WO2015128724A1

WO2015128724A1 - Turbocharger

Info

Publication number: WO2015128724A1
Application number: PCT/IB2015/000233
Authority: WO
Inventors: Koichi Yonezawa; Hiroaki Ikegami; Ryu Osuka; Tetsuya Niwa
Original assignee: Toyota Motor Corp; Otics Corp
Current assignee: Toyota Motor Corp; Otics Corp
Priority date: 2014-02-28
Filing date: 2015-02-26
Publication date: 2015-09-03
Anticipated expiration: 2016-08-28
Also published as: JP2015163776A

Abstract

A turbocharger includes a compressor housing, a bearing housing, a liquid gasket, and a recessed portion. The bearing housing is fixedly fastened to the compressor housing. The liquid gasket is configured to seal fastening surfaces of the compressor housing and the bearing housing. The recessed portion is provided on at least one of the fastening surfaces of the compressing housing and the bearing housing. The liquid gasket is provided between the fastening surfaces in a portion which the recessed portion is provided.

Description

TURBOCHARGER

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a turbocharger in which fastening surfaces of a compressor housing and a bearing housing are sealed by a liquid gasket.

2. Description of Related Art

[0002] Conventionally, as described in Japanese Patent Application Publication No. 2009-2433396 (JP 2009-2433396 A), there has been known a turbocharger in which a compressor housing is fixedly fastened to a bearing housing by bolts, and fastening surfaces thereof are sealed by a liquid gasket.

SUMMARY OF THE INVENTION

[0003] In such a turbocharger, a thermal expansion "difference between the compressor housing and the bearing housing causes a relative displacement between the fastening surfaces of the compressor housing and the bearing housing according to a temperature change. Particularly, in a case where the compressor housing and the bearing housing are made of different materials, such a relative displacement between the fastening surfaces easily becomes large due to a difference in thermal expansion coefficient between the materials. If such a relative displacement becomes large, a large shear load is caused between the fastening surfaces and the liquid gasket, so that the liquid gasket peels off from the fastening surfaces, which may decrease sealing characteristics of the fastening surfaces.

[0004] The present invention provides a turbocharger that can improve sealing characteristics of fastening surfaces of a compressor housing and a bearing housing.

[0005] A turbocharger according to one aspect of the present invention includes a compressor housing, a bearing housing, a liquid gasket, and a recessed portion. The bearing housing is fixedl fastened to the compressor housing. The liquid gasket is configured to seal fastening surfaces of the compressor housing and the bearing housing. The recessed portion is provided on at least one of the fastening surfaces of the compressing housing and the bearing housing. The liquid gasket is provided between the fastening surfaces in a portion where the recessed portion is provided.

[0006] In a case where the thickness of the liquid gasket is sufficiently thick, even if a relative displacement occurs between the fastening surfaces, the relative displacement can be absorbed by an elastic deformation of the liquid gasket itself. Accordingly, the liquid gasket is hard to peel off. According to the above aspect, even if the compressor housing is fastened to the bearing housing until their fastening surfaces make close contact with each other, a clearance having at least a spacing between the fastening surfaces remains in a portion where the recessed portion is provided. This makes it possible to thicken the thickness of the liquid gasket, thereby making it possible to prevent the liquid gasket from easily peeling off due to the relative displacement between the fastening surfaces, caused due to a thermal expansion difference between the compressor housing and the bearing housing. Accordingly, it is possible to improve sealing characteristics of the fastening surfaces of the compressor housing and the bearing housing.

[0007] It is preferable to set the spacing between the fastening surfaces in a portion where the recessed portion is provided such that, when a relative displacement between the fastening surfaces, caused due to a thermal expansion difference between the compressor housing and the bearing housing, reaches a maximum value in an operating temperature range, the spacing becomes that minimum thickness or more of the liquid gasket which maintains adhesion of the liquid gasket to the fastening surfaces. The spacing between the fastening surfaces in a portion where the recessed portion is provided is preferably 28 μπι or more.

[0008] Meanwhile, if the spacing is too large, the liquid gasket may be filled into the recessed portion insufficiently. In order to avoid such insufficient filling, the spacing is preferably 150 μπι or less.

[0009] Note that, in a case where the compressor housing and the bearing housing are made of different materials having linear different expansion coefficients, the relative displacement between the fastening surfaces caused due to the thermal expansion difference becomes larger. The turbocharger of the above aspect can be particularly preferably applied to such a case.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a sectional view illustrating a side sectional configuration of a turbocharger according to one embodiment;

FIG. 2 is a sectional view illustrating a side sectional configuration of a compressor housing and its vicinal area in the turbocharger according to the embodiment;

FIG. 3 is an enlarged sectional view of a region C in FIG 2;

FIG. 4 is a front view illustrating a front face structure of a bearing housing when viewed from a compressor housing side;

FIG. 5A is a sectional view illustrating a state of an FIPG before a relative displacement occurs between fastening surfaces when a thickness of the FIPG is thin;

FIG 5B is a sectional view illustrating a state of the FIPG after the relative displacement occurs between the fastening surfaces when the thickness of the FIPG is thin;

FIG. 6A is a sectional view illustrating a state of an FIPG before a relative displacement occurs between fastening surfaces when a thickness of the FIPG is thick;

FIG 6B is a sectional view illustrating a state of the FIPG after the relative displacement occurs between the fastening surfaces when the thickness of the FIPG is thick;

FIG. 7 is a graph showing a setting mode of a recommended setting range of a spacing between the fastening surfaces in a portion where the recessed portion is provided;

FIG. 8 is a sectional view illustrating a side sectional configuration of fastening surfaces of a compressor housing and a bearing housing and their vicinal area according to a modification of the embodiment;

FIG. 9 is a sectional view illustrating a side sectional configuration of fastening surfaces of a compressor housing and a bearing housing and their vicinal area according to another modification of the embodiment; and

FIG. 10 is a sectional view illustrating a side sectional configuration of fastening surfaces of a compressor housing and a bearing housing and their vicinal area according to further another modification of the embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0011] One embodiment of a turbocharger is described below in detail with reference to FIGS. 1 to 7. The turbocharger is applied to an in-vehicle internal combustion engine, and serves as a supercharger configured to pressurize and supply intake air to the internal combustion engine by use of energy of exhaust gas.

[0012] As illustrated in FIG. 1, the turbocharger of the present embodiment accommodates therein two wheels, i.e., a compressor wheel 10 configured to pressurize and discharge intake air in association with rotation, and a turbine wheel 11 configured to be rotated in association with blowing of exhaust gas. These two wheels (10, 11) are connected to opposite ends of a turbine shaft 12 in an integrally rotatable manner.

[0013] A housing of such a turbocharger is roughly divided into three parts, i.e., a compressor housing 13 configured to accommodate the compressor wheel 10 therein, a turbine housing 14 configured to accommodate the turbine wheel 11 therein, and a bearing housing 15 configured to support the turbine shaft 12 in a bearing manner. The compressor housing 13 is fastened to an end part of the bearing housing 15 on the left side in the figure, by a plurality of bolts 16A. Similarly, the turbine housing 14 is also fastened to an end part of the bearing housing 15 on the right side in the figure, by a plurality of bolts 16B. Note that, in the following description, in terms of the compressor housing 13 and the turbine shaft 12, respective ends thereof fastened to the bearing housing 15 are referred to as base ends, and their opposite ends are referred to as tip ends.

[0014] A compressor room 17 configured to accommodate the compressor wheel 10 therein is formed in a base end portion of the compressor housing 13 inside the compressor housing 13. The compressor room 17 is opened outward toward a tip end side of the compressor housing 13 through a generally cylindrical air intake port 18 extending along a rotating axis L of the compressor wheel 10. Further, a scroll passage 19 going around an outer periphery of the compressor wheel 10 in a spiral manner is formed inside the compressor housing 13.

[0015] In the meantime, a turbine room 20 configured to accommodate the turbine wheel 11 therein is formed inside the turbine housing 14. The turbine room 20 is opened outward toward a tip end side of the turbine housing 14 through a generally cylindrical exhaust port 21 extending along a rotating axis L of the turbine wheel 11. Further, a scroll passage 22 going around an outer periphery of the turbine wheel 11 in a spiral manner is formed inside the turbine housing 14.

[0016] A supercharging operation of such a turbocharger is performed in the following manner. Exhaust gas introduced into the turbocharger is compressed in the scroll passage 22 of the turbine housing 14, and blown against the turbine wheel 11. The exhaust gas thus blown rotates the turbine wheel 11 by its flow force, arid the exhaust gas is exhausted through the exhaust port 21 toward a downstream side of an exhaust passage. When the turbine wheel 11 is rotated, the compressor wheel 10 connected thereto via the turbine shaft 12 is also rotated integrally. The compressor wheel 10 sends intake air taken from the air intake port 18 toward the outer periphery in association with the rotation. The intake air is compressed in the scroll passage 19 of the compressor housing 13, and then supplied to the internal combustion engine.

[0017] Note that the turbocharger of the present embodiment employs a housing having a three-piece configuration that is divided into three pieces, as the compressor housing 13. Next will be described a divided structure of the compressor housing 13 and a fastening structure between the compressor housing 13 and the bearing housing 15.

[0018] As illustrated in FIG. 2, the compressor housing 13 is formed so as to be divided into three pieces, i.e., a scroll piece 23, a shroud piece 24, and an R piece 25. These three pieces (23, 24, 25) are manufactured by die-casting of aluminum alloy. [0019] The scroll piece 23 constitutes a wall surface of the air intake port 18 and a wall surface, on the tip end side, of the scroll passage 19 in the compressor housing 13. Further, the shroud piece 24 constitutes a wall surface of the compressor room 17 and a wall surface, on a base end side, of the scroll passage 19 in the compressor housing 13. Further, the R piece 25 constitutes an outer peripheral part of the wall surface, on the base end side, of the scroll passage 19 in the compressor housing 13.

[0020] Note that the scroll piece 23 is extended to the base end of the compressor housing 13 through an outer periphery of the R piece 25. A plurality of screw holes 26 screwed by the bolts 16A is formed on an outer periphery of that end part of the scroll piece 23 which is closer to the base end of the compressor housing 13.

[0021] In the meantime, a flange 27 is formed in that end part of the bearing housing 15 which is closer to the compressor housing 13, so that the flange 27 projects in its circumferential direction. In the flange 27, a plurality of through holes 28 through which the bolts 16A pass is formed. Then, the shroud piece 24 and the R piece 25 are sandwiched between the scroll piece 23 and the bearing housing 15, and the screw holes 26 are screwed by the bolts 16A through the through holes 28, so that the scroll piece 23 is fastened to the bearing housing 15. Hereby, the compressor housing 13 is fixed to the bearing housing 15. Note that the bearing housing 15 is made of casting iron.

[0022] Note that, in such fastening, a fastening surface SI on a compressor-housing-13 side is constituted by that end surface of the scroll piece 23 which is placed on the base end side of the compressor housing 13, and an outer peripheral part of that end surface of the R piece 25 which is placed on the base end side of the compressor housing 13. Further, a fastening surface S2 on a bearing-housing-15 side is constituted by an outer peripheral part of that end surface of the flange 27 which is placed on the compressor-housing-13 side. The fastening of the bolts 16A at this time is performed so that the bolts 16A are fastened until the fastening surfaces SI, S2 completely abut with each other, that is, the fastening of the bolts 16A is performed by sizing fastening.

[0023] In the meantime, in the turbocharger having a structure in which the compressor housing 13 and the bearing housing 15 are fixed by fastening, oil or air may leak from inside through a clearance between the fastening surfaces SI, S2. In view of this, in the turbocharger of the present embodiment, the fastening surfaces SI, S2 of the compressor housing 13 and the bearing housing 15 are sealed by an FIPG (Formed In Place Gasket) as a liquid gasket. The FIPG is a liquid gasket configured such that the gasket is applied to mating surfaces in a liquid state, and then, the gasket is hardened to become an elastic body by heating or absorption of water content in the air, so as to seal and bond the mating surfaces with each other.

[0024] The following more specifically describes such a sealing structure of the fastening surfaces SI, S2. FIG 3 illustrates, in an enlarged manner, a sectional structure of a region C surrounded b an alternate long and two short dashes line in FIG. 2. As illustrated in the figure, a recessed portion 29 is formed on the fastening surface S2 on the bearing-housing- 15 side so that the recessed portion 29 is placed in an inner peripheral part relative to a fastening position of the bolt 16A. The recessed portion 29 is recessed more than the other parts in the fastening surface S2. Note that, in the turbocharger, the recessed portion 29 is formed so as to sandwich, between its outer peripheral end and its inner peripheral end, a three-surface mating position D of the scroll piece 23, the R piece 25, and the bearing housing 15.

[0025] FIG. 4 illustrates a front face structure of the bearing housing 15 when viewed from the compressor-housing-13 side. As illustrated in the figure, the recessed portion 29 is extended so as to go around a central part in a circumferential direction of the fastening surface S2.

[0026] Due to such a recessed portion 29, even after the sizing fastening of the bolts 16A is performed, a part where a clearance having a given width is formed between the fastening surfaces SI, S2. Note that, in the turbocharger, a spacing between the fastening surfaces h in a portion where the recessed portion 29 is provided is 100 ± 50 μπι. An FIPG 30 is filled in the spacing formed between the recessed portion 29 and the fastening surface Si on the compressor-housing 13 side.

[0027] Subsequently, the following describes an operation of the turbocharger configured as described above. Temperatures of the fastening surfaces SI, S2 between which the FIPG 30 is provided are changed largely due to an outdoor temperature, heat transmission from the turbine housing 14 through which high-temperature exhaust gas passes, a temperature increase in the compressor housing 13 due to adiabatic compression of intake air, and the like. In the turbocharger, it is assumed that the temperatures of the fastening surfaces SI, S2 change in a range from -40 °C to 160 °C during the use of the turbocharger.

[0028] In the meantime, a relative displacement in the circumferential direction is caused between the fastening surfaces SI, S2. The relative displacement is caused due to a thermal expansion difference between the compressor housing 13 made of aluminum alloy and the bearing housing 15 made of iron in association with the temperature change. Due to such a relative displacement, a shearing force occurs on adhesive surfaces of the FIPG 30 relative to the fastening surfaces S , S2.

[0029] In a case where a thickness of the FIPG 30 is thin as illustrated in FIG. 5A, when a relative displacement occurs between the fastening surface SI, S2 as illustrated in FIG. 5B, the relative displacement cannot be absorbed sufficiently by an elastic deformation of the FIPG 30. Because of this, a large shearing force acts on the adhesive surfaces of the FIPG 30 relative to the fastening surfaces SI, S2, so that the FIPG 30 peels off from the fastening surfaces SI, S2 and a sealing characteristic between the fastening surfaces SI, S2 is decreased.

[0030] In a case where a thickness of the FEPG 30 is sufficiently thick as illustrated in FIG 6A, when a relative displacement occurs between the fastening surface SI, S2 as illustrated in FIG. 6B, the relative displacement can be absorbed sufficiently by an elastic deformation of the FIPG 30. Accordingly, a shearing force acting on the adhesive surfaces of the FIPG 30 relative to the fastening surfaces SI, S2 at this time is decreased, thereby making it possible to restrain the FEPG 30 from peeling off from the fastening surfaces SI, S2.

[0031] Here, if the recessed portion 29 is not provided on the fastening surface S2, the FIPG 30 is compressed by the sizing fastening of the bolts 16A, so that the thickness of the FIPG 30 becomes around 5 μπι, which is very thin. In the meantime, in the present embodiment, even if the bolts 16A are fastened by the sizing fastening, a spacing having at least the spacing h corresponding to the recessed portion 29 remains between the fastening surfaces SI, S2 in the portion where the recessed portion 29 is provided, so that the thickness of the FIPG 30 in that portion is the spacing h or more. On that account, if the recessed portion 29 is formed to have a sufficiently large spacing h, it is possible to prevent the FEPG 30 from peeling off due to the relative displacement between the fastening surfaces SI, S2, caused due to the thermal expansion difference between the compressor housing 13 and the bearing housing 15.

[0032] Next will be examined an appropriate value of the spacing h in a portion where the recessed portion 29 is provided in order to prevent the peeling of the FIPG 30 caused due to the thermal expansion difference. A tracking limit line shown in the graph of FIG. 7 is obtained by connecting, in a line, those minimum values of the thickness of the FIPG 30 which are required for the prevention of the peeling at respective fastening-surface temperatures. Note that the figure indicates a tracking limit line in a case where the fastening-surface temperature at the time when the FIPG 30 is provided is 20 °C, that is, in a case where a relative displacement between the fastening surfaces SI, S2 is "0" at a fastening-surface temperature of 20 °C.

[0033] A fastening-surface temperature and a thickness of the FIPG 30 at this time are plotted in the graph in the figure. If a coordinate point obtained herein is within a region on the right side relative to the tracking limit line, the peeling of the FIPG 30 does not occur. Here, as described above, in the present embodiment, an operating temperature range of the fastening surfaces SI, S2 is in a range of - 40 °C to 160 °C, and a maximum value of the thickness of the FIPG 30 on the tracking limit line in the temperature range is 28 μιη. Accordingly, if the spacing h is set so that a thickness of the FIPG 30 is 28 μι^η or more, that is, if the spacing h is set to 28 μπ. or more, it is possible to prevent the peeling of the FIPG 30 due to the thermal expansion difference in the operating temperature range.

[0034] Meanwhile, if the spacing h is too large, undiluted solution of the FIPG 30 is not compressed sufficiently by the sizing fastening of the bolts 16A, which may cause the FIPG 30 not to be completely filled in the recessed portion 29. That upper limit of the spacing h which can surely prevent such insufficient filling is 150 μπι. Accordingly, a recommended setting range of the spacing h is a range of 28 to 150 μιη.

[0035] Note that such a recommended setting range is obtained in consideration of a range of a bolt fastening torque generally employed in the sizing fastening of the bolts at the time of fastening the compressor housing and the bearing housing, and ranges of characteristic values (viscosity and adhesive strength) of various types of the FIPG generally used for the fastening surfaces of the compressor housing and the bearing housing. On that account, the recommended setting range is common to general turbochargers.

[0036] According to the turbocharger of the present embodiment described above, the following effects can be obtained. (1) In the present embodiment, the recessed portion 29 is formed in a setting portion for the FIPG 30 on the fastening surface S2 so that the recessed portion 29 is recessed more than the other parts of the fastening surface S2. Accordingly, it is possible to thicken the thickness of the FIPG 30, thereby making it hard to cause the peeling of the FIPG 30 even if a relative displacement between the fastening surfaces SI, S2 is caused due to a thermal expansion difference between the compressor housing 13 and the bearing housing 15. Accordingly, it is possible to improve sealing characteristics of the fastening surfaces SI, S2 of the compressor housing 13 and the bearing housing 15.

[0037] (2) In the present embodiment, the spacing h is set in the following manner. That is, a maximum value of the relative displacement between the fastening surfaces SI, S2 caused due to the thermal expansion difference between the compressor housing 13 and the bearing housing 15 is first obtained in the operating temperature range of the fastening surfaces SI, S2. Further, the spacing h is set so that, when the relative displacement between the fastening surfaces SI, S2 reaches the maximum value, the spacing h becomes a minimum thickness or more of the FIPG 30 which minimum thickness allows the FIPG 30 to be adhered to the fastening surfaces SI, S2. A specific value of the spacing h to be set is 28 μπι or more. This makes it possible to surely prevent the peeling of the FIPG 30 due to the thermal expansion difference. [0038] (3) In the present embodiment, the spacing h is 150 pun or less. This makes it possible to prevent insufficient filling of the FIPG 30 into the recessed portion 29, thereby resulting in that the sealing characteristics of the fastening surfaces can be secured more appropriately.

[0039] Note that the above embodiment can be modified as follows. - As illustrated in FIG. 8, a recessed portion 31 may be provided on the fastening surface SI on the compressor-housing- 13 side. Even in such a case, it is possible to obtain the same effect as in the above embodiment. Further, a recommended setting range of a spacing h in a portion where the recessed portion 31 is provided is also 28 to 150 μιη.

[0040] - As illustrated in FIG. 9, recessed portions 32, 33 may be provided on both of the fastening surfaces SI, S2 on the compressor-housing-13 side and on the 6earing-housing-15 side. Even in such a case, it is possible to obtain the same effect as in the above embodiment. Note that, in a case where the recessed portions 32, 33 are formed at positions opposed to each other, the recessed portions 32, 33 are formed on the fastening surfaces SI, S2 such that the recessed portions 32, 33 have a spacing corresponding to a sum (= hi + h2) of a spacing hi of the recessed portion 32 and a spacing h2 of the recessed portion 33. Accordingly, in such a case, if the recessed portions 32, 33 are formed so that a sum of the spacings hi, h2 is in a range of 28 to 150 μιη, it is possible to prevent the peeling of the FIPG 30 due to the thermal expansion difference appropriately.

[0041] As illustrated in FIG 10, the whole recessed portion 29 may be formed in that two-surface mating part of the scroll piece 23 and the bearing housing 15 which is closer to the outer periphery of the turbocharger than the three-surface mating position D. Even in such a case, the FIPG 30 provided in the recessed portion 29 can prevent leakage of the air or the like through a clearance between mating surfaces S3, S4 of the scroll piece 23 and the R piece 25, as well.

[0042] - The recessed portion 29 and the FIPG 30 may be provided in that two-surface mating part of the R piece 25 and the bearing housing 15 which is closer to the inner periphery of the turbocharger than the three-surface mating position D. Even in such a case, if another sealing structure is provided on mating surfaces S3, S4 of the scroll piece 23 and the R piece 25, leakage of the air or the like through the mating surface S3, S4 can be prevented. Further, such a structure can be employed even when the sealing characteristics of the mating surfaces S3, S4 are not demanded.

[0043] - In the above embodiment, the FIPG 30 is provided on an inner peripheral side relative to the bolts 16A. However, the FIPG 30 may be provided in that two-surface mating part of the scroll piece 23 and the bearing housing 15 which is placed on an outer peripheral side relative to the bolts 16A. Even in such a case, if a recessed portion is formed in a setting portion for the FIPG 30 on the fastening surfaces of the compressor housing 13 and the bearing housing 15 such that the recessed portion is recessed more than the other parts of the fastening surfaces, it is possible to prevent the peeling of the FIPG 30 due to the thermal expansion difference, thereby making it possible to improve the sealing characteristics of the fastening surfaces.

[0044] - In the above embodiment, the compressor housing 13 has a three-piece divided structure, but may have a two-piece divided structure or a one-piece structure. In any case, if the recessed portion is formed on the fastening surfaces of the compressor housing and the bearing housing and the liquid gasket is provided in the recessed portion, the thickness of the liquid gasket can be secured, thereby making it possible to improve the sealing characteristics of the fastening surfaces of the housings.

[0045] - In the above embodiment, the compressor housing 13 is made of aluminum alloy, and the bearing housing 15 is made of casting iron. However, the material of either one of them or the materials of both of them may be changed. Even in such a case, if the housings are made of different materials, the relative displacement between the fastening surfaces SI, S2 due to a thermal expansion difference becomes large due to a difference in linear expansion coefficient between the materials, thereby making it possible to largely improve the sealing characteristics by forming the recessed portion on the fastening surfaces. In the meantime, even in a case where the compressor housing 13 and the bearing housing 15 are made of the same material, e.g., aluminum alloy, a thermal expansion difference may occur between them because of a difference in shape. Accordingly, even in a case where the compressor housing 13 and the bearing housing 15 are made of the same material, the formation of the recessed portion on the fastening surfaces yields an effect of improving the sealing characteristics.

Claims

CLAIMS:

1. A turbocharger comprising:

a compressor housing;

a bearing housing fixedly fastened to the compressor housing;

a liquid gasket configured to seal fastening surfaces of the compressor housing and the bearing housing; and

a recessed portion provided on at least one of the fastening surfaces of the compressing housing and the bearing housing;

wherein the liquid gasket is provided between the fastening surfaces in a portion where the recessed portion is provided.

2. The turbocharger according to claim 1, wherein

a spacing between the fastening surfaces in a portion where the recessed portion is provided is set such that, when a relative displacement between the fastening surfaces, caused due to a thermal expansion difference between the compressor housing and the bearing housing, reaches a maximum value in an operating temperature range of the turbocharger, a thickness of the liquid gasket becomes a minimum thickness or more that maintains adhesion of the liquid gasket to the fastening surfaces.

3. The turbocharger according to claim 1 or 2, wherein

a spacing between the fastening surfaces in a portion where the recessed portion is provided is 28 μηι or more.

4. The turbocharger according to any one of claims 1 to 3, wherein

a spacing between the fastening surfaces in a portion where the recessed portion is provided is 150 μπι or less.

5. The turbocharger according to any one of claims 1 to 4, wherein a material of the compressor housing is different from a material of the bearing housing.