Abstract:
It is intended to achieve weight reduction and production reduction of a nozzle mount for pivotably supporting a drive ring constituting a variable nozzle mechanism, and is characterized by: providing on an end face of a guide part  5   a  a nail pin  20  having a flange portion and being positioned so as to hold a drive ring  3  of a variable nozzle mechanism  100  to the guide part  5   a  of a nozzle mount  5  in the thrust direction, and setting the thrust-directional width of the drive ring  3  smaller than the width of the guide part  5   a , and providing an adjusting member  20   c  between the flange portion of the nail pin  20  and the end face of the guide part  5   a  to adjust a distance between the side face of the nozzle mount and the flange portion of the nail pin  20.

Description:
TECHNICAL FIELD 
     The present invention relates to a structure for retaining a drive ring rotatable with respect to a nozzle mount in a variable displacement exhaust turbocharger, which is used for an exhaust turbocharger of an internal combustion engine and which is equipped with a variable nozzle mechanism for varying a vane angle of a plurality of nozzle vanes. 
     BACKGROUND ART 
     As one variable displacement exhaust turbocharger which is used for an exhaust turbocharger of an internal combustion engine and which is equipped with a variable nozzle mechanism for varying a vane angle of a plurality of nozzle vanes, the technique of JP 2010-19252 (Patent Document 1) is provided. 
     This technique of the related art is illustrated in the attached drawings.  FIG. 6A  is an illustration of a turbine housing  010 .  FIG. 6B  is a partial enlarged view of section P of  FIG. 6A .  FIG. 6C  is an exploded view of components of  FIG. 6B . 
     A variable nozzle mechanism  0100  is configured such that a plurality of guide vanes (nozzle vanes)  080  is positioned between a lower vane ring  020  and an upper vane ring  030 . The guide vane  080  is rotatably supported about an axis to control a flow rate of exhaust gas flowing in a turbine. The distance between the lower vane ring  020  and the upper vane ring  030  is maintained by a stepped spacer  050  which is positioned therebetween. The upper vane ring  030  and the lower vane ring  020  are attached to the turbine housing  010  by nuts  040  and metal fastening members  042 . 
     Further, the stepped spacer  050  has a through-hole formed in the center so that the fastening member  042  can pass through the stepped spacer  050 . 
     Meanwhile, another technique is disclosed in JP 4545068B (Patent Document 2). A variable displacement exhaust turbocharger of JP 4545068B is configured, as illustrated in  FIG. 7 , such that a drive ring  064  is arranged on a peripheral circumferential surface of a guide part  057  of a nozzle mount  055  to be disposed between a side face of a lever plate (not shown, disposed on a left side of the drive ring  064 ) and a side face of the nozzle mount  055  so that they are next to each other in the axial direction and a stud with a flange (a nail pin)  066  is fixed to a side part of the nozzle mount  055  to be in contact with an outer surface  064   a  of the drive ring  064  so as to prevent the drive ring  064  from moving in the axial direction, i.e. coming off toward the lever plate side. 
     In  FIG. 7 , a nozzle vane  068  is provided between the nozzle mount  055  and an annular support plate  070 . 
     CITATION DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] 
         JP 2010-095252 A 
         [Patent Document 2] 
         JP 4545068 B (FIG. 3) 
       
    
     SUMMARY 
     Technical Problem 
     However, the stepped spacer  050  described in Patent Literature 1 has the central through-hole for the fastening member  042  to pass through. Further, this stepped space  050  is provided to maintain the distance between the lower vane ring  020  and the upper vane ring  030  where the plurality of guide vanes (nozzle vanes)  080  is arranged. 
     Patent Document 1 teaches to use the stepped spacer  050  for positioning. However, there is no disclosure as to the use of the stepped spacer  050  for positioning of the drive ring in a thrust direction by fitting the drive ring for varying a vane angle of the nozzle vane to the guide part of the nozzle mount. 
     In the fixing mechanism of Patent Document 2 using the nail pin  066  capable of abutting to the outer surface  064   a  of the drive ring  064 , the guide part  057  of the nozzle mount  055  is required to have a space to accommodate a mounting width of the drive ring  064 . Correspondingly, the nozzle mount  055  is required to have a significant width in the axial direction of the nozzle mount  055 . It results in increase of the nozzle mount  055  in size and weight, and this also makes it difficult to manufacture the nozzle mount  055  by press-molding. Moreover, as the width dimension of the guide part  057  of the nozzle mount  055  needs to be machined with high precision in relation to the width dimension of the drive ring  064 , and this causes an increase in the number of the processing steps. 
     In view of the above issues, it is an object of the present invention to reduce the weight and production cost of a nozzle mount by pres-fitting a pin with a flange portion into a press-fitting hole formed in an end face of a guide part along a thrust direction so as to retain the drive ring to the guide part of the nozzle mount in the thrust direction and providing an adjusting member (a spacer member) between the flange portion and the end face for adjustment in the thrust direction. 
     Solution to Problem 
     To solve the above issues, the present invention provides a variable displacement exhaust turbocharger which is equipped with a variable nozzle mechanism and is driven by exhaust gas from an engine, and the variable displacement exhaust turbocharger comprises: 
     a plurality of nozzle vanes supported rotatably by a nozzle mount which is fixed to a case including a turbine casing of the variable displacement exhaust turbocharger; 
     a drive ring which is interlocked with an actuator and is fitted to an annular guide part protruding from a center part of the nozzle mount in an axial direction, the guide part having a width in a thrust direction which is smaller than a width of the drive ring; 
     a plurality of lever plates each of which is fitted to a groove formed in the drive ring at one end via a connection pin and is connected to the nozzle vane at the other end; 
     a press-fitting pin which has a flange portion facing a side face of the drive ring, the press-fitting pin being press-fitted into a press-fitting hole formed in an end face of the guide part along a thrust direction of the guide part so as to retain the drive ring in the thrust direction; and 
     an adjusting member arranged between the flange portion of the press-fitting pin and the end face of the guide part, 
     wherein the adjusting member is configured to adjust a distance between the flange portion of the press-fitting pin and a side face of the nozzle mount, the drive ring being sandwiched between the flange portion and the side face of the nozzle mount. 
     According to the present invention, by reducing the thrust-directional thickness of the guide part of the nozzle mount and providing the adjusting member for adjustment in the thrust direction between the guide part and the flange portion for restricting rocking of the drive ring in the thrust direction, it is possible to form an appropriate amount of clearance in the thrust direction of the drive ring. 
     Therefore, as the guide part can be shortened in the thrust direction by the amount equivalent to the thickness of the adjusting member (in the thrust direction of the guide part), it is possible to achieve weight reduction and cost reduction of materials. 
     Further, by reducing the thrust-directional thickness of the guide part of the nozzle mount, it is possible to reduce the thrust-directional thickness of the nozzle mount including the guide part in the thrust direction. This enables production by press working, thereby reducing the production cost. 
     In a preferred embodiment of the present invention, the adjusting member comprises the press-fitting pin formed integrally with the flange portion. 
     By forming the adjusting member integrally with the press-fitting pin, it is possible to simplify the mounting work and production of the adjusting member. 
     It is also preferable in the present invention that the adjusting member has an annular shape and is formed by a separate member from the press-fitting pin. 
     With this configuration, the adjusting member can be formed separately, and thus it is possible to precisely process the adjusting member to a desired thickness. 
     Advantageous Effects 
     With the configuration that the thrust-directional width of the guide part is made smaller than the width of the drive ring, the adjusting member is sandwiched between the flange portion of the press-fitting pin and the end face of the guide part, the distance between the side face of the nozzle mount supporting the drive ring and the flange portion of the press-fitting pin is adjusted by the adjusting member, an amount of clearance at the guide part in the thrust direction of the drive ring is adjustable using the adjusting member. Thus, compared to the case where the thrust-directional length of the guide part is precisely processed by end mill machining or the like, the production cost can be reduced. 
     Moreover, as the thrust-directional length of the nozzle mount can be reduced by the amount of the thickness of the adjusting member (in the thrust direction of the guide part), it is possible to achieve the weight reduction and cost reduction of the materials. Further, by reducing the thrust-directional thickness of the guide part of the nozzle mount, it is possible to reduce the thrust-directional thickness of the nozzle mount including the guide part. This enables production by press working, thereby reducing the production cost. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view of a main part of a variable displacement exhaust turbocharger equipped with a variable nozzle mechanism according to an embodiment of the present invention. 
         FIG. 2A  is a front view of a variable nozzle mechanism according to a first embodiment of the present invention, which is taken from a lever plate side. 
         FIG. 2B  is a cross-sectional view in A-A of  FIG. 2A . 
         FIG. 3A  is an enlarged cross-sectional view of a part where a nail pin is press-fitted in a nozzle mount according to a first embodiment of the present invention, which is taken in B-B of  FIG. 2A . 
         FIG. 3B  is an enlarged view of a press-fitting hole on a nozzle mount side according to the first embodiment of the present invention. 
         FIG. 3C  is a schematic view of the nail pin according to the first embodiment of the present invention. 
         FIG. 4A  is an enlarged cross-sectional view of a section where a nail pin according to a second embodiment of the present invention is press-fitted in the nozzle mount. 
         FIG. 4B  is an enlarged view of a press-fitting hole on the nozzle mount side according to the second embodiment of the present invention. 
         FIG. 4C  is a schematic view of the nail pin according to the second embodiment of the present invention. 
         FIG. 5  illustrates a schematic configuration of the nail pin according to a third embodiment. 
         FIG. 6A  illustrates a turbine housing  010  of the related art. 
         FIG. 6B  is a partial enlarged view of section P of  FIG. 6A . 
         FIG. 6C  is an exploded view of components of  FIG. 6B . 
         FIG. 7  is an illustration of the related art. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     It is intended, however, that unless particularly specified, dimensions, materials, shapes, relative positions and the like of components described in the embodiments shall be interpreted as illustrative only and not limitative of the scope of the present invention. 
     (First Embodiment) 
       FIG. 1  is a longitudinal cross-sectional view of a main part of a variable displacement exhaust turbocharger equipped with a variable nozzle mechanism according to an embodiment of the present invention. 
       FIG. 1  illustrates a turbine casing  30 , a scroll  38  of a scroll shape formed in an outer peripheral part of the turbine casing  30 , a turbine rotor of a radial flow type  34 , a compressor  35 , a turbine shaft  32  for connecting the turbine rotor  34  and the compressor  35 , a compressor housing  31  and a bearing housing  36 . 
     The turbine shaft  32  connecting the turbine rotor  34  and the compressor  35  is rotatably supported by the bearing housing  36  via two bearings  37 ,  37 . The drawing also illustrates an exhaust gas outlet  8  and a rotation axis CL of the exhaust turbocharger. 
     A plurality of nozzle vanes  2  is arranged on an inner circumferential side of the scroll  38  at equal intervals in the circumferential direction of a turbine and is supported rotatably by a nozzle mount  5 . A nozzle shaft  2   a  is formed on a vane end of the nozzle vane  2  and is rotatably supported by the nozzle mount  5  which is fixed to the turbine casing  30 . 
     On an opposite side of the nozzle shaft  2   a  from the vane end, a lever plate  1  for varying a vane angle of the nozzle vane  2  by rotation of the nozzle shaft  2   a  is connected to the drive ring  3  via a connecting pin  10 . 
     An actuator rod  33  is configured to transmit a reciprocating motion from an actuator (not shown). A drive mechanism  39  is configured to convert the reciprocating motion of the actuator rod  33  (a reciprocating motion in a direction substantially perpendicular to the drawing) into a rotational motion by a rotation shaft  15   a , and rotate the drive ring  3  by a drive pin  15   c  disposed at an end of a lever  15   b  fixed to the rotation shaft  15   a.    
     A section  100  surrounded by a dotted line is a part of a variable nozzle mechanism for varying a vane angle of the nozzle vane  2 . 
     In the operation of the variable displacement exhaust turbocharger equipped with the variable nozzle mechanism which is configured as illustrated in  FIG. 1 , exhaust gas from an internal combustion engine (not shown) enters the scroll  38  and flows into the nozzle vanes  2  while swirling along the scroll shape of the scroll  38 . After flowing past between the nozzle vanes, the exhaust gas flows in the turbine rotor  34  from its outer peripheral side. Then, the exhaust gas flows radially toward the center to perform expansion work in the turbine rotor  34 . After performing the expansion work, the exhaust gas flows out in the axial direction and then guided toward the exhaust gas outlet  8  and sent outside of the turbine rotor  34 . 
     In order to control the displacement of this variable displacement turbine, a vane angle of the nozzle vanes  2  at which a flow rate of the exhaust gas through the nozzle vanes  2   a  reaches a desired flow rate is set by a vane angle controller (not shown) with respect to the actuator. The reciprocal displacement of the actuator with respect to this vane angle is transmitted to the drive ring  3  via the drive mechanism  39  so as to drive and rotate the drive ring  3 . 
     By rotation of the drive ring  3 , the lever plate  1  is caused to rotate around the nozzle shaft  2   a  via a connection pin  19  which is described later. By rotation of the nozzle shaft  2   a , the nozzle vane  2  is rotated to the vane angle which is set as to the actuator. 
       FIG. 2A  is a front view of the variable nozzle mechanism, which is taken from the lever plate  1  side.  FIG. 2B  is a cross-sectional view in A-A of  FIG. 2A . The drawings illustrate a variable nozzle mechanism  100  for varying the vane angle of the nozzle vanes  2 . The variable nozzle mechanism  100  is configured as described below. 
     The drive ring  3  formed in a disk shape is externally fitted to a guide part  5   a  (see  FIG. 2B ) of a cylinder shape which protrudes in the direction of the axis CL of the nozzle mount  5  (in the same direction as the rotation axis of the exhaust turbocharger) to be rotatably supported. Further, grooves  3   y , with which the connection pins  10  engage, are formed in drive ring  3  at equal intervals in the circumferential direction. The grooves  3   y  are described later. The drive mechanism  39  has a drive groove  3   z  where the actuator rod  33  engages. 
     The same number of the lever plates  1  as the grooves  3   y  of the drive ring  3  is provided at equal intervals in the circumferential direction. On the outer peripheral side of each of the lever plates  1 , the connection pin  10  is formed. On the inner peripheral side of each of the lever plates  1 , the nozzle shaft  2   a  of the nozzle vane  2  is fixed. 
     A nozzle plate  6  of an annular shape is connected to the nozzle mount  5  by a plurality of nozzle supports  61 . 
     In the variable nozzle mechanism, as illustrated in  FIG. 2B , the lever plate  1  is arranged on an inner side in the axial direction (on the compressor housing  31  side in  FIG. 1 ), and between a side face of the lever plate  1  and a side face of the nozzle mount  5 , the drive ring  3  is arranged in the state where the drive ring  3 , the lever plate  1  and the nozzle mount  5  are arranged next to one another in the axial direction. 
     The connection pin  10  is formed integrally with a base material by pressurizing one side face of each of the lever plates  1  by a press machine so that a rectangular depression  10   a  is formed on the side face and a rectangular protrusion is formed on the other side face by extrusion. 
     The drive ring  3  of the variable nozzle mechanism  100  which is formed in the above manner, needs to be retained with respective appropriate clearances between the nozzle mount  5  and the flange portion  20   a  of the nail pin  20 , and between the inner peripheral surface of the drive ring  3  and the outer peripheral surface of the guide part  5   a.    
     If the clearance is greater than a specified value, the drive ring  3  rocks in the axial direction of the nozzle mount  5 . This can result in one-side hitting of a thrust-direction end of a sliding face of the drive ring  3  against the guide part (one-side contact), which causes fixation. 
     On the other hand, if the clearance is smaller than the specified value, the sliding resistance of the nozzle mount  5  increases, which causes fixation of the sliding portion. 
     To prevent the fixation, it is desired to ensure an appropriate amount of a thrust-directional clearance L 8  (see  FIG. 3B ) in the thrust direction of the nozzle mount  5  and the drive ring  3 . To maintain the appropriate amount of clearance L 8 , a nail pin  20  which is a pin with a flange portion  20   a  is press-fitted in the press-fitting hole  5   b  formed at an outer peripheral edge part of the end face of the guide part  5   a  in the thrust direction, so as to secure an appropriate clearance by means of the flange. 
       FIG. 3A  is an enlarged cross-sectional view of a part where a nail pin serving as the press-fitting pin is press-fitted in the nozzle mount  5  according to a first embodiment of the present invention, which is taken in B-B of  FIG. 2A .  FIG. 3B  is an enlarged view of a press-fitting hole on the nozzle mount.  FIG. 3C  is a schematic view of the nail pin to be press-inserted in the press-fitting hole of  FIG. 3B . 
     At the end face of the guide part  5   a , a nail pin  20  with a flange portion  20   a  is press-fitted in a press-fitting hole  5   b . The nail pin  20  has the flange portion  20   a  to prevent rocking of the drive ring  3  in the direction of the axis CL of the nozzle mount  5  during rotation of the drive ring  3 . 
     In  FIG. 3A , the disc-shaped drive ring  3  is externally fitted to the cylindrical guide part  5   a  protruding in the direction of the axis CL of the nozzle mount  5  such that there is a small clearance L 7  therebetween in the radial direction. 
     The length L 1  of the guide part  5   a  (a protrusion amount) is set smaller than a thickness T 2  of the drive ring  3  which is externally fitted to the nozzle mount  5  such that the drive ring  3  contacts a section of the nozzle mount  5  disposed between a contact portion  5   c  where the drive ring  3  contacts and the end face of the guide part  5   a.    
     A thickness T 1  of the nozzle mount  5  (in the thrust direction) is set to the maximum length that can be machined by press so as to reduce the process cost and weight of the nozzle mount  5 . 
     As for the thickness T 1  of the nozzle mount  5 , the press-machining precision is improved, whereby maintaining a fixed strength and a perpendicularity of a stopper pin (not shown) for restricting a swing amount of the lever plate  1  which swings to define a fully-closed position of the vane angle of the nozzle vane  2  and the nail pin which is press-fitted in the nozzle mount  5 . 
       FIG. 3B  is a detailed view of the press-fitting hole  5   b .  FIG. 3C  is an illustration of the nail pin  20  to be press-fitted in the press-fitting hole  5   b.    
     The press-fitting hole  5   b  is formed in the outer peripheral edge part of the end face of the guide part  5   a  along the axis CL of the nozzle mount  5 , and a plurality of the press-fitting holes  5   b  is arranged at equal intervals in the circumferential direction. 
     The press-fitting hole  5   b  changes in hole diameter at two stages along an axis of the hole. Specifically, the hole diameter of the press-fitting hole  5   b  is ø 1  on an opening side (L 4  area) where the nail pin  20  is inserted and changes to ø 2  on its deeper side (L 3 -L 4  area) to satisfy the relationship of ø 1 &gt;ø 2 . 
     The area of the length L 4  of the section with the hole diameter ø 1  extends from a deeper side of the contact portion  5   c  (a position on left side of the contact portion  5   c  on the drawing) to the end face of the guide part  5   a.    
     The nail pin  20  includes a pin portion  20   b  to be press-fitted in the press-fitting hole  5   b , the flange portion  20   a , a stepped portion  20   c  which is an adjusting member for forming the appropriate clearance L 8  between the drive ring  3  and the flange portion  20   a , and a protruding portion  20   d  which protrudes from the flange portion  20   a  which is opposite from the flange portion  20   a.    
     The nail pin  20  is integrally formed with the stepped portion  20   c.    
     By a thrust-directional thickness L 5  of the nail pin  20 , the appropriate amount of the clearance L 8  is formed. 
     The hole diameter ø 2  is smaller than a diameter ø 3  of a tip part of the nail pin  20 , and the hole diameter ø 2  and the diameter ø 3  are formed according to a dimensional relationship of press-fitting. The length L 9  of the tip part of the pin  20  (a press-fit margin) which is inserted in the hole diameter ø 2  is long enough to possess a fixing strength to prevent the nail pin  20  from coming out from the press-fitting hole  5   b  easily during the operation of the drive ring  3 . 
     Further, the outer peripheral surface of the outer diameter ø 4  of the stepped portion is set so as not to project beyond the outer peripheral surface of the guide part  5   a  in the radial direction when the nail pin  20  is press-fitted in the press-fitting hole  5   b.    
     The protruding portion  20   d  is a portion where a press-fitting tool is abutted when press-fitting the nail pin  20  into the press-fitting hole  5   b . Without the protruding portion  20   d , the pin portion  20   b  deforms during insertion of the nail pin  20  due to the press-fitting pressure acting on the pin portion  20   b . The deformation of the pin portion  20   b  accompanies deformation of the flange portion  20   a . Therefore, the protruding portion  20   d  is provided to prevent deformation of the nail pin  20  and facilitate assembling thereof. 
     Further, the height L 1  of the guide part  5   a  and the thickness L 5  of the stepped portion  20   c  are set so that an appropriate clearance L 8  is secured between the flange portion  20   a  of the nail pin  20  and the drive ring  3  when the nail pin  20  is press-fitted into the press-fitting hole  5   b.    
     Furthermore, in a section where the sliding face width (T 2 ) of the drive ring  3  is located, a space  5   e  is formed in L 1  section of the press-fitting hole  5   b.    
     Thus, although a section of the press-fitting hole  5   b  of the nozzle mount  5  on the drive ring  3  side is thin and has low rigidity, it is possible to prevent outward bulging of the section caused by the press-fitting of the nail pin  20 . 
     This is, however, not restrictive and it is not a problem in this embodiment even if the space  5   e  is not provided. 
     A relief R is provided in a continuous portion between the contact portion  5   c  and the guide part  5   a  of the nozzle mount  5  so that the edge of the sliding face width (T 2 ) of the drive ring  3  reliably contacts the guide part  5   a.    
     By ensuring that the slide face of the drive ring  3  contacts across the guide part  5   a , it is possible to reduce rocking of the drive ring  3  in the thrust direction during rotation of the drive ring  3 , thereby preventing the fixation of the edge of the sliding face width of the drive ring and the guide part  5   a.    
     On an outer circumferential side of the relief R of the side face, the contact portion  5   c  of a disk shape is formed so that the radial-direction side face of the drive ring  3  contacts the disk-shaped contact portion  5   c . The contact portion  5   c  is provided to reduce frictional resistance between the side face of the nozzle mount  5  and the radial-direction side face of the drive ring  3 , thereby enhancing smooth rotation of the drive ring  3 . 
     With the above configuration, by press-machining the nozzle mount  5 , the length L 1  of the guide part  5   a  of the nozzle mount  5  becomes small and the thrust-directional thickness T 1  of the entire nozzle mount  5  is reduced by an amount of the thickness L 5  of the stepped portion  20   c . Thus, it is possible to achieve the weight reduction and cost reduction of materials. 
     The configuration of the nozzle mount  5  (the configuration around the guide part) was conventionally complicated and it required many steps to achieve machining precision when machining the guide part  5   a  in the thrust direction (end mill machining). However, with the integral configuration in which the stepped portion serving as the adjusting member is integrally provided in the nail pin  20 , high machining precision can be easily achieved by adopting lathe machining, whereby achieving significant reduction in the machining cost. 
     Further, as the space  5   e  is formed in L 4  section of the nail pin  20  and the press-fitting hole  5   b , press-fitting of the nail pin  20  does not generate a bulging portion on the surface of the guide part  5   a  in the section where the sliding face T 2  of the drive ring  3  is located. Therefore, it is possible to maintain the surface of the guide part  5   a  smooth and avoid the fixation of the drive ring  3  and the guide part  5   a.    
     In the case where the space  5   e  is not provided, the fitting dimension of the pin portion  20   b  and the press-fitting hole  5   b  in the L 4  section may be adjusted to avoid generation of the bulging portion. 
     Moreover, as the diameter of the press-fitting hole  5   b  in the L 4  section is large, press-fitting work is facilitated. 
     (Second Embodiment) 
     A second embodiment will be described in reference to  FIG. 4A ,  FIG. 4B  and  FIG. 4C . 
     The structure is the same as the first embodiment, except for press-fitting of a nail pin  21  in the nozzle mount  51 . Thus, structures such as the variable nozzle mechanism will not be described further herein. 
     In addition, for parts of the same shape with the same effect, are assigned the same reference numerals, and a description thereof will be omitted. 
       FIG. 4A  is an enlarged cross-sectional view of a section where a nail pin according to the second embodiment of the present invention is press-fitted in the nozzle mount.  FIG. 4B  is an enlarged view of a press-fitting hole on the nozzle mount side.  FIG. 4C  is a schematic view of the nail pin to be inserted in the press-fitting hole of  FIG. 4B . 
       FIG. 4A  shows a nozzle mount  51  and a lever plate  1 . In  FIG. 4A , the drive ring  3  is externally fitted to a guide part  51   a  of the nozzle mount  51 . 
       FIG. 4B  illustrates a press-fitting hole  51   b  where a nail pin  21  is press-fitted.  FIG. 4C  illustrates the nail pin  21  to be fitted to the press-fitting hole  51   b.    
     The press-fitting hole  51   b  has a diameter ø 2  and is formed in the outer peripheral edge part of the end face of the guide part  51   a  along the axis CL of the nozzle mount  51 , and a plurality of the press-fitting holes  51   b  is arranged in the outer peripheral edge part at equal intervals in the circumferential direction. 
     The area of the length L 4  of the section with the hole diameter ø 2  extends from the end face of the guide part  51   a  to a deeper side of a contact portion  51   c  (a position on left side of the contact portion  51   c  on the drawing). 
     The length L 1  of the guide part  51   a  (a protrusion amount) is set smaller than an amount equivalent to the thickness T 2  of the drive ring  3  which is externally fitted to the nozzle mount  5  such that the drive ring  3  contacts a section of the nozzle mount  51  disposed between the contact portion  51   c  where the drive ring  3  contacts and the end face of the guide part  5   a.    
     The nail pin  21  comprises a pin tip portion  21   b  to be press-fitted in the press-fitting hole  51   b , a reduced diameter part  21   c  with smaller diameter than the pin tip portion  21   b , a stepped portion  21   f  which is a disc-shape adjusting member having an outer diameter portion does not project beyond the outer peripheral surface of the guide part  51   a  in the radial direction, a flange portion  21   a  for maintaining an appropriate clearance L 8  (see  FIG. 4B ) with respect to the side face of the drive ring  3  and restricting rocking of the side face of the drive ring  3  in the thrust direction, and a protruding portion  21   d  from the flange portion  21   a  to a side which is opposite from the stepped portion  21   f . The nail pin  21  is integrally formed. 
     The nail pin  21  to be press-fitted in the press-fitting hole  51   b  is configured so that the pin tip part  21   b  has diameter ø 3  and the reduced diameter part  21   c  between the pin tip part  21   b  and the stepped portion  21   f  has diameter ø 5 , and diameter ø 3 &gt;diameter ø 5 . 
     The thrust-directional length L 5  of the stepped portion  21   f  is determined to secure an appropriate clearance L 8  between the side face of the drive ring  3  and the flange portion  21   a.    
     A length L 10  of the diameter ø 3  of the tip part  21   b  (press-fit margin) has a length that achieves fixing strength so that the nail pin  21  does not come out from the press-fitting hole  51   b  easily at the operation of the drive ring  3  when inserting the nail pin  21  into the press-fitting hole  51   b.    
     Further, each of the tip part  21   b  of the nail pin  21  and the press-fitting hole  51   b  is formed in interference-fitting dimension of a respective elastic deformation region so that the section (L 1 ) of the press-fitting hole  51   b  opposing the drive ring  3  does not plastically deform when press-fitting the nail pin  21  into the press-fitting hole  51   b.    
     Thus, by press-fitting the nail pin  21  into the press-fitting hole  51   b , the stepped portion  21   b  is abutted to the end face of the guide part  51   a  to form the appropriate clearance L 8 . 
     With this configuration, the thrust-directional thickness T 1  of the nozzle mount  51  is reduced by the amount equivalent to the thickness L 5  of the stepped portion  21   f . Thus, it is possible to achieve the weight reduction and cost reduction of materials. 
     The configuration of the nozzle mount  51  (the configuration around the guide part) was conventionally complicated and it required many steps to achieve machining precision when machining the guide part  51   a  in the thrust direction (end mill machining). However, with the integral configuration in which the stepped portion serving as the adjusting member is integrally provided in the nail pin  21 , high machining precision can be easily achieved by adopting lathe machining, whereby achieving significant reduction in the machining cost. 
     Further, as the space  21   e  is formed in L 4  section of the nail pin  20  and the press-fitting hole  5   b , press-fitting of the nail pin  21  does not generate a bulging portion on the surface of the guide part  51   a  in the section where the sliding face T 2  of the drive ring  3  is located. Therefore, it is possible to maintain the surface of the guide part  51   a  smooth and avoid the fixation of the drive ring  3  and the guide part  51   a.    
     (Third Embodiment) 
     A third embodiment will be described in reference to  FIG. 5 . 
     The structure is the same as the first embodiment, except for a shape of the nail pin. Thus, structures except for the nail pin will not be described further herein. 
     A nail pin  22  comprises a pin portion  22   b  to be press-fitted in the press-fitting hole  5   b  (see  FIG. 3B ), a flange portion  22   a  for restricting rocking of the drive ring  3  (see  FIG. 3B ) in the thrust direction, and a press-fitting tool receiving part  22   d  where a press-fitting strikes when the nail pin  22  protruding from the flange portion  22   a  to a side which is opposite from the pin portion  22   b  is press-fitted into the press-fitting hole  5   b . The nail pin  21  is integrally formed. 
     Moreover, in a section where the pin portion  22   b  contacts the flange portion  22   a , a spacer  23  (corresponding to the stepped portion  20   c  of the first embodiment) serving as an adjusting member is press-fitted. 
     The dimension of the spacer  23  is adjusted so that the outer peripheral surface of the space  23  does project beyond the outer peripheral surface of the guide part  5   a  (see  FIG. 3B ) when the nail pin  22  is press-fitted in the press-fitting hole  5   b.    
     In this embodiment, the spacer  23  is press-fitted to the nail pin  22 . Thus, by eliminating a gap between an inner peripheral surface of the spacer  23  and the pin portion  22   b  and setting the outer diameter of the spacer  23  to the maximum diameter which is twice as large as the distance between the axis of the press-fitting hole  5   b  and the outer peripheral surface of the guide part  5   a , it is possible to prevent the spacer  23  from projecting beyond the outer peripheral surface of the guide part  5   a  to secure the clearance L 7  (see  FIG. 3B ) between the inner peripheral surface of the drive ring  3  and the spacer  23 , prevent fixation of these parts and also secure the clearance L 8  in the thrust direction of the drive ring  3 . 
     In this embodiment, the configuration in which the spacer  23  is press-fitted to the pin portion  22   b  is described. This is, however, not restrictive, and the spacer  23  may be inserted in a manner other than press-fitting to achieve the same effects as long as, with the clearance between the pin portion  22   b  and the inner peripheral surface of the spacer  23 , even if the spacer  23  is disposed closer to the guide part  5   a  side when the nail pin  22  is press-fitted in the press-fitting hole  5   b , the outer peripheral part of the spacer  23  is either flush with the outer peripheral surface of the guide part  5   a  or slightly closer to the center of the spacer  23  without projecting beyond the outer peripheral surface of the guide part  5   a.    
     INDUSTRIAL APPLICABILITY 
     According to the present invention, it is possible to provide a variable displacement exhaust turbocharger equipped with a variable nozzle mechanism for varying a vane angle of a plurality of nozzle vanes, whereby the drive ring of the variable nozzle mechanism is easily retained to the guide part with an appropriate clearance and fixation of the inner peripheral surface of the drive ring and the outer peripheral surface of the guide part is prevented so as to achieve cost reduction and improved durable reliability.