Patent Publication Number: US-6705650-B2

Title: Fastening structure

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2000-127339 filed on Apr. 27, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a fastening device for fastening two parts at a peripheral portion. 
     2. Description of Related Art 
     For example, an air cleaner apparatus for a vehicle is constituted by a case (first housing) having a first opening and an air inlet, a cap (second housing) having a second opening which is facing to the first opening and an air outlet, a filter element wherein a seal member is mounted to the outer peripheral portion and sandwiched at each of the peripheral portion of the case and the cap, and the like. By connecting the case and the cap, for example, with a hinge structure, at one side of the peripheral portion, they are integrated to be relatively turnable around the hinge. By placing one peripheral portion over the other with the filter element sandwiched therebetween to be in a state where the first opening and the second opening are closed each other, they are fastened at other side in the peripheral portion with a metal clamp or the like. 
     FIG. 21 shows an example of the above-mentioned fastening structure, for example, as described in Japanese Laid-Open Publication No. Hei 8-281033. In FIG. 21 a clamp  194  is mounted to a flange  192  provided to project toward the outer peripheral portion on top end of a case  190  so as to be turnable around the axis center vertical to the paper face. The clamp  194  is formed by bending a thin metal plate in the direction of its surface to be apart from the flange  192  at the intermediate part in the longitudinal direction and having an engaging potion  196  formed by bending further greatly to face to the flange  192  at the extreme end side on the opposite side to the turning axis center. When the case  190  and the cap  198  are fastened with such a clamp  194 , these flanges  192 ,  200  are put together and the clamp  194  is turned to the left direction in the drawing and the engaging portion  196  is projected to the flange  200  by pressing an operating part  202  provided at the extreme end toward the cap  198 . 
     However, in the fastening structure by means of the above-mentioned clamp  194 , applied force F 1  required for fastening is given by F 1 =(L 2 /L 1 )F 2 ; where resisting force F 2  is for the engaging portion  196  to go over an angular portion at the edge of the flange  200 , and L 2  which cannot be universally set is defined by thickness of the flanges  192 ,  200 , and thickness of a filter element not shown in the drawing. Therefore, since L 1  to L 2  cannot be set that long in the engine room of a vehicle where a dead space is desirably diminished as much as possible, there has been a problem that workability is bad because assembly load cannot be reduced at the time of fastening. such a problem is not limited to the above-mentioned air cleaner fastening structure for a vehicle, and it possibly occurs similarly as long as fastening structure where two parts are laid one over-the other at their peripheral portion and fastened with a clamp or the like. 
     SUMMARY OF THE INVENTION 
     The invention has been accomplished against the background of the foregoing circumstances and its object is to provide a fastening structure capable of reducing assembly load with a simple constitution. 
     In an aspect of a fastening structure according to the invention to accomplish such an object, a first peripheral portion of a first part and a second peripheral portion of a second part are put together and pressed to each other, whereby the first part and the second part are fastened. This fastening structure includes a first engaging portion provided with a first sliding contact surface facing to the second peripheral portion side at the opposite side to the first part in relation to the second peripheral portion and extending to the second part from the first part, a second engaging portion provided to the fastening part so as to be engaged with the first engaging portion and be relatively turnable around the predetermined turning axis, a second sliding contact surface provided to the second engaging portion so as to come in contact with the first sliding contact surface in the engaged state of the fastening part with the first engaging portion wherein pressing force applied from the first sliding contact surface increases as the fastening part is turned around a predetermined turning axis in the fastening direction, a peripheral portion pressing surface provided to the fastening part so as to press the second peripheral portion toward the first peripheral portion based on the pressing force and an operating part provided to the fastening part at a predetermined interval from the turning axis in order to turn the second engaging part around the turning axis against the first engaging part in the predetermined turning axis direction. 
     In such a manner, when the first peripheral portion of the first part and the second peripheral portion of the second part are put together and the second engaging portion of the fastening part is engaged with the first engaging portion extending from the first part and then the second engaging portion is turned against the first engaging portion in the fastening direction by operating the operating part of the fastening part, pressing force according to the turning amount is applied to the second sliding contact surface from the first sliding contact surface facing to the side of the second peripheral portion and based on this pressing force the peripheral portion pressing surface of the fastening part presses the second peripheral portion toward the first peripheral portion, whereby the first peripheral portion and the second peripheral portion are fastened. At this time, the required force for turning the second engaging portion, that is, assembly load is smaller as a fulcrum-point of force-application distance from the turning axis center to the operating part in relation to a fulcrum-working point distance from the turning axis center to the peripheral portion pressing surface increases, however, the fulcrum-working point distance can be set small regardless of a thickness of the first peripheral portion and the second peripheral portion to such an extent that the torsional stress being applied to the fulcrum does not exceed the tolerable value. Therefore, a fastening structure capable of reducing the assembly load with a simple constitution can be obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view explaining the entire constitution of an air cleaner apparatus to which a fastening structure according to an embodiment of the invention is applied; 
     FIG. 2 is a plan view of the air cleaner apparatus of FIG. 1; 
     FIG. 3 is a front view explaining the constitution of the fastening device in detail with enlarged essence of the air cleaner apparatus of FIG. 1; 
     FIG. 4 is a plan view of the fastening device of FIG. 3; 
     FIG. 5 is a sectional view viewed along line V—V of FIG. 4; 
     FIG. 6 is a view corresponding to FIG. 3 for explaining the constitution of a fastening device according to another embodiment of the invention; 
     FIG. 7 is a sectional view viewed along line VII—VII of FIG. 6; 
     FIG. 8 is a plan view of the fastening device of FIG. 6; 
     FIG. 9 is a plan view showing the entirety of an air cleaner apparatus provided with a fastening device according to still another embodiment of the invention; 
     FIG. 10 is a front view of the air cleaner apparatus of FIG. 9; 
     FIG. 11A, FIG.  11 B and FIG. 11C are a plan view, a front view and a view from below, respectively, for explaining the constituent hook rod in the fastening device which is provided to the air cleaner apparatus of FIG. 9; 
     FIG. 12A, FIG.  12 B and FIG. 12C are a plan view, a front view and a view from below, respectively, for explaining the constituent hook rod inserting part in the fastening device which is provided to the air cleaner apparatus of FIG. 9; 
     FIG. 13A, FIG.  13 B and FIG. 13C are a plan view, a front view and a view from below, respectively, for explaining the constituent clamp in the fastening device which is provided to the air cleaner apparatus of FIG. 9; 
     FIG.  14 A and FIG. 14B are a plan view and a front view, respectively, for explaining a fastening operation by means of the fastening device which is provided to the air cleaner apparatus as shown in FIG. 9; 
     FIG. 15 is a plan view explaining a state where the fastening operation of FIG. 14 has been completed; 
     FIG. 16 is an explanatory view of a molding form of a case or a cap in the air cleaner apparatus of FIG. 9; 
     FIG. 17 is a sectional view viewed along line XVH—XVH of FIG. 16; 
     FIG.  18 A and FIG. 18B are a plan view and a front view of a constituent hook rod in a fastening device according to still another embodiment of the invention, respectively; 
     FIG. 19A is a plan view showing a clamp to constitute a fastening device in combination with the hook rod of FIG. 18, FIG. 19B is a sectional view viewed along line XIXB—XIXB of FIG. 19A; 
     FIG. 20 is an explanatory view of a fastening method by means of the fastening device shown in FIG.  18  and FIG. 19; and 
     FIG. 21 is a view explaining problems of the fastening structure with the conventional clamp. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the invention will be explained particularly with reference to the drawings. 
     FIG.  1  and FIG. 2 are a front view and a plan view showing the entirety of an air cleaner apparatus  10  to which a fastening structure of the invention is applied, respectively. As shown in FIG.  1  and FIG. 2, the air cleaner apparatus  10  is provided with a case  16  having an air inlet  12  and an opening  14 , and a cap  22  having an air outlet  18  and an opening  20 . The case  16  and the cap  22  are connected in such a manner that the opening  14  and the opening  20  are facing to each other and closing each other. And an internal space which is substantially airtight is formed between the case  16  and the cap  22 . For example, the case  16  is provided with a thread or the like (not shown) for securing in an engine room of a vehicle at a suitable position of the outer peripheral face. Both of the case  16  and the cap  22  are made of thermosetting resin. In this embodiment, the case  16  and the cap  22  correspond to the first part and the second part, respectively. 
     Moreover, FIG. 1 shows an internal structure being partially broken away in the vicinity of the boundary between the case  16  and the cap  22 . A filter element  24  is provided in the internal part of a container constituted by the case  16  and the cap  22 . Flanges  28 , 30  are provided to the case  16  and the cap  22  in such a manner that they expand outward from the entire periphery of the opening ends and the filter element  24  is held by being sandwiched between the case  16  and the flanges  28 , 30  of the cap at the peripheral portion  26 . The filter element  24  is positioned in the intermediate part in the direction of height inside the container. The element peripheral portion  26  is constituted, for example, by rubber; resin coated with rubber or the like, and is held in a state where it is elastically pressed to shrink by the flanges  28 , 30 . Incidentally, FIG.  5  and so on as described later show a case where the peripheral portion  26  is constituted only by rubber for convenience. In this embodiment, the flanges  28 , 30  correspond to a first peripheral portion and a second peripheral portion, respectively. 
     A pair of hinge devices  32  is provided to one side positioned at the left end in FIG.  1  and FIG. 2 at the boundary between the case  16  and the cap  22 . In this embodiment the hinge device  32  is constituted, for example, by parts respectively projecting from flanges  28 ,  30  of the case  16  and the cap  22 , and pinching each other. The cap  22  is turnable can be around the axis center vertical to the paper surface of FIG. 1 in relative to the case  16  with the hinge device  32  as a turning axis. When the cap  22  is turned to the left from the position shown in FIG. 1, the opposite side to a side provided with a hinge device  26  (the other side positioned at the right end in FIG.  1  and FIG. 2) comes apart from each other, and the internal space between the case  16  and the cap  22  becomes opened. Along with that, the held state of the filter element  24  by flanges  28 , 30  of the element peripheral portion  26  is released. The filter element provided inside is exchangeable by releasing the internal portion in such a manner. 
     Two sides parallel to each other extending from one side where the hinge device  32  is provided in the flanges  28 , 30  to the other side to be open are provided, for example, with a pair of fastening devices  34 , respectively, in the adjacent portion to the other side that is the opening end side. The fastening device  34  is provided with a hook  36 , a hook  38  and a hook rod  40 . The hook  36  is formed to project outward from a top end side surface of the case  16  and extend toward the cap  22 . The hook  38  is provided to face to the extreme end of the hook  36  on the flange  30  of the cap  22 . The hook rod  40  is engaged with these hooks  36 , 38 . The fastening device maintains a fastened state wherein the flanges  28 , 30  put the case  16  and the cap  22  together to be substantially airtight trough the filter element  24 . All the hooks  36 , 38  and the hook rod  40  are made of thermosetting resin material similar to that of the case  16  and the cap  22  and are independent parts from one another as will be mentioned later. In this embodiment, the hook  36  and the hook  38  correspond to the first engaging portion and the third engaging portion, respectively. 
     FIG.  3  and FIG. 4 are a front view and a plan view showing the enlarged essential portion in FIG.  1  and FIG. 2, respectively, for explaining the constitution of the fastening device  34 . FIG. 5 is a sectional view viewed along line V—V in FIG.  4 . The hook  36  is constituted by a first part  42 , a second part  44  and a third part  48 . The first part is formed to extend from the side wall of the case  16 , and is positioned lower than the flange  30  of the cap  22  (at the side of the case  16 ) and corresponds to the lower end of the hook  36 . The second part  44  of thinner width than that of the first part  42  extend upward so as to be apart from the case  16 . The third part extends parallel to an upper surface  46  of the flange  30  from the top end of the second part  44 . The second part  44  and the third part  48  are positioned higher than the flange  30  of the cap  22  (at the side of the cap  22 ) and correspond to the top end of the hook  36 . Therefore, the top end of the hook  36  is formed to extend from the lower end in the size of a thinner width and to be bent from the top end of the extending portion toward the right in FIG.  3  and FIG. 4 so as to have a hook-like shape with the extending part whose right end is open. The lower surface  50  facing to the side of the flange  30  of the third part  48  is parallel to the upper surface  52  of the first part  42 . Thereby, the hook  36  is formed with a recess  54  having a right end portion being open in FIG.  3  and FIG. 4 among the first part  42 , the second part  44  and the third part  48 . Incidentally, the upper surface  52  of the first part  42  is positioned substantially on the same surface as the upper surface  46  of the flange  30  or slightly lower than that in the fastened state as shown in FIG.  5 . In this embodiment, the first part  42  and the second part  44  correspond to a leg portion; the third part  48  corresponds to a first sliding contact portion; and the lower surface  50  corresponds to the first sliding contactsurface, respectively. 
     Moreover, the hook  38  is constituted by a first part  56  extending upwardly from the flange  30  and a second part  58  extending parallel to the upper surface  46  of the flange  30  from the extreme end of the first part  56 . The first part  56  extends from the flange  30  and the second part  58  extends from the side wall of the cap  22 . Therefore, the hook  38  bends toward the right at its top end in FIG.  3  and FIG. 4, with a hook-like shape having the right end open and formed with a recess  60  having an opened right end in FIG.  3  and FIG. 4 between the flange  30  and the side wall of the cap  22 . In the inner surface of the part having the hook-like shape, that is the inner surface  62  of the first part  56  and the lower surface  64  of the second part  58 , the inner surface  62  is on the same plan surface as the inner surface  66  of the second part  44  of the hook  36 , and the lower surface  64  is on the same plan surface with or slightly lower than the lower surface  50  of the third part  48  of the hook  36 . 
     Moreover, the hook rod  40  forming entirely a substantially T-shape is provided with a first column-like portion  68  having a column-like configuration of a substantially oval cross section and the second column-like portion  70  having a column-like shape of a substantially circular cross section whose axis center direction extending along the substantially vertical direction to the center of the first column-like portion  68  in the direction of the axis center, forming from that center having a substantially T-shape as an entirety. The first column-like portion  68  has a pair of flat surfaces  74  at the both ends in the longitudinal direction of a substantially oval-shaped section in an outer peripheral surface  72 . The second column-like portion  70  continues in the center between the pair of the flat surfaces  74  in the outer peripheral surface  72 . The diameter of the second column-like portion  70  is substantially equal to the shorter diameter of the first column-like portion  68 , therefore, the pair of the flat surfaces  74  project in its diametric direction further than the second column-like portion  70 . The shorter diameter of the first column-like portion  68  is relatively smaller than space A between the upper and lower surfaces  50 , 52  of the hook  36 , or the substantially same space of the upper and lower surfaces  64 , 46  of the hook  38 , and the longer diameter (a relative space between the flat surfaces  74 , 74 ) is the same as or relatively larger that the space A. 
     The hook rod  40  having such a configuration is removed from the hooks  36 , 38  at such a time as exchanging of a filter element  24  held between the case  16  and the cap  22  and is operated as below when the case  16  and the cap  22  are fastened. First, after closing the case  16  and the cap  22  in the state shown in FIG. 1 etc., the first column-like portion  68  is fitted in the direction of the arrow B as shown in FIG. 1 from the right hand in FIG.  1  and FIG. 3 etc. so that one of the end surface sides rather than the second column-like portion  70  in the first column-like portion enters a recess  54  within the hook  36  and the other end surface side part enters a recess  60  within the hook  38  in the axis center direction of the first column-like portion  68  being substantially vertical to the edge of the flange  30  and substantially parallel to its upper surface  46 . In this stage, the flange  30  of the cap  22  is pushed up higher than the position shown in FIG. 5, that is, in the direction apart from the case  16 , by means of an element peripheral portion  26 . Therefore, the upper surface  46  of the flange  30  is positioned closer to the lower surface  50  than the upper surface  52  of the hook  36 , and the space between the upper surface  46  and the lower surface  50  is slightly smaller than A. At that time, a direction of the second column-like portion  70  of the hook rod  40  is the up-down direction in FIG.  3 . That is, the direction of the shorter diameter of the first column-like portion  68  being smaller than the space A between the upper and lower surfaces  50 , 52  of the hook  36  is in the up-down direction in the drawing, therefore, pressing force is not applied at all among the first column-like portion  68 , the hook  36  and the flange  30 . However, because the space between the upper and lower surfaces  46 , 50  is smaller than A as described above, there is a case where small pressing force occurs in the first place depending on the relative sizes of the flange and fastener components. 
     After fitted into the position in the direction as shown by dot-dash lines in FIG. 3, the second column-like portion  70  is turned by about 90° to the position shown by a solid line in the arrow C direction about the axial turning of the first column-like potion  68  along the side wall surface of the cap  22 . In this process of turning, due to the substantially oval-shaped section of the first column-like portion  68  as the second-column-like portion  70  is turned from the vertical direction to the lower surface  50  of the hook  36 , an outer peripheral surface  72  contacts with the lower surface  50  at a turning angle where the degree corresponds to A, (precisely a turning angle corresponding to the distance between the upper and lower surfaces  46 , 50  becoming slightly smaller than A), thereafter, the larger the turning angle becomes, the larger pressing force is applied from the lower surface  50  to the outer peripheral surface  72 . In other words, the outer peripheral surface  72  in the oval shape functions as a cam surface, the pressing force is corresponding to the gap between the diameter of a contacting part with the lower surface  50  of the hook  36  in the outer peripheral surface  72  of the first column-like portion  68  and the space of the upper surface  46  and the lower surface  50  in the initial state where flange  30  is pushed up to the element peripheral portion  26 . Therefore, the upper surface  46  of the flange  30  is pressed toward the flange  28  of the case  16  by the lower end positioning portion in the outer peripheral surface  72  based on the pressing force, the flanges  28 , 30  and the element peripheral portion  26  sandwiched therebetween are elastically pressed to shrink by the pressing force, whereby the case  16  and the cap  22  are fastened by a simple operation of only fitting the first column-like portion  68  in the recesses  54 , 60  of the hooks  36 , 38  and turning the same. Since there is a space between the flanges  28 , 30  in this fastened state, even if there is a manufacturing error in the thickness or the like of the flange  30 , the error is absorbed by elastic deformation of the element peripheral portion  26 , and a sealed state can be positively obtained. 
     In turning the hook rod  40  for fastening, a fulcrum of the first column-like portion  68  to be turned is on the axis center and its point of force-application is on the extreme end of the second column-like portion  70  a distance L 1  away from the fulcrum. The working point (load point) is on the peripheral surface  72  of the first column-like portion  68  a distance L 2  away from the axis center, therefore, the distance L 1  can be set relatively large to the distance L 2  regardless of the thickness dimensions of the flanges  28 , 30  and the element peripheral portion  26 . Thus, a required force for turning the hook rod  40 , or assemble load for fastening to be defined by the above ratio L 2 /L 1  may be relatively small. Incidentally, as clear from the above description, in this embodiment, a part to be fitted in the hook  36  in the first column-like portion  68 , the outer peripheral surface  72  and the flat surface  74   a , the outer peripheral surface  72  and the flat surface  74   b , and the column-like portion  70  correspond to the second engaging portion, the second sliding contact surface, peripheral portion pressing surface and an operating part, respectively. 
     Moreover, in a state where a turning is completed as shown by a solid line in FIG. 3, that is a fastened state, the flat surface  74   a  comes in contact with the lower surface  50  of the hook  36 , and the diameter of the first column-like portion  68  provided with the flat surface  74  at the side of the longer diameter is the largest at the ridge of the boundary between the curved portion of the outer peripheral surface  72  and the flat surface  74 . Therefore, the pressing force applied from the lower surface  50  to the outer peripheral surface  72  based on the gap between the diameter of the contacting portion and the space A becomes larger as it turns to the right, that is, in the loosening direction, in the range of turning angles from the position as shown by a solid line in the drawing to the highest position of the ridge of the above boundary. Therefore, in order to turn the first column-like portion  68  to the right from the position shown in FIG. 3 it is required to overcome a larger pressing force than in the fastened state in the drawing. Slight turning of the first column-like portion  68  increases pressing force, whereby turning force occurs in the direction of returning to the fastened state as shown in the drawing, therefore, turning of the hook rod  40  and further unfastening due to external causes such as vibration are preferably controlled. 
     In this embodiment, the hook  38  corresponding to a third engaging portion is provided to the cap  22  in addition to the hook  36  on the side of the case  16 . In fastening the case  16  and the cap  22 , the hook  38  is fitted in a part positioned opposite to the hook  36  in relation to the second column-like portion  70  in the first column-like portion  68 . Therefore, in the fastened state where pressing force is applied to the first column-like portion  68  from the lower surface  50  of the hook  36  and repulsive force is applied from the upper surface  46  of the flange  30  to the first column-like portion  68 , the repulsive force applied from a flange upper surface  46  pushes up one of ends at the side of the hook  38  of the first column-like portion  68 , and inclination of the first column-like portion  68  and further the other end are preferably inhibited from coming off from the hook  36 . In other words, the hook  38  functions as a device to control such an inclination of the first column-like portion  68  of the hook rod  40 . Such a function to control the inclination can be obtained by contacting the outer peripheral surface  74  of the first column-like portion  68  with either the lower surface  58  of the hook  38  or the upper surface  52  of the hook  36 , therefore, a constitution in which at least one of the lower surface  58  and the upper surface  52  comes in contact with the outer peripheral surface  74  in a fastened state is sufficient. 
     Moreover, in this embodiment, the hooks  36 , 38  have a configuration of a hook having a right end portion open in FIG.  3 . Therefore, the first column-like portion  68  of the hook rod  40  can be easily fitted in between the lower surface  50  of the hook  36  and the upper surface  46  of the flange  30  from the opening side. Thus, the fastening operation becomes further easier. 
     Next, another embodiment of the invention will be described. Incidentally, in the following embodiments, description regarding a common part to the following embodiments and the previous embodiment will be omitted with the same reference numerals. 
     FIG. 6 to FIG. 8 is drawings corresponding to FIG. 3, FIG.  5  and FIG. 4 of the previously-mentioned embodiment for explaining the essence in a constitution of another fastening device  76  capable of being employed in place of previously-mentioned fastening device  34 . A case  16  and a cap  22  are put together with an element  24  inserted therebetween, however, FIG. 6 to FIG. 8 show a state where the flanges  28 , 30  are not pressed in the fastening device  76 , that is, they are unfastened. In FIG. 6 to FIG. 8 a hook  78  continuing to the flange  28  is provided to project from the opening end to the side of the cap  22  at the side surface of the case  16 . The hook  78  comprises a pair of first parts  80   a , 80   b  extending to the side of the cap  22  from the flange  28  and a second part  82  provided between their upper ends positioned at a side upper than an upper surface  46  of the flange  30  (that is, the side apart from the case  16 ). Therefore, in a front view shown in FIG. 6, the hook  78  has a reversed U-shape entirely in a front view shown in FIG. 6, and a lower surface  84  facing to the side of the flange  30  of the second part  82  is substantially parallel to the upper surface  46 . Moreover one first part  80   a  with removed ridged part between one surface on the side of the flange  30  and one surface on the side of the other first part  80   b  where a cylindrical recessed surface  86  is provided in the direction of the axis center extending along the vertical direction to the paper surface in FIG.  8 . 
     Moreover, the hook  38  at the opposite position to the hook  78  is provided at the side surface of the cap  22 . The hook  38  is constituted in a substantially similar shape to that provided at the previously-mentioned fastening device  34 . However, in an unfastened state as shown in FIG. 7, a lower surface  64  of the second part  58  is positioned somewhat higher than the lower surface  84  of the second part  82  of the hook  78 . 
     Moreover, a hook rod  88  to be fitted in the hooks  78 ,  38  is constituted by a first column-like portion  90  having a substantially egg-shape in cross section and a second column-like portion  92  extending vertically from the center part in the direction of the axis center, having the shape of a substantially circle or a chamfered square in cross section. The position relationships of the first column-like potion  90  and the second column-like potion  92  are such that the center of the circular sectional part at the inner periphery side of the arch of the first column-like portion  90  shown by dot-dash lines in FIG. 6 is positioned on a straight line passing the axial center of the second column-like portion  92 . Moreover, in the unfastened state shown in the drawing, the second column-like portion  92  is substantially vertical to the upper surface  46  of the flange  30 . However, in the vertical state, a line connecting a center of the above mentioned circular sectional part and the vertex of a shaded part shown in an enlarged drawing at the outer periphery side from the dot-dash lines (nose)  94  is ahead of the turning direction to the left at an angle θ to the upper surface  46 . 
     A guide groove  96  is provided to the central outer peripheral surface in the direction of axis-center of the first column-like portion  90 , along the periphery direction. The guide groove  96  is formed in the range of about 90° from the lower end position in the drawing with a larger diameter than width of the guide groove  96  at the end in the right-turning direction and has a depression  98  of a hemisphere-shape deeper than the depth of the groove. The depression  98  is formed in a size corresponding to the size of a protrusion  100  in the shape of a hemisphere provided to the upper surface  46  of the flange  30 . In other words, the protrusion  100  is in the size to enter the guide groove  96  at its extreme end and to enter the depression  98  as the entirety. 
     When the case  16  and the cap  22  are fastened by the fastening device  76  constituted as the foregoing, they are put together so as to have a cross section as shown in FIG. 7, and then the hook rod  88  is inserted between the hooks  78 , 38  in which the direction of the axis center of the first column-like portion  90  is parallel to the upper surface  46  of the flange  30  and along the longitudinal direction as shown by the dot-dash lines in FIG. 8 at the position where the axial center of the second column-like portion  92  correspond to the axis center of the protrusion  100  in the direction vertical to the upper surface  46 . At this time, the protrusion  100  is fitted in the guide groove  96  at its extreme ends. Incidentally, in this stage, since the entirety of the protrusion  100  does not enter the guide groove  96 , the first column-like portion  90  is positioned slightly apart from the upper surface  46 . 
     Next, the hook rod  88  is turned to the axis center of the second column-like portion  92  to the left direction as shown by an arrow D in FIG. 8 by 90°. Whereby, as shown by a solid line in FIG. 8, one end of the first column-like portion  90  and the other end are inserted into the hook  78  and the hook  38 , respectively. At this time, since the cylindrical recessed surface  86  is provided to the first part  80   a  of the hook  78  by removing a ridge portion at the side of the protrusion  100 , the first column-like portion  90  does not interfere with the first part  80   a  during turning Moreover, since movement of the first column-like portion  90  in the direction along the upper surface  46  by engagement of the guide groove  96  and the protrusion  100  is controlled, the first column-like portion  90  and the hooks  78 , 38  are positioned in the predetermined relationship of position when the turning is completed. 
     Then, the second column-like portion  92  is turned by about 90° to the direction of an arrow E as shown in FIG. 6 to the axis center of the circular sectional part of the first column-like portion  90  as shown in FIG. 6 along the side wall surface of the cap  22 . In the process of turning, the diameter in the vertical direction facing to the lower surface  84  of the hook  78  from the turning center of the first column-like portion  90  having a substantially egg-shaped in cross section increases from the diameter at the time of inserting to the hook  78  as it turns, therefore, pressing force which becomes larger as a turning angle gets larger is applied to an outer peripheral surface  102  of the first column-like portion  90  from the lower surface  84 . That is, in this embodiment, the substantially egg-shaped outer peripheral surface  102  functions as a cum surface. Therefore, based on the pressing force the upper surface  46  of the flange  30  is pressed to the flange  28  of the case  16  by a part positioned at the lower end in the outer peripheral surface  102  and based on the pressing force the flanges  28 , 30  and based on that pressing force the element peripheral portion  26  sandwiched therebetween are elastically pressed to shrink. Whereby the case  16  and the cap  22  are fastened by a simple operation of fitting the first column-like portion  90  in the hooks  78 , 38  and turning. 
     In the above-mentioned fastened state where the hook rod  88  is turned by as much as 90°, the extreme end positioned at the outermost outer periphery side from the turning axis of the outer peripheral surface  102  in the substantially egg-shape further turned by the angle θ to the left direction from the contacting position with the lower surface  84  in the drawing. Therefore, since the distance to the outer peripheral surface  102  from the turning center at a contacting position with the lower surface  84  in the position where the fastening is completed becomes smaller than its largest value, when turned in the opposite direction to the arrow E direction, pressing force applied to the outer peripheral surface  102  from the lower surface  84  increases as it turns in the beginning of the turning, and turning force in the arrow E direction that is in the fastening direction is applied to the first column like portion  90  based on the pressing force. Therefore, in the structure of this embodiment, unfastening due to vibration or the like during use is preferably controlled. 
     In turning in the direction of the arrow E as above, a state where an extreme of protrusion  100  of the flange upper surface  46  is fitted in the guide groove  96  of the first column-like portion  90  is maintained. Thus, even if pressing force is applied to the first column-like portion  90  from the hook  78  with the turning there is no such a case that slanting of the hook rod  88  position caused by that makes the fastening work difficult or unfastening occurs easily. At the position where turning is completed, the entirety of the protrusion  100  is fitted in the depression  98  provided at the extreme end of the guide groove  96 , whereby the outer peripheral surface  102  of the first column-like portion  90  becomes to contact with the flange upper surface  46 . Therefore, since it is necessary for turning from the fastened state in the loosening direction that the engaged state of the protrusion  100  and the depression  98  is released and the outer peripheral surface  102  becomes apart from the flange upper surface  46 , pressing force applied to the outer peripheral surface  102  from the lower surface  84  of the hook  78  in the beginning of the turning in the unfastening direction increases further. In this embodiment, unfastening is further controlled also by such an engagement of the protrusion  100  and the depression  98 . 
     FIG.  9  and FIG. 10 are a plan view and a front view showing the entirety of an air cleaner apparatus  10  provided with a fastening device  104  of still another embodiment, respectively. In this embodiment, the fastening device  104  is constituted by a hook rod  106  formed to be integrated with the case  16 , a hook rod inserting portion  108  formed to be integrated with the cap  22  and a clamp (fastening part)  110  being independent from them. As a plan view, a front view and a view from below are shown in FIG. 11A, FIG.  11 B and FIG. 11C, respectively, the hook rod  106  is provided with a base portion  112 , an axial portion  114  and a protrusion  116 . The base portion  112  is formed to project outwardly from the flange  28  of the case  16 , having a square-shap in plan surface. The thickness of the base portion  112  is the thickness of the flange  28 . The axial portion  114  has a column-like shape formed to project from the base portion  112  in the direction of axis center vertical to the upper surface of the base portion. The protrusion  116  is formed to project in the diametric direction from the side surface of the axial portion in the adjacent of the extreme end of the axial portion  114  in a column like shape. The protrusion  116  is provided with an axis at right angles to the axis center of the axial portion  114 . Its projecting direction is as same as the direction of the base portion  112  projects from flange  28 , that is parallel to the upper surface  118  of the flange  28  and vertical to its edge. Such a hook rod  106  may be constituted of resin injected to a gate by providing the gate to which resin is injected in the vertical direction to the flange  28 , for example, in an injection molding of the case  16 . In case of such a molding constitution, a hook rod  106  of a sufficiently thick diameter can be easily obtained. 
     Moreover, the hook rod inserting portion  108  is provided with a pair of projecting portions  120 , a concave  122  and a protrusion  124  as a plan view, a front view and a view from below are shown in FIG. 12A, FIG.  12 B and FIG. 12C, respectively. The pair of projecting portions  120  are formed to project outward from a flange  30  having a rectangular shape in cross section in the cap  22  and having a plan shape of square. The height of the projecting portion  120  is similar in size to that of the flange  30 . A concave U-spaced wall  122  is formed between the projecting portions  120 , 120 . The protrusion  124  is provided at a position surrounding the concave  122  of the flange upper surface  46  in the shape of semicircle. The concave wall  122  has an opening width size sufficiently larger than the diameter of the hook rod  106 , and an inner surface at the inner side of the concave wall  122  is positioned at the inner side from the edge of the flange  30  and provided with a portion sagging downward in the flange  30  in the concave wall  122 . As a plan view, a front view and a view from below are shown in FIG. 13A, FIG.  13 B and FIG. 13C, respectively, the clamp  110  having a part in the periphery direction in the shape of plan surface which becomes hollow to the central portion and another part being in a considerably enlarged shape. The clamp  110  is a column-like body comprising an engaging portion  128  including the hollow part and an operating part  130  constituted by an enlarged part in the periphery direction. Incidentally, the clamp  110  has upper and lower surfaces  132 , 134  being parallel to each other. The clamp  110  is made of similar resin material to that of the case  16  and the cap  22 . 
     A recess  136  formed by the above-mentioned hollow provided to the engaging portion  128  bored through upper and lower surfaces  132 , 134 , and the internal wall surface of the innermost part is formed to a cylindrical recessed surface  136   a . The size of the opening width at the side surface  138  is as much as slightly larger than the diameter of the axial portion  114  of the hook rod  106  at the side of the lower surface  134 . The recess  136  has an opening width enlarged to a size substantially two times as large as the intermediate portion in the height direction in the range of the upper surface  132  side. A protrusion support surface  140  provided to the enlarged portion for supporting the protrusion  116  of the hook rod  106  at the time of the fastening operation as will be described later. The protrusion support surface  140  is a smoothly inclined surface at substantially regular inclining angles so as to incline to approach the upper surface  132  as approaching the inner peripheral portion from the side of a side surface  138  in a substantially regular width size. However, a cavity  142  is provided at the end positioned at inner part of the cylindrical recessed surface  136 a in the inner periphery side of the inclined surface. Therefore, the height from the lower surface  134  is positioned slightly lower than the proximate portion of where the inclined surface reaches the cavity from the side surface  138 . 
     Moreover, a groove  144  in the shape of semicircle is provided to the lower surface  134  of the engaging portion  128  at the peripheral portion of the cylindrical recessed surface  136   a . The semicircle-shaped groove  144  is to be fitted in by the semicircle-shaped protrusion  124  as will be described later. The semicircle-shaped groove  144  has a width slightly larger than the width in the diametric direction of the semicircle-shaped protrusion  124  and the depth slightly larger than the height in size. 
     In fastening of the case  16  and the cap  22  by the fastening device  104  constituted by each member through the filter element  24  as the foregoing, first, they are put together in such a manner that the hook rod  106  is inserted in the recess  122  of the hook rod inserting portion  108 . In such a placed state the axis center in the axial portion  114  of the hook rod  106  corresponds to the axis center of a semicircular protrusion  124 . FIG. 14A shows the time of being placed on over the other as such, about half of the entire length of the hook rod  106  is positioned at the upper side of the flange  30 . The protrusion  116  is positioned at the opposite side to the flange  28  in relation to the flange  30  sufficiently upwardly apart from the flange upper side  46  and the semicircular protrusion  124 . 
     In a successive stage as shown by the arrow in above FIG. 14A the hook rod  106  is fitted in the clamp  110  from its extreme end. FIG. 14B shows the fitting stage. At this time, in the clamp  110  the axis center of the semicircular groove  144  provided to the lower surface  134  corresponds to the axis center of the axial part  114  to fit the semicircular protrusion  124  in the semicircular groove  144 . Thereby, a clamp lower surface  134  comes closely contact with the flange upper surface  46 , and the recess  136  accommodates substantially entirety of the portion projecting upper from the upper surface  46  of the flange  30  in the hook rod  106 . Moreover, the protrusion  116  of the hook rod  106  is positioned slightly higher than the height position at the side end portion in the side surface  138  of the protrusion support surface  140 . 
     After the hook rod  106  is fitted in the clamp  110  as mentioned above the operating part  130  is grabbed to turn around axis center of the hook rod  106  in the right direction from the plan view, while pressing the clamp  110  toward the flange  30 . At the time of slightly turning the operating part  130 , the protrusion support surface  140  of the clamp  110  is positioned at the lower side of the protrusion  116  of the hook rod  106  in a non-contact state. By further turning the operating part  130  the protrusion support surface  140  being inclined apart from the lower surface  134  comes in contact with the lower surface of the protrusion  116  as approaching the inner periphery side and the protrusion  116  pushes down the protrusion support surface  140  toward the flange upper surface  46 . At the time of turning the operating part  130 , since the semicircular protrusion  124  is fitted in the semicircular groove  144  and the turning axis center corresponds to the axis center of the protrusion  124  and the groove  144 , the groove  144  is guided to the protrusion  124 , thereby the clamp  110  is turned without slanting the position in the surface direction of the upper surface  46  of the flange  30 . While the protrusion support surface  140  slides to be in contact with the outer peripheral surface lower end  146  of the protrusion  116 , the clamp  110  is turned, whereby the protrusion  116  is guided relatively apart from the flange  30  by the protrusion support surface  140  whose height gradually increases. Moreover, pressing force gradually increasing according to the height of the protrusion support surface  140  is applied to the upper surface  46  of the flange  30  through the lower surface  134  of the clamp  110  from the protrusion  116 . Therefore, the flange  30  is pressed by the flange  28  through the element peripheral portion  26 , which are secured in the pressing state. FIG. 15 shows a fastened state of being turned to the right direction by about 180° from the beginning position where the clamp  110  is fitted in with the hook rod  106  as described above. In the turning operation for fastening the axis center of the axial part  114 , the operating part  130  and the protrusion become the fulcrum, the point of force-application and the working point, respectively. Therefore, as shown in the drawing, both of a distance L 1  between the fulcrum and the point of force-application and a distance L 2  between the fulcrum and the working point are set regardless of the thickness of the flanges  28 , 30  and so on, and L 1  sufficiently increases compared to L 2 . Therefore, in this embodiment, the assembly load can be reduced without particularly complicated constitution. Incidentally in this embodiment, the operating part  130  is to project to the outer periphery side of the flanges  28 , 30  in turning of the clamp  110 . Although the long length of the operating part  130  is not preferable, the distance L 2  between the fulcrum and the working point becomes extremely small as clear from above FIG. 15, therefore, a function as a force increasing device can be adequately obtained with a relatively small L 1  between the fulcrum and the point of force-application. In this embodiment, the hook rod  106 , the outer peripheral surface lower end  146  of the protrusion  116 , the engaging part  128  of the clamp  110 , the protrusion support surface  140  and the lower surface  134  of the clamp  110  correspond to the first engaging part, the first sliding contact surface, the second engaging part, the second sliding contact surface and the peripheral portion pressing surface, respectively. 
     Moreover, in the fastened state shown in above FIG. 15, the protrusion  116  of the hook rod  106  is being fitted in a depression  142  provided to the inner periphery side ends of the protrusion support surface  140 , in a case where the fastened state is released by turning the clamp  110  in the loosening direction of the left turning in FIG. 15, it is necessary to push down the upper surface  46  by pressing the flange  30  with larger pressing force than that in the fastened state for removing the protrusion  116  from the depression  142 . Accordingly, when the clamp  110  turns slightly in the loosening direction due to vibration and so on during use of the air cleaner apparatus  10 , turning force in the fastening direction is applied by pressing force increasing until going over the boundary with the protrusion support surface  140  at a higher position than the depression, thereby unfastening is preferably controlled in this embodiment. Incidentally above-mentioned FIG.  9  and FIG. 10 show the unfastened state where the clamp  110  is only mounted on the flange  30  as shown in FIG.  14 B. 
     Now that, as mentioned above, all of the case  16 , the cap  22 , and the clamp  110  are made of similar resin material and manufactured by injecting molding. FIG. 16 is a plan view showing essence of the case  16  or cap  22 , which is molded, and FIG. 17 shows a cross sectional viewed on line XVH—XVH in FIG. 16. A cavity for molding the clamp  110  is integrally formed to a part of a mold of the case  16  or the cap  22  which is not shown. The cavities of the case  16  or the cap  22  and the clamp  110  are connected through a gate for resin injection. Therefore, as shown in the drawing, the case  16  or the cap  22  and the clamp  110  which are molded are connected by a connecting part  148  derived from the gate and integrated. Thus, since it is not necessary to prepare a separate mold for molding the clamp  110 , a cost of molds can be saved, and the clamp  110  can be adequately prevented from being lost by maintaining the connected state of the clamp  110  by the connecting part  148  at least until an air cleaner apparatus  10  is assembled at the assembly site where the clamp  110  is removed. Incidentally, if there is no trouble in the fastening operation, the clamp  110  can be prevented from being lost also at the time of exchanging elements by maintaining the state where the clamp  110  is connected with the case  16  and the cap  22  by the connecting part  148 . 
     FIG. 18 to FIG. 20 are explanatory views of still another fastening structure; FIG. 18B is a front view showing a hook rod  150  to be employed in the fastening structure in a placing over state for fastening the case  16  and the cap  22 , and FIG. 18A is a plan view of the hook rod  150 . The hook rod  150  is integrally formed to project from the flange  28  of the case  16  in the vertical direction to the upper surface  118 . In fastening the extreme end of the hook rod  150  is positioned upper than the flange  30  of the cap  22 . The outer peripheral surface  152  is provided with a pair of protrusion inserting grooves  154  and a pair of protrusion engaging grooves  156  at two symmetrical positions respectively in the periphery direction to an extent of projection above the flange  30 . Incidentally, as required for explanation of the protrusion inserting grooves  154  and the protrusion engaging grooves  156 , FIG. 18B shows only one for each. 
     The above-mentioned pair of protrusion inserting grooves  154  are provided in the direction substantially along the direction of the axis center of the hook rod  150  to an extent from the extreme end surface  158  to the intermediate part in the direction of the axis center. The above-mentioned pair of protrusion engaging grooves  156  are provided in the direction substantially along the peripheral direction of the hook rod  150  to an extent which is less than halfway round the periphery with its one end (base end) continuing to the lower end of the side of the flange  28  in the protrusion inserting groove  154 . The inner wall surface  160  in a spiral shape at the side of the extreme end surface  158  approaches flange  28  as the protrusion engaging groove  156  becomes apart from the protrusion inserting groove  154 , that is, as it directs to the end side in the peripheral direction from the base end of the protrusion engaging groove  156  connecting to the protrusion inserting groove  154 . The protrusion engaging groove  156  tends to approach the flange  28  toward the end side as an entirety, the end side is provided with a depression  162  extending to a slight length toward the side of the extreme end surface  158 . Therefore, the depression  162  is positioned at the side of the extreme end surface  158  compared to a part just before the inner wall surface  160  which approaches the flange  28  toward the end side. Incidentally, the protrusion engaging groove  156  has the depth in the diametric direction of the hook rod  150  and the width which are substantially same over the entire length from the base end of the extreme end surface  158  side of the protrusion inserting groove  154  to the depression  162 , the end side provided with the depression  162  has a circular arch-shape of a substantially equal diameter to the other part. 
     Moreover, FIG. 19A is a plan view showing another constituent element of the fastening structure, a clamp  164  to be fitted in the hook rod  150 ; FIG. 19B is a sectional view viewed on line XIXB—XIXB of FIG.  19 A. The clamp  164  is a part made of resin material which is similar to that of the case  16  and so on, comprising an engaging part  166  in a substantially annular configuration in the plan view and an operating part  170  integrally provided by enlarging a part of the outer peripheral surface  168  to the outer periphery side. The engaging part  166  and the operating part  170  have substantially equal thickness in size and upper and lower surfaces  172 , 174  parallel to each other. The substantially annular engaging part  166  has a hole bored through in the direction of thickness, that is a cylindrical inner peripheral surface  176  and a pair of column-shaped protrusions  178  formed to project at two symmetrical positions in the peripheral direction which are the center in the direction of the thickness. The pair of protrusions  178  in a similar size to each other are positioned to face to each other and their axis center directions are both facing to the radial direction of the inner peripheral surface  176 . The diameter of the inner peripheral surface  176  is slightly larger than the diameter of the hook rod  150 . Moreover, the length of the protrusion  178  is slightly shorter than the depth of the protrusion engaging groove  156  and so on. Its diameter is slightly smaller than the opening width of the protrusion engaging groove  156 . 
     The fastening device constituted by the above mentioned hook rod  150  and the clamp  164  is used as follows. First, the case  16  and the cap  22  are put together as shown in FIG. 18B, whereby the clamp  164  is fitted from its extreme end in the hook rod  150  positioned in a square-shaped or circular arch-shaped notch  180  provided to the side of the flange  30  of the cap  22  or the flange  30  as shown in FIG.  20 . At this time, the lower surface  172  becomes parallel to the upper surface  46  of the flange  30  and in a posture where the protrusion  178  positions on the protrusion inserting groove  154 , for example when the protrusion inserting groove  154  is provided on a straight line along the longitudinal direction of the flange  30 , the protrusion  178  is positioned on the straight line and the clamp  164  is fitted in the direction where the operating part  170  is substantially vertical to the edge of the flange  30 . 
     Next, the clamp  164  is inserted to the position where the protrusion  178  contacts with the lower end surface  182  of the protrusion inserting groove  154 , followed by grabbing the operation part  170  and turning the clamp  164  to the axis center of the hook rod  150  in the direction shown by the arrow of FIG. 20, that is the right direction in FIG.  18 A. By this turning operation, the clamp  164  is turned while the protrusion  178  is guided in the protrusion engaging groove  156 . Since the protrusion engaging groove  156  is inclined so as to approach the flange  30  toward the end side, the protrusion  178  guided toward the end side approaches the flange  30  as the turning angle gets larger. Therefore, an outer peripheral surface top end  184  of the protrusion  178  is pressed toward the flange  30  side by the upper inner wall surface  160  of the protrusion engaging groove  156 , and further the clamp  164  is pressed toward the upper surface  46  of the flange  30 , whereby the lower surface  172  presses the flange  30  toward the flange  28 . In this embodiment, the upper inner wall surface  160 , the outer peripheral surface top end  184  of the protrusion  178  and the lower surface  172  of the clamp  164  correspond to the first sliding contact surface, the second sliding contact surface and the peripheral end pressing surface, respectively. The fulcrum is the axis center of the hook rod  150 ; the point of force-application is the extreme end of the operating part  170 ; and the working point is the contact point of the protrusion  178  and the inner wall surface  160 . Therefore, similarly to the case of previously-mentioned fastening device  104 , a distance between the fulcrum and the point of force-application can be set sufficiently large compared to a distance between the fulcrum and the working point, which makes it possible to reduce the assembly load without particularly complicated constitution. 
     When the protrusion  178  reaches the end portion of the protrusion engaging groove  156  by turning the clamp  164  by a little over 90° as mentioned above, the protrusion  178  is pushed up so as to enter the depression  162  by applying repulsive force of the element peripheral end portion  26  (see FIG. 18B) elastically pressed to shrink by the flange  30  pushed down by the lower surface  172 . The dot-dash lines in FIG. 20 shows a state where the fastening is completed by turning to the end as such. Therefore, in the fastening completed state, pressing force applied to the outer peripheral surfacetop end  184  of the protrusion  178  from the inner wall surface  160  of the protrusion engaging groove  156  becomes slightly smaller than that just before entering the depression  162 . Accordingly, the protrusion  178  needs to return in the protrusion engaging groove  156  and further move to the base end against larger pressing force than the pressing force in the fastened state in order to get out of the depression  162 , therefore, in this embodiment, unfastening due to vibration and so on during use is preferably controlled. 
     An embodiment according to the invention has been described in detail with reference to the drawings; however, the invention is capable of being practiced in still another form. 
     In the previously described embodiment, for example, a case where the fastening structure of the invention is applied to the air cleaner apparatus  10  has been described, however, it may be equally applied to a fastening structure of apparatuses or articles for other various uses as long as two parts are elastically pressed and fastened at their peripheries. 
     Moreover, in the embodiment a case in which the flanges  28 , 30  of relatively high elastic modulus are fastened with the element peripheral portion  26  of relatively low elastic modulus sandwiched therebetween, whereby a strong fastening structure can be obtained solely based on repulsive force of the element peripheral portion  26  and unfastening is controlled has been described, however, the existence of such an intermediate member of lower elastic modulus is not essential. For example, in a case when two parts whose a constituent member (flange  30  in the embodiment) of a surface to be pressed by a fastening part (hook rod or clamp)  40 ,  88 ,  110 ,  164  and so on having adequately low elastic modulus a strong fastening structure similar to in the embodiments can be obtained based on elastic deformation of the part having the low elastic modulus. 
     Although a case in which both of the case  16  and the cap  22  made of resin are fastened with a fastening part (hook rod  40  and so on) made of the similar resin as has been described in the embodiments, the invention is similarly applied to such a case that parts made of metal material are fastened, or a fastening part made of metal material is employed, as long as they are made of materials capable of applying above described elastic deformation. Both of two parts to be fastened may be made of inorganic materials or the like having an extremely low elastic modulus without any trouble as long as they are fastened through a member having a low elastic modulus such as the element peripheral portion  26 . 
     In the fastening devices  34 , 76  as shown in FIG. 1 or FIG. 6 etc. first column-like portions  68 , 90  of hook rods  40 , 88  pressing the flange  30  has an oval-shape or an egg-shape in cross section having flat ends at the side of longer diameter, however, these shapes may suitably modified. In other words, as long as a cam surface is provided so that a distance from the turning axis center to the outer peripheral surface gradually increases in the peripheral direction, the first column-like portions  68 , 90  may have suitable configurations in cross section such as a full oval configuration without a flat surface  74 , a circle-shape provided with a part having a large diameter, or rectangular or square shape being chamfered off. 
     In the previously described fastening apparatuses  34 , 76  the lower surfaces  50 , 84  provided to the hooks  36 , 78  for pressing the first column-like portions  68 , 90  toward the flange  30  as well as the hook  38  into which another end of the first column-like potions  68 , 90  is inserted are provided to the cap  22 . However, in a case where inclination of the column-like potions  68 , 90  to be pressed by the hooks  36 , 78  can be controlled at the time of fastening or in the fastening state, the hook  38  may not be necessarily provided, for example, by having sufficiently high rigidity of the hooks  36 , 78  or sufficiently enlarged width of the lower surface  50 . 
     Although the case  16  and the cap  22  are constituted to be turnable around the hinge device  32  provided at one side of their peripheries in the embodiment, the invention is equally applied to an air cleaner apparatus  10  being constituted so that the cap  22  is removed from the case  16  at the time of exchanging filter elements  24 . In such a constitution, in order to positively maintain the fastened state of the case  16  and the cap  22 , for example some kind of engaging structure may be provided to one side which was provided with the hinge device  32  or a fastening device  34  or the like may be provided to one side where the hinge device  32  was provided or the vicinity thereof. 
     Moreover, in the embodiment, a case in which the fastening device  34  or the like is provided at two positions at the peripheral portion of the case  16  and the cap  22  has been described, and the number thereof suitably set to such an extent that an adequate fastened state can be assured may be one or over three. 
     Although a case of fastening state in the fastening devices  34 , 76  by turning the hook rods  40 , 88  by about 90° from the direction substantially vertical to the flange  30  has been described, an initial direction or turning angles may be suitably modified. However, in order to control the situation of being unfastened by accidentally touching the hook roods  40 , 88  it is preferable that the hook rods  40 , 88  are constituted in the direction of axis center along the longitudinal direction of the flange  30  in the fastening state as shown in the embodiment. 
     In the previously mentioned fastening device  76 , the guide groove  96  is provided to the peripheral surface  102  of the column-like portion  90  for guiding the hook rod  88  to stop at a predetermined position, when being turned in the direction of the arrow E as shown in FIG. 6, and guiding the protrusion  100  of the flange upper surface  46  with the depression  98  provided at the end portion to control the turning from the turning completed position, that is, the fastening position. However, the guide groove  96  may not be necessarily provided. In other words, since the hook rod  88  is turned in a state where both ends of the first column-like portion  90  are inserted to the hooks  78 , 38 , the position of the protrusion  100  does not change so much even without the guide groove  96  being engaged thereto, and the turning to the loosening direction hardly occurs because the first column-like portion  90  has been turned further by the angle θ from a vertex of an egg-shaped section in the fastened state, therefore, there is no particular trouble in fastening the case  16  and the cap  22  even without an engaging structure such as above. 
     Moreover, the first column-like portions  68 , 90  of the hook rods  40 , 88  are formed to have substantially equal section in the direction of axis center in the fastening devices  34 , 76 , however, they do not contribute to pressing of the flange  30  except a part with which the hooks  36 , 78  slides to contact and may have a full circular section without any trouble. 
     Moreover, in the fastening devices  34 , 76  relations in size of the longer diameter-the shorter diameter of the first column-like portions  68 , 90  and the diameters of the second column-like portions  70 , 92  are not limited to those shown in the embodiment, and the first column-like portions  68 , 90  may not be necessarily provided to project in the radial direction of the second column-like portions  70 , 92 . 
     In the fastening device  76 , a part in the outer peripheral surface  102  of the first column-like portion  90  with which the lower surface  84  of the hook  78  slides to be in contact was constituted so that the distance from the turning axis center changes in the peripheral direction, however, even if the part to be slidably contacted with has a full circular section and the part with which the upper surface  46  of the flange  30  slides to be in contact is constituted so that the distance from the turning axis center changes in the peripheral direction, similar effects in pressing and fastening can be obtained. 
     In the previously-mentioned fastening device  104 , its constituent element, a hook rod inserting portion  108 , is formed to project to the outer peripheral side from a part of the flange  30  of the cap  22 . However, the length of the projecting portion  120  is set based on relations in size of the width of the flange  30  and the diameter of the engaging portion  128  of the clamp  110  so that an area required to turn the clamp  110  can be assured. In other words, when the diameter of the clamp  110  is made larger relative to width of the flange  30  than that shown in the embodiment the projecting portion  120  is preferably made larger, and when the diameter of the clamp  110  is small, the length of the projecting portion  120  may be small or may not be provided by providing a hole or a notch to be inserted by the hook rod  110 . 
     Moreover, in the previously-mentioned fastening apparatus  104 , the protrusion support surface  140  with which the protrusion  116  of the hook rod  106  is to be in contact is positioned as the entirety lower than the upper surface  132  of the clamp  110 . However, the inner periphery side end portion is formed on the same level as the plan surface of the upper surface  132 , depression  142  may be formed by recessing at a part of the upper surface  132 . 
     In the fastening device as shown in FIG. 18 to FIG. 20, the protrusion inserting groove  154  and the protrusion engaging groove  156  which are provided to the hook rod  150  have the opening width being the same as the diameter of the protrusion  178  provided to the clamp  164 , however, the size of opening width may be suitably modified to an extent that it is larger than the diameter of the protrusion  178 . 
     While the protrusion inserting groove  154  and the protrusion engaging groove  156  which are provided to the hook rod  150  and the protrusion  178  provided to the clamp  164  are provided at two symmetrical positions in the turning axis center direction in the embodiment, only one or about three thereof may be provided. 
     Other embodiments have not be illustrated. However, the invention is capable of being practiced as an embodiment in which various modifications are made without departing from the point. 
     The present invention includes a first peripheral portion of a first part and a second peripheral portion of a second part are put together and pressed to each other, whereby the first part and the second part are fastened. This fastening structure includes a first engaging portion provided with a first sliding contact surface facing to the second peripheral portion side at the opposite side to the first part in relation to the second peripheral portion and extending to the second part from the first part, a second engaging portion provided to the fastening part so as to be engaged with the first engaging portion and be relatively turnable around the predetermined turning axis, a second sliding contact surface provided to the second engaging portion so as to come in contact with the first sliding contact surface in the engaged state of the fastening part with the first engaging portion wherein pressing force applied from the first sliding contact surface increases as the fastening part is turned around a predetermined turning axis in the fastening direction, a peripheral portion pressing surface provided to the fastening part so as to press the second peripheral portion toward the first peripheral portion based on the pressing force and an operating part provided to the fastening part at a predetermined interval from the turning axis in order to turn the second engaging part around the turning axis against the first engaging part in the predetermined turning axis direction. 
     In such a manner, when the first peripheral portion of the first part and the second peripheral portion of the second part are put together and the second engaging portion of the fastening part is engaged with the first engaging portion extending from the first part and then the second engaging portion is turned against the first engaging portion in the fastening direction by operating the operating part of the fastening part, pressing force according to the turning amount is applied to the second sliding contact surface from the first sliding contact surface facing to the side of the second peripheral portion and based on this pressing force the peripheral portion pressing surface of the fastening part presses the second peripheral portion toward the first peripheral portion, whereby the first peripheral portion and the second peripheral portion are fastened. At this time, the required force for turning the second engaging portion, that is, assembly load is smaller as a fulcrum-point of force-application distance from the turning axis center to the operating part in relation to a fulcrum-working point distance from the turning axis center to the peripheral portion pressing surface increases, however, the fulcrum-working point distance can be set small regardless of a thickness of the first peripheral portion and the second peripheral portion to such an extent that the torsional stress being applied to the fulcrum does not exceed the tolerable value. Therefore, a fastening structure capable of reducing the assembly load with a simple constitution can be obtained. 
     In the fastening structure of this aspect, the second sliding contact surface may preferably be provided so that the pressing force being applied from the first sliding contact surface in the fastened state is smaller than pressing force at the position where the second engaging portion is slightly turned in the opposite direction to the fastening direction, that is, in the loosening direction. As a result, because a larger pressing force than that in the fastened state is required to be applied to the second sliding contact surface from the first sliding contact surface for releasing the fastened state, the occurrence of unfastening by turning the second engaging portion in the reverse direction to the fastening direction due to external causes such as vibration is preferably controlled. The above-mentioned pressing force to be larger as relatively turning in the fastening direction is not limited to those embodiments strictly satisfying the condition in the entire area of the relative turning of the second engaging portion and the first engaging portion, but it is sufficient even if the large-small relations of the pressing force may be reversed in the vicinity of the fastening completed position as mentioned above as long as there is a tendency of increasing in the fastening direction as the entirety. 
     Moreover, in the fastening structure of the aspect, the fastening part preferably has a T-shape provided with a second column-like portion vertical to the direction of the axis center at the intermediate portion in the direction of the axis center of the first column-like portion, the first engaging portion is constituted by a leg portion extending to the second part side from the first peripheral portion, a first sliding contact portion extending along the second peripheral portion from the extreme ends of the leg portion and provided with the first sliding contact surface parallel to the opposite surface to the first part in relation to the second peripheral portion, wherein the second engaging portion is constituted by one end portion of the first column-like portion to turn around the direction of the axis center by being fitted in between the surface of the outer peripheral portion and the first sliding contact surface in the direction of the axial center vertical to the longitudinal direction of the second peripheral portion and parallel to the first sliding contact surface, the second sliding contact surface is provided to an outer peripheral surface of the second engaging portion in which a distance from the turning axis in the contacting point with the first sliding contact surface increases as the second engaging portion is turned in the fastening direction, the peripheral portion pressing surface is constituted at a part opposite to the second sliding contact surface in the peripheral direction on the outer periphery surface of the first column-like potion, and the operating part may be constituted by the extreme end at the opposite side to the first column-like portion of the second column-like portion. 
     In such a manner, the second engaging portion is fitted in between the surface of the second peripheral portion and the first sliding contact surface to be engaged with the first engaging portion, an operating part constituted by an extreme end of the second column-like portion is turned within a surface vertical to the direction of the axis center of the first column-like portion, that is, a surface parallel to the side surface of the second part, whereby the second sliding contact surface wherein a distance from the turning axis center increases as turned to the fastening direction is pressed by the first sliding contact surface, and further the second peripheral portion is pressed toward the first peripheral portion by the peripheral portion pressing surface of the second engaging portion to fasten the first part and the second part. Therefore, a strong fastened state can be obtained by a simple operation of fitting the second engaging portion in the first engaging portion and turning the same. Moreover, since the operating part turns in a direction within a surface parallel to the side surface of the second part, a distance between a point of force-application and a fulcrum point may be large without obtaining a space for the turning. Therefore, the assembly load can be further reduced. 
     Moreover, a third engaging portion to control the movement of the first column-like portion in the vertical direction to the direction of the axis center may be included by fitting the other end opposite to the second engaging portion of the first column-like portion provided to the side surface of the second part at a facing position to the first engaging portion. In such a manner, the useless movement of the first column-like portion in the vertical direction to the direction of the axis center can be controlled by the third engaging portion, whereby the second engaging portion can be turned more easily and unfastening due to the movement of the other end is further inhibited. 
     Further, a fitting convex portion and a fitting concave portion which control the movement of the second column-like portion in the direction of the axis center may be provided to one and the other of the surface of the second peripheral portion and the first column-like portion, respectively, by being fitted in each other in the fastened state. Thus, since the movement of the second column-like portion in the direction of the axis center in the fastened state can be controlled, unfastening is further inhibited. For example, in a form provided with the third engaging portion as described above, the other end of the first column-like portion is inhibited from coming off from the third engaging portion and further the second engaging portion and the first engaging portion are inhibited from being disengaged. The fitting concave portion may be constituted, for example, by one or a plurality of peripheral grooves provided to the first column-like portion, and the fitting convex portion may be constituted, for example, by a protrusion provided on the surface of the second peripheral portion. 
     Moreover, in the fastened state the second column-like portion may have an oval-shape in cross section in the longitudinal direction substantially corresponding to the direction facing to the first sliding contact surface from the surface of the second peripheral portion. In such a manner, the second engaging portion is turned to the fastening direction, whereby a distance from the turning axis center to the second sliding contact surface in the contact portion with the first sliding contact surface is gradually increased, therefore, the first peripheral portion and the second peripheral portion are fastened while being pressed. More preferably, both ends of the cross section of the second column-like portion in the longitudinal direction may be formed to be substantially flat surfaces. In such a manner, the substantially flat surfaces are pressed by the first sliding contact surface in the fastened state, whereby the turning from the fastening state to the opposite direction to the fastening direction or unfastening can be preferably controlled. 
     Further preferably, the first engaging portion has a hook-configuration having an opened extreme end of the first sliding contact portion. Such a configuration enables the second engaging portion to fit between the first sliding contact surface and the surface of the second peripheral portion from the opening side, therefore, the second engaging portion can be more easily engaged with the first engaging portion compared to the first engaging portion having a square-shape formed by laying the first sliding contact portion between the extreme ends of a pair of leg portions. 
     Moreover, preferably, in the fastening structure of the aspect, the first engaging portion may be constituted in a column-like shape in the direction of the axis center parallel to the direction vertical to the surface of the second peripheral portion with an engaging convex portion provided to project in the radial direction at a position apart from the first part further than the surface in which a part on the surface side of the second peripheral portion in the outer peripheral surface functions as the first sliding contact surface. The second engaging portion may be constituted with an inner peripheral surface facing to an outer peripheral surface of the first engaging portion so as to be engaged with the outer periphery side. The second sliding contact surface may be formed on the outer periphery side of the inner peripheral surface with inclination wherein a part contacting with the engaging convex portion in the surface side of the second engaging portion positioned on the opposite side to the second peripheral portion departs from the second peripheral portion as the second engaging portion turns in the fastening direction. 
     As a result, when the second engaging portion is engaged with the outer periphery side of the first engaging portion and the second engaging portion is turned in the fastening direction in relation to the first engaging portion while the engaging convex portion slides to contact with the second sliding contact surface, the engaging convex portion is guided in the direction apart from the second peripheral portion while sliding to contact with the second sliding contact surface according to the inclination of the second sliding contact surface. Therefore, pressing force applied to the second sliding contact surface is increased and further the entire fastening part is pressed by the second peripheral portion side, whereby the peripheral portion pressing surface presses the second peripheral portion toward the first peripheral portion to fasten them in the pressing state. 
     Moreover, the second sliding contact surface may be constituted to have a engaging convex portion securing groove formed by making the interval with the second peripheral portion slightly smaller than a part of the other end side in one end portion of the direction apart from the second peripheral portion. Thus, pressing force applied to the second sliding contact surface from the engaging convex portion positioned in the engaging convex portion securing groove becomes smaller than pressing force in a case of positioning an engaging concave portion on the side of the other end. Therefore, the fastened state that hardly comes off is preferably realized even in case of external causes such as vibration or the like. 
     One and the other of a peripheral protrusion and peripheral groove to be engaged with each other concentric with the axis center of the first engaging portion that is the turning axis center are respectively provided to an extent of contacting with each other on the surface of the second peripheral portion and the back surface of the fastening part. Thus, in turning the fastening part, the turning axis center can be easily maintained as being concentric with the axis center of the first engaging portion, whereby the turning and further fastening of the first part and the second part become easier. 
     Moreover, preferably, in the fastening structure of the aspect, the first engaging portion may be constituted in a column-like shape extending in the direction of the axis center along the vertical direction to the surface of the second peripheral portion with a periphery groove in which an inner wall surface at the extreme end side formed at the outer peripheral surface to be apart from the extreme end as proceeding in a direction of the peripheral direction functions as the first sliding contact surface and an inserting opening ranging from the extreme end surface to the peripheral groove. The second engaging portion may have an inner peripheral surface facing to the outer peripheral surface of the first engaging portion so as to be engaged with the outer peripheral side. The second sliding contact surface may exist at a part of the extreme end side in the outer peripheral surface of the protrusion to be fitted in the peripheral groove formed to project at the inner peripheral surface of the second engaging portion. 
     As a result, when the second engaging portion is engaged with the outer periphery side of the first engaging portion and the protrusion provided to the inner peripheral surface is fitted in the peripheral groove through the inserting opening followed by turning the second engaging portion against the first engaging portion in the above-mentioned direction, that is, in the fastening direction, the protrusion of the second engaging portion wherein the outer peripheral surface serves as the second sliding contact surface is guided in the approaching direction to the second peripheral portion, while sliding to be in contact with the extreme end side inner wall surface along the inclination of the peripheral groove extreme end inner wall surface serving as the first sliding contact surface. Therefore, pressing force applied to the protrusion from the extreme end inner wall surface increases as engagement increases as the fastening part as the entirety is pressed to the second peripheral portion end side, whereby the peripheral portion pressing surface is pressed by the second peripheral portion toward the first peripheral portion to be brought into fastening in the pressing state. 
     Further, there may be provided a pair of the inserting openings and the peripheral grooves at symmetrical positions in the peripheral direction on the outer peripheral surface of the first engaging portion and a pair of the protrusions to be fitted in the pair of the peripheral grooves to the inner peripheral surface of the second engaging portion. As a result, since the pair of the peripheral grooves and the pair of the protrusions are provided at the symmetrical positions, respectively, the second engaging portion is generally uniformly pressed in the peripheral direction from the first engaging portion through the pair of the protrusions. Therefore, at the time of the fastening operation wherein the second engaging portion is relatively turned against the first engaging portion, the second engaging portion is inclined to the first engaging portion resulting in preferably controlling the increase in the assembly load to further ease the required engagement effort, and at the same time inclination in the direction of the axis center of the first engaging portion is inhibited so that the occurrence of unfastening is further controlled. 
     Preferably, the first part and the second part may be constructed to be fastened with intervention of a third part whose elastic modulus is lower than that of the first part or the second part. As a result, pressing force applied to the second sliding contact surface from the first sliding contact surface increases to elastically deform solely the third part, therefore further increasing the strength of the fastening structure according to the elastic modulus and further restraining force can be obtained. 
     Preferably, the first part and the second part are a case and a cap, respectively, in an air cleaner apparatus for a vehicle, and the third part is a filter element accommodated therein. Thus, in an engine room in which the space volume is required to be reduced as much as possible for facilities, safety and the like, the air cleaner preferably does not require a large volume as a result of use of the fastening structure of the present invention. 
     Moreover, all of the first part, the second part and the fastening part may be preferably made of resin. Since the elastic deformed volume required to the fastening part and the like in each form of the fastening structure as previously mentioned is small compared to a clamp made of metal, resin of larger elastic modulus than that of metal may be employed. Therefore, since a fastening part can be molded with one mold simultaneously with the first part and the second part, the manufacturing processes are simplified and the manufacturing costs are advantageously lowered compared to the case of employing a metal part. 
     Further, the fastening part may be molded in a connected state with either of the first part and the second part. Thus, the fastening part is molded integrally with the first part or the second part to maintain the integral state during the storage, the conveyance and the like, whereby labor in connection with the control of a small fastening part relative to the first part and the second part can be reduced. Incidentally, the fastening part may be used as being integrated with the first part and the second part if there is no trouble at the time of fastening and may be departed from them at the assembly site, if necessary.