Abstract:
A variable nozzle device comprises a wall member, a unison ring provided on a first side of the wall member, and a vane, a vane body of which is provided on a second side of the wall member, said second side being opposite to said first side, wherein said vane further having a tab member comprising a tab portion and a shaft portion, said shaft portion being movably inserted in a slot of the wall member; and said tab portion being adapted to hold the vane body by abutting against a portion of the wall member which defines the slot, wherein the vane body and the tab member are provided as separate, parts and are fixable to each other.

Description:
FIELD OF THE INVENTION 
   The invention relates to a variable nozzle device having at least a vane mounted thereto, and a method of assembling the vane to the wall member of the variable nozzle device. 
   BACKGROUND 
   Variable geometry nozzle systems with adjustable pivot vane configurations require the vanes to be positioned in a nozzle of a compressor, for example. For this purpose, a preassembled variable nozzle cartridge already comprising vanes can be mounted to the compressor of a turbocharger. 
   One possibility of such a variable nozzle cartridge comprises among other parts two parallel wall members, i.e. a disk insert or diffuser plate and a back plate, between which vanes are disposed. Each vane is pivotally mounted to the back plate by means of a pivot axle of the vane about which the vane can pivot, and by means of a tab member having an elongated head and being integrally provided on the vane. When mounting the vane to the back plate, the pivot axle is stuck into a respective hole of the back plate and the tab member is inserted into a respective assembly slot of the back plate as well as into an actuating slot of a unison ring positioned on the backside of the back plate. The back plate also has guide slots each of which is substantially perpendicular to the associated assembly slot and is in connection therewith such that one guide slot and one assembly slot established a T-shaped slot in the back plate. The guide slots guide shafts of the tab members when the unison ring is rotated relative to the back plate so as to pivot the vanes. 
   Furthermore, spacers are provided between the back plate and the diffuser plate so as to secure a certain distance there between. The diffuser plate provides a sliding surface for the vanes. 
   There exists a need for a variable nozzle device having a high performance and a high functionality. 
   SUMMARY OF THE INVENTION 
   According to a first aspect, the above need is met with a variable nozzle device comprising a wall member, a unison ring, and a plurality of vanes, wherein each vane has a vane body and a tab member comprising a tab portion and a shaft portion, said shaft portion passing through a slot of the wall member, and said tab portion overlapping the slot to hold the vane, wherein the vane body and the tab member are provided as separate parts and are fixable to each other. Since the vane is provided from separate parts which are fixable to each other, the vane can be mounted to the wall member by arranging the vane body on the first side of the wall member and by inserting the tab member from the second side thereof. Consequently, the tab portion does not need to be inserted through the slot of the wall member from the first side. As a result, the slot does not need to have a shape or a portion through which the tab portion can be passed. The slots only need to be shaped for guiding purposes of the shaft portion of the vane. Prom the view of the guiding purpose, the slot is preferably curvilinear. 
   Furthermore, since the slot does not need to have a portion through which the tab portion can be passed for mounting, there is no fear that, after mounting, the vane falls out of the slot. Accordingly, there exists no position of the vane in which the vane is not held by the abutting action of the tab portion to the wall member. As a result, the entire extent of the slot can be used for guiding the vane. For the same reason, no diffuser plate, which would support the vane, needs to be provided as a part of the variable nozzle device. 
   Preferably, the unison ring is provided on a first side of the wall member and the vane body is provided on a second side of the wall member, which sides. are opposite to each other. Further preferably, the tab portion holds the vane by the tab member abutting against a portion of the wall member which defines the slot. 
   Preferably, a mounting hole is provided in the vane body at a side of the vane body which faces the wall member when the vane body is mounted to the wall member, and a tip section of the shaft portion is insertable into the mounting hole of the vane body. 
   The tab member can be fixable to the vane body by press-fitting the tip section of the shaft portion into the mounting hole. This allows a simple and effective mounting procedure of the vane to the wall member. 
   Furthermore, the tip section and the mounting hole may have corresponding cross-sectional shapes which fit to each other and which provide a relative rotation preventing means for preventing a rotation of the tab member relative to the vane body. This allows an improved mounting performance when mounting the vane to a variable nozzle device having unison ring comprising an actuating slot in which the tab portion is to be located and wherein the tab portion requires a specified orientation with respect to the actuating slot. Especially, the relative rotation preventing means provides a predetermined orientation of the vane body with respect to the rotational position of the unison ring. 
   The shaft portion may comprise a spacing section disposed between the tip section and the tab portion, wherein said spacing section defines a predetermined distance between the tip section and the tab portion. The cross-sectional area of the spacing section can be larger than the cross-sectional area of the tip section to form a stop face which restricts the insertion depth of the tab member. Thus, when mounting the vane to the wall member, the tip portion of the tab member can be press-fitted into the mounting hole of the vane body until the stop face abuts against the vane body. As a result, the above explained distance between the vane body and the tab portion can easily be secured in the mounting process of the vane. Said distance is preferably set such that the vane body is prevented from floating away from the wall member. 
   The wall member may comprise a slotted portion having the slot through which the shaft portion of the tab member is to be passed for mounting the vane to the wall member, and the length of the spacing section is set based on a thickness of the slotted portion such that the tab portion and the vane body slidingly grip the wall member there between when the vane assembly is mounted to the wall member. As a result, the vane body can be prevented from floating from the vane side surface of the insert. Consequently, the variable nozzle device is not required to have a diffuser plate for supporting the vane body in the axial direction of the wall member which is the direction perpendicular to the surface on which the vane body is mounted. As a result; spacers for securing a distance between the wall member and the diffuser plate can be omitted. Since the conventionally known spacers and diffuser plate have resulted in adverse aerodynamic effects, the aerodynamic performance of a variable nozzle device having the vane according the invention is improved. 
   Preferably, the slot acts as a guide slot for guiding the shaft portion of the tab member. 
   The vane body may also comprise a pivot axle about which the vane body can pivot when being mounted to the wall member. The pivot axle is preferably provided on the same side of the vane body on which the mounting hole for mounting the tab member is provided. This allows for mounting the vane to only one wall member without a second wall member necessary on the side of the vane body opposite to the side on which the tab member is to be mounted. 
   According to a second aspect of the invention, the above need is met with a method of assembling a variable nozzle device having the above features. The method includes the steps of arranging the vane body on one side of the wall member, passing the shaft portion of the tab member through the slot from the other side of the wall member, and fixing the shaft portion to the vane body. According to this method, an assembly slot for passing through the elongated tab portion of the tab member from the one side must not be provided in the wall member. Since a conventionally known assembly slot adversely affects the aerodynamic performance of a variable nozzle device, the method according to the invention leads to a variable nozzle device having an improved aerodynamic performance. 
   Preferably, the shaft portion is fixed to the vane body by inserting the tip section of the shaft portion into the mounting hole of the vane body. 
   Furthermore, the mounting hole of the vane body can be aligned with the slot of the wall member before passing the shaft portion of the tab member through the slot, and fixing of the shaft portion to the vane body can be made by press-fitting the tip section into the mounting hole. 
   Preferably, before performing the step of inserting the shaft portion of the tab member through the slot of the wall member into the mounting hole, the following steps are performed: arranging the unison ring having an actuating slot on said second side of the wall member, aligning the actuating slot with the slot of the wall member, and then inserting the shaft portion through said actuating slot of the unison ring to place the tab portion in said actuating slot. 
   The method may further comprise the step of pressing the tip portion of the tab member into the mounting hole of the vane body until the stop face of the tab member abuts against the vane body. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the invention will become apparent from the description that follows with reference being made to the enclosed drawings, in which: 
       FIG. 1  is cross-sectional view of a compressor housing and a center housing between which a variable nozzle device having pivotable vanes according to an embodiment of the invention is mounted; 
       FIGS. 2A to 2C  are views of a vane according to the embodiment of the invention,  FIG. 2D  is a top view of a tab member according to the embodiment of the invention; 
       FIGS. 3A to 3D  are cross-sectional views of a portion of an insert member to which the vane and a unison ring are being mounted, illustrating different stages of the mounting process; 
       FIG. 4  is a front view of the variable nozzle device from a side on which the unison ring is provided; 
       FIG. 5  is an enlarged cut-away view of the variable nozzle device from the side to which the unison ring is mounted, showing a closed position of the vanes; 
       FIG. 6  is an enlarged cut-away view of the variable nozzle device from the side to which the unison ring is mounted, showing an opened position of the vanes; 
       FIG. 7  is a cross-sectional view of the compressor housing and the center housing, with the variable nozzle device being mounted to the compressor housing before the same is mounted to the center housing. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a cross-sectional view of a portion of a compressor housing and a center housing of a turbocharger having a variable nozzle device according to an embodiment of the invention. Air is compressed by a compressor wheel  47  through a nozzle into a volute. The nozzle is formed between a nozzle portion  33  of the compressor housing and a wall member  10  which in the following is referred to as an insert. 
   Pivotable vanes  1  are provided in the nozzle and the cross sectional area of the nozzle can be adjusted by pivoting the vanes  1 . A unison ring  12  is provided on the side of the insert  10  opposite to the vanes  1  and the vanes  1  can be actuated by a later described actuating mechanism according to which the unison ring  12  is rotated relatively to the insert  10 . 
     FIG. 2A  shows a side view of the vane  1  according to the invention before being mounted to the insert  10 . The vane  1  comprises a vane body  2  and tab member  9  which are separate parts. The vane body  2  has a pivot axle  8  about which the vane  1  can pivot when being mounted to the insert  10  as well as a mounting hole  7  into which the tab member  9  can be mounted. 
   The tab member  9  comprises a head  5  (tab portion) and a shaft  6  (shaft portion). The head  5  has an elongated shape (see  FIG. 2D ) which, with respect to the view of  FIG. 2A , substantially extends in parallel to the vane body  2 . With respect to the top view of the head  5 , the elongated shape of the head  5  extends in a direction which can deviate from the direction in which the vane body  2  extends. As seen in  FIG. 2A , the shaft  6  extends perpendicular to the head  5  and has a spacing section  4  and a tip section  3 , wherein the spacing section  4  is provided close to the head  5  and the tip section is provided at the distal end of the shaft  6 . 
   The cross-sectional area of the spacing section  4  is larger than that of the tip section  3  such that a stop face  14  is formed at the transition between these sections. In the present embodiment, the spacing section  4  has a circular cross-sectional shape while the tip section  3  has a D-shaped cross section (see  FIG. 2G ). 
   Also the mounting hole  7  provided in the vane body  2  has a D-shaped cross section which is slightly smaller than the D-shaped cross-section of the tip section  3  of the shaft  6  such that the tip section  3  can be press-fitted into the mounting hole  7 . As a result of these cross-sectional shapes, the tab member  9  can be mounted to the vane body  2  in a very easy manner. Furthermore, the D-shaped cross sections of the tip section  3  and of the mounting hole  7  provide a relative rotation preventing means which sets the orientation of the elongated head  5  with respect to the vane body  2 . 
   Furthermore, the spacing section  4  of the shaft  6  defines a predetermined length between the stop face  14  and the head  5 . Thus, when the tab member  9  is mounted to the valve body  2  by press-fitting the tip section  3  into the mounting hole  7  until the stop face  14  abuts against the valve body  2 , a predetermined distance between the head  5  and the vane body  2  is obtained. The significance of this distance is described later. 
   As can be seen in  FIG. 2C , the vane body  2  has an elongated triangular shape. The more narrow end of the triangular shape is provided at the side of the pivot axle  8  while the broader end is provided at the side of the tab member  9 . 
     FIG. 3A  shows a cross-sectional view of a portion of the insert  10 . The insert  10  has a circular shape (see  FIG. 4 ) and is provided with an annular groove  16  (see  FIG. 3 ) into which the unison ring  12  is to be mounted. The insert  10  has an annular projection  17  which protrudes from a boundary line defining the radial outer circumference of the annular groove  16  in the radial inward direction into the annular groove  16 . The unison ring  12  is to be placed into the annular groove  16  such that it is held in the axial direction by the projection  17 , as can be understood from the following description. 
   When viewed from the back side, as is shown in  FIG. 4 , the circular insert  10  has three recesses  18  which are formed in the annular projection  17  and which are circumferentially arranged by equal intervals. Three protrusions  19  extend radial outwardly from the unison ring  12  and are also circumferentially arranged by equal intervals. The protrusions  19  fit into the recesses  1 B. When mounting the unison ring  12  to the insert  10 , the three protrusion  19  are aligned with the three recesses  18  of the insert  10  such that the unison ring  12  can be inserted into the groove  16  of the insert  10 . Then, the unison ring  12  is rotated with respect to the insert  10 , such that the protrusions  19  are moved behind the annular projection  17 . As a result, the unison ring  12  is held in the axial direction by the projection  17  of the insert  10 . This state is shown in  FIG. 3B . 
     FIGS. 5 and 6  show views of the variable nozzle device from the side to which the unison ring  12  is mounted. The unison ring  12  is only partly shown, i.e. the thick-lined portion represents a view on a part of the unison ring  12  while the thin lined portion is a view on the insert  10 . The insert  10  has a guide slot  11 , which is a curvilinear slot, for guiding the shaft  6  of the tab member  9  of the associated vane  1 . The unison ring  12  has an actuating slot  23  for actuating the vane  1  via the head  5  of the tab member  9 . Furthermore, the insert  10  has a pivot hole  20  which is open to the side of the insert  10  to which the vane  1  is to be mounted. A set of guide slot  11 , actuating slot  23  and pivot hole  20  is provided for each of the vanes  1 . 
   Back to  FIG. 3C , the mounting of the vane  1  to the insert  10  having the unison ring  12  attached thereto is described. When the unison ring  12  is rotated so as to bring the protrusion  19  behind the projection  17  of the insert  10 , as was described above, the unison ring  12  is rotated about such an extent that the actuating slots  23  of the unison ring  12  and the guide slots  11  of the insert  10  are aligned to each other. 
   Then, with reference to  FIG. 3D , the vane  1  is mounted to the assembly of the insert  10  and the unison ring  12  by inserting the pivot axle  8  into the pivot hole  20  and bringing the mounting hole  7  of the vane body  2  into alignment with the guide slot  11  of the insert  10 . As a next step, the tab member  9  is inserted from the unison ring side through the actuating slot  23  of the unison ring  12  and the guide slot  11  of the insert  10  into the mounting hole  7  of the vane body  2 . The tab member  9  is press-fitted into the vane body  2  by pressing it towards the vane body  2  until the stop face  14  abuts against the insert side surface of the vane body  2 . 
   In this state, the head  5  of the tab member  9  is accommodated in the actuating slot  23  as can be seen in  FIG. 3D . Furthermore, due to the elongated shape of the actuating slot  23 , the elongated shape of the head  5  and the D-shaped cross sectional shapes of the tip section  3  and of the mounting hole  7 , respectively, the orientation of the vane body  2  with respect to the position of the unison ring  12  is set in an appropriate manner. 
   As can be seen in  FIGS. 3A to 3D , the insert  10  has a slotted portion  15  through which the guide slot  11  extends. The length of the spacing section  4  is set as long as the thickness of the slotted portion  15 , i.e. as long as the depth of the guide slot  11 . Thus, the head  5  and the insert side surface of the vane body  2  slidingly grip the slotted portion  15  between each other. As a result, the vane body  2  is restricted in its movement away from the insert  10  in the axial direction thereof by the head  5  being in close contact with the unison ring side surface of the insert  10 . In other words, the head  5  creates a stop which controls the vane end float with respect to the insert  10 . 
   Furthermore, since the guide slot  11  is a curvilinear slot and not a T-shaped slot, the head  5  cannot pass through the guide slot  11  at any position of the guide slot. Thus, the entire guide slot  11  can be used for guiding the shaft  6  of the vane  1  without running the risk of the vane  1  falling from the insert  10  due to the tab portion  5  passing through an assembly slot. 
   An operation mode of the variable nozzle device is described based on  FIGS. 5 and 6 . With the vanes  1  being mounted to the insert  10 , the head  5  of the tab member  9  is guided in the actuating slots  23  of the unison ring  12  while the shaft  6  is guided in the guide slots  11  of the insert  11 . Herein,  FIG. 5  shows the state in which the vanes  1  are in the closed position. In this state, the head  5  is located at the radial inner end of the actuating slot  23  and the shaft  6  is located at the radial inner end of the guide slot  11 . 
   Now, when the unison ring  12  is rotated with respect to the insert  10  in the clockwise direction as seen in  FIG. 4 , the actuating slot  23  exerts a force to the head  5  of the tab member  9  which urges the tab member  9  toward the radial outward side of the insert  10  while the shaft  6  of the tab-member  9  is allowed to slide within the guide slot  11 . Accordingly, the vane  1  is moved to its opened position with the shaft  6  sliding in the guide slot  11 . In the fully opened state of the vane  1 , the head S is located at the radial outer end of the actuating slot  23  while the shaft  6  is located at the radial outer end of the guide slot  11 . 
   Thus, a variable nozzle device comprising the insert  10 , the unison ring  12  as well as a plurality of vanes  1  is provided in the form of a preassembled cartridge. 
   A cartridge as described above can be used with a compressor of a turbocharger. Basically, a turbocharger is a device that uses exhaust gases produced by the engine to supply additional air into cylinders of the combustion engine. The turbocharger is mounted directly on the exhaust manifold, where exhaust gases pass over a turbine impeller that is attached to a shaft. 
   On the other side of this shaft, a compressor wheel is provided and is driven by the turbine via the shaft. The compressor wheel is located in a housing and draws suction air through an air filter, compresses this suction air and supplies it into an intake manifold of the engine via a volute in the housing. Thus, the energy from the exhaust gases, which would be wasted on a non-charged engine, is being used to supply additional air into the combustion engine leading to an increased engine power. 
     FIG. 7  is a sectional view of a compressor nozzle device, in which the cartridge comprising the insert  10 , the vanes  1  and the unison ring  12 , is attached to a volute  31  of a compressor. 
   On the right side of  FIG. 7 , a center housing and rotating assembly  50  can be seen. The center housing and rotating assembly  50  connects a turbine side of a turbocharger with a compressor side via a shaft supported in the center housing. A compressor wheel  47  is attached to the shaft at its compressor side end. 
   Since the cartridge is manufactured as a sub assembly, the vanes  1  of the cartridge are already fully calibrated and after the cartridge has been attached to the volute, both can be aerodynamically tested, e.g. by using a certain testing device, before being attached to the housing  50 . 
   The insert  10  of the cartridge is fixedly mounted to the volute  31  at a radial outer portion of the insert  10 . In this way, the insert  10  projects into a circular groove  43  provided in a radial outer portion of the volute  31 . At the bottom of this circular groove  43 , a seal  41  is provided, which is kept in position by means of the insert  10 . 
   The angular position of the cartridge relative to the volute  31  is maintained by an angular orientation pin  35  which is passed through respective bores in the volute  31 , the insert  10  and the housing  50  of the center housing and rotating assembly. 
   The cartridge, the volute  31  and the inlet  37 , shown on the left side of  FIG. 7 , form the compressor side of a turbocharger and are attached to the center housing  50  by known means, such as bolts  49 . 
   As can be seen in  FIG. 7 , the cartridge does not comprise a diffuser plate and the vanes body  2  is directly, adjacent to a wall portion of the compressor housing which is also referred to as diffuser face. The vanes  1  do not need to touch the diffuser face, because they are held by the head  5  of the tab member  9 . A gap can be present between the vanes  1  and the diffuser face. 
   Since no diffuser plate is present, no gaps or steps between the diffuser plate and compressor housing can occur, which gaps or steps would adversely affect the aerodynamic performance of the compressor. Furthermore, since the cartridge does not comprise a diffuser plate, no spacers between the diffuser plate and the insert are necessary for securing the distance between the diffuser plate and the insert, which spacer would adversely affect the aerodynamic performance of the compressor. The spacers and the diffuser plate are not necessary because the vane body  2  is held by the head S of the tab members in the axial direction of the insert  10  such that a vane end float is prevented. Accordingly, a support surface on which the vane body  2  can be supported in the axial direction of the insert and which conventionally was provided by the diffuser plate is not necessary. As a result, the vane  1  according to the invention makes it possible to manufacture a compressor having an improved aerodynamic performance. 
   Furthermore, since the tab member  9  of the vane  1  is mounted from the unison ring side surface of the insert  10  and not from the vane side of the insert  10 , the head  5  of the tab member  9  does not need to be threaded through an assembly hole of the insert. Accordingly, such an assembly hale can be omitted. Since the conventional assembly hole has adversely affected the aerodynamic performance of the compressor, the vane  1  according to the invention makes it possible to manufacture a compressor having an improved aerodynamic performance. 
   Preferably, this cartridge concept having the variable nozzle device according to the invention is used for compressor housings a deformation of which does not largely affect a gap between the vanes and the diffuser face. 
   In the foregoing, a preferred embodiment of the invention has been described with reference to the Figures. However, it will be apparent to a person skilled in the art that further modifications can be carried out without departing from the scope of the claims. 
   For example, the spacing section  4  of the tab member can be set to be slightly shorter than the depth of the guide slot  11 . As a result, with the tab member  9  press-fitted into the mounting hole  7  of the vane body, the head  5  rubs on the unison ring side surface of the insert  10 . Accordingly, the vane end float can more securely be restricted. 
   Furthermore, the tab member does not need to be fixed to the vane body by press-fitting. These parts can also be fixed to each other by any other fixing methods. For example, they can be fixed by mutually brazing them to each other. 
   For example, the number of vanes and, thus, the number of assembly slots, pivot holes, actuating slots in the unison ring etc. are not restricted but can be adapted to the individual requirements. 
   Furthermore, the shape of the vanes can advantageously be adapted. For example, instead of the triangle shape, the vanes may e.g. have a curved shape, or the longer edges of the vanes may be substantially parallel to each other. 
   Although the nozzle device was described as a compressor nozzle device, it will be obvious to a person skilled in the art to use an equivalent nozzle device for a turbine, e.g. on a turbine side of a turbocharger. 
   Furthermore, the nozzle device is not restricted to be used with a turbocharger, but is suitable for any apparatus where fluids pass a flow path having a variable sectional area.