Patent Publication Number: US-2023160320-A1

Title: Turbocharger

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of PCT Application No. PCT/JP2021/032704, filed on Sep. 6, 2021, which claims the benefit of priority from Japanese Patent Application No. 2020-153766, filed on Sep. 14, 2020. The entire contents of the above listed PCT and priority applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a turbocharger. 
     A turbocharger described in Japanese Unexamined Patent Publication No. 2013-68153 has been known. The turbocharger includes a variable nozzle for adjusting an opening degree of a nozzle passage of a turbine. When this type of the variable nozzle is completely fixed to a housing (for example, fixed with a fastening member), there is a possibility that operation of the variable nozzle is adversely affected during thermal expansion. Therefore, the variable nozzle is fixed at a position by being appropriately pressed against a turbine housing to the extent that thermal deformation is allowed. For this reason, a disk spring is provided between the variable nozzle and a bearing housing. Then, the variable nozzle is pressed against the turbine housing and is aligned by being biased by the disk spring. 
     During operation of the turbocharger, one variable nozzle side with which the disk spring is in contact is at high temperature, whereas the other bearing housing side is at relatively low temperature due to being cooled by water cooling, oil cooling, or the like. Due to such a temperature difference, during operation of the turbocharger, the disk spring has a temperature distribution in which an outer peripheral side is at high temperature and an inner peripheral side is at low temperature. Furthermore, according to this temperature distribution, since the disk spring is thermally deformed to reduce a spring load, the load that presses the variable nozzle against the turbine housing may decrease. When the pressing load is small, abnormal noise, abrasion, contact between the variable nozzle and an impeller, performance change, control deviation of the variable nozzle, or the like may occur. 
     Therefore, the present disclosure describes a turbocharger that suppresses a reduction in spring load when a spring member that biases a variable nozzle is at high temperature. 
     SUMMARY 
     A turbocharger according to one aspect of the present disclosure includes a variable nozzle disposed between a turbine housing and a bearing housing and a spring having an annular shape. The spring is disposed between the variable nozzle and the bearing housing, and is configured to generate a biasing force that biases the variable nozzle away from the bearing housing to widen a spacing between the variable nozzle and the bearing housing in a rotation axis direction. The spring includes an outer peripheral portion that applies the biasing force to the variable nozzle and an inner peripheral portion that comes into contact with the bearing housing. The outer peripheral portion of the spring is located further away from the turbine housing than the inner peripheral portion of the spring in the rotation axis direction. 
     According to the turbocharger of the present disclosure, a reduction in spring load when the spring that biases the variable nozzle is at high temperature may be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional view showing an example turbocharger. 
         FIG.  2    is an enlarged cross-sectional view showing the vicinity of a variable nozzle of the turbocharger. 
         FIG.  3    is a cross-sectional view showing a disk spring of the turbocharger. 
         FIG.  4 A  is a cross-sectional view showing a deformed state of the disk spring of  FIG.  3   , and  FIG.  4 B  is a cross-sectional view showing a deformed state of a disk spring of a comparative example. 
         FIG.  5    is another enlarged cross-sectional view showing the vicinity of a variable nozzle of the turbocharger. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. A turbocharger according to one aspect of the present disclosure includes a variable nozzle disposed between a turbine housing and a bearing housing and a spring having an annular shape. The spring is disposed between the variable nozzle and the bearing housing, and is configured to generate a biasing force that biases the variable nozzle away from the bearing housing to widen a spacing between the variable nozzle and the bearing housing in a rotation axis direction. The spring includes an outer peripheral portion that applies the biasing force to the variable nozzle and an inner peripheral portion that comes into contact with the bearing housing. The outer peripheral portion of the spring is located further away from the turbine housing than the inner peripheral portion of the spring in the rotation axis direction. 
     The spring may be a disk spring that exists along a conical surface of an imaginary cone having a rotation axis as a cone axis. In addition, the turbocharger of the present disclosure may further include a heat shield plate sandwiched between the variable nozzle and the spring in the rotation axis direction to shield the spring from heat of a turbine. The first contact point of the spring may be in contact with the heat shield plate. 
     In addition, the variable nozzle may include two nozzle rings arranged in the rotation axis direction. One of the two nozzle rings located on a side of the bearing housing may be pressed against a predetermined portion of the turbine housing in the rotation axis direction by a biasing force of the spring. 
       FIG.  1    is a cross-sectional view of a variable capacity turbocharger  1  taken along a cross section including a rotation axis H. The turbocharger  1  is applied to, for example, internal combustion engines for ships or vehicles. 
     As shown in  FIG.  1   , the turbocharger  1  includes a turbine  2  and a compressor  3 . The turbine  2  includes a turbine housing  4  and a turbine impeller  6  accommodated in the turbine housing  4 . The turbine housing  4  has a scroll passage  16  extending in a circumferential direction around the turbine impeller  6 . The compressor  3  includes a compressor housing  5  and a compressor impeller  7  accommodated in the compressor housing  5 . The compressor housing  5  has a scroll passage  17  extending in the circumferential direction around the compressor impeller  7 . 
     The turbine impeller  6  is provided at one end of a rotation shaft  14 , and the compressor impeller  7  is provided at the other end of the rotation shaft  14 . A bearing housing  13  is provided between the turbine housing  4  and the compressor housing  5 . The rotation shaft  14  is rotatably supported by the bearing housing  13  via a bearing  15 , and the rotation shaft  14 , the turbine impeller  6 , and the compressor impeller  7  integrally rotate around the rotation axis H as a rotating body  12 . 
     The turbine housing  4  is provided with an exhaust gas inlet (not shown) and with an exhaust gas outlet  10 . Exhaust gas discharged from an internal combustion engine (not shown) flows into the turbine housing  4  through the exhaust gas inlet, and flows into the turbine impeller  6  through the scroll passage  16  to rotate the turbine impeller  6 . Thereafter, the exhaust gas flows to the outside of the turbine housing  4  through the exhaust gas outlet  10 . 
     The compressor housing  5  is provided with an inlet port  9  and with an outlet port (not shown). When the turbine impeller  6  rotates as described above, the compressor impeller  7  rotates via the rotation shaft  14 . The rotating compressor impeller  7  suctions outside air through the inlet port  9 . The air is compressed while passing through the compressor impeller  7  and through the scroll passage  17 , and is discharged from the outlet port. The compressed air discharged from the outlet port is supplied to the internal combustion engine described above. 
     The turbine  2  of the turbocharger  1  will be further described. An “axial direction”, a “radial direction”, and a “circumferential direction” simply referred to in the following description mean a rotation axial direction (rotation axis H direction), a rotation radial direction, and a rotation circumferential direction of the turbine impeller  6 , respectively. 
     As shown in  FIG.  2   , the turbine  2  of the turbocharger  1  is provided with a nozzle passage  19  that connects the scroll passage  16  and the turbine impeller  6 . A plurality of movable nozzle vanes  21  are provided in the nozzle passage  19 . The plurality of nozzle vanes  21  are disposed at regular intervals on a circle around the rotation axis H. Each of the nozzle vanes  21  rotates synchronously around respective axes parallel to the rotation axis H. When the plurality of nozzle vanes  21  rotate as described above, a spacing between the nozzle vanes  21  adjacent to each other widens and narrows, so that an opening degree of the nozzle passage  19  is adjusted. 
     The turbine  2  includes a variable nozzle  20  for driving the nozzle vanes  21  as described above. The variable nozzle  20  is fitted inside the turbine housing  4 . The variable nozzle  20  includes the plurality of nozzle vanes  21  and two nozzle rings  23  and  27  that sandwich the nozzle vanes  21  therebetween in the axis direction. The two nozzle rings  23  and  27  are arranged in the axial direction, and the nozzle ring  23  (second nozzle ring) is disposed closer to a bearing housing  13  than the nozzle ring  27  (first nozzle ring). The nozzle rings  23  and  27  each have a ring shape around the rotation axis H, and are disposed to surround the turbine impeller  6  in the circumferential direction. A region sandwiched between the two nozzle rings  23  and  27  in the axial direction forms the nozzle passage  19  described above. Further, the variable nozzle  20  includes a drive mechanism  29  for driving the nozzle vanes  21 . The drive mechanism  29  is accommodated in a space between the nozzle ring  23  and the bearing housing  13 , and transmits a driving force from an external actuator (not shown) to the nozzle vanes  21 . 
     A heat shield plate  31  is provided between the turbine impeller  6  and the bearing housing  13 . The heat shield plate  31  shields the bearing housing  13  from radiant heat on a turbine housing  4  side of high temperature to suppress an increase in temperature of the bearing housing  13 . The heat shield plate  31  has an annular shape that surrounds the rotation shaft  14  in the circumferential direction. The heat shield plate  31  is fitted into a central opening of the nozzle ring  23  from a side of the bearing housing  13 . 
     A disk spring  35  (spring member) is sandwiched between the heat shield plate  31  and the bearing housing  13 . The disk spring  35  is disposed such that the rotation shaft  14  is inserted through a central hole of the disk spring  35 , and is disposed along a conical surface having the rotation axis H as an axis. One end portion of the disk spring  35  in the axial direction is in contact with the bearing housing  13 , and the other end portion of the disk spring  35  in the axial direction is in contact with the heat shield plate  31 . Then, the disk spring  35  biases the bearing housing  13  and the heat shield plate  31  away from each other in the axial direction. Details of the disk spring  35  will be described later. 
     The disk spring  35  biases the variable nozzle  20  and the heat shield plate  31  in the axial direction toward the turbine housing  4  side. Then, the variable nozzle  20  is pressed against the turbine housing  4  and is aligned in the axial direction by a biasing force of the disk spring  35 . The nozzle ring  23  is located between the bearing housing  13  and the nozzle ring  27  and is pressed against the turbine housing  4  in the rotation axis direction by the biasing force of the disk spring  35 . Specifically, of the two nozzle rings  23  and  27  of the variable nozzle  20 , the nozzle ring  23  located on the bearing housing  13  side includes a flange  23   a  formed to extend to an outer peripheral side. On the other hand, a protruding strip portion  4   a  that receives the flange  23   a  is formed on the turbine housing  4 . Then, an end surface of the flange  23   a  on a side of the turbine housing  4  is pressed against an end surface of the protruding strip portion  4   a  on a side of the bearing housing  13  by the biasing force of the disk spring  35 . The flange  23   a  is allowed to slide on the protruding strip portion  4   a  in the radial direction and a difference in thermal expansion in the radial direction between the variable nozzle  20  and the turbine housing  4  is absorbed. 
     The disk spring  35  will be further described.  FIG.  3    is a cross-sectional view schematically showing the vicinity of the disk spring  35  inside the turbocharger  1 . In  FIG.  3   , the left side of the drawing is the turbine housing  4  side, the right side is the bearing housing  13  side, and a shape of the disk spring  35  is exaggeratedly depicted compared to the actual shape. 
     As shown in  FIG.  3   , the disk spring  35  exists along a conical surface of an imaginary cone T. The imaginary cone T is a cone having the rotation axis H as a cone axis, and a cone bottom surface Tb of the imaginary cone T is located closer to the bearing housing  13  side than a cone apex Ta. 
     As shown in  FIG.  2   , a contact point on a radially outer periphery of the disk spring  35  (hereinafter, referred to as a “first contact point P1”) is in contact with the heat shield plate  31 . In addition, a contact point on a radially inner periphery of the disk spring  35  (hereinafter, referred to as a “second contact point P2”) is in contact with the bearing housing  13 . Then, the first contact point P1 at which the disk spring  35  comes into contact with the heat shield plate  31  is located closer to the bearing housing  13  side than the second contact point P2 at which the disk spring  35  comes into contact with the bearing housing  13 . The first contact point P1 is located further away from the turbine housing  4  than the second contact point P2 in the rotation axis direction. 
     A protruding strip portion  31   a  protruding in the axial direction toward the bearing housing  13  is formed on a surface facing the bearing housing  13  of an outer peripheral edge portion of the heat shield plate  31  such that the heat shield plate  31  comes into contact with the first contact point P1 of the disk spring  35 . The protruding strip portion  31   a  extends further to the bearing housing  13  than the second contact point P2 of the disk spring  35 , and a tip of the protruding strip portion  31   a  is in contact with the first contact point P1 of the disk spring  35 . 
       FIG.  4 A  is a cross-sectional view showing a deformed state of the disk spring  35 .  FIG.  4 B  is a cross-sectional view showing a deformed state of a disk spring  85  of the comparative example (for example, described in Japanese Unexamined Patent Publication No. 2013-68153 described above), when applied to the turbocharger  1  for comparison. In  FIGS.  4 ( a ) and  4 ( b ) , the left side of the drawings is the turbine housing  4  side, the right side is the bearing housing  13  side, and in each drawing, shapes of the disk springs  35  and  85  are exaggeratedly depicted compared to the actual shapes. 
     As shown in  FIG.  4 A , the disk spring  35  receives a reaction force F1 that pushes the first contact point P1 toward the bearing housing  13  side, from the heat shield plate  31 . In addition, the disk spring  35  receives a reaction force F2 that pushes the second contact point P2 toward a variable nozzle  20  side, from the bearing housing  13 . As indicated by a chain double-dashed line in  FIG.  4 A , the disk spring  35  is elastically deformed by these reaction forces F1 and F2 such that the first contact point P1 and the second contact point P2 move away from each other in the axial direction. Furthermore, the disk spring  35  has a repulsive force that tries to restore the deformation, and as described above, biases the variable nozzle  20  and the bearing housing  13  to widen a spacing therebetween in the axial direction. The disk spring  35  is configured to generate a biasing force that biases the variable nozzle  20  away from the bearing housing  13  to widen a spacing between the variable nozzle  20  and the bearing housing  13  in a rotation axis direction. The disk spring  35  includes an outer peripheral portion that applies the biasing force to the variable nozzle  20  and an inner peripheral portion that comes into contact with the bearing housing  13 . The outer peripheral portion of the disk spring  35  is located further away from the turbine housing  4  than the inner peripheral portion of the disk spring  35  in the rotation axis direction. Namely, the disk spring  35  is used in a state where the disk spring  35  is elastically deformed to extend in the axial direction by receiving a tensile load in the axial direction. In such a manner, the disk spring  35  is used in a load state opposite that of the ordinary disk spring that is elastically deformed to contract in the axial direction by receiving a compressive load in the axial direction. As described above, the variable nozzle  20  is pressed against the turbine housing  4  and is aligned in the axial direction by the biasing force of the disk spring  35 . 
     On the other hand, a case where the disk spring  85  of the comparative example shown in  FIG.  4 B  is applied to the turbocharger  1  will be described. In this case, as shown in  FIG.  4 B , the disk spring  85  receives the reaction force F1 that pushes an outer peripheral side  85   a  toward the bearing housing  13 , from the heat shield plate  31 . In addition, the disk spring  85  receives the reaction force F2 that pushes an inner peripheral side  85   b  toward the variable nozzle  20  side, from the bearing housing  13 . As indicated by a chain double-dashed line in  FIG.  4 B , the disk spring  85  is elastically deformed by these reaction forces F1 and F2 such that the outer peripheral side  85   a  and the inner peripheral side  85   b  approach each other in the axial direction. Furthermore, the disk spring  85  has a repulsive force that tries to restore the deformation, and as described above, biases the variable nozzle  20  and the bearing housing  13  to widen the spacing therebetween in the axial direction. As described above, the variable nozzle  20  is pressed against the turbine housing  4  and is aligned in the axial direction by a biasing force of the disk spring  85 . 
     Subsequently, actions and effects obtained by the turbocharger  1  of the present example including the disk spring  35  described above will be described. In the turbocharger  1  that is in operation, the variable nozzle  20  side is at high temperature due to being affected by high temperature gas, whereas the bearing housing  13  side is at relatively low temperature due to being cooled by water cooling, oil cooling, or the like. For example, a cooling water passage  13   a  (refer to  FIG.  2   ) for cooling is formed in the bearing housing  13 . 
     Under this condition, when the disk spring  85  of the comparative example in  FIG.  4 B  is used, the outer peripheral side  85   a  of the disk spring  85  comes into contact with the heat shield plate  31  on the variable nozzle  20  side and is at relatively high temperature, whereas the inner peripheral side  85   b  comes into contact with the bearing housing  13  and is at relatively low temperature. Accordingly, the disk spring  85  has a temperature distribution in which the outer peripheral side is at high temperature and the inner peripheral side is at low temperature. Then, according to this temperature distribution, the outer peripheral side of the disk spring  85  extends in the circumferential direction compared to the inner peripheral side, and as a result, thermal deformation occurs in the disk spring  85  in the same direction as that of the above-described deformation by the reaction forces F1 and F2 (chain double-dashed line in  FIG.  4 B ). Then, a spring load with which the disk spring  85  biases the variable nozzle  20  decreases due to the thermal deformation. 
     On the other hand, in the turbocharger  1  of the present example in which the disk spring  35  is used, similarly to the above description, the first contact point P1 on the outer peripheral side is at relatively high temperature, and the second contact point P2 on the inner peripheral side is at relatively low temperature, so that the disk spring  35  has a temperature distribution in which the outer peripheral side is at high temperature and the inner peripheral side is at low temperature similarly to the above description. Then, according to this temperature distribution, thermal deformation occurs in the disk spring  35  in a direction opposite that of the above-described deformation by the reaction forces F1 and F2 (chain double-dashed line in  FIG.  4 A ). Namely, the thermal deformation of the disk spring  35  in this case is deformation in a direction in which the reaction forces F1 and F2 are pushed back. Then, a spring load with which the disk spring  35  biases the variable nozzle  20  further increases due to the thermal deformation. Therefore, according to the turbocharger  1  of the present example, a reduction in the spring load of the disk spring  35  at high temperature may be suppressed. 
     In addition, in the case of employing the disk spring  85  of  FIG.  4 B , it may be needed to repeatedly perform a thermal deformation analysis while finely adjusting the shape of the disk spring  85 , and to design the shape of the disk spring  85  so as to reduce the reduction in the spring load while also considering influences such as thermal deformation of components around the disk spring  85 . In addition, since the above-described design loop may be needed for each model change of the turbocharger  1 , it may not be said that efficiency of the design process is good. On the other hand, according to the disk spring  35  of the present example, such a complicated design process may be simplified. 
     In addition, according to the disk spring  35  of the present example, since radial stress generated in the disk spring  35  is tensile stress in the deformation by the reaction forces F1 and F2, there is also an effect that buckling distortion of the disk spring  35  is unlikely to occur. 
     In addition, in the turbocharger  1  of the present example, the heat shield plate  31  exists to reduce heat input to the disk spring  35 . As a result, a reduction in the Young’s modulus of a material of the disk spring  35  due to an increase in temperature is suppressed, and a reduction in the spring load is further suppressed. In addition, the possibility of occurrence of the creeping of the disk spring  35  due to an increase in temperature, a reduction in yield stress, or the like is reduced. 
     In addition, in the turbocharger  1  of the present example, the alignment of the variable nozzle  20  in the axial direction is achieved by pressing of the flange  23   a  of the nozzle ring  23  against the protruding strip portion  4   a  of the turbine housing  4 . During operation of the turbocharger  1 , the protruding strip portion  4   a  is displaced by thermal deformation of the turbine housing  4 , and the variable nozzle  20  is deformed according to the deformation of the protruding strip portion 4a. 
     Here, it is considered that during operation of the turbocharger  1 , among portions of the turbine housing  4 , the closer a portion is to a joint with the bearing housing  13 , the smaller a displacement of the portion due to thermal deformation is. Among other parts of the variable nozzle  20 , the nozzle ring  23  of the variable nozzle  20  is located relatively close to the bearing housing  13 . For this reason, the protruding strip portion  4   a  of the turbine housing  4  is also located close to the joint with the bearing housing  13 . Therefore, during operation of the turbocharger  1 , a displacement of the protruding strip portion  4   a  is kept relatively small, and as a result, deformation of the variable nozzle  20  due to the displacement of the protruding strip portion  4   a  is also kept relatively small. 
     The turbocharger of the present disclosure can be implemented in various modes with various changes or improvements made based on the knowledge of those skilled in the art, including the example described above. For example, in the example described above, the turbocharger  1  includes the heat shield plate  31 , but as shown in  FIG.  5   , the heat shield plate  31  may be omitted and the spring member  35  may come into direct contact with the nozzle ring  23 . In this case, the shape of the nozzle ring  23  is changed, so that the spring member  35  comes into contact with the nozzle ring  23  (variable nozzle side) at the first contact point P1 on the outer peripheral side of the spring member  35 , and comes into contact with the bearing housing  13  at the second contact point P2 on the inner peripheral side, and the first contact point P1 is located closer to the bearing housing side than the second contact point P2 in the rotation axis direction. For example, in this case, instead of the protruding strip portion  31   a  described above, a protruding strip portion which extends further to the bearing housing  13  than the second contact point P2 of the spring member  35  and of which a tip comes into contact with the first contact point P1 of the spring member  35  may be provided on the nozzle ring  23 . The spring member  35  comes into contact with the nozzle ring  23  at a first contact point P1 located on an outer peripheral portion of the spring member  35 , and comes into contact with the bearing housing  13  at a second contact point P2 located on an inner peripheral portion of the spring member  35 . The first contact point P1 is located further away from the turbine housing  4  than the second contact point P2 in the rotation axis direction.