Turbocharger

Abstract

To provide a turbocharger capable of suppressing repetitive turn of a vane shaft which occur at the time of exhaust braking, and also suppressing the wear of the vane shaft.SOLUTION: A turbocharge 10 includes a turbine wheel, a plurality of variable nozzle vanes 30 provided turnably around a vane shaft for adjusting the flow speed of an exhaust gas to the turbine wheel, an annular first plate for turnably supporting the vane shaft 31 of the plurality of variable nozzle vanes 30, and an annular second plate arranged so as to sandwich the variable nozzle vanes 30 together with the first plate. Herein, a spring member is locked to the vane shaft 31 and the first plate. The spring member gives energizing force to the vane shaft 31 in the direction of opening the variable nozzle vane 30.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a turbocharger. [Background technology]

[0002] As a conventional technique related to turbochargers, for example, a variable displacement mechanism disclosed in Patent Document 1 is known. In the variable displacement mechanism disclosed in Patent Document 1, a variable nozzle mechanism changes the nozzle opening by rotating multiple nozzle vanes of a turbocharger. The variable nozzle mechanism includes a drive ring that rotates by an external driving force, a nozzle link plate that is provided on the vane shaft of the nozzle vane and rotates together with the nozzle vane due to the rotation of the drive ring, and an engagement portion that converts the rotation of the drive ring into the rotation of the nozzle link plate.

[0003] The engagement portion has a groove provided in the drive ring and a nozzle link plate head portion that is fitted into the groove with a clearance and is displaced when pushed by the groove. The amount of clearance varies according to the nozzle opening. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-8819 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the variable displacement mechanism disclosed in Patent Document 1, the engagement portion is fitted with a groove provided in the drive ring and a groove provided in the nozzle link plate with a clearance. Therefore, when an exhaust brake valve is provided downstream of the turbocharger, when the exhaust brake is used, the exhaust gas downstream of the turbocharger becomes higher in pressure than the exhaust gas upstream of the turbocharger. At this time, the nozzle vane rotates in a closing direction due to the high-pressure exhaust gas downstream. When the exhaust brake is used, the vane shaft of the nozzle vane rotates repeatedly according to the clearance of the engagement portion with respect to the groove of the nozzle link plate. This repeated rotation of the vane shaft causes a problem of accelerating wear of the vane shaft. Incidentally, in the variable displacement mechanism of Patent Document 1, the amount of clearance at the engagement portion is configured to vary according to the nozzle opening of the turbine, but even when the clearance is small, the repeated rotation of the vane shaft cannot be avoided.

[0006] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a turbocharger that can suppress repeated rotation of the vane shaft that occurs during exhaust braking and suppress wear on the vane shaft. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a turbocharger comprising a turbine wheel, a plurality of variable nozzle vanes rotatably arranged around a vane shaft and adjusting the flow speed of exhaust gas to the turbine wheel, a circular first plate rotatably supporting the vane shaft of the plurality of variable nozzle vanes, and a circular second plate arranged to sandwich the variable nozzle vanes together with the first plate, the turbocharger having a spring member engaged with the vane shaft and the first plate, the spring member applying a biasing force in a direction to open the variable nozzle vanes relative to the vane shaft.

[0008] In the present invention, a spring member connects the vane shaft and the first plate. The spring member applies a biasing force to the vane shaft in a direction to open the variable nozzle vane. Therefore, even if the exhaust brake is used and the variable nozzle vane receives a force in a closing direction, the rotation of the vane shaft in the closing direction of the variable nozzle vane is restricted. In other words, even if the exhaust brake is used and the exhaust gas pressure fluctuates, the variable nozzle vane is biased in the opening direction by the biasing force of the spring member, and the position of the vane shaft is maintained. As a result, repeated rotation of the vane shaft is prevented, and wear of the vane shaft can be suppressed.

[0009] The above turbocharger may also be configured to have a variable nozzle mechanism that rotates the vane shaft to open and close the variable nozzle vane, and an actuator that operates the variable nozzle mechanism, and the biasing force of the spring member may be greater than the fluid pressure of the exhaust gas and less than the driving force of the actuator. In this case, the biasing force of the spring member is greater than the fluid pressure of the exhaust gas and less than the driving force of the actuator. Therefore, the variable nozzle mechanism can adjust the opening of the variable nozzle vane by operating the actuator. Furthermore, even if the fluid pressure of the exhaust gas fluctuates, the vane shaft is not rotated in the closing direction by the exhaust gas.

[0010] Also, in the above turbocharger, the spring member may be a spiral spring, one end of the spiral spring being engaged with the vane shaft, and the other end of the spiral spring being engaged with the first plate. In this case, since the spring member is a spiral spring, it is possible to apply a biasing force to the vane shaft in a direction that opens the variable nozzle vane.

[0011] Also, in the above turbocharger, the spring member may be a leaf spring, a plurality of the leaf springs may be arranged circumferentially around the vane shaft, one end of each of the leaf springs may be engaged with the vane shaft, and the other end of each of the leaf springs may be engaged with the first plate. In this case, the spring member is a leaf spring, and multiple leaf springs are arranged circumferentially around the vane shaft, so that variation in the spring force of the spring member can be suppressed and the concentricity of the axial hole in the first plate and the axial center of the vane shaft can be increased.

[0012] Also, in the above turbocharger, the first plate may have a plate body and a cylindrical ring guide portion formed concentrically with the vane shaft, and one end of the spring member may be engaged with the vane shaft, and the other end of the spring member may be engaged with the ring guide portion. In this case, a cylindrical ring guide is formed on the plate body concentrically with the vane shaft. One end of the spring member is connected to the vane shaft, and the other end of the spring member is connected to the ring guide portion. Therefore, the ring guide portion can easily protect the spring member from foreign matter, etc. In addition, since the ring guide is formed concentrically with the vane shaft, the connection position of the spring member can be freely set in the circumferential direction of the vane shaft, and is not subject to any restrictions. Effect of the Invention

[0013] According to the present invention, it is possible to provide a turbocharger that can suppress repeated rotation of the vane shaft that occurs during exhaust braking and suppress wear of the vane shaft. [Brief description of the drawings]

[0014] [Figure 1] 1 is a vertical sectional view showing a schematic configuration of a turbocharger according to a first embodiment. [Diagram 2] FIG. 2 is a rear view of the variable nozzle vane drive mechanism in the turbocharger. [Diagram 3] 1 is a front view of a variable nozzle vane in a turbocharger. [Figure 4] FIG. 2 is an enlarged vertical cross-sectional view of a main portion of the turbocharger. [Diagram 5] 5 is a view taken along line AA in FIG. 4. [Figure 6] FIG. 6 is an enlarged view of a main portion of a turbocharger according to a second embodiment. [Figure 7] 1A is an enlarged view of a main portion of a turbocharger according to a first modified example, and FIG. 1B is an enlarged view of a main portion of a turbocharger according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (First embodiment) A turbocharger according to a first embodiment will be described below with reference to the drawings. The turbocharger of this embodiment is an on-board turbocharger that is mounted on a vehicle. This vehicle is equipped with an internal combustion engine. The internal combustion engine combusts a mixture of air supplied to a combustion chamber through an intake passage and fuel supplied to the combustion chamber. The turbocharger of this embodiment is provided on this internal combustion engine. In this embodiment, for convenience of explanation, the right side in FIG. 1 is one side, and the left side is the other side.

[0016] As shown in Fig. 1, turbocharger 10 includes a bearing housing 11 located in the center of turbocharger 10, and a turbine 12 provided on one side of the bearing housing 11. A compressor (not shown) is provided on the other side of the bearing housing 11. A bearing 13 that rotatably supports a turbine shaft 14 is accommodated inside the bearing housing 11. One end of the turbine shaft 14 reaches the turbine 12, and the other end of the turbine shaft 14 reaches the compressor. An axis P of the turbine shaft 14 extends in the left-right direction in Fig. 1.

[0017] A turbine housing 15 is joined to one side of the bearing housing 11. The turbine housing 15 forms the outer shell of the turbine 12. A cylindrical turbine chamber 16 extending in the direction of the axis P is formed in the center of the turbine housing 15. A turbine wheel 17 that rotates in the turbine chamber 16 is fixed to one end of the turbine shaft 14. A compressor wheel (not shown) that rotates in the compressor housing is fixed to the other end of the turbine shaft 14. The turbine housing 15 and the compressor housing are each fastened and fixed to the bearing housing 11 by bolts. The bearing housing 11, the turbine housing 15 and the compressor housing form the housing of the turbocharger 10.

[0018] 1, the turbine wheel 17 has a turbine hub portion 18 fixed to one end of the turbine shaft 14. The outer circumferential surface of the turbine hub portion 18 extends radially outward from the back surface to the front surface of the turbine wheel 17. A plurality of turbine blades 19 are provided on the outer circumferential surface of the turbine hub portion 18 at intervals in the circumferential direction.

[0019] A spiral scroll passage 20 is formed around the turbine chamber 16 in the turbine housing 15. A gas intake port (not shown) is formed in the scroll passage 20 as an inlet for exhaust gas. This gas intake port is connected to an exhaust manifold (not shown) of the internal combustion engine. A gas discharge port 21 for discharging exhaust gas is formed in the turbine housing 15. The gas discharge port 21 is an outlet for exhaust gas, communicates with the scroll passage 20, and is connected to an exhaust pipe (not shown). The turbine 12 is disposed in the exhaust passage of the internal combustion engine. An exhaust brake valve (not shown) is provided downstream of the turbocharger 10.

[0020] The scroll passage 20 is formed outside the turbine chamber 16 in the radial direction of the turbine shaft 14. The turbine chamber 16 and the scroll passage 20 communicate with each other via a communication passage 22. A bulge 23 extending toward the bearing housing 11 is formed integrally with the turbine housing 15. The bulge 23 has an annular shape centered on the axis P and constitutes a part of the inner wall surface of the turbine chamber 16.

[0021] The turbocharger 10 is equipped with a variable nozzle mechanism 25. The variable nozzle mechanism 25 changes the exhaust flow area of ​​the communication passage 22 to vary the flow speed of the exhaust gas E blown against the turbine wheel 17. By varying the flow speed of the exhaust gas E, the variable nozzle mechanism 25 adjusts the rotation speed of the turbocharger 10 and adjusts the amount of air forcibly sent into the combustion chamber of the internal combustion engine.

[0022] Next, we will explain the schematic configuration of this variable nozzle mechanism 25. As shown in Figures 2, 3, and 4, variable nozzle mechanism 25 includes a nozzle plate 26 as a first plate, and a unison ring 27. Nozzle plate 26 and unison ring 27 have an annular shape centered on axis P.

[0023] As shown in FIG. 4, the nozzle plate 26 has a plate-shaped plate body 29. A plurality of shaft holes 28 are formed in the plate body 29. The plurality of shaft holes 28 are located on a circle centered on the axis P in the nozzle plate 26, and are arranged at equal angles. A vane shaft 31 provided on the variable nozzle vane 30 is inserted into the shaft hole 28 and connected thereto. The axis Q of the shaft hole 28 and the vane shaft 31 is parallel to the axis P. The vane shaft 31 is rotatable with respect to the nozzle plate 26. The tip end of the vane shaft 31 protrudes from the shaft hole 28 of the nozzle plate 26 and faces the bearing housing 11. The base end of the arm 32 is fixed to the tip end of the vane shaft 31. The variable nozzle vane 30 is fixed to the base end of the vane shaft 31.

[0024] The unison ring 27 has recesses 33 at multiple locations on its inner circumferential surface. The tips of the arms 32 are engaged with these recesses 33. The unison ring 27 is rotated via a link 34 by an electric motor 41 serving as an actuator provided outside the turbocharger 10. A lever member 42 extending radially is provided on a rotating shaft (not shown) of the electric motor 41, and one end of the link 34 is axially attached to the tip of the lever member.

[0025] An arm 36 is fixed to a shaft 35 fixed to the other end of the link 34. The tip of the arm 36 is engaged with a recess 37 provided on the inner circumferential surface of the unison ring 27. A pin 38 that abuts against the side of the arm 36 is provided on the nozzle plate 26. When the unison ring 27 is rotated about the axis P via the link 34, shaft 35, and arm 36 by the operation of the electric motor 41, the arms 32 engaged with the multiple recesses 33 of the unison ring 27 are rotated synchronously about the vane shaft 31.

[0026] As the vane shafts 31 rotate, the variable nozzle vanes 30 rotate about the vane shafts 31. The rotation of the variable nozzle vanes 30 changes the opening degree of the variable nozzle vanes 30, changing the exhaust flow area in the communication passage 22. This adjusts the flow speed of the exhaust gas E blown onto the turbine wheel 17 through the gap between adjacent variable nozzle vanes 30. The variable nozzle vane 30 shown in Fig. 3 is in a state in which the communication passage 22 is opened to the maximum.

[0027] In Fig. 2, when the arm 36 is rotated counterclockwise around the pin 38 as a fulcrum, the unison ring 27 rotates in the direction of the arrow. The counterclockwise rotation of the unison ring 27 rotates the vane shaft 31 in the counterclockwise direction. The counterclockwise rotation of the vane shaft 31 in Fig. 2 corresponds to the clockwise rotation of the vane shaft 31 in Fig. 3. The clockwise rotation of the vane shaft 31 in Fig. 3 rotates the variable nozzle vane 30 to the closing side, and the flow velocity of the exhaust gas E blown against the turbine wheel 17 increases. When the variable nozzle vane 30 rotates to the opening side, the flow velocity of the exhaust gas E blown against the turbine wheel 17 becomes lower than when the variable nozzle vane 30 rotates to the closing side.

[0028] The variable nozzle mechanism 25 includes an annular shroud plate 40 centered on the axis P. The nozzle plate 26 as a first plate and the shroud plate 40 as a second plate are disposed at a distance from each other in the direction of the axis Q of the vane shaft 31. The variable nozzle vane 30 is located between the nozzle plate 26 and the shroud plate 40. That is, the nozzle plate 26 and the shroud plate 40 are disposed with the variable nozzle vane 30 sandwiched therebetween. The shroud plate 40 is provided at a position farther away from the bearing housing 11 than the nozzle plate 26. In this embodiment, the shroud plate 40 is formed by press molding.

[0029] The variable nozzle vane 30 is supported by the nozzle plate 26 in a so-called "cantilever" manner by the vane shaft 31. A plurality of spacer members 43 are provided between the nozzle plate 26 and the shroud plate 40. The spacer members 43 determine the distance between the nozzle plate 26 and the shroud plate 40. The spacer members 43 are provided at positions where they do not interfere with the variable nozzle vane 30.

[0030] A shielding member 45 and a disc spring 46 are provided between the shroud plate 40 and the bulging portion 23 of the turbine housing 15. The shielding member 45 is disposed around the turbine wheel 17 and abuts against the vicinity of the outer periphery of the shroud plate 40 and the tip surface of the bulging portion 23. A space portion 47 isolated from the scroll passage 20 is formed by the shroud plate 40 and the shielding member 45. The disc spring 46 is provided in the space portion 47 and abuts against the shroud plate 40 and the shielding member 45 in the direction of the axis P. The biasing force of the disc spring 46 presses the shroud plate 40 toward the nozzle plate 26. As shown in FIG. 4, the surface of the nozzle plate 26 facing the variable nozzle vane 30 is a first plate surface 48, and the surface of the nozzle plate 26 facing the unison ring 27 is a second plate surface 49.

[0031] In this embodiment, a spiral spring 50 is provided as a spring member connecting the vane shaft 31 and the nozzle plate 26 so that the variable nozzle vane 30 always receives a biasing force in the direction of fully opening. The reason for providing the spiral spring 50 is to prevent repeated rotation of the vane shaft 31 due to the high pressure of the exhaust gas when the exhaust brake is in use.

[0032] 5, the second plate surface 49 of the plate body 29 is provided with a cylindrical ring guide portion 51 formed concentrically with the shaft hole 28. The ring guide portion 51 protrudes from the second plate surface 49 toward the arm 32. The ring guide portion 51 in this embodiment is formed integrally with the plate body 29, and one end 52 of the spiral spring 50 is connected to the vane shaft 31. The other end 53 of the spiral spring 50 is connected to the inner wall of the ring guide portion 51. The width of the spiral spring 50 is smaller than the length of the ring guide portion 51 in the protruding direction.

[0033] The spiral spring 50 is wound in a direction such that the variable nozzle vane 30 is always biased in an opening direction. In Fig. 5, the counterclockwise direction indicated by the arrow F is the direction in which the variable nozzle vane 30 opens, and the clockwise direction is the direction in which the variable nozzle vane 30 closes. When the vane shaft 31 is rotated in the clockwise direction, which is the direction in which the variable nozzle vane 30 closes, the vane shaft 31 is biased by the restoring force of the spiral spring 50 to rotate in the counterclockwise direction, which is the direction in which the variable nozzle vane 30 closes. In this way, the rotation of the vane shaft 31 in the direction in which the variable nozzle vane 30 closes is restricted by the biasing force of the spiral spring 50, and the rotation of the vane shaft 31 in the direction in which the variable nozzle vane 30 opens is promoted by the biasing force.

[0034] The biasing force of the spiral spring 50 is set to be greater than the exhaust gas pressure in the turbocharger 10. Also, the biasing force of the spiral spring 50 is set to be smaller than the driving force of the electric motor 41. This prevents the vane shaft 31 from repeatedly rotating due to increased exhaust gas pressure. On the other hand, it is possible to adjust the opening of the variable nozzle vane 30 by driving the electric motor 41. Although the exhaust gas pressure in the turbocharger 10 fluctuates, it can be grasped in advance, making it easy to select the spiral spring 50.

[0035] Next, the operation of the turbocharger 10 according to this embodiment will be described. Exhaust gas E discharged during operation of the internal combustion engine flows into the turbocharger 10 while flowing through the exhaust passage. The exhaust gas E flows along the scroll passage 20 of the turbine housing 15. The exhaust gas E flowing through the scroll passage 20 passes through the communication passage 22, and when passing through the communication passage 22, it passes between adjacent variable nozzle vanes 30. The exhaust gas E that has passed through the communication passage 22 is blown against the turbine wheel 17 in the turbine chamber 16.

[0036] The exhaust gas E is blown against the turbine wheel 17, which is driven to rotate. As the turbine wheel 17 rotates, a compressor wheel coaxial with the turbine wheel 17 rotates integrally with the turbine wheel 17. As a result, in an internal combustion engine, air is sucked in by negative pressure generated in the combustion chamber as the piston moves, and is forcibly sent into the combustion chamber by the rotation of the compressor wheel of the turbocharger 10. In other words, the efficiency of air filling the combustion chamber is increased by supercharging the air into the combustion chamber.

[0037] The opening degree of the variable nozzle vane 30 is changed by rotating the variable nozzle vane 30 through the operation of the link 34 etc. driven by the electric motor 41. Changing the opening degree of the variable nozzle vane 30 changes the flow velocity of the exhaust gas E blown onto the turbine wheel 17. As a result, the rotation speed of the turbocharger 10 is changed and the boost pressure of the internal combustion engine is adjusted.

[0038] Normally, the exhaust gas upstream of the turbocharger 10 has a lower pressure than the exhaust gas downstream of the turbocharger 10. Therefore, a force acts on the variable nozzle vane 30, which tends to rotate the vane shaft 31 in the opening direction, due to the exhaust gas introduced into the variable nozzle vane 30. For this reason, even if a play is set taking into account thermal expansion in the variable nozzle mechanism 25, the opening degree of the variable nozzle vane 30, which is determined by the position of the link 34, will not change.

[0039] Incidentally, while the internal combustion engine is running, the driver may activate the exhaust brake. When the exhaust brake is activated, the exhaust brake valve located downstream of the turbocharger 10 is fully closed. This causes the exhaust gas pressure in the turbocharger 10 to become high, and the exhaust gas pressure on the inlet side of the variable nozzle vane 30 and the exhaust gas pressure on the outlet side are reversed. As a result, a force is applied by the exhaust gas pressure on the downstream side of the variable nozzle vane 30 to rotate the vane shaft 31 in a direction to close the variable nozzle vane 30.

[0040] In this embodiment, the spiral spring 50 applies a biasing force to the vane shaft 31 in a direction to open the variable nozzle vane 30, so that it can counter the force that rotates the vane shaft 31 in a direction to close the variable nozzle vane 30 due to the exhaust gas pressure on the downstream side, and regulates the rotation of the vane shaft 31. Incidentally, in a case where the spiral spring 50 is not provided, the vane shaft 31 is rotated in a direction to close the variable nozzle vane 30 by the exhaust gas pressure on the downstream side. Then, due to the fluctuation in exhaust gas pressure, the vane shaft 31 is repeatedly rotated in a direction to open the variable nozzle vane 30 and in a direction to close the variable nozzle vane 30, and wear of the vane shaft 31 is accelerated.

[0041] The turbocharger 10 according to the above embodiment provides the following advantages. (1) A spring member connects the vane shaft 31 and the nozzle plate 26. The spring member applies a biasing force to the vane shaft 31 in a direction that opens the variable nozzle vane 30. Therefore, even if the exhaust brake is used and the variable nozzle vane 30 receives a force in a closing direction, the rotation of the vane shaft 31 in the closing direction of the variable nozzle vane 30 is restricted. In other words, even if the exhaust gas pressure fluctuates when the exhaust brake is used, the variable nozzle vane 30 is biased in the opening direction by the biasing force of the spring member, and the position of the vane shaft 31 is maintained. As a result, repeated rotation of the vane shaft 31 is prevented, and wear on the vane shaft 31 can be suppressed.

[0042] (2) The turbocharger 10 has a variable nozzle mechanism 25 that rotates the vane shaft 31 to open and close the variable nozzle vane 30, and an electric motor 41 that operates the variable nozzle mechanism 25. The biasing force of the spring member is greater than the fluid pressure of the exhaust gas and less than the driving force of the electric motor 41. Therefore, the variable nozzle mechanism 25 can adjust the opening of the variable nozzle vane 30 by operating the electric motor 41. Furthermore, even if the fluid pressure of the exhaust gas fluctuates, the vane shaft 31 is not rotated in the closing direction by the exhaust gas.

[0043] (3) The spring member is a spiral spring 50, and one end 52 of the spiral spring 50 is connected to the vane shaft 31, and the other end 53 of the spiral spring 50 is connected to the nozzle plate 26. Since the spring member is the spiral spring 50, a biasing force can be applied to the vane shaft 31 in a direction to open the variable nozzle vane 30.

[0044] (4) The nozzle plate 26 has a plate body 29 and a cylindrical ring guide portion 51 formed concentrically with the vane shaft 31. One end 52 of the spiral spring 50 is connected to the vane shaft 31, and the other end 53 of the spiral spring 50 is connected to the ring guide portion 51. Therefore, the ring guide portion 51 can easily protect the spiral spring 50 from interference with other members, foreign objects, and the like. In particular, since the width of the spiral spring 50 is smaller than the length of the ring guide portion 51 in the protruding direction, the spiral spring 50 can be more easily protected. In addition, since the ring guide portion 51 is formed concentrically with the vane shaft 31, the connection position with the spiral spring 50 can be freely set in the circumferential direction of the vane shaft 31, and is not subject to any restrictions.

[0045] (5) The provision of the ring guide portion 51 can improve the strength of the nozzle plate 26. In particular, the ring guide portion 51 is integrated with the plate body 29, so that the strength of the nozzle plate 26 is further improved.

[0046] (6) The rotation of the vane shaft 31 in the direction to close the variable nozzle vane 30 is restricted by the biasing force of the spiral spring 50, and the rotation of the vane shaft 31 in the direction to open the variable nozzle vane 30 is promoted by the biasing force. Therefore, the spiral spring 50 does not interfere with the adjustment of the opening degree of the variable nozzle vane 30 by the variable nozzle mechanism 25.

[0047] Second embodiment Next, a turbocharger according to a second embodiment will be described. The second embodiment differs from the first embodiment in that the spring member is a leaf spring. In this embodiment, the same configuration as in the first embodiment will be described with reference to the first embodiment, and common reference numerals will be used.

[0048] In the turbocharger 60 of this embodiment shown in FIG. 6, a plurality of leaf springs 61 are used as spring members. Specifically, the leaf springs 61 are long metal plates and are curved at two points. One end 62 of the leaf springs 61 is connected to the vane shaft 31. The other end 63 of the leaf springs 61 is connected to the inner wall of the ring guide portion 51. In this embodiment, three leaf springs 61 are used, and the three leaf springs 61 are arranged at intervals of 120° in the circumferential direction of the vane shaft 31 and the ring guide portion 51. The width of the leaf springs 61 is smaller than the length of the ring guide portion 51 in the protruding direction. Note that FIG. 6 corresponds to FIG. 5 of the first embodiment.

[0049] The leaf spring 61 has an extension direction set so that the variable nozzle vane 30 is always biased in the opening direction. In Fig. 6, the counterclockwise direction indicated by the arrow F is the direction in which the variable nozzle vane 30 opens, and the clockwise direction is the direction in which the variable nozzle vane 30 closes. When the vane shaft 31 is rotated clockwise, which is the direction in which the variable nozzle vane 30 closes, the vane shaft 31 is biased by the restoring force of the leaf spring 61 to rotate counterclockwise, which is the direction in which the variable nozzle vane 30 closes. In this way, the rotation of the vane shaft 31 in the direction in which the variable nozzle vane 30 closes is restricted by the biasing force of the leaf spring 61, and the rotation of the vane shaft 31 in the direction in which the variable nozzle vane 30 opens is promoted by the biasing force.

[0050] The biasing force of the leaf spring 61 is set to be larger than the fluid pressure of the exhaust gas in the turbocharger 10. Also, the biasing force of the leaf spring 61 is set to be smaller than the driving force of the electric motor 41. This prevents the vane shaft 31 from repeatedly rotating due to increased exhaust gas pressure. On the other hand, the opening degree of the variable nozzle vane 30 can be adjusted by driving the electric motor 41.

[0051] According to this embodiment, the same effects as the effects (1) and (2) of the first embodiment are achieved. In addition, since the spring members are leaf springs 61 and a plurality of leaf springs 61 are arranged in the circumferential direction of the vane shaft 31, the variation in the biasing force of the spring members can be suppressed and the concentricity of the axis Q of the vane shaft 31 in the nozzle plate 26 with respect to the shaft hole 28 can be improved.

[0052] (Modification) Next, modified examples of the turbocharger will be described. In modified example 1 shown in Fig. 7(a), a spiral spring 50 is used as the spring member, but a ring guide portion is not provided on a nozzle plate 71. A shaft portion 72 that connects the other end portion 53 of the spiral spring 50 is formed on the nozzle plate 71.

[0053] In the second modification shown in FIG. 7(b), the spring member is a coil spring 81. The vane shaft 31 is provided with an arm portion 82 that protrudes radially outward. The nozzle plate 80 is provided with a shaft portion 83 that is erected away from the shaft hole 28. One end 84 of the coil spring 81 is engaged with the tip of the arm portion 82, and the other end 85 of the coil spring 81 is engaged with the shaft portion 83. According to the first and second modifications, an exhaust brake is used, and even if a force is applied in the closing direction of the variable nozzle vane 30, the rotation of the vane shaft 31 in the closing direction of the variable nozzle vane 30 is restricted. The first and second modifications can prevent repeated rotation of the vane shaft 31 and suppress wear of the vane shaft 31. Note that FIG. 7(a) and FIG. 7(b) are views corresponding to FIG. 5 of the first embodiment.

[0054] It should be noted that the above embodiment shows one embodiment of the present invention, and the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the spirit of the invention as described below.

[0055] In the above embodiment, the variable nozzle vane is supported by the first plate in a cantilevered manner, but this is not limited to the above. For example, the variable nozzle vane may be supported by the first plate and the second plate via a vane shaft in a cantilevered manner. In the above embodiment, the ring guide portion is integrally formed with the plate body of the first plate, but this is not limiting. For example, the ring guide portion may be provided on the first plate by welding. In the above embodiment (including the modified example), the spring member is a spiral spring, a leaf spring, and a coil spring, but is not limited to these. The spring member may be a type other than a spiral spring, a leaf spring, and a coil spring, such as a torsion coil spring or a torsion bar. [Explanation of symbols]

[0056] 10, 60 Turbocharger 11 Bearing housing 12 Turbine 15 Turbine housing 16 Turbine Room 17 Turbine Wheel 19 Turbine blades 20 Scroll Passage 21 Gas exhaust port 22 Communication path 25 Variable nozzle mechanism 26, 71, 80 Nozzle plate (first plate) 27 Unison Ring 28 Shaft hole 29 Plate body 30 Variable Nozzle Vane 31 Vane shaft 34 Links 40 Shroud plate (second plate) 41 Electric motor (actuator) 50 Spiral spring (spring component) 51 Ring guide part 52, 62, 84 End (one side) 53, 63, 85 End (other side) 61 Leaf spring (spring component) 72, 83 Shaft 81 Coil springs (spring components) 82 Arm section F Arrow P Shaft center (turbine shaft) Q Shaft center (vane shaft) E. Exhaust gas

Claims

1. A turbine wheel; a plurality of variable nozzle vanes that are rotatably provided around a vane shaft and adjust a flow rate of exhaust gas to the turbine wheel; a first plate having an annular shape that rotatably supports the vane shafts of the plurality of variable nozzle vanes; and an annular second plate arranged to sandwich the variable nozzle vane together with the first plate, a spring member engaged with the vane shaft and the first plate, The spring member applies a biasing force to the vane shaft in a direction to open the variable nozzle vane.

2. a variable nozzle mechanism that rotates the vane shaft to open and close the variable nozzle vane; an actuator that operates the variable nozzle mechanism, 2. The turbocharger according to claim 1, wherein the biasing force of the spring member is greater than a fluid pressure of the exhaust gas and less than a driving force of the actuator.

3. the spring member is a spiral spring, One end of the spiral spring is engaged with the vane shaft, 3. The turbocharger according to claim 1, wherein the other end of the spiral spring is anchored to the first plate.

4. the spring member is a leaf spring, A plurality of the leaf springs are arranged in a circumferential direction of the vane shaft, 3. The turbocharger according to claim 1, wherein one end of the leaf spring is anchored to the vane shaft, and the other end of the leaf spring is anchored to the first plate.

5. The first plate is The plate body, a cylindrical ring guide portion formed concentrically with the vane shaft, One end of the spring member is engaged with the vane shaft, 3. The turbocharger according to claim 1, wherein the other end of the spring member is engaged with the ring guide portion.

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