A wastegate valve device for a turbocharger includes a valve body, a swing arm configured to support the valve body, a rotating shaft to which the swing arm is fixed, a drive arm fixed to the rotating shaft, and a rod connected to the drive arm. The drive arm includes a fixed portion to which the rotating shaft is fixed, a first extension portion where the rod is connected, and a second extension portion extending on the opposite side of the first extension portion. The turbine housing is provided with a stopper with which the second extension portion abuts at the time when the valve body is distanced from the wastegate port due to a rotation of the rotating shaft in a valve-opening direction.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-047387 filed on Mar. 13, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a turbocharger including a wastegate valve device.

2. Description of Related Art

Inside a turbine housing for a turbocharger described in Japanese Unexamined Patent Application Publication No. 2012-67698 (JP 2012-67698 A), a wastegate port through which exhaust gas flows by detouring around a turbine wheel is formed. A wastegate valve device for the turbocharger includes a valve body configured to open and close the wastegate port, a rotating shaft inserted through an insertion hole formed on a side wall of the turbine housing, and a swing arm fixed to the rotating shaft. The swing arm supports the valve body at a position distanced from a part fixed to the rotating shaft in the radial direction of the rotating shaft. Accordingly, the valve body is configured to open and close the wastegate port such that the rotating shaft and the swing arm rotate around the rotating shaft as the axial center. More specifically, when the rotating shaft and the swing arm are rotated in a first direction, the valve body can approach the wastegate port, and when the rotating shaft and the swing arm are rotated in a second direction that is a reverse direction with respect to the first direction, the valve body can be distanced from the wastegate port.

Further, the wastegate valve device is provided with a drive arm placed outside the turbine housing and fixed to the rotating shaft, and a rod rotatably connected to the drive arm. More specifically, the rod is rotatably connected to the drive arm at a position distanced from a part fixed to the rotating shaft in the radial direction of the rotating shaft. When the rod is pulled toward a compressor housing of the turbocharger by driving of an electric actuator, the drive arm, the rotating shaft, and the swing arm are rotated in the second direction, so that the valve body is distanced from the wastegate port. Hereby, the exhaust gas flowing into the turbine wheel passes through the wastegate port.

SUMMARY

In the meantime, in the wastegate valve device, the valve body is placed on the downstream side from the wastegate port in the turbine housing. Accordingly, when the valve body is distanced from the wastegate port, the exhaust gas passing through the wastegate port interferes with the valve body. That is, the valve body receives a load corresponding to the pressure of the exhaust gas. At this time, when a load to be received by the valve body fluctuates due to pulsation of the pressure of the exhaust gas that interferes with the valve body, the rotating shaft connected to the valve body via the swing arm vibrates. As a result, an abnormal noise might occur due to the rotating shaft abutting with the peripheral wall of the insertion hole.

An aspect of the present disclosure is related to a turbocharger in which a turbine housing and a compressor housing are arranged in a reference direction, an outflow portion via which exhaust gas flowing through the turbine housing flows out into an exhaust pipe is provided, the outflow portion is provided on a distant side of the turbine housing from the compressor housing in the reference direction.

The turbocharger includes a valve body placed on an outflow portion side in the reference direction from a wastegate port and configured to open and close the wastegate port, the wastegate port inside the turbine housing being configured to cause the exhaust gas to detour around a turbine wheel. The turbocharger also includes a rotating shaft extending in a direction intersecting with the reference direction, the rotating shaft being inserted through an insertion hole provided on a side wall of the turbine housing. The turbocharger also includes a swing arm fixed to the rotating shaft and configured to support the valve body at a position distanced from a part of the swing arm fixed to the rotating shaft in a radial direction of the rotating shaft, a drive arm placed outside the turbine housing and fixed to the rotating shaft, a rod rotatably connected to the drive arm at a position distanced from a part where the rotating shaft is fixed to the drive arm, and an actuator. The rod is displaced toward a side approaching the compressor housing in the reference direction by driving of the actuator. The drive arm, the rotating shaft, and the swing arm rotate in a valve-opening direction when the rod is displaced, so that the valve body is displaced toward a side approaching the outflow portion so as to be distanced from the wastegate port.

The drive arm includes a fixed portion to which the rotating shaft is fixed, a first extension portion, and a second extension portion. The first extension portion extends from the fixed portion in a first direction intersecting with an extending direction of the rotating shaft and the rod is connected to the first extension portion. The second extension portion extends in a second direction intersecting with the extending direction of the rotating shaft from a part of the fixed portion on an opposite side from the first extension portion. The turbine housing is provided with a stopper configured to abut with the second extension portion. The stopper is on a valve-opening direction side from the second extension portion when the valve body closes the wastegate port. The stopper is configured to abut with the second extension portion when the valve body is distanced from the wastegate port. The valve-opening direction is one rotation direction around the rotating shaft.

In the above aspect, when the drive arm, the rotating shaft, and the swing arm rotate in the valve-opening direction due to driving of the actuator, the valve body is displaced to approach the outflow portion, so that the wastegate port is opened. Hereby, the exhaust gas flows through the wastegate port.

Further, when the second extension portion abuts with the stopper while the drive arm is rotating in the valve-opening direction, further rotations of the drive arm, the rotating shaft, and the swing arm in the valve-opening direction are restricted. When a driving force from the actuator is still input into the first extension portion of the drive arm after the rotations of the drive arm, the rotating shaft, and the swing arm are restricted, a force to displace the fixed portion toward the compressor housing side in the reference direction is applied to the drive arm, with a part abutting with the stopper serving as a fulcrum. Accordingly, an outer end of the rotating shaft is pressed toward the compressor housing side in the reference direction by the driving force input via the first extension portion, the outer end being an end placed outside the turbine housing.

In the meantime, when the valve body is distanced from the wastegate port, the exhaust gas passing through the wastegate port interferes with the valve body. The exhaust gas passing through the wastegate port flows toward the outflow portion. Accordingly, an inner end of the rotating shaft, which is an end placed inside the turbine housing, is pressed by a load received by the valve body from the exhaust gas, toward the opposite side with respect to the compressor housing side in the reference direction, namely, toward the outflow portion side.

That is, in the above aspect, when the valve body is distanced from the wastegate port, the rotating shaft is inclined with respect to the central axis of the insertion hole due to the driving force from the actuator, which is transmitted to the rotating shaft via the drive arm, and the load received by the valve body from the exhaust gas. Hereby, the rotating shaft is pressed against an inside opening edge of the insertion hole and an outside opening edge of the insertion hole, the inside opening edge being inside the turbine housing, the outside opening edge being outside the turbine housing. Besides, the direction of the load received by the inner end of the rotating shaft is different by approximately 180° from the direction of the driving force input into the outer end of the rotating shaft. Accordingly, a position of a part of the inside opening edge abutting with the rotating shaft relative to the central axis of the insertion hole is different by approximately 180° from a position of a part of the outside opening edge abutting with the rotating shaft relative to the central axis of the insertion hole.

Hereby, in the above aspect, when the wastegate port is distanced from the valve body, the drive arm is pressed against the stopper. Further, the rotating shaft is inclined such that the rotating shaft is pressed against the inside opening edge at a position on the outflow portion side, and the rotating shaft is pressed against the outside opening edge at a position on the compressor housing side. Accordingly, even if a load to displace the valve body toward the outflow portion side is applied to the valve body, the rotating shaft is not displaced. Further, even if the pressure of the exhaust gas interfering with the valve body pulsates and the load received by the inner end of the rotating shaft from the exhaust gas fluctuates, the forces to press the rotating shaft against the opening edges just fluctuate, so that it is possible to restrain the rotating shaft, the swing arm, and the valve body from vibrating. Accordingly, it is possible to restrain the occurrence of abnormal noise caused due to vibration of the rotating shaft at the time when the valve body is distanced from the wastegate port.

In the above aspect, the stopper may be placed on a rotational locus of a distal part which is a part of the second extension portion on a distal end side from a center of the second extension portion. The outflow portion may include a flange configured to connect the exhaust pipe to the turbine housing. A distal end side of a front edge of the second extension portion may be on a valve-closing direction side from a base end side of the front edge of the second extension portion. The stopper may be placed on a compressor housing side in the reference direction from the flange. The valve-closing direction is a rotation direction reverse to the valve-opening direction. The front edge of the second extension portion is an edge of the second extension portion on the valve-opening direction side.

According to the above aspect, the interval between the stopper and the flange can hardly become short in the reference direction. Further, when the wastegate port is closed by the valve body, the distal end of the first extension portion in the drive arm can hardly approach the outflow portion in the reference direction. On this account, it is not necessary to set a large difference between the position of the rotating shaft and the position of the flange in the reference direction. That is, even if the flange is placed so as not to be distanced from the rotating shaft in the reference direction, the driving arm does not make contact with the flange. Accordingly, it is possible to restrain upsizing of the turbine housing in the reference direction.

DETAILED DESCRIPTION OF EMBODIMENTS

One embodiment of a turbocharger is described below with reference to the drawings. As illustrated inFIG. 1, a turbocharger10of the present embodiment includes a compressor housing21constituting a compressor20, a turbine housing31constituting a turbine30, and a bearing housing11placed between the compressor housing21and the turbine housing31. The direction where three housings11,21,31are arranged is referred to as a “reference direction X.” A compressor wheel is accommodated inside the compressor housing21, and a turbine wheel32is accommodated inside the turbine housing31as illustrated inFIG. 2. The bearing housing11rotatably supports a connecting shaft connecting the compressor wheel to the turbine wheel32.

As illustrated inFIGS. 1 and 2, in terms of the opposite ends of the turbine housing31in the reference direction X, the end on the side distant from the compressor housing21serves as an outflow portion33to which an exhaust pipe100is connected. The exhaust pipe100is configured such that exhaust gas flowing out from the turbine housing31flows through the exhaust pipe100. The outflow portion33is provided with a flange331to be connected to the exhaust pipe100.

As illustrated inFIG. 2, the turbine housing31includes a scroll passage34formed therein such that the scroll passage34extends so as to surround the turbine wheel32. The turbine wheel32rotates when the exhaust gas flowing into the scroll passage34is blown to the turbine wheel32. Hereby, the compressor wheel connected to the turbine wheel32via the connecting shaft rotates, so that forced induction is performed in the compressor housing21. Note that the exhaust gas blown to the turbine wheel32flows through a discharge passage35and then flows out into the exhaust pipe100via the outflow portion33.

Further, the turbine housing31is provided with a wastegate port36formed therein. The wastegate port36is a passage that connects the scroll passage34to the discharge passage35by detouring around the turbine wheel32. Note that, in the present embodiment, the wastegate port36extends in the reference direction X.

Next, a wastegate valve device40of the turbocharger10will be described. As illustrated inFIGS. 2 and 3, the wastegate valve device40includes a valve body41configured to open and close the wastegate port36. The valve body41is placed on the opposite side of the wastegate port36with respect to the turbine wheel32in the reference direction X, that is, placed closer to the outflow portion33than the wastegate port36. When the valve body41abuts with the turbine housing31as illustrated inFIG. 2, the wastegate port36is closed by the valve body41.

In the meantime, when the valve body41is distanced from the turbine housing31toward the outflow portion33side (the right side inFIG. 3) as illustrated inFIG. 3and the wastegate port36is not closed by the valve body41, that is, when the wastegate port36is opened, the exhaust gas flowing through the scroll passage34flows into the discharge passage35through the wastegate port36. When the exhaust gas passing through the scroll passage34flows into the discharge passage35via the wastegate port36in a way described as above, the amount of the exhaust gas to be blown to the turbine wheel32is decreased. Accordingly, when the wastegate port36is opened, rotations of the turbine wheel32and the compressor wheel are restrained, thereby restraining forced induction,

Further, as illustrated inFIG. 4, a side wall311of the turbine housing31has a communicating hole311avia which the inside of the turbine housing31communicates with the outside of the turbine housing31, and a bush312having a cylindrical shape is press-fitted to the communicating hole311a. The extending direction of the communicating hole311a, that is, the extending direction of the bush312, is perpendicular to the reference direction X. The reference direction X is the direction perpendicular to the plane of paper ofFIG. 4. Note that the extending direction of the bush312may not necessarily be perpendicular to the reference direction X as long as the extending direction of the bush312intersects with the reference direction X.

As illustrated inFIGS. 2 and 4, the wastegate valve device40is provided with a rotating shaft42inserted through an insertion hole312aformed inside the bush312. That is, the rotating shaft42is supported by the side wall311in a rotatable state. A swing arm43is fixed to an inner portion421that is a part of the rotating shaft42, the part being placed inside the turbine housing31. The swing arm43supports the valve body41at a position distanced, in the radial direction of the rotating shaft42, from a part of the swing arm43where the swing arm43is fixed to the rotating shaft42. Since the valve body41is connected to the rotating shaft42via the swing arm43, when the rotating shaft42and the swing arm43rotate, the valve body41rotates. That is, when the rotating shaft42and the swing arm43rotate in a valve-closing direction C1that is the clockwise direction inFIGS. 2 and 3, the valve body41is displaced to a side approaching the wastegate port36. In the meantime, when the rotating shaft42and the swing arm43rotate in a valve-opening direction C2that is the counterclockwise direction inFIGS. 2 and 3, the valve body41is displaced to a side distanced from the wastegate port36.

Further, as illustrated inFIG. 4, the wastegate valve device40includes a drive arm44placed outside the turbine housing31, and a rod45rotatably connected to the drive arm44. As illustrated inFIG. 1, a first end of the rod45is connected to the drive arm44, while a second end of the rod45is connected to an electrically-driven actuator46supported by the compressor housing21.

As illustrated inFIG. 4, an outer portion422of the rotating shaft42is fixed to the drive arm44. The outer portion422is a part placed outside the turbine housing31. Hereby, the drive arm44rotates in an integrated manner together with the rotating shaft42and the swing arm43around the rotating shaft42. Further, as illustrated inFIGS. 4 and 5, the drive arm44includes a fixed portion441to which the rotating shaft42is fixed, and two extension portions442,443extending from the fixed portion441in a direction perpendicular to the extending direction of the rotating shaft42. Note that the extending direction of the extension portions442,443may not necessarily be perpendicular to the extending direction of the rotating shaft42as long as the extending direction of the extension portions442,443intersects with the extending direction of the rotating shaft42.

The rod45is connected to a distal part of the first extension portion442out of the extension portions442,443. That is, the rod45is connected to the drive arm44at a position different from the fixed portion441that is a part to which the rotating shaft42is fixed. Further, the second extension portion443out of the extension portions442,443extends from a part of the fixed portion441on the opposite side from the first extension portion442.

As illustrated inFIG. 5, in the second extension portion443, an edge on the valve-opening direction C2side is referred to as a front edge443f, and an edge on the valve-closing direction C1side is referred to as a rear edge443b. In this case, the front edge443fis inclined to a line L2extending in the extending direction of the second extension portion443, so that a distal end side thereof is placed on the valve-closing direction C1side from a base end side thereof. Further, the interval between the front edge443fand the rear edge443bis gradually narrowed as it goes from the base end side of the second extension portion443toward the distal end side thereof. Further, the line L2extending in the extending direction of the second extension portion443deviates from a line L1extending in the extending direction of the first extension portion442, along the valve-closing direction C1. That is, the drive arm44has a bending shape as a whole.

Further, as illustrated inFIGS. 1 and 5, the wastegate valve device40includes a stopper47placed on the valve-opening direction C2side from the second extension portion443at the time when the valve body41closes the wastegate port36. The stopper47is placed generally right below the rotating shaft42inFIG. 5on the turbine housing31. That is, the position of the stopper47is placed generally at the same position as the rotating shaft42in the reference direction X. Further, the stopper47is placed on a rotation locus of a distal part443tof the second extension portion443. When the valve body41is distanced from the wastegate port36, the front edge443fof the second extension portion443abuts with the stopper47. Note that the distal part443tof the second extension portion443is a part disposed on the distal side from the center of the second extension portion443in the extending direction of the second extension portion443.

Note that the linear distance between an abutting part of the drive arm44with the stopper47and a fixed part of the drive arm44to the rotating shaft42is referred to as a first linear distance B1, and the linear distance between the fixed part of the drive arm44to the rotating shaft42and a connection part of the drive arm44to the rod45is referred to as a second linear distance B2. In this case, in the present embodiment, the first linear distance B1is shorter than the second linear distance B2.

Next, operations and effects of the turbocharger10will be described. When the rod45is displaced due to driving of the actuator46in a state where the wastegate port36is closed by the valve body41, so as to pull the drive arm44toward the compressor housing21side in the reference direction X as indicated by an arrow inFIG. 5, the drive arm44, the rotating shaft42, and the swing arm43are rotated in the valve-opening direction C2. When the rotating shaft42and the swing arm43are rotated in the valve-opening direction C2as such, the valve body41connected to the rotating shaft42via the swing arm43is displaced so as to come closer to the outflow portion33. Hereby, the valve body41is distanced from the wastegate port36, so that the exhaust gas passes through the wastegate port36inside the turbine housing31, as indicated by an arrow inFIG. 3.

In this case, the exhaust gas passing through the wastegate port36interferes with the valve body41, and then flows out into the exhaust pipe100via the outflow portion33. That is, the valve body41receives a load from the exhaust gas directed toward the outflow portion33through the wastegate port36. Accordingly, the inner portion421of the rotating shaft42to which the valve body41is connected via the swing arm43is pushed toward the outflow portion33side in the reference direction X, namely, toward the opposite side from the compressor housing21, as illustrated inFIG. 6.

Further, when the drive arm44rotates in the valve-opening direction C2due to driving of the actuator46, the front edge443fof the second extension portion443in the drive arm44abuts with the stopper47, so that further rotations of the drive arm44and the rotating shaft42in the valve-opening direction C2are restricted. Even in this state, the driving of the actuator46is continued, so that the fixed portion441of the drive arm44is displaced toward the compressor housing21side in the reference direction X with the part of the drive arm44abutting with the stopper47serving as a fulcrum. Consequently, as illustrated inFIG. 6, the outer portion422of the rotating shaft42is pulled toward the compressor housing21side in the reference direction X due to a driving force P2input into the first extension portion442from the actuator46.

That is, when the wastegate port36is opened, the rotating shaft42is inclined with respect to the central axis Z of the insertion hole312adue to the driving force P2transmitted from the actuator46to the rotating shaft42via the drive arm44and a load P1received by the valve body41from the exhaust gas, as illustrated inFIG. 6. That is, due to actions of two forces in directions different from each other by approximately 180°, the rotating shaft42is pressed against an inside opening edge312a1and an outside opening edge312a2of the insertion hole312a, the inside opening edge312a1being on the inside of the turbine housing31, the outside opening edge312a2being on the outside of the turbine housing31. In this case, as illustrated inFIG. 7, the position of a part of the inside opening edge312a1abutting with the rotating shaft42is different by approximately 180° from the position of a part of the outside opening edge312a2abutting with the rotating shaft42with respect to the central axis Z.

Accordingly, in the present embodiment, when the wastegate port36is opened, the drive arm44is pressed against the stopper47. Further, by using two forces in application directions different from each other by approximately 180°, that is, the driving force P2from the actuator46and the load P1received by the valve body41from the exhaust gas, the rotating shaft42is pressed against the opening edges312a1,312a2. More specifically, the rotating shaft42is pressed against the inside opening edge312a1at a position on the outflow portion33side, and the rotating shaft42is pressed against the outside opening edge312a2at a position on the compressor housing21side. Accordingly, even if a force to displace the valve body41toward the outflow portion33side is applied to the valve body41, the rotating shaft42is not displaced. That is, a state where the rotating shaft42is inclined is maintained. Further, even if the pressure of the exhaust gas interfering with the valve body41pulsates, the forces to press the rotating shaft42against the opening edges312a1,312a2just fluctuate, so that it is possible to restrain the rotating shaft42, the swing arm43, and the valve body41from vibrating. That is, it is possible to restrain the occurrence of abnormal noise caused when the rotating shaft42abuts with the opening edges312a1,312a2.

As illustrated inFIGS. 6 and 7, a small gap S is provided between a peripheral wall312bof the insertion hole312aand the rotating shaft42, so that the exhaust gas flowing through the turbine housing31might leak outside via the gap S. The possibility that the exhaust gas leaks outside as such becomes lower as the occupying ratio of the rotating shaft42in the volume of the insertion hole312ais larger.

Here, when the rotating shaft42vibrates, the occupying ratio of the rotating shaft42in the volume of the insertion hole312afluctuates. That is, the possibility that the exhaust gas leaks outside fluctuates. In this regard, in the present embodiment, it is possible to maintain the rotating shaft42to be inclined in the insertion hole312aas illustrated inFIG. 6. In this case, since the position of the part of the inside opening edge312a1abutting with the rotating shaft42is different by approximately 180° from the position of the part of the outside opening edge312a2abutting with the rotating shaft42with respect to the central axis Z, it is possible to maintain the maximum occupying ratio of the rotating shaft42in the volume of the insertion hole312a. Accordingly, in comparison with a case where the rotating shaft42vibrates in the insertion hole312a, the exhaust gas flow through the turbine housing31can hardly leak outside via the gap S.

Note that, in the present embodiment, the stopper47is placed on the rotation locus of the distal part443tof the second extension portion443in the drive arm44, and the first linear distance B1is shorter than the second linear distance B2. As a result, in comparison with a case where the first linear distance B1is equal to or more than the second linear distance B2, it is possible to increase a force to be input into the outer portion422of the rotating shaft42at the time when the rotation of the drive arm44in the valve-opening direction C2is restricted by the stopper47. As a result, it is possible to increase the forces to press the rotating shaft42against the opening edges312a1,312a2, and eventually, it is possible to enhance vibration restraint effects of the rotating shaft42, the swing arm43, and the valve body41.

Further, the front edge443fof the second extension portion443in the drive arm44is inclined so that its distal end side is placed on the valve-closing direction C1side with respect to its base end side. This makes it possible to restrain a difference between the position of the rotating shaft42and the position of the stopper47from increasing in the reference direction X.

Here, a comparative example in which the front edge443fis not inclined like the present embodiment is illustrated inFIG. 9. In the comparative example, as illustrated inFIG. 9, when the stopper47is placed on the outflow portion33side in the reference direction X, the front edge443fcan be placed so as not to abut with the stopper47at the time when the wastegate port36is closed by the valve body41.

In this regard, in the present embodiment, the stopper47can be placed distanced from the outflow portion33, in comparison with the comparative example. That is, it is not necessary to place the stopper47closer to the outflow portion33in the reference direction X. Further, when the stopper47is placed distanced from the outflow portion33as such, the distal end of the first extension portion442in the drive arm44can hardly approach the outflow portion33in the reference direction X in a state where the wastegate port36is closed by the valve body41. That is, it is not necessary to set a large difference between the position of the flange331and the position of the rotating shaft42in the reference direction X. This accordingly makes it possible to restrain upsizing of the turbine housing31in the reference direction X.

Further, the stopper47is placed at a position which is closer to the drive arm44than the flange331. Accordingly, even if the rotating shaft42is placed near the flange331like the present embodiment, it is possible to avoid such a situation that the drive arm44makes contact with the flange331at the time when the drive arm44is rotated in the valve-opening direction C2.

Note that the above embodiment can be modified to the following other embodiments. The second extension portion443in the drive arm44may have any given shape other than the shape described in the embodiment, provided that the front edge443fis inclined so that the distal end side is placed on the valve-closing direction C1side with respect to the base end side. For example, as illustrated inFIG. 8, the second extension portion443may have such a shape in which the front edge443fis inclined so that the distal end side is placed on the valve-closing direction C1side with respect to the base end side, but the rear edge443bis not inclined. That is, differently from the description in the embodiment, the drive arm44may have a shape that is not bent in the middle from the distal end of the first extension portion442toward the distal end of the second extension portion443.

The second extension portion443in the drive arm44may have any given configuration other than the configuration described in the embodiment, provided that the second extension portion443extends from the part of the fixed portion441on the opposite side from the first extension portion442. For example, as illustrated inFIG. 9, the second extension portion443may be configured such that the front edge443fis not inclined.

In the embodiment, the stopper47is configured to abut with the distal part443tof the second extension portion443. However, the stopper47may be placed so that a part of the second extension portion443on the base end side from the distal part thereof abuts with the stopper47, as indicated by the alternate long and short dash line inFIG. 9, provided that the stopper47abuts with the front edge443fof the second extension portion443.