SCROLL TYPE FLUID MACHINE

Abstract

A shell-integrated fixed scroll includes a cylindrical shell that is integrated with an end plate on which a scroll wrap is erected, and has a proximal end entirely connected with an outer periphery of the end plate and a leading end extending in the axial direction. The wall of the shell partially forms a thick portion having a large thickness from a proximal-end-side end (first) surface to a leading-end-side end (second) surface. In the thick portion, a screw hole for a bolt for fastening a rear housing to the first surface extends from the first surface toward the second surface. A screw hole for a bolt for fastening a front housing to the second surface extends from the second surface toward the first surface. The thick portion is partially cut away in the circumferential direction between the two surfaces to form opposing surfaces facing each other in the axial direction.

Description

TECHNICAL FIELD

The present invention relates to a scroll type fluid machine equipped with an orbiting scroll and a fixed scroll, and more particularly to the fixing structure used for processing a shell-integrated fixed scroll having a shell integrated with the fixed scroll.

BACKGROUND ART

A scroll type compressor as disclosed in Patent Document 1 has been known as the scroll type fluid machine. Such scroll type compressor includes a fixed scroll and an orbiting scroll, which are arranged opposite each other in the axial direction so as to engage together their own volute scroll wraps that are erected on respective end plates. The compressor revolves the orbiting scroll around the center axis of the fixed scroll to thereby compress a fluid introduced into a gap between the fixed and orbiting scrolls and discharge the compressed fluid. Of these, the fixed scroll has a cylindrical shell integrated with the end plate to constitute a shell-integrated fixed scroll. In this case, the shell extends from the outer periphery of the end plate in the center axis direction. The shell-integrated fixed scroll of this type is roughly produced by, for example, molding, forging, etc. and then partially subjected to intermediate or finish processing such as cutting or grinding (hereinafter referred to as “finish processing, etc.”) with a view to enhancing its dimensional precision.

REFERENCE DOCUMENT LIST

Patent Document

Patent Document 1: JP 2002-13486 A

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

If the cylindrical shell is firmly held in the horizontal direction in order to fix the shell-integrated fixed scroll upon the finish processing, etc., the shell may possibly deform because there is no supporting structure for maintaining the space between the shell and the scroll wrap. On this account, there is a fear that the shell-integrated fixed scroll cannot maintain appropriate dimensional precision and the productivity of the scroll type fluid machine is lowered.

Moreover, end surfaces of the shell and scroll wraps, etc. have to undergo the finish processing, etc. in order to satisfy requirements for dimensional precision. Thus, it is not desirable to firmly hold and fix the shell-integrated fixed scroll in the axial direction at these end surfaces, etc.

The present invention has been accomplished in view of some of the above problems and it is accordingly an object of the present invention to provide a scroll type fluid machine that improves the fixing structure for a shell-integrated fixed scroll upon finish processing, etc. to hereby enhance its productivity.

Means for Solving the Problems

In order to achieve the above object, the present invention provides a scroll type fluid machine comprising an orbiting scroll and a fixed scroll, in which the fixed scroll comprises: a volute scroll wrap that is erected on an end plate; a cylindrical shell that is integrated with the end plate and has a proximal end entirely connected with an outer periphery of the end plate and a leading end extending in the direction in which the scroll wrap is erected; and a thick portion formed by partially increasing the thickness of a wall of the shell from a proximal-end-side end surface of the shell to a leading-end-side end surface of the shell so that in the thick wall of the shell, a screw hole for a first bolt for fastening a first housing to the proximal-end-side end surface extends from the proximal-end-side end surface toward the leading-end-side end surface, and a screw hole for a second bolt for fastening a second housing to the leading-end-side end surface extends from the leading-end-side end surface toward the proximal-end-side end surface, wherein the thick portion is partially cut away in a circumferential direction of the shell between the proximal-end-side end surface and the leading-end-side end surface to form opposing surfaces facing each other in the axial direction.

Effects of the Invention

According to the scroll type fluid machine of the present invention, the shell-integrated fixed scroll can be fixed while being applied with a load in the axial direction. This contributes to improvements in fixing structure for the shell-integrated fixed scroll upon finish processing, etc. so as to easily maintain appropriate dimensional precision of the shell-integrated fixed scroll and enhance its productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the overall configuration of a scroll type compressor.

FIG. 2 is a perspective view of the shell-integrated fixed scroll on its opening side.

FIG. 3 is a perspective view of the shell-integrated fixed scroll on its bottom plate side.

FIG. 4 is a partial cross-sectional view of another example of a notch in a thick portion.

FIG. 5 is an explanatory view illustrating how to fix the shell-integrated fixed scroll.

FIG. 6 is a partial cross-sectional view of another example of a screw hole.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention for carrying out the invention will be described in detail with reference to the accompanying drawings. Note that a scroll type fluid machine of the present invention can be used as a compressor or expander. In the following, the compressor is described by way of example.

FIGS. 1 to 3 show an example of the scroll type compressor according to an embodiment of the present invention. A scroll type compressor 10 includes a fixed scroll 12 and an orbiting scroll 14, which are arranged opposite each other in the center axis direction. The fixed scroll 12 includes a volute scroll wrap 12b integrally erected on an end plate 12a. Likewise, the orbiting scroll 14 includes a volute scroll wrap 14b integrally erected on an end plate 14a.

The fixed scroll 12 and the orbiting scroll 14 are arranged as follows: the scroll wraps 12b and 14b are engaged together in the axial direction so that protruding ends of the scroll wraps 12b and 14b could come into contact with the end plates 14a and 12a, respectively. A chipseal (not shown) is embedded at the protruding end of the scroll wrap 12b, 14b.

Furthermore, the fixed scroll 12 and the orbiting scroll 14 are disposed so that side walls of the scroll wraps 12b and 14b partially contact with each other. With this arrangement, a crescentic fluid pocket 16 is formed as sealed space between the two scroll wraps 12b and 14b as viewed in the axial direction.

The orbiting scroll 14 revolves around the center axis of the fixed scroll 12 by means of a driving mechanism 18 and also an anti-rotation mechanism 20 inhibits its rotation as below. As the fluid pocket 16 defined between the two scroll wraps 12b and 14b moves from the outer edge of the scroll wrap 12b, 14b to the center portion, the volume of the fluid pocket 16 gradually reduces. Accordingly, a fluid (e.g., refrigerant gas) taken into the fluid pocket 16 from the outer edge side of the scroll wrap 12b, 14b is compressed.

As for an expander, the fluid pocket 16 conversely moves from the center portion of the scroll wrap 12b, 14b to the outer edge. Thus, the volume of the fluid pocket 16 gradually increases and a fluid taken into the fluid pocket 16 from the center portion of the scroll wrap 12b, 14b is expanded.

A housing for the scroll type compressor 10 is composed of a center housing 22 that integrally includes the fixed scroll 12, a rear housing (first housing) 24 disposed on the back of the end plate 12a at which the scroll wrap 12b of the fixed scroll 12 does not protrude, and a front housing (second housing) 26 disposed on the front of the end plate 12a at which the scroll wrap 12b of the fixed scroll 12 protrudes.

The center housing 22 is a cylindrical casing (shell), the proximal end of which is entirely connected with the outer periphery of the end plate 12a of the fixed scroll 12 and the leading end of which extends in the direction in which the scroll wrap 12b is erected. The center housing is integrated with the fixed scroll 12 to constitute a shell-integrated fixed scroll 28. In other words, the shell-integrated fixed scroll 28 has such structure that an opening on the rear housing 24 side, out of two openings of the cylindrical center housing 22, is closed by the end plate 12a of the fixed scroll 12, and the other opening on the front housing 26 side is opened. In this way, the shell-integrated fixed scroll 28 has a bottomed cylindrical shape with the end plate 12a serving as the bottom plate thereof.

The rear housing 24 is fastened by use of plural bolts 30 (first bolts) to a proximal-end-side end surface 22a of the center housing 22. A discharge chamber 32 is defined between the rear housing and the end plate 12a. The end plate 12a has an outlet 34 at its center so as to introduce the fluid in the fluid pocket 16, compressed by revolutions of the orbiting scroll 14, toward the discharge chamber 32. At the exit of the outlet 34, a one-way valve 36 is provided to avoid backflow. In addition, the outer wall of the rear housing 24 has a discharge port (not shown) through which the fluid flows from the discharge chamber 32 to the outside.

The front housing 26 is fastened by use of plural bolts 40 (second bolts) to a leading-end-side end surface 22b of the center housing 22. The front housing 26 includes an accommodating space 42 that accommodates the driving mechanism 18 for the orbiting scroll 14. Provided at one end of the accommodating space 42 are a bearing 46 for axially supporting a drive shaft 44 of the driving mechanism 18, and a shaft seal 48. Provided at the other end of the accommodating space 42 is a thrust receiving unit 52 for supporting the orbiting scroll 14 in the thrust direction by means of an annular thrust plate 50. Furthermore, a fluid intake chamber 54 is formed in the front housing 26, being spaced away from the accommodating space 42 by the orbiting scroll 14 and the thrust plate 50. The fluid is taken into the fluid intake chamber 54 from the outside through an intake port (not shown) at the outer wall of the front housing 26.

A bulging portion 58 is formed in the front housing 26 and the center housing 22 partially in the circumferential direction. A fluid passage space 60 is formed inside the bulging portion 58. The space extends in parallel with the center axis of the compressor and guides the fluid from the intake chamber 54 on the front housing 26 side to around the outer edge of the scroll wrap 12b, 14b on the center housing 22 side.

The fluid is introduced into the intake chamber 54 inside the front housing 26 form the intake port of the front housing 26 and then passes through the fluid passage space 60 inside the bulging portion 58 of the front housing 26 and center housing 22. After that, the fluid is taken into the above fluid pocket 16 from the outer edge side of the scroll wrap 12b, 14b and then compressed. The compressed fluid is discharged to the discharge chamber 32 inside the rear housing 24 from the outlet 34 formed at the center of the end plate 12a of the fixed scroll 12. Then, the fluid is sent out to the outside from the discharge chamber 32 through the discharge port.

As disclosed in, for example, JP 2012-237288 A, the driving mechanism 18 installed in the accommodating space 42 of the front housing 26 is configured such that a crank mechanism is provided on the drive shaft 44 rotated with externally applied rotational driving force, and the driving mechanism is connected to the orbiting scroll 14 by means of the crank mechanism.

In the driving mechanism 18, the drive shaft 44 is axially supported in a rotatable manner by the bearing 46 at one end of the accommodating space 42. One end of the drive shaft 44 protrudes outward from the front housing 26, and a pulley 64 is attached there through an electromagnetic clutch 62. With this arrangement, the drive shaft 44 is rotated with the rotational driving force transmitted from the pulley 64 through the electromagnetic clutch 62. The crank mechanism disposed on the other side of the drive shaft 44 is composed of a crank 68 axially supported to the inner peripheral wall of the accommodating space 42 by means of the bearing 66, and an eccentric bushing 70 attached to the crank 68 eccentrically to the center axis of the drive shaft 44. The eccentric bushing 70 is fitted into a cylindrical boss 72 that protrudes from the back of the end plate 14a of the orbiting scroll 14 by means of a bearing 74. In FIG. 1, components including from the drive shaft 44 to the eccentric bushing 70 are collectively referred to as the driving mechanism 18 for ease of illustration.

The anti-rotation mechanism 20 of the orbiting scroll 14 includes: a circular hole 76 formed on the back of the end plate 14a of the orbiting scroll 14 (opposite to the thrust receiving unit 52 of the front housing 26); a pin 78 that protrudes on the thrust receiving unit 52 side of the front housing 26 and penetrates through the thrust plate 50; and a disk plate 82 having an eccentric hole 80 and accommodated in the circular hole 76 with some space. The pin 78 is fitted into the eccentric hole 80 of the disk plate 82 with some space. Fitting the pin 78 into the eccentric hole 80 inhibits the orbiting scroll 14 from rotating.

Thus, the orbiting scroll 14 revolves along with the rotation of the drive shaft 44 by means of the crank mechanism, the anti-rotation mechanism 20 inhibits the orbiting scroll 14 from rotating, and the orbiting scroll 14 revolves around the center axis of the fixed scroll 12.

Referring to FIGS. 2 and 3 as well as FIG. 1, the configuration of the shell-integrated fixed scroll 28 is detailed below. FIGS. 2 and 3 show the shell-integrated fixed scroll 28.

The shell-integrated fixed scroll 28 includes a thick portion 84 corresponding to a part of the wall of the center housing 22, which is formed with large thickness from the proximal-end-side end surface 22a to the leading-end-side end surface 22b. Inside the wall of the thick portion 84, screw holes 22c for the bolts 30 that fasten the rear housing 24 to the proximal-end-side end surface 22a of the center housing 22 extend from the proximal-end-side end surface 22a toward the leading-end-side end surface 22b. Moreover, screw holes 22d for the bolts 40 that fasten the front housing 26 to the leading-end-side end surface 22b of the center housing 22 extend from the leading-end-side end surface 22b toward the proximal-end-side end surface 22a. In other words, in the thick portion 84, each screw hole 22c for the bolt 30 and each screw hole 22d for the bolt 40 are paired in the axial direction at substantially the same positions in the circumferential direction.

The thickness t of the wall of the center housing 22 except the thick portion 84 is reduced to the minimum value that allows a certain strength when the shell-integrated fixed scroll 28 is produced by, for example, forging, not molding, in order to achieve the lightweight shell-integrated fixed scroll 28 with requisite strength. Thus, the thickness t allows little space for forming the screw holes 22c and 22d of the bolts 40 and 30, respectively. For that reason, the center housing 22 has the thick portion 84 so as to form the screw holes 22c and 22d of the bolts 40 and 30, respectively.

Out of the thick portion 84, a portion between the proximal-end-side end surface 22a and the leading-end-side end surface 22b is partially cut away by a turning process, etc. in the circumferential direction of the center housing 22. The thus-formed notch divides the thick portion 84 into two: a first thick portion 84a where the screw holes 22c for the bolts 30 are formed and a second thick portion 84b where the screw holes 22d for the bolts 40 are formed. Opposing surfaces 86 are formed opposite each other in the substantially axial direction, between the first thick portion 84a and the second thick portion 84b. In the following description, out of the opposing surfaces 86, surfaces on the first thick portion 84a side and the second thick portion 84b side are referred to as a first opposing surface 86a and a second opposing surface 86b, respectively.

In FIG. 1, the screw hole 22d for the bolt 40 is visible at the opposing surface 86 formed by cutting away, whereas the screw hole 22c for the bolt 30 is invisible. As shown in FIG. 4, however, both the screw holes 22c and 22d may be visible. The following structure is also applicable. That is, the screw hole 22c for the bolt 30 is visible at the opposing surface 86 formed by cutting away, whereas the screw hole 22d for the bolt 40 is invisible. Alternatively, both the screw holes 22c and 22d may be invisible.

The preferable notch depth in the thick portion 84 in the direction toward the inside of the center housing 22 is up to the outer periphery of the center housing 22 without figuring in the thick portion 84. This is to reduce the risk of lowering the strength of the shell-integrated fixed scroll 28 in the case of reducing the initial wall thickness of the center housing 22.

In this embodiment, since the number of bolts 40 for fastening the front housing 26 is larger than that of bolts 30 for fastening the rear housing 24, an independent thick portion 88 is formed aside from the thick portion 84 so that it extends from the proximal-end-side end surface 22a toward the leading-end-side end surface 22b, in order to form the screw holes 22c for the bolts 30 in excess of the bolts 40, in the wall of the center housing 22. The independent thick portion 88 may be cut away in the circumferential direction of the center housing 22 by a turning process, etc. like the notch in the above thick portion 84 so as to form a step 88a in the axial direction.

Note that the proximal-end-side end surface 22a of the center housing 22 may have at least two concave portions 22e, which are far enough away from each other and able to fit with convex portions of a work table 92 upon the finish processing, etc. for the shell-integrated fixed scroll 28 as described below.

Referring to FIG. 5, a fixing method for the shell-integrated fixed scroll 28 upon the finish processing, etc. is described next. The finish processing, etc. of the shell-integrated fixed scroll 28 is carried out as below. That is, after the shell-integrated fixed scroll 28 has been roughly formed through molding or forging with two movable and fixed metal molds, the finish processing, etc. are executed through cutting and grinding so as to enhance the dimensional precision of the scroll wrap 12b, etc. Upon the finish processing, etc. of the shell-integrated fixed scroll 28, the shell-integrated fixed scroll 28 is stably fixed to ensure a certain level of processing precision.

According to the conventional finish processing, etc., the shell-integrated fixed scroll 28 is fixed by firmly holding the center housing 22 in the horizontal direction. However, since there is no supporting structure for maintaining the space between the center housing 22 and the scroll wrap 12b, the center housing 22 may possibly deform. On this account, there is a fear that the shell-integrated fixed scroll 28 cannot maintain appropriate dimensional precision, and the productivity of the scroll type compressor 10 is lowered. To deal with the above problem, in this embodiment, a locking member 90 is locked to the first opposing surface 86a to apply a load in the axial direction to the shell-integrated fixed scroll 28 through it. In this case, the first opposing surface 86a is used as a so-called operating point, whereby the shell-integrated fixed scroll 28 can be fixed in the axial direction.

More specifically, in the case of executing finish processing, etc. from the opening side of the center housing 22 out of the shell-integrated fixed scroll 28 (for example, on the scroll wrap 12b, etc.), the shell-integrated fixed scroll 28 is placed on the work table 92 with the proximal-end-side end surface 22a of the center housing 22 facing toward a mounting surface 92a of the work table 92. The shell-integrated fixed scroll 28 can be placed on the work table 92 by, for example, fitting convex portions (not shown) preformed on the work table 92 to the concave portions 22e formed at the proximal-end-side end surface 22a of the center housing 22 or other positioning methods so as not to displace the shell-integrated fixed scroll 28 on the work table 92 in the direction parallel with the mounting surface 92a.

The locking member 90 is a rigid member having, for example, an L shape or other such shape capable of locking one end 90a to the first opposing surface 86a. From the viewpoint of stable locking, the one end 90a of the locking member 90 may be shaped with a smaller contact area to increase the vertical gradient upon contact with the first opposing surface 86a and may be formed of a material having relatively high coefficient of friction, which is used for a portion that comes into contact with the first opposing surface 86a. As above, the one end 90a can be prepared in various known shapes or with various known materials insofar as the frictional force with the first opposing surface 86a can be increased. An adjustment bolt 94 is screwed to the other end 90b of the locking member 90. The adjustment bolt is inserted into a through hole 92c of the work table 92 from an opposing surface 92b to the mounting surface 92a. A head portion 94a of the adjustment bolt 94 has larger diameter than the through hole 92c of the work table 92. Besides the above structure, the locking member 90 can have any other structure insofar as a load toward the work table 92 can be applied to the first opposing surface 86a of the shell-integrated fixed scroll 28 placed on the work table 92.

The shell-integrated fixed scroll 28 is fixed with the locking member 90 to the work table 92 by locking the one end 90a to the first opposing surface 86a and adjusting the degree of tightening the adjustment bolt 94 screwed to the other end 90b. As a result, the head portion 94a of the adjustment bolt 94 presses the opposing surface 92b of the work table 92, while the one end 90a of the locking member 90 presses the first opposing surface 86a to apply a load to the shell-integrated fixed scroll 28 in the axial direction. Thus, the shell-integrated fixed scroll 28 is pressed against the work table 92 and thus fixed thereto. If the independent thick portion 88 has the step 88a in the axial direction as above, the locking member 90 may be locked to the step 88a to apply a load to the shell-integrated fixed scroll 28 in the axial direction.

In the case of executing finish processing, etc. on the proximal-end-side end surface 22a of the center housing 22 to which the rear housing 24 is fastened, the shell-integrated fixed scroll 28 is placed with the unfinished leading-end-side end surface 22b of the center housing 22 facing toward the mounting surface 92a of the work table 92, after which the shell-integrated fixed scroll 28 can be fixed in the same way as the case of performing finish processing, etc. from the opening side of the center housing 22 out of the shell-integrated fixed scroll 28. More specifically, the shell-integrated fixed scroll 28 can be also fixed to the work table 92 with the locking member 90 by locking the one end 90a of the locking member 90 to the second opposing surface 86b and adjusting the degree of tightening the adjustment bolt 94 screwed to the other end 90b.

According to the scroll type compressor 10 thus configured, in the shell-integrated fixed scroll 28, the thick portion 84 has the screw holes for the bolts 30 and 40, which are paired in the axial direction at substantially the same positions in the circumferential direction; the thick portion 84 extends from the proximal-end-side end surface 22a to the leading-end-side end surface 22b. Out of the thick portion 84, a portion between the proximal-end-side end surface 22a and the leading-end-side end surface 22b is partially cut away in the circumferential direction of the center housing 22 to form the opposing surfaces 86 facing each other in the axial direction.

Accordingly, the locking member 90 is locked to each opposing surface 86 and a load is applied to the shell-integrated fixed scroll 28 by means of the locking member 90 in the axial direction so as to fix the shell-integrated fixed scroll 28 in the axial direction. This improves the fixing structure for the shell-integrated fixed scroll 28 upon the finish processing, etc., whereby the shell-integrated fixed scroll 28 can maintain appropriate dimensional precision and enhance its productivity.

Moreover, it is conceivable to cut away the outer periphery of the center housing 22 in the circumferential direction to form a groove for locking the locking member 90. However, such groove is not preferable because, in the case of producing the shell-integrated fixed scroll 28 with a smaller wall thickness by forging, not molding, so as to reduce the weight, the strength of the shell-integrated fixed scroll 28 becomes lower than the one produced by molding. However, according to the scroll type compressor 10 of this embodiment, the thick portion 84 for forming the screw holes for the bolts 40 and 30 is cut away in the circumferential direction to thereby form the opposing surfaces 86 facing each other in the axial direction. Thus, the shell-integrated fixed scroll 28 can be fixed in the axial direction without the fear of lowering the strength of the shell-integrated fixed scroll 28 when cutting away the wall of the center housing 22.

Note that in the above embodiment, as shown in FIG. 6, the screw hole 22c of the first thick portion 84a and the screw hole 22b of the second thick portion 84d can overlap with each other in the axial direction. In addition, if the screw holes for the bolts 30 and 40 are the same in terms of the screwing direction, diameter, pitch, etc., a single type of bolts (bolts 40) can fasten the front housing 26, the center housing 22, and the rear housing 24 together, whereby the number of components can be reduced.

Moreover, the scroll type compressor 10 of the above embodiment is only an application of the present invention. Insofar as the shell-integrated fixed scroll 28 is provided, the present invention is applicable to any other scroll type compressors. Furthermore, the present invention is applicable to all scroll type fluid machines inclusive of a scroll type expander as well as the scroll type compressor as set forth above.

REFERENCE SYMBOL LIST

• 10 scroll type compressor
• 12 fixed scroll
• 12a end plate
• 12b scroll wrap
• 14 orbiting scroll
• 22 center housing
• 22a proximal-end-side end surface
• 22b leading-end-side end surface
• 22c screw hole (for first bolt)
• 22d screw hole (for second bolt)
• 24 rear housing
• 26 front housing
• 28 shell-integrated fixed scroll
• 30 (first) bolt
• 40 (second) bolt
• 84 thick portion
• 84a first thick portion
• 84b second thick portion
• 86 opposing surface
• 86a first opposing surface
• 86b second opposing surface
• 90 locking member
• 90a one end
• 90b other end
• t wall thickness of center housing

Claims

1. A scroll type fluid machine comprising an orbiting scroll and a fixed scroll, in which the fixed scroll comprises:

a volute scroll wrap that is erected on an end plate;

a cylindrical shell that is integrated with the end plate and has a proximal end entirely connected with an outer periphery of the end plate and a leading end extending in the direction in which the scroll wrap is erected; and

a thick portion formed by partially increasing the thickness of a wall of the shell from a proximal-end-side end surface of the shell to a leading-end-side end surface of the shell so that in the thick wall of the shell, a screw hole for a first bolt for fastening a first housing to the proximal-end-side end surface extends from the proximal-end-side end surface toward the leading-end-side end surface, and a screw hole for a second bolt for fastening a second housing to the leading-end-side end surface extends from the leading-end-side end surface toward the proximal-end-side end surface,

wherein the thick portion is partially cut away in a circumferential direction of the shell between the proximal-end-side end surface and the leading-end-side end surface to form opposing surfaces that face each other in the axial direction.

2. The scroll type fluid machine according to claim 1, wherein the opposing surfaces are respectively locked with a locking member, and function as an operating point at which a load is applied to the fixed scroll in the axial direction by way of the locking member.

3. The scroll type fluid machine according to claim 1 or 2, wherein the wall of the shell except the thick portion is formed with a thickness not enough to cut away in the circumferential direction so as to maintain strength of the shell.

4. The scroll type fluid machine according to claim 3, wherein the thickness of the wall of the shell except the thick portion is not enough to form a screw hole for the first bolt and a screw hole for the second bolt.

5. The scroll type fluid machine according to claim 1, wherein the screw hole for the first bolt and the screw hole for the second bolt overlap each other in the axial direction.

6. The scroll type fluid machine according to claim 2, wherein the wall of the shell except the thick portion is formed with a thickness not enough to cut away in the circumferential direction so as to maintain strength of the shell.

7. The scroll type fluid machine according to any one of claim 2, wherein the screw hole for the first bolt and the screw hole for the second bolt overlap each other in the axial direction.

8. The scroll type fluid machine according to any one of claim 3, wherein the screw hole for the first bolt and the screw hole for the second bolt overlap each other in the axial direction.

9. The scroll type fluid machine according to any one of claim 4, wherein the screw hole for the first bolt and the screw hole for the second bolt overlap each other in the axial direction.