JP2002202076A - Scroll fluid machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a stationary scroll relatively displaceable in the axial direction from inclining in an air compressor applying pressure from an end plate back surface of the stationary scroll and keeping clearance between teeth tip of the stationary and a rotary scrolls and the end plate appropriate for high compression performance. SOLUTION: First seal members 41A, 41B provided in suction side axial direction annular openings 51A, 51B for preventing the stationary scrolls 6A, 6B attached relatively displacement in the axial direction to a casing 1 and having a back pressure chamber on the back surface of the end plate from inclining, and second seal members 42A, 42B provided in delivery side axial direction annular openings 52A, 52B are arranged with shifting in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scroll fluid machine suitable for use in a gas compressor, a vacuum pump or the like.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 2000-13
No. 0365. The scroll fluid machine is mounted so as to be displaceable relative to the casing in the axial direction with respect to the casing. A back pressure chamber is formed by the casing and the rear surface of the head plate, and a spiral wrap is provided upright on the front surface of the head plate. A fixed scroll, and a discharge port provided at the center of the end plate of the fixed scroll for discharging compressed gas to the outside;
A spiral scroll wrap portion, which overlaps with the wrap portion of the fixed scroll to form a compression chamber, is provided on a mirror plate, and includes a drive shaft mounted on the rear surface of the orbiting scroll and driving the orbiting scroll to rotate. By introducing compressed air into the back pressure chamber from the compression chamber via the back pressure introduction path, pressure is applied to the back of the fixed scroll, and the fixed scroll is pressed axially toward the orbiting scroll.

For this reason, a gap (discharge-side axial annular gap and suction-side axial annular gap) is provided between the fixed scroll and the casing in the axial direction, so that the fixed scroll can be smoothly displaced in the axial direction relative to the casing. I can do it. Further, in order to prevent the compressed gas in the back pressure chamber from leaking to the outside through the axial gap between the fixed scroll and the casing, a first sealing member and a suction-side axial annular ring are provided in the discharge-side axial annular gap. A second seal member is provided in the gap. The first seal member prevents the compressed gas in the back pressure chamber from flowing out to the discharge port side, and also prevents the high temperature compressed gas discharged from the discharge port of the fixed scroll from flowing into the back pressure chamber. Things. The second seal member seals the back pressure chamber from the outside air to prevent the compressed gas in the back pressure chamber from leaking to the outside. Here, these first and second seal members are provided on the same plane in the axial direction.

[0004]

By the way, in the above-described scroll fluid machine according to the prior art, since an axial gap is provided between the fixed scroll and the casing, pressure acts on the back pressure chamber of the fixed scroll. When the fixed scroll is relatively displaced, there is a problem that the fixed scroll is inclined with respect to the axial direction with the first and second seal members located on the same plane in the axial direction as fulcrums. When the fixed scroll is tilted and the fixed scroll and the casing come into contact with each other, the fixed scroll does not move even if it receives a back pressure. As a result, gaps are generated between the tooth tips of the fixed scroll and the orbiting scroll and the mirror plate surface. However, the compressed gas leaks from this gap, causing a reduction in compression performance.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a scroll fluid machine having improved compression performance by preventing a fixed scroll from tilting.

[0006]

In order to solve the above-mentioned problems, a scroll fluid machine according to the present invention is mounted on a casing and the casing so as to be relatively displaceable in an axial direction with respect to the casing. A fixed scroll in which a back pressure chamber is formed by the back surface and a spiral wrap is erected in front of the end plate; and a discharge port provided in the center of the fixed scroll for discharging compressed gas to the outside. A spiral scroll wrap portion overlapping the wrap portion of the fixed scroll to form a compression chamber is mounted on the end plate and attached to the back of the orbiting scroll;
And a drive shaft for orbiting the orbiting scroll, wherein the back pressure chamber is formed by a back pressure introduction path for introducing pressure to the back pressure chamber, the casing and the fixed scroll. A first annular seal member provided in a discharge-side axial annular gap between the first and second discharge ports, and the casing and the fixed scroll, which communicate between the outside and the back pressure chamber. An annular second seal member provided in the suction-side axial annular gap, wherein the second seal member is axially shifted with respect to the first seal member. .

[0007] The invention according to claim 2 is characterized in that a casing,
A fixed scroll attached to the casing so as to be relatively displaceable in the axial direction, a back pressure chamber is formed by the casing and the rear surface of the end plate, and a spiral wrap is erected on the front surface of the end plate; An orbiting scroll provided in the center of the orifice and having a discharge port for discharging the compressed gas to the outside, and a spiral wrap formed on the end plate with a spiral wrap that overlaps the wrap of the fixed scroll to form a compression chamber; A drive shaft mounted on the back of the orbiting scroll and revolving the orbiting scroll, wherein a back pressure introduction path for introducing pressure into the back pressure chamber, the casing and the fixed scroll are provided. An annular first seal member provided in a discharge-side axial annular gap between the back pressure chamber and the discharge port; An annular second seal member formed by the fixed scroll and provided in the suction-side axial annular gap communicating between the outside and the back pressure chamber; and provided in the suction-side axial annular gap. A guide member,
And the guide member is arranged to be displaced in the axial direction with respect to the second seal member.

Further, the invention according to claim 3 is characterized in that the guide member is a rider.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A scroll type air compressor will be described as an example of a scroll fluid machine according to an embodiment of the present invention and will be described in detail with reference to the accompanying drawings.

FIGS. 1 to 3 show first to third embodiments of the present invention.
A third embodiment will be described. First, the configuration common to the first to third embodiments will be described below. Reference numeral 1 denotes an outer frame of a scroll type air compressor, and a fixed scroll 6 described later.
A and 6B show a cylindrical casing constituting a fixed side member. The casing 1 has a cylindrical portion 2 having an axis O1-O1, and a bearing mounting tube 4 which will be described later and which is located at both ends of the cylindrical portion 2.
A, 3B, bottomed tubular lids fixed to A, 4B
B.

Reference numerals 4A and 4B denote first and second bearing mounting cylinders provided between the cylindrical portion 2 and the lid portions 3A and 3B, respectively, and constituting a part of the casing 1. The outer peripheral side of the bearing mounting cylinder 4A is fixedly attached to the cylindrical part 2 together with the lid 3A by bolts 5A, and an eccentric bearing 16A described later is mounted on the inner peripheral side.

The bearing mounting cylinder 4A is provided with two receiving holes 4A1, 4A2. A bearing 38 described later is housed inside the housing hole 4A1.

The second bearing mounting cylinder 4B is formed at a position shifted from the two receiving holes of the first bearing mounting cylinder 4A by 180 °, and is bolted to the cylinder 2 together with the lid 3B. Fixedly mounted.

Reference numerals 6A and 6B denote first and second fixed scrolls which are provided on both sides in the axial direction of the casing 1 and are movably provided on the inner peripheral side of the cylindrical portion 2, respectively. Is formed in a substantially disk shape, and is disposed such that the center thereof is coincident with the axis O1-O1 of the casing 1;
Spiral wrap portion 8A erected on the surface of end plate 7A
And a fitting tube portion 9A which protrudes in the axial direction from the outer peripheral side of the end plate 7A so as to surround the wrap portion 8A, fits on the inner peripheral side of the cylindrical portion 2 and is movably provided in the axial direction. It is configured. A plurality of pin holes 10A (only two are shown) are recessed in the axial direction on the back side of the end plate 7A so as to be spaced apart in the circumferential direction.

The second fixed scroll 6B also includes a head plate 7B, a wrap portion 8B, a fitting cylinder 9B, and a pin hole (not shown).

11A and 11B (not shown) are a plurality of guide pins (only two shown) projecting from the lids 3A and 3B of the casing 1 toward the fixed scrolls 6A and 6B.
The one guide pin 11A has a casing 1
Of the fixed scroll 6A, and the distal end is slidably inserted into the pin hole 10A of the fixed scroll 6A.

The guide pin 11A holds the fixed scroll 6A in a detented state with respect to the casing 1 and guides the fixed scroll 6A in the axial direction. The other guide pin 11B has the same configuration as the guide pin 11A.

12A and 12B are lids 3 of the casing 1.
A, 3B and end plates 7A, 7B of fixed scrolls 6A, 6B
The first and second back pressure chambers are provided between the first and second back pressure chambers. The first back pressure chamber 12A is provided with a communication hole 40A in which an intermediate pressure in a compression chamber 36A described later is provided in the end plate 7A. The stationary scroll 6A is axially pressed toward the orbiting scroll 30A by this intermediate pressure, thereby increasing the degree of sealing in the compression chamber 36A. In addition, the second back pressure chamber 12B also includes the back pressure chamber 12B.
It has the same configuration as A.

Reference numeral 13 denotes an electric motor located between the fixed scrolls 6A and 6B and provided at an intermediate portion in the casing 1. The electric motor 13 includes a stator 14 fixedly provided on the inner peripheral side of the casing 1, The rotor 14 is provided on the inner peripheral side of the stator 14 so as to be rotated by the stator 14. The axis of the stator 14 and the axis of the rotor 15 are arranged on the same axis as the axis O1-O1 of the casing 1. Have been. The electric motor 13 drives a rotating shaft 23 described later by rotating the rotor 15.

16A and 16B are fixed scrolls 6A and 6B.
B and the electric motor 13, respectively.
A first and second eccentric bearings provided on the inner peripheral side of A and 4B, the first eccentric bearing 16A includes an outer ring 17A and a plurality of spheres serving as outer rolling elements on the inner peripheral side of the outer ring 17A. 18A, an outer middle wheel 19A fixed to the outer peripheral side of the rotating shaft 23, an inner middle wheel 20A fixed to the inner peripheral side of the rotating shaft 23, and an inner peripheral side of the inner middle wheel 20A. And an inner ring 22A rotatably provided by a plurality of spheres 21A serving as inner rolling elements.

Here, the outer ring 17A is press-fitted and mounted on the inner peripheral side of the bearing mounting cylinder 4A, and is disposed on the axis O1-O1. Further, the outer middle wheel 19A is positioned on the inner peripheral side of the outer wheel 17A by the spherical body 18A, and the axis O1-O1 is formed.
Is placed on top. In this state, the sphere 18A rolls about the axis O1-O1 between the outer ring 17A and the outer middle wheel 19A.

On the other hand, the inner middle wheel 20A is
It is arranged on an eccentric axis O2-O2 which is eccentric by a fixed dimension δ in the radial direction with respect to the axis O1-O1 of A. Also,
The inner race 22A is positioned on the inner peripheral side of the inner middle race 20A by the sphere 21A, and is disposed on the eccentric axis O2-O2. Then, in this state, the sphere 21A is shifted to the eccentric axis O2.
Roll around -O2.

Thus, the eccentric bearing 16A has the outer middle ring 1
9A and the inner middle wheel 20A rotate integrally with the rotating shaft 23, so that the inner ring 22A integrated with the turning shaft 24 performs a turning motion having a turning radius of a dimension δ about the axis O1-O1. It is.

The second eccentric bearing 16B also
Outer ring 17B, sphere 18B, outer middle wheel 19B, inner middle wheel 2
0B, a sphere 21B and an inner ring 22B.

Reference numeral 23 denotes a rotating shaft provided on eccentric bearings 16A and 16B at both ends with the rotor 15 of the electric motor 13 interposed therebetween.
The rotating shaft 23 is formed as a hollow shaft body, and
And is fixedly provided to be inserted into the inner peripheral side of the rotor 15. The rotating shaft 23 is fixedly attached at both ends to the inner peripheral side of the outer middle wheel 19A and the outer peripheral side of the inner middle wheel 20A, respectively. This is for rotating the inner middle wheel 20A.

As shown in FIG. 2, the rotating shaft 23 has a thickness d1 on the side opposite to the eccentric axis O2-O2 with respect to the axis O1-O1 as shown in FIG. 2, and the eccentric axis O2-O2 side. Is defined as d1> d2. For this reason, the outer peripheral side of the rotating shaft 23 is the outer ring 17A,
17B is disposed on the axis O1-O1 while the inner peripheral side is disposed on the eccentric axis O2-O2 which is eccentric by a fixed dimension .delta. In the radial direction with respect to the axis O1-O1.

The reference numeral 24 designates a free fit inside the rotary shaft 23,
The turning shaft 24 is fixedly supported on the inner rings 22A, 22B of the eccentric bearings 16A, 16B, and the turning shaft 24 is formed as a solid cylindrical body and is disposed on the eccentric axis O2-O2. Further, both ends of the turning shaft 24 are inserted and fixed to the inner peripheral sides of the inner rings 22A and 22B.

Here, at both end surfaces of the orbiting shaft 24, a circular bottomed mounting hole 2 for mounting the orbiting scroll receiving plate 26A.
5A and 25B are provided. And this mounting hole 2
Screw holes 25A1, 25B1 are formed on the bottom side of 5A, 25B at positions substantially corresponding to the axes O1-O1. Then, the turning shaft 24 makes a turning motion integrally with the inner rings 22A and 22B by the rotation of the rotating shaft 23,
Orbiting scroll receiving plate 2 for orbiting scrolls 30A and 30B
6A and 26B.

The orbiting scroll 30A makes an orbiting motion having an orbital radius of dimension δ integrally with the orbiting shaft 24. The wrap portion 31A of the orbiting scroll 30A is disposed so as to overlap with the wrap portion 8A of the fixed scroll 6A by, for example, 180 degrees, and a plurality of compression chambers are defined between the wrap portions 8A and 31A. Is done.

During operation of the scroll type air compressor, air is sucked into a compression chamber on the outer peripheral side from a suction port (not shown), which will be described later, and this air is supplied to each compression chamber while the orbiting scroll 30A orbits. , And finally, compressed air is discharged from the compression chamber on the center side to the outside through the discharge port.

The second orbiting scroll 30B has the same configuration.

Reference numeral 37 denotes a bearing mounting cylinder 4A and a thrust receiving plate 26.
A is a crankshaft as a rotation preventing mechanism provided between the bearing mounting cylinder 4A and the housing hole 4A of the bearing mounting cylinder 4A.
1 and a shaft 37A rotatably supported by a bearing 38, and a receiving hole 27A2 of the orbiting scroll receiving plate 26A.
Shaft part 3 rotatably supported by a bearing 39 therein.
7B. And the crankshaft 3
7, the other side shaft portion 37B is disposed eccentrically by a dimension δ with respect to the one side shaft portion 37A, and these shaft portions 37A, 37 during operation.
The relative rotation of B in the accommodation holes 4A1 and 27A2 prevents the orbiting scroll 30A integrated with the thrust receiving plate 26A from rotating.

The scroll type air compressor according to the present embodiment has the above-described configuration, and its operation will be described below.

First, when the rotor 15 of the electric motor 13 is rotated, the rotating shaft 23 integrated with the rotor 15 rotates by the spheres 18A and 18B of the eccentric bearings 16A and 16B. Spheres 21A, 21B
As a result, it rotates on the inner peripheral side of the rotating shaft 23.

Here, the spheres 18A and 18B rotate about the axis O1-O1 of the casing 1 (outer rings 17A and 17B), while the spheres 21A and 21B are in a radial direction with respect to the axis O1-O1. Are rotated about an eccentric axis O2-O2 which is eccentric by the dimension .delta.
Turning shaft 2 integrated with inner rings 22A and 22B by 1B
Reference numeral 4 denotes a revolving motion having a revolving radius of a dimension .delta. Around the axis O1-O1, and the revolving shafts 24 revolve the revolving scrolls 30A and 30B, respectively.

And, as described above, the orbiting scroll 30
When A and 30B orbit, orbiting scrolls 30A and 30B
30B is prevented from rotating by the crankshaft 37 and performs only revolution.

As a result, each of the compression chambers defined between the first fixed scroll 6A and the first orbiting scroll 30A is continuously reduced, whereby the first fixed scroll 6A is indicated by a broken line. The compressed air is stored in an external air tank (not shown) from the suction port of the first fixed scroll 6A while sequentially compressing the outside air sucked from the suction ports 53A and 53B shown in the respective compression chambers.

Each compression chamber 36 defined between the second fixed scroll 6B and the second orbiting scroll 30B.
As for B, the compressed air is stored in the air tank or the like by continuously reducing the size.

Next, a configuration which is a feature of the first embodiment will be described with reference to FIG.

The fixed scrolls 6A and 6B according to the present embodiment.
Are provided with introduction holes 40A, 40B for communicating the surfaces on which the wraps 8A, 8B are formed with the back surfaces of the fixed scrolls 6A, 6B.
(Back pressure introduction passage) is provided, and the compressed air in the compression chambers 36A, 36B flows through the back pressure chamber 12 through the introduction holes 40A, 40B.
A, 12B. First sealing members 41A and 41B are provided in discharge-side axial annular gaps 51A and 51B between the back pressure chambers 12A and 12B of the fixed scrolls 6A and 6B and the discharge ports 50A and 50B, respectively.
1A and 41B are discharge ports 50 of the fixed scrolls 6A and 6B.
A, 50B high-pressure compressed air discharged from the back pressure chamber 12
A and 12B are prevented from flowing. Further, it is formed by the casing 1 and the fixed scrolls 6A and 6B,
Second suction members 42A and 42B are provided in the suction-side axial annular gaps 52A and 52B communicating between the outside and the back pressure chambers 12A and 12B.
A and 42B prevent the compressed air in the back pressure chambers 12A and 12B from leaking outside by sealing the inside of the back pressure chambers 12A and 12B and the outside air.

At this time, the first seal members 41A, 41
B and the second seal members 42A and 42B are separated by a distance L in the axial direction.
It is provided only at a distance. As a result, even if a force that inclines the fixed scrolls 6A, 6B acts on the fixed scrolls 6A, 6B during operation, the first and second seal members 41A, 41B that are provided to be displaced in the axial direction even if they are applied. , 42
Since the fixed scrolls 6A and 6B are supported by A and 42B, the fixed scrolls 6A and 6B themselves can be prevented from tilting.

Thus, even if a force is applied to the fixed scrolls 6A, 6B to tilt them in the axial direction, the first seal members 41A, 41B provided in the discharge side axial gaps 51A, 51B and the suction side. Axial annular gap 52A, 5
By disposing the second seal members 42A and 42B provided on the second scroll 2A in the axial direction, the fixed scrolls 6A and 6B can be prevented from tilting, and the teeth of the fixed and orbiting scrolls 6A, 6B, 30A and 30B can be prevented. The tip and the end plates 7A, 7B,
The gap with 31A, 31B can be maintained appropriately, and the gas compression performance is improved.

Further, since the inclination of the fixed scrolls 6A and 6B can be suppressed, the orbiting scroll 30
The wrap portions 32A and 32B of the fixed scrolls 6A and 6B have the wrap portions 32A and 32B of the fixed scrolls 6A and 6B as described in the related art.
As a result, it is possible to prevent wear of the wrap portions 8A and 8B and to reduce noise.

Next, a configuration which is a feature of the second embodiment will be described with reference to FIG. In the present embodiment, the positions of the second seal members 42A, 42B in the first embodiment are changed to the first seal members 41A, 41A.
At the same position in the axial direction as the position of B,
It is characterized in that third sealing members 43A, 43B (guide members) are provided in the suction-side axial gaps 52A, 52B. The third seal members 43A, 43B are provided at positions separated by a distance L from the second seal members 42A, 43B. Thereby, the fixed scroll 6
Even if a force is applied to A, 6B itself to tilt in the axial direction, the first seal members 41A, 41B provided in the discharge-side axial annular gaps 51A, 51B and the suction-side axial annular gaps 52A, 52B. The third sealing member 43 provided in the
A, 43B (guide member) is displaced in the axial direction, so that the fixed scrolls 6A, 6B can be prevented from tilting, and the fixed / orbiting scrolls 6A, 6B, 30A, 3 can be prevented.
The gap between the 0B tooth tip and the head plates 7A, 7B, 31A, 31B can be appropriately maintained, and the gas compression performance is improved.

Next, a third embodiment will be described with reference to FIG. In the present embodiment, the suction-side axial gaps 52A, 52B in the second embodiment described above are used.
Instead of the third seal members 43A and 43B (guide members) provided in the first embodiment, rider rings 44A and 44B are used.

As a result, since the guide members according to the second aspect are formed as the rider rings 44A, 44B, the fixed scrolls 6A, 6B can be smoothly displaced in the axial direction with respect to the casing 1, and the second embodiment In addition to the effects of the embodiment, it is possible to further prevent the fixed scrolls 6A and 6B from tilting.

In the first to third embodiments, two orbiting scrolls 30A and 30B are provided at both ends of the orbiting shaft 24, and these orbiting scrolls 30A and 30B are disposed on both sides of the casing 1. Two fixed scrolls 6A, 6
Although the above description has been made with reference to the example of the opposed scroll air compressor arranged to face B, the present invention is not limited to this.
For example, the second fixed scroll 6B and the second orbiting scroll 30B are eliminated, and the first fixed scroll 6A and the first
The scroll type air compressor may be constituted only by the orbiting scroll 30A.

In the first to third embodiments, a scroll air compressor has been described as an example of a scroll fluid machine. However, the present invention is not limited to this. For example, a refrigerant compressor for compressing a refrigerant, etc. It can be applied widely.

Further, for introducing compressed air into the back pressure chambers 12A and 12B for pressing the fixed scrolls 6A and 6B in the axial direction, introduction passages 40A and 40B are provided to introduce the compressed air generated between the wrap portions. In addition to the above method, for example, a passage communicating the back pressure chambers 12A, 12B with the outside of the lids 3A, 3B is provided in the lids 3A, 3B constituting a part of the casing 1 so that the compressed air generated by the compressor is May be supplied to the back pressure chambers 12A and 12B.

[0050]

As described above, according to the first aspect of the present invention, the first seal provided in the discharge-side axial annular gap even if a force for inclining the fixed scroll itself in the axial direction acts. A second member provided in the member and the suction side axial annular gap.
The fixed scroll can be prevented from tilting by displacing the seal member in the axial direction, and the gap between the tip of the fixed / orbiting scroll and the end plate can be properly maintained, improving the gas compression performance. I do.

According to the second aspect of the present invention, even if a force that inclines the fixed scroll itself in the axial direction acts on the fixed scroll itself,
Since the first seal member provided in the discharge-side axial annular gap and the guide member provided in the suction-side axial annular gap are displaced in the axial direction, the fixed scroll can be prevented from tilting and fixed. -The gap between the tip of the orbiting scroll and the end plate can be appropriately maintained, and the gas compression performance is improved.

According to the invention of claim 3, according to claim 2,
Since the guide member described in (1) is a rider, the fixed scroll can be smoothly displaced in the axial direction with respect to the casing, and in addition to the effect of the invention of claim 2, the fixed scroll is further prevented from being tilted. be able to.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a scroll type air compressor according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a scroll type air compressor according to a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a scroll type air compressor according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Casing 6A, 6B Fixed scroll 7A, 7B End plate (fixed scroll) 8A, 8B Wrap (fixed scroll) 12A, 12B Back pressure chamber 23 Drive shaft 30A, 30B Orbiting scroll 31A, 31B End plate (orbiting scroll) 32A, 32B wrap ( Orbiting scroll) 36A, 36B Compression chambers 40A, 40B Back pressure introduction paths 41A, 41B First seal member 42A, 42B Second seal member 43A, 43B Guide member 44A, 44B Lidaring (guide member) 50A, 50B Discharge port 51A, 51B Discharge-side axial annular gap 52A, 52B Suction-side axial annular gap 100 Scroll fluid machine

Claims (3)

[Claims] 1. A back pressure chamber is formed by a casing and an axially displaceable relative to the casing, and a back pressure chamber is formed by the casing and a rear surface of a head plate, and a spiral wrap is erected on the front surface of the head plate. A fixed scroll, a discharge port provided at the center of the end plate of the fixed scroll for discharging compressed gas to the outside, and a spiral wrap portion overlapping the wrap portion of the fixed scroll to form a compression chamber. A scroll fluid machine comprising: an orbiting scroll provided upright; a drive shaft attached to the back of the orbiting scroll for orbiting the orbiting scroll; and a back pressure introduction path for introducing pressure into the back pressure chamber. A first annular ring formed by the casing and the fixed scroll and provided in a discharge-side axial annular gap between the back pressure chamber and the discharge port. A second sealing member formed by the casing and the fixed scroll, and provided in a suction-side axial annular gap communicating between the outside and the back pressure chamber; 2. A scroll fluid machine according to claim 1, wherein said second seal member is axially displaced from said first seal member. 2. A back pressure chamber is formed by a casing and an axially displaceable relative to the casing, and a back pressure chamber is formed by the casing and a back surface of the end plate. A fixed scroll, a discharge port provided at the center of the end plate of the fixed scroll, for discharging compressed gas to the outside, and a spiral wrap portion overlapping the wrap portion of the fixed scroll to form a compression chamber. A scroll fluid machine comprising: an orbiting scroll provided upright; a drive shaft mounted on the back surface of the orbiting scroll for orbiting the orbiting scroll; and a back pressure introduction path for introducing pressure into the back pressure chamber. An annular first shell formed by the casing and the fixed scroll and provided in a discharge-side axial annular gap between the back pressure chamber and the discharge port. An annular second seal member formed by the casing and the fixed scroll and provided in a suction-side axial annular gap communicating between the outside and the back pressure chamber; and the suction-side shaft. And a guide member provided in the direction annular gap, wherein the guide member is arranged to be shifted in the axial direction with respect to the first seal member. 3. The scroll fluid machine according to claim 2, wherein said guide member is a rider.