of the heat retention material cartridge according to the second aspect of the present invention, so that the portions adjacent to both edges of the heat retention material cartridge according to the second aspect of the present invention are separated from the support member and deform in such a way as to press the thermosensitive expansion rubber toward the cylinder bore-side wall surface of the groove-like cooling water passage, independently of the support member. Further, it is preferable that the elastic members are attached at three positions in total, at one place at or near the center in the circular arc direction of the heat retention material cartridge according to the second aspect of the present invention, at one place near one end and at another place near the other end of the heat retention material cartridge according to the second aspect of the present invention, so that the heat retention material cartridge according to the second aspect of the present invention is entirely pressed and the portions adjacent to both edges of the heat retention material cartridge according to the second aspect of the present invention are pressed independently of the support member. Further, to enhance the adhesion of the thermosensitive expansion rubber of the heat retention material cartridge according to the first aspect of the present invention to the cylinder bore-side wall surface of the groove-like cooling water passage, the elastic members can be attached at four portions or more in the circular arc direction. 
     The elastic member relating to the heat retention material cartridge according to the second aspect of the present invention is similar to the elastic member relating to the heat retention material cartridge according to the first aspect of the present invention, although the member to which the elastic member is attached is different. 
     Among the bendable portions formed on the back-side pressing member, the bendable portions formed at the right and left ends can be formed over the whole of the up-and-down direction at the right end or the left end of the back-side pressing member, or can be formed partly at the right end or the left end of the back-side pressing member in the up-and-down direction. In the case where the bendable portions are partly formed at the right end or the left end of the back-side pressing member, convex portions are formed at portions of the front-side abutting plate not sandwiched at the outer end thereof by the bendable portions. Since the bendable portions at the right and left ends of the back-side pressing member are linearly bendable, they can be bent properly even when they are formed over the whole of the up-and-down direction at the right end or the left end of the back-side pressing member. Forming the bendable portions over the whole of the up-and-down direction at the right end or the left end of the back-side pressing member so as to sandwich the thermosensitive expansion rubber and the front-side abutting plate at the right or left side thereof in the up-and-down direction is preferable in that cooling water can be prevented from strongly flowing from the right or left side of the heat retention material cartridge according to the second aspect of the present invention between the back-side pressing member and the front-side abutting plate. 
     The upper and lower ends of the heat retention material cartridge according to the second aspect of the present invention are arc shaped when viewed from above. Therefore, if the bendable portions formed at the upper and lower ends of the back-side pressing member are excessively long in width, the bendable portions cannot be bent properly, and further the thermosensitive expansion rubber and the front-side abutting plate cannot be fixed properly. Therefore, the bendable portions formed at the upper and lower ends of the back-side pressing member can be appropriately selected in width, in a range in which normal bending is feasible and normal fixing of the thermosensitive expansion rubber and the front-side abutting plate is feasible. The number of the bendable portions formed at the upper and lower ends of the back-side pressing member is two or more in the circular arc direction of the heat retention material cartridge according to the second aspect of the present invention, when the heat retention material cartridge according to the second aspect of the present invention is viewed from above. 
     The bendable portions for fixing the heat retention material cartridge according to the second aspect of the present invention are formed at or near the center of the upper and lower ends of the back-side pressing member. The bendable portions formed at the upper and lower ends of the back-side pressing member can be appropriately selected in width, in a range in which normal bending is feasible and fixing to the support member is feasible. 
     As the back-side pressing member to which the elastic member is attached, for example, an embodied example illustrated in  FIG. 24  may be employed. In the embodied example illustrated in  FIG. 24 , the metal plate spring  39  made of a longitudinally long rectangular metal plate is welded to a back pressing member  47  made of a metal plate and having bendable portions  331   c ,  331   d ,  332   e , and  332   f  formed at the upper, lower, right, and left ends thereof. Further, instead of using the metal plate spring, for example, another embodied example using a metal elastic member such as a metal coil spring, a leaf spring, or a torsion spring welded to the back pressing member made of a metal plate and having bendable portions formed at the upper, lower, right, and left ends thereof may be employed. 
     The front-side abutting plate relating to the heat retention material cartridge according to the second aspect of the present invention is similar to the front-side abutting plate relating to the heat retention material cartridge according to the first aspect of the present invention. 
     Further, in the heat retention material cartridge according to the second aspect of the present invention, the outer edge portion of the thermosensitive expansion rubber is formed in such a manner that the outer end of the thermosensitive expansion rubber is positioned inside the apex of the convex portion of the front abutting plate, at the portion of the front abutting plate where the convex portion is formed. 
     The cylinder bore wall heat retention tool according to the present invention is the heat retention tool installed in the groove-like cooling water passage of the cylinder block of an internal combustion engine having cylinder bores for heat retention of bore walls of the cylinder bores, 
     having the heat retention material cartridge according to the present invention, and the metal-made or synthetic resin-made support member having the shape along the shape of the groove-like cooling water passage at the installation position of the heat retention tool, to which the heat retention material cartridge is fixed, wherein 
     the heat retention material cartridge is fixed to the support member only at or near the center in the circular arc direction. The heat retention material cartridge according to the first aspect of the present invention and the heat retention material cartridge according to the second aspect of the present invention are collectively referred to as the heat retention material cartridge according to the present invention. 
     The support member is formed in the shape in which plural arcs are continuous when viewed from above, and the shape of the support member is the shape along one side half of the groove-like cooling water passage. Further, the support member has the opening so that the elastic member attached to the heat retention material cartridge according to the present invention can pass through the support member, from the back side of the cylinder bore wall heat retention tool according to the present invention, and protrude toward the wall surface on the side opposite to the cylinder bore-side wall surface of the groove-like cooling water passage. 
     The support member is the member to which the heat retention material cartridge according to the present invention is fixed, and plays a role in determining the position of the heat retention material cartridge according to the present invention so that the position of the heat retention material cartridge according to the present invention does not shift in the groove-like cooling water passage. The support member is a metal plate or a molded body of a synthetic resin. 
     Then, in the cylinder bore wall heat retention tool according to the present invention, the heat retention material cartridge according to the present invention is fixed to the support member only at or near the center in the circular arc direction when viewed from above (at or near the center of the arc-shaped heat retention material cartridge according to the present invention when the heat retention material cartridge according to the present invention is viewed from above). On the other hand, the portion adjacent to the edge of the heat retention material cartridge according to the present invention is not fixed to the support member. 
     After the cylinder bore wall heat retention tool according to the present invention is installed in the groove-like cooling water passage of the cylinder block, when the internal combustion engine is driven, the thermosensitive expansion rubber is heated and thermo-sensitively expands. Then, the thermosensitive expansion rubber expands toward the cylinder bore-side wall surface through the opening formed in the inner portion of the front-side abutting plate, and the contact surface comes into contact with the cylinder bore wall surface. Even after the contact surface has contacted the cylinder bore-side wall surface, the thermosensitive expansion rubber continues to expand until it reaches an opened state. Therefore, the elastic member is subjected to the force directing toward the back side of the heat retention material cartridge according to the present invention. As a result, the elastic member deforms and the elastic member generates the elastic force for returning to the original position. Then, by this elastic force, the elastic member attached member to which the elastic member is attached or the back-side pressing member to which the attachment member is attached is pushed toward the cylinder bore-side wall surface of the groove-like cooling water passage. As a result, the back-side pressing member pushes the thermal expansion rubber, the thermosensitive expansion rubber is pressed against the cylinder bore-side wall surface of the groove-like cooling water passage. That is, when the cylinder bore wall heat retention tool according to the present invention is installed in the groove-like cooling water passage and the thermosensitive expansion rubber is heated and thermo-sensitively expands, the elastic member deforms and the elastic force generated to restore from the deformation urges the back-side pressing member in such a way as to press the thermosensitive expansion rubber against the cylinder bore-side wall surface of the groove-like cooling water passage. Thus, the thermosensitive expansion rubber of the heat retention material cartridge according to the present invention comes into contact with the bore wall surfaces of the respective cylinder bores of the cylinder bore-side wall surface of the groove-like cooling water passage. 
     In the cylinder bore wall heat retention tool according to the present invention, the heat retention material cartridge according to the present invention is fixed to the support member only at or near the center in the circular arc direction when the heat retention material cartridge according to the present invention is viewed from above, when the elastic member urges the elastic member attached member or the back-side pressing member of the heat retention material cartridge according to the present invention, the elastic member attached member (only in the case of the first heat retention material cartridge according to the present invention, the same applies hereinafter), the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate can deform independently of the support member. In the manufacturing of the cylinder bore wall heat retention tool according to the present invention, the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are processed so that their curvatures match the curvatures of the wall surfaces of the bore walls of the respective cylinder bores with which the thermosensitive expansion rubber comes into contact. However, in fact, processing errors occur with respect to design values in any of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, the front-side abutting plate, and the wall surfaces of the bore walls of the respective cylinder bores. Then, when the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate become smaller than the curvatures of the wall surfaces of the bore walls of the respective cylinder bores due to processing errors of these members or the wall surfaces of the bore walls of the respective cylinder bores, if the heat retention material cartridge is entirely fixed to the support portion (for example, fixed to the support member at a total of three positions near the center and both ends in the circular arc direction when the heat retention portion is viewed from above), the thermosensitive expansion rubber can come into contact with the bore walls of the respective cylinder bores at the portion near the center in the circular arc direction but cannot contact the bore walls at the portion adjacent to the edge, when urged by the elastic member. On the other hand, when the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate become smaller than the curvatures of the wall surfaces of the bore walls of the respective cylinder bores, if the heat retention material cartridge according to the present invention is fixed to the support member only at or near the center in the circular arc direction when the heat retention material cartridge is viewed from above, the portion adjacent to the edge of the heat retention material cartridge according to the present invention is separated from the support member and can deform toward the bore walls of the respective cylinder bores when urged by the elastic member. Therefore, the thermosensitive expansion rubber can come into contact with the bore walls of the respective cylinder bores not only at the portion near the center but also at the portion adjacent to the edge in the circular arc direction. Because of this, in the cylinder bore wall heat retention tool according to the present invention, even if the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are different from the curvatures of the wall surfaces of the bore walls of the respective cylinder bores due to processing errors, the thermosensitive expansion rubber can be surely brought into contact with the wall surfaces of the bore walls of respective cylinder bores. Therefore, the adhesion of the thermosensitive expansion rubber to the wall surfaces of the bore walls of the respective cylinder bores (the cylinder bore-side wall surface of the groove-like cooling water passage) is enhanced. 
     Further, when the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are larger than the curvatures of the bore walls of respective cylinder bores, if the heat retention material cartridge is entirely fixed to the support member, the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate do not change. Therefore, there is a possibility that a gap may be formed between the thermosensitive expansion rubber and the bore walls in the vicinity of the center in the circular arc direction when viewed from above. On the other hand, in the cylinder bore wall heat retention tool according to the present invention, even if the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are larger than the curvatures of the bore walls of respective cylinder bores, since the heat retention material cartridge according to the present invention is fixed to the support member only at or near the center in the circular arc direction, the heat retention material cartridge according to the present invention is pushed by the elastic member from the back side at or near the center in the circular arc direction, and the portions of the heat retention material cartridge according to the present invention other than the center or portions near the center in the circular arc direction deform in such a manner that the heat retention material cartridge according to the present invention opens outward at the portions adjacent to both ends in the circular arc direction, independently of the support member. Therefore, the thermosensitive expansion rubber can come into contact with the bore walls of the respective cylinder bores not only at the portion near the center but also the portion adjacent to the edge in the circular arc direction. Because of this, in the cylinder bore wall heat retention tool according to the present invention, even if the curvatures of the elastic member attached member, the back-side pressing member, the thermosensitive expansion rubber, and the front-side abutting plate are different from the curvatures of the wall surfaces of the bore walls of the respective cylinder bores due to processing errors, the thermosensitive expansion rubber can be surely brought into contact with the wall surfaces of the bore walls of the respective cylinder bores. Therefore, the adhesion of the thermosensitive expansion rubber to the wall surfaces of the bore walls of the respective cylinder bores (the cylinder bore-side wall surface of the groove-like cooling water passage) is enhanced. 
     In the heat retention material cartridge according to the present invention, the bendable portions are present in such a way as to cover the outer end of the thermosensitive expansion rubber in the portions of the front-side abutting plate sandwiched by the bendable portions. Therefore, even when the thermosensitive expansion rubber expands, the outer edge portion of the thermosensitive expansion rubber does not protrude from the heat retention material cartridge according to the present invention. Further, since the bendable portions are present in such a way as to cover the outer end of the thermosensitive expansion rubber, it is insensitive to the flow of cooling water. Therefore, the problem of breakage of the thermosensitive expansion rubber by the cooling water does not occur. 
     In the heat retention material cartridge according to the present invention, in the portions of the front-side abutting plate not sandwiched by the bendable portions, the convex portions extending in the longitudinal direction of the front-side abutting plate are present in such a way as to protrude toward the back-side pressing member at the outer positions than the outer end of thermosensitive expansion rubber. Therefore, even when the thermosensitive expansion rubber expands, the outer edge portion of the thermosensitive expansion rubber cannot easily protrude from the heat retention material cartridge according to the present invention. Further, since the convex portions are present at the outer positions as compared with the outer end of the thermosensitive expansion rubber, the flow velocity of the cooling water flowing toward the outer end of the thermosensitive expansion rubber becomes very slow due to the presence of the convex portions even when the cooling water flows into the gap between the back-side pressing member and the front-side abutting plate. Therefore, the problem of breakage of the thermosensitive expansion rubber by the cooling water does not occur. 
     The internal combustion engine according to the present invention is an internal combustion engine in which the cylinder bore wall heat retention tool according to the present invention is installed. 
     An automotive vehicle according to the present invention is an automotive vehicle having the internal combustion engine according to the present invention. 
     REFERENCE SIGNS LIST 
     
         
           8  lowermost portion 
           9  uppermost portion 
           10  intermediate position 
           11  cylinder block 
           12  bore 
           12   a   1 ,  12   a   2  end bore 
           12   b   1 ,  12   b   2  intermediate bore 
           13  cylinder bore wall 
           14  groove-like cooling water passage 
           15  cooling water supply port 
           16  cooling water discharge port 
           17  cylinder bore-side wall surface of groove-like cooling water passage  14   
           17   a ,  17   b  one side half wall surface 
           18  wall surface on side opposite to cylinder bore-side wall surface of groove-like cooling water passage  14   
           21   a ,  21   b  one side half bore wall 
           23   a   1 ,  23   a   2 ,  23   b   1 ,  23   b   2  bore walls of respective cylinder bores 
           26  contact surface 
           27  tip end 
           30  front-side abutting plate 
           31  thermosensitive expansion rubber 
           32  back-side pressing member 
           33  elastic member attached member 
           34  support member 
           35 ,  35   a  heat retention material cartridge 
           36 ,  36   b ,  36   c  cylinder bore wall heat retention tool 
           37 ,  37   a ,  331   a ,  331   b ,  331   c ,  331   d ,  332   a ,  332   b ,  332   c ,  332   d,    
           332   e ,  332   f  bendable portion 
           38  cooling water flow partition member 
           39  metal plate spring 
           42  opening 
           43  metal plate 
           45  metal plate punched product 
           191  inter-bore portion 
           192  boundary of bore walls of respective cylinder bores of cylinder bore-side wall surface of groove-like cooling water passage 
           301  opening 
           302 ,  302   a ,  302   b ,  302   c ,  302   d  convex portion 
           303 ,  303   a ,  303   b ,  303   c ,  303   d  portion of front-side abutting plate sandwiched at outer end thereof by bendable portion 
           304 ,  304   a ,  304   b  portion of front-side abutting plate not sandwiched at outer end thereof by bendable portion 
           308   a  upper-side portion of front-side abutting plate 
           308   b  lower-side portion of front-side abutting plate 
           311  contour of thermosensitive expansion rubber 
           312   a ,  312   b ,  313   a ,  313   b ,  313   c ,  313   d  outer end of thermosensitive expansion rubber 
           319  cutout portion