Scroll compressor having a supply passage connecting the back pressure chamber to discharge pressure region and passing a clearance at a sliding portion

A scroll type compressor includes a housing defining a discharge pressure region, a fixed scroll member having a fixed base plate and a fixed scroll wall, a movable scroll member having a movable base plate and a movable scroll wall, a fixed wall slidably supporting the movable scroll member, a back pressure chamber defined on a back surface side of the movable base plate. A supply passage connects the back pressure chamber to the discharge pressure region and passes through a sliding portion between the movable scroll member and the fixed wall. A clearance at the sliding portion varies in response to a position of the movable scroll member in a direction in which the movable scroll member approaches to or leaves from the fixed wall, whereby cross-sectional area of the clearance where gas passes is varied to adjust pressure in the back pressure chamber.

BACKGROUND OF THE INVENTION

The present invention relates to a scroll type compressor for compressing refrigerant, which is a part of a refrigerant circuit of an air conditioner.

In such a scroll type compressor, the housing includes a fixed scroll member, which has a fixed base plate and a fixed scroll wall that extends from the fixed base plate, and a movable scroll member, which has a movable base plate and a movable scroll wall that extends from the movable base plate and engages with the fixed scroll wall. By the orbital motion of the movable scroll member with the self-rotation thereof being blocked, compression chambers defined between the fixed scroll wall and the movable scroll wall move radially and inwardly to progressively reduce their volumes, thus compressing refrigerant gas.

Recently, carbon dioxide has generally been employed as refrigerant for the refrigerant circuit. Pressure in the refrigerant circuit when employing carbon dioxide as refrigerant is higher than that when employing fluorocarbon as refrigerant. Accordingly, in a scroll type compressor, unusually large thrust force is applied to the movable scroll member based upon the high pressure in the compression chamber. Then, the movable scroll member slides under the hard condition, and durability of the scroll type compressor is deteriorated.

In order to solve such problems, according to pages 4 and 5, and FIG. 1 of Unexamined Japanese Patent Publication No. 2000-249086, the movable scroll member forms a recess on its back surface of the movable base plate, and the recess is closed by a fixed wall on the back surface side provided in the housing, thus defining a back pressure chamber. The compression chamber during volume-reducing process is in communication with the back pressure chamber through a supply passage. High-pressure refrigerant gas is introduced from the compression chamber into the back pressure chamber through the supply passage. In the movable scroll member, a check valve is arranged in the supply passage for blocking the refrigerant gas from back-flowing from the back pressure chamber to the compression chamber.

Accordingly, the pressure in the back pressure chamber applies back pressure force, which opposes thrust force based upon the pressure in the compression chamber, to the movable scroll member. Thus, sliding resistance is reduced between the movable base plate of the movable scroll member and the fixed wall on the back surface side, on which the back surface of the movable base plate slides.

The pressure in the back pressure chamber, that is, the back pressure force applied to the movable scroll member, is appropriately adjusted so that the clearance (passing cross-sectional area of the refrigerant gas) between the movable base plate of the movable scroll member and the fixed wall on the back surface side varies. In other words, for example, as the pressure in the compression chamber rises, the thrust force applied to the movable scroll member increases, with the result of the minimum (zero) clearance between the movable base plate and the fixed wall on the back surface side. Accordingly, the refrigerant gas is blocked from being bled from the back pressure chamber to the suction pressure region through the clearance, and the pressure in the back pressure chamber, that is, the back pressure force applied to the movable scroll member tends to increase.

On the contrary, as the pressure in the compression chamber falls, the thrust force applied to the movable scroll member decreases, with the result of the increased clearance between the movable base plate and the fixed wall on the back surface side. Accordingly, the amount of refrigerant gas bled from the back pressure chamber to the suction pressure region through the clearance increases, and the pressure in the back pressure chamber, that is, the back pressure force applied to the movable scroll member tends to decrease.

Then, the valve-opening operation of the check valve bleeds the refrigerant gas in the back pressure chamber to the suction pressure region before the high-pressure refrigerant gas in the compression chamber is bled to the back pressure chamber. Accordingly, the movable scroll member instantaneously contacts the fixed wall on the back surface side with its movable base plate by the thrust force, so that the high-pressure refrigerant gas in the compression chamber, that is, the refrigerant gas that has finished its compression work is prevented from uselessly flowing out to the suction pressure region through the supply passage and the back pressure chamber. This leads to improved efficiency of the scroll type compressor.

In the Unexamined Japanese Patent Publication No. 2000-249086, in addition to the clearance (a portion that functions as a valve) between the movable base plate and the fixed wall on the back surface side, the check valve needs to be arranged in the supply passage in the movable scroll member, therefore, there has particularly been a problem that it needs much effort to assemble the check valve to the movable scroll member. That is, in the Unexamined Japanese Patent Publication No. 2000-249086 with the complicated valve structure for adjusting the back pressure, there has been a problem that it needs much cost and work for manufacturing a scroll type compressor. Therefore, there is a need for providing a scroll type compressor that has a simple valve structure for adjusting back pressure force.

SUMMARY OF THE INVENTION

In accordance with the present invention, a scroll type compressor comprising a housing, a fixed scroll member, a movable scroll member, a first fixed wall, a back pressure chamber, and a supply passage. The housing defines a discharge pressure region. The fixed scroll member has a fixed base plate and a fixed scroll wall extending from a surface of the fixed base plate. The movable scroll member has a movable base plate and a movable scroll wall extending from a surface of the movable base plate. The movable scroll wall is engaged with the fixed scroll wall. The fixed scroll member and the movable scroll member are arranged in the housing and define therebetween a compression chamber, which moves radially and inwardly to progressively reduce the volume of the compression chamber for compressing gas by orbital motion of the movable scroll member. The first fixed wall is provided in the housing for slidably supporting a surface of the movable scroll member. The back pressure chamber is defined on a back surface side of the movable base plate in the housing. The supply passage connects the back pressure chamber to the discharge pressure region and passes through a sliding portion between the movable scroll member and the first fixed wall, wherein a clearance at the sliding portion varies in response to a position of the movable scroll member in a direction in which the movable scroll member approaches to or leaves from the first fixed wall, whereby cross-sectional area of the clearance where the gas passes is varied to adjust pressure in the back pressure chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment in which a scroll type compressor according to the present invention is applied to a motor compressor for use in a refrigerant circuit of a vehicle air conditioner will now be described. It is noted that refrigerant for the refrigerant circuit employs carbon dioxide.

As shown inFIG. 1, the motor compressor has a housing11, which is made by fixedly connecting a first housing component12with a second housing component13. The first housing component12has a cylindrical shape that has a bottom on the left side inFIG. 1. The second housing component13has a cylindrical shape that has a bottom on the right side inFIG. 1.

The first housing component12has a cylindrical shaft support portion12a, which is integrally formed on the bottom center of the inner wall surface of the first housing component12. The first housing component12fixedly accommodates a shaft support member14at the opening end thereof. The shaft support member14includes a cylindrical portion15at the center, which forms therein a hole15a, and a flange-like disc-shaped portion or a second fixed wall16, which is formed at the right end of the cylindrical portion15inFIG. 1.

The first housing component12accommodates a rotary shaft18. The rotary shaft18is rotatably supported at its left end by a bearing19, which is placed in the shaft support portion12a, and is accommodated and rotatably supported at its right end in the hole15aof the cylindrical portion15of the shaft support member14by a bearing20.

The housing11forms therein a motor chamber22in a region at the left side inFIG. 1with respect to the shaft support member14. In the motor chamber22, a stator25is fixed to the inner cylindrical surface of the first housing component12, and a rotor26is secured to the rotary shaft18and located radially inside the stator25. The stator25and the rotor26cooperate to form an electric motor. Accordingly, as the stator25is externally supplied with electric current, the rotor26and the rotary shaft18are integrally rotated.

A fixed scroll member31is accommodated in the first housing component12and located on the right side with respect to the shaft support member14inFIG. 1. The fixed scroll member31has a disc-shaped fixed base plate32. A cylindrical outer peripheral wall33extends from the outermost peripheral portion of a front surface32aof the fixed base plate32. A fixed scroll wall34extends from the radially inner portion of the front surface32aof the fixed base plate32with respect to the outer peripheral wall33. A tip seal35is provided on the distal end surface of the fixed scroll wall34. The fixed scroll member31is fixedly connected at the end surface of the outer peripheral wall33to the outermost peripheral portion of the disc-shaped portion16of the shaft support member14.

A crankshaft36is formed on the right end surface of the rotary shaft18and accommodated in the right side of the shaft support member14and is offset from the axis L of the rotary shaft18. A bushing37is fixedly fitted around the crankshaft36. A bearing49is supported on the bushing37. A movable scroll member38is supported on the bearing49. A balancer37ais provided on one end of the bushing37on the side of the bearing20. The balancer37areduces rotational imbalance of the rotary shaft18due to the offset arrangement of the movable scroll member38around the axis L.

The movable scroll member38has a disc-shaped movable base plate40and a movable scroll wall41that extends from a front surface40aof the movable base plate40toward the fixed base plate32. A tip seal44is provided on the distal end surface of the movable scroll wall41. The movable scroll member38has a boss43that extends from the center of a back surface40bof the movable base plate40. The boss43is fitted around the bearing49on the bushing37. The movable base plate40slidably contacts the back surface16aof the disc-shaped portion16(or a second fixed wall) of the shaft support member14at its outer peripheral portion of the back surface40b.

The fixed scroll member31and the movable scroll member38are engaged with each other by their scroll walls34,41, and slidably contact at their end surfaces of the scroll walls34,41with the base plates40,32of the opposing scroll members38,31, respectively. Accordingly, The fixed scroll member31and the movable scroll member38define therebetween compression chambers47by their base plates32,40and scroll walls34,41. Incidentally, in the movable and fixed scroll members38,31, “front” is the facing side of the compression chambers47and “back” is the opposite side of the compression chambers47.

A plurality of self-rotation blocking mechanisms48(only one of them shown inFIG. 1) are provided between the front surface40aof the movable base plate40of the movable scroll member38and the front surface32aof the fixed base plate32of the fixed scroll member31. Each of the self-rotation blocking mechanisms48includes a pair of pins48a,48b, and a ring48c. One pin48ais fixed to the outermost peripheral portion of the front surface40ain the movable base plate40. The other pin48bis fixed to the outer peripheral portion (which is inside the outer peripheral wall32) of the front surface32aof the fixed base plate32. The ring48cis located outside the pins48a,48bto prevent the pins48a,48bfrom being radially spaced away from each other.

The outer peripheral wall33of the fixed scroll member31and the outermost peripheral portion of the movable scroll wall41of the movable scroll member38define therebetween a suction chamber51. The outer peripheral portion of the disc-shaped portion16of the shaft support member14forms therein a suction port39that connects the suction chamber51to the motor chamber22. The first housing component12forms therein an inlet50that communicates with the motor chamber22. An external conduit that connects with the outlet of an evaporator of an external refrigerant circuit (not shown) is connected to the inlet50. Accordingly, low-pressure refrigerant gas from the external refrigerant circuit is introduced into the suction chamber51through the inlet50, the motor chamber22, and the suction port39.

The second housing component13and the fixed scroll member31define therebetween a discharge chamber52in the housing11. The fixed scroll member31forms a discharge port31a at the center of the fixed base plate32thereof. In the discharge chamber52, a discharge valve58made of a flapper valve is attached to the back surface32bof the fixed base plate32of the fixed scroll member31. The innermost compression chamber47communicates with the discharge chamber52through the discharge port31a. The second housing component13forms therein an outlet53that communicates with the discharge chamber52.

In the discharge chamber52, a separation pipe68is attached to the opening of the outlet53. The separation pipe68, for example, prevents lubricating oil (refrigerating machine oil) in the discharge chamber52from flowing to the outlet53along the inner wall surface of the discharge chamber52, thus functioning as a kind of oil separator. An external conduit, which connects with the inlet of a gas cooler of the external refrigerant circuit (not shown), is connected to the outlet53outside the second housing component13. Accordingly, the refrigerant gas in the discharge chamber52is bled to the external refrigerant circuit through the separation pipe68and the outlet53.

As the rotary shaft18is rotated, the movable scroll member38is orbited around the axis (the axis L of the rotary shaft18) of the fixed scroll member31through the crankshaft36. At the same time, the self-rotation blocking mechanism48blocks the self-rotating motion of the movable scroll member38, and only the orbital motion thereof is permitted. By the orbital motion of the movable scroll member38, the compression chambers47progressively reduce their volumes as they move radially and inwardly from the outer peripheral side of the scroll walls34,41of the scroll members31,38toward the center thereof, thus compressing the low-pressure refrigerant gas, which is introduced into the compression chamber47from the suction chamber51. The high-pressure refrigerant gas, which has been compressed, is discharged from the innermost compression chamber47to the discharge chamber52through the discharge port31aby pushing away the discharge valve58.

The adjustment function for the back pressure force applied to the movable scroll member38will now be described.

As shown inFIGS. 2 and 3, in the movable base plate40of the movable scroll member38, an annular recess55is recessed on the outer peripheral portion of the back surface40bin the annular region along the outline circle of the movable base plate40. The annular recess55is closed by the back surface16aof the disc-shaped portion16of the shaft support member14. Accordingly, the back surface40bof the movable base plate40and the back surface16aof the disc-shaped portion16of the shaft support member14, which form therebetween an inner space of the annular recess55that is closed by the disc-shaped portion16, define a back pressure chamber56.

As shown inFIG. 2, in the shaft support member14, an inner tip seal66is provided radially inward with respect to the back pressure chamber56on the back surface16aof the disc-shaped portion16. In the movable scroll member38, an outer tip seal67is provided radially outward with respect to the back pressure chamber56on the back surface40bof the movable base plate40. The inner tip seal66slidably contacts the back surface40bof the movable base plate40, and the outer tip seal67slidably contacts the back surface16aof the disc-shaped portion16of the shaft support member14, so that the back pressure chamber56is sealed from the ambient atmosphere.

The shaft support member14forms therein a bleed passage57that coordinates with the back pressure chamber56. The bleed passage57opens at its one end (an opening57a) at the back surface16aof the disc-shaped portion16of the shaft support member14to communicate with the back pressure chamber56, and opens at its other end (an opening57b) into the hole15aof the cylindrical portion15of the shaft support member14. The hole15aof the cylindrical portion15communicates with the motor chamber22(shown inFIG. 1) to have the same atmospheric pressure as the motor chamber22, that is, the hole15ais a part of a suction pressure region. In the bleed passage57, a fixed throttle57cis provided between the opening57band the hole15a.

In the movable scroll member38, a movable passage59is formed around the lowermost portion of the movable base plate40to coordinate with the back pressure chamber56. The movable passage59opens at its one end (an opening59a) into the back pressure chamber56, and opens at its other end (an opening59b) at the front surface40aof the movable base plate40. In the fixed scroll member31, a fixed passage60is formed around the lowermost portion of the fixed base plate32to coordinate with the movable passage59.

In the fixed base plate32of the fixed scroll member31, a first fixed wall69, which is formed to face the front surface40aof the movable base plate40, is located radially inside the outer peripheral wall33and radially outside the fixed scroll wall34around the lowermost portion of the fixed base plate32. That is, the first fixed wall69is provided at a portion of the front surface32aof the fixed base plate32that is different from the fixed scroll wall34. An end surface69aof the first fixed wall69and the front surface40aof the movable base plate40slidably contact each other (a sliding portion between the movable scroll member38and the first fixed wall69).

The fixed passage60extends through the first fixed wall69from the fixed base plate32toward the movable base plate40. The fixed passage60opens at its one end (an opening60a) on the end surface69aof the first fixed wall69, and opens at its other end (an opening60b) around the lowermost portion of the back surface32bof the fixed base plate32, that is, around the lowermost portion in the discharge chamber52.

The lubricating oil, which is separated from the refrigerant gas by the separation pipe68, drops to be reserved around the lowermost portion of the discharge chamber52. That is, the region around the lowermost portion in the discharge chamber52is regarded as a reservoir space52afor reserving the lubricating oil that is separated by the separation pipe68. In the reservoir space52a, a filter61is provided at the opening60bof the fixed passage60on the back surface32bof the fixed base plate32of the fixed scroll member31. The filter61is to remove foreign substances from the lubricating oil that flows from the reservoir space52ato the fixed passage60.

On the end surface69aof the first fixed wall69of the fixed scroll member31, a communication recess62is formed around the opening60aof the fixed passage60. The communication recess62has an annular shape that extends along a locus that the opening59bof the movable passage59tracks by the orbital motion of the movable scroll member38. Accordingly, the opening59bof the movable passage59constantly faces the communication recess62even if the movable scroll member38is located at any orbital position. The fixed passage60, the communication recess62and the movable passage59cooperate to form a supply passage that connects the discharge chamber or a discharge pressure region52(the reservoir space52a) to the back pressure chamber56.

On the end surface69aof the first fixed wall69of the fixed scroll member31, a tip seal63is placed around the communication recess62to slidably contact the front surface40aof the movable base plate40of the movable scroll member38. The communication recess62and the opening59bof the movable passage59are in communication with each other inside the tip seal63, that is, in a state where they are sealed by the tip seal63from the ambient atmosphere. This leads to prevented leakage of high-pressure refrigerant gas from the supply passage, that is, prevented decrease in efficiency of the motor compressor.

On the end surface69aof the first fixed wall69of the fixed scroll member31, a region around the opening60aof the fixed passage60and surrounded by the communication recess62functions as a valve seat64. On the end surface69aof the first fixed wall69, a region around the opening59bof the movable passage59and facing the valve seat64functions as a valve portion65.

As the movable scroll member38(the movable base plate40) moves away from the fixed scroll member31(the first fixed wall69) with respect to the direction along the axis L of the rotary shaft18, the valve portion65leaves from the valve seat64to increase the clearance therebetween. On the contrary, as the movable scroll member38moves to approach the fixed scroll member31, the valve portion65approaches the valve seat64to reduce the clearance therebetween.

As the pressure in the discharge chamber52rises by starting the operation of the motor compressor, the high-pressure refrigerant gas in the discharge chamber52is introduced into the back pressure chamber56through the fixed passage60, the communication recess62, and the movable passage59. The refrigerant gas in the back pressure chamber56is bled to the motor chamber22through the bleed passage57and the hole15a. The pressure in the back pressure chamber56is determined based upon the balance between the amount of high-pressure refrigerant gas from the discharge chamber52into the back pressure chamber56and the amount of refrigerant gas bled through the bleed passage57.

The back pressure force is applied to the movable scroll member38based upon the pressure in the back pressure chamber56to urge the movable scroll member38toward the fixed scroll member31in the direction along the axis L. The thrust force is applied to the movable scroll member38based upon the pressure in the compression chamber47in the direction away from the fixed scroll member31along the axis L. Thus, in response to the balance between the back pressure force and the thrust force, a position of the movable scroll member38relative to the fixed scroll member31in the direction along the axis L is determined.

For example, as the pressure in the compression chamber47reduces to let the thrust force be below the back pressure force, the back surface40bof the movable base plate40of the movable scroll member38is moved by the back pressure force away from the back surface16aof the disc-shaped portion16of the shaft support member14. The movable base plate40of the movable scroll member38leaves away from the disc-shaped portion16, and the front surface40aof the movable base plate40contacts with the end surface69aof the first fixed wall69of the fixed scroll member31, thus the clearance between the valve seat64and the valve portion65becomes minimum (zero).

As the clearance between the valve seat64and the valve portion65becomes minimum, the passing cross-sectional area of refrigerant gas between the fixed passage60and the communication recess62, that is, the opening degree of the supply passage, becomes minimum (zero). Accordingly, the high-pressure refrigerant gas is prevented from being introduced from the discharge chamber52to the back pressure chamber56through the fixed passage60, the communication recess62, and the movable passage59. Then, the pressure in the back pressure chamber56tends to fall, and the back pressure force applied to the movable scroll member38reduces.

For reducing the back pressure force applied to the movable scroll member38, the clearance between the valve seat64and the valve portion65becomes minimum to prevent the high-pressure refrigerant gas from being introduced from the discharge chamber52to the back pressure chamber56. Accordingly, the high-pressure refrigerant gas in the discharge chamber52, that is, the compressed refrigerant gas, is prevented from uselessly flowing to the motor chamber22through the supply passage, the back pressure chamber56and the bleed passage57. This leads to improved performance of the motor compressor.

As the thrust force exceeds the back pressure force due to increase in pressure in the compression chamber47, the movable scroll member38is moved by the thrust force in the direction in which the back surface40bof the movable base plate40approaches the back surface16aof the disc-shaped portion16of the shaft support member14. As the front surface40aof the movable base plate40leaves away from the end surface69aof the first fixed wall69of the fixed scroll member31so that the movable base plate40of the movable scroll member38contacts the disc-shaped portion16of the shaft support member14, the clearance between the valve seat64and the valve portion65becomes maximum.

As the clearance between the valve seat64and the valve portion65becomes maximum, the passing cross-sectional area of the refrigerant gas between the fixed passage60and the communication recess62, that is, the opening degree of the supply passage becomes maximum. Accordingly, the high-pressure refrigerant gas is introduced from the discharge chamber52to the back pressure chamber56through the fixed passage60, the communication recess62and the movable passage59. Thus, the pressure in the back pressure chamber tends to increase, and the back pressure force applied to the movable scroll member38increases.

At the same time, the refrigerant gas is slowly bled from the back pressure chamber56to the motor chamber22through the bleed passage57due to the fixed throttle57cin the bleed passage57. Accordingly, the high-pressure refrigerant gas in the discharge chamber52, that is, the compressed refrigerant gas is prevented from uselessly flowing to the motor chamber22through the supply passage, the back pressure chamber56and the bleed passage57. This leads to improved performance of the motor compressor.

As described above, the movable scroll member38varies the clearance between the front surface40aof the movable base plate40and the end surface69aof the first fixed wall69of the fixed scroll member31(the clearance between the valve seat64and the valve portion65) so that the back pressure force based upon the pressure in the back pressure chamber56becomes an appropriate value in response to the thrust force based upon the pressure in the compression chambers47, thus autonomously adjusting the pressure in the back pressure chamber56. As the pressure in the back pressure chamber56is appropriately adjusted, generation of sliding resistance due to the orbital motion of the movable scroll member38is reduced.

According to the preferred embodiment, the following advantageous effects are obtained.(1) To adjust the pressure in the back pressure chamber56, that is, to adjust the back pressure force applied to the movable scroll member38, the opening degree of the supply passage (the fixed passage60, the movable passage59, and the communication recess62) is adjusted by varying the clearance at the sliding portion between the movable scroll member38and the first fixed wall69. Accordingly, to decrease the back pressure force applied to the movable scroll member38, the introduction of the high-pressure refrigerant gas from the discharge chamber52to the back pressure chamber56is prevented by minimizing clearance at the sliding portion between the movable scroll member38and the first fixed wall69. Thus, for example, the check valve disclosed in Unexamined Japanese Patent Publication No. 2000-249086 is not required for closing the supply passage, so that the valve structure for adjusting the back pressure force is simple, and costs and processes are reduced for manufacturing the motor compressor.(2) In the preferred embodiment, the front surface40aof the movable base plate40is the front surface of the movable scroll member according to the present invention, and the first fixed wall69is provided on the front surface32aof the fixed base plate32at a position that is different from the fixed scroll wall34. That is, the first fixed wall69is provided in the fixed scroll member31exclusively for the supply passage and independently from the fixed base plate32and the fixed scroll wall34. Accordingly, in comparison to employment of the radially thin fixed scroll wall34as a first fixed wall, or in comparison to employment of the region that slides on the movable scroll wall41in the fixed base plate32as a first fixed wall, the supply passage easily passes through the sliding portion between the movable scroll member38and the first fixed wall69, that is, the arrangement of the supply passage (especially, the formation of the valve seat64and the valve portion65) becomes easy.(3) The back pressure chamber56is defined between the movable base plate40and the disc-shaped portion16of the shaft support member14. The self-rotation blocking mechanism48is provided between the movable base plate40and the fixed base plate32. In other words, the arrangement of the self-rotation blocking mechanism48between the movable base plate40and the fixed base plate32prevents a complicated space on the side of the back surface40bof the movable base plate40. Accordingly, the back pressure chamber56defined between the movable base plate40and the disc-shaped portion16of the shaft support member14becomes relatively free in arrangement and formation. Thus, in the preferred embodiment, the annular back pressure chamber56(the annular recess55) is arranged along the outline of the movable base plate40at the outer peripheral portion of the back surface40bof the movable base plate40.(4) Lubricating oil is introduced together with the high-pressure refrigerant gas from the region around the lowermost portion of the discharge chamber52, that is, the reservoir space52for lubricating oil to the back pressure chamber56. Accordingly, a sufficient amount of lubricating oil is supplied to, for example, the sliding portion between the movable base plate40of the movable scroll member38and the disc-shaped portion16of the shaft support member14, and the sliding portion between the movable base plate40and the first fixed wall69of the fixed scroll member31, thus appropriately lubricating the sliding portions.(5) The filter61is placed at the opening60bof the fixed passage60in the reservoir space52a. Accordingly, foreign substances in the reservoir space52aare prevented from being introduced into the fixed passage60, and also prevented from being introduced, for example, into the sliding portion between the movable base plate40and the first fixed wall69of the fixed scroll member31, the sliding portion between the movable base plate40and the disc-shaped portion16of the shaft support member14, or the like. Thus, the front surface40aand the back surface40bof the movable base plate40, the end surface69aof the first fixed wall69, the back surface16aof the disc-shaped portion16and the like are prevented from being damaged by foreign substances.(6) Carbon dioxide is employed as refrigerant for the refrigerant circuit. The present invention is particularly efficient in carbon dioxide refrigerant in which large thrust force is applied to the movable scroll member38.

The present invention is not limited to the embodiments described above but may be modified into the following alternative embodiments.

In an alternative embodiment to the above preferred embodiment, the bleed passage57is omitted. In this case, a decrease in the pressure in the back pressure chamber56is achieved by the leakage of refrigerant gas from the inner tip seal66or the outer tip seal67. Alternatively, one of the inner tip seal66and the outer tip seal67is omitted, and refrigerant gas in the back pressure chamber56is leaked through the clearance at the sliding portion between the back surface40bof the movable base plate40and the back surface16aof the disc-shaped portion16of the shaft support member14. Furthennore, in at least one of the inner tip seal66and the outer tip seal67, sealing performance is partially decreased by forming a notch, and refrigerant gas is leaked from the back pressure chamber56through the portion that is decreased in sealing performance. Anyway, a path through which refrigerant gas is bled from the back pressure chamber56may be regarded as a bleed passage.

In the preferred embodiment, the high-pressure refrigerant gas is introduced from the discharge chamber52into the back pressure chamber56through the reservoir space52a. In an alternative embodiment, the high-pressure refrigerant gas is introduced from the upper side of the discharge chamber52(the region other than the reservoir space52a) to the back pressure chamber56, or is introduced from the discharge port31ato the back pressure chamber56, or is introduced from the compression chamber47that is in a discharge process (the compression chamber47that is in communication with the discharge port31a) to the back pressure chamber56. Additionally, the high-pressure refrigerant gas is introduced from an external conduit that communicates with, for example, the outlet53, to the back pressure chamber56.

In the preferred embodiment, the first fixed wall69is exclusively provided for the supply passage in the fixed scroll member31and independently from the fixed base plate32and the fixed scroll wall34. However, the structure is not limited. In an alternative embodiment, the first fixed wall69is omitted, and the fixed base plate32doubles as the first fixed wall (the former), or the fixed scroll wall34doubles as the first fixed wall (the latter). Thus, in comparison to the structure that the first fixed wall is provided exclusively for the supply passage, the structure of the fixed scroll member31is simplified.

In the former case, the supply passage passes through the sliding portion between the front surface32aof the fixed base plate32of the fixed scroll member31and, for example, the distal end surface of the movable scroll wall41of the movable scroll member38. Also, in the latter case, the supply passage passes through the sliding portion between the distal end surface of the fixed scroll wall34of the fixed scroll member31and the front surface40aof the movable base plate40of the movable scroll member38.

It is noted that in the former case, a wall (a wall other than the movable scroll wall41) is provided exclusively for the supply passage on the front surface40aof the movable base plate40, and the supply passage passes through the sliding portion between the end surface of the wall and the front surface32aof the fixed base plate32.

In the preferred embodiment, the first fixed wall69is provided for the fixed scroll member31. However, it is not limited. In an alternative embodiment, for example, a member corresponding to the first fixed wall69is provided independently from the fixed scroll member31.

In an alternative embodiment to the preferred embodiment, the hole15ais isolated from the motor chamber22to use the isolated space as the back pressure chamber by placing a seal member in the boss15of the shaft support member14for sealing the rotary shaft18. In this case, the portion corresponding to the bleed passage57and the back pressure chamber56is regarded as a part of the supply passage by omitting the fixed throttle57cfrom the bleed passage57in the preferred embodiment. Also, in this case, a bleed passage having a fixed throttle may, for example, be provided for the shaft support member14so as to connect the above isolated space to the suction pressure region (for example, the motor chamber22or the suction chamber51).

In an alternative embodiment to the preferred embodiment, the suction port39is omitted, while the inlet50directly opens to the suction chamber51. Then, the hole15aof the boss15of the shaft support member14is used as a back pressure chamber. Accordingly, the motor chamber22that communicates with the hole15ais an atmosphere of the pressure in the back pressure chamber. In this case, the portion corresponding to the bleed passage57and the back pressure chamber56is regarded as a part of the supply passage by omitting the fixed throttle57cfrom the bleed passage57in the preferred embodiment. Also, in this case, for example, a bleed passage having a fixed throttle may be provided for the shaft support member14so as to connect the motor chamber22to the suction pressure region (for example, the suction chamber51).

In the preferred embodiment, the self-rotation blocking mechanism48includes the pin48afixed to the movable base plate40, the pin48bfixed to the fixed base plate32, and the ring48carranged outside the pins48a,48b. However, it is not limited. In an alternative embodiment, a pin is fixed to the front surface40aof the movable base plate40, while a circular recess for guiding the orbital motion of the pin is formed in the front surface32aof the fixed base plate32.

In the preferred embodiment, the self-rotation blocking mechanisms48are provided between the movable base plate40and the fixed base plate32. In an alternative embodiment, the self-rotation blocking mechanisms48are provided between the movable base plate40and the disc-shaped portion16of the shaft support member14. In this case, the back pressure chamber56is formed to avoid the self-rotation blocking mechanism48.

The present invention is not limited to a motor compressor, that is, a scroll type compressor that only employs an electric motor as a drive source, but may be a scroll type compressor that employs a vehicular engine as a drive source or a hybrid scroll type compressor that employs an electric motor and an engine as a drive source.

The present invention may be applied to a scroll type compressor for a refrigerant circuit employing fluorocarbon refrigerant.

The present invention may be applied to, for example, an air compressor used for other than a refrigerant circuit.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.