JP2002048080A - Gas compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the wasteful power consumption by lowering the vane back pressure in a suction stroke, and to prevent the deterioration of the lubrication and the seal of slide-contact surfaces between a rotor side surface, a vane side surface and a side block. SOLUTION: A radius of a back pressure fluid inlet 15 at a part in a suction stroke is formed small, and a L-shaped lubricating oil passage 31 is provided so as to be extended from a suction stroke side of the back pressure fluid inlet in the radial direction of a rotor 2 opposite to this inlet in a range riding over a side surface of a back pressure chamber 5 and not riding over a side surface of the rotor, and thereafter, extended in the circumferential direction toward a compression stroke side. The lubricating oil is sufficiently supplied to slide-contact surfaces 30 and 30 between the rotor 2, the vane 4 and the side blocks 21, 21 through the L-shaped lubricating oil passage, and the pressure (back pressure) of the lubricating oil at a small-radius part of the back pressure fluid inlet is lowered by increasing the flow speed of the lubricating oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vane type gas compressor used for a car air conditioner or the like.

[0002]

2. Description of the Related Art As shown in FIG. 6, a vane type gas compressor is provided with a rotor 2 rotatably provided in a cylinder chamber 1a of a cylinder block 1, and a substantially radially engraved rotor 2. Slides in and out of the vane groove 3 and
a is formed at the bottom of the vane groove 3 and slides in contact with the inner cylinder surface 1b of the cylinder chamber 1a, and pressurized fluid is introduced to attach the vane 4 to the inner cylinder surface 1b of the cylinder chamber 1a. And a compression chamber 6 formed by dividing the cylinder chamber 1 a by the vane 4. The volume of the compression chamber 6 is increased or decreased with the rotation of the rotor 2. A gas (refrigerant gas) is sucked through a suction hole 7 opened in the chamber 1a, compressed in the compression chamber 6, and
The compressed gas is discharged to a discharge hole 8 opened at a.

[Pressing Force of Vane] During operation of the gas compressor, the vane 4 must be in sliding contact with the tip 4a of the vane 4 being pressed against the inner cylindrical surface 1b of the cylinder chamber 1a with a moderately strong force. . If the pressing force F is weak, the cylinder chamber 1
Compressed gas leaks from the gap between the sliding contact surface of a and the vane 4 into the adjacent compression chamber, and the vane 4 vibrates and chatter occurs on the sliding contact surface. Leakage of the compressed gas lowers the compression efficiency, lowers the cooling capacity, and chattering not only causes noise, but also significantly promotes wear of the cylinder block 1, the vane 4, and the vane groove 3. On the other hand, if the pressing force F is excessively strong, the power loss increases, and the wear of the vane 4, the cylinder block 1, and the vane groove 3 increases.

[0004] The pressing force F is not large enough to increase power loss and wear, not small enough to cause chattering or to cause poor sealing, and is substantially constant irrespective of the rotational angle position of the vane 4. It is desirable.

[0005] The pressing force F for pressing the vane 4 against the inner cylindrical surface 1b of the cylinder 1 mainly includes a vane popping force generated by the pressure of the back pressure chamber 5 and the centrifugal force of the vane itself, and a compression chamber 6 adjacent to the vane 4. This is the difference from the pushing force toward the center of rotation of the rotor, which is mainly caused by the gas pressure in the inside.

The pushing force changes periodically with the rotation of the rotor 2. In the suction stroke S, the gas pressure in the compression chamber 6 is further lowered than the gas pressure in the suction chamber 14 (see FIG. 1) connected to the suction hole 7, and in the compression stroke C, the sucked gas is compressed to a high pressure. become. Therefore, in the suction stroke C, the back pressure in the back pressure chamber 5 is reduced, and in the compression stroke S, the back pressure in the back pressure chamber 5 is increased to balance with the pushing force.

In order to increase or decrease the back pressure of the back pressure chamber 5, the back pressure chamber 5 and the back pressure fluid inlet 15 provided in the side blocks 21 and 22 (see FIG. 1) in the initial stage of the suction stroke C and the compression stroke S. ,
And 15. When the suction stroke C starts, the high-pressure lubricating oil trapped in the back pressure chamber 5 is supplied to the back pressure fluid inlet 1.
The lubricating oil from the pressurized lubricating oil passage 9 is supplied to the back pressure chamber 5 in the reverse direction by the lubricating oil passage 9 (see FIG. 1). The inner cylinder surface 1b is made to follow the retreat (outward transition). Even in the early stage of the compression stroke C, the pressure of the lubricating oil from the pressurized lubricating oil passage 9 overcomes the above-mentioned pushing force, and therefore the back pressure chamber 5 and the back pressure fluid inlet 1
5 and the pressing force F is maintained. Further, when the pressure of the compression chamber 6 rises due to the rotation of the rotor 2, the pressure of the lubricating oil from the pressurized lubricating oil passage 9 comes to lose the pushing force, so that the communication with the back pressure fluid inlet 15 is closed, Back pressure chamber 5
The lubricating oil is confined, and the confined lubricating oil is further pressurized by pushing a vane into the cylinder inner cylinder surface 1b,
The pressing force F is maintained.

In this case, the pressing force F of the vane is obtained.
Is relatively stable, but still, the pressing force in the suction stroke S is too high, and wasteful power tends to be consumed.

[Conventional measures for reducing the vane pressing force in the suction stroke and its problems] Japanese Utility Model Laid-Open Publication No. Sho 63-78183 discloses that, as shown in FIG. Groove 15a along the diameter of the bearing 12
A gas compressor is disclosed in which the first half of the compression stroke is a wide groove 15b to reduce the back pressure in the suction stroke S and prevent the pressing force F of the vane 4 from becoming excessive.

Lubricating oil is supplied to the back pressure chamber 5 from the narrow groove 15a in the suction stroke portion, and leaks to the sliding contact surface between the rotor 2 and the side blocks 21 and 22. At this time, since the flow of the lubricating oil is restricted by the narrow groove 15a, the pressure is reduced, and thereby the back pressure applied to the vane 4 is reduced.

However, this back pressure reduction does not always sufficiently follow the pressure drop on the compression chamber 6 side due to sudden suction at the beginning of the suction stroke, and the back pressure is somewhat too high. Also,
On the other hand, the amount of the lubricating oil leaking to the sliding contact surfaces between the rotor 2 and the side blocks 21 and 22 tends to be insufficient, resulting in incomplete lubrication and sealing.

[0012]

SUMMARY OF THE INVENTION In the present invention, during the suction stroke, the back pressure is sufficiently reduced to eliminate unnecessary power consumption, and the lubrication of the sliding contact surfaces between both side blocks, the rotor side surface and the vane side surface is improved. It is to provide a maintained gas compressor.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a cylinder chamber formed in a cylinder block with front and rear portions closed by side blocks, A rotor that rotates while sliding the two side surfaces against the side block, a vane groove formed substantially radially on the rotor, and a slidably protruding / retracting part in the vane groove, the tip of which is the inner cylindrical surface of the cylinder chamber. , A back pressure chamber formed at the bottom of the vane groove, a compression chamber formed by dividing the cylinder chamber by the vane, and a sliding contact surface of both side blocks slidingly contacting the rotor side surface. A back-pressure fluid inlet opposed to the back-pressure chamber and communicating with an outlet of the pressurized lubricating oil passage, and pressurized lubrication from the pressurized lubricating oil passage with rotation of the rotor. The oil causes the back pressure chamber to The cylinder is urged against the inner cylinder surface of the cylinder, and while the vane slides on the inner cylinder surface of the cylinder chamber, the volume of the compression chamber is increased or decreased, and the gas in the suction chamber is sucked through the suction hole opened in the cylinder chamber. In the gas compressor, which compresses the gas in the compression chamber and discharges the compressed gas into the discharge chamber from the discharge hole opened in the cylinder chamber, the back-pressure fluid inlet is connected between the suction stroke of the cylinder chamber and the initial stage of the compression stroke. And from the suction stroke side of the back pressure fluid inlet to a region not exceeding the side surface of the rotor and extending beyond the side surface of the back pressure chamber in the radial direction of the opposed rotor in the radial direction. And an L-shaped lubricating oil passage having a circumferential groove extending in the circumferential direction toward the compression stroke.

Further, in this gas compressor, the inner wall of the circumferential groove of the L-shaped lubricating oil passage is formed in such a manner that the inner wall of the back pressure chamber expands in accordance with the increase of the volume of the back pressure chamber as the rotor rotates. Or make the outlet of the pressurized lubricating oil passage communicate with the back pressure fluid inlet at a position on the compression stroke side,
Further, it is preferable that the suction stroke side of the back pressure fluid inlet is narrowed down to the circumferential side where the bottom of the back pressure chamber passes.

The leakage of the lubricating oil from the L-shaped lubricating oil passage and the outflow of the lubricating oil from the back-pressure fluid inlet to the back-pressure chamber cause the lubricating oil to flow at the L-shaped lubricating oil passage and the back-pressure fluid inlet. This lubricating oil flow reduces the pressure of the lubricating oil. Assuming that the flow rate of the lubricating oil is Q, the pressure drop ΔP, the viscosity coefficient μ of the lubricating oil, the length L, the width b, and the depth h of the flow path,

(Equation 1) Becomes That is, in the present invention, the flow rate Q of the lubricating oil is increased by the L-shaped lubricating oil passage, and the back pressure on the vane on the downstream side (the suction stroke side) of the back pressure fluid inlet is reduced. Further, when a portion having a small width b and a long length L at the back pressure fluid inlet with respect to the flow of the lubricating oil is formed, the pressure drop ΔP is further increased.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of a gas compressor according to an embodiment of the present invention, and FIG.
3 is a cross-sectional view taken along the line III-III in FIG. 1, and FIG. 4 is a cross-sectional view showing a state in which the rotor has rotated more than the state shown in FIG. FIG.

2, 3, and 4, the same parts as those in FIG. 6 are denoted by the same reference numerals, and the description thereof will be partially omitted.

As shown in FIGS. 1 and 2, the gas compressor of this embodiment has a front side block
1. A cylinder chamber 1a formed in a cylinder block 1 closed by a rear side block 22, and a rotor 2 in the cylinder chamber 1a which rotates while sliding on both side surfaces of the side blocks 21 and 22. A vane groove 3 engraved substantially radially on the rotor 2;
The tip 4a is slidably protruded from the cylinder chamber 1a.
, A back pressure chamber 5 formed at the bottom of the vane groove 3 (rotor center side), and a compression chamber 6 formed by dividing the cylinder chamber 1 a by the vane 4. And both side blocks 2 slidingly contacting the side surface of the rotor 2
A back pressure fluid inlet 15 which is formed on the sliding contact surfaces 30 of the compressor 1 and 22 and communicates with an outlet 9a of a pressurized lubricating oil passage 9 which sends lubricating oil to a required portion inside the compressor; Having.

The suction hole 7 is provided in the front side block 21.
And a cylinder chamber 1 having a substantially elliptical cross section, provided on a contact surface of the rear side block 22 with the cylinder block 1.
a, and opens at a suction stroke position closer to the rotor traveling direction than the minor diameter portions 17, 17.
Is connected to the suction hole 7 on the front side block 21 side through a communication path 23 penetrating the cylinder block 1,
Further, the suction hole 7 on the front side block 21 side is connected to the suction chamber 14. The suction chamber 14 is connected to a suction port 24 opened to the outside of the gas compressor, and sucks refrigerant gas from a piping of an air conditioner system (not shown).

The discharge hole 8 is provided in the cylinder block 1 and opens at a compression stroke position nearer to the rotor traveling direction (arrow) than the short diameter portions 17 and 17 of the cylinder chamber 1a. Through the discharge chamber 10. The discharge chamber 10 is connected to a discharge port 27 which opens to the outside of the gas compressor, and discharges the compressed refrigerant gas to the piping of the air conditioner system. In addition, 28, 28 of FIG. 2 is a discharge valve of a leaf valve structure for preventing backflow of the refrigerant gas (gas) from the compression chamber communication paths 25, 25 to the compression chamber 6, and 29 of FIG. Is an oil separator protruding from the outlet of the oil discharge chamber 10 into the discharge chamber 10. The lubricating oil in the refrigerant gas separated by the oil separator 29 falls into and accumulates in the oil sump 11 and is circulated and used again as lubricating oil via the pressurized lubricating oil passage 9.

The pressurized lubricating oil passage 9 is not shown in detail, but guides the lubricating oil from an oil sump 11 and the lubricating oil rotatably supports the rotor shaft 2 a of the rotor 2. , 12 are formed in both side blocks 21, 22 and the cylinder block 1 so as to reach the back pressure fluid inlets 15, 15 and to be reduced in pressure by being squeezed by the gap between the bearings 12, 12. .

The back pressure fluid inlets 15, 15 are opened at sliding contact surfaces 30, 30 of the side blocks 21, 22 with the rotor 2, and lubricating oil leaks from the back pressure fluid inlet 15 to the sliding contact surface 30. Take out the rotor 2 of both side blocks 21 and 22
And lubricating the sliding surface with the vane 4. In addition, rotor 2
When the back pressure fluid inlet 15 communicates with the back pressure chamber 5 due to the rotation of, the pressure presses the vane 4 against the inner cylindrical surface 1b of the cylinder chamber 1a. The lubricating oil in the back pressure chamber 5 leaks into the gap between the vane 4 and the vane groove 3 to lubricate, and further lubricates between the vane tip 4a and the cylinder surface 1b. The lubricating oil mixes with the refrigerant gas in the compression chamber 6 and is sent to the oil separator 29 via the compression chamber communication paths 25 and 26.

The back pressure fluid inlets 15, 15 are provided in a shallow groove shape in each of the front side block 21 and the rear side block 22, and are disposed at positions from the suction stroke of the cylinder chamber 1a to the initial stage of the compression stroke. At the position of the suction stroke of the compression chamber 6 distant from the outlet 9 a of the pressurized lubricating oil passage 9, a narrow groove whose width in the radial direction of the rotor is narrowed toward the pitch circumferential side passing through the bottom of the back pressure chamber 5. As 15a, the fluid resistance in the middle is increased so that a very strong pressure is not applied to the back pressure chamber 5, while the rotor radius is set at a position in the first half of the compression stroke arranged near the outlet 9a of the pressurized lubricating oil passage 9. A wide groove 15b having a wide width in the direction is formed to oppose a high compression pressure of the compression chamber 6. This is the same as the conventional gas compressor.

An L-shaped lubricating oil passage 31 is connected to the leading end of the narrow groove 15a on the suction stroke side of the back pressure fluid inlet 15. The L-shaped lubricating oil passage 31 has a radial groove 31 a extending in the radial direction of the opposed rotor from the narrow groove 15 a to a range not exceeding the side surface of the rotor 2 and extending beyond the side surface of the back pressure chamber 5. After being provided, it has a shape in which a circumferential groove 31b extends in the circumferential direction toward the compression stroke side, and lubricating oil flowing from the narrow groove 15a is supplied to both side blocks 2a.
The lubrication and sealing of the sliding surfaces 30, 30 are supplied to the sliding surfaces 30, 30 between the rotors 1, 2 and the rotor 2 and the vane 4, respectively. When the L-shaped lubricating oil passage 31 extends to a position beyond the side surface of the rotor 2 and opens into the cylinder chamber 1a, a large amount of lubricating oil flows out into the cylinder chamber 1a and mixes with the refrigerant. When the back pressure of the back pressure chamber 5 is excessively reduced, the air conditioner system does not operate normally, and the volume and side size of the back pressure chamber 5 change according to the rotational angle position in the cylinder chamber 1a (see FIG. 2). If it does not bend after being extended to the range beyond the side surface of (1), the back pressure is excessively increased by communicating with the back pressure chamber 5, and the function as a lubrication groove is lost. Therefore, the L-shaped lubricating oil passage 31 is limited to the shape described above.

As shown in FIG. 4, the distal end of the circumferentially extending portion 31b of the L-shaped lubricating oil passage 31 has a vane 4 of the vane 4 in the cylinder chamber long diameter portion 16 which protrudes most in the cylinder chamber 1a. It extends to the groove 3. This is because up to this range, lubrication and sealing of the sliding surfaces 30, 30 will be insufficient if only lubricating oil is supplied from the narrow groove 15a of the back pressure fluid inlet 15.

In order to prevent the pressing force F of the vane 4 against the cylinder surface 1b in the suction stroke from becoming excessive, it is desirable that the back pressure in the back pressure chamber 5 on the suction stroke side is sufficiently low. Therefore, the outlet 9a of the pressurized lubricating oil passage 9 to the back pressure fluid inlet 15
Is effective at the position of the wide groove 15b on the compression stroke side, and flowing the lubricating oil to the L-shaped lubricating oil passage 31 far from this position is effective because the pressure of the lubricating oil is reduced on the way. In the middle of the flow, if the suction stroke side is narrowed down to the bottom side of the back pressure chamber 5 like the narrow groove 15a, for example, the lubricating oil pressure reducing action is performed according to [Equation 1] described above. Becomes noticeable.

With this configuration, when the rotor 2 rotates,
The pressurized lubricating oil from the pressurized lubricating oil passage 9 is supplied from the back pressure fluid inlets 15, 15 of both side blocks 21, 22 to the back pressure chamber 5.
And the back pressure chamber 5 continues to urge the vane 4 toward the cylinder inner cylinder surface 1b. The urging force is weak during the suction stroke because the lubricating oil passes through the narrow groove 15a, and becomes strong at the beginning of the compression stroke because the lubricating oil flows into the back pressure chamber 5 directly from the wide groove 15b. Further, the lubricating oil that has reached the L-shaped lubricating oil passage 31 while being depressurized at the back pressure fluid inlet 15 leaks out mainly to the suction stroke area of the sliding contact surfaces 30, 30 to ensure lubrication and sealing. . The sliding contact surfaces 30, 30 in the region of the compression stroke include:
The lubricating oil in the wide groove 15b of the back pressure fluid inlet 15 leaks out,
Lubricate and seal.

As described above, in this embodiment, the vane 4 is in sliding contact with the cylinder surface 1b with an appropriate pressing force F in the entire cycle, and is sufficiently lubricated and sealed. The volume of the compression chamber 6 increases and decreases, and the gas in the suction chamber 14 is sucked from the suction hole 7 opened to the cylinder chamber 1a, and the gas is compressed in the compression chamber 6 so that the cylinder chamber 1
The compressed gas compressed to the discharge chamber 10 is discharged from the discharge hole 8 opening at a.

FIG. 5 is a front view showing a rear side block according to another embodiment of the present invention. In FIG. 5, the shape of the L-shaped lubricating oil passage 32 extending to the back pressure fluid inlet 15 of the side blocks 21 and 22 differs from the embodiment of FIGS. Other configurations are the same as those of the embodiment of FIGS. The same parts as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

The circumferential groove 32 of the L-shaped lubricating oil passage 32
The inner wall 32c of the b. increases the volume of the back pressure chamber 5 due to the rotation of the rotor 2 (during the suction stroke, the vane 4
(The back pressure chamber 5 is widened by going out from the vane groove 3 to the compression chamber 6 side), so that the rotor is displaced in the outer radial direction of the rotor from the radial groove 32a to the tip 32d on the compression stroke side. Thus, the displacement locus of the vane 4 is adjusted. By doing so, the width of the circumferential groove 32b is maximized, the more lubricating oil flows out, and the pressure of the back pressure chamber 5 during the suction stroke is further reduced.

The inner wall 32c is always near the boundary between the vane 4 and the back pressure chamber 5 in the suction stroke, while always isolating the circumferential groove 32b and the back pressure chamber 5 from each other. 32b is a range beyond the side surface of the back pressure chamber 5.

In the above-described embodiment, the radial groove of the L-shaped lubricating oil passage is connected from the tip of the narrow groove at the back pressure fluid inlet,
Extending straight in the radial direction, connecting the circumferential groove ahead of it, for example, connecting the radial groove slightly shifted from the tip of the narrow groove, or even slightly tilting the radial groove from the radial direction, The present invention can be implemented as long as the root of the radial groove is not directly opposed to the expanding back pressure chamber. The wall of the circumferential groove of the L-shaped lubricating oil passage on the outer peripheral side of the rotor may also be slightly inclined from the circumferential direction of the rotor as long as the circumferential groove exceeds the radius of the rotor and the circumferential groove is not exposed to the compression chamber. The present invention can be implemented.

Also, the narrow groove at the back pressure fluid inlet can be deformed such as to be tapered instead of having a uniform width during the suction stroke.

[0034]

As described above in detail, according to the present invention, in the radial direction of the rotor facing from the suction stroke side of the back pressure fluid inlet, the side surface of the back pressure chamber does not exceed the side surface of the rotor. Since the L-shaped lubricating oil passage extending in the circumferential direction toward the compression stroke side is provided after being extended in a range exceeding the
The lubricating oil is sufficiently supplied from the L-shaped lubricating oil passage to a sliding contact surface in a suction stroke region between the rotor, the vane, and the side block. Reduce pressure (back pressure). Therefore, good lubrication and sealing of the sliding surface between the rotor and the vane and the side block are maintained well, and at the same time, the vane back pressure during the suction stroke is reduced, and wasteful power consumption is reduced.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a cross-sectional view showing a state in which a vane pop-out amount is maximized in FIG. 2;

FIG. 5 is a front view showing a rear side block of a gas compressor according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a conventional gas compressor.

[Explanation of symbols]

 Reference Signs List 1 cylinder block 1a cylinder chamber 1b inner cylinder surface 2 rotor 3 vane groove 4 vane 4a vane tip 5 back pressure chamber 6 compression chamber 7 suction hole 8 discharge hole 9 pressurized lubricating oil passage 10 discharge chamber 12 bearing 14 suction chamber 15 back pressure Fluid inlet 15a Narrow groove 15b Wide groove 21 Front side block 22 Rear side block 30 Sliding contact surface 31 L-shaped lubricating oil passage 31a Radial groove 31b Circumferential groove 32 L-shaped lubricating oil passage 32a Radial groove 32b Circumferential direction groove

Claims (4)

[Claims] 1. A cylinder chamber formed in a cylinder block with front and rear sides closed by a side block, a rotor in the cylinder chamber, which rotates while sliding on both sides of the side block, and a rotor A vane groove engraved almost radially on the vane, a vane slidably protruding and retracting in the vane groove, and having a tip slidably in contact with the inner cylinder surface of the cylinder chamber, and a back pressure chamber formed in the bottom of the vane groove. A compression chamber formed by dividing the cylinder chamber by the vane; and a sliding surface of both side blocks slidingly contacting a rotor side surface, and communicating with an outlet of the pressurized lubricating oil passage and the back pressure. The back pressure chamber has a back pressure fluid inlet facing the chamber, and the back pressure chamber urges the vane against the inner cylinder surface of the cylinder with the pressurized lubricating oil from the pressurized lubricating oil passage with the rotation of the rotor. And move the vane into the cylinder chamber. While sliding on the cylinder surface, the volume of the compression chamber is increased or decreased, and the gas in the suction chamber is sucked from the suction hole opened in the cylinder chamber, and the gas is compressed in the compression chamber and discharged from the discharge hole opened in the cylinder chamber. In the gas compressor that discharges the compressed gas compressed into the chamber, the back pressure fluid inlet is formed at a position extending from a suction stroke of the cylinder chamber to an early stage of a compression stroke, and is formed from a suction stroke side of the back pressure fluid inlet. After a radial groove is extended in the radial direction of the opposed rotor to a range not exceeding the side surface of the rotor and beyond the side surface of the back pressure chamber, a circular groove is formed in the circumferential direction toward the compression stroke side. A gas compressor comprising an L-shaped lubricating oil passage having a circumferential groove extending therethrough. 2. The inner wall of the circumferential groove of the L-shaped lubricating oil passage is displaced in the outer radial direction of the rotor as it goes further in response to the expansion of the volume of the back pressure chamber due to the rotation of the rotor. The gas compressor according to claim 1, wherein: 3. The gas compressor according to claim 1, wherein an outlet of the pressurized lubricating oil passage communicates with a back pressure fluid inlet at a position on a compression stroke side. 4. The gas compressor according to claim 3, wherein a suction stroke side of the back pressure fluid inlet is narrowed toward a pitch circumferential side passing through a bottom of the back pressure chamber.