Patent Publication Number: US-11047295-B2

Title: Manufacturing method for turbocharger

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2017-201989 filed on Oct. 18, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to a manufacturing method for a turbocharger. 
     2. Description of Related Art 
     Japanese Unexamined Patent Application Publication No. 2014-5789 (JP 2014-5789 A) discloses a turbocharger provided with a wastegate valve that includes a shaft driven by an actuator, and a valve body that comes into contact with a bearing surface and closes a wastegate port. In the turbocharger, the valve body and the shaft are welded to each other in a state where a contact surface of the valve body is brought into contact with the bearing surface in order to eliminate a gap between the valve body and the bearing surface caused by manufacturing tolerance. 
     SUMMARY 
     There is a gap between a bush supporting the shaft, and the shaft in order to allow the shaft to revolve. Therefore, even when the shaft and the valve body are fixed to each other in the state where the contact surface of the valve body is brought into contact with the bearing surface and a gap caused by manufacturing tolerance is eliminated as described above, the shaft can be tilted inside the bush as the actuator is driven to drive the wastegate valve and cause displacement of the valve body. 
     A turbocharger to which a manufacturing method for a turbocharger according to the disclosure is applied includes a wastegate valve. The wastegate valve includes a shaft-side member and a valve body-side member. The shaft-side member includes a shaft that is supported by a bush provided in a turbine housing so that the shaft is able to revolve. The valve body-side member includes a valve body that sits on a bearing surface of the turbine housing and closes a wastegate port. In the turbocharger, the wastegate valve is configured to open and close as the shaft-side member is driven by an actuator that is provided outside the turbine housing. The manufacturing method for the turbocharger includes: connecting the shaft-side member to the actuator while the shaft-side member is inserted into the bush; combining the shaft-side member with the valve body-side member; and fixing the shaft-side member to the valve body-side member in the state where the wastegate valve is driven by the actuator so as to close the wastegate valve and a contact surface of the valve body is pressed against the bearing surface. 
     With the manufacturing method, the shaft-side member and the valve body-side member are fixed to each other in the state where the shaft is tilted inside the bush as the actuator is driven, and the contact surface of the valve body is pressed against the bearing surface. Therefore, the shaft-side member and the valve body-side member are fixed to each other in the same positions as those when the actuator is driven to close the wastegate valve. Hence, even if there were gaps among parts including a gap between the bush and the shaft and manufacturing tolerance, it is possible to assemble the wastegate valve in a state where gaps thus caused are eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a perspective view of a turbocharger; 
         FIG. 2  is a partial sectional view of a turbine housing; 
         FIG. 3  is a top view of a wastegate valve; 
         FIG. 4  is a sectional view taken along the arrows IV-IV in  FIG. 3 ; 
         FIG. 5  is a flowchart showing a process flow for assembly of the wastegate valve; 
         FIG. 6  is an enlarged sectional view of the wastegate port and its vicinity; and 
         FIG. 7  is a sectional view taken along the arrows VII-VII in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An embodiment of a turbocharger and a manufacturing method for the turbocharger is described below with reference to  FIG. 1  to  FIG. 7 . As shown in  FIG. 1 , a turbocharger  100  is structured by combining a compressor housing  110 , a bearing housing  120 , and a turbine housing  130 . The compressor housing  110  is a housing that accommodates a compressor wheel, and the turbine housing  130  is a housing that accommodates a turbine wheel. The bearing housing  120  is a housing that supports a connecting shaft that connects the compressor wheel and the turbine wheel. 
     The bearing housing  120  is fastened to the compressor housing  110  by bolts. The turbine housing  130  is assembled to the bearing housing  120  by a clamp  140 . 
     As shown in  FIG. 2 , a turbine wheel  135  is accommodated in the turbine housing  130 , and a scroll passage  131  is formed in the turbine housing  130 . The scroll passage  131  extends so as to surround the turbine wheel  135 . Exhaust gas that passes in the scroll passage  131  and is blown on the turbine wheel  135  is discharged to an exhaust gas passage from the turbine housing  130  through a discharge passage  132 . 
     In the turbocharger  100 , as exhaust gas that passes in the scroll passage  131  is blown onto the turbine wheel  135 , the turbine wheel  135  rotates. As the turbine wheel  135  rotates, the compressor wheel connected with the turbine wheel  135  through the connecting shaft rotates, and supercharging of intake air happens. 
     As shown in  FIG. 2 , the turbine housing  130  is provided with a wastegate port  133 . The wastegate port  133  is a passage that circumvents the turbine wheel  135  and connects the scroll passage  131  and the discharge passage  132  with each other, and allows exhaust gas to flow while circumventing the turbine wheel  135 . The wastegate port  133  has a circular section. 
     The turbocharger  100  includes a wastegate valve  10 . The wastegate valve  10  has a disc-shaped valve plate  12  that closes the wastegate port  133 , and the wastegate valve  10  revolves around a shaft  15  so as to open and close the wastegate port  133 . The shaft  15  is supported by a bush provided in the turbine housing  130  so that the shaft  15  is able to revolve. 
     As shown in  FIG. 2 , when the valve plate  12  is in contact with a bearing surface  130   a  of the turbine housing  130 , the wastegate port  133  is closed by a contact surface  12   a  of the valve plate  12 . Meanwhile, when the contact surface  12   a  of the valve plate  12  is separated from the wastegate port  133  and the wastegate port  133  is open, in other words, when the wastegate valve  10  is open, exhaust gas that has passed in the scroll passage  131  flows into the discharge passage  132  through the wastegate port  133 . As exhaust gas that has passed in the scroll passage  131  flows into the discharge passage  132  through the wastegate port  133 , an amount of exhaust gas blown onto the turbine wheel  135  is reduced. Therefore, when the wastegate valve  10  is open, rotation of the turbine wheel  135  and the compressor wheel is restrained, thus restraining supercharging. 
     In the turbocharger  100 , the shaft  15  of the wastegate valve  10  goes through the turbine housing  130  and extends to an outer side of the turbine housing  130 . As shown in  FIG. 1  and  FIG. 2 , a plate-shaped wastegate-side link arm  25  is fixed to a distal end portion of the shaft  15  projecting to the outer side of the turbine housing  130 . A columnar connecting pin  26  is fixed at a position that is separated from the portion of the wastegate-side link arm  25  where the shaft  15  is fixed so that the center axis of the connecting pin  26  becomes parallel to the center axis of the shaft  15 . 
     Also, as shown in  FIG. 1 , an actuator  20  for driving the wastegate valve  10  is fixed to the compressor housing  110 . A motor is incorporated in the actuator  20  and drives a rotating shaft  22 . A plate-shaped actuator-side link arm  23  is fixed to the rotating shaft  22 . The connecting pin  26  is fixed at a position separated from the portion of the actuator-side link arm  23  where the rotating shaft  22  is fixed so that the center axis of the connecting pin  26  becomes parallel to the center axis of the rotating shaft  22 . 
     In the turbocharger  100 , a driving rod  28  connects the actuator-side link arm  23  and the wastegate-side link arm  25  with each other. In both end portions of the driving rod  28 , through-holes are provided, respectively. A diameter of each of the through-holes is slightly larger than a diameter of each of the connecting pins  26 . A first end of the driving rod  28  is assembled to the wastegate-side link arm  25  by inserting the connecting pin  26  into the through-hole, and an E-ring  24  is fitted into a groove provided in a distal end portion of the connecting pin  26 , thus retaining the first end of the driving rod  28 . 
     A second end of the driving rod  28  is assembled to the actuator-side link arm  23  by inserting the connecting pin  26  into the through-hole, and the E-ring  24  is fitted into a groove provided in a distal end portion of the connecting pin  26 , thus retaining the second end of the driving rod  28 . 
     Hence, when the actuator  20  drives the rotating shaft  22  and the actuator-side link arm  23  revolves around the rotating shaft  22 , driving force of the actuator  20  is transmitted to the wastegate-side link arm  25  through the driving rod  28 . Then, the wastegate-side link arm  25  revolves around the shaft  15 , and the wastegate valve  10  is driven to move closer to or away from the wastegate port  133 . In the turbocharger  100 , it is possible to open and close the wastegate port  133  by driving the actuator  20  as described above. 
     Next, with reference to  FIG. 3  and  FIG. 4 , a structure of the wastegate valve  10  is described in detail. As shown in  FIG. 3 , the wastegate valve  10  is made by assembling a valve body  11  to a swing arm  14  provided with the shaft  15 . The valve body  11  is assembled to a lever  16  of the swing arm  14 . 
     The lever  16  connected with the shaft  15  is curved, and a portion of the lever  16  on the opposite side from the portion of the lever  16  connected with the shaft  15  has a plate shape. The valve body  11  is fixed to the plate-shaped portion, and the portion where the valve body  11  is fixed is at a position that is shifted from the center axis of the shaft  15  in a direction orthogonal to the center axis. 
     Further, the shaft  15  includes a large diameter portion  15   a  connected with the lever  16 , and a small diameter portion  15   b  having a diameter smaller than that of the large diameter portion  15   a . The large diameter portion  15   a  and the small diameter portion  15   b  are connected with each other so that the center axes thereof coincide with each other. In the turbocharger  100 , the large diameter portion  15   a  of the shaft  15  is supported by the bush fitted into the turbine housing  130  so that the large diameter portion  15   a  is able to revolve. Then, wastegate-side link arm  25  is fixed to the small diameter portion  15   b  projecting to the outer side of the turbine housing  130 . Thus, the wastegate valve  10  revolves around the shaft  15 , and the valve body  11  thus opens and closes the wastegate port  133 . 
     As shown in  FIG. 4 , the valve body  11  is fixed to the lever  16  in a state where a valve stem  13  is inserted into a through-hole  16   a  provided in the lever  16 . The valve stem  13  extends from a back surface  12   b  of the valve plate  12  perpendicularly to the valve plate  12 . The back surface  12   b  is on the opposite side of valve plate  12  from the contact surface  12   a . The valve stem  13  is provided in the center of the valve plate  12 . 
     As shown in  FIG. 3 , the through-hole  16   a  includes two curved surface portions  16   c  and two planar portions  16   b . The two planar portions  16   b  link these two curved surface portions  16   c  and are parallel to a plane orthogonal to the center axis of the shaft  15 . The curved surface portions  16   c  are semicircular curved surfaces that are projecting outwardly in a radial direction of the through-hole  16   a.    
     As described above, because the planar portions  16   b  are present between the two semicircular curved surface portions  16   c , the through-hole  16   a  of the lever  16  is a long hole having a longitudinal direction that is parallel to the contact surface  12   a  of the valve plate  12  and also orthogonal to the center axis of the shaft  15 . 
     Also, as shown in  FIG. 4 , a portion of the through-hole  16   a  on the valve plate  12  side has a tapered surface  16   d  that is inclined more largely as the tapered surface  16   d  becomes closer to the valve plate  12 . A diameter of the valve stem  13  is slightly smaller than a distance between the two planar portions  16   b  of the through-hole  16   a . Although the valve stem  13  is almost columnar, portions facing the planar portions  16   b  of the through-hole  16   a  are flat. 
     Thus, as shown in  FIG. 4 , in a state where the valve stem  13  is inserted into the through-hole  16   a , a gap between each of the planar portions  16   b  of the through-hole  16   a  and the valve stem  13  is extremely small. Meanwhile, as shown in  FIG. 3 , there is a larger gap between each of the curved surface portions  16   c  of the through-hole  16   a  and the valve stem  13  than the gap between each of the planar portions  16   b  of the through-hole  16   a  and the valve stem  13 . 
     Next, description is given regarding the manufacturing method for the turbocharger  100 , especially a method for assembling the wastegate valve  10 . As described earlier, the wastegate valve  10  includes the swing arm  14  that is a shaft-side member including the shaft  15 , and the valve body  11  including the valve plate  12  and the valve stem  13 . 
     When the wastegate valve  10  is assembled, first of all, the swing arm  14  that is not yet combined with the valve body  11  is attached to the turbine housing  130 . Specifically, as shown in  FIG. 5 , as a process in step S 10 , the shaft  15  of the swing arm  14  is inserted into the bush that is fitted into the turbine housing  130 . 
     Then, as a process in step S 20 , the wastegate-side link arm  25  is fixed to the small diameter portion  15   b  of the shaft  15  that projects to the outer side of the turbine housing  130 . The wastegate-side link arm  25  is provided with the through-hole into which the small diameter portion  15   b  of the shaft  15  is fitted. As the small diameter portion  15   b  is welded in a state where the small diameter portion  15   b  is fitted into the through-hole, the wastegate-side link arm  25  is fixed to the shaft  15 . 
     Next, as a process in step S 30 , the link arms  23 ,  25  are connected with each other through the driving rod  28 . Specifically, the first end of the driving rod  28  is assembled to the wastegate-side link arm  25  by inserting the connecting pin  26  into the through-hole, and the E-ring  24  is fitted into the groove of the connecting pin  26  so as to retain the first end of the driving rod  28 . Also, the second end of the driving rod  28  is assembled to the actuator-side link arm  23  by inserting the connecting pin  26  into the through-hole, and the E-ring  24  is fitted into the groove of the connecting pin  26  so as to retain the second end of the driving rod  28 . Thus, the link arms  23 ,  25  are connected with each other by the driving rod  28  and driving force of the actuator  20  is transmitted to the swing arm  14 . 
     Next, as a process in step S 40 , the swing arm  14  and the valve body  11  are combined. Specifically, the valve stem  13  of the valve body  11  is inserted into the through-hole  16   a  of the swing arm  14 . In this stage, the swing arm  14  and the valve body  11  are not fixed to each other, and thus allowed to move relative to each other. 
     Next, as a process in step S 50 , the actuator  20  is driven in a valve closing direction. In other words, the actuator  20  is driven in a direction of closing the wastegate valve  10 . 
     As shown in  FIG. 6  and  FIG. 7 , by driving the actuator  20  in the valve closing direction as described above, the contact surface  12   a  of the valve plate  12  comes into contact with the bearing surface  130   a , and the valve plate  12  is thus pressed against the bearing surface  130   a  so that the valve plate  12  closes the wastegate port  133 .  FIG. 6  is a sectional view taken in a direction of arrows VI-VI in  FIG. 3 , and  FIG. 7  is a sectional view taken along the arrows VII-VII in  FIG. 6 . 
     As stated above, in the wastegate valve  10 , the through-hole  16   a  provided in the lever  16  is a long hole, and a gap is created between each of the curved surface portions  16   c  of the through-hole  16   a  and the valve stem  13 . Therefore, the valve body  11  of the wastegate valve  10  is able to tilt with respect to the lever  16  of the swing arm  14  at the stage of the process in the step S 50 . 
     Thus, as shown in  FIG. 6 , when the wastegate valve  10  is driven to a valve closing side, the valve body  11  is tilted with respect to the lever  16 , and the contact surface  12   a  of the valve plate  12  comes into close contact with the bearing surface  130   a  of the turbine housing  130 . Thus, the valve body  11  closes the wastegate port  133  tightly. 
     As shown in  FIG. 7 , the actuator  20  is pulling the driving rod  28  in a direction shown by an arrow. Therefore, when there is a gap between the bush  150  and the shaft  15 , the shaft  15  is tilted inside the bush  150 . 
     Next, as a process in step S 60 , the valve stem  13  of the valve body  11  is welded to the lever  16  in the state where the actuator  20  is driven in the valve closing direction, and the contact surface  12   a  of the valve body  11  is pressed against the bearing surface  130   a  as described above. Thus, the swing arm  14  and the valve body  11  are fixed to each other. 
     In the manufacturing method for the turbocharger, the wastegate valve  10  is assembled through the steps S 10  to S 60  as described above. Among the processes in the step S 10  to S 60 , the processes in the steps S 10  to S 30  correspond to a connecting process in which the swing arm  14  is inserted into the bush  150  and is thus connected with the actuator  20 , and the process in the step S 40  corresponds to a combining process in which the swing arm  14  and the valve body  11  are combined. The process of the step S 60  corresponds to a fixing process in which the swing arm  14  and the valve body  11  are fixed to each other. 
     Next, actions and effects of the manufacturing method are described. (1) In the manufacturing method, the wastegate valve  10  arranged in the turbine housing  130  through the connecting process (step S 10  to step S 30 ) and the combining process (step S 40 ) is driven by the actuator  20  to the valve closing side (step S 50 ). Then, the fixing process (step S 60 ) is carried out in the state where the contact surface  12   a  of the valve body  11  is pressed against the bearing surface  130   a . With the manufacturing method, the shaft  15  is tilted inside the bush  150  as the actuator  20  is driven, and the swing arm  14  and the valve body  11  are fixed to each other in the state where the contact surface  12   a  of the valve body  11  is pressed against the bearing surface  130   a . Therefore, the swing arm  14  and the valve body  11  are fixed to each other in the same positions as those when actuator  20  is driven to close the wastegate valve  10 . Accordingly, even if there were gaps among parts including the gap between the bush  150  and the shaft  15 , and manufacturing tolerance, it is possible to assemble the wastegate valve  10  in a state where gaps thus caused are eliminated. As a result, it is possible to manufacture the turbocharger  100  that is able to close the wastegate port  133  tightly in an actual usage state. 
     The foregoing embodiment may be modified as follows and carried out. The embodiment and modified examples below may be combined with one another and carried out unless there is technical inconsistency. 
     The order of the combining process and the connecting process may be changed. In other words, the combining process (step S 40 ) may be carried out first, and then the connecting process (step S 10  to step S 30 ) may be carried out in a state where the swing arm  14  and the valve body  11  are combined. 
     In the embodiment, the wastegate valve  10  is made of two members, the shaft-side member is the swing arm  14 , and the valve body-side member is the valve body  11  itself. However, the manufacturing method may also be applied to a wastegate valve in which the valve body-side member is a member in which the valve body  11  and the lever  16  are integrated, and the shaft-side member is the shaft  15  only. This means that the manufacturing method only needs to include the connecting process in which the shaft-side member is inserted into the bush  150  and thus connected with the actuator  20 , the combining process in which the shaft-side member is combined with the valve body-side member, and the fixing process in which the shaft-side member and the valve body-side member are fixed to each other. The same effects as (1) stated above are obtained as long as the wastegate valve  10  that is arranged in the turbine housing  130  through the connecting process and the combining process is driven by the actuator  20  to the valve closing side, and then the fixing process is carried out in the state where the contact surface  12   a  of the valve body  11  is pressed against the bearing surface  130   a.    
     Further, the shaft-side member may be a member in which the wastegate-side link arm  25  and the shaft  15  are integrated. However, in a case of a structure in which the shaft  15  is fixed to the valve body-side member, torque caused by pressure of exhaust gas that flows in the wastegate port  133  when the wastegate valve  10  is open acts as stress that shears a fixing portion between the lever  16  and the shaft  15 . 
     On the contrary, as described in the embodiment above, with the structure in which the wastegate valve  10  is divided into the swing arm  14  and the valve body  11 , and the valve stem  13  is inserted into the through-hole  16   a  of the lever  16  so that the swing arm  14  and the valve body  11  are combined, pressure of exhaust gas acts in a direction of pressing the valve plate  12  against the lever  16 . Therefore, stress caused by pressure of exhaust gas is dispersed instead of concentrating only on a fixing portion between the lever  16  and the valve stem  13 . Therefore, compared to the structure in which the shaft  15  is fixed to the valve body-side member, durability is improved. 
     The actuator  20  does not need to be an electric actuator  20 . For example, the actuator  20  may be an actuator driven by use of pneumatic pressure, or an actuator driven by use of hydraulic pressure. 
     The technical idea that is understood from the embodiment and the modified examples is described. A turbocharger includes a wastegate valve that opens and closes a wastegate port, and an actuator that drives the wastegate valve. In the turbocharger, the wastegate valve includes a valve body and a swing arm. The valve body is made of a valve plate and a valve stem. The valve plate comes into contact with a bearing surface of a turbine housing and closes the wastegate port, and the valve stem is provided in a back surface of the valve plate. The back surface is on the opposite side of the valve plate from a contact surface that comes into contact with the bearing surface. The swing arm is made of a shaft and a lever. The shaft is supported by a bush provided in a turbine housing so that the shaft is able to revolve, and the lever has a through-hole into which the valve stem is inserted. The valve stem that is inserted into the through-hole, and the lever are fixed to each other at positions when the actuator is driven so that the wastegate valve closes the wastegate port.