Seal system and scroll type fluid machine

In a seal system for a scroll type fluid machine, a seal mechanism is provided between a backpressure plate and a holder, so as to surround an orbiting backpressure chamber. The seal member comprises a seal attachment groove, a seal member and a Y-shaped packing. The seal attachment groove is stepped on its outer circumference to define a shallow bottom portion. The seal member includes, on its outer circumference side, a cutout portion matching the shallow bottom portion. The Y-shaped packing is disposed between a deep groove peripheral wall of the seal attachment groove and the cutout portion of the seal member, and a backpressure chamber is defined on a reverse surface side of the seal member. By this arrangement, a slide surface of the seal member can be larger than an effective area of the backpressure side of the seal member. Thereby it is possible to reduce a difference between a load Ff acting on the slide surface and a load Fb acting on the reverse surface.

BACKGROUND OF THE INVENTION

The present invention relates to a seal system comprising an annular groove and a seal member that is fittedly inserted in the groove, and to a scroll type fluid machine that is provided with a seal mechanism comprising such a groove and seal member.

Generally, a scroll type fluid machine comprises a fixed scroll and an orbiting scroll which face each other, and each scroll includes a spiral wrap portion that is erected from a bottom surface of an end plate of the scroll. The two scrolls are disposed to face each other so that the two wrap portions overlap to define a plurality of sealed chambers. Therefore, when the orbiting scroll is driven to perform an orbiting motion relative to the fixed scroll, the sealed chambers successively contract or expand, thereby compressing or expanding air, catalytic gas or the like.

As a conventional art, there is known, for example, a seal mechanism that is provided on a periphery side of a wrap portion of a fixed scroll for preventing leakage of air or the like. (For example, refer to Japanese Patent Application Public Disclosures No. 2005-61304, 2004-301093, H01-250675.) This conventional seal mechanism comprises an annular groove provided on the periphery side so as to surround the warp portion of the fixed scroll, and an annular seal member fittedly inserted in the groove.

SUMMARY OF THE INVENTION

Conventionally, in a typical seal mechanism, each of a groove and a seal member has a rectangular cross section. In such a seal mechanism, when a pressure difference between pressures on a high pressure side and a low pressure side is larger than or equal to a certain level, the seal member, which has a rectangular cross section and is disposed in the groove having a rectangular cross section, is pressed against a facing orbiting scroll with a heavy pressing load, as a result of which serious friction loss and abrasion is caused.

With the aim of solving this problem, the above-mentioned Japanese Patent Application Public Disclosure No. 2005-61304 discloses a seal mechanism in which only a seal member is formed to have a stepped cross section, so as to reduce a pressing load. However, in this invention also, a surface pressure of the seal member still consists of a differential pressure between a pressure on a reverse surface of the seal member on a bottom side of a groove and a pressure on a front surface which is a slide surface relative to an orbiting scroll. Therefore, the surface pressure of the seal member cannot be reduced sufficiently to extend a lifetime of the seal member.

Japanese Patent Application Public Disclosure No. 2004-301093 discloses a seal mechanism including a seal member provided with a pressure introduction hole by which pressures on a reverse surface and a front surface of the seal member are balanced. However, this invention has a problem in that the seal member and the like have a complicated configuration and thereby require additional processing, resulting in an increase in manufacturing costs.

Japanese Patent Application Public Disclosure No. H01-250675 discloses a seal mechanism for sealing an inner circumferential surface of a cylinder (cylinder surface), by which it becomes possible to reduce a load on a slide surface of a seal member. In this invention, a pressure on the slide surface of the seal member with the cylinder is reduced by partially introducing a pressure of a low pressure side into an inner circumferential surface of the seal member, thereby reducing an area on which a pressure of a high pressure side acts. While this invention succeeds in reducing a pressure acting on the slide surface of the seal member with the cylinder, it requires introduction of pressure of the low pressure side into a significant area of a peripheral wall of the low pressure side of the seal groove, which is originally supposed to receive pressures distributed in the range of the low pressure to the high pressure. As a result, it is not possible to prevent the seal member from being pressed from the high pressure side toward the low pressure side by a stronger force, and therefore the seal member is brought into frictional contact with the peripheral wall of the seal groove, whereby movement of the seal member is restrained and abrasion of the seal member is aggravated by friction produced between the seal member and the peripheral wall.

The present invention has been contrived in consideration of the problem of the above-mentioned conventional arts, and an object thereof is to provide a seal system and a scroll type fluid machine in which a surface pressure of a seal member is reduced to improve durability of the seal member.

In order to achieve the forgoing and other objects, the present invention provides a seal system comprising: a member on one side and a member on the other side which are disposed to face each other and one or both of which perform a sliding motion; an annular groove provided on a slide surface of the member on the other side, the slide surface with which the member on the other side slides on the member on the one side; and an annular seal member fittedly inserted in the groove and having a surface used as a slide surface, wherein the slide surface of the seal member contacts a slide surface of the member on the one side on their flat surfaces; a high pressure side and a low pressure side are defined; a leak preventer for preventing a pressure of the high pressure side from leaking into the low pressure side is disposed between the seal member and the groove; the leak preventer, a bottom portion side of the groove and the seal member define a backpressure chamber in communication with the high pressure side; and when the seal member is in a used state, a contact area of the slide surface of the seal member with the member on the one side is large compared to an effective area of the backpressure side of the seal member which pushes the seal member toward the member on the one side.

Further, the present invention provides A seal system comprising: a member on one side and a member on the other side which are disposed to face each other and one or both of which perform a sliding motion; an annular groove provided on a slide surface of the member on the other side, the slide surface with which the member on the other side slides on the member on the one side; and an annular seal member fittedly inserted in the groove and having a surface used as a slide surface, wherein the slide surface of the seal member contacts a slide surface of the member on the one side on their flat surfaces; a high pressure side and a low pressure side are defined; a leak preventer for preventing a pressure of the high pressure side from leaking into the low pressure side is disposed between the seal member and the groove so as to be positioned on the low pressure side on an inner circumference side or an outer circumference side of the seal member; the leak preventer, a bottom portion side of the groove and the seal member define a backpressure chamber in communication with the high pressure side; and when the seal member is in a used state, the slide surface of the seal member extends radially toward the low pressure side relative to a boundary of the low pressure side of the backpressure chamber.

The slide surface of the seal member may be configured such that the contact area of the slide surface of the seal member with the member on the one side increases due to abrasion of the slide surface of the seal member.

The slide surface of the seal member may include a portion which is gradually spaced apart relative to the member on the one side from the slide surface of the seal member toward the low pressure side.

The seal member may include, on the high pressure side of the slide surface thereof, a high-pressure-side stepped portion facing the member on the one side in a spaced-apart relationship with the member on the one side.

In the seal system, a shallow bottom portion having a lesser depth than that of the bottom portion of the groove may be formed on the low pressure side of the groove; a cutout portion configured to match the shallow bottom portion may be formed on the seal member; and the leak preventer may be disposed between the cutout portion of the seal member and a low-pressure-side deep groove peripheral wall positioned between the bottom portion and the shallow bottom portion of the groove.

In the seal system, a low-pressure-side shallow groove peripheral wall positioned between the shallow bottom portion of the groove and an opening may be formed; and a first gap defined between the seal member and the low-pressure-side deep groove peripheral wall of the groove may be larger than a second gap defined between the seal member and the low-pressure-side shallow groove peripheral wall of the groove.

A raised or gullet portion extending in a direction toward the bottom portion of the groove may be formed on a portion of the seal member, the portion facing the second gap.

Further, the present invention provides a scroll type fluid machine wherein: a wrap portion of a scroll on one side and a wrap portion of a scroll on the other side overlap to define a sealed chamber; fluid drawn or introduced from outside is compressed or expanded while an orbiting motion is performed; a seal mechanism comprises an annular groove provided on a periphery side of the wrap portion of the scroll on the other side, and an annular seal member fittedly inserted in the groove and having a surface used as a slide surface; in the seal mechanism, the slide surface of the seal member contacts a slide surface of the scroll on the one side on their flat surfaces, and a high pressure side and a low pressure side are defined; a leak preventer for preventing a pressure of the high pressure side from leaking into the low pressure side is disposed between the seal member and the groove so as to be positioned on the low pressure side on an inner circumference side or an outer circumference side of the seal member; the leak preventer, a bottom portion side of the groove and the seal member define a backpressure chamber in communication with the high pressure side; and when the seal member is in a used state, the slide surface of the seal member extends radially toward the low pressure side relative to a boundary of the low pressure side of the backpressure chamber.

Further, the present invention provides a scroll type fluid machine comprising: a casing; a fixed scroll disposed in the casing and having a spiral wrap portion extending from a surface of an end plate thereof; and an orbiting scroll disposed so as to face the fixed scroll and having a wrap portion which extends from a surface of an end plate thereof and overlaps with the wrap portion of the fixed scroll to define a plurality of sealed chambers therebetween, wherein a backpressure chamber defining member for defining an orbiting backpressure chamber which pushes the orbiting scroll toward the fixed scroll is disposed in the casing so as to be positioned on a reverse surface of the orbiting scroll; a seal mechanism for sealing the orbiting backpressure chamber from outside is provided on an outer circumference side or an inner circumference side of the orbiting backpressure chamber; the seal mechanism comprises an annular groove provided on a slide surface of the backpressure chamber defining member, with which the backpressure chamber defining member slides on the orbiting scroll, and an annular seal member fittedly inserted in the groove and having a surface used as a slide surface; the slide surface of the seal member contacts a slide surface of the orbiting scroll on their flat surfaces; the orbiting backpressure chamber on a high pressure side and outside on a low pressure side are defined; a leak preventer for preventing a pressure of the high pressure side from leaking into the low pressure side is disposed between the seal member and the groove so as to be positioned on the low pressure side on an inner circumference side or an outer circumference side of the seal member; the leak preventer, a bottom portion side of the groove and the seal member define a backpressure chamber in communication with the orbiting backpressure chamber on the high pressure side; and when the seal member is in a used state, the slide surface of the seal member extends radially toward the low pressure side relative to a boundary of the low pressure side of the backpressure chamber.

The slide surface of the seal member may be configured such that a contact area of the slide surface of the seal member with the orbiting scroll increases due to abrasion of the slide surface of the seal member.

The slide surface of the seal member may include a portion which is gradually being spaced apart relative to the orbiting scroll from the slide surface of the seal member toward the low pressure side.

The seal member may include, on the high pressure side of the slide surface thereof, a high-pressure-side stepped portion facing the orbiting scroll in a spaced-apart relationship with the orbiting scroll.

A shallow bottom portion having a shallower depth than that of the bottom portion of the groove may be formed on the low pressure side of the groove; a cutout portion configured to match the shallow bottom portion may be formed on the seal member; and the leak preventer may be disposed between the cutout portion of the seal member and a low-pressure-side deep groove peripheral wall positioned between the bottom portion and the shallow bottom portion of the groove.

A low-pressure-side shallow groove peripheral wall positioned between the shallow bottom portion of the groove and an opening may be formed; and a first gap defined between the seal member and the low-pressure-side deep groove peripheral wall of the groove may be larger than a second gap defined between the seal member and the low-pressure-side shallow groove peripheral wall of the groove.

The fixed scroll and the orbiting scroll may be formed with use of a member in which an alumite treatment is performed on an aluminum material, and the seal member may be mainly made of polytetrafluoroethylene.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinbelow, a scroll type fluid machine embodying the present invention will be described in detail with reference to the accompanying drawings, taking as an example thereof a booster air compressor which further compresses compressed air.

FIGS. 1 to 6show a first embodiment of the present invention. In the drawings, reference numeral1denotes a cylindrical casing forming an outer frame of the booster air compressor. The casing1comprises a large-diameter cylinder portion1A, a small-diameter bearing cylinder portion1B which has a form of a cylinder having a smaller diameter than the large-diameter cylinder portion1A and protrudes outwardly from one axial side of the large-diameter cylinder portion1A, and an annular portion1C formed between the large-diameter cylinder portion1A and the bearing cylinder portion1B. Further, cylindrical bearing-accommodating portions1D, each of which accommodates a bearing23A of an auxiliary crank mechanism23described later, is provided in the annular portion1C. The number of bearing-accommodating portions1D provided may be, for example, three. The bearing-accommodating portions1D are evenly spaced-apart around a circumference of the annular portion1C.

Reference numeral2denotes a fixed scroll disposed in the casing1through a holder17which will be described later. The fixed scroll2may be formed by, for example, performing an alumite treatment on a surface of an aluminum material. The fixed scroll2is attached to an attachment cylinder portion17A of the holder17so as to close the large-diameter cylinder portion1A of the casing1from the other axial side. In this way, the fixed scroll2is fixed to the other side (open side) of the large-diameter cylinder portion1A with the holder17sandwiched therebetween. The fixed scroll2generally comprises a disk-like end plate2A, and a spiral wrap portion2B erected from a surface of the end plate2A with a start end of the spiral positioned on a center side of the surface of the end plate2A and a stop end of the spiral positioned on a periphery side of the surface of the end plate2A.

A tip seal3is disposed on a tip surface of the wrap portion2B to provide a seal between the wrap portion2B and an end plate9A of an orbiting scroll8which will be described later. An annular seal member4is disposed on the surface of the end plate2A of the fixed scroll2. The seal member4prevents compressed air from leaking from compression chambers12by providing a seal between the end plate2A and the end plate9A of the orbiting scroll8.

A plurality of cooling fins2C is formed on a reverse surface side of the end plate2A of the fixed scroll2so as to extend in parallel. The cooling fins2C cool the end plate2A of the fixed scroll2and the like from the reverse surface side by circulating a cooling air flow between the cooling fins2C.

Reference numeral5denotes a driving shaft which is a rotational shaft rotatably disposed within the bearing cylinder portion1B of the casing1through bearings6and7. The one axial side of the driving shaft5protrudes from the bearing cylinder portion1B toward the outside of the casing1, while the other axial side (front side) thereof forms a crank portion5A extending in the large cylinder portion1A of the casing1. A pulley (not shown) is attached to one side of the driving shaft5. The driving shaft5is coupled through the pulley to an electric motor (not shown) which serves as a driving source. Accordingly, the driving shaft5is driven by the electric motor to rotate.

The crank portion5A is formed so that its axis is eccentric relative to the axis of the driving shaft5by a predetermined distance. The crank portion5A is rotatably attached within a boss portion20B of a coupling member20through an orbiting bearing22which will be described later. A balancing weight portion5B is integrally formed with the driving shaft5to achieve rotational balance of the driving shaft5.

Reference numeral8denotes an orbiting scroll rotatably disposed within the large-diameter cylinder portion1A of the casing1. The orbiting scroll8may be formed by, for example, performing an alumite treatment on a surface of an aluminum material. The orbiting scroll8is positioned so as to face the fixed scroll2. The orbiting scroll8comprises an orbiting scroll body9facing the fixed scroll2in the axial direction of the casing1, and a joint member10fixedly attached to a reverse surface side of the orbiting scroll body9to serve as a pressure receiver.

The orbiting scroll body9comprises the substantially cylindrical end plate9A, and a spiral wrap portion9B erected from the end plate9A toward the fixed scroll2side. A tip seal11is disposed on a tip surface of the wrap portion9B to provide a seal between the wrap portion9B and the end plate2A of the fixed scroll2.

The orbiting scroll8is arranged so that the orbiting scroll8and the fixed scroll2overlap each other with an angular displacement of, for example, 180 degrees. By this arrangement, the plurality of compression chambers12(sealed chambers) are defined between the wrap portions2B and9B from the radially outer side to the radially inner side (center) of the scrolls. When the compressor operates, compressed air is drawn through an inlet13provided on the periphery side of the fixed scroll2into the compression chamber12on the radially outer side, and is successively compressed in each compression chamber12. Then, the compressed air contained in the compression chamber12on the center side is discharged toward the outside through an outlet14provided on the center side of the fixed scroll2.

A plurality of cooling fins9C are formed on the end plate9A of the orbiting scroll body9between the end plate9A and the joint member10. The cooling fins9C horizontally extend in the same direction as the cooling fins2C of the fixed scroll2extend, and the cooling fins9C cool the end plate9A of the orbiting scroll8and the like by means of a cool air flow.

The joint member10of the orbiting scroll8is fixed to the reverse surface side of the end plate9A by a plurality of bolts15. A recessed portion10A is provided on a center side of a reverse surface of the joint member10as a circular recess formed over the substantially entire surface. For example, the recessed portion10A may have a dimension such that it covers the entire area of the wrap portion9B. A backpressure plate16, which will be described later, is attached in the recessed portion10A. By this arrangement, the joint member10receives a pressure within an orbiting backpressure chamber18, which will be described later, through the backpressure plate16. A net-like rib10B is provided in the recessed portion10A of the reverse surface of the joint member10so as to cover substantially the entire surface. The rib10B increases a strength of the joint member10.

Reference numeral16denotes a backpressure plate (member on one side) attached to the reverse surface of the joint member10. The backpressure plate16may be formed by, for example, performing an alumite treatment on a surface of an aluminum material. The backpressure plate16has a dimension substantially equal to the recessed portion10A of the joint member10, and is formed as a disk. The backpressure plate16is attached in the recessed portion10A of the joint member10in a spaced-apart relationship with the end plate9A of the orbiting scroll8. The backpressure plate16includes a front surface in contact with a bottom surface of the recessed portion10A, and a reverse surface16A defining the orbiting backpressure chamber18which will be described later. By this arrangement, the backpressure plate16receives a pressure within the orbiting backpressure chamber18and pushes the entire orbiting scroll8toward the fixed scroll2through the joint member10. Further, a net-like rib16B is provided to the front (front surface) of the backpressure plate16so as to cover substantially the entire surface for increasing a strength of the backpressure plate16.

Reference numeral17denotes a holder (member on the other side) which is a member fixedly disposed to the casing1side behind the orbiting scroll8to define the backpressure chamber. The holder17may be formed by, for example, performing an alumite treatment on a surface of an aluminum material. The holder17is integrally formed with the casing1. The holder17comprises the attachment cylinder portion17A attached to an open end of the large-diameter cylinder portion1A of the casing1, and a substantially disk-like bottom plate portion17B which is positioned on the other end side in an axial direction of the attachment cylinder portion17A, and forms a bottom surface. The attachment cylinder portion17A is sandwiched on the outer circumference side thereof between the fixed scroll2and the large-diameter cylinder portion1A of the casing1, and accommodates therein the joint member10of the orbiting scroll8and the backpressure plate16.

A seal mechanism24, which will be described later, is disposed on a periphery side of the bottom plate portion17B. Further, a compressed-air-containing portion17C is provided on a center side of the bottom plate portion17B so as to be positioned on a radially inner side of the seal mechanism24. The compressed-air-containing portion17C is in the form of a bottomed cylinder recessed toward a reverse surface side of the portion17B. The compressed-air-containing portion17C is disposed so as to face the backpressure plate16, has an area smaller the backpressure plate16, and is open to the backpressure plate16side. By these arrangements and dimensions, the holder17defines the disk-like orbiting backpressure chamber18positioned in the compressed-air-containing portion17C between the holder17and the backpressure plate16. The orbiting backpressure chamber18is airtightly sealed by the seal mechanism24around the circumference thereof.

A net-like rib17D is provided on the bottom plate portion17B within the compressed-air-containing portion17C for increasing a strength of the bottom plate portion17B.

Three spill ports17E are provided outside of the seal mechanism24on the bottom plate portion17B so as to axially extend through the portion17B. The spill ports17E may be, for example, disposed in an evenly spaced-apart relationship around the circumference. Coupling protrusion portions20A of the coupling member20, which will be described later, are inserted through the spill ports17E. Due to the spill ports17E, when the orbiting scroll8performs an orbiting motion together with the coupling member20, the coupling protrusion portions20A coupling them are prevented from interfering with the holder17. Reference numeral19denotes a backpressure introduction tube19attached between the orbiting scroll body9of the orbiting scroll8and the joint member10as an coupling member therebetween. The number of the attached backpressure introduction tube19may be, for example, two. The backpressure introduction tube19penetrates through the backpressure plate16and the joint member10, and is threaded to the reverse surface side of the orbiting scroll8. The back pressure introduction tube19includes therein a backpressure introduction hole (not shown) axially extending therethrough. The backpressure introduction tube19has one end in communication with the orbiting backpressure chamber18, and the other end in communication with the compression chamber12by penetration of the end plate9A of the orbiting scroll8. By this arrangement, the backpressure introduction tube19guides compressed air within the compression chamber12into the orbiting backpressure chamber18. The backpressure introduction tube19also serves as a coupling member securely coupling the orbiting scroll body9and the joint member10.

The reference numeral20denotes a coupling member sandwiching the holder17and disposed on the one axial side. The coupling member20has a substantially disk-like form, and includes the three coupling protrusion portions20A disposed on the front side thereof. The coupling protrusion portions20A protrude toward the holder17. The coupling protrusion portions20A are disposed in a evenly spaced-apart relationship around the circumference of the coupling member20. The coupling protrusion portions20A are integrated with the orbiting scroll8by being respectively inserted through the spill ports17E of the holder17to be coupled to the joint member10of the orbiting scroll8by coupling bolts21.

The cylindrical boss portion20B is integrally formed in a center side on a reverse surface of the coupling member20. The crank portion5A of the driving shaft5, which will be described later, is rotatably attached in the boss portion20B through the orbiting bearing22. By this arrangement, the coupling member20couples the orbiting scroll8and the driving shaft5with the holder17sandwiched therebetween, so that the coupling member20performs an orbiting motion together with the orbiting scroll8when the driving shaft5rotates.

Cylindrical bearing-accommodating portions20C, each of which accommodates a bearing23B of the auxiliary crank mechanism23described later, are provided on a periphery side of the reverse surface of the coupling member20. The number of the provided bearing-accommodating portions20C may be, for example, three. The bearing-accommodating portion20C is positioned to face the bearing-accommodating portion1D of the casing1, and is also positioned on the one axial side of the coupling protrusion portion20A.

Reference numeral23denotes an auxiliary crank mechanism disposed between the coupling member20and the casing1as a mechanism for preventing a self-rotation. The auxiliary crank mechanism23comprises the bearing23A accommodated in the bearing-accommodating portion1D of the casing1, the bearing23B accommodated in the bearing-accommodating portion20C of the coupling member20, and a crank member23C rotatably attached to the bearings23A and23B. The auxiliary crank mechanism23prevents the orbiting scroll8from rotating on its own axis in the casing1when performing an orbiting motion.

Reference numeral24denotes a seal mechanism provided between the holder17and the backpressure plate16. The seal mechanism24comprises a seal attachment groove25which will be described later, a seal member26, a Y-shaped packing27, and the like.

Reference numeral25denotes an annular seal attachment groove provided along the periphery of the bottom plate portion17B. The seal attachment groove25is provided on a slide surface of the bottom plate portion17B, with which the portion17B slides on the backpressure plate16(orbiting scroll8), so as to be open to the backpressure plate16. A bottom portion25A having a large depth is formed on an inner circumference side of the seal attachment groove25, i.e., a high pressure side (an orbiting backpressure chamber18side). On the other hand, the seal attachment groove25is stepped on an outer circumference side thereof, i.e., a low pressure side (an outer side), defining a shallow bottom portion25B having a little depth. In other words, the seal attachment groove25includes the bottom portion25A having a large depth and the shallow bottom portion25B having a shallow depth which are formed on the basis of a radially intermediate diameter R0between a radially inner diameter and a radially outer diameter of an opening side, i.e., the bottom portion25A formed in a part having a diameter smaller than the radially intermediate diameter R0and the shallow bottom portion25B formed in a part having a diameter larger than the radially intermediate diameter R0. The seal attachment groove25further includes, on the low pressure side, a deep groove peripheral wall25C positioned between the bottom portion25A and the shallow bottom portion25B, and a shallow groove peripheral wall25D positioned between the shallow bottom portion25B and the opening.

Reference numeral26denotes an annular seal member fittedly inserted in the seal attachment groove25. The seam member26may be mainly made of a tetrafluoride resin material such as polytetrafluoroethylene (PTFE) which has excellent lubricating property and anti-abrasion property. The seal member26comprises an annular continuous body without any discontinuity around the circumference. The seal member26is configured to be prevented from radially expanding and to achieve a balance of loads acting in the radial direction perpendicular to the groove periphery walls25C and25D of the seal attachment groove25, even when the seal member26receives a pressure from the orbiting backpressure chamber18on an inner circumference side thereof, and an atmospheric pressure on an outer circumference thereof.

In the seal member26, a surface facing the axial direction (front surface) serves as a slide surface26A in sliding contact with the backpressure plate16. The slide surface26A of the seal member26contacts a reverse surface16A serving as a slide surface of the backpressure plate16, on their surfaces. On the other hand, a reverse surface26B of the seal member26is inserted in a deep part of the seal attachment groove25to be disposed to face the bottom portion25A, thereby defining a backpressure chamber28which will be described later.

Further, in the seal member26, a high pressure side (inner circumference side) of the slide surface26A is rectangularly cut out to define a high-pressure-side stepped portion26C. The high-pressure-side stepped portion26C is positioned so as to face the backpressure plate16in a spaced-apart relationship with the backpressure plate16. In other words, the slide surface26A of the seal member26has a front-surface radially inner diameter R1and a front-surface radially outer diameter R2, and the high-pressure-side stepped portion26C is positioned radially inside the front-surface radially inner diameter R1of the seal member26. Compressed air in the orbiting backpressure chamber18is supplied into a space between the high-pressure-side stepped portion26C of the seal member26and the backpressure plate16.

On the other hand, a rectangular cutout portion26D matching the shallow bottom portion25B of the seal attachment groove25is formed on a low pressure side (outer circumference side) of the reverse surface26B of the seal member26. Therefore, the seal member26has a cross section in the form of a crank, and due to the cutout portion26D, the reverse surface26B can be inserted to the bottom portion25A without interference with the shallow bottom portion25B.

A low-pressure-side extension portion26E extending to the outer circumference side relative to the deep groove peripheral wall25C is formed on the low pressure side of the seal member26. The low-pressure-side extension portion26E is positioned radially inside the shallow groove peripheral wall25D. Therefore, the seal member26is fittedly inserted into the seal attachment groove25without interference with the shallow groove peripheral wall25D.

Further, a first gap S1is defined between the seal member26and the deep groove peripheral wall25C, and a second gap S2is defined between the seal member26and the shallow groove peripheral wall25D. The first gap S1is larger than the second gap S2.

Reference numeral27denotes a Y-shaped packing which is a leak prevention means disposed between the seal attachment groove25and the seal member26. The Y-shaped packing27is disposed in the first gap S1between the seal member26and the deep groove peripheral wall25C. The Y-shaped packing27includes two lips portion27A split from the one axial side to the other axial side so as to be V-shaped. The two lips portion27A is open while facing the bottom portion25A of the seal attachment groove25, and its lips respectively contact the seal member26and the deep groove peripheral wall25C. The Y-shaped packing27, together with the bottom portion25A side of the seal attachment groove25and the seal member26, defines the backpressure chamber28in communication with the orbiting backpressure chamber18on the high pressure side. Therefore, the lips portion27A of the Y-shaped packing27receives a pressure from the orbiting backpressure chamber18, and the two lips portion27A is made open by this pressure. In this way, the Y-shaped packing27prevents a pressure of the orbiting backpressure chamber18on the high pressure side from leaking into the low pressure side.

Since the Y-shaped packing27is disposed between the seal member26and the deep groove peripheral wall25C, the backpressure chamber28is kept inside the bottom portion25A of the seal attachment groove25, and does not extend to the outer circumference side beyond the shallow bottom portion25B. Therefore, the slide surface26A of the seal member26always extends toward the low pressure side in the radially outer direction relative to the deep groove peripheral wall25C which serves as a boundary of the low pressure side of the backpressure chamber28.

Here, an effective area of the backpressure side of the seal member26is defined as a difference between the area of the slide surface26A side (backpressure plate16side), on which a pressure from the high pressure side of the seal member26directly acts, and the area of the reverse surface26B side (holder17side). Therefore, the effective area of the backpressure side of the seal member26is an area of an annular portion between the front-surface radially inner diameter R1and the radially intermediate diameter R0.

The booster air compressor in the present embodiment is configured as described above. Next, an operation of this compressor will be described.

When the driving shaft5is driven to rotate by the driving source such as an electric motor, the rotation of the driving shaft5is transmitted to the orbiting scroll8through the orbiting bearing22. Then, the orbiting scroll8starts to perform an orbiting motion about the driving shaft5while being prevented from rotating on its own axis by the auxiliary crank mechanism23.

The compression chambers12defined between the wrap portion2B of the fixed scroll2and the wrap portion9B of the orbiting scroll8become successively smaller from the radially outer side to the radially inner side. The compressor, while drawing compressed air supplied from, for example, a factory pipe through the inlet13, successively compresses the drawn compressed air in the compression chambers12, and then discharges the compressed high pressure air through the outlet14to, for example, an external tank (not shown).

The compressed air which has been further compressed in the compression chambers12is partially introduced through the backpressure introduction tube19into the orbiting backpressure chamber18defined on the reverse surface side of the orbiting scroll8. By this arrangement, even when an excessive thrust load, which pushes the orbiting scroll8away from the fixed scroll2, is generated due to the pressure of the compressed air, it is possible that the orbiting scroll8may be pushed back toward the fixed scroll2side due to the pressure in the orbiting backpressure18, thereby decreasing the influence of the thrust load.

Next, an operation of the seal mechanism24will be described in detail with reference toFIGS. 5 to 6.

First, analysis will be made with regards to a pressure on the slide surface26A side, which acts on the slide surface26A toward the reverse surface26B of the seam member26. An inner pressure P1, which is as high as the pressure in the orbiting backpressure chamber18, acts on the radially inner side of the seal member26relative to the front-surface radially inner diameter R1. On the other hand, an outer pressure P2, which is as low as the pressure in the casing1, acts on the radially outer side of the seal member26relative to the front-surface radially outer diameter R2. The slide surface26A of the seal member26is positioned in the portion having a width a between the front-surface radially inner diameter R1and the front-surface radially outer diameter R2, and the surface26A contacts the backpressure plate16. Therefore, a pressure acting on the slide surface26A (the portion having the width a) of the seal member26has values that vary consecutively from the pressure P1to the pressure P2.

Next, analysis will be made with regards to a pressure on the reverse surface26B side, which acts on the reverse surface26B toward the slide surface26A of the seam member26. The Y-shaped packing27is disposed between the seal member26and the deep groove peripheral wall25C of the seal attachment groove25. Therefore, the high inner pressure P1acts on the radially inner side of the seal member26relative to the radially intermediate diameter R0of the seal attachment groove25. On the other hand, the low outer pressure P2acts on the radially outer side of the seal member26relative to the radially intermediate diameter R0of the seal attachment groove25.

On the high-pressure-side stepped portion26C of the seal member26, both of the pressure P1from the slide surface26A side and the pressure P1from the reverse surface26B side act, and therefore the pressures are balanced out. As a result, in the seal member26, only the portion positioned radially outside the high-pressure-side stepped portion26C is subject to a load generated due to the pressure difference.

A load Ff obtained by integrating the distributed pressures over the portion having the width a acts on the slide surface26A of the seal member26. On the other hand, a load Fb acts on the reverse surface26B side of the seal member26. The load Fb is a resultant force obtained by adding a load obtained by integrating the pressure P1over the portion (the portion of the effective area) having a width b between the front-surface radially inner diameter R1and the radially intermediate diameter R0, and a load obtained by integrating the pressure P2over the portion having a width c between the front-surface radially outer diameter R2and the radially intermediate diameter R0

If the front-surface radially outer diameter R2is equal to or less than the radially intermediate diameter R0(R2=R0or R2<R0), a difference between the load Fb of the reverse surface26B and the load Ff of the slide surface26A cannot be smaller than a difference between the reverse surface26B side load obtained by integrating the pressure P1over the portion having the width b and the slide surface26A side load obtained by integrating the pressures distributed in the range of the pressure p1to the pressure P2. Assuming that the change in the pressure over the portion having the width a is substantially liner, a load obtained by integrating the pressure (P1-P2)/2 acts on the seal member26over the portion having the width b, and therefore the seal member26is pressed from the reverse surface26B toward the slide surface26A.

In the present embodiment, the front-surface radially outer diameter R2is set to be larger than the radially intermediate diameter R0(R2>R0), and the slide surface26A extends to the low pressure side (radially outer side) beyond the deep groove peripheral wall25C. With the portion having the width a extending outwardly, the area receiving a pressure higher than the pressure P2increases on the slide surface26A, while the area receiving the pressure P2(the portion with the width c) increases on the reverse surface26B side. Therefore, the difference between the load Fb on the reverse surface26B and the load Ff on the slide surface26A is reduced, so that it becomes possible to reduce a pressing force of the seal member26according to expansion of the portion with the width C. As a result, it becomes possible to slow down a rate of abrasion of the seal member26.

Further, the low pressure P2is introduced over an extensive area on an outer circumferential surface of the seal member26, and due to the difference between the pressures P1and P2, a load pushing the seal member26toward the radially outer side acts on the seal member26. However, the seal member26is formed into a continuous body without any discontinuity and therefore is configured to be unexpanded without being affected by the pressure difference. Furthermore, because the loads acting radially on the seal member26are balanced on the seal member26, the seal member is not pressed to the deep groove peripheral wall25C and the shallow groove peripheral wall25D of the seal attachment groove25. As a result, an operation of the seal member26is not restrained and no abrasion occurs, and therefore the outer circumferential surface of the seal member26does not suffer from advancing abrasion.

In the present embodiment, the area where the seal member26contacts the backpressure plate (the area of the slide surface26A) is set so as to be larger than the effective area of the backpressure side of the seal member26when the seal member26is in a used state. While the pressure P1on the high pressure side acts on the effective area of the backpressure side of the seal member26, consecutive pressures distributed in the range of the pressure P1on the high pressure side to the pressure P2on the low pressure side acts on the slide surface26A of the seal member26. Therefore, it is possible to reduce increasingly the difference between the load acting on the slide surface26A side and the load acting on the effective area of the backpressure side of the seal member26, as the area of the slide surface26A of the seal member26becomes larger than the effective area of the backpressure chamber28. In this way, it is possible to reduce the pressing force of the seal member26even if a sealed pressure is high. As a result, it becomes possible to decrease a rate of abrasion of the seal member26, and it is therefore possible to extend a lifetime of the seal member26and to improve a reliability and durability thereof.

Further, when the seal member26is in a used state, the slide surface26A of the seal member26extends radially outwardly toward the low pressure side relative to the deep groove peripheral wall25C which is a boundary of the low pressure side of the backpressure chamber28. While the pressure P2of the low pressure side acts on the radially outer side of the reverse surface26B, relative to the radially intermediate diameter R0, of the low-pressure-side extension portion26E of the seal member26which extends to the low pressure side beyond the deep groove peripheral wall25C, the distributed pressures between the pressure P1of the high pressure side and the pressure P2of the low pressure side act on the slide surface26A. Therefore, in the low-pressure-side extension portion26E of the seal member26, the slide surface26A side receives a higher pressure than the reverse surface26B side.

As a result, the low-pressure-side extension portion26E of the seal member26enables the contact area between the slide surface26A of the seal member26and the backpressure plate16to be larger than the effective area of the backpressure side of the seal member26. Therefore, it becomes possible to reduce a difference between the load acting on the slide surface26A side of the seal member26and the load acting on the reverse surface26B side of the seal member26, whereby the pressing force of the seal member26can be reduced.

Further, since the seal member26is formed into a continuous body without any discontinuity around the circumference, even though a pressure difference exists between the inner circumferential surface and outer circumferential surface of the seal member26, the seal member26is not affected by the pressure difference, thereby being prevented from expanding. Further, since radially acting loads are balanced on the seal member26alone, the seal member26is not radially displaced so that the seal member26is not pressed to the deep groove peripheral wall25C and the shallow groove peripheral wall25D of the seal attachment groove25. Therefore, a movement of the seal member26is not restrained by friction between the seal member26and the peripheral walls25C,25D of the seal attachment groove25, and in addition to that, reliability and durability of the seal member26can be improved as the abrasion does not advance.

Further, since the seal member26includes, on the high pressure side of the slide surface26A, the high-pressure-side stepped portion26C facing the backpressure plate16in a spaced-apart relationship to the backpressure plate16, the pressure P1of the high pressure side can act on between the high-pressure-side stepped portion26C and the backpressure plate16. Therefore, it is possible to offset the force acting on the reverse surface26B of the seal member26with the force acting on the high-pressure-side stepped portion26C, so that the effective area of the backpressure side of the seal member26, and therefore the pressing load of the seal member26can be reduced.

Further, the Y-shaped packing27is disposed in the first gap S1between the deep groove peripheral wall25C of the seal attachment groove25and the cutout portion26D of the seal member26. Due to provision of the Y-shaped packing, it is possible to prevent the pressure P1of the high pressure side, which acts on the reverse surface26B of the seal member26, from leaking into the low pressure side.

Further, since the first gap S1is larger than the second gap S2, even if the seal member26is radially displaced, the second gap S2disappears before the first gap S1does. Therefore, the presence of the first gap S1is always ensured, so that the Y-shaped packing disposed in the first gap S1is not compressed to be flattened.

Furthermore, in the present embodiment, each of the backpressure plate16and the holder17may be formed with use of a material in which an alumite treatment is performed on an aluminum material, and the seal member26may be mainly made of polytetrafluoroethylene (PTFE). If the seal member26is mainly made of a polytetrafluoroethylene material having excellent lubricating property and anti-abrasion property, it is possible to further enhance durability and reliability of the seal member26.

FIGS. 7 to 9show a second embodiment of the present invention. This embodiment is characterized in that a seal member is configured to increase a contact area of a slide surface of the seal member with a backpressure plate as an abrasion of the slide surface advances. In the second embodiment, elements corresponding to the above-described elements of the first embodiment will be assigned the same reference numerals as those used in the first embodiment, and the descriptions thereof will not be made in further detail.

Reference numeral31denotes a seal mechanism in the second embodiment, which is disposed between a holder17and a backpressure plate16. The seal mechanism31comprises a seal attachment groove25, a seal member32, a Y-shaped packing27and the like, similarly to the seal mechanism24in the first embodiment.

Reference numeral32denotes an annular seal member fittedly inserted in the seal attachment groove25. Substantially similarly to the seal member26in the first embodiment, the seal member32may be mainly made of a tetrafluoride resin material such as polytetrafluoroethylene (PTFE) which has excellent lubricating property and anti-abrasion property. The seal member32comprises an annular continuous body without any discontinuity around the circumference, and is configured such that radially acting loads thereon are balanced.

In the seal member32, a surface facing the axial direction (front surface) serves as a slide surface32A in sliding contact with the backpressure plate16. The slide surface32A of the seal member32contacts a reverse surface16A serving as a slide surface of the backpressure plate16, on their surfaces. On the other hand, a reverse surface32B of the seal member32is inserted in a deep part of the seal attachment groove25to be disposed to face a bottom portion25A, thereby defining a backpressure chamber28.

Further, in the seal member32, a high pressure side (inner circumference side) of the slide surface32A is rectangularly cut out to define a high-pressure-side stepped portion32C. The high-pressure-side stepped portion32C is positioned so as to face the backpressure plate16in a spaced-apart relationship with the backpressure plate16. On the other hand, a rectangular cutout portion32D matching a shallow bottom portion25B of the seal attachment groove25is formed on a low pressure side (outer circumference side) of the reverse surface32B of the seal member32.

A low-pressure-side extension portion26E extending to an outer circumference side beyond a deep groove peripheral wall25C is formed on a low pressure side of the seal member32. The low-pressure-side extension portion26E is positioned radially inside a shallow groove peripheral wall25D. Further, a first gap S1is defined between the seal member32and the deep groove peripheral wall25C, and a second gap S2is defined between the seal member32and the shallow groove peripheral wall25D. The first gap S1is larger than the second gap S2. A Y-shaped packing27is disposed in the first gap S1.

A chamfered inclined portion32F is formed on the outer circumference side of the seal member32such that the front surface of the seal member32is gradually being spaced apart from the backpressure plate16as tapering from the slide surface32A toward the low pressure side. This inclined portion32F enables a contact area of the slide surface32A with the backpressure portion16to increase due to an abrasion of the slide surface32A. In other words, the slide surface32A of the seal member32has a front-surface radially inner diameter R1and a front-surface radially outer diameter R2, and is configured such that the front-surface radially outer diameter R2increases as the slide surface32A is abrading away.

Next, an operation of the seal mechanism31will be described in detail with reference toFIGS. 7 to 9.FIG. 8shows an initial state of the seal member32which has been just attached.FIGS. 7 and 9each show a state of the used seal member32which has slid relative to the backpressure plate16, and has been adapted to the surroundings.

FIG. 8shows an initial state in which the seal member32before abrading away has been just attached in the seal attachment groove25. In this initial state, the front-surface radially outer diameter R2of the slide surface32A of the seal member32may be, for example, set smaller than an radially intermediate diameter R0. Therefore, a portion having a width a between the front-surface radially inner diameter R1and the front-surface radially outer diameter R2(portion of the slide surface32A) is smaller than a portion having a width b between the front-surface radially inner diameter R1and the radially intermediate diameter R0(portion of an effective area on the reverse surface32B side). In addition, the pressure P1of the effective area on the reverse surface32B side is higher than the pressure on the slide surface32A side. Therefore, the difference between a load Fb on the reverse surface32B and a load Ff on the slide surface32A is large and the seal member32is strongly pressed toward the backpressure plate16. Then, the slide surface32A is rapidly being adapted to the surroundings and its abrasion comparably quickly advances.

FIG. 9shows the seal member32in which the abrasion of the slide surface32A has advanced to a certain degree. In this state, the area of the slide surface32A increases toward the outer circumference side, the width a increases, and the front-surface radially outer diameter R2becomes a little larger than the radially intermediate diameter R0. In this way, when the front-surface radially outer diameter R2becomes larger than the radially intermediate diameter R0, the difference between the load Fb on the reverse surface32B and the load Ff on the slide surface32A decreases, according to increase in the area of the portion with a width C between the front-surface radially outer diameter R2and the radially intermediate diameter R0, as shown in the first embodiment. As a result, the speed at which an abrasion of the seal member32advances is gradually getting slower, since the pressing force of the seal member32becomes smaller compared to that under the initial state.

FIG. 7shows the seal member32in which the abrasion of the slide surface32A has further advanced. In this state, the width a further increases, and the front-surface radially outer diameter R2becomes considerably larger than the radially intermediate diameter R0. Since the difference between the load Fb on the reverse surface32B and the load Ff on the slide surface32A further decreases in this state, the pressing force of the seal member32further decreases, and therefore the speed at which an abrasion of the seal member32advances becomes extremely slow.

The second embodiment configured as mentioned above can bring about the substantially similar effect to the first embodiment. Particularly, the second embodiment is characterized in that the contact area of the seal member32with the backpressure plate16increases due to an abrasion of the slide surface32A of the seal member32. The seal member32includes the inclined portion32F configured such that the front surface of the seal member32is being gradually spaced apart from the backpressure plate16as tapering from the slide surface32A to the low pressure side. Therefore, as the seal member32is abrading away, the area of the slide surface32A of the seal member32can increase in the portion receiving only the pressure P2of the low pressure side on the reverse surface32B side of the seal member32(low-pressure-side extension portion32E). As a result, as an abrasion of the seal member32advances, the pressing force of the seal member32gradually decreases finally to a level of not causing further abrasion of the seal member32. Therefore, it is possible to further extend the lifetime of the seal member32.

Next,FIGS. 10 to 12show a third embodiment of the present invention. The third embodiment is characterized in that a seal member includes, on a portion facing a shallow groove peripheral wall of a seal attachment groove on an outer circumference side of the seal member, a raised portion extending in a direction toward a bottom of the groove. In the third embodiment, elements corresponding to the above-described elements of the first embodiment will be assigned the same reference numerals as those used in the first embodiment, and the descriptions thereof will not be made in further detail.

Reference numeral41denotes a seal mechanism in the third embodiment, which is disposed between a holder17and a backpressure plate16. The seal mechanism41comprises a seal attachment groove25, a seal member42, a Y-shaped packing27and the like, similarly to the seal mechanism24in the first embodiment.

Reference numeral42denotes an annular seal member fittedly inserted in the seal attachment groove25. Substantially similarly to the seal member26in the first embodiment, the seal member42may be mainly made of a tetrafluoride resin material such as polytetrafluoroethylene (PTFE). The seal member42comprises an annular continuous body without any discontinuity around the circumference, and is configured such that radially acting loads thereon are balanced.

Further, substantially similarly to the seal member26in the first embodiment, the seal member42comprises a slide surface42A, a reverse surface42B, a high-pressure-side stepped portion42C, a cutout portion42D, and a low-pressure-side extension portion42E. A first gap S1is defined between the seal member42and a deep groove peripheral wall25C, and a second gap S2is defined between the seal member42and a shallow groove peripheral wall25D. The first gap S1is larger than the second gap S2. A Y-shaped packing27is disposed in the first gap S1.

Further, the seal member42includes a plurality of raised portions42F formed on a portion facing the second gap S2. The raised portions42F extend in the direction toward a bottom of the seal attachment groove25(axial direction). The seal member42further includes gullet portions formed between the adjacent raised portions42F. In other words, the raised portions42F are formed on an outer circumference side of the low-pressure-side extension portion42E of the seal member42, which faces the shallow groove peripheral wall25D of the seal attachment groove25. The raise portions42F are provided around the entire circumference of the seal member42, and surround the outer surface of the seal member42.

The third embodiment configured as mentioned above can bring about the substantially similar effect to the first embodiment. Particularly, the third embodiment is characterized in that the raised portions42F extending in the direction toward the bottom of the groove are formed on the outer circumference side of the low-pressure-side extension portion42E of the seal member42, which faces the second gap S2. Therefore, even if the seal member42is radially displaced, the tips of the raised portions are made abut against the shallow groove peripheral wall25D of the seal attachment groove25so that the presence of the second gap S2can be ensured. Due to provision of the raised portions42F of the seal member42, the pressure P2of the low pressure side can be easily introduced into the outer circumference side of the seal member42. In the low-pressure-side extension portion42E of the seal member42, the reverse surface42B side receives only the pressure P2of the low pressure side, while the slide surface42A side receives pressures between the pressure P1of the high pressure side and the pressure P2of the low pressure side. As a result, in the low-pressure-side extension portion42E of the seal member42, the slide surface42A side receives a higher pressure than the reverse surface42B side, so that the difference between a load Ff acting on the slide surface42A of the seal member42and a load Fb acting on the reverse surface42B of the seal member42can be securely reduced.

In the third embodiment, raised portions42F are provided on the outer surface of the seal member42. However, this does not limit the present invention. In some embodiments, groove-like gullet portions extending in a direction toward a bottom of a shallow groove peripheral wall25D of a seal attachment groove25may be provided. In this case, raised portions may be formed between the adjacent gullet portions, and a pressure of a low pressure side can be introduced into an outer circumference side of the seal member42due to provision of the gullet portions.

In the third embodiment, the raised portions42F and the gullet portions42G are provided to the seal member42which is similar to the seal member26in the first embodiment. However, this does not limit the present invention. In some embodiments, raised portions or gullet portions may be provided to, for example, a seal member which is similar to the seal member32in the second embodiment.

Next,FIG. 13shows a fourth embodiment of the present invention. The fourth embodiment is characterized in that a seal mechanism includes a circular seal attachment groove including an annular outer circumference side and including an inner circumference side with no peripheral wall. In the fourth embodiment, elements corresponding to the above-described elements of the first embodiment will be assigned the same reference numerals as those used in the first embodiment, and the descriptions thereof will not be made in further detail.

Reference numeral51denotes a seal mechanism disposed between a holder17and a backpressure plate16. The seal mechanism51comprises a seal attachment groove52, a seal member26, a Y-shaped packing27and the like, similarly to the seal mechanism24in the first embodiment.

Reference numeral52denotes a seal attachment groove provided to a bottom plate portion17B. The seal attachment groove52comprises a circular concave having an annular outer circumference side and having an inner circumference side with no peripheral wall. The seal attachment groove52is provided on a slide surface of the bottom plate portion17B, with which the portion17B slides on the backpressure plate16, so as to be open to the backpressure plate16. A bottom portion52A having a large depth is formed on the inner circumference side of the seal attachment groove52, and the bottom portion52A is in communication with a compressed-air-containing portion17C. On the other hand, the outer circumference side of the seal attachment groove52is stepped to define a shallow bottom portion52B having a shallow depth. Further, on the low pressure side of the seal attachment groove52, a deep groove peripheral wall52cis formed between the bottom portion52A and the shallow bottom portion52B, and a shallow groove peripheral wall52D is formed between the shallow bottom portion52B and an opening.

The seal member26is fittedly inserted in the seal attachment groove52, and the Y-shaped packing is attached between the seal attachment groove52and the seal member26. By this arrangement, the seal mechanism51airtightly seals an orbiting backpressure chamber18positioned on an inner circumference side of the seal member26from outside.

The fourth embodiment configured as mentioned above can bring about the substantially similar effect to the first embodiment. When high pressure air is always contained in the orbiting backpressure chamber18positioned on the inner circumference side of the seal member26, and low pressure air is contained in the outer circumference side of the seal member26(outside), there is no need for supporting the seal member26on the inner circumference side thereof. Therefore, the forth embodiment with use of the seal attachment groove52without a peripheral wall on the inner circumference side thereof can bring about the effect similar to the first embodiment.

In the seal mechanism51in the forth embodiment, the seal attachment groove52includes the stepped shallow bottom portion52B. However, this does not limit the present invention. Some embodiments may use a seal attachment groove not having a shallow bottom portion, such as a seal attachment groove52′ in a seal mechanism51′ in a modification of the first embodiment shown inFIG. 14. If a rigid seal member26is used, such a seal member26is rarely deformed. Therefore, an embodiment with use of the seal attachment groove52′ as described above can also bring about the effect similar to the first embodiment.

Next,FIG. 15shows a fifth embodiment of the present invention. The fifth embodiment is characterized in that a seal mechanism is disposed between a fixed scroll and an orbiting scroll. In the fifth embodiment, elements corresponding to the above-described elements of the first embodiment will be assigned the same reference numerals as those used in the first embodiment, and the descriptions thereof will not be made in further detail.

Reference numeral61denotes a seal mechanism disposed between a fixed scroll2and an orbiting scroll8. The seal mechanism61comprises a seal attachment groove25, a seal member26, a Y-shaped packing27and the like, similarly to the seal mechanism24in the first embodiment. The seal attachment groove25is provide to the fixed scroll2which is stationary by being fixed to the casing1. The seal attachment groove25is positioned on a side of a slide surface of the fixed scroll2, with which the fixed scroll2slides on the orbiting scroll8, and is provided in an end plate2A, surrounding compression chambers (wrap portion2B).

The seal member26is fittedly inserted in the seal attachment groove25, and the Y-shaped packing27is attached between the seal attachment groove25and the seal member26. By this arrangement, the seal mechanism61airtightly seal the compression chambers12positioned on an inner circumference side of the seal member26from outside.

The fifth embodiment configured as mentioned above can bring about the substantially similar effect to the first embodiment. A particular advantage of the fifth embodiment is that, since the seal mechanism61is disposed in the stationary fixed scroll2, easiness of assembling and productivity can be improved, compared to an fluid machine in which the seal mechanism is disposed in the orbiting scroll8to which an orbiting bearing22and the like are attached.

In the fifth embodiment, the seal mechanism61similar to the seal mechanism24in the first embodiment is disposed between the fixed scroll2and the orbiting scroll8. However, this does not limit the present invention. In some embodiments, for example, a seal mechanism similar to the seal mechanism31or41in the second or third embodiment may be disposed in a fixed scroll2and a orbiting scroll8.

In the fifth embodiment, the orbiting backpressure chamber18is formed on a reverse surface side of the orbiting scroll8. In some embodiments, as in a second modification shown inFIGS. 16 and 17, a seal mechanism71may be disposed between a fixed scroll2and an orbiting scroll8in a booster compressor or a scroll expander which does not have an orbiting backpressure chamber. In this case, an orbiting bearing22and an auxiliary crank mechanism23may be attached on a reverse surface side of the orbiting scroll8. The seal mechanism71may be, for example, similar to any one of the seal mechanisms24,31and41in the first, second and third embodiments.

When a scroll type fluid machine is used as a vacuum pump, for example, a seal mechanism81, which has a reverse configuration to the seal mechanism24in the first embodiment in terms of inner circumference side and outer circumference side, may be disposed in a fixed scroll2and an orbiting scroll8, as in a third modification shown inFIG. 18.

In this case, sealed chambers12defined between a wrap portion2B of the fixed scroll2and a wrap portion9B of the orbiting scroll8contains air having lower pressure than that of outside. Therefore, although a seal attachment groove82, similarly to the seal attachment groove25, includes a bottom portion82A, a shallow bottom portion82B, a deep groove peripheral wall82C and a shallow groove peripheral wall82D, the shallow bottom portion82B, the deep groove peripheral wall82C and the shallow groove peripheral wall82D are disposed on an inner circumference side of the seal attachment groove82.

The seal member83, similarly to the seal member26, comprises a slide surface83A, a reverse surface83B, a high-pressure-side stepped portion83C, a cutout portion83D and a low-pressure-side extension portion83E. However, the high-pressure-side stepped portion83C is provided on an outer circumference side of the seal member83, and the cutout portion83D and the low-pressure-side extension portion83E are provided on an inner circumference side of the seal member83. A Y-shaped packing84is attached between the inner circumference side of the seal member83and the deep groove peripheral wall82C of the seal attachment groove82.

In the embodiments discussed above, the Y-shaped packing27or84having a Y-shaped cross section is used as a leak prevention means. In some embodiments, a V-shaped packing having a V-shaped cross section or a U-shaped packing having a U-shaped cross section may be used. In other embodiments, a leak prevention means may comprise an O-ring attached to a cutout portion provided on a bottom portion or a peripheral wall of a seal attachment groove.

In the embodiments discussed above, the seal members26,32,42and83respectively include the high-pressure-side stepped portions26C,32C,42C and83C. In some embodiments, a high-pressure-side stepped portion may not be provided, and a seal member may have a L-shaped cross section without a high-pressure-side stepped portion.

In the embodiments discussed above, the seal members26,32,42and83are formed using a material mainly made of PTFE. However, in the present invention, a material used for a seal member is not limited to this kind. In some embodiments, a seal member may be formed using, for example, a resin composite made of a material other than PTFE.

In the embodiments discussed above, the fixed scroll2, the orbiting scroll8, the backpressure plate16and the holder17are formed using a member in which an alumite treatment is performed on an aluminum material. In some embodiments, a fixed scroll, an orbiting scroll, a backpressure plate and a holder may be formed using another material.

In the first to fourth embodiments discussed above, the seal attachment grooves25,25,52and52′ are provided on the holder17on the casing1side, not on the backpressure plate16on the orbiting scroll8side. However, this does not limit the present invention. In some embodiments, for example, a seal attachment groove may be provide on a backpressure plate16, and a seal member fittedly inserted in the seal attachment groove may be made in sliding contact with a planate slide surface of the holder17.

In the fifth embodiment discussed above, the seal attachment groove25,82is provided on the end plate2A of the fixed scroll2, not on the end plate9A of the orbiting scroll8. However, this does not limit the present invention. In some embodiments, for example, a seal attachment groove may be provided on an end plate9A of an orbiting scroll8, and a seal member fittedly inserted in the seal attachment groove may be made in sliding contact with a planate end plate of a fixed scroll2.

Although the embodiments have been discussed taking as an example the scroll type fluid machine in which the orbiting scroll8performs an orbiting motion to the fixed scroll2fixed to the casing1for better understanding of the present invention, it should be understood that the present invention is not limited to these embodiments. For example, the present invention may be employed in a two-scrolls-rotation-type scroll fluid machine in which two scrolls disposed so as to face each other are respectively driven to rotate, as disclosed in Japanese Patent Publication H09-133087.

Although the embodiments have been discussed taking a scroll compressor, a scroll expander, a vacuum pump or others as an example of a scroll type fluid machine, the present invention is not limited to these embodiments and may be employed in more wide-range machinery including a refrigerant compressor or others.

Although the embodiments employing the seal mechanisms24,31,41,51,51′,61,71and81as a seal system for a scroll type fluid machine have been discussed above, the present invention is not limited to these embodiments and may be employed in more wide-range machinery or others. For example, the present invention may be employed in any machinery in which, while a sliding motion is performed between two components facing each other, a sealed chamber or the like containing fluid with a pressure different from an outside pressure is defined between the two components.

As described above, according to the embodiments of the present invention, the seal member is configured such that, when the seal member is in a used state, the contact area of the slide surface of the seal member with the member on the one side is large compared to the effective area of the backpressure side of the seal member which pushes the seal member toward the member on the one side. The term “effective area of the backpressure side of the seal member” is used to denote a difference between areas of the one side member side and the other side member side on which the pressure of the high pressure side of the seal member directly acts. The term “used state” is used to denote a state in which the seal member has slid to the member on the one side and has adapted to the surroundings. Therefore, “used state” includes a state in which the contact area of the slide surface of the seal member with the member on the one side may be equal to or smaller than the effective area of the backpressure side of the seal member at first, but the contact area of the slide surface of the seal member with the member on the one side becomes larger than the effective area of the backpressure side of the seal member after the seal member has abraded and has adapted to the surroundings. Since the pressure of the high pressure side acts on the effective area of the backpressure side of the seal member, the load (pressing load) obtained by integrating the pressure of the high pressure side acts on the effective area on the reverse surface side of the seal member. On the other hand, since the pressures (distributed pressures) consecutively distributed in the range of the low pressure side pressure to the high pressure side pressure act on the contact area of the seal member with the member on the one side, the load obtained by integrating the distributed pressures acts on the contact area on the slide surface side of the seal member. Because the contact area of the slide surface of the seal member with the member on the one side is large compared to the effective area of the backpressure side of the seal member, it is possible to reduce a difference between the load from the pressure acting on the slide surface of the seal member and the load from the pressure acting on the reverse surface of the seal member. As a result, it becomes possible to reduce the pressing force of the seal member even when a pressure of sealed fluid is high. Therefore it becomes possible to decrease a rate of abrasion of the seal member and to extend the lifetime of the seal member, thereby improving reliability and durability thereof.

When the seal member is in a used state, the slide surface of the seal member extends radially toward the low pressure side relative to the boundary of the low pressure side of the backpressure chamber. In the low-pressure-side extension portion of the seal member, which extends toward the low pressure side beyond the boundary of the low pressure side of the backpressure chamber, while the pressure of the low pressure side acts on the reverse side thereof, the pressures distributed between the low pressure side pressure and the high pressure side pressure act on the slide surface (contact surface) thereof. Therefore, in the low-pressure-side extension portion of the seal member, the slide surface side receives a higher pressure than the reverse surface side does. Due to the provision of the low-pressure-side extension portion of the seal member, the contact area of the slide surface of the seal member with the member on the one side becomes large compared to the effective area of the backpressure side of the seal member. Therefore, it is possible to reduce the difference between the load from the pressure acting on the slide surface of the seal member and the load from the pressure acting on the reverse surface of the seal member. As a result, it becomes possible to reduce the pressing force of the seal member even when a pressure of sealed air is high. Therefore it becomes possible to decrease a rate of abrasion of the seal member and to extend the lifetime of the seal member, thereby improving reliability and durability.

Since the seal member comprises a continuous body without any discontinuity around the circumference, even though a pressure difference exists between the inner surface and the outer surface of the seal member, the seal member is not affected by the pressure difference, and is prevented from expanding. In addition, since radially acting loads are balanced on the seal member alone, the seal member is not radially displaced, and is thereby prevented from being pushed against the peripheral wall of the groove. Therefore, a movement of the seal member is not restrained by friction between the seal member and the peripheral wall of the groove, and there is no advancement of abrasion, whereby a reliability and durability of the seal member is improved.

Since the seal member is configured such that loads acting in a direction (radial direction) perpendicular to the peripheral wall of the groove are balanced thereon, the seal member is not radially displaced, thereby being prevented from being pushed against the peripheral wall of the groove. Therefore, movement of the seal member is not restrained by friction between the seal member and the peripheral wall of the groove, and there is no advancement of abrasion, whereby a reliability and durability of the seal member can be improved.

When the seal member is configured such that the contact area with the member on the one side increases due to an abrasion of the slide surface of the seal member, as shown in the second embodiment, the area of the slide surface of the seal member can be increased in the portion in which only the pressure of the low pressure side acts on the reverse surface side of the seal member, for example, as the seal member is abrading away. As abrasion of the seal member advances, the pressing load of the seal member can be reduced. Therefore, it is possible to reduce the pressing load of the seal member to such a degree as to prevent further abrasion, and therefore to further extend the lifetime of the seal member.

In this case, since the seal member includes a portion which is gradually being spaced apart from the member on the one side as tapering from the slide surface to the low pressure side, it is possible that, due to abrasion of the slide surface of the seal member, the area of the slide surface of the seal member can be increased in the portion in which only the pressure of the low pressure side acts on the reverse surface side of the seal member. Therefore, it is possible to reduce the pressing load of the seal member as abrasion of the seal member advances, and therefore to further extend the lifetime of the seal member.

According to the embodiments discussed above, the seal member includes, on the high pressure side of the slide surface, the high-pressure-side stepped portion which faces the member on the one side in a spaced-apart relationship with the member on the one side. By this arrangement, the pressure of the high pressure side acts on between the high-pressure-side stepped portion and the member on the one side. Therefore, the force acting on the reverse surface of the seal member can be offset with the force acting on the high-pressure-side stepped portion, so that it is possible to reduce the effective area of the backpressure side of the seal member, and thereby to reduce the pressing load of the seal member.

In the embodiments discussed above, since a leak prevention means is disposed between the deep groove peripheral wall on the low pressure side of the groove and the cutout portion of the seal member, the high pressure side pressure acting on the reverse surface of the seal member can be prevented from leaking into the low pressure side due to the leak prevention means.

In the embodiments discussed above, the first gap defined between the seal member and the deep groove peripheral wall on the low pressure side of the groove is larger than the second gap defined between the seal member and the shallow peripheral wall of the low pressure side of the groove. By this arrangement, even if the seal member is radially displaced, the second gap disappears before the first gap disappears. Therefore, the presence of the first gap can be always ensured, so that any packing disposed in the first gap as a leak prevention means can be prevented from being compressed to become flattened.

In the embodiments discussed above, since the leak prevention means is disposed in the first gap, the high pressure side pressure acting on the reverse surface of the seal member can be prevented from leaking into the low pressure side due to the provision of the leak prevention means.

If a raised or gullet portion extending toward the bottom of the groove is formed on the portion of the seal member which faces the second gap, as shown in the third embodiment, the pressure of the low pressure side can be easily introduced through the second gap due to the provision of the raised or gullet portion of the seal member.

According to the above-discussed embodiments of present invention, either of the member on the one side or the member on the other side can be configured to perform an orbiting motion. Therefore, a seal system according to the present invention can be employed in a scroll type fluid machine in which, for example, two scrolls overlap and an orbiting motion is performed therebetween.

In the embodiments discussed above, the member on the one side and the member on the other side are formed using a member in which an alumite treatment is performed on an aluminum material, and the seal member is mainly made of polytetrafluoroethylene. Since the seal member is mainly made of a polytetrafluoroethylene material which has excellent lubricating properties and anti-abrasion properties, reliability and durability of the seal member can be further improved.

In a scroll type fluid machine according to the present invention, when the seal member is in a used state, the above-mentioned effect of the seal member can be obtained, since the seal member is configured such that the slide surface of the seal member extends radially toward the low pressure side beyond the boundary of the low pressure side of the backpressure chamber. Therefore, even when a significant pressure difference exists between the outside and the sealed chamber between the two scrolls, it is possible to seal the sealed chamber from the outside with use of the seal mechanism, and also it is possible to maintain the excellent seal function of the seal mechanism over a long period of time.

In the fifth embodiment, a scroll on the one side is an orbiting scroll which performs an orbiting motion, and a scroll on the other side is a stationary fixed scroll. Therefore, the seal mechanism can be provided to the stationary fixed scroll, and ease of assembly and productivity can be improved as compared to a scroll type fluid machine in which a seal mechanism is provided to an orbiting scroll to which an orbiting bearing and the like are attached.

Since the seal member is configured such that the slide surface of the seal member extends radially toward the low pressure side beyond the boundary of the low pressure side of the backpressure chamber when the seal member is in a used state, an effect similar to the above-mentioned scroll type fluid machine can be obtained. Therefore, even when a significant pressure difference exists between the orbiting backpressure chamber and the outside, it is possible to seal the orbiting backpressure chamber from the outside by using the seal mechanism, and also it is possible to maintain the excellent seal function of the seal mechanism over a long period of time.

When the seal member is configured such that the contact area with the orbiting scroll increases due to abrasion of the slide surface of the seal member as shown in the second embodiment, the area of the slide surface of the seal member can be increased in the portion in which only the pressure of the low pressure side acts on the reverse surface side of the seal member, for example, as the seal member is abrading away. As the abrasion of the seal member advances, the pressing load of the seal member can be reduced. Therefore, it is possible to reduce the pressing load of the seal member to such a degree that no further abrasion is caused, and therefore to further extend the lifetime of the seal member.

In this case, since the seal member includes a portion which is gradually spaced apart from the member on the one side as tapering from the slide surface to the low pressure side, it is possible that, due to abrasion of the slide surface of the seal member, the area of the slide surface of the seal member can be increased in the portion in which only the pressure of the low pressure side acts on the reverse surface side of the seal member. Therefore, it is possible to reduce the pressing load of the seal member as an abrasion of the seal member advances, and therefore to further extend the lifetime of the seal member.

In a scroll type fluid machine according to the present invention, the seal member includes, on the high pressure side of the slide surface, the high-pressure-side stepped portion which faces the member on the one side in a spaced-apart relationship with the member on the one side. By this arrangement, the pressure of the high pressure side acts on between the high-pressure-side stepped portion and the member on the one side. Therefore, the force acting on the reverse surface of the seal member can be offset with the force acting on the high-pressure-side stepped portion, so that it is possible to reduce the effective area of the backpressure side of the seal member, and thereby to reduce the pressing load of the seal member.

Since the leak prevention means is disposed between the deep groove peripheral wall on the low pressure side of the groove and the cutout portion of the seal member, the high pressure side pressure acting on the reverse surface of the seal member can be prevented from leaking into the low pressure side due to the provision of the leak prevention means.

The first gap defined between the seal member and the deep groove peripheral wall on the low pressure side of the groove is larger than the second gap defined between the seal member and the shallow peripheral wall on the low pressure side of the groove. By this arrangement, even if the seal member is radially displaced, the second gap disappears before the first gap does. Therefore, the presence of the first gap can be always ensured, and even when the high-pressure-side stepped portion of the seal member is formed to extend as high as near the first gap for example, the effective area of the backpressure side of the seal member can be securely obtained so that it is possible to press the seal member against the member on the one side.

In a scroll type fluid machine according to the present invention, the orbiting scroll and the fixed scroll are formed using a member in which an alumite treatment is performed on an aluminum material, and the seal member is mainly made of polytetrafluoroethylene. Since the seal member is mainly made of a polytetrafluoroethylene material which has excellent lubricating properties and anti-abrasion properties, reliability and durability of the seal member can be further improved.

The present application claims priority under 35 U.S.C. section 119 to Japanese Patent Application No. 2007-50577, filed on Feb. 28, 2007. The entire disclosure of Japanese Patent Application No. 2007-50577, filed on Feb. 28, 2006 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.

The Japanese Patent Application Public Disclosures No. 2005-61304, 2004-301093, H01-250675 are incorporated herein by reference in its entirety.