Turbocharger

Abstract

The turbocharger includes a turbine housing and an exhaust bypass valve. The turbine housing divides a bypass passage. The turbine housing includes a flat valve seat surface for the exhaust bypass valve to contact. The exhaust bypass valve opens and closes the bypass passage. The exhaust bypass valve includes a flat valve surface facing the valve seat surface. When the geometric center of the outer edge shape of the valve surface is set as the valve center and the geometric center of the opening shape of the bypass passage in the valve seat surface is set as the opening center, the shortest distance from the valve center to the central axis of the shaft is greater than the shortest distance from the opening center to the central axis of the shaft.

Description

Technical Field

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

[0002] The turbocharger described in Japanese Patent Publication No. 2020-084923 includes a turbine impeller, a turbine housing, and an exhaust bypass valve. The turbine housing accommodates the turbine impeller. The turbine housing divides a bypass passage. The bypass passage bypasses the exhaust gas upstream side and the exhaust gas downstream side of the turbine impeller. The turbine housing includes a valve seat surface that contacts the exhaust gas bypass valve when the exhaust gas bypass valve is in a closed state. In addition, the turbine housing includes a through hole that penetrates the wall of the turbine housing.

[0003] The waste gas bypass valve opens and closes the bypass passage. The waste gas bypass valve includes a shaft and a valve core. The shaft penetrates the through hole and is supported on the turbine housing in a rotatable manner. The valve core extends radially from the end of the shaft on the inner side of the turbine housing. The valve core includes a flat valve face facing the valve seat face when the waste gas bypass valve is in a closed state. The shaft and the valve core are integrally formed. Summary of the invention

[0004] In a turbocharger such as Japanese Patent Application Laid-Open No. 2020-084923, manufacturing errors may occur in the turbine housing and the wastegate valve. When excessive manufacturing errors occur, the valve seat surface and the valve face do not contact each other as designed when the wastegate valve is closed, and exhaust leakage increases. In particular, when the valve face and the valve seat surface interfere with each other before the wastegate valve is completely closed, the gap between the valve seat surface and the valve face increases, and exhaust leakage cannot be ignored.

[0005] The turbocharger for solving the above-mentioned problems comprises: a turbine impeller that rotates due to the flow of exhaust gas; a turbine housing that accommodates the turbine impeller and divides a bypass passage that bypasses the exhaust gas upstream side and the exhaust gas downstream side of the turbine impeller; and an exhaust gas bypass valve that opens and closes the bypass passage, the turbine housing having a flat valve seat surface that contacts the exhaust gas bypass valve when the exhaust gas bypass valve is in a closed state and a through hole that penetrates the wall of the turbine housing, the exhaust gas bypass valve having a shaft that penetrates the through hole and is rotatably supported by the turbine housing, and a shaft extending from an end of the shaft on the inner side of the turbine housing to a position adjacent to the exhaust gas bypass valve. The valve core extends radially of the shaft, and the valve core has a valve face that is flat and faces the valve seat face when the exhaust gas bypass valve is in a closed state. The shaft and the valve core are an integrally formed product. When the exhaust gas bypass valve is in a closed state, the entire opening of the bypass passage is covered by the valve core when viewed from a direction orthogonal to the valve seat face. When the geometric center of the outer edge shape of the valve face is set as the valve center and the geometric center of the opening shape of the bypass passage in the valve seat face is set as the opening center, the shortest distance from the valve center to the central axis of the shaft is greater than the shortest distance from the opening center to the central axis of the shaft.

[0006] In the above-mentioned turbocharger, when the valve face and the valve seat face interfere with each other before the exhaust bypass valve is completely closed, a gap between the valve face and the valve seat face is generated at a position farther from the opening of the bypass passage when viewed from the central axis of the shaft. Therefore, a part of the exhaust gas leaking from the bypass passage flows in a direction away from the shaft. According to the relationship between the valve center and the opening center, the area of ​​the valve face located at a position farther from the opening of the bypass passage when viewed from the central axis of the shaft is large. As a result, the existence of the valve face becomes an obstacle to the exhaust gas flowing in a direction away from the shaft, so the amount of exhaust gas leaking from the bypass passage can be suppressed.

[0007] In the above structure, when the geometric center of the outer edge shape of the valve seat surface is set as the valve seat center, the shortest distance from the valve seat center to the central axis of the shaft may be greater than the shortest distance from the opening center to the central axis of the shaft.

[0008] According to the above structure, the valve seat surface exists in a portion farther from the opening of the bypass passage when viewed from the central axis of the shaft. Therefore, when the valve surface and the valve seat surface interfere with each other before the exhaust gas bypass valve is completely closed, a narrow passage is defined by the valve seat surface and the valve surface in a portion farther from the opening of the bypass passage when viewed from the central axis of the shaft. In this passage, the flow resistance of the exhaust gas is large, so the amount of exhaust gas leaking from the bypass passage can be suppressed.

[0009] In the above configuration, a maximum dimension of the opening of the bypass passage orthogonal to the central axis of the shaft may be smaller than a maximum dimension of the opening of the bypass passage along the central axis of the shaft.

[0010] According to the above configuration, the above positional relationship between the valve center and the opening center can be easily achieved without excessively increasing the size of the valve surface in the direction perpendicular to the central axis of the shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Features, advantages and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0012] Figure 1 It is a schematic diagram of an internal combustion engine.

[0013] Figure 2 It is a cross-sectional view showing the peripheral structure of the turbine casing.

[0014] Figure 3 It is a cross-sectional view showing the peripheral structure of the wastegate valve.

[0015] Figure 4 It is a plan view showing the surrounding structure of the valve seat surface.

[0016] Figure 5 is a side view of the wastegate valve.

[0017] Figure 6 It is an explanatory diagram showing the peripheral structure of the wastegate valve.

[0018] Figure 7 It is shown Figure 6 An explanatory diagram of the cross-sectional structure of the wastegate valve, etc., at line 7-7 in FIG.

[0019] Figure 8 It is an explanatory diagram showing a cross-sectional structure of a wastegate valve and the like. DETAILED DESCRIPTION

[0020] <Schematic Structure of Internal Combustion Engine>

[0021] Below, according to Figures 1 to 8 First, a schematic structure of a vehicle internal combustion engine 10 to which a turbocharger 20 according to the present invention is applied will be described.

[0022] like Figure 1As shown, the internal combustion engine 10 includes an intake passage 11, a cylinder 12, an exhaust passage 13, a catalyst 15, and a turbocharger 20. The intake passage 11 introduces intake air from outside the internal combustion engine 10. The cylinder 12 is connected to the intake passage 11. The cylinder 12 mixes fuel and intake air and burns them. The exhaust passage 13 is connected to the cylinder 12. The exhaust passage 13 discharges exhaust gas from the cylinder 12. The catalyst 15 is located in the middle of the exhaust passage 13. The catalyst 15 purifies the exhaust gas flowing in the exhaust passage 13.

[0023] The turbocharger 20 includes a compressor housing 30 , a bearing housing 50 , a turbine housing 60 , a compressor impeller 70 , a connecting shaft 80 , and a turbine impeller 90 .

[0024] The compressor housing 30 is installed in the middle of the intake passage 11. The turbine housing 60 is installed in the exhaust passage 13 at a portion upstream of the catalyst 15. The bearing housing 50 is fixed to the compressor housing 30 and the turbine housing 60, respectively, and connects the compressor housing 30 and the turbine housing 60. In this way, the turbocharger 20 is provided across the intake passage 11 and the exhaust passage 13.

[0025] The turbine housing 60 accommodates a turbine impeller 90. The bearing housing 50 accommodates a connecting shaft 80. The bearing housing 50 rotatably supports the connecting shaft 80 via a bearing (not shown). A first end of the connecting shaft 80 is connected to the turbine impeller 90. The compressor housing 30 accommodates a compressor impeller 70. The compressor impeller 70 is connected to a second end of the connecting shaft 80. That is, the compressor impeller 70 is connected to the turbine impeller 90 via the connecting shaft 80.

[0026] When the turbine impeller 90 is rotated by the flow of exhaust gas in the turbine housing 60, the compressor impeller 70 is rotated together via the connecting shaft 80. Then, the intake air in the compressor housing 30 is compressed by the rotation of the compressor impeller 70.

[0027] <Structure of turbocharger>

[0028] Next, the specific structure of the turbocharger 20 will be described.

[0029] like Figure 2 As shown, the turbine housing 60 includes an arc portion 60A, a cylindrical portion 60B and a flange portion 60C. The cylindrical portion 60B is substantially cylindrical. The cylindrical portion 60B extends substantially along the rotation axis 90A, which is the rotation center of the turbine impeller 90. The arc portion 60A extends in a manner surrounding the outer circumference of the cylindrical portion 60B and is substantially arc-shaped. The flange portion 60C is located at the upstream end of the arc portion 60A. The flange portion 60C is fixed to a portion of the exhaust passage 13 that is closer to the upstream side than the turbine housing 60.

[0030] like Figure 2 As shown in FIG. 1 , the turbine housing 60 is divided into two vortex passages 61, a storage space 62, a discharge passage 63 and two bypass passages 64 as spaces for exhaust gas to flow. Figure 2 In the figure, a bypass passage 64 is shown. Each vortex passage 61 is located inside the arc portion 60A and the cylindrical portion 60B. The vortex passage 61 extends in an arc shape so as to surround the turbine impeller 90. The upstream end of the vortex passage 61 is connected to the exhaust passage 13 on the upstream side of the turbine housing 60. The downstream end of the vortex passage 61 is connected to the accommodation space 62. The two vortex passages 61 extend roughly parallel to each other. The accommodation space 62 is a space in the internal space of the cylindrical portion 60B where the turbine impeller 90 is located. The accommodation space 62 is connected to the discharge passage 63. The discharge passage 63 is the end of the internal space of the cylindrical portion 60B that includes the side opposite to the bearing housing 50. Figure 2 The downstream end of the discharge passage 63 is connected to the exhaust passage 13 on the downstream side of the turbine housing 60. Each bypass passage 64 is located inside the arc portion 60A and the cylindrical portion 60B. Each bypass passage 64 connects the swirl passage 61 and the discharge passage 63. That is, the bypass passage 64 bypasses the exhaust upstream side and the exhaust downstream side of the turbine impeller 90.

[0031] like Figure 3 As shown, the turbine housing 60 includes a valve seat surface 66 and a through hole 69. Figure 4 As shown, the valve seat surface 66 is a plane surrounding the opening edges of the two bypass passages 64 in the inner wall surface of the turbine housing 60 that divides the discharge passage 63. That is, each bypass passage 64 opens at the valve seat surface 66. In addition, the outer edge shape of the valve seat surface 66 is substantially circular. Figure 3 As shown, a portion of the inner surface of the turbine housing 60 including the valve seat surface 66 is raised relative to the other portions.

[0032] like Figure 3 As shown in FIG. 1 , the through hole 69 penetrates the wall of the turbine housing 60. The through hole 69 is located in the portion of the wall of the turbine housing 60 that defines the discharge passage 63. The central axis 69A of the through hole 69 is parallel to the valve seat surface 66. In addition, the central axis 69A of the through hole 69 is in the direction in which the two adjacent bypass passages 64 are arranged, that is, Figure 3 When viewed from a direction along the central axis 69A of the through hole 69, the through hole 69 is substantially circular.

[0033] like Figure 1 and Figure 3 As shown in FIG. 1 , the turbocharger 20 includes a wastegate valve 110, a bushing 120, a link mechanism 130, and an actuator 140. Figure 3As shown, the bushing 120 is substantially cylindrical in shape. The outer diameter of the bushing 120 is substantially the same as the inner diameter of the through hole 69. The bushing 120 is located inside the through hole 69.

[0034] like Figure 3 As shown, the wastegate valve 110 includes a shaft 111 and a valve core 112. The shape of the shaft 111 is roughly cylindrical. The outer diameter of the shaft 111 is roughly the same as the inner diameter of the bushing 120. The shaft 111 is inserted into the bushing 120. That is, the shaft 111 passes through the through hole 69 of the turbine housing 60. The turbine housing 60 supports the shaft 111 in a rotatable manner via the bushing 120. It should be noted that the center axis 111A of the shaft 111 is consistent with the center axis 69A of the through hole 69.

[0035] like Figure 5 As shown in FIG. 1 , the valve core 112 includes a connecting portion 113 and a valve body 114. The connecting portion 113 extends from the shaft 111 in the radial direction of the shaft 111. Figure 3 As shown, the connection portion 113 is located at the end of the shaft 111 on the inner side of the turbine housing 60. Figure 3 The right end of the shaft 111 in FIG. Figure 5 As shown in FIG. 1 , the valve body 114 is connected to the radially outer end of the shaft 111 in the connecting portion 113. Figure 6 As shown, the shape of the valve body 114 is generally a circular plate shape. Figure 5 As shown, the surface of the valve body 114 opposite to the connecting portion 113 is Figure 5 The lower surface in the valve seat 66 functions as the valve face 116. The valve face 116 is a plane. In addition, the outer edge shape of the valve face 116 is substantially circular. The outer edge shape of the valve face 116 is large enough to cover the openings of the two bypass passages 64 opened on the valve seat surface 66. Figure 6 As shown, when the wastegate valve 110 is in a closed state, the valve body 114 of the valve core 112 covers the entire opening of the two bypass passages 64 when viewed from a direction perpendicular to the valve seat surface 66. The valve surface 116 faces the valve seat surface 66 when the wastegate valve 110 is in a closed state. The wastegate valve 110 is an integrally formed product in which the shaft 111 and the valve core 112 are integrally formed. It should be noted that the wastegate valve 110 is integrally formed, for example, by casting.

[0036] Here, if Figure 5 As shown in FIG. 1 , in a direction perpendicular to the valve face 116, the distance from the imaginary plane including the valve face 116 to the central axis 111A of the shaft 111 is defined as a distance A. Figure 3 As shown, the distance from the imaginary plane including the valve seat surface 66 to the central axis 69A of the through hole 69 in the direction perpendicular to the valve seat surface 66 is defined as distance B. In the present embodiment, distance A and distance B are equal in design.

[0037] like Figure 3 As shown, the link mechanism 130 is connected to the end of the shaft 111 on the outer side of the turbine housing 60. Figure 1 As shown, the actuator 140 is connected to the link mechanism 130. The actuator 140 transmits a driving force to the link mechanism 130. The link mechanism 130 transmits the driving force from the actuator 140 to the wastegate valve 110, thereby opening and closing the bypass passage 64.

[0038] Specifically, when the wastegate valve 110 changes from an open state to a closed state, the driving force of the actuator 140 is transmitted to the shaft 111 via the link mechanism 130, and the shaft 111 rotates relative to the turbine housing 60 in a first rotation direction in the circumferential direction of the shaft 111. Then, the valve face 116 of the wastegate valve 110 contacts the valve seat face 66 of the turbine housing 60. Therefore, when the wastegate valve 110 is in a closed state, the downstream end of the bypass passage 64 is covered by the valve face 116 of the wastegate valve 110 because the valve face 116 of the wastegate valve 110 faces the valve seat face 66 of the turbine housing 60. It should be noted that in the present embodiment, the state in which the valve face 116 of the wastegate valve 110 contacts the valve seat face 66 of the turbine housing 60 and the wastegate valve 110 cannot rotate further to the closed side is the closed state.

[0039] On the other hand, when the wastegate valve 110 changes from the closed state to the open state, the driving force of the actuator 140 is transmitted to the shaft 111 via the link mechanism 130, and the shaft 111 rotates in the second rotation direction of the circumference of the shaft 111 relative to the turbine housing 60. Then, the valve face 116 of the wastegate valve 110 is separated from the valve seat face 66 of the turbine housing 60. Therefore, when the wastegate valve 110 is in the open state, the downstream end of the bypass passage 64 is not covered by the valve face 116 of the wastegate valve 110.

[0040] <Shape of bypass passage>

[0041] Next, the opening shape of the bypass passage 64 in the valve seat surface 66 will be described in detail.

[0042] like Figure 4As shown, the openings of the two bypass passages 64 are arranged in the direction along the central axis 111A of the shaft 111. When viewed from a direction perpendicular to the valve seat surface 66, the opening shape of each bypass passage 64 is a substantially elliptical shape. Specifically, when viewed from a direction perpendicular to the valve seat surface 66, the maximum value of the dimension along the central axis 111A of the shaft 111 among the dimensions of the opening of the bypass passage 64 is referred to as the maximum dimension 64H. In addition, the maximum value of the dimension perpendicular to the central axis 111A of the shaft 111 among the dimensions of the opening of the bypass passage 64 is referred to as the maximum dimension 64V. In this case, the maximum dimension 64V is smaller than the maximum dimension 64H. An example of the size of the maximum dimension 64V is about 60 to 90% of the maximum dimension 64H. The opening shapes of the two bypass passages 64 are line symmetrical to each other with an imaginary line that can be drawn between the two bypass passages 64 interposed therebetween.

[0043] <Location of bypass passage, etc.>

[0044] Next, the positional relationship among the bypass passage 64 , the valve seat surface 66 , and the valve surface 116 will be described in detail.

[0045] like Figure 4 As shown in FIG. 6A , when viewed from a direction perpendicular to the valve seat surface 66, the geometric center of the opening shape of the bypass passage 64 in the valve seat surface 66 is referred to as the opening center 64A. In addition, the geometric center of the outer edge shape of the valve seat surface 66 is referred to as the valve seat center 66A. Since the outer edge shape of the valve seat surface 66 is substantially circular, the valve seat center 66A is substantially consistent with the center of the circle. Figure 6 As shown, the geometric center of the outer edge shape of the valve face 116 is referred to as the valve center 116A when viewed from a direction perpendicular to the valve face 116. Since the outer edge shape of the valve face 116 is substantially circular, the valve center 116A substantially coincides with the center of the circle.

[0046] like Figure 7 As shown, the shortest distance X from the valve center 116A to the central axis 111A of the shaft 111 is greater than the shortest distance Z from the opening center 64A to the central axis 111A of the shaft 111. In addition, the shortest distance Y from the valve seat center 66A to the central axis 111A of the shaft 111 is greater than the shortest distance Z. It should be noted that in this embodiment, the shortest distance X and the shortest distance Y are the same.

[0047] <Function of this embodiment>

[0048] In the turbocharger 20, even if the distance A and the distance B are designed to be the same, there may be a difference between the distances A and B due to manufacturing errors of the turbine housing 60 and the wastegate valve 110. In this case, when the wastegate valve 110 is in a closed state, the valve face 116 does not contact the valve seat face 66, and a gap is generated between the valve face 116 and the valve seat face 66. In particular, if Figure 8 As shown in FIG. 1 , if the actual distance A1 is longer than the distance A as the design value, the valve face 116 interferes with the valve seat face 66 before the wastegate valve 110 is completely closed. In this case, a large gap is generated between the valve face 116 and the valve seat face 66 at a position farther from the opening of the bypass passage 64 when viewed from the central axis 111A of the shaft 111. Figure 8 As shown by the double-dashed arrow, the exhaust gas that has reached the gap between the valve face 116 and the valve seat face 66 from the bypass passage 64 flows along the valve face 116 in a direction generally away from the axis 111, that is, Figure 8 Furthermore, the exhaust gas flowing in the vicinity of the valve surface 116 leaks out to the exhaust passage 63 .

[0049] <Effects of the present embodiment>

[0050] (1) In this embodiment, Figure 7 As shown in FIG. 1 , the shortest distance X from the valve center 116A to the central axis 111A of the shaft 111 is greater than the shortest distance Z from the opening center 64A to the central axis 111A of the shaft 111. According to this structure, the area of ​​the valve face 116 located farther from the opening of the bypass passage 64 as viewed from the central axis 111A of the shaft 111 is larger. As a result, the presence of the valve face 116 becomes an obstacle to the exhaust gas flowing in the direction away from the shaft 111, so the amount of exhaust gas leaking from the bypass passage 64 can be suppressed.

[0051] (2) In this embodiment, if Figure 7 As shown in FIG. 1 , the shortest distance Y from the valve seat center 66A to the central axis 111A of the shaft 111 is greater than the shortest distance Z from the opening center 64A to the central axis 111A of the shaft 111. According to this structure, the valve seat surface 66 exists at a position farther from the opening of the bypass passage 64 when viewed from the central axis 111A of the shaft 111. Figure 8 As shown in FIG. 1 , when the valve face 116 and the valve seat face 66 interfere with each other before the wastegate valve 110 is completely closed, a narrow passage is defined by the valve seat face 66 and the valve face 116 at a location farther from the opening of the bypass passage 64 as viewed from the central axis 111A of the shaft 111. Furthermore, according to the above-described structure, the distance of the narrow passage defined by the valve seat face 66 and the valve face 116 becomes longer. In such a passage, the flow resistance of the exhaust gas becomes larger, so the amount of exhaust gas leaking from the bypass passage 64 can be suppressed.

[0052] (3) In the present embodiment, the maximum dimension 64V is smaller than the maximum dimension 64H. According to this structure, when the shortest distance X is larger than the shortest distance Z, the maximum dimension 64V is smaller than the maximum dimension 64H. Figure 6 Therefore, even if the size of the valve surface 116 is not excessively increased in the direction orthogonal to the central axis 111A of the shaft 111, the positional relationship between the valve center 116A and the opening center 64A described above can be easily achieved.

[0053] <Change example>

[0054] The present embodiment can be implemented by being modified as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a range that does not technically contradict each other.

[0055] “Regarding the shape of the wastegate valve 110 ”

[0056] The shape of the wastegate valve 110 can be changed as appropriate. For example, as long as the valve body 114 has a flat valve surface 116 , the wastegate valve 110 may have a portion protruding from the valve surface 116 or a portion recessed from the valve surface 116 .

[0057] "Regarding the shape of the turbine housing 60"

[0058] The shape of the turbine housing 60 , especially the shape around the valve seat surface 66 , can be changed as appropriate. For example, the turbine housing 60 only needs to have a flat valve seat surface 66 , and the turbine housing 60 may have a portion recessed from the valve seat surface 66 .

[0059] "Regarding the Positional Relationship between the Valve Seat Surface 66 and the Valve Surface 116"

[0060] In the above embodiment, the distance A and the distance B are designed to be the same, but the distance A and the distance B may be designed to be different values. That is, in terms of design, the valve seat surface 66 and the valve surface 116 may not be in surface contact. It should be noted that from the viewpoint of preventing the valve surface 116 from interfering with the valve seat surface 66 before the wastegate valve 110 is completely closed, it is preferred that the distance A is less than the distance B.

[0061] "About the shortest distance Y and the shortest distance Z"

[0062] In the above embodiment, the shortest distance Y may be the same as the shortest distance Z, or may be smaller than the shortest distance Z. In this configuration as well, as long as the shortest distance X is larger than the shortest distance Z, the amount of exhaust gas leaking from the bypass passage 64 can be suppressed by the presence of the valve surface 116 located farther from the opening of the bypass passage 64.

[0063] "About Bypass 64"

[0064] In the above embodiment, the opening shape of the bypass passage 64 in the valve seat surface 66 can be changed appropriately. For example, the maximum dimension 64V can be the same as or larger than the maximum dimension 64H. In this case, the positional relationship between the valve center 116A and the opening center 64A described above can be achieved by setting the size of the valve surface 116 in accordance with the size of the bypass passage 64. In addition, the positional relationship between the valve seat center 66A and the opening center 64A described above can be achieved by setting the size of the valve seat surface 66 in accordance with the size of the bypass passage 64.

[0065] In the above-mentioned embodiment, the opening shape of the bypass passage 64 can be changed. For example, the opening shape of the bypass passage 64 may be a perfect circle or a polygon.

[0066] In the above embodiment, the number of bypass passages 64 can be changed. For example, the number of bypass passages 64 may be 1 or 3 or more. It should be noted that, when there are a plurality of bypass passages 64, at least one of the plurality of bypass passages 64 only needs to satisfy the requirement that the shortest distance X is greater than the shortest distance Z.

Claims

1. A turbocharger comprising: a turbine wheel, which is rotated by the flow of exhaust gas; a turbine housing that accommodates the turbine impeller and defines a plurality of bypass passages for bypassing an exhaust gas upstream side and an exhaust gas downstream side of the turbine impeller; and a wastegate valve, opening and closing the plurality of bypass passages, The turbine housing has: a flat valve seat surface that contacts the wastegate valve when the wastegate valve is in a closed state; and a through hole that penetrates the wall of the turbine housing. The wastegate valve includes: a shaft that passes through the through hole and is rotatably supported by the turbine housing; and a valve element that extends from an end of the shaft on the inner side of the turbine housing in a radial direction of the shaft. The valve element has a flat valve surface facing the valve seat surface when the wastegate valve is in a closed state. The shaft and the valve core are integrally formed. in, When the wastegate valve is in a closed state, the entire openings of the plurality of bypass passages are covered by the valve element when viewed from a direction perpendicular to the valve seat surface. When the geometric center of the outer edge shape of the valve face is set as the valve center, the geometric center of the opening shape of the first bypass passage among the plurality of bypass passages in the valve seat face is set as the first opening center, and the geometric center of the opening shape of the second bypass passage different from the first bypass passage among the plurality of bypass passages in the valve seat face is set as the second opening center, The shortest distance from the valve center to the central axis of the shaft is greater than the shortest distance from the first opening center to the central axis of the shaft, and greater than the shortest distance from the second opening center to the central axis of the shaft.

2. The turbocharger according to claim 1, When the geometric center of the outer edge shape of the valve seat surface is set as the valve seat center, The shortest distance from the center of the valve seat to the central axis of the shaft is greater than the shortest distance from the center of the first opening to the central axis of the shaft, and greater than the shortest distance from the center of the second opening to the central axis of the shaft.

3. The turbocharger according to claim 1 or 2, A maximum dimension of the opening of the bypass passage orthogonal to the central axis of the shaft is smaller than a maximum dimension of the opening of the bypass passage along the central axis of the shaft.

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