Wastegate Valve

Abstract

A wastegate valve may be formed such that the overall shape thereof is approximately L-shaped as seen in plan view and such that a rotary shaft extends, in a direction approximately perpendicular to a central axis of a valve body and in such fashion as to be offset from the valve body, from an attachment plate which supports the valve body. Furthermore, a rotary shaft main body may be secured by solid-phase welding to a side of the attachment plate. By making the attachment plate more compact, reduction in overall weight, decrease in valve cost, and/or alleviation of constraints that would otherwise apply to design of an exhaust gas flow path provided with a bypass flow path may be achieved.

Claims

1. A wastegate valve formed such that the overall shape thereof is approximately L-shaped as seen in plan view and such that a rotary shaft extends, in a direction approximately perpendicular to a central axis of a valve body and in such fashion as to be offset from the valve body, from an attachment plate which supports the valve body, wherein the rotary shaft bears on a through-hole provided at a turbine housing of an exhaust turbine turbocharger; wherein the rotary shaft is constituted from a boss which is formed in protruding fashion at a side of the attachment plate, and a rotary shaft main body which is solid-phase-welded to the boss; wherein the valve body and the attachment plate are constituted from a first metal having a first heat resistance that is capable of accommodating a maximum temperature of exhaust gas within the turbine housing; wherein the rotary shaft main body is constituted from a second metal having a second heat resistance that is lower than the first heat resistance; and wherein a length by which the boss protrudes is chosen based on the second heat resistance and the exhaust gas maximum temperature.

2. The wastegate valve according to claim 1 wherein the boss is formed so as to be approximately identical in diameter to the rotary shaft main body; and the rotary shaft bears on a circular-pipe-like bearing constituting the through-hole, an extending tip portion of which is exposed to an exterior of the turbine housing.

3. The wastegate valve according to claim 1 wherein the rotary shaft main body is constituted from a hollow pipe.

4. The wastegate valve according to claim 3 wherein the rotary shaft main body extends all the way through the turbine housing, and a hollow portion of said rotary shaft main body is open to an exterior of the turbine housing.

5. The wastegate valve according to claim 1 wherein the valve body is secured to the attachment plate as a result of swaging by way of an attachment dowel and a washer so as not to come free therefrom, and the attachment plate has been shaped as a result of having been forged.

6. The wastegate valve according to claim 1 wherein the valve body and the attachment plate have been formed into their respective shapes in integral fashion by forging.

7. The wastegate valve according to claim 1 wherein the valve body and the attachment plate have been formed into their respective shapes in integral fashion by lost wax casting.

8. The wastegate valve according to claim 2 wherein the rotary shaft main body is constituted from a hollow pipe.

9. The wastegate valve according to claim 8 wherein the rotary shaft main body extends all the way through the turbine housing, and a hollow portion of said rotary shaft main body is open to an exterior of the turbine housing.

10. The wastegate valve according to claim 2 wherein the valve body is secured to the attachment plate as a result of swaging by way of an attachment dowel and a washer so as not to come free therefrom, and the attachment plate has been shaped as a result of having been forged.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0051] Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

[0052] FIG. 1 is a side view of an exhaust turbine turbocharger provided with a wastegate valve associated with a first embodiment.

[0053] FIG. 2 is a front view of same exhaust turbine turbocharger.

[0054] FIG. 3 is a rear view of same exhaust turbine turbocharger.

[0055] FIG. 4 is a sectional view (sectional view along section IV-IV shown in FIG. 2) showing an exhaust gas flow path and a bypass flow path.

[0056] FIG. 5 is a front perspective view of the wastegate valve associated with the first embodiment.

[0057] FIG. 6 is an exploded perspective view of same wastegate valve.

[0058] FIG. 7 is a perspective view showing a boss formed in protruding fashion at an attachment plate.

[0059] FIG. 8 is (a) a front view of same wastegate valve; and (b) a plan view of same wastegate valve.

[0060] FIG. 9 is a vertical sectional view (sectional view along section IX-IX shown in FIG. 8) of same wastegate valve.

[0061] FIG. 10 is a sectional view showing a wastegate valve installed at a turbine housing.

[0062] FIG. 11 is (a) a perspective view of an attachment plate manufactured through employment of a forging operation; and (b) a vertical sectional view (enlarged sectional view along section X-X shown at (a) in FIG. 10) of same attachment plate.

[0063] FIG. 12 is a sectional view showing a wastegate valve installed at a turbine housing, this wastegate valve being associated with a second embodiment.

[0064] FIG. 13 is a sectional view showing a wastegate valve installed at a turbine housing, this wastegate valve being associated with a third embodiment.

[0065] FIG. 14 is a sectional view showing a wastegate valve installed at a turbine housing, this wastegate valve being associated with a fourth embodiment.

[0066] FIG. 15 is an exploded front perspective view of same wastegate valve.

DETAILED DESCRIPTION

[0067] Below, embodiments of the present invention are described with reference to the drawings.

[0068] FIGS. 1 through 4 show a working example of an exhaust turbine turbocharger provided with a wastegate valve in accordance with a preferred embodiment of the present invention. More specifically, FIG. 1 is a side view of same exhaust turbine turbocharger, FIG. 2 is a front view of same exhaust turbine turbocharger, FIG. 3 is rear view of same exhaust turbine turbocharger, and FIG. 4 is a sectional view (sectional view along section IV-IV shown in FIG. 2) showing an exhaust gas flow path and a bypass flow path. Furthermore, FIGS. 5 through 10 are drawings showing wastegate valve 50 associated with a first embodiment.

[0069] At these drawings, reference numeral 1 is the turbine housing of exhaust turbine turbocharger 100, and within turbine housing 1 exhaust gas from the exhaust manifold of the engine is directed toward exhaust gas inlet 3 (see FIG. 4) of turbine scroll 2, exhaust gas supplied to turbine scroll 2 causing rotation of turbine impeller 4 (see FIG. 4).

[0070] Provided within compressor scroll 6 of compressor housing 5 is a compressor impeller (not shown) which is coaxial with turbine impeller 4, rotation of the compressor impeller causing compression of air drawn thereinto from axially centered air intake port 7a, the compressed air being supplied to the engine from compressed air outtake port 7b to turbocharge the engine.

[0071] As shown in FIG. 4, after the exhaust gas drives turbine impeller 4, it is discharged to exhaust gas flow path 9 from exhaust gas outlet 8. Furthermore, to control the turbocharged pressure of the compressed air that is supplied to the engine, a bypass flow path 10 for bypass of the exhaust gas is provided between exhaust gas inlet 3 and exhaust gas outlet 8.

[0072] In addition, annular valve seat surface 10a is formed at the periphery of circular opening 10b to exhaust gas flow path 9 of bypass flow path 10, wastegate valve 50which is equipped with valve body 56 that opens and closes opening 10b, which is to say that it opens and closes bypass flow path 10being provided at a location which is downstream from and in the vicinity of opening 10b (valve seat surface 10a) in such fashion as to make contact with valve seat surface 10a. When turbocharged pressure to the engine exceeds a set value, wastegate valve 50 is such that valve body 56 moves in a direction (downward in FIG. 4) causing it to be separated from valve seat surface 10a, and a portion of the exhaust gas is made to bypass turbine impeller 4 as a result of being sent from bypass flow path 10 to exhaust gas flow path 9.

[0073] As shown in FIGS. 5 through 10, wastegate valve 50 has a structure such that it is provided with rotary shaft 58 that extends, in offset fashion with respect to valve body 56, from attachment plate 52, which is more or less rectangular as seen in front view and which supports valve body 56; and as shown in FIG. 10, rotary shaft 58 bears on circular-pipe-like bearing 13A which extends all the way through the wall at which turbine housing 1 is formed, the other end 58a thereof being exposed to the exterior of turbine housing 1. Bearing 13A is secured as a result of having been press-fit into through-hole 1a in the wall at which turbine housing 1 is formed. As shown in FIGS. 1, 2, and 10, rotary lever 14 is secured in crankshaft-like fashion to the outer end (other end) 58a of rotary shaft 58, the tip of reciprocating rod 16a of actuator 16 which is secured to compressor housing 5 being coupled by way of drive pin 15 to pivoting tip 14a of rotary lever 14

[0074] This being the case, reciprocating action of reciprocating rod 16a due to driving by actuator 16 in the direction indicated by arrow A in FIG. 1 causes rotary lever 14 to pivot in the direction indicated by arrow B at FIG. 1, causing rotary shaft 58 which is secured to rotary lever 14 to rotate in a circumferential direction with respect to bearing 13A. That is, as a result of driving of actuator 16, wastegate valve 50 is made to pivot (rotate) about bearing 13A as indicated by reference numeral C in FIG. 5, which causes opening and closing of valve body 56 with respect to opening 10b (valve seat surface 10a).

[0075] As shown in FIG. 10, note that small gaps S1, S2 (e.g., S1+S2=1 mm) are provided between bearing 13A and rotary lever 14 and between bearing 13A and attachment plate 52 of valve 50; while there is play (e.g., 1 mm) in the axial direction between bearing 13A and wastegate valve 50, by causing sealing surface 56a of valve body 56 to be formed large relative to annular valve seat surface 10a which is provided at exhaust gas flow path 9 (bypass flow path 10), it is possible to eliminate this play (see FIG. 4).

[0076] Actuator 16 might, for example, be constituted as an air-driven diaphragm-type driving apparatus, such that when turbocharged pressure of compressed air exceeds a set value, wastegate valve 50 opens, causing a portion of the exhaust gas to bypass turbine impeller 4 and be discharged from exhaust gas inlet 3 to exhaust gas flow path 9 (see FIG. 4).

[0077] The structure of wastegate valve 50 will next be described in detail with reference to FIGS. 5 through 10.

[0078] Wastegate valve 50 is provided with attachment plate 52 which is more or less rectangular as seen in front view and which supports valve body 56, and rotary shaft 58 which is joined (secured) by means of friction welding to the side of attachment plate 52 and which extends, in offset fashion with respect to valve body 56, in a direction perpendicular to central axis O of valve body 56, being formed such that the overall shape thereof is approximately L-shaped as seen in plan view (see FIG. 5 and see (a) at FIG. 8).

[0079] In addition, rotation of valve 50 about center of rotation L as indicated by arrow C in FIG. 5 causes opening and closing of valve body 56 with respect to valve seat surface 10a (opening 10b).

[0080] As shown at (a) and (b) in FIG. 8, discoid protuberance 52a perpendicular to rotary shaft 58 is formed at the side of attachment plate 52 from which rotary shaft 58 extends, cylindrical rotary shaft 58 extending from the end face of protuberance 52a.

[0081] Rotary shaft 58 is constituted by using a friction welding operation, described below, to cause one end face of rotary shaft main body 58A to be joined by means of friction welding to and made integral with the distal face of boss 53 (see FIGS. 6 and 7) which protrudes slightly from the end face of protuberance 52a. Note that reference numeral 59 at FIGS. 5, 8, and 10 indicates the joint (joint surface) between the two members 53, 58A.

[0082] Furthermore, the side of attachment plate 52 which is opposite the side at which protuberance 52a is formed is formed in downwardly extending flattened plate-like fashion, and the upper edge 52b thereof is formed in cristate fashion such that what would otherwise be an upper edge right-triangular corner is notched in right-triangular fashion as indicated by the alternating long and short chain line at (a) in FIG. 8, being constituted so as to reduce the amount by which attachment plate 52 protrudes into exhaust gas flow path 9.

[0083] That is, as shown in FIGS. 2 and 4, in contradistinction to exhaust gas flow path 9 which is directed toward the front of turbine housing 1 from exhaust gas outlet 8, bypass flow path 10 is provided in parallel fashion with respect to exhaust gas flow path 9 at a location adjacent to and diagonally downward and to the right from said exhaust gas flow path 9 as the exhaust turbine turbocharger is seen in front view, such that it is in communication with exhaust gas flow path 9 by way of opening 10b at which annular valve seat surface 10a is formed.

[0084] In addition, wastegate valve 50 is such that sealing surface 56a of the valve body 56 thereof is in intimate contact with valve seat surface 10a, and is such that the rotary shaft 58 thereof is disposed in a horizontal direction (the direction connecting the left and right sides in FIGS. 2 and 4) which is more or less perpendicular to bypass flow path 10, as a result of which the side of attachment plate 52 which is opposite the side at which protuberance 52a is formed protrudes into exhaust gas flow path 9. However, because upper edge 52b of attachment plate 52 which protrudes into exhaust gas flow path 9 is formed in cristate fashion such that what would otherwise be an upper edge right-triangular corner is notched in right-triangular fashion as has been described above, the amount by which attachment plate 52 protrudes into exhaust gas flow path 9 is made small, wastegate valve 50 being such that the cross-sectional area of exhaust gas flow path 9 is not reduced by attachment plate 52.

[0085] Furthermore, through-hole 54 is provided at discoid lower region 52c of attachment plate 52, swaging being carried out to secure valve body 56 by way of attachment dowel 56c and washer 57 to this through-hole 54 so that it does not come free therefrom.

[0086] More specifically, valve body 56 is such that projecting shaft 56b which is capable of passing through through-hole 54 of attachment plate 52 is formed in protruding fashion at the rear surface side of flat sealing surface 56a, attachment dowel 56c which is capable of engaging with through-hole 57a of washer 57 being formed in protruding fashion at the tip of projecting shaft 56b. In addition, as shown in FIG. 9, projecting shaft 56b of valve body 56 is made to pass through through-hole 54 of attachment plate 52, washer 57 is further made to engage with attachment dowel 56c, and the tip of attachment dowel 56c which protrudes from through-hole 57a of washer 57 is subjected to a swaging process so as to form swaged portion 56c, as a result of which valve body 56 is attached in such state that it is prevented from coming free from through-hole 54 of attachment plate 52 by way of washer 57. Moreover, tapered bevel 57b (see FIG. 9) is formed at the periphery of through-hole 57a of washer 57 on the side thereof at which attachment dowel 56c protrudes, increasing the surface area with which intimate contact is made between swaged portion 56c and washer 57, and increasing the strength with which valve body 56 is prevented from coming free therefrom.

[0087] Furthermore, as shown in FIG. 4, as wastegate valve 50 is arranged in the vicinity of valve seat surface 10a provided at exhaust gas flow path 9 (bypass flow path 10) within turbine housing 1, it is exposed to high-temperature exhaust gas. Moreover, while depending on the specifications of the exhaust turbine turbocharger the temperature of the exhaust gas within exhaust gas flow path 9 (bypass flow path 10) may reach 1000 C. or higher, the present working example is such that wastegate valve 50 is constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.) so as to permit it to accommodate the specifications of exhaust turbine turbochargers (maximum exhaust gas temperature 900 C.). That is, attachment plate 52, valve body 56, washer 57, and rotary shaft 58 are all constituted from the high-Ni alloy NCF751.

[0088] Operations for the manufacture of wastegate valve 50 will next be described.

[0089] To manufacture wastegate valve 50, an operation in which attachment plate 52 is forged, an operation in which rotary shaft main body 58A is friction-welded, a deburring operation, and an operation in which through-hole 54 in attachment plate 52 is formed are conducted during the course of manufacturing a valve manufacturing intermediary U (not shown) at which rotary shaft 58 extends from the side of attachment plate 52 and the overall shape of which is approximately L-shaped as seen in plan view, and an operation is lastly carried out in which swaging is performed to secure valve body 56 to (through-hole 54 of) attachment plate 52 of valve manufacturing intermediary U.

[0090] During the operation in which attachment plate 52 is forged, the side of attachment plate 52 is formed into the shape of boss 53, the forming of this into the shape of boss 53 during the forging operation being simplified to the extent that the length by which boss 53 protrudes therefrom is small.

[0091] Furthermore, during the operation in which attachment plate 52 is forged, by also forming this into the shape of a concavity (thin-walled region) 54b (see FIG. 11) corresponding to through-hole 54 for causing valve body 56 to be secured thereto by swaging, this will facilitate the operation in which the through-hole 54 for attachment plate 52 is formed that is carried out following the deburring operation which takes place after the friction welding operation. That is, the procedure by which through-hole 54 is formed in concavity (thin-walled region) 54b will be made simple to the extent that the thickness of the material at the bottom of the concavity (thin-walled region) 54b formed in attachment plate 52 is made small.

[0092] Furthermore, during the friction welding operation in which rotary shaft main body 58A is joined to the side of attachment plate 52, using any suitable friction welding apparatus, rotary shaft main body 58A and boss 53 formed in protruding fashion at the side of attachment plate 52 are arranged in mutually opposed and coaxial fashion in the horizontal direction, attachment plate 52 is made to move in a direction such as will cause it to approach rotary shaft main body 58A as rotary shaft main body 58A is made to rotate at prescribed speed, application of pressure to the abutting surfaces of rotary shaft main body 58A and boss 53 of attachment plate 52 causing rotary shaft main body 58A to be joined (secured) by friction welding to boss 53 of attachment plate 52.

[0093] Because burrs are produced at the outside circumference of joint (joint surface) 59 between rotary shaft main body 58A and boss 53 of attachment plate 52, the burrs are removed during the deburring operation that takes place following the friction welding operation.

[0094] Next, during the operation in which the through-hole is formed, procedures are employed to cause formation of a hole at concavity (thin-walled region) 54b corresponding to through-hole 54 provided at attachment plate 52. Note that procedures to cause formation of the hole may be employed at the deburring operation.

[0095] As a result of the foregoing operations having been carried out, a valve manufacturing intermediary U at which rotary shaft 58 extends from the side of attachment plate 52 and the overall shape of which is approximately L-shaped as seen in plan view is manufactured. In addition, an operation is lastly carried out in which swaging is performed to secure valve body 56 by way of attachment dowel 56c and washer 57 to (through-hole 54 of) attachment plate 52 of valve manufacturing intermediary U to complete wastegate valve 50 shown in FIGS. 5 and 8.

[0096] Rotary shaft 58 of wastegate valve 50 of the present embodiment is thus constituted from boss 53 which is formed so as to protrude slightly from the side of attachment plate 52, and rotary shaft main body 58A which is joined (secured) by means of friction welding to this boss 53, employment of friction welding in particular making it possible to achieve a situation in which there is almost no variation in joint strength at joint (joint surface) 59. This being the case, the joint strength at rotary shaft main body 58A of the wastegate valve 50 that is manufactured is more easily made uniform, and it will be possible to that extent to assure the quality of wastegate valve 50.

[0097] Moreover, at wastegate valve 50 in accordance with the present embodiment, because rotary shaft main body 58A is joined (secured) by means of friction welding to boss 53 of attachment plate 52, it is possible to make attachment plate 52, which is made of the expensive high-Ni alloy NCF751, more compact. For this reason, it is firstly the case that the cost of wastegate valve 50 can be reduced, and it will also be possible to reduce overall weight. It is secondly the case that as wastegate valve 50 is arranged in the vicinity of valve seat surface 10a provided at exhaust gas flow path 9 (bypass flow path 10) within turbine housing 1, because the space for arrangement of valve 50 is made small, this alleviates any constraint that might otherwise exist when designing an exhaust gas flow path 9 provided with a bypass flow path 10.

[0098] FIG. 12 shows a wastegate valve 50A associated with a second embodiment, this being shown as it would exist when installed at a turbine housing 1.

[0099] Rotary shaft 58 of wastegate valve 50A, i.e., rotary shaft 58 which extends from the side of attachment plate 52, is constituted from boss 53A which is formed in protruding fashion at the side of attachment plate 52, and rotary shaft main body 58B which is identical in diameter to boss 53A and which is joined by means of friction welding to boss 53A. Stating this another way, boss 53A which is formed in protruding fashion at the side of attachment plate 52, and rotary shaft main body 58B which is joined to boss 53A, cooperate to constitute rotary shaft 58 which bears on bearing 13A provided at turbine housing 1. Note that the length L1 by which boss 53A protrudes is greater than that of boss 53 formed at attachment plate 52 of wastegate valve 50 at the foregoing first embodiment.

[0100] Furthermore, while valve body 56 and attachment plate 52 which are directly exposed to exhaust gas are constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.), rotary shaft main body 58B which is in a region distant from attachment plate 52 is constituted from stainless steel (operating temperature limit 850 C.).

[0101] That is, to the extent that rotary shaft 58 which extends from attachment plate 52 is able to cause the heat that is transmitted thereto from attachment plate 52 to be dissipated to turbine housing 1 it will not need to be as heat-resistant as valve body 56 or attachment plate 52, but regions of rotary shaft 58 that are near attachment plate 52 will reach temperatures (elevated temperatures) close to the temperatures (elevated temperatures) experienced by attachment plate 52 as a result of transmission thereto of heat from the exhaust gas.

[0102] For this reason, regions of rotary shaft 58 that are near attachment plate 52 are constituted as boss 53A which is formed in protruding fashion at attachment plate 52, i.e., they are constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.) which has excellent heat resistance. On the other hand, to the extent that exhaust gas heat transmitted to rotary shaft main body 58B which is in a region of rotary shaft 58 that is distant from attachment plate 52 can be dissipated from a location partway therealong to turbine housing 1 by way of boss 53A, this will permit the amount thereof to be reduced; and because it will not reach temperatures as high as those experienced by regions (boss 53A) of rotary shaft 58 near attachment plate 52, the possibility that the mechanical strength thereof will be reduced due to the influence of high temperature is eliminated. Accordingly, as a result of causing rotary shaft main body 58B to be constituted from stainless steel (operating temperature limit 850 C.) which is less expensive than the high-Ni alloy NCF751, it is possible to achieve reduction in the unit cost of wastegate valve 50.

[0103] FIG. 13 shows a wastegate valve 50B associated with a third embodiment, this being shown as it would exist when installed at a turbine housing 1.

[0104] Rotary shaft 58 of wastegate valve 50B is constituted from boss 53 which is formed in protruding fashion at the side of attachment plate 52 constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.), and rotary shaft main body 58C which is in the shape of a hollow pipe, which is constituted from stainless steel (operating temperature limit 850 C.), and which is joined (secured) by means of friction welding to boss 53.

[0105] In addition, rotary shaft 58 bears on bearing 13A provided at turbine housing 1, and the hollow portion of rotary shaft main body 58C which makes up rotary shaft 58 extends all the way through turbine housing 1 in such fashion as to be open to the exterior of turbine housing 1.

[0106] Because rotary shaft main body 58C is hollow and lightweight, the overall weight of wastegate valve 50B will be reduced to a corresponding extent.

[0107] Furthermore, convection of the air outside turbine housing 1 occurs where the hollow portion of rotary shaft main body (hollow pipe) 58C is open to the exterior of turbine housing 1. For this reason, because rotary shaft main body 58C is such that heat transmitted thereto from attachment plate 52 is dissipated to turbine housing 1 by way of bearing 13A and is further dissipated by convection of air occurring at the hollow portion, rotary shaft main body 58C need not be as heat-resistant as valve body 56 or attachment plate 52.

[0108] That is, even where rotary shaft main body 58C is constituted from metal of lower heat resistance than valve body 56 and attachment plate 52 which are constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.), it is very unlikely that the heat resistance of rotary shaft 58 will pose a problem. Accordingly, in accordance with the present embodiment, by causing rotary shaft main body 58C to be constituted from stainless steel (operating temperature limit 850 C.) which is less expensive than the high-Ni alloy NCF751, it is possible to achieve reduction in the unit cost of wastegate valve 50B.

[0109] FIGS. 14 and 15 show a wastegate valve 50C associated with a fourth embodiment of the present invention, FIG. 14 being a front view of same wastegate valve 50C, and FIG. 15 being an exploded front perspective view of same wastegate valve 50C.

[0110] Wastegate valve 50C is such that valve body 56A and cylindrical attachment plate 52A are formed in integral fashion, and such that rotary shaft 58 extends, in offset fashion with respect to valve body 56A, in a direction perpendicular to central axis O of valve body 56A, from the side of attachment plate 52A which supports valve body 56A, being formed such that the overall shape thereof is approximately L-shaped as seen in plan view.

[0111] Rotary shaft 58 which extends from cylindrical attachment plate 52A is constituted from boss 53B which is formed so as to protrude from the side of attachment plate 52A, and rotary shaft main body 58D which is joined (secured) to boss 53B by means of friction welding. Boss 53B and rotary shaft main body 58D are formed so as to be of identical diameter.

[0112] Sealing surface 56a1 of valve body 56A is formed as a continuous curved surface that is capable of making contact with annular valve seat surface 10a which is provided at exhaust gas flow path 9 (bypass flow path 10). Provided at the rear surface side of sealing surface 56a1 of valve body 56A is concavity 56A1 for reducing the weight of valve body 56A.

[0113] Furthermore, inclined upper edge 52A1 at which what would otherwise be an upper edge right-triangular corner is notched in right-triangular fashion as indicated by the alternating long and short chain line at FIGS. 14 and 15 is provided at the side of attachment plate 52A which is opposite the side at which boss 53B is formed, such that, in similar fashion as with upper edge 52b (see (a) at FIG. 8) formed in cristate fashion at attachment plate 52 of wastegate valve 50 of the first embodiment, there is no reduction in the cross-sectional area of exhaust gas flow path 9 as a result of protrusion by attachment plate 52A into exhaust gas flow path 9.

[0114] Furthermore, valve body 56A which is equipped with attachment plate 52A, and rotary shaft main body 58D, which make up wastegate valve 50C, are each constituted from the high-Ni alloy 713c (operating temperature limit 1050 C.), these being constituted so as to permit satisfaction of the specifications of exhaust turbine turbochargers for which the temperature of the exhaust gas within exhaust gas flow path 9 (bypass flow path 10) may reach 1000 C. or higher.

[0115] Furthermore, because rotary shaft main body 58D is disposed at a location which is distant from attachment plate 52A by an amount corresponding to the length by which boss 53B protrudes therefrom, it may be constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.) which has a lower operating temperature limit than that of the high-Ni alloy 713c. Furthermore, rotary shaft main body 58D may be constituted from a hollow pipe (see FIG. 13) so as to increase ability of rotary shaft 58 (rotary shaft main body 58D) to dissipate heat.

[0116] In accordance with this embodiment, as wastegate valve 50C is constituted from a small number of parts, the constitution of wastegate valve 50C is simplified to a corresponding extent.

[0117] However, because manufacture of valve body 56A which is equipped with attachment plate 52A is limited to lost wax casting due to the fact that forging of the high-Ni alloy 713c is difficult, and there is no avoiding the fact that the unit manufacturing cost of wastegate valve 50C will be high.

[0118] Note that where the specifications of the exhaust turbine turbocharger specify that the temperature of the exhaust gas is 900 C., it will also be possible for wastegate valve 50C to be constituted from the high-Ni alloy NCF751 (operating temperature limit 950 C.), which is a heat-resistant alloy. In addition, where wastegate valve 50C is constituted from the high-Ni alloy NCF751, wastegate valve 50C may be manufactured by carrying out an operation in which a valve body 56A equipped with an attachment plate 52A is forged, an operation in which rotary shaft main body 58D is friction-welded, and a deburring operation. That is, among the operations carried out during manufacture of wastegate valve 50 of the first embodiment, as the operation in which through-hole 54 was formed in attachment plate 52 and the operation in which swaging was performed to secure valve body 56 to attachment plate 52 are unnecessary, it will be possible to that extent to reduce the number of manufacturing operations and to manufacture wastegate valve 50C in a short amount of time.

[0119] Whereas at the first through third embodiments described above swaging was performed to secure valve body 56 by way of attachment dowel 56c and washer 57 to through-hole 54 provided at attachment plate 52 so that it would not come free therefrom, at wastegate valve 50C associated with this fourth embodiment forging or lost wax casting is performed to integrally form this into the shapes of valve body 56A and attachment plate 52A as shown in FIGS. 14 and 15, the number of parts from which wastegate valve 50C is constituted being made small to a corresponding extent.

[0120] Furthermore, whereas the first through fourth embodiments described above were each constituted such that a rotary shaft was made to extend from the side of an attachment plate as a result of causing a rotary shaft main body to be joined (secured) by means of friction welding to the side of the attachment plate, it is also possible for the structure to be such that the rotary shaft main body is joined (secured) to the side of the attachment plate by solid-phase welding other than friction welding; e.g., by resistance welding.

[0121] In addition, during the resistance welding operation in which the rotary shaft main body is joined to the side of the attachment plate, any suitable resistance welding apparatus might be used, and, for example, rotary shaft main body 58A and boss 53 formed in protruding fashion at the side of attachment plate 52 might, for example, be arranged in mutually abutting and coaxial fashion in the horizontal direction, the two members 52, 58A might be straddled between electrodes, and a prescribed pressure might be applied thereto and electric current might be made to flow therethrough, so as to cause rotary shaft main body 58A to be joined (secured) by resistance welding to boss 53 of attachment plate 52.

EXPLANATION OF REFERENCE NUMERALS

[0122] 1 Turbine housing [0123] 9 Exhaust gas flow path [0124] 10 Bypass flow path [0125] 10a Valve seat surface [0126] 10b Opening to exhaust gas flow path of bypass flow path [0127] 13A Bearing [0128] 14 Rotary lever [0129] 50, 50A, 50B, 50C Wastegate valve [0130] 52, 52A Attachment plate [0131] 52b Cristate upper edge of attachment plate [0132] 52A1 Inclined upper edge of attachment plate [0133] 52c Discoid lower region [0134] 53, 53A, 53B Boss [0135] 54 Through-hole [0136] 56 Valve body [0137] 56A Valve body equipped with attachment plate [0138] O Central axis of valve body [0139] 56a, 56a1 Sealing surface of valve body [0140] 56c Attachment dowel [0141] 57 Washer [0142] 58 Rotary shaft [0143] 58A, 58B, 58C, 58D Rotary shaft main body [0144] 59 Joint surface