EP2980409A1

EP2980409A1 - Scroll-type fluid machine

Info

Publication number: EP2980409A1
Application number: EP14774465.0A
Authority: EP
Inventors: Tamotsu Fujioka; Junichi Asami
Original assignee: Anest Iwata Corp
Current assignee: Anest Iwata Corp
Priority date: 2013-03-29
Filing date: 2014-03-27
Publication date: 2016-02-03
Also published as: JP2014196688A; JP6195722B2; EP2980409A4; CN105102818B; WO2014157452A1; CN105102818A

Abstract

The invention improves a cooling effect particularly on the center of a sealed chamber, in which temperature becomes high, reduces power consumption of a cooling fan that creates cooling air, and prevents an increase in size of a casing. A scroll compressor 10 includes a centrifugal fan 50 attached to a drive shaft 18. Inside the scroll compressor 10, there are first and second cooling-air passages. The first cooling-air passage extends from the opening of an inlet duct 16 along a rear face 33 of a fixed scroll 32, further extends between inlet ducts 22a to 22e in the outer peripheral end of the fixed scroll 32 and between ducts 56 and 58 to reach an outlet duct 20. The second cooling-air passage extends from the openings of the inlet ducts 22a to 22e and passes inside the duct 56 to reach the outlet duct 20.

Description

TECHNICAL FIELD

The present invention relates to scroll fluid machines applied, for example, to compressors, vacuum pumps, expansion machines, etc., and particularly including a cooling mechanism capable of effectively cooling compression heat generated during a compression process.

BACKGROUND ART

Scroll compressors become hot during the compression process, with a temperature as high as 200 degrees centigrade, and therefore need a cooling mechanism. The scroll compressors have high temperature particularly in the center of a compression chamber formed between a fixed scroll and an orbiting scroll.
In a conventional cooling mechanism, for example, a plurality of cooling fins are formed in the fixed and orbiting scrolls to be parallel to one another, and a sirocco fan is attached to a drive shaft for driving the orbiting scroll. The sirocco fan circulates cooling air between the cooling fins and thus achieves air cooling.
On the other hand, cooling temperature differs from the upstream to the downstream of the cooling air passing between the cooling fins, and this makes it difficult to effectively cool a high-temperature area (which is one of characteristics of scroll compressors) in the center of the compression chamber. Balance between the volume of air directed to the fixed scroll and the volume of air directed to the orbiting scroll is controlled by air-deflector plates or the like disposed in cooling-air passages. According to this method, however, it is not easy to effectively cool the orbiting scroll in orbital motion, resulting in the increase of the power consumption required for the cooling.
The cooling mechanism of the scroll air compressor disclosed in Patent Document 1 has a cooling-air inlet in the center of the rear face of the fixed scroll. Also, a long cooling passage is continuously formed between the casing and the rear face of the fixed scroll, in the rear face of the orbiting scroll, and between the casing and the electric motor. Air is taken in from the inlet by a single cooling fan attached to the drive shaft, and cooling air is made to flow through the cooling passage. As the result, the fixed and orbiting scrolls, the electric motor, and the like are forcefully cooled in sequence.
In the cooling mechanism of the scroll air compressor disclosed in Patent Document 2, a fixed-side cooling-air passage formed along the rear face of the fixed scroll and an orbiting-side cooling-air passage formed along the rear face of the orbiting scroll are separately formed. Rotation of the centrifugal fan attached to the drive shaft causes cooling air to flow through these two cooling-air passages. Cooling air flows passing through the cooling-air passages form parallel flows running in the same direction after entering from two adjacent inflow openings. The cooling air flows then join together at the outlets formed in the rear faces of the scrolls to be guided by the centrifugal fan.

CITATION LIST

PATENT DOCUMENTS

Patent Document 1: Japanese Unexamined Patent Application Publication (Kokai) No. H09-53589
Patent Document 2: Japanese Unexamined Patent Application Publication (Kokai) No. 2010-203289

SUMMARY OF INVENTION

TECHNICAL PROBLEM

In the cooling mechanism disclosed in the Patent Document 1, because of the single long cooling passage which is continuously formed through the scroll air compressor, the pressure loss of the cooling air which flows through the cooling passage is increased. The cooling mechanism therefore requires a cooling fan with large power, and this causes the problem that power consumption is increased. There is also another problem. The temperature of the cooling air rises in the downstream of the cooling passage, which decreases a cooling effect. It is then impossible to improve the cooling effect particularly on the center of the compression chamber in which temperature becomes high. In addition, according to the Patent Document 1 using an axial fan as a cooling fan, static pressure does not rise, so that air volume cannot be increased.
The cooling mechanism disclosed in the Patent Document 2 creates cooling air flowing in one direction from the inlet to the outlet. A cooling mechanism of this type is not capable of improving a cooling effect particularly on the center of the compression chamber in which temperature becomes high. The mechanism also requires a large-size duct for guiding the cooling air flows to the centrifugal fan, which join together at the outlets of the passages formed in the rear faces of the scrolls, so that the casing is increased in size.
In light of the foregoing problems, an object of the present invention is at least one of improving a cooling effect particularly on the center of a sealed chamber in which temperature becomes high, reducing power consumption of a cooling fan for creating cooling air, and suppressing an increase in size of a casing, in a scroll fluid machine.

SOLUTION TO PROBLEM

The invention is applied to a scroll fluid machine including a casing formed into a cylindrical shape and having open axial ends; a fixed scroll attached to the casing; an orbiting scroll situated to face the fixed scroll; a drive shaft to which the orbiting scroll is connected through an eccentric shaft that is eccentric to a rotation axis of the drive shaft, the drive shaft that rotates to bring the orbiting scroll into orbital motion; and a rotation-preventing mechanism configured to prevent rotation of the orbiting scroll. A plurality of sealed chambers are formed between the fixed scroll and the orbiting scroll. For example, if the scroll fluid machine to be applied is a scroll compressor, a scroll vacuum pump or the like, a plurality of compression chambers as the plurality of sealed chambers are formed between the fixed scroll and the orbiting scroll. A working medium is compressed in the plurality of compression chambers. If the scroll fluid machine to be applied is a scroll expander, a plurality of expansion chambers as the plurality of sealed chambers are formed between the fixed scroll and the orbiting scroll. A working medium is expanded in the plurality of expansion chambers.
To achieve the above object, the scroll fluid machine of the invention includes a cooling fan that is attached to the drive shaft and creates cooling air inside the casing by rotation of the drive shaft, and an outlet opening that is formed in a partition wall of the casing, which faces an outer peripheral end of the cooling fan. The scroll fluid machine further includes first and second cooling-air passages configured as described below. The scroll fluid machine is configured so that the cooling fan causes cooling air to flow through the first and second cooling-air passages.
According to the invention, the cylindrical casing may have an arbitrary shape provided with openings at both ends and may have another shape, such as a square shape, other than the cylindrical shape.
The first cooling-air passage has a first inlet opening formed in a partition wall of the casing, which faces the center of a rear face of the fixed scroll, extends along the rear face of the fixed scroll, curves near an outer peripheral end of the fixed scroll, extends along a rear face of the orbiting scroll, further extends from the center of the rear face of the orbiting scroll along the drive shaft, and reaches the outlet opening. The second cooling-air passage has a plurality of second inlet openings formed in a partition wall of the casing, which faces an outer peripheral end of the orbiting scroll, the plurality of second inlet openings being arranged dispersedly in a circumferential direction of the orbiting scroll, extends along the rear face of the orbiting scroll, extends from the center of the rear face of the orbiting scroll along the drive shaft, and reaches the outlet opening.
Since the first inlet opening of the first cooling-air passage faces the center of the rear face of the fixed scroll, the center of the sealed chamber is cooled first by low-temperature air which has freshly been introduced from the first inlet opening. Even in the downstream thereof, it is possible to increase a cooling effect on the center of the sealed chamber and the drive shaft to which heat is easily transmitted from the center of the sealed chamber since the first and second cooling-air passages are formed along the rear faces of the fixed and orbiting scrolls and the periphery of the drive shaft.
In contrast, the cooling-air passage of the Patent Document 1 is formed outside a bearing portion supporting a drive shaft and an electric motor, so that a cooling effect on the drive shaft to which heat is easily transmitted from the center of the sealed chamber is smaller than that in the configuration of the present invention. Moreover, the second cooling-air passage of the Patent Document 2 is formed outside the tubular portion of a bearing, which surrounds the drive shaft, so that a cooling effect on the drive shaft is smaller than that in the configuration of the present invention.
Since the first and second cooling-air passages are formed separately, the invention decreases pressure loss of the cooling air and then reduces power consumption of the cooling fan. Also, the second inlet openings are arranged dispersedly in the circumferential direction of the orbiting scroll, so that the casing is not increased in size.
According to one aspect of the invention, the first cooling-air passage may be situated in the outer peripheral end of the orbiting scroll to be located between the plurality of second inlet openings arranged dispersedly in the circumferential direction. This makes it possible to arrange the first cooling-air passage dispersedly in the circumferential direction in the outer peripheral ends of the fixed and orbiting scrolls. This eliminates the need to place the large-size duct for the first cooling-air passage in a circumferential portion of the casing, which suppresses the increase in size of the casing.
According to another aspect of the invention, a first cooling fin group may be provided, which includes a plurality of cooling fins formed in the rear face of the fixed scroll to radially extend from the center of the rear face of the fixed scroll. This makes it possible to improve the cooling effect on the fixed scroll by the cooling air introduced from the first inlet opening, and decrease the pressure loss of the cooling air flowing from the center of the rear face of the fixed scroll toward the outer peripheral end of the fixed scroll, thereby reducing the power consumption of the scroll fluid machine.
According to still another aspect of the invention, a second cooling fin group may be provided, which includes a plurality of cooling fins formed in the rear face of the orbiting scroll to radially extend from the center of the rear face of the orbiting scroll. The second cooling-air passage may be formed between the rear face of the orbiting scroll and the first cooling-air passage. The first and second cooling-air passages may be situated concentrically on the rear face side of the orbiting scroll and around the drive shaft with the drive shaft positioned at the center, so as to surround the drive shaft.
It is then possible to improve the cooling effect on the orbiting scroll (center, in particular) by the cooling air flowing through the second cooling-air passage, and decrease the pressure loss of the cooling air flowing from the outer peripheral end of the orbiting scroll toward the center of the rear face of the orbiting scroll. This enables the reduction of power consumption of the scroll fluid machine. Since the first and second cooling-air passages are situated concentrically with the drive shaft positioned at the center, so as to surround the drive shaft, the configuration of the duct for forming these passages can be downsized, which also decreases the size of the casing.
According to still another aspect of the invention, the rotation-preventing mechanism may be situated between the fixed scroll and the orbiting scroll. The rotation-preventing mechanism may include a crank member with which a pair of shafts whose axes are eccentric to each other are integrally formed. The rotation-preventing mechanism may be a crankshaft mechanism in which one of the pair of shafts is rotatably supported by the fixed scroll, and the other of the pair of shafts is rotatably supported by the orbiting scroll.
This enables simplification and cost reduction of the rotation-preventing mechanism, and also prevents the increase in size of the casing.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the invention, the first and second cooling-air passages improve the cooling effect on the fixed and orbiting scrolls (particularly the center of the sealed chamber). The invention also decreases the pressure loss of the cooling air, thus reduces the power consumption of the scroll fluid machine, and downsizes the casing.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a perspective view of a scroll compressor according to one embodiment of the invention.
Fig. 2 is a rear view of the scroll compressor.
Fig. 3 is a sectional view of the scroll compressor, taken along line A-A of Fig. 2.
Fig. 4 is a sectional view of the scroll compressor, taken along line B-B of Fig. 2.
Fig. 5 is a perspective view showing a configuration of a part of the scroll compressor.
Fig. 6 is a perspective view of the configuration of the part of the scroll compressor as viewed from another direction.

DESCRIPTION OF EMBODIMENTS

The invention will be described below in details with reference to embodiments illustrated in the drawings. The description is not intended to limit the scope of the invention to the dimensions, material, shape, relative arrangement and the like of components as mentioned in the embodiments unless otherwise specifically stated.
One embodiment in which the invention is applied to a scroll compressor will be described with reference to Figs. 1 to 6. Referring to Figs. 1 and 2 showing a full view of a scroll compressor 10 according to the present embodiment, a casing of the scroll compressor 10 includes a cylindrical casing 12a that covers a drive (driving) shaft side and a casing 12b that covers orbiting and fixed scroll side and has a substantially oval tube-like shape. A circular opening 14 is formed in one end of the casing 12a as viewed in an axial direction of the drive shaft. The opening 14 is formed for the purpose of inserting a drive shaft 18 therein and also attaching an electric motor (not shown) for driving the drive shaft 18 into rotation.
In the center of one end of the casing 12b as viewed in an axial direction, a hollow cylinder-like inlet duct 16 forming an inlet opening through which cooling air is taken in is disposed integrally with the center of the casing 12b. In an outer peripheral face of the casing 12a, a square cross-sectional outlet duct 20 forming an outlet opening through which the cooling air is discharged is disposed integrally with the casing 12a. In an outer peripheral face of the casing 12b, five square cross-sectional inlet ducts 22a to 22e forming inlet openings through which the cooling air is taken in are arranged dispersedly in a circumferential direction.
Referring to Figs. 3 and 4, an eccentric (off-center) shaft 24 is integrally formed in an end face of the drive shaft 18. The eccentric shaft 24 has an axis positioned parallel and eccentric to an axis of the drive shaft 18. When the drive shaft 18 rotates, the eccentric shaft 24 comes into swivel (orbital) motion.
An orbiting scroll 26 includes a circular end plate 26a and a spiral lap 26b formed integrally with the end plate 26a. A cylindrical bearing 28 is fitted to the center of a rear face (opposite side to a fixed scroll 32) 27 of the orbiting scroll 26, and the eccentric shaft 24 is rotatably supported by the bearing 28 with a roller bearing 30 interposed therebetween. This enables the orbiting scroll 26 to make orbital motion with the eccentric shaft 24.
The fixed scroll 32 includes a circular end plate 32a and a spiral lap 32b formed integrally with the end plate 32a. The fixed scroll 32 is fixed to the casing 12b. A plurality of compression chambers c are formed between the fixed scroll 32 and the orbiting scroll 26. In reaction to the orbital motion of the orbiting scroll 26, air is sucked in from an intake port 34 (see Fig. 5) and compressed in the plurality of compression chambers c. The air is then discharged from a discharge port 36 formed in the center of the fixed scroll 32. The compressed air discharged from the discharge port 36 is supplied to a demander from a discharge pipe 38 connected to the discharge port 36. The center of a rear face (opposite side to the orbiting scroll 26) 33 of the fixed scroll 32 is located to face the opening of the inlet duct 16.
In outer peripheral ends of the orbiting scroll 26 and the fixed scroll 32, pin crank mechanisms 40 as rotation-preventing mechanisms are disposed in three points at intervals of 120 degrees in a circumferential direction. The pin crank mechanisms 40 each include a crank member 42 provided with a pair of pin shafts (pivots) 44a and 44b. The pair of pin shafts 44a and 44b are positioned so that axes thereof are parallel and eccentric to each other. The pin shaft 44a is rotatably supported by the end plate 26a with a roller bearing 46 interposed therebetween. The pin shaft 44b is rotatably supported by the end plate 32a with a roller bearing 48 interposed therebetween. The pin crank mechanisms 40 thus configured prevent the rotation of the orbiting scroll 26.
As illustrated in Fig. 6, a centrifugal fan 50 is attached to the drive shaft 18. The centrifugal fan 50 has a circular end plate 50a attached to the drive shaft 18 and a plurality of blades 50b attached to the end plate 50a. The plurality of blades 50b are arranged along a circumferential direction. The centrifugal fan 50 rotates with the drive shaft 18 to send cooling air which has entered along the drive shaft 18, in a radially outward direction.
As illustrated in Fig. 5, a first cooling fin group 52 is formed in the rear face 33 of the end plate 32a. The first cooling fin group 52 includes a large number of straight-line cooling fins 52a radially extending from an area surrounding the discharge port 36 in a radially outward direction with the discharge port 36 positioned in the center.
As illustrated in Fig. 6, a second cooling fin group 54 is formed in the rear face 27 of the end plate 26a. The second cooling fin group 54 includes a large number of straight-line cooling fins 54a radially extending from an area surrounding the bearing 28 in a radially outward direction with the bearing 28 positioned in the center.
The scroll compressor 10 is further provided with a first cooling-air passage mainly for cooling the fixed scroll 32, and a second cooling-air passage mainly for cooling the orbiting scroll 26. When the centrifugal fan 50 rotates, cooling air is introduced into the cooling-air passages. A duct 56 is disposed with a clearance from the rear face 27 of the orbiting scroll 26 and a tip end portion of the drive shaft 18. The duct 56 has a shape that covers the rear face 27 and the tip end portion of the drive shaft 18. An interior space of the duct 56 forms the second cooling-air passage leading to the inlet ducts 22a to 22e.
A duct 58 is disposed outside the duct 56 so as to surround the duct 56 with a clearance from the duct 56. In the outer peripheral ends of the fixed scroll 32 and the orbiting scroll 26, the first cooling-air passage leading to the inlet duct 16 is formed between the inlet ducts 22a to 22e. An interior space of the duct 58 forms the cooling-air passages leading to the inlet duct 16. The ducts 56 and 58 are arranged coaxially with the drive shaft 18.
A configuration of the first cooling-air passage will now be described. The rotation of the centrifugal fan 50 causes cooling air a1 to be sucked in from the inlet duct 16. The cooling air a1 enters toward the center of the rear face 33 of the fixed scroll 32, and flows from the center toward the outer peripheral end, passing between the cooling fins 52a along the rear face 33 of the fixed scroll 32, to thereby cool the fixed scroll 32. After reaching the outer peripheral end of the fixed scroll 32, the cooling air a1 flows through the passages formed between the inlet ducts 22a to 22e into a passage formed between the ducts 56 and 58, namely, a passage extending along the rear face 27 of the orbiting scroll 26, and cools the orbiting scroll 26 and the drive shaft 18 in the passage. The cooling air a1 then reaches the centrifugal fan 50. The cooling air a1 is delivered by the centrifugal fan 50 in a radially outward direction of the centrifugal fan 50 and discharged from the discharge duct 20.
A configuration of the second cooling-air passage will now be described. The rotation of the centrifugal fan 50 causes cooling air a2 to be sucked in from the inlet ducts 22a to 22e into the inside of the casing 12b. The cooling air a2 flows through the second cooling-air passage formed inside the duct 56. In other words, the cooling air a2 flows between the cooling fins 54a along the rear face 27 of the orbiting scroll 26, to thereby cool the orbiting scroll 26. The cooling air a2 then veers away and flows around the drive shaft 18, cools the drive shaft 18, and then reaches the centrifugal fan 50. The cooling air a2 is delivered by the centrifugal fan 50 in the radially outward direction of the centrifugal fan 50 and discharged from the outlet duct 20.
According to the present embodiment, in the first cooling-air passage, particularly the center of the fixed scroll 32, in which temperature becomes high, can be cooled by the low-temperature cooling air a1 which has freshly entered from the inlet duct 16. A cooling effect is therefore improved. Also, the cooling air a1 passing through the first cooling-air passage flows between the cooling fins 52a, which improves the cooling effect on the fixed scroll 32.
In the second cooling-air passage, the cooling air a2 that has been sucked in from the inlet ducts 22a to 22e flows between the cooling fins 54a, to thereby improve a cooling effect on the orbiting scroll 26. The cooling air a1 and the cooling air a2, which pass through the ducts 56 and 58, are directed to be collected in the center of the compression chambers. This increases a flow rate of the cooling air in the center of the compression chambers and thus improves the cooling effect on the center of the compression chambers.
The cooling-air passage is divided into the first and second cooling-air passages, and the cooling fins 52a and 54a are arranged to extend along a substantially parallel direction to the flowing direction of the cooling air, so that pressure loss of the cooling air can be decreased. This reduces power consumption of the scroll compressor 10.
The inlet ducts 22a to 22e are arranged dispersedly in a circumferential direction in the casing 12b, and the first cooling-air passage is dispersedly arranged between the inlet ducts 22a to 22e, which makes it possible to avoid an increase in size of the casing 12b. Since the ducts 56 and 58 are arranged coaxially with the drive shaft 18, the casing 12a can be downsized, which decreases the size of the casing 12a.
Since the pin crank mechanisms 40 are provided as a rotation-preventing mechanism, this enables simplification and cost reduction of the rotation-preventing mechanism, and also prevents the increase in size of the casing.
The centrifugal fan 50 capable of increasing static pressure is provided as a cooling fan, which increases flow rates of the cooling air a1 and the cooling air a2. This also improves the cooling effect.
It is possible to obtain a similar cooling effect by using a centrifugal fan of another type, such as a sirocco fan, as a cooling fan.

INDUSTRIAL APPLICABILITY

The invention makes it possible to materialize the scroll fluid machine in which the cooling effect on the center of the sealed chamber is improved; power consumption is reduced; and the casing is downsized.

REFERENCE SIGNS LIST

10: scroll compressor
12a, 12b: casing
14: opening
16, 22a to 22e: inlet duct
18: drive shaft
20: outlet duct
24: eccentric shaft
26: orbiting scroll
26a: end plate
26b: lap
27: rear face
28: bearing
30, 46, 48: roller bearing
32: fixed scroll
32a: end plate
32b: lap
33: rear face
34: intake port
36: discharge port
38: discharge pipe
40: pin crank mechanism (crankshaft mechanism)
42: crank member
44a, 44b: pin shaft
50: centrifugal fan
50a: end plate
50b: blade
52: first cooling fin group
52a: cooling fin
54: second cooling fin group
54a: cooling fin
56, 58: duct
a1, a2: cooling air
c: compression chamber

Claims

A scroll fluid machine comprising:
a casing formed into a cylindrical shape and having open axial ends;

a fixed scroll fixed to the casing within the casing;

an orbiting scroll situated to face the fixed scroll and including a plurality of sealed chambers formed between the orbiting scroll and the fixed scroll;

a drive shaft to which the orbiting scroll is connected through an eccentric shaft that is eccentric to a rotation axis of the drive shaft, the drive shaft configured to rotate to bring the orbiting scroll into orbital motion; and

a rotation-preventing mechanism configured to prevent rotation of the orbiting scroll, the scroll fluid machine further including:
a cooling fan that is attached to the drive shaft and creates cooling air inside the casing by rotation of the drive shaft;

an outlet opening that is formed in a partition wall of the casing, which faces an outer peripheral end of the cooling fan;

a first cooling-air passage including a first inlet opening formed in a partition wall of the casing, which faces the center of a rear face of the fixed scroll, the first cooling-air passage extending along the rear face of the fixed scroll, curving near an outer peripheral end of the fixed scroll, extending along a rear face of the orbiting scroll, and further extending from the center of the rear face of the orbiting scroll along the drive shaft to reach the output opening; and

a second cooling-air passage including a plurality of second inlet openings formed in a partition wall of the casing, which faces an outer peripheral end of the orbiting scroll and arranged dispersedly in a circumferential direction of the orbiting scroll, the second cooling-air passage extending along the rear face of the orbiting scroll and extending from the center of the rear face of the orbiting scroll along the drive shaft to reach the outlet opening.
The scroll fluid machine of claim 1, wherein:
the first cooling-air passage is situated between the plurality of second inlet openings in the outer peripheral end of the fixed scroll.
The scroll fluid machine of either claim 1 or 2, wherein:
a first cooling fin group is provided, which includes a plurality of cooling fins formed in the rear face of the fixed scroll to radially extend from the center of the rear face of the fixed scroll.
The scroll fluid machine of any one of claims 1 to 3, wherein:
a second cooling fin group is provided, which includes a plurality of cooling fins formed in the rear face of the orbiting scroll to radially extend from the center of the rear face of the orbiting scroll;

the second cooling-air passage is formed between the rear face of the orbiting scroll and the first cooling-air passage; and

the first and second cooling-air passages are situated concentrically on the rear face side of the orbiting scroll and around the drive shaft with the drive shaft positioned at the center, so as to surround the drive shaft.
The scroll fluid machine of any one of claims 1 to 4, wherein:
the rotation-preventing mechanism is situated between the fixed scroll and the orbiting scroll and includes a crank member with a pair of shafts;

axes of the pair of shafts are eccentric to each other;

the pair of shafts are integrally formed; and

the rotation-preventing mechanism is a crankshaft mechanism in which one of the pair of shafts is rotatably supported by the fixed scroll, and the other of the pair of shafts is rotatably supported by the orbiting scroll.
A scroll fluid machine comprising:
a casing;

a fixed scroll fixed to the casing within the casing; an orbiting scroll situated to face the fixed scroll and including a plurality of sealed chambers formed between the orbiting scroll and the fixed scroll; and

a drive shaft to which the orbiting scroll is connected through an eccentric shaft that is eccentric to a rotation axis of the drive shaft, the drive shaft configured to rotate to bring the orbiting scroll into orbital motion, the scroll fluid machine further including:
a cooling fan that is attached to the drive shaft and creates cooling air inside the casing by rotation of the drive shaft;

a first cooling-air passage including a first inlet opening formed in a partition wall of the casing, which faces the center of a rear face of the fixed scroll, the first cooling-air passage having a path extending along the rear face of the fixed scroll; and

a second cooling-air passage into which cooling air enters through a different path from the first cooling-air passage, the second cooling-air passage having a path extending along the rear face of the orbiting scroll.
A scroll fluid machine comprising:
a casing;

a fixed scroll fixed to the casing within the casing;

an orbiting scroll situated to face the fixed scroll and including a plurality of sealed chambers formed between the orbiting scroll and the fixed scroll; and

a drive shaft to which the orbiting scroll is connected through an eccentric shaft that is eccentric to a rotation axis of the drive shaft, the drive shaft configured to rotate to bring the orbiting scroll into orbital motion, the scroll fluid machine further including:
a cooling fan that is attached to the drive shaft and creates cooling air inside the casing by rotation of the drive shaft;

a first cooling-air passage having a path extending along the rear face of the fixed scroll; and

a second cooling-air passage into which cooling air enters through a different path from the first cooling-air passage, the second cooling-air passage having a path extending along the rear face of the orbiting scroll, wherein:

the first and second cooling-air passages are formed so as to join together around the drive shaft and reach a cooling-air outlet opening formed in the casing.