JP2013253486A - Scroll compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scroll compressor with less sliding losses, high efficiency, and less abrasion.SOLUTION: In a scroll compressor, the thrust load of a movable scroll 2 is supported by the pressure of center and outer peripheral back pressure units 9, 19 on a back surface of the movable scroll 2. The maximum reduction effect of the thrust load for supporting the movable scroll in the axial direction is defined to be 100%. In this condition, the parameter M for setting the thrust load reduction effect to be substantially ≥10% is set to be in a range of 0.36≤M≤1.8 in a range of 0.56≤D2/D1≤0.65, 1≤εm2≤2.33 (wherein, D1: the diameter of an end plate of the movable scroll, D2: the diameter of an annular shaft seal member, εm2: the average pressure ratio to the suction pressure of the outer peripheral back pressure unit). Thus, the thrust load to be applied to the movable scroll can be set smaller than that of a conventional configuration in an area of the higher discharge pressure, and thus, there is provided the scroll compressor with less sliding losses and high efficiency.

Description

  The present invention relates to a scroll compressor used in an automobile air conditioning apparatus or the like.

  Conventionally, this type of scroll compressor is provided with an annular seal groove in a bearing holder adjacent to the back surface of the movable scroll, in order to urge the movable scroll toward the fixed scroll to make a turning motion. Is inserted so as to be movable in the axial direction, and oil is supplied into the annular shaft seal member by an oil pump and a high pressure in which the discharge pressure is increased is introduced (for example, see Patent Document 1).

  FIG. 10 shows a cross section of a conventional scroll compressor. As shown in the figure, a fixed scroll 101 having spiral wings, a movable scroll 102 having a pair of honey with the fixed scroll 101 and rotating eccentrically, a shaft 103 for driving the movable scroll 102, A bearing holder 104 that supports the shaft 103 and closes the movable scroll 102 so as to be turnable from the back; an annular shaft seal groove 105 installed on a surface adjacent to the back surface of the movable scroll 102 in the bearing holder 104; It is composed of an annular shaft seal member 106 that is movable in the axial direction and is arranged to seal at a contact portion between the outer peripheral portion and the back surface of the movable scroll 102.

  An oil pump 107 is disposed at the tip of the shaft 103 on the side opposite to the scroll, and the oil stored in the lower portion of the compressor case 108 is sucked up by the rotation of the shaft 103 and passes through the oil passage in the shaft 103 and the annular shaft seal. Oil in which the refrigerant gas is melted by being pressurized by the discharge pressure into the member 106 is supplied. The oil described above lubricates the main bearing 109 that supports the shaft 103, the drive bearing 110 that drives and supports the movable scroll 102, and the like, and the contact surface between the metals when the movable scroll 102 is urged toward the fixed scroll 101 side. The structure is designed to perform a reliable compression action by lubricating the material and sealing a minute gap.

JP-A-1-178785

  However, in the conventional configuration, the tangential force Ft of the compressed gas acting on the movable scroll 102 in addition to the internal pressure gas force Fi in the axial direction of the compressed gas force as shown in FIG. It acts as a moment in the direction of detachment from the head or so-called capsize. Therefore, the back surface of the movable scroll 102 is provided with a central back pressure portion gas force Fm1 in which a high pressure is applied to the inside of the annular shaft seal member 106, and the outer periphery of the annular shaft seal member 106 is set at a low intermediate pressure. The pressure part gas force Fm2 is applied. In this case, in the low compression ratio operation region such as when pressure equalization is activated, it is necessary to increase the resultant force by enlarging the diameter of the annular shaft seal member 106 or the like. As a result, the axial support reaction forces (thrust loads) Fth1 and Fth2 of the fixed scroll 101 and the movable scroll 102 become large values under high-load operation conditions, which causes a decrease in energy efficiency due to an increase in friction loss and causes wear. Had problems.

The present invention solves the above-mentioned conventional problems, and eliminates the phenomenon of movable scroll disengagement (or rollover), and does not result in excessive axial support reaction force (thrust load) under high load operation conditions with high discharge pressure. A scroll compressor is provided.

  In order to solve the conventional problem, a scroll compressor according to the invention includes a fixed scroll having a spiral hood, a movable scroll that forms a compression chamber in pairs with the fixed scroll, and the movable scroll. A shaft to be driven; a bearing holder that supports the shaft and has an annular shaft seal groove on a surface adjacent to the back surface of the movable scroll; and a central back pressure disposed in the annular shaft seal groove so as to be movable in the axial direction. An annular shaft seal member formed with a portion, an inflow side pressure reducing portion for reducing pressure of oil supplied under pressure during operation and supplying the oil to the central back pressure portion, and the annular shaft seal from the central back pressure portion An outflow side pressure reducing portion provided in an outflow passage connected to an outer peripheral back pressure portion on the outer periphery of the member, and the outer peripheral back pressure portion of the annular shaft seal member is set to a suction pressure or a suction pressure. A differential pressure oil supply type scroll compressor having an intermediate pressure, wherein the movable scroll end plate diameter is D1, the annular shaft seal member diameter is D2, and the average pressure with respect to the suction pressure of the outer peripheral back pressure portion of the annular shaft seal member The ratio M is εm2, the minimum cross-sectional area of the inflow side pressure reducing part in differential pressure oiling is A1, the minimum cross-sectional area of the outflow side pressure reducing part is A2, and the parameter M = (D2 / D1) ^ m * εm2 ^ n * A1 / A2 When the definition is m = 2 + (D2 / D1-0.5) * 3 and n = 0.4, the central back pressure part is discharged within a range in which the movable scroll is not detached (or overturned). When the maximum reduction effect of the thrust load in which the fixed scroll supports the movable scroll in the axial direction when the pressure is changed to the intermediate pressure is 100%, the parameter M that makes the thrust load reduction effect approximately 10% or more is set to 0. . It is obtained as a range of 0.36 ≦ M ≦ 1.8 in the range of 6 ≦ D2 / D1 ≦ 0.65,1 ≦ εm2 ≦ 2.33.

  Thereby, it is possible to prevent the thrust load (axial support reaction force) of the fixed scroll and the movable scroll from becoming excessively large as compared with the conventional case in a high load operation region where the discharge pressure is large.

  The scroll compressor of the present invention can prevent the thrust load (axial reaction force) of the fixed scroll and the movable scroll from becoming excessively large compared to the conventional case in a high load operation region where the discharge pressure is large. Loss is reduced, and a structure with high efficiency and low wear can be obtained.

Sectional drawing of the scroll compressor in Embodiment 1 of this invention Explanatory drawing of back pressure part structure of movable scroll in the scroll compressor Explanatory drawing of thrust load distribution in the conventional example Explanatory drawing of thrust load distribution in overturn limit state Explanatory drawing which shows the change of the total thrust load by the center back pressure part pressure in Embodiment 1. FIG. Explanatory drawing of the pressure change of the center back pressure part by the differential pressure oil supply of the scroll compressor in Embodiment 1 Explanatory drawing of the rollover limit factor group of the scroll compressor in the first embodiment Explanatory drawing of the change of the parameter M using the factors influencing the back pressure structure in the first embodiment Explanatory drawing of the range and value of parameter M, which is the back pressure structure determining factor in the first embodiment Sectional view of a conventional scroll compressor Sectional drawing of the compression part explaining the force which acts on the movable scroll of the conventional scroll compressor

  1st invention supports the fixed scroll which has spiral spiral, the movable scroll which carries out a turning motion paired with the fixed scroll, and forms a compression chamber, the shaft which drives the movable scroll, and the shaft And a bearing holder having an annular shaft seal groove on a surface adjacent to the back surface of the movable scroll, and an annular shaft seal member that is arranged so as to be movable in the axial direction in the annular shaft seal groove to form a central back pressure portion, During operation, the oil supplied under pressure by the discharge pressure is reduced and supplied to the central back pressure portion. The inflow side pressure reducing portion is connected to the outer peripheral back pressure portion around the annular shaft seal member from the central back pressure portion. A differential pressure lubrication type scroll pressure having an outflow side pressure reducing portion provided in the outflow passage, wherein the outer peripheral back pressure portion of the annular shaft seal member is an intermediate pressure higher than the suction pressure or the suction pressure. The diameter of the end plate of the movable scroll is D1, the diameter of the annular shaft seal member is D2, the average pressure ratio to the suction pressure of the outer peripheral back pressure portion of the annular shaft seal member is εm2, and the inflow side pressure reducing portion in the differential pressure oil supply The minimum cross-sectional area of A1 is A1, the minimum cross-sectional area of the outflow side decompression section is A2, and the parameter M = (D2 / D1) ^ m * εm2 ^ n * A1 / A2 is defined, and m = 2 + (D2 / D1-0 .5) * 3, when n = 0.4, the fixed scroll when the central back pressure portion is changed from the discharge pressure to the intermediate pressure within a range where the movable scroll is not detached (or overturned) occurs. Assuming that the maximum reduction effect of the thrust load for supporting the movable scroll in the axial direction is 100%, the parameter M that makes the above-mentioned thrust load reduction effect approximately 10% or more is 0.56 ≦ D2 / D1 ≦ 0.65, ≦ εm2 ≦ 2. In 3 of the range in which was set to be a range of 0.36 ≦ M ≦ 1.8.

  Thereby, it is possible to prevent the thrust load (axial support reaction force) of the fixed scroll and the movable scroll from becoming excessively large as compared with the conventional case in a high load operation region where the discharge pressure is large.

  According to a second aspect of the present invention, in the scroll compressor structure of the first aspect, a thrust load when the central back pressure portion is changed from a discharge pressure to an intermediate pressure within a range in which the movable scroll is not detached (or overturned). When the maximum reduction effect of 100% is taken as 100%, the parameter M for obtaining a reduction effect of approximately 50% or more of the thrust load is set to 0.56 ≦ D2 / D1 ≦ 0.65, 1 ≦ εm2 ≦ 2.33. In the range of 0.36 ≦ M ≦ 0.7, the thrust load (axial support reaction force of the fixed scroll and the movable scroll in the high load operation region where the discharge pressure is large as in the first aspect of the invention. ) Can be prevented from becoming excessively large as compared with the conventional case.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments. In the present embodiment, a horizontal structure type electric scroll compressor incorporating a motor will be described as an example.

(Embodiment 1)
1 is a sectional view of a scroll compressor according to Embodiment 1 of the present invention.

  In FIG. 1, this scroll compressor has a fixed scroll 1 having a spiral wing, a movable scroll 2 having a pair of hoods and a pair of hoods, and an eccentric orbiting motion, and driving the movable scroll 2. The shaft 3 is mounted on the surface adjacent to the back of the movable scroll 2 of the bearing holder 4 and the bearing holder 4 that supports the shaft 3 in the radial direction and closes the movable scroll 2 from the back so as to be rotatable. Annular shaft seal groove 5 and an annular shaft seal member disposed therein so as to be movable in the axial direction in order to prevent leakage by contacting the outer diameter portion in the annular shaft seal groove and the back surface of the movable scroll 2. It is comprised from 6.

  The bearing holder 4 is provided with a main bearing 8 that supports the shaft 3 and a shaft seal 7 that is in sliding contact with the outer periphery of the shaft 3 to form a bearing chamber 9. The bearing chamber 9 is surrounded by the annular shaft seal member 6 and serves as a central back pressure portion. A drive bearing 10 is arranged on the opposite side of the spiral scroll of the movable scroll 2, and drives the movable scroll 2 via an eccentric bush 3 a that is eccentric with respect to the shaft 3. Further, an Oldham ring is provided between the bearing holder 4 and the movable scroll 2, and the movable scroll 2 is swung while preventing the movable scroll 2 from rotating.

  The shaft 3 is rotationally driven by a motor 11, and the motor 11 is provided in a comp case 12. An oil reservoir 13 is formed in the comb case 12 at the lower part of the motor chamber where the discharge pressure is applied.

  In this embodiment, the refrigerant gas sucked, compressed and discharged by the pair of spiral ridges flows in the direction of the arrow shown in the figure, and cools the motor 11 on the inner wall of the compcase 12 at the right end in the figure. The refrigerant gas flows out of the discharge pipe arranged at the upper part of the comp case 12 by collision. On the other hand, the oil mist in the refrigerant is condensed by the above-mentioned collision with the inner wall of the comp case 12, moves below the comp case 12 by gravity, and accumulates in the oil reservoir 13.

  The above-described oil inlet 14 is provided in the lower part of the bearing holder 4, and an inflow passage 15 communicating from the inlet 14 to the bearing chamber 9 serving as the central back pressure portion is formed. An inflow side pressure reducing portion 16 that defines a minimum cross-sectional area of the inflow passage is formed in the middle of the inflow passage 15.

  On the other hand, an outflow passage 17 is formed in the end plate 2a of the movable scroll 2 in the radial direction from the inner space of the drive bearing 10 that is mounted on the movable scroll 2 and is located in the central back pressure chamber. A small hole serving as the outflow side pressure reducing portion 18 is formed in the end plate 2a at a position crossed by the swivel motion so as to be orthogonal to the outflow passage 17, and the outer peripheral back pressure portion 19 outside the annular shaft seal member 6 is intermittently provided during operation. To let it flow out. In addition, when the operation is stopped, the oil is completely stopped at the timing when the small hole is present in the internal space of the annular shaft seal member 6, so that the oil can be prevented from flowing out to the low pressure side after the operation is stopped.

  The configuration described above is the basic structure of the differential pressure oil supply type scroll compressor of the present embodiment, and the contents of the present invention will be described below.

  Various structures have been devised for biasing the movable scroll toward the fixed scroll by applying gas pressure to the back of the movable scroll as described in the conventional example. However, an annular shaft seal member is provided to discharge in the center. When a high pressure according to the pressure or the discharge pressure is introduced, if the discharge pressure becomes about 3 MPa with the R134a refrigerant, an excessive biasing force is obtained. Therefore, in the present invention, the passage cross-sectional area of the inflow side decompression unit 16 and the outflow side decompression unit 18 is appropriately designed to prevent the urging force from becoming excessive, and the rollover phenomenon at the low compression ratio of the scroll compressor is prevented. It is possible to avoid it as much as possible, and also to prevent the deterioration of compressor efficiency due to excessive supply amount, which is a precaution for the differential pressure lubrication method, and to prevent the oil and high pressure gas from flowing out to the low pressure side due to the differential pressure at the time of shutdown Provide an appropriate ratio range in the design of the minimum cross-sectional area of the inflow and outflow passages.

  In general, if Bernoulli's equation and continuous equation are used for an incompressible fluid such as oil, the high pressure P1, the low pressure P3, the minimum cross-sectional area A1 of the inflow-side decompression unit 16, and the minimum cross-sectional area A2 of the outflow-side decompression unit 18 are obtained. Sometimes, the intermediate pressure P2 in the space between the high pressure and the low pressure is expressed as P2 = (A1 ^ 2 * P1 + A2 ^ 2 * P3) / (A1 ^ 2 + A2 ^ 2).

  The minimum cross-sectional area A2 of the outflow side pressure reducing unit 18 varies depending on the compressor structure, model, displacement, etc., but is determined in consideration of an oil heating loss due to excessive inflow and an appropriate oil amount for gap sealing.

  In order to achieve the object of the present invention, first, in the schematic structure as shown in FIG. 2, the ratio of the cross-sectional area between the minimum cross-sectional area A1 of the inflow-side decompression unit 16 to the minimum cross-sectional area A2 of the outflow-side decompression unit 18 in the differential pressure system. Consider A1 / A2.

  Further, if the diameter of the annular shaft seal member 6 is D2, the relationship with the end plate diameter D1 of the movable scroll 2 is important, and it is necessary to consider the diameter ratio D2 / D1.

  Further, the correlation with the pressure Pm2 of the outer peripheral back pressure portion 19 on the outflow side is also examined.

  The optimum back pressure structure is defined as a back pressure distribution structure of the movable scroll 2 in which the movable scroll 2 does not roll over (or disengages) from the fixed scroll 1 and the thrust load is minimized, and the diameter ratio D2 / D1, First, calculation was performed using the pressure ratio εm2 of the outer peripheral back pressure portion 19 of the annular shaft seal member 6 as a parameter.

  As a calculation example, FIG. 3 shows the thrust load distribution during one rotation in the case of the conventional configuration in which the discharge pressure is applied to the central back pressure portion inside the annular shaft seal member 6. In the figure, Fth1 and Fth2 are the representative thrust loads described with reference to FIG.

  FIG. 4 shows the thrust load distribution when the pressure of the central back pressure portion (central back pressure) is reduced to just before so-called partial rollover where the thrust load Fth2 of the movable scroll is partially negative. It can be seen that the value of the thrust load can be considerably reduced compared to the conventional configuration.

  FIG. 5 shows changes in the total thrust load with respect to the pressure in the central back pressure portion (central back pressure). In this case, when the pressure in the central back pressure portion becomes less than 18.5 kg / cm 2, Fth2 is partially negative, and the movable scroll partially disengages from the fixed scroll during one rotation. This phenomenon is defined as capsize. This result shows that the total thrust load can be reduced by about 70% at maximum under this condition.

  Here, when the maximum thrust load reduction effect when the central back pressure part is changed from the discharge pressure to the intermediate pressure is assumed to be 100%, as a guideline, various factors that can obtain a thrust load reduction effect of 50% and 10%, respectively. We will examine it later.

  By the above-described method, the pressure of the central back pressure part which becomes the rollover limit in the state of Pd / Ps = 30/5 (kg / cm 2 abs) with respect to the various influencing factors described above is obtained by calculation, and becomes the pressure. The minimum passage cross-sectional areas A1 and A2 of the inflow / outflow side decompression section are selected.

  FIG. 6 shows an example of the change in the central back pressure (pressure at the central back pressure portion) when the discharge pressure is changed while the A1 / A2 is fixed and the suction pressure Ps is kept constant.

Under this condition, the pressure ratio Pm1 / Pd of the central back pressure portion that does not roll over at the discharge pressure Pd = 30 kg / cm 2 may be about 0.5, and when the discharge pressure Pd is reduced to 6 kg / cm 2, the pressure ratio Pm1 / Pm1 / of the central back pressure portion. Pd rises to approximately 0.9. In other words, since the differential pressure generated by the restriction of the inflow passage becomes small at a low compression ratio where the discharge pressure is low, rollover is prevented by a diameter D2 of the annular shaft seal portion and a pressure ratio εm2 of the outer peripheral back pressure portion. It can be seen that a fine correction design to add

  In FIG. 7, as described above, the diameter ratio D2 / D1 is changed from 0.5 to 0.683, and the pressure ratio εm2 of the outer peripheral back pressure portion of the annular shaft seal portion is changed from 1 to 2.33 as parameters. The calculation results of the limit pressure ratio Pm1 / Pd that does not occur and the minimum cross-sectional area ratio A1 / A2 of the inflow / outflow-side decompression section that gives the limit pressure ratio Pm1 / Pd are shown. As a matter of course, when the diameter D2 of the annular shaft seal portion is small, the pressure of the central back pressure portion may be increased or the pressure ratio of the outer peripheral back pressure portion may be increased. -As for the minimum cross-sectional area ratio of the outflow side decompression parts 16, 18, it is necessary to increase the minimum cross-sectional area A1 of the inflow side decompression part as the central back pressure part is increased.

  Since the above results show that various factors have complicated correlations, the parameter M = (D2 / D1) ^ m * εm2 ^ n * A1 / A2 is defined in order to grasp the overall tendency. When m = 2 + (D2 / D1-0.5) * 3 and n = 0.4, and rearranging by the parameter M, FIG. 7 is rearranged as shown in FIG.

  Here, the parameter Mmin represents a limit parameter M at which the phenomenon of the movable scroll disengagement (or rollover) does not occur at Pd / Ps = 30/5 (unit: kg / cm 2).

  Further, M10% is a parameter M that governs the intermediate pressure inside the annular shaft seal member that is reduced by approximately 10% when the maximum reduction effect of the thrust load is 100% within a range in which there is no rollover phenomenon. .

  Further, M50% is a parameter M that governs the intermediate pressure inside the annular shaft seal member that is reduced by about 50% when the maximum reduction effect of the thrust load is 100% in a range where the above rollover phenomenon does not occur. .

  From this figure, the values of Mmin, M50%, and M10% tend to be almost constant values except when the diameter ratio D2 / D1 is the smallest 0.5 and the largest 0.683. In D2 / D1 at both ends, the tendency of the value of M10% is different from the central portion.

  Upon further examination, at 2.67 where εm2 is the largest, the value of Mmin tends to be slightly smaller than 1 ≦ εm2 ≦ 2.33.

  As described above, when the range of the diameter ratio D2 / D1 at which the value of the parameter M is almost constant and the pressure ratio of the outer peripheral back pressure portion is limited to 0.56 ≦ D2 / D1 ≦ 0.65, 1 ≦ εm2 ≦ 2.33 The value of the parameter Mmin is in the range of 0.43 ± 0.08. On the condition that there is no rollover, Mmin is 0.36 or more.

  In addition, the parameter M10% at which a reduction effect of about 10% is obtained is about 1.8 with the maximum reduction effect being 100% as the reduction effect of the thrust load, and the value of the parameter M50% at which a reduction effect of about 50% is obtained is about It turns out that it is about 0.7.

When the above is arranged, the fixed scroll 1 having a spiral honey, the movable scroll 2 having a spiral honey that forms a compression chamber in a pair with the fixed scroll, and a shaft that drives the movable scroll. 3, a bearing holder 4 that supports the shaft and has an annular shaft seal groove 5 on a surface adjacent to the back surface of the movable scroll, and an annular shaft seal member that is disposed in the annular shaft seal groove so as to be movable in the axial direction. 6, during operation, the central back pressure part surrounded by the annular shaft seal member 6 is depressurized by the inflow side decompression part 16 with the oil supplied under pressure by the discharge pressure, and is discharged to the outflow side decompression part 18. Is also configured to have an intermediate pressure generated by forming a passage resistance, while the outer peripheral back pressure portion space outside the annular shaft seal member 6 is set to a suction pressure or a suction pressure. The intermediate scroll pressure is D1, the diameter of the movable scroll 2 is D1, the diameter of the annular shaft seal member 6 is D2, the average pressure ratio to the suction pressure of the outer periphery of the annular shaft seal member is εm2, and the inflow side pressure reducing portion in the differential pressure oil supply 16 is defined as parameter M = (D2 / D1) ^ m * εm2 ^ n * A1 / A2, where A1 is the minimum cross-sectional area of A16 and A2 is the minimum cross-sectional area of the outflow side decompression unit 18, and m = 2 + (D2 / D1 -0.5) * 3, when n = 0.4, the thrust when the central back pressure portion is changed from the discharge pressure to the intermediate pressure within a range where the movable scroll 2 is not detached (or overturned). When the maximum load reduction effect is 100%, the parameter M is in the range of 0.56 ≦ D2 / D1 ≦ 0.65, 1 ≦ εm2 ≦ 2.33 in order to make the thrust load reduction effect approximately 10% or more. 0.36 ≦ M ≦ 1.8 The end plate diameter D1 of the movable scroll 2, the diameter D2 of the annular shaft seal member 6, the average pressure ratio εm2 of the outer peripheral back pressure of the annular shaft seal member 6 to the suction pressure, the minimum cross-sectional area of the inflow and outflow passages A1 , A2 should be selected.

  In addition, when the central back pressure part is changed from the discharge pressure to the intermediate pressure within a range where the phenomenon of separation (or rollover) of the movable scroll 2 does not occur, the maximum reduction effect of the thrust load is assumed to be approximately 50%. The above defined parameter M for obtaining the above reduction effect is 0.36 ≦ M ≦ 0.7 in the range of 0.56 ≦ D2 / D1 ≦ 0.65, 1 ≦ εm2 ≦ 2.33. It means that the above-mentioned factors should be selected so as to be within the range.

  As described above, the scroll compressor according to the present invention can be configured to reduce the axial support reaction force (thrust load) acting on the movable scroll in the high load operation region where the discharge pressure is high. As a result, the compressor can be made highly energy efficient. Therefore, it can be applied as a scroll compressor in many fields such as room air conditioners and water heaters.

DESCRIPTION OF SYMBOLS 1 Fixed scroll 2 Movable scroll 2a Movable scroll end plate 3 Shaft 4 Bearing holder 5 Annular shaft seal groove 6 Annular shaft seal member 7 Shaft seal 8 Main bearing 9 Bearing chamber (central back pressure part)
DESCRIPTION OF SYMBOLS 10 Drive bearing 11 Motor 13 Oil reservoir 15 Inflow passage 16 Inflow side pressure reduction part (minimum cross-sectional area part of inflow passage)
17 Outflow passage 18 Outflow side decompression section (minimum cross-sectional area of outflow passage)
19 Outer back pressure part

Claims (2)

A fixed scroll having a spiral fold, a movable scroll that forms a compression chamber in a pair with the fixed scroll, a shaft that drives the movable scroll, a shaft that supports the shaft, and a back surface of the movable scroll A bearing holder having an annular shaft seal groove on an adjacent surface, an annular shaft seal member that is movably disposed in the axial direction in the annular shaft seal groove to form a central back pressure portion, and is applied by discharge pressure during operation. An inflow side decompression unit that decompresses pressure-supplied oil and supplies it to the central back pressure part, and an outflow side provided in an outflow passage that leads from the central back pressure part to the outer peripheral back pressure part on the outer periphery of the annular shaft seal member A differential pressure oil supply type scroll compressor having a pressure reducing portion, wherein the outer peripheral back pressure portion of the annular shaft seal member is an intermediate pressure higher than a suction pressure or a suction pressure, The diameter of the end plate of the movable scroll is D1, the diameter of the annular shaft seal member is D2, the average pressure ratio with respect to the suction pressure of the outer peripheral back pressure portion of the annular shaft seal member is εm2, and the minimum cross-sectional area of the inflow side pressure reducing portion in the differential pressure oil supply is A1, the minimum cross-sectional area of the outflow side decompression section is A2, and defined as parameter M = (D2 / D1) ^ m * εm2 ^ n * A1 / A2, m = 2 + (D2 / D1-0.5) * 3 When n = 0.4, the fixed scroll moves in the axial direction when the central back pressure portion is changed from the discharge pressure to the intermediate pressure within a range in which the movable scroll is not detached (or overturned). When the maximum reduction effect of the thrust load supported by 100 is 100%, the parameter M for making the thrust load reduction effect approximately 10% or more is set to 0.56 ≦ D2 / D1 ≦ 0.65, 1 ≦ εm2 ≦ 2.33. In the range .36 scroll compressor as in the range of ≦ M ≦ 1.8. The maximum effect of reducing the thrust load by which the fixed scroll supports the movable scroll in the axial direction when the central back pressure portion is changed from the discharge pressure to the intermediate pressure within a range in which the movable scroll is not separated (or overturned) occurs. %, The parameter M for obtaining a reduction effect of approximately 50% or more is 0.36 ≦ M ≦ in the range of 0.56 ≦ D2 / D1 ≦ 0.65, 1 ≦ εm2 ≦ 2.33. The scroll compressor according to claim 1, wherein the range is 0.7.