JP2009167872A - Turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbocharger which enhances rotational characteristics. <P>SOLUTION: A turbocharger includes a compressor-side floated bush 18 for rotatably supporting a turbine shaft. Irregularities are formed on the inner peripheral surface 18d and the outer peripheral surface 18e of the compressor-side floated bush 18, wherein phase differences exist between the irregularities of the inner peripheral surface 18d and the outer peripheral surface 18e. A through-hole 118 passing though from the recess 118d in the inner peripheral surface 18d to a projection 218e on the outer peripheral surface 18e is also included. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a supercharger, and more particularly, to a supercharger including a floating bush as a bearing for a shaft connecting between a compressor and a turbine.

Conventional turbochargers include, for example, Japanese Patent Application Laid-Open No. 2002-213450 (Patent Document 1), Japanese Patent Application Laid-Open No. 2007-46642 (Patent Document 2), Japanese Patent Application Laid-Open No. 2005-248856 (Patent Document 3), JP-A-336744 (Patent Document 4) and JP-A-6-137157 (Patent Document 5) are disclosed.
JP 2002-213450 A JP 2007-46642 A JP 2005-248856 A JP 11-336744 A JP-A-6-137157

  In Patent Document 1, in claim 1, a rotary shaft, a full float cylindrical floating bush having a perfectly circular cross section whose inner peripheral side is in sliding contact with the outer periphery of the rotating shaft, and a sliding contact with the outer peripheral surface of the floating bush. It is disclosed that a plurality of grooves extending in the axial direction are disposed on the inner peripheral surface or outer peripheral surface of the floating bush.

  In patent document 2, in Claim 1, it is a full float bearing, Comprising: The structure by which a spiral groove is provided in at least one of an internal peripheral surface and an outer peripheral surface is disclosed.

  Patent Document 3 discloses a configuration in which a damping member is interposed between each thrust dynamic pressure bearing and the housing in claim 1.

  In Patent Document 4, it is disclosed in Claim 1 that the inner peripheral surface of the bearing is formed into a curved surface shape in which a plurality of sine curves are placed on a neutral circle concentric with the shaft center.

  Patent Document 5 discloses a plurality of oil discharge holes in which a cylindrical bush is fixed to a center housing, and oil from an oil passage is supplied to the bush in the same direction as the rotation direction of the rotary shaft to the float bearing side. .

  In the conventional technology, in the configuration using the floating bush, it is difficult to achieve both the effects of reducing friction and axial displacement, and improving the seizure resistance and damping. It was a trade-off relationship.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a supercharger having excellent rotational characteristics.

  A turbocharger according to one aspect of the present invention includes a turbine shaft that is connected to a compressor and a turbine and is rotatably supported, a floating bush that rotatably supports the turbine shaft, and a turbine shaft and a floating bush. And a housing that can be accommodated. The inner and outer peripheral surfaces of the floating bush are provided with concavo-convex portions extending in the axial direction, the concavo-convex portions of the inner and outer peripheral surfaces are provided with a phase difference, and penetrates from the concave portion of the inner peripheral surface to the convex portion of the outer peripheral surface. A hole is provided.

  In the supercharger configured as described above, since the through hole is provided in the convex portion of the outer peripheral surface, the release pressure of the hydraulic pressure is less than that of the concave portion, so that the oil supply property to the inner peripheral side of the floating bush is improved. As a result, it is possible to reduce the friction and obtain a preferable rotational characteristic.

  A turbocharger according to another aspect of the present invention includes a compressor and a turbine connected to each other, a turbine shaft rotatably supported, a floating bush rotatably supporting the turbine shaft, and a turbine shaft and a floating bush. The inner surface and the outer peripheral surface of the floating bush are provided with uneven portions extending in the axial direction, and the step of the uneven portion on the inner peripheral surface is larger than the step of the uneven portion on the outer peripheral surface. .

  Usually, the floating bush rotates at about 0.3Ω (rpm) with respect to the turbine shaft rotational speed ω (rpm). In this case, the peripheral speed of the turbine shaft and the floating bush is faster than the peripheral speed of the floating bush and the casing, and the load on the inner peripheral surface side of the floating bush is high as a bearing. Here, by making the unevenness step on the inner peripheral surface side larger than the unevenness portion on the outer peripheral surface side, it becomes easier for the floating bush to follow the rotation of the turbine shaft. (Rpm) can be adjusted to improve the rotation characteristics.

  Preferably, the area between the turbine shaft and the inner peripheral surface of the floating bush is equal to the area between the housing and the outer peripheral surface of the turbine shaft.

A turbocharger according to still another aspect of the present invention includes a turbine shaft rotatably connected to a compressor and a turbine, and a compressor side floating bush and a turbine side floating bush that rotatably support the turbine shaft. And a housing capable of accommodating the turbine shaft, the compressor side floating bush, and the turbine side floating bush. The inner and outer peripheral surfaces of the compressor side floating bush are provided with uneven portions extending in the axial direction. On the inner and outer peripheral surfaces of the bush, there are uneven portions extending in the axial direction. In the cross section perpendicular to the turbine shaft, the width of the concave portion (Ho _1C ) of the outer peripheral surface of the compressor side floating bush and the compressor side floating bush The ratio Ro _C (= Ho _2C / Ho _1C ) with the width (Ho _2C ) of the convex portion on the outer peripheral surface is _Greater than the ratio Ro _T (= Ho _2T / Ho _1T ) between the width of the concave portion (Ho _1T ) on the outer peripheral surface of the engine-side floating bush and the width of the convex portion (Ho _2T ) on the outer peripheral surface of the turbine-side floating bush; The ratio Ri _C (= Hi _2C / Hi _1C ) between the width of the concave portion (Hi _1C ) on the inner peripheral surface of the compressor side floating bush and the width of the convex portion (Hi _2C ) on the inner peripheral surface of the compressor side floating bush is determined by the turbine This is larger than the ratio Ri _T (= Hi _2T / Hi _1T ) between the width of the concave portion (Hi _1T ) on the inner peripheral surface of the side floating bush and the width of the convex portion (Hi _2T ) on the inner peripheral surface of the turbine side floating bush.

  Generally, the gravity center position of the supercharger rotor is located on the turbine side because the mass of the turbine wheel is larger than the mass of the impeller. Therefore, the load on the turbine side floating bush tends to increase. Further, since the turbine wheel is driven by injecting exhaust gas exceeding 850 ° C., the oil temperature of the turbine side floating bush tends to rise.

By reducing the ratio of the convex part on the turbine side (Ro _T , Ri _T ) relative to the ratio of the convex part on the compressor side (Ro _C , Ri _C ), the load of the center of gravity is biased toward the turbine side. As a result, wear of the turbine-side floating bush can be prevented and oil supply to the turbine side can be increased, so that seizure of the floating bush can be prevented. Therefore, rotation characteristics are improved.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In addition, the embodiments can be combined.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a supercharger (turbocharger) according to Embodiment 1 of the present invention. Referring to FIG. 1, turbocharger 10 surrounds turbine shaft 21 extending along central axis 101, compressor 23 and turbine 22 connected to both sides of turbine shaft 21, and the outer periphery of turbine shaft 21. And a compressor side floating bush 18 and a turbine side floating bush 19 that support the turbine shaft 21.

  The center housing 30 defines an accommodation space 30 a for accommodating the turbine shaft 21, the compressor side floating bush 18 and the turbine side floating bush 19.

  Further, the compressor 23 and the turbine 22 are connected to each other by a turbine shaft 21. The compressor 23 and the turbine 22 are provided at a distance in the axial direction of the central shaft 101. The compressor 23 is made of aluminum, for example. Since the turbine 22 is directly exposed to the exhaust gas and becomes very hot, the turbine 22 is made of a super heat resistant alloy or ceramics having heat resistance and durability.

  The compressor side floating bush 18 and the turbine side floating bush 19 support the turbine shaft 21 rotatably with respect to the center housing 30. The turbine shaft 21 supported by the compressor side floating bush 18 and the turbine side floating bush 19 rotates around the central shaft 101 together with the compressor 23 and the turbine 22.

  The compressor side floating bush 18 and the turbine side floating bush 19 are formed in a cylindrical shape, and are formed with inner peripheral surfaces 18d, 19d extending in the axial direction of the compressor side floating bush 18 and the turbine side floating bush 19, The peripheral surfaces 18d and 19d define through holes. A turbine shaft 21 is inserted into the inner peripheral surfaces 18d and 19d. Thus, the compressor side floating bush 18 and the turbine side floating bush 19 support the turbine shaft 21 rotatably.

  The compressor side floating bush 18 and the turbine side floating bush 19 are provided between the compressor 23 and the turbine 22. The compressor side floating bush 18 and the turbine side floating bush 19 are provided at an interval in the axial direction of the central shaft 101. The turbine side floating bush 19 is provided on the turbine 22 side, and the compressor side floating bush 18 is provided on the compressor 23 side.

  For example, the distance between the turbine 22 and the turbine side floating bush 19 is relatively small, and the distance between the turbine 22 and the compressor side floating bush 18 is relatively large. Further, the distance between the compressor 23 and the turbine side floating bush 19 is relatively large, and the distance between the compressor 23 and the compressor side floating bush 18 is relatively small. In other words, the turbine side floating bush 19 is arranged between the turbine 22 and the compressor side floating bush 18 in the axial direction of the central shaft 101. The compressor side floating bush 18 is disposed between the compressor 23 and the turbine side floating bush 19.

  The turbocharger 10 further includes a thrust bush 14 and a thrust bearing 13. The thrust bush 14 is fixed to the outer peripheral surface of the turbine shaft 21. The thrust bush 14 is disposed between the compressor side floating bush 18 and the compressor 23. The thrust bearing 13 is engaged with the thrust bush 14 with a minute gap in the axial direction of the central shaft 101. The turbine shaft 21 is supported in the axial direction of the central shaft 101 by supplying lubricating oil to the gap.

  The center housing 30 is provided with an oil supply passage (oil supply mechanism) 35 through which lubricating oil flows. The lubricating oil flowing in the oil supply passage 35 is supplied as a lubricating oil to the compressor side floating bush 18, the turbine side floating bush 19 and the thrust bearing 13.

  Here, the oil supply passage 35 is formed with a supply port 36a through which lubricating oil is supplied, and is lubricated through an oil supply pipe 36 for supplying the lubricating oil to the compressor-side floating bush 18 through the discharge port 18a and the discharge port 19a. An oil supply pipe 38 that supplies oil to the turbine-side floating bush 19, and an oil supply pipe 37 that connects the oil supply pipe 38 and the oil supply pipe 36 and guides part of the lubricating oil supplied to the oil supply pipe 36 to the oil supply pipe 38. It has.

  Here, when lubricating oil is supplied from the discharge port 18 a to the compressor side floating bush 18, an oil film is formed between the inner peripheral surface 18 d of the compressor side floating bush 18 and the outer peripheral surface 21 a of the turbine shaft 21. An oil film is also formed between the outer peripheral surface 18e of the compressor-side floating bush 18 and the inner wall surface that defines the accommodation space 30a. For this reason, the compressor side floating bush 18 is separated from both the inner wall surface defining the accommodation space 30a and the outer peripheral surface 21a of the turbine shaft 21, and is in a floating state.

  When lubricating oil is supplied from the discharge port 19a to the turbine-side floating bush 19, an oil film is formed between the inner peripheral surface 19d of the turbine-side floating bush 19 and the outer peripheral surface 21a of the turbine shaft 21, An oil film is also formed between the outer peripheral surface 19e of the turbine-side floating bush 19 and the inner wall surface that defines the accommodation space 30a. For this reason, the turbine-side floating bush 19 is also separated from both the inner wall surface defining the accommodation space 30a and the outer peripheral surface 21a of the turbine shaft 21, and is in a floating state.

  Note that one end of the oil supply pipe 37 is connected to the oil supply pipe 38, and the other end is formed with a discharge port 13 a that discharges the lubricating oil toward the thrust bearing 13.

  The operation of the turbocharger 10 will be briefly described. Exhaust gas exhausted from the engine is guided to the vortex chamber of the turbine housing from an exhaust manifold connected to each cylinder of the engine. The exhaust gas then rotates the turbine 22 and the rotational force is transmitted to the turbine shaft 21. Thereafter, the air introduced from the outside of the vehicle for supplying to the engine is filtered by an air cleaner (not shown) and then guided into the compressor housing. The air is pressurized by a compressor 23 that rotates integrally with the turbine shaft 21, and the pressurized air is guided to an intercooler and introduced into an intake manifold of the engine in a cooled state.

  FIG. 2 is a perspective view showing the configuration of the compressor side floating bush. Referring to FIG. 2, the compressor-side floating bush 18 has a cylindrical shape, and a concave portion 118d and a convex portion 218d are provided on the inner peripheral surface 18d. The outer peripheral surface 18e is also provided with a concave portion 118e and a convex portion 218e. A through hole 118 is provided so as to penetrate from the inner peripheral surface 18d to the outer peripheral surface 18e.

  FIG. 3 is a diagram showing the phase of the unevenness on the inner peripheral surface and the phase of the unevenness on the outer peripheral surface. Referring to FIG. 3, the phase of the recess 118 d on the inner peripheral surface and the recess 118 e on the outer peripheral surface 18 e are out of phase. Moreover, the phase of the convex part 218d of the inner peripheral surface 18d and the convex part 218e of the outer peripheral surface 18e are shifted. That is, the phase difference is provided so that the convex portion 218e of the outer peripheral surface 18e and the concave portion 118d of the inner peripheral surface 18d have the same phase.

  FIG. 4 is a diagram illustrating a through hole. Referring to FIG. 4, through hole 118 serving as an oil supply hole is provided to connect concave portion 118d on inner peripheral surface 18d and convex portion 218e on outer peripheral surface 18e. The through-hole reaches the recess 118e of the inner peripheral surface 18d, and the gap is wide in this portion, so that the pressure difference with respect to the outer peripheral surface 18e increases and oil is supplied further inside.

  3 and 4 can be provided not only on the compressor side floating bush 18 but also on the turbine side floating bush 19. That is, the configuration shown in FIGS. 3 and 4 can be adopted in either the compressor side floating bush 18 or the turbine side floating bush 19.

  A turbocharger 10 according to the first embodiment connects a compressor 23 and a turbine 22 and rotatably supports a turbine shaft 21, a compressor-side floating bush 18 that rotatably supports the turbine shaft 21, and a turbine side The floating bush 19 includes a turbine housing 21, a compressor-side floating bush 18, and a center housing 30 that can accommodate the turbine-side floating bush 19. On either one of the inner peripheral surfaces 18d and 19d and the outer peripheral surfaces 18e and 19e of the compressor side floating bush 18 and the turbine side floating bush 19, an uneven portion extending in the axial direction is provided. The unevenness of the inner peripheral surfaces 18d, 19d and the outer peripheral surfaces 18e, 19e is provided with a phase difference, and through holes 118, 119 penetrating from the concave portions of the inner peripheral surfaces 18d, 19d to the convex portions of the outer peripheral surfaces 18e, 19e are provided. ing.

  As shown in FIG. 3, a phase difference of an angle θ is provided on the unevenness of the inner peripheral surface 18 d and the outer peripheral surface 18 e of the compressor side floating bush 18. The through hole 118 of the compressor side floating bush 18 is configured to connect the concave portion 118d of the inner peripheral surface 18d and the convex portion 218e of the outer peripheral surface 18e. Thereby, the oil film thickness can be reduced at the convex portion, contributing to reduction of friction and axial displacement, and seizure resistance and attenuation can be ensured at the concave portion. Furthermore, since the through hole 118 for supplying oil is provided in the convex portion 218e of the outer peripheral surface 18e and the release pressure of the hydraulic pressure is less than that of the concave portion, the oil supply to the inner peripheral surface 18d side of the compressor side floating bush 18 is performed. Improves.

(Embodiment 2)
FIG. 5 is a cross-sectional view of a turbocharger according to the second embodiment of the present invention. Referring to FIG. 5, in turbocharger 10 according to the second embodiment of the present invention, the uneven step on inner peripheral surface 18d is larger than the uneven step on outer peripheral surface 18e. Since the uneven step varies depending on the bearing area, oil viscosity, and the like, it must be set to an optimum value by a turbocharger. In this embodiment, each parameter is adjusted so that the following expression is established.

  Here, in the cross section orthogonal to the rotation axis, ri is the diameter of the turbine shaft 21, ci is the clearance between the outer peripheral surface 21a of the turbine shaft 21 and the convex portion 218d, Li is the step between the concave portion 118d and the convex portion 218d, and ro is The inner diameter of the accommodation space 30a, Co is the clearance between the accommodation space 30a and the projection 218e, and Lo is the step between the recess 118e and the projection 218e.

When the above formula is established, the area between the inner peripheral surface 18d and the outer peripheral surface 21a and the area between the wall surface of the accommodation space 30a and the outer peripheral surface 18e become equal. In the above equation, π (ri + ci) ² −πri ² is an area formed between the turbine shaft 21 and a circle connecting the convex portion 218d of the inner peripheral surface 18d in a cross section orthogonal to the rotation axis, 1/2 {π (ri + Li + Ci) 2 -π (ri + Ci) 2} is the area formed by the recess 118d.

^{Πro 2 -π (ro-Co)} 2 in the above equation is the area formed between the circle connecting wall and the convex portion 218e of the housing space 30a in a cross section perpendicular to the rotation axis, 1/2 {[pi (Ro-Co) ^{2- [} pi] (ro-Co-Lo) ² } is an area formed by the recess 118e.

  Ci and Co are values when the rotation centers of the turbine shaft 21 and the compressor-side floating bush 18 coincide with the central axis, respectively.

  In the second embodiment, the turbocharger 10 includes a turbine shaft 21 that rotatably connects the compressor and the turbine, a compressor-side floating bush 18 that rotatably supports the turbine shaft 21, and the turbine shaft 21 and the compressor. A center housing 30 capable of accommodating the side floating bush 18 is provided. The structure shown in FIG. 5 may be realized not only by the compressor side floating bush 18 but also by the turbine side floating bush.

  Usually, the compressor side floating bush 18 and the turbine side floating bush 19 rotate at a speed of about 0.3 Ω (rpm) with respect to the rotational speed ω (rpm) of the turbine shaft 21.

  In this case, the peripheral speed between the turbine shaft 21 and the inside of the floating bush is faster than the peripheral speed of the floating bush and the center housing 30, and the load on the inner peripheral surface side is high. By establishing the above mathematical relationship, the inner unevenness is increased and the floating bush easily follows the rotation of the shaft, thereby adjusting the rotational speed αω (rpm) of the floating bush with respect to the turbine shaft 21, It is possible to rotate the floating bush quickly. Moreover, since the uneven widths H1 and H2 do not change, there is no change in the load capacity as a bearing.

(Embodiment 3)
FIG. 6 is a sectional view of a turbocharger according to the third embodiment of the present invention. Referring to FIG. 6, in turbocharger 10 according to the third embodiment of the present invention, the concave and convex shapes of turbine side floating bush 19 and compressor side floating bush 18 are different. Specifically, Ro _C > Ro _T is established and Ri _C > Ri _T is established.

  Here, referring to FIG. 6, the position of the center of gravity 10G of the rotating body is generally located on the turbine 22 side. This is because the mass of the turbine 22 is larger than the mass of the compressor 23. For this reason, the load on the turbine side floating bush 19 tends to increase. Further, since the turbocharger 10 is driven by injecting exhaust gas exceeding 850 ° C. to the turbine 22, the oil temperature of the turbine side floating bush 19 tends to increase.

FIG. 7 is a perspective view for explaining the shape of the compressor side floating bush. FIG. 8 is a perspective view for explaining the shape of the turbine-side floating bush. Ro _C is the fraction of the convex portion 218e on the outer peripheral surface 18e of the compressor side floating bush 18, is defined as shown by _{Ro C = Ho 2C / Ho 1C} . Here, Ho _2C is the width of the convex portion 218e, and Ho _1C is the width of the concave portion 118e.

The ratio Ri _C of the convex portion 218d on the inner peripheral surface 18d is defined by Ri _C = Hi _2C / Hi _1C . Here, Hi _2C is the width of the convex portion 218d, and Hi _1C is the width of the concave portion 118d.

The ratio Ro _T of the convex portion 219e is defined by Ro _T = Ho _2T / Ho _1T . Here, Ho _2T is the width of the convex portion 219e, and Ho _1T is the width of the concave portion 119e. The ratio Ri _T of the convex portion 219d is defined as Ri _T = Hi _2T / Hi _1T . Here, Hi _2T is the width of the convex portion 219d, and Hi _1T is the width of the concave portion 119d.

In this embodiment, the ratio Ro _T , Ri _T of the convex part in the turbine side floating bush 19 is made smaller than the ratio Ro _C , Ri _C of the convex part of the compressor side floating bush 18 so that the position of the center of gravity is the turbine side. The turbine side floating bush 19 can be prevented from wearing due to uneven wear caused by being biased, and the amount of oil supplied to the turbine side floating bush 19 can be increased. It is possible to prevent seizure of the bush 19.

  FIG. 9 is a perspective view of a compressor side floating bush according to another example. FIG. 10 is a view showing a state in which the compressor side floating bush 18 and the turbine shaft 21 are close to each other. Referring to FIG. 9, in this example, the phases of the concave portion 118e and the convex portion 218e are opposite in the axial direction. That is, the phases of the concave portion 118e and the convex portion 218e are different in the axial direction.

  As shown in FIG. 10, when the recesses 118e and 118d come into contact with the center housing 30 and the turbine shaft 21, the recesses come into contact with the mating member, and the shaft displacement may not be effectively suppressed. On the other hand, by adopting the configuration shown in FIG. 9, it is possible to always guarantee contact with the convex portions 218e and 218d regardless of the position of the compressor side floating bush 18, so that it is effective in suppressing axial displacement. .

  FIG. 11 is a perspective view showing a compressor-side floating bush according to another example. As shown in FIG. 11, holes 318e and 318d extending in the axial direction may be provided at the bases of the convex portions 218d and 218e. As a result, it is possible to further improve seizure and wear resistance when an external force is applied to the convex portions 218d and 218e. Specifically, by reducing the rigidity of the protrusions 218d and 218e, if an excessive outline is added, the displacement is absorbed by the holes 318d and 318e as a mechanism for reducing the rigidity, thereby avoiding bearing seizure. can do.

  The holes may be square holes instead of round holes. Furthermore, the holes 318d and 318e may be filled with a material such as rubber.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing of the supercharger (turbocharger) according to Embodiment 1 of this invention. It is a perspective view which shows the structure of a compressor side floating bush. It is a figure which shows the phase of the unevenness | corrugation of an internal peripheral surface, and the phase of the unevenness | corrugation of an outer peripheral surface. It is a figure which shows a through-hole. It is sectional drawing of the turbocharger according to Embodiment 2 of this invention. It is sectional drawing of the turbocharger according to Embodiment 3 of this invention. It is a perspective view for demonstrating the shape of a compressor side floating bush. It is a perspective view for demonstrating the shape of a turbine side floating bush. It is a perspective view of the compressor side floating bush according to another example. It is a figure which shows the state which the compressor side floating bush 18 and the turbine shaft 21 approached. It is a perspective view which shows the compressor side floating bush according to another example.

Explanation of symbols

  10 turbocharger, 10G center of gravity, 13 thrust bearing, 13a discharge port, 14 thrust bushing, 18 compressor side floating bush, 18d, 19d inner peripheral surface, 18e, 19e outer peripheral surface, 19 turbine side floating bush, 21 turbine shaft, 21a outer periphery Surface, 22 turbine, 23 compressor, 30 center housing, 30a accommodating space, 35 oil supply passage, 36a supply port, 36, 37, 38 oil supply pipe, 101 central axis, 118, 119 through hole, 118d, 118e, 119d, 119e recess 218d, 218e, 219d, 219e Convex part, 318d, 318e Hole.

Claims (4)

A turbine shaft that connects the compressor and the turbine and is rotatably supported;
A floating bush rotatably supporting the turbine shaft;
A housing capable of accommodating the turbine shaft and the floating bush,
On the inner and outer peripheral surfaces of the floating bush, there are provided concavo-convex portions extending in the axial direction,
Each unevenness of the inner and outer peripheral surfaces is provided with a phase difference,
The supercharger in which the through-hole penetrated from the recessed part of the said internal peripheral surface to the convex part of the said outer peripheral surface is provided. A turbine shaft that connects the compressor and the turbine and is rotatably supported;
A floating bush rotatably supporting the turbine shaft;
A housing capable of accommodating the turbine shaft and the floating bush;
Concave and convex portions are provided on the inner and outer peripheral surfaces of the floating bush,
The supercharger in which a step of the uneven portion on the inner peripheral surface side is larger than a step of the uneven portion on the outer peripheral surface side.   The supercharger according to claim 2, wherein an area between the turbine shaft and the inner peripheral surface and an area between the housing and the outer peripheral surface are equal in a cross section orthogonal to the turbine shaft. A turbine shaft that connects the compressor and the turbine and is rotatably supported;
A compressor-side floating bush and a turbine-side floating bush that rotatably support the turbine shaft;
A housing capable of accommodating the turbine shaft, the compressor side floating bush, and the turbine side floating bush;
The inner and outer peripheral surfaces of the compressor side floating bush are provided with uneven portions extending in the axial direction,
On the inner peripheral surface and the outer peripheral surface of the turbine-side floating bush, an uneven portion extending in the axial direction is provided,
In a cross section orthogonal to the turbine shaft, the ratio Ro _C (= Ho) between the width of the concave portion (Ho _1C ) on the outer peripheral surface of the compressor side floating bush and the width of the convex portion (Ho _2C ) on the outer peripheral surface of the compressor side floating bush. _2C / Ho _1C ) is a ratio Ro _T (= Ho _2T / Ho) between the width of the concave portion (Ho _1T ) of the outer peripheral surface of the turbine side floating bush and the width of the convex portion (Ho _2T ) of the outer peripheral surface of the turbine side floating bush. _1T) greater than, and the ratio Ri _C of the width of the recess of the inner peripheral surface of the compressor side floating bush (Hi _1C) and the compressor side floating bush of the inner peripheral surface of the projection width (Hi _2C) (= Hi _2C / Hi _1C ) is a ratio Ri _T (= Hi _2T /) between the width of the concave portion (Hi _1T ) of the inner peripheral surface of the turbine side floating bush and the width of the convex portion (Hi _2T ) of the inner peripheral surface of the turbine side floating bush. Supercharger larger than _Hi1T ).

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