Scroll Fluid Machine

Abstract

Disclosed is a scroll fluid machine configured from inexpensive materials and provided with a rotation prevention mechanism with excellent durability. In the scroll fluid machine, a fixed scroll, the spiral body of which has been vertically disposed on one end surface of an endplate, and a movable scroll, the spiral body of which has been vertically disposed on one end surface of the endplate, are arranged eccentrically to and out of phase with each other such that the spiral bodies engage with each other and the movable scroll turns relative to the fixed scroll. The scroll fluid machine is characterized by being provided with a rotation prevention mechanism comprising a movable-side pin that protrudes from the other surface of the endplate of the movable scroll, a fixed-side pin that protrudes from the housing side towards the other surface of the endplate of the movable scroll, and a rotation prevention member held from both sides by the movable-side pin and the fixed-side pin.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a scroll-type fluid machine, and specifically relates to a rotation-preventing mechanism of a movable scroll which is provided to constitute a compression mechanism of a scroll-type fluid machine.

BACKGROUND ART OF THE INVENTION

A compression mechanism and an expansion mechanism of scroll-type compressors or expanders generally consist of a combination of fixed scroll and movable scroll. The movable scroll is provided so as to freely revolve but not to rotate, relative to the fixed scroll. Some kinds of mechanisms are known as a rotation-preventing mechanism which makes it impossible to rotate a movable scroll.

For example, Patent document 1 discloses a scroll-type fluid machine where a swing pin, which is provided on a swing scroll as protruding, and a housing pin, which is provided on a fixed scroll as protruding, are contacted slidably with inner peripheral surfaces of 2 holes which are formed in a protrusion binding member for regulating a relative distance between both pins, in order to prevent the swing scroll from rotating.

In addition, Patent document 2 discloses a scroll-type compressor where a movable pin member, which is provided on a movable scroll as protruding, and a fixed pin member, which is provided on a fixed scroll as protruding, are engaged to be contacted in pairs, in order to prevent the movable scroll from rotating.

Prior Art Documents

Patent Documents

Patent Document 1: JP-4088392-B

Patent Document 2: JP-3337831-B

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In the rotation-preventing mechanism of the scroll-type fluid machine disclosed by Patent document 1, the protrusion binding member rotates as sweeping a larger area because the swing radius is held at the side of the swing pin of the protrusion binding member, and therefore a thrust bearing cannot be easily extended. In addition, because the protrusion binding member is subject to tensile stress, materials, such as various resins, light metals and sintered materials, which are fragile with low tension strength cannot be utilized, and therefore the cost has not been able to reduce. Further, a complicated work for fitting the pin into the hole is required when the swing scroll and the fixed scroll are assembled. Therefore it has been difficult to improve the productivity, as well as to form a flow path for lubricating oil between the pin and the protrusion binding member.

Furthermore, in the rotation-preventing mechanism of the scroll-type compressor disclosed by Patent document 2, because surface pressure increases because of contact between the movable pin member and the fixed pin member, oil film tends to be made imperfect so as to cause abrasion of members.

Accordingly, an object of the present invention is to provide a scroll-type fluid machine which is made by inexpensive members and which is provided with a rotation-preventing mechanism having excellent durability.

Means for Solving the Problems

To achieve the above-described object, a scroll-type fluid machine according to the present invention is a scroll-type fluid machine, wherein a fixed scroll, which is provided with a scroll body standing on an end surface of an end plate, and a movable scroll, which is provided with a scroll body standing on an end surface of an end plate, are provided eccentrically out of phase by engaging scroll bodies with each other so that the movable scroll is rotated relative to the fixed scroll, characterized in that a rotation-preventing mechanism, which comprises a movable-side pin protruding from another end surface of the end plate of the movable scroll, a fixed-side pin protruding from a housing-side toward another side of the end surface of the end plate of the fixed scroll, and a rotation-preventing member which is supported between both sides of the movable-side pin and the fixed-side pin, is provided.

Because a fixed-side pin and a movable-side pin support a rotation-preventing member from both sides in a scroll-type fluid machine, the rotation-preventing member is not subject to tensile stress but is only subject to compressive stress basically, so that the rotation-preventing member can be manufactured at a low cost by sintering, etc. In addition, the rotation-preventing member can be formed as extremely small, so as to suppress centrifugal force and reduce noise generated by device vibration.

In the scroll-type fluid machine according to the present invention, it is preferable that the rotation-preventing member has a movable-side depressed part which engages the movable-side pin, and has a fixed-side depressed part which engages the fixed-side pin. Because the rotation-preventing member is not subject to tensile stress, it becomes unnecessary that the movable-side pin and the fixed-side pin are holes. Therefore, the rotation-preventing member can be downsized and lightweight, by forming the rotation-preventing member having a depressed part at least.

In the scroll-type fluid machine according to the present invention, it is possible that at least one of the movable-side depressed part and the fixed-side depressed part is formed as a part of a hole in the rotation-preventing member. When at least one of the depressed parts is formed as a part of the hole, simplified can be a working to fit the rotation-preventing member with the movable-side depressed part or the fixed-side depressed part.

In the scroll-type fluid machine according to the present invention, it is preferable that either or both depths of the movable-side depressed part and the fixed-side depressed part are set as making minimum value (Lor) of a center distance (L) between the movable-side pin and the fixed-side pin smaller than a swing radius (AOR) of the movable scroll. When the depths of the depressed parts are set as satisfying the formula (Lor<AOR), operations such as engaging and sliding of the pins can be smoothly performed even if the accuracy of component parts is somewhat bad and sizes have some errors. Therefore, the rotation-preventing mechanism is ensured in durability as preventing excessive load generation, even when troubles, such as liquid compression and foreign substance bite, are caused. Further, it is preferable that a difference between the minimum value (Lor) of the center distance (L) between the movable-side pin and the fixed-side pin, and the swing radius (AOR) of the movable scroll is within 0.1 mm. Namely, when the rotation-preventing mechanism is designed to satisfy the magnitude relation (Lor<AOR≦Lor+0.1 mm), the scroll can be smoothly operated without being affected by dimensional precision of component parts. Therefore a low-noise scroll-type fluid machine, which is excellent in durability even in an abnormal condition, can be achieved.

In the scroll-type fluid machine according to the present invention, it is preferable that a difference between the minimum value (Lor) of the center distance (L) between the movable-side pin and the fixed-side pin, and the swing radius (AOR) of the movable scroll is set smaller than a difference between a depth (B1) of the movable-side depressed part and an axial radius (R1) of the movable-side pin. Namely, when the rotation-preventing member is designed to satisfy the magnitude relation (AOR−Lor≦B1−R1), the rotation-preventing member can be surely supported between the movable-side pin and the fixed-side pin thereby. In addition, because the depth of the movable-side depressed part becomes sufficiently greater than the axial radius of the movable-side pin, the contact area between the movable-side pin and the movable-side depressed part can be set wider, so as to suppress surface pressure as preventing oil film from being made imperfect.

In addition, the fixed side is similar to the movable side. Namely in the scroll-type fluid machine according to the present invention, it is preferable that a difference between the minimum value (Lor) of the center distance (L) between the movable-side pin and the fixed-side pin, and the swing radius (AOR) of the movable scroll is set smaller than a difference between a depth (B2) of the fixed-side depressed part and an axial radius (R2) of the fixed-side pin. Namely, when the rotation-preventing member is designed to satisfy the magnitude relation (AOR−Lor≦B2−R2), the rotation-preventing member can be surely supported between the movable-side pin and the fixed-side pin. In addition, because the depth of the fixed-side depressed part becomes sufficiently greater than the axial radius of the fixed-side pin, the contact area between the fixed-side pin and the fixed-side depressed part can be set wider, so as to suppress surface pressure as preventing oil film from being made imperfect.

In the scroll-type fluid machine of the present invention, it is preferable that movable-side pins and fixed-side pins are plurally placed along circumferences of placement-pitch circles having placement-pitch angles (Ap), which are equal to each other, and diameters, which are equal to each other. When a pair of rotation-preventing elements composed of the movable-side pin, the fixed-side pin and the rotation-preventing member is provided on circumferences along circumferences of the scrolls, the movable scroll can be effectively and smoothly prevented from rotating. Particularly, the movable scroll can be further effectively prevented from rotating when the fixed-side pin and the movable-side pin are placed out of phase with each other by a predetermined angle (θ) satisfying Formula 1 toward a direction to eliminate a distortion of the movable scroll relative to the fixed scroll. Actually in scroll-type fluid machine, there is a tolerance to each set of the fixed-side pin, the movable-side pin and the rotation-preventing member, so θ is determined so as not to interfere, as considering the tolerance.

θ≦2·tan⁻¹[(AOR−Lor)/Dp]  [Formula 1]

In the scroll-type fluid machine according to the present invention, it is preferable that the fixed scroll and the movable scroll are assembled so that an initial value of a center distance (L) between the fixed-side pin and the movable-side pin is set to a minimum value (Lor) for one rotation-preventing member while the initial value of the center distance (L) between the fixed-side pin and the movable-side pin is set to a swing radius (AOR) of the movable scroll for another rotation-preventing member. The supported condition of the rotation-preventing member supported between the movable-side pin and the fixed-side pin thereby progresses as being passed on to adjacent rotation-preventing element with swing of the movable scroll, so as to repeat a cycle. As described above, the fixed scroll and the movable scroll are assembled in such a condition that the initial value of the center distance (L) between the fixed-side pin and the movable-side pin is set to the minimum value (Lor) for one rotation-preventing member while the initial value of the center distance (L) between the fixed-side pin and the movable-side pin is set equal to the swing radius (AOR) of the movable scroll for another rotation-preventing member. The movable scroll starts to rotate from such an initial condition, so that the rotation-preventing member is smoothly transited between supported conditions. And, as a result, the movable scroll can be smoothly rotated.

In the scroll-type fluid machine according to the present invention, it is preferable that a thickness of the rotation-preventing member in an axial direction is set to a maximum value under a condition where an axial interval between the movable scroll and a housing is kept equal to or greater than an oil film thickness as not interfering within a dimensional tolerance. Thus the scroll-type fluid machine according to the present invention makes it possible that the rotation-preventing member is easily enhanced in durability because the axial thickness of the rotation-preventing member can be maximized, as far as the movable scroll swings without any problem.

EFFECT ACCORDING TO THE INVENTION

Thus a scroll-type fluid machine according to the present invention makes it possible that a rotation-preventing member is manufactured by sintering, etc. as reducing a cost because the rotation-preventing member has a configuration which is subject only to compressive stress. Further, the rotation-preventing member can be designed to be extremely small, so as to achieve a scroll-type fluid machine which generates little centrifugal force and which has been improved in vibration noise. Furthermore, a counterweight can be easily ensured in weight because the rotation-preventing member is downsized so as to extend an area in which the rotation-preventing member does not interfere.

In the scroll-type fluid machine according to the present invention, the contact area of the rotation-preventing member to the movable-side pin or the fixed-side pin can be easily broaden, so that a durable rotation-preventing mechanism which is suppressed from imperfect oil film with low surface pressure can be easily achieved. Further, when the movable-side depressed part of the rotation-preventing member to engage with the movable-side pin is formed as opening outward, the work to assemble the movable scroll to the fixed scroll can be simplified.

In the scroll-type fluid machine according to the present invention, because the minimum swing radius is determined only by a structure of the rotation-preventing mechanism, a protrusion of the eccentric bush can be abolished. Furthermore, when the dimension of the rotation-preventing member is designed within a predetermined range, achieved can be a scroll-type fluid machine which can operate smoothly without being affected by dimensional accuracy of component parts and which is ensured to be durable without generating excessive load even when troubles, such as liquid compression and foreign substance bite, are caused.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a longitudinal section view showing a compressor according to an embodiment of the present invention.

FIG. 2 is a cross section view showing a rotation-preventing mechanism of the compressor in FIG. 1.

FIG. 3 is an explanation diagram for explaining discordant placement angle of the movable scroll, which is caused by rotation power applied to the movable scroll in FIG. 1.

FIG. 4 is a plan view showing a rotation-preventing member for preventing a movable scroll in FIG. 1 from rotating, where (A) is an example in which both depressed parts are not a part of a hole, and (B) is an example in which one of depressed parts is a part of a hole.

FIG. 5 is a cross section view showing a rotation-preventing mechanism of a scroll-type compressor according to another embodiment of the present invention.

FIG. 6 is a cross section view showing a rotation-preventing mechanism of a scroll-type compressor according to yet another embodiment of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, desirable embodiments of the present invention will be explained as referring to figures.

FIG. 1 shows a whole of a scroll-type compressor 1 according to an embodiment of the present invention. In FIG. 1, compression mechanism 2 comprises fixed scroll 3 consisting of a scroll body and movable scroll 4 consisting of a scroll body and end plate 5. Movable scroll 4 is swung relative to fixed scroll 3 as being prevented from rotating by rotation-preventing elements 36 comprised of rotation-preventing members 31, fixed-side pins 34 and movable-side pins 35. Main shaft 8 (rotational axis) is driven to rotate while compressor 1 operates, and a rotational motion of main shaft 8 is converted into a swing motion of movable scroll 4, through eccentric pin 9 provided at one side of main shaft 8 and through eccentric bush 10 rotatably engaged therewith. The refrigerant sucked as fluid to be compressed is led to compression mechanism 2 so as to be compressed, and is delivered outside compressor 1 from casing 6 through discharge hole 13 and discharge chamber 14.

FIG. 2 is a cross section view showing a rotation-preventing mechanism of compressor 1 in FIG. 1. Inside compressor housing 6, fixed scroll 3 and movable scroll 4 are assembled to be engaged by scroll bodies with each other as forming compression mechanism 2. Movable scroll 4 swings by a predetermined swing radius (AOR), around the center axis of fixed scroll 3 which is always standing still. Accompanying such a swing motion of movable scroll 4, fluid, such as refrigerant, to be compressed is compressed.

Movable scroll 4 is prevented from rotating by movable-side pins 35 (35a-35d) protruding on the surface which is opposite to fixed scroll 3 of end plate 5 of movable scroll 4, fixed-side pins 34 (34a-34d) protruding toward movable-side pins 35 (35a-35d) in housing 6, and rotation-preventing members 31 (31a-31d). Rotation-preventing members 31 (31a-31d) of which planar shapes are formed in a schematic H-shape are provided with fixed-side depressed parts 32 (32a-32d) engaging fixed-side pins 34 (34a-34d) and with movable-side depressed parts 33 (33a-33d) engaging movable-side pins 35 (35a-35d), and are supported between movable-side pins 35 (35a-35d) and fixed-side pins 34 (34a-34d) thereby.

In this embodiment, fixed-side pins 34 and movable-side pins 35 are placed on end plate 5 of movable scroll 4 along placement-pitch circles, which have placement-pitch angles of 90 degrees each and diameters (Dp) which are equal to each other. Thus placed fixed-side pins 34 and movable-side pins 35 constitute rotation-preventing elements 36 (36a-36d) together with rotation-preventing members 31 supported between them. Such combinations of rotation-preventing elements 36 constitute rotation-preventing mechanism of movable scroll 4.

In this embodiment, the distance between fixed-side pin 34 and movable-side pin 35 in one rotation-preventing element 36 is not completely constant but is provided with some looseness. For example, some gaps are formed between movable-side pins 35b-35d and rotation-preventing members 31b-31d, as shown in FIG. 2. Specifically the distance between fixed-side pin 34c and movable-side pin 35c is comparatively great. In contrast, as to fixed-side pin 34a or movable-side pin 35a, there is no gap between it and rotation-preventing member 31a. Thus, the depth (B) of rotation-preventing member 31 is determined appropriately, so as to determine the minimum value (Lor) of the center distance (L) between fixed-side pin 34 and movable-side pin 35. Such a center distance (L) between fixed-side pin 34 and movable-side pin 35 is preferably set as being provided with some looseness as described above. Specifically, the depth (B) of rotation-preventing member 31 is preferably designed as making the minimum value (Lor) of the center distance (L) smaller than the swing radius (AOR) of movable scroll 4. However, movable scroll 4 cannot swing smoothly if the difference between Lor and AOR is too big. Therefore the difference is preferably within 0.1 mm.

Further, as shown in FIG. 2, it is preferable that fixed scroll 3 and movable scroll 4 are assembled in such an initial condition that the value of the center distance (L) is set to the minimum value (Lor) for rotation-preventing element 36a and is set equal to the swing radius (AOR) of movable scroll 4 for rotation-preventing element 36c located the furthest from rotation-preventing member 36a. If the looseness of the center distance (L) is scattered over rotation-preventing elements 36a-36d in an initial condition, the looseness of the center distance (L) assumed by the depth (B) of rotation-preventing member 31 may not work during swing motion of movability scroll 4 sufficiently. Accordingly, it is preferable to assemble them as making angle α which satisfies Formula 2, between a line segment (length=Dp) extending from movable-side pin 35a to movable-side pin 35c and another line segment (length=Dp) extending from fixed-side pin 34a to fixed-side pin 34c. Movable-side pins 35a-35d and fixed-side pins 34a-34d are placed as satisfying such a relational formula, so that the cycle of supporting conditions of rotation-preventing members 31a-31d is smoothly progressed. Besides, because rotation-preventing member 31 of this embodiment can be easily made extremely compact, counterweight 37, even if it is comparatively large, is unlikely to interfere rotation-preventing member 31.

tan α=(AOR−Lor)/Dp  [Formula 2]

In Formula 2, angle α is a small angle such as being less than 0.2 degrees. When compressor 1 is operating, movable scroll 4 is subject to a rotation power. Utilizing this rotation power, fixed-side pin 34 and movable-side pin 35 support rotation-preventing member 32 therebetween at one or more places each on the circumference of each placement-pitch circle so as to prevent movable scroll 4 from rotating. Under such a rotation power, fixed-side pin 34 and movable-side pin 35 are placed out of phase with each other by a predetermined angle (θ) toward a direction to eliminate a distortion of movable scroll 4 relative to fixed scroll 3. Such a condition will be explained by referring to FIG. 3.

FIG. 3 is an explanation diagram for explaining discordant placement angle of the movable scroll, which is caused by rotation power applied to the movable scroll in FIG. 1. When the scroll wall of movable scroll 4 swings as contacting the scroll wall of fixed scroll 3 while movable scroll 4 is prevented from rotating, movable scroll 4 is reciprocated with the amplitude equal to the swing radius (AOR) in axis-Y direction. In this case, the distance from the center O of placement-pitch circle 38 of movable-side pin 35 to the center of another placement-pitch circle of fixed-side pin 34 is not less than the minimum value (Lor) of the center distance (L) between fixed-side pin 34 and movable-side pin 35 because of the presence of rotation-preventing members 31a-31d. The placement-pitch circle of fixed-side pin 34 has approximately the same diameter (Dp) of the placement-pitch circle 38 of movable-side pin 35. The condition to be satisfied by the predetermined angle (θ) by which movable scroll 4 rotates under the rotation power applied to movable scroll 4 is as shown in Formula 1. Here the predetermined angle (θ) links to angle α in Formula 2 by the relation between a central angle and an inscribed angle, and therefore the relation θ=2α is satisfied obvious from FIG. 3.

θ≦·tan⁻¹[(AOR−Lor)/Dp]  [Formula 1]

FIG. 4 is a plan view showing rotation-preventing member 31 for preventing movable scroll 4 in FIG. 1 from rotating, where (A) is an example in which both fixed-side depressed part 32 and movable-side depressed part 33 are not a part of a hole, and (B) is an example in which only movable-side depressed part 33 is a part of a hole. As shown in FIG. 4 (A), because rotation-preventing member 31 is not subject to tensile stress in this embodiment, rotation-preventing member 31 can be supported between fixed-side pin 34 and movable-side pin 35 even if both ends of depressed parts of fixed-side depressed part 32 and movable-side depressed part 33 are open. Specifically the depth (B) of the depressed part is set greater than the axial radius (R) of fixed-side pin 34 or movable-side pin 35, so that rotation-preventing member 31 is further surely supported between fixed-side pin 34 and movable-side pin 35 thereby. Further, when the difference between the minimum value (Lor) of the center distance (L) and the swing radius (AOR) of movable scroll 4 is set smaller than the difference between the depth (B1) of movable-side depressed part 33 and the axial radius (R1) of movable-side pin 35, movable-side pin 35 can be more surely engaged with movable-side depressed part 33 of rotation-preventing member 31 while movable scroll 4 swings. The fixed side is similar to the movable side. When the difference between the minimum value (Lor) of the center distance (L) and the swing radius (AOR) of movable scroll 4 is set smaller than the difference between the depth (B2) of fixed-side depressed part 32 and the axial radius (R2) of fixed-side pin 34, fixed-side pin 34 can be more surely engaged with fixed-side depressed part 32 of rotation-preventing member 31 while movable scroll 4 swings.

Further, rotation-preventing member 41 can be provided with a hole by closing both depressed parts of fixed-side depressed part 32 as shown in FIG. 4 (B). Thus, if either fixed-side depressed part 34 or movable-side depressed part 33 becomes a part of a hole, fixed-side pin 34 can be put through the hole when movable scroll 4 is assembled together with fixed scroll 3, so that the assembling work is simplified.

FIG. 5 is a cross section view showing a rotation-preventing mechanism of a scroll-type compressor according to another embodiment of the present invention, where rotation-preventing members 31 (31a-31d) in FIG. 2 have been replaced by rotation members 41 (41a-41d) in FIG. 4 (B). The other aspects are the same as FIG. 2, so the explanation of the embodiment is omitted as giving the same symbols. When fixed-side depressed part 32 is a part of the hole, a scroll-type compressor can be improved in assembly easiness.

FIG. 6 is a cross section view showing a rotation-preventing mechanism of a scroll-type compressor according to yet another embodiment of the present invention. Rotation-preventing members 51 (51a-51d) in this embodiment are formed in a modified shape of rotation-preventing member 41 shown in FIG. 4(B), where fixed-side depressed part 32 is replaced by the movable-side depressed part. Namely, just like being opposite to rotation-preventing member 41 in FIG. 4(B), both ends of a depressed part of fixed-side depressed part 32 are opened while both ends of a depressed part of movable-side depressed part 33 are closed. Thus, even if movable-side depressed part 33 is a part of a hole, the assembly easiness of a scroll-type compressor can be improved similarly to a case where fixed-side depressed part 32 is a part of a hole.

INDUSTRIAL APPLICATIONS OF THE INVENTION

A scroll-type compressor according to the present invention is applicable to all types of scroll-type compressor having a rotation-preventing mechanism with a rotation-preventing member.

EXPLANATION OF SYMBOLS

• 1: compressor
• 2: compression mechanism
• 3: fixed scroll
• 4: movable scroll
• 5: end plate
• 6: casing
• 7: housing
• 8: main shaft
• 9: eccentric pin
• 10: eccentric bush
• 13: discharge hole
• 14: discharge chamber
• 31, 41, 51, 31a, 31b, 31c, 31d: rotation-preventing member
• 32: fixed-side depressed part
• 33: movable-side depressed part
• 34, 34a, 34b, 34c, a 34d: fixed-side pin
• 35, 35a, 35b, 35c, 35d: movable-side pin
• 36, 36a, 36b, 36c, 36d: rotation-preventing element
• 37: counterweight
• 38: placement-pitch circle

Claims

1. A scroll-type fluid machine, wherein a fixed scroll, which is provided with a scroll body standing on an end surface of an end plate, and a movable scroll, which is provided with a scroll body standing on an end surface of an end plate, are provided eccentrically out of phase by engaging scroll bodies with each other so that said movable scroll is rotated relative to said fixed scroll, wherein the machine comprises a rotation-preventing mechanism comprising a movable-side pin protruding from another end surface of said end plate of said movable scroll, a fixed-side pin protruding from a housing-side toward another side of said end surface of said end plate of said fixed scroll, and a rotation-preventing member which is supported between both sides of said movable-side pin and said fixed-side pin.

2. The scroll-type fluid machine according to claim 1, wherein said rotation-preventing member has a movable-side depressed part which engages said movable-side pin and a fixed-side depressed part which engages said fixed-side pin.

3. The scroll-type fluid machine according to claim 2, wherein at least one of said movable-side depressed part and said fixed-side depressed part is formed as a part of a hole in said rotation-preventing member.

4. The scroll-type fluid machine according to claim 2, wherein either or both depths of said movable-side depressed part and said fixed-side depressed part

5. The scroll-type fluid machine according to claim 4, wherein a difference between said minimum value (Lor) of said center distance (L) between said movable-side pin and said fixed-side pin, and said swing radius (AOR) of said movable scroll is within 0.1 mm.

6. The scroll-type fluid machine according to claim 4, wherein a difference between said minimum value (Lor) of said center distance (L) between said movable-side pin and said fixed-side pin, and said swing radius (AOR) of said movable scroll is set smaller than a difference between a depth (B1) of said movable-side depressed part and an axial radius (R1) of said movable-side pin.

7. The scroll-type fluid machine according to claim 4, wherein a difference between said minimum value (Lor) of said center distance (L) between said movable-side pin and said fixed-side pin, and said swing radius (AOR) of said movable scroll is set smaller than a difference between a depth (B2) of said fixed-side depressed part and an axial radius (R2) of said fixed-side pin.

8. The scroll-type fluid machine according to claim 1, wherein movable-side pins and fixed-side pins are plurally placed along circumferences of placement-pitch circles having placement-pitch angles (Ap), which are equal to each other, and diameters, which are equal to each other.

9. The scroll-type fluid machine according to claim 8, wherein said fixed-side pin and said movable-side pin are placed out of phase with each other by a predetermined angle (θ) satisfying Formula 1 toward a direction to eliminate a distortion of said movable scroll relative to said fixed scroll.

θ≦2·tan−1[(AOR−Lor)/Dp]  [Formula 1]

10. The scroll-type fluid machine according to claim 1, wherein said fixed scroll and said movable scroll are assembled so that an initial value of a center distance (L) between said fixed-side pin and said movable-side pin is set to a minimum value (Lor) for one rotation-preventing member while said initial value of said center distance (L) between said fixed-side pin and said movable-side pin is set to a swing radius (AOR) of said movable scroll for another rotation-preventing member.

11. The scroll-type fluid machine according to claim 1, wherein a thickness of said rotation-preventing member in an axial direction is set to a maximum value under a condition where an axial interval between said movable scroll and a housing is kept equal to or greater than an oil film thickness as not interfering within a dimensional tolerance.