JP2015124606A - Turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbocharger capable of preventing adhesion of deposit in a diffuser passage.SOLUTION: A turbocharger 1 includes a compressor housing 2 and a bearing housing 3. The compressor housing 2 has a diffuser surface 222, and the bearing housing 3 has a confronting surface 311. An adhesion preventing part 4 is provided on at least one of the diffuser surface and the confronting surface. The adhesion preventing part has a surface forming part 42 and an air tank part 41. The air tank part is communicated with an air flow passage in the downstream side of a diffuser passage through a circulation supply passage 5. Circulation air supplied to the air tank part is ejected to the diffuser passage via a through hole 43 by ejector effect. An opening and closing valve 6 capable of switching inflow and cutoff of the circulation air to the air tank part is provided in the circulation supply passage.

Description

  The present invention relates to a turbocharger including a compressor housing and a bearing housing.

A turbocharger mounted in an automobile or the like is configured to compress air taken in by a compressor and discharge the compressed air toward an internal combustion engine (see Patent Document 1).
That is, the turbocharger includes a compressor housing having an air flow path on which an impeller is disposed on the inside, and a bearing housing that rotatably supports a rotor shaft having the impeller fixed to one end. The air flow path has an intake port that sucks air toward the impeller, and a discharge scroll chamber into which compressed air discharged from the impeller flows.

The compressor housing has a shroud surface facing the impeller and a diffuser surface extending from the shroud surface toward the discharge scroll chamber. The bearing housing forms a diffuser passage with the diffuser surface of the compressor housing.
The turbocharger is configured such that compressed air discharged from the impeller passes through the diffuser passage, flows into the discharge scroll chamber, and is discharged from the discharge scroll chamber to the internal combustion engine side.

Japanese Patent Laid-Open No. 2002-180841

  For example, an internal combustion engine includes a blow-by gas recirculation device (hereinafter referred to as PCV) that recirculates blow-by gas (mainly unburned gas) generated in a crankcase to an intake passage to clean the crankcase and the head cover. There is something to prepare. In this case, oil (oil mist) contained in the blow-by gas may flow out from the PCV to the intake passage on the upstream side of the compressor in the turbocharger.

  At this time, if the outlet air pressure of the compressor is high, the outlet air temperature also rises. Therefore, the oil flowing out from the PCV is concentrated and thickened due to evaporation, and the compressor housing diffuser surface and the surface of the bearing housing opposite to the compressor housing surface. It may be deposited as a deposit. Then, the diffuser passage is narrowed by the deposited deposit, which may cause a decrease in performance of the turbocharger, and further a decrease in output of the internal combustion engine.

  In order to prevent deposit accumulation in the diffuser passage as described above, it is conceivable to suppress the air temperature at the outlet of the compressor to some extent. However, in this case, the performance of the turbocharger cannot be fully exhibited. It is difficult to sufficiently increase the output of the internal combustion engine.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a turbocharger that can prevent deposits from adhering to a diffuser passage.

One aspect of the present invention is a compressor housing having an air flow path on which an impeller is disposed on the inside,
A bearing housing that rotatably supports a rotor shaft having the impeller fixed to one end;
The air flow path has an intake port that sucks air toward the impeller, and a discharge scroll chamber that is formed in the circumferential direction on the outer peripheral side of the impeller and guides compressed air discharged from the impeller to the outside.
The compressor housing has a shroud surface facing the impeller, and a diffuser surface extending from the shroud surface toward the discharge scroll chamber,
The bearing housing has a facing surface that faces the diffuser surface of the compressor housing and forms a diffuser passage with the diffuser surface.
At least one of the diffuser surface of the compressor housing and the opposing surface of the bearing housing is provided with an adhesion preventing portion for preventing deposit adhesion,
The adhesion preventing portion includes a surface forming portion having a large number of fine through-holes opened to the diffuser passage side, and an air tank portion covered from the diffuser passage side by the surface forming portion,
The air tank portion is configured to communicate with the air flow path on the downstream side of the diffuser passage via a circulation supply path and to supply circulating air that is a part of the compressed air. ,
Due to the ejector effect that occurs when the compressed air passes through the diffuser passage, the circulating air supplied to the air tank portion is configured to be ejected to the diffuser passage through the through hole,
The turbocharger is characterized in that an on-off valve capable of switching between inflow and shut-off of the circulating air to the air tank portion is disposed in the circulation supply path.

  In the turbocharger, an adhesion preventing portion is provided on at least one of the diffuser surface of the compressor housing and the opposing surface of the bearing housing. The adhesion preventing part has a surface forming part having a large number of fine through-holes opened to the diffuser passage side, and an air tank part to which circulating air is supplied on the surface forming part opposite to the diffuser passage. Then, when the compressed air passes through the diffuser passage, an ejector effect (entrainment effect) occurs in the adhesion preventing portion, and the circulating air in the air tank portion passes through the numerous fine through holes in the surface forming portion. To erupt. As a result, the distance between the deposit that has come to the adhesion preventing portion and the surface on the diffuser passage side in the adhesion preventing portion can be secured, so the intermolecular distance between the deposit and the surface on the diffuser passage side in the adhesion preventing portion. Force can be suppressed. Therefore, the deposit that has come to the adhesion preventing portion is blown away by the supply air (compressed air) flowing through the diffuser passage. As a result, the deposit is prevented from adhering to the surface on the diffuser passage side in the adhesion preventing portion.

  Further, in the adhesion preventing portion, circulating air that is a part of compressed air discharged from the impeller is used as gas ejected to the diffuser passage through the through hole. Such circulating air has a slightly lower pressure than the supply air (compressed air) passing through the diffuser passage, but due to the ejector effect of the supply air, it is not particularly pressurized by a pressurizing pump or provided with a backflow prevention valve. It is possible to prevent the compressed air in the passage from flowing backward to the air tank part side through the through hole.

  When the outlet temperature of the compressor is relatively low, liquid oil mist may fly into the diffuser passage, but the liquid oil mist is repelled by the circulating air ejected from the adhesion preventing portion to the diffuser passage. Blowed away by air supply. Therefore, oil mist can be prevented from depositing in the diffuser passage as a deposit.

  The circulation supply path is provided with an on-off valve that can switch between circulating air flowing into and shutting off the air tank. Therefore, when it is not necessary to supply the circulating air to the diffuser passage, the on-off valve can be closed to block the introduction of the circulating air to the adhesion preventing portion. That is, deposit adhesion in the diffuser passage is likely to occur due to, for example, various conditions such as the degree of deterioration of oil that is the cause of deposit and the temperature of the compressed air (supercharging temperature) flowing through the diffuser passage. Arise. Therefore, in a situation where deposits do not easily adhere, the on-off valve is closed to prevent the inflow of circulating air, and the compression efficiency of air in the compressor is ensured. On the other hand, under circumstances where deposits are likely to adhere, the on-off valve can be opened to circulate air from the adhesion preventing part to prevent deposits from adhering to the diffuser passage. Therefore, by providing the on-off valve, deposit adhesion can be efficiently suppressed while suppressing a decrease in efficiency of the turbocharger as much as possible.

  As described above, according to the present invention, it is possible to provide a turbocharger that can prevent deposits from adhering to the diffuser passage.

FIG. 3 is a cross-sectional explanatory view showing a turbocharger in the first embodiment. FIG. 3 is an enlarged cross-sectional explanatory view showing a turbocharger in the first embodiment. FIG. 3 is a top explanatory view showing a diffuser passage, a discharge scroll chamber, and an impeller in the first embodiment. FIG. 3 is an enlarged cross-sectional explanatory view showing an adhesion preventing portion in the first embodiment. FIG. 3 is an explanatory top view illustrating a facing surface and an impeller that form a diffuser passage in the first embodiment. FIG. 3 is an enlarged cross-sectional explanatory diagram illustrating a situation where the ejector effect is generated in the first embodiment. FIG. 3 is a flowchart of an on-off valve control method according to the first embodiment. The cross-sectional enlarged explanatory view which shows the adhesion prevention part which has the surface formation part which consists of porous bodies in Example 2. FIG. FIG. 6 is a cross-sectional explanatory view of a turbocharger in Embodiment 3. FIG. 6 is an enlarged cross-sectional explanatory view of a turbocharger in Embodiment 4.

  The bearing housing may be an integrally configured housing, or may be a housing configured by combining a plurality of members. That is, in the latter case, for example, the bearing housing has a separate structure including a bearing main body and a back plate disposed between the bearing main body and the compressor housing and facing a part of the air flow path. can do. In this case, an opposing surface is formed on the compressor side surface of the back plate. And an adhesion prevention part can be formed in a backplate.

  Moreover, it is preferable that the said adhesion prevention part is cyclically | annularly provided over the whole circumferential direction in a diffuser surface and an opposing surface. In this case, it is possible to prevent the deposit prevention effect in the diffuser passage from being varied over the entire circumferential direction.

  Moreover, it is preferable that the said adhesion prevention part is formed in the length area | region more than half of the full length of the diffuser channel | path in a radial direction in a diffuser surface and an opposing surface. In this case, deposits can be effectively prevented from adhering to the diffuser passage. Here, the total length of the diffuser passage is the length in the radial direction of a region where the diffuser surface and the opposing surface are arranged in parallel to each other. In addition, the said adhesion prevention part can also be formed over the full length of the diffuser channel | path in radial direction.

  In the turbocharger, the adhesion preventing portion is provided on both the diffuser surface of the compressor housing and the facing surface of the bearing housing, and the circulation supply path is a common supply path connected to the air flow path. And a branch supply path that branches off from the common supply path and is connected to the air tank section in each adhesion preventing section, and the on-off valve is preferably provided in the common supply path. In this case, it is possible to effectively prevent deposits on both the diffuser surface of the compressor housing and the opposing surface of the bearing housing. And since circulation air can be supplied with respect to two adhesion prevention parts from one common supply path, simplification of an apparatus can be achieved. In addition, since the on / off valve is provided in the common supply path, the inflow and shutoff of the circulating air to the two adhesion preventing units can be controlled by one on / off valve.

  Further, the on-off valve is configured to be controlled to open and close based on the degree of deterioration of the oil of the internal combustion engine to which the turbocharger is connected and the temperature of the compressed air passing through the air flow path. Is preferred. In this case, deposit adhesion in the diffuser passage can be prevented more efficiently.

Moreover, the said surface formation part shall consist of a porous body. In this case, the numerous fine through holes can be easily configured. Moreover, the surface forming part can be formed at low cost by using the porous body.
Examples of the porous body include porous resin, metal, ceramics, glass fiber, carbon graphite, and the like (for example, a product in which a resin film is wound, a product in which resin paper is stacked, a resin, etc. For example, a knitted yarn) can be used.

  In addition, the surface forming portion can be made of a material other than porous. For example, the surface forming portion can be formed by perforating a metal plate or a resin plate in the thickness direction to provide a large number of fine through holes. Drilling in a metal plate or a resin plate can be performed by a drill, laser, electric discharge machining or the like.

  In the turbocharger, each of the plurality of fine through holes is formed such that a direction in which holes are formed from the opening on the air tank side toward the opening on the diffuser passage side is inclined toward the downstream side of the diffuser passage. It can be formed. In this case, since each through hole is formed toward the downstream side of the diffuser passage, the direction in which the compressed air flows in the through hole is similar to the direction in which the compressed air flows in the diffuser passage. From upstream to downstream. As a result, the compressed air in the air tank portion smoothly flows into the diffuser passage through the through hole. And the effect of entrainment of the compressed air in the air tank part through the through hole, which is generated when the compressed air flows through the diffuser passage, is improved. This improves the deposit adhesion preventing effect in the adhesion preventing portion.

  It is preferable that the circulation supply path is connected to an outlet port for leading the compressed air guided by the discharge scroll chamber or an air flow path downstream of the outlet port. In this case, oil mist and deposits are prevented from flowing into the circulation supply path, and a reduction in deposit adhesion preventing effect in the adhesion preventing portion can be prevented.

  In addition, the inlet of the circulation supply path at the connection between the circulation supply path and the air flow path opens in the direction in which the compressed air flows in the outlet port or the air flow path downstream of the outlet port. It is preferable. In this case, oil mist and deposits scattered along the flow direction of the compressed air can be prevented from flowing into the circulation supply path.

Example 1
Examples of the turbocharger will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the turbocharger 1 of the present example is capable of rotating a compressor housing 2 having an air flow path 10 in which an impeller 13 is disposed, and a rotor shaft 14 having the impeller 13 fixed to one end. And a bearing housing 3 to be supported.
The air flow path 10 includes an intake port 11 that sucks air toward the impeller 13, and a discharge scroll chamber 12 that is formed in the circumferential direction on the outer peripheral side of the impeller 13 and guides compressed air discharged from the impeller 13 to the outside. Have.

The compressor housing 2 has a shroud surface 221 that faces the impeller 13, and a diffuser surface 222 that extends from the shroud surface 221 toward the discharge scroll chamber 12.
The bearing housing 3 has a facing surface 311 that faces the diffuser surface 222 of the compressor housing 2 and forms the diffuser passage 15 between the bearing housing 3 and the diffuser surface 222.

On the diffuser surface 222 of the compressor housing 2 and the opposing surface 311 of the bearing housing 3, an adhesion preventing portion 4 for preventing adhesion of deposits is provided.
The adhesion preventing portion 4 includes a surface forming portion 42 having a large number of fine through holes 43 opened to the diffuser passage 15 side, and an air tank portion 41 covered by the surface forming portion 42 from the diffuser passage 15 side. .

As shown in FIG. 3, the air tank portion 41 communicates with an air flow path downstream of the diffuser passage 15 via the circulation supply path 5 and is supplied with the circulating air G that is a part of the compressed air. It is configured as follows.
As shown in FIGS. 4 and 6, the circulating air G supplied to the air tank portion 41 is jetted to the diffuser passage 15 through the through-hole 43 by the ejector effect generated when the compressed air passes through the diffuser passage 15. It is configured.
As shown in FIGS. 1 and 2, the circulation supply path 5 is provided with an on-off valve 6 that can switch between inflow and interruption of the circulating air G to the air tank portion 41.

The turbocharger 1 can be used by being connected to an internal combustion engine having a PCV.
As shown in FIG. 1, the turbocharger 1 rotates a turbine by exhaust gas discharged from an internal combustion engine such as an automobile, compresses intake air in the compressor using the rotational force, and sends the compressed air to the internal combustion engine. It is configured as follows. Therefore, the turbocharger 1 includes a turbine housing (not shown) on the opposite side of the compressor housing 2 that forms the outer shell of the compressor in the axial direction.

  An exhaust gas flow path in which a turbine impeller is disposed is formed inside the turbine housing. The turbine impeller is fixed to the rotor shaft 14. That is, the impeller 13 of the compressor and the turbine impeller are connected by the rotor shaft 14. Thereby, it is comprised so that the impeller 13 of a compressor may rotate with rotation of a turbine impeller.

  As shown in FIG. 1, the compressor housing 2 includes a cylindrical intake port forming portion 21 that forms the intake port 11, a shroud portion 22 that forms the shroud surface 221 and the diffuser surface 222, and a discharge that forms the discharge scroll chamber 12. And a scroll chamber forming portion 23. The diffuser surface 222 is formed in an annular shape so as to face the facing surface 311 of the bearing housing 3. The diffuser surface 222 forms a diffuser passage 15 between the diffuser surface 222 and the facing surface 311 of the bearing housing 3. In the diffuser passage 15, the compressed air compressed by an impeller 13 described later flows from the upstream impeller 13 side to the downstream discharge scroll chamber 12 side as indicated by an arrow P in FIG. 4.

  As shown by an arrow P1 in FIG. 3, the compressed air that has flowed from the impeller 13 side to the discharge scroll chamber 12 side swirls in the discharge scroll chamber 12 in a spiral shape, and as shown by an arrow P2, the downstream outlet port 16 To flow down. Thereafter, the air is led out from the outlet port 16 (internal combustion engine side) as indicated by an arrow P3.

  Further, as shown in FIG. 2, an impeller 13 is disposed on the inner peripheral side of the shroud portion 22 of the compressor housing 2. The impeller 13 includes a hub 131 that is fixed to the rotor shaft 14 by a shaft end nut 141, and a plurality of blades 132 that protrude from the outer peripheral surface of the hub 131 and are arranged in the circumferential direction. The plurality of blades 132 are disposed to face the shroud surface 221 of the compressor housing 2. As shown in FIG. 5, the blade 132 is inclined with respect to a virtual straight line L <b> 2 along the tangent (exit tangent) direction at the outer edge 13 a of the impeller 13. In this example, the angle (backward angle) α formed by the blade 132 and the virtual straight line L2 at the outer edge 13a of the impeller 13 is about 60 degrees.

  As shown in FIGS. 1 and 2, a bearing housing 3 that rotatably supports the rotor shaft 14 is disposed between the compressor housing 2 and the turbine housing. A substantially disc-shaped flange portion 33 is provided on one end side in the axial direction of the bearing housing 3. An opposing surface 311 facing the diffuser surface 222 of the compressor housing 2 is formed in an annular shape on the compressor side surface of the flange portion 33.

  As shown in FIGS. 1, 2, and 6, the compressor housing 2 and the bearing housing 3 are each provided with an adhesion preventing portion 4. Each adhesion preventing portion 4 is provided in an annular shape over the entire circumferential direction on the diffuser surface 222 of the compressor housing 2 and the facing surface 311 of the bearing housing 3. Further, the adhesion preventing portion 4 is formed in a length region of more than half of the entire length of the diffuser passage 15 in the radial direction on the diffuser surface 222 and the facing surface 311.

  The adhesion preventing unit 4 includes an air tank unit 41 and a surface forming unit 42. The air tank portion 41 has an annular shape formed by covering the diffuser passage 15 side of the groove portion formed in an annular shape on the diffuser surface 222 of the compressor housing 2 and the facing surface 311 of the bearing housing 3 with the surface forming portion 42. It is space. A circulation supply path 5 is connected to the air tank portion 41.

  As shown in FIG. 3, the circulation supply path 5 is connected at its end opposite to the air tank 41 side to an outlet port 16 or an air flow path located downstream of the outlet port 16. In other words, in FIG. 3, the external port 17 is connected to the outlet port 16 at the outlet flange portion 24, but the suction port 511 of the circulation supply path 5 is connected to the air flow path in the external tube 17. ing. Thus, the air tank portion 41 communicates with the air flow path via the circulation supply path 5 on the downstream side of the diffuser passage 15, particularly on the downstream side of the outlet port 16 in this example. A part of the compressed air is supplied to the air tank 41 as the circulating air G.

  The suction port 511 of the circulation supply path 5 opens in the direction P3 in which the compressed air flows in the air flow path. The direction R of the compressed air flowing into the suction port 511 is opposite to the direction P3.

  As shown in FIG. 2, the circulation supply path 5 includes a common supply path 51 connected to the air flow path, and a branch supply branched from the common supply path 51 and connected to the air tank section 41 in each adhesion prevention section 4. Road 52. The on-off valve 6 is provided in the common supply path 51. The on-off valve 6 can be constituted by, for example, an electromagnetic valve. And it opens and closes by the opening / closing control method mentioned later.

  As shown in FIGS. 3 and 5, the surface forming portion 42 is an annular (donut-shaped) plate-like member. The material of the surface forming portion 42 can be, for example, aluminum or iron.

  A large number of fine through-holes 43 that open to the diffuser passage 15 side are formed in the surface forming portion 42. As shown in FIG. 4, the through hole 43 penetrates from the air tank portion 41 to the diffuser passage 15. The diameter of each through-hole 43 can be about 0.5 μm to about 50 μm, for example. Thereby, the backflow of the compressed air through the through hole 43 can be effectively prevented while appropriately suppressing the pressure loss when the circulating air G passes through the through hole 43. In this example, the diameter of each through-hole 43 is about 1.0 μm.

  As shown in FIG. 4, each of the numerous fine through holes 43 has a hole forming direction Q from the opening on the air tank 41 side toward the opening on the diffuser passage 15, and the downstream side of the diffuser passage 15 ( It is formed so as to incline toward the discharge scroll chamber 12 side. That is, the angle θ formed by the formation direction Q of the through hole 43 and the flow direction P of the compressed air in the diffuser passage 15 is less than 90 degrees. In this example, the angle θ is about 40 degrees. The flow direction P is a direction parallel to the diffuser surface 222 and the facing surface 311.

  As shown in FIG. 5, a large number of fine through holes 43 are formed along a virtual curve C in the diffuser passage 15. The imaginary curve C starts from the outer edge 13a of the impeller 13 with respect to the imaginary straight line L1 whose angle with the tangent line (virtual straight line L2) at the outer edge 13a coincides with the backward angle α from the starting point (outer edge 13a) to the diffuser passage. 15 is curved so as to be away from the rotation direction r of the impeller 13 toward the downstream side (discharge scroll chamber 12 side). And the through-hole 43 is each formed in each position which rotated the virtual curve C in FIG. 5 by the space | interval of the predetermined angle centering on the axial center 13b of the impeller 13. FIG.

  The density at which the through holes 43 are provided is not particularly limited, and may be appropriately changed within a range in which a necessary adhesion preventing effect is obtained. For example, the ratio of the area occupied by the opening of the through hole 43 on the surface of the diffuser passage 15 can be about 20% to about 50%.

  For example, as shown in FIG. 7, the opening / closing control of the on-off valve 6 provided in the circulation supply path 5 is performed by the degree of deterioration of the oil in the internal combustion engine and the compression passing through the air passage (diffuser passage 15) in the compressor housing 2. It can be performed based on the temperature of air (supercharging temperature). The degree of deterioration of oil can be determined based on information such as the engine speed, load, and oil temperature, for example, using a determination method disclosed in Japanese Patent Application Laid-Open No. 2008-50972. And it is determined whether the deterioration degree of oil is more than predetermined value (step S1).

  If it is determined that the oil has deteriorated, it is next determined whether the supercharging temperature is equal to or higher than a predetermined value (for example, 165 to 180 ° C.) (step S2). When it is determined that the supercharging temperature is equal to or higher than the predetermined value, the on-off valve 6 is opened (step S3). The threshold value for the degree of deterioration of the oil and the threshold value for the supercharging temperature are set in advance in consideration of the ease of deposit adhesion.

  Thus, based on the degree of deterioration of the oil and the supercharging temperature, when it is determined that deposits are likely to adhere, the on-off valve 6 is opened, and in other cases, the on-off valve 6 is closed. In addition, the method of opening / closing control of the on-off valve 6 is not restricted to this, A various method is employable.

Next, the function and effect of the turbocharger 1 of this example will be described.
In the turbocharger 1 of this example, when the compressed air passes through the diffuser passage 15 from the impeller 13 side, an ejector effect is generated in the adhesion preventing portion 4. That is, the circulating air G in the air tank portion 41 is ejected to the diffuser passage 15 through a large number of fine through holes 43 in the surface forming portion 42. Thereby, since the distance between the deposit that has come to the adhesion preventing portion 4 and the surface on the diffuser passage 15 side in the adhesion preventing portion 4 can be secured, the deposit and the surface on the diffuser passage 15 side in the adhesion preventing portion 4 The intermolecular force between the two can be suppressed. Therefore, the deposit that has come to the adhesion preventing unit 4 is blown away by the supply air (compressed air) flowing through the diffuser passage 15. As a result, the deposit is prevented from adhering to the surface on the diffuser passage 15 side in the adhesion preventing unit 4.

  Further, in the adhesion preventing unit 4, the circulating air G that is a part of the compressed air discharged from the impeller 13 is used as the gas ejected to the diffuser passage 15 through the through hole 43. The circulating air G is slightly lower in pressure than the compressed air in the diffuser passage 15, but due to the ejector effect of the supply air, the circulating air G is not particularly pressurized by a pressurizing pump or provided with a backflow prevention valve. It is possible to prevent the compressed air from flowing back to the air tank portion 41 side through the through hole 42.

  When the outlet temperature of the compressor is relatively low, liquid oil mist may fly into the diffuser passage 15, but the liquid oil mist is caused by the circulating air G ejected from the adhesion preventing unit 4 to the diffuser passage 15. It is repelled and blown away by air supply. Therefore, oil mist can be prevented from depositing in the diffuser passage 15 as a deposit.

  In addition, the circulation supply path 5 is provided with an on-off valve 6 that can switch between the flow of the circulation air G to the air tank portion 41 and the cutoff thereof. Therefore, when it is not necessary to supply the circulating air G to the diffuser passage 15, the on-off valve 6 can be closed to block the introduction of the circulating air G to the adhesion preventing unit 4. That is, deposit adhesion in the diffuser passage 15 is likely to occur due to, for example, various conditions such as the degree of deterioration of the oil that is the cause of the deposit and the temperature of the compressed air flowing through the diffuser passage 15 (supercharging temperature). A situation arises. Therefore, in a situation where deposits do not easily adhere, the on-off valve 6 is closed to prevent the inflow of the circulating air G, thereby ensuring the air compression efficiency in the compressor. On the other hand, in a situation where deposits are likely to adhere, the on-off valve 6 can be opened and the circulating air G can be ejected from the adhesion preventing unit 4 to prevent deposits from adhering to the diffuser passage 15. Therefore, by providing the on-off valve 6, it is possible to efficiently suppress deposit adhesion while suppressing the decrease in efficiency of the turbocharger 1 as much as possible.

  Further, the adhesion preventing unit 4 is provided on both the diffuser surface 22 and the opposing surface 311. Therefore, deposit adhesion can be effectively prevented on both the diffuser surface 222 and the opposing surface 311. The circulation supply path 5 includes a common supply path 51 and a branch supply path 52. Therefore, since the circulating air G can be supplied from the single common supply path 51 to the two adhesion preventing units 4, the apparatus can be simplified. In addition, since the on / off valve 6 is provided in the common supply path 51, the inflow and shutoff of the circulating air G to the two adhesion preventing units 4 can be controlled by one on / off valve 6.

  Further, in the surface forming portion 42 of the adhesion preventing portion 4, each of the many fine through holes 43 has a hole forming direction Q from the opening on the air tank portion 41 side toward the opening on the diffuser passage 15 side. 15 is formed so as to incline to the downstream side (discharge scroll chamber 12 side). Thereby, the flow direction of the circulating air G passing through each through-hole 43 has a vector component in the direction of the flow of compressed air in the diffuser passage 15 (from the impeller 13 side to the discharge scroll chamber 12 side). As a result, the circulating air G in the air tank portion 41 flows smoothly into the diffuser passage 15 through the through hole 43. And the entrainment effect of the circulating air G of the air tank part 41 through the through-hole 43 which arises when compressed air flows through the diffuser channel | path 15 in the direction of the arrow P improves. Thereby, the deposit adhesion preventing effect in the adhesion preventing portion 4 is improved.

  In this example, the angle θ between the formation direction Q of each through-hole 43 and the direction P in which the compressed air flows is about 40. Thereby, compared with the case where the said angle (theta) is close to 90 degree | times, the entrainment effect of the circulating air G of the air tank part 41 via the through-hole 43 is fully exhibited. In addition, since the length of each through hole 43 is shorter than when the angle θ is close to 0 degrees, that is, when the angle θ is nearly parallel to the compressed air flow direction P of the diffuser passage 15, the through holes 43. The pressure loss at is moderately suppressed. In addition, a sufficient number of through holes 43 can be secured, and formation of the through holes 43 is facilitated.

  In the turbocharger 1, the through hole 43 is formed along the virtual curve C in the diffuser passage 15. As shown in FIG. 5, in the diffuser passage 15, the compressed air discharged from the impeller 13 gradually decreases in the backward angle α of the impeller 13 as it proceeds to the downstream side (discharge scroll chamber 12 side) of the diffuser passage 15. It flows in the direction. That is, the compressed air discharged from the impeller 13 flows along the virtual curve C. Therefore, a large number of fine through holes 43 are arranged along the direction P in which the compressed air flows. Thereby, the circulating air G in the air tank 41 is smoothly ejected into the diffuser passage 15 through the through-hole 43 and smoothly flows in the direction P in which the compressed air in the diffuser passage 15 flows. As a result, the deposit adhesion preventing effect in the adhesion preventing portion 4 is improved.

  The circulation supply path 5 is connected to an air flow path on the downstream side of the outlet port 16. As a result, the compressed air is rectified to some extent at the portion to which the circulation supply path 5 is connected, so that oil mist and deposits are prevented from flowing into the circulation supply path 5, and deposit adherence in the adhesion prevention unit 4. Reduction of the prevention effect can be prevented.

  Further, in the turbocharger 1, the suction port 511 of the circulation supply path 5 is opened in the direction P <b> 3 in which the compressed air flows in the external pipe 17. Thereby, it is possible to prevent oil mist and deposits scattered along the flow direction P3 of the compressed air from flowing into the circulation supply path 5.

  Further, the adhesion preventing portion 4 is provided in an annular shape over the entire circumferential direction on the diffuser surface 222 and the facing surface 311. Thereby, it is possible to prevent the deposit prevention effect in the diffuser passage 15 from varying over the entire circumferential direction.

  Further, the adhesion preventing portion 4 is formed in a length region of more than half of the entire length of the diffuser passage 15 in the radial direction on the diffuser surface 222 and the facing surface 311. Thereby, deposits can be effectively prevented from adhering to the diffuser passage 15.

  As described above, according to the turbocharger 1, deposits can be prevented from adhering to the diffuser passage 15.

  In this example, the adhesion preventing portion 4 is provided on both the diffuser surface 222 and the opposing surface 311, but is not limited thereto, and the adhesion preventing portion 4 is provided on either the diffuser surface 222 or the opposing surface 311. It is good also as providing only. In this case, the above-described operational effects are obtained except for the operational effects provided by providing the adhesion preventing portions 4 on both sides.

  In this example, the circulation supply path 5 is connected to the air flow path downstream of the outlet port 16, but is not limited to this, and is connected to the air flow path downstream of the diffuser passage 15. Just do it. For example, a circulation supply path may be connected to the intake manifold connecting the discharge scroll chamber 12 and the internal combustion engine so that a part of the compressed air is circulated from the intake manifold to the air tank portion 41.

(Example 2)
As shown in FIG. 8, the turbocharger 1 of this example includes a surface forming part 420 made of a porous material, instead of the surface forming part 42 made of a metal plate in the first embodiment. In addition, the same code | symbol is attached | subjected to the component equivalent to the turbocharger 1 of Example 1, and the description is abbreviate | omitted.

  The surface forming portion 420 has a large number of fine through holes 430 as shown in FIG. In the surface formation part 420, the formation direction of each through-hole 430 is irregular. Therefore, each through-hole 430 is not formed in the predetermined direction Q like the surface forming portion 42 in the first embodiment, and is not formed along the virtual curve C. Also in the surface forming portion 420 having such a through hole 430, the compressed air flows in the P direction in the diffuser passage 15 to produce an ejector effect. As shown by an arrow G1 in FIG. Circulating air in the tank part 41 is ejected. In addition, the direction of arrow G1 represents the ejection direction as the whole circulating air which ejects from the surface formation part 420. FIG.

  Thereby, deposits can be prevented from adhering to the diffuser passage 15. Furthermore, since the surface forming portion 420 is made of a porous resin, the through hole 430 can be easily configured, and the surface forming portion 420 can be formed at a low cost.

  In addition, in Example 1, it implements also in this example except the effect by the through-hole 43 being formed in the predetermined direction Q and the through-hole 43 being formed along the virtual curve C. The same effects as in Example 1 are achieved.

(Example 3)
In this example, as shown in FIG. 9, the bearing housing 3 includes a bearing body 30, a back plate 31 disposed between the bearing body 30 and the compressor housing 2 and facing a part of the air flow path. It is an example configured by combining. That is, a part of the bearing housing 3 including the flange portion 33 shown in the first embodiment is configured by the pack plate 31 that is a separate member from the bearing main body portion 30.

In the case of this example, an opposing surface 311 is formed on the compressor side surface of the back plate 31. Then, the adhesion preventing part 4 is formed on the back plate 31.
Others are the same as in the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.
Also in the case of this example, the same effect as Example 1 can be obtained.

Example 4
In this example, as shown in FIG. 10, the circulation supply path 5 is formed in the compressor housing 2 and the bearing housing 3.
The circulation supply path 5 has one common supply path 51 and two branch supply paths 52 as in the first embodiment. Of the two branch supply paths 52, the branch supply path 52 a connected to the adhesion prevention section 4 provided on the diffuser surface 222 is formed only in the compressor housing 2, but the adhesion prevention section 4 provided on the facing surface 311. A branch supply path 52b connected to the compressor housing 2 and the bearing housing 3 is formed.

  That is, the branch supply path 52 b is formed by connecting the first flow path 521 formed in the compressor housing 2 and the second flow path 522 formed in the bearing housing 3 in series. The first flow path 521 is formed so as to be connected to the common supply path 51 in a straight line in the compressor housing 2. The second flow path 522 has an outer axial direction part 523 that opens to the compressor housing 2 side so as to connect to the first flow path 521, a radial direction part 524 that extends radially inward from the outer axial direction part 523, An inner axial direction portion 525 is formed in the axial direction from the radial direction portion 524 and is connected to the air tank portion 41.

  The branch supply path 52 b is formed by connecting the first flow path 521 and the second flow path 522 on the mating surface 18 between the compressor housing 2 and the bearing housing 3. If necessary, a seal member such as an O-ring may be interposed around the connection portion between the opening of the first flow path 521 and the opening of the second flow path 522 in the mating surface 18.

The branch supply path 52a connected to the adhesion preventing section 4 provided on the diffuser surface 222 includes a radial direction portion 526 extending radially inward from the common supply path 51 and an axial direction from the radial direction portion 526. And an axial portion 527 that extends and is connected to the tank portion 421a.
The shape of the circulation supply path 5 described above is not particularly limited, and various shapes are conceivable.

  The branch supply path 52 is formed by appropriately perforating the compressor housing 2 and the bearing housing 3. That is, the compressor housing 2 and the bearing housing 3 can be formed by casting a metal such as an aluminum alloy. And with respect to these cast products, a plurality of appropriate holes are formed at appropriate positions in a straight line by a drill or the like. For example, the compressor housing 2 is perforated from the outer peripheral surface inward in the radial direction to form the radial portion 526 of the branch supply path 52a. In addition, a hole formed through the compressor housing 2 in the axial direction outside the scroll chamber 12 serves as the first flow path 521 and the common supply path 51 of the branch supply path 52b. Further, the flange portion 33 of the bearing housing 3 is pierced from the outer peripheral surface inward in the radial direction to form the radial portion 524 of the second flow path 522 of the branch supply path 52b.

  In addition, although the hole drilled from the outer peripheral surface toward the radially inner side with respect to the compressor housing 2 and the bearing housing 3 opens in the outer peripheral surface, these openings are closed by the plug member 65. Thereby, the circulating air introduced from the common supply path 51 via the on-off valve 6 can be supplied to the air tank unit 41 through the branch supply path 52 without leaking outside.

  The on / off valve 6 is disposed in the common supply path 51. In this example, the on-off valve 6 has a through-hole that becomes a part of the common supply path 51 and is rotatably disposed in the compressor housing 2. The on-off valve 6 is configured to be able to connect or shut off the front and rear common supply paths 51 by rotating in the compressor housing 2.

  Further, the common supply path 51 is extended by an extension pipe (not shown) and connected to an air flow path on the downstream side of the diffuser passage 15. In this example, the on-off valve 6 is provided inside the compressor housing 2, but the on-off valve may be provided on the extended pipe.

  Others are the same as in the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.

  In the case of this example, a circulation supply path 5 for supplying the circulation air G to the air tank portion 41 is formed in the compressor housing 2 and the bearing housing 3. Thereby, members, such as piping for supplying the circulating air to the air tank part 41, can be reduced, the number of parts of the turbocharger can be reduced, and compactness can be achieved.

At least one circulation supply path 5 is formed by connecting a first supply path 521 formed in the compressor housing 2 and a second supply path 522 formed in the bearing housing 3 in series. Thus, air can be supplied from the compressor housing 2 side to the air tank portion 41 provided in the bearing housing 3 via the circulation supply path 5. Thereby, it becomes possible to supply air to the two air tank parts 41 (adhesion prevention part 4) from the common supply path 51 provided in the compressor housing 2. FIG. As a result, the circulating air supply path to the air tank unit 41 can be simplified. Therefore, the number of parts of the turbocharger 1 can be reduced, the number of assembling steps can be reduced, and further, the mounting property to a vehicle or the like can be improved.
In addition, the same effects as those of the first embodiment are obtained.

  For example, a configuration in which the third embodiment and the fourth embodiment are combined may be employed. That is, the branch supply path 52 b connected to the porous supply portion 41 provided on the facing surface 311 can be formed across the back plate 31 and the compressor housing 2.

  In the above-described embodiment, the circulation supply path 5 is configured by the common supply path 51 and the two branched supply paths 52. However, for example, the adhesion prevention unit and the diffuser are formed by two independent circulation supply paths. It is also possible to connect an air flow path downstream from the passage. In this case, an open / close valve is provided in each circulation supply path.

  Moreover, in the said Example, although the angle (theta) (FIG. 4) which the formation direction Q of the through-hole 43 and the flow direction P of the compressed air in the diffuser channel | path 15 make is less than 90 degree | times, the example shown is not necessarily shown. However, the present invention is not limited to this, and θ may be 90 degrees.

DESCRIPTION OF SYMBOLS 1 Turbocharger 10 Air flow path 11 Intake port 12 Discharge scroll chamber 13 Impeller 14 Rotor shaft 2 Compressor housing 221 Shroud surface 222 Diffuser surface 3 Bearing housing 311 Opposing surface 4 Adhesion prevention part 41 Air tank part 42, 420 Surface formation part 43, 430 Through hole 5 Circulation supply path 6 On-off valve

Claims (3)

A compressor housing having an air flow path on which an impeller is arranged, and
A bearing housing that rotatably supports a rotor shaft having the impeller fixed to one end;
The air flow path has an intake port that sucks air toward the impeller, and a discharge scroll chamber that is formed in the circumferential direction on the outer peripheral side of the impeller and guides compressed air discharged from the impeller to the outside.
The compressor housing has a shroud surface facing the impeller, and a diffuser surface extending from the shroud surface toward the discharge scroll chamber,
The bearing housing has a facing surface that faces the diffuser surface of the compressor housing and forms a diffuser passage with the diffuser surface.
At least one of the diffuser surface of the compressor housing and the opposing surface of the bearing housing is provided with an adhesion preventing portion for preventing deposit adhesion,
The adhesion preventing portion includes a surface forming portion having a large number of fine through-holes opened to the diffuser passage side, and an air tank portion covered from the diffuser passage side by the surface forming portion,
The air tank portion is configured to communicate with the air flow path on the downstream side of the diffuser passage via a circulation supply path and to supply circulating air that is a part of the compressed air. ,
Due to the ejector effect that occurs when the compressed air passes through the diffuser passage, the circulating air supplied to the air tank portion is configured to be ejected to the diffuser passage through the through hole,
The turbocharger is characterized in that an on-off valve capable of switching between inflow and shut-off of the circulating air to the air tank portion is disposed in the circulation supply path.   The adhesion preventing portion is provided on both the diffuser surface of the compressor housing and the opposing surface of the bearing housing, and the circulation supply path includes a common supply path connected to the air flow path and the common supply. 2. The branch supply path branched from the path and connected to the air tank section in each adhesion preventing section, and the on-off valve is provided in the common supply path. Turbocharger.   The on-off valve is configured to be controlled to open and close based on a deterioration degree of oil of an internal combustion engine to which the turbocharger is connected and a temperature of compressed air passing through the air flow path. The turbocharger according to claim 1 or 2.

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