JP2009167971A - Housing fastening method and supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a housing fastening method and a supercharger capable of inhibiting drop of fastening force of a G-coupling even if a housing is exposed under a high temperature condition by devising a housing structure. <P>SOLUTION: The supercharger includes a turbine 1 rotating a moving blade 1a by supply of fluid, a compressor 2 sucking air by an impeller 2a connected to the moving blade 1a via the rotary shaft 3a, a turbine housing 1b constructing an outer shape of the turbine 1, and a bearing housing 3 rotatably supporting the rotary shaft 3a. A projection part 3b of the bearing housing 3 is inserted into a recess part 1c of the turbine housing 1b. Each housing 1b, 3 are fastened by fastening outer circumferences of flanges 1e, 3d formed on outer circumferences of the recess part 1c and the projection part 3b after locking an end surface 3c of the projection part 3b by a stepped part 1d of the recess part 1c together by the G-coupling 4. Shapes of the recess part 1c and the projection part 3b are designed with adjusting axial direction position of a lock surface of the stepped part 1d. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a housing fastening method in which a housing is fastened by a fastener such as a G coupling and a supercharger in which the housing is fastened by a fastener such as a G coupling. In particular, the fastening force of the fastener is reduced. The present invention relates to a housing fastening method and a supercharger that can be suppressed.

  A rotary prime mover that obtains power by supplying fluid to a moving blade and converting the kinetic energy of the fluid into rotational motion is generally called a turbine. In particular, a type that supplies fluid from the radial direction of the moving blade and discharges it in the axial direction is called a radial turbine. One of the apparatuses using such a radial turbine is a vehicle supercharger. Here, the vehicle supercharger (turbocharger) includes a gas turbine that rotates a turbine blade by supplying exhaust gas, and a compressor that sucks air by an impeller that is coaxially connected to the turbine blade. I have. The air taken in by the compressor is compressed and supplied to the engine, mixed with fuel and burned. The exhaust gas after combustion is sent to the gas turbine for work, and finally discharged into the atmosphere. The flow path for supplying the exhaust gas to the turbine rotor blade has a scroll portion formed in a spiral shape around the rotation axis of the turbine rotor blade to accelerate the exhaust gas, and the radius of the turbine rotor blade The exhaust gas is supplied from the direction.

Such a supercharger for a vehicle has a rotating shaft that connects a turbine moving blade of a gas turbine and an impeller of a compressor, and the rotating shaft is rotatably supported by a bearing housing. When the turbine housing and the bearing housing are fastened, the flange portions formed on the turbine housing and the bearing housing may be fastened together with a fastening tool such as a G coupling (for example, FIG. 12 of Patent Document 1). reference).
Japanese Patent Laying-Open No. 2006-258108, FIG.

  However, as in Patent Document 1, when the turbine housing and the bearing housing are fastened by a fastening tool such as a G coupling, the linear expansion coefficients of the flange portion and the fastening tool are different. Due to thermal expansion of the flange portion and the fastener, a gap is formed between the flange portion and the fastener, and the fastening force of the fastener may be reduced. Further, when the inside of the turbine housing is exposed to high-temperature exhaust gas, the flange portion is thermally expanded to deform the fastener, and the fastener is fastened when the temperature of the exhaust gas becomes low. In some cases, the power was reduced.

  The present invention has been devised in view of the above-mentioned problems, and by devising the housing structure, the fastening force of a fastener such as a G coupling is reduced even when the housing is exposed to a high temperature state. It is an object of the present invention to provide a housing fastening method and a supercharger capable of suppressing the above-described problem.

  According to the present invention, after inserting the convex portion formed in the other housing into the concave portion formed in one housing and locking the end surface of the convex portion by the step portion formed in the concave portion, In the housing fastening method of fastening the housing by fastening the outer periphery of each flange portion formed on the outer periphery of the concave portion and the convex portion with a fastener, the axial position of the locking surface of the stepped portion is adjusted, A housing fastening method is provided in which the fastening force of the fastener is adjusted by designing the shape of the recess and the protrusion.

  When adjusting the axial position, the axial position of the locking surface of the stepped portion may be set to be included in the range of the axial projection width of the fastener, or the locking of the stepped portion The shape of the convex portion may be designed in consideration of the thickness of the thin plate sandwiched between the surface and the end surface of the convex portion. Furthermore, you may make it form the outer diameter of the flange part in the housing of the side which is hard to thermally expand larger than the outer diameter of the flange part in the housing of the side which is easy to thermally expand.

  Further, the axial length Az of the contact with the fastening tool in the flange portion on the concave portion side and the locking surface of the stepped portion, the contact point with the fastening tool on the flange portion on the convex portion side, and the An axial length Bz with the end surface, an axial length C between the contacts of the flange portion, and an axial length Cg between the contacts of the fastener are defined, and 0 ≦ Cg−C ≦ allowable The axial lengths Az and Bz may be designed so as to satisfy the value k. Here, it is preferable that the allowable value k is set by a clearance between the fastening tool and the flange portion that can be allowed at a predetermined temperature. Specifically, the allowable value k is set to a numerical value within the range of 0 ≦ k <0.0388 / cos (θ / 2) with respect to the opening degree θ of the gripping portion of the fastener. Is preferred.

  Further, according to the present invention, a turbine that rotates a moving blade by supplying fluid, a compressor that sucks air by an impeller connected to the moving blade via a rotating shaft, and a turbine that constitutes the outer shape of the turbine And a stepped portion formed in the concave portion by inserting a convex portion formed in the bearing housing into a concave portion formed in the turbine housing. After locking the end surface of the convex portion by the above, the outer periphery of each flange portion formed on the outer periphery of the concave portion and the convex portion is tightened together with a fastener to fasten the turbine housing and the bearing housing In the turbocharger, by adjusting the axial position of the locking surface of the stepped portion and designing the shape of the concave portion and the convex portion, Supercharger is provided, characterized in that to adjust the force.

  When adjusting the axial position, the axial position of the locking surface of the stepped portion may be set to be included in the range of the axial projection width of the fastener, or the locking of the stepped portion The shape of the convex portion may be designed in consideration of the thickness of the thin plate sandwiched between the surface and the end surface of the convex portion. Furthermore, the outer diameter of the flange portion in the bearing housing on the side where thermal expansion is difficult may be formed larger than the outer diameter of the flange portion in the turbine housing on the side where thermal expansion is likely to occur.

  Further, the axial length Az of the contact with the fastening tool in the flange portion on the concave portion side and the locking surface of the stepped portion, the contact point with the fastening tool on the flange portion on the convex portion side, and the An axial length Bz with the end surface, an axial length C between the contacts of the flange portion, and an axial length Cg between the contacts of the fastener are defined, and 0 ≦ Cg−C ≦ allowable The axial lengths Az and Bz may be designed so as to satisfy the value k. Here, it is preferable that the allowable value k is set by a clearance between the fastening tool and the flange portion that can be allowed at a predetermined temperature. Specifically, the allowable value k is set to a numerical value within the range of 0 ≦ k <0.0388 / cos (θ / 2) with respect to the opening degree θ of the gripping portion of the fastener. Is preferred.

  The above-described housing fastening method and supercharger according to the present invention are the result of intensive research on the decrease in fastening force due to thermal expansion in the housing fastened by the inventor with a fastener such as a G coupling. It is an invention that was invented by finding that there is a relationship between the axial position of the fastener and the fastening force of the fastener. That is, by adjusting the axial position of the locking surface of the stepped portion, it is possible to suppress a decrease in the fastening force of the fastener without sequentially elucidating the entire thermal expansion of the flange portion and the fastener. For example, by setting the axial position of the locking surface of the stepped portion closer to the end than the conventionally set position (decreasing the depth of the recess), the interior of the housing is heated to a high temperature (for example, about 1000 ° C. ), It is possible to suppress a decrease in fastening force of the fastener due to thermal expansion. In particular, it is effective to set the axial position of the locking surface of the stepped portion so as to be included in the range of the axial projection width of the fastener. In addition, when a spacer or a heat shield plate of an adjacent housing is sandwiched between the locking surface of the stepped portion and the end surface of the convex portion, if the plate thickness is taken into consideration, it is more effectively caused by thermal expansion. A decrease in the fastening force of the fastener can be suppressed. Furthermore, when the degree of thermal expansion of the housing to be fastened is different, the outer diameter of the side that is difficult to thermally expand is made larger than the outer diameter of the side that is likely to be thermally expanded, so that the position of the flange portion in the high temperature state Can be made substantially parallel to the axial direction, and the axial position of the locking surface of the stepped portion can be easily adjusted.

  Also, by setting the axial length Az on the concave side and the axial length Bz on the convex side under predetermined conditions, it is possible to suppress a decrease in the fastening force of the fastening tool depending on the housing in which the fastening tool is used. can do. Further, when the allowable value k is set to a value within the range of 0 ≦ k <0.0388 / cos (θ / 2), the inside of the housing is exposed to a high temperature (for example, about 1000 ° C.). And the fall of the fastening force of the fastener in a high temperature state can be suppressed rather than the conventional supercharger.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. Here, FIG. 1 is a figure which shows the supercharger which concerns on this invention, (A) is side sectional drawing, (B) is a front view of G coupling. FIG. 2 is an enlarged view of a portion II in FIG. 1A, where FIG. 2A shows the present invention and FIG. 2B shows the prior art.

  The supercharger of the present invention shown in FIG. 1 (A) sucks air by a turbine 1 that rotates a moving blade 1a by supplying fluid and an impeller 2a that is connected to the moving blade 1a via a rotating shaft 3a. A compressor housing 2, a turbine housing 1 b that forms the outer shape of the turbine 1, and a bearing housing 3 that rotatably supports the rotating shaft 3 a, and is formed in the bearing housing 3 in a recess 1 c formed in the turbine housing 1 b. After inserting the projected portion 3b and engaging the end surface 3c of the projected portion 3b with the stepped portion 1d formed in the recessed portion 1c, the flange portions 1e and 3d formed on the outer periphery of the recessed portion 1c and the projected portion 3b. Is a turbocharger in which the turbine housing 1b and the bearing housing 3 are fastened together with the G coupling 4 and the axial position of the locking surface of the stepped portion 1d is adjusted. It is obtained by designing the shape of the recess 1c and the convex portion 3b. In addition, although the supercharger shown in FIG. 1 (A) forms the scroll part 1f of the turbine 1 in multiple chambers, this invention is not limited to the structure which concerns, A scroll part of a single chamber Or a turbocharger in which a variable nozzle for adjusting the flow rate is arranged between the scroll portion 1f and the moving blade 1a. Further, the compressor housing 2b and the bearing housing 3 are often fastened by a plurality of bolts 2c arranged in the circumferential direction.

  In the supercharger shown in FIG. 1 (A), the axial position of the locking surface of the stepped portion 1d is, for example, the axial position of the locking surface of the stepped portion 1d as shown in FIG. 2 (A). Is included in the range of the axial projection width Zg of the G coupling 4. Here, assuming that the axial width of the end surface of the flange portion 1e of the turbine housing 1b and the locking surface of the step portion 1d is Za, the axial width of the flange portion 1e and the flange portion 3d is assumed to be substantially equal. ≦ 0.5 Zg. On the other hand, in the case of the prior art shown in FIG. 2B, the axial position of the locking surface of the stepped portion 1d is set outside the range of the axial projection width Zg of the G coupling 4. That is, there is a relationship of Za> 0.5Zg. In the shape shown in FIG. 2B, when the inside of the turbine housing 1b is exposed to a high temperature (for example, about 1000 ° C.), the thermal expansion of each member causes a gap between the G coupling 4 and the flange portion 3d. As a result, a gap is formed and the fastening force is reduced, or the flange portions 1e, 3d push the G coupling 4 to be deformed. As a result of intensive studies by the inventor on such problems, it has been found that there is a relationship between the axial position of the locking surface of the stepped portion 1d and the fastening force of the G coupling 4. Therefore, in the present invention, the above-described problem is solved by setting the axial position of the locking surface of the stepped portion 1d closer to the end of the flange portion 1e than in the prior art. In other words, the supercharger of the present invention is such that the depth (= Za) of the recess 1c is set shallower than that of the prior art.

  The G coupling 4 is a kind of fastener and is formed at a pair of semicircular arc portions 4a and 4a and end portions on the same side of the semicircular arc portions 4a as shown in FIG. Flange portions 4b, 4b, folded portions 4c, 4c formed at opposite ends of the semicircular arc portions 4a, fasteners 4d such as bolts and nuts inserted through the flange portions 4b, and folded portions 4c, And an annular ring 4e for restraining 4c. Moreover, the cross section of the semicircular arc part 4a has the inclined surface arrange | positioned in C shape, as shown to FIG. 2 (A). Further, the flange portion 1 e of the turbine housing 1 b and the flange portion 3 d of the bearing housing 3 are formed in a tapered shape so as to come into contact with the inclined surface of the G coupling 4. The inclined surface of the G coupling 4 and the tapered surfaces of the flange portions 1e and 3d are in point contact in the cross-sectional view shown in FIG. 2A, and each semicircular arc portion 4a shown in FIG. Is in line contact. The turbine housing 1b and the bearing housing 3 are fastened by sandwiching the flange portion 1e of the turbine housing 1b and the flange portion 3d of the bearing housing 3 between the inclined surfaces of the G coupling 4 and tightening the fastener 4d. . The G coupling 4 may also be referred to as V band coupling.

  Further, as shown in FIGS. 1A and 2A, a thin plate is formed in a cylindrical shape between the locking surface of the stepped portion 1d of the turbine housing 1b and the end surface 3c of the convex portion 3b of the bearing housing 3. The end portions of the heat shield plate 5 formed in the above are bitten and pinched. The heat shield plate 5 is a member that protects the bearing housing 3 from high-temperature exhaust gas fed by the turbine housing 1b. As shown in FIG. 2B, this configuration itself is not different from the prior art, but in the present invention, the axial position of the locking surface of the stepped portion 1d is shifted closer to the end of the flange portion 1e. Accordingly, the axial length of the heat shield plate 5 is set longer than that of the prior art. As described above, when the heat shield plate 5 is sandwiched between the engaging surface of the stepped portion 1d of the turbine housing 1b and the end surface 3c of the convex portion 3b of the bearing housing 3, the thickness of the heat shield plate 5 is taken into consideration. It is necessary to design the shape of the portion 3b. Note that the heat shield plate 5 is not an essential component, and instead of the heat shield plate 5, a spacer in which a thin plate constituting a seal member is formed in an annular shape may be sandwiched, or the step of the turbine housing 1 b may be sandwiched. The locking surface of the portion 1d and the end surface 3c of the convex portion 3b of the bearing housing 3 may be brought into direct contact.

  Next, an embodiment of the housing fastening method according to the present invention will be described in detail. Here, FIG. 3 is explanatory drawing which defines the dimension required for description of one Embodiment of the housing fastening method which concerns on this invention. 4A and 4B are explanatory views showing a method for setting the allowable value k, where FIG. 4A is an enlarged view at normal temperature, FIG. 4B is an enlarged view at high temperature, and FIG. 4C is a gap between the G coupling and the flange portion. And a permissible value k.

As shown in FIG. 3, the dimensions of each part are defined.
Pa: Contact point with the G coupling 4 in the turbine housing 1b.
Az: A length in the axial direction between the locking surface of the step portion 1d and the contact point Pa in the turbine housing 1b.
Ar: The radial length of the contact point Pa in the turbine housing 1b (length from the axis Z).
Pb: Contact point with the G coupling 4 in the bearing housing 3.
Bz: A length in the axial direction between the end surface 3c of the convex portion 3b and the contact Pb in the bearing housing 3.
Br: Length in the radial direction of the contact Pb in the bearing housing 3 (length from the axis Z).
θ: Opening degree of G coupling 4.
t: The thickness of the heat shield 5.
C: Length in the axial direction between the contacts Pa and Pb.

Moreover, the linear expansion coefficient at the time of high temperature in each part and the temperature difference with normal temperature are defined as follows. α: Linear expansion coefficient of the turbine housing 1b at a high temperature.
β: Linear expansion coefficient of the bearing housing 3 at a high temperature.
γ: Linear expansion coefficient of the G coupling 4 at a high temperature.
ε: coefficient of linear expansion of the heat shield 5 at a high temperature.
ΔTa: Temperature difference from normal temperature when the turbine housing 1b is at a high temperature.
ΔTb: temperature difference from the normal temperature when the bearing housing 3 is at a high temperature.
ΔTg: temperature difference from normal temperature when the G coupling 4 is at a high temperature.
ΔTs: temperature difference from the normal temperature when the heat shield 5 is at a high temperature.

  Further, as shown in FIG. 4A, in the normal temperature state, the flange portion 1e of the turbine housing 1b and the flange portion 3d of the bearing housing 3 are in contact with the G coupling 4 through the contact points Pa and Pb, respectively. In general, there is a slight gap Δp between the flange portions 1e and 3d, and an exaggerated state is illustrated here. When the inside of the turbine housing 1b is exposed to a high temperature (for example, about 1000 ° C.) due to the existence of the gap Δp, the flange of the bearing housing 3 is caused by the thermal expansion of each component as shown in FIG. The inventor's research has confirmed that a gap Δg is formed between the portion 3d and the G coupling 4. For example, in the prior art shown in FIG. 2B, when the temperature of the exhaust gas supplied to the turbine 1 is 1050 ° C., a gap Δg of 0.0388 mm is formed. Even in such a gap, the fastening force of the G coupling 4 is reduced. Therefore, in the present invention, when the temperature of the exhaust gas supplied to the turbine 1 is 1050 ° C., it is necessary to make it at least smaller than the gap Δg (= 0.0388 mm) of this prior art.

  Here, if the contact on the G coupling 4 side corresponding to the contact Pb in the normal temperature state is Pg, the axial length Cg between the contacts Pa and Pg of the G coupling 4 in the high temperature state is the flange portion 1e. , Longer than the axial length C between the contact points Pa and Pb on the 3d side. This difference (Cg−C) is assumed to be ΔC. Here, if the relationship between ΔC and Δg is obtained from the diagram shown in FIG. 4C, ΔC = Δg / cos (θ / 2). As described above, Δg needs to satisfy at least Δg <0.0388 mm, and thus the difference ΔC needs to satisfy ΔC <0.0388 / cos (θ / 2) mm. An allowable value of the difference ΔC is set as the allowable value k. That is, in order to improve the fastening force even slightly compared with the conventional G coupling 4 when the exhaust gas temperature supplied to the turbine 1 is 1050 ° C., the allowable value k is 0 ≦ k <0.0388 / It can be defined as a numerical value within the range of cos (θ / 2) (unit is mm). Further, in the present invention, in order to effectively suppress a decrease in the fastening force of the G coupling 4, the gap Δg is preferably about 0.002 mm. In this case, the allowable value k can be defined as a numerical value within a range of 0 ≦ k ≦ 0.002 / cos (θ / 2) (unit is mm). Further, if the allowable value k when the standard G coupling 4 is used is defined by a numerical value, it can be defined as 0 ≦ k ≦ 0.0016 (unit: mm).

  From the above definition, if the axial length C between the contacts Pa and Pb in the high temperature state is calculated, C = {t (1 + εΔTs) + Bz (1 + βΔTb)} − Az (1 + αΔTa) (1) Can be written. The axial length Cg between the contacts Pa and Pg in a high temperature state is Cg = (t + Bz−Az) (1 + γΔTg) − {Ar (1 + αΔTa) − (Ar + Br) (1 + γΔTg) + Br (1 + βΔTb)} tan (θ / 2) It is written as (2). Therefore, when the allowable value k is set, the axial length Az between the locking surface of the stepped portion 1d and the contact Pa in the turbine housing 1b so as to satisfy the relationship of 0 ≦ ΔC ≦ k (3). And the axial direction length Bz of the end surface 3c of the convex part 3b in the bearing housing 3 and the contact Pb can be calculated | required. That is, in the present embodiment, by using the above formulas (1), (2), and (3), a parameter (axial length) regarding the shape of the convex portion 3b in consideration of the plate thickness t (thickness of the thin plate). Bz, radial length Br, opening degree θ, etc.) can be determined, and consequently the shape of the convex portion 3b can be designed in consideration of the plate thickness t.

  By setting the axial length Az on the concave side and the axial length Bz on the convex side by the housing fastening method described above, the fastening force of the G coupling 4 is reduced regardless of the type and capacity of the supercharger. Can be suppressed. Further, as long as the housing is fastened by using the G coupling 4, it can be applied to products other than the supercharger (for example, a wastegate valve, an exhaust manifold, a muffler, etc.).

  Next, another embodiment of the housing fastening method according to the present invention will be described with reference to FIG. Here, FIG. 5 is a side cross-sectional view of a fastening portion showing another embodiment of the housing fastening method according to the present invention. FIG. 5A shows a case where one flange portion is enlarged, and FIG. The case where it does not have a board is shown. Note that the same parts as those shown in FIG. 2A are denoted by the same reference numerals, and redundant description is omitted.

  In the embodiment shown in FIG. 5A, the outer diameter (radius) of the flange portion 3d of the bearing housing 3 is expanded by Δh than the outer diameter (radius) of the flange portion 1e of the turbine housing 1b. This is because the turbine housing 1b is in a higher temperature state than the bearing housing 3 and thus is likely to thermally expand. That is, considering that the contact Pa and the contact Pb are displaced in the radial direction due to the difference in thermal expansion, the contact Pa and the contact pb are made substantially parallel to the axial direction in a high temperature state. In this case, the calculation formulas for the axial length C between the contacts Pa and Pb and the axial length Cg between the contacts Pa and Pg can be applied as they are. Even if the housing fastening method shown in FIG. 5 (A) is not adopted, the angle between the line segment connecting the contact Pa and the contact pb and the axial direction can be easily considered between the contacts Pa and Pb. An axial length C can be calculated.

  In the embodiment shown in FIG. 5B, the locking surface of the step portion 1d in the recess 1c of the turbine housing 1b and the end surface 3c of the projection 3b of the bearing housing 3 are in direct contact with each other. That is, this is a case where the heat shield plate 5 shown in FIG. This considers the case where the heat shield 5 is not required depending on the type of the supercharger. In this case, if the variables (t, ε, ΔTs) relating to the heat shield plate 5 are excluded from the calculation formulas of the axial length C between the contacts Pa and Pb and the axial length Cg between the contacts Pa and Pg, The axial lengths C and Cg can be easily calculated. When a spacer or a seal member is sandwiched between the locking surface of the stepped portion 1d and the end surface 3c of the convex portion 3b in place of the heat shield plate 5, the plate thickness, linear expansion coefficient, etc. of the sandwiching member The axial lengths C and Cg may be calculated using

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention, for example, it can be applied to a fastening tool other than the G coupling. is there.

It is a figure which shows the supercharger which concerns on this invention, (A) is side sectional drawing, (B) is a front view of G coupling. It is an enlarged view of the II section in Drawing 1 (A), (A) shows the present invention and (B) shows the prior art. It is explanatory drawing which defines the dimension required for description of one Embodiment of the housing fastening method which concerns on this invention. It is explanatory drawing which shows the setting method of the allowable value k, (A) is a normal temperature state, (B) is a high temperature state, (C) is a figure which shows the relationship between the clearance gap between G coupling and a flange part, and the allowable value k. It is side surface sectional drawing of the fastening part which shows other embodiment of the housing fastening method which concerns on this invention, (A) shows the case where it does not have a heat shield, when (B) expands one flange part. ing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbine 1a Rotor blade 1b Turbine housing 1c Recessed part 1d Step part 1e Flange part 1f Scroll part 2 Compressor 2a Impeller 3 Bearing housing 3a Rotating shaft 3b Convex part 3c End surface 3d Flange part 4 G coupling (clamp)
4a Semicircular arc part 4b Flange part 4c Folding part 4d Fastener 4e Annular ring 5 Heat shield

Claims (8)

After inserting the convex part formed in the other housing into the concave part formed in one housing and locking the end surface of the convex part by the step part formed in the concave part, the concave part and the convex part In the housing fastening method of fastening the housing by fastening together the outer circumference of each flange portion formed on the outer circumference with a fastener,
A housing fastening method, wherein the fastening force of the fastening tool is adjusted by adjusting the axial position of the locking surface of the stepped portion and designing the shape of the concave portion and the convex portion.   The housing fastening method according to claim 1, wherein the axial position of the locking surface of the stepped portion is set so as to be included in the range of the axial projection width of the fastener.   2. The housing fastening according to claim 1, wherein the shape of the convex portion is designed in consideration of a thickness of a thin plate sandwiched between a locking surface of the stepped portion and an end surface of the convex portion. Method.   The housing fastening method according to claim 1, wherein an outer diameter of the flange portion in the housing on the side where thermal expansion is difficult is formed to be larger than an outer diameter of the flange portion in the housing on the side where thermal expansion is likely to occur.   Axial length Az between the contact point of the flange portion on the concave portion side and the locking surface of the stepped portion, and a contact point between the flange portion on the convex portion side and the end surface. The axial length Bz, the axial length C between the contact points of the flange portion, and the axial length Cg between the contact points of the fastener are defined as follows: 0 ≦ Cg−C ≦ allowable value k The housing fastening method according to claim 1, wherein the axial lengths Az and Bz are designed to satisfy the following conditions.   6. The housing fastening method according to claim 5, wherein the allowable value k is set by a clearance between the fastener and the flange portion that can be allowed at a predetermined temperature.   The allowable value k is a numerical value within a range of 0 ≦ k <0.0388 / cos (θ / 2) with respect to an opening θ of a gripping portion of the fastener. The housing fastening method according to claim 5. A turbine that rotates a moving blade by supplying fluid, a compressor that sucks air by an impeller connected to the moving blade via a rotating shaft, a turbine housing that forms an outer shape of the turbine, and a rotating shaft A bearing housing that supports the bearing housing, and a convex portion formed in the bearing housing is inserted into a concave portion formed in the turbine housing, and an end surface of the convex portion is engaged by a step portion formed in the concave portion. After stopping, in the supercharger in which the outer periphery of each flange portion formed on the outer periphery of the concave portion and the convex portion is fastened together with a fastener to fasten the turbine housing and the bearing housing,
A supercharger, wherein the bearing housing and the turbine housing are fastened by the fasteners according to the housing fastening method according to any one of claims 1 to 7.