U.S. patent application number 11/564578 was filed with the patent office on 2007-06-07 for fluid machine.
This patent application is currently assigned to FANUC LTD. Invention is credited to Akira EGAWA, Satoru KAWAI, Kazuya OHTA.
Application Number | 20070128044 11/564578 |
Document ID | / |
Family ID | 37490911 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070128044 |
Kind Code |
A1 |
KAWAI; Satoru ; et
al. |
June 7, 2007 |
FLUID MACHINE
Abstract
A fluid machine including a shaft and an impeller, wherein the
impeller has a shaft bore into which the shaft is inserted, and
wherein the impeller is coupled to the shaft by an interference
fit. The fluid machine further includes a positioning part provided
between the shaft and the impeller, for positioning the impeller at
a predetermined position on the shaft; a fitting part provided
inside the shaft bore and adjacent to the positioning part, for
forming the interference fit between the shaft and the impeller;
and a loose-insertion part provided inside the shaft bore and
adjacent to the fitting part, for forming a clearance between the
shaft and the impeller.
Inventors: |
KAWAI; Satoru; (Yamanashi,
JP) ; OHTA; Kazuya; (Yamanashi, JP) ; EGAWA;
Akira; (Shizuoka, JP) |
Correspondence
Address: |
LOWE HAUPTMAN BERNER, LLP
1700 DIAGONAL ROAD
SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
FANUC LTD
3580, Shibokusa Aza-Komanba, Oshino-mura Minamitsuru-gun
Yamanashi
JP
401-0597
|
Family ID: |
37490911 |
Appl. No.: |
11/564578 |
Filed: |
November 29, 2006 |
Current U.S.
Class: |
416/244A |
Current CPC
Class: |
F04D 29/266 20130101;
F04D 29/20 20130101 |
Class at
Publication: |
416/244.00A |
International
Class: |
F04D 29/00 20060101
F04D029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2005 |
JP |
2005-347533 |
Claims
1. A fluid machine comprising: a shaft; an impeller having a shaft
bore into which said shaft is inserted, said impeller being coupled
to said shaft by an interference fit; a positioning part provided
between said shaft and said impeller, for positioning said impeller
at a predetermined position on said shaft; a fitting part provided
inside said shaft bore and adjacent to said positioning part, for
forming said interference fit between said shaft and said impeller;
and a loose-insertion part provided inside said shaft bore and
adjacent to said fitting part, for forming a clearance between said
shaft and said impeller.
2. A fluid machine as set forth in claim 1, wherein said
positioning part comprises a member separated from said shaft and
said impeller.
3. A fluid machine as set forth in claim 1, wherein said
positioning part comprises a part of at least one of said shaft and
said impeller.
4. A fluid machine as set forth in claim 1, wherein said fitting
part and said loose-insertion part are formed by varying, along an
axial lengthwise direction, at least one of an outer diameter of
said shaft and an inner diameter of said shaft bore of said
impeller.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to fluid machinery
and, more particularly, to a fluid machine including a shaft and an
impeller coupled to each other by an interference fit.
[0003] 2. Description of the Related Art
[0004] In a fluid machine of a high-speed rotation type, such as a
blower used in a laser oscillator, it is required to firmly or
fixedly attach an impeller to a shaft (or a rotary shaft) with high
positional accuracy. To this end, conventionally, the impeller is
fitted to the shaft by a shrinkage fit, so as to prevent a relative
positional deviation in a circumferential direction of the impeller
and the shaft, which may occur during the high-speed rotation
thereof, and to allow them to rotate stably at high speed, as
described in, e.g., Japanese Unexamined Patent Publication (Kokai)
No. 7-063193 (JP-A-7-063193).
[0005] Further, there is known a configuration in which the
impeller is fitted, at only a part of a shaft bore thereof, to the
shaft by the shrinkage fit, as described in Japanese Unexamined
Patent Publication 2004-060460 (JP-A-2004-060460). JP-A-2004-060460
also describes a technique in which the impeller is mounted on a
surface plate with the gas-intake side of the impeller being
directed upward and, in this state, a fitting part provided at the
gas-intake side in the shaft bore of the impeller is subjected to
heat to increase the inner diameter of the fitting part and, after
the shaft is inserted downward into the shaft bore up to a
predetermined position from an upper side of the impeller, the heat
is removed to complete the shrinkage fit.
[0006] In a conventional fluid machine in which the impeller is
fitted to the shaft by the shrinkage fit, a relative fixing
position between the impeller and the shaft is typically determined
based on a point at which the impeller is first engaged with the
shaft during the shrinkage of the impeller and, thereafter, the
impeller completely shrinks to be firmly fixed to the shaft. In
this connection, it is generally difficult to accurately estimate
the fixing position of the impeller on the shaft (i.e., the
position of the first engagement point) due to, e.g., uneven
machining accuracy of the impeller and the shaft. Therefore, it is
difficult to accurately locate and fix the impeller at a
predetermined position in an axial direction on the shaft and, as a
result, the operational reliability and/or performance of the fluid
machine may be adversely affected.
[0007] For example, in a configuration in which a shaft seal and/or
a bearing are mounted adjacent to the impeller, if the axial
position of the impeller on the shaft is deviated from a set
position, the axial positions of the shaft seal and the bearing are
also deviated from set positions thereof accordingly. In
particular, if the positional deviation of the bearing is caused,
abnormal vibration may occur and thus the bearing or the body of
the fluid machine may be damaged during the high-speed rotation of
the shaft. This problem may arise not only in the configuration in
which the impeller is fixed to the shaft at the entire length of
the shaft bore, as described in JP-A-7-063193, but also in the
configuration in which the impeller is fixed to the shaft at a part
of the shaft bore, as described in JP-A-2004-060460, because of the
fact that the fixing position of the impeller on the shaft (i.e.,
the position of the first engagement point) is difficult to
specify.
[0008] In order to solve the above problem, it is known that, in
the shrinkage fit process, the impeller and the shaft are securely
bound or held by, e.g., a press machine, to prevent the relative
positional deviation in the axial direction therebetween, until the
impeller shrinks completely. Further, it is known that, for the
sake of reducing a time spent for the complete shrinkage of the
impeller, a cooling mechanism for an exclusive use is provided.
However, these subsidiary apparatuses, such as the press machine,
the cooling mechanism and the like, may result in increase in the
manufacturing costs of the fluid machine.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a fluid
machine including a shaft and an impeller, coupled to each other by
an interference fit, wherein it is possible to surely prevent, by a
simple structure, a relative positional deviation in an axial
direction caused between the shaft and the impeller during a
coupling work thereof, and thereby to ensure an inexpensive and
high-performance configuration with an excellent safety and
operational reliability.
[0010] To accomplish the above object, the present invention
provides a fluid machine comprising a shaft; an impeller having a
shaft bore into which the shaft is inserted, the impeller being
coupled to the shaft by an interference fit; a positioning part
provided between the shaft and the impeller, for positioning the
impeller at a predetermined position on the shaft; a fitting part
provided inside the shaft bore and adjacent to the positioning
part, for forming the interference fit between the shaft and the
impeller; and a loose-insertion part provided inside the shaft bore
and adjacent to the fitting part, for forming a clearance between
the shaft and the impeller.
[0011] In the above-described fluid machine, the positioning part
may comprise a member separated from the shaft and the
impeller.
[0012] Also, the positioning part may comprise a part of at least
one of the shaft and the impeller.
[0013] Also, the fitting part and the loose-insertion part may be
formed by varying, along an axial lengthwise direction, at least
one of an outer diameter of the shaft and an inner diameter of the
shaft bore of the impeller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above and other objects, features and advantages of the
present invention will become more apparent from the following
description of preferred embodiments in connection with the
accompanying drawings, wherein:
[0015] FIG. 1 is a sectional view showing a shaft and an impeller
of a fluid machine according to an embodiment of the present
invention;
[0016] FIG. 2 is a sectional view showing a modification of the
fluid machine of FIG. 1;
[0017] FIG. 3 is a sectional view showing another modification of
the fluid machine of FIG. 1;
[0018] FIG. 4 is a sectional view showing a further modification of
the fluid machine of FIG. 1; and
[0019] FIG. 5 is a sectional view showing an yet further
modification of the fluid machine of FIG. 1.
DETAILED DESCRIPTION
[0020] The embodiments of the present invention are described
below, and in detail, with reference to the accompanying drawings.
In the drawings, the same or similar components are denoted by
common reference numerals.
[0021] Referring to the drawings, FIG. 1 shows a shaft 12 and an
impeller 14 of a fluid machine 10 according to an embodiment of the
present invention. The fluid machine 10 according to the
illustrated embodiment is configured as a centrifugal blower, and a
known blade structure of the impeller 14 and a known structure of a
housing (not shown) can be used for the fluid machine 10, the
descriptions of which are thus omitted. It should be noted that the
present invention can be applied not only to the centrifugal blower
but also to other various fluid machines.
[0022] The fluid machine 10 includes a shaft 12 and an impeller 14
having a shaft bore 16 into which the shaft 12 is inserted, and is
configured so that the impeller 14 is coupled to the shaft 12
through an interference fit. The fluid machine 10 further includes
a positioning part 18 provided between the shaft 12 and the
impeller 14, for positioning the impeller 14 at a predetermined
position on the shaft 12; a fitting part 20 provided inside the
shaft bore 16 and adjacent to the positioning part 18, for forming
the interference fit between the shaft 12 and the impeller 14; and
a loose-insertion part 22 provided inside the shaft bore 16 and
adjacent to the fitting part 20, for forming a clearance between
the shaft 12 and the impeller 14.
[0023] The shaft 12 is provided with a stepped cylindrical outer
circumferential surface 12a extending along the rotation axis A of
the shaft 12 and impeller 14 with the outer diameter of the outer
circumferential surface 12a varying in a stepped manner. The
impeller 14 is coaxially fixed to the outer circumferential surface
12a of the impeller 14 at the predetermined axial position of the
outer circumferential surface 12a. The shaft bore 16 of the
impeller 14 has a cylindrical inner circumferential surface 16a
extending along the rotation axis A of the shaft 12 and the
impeller 14 with the inner diameter of the inner circumferential
surface 16a being kept constant. The shaft 12, to which the
impeller 14 is fixed, is rotatably supported by the housing (not
shown) through a bearing 24 attached to the shaft 12 at its
predetermined axial position. A shaft seal 26 is securely mounted
to the shaft 12 at a predetermined axial position between the
impeller 14 and the bearing 24.
[0024] The outer circumferential surface 12a of the shaft 12
includes a cylindrical large-diameter portion 28, on which the
bearing 24 and the shaft seal 26 are mounted; a cylindrical
intermediate-diameter portion 30 disposed axially adjacent to the
large-diameter portion 28, the diameter of which is slightly
reduced in comparison with the large-diameter portion 28 through a
first annular-shoulder surface 12b generally orthogonal to the
rotation axis A; and a cylindrical small-diameter portion 32
disposed axially adjacent to the intermediate-diameter portion 30,
the diameter of which is slightly reduced in comparison with the
intermediate-diameter portion 30 through a second annular-shoulder
surface 12c generally orthogonal to the rotation axis A. The shaft
seal 26 includes a cylindrical base 34 adapted to be fitted to the
large-diameter portion 28 of the shaft 12. The base 34 of the shaft
seal 26 is disposed to be aligned, at one axial end (an upper end,
in the drawing) thereof, with the first annular-shoulder surface
12b of the shaft 12, and is disposed to be adjacent, at the other
end (a lower end, in the drawing) thereof, to the bearing 24. The
impeller 14 is fixed to the intermediate-diameter portion 30 of the
shaft 12 at a first region 36 of the inner circumferential surface
16a of the shaft bore 16, which extends over a predetermined length
from one axial end (a lower end, in the drawing) of the inner
circumferential surface 16a. A remaining region (or a second
region) 38 of the inner circumferential surface 16a of the shaft
bore 16 of the impeller 14 is disposed so as not to contact the
small-diameter portion 32 of the shaft 12.
[0025] In the illustrated embodiment, the positioning part 18 is
configured from the first annular-shoulder surface 12b of the shaft
12 and the base 34 of the shaft seal 26, the base 34 being a member
separated from both of the shaft 12 and the impeller 14. The
impeller 14 receives the small-diameter portion 32 and the
intermediate-diameter portion 30 of the shaft 12 successively in
this order from one axial end (a lower end, in the drawing) of the
shaft bore 16, and is abutted, at an annular area 14a of an axial
end face adjacent to an opening at one axial end of the shaft bore
16, against both of the first annular-shoulder surface 12b of the
shaft 12 and one axial end face (an upper end face, in the drawing)
of the base 34 of the shaft seal 26. In this state, the impeller 14
is accurately located at the predetermined axial position on the
shaft 12.
[0026] Further, in the illustrated embodiment, the fitting part 20
is configured by the cooperation between the intermediate-diameter
portion 30 of the outer circumferential surface 12a of the shaft 12
and the first region 36 of the inner circumferential surface 16a of
the shaft bore 16. The interference-fit configuration in the
fitting part 20 can be surely obtained by at least one (or both) of
processes of "a shrinkage fit" in which the impeller 14 is heated
to be attached to the shaft 12 and "an expansion or cooling fit" in
which the shaft 12 is cooled to be attached to the impeller 14. The
outer diameter of the intermediate-diameter portion 30 of the shaft
12 and the inner diameter of the first region 36 of the shaft bore
16 are determined so as to ensure an interference sufficient to
achieve an interference-fit structure having a desired strength.
Also, the axial length of the intermediate-diameter portion 30 of
the shaft 12 is determined so as to be sufficient to eliminate an
inclination of the axis of the impeller 14 relative to the shaft
12. Still further, in the illustrated embodiment, the
loose-insertion part 22 is configured by the cooperation between
the small-diameter portion 32 of the outer circumferential surface
12a of the shaft 12 and the second region 38 of the inner
circumferential surface 16a of the shaft bore 16.
[0027] In the fluid machine 10 configured as described above, when
the shaft 12 is fixed to the impeller 14 by at least one of the
shrinkage fit process and the expansion fit process, the
small-diameter portion 32 and the intermediate-diameter portion 30
of the shaft 12 are first inserted successively in this order into
the shaft bore 16 of the impeller 14, and the annular area 14a of
the axial end face of the impeller 14 is brought into abutment with
the positioning part 18 (i.e., the first annular-shoulder surface
12b of the shaft 12 and the base 34 of the shaft seal 26), whereby
it is possible to accurately locate the impeller 14 at the
predetermined axial position on the shaft 12. Then, the shaft 12
and the impeller 14 are left standing in this state, so that the
impeller 14 as heated can shrink in the case of the shrinkage fit,
or alternatively the shaft 12 as cooled can expand in the case of
the expansion fit, and thereby the shaft 12 and the impeller 14 are
engaged with each other first in the fitting part 20 (i.e., the
intermediate-diameter portion 30 of the shaft 12 and the first
region 36 of the shaft bore 16). During this step, due to the
weight of the impeller 14 or a slight external force, the state
where the annular area 14a of the impeller 14 abuts against the
positioning part 18 can be easily maintained and, therefore, the
shaft 12 and the impeller 14 are engaged with each other first at a
certain point in the fitting part 20 in the state where the
impeller 14 is surely located at the predetermined axial position
on the shaft 12.
[0028] Thereafter, heat is exchanged between the shaft 12 and the
impeller 14 that are in contact with each other and, thereby, the
expansion of the shaft 12 and the shrinkage of the impeller 14 are
substantially simultaneously performed, so that the interference
fit in the fitting part 20 is completed. The subsequent expansion
of the shaft 12 and the subsequent shrinkage of the impeller 14,
after the completion of the interference fit, advance in directions
reverse to each other, as shown by arrows in FIG. 1. Such thermal
deformations of both the shaft 12 and the impeller 14 in the
reverse directions can be smoothly performed, due to the provision
of the loose-insertion part 22 (i.e., the small-diameter portion 32
of the shaft 12 and the second region 38 of the shaft bore 16).
Then, at an instant when the thermal deformations of both the shaft
12 and the impeller 14 are finished, the operation for attaching
the impeller 14 to the shaft 12 is completed. The impeller 14 thus
attached to the shaft 12 possesses a significantly high positional
accuracy in the axial direction.
[0029] As described above, in the fluid machine 10 in which the
fitting part 20 is provided adjacent to the positioning part 18
inside the shaft bore 16, it is possible, when the shaft 12 is
fixed to the impeller 14 by at least one of the processes of the
shrinkage fit and the expansion fit, to easily and surely specify
the fixing position of the impeller 14 on the shaft 12 (i.e., the
position of the first engagement point) and thus to establish the
interference fit in the fitting part 20. Further, the
loose-insertion part 22 is provided adjacent to the fitting part 20
inside the shaft bore 16, so that it is possible to control the
expansion of the shaft 12 and the shrink of the impeller 14, after
the completion of the interference fit, in the predetermined
directions. As a result, it is possible to surely prevent, by a
simple structure, a relative positional deviation in an axial
direction caused between the shaft 12 and the impeller 14 during
the coupling work thereof, so as to improve the positional accuracy
in the axial direction of the impeller 14 on the shaft 12, as well
as of the other components attached to the shaft 12, such as the
bearing 24, the shaft seal 26 and the like. Accordingly, the fluid
machine 10 can ensure an inexpensive and high-performance
configuration with an excellent safety and operational
reliability.
[0030] It should be noted that, in the above-described
configuration in which the interference fit between the shaft 12
and the impeller 14 is ensured by at least one of the processes of
the shrinkage fit and the expansion fit, it is advantageous that
the shaft 12 and the impeller 14 are made of materials having
mutually different heat-shrinkage rates, in view of facilitating
the effect of the interference fit.
[0031] In the fluid machine 10 described above, the positioning
part 18 may also be configured by either one of the base 34 of the
shaft seal 26 (i.e., a member separated from the shaft 12 and
impeller 14) and the first annular-shoulder surface 12b of the
shaft 12 (i.e., a part of the shaft 12). In the case where the
positioning part 18 is configured by using a component provided for
other purposes, such as the shaft seal 26 attached to the shaft 12
and adjacent to the impeller 14, it is possible to reduce the
number of manufacturing steps and the number of components. On the
other hand, in the case where the positioning part 18 is configured
by a part of at least one of the shaft 12 and the impeller 14, it
is possible to maintain the stable positioning function.
[0032] Further, the fitting part 20 and the loose-insertion part 22
may be defined by varying, along an axial lengthwise direction, a
diametral dimension of at least one of the outer circumferential
surface 12a of the shaft 12 and the inner circumferential surface
16a of the shaft bore 16 of the impeller 14. According to this
configuration, the fitting part 20 and the loose-insertion part 22
can be configured very simply and easily. Hereinafter, various
modifications of the above-described fluid machine 10 will be
described with reference to FIGS. 2 to 5. The components shown in
FIGS. 2 to 5, corresponding to those of the fluid machine 10 in
FIG. 1, are designated by common reference numerals, and the
descriptions thereof are not repeated.
[0033] In a modification shown in FIG. 2, in place of the
above-described intermediate-diameter portion 30, the shaft 12 is
provided, at the outer circumferential surface 12a thereof, with a
tapered portion 40 defined between the first annular-shoulder
surface 12b and the small-diameter portion 32, the outer diameter
of the tapered portion 40 being gradually reduced starting from the
first annular-shoulder surface 12b up to the small-diameter portion
32. The tapered portion 40 is engaged, at a point adjacent to the
first annular-shoulder surface 12b, with an end portion 36a of the
above-described first region 36 in an interference-fit condition,
the end portion 36a being adjacent to the opening end (the lower
end, in the drawing) of the shaft bore 16 of the impeller 14,
opening to the positioning part 18, and thereby the fitting part 20
is constituted. In this configuration, provided that a sufficient
interference is obtained for the interference fit in the fitting
part 20, it is possible to establish a fitting structure having a
required strength, and also to eliminate the inclination of the
axis of the impeller 14 relative to the shaft 12 by the function of
the positioning part 18 (i.e., the first annular-shoulder surface
12b of the shaft 12 and the base 34 of the shaft seal 26).
According to this configuration, characteristic effects, equivalent
to those of the fluid machine 10 shown in FIG. 1, are also
ensured.
[0034] In a modification shown in FIG. 3, the intermediate-diameter
portion 30 and the second annular-shoulder surface 12c, as
described above, are eliminated from the outer circumferential
surface 12a of the shaft 12, so that the large-diameter portion 28
and the small-diameter portion 32 are adjacent to each other with
the first annular-shoulder surface 12b arranged therebetween. On
the other hand, the inner circumferential surface 16a of the shaft
bore 16 of the impeller 14 is formed to have a stepped cylindrical
shape including the above-described first region 36 defined by a
small-diameter cylindrical surface and the above-described second
region 38 defined by a cylindrical surface having a diameter larger
than the first region 36. The first region 36 of the shaft bore 16
of the impeller 14 is engaged with a distal end area 42 of the
small-diameter portion 32 of the shaft 12 in an interference-fit
condition, the distal end area 42 being adjacent to the first
annular-shoulder surface 12b, and thereby the fitting part 20 is
constituted. In this configuration, provided that a sufficient
interference and a sufficient axial length are obtained for the
interference fit in the fitting part 20, it is possible to
establish a fitting structure having a required strength, and also
to eliminate the inclination of the axis of the impeller 14
relative to the shaft 12. According to this configuration,
characteristic effects, equivalent to those of the fluid machine 10
shown in FIG. 1, are also ensured.
[0035] In a modification shown in FIG. 4, the outer circumferential
surface 12a of the shaft 12 is formed so that the large-diameter
portion 28 and the small-diameter portion 32 are adjacent to each
other with the first annular-shoulder surface 12b arranged
therebetween, in a manner similar to the configuration of FIG. 3.
On the other hand, the shaft bore 16 of the impeller 14 is provided
in the inner circumferential surface 16a thereof with the
above-described second region 38 defined by a large-diameter
cylindrical surface and a tapered region 44 defined between the
second region 38 and the opening end (the lower end, in the
drawing) opening to the positioning part 18, the inner diameter of
the tapered region 44 being gradually reduced starting from the
second region 38 up to the opening end. The tapered region 44 of
the shaft bore 16 is engaged, at a point adjacent to the opening
end opening to the positioning part 18, with an end portion 32a of
the small-diameter portion 32 of the shaft 12 in an
interference-fit condition, the end portion 32a being adjacent to
the first annular-shoulder surface 12b, and thereby the fitting
part 20 is constituted. In this configuration, provided that a
sufficient interference is obtained for the interference fit in the
fitting part 20, it is possible to establish a fitting structure
having a required strength, and also to eliminate the inclination
of the axis of the impeller 14 relative to the shaft 12 by the
function of the positioning part 18 (i.e., the first
annular-shoulder surface 12b of the shaft 12 and the base 34 of the
shaft seal 26). According to this configuration, characteristic
effects, equivalent to those of the fluid machine 10 shown in FIG.
1, are also ensured.
[0036] In a modification shown in FIG. 5, in place of the
above-described positioning part 18 using the shaft seal 26, a
positioning part 46 formed by parts of both the shaft 12 and the
impeller 14 is provided inside the shaft bore 16 of the impeller
14. More specifically, the outer circumferential surface 12a of the
shaft 12 is formed so that the large-diameter portion 28 and the
small-diameter portion 32 are adjacent to each other with the first
annular-shoulder surface 12b arranged therebetween, and that the
large-diameter portion 28 is extended to protrude from the base 34
of the shaft seal 26 and inserted into the shaft bore 16 of the
impeller 14. On the other hand, the inner circumferential surface
16a of the shaft bore 16 of the impeller 14 is formed to have a
stepped cylindrical shape including the large-diameter first region
36 adjacent to the opening end (the lower end, in the drawing)
opening to the shaft seal 26, the large-diameter second region 38
adjacent to the opposite opening end, and a small-diameter third
region 48 defined between the first region 36 and the second region
38. Also, in the shaft bore 16 of the impeller 14, an
annular-shoulder surface 16b substantially orthogonal to the axis A
is formed between the first region 36 and the third region 48. The
annular-shoulder surface 16b of the shaft bore 16 of the impeller
14 cooperates with the first annular-shoulder surface 12b of the
shaft 12 and, thereby, the positioning part 46 is constituted.
Further, the third region 48 of the shaft bore 16 of the impeller
14 is engaged with a distal end area 50 of the small-diameter
portion 32 of the shaft 12 in an interference-fit condition, the
distal end area 42 being adjacent to the first annular-shoulder
surface 12b and, thereby, the fitting part 20 is constituted.
[0037] In the above configuration, when the shaft 12 is fixed to
the impeller 14 by at least one of the shrinkage fit process and
the expansion fit process, the small-diameter portion 32 and the
large-diameter portion 28 of the shaft 12 are first inserted
successively in this order into the shaft bore 16 of the impeller
14, and the first annular-shoulder surface 12b of the shaft 12 is
brought into abutment with the annular-shoulder surface 16b of the
shaft bore 16 of the impeller 14, whereby it is possible to
accurately locate the impeller 14 at the predetermined axial
position on the shaft 12 by the function of the positioning part
46. In this state, the interference fit is completed in the fitting
part 20 (i.e., the distal end area 50 of the small-diameter portion
32 of the shaft 12 and the third region 48 of the shaft bore 16),
so that it is possible to attach the impeller 14 to the shaft 12 in
the state where the impeller 14 is accurately located at the
predetermined axial position on the shaft 12. During a period when
heat is exchanged between the shaft 12 and the impeller 14, that
are in contact with each other at the fitting part 20, the thermal
deformations of the shaft 12 and the impeller 14 advance in the
directions shown by arrows in FIG. 5. According to this
configuration, as the positioning part 46 and the fitting part 20
are provided adjacent to each other inside the shaft bore 16, it is
also possible to easily and surely specify the fixing position of
the impeller 14 on the shaft 12 (i.e., the position of the first
engagement point) and thus to establish the interference fit in the
fitting part 20. As a result, characteristic effects, equivalent to
those of the fluid machine 10 shown in FIG. 1, are also
ensured.
[0038] While the invention has been described with reference to
specific preferred embodiments, it will be understood, by those
skilled in the art, that various changes and modifications may be
made thereto without departing from the scope of the following
claims.
* * * * *